1 | NAME |
1 | NAME |
2 | AnyEvent - provide framework for multiple event loops |
2 | AnyEvent - the DBI of event loop programming |
3 | |
3 | |
4 | EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event |
4 | EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, |
5 | loops |
5 | Qt, FLTK and POE are various supported event loops/environments. |
6 | |
6 | |
7 | SYNOPSIS |
7 | SYNOPSIS |
8 | use AnyEvent; |
8 | use AnyEvent; |
9 | |
9 | |
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10 | # if you prefer function calls, look at the AE manpage for |
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11 | # an alternative API. |
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12 | |
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13 | # file handle or descriptor readable |
10 | my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { |
14 | my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); |
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15 | |
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16 | # one-shot or repeating timers |
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17 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
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18 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...); |
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19 | |
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20 | print AnyEvent->now; # prints current event loop time |
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21 | print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. |
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22 | |
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23 | # POSIX signal |
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24 | my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); |
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25 | |
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26 | # child process exit |
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27 | my $w = AnyEvent->child (pid => $pid, cb => sub { |
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28 | my ($pid, $status) = @_; |
11 | ... |
29 | ... |
12 | }); |
30 | }); |
13 | |
31 | |
14 | my $w = AnyEvent->timer (after => $seconds, cb => sub { |
32 | # called when event loop idle (if applicable) |
15 | ... |
33 | my $w = AnyEvent->idle (cb => sub { ... }); |
16 | }); |
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17 | |
34 | |
18 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
35 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
19 | $w->send; # wake up current and all future recv's |
36 | $w->send; # wake up current and all future recv's |
20 | $w->recv; # enters "main loop" till $condvar gets ->send |
37 | $w->recv; # enters "main loop" till $condvar gets ->send |
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38 | # use a condvar in callback mode: |
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39 | $w->cb (sub { $_[0]->recv }); |
21 | |
40 | |
22 | INTRODUCTION/TUTORIAL |
41 | INTRODUCTION/TUTORIAL |
23 | This manpage is mainly a reference manual. If you are interested in a |
42 | This manpage is mainly a reference manual. If you are interested in a |
24 | tutorial or some gentle introduction, have a look at the AnyEvent::Intro |
43 | tutorial or some gentle introduction, have a look at the AnyEvent::Intro |
25 | manpage. |
44 | manpage. |
26 | |
45 | |
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46 | SUPPORT |
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47 | An FAQ document is available as AnyEvent::FAQ. |
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48 | |
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49 | There also is a mailinglist for discussing all things AnyEvent, and an |
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50 | IRC channel, too. |
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51 | |
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52 | See the AnyEvent project page at the Schmorpforge Ta-Sa Software |
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53 | Repository, at <http://anyevent.schmorp.de>, for more info. |
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54 | |
27 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
55 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
28 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
56 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
29 | nowadays. So what is different about AnyEvent? |
57 | nowadays. So what is different about AnyEvent? |
30 | |
58 | |
31 | Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of |
59 | Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of |
32 | policy* and AnyEvent is *small and efficient*. |
60 | policy* and AnyEvent is *small and efficient*. |
33 | |
61 | |
34 | First and foremost, *AnyEvent is not an event model* itself, it only |
62 | First and foremost, *AnyEvent is not an event model* itself, it only |
35 | interfaces to whatever event model the main program happens to use in a |
63 | interfaces to whatever event model the main program happens to use, in a |
36 | pragmatic way. For event models and certain classes of immortals alike, |
64 | pragmatic way. For event models and certain classes of immortals alike, |
37 | the statement "there can only be one" is a bitter reality: In general, |
65 | the statement "there can only be one" is a bitter reality: In general, |
38 | only one event loop can be active at the same time in a process. |
66 | only one event loop can be active at the same time in a process. |
39 | AnyEvent helps hiding the differences between those event loops. |
67 | AnyEvent cannot change this, but it can hide the differences between |
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68 | those event loops. |
40 | |
69 | |
41 | The goal of AnyEvent is to offer module authors the ability to do event |
70 | The goal of AnyEvent is to offer module authors the ability to do event |
42 | programming (waiting for I/O or timer events) without subscribing to a |
71 | programming (waiting for I/O or timer events) without subscribing to a |
43 | religion, a way of living, and most importantly: without forcing your |
72 | religion, a way of living, and most importantly: without forcing your |
44 | module users into the same thing by forcing them to use the same event |
73 | module users into the same thing by forcing them to use the same event |
45 | model you use. |
74 | model you use. |
46 | |
75 | |
47 | For modules like POE or IO::Async (which is a total misnomer as it is |
76 | For modules like POE or IO::Async (which is a total misnomer as it is |
48 | actually doing all I/O *synchronously*...), using them in your module is |
77 | actually doing all I/O *synchronously*...), using them in your module is |
49 | like joining a cult: After you joined, you are dependent on them and you |
78 | like joining a cult: After you join, you are dependent on them and you |
50 | cannot use anything else, as it is simply incompatible to everything |
79 | cannot use anything else, as they are simply incompatible to everything |
51 | that isn't itself. What's worse, all the potential users of your module |
80 | that isn't them. What's worse, all the potential users of your module |
52 | are *also* forced to use the same event loop you use. |
81 | are *also* forced to use the same event loop you use. |
53 | |
82 | |
54 | AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
83 | AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
55 | fine. AnyEvent + Tk works fine etc. etc. but none of these work together |
84 | fine. AnyEvent + Tk works fine etc. etc. but none of these work together |
56 | with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your |
85 | with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module |
57 | module uses one of those, every user of your module has to use it, too. |
86 | uses one of those, every user of your module has to use it, too. But if |
58 | But if your module uses AnyEvent, it works transparently with all event |
87 | your module uses AnyEvent, it works transparently with all event models |
59 | models it supports (including stuff like POE and IO::Async, as long as |
88 | it supports (including stuff like IO::Async, as long as those use one of |
60 | those use one of the supported event loops. It is trivial to add new |
89 | the supported event loops. It is easy to add new event loops to |
61 | event loops to AnyEvent, too, so it is future-proof). |
90 | AnyEvent, too, so it is future-proof). |
62 | |
91 | |
63 | In addition to being free of having to use *the one and only true event |
92 | In addition to being free of having to use *the one and only true event |
64 | model*, AnyEvent also is free of bloat and policy: with POE or similar |
93 | model*, AnyEvent also is free of bloat and policy: with POE or similar |
65 | modules, you get an enormous amount of code and strict rules you have to |
94 | modules, you get an enormous amount of code and strict rules you have to |
66 | follow. AnyEvent, on the other hand, is lean and up to the point, by |
95 | follow. AnyEvent, on the other hand, is lean and to the point, by only |
67 | only offering the functionality that is necessary, in as thin as a |
96 | offering the functionality that is necessary, in as thin as a wrapper as |
68 | wrapper as technically possible. |
97 | technically possible. |
69 | |
98 | |
70 | Of course, AnyEvent comes with a big (and fully optional!) toolbox of |
99 | Of course, AnyEvent comes with a big (and fully optional!) toolbox of |
71 | useful functionality, such as an asynchronous DNS resolver, 100% |
100 | useful functionality, such as an asynchronous DNS resolver, 100% |
72 | non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms |
101 | non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms |
73 | such as Windows) and lots of real-world knowledge and workarounds for |
102 | such as Windows) and lots of real-world knowledge and workarounds for |
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76 | Now, if you *do want* lots of policy (this can arguably be somewhat |
105 | Now, if you *do want* lots of policy (this can arguably be somewhat |
77 | useful) and you want to force your users to use the one and only event |
106 | useful) and you want to force your users to use the one and only event |
78 | model, you should *not* use this module. |
107 | model, you should *not* use this module. |
79 | |
108 | |
80 | DESCRIPTION |
109 | DESCRIPTION |
81 | AnyEvent provides an identical interface to multiple event loops. This |
110 | AnyEvent provides a uniform interface to various event loops. This |
82 | allows module authors to utilise an event loop without forcing module |
111 | allows module authors to use event loop functionality without forcing |
83 | users to use the same event loop (as only a single event loop can |
112 | module users to use a specific event loop implementation (since more |
84 | coexist peacefully at any one time). |
113 | than one event loop cannot coexist peacefully). |
85 | |
114 | |
86 | The interface itself is vaguely similar, but not identical to the Event |
115 | The interface itself is vaguely similar, but not identical to the Event |
87 | module. |
116 | module. |
88 | |
117 | |
89 | During the first call of any watcher-creation method, the module tries |
118 | During the first call of any watcher-creation method, the module tries |
90 | to detect the currently loaded event loop by probing whether one of the |
119 | to detect the currently loaded event loop by probing whether one of the |
91 | following modules is already loaded: EV, Event, Glib, |
120 | following modules is already loaded: EV, AnyEvent::Loop, Event, Glib, |
92 | AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is |
121 | Tk, Event::Lib, Qt, POE. The first one found is used. If none are |
93 | used. If none are found, the module tries to load these modules |
122 | detected, the module tries to load the first four modules in the order |
94 | (excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should |
123 | given; but note that if EV is not available, the pure-perl |
95 | always succeed) in the order given. The first one that can be |
124 | AnyEvent::Loop should always work, so the other two are not normally |
96 | successfully loaded will be used. If, after this, still none could be |
125 | tried. |
97 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
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98 | very efficient, but should work everywhere. |
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99 | |
126 | |
100 | Because AnyEvent first checks for modules that are already loaded, |
127 | Because AnyEvent first checks for modules that are already loaded, |
101 | loading an event model explicitly before first using AnyEvent will |
128 | loading an event model explicitly before first using AnyEvent will |
102 | likely make that model the default. For example: |
129 | likely make that model the default. For example: |
103 | |
130 | |
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105 | use AnyEvent; |
132 | use AnyEvent; |
106 | |
133 | |
107 | # .. AnyEvent will likely default to Tk |
134 | # .. AnyEvent will likely default to Tk |
108 | |
135 | |
109 | The *likely* means that, if any module loads another event model and |
136 | The *likely* means that, if any module loads another event model and |
110 | starts using it, all bets are off. Maybe you should tell their authors |
137 | starts using it, all bets are off - this case should be very rare |
111 | to use AnyEvent so their modules work together with others seamlessly... |
138 | though, as very few modules hardcode event loops without announcing this |
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139 | very loudly. |
112 | |
140 | |
113 | The pure-perl implementation of AnyEvent is called |
141 | The pure-perl implementation of AnyEvent is called "AnyEvent::Loop". |
114 | "AnyEvent::Impl::Perl". Like other event modules you can load it |
142 | Like other event modules you can load it explicitly and enjoy the high |
115 | explicitly and enjoy the high availability of that event loop :) |
143 | availability of that event loop :) |
116 | |
144 | |
117 | WATCHERS |
145 | WATCHERS |
118 | AnyEvent has the central concept of a *watcher*, which is an object that |
146 | AnyEvent has the central concept of a *watcher*, which is an object that |
119 | stores relevant data for each kind of event you are waiting for, such as |
147 | stores relevant data for each kind of event you are waiting for, such as |
120 | the callback to call, the file handle to watch, etc. |
148 | the callback to call, the file handle to watch, etc. |
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122 | These watchers are normal Perl objects with normal Perl lifetime. After |
150 | These watchers are normal Perl objects with normal Perl lifetime. After |
123 | creating a watcher it will immediately "watch" for events and invoke the |
151 | creating a watcher it will immediately "watch" for events and invoke the |
124 | callback when the event occurs (of course, only when the event model is |
152 | callback when the event occurs (of course, only when the event model is |
125 | in control). |
153 | in control). |
126 | |
154 | |
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155 | Note that callbacks must not permanently change global variables |
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156 | potentially in use by the event loop (such as $_ or $[) and that |
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157 | callbacks must not "die". The former is good programming practice in |
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158 | Perl and the latter stems from the fact that exception handling differs |
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159 | widely between event loops. |
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160 | |
127 | To disable the watcher you have to destroy it (e.g. by setting the |
161 | To disable a watcher you have to destroy it (e.g. by setting the |
128 | variable you store it in to "undef" or otherwise deleting all references |
162 | variable you store it in to "undef" or otherwise deleting all references |
129 | to it). |
163 | to it). |
130 | |
164 | |
131 | All watchers are created by calling a method on the "AnyEvent" class. |
165 | All watchers are created by calling a method on the "AnyEvent" class. |
132 | |
166 | |
133 | Many watchers either are used with "recursion" (repeating timers for |
167 | Many watchers either are used with "recursion" (repeating timers for |
134 | example), or need to refer to their watcher object in other ways. |
168 | example), or need to refer to their watcher object in other ways. |
135 | |
169 | |
136 | An any way to achieve that is this pattern: |
170 | One way to achieve that is this pattern: |
137 | |
171 | |
138 | my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
172 | my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
139 | # you can use $w here, for example to undef it |
173 | # you can use $w here, for example to undef it |
140 | undef $w; |
