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Revision 1.89 by root, Fri Apr 25 14:19:23 2008 UTC vs.
Revision 1.114 by root, Sat May 10 21:12:49 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->send; # wake up current and all future recv's
20 $w->wait; # enters "main loop" till $condvar gets ->broadcast 21 $w->recv; # enters "main loop" till $condvar gets ->send
21 $w->broadcast; # 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
280 279
281Example: fork a process and wait for it 280Example: fork a process and wait for it
282 281
283 my $done = AnyEvent->condvar; 282 my $done = AnyEvent->condvar;
284 283
285 AnyEvent::detect; # force event module to be initialised
286
287 my $pid = fork or exit 5; 284 my $pid = fork or exit 5;
288 285
289 my $w = AnyEvent->child ( 286 my $w = AnyEvent->child (
290 pid => $pid, 287 pid => $pid,
291 cb => sub { 288 cb => sub {
292 my ($pid, $status) = @_; 289 my ($pid, $status) = @_;
293 warn "pid $pid exited with status $status"; 290 warn "pid $pid exited with status $status";
294 $done->broadcast; 291 $done->send;
295 }, 292 },
296 ); 293 );
297 294
298 # do something else, then wait for process exit 295 # do something else, then wait for process exit
299 $done->wait; 296 $done->recv;
300 297
301=head2 CONDITION VARIABLES 298=head2 CONDITION VARIABLES
302 299
300If you are familiar with some event loops you will know that all of them
301require you to run some blocking "loop", "run" or similar function that
302will actively watch for new events and call your callbacks.
303
304AnyEvent is different, it expects somebody else to run the event loop and
305will only block when necessary (usually when told by the user).
306
307The instrument to do that is called a "condition variable", so called
308because they represent a condition that must become true.
309
303Condition variables can be created by calling the C<< AnyEvent->condvar >> 310Condition variables can be created by calling the C<< AnyEvent->condvar
304method without any arguments. 311>> method, usually without arguments. The only argument pair allowed is
312C<cb>, which specifies a callback to be called when the condition variable
313becomes true.
305 314
306A condition variable waits for a condition - precisely that the C<< 315After creation, the conditon variable is "false" until it becomes "true"
307->broadcast >> method has been called. 316by calling the C<send> method.
308 317
309They are very useful to signal that a condition has been fulfilled, for 318Condition variables are similar to callbacks, except that you can
319optionally wait for them. They can also be called merge points - points
320in time where multiple outstandign events have been processed. And yet
321another way to call them is transations - each condition variable can be
322used to represent a transaction, which finishes at some point and delivers
323a result.
324
325Condition variables are very useful to signal that something has finished,
310example, if you write a module that does asynchronous http requests, 326for example, if you write a module that does asynchronous http requests,
311then a condition variable would be the ideal candidate to signal the 327then a condition variable would be the ideal candidate to signal the
312availability of results. 328availability of results. The user can either act when the callback is
329called or can synchronously C<< ->recv >> for the results.
313 330
314You can also use condition variables to block your main program until 331You can also use them to simulate traditional event loops - for example,
315an event occurs - for example, you could C<< ->wait >> in your main 332you 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<< 333could C<< ->recv >> in your main program until the user clicks the Quit
317->broadcast >> the "quit" event. 334button of your app, which would C<< ->send >> the "quit" event.
318 335
319Note that condition variables recurse into the event loop - if you have 336Note 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 337two pieces of code that call C<< ->recv >> in a round-robbin fashion, you
321lose. Therefore, condition variables are good to export to your caller, but 338lose. Therefore, condition variables are good to export to your caller, but
322you should avoid making a blocking wait yourself, at least in callbacks, 339you should avoid making a blocking wait yourself, at least in callbacks,
323as this asks for trouble. 340as this asks for trouble.
324 341
325This object has two methods: 342Condition variables are represented by hash refs in perl, and the keys
343used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
344easy (it is often useful to build your own transaction class on top of
345AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
346it's C<new> method in your own C<new> method.
