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Revision 1.36 by root, Fri Mar 27 10:49:50 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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321 342
322 CHILD PROCESS WATCHERS 343 CHILD PROCESS WATCHERS
323 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.
324 345
325 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
326 watches for any child process exit). The watcher will trigger as often 347 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 348 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 349 on any trace events (stopped/continued).
329 and exit status (as returned by waitpid), so unlike other watcher types, 350
330 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).
331 359
332 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
333 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
334 could have exited already (and no SIGCHLD will be sent anymore). 362 could have exited already (and no SIGCHLD will be sent anymore).
335 363
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371 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
372 because they represent a condition that must become true. 400 because they represent a condition that must become true.
373 401
374 Condition variables can be created by calling the "AnyEvent->condvar" 402 Condition variables can be created by calling the "AnyEvent->condvar"
375 method, usually without arguments. The only argument pair allowed is 403 method, usually without arguments. The only argument pair allowed is
404
376 "cb", which specifies a callback to be called when the condition 405 "cb", which specifies a callback to be called when the condition
377 variable becomes true. 406 variable becomes true, with the condition variable as the first argument
407 (but not the results).
378 408
379 After creation, the condition variable is "false" until it becomes 409 After creation, the condition variable is "false" until it becomes
380 "true" by calling the "send" method (or calling the condition variable 410 "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 411 as if it were a callback, read about the caveats in the description for
382 the "->send" method). 412 the "->send" method).
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438 468
439 my $done = AnyEvent->condvar; 469 my $done = AnyEvent->condvar;
440 my $delay = AnyEvent->timer (after => 5, cb => $done); 470 my $delay = AnyEvent->timer (after => 5, cb => $done);
441 $done->recv; 471 $done->recv;
442 472
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
443 METHODS FOR PRODUCERS 490 METHODS FOR PRODUCERS
444 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
445 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
446 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
447 uncommon for the consumer to create it as well. 494 uncommon for the consumer to create it as well.
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567 614
568 $bool = $cv->ready 615 $bool = $cv->ready
569 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
570 "croak" have been called. 617 "croak" have been called.
571 618
572 $cb = $cv->cb ([new callback]) 619 $cb = $cv->cb ($cb->($cv))
573 This is a mutator function that returns the callback set and 620 This is a mutator function that returns the callback set and
574 optionally replaces it before doing so. 621 optionally replaces it before doing so.
575 622
576 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.
577 when "send" or "croak" are called, with the only argument being the 624 when "send" or "croak" are called, with the only argument being the
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742 789
743 AnyEvent::IGS 790 AnyEvent::IGS
744 A non-blocking interface to the Internet Go Server protocol (used by 791 A non-blocking interface to the Internet Go Server protocol (used by
745 App::IGS). 792 App::IGS).
746 793
794 AnyEvent::IRC
795 AnyEvent based IRC client module family (replacing the older
747 Net::IRC3 796 Net::IRC3).
748 AnyEvent based IRC client module family.
749 797
750 Net::XMPP2 798 Net::XMPP2
751 AnyEvent based XMPP (Jabber protocol) module family. 799 AnyEvent based XMPP (Jabber protocol) module family.
752 800
753 Net::FCP 801 Net::FCP
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762 810
763 IO::Lambda 811 IO::Lambda
764 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
765 AnyEvent. 813 AnyEvent.
766 814
767SUPPLYING YOUR OWN EVENT MODEL INTERFACE 815ERROR AND EXCEPTION HANDLING
768 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
769 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
770 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.
771 821
772 If you need to support another event library which isn't directly 822 As for exception handling (i.e. runtime errors and exceptions thrown
773 supported by AnyEvent, you can supply your own interface to it by 823 while executing a callback), this is not only highly event-loop
774 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
775 event module and the package name of the interface to use onto 825 job of the main program.
776 @AnyEvent::REGISTRY. You can do that before and even without loading
777 AnyEvent, so it is reasonably cheap.
778 826
779 Example: 827 The pure perl event loop simply re-throws the exception (usually within
780 828 "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
781 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 829 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.
