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1=> NAME 1NAME
2 AnyEvent - provide framework for multiple event loops 2 AnyEvent - provide framework for multiple event loops
3 3
4 EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event 4 EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event
5 loops 5 loops
6 6
7SYNOPSIS 7SYNOPSIS
8 use AnyEvent; 8 use AnyEvent;
9 9
10 my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { 10 my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... });
11 ...
12 });
13 11
14 my $w = AnyEvent->timer (after => $seconds, cb => sub { 12 my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
13 my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
14
15 print AnyEvent->now; # prints current event loop time
16 print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
17
18 my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
19
20 my $w = AnyEvent->child (pid => $pid, cb => sub {
21 my ($pid, $status) = @_;
15 ... 22 ...
16 }); 23 });
17 24
18 my $w = AnyEvent->condvar; # stores whether a condition was flagged 25 my $w = AnyEvent->condvar; # stores whether a condition was flagged
19 $w->send; # wake up current and all future recv's 26 $w->send; # wake up current and all future recv's
20 $w->recv; # enters "main loop" till $condvar gets ->send 27 $w->recv; # enters "main loop" till $condvar gets ->send
28 # use a condvar in callback mode:
29 $w->cb (sub { $_[0]->recv });
30
31INTRODUCTION/TUTORIAL
32 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
34 manpage.
21 35
22WHY YOU SHOULD USE THIS MODULE (OR NOT) 36WHY YOU SHOULD USE THIS MODULE (OR NOT)
23 Glib, POE, IO::Async, Event... CPAN offers event models by the dozen 37 Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
24 nowadays. So what is different about AnyEvent? 38 nowadays. So what is different about AnyEvent?
25 39
26 Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of 40 Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of
27 policy* and AnyEvent is *small and efficient*. 41 policy* and AnyEvent is *small and efficient*.
28 42
29 First and foremost, *AnyEvent is not an event model* itself, it only 43 First and foremost, *AnyEvent is not an event model* itself, it only
30 interfaces to whatever event model the main program happens to use in a 44 interfaces to whatever event model the main program happens to use, in a
31 pragmatic way. For event models and certain classes of immortals alike, 45 pragmatic way. For event models and certain classes of immortals alike,
32 the statement "there can only be one" is a bitter reality: In general, 46 the statement "there can only be one" is a bitter reality: In general,
33 only one event loop can be active at the same time in a process. 47 only one event loop can be active at the same time in a process.
34 AnyEvent helps hiding the differences between those event loops. 48 AnyEvent cannot change this, but it can hide the differences between
49 those event loops.
35 50
36 The goal of AnyEvent is to offer module authors the ability to do event 51 The goal of AnyEvent is to offer module authors the ability to do event
37 programming (waiting for I/O or timer events) without subscribing to a 52 programming (waiting for I/O or timer events) without subscribing to a
38 religion, a way of living, and most importantly: without forcing your 53 religion, a way of living, and most importantly: without forcing your
39 module users into the same thing by forcing them to use the same event 54 module users into the same thing by forcing them to use the same event
40 model you use. 55 model you use.
41 56
42 For modules like POE or IO::Async (which is a total misnomer as it is 57 For modules like POE or IO::Async (which is a total misnomer as it is
43 actually doing all I/O *synchronously*...), using them in your module is 58 actually doing all I/O *synchronously*...), using them in your module is
44 like joining a cult: After you joined, you are dependent on them and you 59 like joining a cult: After you joined, you are dependent on them and you
45 cannot use anything else, as it is simply incompatible to everything 60 cannot use anything else, as they are simply incompatible to everything
46 that isn't itself. What's worse, all the potential users of your module 61 that isn't them. What's worse, all the potential users of your module
47 are *also* forced to use the same event loop you use. 62 are *also* forced to use the same event loop you use.
48 63
49 AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works 64 AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50 fine. AnyEvent + Tk works fine etc. etc. but none of these work together 65 fine. AnyEvent + Tk works fine etc. etc. but none of these work together
51 with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your 66 with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your
52 module uses one of those, every user of your module has to use it, too. 67 module uses one of those, every user of your module has to use it, too.
53 But if your module uses AnyEvent, it works transparently with all event 68 But if your module uses AnyEvent, it works transparently with all event
54 models it supports (including stuff like POE and IO::Async, as long as 69 models it supports (including stuff like IO::Async, as long as those use
55 those use one of the supported event loops. It is trivial to add new 70 one of the supported event loops. It is trivial to add new event loops
56 event loops to AnyEvent, too, so it is future-proof). 71 to AnyEvent, too, so it is future-proof).
