[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 1.133 by root, Sun May 25 03:44:03 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).
…		…
238		237
239	Although the callback might get passed parameters, their value and	238	Although the callback might get passed parameters, their value and
240	presence is undefined and you cannot rely on them. Portable AnyEvent	239	presence is undefined and you cannot rely on them. Portable AnyEvent
241	callbacks cannot use arguments passed to signal watcher callbacks.	240	callbacks cannot use arguments passed to signal watcher callbacks.
242		241
243	Multiple signal occurances can be clumped together into one callback	242	Multiple signal occurrences can be clumped together into one callback
244	invocation, and callback invocation will be synchronous. synchronous means	243	invocation, and callback invocation will be synchronous. Synchronous means
245	that it might take a while until the signal gets handled by the process,	244	that it might take a while until the signal gets handled by the process,
246	but it is guarenteed not to interrupt any other callbacks.	245	but it is guaranteed not to interrupt any other callbacks.
247		246
248	The main advantage of using these watchers is that you can share a signal	247	The main advantage of using these watchers is that you can share a signal
249	between multiple watchers.	248	between multiple watchers.
250		249
251	This watcher might use C<%SIG>, so programs overwriting those signals	250	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
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 condition variable is "false" until it becomes "true"
307	->broadcast >> method has been called.	316	by calling the C<send> method (or calling the condition variable as if it
		317	were a callback).
308		318
309	They are very useful to signal that a condition has been fulfilled, for	319	Condition variables are similar to callbacks, except that you can
		320	optionally wait for them. They can also be called merge points - points
		321	in time where multiple outstanding events have been processed. And yet
		322	another way to call them is transactions - each condition variable can be
		323	used to represent a transaction, which finishes at some point and delivers
		324	a result.
		325
		326	Condition variables are very useful to signal that something has finished,
310	example, if you write a module that does asynchronous http requests,	327	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	328	then a condition variable would be the ideal candidate to signal the
312	availability of results.	329	availability of results. The user can either act when the callback is
		330	called or can synchronously C<< ->recv >> for the results.
313		331
314	You can also use condition variables to block your main program until	332	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	333	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<<	334	could C<< ->recv >> in your main program until the user clicks the Quit
317	->broadcast >> the "quit" event.	335	button of your app, which would C<< ->send >> the "quit" event.
318		336
319	Note that condition variables recurse into the event loop - if you have	337	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	338	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
321	lose. Therefore, condition variables are good to export to your caller, but	339	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,	340	you should avoid making a blocking wait yourself, at least in callbacks,
323	as this asks for trouble.	341	as this asks for trouble.
324		342
325	This object has two methods:	343	Condition variables are represented by hash refs in perl, and the keys
		344	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		345	easy (it is often useful to build your own transaction class on top of
		346	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		347	it's C<new> method in your own C<new> method.
		348
		349	There are two "sides" to a condition variable - the "producer side" which
		350	eventually calls C<< -> send >>, and the "consumer side", which waits
		351	for the send to occur.
		352
		353	Example: wait for a timer.
		354
		355	# wait till the result is ready
		356	my $result_ready = AnyEvent->condvar;
		357
		358	# do something such as adding a timer
		359	# or socket watcher the calls $result_ready->send
		360	# when the "result" is ready.
		361	# in this case, we simply use a timer:
		362	my $w = AnyEvent->timer (
		363	after => 1,
		364	cb => sub { $result_ready->send },
		365	);
		366
		367	# this "blocks" (while handling events) till the callback
		368	# calls send
		369	$result_ready->recv;
		370
		371	Example: wait for a timer, but take advantage of the fact that
		372	condition variables are also code references.
		373
		374	my $done = AnyEvent->condvar;
		375	my $delay = AnyEvent->timer (after => 5, cb => $done);
		376	$done->recv;
		377
		378	=head3 METHODS FOR PRODUCERS
		379
		380	These methods should only be used by the producing side, i.e. the
		381	code/module that eventually sends the signal. Note that it is also
		382	the producer side which creates the condvar in most cases, but it isn't
		383	uncommon for the consumer to create it as well.
326		384
327	=over 4	385	=over 4
328		386
		387	=item $cv->send (...)
		388
		389	Flag the condition as ready - a running C<< ->recv >> and all further
		390	calls to C<recv> will (eventually) return after this method has been
		391	called. If nobody is waiting the send will be remembered.
		392
		393	If a callback has been set on the condition variable, it is called
		394	immediately from within send.
		395
		396	Any arguments passed to the C<send> call will be returned by all
		397	future C<< ->recv >> calls.
		398
		399	Condition variables are overloaded so one can call them directly (as a
		400	code reference). Calling them directly is the same as calling C<send>.
