… | |
… | |
5 | loops |
5 | loops |
6 | |
6 | |
7 | SYNOPSIS |
7 | SYNOPSIS |
8 | use AnyEvent; |
8 | use AnyEvent; |
9 | |
9 | |
10 | my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { |
10 | my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... }); |
11 | ... |
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12 | }); |
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13 | |
11 | |
14 | my $w = AnyEvent->timer (after => $seconds, cb => sub { |
12 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
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13 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... |
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14 | |
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15 | print AnyEvent->now; # prints current event loop time |
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16 | print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. |
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17 | |
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18 | my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); |
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19 | |
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20 | my $w = AnyEvent->child (pid => $pid, cb => sub { |
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21 | my ($pid, $status) = @_; |
15 | ... |
22 | ... |
16 | }); |
23 | }); |
17 | |
24 | |
18 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
25 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
19 | $w->send; # wake up current and all future recv's |
26 | $w->send; # wake up current and all future recv's |
20 | $w->recv; # enters "main loop" till $condvar gets ->send |
27 | $w->recv; # enters "main loop" till $condvar gets ->send |
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28 | # use a condvar in callback mode: |
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29 | $w->cb (sub { $_[0]->recv }); |
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30 | |
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31 | INTRODUCTION/TUTORIAL |
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32 | This manpage is mainly a reference manual. If you are interested in a |
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33 | tutorial or some gentle introduction, have a look at the AnyEvent::Intro |
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34 | manpage. |
21 | |
35 | |
22 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
36 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
23 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
37 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
24 | nowadays. So what is different about AnyEvent? |
38 | nowadays. So what is different about AnyEvent? |
25 | |
39 | |
26 | Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of |
40 | Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of |
27 | policy* and AnyEvent is *small and efficient*. |
41 | policy* and AnyEvent is *small and efficient*. |
28 | |
42 | |
29 | First and foremost, *AnyEvent is not an event model* itself, it only |
43 | First and foremost, *AnyEvent is not an event model* itself, it only |
30 | interfaces to whatever event model the main program happens to use in a |
44 | interfaces to whatever event model the main program happens to use, in a |
31 | pragmatic way. For event models and certain classes of immortals alike, |
45 | pragmatic way. For event models and certain classes of immortals alike, |
32 | the statement "there can only be one" is a bitter reality: In general, |
46 | the statement "there can only be one" is a bitter reality: In general, |
33 | only one event loop can be active at the same time in a process. |
47 | only one event loop can be active at the same time in a process. |
34 | AnyEvent helps hiding the differences between those event loops. |
48 | AnyEvent cannot change this, but it can hide the differences between |
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49 | those event loops. |
35 | |
50 | |
36 | The goal of AnyEvent is to offer module authors the ability to do event |
51 | The goal of AnyEvent is to offer module authors the ability to do event |
37 | programming (waiting for I/O or timer events) without subscribing to a |
52 | programming (waiting for I/O or timer events) without subscribing to a |
38 | religion, a way of living, and most importantly: without forcing your |
53 | religion, a way of living, and most importantly: without forcing your |
39 | module users into the same thing by forcing them to use the same event |
54 | module users into the same thing by forcing them to use the same event |
40 | model you use. |
55 | model you use. |
41 | |
56 | |
42 | For modules like POE or IO::Async (which is a total misnomer as it is |
57 | For modules like POE or IO::Async (which is a total misnomer as it is |
43 | actually doing all I/O *synchronously*...), using them in your module is |
58 | actually doing all I/O *synchronously*...), using them in your module is |
44 | like joining a cult: After you joined, you are dependent on them and you |
59 | like joining a cult: After you joined, you are dependent on them and you |
45 | cannot use anything else, as it is simply incompatible to everything |
60 | cannot use anything else, as they are simply incompatible to everything |
46 | that isn't itself. What's worse, all the potential users of your module |
61 | that isn't them. What's worse, all the potential users of your module |
47 | are *also* forced to use the same event loop you use. |
62 | are *also* forced to use the same event loop you use. |
48 | |
63 | |
49 | AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
64 | AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
50 | fine. AnyEvent + Tk works fine etc. etc. but none of these work together |
65 | fine. AnyEvent + Tk works fine etc. etc. but none of these work together |
51 | with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if your |
66 | with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your |
52 | module uses one of those, every user of your module has to use it, too. |
67 | module uses one of those, every user of your module has to use it, too. |
53 | But if your module uses AnyEvent, it works transparently with all event |
68 | But if your module uses AnyEvent, it works transparently with all event |
54 | models it supports (including stuff like POE and IO::Async, as long as |
69 | models it supports (including stuff like IO::Async, as long as those use |
55 | those use one of the supported event loops. It is trivial to add new |
70 | one of the supported event loops. It is trivial to add new event loops |
56 | event loops to AnyEvent, too, so it is future-proof). |
71 | to AnyEvent, too, so it is future-proof). |
57 | |
72 | |
58 | In addition to being free of having to use *the one and only true event |
73 | In addition to being free of having to use *the one and only true event |
59 | model*, AnyEvent also is free of bloat and policy: with POE or similar |
74 | model*, AnyEvent also is free of bloat and policy: with POE or similar |
60 | modules, you get an enourmous amount of code and strict rules you have |
75 | modules, you get an enormous amount of code and strict rules you have to |
61 | to follow. AnyEvent, on the other hand, is lean and up to the point, by |
76 | follow. AnyEvent, on the other hand, is lean and up to the point, by |
62 | only offering the functionality that is necessary, in as thin as a |
77 | only offering the functionality that is necessary, in as thin as a |
63 | wrapper as technically possible. |
78 | wrapper as technically possible. |
64 | |
79 | |
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80 | Of course, AnyEvent comes with a big (and fully optional!) toolbox of |
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81 | useful functionality, such as an asynchronous DNS resolver, 100% |
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82 | non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms |
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83 | such as Windows) and lots of real-world knowledge and workarounds for |
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84 | platform bugs and differences. |
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85 | |
65 | Of course, if you want lots of policy (this can arguably be somewhat |
86 | Now, if you *do want* lots of policy (this can arguably be somewhat |
66 | useful) and you want to force your users to use the one and only event |
87 | useful) and you want to force your users to use the one and only event |
67 | model, you should *not* use this module. |
88 | model, you should *not* use this module. |
68 | |
89 | |
69 | DESCRIPTION |
90 | DESCRIPTION |
70 | AnyEvent provides an identical interface to multiple event loops. This |
91 | AnyEvent provides an identical interface to multiple event loops. This |
… | |
… | |
99 | starts using it, all bets are off. Maybe you should tell their authors |
120 | starts using it, all bets are off. Maybe you should tell their authors |
100 | to use AnyEvent so their modules work together with others seamlessly... |
121 | to use AnyEvent so their modules work together with others seamlessly... |
101 | |
122 | |
102 | The pure-perl implementation of AnyEvent is called |
123 | The pure-perl implementation of AnyEvent is called |
103 | "AnyEvent::Impl::Perl". Like other event modules you can load it |
124 | "AnyEvent::Impl::Perl". Like other event modules you can load it |
104 | explicitly. |
125 | explicitly and enjoy the high availability of that event loop :) |
105 | |
126 | |
106 | WATCHERS |
127 | WATCHERS |
107 | AnyEvent has the central concept of a *watcher*, which is an object that |
128 | AnyEvent has the central concept of a *watcher*, which is an object that |
