[ViewVC] Diff of: cvs/AnyEvent/lib/AnyEvent.pm

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.90 by root, Fri Apr 25 14:24:29 2008 UTC vs.
Revision 1.112 by root, Sat May 10 01:04:42 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, 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
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	26	nowadays. So what is different about AnyEvent?
…		…
66		66
67	Of course, if you want lots of policy (this can arguably be somewhat	67	Of course, if you want lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	68	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	69	model, you should I<not> use this module.
70		70
71
72	=head1 DESCRIPTION	71	=head1 DESCRIPTION
73		72
74	L<AnyEvent> provides an identical interface to multiple event loops. This	73	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	74	allows module authors to utilise an event loop without forcing module
76	users to use the same event loop (as only a single event loop can coexist	75	users to use the same event loop (as only a single event loop can coexist
…		…
79	The interface itself is vaguely similar, but not identical to the L<Event>	78	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	79	module.
81		80
82	During the first call of any watcher-creation method, the module tries	81	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of the	82	to detect the currently loaded event loop by probing whether one of the
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	83	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	84	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	L<POE>. The first one found is used. If none are found, the module tries	85	L<POE>. The first one found is used. If none are found, the module tries
87	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	86	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
88	adaptor should always succeed) in the order given. The first one that can	87	adaptor should always succeed) in the order given. The first one that can
89	be successfully loaded will be used. If, after this, still none could be	88	be 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
		302	If you are familiar with some event loops you will know that all of them
		303	require you to run some blocking "loop", "run" or similar function that
		304	will actively watch for new events and call your callbacks.
		305
		306	AnyEvent is different, it expects somebody else to run the event loop and
		307	will only block when necessary (usually when told by the user).
		308
		309	The instrument to do that is called a "condition variable", so called
		310	because they represent a condition that must become true.
		311
303	Condition variables can be created by calling the C<< AnyEvent->condvar >>	312	Condition variables can be created by calling the C<< AnyEvent->condvar
304	method without any arguments.	313	>> method, usually without arguments. The only argument pair allowed is
		314	C<cb>, which specifies a callback to be called when the condition variable
		315	becomes true.
305		316
306	A condition variable waits for a condition - precisely that the C<<	317	After creation, the conditon variable is "false" until it becomes "true"
307	->broadcast >> method has been called.	318	by calling the C<send> method.
308		319
309	They are very useful to signal that a condition has been fulfilled, for	320	Condition variables are similar to callbacks, except that you can
		321	optionally wait for them. They can also be called merge points - points
		322	in time where multiple outstandign events have been processed. And yet
		323	another way to call them is transations - each condition variable can be
		324	used to represent a transaction, which finishes at some point and delivers
		325	a result.
		326
		327	Condition variables are very useful to signal that something has finished,
310	example, if you write a module that does asynchronous http requests,	328	for example, if you write a module that does asynchronous http requests,
311	then a condition variable would be the ideal candidate to signal the	329	then a condition variable would be the ideal candidate to signal the
312	availability of results.	330	availability of results. The user can either act when the callback is
		331	called or can synchronously C<< ->wait >> for the results.
313		332
314	You can also use condition variables to block your main program until	333	You can also use them to simulate traditional event loops - for example,
315	an event occurs - for example, you could C<< ->wait >> in your main	334	you can block your main program until an event occurs - for example, you
316	program until the user clicks the Quit button in your app, which would C<<	335	could C<< ->wait >> in your main program until the user clicks the Quit
317	->broadcast >> the "quit" event.	336	button of your app, which would C<< ->send >> the "quit" event.
318		337
319	Note that condition variables recurse into the event loop - if you have	338	Note that condition variables recurse into the event loop - if you have
320	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	339	two pieces of code that call C<< ->wait >> in a round-robbin fashion, you
321	lose. Therefore, condition variables are good to export to your caller, but	340	lose. Therefore, condition variables are good to export to your caller, but
322	you should avoid making a blocking wait yourself, at least in callbacks,	341	you should avoid making a blocking wait yourself, at least in callbacks,
323	as this asks for trouble.	342	as this asks for trouble.
324		343
325	This object has two methods:	344	Condition variables are represented by hash refs in perl, and the keys
		345	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		346	easy (it is often useful to build your own transaction class on top of
		347	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		348	it's C<new> method in your own C<new> method.
