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 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 { ... }); |
11 | |
15 | |
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16 | # one-shot or repeating timers |
12 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
17 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
13 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... |
18 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...); |
14 | |
19 | |
15 | print AnyEvent->now; # prints current event loop time |
20 | print AnyEvent->now; # prints current event loop time |
16 | print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. |
21 | print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. |
17 | |
22 | |
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23 | # POSIX signal |
18 | my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); |
24 | my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); |
19 | |
25 | |
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26 | # child process exit |
20 | my $w = AnyEvent->child (pid => $pid, cb => sub { |
27 | my $w = AnyEvent->child (pid => $pid, cb => sub { |
21 | my ($pid, $status) = @_; |
28 | my ($pid, $status) = @_; |
22 | ... |
29 | ... |
23 | }); |
30 | }); |
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31 | |
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32 | # called when event loop idle (if applicable) |
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33 | my $w = AnyEvent->idle (cb => sub { ... }); |
24 | |
34 | |
25 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
35 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
26 | $w->send; # wake up current and all future recv's |
36 | $w->send; # wake up current and all future recv's |
27 | $w->recv; # enters "main loop" till $condvar gets ->send |
37 | $w->recv; # enters "main loop" till $condvar gets ->send |
28 | # use a condvar in callback mode: |
38 | # use a condvar in callback mode: |
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30 | |
40 | |
31 | INTRODUCTION/TUTORIAL |
41 | INTRODUCTION/TUTORIAL |
32 | 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 |
33 | 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 |
34 | manpage. |
44 | manpage. |
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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. |
35 | |
54 | |
36 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
55 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
37 | 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 |
38 | nowadays. So what is different about AnyEvent? |
57 | nowadays. So what is different about AnyEvent? |
39 | |
58 | |
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54 | 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 |
55 | model you use. |
74 | model you use. |
56 | |
75 | |
57 | 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 |
58 | 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 |
59 | 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 |
60 | cannot use anything else, as they are simply incompatible to everything |
79 | cannot use anything else, as they are simply incompatible to everything |
61 | that isn't them. 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 |
62 | are *also* forced to use the same event loop you use. |
81 | are *also* forced to use the same event loop you use. |
63 | |
82 | |
64 | AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
83 | AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
65 | 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 |
66 | with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your |
85 | with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your |
67 | module uses one of those, every user of your module has to use it, too. |
86 | module uses one of those, every user of your module has to use it, too. |
68 | But if your module uses AnyEvent, it works transparently with all event |
87 | But if your module uses AnyEvent, it works transparently with all event |
69 | models it supports (including stuff like IO::Async, as long as those use |
88 | models it supports (including stuff like IO::Async, as long as those use |
70 | one of the supported event loops. It is trivial to add new event loops |
89 | one of the supported event loops. It is easy to add new event loops to |
71 | to AnyEvent, too, so it is future-proof). |
90 | AnyEvent, too, so it is future-proof). |
72 | |
91 | |
73 | 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 |
74 | 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 |
75 | 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 |
76 | 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 |
77 | 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 |
78 | wrapper as technically possible. |
97 | technically possible. |
79 | |
98 | |
80 | 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 |
81 | useful functionality, such as an asynchronous DNS resolver, 100% |
100 | useful functionality, such as an asynchronous DNS resolver, 100% |
82 | 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 |
83 | 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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86 | 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 |
87 | 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 |
88 | model, you should *not* use this module. |
107 | model, you should *not* use this module. |
89 | |
108 | |
90 | DESCRIPTION |
109 | DESCRIPTION |
91 | AnyEvent provides an identical interface to multiple event loops. This |
110 | AnyEvent provides a uniform interface to various event loops. This |
92 | allows module authors to utilise an event loop without forcing module |
111 | allows module authors to use event loop functionality without forcing |
93 | 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 |
94 | coexist peacefully at any one time). |
113 | than one event loop cannot coexist peacefully). |
95 | |
114 | |
96 | 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 |
97 | module. |
116 | module. |
98 | |
117 | |
99 | 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 |
100 | 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 |
101 | following modules is already loaded: EV, Event, Glib, |
120 | following modules is already loaded: EV, AnyEvent::Impl::Perl, Event, |
102 | AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is |
121 | Glib, Tk, Event::Lib, Qt, POE. The first one found is used. If none are |
103 | 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 |
104 | (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 |
105 | always succeed) in the order given. The first one that can be |
124 | AnyEvent::Impl::Perl should always work, so the other two are not |
106 | successfully loaded will be used. If, after this, still none could be |
125 | normally tried. |
107 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
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108 | very efficient, but should work everywhere. |
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109 | |
126 | |
110 | Because AnyEvent first checks for modules that are already loaded, |
127 | Because AnyEvent first checks for modules that are already loaded, |
111 | loading an event model explicitly before first using AnyEvent will |
128 | loading an event model explicitly before first using AnyEvent will |
112 | likely make that model the default. For example: |
129 | likely make that model the default. For example: |
113 | |
130 | |
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115 | use AnyEvent; |
132 | use AnyEvent; |
116 | |
133 | |
117 | # .. AnyEvent will likely default to Tk |
134 | # .. AnyEvent will likely default to Tk |
118 | |
135 | |
119 | 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 |
120 | 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 |
121 | 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. |
122 | |
140 | |
123 | The pure-perl implementation of AnyEvent is called |
141 | The pure-perl implementation of AnyEvent is called |
124 | "AnyEvent::Impl::Perl". Like other event modules you can load it |
142 | "AnyEvent::Impl::Perl". Like other event modules you can load it |
125 | explicitly and enjoy the high availability of that event loop :) |
143 | explicitly and enjoy the high availability of that event loop :) |
126 | |
144 | |
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132 | These watchers are normal Perl objects with normal Perl lifetime. After |
150 | These watchers are normal Perl objects with normal Perl lifetime. After |
133 | 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 |
134 | 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 |
135 | in control). |
153 | in control). |
136 | |
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 | |
137 | 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 |
138 | 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 |
139 | to it). |
163 | to it). |
140 | |
164 | |
141 | 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. |
142 | |
166 | |
143 | Many watchers either are used with "recursion" (repeating timers for |
167 | Many watchers either are used with "recursion" (repeating timers for |
144 | 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. |
145 | |
169 | |
146 | An any way to achieve that is this pattern: |
170 | One way to achieve that is this pattern: |
147 | |
171 | |
148 | my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
172 | my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
149 | # you can use $w here, for example to undef it |
173 | # you can use $w here, for example to undef it |
150 | undef $w; |
174 | undef $w; |
151 | }); |
175 | }); |
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153 | 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, |
154 | 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 |
155 | declared. |
179 | declared. |
156 | |
180 | |
157 | 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 | |
158 | 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 |
159 | the following mandatory key-value pairs as arguments: |
189 | the following mandatory key-value pairs as arguments: |
160 | |
190 | |
161 | "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 |
162 | (AnyEvent might or might not keep a reference to this file handle). |
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 | |
163 | "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 |
164 | 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 | |
165 | 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. |
166 | |
202 | |
167 | Although the callback might get passed parameters, their value and |
203 | Although the callback might get passed parameters, their value and |
168 | presence is undefined and you cannot rely on them. Portable AnyEvent |
204 | presence is undefined and you cannot rely on them. Portable AnyEvent |
169 | callbacks cannot use arguments passed to I/O watcher callbacks. |
205 | callbacks cannot use arguments passed to I/O watcher callbacks. |
170 | |
206 | |
171 | 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 |
172 | 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 |
173 | the underlying file descriptor. |
209 | the underlying file descriptor. |
174 | |
210 | |
175 | Some event loops issue spurious readyness notifications, so you should |
211 | Some event loops issue spurious readiness notifications, so you should |
176 | 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 |
177 | handles. |
213 | handles. |
178 | |
214 | |
179 | Example: wait for readability of STDIN, then read a line and disable the |
215 | Example: wait for readability of STDIN, then read a line and disable the |
180 | watcher. |
216 | watcher. |
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184 | warn "read: $input\n"; |
220 | warn "read: $input\n"; |
185 | undef $w; |
221 | undef $w; |
186 | }); |
222 | }); |
187 | |
223 | |
188 | 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 | |
189 | 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 |
190 | with the following mandatory arguments: |
234 | with the following mandatory arguments: |
191 | |
235 | |
192 | "after" specifies after how many seconds (fractional values are |
236 | "after" specifies after how many seconds (fractional values are |
193 | 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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195 | |
239 | |
196 | Although the callback might get passed parameters, their value and |
240 | Although the callback might get passed parameters, their value and |
197 | presence is undefined and you cannot rely on them. Portable AnyEvent |
241 | presence is undefined and you cannot rely on them. Portable AnyEvent |
198 | callbacks cannot use arguments passed to time watcher callbacks. |
242 | callbacks cannot use arguments passed to time watcher callbacks. |
199 | |
243 | |
200 | The callback will normally be invoked once only. If you specify another |