108 | stores relevant data for each kind of event you are waiting for, such as |
129 | stores relevant data for each kind of event you are waiting for, such as |
109 | the callback to call, the filehandle to watch, etc. |
130 | the callback to call, the file handle to watch, etc. |
110 | |
131 | |
111 | These watchers are normal Perl objects with normal Perl lifetime. After |
132 | These watchers are normal Perl objects with normal Perl lifetime. After |
112 | creating a watcher it will immediately "watch" for events and invoke the |
133 | creating a watcher it will immediately "watch" for events and invoke the |
113 | callback when the event occurs (of course, only when the event model is |
134 | callback when the event occurs (of course, only when the event model is |
114 | in control). |
135 | in control). |
115 | |
136 | |
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137 | Note that callbacks must not permanently change global variables |
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138 | potentially in use by the event loop (such as $_ or $[) and that |
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139 | callbacks must not "die". The former is good programming practise in |
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140 | Perl and the latter stems from the fact that exception handling differs |
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141 | widely between event loops. |
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142 | |
116 | To disable the watcher you have to destroy it (e.g. by setting the |
143 | To disable the watcher you have to destroy it (e.g. by setting the |
117 | variable you store it in to "undef" or otherwise deleting all references |
144 | variable you store it in to "undef" or otherwise deleting all references |
118 | to it). |
145 | to it). |
119 | |
146 | |
120 | All watchers are created by calling a method on the "AnyEvent" class. |
147 | All watchers are created by calling a method on the "AnyEvent" class. |
… | |
… | |
122 | Many watchers either are used with "recursion" (repeating timers for |
149 | Many watchers either are used with "recursion" (repeating timers for |
123 | example), or need to refer to their watcher object in other ways. |
150 | example), or need to refer to their watcher object in other ways. |
124 | |
151 | |
125 | An any way to achieve that is this pattern: |
152 | An any way to achieve that is this pattern: |
126 | |
153 | |
127 | my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
154 | my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
128 | # you can use $w here, for example to undef it |
155 | # you can use $w here, for example to undef it |
129 | undef $w; |
156 | undef $w; |
130 | }); |
157 | }); |
131 | |
158 | |
132 | Note that "my $w; $w =" combination. This is necessary because in Perl, |
159 | Note that "my $w; $w =" combination. This is necessary because in Perl, |
133 | my variables are only visible after the statement in which they are |
160 | my variables are only visible after the statement in which they are |
134 | declared. |
161 | declared. |
135 | |
162 | |
136 | I/O WATCHERS |
163 | I/O WATCHERS |
137 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
164 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
138 | the following mandatory key-value pairs as arguments: |
165 | the following mandatory key-value pairs as arguments: |
139 | |
166 | |
140 | "fh" the Perl *file handle* (*not* file descriptor) to watch for events. |
167 | "fh" is the Perl *file handle* (*not* file descriptor) to watch for |
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168 | events (AnyEvent might or might not keep a reference to this file |
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169 | handle). Note that only file handles pointing to things for which |
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170 | non-blocking operation makes sense are allowed. This includes sockets, |
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171 | most character devices, pipes, fifos and so on, but not for example |
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172 | files or block devices. |
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173 | |
141 | "poll" must be a string that is either "r" or "w", which creates a |
174 | "poll" must be a string that is either "r" or "w", which creates a |
142 | watcher waiting for "r"eadable or "w"ritable events, respectively. "cb" |
175 | watcher waiting for "r"eadable or "w"ritable events, respectively. |
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176 | |
143 | is the callback to invoke each time the file handle becomes ready. |
177 | "cb" is the callback to invoke each time the file handle becomes ready. |
144 | |
178 | |
145 | Although the callback might get passed parameters, their value and |
179 | Although the callback might get passed parameters, their value and |
146 | presence is undefined and you cannot rely on them. Portable AnyEvent |
180 | presence is undefined and you cannot rely on them. Portable AnyEvent |
147 | callbacks cannot use arguments passed to I/O watcher callbacks. |
181 | callbacks cannot use arguments passed to I/O watcher callbacks. |
148 | |
182 | |
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152 | |
186 | |
153 | Some event loops issue spurious readyness notifications, so you should |
187 | Some event loops issue spurious readyness notifications, so you should |
154 | always use non-blocking calls when reading/writing from/to your file |
188 | always use non-blocking calls when reading/writing from/to your file |
155 | handles. |
189 | handles. |
156 | |
190 | |
157 | Example: |
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158 | |
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159 | # wait for readability of STDIN, then read a line and disable the watcher |
191 | Example: wait for readability of STDIN, then read a line and disable the |
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192 | watcher. |
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193 | |
160 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
194 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
161 | chomp (my $input = <STDIN>); |
195 | chomp (my $input = <STDIN>); |
162 | warn "read: $input\n"; |
196 | warn "read: $input\n"; |
163 | undef $w; |
197 | undef $w; |
164 | }); |
198 | }); |
… | |
… | |
173 | |
207 | |
174 | Although the callback might get passed parameters, their value and |
208 | Although the callback might get passed parameters, their value and |
175 | presence is undefined and you cannot rely on them. Portable AnyEvent |
209 | presence is undefined and you cannot rely on them. Portable AnyEvent |
176 | callbacks cannot use arguments passed to time watcher callbacks. |
210 | callbacks cannot use arguments passed to time watcher callbacks. |
177 | |
211 | |
178 | The timer callback will be invoked at most once: if you want a repeating |
212 | The callback will normally be invoked once only. If you specify another |
179 | timer you have to create a new watcher (this is a limitation by both Tk |
213 | parameter, "interval", as a strictly positive number (> 0), then the |
180 | and Glib). |
214 | callback will be invoked regularly at that interval (in fractional |
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215 | seconds) after the first invocation. If "interval" is specified with a |
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216 | false value, then it is treated as if it were missing. |
181 | |
217 | |
182 | Example: |
218 | The callback will be rescheduled before invoking the callback, but no |
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219 | attempt is done to avoid timer drift in most backends, so the interval |
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220 | is only approximate. |
183 | |
221 | |
184 | # fire an event after 7.7 seconds |
222 | Example: fire an event after 7.7 seconds. |
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223 | |
185 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
224 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
186 | warn "timeout\n"; |
225 | warn "timeout\n"; |
187 | }); |
226 | }); |
188 | |
227 | |
189 | # to cancel the timer: |
228 | # to cancel the timer: |
190 | undef $w; |
229 | undef $w; |
191 | |
230 | |
192 | Example 2: |
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193 | |
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194 | # fire an event after 0.5 seconds, then roughly every second |
231 | Example 2: fire an event after 0.5 seconds, then roughly every second. |
195 | my $w; |
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196 | |
232 | |
197 | my $cb = sub { |
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198 | # cancel the old timer while creating a new one |
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199 | $w = AnyEvent->timer (after => 1, cb => $cb); |
233 | my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub { |
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234 | warn "timeout\n"; |
200 | }; |
235 | }; |
201 | |
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202 | # start the "loop" by creating the first watcher |
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203 | $w = AnyEvent->timer (after => 0.5, cb => $cb); |
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204 | |
236 | |
205 | TIMING ISSUES |
237 | TIMING ISSUES |
206 | There are two ways to handle timers: based on real time (relative, "fire |
238 | There are two ways to handle timers: based on real time (relative, "fire |
207 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
239 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
208 | o'clock"). |
240 | o'clock"). |
… | |
