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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.89 by root, Fri Apr 25 14:19:23 2008 UTC vs.
Revision 1.128 by root, Sat May 24 02:50:45 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->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
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?
…		…
57	as those use one of the supported event loops. It is trivial to add new	57	as those use one of the supported event loops. It is trivial to add new
58	event loops to AnyEvent, too, so it is future-proof).	58	event loops to AnyEvent, too, so it is future-proof).
59		59
60	In addition to being free of having to use I<the one and only true event	60	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	61	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	62	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	63	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	64	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	65	technically possible.
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
71		70
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
…		…
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
…		…
109		108
110	=head1 WATCHERS	109	=head1 WATCHERS
111		110
112	AnyEvent has the central concept of a I<watcher>, which is an object that	111	AnyEvent has the central concept of a I<watcher>, which is an object that
113	stores relevant data for each kind of event you are waiting for, such as	112	stores relevant data for each kind of event you are waiting for, such as
114	the callback to call, the filehandle to watch, etc.	113	the callback to call, the file handle to watch, etc.
115		114
116	These watchers are normal Perl objects with normal Perl lifetime. After	115	These watchers are normal Perl objects with normal Perl lifetime. After
117	creating a watcher it will immediately "watch" for events and invoke the	116	creating a watcher it will immediately "watch" for events and invoke the
118	callback when the event occurs (of course, only when the event model	117	callback when the event occurs (of course, only when the event model
119	is in control).	118	is in control).
…		…
280		279
281	Example: fork a process and wait for it	280	Example: 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
		300	If you are familiar with some event loops you will know that all of them
		301	require you to run some blocking "loop", "run" or similar function that
		302	will actively watch for new events and call your callbacks.
		303
		304	AnyEvent is different, it expects somebody else to run the event loop and
		305	will only block when necessary (usually when told by the user).
		306
		307	The instrument to do that is called a "condition variable", so called
		308	because they represent a condition that must become true.
		309
303	Condition variables can be created by calling the C<< AnyEvent->condvar >>	310	Condition variables can be created by calling the C<< AnyEvent->condvar
304	method without any arguments.	311	>> method, usually without arguments. The only argument pair allowed is
		312	C<cb>, which specifies a callback to be called when the condition variable
		313	becomes true.
305		314
306	A condition variable waits for a condition - precisely that the C<<	315	After creation, the conditon variable is "false" until it becomes "true"
307	->broadcast >> method has been called.	316	by calling the C<send> method.
308		317
309	They are very useful to signal that a condition has been fulfilled, for	318	Condition variables are similar to callbacks, except that you can
		319	optionally wait for them. They can also be called merge points - points
		320	in time where multiple outstandign events have been processed. And yet
		321	another way to call them is transations - each condition variable can be
		322	used to represent a transaction, which finishes at some point and delivers
		323	a result.
		324
		325	Condition variables are very useful to signal that something has finished,
310	example, if you write a module that does asynchronous http requests,	326	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	327	then a condition variable would be the ideal candidate to signal the
312	availability of results.	328	availability of results. The user can either act when the callback is
		329	called or can synchronously C<< ->recv >> for the results.
313		330
314	You can also use condition variables to block your main program until	331	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	332	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<<	333	could C<< ->recv >> in your main program until the user clicks the Quit
317	->broadcast >> the "quit" event.	334	button of your app, which would C<< ->send >> the "quit" event.
318		335
319	Note that condition variables recurse into the event loop - if you have	336	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	337	two pieces of code that call C<< ->recv >> in a round-robbin fashion, you
321	lose. Therefore, condition variables are good to export to your caller, but	338	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,	339	you should avoid making a blocking wait yourself, at least in callbacks,
323	as this asks for trouble.	340	as this asks for trouble.
324		341
325	This object has two methods:	342	Condition variables are represented by hash refs in perl, and the keys
		343	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		344	easy (it is often useful to build your own transaction class on top of
		345	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		346	it's C<new> method in your own C<new> method.
		347
		348	There are two "sides" to a condition variable - the "producer side" which
		349	eventually calls C<< -> send >>, and the "consumer side", which waits
		350	for the send to occur.