347
348There are two "sides" to a condition variable - the "producer side" which
349eventually calls C<< -> send >>, and the "consumer side", which waits
350for the send to occur.
351
352Example:
353
354 # wait till the result is ready
355 my $result_ready = AnyEvent->condvar;
356
357 # do something such as adding a timer
358 # or socket watcher the calls $result_ready->send
359 # when the "result" is ready.
360 # in this case, we simply use a timer:
361 my $w = AnyEvent->timer (
362 after => 1,
363 cb => sub { $result_ready->send },
364 );
365
366 # this "blocks" (while handling events) till the callback
367 # calls send
368 $result_ready->recv;
369
370=head3 METHODS FOR PRODUCERS
371
372These methods should only be used by the producing side, i.e. the
373code/module that eventually sends the signal. Note that it is also
374the producer side which creates the condvar in most cases, but it isn't
375uncommon for the consumer to create it as well.
326 376
327=over 4 377=over 4
328 378
379=item $cv->send (...)
380
381Flag the condition as ready - a running C<< ->recv >> and all further
382calls to C<recv> will (eventually) return after this method has been
383called. If nobody is waiting the send will be remembered.
384
385If a callback has been set on the condition variable, it is called
386immediately from within send.
387
388Any arguments passed to the C<send> call will be returned by all
389future C<< ->recv >> calls.
390
391=item $cv->croak ($error)
392
393Similar to send, but causes all call's to C<< ->recv >> to invoke
394C<Carp::croak> with the given error message/object/scalar.
395
396This can be used to signal any errors to the condition variable
397user/consumer.
398
399=item $cv->begin ([group callback])
400
329=item $cv->wait 401=item $cv->end
330 402
331Wait (blocking if necessary) until the C<< ->broadcast >> method has been 403These two methods are EXPERIMENTAL and MIGHT CHANGE.
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
459=item $cv->recv
460
461Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
332called on c<$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
341condition variables with some kind of request results and supporting 478condition variables with some kind of request results and supporting
342callbacks so the caller knows that getting the result will not block, 479callbacks so the caller knows that getting the result will not block,
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<< ->recv >> in a module is that you cannot
346sensibly have two C<< ->wait >>'s in parallel, as that would require 483sensibly have two C<< ->recv >>'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<< ->recv >> 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<< -recv >> never blocks by setting a callback and
355calls to C<wait> will (eventually) return after this method has been 494only calling C<< ->recv >> 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<recv> 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 $guard = AnyEvent::post_detect { BLOCK }
555
556Arranges for the code block to be executed as soon as the event model is
557autodetected (or immediately if this has already happened).
558
559If called in scalar or list context, then it creates and returns an object
560that automatically removes the callback again when it is destroyed. See
561L<Coro::BDB> for a case where this is useful.
562
563=item @AnyEvent::post_detect
564
565If there are any code references in this array (you can C<push> to it
566before or after loading AnyEvent), then they will called directly after
567the event loop has been chosen.
568
569You should check C<$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
420=back 575=back
421 576
422=head1 WHAT TO DO IN A MODULE 577=head1 WHAT TO DO IN A MODULE
423 578
424As 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
427Be careful when you create watchers in the module body - AnyEvent will 582Be careful when you create watchers in the module body - AnyEvent will
428decide 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
429by 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
430to load the event module first. 585to load the event module first.
431 586
432Never call C<< ->wait >> on a condition variable unless you I<know> that 587Never call C<< ->recv >> on a condition variable unless you I<know> that
433the C<< ->broadcast >> method has been called on it already. This is 588the C<< ->send >> method has been called on it already. This is
434because 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
435events is to stay interactive. 590events is to stay interactive.
436 591
437It is fine, however, to call C<< ->wait >> when the user of your module 592It is fine, however, to call C<< ->recv >> when the user of your module
438requests 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
439called C<results> that returns the results, it should call C<< ->wait >> 594called C<results> that returns the results, it should call C<< ->recv >>
440freely, as the user of your module knows what she is doing. always). 595freely, as the user of your module knows what she is doing. always).
