[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 1.136 by root, Sun May 25 23:52:02 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, read about the caveats in the description for the C<<
		318	->send >> method).
308		319
309	They are very useful to signal that a condition has been fulfilled, for	320	Condition variables are similar to callbacks, except that you can
		321	optionally wait for them. They can also be called merge points - points
		322	in time where multiple outstanding events have been processed. And yet
		323	another way to call them is transactions - each condition variable can be
		324	used to represent a transaction, which finishes at some point and delivers
		325	a result.
		326
		327	Condition variables are very useful to signal that something has finished,
310	example, if you write a module that does asynchronous http requests,	328	for example, if you write a module that does asynchronous http requests,
311	then a condition variable would be the ideal candidate to signal the	329	then a condition variable would be the ideal candidate to signal the
312	availability of results.	330	availability of results. The user can either act when the callback is
		331	called or can synchronously C<< ->recv >> for the results.
313		332
314	You can also use condition variables to block your main program until	333	You can also use them to simulate traditional event loops - for example,
315	an event occurs - for example, you could C<< ->wait >> in your main	334	you can block your main program until an event occurs - for example, you
316	program until the user clicks the Quit button in your app, which would C<<	335	could C<< ->recv >> in your main program until the user clicks the Quit
317	->broadcast >> the "quit" event.	336	button of your app, which would C<< ->send >> the "quit" event.
318		337
319	Note that condition variables recurse into the event loop - if you have	338	Note that condition variables recurse into the event loop - if you have
320	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	339	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
321	lose. Therefore, condition variables are good to export to your caller, but	340	lose. Therefore, condition variables are good to export to your caller, but
322	you should avoid making a blocking wait yourself, at least in callbacks,	341	you should avoid making a blocking wait yourself, at least in callbacks,
323	as this asks for trouble.	342	as this asks for trouble.
324		343
325	This object has two methods:	344	Condition variables are represented by hash refs in perl, and the keys
		345	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		346	easy (it is often useful to build your own transaction class on top of
		347	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		348	it's C<new> method in your own C<new> method.
		349
		350	There are two "sides" to a condition variable - the "producer side" which
		351	eventually calls C<< -> send >>, and the "consumer side", which waits
		352	for the send to occur.
		353
		354	Example: wait for a timer.
		355
		356	# wait till the result is ready
		357	my $result_ready = AnyEvent->condvar;
		358
		359	# do something such as adding a timer
		360	# or socket watcher the calls $result_ready->send
		361	# when the "result" is ready.
		362	# in this case, we simply use a timer:
		363	my $w = AnyEvent->timer (
		364	after => 1,
		365	cb => sub { $result_ready->send },
		366	);
		367
		368	# this "blocks" (while handling events) till the callback
		369	# calls send
		370	$result_ready->recv;
		371
		372	Example: wait for a timer, but take advantage of the fact that
		373	condition variables are also code references.
		374
		375	my $done = AnyEvent->condvar;
		376	my $delay = AnyEvent->timer (after => 5, cb => $done);
		377	$done->recv;
		378
		379	=head3 METHODS FOR PRODUCERS
		380
		381	These methods should only be used by the producing side, i.e. the
		382	code/module that eventually sends the signal. Note that it is also
		383	the producer side which creates the condvar in most cases, but it isn't
		384	uncommon for the consumer to create it as well.
326		385
327	=over 4	386	=over 4
328		387
		388	=item $cv->send (...)
		389
		390	Flag the condition as ready - a running C<< ->recv >> and all further
		391	calls to C<recv> will (eventually) return after this method has been
		392	called. If nobody is waiting the send will be remembered.
		393
		394	If a callback has been set on the condition variable, it is called
		395	immediately from within send.
		396
		397	Any arguments passed to the C<send> call will be returned by all
		398	future C<< ->recv >> calls.
		399
		400	Condition variables are overloaded so one can call them directly
		401	(as a code reference). Calling them directly is the same as calling
		402	C<send>. Note, however, that many C-based event loops do not handle
		403	overloading, so as tempting as it may be, passing a condition variable
		404	instead of a callback does not work. Both the pure perl and EV loops
		405	support overloading, however, as well as all functions that use perl to
		406	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		407	example).
		408
		409	=item $cv->croak ($error)
		410
		411	Similar to send, but causes all call's to C<< ->recv >> to invoke
		412	C<Carp::croak> with the given error message/object/scalar.
		413
		414	This can be used to signal any errors to the condition variable
		415	user/consumer.
		416
		417	=item $cv->begin ([group callback])
		418
329	=item $cv->wait	419	=item $cv->end
330		420
331	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	421	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		422
		423	These two methods can be used to combine many transactions/events into
		424	one. For example, a function that pings many hosts in parallel might want
		425	to use a condition variable for the whole process.