57 72
58 In addition to being free of having to use *the one and only true event 73 In addition to being free of having to use *the one and only true event
59 model*, AnyEvent also is free of bloat and policy: with POE or similar 74 model*, AnyEvent also is free of bloat and policy: with POE or similar
60 modules, you get an enormous amount of code and strict rules you have to 75 modules, you get an enormous amount of code and strict rules you have to
61 follow. AnyEvent, on the other hand, is lean and up to the point, by 76 follow. AnyEvent, on the other hand, is lean and up to the point, by
… …
117 These watchers are normal Perl objects with normal Perl lifetime. After 132 These watchers are normal Perl objects with normal Perl lifetime. After
118 creating a watcher it will immediately "watch" for events and invoke the 133 creating a watcher it will immediately "watch" for events and invoke the
119 callback when the event occurs (of course, only when the event model is 134 callback when the event occurs (of course, only when the event model is
120 in control). 135 in control).
121 136
137 Note that callbacks must not permanently change global variables
138 potentially in use by the event loop (such as $_ or $[) and that
139 callbacks must not "die". The former is good programming practise in
140 Perl and the latter stems from the fact that exception handling differs
141 widely between event loops.
142
122 To disable the watcher you have to destroy it (e.g. by setting the 143 To disable the watcher you have to destroy it (e.g. by setting the
123 variable you store it in to "undef" or otherwise deleting all references 144 variable you store it in to "undef" or otherwise deleting all references
124 to it). 145 to it).
125 146
126 All watchers are created by calling a method on the "AnyEvent" class. 147 All watchers are created by calling a method on the "AnyEvent" class.
… …
128 Many watchers either are used with "recursion" (repeating timers for 149 Many watchers either are used with "recursion" (repeating timers for
129 example), or need to refer to their watcher object in other ways. 150 example), or need to refer to their watcher object in other ways.
130 151
131 An any way to achieve that is this pattern: 152 An any way to achieve that is this pattern:
132 153
133 my $w; $w = AnyEvent->type (arg => value ..., cb => sub { 154 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
134 # you can use $w here, for example to undef it 155 # you can use $w here, for example to undef it
135 undef $w; 156 undef $w;
136 }); 157 });
137 158
138 Note that "my $w; $w =" combination. This is necessary because in Perl, 159 Note that "my $w; $w =" combination. This is necessary because in Perl,
139 my variables are only visible after the statement in which they are 160 my variables are only visible after the statement in which they are
140 declared. 161 declared.
141 162
142 I/O WATCHERS 163 I/O WATCHERS
143 You can create an I/O watcher by calling the "AnyEvent->io" method with 164 You can create an I/O watcher by calling the "AnyEvent->io" method with
144 the following mandatory key-value pairs as arguments: 165 the following mandatory key-value pairs as arguments:
145 166
146 "fh" the Perl *file handle* (*not* file descriptor) to watch for events. 167 "fh" is the Perl *file handle* (*not* file descriptor) to watch for
168 events (AnyEvent might or might not keep a reference to this file
169 handle). Note that only file handles pointing to things for which
170 non-blocking operation makes sense are allowed. This includes sockets,
171 most character devices, pipes, fifos and so on, but not for example
172 files or block devices.
173
147 "poll" must be a string that is either "r" or "w", which creates a 174 "poll" must be a string that is either "r" or "w", which creates a
148 watcher waiting for "r"eadable or "w"ritable events, respectively. "cb" 175 watcher waiting for "r"eadable or "w"ritable events, respectively.
176
149 is the callback to invoke each time the file handle becomes ready. 177 "cb" is the callback to invoke each time the file handle becomes ready.
150 178
151 Although the callback might get passed parameters, their value and 179 Although the callback might get passed parameters, their value and
152 presence is undefined and you cannot rely on them. Portable AnyEvent 180 presence is undefined and you cannot rely on them. Portable AnyEvent
153 callbacks cannot use arguments passed to I/O watcher callbacks. 181 callbacks cannot use arguments passed to I/O watcher callbacks.
154 182
… …
158 186
159 Some event loops issue spurious readyness notifications, so you should 187 Some event loops issue spurious readyness notifications, so you should
160 always use non-blocking calls when reading/writing from/to your file 188 always use non-blocking calls when reading/writing from/to your file
161 handles. 189 handles.
162 190
163 Example:
164
165 # wait for readability of STDIN, then read a line and disable the watcher 191 Example: wait for readability of STDIN, then read a line and disable the
192 watcher.