441 596
442=head1 WHAT TO DO IN THE MAIN PROGRAM 597=head1 WHAT TO DO IN THE MAIN PROGRAM
443 598
444There will always be a single main program - the only place that should 599There will always be a single main program - the only place that should
458 613
459You can chose to use a rather inefficient pure-perl implementation by 614You can chose to use a rather inefficient pure-perl implementation by
460loading the C<AnyEvent::Impl::Perl> module, which gives you similar 615loading the C<AnyEvent::Impl::Perl> module, which gives you similar
461behaviour everywhere, but letting AnyEvent chose is generally better. 616behaviour everywhere, but letting AnyEvent chose is generally better.
462 617
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
463=cut 687=cut
464 688
465package AnyEvent; 689package AnyEvent;
466 690
467no warnings; 691no warnings;
468use strict; 692use strict;
469 693
470use Carp; 694use Carp;
471 695
472our $VERSION = '3.3'; 696our $VERSION = '3.4';
473our $MODEL; 697our $MODEL;
474 698
475our $AUTOLOAD; 699our $AUTOLOAD;
476our @ISA; 700our @ISA;
477 701
478our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; 702our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479 703
480our @REGISTRY; 704our @REGISTRY;
481 705
482my @models = ( 706my @models = (
483 [Coro::EV:: => AnyEvent::Impl::CoroEV::],
484 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485 [EV:: => AnyEvent::Impl::EV::], 707 [EV:: => AnyEvent::Impl::EV::],
486 [Event:: => AnyEvent::Impl::Event::], 708 [Event:: => AnyEvent::Impl::Event::],
487 [Glib:: => AnyEvent::Impl::Glib::],
488 [Tk:: => AnyEvent::Impl::Tk::], 709 [Tk:: => AnyEvent::Impl::Tk::],
489 [Wx:: => AnyEvent::Impl::POE::], 710 [Wx:: => AnyEvent::Impl::POE::],
490 [Prima:: => AnyEvent::Impl::POE::], 711 [Prima:: => AnyEvent::Impl::POE::],
491 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 712 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
492 # everything below here will not be autoprobed as the pureperl backend should work everywhere 713 # everything below here will not be autoprobed as the pureperl backend should work everywhere
714 [Glib:: => AnyEvent::Impl::Glib::],
493 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy 715 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
494 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program 716 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
495 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza 717 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
496); 718);
497 719
498our %method = map +($_ => 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}
499 743
500sub detect() { 744sub detect() {
501 unless ($MODEL) { 745 unless ($MODEL) {
502 no strict 'refs'; 746 no strict 'refs';
503 747
537 last; 781 last;
538 } 782 }
539 } 783 }
540 784
541 $MODEL 785 $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."; 786 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
543 } 787 }
544 } 788 }
545 789
546 unshift @ISA, $MODEL; 790 unshift @ISA, $MODEL;
547 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 791 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
792
793 (shift @post_detect)->() while @post_detect;
548 } 794 }
549 795
550 $MODEL 796 $MODEL
551} 797}
552 798
562 $class->$func (@_); 808 $class->$func (@_);
563} 809}
564 810
565package AnyEvent::Base; 811package AnyEvent::Base;
566 812
567# default implementation for ->condvar, ->wait, ->broadcast 813# default implementation for ->condvar
568 814
569sub condvar { 815sub condvar {
570 bless \my $flag, "AnyEvent::Base::CondVar" 816 bless {}, "AnyEvent::Base::CondVar"
571}
572
573sub AnyEvent::Base::CondVar::broadcast {
574 ${$_[0]}++;
575}
576
577sub AnyEvent::Base::CondVar::wait {
578 AnyEvent->one_event while !${$_[0]};
579} 817}
580 818
581# default implementation for ->signal 819# default implementation for ->signal
582 820
583our %SIG_CB; 821our %SIG_CB;
656 delete $PID_CB{$pid}{$cb}; 894 delete $PID_CB{$pid}{$cb};
