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1NAME 1NAME
2 AnyEvent - provide framework for multiple event loops 2 AnyEvent - the DBI of event loop programming
3 3
4 EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported 4 EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
5 event loops. 5 Qt and POE are various supported event loops/environments.
6 6
7SYNOPSIS 7SYNOPSIS
8 use AnyEvent; 8 use AnyEvent;
9 9
10 # file descriptor readable 10 # file descriptor readable
37 37
38INTRODUCTION/TUTORIAL 38INTRODUCTION/TUTORIAL
39 This manpage is mainly a reference manual. If you are interested in a 39 This manpage is mainly a reference manual. If you are interested in a
40 tutorial or some gentle introduction, have a look at the AnyEvent::Intro 40 tutorial or some gentle introduction, have a look at the AnyEvent::Intro
41 manpage. 41 manpage.
42
43SUPPORT
44 There is a mailinglist for discussing all things AnyEvent, and an IRC
45 channel, too.
46
47 See the AnyEvent project page at the Schmorpforge Ta-Sa Software
48 Repository, at <http://anyevent.schmorp.de>, for more info.
42 49
43WHY YOU SHOULD USE THIS MODULE (OR NOT) 50WHY YOU SHOULD USE THIS MODULE (OR NOT)
44 Glib, POE, IO::Async, Event... CPAN offers event models by the dozen 51 Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
45 nowadays. So what is different about AnyEvent? 52 nowadays. So what is different about AnyEvent?
46 53
166 Note that "my $w; $w =" combination. This is necessary because in Perl, 173 Note that "my $w; $w =" combination. This is necessary because in Perl,
167 my variables are only visible after the statement in which they are 174 my variables are only visible after the statement in which they are
168 declared. 175 declared.
169 176
170 I/O WATCHERS 177 I/O WATCHERS
178 $w = AnyEvent->io (
179 fh => <filehandle_or_fileno>,
180 poll => <"r" or "w">,
181 cb => <callback>,
182 );
183
171 You can create an I/O watcher by calling the "AnyEvent->io" method with 184 You can create an I/O watcher by calling the "AnyEvent->io" method with
172 the following mandatory key-value pairs as arguments: 185 the following mandatory key-value pairs as arguments:
173 186
174 "fh" is the Perl *file handle* (or a naked file descriptor) to watch for 187 "fh" is the Perl *file handle* (or a naked file descriptor) to watch for
175 events (AnyEvent might or might not keep a reference to this file 188 events (AnyEvent might or might not keep a reference to this file
203 warn "read: $input\n"; 216 warn "read: $input\n";
204 undef $w; 217 undef $w;
205 }); 218 });
206 219
207 TIME WATCHERS 220 TIME WATCHERS
221 $w = AnyEvent->timer (after => <seconds>, cb => <callback>);
222
223 $w = AnyEvent->timer (
224 after => <fractional_seconds>,
225 interval => <fractional_seconds>,
226 cb => <callback>,
227 );
228
208 You can create a time watcher by calling the "AnyEvent->timer" method 229 You can create a time watcher by calling the "AnyEvent->timer" method
209 with the following mandatory arguments: 230 with the following mandatory arguments:
210 231
211 "after" specifies after how many seconds (fractional values are 232 "after" specifies after how many seconds (fractional values are
212 supported) the callback should be invoked. "cb" is the callback to 233 supported) the callback should be invoked. "cb" is the callback to
336 the event loop's idea of "current time". 357 the event loop's idea of "current time".
337 358
338 Note that updating the time *might* cause some events to be handled. 359 Note that updating the time *might* cause some events to be handled.
339 360
340 SIGNAL WATCHERS 361 SIGNAL WATCHERS
362 $w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
363
341 You can watch for signals using a signal watcher, "signal" is the signal 364 You can watch for signals using a signal watcher, "signal" is the signal
342 *name* in uppercase and without any "SIG" prefix, "cb" is the Perl 365 *name* in uppercase and without any "SIG" prefix, "cb" is the Perl
343 callback to be invoked whenever a signal occurs. 366 callback to be invoked whenever a signal occurs.
344 367
345 Although the callback might get passed parameters, their value and 368 Although the callback might get passed parameters, their value and
350 invocation, and callback invocation will be synchronous. Synchronous 373 invocation, and callback invocation will be synchronous. Synchronous
351 means that it might take a while until the signal gets handled by the 374 means that it might take a while until the signal gets handled by the
352 process, but it is guaranteed not to interrupt any other callbacks. 375 process, but it is guaranteed not to interrupt any other callbacks.
