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Revision 1.172 by root, Thu Jul 17 15:21:02 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
		23	=head1 INTRODUCTION/TUTORIAL
		24
		25	This manpage is mainly a reference manual. If you are interested
		26	in a tutorial or some gentle introduction, have a look at the
		27	L<AnyEvent::Intro> manpage.
22		28
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	29	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		30
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	31	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	32	nowadays. So what is different about AnyEvent?
27		33
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	34	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	35	policy> and AnyEvent is I<small and efficient>.
30		36
31	First and foremost, I<AnyEvent is not an event model> itself, it only	37	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	38	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	39	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	40	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	41	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	42	cannot change this, but it can hide the differences between those event
		43	loops.
37		44
38	The goal of AnyEvent is to offer module authors the ability to do event	45	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	46	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	47	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	48	module users into the same thing by forcing them to use the same event
42	model you use.	49	model you use.
43		50
44	For modules like POE or IO::Async (which is a total misnomer as it is	51	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	52	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	53	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	54	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	55	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	56	module are I<also> forced to use the same event loop you use.
50		57
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	58	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	59	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	60	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	61	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	62	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	63	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	64	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	65	to AnyEvent, too, so it is future-proof).
59		66
60	In addition to being free of having to use I<the one and only true event	67	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	68	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	69	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	70	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	71	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	72	technically possible.
66		73
		74	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		75	of useful functionality, such as an asynchronous DNS resolver, 100%
		76	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		77	such as Windows) and lots of real-world knowledge and workarounds for
		78	platform bugs and differences.
		79
67	Of course, if you want lots of policy (this can arguably be somewhat	80	Now, if you I<do 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	81	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	82	model, you should I<not> use this module.
70
71		83
72	=head1 DESCRIPTION	84	=head1 DESCRIPTION
73		85
74	L<AnyEvent> provides an identical interface to multiple event loops. This	86	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	87	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>	91	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	92	module.
81		93
82	During the first call of any watcher-creation method, the module tries	94	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	95	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>,	96	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	97	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	98	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	99	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	100	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	101	be successfully loaded will be used. If, after this, still none could be
…		…
103	starts using it, all bets are off. Maybe you should tell their authors to	115	starts using it, all bets are off. Maybe you should tell their authors to
104	use AnyEvent so their modules work together with others seamlessly...	116	use AnyEvent so their modules work together with others seamlessly...
105		117
106	The pure-perl implementation of AnyEvent is called	118	The pure-perl implementation of AnyEvent is called
107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	119	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
108	explicitly.	120	explicitly and enjoy the high availability of that event loop :)
109		121
110	=head1 WATCHERS	122	=head1 WATCHERS
111		123
112	AnyEvent has the central concept of a I<watcher>, which is an object that	124	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	125	stores relevant data for each kind of event you are waiting for, such as
114	the callback to call, the filehandle to watch, etc.	126	the callback to call, the file handle to watch, etc.
115		127
116	These watchers are normal Perl objects with normal Perl lifetime. After	128	These watchers are normal Perl objects with normal Perl lifetime. After
117	creating a watcher it will immediately "watch" for events and invoke the	129	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	130	callback when the event occurs (of course, only when the event model
119	is in control).	131	is in control).
…		…
127	Many watchers either are used with "recursion" (repeating timers for	139	Many watchers either are used with "recursion" (repeating timers for
128	example), or need to refer to their watcher object in other ways.	140	example), or need to refer to their watcher object in other ways.
129		141
130	An any way to achieve that is this pattern:	142	An any way to achieve that is this pattern:
131		143
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	144	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	145	# you can use $w here, for example to undef it
134	undef $w;	146	undef $w;
135	});	147	});
136		148
137	Note that C<my $w; $w => combination. This is necessary because in Perl,	149	Note that C<my $w; $w => combination. This is necessary because in Perl,
138	my variables are only visible after the statement in which they are	150	my variables are only visible after the statement in which they are
139	declared.	151	declared.
140		152
141	=head2 I/O WATCHERS	153	=head2 I/O WATCHERS
142		154
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	155	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	156	with the following mandatory key-value pairs as arguments:
145		157
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	158	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for events
147	for events. C<poll> must be a string that is either C<r> or C<w>,	159	(AnyEvent might or might not keep a reference to this file handle). C<poll>
148	which creates a watcher waiting for "r"eadable or "w"ritable events,	160	must be a string that is either C<r> or C<w>, which creates a watcher
149	respectively. C<cb> is the callback to invoke each time the file handle	161	waiting for "r"eadable or "w"ritable events, respectively. C<cb> is the
150	becomes ready.	162	callback to invoke each time the file handle becomes ready.
151		163
152	Although the callback might get passed parameters, their value and	164	Although the callback might get passed parameters, their value and
153	presence is undefined and you cannot rely on them. Portable AnyEvent	165	presence is undefined and you cannot rely on them. Portable AnyEvent
154	callbacks cannot use arguments passed to I/O watcher callbacks.	166	callbacks cannot use arguments passed to I/O watcher callbacks.
155		167
…		…
159		171
160	Some event loops issue spurious readyness notifications, so you should	172	Some event loops issue spurious readyness notifications, so you should
161	always use non-blocking calls when reading/writing from/to your file	173	always use non-blocking calls when reading/writing from/to your file
162	handles.	174	handles.
163		175
164	Example:
165
166	# wait for readability of STDIN, then read a line and disable the watcher	176	Example: wait for readability of STDIN, then read a line and disable the
		177	watcher.
		178
167	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	179	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
168	chomp (my $input = <STDIN>);	180	chomp (my $input = <STDIN>);
169	warn "read: $input\n";	181	warn "read: $input\n";
170	undef $w;	182	undef $w;
171	});	183	});
…		…
181		193
182	Although the callback might get passed parameters, their value and	194	Although the callback might get passed parameters, their value and
183	presence is undefined and you cannot rely on them. Portable AnyEvent	195	presence is undefined and you cannot rely on them. Portable AnyEvent
184	callbacks cannot use arguments passed to time watcher callbacks.	196	callbacks cannot use arguments passed to time watcher callbacks.
185		197
186	The timer callback will be invoked at most once: if you want a repeating	198	The callback will normally be invoked once only. If you specify another
187	timer you have to create a new watcher (this is a limitation by both Tk	199	parameter, C<interval>, as a strictly positive number (> 0), then the
188	and Glib).	200	callback will be invoked regularly at that interval (in fractional
		201	seconds) after the first invocation. If C<interval> is specified with a
		202	false value, then it is treated as if it were missing.
189		203
190	Example:	204	The callback will be rescheduled before invoking the callback, but no
		205	attempt is done to avoid timer drift in most backends, so the interval is
		206	only approximate.
191		207
192	# fire an event after 7.7 seconds	208	Example: fire an event after 7.7 seconds.