657 delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} }; 895 delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
658 896
659 undef $CHLD_W unless keys %PID_CB; 897 undef $CHLD_W unless keys %PID_CB;
660} 898}
899
900package AnyEvent::Base::CondVar;
901
902# wake up the waiter
903sub _send {
904 &{ $_[0]{_ae_cb} } if $_[0]{_ae_cb};
905}
906
907sub send {
908 $_[0]{_ae_sent} = [@_];
909 $_[0]->_send;
910}
911
912sub croak {
913 $_[0]{_ae_croak} = $_[0];
914 $_[0]->send;
915}
916
917sub ready {
918 $_[0]{_ae_sent}
919}
920
921sub recv {
922 AnyEvent->one_event while !$_[0]{_ae_sent};
923
924 Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
925 wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
926}
927
928sub cb {
929 $_[0]{_ae_cb} = $_[1] if @_ > 1;
930 $_[0]{_ae_cb}
931}
932
933sub begin {
934 ++$_[0]{_ae_counter};
935 $_[0]{_ae_end_cb} = $_[1] if @_ > 1;
936}
937
938sub end {
939 return if --$_[0]{_ae_counter};
940 &{ $_[0]{_ae_end_cb} } if $_[0]{_ae_end_cb};
941}
942
943# undocumented/compatibility with pre-3.4
944*broadcast = \&send;
945*wait = \&recv;
661 946
662=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 947=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
663 948
664This is an advanced topic that you do not normally need to use AnyEvent in 949This is an advanced topic that you do not normally need to use AnyEvent in
665a module. This section is only of use to event loop authors who want to 950a module. This section is only of use to event loop authors who want to
894 }); 1179 });
895 1180
896 $quit->wait; 1181 $quit->wait;
897 1182
898 1183
899=head1 BENCHMARK 1184=head1 BENCHMARKS
900 1185
901To give you an idea of the performance and overheads that AnyEvent adds 1186To give you an idea of the performance and overheads that AnyEvent adds
902over the event loops themselves (and to give you an impression of the 1187over the event loops themselves and to give you an impression of the speed
903speed of various event loops), here is a benchmark of various supported 1188of various event loops I prepared some benchmarks.
904event models natively and with anyevent. The benchmark creates a lot of 1189
905timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to 1190=head2 BENCHMARKING ANYEVENT OVERHEAD
1191
1192Here is a benchmark of various supported event models used natively and
1193through anyevent. The benchmark creates a lot of timers (with a zero
1194timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
906become writable, which it is), lets them fire exactly once and destroys 1195which it is), lets them fire exactly once and destroys them again.
907them again.
908 1196
909Rewriting the benchmark to use many different sockets instead of using 1197Source code for this benchmark is found as F<eg/bench> in the AnyEvent
910the same filehandle for all I/O watchers results in a much longer runtime 1198distribution.
911(socket creation is expensive), but qualitatively the same figures, so it
912was not used.
913 1199
914=head2 Explanation of the columns 1200=head3 Explanation of the columns
915 1201
916I<watcher> is the number of event watchers created/destroyed. Since 1202I<watcher> is the number of event watchers created/destroyed. Since
917different event models feature vastly different performances, each event 1203different event models feature vastly different performances, each event
918loop was given a number of watchers so that overall runtime is acceptable 1204loop was given a number of watchers so that overall runtime is acceptable
919and similar between tested event loop (and keep them from crashing): Glib 1205and similar between tested event loop (and keep them from crashing): Glib
935signal the end of this phase. 1221signal the end of this phase.
936 1222
937I<destroy> is the time, in microseconds, that it takes to destroy a single 1223I<destroy> is the time, in microseconds, that it takes to destroy a single
938watcher. 1224watcher.
