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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").
… …
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
293 SIGNAL WATCHERS 319 SIGNAL WATCHERS
294 You can watch for signals using a signal watcher, "signal" is the signal 320 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 321 *name* in uppercase and without any "SIG" prefix, "cb" is the Perl
296 whenever a signal occurs. 322 callback to be invoked whenever a signal occurs.
297 323
298 Although the callback might get passed parameters, their value and 324 Although the callback might get passed parameters, their value and
299 presence is undefined and you cannot rely on them. Portable AnyEvent 325 presence is undefined and you cannot rely on them. Portable AnyEvent
300 callbacks cannot use arguments passed to signal watcher callbacks. 326 callbacks cannot use arguments passed to signal watcher callbacks.
301 327
… …
316 342
317 CHILD PROCESS WATCHERS 343 CHILD PROCESS WATCHERS
318 You can also watch on a child process exit and catch its exit status. 344 You can also watch on a child process exit and catch its exit status.
319 345
320 The child process is specified by the "pid" argument (if set to 0, it 346 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 347 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 348 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 349 on any trace events (stopped/continued).
324 and exit status (as returned by waitpid), so unlike other watcher types, 350
325 you *can* rely on child watcher callback arguments. 351 The callback will be called with the pid and exit status (as returned by
352 waitpid), so unlike other watcher types, you *can* rely on child watcher
353 callback arguments.
354
355 This watcher type works by installing a signal handler for "SIGCHLD",
356 and since it cannot be shared, nothing else should use SIGCHLD or reap
357 random child processes (waiting for specific child processes, e.g.
358 inside "system", is just fine).
326 359
327 There is a slight catch to child watchers, however: you usually start 360 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 361 them *after* the child process was created, and this means the process
329 could have exited already (and no SIGCHLD will be sent anymore). 362 could have exited already (and no SIGCHLD will be sent anymore).
330 363
… …
337 an AnyEvent program, you *have* to create at least one watcher before 370 an AnyEvent program, you *have* to create at least one watcher before
338 you "fork" the child (alternatively, you can call "AnyEvent::detect"). 371 you "fork" the child (alternatively, you can call "AnyEvent::detect").
339 372
340 Example: fork a process and wait for it 373 Example: fork a process and wait for it
341 374
342 my $done = AnyEvent->condvar; 375 my $done = AnyEvent->condvar;
343 376
344 my $pid = fork or exit 5; 377 my $pid = fork or exit 5;
345 378
346 my $w = AnyEvent->child ( 379 my $w = AnyEvent->child (
347 pid => $pid, 380 pid => $pid,
348 cb => sub { 381 cb => sub {
349 my ($pid, $status) = @_; 382 my ($pid, $status) = @_;
350 warn "pid $pid exited with status $status"; 383 warn "pid $pid exited with status $status";
351 $done->send; 384 $done->send;
352 }, 385 },
353 ); 386 );
354 387
355 # do something else, then wait for process exit 388 # do something else, then wait for process exit
356 $done->recv; 389 $done->recv;
357 390
358 CONDITION VARIABLES 391 CONDITION VARIABLES
359 If you are familiar with some event loops you will know that all of them 392 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 393 require you to run some blocking "loop", "run" or similar function that
361 will actively watch for new events and call your callbacks. 394 will actively watch for new events and call your callbacks.
… …
366 The instrument to do that is called a "condition variable", so called 399 The instrument to do that is called a "condition variable", so called
367 because they represent a condition that must become true. 400 because they represent a condition that must become true.
368 401
369 Condition variables can be created by calling the "AnyEvent->condvar" 402 Condition variables can be created by calling the "AnyEvent->condvar"
370 method, usually without arguments. The only argument pair allowed is 403 method, usually without arguments. The only argument pair allowed is
404
371 "cb", which specifies a callback to be called when the condition 405 "cb", which specifies a callback to be called when the condition
372 variable becomes true. 406 variable becomes true, with the condition variable as the first argument
407 (but not the results).