		209
193	my $w = AnyEvent->timer (after => 7.7, cb => sub {	210	my $w = AnyEvent->timer (after => 7.7, cb => sub {
194	warn "timeout\n";	211	warn "timeout\n";
195	});	212	});
196		213
197	# to cancel the timer:	214	# to cancel the timer:
198	undef $w;	215	undef $w;
199		216
200	Example 2:
201
202	# fire an event after 0.5 seconds, then roughly every second	217	Example 2: fire an event after 0.5 seconds, then roughly every second.
203	my $w;
204		218
205	my $cb = sub {
206	# cancel the old timer while creating a new one
207	$w = AnyEvent->timer (after => 1, cb => $cb);	219	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		220	warn "timeout\n";
208	};	221	};
209
210	# start the "loop" by creating the first watcher
211	$w = AnyEvent->timer (after => 0.5, cb => $cb);
212		222
213	=head3 TIMING ISSUES	223	=head3 TIMING ISSUES
214		224
215	There are two ways to handle timers: based on real time (relative, "fire	225	There are two ways to handle timers: based on real time (relative, "fire
216	in 10 seconds") and based on wallclock time (absolute, "fire at 12	226	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
228	timers.	238	timers.
229		239
230	AnyEvent always prefers relative timers, if available, matching the	240	AnyEvent always prefers relative timers, if available, matching the
231	AnyEvent API.	241	AnyEvent API.
232		242
		243	AnyEvent has two additional methods that return the "current time":
		244
		245	=over 4
		246
		247	=item AnyEvent->time
		248
		249	This returns the "current wallclock time" as a fractional number of
		250	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		251	return, and the result is guaranteed to be compatible with those).
		252
		253	It progresses independently of any event loop processing, i.e. each call
		254	will check the system clock, which usually gets updated frequently.
		255
		256	=item AnyEvent->now
		257
		258	This also returns the "current wallclock time", but unlike C<time>, above,
		259	this value might change only once per event loop iteration, depending on
		260	the event loop (most return the same time as C<time>, above). This is the
		261	time that AnyEvent's timers get scheduled against.
		262
		263	I<In almost all cases (in all cases if you don't care), this is the
		264	function to call when you want to know the current time.>
		265
		266	This function is also often faster then C<< AnyEvent->time >>, and
		267	thus the preferred method if you want some timestamp (for example,
		268	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		269
		270	The rest of this section is only of relevance if you try to be very exact
		271	with your timing, you can skip it without bad conscience.
		272
		273	For a practical example of when these times differ, consider L<Event::Lib>
		274	and L<EV> and the following set-up:
		275
		276	The event loop is running and has just invoked one of your callback at
		277	time=500 (assume no other callbacks delay processing). In your callback,
		278	you wait a second by executing C<sleep 1> (blocking the process for a
		279	second) and then (at time=501) you create a relative timer that fires
		280	after three seconds.
		281
		282	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		283	both return C<501>, because that is the current time, and the timer will
		284	be scheduled to fire at time=504 (C<501> + C<3>).
		285
		286	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		287	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		288	last event processing phase started. With L<EV>, your timer gets scheduled
		289	to run at time=503 (C<500> + C<3>).
		290
		291	In one sense, L<Event::Lib> is more exact, as it uses the current time
		292	regardless of any delays introduced by event processing. However, most
		293	callbacks do not expect large delays in processing, so this causes a
		294	higher drift (and a lot more system calls to get the current time).
		295
		296	In another sense, L<EV> is more exact, as your timer will be scheduled at
		297	the same time, regardless of how long event processing actually took.
		298
		299	In either case, if you care (and in most cases, you don't), then you
		300	can get whatever behaviour you want with any event loop, by taking the
		301	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		302	account.
		303
		304	=back
		305
233	=head2 SIGNAL WATCHERS	306	=head2 SIGNAL WATCHERS
234		307
235	You can watch for signals using a signal watcher, C<signal> is the signal	308	You can watch for signals using a signal watcher, C<signal> is the signal
236	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	309	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
237	be invoked whenever a signal occurs.	310	callback to be invoked whenever a signal occurs.
238		311
239	Although the callback might get passed parameters, their value and	312	Although the callback might get passed parameters, their value and
240	presence is undefined and you cannot rely on them. Portable AnyEvent	313	presence is undefined and you cannot rely on them. Portable AnyEvent
241	callbacks cannot use arguments passed to signal watcher callbacks.	314	callbacks cannot use arguments passed to signal watcher callbacks.
242		315
243	Multiple signal occurances can be clumped together into one callback	316	Multiple signal occurrences can be clumped together into one callback
244	invocation, and callback invocation will be synchronous. synchronous means	317	invocation, and callback invocation will be synchronous. Synchronous means
245	that it might take a while until the signal gets handled by the process,	318	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.	319	but it is guaranteed not to interrupt any other callbacks.
247		320
248	The main advantage of using these watchers is that you can share a signal	321	The main advantage of using these watchers is that you can share a signal
249	between multiple watchers.	322	between multiple watchers.
250		323
251	This watcher might use C<%SIG>, so programs overwriting those signals	324	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
278	AnyEvent program, you I<have> to create at least one watcher before you	351	AnyEvent program, you I<have> to create at least one watcher before you
279	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	352	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
280		353
281	Example: fork a process and wait for it	354	Example: fork a process and wait for it
282		355
283	my $done = AnyEvent->condvar;	356	my $done = AnyEvent->condvar;
284		357
285	AnyEvent::detect; # force event module to be initialised
286
287	my $pid = fork or exit 5;	358	my $pid = fork or exit 5;
288		359
289	my $w = AnyEvent->child (	360	my $w = AnyEvent->child (
290	pid => $pid,	361	pid => $pid,
291	cb => sub {	362	cb => sub {
292	my ($pid, $status) = @_;	363	my ($pid, $status) = @_;
293	warn "pid $pid exited with status $status";	364	warn "pid $pid exited with status $status";
294	$done->broadcast;	365	$done->send;
295	},	366	},
296	);	367	);
297		368
298	# do something else, then wait for process exit	369	# do something else, then wait for process exit
299	$done->wait;	370	$done->recv;
300		371
301	=head2 CONDITION VARIABLES	372	=head2 CONDITION VARIABLES
302		373
		374	If you are familiar with some event loops you will know that all of them
		375	require you to run some blocking "loop", "run" or similar function that
		376	will actively watch for new events and call your callbacks.
		377
		378	AnyEvent is different, it expects somebody else to run the event loop and
		379	will only block when necessary (usually when told by the user).
		380
		381	The instrument to do that is called a "condition variable", so called
		382	because they represent a condition that must become true.
		383
303	Condition variables can be created by calling the C<< AnyEvent->condvar >>	384	Condition variables can be created by calling the C<< AnyEvent->condvar
304	method without any arguments.	385	>> method, usually without arguments. The only argument pair allowed is
		386	C<cb>, which specifies a callback to be called when the condition variable
		387	becomes true.
305		388
306	A condition variable waits for a condition - precisely that the C<<	389	After creation, the condition variable is "false" until it becomes "true"
307	->broadcast >> method has been called.	390	by calling the C<send> method (or calling the condition variable as if it
		391	were a callback, read about the caveats in the description for the C<<
		392	->send >> method).