		349
		350	There are two "sides" to a condition variable - the "producer side" which
		351	eventually calls C<< -> send >>, and the "consumer side", which waits
		352	for the send to occur.
		353
		354	Example:
		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
		374	These methods should only be used by the producing side, i.e. the
		375	code/module that eventually sends the signal. Note that it is also
		376	the producer side which creates the condvar in most cases, but it isn't
		377	uncommon for the consumer to create it as well.
326		378
327	=over 4	379	=over 4
328		380
		381	=item $cv->send (...)
		382
		383	Flag the condition as ready - a running C<< ->wait >> and all further
		384	calls to C<wait> will (eventually) return after this method has been
		385	called. If nobody is waiting the send will be remembered.
		386
		387	If a callback has been set on the condition variable, it is called
		388	immediately from within send.
		389
		390	Any arguments passed to the C<send> call will be returned by all
		391	future C<< ->wait >> calls.
		392
		393	=item $cv->croak ($error)
		394
		395	Similar to send, but causes all call's wait C<< ->wait >> to invoke
		396	C<Carp::croak> with the given error message/object/scalar.
		397
		398	This can be used to signal any errors to the condition variable
		399	user/consumer.
		400
		401	=item $cv->begin ([group callback])
		402
		403	=item $cv->end
		404
		405	These two methods can be used to combine many transactions/events into
		406	one. For example, a function that pings many hosts in parallel might want
		407	to use a condition variable for the whole process.
		408
		409	Every call to C<< ->begin >> will increment a counter, and every call to
		410	C<< ->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
		412	is I<supposed> to call C<< ->send >>, but that is not required. If no
		413	callback was set, C<send> will be called without any arguments.
		414
		415	Let'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
		432	This code fragment supposedly pings a number of hosts and calls
		433	C<send> after results for all then have have been gathered - in any
		434	order. To achieve this, the code issues a call to C<begin> when it starts
		435	each ping request and calls C<end> when it has received some result for
		436	it. Since C<begin> and C<end> only maintain a counter, the order in which
		437	results arrive is not relevant.
		438
		439	There is an additional bracketing call to C<begin> and C<end> outside the
		440	loop, which serves two important purposes: first, it sets the callback
		441	to be called once the counter reaches C<0>, and second, it ensures that
		442	C<send> is called even when C<no> hosts are being pinged (the loop
		443	doesn't execute once).
		444
		445	This is the general pattern when you "fan out" into multiple subrequests:
		446	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		447	is called at least once, and then, for each subrequest you start, call
		448	C<begin> and for eahc subrequest you finish, call C<end>.
		449
		450	=back
		451
		452	=head3 METHODS FOR CONSUMERS
		453
		454	These methods should only be used by the consuming side, i.e. the
		455	code awaits the condition.
		456
		457	=over 4
		458
329	=item $cv->wait	459	=item $cv->wait
330		460
331	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
332	called on c<$cv>, while servicing other watchers normally.	462	>> methods have been called on c<$cv>, while servicing other watchers
		463	normally.
333		464
334	You can only wait once on a condition - additional calls will return	465	You can only wait once on a condition - additional calls are valid but
335	immediately.	466	will return immediately.
		467
		468	If an error condition has been set by calling C<< ->croak >>, then this
		469	function will call C<croak>.
		470
		471	In list context, all parameters passed to C<send> will be returned,
		472	in scalar context only the first one will be returned.
336		473
337	Not all event models support a blocking wait - some die in that case	474	Not 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
339	using this from a module, never require a blocking wait>, but let the	476	using this from a module, never require a blocking wait>, but let the
340	caller decide whether the call will block or not (for example, by coupling	477	caller decide whether the call will block or not (for example, by coupling
…		…
343	while still suppporting blocking waits if the caller so desires).	480	while still suppporting blocking waits if the caller so desires).
344		481
345	Another reason I<never> to C<< ->wait >> in a module is that you cannot	482	Another reason I<never> to C<< ->wait >> in a module is that you cannot
346	sensibly have two C<< ->wait >>'s in parallel, as that would require	483	sensibly have two C<< ->wait >>'s in parallel, as that would require
347	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
348	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	485	can supply.
349	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
350	from different coroutines, however).
351		486
352	=item $cv->broadcast	487	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		488	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		489	versions and also integrates coroutines into AnyEvent, making blocking
		490	C<< ->wait >> calls perfectly safe as long as they are done from another
		491	coroutine (one that doesn't run the event loop).