373 408
374 After creation, the condition variable is "false" until it becomes 409 After creation, the condition variable is "false" until it becomes
375 "true" by calling the "send" method (or calling the condition variable 410 "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 411 as if it were a callback, read about the caveats in the description for
377 the "->send" method). 412 the "->send" method).
… …
433 468
434 my $done = AnyEvent->condvar; 469 my $done = AnyEvent->condvar;
435 my $delay = AnyEvent->timer (after => 5, cb => $done); 470 my $delay = AnyEvent->timer (after => 5, cb => $done);
436 $done->recv; 471 $done->recv;
437 472
473 Example: Imagine an API that returns a condvar and doesn't support
474 callbacks. This is how you make a synchronous call, for example from the
475 main program:
476
477 use AnyEvent::CouchDB;
478
479 ...
480
481 my @info = $couchdb->info->recv;
482
483 And this is how you would just ste a callback to be called whenever the
484 results are available:
485
486 $couchdb->info->cb (sub {
487 my @info = $_[0]->recv;
488 });
489
438 METHODS FOR PRODUCERS 490 METHODS FOR PRODUCERS
439 These methods should only be used by the producing side, i.e. the 491 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 492 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 493 producer side which creates the condvar in most cases, but it isn't
442 uncommon for the consumer to create it as well. 494 uncommon for the consumer to create it as well.
… …
562 614
563 $bool = $cv->ready 615 $bool = $cv->ready
564 Returns true when the condition is "true", i.e. whether "send" or 616 Returns true when the condition is "true", i.e. whether "send" or
565 "croak" have been called. 617 "croak" have been called.
566 618
567 $cb = $cv->cb ([new callback]) 619 $cb = $cv->cb ($cb->($cv))
568 This is a mutator function that returns the callback set and 620 This is a mutator function that returns the callback set and
569 optionally replaces it before doing so. 621 optionally replaces it before doing so.
570 622
571 The callback will be called when the condition becomes "true", i.e. 623 The callback will be called when the condition becomes "true", i.e.
572 when "send" or "croak" are called. Calling "recv" inside the 624 when "send" or "croak" are called, with the only argument being the
625 condition variable itself. Calling "recv" inside the callback or at
573 callback or at any later time is guaranteed not to block. 626 any later time is guaranteed not to block.
574 627
575GLOBAL VARIABLES AND FUNCTIONS 628GLOBAL VARIABLES AND FUNCTIONS
576 $AnyEvent::MODEL 629 $AnyEvent::MODEL
577 Contains "undef" until the first watcher is being created. Then it 630 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 631 contains the event model that is being used, which is the name of
… …
692 AnyEvent::Util 745 AnyEvent::Util
693 Contains various utility functions that replace often-used but 746 Contains various utility functions that replace often-used but
694 blocking functions such as "inet_aton" by event-/callback-based 747 blocking functions such as "inet_aton" by event-/callback-based
695 versions. 748 versions.
696 749
697 AnyEvent::Handle
698 Provide read and write buffers and manages watchers for reads and
699 writes.
700
701 AnyEvent::Socket 750 AnyEvent::Socket
702 Provides various utility functions for (internet protocol) sockets, 751 Provides various utility functions for (internet protocol) sockets,
703 addresses and name resolution. Also functions to create non-blocking 752 addresses and name resolution. Also functions to create non-blocking
704 tcp connections or tcp servers, with IPv6 and SRV record support and 753 tcp connections or tcp servers, with IPv6 and SRV record support and
705 more. 754 more.
706 755
756 AnyEvent::Handle
757 Provide read and write buffers, manages watchers for reads and
758 writes, supports raw and formatted I/O, I/O queued and fully
759 transparent and non-blocking SSL/TLS.
760
707 AnyEvent::DNS 761 AnyEvent::DNS
708 Provides rich asynchronous DNS resolver capabilities. 762 Provides rich asynchronous DNS resolver capabilities.
709 763
764 AnyEvent::HTTP
765 A simple-to-use HTTP library that is capable of making a lot of
766 concurrent HTTP requests.