193
166 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 194 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167 chomp (my $input = <STDIN>); 195 chomp (my $input = <STDIN>);
168 warn "read: $input\n"; 196 warn "read: $input\n";
169 undef $w; 197 undef $w;
170 }); 198 });
… …
179 207
180 Although the callback might get passed parameters, their value and 208 Although the callback might get passed parameters, their value and
181 presence is undefined and you cannot rely on them. Portable AnyEvent 209 presence is undefined and you cannot rely on them. Portable AnyEvent
182 callbacks cannot use arguments passed to time watcher callbacks. 210 callbacks cannot use arguments passed to time watcher callbacks.
183 211
184 The timer callback will be invoked at most once: if you want a repeating 212 The callback will normally be invoked once only. If you specify another
185 timer you have to create a new watcher (this is a limitation by both Tk 213 parameter, "interval", as a strictly positive number (> 0), then the
186 and Glib). 214 callback will be invoked regularly at that interval (in fractional
215 seconds) after the first invocation. If "interval" is specified with a
216 false value, then it is treated as if it were missing.
187 217
188 Example: 218 The callback will be rescheduled before invoking the callback, but no
219 attempt is done to avoid timer drift in most backends, so the interval
220 is only approximate.
189 221
190 # fire an event after 7.7 seconds 222 Example: fire an event after 7.7 seconds.
223
191 my $w = AnyEvent->timer (after => 7.7, cb => sub { 224 my $w = AnyEvent->timer (after => 7.7, cb => sub {
192 warn "timeout\n"; 225 warn "timeout\n";
193 }); 226 });
194 227
195 # to cancel the timer: 228 # to cancel the timer:
196 undef $w; 229 undef $w;
197 230
198 Example 2:
199
200 # fire an event after 0.5 seconds, then roughly every second 231 Example 2: fire an event after 0.5 seconds, then roughly every second.
201 my $w;
202 232
203 my $cb = sub {
204 # cancel the old timer while creating a new one
205 $w = AnyEvent->timer (after => 1, cb => $cb); 233 my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
234 warn "timeout\n";
206 }; 235 };
207
208 # start the "loop" by creating the first watcher
209 $w = AnyEvent->timer (after => 0.5, cb => $cb);
210 236
211 TIMING ISSUES 237 TIMING ISSUES
212 There are two ways to handle timers: based on real time (relative, "fire 238 There are two ways to handle timers: based on real time (relative, "fire
213 in 10 seconds") and based on wallclock time (absolute, "fire at 12 239 in 10 seconds") and based on wallclock time (absolute, "fire at 12
214 o'clock"). 240 o'clock").
… …
288 In either case, if you care (and in most cases, you don't), then you 314 In either case, if you care (and in most cases, you don't), then you
289 can get whatever behaviour you want with any event loop, by taking 315 can get whatever behaviour you want with any event loop, by taking
290 the difference between "AnyEvent->time" and "AnyEvent->now" into 316 the difference between "AnyEvent->time" and "AnyEvent->now" into
291 account. 317 account.
292 318
319 AnyEvent->now_update
320 Some event loops (such as EV or AnyEvent::Impl::Perl) cache the
321 current time for each loop iteration (see the discussion of
322 AnyEvent->now, above).
323
324 When a callback runs for a long time (or when the process sleeps),
325 then this "current" time will differ substantially from the real
326 time, which might affect timers and time-outs.
327
328 When this is the case, you can call this method, which will update
329 the event loop's idea of "current time".
330
331 Note that updating the time *might* cause some events to be handled.
332
293 SIGNAL WATCHERS 333 SIGNAL WATCHERS
294 You can watch for signals using a signal watcher, "signal" is the signal 334 You can watch for signals using a signal watcher, "signal" is the signal
295 *name* without any "SIG" prefix, "cb" is the Perl callback to be invoked 335 *name* in uppercase and without any "SIG" prefix, "cb" is the Perl
296 whenever a signal occurs. 336 callback to be invoked whenever a signal occurs.
297 337
298 Although the callback might get passed parameters, their value and 338 Although the callback might get passed parameters, their value and
299 presence is undefined and you cannot rely on them. Portable AnyEvent 339 presence is undefined and you cannot rely on them. Portable AnyEvent
300 callbacks cannot use arguments passed to signal watcher callbacks. 340 callbacks cannot use arguments passed to signal watcher callbacks.
301 341
… …
316 356
317 CHILD PROCESS WATCHERS 357 CHILD PROCESS WATCHERS
318 You can also watch on a child process exit and catch its exit status. 358 You can also watch on a child process exit and catch its exit status.