353		492
354	Flag the condition as ready - a running C<< ->wait >> and all further	493	You can ensure that C<< -wait >> never blocks by setting a callback and
355	calls to C<wait> will (eventually) return after this method has been	494	only calling C<< ->wait >> from within that callback (or at a later
356	called. If nobody is waiting the broadcast will be remembered..	495	time). This will work even when the event loop does not support blocking
		496	waits otherwise.
		497
		498	=item $bool = $cv->ready
		499
		500	Returns true when the condition is "true", i.e. whether C<send> or
		501	C<croak> have been called.
		502
		503	=item $cb = $cv->cb ([new callback])
		504
		505	This is a mutator function that returns the callback set and optionally
		506	replaces it before doing so.
		507
		508	The callback will be called when the condition becomes "true", i.e. when
		509	C<send> or C<croak> are called. Calling C<wait> inside the callback
		510	or at any later time is guaranteed not to block.
357		511
358	=back	512	=back
359
360	Example:
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	$result_ready->wait;
377		513
378	=head1 GLOBAL VARIABLES AND FUNCTIONS	514	=head1 GLOBAL VARIABLES AND FUNCTIONS
379		515
380	=over 4	516	=over 4
381		517
…		…
387	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	523	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
388	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	524	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
389		525
390	The known classes so far are:	526	The known classes so far are:
391		527
392	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
393	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
394	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	528	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
395	AnyEvent::Impl::Event based on Event, second best choice.	529	AnyEvent::Impl::Event based on Event, second best choice.
		530	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
396	AnyEvent::Impl::Glib based on Glib, third-best choice.	531	AnyEvent::Impl::Glib based on Glib, third-best choice.
397	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
398	AnyEvent::Impl::Tk based on Tk, very bad choice.	532	AnyEvent::Impl::Tk based on Tk, very bad choice.
399	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	533	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
400	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	534	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
401	AnyEvent::Impl::POE based on POE, not generic enough for full support.	535	AnyEvent::Impl::POE based on POE, not generic enough for full support.
402		536
…		…
415	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	549	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
416	if necessary. You should only call this function right before you would	550	if necessary. You should only call this function right before you would
417	have created an AnyEvent watcher anyway, that is, as late as possible at	551	have created an AnyEvent watcher anyway, that is, as late as possible at
418	runtime.	552	runtime.
419		553
		554	=item $guard = AnyEvent::post_detect { BLOCK }
		555
		556	Arranges for the code block to be executed as soon as the event model is
		557	autodetected (or immediately if this has already happened).
		558
		559	If called in scalar or list context, then it creates and returns an object
		560	that automatically removes the callback again when it is destroyed. See
		561	L<Coro::BDB> for a case where this is useful.
		562
		563	=item @AnyEvent::post_detect
		564
		565	If there are any code references in this array (you can C<push> to it
		566	before or after loading AnyEvent), then they will called directly after
		567	the event loop has been chosen.
		568
		569	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		570	if it contains a true value then the event loop has already been detected,
		571	and the array will be ignored.
		572
		573	Best 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
424	As a module author, you should C<use AnyEvent> and call AnyEvent methods	579	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
428	decide which event module to use as soon as the first method is called, so	583	decide which event module to use as soon as the first method is called, so
429	by calling AnyEvent in your module body you force the user of your module	584	by calling AnyEvent in your module body you force the user of your module
430	to load the event module first.	585	to load the event module first.
431		586
432	Never call C<< ->wait >> on a condition variable unless you I<know> that	587	Never call C<< ->wait >> on a condition variable unless you I<know> that
433	the C<< ->broadcast >> method has been called on it already. This is	588	the C<< ->send >> method has been called on it already. This is
434	because it will stall the whole program, and the whole point of using	589	because it will stall the whole program, and the whole point of using
435	events is to stay interactive.	590	events is to stay interactive.
436		591
437	It is fine, however, to call C<< ->wait >> when the user of your module	592	It is fine, however, to call C<< ->wait >> when the user of your module
438	requests it (i.e. if you create a http request object ad have a method	593	requests it (i.e. if you create a http request object ad have a method
…		…
458		613
459	You can chose to use a rather inefficient pure-perl implementation by	614	You can chose to use a rather inefficient pure-perl implementation by
460	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	615	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
461	behaviour everywhere, but letting AnyEvent chose is generally better.	616	behaviour everywhere, but letting AnyEvent chose is generally better.