174 | undef $w; |
141 | }); |
175 | }); |
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143 | Note that "my $w; $w =" combination. This is necessary because in Perl, |
177 | Note that "my $w; $w =" combination. This is necessary because in Perl, |
144 | my variables are only visible after the statement in which they are |
178 | my variables are only visible after the statement in which they are |
145 | declared. |
179 | declared. |
146 | |
180 | |
147 | I/O WATCHERS |
181 | I/O WATCHERS |
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182 | $w = AnyEvent->io ( |
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183 | fh => <filehandle_or_fileno>, |
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184 | poll => <"r" or "w">, |
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185 | cb => <callback>, |
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186 | ); |
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187 | |
148 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
188 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
149 | the following mandatory key-value pairs as arguments: |
189 | the following mandatory key-value pairs as arguments: |
150 | |
190 | |
151 | "fh" the Perl *file handle* (*not* file descriptor) to watch for events. |
191 | "fh" is the Perl *file handle* (or a naked file descriptor) to watch for |
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192 | events (AnyEvent might or might not keep a reference to this file |
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193 | handle). Note that only file handles pointing to things for which |
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194 | non-blocking operation makes sense are allowed. This includes sockets, |
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195 | most character devices, pipes, fifos and so on, but not for example |
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196 | files or block devices. |
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197 | |
152 | "poll" must be a string that is either "r" or "w", which creates a |
198 | "poll" must be a string that is either "r" or "w", which creates a |
153 | watcher waiting for "r"eadable or "w"ritable events, respectively. "cb" |
199 | watcher waiting for "r"eadable or "w"ritable events, respectively. |
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200 | |
154 | is the callback to invoke each time the file handle becomes ready. |
201 | "cb" is the callback to invoke each time the file handle becomes ready. |
155 | |
202 | |
156 | Although the callback might get passed parameters, their value and |
203 | Although the callback might get passed parameters, their value and |
157 | presence is undefined and you cannot rely on them. Portable AnyEvent |
204 | presence is undefined and you cannot rely on them. Portable AnyEvent |
158 | callbacks cannot use arguments passed to I/O watcher callbacks. |
205 | callbacks cannot use arguments passed to I/O watcher callbacks. |
159 | |
206 | |
160 | The I/O watcher might use the underlying file descriptor or a copy of |
207 | The I/O watcher might use the underlying file descriptor or a copy of |
161 | it. You must not close a file handle as long as any watcher is active on |
208 | it. You must not close a file handle as long as any watcher is active on |
162 | the underlying file descriptor. |
209 | the underlying file descriptor. |
163 | |
210 | |
164 | Some event loops issue spurious readyness notifications, so you should |
211 | Some event loops issue spurious readiness notifications, so you should |
165 | always use non-blocking calls when reading/writing from/to your file |
212 | always use non-blocking calls when reading/writing from/to your file |
166 | handles. |
213 | handles. |
167 | |
214 | |
168 | Example: |
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169 | |
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170 | # wait for readability of STDIN, then read a line and disable the watcher |
215 | Example: wait for readability of STDIN, then read a line and disable the |
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216 | watcher. |
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217 | |
171 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
218 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
172 | chomp (my $input = <STDIN>); |
219 | chomp (my $input = <STDIN>); |
173 | warn "read: $input\n"; |
220 | warn "read: $input\n"; |
174 | undef $w; |
221 | undef $w; |
175 | }); |
222 | }); |
176 | |
223 | |
177 | TIME WATCHERS |
224 | TIME WATCHERS |
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225 | $w = AnyEvent->timer (after => <seconds>, cb => <callback>); |
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226 | |
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227 | $w = AnyEvent->timer ( |
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228 | after => <fractional_seconds>, |
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229 | interval => <fractional_seconds>, |
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230 | cb => <callback>, |
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231 | ); |
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232 | |
178 | You can create a time watcher by calling the "AnyEvent->timer" method |
233 | You can create a time watcher by calling the "AnyEvent->timer" method |
179 | with the following mandatory arguments: |
234 | with the following mandatory arguments: |
180 | |
235 | |
181 | "after" specifies after how many seconds (fractional values are |
236 | "after" specifies after how many seconds (fractional values are |
182 | supported) the callback should be invoked. "cb" is the callback to |
237 | supported) the callback should be invoked. "cb" is the callback to |
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184 | |
239 | |
185 | Although the callback might get passed parameters, their value and |
240 | Although the callback might get passed parameters, their value and |
186 | presence is undefined and you cannot rely on them. Portable AnyEvent |
241 | presence is undefined and you cannot rely on them. Portable AnyEvent |
187 | callbacks cannot use arguments passed to time watcher callbacks. |
242 | callbacks cannot use arguments passed to time watcher callbacks. |
188 | |
243 | |
189 | The timer callback will be invoked at most once: if you want a repeating |
244 | The callback will normally be invoked only once. If you specify another |
190 | timer you have to create a new watcher (this is a limitation by both Tk |
245 | parameter, "interval", as a strictly positive number (> 0), then the |
191 | and Glib). |
246 | callback will be invoked regularly at that interval (in fractional |
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247 | seconds) after the first invocation. If "interval" is specified with a |
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248 | false value, then it is treated as if it were not specified at all. |
192 | |
249 | |
193 | Example: |
250 | The callback will be rescheduled before invoking the callback, but no |
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251 | attempt is made to avoid timer drift in most backends, so the interval |
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252 | is only approximate. |
194 | |
253 | |
195 | # fire an event after 7.7 seconds |
254 | Example: fire an event after 7.7 seconds. |
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255 | |
196 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
256 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
197 | warn "timeout\n"; |
257 | warn "timeout\n"; |
198 | }); |
258 | }); |
199 | |
259 | |
200 | # to cancel the timer: |
260 | # to cancel the timer: |
201 | undef $w; |
261 | undef $w; |
202 | |
262 | |
203 | Example 2: |
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204 | |
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205 | # fire an event after 0.5 seconds, then roughly every second |
263 | Example 2: fire an event after 0.5 seconds, then roughly every second. |
206 | my $w; |
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207 | |
264 | |
208 | my $cb = sub { |
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209 | # cancel the old timer while creating a new one |
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210 | $w = AnyEvent->timer (after => 1, cb => $cb); |
265 | my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub { |
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266 | warn "timeout\n"; |
211 | }; |
267 | }); |
212 | |
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213 | # start the "loop" by creating the first watcher |
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214 | $w = AnyEvent->timer (after => 0.5, cb => $cb); |
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215 | |
268 | |
216 | TIMING ISSUES |
269 | TIMING ISSUES |
217 | There are two ways to handle timers: based on real time (relative, "fire |
270 | There are two ways to handle timers: based on real time (relative, "fire |
218 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
271 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
219 | o'clock"). |
272 | o'clock"). |
220 | |
273 | |
221 | While most event loops expect timers to specified in a relative way, |
274 | While most event loops expect timers to specified in a relative way, |
222 | they use absolute time internally. This makes a difference when your |
275 | they use absolute time internally. This makes a difference when your |
223 | clock "jumps", for example, when ntp decides to set your clock backwards |
276 | clock "jumps", for example, when ntp decides to set your clock backwards |
224 | from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is |
277 | from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is |
225 | supposed to fire "after" a second might actually take six years to |
278 | supposed to fire "after a second" might actually take six years to |
226 | finally fire. |
279 | finally fire. |
227 | |
280 | |
228 | AnyEvent cannot compensate for this. The only event loop that is |
281 | AnyEvent cannot compensate for this. The only event loop that is |
229 | conscious about these issues is EV, which offers both relative |
282 | conscious of these issues is EV, which offers both relative (ev_timer, |
230 | (ev_timer, based on true relative time) and absolute (ev_periodic, based |
283 | based on true relative time) and absolute (ev_periodic, based on |
231 | on wallclock time) timers. |
284 | wallclock time) timers. |
232 | |
285 | |
233 | AnyEvent always prefers relative timers, if available, matching the |
286 | AnyEvent always prefers relative timers, if available, matching the |
234 | AnyEvent API. |
287 | AnyEvent API. |
235 | |
288 | |
236 | AnyEvent has two additional methods that return the "current time": |
289 | AnyEvent has two additional methods that return the "current time": |
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255 | *In almost all cases (in all cases if you don't care), this is the |
308 | *In almost all cases (in all cases if you don't care), this is the |
256 | function to call when you want to know the current time.* |
309 | function to call when you want to know the current time.* |
257 | |
310 | |
258 | This function is also often faster then "AnyEvent->time", and thus |
311 | This function is also often faster then "AnyEvent->time", and thus |
259 | the preferred method if you want some timestamp (for example, |
312 | the preferred method if you want some timestamp (for example, |
260 | AnyEvent::Handle uses this to update it's activity timeouts). |
313 | AnyEvent::Handle uses this to update its activity timeouts). |
261 | |
314 | |
262 | The rest of this section is only of relevance if you try to be very |
315 | The rest of this section is only of relevance if you try to be very |
263 | exact with your timing, you can skip it without bad conscience. |
316 | exact with your timing; you can skip it without a bad conscience. |
264 | |
317 | |
265 | For a practical example of when these times differ, consider |
318 | For a practical example of when these times differ, consider |
266 | Event::Lib and EV and the following set-up: |
319 | Event::Lib and EV and the following set-up: |
267 | |
320 | |
268 | The event loop is running and has just invoked one of your callback |
321 | The event loop is running and has just invoked one of your callbacks |
269 | at time=500 (assume no other callbacks delay processing). In your |
322 | at time=500 (assume no other callbacks delay processing). In your |
270 | callback, you wait a second by executing "sleep 1" (blocking the |
323 | callback, you wait a second by executing "sleep 1" (blocking the |
271 | process for a second) and then (at time=501) you create a relative |
324 | process for a second) and then (at time=501) you create a relative |
272 | timer that fires after three seconds. |
325 | timer that fires after three seconds. |
273 | |
326 | |
… | |
… | |
293 | In either case, if you care (and in most cases, you don't), then you |
346 | In either case, if you care (and in most cases, you don't), then you |
294 | can get whatever behaviour you want with any event loop, by taking |
347 | can get whatever behaviour you want with any event loop, by taking |
295 | the difference between "AnyEvent->time" and "AnyEvent->now" into |
348 | the difference between "AnyEvent->time" and "AnyEvent->now" into |
296 | account. |
349 | account. |
297 | |
350 | |
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351 | AnyEvent->now_update |
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352 | Some event loops (such as EV or AnyEvent::Loop) cache the current |
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353 | time for each loop iteration (see the discussion of AnyEvent->now, |
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354 | above). |
|
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355 | |
|
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356 | When a callback runs for a long time (or when the process sleeps), |
|
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357 | then this "current" time will differ substantially from the real |
|
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358 | time, which might affect timers and time-outs. |
|
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359 | |
|
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360 | When this is the case, you can call this method, which will update |
|
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361 | the event loop's idea of "current time". |
|
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362 | |
|
|
363 | A typical example would be a script in a web server (e.g. |
|
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364 | "mod_perl") - when mod_perl executes the script, then the event loop |
|
|
365 | will have the wrong idea about the "current time" (being potentially |
|
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366 | far in the past, when the script ran the last time). In that case |
|
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367 | you should arrange a call to "AnyEvent->now_update" each time the |
|
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368 | web server process wakes up again (e.g. at the start of your script, |
|
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369 | or in a handler). |
|
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370 | |
|
|
371 | Note that updating the time *might* cause some events to be handled. |
|
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372 | |
298 | SIGNAL WATCHERS |
373 | SIGNAL WATCHERS |
|
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374 | $w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>); |
|
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375 | |
299 | You can watch for signals using a signal watcher, "signal" is the signal |
376 | You can watch for signals using a signal watcher, "signal" is the signal |
300 | *name* without any "SIG" prefix, "cb" is the Perl callback to be invoked |
377 | *name* in uppercase and without any "SIG" prefix, "cb" is the Perl |
301 | whenever a signal occurs. |
378 | callback to be invoked whenever a signal occurs. |
302 | |
379 | |
303 | Although the callback might get passed parameters, their value and |
380 | Although the callback might get passed parameters, their value and |
304 | presence is undefined and you cannot rely on them. Portable AnyEvent |
381 | presence is undefined and you cannot rely on them. Portable AnyEvent |
305 | callbacks cannot use arguments passed to signal watcher callbacks. |
382 | callbacks cannot use arguments passed to signal watcher callbacks. |
306 | |
383 | |
… | |
… | |
308 | invocation, and callback invocation will be synchronous. Synchronous |
385 | invocation, and callback invocation will be synchronous. Synchronous |
309 | means that it might take a while until the signal gets handled by the |
386 | means that it might take a while until the signal gets handled by the |
310 | process, but it is guaranteed not to interrupt any other callbacks. |
387 | process, but it is guaranteed not to interrupt any other callbacks. |