244 | The callback will normally be invoked only once. If you specify another |
201 | parameter, "interval", as a strictly positive number (> 0), then the |
245 | parameter, "interval", as a strictly positive number (> 0), then the |
202 | callback will be invoked regularly at that interval (in fractional |
246 | callback will be invoked regularly at that interval (in fractional |
203 | seconds) after the first invocation. If "interval" is specified with a |
247 | seconds) after the first invocation. If "interval" is specified with a |
204 | false value, then it is treated as if it were missing. |
248 | false value, then it is treated as if it were not specified at all. |
205 | |
249 | |
206 | The callback will be rescheduled before invoking the callback, but no |
250 | The callback will be rescheduled before invoking the callback, but no |
207 | attempt is done to avoid timer drift in most backends, so the interval |
251 | attempt is made to avoid timer drift in most backends, so the interval |
208 | is only approximate. |
252 | is only approximate. |
209 | |
253 | |
210 | Example: fire an event after 7.7 seconds. |
254 | Example: fire an event after 7.7 seconds. |
211 | |
255 | |
212 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
256 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
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229 | |
273 | |
230 | 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, |
231 | they use absolute time internally. This makes a difference when your |
275 | they use absolute time internally. This makes a difference when your |
232 | 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 |
233 | 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 |
234 | 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 |
235 | finally fire. |
279 | finally fire. |
236 | |
280 | |
237 | AnyEvent cannot compensate for this. The only event loop that is |
281 | AnyEvent cannot compensate for this. The only event loop that is |
238 | conscious about these issues is EV, which offers both relative |
282 | conscious of these issues is EV, which offers both relative (ev_timer, |
239 | (ev_timer, based on true relative time) and absolute (ev_periodic, based |
283 | based on true relative time) and absolute (ev_periodic, based on |
240 | on wallclock time) timers. |
284 | wallclock time) timers. |
241 | |
285 | |
242 | AnyEvent always prefers relative timers, if available, matching the |
286 | AnyEvent always prefers relative timers, if available, matching the |
243 | AnyEvent API. |
287 | AnyEvent API. |
244 | |
288 | |
245 | 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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264 | *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 |
265 | function to call when you want to know the current time.* |
309 | function to call when you want to know the current time.* |
266 | |
310 | |
267 | This function is also often faster then "AnyEvent->time", and thus |
311 | This function is also often faster then "AnyEvent->time", and thus |
268 | the preferred method if you want some timestamp (for example, |
312 | the preferred method if you want some timestamp (for example, |
269 | AnyEvent::Handle uses this to update it's activity timeouts). |
313 | AnyEvent::Handle uses this to update its activity timeouts). |
270 | |
314 | |
271 | 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 |
272 | exact with your timing, you can skip it without bad conscience. |
316 | exact with your timing; you can skip it without a bad conscience. |
273 | |
317 | |
274 | For a practical example of when these times differ, consider |
318 | For a practical example of when these times differ, consider |
275 | Event::Lib and EV and the following set-up: |
319 | Event::Lib and EV and the following set-up: |
276 | |
320 | |
277 | 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 |
278 | at time=500 (assume no other callbacks delay processing). In your |
322 | at time=500 (assume no other callbacks delay processing). In your |
279 | callback, you wait a second by executing "sleep 1" (blocking the |
323 | callback, you wait a second by executing "sleep 1" (blocking the |
280 | 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 |
281 | timer that fires after three seconds. |
325 | timer that fires after three seconds. |
282 | |
326 | |
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302 | 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 |
303 | 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 |
304 | the difference between "AnyEvent->time" and "AnyEvent->now" into |
348 | the difference between "AnyEvent->time" and "AnyEvent->now" into |
305 | account. |
349 | account. |
306 | |
350 | |
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351 | AnyEvent->now_update |
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352 | Some event loops (such as EV or AnyEvent::Impl::Perl) cache the |
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353 | current time for each loop iteration (see the discussion of |
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354 | AnyEvent->now, 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 | |
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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 |
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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 | |
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371 | Note that updating the time *might* cause some events to be handled. |
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372 | |
307 | SIGNAL WATCHERS |
373 | SIGNAL WATCHERS |
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374 | $w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>); |
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375 | |
308 | 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 |
309 | *name* in uppercase and without any "SIG" prefix, "cb" is the Perl |
377 | *name* in uppercase and without any "SIG" prefix, "cb" is the Perl |
310 | callback to be invoked whenever a signal occurs. |
378 | callback to be invoked whenever a signal occurs. |
311 | |
379 | |
312 | Although the callback might get passed parameters, their value and |
380 | Although the callback might get passed parameters, their value and |
… | |
… | |
317 | invocation, and callback invocation will be synchronous. Synchronous |
385 | invocation, and callback invocation will be synchronous. Synchronous |
318 | 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 |
319 | process, but it is guaranteed not to interrupt any other callbacks. |
387 | process, but it is guaranteed not to interrupt any other callbacks. |
320 | |
388 | |
321 | 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 |
322 | 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. |
323 | |
392 | |
324 | This watcher might use %SIG, so programs overwriting those signals |
393 | This watcher might use %SIG (depending on the event loop used), so |
325 | directly will likely not work correctly. |
394 | programs overwriting those signals directly will likely not work |
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395 | correctly. |
326 | |
396 | |
327 | Example: exit on SIGINT |
397 | Example: exit on SIGINT |
328 | |
398 | |
329 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
399 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
330 | |
400 | |
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401 | Restart Behaviour |
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402 | While restart behaviour is up to the event loop implementation, most |
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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 | |
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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 get delayed indefinitely, the |
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409 | latter might corrupt your memory. |
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410 | |
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411 | AnyEvent signal handlers are, in addition, synchronous to the event |
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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 |
|
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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 |
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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 specified |
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422 | in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable |
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423 | can be changed only before the first signal watcher is created, and |
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424 | should be left alone otherwise. This variable determines how often |
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425 | AnyEvent polls for signals (in case a wake-up was missed). Higher values |
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426 | will cause fewer spurious wake-ups, which is better for power and CPU |
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427 | saving. |
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428 | |
|
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429 | All these problems can be avoided by installing the optional |
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430 | Async::Interrupt module, which works with most event loops. It will not |
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431 | work with inherently broken event loops such as Event or Event::Lib (and |
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432 | not with POE currently, as POE does its own workaround with one-second |
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433 | latency). For those, you just have to suffer the delays. |
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434 | |
331 | CHILD PROCESS WATCHERS |
435 | CHILD PROCESS WATCHERS |
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436 | $w = AnyEvent->child (pid => <process id>, cb => <callback>); |
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437 | |
332 | You can also watch on a child process exit and catch its exit status. |
438 | You can also watch for a child process exit and catch its exit status. |
333 | |
439 | |
334 | The child process is specified by the "pid" argument (if set to 0, it |
440 | The child process is specified by the "pid" argument (on some backends, |
335 | watches for any child process exit). The watcher will triggered only |
441 | using 0 watches for any child process exit, on others this will croak). |
336 | when the child process has finished and an exit status is available, not |
442 | The watcher will be triggered only when the child process has finished |
337 | on any trace events (stopped/continued). |
443 | and an exit status is available, not on any trace events |
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444 | (stopped/continued). |
338 | |
445 | |
339 | The callback will be called with the pid and exit status (as returned by |
446 | The callback will be called with the pid and exit status (as returned by |
340 | waitpid), so unlike other watcher types, you *can* rely on child watcher |
447 | waitpid), so unlike other watcher types, you *can* rely on child watcher |
341 | callback arguments. |
448 | callback arguments. |
342 | |
449 | |
… | |
… | |
347 | |
454 | |
348 | There is a slight catch to child watchers, however: you usually start |
455 | There is a slight catch to child watchers, however: you usually start |
349 | them *after* the child process was created, and this means the process |
456 | them *after* the child process was created, and this means the process |
350 | could have exited already (and no SIGCHLD will be sent anymore). |
457 | could have exited already (and no SIGCHLD will be sent anymore). |
351 | |
458 | |
352 | Not all event models handle this correctly (POE doesn't), but even for |
459 | Not all event models handle this correctly (neither POE nor IO::Async |
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460 | do, see their AnyEvent::Impl manpages for details), but even for event |
353 | event models that *do* handle this correctly, they usually need to be |
461 | models that *do* handle this correctly, they usually need to be loaded |
354 | loaded before the process exits (i.e. before you fork in the first |
462 | before the process exits (i.e. before you fork in the first place). |
355 | place). |
463 | AnyEvent's pure perl event loop handles all cases correctly regardless |
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464 | of when you start the watcher. |
356 | |
465 | |
357 | This means you cannot create a child watcher as the very first thing in |
466 | This means you cannot create a child watcher as the very first thing in |
