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Revision 1.166 by root, Tue Jul 8 23:10:20 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 - 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
…		…
78		89
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	94	to detect the currently loaded event loop by probing whether one of the
84	the following modules is already loaded: L<Coro::EV>, L<Coro::Event>,	95	following modules is already loaded: L<EV>,
85	L<EV>, L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>. The first one	96	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	found is used. If none are found, the module tries to load these modules	97	L<POE>. The first one found is used. If none are found, the module tries
87	(excluding Event::Lib and Qt) in the order given. The first one that can	98	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
		99	adaptor should always succeed) in the order given. The first one that can
88	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
89	found, AnyEvent will fall back to a pure-perl event loop, which is not	101	found, AnyEvent will fall back to a pure-perl event loop, which is not
90	very efficient, but should work everywhere.	102	very efficient, but should work everywhere.
91		103
92	Because AnyEvent first checks for modules that are already loaded, loading	104	Because AnyEvent first checks for modules that are already loaded, loading
…		…
102	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
103	use AnyEvent so their modules work together with others seamlessly...	115	use AnyEvent so their modules work together with others seamlessly...
104		116
105	The pure-perl implementation of AnyEvent is called	117	The pure-perl implementation of AnyEvent is called
106	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
107	explicitly.	119	explicitly and enjoy the high availability of that event loop :)
108		120
109	=head1 WATCHERS	121	=head1 WATCHERS
110		122
111	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
112	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
113	the callback to call, the filehandle to watch, etc.	125	the callback to call, the file handle to watch, etc.
114		126
115	These watchers are normal Perl objects with normal Perl lifetime. After	127	These watchers are normal Perl objects with normal Perl lifetime. After
116	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
117	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
118	is in control).	130	is in control).
…		…
126	Many watchers either are used with "recursion" (repeating timers for	138	Many watchers either are used with "recursion" (repeating timers for
127	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.
128		140
129	An any way to achieve that is this pattern:	141	An any way to achieve that is this pattern:
130		142
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	143	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	144	# you can use $w here, for example to undef it
133	undef $w;	145	undef $w;
134	});	146	});
135		147
136	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,
137	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
138	declared.	150	declared.
139		151
140	=head2 IO WATCHERS	152	=head2 I/O WATCHERS
141		153
142	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
143	with the following mandatory key-value pairs as arguments:	155	with the following mandatory key-value pairs as arguments:
144		156
145	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 for events
		158	(AnyEvent might or might not keep a reference to this file handle). C<poll>
146	events. C<poll> must be a string that is either C<r> or C<w>, which	159	must be a string that is either C<r> or C<w>, which creates a watcher
147	creates a watcher waiting for "r"eadable or "w"ritable events,	160	waiting for "r"eadable or "w"ritable events, respectively. C<cb> is the
148	respectively. C<cb> is the callback to invoke each time the file handle	161	callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		162
151	As long as the I/O watcher exists it will keep the file descriptor or a	163	Although the callback might get passed parameters, their value and
152	copy of it alive/open.	164	presence is undefined and you cannot rely on them. Portable AnyEvent
		165	callbacks cannot use arguments passed to I/O watcher callbacks.
153		166
		167	The I/O watcher might use the underlying file descriptor or a copy of it.
154	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
155	on the underlying file descriptor.	169	underlying file descriptor.
156		170
157	Some event loops issue spurious readyness notifications, so you should	171	Some event loops issue spurious readyness notifications, so you should
158	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
159	handles.	173	handles.
160		174
161	Example:
162
163	# 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
164	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	178	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
165	chomp (my $input = <STDIN>);	179	chomp (my $input = <STDIN>);
166	warn "read: $input\n";	180	warn "read: $input\n";
167	undef $w;	181	undef $w;
168	});	182	});
…		…
171		185
172	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 >>
173	method with the following mandatory arguments:	187	method with the following mandatory arguments:
174		188
175	C<after> specifies after how many seconds (fractional values are	189	C<after> specifies after how many seconds (fractional values are
176	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
177	case.	191	in that case.
178		192
179	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
180	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
181	and Glib).	195	callbacks cannot use arguments passed to time watcher callbacks.
182		196
183	Example:	197	The callback will normally be invoked once only. If you specify another
		198	parameter, C<interval>, as a strictly positive number (> 0), then the
		199	callback will be invoked regularly at that interval (in fractional
		200	seconds) after the first invocation. If C<interval> is specified with a
		201	false value, then it is treated as if it were missing.
184		202
		203	The callback will be rescheduled before invoking the callback, but no
		204	attempt is done to avoid timer drift in most backends, so the interval is
		205	only approximate.
		206
185	# fire an event after 7.7 seconds	207	Example: fire an event after 7.7 seconds.