353 376
354 The main advantage of using these watchers is that you can share a 377 The main advantage of using these watchers is that you can share a
355 signal between multiple watchers. 378 signal between multiple watchers, and AnyEvent will ensure that signals
379 will not interrupt your program at bad times.
356 380
357 This watcher might use %SIG, so programs overwriting those signals 381 This watcher might use %SIG (depending on the event loop used), so
358 directly will likely not work correctly. 382 programs overwriting those signals directly will likely not work
383 correctly.
359 384
360 Example: exit on SIGINT 385 Example: exit on SIGINT
361 386
362 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); 387 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
363 388
389 Signal Races, Delays and Workarounds
390 Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
391 callbacks to signals in a generic way, which is a pity, as you cannot do
392 race-free signal handling in perl, requiring C libraries for this.
393 AnyEvent will try to do it's best, which means in some cases, signals
394 will be delayed. The maximum time a signal might be delayed is specified
395 in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
396 can be changed only before the first signal watcher is created, and
397 should be left alone otherwise. This variable determines how often
398 AnyEvent polls for signals (in case a wake-up was missed). Higher values
399 will cause fewer spurious wake-ups, which is better for power and CPU
400 saving.
401
402 All these problems can be avoided by installing the optional
403 Async::Interrupt module, which works with most event loops. It will not
404 work with inherently broken event loops such as Event or Event::Lib (and
405 not with POE currently, as POE does it's own workaround with one-second
406 latency). For those, you just have to suffer the delays.
407
364 CHILD PROCESS WATCHERS 408 CHILD PROCESS WATCHERS
409 $w = AnyEvent->child (pid => <process id>, cb => <callback>);
410
365 You can also watch on a child process exit and catch its exit status. 411 You can also watch on a child process exit and catch its exit status.
366 412
367 The child process is specified by the "pid" argument (if set to 0, it 413 The child process is specified by the "pid" argument (one some backends,
368 watches for any child process exit). The watcher will triggered only 414 using 0 watches for any child process exit, on others this will croak).
369 when the child process has finished and an exit status is available, not 415 The watcher will be triggered only when the child process has finished
370 on any trace events (stopped/continued). 416 and an exit status is available, not on any trace events
417 (stopped/continued).
371 418
372 The callback will be called with the pid and exit status (as returned by 419 The callback will be called with the pid and exit status (as returned by
373 waitpid), so unlike other watcher types, you *can* rely on child watcher 420 waitpid), so unlike other watcher types, you *can* rely on child watcher
374 callback arguments. 421 callback arguments.
375 422
390 of when you start the watcher. 437 of when you start the watcher.
391 438
392 This means you cannot create a child watcher as the very first thing in 439 This means you cannot create a child watcher as the very first thing in
393 an AnyEvent program, you *have* to create at least one watcher before 440 an AnyEvent program, you *have* to create at least one watcher before
394 you "fork" the child (alternatively, you can call "AnyEvent::detect"). 441 you "fork" the child (alternatively, you can call "AnyEvent::detect").
442
443 As most event loops do not support waiting for child events, they will
444 be emulated by AnyEvent in most cases, in which the latency and race
445 problems mentioned in the description of signal watchers apply.
395 446
396 Example: fork a process and wait for it 447 Example: fork a process and wait for it
397 448
398 my $done = AnyEvent->condvar; 449 my $done = AnyEvent->condvar;
399 450
410 461
411 # do something else, then wait for process exit 462 # do something else, then wait for process exit
412 $done->recv; 463 $done->recv;
413 464
414 IDLE WATCHERS 465 IDLE WATCHERS
466 $w = AnyEvent->idle (cb => <callback>);
467
415 Sometimes there is a need to do something, but it is not so important to 468 Sometimes there is a need to do something, but it is not so important to
416 do it instantly, but only when there is nothing better to do. This 469 do it instantly, but only when there is nothing better to do. This
417 "nothing better to do" is usually defined to be "no other events need 470 "nothing better to do" is usually defined to be "no other events need
418 attention by the event loop". 471 attention by the event loop".