		426
		427	Every call to C<< ->begin >> will increment a counter, and every call to
		428	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		429	>>, the (last) callback passed to C<begin> will be executed. That callback
		430	is I<supposed> to call C<< ->send >>, but that is not required. If no
		431	callback was set, C<send> will be called without any arguments.
		432
		433	Let's clarify this with the ping example:
		434
		435	my $cv = AnyEvent->condvar;
		436
		437	my %result;
		438	$cv->begin (sub { $cv->send (\%result) });
		439
		440	for my $host (@list_of_hosts) {
		441	$cv->begin;
		442	ping_host_then_call_callback $host, sub {
		443	$result{$host} = ...;
		444	$cv->end;
		445	};
		446	}
		447
		448	$cv->end;
		449
		450	This code fragment supposedly pings a number of hosts and calls
		451	C<send> after results for all then have have been gathered - in any
		452	order. To achieve this, the code issues a call to C<begin> when it starts
		453	each ping request and calls C<end> when it has received some result for
		454	it. Since C<begin> and C<end> only maintain a counter, the order in which
		455	results arrive is not relevant.
		456
		457	There is an additional bracketing call to C<begin> and C<end> outside the
		458	loop, which serves two important purposes: first, it sets the callback
		459	to be called once the counter reaches C<0>, and second, it ensures that
		460	C<send> is called even when C<no> hosts are being pinged (the loop
		461	doesn't execute once).
		462
		463	This is the general pattern when you "fan out" into multiple subrequests:
		464	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		465	is called at least once, and then, for each subrequest you start, call
		466	C<begin> and for each subrequest you finish, call C<end>.
		467
		468	=back
		469
		470	=head3 METHODS FOR CONSUMERS
		471
		472	These methods should only be used by the consuming side, i.e. the
		473	code awaits the condition.
		474
		475	=over 4
		476
		477	=item $cv->recv
		478
		479	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
332	called on c<$cv>, while servicing other watchers normally.	480	>> methods have been called on c<$cv>, while servicing other watchers
		481	normally.
333		482
334	You can only wait once on a condition - additional calls will return	483	You can only wait once on a condition - additional calls are valid but
335	immediately.	484	will return immediately.
		485
		486	If an error condition has been set by calling C<< ->croak >>, then this
		487	function will call C<croak>.
		488
		489	In list context, all parameters passed to C<send> will be returned,
		490	in scalar context only the first one will be returned.
336		491
337	Not all event models support a blocking wait - some die in that case	492	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	493	(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	494	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	495	caller decide whether the call will block or not (for example, by coupling
341	condition variables with some kind of request results and supporting	496	condition variables with some kind of request results and supporting
342	callbacks so the caller knows that getting the result will not block,	497	callbacks so the caller knows that getting the result will not block,
343	while still suppporting blocking waits if the caller so desires).	498	while still supporting blocking waits if the caller so desires).
344		499
345	Another reason I<never> to C<< ->wait >> in a module is that you cannot	500	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	501	sensibly have two C<< ->recv >>'s in parallel, as that would require
347	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	502	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
348	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	503	can supply.
349	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
350	from different coroutines, however).
351		504
352	=item $cv->broadcast	505	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		506	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		507	versions and also integrates coroutines into AnyEvent, making blocking
		508	C<< ->recv >> calls perfectly safe as long as they are done from another
		509	coroutine (one that doesn't run the event loop).
353		510
354	Flag the condition as ready - a running C<< ->wait >> and all further	511	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	512	only calling C<< ->recv >> from within that callback (or at a later
356	called. If nobody is waiting the broadcast will be remembered..	513	time). This will work even when the event loop does not support blocking
		514	waits otherwise.
		515
		516	=item $bool = $cv->ready
		517
		518	Returns true when the condition is "true", i.e. whether C<send> or
		519	C<croak> have been called.
		520
		521	=item $cb = $cv->cb ([new callback])
		522
		523	This is a mutator function that returns the callback set and optionally
		524	replaces it before doing so.
		525
		526	The callback will be called when the condition becomes "true", i.e. when
		527	C<send> or C<croak> are called. Calling C<recv> inside the callback
		528	or at any later time is guaranteed not to block.
357		529
358	=back	530	=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	$result_ready->wait;
377		531
378	=head1 GLOBAL VARIABLES AND FUNCTIONS	532	=head1 GLOBAL VARIABLES AND FUNCTIONS
379		533
380	=over 4	534	=over 4
381		535
…		…
387	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	541	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
388	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	542	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
389		543
390	The known classes so far are:	544	The known classes so far are:
391		545
392	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
393	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
394	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	546	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
395	AnyEvent::Impl::Event based on Event, second best choice.	547	AnyEvent::Impl::Event based on Event, second best choice.