319 359
320 The child process is specified by the "pid" argument (if set to 0, it 360 The child process is specified by the "pid" argument (if set to 0, it
321 watches for any child process exit). The watcher will trigger as often 361 watches for any child process exit). The watcher will triggered only
322 as status change for the child are received. This works by installing a 362 when the child process has finished and an exit status is available, not
323 signal handler for "SIGCHLD". The callback will be called with the pid 363 on any trace events (stopped/continued).
324 and exit status (as returned by waitpid), so unlike other watcher types, 364
325 you *can* rely on child watcher callback arguments. 365 The callback will be called with the pid and exit status (as returned by
366 waitpid), so unlike other watcher types, you *can* rely on child watcher
367 callback arguments.
368
369 This watcher type works by installing a signal handler for "SIGCHLD",
370 and since it cannot be shared, nothing else should use SIGCHLD or reap
371 random child processes (waiting for specific child processes, e.g.
372 inside "system", is just fine).
326 373
327 There is a slight catch to child watchers, however: you usually start 374 There is a slight catch to child watchers, however: you usually start
328 them *after* the child process was created, and this means the process 375 them *after* the child process was created, and this means the process
329 could have exited already (and no SIGCHLD will be sent anymore). 376 could have exited already (and no SIGCHLD will be sent anymore).
330 377
… …
337 an AnyEvent program, you *have* to create at least one watcher before 384 an AnyEvent program, you *have* to create at least one watcher before
338 you "fork" the child (alternatively, you can call "AnyEvent::detect"). 385 you "fork" the child (alternatively, you can call "AnyEvent::detect").
339 386
340 Example: fork a process and wait for it 387 Example: fork a process and wait for it
341 388
342 my $done = AnyEvent->condvar; 389 my $done = AnyEvent->condvar;
343 390
344 my $pid = fork or exit 5; 391 my $pid = fork or exit 5;
345 392
346 my $w = AnyEvent->child ( 393 my $w = AnyEvent->child (
347 pid => $pid, 394 pid => $pid,
348 cb => sub { 395 cb => sub {
349 my ($pid, $status) = @_; 396 my ($pid, $status) = @_;
350 warn "pid $pid exited with status $status"; 397 warn "pid $pid exited with status $status";
351 $done->send; 398 $done->send;
352 }, 399 },
353 ); 400 );
354 401
355 # do something else, then wait for process exit 402 # do something else, then wait for process exit
356 $done->recv; 403 $done->recv;
357 404
358 CONDITION VARIABLES 405 CONDITION VARIABLES
359 If you are familiar with some event loops you will know that all of them 406 If you are familiar with some event loops you will know that all of them
360 require you to run some blocking "loop", "run" or similar function that 407 require you to run some blocking "loop", "run" or similar function that
361 will actively watch for new events and call your callbacks. 408 will actively watch for new events and call your callbacks.
… …
366 The instrument to do that is called a "condition variable", so called 413 The instrument to do that is called a "condition variable", so called
367 because they represent a condition that must become true. 414 because they represent a condition that must become true.
368 415
369 Condition variables can be created by calling the "AnyEvent->condvar" 416 Condition variables can be created by calling the "AnyEvent->condvar"
370 method, usually without arguments. The only argument pair allowed is 417 method, usually without arguments. The only argument pair allowed is
418
371 "cb", which specifies a callback to be called when the condition 419 "cb", which specifies a callback to be called when the condition
372 variable becomes true. 420 variable becomes true, with the condition variable as the first argument
421 (but not the results).
373 422
374 After creation, the condition variable is "false" until it becomes 423 After creation, the condition variable is "false" until it becomes
375 "true" by calling the "send" method (or calling the condition variable 424 "true" by calling the "send" method (or calling the condition variable
376 as if it were a callback, read about the caveats in the description for 425 as if it were a callback, read about the caveats in the description for
377 the "->send" method). 426 the "->send" method).
… …
433 482
434 my $done = AnyEvent->condvar; 483 my $done = AnyEvent->condvar;
435 my $delay = AnyEvent->timer (after => 5, cb => $done); 484 my $delay = AnyEvent->timer (after => 5, cb => $done);
436 $done->recv; 485 $done->recv;
437 486
487 Example: Imagine an API that returns a condvar and doesn't support
488 callbacks. This is how you make a synchronous call, for example from the
489 main program:
490
491 use AnyEvent::CouchDB;
492
493 ...