419 472
444 } 497 }
445 }); 498 });
446 }); 499 });
447 500
448 CONDITION VARIABLES 501 CONDITION VARIABLES
502 $cv = AnyEvent->condvar;
503
504 $cv->send (<list>);
505 my @res = $cv->recv;
506
449 If you are familiar with some event loops you will know that all of them 507 If you are familiar with some event loops you will know that all of them
450 require you to run some blocking "loop", "run" or similar function that 508 require you to run some blocking "loop", "run" or similar function that
451 will actively watch for new events and call your callbacks. 509 will actively watch for new events and call your callbacks.
452 510
453 AnyEvent is slightly different: it expects somebody else to run the 511 AnyEvent is slightly different: it expects somebody else to run the
473 Condition variables are similar to callbacks, except that you can 531 Condition variables are similar to callbacks, except that you can
474 optionally wait for them. They can also be called merge points - points 532 optionally wait for them. They can also be called merge points - points
475 in time where multiple outstanding events have been processed. And yet 533 in time where multiple outstanding events have been processed. And yet
476 another way to call them is transactions - each condition variable can 534 another way to call them is transactions - each condition variable can
477 be used to represent a transaction, which finishes at some point and 535 be used to represent a transaction, which finishes at some point and
478 delivers a result. 536 delivers a result. And yet some people know them as "futures" - a
537 promise to compute/deliver something that you can wait for.
479 538
480 Condition variables are very useful to signal that something has 539 Condition variables are very useful to signal that something has
481 finished, for example, if you write a module that does asynchronous http 540 finished, for example, if you write a module that does asynchronous http
482 requests, then a condition variable would be the ideal candidate to 541 requests, then a condition variable would be the ideal candidate to
483 signal the availability of results. The user can either act when the 542 signal the availability of results. The user can either act when the
517 after => 1, 576 after => 1,
518 cb => sub { $result_ready->send }, 577 cb => sub { $result_ready->send },
519 ); 578 );
520 579
521 # this "blocks" (while handling events) till the callback 580 # this "blocks" (while handling events) till the callback
522 # calls -<send 581 # calls ->send
523 $result_ready->recv; 582 $result_ready->recv;
524 583
525 Example: wait for a timer, but take advantage of the fact that condition 584 Example: wait for a timer, but take advantage of the fact that condition
526 variables are also callable directly. 585 variables are also callable directly.
527 586
584 into one. For example, a function that pings many hosts in parallel 643 into one. For example, a function that pings many hosts in parallel
585 might want to use a condition variable for the whole process. 644 might want to use a condition variable for the whole process.
586 645
587 Every call to "->begin" will increment a counter, and every call to 646 Every call to "->begin" will increment a counter, and every call to
588 "->end" will decrement it. If the counter reaches 0 in "->end", the 647 "->end" will decrement it. If the counter reaches 0 in "->end", the
589 (last) callback passed to "begin" will be executed. That callback is 648 (last) callback passed to "begin" will be executed, passing the
590 *supposed* to call "->send", but that is not required. If no 649 condvar as first argument. That callback is *supposed* to call
650 "->send", but that is not required. If no group callback was set,
591 callback was set, "send" will be called without any arguments. 651 "send" will be called without any arguments.
592 652
593 You can think of "$cv->send" giving you an OR condition (one call 653 You can think of "$cv->send" giving you an OR condition (one call
594 sends), while "$cv->begin" and "$cv->end" giving you an AND 654 sends), while "$cv->begin" and "$cv->end" giving you an AND
595 condition (all "begin" calls must be "end"'ed before the condvar 655 condition (all "begin" calls must be "end"'ed before the condvar
596 sends). 656 sends).
624 that are begung can potentially be zero: 684 that are begung can potentially be zero:
625 685
626 my $cv = AnyEvent->condvar; 686 my $cv = AnyEvent->condvar;
627 687
628 my %result; 688 my %result;
629 $cv->begin (sub { $cv->send (\%result) }); 689 $cv->begin (sub { shift->send (\%result) });
630 690
631 for my $host (@list_of_hosts) { 691 for my $host (@list_of_hosts) {
632 $cv->begin; 692 $cv->begin;
633 ping_host_then_call_callback $host, sub { 693 ping_host_then_call_callback $host, sub {
634 $result{$host} = ...; 694 $result{$host} = ...;
701 761
702 $cb = $cv->cb ($cb->($cv)) 762 $cb = $cv->cb ($cb->($cv))
703 This is a mutator function that returns the callback set and 763 This is a mutator function that returns the callback set and
704 optionally replaces it before doing so. 764 optionally replaces it before doing so.