		548	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
396	AnyEvent::Impl::Glib based on Glib, third-best choice.	549	AnyEvent::Impl::Glib based on Glib, third-best choice.
397	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
398	AnyEvent::Impl::Tk based on Tk, very bad choice.	550	AnyEvent::Impl::Tk based on Tk, very bad choice.
399	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	551	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
400	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	552	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
401	AnyEvent::Impl::POE based on POE, not generic enough for full support.	553	AnyEvent::Impl::POE based on POE, not generic enough for full support.
402		554
…		…
415	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	567	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
416	if necessary. You should only call this function right before you would	568	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	569	have created an AnyEvent watcher anyway, that is, as late as possible at
418	runtime.	570	runtime.
419		571
		572	=item $guard = AnyEvent::post_detect { BLOCK }
		573
		574	Arranges for the code block to be executed as soon as the event model is
		575	autodetected (or immediately if this has already happened).
		576
		577	If called in scalar or list context, then it creates and returns an object
		578	that automatically removes the callback again when it is destroyed. See
		579	L<Coro::BDB> for a case where this is useful.
		580
		581	=item @AnyEvent::post_detect
		582
		583	If there are any code references in this array (you can C<push> to it
		584	before or after loading AnyEvent), then they will called directly after
		585	the event loop has been chosen.
		586
		587	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		588	if it contains a true value then the event loop has already been detected,
		589	and the array will be ignored.
		590
		591	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		592
420	=back	593	=back
421		594
422	=head1 WHAT TO DO IN A MODULE	595	=head1 WHAT TO DO IN A MODULE
423		596
424	As a module author, you should C<use AnyEvent> and call AnyEvent methods	597	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	600	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	601	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	602	by calling AnyEvent in your module body you force the user of your module
430	to load the event module first.	603	to load the event module first.
431		604
432	Never call C<< ->wait >> on a condition variable unless you I<know> that	605	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	606	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	607	because it will stall the whole program, and the whole point of using
435	events is to stay interactive.	608	events is to stay interactive.
436		609
437	It is fine, however, to call C<< ->wait >> when the user of your module	610	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	611	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 >>	612	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).	613	freely, as the user of your module knows what she is doing. always).
441		614
442	=head1 WHAT TO DO IN THE MAIN PROGRAM	615	=head1 WHAT TO DO IN THE MAIN PROGRAM
443		616
444	There will always be a single main program - the only place that should	617	There will always be a single main program - the only place that should
…		…
446		619
447	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	620	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
448	do anything special (it does not need to be event-based) and let AnyEvent	621	do anything special (it does not need to be event-based) and let AnyEvent
449	decide which implementation to chose if some module relies on it.	622	decide which implementation to chose if some module relies on it.
450		623
451	If the main program relies on a specific event model. For example, in	624	If the main program relies on a specific event model - for example, in
452	Gtk2 programs you have to rely on the Glib module. You should load the	625	Gtk2 programs you have to rely on the Glib module - you should load the
453	event module before loading AnyEvent or any module that uses it: generally	626	event module before loading AnyEvent or any module that uses it: generally
454	speaking, you should load it as early as possible. The reason is that	627	speaking, you should load it as early as possible. The reason is that
455	modules might create watchers when they are loaded, and AnyEvent will	628	modules might create watchers when they are loaded, and AnyEvent will
456	decide on the event model to use as soon as it creates watchers, and it	629	decide on the event model to use as soon as it creates watchers, and it
457	might chose the wrong one unless you load the correct one yourself.	630	might chose the wrong one unless you load the correct one yourself.
458		631
459	You can chose to use a rather inefficient pure-perl implementation by	632	You can chose to use a pure-perl implementation by loading the
460	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	633	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
461	behaviour everywhere, but letting AnyEvent chose is generally better.	634	everywhere, but letting AnyEvent chose the model is generally better.
		635
		636	=head2 MAINLOOP EMULATION
		637
		638	Sometimes (often for short test scripts, or even standalone programs who
		639	only want to use AnyEvent), you do not want to run a specific event loop.
		640
		641	In that case, you can use a condition variable like this:
		642
		643	AnyEvent->condvar->recv;
		644
		645	This has the effect of entering the event loop and looping forever.
		646
		647	Note that usually your program has some exit condition, in which case
		648	it is better to use the "traditional" approach of storing a condition
		649	variable somewhere, waiting for it, and sending it when the program should
		650	exit cleanly.
		651
		652
		653	=head1 OTHER MODULES
		654
		655	The following is a non-exhaustive list of additional modules that use
		656	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		657	in the same program. Some of the modules come with AnyEvent, some are
		658	available via CPAN.
		659
		660	=over 4
		661
		662	=item L<AnyEvent::Util>
		663
		664	Contains various utility functions that replace often-used but blocking
		665	functions such as C<inet_aton> by event-/callback-based versions.
		666
		667	=item L<AnyEvent::Handle>
		668
		669	Provide read and write buffers and manages watchers for reads and writes.
		670
		671	=item L<AnyEvent::Socket>
		672
		673	Provides various utility functions for (internet protocol) sockets,
		674	addresses and name resolution. Also functions to create non-blocking tcp
		675	connections or tcp servers, with IPv6 and SRV record support and more.