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220 | on wallclock time) timers. |
252 | on wallclock time) timers. |
221 | |
253 | |
222 | AnyEvent always prefers relative timers, if available, matching the |
254 | AnyEvent always prefers relative timers, if available, matching the |
223 | AnyEvent API. |
255 | AnyEvent API. |
224 | |
256 | |
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257 | AnyEvent has two additional methods that return the "current time": |
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258 | |
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259 | AnyEvent->time |
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260 | This returns the "current wallclock time" as a fractional number of |
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261 | seconds since the Epoch (the same thing as "time" or |
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262 | "Time::HiRes::time" return, and the result is guaranteed to be |
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263 | compatible with those). |
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264 | |
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265 | It progresses independently of any event loop processing, i.e. each |
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266 | call will check the system clock, which usually gets updated |
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267 | frequently. |
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268 | |
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269 | AnyEvent->now |
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270 | This also returns the "current wallclock time", but unlike "time", |
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271 | above, this value might change only once per event loop iteration, |
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272 | depending on the event loop (most return the same time as "time", |
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273 | above). This is the time that AnyEvent's timers get scheduled |
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274 | against. |
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275 | |
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276 | *In almost all cases (in all cases if you don't care), this is the |
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277 | function to call when you want to know the current time.* |
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278 | |
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279 | This function is also often faster then "AnyEvent->time", and thus |
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280 | the preferred method if you want some timestamp (for example, |
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281 | AnyEvent::Handle uses this to update it's activity timeouts). |
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282 | |
|
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283 | The rest of this section is only of relevance if you try to be very |
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284 | exact with your timing, you can skip it without bad conscience. |
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285 | |
|
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286 | For a practical example of when these times differ, consider |
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287 | Event::Lib and EV and the following set-up: |
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288 | |
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289 | The event loop is running and has just invoked one of your callback |
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290 | at time=500 (assume no other callbacks delay processing). In your |
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291 | callback, you wait a second by executing "sleep 1" (blocking the |
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292 | process for a second) and then (at time=501) you create a relative |
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293 | timer that fires after three seconds. |
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294 | |
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295 | With Event::Lib, "AnyEvent->time" and "AnyEvent->now" will both |
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296 | return 501, because that is the current time, and the timer will be |
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297 | scheduled to fire at time=504 (501 + 3). |
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298 | |
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299 | With EV, "AnyEvent->time" returns 501 (as that is the current time), |
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300 | but "AnyEvent->now" returns 500, as that is the time the last event |
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301 | processing phase started. With EV, your timer gets scheduled to run |
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302 | at time=503 (500 + 3). |
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303 | |
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304 | In one sense, Event::Lib is more exact, as it uses the current time |
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305 | regardless of any delays introduced by event processing. However, |
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306 | most callbacks do not expect large delays in processing, so this |
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307 | causes a higher drift (and a lot more system calls to get the |
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308 | current time). |
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309 | |
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310 | In another sense, EV is more exact, as your timer will be scheduled |
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311 | at the same time, regardless of how long event processing actually |
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312 | took. |
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313 | |
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314 | In either case, if you care (and in most cases, you don't), then you |
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315 | can get whatever behaviour you want with any event loop, by taking |
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316 | the difference between "AnyEvent->time" and "AnyEvent->now" into |
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317 | account. |
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318 | |
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319 | AnyEvent->now_update |
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320 | Some event loops (such as EV or AnyEvent::Impl::Perl) cache the |
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321 | current time for each loop iteration (see the discussion of |
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322 | AnyEvent->now, above). |
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323 | |
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324 | When a callback runs for a long time (or when the process sleeps), |
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325 | then this "current" time will differ substantially from the real |
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326 | time, which might affect timers and time-outs. |
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327 | |
|
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328 | When this is the case, you can call this method, which will update |
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329 | the event loop's idea of "current time". |
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330 | |
|
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331 | Note that updating the time *might* cause some events to be handled. |
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332 | |
225 | SIGNAL WATCHERS |
333 | SIGNAL WATCHERS |
226 | You can watch for signals using a signal watcher, "signal" is the signal |
334 | You can watch for signals using a signal watcher, "signal" is the signal |
227 | *name* without any "SIG" prefix, "cb" is the Perl callback to be invoked |
335 | *name* in uppercase and without any "SIG" prefix, "cb" is the Perl |
228 | whenever a signal occurs. |
336 | callback to be invoked whenever a signal occurs. |
229 | |
337 | |
230 | Although the callback might get passed parameters, their value and |
338 | Although the callback might get passed parameters, their value and |
231 | presence is undefined and you cannot rely on them. Portable AnyEvent |
339 | presence is undefined and you cannot rely on them. Portable AnyEvent |
232 | callbacks cannot use arguments passed to signal watcher callbacks. |
340 | callbacks cannot use arguments passed to signal watcher callbacks. |
233 | |
341 | |
234 | Multiple signal occurances can be clumped together into one callback |
342 | Multiple signal occurrences can be clumped together into one callback |
235 | invocation, and callback invocation will be synchronous. synchronous |
343 | invocation, and callback invocation will be synchronous. Synchronous |
236 | means that it might take a while until the signal gets handled by the |
344 | means that it might take a while until the signal gets handled by the |
237 | process, but it is guarenteed not to interrupt any other callbacks. |
345 | process, but it is guaranteed not to interrupt any other callbacks. |
238 | |
346 | |
239 | The main advantage of using these watchers is that you can share a |
347 | The main advantage of using these watchers is that you can share a |
240 | signal between multiple watchers. |