308		393
309	They are very useful to signal that a condition has been fulfilled, for	394	Condition variables are similar to callbacks, except that you can
		395	optionally wait for them. They can also be called merge points - points
		396	in time where multiple outstanding events have been processed. And yet
		397	another way to call them is transactions - each condition variable can be
		398	used to represent a transaction, which finishes at some point and delivers
		399	a result.
		400
		401	Condition variables are very useful to signal that something has finished,
310	example, if you write a module that does asynchronous http requests,	402	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	403	then a condition variable would be the ideal candidate to signal the
312	availability of results.	404	availability of results. The user can either act when the callback is
		405	called or can synchronously C<< ->recv >> for the results.
313		406
314	You can also use condition variables to block your main program until	407	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	408	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<<	409	could C<< ->recv >> in your main program until the user clicks the Quit
317	->broadcast >> the "quit" event.	410	button of your app, which would C<< ->send >> the "quit" event.
318		411
319	Note that condition variables recurse into the event loop - if you have	412	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	413	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	414	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,	415	you should avoid making a blocking wait yourself, at least in callbacks,
323	as this asks for trouble.	416	as this asks for trouble.
324		417
325	This object has two methods:	418	Condition variables are represented by hash refs in perl, and the keys
		419	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		420	easy (it is often useful to build your own transaction class on top of
		421	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		422	it's C<new> method in your own C<new> method.
		423
		424	There are two "sides" to a condition variable - the "producer side" which
		425	eventually calls C<< -> send >>, and the "consumer side", which waits
		426	for the send to occur.
		427
		428	Example: wait for a timer.
		429
		430	# wait till the result is ready
		431	my $result_ready = AnyEvent->condvar;
		432
		433	# do something such as adding a timer
		434	# or socket watcher the calls $result_ready->send
		435	# when the "result" is ready.
		436	# in this case, we simply use a timer:
		437	my $w = AnyEvent->timer (
		438	after => 1,
		439	cb => sub { $result_ready->send },
		440	);
		441
		442	# this "blocks" (while handling events) till the callback
		443	# calls send
		444	$result_ready->recv;
		445
		446	Example: wait for a timer, but take advantage of the fact that
		447	condition variables are also code references.
		448
		449	my $done = AnyEvent->condvar;
		450	my $delay = AnyEvent->timer (after => 5, cb => $done);
		451	$done->recv;
		452
		453	=head3 METHODS FOR PRODUCERS
		454
		455	These methods should only be used by the producing side, i.e. the
		456	code/module that eventually sends the signal. Note that it is also
		457	the producer side which creates the condvar in most cases, but it isn't
		458	uncommon for the consumer to create it as well.
326		459
327	=over 4	460	=over 4
328		461
		462	=item $cv->send (...)
		463
		464	Flag the condition as ready - a running C<< ->recv >> and all further
		465	calls to C<recv> will (eventually) return after this method has been
		466	called. If nobody is waiting the send will be remembered.
		467
		468	If a callback has been set on the condition variable, it is called
		469	immediately from within send.
		470
		471	Any arguments passed to the C<send> call will be returned by all
		472	future C<< ->recv >> calls.
		473
		474	Condition variables are overloaded so one can call them directly
		475	(as a code reference). Calling them directly is the same as calling
		476	C<send>. Note, however, that many C-based event loops do not handle
		477	overloading, so as tempting as it may be, passing a condition variable
		478	instead of a callback does not work. Both the pure perl and EV loops
		479	support overloading, however, as well as all functions that use perl to
		480	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		481	example).
		482
		483	=item $cv->croak ($error)
		484
		485	Similar to send, but causes all call's to C<< ->recv >> to invoke
		486	C<Carp::croak> with the given error message/object/scalar.
		487
		488	This can be used to signal any errors to the condition variable
		489	user/consumer.
		490
		491	=item $cv->begin ([group callback])
		492
329	=item $cv->wait	493	=item $cv->end
330		494
331	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	495	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		496
		497	These two methods can be used to combine many transactions/events into
		498	one. For example, a function that pings many hosts in parallel might want
		499	to use a condition variable for the whole process.
		500
		501	Every call to C<< ->begin >> will increment a counter, and every call to
		502	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		503	>>, the (last) callback passed to C<begin> will be executed. That callback
		504	is I<supposed> to call C<< ->send >>, but that is not required. If no
		505	callback was set, C<send> will be called without any arguments.
		506
		507	Let's clarify this with the ping example:
		508
		509	my $cv = AnyEvent->condvar;
		510
		511	my %result;
		512	$cv->begin (sub { $cv->send (\%result) });
		513
		514	for my $host (@list_of_hosts) {
		515	$cv->begin;
		516	ping_host_then_call_callback $host, sub {
		517	$result{$host} = ...;
		518	$cv->end;
		519	};
		520	}
		521
		522	$cv->end;
		523
		524	This code fragment supposedly pings a number of hosts and calls
		525	C<send> after results for all then have have been gathered - in any
		526	order. To achieve this, the code issues a call to C<begin> when it starts
		527	each ping request and calls C<end> when it has received some result for
		528	it. Since C<begin> and C<end> only maintain a counter, the order in which
		529	results arrive is not relevant.
		530
		531	There is an additional bracketing call to C<begin> and C<end> outside the
		532	loop, which serves two important purposes: first, it sets the callback
		533	to be called once the counter reaches C<0>, and second, it ensures that
		534	C<send> is called even when C<no> hosts are being pinged (the loop
		535	doesn't execute once).
		536
		537	This is the general pattern when you "fan out" into multiple subrequests:
		538	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		539	is called at least once, and then, for each subrequest you start, call
		540	C<begin> and for each subrequest you finish, call C<end>.
		541
		542	=back
		543
		544	=head3 METHODS FOR CONSUMERS
		545
		546	These methods should only be used by the consuming side, i.e. the
		547	code awaits the condition.
		548
		549	=over 4
		550
		551	=item $cv->recv
		552
		553	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
332	called on c<$cv>, while servicing other watchers normally.	554	>> methods have been called on c<$cv>, while servicing other watchers
		555	normally.
333		556
334	You can only wait once on a condition - additional calls will return	557	You can only wait once on a condition - additional calls are valid but
335	immediately.	558	will return immediately.
		559
		560	If an error condition has been set by calling C<< ->croak >>, then this
		561	function will call C<croak>.
		562
		563	In list context, all parameters passed to C<send> will be returned,
		564	in scalar context only the first one will be returned.
336		565
337	Not all event models support a blocking wait - some die in that case	566	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	567	(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	568	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	569	caller decide whether the call will block or not (for example, by coupling
341	condition variables with some kind of request results and supporting	570	condition variables with some kind of request results and supporting
342	callbacks so the caller knows that getting the result will not block,	571	callbacks so the caller knows that getting the result will not block,
343	while still suppporting blocking waits if the caller so desires).	572	while still supporting blocking waits if the caller so desires).