939 1225
940=head2 Results 1226=head3 Results
941 1227
942 name watchers bytes create invoke destroy comment 1228 name watchers bytes create invoke destroy comment
943 EV/EV 400000 244 0.56 0.46 0.31 EV native interface 1229 EV/EV 400000 244 0.56 0.46 0.31 EV native interface
944 EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers 1230 EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
945 CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal 1231 CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
946 Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation 1232 Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
947 Event/Event 16000 516 31.88 31.30 0.85 Event native interface 1233 Event/Event 16000 516 31.88 31.30 0.85 Event native interface
948 Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers 1234 Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
949 Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour 1235 Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
950 Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers 1236 Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
951 POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event 1237 POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
952 POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select 1238 POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
953 1239
954=head2 Discussion 1240=head3 Discussion
955 1241
956The benchmark does I<not> measure scalability of the event loop very 1242The benchmark does I<not> measure scalability of the event loop very
957well. For example, a select-based event loop (such as the pure perl one) 1243well. For example, a select-based event loop (such as the pure perl one)
958can never compete with an event loop that uses epoll when the number of 1244can never compete with an event loop that uses epoll when the number of
959file descriptors grows high. In this benchmark, all events become ready at 1245file descriptors grows high. In this benchmark, all events become ready at
960the same time, so select/poll-based implementations get an unnatural speed 1246the same time, so select/poll-based implementations get an unnatural speed
961boost. 1247boost.
962 1248
1249Also, note that the number of watchers usually has a nonlinear effect on
1250overall speed, that is, creating twice as many watchers doesn't take twice
1251the time - usually it takes longer. This puts event loops tested with a
1252higher number of watchers at a disadvantage.
1253
1254To put the range of results into perspective, consider that on the
1255benchmark machine, handling an event takes roughly 1600 CPU cycles with
1256EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1257cycles with POE.
1258
963C<EV> is the sole leader regarding speed and memory use, which are both 1259C<EV> is the sole leader regarding speed and memory use, which are both
964maximal/minimal, respectively. Even when going through AnyEvent, it uses 1260maximal/minimal, respectively. Even when going through AnyEvent, it uses
965far less memory than any other event loop and is still faster than Event 1261far less memory than any other event loop and is still faster than Event
966natively. 1262natively.
967 1263
970interpreter and the backend itself). Nevertheless this shows that it 1266interpreter and the backend itself). Nevertheless this shows that it
971adds very little overhead in itself. Like any select-based backend its 1267adds very little overhead in itself. Like any select-based backend its
972performance becomes really bad with lots of file descriptors (and few of 1268performance becomes really bad with lots of file descriptors (and few of
973them active), of course, but this was not subject of this benchmark. 1269them active), of course, but this was not subject of this benchmark.
974 1270
975The C<Event> module has a relatively high setup and callback invocation cost, 1271The C<Event> module has a relatively high setup and callback invocation
976but overall scores on the third place. 1272cost, but overall scores in on the third place.
977 1273
978C<Glib>'s memory usage is quite a bit bit higher, but it features a 1274C<Glib>'s memory usage is quite a bit higher, but it features a
979faster callback invocation and overall ends up in the same class as 1275faster callback invocation and overall ends up in the same class as
980C<Event>. However, Glib scales extremely badly, doubling the number of 1276C<Event>. However, Glib scales extremely badly, doubling the number of
981watchers increases the processing time by more than a factor of four, 1277watchers increases the processing time by more than a factor of four,
982making it completely unusable when using larger numbers of watchers 1278making it completely unusable when using larger numbers of watchers
983(note that only a single file descriptor was used in the benchmark, so 1279(note that only a single file descriptor was used in the benchmark, so
989file descriptor is dup()ed for each watcher. This shows that the dup() 1285file descriptor is dup()ed for each watcher. This shows that the dup()
990employed by some adaptors is not a big performance issue (it does incur a 1286employed by some adaptors is not a big performance issue (it does incur a
991hidden memory cost inside the kernel which is not reflected in the figures 1287hidden memory cost inside the kernel which is not reflected in the figures
992above). 1288above).