		676
		677	=item L<AnyEvent::DNS>
		678
		679	Provides rich asynchronous DNS resolver capabilities.
		680
		681	=item L<AnyEvent::HTTPD>
		682
		683	Provides a simple web application server framework.
		684
		685	=item L<AnyEvent::FastPing>
		686
		687	The fastest ping in the west.
		688
		689	=item L<Net::IRC3>
		690
		691	AnyEvent based IRC client module family.
		692
		693	=item L<Net::XMPP2>
		694
		695	AnyEvent based XMPP (Jabber protocol) module family.
		696
		697	=item L<Net::FCP>
		698
		699	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		700	of AnyEvent.
		701
		702	=item L<Event::ExecFlow>
		703
		704	High level API for event-based execution flow control.
		705
		706	=item L<Coro>
		707
		708	Has special support for AnyEvent via L<Coro::AnyEvent>.
		709
		710	=item L<AnyEvent::AIO>, L<IO::AIO>
		711
		712	Truly asynchronous I/O, should be in the toolbox of every event
		713	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		714	together.
		715
		716	=item L<AnyEvent::BDB>, L<BDB>
		717
		718	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
		719	IO::AIO and AnyEvent together.
		720
		721	=item L<IO::Lambda>
		722
		723	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		724
		725	=back
462		726
463	=cut	727	=cut
464		728
465	package AnyEvent;	729	package AnyEvent;
466		730
467	no warnings;	731	no warnings;
468	use strict;	732	use strict;
469		733
470	use Carp;	734	use Carp;
471		735
472	our $VERSION = '3.3';	736	our $VERSION = '4.03';
473	our $MODEL;	737	our $MODEL;
474		738
475	our $AUTOLOAD;	739	our $AUTOLOAD;
476	our @ISA;	740	our @ISA;
477		741
		742	our @REGISTRY;
		743
478	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	744	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479		745
480	our @REGISTRY;	746	our %PROTOCOL; # (ipv4\|ipv6) => (1\|2), higher numbers are preferred
		747
		748	{
		749	my $idx;
		750	$PROTOCOL{$_} = ++$idx
		751	for reverse split /\s,\s/,
		752	$ENV{PERL_ANYEVENT_PROTOCOLS} \|\| "ipv4,ipv6";
		753	}
481		754
482	my @models = (	755	my @models = (
483	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
484	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485	[EV:: => AnyEvent::Impl::EV::],	756	[EV:: => AnyEvent::Impl::EV::],
486	[Event:: => AnyEvent::Impl::Event::],	757	[Event:: => AnyEvent::Impl::Event::],
487	[Glib:: => AnyEvent::Impl::Glib::],
488	[Tk:: => AnyEvent::Impl::Tk::],
489	[Wx:: => AnyEvent::Impl::POE::],
490	[Prima:: => AnyEvent::Impl::POE::],
491	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	758	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
492	# everything below here will not be autoprobed as the pureperl backend should work everywhere	759	# everything below here will not be autoprobed
		760	# as the pureperl backend should work everywhere
		761	# and is usually faster
		762	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		763	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
493	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	764	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
494	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	765	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
495	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	766	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		767	[Wx:: => AnyEvent::Impl::POE::],
		768	[Prima:: => AnyEvent::Impl::POE::],
496	);	769	);
497		770
498	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	771	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);
		772
		773	our @post_detect;
		774
		775	sub post_detect(&) {
		776	my ($cb) = @_;
		777
		778	if ($MODEL) {
		779	$cb->();
		780
		781	1
		782	} else {
		783	push @post_detect, $cb;
		784
		785	defined wantarray
		786	? bless \$cb, "AnyEvent::Util::PostDetect"
		787	: ()
		788	}
		789	}
		790
		791	sub AnyEvent::Util::PostDetect::DESTROY {
		792	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		793	}
499		794
500	sub detect() {	795	sub detect() {
501	unless ($MODEL) {	796	unless ($MODEL) {
502	no strict 'refs';	797	no strict 'refs';
503		798
…		…
537	last;	832	last;
538	}	833	}
539	}	834	}
540		835
541	$MODEL	836	$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.";	837	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
543	}	838	}
544	}	839	}
545		840
546	unshift @ISA, $MODEL;	841	unshift @ISA, $MODEL;
547	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	842	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		843
		844	(shift @post_detect)->() while @post_detect;
548	}	845	}
549		846
550	$MODEL	847	$MODEL
551	}	848	}
552		849
…		…
562	$class->$func (@_);	859	$class->$func (@_);
563	}	860	}
564		861
565	package AnyEvent::Base;	862	package AnyEvent::Base;
566		863