348 | signal between multiple watchers. |
241 | |
349 | |
242 | This watcher might use %SIG, so programs overwriting those signals |
350 | This watcher might use %SIG, so programs overwriting those signals |
… | |
… | |
248 | |
356 | |
249 | CHILD PROCESS WATCHERS |
357 | CHILD PROCESS WATCHERS |
250 | You can also watch on a child process exit and catch its exit status. |
358 | You can also watch on a child process exit and catch its exit status. |
251 | |
359 | |
252 | The child process is specified by the "pid" argument (if set to 0, it |
360 | The child process is specified by the "pid" argument (if set to 0, it |
253 | watches for any child process exit). The watcher will trigger as often |
361 | watches for any child process exit). The watcher will triggered only |
254 | as status change for the child are received. This works by installing a |
362 | when the child process has finished and an exit status is available, not |
255 | signal handler for "SIGCHLD". The callback will be called with the pid |
363 | on any trace events (stopped/continued). |
256 | and exit status (as returned by waitpid), so unlike other watcher types, |
364 | |
257 | you *can* rely on child watcher callback arguments. |
365 | The callback will be called with the pid and exit status (as returned by |
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366 | waitpid), so unlike other watcher types, you *can* rely on child watcher |
|
|
367 | callback arguments. |
|
|
368 | |
|
|
369 | This watcher type works by installing a signal handler for "SIGCHLD", |
|
|
370 | and since it cannot be shared, nothing else should use SIGCHLD or reap |
|
|
371 | random child processes (waiting for specific child processes, e.g. |
|
|
372 | inside "system", is just fine). |
258 | |
373 | |
259 | There is a slight catch to child watchers, however: you usually start |
374 | There is a slight catch to child watchers, however: you usually start |
260 | them *after* the child process was created, and this means the process |
375 | them *after* the child process was created, and this means the process |
261 | could have exited already (and no SIGCHLD will be sent anymore). |
376 | could have exited already (and no SIGCHLD will be sent anymore). |
262 | |
377 | |
… | |
… | |
269 | an AnyEvent program, you *have* to create at least one watcher before |
384 | an AnyEvent program, you *have* to create at least one watcher before |
270 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
385 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
271 | |
386 | |
272 | Example: fork a process and wait for it |
387 | Example: fork a process and wait for it |
273 | |
388 | |
274 | my $done = AnyEvent->condvar; |
389 | my $done = AnyEvent->condvar; |
275 | |
390 | |
276 | my $pid = fork or exit 5; |
391 | my $pid = fork or exit 5; |
277 | |
392 | |
278 | my $w = AnyEvent->child ( |
393 | my $w = AnyEvent->child ( |
279 | pid => $pid, |
394 | pid => $pid, |
280 | cb => sub { |
395 | cb => sub { |
281 | my ($pid, $status) = @_; |
396 | my ($pid, $status) = @_; |
282 | warn "pid $pid exited with status $status"; |
397 | warn "pid $pid exited with status $status"; |
283 | $done->send; |
398 | $done->send; |
284 | }, |
399 | }, |
285 | ); |
400 | ); |
286 | |
401 | |
287 | # do something else, then wait for process exit |
402 | # do something else, then wait for process exit |
288 | $done->recv; |
403 | $done->recv; |
289 | |
404 | |
290 | CONDITION VARIABLES |
405 | CONDITION VARIABLES |
291 | If you are familiar with some event loops you will know that all of them |
406 | If you are familiar with some event loops you will know that all of them |
292 | require you to run some blocking "loop", "run" or similar function that |
407 | require you to run some blocking "loop", "run" or similar function that |
293 | will actively watch for new events and call your callbacks. |
408 | will actively watch for new events and call your callbacks. |
… | |
… | |
298 | The instrument to do that is called a "condition variable", so called |
413 | The instrument to do that is called a "condition variable", so called |
299 | because they represent a condition that must become true. |
414 | because they represent a condition that must become true. |
300 | |
415 | |
301 | Condition variables can be created by calling the "AnyEvent->condvar" |
416 | Condition variables can be created by calling the "AnyEvent->condvar" |
302 | method, usually without arguments. The only argument pair allowed is |
417 | method, usually without arguments. The only argument pair allowed is |
|
|
418 | |
303 | "cb", which specifies a callback to be called when the condition |
419 | "cb", which specifies a callback to be called when the condition |
304 | variable becomes true. |
420 | variable becomes true, with the condition variable as the first argument |
|
|
421 | (but not the results). |
305 | |
422 | |
306 | After creation, the conditon variable is "false" until it becomes "true" |
423 | After creation, the condition variable is "false" until it becomes |
|
|
424 | "true" by calling the "send" method (or calling the condition variable |
|
|
425 | as if it were a callback, read about the caveats in the description for |
307 | by calling the "send" method. |
426 | the "->send" method). |
308 | |
427 | |
309 | Condition variables are similar to callbacks, except that you can |
428 | Condition variables are similar to callbacks, except that you can |
310 | optionally wait for them. They can also be called merge points - points |
429 | optionally wait for them. They can also be called merge points - points |
311 | in time where multiple outstandign events have been processed. And yet |
430 | in time where multiple outstanding events have been processed. And yet |
312 | another way to call them is transations - each condition variable can be |
431 | another way to call them is transactions - each condition variable can |
313 | used to represent a transaction, which finishes at some point and |
432 | be used to represent a transaction, which finishes at some point and |
314 | delivers a result. |
433 | delivers a result. |
315 | |
434 | |
316 | Condition variables are very useful to signal that something has |
435 | Condition variables are very useful to signal that something has |
317 | finished, for example, if you write a module that does asynchronous http |
436 | finished, for example, if you write a module that does asynchronous http |
318 | requests, then a condition variable would be the ideal candidate to |
437 | requests, then a condition variable would be the ideal candidate to |
… | |
… | |
323 | you can block your main program until an event occurs - for example, you |
442 | you can block your main program until an event occurs - for example, you |
324 | could "->recv" in your main program until the user clicks the Quit |
443 | could "->recv" in your main program until the user clicks the Quit |
325 | button of your app, which would "->send" the "quit" event. |
444 | button of your app, which would "->send" the "quit" event. |
326 | |
445 | |
327 | Note that condition variables recurse into the event loop - if you have |
446 | Note that condition variables recurse into the event loop - if you have |
328 | two pieces of code that call "->recv" in a round-robbin fashion, you |
447 | two pieces of code that call "->recv" in a round-robin fashion, you |
329 | lose. Therefore, condition variables are good to export to your caller, |
448 | lose. Therefore, condition variables are good to export to your caller, |
330 | but you should avoid making a blocking wait yourself, at least in |
449 | but you should avoid making a blocking wait yourself, at least in |
331 | callbacks, as this asks for trouble. |
450 | callbacks, as this asks for trouble. |
332 | |
451 | |
333 | Condition variables are represented by hash refs in perl, and the keys |
452 | Condition variables are represented by hash refs in perl, and the keys |
… | |
… | |
338 | |
457 | |
339 | There are two "sides" to a condition variable - the "producer side" |
458 | There are two "sides" to a condition variable - the "producer side" |
340 | which eventually calls "-> send", and the "consumer side", which waits |
459 | which eventually calls "-> send", and the "consumer side", which waits |
341 | for the send to occur. |
460 | for the send to occur. |
342 | |
461 | |
343 | Example: |
462 | Example: wait for a timer. |
344 | |
463 | |
345 | # wait till the result is ready |
464 | # wait till the result is ready |
346 | my $result_ready = AnyEvent->condvar; |
465 | my $result_ready = AnyEvent->condvar; |
347 | |
466 | |
348 | # do something such as adding a timer |
467 | # do something such as adding a timer |
… | |
… | |
356 | |
475 | |
357 | # this "blocks" (while handling events) till the callback |
476 | # this "blocks" (while handling events) till the callback |
358 | # calls send |
477 | # calls send |
359 | $result_ready->recv; |
478 | $result_ready->recv; |
360 | |
479 | |
|
|
480 | Example: wait for a timer, but take advantage of the fact that condition |
|
|
481 | variables are also code references. |
|
|
482 | |
|
|
483 | my $done = AnyEvent->condvar; |
|
|
484 | my $delay = AnyEvent->timer (after => 5, cb => $done); |
|
|
485 | $done->recv; |
|
|
486 | |
|
|
487 | Example: Imagine an API that returns a condvar and doesn't support |
|
|
488 | callbacks. This is how you make a synchronous call, for example from the |
|
|
489 | main program: |
|
|
490 | |
|
|
491 | use AnyEvent::CouchDB; |
|
|
492 | |
|
|
493 | ... |
|
|
494 | |
|
|
495 | my @info = $couchdb->info->recv; |
|
|
496 | |
|
|
497 | And this is how you would just ste a callback to be called whenever the |
|
|
498 | results are available: |
|
|
499 | |
|
|
500 | $couchdb->info->cb (sub { |
|
|
501 | my @info = $_[0]->recv; |
|
|
502 | }); |
|
|
503 | |