311 | |
388 | |
312 | The main advantage of using these watchers is that you can share a |
389 | The main advantage of using these watchers is that you can share a |
313 | signal between multiple watchers. |
390 | signal between multiple watchers, and AnyEvent will ensure that signals |
|
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391 | will not interrupt your program at bad times. |
314 | |
392 | |
315 | This watcher might use %SIG, so programs overwriting those signals |
393 | This watcher might use %SIG (depending on the event loop used), so |
316 | directly will likely not work correctly. |
394 | programs overwriting those signals directly will likely not work |
|
|
395 | correctly. |
317 | |
396 | |
318 | Example: exit on SIGINT |
397 | Example: exit on SIGINT |
319 | |
398 | |
320 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
399 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
321 | |
400 | |
|
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401 | Restart Behaviour |
|
|
402 | While restart behaviour is up to the event loop implementation, most |
|
|
403 | will not restart syscalls (that includes Async::Interrupt and AnyEvent's |
|
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404 | pure perl implementation). |
|
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405 | |
|
|
406 | Safe/Unsafe Signals |
|
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407 | Perl signals can be either "safe" (synchronous to opcode handling) or |
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408 | "unsafe" (asynchronous) - the former might delay signal delivery |
|
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409 | indefinitely, the latter might corrupt your memory. |
|
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410 | |
|
|
411 | AnyEvent signal handlers are, in addition, synchronous to the event |
|
|
412 | loop, i.e. they will not interrupt your running perl program but will |
|
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413 | only be called as part of the normal event handling (just like timer, |
|
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414 | I/O etc. callbacks, too). |
|
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415 | |
|
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416 | Signal Races, Delays and Workarounds |
|
|
417 | Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching |
|
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418 | callbacks to signals in a generic way, which is a pity, as you cannot do |
|
|
419 | race-free signal handling in perl, requiring C libraries for this. |
|
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420 | AnyEvent will try to do its best, which means in some cases, signals |
|
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421 | will be delayed. The maximum time a signal might be delayed is 10 |
|
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422 | seconds by default, but can be overriden via |
|
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423 | $ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} or $AnyEvent::MAX_SIGNAL_LATENCY |
|
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424 | - see the "ENVIRONMENT VARIABLES" section for details. |
|
|
425 | |
|
|
426 | All these problems can be avoided by installing the optional |
|
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427 | Async::Interrupt module, which works with most event loops. It will not |
|
|
428 | work with inherently broken event loops such as Event or Event::Lib (and |
|
|
429 | not with POE currently). For those, you just have to suffer the delays. |
|
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430 | |
322 | CHILD PROCESS WATCHERS |
431 | CHILD PROCESS WATCHERS |
|
|
432 | $w = AnyEvent->child (pid => <process id>, cb => <callback>); |
|
|
433 | |
323 | You can also watch on a child process exit and catch its exit status. |
434 | You can also watch for a child process exit and catch its exit status. |
324 | |
435 | |
325 | The child process is specified by the "pid" argument (if set to 0, it |
436 | The child process is specified by the "pid" argument (on some backends, |
326 | watches for any child process exit). The watcher will trigger as often |
437 | using 0 watches for any child process exit, on others this will croak). |
327 | as status change for the child are received. This works by installing a |
438 | The watcher will be triggered only when the child process has finished |
328 | signal handler for "SIGCHLD". The callback will be called with the pid |
439 | and an exit status is available, not on any trace events |
329 | and exit status (as returned by waitpid), so unlike other watcher types, |
440 | (stopped/continued). |
330 | you *can* rely on child watcher callback arguments. |
441 | |
|
|
442 | The callback will be called with the pid and exit status (as returned by |
|
|
443 | waitpid), so unlike other watcher types, you *can* rely on child watcher |
|
|
444 | callback arguments. |
|
|
445 | |
|
|
446 | This watcher type works by installing a signal handler for "SIGCHLD", |
|
|
447 | and since it cannot be shared, nothing else should use SIGCHLD or reap |
|
|
448 | random child processes (waiting for specific child processes, e.g. |
|
|
449 | inside "system", is just fine). |
331 | |
450 | |
332 | There is a slight catch to child watchers, however: you usually start |
451 | There is a slight catch to child watchers, however: you usually start |
333 | them *after* the child process was created, and this means the process |
452 | them *after* the child process was created, and this means the process |
334 | could have exited already (and no SIGCHLD will be sent anymore). |
453 | could have exited already (and no SIGCHLD will be sent anymore). |
335 | |
454 | |
336 | Not all event models handle this correctly (POE doesn't), but even for |
455 | Not all event models handle this correctly (neither POE nor IO::Async |
|
|
456 | do, see their AnyEvent::Impl manpages for details), but even for event |
337 | event models that *do* handle this correctly, they usually need to be |
457 | models that *do* handle this correctly, they usually need to be loaded |
338 | loaded before the process exits (i.e. before you fork in the first |
458 | before the process exits (i.e. before you fork in the first place). |
339 | place). |
459 | AnyEvent's pure perl event loop handles all cases correctly regardless |
|
|
460 | of when you start the watcher. |
340 | |
461 | |
341 | This means you cannot create a child watcher as the very first thing in |
462 | This means you cannot create a child watcher as the very first thing in |
342 | an AnyEvent program, you *have* to create at least one watcher before |
463 | an AnyEvent program, you *have* to create at least one watcher before |
343 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
464 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
344 | |
465 | |
|
|
466 | As most event loops do not support waiting for child events, they will |
|
|
467 | be emulated by AnyEvent in most cases, in which case the latency and |
|
|
468 | race problems mentioned in the description of signal watchers apply. |
|
|
469 | |
345 | Example: fork a process and wait for it |
470 | Example: fork a process and wait for it |
346 | |
471 | |
347 | my $done = AnyEvent->condvar; |
472 | my $done = AnyEvent->condvar; |
348 | |
473 | |
349 | my $pid = fork or exit 5; |
474 | my $pid = fork or exit 5; |
350 | |
475 | |
351 | my $w = AnyEvent->child ( |
476 | my $w = AnyEvent->child ( |
352 | pid => $pid, |
477 | pid => $pid, |
353 | cb => sub { |
478 | cb => sub { |
354 | my ($pid, $status) = @_; |
479 | my ($pid, $status) = @_; |
355 | warn "pid $pid exited with status $status"; |
480 | warn "pid $pid exited with status $status"; |
356 | $done->send; |
481 | $done->send; |
357 | }, |
482 | }, |
358 | ); |
483 | ); |
359 | |
484 | |
360 | # do something else, then wait for process exit |
485 | # do something else, then wait for process exit |
361 | $done->recv; |
486 | $done->recv; |
362 | |
487 | |
|
|
488 | IDLE WATCHERS |
|
|
489 | $w = AnyEvent->idle (cb => <callback>); |
|
|
490 | |
|
|
491 | This will repeatedly invoke the callback after the process becomes idle, |
|
|
492 | until either the watcher is destroyed or new events have been detected. |
|
|
493 | |
|
|
494 | Idle watchers are useful when there is a need to do something, but it is |
|
|
495 | not so important (or wise) to do it instantly. The callback will be |
|
|
496 | invoked only when there is "nothing better to do", which is usually |
|
|
497 | defined as "all outstanding events have been handled and no new events |
|
|
498 | have been detected". That means that idle watchers ideally get invoked |
|
|
499 | when the event loop has just polled for new events but none have been |
|
|
500 | detected. Instead of blocking to wait for more events, the idle watchers |
|
|
501 | will be invoked. |
|
|
502 | |
|
|
503 | Unfortunately, most event loops do not really support idle watchers |
|
|
504 | (only EV, Event and Glib do it in a usable fashion) - for the rest, |
|
|
505 | AnyEvent will simply call the callback "from time to time". |
|
|
506 | |
|
|
507 | Example: read lines from STDIN, but only process them when the program |
|
|
508 | is otherwise idle: |
|
|
509 | |
|
|
510 | my @lines; # read data |
|
|
511 | my $idle_w; |
|
|
512 | my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
|
|
513 | push @lines, scalar <STDIN>; |
|
|
514 | |
|
|
515 | # start an idle watcher, if not already done |
|
|
516 | $idle_w ||= AnyEvent->idle (cb => sub { |
|
|
517 | # handle only one line, when there are lines left |
|
|
518 | if (my $line = shift @lines) { |
|
|
519 | print "handled when idle: $line"; |
|
|
520 | } else { |
|
|
521 | # otherwise disable the idle watcher again |
|
|
522 | undef $idle_w; |
|
|
523 | } |
|
|
524 | }); |
|
|
525 | }); |
|
|
526 | |
363 | CONDITION VARIABLES |
527 | CONDITION VARIABLES |
|
|
528 | $cv = AnyEvent->condvar; |
|
|
529 | |
|
|
530 | $cv->send (<list>); |
|
|
531 | my @res = $cv->recv; |
|
|
532 | |
364 | If you are familiar with some event loops you will know that all of them |
533 | If you are familiar with some event loops you will know that all of them |
365 | require you to run some blocking "loop", "run" or similar function that |
534 | require you to run some blocking "loop", "run" or similar function that |
366 | will actively watch for new events and call your callbacks. |
535 | will actively watch for new events and call your callbacks. |
367 | |
536 | |
368 | AnyEvent is different, it expects somebody else to run the event loop |
537 | AnyEvent is slightly different: it expects somebody else to run the |
369 | and will only block when necessary (usually when told by the user). |
538 | event loop and will only block when necessary (usually when told by the |
|
|
539 | user). |
370 | |
540 | |
371 | The instrument to do that is called a "condition variable", so called |
541 | The tool to do that is called a "condition variable", so called because |
372 | because they represent a condition that must become true. |
542 | they represent a condition that must become true. |
|
|
543 | |
|
|
544 | Now is probably a good time to look at the examples further below. |
373 | |
545 | |
374 | Condition variables can be created by calling the "AnyEvent->condvar" |
546 | Condition variables can be created by calling the "AnyEvent->condvar" |
375 | method, usually without arguments. The only argument pair allowed is |
547 | method, usually without arguments. The only argument pair allowed is |
376 | "cb", which specifies a callback to be called when the condition |
548 | "cb", which specifies a callback to be called when the condition |
377 | variable becomes true. |
549 | variable becomes true, with the condition variable as the first argument |
|
|
550 | (but not the results). |
378 | |
551 | |
379 | After creation, the condition variable is "false" until it becomes |
552 | After creation, the condition variable is "false" until it becomes |
380 | "true" by calling the "send" method (or calling the condition variable |
553 | "true" by calling the "send" method (or calling the condition variable |
381 | as if it were a callback, read about the caveats in the description for |
554 | as if it were a callback, read about the caveats in the description for |
382 | the "->send" method). |
555 | the "->send" method). |
383 | |
556 | |
384 | Condition variables are similar to callbacks, except that you can |
557 | Since condition variables are the most complex part of the AnyEvent API, |
385 | optionally wait for them. They can also be called merge points - points |
558 | here are some different mental models of what they are - pick the ones |
386 | in time where multiple outstanding events have been processed. And yet |
559 | you can connect to: |
387 | another way to call them is transactions - each condition variable can |
560 | |
388 | be used to represent a transaction, which finishes at some point and |
561 | * Condition variables are like callbacks - you can call them (and pass |
389 | delivers a result. |
562 | them instead of callbacks). Unlike callbacks however, you can also |
|
|
563 | wait for them to be called. |
|
|
564 | |
|
|
565 | * Condition variables are signals - one side can emit or send them, |
|
|
566 | the other side can wait for them, or install a handler that is |
|
|
567 | called when the signal fires. |
|
|
568 | |
|
|
569 | * Condition variables are like "Merge Points" - points in your program |
|
|
570 | where you merge multiple independent results/control flows into one. |
|
|
571 | |
|
|
572 | * Condition variables represent a transaction - functions that start |
|
|
573 | some kind of transaction can return them, leaving the caller the |
|
|
574 | choice between waiting in a blocking fashion, or setting a callback. |
|
|
575 | |
|
|
576 | * Condition variables represent future values, or promises to deliver |
|
|
577 | some result, long before the result is available. |
390 | |
578 | |
391 | Condition variables are very useful to signal that something has |
579 | Condition variables are very useful to signal that something has |
392 | finished, for example, if you write a module that does asynchronous http |
580 | finished, for example, if you write a module that does asynchronous http |
393 | requests, then a condition variable would be the ideal candidate to |
581 | requests, then a condition variable would be the ideal candidate to |
394 | signal the availability of results. The user can either act when the |
582 | signal the availability of results. The user can either act when the |
… | |
… | |
407 | |
595 | |
408 | Condition variables are represented by hash refs in perl, and the keys |
596 | Condition variables are represented by hash refs in perl, and the keys |
409 | used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy |
597 | used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy |
410 | (it is often useful to build your own transaction class on top of |
598 | (it is often useful to build your own transaction class on top of |
411 | AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call |
599 | AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call |
412 | it's "new" method in your own "new" method. |
600 | its "new" method in your own "new" method. |
413 | |
601 | |
414 | There are two "sides" to a condition variable - the "producer side" |
602 | There are two "sides" to a condition variable - the "producer side" |
415 | which eventually calls "-> send", and the "consumer side", which waits |
603 | which eventually calls "-> send", and the "consumer side", which waits |
416 | for the send to occur. |
604 | for the send to occur. |
417 | |
605 | |
418 | Example: wait for a timer. |
606 | Example: wait for a timer. |
419 | |
607 | |
420 | # wait till the result is ready |
608 | # condition: "wait till the timer is fired" |
421 | my $result_ready = AnyEvent->condvar; |
609 | my $timer_fired = AnyEvent->condvar; |
422 | |
610 | |
423 | # do something such as adding a timer |
611 | # create the timer - we could wait for, say |
424 | # or socket watcher the calls $result_ready->send |
612 | # a handle becomign ready, or even an |
425 | # when the "result" is ready. |
613 | # AnyEvent::HTTP request to finish, but |
426 | # in this case, we simply use a timer: |
614 | # in this case, we simply use a timer: |
427 | my $w = AnyEvent->timer ( |
615 | my $w = AnyEvent->timer ( |
428 | after => 1, |
616 | after => 1, |
429 | cb => sub { $result_ready->send }, |
617 | cb => sub { $timer_fired->send }, |
430 | ); |
618 | ); |
431 | |
619 | |
432 | # this "blocks" (while handling events) till the callback |
620 | # this "blocks" (while handling events) till the callback |
433 | # calls send |
621 | # calls ->send |
434 | $result_ready->recv; |
622 | $timer_fired->recv; |
435 | |
623 | |
436 | Example: wait for a timer, but take advantage of the fact that condition |
624 | Example: wait for a timer, but take advantage of the fact that condition |
437 | variables are also code references. |
625 | variables are also callable directly. |
438 | |
626 | |
439 | my $done = AnyEvent->condvar; |