		401
		402	=item $cv->croak ($error)
		403
		404	Similar to send, but causes all call's to C<< ->recv >> to invoke
		405	C<Carp::croak> with the given error message/object/scalar.
		406
		407	This can be used to signal any errors to the condition variable
		408	user/consumer.
		409
		410	=item $cv->begin ([group callback])
		411
329	=item $cv->wait	412	=item $cv->end
330		413
331	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	414	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		415
		416	These two methods can be used to combine many transactions/events into
		417	one. For example, a function that pings many hosts in parallel might want
		418	to use a condition variable for the whole process.
		419
		420	Every call to C<< ->begin >> will increment a counter, and every call to
		421	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		422	>>, the (last) callback passed to C<begin> will be executed. That callback
		423	is I<supposed> to call C<< ->send >>, but that is not required. If no
		424	callback was set, C<send> will be called without any arguments.
		425
		426	Let's clarify this with the ping example:
		427
		428	my $cv = AnyEvent->condvar;
		429
		430	my %result;
		431	$cv->begin (sub { $cv->send (\%result) });
		432
		433	for my $host (@list_of_hosts) {
		434	$cv->begin;
		435	ping_host_then_call_callback $host, sub {
		436	$result{$host} = ...;
		437	$cv->end;
		438	};
		439	}
		440
		441	$cv->end;
		442
		443	This code fragment supposedly pings a number of hosts and calls
		444	C<send> after results for all then have have been gathered - in any
		445	order. To achieve this, the code issues a call to C<begin> when it starts
		446	each ping request and calls C<end> when it has received some result for
		447	it. Since C<begin> and C<end> only maintain a counter, the order in which
		448	results arrive is not relevant.
		449
		450	There is an additional bracketing call to C<begin> and C<end> outside the
		451	loop, which serves two important purposes: first, it sets the callback
		452	to be called once the counter reaches C<0>, and second, it ensures that
		453	C<send> is called even when C<no> hosts are being pinged (the loop
		454	doesn't execute once).
		455
		456	This is the general pattern when you "fan out" into multiple subrequests:
		457	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		458	is called at least once, and then, for each subrequest you start, call
		459	C<begin> and for each subrequest you finish, call C<end>.
		460
		461	=back
		462
		463	=head3 METHODS FOR CONSUMERS
		464
		465	These methods should only be used by the consuming side, i.e. the
		466	code awaits the condition.
		467
		468	=over 4
		469
		470	=item $cv->recv
		471
		472	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
332	called on c<$cv>, while servicing other watchers normally.	473	>> methods have been called on c<$cv>, while servicing other watchers
		474	normally.
333		475
334	You can only wait once on a condition - additional calls will return	476	You can only wait once on a condition - additional calls are valid but
335	immediately.	477	will return immediately.
		478
		479	If an error condition has been set by calling C<< ->croak >>, then this
		480	function will call C<croak>.
		481
		482	In list context, all parameters passed to C<send> will be returned,
		483	in scalar context only the first one will be returned.
336		484
337	Not all event models support a blocking wait - some die in that case	485	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	486	(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	487	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	488	caller decide whether the call will block or not (for example, by coupling
341	condition variables with some kind of request results and supporting	489	condition variables with some kind of request results and supporting
342	callbacks so the caller knows that getting the result will not block,	490	callbacks so the caller knows that getting the result will not block,
343	while still suppporting blocking waits if the caller so desires).	491	while still supporting blocking waits if the caller so desires).
344		492
345	Another reason I<never> to C<< ->wait >> in a module is that you cannot	493	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	494	sensibly have two C<< ->recv >>'s in parallel, as that would require
347	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	495	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
348	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	496	can supply.
349	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
350	from different coroutines, however).
351		497
352	=item $cv->broadcast	498	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		499	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		500	versions and also integrates coroutines into AnyEvent, making blocking
		501	C<< ->recv >> calls perfectly safe as long as they are done from another
		502	coroutine (one that doesn't run the event loop).
353		503
354	Flag the condition as ready - a running C<< ->wait >> and all further	504	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	505	only calling C<< ->recv >> from within that callback (or at a later
356	called. If nobody is waiting the broadcast will be remembered..	506	time). This will work even when the event loop does not support blocking
		507	waits otherwise.
		508
		509	=item $bool = $cv->ready
		510
		511	Returns true when the condition is "true", i.e. whether C<send> or
		512	C<croak> have been called.
		513
		514	=item $cb = $cv->cb ([new callback])
		515
		516	This is a mutator function that returns the callback set and optionally
		517	replaces it before doing so.