494
495 my @info = $couchdb->info->recv;
496
497 And this is how you would just ste a callback to be called whenever the
498 results are available:
499
500 $couchdb->info->cb (sub {
501 my @info = $_[0]->recv;
502 });
503
438 METHODS FOR PRODUCERS 504 METHODS FOR PRODUCERS
439 These methods should only be used by the producing side, i.e. the 505 These methods should only be used by the producing side, i.e. the
440 code/module that eventually sends the signal. Note that it is also the 506 code/module that eventually sends the signal. Note that it is also the
441 producer side which creates the condvar in most cases, but it isn't 507 producer side which creates the condvar in most cases, but it isn't
442 uncommon for the consumer to create it as well. 508 uncommon for the consumer to create it as well.
… …
562 628
563 $bool = $cv->ready 629 $bool = $cv->ready
564 Returns true when the condition is "true", i.e. whether "send" or 630 Returns true when the condition is "true", i.e. whether "send" or
565 "croak" have been called. 631 "croak" have been called.
566 632
567 $cb = $cv->cb ([new callback]) 633 $cb = $cv->cb ($cb->($cv))
568 This is a mutator function that returns the callback set and 634 This is a mutator function that returns the callback set and
569 optionally replaces it before doing so. 635 optionally replaces it before doing so.
570 636
571 The callback will be called when the condition becomes "true", i.e. 637 The callback will be called when the condition becomes "true", i.e.
572 when "send" or "croak" are called. Calling "recv" inside the 638 when "send" or "croak" are called, with the only argument being the
639 condition variable itself. Calling "recv" inside the callback or at
573 callback or at any later time is guaranteed not to block. 640 any later time is guaranteed not to block.
574 641
575GLOBAL VARIABLES AND FUNCTIONS 642GLOBAL VARIABLES AND FUNCTIONS
576 $AnyEvent::MODEL 643 $AnyEvent::MODEL
577 Contains "undef" until the first watcher is being created. Then it 644 Contains "undef" until the first watcher is being created. Then it
578 contains the event model that is being used, which is the name of 645 contains the event model that is being used, which is the name of
… …
692 AnyEvent::Util 759 AnyEvent::Util
693 Contains various utility functions that replace often-used but 760 Contains various utility functions that replace often-used but
694 blocking functions such as "inet_aton" by event-/callback-based 761 blocking functions such as "inet_aton" by event-/callback-based
695 versions. 762 versions.
696 763
697 AnyEvent::Handle
698 Provide read and write buffers and manages watchers for reads and
699 writes.
700
701 AnyEvent::Socket 764 AnyEvent::Socket
702 Provides various utility functions for (internet protocol) sockets, 765 Provides various utility functions for (internet protocol) sockets,
703 addresses and name resolution. Also functions to create non-blocking 766 addresses and name resolution. Also functions to create non-blocking
704 tcp connections or tcp servers, with IPv6 and SRV record support and 767 tcp connections or tcp servers, with IPv6 and SRV record support and
705 more. 768 more.
706 769
770 AnyEvent::Handle
771 Provide read and write buffers, manages watchers for reads and
772 writes, supports raw and formatted I/O, I/O queued and fully
773 transparent and non-blocking SSL/TLS.
774
707 AnyEvent::DNS 775 AnyEvent::DNS
708 Provides rich asynchronous DNS resolver capabilities. 776 Provides rich asynchronous DNS resolver capabilities.
709 777
778 AnyEvent::HTTP
779 A simple-to-use HTTP library that is capable of making a lot of
780 concurrent HTTP requests.
781
710 AnyEvent::HTTPD 782 AnyEvent::HTTPD
711 Provides a simple web application server framework. 783 Provides a simple web application server framework.
712 784
713 AnyEvent::FastPing 785 AnyEvent::FastPing
714 The fastest ping in the west. 786 The fastest ping in the west.
715 787
788 AnyEvent::DBI
789 Executes DBI requests asynchronously in a proxy process.
790
791 AnyEvent::AIO
792 Truly asynchronous I/O, should be in the toolbox of every event
793 programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
794 together.
795
796 AnyEvent::BDB
797 Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
798 fuses BDB and AnyEvent together.
799
800 AnyEvent::GPSD
801 A non-blocking interface to gpsd, a daemon delivering GPS
802 information.