361 | METHODS FOR PRODUCERS |
504 | METHODS FOR PRODUCERS |
362 | These methods should only be used by the producing side, i.e. the |
505 | These methods should only be used by the producing side, i.e. the |
363 | code/module that eventually sends the signal. Note that it is also the |
506 | code/module that eventually sends the signal. Note that it is also the |
364 | producer side which creates the condvar in most cases, but it isn't |
507 | producer side which creates the condvar in most cases, but it isn't |
365 | uncommon for the consumer to create it as well. |
508 | uncommon for the consumer to create it as well. |
… | |
… | |
372 | If a callback has been set on the condition variable, it is called |
515 | If a callback has been set on the condition variable, it is called |
373 | immediately from within send. |
516 | immediately from within send. |
374 | |
517 | |
375 | Any arguments passed to the "send" call will be returned by all |
518 | Any arguments passed to the "send" call will be returned by all |
376 | future "->recv" calls. |
519 | future "->recv" calls. |
|
|
520 | |
|
|
521 | Condition variables are overloaded so one can call them directly (as |
|
|
522 | a code reference). Calling them directly is the same as calling |
|
|
523 | "send". Note, however, that many C-based event loops do not handle |
|
|
524 | overloading, so as tempting as it may be, passing a condition |
|
|
525 | variable instead of a callback does not work. Both the pure perl and |
|
|
526 | EV loops support overloading, however, as well as all functions that |
|
|
527 | use perl to invoke a callback (as in AnyEvent::Socket and |
|
|
528 | AnyEvent::DNS for example). |
377 | |
529 | |
378 | $cv->croak ($error) |
530 | $cv->croak ($error) |
379 | Similar to send, but causes all call's to "->recv" to invoke |
531 | Similar to send, but causes all call's to "->recv" to invoke |
380 | "Carp::croak" with the given error message/object/scalar. |
532 | "Carp::croak" with the given error message/object/scalar. |
381 | |
533 | |
… | |
… | |
427 | (the loop doesn't execute once). |
579 | (the loop doesn't execute once). |
428 | |
580 | |
429 | This is the general pattern when you "fan out" into multiple |
581 | This is the general pattern when you "fan out" into multiple |
430 | subrequests: use an outer "begin"/"end" pair to set the callback and |
582 | subrequests: use an outer "begin"/"end" pair to set the callback and |
431 | ensure "end" is called at least once, and then, for each subrequest |
583 | ensure "end" is called at least once, and then, for each subrequest |
432 | you start, call "begin" and for eahc subrequest you finish, call |
584 | you start, call "begin" and for each subrequest you finish, call |
433 | "end". |
585 | "end". |
434 | |
586 | |
435 | METHODS FOR CONSUMERS |
587 | METHODS FOR CONSUMERS |
436 | These methods should only be used by the consuming side, i.e. the code |
588 | These methods should only be used by the consuming side, i.e. the code |
437 | awaits the condition. |
589 | awaits the condition. |
… | |
… | |
453 | (programs might want to do that to stay interactive), so *if you are |
605 | (programs might want to do that to stay interactive), so *if you are |
454 | using this from a module, never require a blocking wait*, but let |
606 | using this from a module, never require a blocking wait*, but let |
455 | the caller decide whether the call will block or not (for example, |
607 | the caller decide whether the call will block or not (for example, |
456 | by coupling condition variables with some kind of request results |
608 | by coupling condition variables with some kind of request results |
457 | and supporting callbacks so the caller knows that getting the result |
609 | and supporting callbacks so the caller knows that getting the result |
458 | will not block, while still suppporting blocking waits if the caller |
610 | will not block, while still supporting blocking waits if the caller |
459 | so desires). |
611 | so desires). |
460 | |
612 | |
461 | Another reason *never* to "->recv" in a module is that you cannot |
613 | Another reason *never* to "->recv" in a module is that you cannot |
462 | sensibly have two "->recv"'s in parallel, as that would require |
614 | sensibly have two "->recv"'s in parallel, as that would require |
463 | multiple interpreters or coroutines/threads, none of which |
615 | multiple interpreters or coroutines/threads, none of which |
… | |
… | |
476 | |
628 | |
477 | $bool = $cv->ready |
629 | $bool = $cv->ready |
478 | Returns true when the condition is "true", i.e. whether "send" or |
630 | Returns true when the condition is "true", i.e. whether "send" or |
479 | "croak" have been called. |
631 | "croak" have been called. |
480 | |
632 | |
481 | $cb = $cv->cb ([new callback]) |
633 | $cb = $cv->cb ($cb->($cv)) |
482 | This is a mutator function that returns the callback set and |
634 | This is a mutator function that returns the callback set and |
483 | optionally replaces it before doing so. |
635 | optionally replaces it before doing so. |
484 | |
636 | |
485 | The callback will be called when the condition becomes "true", i.e. |
637 | The callback will be called when the condition becomes "true", i.e. |
486 | when "send" or "croak" are called. Calling "recv" inside the |
638 | when "send" or "croak" are called, with the only argument being the |
|
|
639 | condition variable itself. Calling "recv" inside the callback or at |
487 | callback or at any later time is guaranteed not to block. |
640 | any later time is guaranteed not to block. |
488 | |
641 | |
489 | GLOBAL VARIABLES AND FUNCTIONS |
642 | GLOBAL VARIABLES AND FUNCTIONS |
490 | $AnyEvent::MODEL |
643 | $AnyEvent::MODEL |
491 | Contains "undef" until the first watcher is being created. Then it |
644 | Contains "undef" until the first watcher is being created. Then it |
492 | contains the event model that is being used, which is the name of |
645 | contains the event model that is being used, which is the name of |
… | |
… | |
566 | If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
719 | If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
567 | do anything special (it does not need to be event-based) and let |
720 | do anything special (it does not need to be event-based) and let |
568 | AnyEvent decide which implementation to chose if some module relies on |
721 | AnyEvent decide which implementation to chose if some module relies on |
569 | it. |
722 | it. |
570 | |
723 | |
571 | If the main program relies on a specific event model. For example, in |
724 | If the main program relies on a specific event model - for example, in |
572 | Gtk2 programs you have to rely on the Glib module. You should load the |
725 | Gtk2 programs you have to rely on the Glib module - you should load the |
573 | event module before loading AnyEvent or any module that uses it: |
726 | event module before loading AnyEvent or any module that uses it: |
574 | generally speaking, you should load it as early as possible. The reason |
727 | generally speaking, you should load it as early as possible. The reason |
575 | is that modules might create watchers when they are loaded, and AnyEvent |
728 | is that modules might create watchers when they are loaded, and AnyEvent |
576 | will decide on the event model to use as soon as it creates watchers, |
729 | will decide on the event model to use as soon as it creates watchers, |
577 | and it might chose the wrong one unless you load the correct one |
730 | and it might chose the wrong one unless you load the correct one |
578 | yourself. |
731 | yourself. |
579 | |
732 | |
580 | You can chose to use a rather inefficient pure-perl implementation by |
733 | You can chose to use a pure-perl implementation by loading the |
581 | loading the "AnyEvent::Impl::Perl" module, which gives you similar |
734 | "AnyEvent::Impl::Perl" module, which gives you similar behaviour |
582 | behaviour everywhere, but letting AnyEvent chose is generally better. |
735 | everywhere, but letting AnyEvent chose the model is generally better. |
|
|
736 | |
|
|
737 | MAINLOOP EMULATION |
|
|
738 | Sometimes (often for short test scripts, or even standalone programs who |
|
|
739 | only want to use AnyEvent), you do not want to run a specific event |
|
|
740 | loop. |
|
|
741 | |
|
|
742 | In that case, you can use a condition variable like this: |
|
|
743 | |
|
|
744 | AnyEvent->condvar->recv; |
|
|
745 | |
|
|
746 | This has the effect of entering the event loop and looping forever. |
|
|
747 | |
|
|
748 | Note that usually your program has some exit condition, in which case it |
|
|
749 | is better to use the "traditional" approach of storing a condition |
|
|
750 | variable somewhere, waiting for it, and sending it when the program |
|
|
751 | should exit cleanly. |
583 | |
752 | |
584 | OTHER MODULES |
753 | OTHER MODULES |
585 | The following is a non-exhaustive list of additional modules that use |
754 | The following is a non-exhaustive list of additional modules that use |
586 | AnyEvent and can therefore be mixed easily with other AnyEvent modules |
755 | AnyEvent and can therefore be mixed easily with other AnyEvent modules |
587 | in the same program. Some of the modules come with AnyEvent, some are |
756 | in the same program. Some of the modules come with AnyEvent, some are |
… | |
… | |
590 | AnyEvent::Util |
759 | AnyEvent::Util |
591 | Contains various utility functions that replace often-used but |
760 | Contains various utility functions that replace often-used but |
592 | blocking functions such as "inet_aton" by event-/callback-based |
761 | blocking functions such as "inet_aton" by event-/callback-based |
593 | versions. |
762 | versions. |
594 | |
763 | |
|
|
764 | AnyEvent::Socket |
|
|
765 | Provides various utility functions for (internet protocol) sockets, |