		518
		519	The callback will be called when the condition becomes "true", i.e. when
		520	C<send> or C<croak> are called. Calling C<recv> inside the callback
		521	or at any later time is guaranteed not to block.
357		522
358	=back	523	=back
359		524
360	Example:	525	=head3 MAINLOOP EMULATION
361		526
362	# wait till the result is ready	527	Sometimes (often for short test scripts, or even standalone programs
363	my $result_ready = AnyEvent->condvar;	528	who only want to use AnyEvent), you I<do> want your program to block
		529	indefinitely in some event loop.
364		530
365	# do something such as adding a timer	531	In that case, you cna use a condition variable like this:
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		532
374	# this "blocks" (while handling events) till the watcher	533	AnyEvent->condvar->recv;
375	# calls broadcast	534
376	$result_ready->wait;	535	This has the effect of entering the event loop and looping forever.
		536
		537	Note that usually your program has some exit condition, in which case
		538	it is better to use the "traditional" approach of storing a condition
		539	variable, waiting for it, and sending it when the program should exit
		540	cleanly.
		541
377		542
378	=head1 GLOBAL VARIABLES AND FUNCTIONS	543	=head1 GLOBAL VARIABLES AND FUNCTIONS
379		544
380	=over 4	545	=over 4
381		546
…		…
387	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	552	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>).	553	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
389		554
390	The known classes so far are:	555	The known classes so far are:
391		556
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).	557	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
395	AnyEvent::Impl::Event based on Event, second best choice.	558	AnyEvent::Impl::Event based on Event, second best choice.
		559	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
396	AnyEvent::Impl::Glib based on Glib, third-best choice.	560	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.	561	AnyEvent::Impl::Tk based on Tk, very bad choice.
399	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	562	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
400	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	563	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
401	AnyEvent::Impl::POE based on POE, not generic enough for full support.	564	AnyEvent::Impl::POE based on POE, not generic enough for full support.
402		565
…		…
415	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	578	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
416	if necessary. You should only call this function right before you would	579	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	580	have created an AnyEvent watcher anyway, that is, as late as possible at
418	runtime.	581	runtime.
419		582
		583	=item $guard = AnyEvent::post_detect { BLOCK }
		584
		585	Arranges for the code block to be executed as soon as the event model is
		586	autodetected (or immediately if this has already happened).
		587
		588	If called in scalar or list context, then it creates and returns an object
		589	that automatically removes the callback again when it is destroyed. See
		590	L<Coro::BDB> for a case where this is useful.
		591
		592	=item @AnyEvent::post_detect
		593
		594	If there are any code references in this array (you can C<push> to it
		595	before or after loading AnyEvent), then they will called directly after
		596	the event loop has been chosen.
		597
		598	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		599	if it contains a true value then the event loop has already been detected,
		600	and the array will be ignored.
		601
		602	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		603
420	=back	604	=back
421		605
422	=head1 WHAT TO DO IN A MODULE	606	=head1 WHAT TO DO IN A MODULE
423		607
424	As a module author, you should C<use AnyEvent> and call AnyEvent methods	608	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	611	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	612	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	613	by calling AnyEvent in your module body you force the user of your module
430	to load the event module first.	614	to load the event module first.
431		615
432	Never call C<< ->wait >> on a condition variable unless you I<know> that	616	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	617	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	618	because it will stall the whole program, and the whole point of using
435	events is to stay interactive.	619	events is to stay interactive.
436		620
437	It is fine, however, to call C<< ->wait >> when the user of your module	621	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	622	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 >>	623	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).	624	freely, as the user of your module knows what she is doing. always).
441		625
442	=head1 WHAT TO DO IN THE MAIN PROGRAM	626	=head1 WHAT TO DO IN THE MAIN PROGRAM
443		627
444	There will always be a single main program - the only place that should	628	There will always be a single main program - the only place that should
…		…
458		642
459	You can chose to use a rather inefficient pure-perl implementation by	643	You can chose to use a rather inefficient pure-perl implementation by
460	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	644	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
461	behaviour everywhere, but letting AnyEvent chose is generally better.	645	behaviour everywhere, but letting AnyEvent chose is generally better.
462		646
		647	=head1 OTHER MODULES
		648
		649	The following is a non-exhaustive list of additional modules that use
		650	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		651	in the same program. Some of the modules come with AnyEvent, some are
		652	available via CPAN.
		653
		654	=over 4
		655
		656	=item L<AnyEvent::Util>
		657
		658	Contains various utility functions that replace often-used but blocking
		659	functions such as C<inet_aton> by event-/callback-based versions.