		208
186	my $w = AnyEvent->timer (after => 7.7, cb => sub {	209	my $w = AnyEvent->timer (after => 7.7, cb => sub {
187	warn "timeout\n";	210	warn "timeout\n";
188	});	211	});
189		212
190	# to cancel the timer:	213	# to cancel the timer:
191	undef $w;	214	undef $w;
192		215
193	Example 2:
194
195	# fire an event after 0.5 seconds, then roughly every second	216	Example 2: fire an event after 0.5 seconds, then roughly every second.
196	my $w;
197		217
198	my $cb = sub {
199	# cancel the old timer while creating a new one
200	$w = AnyEvent->timer (after => 1, cb => $cb);	218	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		219	warn "timeout\n";
201	};	220	};
202
203	# start the "loop" by creating the first watcher
204	$w = AnyEvent->timer (after => 0.5, cb => $cb);
205		221
206	=head3 TIMING ISSUES	222	=head3 TIMING ISSUES
207		223
208	There are two ways to handle timers: based on real time (relative, "fire	224	There are two ways to handle timers: based on real time (relative, "fire
209	in 10 seconds") and based on wallclock time (absolute, "fire at 12	225	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
221	timers.	237	timers.
222		238
223	AnyEvent always prefers relative timers, if available, matching the	239	AnyEvent always prefers relative timers, if available, matching the
224	AnyEvent API.	240	AnyEvent API.
225		241
		242	AnyEvent has two additional methods that return the "current time":
		243
		244	=over 4
		245
		246	=item AnyEvent->time
		247
		248	This returns the "current wallclock time" as a fractional number of
		249	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		250	return, and the result is guaranteed to be compatible with those).
		251
		252	It progresses independently of any event loop processing, i.e. each call
		253	will check the system clock, which usually gets updated frequently.
		254
		255	=item AnyEvent->now
		256
		257	This also returns the "current wallclock time", but unlike C<time>, above,
		258	this value might change only once per event loop iteration, depending on
		259	the event loop (most return the same time as C<time>, above). This is the
		260	time that AnyEvent's timers get scheduled against.
		261
		262	I<In almost all cases (in all cases if you don't care), this is the
		263	function to call when you want to know the current time.>
		264
		265	This function is also often faster then C<< AnyEvent->time >>, and
		266	thus the preferred method if you want some timestamp (for example,
		267	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		268
		269	The rest of this section is only of relevance if you try to be very exact
		270	with your timing, you can skip it without bad conscience.
		271
		272	For a practical example of when these times differ, consider L<Event::Lib>
		273	and L<EV> and the following set-up:
		274
		275	The event loop is running and has just invoked one of your callback at
		276	time=500 (assume no other callbacks delay processing). In your callback,
		277	you wait a second by executing C<sleep 1> (blocking the process for a
		278	second) and then (at time=501) you create a relative timer that fires
		279	after three seconds.
		280
		281	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		282	both return C<501>, because that is the current time, and the timer will
		283	be scheduled to fire at time=504 (C<501> + C<3>).
		284
		285	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		286	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		287	last event processing phase started. With L<EV>, your timer gets scheduled
		288	to run at time=503 (C<500> + C<3>).
		289
		290	In one sense, L<Event::Lib> is more exact, as it uses the current time
		291	regardless of any delays introduced by event processing. However, most
		292	callbacks do not expect large delays in processing, so this causes a
		293	higher drift (and a lot more system calls to get the current time).
		294
		295	In another sense, L<EV> is more exact, as your timer will be scheduled at
		296	the same time, regardless of how long event processing actually took.
		297
		298	In either case, if you care (and in most cases, you don't), then you
		299	can get whatever behaviour you want with any event loop, by taking the
		300	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		301	account.
		302
		303	=back
		304
226	=head2 SIGNAL WATCHERS	305	=head2 SIGNAL WATCHERS
227		306
228	You can watch for signals using a signal watcher, C<signal> is the signal	307	You can watch for signals using a signal watcher, C<signal> is the signal
229	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	308	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
230	be invoked whenever a signal occurs.	309	be invoked whenever a signal occurs.
231		310
		311	Although the callback might get passed parameters, their value and
		312	presence is undefined and you cannot rely on them. Portable AnyEvent
		313	callbacks cannot use arguments passed to signal watcher callbacks.
		314
232	Multiple signal occurances can be clumped together into one callback	315	Multiple signal occurrences can be clumped together into one callback
233	invocation, and callback invocation will be synchronous. synchronous means	316	invocation, and callback invocation will be synchronous. Synchronous means
234	that it might take a while until the signal gets handled by the process,	317	that it might take a while until the signal gets handled by the process,
235	but it is guarenteed not to interrupt any other callbacks.	318	but it is guaranteed not to interrupt any other callbacks.