|
|
766 | addresses and name resolution. Also functions to create non-blocking |
|
|
767 | tcp connections or tcp servers, with IPv6 and SRV record support and |
|
|
768 | more. |
|
|
769 | |
595 | AnyEvent::Handle |
770 | AnyEvent::Handle |
596 | Provide read and write buffers and manages watchers for reads and |
771 | Provide read and write buffers, manages watchers for reads and |
597 | writes. |
772 | writes, supports raw and formatted I/O, I/O queued and fully |
|
|
773 | transparent and non-blocking SSL/TLS. |
|
|
774 | |
|
|
775 | AnyEvent::DNS |
|
|
776 | Provides rich asynchronous DNS resolver capabilities. |
|
|
777 | |
|
|
778 | AnyEvent::HTTP |
|
|
779 | A simple-to-use HTTP library that is capable of making a lot of |
|
|
780 | concurrent HTTP requests. |
598 | |
781 | |
599 | AnyEvent::HTTPD |
782 | AnyEvent::HTTPD |
600 | Provides a simple web application server framework. |
783 | Provides a simple web application server framework. |
601 | |
784 | |
602 | AnyEvent::DNS |
|
|
603 | Provides asynchronous DNS resolver capabilities, beyond what |
|
|
604 | AnyEvent::Util offers. |
|
|
605 | |
|
|
606 | AnyEvent::FastPing |
785 | AnyEvent::FastPing |
607 | The fastest ping in the west. |
786 | The fastest ping in the west. |
608 | |
787 | |
|
|
788 | AnyEvent::DBI |
|
|
789 | Executes DBI requests asynchronously in a proxy process. |
|
|
790 | |
|
|
791 | AnyEvent::AIO |
|
|
792 | Truly asynchronous I/O, should be in the toolbox of every event |
|
|
793 | programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent |
|
|
794 | together. |
|
|
795 | |
|
|
796 | AnyEvent::BDB |
|
|
797 | Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently |
|
|
798 | fuses BDB and AnyEvent together. |
|
|
799 | |
|
|
800 | AnyEvent::GPSD |
|
|
801 | A non-blocking interface to gpsd, a daemon delivering GPS |
|
|
802 | information. |
|
|
803 | |
|
|
804 | AnyEvent::IGS |
|
|
805 | A non-blocking interface to the Internet Go Server protocol (used by |
|
|
806 | App::IGS). |
|
|
807 | |
|
|
808 | AnyEvent::IRC |
|
|
809 | AnyEvent based IRC client module family (replacing the older |
609 | Net::IRC3 |
810 | Net::IRC3). |
610 | AnyEvent based IRC client module family. |
|
|
611 | |
811 | |
612 | Net::XMPP2 |
812 | Net::XMPP2 |
613 | AnyEvent based XMPP (Jabber protocol) module family. |
813 | AnyEvent based XMPP (Jabber protocol) module family. |
614 | |
814 | |
615 | Net::FCP |
815 | Net::FCP |
… | |
… | |
620 | High level API for event-based execution flow control. |
820 | High level API for event-based execution flow control. |
621 | |
821 | |
622 | Coro |
822 | Coro |
623 | Has special support for AnyEvent via Coro::AnyEvent. |
823 | Has special support for AnyEvent via Coro::AnyEvent. |
624 | |
824 | |
625 | AnyEvent::AIO, IO::AIO |
|
|
626 | Truly asynchronous I/O, should be in the toolbox of every event |
|
|
627 | programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent |
|
|
628 | together. |
|
|
629 | |
|
|
630 | AnyEvent::BDB, BDB |
|
|
631 | Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently |
|
|
632 | fuses IO::AIO and AnyEvent together. |
|
|
633 | |
|
|
634 | IO::Lambda |
825 | IO::Lambda |
635 | The lambda approach to I/O - don't ask, look there. Can use |
826 | The lambda approach to I/O - don't ask, look there. Can use |
636 | AnyEvent. |
827 | AnyEvent. |
|
|
828 | |
|
|
829 | ERROR AND EXCEPTION HANDLING |
|
|
830 | In general, AnyEvent does not do any error handling - it relies on the |
|
|
831 | caller to do that if required. The AnyEvent::Strict module (see also the |
|
|
832 | "PERL_ANYEVENT_STRICT" environment variable, below) provides strict |
|
|
833 | checking of all AnyEvent methods, however, which is highly useful during |
|
|
834 | development. |
|
|
835 | |
|
|
836 | As for exception handling (i.e. runtime errors and exceptions thrown |
|
|
837 | while executing a callback), this is not only highly event-loop |
|
|
838 | specific, but also not in any way wrapped by this module, as this is the |
|
|
839 | job of the main program. |
|
|
840 | |
|
|
841 | The pure perl event loop simply re-throws the exception (usually within |
|
|
842 | "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()", |
|
|
843 | Glib uses "install_exception_handler" and so on. |
|
|
844 | |
|
|
845 | ENVIRONMENT VARIABLES |
|
|
846 | The following environment variables are used by this module or its |
|
|
847 | submodules: |
|
|
848 | |
|
|
849 | "PERL_ANYEVENT_VERBOSE" |
|
|
850 | By default, AnyEvent will be completely silent except in fatal |
|
|
851 | conditions. You can set this environment variable to make AnyEvent |
|
|
852 | more talkative. |
|
|
853 | |
|
|
854 | When set to 1 or higher, causes AnyEvent to warn about unexpected |
|
|
855 | conditions, such as not being able to load the event model specified |
|
|
856 | by "PERL_ANYEVENT_MODEL". |
|
|
857 | |
|
|
858 | When set to 2 or higher, cause AnyEvent to report to STDERR which |
|
|
859 | event model it chooses. |
|
|
860 | |
|
|
861 | "PERL_ANYEVENT_STRICT" |
|
|
862 | AnyEvent does not do much argument checking by default, as thorough |
|
|
863 | argument checking is very costly. Setting this variable to a true |
|
|
864 | value will cause AnyEvent to load "AnyEvent::Strict" and then to |
|
|
865 | thoroughly check the arguments passed to most method calls. If it |
|
|
866 | finds any problems it will croak. |
|
|
867 | |
|
|
868 | In other words, enables "strict" mode. |
|
|
869 | |
|
|
870 | Unlike "use strict", it is definitely recommended ot keep it off in |
|
|
871 | production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment |
|
|
872 | while developing programs can be very useful, however. |
|
|
873 | |
|
|
874 | "PERL_ANYEVENT_MODEL" |
|
|
875 | This can be used to specify the event model to be used by AnyEvent, |
|
|
876 | before auto detection and -probing kicks in. It must be a string |
|
|
877 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
|
|
878 | gets prepended and the resulting module name is loaded and if the |
|
|
879 | load was successful, used as event model. If it fails to load |
|
|
880 | AnyEvent will proceed with auto detection and -probing. |
|
|
881 | |
|
|
882 | This functionality might change in future versions. |
|
|
883 | |
|
|
884 | For example, to force the pure perl model (AnyEvent::Impl::Perl) you |
|
|
885 | could start your program like this: |
|
|
886 | |
|
|
887 | PERL_ANYEVENT_MODEL=Perl perl ... |
|
|
888 | |
|
|
889 | "PERL_ANYEVENT_PROTOCOLS" |
|
|
890 | Used by both AnyEvent::DNS and AnyEvent::Socket to determine |
|
|
891 | preferences for IPv4 or IPv6. The default is unspecified (and might |
|
|
892 | change, or be the result of auto probing). |
|
|
893 | |
|
|
894 | Must be set to a comma-separated list of protocols or address |
|
|
895 | families, current supported: "ipv4" and "ipv6". Only protocols |
|
|
896 | mentioned will be used, and preference will be given to protocols |
|
|
897 | mentioned earlier in the list. |
|
|
898 | |
|
|
899 | This variable can effectively be used for denial-of-service attacks |
|
|
900 | against local programs (e.g. when setuid), although the impact is |
|
|
901 | likely small, as the program has to handle conenction and other |
|
|
902 | failures anyways. |
|
|
903 | |
|
|
904 | Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
|
|
905 | IPv6, but support both and try to use both. |
|
|
906 | "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
|
|
907 | resolve or contact IPv6 addresses. |
|
|
908 | "PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but |
|
|
909 | prefer IPv6 over IPv4. |
|
|
910 | |
|
|
911 | "PERL_ANYEVENT_EDNS0" |
|
|
912 | Used by AnyEvent::DNS to decide whether to use the EDNS0 extension |
|
|
913 | for DNS. This extension is generally useful to reduce DNS traffic, |
|
|
914 | but some (broken) firewalls drop such DNS packets, which is why it |
|
|
915 | is off by default. |
|
|
916 | |
|
|
917 | Setting this variable to 1 will cause AnyEvent::DNS to announce |
|
|
918 | EDNS0 in its DNS requests. |
|
|
919 | |
|
|
920 | "PERL_ANYEVENT_MAX_FORKS" |
|
|
921 | The maximum number of child processes that |
|
|
922 | "AnyEvent::Util::fork_call" will create in parallel. |
637 | |
923 | |
638 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
924 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
639 | This is an advanced topic that you do not normally need to use AnyEvent |
925 | This is an advanced topic that you do not normally need to use AnyEvent |
640 | in a module. This section is only of use to event loop authors who want |
926 | in a module. This section is only of use to event loop authors who want |
641 | to provide AnyEvent compatibility. |
927 | to provide AnyEvent compatibility. |
… | |
… | |
675 | |
961 | |
676 | *rxvt-unicode* also cheats a bit by not providing blocking access to |
962 | *rxvt-unicode* also cheats a bit by not providing blocking access to |
677 | condition variables: code blocking while waiting for a condition will |
963 | condition variables: code blocking while waiting for a condition will |
678 | "die". This still works with most modules/usages, and blocking calls |
964 | "die". This still works with most modules/usages, and blocking calls |
679 | must not be done in an interactive application, so it makes sense. |
965 | must not be done in an interactive application, so it makes sense. |
680 | |
|
|
681 | ENVIRONMENT VARIABLES |
|
|
682 | The following environment variables are used by this module: |
|
|
683 | |
|
|
684 | "PERL_ANYEVENT_VERBOSE" |
|
|
685 | By default, AnyEvent will be completely silent except in fatal |
|
|
686 | conditions. You can set this environment variable to make AnyEvent |
|
|
687 | more talkative. |
|
|
688 | |
|
|
689 | When set to 1 or higher, causes AnyEvent to warn about unexpected |
|
|