		660
		661	=item L<AnyEvent::Handle>
		662
		663	Provide read and write buffers and manages watchers for reads and writes.
		664
		665	=item L<AnyEvent::Socket>
		666
		667	Provides various utility functions for (internet protocol) sockets,
		668	addresses and name resolution. Also functions to create non-blocking tcp
		669	connections or tcp servers, with IPv6 and SRV record support and more.
		670
		671	=item L<AnyEvent::HTTPD>
		672
		673	Provides a simple web application server framework.
		674
		675	=item L<AnyEvent::DNS>
		676
		677	Provides rich asynchronous DNS resolver capabilities.
		678
		679	=item L<AnyEvent::FastPing>
		680
		681	The fastest ping in the west.
		682
		683	=item L<Net::IRC3>
		684
		685	AnyEvent based IRC client module family.
		686
		687	=item L<Net::XMPP2>
		688
		689	AnyEvent based XMPP (Jabber protocol) module family.
		690
		691	=item L<Net::FCP>
		692
		693	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		694	of AnyEvent.
		695
		696	=item L<Event::ExecFlow>
		697
		698	High level API for event-based execution flow control.
		699
		700	=item L<Coro>
		701
		702	Has special support for AnyEvent via L<Coro::AnyEvent>.
		703
		704	=item L<AnyEvent::AIO>, L<IO::AIO>
		705
		706	Truly asynchronous I/O, should be in the toolbox of every event
		707	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		708	together.
		709
		710	=item L<AnyEvent::BDB>, L<BDB>
		711
		712	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
		713	IO::AIO and AnyEvent together.
		714
		715	=item L<IO::Lambda>
		716
		717	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		718
		719	=back
		720
463	=cut	721	=cut
464		722
465	package AnyEvent;	723	package AnyEvent;
466		724
467	no warnings;	725	no warnings;
468	use strict;	726	use strict;
469		727
470	use Carp;	728	use Carp;
471		729
472	our $VERSION = '3.3';	730	our $VERSION = '4.03';
473	our $MODEL;	731	our $MODEL;
474		732
475	our $AUTOLOAD;	733	our $AUTOLOAD;
476	our @ISA;	734	our @ISA;
477		735
478	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	736	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479		737
480	our @REGISTRY;	738	our @REGISTRY;
481		739
		740	our %PROTOCOL; # (ipv4\|ipv6) => (1\|2)
		741
		742	{
		743	my $idx;
		744	$PROTOCOL{$_} = ++$idx
		745	for split /\s,\s/, $ENV{PERL_ANYEVENT_PROTOCOLS} \|\| "ipv4,ipv6";
		746	}
		747
482	my @models = (	748	my @models = (
483	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
484	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485	[EV:: => AnyEvent::Impl::EV::],	749	[EV:: => AnyEvent::Impl::EV::],
486	[Event:: => AnyEvent::Impl::Event::],	750	[Event:: => AnyEvent::Impl::Event::],
487	[Glib:: => AnyEvent::Impl::Glib::],
488	[Tk:: => AnyEvent::Impl::Tk::],	751	[Tk:: => AnyEvent::Impl::Tk::],
489	[Wx:: => AnyEvent::Impl::POE::],	752	[Wx:: => AnyEvent::Impl::POE::],
490	[Prima:: => AnyEvent::Impl::POE::],	753	[Prima:: => AnyEvent::Impl::POE::],
491	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	754	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
492	# everything below here will not be autoprobed as the pureperl backend should work everywhere	755	# everything below here will not be autoprobed as the pureperl backend should work everywhere
		756	[Glib:: => AnyEvent::Impl::Glib::],
493	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	757	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
494	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	758	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
495	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	759	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
496	);	760	);
497		761
498	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	762	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);
		763
		764	our @post_detect;
		765
		766	sub post_detect(&) {
		767	my ($cb) = @_;
		768
		769	if ($MODEL) {
		770	$cb->();
		771
		772	1
		773	} else {
		774	push @post_detect, $cb;
		775
		776	defined wantarray
		777	? bless \$cb, "AnyEvent::Util::PostDetect"
		778	: ()
		779	}
		780	}
		781
		782	sub AnyEvent::Util::PostDetect::DESTROY {
		783	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		784	}
499		785
500	sub detect() {	786	sub detect() {
501	unless ($MODEL) {	787	unless ($MODEL) {
502	no strict 'refs';	788	no strict 'refs';
503		789
…		…
537	last;	823	last;
538	}	824	}
539	}	825	}
540		826
541	$MODEL	827	$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.";	828	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
543	}	829	}
544	}	830	}
545		831
546	unshift @ISA, $MODEL;	832	unshift @ISA, $MODEL;
547	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	833	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		834
		835	(shift @post_detect)->() while @post_detect;
548	}	836	}
549		837
550	$MODEL	838	$MODEL
551	}	839	}
552		840
…		…
