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Revision 1.98 by root, Sun Apr 27 16:31:48 2008 UTC vs.
Revision 1.113 by root, Sat May 10 20:30:35 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#TODO#
72
73Net::IRC3
74AnyEvent::HTTPD
75AnyEvent::DNS
76IO::AnyEvent
77Net::FPing
78Net::XMPP2
79Coro
80
81AnyEvent::IRC
82AnyEvent::HTTPD
83AnyEvent::DNS
84AnyEvent::Handle
85AnyEvent::Socket
86AnyEvent::FPing
87AnyEvent::XMPP
88AnyEvent::SNMP
89Coro
90
91=head1 DESCRIPTION 71=head1 DESCRIPTION
92 72
93L<AnyEvent> provides an identical interface to multiple event loops. This 73L<AnyEvent> provides an identical interface to multiple event loops. This
94allows module authors to utilise an event loop without forcing module 74allows module authors to utilise an event loop without forcing module
95users 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
98The 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>
99module. 79module.
100 80
101During the first call of any watcher-creation method, the module tries 81During the first call of any watcher-creation method, the module tries
102to 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
103following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>, 83following modules is already loaded: L<EV>,
104L<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>,
105L<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
106to 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
107adaptor 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
108be 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
308 my $w = AnyEvent->child ( 288 my $w = AnyEvent->child (
309 pid => $pid, 289 pid => $pid,
310 cb => sub { 290 cb => sub {
311 my ($pid, $status) = @_; 291 my ($pid, $status) = @_;
312 warn "pid $pid exited with status $status"; 292 warn "pid $pid exited with status $status";
313 $done->broadcast; 293 $done->send;
314 }, 294 },
315 ); 295 );
316 296
317 # do something else, then wait for process exit 297 # do something else, then wait for process exit
318 $done->wait; 298 $done->wait;
319 299
320=head2 CONDITION VARIABLES 300=head2 CONDITION VARIABLES
321 301
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
322Condition variables can be created by calling the C<< AnyEvent->condvar >> 312Condition variables can be created by calling the C<< AnyEvent->condvar
323method 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.
324 316
325A condition variable waits for a condition - precisely that the C<< 317After creation, the conditon variable is "false" until it becomes "true"
326->broadcast >> method has been called. 318by calling the C<send> method.
327 319
328They 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,
329example, if you write a module that does asynchronous http requests, 328for example, if you write a module that does asynchronous http requests,
330then a condition variable would be the ideal candidate to signal the 329then a condition variable would be the ideal candidate to signal the
331availability of results. 330availability of results. The user can either act when the callback is
331called or can synchronously C<< ->wait >> for the results.
332 332
333You can also use condition variables to block your main program until 333You can also use them to simulate traditional event loops - for example,
334an event occurs - for example, you could C<< ->wait >> in your main 334you can block your main program until an event occurs - for example, you
335program 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
336->broadcast >> the "quit" event. 336button of your app, which would C<< ->send >> the "quit" event.
337 337
338Note that condition variables recurse into the event loop - if you have 338Note that condition variables recurse into the event loop - if you have
339two 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
340lose. Therefore, condition variables are good to export to your caller, but 340lose. Therefore, condition variables are good to export to your caller, but
341you should avoid making a blocking wait yourself, at least in callbacks, 341you should avoid making a blocking wait yourself, at least in callbacks,
342as this asks for trouble. 342as this asks for trouble.
343 343
344This 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.
345 378
346=over 4 379=over 4
347 380
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
348=item $cv->wait 459=item $cv->wait
349 460
350Wait (blocking if necessary) until the C<< ->broadcast >> method has been 461Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
351called on c<$cv>, while servicing other watchers normally. 462>> methods have been called on c<$cv>, while servicing other watchers
463normally.
352 464
353You can only wait once on a condition - additional calls will return 465You can only wait once on a condition - additional calls are valid but
354immediately. 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.
355 473
356Not 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
357(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
358using 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
359caller 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
362while still suppporting blocking waits if the caller so desires). 480while still suppporting blocking waits if the caller so desires).
