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Revision 1.37 by root, Mon Apr 20 14:34:18 2009 UTC

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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 });
21 30
22INTRODUCTION/TUTORIAL 31INTRODUCTION/TUTORIAL
23 This manpage is mainly a reference manual. If you are interested in a 32 This manpage is mainly a reference manual. If you are interested in a
24 tutorial or some gentle introduction, have a look at the AnyEvent::Intro 33 tutorial or some gentle introduction, have a look at the AnyEvent::Intro
25 manpage. 34 manpage.
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123 These watchers are normal Perl objects with normal Perl lifetime. After 132 These watchers are normal Perl objects with normal Perl lifetime. After
124 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
125 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
126 in control). 135 in control).
127 136
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
128 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
129 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
130 to it). 145 to it).
131 146
132 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.
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147 162
148 I/O WATCHERS 163 I/O WATCHERS
149 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
150 the following mandatory key-value pairs as arguments: 165 the following mandatory key-value pairs as arguments:
151 166
152 "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
153 (AnyEvent might or might not keep a reference to this file handle). 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
154 "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
155 watcher waiting for "r"eadable or "w"ritable events, respectively. "cb" 175 watcher waiting for "r"eadable or "w"ritable events, respectively.
176
156 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.
157 178
158 Although the callback might get passed parameters, their value and 179 Although the callback might get passed parameters, their value and
159 presence is undefined and you cannot rely on them. Portable AnyEvent 180 presence is undefined and you cannot rely on them. Portable AnyEvent
160 callbacks cannot use arguments passed to I/O watcher callbacks. 181 callbacks cannot use arguments passed to I/O watcher callbacks.
161 182
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293 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
294 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
295 the difference between "AnyEvent->time" and "AnyEvent->now" into 316 the difference between "AnyEvent->time" and "AnyEvent->now" into
296 account. 317 account.
297 318
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
298 SIGNAL WATCHERS 333 SIGNAL WATCHERS
299 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
300 *name* in uppercase and without any "SIG" prefix, "cb" is the Perl 335 *name* in uppercase and without any "SIG" prefix, "cb" is the Perl
301 callback to be invoked whenever a signal occurs. 336 callback to be invoked whenever a signal occurs.
302 337
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321 356
322 CHILD PROCESS WATCHERS 357 CHILD PROCESS WATCHERS
323 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.
324 359
325 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
326 watches for any child process exit). The watcher will trigger as often 361 watches for any child process exit). The watcher will triggered only
327 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
328 signal handler for "SIGCHLD". The callback will be called with the pid 363 on any trace events (stopped/continued).
329 and exit status (as returned by waitpid), so unlike other watcher types, 364
330 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).
331 373
332 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
333 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
334 could have exited already (and no SIGCHLD will be sent anymore). 376 could have exited already (and no SIGCHLD will be sent anymore).
335 377
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371 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
372 because they represent a condition that must become true. 414 because they represent a condition that must become true.
373 415
374 Condition variables can be created by calling the "AnyEvent->condvar" 416 Condition variables can be created by calling the "AnyEvent->condvar"
375 method, usually without arguments. The only argument pair allowed is 417 method, usually without arguments. The only argument pair allowed is
418
376 "cb", which specifies a callback to be called when the condition 419 "cb", which specifies a callback to be called when the condition
377 variable becomes true. 420 variable becomes true, with the condition variable as the first argument
421 (but not the results).
378 422
379 After creation, the condition variable is "false" until it becomes 423 After creation, the condition variable is "false" until it becomes
380 "true" by calling the "send" method (or calling the condition variable 424 "true" by calling the "send" method (or calling the condition variable
381 as if it were a callback, read about the caveats in the description for 425 as if it were a callback, read about the caveats in the description for
382 the "->send" method). 426 the "->send" method).