		351
		352	Example:
		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
		372	These methods should only be used by the producing side, i.e. the
		373	code/module that eventually sends the signal. Note that it is also
		374	the producer side which creates the condvar in most cases, but it isn't
		375	uncommon for the consumer to create it as well.
326		376
327	=over 4	377	=over 4
328		378
		379	=item $cv->send (...)
		380
		381	Flag the condition as ready - a running C<< ->recv >> and all further
		382	calls to C<recv> will (eventually) return after this method has been
		383	called. If nobody is waiting the send will be remembered.
		384
		385	If a callback has been set on the condition variable, it is called
		386	immediately from within send.
		387
		388	Any arguments passed to the C<send> call will be returned by all
		389	future C<< ->recv >> calls.
		390
		391	=item $cv->croak ($error)
		392
		393	Similar to send, but causes all call's to C<< ->recv >> to invoke
		394	C<Carp::croak> with the given error message/object/scalar.
		395
		396	This can be used to signal any errors to the condition variable
		397	user/consumer.
		398
		399	=item $cv->begin ([group callback])
		400
329	=item $cv->wait	401	=item $cv->end
330		402
331	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	403	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		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
		459	=item $cv->recv
		460
		461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
332	called on c<$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
341	condition variables with some kind of request results and supporting	478	condition variables with some kind of request results and supporting
342	callbacks so the caller knows that getting the result will not block,	479	callbacks so the caller knows that getting the result will not block,
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<< ->recv >> 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<< ->recv >>'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<< ->recv >> 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<< -recv >> never blocks by setting a callback and
355	calls to C<wait> will (eventually) return after this method has been	494	only calling C<< ->recv >> 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<recv> 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
…		…
427	Be careful when you create watchers in the module body - AnyEvent will	582	Be careful when you create watchers in the module body - AnyEvent will
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<< ->recv >> 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<< ->recv >> 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
439	called C<results> that returns the results, it should call C<< ->wait >>	594	called C<results> that returns the results, it should call C<< ->recv >>
440	freely, as the user of your module knows what she is doing. always).	595	freely, 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
444	There will always be a single main program - the only place that should	599	There will always be a single main program - the only place that should
…		…
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 various utility functions for (internet protocol) sockets,
		639	addresses and name resolution. Also functions to create non-blocking tcp
		640	connections or tcp servers, with IPv6 and SRV record support and more.
		641
		642	=item L<AnyEvent::HTTPD>
		643
		644	Provides a simple web application server framework.
		645
		646	=item L<AnyEvent::DNS>
		647
		648	Provides rich asynchronous DNS resolver capabilities.
		649
		650	=item L<AnyEvent::FastPing>
		651
		652	The fastest ping in the west.
		653
		654	=item L<Net::IRC3>
		655
		656	AnyEvent based IRC client module family.
		657
		658	=item L<Net::XMPP2>
		659
		660	AnyEvent based XMPP (Jabber protocol) module family.
		661
		662	=item L<Net::FCP>
		663
		664	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		665	of AnyEvent.
		666
		667	=item L<Event::ExecFlow>
		668
		669	High level API for event-based execution flow control.
		670
		671	=item L<Coro>
		672
		673	Has special support for AnyEvent via L<Coro::AnyEvent>.
		674
		675	=item L<AnyEvent::AIO>, L<IO::AIO>
		676
		677	Truly asynchronous I/O, should be in the toolbox of every event
		678	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		679	together.