344		573
345	Another reason I<never> to C<< ->wait >> in a module is that you cannot	574	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	575	sensibly have two C<< ->recv >>'s in parallel, as that would require
347	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	576	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
348	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	577	can supply.
349	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
350	from different coroutines, however).
351		578
352	=item $cv->broadcast	579	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		580	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		581	versions and also integrates coroutines into AnyEvent, making blocking
		582	C<< ->recv >> calls perfectly safe as long as they are done from another
		583	coroutine (one that doesn't run the event loop).
353		584
354	Flag the condition as ready - a running C<< ->wait >> and all further	585	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	586	only calling C<< ->recv >> from within that callback (or at a later
356	called. If nobody is waiting the broadcast will be remembered..	587	time). This will work even when the event loop does not support blocking
		588	waits otherwise.
		589
		590	=item $bool = $cv->ready
		591
		592	Returns true when the condition is "true", i.e. whether C<send> or
		593	C<croak> have been called.
		594
		595	=item $cb = $cv->cb ([new callback])
		596
		597	This is a mutator function that returns the callback set and optionally
		598	replaces it before doing so.
		599
		600	The callback will be called when the condition becomes "true", i.e. when
		601	C<send> or C<croak> are called, with the only argument being the condition
		602	variable itself. Calling C<recv> inside the callback or at any later time
		603	is guaranteed not to block.
357		604
358	=back	605	=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	$result_ready->wait;
377		606
378	=head1 GLOBAL VARIABLES AND FUNCTIONS	607	=head1 GLOBAL VARIABLES AND FUNCTIONS
379		608
380	=over 4	609	=over 4
381		610
…		…
387	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	616	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
388	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	617	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
389		618
390	The known classes so far are:	619	The known classes so far are:
391		620
392	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
393	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
394	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	621	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
395	AnyEvent::Impl::Event based on Event, second best choice.	622	AnyEvent::Impl::Event based on Event, second best choice.
		623	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
396	AnyEvent::Impl::Glib based on Glib, third-best choice.	624	AnyEvent::Impl::Glib based on Glib, third-best choice.
397	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
398	AnyEvent::Impl::Tk based on Tk, very bad choice.	625	AnyEvent::Impl::Tk based on Tk, very bad choice.
399	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	626	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
400	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	627	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
401	AnyEvent::Impl::POE based on POE, not generic enough for full support.	628	AnyEvent::Impl::POE based on POE, not generic enough for full support.
402		629
…		…
415	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	642	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
416	if necessary. You should only call this function right before you would	643	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	644	have created an AnyEvent watcher anyway, that is, as late as possible at
418	runtime.	645	runtime.
419		646
		647	=item $guard = AnyEvent::post_detect { BLOCK }
		648
		649	Arranges for the code block to be executed as soon as the event model is
		650	autodetected (or immediately if this has already happened).
		651
		652	If called in scalar or list context, then it creates and returns an object
		653	that automatically removes the callback again when it is destroyed. See
		654	L<Coro::BDB> for a case where this is useful.
		655
		656	=item @AnyEvent::post_detect
		657
		658	If there are any code references in this array (you can C<push> to it
		659	before or after loading AnyEvent), then they will called directly after
		660	the event loop has been chosen.
		661
		662	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		663	if it contains a true value then the event loop has already been detected,
		664	and the array will be ignored.
		665
		666	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		667
420	=back	668	=back
421		669
422	=head1 WHAT TO DO IN A MODULE	670	=head1 WHAT TO DO IN A MODULE
423		671
424	As a module author, you should C<use AnyEvent> and call AnyEvent methods	672	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	675	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	676	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	677	by calling AnyEvent in your module body you force the user of your module
430	to load the event module first.	678	to load the event module first.
431		679
432	Never call C<< ->wait >> on a condition variable unless you I<know> that	680	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	681	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	682	because it will stall the whole program, and the whole point of using
435	events is to stay interactive.	683	events is to stay interactive.
436		684
437	It is fine, however, to call C<< ->wait >> when the user of your module	685	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	686	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 >>	687	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).	688	freely, as the user of your module knows what she is doing. always).
441		689
442	=head1 WHAT TO DO IN THE MAIN PROGRAM	690	=head1 WHAT TO DO IN THE MAIN PROGRAM
443		691
444	There will always be a single main program - the only place that should	692	There will always be a single main program - the only place that should
…		…
446		694
447	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	695	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	696	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.	697	decide which implementation to chose if some module relies on it.
450		698
451	If the main program relies on a specific event model. For example, in	699	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	700	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	701	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	702	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	703	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	704	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.	705	might chose the wrong one unless you load the correct one yourself.
458		706
459	You can chose to use a rather inefficient pure-perl implementation by	707	You can chose to use a pure-perl implementation by loading the
460	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	708	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
461	behaviour everywhere, but letting AnyEvent chose is generally better.	709	everywhere, but letting AnyEvent chose the model is generally better.
		710
		711	=head2 MAINLOOP EMULATION
		712
		713	Sometimes (often for short test scripts, or even standalone programs who
		714	only want to use AnyEvent), you do not want to run a specific event loop.
		715
		716	In that case, you can use a condition variable like this:
		717
		718	AnyEvent->condvar->recv;
		719
		720	This has the effect of entering the event loop and looping forever.
		721
		722	Note that usually your program has some exit condition, in which case
		723	it is better to use the "traditional" approach of storing a condition
		724	variable somewhere, waiting for it, and sending it when the program should
		725	exit cleanly.
		726
		727
		728	=head1 OTHER MODULES
		729
		730	The following is a non-exhaustive list of additional modules that use
		731	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		732	in the same program. Some of the modules come with AnyEvent, some are
		733	available via CPAN.
		734
		735	=over 4
		736
		737	=item L<AnyEvent::Util>
		738
		739	Contains various utility functions that replace often-used but blocking
		740	functions such as C<inet_aton> by event-/callback-based versions.
		741
		742	=item L<AnyEvent::Socket>
		743
		744	Provides various utility functions for (internet protocol) sockets,
		745	addresses and name resolution. Also functions to create non-blocking tcp
		746	connections or tcp servers, with IPv6 and SRV record support and more.
		747
		748	=item L<AnyEvent::Handle>
		749
		750	Provide read and write buffers, manages watchers for reads and writes,
		751	supports raw and formatted I/O, I/O queued and fully transparent and
		752	non-blocking SSL/TLS.
		753
		754	=item L<AnyEvent::DNS>
		755
		756	Provides rich asynchronous DNS resolver capabilities.
		757
		758	=item L<AnyEvent::HTTP>
		759
		760	A simple-to-use HTTP library that is capable of making a lot of concurrent
		761	HTTP requests.
		762
		763	=item L<AnyEvent::HTTPD>
		764
		765	Provides a simple web application server framework.
		766
		767	=item L<AnyEvent::FastPing>
		768
		769	The fastest ping in the west.
		770
		771	=item L<AnyEvent::DBI>
		772
		773	Executes L<DBI> requests asynchronously in a proxy process.
		774
		775	=item L<AnyEvent::AIO>
		776
		777	Truly asynchronous I/O, should be in the toolbox of every event
		778	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		779	together.
