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Revision 1.164 by root, Tue Jul 8 19:50:25 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?
…		…
48	isn't itself. What's worse, all the potential users of your module are	54	isn't itself. What's worse, all the potential users of your module are
49	I<also> forced to use the same event loop you use.	55	I<also> forced to use the same event loop you use.
50		56
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	57	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	58	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	59	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,	60	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	61	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	62	event models it supports (including stuff like POE and IO::Async, as long
57	as those use one of the supported event loops. It is trivial to add new	63	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).	64	event loops to AnyEvent, too, so it is future-proof).
59		65
60	In addition to being free of having to use I<the one and only true event	66	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	67	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	68	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	69	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	70	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	71	technically possible.
66		72
		73	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		74	of useful functionality, such as an asynchronous DNS resolver, 100%
		75	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		76	such as Windows) and lots of real-world knowledge and workarounds for
		77	platform bugs and differences.
		78
67	Of course, if you want lots of policy (this can arguably be somewhat	79	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	80	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	81	model, you should I<not> use this module.
70
71		82
72	=head1 DESCRIPTION	83	=head1 DESCRIPTION
73		84
74	L<AnyEvent> provides an identical interface to multiple event loops. This	85	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	86	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>	90	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	91	module.
81		92
82	During the first call of any watcher-creation method, the module tries	93	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	94	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>,	95	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	96	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	97	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	98	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	99	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	100	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	114	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...	115	use AnyEvent so their modules work together with others seamlessly...
105		116
106	The pure-perl implementation of AnyEvent is called	117	The pure-perl implementation of AnyEvent is called
107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	118	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
108	explicitly.	119	explicitly and enjoy the high availability of that event loop :)
109		120
110	=head1 WATCHERS	121	=head1 WATCHERS
111		122
112	AnyEvent has the central concept of a I<watcher>, which is an object that	123	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	124	stores relevant data for each kind of event you are waiting for, such as
114	the callback to call, the filehandle to watch, etc.	125	the callback to call, the file handle to watch, etc.
115		126
116	These watchers are normal Perl objects with normal Perl lifetime. After	127	These watchers are normal Perl objects with normal Perl lifetime. After
117	creating a watcher it will immediately "watch" for events and invoke the	128	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	129	callback when the event occurs (of course, only when the event model
119	is in control).	130	is in control).
…		…
127	Many watchers either are used with "recursion" (repeating timers for	138	Many watchers either are used with "recursion" (repeating timers for
128	example), or need to refer to their watcher object in other ways.	139	example), or need to refer to their watcher object in other ways.
129		140
130	An any way to achieve that is this pattern:	141	An any way to achieve that is this pattern:
131		142
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	143	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	144	# you can use $w here, for example to undef it
134	undef $w;	145	undef $w;
135	});	146	});
136		147
137	Note that C<my $w; $w => combination. This is necessary because in Perl,	148	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	149	my variables are only visible after the statement in which they are
139	declared.	150	declared.
140		151
141	=head2 I/O WATCHERS	152	=head2 I/O WATCHERS
142		153
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	154	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	155	with the following mandatory key-value pairs as arguments:
145		156
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	157	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch
147	events. C<poll> must be a string that is either C<r> or C<w>, which	158	for events. C<poll> must be a string that is either C<r> or C<w>,
148	creates a watcher waiting for "r"eadable or "w"ritable events,	159	which creates a watcher waiting for "r"eadable or "w"ritable events,
149	respectively. C<cb> is the callback to invoke each time the file handle	160	respectively. C<cb> is the callback to invoke each time the file handle
150	becomes ready.	161	becomes ready.
151		162
		163	Although the callback might get passed parameters, their value and
		164	presence is undefined and you cannot rely on them. Portable AnyEvent
		165	callbacks cannot use arguments passed to I/O watcher callbacks.
		166
152	The I/O watcher might use the underlying file descriptor or a copy of it.	167	The I/O watcher might use the underlying file descriptor or a copy of it.
153	It is not allowed to close a file handle as long as any watcher is active	168	You must not close a file handle as long as any watcher is active on the
154	on the underlying file descriptor.	169	underlying file descriptor.
155		170
156	Some event loops issue spurious readyness notifications, so you should	171	Some event loops issue spurious readyness notifications, so you should
157	always use non-blocking calls when reading/writing from/to your file	172	always use non-blocking calls when reading/writing from/to your file
158	handles.	173	handles.
159		174
160	Example:
161
162	# wait for readability of STDIN, then read a line and disable the watcher	175	Example: wait for readability of STDIN, then read a line and disable the
		176	watcher.
		177
163	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	178	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
164	chomp (my $input = <STDIN>);	179	chomp (my $input = <STDIN>);
165	warn "read: $input\n";	180	warn "read: $input\n";
166	undef $w;	181	undef $w;
167	});	182	});
…		…
170		185
171	You can create a time watcher by calling the C<< AnyEvent->timer >>	186	You can create a time watcher by calling the C<< AnyEvent->timer >>
172	method with the following mandatory arguments:	187	method with the following mandatory arguments:
173		188
174	C<after> specifies after how many seconds (fractional values are	189	C<after> specifies after how many seconds (fractional values are
175	supported) should the timer activate. C<cb> the callback to invoke in that	190	supported) the callback should be invoked. C<cb> is the callback to invoke
176	case.	191	in that case.
177		192
178	The timer callback will be invoked at most once: if you want a repeating	193	Although the callback might get passed parameters, their value and
179	timer you have to create a new watcher (this is a limitation by both Tk	194	presence is undefined and you cannot rely on them. Portable AnyEvent
180	and Glib).	195	callbacks cannot use arguments passed to time watcher callbacks.
181		196
182	Example:	197	The callback will normally be invoked once only. If you specify another
		198	parameter, C<interval>, as a positive number, then the callback will be
		199	invoked regularly at that interval (in fractional seconds) after the first
		200	invocation.
183		201
		202	The callback will be rescheduled before invoking the callback, but no
		203	attempt is done to avoid timer drift in most backends, so the interval is
		204	only approximate.
		205
184	# fire an event after 7.7 seconds	206	Example: fire an event after 7.7 seconds.
		207
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	208	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	209	warn "timeout\n";
187	});	210	});
188		211
189	# to cancel the timer:	212	# to cancel the timer:
190	undef $w;	213	undef $w;
191		214
192	Example 2:
193
194	# fire an event after 0.5 seconds, then roughly every second	215	Example 2: fire an event after 0.5 seconds, then roughly every second.
195	my $w;
196		216
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	217	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		218	warn "timeout\n";
200	};	219	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		220
205	=head3 TIMING ISSUES	221	=head3 TIMING ISSUES
206		222
207	There are two ways to handle timers: based on real time (relative, "fire	223	There are two ways to handle timers: based on real time (relative, "fire
208	in 10 seconds") and based on wallclock time (absolute, "fire at 12	224	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
220	timers.	236	timers.
221		237
222	AnyEvent always prefers relative timers, if available, matching the	238	AnyEvent always prefers relative timers, if available, matching the
223	AnyEvent API.	239	AnyEvent API.
224		240
		241	AnyEvent has two additional methods that return the "current time":
		242
		243	=over 4
		244
		245	=item AnyEvent->time
		246
		247	This returns the "current wallclock time" as a fractional number of
		248	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		249	return, and the result is guaranteed to be compatible with those).
		250
		251	It progresses independently of any event loop processing, i.e. each call
		252	will check the system clock, which usually gets updated frequently.
		253
		254	=item AnyEvent->now
		255
		256	This also returns the "current wallclock time", but unlike C<time>, above,
		257	this value might change only once per event loop iteration, depending on
		258	the event loop (most return the same time as C<time>, above). This is the
		259	time that AnyEvent's timers get scheduled against.