		680
		681	=item L<AnyEvent::BDB>, L<BDB>
		682
		683	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
		684	IO::AIO and AnyEvent together.
		685
		686	=item L<IO::Lambda>
		687
		688	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		689
		690	=back
		691
463	=cut	692	=cut
464		693
465	package AnyEvent;	694	package AnyEvent;
466		695
467	no warnings;	696	no warnings;
468	use strict;	697	use strict;
469		698
470	use Carp;	699	use Carp;
471		700
472	our $VERSION = '3.3';	701	our $VERSION = '3.6';
473	our $MODEL;	702	our $MODEL;
474		703
475	our $AUTOLOAD;	704	our $AUTOLOAD;
476	our @ISA;	705	our @ISA;
477		706
478	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	707	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479		708
480	our @REGISTRY;	709	our @REGISTRY;
481		710
		711	our %PROTOCOL; # (ipv4\|ipv6) => (1\|2)
		712
		713	{
		714	my $idx;
		715	$PROTOCOL{$_} = ++$idx
		716	for split /\s,\s/, $ENV{PERL_ANYEVENT_PROTOCOLS} \|\| "ipv4,ipv6";
		717	}
		718
482	my @models = (	719	my @models = (
483	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
484	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485	[EV:: => AnyEvent::Impl::EV::],	720	[EV:: => AnyEvent::Impl::EV::],
486	[Event:: => AnyEvent::Impl::Event::],	721	[Event:: => AnyEvent::Impl::Event::],
487	[Glib:: => AnyEvent::Impl::Glib::],
488	[Tk:: => AnyEvent::Impl::Tk::],	722	[Tk:: => AnyEvent::Impl::Tk::],
489	[Wx:: => AnyEvent::Impl::POE::],	723	[Wx:: => AnyEvent::Impl::POE::],
490	[Prima:: => AnyEvent::Impl::POE::],	724	[Prima:: => AnyEvent::Impl::POE::],
491	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	725	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
492	# everything below here will not be autoprobed as the pureperl backend should work everywhere	726	# everything below here will not be autoprobed as the pureperl backend should work everywhere
		727	[Glib:: => AnyEvent::Impl::Glib::],
493	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	728	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
494	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	729	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
495	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	730	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
496	);	731	);
497		732
498	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	733	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);
		734
		735	our @post_detect;
		736
		737	sub post_detect(&) {
		738	my ($cb) = @_;
		739
		740	if ($MODEL) {
		741	$cb->();
		742
		743	1
		744	} else {
		745	push @post_detect, $cb;
		746
		747	defined wantarray
		748	? bless \$cb, "AnyEvent::Util::PostDetect"
		749	: ()
		750	}
		751	}
		752
		753	sub AnyEvent::Util::PostDetect::DESTROY {
		754	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		755	}
499		756
500	sub detect() {	757	sub detect() {
501	unless ($MODEL) {	758	unless ($MODEL) {
502	no strict 'refs';	759	no strict 'refs';
503		760
…		…
537	last;	794	last;
538	}	795	}
539	}	796	}
540		797
541	$MODEL	798	$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.";	799	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
543	}	800	}
544	}	801	}
545		802
546	unshift @ISA, $MODEL;	803	unshift @ISA, $MODEL;
547	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	804	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		805
		806	(shift @post_detect)->() while @post_detect;
548	}	807	}
549		808
550	$MODEL	809	$MODEL
551	}	810	}
552		811
…		…
562	$class->$func (@_);	821	$class->$func (@_);
563	}	822	}
564		823
565	package AnyEvent::Base;	824	package AnyEvent::Base;
566		825
567	# default implementation for ->condvar, ->wait, ->broadcast	826	# default implementation for ->condvar
568		827
569	sub condvar {	828	sub condvar {
570	bless \my $flag, "AnyEvent::Base::CondVar"	829	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
571	}
572
573	sub AnyEvent::Base::CondVar::broadcast {
574	${$_[0]}++;
575	}
576
577	sub AnyEvent::Base::CondVar::wait {
578	AnyEvent->one_event while !${$_[0]};
579	}	830	}
580		831
581	# default implementation for ->signal	832	# default implementation for ->signal
582		833
583	our %SIG_CB;	834	our %SIG_CB;
…		…
657	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	908	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
658		909
659	undef $CHLD_W unless keys %PID_CB;	910	undef $CHLD_W unless keys %PID_CB;