993 1289
994C<POE>, regardless of underlying event loop (whether using its pure 1290C<POE>, regardless of underlying event loop (whether using its pure perl
995perl select-based backend or the Event module, the POE-EV backend 1291select-based backend or the Event module, the POE-EV backend couldn't
996couldn't be tested because it wasn't working) shows abysmal performance 1292be tested because it wasn't working) shows abysmal performance and
997and memory usage: Watchers use almost 30 times as much memory as 1293memory usage with AnyEvent: Watchers use almost 30 times as much memory
998EV watchers, and 10 times as much memory as Event (the high memory 1294as EV watchers, and 10 times as much memory as Event (the high memory
999requirements are caused by requiring a session for each watcher). Watcher 1295requirements are caused by requiring a session for each watcher). Watcher
1000invocation speed is almost 900 times slower than with AnyEvent's pure perl 1296invocation speed is almost 900 times slower than with AnyEvent's pure perl
1297implementation.
1298
1001implementation. The design of the POE adaptor class in AnyEvent can not 1299The design of the POE adaptor class in AnyEvent can not really account
1002really account for this, as session creation overhead is small compared 1300for the performance issues, though, as session creation overhead is
1003to execution of the state machine, which is coded pretty optimally within 1301small compared to execution of the state machine, which is coded pretty
1004L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. 1302optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
1303using multiple sessions is not a good approach, especially regarding
1304memory usage, even the author of POE could not come up with a faster
1305design).
1005 1306
1006=head2 Summary 1307=head3 Summary
1007 1308
1008=over 4 1309=over 4
1009 1310
1010=item * Using EV through AnyEvent is faster than any other event loop 1311=item * Using EV through AnyEvent is faster than any other event loop
1011(even when used without AnyEvent), but most event loops have acceptable 1312(even when used without AnyEvent), but most event loops have acceptable
1013 1314
1014=item * The overhead AnyEvent adds is usually much smaller than the overhead of 1315=item * The overhead AnyEvent adds is usually much smaller than the overhead of
1015the actual event loop, only with extremely fast event loops such as EV 1316the actual event loop, only with extremely fast event loops such as EV
1016adds AnyEvent significant overhead. 1317adds AnyEvent significant overhead.
1017 1318
1018=item * You should simply avoid POE like the plague if you want performance or 1319=item * You should avoid POE like the plague if you want performance or
1019reasonable memory usage. 1320reasonable memory usage.
1020 1321
1021=back 1322=back
1022 1323
1324=head2 BENCHMARKING THE LARGE SERVER CASE
1325
1326This benchmark atcually benchmarks the event loop itself. It works by
1327creating a number of "servers": each server consists of a socketpair, a
1328timeout watcher that gets reset on activity (but never fires), and an I/O
1329watcher waiting for input on one side of the socket. Each time the socket
1330watcher reads a byte it will write that byte to a random other "server".
1331
1332The effect is that there will be a lot of I/O watchers, only part of which
1333are active at any one point (so there is a constant number of active
1334fds for each loop iterstaion, but which fds these are is random). The
1335timeout is reset each time something is read because that reflects how
1336most timeouts work (and puts extra pressure on the event loops).
1337
1338In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
1339(1%) are active. This mirrors the activity of large servers with many
1340connections, most of which are idle at any one point in time.
1341
1342Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1343distribution.
1344
1345=head3 Explanation of the columns
1346
1347I<sockets> is the number of sockets, and twice the number of "servers" (as
1348each server has a read and write socket end).
1349
1350I<create> is the time it takes to create a socketpair (which is
1351nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1352
1353I<request>, the most important value, is the time it takes to handle a
1354single "request", that is, reading the token from the pipe and forwarding
1355it to another server. This includes deleting the old timeout and creating
1356a new one that moves the timeout into the future.
1357
1358=head3 Results
1359
1360 name sockets create request
1361 EV 20000 69.01 11.16
1362 Perl 20000 73.32 35.87
1363 Event 20000 212.62 257.32
1364 Glib 20000 651.16 1896.30
1365 POE 20000 349.67 12317.24 uses POE::Loop::Event
1366
1367=head3 Discussion
1368
1369This benchmark I<does> measure scalability and overall performance of the
1370particular event loop.