627 | my $done = AnyEvent->condvar; |
440 | my $delay = AnyEvent->timer (after => 5, cb => $done); |
628 | my $delay = AnyEvent->timer (after => 5, cb => $done); |
441 | $done->recv; |
629 | $done->recv; |
|
|
630 | |
|
|
631 | Example: Imagine an API that returns a condvar and doesn't support |
|
|
632 | callbacks. This is how you make a synchronous call, for example from the |
|
|
633 | main program: |
|
|
634 | |
|
|
635 | use AnyEvent::CouchDB; |
|
|
636 | |
|
|
637 | ... |
|
|
638 | |
|
|
639 | my @info = $couchdb->info->recv; |
|
|
640 | |
|
|
641 | And this is how you would just set a callback to be called whenever the |
|
|
642 | results are available: |
|
|
643 | |
|
|
644 | $couchdb->info->cb (sub { |
|
|
645 | my @info = $_[0]->recv; |
|
|
646 | }); |
442 | |
647 | |
443 | METHODS FOR PRODUCERS |
648 | METHODS FOR PRODUCERS |
444 | These methods should only be used by the producing side, i.e. the |
649 | These methods should only be used by the producing side, i.e. the |
445 | code/module that eventually sends the signal. Note that it is also the |
650 | code/module that eventually sends the signal. Note that it is also the |
446 | producer side which creates the condvar in most cases, but it isn't |
651 | producer side which creates the condvar in most cases, but it isn't |
… | |
… | |
456 | |
661 | |
457 | Any arguments passed to the "send" call will be returned by all |
662 | Any arguments passed to the "send" call will be returned by all |
458 | future "->recv" calls. |
663 | future "->recv" calls. |
459 | |
664 | |
460 | Condition variables are overloaded so one can call them directly (as |
665 | Condition variables are overloaded so one can call them directly (as |
461 | a code reference). Calling them directly is the same as calling |
666 | if they were a code reference). Calling them directly is the same as |
462 | "send". Note, however, that many C-based event loops do not handle |
667 | calling "send". |
463 | overloading, so as tempting as it may be, passing a condition |
|
|
464 | variable instead of a callback does not work. Both the pure perl and |
|
|
465 | EV loops support overloading, however, as well as all functions that |
|
|
466 | use perl to invoke a callback (as in AnyEvent::Socket and |
|
|
467 | AnyEvent::DNS for example). |
|
|
468 | |
668 | |
469 | $cv->croak ($error) |
669 | $cv->croak ($error) |
470 | Similar to send, but causes all call's to "->recv" to invoke |
670 | Similar to send, but causes all calls to "->recv" to invoke |
471 | "Carp::croak" with the given error message/object/scalar. |
671 | "Carp::croak" with the given error message/object/scalar. |
472 | |
672 | |
473 | This can be used to signal any errors to the condition variable |
673 | This can be used to signal any errors to the condition variable |
474 | user/consumer. |
674 | user/consumer. Doing it this way instead of calling "croak" directly |
|
|
675 | delays the error detection, but has the overwhelming advantage that |
|
|
676 | it diagnoses the error at the place where the result is expected, |
|
|
677 | and not deep in some event callback with no connection to the actual |
|
|
678 | code causing the problem. |
475 | |
679 | |
476 | $cv->begin ([group callback]) |
680 | $cv->begin ([group callback]) |
477 | $cv->end |
681 | $cv->end |
478 | These two methods are EXPERIMENTAL and MIGHT CHANGE. |
|
|
479 | |
|
|
480 | These two methods can be used to combine many transactions/events |
682 | These two methods can be used to combine many transactions/events |
481 | into one. For example, a function that pings many hosts in parallel |
683 | into one. For example, a function that pings many hosts in parallel |
482 | might want to use a condition variable for the whole process. |
684 | might want to use a condition variable for the whole process. |
483 | |
685 | |
484 | Every call to "->begin" will increment a counter, and every call to |
686 | Every call to "->begin" will increment a counter, and every call to |
485 | "->end" will decrement it. If the counter reaches 0 in "->end", the |
687 | "->end" will decrement it. If the counter reaches 0 in "->end", the |
486 | (last) callback passed to "begin" will be executed. That callback is |
688 | (last) callback passed to "begin" will be executed, passing the |
487 | *supposed* to call "->send", but that is not required. If no |
689 | condvar as first argument. That callback is *supposed* to call |
|
|
690 | "->send", but that is not required. If no group callback was set, |
488 | callback was set, "send" will be called without any arguments. |
691 | "send" will be called without any arguments. |
489 | |
692 | |
490 | Let's clarify this with the ping example: |
693 | You can think of "$cv->send" giving you an OR condition (one call |
|
|
694 | sends), while "$cv->begin" and "$cv->end" giving you an AND |
|
|
695 | condition (all "begin" calls must be "end"'ed before the condvar |
|
|
696 | sends). |
|
|
697 | |
|
|
698 | Let's start with a simple example: you have two I/O watchers (for |
|
|
699 | example, STDOUT and STDERR for a program), and you want to wait for |
|
|
700 | both streams to close before activating a condvar: |
491 | |
701 | |
492 | my $cv = AnyEvent->condvar; |
702 | my $cv = AnyEvent->condvar; |
493 | |
703 | |
|
|
704 | $cv->begin; # first watcher |
|
|
705 | my $w1 = AnyEvent->io (fh => $fh1, cb => sub { |
|
|
706 | defined sysread $fh1, my $buf, 4096 |
|
|
707 | or $cv->end; |
|
|
708 | }); |
|
|
709 | |
|
|
710 | $cv->begin; # second watcher |
|
|
711 | my $w2 = AnyEvent->io (fh => $fh2, cb => sub { |
|
|
712 | defined sysread $fh2, my $buf, 4096 |
|
|
713 | or $cv->end; |
|
|
714 | }); |
|
|
715 | |
|
|
716 | $cv->recv; |
|
|
717 | |
|
|
718 | This works because for every event source (EOF on file handle), |
|
|
719 | there is one call to "begin", so the condvar waits for all calls to |
|
|
720 | "end" before sending. |
|
|
721 | |
|
|
722 | The ping example mentioned above is slightly more complicated, as |
|
|
723 | the there are results to be passwd back, and the number of tasks |
|
|
724 | that are begun can potentially be zero: |
|
|
725 | |
|
|
726 | my $cv = AnyEvent->condvar; |
|
|
727 | |
494 | my %result; |
728 | my %result; |
495 | $cv->begin (sub { $cv->send (\%result) }); |
729 | $cv->begin (sub { shift->send (\%result) }); |
496 | |
730 | |
497 | for my $host (@list_of_hosts) { |
731 | for my $host (@list_of_hosts) { |
498 | $cv->begin; |
732 | $cv->begin; |
499 | ping_host_then_call_callback $host, sub { |
733 | ping_host_then_call_callback $host, sub { |
500 | $result{$host} = ...; |
734 | $result{$host} = ...; |
… | |
… | |
502 | }; |
736 | }; |
503 | } |
737 | } |
504 | |
738 | |
505 | $cv->end; |
739 | $cv->end; |
506 | |
740 | |
|
|
741 | ... |
|
|
742 | |
|
|
743 | my $results = $cv->recv; |
|
|
744 | |
507 | This code fragment supposedly pings a number of hosts and calls |
745 | This code fragment supposedly pings a number of hosts and calls |
508 | "send" after results for all then have have been gathered - in any |
746 | "send" after results for all then have have been gathered - in any |
509 | order. To achieve this, the code issues a call to "begin" when it |
747 | order. To achieve this, the code issues a call to "begin" when it |
510 | starts each ping request and calls "end" when it has received some |
748 | starts each ping request and calls "end" when it has received some |
511 | result for it. Since "begin" and "end" only maintain a counter, the |
749 | result for it. Since "begin" and "end" only maintain a counter, the |
… | |
… | |
515 | the loop, which serves two important purposes: first, it sets the |
753 | the loop, which serves two important purposes: first, it sets the |
516 | callback to be called once the counter reaches 0, and second, it |
754 | callback to be called once the counter reaches 0, and second, it |
517 | ensures that "send" is called even when "no" hosts are being pinged |
755 | ensures that "send" is called even when "no" hosts are being pinged |
518 | (the loop doesn't execute once). |
756 | (the loop doesn't execute once). |
519 | |
757 | |
520 | This is the general pattern when you "fan out" into multiple |
758 | This is the general pattern when you "fan out" into multiple (but |
521 | subrequests: use an outer "begin"/"end" pair to set the callback and |
759 | potentially zero) subrequests: use an outer "begin"/"end" pair to |
522 | ensure "end" is called at least once, and then, for each subrequest |
760 | set the callback and ensure "end" is called at least once, and then, |
523 | you start, call "begin" and for each subrequest you finish, call |
761 | for each subrequest you start, call "begin" and for each subrequest |
524 | "end". |
762 | you finish, call "end". |
525 | |
763 | |
526 | METHODS FOR CONSUMERS |
764 | METHODS FOR CONSUMERS |
527 | These methods should only be used by the consuming side, i.e. the code |
765 | These methods should only be used by the consuming side, i.e. the code |
528 | awaits the condition. |
766 | awaits the condition. |
529 | |
767 | |
530 | $cv->recv |
768 | $cv->recv |
531 | Wait (blocking if necessary) until the "->send" or "->croak" methods |
769 | Wait (blocking if necessary) until the "->send" or "->croak" methods |
532 | have been called on c<$cv>, while servicing other watchers normally. |
770 | have been called on $cv, while servicing other watchers normally. |
533 | |
771 | |
534 | You can only wait once on a condition - additional calls are valid |
772 | You can only wait once on a condition - additional calls are valid |
535 | but will return immediately. |
773 | but will return immediately. |
536 | |
774 | |
537 | If an error condition has been set by calling "->croak", then this |
775 | If an error condition has been set by calling "->croak", then this |
538 | function will call "croak". |
776 | function will call "croak". |
539 | |
777 | |
540 | In list context, all parameters passed to "send" will be returned, |
778 | In list context, all parameters passed to "send" will be returned, |
541 | in scalar context only the first one will be returned. |
779 | in scalar context only the first one will be returned. |
542 | |
780 | |
|
|
781 | Note that doing a blocking wait in a callback is not supported by |
|
|
782 | any event loop, that is, recursive invocation of a blocking "->recv" |
|
|
783 | is not allowed and the "recv" call will "croak" if such a condition |
|
|
784 | is detected. This requirement can be dropped by relying on |
|
|
785 | Coro::AnyEvent , which allows you to do a blocking "->recv" from any |
|
|
786 | thread that doesn't run the event loop itself. Coro::AnyEvent is |
|
|
787 | loaded automatically when Coro is used with AnyEvent, so code does |
|
|
788 | not need to do anything special to take advantage of that: any code |
|
|
789 | that would normally block your program because it calls "recv", be |
|
|
790 | executed in an "async" thread instead without blocking other |
|
|
791 | threads. |
|
|
792 | |
543 | Not all event models support a blocking wait - some die in that case |
793 | Not all event models support a blocking wait - some die in that case |
544 | (programs might want to do that to stay interactive), so *if you are |
794 | (programs might want to do that to stay interactive), so *if you are |
545 | using this from a module, never require a blocking wait*, but let |
795 | using this from a module, never require a blocking wait*. Instead, |
546 | the caller decide whether the call will block or not (for example, |
796 | let the caller decide whether the call will block or not (for |
547 | by coupling condition variables with some kind of request results |
797 | example, by coupling condition variables with some kind of request |
548 | and supporting callbacks so the caller knows that getting the result |
798 | results and supporting callbacks so the caller knows that getting |
549 | will not block, while still supporting blocking waits if the caller |
799 | the result will not block, while still supporting blocking waits if |
550 | so desires). |
800 | the caller so desires). |
551 | |
801 | |
552 | Another reason *never* to "->recv" in a module is that you cannot |
|
|
553 | sensibly have two "->recv"'s in parallel, as that would require |
|
|
554 | multiple interpreters or coroutines/threads, none of which |
|
|
555 | "AnyEvent" can supply. |
|
|
556 | |
|
|
557 | The Coro module, however, *can* and *does* supply coroutines and, in |
|
|
558 | fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe |
|
|
559 | versions and also integrates coroutines into AnyEvent, making |
|
|
560 | blocking "->recv" calls perfectly safe as long as they are done from |
|
|
561 | another coroutine (one that doesn't run the event loop). |
|
|
562 | |
|
|
563 | You can ensure that "-recv" never blocks by setting a callback and |
802 | You can ensure that "->recv" never blocks by setting a callback and |
564 | only calling "->recv" from within that callback (or at a later |
803 | only calling "->recv" from within that callback (or at a later |
565 | time). This will work even when the event loop does not support |
804 | time). This will work even when the event loop does not support |
566 | blocking waits otherwise. |
805 | blocking waits otherwise. |
567 | |
806 | |
568 | $bool = $cv->ready |
807 | $bool = $cv->ready |
569 | Returns true when the condition is "true", i.e. whether "send" or |
808 | Returns true when the condition is "true", i.e. whether "send" or |
570 | "croak" have been called. |
809 | "croak" have been called. |
571 | |
810 | |
572 | $cb = $cv->cb ([new callback]) |
811 | $cb = $cv->cb ($cb->($cv)) |
573 | This is a mutator function that returns the callback set and |
812 | This is a mutator function that returns the callback set and |
574 | optionally replaces it before doing so. |
813 | optionally replaces it before doing so. |
575 | |
814 | |
576 | The callback will be called when the condition becomes "true", i.e. |
815 | The callback will be called when the condition becomes "true", i.e. |
577 | when "send" or "croak" are called, with the only argument being the |
816 | when "send" or "croak" are called, with the only argument being the |
578 | condition variable itself. Calling "recv" inside the callback or at |
817 | condition variable itself. If the condition is already true, the |
|
|
818 | callback is called immediately when it is set. Calling "recv" inside |
579 | any later time is guaranteed not to block. |
819 | the callback or at any later time is guaranteed not to block. |
|
|
820 | |
|
|
821 | SUPPORTED EVENT LOOPS/BACKENDS |
|
|
822 | The available backend classes are (every class has its own manpage): |
|
|
823 | |
|
|
824 | Backends that are autoprobed when no other event loop can be found. |
|
|
825 | EV is the preferred backend when no other event loop seems to be in |
|
|
826 | use. If EV is not installed, then AnyEvent will fall back to its own |
|
|
827 | pure-perl implementation, which is available everywhere as it comes |
|
|
828 | with AnyEvent itself. |
|
|
829 | |
|
|
830 | AnyEvent::Impl::EV based on EV (interface to libev, best choice). |
|
|
831 | AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable. |
|
|
832 | |
|
|
833 | Backends that are transparently being picked up when they are used. |
|
|
834 | These will be used if they are already loaded when the first watcher |
|
|
835 | is created, in which case it is assumed that the application is |
|
|
836 | using them. This means that AnyEvent will automatically pick the |
|
|
837 | right backend when the main program loads an event module before |
|
|
838 | anything starts to create watchers. Nothing special needs to be done |
|
|
839 | by the main program. |
|
|
840 | |
|
|
841 | AnyEvent::Impl::Event based on Event, very stable, few glitches. |
|
|
842 | AnyEvent::Impl::Glib based on Glib, slow but very stable. |
|
|
843 | AnyEvent::Impl::Tk based on Tk, very broken. |
|
|
844 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
|
|
845 | AnyEvent::Impl::POE based on POE, very slow, some limitations. |
|
|
846 | AnyEvent::Impl::Irssi used when running within irssi. |
|
|
847 | AnyEvent::Impl::IOAsync based on IO::Async. |
|
|
848 | AnyEvent::Impl::Cocoa based on Cocoa::EventLoop. |
|
|
849 | AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding). |
|
|
850 | |
|
|
851 | Backends with special needs. |
|
|
852 | Qt requires the Qt::Application to be instantiated first, but will |
|
|
853 | otherwise be picked up automatically. As long as the main program |
|
|
854 | instantiates the application before any AnyEvent watchers are |
|
|
855 | created, everything should just work. |
|
|
856 | |
|
|
857 | AnyEvent::Impl::Qt based on Qt. |
|
|
858 | |
|
|
859 | Event loops that are indirectly supported via other backends. |
|
|
860 | Some event loops can be supported via other modules: |
|
|
861 | |
|
|
862 | There is no direct support for WxWidgets (Wx) or Prima. |
|
|
863 | |
|
|
864 | WxWidgets has no support for watching file handles. However, you can |
|
|
865 | use WxWidgets through the POE adaptor, as POE has a Wx backend that |
|
|
866 | simply polls 20 times per second, which was considered to be too |
|
|
867 | horrible to even consider for AnyEvent. |
|
|
868 | |
|
|
869 | Prima is not supported as nobody seems to be using it, but it has a |