562	$class->$func (@_);	850	$class->$func (@_);
563	}	851	}
564		852
565	package AnyEvent::Base;	853	package AnyEvent::Base;
566		854
567	# default implementation for ->condvar, ->wait, ->broadcast	855	# default implementation for ->condvar
568		856
569	sub condvar {	857	sub condvar {
570	bless \my $flag, "AnyEvent::Base::CondVar"	858	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	}	859	}
580		860
581	# default implementation for ->signal	861	# default implementation for ->signal
582		862
583	our %SIG_CB;	863	our %SIG_CB;
…		…
657	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	937	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
658		938
659	undef $CHLD_W unless keys %PID_CB;	939	undef $CHLD_W unless keys %PID_CB;
660	}	940	}
661		941
		942	package AnyEvent::CondVar;
		943
		944	our @ISA = AnyEvent::CondVar::Base::;
		945
		946	package AnyEvent::CondVar::Base;
		947
		948	use overload
		949	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		950	fallback => 1;
		951
		952	sub _send {
		953	# nop
		954	}
		955
		956	sub send {
		957	my $cv = shift;
		958	$cv->{_ae_sent} = [@_];
		959	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		960	$cv->_send;
		961	}
		962
		963	sub croak {
		964	$_[0]{_ae_croak} = $_[1];
		965	$_[0]->send;
		966	}
		967
		968	sub ready {
		969	$_[0]{_ae_sent}
		970	}
		971
		972	sub _wait {
		973	AnyEvent->one_event while !$_[0]{_ae_sent};
		974	}
		975
		976	sub recv {
		977	$_[0]->_wait;
		978
		979	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		980	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		981	}
		982
		983	sub cb {
		984	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		985	$_[0]{_ae_cb}
		986	}
		987
		988	sub begin {
		989	++$_[0]{_ae_counter};
		990	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		991	}
		992
		993	sub end {
		994	return if --$_[0]{_ae_counter};
		995	&{ $_[0]{_ae_end_cb} \|\| sub { $_[0]->send } };
		996	}
		997
		998	# undocumented/compatibility with pre-3.4
		999	*broadcast = \&send;
		1000	*wait = \&_wait;
		1001
662	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1002	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
663		1003
664	This is an advanced topic that you do not normally need to use AnyEvent in	1004	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	1005	a module. This section is only of use to event loop authors who want to
666	provide AnyEvent compatibility.	1006	provide AnyEvent compatibility.
…		…
722	model it chooses.	1062	model it chooses.
723		1063
724	=item C<PERL_ANYEVENT_MODEL>	1064	=item C<PERL_ANYEVENT_MODEL>
725		1065
726	This can be used to specify the event model to be used by AnyEvent, before	1066	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	1067	auto detection and -probing kicks in. It must be a string consisting
728	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended	1068	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,	1069	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	1070	used as event model. If it fails to load AnyEvent will proceed with
731	autodetection and -probing.	1071	auto detection and -probing.
732		1072
733	This functionality might change in future versions.	1073	This functionality might change in future versions.
734		1074
735	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you	1075	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
736	could start your program like this:	1076	could start your program like this:
737		1077
738	PERL_ANYEVENT_MODEL=Perl perl ...	1078	PERL_ANYEVENT_MODEL=Perl perl ...
		1079
		1080	=item C<PERL_ANYEVENT_PROTOCOLS>
		1081
		1082	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1083	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1084	of auto probing).
		1085
		1086	Must be set to a comma-separated list of protocols or address families,
		1087	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1088	used, and preference will be given to protocols mentioned earlier in the
		1089	list.
		1090
		1091	This variable can effectively be used for denial-of-service attacks
		1092	against local programs (e.g. when setuid), although the impact is likely
		1093	small, as the program has to handle connection errors already-
		1094
		1095	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1096	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1097	- only support IPv4, never try to resolve or contact IPv6
		1098	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1099	IPv6, but prefer IPv6 over IPv4.
		1100
		1101	=item C<PERL_ANYEVENT_EDNS0>
		1102
		1103	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1104	for DNS. This extension is generally useful to reduce DNS traffic, but
		1105	some (broken) firewalls drop such DNS packets, which is why it is off by
		1106	default.
		1107
		1108	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1109	EDNS0 in its DNS requests.