363 481
364Another 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
365sensibly have two C<< ->wait >>'s in parallel, as that would require 483sensibly have two C<< ->wait >>'s in parallel, as that would require
366multiple interpreters or coroutines/threads, none of which C<AnyEvent> 484multiple interpreters or coroutines/threads, none of which C<AnyEvent>
367can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and 485can supply.
368L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
369from different coroutines, however).
370 486
371=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).
372 492
373Flag the condition as ready - a running C<< ->wait >> and all further 493You can ensure that C<< -wait >> never blocks by setting a callback and
374calls to C<wait> will (eventually) return after this method has been 494only calling C<< ->wait >> from within that callback (or at a later
375called. 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.
376 511
377=back 512=back
378
379Example:
380
381 # wait till the result is ready
382 my $result_ready = AnyEvent->condvar;
383
384 # do something such as adding a timer
385 # or socket watcher the calls $result_ready->broadcast
386 # when the "result" is ready.
387 # in this case, we simply use a timer:
388 my $w = AnyEvent->timer (
389 after => 1,
390 cb => sub { $result_ready->broadcast },
391 );
392
393 # this "blocks" (while handling events) till the watcher
394 # calls broadcast
395 $result_ready->wait;
396 513
397=head1 GLOBAL VARIABLES AND FUNCTIONS 514=head1 GLOBAL VARIABLES AND FUNCTIONS
398 515
399=over 4 516=over 4
400 517
406C<AnyEvent::Impl:xxx> modules, but can be any other class in the case 523C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
407AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). 524AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
408 525
409The known classes so far are: 526The known classes so far are:
410 527
411 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
412 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
413 AnyEvent::Impl::EV based on EV (an interface to libev, best choice). 528 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
414 AnyEvent::Impl::Event based on Event, second best choice. 529 AnyEvent::Impl::Event based on Event, second best choice.
530 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
415 AnyEvent::Impl::Glib based on Glib, third-best choice. 531 AnyEvent::Impl::Glib based on Glib, third-best choice.
416 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
417 AnyEvent::Impl::Tk based on Tk, very bad choice. 532 AnyEvent::Impl::Tk based on Tk, very bad choice.
418 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). 533 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
419 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. 534 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
420 AnyEvent::Impl::POE based on POE, not generic enough for full support. 535 AnyEvent::Impl::POE based on POE, not generic enough for full support.
421 536
434Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model 549Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
435if necessary. You should only call this function right before you would 550if necessary. You should only call this function right before you would
436have 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
437runtime. 552runtime.
438 553
554=item $guard = AnyEvent::post_detect { BLOCK }
555
556Arranges for the code block to be executed as soon as the event model is
557autodetected (or immediately if this has already happened).
558
559If called in scalar or list context, then it creates and returns an object
560that automatically removes the callback again when it is destroyed. See
561L<Coro::BDB> for a case where this is useful.
562
563=item @AnyEvent::post_detect
564
565If there are any code references in this array (you can C<push> to it
566before or after loading AnyEvent), then they will called directly after
567the event loop has been chosen.
568
569You should check C<$AnyEvent::MODEL> before adding to this array, though:
570if it contains a true value then the event loop has already been detected,
571and the array will be ignored.
572
573Best use C<AnyEvent::post_detect { BLOCK }> instead.
574
439=back 575=back
440 576
441=head1 WHAT TO DO IN A MODULE 577=head1 WHAT TO DO IN A MODULE
442 578
443As a module author, you should C<use AnyEvent> and call AnyEvent methods 579As a module author, you should C<use AnyEvent> and call AnyEvent methods
447decide which event module to use as soon as the first method is called, so 583decide which event module to use as soon as the first method is called, so
448by calling AnyEvent in your module body you force the user of your module 584by calling AnyEvent in your module body you force the user of your module
449to load the event module first. 585to load the event module first.
