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Revision 1.95 by root, Sat Apr 26 11:06:45 2008 UTC vs.
Revision 1.110 by root, Sat May 10 00:57:31 2008 UTC

1=head1 NAME 1=head1 NAME
2 2
3AnyEvent - provide framework for multiple event loops 3AnyEvent - provide framework for multiple event loops
4 4
5EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops 5EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
6 6
7=head1 SYNOPSIS 7=head1 SYNOPSIS
8 8
9 use AnyEvent; 9 use AnyEvent;
10 10
15 my $w = AnyEvent->timer (after => $seconds, cb => sub { 15 my $w = AnyEvent->timer (after => $seconds, cb => sub {
16 ... 16 ...
17 }); 17 });
18 18
19 my $w = AnyEvent->condvar; # stores whether a condition was flagged 19 my $w = AnyEvent->condvar; # stores whether a condition was flagged
20 $w->wait; # enters "main loop" till $condvar gets ->broadcast 20 $w->wait; # enters "main loop" till $condvar gets ->send
21 $w->broadcast; # wake up current and all future wait's 21 $w->send; # wake up current and all future wait's
22 22
23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) 23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24 24
25Glib, POE, IO::Async, Event... CPAN offers event models by the dozen 25Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26nowadays. So what is different about AnyEvent? 26nowadays. So what is different about AnyEvent?
66 66
67Of course, if you want lots of policy (this can arguably be somewhat 67Of course, if you want lots of policy (this can arguably be somewhat
68useful) and you want to force your users to use the one and only event 68useful) and you want to force your users to use the one and only event
69model, you should I<not> use this module. 69model, you should I<not> use this module.
70 70
71
72=head1 DESCRIPTION 71=head1 DESCRIPTION
73 72
74L<AnyEvent> provides an identical interface to multiple event loops. This 73L<AnyEvent> provides an identical interface to multiple event loops. This
75allows module authors to utilise an event loop without forcing module 74allows module authors to utilise an event loop without forcing module
76users to use the same event loop (as only a single event loop can coexist 75users to use the same event loop (as only a single event loop can coexist
79The interface itself is vaguely similar, but not identical to the L<Event> 78The interface itself is vaguely similar, but not identical to the L<Event>
80module. 79module.
81 80
82During the first call of any watcher-creation method, the module tries 81During the first call of any watcher-creation method, the module tries
83to detect the currently loaded event loop by probing whether one of the 82to detect the currently loaded event loop by probing whether one of the
84following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>, 83following modules is already loaded: L<EV>,
85L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>, 84L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86L<POE>. The first one found is used. If none are found, the module tries 85L<POE>. The first one found is used. If none are found, the module tries
87to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl 86to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
88adaptor should always succeed) in the order given. The first one that can 87adaptor should always succeed) in the order given. The first one that can
89be successfully loaded will be used. If, after this, still none could be 88be successfully loaded will be used. If, after this, still none could be
289 my $w = AnyEvent->child ( 288 my $w = AnyEvent->child (
290 pid => $pid, 289 pid => $pid,
291 cb => sub { 290 cb => sub {
292 my ($pid, $status) = @_; 291 my ($pid, $status) = @_;
293 warn "pid $pid exited with status $status"; 292 warn "pid $pid exited with status $status";
294 $done->broadcast; 293 $done->send;
295 }, 294 },
296 ); 295 );
297 296
298 # do something else, then wait for process exit 297 # do something else, then wait for process exit
299 $done->wait; 298 $done->wait;
300 299
301=head2 CONDITION VARIABLES 300=head2 CONDITION VARIABLES
302 301
302If you are familiar with some event loops you will know that all of them
303require you to run some blocking "loop", "run" or similar function that
304will actively watch for new events and call your callbacks.
305
306AnyEvent is different, it expects somebody else to run the event loop and
307will only block when necessary (usually when told by the user).
308
309The instrument to do that is called a "condition variable", so called
310because they represent a condition that must become true.
311
303Condition variables can be created by calling the C<< AnyEvent->condvar >> 312Condition variables can be created by calling the C<< AnyEvent->condvar
304method without any arguments. 313>> method, usually without arguments. The only argument pair allowed is
314C<cb>, which specifies a callback to be called when the condition variable
315becomes true.