358 | an AnyEvent program, you *have* to create at least one watcher before |
467 | an AnyEvent program, you *have* to create at least one watcher before |
359 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
468 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
360 | |
469 | |
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470 | As most event loops do not support waiting for child events, they will |
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471 | be emulated by AnyEvent in most cases, in which the latency and race |
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472 | problems mentioned in the description of signal watchers apply. |
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473 | |
361 | Example: fork a process and wait for it |
474 | Example: fork a process and wait for it |
362 | |
475 | |
363 | my $done = AnyEvent->condvar; |
476 | my $done = AnyEvent->condvar; |
364 | |
477 | |
365 | my $pid = fork or exit 5; |
478 | my $pid = fork or exit 5; |
366 | |
479 | |
367 | my $w = AnyEvent->child ( |
480 | my $w = AnyEvent->child ( |
368 | pid => $pid, |
481 | pid => $pid, |
369 | cb => sub { |
482 | cb => sub { |
370 | my ($pid, $status) = @_; |
483 | my ($pid, $status) = @_; |
371 | warn "pid $pid exited with status $status"; |
484 | warn "pid $pid exited with status $status"; |
372 | $done->send; |
485 | $done->send; |
373 | }, |
486 | }, |
374 | ); |
487 | ); |
375 | |
488 | |
376 | # do something else, then wait for process exit |
489 | # do something else, then wait for process exit |
377 | $done->recv; |
490 | $done->recv; |
378 | |
491 | |
|
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492 | IDLE WATCHERS |
|
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493 | $w = AnyEvent->idle (cb => <callback>); |
|
|
494 | |
|
|
495 | This will repeatedly invoke the callback after the process becomes idle, |
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496 | until either the watcher is destroyed or new events have been detected. |
|
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497 | |
|
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498 | Idle watchers are useful when there is a need to do something, but it is |
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499 | not so important (or wise) to do it instantly. The callback will be |
|
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500 | invoked only when there is "nothing better to do", which is usually |
|
|
501 | defined as "all outstanding events have been handled and no new events |
|
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502 | have been detected". That means that idle watchers ideally get invoked |
|
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503 | when the event loop has just polled for new events but none have been |
|
|
504 | detected. Instead of blocking to wait for more events, the idle watchers |
|
|
505 | will be invoked. |
|
|
506 | |
|
|
507 | Unfortunately, most event loops do not really support idle watchers |
|
|
508 | (only EV, Event and Glib do it in a usable fashion) - for the rest, |
|
|
509 | AnyEvent will simply call the callback "from time to time". |
|
|
510 | |
|
|
511 | Example: read lines from STDIN, but only process them when the program |
|
|
512 | is otherwise idle: |
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513 | |
|
|
514 | my @lines; # read data |
|
|
515 | my $idle_w; |
|
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516 | my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
|
|
517 | push @lines, scalar <STDIN>; |
|
|
518 | |
|
|
519 | # start an idle watcher, if not already done |
|
|
520 | $idle_w ||= AnyEvent->idle (cb => sub { |
|
|
521 | # handle only one line, when there are lines left |
|
|
522 | if (my $line = shift @lines) { |
|
|
523 | print "handled when idle: $line"; |
|
|
524 | } else { |
|
|
525 | # otherwise disable the idle watcher again |
|
|
526 | undef $idle_w; |
|
|
527 | } |
|
|
528 | }); |
|
|
529 | }); |
|
|
530 | |
379 | CONDITION VARIABLES |
531 | CONDITION VARIABLES |
|
|
532 | $cv = AnyEvent->condvar; |
|
|
533 | |
|
|
534 | $cv->send (<list>); |
|
|
535 | my @res = $cv->recv; |
|
|
536 | |
380 | If you are familiar with some event loops you will know that all of them |
537 | If you are familiar with some event loops you will know that all of them |
381 | require you to run some blocking "loop", "run" or similar function that |
538 | require you to run some blocking "loop", "run" or similar function that |
382 | will actively watch for new events and call your callbacks. |
539 | will actively watch for new events and call your callbacks. |
383 | |
540 | |
384 | AnyEvent is different, it expects somebody else to run the event loop |
541 | AnyEvent is slightly different: it expects somebody else to run the |
385 | and will only block when necessary (usually when told by the user). |
542 | event loop and will only block when necessary (usually when told by the |
|
|
543 | user). |
386 | |
544 | |
387 | The instrument to do that is called a "condition variable", so called |
545 | The tool to do that is called a "condition variable", so called because |
388 | because they represent a condition that must become true. |
546 | they represent a condition that must become true. |
|
|
547 | |
|
|
548 | Now is probably a good time to look at the examples further below. |
389 | |
549 | |
390 | Condition variables can be created by calling the "AnyEvent->condvar" |
550 | Condition variables can be created by calling the "AnyEvent->condvar" |
391 | method, usually without arguments. The only argument pair allowed is |
551 | method, usually without arguments. The only argument pair allowed is |
392 | |
|
|
393 | "cb", which specifies a callback to be called when the condition |
552 | "cb", which specifies a callback to be called when the condition |
394 | variable becomes true, with the condition variable as the first argument |
553 | variable becomes true, with the condition variable as the first argument |
395 | (but not the results). |
554 | (but not the results). |
396 | |
555 | |
397 | After creation, the condition variable is "false" until it becomes |
556 | After creation, the condition variable is "false" until it becomes |
398 | "true" by calling the "send" method (or calling the condition variable |
557 | "true" by calling the "send" method (or calling the condition variable |
399 | as if it were a callback, read about the caveats in the description for |
558 | as if it were a callback, read about the caveats in the description for |
400 | the "->send" method). |
559 | the "->send" method). |
401 | |
560 | |
402 | Condition variables are similar to callbacks, except that you can |
561 | Since condition variables are the most complex part of the AnyEvent API, |
403 | optionally wait for them. They can also be called merge points - points |
562 | here are some different mental models of what they are - pick the ones |
404 | in time where multiple outstanding events have been processed. And yet |
563 | you can connect to: |
405 | another way to call them is transactions - each condition variable can |
564 | |
406 | be used to represent a transaction, which finishes at some point and |
565 | * Condition variables are like callbacks - you can call them (and pass |
407 | delivers a result. |
566 | them instead of callbacks). Unlike callbacks however, you can also |
|
|
567 | wait for them to be called. |
|
|
568 | |
|
|
569 | * Condition variables are signals - one side can emit or send them, |
|
|
570 | the other side can wait for them, or install a handler that is |
|
|
571 | called when the signal fires. |
|
|
572 | |
|
|
573 | * Condition variables are like "Merge Points" - points in your program |
|
|
574 | where you merge multiple independent results/control flows into one. |
|
|
575 | |
|
|
576 | * Condition variables represent a transaction - functions that start |
|
|
577 | some kind of transaction can return them, leaving the caller the |
|
|
578 | choice between waiting in a blocking fashion, or setting a callback. |
|
|
579 | |
|
|
580 | * Condition variables represent future values, or promises to deliver |
|
|
581 | some result, long before the result is available. |
408 | |
582 | |
409 | Condition variables are very useful to signal that something has |
583 | Condition variables are very useful to signal that something has |
410 | finished, for example, if you write a module that does asynchronous http |
584 | finished, for example, if you write a module that does asynchronous http |
411 | requests, then a condition variable would be the ideal candidate to |
585 | requests, then a condition variable would be the ideal candidate to |
412 | signal the availability of results. The user can either act when the |
586 | signal the availability of results. The user can either act when the |
… | |
… | |
425 | |
599 | |
426 | Condition variables are represented by hash refs in perl, and the keys |
600 | Condition variables are represented by hash refs in perl, and the keys |
427 | used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy |
601 | used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy |
428 | (it is often useful to build your own transaction class on top of |
602 | (it is often useful to build your own transaction class on top of |
429 | AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call |
603 | AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call |
430 | it's "new" method in your own "new" method. |
604 | its "new" method in your own "new" method. |
431 | |
605 | |
432 | There are two "sides" to a condition variable - the "producer side" |
606 | There are two "sides" to a condition variable - the "producer side" |
433 | which eventually calls "-> send", and the "consumer side", which waits |
607 | which eventually calls "-> send", and the "consumer side", which waits |
434 | for the send to occur. |
608 | for the send to occur. |
435 | |
609 | |
436 | Example: wait for a timer. |
610 | Example: wait for a timer. |
437 | |
611 | |
438 | # wait till the result is ready |
612 | # condition: "wait till the timer is fired" |
439 | my $result_ready = AnyEvent->condvar; |
613 | my $timer_fired = AnyEvent->condvar; |
440 | |
614 | |
441 | # do something such as adding a timer |
615 | # create the timer - we could wait for, say |
442 | # or socket watcher the calls $result_ready->send |
616 | # a handle becomign ready, or even an |
443 | # when the "result" is ready. |
617 | # AnyEvent::HTTP request to finish, but |
444 | # in this case, we simply use a timer: |
618 | # in this case, we simply use a timer: |
445 | my $w = AnyEvent->timer ( |
619 | my $w = AnyEvent->timer ( |
446 | after => 1, |
620 | after => 1, |
447 | cb => sub { $result_ready->send }, |
621 | cb => sub { $timer_fired->send }, |
448 | ); |
622 | ); |
449 | |
623 | |
450 | # this "blocks" (while handling events) till the callback |
624 | # this "blocks" (while handling events) till the callback |
451 | # calls send |
625 | # calls ->send |
452 | $result_ready->recv; |
626 | $timer_fired->recv; |
453 | |
627 | |
454 | Example: wait for a timer, but take advantage of the fact that condition |
628 | Example: wait for a timer, but take advantage of the fact that condition |
455 | variables are also code references. |
629 | variables are also callable directly. |
456 | |
630 | |
457 | my $done = AnyEvent->condvar; |
631 | my $done = AnyEvent->condvar; |
458 | my $delay = AnyEvent->timer (after => 5, cb => $done); |
632 | my $delay = AnyEvent->timer (after => 5, cb => $done); |
459 | $done->recv; |
633 | $done->recv; |
460 | |
634 | |
… | |
… | |
466 | |
640 | |
467 | ... |
641 | ... |
468 | |
642 | |
469 | my @info = $couchdb->info->recv; |
643 | my @info = $couchdb->info->recv; |
470 | |
644 | |
471 | And this is how you would just ste a callback to be called whenever the |
645 | And this is how you would just set a callback to be called whenever the |
472 | results are available: |
646 | results are available: |
473 | |
647 | |
474 | $couchdb->info->cb (sub { |
648 | $couchdb->info->cb (sub { |
475 | my @info = $_[0]->recv; |
649 | my @info = $_[0]->recv; |
476 | }); |
650 | }); |
… | |
… | |
491 | |
665 | |
492 | Any arguments passed to the "send" call will be returned by all |
666 | Any arguments passed to the "send" call will be returned by all |
493 | future "->recv" calls. |
667 | future "->recv" calls. |
494 | |
668 | |
495 | Condition variables are overloaded so one can call them directly (as |
669 | Condition variables are overloaded so one can call them directly (as |
496 | a code reference). Calling them directly is the same as calling |
670 | if they were a code reference). Calling them directly is the same as |
497 | "send". Note, however, that many C-based event loops do not handle |
671 | calling "send". |
498 | overloading, so as tempting as it may be, passing a condition |
|
|
499 | variable instead of a callback does not work. Both the pure perl and |