803
804 AnyEvent::IGS
805 A non-blocking interface to the Internet Go Server protocol (used by
806 App::IGS).
807
808 AnyEvent::IRC
809 AnyEvent based IRC client module family (replacing the older
716 Net::IRC3 810 Net::IRC3).
717 AnyEvent based IRC client module family.
718 811
719 Net::XMPP2 812 Net::XMPP2
720 AnyEvent based XMPP (Jabber protocol) module family. 813 AnyEvent based XMPP (Jabber protocol) module family.
721 814
722 Net::FCP 815 Net::FCP
… …
727 High level API for event-based execution flow control. 820 High level API for event-based execution flow control.
728 821
729 Coro 822 Coro
730 Has special support for AnyEvent via Coro::AnyEvent. 823 Has special support for AnyEvent via Coro::AnyEvent.
731 824
732 AnyEvent::AIO, IO::AIO
733 Truly asynchronous I/O, should be in the toolbox of every event
734 programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
735 together.
736
737 AnyEvent::BDB, BDB
738 Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
739 fuses IO::AIO and AnyEvent together.
740
741 IO::Lambda 825 IO::Lambda
742 The lambda approach to I/O - don't ask, look there. Can use 826 The lambda approach to I/O - don't ask, look there. Can use
743 AnyEvent. 827 AnyEvent.
744 828
745SUPPLYING YOUR OWN EVENT MODEL INTERFACE 829ERROR AND EXCEPTION HANDLING
746 This is an advanced topic that you do not normally need to use AnyEvent 830 In general, AnyEvent does not do any error handling - it relies on the
747 in a module. This section is only of use to event loop authors who want 831 caller to do that if required. The AnyEvent::Strict module (see also the
748 to provide AnyEvent compatibility. 832 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict
833 checking of all AnyEvent methods, however, which is highly useful during
834 development.
749 835
750 If you need to support another event library which isn't directly 836 As for exception handling (i.e. runtime errors and exceptions thrown
751 supported by AnyEvent, you can supply your own interface to it by 837 while executing a callback), this is not only highly event-loop
752 pushing, before the first watcher gets created, the package name of the 838 specific, but also not in any way wrapped by this module, as this is the
753 event module and the package name of the interface to use onto 839 job of the main program.
754 @AnyEvent::REGISTRY. You can do that before and even without loading
755 AnyEvent, so it is reasonably cheap.
756 840
757 Example: 841 The pure perl event loop simply re-throws the exception (usually within
758 842 "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
759 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 843 Glib uses "install_exception_handler" and so on.
760
761 This tells AnyEvent to (literally) use the "urxvt::anyevent::"
762 package/class when it finds the "urxvt" package/module is already
763 loaded.
764
765 When AnyEvent is loaded and asked to find a suitable event model, it
766 will first check for the presence of urxvt by trying to "use" the
767 "urxvt::anyevent" module.
768
769 The class should provide implementations for all watcher types. See
770 AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
771 so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
772 the sources.
773
774 If you don't provide "signal" and "child" watchers than AnyEvent will
775 provide suitable (hopefully) replacements.
776
777 The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt)
778 terminal emulator uses the above line as-is. An interface isn't included
779 in AnyEvent because it doesn't make sense outside the embedded
780 interpreter inside *rxvt-unicode*, and it is updated and maintained as
781 part of the *rxvt-unicode* distribution.
782
783 *rxvt-unicode* also cheats a bit by not providing blocking access to
784 condition variables: code blocking while waiting for a condition will
785 "die". This still works with most modules/usages, and blocking calls
786 must not be done in an interactive application, so it makes sense.
787 844
788ENVIRONMENT VARIABLES 845ENVIRONMENT VARIABLES
789 The following environment variables are used by this module: 846 The following environment variables are used by this module or its
847 submodules:
790 848
791 "PERL_ANYEVENT_VERBOSE" 849 "PERL_ANYEVENT_VERBOSE"
792 By default, AnyEvent will be completely silent except in fatal 850 By default, AnyEvent will be completely silent except in fatal
793 conditions. You can set this environment variable to make AnyEvent 851 conditions. You can set this environment variable to make AnyEvent
794 more talkative. 852 more talkative.
… …
797 conditions, such as not being able to load the event model specified 855 conditions, such as not being able to load the event model specified
798 by "PERL_ANYEVENT_MODEL". 856 by "PERL_ANYEVENT_MODEL".
799 857
800 When set to 2 or higher, cause AnyEvent to report to STDERR which 858 When set to 2 or higher, cause AnyEvent to report to STDERR which
801 event model it chooses. 859 event model it chooses.
860
861 "PERL_ANYEVENT_STRICT"
862 AnyEvent does not do much argument checking by default, as thorough
863 argument checking is very costly. Setting this variable to a true
864 value will cause AnyEvent to load "AnyEvent::Strict" and then to
865 thoroughly check the arguments passed to most method calls. If it
866 finds any problems it will croak.