		260
		261	I<In almost all cases (in all cases if you don't care), this is the
		262	function to call when you want to know the current time.>
		263
		264	This function is also often faster then C<< AnyEvent->time >>, and
		265	thus the preferred method if you want some timestamp (for example,
		266	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		267
		268	The rest of this section is only of relevance if you try to be very exact
		269	with your timing, you can skip it without bad conscience.
		270
		271	For a practical example of when these times differ, consider L<Event::Lib>
		272	and L<EV> and the following set-up:
		273
		274	The event loop is running and has just invoked one of your callback at
		275	time=500 (assume no other callbacks delay processing). In your callback,
		276	you wait a second by executing C<sleep 1> (blocking the process for a
		277	second) and then (at time=501) you create a relative timer that fires
		278	after three seconds.
		279
		280	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		281	both return C<501>, because that is the current time, and the timer will
		282	be scheduled to fire at time=504 (C<501> + C<3>).
		283
		284	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		285	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		286	last event processing phase started. With L<EV>, your timer gets scheduled
		287	to run at time=503 (C<500> + C<3>).
		288
		289	In one sense, L<Event::Lib> is more exact, as it uses the current time
		290	regardless of any delays introduced by event processing. However, most
		291	callbacks do not expect large delays in processing, so this causes a
		292	higher drift (and a lot more system calls to get the current time).
		293
		294	In another sense, L<EV> is more exact, as your timer will be scheduled at
		295	the same time, regardless of how long event processing actually took.
		296
		297	In either case, if you care (and in most cases, you don't), then you
		298	can get whatever behaviour you want with any event loop, by taking the
		299	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		300	account.
		301
		302	=back
		303
225	=head2 SIGNAL WATCHERS	304	=head2 SIGNAL WATCHERS
226		305
227	You can watch for signals using a signal watcher, C<signal> is the signal	306	You can watch for signals using a signal watcher, C<signal> is the signal
228	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	307	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
229	be invoked whenever a signal occurs.	308	be invoked whenever a signal occurs.
230		309
		310	Although the callback might get passed parameters, their value and
		311	presence is undefined and you cannot rely on them. Portable AnyEvent
		312	callbacks cannot use arguments passed to signal watcher callbacks.
		313
231	Multiple signal occurances can be clumped together into one callback	314	Multiple signal occurrences can be clumped together into one callback
232	invocation, and callback invocation will be synchronous. synchronous means	315	invocation, and callback invocation will be synchronous. Synchronous means
233	that it might take a while until the signal gets handled by the process,	316	that it might take a while until the signal gets handled by the process,
234	but it is guarenteed not to interrupt any other callbacks.	317	but it is guaranteed not to interrupt any other callbacks.
235		318
236	The main advantage of using these watchers is that you can share a signal	319	The main advantage of using these watchers is that you can share a signal
237	between multiple watchers.	320	between multiple watchers.
238		321
239	This watcher might use C<%SIG>, so programs overwriting those signals	322	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
249		332
250	The child process is specified by the C<pid> argument (if set to C<0>, it	333	The child process is specified by the C<pid> argument (if set to C<0>, it
251	watches for any child process exit). The watcher will trigger as often	334	watches for any child process exit). The watcher will trigger as often
252	as status change for the child are received. This works by installing a	335	as status change for the child are received. This works by installing a
253	signal handler for C<SIGCHLD>. The callback will be called with the pid	336	signal handler for C<SIGCHLD>. The callback will be called with the pid
254	and exit status (as returned by waitpid).	337	and exit status (as returned by waitpid), so unlike other watcher types,
		338	you I<can> rely on child watcher callback arguments.
255		339
256	There is a slight catch to child watchers, however: you usually start them	340	There is a slight catch to child watchers, however: you usually start them
257	I<after> the child process was created, and this means the process could	341	I<after> the child process was created, and this means the process could
258	have exited already (and no SIGCHLD will be sent anymore).	342	have exited already (and no SIGCHLD will be sent anymore).
259		343
…		…
265	AnyEvent program, you I<have> to create at least one watcher before you	349	AnyEvent program, you I<have> to create at least one watcher before you
266	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	350	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
267		351
268	Example: fork a process and wait for it	352	Example: fork a process and wait for it
269		353
270	my $done = AnyEvent->condvar;	354	my $done = AnyEvent->condvar;
271		355
272	AnyEvent::detect; # force event module to be initialised
273
274	my $pid = fork or exit 5;	356	my $pid = fork or exit 5;
275		357
276	my $w = AnyEvent->child (	358	my $w = AnyEvent->child (
277	pid => $pid,	359	pid => $pid,
278	cb => sub {	360	cb => sub {
279	my ($pid, $status) = @_;	361	my ($pid, $status) = @_;
280	warn "pid $pid exited with status $status";	362	warn "pid $pid exited with status $status";
281	$done->broadcast;	363	$done->send;
282	},	364	},
283	);	365	);
284		366
285	# do something else, then wait for process exit	367	# do something else, then wait for process exit
286	$done->wait;	368	$done->recv;
287		369
288	=head2 CONDITION VARIABLES	370	=head2 CONDITION VARIABLES
289		371
		372	If you are familiar with some event loops you will know that all of them
		373	require you to run some blocking "loop", "run" or similar function that
		374	will actively watch for new events and call your callbacks.
		375
		376	AnyEvent is different, it expects somebody else to run the event loop and
		377	will only block when necessary (usually when told by the user).
		378
		379	The instrument to do that is called a "condition variable", so called
		380	because they represent a condition that must become true.
		381
290	Condition variables can be created by calling the C<< AnyEvent->condvar >>	382	Condition variables can be created by calling the C<< AnyEvent->condvar
291	method without any arguments.	383	>> method, usually without arguments. The only argument pair allowed is
		384	C<cb>, which specifies a callback to be called when the condition variable
		385	becomes true.
292		386
293	A condition variable waits for a condition - precisely that the C<<	387	After creation, the condition variable is "false" until it becomes "true"
294	->broadcast >> method has been called.	388	by calling the C<send> method (or calling the condition variable as if it
		389	were a callback, read about the caveats in the description for the C<<
		390	->send >> method).
295		391
296	They are very useful to signal that a condition has been fulfilled, for	392	Condition variables are similar to callbacks, except that you can
		393	optionally wait for them. They can also be called merge points - points
		394	in time where multiple outstanding events have been processed. And yet
		395	another way to call them is transactions - each condition variable can be
		396	used to represent a transaction, which finishes at some point and delivers
		397	a result.
		398
		399	Condition variables are very useful to signal that something has finished,
297	example, if you write a module that does asynchronous http requests,	400	for example, if you write a module that does asynchronous http requests,
298	then a condition variable would be the ideal candidate to signal the	401	then a condition variable would be the ideal candidate to signal the
299	availability of results.	402	availability of results. The user can either act when the callback is
		403	called or can synchronously C<< ->recv >> for the results.
300		404
301	You can also use condition variables to block your main program until	405	You can also use them to simulate traditional event loops - for example,
302	an event occurs - for example, you could C<< ->wait >> in your main	406	you can block your main program until an event occurs - for example, you
303	program until the user clicks the Quit button in your app, which would C<<	407	could C<< ->recv >> in your main program until the user clicks the Quit
304	->broadcast >> the "quit" event.	408	button of your app, which would C<< ->send >> the "quit" event.
305		409
306	Note that condition variables recurse into the event loop - if you have	410	Note that condition variables recurse into the event loop - if you have
307	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	411	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
308	lose. Therefore, condition variables are good to export to your caller, but	412	lose. Therefore, condition variables are good to export to your caller, but
309	you should avoid making a blocking wait yourself, at least in callbacks,	413	you should avoid making a blocking wait yourself, at least in callbacks,
310	as this asks for trouble.	414	as this asks for trouble.