705 765
706 The callback will be called when the condition becomes "true", i.e. 766 The callback will be called when the condition becomes (or already
707 when "send" or "croak" are called, with the only argument being the 767 was) "true", i.e. when "send" or "croak" are called (or were
708 condition variable itself. Calling "recv" inside the callback or at 768 called), with the only argument being the condition variable itself.
769 Calling "recv" inside the callback or at any later time is
709 any later time is guaranteed not to block. 770 guaranteed not to block.
710 771
711SUPPORTED EVENT LOOPS/BACKENDS 772SUPPORTED EVENT LOOPS/BACKENDS
712 The available backend classes are (every class has its own manpage): 773 The available backend classes are (every class has its own manpage):
713 774
714 Backends that are autoprobed when no other event loop can be found. 775 Backends that are autoprobed when no other event loop can be found.
715 EV is the preferred backend when no other event loop seems to be in 776 EV is the preferred backend when no other event loop seems to be in
716 use. If EV is not installed, then AnyEvent will try Event, and, 777 use. If EV is not installed, then AnyEvent will fall back to its own
717 failing that, will fall back to its own pure-perl implementation, 778 pure-perl implementation, which is available everywhere as it comes
718 which is available everywhere as it comes with AnyEvent itself. 779 with AnyEvent itself.
719 780
720 AnyEvent::Impl::EV based on EV (interface to libev, best choice). 781 AnyEvent::Impl::EV based on EV (interface to libev, best choice).
721 AnyEvent::Impl::Event based on Event, very stable, few glitches.
722 AnyEvent::Impl::Perl pure-perl implementation, fast and portable. 782 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
723 783
724 Backends that are transparently being picked up when they are used. 784 Backends that are transparently being picked up when they are used.
725 These will be used when they are currently loaded when the first 785 These will be used when they are currently loaded when the first
726 watcher is created, in which case it is assumed that the application 786 watcher is created, in which case it is assumed that the application
727 is using them. This means that AnyEvent will automatically pick the 787 is using them. This means that AnyEvent will automatically pick the
728 right backend when the main program loads an event module before 788 right backend when the main program loads an event module before
729 anything starts to create watchers. Nothing special needs to be done 789 anything starts to create watchers. Nothing special needs to be done
730 by the main program. 790 by the main program.
731 791
792 AnyEvent::Impl::Event based on Event, very stable, few glitches.
732 AnyEvent::Impl::Glib based on Glib, slow but very stable. 793 AnyEvent::Impl::Glib based on Glib, slow but very stable.
733 AnyEvent::Impl::Tk based on Tk, very broken. 794 AnyEvent::Impl::Tk based on Tk, very broken.
734 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. 795 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
735 AnyEvent::Impl::POE based on POE, very slow, some limitations. 796 AnyEvent::Impl::POE based on POE, very slow, some limitations.
797 AnyEvent::Impl::Irssi used when running within irssi.
736 798
737 Backends with special needs. 799 Backends with special needs.
738 Qt requires the Qt::Application to be instantiated first, but will 800 Qt requires the Qt::Application to be instantiated first, but will
739 otherwise be picked up automatically. As long as the main program 801 otherwise be picked up automatically. As long as the main program
740 instantiates the application before any AnyEvent watchers are 802 instantiates the application before any AnyEvent watchers are
805 creates and installs the global IO::AIO watcher in a "post_detect" 867 creates and installs the global IO::AIO watcher in a "post_detect"
806 block to avoid autodetecting the event module at load time. 868 block to avoid autodetecting the event module at load time.
807 869
808 If called in scalar or list context, then it creates and returns an 870 If called in scalar or list context, then it creates and returns an
809 object that automatically removes the callback again when it is 871 object that automatically removes the callback again when it is
872 destroyed (or "undef" when the hook was immediately executed). See
810 destroyed. See Coro::BDB for a case where this is useful. 873 AnyEvent::AIO for a case where this is useful.
874
875 Example: Create a watcher for the IO::AIO module and store it in
876 $WATCHER. Only do so after the event loop is initialised, though.
877
878 our WATCHER;
879
880 my $guard = AnyEvent::post_detect {
881 $WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
882 };
883
884 # the ||= is important in case post_detect immediately runs the block,
885 # as to not clobber the newly-created watcher. assigning both watcher and
886 # post_detect guard to the same variable has the advantage of users being
887 # able to just C<undef $WATCHER> if the watcher causes them grief.