|
|
500 | EV loops support overloading, however, as well as all functions that |
|
|
501 | use perl to invoke a callback (as in AnyEvent::Socket and |
|
|
502 | AnyEvent::DNS for example). |
|
|
503 | |
672 | |
504 | $cv->croak ($error) |
673 | $cv->croak ($error) |
505 | Similar to send, but causes all call's to "->recv" to invoke |
674 | Similar to send, but causes all calls to "->recv" to invoke |
506 | "Carp::croak" with the given error message/object/scalar. |
675 | "Carp::croak" with the given error message/object/scalar. |
507 | |
676 | |
508 | This can be used to signal any errors to the condition variable |
677 | This can be used to signal any errors to the condition variable |
509 | user/consumer. |
678 | user/consumer. Doing it this way instead of calling "croak" directly |
|
|
679 | delays the error detection, but has the overwhelming advantage that |
|
|
680 | it diagnoses the error at the place where the result is expected, |
|
|
681 | and not deep in some event callback with no connection to the actual |
|
|
682 | code causing the problem. |
510 | |
683 | |
511 | $cv->begin ([group callback]) |
684 | $cv->begin ([group callback]) |
512 | $cv->end |
685 | $cv->end |
513 | These two methods are EXPERIMENTAL and MIGHT CHANGE. |
|
|
514 | |
|
|
515 | These two methods can be used to combine many transactions/events |
686 | These two methods can be used to combine many transactions/events |
516 | into one. For example, a function that pings many hosts in parallel |
687 | into one. For example, a function that pings many hosts in parallel |
517 | might want to use a condition variable for the whole process. |
688 | might want to use a condition variable for the whole process. |
518 | |
689 | |
519 | Every call to "->begin" will increment a counter, and every call to |
690 | Every call to "->begin" will increment a counter, and every call to |
520 | "->end" will decrement it. If the counter reaches 0 in "->end", the |
691 | "->end" will decrement it. If the counter reaches 0 in "->end", the |
521 | (last) callback passed to "begin" will be executed. That callback is |
692 | (last) callback passed to "begin" will be executed, passing the |
522 | *supposed* to call "->send", but that is not required. If no |
693 | condvar as first argument. That callback is *supposed* to call |
|
|
694 | "->send", but that is not required. If no group callback was set, |
523 | callback was set, "send" will be called without any arguments. |
695 | "send" will be called without any arguments. |
524 | |
696 | |
525 | Let's clarify this with the ping example: |
697 | You can think of "$cv->send" giving you an OR condition (one call |
|
|
698 | sends), while "$cv->begin" and "$cv->end" giving you an AND |
|
|
699 | condition (all "begin" calls must be "end"'ed before the condvar |
|
|
700 | sends). |
|
|
701 | |
|
|
702 | Let's start with a simple example: you have two I/O watchers (for |
|
|
703 | example, STDOUT and STDERR for a program), and you want to wait for |
|
|
704 | both streams to close before activating a condvar: |
526 | |
705 | |
527 | my $cv = AnyEvent->condvar; |
706 | my $cv = AnyEvent->condvar; |
528 | |
707 | |
|
|
708 | $cv->begin; # first watcher |
|
|
709 | my $w1 = AnyEvent->io (fh => $fh1, cb => sub { |
|
|
710 | defined sysread $fh1, my $buf, 4096 |
|
|
711 | or $cv->end; |
|
|
712 | }); |
|
|
713 | |
|
|
714 | $cv->begin; # second watcher |
|
|
715 | my $w2 = AnyEvent->io (fh => $fh2, cb => sub { |
|
|
716 | defined sysread $fh2, my $buf, 4096 |
|
|
717 | or $cv->end; |
|
|
718 | }); |
|
|
719 | |
|
|
720 | $cv->recv; |
|
|
721 | |
|
|
722 | This works because for every event source (EOF on file handle), |
|
|
723 | there is one call to "begin", so the condvar waits for all calls to |
|
|
724 | "end" before sending. |
|
|
725 | |
|
|
726 | The ping example mentioned above is slightly more complicated, as |
|
|
727 | the there are results to be passwd back, and the number of tasks |
|
|
728 | that are begun can potentially be zero: |
|
|
729 | |
|
|
730 | my $cv = AnyEvent->condvar; |
|
|
731 | |
529 | my %result; |
732 | my %result; |
530 | $cv->begin (sub { $cv->send (\%result) }); |
733 | $cv->begin (sub { shift->send (\%result) }); |
531 | |
734 | |
532 | for my $host (@list_of_hosts) { |
735 | for my $host (@list_of_hosts) { |
533 | $cv->begin; |
736 | $cv->begin; |
534 | ping_host_then_call_callback $host, sub { |
737 | ping_host_then_call_callback $host, sub { |
535 | $result{$host} = ...; |
738 | $result{$host} = ...; |
… | |
… | |
550 | the loop, which serves two important purposes: first, it sets the |
753 | the loop, which serves two important purposes: first, it sets the |
551 | 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 |
552 | 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 |
553 | (the loop doesn't execute once). |
756 | (the loop doesn't execute once). |
554 | |
757 | |
555 | This is the general pattern when you "fan out" into multiple |
758 | This is the general pattern when you "fan out" into multiple (but |
556 | subrequests: use an outer "begin"/"end" pair to set the callback and |
759 | potentially zero) subrequests: use an outer "begin"/"end" pair to |
557 | 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, |
558 | you start, call "begin" and for each subrequest you finish, call |
761 | for each subrequest you start, call "begin" and for each subrequest |
559 | "end". |
762 | you finish, call "end". |
560 | |
763 | |
561 | METHODS FOR CONSUMERS |
764 | METHODS FOR CONSUMERS |
562 | 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 |
563 | awaits the condition. |
766 | awaits the condition. |
564 | |
767 | |
565 | $cv->recv |
768 | $cv->recv |
566 | Wait (blocking if necessary) until the "->send" or "->croak" methods |
769 | Wait (blocking if necessary) until the "->send" or "->croak" methods |
567 | have been called on c<$cv>, while servicing other watchers normally. |
770 | have been called on $cv, while servicing other watchers normally. |
568 | |
771 | |
569 | 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 |
570 | but will return immediately. |
773 | but will return immediately. |
571 | |
774 | |
572 | 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 |
573 | function will call "croak". |
776 | function will call "croak". |
574 | |
777 | |
575 | In list context, all parameters passed to "send" will be returned, |
778 | In list context, all parameters passed to "send" will be returned, |
576 | in scalar context only the first one will be returned. |
779 | in scalar context only the first one will be returned. |
577 | |
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 condition can be slightly loosened by using |
|
|
785 | Coro::AnyEvent, which allows you to do a blocking "->recv" from any |
|
|
786 | thread that doesn't run the event loop itself. |
|
|
787 | |
578 | Not all event models support a blocking wait - some die in that case |
788 | Not all event models support a blocking wait - some die in that case |
579 | (programs might want to do that to stay interactive), so *if you are |
789 | (programs might want to do that to stay interactive), so *if you are |
580 | using this from a module, never require a blocking wait*, but let |
790 | using this from a module, never require a blocking wait*. Instead, |
581 | the caller decide whether the call will block or not (for example, |
791 | let the caller decide whether the call will block or not (for |
582 | by coupling condition variables with some kind of request results |
792 | example, by coupling condition variables with some kind of request |
583 | and supporting callbacks so the caller knows that getting the result |
793 | results and supporting callbacks so the caller knows that getting |
584 | will not block, while still supporting blocking waits if the caller |
794 | the result will not block, while still supporting blocking waits if |
585 | so desires). |
795 | the caller so desires). |
586 | |
796 | |
587 | Another reason *never* to "->recv" in a module is that you cannot |
|
|
588 | sensibly have two "->recv"'s in parallel, as that would require |
|
|
589 | multiple interpreters or coroutines/threads, none of which |
|
|
590 | "AnyEvent" can supply. |
|
|
591 | |
|
|
592 | The Coro module, however, *can* and *does* supply coroutines and, in |
|
|
593 | fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe |
|
|
594 | versions and also integrates coroutines into AnyEvent, making |
|
|
595 | blocking "->recv" calls perfectly safe as long as they are done from |
|
|
596 | another coroutine (one that doesn't run the event loop). |
|
|
597 | |
|
|
598 | You can ensure that "-recv" never blocks by setting a callback and |
797 | You can ensure that "->recv" never blocks by setting a callback and |
599 | only calling "->recv" from within that callback (or at a later |
798 | only calling "->recv" from within that callback (or at a later |
600 | time). This will work even when the event loop does not support |
799 | time). This will work even when the event loop does not support |
601 | blocking waits otherwise. |
800 | blocking waits otherwise. |
602 | |
801 | |
603 | $bool = $cv->ready |
802 | $bool = $cv->ready |
… | |
… | |
608 | This is a mutator function that returns the callback set and |
807 | This is a mutator function that returns the callback set and |
609 | optionally replaces it before doing so. |
808 | optionally replaces it before doing so. |
610 | |
809 | |
611 | The callback will be called when the condition becomes "true", i.e. |
810 | The callback will be called when the condition becomes "true", i.e. |
612 | when "send" or "croak" are called, with the only argument being the |
811 | when "send" or "croak" are called, with the only argument being the |
613 | condition variable itself. Calling "recv" inside the callback or at |
812 | condition variable itself. If the condition is already true, the |
|
|
813 | callback is called immediately when it is set. Calling "recv" inside |
614 | any later time is guaranteed not to block. |
814 | the callback or at any later time is guaranteed not to block. |
|
|
815 | |
|
|
816 | SUPPORTED EVENT LOOPS/BACKENDS |
|
|
817 | The available backend classes are (every class has its own manpage): |
|
|
818 | |
|
|
819 | Backends that are autoprobed when no other event loop can be found. |
|
|
820 | EV is the preferred backend when no other event loop seems to be in |
|
|
821 | use. If EV is not installed, then AnyEvent will fall back to its own |
|
|
822 | pure-perl implementation, which is available everywhere as it comes |
|
|
823 | with AnyEvent itself. |
|
|
824 | |
|
|
825 | AnyEvent::Impl::EV based on EV (interface to libev, best choice). |
|
|
826 | AnyEvent::Impl::Perl pure-perl implementation, fast and portable. |
|
|
827 | |
|
|
828 | Backends that are transparently being picked up when they are used. |
|
|
829 | These will be used if they are already loaded when the first watcher |
|
|
830 | is created, in which case it is assumed that the application is |
|
|
831 | using them. This means that AnyEvent will automatically pick the |
|
|
832 | right backend when the main program loads an event module before |
|
|
833 | anything starts to create watchers. Nothing special needs to be done |
|
|
834 | by the main program. |
|
|
835 | |
|
|
836 | AnyEvent::Impl::Event based on Event, very stable, few glitches. |
|
|
837 | AnyEvent::Impl::Glib based on Glib, slow but very stable. |
|
|
838 | AnyEvent::Impl::Tk based on Tk, very broken. |
|
|
839 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
|
|
840 | AnyEvent::Impl::POE based on POE, very slow, some limitations. |
|
|
841 | AnyEvent::Impl::Irssi used when running within irssi. |
|
|
842 | |
|
|
843 | Backends with special needs. |
|
|
844 | Qt requires the Qt::Application to be instantiated first, but will |
|
|
845 | otherwise be picked up automatically. As long as the main program |
|
|
846 | instantiates the application before any AnyEvent watchers are |
|
|
847 | created, everything should just work. |
|
|
848 | |
|
|
849 | AnyEvent::Impl::Qt based on Qt. |
|
|
850 | |
|
|
851 | Support for IO::Async can only be partial, as it is too broken and |
|
|
852 | architecturally limited to even support the AnyEvent API. It also is |
|
|
853 | the only event loop that needs the loop to be set explicitly, so it |
|
|
854 | can only be used by a main program knowing about AnyEvent. See |
|
|
855 | AnyEvent::Impl::IOAsync for the gory details. |
|
|
856 | |
|
|
857 | AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed. |
|
|
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. |
615 | |
875 | |
616 | 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 | |
617 | $AnyEvent::MODEL |
880 | $AnyEvent::MODEL |
618 | 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 | |
619 | 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 |
620 | 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 |