311		415
312	This object has two methods:	416	Condition variables are represented by hash refs in perl, and the keys
		417	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		418	easy (it is often useful to build your own transaction class on top of
		419	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		420	it's C<new> method in your own C<new> method.
		421
		422	There are two "sides" to a condition variable - the "producer side" which
		423	eventually calls C<< -> send >>, and the "consumer side", which waits
		424	for the send to occur.
		425
		426	Example: wait for a timer.
		427
		428	# wait till the result is ready
		429	my $result_ready = AnyEvent->condvar;
		430
		431	# do something such as adding a timer
		432	# or socket watcher the calls $result_ready->send
		433	# when the "result" is ready.
		434	# in this case, we simply use a timer:
		435	my $w = AnyEvent->timer (
		436	after => 1,
		437	cb => sub { $result_ready->send },
		438	);
		439
		440	# this "blocks" (while handling events) till the callback
		441	# calls send
		442	$result_ready->recv;
		443
		444	Example: wait for a timer, but take advantage of the fact that
		445	condition variables are also code references.
		446
		447	my $done = AnyEvent->condvar;
		448	my $delay = AnyEvent->timer (after => 5, cb => $done);
		449	$done->recv;
		450
		451	=head3 METHODS FOR PRODUCERS
		452
		453	These methods should only be used by the producing side, i.e. the
		454	code/module that eventually sends the signal. Note that it is also
		455	the producer side which creates the condvar in most cases, but it isn't
		456	uncommon for the consumer to create it as well.
313		457
314	=over 4	458	=over 4
315		459
		460	=item $cv->send (...)
		461
		462	Flag the condition as ready - a running C<< ->recv >> and all further
		463	calls to C<recv> will (eventually) return after this method has been
		464	called. If nobody is waiting the send will be remembered.
		465
		466	If a callback has been set on the condition variable, it is called
		467	immediately from within send.
		468
		469	Any arguments passed to the C<send> call will be returned by all
		470	future C<< ->recv >> calls.
		471
		472	Condition variables are overloaded so one can call them directly
		473	(as a code reference). Calling them directly is the same as calling
		474	C<send>. Note, however, that many C-based event loops do not handle
		475	overloading, so as tempting as it may be, passing a condition variable
		476	instead of a callback does not work. Both the pure perl and EV loops
		477	support overloading, however, as well as all functions that use perl to
		478	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		479	example).
		480
		481	=item $cv->croak ($error)
		482
		483	Similar to send, but causes all call's to C<< ->recv >> to invoke
		484	C<Carp::croak> with the given error message/object/scalar.
		485
		486	This can be used to signal any errors to the condition variable
		487	user/consumer.
		488
		489	=item $cv->begin ([group callback])
		490
316	=item $cv->wait	491	=item $cv->end
317		492
318	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	493	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		494
		495	These two methods can be used to combine many transactions/events into
		496	one. For example, a function that pings many hosts in parallel might want
		497	to use a condition variable for the whole process.
		498
		499	Every call to C<< ->begin >> will increment a counter, and every call to
		500	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		501	>>, the (last) callback passed to C<begin> will be executed. That callback
		502	is I<supposed> to call C<< ->send >>, but that is not required. If no
		503	callback was set, C<send> will be called without any arguments.
		504
		505	Let's clarify this with the ping example:
		506
		507	my $cv = AnyEvent->condvar;
		508
		509	my %result;
		510	$cv->begin (sub { $cv->send (\%result) });
		511
		512	for my $host (@list_of_hosts) {
		513	$cv->begin;
		514	ping_host_then_call_callback $host, sub {
		515	$result{$host} = ...;
		516	$cv->end;
		517	};
		518	}
		519
		520	$cv->end;
		521
		522	This code fragment supposedly pings a number of hosts and calls
		523	C<send> after results for all then have have been gathered - in any
		524	order. To achieve this, the code issues a call to C<begin> when it starts
		525	each ping request and calls C<end> when it has received some result for
		526	it. Since C<begin> and C<end> only maintain a counter, the order in which
		527	results arrive is not relevant.
		528
		529	There is an additional bracketing call to C<begin> and C<end> outside the
		530	loop, which serves two important purposes: first, it sets the callback
		531	to be called once the counter reaches C<0>, and second, it ensures that
		532	C<send> is called even when C<no> hosts are being pinged (the loop
		533	doesn't execute once).
		534
		535	This is the general pattern when you "fan out" into multiple subrequests:
		536	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		537	is called at least once, and then, for each subrequest you start, call
		538	C<begin> and for each subrequest you finish, call C<end>.
		539
		540	=back
		541
		542	=head3 METHODS FOR CONSUMERS
		543
		544	These methods should only be used by the consuming side, i.e. the
		545	code awaits the condition.
		546
		547	=over 4
		548
		549	=item $cv->recv
		550
		551	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
319	called on c<$cv>, while servicing other watchers normally.	552	>> methods have been called on c<$cv>, while servicing other watchers
		553	normally.
320		554
321	You can only wait once on a condition - additional calls will return	555	You can only wait once on a condition - additional calls are valid but
322	immediately.	556	will return immediately.
		557
		558	If an error condition has been set by calling C<< ->croak >>, then this
		559	function will call C<croak>.
		560
		561	In list context, all parameters passed to C<send> will be returned,
		562	in scalar context only the first one will be returned.
323		563
324	Not all event models support a blocking wait - some die in that case	564	Not all event models support a blocking wait - some die in that case
325	(programs might want to do that to stay interactive), so I<if you are	565	(programs might want to do that to stay interactive), so I<if you are
326	using this from a module, never require a blocking wait>, but let the	566	using this from a module, never require a blocking wait>, but let the
327	caller decide whether the call will block or not (for example, by coupling	567	caller decide whether the call will block or not (for example, by coupling
328	condition variables with some kind of request results and supporting	568	condition variables with some kind of request results and supporting
329	callbacks so the caller knows that getting the result will not block,	569	callbacks so the caller knows that getting the result will not block,
330	while still suppporting blocking waits if the caller so desires).	570	while still supporting blocking waits if the caller so desires).
331		571
332	Another reason I<never> to C<< ->wait >> in a module is that you cannot	572	Another reason I<never> to C<< ->recv >> in a module is that you cannot
333	sensibly have two C<< ->wait >>'s in parallel, as that would require	573	sensibly have two C<< ->recv >>'s in parallel, as that would require
334	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	574	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
335	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	575	can supply.
336	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
337	from different coroutines, however).
338		576
339	=item $cv->broadcast	577	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		578	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		579	versions and also integrates coroutines into AnyEvent, making blocking
		580	C<< ->recv >> calls perfectly safe as long as they are done from another
		581	coroutine (one that doesn't run the event loop).
340		582
341	Flag the condition as ready - a running C<< ->wait >> and all further	583	You can ensure that C<< -recv >> never blocks by setting a callback and
342	calls to C<wait> will (eventually) return after this method has been	584	only calling C<< ->recv >> from within that callback (or at a later
343	called. If nobody is waiting the broadcast will be remembered..	585	time). This will work even when the event loop does not support blocking
		586	waits otherwise.
		587
		588	=item $bool = $cv->ready
		589
		590	Returns true when the condition is "true", i.e. whether C<send> or
		591	C<croak> have been called.
		592
		593	=item $cb = $cv->cb ([new callback])
		594
		595	This is a mutator function that returns the callback set and optionally
		596	replaces it before doing so.
		597
		598	The callback will be called when the condition becomes "true", i.e. when
		599	C<send> or C<croak> are called, with the only argument being the condition
		600	variable itself. Calling C<recv> inside the callback or at any later time
		601	is guaranteed not to block.