|
|
870 | POE backend, so it can be supported through POE. |
|
|
871 | |
|
|
872 | AnyEvent knows about both Prima and Wx, however, and will try to |
|
|
873 | load POE when detecting them, in the hope that POE will pick them |
|
|
874 | up, in which case everything will be automatic. |
580 | |
875 | |
581 | GLOBAL VARIABLES AND FUNCTIONS |
876 | GLOBAL VARIABLES AND FUNCTIONS |
|
|
877 | These are not normally required to use AnyEvent, but can be useful to |
|
|
878 | write AnyEvent extension modules. |
|
|
879 | |
582 | $AnyEvent::MODEL |
880 | $AnyEvent::MODEL |
583 | Contains "undef" until the first watcher is being created. Then it |
881 | Contains "undef" until the first watcher is being created, before |
|
|
882 | the backend has been autodetected. |
|
|
883 | |
584 | contains the event model that is being used, which is the name of |
884 | Afterwards it contains the event model that is being used, which is |
585 | the Perl class implementing the model. This class is usually one of |
885 | the name of the Perl class implementing the model. This class is |
586 | the "AnyEvent::Impl:xxx" modules, but can be any other class in the |
886 | usually one of the "AnyEvent::Impl::xxx" modules, but can be any |
587 | case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*). |
887 | other class in the case AnyEvent has been extended at runtime (e.g. |
588 | |
888 | in *rxvt-unicode* it will be "urxvt::anyevent"). |
589 | The known classes so far are: |
|
|
590 | |
|
|
591 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
|
|
592 | AnyEvent::Impl::Event based on Event, second best choice. |
|
|
593 | AnyEvent::Impl::Perl pure-perl implementation, fast and portable. |
|
|
594 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
|
|
595 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
|
|
596 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
|
|
597 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
|
|
598 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
|
|
599 | |
|
|
600 | There is no support for WxWidgets, as WxWidgets has no support for |
|
|
601 | watching file handles. However, you can use WxWidgets through the |
|
|
602 | POE Adaptor, as POE has a Wx backend that simply polls 20 times per |
|
|
603 | second, which was considered to be too horrible to even consider for |
|
|
604 | AnyEvent. Likewise, other POE backends can be used by AnyEvent by |
|
|
605 | using it's adaptor. |
|
|
606 | |
|
|
607 | AnyEvent knows about Prima and Wx and will try to use POE when |
|
|
608 | autodetecting them. |
|
|
609 | |
889 | |
610 | AnyEvent::detect |
890 | AnyEvent::detect |
611 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
891 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
612 | if necessary. You should only call this function right before you |
892 | if necessary. You should only call this function right before you |
613 | would have created an AnyEvent watcher anyway, that is, as late as |
893 | would have created an AnyEvent watcher anyway, that is, as late as |
614 | possible at runtime. |
894 | possible at runtime, and not e.g. during initialisation of your |
|
|
895 | module. |
|
|
896 | |
|
|
897 | The effect of calling this function is as if a watcher had been |
|
|
898 | created (specifically, actions that happen "when the first watcher |
|
|
899 | is created" happen when calling detetc as well). |
|
|
900 | |
|
|
901 | If you need to do some initialisation before AnyEvent watchers are |
|
|
902 | created, use "post_detect". |
615 | |
903 | |
616 | $guard = AnyEvent::post_detect { BLOCK } |
904 | $guard = AnyEvent::post_detect { BLOCK } |
617 | Arranges for the code block to be executed as soon as the event |
905 | Arranges for the code block to be executed as soon as the event |
618 | model is autodetected (or immediately if this has already happened). |
906 | model is autodetected (or immediately if that has already happened). |
|
|
907 | |
|
|
908 | The block will be executed *after* the actual backend has been |
|
|
909 | detected ($AnyEvent::MODEL is set), but *before* any watchers have |
|
|
910 | been created, so it is possible to e.g. patch @AnyEvent::ISA or do |
|
|
911 | other initialisations - see the sources of AnyEvent::Strict or |
|
|
912 | AnyEvent::AIO to see how this is used. |
|
|
913 | |
|
|
914 | The most common usage is to create some global watchers, without |
|
|
915 | forcing event module detection too early, for example, AnyEvent::AIO |
|
|
916 | creates and installs the global IO::AIO watcher in a "post_detect" |
|
|
917 | block to avoid autodetecting the event module at load time. |
619 | |
918 | |
620 | If called in scalar or list context, then it creates and returns an |
919 | If called in scalar or list context, then it creates and returns an |
621 | object that automatically removes the callback again when it is |
920 | object that automatically removes the callback again when it is |
|
|
921 | destroyed (or "undef" when the hook was immediately executed). See |
622 | destroyed. See Coro::BDB for a case where this is useful. |
922 | AnyEvent::AIO for a case where this is useful. |
|
|
923 | |
|
|
924 | Example: Create a watcher for the IO::AIO module and store it in |
|
|
925 | $WATCHER, but do so only do so after the event loop is initialised. |
|
|
926 | |
|
|
927 | our WATCHER; |
|
|
928 | |
|
|
929 | my $guard = AnyEvent::post_detect { |
|
|
930 | $WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb); |
|
|
931 | }; |
|
|
932 | |
|
|
933 | # the ||= is important in case post_detect immediately runs the block, |
|
|
934 | # as to not clobber the newly-created watcher. assigning both watcher and |
|
|
935 | # post_detect guard to the same variable has the advantage of users being |
|
|
936 | # able to just C<undef $WATCHER> if the watcher causes them grief. |
|
|
937 | |
|
|
938 | $WATCHER ||= $guard; |
623 | |
939 | |
624 | @AnyEvent::post_detect |
940 | @AnyEvent::post_detect |
625 | If there are any code references in this array (you can "push" to it |
941 | If there are any code references in this array (you can "push" to it |
626 | before or after loading AnyEvent), then they will called directly |
942 | before or after loading AnyEvent), then they will be called directly |
627 | after the event loop has been chosen. |
943 | after the event loop has been chosen. |
628 | |
944 | |
629 | You should check $AnyEvent::MODEL before adding to this array, |
945 | You should check $AnyEvent::MODEL before adding to this array, |
630 | though: if it contains a true value then the event loop has already |
946 | though: if it is defined then the event loop has already been |
631 | been detected, and the array will be ignored. |
947 | detected, and the array will be ignored. |
632 | |
948 | |
633 | Best use "AnyEvent::post_detect { BLOCK }" instead. |
949 | Best use "AnyEvent::post_detect { BLOCK }" when your application |
|
|
950 | allows it, as it takes care of these details. |
|
|
951 | |
|
|
952 | This variable is mainly useful for modules that can do something |
|
|
953 | useful when AnyEvent is used and thus want to know when it is |
|
|
954 | initialised, but do not need to even load it by default. This array |
|
|
955 | provides the means to hook into AnyEvent passively, without loading |
|
|
956 | it. |
|
|
957 | |
|
|
958 | Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used |
|
|
959 | together, you could put this into Coro (this is the actual code used |
|
|
960 | by Coro to accomplish this): |
|
|
961 | |
|
|
962 | if (defined $AnyEvent::MODEL) { |
|
|
963 | # AnyEvent already initialised, so load Coro::AnyEvent |
|
|
964 | require Coro::AnyEvent; |
|
|
965 | } else { |
|
|
966 | # AnyEvent not yet initialised, so make sure to load Coro::AnyEvent |
|
|
967 | # as soon as it is |
|
|
968 | push @AnyEvent::post_detect, sub { require Coro::AnyEvent }; |
|
|
969 | } |
|
|
970 | |
|
|
971 | AnyEvent::postpone { BLOCK } |
|
|
972 | Arranges for the block to be executed as soon as possible, but not |
|
|
973 | before the call itself returns. In practise, the block will be |
|
|
974 | executed just before the event loop polls for new events, or shortly |
|
|
975 | afterwards. |
|
|
976 | |
|
|
977 | This function never returns anything (to make the "return postpone { |
|
|
978 | ... }" idiom more useful. |
|
|
979 | |
|
|
980 | To understand the usefulness of this function, consider a function |
|
|
981 | that asynchronously does something for you and returns some |
|
|
982 | transaction object or guard to let you cancel the operation. For |
|
|
983 | example, "AnyEvent::Socket::tcp_connect": |
|
|
984 | |
|
|
985 | # start a conenction attempt unless one is active |
|
|
986 | $self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub { |
|
|
987 | delete $self->{connect_guard}; |
|
|
988 | ... |
|
|
989 | }; |
|
|
990 | |
|
|
991 | Imagine that this function could instantly call the callback, for |
|
|
992 | example, because it detects an obvious error such as a negative port |
|
|
993 | number. Invoking the callback before the function returns causes |
|
|
994 | problems however: the callback will be called and will try to delete |
|
|
995 | the guard object. But since the function hasn't returned yet, there |
|
|
996 | is nothing to delete. When the function eventually returns it will |
|
|
997 | assign the guard object to "$self->{connect_guard}", where it will |
|
|
998 | likely never be deleted, so the program thinks it is still trying to |
|
|
999 | connect. |
|
|
1000 | |
|
|
1001 | This is where "AnyEvent::postpone" should be used. Instead of |
|
|
1002 | calling the callback directly on error: |
|
|
1003 | |
|
|
1004 | $cb->(undef), return # signal error to callback, BAD! |
|
|
1005 | if $some_error_condition; |
|
|
1006 | |
|
|
1007 | It should use "postpone": |
|
|
1008 | |
|
|
1009 | AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later |
|
|
1010 | if $some_error_condition; |
|
|
1011 | |
|
|
1012 | AnyEvent::log $level, $msg[, @args] |
|
|
1013 | Log the given $msg at the given $level. |
|
|
1014 | |
|
|
1015 | If AnyEvent::Log is not loaded then this function makes a simple |
|
|
1016 | test to see whether the message will be logged. If the test succeeds |
|
|
1017 | it will load AnyEvent::Log and call "AnyEvent::Log::log" - |
|
|
1018 | consequently, look at the AnyEvent::Log documentation for details. |
|
|
1019 | |
|
|
1020 | If the test fails it will simply return. Right now this happens when |
|
|
1021 | a numerical loglevel is used and it is larger than the level |
|
|
1022 | specified via $ENV{PERL_ANYEVENT_VERBOSE}. |
|
|
1023 | |
|
|
1024 | If you want to sprinkle loads of logging calls around your code, |
|
|
1025 | consider creating a logger callback with the "AnyEvent::Log::logger" |
|
|
1026 | function, which can reduce typing, codesize and can reduce the |
|
|
1027 | logging overhead enourmously. |
634 | |
1028 | |
635 | WHAT TO DO IN A MODULE |
1029 | WHAT TO DO IN A MODULE |
636 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
1030 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
637 | freely, but you should not load a specific event module or rely on it. |
1031 | freely, but you should not load a specific event module or rely on it. |
638 | |
1032 | |
… | |
… | |
646 | stall the whole program, and the whole point of using events is to stay |
1040 | stall the whole program, and the whole point of using events is to stay |
647 | interactive. |
1041 | interactive. |
648 | |
1042 | |
649 | It is fine, however, to call "->recv" when the user of your module |
1043 | It is fine, however, to call "->recv" when the user of your module |
650 | requests it (i.e. if you create a http request object ad have a method |
1044 | requests it (i.e. if you create a http request object ad have a method |
651 | called "results" that returns the results, it should call "->recv" |
1045 | called "results" that returns the results, it may call "->recv" freely, |
652 | freely, as the user of your module knows what she is doing. always). |
1046 | as the user of your module knows what she is doing. Always). |
653 | |
1047 | |
654 | WHAT TO DO IN THE MAIN PROGRAM |
1048 | WHAT TO DO IN THE MAIN PROGRAM |
655 | There will always be a single main program - the only place that should |
1049 | There will always be a single main program - the only place that should |
656 | dictate which event model to use. |
1050 | dictate which event model to use. |
657 | |
1051 | |
658 | If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
1052 | If the program is not event-based, it need not do anything special, even |
659 | do anything special (it does not need to be event-based) and let |
1053 | when it depends on a module that uses an AnyEvent. If the program itself |
660 | AnyEvent decide which implementation to chose if some module relies on |
1054 | uses AnyEvent, but does not care which event loop is used, all it needs |
661 | it. |
1055 | to do is "use AnyEvent". In either case, AnyEvent will choose the best |
|
|
1056 | available loop implementation. |
662 | |
1057 | |
663 | If the main program relies on a specific event model - for example, in |
1058 | If the main program relies on a specific event model - for example, in |
664 | Gtk2 programs you have to rely on the Glib module - you should load the |
1059 | Gtk2 programs you have to rely on the Glib module - you should load the |
665 | event module before loading AnyEvent or any module that uses it: |
1060 | event module before loading AnyEvent or any module that uses it: |
666 | generally speaking, you should load it as early as possible. The reason |
1061 | generally speaking, you should load it as early as possible. The reason |
667 | is that modules might create watchers when they are loaded, and AnyEvent |
1062 | is that modules might create watchers when they are loaded, and AnyEvent |
668 | will decide on the event model to use as soon as it creates watchers, |
1063 | will decide on the event model to use as soon as it creates watchers, |
669 | and it might chose the wrong one unless you load the correct one |
1064 | and it might choose the wrong one unless you load the correct one |
670 | yourself. |
1065 | yourself. |
671 | |
1066 | |
672 | You can chose to use a pure-perl implementation by loading the |
1067 | You can chose to use a pure-perl implementation by loading the |
673 | "AnyEvent::Impl::Perl" module, which gives you similar behaviour |
1068 | "AnyEvent::Loop" module, which gives you similar behaviour everywhere, |
674 | everywhere, but letting AnyEvent chose the model is generally better. |
1069 | but letting AnyEvent chose the model is generally better. |
675 | |
1070 | |
676 | MAINLOOP EMULATION |
1071 | MAINLOOP EMULATION |
677 | Sometimes (often for short test scripts, or even standalone programs who |
1072 | Sometimes (often for short test scripts, or even standalone programs who |
678 | only want to use AnyEvent), you do not want to run a specific event |
1073 | only want to use AnyEvent), you do not want to run a specific event |
679 | loop. |
1074 | loop. |
… | |
… | |
689 | variable somewhere, waiting for it, and sending it when the program |
1084 | variable somewhere, waiting for it, and sending it when the program |
690 | should exit cleanly. |
1085 | should exit cleanly. |
691 | |
1086 | |
692 | OTHER MODULES |
1087 | OTHER MODULES |
693 | The following is a non-exhaustive list of additional modules that use |
1088 | The following is a non-exhaustive list of additional modules that use |
694 | AnyEvent and can therefore be mixed easily with other AnyEvent modules |
1089 | AnyEvent as a client and can therefore be mixed easily with other |
695 | in the same program. Some of the modules come with AnyEvent, some are |
1090 | AnyEvent modules and other event loops in the same program. Some of the |
696 | available via CPAN. |
1091 | modules come as part of AnyEvent, the others are available via CPAN (see |
|
|
1092 | <http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer |
|
|
1093 | non-exhaustive list), and the list is heavily biased towards modules of |
|
|
1094 | the AnyEvent author himself :) |
697 | |
1095 | |
698 | AnyEvent::Util |
1096 | AnyEvent::Util (part of the AnyEvent distribution) |
699 | Contains various utility functions that replace often-used but |
1097 | Contains various utility functions that replace often-used blocking |
700 | blocking functions such as "inet_aton" by event-/callback-based |
1098 | functions such as "inet_aton" with event/callback-based versions. |
701 | versions. |
|
|
702 | |
1099 | |
703 | AnyEvent::Handle |
1100 | AnyEvent::Socket (part of the AnyEvent distribution) |
704 | Provide read and write buffers and manages watchers for reads and |
|
|
705 | writes. |
|
|
706 | |
|
|
707 | AnyEvent::Socket |
|
|
708 | Provides various utility functions for (internet protocol) sockets, |
1101 | Provides various utility functions for (internet protocol) sockets, |
709 | addresses and name resolution. Also functions to create non-blocking |
1102 | addresses and name resolution. Also functions to create non-blocking |
710 | tcp connections or tcp servers, with IPv6 and SRV record support and |
1103 | tcp connections or tcp servers, with IPv6 and SRV record support and |