1371
1372EV is again fastest. Since it is using epoll on my system, the setup time
1373is relatively high, though.
1374
1375Perl surprisingly comes second. It is much faster than the C-based event
1376loops Event and Glib.
1377
1378Event suffers from high setup time as well (look at its code and you will
1379understand why). Callback invocation also has a high overhead compared to
1380the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1381uses select or poll in basically all documented configurations.
1382
1383Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
1384clearly fails to perform with many filehandles or in busy servers.
1385
1386POE is still completely out of the picture, taking over 1000 times as long
1387as EV, and over 100 times as long as the Perl implementation, even though
1388it uses a C-based event loop in this case.
1389
1390=head3 Summary
1391
1392=over 4
1393
1394=item * The pure perl implementation performs extremely well.
1395
1396=item * Avoid Glib or POE in large projects where performance matters.
1397
1398=back
1399
1400=head2 BENCHMARKING SMALL SERVERS
1401
1402While event loops should scale (and select-based ones do not...) even to
1403large servers, most programs we (or I :) actually write have only a few
1404I/O watchers.
1405
1406In this benchmark, I use the same benchmark program as in the large server
1407case, but it uses only eight "servers", of which three are active at any
1408one time. This should reflect performance for a small server relatively
1409well.
1410
1411The columns are identical to the previous table.
1412
1413=head3 Results
1414
1415 name sockets create request
1416 EV 16 20.00 6.54
1417 Perl 16 25.75 12.62
1418 Event 16 81.27 35.86
1419 Glib 16 32.63 15.48
1420 POE 16 261.87 276.28 uses POE::Loop::Event
1421
1422=head3 Discussion
1423
1424The benchmark tries to test the performance of a typical small
1425server. While knowing how various event loops perform is interesting, keep
1426in mind that their overhead in this case is usually not as important, due
1427to the small absolute number of watchers (that is, you need efficiency and
1428speed most when you have lots of watchers, not when you only have a few of
1429them).
1430
1431EV is again fastest.
1432
1433Perl again comes second. It is noticably faster than the C-based event
1434loops Event and Glib, although the difference is too small to really
1435matter.
1436
1437POE also performs much better in this case, but is is still far behind the
1438others.
1439
1440=head3 Summary
1441
1442=over 4
1443
1444=item * C-based event loops perform very well with small number of
1445watchers, as the management overhead dominates.
1446
1447=back
1448
1023 1449
1024=head1 FORK 1450=head1 FORK
1025 1451
1026Most event libraries are not fork-safe. The ones who are usually are 1452Most event libraries are not fork-safe. The ones who are usually are
1027because they are so inefficient. Only L<EV> is fully fork-aware. 1453because they rely on inefficient but fork-safe C<select> or C<poll>
1454calls. Only L<EV> is fully fork-aware.
1028 1455
1029If you have to fork, you must either do so I<before> creating your first 1456If you have to fork, you must either do so I<before> creating your first
1030watcher OR you must not use AnyEvent at all in the child. 1457watcher OR you must not use AnyEvent at all in the child.
1031 1458
1032 1459
1044 1471
1045 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 1472 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1046 1473
1047 use AnyEvent; 1474 use AnyEvent;
1048 1475
1476Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1477be used to probe what backend is used and gain other information (which is
1478probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
1479
1049 1480
1050=head1 SEE ALSO 1481=head1 SEE ALSO
1051 1482
1052Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, 1483Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1053L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
1054L<Event::Lib>, L<Qt>, L<POE>. 1484L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1055 1485
1056Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, 1486Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1057L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, 1487L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1058L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, 1488L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1059L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. 1489L<AnyEvent::Impl::POE>.
1490
1491Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
1060 1492
1061Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. 1493Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
1062 1494
1063 1495
1064=head1 AUTHOR 1496=head1 AUTHOR

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