		780
		781	=item L<AnyEvent::BDB>
		782
		783	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		784	L<BDB> and AnyEvent together.
		785
		786	=item L<AnyEvent::GPSD>
		787
		788	A non-blocking interface to gpsd, a daemon delivering GPS information.
		789
		790	=item L<AnyEvent::IGS>
		791
		792	A non-blocking interface to the Internet Go Server protocol (used by
		793	L<App::IGS>).
		794
		795	=item L<Net::IRC3>
		796
		797	AnyEvent based IRC client module family.
		798
		799	=item L<Net::XMPP2>
		800
		801	AnyEvent based XMPP (Jabber protocol) module family.
		802
		803	=item L<Net::FCP>
		804
		805	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		806	of AnyEvent.
		807
		808	=item L<Event::ExecFlow>
		809
		810	High level API for event-based execution flow control.
		811
		812	=item L<Coro>
		813
		814	Has special support for AnyEvent via L<Coro::AnyEvent>.
		815
		816	=item L<IO::Lambda>
		817
		818	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		819
		820	=back
462		821
463	=cut	822	=cut
464		823
465	package AnyEvent;	824	package AnyEvent;
466		825
467	no warnings;	826	no warnings;
468	use strict;	827	use strict;
469		828
470	use Carp;	829	use Carp;
471		830
472	our $VERSION = '3.3';	831	our $VERSION = 4.22;
473	our $MODEL;	832	our $MODEL;
474		833
475	our $AUTOLOAD;	834	our $AUTOLOAD;
476	our @ISA;	835	our @ISA;
477		836
		837	our @REGISTRY;
		838
		839	our $WIN32;
		840
		841	BEGIN {
		842	my $win32 = ! ! ($^O =~ /mswin32/i);
		843	eval "sub WIN32(){ $win32 }";
		844	}
		845
478	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	846	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479		847
480	our @REGISTRY;	848	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		849
		850	{
		851	my $idx;
		852	$PROTOCOL{$_} = ++$idx
		853	for reverse split /\s*,\s*/,
		854	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		855	}
481		856
482	my @models = (	857	my @models = (
483	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
484	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485	[EV:: => AnyEvent::Impl::EV::],	858	[EV:: => AnyEvent::Impl::EV::],
486	[Event:: => AnyEvent::Impl::Event::],	859	[Event:: => AnyEvent::Impl::Event::],
487	[Glib:: => AnyEvent::Impl::Glib::],
488	[Tk:: => AnyEvent::Impl::Tk::],
489	[Wx:: => AnyEvent::Impl::POE::],
490	[Prima:: => AnyEvent::Impl::POE::],
491	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	860	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
492	# everything below here will not be autoprobed as the pureperl backend should work everywhere	861	# everything below here will not be autoprobed
		862	# as the pureperl backend should work everywhere
		863	# and is usually faster
		864	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		865	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
493	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	866	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
494	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	867	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
495	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	868	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		869	[Wx:: => AnyEvent::Impl::POE::],
		870	[Prima:: => AnyEvent::Impl::POE::],
496	);	871	);
497		872
498	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	873	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);
		874
		875	our @post_detect;
		876
		877	sub post_detect(&) {
		878	my ($cb) = @_;
		879
		880	if ($MODEL) {
		881	$cb->();
		882
		883	1
		884	} else {
		885	push @post_detect, $cb;
		886
		887	defined wantarray
		888	? bless \$cb, "AnyEvent::Util::PostDetect"
		889	: ()
		890	}
		891	}
		892
		893	sub AnyEvent::Util::PostDetect::DESTROY {
		894	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		895	}
499		896
500	sub detect() {	897	sub detect() {
501	unless ($MODEL) {	898	unless ($MODEL) {
502	no strict 'refs';	899	no strict 'refs';
		900	local $SIG{__DIE__};
503		901
504	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	902	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
505	my $model = "AnyEvent::Impl::$1";	903	my $model = "AnyEvent::Impl::$1";
506	if (eval "require $model") {	904	if (eval "require $model") {
507	$MODEL = $model;	905	$MODEL = $model;
…		…
537	last;	935	last;
538	}	936	}
539	}	937	}
540		938
541	$MODEL	939	$MODEL
542	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	940	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
543	}	941	}
544	}	942	}
545		943
		944	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		945
546	unshift @ISA, $MODEL;	946	unshift @ISA, $MODEL;
547	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	947
		948	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		949
		950	(shift @post_detect)->() while @post_detect;
548	}	951	}
549		952
550	$MODEL	953	$MODEL
551	}	954	}
552		955
…		…
560		963
561	my $class = shift;	964	my $class = shift;
562	$class->$func (@_);	965	$class->$func (@_);
563	}	966	}
564		967
		968	# utility function to dup a filehandle. this is used by many backends
		969	# to support binding more than one watcher per filehandle (they usually
		970	# allow only one watcher per fd, so we dup it to get a different one).