711 | more. |
1104 | more. |
712 | |
1105 | |
713 | AnyEvent::DNS |
1106 | AnyEvent::Handle (part of the AnyEvent distribution) |
|
|
1107 | Provide read and write buffers, manages watchers for reads and |
|
|
1108 | writes, supports raw and formatted I/O, I/O queued and fully |
|
|
1109 | transparent and non-blocking SSL/TLS (via AnyEvent::TLS). |
|
|
1110 | |
|
|
1111 | AnyEvent::DNS (part of the AnyEvent distribution) |
714 | Provides rich asynchronous DNS resolver capabilities. |
1112 | Provides rich asynchronous DNS resolver capabilities. |
715 | |
1113 | |
|
|
1114 | AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD, |
|
|
1115 | AnyEvent::IGS, AnyEvent::FCP |
|
|
1116 | Implement event-based interfaces to the protocols of the same name |
|
|
1117 | (for the curious, IGS is the International Go Server and FCP is the |
|
|
1118 | Freenet Client Protocol). |
|
|
1119 | |
|
|
1120 | AnyEvent::AIO (part of the AnyEvent distribution) |
|
|
1121 | Truly asynchronous (as opposed to non-blocking) I/O, should be in |
|
|
1122 | the toolbox of every event programmer. AnyEvent::AIO transparently |
|
|
1123 | fuses IO::AIO and AnyEvent together, giving AnyEvent access to |
|
|
1124 | event-based file I/O, and much more. |
|
|
1125 | |
|
|
1126 | AnyEvent::Filesys::Notify |
|
|
1127 | AnyEvent is good for non-blocking stuff, but it can't detect file or |
|
|
1128 | path changes (e.g. "watch this directory for new files", "watch this |
|
|
1129 | file for changes"). The AnyEvent::Filesys::Notify module promises to |
|
|
1130 | do just that in a portbale fashion, supporting inotify on GNU/Linux |
|
|
1131 | and some weird, without doubt broken, stuff on OS X to monitor |
|
|
1132 | files. It can fall back to blocking scans at regular intervals |
|
|
1133 | transparently on other platforms, so it's about as portable as it |
|
|
1134 | gets. |
|
|
1135 | |
|
|
1136 | (I haven't used it myself, but I haven't heard anybody complaining |
|
|
1137 | about it yet). |
|
|
1138 | |
|
|
1139 | AnyEvent::DBI |
|
|
1140 | Executes DBI requests asynchronously in a proxy process for you, |
|
|
1141 | notifying you in an event-based way when the operation is finished. |
|
|
1142 | |
716 | AnyEvent::HTTPD |
1143 | AnyEvent::HTTPD |
717 | Provides a simple web application server framework. |
1144 | A simple embedded webserver. |
718 | |
1145 | |
719 | AnyEvent::FastPing |
1146 | AnyEvent::FastPing |
720 | The fastest ping in the west. |
1147 | The fastest ping in the west. |
721 | |
1148 | |
722 | Net::IRC3 |
|
|
723 | AnyEvent based IRC client module family. |
|
|
724 | |
|
|
725 | Net::XMPP2 |
|
|
726 | AnyEvent based XMPP (Jabber protocol) module family. |
|
|
727 | |
|
|
728 | Net::FCP |
|
|
729 | AnyEvent-based implementation of the Freenet Client Protocol, |
|
|
730 | birthplace of AnyEvent. |
|
|
731 | |
|
|
732 | Event::ExecFlow |
|
|
733 | High level API for event-based execution flow control. |
|
|
734 | |
|
|
735 | Coro |
1149 | Coro |
736 | Has special support for AnyEvent via Coro::AnyEvent. |
1150 | Has special support for AnyEvent via Coro::AnyEvent, which allows |
|
|
1151 | you to simply invert the flow control - don't call us, we will call |
|
|
1152 | you: |
737 | |
1153 | |
738 | AnyEvent::AIO, IO::AIO |
1154 | async { |
739 | Truly asynchronous I/O, should be in the toolbox of every event |
1155 | Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it |
740 | programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent |
1156 | print "5 seconds later!\n"; |
741 | together. |
|
|
742 | |
1157 | |
743 | AnyEvent::BDB, BDB |
1158 | Coro::AnyEvent::readable *STDIN; # uses an I/O watcher |
744 | Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently |
1159 | my $line = <STDIN>; # works for ttys |
745 | fuses IO::AIO and AnyEvent together. |
|
|
746 | |
1160 | |
747 | IO::Lambda |
1161 | AnyEvent::HTTP::http_get "url", Coro::rouse_cb; |
748 | The lambda approach to I/O - don't ask, look there. Can use |
1162 | my ($body, $hdr) = Coro::rouse_wait; |
|
|
1163 | }; |
|
|
1164 | |
|
|
1165 | SIMPLIFIED AE API |
|
|
1166 | Starting with version 5.0, AnyEvent officially supports a second, much |
|
|
1167 | simpler, API that is designed to reduce the calling, typing and memory |
|
|
1168 | overhead by using function call syntax and a fixed number of parameters. |
|
|
1169 | |
|
|
1170 | See the AE manpage for details. |
|
|
1171 | |
|
|
1172 | ERROR AND EXCEPTION HANDLING |
|
|
1173 | In general, AnyEvent does not do any error handling - it relies on the |
|
|
1174 | caller to do that if required. The AnyEvent::Strict module (see also the |
|
|
1175 | "PERL_ANYEVENT_STRICT" environment variable, below) provides strict |
|
|
1176 | checking of all AnyEvent methods, however, which is highly useful during |
|
|
1177 | development. |
|
|
1178 | |
|
|
1179 | As for exception handling (i.e. runtime errors and exceptions thrown |
|
|
1180 | while executing a callback), this is not only highly event-loop |
|
|
1181 | specific, but also not in any way wrapped by this module, as this is the |
|
|
1182 | job of the main program. |
|
|
1183 | |
|
|
1184 | The pure perl event loop simply re-throws the exception (usually within |
|
|
1185 | "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()", |
|
|
1186 | Glib uses "install_exception_handler" and so on. |
|
|
1187 | |
|
|
1188 | ENVIRONMENT VARIABLES |
|
|
1189 | AnyEvent supports a number of environment variables that tune the |
|
|
1190 | runtime behaviour. They are usually evaluated when AnyEvent is loaded, |
|
|
1191 | initialised, or a submodule that uses them is loaded. Many of them also |
|
|
1192 | cause AnyEvent to load additional modules - for example, |
|
|
1193 | "PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be |
|
|
1194 | loaded. |
|
|
1195 | |
|
|
1196 | All the environment variables documented here start with |
|
|
1197 | "PERL_ANYEVENT_", which is what AnyEvent considers its own namespace. |
|
|
1198 | Other modules are encouraged (but by no means required) to use |
|
|
1199 | "PERL_ANYEVENT_SUBMODULE" if they have registered the |
|
|
1200 | AnyEvent::Submodule namespace on CPAN, for any submodule. For example, |
|
|
1201 | AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it |
|
|
1202 | should not access env variables starting with "AE_", see below). |
|
|
1203 | |
|
|
1204 | All variables can also be set via the "AE_" prefix, that is, instead of |
|
|
1205 | setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case |
|
|
1206 | there is a clash btween anyevent and another program that uses |
|
|
1207 | "AE_something" you can set the corresponding "PERL_ANYEVENT_something" |
|
|
1208 | variable to the empty string, as those variables take precedence. |
|
|
1209 | |
|
|
1210 | When AnyEvent is first loaded, it copies all "AE_xxx" env variables to |
|
|
1211 | their "PERL_ANYEVENT_xxx" counterpart unless that variable already |
|
|
1212 | exists. If taint mode is on, then AnyEvent will remove *all* environment |
|
|
1213 | variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with |
|
|
1214 | "undef" or the empty string, if the corresaponding "AE_" variable is |
|
|
1215 | set). |
|
|
1216 | |
|
|
1217 | The exact algorithm is currently: |
|
|
1218 | |
|
|
1219 | 1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV |
|
|
1220 | 2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists |
|
|
1221 | 3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef. |
|
|
1222 | |
|
|
1223 | This ensures that child processes will not see the "AE_" variables. |
|
|
1224 | |
|
|
1225 | The following environment variables are currently known to AnyEvent: |
|
|
1226 | |
|
|
1227 | "PERL_ANYEVENT_VERBOSE" |
|
|
1228 | By default, AnyEvent will log messages with loglevel 4 ("error") or |
|
|
1229 | higher (see AnyEvent::Log). You can set this environment variable to |
|
|
1230 | a numerical loglevel to make AnyEvent more (or less) talkative. |
|
|
1231 | |
|
|
1232 | If you want to do more than just set the global logging level you |
|
|
1233 | should have a look at "PERL_ANYEVENT_LOG", which allows much more |
|
|
1234 | complex specifications. |
|
|
1235 | |
|
|
1236 | When set to 0 ("off"), then no messages whatsoever will be logged |
|
|
1237 | with everything else at defaults. |
|
|
1238 | |
|
|
1239 | When set to 5 or higher ("warn"), AnyEvent warns about unexpected |
|
|
1240 | conditions, such as not being able to load the event model specified |
|
|
1241 | by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception |
|
|
1242 | - this is the minimum recommended level for use during development. |
|
|
1243 | |
|
|
1244 | When set to 7 or higher (info), AnyEvent reports which event model |
|
|
1245 | it chooses. |
|
|
1246 | |
|
|
1247 | When set to 8 or higher (debug), then AnyEvent will report extra |
|
|
1248 | information on which optional modules it loads and how it implements |
|
|
1249 | certain features. |
|
|
1250 | |
|
|
1251 | "PERL_ANYEVENT_LOG" |
|
|
1252 | Accepts rather complex logging specifications. For example, you |
|
|
1253 | could log all "debug" messages of some module to stderr, warnings |
|
|
1254 | and above to stderr, and errors and above to syslog, with: |
|
|
1255 | |
|
|
1256 | PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog |
|
|
1257 | |
|
|
1258 | For the rather extensive details, see AnyEvent::Log. |
|
|
1259 | |
|
|
1260 | This variable is evaluated when AnyEvent (or AnyEvent::Log) is |
|
|
1261 | loaded, so will take effect even before AnyEvent has initialised |
|
|
1262 | itself. |
|
|
1263 | |
|
|
1264 | Note that specifying this environment variable causes the |
|
|
1265 | AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE" |
|
|
1266 | does not, so only using the latter saves a few hundred kB of memory |
|
|
1267 | unless a module explicitly needs the extra features of |
749 | AnyEvent. |
1268 | AnyEvent::Log. |
|
|
1269 | |
|
|
1270 | "PERL_ANYEVENT_STRICT" |
|
|
1271 | AnyEvent does not do much argument checking by default, as thorough |
|
|
1272 | argument checking is very costly. Setting this variable to a true |
|
|
1273 | value will cause AnyEvent to load "AnyEvent::Strict" and then to |
|
|
1274 | thoroughly check the arguments passed to most method calls. If it |
|
|
1275 | finds any problems, it will croak. |
|
|
1276 | |
|
|
1277 | In other words, enables "strict" mode. |
|
|
1278 | |
|
|
1279 | Unlike "use strict" (or its modern cousin, "use common::sense", it |
|
|
1280 | is definitely recommended to keep it off in production. Keeping |
|
|
1281 | "PERL_ANYEVENT_STRICT=1" in your environment while developing |
|
|
1282 | programs can be very useful, however. |
|
|
1283 | |
|
|
1284 | "PERL_ANYEVENT_DEBUG_SHELL" |
|
|
1285 | If this env variable is nonempty, then its contents will be |
|
|
1286 | interpreted by "AnyEvent::Socket::parse_hostport" and |
|
|
1287 | "AnyEvent::Debug::shell" (after replacing every occurance of $$ by |
|
|
1288 | the process pid). The shell object is saved in |
|
|
1289 | $AnyEvent::Debug::SHELL. |
|
|
1290 | |
|
|
1291 | This happens when the first watcher is created. |
|
|
1292 | |
|
|
1293 | For example, to bind a debug shell on a unix domain socket in |
|
|
1294 | /tmp/debug<pid>.sock, you could use this: |
|
|
1295 | |
|
|
1296 | PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog |
|
|
1297 | # connect with e.g.: socat readline /tmp/debug123.sock |
|
|
1298 | |
|
|
1299 | Or to bind to tcp port 4545 on localhost: |
|
|
1300 | |
|
|
1301 | PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog |
|
|
1302 | # connect with e.g.: telnet localhost 4545 |
|
|
1303 | |
|
|
1304 | Note that creating sockets in /tmp or on localhost is very unsafe on |
|
|
1305 | multiuser systems. |
|
|
1306 | |
|
|
1307 | "PERL_ANYEVENT_DEBUG_WRAP" |
|
|
1308 | Can be set to 0, 1 or 2 and enables wrapping of all watchers for |
|
|
1309 | debugging purposes. See "AnyEvent::Debug::wrap" for details. |
|
|
1310 | |
|
|
1311 | "PERL_ANYEVENT_MODEL" |
|
|
1312 | This can be used to specify the event model to be used by AnyEvent, |
|
|
1313 | before auto detection and -probing kicks in. |
|
|
1314 | |
|
|
1315 | It normally is a string consisting entirely of ASCII letters (e.g. |
|
|
1316 | "EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and |
|
|
1317 | the resulting module name is loaded and - if the load was successful |
|
|
1318 | - used as event model backend. If it fails to load then AnyEvent |
|
|
1319 | will proceed with auto detection and -probing. |
|
|
1320 | |
|
|
1321 | If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::") |
|
|
1322 | then nothing gets prepended and the module name is used as-is (hint: |
|
|
1323 | "::" at the end of a string designates a module name and quotes it |
|
|
1324 | appropriately). |
|
|
1325 | |
|
|
1326 | For example, to force the pure perl model (AnyEvent::Loop::Perl) you |
|
|
1327 | could start your program like this: |
|
|
1328 | |
|
|
1329 | PERL_ANYEVENT_MODEL=Perl perl ... |
|
|
1330 | |
|
|
1331 | "PERL_ANYEVENT_IO_MODEL" |
|
|
1332 | The current file I/O model - see AnyEvent::IO for more info. |
|
|
1333 | |
|
|
1334 | At the moment, only "Perl" (small, pure-perl, synchronous) and |
|
|
1335 | "IOAIO" (truly asynchronous) are supported. The default is "IOAIO" |
|
|
1336 | if AnyEvent::AIO can be loaded, otherwise it is "Perl". |
|
|
1337 | |
|
|
1338 | "PERL_ANYEVENT_PROTOCOLS" |
|
|
1339 | Used by both AnyEvent::DNS and AnyEvent::Socket to determine |
|
|
1340 | preferences for IPv4 or IPv6. The default is unspecified (and might |
|
|
1341 | change, or be the result of auto probing). |
|
|
1342 | |
|
|
1343 | Must be set to a comma-separated list of protocols or address |
|
|
1344 | families, current supported: "ipv4" and "ipv6". Only protocols |
|
|
1345 | mentioned will be used, and preference will be given to protocols |
|
|
1346 | mentioned earlier in the list. |
|
|
1347 | |
|
|
1348 | This variable can effectively be used for denial-of-service attacks |
|
|
1349 | against local programs (e.g. when setuid), although the impact is |
|
|
1350 | likely small, as the program has to handle conenction and other |
|
|
1351 | failures anyways. |
|
|
1352 | |
|
|
1353 | Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
|
|
1354 | IPv6, but support both and try to use both. |
|
|
1355 | "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
|
|
1356 | resolve or contact IPv6 addresses. |
|
|
1357 | "PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but |
|
|
1358 | prefer IPv6 over IPv4. |
|
|
1359 | |
|
|
1360 | "PERL_ANYEVENT_HOSTS" |
|
|
1361 | This variable, if specified, overrides the /etc/hosts file used by |
|
|
1362 | AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be |
|
|
1363 | read from that file instead. |
|
|
1364 | |
|
|
1365 | "PERL_ANYEVENT_EDNS0" |
|
|
1366 | Used by AnyEvent::DNS to decide whether to use the EDNS0 extension |
|
|
1367 | for DNS. This extension is generally useful to reduce DNS traffic, |
|
|
1368 | especially when DNSSEC is involved, but some (broken) firewalls drop |
|
|
1369 | such DNS packets, which is why it is off by default. |
|
|
1370 | |
|
|
1371 | Setting this variable to 1 will cause AnyEvent::DNS to announce |
|
|
1372 | EDNS0 in its DNS requests. |
|
|
1373 | |
|
|
1374 | "PERL_ANYEVENT_MAX_FORKS" |
|
|
1375 | The maximum number of child processes that |
|
|
1376 | "AnyEvent::Util::fork_call" will create in parallel. |
|
|
1377 | |
|
|
1378 | "PERL_ANYEVENT_MAX_OUTSTANDING_DNS" |
|
|
1379 | The default value for the "max_outstanding" parameter for the |
|
|
1380 | default DNS resolver - this is the maximum number of parallel DNS |
|
|
1381 | requests that are sent to the DNS server. |
|
|
1382 | |
|
|
1383 | "PERL_ANYEVENT_MAX_SIGNAL_LATENCY" |
|
|
1384 | Perl has inherently racy signal handling (you can basically choose |
|
|
1385 | between losing signals and memory corruption) - pure perl event |
|
|
1386 | loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't |
|
|
1387 | available) therefore have to poll regularly to avoid losing signals. |
|
|
1388 | |
|
|
1389 | Some event loops are racy, but don't poll regularly, and some event |
|
|
1390 | loops are written in C but are still racy. For those event loops, |
|
|
1391 | AnyEvent installs a timer that regularly wakes up the event loop. |
|
|
1392 | |
|
|
1393 | By default, the interval for this timer is 10 seconds, but you can |
|
|
1394 | override this delay with this environment variable (or by setting |
|
|
1395 | the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal |
|
|
1396 | watchers). |
|
|
1397 | |
|
|
1398 | Lower values increase CPU (and energy) usage, higher values can |
|
|
1399 | introduce long delays when reaping children or waiting for signals. |
|
|
1400 | |
|
|
1401 | The AnyEvent::Async module, if available, will be used to avoid this |
|
|
1402 | polling (with most event loops). |
|
|
1403 | |
|
|
1404 | "PERL_ANYEVENT_RESOLV_CONF" |
|
|
1405 | The absolute path to a resolv.conf-style file to use instead of |
|
|
1406 | /etc/resolv.conf (or the OS-specific configuration) in the default |
|
|
1407 | resolver, or the empty string to select the default configuration. |
|
|
1408 | |
|
|
1409 | "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH". |
|
|