450 586
451Never call C<< ->wait >> on a condition variable unless you I<know> that 587Never call C<< ->wait >> on a condition variable unless you I<know> that
452the C<< ->broadcast >> method has been called on it already. This is 588the C<< ->send >> method has been called on it already. This is
453because it will stall the whole program, and the whole point of using 589because it will stall the whole program, and the whole point of using
454events is to stay interactive. 590events is to stay interactive.
455 591
456It is fine, however, to call C<< ->wait >> when the user of your module 592It is fine, however, to call C<< ->wait >> when the user of your module
457requests it (i.e. if you create a http request object ad have a method 593requests it (i.e. if you create a http request object ad have a method
477 613
478You can chose to use a rather inefficient pure-perl implementation by 614You can chose to use a rather inefficient pure-perl implementation by
479loading the C<AnyEvent::Impl::Perl> module, which gives you similar 615loading the C<AnyEvent::Impl::Perl> module, which gives you similar
480behaviour everywhere, but letting AnyEvent chose is generally better. 616behaviour everywhere, but letting AnyEvent chose is generally better.
481 617
618=head1 OTHER MODULES
619
620The following is a non-exhaustive list of additional modules that use
621AnyEvent and can therefore be mixed easily with other AnyEvent modules
622in the same program. Some of the modules come with AnyEvent, some are
623available via CPAN.
624
625=over 4
626
627=item L<AnyEvent::Util>
628
629Contains various utility functions that replace often-used but blocking
630functions such as C<inet_aton> by event-/callback-based versions.
631
632=item L<AnyEvent::Handle>
633
634Provide read and write buffers and manages watchers for reads and writes.
635
636=item L<AnyEvent::HTTPD>
637
638Provides a simple web application server framework.
639
640=item L<AnyEvent::DNS>
641
642Provides asynchronous DNS resolver capabilities, beyond what
643L<AnyEvent::Util> offers.
644
645=item L<AnyEvent::FastPing>
646
647The fastest ping in the west.
648
649=item L<Net::IRC3>
650
651AnyEvent based IRC client module family.
652
653=item L<Net::XMPP2>
654
655AnyEvent based XMPP (Jabber protocol) module family.
656
657=item L<Net::FCP>
658
659AnyEvent-based implementation of the Freenet Client Protocol, birthplace
660of AnyEvent.
661
662=item L<Event::ExecFlow>
663
664High level API for event-based execution flow control.
665
666=item L<Coro>
667
668Has special support for AnyEvent via L<Coro::AnyEvent>.
669
670=item L<AnyEvent::AIO>, L<IO::AIO>
671
672Truly asynchronous I/O, should be in the toolbox of every event
673programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
674together.
675
676=item L<AnyEvent::BDB>, L<BDB>
677
678Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
679IO::AIO and AnyEvent together.
680
681=item L<IO::Lambda>
682
683The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
684
685=back
686
482=cut 687=cut
483 688
484package AnyEvent; 689package AnyEvent;
485 690
486no warnings; 691no warnings;
487use strict; 692use strict;
488 693
489use Carp; 694use Carp;
490 695
491our $VERSION = '3.3'; 696our $VERSION = '3.4';
492our $MODEL; 697our $MODEL;
493 698
494our $AUTOLOAD; 699our $AUTOLOAD;
495our @ISA; 700our @ISA;
496 701
497our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; 702our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
498 703
499our @REGISTRY; 704our @REGISTRY;
500 705
501my @models = ( 706my @models = (
502 [Coro::EV:: => AnyEvent::Impl::CoroEV::],
503 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
504 [EV:: => AnyEvent::Impl::EV::], 707 [EV:: => AnyEvent::Impl::EV::],
505 [Event:: => AnyEvent::Impl::Event::], 708 [Event:: => AnyEvent::Impl::Event::],
506 [Glib:: => AnyEvent::Impl::Glib::],
507 [Tk:: => AnyEvent::Impl::Tk::], 709 [Tk:: => AnyEvent::Impl::Tk::],
508 [Wx:: => AnyEvent::Impl::POE::], 710 [Wx:: => AnyEvent::Impl::POE::],
509 [Prima:: => AnyEvent::Impl::POE::], 711 [Prima:: => AnyEvent::Impl::POE::],