305 316
306A condition variable waits for a condition - precisely that the C<< 317After creation, the conditon variable is "false" until it becomes "true"
307->broadcast >> method has been called. 318by calling the C<send> method.
308 319
309They are very useful to signal that a condition has been fulfilled, for 320Condition variables are similar to callbacks, except that you can
321optionally wait for them. They can also be called merge points - points
322in time where multiple outstandign events have been processed. And yet
323another way to call them is transations - each condition variable can be
324used to represent a transaction, which finishes at some point and delivers
325a result.
326
327Condition variables are very useful to signal that something has finished,
310example, if you write a module that does asynchronous http requests, 328for example, if you write a module that does asynchronous http requests,
311then a condition variable would be the ideal candidate to signal the 329then a condition variable would be the ideal candidate to signal the
312availability of results. 330availability of results. The user can either act when the callback is
331called or can synchronously C<< ->wait >> for the results.
313 332
314You can also use condition variables to block your main program until 333You can also use them to simulate traditional event loops - for example,
315an event occurs - for example, you could C<< ->wait >> in your main 334you can block your main program until an event occurs - for example, you
316program until the user clicks the Quit button in your app, which would C<< 335could C<< ->wait >> in your main program until the user clicks the Quit
317->broadcast >> the "quit" event. 336button of your app, which would C<< ->send >> the "quit" event.
318 337
319Note that condition variables recurse into the event loop - if you have 338Note that condition variables recurse into the event loop - if you have
320two pirces of code that call C<< ->wait >> in a round-robbin fashion, you 339two pieces of code that call C<< ->wait >> in a round-robbin fashion, you
321lose. Therefore, condition variables are good to export to your caller, but 340lose. Therefore, condition variables are good to export to your caller, but
322you should avoid making a blocking wait yourself, at least in callbacks, 341you should avoid making a blocking wait yourself, at least in callbacks,
323as this asks for trouble. 342as this asks for trouble.
324 343
325This object has two methods: 344Condition variables are represented by hash refs in perl, and the keys
345used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
346easy (it is often useful to build your own transaction class on top of
347AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
348it's C<new> method in your own C<new> method.
349
350There are two "sides" to a condition variable - the "producer side" which
351eventually calls C<< -> send >>, and the "consumer side", which waits
352for the send to occur.
353
354Example:
355
356 # wait till the result is ready
357 my $result_ready = AnyEvent->condvar;
358
359 # do something such as adding a timer
360 # or socket watcher the calls $result_ready->send
361 # when the "result" is ready.
362 # in this case, we simply use a timer:
363 my $w = AnyEvent->timer (
364 after => 1,
365 cb => sub { $result_ready->send },
366 );
367
368 # this "blocks" (while handling events) till the callback
369 # calls send
370 $result_ready->wait;
371
372=head3 METHODS FOR PRODUCERS
373
374These methods should only be used by the producing side, i.e. the
375code/module that eventually sends the signal. Note that it is also
376the producer side which creates the condvar in most cases, but it isn't
377uncommon for the consumer to create it as well.
326 378
327=over 4 379=over 4
328 380
381=item $cv->send (...)
382
383Flag the condition as ready - a running C<< ->wait >> and all further
384calls to C<wait> will (eventually) return after this method has been
385called. If nobody is waiting the send will be remembered.
386
387If a callback has been set on the condition variable, it is called
388immediately from within send.
389
390Any arguments passed to the C<send> call will be returned by all
391future C<< ->wait >> calls.
392
393=item $cv->croak ($error)
394
395Similar to send, but causes all call's wait C<< ->wait >> to invoke
396C<Carp::croak> with the given error message/object/scalar.
397
398This can be used to signal any errors to the condition variable
399user/consumer.
400
401=item $cv->begin ([group callback])
402
403=item $cv->end
404
405These two methods can be used to combine many transactions/events into
406one. For example, a function that pings many hosts in parallel might want
407to use a condition variable for the whole process.
408
409Every call to C<< ->begin >> will increment a counter, and every call to
410C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
411>>, the (last) callback passed to C<begin> will be executed. That callback
412is I<supposed> to call C<< ->send >>, but that is not required. If no
413callback was set, C<send> will be called without any arguments.