660	}	911	}
661		912
		913	package AnyEvent::CondVar;
		914
		915	our @ISA = AnyEvent::CondVar::Base::;
		916
		917	package AnyEvent::CondVar::Base;
		918
		919	sub _send {
		920	# nop
		921	}
		922
		923	sub send {
		924	my $cv = shift;
		925	$cv->{_ae_sent} = [@_];
		926	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		927	$cv->_send;
		928	}
		929
		930	sub croak {
		931	$_[0]{_ae_croak} = $_[1];
		932	$_[0]->send;
		933	}
		934
		935	sub ready {
		936	$_[0]{_ae_sent}
		937	}
		938
		939	sub _wait {
		940	AnyEvent->one_event while !$_[0]{_ae_sent};
		941	}
		942
		943	sub recv {
		944	$_[0]->_wait;
		945
		946	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		947	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		948	}
		949
		950	sub cb {
		951	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		952	$_[0]{_ae_cb}
		953	}
		954
		955	sub begin {
		956	++$_[0]{_ae_counter};
		957	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		958	}
		959
		960	sub end {
		961	return if --$_[0]{_ae_counter};
		962	&{ $_[0]{_ae_end_cb} \|\| sub { $_[0]->send } };
		963	}
		964
		965	# undocumented/compatibility with pre-3.4
		966	*broadcast = \&send;
		967	*wait = \&_wait;
		968
662	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	969	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
663		970
664	This is an advanced topic that you do not normally need to use AnyEvent in	971	This is an advanced topic that you do not normally need to use AnyEvent in
665	a module. This section is only of use to event loop authors who want to	972	a module. This section is only of use to event loop authors who want to
666	provide AnyEvent compatibility.	973	provide AnyEvent compatibility.
…		…
722	model it chooses.	1029	model it chooses.
723		1030
724	=item C<PERL_ANYEVENT_MODEL>	1031	=item C<PERL_ANYEVENT_MODEL>
725		1032
726	This can be used to specify the event model to be used by AnyEvent, before	1033	This can be used to specify the event model to be used by AnyEvent, before
727	autodetection and -probing kicks in. It must be a string consisting	1034	auto detection and -probing kicks in. It must be a string consisting
728	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended	1035	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
729	and the resulting module name is loaded and if the load was successful,	1036	and the resulting module name is loaded and if the load was successful,
730	used as event model. If it fails to load AnyEvent will proceed with	1037	used as event model. If it fails to load AnyEvent will proceed with
731	autodetection and -probing.	1038	auto detection and -probing.
732		1039
733	This functionality might change in future versions.	1040	This functionality might change in future versions.
734		1041
735	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you	1042	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
736	could start your program like this:	1043	could start your program like this:
737		1044
738	PERL_ANYEVENT_MODEL=Perl perl ...	1045	PERL_ANYEVENT_MODEL=Perl perl ...
		1046
		1047	=item C<PERL_ANYEVENT_PROTOCOLS>
		1048
		1049	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1050	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1051	of auto probing).
		1052
		1053	Must be set to a comma-separated list of protocols or address families,
		1054	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1055	used, and preference will be given to protocols mentioned earlier in the
		1056	list.
		1057
		1058	This variable can effectively be used for denial-of-service attacks
		1059	against local programs (e.g. when setuid), although the impact is likely
		1060	small, as the program has to handle connection errors already-
		1061
		1062	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1063	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1064	- only support IPv4, never try to resolve or contact IPv6
		1065	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1066	IPv6, but prefer IPv6 over IPv4.
		1067
		1068	=item C<PERL_ANYEVENT_EDNS0>
		1069
		1070	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1071	for DNS. This extension is generally useful to reduce DNS traffic, but
		1072	some (broken) firewalls drop such DNS packets, which is why it is off by
		1073	default.
		1074
		1075	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1076	EDNS0 in its DNS requests.