567	# default implementation for ->condvar, ->wait, ->broadcast	864	# default implementation for ->condvar
568		865
569	sub condvar {	866	sub condvar {
570	bless \my $flag, "AnyEvent::Base::CondVar"	867	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	}	868	}
580		869
581	# default implementation for ->signal	870	# default implementation for ->signal
582		871
583	our %SIG_CB;	872	our %SIG_CB;
…		…
657	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	946	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
658		947
659	undef $CHLD_W unless keys %PID_CB;	948	undef $CHLD_W unless keys %PID_CB;
660	}	949	}
661		950
		951	package AnyEvent::CondVar;
		952
		953	our @ISA = AnyEvent::CondVar::Base::;
		954
		955	package AnyEvent::CondVar::Base;
		956
		957	use overload
		958	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		959	fallback => 1;
		960
		961	sub _send {
		962	# nop
		963	}
		964
		965	sub send {
		966	my $cv = shift;
		967	$cv->{_ae_sent} = [@_];
		968	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		969	$cv->_send;
		970	}
		971
		972	sub croak {
		973	$_[0]{_ae_croak} = $_[1];
		974	$_[0]->send;
		975	}
		976
		977	sub ready {
		978	$_[0]{_ae_sent}
		979	}
		980
		981	sub _wait {
		982	AnyEvent->one_event while !$_[0]{_ae_sent};
		983	}
		984
		985	sub recv {
		986	$_[0]->_wait;
		987
		988	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		989	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		990	}
		991
		992	sub cb {
		993	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		994	$_[0]{_ae_cb}
		995	}
		996
		997	sub begin {
		998	++$_[0]{_ae_counter};
		999	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1000	}
		1001
		1002	sub end {
		1003	return if --$_[0]{_ae_counter};
		1004	&{ $_[0]{_ae_end_cb} \|\| sub { $_[0]->send } };
		1005	}
		1006
		1007	# undocumented/compatibility with pre-3.4
		1008	*broadcast = \&send;
		1009	*wait = \&_wait;
		1010
662	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1011	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
663		1012
664	This is an advanced topic that you do not normally need to use AnyEvent in	1013	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	1014	a module. This section is only of use to event loop authors who want to
666	provide AnyEvent compatibility.	1015	provide AnyEvent compatibility.
…		…
722	model it chooses.	1071	model it chooses.
723		1072
724	=item C<PERL_ANYEVENT_MODEL>	1073	=item C<PERL_ANYEVENT_MODEL>
725		1074
726	This can be used to specify the event model to be used by AnyEvent, before	1075	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	1076	auto detection and -probing kicks in. It must be a string consisting
728	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended	1077	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,	1078	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	1079	used as event model. If it fails to load AnyEvent will proceed with
731	autodetection and -probing.	1080	auto detection and -probing.
732		1081
733	This functionality might change in future versions.	1082	This functionality might change in future versions.
734		1083
735	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you	1084	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
736	could start your program like this:	1085	could start your program like this:
737		1086
738	PERL_ANYEVENT_MODEL=Perl perl ...	1087	PERL_ANYEVENT_MODEL=Perl perl ...
		1088
		1089	=item C<PERL_ANYEVENT_PROTOCOLS>
		1090
		1091	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1092	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1093	of auto probing).
		1094
		1095	Must be set to a comma-separated list of protocols or address families,
		1096	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1097	used, and preference will be given to protocols mentioned earlier in the
		1098	list.
		1099
		1100	This variable can effectively be used for denial-of-service attacks
		1101	against local programs (e.g. when setuid), although the impact is likely
		1102	small, as the program has to handle connection errors already-
		1103
		1104	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1105	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1106	- only support IPv4, never try to resolve or contact IPv6
		1107	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1108	IPv6, but prefer IPv6 over IPv4.
		1109
		1110	=item C<PERL_ANYEVENT_EDNS0>
		1111
		1112	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1113	for DNS. This extension is generally useful to reduce DNS traffic, but
		1114	some (broken) firewalls drop such DNS packets, which is why it is off by
		1115	default.
		1116
		1117	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1118	EDNS0 in its DNS requests.