414
415Let's clarify this with the ping example:
416
417 my $cv = AnyEvent->condvar;
418
419 my %result;
420 $cv->begin (sub { $cv->send (\%result) });
421
422 for my $host (@list_of_hosts) {
423 $cv->begin;
424 ping_host_then_call_callback $host, sub {
425 $result{$host} = ...;
426 $cv->end;
427 };
428 }
429
430 $cv->end;
431
432This code fragment supposedly pings a number of hosts and calls
433C<send> after results for all then have have been gathered - in any
434order. To achieve this, the code issues a call to C<begin> when it starts
435each ping request and calls C<end> when it has received some result for
436it. Since C<begin> and C<end> only maintain a counter, the order in which
437results arrive is not relevant.
438
439There is an additional bracketing call to C<begin> and C<end> outside the
440loop, which serves two important purposes: first, it sets the callback
441to be called once the counter reaches C<0>, and second, it ensures that
442C<send> is called even when C<no> hosts are being pinged (the loop
443doesn't execute once).
444
445This is the general pattern when you "fan out" into multiple subrequests:
446use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
447is called at least once, and then, for each subrequest you start, call
448C<begin> and for eahc subrequest you finish, call C<end>.
449
450=back
451
452=head3 METHODS FOR CONSUMERS
453
454These methods should only be used by the consuming side, i.e. the
455code awaits the condition.
456
457=over 4
458
329=item $cv->wait 459=item $cv->wait
330 460
331Wait (blocking if necessary) until the C<< ->broadcast >> method has been 461Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
332called on c<$cv>, while servicing other watchers normally. 462>> methods have been called on c<$cv>, while servicing other watchers
463normally.
333 464
334You can only wait once on a condition - additional calls will return 465You can only wait once on a condition - additional calls are valid but
335immediately. 466will return immediately.
467
468If an error condition has been set by calling C<< ->croak >>, then this
469function will call C<croak>.
470
471In list context, all parameters passed to C<send> will be returned,
472in scalar context only the first one will be returned.
336 473
337Not all event models support a blocking wait - some die in that case 474Not all event models support a blocking wait - some die in that case
338(programs might want to do that to stay interactive), so I<if you are 475(programs might want to do that to stay interactive), so I<if you are
339using this from a module, never require a blocking wait>, but let the 476using this from a module, never require a blocking wait>, but let the
340caller decide whether the call will block or not (for example, by coupling 477caller decide whether the call will block or not (for example, by coupling
343while still suppporting blocking waits if the caller so desires). 480while still suppporting blocking waits if the caller so desires).
344 481
345Another reason I<never> to C<< ->wait >> in a module is that you cannot 482Another reason I<never> to C<< ->wait >> in a module is that you cannot
346sensibly have two C<< ->wait >>'s in parallel, as that would require 483sensibly have two C<< ->wait >>'s in parallel, as that would require
347multiple interpreters or coroutines/threads, none of which C<AnyEvent> 484multiple interpreters or coroutines/threads, none of which C<AnyEvent>
348can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and 485can supply.
349L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
350from different coroutines, however).
351 486
352=item $cv->broadcast 487The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
488fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
489versions and also integrates coroutines into AnyEvent, making blocking
490C<< ->wait >> calls perfectly safe as long as they are done from another
491coroutine (one that doesn't run the event loop).
353 492
354Flag the condition as ready - a running C<< ->wait >> and all further 493You can ensure that C<< -wait >> never blocks by setting a callback and
355calls to C<wait> will (eventually) return after this method has been 494only calling C<< ->wait >> from within that callback (or at a later
356called. If nobody is waiting the broadcast will be remembered.. 495time). This will work even when the event loop does not support blocking
496waits otherwise.
497
498=item $bool = $cv->ready
499
500Returns true when the condition is "true", i.e. whether C<send> or
501C<croak> have been called.
502
503=item $cb = $cv->cb ([new callback])
504
505This is a mutator function that returns the callback set and optionally
506replaces it before doing so.
507
508The callback will be called when the condition becomes "true", i.e. when
509C<send> or C<croak> are called. Calling C<wait> inside the callback
510or at any later time is guaranteed not to block.
357 511
358=back 512=back
359
360Example:
361
362 # wait till the result is ready
363 my $result_ready = AnyEvent->condvar;
364
365 # do something such as adding a timer
366 # or socket watcher the calls $result_ready->broadcast
367 # when the "result" is ready.