510 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 712 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
511 # everything below here will not be autoprobed as the pureperl backend should work everywhere 713 # everything below here will not be autoprobed as the pureperl backend should work everywhere
714 [Glib:: => AnyEvent::Impl::Glib::],
512 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy 715 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
513 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program 716 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
514 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza 717 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
515); 718);
516 719
517our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); 720our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);
721
722our @post_detect;
723
724sub post_detect(&) {
725 my ($cb) = @_;
726
727 if ($MODEL) {
728 $cb->();
729
730 1
731 } else {
732 push @post_detect, $cb;
733
734 defined wantarray
735 ? bless \$cb, "AnyEvent::Util::Guard"
736 : ()
737 }
738}
739
740sub AnyEvent::Util::Guard::DESTROY {
741 @post_detect = grep $_ != ${$_[0]}, @post_detect;
742}
518 743
519sub detect() { 744sub detect() {
520 unless ($MODEL) { 745 unless ($MODEL) {
521 no strict 'refs'; 746 no strict 'refs';
522 747
556 last; 781 last;
557 } 782 }
558 } 783 }
559 784
560 $MODEL 785 $MODEL
561 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."; 786 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
562 } 787 }
563 } 788 }
564 789
565 unshift @ISA, $MODEL; 790 unshift @ISA, $MODEL;
566 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 791 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
792
793 (shift @post_detect)->() while @post_detect;
567 } 794 }
568 795
569 $MODEL 796 $MODEL
570} 797}
571 798
1019file descriptor is dup()ed for each watcher. This shows that the dup() 1246file descriptor is dup()ed for each watcher. This shows that the dup()
1020employed by some adaptors is not a big performance issue (it does incur a 1247employed by some adaptors is not a big performance issue (it does incur a
1021hidden memory cost inside the kernel which is not reflected in the figures 1248hidden memory cost inside the kernel which is not reflected in the figures
1022above). 1249above).
1023 1250
1024C<POE>, regardless of underlying event loop (whether using its pure 1251C<POE>, regardless of underlying event loop (whether using its pure perl
1025perl select-based backend or the Event module, the POE-EV backend 1252select-based backend or the Event module, the POE-EV backend couldn't
1026couldn't be tested because it wasn't working) shows abysmal performance 1253be tested because it wasn't working) shows abysmal performance and
1027and memory usage: Watchers use almost 30 times as much memory as 1254memory usage with AnyEvent: Watchers use almost 30 times as much memory
1028EV watchers, and 10 times as much memory as Event (the high memory 1255as EV watchers, and 10 times as much memory as Event (the high memory
1029requirements are caused by requiring a session for each watcher). Watcher 1256requirements are caused by requiring a session for each watcher). Watcher
1030invocation speed is almost 900 times slower than with AnyEvent's pure perl 1257invocation speed is almost 900 times slower than with AnyEvent's pure perl
1258implementation.
1259
1031implementation. The design of the POE adaptor class in AnyEvent can not 1260The design of the POE adaptor class in AnyEvent can not really account
1032really account for this, as session creation overhead is small compared 1261for the performance issues, though, as session creation overhead is
1033to execution of the state machine, which is coded pretty optimally within 1262small compared to execution of the state machine, which is coded pretty
1034L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. 1263optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
1264using multiple sessions is not a good approach, especially regarding
1265memory usage, even the author of POE could not come up with a faster
1266design).