621 | 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 |
622 | 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. |
623 | |
888 | in *rxvt-unicode* it will be "urxvt::anyevent"). |
624 | The known classes so far are: |
|
|
625 | |
|
|
626 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
|
|
627 | AnyEvent::Impl::Event based on Event, second best choice. |
|
|
628 | AnyEvent::Impl::Perl pure-perl implementation, fast and portable. |
|
|
629 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
|
|
630 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
|
|
631 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
|
|
632 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
|
|
633 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
|
|
634 | |
|
|
635 | There is no support for WxWidgets, as WxWidgets has no support for |
|
|
636 | watching file handles. However, you can use WxWidgets through the |
|
|
637 | POE Adaptor, as POE has a Wx backend that simply polls 20 times per |
|
|
638 | second, which was considered to be too horrible to even consider for |
|
|
639 | AnyEvent. Likewise, other POE backends can be used by AnyEvent by |
|
|
640 | using it's adaptor. |
|
|
641 | |
|
|
642 | AnyEvent knows about Prima and Wx and will try to use POE when |
|
|
643 | autodetecting them. |
|
|
644 | |
889 | |
645 | AnyEvent::detect |
890 | AnyEvent::detect |
646 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
891 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
647 | if necessary. You should only call this function right before you |
892 | if necessary. You should only call this function right before you |
648 | 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 |
649 | possible at runtime. |
894 | possible at runtime, and not e.g. during initialisation of your |
|
|
895 | module. |
|
|
896 | |
|
|
897 | If you need to do some initialisation before AnyEvent watchers are |
|
|
898 | created, use "post_detect". |
650 | |
899 | |
651 | $guard = AnyEvent::post_detect { BLOCK } |
900 | $guard = AnyEvent::post_detect { BLOCK } |
652 | Arranges for the code block to be executed as soon as the event |
901 | Arranges for the code block to be executed as soon as the event |
653 | model is autodetected (or immediately if this has already happened). |
902 | model is autodetected (or immediately if that has already happened). |
|
|
903 | |
|
|
904 | The block will be executed *after* the actual backend has been |
|
|
905 | detected ($AnyEvent::MODEL is set), but *before* any watchers have |
|
|
906 | been created, so it is possible to e.g. patch @AnyEvent::ISA or do |
|
|
907 | other initialisations - see the sources of AnyEvent::Strict or |
|
|
908 | AnyEvent::AIO to see how this is used. |
|
|
909 | |
|
|
910 | The most common usage is to create some global watchers, without |
|
|
911 | forcing event module detection too early, for example, AnyEvent::AIO |
|
|
912 | creates and installs the global IO::AIO watcher in a "post_detect" |
|
|
913 | block to avoid autodetecting the event module at load time. |
654 | |
914 | |
655 | If called in scalar or list context, then it creates and returns an |
915 | If called in scalar or list context, then it creates and returns an |
656 | object that automatically removes the callback again when it is |
916 | object that automatically removes the callback again when it is |
|
|
917 | destroyed (or "undef" when the hook was immediately executed). See |
657 | destroyed. See Coro::BDB for a case where this is useful. |
918 | AnyEvent::AIO for a case where this is useful. |
|
|
919 | |
|
|
920 | Example: Create a watcher for the IO::AIO module and store it in |
|
|
921 | $WATCHER, but do so only do so after the event loop is initialised. |
|
|
922 | |
|
|
923 | our WATCHER; |
|
|
924 | |
|
|
925 | my $guard = AnyEvent::post_detect { |
|
|
926 | $WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb); |
|
|
927 | }; |
|
|
928 | |
|
|
929 | # the ||= is important in case post_detect immediately runs the block, |
|
|
930 | # as to not clobber the newly-created watcher. assigning both watcher and |
|
|
931 | # post_detect guard to the same variable has the advantage of users being |
|
|
932 | # able to just C<undef $WATCHER> if the watcher causes them grief. |
|
|
933 | |
|
|
934 | $WATCHER ||= $guard; |
658 | |
935 | |
659 | @AnyEvent::post_detect |
936 | @AnyEvent::post_detect |
660 | If there are any code references in this array (you can "push" to it |
937 | If there are any code references in this array (you can "push" to it |
661 | before or after loading AnyEvent), then they will called directly |
938 | before or after loading AnyEvent), then they will be called directly |
662 | after the event loop has been chosen. |
939 | after the event loop has been chosen. |
663 | |
940 | |
664 | You should check $AnyEvent::MODEL before adding to this array, |
941 | You should check $AnyEvent::MODEL before adding to this array, |
665 | though: if it contains a true value then the event loop has already |
942 | though: if it is defined then the event loop has already been |
666 | been detected, and the array will be ignored. |
943 | detected, and the array will be ignored. |
667 | |
944 | |
668 | Best use "AnyEvent::post_detect { BLOCK }" instead. |
945 | Best use "AnyEvent::post_detect { BLOCK }" when your application |
|
|
946 | allows it, as it takes care of these details. |
|
|
947 | |
|
|
948 | This variable is mainly useful for modules that can do something |
|
|
949 | useful when AnyEvent is used and thus want to know when it is |
|
|
950 | initialised, but do not need to even load it by default. This array |
|
|
951 | provides the means to hook into AnyEvent passively, without loading |
|
|
952 | it. |
|
|
953 | |
|
|
954 | Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used |
|
|
955 | together, you could put this into Coro (this is the actual code used |
|
|
956 | by Coro to accomplish this): |
|
|
957 | |
|
|
958 | if (defined $AnyEvent::MODEL) { |
|
|
959 | # AnyEvent already initialised, so load Coro::AnyEvent |
|
|
960 | require Coro::AnyEvent; |
|
|
961 | } else { |
|
|
962 | # AnyEvent not yet initialised, so make sure to load Coro::AnyEvent |
|
|
963 | # as soon as it is |
|
|
964 | push @AnyEvent::post_detect, sub { require Coro::AnyEvent }; |
|
|
965 | } |
669 | |
966 | |
670 | WHAT TO DO IN A MODULE |
967 | WHAT TO DO IN A MODULE |
671 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
968 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
672 | freely, but you should not load a specific event module or rely on it. |
969 | freely, but you should not load a specific event module or rely on it. |
673 | |
970 | |
… | |
… | |
681 | stall the whole program, and the whole point of using events is to stay |
978 | stall the whole program, and the whole point of using events is to stay |
682 | interactive. |
979 | interactive. |
683 | |
980 | |
684 | It is fine, however, to call "->recv" when the user of your module |
981 | It is fine, however, to call "->recv" when the user of your module |
685 | requests it (i.e. if you create a http request object ad have a method |
982 | requests it (i.e. if you create a http request object ad have a method |
686 | called "results" that returns the results, it should call "->recv" |
983 | called "results" that returns the results, it may call "->recv" freely, |
687 | freely, as the user of your module knows what she is doing. always). |
984 | as the user of your module knows what she is doing. Always). |
688 | |
985 | |
689 | WHAT TO DO IN THE MAIN PROGRAM |
986 | WHAT TO DO IN THE MAIN PROGRAM |
690 | There will always be a single main program - the only place that should |
987 | There will always be a single main program - the only place that should |
691 | dictate which event model to use. |
988 | dictate which event model to use. |
692 | |
989 | |
693 | If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
990 | If the program is not event-based, it need not do anything special, even |
694 | do anything special (it does not need to be event-based) and let |
991 | when it depends on a module that uses an AnyEvent. If the program itself |
695 | AnyEvent decide which implementation to chose if some module relies on |
992 | uses AnyEvent, but does not care which event loop is used, all it needs |
696 | it. |
993 | to do is "use AnyEvent". In either case, AnyEvent will choose the best |
|
|
994 | available loop implementation. |
697 | |
995 | |
698 | If the main program relies on a specific event model - for example, in |
996 | If the main program relies on a specific event model - for example, in |
699 | Gtk2 programs you have to rely on the Glib module - you should load the |
997 | Gtk2 programs you have to rely on the Glib module - you should load the |
700 | event module before loading AnyEvent or any module that uses it: |
998 | event module before loading AnyEvent or any module that uses it: |
701 | generally speaking, you should load it as early as possible. The reason |
999 | generally speaking, you should load it as early as possible. The reason |
702 | is that modules might create watchers when they are loaded, and AnyEvent |
1000 | is that modules might create watchers when they are loaded, and AnyEvent |
703 | will decide on the event model to use as soon as it creates watchers, |
1001 | will decide on the event model to use as soon as it creates watchers, |
704 | and it might chose the wrong one unless you load the correct one |
1002 | and it might choose the wrong one unless you load the correct one |
705 | yourself. |
1003 | yourself. |
706 | |
1004 | |
707 | You can chose to use a pure-perl implementation by loading the |
1005 | You can chose to use a pure-perl implementation by loading the |
708 | "AnyEvent::Impl::Perl" module, which gives you similar behaviour |
1006 | "AnyEvent::Impl::Perl" module, which gives you similar behaviour |
709 | everywhere, but letting AnyEvent chose the model is generally better. |
1007 | everywhere, but letting AnyEvent chose the model is generally better. |
… | |
… | |
724 | variable somewhere, waiting for it, and sending it when the program |
1022 | variable somewhere, waiting for it, and sending it when the program |
725 | should exit cleanly. |
1023 | should exit cleanly. |
726 | |
1024 | |
727 | OTHER MODULES |
1025 | OTHER MODULES |
728 | The following is a non-exhaustive list of additional modules that use |
1026 | The following is a non-exhaustive list of additional modules that use |
729 | AnyEvent and can therefore be mixed easily with other AnyEvent modules |
1027 | AnyEvent as a client and can therefore be mixed easily with other |
730 | in the same program. Some of the modules come with AnyEvent, some are |
1028 | AnyEvent modules and other event loops in the same program. Some of the |
731 | available via CPAN. |
1029 | modules come as part of AnyEvent, the others are available via CPAN. |
732 | |
1030 | |
733 | AnyEvent::Util |
1031 | AnyEvent::Util |
734 | Contains various utility functions that replace often-used but |
1032 | Contains various utility functions that replace often-used blocking |
735 | blocking functions such as "inet_aton" by event-/callback-based |
1033 | functions such as "inet_aton" with event/callback-based versions. |
736 | versions. |
|
|
737 | |
1034 | |
738 | AnyEvent::Socket |
1035 | AnyEvent::Socket |
739 | Provides various utility functions for (internet protocol) sockets, |
1036 | Provides various utility functions for (internet protocol) sockets, |
740 | addresses and name resolution. Also functions to create non-blocking |
1037 | addresses and name resolution. Also functions to create non-blocking |
741 | tcp connections or tcp servers, with IPv6 and SRV record support and |
1038 | tcp connections or tcp servers, with IPv6 and SRV record support and |
742 | more. |
1039 | more. |
743 | |
1040 | |
744 | AnyEvent::Handle |
1041 | AnyEvent::Handle |
745 | Provide read and write buffers, manages watchers for reads and |
1042 | Provide read and write buffers, manages watchers for reads and |
746 | writes, supports raw and formatted I/O, I/O queued and fully |
1043 | writes, supports raw and formatted I/O, I/O queued and fully |
747 | transparent and non-blocking SSL/TLS. |
1044 | transparent and non-blocking SSL/TLS (via AnyEvent::TLS). |
748 | |
1045 | |
749 | AnyEvent::DNS |
1046 | AnyEvent::DNS |
750 | Provides rich asynchronous DNS resolver capabilities. |
1047 | Provides rich asynchronous DNS resolver capabilities. |
751 | |
1048 | |
|
|
1049 | AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD, |
|
|
1050 | AnyEvent::IGS, AnyEvent::FCP |
|
|
1051 | Implement event-based interfaces to the protocols of the same name |
|
|
1052 | (for the curious, IGS is the International Go Server and FCP is the |
|
|
1053 | Freenet Client Protocol). |
|
|
1054 | |
|
|
1055 | AnyEvent::Handle::UDP |
|
|
1056 | Here be danger! |
|
|
1057 | |
|
|
1058 | As Pauli would put it, "Not only is it not right, it's not even |