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438 482
439 my $done = AnyEvent->condvar; 483 my $done = AnyEvent->condvar;
440 my $delay = AnyEvent->timer (after => 5, cb => $done); 484 my $delay = AnyEvent->timer (after => 5, cb => $done);
441 $done->recv; 485 $done->recv;
442 486
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
443 METHODS FOR PRODUCERS 504 METHODS FOR PRODUCERS
444 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
445 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
446 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
447 uncommon for the consumer to create it as well. 508 uncommon for the consumer to create it as well.
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567 628
568 $bool = $cv->ready 629 $bool = $cv->ready
569 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
570 "croak" have been called. 631 "croak" have been called.
571 632
572 $cb = $cv->cb ([new callback]) 633 $cb = $cv->cb ($cb->($cv))
573 This is a mutator function that returns the callback set and 634 This is a mutator function that returns the callback set and
574 optionally replaces it before doing so. 635 optionally replaces it before doing so.
575 636
576 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.
577 when "send" or "croak" are called, with the only argument being the 638 when "send" or "croak" are called, with the only argument being the
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742 803
743 AnyEvent::IGS 804 AnyEvent::IGS
744 A non-blocking interface to the Internet Go Server protocol (used by 805 A non-blocking interface to the Internet Go Server protocol (used by
745 App::IGS). 806 App::IGS).
746 807
808 AnyEvent::IRC
809 AnyEvent based IRC client module family (replacing the older
747 Net::IRC3 810 Net::IRC3).
748 AnyEvent based IRC client module family.
749 811
750 Net::XMPP2 812 Net::XMPP2
751 AnyEvent based XMPP (Jabber protocol) module family. 813 AnyEvent based XMPP (Jabber protocol) module family.
752 814
753 Net::FCP 815 Net::FCP
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762 824
763 IO::Lambda 825 IO::Lambda
764 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
765 AnyEvent. 827 AnyEvent.
766 828
767SUPPLYING YOUR OWN EVENT MODEL INTERFACE 829ERROR AND EXCEPTION HANDLING
768 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
769 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
770 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.
771 835
772 If you need to support another event library which isn't directly 836 As for exception handling (i.e. runtime errors and exceptions thrown
773 supported by AnyEvent, you can supply your own interface to it by 837 while executing a callback), this is not only highly event-loop
774 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
775 event module and the package name of the interface to use onto 839 job of the main program.
776 @AnyEvent::REGISTRY. You can do that before and even without loading
777 AnyEvent, so it is reasonably cheap.
778 840
779 Example: 841 The pure perl event loop simply re-throws the exception (usually within
780 842 "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
781 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 843 Glib uses "install_exception_handler" and so on.
782
783 This tells AnyEvent to (literally) use the "urxvt::anyevent::"
784 package/class when it finds the "urxvt" package/module is already
785 loaded.
786
787 When AnyEvent is loaded and asked to find a suitable event model, it
788 will first check for the presence of urxvt by trying to "use" the
789 "urxvt::anyevent" module.
790
791 The class should provide implementations for all watcher types. See
792 AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
793 so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
794 the sources.
795
796 If you don't provide "signal" and "child" watchers than AnyEvent will
797 provide suitable (hopefully) replacements.
798
799 The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt)
800 terminal emulator uses the above line as-is. An interface isn't included
801 in AnyEvent because it doesn't make sense outside the embedded
802 interpreter inside *rxvt-unicode*, and it is updated and maintained as
803 part of the *rxvt-unicode* distribution.
804
805 *rxvt-unicode* also cheats a bit by not providing blocking access to
806 condition variables: code blocking while waiting for a condition will
807 "die". This still works with most modules/usages, and blocking calls
808 must not be done in an interactive application, so it makes sense.
809 844
810ENVIRONMENT VARIABLES 845ENVIRONMENT VARIABLES
811 The following environment variables are used by this module: 846 The following environment variables are used by this module or its
847 submodules:
812 848
813 "PERL_ANYEVENT_VERBOSE" 849 "PERL_ANYEVENT_VERBOSE"
814 By default, AnyEvent will be completely silent except in fatal 850 By default, AnyEvent will be completely silent except in fatal
815 conditions. You can set this environment variable to make AnyEvent 851 conditions. You can set this environment variable to make AnyEvent
816 more talkative. 852 more talkative.