739		1077
740	=back	1078	=back
741		1079
742	=head1 EXAMPLE PROGRAM	1080	=head1 EXAMPLE PROGRAM
743		1081
…		…
754	poll => 'r',	1092	poll => 'r',
755	cb => sub {	1093	cb => sub {
756	warn "io event <$_[0]>\n"; # will always output <r>	1094	warn "io event <$_[0]>\n"; # will always output <r>
757	chomp (my $input = <STDIN>); # read a line	1095	chomp (my $input = <STDIN>); # read a line
758	warn "read: $input\n"; # output what has been read	1096	warn "read: $input\n"; # output what has been read
759	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1097	$cv->send if $input =~ /^q/i; # quit program if /^q/i
760	},	1098	},
761	);	1099	);
762		1100
763	my $time_watcher; # can only be used once	1101	my $time_watcher; # can only be used once
764		1102
…		…
769	});	1107	});
770	}	1108	}
771		1109
772	new_timer; # create first timer	1110	new_timer; # create first timer
773		1111
774	$cv->wait; # wait until user enters /^q/i	1112	$cv->recv; # wait until user enters /^q/i
775		1113
776	=head1 REAL-WORLD EXAMPLE	1114	=head1 REAL-WORLD EXAMPLE
777		1115
778	Consider the L<Net::FCP> module. It features (among others) the following	1116	Consider the L<Net::FCP> module. It features (among others) the following
779	API calls, which are to freenet what HTTP GET requests are to http:	1117	API calls, which are to freenet what HTTP GET requests are to http:
…		…
829	syswrite $txn->{fh}, $txn->{request}	1167	syswrite $txn->{fh}, $txn->{request}
830	or die "connection or write error";	1168	or die "connection or write error";
831	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1169	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
832		1170
833	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1171	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
834	result and signals any possible waiters that the request ahs finished:	1172	result and signals any possible waiters that the request has finished:
835		1173
836	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1174	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
837		1175
838	if (end-of-file or data complete) {	1176	if (end-of-file or data complete) {
839	$txn->{result} = $txn->{buf};	1177	$txn->{result} = $txn->{buf};
840	$txn->{finished}->broadcast;	1178	$txn->{finished}->send;
841	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1179	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
842	}	1180	}
843		1181
844	The C<result> method, finally, just waits for the finished signal (if the	1182	The C<result> method, finally, just waits for the finished signal (if the
845	request was already finished, it doesn't wait, of course, and returns the	1183	request was already finished, it doesn't wait, of course, and returns the
846	data:	1184	data:
847		1185
848	$txn->{finished}->wait;	1186	$txn->{finished}->recv;
849	return $txn->{result};	1187	return $txn->{result};
850		1188
851	The actual code goes further and collects all errors (C<die>s, exceptions)	1189	The actual code goes further and collects all errors (C<die>s, exceptions)
852	that occured during request processing. The C<result> method detects	1190	that occurred during request processing. The C<result> method detects
853	whether an exception as thrown (it is stored inside the $txn object)	1191	whether an exception as thrown (it is stored inside the $txn object)
854	and just throws the exception, which means connection errors and other	1192	and just throws the exception, which means connection errors and other
855	problems get reported tot he code that tries to use the result, not in a	1193	problems get reported tot he code that tries to use the result, not in a
856	random callback.	1194	random callback.
857		1195
…		…
888		1226
889	my $quit = AnyEvent->condvar;	1227	my $quit = AnyEvent->condvar;
890		1228
891	$fcp->txn_client_get ($url)->cb (sub {	1229	$fcp->txn_client_get ($url)->cb (sub {
892	...	1230	...
893	$quit->broadcast;	1231	$quit->send;
894	});	1232	});
895		1233
896	$quit->wait;	1234	$quit->recv;
897		1235
898		1236
899	=head1 BENCHMARK	1237	=head1 BENCHMARKS
900		1238
901	To give you an idea of the performance and overheads that AnyEvent adds	1239	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	1240	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	1241	of various event loops I prepared some benchmarks.
904	event models natively and with anyevent. The benchmark creates a lot of	1242
905	timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to	1243	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1244
		1245	Here is a benchmark of various supported event models used natively and
		1246	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1247	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	1248	which it is), lets them fire exactly once and destroys them again.
907	them again.
908		1249
909	Rewriting the benchmark to use many different sockets instead of using	1250	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	1251	distribution.
911	(socket creation is expensive), but qualitatively the same figures, so it
912	was not used.