462		617
		618	=head1 OTHER MODULES
		619
		620	The following is a non-exhaustive list of additional modules that use
		621	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		622	in the same program. Some of the modules come with AnyEvent, some are
		623	available via CPAN.
		624
		625	=over 4
		626
		627	=item L<AnyEvent::Util>
		628
		629	Contains various utility functions that replace often-used but blocking
		630	functions such as C<inet_aton> by event-/callback-based versions.
		631
		632	=item L<AnyEvent::Handle>
		633
		634	Provide read and write buffers and manages watchers for reads and writes.
		635
		636	=item L<AnyEvent::Socket>
		637
		638	Provides a means to do non-blocking connects, accepts etc.
		639
		640	=item L<AnyEvent::HTTPD>
		641
		642	Provides a simple web application server framework.
		643
		644	=item L<AnyEvent::DNS>
		645
		646	Provides asynchronous DNS resolver capabilities, beyond what
		647	L<AnyEvent::Util> offers.
		648
		649	=item L<AnyEvent::FastPing>
		650
		651	The fastest ping in the west.
		652
		653	=item L<Net::IRC3>
		654
		655	AnyEvent based IRC client module family.
		656
		657	=item L<Net::XMPP2>
		658
		659	AnyEvent based XMPP (Jabber protocol) module family.
		660
		661	=item L<Net::FCP>
		662
		663	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		664	of AnyEvent.
		665
		666	=item L<Event::ExecFlow>
		667
		668	High level API for event-based execution flow control.
		669
		670	=item L<Coro>
		671
		672	Has special support for AnyEvent via L<Coro::AnyEvent>.
		673
		674	=item L<IO::Lambda>
		675
		676	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		677
		678	=item L<IO::AIO>
		679
		680	Truly asynchronous I/O, should be in the toolbox of every event
		681	programmer. Can be trivially made to use AnyEvent.
		682
		683	=item L<BDB>
		684
		685	Truly asynchronous Berkeley DB access. Can be trivially made to use
		686	AnyEvent.
		687
		688	=back
		689
463	=cut	690	=cut
464		691
465	package AnyEvent;	692	package AnyEvent;
466		693
467	no warnings;	694	no warnings;
468	use strict;	695	use strict;
469		696
470	use Carp;	697	use Carp;
471		698
472	our $VERSION = '3.3';	699	our $VERSION = '3.4';
473	our $MODEL;	700	our $MODEL;
474		701
475	our $AUTOLOAD;	702	our $AUTOLOAD;
476	our @ISA;	703	our @ISA;
477		704
478	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	705	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479		706
480	our @REGISTRY;	707	our @REGISTRY;
481		708
482	my @models = (	709	my @models = (
483	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
484	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485	[EV:: => AnyEvent::Impl::EV::],	710	[EV:: => AnyEvent::Impl::EV::],
486	[Event:: => AnyEvent::Impl::Event::],	711	[Event:: => AnyEvent::Impl::Event::],
487	[Glib:: => AnyEvent::Impl::Glib::],
488	[Tk:: => AnyEvent::Impl::Tk::],	712	[Tk:: => AnyEvent::Impl::Tk::],
489	[Wx:: => AnyEvent::Impl::POE::],	713	[Wx:: => AnyEvent::Impl::POE::],
490	[Prima:: => AnyEvent::Impl::POE::],	714	[Prima:: => AnyEvent::Impl::POE::],
491	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	715	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
492	# everything below here will not be autoprobed as the pureperl backend should work everywhere	716	# everything below here will not be autoprobed as the pureperl backend should work everywhere
		717	[Glib:: => AnyEvent::Impl::Glib::],
493	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	718	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
494	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	719	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
495	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	720	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
496	);	721	);
497		722
498	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	723	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);
		724
		725	our @post_detect;
		726
		727	sub post_detect(&) {
		728	my ($cb) = @_;
		729
		730	if ($MODEL) {
		731	$cb->();
		732
		733	1
		734	} else {
		735	push @post_detect, $cb;
		736
		737	defined wantarray
		738	? bless \$cb, "AnyEvent::Util::Guard"
		739	: ()
		740	}
		741	}
		742
		743	sub AnyEvent::Util::Guard::DESTROY {
		744	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		745	}
499		746
500	sub detect() {	747	sub detect() {
501	unless ($MODEL) {	748	unless ($MODEL) {
502	no strict 'refs';	749	no strict 'refs';
503		750
…		…
537	last;	784	last;
538	}	785	}
539	}	786	}
540		787
541	$MODEL	788	$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.";	789	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
543	}	790	}
544	}	791	}
545		792
546	unshift @ISA, $MODEL;	793	unshift @ISA, $MODEL;
547	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	794	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		795
		796	(shift @post_detect)->() while @post_detect;
548	}	797	}
549		798
550	$MODEL	799	$MODEL
551	}	800	}
552		801
…		…
894	});	1143	});
895		1144
896	$quit->wait;	1145	$quit->wait;
897		1146
898		1147
899	=head1 BENCHMARK	1148	=head1 BENCHMARKS
900		1149
901	To give you an idea of the performance and overheads that AnyEvent adds	1150	To give you an idea of the performance and overheads that AnyEvent adds
902	over the event loops themselves (and to give you an impression of the	1151	over the event loops themselves and to give you an impression of the speed
903	speed of various event loops), here is a benchmark of various supported	1152	of various event loops I prepared some benchmarks.