344		602
345	=back	603	=back
346
347	Example:
348
349	# wait till the result is ready
350	my $result_ready = AnyEvent->condvar;
351
352	# do something such as adding a timer
353	# or socket watcher the calls $result_ready->broadcast
354	# when the "result" is ready.
355	# in this case, we simply use a timer:
356	my $w = AnyEvent->timer (
357	after => 1,
358	cb => sub { $result_ready->broadcast },
359	);
360
361	# this "blocks" (while handling events) till the watcher
362	# calls broadcast
363	$result_ready->wait;
364		604
365	=head1 GLOBAL VARIABLES AND FUNCTIONS	605	=head1 GLOBAL VARIABLES AND FUNCTIONS
366		606
367	=over 4	607	=over 4
368		608
…		…
374	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	614	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
375	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	615	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
376		616
377	The known classes so far are:	617	The known classes so far are:
378		618
379	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
380	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
381	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	619	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
382	AnyEvent::Impl::Event based on Event, second best choice.	620	AnyEvent::Impl::Event based on Event, second best choice.
		621	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
383	AnyEvent::Impl::Glib based on Glib, third-best choice.	622	AnyEvent::Impl::Glib based on Glib, third-best choice.
384	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
385	AnyEvent::Impl::Tk based on Tk, very bad choice.	623	AnyEvent::Impl::Tk based on Tk, very bad choice.
386	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	624	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
387	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	625	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
388	AnyEvent::Impl::POE based on POE, not generic enough for full support.	626	AnyEvent::Impl::POE based on POE, not generic enough for full support.
389		627
…		…
402	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	640	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
403	if necessary. You should only call this function right before you would	641	if necessary. You should only call this function right before you would
404	have created an AnyEvent watcher anyway, that is, as late as possible at	642	have created an AnyEvent watcher anyway, that is, as late as possible at
405	runtime.	643	runtime.
406		644
		645	=item $guard = AnyEvent::post_detect { BLOCK }
		646
		647	Arranges for the code block to be executed as soon as the event model is
		648	autodetected (or immediately if this has already happened).
		649
		650	If called in scalar or list context, then it creates and returns an object
		651	that automatically removes the callback again when it is destroyed. See
		652	L<Coro::BDB> for a case where this is useful.
		653
		654	=item @AnyEvent::post_detect
		655
		656	If there are any code references in this array (you can C<push> to it
		657	before or after loading AnyEvent), then they will called directly after
		658	the event loop has been chosen.
		659
		660	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		661	if it contains a true value then the event loop has already been detected,
		662	and the array will be ignored.
		663
		664	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		665
407	=back	666	=back
408		667
409	=head1 WHAT TO DO IN A MODULE	668	=head1 WHAT TO DO IN A MODULE
410		669
411	As a module author, you should C<use AnyEvent> and call AnyEvent methods	670	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
414	Be careful when you create watchers in the module body - AnyEvent will	673	Be careful when you create watchers in the module body - AnyEvent will
415	decide which event module to use as soon as the first method is called, so	674	decide which event module to use as soon as the first method is called, so
416	by calling AnyEvent in your module body you force the user of your module	675	by calling AnyEvent in your module body you force the user of your module
417	to load the event module first.	676	to load the event module first.
418		677
419	Never call C<< ->wait >> on a condition variable unless you I<know> that	678	Never call C<< ->recv >> on a condition variable unless you I<know> that
420	the C<< ->broadcast >> method has been called on it already. This is	679	the C<< ->send >> method has been called on it already. This is
421	because it will stall the whole program, and the whole point of using	680	because it will stall the whole program, and the whole point of using
422	events is to stay interactive.	681	events is to stay interactive.
423		682
424	It is fine, however, to call C<< ->wait >> when the user of your module	683	It is fine, however, to call C<< ->recv >> when the user of your module
425	requests it (i.e. if you create a http request object ad have a method	684	requests it (i.e. if you create a http request object ad have a method
426	called C<results> that returns the results, it should call C<< ->wait >>	685	called C<results> that returns the results, it should call C<< ->recv >>
427	freely, as the user of your module knows what she is doing. always).	686	freely, as the user of your module knows what she is doing. always).
428		687
429	=head1 WHAT TO DO IN THE MAIN PROGRAM	688	=head1 WHAT TO DO IN THE MAIN PROGRAM
430		689
431	There will always be a single main program - the only place that should	690	There will always be a single main program - the only place that should
…		…
433		692
434	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	693	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
435	do anything special (it does not need to be event-based) and let AnyEvent	694	do anything special (it does not need to be event-based) and let AnyEvent
436	decide which implementation to chose if some module relies on it.	695	decide which implementation to chose if some module relies on it.
437		696
438	If the main program relies on a specific event model. For example, in	697	If the main program relies on a specific event model - for example, in
439	Gtk2 programs you have to rely on the Glib module. You should load the	698	Gtk2 programs you have to rely on the Glib module - you should load the
440	event module before loading AnyEvent or any module that uses it: generally	699	event module before loading AnyEvent or any module that uses it: generally
441	speaking, you should load it as early as possible. The reason is that	700	speaking, you should load it as early as possible. The reason is that
442	modules might create watchers when they are loaded, and AnyEvent will	701	modules might create watchers when they are loaded, and AnyEvent will
443	decide on the event model to use as soon as it creates watchers, and it	702	decide on the event model to use as soon as it creates watchers, and it
444	might chose the wrong one unless you load the correct one yourself.	703	might chose the wrong one unless you load the correct one yourself.
445		704
446	You can chose to use a rather inefficient pure-perl implementation by	705	You can chose to use a pure-perl implementation by loading the
447	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	706	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
448	behaviour everywhere, but letting AnyEvent chose is generally better.	707	everywhere, but letting AnyEvent chose the model is generally better.
		708
		709	=head2 MAINLOOP EMULATION
		710
		711	Sometimes (often for short test scripts, or even standalone programs who
		712	only want to use AnyEvent), you do not want to run a specific event loop.
		713
		714	In that case, you can use a condition variable like this:
		715
		716	AnyEvent->condvar->recv;
		717
		718	This has the effect of entering the event loop and looping forever.
		719
		720	Note that usually your program has some exit condition, in which case
		721	it is better to use the "traditional" approach of storing a condition
		722	variable somewhere, waiting for it, and sending it when the program should
		723	exit cleanly.
		724
		725
		726	=head1 OTHER MODULES
		727
		728	The following is a non-exhaustive list of additional modules that use
		729	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		730	in the same program. Some of the modules come with AnyEvent, some are
		731	available via CPAN.
		732
		733	=over 4
		734
		735	=item L<AnyEvent::Util>
		736
		737	Contains various utility functions that replace often-used but blocking
		738	functions such as C<inet_aton> by event-/callback-based versions.
		739
		740	=item L<AnyEvent::Socket>
		741
		742	Provides various utility functions for (internet protocol) sockets,
		743	addresses and name resolution. Also functions to create non-blocking tcp
		744	connections or tcp servers, with IPv6 and SRV record support and more.
		745
		746	=item L<AnyEvent::Handle>
		747
		748	Provide read and write buffers, manages watchers for reads and writes,
		749	supports raw and formatted I/O, I/O queued and fully transparent and
		750	non-blocking SSL/TLS.
		751
		752	=item L<AnyEvent::DNS>
		753
		754	Provides rich asynchronous DNS resolver capabilities.
		755
		756	=item L<AnyEvent::HTTP>
		757
		758	A simple-to-use HTTP library that is capable of making a lot of concurrent
		759	HTTP requests.
		760
		761	=item L<AnyEvent::HTTPD>
		762
		763	Provides a simple web application server framework.
		764
		765	=item L<AnyEvent::FastPing>
		766
		767	The fastest ping in the west.
		768
		769	=item L<AnyEvent::DBI>
		770
		771	Executes L<DBI> requests asynchronously in a proxy process.
		772
		773	=item L<AnyEvent::AIO>
		774
		775	Truly asynchronous I/O, should be in the toolbox of every event
		776	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		777	together.