888
889 $WATCHER ||= $guard;
811 890
812 @AnyEvent::post_detect 891 @AnyEvent::post_detect
813 If there are any code references in this array (you can "push" to it 892 If there are any code references in this array (you can "push" to it
814 before or after loading AnyEvent), then they will called directly 893 before or after loading AnyEvent), then they will called directly
815 after the event loop has been chosen. 894 after the event loop has been chosen.
955 High level API for event-based execution flow control. 1034 High level API for event-based execution flow control.
956 1035
957 Coro 1036 Coro
958 Has special support for AnyEvent via Coro::AnyEvent. 1037 Has special support for AnyEvent via Coro::AnyEvent.
959 1038
1039SIMPLIFIED AE API
1040 Starting with version 5.0, AnyEvent officially supports a second, much
1041 simpler, API that is designed to reduce the calling, typing and memory
1042 overhead.
1043
1044 See the AE manpage for details.
1045
960ERROR AND EXCEPTION HANDLING 1046ERROR AND EXCEPTION HANDLING
961 In general, AnyEvent does not do any error handling - it relies on the 1047 In general, AnyEvent does not do any error handling - it relies on the
962 caller to do that if required. The AnyEvent::Strict module (see also the 1048 caller to do that if required. The AnyEvent::Strict module (see also the
963 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict 1049 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict
964 checking of all AnyEvent methods, however, which is highly useful during 1050 checking of all AnyEvent methods, however, which is highly useful during
991 by "PERL_ANYEVENT_MODEL". 1077 by "PERL_ANYEVENT_MODEL".
992 1078
993 When set to 2 or higher, cause AnyEvent to report to STDERR which 1079 When set to 2 or higher, cause AnyEvent to report to STDERR which
994 event model it chooses. 1080 event model it chooses.
995 1081
1082 When set to 8 or higher, then AnyEvent will report extra information
1083 on which optional modules it loads and how it implements certain
1084 features.
1085
996 "PERL_ANYEVENT_STRICT" 1086 "PERL_ANYEVENT_STRICT"
997 AnyEvent does not do much argument checking by default, as thorough 1087 AnyEvent does not do much argument checking by default, as thorough
998 argument checking is very costly. Setting this variable to a true 1088 argument checking is very costly. Setting this variable to a true
999 value will cause AnyEvent to load "AnyEvent::Strict" and then to 1089 value will cause AnyEvent to load "AnyEvent::Strict" and then to
1000 thoroughly check the arguments passed to most method calls. If it 1090 thoroughly check the arguments passed to most method calls. If it
1001 finds any problems, it will croak. 1091 finds any problems, it will croak.
1002 1092
1003 In other words, enables "strict" mode. 1093 In other words, enables "strict" mode.
1004 1094
1005 Unlike "use strict", it is definitely recommended to keep it off in 1095 Unlike "use strict" (or it's modern cousin, "use common::sense", it
1006 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment 1096 is definitely recommended to keep it off in production. Keeping
1097 "PERL_ANYEVENT_STRICT=1" in your environment while developing
1007 while developing programs can be very useful, however. 1098 programs can be very useful, however.
1008 1099
1009 "PERL_ANYEVENT_MODEL" 1100 "PERL_ANYEVENT_MODEL"
1010 This can be used to specify the event model to be used by AnyEvent, 1101 This can be used to specify the event model to be used by AnyEvent,
1011 before auto detection and -probing kicks in. It must be a string 1102 before auto detection and -probing kicks in. It must be a string
1012 consisting entirely of ASCII letters. The string "AnyEvent::Impl::" 1103 consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
1069 "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH". 1160 "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1070 When neither "ca_file" nor "ca_path" was specified during 1161 When neither "ca_file" nor "ca_path" was specified during
1071 AnyEvent::TLS context creation, and either of these environment 1162 AnyEvent::TLS context creation, and either of these environment
1072 variables exist, they will be used to specify CA certificate 1163 variables exist, they will be used to specify CA certificate
1073 locations instead of a system-dependent default. 1164 locations instead of a system-dependent default.