904	event models natively and with anyevent. The benchmark creates a lot of	1153
905	timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to	1154	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1155
		1156	Here is a benchmark of various supported event models used natively and
		1157	through anyevent. The benchmark creates a lot of timers (with a zero
		1158	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
906	become writable, which it is), lets them fire exactly once and destroys	1159	which it is), lets them fire exactly once and destroys them again.
907	them again.
908		1160
909	Rewriting the benchmark to use many different sockets instead of using	1161	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
910	the same filehandle for all I/O watchers results in a much longer runtime	1162	distribution.
911	(socket creation is expensive), but qualitatively the same figures, so it
912	was not used.
913		1163
914	=head2 Explanation of the columns	1164	=head3 Explanation of the columns
915		1165
916	I<watcher> is the number of event watchers created/destroyed. Since	1166	I<watcher> is the number of event watchers created/destroyed. Since
917	different event models feature vastly different performances, each event	1167	different event models feature vastly different performances, each event
918	loop was given a number of watchers so that overall runtime is acceptable	1168	loop was given a number of watchers so that overall runtime is acceptable
919	and similar between tested event loop (and keep them from crashing): Glib	1169	and similar between tested event loop (and keep them from crashing): Glib
…		…
935	signal the end of this phase.	1185	signal the end of this phase.
936		1186
937	I<destroy> is the time, in microseconds, that it takes to destroy a single	1187	I<destroy> is the time, in microseconds, that it takes to destroy a single
938	watcher.	1188	watcher.
939		1189
940	=head2 Results	1190	=head3 Results
941		1191
942	name watchers bytes create invoke destroy comment	1192	name watchers bytes create invoke destroy comment
943	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1193	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	1194	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	1195	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	1196	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	1197	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	1198	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	1199	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	1200	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	1201	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	1202	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
953		1203
954	=head2 Discussion	1204	=head3 Discussion
955		1205
956	The benchmark does I<not> measure scalability of the event loop very	1206	The benchmark does I<not> measure scalability of the event loop very
957	well. For example, a select-based event loop (such as the pure perl one)	1207	well. For example, a select-based event loop (such as the pure perl one)
958	can never compete with an event loop that uses epoll when the number of	1208	can never compete with an event loop that uses epoll when the number of
959	file descriptors grows high. In this benchmark, all events become ready at	1209	file descriptors grows high. In this benchmark, all events become ready at
960	the same time, so select/poll-based implementations get an unnatural speed	1210	the same time, so select/poll-based implementations get an unnatural speed
961	boost.	1211	boost.
		1212
		1213	Also, note that the number of watchers usually has a nonlinear effect on
		1214	overall speed, that is, creating twice as many watchers doesn't take twice
		1215	the time - usually it takes longer. This puts event loops tested with a
		1216	higher number of watchers at a disadvantage.
		1217
		1218	To put the range of results into perspective, consider that on the
		1219	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1220	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1221	cycles with POE.
962		1222
963	C<EV> is the sole leader regarding speed and memory use, which are both	1223	C<EV> is the sole leader regarding speed and memory use, which are both
964	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1224	maximal/minimal, respectively. Even when going through AnyEvent, it uses
965	far less memory than any other event loop and is still faster than Event	1225	far less memory than any other event loop and is still faster than Event
966	natively.	1226	natively.