368 # in this case, we simply use a timer:
369 my $w = AnyEvent->timer (
370 after => 1,
371 cb => sub { $result_ready->broadcast },
372 );
373
374 # this "blocks" (while handling events) till the watcher
375 # calls broadcast
376 $result_ready->wait;
377 513
378=head1 GLOBAL VARIABLES AND FUNCTIONS 514=head1 GLOBAL VARIABLES AND FUNCTIONS
379 515
380=over 4 516=over 4
381 517
387C<AnyEvent::Impl:xxx> modules, but can be any other class in the case 523C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
388AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). 524AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
389 525
390The known classes so far are: 526The known classes so far are:
391 527
392 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
393 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
394 AnyEvent::Impl::EV based on EV (an interface to libev, best choice). 528 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
395 AnyEvent::Impl::Event based on Event, second best choice. 529 AnyEvent::Impl::Event based on Event, second best choice.
530 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
396 AnyEvent::Impl::Glib based on Glib, third-best choice. 531 AnyEvent::Impl::Glib based on Glib, third-best choice.
397 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
398 AnyEvent::Impl::Tk based on Tk, very bad choice. 532 AnyEvent::Impl::Tk based on Tk, very bad choice.
399 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). 533 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
400 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. 534 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
401 AnyEvent::Impl::POE based on POE, not generic enough for full support. 535 AnyEvent::Impl::POE based on POE, not generic enough for full support.
402 536
415Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model 549Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
416if necessary. You should only call this function right before you would 550if necessary. You should only call this function right before you would
417have created an AnyEvent watcher anyway, that is, as late as possible at 551have created an AnyEvent watcher anyway, that is, as late as possible at
418runtime. 552runtime.
419 553
554=item $guard = AnyEvent::on_detect { BLOCK }
555
556Arranges for the code block to be executed as soon as the event model is
557autodetected (or immediately if this has already happened).
558
559If called in scalar or list context, then it creates and returns an object
560that automatically removes the callback again when it is destroyed.
561
562=item @AnyEvent::on_detect
563
564If there are any code references in this array (you can C<push> to it
565before or after loading AnyEvent), then they will called directly after
566the event loop has been chosen.
567
568You should check C<$AnyEvent::MODEL> before adding to this array, though:
569if it contains a true value then the event loop has already been detected,
570and the array will be ignored.
571
572Best use C<AnyEvent::on_detect { BLOCK }> instead.
573
420=back 574=back
421 575
422=head1 WHAT TO DO IN A MODULE 576=head1 WHAT TO DO IN A MODULE
423 577
424As a module author, you should C<use AnyEvent> and call AnyEvent methods 578As a module author, you should C<use AnyEvent> and call AnyEvent methods
428decide which event module to use as soon as the first method is called, so 582decide which event module to use as soon as the first method is called, so
429by calling AnyEvent in your module body you force the user of your module 583by calling AnyEvent in your module body you force the user of your module
430to load the event module first. 584to load the event module first.
431 585
432Never call C<< ->wait >> on a condition variable unless you I<know> that 586Never call C<< ->wait >> on a condition variable unless you I<know> that
433the C<< ->broadcast >> method has been called on it already. This is 587the C<< ->send >> method has been called on it already. This is
434because it will stall the whole program, and the whole point of using 588because it will stall the whole program, and the whole point of using
435events is to stay interactive. 589events is to stay interactive.
436 590
437It is fine, however, to call C<< ->wait >> when the user of your module 591It is fine, however, to call C<< ->wait >> when the user of your module
438requests it (i.e. if you create a http request object ad have a method 592requests it (i.e. if you create a http request object ad have a method
458 612
459You can chose to use a rather inefficient pure-perl implementation by 613You can chose to use a rather inefficient pure-perl implementation by
460loading the C<AnyEvent::Impl::Perl> module, which gives you similar 614loading the C<AnyEvent::Impl::Perl> module, which gives you similar
461behaviour everywhere, but letting AnyEvent chose is generally better. 615behaviour everywhere, but letting AnyEvent chose is generally better.
462 616
617=head1 OTHER MODULES
618
619The following is a non-exhaustive list of additional modules that use
620AnyEvent and can therefore be mixed easily with other AnyEvent modules
621in the same program. Some of the modules come with AnyEvent, some are
622available via CPAN.