1165
1166 "PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
1167 When these are set to 1, then the respective modules are not loaded.
1168 Mostly good for testing AnyEvent itself.
1074 1169
1075SUPPLYING YOUR OWN EVENT MODEL INTERFACE 1170SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1076 This is an advanced topic that you do not normally need to use AnyEvent 1171 This is an advanced topic that you do not normally need to use AnyEvent
1077 in a module. This section is only of use to event loop authors who want 1172 in a module. This section is only of use to event loop authors who want
1078 to provide AnyEvent compatibility. 1173 to provide AnyEvent compatibility.
1133 warn "read: $input\n"; # output what has been read 1228 warn "read: $input\n"; # output what has been read
1134 $cv->send if $input =~ /^q/i; # quit program if /^q/i 1229 $cv->send if $input =~ /^q/i; # quit program if /^q/i
1135 }, 1230 },
1136 ); 1231 );
1137 1232
1138 my $time_watcher; # can only be used once
1139
1140 sub new_timer {
1141 $timer = AnyEvent->timer (after => 1, cb => sub { 1233 my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1142 warn "timeout\n"; # print 'timeout' about every second 1234 warn "timeout\n"; # print 'timeout' at most every second
1143 &new_timer; # and restart the time
1144 });
1145 } 1235 });
1146
1147 new_timer; # create first timer
1148 1236
1149 $cv->recv; # wait until user enters /^q/i 1237 $cv->recv; # wait until user enters /^q/i
1150 1238
1151REAL-WORLD EXAMPLE 1239REAL-WORLD EXAMPLE
1152 Consider the Net::FCP module. It features (among others) the following 1240 Consider the Net::FCP module. It features (among others) the following
1279 through AnyEvent. The benchmark creates a lot of timers (with a zero 1367 through AnyEvent. The benchmark creates a lot of timers (with a zero
1280 timeout) and I/O watchers (watching STDOUT, a pty, to become writable, 1368 timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1281 which it is), lets them fire exactly once and destroys them again. 1369 which it is), lets them fire exactly once and destroys them again.
1282 1370
1283 Source code for this benchmark is found as eg/bench in the AnyEvent 1371 Source code for this benchmark is found as eg/bench in the AnyEvent
1284 distribution. 1372 distribution. It uses the AE interface, which makes a real difference
1373 for the EV and Perl backends only.
1285 1374
1286 Explanation of the columns 1375 Explanation of the columns
1287 *watcher* is the number of event watchers created/destroyed. Since 1376 *watcher* is the number of event watchers created/destroyed. Since
1288 different event models feature vastly different performances, each event 1377 different event models feature vastly different performances, each event
1289 loop was given a number of watchers so that overall runtime is 1378 loop was given a number of watchers so that overall runtime is
1308 *destroy* is the time, in microseconds, that it takes to destroy a 1397 *destroy* is the time, in microseconds, that it takes to destroy a
1309 single watcher. 1398 single watcher.
1310 1399
1311 Results 1400 Results
1312 name watchers bytes create invoke destroy comment 1401 name watchers bytes create invoke destroy comment
1313 EV/EV 400000 224 0.47 0.35 0.27 EV native interface 1402 EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1314 EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers 1403 EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1315 CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal 1404 Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1316 Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation 1405 Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1317 Event/Event 16000 517 32.20 31.80 0.81 Event native interface 1406 Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1318 Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers 1407 Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
1319 IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll 1408 IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
1320 IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll 1409 IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1321 Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour 1410 Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1322 Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers 1411 Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1323 POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event 1412 POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1324 POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select 1413 POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1325 1414
1326 Discussion 1415 Discussion
1327 The benchmark does *not* measure scalability of the event loop very 1416 The benchmark does *not* measure scalability of the event loop very
1328 well. For example, a select-based event loop (such as the pure perl one) 1417 well. For example, a select-based event loop (such as the pure perl one)
1329 can never compete with an event loop that uses epoll when the number of 1418 can never compete with an event loop that uses epoll when the number of
1340 benchmark machine, handling an event takes roughly 1600 CPU cycles with 1429 benchmark machine, handling an event takes roughly 1600 CPU cycles with
1341 EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 1430 EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1342 CPU cycles with POE. 1431 CPU cycles with POE.
1343 1432
1344 "EV" is the sole leader regarding speed and memory use, which are both 1433 "EV" is the sole leader regarding speed and memory use, which are both
1345 maximal/minimal, respectively. Even when going through AnyEvent, it uses 1434 maximal/minimal, respectively. When using the AE API there is zero
1435 overhead (when going through the AnyEvent API create is about 5-6 times
1436 slower, with other times being equal, so still uses far less memory than
1346 far less memory than any other event loop and is still faster than Event 1437 any other event loop and is still faster than Event natively).