739		1110
740	=back	1111	=back
741		1112
742	=head1 EXAMPLE PROGRAM	1113	=head1 EXAMPLE PROGRAM
743		1114
…		…
754	poll => 'r',	1125	poll => 'r',
755	cb => sub {	1126	cb => sub {
756	warn "io event <$_[0]>\n"; # will always output <r>	1127	warn "io event <$_[0]>\n"; # will always output <r>
757	chomp (my $input = <STDIN>); # read a line	1128	chomp (my $input = <STDIN>); # read a line
758	warn "read: $input\n"; # output what has been read	1129	warn "read: $input\n"; # output what has been read
759	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1130	$cv->send if $input =~ /^q/i; # quit program if /^q/i
760	},	1131	},
761	);	1132	);
762		1133
763	my $time_watcher; # can only be used once	1134	my $time_watcher; # can only be used once
764		1135
…		…
769	});	1140	});
770	}	1141	}
771		1142
772	new_timer; # create first timer	1143	new_timer; # create first timer
773		1144
774	$cv->wait; # wait until user enters /^q/i	1145	$cv->recv; # wait until user enters /^q/i
775		1146
776	=head1 REAL-WORLD EXAMPLE	1147	=head1 REAL-WORLD EXAMPLE
777		1148
778	Consider the L<Net::FCP> module. It features (among others) the following	1149	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:	1150	API calls, which are to freenet what HTTP GET requests are to http:
…		…
829	syswrite $txn->{fh}, $txn->{request}	1200	syswrite $txn->{fh}, $txn->{request}
830	or die "connection or write error";	1201	or die "connection or write error";
831	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1202	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
832		1203
833	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1204	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:	1205	result and signals any possible waiters that the request has finished:
835		1206
836	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1207	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
837		1208
838	if (end-of-file or data complete) {	1209	if (end-of-file or data complete) {
839	$txn->{result} = $txn->{buf};	1210	$txn->{result} = $txn->{buf};
840	$txn->{finished}->broadcast;	1211	$txn->{finished}->send;
841	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1212	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
842	}	1213	}
843		1214
844	The C<result> method, finally, just waits for the finished signal (if the	1215	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	1216	request was already finished, it doesn't wait, of course, and returns the
846	data:	1217	data:
847		1218
848	$txn->{finished}->wait;	1219	$txn->{finished}->recv;
849	return $txn->{result};	1220	return $txn->{result};
850		1221
851	The actual code goes further and collects all errors (C<die>s, exceptions)	1222	The actual code goes further and collects all errors (C<die>s, exceptions)
852	that occured during request processing. The C<result> method detects	1223	that occurred during request processing. The C<result> method detects
853	whether an exception as thrown (it is stored inside the $txn object)	1224	whether an exception as thrown (it is stored inside the $txn object)
854	and just throws the exception, which means connection errors and other	1225	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	1226	problems get reported tot he code that tries to use the result, not in a
856	random callback.	1227	random callback.
857		1228
…		…
888		1259
889	my $quit = AnyEvent->condvar;	1260	my $quit = AnyEvent->condvar;
890		1261
891	$fcp->txn_client_get ($url)->cb (sub {	1262	$fcp->txn_client_get ($url)->cb (sub {
892	...	1263	...
893	$quit->broadcast;	1264	$quit->send;
894	});	1265	});
895		1266
896	$quit->wait;	1267	$quit->recv;
897		1268
898		1269
899	=head1 BENCHMARK	1270	=head1 BENCHMARKS
900		1271
901	To give you an idea of the performance and overheads that AnyEvent adds	1272	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	1273	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	1274	of various event loops I prepared some benchmarks.
904	event models natively and with anyevent. The benchmark creates a lot of	1275
905	timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to	1276	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1277
		1278	Here is a benchmark of various supported event models used natively and
		1279	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1280	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	1281	which it is), lets them fire exactly once and destroys them again.
907	them again.
908		1282
909	Rewriting the benchmark to use many different sockets instead of using	1283	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	1284	distribution.
911	(socket creation is expensive), but qualitatively the same figures, so it
912	was not used.
913		1285
914	=head2 Explanation of the columns	1286	=head3 Explanation of the columns
915		1287
916	I<watcher> is the number of event watchers created/destroyed. Since	1288	I<watcher> is the number of event watchers created/destroyed. Since
917	different event models feature vastly different performances, each event	1289	different event models feature vastly different performances, each event
918	loop was given a number of watchers so that overall runtime is acceptable	1290	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	1291	and similar between tested event loop (and keep them from crashing): Glib
…		…
929	all watchers, to avoid adding memory overhead. That means closure creation	1301	all watchers, to avoid adding memory overhead. That means closure creation
930	and memory usage is not included in the figures.	1302	and memory usage is not included in the figures.
931		1303
932	I<invoke> is the time, in microseconds, used to invoke a simple	1304	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	1305	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	1306	invoked "watcher" times, it would C<< ->send >> a condvar once to
935	signal the end of this phase.	1307	signal the end of this phase.