690 | conditions, such as not being able to load the event model specified |
|
|
691 | by "PERL_ANYEVENT_MODEL". |
|
|
692 | |
|
|
693 | When set to 2 or higher, cause AnyEvent to report to STDERR which |
|
|
694 | event model it chooses. |
|
|
695 | |
|
|
696 | "PERL_ANYEVENT_MODEL" |
|
|
697 | This can be used to specify the event model to be used by AnyEvent, |
|
|
698 | before autodetection and -probing kicks in. It must be a string |
|
|
699 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
|
|
700 | gets prepended and the resulting module name is loaded and if the |
|
|
701 | load was successful, used as event model. If it fails to load |
|
|
702 | AnyEvent will proceed with autodetection and -probing. |
|
|
703 | |
|
|
704 | This functionality might change in future versions. |
|
|
705 | |
|
|
706 | For example, to force the pure perl model (AnyEvent::Impl::Perl) you |
|
|
707 | could start your program like this: |
|
|
708 | |
|
|
709 | PERL_ANYEVENT_MODEL=Perl perl ... |
|
|
710 | |
966 | |
711 | EXAMPLE PROGRAM |
967 | EXAMPLE PROGRAM |
712 | The following program uses an I/O watcher to read data from STDIN, a |
968 | The following program uses an I/O watcher to read data from STDIN, a |
713 | timer to display a message once per second, and a condition variable to |
969 | timer to display a message once per second, and a condition variable to |
714 | quit the program when the user enters quit: |
970 | quit the program when the user enters quit: |
… | |
… | |
722 | poll => 'r', |
978 | poll => 'r', |
723 | cb => sub { |
979 | cb => sub { |
724 | warn "io event <$_[0]>\n"; # will always output <r> |
980 | warn "io event <$_[0]>\n"; # will always output <r> |
725 | chomp (my $input = <STDIN>); # read a line |
981 | chomp (my $input = <STDIN>); # read a line |
726 | warn "read: $input\n"; # output what has been read |
982 | warn "read: $input\n"; # output what has been read |
727 | $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i |
983 | $cv->send if $input =~ /^q/i; # quit program if /^q/i |
728 | }, |
984 | }, |
729 | ); |
985 | ); |
730 | |
986 | |
731 | my $time_watcher; # can only be used once |
987 | my $time_watcher; # can only be used once |
732 | |
988 | |
… | |
… | |
737 | }); |
993 | }); |
738 | } |
994 | } |
739 | |
995 | |
740 | new_timer; # create first timer |
996 | new_timer; # create first timer |
741 | |
997 | |
742 | $cv->wait; # wait until user enters /^q/i |
998 | $cv->recv; # wait until user enters /^q/i |
743 | |
999 | |
744 | REAL-WORLD EXAMPLE |
1000 | REAL-WORLD EXAMPLE |
745 | Consider the Net::FCP module. It features (among others) the following |
1001 | Consider the Net::FCP module. It features (among others) the following |
746 | API calls, which are to freenet what HTTP GET requests are to http: |
1002 | API calls, which are to freenet what HTTP GET requests are to http: |
747 | |
1003 | |
… | |
… | |
796 | syswrite $txn->{fh}, $txn->{request} |
1052 | syswrite $txn->{fh}, $txn->{request} |
797 | or die "connection or write error"; |
1053 | or die "connection or write error"; |
798 | $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
1054 | $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
799 | |
1055 | |
800 | Again, "fh_ready_r" waits till all data has arrived, and then stores the |
1056 | Again, "fh_ready_r" waits till all data has arrived, and then stores the |
801 | result and signals any possible waiters that the request ahs finished: |
1057 | result and signals any possible waiters that the request has finished: |
802 | |
1058 | |
803 | sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
1059 | sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
804 | |
1060 | |
805 | if (end-of-file or data complete) { |
1061 | if (end-of-file or data complete) { |
806 | $txn->{result} = $txn->{buf}; |
1062 | $txn->{result} = $txn->{buf}; |
807 | $txn->{finished}->broadcast; |
1063 | $txn->{finished}->send; |
808 | $txb->{cb}->($txn) of $txn->{cb}; # also call callback |
1064 | $txb->{cb}->($txn) of $txn->{cb}; # also call callback |
809 | } |
1065 | } |
810 | |
1066 | |
811 | The "result" method, finally, just waits for the finished signal (if the |
1067 | The "result" method, finally, just waits for the finished signal (if the |
812 | request was already finished, it doesn't wait, of course, and returns |
1068 | request was already finished, it doesn't wait, of course, and returns |
813 | the data: |
1069 | the data: |
814 | |
1070 | |
815 | $txn->{finished}->wait; |
1071 | $txn->{finished}->recv; |
816 | return $txn->{result}; |
1072 | return $txn->{result}; |
817 | |
1073 | |
818 | The actual code goes further and collects all errors ("die"s, |
1074 | The actual code goes further and collects all errors ("die"s, |
819 | exceptions) that occured during request processing. The "result" method |
1075 | exceptions) that occurred during request processing. The "result" method |
820 | detects whether an exception as thrown (it is stored inside the $txn |
1076 | detects whether an exception as thrown (it is stored inside the $txn |
821 | object) and just throws the exception, which means connection errors and |
1077 | object) and just throws the exception, which means connection errors and |
822 | other problems get reported tot he code that tries to use the result, |
1078 | other problems get reported tot he code that tries to use the result, |
823 | not in a random callback. |
1079 | not in a random callback. |
824 | |
1080 | |
… | |
… | |
855 | |
1111 | |
856 | my $quit = AnyEvent->condvar; |
1112 | my $quit = AnyEvent->condvar; |
857 | |
1113 | |
858 | $fcp->txn_client_get ($url)->cb (sub { |
1114 | $fcp->txn_client_get ($url)->cb (sub { |
859 | ... |
1115 | ... |
860 | $quit->broadcast; |
1116 | $quit->send; |
861 | }); |
1117 | }); |
862 | |
1118 | |
863 | $quit->wait; |
1119 | $quit->recv; |
864 | |
1120 | |
865 | BENCHMARKS |
1121 | BENCHMARKS |
866 | To give you an idea of the performance and overheads that AnyEvent adds |
1122 | To give you an idea of the performance and overheads that AnyEvent adds |
867 | over the event loops themselves and to give you an impression of the |
1123 | over the event loops themselves and to give you an impression of the |
868 | speed of various event loops I prepared some benchmarks. |
1124 | speed of various event loops I prepared some benchmarks. |
869 | |
1125 | |
870 | BENCHMARKING ANYEVENT OVERHEAD |
1126 | BENCHMARKING ANYEVENT OVERHEAD |
871 | Here is a benchmark of various supported event models used natively and |
1127 | Here is a benchmark of various supported event models used natively and |
872 | through anyevent. The benchmark creates a lot of timers (with a zero |
1128 | through AnyEvent. The benchmark creates a lot of timers (with a zero |
873 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
1129 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
874 | which it is), lets them fire exactly once and destroys them again. |
1130 | which it is), lets them fire exactly once and destroys them again. |
875 | |
1131 | |
876 | Source code for this benchmark is found as eg/bench in the AnyEvent |
1132 | Source code for this benchmark is found as eg/bench in the AnyEvent |
877 | distribution. |
1133 | distribution. |
… | |
… | |
893 | between all watchers, to avoid adding memory overhead. That means |
1149 | between all watchers, to avoid adding memory overhead. That means |
894 | closure creation and memory usage is not included in the figures. |
1150 | closure creation and memory usage is not included in the figures. |
895 | |
1151 | |
896 | *invoke* is the time, in microseconds, used to invoke a simple callback. |
1152 | *invoke* is the time, in microseconds, used to invoke a simple callback. |
897 | The callback simply counts down a Perl variable and after it was invoked |
1153 | The callback simply counts down a Perl variable and after it was invoked |
898 | "watcher" times, it would "->broadcast" a condvar once to signal the end |
1154 | "watcher" times, it would "->send" a condvar once to signal the end of |
899 | of this phase. |
1155 | this phase. |
900 | |
1156 | |
901 | *destroy* is the time, in microseconds, that it takes to destroy a |
1157 | *destroy* is the time, in microseconds, that it takes to destroy a |
902 | single watcher. |
1158 | single watcher. |
903 | |
1159 | |
904 | Results |
1160 | Results |
905 | name watchers bytes create invoke destroy comment |
1161 | name watchers bytes create invoke destroy comment |
906 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
1162 | EV/EV 400000 224 0.47 0.35 0.27 EV native interface |
907 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
1163 | EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers |
908 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
1164 | CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal |
909 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
1165 | Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation |
910 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
1166 | Event/Event 16000 517 32.20 31.80 0.81 Event native interface |
911 | Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers |
1167 | Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers |
912 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
1168 | Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour |
913 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
1169 | Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers |
914 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
1170 | POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event |
915 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
1171 | POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select |
916 | |
1172 | |
917 | Discussion |
1173 | Discussion |
918 | The benchmark does *not* measure scalability of the event loop very |