1347 natively.
1348 1438
1349 The pure perl implementation is hit in a few sweet spots (both the 1439 The pure perl implementation is hit in a few sweet spots (both the
1350 constant timeout and the use of a single fd hit optimisations in the 1440 constant timeout and the use of a single fd hit optimisations in the
1351 perl interpreter and the backend itself). Nevertheless this shows that 1441 perl interpreter and the backend itself). Nevertheless this shows that
1352 it adds very little overhead in itself. Like any select-based backend 1442 it adds very little overhead in itself. Like any select-based backend
1422 In this benchmark, we use 10000 socket pairs (20000 sockets), of which 1512 In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1423 100 (1%) are active. This mirrors the activity of large servers with 1513 100 (1%) are active. This mirrors the activity of large servers with
1424 many connections, most of which are idle at any one point in time. 1514 many connections, most of which are idle at any one point in time.
1425 1515
1426 Source code for this benchmark is found as eg/bench2 in the AnyEvent 1516 Source code for this benchmark is found as eg/bench2 in the AnyEvent
1427 distribution. 1517 distribution. It uses the AE interface, which makes a real difference
1518 for the EV and Perl backends only.
1428 1519
1429 Explanation of the columns 1520 Explanation of the columns
1430 *sockets* is the number of sockets, and twice the number of "servers" 1521 *sockets* is the number of sockets, and twice the number of "servers"
1431 (as each server has a read and write socket end). 1522 (as each server has a read and write socket end).
1432 1523
1438 forwarding it to another server. This includes deleting the old timeout 1529 forwarding it to another server. This includes deleting the old timeout
1439 and creating a new one that moves the timeout into the future. 1530 and creating a new one that moves the timeout into the future.
1440 1531
1441 Results 1532 Results
1442 name sockets create request 1533 name sockets create request
1443 EV 20000 69.01 11.16 1534 EV 20000 62.66 7.99
1444 Perl 20000 73.32 35.87 1535 Perl 20000 68.32 32.64
1445 IOAsync 20000 157.00 98.14 epoll 1536 IOAsync 20000 174.06 101.15 epoll
1446 IOAsync 20000 159.31 616.06 poll 1537 IOAsync 20000 174.67 610.84 poll
1447 Event 20000 212.62 257.32 1538 Event 20000 202.69 242.91
1448 Glib 20000 651.16 1896.30 1539 Glib 20000 557.01 1689.52
1449 POE 20000 349.67 12317.24 uses POE::Loop::Event 1540 POE 20000 341.54 12086.32 uses POE::Loop::Event
1450 1541
1451 Discussion 1542 Discussion
1452 This benchmark *does* measure scalability and overall performance of the 1543 This benchmark *does* measure scalability and overall performance of the
1453 particular event loop. 1544 particular event loop.
1454 1545
1567 As you can see, the AnyEvent + EV combination even beats the 1658 As you can see, the AnyEvent + EV combination even beats the
1568 hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl 1659 hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1569 backend easily beats IO::Lambda and POE. 1660 backend easily beats IO::Lambda and POE.
1570 1661
1571 And even the 100% non-blocking version written using the high-level (and 1662 And even the 100% non-blocking version written using the high-level (and
1572 slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a 1663 slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
1573 large margin, even though it does all of DNS, tcp-connect and socket I/O 1664 higher level ("unoptimised") abstractions by a large margin, even though
1574 in a non-blocking way. 1665 it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
1575 1666
1576 The two AnyEvent benchmarks programs can be found as eg/ae0.pl and 1667 The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
1577 eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are 1668 eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1578 part of the IO::lambda distribution and were used without any changes. 1669 part of the IO::Lambda distribution and were used without any changes.
1579 1670
1580SIGNALS 1671SIGNALS
1581 AnyEvent currently installs handlers for these signals: 1672 AnyEvent currently installs handlers for these signals:
1582 1673
1583 SIGCHLD 1674 SIGCHLD
1603 it is that this way, the handler will be restored to defaults on 1694 it is that this way, the handler will be restored to defaults on
1604 exec. 1695 exec.
1605 1696
1606 Feel free to install your own handler, or reset it to defaults. 1697 Feel free to install your own handler, or reset it to defaults.