1410 | When neither "ca_file" nor "ca_path" was specified during |
|
|
1411 | AnyEvent::TLS context creation, and either of these environment |
|
|
1412 | variables are nonempty, they will be used to specify CA certificate |
|
|
1413 | locations instead of a system-dependent default. |
|
|
1414 | |
|
|
1415 | "PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT" |
|
|
1416 | When these are set to 1, then the respective modules are not loaded. |
|
|
1417 | Mostly good for testing AnyEvent itself. |
750 | |
1418 | |
751 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
1419 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
752 | This is an advanced topic that you do not normally need to use AnyEvent |
1420 | This is an advanced topic that you do not normally need to use AnyEvent |
753 | in a module. This section is only of use to event loop authors who want |
1421 | in a module. This section is only of use to event loop authors who want |
754 | to provide AnyEvent compatibility. |
1422 | to provide AnyEvent compatibility. |
… | |
… | |
788 | |
1456 | |
789 | *rxvt-unicode* also cheats a bit by not providing blocking access to |
1457 | *rxvt-unicode* also cheats a bit by not providing blocking access to |
790 | condition variables: code blocking while waiting for a condition will |
1458 | condition variables: code blocking while waiting for a condition will |
791 | "die". This still works with most modules/usages, and blocking calls |
1459 | "die". This still works with most modules/usages, and blocking calls |
792 | must not be done in an interactive application, so it makes sense. |
1460 | must not be done in an interactive application, so it makes sense. |
793 | |
|
|
794 | ENVIRONMENT VARIABLES |
|
|
795 | The following environment variables are used by this module: |
|
|
796 | |
|
|
797 | "PERL_ANYEVENT_VERBOSE" |
|
|
798 | By default, AnyEvent will be completely silent except in fatal |
|
|
799 | conditions. You can set this environment variable to make AnyEvent |
|
|
800 | more talkative. |
|
|
801 | |
|
|
802 | When set to 1 or higher, causes AnyEvent to warn about unexpected |
|
|
803 | conditions, such as not being able to load the event model specified |
|
|
804 | by "PERL_ANYEVENT_MODEL". |
|
|
805 | |
|
|
806 | When set to 2 or higher, cause AnyEvent to report to STDERR which |
|
|
807 | event model it chooses. |
|
|
808 | |
|
|
809 | "PERL_ANYEVENT_MODEL" |
|
|
810 | This can be used to specify the event model to be used by AnyEvent, |
|
|
811 | before auto detection and -probing kicks in. It must be a string |
|
|
812 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
|
|
813 | gets prepended and the resulting module name is loaded and if the |
|
|
814 | load was successful, used as event model. If it fails to load |
|
|
815 | AnyEvent will proceed with auto detection and -probing. |
|
|
816 | |
|
|
817 | This functionality might change in future versions. |
|
|
818 | |
|
|
819 | For example, to force the pure perl model (AnyEvent::Impl::Perl) you |
|
|
820 | could start your program like this: |
|
|
821 | |
|
|
822 | PERL_ANYEVENT_MODEL=Perl perl ... |
|
|
823 | |
|
|
824 | "PERL_ANYEVENT_PROTOCOLS" |
|
|
825 | Used by both AnyEvent::DNS and AnyEvent::Socket to determine |
|
|
826 | preferences for IPv4 or IPv6. The default is unspecified (and might |
|
|
827 | change, or be the result of auto probing). |
|
|
828 | |
|
|
829 | Must be set to a comma-separated list of protocols or address |
|
|
830 | families, current supported: "ipv4" and "ipv6". Only protocols |
|
|
831 | mentioned will be used, and preference will be given to protocols |
|
|
832 | mentioned earlier in the list. |
|
|
833 | |
|
|
834 | This variable can effectively be used for denial-of-service attacks |
|
|
835 | against local programs (e.g. when setuid), although the impact is |
|
|
836 | likely small, as the program has to handle connection errors |
|
|
837 | already- |
|
|
838 | |
|
|
839 | Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
|
|
840 | IPv6, but support both and try to use both. |
|
|
841 | "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
|
|
842 | resolve or contact IPv6 addresses. |
|
|
843 | "PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but |
|
|
844 | prefer IPv6 over IPv4. |
|
|
845 | |
|
|
846 | "PERL_ANYEVENT_EDNS0" |
|
|
847 | Used by AnyEvent::DNS to decide whether to use the EDNS0 extension |
|
|
848 | for DNS. This extension is generally useful to reduce DNS traffic, |
|
|
849 | but some (broken) firewalls drop such DNS packets, which is why it |
|
|
850 | is off by default. |
|
|
851 | |
|
|
852 | Setting this variable to 1 will cause AnyEvent::DNS to announce |
|
|
853 | EDNS0 in its DNS requests. |
|
|
854 | |
|
|
855 | "PERL_ANYEVENT_MAX_FORKS" |
|
|
856 | The maximum number of child processes that |
|
|
857 | "AnyEvent::Util::fork_call" will create in parallel. |
|
|
858 | |
1461 | |
859 | EXAMPLE PROGRAM |
1462 | EXAMPLE PROGRAM |
860 | The following program uses an I/O watcher to read data from STDIN, a |
1463 | The following program uses an I/O watcher to read data from STDIN, a |
861 | timer to display a message once per second, and a condition variable to |
1464 | timer to display a message once per second, and a condition variable to |
862 | quit the program when the user enters quit: |
1465 | quit the program when the user enters quit: |
… | |
… | |
874 | warn "read: $input\n"; # output what has been read |
1477 | warn "read: $input\n"; # output what has been read |
875 | $cv->send if $input =~ /^q/i; # quit program if /^q/i |
1478 | $cv->send if $input =~ /^q/i; # quit program if /^q/i |
876 | }, |
1479 | }, |
877 | ); |
1480 | ); |
878 | |
1481 | |
879 | my $time_watcher; # can only be used once |
|
|
880 | |
|
|
881 | sub new_timer { |
|
|
882 | $timer = AnyEvent->timer (after => 1, cb => sub { |
1482 | my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub { |
883 | warn "timeout\n"; # print 'timeout' about every second |
1483 | warn "timeout\n"; # print 'timeout' at most every second |
884 | &new_timer; # and restart the time |
|
|
885 | }); |
|
|
886 | } |
1484 | }); |
887 | |
|
|
888 | new_timer; # create first timer |
|
|
889 | |
1485 | |
890 | $cv->recv; # wait until user enters /^q/i |
1486 | $cv->recv; # wait until user enters /^q/i |
891 | |
1487 | |
892 | REAL-WORLD EXAMPLE |
1488 | REAL-WORLD EXAMPLE |
893 | Consider the Net::FCP module. It features (among others) the following |
1489 | Consider the Net::FCP module. It features (among others) the following |
… | |
… | |
965 | |
1561 | |
966 | The actual code goes further and collects all errors ("die"s, |
1562 | The actual code goes further and collects all errors ("die"s, |
967 | exceptions) that occurred during request processing. The "result" method |
1563 | exceptions) that occurred during request processing. The "result" method |
968 | detects whether an exception as thrown (it is stored inside the $txn |
1564 | detects whether an exception as thrown (it is stored inside the $txn |
969 | object) and just throws the exception, which means connection errors and |
1565 | object) and just throws the exception, which means connection errors and |
970 | other problems get reported tot he code that tries to use the result, |
1566 | other problems get reported to the code that tries to use the result, |
971 | not in a random callback. |
1567 | not in a random callback. |
972 | |
1568 | |
973 | All of this enables the following usage styles: |
1569 | All of this enables the following usage styles: |
974 | |
1570 | |
975 | 1. Blocking: |
1571 | 1. Blocking: |
… | |
… | |
1020 | through AnyEvent. The benchmark creates a lot of timers (with a zero |
1616 | through AnyEvent. The benchmark creates a lot of timers (with a zero |
1021 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
1617 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
1022 | which it is), lets them fire exactly once and destroys them again. |
1618 | which it is), lets them fire exactly once and destroys them again. |
1023 | |
1619 | |
1024 | Source code for this benchmark is found as eg/bench in the AnyEvent |
1620 | Source code for this benchmark is found as eg/bench in the AnyEvent |
1025 | distribution. |
1621 | distribution. It uses the AE interface, which makes a real difference |
|
|
1622 | for the EV and Perl backends only. |
1026 | |
1623 | |
1027 | Explanation of the columns |
1624 | Explanation of the columns |
1028 | *watcher* is the number of event watchers created/destroyed. Since |
1625 | *watcher* is the number of event watchers created/destroyed. Since |
1029 | different event models feature vastly different performances, each event |
1626 | different event models feature vastly different performances, each event |
1030 | loop was given a number of watchers so that overall runtime is |
1627 | loop was given a number of watchers so that overall runtime is |
… | |
… | |
1049 | *destroy* is the time, in microseconds, that it takes to destroy a |
1646 | *destroy* is the time, in microseconds, that it takes to destroy a |
1050 | single watcher. |
1647 | single watcher. |
1051 | |
1648 | |
1052 | Results |
1649 | Results |
1053 | name watchers bytes create invoke destroy comment |
1650 | name watchers bytes create invoke destroy comment |
1054 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
1651 | EV/EV 100000 223 0.47 0.43 0.27 EV native interface |
1055 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
1652 | EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers |
1056 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
1653 | Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal |
1057 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
1654 | Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation |
1058 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
1655 | Event/Event 16000 516 31.16 31.84 0.82 Event native interface |
1059 | Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers |
1656 | Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers |
|
|
1657 | IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll |
|
|
1658 | IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll |
1060 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
1659 | Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour |
1061 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
1660 | Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers |
1062 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
1661 | POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event |
1063 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
1662 | POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select |
1064 | |
1663 | |
1065 | Discussion |
1664 | Discussion |
1066 | The benchmark does *not* measure scalability of the event loop very |
1665 | The benchmark does *not* measure scalability of the event loop very |
1067 | well. For example, a select-based event loop (such as the pure perl one) |
1666 | well. For example, a select-based event loop (such as the pure perl one) |
1068 | can never compete with an event loop that uses epoll when the number of |
1667 | can never compete with an event loop that uses epoll when the number of |
… | |
… | |
1079 | benchmark machine, handling an event takes roughly 1600 CPU cycles with |
1678 | benchmark machine, handling an event takes roughly 1600 CPU cycles with |
1080 | EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 |
1679 | EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 |
1081 | CPU cycles with POE. |
1680 | CPU cycles with POE. |
1082 | |
1681 | |
1083 | "EV" is the sole leader regarding speed and memory use, which are both |
1682 | "EV" is the sole leader regarding speed and memory use, which are both |
1084 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
1683 | maximal/minimal, respectively. When using the AE API there is zero |
|
|
1684 | overhead (when going through the AnyEvent API create is about 5-6 times |
|
|
1685 | slower, with other times being equal, so still uses far less memory than |
1085 | far less memory than any other event loop and is still faster than Event |
1686 | any other event loop and is still faster than Event natively). |
1086 | natively. |
|
|
1087 | |
1687 | |
1088 | The pure perl implementation is hit in a few sweet spots (both the |
1688 | The pure perl implementation is hit in a few sweet spots (both the |
1089 | constant timeout and the use of a single fd hit optimisations in the |
1689 | constant timeout and the use of a single fd hit optimisations in the |
1090 | perl interpreter and the backend itself). Nevertheless this shows that |
1690 | perl interpreter and the backend itself). Nevertheless this shows that |
1091 | it adds very little overhead in itself. Like any select-based backend |
1691 | it adds very little overhead in itself. Like any select-based backend |
… | |
… | |
1093 | few of them active), of course, but this was not subject of this |
1693 | few of them active), of course, but this was not subject of this |
1094 | benchmark. |
1694 | benchmark. |
1095 | |
1695 | |
1096 | The "Event" module has a relatively high setup and callback invocation |
1696 | The "Event" module has a relatively high setup and callback invocation |
1097 | cost, but overall scores in on the third place. |
1697 | cost, but overall scores in on the third place. |
|
|
1698 | |
|
|
1699 | "IO::Async" performs admirably well, about on par with "Event", even |
|
|
1700 | when using its pure perl backend. |
1098 | |
1701 | |
1099 | "Glib"'s memory usage is quite a bit higher, but it features a faster |
1702 | "Glib"'s memory usage is quite a bit higher, but it features a faster |
1100 | callback invocation and overall ends up in the same class as "Event". |
1703 | callback invocation and overall ends up in the same class as "Event". |
1101 | However, Glib scales extremely badly, doubling the number of watchers |
1704 | However, Glib scales extremely badly, doubling the number of watchers |
1102 | increases the processing time by more than a factor of four, making it |
1705 | increases the processing time by more than a factor of four, making it |
… | |
… | |
1134 | when used without AnyEvent), but most event loops have acceptable |
1737 | when used without AnyEvent), but most event loops have acceptable |
1135 | performance with or without AnyEvent. |
1738 | performance with or without AnyEvent. |
1136 | |
1739 | |
1137 | * The overhead AnyEvent adds is usually much smaller than the overhead |
1740 | * The overhead AnyEvent adds is usually much smaller than the overhead |
1138 | of the actual event loop, only with extremely fast event loops such |
1741 | of the actual event loop, only with extremely fast event loops such |
1139 | as EV adds AnyEvent significant overhead. |
1742 | as EV does AnyEvent add significant overhead. |
1140 | |
1743 | |
1141 | * You should avoid POE like the plague if you want performance or |
1744 | * You should avoid POE like the plague if you want performance or |
1142 | reasonable memory usage. |
1745 | reasonable memory usage. |
1143 | |
1746 | |
1144 | BENCHMARKING THE LARGE SERVER CASE |
1747 | BENCHMARKING THE LARGE SERVER CASE |
… | |
… | |
1158 | In this benchmark, we use 10000 socket pairs (20000 sockets), of which |
1761 | In this benchmark, we use 10000 socket pairs (20000 sockets), of which |
1159 | 100 (1%) are active. This mirrors the activity of large servers with |
1762 | 100 (1%) are active. This mirrors the activity of large servers with |
1160 | many connections, most of which are idle at any one point in time. |
1763 | many connections, most of which are idle at any one point in time. |
1161 | |
1764 | |
1162 | Source code for this benchmark is found as eg/bench2 in the AnyEvent |
1765 | Source code for this benchmark is found as eg/bench2 in the AnyEvent |
1163 | distribution. |
1766 | distribution. It uses the AE interface, which makes a real difference |
|
|
1767 | for the EV and Perl backends only. |
1164 | |
1768 | |
1165 | Explanation of the columns |
1769 | Explanation of the columns |
1166 | *sockets* is the number of sockets, and twice the number of "servers" |
1770 | *sockets* is the number of sockets, and twice the number of "servers" |
1167 | (as each server has a read and write socket end). |
1771 | (as each server has a read and write socket end). |
1168 | |
1772 | |
… | |
… | |
1173 | single "request", that is, reading the token from the pipe and |
1777 | single "request", that is, reading the token from the pipe and |
1174 | forwarding it to another server. This includes deleting the old timeout |
1778 | forwarding it to another server. This includes deleting the old timeout |
1175 | and creating a new one that moves the timeout into the future. |
1779 | and creating a new one that moves the timeout into the future. |
1176 | |
1780 | |
1177 | Results |
1781 | Results |
1178 | name sockets create request |
1782 | name sockets create request |
1179 | EV 20000 69.01 11.16 |
1783 | EV 20000 62.66 7.99 |
1180 | Perl 20000 73.32 35.87 |
1784 | Perl 20000 68.32 32.64 |
1181 | Event 20000 212.62 257.32 |
1785 | IOAsync 20000 174.06 101.15 epoll |
1182 | Glib 20000 651.16 1896.30 |
1786 | IOAsync 20000 174.67 610.84 poll |
|
|
1787 | Event 20000 202.69 242.91 |
|
|
1788 | Glib 20000 557.01 1689.52 |