623
624=over 4
625
626=item L<AnyEvent::Util>
627
628Contains various utility functions that replace often-used but blocking
629functions such as C<inet_aton> by event-/callback-based versions.
630
631=item L<AnyEvent::Handle>
632
633Provide read and write buffers and manages watchers for reads and writes.
634
635=item L<AnyEvent::Socket>
636
637Provides a means to do non-blocking connects, accepts etc.
638
639=item L<AnyEvent::HTTPD>
640
641Provides a simple web application server framework.
642
643=item L<AnyEvent::DNS>
644
645Provides asynchronous DNS resolver capabilities, beyond what
646L<AnyEvent::Util> offers.
647
648=item L<AnyEvent::FastPing>
649
650The fastest ping in the west.
651
652=item L<Net::IRC3>
653
654AnyEvent based IRC client module family.
655
656=item L<Net::XMPP2>
657
658AnyEvent based XMPP (Jabber protocol) module family.
659
660=item L<Net::FCP>
661
662AnyEvent-based implementation of the Freenet Client Protocol, birthplace
663of AnyEvent.
664
665=item L<Event::ExecFlow>
666
667High level API for event-based execution flow control.
668
669=item L<Coro>
670
671Has special support for AnyEvent via L<Coro::AnyEvent>.
672
673=item L<IO::Lambda>
674
675The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
676
677=item L<IO::AIO>
678
679Truly asynchronous I/O, should be in the toolbox of every event
680programmer. Can be trivially made to use AnyEvent.
681
682=item L<BDB>
683
684Truly asynchronous Berkeley DB access. Can be trivially made to use
685AnyEvent.
686
687=back
688
463=cut 689=cut
464 690
465package AnyEvent; 691package AnyEvent;
466 692
467no warnings; 693no warnings;
468use strict; 694use strict;
469 695
470use Carp; 696use Carp;
471 697
472our $VERSION = '3.3'; 698our $VERSION = '3.4';
473our $MODEL; 699our $MODEL;
474 700
475our $AUTOLOAD; 701our $AUTOLOAD;
476our @ISA; 702our @ISA;
477 703
478our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; 704our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479 705
480our @REGISTRY; 706our @REGISTRY;
481 707
482my @models = ( 708my @models = (
483 [Coro::EV:: => AnyEvent::Impl::CoroEV::],
484 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485 [EV:: => AnyEvent::Impl::EV::], 709 [EV:: => AnyEvent::Impl::EV::],
486 [Event:: => AnyEvent::Impl::Event::], 710 [Event:: => AnyEvent::Impl::Event::],
487 [Glib:: => AnyEvent::Impl::Glib::],
488 [Tk:: => AnyEvent::Impl::Tk::], 711 [Tk:: => AnyEvent::Impl::Tk::],
489 [Wx:: => AnyEvent::Impl::POE::], 712 [Wx:: => AnyEvent::Impl::POE::],
490 [Prima:: => AnyEvent::Impl::POE::], 713 [Prima:: => AnyEvent::Impl::POE::],
491 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 714 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
492 # everything below here will not be autoprobed as the pureperl backend should work everywhere 715 # everything below here will not be autoprobed as the pureperl backend should work everywhere
716 [Glib:: => AnyEvent::Impl::Glib::],
493 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy 717 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
494 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program 718 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
495 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza 719 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
496); 720);
497 721
498our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); 722our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);
723
724our @on_detect;
725
726sub on_detect(&) {
727 my ($cb) = @_;
728
729 if ($MODEL) {
730 $cb->();
731
732 1
733 } else {
734 push @on_detect, $cb;
735
736 defined wantarray
737 ? bless \$cb, "AnyEvent::Util::Guard"
738 : ()
739 }
740}
741
742sub AnyEvent::Util::Guard::DESTROY {
743 @on_detect = grep $_ != ${$_[0]}, @on_detect;
744}
499 745
500sub detect() { 746sub detect() {
501 unless ($MODEL) { 747 unless ($MODEL) {
502 no strict 'refs'; 748 no strict 'refs';
503 749
537 last; 783 last;
538 } 784 }
539 } 785 }
540 786
541 $MODEL 787 $MODEL
542 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib."; 788 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
543 } 789 }
544 } 790 }
545 791
546 unshift @ISA, $MODEL; 792 unshift @ISA, $MODEL;
547 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 793 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
794
795 (shift @on_detect)->() while @on_detect;
548 } 796 }
549 797
550 $MODEL 798 $MODEL
551} 799}
552 800
944 EV/EV 400000 244 0.56 0.46 0.31 EV native interface 1192 EV/EV 400000 244 0.56 0.46 0.31 EV native interface
945 EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers 1193 EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