		778
		779	=item L<AnyEvent::BDB>
		780
		781	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		782	L<BDB> and AnyEvent together.
		783
		784	=item L<AnyEvent::GPSD>
		785
		786	A non-blocking interface to gpsd, a daemon delivering GPS information.
		787
		788	=item L<AnyEvent::IGS>
		789
		790	A non-blocking interface to the Internet Go Server protocol (used by
		791	L<App::IGS>).
		792
		793	=item L<Net::IRC3>
		794
		795	AnyEvent based IRC client module family.
		796
		797	=item L<Net::XMPP2>
		798
		799	AnyEvent based XMPP (Jabber protocol) module family.
		800
		801	=item L<Net::FCP>
		802
		803	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		804	of AnyEvent.
		805
		806	=item L<Event::ExecFlow>
		807
		808	High level API for event-based execution flow control.
		809
		810	=item L<Coro>
		811
		812	Has special support for AnyEvent via L<Coro::AnyEvent>.
		813
		814	=item L<IO::Lambda>
		815
		816	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		817
		818	=back
449		819
450	=cut	820	=cut
451		821
452	package AnyEvent;	822	package AnyEvent;
453		823
454	no warnings;	824	no warnings;
455	use strict;	825	use strict;
456		826
457	use Carp;	827	use Carp;
458		828
459	our $VERSION = '3.3';	829	our $VERSION = 4.2;
460	our $MODEL;	830	our $MODEL;
461		831
462	our $AUTOLOAD;	832	our $AUTOLOAD;
463	our @ISA;	833	our @ISA;
464		834
		835	our @REGISTRY;
		836
		837	our $WIN32;
		838
		839	BEGIN {
		840	my $win32 = ! ! ($^O =~ /mswin32/i);
		841	eval "sub WIN32(){ $win32 }";
		842	}
		843
465	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	844	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
466		845
467	our @REGISTRY;	846	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		847
		848	{
		849	my $idx;
		850	$PROTOCOL{$_} = ++$idx
		851	for reverse split /\s*,\s*/,
		852	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		853	}
468		854
469	my @models = (	855	my @models = (
470	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
471	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
472	[EV:: => AnyEvent::Impl::EV::],	856	[EV:: => AnyEvent::Impl::EV::],
473	[Event:: => AnyEvent::Impl::Event::],	857	[Event:: => AnyEvent::Impl::Event::],
474	[Glib:: => AnyEvent::Impl::Glib::],
475	[Tk:: => AnyEvent::Impl::Tk::],
476	[Wx:: => AnyEvent::Impl::POE::],
477	[Prima:: => AnyEvent::Impl::POE::],
478	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	858	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
479	# everything below here will not be autoprobed as the pureperl backend should work everywhere	859	# everything below here will not be autoprobed
		860	# as the pureperl backend should work everywhere
		861	# and is usually faster
		862	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		863	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
480	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	864	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
481	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	865	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
482	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	866	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		867	[Wx:: => AnyEvent::Impl::POE::],
		868	[Prima:: => AnyEvent::Impl::POE::],
483	);	869	);
484		870
485	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	871	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);
		872
		873	our @post_detect;
		874
		875	sub post_detect(&) {
		876	my ($cb) = @_;
		877
		878	if ($MODEL) {
		879	$cb->();
		880
		881	1
		882	} else {
		883	push @post_detect, $cb;
		884
		885	defined wantarray
		886	? bless \$cb, "AnyEvent::Util::PostDetect"
		887	: ()
		888	}
		889	}
		890
		891	sub AnyEvent::Util::PostDetect::DESTROY {
		892	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		893	}
486		894
487	sub detect() {	895	sub detect() {
488	unless ($MODEL) {	896	unless ($MODEL) {
489	no strict 'refs';	897	no strict 'refs';
		898	local $SIG{__DIE__};
490		899
491	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	900	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
492	my $model = "AnyEvent::Impl::$1";	901	my $model = "AnyEvent::Impl::$1";
493	if (eval "require $model") {	902	if (eval "require $model") {
494	$MODEL = $model;	903	$MODEL = $model;
…		…
524	last;	933	last;
525	}	934	}
526	}	935	}
527		936
528	$MODEL	937	$MODEL
529	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.";	938	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
530	}	939	}
531	}	940	}
532		941
533	unshift @ISA, $MODEL;	942	unshift @ISA, $MODEL;
534	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	943	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		944
		945	(shift @post_detect)->() while @post_detect;
535	}	946	}
536		947
537	$MODEL	948	$MODEL
538	}	949	}
539		950
…		…
549	$class->$func (@_);	960	$class->$func (@_);
550	}	961	}
551		962
552	package AnyEvent::Base;	963	package AnyEvent::Base;
553		964
		965	# default implementation for now and time
		966
		967	use Time::HiRes ();
		968
		969	sub time { Time::HiRes::time }
		970	sub now { Time::HiRes::time }
		971
554	# default implementation for ->condvar, ->wait, ->broadcast	972	# default implementation for ->condvar
555		973
556	sub condvar {	974	sub condvar {
557	bless \my $flag, "AnyEvent::Base::CondVar"	975	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
558	}
559
560	sub AnyEvent::Base::CondVar::broadcast {
561	${$_[0]}++;
562	}
563
564	sub AnyEvent::Base::CondVar::wait {
565	AnyEvent->one_event while !${$_[0]};
566	}	976	}
567		977
568	# default implementation for ->signal	978	# default implementation for ->signal
569		979
570	our %SIG_CB;	980	our %SIG_CB;
…		…
586	sub AnyEvent::Base::Signal::DESTROY {	996	sub AnyEvent::Base::Signal::DESTROY {
587	my ($signal, $cb) = @{$_[0]};	997	my ($signal, $cb) = @{$_[0]};
588		998
589	delete $SIG_CB{$signal}{$cb};	999	delete $SIG_CB{$signal}{$cb};
590		1000
591	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1001	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
592	}	1002	}
593		1003
594	# default implementation for ->child	1004	# default implementation for ->child
595		1005
596	our %PID_CB;	1006	our %PID_CB;
…		…
623	or Carp::croak "required option 'pid' is missing";	1033	or Carp::croak "required option 'pid' is missing";
624		1034
625	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1035	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
626		1036
627	unless ($WNOHANG) {	1037	unless ($WNOHANG) {
628	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1038	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
629	}	1039	}
630		1040
631	unless ($CHLD_W) {	1041	unless ($CHLD_W) {
632	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1042	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
633	# child could be a zombie already, so make at least one round	1043	# child could be a zombie already, so make at least one round
…		…
643	delete $PID_CB{$pid}{$cb};	1053	delete $PID_CB{$pid}{$cb};
644	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1054	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
645		1055
646	undef $CHLD_W unless keys %PID_CB;	1056	undef $CHLD_W unless keys %PID_CB;
647	}	1057	}
		1058
		1059	package AnyEvent::CondVar;
		1060
		1061	our @ISA = AnyEvent::CondVar::Base::;
		1062
		1063	package AnyEvent::CondVar::Base;
		1064
		1065	use overload
		1066	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1067	fallback => 1;
		1068
		1069	sub _send {
		1070	# nop
		1071	}
		1072
		1073	sub send {
		1074	my $cv = shift;
		1075	$cv->{_ae_sent} = [@_];
		1076	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1077	$cv->_send;
		1078	}
		1079
		1080	sub croak {
		1081	$_[0]{_ae_croak} = $_[1];
		1082	$_[0]->send;
		1083	}
		1084
		1085	sub ready {
		1086	$_[0]{_ae_sent}
		1087	}
		1088
		1089	sub _wait {
		1090	AnyEvent->one_event while !$_[0]{_ae_sent};
		1091	}
		1092
		1093	sub recv {
		1094	$_[0]->_wait;
		1095
		1096	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1097	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1098	}
		1099
		1100	sub cb {
		1101	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1102	$_[0]{_ae_cb}
		1103	}
		1104
		1105	sub begin {
		1106	++$_[0]{_ae_counter};
		1107	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1108	}
		1109
		1110	sub end {
		1111	return if --$_[0]{_ae_counter};
		1112	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1113	}
		1114
		1115	# undocumented/compatibility with pre-3.4
		1116	*broadcast = \&send;
		1117	*wait = \&_wait;
648		1118
649	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1119	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
650		1120
651	This is an advanced topic that you do not normally need to use AnyEvent in	1121	This is an advanced topic that you do not normally need to use AnyEvent in
652	a module. This section is only of use to event loop authors who want to	1122	a module. This section is only of use to event loop authors who want to
…		…
709	model it chooses.	1179	model it chooses.