1607 1698
1699RECOMMENDED/OPTIONAL MODULES
1700 One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
1701 it's built-in modules) are required to use it.
1702
1703 That does not mean that AnyEvent won't take advantage of some additional
1704 modules if they are installed.
1705
1706 This section epxlains which additional modules will be used, and how
1707 they affect AnyEvent's operetion.
1708
1709 Async::Interrupt
1710 This slightly arcane module is used to implement fast signal
1711 handling: To my knowledge, there is no way to do completely
1712 race-free and quick signal handling in pure perl. To ensure that
1713 signals still get delivered, AnyEvent will start an interval timer
1714 to wake up perl (and catch the signals) with some delay (default is
1715 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
1716
1717 If this module is available, then it will be used to implement
1718 signal catching, which means that signals will not be delayed, and
1719 the event loop will not be interrupted regularly, which is more
1720 efficient (And good for battery life on laptops).
1721
1722 This affects not just the pure-perl event loop, but also other event
1723 loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
1724
1725 Some event loops (POE, Event, Event::Lib) offer signal watchers
1726 natively, and either employ their own workarounds (POE) or use
1727 AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
1728 Installing Async::Interrupt does nothing for those backends.
1729
1730 EV This module isn't really "optional", as it is simply one of the
1731 backend event loops that AnyEvent can use. However, it is simply the
1732 best event loop available in terms of features, speed and stability:
1733 It supports the AnyEvent API optimally, implements all the watcher
1734 types in XS, does automatic timer adjustments even when no monotonic
1735 clock is available, can take avdantage of advanced kernel interfaces
1736 such as "epoll" and "kqueue", and is the fastest backend *by far*.
1737 You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
1738 Glib::EV).
1739
1740 Guard
1741 The guard module, when used, will be used to implement
1742 "AnyEvent::Util::guard". This speeds up guards considerably (and
1743 uses a lot less memory), but otherwise doesn't affect guard
1744 operation much. It is purely used for performance.
1745
1746 JSON and JSON::XS
1747 One of these modules is required when you want to read or write JSON
1748 data via AnyEvent::Handle. It is also written in pure-perl, but can
1749 take advantage of the ultra-high-speed JSON::XS module when it is
1750 installed.
1751
1752 In fact, AnyEvent::Handle will use JSON::XS by default if it is
1753 installed.
1754
1755 Net::SSLeay
1756 Implementing TLS/SSL in Perl is certainly interesting, but not very
1757 worthwhile: If this module is installed, then AnyEvent::Handle (with
1758 the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
1759
1760 Time::HiRes
1761 This module is part of perl since release 5.008. It will be used
1762 when the chosen event library does not come with a timing source on
1763 it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
1764 additionally use it to try to use a monotonic clock for timing
1765 stability.
1766
1608FORK 1767FORK
1609 Most event libraries are not fork-safe. The ones who are usually are 1768 Most event libraries are not fork-safe. The ones who are usually are
1610 because they rely on inefficient but fork-safe "select" or "poll" calls. 1769 because they rely on inefficient but fork-safe "select" or "poll" calls.
1611 Only EV is fully fork-aware. 1770 Only EV is fully fork-aware.
1612 1771
1613 If you have to fork, you must either do so *before* creating your first 1772 If you have to fork, you must either do so *before* creating your first
1614 watcher OR you must not use AnyEvent at all in the child. 1773 watcher OR you must not use AnyEvent at all in the child OR you must do
1774 something completely out of the scope of AnyEvent.
1615 1775
1616SECURITY CONSIDERATIONS 1776SECURITY CONSIDERATIONS
1617 AnyEvent can be forced to load any event model via 1777 AnyEvent can be forced to load any event model via
1618 $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used 1778 $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1619 to execute arbitrary code or directly gain access, it can easily be used 1779 to execute arbitrary code or directly gain access, it can easily be used
1651 Event::Lib, Qt, POE. 1811 Event::Lib, Qt, POE.
1652 1812
1653 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, 1813 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1654 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, 1814 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1655 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE, 1815 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1656 AnyEvent::Impl::IOAsync. 1816 AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1657 1817
1658 Non-blocking file handles, sockets, TCP clients and servers: 1818 Non-blocking file handles, sockets, TCP clients and servers:
1659 AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS. 1819 AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1660 1820
1661 Asynchronous DNS: AnyEvent::DNS. 1821 Asynchronous DNS: AnyEvent::DNS.

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