		971	sub _dupfh($$$$) {
		972	my ($poll, $fh, $r, $w) = @_;
		973
		974	require Fcntl;
		975
		976	# cygwin requires the fh mode to be matching, unix doesn't
		977	my ($rw, $mode) = $poll eq "r" ? ($r, "<")
		978	: $poll eq "w" ? ($w, ">")
		979	: Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
		980
		981	open my $fh2, "$mode&" . fileno $fh
		982	or die "cannot dup() filehandle: $!";
		983
		984	# we assume CLOEXEC is already set by perl in all important cases
		985
		986	($fh2, $rw)
		987	}
		988
565	package AnyEvent::Base;	989	package AnyEvent::Base;
566		990
		991	# default implementation for now and time
		992
		993	use Time::HiRes ();
		994
		995	sub time { Time::HiRes::time }
		996	sub now { Time::HiRes::time }
		997
567	# default implementation for ->condvar, ->wait, ->broadcast	998	# default implementation for ->condvar
568		999
569	sub condvar {	1000	sub condvar {
570	bless \my $flag, "AnyEvent::Base::CondVar"	1001	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	}	1002	}
580		1003
581	# default implementation for ->signal	1004	# default implementation for ->signal
582		1005
583	our %SIG_CB;	1006	our %SIG_CB;
…		…
599	sub AnyEvent::Base::Signal::DESTROY {	1022	sub AnyEvent::Base::Signal::DESTROY {
600	my ($signal, $cb) = @{$_[0]};	1023	my ($signal, $cb) = @{$_[0]};
601		1024
602	delete $SIG_CB{$signal}{$cb};	1025	delete $SIG_CB{$signal}{$cb};
603		1026
604	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1027	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
605	}	1028	}
606		1029
607	# default implementation for ->child	1030	# default implementation for ->child
608		1031
609	our %PID_CB;	1032	our %PID_CB;
…		…
636	or Carp::croak "required option 'pid' is missing";	1059	or Carp::croak "required option 'pid' is missing";
637		1060
638	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1061	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
639		1062
640	unless ($WNOHANG) {	1063	unless ($WNOHANG) {
641	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1064	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
642	}	1065	}
643		1066
644	unless ($CHLD_W) {	1067	unless ($CHLD_W) {
645	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1068	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
646	# child could be a zombie already, so make at least one round	1069	# child could be a zombie already, so make at least one round
…		…
656	delete $PID_CB{$pid}{$cb};	1079	delete $PID_CB{$pid}{$cb};
657	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1080	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
658		1081
659	undef $CHLD_W unless keys %PID_CB;	1082	undef $CHLD_W unless keys %PID_CB;
660	}	1083	}
		1084
		1085	package AnyEvent::CondVar;
		1086
		1087	our @ISA = AnyEvent::CondVar::Base::;
		1088
		1089	package AnyEvent::CondVar::Base;
		1090
		1091	use overload
		1092	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1093	fallback => 1;
		1094
		1095	sub _send {
		1096	# nop
		1097	}
		1098
		1099	sub send {
		1100	my $cv = shift;
		1101	$cv->{_ae_sent} = [@_];
		1102	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1103	$cv->_send;
		1104	}
		1105
		1106	sub croak {
		1107	$_[0]{_ae_croak} = $_[1];
		1108	$_[0]->send;
		1109	}
		1110
		1111	sub ready {
		1112	$_[0]{_ae_sent}
		1113	}
		1114
		1115	sub _wait {
		1116	AnyEvent->one_event while !$_[0]{_ae_sent};
		1117	}
		1118
		1119	sub recv {
		1120	$_[0]->_wait;
		1121
		1122	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1123	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1124	}
		1125
		1126	sub cb {
		1127	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1128	$_[0]{_ae_cb}
		1129	}
		1130
		1131	sub begin {
		1132	++$_[0]{_ae_counter};
		1133	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1134	}
		1135
		1136	sub end {
		1137	return if --$_[0]{_ae_counter};
		1138	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1139	}
		1140
		1141	# undocumented/compatibility with pre-3.4
		1142	*broadcast = \&send;
		1143	*wait = \&_wait;
661		1144
662	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1145	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
663		1146
664	This is an advanced topic that you do not normally need to use AnyEvent in	1147	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	1148	a module. This section is only of use to event loop authors who want to
…		…
719	C<PERL_ANYEVENT_MODEL>.	1202	C<PERL_ANYEVENT_MODEL>.
720		1203
721	When set to C<2> or higher, cause AnyEvent to report to STDERR which event	1204	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
722	model it chooses.	1205	model it chooses.
723		1206
		1207	=item C<PERL_ANYEVENT_STRICT>
		1208
		1209	AnyEvent does not do much argument checking by default, as thorough
		1210	argument checking is very costly. Setting this variable to a true value
		1211	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1212	check the arguments passed to most method calls. If it finds any problems
		1213	it will croak.
		1214
		1215	In other words, enables "strict" mode.
		1216
		1217	Unlike C<use strict> it is definitely recommended ot keep it off in
		1218	production.
		1219
724	=item C<PERL_ANYEVENT_MODEL>	1220	=item C<PERL_ANYEVENT_MODEL>
725		1221
726	This can be used to specify the event model to be used by AnyEvent, before	1222	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	1223	auto detection and -probing kicks in. It must be a string consisting
728	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended	1224	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,	1225	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	1226	used as event model. If it fails to load AnyEvent will proceed with
731	autodetection and -probing.	1227	auto detection and -probing.
732		1228
733	This functionality might change in future versions.	1229	This functionality might change in future versions.
734		1230
735	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you	1231	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
736	could start your program like this:	1232	could start your program like this:
737		1233
738	PERL_ANYEVENT_MODEL=Perl perl ...	1234	PERL_ANYEVENT_MODEL=Perl perl ...
		1235
		1236	=item C<PERL_ANYEVENT_PROTOCOLS>
		1237
		1238	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1239	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1240	of auto probing).
		1241
		1242	Must be set to a comma-separated list of protocols or address families,
		1243	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1244	used, and preference will be given to protocols mentioned earlier in the
		1245	list.
		1246
		1247	This variable can effectively be used for denial-of-service attacks
		1248	against local programs (e.g. when setuid), although the impact is likely
		1249	small, as the program has to handle connection errors already-
		1250
		1251	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1252	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1253	- only support IPv4, never try to resolve or contact IPv6
		1254	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1255	IPv6, but prefer IPv6 over IPv4.
		1256
		1257	=item C<PERL_ANYEVENT_EDNS0>
		1258
		1259	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1260	for DNS. This extension is generally useful to reduce DNS traffic, but
		1261	some (broken) firewalls drop such DNS packets, which is why it is off by
		1262	default.
		1263
		1264	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1265	EDNS0 in its DNS requests.
		1266
		1267	=item C<PERL_ANYEVENT_MAX_FORKS>
		1268
		1269	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1270	will create in parallel.
739		1271
740	=back	1272	=back
741		1273
742	=head1 EXAMPLE PROGRAM	1274	=head1 EXAMPLE PROGRAM
743		1275
…		…
754	poll => 'r',	1286	poll => 'r',
755	cb => sub {	1287	cb => sub {
756	warn "io event <$_[0]>\n"; # will always output <r>	1288	warn "io event <$_[0]>\n"; # will always output <r>
757	chomp (my $input = <STDIN>); # read a line	1289	chomp (my $input = <STDIN>); # read a line
758	warn "read: $input\n"; # output what has been read	1290	warn "read: $input\n"; # output what has been read
759	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1291	$cv->send if $input =~ /^q/i; # quit program if /^q/i
760	},	1292	},
761	);	1293	);
762		1294
763	my $time_watcher; # can only be used once	1295	my $time_watcher; # can only be used once
764		1296
…		…
769	});	1301	});
770	}	1302	}
771		1303
772	new_timer; # create first timer	1304	new_timer; # create first timer
773		1305
774	$cv->wait; # wait until user enters /^q/i	1306	$cv->recv; # wait until user enters /^q/i
775		1307
776	=head1 REAL-WORLD EXAMPLE	1308	=head1 REAL-WORLD EXAMPLE
777		1309
778	Consider the L<Net::FCP> module. It features (among others) the following	1310	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:	1311	API calls, which are to freenet what HTTP GET requests are to http:
…		…
829	syswrite $txn->{fh}, $txn->{request}	1361	syswrite $txn->{fh}, $txn->{request}
830	or die "connection or write error";	1362	or die "connection or write error";
831	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1363	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
832		1364
833	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1365	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:	1366	result and signals any possible waiters that the request has finished:
835		1367
836	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1368	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
837		1369
838	if (end-of-file or data complete) {	1370	if (end-of-file or data complete) {
839	$txn->{result} = $txn->{buf};	1371	$txn->{result} = $txn->{buf};
840	$txn->{finished}->broadcast;	1372	$txn->{finished}->send;
841	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1373	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
842	}	1374	}
843		1375
844	The C<result> method, finally, just waits for the finished signal (if the	1376	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	1377	request was already finished, it doesn't wait, of course, and returns the
846	data:	1378	data:
847		1379
848	$txn->{finished}->wait;	1380	$txn->{finished}->recv;
849	return $txn->{result};	1381	return $txn->{result};
850		1382
851	The actual code goes further and collects all errors (C<die>s, exceptions)	1383	The actual code goes further and collects all errors (C<die>s, exceptions)
852	that occured during request processing. The C<result> method detects	1384	that occurred during request processing. The C<result> method detects
853	whether an exception as thrown (it is stored inside the $txn object)	1385	whether an exception as thrown (it is stored inside the $txn object)
854	and just throws the exception, which means connection errors and other	1386	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	1387	problems get reported tot he code that tries to use the result, not in a
856	random callback.	1388	random callback.