710		1180
711	=item C<PERL_ANYEVENT_MODEL>	1181	=item C<PERL_ANYEVENT_MODEL>
712		1182
713	This can be used to specify the event model to be used by AnyEvent, before	1183	This can be used to specify the event model to be used by AnyEvent, before
714	autodetection and -probing kicks in. It must be a string consisting	1184	auto detection and -probing kicks in. It must be a string consisting
715	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended	1185	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
716	and the resulting module name is loaded and if the load was successful,	1186	and the resulting module name is loaded and if the load was successful,
717	used as event model. If it fails to load AnyEvent will proceed with	1187	used as event model. If it fails to load AnyEvent will proceed with
718	autodetection and -probing.	1188	auto detection and -probing.
719		1189
720	This functionality might change in future versions.	1190	This functionality might change in future versions.
721		1191
722	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you	1192	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
723	could start your program like this:	1193	could start your program like this:
724		1194
725	PERL_ANYEVENT_MODEL=Perl perl ...	1195	PERL_ANYEVENT_MODEL=Perl perl ...
		1196
		1197	=item C<PERL_ANYEVENT_PROTOCOLS>
		1198
		1199	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1200	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1201	of auto probing).
		1202
		1203	Must be set to a comma-separated list of protocols or address families,
		1204	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1205	used, and preference will be given to protocols mentioned earlier in the
		1206	list.
		1207
		1208	This variable can effectively be used for denial-of-service attacks
		1209	against local programs (e.g. when setuid), although the impact is likely
		1210	small, as the program has to handle connection errors already-
		1211
		1212	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1213	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1214	- only support IPv4, never try to resolve or contact IPv6
		1215	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1216	IPv6, but prefer IPv6 over IPv4.
		1217
		1218	=item C<PERL_ANYEVENT_EDNS0>
		1219
		1220	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1221	for DNS. This extension is generally useful to reduce DNS traffic, but
		1222	some (broken) firewalls drop such DNS packets, which is why it is off by
		1223	default.
		1224
		1225	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1226	EDNS0 in its DNS requests.
		1227
		1228	=item C<PERL_ANYEVENT_MAX_FORKS>
		1229
		1230	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1231	will create in parallel.
726		1232
727	=back	1233	=back
728		1234
729	=head1 EXAMPLE PROGRAM	1235	=head1 EXAMPLE PROGRAM
730		1236
…		…
741	poll => 'r',	1247	poll => 'r',
742	cb => sub {	1248	cb => sub {
743	warn "io event <$_[0]>\n"; # will always output <r>	1249	warn "io event <$_[0]>\n"; # will always output <r>
744	chomp (my $input = <STDIN>); # read a line	1250	chomp (my $input = <STDIN>); # read a line
745	warn "read: $input\n"; # output what has been read	1251	warn "read: $input\n"; # output what has been read
746	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1252	$cv->send if $input =~ /^q/i; # quit program if /^q/i
747	},	1253	},
748	);	1254	);
749		1255
750	my $time_watcher; # can only be used once	1256	my $time_watcher; # can only be used once
751		1257
…		…
756	});	1262	});
757	}	1263	}
758		1264
759	new_timer; # create first timer	1265	new_timer; # create first timer
760		1266
761	$cv->wait; # wait until user enters /^q/i	1267	$cv->recv; # wait until user enters /^q/i
762		1268
763	=head1 REAL-WORLD EXAMPLE	1269	=head1 REAL-WORLD EXAMPLE
764		1270
765	Consider the L<Net::FCP> module. It features (among others) the following	1271	Consider the L<Net::FCP> module. It features (among others) the following
766	API calls, which are to freenet what HTTP GET requests are to http:	1272	API calls, which are to freenet what HTTP GET requests are to http:
…		…
816	syswrite $txn->{fh}, $txn->{request}	1322	syswrite $txn->{fh}, $txn->{request}
817	or die "connection or write error";	1323	or die "connection or write error";
818	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1324	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
819		1325
820	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1326	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
821	result and signals any possible waiters that the request ahs finished:	1327	result and signals any possible waiters that the request has finished:
822		1328
823	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1329	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
824		1330
825	if (end-of-file or data complete) {	1331	if (end-of-file or data complete) {
826	$txn->{result} = $txn->{buf};	1332	$txn->{result} = $txn->{buf};
827	$txn->{finished}->broadcast;	1333	$txn->{finished}->send;
828	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1334	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
829	}	1335	}
830		1336
831	The C<result> method, finally, just waits for the finished signal (if the	1337	The C<result> method, finally, just waits for the finished signal (if the
832	request was already finished, it doesn't wait, of course, and returns the	1338	request was already finished, it doesn't wait, of course, and returns the
833	data:	1339	data:
834		1340
835	$txn->{finished}->wait;	1341	$txn->{finished}->recv;
836	return $txn->{result};	1342	return $txn->{result};
837		1343
838	The actual code goes further and collects all errors (C<die>s, exceptions)	1344	The actual code goes further and collects all errors (C<die>s, exceptions)
839	that occured during request processing. The C<result> method detects	1345	that occurred during request processing. The C<result> method detects
840	whether an exception as thrown (it is stored inside the $txn object)	1346	whether an exception as thrown (it is stored inside the $txn object)
841	and just throws the exception, which means connection errors and other	1347	and just throws the exception, which means connection errors and other
842	problems get reported tot he code that tries to use the result, not in a	1348	problems get reported tot he code that tries to use the result, not in a
843	random callback.	1349	random callback.
844		1350
…		…
875		1381
876	my $quit = AnyEvent->condvar;	1382	my $quit = AnyEvent->condvar;
877		1383
878	$fcp->txn_client_get ($url)->cb (sub {	1384	$fcp->txn_client_get ($url)->cb (sub {
879	...	1385	...
880	$quit->broadcast;	1386	$quit->send;
881	});	1387	});
882		1388
883	$quit->wait;	1389	$quit->recv;
884		1390
885		1391
886	=head1 BENCHMARK	1392	=head1 BENCHMARKS
887		1393
888	To give you an idea of the performance and overheads that AnyEvent adds	1394	To give you an idea of the performance and overheads that AnyEvent adds
889	over the event loops themselves (and to give you an impression of the	1395	over the event loops themselves and to give you an impression of the speed
890	speed of various event loops), here is a benchmark of various supported	1396	of various event loops I prepared some benchmarks.
891	event models natively and with anyevent. The benchmark creates a lot of	1397
892	timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to	1398	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1399
		1400	Here is a benchmark of various supported event models used natively and
		1401	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1402	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
893	become writable, which it is), lets them fire exactly once and destroys	1403	which it is), lets them fire exactly once and destroys them again.