767
710 AnyEvent::HTTPD 768 AnyEvent::HTTPD
711 Provides a simple web application server framework. 769 Provides a simple web application server framework.
712 770
713 AnyEvent::FastPing 771 AnyEvent::FastPing
714 The fastest ping in the west. 772 The fastest ping in the west.
715 773
774 AnyEvent::DBI
775 Executes DBI requests asynchronously in a proxy process.
776
777 AnyEvent::AIO
778 Truly asynchronous I/O, should be in the toolbox of every event
779 programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
780 together.
781
782 AnyEvent::BDB
783 Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
784 fuses BDB and AnyEvent together.
785
786 AnyEvent::GPSD
787 A non-blocking interface to gpsd, a daemon delivering GPS
788 information.
789
790 AnyEvent::IGS
791 A non-blocking interface to the Internet Go Server protocol (used by
792 App::IGS).
793
794 AnyEvent::IRC
795 AnyEvent based IRC client module family (replacing the older
716 Net::IRC3 796 Net::IRC3).
717 AnyEvent based IRC client module family.
718 797
719 Net::XMPP2 798 Net::XMPP2
720 AnyEvent based XMPP (Jabber protocol) module family. 799 AnyEvent based XMPP (Jabber protocol) module family.
721 800
722 Net::FCP 801 Net::FCP
… …
727 High level API for event-based execution flow control. 806 High level API for event-based execution flow control.
728 807
729 Coro 808 Coro
730 Has special support for AnyEvent via Coro::AnyEvent. 809 Has special support for AnyEvent via Coro::AnyEvent.
731 810
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 811 IO::Lambda
742 The lambda approach to I/O - don't ask, look there. Can use 812 The lambda approach to I/O - don't ask, look there. Can use
743 AnyEvent. 813 AnyEvent.
744 814
745SUPPLYING YOUR OWN EVENT MODEL INTERFACE 815ERROR AND EXCEPTION HANDLING
746 This is an advanced topic that you do not normally need to use AnyEvent 816 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 817 caller to do that if required. The AnyEvent::Strict module (see also the
748 to provide AnyEvent compatibility. 818 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict
819 checking of all AnyEvent methods, however, which is highly useful during
820 development.
749 821
750 If you need to support another event library which isn't directly 822 As for exception handling (i.e. runtime errors and exceptions thrown
751 supported by AnyEvent, you can supply your own interface to it by 823 while executing a callback), this is not only highly event-loop
752 pushing, before the first watcher gets created, the package name of the 824 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 825 job of the main program.
754 @AnyEvent::REGISTRY. You can do that before and even without loading
755 AnyEvent, so it is reasonably cheap.
756 826
757 Example: 827 The pure perl event loop simply re-throws the exception (usually within
758 828 "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
759 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 829 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.
787 830
788ENVIRONMENT VARIABLES 831ENVIRONMENT VARIABLES
789 The following environment variables are used by this module: 832 The following environment variables are used by this module or its
833 submodules:
790 834
791 "PERL_ANYEVENT_VERBOSE" 835 "PERL_ANYEVENT_VERBOSE"
792 By default, AnyEvent will be completely silent except in fatal 836 By default, AnyEvent will be completely silent except in fatal
793 conditions. You can set this environment variable to make AnyEvent 837 conditions. You can set this environment variable to make AnyEvent
794 more talkative. 838 more talkative.
… …
797 conditions, such as not being able to load the event model specified 841 conditions, such as not being able to load the event model specified
798 by "PERL_ANYEVENT_MODEL". 842 by "PERL_ANYEVENT_MODEL".
799 843
800 When set to 2 or higher, cause AnyEvent to report to STDERR which 844 When set to 2 or higher, cause AnyEvent to report to STDERR which
801 event model it chooses. 845 event model it chooses.
846
847 "PERL_ANYEVENT_STRICT"
848 AnyEvent does not do much argument checking by default, as thorough
849 argument checking is very costly. Setting this variable to a true
850 value will cause AnyEvent to load "AnyEvent::Strict" and then to
851 thoroughly check the arguments passed to most method calls. If it
852 finds any problems it will croak.
853
854 In other words, enables "strict" mode.
855
856 Unlike "use strict", it is definitely recommended ot keep it off in
857 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
858 while developing programs can be very useful, however.