…		…
989	file descriptor is dup()ed for each watcher. This shows that the dup()	1249	file descriptor is dup()ed for each watcher. This shows that the dup()
990	employed by some adaptors is not a big performance issue (it does incur a	1250	employed by some adaptors is not a big performance issue (it does incur a
991	hidden memory cost inside the kernel which is not reflected in the figures	1251	hidden memory cost inside the kernel which is not reflected in the figures
992	above).	1252	above).
993		1253
994	C<POE>, regardless of underlying event loop (whether using its pure	1254	C<POE>, regardless of underlying event loop (whether using its pure perl
995	perl select-based backend or the Event module, the POE-EV backend	1255	select-based backend or the Event module, the POE-EV backend couldn't
996	couldn't be tested because it wasn't working) shows abysmal performance	1256	be tested because it wasn't working) shows abysmal performance and
997	and memory usage: Watchers use almost 30 times as much memory as	1257	memory usage with AnyEvent: Watchers use almost 30 times as much memory
998	EV watchers, and 10 times as much memory as Event (the high memory	1258	as EV watchers, and 10 times as much memory as Event (the high memory
999	requirements are caused by requiring a session for each watcher). Watcher	1259	requirements are caused by requiring a session for each watcher). Watcher
1000	invocation speed is almost 900 times slower than with AnyEvent's pure perl	1260	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1261	implementation.
		1262
1001	implementation. The design of the POE adaptor class in AnyEvent can not	1263	The design of the POE adaptor class in AnyEvent can not really account
1002	really account for this, as session creation overhead is small compared	1264	for the performance issues, though, as session creation overhead is
1003	to execution of the state machine, which is coded pretty optimally within	1265	small compared to execution of the state machine, which is coded pretty
1004	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1266	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1267	using multiple sessions is not a good approach, especially regarding
		1268	memory usage, even the author of POE could not come up with a faster
		1269	design).
1005		1270
1006	=head2 Summary	1271	=head3 Summary
1007		1272
1008	=over 4	1273	=over 4
1009		1274
1010	=item * Using EV through AnyEvent is faster than any other event loop	1275	=item * Using EV through AnyEvent is faster than any other event loop
1011	(even when used without AnyEvent), but most event loops have acceptable	1276	(even when used without AnyEvent), but most event loops have acceptable
…		…
1018	=item * You should avoid POE like the plague if you want performance or	1283	=item * You should avoid POE like the plague if you want performance or
1019	reasonable memory usage.	1284	reasonable memory usage.
1020		1285
1021	=back	1286	=back
1022		1287
		1288	=head2 BENCHMARKING THE LARGE SERVER CASE
		1289
		1290	This benchmark atcually benchmarks the event loop itself. It works by
		1291	creating a number of "servers": each server consists of a socketpair, a
		1292	timeout watcher that gets reset on activity (but never fires), and an I/O
		1293	watcher waiting for input on one side of the socket. Each time the socket
		1294	watcher reads a byte it will write that byte to a random other "server".
		1295
		1296	The effect is that there will be a lot of I/O watchers, only part of which
		1297	are active at any one point (so there is a constant number of active
		1298	fds for each loop iterstaion, but which fds these are is random). The
		1299	timeout is reset each time something is read because that reflects how
		1300	most timeouts work (and puts extra pressure on the event loops).
		1301
		1302	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
		1303	(1%) are active. This mirrors the activity of large servers with many
		1304	connections, most of which are idle at any one point in time.
		1305
		1306	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1307	distribution.
		1308
		1309	=head3 Explanation of the columns
		1310
		1311	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1312	each server has a read and write socket end).
		1313
		1314	I<create> is the time it takes to create a socketpair (which is
		1315	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1316
		1317	I<request>, the most important value, is the time it takes to handle a
		1318	single "request", that is, reading the token from the pipe and forwarding
		1319	it to another server. This includes deleting the old timeout and creating
		1320	a new one that moves the timeout into the future.
		1321
		1322	=head3 Results
		1323
		1324	name sockets create request
		1325	EV 20000 69.01 11.16
		1326	Perl 20000 73.32 35.87
		1327	Event 20000 212.62 257.32
		1328	Glib 20000 651.16 1896.30
		1329	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1330
		1331	=head3 Discussion
		1332
		1333	This benchmark I<does> measure scalability and overall performance of the
		1334	particular event loop.