857		1389
…		…
888		1420
889	my $quit = AnyEvent->condvar;	1421	my $quit = AnyEvent->condvar;
890		1422
891	$fcp->txn_client_get ($url)->cb (sub {	1423	$fcp->txn_client_get ($url)->cb (sub {
892	...	1424	...
893	$quit->broadcast;	1425	$quit->send;
894	});	1426	});
895		1427
896	$quit->wait;	1428	$quit->recv;
897		1429
898		1430
899	=head1 BENCHMARK	1431	=head1 BENCHMARKS
900		1432
901	To give you an idea of the performance and overheads that AnyEvent adds	1433	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	1434	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	1435	of various event loops I prepared some benchmarks.
904	event models natively and with anyevent. The benchmark creates a lot of	1436
905	timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to	1437	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1438
		1439	Here is a benchmark of various supported event models used natively and
		1440	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1441	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	1442	which it is), lets them fire exactly once and destroys them again.
907	them again.
908		1443
909	Rewriting the benchmark to use many different sockets instead of using	1444	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	1445	distribution.
911	(socket creation is expensive), but qualitatively the same figures, so it
912	was not used.
913		1446
914	=head2 Explanation of the columns	1447	=head3 Explanation of the columns
915		1448
916	I<watcher> is the number of event watchers created/destroyed. Since	1449	I<watcher> is the number of event watchers created/destroyed. Since
917	different event models feature vastly different performances, each event	1450	different event models feature vastly different performances, each event
918	loop was given a number of watchers so that overall runtime is acceptable	1451	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	1452	and similar between tested event loop (and keep them from crashing): Glib
…		…
929	all watchers, to avoid adding memory overhead. That means closure creation	1462	all watchers, to avoid adding memory overhead. That means closure creation
930	and memory usage is not included in the figures.	1463	and memory usage is not included in the figures.
931		1464
932	I<invoke> is the time, in microseconds, used to invoke a simple	1465	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	1466	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	1467	invoked "watcher" times, it would C<< ->send >> a condvar once to
935	signal the end of this phase.	1468	signal the end of this phase.
936		1469
937	I<destroy> is the time, in microseconds, that it takes to destroy a single	1470	I<destroy> is the time, in microseconds, that it takes to destroy a single
938	watcher.	1471	watcher.
939		1472
940	=head2 Results	1473	=head3 Results
941		1474
942	name watchers bytes create invoke destroy comment	1475	name watchers bytes create invoke destroy comment
943	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1476	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	1477	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	1478	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	1479	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	1480	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	1481	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	1482	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	1483	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	1484	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	1485	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
953		1486
954	=head2 Discussion	1487	=head3 Discussion
955		1488
956	The benchmark does I<not> measure scalability of the event loop very	1489	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)	1490	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	1491	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	1492	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	1493	the same time, so select/poll-based implementations get an unnatural speed
961	boost.	1494	boost.
962		1495
		1496	Also, note that the number of watchers usually has a nonlinear effect on
		1497	overall speed, that is, creating twice as many watchers doesn't take twice
		1498	the time - usually it takes longer. This puts event loops tested with a
		1499	higher number of watchers at a disadvantage.
		1500
		1501	To put the range of results into perspective, consider that on the
		1502	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1503	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1504	cycles with POE.
		1505
963	C<EV> is the sole leader regarding speed and memory use, which are both	1506	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	1507	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	1508	far less memory than any other event loop and is still faster than Event
966	natively.	1509	natively.
967		1510
…		…
970	interpreter and the backend itself). Nevertheless this shows that it	1513	interpreter and the backend itself). Nevertheless this shows that it
971	adds very little overhead in itself. Like any select-based backend its	1514	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	1515	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.	1516	them active), of course, but this was not subject of this benchmark.
974		1517
975	The C<Event> module has a relatively high setup and callback invocation cost,	1518	The C<Event> module has a relatively high setup and callback invocation
976	but overall scores on the third place.	1519	cost, but overall scores in on the third place.
977		1520
978	C<Glib>'s memory usage is quite a bit bit higher, but it features a	1521	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	1522	faster callback invocation and overall ends up in the same class as
980	C<Event>. However, Glib scales extremely badly, doubling the number of	1523	C<Event>. However, Glib scales extremely badly, doubling the number of
981	watchers increases the processing time by more than a factor of four,	1524	watchers increases the processing time by more than a factor of four,
982	making it completely unusable when using larger numbers of watchers	1525	making it completely unusable when using larger numbers of watchers
983	(note that only a single file descriptor was used in the benchmark, so	1526	(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()	1532	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	1533	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	1534	hidden memory cost inside the kernel which is not reflected in the figures
992	above).	1535	above).
993		1536
994	C<POE>, regardless of underlying event loop (whether using its pure	1537	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	1538	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	1539	be tested because it wasn't working) shows abysmal performance and
997	and memory usage: Watchers use almost 30 times as much memory as	1540	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	1541	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	1542	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	1543	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1544	implementation.
		1545
1001	implementation. The design of the POE adaptor class in AnyEvent can not	1546	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	1547	for the performance issues, though, as session creation overhead is
1003	to execution of the state machine, which is coded pretty optimally within	1548	small compared to execution of the state machine, which is coded pretty
1004	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1549	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1550	using multiple sessions is not a good approach, especially regarding
		1551	memory usage, even the author of POE could not come up with a faster
		1552	design).
1005		1553
1006	=head2 Summary	1554	=head3 Summary
1007		1555
1008	=over 4	1556	=over 4
1009		1557
1010	=item * Using EV through AnyEvent is faster than any other event loop	1558	=item * Using EV through AnyEvent is faster than any other event loop
1011	(even when used without AnyEvent), but most event loops have acceptable	1559	(even when used without AnyEvent), but most event loops have acceptable
…		…
1013		1561
1014	=item * The overhead AnyEvent adds is usually much smaller than the overhead of	1562	=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	1563	the actual event loop, only with extremely fast event loops such as EV
1016	adds AnyEvent significant overhead.	1564	adds AnyEvent significant overhead.