809 830
810ENVIRONMENT VARIABLES 831ENVIRONMENT VARIABLES
811 The following environment variables are used by this module: 832 The following environment variables are used by this module or its
833 submodules:
812 834
813 "PERL_ANYEVENT_VERBOSE" 835 "PERL_ANYEVENT_VERBOSE"
814 By default, AnyEvent will be completely silent except in fatal 836 By default, AnyEvent will be completely silent except in fatal
815 conditions. You can set this environment variable to make AnyEvent 837 conditions. You can set this environment variable to make AnyEvent
816 more talkative. 838 more talkative.
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829 thoroughly check the arguments passed to most method calls. If it 851 thoroughly check the arguments passed to most method calls. If it
830 finds any problems it will croak. 852 finds any problems it will croak.
831 853
832 In other words, enables "strict" mode. 854 In other words, enables "strict" mode.
833 855
834 Unlike "use strict" it is definitely recommended ot keep it off in 856 Unlike "use strict", it is definitely recommended ot keep it off in
835 production. 857 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
858 while developing programs can be very useful, however.
836 859
837 "PERL_ANYEVENT_MODEL" 860 "PERL_ANYEVENT_MODEL"
838 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,
839 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
840 consisting entirely of ASCII letters. The string "AnyEvent::Impl::" 863 consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
… …
859 mentioned will be used, and preference will be given to protocols 882 mentioned will be used, and preference will be given to protocols
860 mentioned earlier in the list. 883 mentioned earlier in the list.
861 884
862 This variable can effectively be used for denial-of-service attacks 885 This variable can effectively be used for denial-of-service attacks
863 against local programs (e.g. when setuid), although the impact is 886 against local programs (e.g. when setuid), although the impact is
864 likely small, as the program has to handle connection errors 887 likely small, as the program has to handle conenction and other
865 already- 888 failures anyways.
866 889
867 Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over 890 Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
868 IPv6, but support both and try to use both. 891 IPv6, but support both and try to use both.
869 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to 892 "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
870 resolve or contact IPv6 addresses. 893 resolve or contact IPv6 addresses.
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881 EDNS0 in its DNS requests. 904 EDNS0 in its DNS requests.
882 905
883 "PERL_ANYEVENT_MAX_FORKS" 906 "PERL_ANYEVENT_MAX_FORKS"
884 The maximum number of child processes that 907 The maximum number of child processes that
885 "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.
886 952
887EXAMPLE PROGRAM 953EXAMPLE PROGRAM
888 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
889 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
890 quit the program when the user enters quit: 956 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 1143 *destroy* is the time, in microseconds, that it takes to destroy a
1078 single watcher. 1144 single watcher.
1079 1145
1080 Results 1146 Results
1081 name watchers bytes create invoke destroy comment 1147 name watchers bytes create invoke destroy comment
1082 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
1083 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
1084 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
1085 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
1086 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
1087 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
1088 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
1089 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
1090 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
1091 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
1092 1158
1093 Discussion 1159 Discussion
1094 The benchmark does *not* measure scalability of the event loop very 1160 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) 1161 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 1162 can never compete with an event loop that uses epoll when the number of
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1277 1343
1278 Summary 1344 Summary
1279 * 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,
1280 as the management overhead dominates. 1346 as the management overhead dominates.
1281 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
1282FORK 1372FORK
1283 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
1284 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.
1285 Only EV is fully fork-aware. 1375 Only EV is fully fork-aware.
1286 1376
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1309 1399
1310BUGS 1400BUGS
1311 Perl 5.8 has numerous memleaks that sometimes hit this module and are 1401 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 1402 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 1403 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 1404 annoying memleaks, such as leaking on "map" and "grep" but it is usually
1315 not as pronounced). 1405 not as pronounced).
1316 1406
1317SEE ALSO 1407SEE ALSO
1318 Utility functions: AnyEvent::Util. 1408 Utility functions: AnyEvent::Util.
1319 1409

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