867
868 In other words, enables "strict" mode.
869
870 Unlike "use strict", it is definitely recommended ot keep it off in
871 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
872 while developing programs can be very useful, however.
802 873
803 "PERL_ANYEVENT_MODEL" 874 "PERL_ANYEVENT_MODEL"
804 This can be used to specify the event model to be used by AnyEvent, 875 This can be used to specify the event model to be used by AnyEvent,
805 before auto detection and -probing kicks in. It must be a string 876 before auto detection and -probing kicks in. It must be a string
806 consisting entirely of ASCII letters. The string "AnyEvent::Impl::" 877 consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
… …
811 This functionality might change in future versions. 882 This functionality might change in future versions.
812 883
813 For example, to force the pure perl model (AnyEvent::Impl::Perl) you 884 For example, to force the pure perl model (AnyEvent::Impl::Perl) you
814 could start your program like this: 885 could start your program like this:
815 886
816 PERL_ANYEVENT_MODEL=Perl perl ... 887 PERL_ANYEVENT_MODEL=Perl perl ...
817 888
818 "PERL_ANYEVENT_PROTOCOLS" 889 "PERL_ANYEVENT_PROTOCOLS"
819 Used by both AnyEvent::DNS and AnyEvent::Socket to determine 890 Used by both AnyEvent::DNS and AnyEvent::Socket to determine
820 preferences for IPv4 or IPv6. The default is unspecified (and might 891 preferences for IPv4 or IPv6. The default is unspecified (and might
821 change, or be the result of auto probing). 892 change, or be the result of auto probing).
… …
825 mentioned will be used, and preference will be given to protocols 896 mentioned will be used, and preference will be given to protocols
826 mentioned earlier in the list. 897 mentioned earlier in the list.
827 898
828 This variable can effectively be used for denial-of-service attacks 899 This variable can effectively be used for denial-of-service attacks
829 against local programs (e.g. when setuid), although the impact is 900 against local programs (e.g. when setuid), although the impact is
830 likely small, as the program has to handle connection errors 901 likely small, as the program has to handle conenction and other
831 already- 902 failures anyways.
832 903
833 Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over 904 Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
834 IPv6, but support both and try to use both. 905 IPv6, but support both and try to use both.
835 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to 906 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
836 resolve or contact IPv6 addresses. 907 resolve or contact IPv6 addresses.
… …
847 EDNS0 in its DNS requests. 918 EDNS0 in its DNS requests.
848 919
849 "PERL_ANYEVENT_MAX_FORKS" 920 "PERL_ANYEVENT_MAX_FORKS"
850 The maximum number of child processes that 921 The maximum number of child processes that
851 "AnyEvent::Util::fork_call" will create in parallel. 922 "AnyEvent::Util::fork_call" will create in parallel.
923
924SUPPLYING YOUR OWN EVENT MODEL INTERFACE
925 This is an advanced topic that you do not normally need to use AnyEvent
926 in a module. This section is only of use to event loop authors who want
927 to provide AnyEvent compatibility.
928
929 If you need to support another event library which isn't directly
930 supported by AnyEvent, you can supply your own interface to it by
931 pushing, before the first watcher gets created, the package name of the
932 event module and the package name of the interface to use onto
933 @AnyEvent::REGISTRY. You can do that before and even without loading
934 AnyEvent, so it is reasonably cheap.
935
936 Example:
937
938 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
939
940 This tells AnyEvent to (literally) use the "urxvt::anyevent::"
941 package/class when it finds the "urxvt" package/module is already
942 loaded.
943
944 When AnyEvent is loaded and asked to find a suitable event model, it
945 will first check for the presence of urxvt by trying to "use" the
946 "urxvt::anyevent" module.
947
948 The class should provide implementations for all watcher types. See
949 AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
950 so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
951 the sources.
952
953 If you don't provide "signal" and "child" watchers than AnyEvent will
954 provide suitable (hopefully) replacements.
955
956 The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt)
957 terminal emulator uses the above line as-is. An interface isn't included
958 in AnyEvent because it doesn't make sense outside the embedded
959 interpreter inside *rxvt-unicode*, and it is updated and maintained as
960 part of the *rxvt-unicode* distribution.
961
962 *rxvt-unicode* also cheats a bit by not providing blocking access to
963 condition variables: code blocking while waiting for a condition will
964 "die". This still works with most modules/usages, and blocking calls
965 must not be done in an interactive application, so it makes sense.