739		1119
740	=back	1120	=back
741		1121
742	=head1 EXAMPLE PROGRAM	1122	=head1 EXAMPLE PROGRAM
743		1123
…		…
754	poll => 'r',	1134	poll => 'r',
755	cb => sub {	1135	cb => sub {
756	warn "io event <$_[0]>\n"; # will always output <r>	1136	warn "io event <$_[0]>\n"; # will always output <r>
757	chomp (my $input = <STDIN>); # read a line	1137	chomp (my $input = <STDIN>); # read a line
758	warn "read: $input\n"; # output what has been read	1138	warn "read: $input\n"; # output what has been read
759	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1139	$cv->send if $input =~ /^q/i; # quit program if /^q/i
760	},	1140	},
761	);	1141	);
762		1142
763	my $time_watcher; # can only be used once	1143	my $time_watcher; # can only be used once
764		1144
…		…
769	});	1149	});
770	}	1150	}
771		1151
772	new_timer; # create first timer	1152	new_timer; # create first timer
773		1153
774	$cv->wait; # wait until user enters /^q/i	1154	$cv->recv; # wait until user enters /^q/i
775		1155
776	=head1 REAL-WORLD EXAMPLE	1156	=head1 REAL-WORLD EXAMPLE
777		1157
778	Consider the L<Net::FCP> module. It features (among others) the following	1158	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:	1159	API calls, which are to freenet what HTTP GET requests are to http:
…		…
829	syswrite $txn->{fh}, $txn->{request}	1209	syswrite $txn->{fh}, $txn->{request}
830	or die "connection or write error";	1210	or die "connection or write error";
831	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1211	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
832		1212
833	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1213	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:	1214	result and signals any possible waiters that the request has finished:
835		1215
836	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1216	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
837		1217
838	if (end-of-file or data complete) {	1218	if (end-of-file or data complete) {
839	$txn->{result} = $txn->{buf};	1219	$txn->{result} = $txn->{buf};
840	$txn->{finished}->broadcast;	1220	$txn->{finished}->send;
841	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1221	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
842	}	1222	}
843		1223
844	The C<result> method, finally, just waits for the finished signal (if the	1224	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	1225	request was already finished, it doesn't wait, of course, and returns the
846	data:	1226	data:
847		1227
848	$txn->{finished}->wait;	1228	$txn->{finished}->recv;
849	return $txn->{result};	1229	return $txn->{result};
850		1230
851	The actual code goes further and collects all errors (C<die>s, exceptions)	1231	The actual code goes further and collects all errors (C<die>s, exceptions)
852	that occured during request processing. The C<result> method detects	1232	that occurred during request processing. The C<result> method detects
853	whether an exception as thrown (it is stored inside the $txn object)	1233	whether an exception as thrown (it is stored inside the $txn object)
854	and just throws the exception, which means connection errors and other	1234	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	1235	problems get reported tot he code that tries to use the result, not in a
856	random callback.	1236	random callback.
857		1237
…		…
888		1268
889	my $quit = AnyEvent->condvar;	1269	my $quit = AnyEvent->condvar;
890		1270
891	$fcp->txn_client_get ($url)->cb (sub {	1271	$fcp->txn_client_get ($url)->cb (sub {
892	...	1272	...
893	$quit->broadcast;	1273	$quit->send;
894	});	1274	});
895		1275
896	$quit->wait;	1276	$quit->recv;
897		1277
898		1278
899	=head1 BENCHMARK	1279	=head1 BENCHMARKS
900		1280
901	To give you an idea of the performance and overheads that AnyEvent adds	1281	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	1282	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	1283	of various event loops I prepared some benchmarks.
904	event models natively and with anyevent. The benchmark creates a lot of	1284
905	timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to	1285	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1286
		1287	Here is a benchmark of various supported event models used natively and
		1288	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1289	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	1290	which it is), lets them fire exactly once and destroys them again.
907	them again.
908		1291
909	Rewriting the benchmark to use many different sockets instead of using	1292	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	1293	distribution.
911	(socket creation is expensive), but qualitatively the same figures, so it
912	was not used.
913		1294
914	=head2 Explanation of the columns	1295	=head3 Explanation of the columns
915		1296
916	I<watcher> is the number of event watchers created/destroyed. Since	1297	I<watcher> is the number of event watchers created/destroyed. Since
917	different event models feature vastly different performances, each event	1298	different event models feature vastly different performances, each event
918	loop was given a number of watchers so that overall runtime is acceptable	1299	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	1300	and similar between tested event loop (and keep them from crashing): Glib
…		…
929	all watchers, to avoid adding memory overhead. That means closure creation	1310	all watchers, to avoid adding memory overhead. That means closure creation
930	and memory usage is not included in the figures.	1311	and memory usage is not included in the figures.
931		1312
932	I<invoke> is the time, in microseconds, used to invoke a simple	1313	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	1314	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	1315	invoked "watcher" times, it would C<< ->send >> a condvar once to
935	signal the end of this phase.	1316	signal the end of this phase.
936		1317
937	I<destroy> is the time, in microseconds, that it takes to destroy a single	1318	I<destroy> is the time, in microseconds, that it takes to destroy a single
938	watcher.	1319	watcher.
939		1320
940	=head2 Results	1321	=head3 Results
941		1322
942	name watchers bytes create invoke destroy comment	1323	name watchers bytes create invoke destroy comment
943	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1324	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	1325	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	1326	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	1327	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	1328	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	1329	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	1330	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	1331	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	1332	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	1333	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
953		1334
954	=head2 Discussion	1335	=head3 Discussion
955		1336
956	The benchmark does I<not> measure scalability of the event loop very	1337	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)	1338	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	1339	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	1340	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	1341	the same time, so select/poll-based implementations get an unnatural speed
961	boost.	1342	boost.