936		1308
937	I<destroy> is the time, in microseconds, that it takes to destroy a single	1309	I<destroy> is the time, in microseconds, that it takes to destroy a single
938	watcher.	1310	watcher.
939		1311
940	=head2 Results	1312	=head3 Results
941		1313
942	name watchers bytes create invoke destroy comment	1314	name watchers bytes create invoke destroy comment
943	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1315	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	1316	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	1317	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	1318	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	1319	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	1320	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	1321	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	1322	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	1323	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	1324	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
953		1325
954	=head2 Discussion	1326	=head3 Discussion
955		1327
956	The benchmark does I<not> measure scalability of the event loop very	1328	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)	1329	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	1330	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	1331	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	1332	the same time, so select/poll-based implementations get an unnatural speed
961	boost.	1333	boost.
		1334
		1335	Also, note that the number of watchers usually has a nonlinear effect on
		1336	overall speed, that is, creating twice as many watchers doesn't take twice
		1337	the time - usually it takes longer. This puts event loops tested with a
		1338	higher number of watchers at a disadvantage.
		1339
		1340	To put the range of results into perspective, consider that on the
		1341	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1342	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1343	cycles with POE.
962		1344
963	C<EV> is the sole leader regarding speed and memory use, which are both	1345	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	1346	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	1347	far less memory than any other event loop and is still faster than Event
966	natively.	1348	natively.
…		…
989	file descriptor is dup()ed for each watcher. This shows that the dup()	1371	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	1372	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	1373	hidden memory cost inside the kernel which is not reflected in the figures
992	above).	1374	above).
993		1375
994	C<POE>, regardless of underlying event loop (whether using its pure	1376	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	1377	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	1378	be tested because it wasn't working) shows abysmal performance and
997	and memory usage: Watchers use almost 30 times as much memory as	1379	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	1380	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	1381	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	1382	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1383	implementation.
		1384
1001	implementation. The design of the POE adaptor class in AnyEvent can not	1385	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	1386	for the performance issues, though, as session creation overhead is
1003	to execution of the state machine, which is coded pretty optimally within	1387	small compared to execution of the state machine, which is coded pretty
1004	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1388	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1389	using multiple sessions is not a good approach, especially regarding
		1390	memory usage, even the author of POE could not come up with a faster
		1391	design).
1005		1392
1006	=head2 Summary	1393	=head3 Summary
1007		1394
1008	=over 4	1395	=over 4
1009		1396
1010	=item * Using EV through AnyEvent is faster than any other event loop	1397	=item * Using EV through AnyEvent is faster than any other event loop
1011	(even when used without AnyEvent), but most event loops have acceptable	1398	(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	1405	=item * You should avoid POE like the plague if you want performance or
1019	reasonable memory usage.	1406	reasonable memory usage.
1020		1407
1021	=back	1408	=back
1022		1409
		1410	=head2 BENCHMARKING THE LARGE SERVER CASE
		1411
		1412	This benchmark actually benchmarks the event loop itself. It works by
		1413	creating a number of "servers": each server consists of a socket pair, a
		1414	timeout watcher that gets reset on activity (but never fires), and an I/O
		1415	watcher waiting for input on one side of the socket. Each time the socket
		1416	watcher reads a byte it will write that byte to a random other "server".
		1417
		1418	The effect is that there will be a lot of I/O watchers, only part of which
		1419	are active at any one point (so there is a constant number of active
		1420	fds for each loop iteration, but which fds these are is random). The
		1421	timeout is reset each time something is read because that reflects how
		1422	most timeouts work (and puts extra pressure on the event loops).
		1423
		1424	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1425	(1%) are active. This mirrors the activity of large servers with many
		1426	connections, most of which are idle at any one point in time.
		1427
		1428	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1429	distribution.
		1430
		1431	=head3 Explanation of the columns
		1432
		1433	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1434	each server has a read and write socket end).
		1435
		1436	I<create> is the time it takes to create a socket pair (which is
		1437	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1438
		1439	I<request>, the most important value, is the time it takes to handle a
		1440	single "request", that is, reading the token from the pipe and forwarding
		1441	it to another server. This includes deleting the old timeout and creating
		1442	a new one that moves the timeout into the future.
		1443
		1444	=head3 Results
		1445
		1446	name sockets create request
		1447	EV 20000 69.01 11.16
		1448	Perl 20000 73.32 35.87
		1449	Event 20000 212.62 257.32
		1450	Glib 20000 651.16 1896.30
		1451	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1452
		1453	=head3 Discussion
		1454
		1455	This benchmark I<does> measure scalability and overall performance of the
		1456	particular event loop.