913		1252
914	=head2 Explanation of the columns	1253	=head3 Explanation of the columns
915		1254
916	I<watcher> is the number of event watchers created/destroyed. Since	1255	I<watcher> is the number of event watchers created/destroyed. Since
917	different event models feature vastly different performances, each event	1256	different event models feature vastly different performances, each event
918	loop was given a number of watchers so that overall runtime is acceptable	1257	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	1258	and similar between tested event loop (and keep them from crashing): Glib
…		…
929	all watchers, to avoid adding memory overhead. That means closure creation	1268	all watchers, to avoid adding memory overhead. That means closure creation
930	and memory usage is not included in the figures.	1269	and memory usage is not included in the figures.
931		1270
932	I<invoke> is the time, in microseconds, used to invoke a simple	1271	I<invoke> is the time, in microseconds, used to invoke a simple
933	callback. The callback simply counts down a Perl variable and after it was	1272	callback. The callback simply counts down a Perl variable and after it was
934	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1273	invoked "watcher" times, it would C<< ->send >> a condvar once to
935	signal the end of this phase.	1274	signal the end of this phase.
936		1275
937	I<destroy> is the time, in microseconds, that it takes to destroy a single	1276	I<destroy> is the time, in microseconds, that it takes to destroy a single
938	watcher.	1277	watcher.
939		1278
940	=head2 Results	1279	=head3 Results
941		1280
942	name watchers bytes create invoke destroy comment	1281	name watchers bytes create invoke destroy comment
943	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1282	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	1283	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	1284	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	1285	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	1286	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	1287	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	1288	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	1289	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	1290	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	1291	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
953		1292
954	=head2 Discussion	1293	=head3 Discussion
955		1294
956	The benchmark does I<not> measure scalability of the event loop very	1295	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)	1296	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	1297	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	1298	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	1299	the same time, so select/poll-based implementations get an unnatural speed
961	boost.	1300	boost.
962		1301
		1302	Also, note that the number of watchers usually has a nonlinear effect on
		1303	overall speed, that is, creating twice as many watchers doesn't take twice
		1304	the time - usually it takes longer. This puts event loops tested with a
		1305	higher number of watchers at a disadvantage.
		1306
		1307	To put the range of results into perspective, consider that on the
		1308	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1309	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1310	cycles with POE.
		1311
963	C<EV> is the sole leader regarding speed and memory use, which are both	1312	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	1313	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	1314	far less memory than any other event loop and is still faster than Event
966	natively.	1315	natively.
967		1316
…		…
970	interpreter and the backend itself). Nevertheless this shows that it	1319	interpreter and the backend itself). Nevertheless this shows that it
971	adds very little overhead in itself. Like any select-based backend its	1320	adds very little overhead in itself. Like any select-based backend its
972	performance becomes really bad with lots of file descriptors (and few of	1321	performance becomes really bad with lots of file descriptors (and few of
973	them active), of course, but this was not subject of this benchmark.	1322	them active), of course, but this was not subject of this benchmark.
974		1323
975	The C<Event> module has a relatively high setup and callback invocation cost,	1324	The C<Event> module has a relatively high setup and callback invocation
976	but overall scores on the third place.	1325	cost, but overall scores in on the third place.
977		1326
978	C<Glib>'s memory usage is quite a bit bit higher, but it features a	1327	C<Glib>'s memory usage is quite a bit higher, but it features a
979	faster callback invocation and overall ends up in the same class as	1328	faster callback invocation and overall ends up in the same class as
980	C<Event>. However, Glib scales extremely badly, doubling the number of	1329	C<Event>. However, Glib scales extremely badly, doubling the number of
981	watchers increases the processing time by more than a factor of four,	1330	watchers increases the processing time by more than a factor of four,
982	making it completely unusable when using larger numbers of watchers	1331	making it completely unusable when using larger numbers of watchers
983	(note that only a single file descriptor was used in the benchmark, so	1332	(note that only a single file descriptor was used in the benchmark, so
…		…
989	file descriptor is dup()ed for each watcher. This shows that the dup()	1338	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	1339	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	1340	hidden memory cost inside the kernel which is not reflected in the figures
992	above).	1341	above).