		1335
		1336	EV is again fastest. Since it is using epoll on my system, the setup time
		1337	is relatively high, though.
		1338
		1339	Perl surprisingly comes second. It is much faster than the C-based event
		1340	loops Event and Glib.
		1341
		1342	Event suffers from high setup time as well (look at its code and you will
		1343	understand why). Callback invocation also has a high overhead compared to
		1344	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1345	uses select or poll in basically all documented configurations.
		1346
		1347	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1348	clearly fails to perform with many filehandles or in busy servers.
		1349
		1350	POE is still completely out of the picture, taking over 1000 times as long
		1351	as EV, and over 100 times as long as the Perl implementation, even though
		1352	it uses a C-based event loop in this case.
		1353
		1354	=head3 Summary
		1355
		1356	=over 4
		1357
		1358	=item * The pure perl implementation performs extremely well.
		1359
		1360	=item * Avoid Glib or POE in large projects where performance matters.
		1361
		1362	=back
		1363
		1364	=head2 BENCHMARKING SMALL SERVERS
		1365
		1366	While event loops should scale (and select-based ones do not...) even to
		1367	large servers, most programs we (or I :) actually write have only a few
		1368	I/O watchers.
		1369
		1370	In this benchmark, I use the same benchmark program as in the large server
		1371	case, but it uses only eight "servers", of which three are active at any
		1372	one time. This should reflect performance for a small server relatively
		1373	well.
		1374
		1375	The columns are identical to the previous table.
		1376
		1377	=head3 Results
		1378
		1379	name sockets create request
		1380	EV 16 20.00 6.54
		1381	Perl 16 25.75 12.62
		1382	Event 16 81.27 35.86
		1383	Glib 16 32.63 15.48
		1384	POE 16 261.87 276.28 uses POE::Loop::Event
		1385
		1386	=head3 Discussion
		1387
		1388	The benchmark tries to test the performance of a typical small
		1389	server. While knowing how various event loops perform is interesting, keep
		1390	in mind that their overhead in this case is usually not as important, due
		1391	to the small absolute number of watchers (that is, you need efficiency and
		1392	speed most when you have lots of watchers, not when you only have a few of
		1393	them).
		1394
		1395	EV is again fastest.
		1396
		1397	Perl again comes second. It is noticably faster than the C-based event
		1398	loops Event and Glib, although the difference is too small to really
		1399	matter.
		1400
		1401	POE also performs much better in this case, but is is still far behind the
		1402	others.
		1403
		1404	=head3 Summary
		1405
		1406	=over 4
		1407
		1408	=item * C-based event loops perform very well with small number of
		1409	watchers, as the management overhead dominates.
		1410
		1411	=back
		1412
1023		1413
1024	=head1 FORK	1414	=head1 FORK
1025		1415
1026	Most event libraries are not fork-safe. The ones who are usually are	1416	Most event libraries are not fork-safe. The ones who are usually are
1027	because they are so inefficient. Only L<EV> is fully fork-aware.	1417	because they rely on inefficient but fork-safe C<select> or C<poll>
		1418	calls. Only L<EV> is fully fork-aware.
1028		1419
1029	If you have to fork, you must either do so I<before> creating your first	1420	If you have to fork, you must either do so I<before> creating your first
1030	watcher OR you must not use AnyEvent at all in the child.	1421	watcher OR you must not use AnyEvent at all in the child.
1031		1422
1032		1423
…		…
1044		1435
1045	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1436	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1046		1437
1047	use AnyEvent;	1438	use AnyEvent;
1048		1439
		1440	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1441	be used to probe what backend is used and gain other information (which is
		1442	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
		1443
1049		1444
1050	=head1 SEE ALSO	1445	=head1 SEE ALSO
1051		1446
1052	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1447	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1053	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
1054	L<Event::Lib>, L<Qt>, L<POE>.	1448	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1055		1449
1056	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1450	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1057	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1451	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1058	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1452	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1059	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1453	L<AnyEvent::Impl::POE>.
		1454
		1455	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
1060		1456
1061	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1457	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
1062		1458
1063		1459
1064	=head1 AUTHOR	1460	=head1 AUTHOR

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.90 by root, Fri Apr 25 14:24:29 2008 UTC vs. Revision 1.112 by root, Sat May 10 01:04:42 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.90 by root, Fri Apr 25 14:24:29 2008 UTC vs.
Revision 1.112 by root, Sat May 10 01:04:42 2008 UTC