1017		1565
1018	=item * You should simply avoid POE like the plague if you want performance or	1566	=item * You should avoid POE like the plague if you want performance or
1019	reasonable memory usage.	1567	reasonable memory usage.
1020		1568
1021	=back	1569	=back
1022		1570
		1571	=head2 BENCHMARKING THE LARGE SERVER CASE
		1572
		1573	This benchmark actually benchmarks the event loop itself. It works by
		1574	creating a number of "servers": each server consists of a socket pair, a
		1575	timeout watcher that gets reset on activity (but never fires), and an I/O
		1576	watcher waiting for input on one side of the socket. Each time the socket
		1577	watcher reads a byte it will write that byte to a random other "server".
		1578
		1579	The effect is that there will be a lot of I/O watchers, only part of which
		1580	are active at any one point (so there is a constant number of active
		1581	fds for each loop iteration, but which fds these are is random). The
		1582	timeout is reset each time something is read because that reflects how
		1583	most timeouts work (and puts extra pressure on the event loops).
		1584
		1585	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1586	(1%) are active. This mirrors the activity of large servers with many
		1587	connections, most of which are idle at any one point in time.
		1588
		1589	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1590	distribution.
		1591
		1592	=head3 Explanation of the columns
		1593
		1594	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1595	each server has a read and write socket end).
		1596
		1597	I<create> is the time it takes to create a socket pair (which is
		1598	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1599
		1600	I<request>, the most important value, is the time it takes to handle a
		1601	single "request", that is, reading the token from the pipe and forwarding
		1602	it to another server. This includes deleting the old timeout and creating
		1603	a new one that moves the timeout into the future.
		1604
		1605	=head3 Results
		1606
		1607	name sockets create request
		1608	EV 20000 69.01 11.16
		1609	Perl 20000 73.32 35.87
		1610	Event 20000 212.62 257.32
		1611	Glib 20000 651.16 1896.30
		1612	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1613
		1614	=head3 Discussion
		1615
		1616	This benchmark I<does> measure scalability and overall performance of the
		1617	particular event loop.
		1618
		1619	EV is again fastest. Since it is using epoll on my system, the setup time
		1620	is relatively high, though.
		1621
		1622	Perl surprisingly comes second. It is much faster than the C-based event
		1623	loops Event and Glib.
		1624
		1625	Event suffers from high setup time as well (look at its code and you will
		1626	understand why). Callback invocation also has a high overhead compared to
		1627	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1628	uses select or poll in basically all documented configurations.
		1629
		1630	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1631	clearly fails to perform with many filehandles or in busy servers.
		1632
		1633	POE is still completely out of the picture, taking over 1000 times as long
		1634	as EV, and over 100 times as long as the Perl implementation, even though
		1635	it uses a C-based event loop in this case.
		1636
		1637	=head3 Summary
		1638
		1639	=over 4
		1640
		1641	=item * The pure perl implementation performs extremely well.
		1642
		1643	=item * Avoid Glib or POE in large projects where performance matters.
		1644
		1645	=back
		1646
		1647	=head2 BENCHMARKING SMALL SERVERS
		1648
		1649	While event loops should scale (and select-based ones do not...) even to
		1650	large servers, most programs we (or I :) actually write have only a few
		1651	I/O watchers.
		1652
		1653	In this benchmark, I use the same benchmark program as in the large server
		1654	case, but it uses only eight "servers", of which three are active at any
		1655	one time. This should reflect performance for a small server relatively
		1656	well.
		1657
		1658	The columns are identical to the previous table.
		1659
		1660	=head3 Results
		1661
		1662	name sockets create request
		1663	EV 16 20.00 6.54
		1664	Perl 16 25.75 12.62
		1665	Event 16 81.27 35.86
		1666	Glib 16 32.63 15.48
		1667	POE 16 261.87 276.28 uses POE::Loop::Event
		1668
		1669	=head3 Discussion
		1670
		1671	The benchmark tries to test the performance of a typical small
		1672	server. While knowing how various event loops perform is interesting, keep
		1673	in mind that their overhead in this case is usually not as important, due
		1674	to the small absolute number of watchers (that is, you need efficiency and
		1675	speed most when you have lots of watchers, not when you only have a few of
		1676	them).
		1677
		1678	EV is again fastest.
		1679
		1680	Perl again comes second. It is noticeably faster than the C-based event
		1681	loops Event and Glib, although the difference is too small to really
		1682	matter.
		1683
		1684	POE also performs much better in this case, but is is still far behind the
		1685	others.
		1686
		1687	=head3 Summary
		1688
		1689	=over 4
		1690
		1691	=item * C-based event loops perform very well with small number of
		1692	watchers, as the management overhead dominates.
		1693
		1694	=back
		1695
1023		1696
1024	=head1 FORK	1697	=head1 FORK
1025		1698
1026	Most event libraries are not fork-safe. The ones who are usually are	1699	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.	1700	because they rely on inefficient but fork-safe C<select> or C<poll>
		1701	calls. Only L<EV> is fully fork-aware.
1028		1702
1029	If you have to fork, you must either do so I<before> creating your first	1703	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.	1704	watcher OR you must not use AnyEvent at all in the child.
1031		1705
1032		1706
…		…
1040	specified in the variable.	1714	specified in the variable.
1041		1715
1042	You can make AnyEvent completely ignore this variable by deleting it	1716	You can make AnyEvent completely ignore this variable by deleting it
1043	before the first watcher gets created, e.g. with a C<BEGIN> block:	1717	before the first watcher gets created, e.g. with a C<BEGIN> block:
1044		1718
1045	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1719	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1046		1720
1047	use AnyEvent;	1721	use AnyEvent;
		1722
		1723	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1724	be used to probe what backend is used and gain other information (which is
		1725	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		1726	$ENV{PERL_ANYEGENT_STRICT}.
		1727
		1728
		1729	=head1 BUGS
		1730
		1731	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		1732	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		1733	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		1734	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as
		1735	pronounced).
1048		1736
1049		1737
1050	=head1 SEE ALSO	1738	=head1 SEE ALSO
1051		1739
1052	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1740	Utility functions: L<AnyEvent::Util>.
1053	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1741
		1742	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1054	L<Event::Lib>, L<Qt>, L<POE>.	1743	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1055		1744
1056	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1745	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1057	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1746	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>,	1747	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1059	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1748	L<AnyEvent::Impl::POE>.
1060		1749
		1750	Non-blocking file handles, sockets, TCP clients and
		1751	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1752
		1753	Asynchronous DNS: L<AnyEvent::DNS>.
		1754
		1755	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1756
1061	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1757	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1062		1758
1063		1759
1064	=head1 AUTHOR	1760	=head1 AUTHOR
1065		1761
1066	Marc Lehmann <schmorp@schmorp.de>	1762	Marc Lehmann <schmorp@schmorp.de>
1067	http://home.schmorp.de/	1763	http://home.schmorp.de/
1068		1764
1069	=cut	1765	=cut
1070		1766
1071	1	1767	1
1072		1768

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