993		1342
994	C<POE>, regardless of underlying event loop (whether using its pure	1343	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	1344	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	1345	be tested because it wasn't working) shows abysmal performance and
997	and memory usage: Watchers use almost 30 times as much memory as	1346	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	1347	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	1348	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	1349	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1350	implementation.
		1351
1001	implementation. The design of the POE adaptor class in AnyEvent can not	1352	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	1353	for the performance issues, though, as session creation overhead is
1003	to execution of the state machine, which is coded pretty optimally within	1354	small compared to execution of the state machine, which is coded pretty
1004	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1355	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1356	using multiple sessions is not a good approach, especially regarding
		1357	memory usage, even the author of POE could not come up with a faster
		1358	design).
1005		1359
1006	=head2 Summary	1360	=head3 Summary
1007		1361
1008	=over 4	1362	=over 4
1009		1363
1010	=item * Using EV through AnyEvent is faster than any other event loop	1364	=item * Using EV through AnyEvent is faster than any other event loop
1011	(even when used without AnyEvent), but most event loops have acceptable	1365	(even when used without AnyEvent), but most event loops have acceptable
…		…
1013		1367
1014	=item * The overhead AnyEvent adds is usually much smaller than the overhead of	1368	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
1015	the actual event loop, only with extremely fast event loops such as EV	1369	the actual event loop, only with extremely fast event loops such as EV
1016	adds AnyEvent significant overhead.	1370	adds AnyEvent significant overhead.
1017		1371
1018	=item * You should simply avoid POE like the plague if you want performance or	1372	=item * You should avoid POE like the plague if you want performance or
1019	reasonable memory usage.	1373	reasonable memory usage.
1020		1374
1021	=back	1375	=back
1022		1376
		1377	=head2 BENCHMARKING THE LARGE SERVER CASE
		1378
		1379	This benchmark actually benchmarks the event loop itself. It works by
		1380	creating a number of "servers": each server consists of a socket pair, a
		1381	timeout watcher that gets reset on activity (but never fires), and an I/O
		1382	watcher waiting for input on one side of the socket. Each time the socket
		1383	watcher reads a byte it will write that byte to a random other "server".
		1384
		1385	The effect is that there will be a lot of I/O watchers, only part of which
		1386	are active at any one point (so there is a constant number of active
		1387	fds for each loop iteration, but which fds these are is random). The
		1388	timeout is reset each time something is read because that reflects how
		1389	most timeouts work (and puts extra pressure on the event loops).
		1390
		1391	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1392	(1%) are active. This mirrors the activity of large servers with many
		1393	connections, most of which are idle at any one point in time.
		1394
		1395	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1396	distribution.
		1397
		1398	=head3 Explanation of the columns
		1399
		1400	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1401	each server has a read and write socket end).
		1402
		1403	I<create> is the time it takes to create a socket pair (which is
		1404	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1405
		1406	I<request>, the most important value, is the time it takes to handle a
		1407	single "request", that is, reading the token from the pipe and forwarding
		1408	it to another server. This includes deleting the old timeout and creating
		1409	a new one that moves the timeout into the future.
		1410
		1411	=head3 Results
		1412
		1413	name sockets create request
		1414	EV 20000 69.01 11.16
		1415	Perl 20000 73.32 35.87
		1416	Event 20000 212.62 257.32
		1417	Glib 20000 651.16 1896.30
		1418	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1419
		1420	=head3 Discussion
		1421
		1422	This benchmark I<does> measure scalability and overall performance of the
		1423	particular event loop.
		1424
		1425	EV is again fastest. Since it is using epoll on my system, the setup time
		1426	is relatively high, though.
		1427
		1428	Perl surprisingly comes second. It is much faster than the C-based event
		1429	loops Event and Glib.
		1430
		1431	Event suffers from high setup time as well (look at its code and you will
		1432	understand why). Callback invocation also has a high overhead compared to
		1433	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1434	uses select or poll in basically all documented configurations.
		1435
		1436	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1437	clearly fails to perform with many filehandles or in busy servers.