946 CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal 1194 CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
947 Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation 1195 Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
948 Event/Event 16000 516 31.88 31.30 0.85 Event native interface 1196 Event/Event 16000 516 31.88 31.30 0.85 Event native interface
949 Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers 1197 Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
950 Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour 1198 Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
951 Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers 1199 Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
952 POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event 1200 POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
953 POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select 1201 POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
954 1202
963 1211
964Also, note that the number of watchers usually has a nonlinear effect on 1212Also, note that the number of watchers usually has a nonlinear effect on
965overall speed, that is, creating twice as many watchers doesn't take twice 1213overall speed, that is, creating twice as many watchers doesn't take twice
966the time - usually it takes longer. This puts event loops tested with a 1214the time - usually it takes longer. This puts event loops tested with a
967higher number of watchers at a disadvantage. 1215higher number of watchers at a disadvantage.
1216
1217To put the range of results into perspective, consider that on the
1218benchmark machine, handling an event takes roughly 1600 CPU cycles with
1219EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1220cycles with POE.
968 1221
969C<EV> is the sole leader regarding speed and memory use, which are both 1222C<EV> is the sole leader regarding speed and memory use, which are both
970maximal/minimal, respectively. Even when going through AnyEvent, it uses 1223maximal/minimal, respectively. Even when going through AnyEvent, it uses
971far less memory than any other event loop and is still faster than Event 1224far less memory than any other event loop and is still faster than Event
972natively. 1225natively.
995file descriptor is dup()ed for each watcher. This shows that the dup() 1248file descriptor is dup()ed for each watcher. This shows that the dup()
996employed by some adaptors is not a big performance issue (it does incur a 1249employed by some adaptors is not a big performance issue (it does incur a
997hidden memory cost inside the kernel which is not reflected in the figures 1250hidden memory cost inside the kernel which is not reflected in the figures
998above). 1251above).
999 1252
1000C<POE>, regardless of underlying event loop (whether using its pure 1253C<POE>, regardless of underlying event loop (whether using its pure perl
1001perl select-based backend or the Event module, the POE-EV backend 1254select-based backend or the Event module, the POE-EV backend couldn't
1002couldn't be tested because it wasn't working) shows abysmal performance 1255be tested because it wasn't working) shows abysmal performance and
1003and memory usage: Watchers use almost 30 times as much memory as 1256memory usage with AnyEvent: Watchers use almost 30 times as much memory
1004EV watchers, and 10 times as much memory as Event (the high memory 1257as EV watchers, and 10 times as much memory as Event (the high memory
1005requirements are caused by requiring a session for each watcher). Watcher 1258requirements are caused by requiring a session for each watcher). Watcher
1006invocation speed is almost 900 times slower than with AnyEvent's pure perl 1259invocation speed is almost 900 times slower than with AnyEvent's pure perl
1260implementation.
1261
1007implementation. The design of the POE adaptor class in AnyEvent can not 1262The design of the POE adaptor class in AnyEvent can not really account
1008really account for this, as session creation overhead is small compared 1263for the performance issues, though, as session creation overhead is
1009to execution of the state machine, which is coded pretty optimally within 1264small compared to execution of the state machine, which is coded pretty
1010L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. 1265optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
1266using multiple sessions is not a good approach, especially regarding
1267memory usage, even the author of POE could not come up with a faster
1268design).