1183 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
1789 | POE 20000 341.54 12086.32 uses POE::Loop::Event |
1184 | |
1790 | |
1185 | Discussion |
1791 | Discussion |
1186 | This benchmark *does* measure scalability and overall performance of the |
1792 | This benchmark *does* measure scalability and overall performance of the |
1187 | particular event loop. |
1793 | particular event loop. |
1188 | |
1794 | |
1189 | EV is again fastest. Since it is using epoll on my system, the setup |
1795 | EV is again fastest. Since it is using epoll on my system, the setup |
1190 | time is relatively high, though. |
1796 | time is relatively high, though. |
1191 | |
1797 | |
1192 | Perl surprisingly comes second. It is much faster than the C-based event |
1798 | Perl surprisingly comes second. It is much faster than the C-based event |
1193 | loops Event and Glib. |
1799 | loops Event and Glib. |
|
|
1800 | |
|
|
1801 | IO::Async performs very well when using its epoll backend, and still |
|
|
1802 | quite good compared to Glib when using its pure perl backend. |
1194 | |
1803 | |
1195 | Event suffers from high setup time as well (look at its code and you |
1804 | Event suffers from high setup time as well (look at its code and you |
1196 | will understand why). Callback invocation also has a high overhead |
1805 | will understand why). Callback invocation also has a high overhead |
1197 | compared to the "$_->() for .."-style loop that the Perl event loop |
1806 | compared to the "$_->() for .."-style loop that the Perl event loop |
1198 | uses. Event uses select or poll in basically all documented |
1807 | uses. Event uses select or poll in basically all documented |
… | |
… | |
1249 | |
1858 | |
1250 | Summary |
1859 | Summary |
1251 | * C-based event loops perform very well with small number of watchers, |
1860 | * C-based event loops perform very well with small number of watchers, |
1252 | as the management overhead dominates. |
1861 | as the management overhead dominates. |
1253 | |
1862 | |
|
|
1863 | THE IO::Lambda BENCHMARK |
|
|
1864 | Recently I was told about the benchmark in the IO::Lambda manpage, which |
|
|
1865 | could be misinterpreted to make AnyEvent look bad. In fact, the |
|
|
1866 | benchmark simply compares IO::Lambda with POE, and IO::Lambda looks |
|
|
1867 | better (which shouldn't come as a surprise to anybody). As such, the |
|
|
1868 | benchmark is fine, and mostly shows that the AnyEvent backend from |
|
|
1869 | IO::Lambda isn't very optimal. But how would AnyEvent compare when used |
|
|
1870 | without the extra baggage? To explore this, I wrote the equivalent |
|
|
1871 | benchmark for AnyEvent. |
|
|
1872 | |
|
|
1873 | The benchmark itself creates an echo-server, and then, for 500 times, |
|
|
1874 | connects to the echo server, sends a line, waits for the reply, and then |
|
|
1875 | creates the next connection. This is a rather bad benchmark, as it |
|
|
1876 | doesn't test the efficiency of the framework or much non-blocking I/O, |
|
|
1877 | but it is a benchmark nevertheless. |
|
|
1878 | |
|
|
1879 | name runtime |
|
|
1880 | Lambda/select 0.330 sec |
|
|
1881 | + optimized 0.122 sec |
|
|
1882 | Lambda/AnyEvent 0.327 sec |
|
|
1883 | + optimized 0.138 sec |
|
|
1884 | Raw sockets/select 0.077 sec |
|
|
1885 | POE/select, components 0.662 sec |
|
|
1886 | POE/select, raw sockets 0.226 sec |
|
|
1887 | POE/select, optimized 0.404 sec |
|
|
1888 | |
|
|
1889 | AnyEvent/select/nb 0.085 sec |
|
|
1890 | AnyEvent/EV/nb 0.068 sec |
|
|
1891 | +state machine 0.134 sec |
|
|
1892 | |
|
|
1893 | The benchmark is also a bit unfair (my fault): the IO::Lambda/POE |
|
|
1894 | benchmarks actually make blocking connects and use 100% blocking I/O, |
|
|
1895 | defeating the purpose of an event-based solution. All of the newly |
|
|
1896 | written AnyEvent benchmarks use 100% non-blocking connects (using |
|
|
1897 | AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS |
|
|
1898 | resolver), so AnyEvent is at a disadvantage here, as non-blocking |
|
|
1899 | connects generally require a lot more bookkeeping and event handling |
|
|
1900 | than blocking connects (which involve a single syscall only). |
|
|
1901 | |
|
|
1902 | The last AnyEvent benchmark additionally uses AnyEvent::Handle, which |
|
|
1903 | offers similar expressive power as POE and IO::Lambda, using |
|
|
1904 | conventional Perl syntax. This means that both the echo server and the |
|
|
1905 | client are 100% non-blocking, further placing it at a disadvantage. |
|
|
1906 | |
|
|
1907 | As you can see, the AnyEvent + EV combination even beats the |
|
|
1908 | hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl |
|
|
1909 | backend easily beats IO::Lambda and POE. |
|
|
1910 | |
|
|
1911 | And even the 100% non-blocking version written using the high-level (and |
|
|
1912 | slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda |
|
|
1913 | higher level ("unoptimised") abstractions by a large margin, even though |
|
|
1914 | it does all of DNS, tcp-connect and socket I/O in a non-blocking way. |
|
|
1915 | |
|
|
1916 | The two AnyEvent benchmarks programs can be found as eg/ae0.pl and |
|
|
1917 | eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are |
|
|
1918 | part of the IO::Lambda distribution and were used without any changes. |
|
|
1919 | |
|
|
1920 | SIGNALS |
|
|
1921 | AnyEvent currently installs handlers for these signals: |
|
|
1922 | |
|
|
1923 | SIGCHLD |
|
|
1924 | A handler for "SIGCHLD" is installed by AnyEvent's child watcher |
|
|
1925 | emulation for event loops that do not support them natively. Also, |
|
|
1926 | some event loops install a similar handler. |
|
|
1927 | |
|
|
1928 | Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, |
|
|
1929 | then AnyEvent will reset it to default, to avoid losing child exit |
|
|
1930 | statuses. |
|
|
1931 | |
|
|
1932 | SIGPIPE |
|
|
1933 | A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is |
|
|
1934 | "undef" when AnyEvent gets loaded. |
|
|
1935 | |
|
|
1936 | The rationale for this is that AnyEvent users usually do not really |
|
|
1937 | depend on SIGPIPE delivery (which is purely an optimisation for |
|
|
1938 | shell use, or badly-written programs), but "SIGPIPE" can cause |
|
|
1939 | spurious and rare program exits as a lot of people do not expect |
|
|
1940 | "SIGPIPE" when writing to some random socket. |
|
|
1941 | |
|
|
1942 | The rationale for installing a no-op handler as opposed to ignoring |
|
|
1943 | it is that this way, the handler will be restored to defaults on |
|
|
1944 | exec. |
|
|
1945 | |
|
|
1946 | Feel free to install your own handler, or reset it to defaults. |
|
|
1947 | |
|
|
1948 | RECOMMENDED/OPTIONAL MODULES |
|
|
1949 | One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and |
|
|
1950 | its built-in modules) are required to use it. |
|
|
1951 | |
|
|
1952 | That does not mean that AnyEvent won't take advantage of some additional |
|
|
1953 | modules if they are installed. |
|
|
1954 | |
|
|
1955 | This section explains which additional modules will be used, and how |
|
|
1956 | they affect AnyEvent's operation. |
|
|
1957 | |
|
|
1958 | Async::Interrupt |
|
|
1959 | This slightly arcane module is used to implement fast signal |
|
|
1960 | handling: To my knowledge, there is no way to do completely |
|
|
1961 | race-free and quick signal handling in pure perl. To ensure that |
|
|
1962 | signals still get delivered, AnyEvent will start an interval timer |
|
|
1963 | to wake up perl (and catch the signals) with some delay (default is |
|
|
1964 | 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). |
|
|
1965 | |
|
|
1966 | If this module is available, then it will be used to implement |
|
|
1967 | signal catching, which means that signals will not be delayed, and |
|
|
1968 | the event loop will not be interrupted regularly, which is more |
|
|
1969 | efficient (and good for battery life on laptops). |
|
|
1970 | |
|
|
1971 | This affects not just the pure-perl event loop, but also other event |
|
|
1972 | loops that have no signal handling on their own (e.g. Glib, Tk, Qt). |
|
|
1973 | |
|
|
1974 | Some event loops (POE, Event, Event::Lib) offer signal watchers |
|
|
1975 | natively, and either employ their own workarounds (POE) or use |
|
|
1976 | AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY). |
|
|
1977 | Installing Async::Interrupt does nothing for those backends. |
|
|
1978 | |
|
|
1979 | EV This module isn't really "optional", as it is simply one of the |
|
|
1980 | backend event loops that AnyEvent can use. However, it is simply the |
|
|
1981 | best event loop available in terms of features, speed and stability: |
|
|
1982 | It supports the AnyEvent API optimally, implements all the watcher |
|
|
1983 | types in XS, does automatic timer adjustments even when no monotonic |
|
|
1984 | clock is available, can take avdantage of advanced kernel interfaces |
|
|
1985 | such as "epoll" and "kqueue", and is the fastest backend *by far*. |
|
|
1986 | You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and |
|
|
1987 | Glib::EV). |
|
|
1988 | |
|
|
1989 | If you only use backends that rely on another event loop (e.g. |
|
|
1990 | "Tk"), then this module will do nothing for you. |
|
|
1991 | |
|
|
1992 | Guard |
|
|
1993 | The guard module, when used, will be used to implement |
|
|
1994 | "AnyEvent::Util::guard". This speeds up guards considerably (and |
|
|
1995 | uses a lot less memory), but otherwise doesn't affect guard |
|
|
1996 | operation much. It is purely used for performance. |
|
|
1997 | |
|
|
1998 | JSON and JSON::XS |
|
|
1999 | One of these modules is required when you want to read or write JSON |
|
|
2000 | data via AnyEvent::Handle. JSON is also written in pure-perl, but |
|
|
2001 | can take advantage of the ultra-high-speed JSON::XS module when it |
|
|
2002 | is installed. |
|
|
2003 | |
|
|
2004 | Net::SSLeay |
|
|
2005 | Implementing TLS/SSL in Perl is certainly interesting, but not very |
|
|
2006 | worthwhile: If this module is installed, then AnyEvent::Handle (with |
|
|
2007 | the help of AnyEvent::TLS), gains the ability to do TLS/SSL. |
|
|
2008 | |
|
|
2009 | Time::HiRes |
|
|
2010 | This module is part of perl since release 5.008. It will be used |
|
|
2011 | when the chosen event library does not come with a timing source of |
|
|
2012 | its own. The pure-perl event loop (AnyEvent::Loop) will additionally |
|
|
2013 | load it to try to use a monotonic clock for timing stability. |
|
|
2014 | |
|
|
2015 | AnyEvent::AIO (and IO::AIO) |
|
|
2016 | The default implementation of AnyEvent::IO is to do I/O |
|
|
2017 | synchronously, stopping programs while they access the disk, which |
|
|
2018 | is fine for a lot of programs. |
|
|
2019 | |
|
|
2020 | Installing AnyEvent::AIO (and its IO::AIO dependency) makes it |
|
|
2021 | switch to a true asynchronous implementation, so event processing |
|
|
2022 | can continue even while waiting for disk I/O. |
|
|
2023 | |
1254 | FORK |
2024 | FORK |
1255 | Most event libraries are not fork-safe. The ones who are usually are |
2025 | Most event libraries are not fork-safe. The ones who are usually are |
1256 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
2026 | because they rely on inefficient but fork-safe "select" or "poll" calls |
1257 | Only EV is fully fork-aware. |
2027 | - higher performance APIs such as BSD's kqueue or the dreaded Linux |
|
|
2028 | epoll are usually badly thought-out hacks that are incompatible with |
|
|
2029 | fork in one way or another. Only EV is fully fork-aware and ensures that |
|
|
2030 | you continue event-processing in both parent and child (or both, if you |
|
|
2031 | know what you are doing). |
|
|
2032 | |
|
|
2033 | This means that, in general, you cannot fork and do event processing in |
|
|
2034 | the child if the event library was initialised before the fork (which |
|
|
2035 | usually happens when the first AnyEvent watcher is created, or the |
|
|
2036 | library is loaded). |
1258 | |
2037 | |
1259 | If you have to fork, you must either do so *before* creating your first |
2038 | If you have to fork, you must either do so *before* creating your first |
1260 | watcher OR you must not use AnyEvent at all in the child. |
2039 | watcher OR you must not use AnyEvent at all in the child OR you must do |
|
|
2040 | something completely out of the scope of AnyEvent. |
|
|
2041 | |
|
|
2042 | The problem of doing event processing in the parent *and* the child is |
|
|
2043 | much more complicated: even for backends that *are* fork-aware or |
|
|
2044 | fork-safe, their behaviour is not usually what you want: fork clones all |
|
|
2045 | watchers, that means all timers, I/O watchers etc. are active in both |
|
|
2046 | parent and child, which is almost never what you want. USing "exec" to |
|
|
2047 | start worker children from some kind of manage rprocess is usually |
|
|
2048 | preferred, because it is much easier and cleaner, at the expense of |
|
|
2049 | having to have another binary. |
1261 | |
2050 | |
1262 | SECURITY CONSIDERATIONS |
2051 | SECURITY CONSIDERATIONS |
1263 | AnyEvent can be forced to load any event model via |
2052 | AnyEvent can be forced to load any event model via |
1264 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
2053 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
1265 | to execute arbitrary code or directly gain access, it can easily be used |
2054 | to execute arbitrary code or directly gain access, it can easily be used |
… | |
… | |
1269 | |
2058 | |
1270 | You can make AnyEvent completely ignore this variable by deleting it |
2059 | You can make AnyEvent completely ignore this variable by deleting it |
1271 | before the first watcher gets created, e.g. with a "BEGIN" block: |
2060 | before the first watcher gets created, e.g. with a "BEGIN" block: |
1272 | |
2061 | |
1273 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
2062 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1274 | |
2063 | |
1275 | use AnyEvent; |
2064 | use AnyEvent; |
1276 | |
2065 | |
1277 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
2066 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
1278 | be used to probe what backend is used and gain other information (which |
2067 | be used to probe what backend is used and gain other information (which |
1279 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL). |
2068 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), |
|
|
2069 | and $ENV{PERL_ANYEVENT_STRICT}. |
|
|
2070 | |
|
|
2071 | Note that AnyEvent will remove *all* environment variables starting with |
|
|
2072 | "PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is |
|
|
2073 | enabled. |
|
|
2074 | |
|
|
2075 | BUGS |
|
|
2076 | Perl 5.8 has numerous memleaks that sometimes hit this module and are |
|
|
2077 | hard to work around. If you suffer from memleaks, first upgrade to Perl |
|
|
2078 | 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other |
|
|
2079 | annoying memleaks, such as leaking on "map" and "grep" but it is usually |
|
|
2080 | not as pronounced). |
1280 | |
2081 | |
1281 | SEE ALSO |
2082 | SEE ALSO |
1282 | Utility functions: AnyEvent::Util. |
2083 | Tutorial/Introduction: AnyEvent::Intro. |
1283 | |
2084 | |
1284 | Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, |
2085 | FAQ: AnyEvent::FAQ. |
1285 | Event::Lib, Qt, POE. |
2086 | |
|
|
2087 | Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log |
|
|
2088 | (simply logging). |
|
|
2089 | |
|
|
2090 | Development/Debugging: AnyEvent::Strict (stricter checking), |
|
|
2091 | AnyEvent::Debug (interactive shell, watcher tracing). |
|
|
2092 | |
|
|
2093 | Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event, |
|
|
2094 | Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK. |
1286 | |
2095 | |
1287 | Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, |
2096 | Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, |
1288 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, |
2097 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, |
1289 | AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE. |
2098 | AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE, |
|
|
2099 | AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi, AnyEvent::Impl::FLTK. |
1290 | |
2100 | |
1291 | Non-blocking file handles, sockets, TCP clients and servers: |
2101 | Non-blocking handles, pipes, stream sockets, TCP clients and servers: |
1292 | AnyEvent::Handle, AnyEvent::Socket. |
2102 | AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS. |
|
|
2103 | |
|
|
2104 | Asynchronous File I/O: AnyEvent::IO. |
1293 | |
2105 | |
1294 | Asynchronous DNS: AnyEvent::DNS. |
2106 | Asynchronous DNS: AnyEvent::DNS. |
1295 | |
2107 | |
1296 | Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, |
2108 | Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event. |
1297 | |
2109 | |
1298 | Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS. |
2110 | Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC, |
|
|
2111 | AnyEvent::HTTP. |
1299 | |
2112 | |
1300 | AUTHOR |
2113 | AUTHOR |
1301 | Marc Lehmann <schmorp@schmorp.de> |
2114 | Marc Lehmann <schmorp@schmorp.de> |
1302 | http://home.schmorp.de/ |
2115 | http://anyevent.schmorp.de |
1303 | |
2116 | |