1174 | The benchmark does *not* measure scalability of the event loop very |
919 | well. For example, a select-based event loop (such as the pure perl one) |
1175 | well. For example, a select-based event loop (such as the pure perl one) |
920 | can never compete with an event loop that uses epoll when the number of |
1176 | can never compete with an event loop that uses epoll when the number of |
… | |
… | |
992 | |
1248 | |
993 | * You should avoid POE like the plague if you want performance or |
1249 | * You should avoid POE like the plague if you want performance or |
994 | reasonable memory usage. |
1250 | reasonable memory usage. |
995 | |
1251 | |
996 | BENCHMARKING THE LARGE SERVER CASE |
1252 | BENCHMARKING THE LARGE SERVER CASE |
997 | This benchmark atcually benchmarks the event loop itself. It works by |
1253 | This benchmark actually benchmarks the event loop itself. It works by |
998 | creating a number of "servers": each server consists of a socketpair, a |
1254 | creating a number of "servers": each server consists of a socket pair, a |
999 | timeout watcher that gets reset on activity (but never fires), and an |
1255 | timeout watcher that gets reset on activity (but never fires), and an |
1000 | I/O watcher waiting for input on one side of the socket. Each time the |
1256 | I/O watcher waiting for input on one side of the socket. Each time the |
1001 | socket watcher reads a byte it will write that byte to a random other |
1257 | socket watcher reads a byte it will write that byte to a random other |
1002 | "server". |
1258 | "server". |
1003 | |
1259 | |
1004 | The effect is that there will be a lot of I/O watchers, only part of |
1260 | The effect is that there will be a lot of I/O watchers, only part of |
1005 | which are active at any one point (so there is a constant number of |
1261 | which are active at any one point (so there is a constant number of |
1006 | active fds for each loop iterstaion, but which fds these are is random). |
1262 | active fds for each loop iteration, but which fds these are is random). |
1007 | The timeout is reset each time something is read because that reflects |
1263 | The timeout is reset each time something is read because that reflects |
1008 | how most timeouts work (and puts extra pressure on the event loops). |
1264 | how most timeouts work (and puts extra pressure on the event loops). |
1009 | |
1265 | |
1010 | In this benchmark, we use 10000 socketpairs (20000 sockets), of which |
1266 | In this benchmark, we use 10000 socket pairs (20000 sockets), of which |
1011 | 100 (1%) are active. This mirrors the activity of large servers with |
1267 | 100 (1%) are active. This mirrors the activity of large servers with |
1012 | many connections, most of which are idle at any one point in time. |
1268 | many connections, most of which are idle at any one point in time. |
1013 | |
1269 | |
1014 | Source code for this benchmark is found as eg/bench2 in the AnyEvent |
1270 | Source code for this benchmark is found as eg/bench2 in the AnyEvent |
1015 | distribution. |
1271 | distribution. |
1016 | |
1272 | |
1017 | Explanation of the columns |
1273 | Explanation of the columns |
1018 | *sockets* is the number of sockets, and twice the number of "servers" |
1274 | *sockets* is the number of sockets, and twice the number of "servers" |
1019 | (as each server has a read and write socket end). |
1275 | (as each server has a read and write socket end). |
1020 | |
1276 | |
1021 | *create* is the time it takes to create a socketpair (which is |
1277 | *create* is the time it takes to create a socket pair (which is |
1022 | nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
1278 | nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
1023 | |
1279 | |
1024 | *request*, the most important value, is the time it takes to handle a |
1280 | *request*, the most important value, is the time it takes to handle a |
1025 | single "request", that is, reading the token from the pipe and |
1281 | single "request", that is, reading the token from the pipe and |
1026 | forwarding it to another server. This includes deleting the old timeout |
1282 | forwarding it to another server. This includes deleting the old timeout |
… | |
… | |
1090 | and speed most when you have lots of watchers, not when you only have a |
1346 | and speed most when you have lots of watchers, not when you only have a |
1091 | few of them). |
1347 | few of them). |
1092 | |
1348 | |
1093 | EV is again fastest. |
1349 | EV is again fastest. |
1094 | |
1350 | |
1095 | Perl again comes second. It is noticably faster than the C-based event |
1351 | Perl again comes second. It is noticeably faster than the C-based event |
1096 | loops Event and Glib, although the difference is too small to really |
1352 | loops Event and Glib, although the difference is too small to really |
1097 | matter. |
1353 | matter. |
1098 | |
1354 | |
1099 | POE also performs much better in this case, but is is still far behind |
1355 | POE also performs much better in this case, but is is still far behind |
1100 | the others. |
1356 | the others. |
1101 | |
1357 | |
1102 | Summary |
1358 | Summary |
1103 | * C-based event loops perform very well with small number of watchers, |
1359 | * C-based event loops perform very well with small number of watchers, |
1104 | as the management overhead dominates. |
1360 | as the management overhead dominates. |
|
|
1361 | |
|
|
1362 | SIGNALS |
|
|
1363 | AnyEvent currently installs handlers for these signals: |
|
|
1364 | |
|
|
1365 | SIGCHLD |
|
|
1366 | A handler for "SIGCHLD" is installed by AnyEvent's child watcher |
|
|
1367 | emulation for event loops that do not support them natively. Also, |
|
|
1368 | some event loops install a similar handler. |
|
|
1369 | |
|
|
1370 | SIGPIPE |
|
|
1371 | A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is |
|
|
1372 | "undef" when AnyEvent gets loaded. |
|
|
1373 | |
|
|
1374 | The rationale for this is that AnyEvent users usually do not really |
|
|
1375 | depend on SIGPIPE delivery (which is purely an optimisation for |
|
|
1376 | shell use, or badly-written programs), but "SIGPIPE" can cause |
|
|
1377 | spurious and rare program exits as a lot of people do not expect |
|
|
1378 | "SIGPIPE" when writing to some random socket. |
|
|
1379 | |
|
|
1380 | The rationale for installing a no-op handler as opposed to ignoring |
|
|
1381 | it is that this way, the handler will be restored to defaults on |
|
|
1382 | exec. |
|
|
1383 | |
|
|
1384 | Feel free to install your own handler, or reset it to defaults. |
1105 | |
1385 | |
1106 | FORK |
1386 | FORK |
1107 | Most event libraries are not fork-safe. The ones who are usually are |
1387 | Most event libraries are not fork-safe. The ones who are usually are |
1108 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1388 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1109 | Only EV is fully fork-aware. |
1389 | Only EV is fully fork-aware. |
… | |
… | |
1120 | model than specified in the variable. |
1400 | model than specified in the variable. |
1121 | |
1401 | |
1122 | You can make AnyEvent completely ignore this variable by deleting it |
1402 | You can make AnyEvent completely ignore this variable by deleting it |
1123 | before the first watcher gets created, e.g. with a "BEGIN" block: |
1403 | before the first watcher gets created, e.g. with a "BEGIN" block: |
1124 | |
1404 | |
1125 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1405 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1126 | |
1406 | |
1127 | use AnyEvent; |
1407 | use AnyEvent; |
1128 | |
1408 | |
1129 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
1409 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
1130 | be used to probe what backend is used and gain other information (which |
1410 | be used to probe what backend is used and gain other information (which |
1131 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL). |
1411 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), |
|
|
1412 | and $ENV{PERL_ANYEGENT_STRICT}. |
|
|
1413 | |
|
|
1414 | BUGS |
|
|
1415 | Perl 5.8 has numerous memleaks that sometimes hit this module and are |
|
|
1416 | hard to work around. If you suffer from memleaks, first upgrade to Perl |
|
|
1417 | 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other |
|
|
1418 | annoying memleaks, such as leaking on "map" and "grep" but it is usually |
|
|
1419 | not as pronounced). |
1132 | |
1420 | |
1133 | SEE ALSO |
1421 | SEE ALSO |
|
|
1422 | Utility functions: AnyEvent::Util. |
|
|
1423 | |
1134 | Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, |
1424 | Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, |
1135 | Event::Lib, Qt, POE. |
1425 | Event::Lib, Qt, POE. |
1136 | |
1426 | |
1137 | Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, |
1427 | Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, |
1138 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, |
1428 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, |
1139 | AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE. |
1429 | AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE. |
1140 | |
1430 | |
|
|
1431 | Non-blocking file handles, sockets, TCP clients and servers: |
|
|
1432 | AnyEvent::Handle, AnyEvent::Socket. |
|
|
1433 | |
|
|
1434 | Asynchronous DNS: AnyEvent::DNS. |
|
|
1435 | |
1141 | Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, |
1436 | Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, |
1142 | |
1437 | |
1143 | Nontrivial usage examples: Net::FCP, Net::XMPP2. |
1438 | Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS. |
1144 | |
1439 | |
1145 | AUTHOR |
1440 | AUTHOR |
1146 | Marc Lehmann <schmorp@schmorp.de> |
1441 | Marc Lehmann <schmorp@schmorp.de> |
1147 | http://home.schmorp.de/ |
1442 | http://home.schmorp.de/ |
1148 | |
1443 | |