802 859
803 "PERL_ANYEVENT_MODEL" 860 "PERL_ANYEVENT_MODEL"
804 This can be used to specify the event model to be used by AnyEvent, 861 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 862 before auto detection and -probing kicks in. It must be a string
806 consisting entirely of ASCII letters. The string "AnyEvent::Impl::" 863 consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
… …
811 This functionality might change in future versions. 868 This functionality might change in future versions.
812 869
813 For example, to force the pure perl model (AnyEvent::Impl::Perl) you 870 For example, to force the pure perl model (AnyEvent::Impl::Perl) you
814 could start your program like this: 871 could start your program like this:
815 872
816 PERL_ANYEVENT_MODEL=Perl perl ... 873 PERL_ANYEVENT_MODEL=Perl perl ...
817 874
818 "PERL_ANYEVENT_PROTOCOLS" 875 "PERL_ANYEVENT_PROTOCOLS"
819 Used by both AnyEvent::DNS and AnyEvent::Socket to determine 876 Used by both AnyEvent::DNS and AnyEvent::Socket to determine
820 preferences for IPv4 or IPv6. The default is unspecified (and might 877 preferences for IPv4 or IPv6. The default is unspecified (and might
821 change, or be the result of auto probing). 878 change, or be the result of auto probing).
… …
825 mentioned will be used, and preference will be given to protocols 882 mentioned will be used, and preference will be given to protocols
826 mentioned earlier in the list. 883 mentioned earlier in the list.
827 884
828 This variable can effectively be used for denial-of-service attacks 885 This variable can effectively be used for denial-of-service attacks
829 against local programs (e.g. when setuid), although the impact is 886 against local programs (e.g. when setuid), although the impact is
830 likely small, as the program has to handle connection errors 887 likely small, as the program has to handle conenction and other
831 already- 888 failures anyways.
832 889
833 Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over 890 Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
834 IPv6, but support both and try to use both. 891 IPv6, but support both and try to use both.
835 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to 892 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
836 resolve or contact IPv6 addresses. 893 resolve or contact IPv6 addresses.
… …
847 EDNS0 in its DNS requests. 904 EDNS0 in its DNS requests.
848 905
849 "PERL_ANYEVENT_MAX_FORKS" 906 "PERL_ANYEVENT_MAX_FORKS"
850 The maximum number of child processes that 907 The maximum number of child processes that
851 "AnyEvent::Util::fork_call" will create in parallel. 908 "AnyEvent::Util::fork_call" will create in parallel.
909
910SUPPLYING YOUR OWN EVENT MODEL INTERFACE
911 This is an advanced topic that you do not normally need to use AnyEvent
912 in a module. This section is only of use to event loop authors who want
913 to provide AnyEvent compatibility.
914
915 If you need to support another event library which isn't directly
916 supported by AnyEvent, you can supply your own interface to it by
917 pushing, before the first watcher gets created, the package name of the
918 event module and the package name of the interface to use onto
919 @AnyEvent::REGISTRY. You can do that before and even without loading
920 AnyEvent, so it is reasonably cheap.
921
922 Example:
923
924 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
925
926 This tells AnyEvent to (literally) use the "urxvt::anyevent::"
927 package/class when it finds the "urxvt" package/module is already
928 loaded.
929
930 When AnyEvent is loaded and asked to find a suitable event model, it
931 will first check for the presence of urxvt by trying to "use" the
932 "urxvt::anyevent" module.
933
934 The class should provide implementations for all watcher types. See
935 AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
936 so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
937 the sources.
938
939 If you don't provide "signal" and "child" watchers than AnyEvent will
940 provide suitable (hopefully) replacements.
941
942 The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt)
943 terminal emulator uses the above line as-is. An interface isn't included
944 in AnyEvent because it doesn't make sense outside the embedded
945 interpreter inside *rxvt-unicode*, and it is updated and maintained as
946 part of the *rxvt-unicode* distribution.