852 966
853EXAMPLE PROGRAM 967EXAMPLE PROGRAM
854 The following program uses an I/O watcher to read data from STDIN, a 968 The following program uses an I/O watcher to read data from STDIN, a
855 timer to display a message once per second, and a condition variable to 969 timer to display a message once per second, and a condition variable to
856 quit the program when the user enters quit: 970 quit the program when the user enters quit:
… …
1043 *destroy* is the time, in microseconds, that it takes to destroy a 1157 *destroy* is the time, in microseconds, that it takes to destroy a
1044 single watcher. 1158 single watcher.
1045 1159
1046 Results 1160 Results
1047 name watchers bytes create invoke destroy comment 1161 name watchers bytes create invoke destroy comment
1048 EV/EV 400000 244 0.56 0.46 0.31 EV native interface 1162 EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1049 EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers 1163 EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1050 CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal 1164 CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1051 Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation 1165 Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1052 Event/Event 16000 516 31.88 31.30 0.85 Event native interface 1166 Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1053 Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers 1167 Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
1054 Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour 1168 Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1055 Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers 1169 Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1056 POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event 1170 POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1057 POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select 1171 POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1058 1172
1059 Discussion 1173 Discussion
1060 The benchmark does *not* measure scalability of the event loop very 1174 The benchmark does *not* measure scalability of the event loop very
1061 well. For example, a select-based event loop (such as the pure perl one) 1175 well. For example, a select-based event loop (such as the pure perl one)
1062 can never compete with an event loop that uses epoll when the number of 1176 can never compete with an event loop that uses epoll when the number of
… …
1243 1357
1244 Summary 1358 Summary
1245 * C-based event loops perform very well with small number of watchers, 1359 * C-based event loops perform very well with small number of watchers,
1246 as the management overhead dominates. 1360 as the management overhead dominates.
1247 1361
1362SIGNALS
1363 AnyEvent currently installs handlers for these signals:
1364
1365 SIGCHLD
1366 A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1367 emulation for event loops that do not support them natively. Also,
1368 some event loops install a similar handler.
1369
1370 SIGPIPE
1371 A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1372 "undef" when AnyEvent gets loaded.
1373
1374 The rationale for this is that AnyEvent users usually do not really
1375 depend on SIGPIPE delivery (which is purely an optimisation for
1376 shell use, or badly-written programs), but "SIGPIPE" can cause
1377 spurious and rare program exits as a lot of people do not expect
1378 "SIGPIPE" when writing to some random socket.
1379
1380 The rationale for installing a no-op handler as opposed to ignoring
1381 it is that this way, the handler will be restored to defaults on
1382 exec.
1383
1384 Feel free to install your own handler, or reset it to defaults.
1385
1248FORK 1386FORK
1249 Most event libraries are not fork-safe. The ones who are usually are 1387 Most event libraries are not fork-safe. The ones who are usually are
1250 because they rely on inefficient but fork-safe "select" or "poll" calls. 1388 because they rely on inefficient but fork-safe "select" or "poll" calls.
1251 Only EV is fully fork-aware. 1389 Only EV is fully fork-aware.
1252 1390
… …
1262 model than specified in the variable. 1400 model than specified in the variable.
1263 1401
1264 You can make AnyEvent completely ignore this variable by deleting it 1402 You can make AnyEvent completely ignore this variable by deleting it
1265 before the first watcher gets created, e.g. with a "BEGIN" block: 1403 before the first watcher gets created, e.g. with a "BEGIN" block:
1266 1404
1267 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 1405 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1268 1406
1269 use AnyEvent; 1407 use AnyEvent;
1270 1408
1271 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can 1409 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1272 be used to probe what backend is used and gain other information (which 1410 be used to probe what backend is used and gain other information (which
1273 is probably even less useful to an attacker than PERL_ANYEVENT_MODEL). 1411 is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1412 and $ENV{PERL_ANYEGENT_STRICT}.
1413
1414BUGS
1415 Perl 5.8 has numerous memleaks that sometimes hit this module and are
1416 hard to work around. If you suffer from memleaks, first upgrade to Perl
1417 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1418 annoying memleaks, such as leaking on "map" and "grep" but it is usually
1419 not as pronounced).
1274 1420
1275SEE ALSO 1421SEE ALSO
1276 Utility functions: AnyEvent::Util. 1422 Utility functions: AnyEvent::Util.
1277 1423
1278 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, 1424 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
… …
1290 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, 1436 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1291 1437
1292 Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS. 1438 Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.
1293 1439
1294AUTHOR 1440AUTHOR
1295 Marc Lehmann <schmorp@schmorp.de> 1441 Marc Lehmann <schmorp@schmorp.de>
1296 http://home.schmorp.de/ 1442 http://home.schmorp.de/
1297 1443

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