		1457
		1458	EV is again fastest. Since it is using epoll on my system, the setup time
		1459	is relatively high, though.
		1460
		1461	Perl surprisingly comes second. It is much faster than the C-based event
		1462	loops Event and Glib.
		1463
		1464	Event suffers from high setup time as well (look at its code and you will
		1465	understand why). Callback invocation also has a high overhead compared to
		1466	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1467	uses select or poll in basically all documented configurations.
		1468
		1469	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1470	clearly fails to perform with many filehandles or in busy servers.
		1471
		1472	POE is still completely out of the picture, taking over 1000 times as long
		1473	as EV, and over 100 times as long as the Perl implementation, even though
		1474	it uses a C-based event loop in this case.
		1475
		1476	=head3 Summary
		1477
		1478	=over 4
		1479
		1480	=item * The pure perl implementation performs extremely well.
		1481
		1482	=item * Avoid Glib or POE in large projects where performance matters.
		1483
		1484	=back
		1485
		1486	=head2 BENCHMARKING SMALL SERVERS
		1487
		1488	While event loops should scale (and select-based ones do not...) even to
		1489	large servers, most programs we (or I :) actually write have only a few
		1490	I/O watchers.
		1491
		1492	In this benchmark, I use the same benchmark program as in the large server
		1493	case, but it uses only eight "servers", of which three are active at any
		1494	one time. This should reflect performance for a small server relatively
		1495	well.
		1496
		1497	The columns are identical to the previous table.
		1498
		1499	=head3 Results
		1500
		1501	name sockets create request
		1502	EV 16 20.00 6.54
		1503	Perl 16 25.75 12.62
		1504	Event 16 81.27 35.86
		1505	Glib 16 32.63 15.48
		1506	POE 16 261.87 276.28 uses POE::Loop::Event
		1507
		1508	=head3 Discussion
		1509
		1510	The benchmark tries to test the performance of a typical small
		1511	server. While knowing how various event loops perform is interesting, keep
		1512	in mind that their overhead in this case is usually not as important, due
		1513	to the small absolute number of watchers (that is, you need efficiency and
		1514	speed most when you have lots of watchers, not when you only have a few of
		1515	them).
		1516
		1517	EV is again fastest.
		1518
		1519	Perl again comes second. It is noticeably faster than the C-based event
		1520	loops Event and Glib, although the difference is too small to really
		1521	matter.
		1522
		1523	POE also performs much better in this case, but is is still far behind the
		1524	others.
		1525
		1526	=head3 Summary
		1527
		1528	=over 4
		1529
		1530	=item * C-based event loops perform very well with small number of
		1531	watchers, as the management overhead dominates.
		1532
		1533	=back
		1534
1023		1535
1024	=head1 FORK	1536	=head1 FORK
1025		1537
1026	Most event libraries are not fork-safe. The ones who are usually are	1538	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.	1539	because they rely on inefficient but fork-safe C<select> or C<poll>
		1540	calls. Only L<EV> is fully fork-aware.
1028		1541
1029	If you have to fork, you must either do so I<before> creating your first	1542	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.	1543	watcher OR you must not use AnyEvent at all in the child.
1031		1544
1032		1545
…		…
1044		1557
1045	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1558	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1046		1559
1047	use AnyEvent;	1560	use AnyEvent;
1048		1561
		1562	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1563	be used to probe what backend is used and gain other information (which is
		1564	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
		1565
1049		1566
1050	=head1 SEE ALSO	1567	=head1 SEE ALSO
1051		1568
1052	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1569	Utility functions: L<AnyEvent::Util>.
1053	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1570
		1571	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1054	L<Event::Lib>, L<Qt>, L<POE>.	1572	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1055		1573
1056	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1574	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1057	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1575	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>,	1576	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1059	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1577	L<AnyEvent::Impl::POE>.
1060		1578
		1579	Non-blocking file handles, sockets, TCP clients and
		1580	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1581
		1582	Asynchronous DNS: L<AnyEvent::DNS>.
		1583
		1584	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1585
1061	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1586	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1062		1587
1063		1588
1064	=head1 AUTHOR	1589	=head1 AUTHOR
1065		1590
1066	Marc Lehmann <schmorp@schmorp.de>	1591	Marc Lehmann <schmorp@schmorp.de>

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.90 by root, Fri Apr 25 14:24:29 2008 UTC vs. Revision 1.133 by root, Sun May 25 03:44:03 2008 UTC

Diff Legend

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.90 by root, Fri Apr 25 14:24:29 2008 UTC vs.
Revision 1.133 by root, Sun May 25 03:44:03 2008 UTC