1011 1269
1012=head3 Summary 1270=head3 Summary
1013 1271
1014=over 4 1272=over 4
1015 1273
1062 1320
1063=head3 Results 1321=head3 Results
1064 1322
1065 name sockets create request 1323 name sockets create request
1066 EV 20000 69.01 11.16 1324 EV 20000 69.01 11.16
1067 Perl 20000 75.28 112.76 1325 Perl 20000 73.32 35.87
1068 Event 20000 212.62 257.32 1326 Event 20000 212.62 257.32
1069 Glib 20000 651.16 1896.30 1327 Glib 20000 651.16 1896.30
1070 POE 20000 349.67 12317.24 uses POE::Loop::Event 1328 POE 20000 349.67 12317.24 uses POE::Loop::Event
1071 1329
1072=head3 Discussion 1330=head3 Discussion
1094 1352
1095=head3 Summary 1353=head3 Summary
1096 1354
1097=over 4 1355=over 4
1098 1356
1099=item * The pure perl implementation performs extremely well, considering 1357=item * The pure perl implementation performs extremely well.
1100that it uses select.
1101 1358
1102=item * Avoid Glib or POE in large projects where performance matters. 1359=item * Avoid Glib or POE in large projects where performance matters.
1103 1360
1104=back 1361=back
1105 1362
1118 1375
1119=head3 Results 1376=head3 Results
1120 1377
1121 name sockets create request 1378 name sockets create request
1122 EV 16 20.00 6.54 1379 EV 16 20.00 6.54
1380 Perl 16 25.75 12.62
1123 Event 16 81.27 35.86 1381 Event 16 81.27 35.86
1124 Glib 16 32.63 15.48 1382 Glib 16 32.63 15.48
1125 Perl 16 24.62 162.37
1126 POE 16 261.87 276.28 uses POE::Loop::Event 1383 POE 16 261.87 276.28 uses POE::Loop::Event
1127 1384
1128=head3 Discussion 1385=head3 Discussion
1129 1386
1130The benchmark tries to test the performance of a typical small 1387The benchmark tries to test the performance of a typical small
1131server. While knowing how various event loops perform is interesting, keep 1388server. While knowing how various event loops perform is interesting, keep
1132in mind that their overhead in this case is usually not as important, due 1389in mind that their overhead in this case is usually not as important, due
1133to the small absolute number of watchers. 1390to the small absolute number of watchers (that is, you need efficiency and
1391speed most when you have lots of watchers, not when you only have a few of
1392them).
1134 1393
1135EV is again fastest. 1394EV is again fastest.
1136 1395
1137The C-based event loops Event and Glib come in second this time, as the 1396Perl again comes second. It is noticably faster than the C-based event
1138overhead of running an iteration is much smaller in C than in Perl (little 1397loops Event and Glib, although the difference is too small to really
1139code to execute in the inner loop, and perl's function calling overhead is 1398matter.
1140high, and updating all the data structures is costly).
1141 1399
1142The pure perl event loop is much slower, but still competitive.
1143
1144POE also performs much better in this case, but is is stillf ar behind the 1400POE also performs much better in this case, but is is still far behind the
1145others. 1401others.
1146 1402
1147=head3 Summary 1403=head3 Summary
1148 1404
1149=over 4 1405=over 4
1155 1411
1156 1412
1157=head1 FORK 1413=head1 FORK
1158 1414
1159Most event libraries are not fork-safe. The ones who are usually are 1415Most event libraries are not fork-safe. The ones who are usually are
1160because they are so inefficient. Only L<EV> is fully fork-aware. 1416because they rely on inefficient but fork-safe C<select> or C<poll>
1417calls. Only L<EV> is fully fork-aware.
1161 1418
1162If you have to fork, you must either do so I<before> creating your first 1419If you have to fork, you must either do so I<before> creating your first
1163watcher OR you must not use AnyEvent at all in the child. 1420watcher OR you must not use AnyEvent at all in the child.
1164 1421
1165 1422
1177 1434
1178 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 1435 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1179 1436
1180 use AnyEvent; 1437 use AnyEvent;
1181 1438
1439Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1440be used to probe what backend is used and gain other information (which is
1441probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
1442
1182 1443
1183=head1 SEE ALSO 1444=head1 SEE ALSO
1184 1445
1185Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, 1446Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1186L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
1187L<Event::Lib>, L<Qt>, L<POE>. 1447L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1188 1448
1189Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, 1449Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1190L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, 1450L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1191L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, 1451L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1192L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. 1452L<AnyEvent::Impl::POE>.
1453
1454Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
1193 1455
1194Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. 1456Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
1195 1457
1196 1458
1197=head1 AUTHOR 1459=head1 AUTHOR

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