1035 1267
1036=head3 Summary 1268=head3 Summary
1037 1269
1038=over 4 1270=over 4
1039 1271
1086 1318
1087=head3 Results 1319=head3 Results
1088 1320
1089 name sockets create request 1321 name sockets create request
1090 EV 20000 69.01 11.16 1322 EV 20000 69.01 11.16
1091 Perl 20000 75.28 112.76 1323 Perl 20000 73.32 35.87
1092 Event 20000 212.62 257.32 1324 Event 20000 212.62 257.32
1093 Glib 20000 651.16 1896.30 1325 Glib 20000 651.16 1896.30
1094 POE 20000 349.67 12317.24 uses POE::Loop::Event 1326 POE 20000 349.67 12317.24 uses POE::Loop::Event
1095 1327
1096=head3 Discussion 1328=head3 Discussion
1118 1350
1119=head3 Summary 1351=head3 Summary
1120 1352
1121=over 4 1353=over 4
1122 1354
1123=item * The pure perl implementation performs extremely well, considering 1355=item * The pure perl implementation performs extremely well.
1124that it uses select.
1125 1356
1126=item * Avoid Glib or POE in large projects where performance matters. 1357=item * Avoid Glib or POE in large projects where performance matters.
1127 1358
1128=back 1359=back
1129 1360
1142 1373
1143=head3 Results 1374=head3 Results
1144 1375
1145 name sockets create request 1376 name sockets create request
1146 EV 16 20.00 6.54 1377 EV 16 20.00 6.54
1378 Perl 16 25.75 12.62
1147 Event 16 81.27 35.86 1379 Event 16 81.27 35.86
1148 Glib 16 32.63 15.48 1380 Glib 16 32.63 15.48
1149 Perl 16 24.62 162.37
1150 POE 16 261.87 276.28 uses POE::Loop::Event 1381 POE 16 261.87 276.28 uses POE::Loop::Event
1151 1382
1152=head3 Discussion 1383=head3 Discussion
1153 1384
1154The benchmark tries to test the performance of a typical small 1385The benchmark tries to test the performance of a typical small
1158speed most when you have lots of watchers, not when you only have a few of 1389speed most when you have lots of watchers, not when you only have a few of
1159them). 1390them).
1160 1391
1161EV is again fastest. 1392EV is again fastest.
1162 1393
1163The C-based event loops Event and Glib come in second this time, as the 1394Perl again comes second. It is noticably faster than the C-based event
1164overhead of running an iteration is much smaller in C than in Perl (little 1395loops Event and Glib, although the difference is too small to really
1165code to execute in the inner loop, and perl's function calling overhead is 1396matter.
1166high, and updating all the data structures is costly).
1167
1168The pure perl event loop is much slower, but still competitive.
1169 1397
1170POE also performs much better in this case, but is is still far behind the 1398POE also performs much better in this case, but is is still far behind the
1171others. 1399others.
1172 1400
1173=head3 Summary 1401=head3 Summary
1181 1409
1182 1410
1183=head1 FORK 1411=head1 FORK
1184 1412
1185Most event libraries are not fork-safe. The ones who are usually are 1413Most event libraries are not fork-safe. The ones who are usually are
1186because they are so inefficient. Only L<EV> is fully fork-aware. 1414because they rely on inefficient but fork-safe C<select> or C<poll>
1415calls. Only L<EV> is fully fork-aware.
1187 1416
1188If you have to fork, you must either do so I<before> creating your first 1417If you have to fork, you must either do so I<before> creating your first
1189watcher OR you must not use AnyEvent at all in the child. 1418watcher OR you must not use AnyEvent at all in the child.
1190 1419
1191 1420
1203 1432
1204 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 1433 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1205 1434
1206 use AnyEvent; 1435 use AnyEvent;
1207 1436
1437Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1438be used to probe what backend is used and gain other information (which is
1439probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
1440
1208 1441
1209=head1 SEE ALSO 1442=head1 SEE ALSO
1210 1443
1211Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, 1444Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1212L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
1213L<Event::Lib>, L<Qt>, L<POE>. 1445L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1214 1446
1215Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, 1447Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1216L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, 1448L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1217L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, 1449L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1218L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. 1450L<AnyEvent::Impl::POE>.
1451
1452Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
1219 1453
1220Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. 1454Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
1221 1455
1222 1456
1223=head1 AUTHOR 1457=head1 AUTHOR

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