		1438
		1439	POE is still completely out of the picture, taking over 1000 times as long
		1440	as EV, and over 100 times as long as the Perl implementation, even though
		1441	it uses a C-based event loop in this case.
		1442
		1443	=head3 Summary
		1444
		1445	=over 4
		1446
		1447	=item * The pure perl implementation performs extremely well.
		1448
		1449	=item * Avoid Glib or POE in large projects where performance matters.
		1450
		1451	=back
		1452
		1453	=head2 BENCHMARKING SMALL SERVERS
		1454
		1455	While event loops should scale (and select-based ones do not...) even to
		1456	large servers, most programs we (or I :) actually write have only a few
		1457	I/O watchers.
		1458
		1459	In this benchmark, I use the same benchmark program as in the large server
		1460	case, but it uses only eight "servers", of which three are active at any
		1461	one time. This should reflect performance for a small server relatively
		1462	well.
		1463
		1464	The columns are identical to the previous table.
		1465
		1466	=head3 Results
		1467
		1468	name sockets create request
		1469	EV 16 20.00 6.54
		1470	Perl 16 25.75 12.62
		1471	Event 16 81.27 35.86
		1472	Glib 16 32.63 15.48
		1473	POE 16 261.87 276.28 uses POE::Loop::Event
		1474
		1475	=head3 Discussion
		1476
		1477	The benchmark tries to test the performance of a typical small
		1478	server. While knowing how various event loops perform is interesting, keep
		1479	in mind that their overhead in this case is usually not as important, due
		1480	to the small absolute number of watchers (that is, you need efficiency and
		1481	speed most when you have lots of watchers, not when you only have a few of
		1482	them).
		1483
		1484	EV is again fastest.
		1485
		1486	Perl again comes second. It is noticably faster than the C-based event
		1487	loops Event and Glib, although the difference is too small to really
		1488	matter.
		1489
		1490	POE also performs much better in this case, but is is still far behind the
		1491	others.
		1492
		1493	=head3 Summary
		1494
		1495	=over 4
		1496
		1497	=item * C-based event loops perform very well with small number of
		1498	watchers, as the management overhead dominates.
		1499
		1500	=back
		1501
1023		1502
1024	=head1 FORK	1503	=head1 FORK
1025		1504
1026	Most event libraries are not fork-safe. The ones who are usually are	1505	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.	1506	because they rely on inefficient but fork-safe C<select> or C<poll>
		1507	calls. Only L<EV> is fully fork-aware.
1028		1508
1029	If you have to fork, you must either do so I<before> creating your first	1509	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.	1510	watcher OR you must not use AnyEvent at all in the child.
1031		1511
1032		1512
…		…
1044		1524
1045	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1525	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1046		1526
1047	use AnyEvent;	1527	use AnyEvent;
1048		1528
		1529	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1530	be used to probe what backend is used and gain other information (which is
		1531	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
		1532
1049		1533
1050	=head1 SEE ALSO	1534	=head1 SEE ALSO
1051		1535
1052	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1536	Utility functions: L<AnyEvent::Util>.
1053	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1537
		1538	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1054	L<Event::Lib>, L<Qt>, L<POE>.	1539	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1055		1540
1056	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1541	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1057	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1542	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>,	1543	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1059	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1544	L<AnyEvent::Impl::POE>.
1060		1545
		1546	Non-blocking file handles, sockets, TCP clients and
		1547	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1548
		1549	Asynchronous DNS: L<AnyEvent::DNS>.
		1550
		1551	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1552
1061	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1553	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1062		1554
1063		1555
1064	=head1 AUTHOR	1556	=head1 AUTHOR
1065		1557
1066	Marc Lehmann <schmorp@schmorp.de>	1558	Marc Lehmann <schmorp@schmorp.de>

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.89 by root, Fri Apr 25 14:19:23 2008 UTC vs. Revision 1.128 by root, Sat May 24 02:50:45 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.89 by root, Fri Apr 25 14:19:23 2008 UTC vs.
Revision 1.128 by root, Sat May 24 02:50:45 2008 UTC