947
948 *rxvt-unicode* also cheats a bit by not providing blocking access to
949 condition variables: code blocking while waiting for a condition will
950 "die". This still works with most modules/usages, and blocking calls
951 must not be done in an interactive application, so it makes sense.
852 952
853EXAMPLE PROGRAM 953EXAMPLE PROGRAM
854 The following program uses an I/O watcher to read data from STDIN, a 954 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 955 timer to display a message once per second, and a condition variable to
856 quit the program when the user enters quit: 956 quit the program when the user enters quit:
… …
1043 *destroy* is the time, in microseconds, that it takes to destroy a 1143 *destroy* is the time, in microseconds, that it takes to destroy a
1044 single watcher. 1144 single watcher.
1045 1145
1046 Results 1146 Results
1047 name watchers bytes create invoke destroy comment 1147 name watchers bytes create invoke destroy comment
1048 EV/EV 400000 244 0.56 0.46 0.31 EV native interface 1148 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 1149 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 1150 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 1151 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 1152 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 1153 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 1154 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 1155 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 1156 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 1157 POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1058 1158
1059 Discussion 1159 Discussion
1060 The benchmark does *not* measure scalability of the event loop very 1160 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) 1161 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 1162 can never compete with an event loop that uses epoll when the number of
… …
1243 1343
1244 Summary 1344 Summary
1245 * C-based event loops perform very well with small number of watchers, 1345 * C-based event loops perform very well with small number of watchers,
1246 as the management overhead dominates. 1346 as the management overhead dominates.
1247 1347
1348SIGNALS
1349 AnyEvent currently installs handlers for these signals:
1350
1351 SIGCHLD
1352 A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1353 emulation for event loops that do not support them natively. Also,
1354 some event loops install a similar handler.
1355
1356 SIGPIPE
1357 A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1358 "undef" when AnyEvent gets loaded.
1359
1360 The rationale for this is that AnyEvent users usually do not really
1361 depend on SIGPIPE delivery (which is purely an optimisation for
1362 shell use, or badly-written programs), but "SIGPIPE" can cause
1363 spurious and rare program exits as a lot of people do not expect
1364 "SIGPIPE" when writing to some random socket.
1365
1366 The rationale for installing a no-op handler as opposed to ignoring
1367 it is that this way, the handler will be restored to defaults on
1368 exec.
1369
1370 Feel free to install your own handler, or reset it to defaults.
1371
1248FORK 1372FORK
1249 Most event libraries are not fork-safe. The ones who are usually are 1373 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. 1374 because they rely on inefficient but fork-safe "select" or "poll" calls.
1251 Only EV is fully fork-aware. 1375 Only EV is fully fork-aware.
1252 1376
… …
1262 model than specified in the variable. 1386 model than specified in the variable.
1263 1387
1264 You can make AnyEvent completely ignore this variable by deleting it 1388 You can make AnyEvent completely ignore this variable by deleting it
1265 before the first watcher gets created, e.g. with a "BEGIN" block: 1389 before the first watcher gets created, e.g. with a "BEGIN" block:
1266 1390
1267 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 1391 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1268 1392
1269 use AnyEvent; 1393 use AnyEvent;
1270 1394
1271 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can 1395 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 1396 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). 1397 is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1398 and $ENV{PERL_ANYEGENT_STRICT}.
1399
1400BUGS
1401 Perl 5.8 has numerous memleaks that sometimes hit this module and are
1402 hard to work around. If you suffer from memleaks, first upgrade to Perl
1403 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1404 annoying memleaks, such as leaking on "map" and "grep" but it is usually
1405 not as pronounced).
1274 1406
1275SEE ALSO 1407SEE ALSO
1276 Utility functions: AnyEvent::Util. 1408 Utility functions: AnyEvent::Util.
1277 1409
1278 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, 1410 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
… …
1290 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, 1422 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1291 1423
1292 Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS. 1424 Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.
1293 1425
1294AUTHOR 1426AUTHOR
1295 Marc Lehmann <schmorp@schmorp.de> 1427 Marc Lehmann <schmorp@schmorp.de>
1296 http://home.schmorp.de/ 1428 http://home.schmorp.de/
1297 1429

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