|
|
1059 | wrong!" - there are so many things wrong with AnyEvent::Handle::UDP, |
|
|
1060 | most notably its use of a stream-based API with a protocol that |
|
|
1061 | isn't streamable, that the only way to improve it is to delete it. |
|
|
1062 | |
|
|
1063 | It features data corruption (but typically only under load) and |
|
|
1064 | general confusion. On top, the author is not only clueless about UDP |
|
|
1065 | but also fact-resistant - some gems of his understanding: "connect |
|
|
1066 | doesn't work with UDP", "UDP packets are not IP packets", "UDP only |
|
|
1067 | has datagrams, not packets", "I don't need to implement proper error |
|
|
1068 | checking as UDP doesn't support error checking" and so on - he |
|
|
1069 | doesn't even understand what's wrong with his module when it is |
|
|
1070 | explained to him. |
|
|
1071 | |
752 | AnyEvent::HTTP |
1072 | AnyEvent::DBI |
753 | A simple-to-use HTTP library that is capable of making a lot of |
1073 | Executes DBI requests asynchronously in a proxy process for you, |
754 | concurrent HTTP requests. |
1074 | notifying you in an event-based way when the operation is finished. |
|
|
1075 | |
|
|
1076 | AnyEvent::AIO |
|
|
1077 | Truly asynchronous (as opposed to non-blocking) I/O, should be in |
|
|
1078 | the toolbox of every event programmer. AnyEvent::AIO transparently |
|
|
1079 | fuses IO::AIO and AnyEvent together, giving AnyEvent access to |
|
|
1080 | event-based file I/O, and much more. |
755 | |
1081 | |
756 | AnyEvent::HTTPD |
1082 | AnyEvent::HTTPD |
757 | Provides a simple web application server framework. |
1083 | A simple embedded webserver. |
758 | |
1084 | |
759 | AnyEvent::FastPing |
1085 | AnyEvent::FastPing |
760 | The fastest ping in the west. |
1086 | The fastest ping in the west. |
761 | |
1087 | |
762 | AnyEvent::DBI |
|
|
763 | Executes DBI requests asynchronously in a proxy process. |
|
|
764 | |
|
|
765 | AnyEvent::AIO |
|
|
766 | Truly asynchronous I/O, should be in the toolbox of every event |
|
|
767 | programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent |
|
|
768 | together. |
|
|
769 | |
|
|
770 | AnyEvent::BDB |
|
|
771 | Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently |
|
|
772 | fuses BDB and AnyEvent together. |
|
|
773 | |
|
|
774 | AnyEvent::GPSD |
|
|
775 | A non-blocking interface to gpsd, a daemon delivering GPS |
|
|
776 | information. |
|
|
777 | |
|
|
778 | AnyEvent::IGS |
|
|
779 | A non-blocking interface to the Internet Go Server protocol (used by |
|
|
780 | App::IGS). |
|
|
781 | |
|
|
782 | AnyEvent::IRC |
|
|
783 | AnyEvent based IRC client module family (replacing the older |
|
|
784 | Net::IRC3). |
|
|
785 | |
|
|
786 | Net::XMPP2 |
|
|
787 | AnyEvent based XMPP (Jabber protocol) module family. |
|
|
788 | |
|
|
789 | Net::FCP |
|
|
790 | AnyEvent-based implementation of the Freenet Client Protocol, |
|
|
791 | birthplace of AnyEvent. |
|
|
792 | |
|
|
793 | Event::ExecFlow |
|
|
794 | High level API for event-based execution flow control. |
|
|
795 | |
|
|
796 | Coro |
1088 | Coro |
797 | Has special support for AnyEvent via Coro::AnyEvent. |
1089 | Has special support for AnyEvent via Coro::AnyEvent. |
798 | |
1090 | |
799 | IO::Lambda |
1091 | SIMPLIFIED AE API |
800 | The lambda approach to I/O - don't ask, look there. Can use |
1092 | Starting with version 5.0, AnyEvent officially supports a second, much |
801 | AnyEvent. |
1093 | simpler, API that is designed to reduce the calling, typing and memory |
|
|
1094 | overhead by using function call syntax and a fixed number of parameters. |
|
|
1095 | |
|
|
1096 | See the AE manpage for details. |
802 | |
1097 | |
803 | ERROR AND EXCEPTION HANDLING |
1098 | ERROR AND EXCEPTION HANDLING |
804 | In general, AnyEvent does not do any error handling - it relies on the |
1099 | In general, AnyEvent does not do any error handling - it relies on the |
805 | caller to do that if required. The AnyEvent::Strict module (see also the |
1100 | caller to do that if required. The AnyEvent::Strict module (see also the |
806 | "PERL_ANYEVENT_STRICT" environment variable, below) provides strict |
1101 | "PERL_ANYEVENT_STRICT" environment variable, below) provides strict |
… | |
… | |
816 | "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()", |
1111 | "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()", |
817 | Glib uses "install_exception_handler" and so on. |
1112 | Glib uses "install_exception_handler" and so on. |
818 | |
1113 | |
819 | ENVIRONMENT VARIABLES |
1114 | ENVIRONMENT VARIABLES |
820 | The following environment variables are used by this module or its |
1115 | The following environment variables are used by this module or its |
821 | submodules: |
1116 | submodules. |
|
|
1117 | |
|
|
1118 | Note that AnyEvent will remove *all* environment variables starting with |
|
|
1119 | "PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is |
|
|
1120 | enabled. |
822 | |
1121 | |
823 | "PERL_ANYEVENT_VERBOSE" |
1122 | "PERL_ANYEVENT_VERBOSE" |
824 | By default, AnyEvent will be completely silent except in fatal |
1123 | By default, AnyEvent will be completely silent except in fatal |
825 | conditions. You can set this environment variable to make AnyEvent |
1124 | conditions. You can set this environment variable to make AnyEvent |
826 | more talkative. |
1125 | more talkative. |
… | |
… | |
829 | conditions, such as not being able to load the event model specified |
1128 | conditions, such as not being able to load the event model specified |
830 | by "PERL_ANYEVENT_MODEL". |
1129 | by "PERL_ANYEVENT_MODEL". |
831 | |
1130 | |
832 | When set to 2 or higher, cause AnyEvent to report to STDERR which |
1131 | When set to 2 or higher, cause AnyEvent to report to STDERR which |
833 | event model it chooses. |
1132 | event model it chooses. |
|
|
1133 | |
|
|
1134 | When set to 8 or higher, then AnyEvent will report extra information |
|
|
1135 | on which optional modules it loads and how it implements certain |
|
|
1136 | features. |
834 | |
1137 | |
835 | "PERL_ANYEVENT_STRICT" |
1138 | "PERL_ANYEVENT_STRICT" |
836 | AnyEvent does not do much argument checking by default, as thorough |
1139 | AnyEvent does not do much argument checking by default, as thorough |
837 | argument checking is very costly. Setting this variable to a true |
1140 | argument checking is very costly. Setting this variable to a true |
838 | value will cause AnyEvent to load "AnyEvent::Strict" and then to |
1141 | value will cause AnyEvent to load "AnyEvent::Strict" and then to |
839 | thoroughly check the arguments passed to most method calls. If it |
1142 | thoroughly check the arguments passed to most method calls. If it |
840 | finds any problems it will croak. |
1143 | finds any problems, it will croak. |
841 | |
1144 | |
842 | In other words, enables "strict" mode. |
1145 | In other words, enables "strict" mode. |
843 | |
1146 | |
844 | Unlike "use strict", it is definitely recommended ot keep it off in |
1147 | Unlike "use strict" (or its modern cousin, "use common::sense", it |
845 | production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment |
1148 | is definitely recommended to keep it off in production. Keeping |
|
|
1149 | "PERL_ANYEVENT_STRICT=1" in your environment while developing |
846 | while developing programs can be very useful, however. |
1150 | programs can be very useful, however. |
847 | |
1151 | |
848 | "PERL_ANYEVENT_MODEL" |
1152 | "PERL_ANYEVENT_MODEL" |
849 | This can be used to specify the event model to be used by AnyEvent, |
1153 | This can be used to specify the event model to be used by AnyEvent, |
850 | before auto detection and -probing kicks in. It must be a string |
1154 | before auto detection and -probing kicks in. It must be a string |
851 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
1155 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
… | |
… | |
870 | mentioned will be used, and preference will be given to protocols |
1174 | mentioned will be used, and preference will be given to protocols |
871 | mentioned earlier in the list. |
1175 | mentioned earlier in the list. |
872 | |
1176 | |
873 | This variable can effectively be used for denial-of-service attacks |
1177 | This variable can effectively be used for denial-of-service attacks |
874 | against local programs (e.g. when setuid), although the impact is |
1178 | against local programs (e.g. when setuid), although the impact is |
875 | likely small, as the program has to handle connection errors |
1179 | likely small, as the program has to handle conenction and other |
876 | already- |
1180 | failures anyways. |
877 | |
1181 | |
878 | Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
1182 | Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
879 | IPv6, but support both and try to use both. |
1183 | IPv6, but support both and try to use both. |
880 | "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
1184 | "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
881 | resolve or contact IPv6 addresses. |
1185 | resolve or contact IPv6 addresses. |
… | |
… | |
892 | EDNS0 in its DNS requests. |
1196 | EDNS0 in its DNS requests. |
893 | |
1197 | |
894 | "PERL_ANYEVENT_MAX_FORKS" |
1198 | "PERL_ANYEVENT_MAX_FORKS" |
895 | The maximum number of child processes that |
1199 | The maximum number of child processes that |
896 | "AnyEvent::Util::fork_call" will create in parallel. |
1200 | "AnyEvent::Util::fork_call" will create in parallel. |
|
|
1201 | |
|
|
1202 | "PERL_ANYEVENT_MAX_OUTSTANDING_DNS" |
|
|
1203 | The default value for the "max_outstanding" parameter for the |
|
|
1204 | default DNS resolver - this is the maximum number of parallel DNS |
|
|
1205 | requests that are sent to the DNS server. |
|
|
1206 | |
|
|
1207 | "PERL_ANYEVENT_RESOLV_CONF" |
|
|
1208 | The file to use instead of /etc/resolv.conf (or OS-specific |
|
|
1209 | configuration) in the default resolver. When set to the empty |
|
|
1210 | string, no default config will be used. |
|
|
1211 | |
|
|
1212 | "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH". |
|
|
1213 | When neither "ca_file" nor "ca_path" was specified during |
|
|
1214 | AnyEvent::TLS context creation, and either of these environment |
|
|
1215 | variables exist, they will be used to specify CA certificate |
|
|
1216 | locations instead of a system-dependent default. |
|
|
1217 | |
|
|
1218 | "PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT" |
|
|
1219 | When these are set to 1, then the respective modules are not loaded. |
|
|
1220 | Mostly good for testing AnyEvent itself. |
897 | |
1221 | |
898 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
1222 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
899 | This is an advanced topic that you do not normally need to use AnyEvent |
1223 | This is an advanced topic that you do not normally need to use AnyEvent |
900 | in a module. This section is only of use to event loop authors who want |
1224 | in a module. This section is only of use to event loop authors who want |
901 | to provide AnyEvent compatibility. |
1225 | to provide AnyEvent compatibility. |
… | |
… | |
956 | warn "read: $input\n"; # output what has been read |
1280 | warn "read: $input\n"; # output what has been read |
957 | $cv->send if $input =~ /^q/i; # quit program if /^q/i |
1281 | $cv->send if $input =~ /^q/i; # quit program if /^q/i |
958 | }, |
1282 | }, |
959 | ); |
1283 | ); |
960 | |
1284 | |
961 | my $time_watcher; # can only be used once |
|
|
962 | |
|
|
963 | sub new_timer { |
|
|
964 | $timer = AnyEvent->timer (after => 1, cb => sub { |
1285 | my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub { |
965 | warn "timeout\n"; # print 'timeout' about every second |
1286 | warn "timeout\n"; # print 'timeout' at most every second |
966 | &new_timer; # and restart the time |
|
|
967 | }); |
|
|
968 | } |
1287 | }); |
969 | |
|
|
970 | new_timer; # create first timer |
|
|
971 | |
1288 | |
972 | $cv->recv; # wait until user enters /^q/i |
1289 | $cv->recv; # wait until user enters /^q/i |
973 | |
1290 | |
974 | REAL-WORLD EXAMPLE |
1291 | REAL-WORLD EXAMPLE |
975 | Consider the Net::FCP module. It features (among others) the following |
1292 | Consider the Net::FCP module. It features (among others) the following |
… | |
… | |
1047 | |
1364 | |
1048 | The actual code goes further and collects all errors ("die"s, |
1365 | The actual code goes further and collects all errors ("die"s, |
1049 | exceptions) that occurred during request processing. The "result" method |
1366 | exceptions) that occurred during request processing. The "result" method |
1050 | detects whether an exception as thrown (it is stored inside the $txn |
1367 | detects whether an exception as thrown (it is stored inside the $txn |
1051 | object) and just throws the exception, which means connection errors and |
1368 | object) and just throws the exception, which means connection errors and |