962		1343
		1344	Also, note that the number of watchers usually has a nonlinear effect on
		1345	overall speed, that is, creating twice as many watchers doesn't take twice
		1346	the time - usually it takes longer. This puts event loops tested with a
		1347	higher number of watchers at a disadvantage.
		1348
		1349	To put the range of results into perspective, consider that on the
		1350	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1351	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1352	cycles with POE.
		1353
963	C<EV> is the sole leader regarding speed and memory use, which are both	1354	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	1355	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	1356	far less memory than any other event loop and is still faster than Event
966	natively.	1357	natively.
967		1358
…		…
970	interpreter and the backend itself). Nevertheless this shows that it	1361	interpreter and the backend itself). Nevertheless this shows that it
971	adds very little overhead in itself. Like any select-based backend its	1362	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	1363	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.	1364	them active), of course, but this was not subject of this benchmark.
974		1365
975	The C<Event> module has a relatively high setup and callback invocation cost,	1366	The C<Event> module has a relatively high setup and callback invocation
976	but overall scores on the third place.	1367	cost, but overall scores in on the third place.
977		1368
978	C<Glib>'s memory usage is quite a bit bit higher, but it features a	1369	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	1370	faster callback invocation and overall ends up in the same class as
980	C<Event>. However, Glib scales extremely badly, doubling the number of	1371	C<Event>. However, Glib scales extremely badly, doubling the number of
981	watchers increases the processing time by more than a factor of four,	1372	watchers increases the processing time by more than a factor of four,
982	making it completely unusable when using larger numbers of watchers	1373	making it completely unusable when using larger numbers of watchers
983	(note that only a single file descriptor was used in the benchmark, so	1374	(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()	1380	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	1381	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	1382	hidden memory cost inside the kernel which is not reflected in the figures
992	above).	1383	above).
993		1384
994	C<POE>, regardless of underlying event loop (whether using its pure	1385	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	1386	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	1387	be tested because it wasn't working) shows abysmal performance and
997	and memory usage: Watchers use almost 30 times as much memory as	1388	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	1389	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	1390	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	1391	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1392	implementation.
		1393
1001	implementation. The design of the POE adaptor class in AnyEvent can not	1394	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	1395	for the performance issues, though, as session creation overhead is
1003	to execution of the state machine, which is coded pretty optimally within	1396	small compared to execution of the state machine, which is coded pretty
1004	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1397	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1398	using multiple sessions is not a good approach, especially regarding
		1399	memory usage, even the author of POE could not come up with a faster
		1400	design).
1005		1401
1006	=head2 Summary	1402	=head3 Summary
1007		1403
1008	=over 4	1404	=over 4
1009		1405
1010	=item * Using EV through AnyEvent is faster than any other event loop	1406	=item * Using EV through AnyEvent is faster than any other event loop
1011	(even when used without AnyEvent), but most event loops have acceptable	1407	(even when used without AnyEvent), but most event loops have acceptable
…		…
1013		1409
1014	=item * The overhead AnyEvent adds is usually much smaller than the overhead of	1410	=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	1411	the actual event loop, only with extremely fast event loops such as EV
1016	adds AnyEvent significant overhead.	1412	adds AnyEvent significant overhead.
1017		1413
1018	=item * You should simply avoid POE like the plague if you want performance or	1414	=item * You should avoid POE like the plague if you want performance or
1019	reasonable memory usage.	1415	reasonable memory usage.
1020		1416
1021	=back	1417	=back
1022		1418
		1419	=head2 BENCHMARKING THE LARGE SERVER CASE
		1420
		1421	This benchmark actually benchmarks the event loop itself. It works by
		1422	creating a number of "servers": each server consists of a socket pair, a
		1423	timeout watcher that gets reset on activity (but never fires), and an I/O
		1424	watcher waiting for input on one side of the socket. Each time the socket
		1425	watcher reads a byte it will write that byte to a random other "server".
		1426
		1427	The effect is that there will be a lot of I/O watchers, only part of which
		1428	are active at any one point (so there is a constant number of active
		1429	fds for each loop iteration, but which fds these are is random). The
		1430	timeout is reset each time something is read because that reflects how
		1431	most timeouts work (and puts extra pressure on the event loops).
		1432
		1433	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1434	(1%) are active. This mirrors the activity of large servers with many
		1435	connections, most of which are idle at any one point in time.
		1436
		1437	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1438	distribution.
		1439
		1440	=head3 Explanation of the columns
		1441
		1442	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1443	each server has a read and write socket end).
		1444
		1445	I<create> is the time it takes to create a socket pair (which is
		1446	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1447
		1448	I<request>, the most important value, is the time it takes to handle a
		1449	single "request", that is, reading the token from the pipe and forwarding
		1450	it to another server. This includes deleting the old timeout and creating
		1451	a new one that moves the timeout into the future.