894	them again.
895		1404
896	Rewriting the benchmark to use many different sockets instead of using	1405	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
897	the same filehandle for all I/O watchers results in a much longer runtime	1406	distribution.
898	(socket creation is expensive), but qualitatively the same figures, so it
899	was not used.
900		1407
901	=head2 Explanation of the columns	1408	=head3 Explanation of the columns
902		1409
903	I<watcher> is the number of event watchers created/destroyed. Since	1410	I<watcher> is the number of event watchers created/destroyed. Since
904	different event models feature vastly different performances, each event	1411	different event models feature vastly different performances, each event
905	loop was given a number of watchers so that overall runtime is acceptable	1412	loop was given a number of watchers so that overall runtime is acceptable
906	and similar between tested event loop (and keep them from crashing): Glib	1413	and similar between tested event loop (and keep them from crashing): Glib
…		…
916	all watchers, to avoid adding memory overhead. That means closure creation	1423	all watchers, to avoid adding memory overhead. That means closure creation
917	and memory usage is not included in the figures.	1424	and memory usage is not included in the figures.
918		1425
919	I<invoke> is the time, in microseconds, used to invoke a simple	1426	I<invoke> is the time, in microseconds, used to invoke a simple
920	callback. The callback simply counts down a Perl variable and after it was	1427	callback. The callback simply counts down a Perl variable and after it was
921	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1428	invoked "watcher" times, it would C<< ->send >> a condvar once to
922	signal the end of this phase.	1429	signal the end of this phase.
923		1430
924	I<destroy> is the time, in microseconds, that it takes to destroy a single	1431	I<destroy> is the time, in microseconds, that it takes to destroy a single
925	watcher.	1432	watcher.
926		1433
927	=head2 Results	1434	=head3 Results
928		1435
929	name watchers bytes create invoke destroy comment	1436	name watchers bytes create invoke destroy comment
930	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1437	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
931	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1438	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
932	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1439	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
933	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1440	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
934	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1441	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
935	Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers	1442	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
936	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1443	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
937	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1444	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
938	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1445	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
939	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1446	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
940		1447
941	=head2 Discussion	1448	=head3 Discussion
942		1449
943	The benchmark does I<not> measure scalability of the event loop very	1450	The benchmark does I<not> measure scalability of the event loop very
944	well. For example, a select-based event loop (such as the pure perl one)	1451	well. For example, a select-based event loop (such as the pure perl one)
945	can never compete with an event loop that uses epoll when the number of	1452	can never compete with an event loop that uses epoll when the number of
946	file descriptors grows high. In this benchmark, all events become ready at	1453	file descriptors grows high. In this benchmark, all events become ready at
947	the same time, so select/poll-based implementations get an unnatural speed	1454	the same time, so select/poll-based implementations get an unnatural speed
948	boost.	1455	boost.
949		1456
		1457	Also, note that the number of watchers usually has a nonlinear effect on
		1458	overall speed, that is, creating twice as many watchers doesn't take twice
		1459	the time - usually it takes longer. This puts event loops tested with a
		1460	higher number of watchers at a disadvantage.
		1461
		1462	To put the range of results into perspective, consider that on the
		1463	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1464	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1465	cycles with POE.
		1466
950	C<EV> is the sole leader regarding speed and memory use, which are both	1467	C<EV> is the sole leader regarding speed and memory use, which are both
951	maximal/minimal, respectively. Even when going through AnyEvent, there are	1468	maximal/minimal, respectively. Even when going through AnyEvent, it uses
952	only two event loops that use slightly less memory (the C<Event> module	1469	far less memory than any other event loop and is still faster than Event
953	natively and the pure perl backend), and no faster event models, not even	1470	natively.
954	C<Event> natively.
955		1471
956	The pure perl implementation is hit in a few sweet spots (both the	1472	The pure perl implementation is hit in a few sweet spots (both the
957	zero timeout and the use of a single fd hit optimisations in the perl	1473	constant timeout and the use of a single fd hit optimisations in the perl
958	interpreter and the backend itself, and all watchers become ready at the	1474	interpreter and the backend itself). Nevertheless this shows that it
959	same time). Nevertheless this shows that it adds very little overhead in	1475	adds very little overhead in itself. Like any select-based backend its
960	itself. Like any select-based backend its performance becomes really bad	1476	performance becomes really bad with lots of file descriptors (and few of
961	with lots of file descriptors (and few of them active), of course, but	1477	them active), of course, but this was not subject of this benchmark.
962	this was not subject of this benchmark.
963		1478
964	The C<Event> module has a relatively high setup and callback invocation cost,	1479	The C<Event> module has a relatively high setup and callback invocation
965	but overall scores on the third place.	1480	cost, but overall scores in on the third place.
966		1481
967	C<Glib>'s memory usage is quite a bit bit higher, but it features a	1482	C<Glib>'s memory usage is quite a bit higher, but it features a
968	faster callback invocation and overall ends up in the same class as	1483	faster callback invocation and overall ends up in the same class as
969	C<Event>. However, Glib scales extremely badly, doubling the number of	1484	C<Event>. However, Glib scales extremely badly, doubling the number of
970	watchers increases the processing time by more than a factor of four,	1485	watchers increases the processing time by more than a factor of four,
971	making it completely unusable when using larger numbers of watchers	1486	making it completely unusable when using larger numbers of watchers
972	(note that only a single file descriptor was used in the benchmark, so	1487	(note that only a single file descriptor was used in the benchmark, so
…		…
975	The C<Tk> adaptor works relatively well. The fact that it crashes with	1490	The C<Tk> adaptor works relatively well. The fact that it crashes with
976	more than 2000 watchers is a big setback, however, as correctness takes	1491	more than 2000 watchers is a big setback, however, as correctness takes
977	precedence over speed. Nevertheless, its performance is surprising, as the	1492	precedence over speed. Nevertheless, its performance is surprising, as the
978	file descriptor is dup()ed for each watcher. This shows that the dup()	1493	file descriptor is dup()ed for each watcher. This shows that the dup()
979	employed by some adaptors is not a big performance issue (it does incur a	1494	employed by some adaptors is not a big performance issue (it does incur a
980	hidden memory cost inside the kernel, though, that is not reflected in the	1495	hidden memory cost inside the kernel which is not reflected in the figures
981	figures above).	1496	above).
982		1497
983	C<POE>, regardless of underlying event loop (wether using its pure perl	1498	C<POE>, regardless of underlying event loop (whether using its pure perl
984	select-based backend or the Event module) shows abysmal performance and	1499	select-based backend or the Event module, the POE-EV backend couldn't
		1500	be tested because it wasn't working) shows abysmal performance and
985	memory usage: Watchers use almost 30 times as much memory as EV watchers,	1501	memory usage with AnyEvent: Watchers use almost 30 times as much memory
986	and 10 times as much memory as both Event or EV via AnyEvent. Watcher	1502	as EV watchers, and 10 times as much memory as Event (the high memory
		1503	requirements are caused by requiring a session for each watcher). Watcher
987	invocation is almost 900 times slower than with AnyEvent's pure perl	1504	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1505	implementation.
		1506
988	implementation. The design of the POE adaptor class in AnyEvent can not	1507	The design of the POE adaptor class in AnyEvent can not really account
989	really account for this, as session creation overhead is small compared	1508	for the performance issues, though, as session creation overhead is
990	to execution of the state machine, which is coded pretty optimally within	1509	small compared to execution of the state machine, which is coded pretty
991	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1510	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1511	using multiple sessions is not a good approach, especially regarding
		1512	memory usage, even the author of POE could not come up with a faster
		1513	design).