1052 | other problems get reported tot he code that tries to use the result, |
1369 | other problems get reported to the code that tries to use the result, |
1053 | not in a random callback. |
1370 | not in a random callback. |
1054 | |
1371 | |
1055 | All of this enables the following usage styles: |
1372 | All of this enables the following usage styles: |
1056 | |
1373 | |
1057 | 1. Blocking: |
1374 | 1. Blocking: |
… | |
… | |
1102 | through AnyEvent. The benchmark creates a lot of timers (with a zero |
1419 | through AnyEvent. The benchmark creates a lot of timers (with a zero |
1103 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
1420 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
1104 | which it is), lets them fire exactly once and destroys them again. |
1421 | which it is), lets them fire exactly once and destroys them again. |
1105 | |
1422 | |
1106 | Source code for this benchmark is found as eg/bench in the AnyEvent |
1423 | Source code for this benchmark is found as eg/bench in the AnyEvent |
1107 | distribution. |
1424 | distribution. It uses the AE interface, which makes a real difference |
|
|
1425 | for the EV and Perl backends only. |
1108 | |
1426 | |
1109 | Explanation of the columns |
1427 | Explanation of the columns |
1110 | *watcher* is the number of event watchers created/destroyed. Since |
1428 | *watcher* is the number of event watchers created/destroyed. Since |
1111 | different event models feature vastly different performances, each event |
1429 | different event models feature vastly different performances, each event |
1112 | loop was given a number of watchers so that overall runtime is |
1430 | loop was given a number of watchers so that overall runtime is |
… | |
… | |
1131 | *destroy* is the time, in microseconds, that it takes to destroy a |
1449 | *destroy* is the time, in microseconds, that it takes to destroy a |
1132 | single watcher. |
1450 | single watcher. |
1133 | |
1451 | |
1134 | Results |
1452 | Results |
1135 | name watchers bytes create invoke destroy comment |
1453 | name watchers bytes create invoke destroy comment |
1136 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
1454 | EV/EV 100000 223 0.47 0.43 0.27 EV native interface |
1137 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
1455 | EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers |
1138 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
1456 | Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal |
1139 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
1457 | Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation |
1140 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
1458 | Event/Event 16000 516 31.16 31.84 0.82 Event native interface |
1141 | Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers |
1459 | Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers |
|
|
1460 | IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll |
|
|
1461 | IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll |
1142 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
1462 | Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour |
1143 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
1463 | Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers |
1144 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
1464 | POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event |
1145 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
1465 | POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select |
1146 | |
1466 | |
1147 | Discussion |
1467 | Discussion |
1148 | The benchmark does *not* measure scalability of the event loop very |
1468 | The benchmark does *not* measure scalability of the event loop very |
1149 | well. For example, a select-based event loop (such as the pure perl one) |
1469 | well. For example, a select-based event loop (such as the pure perl one) |
1150 | can never compete with an event loop that uses epoll when the number of |
1470 | can never compete with an event loop that uses epoll when the number of |
… | |
… | |
1161 | benchmark machine, handling an event takes roughly 1600 CPU cycles with |
1481 | benchmark machine, handling an event takes roughly 1600 CPU cycles with |
1162 | EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 |
1482 | EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 |
1163 | CPU cycles with POE. |
1483 | CPU cycles with POE. |
1164 | |
1484 | |
1165 | "EV" is the sole leader regarding speed and memory use, which are both |
1485 | "EV" is the sole leader regarding speed and memory use, which are both |
1166 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
1486 | maximal/minimal, respectively. When using the AE API there is zero |
|
|
1487 | overhead (when going through the AnyEvent API create is about 5-6 times |
|
|
1488 | slower, with other times being equal, so still uses far less memory than |
1167 | far less memory than any other event loop and is still faster than Event |
1489 | any other event loop and is still faster than Event natively). |
1168 | natively. |
|
|
1169 | |
1490 | |
1170 | The pure perl implementation is hit in a few sweet spots (both the |
1491 | The pure perl implementation is hit in a few sweet spots (both the |
1171 | constant timeout and the use of a single fd hit optimisations in the |
1492 | constant timeout and the use of a single fd hit optimisations in the |
1172 | perl interpreter and the backend itself). Nevertheless this shows that |
1493 | perl interpreter and the backend itself). Nevertheless this shows that |
1173 | it adds very little overhead in itself. Like any select-based backend |
1494 | it adds very little overhead in itself. Like any select-based backend |
… | |
… | |
1175 | few of them active), of course, but this was not subject of this |
1496 | few of them active), of course, but this was not subject of this |
1176 | benchmark. |
1497 | benchmark. |
1177 | |
1498 | |
1178 | The "Event" module has a relatively high setup and callback invocation |
1499 | The "Event" module has a relatively high setup and callback invocation |
1179 | cost, but overall scores in on the third place. |
1500 | cost, but overall scores in on the third place. |
|
|
1501 | |
|
|
1502 | "IO::Async" performs admirably well, about on par with "Event", even |
|
|
1503 | when using its pure perl backend. |
1180 | |
1504 | |
1181 | "Glib"'s memory usage is quite a bit higher, but it features a faster |
1505 | "Glib"'s memory usage is quite a bit higher, but it features a faster |
1182 | callback invocation and overall ends up in the same class as "Event". |
1506 | callback invocation and overall ends up in the same class as "Event". |
1183 | However, Glib scales extremely badly, doubling the number of watchers |
1507 | However, Glib scales extremely badly, doubling the number of watchers |
1184 | increases the processing time by more than a factor of four, making it |
1508 | increases the processing time by more than a factor of four, making it |
… | |
… | |
1240 | In this benchmark, we use 10000 socket pairs (20000 sockets), of which |
1564 | In this benchmark, we use 10000 socket pairs (20000 sockets), of which |
1241 | 100 (1%) are active. This mirrors the activity of large servers with |
1565 | 100 (1%) are active. This mirrors the activity of large servers with |
1242 | many connections, most of which are idle at any one point in time. |
1566 | many connections, most of which are idle at any one point in time. |
1243 | |
1567 | |
1244 | Source code for this benchmark is found as eg/bench2 in the AnyEvent |
1568 | Source code for this benchmark is found as eg/bench2 in the AnyEvent |
1245 | distribution. |
1569 | distribution. It uses the AE interface, which makes a real difference |
|
|
1570 | for the EV and Perl backends only. |
1246 | |
1571 | |
1247 | Explanation of the columns |
1572 | Explanation of the columns |
1248 | *sockets* is the number of sockets, and twice the number of "servers" |
1573 | *sockets* is the number of sockets, and twice the number of "servers" |
1249 | (as each server has a read and write socket end). |
1574 | (as each server has a read and write socket end). |
1250 | |
1575 | |
… | |
… | |
1255 | single "request", that is, reading the token from the pipe and |
1580 | single "request", that is, reading the token from the pipe and |
1256 | forwarding it to another server. This includes deleting the old timeout |
1581 | forwarding it to another server. This includes deleting the old timeout |
1257 | and creating a new one that moves the timeout into the future. |
1582 | and creating a new one that moves the timeout into the future. |
1258 | |
1583 | |
1259 | Results |
1584 | Results |
1260 | name sockets create request |
1585 | name sockets create request |
1261 | EV 20000 69.01 11.16 |
1586 | EV 20000 62.66 7.99 |
1262 | Perl 20000 73.32 35.87 |
1587 | Perl 20000 68.32 32.64 |
1263 | Event 20000 212.62 257.32 |
1588 | IOAsync 20000 174.06 101.15 epoll |
1264 | Glib 20000 651.16 1896.30 |
1589 | IOAsync 20000 174.67 610.84 poll |
|
|
1590 | Event 20000 202.69 242.91 |
|
|
1591 | Glib 20000 557.01 1689.52 |
1265 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
1592 | POE 20000 341.54 12086.32 uses POE::Loop::Event |
1266 | |
1593 | |
1267 | Discussion |
1594 | Discussion |
1268 | This benchmark *does* measure scalability and overall performance of the |
1595 | This benchmark *does* measure scalability and overall performance of the |
1269 | particular event loop. |
1596 | particular event loop. |
1270 | |
1597 | |
1271 | EV is again fastest. Since it is using epoll on my system, the setup |
1598 | EV is again fastest. Since it is using epoll on my system, the setup |
1272 | time is relatively high, though. |
1599 | time is relatively high, though. |
1273 | |
1600 | |
1274 | Perl surprisingly comes second. It is much faster than the C-based event |
1601 | Perl surprisingly comes second. It is much faster than the C-based event |
1275 | loops Event and Glib. |
1602 | loops Event and Glib. |
|
|
1603 | |
|
|
1604 | IO::Async performs very well when using its epoll backend, and still |
|
|
1605 | quite good compared to Glib when using its pure perl backend. |
1276 | |
1606 | |
1277 | Event suffers from high setup time as well (look at its code and you |
1607 | Event suffers from high setup time as well (look at its code and you |
1278 | will understand why). Callback invocation also has a high overhead |
1608 | will understand why). Callback invocation also has a high overhead |
1279 | compared to the "$_->() for .."-style loop that the Perl event loop |
1609 | compared to the "$_->() for .."-style loop that the Perl event loop |
1280 | uses. Event uses select or poll in basically all documented |
1610 | uses. Event uses select or poll in basically all documented |
… | |
… | |
1331 | |
1661 | |
1332 | Summary |
1662 | Summary |
1333 | * C-based event loops perform very well with small number of watchers, |
1663 | * C-based event loops perform very well with small number of watchers, |
1334 | as the management overhead dominates. |
1664 | as the management overhead dominates. |
1335 | |
1665 | |
|
|
1666 | THE IO::Lambda BENCHMARK |
|
|
1667 | Recently I was told about the benchmark in the IO::Lambda manpage, which |
|
|
1668 | could be misinterpreted to make AnyEvent look bad. In fact, the |
|
|
1669 | benchmark simply compares IO::Lambda with POE, and IO::Lambda looks |
|
|
1670 | better (which shouldn't come as a surprise to anybody). As such, the |
|
|
1671 | benchmark is fine, and mostly shows that the AnyEvent backend from |
|
|
1672 | IO::Lambda isn't very optimal. But how would AnyEvent compare when used |
|
|
1673 | without the extra baggage? To explore this, I wrote the equivalent |
|
|
1674 | benchmark for AnyEvent. |
|
|
1675 | |
|
|
1676 | The benchmark itself creates an echo-server, and then, for 500 times, |
|
|
1677 | connects to the echo server, sends a line, waits for the reply, and then |
|
|
1678 | creates the next connection. This is a rather bad benchmark, as it |
|
|
1679 | doesn't test the efficiency of the framework or much non-blocking I/O, |
|
|
1680 | but it is a benchmark nevertheless. |
|
|
1681 | |
|
|
1682 | name runtime |
|
|
1683 | Lambda/select 0.330 sec |
|
|
1684 | + optimized 0.122 sec |
|
|
1685 | Lambda/AnyEvent 0.327 sec |
|
|
1686 | + optimized 0.138 sec |
|
|
1687 | Raw sockets/select 0.077 sec |
|
|
1688 | POE/select, components 0.662 sec |
|
|
1689 | POE/select, raw sockets 0.226 sec |
|
|
1690 | POE/select, optimized 0.404 sec |
|
|
1691 | |
|
|
1692 | AnyEvent/select/nb 0.085 sec |
|
|
1693 | AnyEvent/EV/nb 0.068 sec |
|
|
1694 | +state machine 0.134 sec |
|
|
1695 | |
|
|
1696 | The benchmark is also a bit unfair (my fault): the IO::Lambda/POE |
|
|
1697 | benchmarks actually make blocking connects and use 100% blocking I/O, |
|
|
1698 | defeating the purpose of an event-based solution. All of the newly |
|
|
1699 | written AnyEvent benchmarks use 100% non-blocking connects (using |