		1452
		1453	=head3 Results
		1454
		1455	name sockets create request
		1456	EV 20000 69.01 11.16
		1457	Perl 20000 73.32 35.87
		1458	Event 20000 212.62 257.32
		1459	Glib 20000 651.16 1896.30
		1460	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1461
		1462	=head3 Discussion
		1463
		1464	This benchmark I<does> measure scalability and overall performance of the
		1465	particular event loop.
		1466
		1467	EV is again fastest. Since it is using epoll on my system, the setup time
		1468	is relatively high, though.
		1469
		1470	Perl surprisingly comes second. It is much faster than the C-based event
		1471	loops Event and Glib.
		1472
		1473	Event suffers from high setup time as well (look at its code and you will
		1474	understand why). Callback invocation also has a high overhead compared to
		1475	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1476	uses select or poll in basically all documented configurations.
		1477
		1478	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1479	clearly fails to perform with many filehandles or in busy servers.
		1480
		1481	POE is still completely out of the picture, taking over 1000 times as long
		1482	as EV, and over 100 times as long as the Perl implementation, even though
		1483	it uses a C-based event loop in this case.
		1484
		1485	=head3 Summary
		1486
		1487	=over 4
		1488
		1489	=item * The pure perl implementation performs extremely well.
		1490
		1491	=item * Avoid Glib or POE in large projects where performance matters.
		1492
		1493	=back
		1494
		1495	=head2 BENCHMARKING SMALL SERVERS
		1496
		1497	While event loops should scale (and select-based ones do not...) even to
		1498	large servers, most programs we (or I :) actually write have only a few
		1499	I/O watchers.
		1500
		1501	In this benchmark, I use the same benchmark program as in the large server
		1502	case, but it uses only eight "servers", of which three are active at any
		1503	one time. This should reflect performance for a small server relatively
		1504	well.
		1505
		1506	The columns are identical to the previous table.
		1507
		1508	=head3 Results
		1509
		1510	name sockets create request
		1511	EV 16 20.00 6.54
		1512	Perl 16 25.75 12.62
		1513	Event 16 81.27 35.86
		1514	Glib 16 32.63 15.48
		1515	POE 16 261.87 276.28 uses POE::Loop::Event
		1516
		1517	=head3 Discussion
		1518
		1519	The benchmark tries to test the performance of a typical small
		1520	server. While knowing how various event loops perform is interesting, keep
		1521	in mind that their overhead in this case is usually not as important, due
		1522	to the small absolute number of watchers (that is, you need efficiency and
		1523	speed most when you have lots of watchers, not when you only have a few of
		1524	them).
		1525
		1526	EV is again fastest.
		1527
		1528	Perl again comes second. It is noticeably faster than the C-based event
		1529	loops Event and Glib, although the difference is too small to really
		1530	matter.
		1531
		1532	POE also performs much better in this case, but is is still far behind the
		1533	others.
		1534
		1535	=head3 Summary
		1536
		1537	=over 4
		1538
		1539	=item * C-based event loops perform very well with small number of
		1540	watchers, as the management overhead dominates.
		1541
		1542	=back
		1543
1023		1544
1024	=head1 FORK	1545	=head1 FORK
1025		1546
1026	Most event libraries are not fork-safe. The ones who are usually are	1547	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.	1548	because they rely on inefficient but fork-safe C<select> or C<poll>
		1549	calls. Only L<EV> is fully fork-aware.
1028		1550
1029	If you have to fork, you must either do so I<before> creating your first	1551	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.	1552	watcher OR you must not use AnyEvent at all in the child.
1031		1553
1032		1554
…		…
1044		1566
1045	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1567	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1046		1568
1047	use AnyEvent;	1569	use AnyEvent;
1048		1570
		1571	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1572	be used to probe what backend is used and gain other information (which is
		1573	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
		1574
1049		1575
1050	=head1 SEE ALSO	1576	=head1 SEE ALSO
1051		1577
1052	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1578	Utility functions: L<AnyEvent::Util>.
1053	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1579
		1580	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1054	L<Event::Lib>, L<Qt>, L<POE>.	1581	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1055		1582
1056	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1583	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1057	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1584	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>,	1585	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1059	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1586	L<AnyEvent::Impl::POE>.
1060		1587
		1588	Non-blocking file handles, sockets, TCP clients and
		1589	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1590
		1591	Asynchronous DNS: L<AnyEvent::DNS>.
		1592
		1593	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1594
1061	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1595	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1062		1596
1063		1597
1064	=head1 AUTHOR	1598	=head1 AUTHOR
1065		1599
1066	Marc Lehmann <schmorp@schmorp.de>	1600	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 1.136 by root, Sun May 25 23:52:02 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 1.136 by root, Sun May 25 23:52:02 2008 UTC