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829 thoroughly check the arguments passed to most method calls. If it 865 thoroughly check the arguments passed to most method calls. If it
830 finds any problems it will croak. 866 finds any problems it will croak.
831 867
832 In other words, enables "strict" mode. 868 In other words, enables "strict" mode.
833 869
834 Unlike "use strict" it is definitely recommended ot keep it off in 870 Unlike "use strict", it is definitely recommended ot keep it off in
835 production. 871 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
872 while developing programs can be very useful, however.
836 873
837 "PERL_ANYEVENT_MODEL" 874 "PERL_ANYEVENT_MODEL"
838 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,
839 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
840 consisting entirely of ASCII letters. The string "AnyEvent::Impl::" 877 consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
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859 mentioned will be used, and preference will be given to protocols 896 mentioned will be used, and preference will be given to protocols
860 mentioned earlier in the list. 897 mentioned earlier in the list.
861 898
862 This variable can effectively be used for denial-of-service attacks 899 This variable can effectively be used for denial-of-service attacks
863 against local programs (e.g. when setuid), although the impact is 900 against local programs (e.g. when setuid), although the impact is
864 likely small, as the program has to handle connection errors 901 likely small, as the program has to handle conenction and other
865 already- 902 failures anyways.
866 903
867 Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over 904 Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
868 IPv6, but support both and try to use both. 905 IPv6, but support both and try to use both.
869 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to 906 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
870 resolve or contact IPv6 addresses. 907 resolve or contact IPv6 addresses.
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881 EDNS0 in its DNS requests. 918 EDNS0 in its DNS requests.
882 919
883 "PERL_ANYEVENT_MAX_FORKS" 920 "PERL_ANYEVENT_MAX_FORKS"
884 The maximum number of child processes that 921 The maximum number of child processes that
885 "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.
886 966
887EXAMPLE PROGRAM 967EXAMPLE PROGRAM
888 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
889 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
890 quit the program when the user enters quit: 970 quit the program when the user enters quit:
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1077 *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
1078 single watcher. 1158 single watcher.
1079 1159
1080 Results 1160 Results
1081 name watchers bytes create invoke destroy comment 1161 name watchers bytes create invoke destroy comment
1082 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
1083 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
1084 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
1085 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
1086 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
1087 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
1088 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
1089 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
1090 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
1091 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
1092 1172
1093 Discussion 1173 Discussion
1094 The benchmark does *not* measure scalability of the event loop very 1174 The benchmark does *not* measure scalability of the event loop very
1095 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)
1096 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
… …
1277 1357
1278 Summary 1358 Summary
1279 * 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,
1280 as the management overhead dominates. 1360 as the management overhead dominates.
1281 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
1282FORK 1386FORK
1283 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
1284 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.
1285 Only EV is fully fork-aware. 1389 Only EV is fully fork-aware.
1286 1390
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1309 1413
1310BUGS 1414BUGS
1311 Perl 5.8 has numerous memleaks that sometimes hit this module and are 1415 Perl 5.8 has numerous memleaks that sometimes hit this module and are
1312 hard to work around. If you suffer from memleaks, first upgrade to Perl 1416 hard to work around. If you suffer from memleaks, first upgrade to Perl
1313 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other 1417 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1314 annoying mamleaks, such as leaking on "map" and "grep" but it is usually 1418 annoying memleaks, such as leaking on "map" and "grep" but it is usually
1315 not as pronounced). 1419 not as pronounced).
1316 1420
1317SEE ALSO 1421SEE ALSO
1318 Utility functions: AnyEvent::Util. 1422 Utility functions: AnyEvent::Util.
1319 1423

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