992		1514
993	=head2 Summary	1515	=head3 Summary
994		1516
		1517	=over 4
		1518
995	Using EV through AnyEvent is faster than any other event loop, but most	1519	=item * Using EV through AnyEvent is faster than any other event loop
996	event loops have acceptable performance with or without AnyEvent.	1520	(even when used without AnyEvent), but most event loops have acceptable
		1521	performance with or without AnyEvent.
997		1522
998	The overhead AnyEvent adds is usually much smaller than the overhead of	1523	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
999	the actual event loop, only with extremely fast event loops such as the EV	1524	the actual event loop, only with extremely fast event loops such as EV
1000	adds AnyEvent significant overhead.	1525	adds AnyEvent significant overhead.
1001		1526
1002	And you should simply avoid POE like the plague if you want performance or	1527	=item * You should avoid POE like the plague if you want performance or
1003	reasonable memory usage.	1528	reasonable memory usage.
1004		1529
		1530	=back
		1531
		1532	=head2 BENCHMARKING THE LARGE SERVER CASE
		1533
		1534	This benchmark actually benchmarks the event loop itself. It works by
		1535	creating a number of "servers": each server consists of a socket pair, a
		1536	timeout watcher that gets reset on activity (but never fires), and an I/O
		1537	watcher waiting for input on one side of the socket. Each time the socket
		1538	watcher reads a byte it will write that byte to a random other "server".
		1539
		1540	The effect is that there will be a lot of I/O watchers, only part of which
		1541	are active at any one point (so there is a constant number of active
		1542	fds for each loop iteration, but which fds these are is random). The
		1543	timeout is reset each time something is read because that reflects how
		1544	most timeouts work (and puts extra pressure on the event loops).
		1545
		1546	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1547	(1%) are active. This mirrors the activity of large servers with many
		1548	connections, most of which are idle at any one point in time.
		1549
		1550	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1551	distribution.
		1552
		1553	=head3 Explanation of the columns
		1554
		1555	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1556	each server has a read and write socket end).
		1557
		1558	I<create> is the time it takes to create a socket pair (which is
		1559	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1560
		1561	I<request>, the most important value, is the time it takes to handle a
		1562	single "request", that is, reading the token from the pipe and forwarding
		1563	it to another server. This includes deleting the old timeout and creating
		1564	a new one that moves the timeout into the future.
		1565
		1566	=head3 Results
		1567
		1568	name sockets create request
		1569	EV 20000 69.01 11.16
		1570	Perl 20000 73.32 35.87
		1571	Event 20000 212.62 257.32
		1572	Glib 20000 651.16 1896.30
		1573	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1574
		1575	=head3 Discussion
		1576
		1577	This benchmark I<does> measure scalability and overall performance of the
		1578	particular event loop.
		1579
		1580	EV is again fastest. Since it is using epoll on my system, the setup time
		1581	is relatively high, though.
		1582
		1583	Perl surprisingly comes second. It is much faster than the C-based event
		1584	loops Event and Glib.
		1585
		1586	Event suffers from high setup time as well (look at its code and you will
		1587	understand why). Callback invocation also has a high overhead compared to
		1588	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1589	uses select or poll in basically all documented configurations.
		1590
		1591	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1592	clearly fails to perform with many filehandles or in busy servers.
		1593
		1594	POE is still completely out of the picture, taking over 1000 times as long
		1595	as EV, and over 100 times as long as the Perl implementation, even though
		1596	it uses a C-based event loop in this case.
		1597
		1598	=head3 Summary
		1599
		1600	=over 4
		1601
		1602	=item * The pure perl implementation performs extremely well.
		1603
		1604	=item * Avoid Glib or POE in large projects where performance matters.
		1605
		1606	=back
		1607
		1608	=head2 BENCHMARKING SMALL SERVERS
		1609
		1610	While event loops should scale (and select-based ones do not...) even to
		1611	large servers, most programs we (or I :) actually write have only a few
		1612	I/O watchers.
		1613
		1614	In this benchmark, I use the same benchmark program as in the large server
		1615	case, but it uses only eight "servers", of which three are active at any
		1616	one time. This should reflect performance for a small server relatively
		1617	well.
		1618
		1619	The columns are identical to the previous table.
		1620
		1621	=head3 Results
		1622
		1623	name sockets create request
		1624	EV 16 20.00 6.54
		1625	Perl 16 25.75 12.62
		1626	Event 16 81.27 35.86
		1627	Glib 16 32.63 15.48
		1628	POE 16 261.87 276.28 uses POE::Loop::Event
		1629
		1630	=head3 Discussion
		1631
		1632	The benchmark tries to test the performance of a typical small
		1633	server. While knowing how various event loops perform is interesting, keep
		1634	in mind that their overhead in this case is usually not as important, due
		1635	to the small absolute number of watchers (that is, you need efficiency and
		1636	speed most when you have lots of watchers, not when you only have a few of
		1637	them).
		1638
		1639	EV is again fastest.
		1640
		1641	Perl again comes second. It is noticeably faster than the C-based event
		1642	loops Event and Glib, although the difference is too small to really
		1643	matter.
		1644
		1645	POE also performs much better in this case, but is is still far behind the
		1646	others.
		1647
		1648	=head3 Summary
		1649
		1650	=over 4
		1651
		1652	=item * C-based event loops perform very well with small number of
		1653	watchers, as the management overhead dominates.
		1654
		1655	=back
		1656
1005		1657
1006	=head1 FORK	1658	=head1 FORK
1007		1659
1008	Most event libraries are not fork-safe. The ones who are usually are	1660	Most event libraries are not fork-safe. The ones who are usually are
1009	because they are so inefficient. Only L<EV> is fully fork-aware.	1661	because they rely on inefficient but fork-safe C<select> or C<poll>
		1662	calls. Only L<EV> is fully fork-aware.
1010		1663
1011	If you have to fork, you must either do so I<before> creating your first	1664	If you have to fork, you must either do so I<before> creating your first
1012	watcher OR you must not use AnyEvent at all in the child.	1665	watcher OR you must not use AnyEvent at all in the child.
1013		1666
1014		1667
…		…
1022	specified in the variable.	1675	specified in the variable.
1023		1676
1024	You can make AnyEvent completely ignore this variable by deleting it	1677	You can make AnyEvent completely ignore this variable by deleting it
1025	before the first watcher gets created, e.g. with a C<BEGIN> block:	1678	before the first watcher gets created, e.g. with a C<BEGIN> block:
1026		1679
1027	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1680	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1028		1681
1029	use AnyEvent;	1682	use AnyEvent;
		1683
		1684	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1685	be used to probe what backend is used and gain other information (which is
		1686	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
		1687
		1688
		1689	=head1 BUGS
		1690
		1691	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		1692	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		1693	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		1694	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as
		1695	pronounced).
1030		1696
1031		1697
1032	=head1 SEE ALSO	1698	=head1 SEE ALSO
1033		1699
1034	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1700	Utility functions: L<AnyEvent::Util>.
1035	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1701
		1702	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1036	L<Event::Lib>, L<Qt>, L<POE>.	1703	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1037		1704
1038	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1705	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1039	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1706	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1040	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1707	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1041	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1708	L<AnyEvent::Impl::POE>.
1042		1709
		1710	Non-blocking file handles, sockets, TCP clients and
		1711	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1712
		1713	Asynchronous DNS: L<AnyEvent::DNS>.
		1714
		1715	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1716
1043	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1717	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1044		1718
1045		1719
1046	=head1 AUTHOR	1720	=head1 AUTHOR
1047		1721
1048	Marc Lehmann <schmorp@schmorp.de>	1722	Marc Lehmann <schmorp@schmorp.de>
1049	http://home.schmorp.de/	1723	http://home.schmorp.de/
1050		1724
1051	=cut	1725	=cut
1052		1726
1053	1	1727	1
1054		1728

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