|
|
1700 | AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS |
|
|
1701 | resolver), so AnyEvent is at a disadvantage here, as non-blocking |
|
|
1702 | connects generally require a lot more bookkeeping and event handling |
|
|
1703 | than blocking connects (which involve a single syscall only). |
|
|
1704 | |
|
|
1705 | The last AnyEvent benchmark additionally uses AnyEvent::Handle, which |
|
|
1706 | offers similar expressive power as POE and IO::Lambda, using |
|
|
1707 | conventional Perl syntax. This means that both the echo server and the |
|
|
1708 | client are 100% non-blocking, further placing it at a disadvantage. |
|
|
1709 | |
|
|
1710 | As you can see, the AnyEvent + EV combination even beats the |
|
|
1711 | hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl |
|
|
1712 | backend easily beats IO::Lambda and POE. |
|
|
1713 | |
|
|
1714 | And even the 100% non-blocking version written using the high-level (and |
|
|
1715 | slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda |
|
|
1716 | higher level ("unoptimised") abstractions by a large margin, even though |
|
|
1717 | it does all of DNS, tcp-connect and socket I/O in a non-blocking way. |
|
|
1718 | |
|
|
1719 | The two AnyEvent benchmarks programs can be found as eg/ae0.pl and |
|
|
1720 | eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are |
|
|
1721 | part of the IO::Lambda distribution and were used without any changes. |
|
|
1722 | |
|
|
1723 | SIGNALS |
|
|
1724 | AnyEvent currently installs handlers for these signals: |
|
|
1725 | |
|
|
1726 | SIGCHLD |
|
|
1727 | A handler for "SIGCHLD" is installed by AnyEvent's child watcher |
|
|
1728 | emulation for event loops that do not support them natively. Also, |
|
|
1729 | some event loops install a similar handler. |
|
|
1730 | |
|
|
1731 | Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, |
|
|
1732 | then AnyEvent will reset it to default, to avoid losing child exit |
|
|
1733 | statuses. |
|
|
1734 | |
|
|
1735 | SIGPIPE |
|
|
1736 | A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is |
|
|
1737 | "undef" when AnyEvent gets loaded. |
|
|
1738 | |
|
|
1739 | The rationale for this is that AnyEvent users usually do not really |
|
|
1740 | depend on SIGPIPE delivery (which is purely an optimisation for |
|
|
1741 | shell use, or badly-written programs), but "SIGPIPE" can cause |
|
|
1742 | spurious and rare program exits as a lot of people do not expect |
|
|
1743 | "SIGPIPE" when writing to some random socket. |
|
|
1744 | |
|
|
1745 | The rationale for installing a no-op handler as opposed to ignoring |
|
|
1746 | it is that this way, the handler will be restored to defaults on |
|
|
1747 | exec. |
|
|
1748 | |
|
|
1749 | Feel free to install your own handler, or reset it to defaults. |
|
|
1750 | |
|
|
1751 | RECOMMENDED/OPTIONAL MODULES |
|
|
1752 | One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and |
|
|
1753 | its built-in modules) are required to use it. |
|
|
1754 | |
|
|
1755 | That does not mean that AnyEvent won't take advantage of some additional |
|
|
1756 | modules if they are installed. |
|
|
1757 | |
|
|
1758 | This section explains which additional modules will be used, and how |
|
|
1759 | they affect AnyEvent's operation. |
|
|
1760 | |
|
|
1761 | Async::Interrupt |
|
|
1762 | This slightly arcane module is used to implement fast signal |
|
|
1763 | handling: To my knowledge, there is no way to do completely |
|
|
1764 | race-free and quick signal handling in pure perl. To ensure that |
|
|
1765 | signals still get delivered, AnyEvent will start an interval timer |
|
|
1766 | to wake up perl (and catch the signals) with some delay (default is |
|
|
1767 | 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). |
|
|
1768 | |
|
|
1769 | If this module is available, then it will be used to implement |
|
|
1770 | signal catching, which means that signals will not be delayed, and |
|
|
1771 | the event loop will not be interrupted regularly, which is more |
|
|
1772 | efficient (and good for battery life on laptops). |
|
|
1773 | |
|
|
1774 | This affects not just the pure-perl event loop, but also other event |
|
|
1775 | loops that have no signal handling on their own (e.g. Glib, Tk, Qt). |
|
|
1776 | |
|
|
1777 | Some event loops (POE, Event, Event::Lib) offer signal watchers |
|
|
1778 | natively, and either employ their own workarounds (POE) or use |
|
|
1779 | AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY). |
|
|
1780 | Installing Async::Interrupt does nothing for those backends. |
|
|
1781 | |
|
|
1782 | EV This module isn't really "optional", as it is simply one of the |
|
|
1783 | backend event loops that AnyEvent can use. However, it is simply the |
|
|
1784 | best event loop available in terms of features, speed and stability: |
|
|
1785 | It supports the AnyEvent API optimally, implements all the watcher |
|
|
1786 | types in XS, does automatic timer adjustments even when no monotonic |
|
|
1787 | clock is available, can take avdantage of advanced kernel interfaces |
|
|
1788 | such as "epoll" and "kqueue", and is the fastest backend *by far*. |
|
|
1789 | You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and |
|
|
1790 | Glib::EV). |
|
|
1791 | |
|
|
1792 | If you only use backends that rely on another event loop (e.g. |
|
|
1793 | "Tk"), then this module will do nothing for you. |
|
|
1794 | |
|
|
1795 | Guard |
|
|
1796 | The guard module, when used, will be used to implement |
|
|
1797 | "AnyEvent::Util::guard". This speeds up guards considerably (and |
|
|
1798 | uses a lot less memory), but otherwise doesn't affect guard |
|
|
1799 | operation much. It is purely used for performance. |
|
|
1800 | |
|
|
1801 | JSON and JSON::XS |
|
|
1802 | One of these modules is required when you want to read or write JSON |
|
|
1803 | data via AnyEvent::Handle. JSON is also written in pure-perl, but |
|
|
1804 | can take advantage of the ultra-high-speed JSON::XS module when it |
|
|
1805 | is installed. |
|
|
1806 | |
|
|
1807 | Net::SSLeay |
|
|
1808 | Implementing TLS/SSL in Perl is certainly interesting, but not very |
|
|
1809 | worthwhile: If this module is installed, then AnyEvent::Handle (with |
|
|
1810 | the help of AnyEvent::TLS), gains the ability to do TLS/SSL. |
|
|
1811 | |
|
|
1812 | Time::HiRes |
|
|
1813 | This module is part of perl since release 5.008. It will be used |
|
|
1814 | when the chosen event library does not come with a timing source of |
|
|
1815 | its own. The pure-perl event loop (AnyEvent::Impl::Perl) will |
|
|
1816 | additionally use it to try to use a monotonic clock for timing |
|
|
1817 | stability. |
|
|
1818 | |
1336 | FORK |
1819 | FORK |
1337 | Most event libraries are not fork-safe. The ones who are usually are |
1820 | Most event libraries are not fork-safe. The ones who are usually are |
1338 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1821 | because they rely on inefficient but fork-safe "select" or "poll" calls |
1339 | Only EV is fully fork-aware. |
1822 | - higher performance APIs such as BSD's kqueue or the dreaded Linux |
|
|
1823 | epoll are usually badly thought-out hacks that are incompatible with |
|
|
1824 | fork in one way or another. Only EV is fully fork-aware and ensures that |
|
|
1825 | you continue event-processing in both parent and child (or both, if you |
|
|
1826 | know what you are doing). |
|
|
1827 | |
|
|
1828 | This means that, in general, you cannot fork and do event processing in |
|
|
1829 | the child if the event library was initialised before the fork (which |
|
|
1830 | usually happens when the first AnyEvent watcher is created, or the |
|
|
1831 | library is loaded). |
1340 | |
1832 | |
1341 | If you have to fork, you must either do so *before* creating your first |
1833 | If you have to fork, you must either do so *before* creating your first |
1342 | watcher OR you must not use AnyEvent at all in the child. |
1834 | watcher OR you must not use AnyEvent at all in the child OR you must do |
|
|
1835 | something completely out of the scope of AnyEvent. |
|
|
1836 | |
|
|
1837 | The problem of doing event processing in the parent *and* the child is |
|
|
1838 | much more complicated: even for backends that *are* fork-aware or |
|
|
1839 | fork-safe, their behaviour is not usually what you want: fork clones all |
|
|
1840 | watchers, that means all timers, I/O watchers etc. are active in both |
|
|
1841 | parent and child, which is almost never what you want. USing "exec" to |
|
|
1842 | start worker children from some kind of manage rprocess is usually |
|
|
1843 | preferred, because it is much easier and cleaner, at the expense of |
|
|
1844 | having to have another binary. |
1343 | |
1845 | |
1344 | SECURITY CONSIDERATIONS |
1846 | SECURITY CONSIDERATIONS |
1345 | AnyEvent can be forced to load any event model via |
1847 | AnyEvent can be forced to load any event model via |
1346 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
1848 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
1347 | to execute arbitrary code or directly gain access, it can easily be used |
1849 | to execute arbitrary code or directly gain access, it can easily be used |
… | |
… | |
1351 | |
1853 | |
1352 | You can make AnyEvent completely ignore this variable by deleting it |
1854 | You can make AnyEvent completely ignore this variable by deleting it |
1353 | before the first watcher gets created, e.g. with a "BEGIN" block: |
1855 | before the first watcher gets created, e.g. with a "BEGIN" block: |
1354 | |
1856 | |
1355 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1857 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1356 | |
1858 | |
1357 | use AnyEvent; |
1859 | use AnyEvent; |
1358 | |
1860 | |
1359 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
1861 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
1360 | be used to probe what backend is used and gain other information (which |
1862 | be used to probe what backend is used and gain other information (which |
1361 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), |
1863 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), |
1362 | and $ENV{PERL_ANYEGENT_STRICT}. |
1864 | and $ENV{PERL_ANYEVENT_STRICT}. |
|
|
1865 | |
|
|
1866 | Note that AnyEvent will remove *all* environment variables starting with |
|
|
1867 | "PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is |
|
|
1868 | enabled. |
1363 | |
1869 | |
1364 | BUGS |
1870 | BUGS |
1365 | Perl 5.8 has numerous memleaks that sometimes hit this module and are |
1871 | Perl 5.8 has numerous memleaks that sometimes hit this module and are |
1366 | hard to work around. If you suffer from memleaks, first upgrade to Perl |
1872 | hard to work around. If you suffer from memleaks, first upgrade to Perl |
1367 | 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other |
1873 | 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other |
1368 | annoying mamleaks, such as leaking on "map" and "grep" but it is usually |
1874 | annoying memleaks, such as leaking on "map" and "grep" but it is usually |
1369 | not as pronounced). |
1875 | not as pronounced). |
1370 | |
1876 | |
1371 | SEE ALSO |
1877 | SEE ALSO |
|
|
1878 | Tutorial/Introduction: AnyEvent::Intro. |
|
|
1879 | |
|
|
1880 | FAQ: AnyEvent::FAQ. |
|
|
1881 | |
1372 | Utility functions: AnyEvent::Util. |
1882 | Utility functions: AnyEvent::Util. |
1373 | |
1883 | |
1374 | Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, |
1884 | Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, |
1375 | Event::Lib, Qt, POE. |
1885 | Event::Lib, Qt, POE. |
1376 | |
1886 | |
1377 | Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, |
1887 | Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, |
1378 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, |
1888 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, |
1379 | AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE. |
1889 | AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE, |
|
|
1890 | AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi. |
1380 | |
1891 | |
1381 | Non-blocking file handles, sockets, TCP clients and servers: |
1892 | Non-blocking file handles, sockets, TCP clients and servers: |
1382 | AnyEvent::Handle, AnyEvent::Socket. |
1893 | AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS. |
1383 | |
1894 | |
1384 | Asynchronous DNS: AnyEvent::DNS. |
1895 | Asynchronous DNS: AnyEvent::DNS. |
1385 | |
1896 | |
1386 | Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, |
1897 | Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event. |
1387 | |
1898 | |
1388 | Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS. |
1899 | Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC, |
|
|
1900 | AnyEvent::HTTP. |
1389 | |
1901 | |
1390 | AUTHOR |
1902 | AUTHOR |
1391 | Marc Lehmann <schmorp@schmorp.de> |
1903 | Marc Lehmann <schmorp@schmorp.de> |
1392 | http://home.schmorp.de/ |
1904 | http://home.schmorp.de/ |
1393 | |
1905 | |