236		319
237	The main advantage of using these watchers is that you can share a signal	320	The main advantage of using these watchers is that you can share a signal
238	between multiple watchers.	321	between multiple watchers.
239		322
240	This watcher might use C<%SIG>, so programs overwriting those signals	323	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
250		333
251	The child process is specified by the C<pid> argument (if set to C<0>, it	334	The child process is specified by the C<pid> argument (if set to C<0>, it
252	watches for any child process exit). The watcher will trigger as often	335	watches for any child process exit). The watcher will trigger as often
253	as status change for the child are received. This works by installing a	336	as status change for the child are received. This works by installing a
254	signal handler for C<SIGCHLD>. The callback will be called with the pid	337	signal handler for C<SIGCHLD>. The callback will be called with the pid
255	and exit status (as returned by waitpid).	338	and exit status (as returned by waitpid), so unlike other watcher types,
		339	you I<can> rely on child watcher callback arguments.
256		340
257	Example: wait for pid 1333	341	There is a slight catch to child watchers, however: you usually start them
		342	I<after> the child process was created, and this means the process could
		343	have exited already (and no SIGCHLD will be sent anymore).
258		344
		345	Not all event models handle this correctly (POE doesn't), but even for
		346	event models that I<do> handle this correctly, they usually need to be
		347	loaded before the process exits (i.e. before you fork in the first place).
		348
		349	This means you cannot create a child watcher as the very first thing in an
		350	AnyEvent program, you I<have> to create at least one watcher before you
		351	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		352
		353	Example: fork a process and wait for it
		354
		355	my $done = AnyEvent->condvar;
		356
		357	my $pid = fork or exit 5;
		358
259	my $w = AnyEvent->child (	359	my $w = AnyEvent->child (
260	pid => 1333,	360	pid => $pid,
261	cb => sub {	361	cb => sub {
262	my ($pid, $status) = @_;	362	my ($pid, $status) = @_;
263	warn "pid $pid exited with status $status";	363	warn "pid $pid exited with status $status";
		364	$done->send;
264	},	365	},
265	);	366	);
		367
		368	# do something else, then wait for process exit
		369	$done->recv;
266		370
267	=head2 CONDITION VARIABLES	371	=head2 CONDITION VARIABLES
268		372
		373	If you are familiar with some event loops you will know that all of them
		374	require you to run some blocking "loop", "run" or similar function that
		375	will actively watch for new events and call your callbacks.
		376
		377	AnyEvent is different, it expects somebody else to run the event loop and
		378	will only block when necessary (usually when told by the user).
		379
		380	The instrument to do that is called a "condition variable", so called
		381	because they represent a condition that must become true.
		382
269	Condition variables can be created by calling the C<< AnyEvent->condvar >>	383	Condition variables can be created by calling the C<< AnyEvent->condvar
270	method without any arguments.	384	>> method, usually without arguments. The only argument pair allowed is
		385	C<cb>, which specifies a callback to be called when the condition variable
		386	becomes true.
271		387
272	A condition variable waits for a condition - precisely that the C<<	388	After creation, the condition variable is "false" until it becomes "true"
273	->broadcast >> method has been called.	389	by calling the C<send> method (or calling the condition variable as if it
		390	were a callback, read about the caveats in the description for the C<<
		391	->send >> method).
274		392
275	They are very useful to signal that a condition has been fulfilled, for	393	Condition variables are similar to callbacks, except that you can
		394	optionally wait for them. They can also be called merge points - points
		395	in time where multiple outstanding events have been processed. And yet
		396	another way to call them is transactions - each condition variable can be
		397	used to represent a transaction, which finishes at some point and delivers
		398	a result.
		399
		400	Condition variables are very useful to signal that something has finished,
276	example, if you write a module that does asynchronous http requests,	401	for example, if you write a module that does asynchronous http requests,
277	then a condition variable would be the ideal candidate to signal the	402	then a condition variable would be the ideal candidate to signal the
278	availability of results.	403	availability of results. The user can either act when the callback is
		404	called or can synchronously C<< ->recv >> for the results.
279		405
280	You can also use condition variables to block your main program until	406	You can also use them to simulate traditional event loops - for example,
281	an event occurs - for example, you could C<< ->wait >> in your main	407	you can block your main program until an event occurs - for example, you
282	program until the user clicks the Quit button in your app, which would C<<	408	could C<< ->recv >> in your main program until the user clicks the Quit
283	->broadcast >> the "quit" event.	409	button of your app, which would C<< ->send >> the "quit" event.
284		410
285	Note that condition variables recurse into the event loop - if you have	411	Note that condition variables recurse into the event loop - if you have
286	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	412	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
287	lose. Therefore, condition variables are good to export to your caller, but	413	lose. Therefore, condition variables are good to export to your caller, but
288	you should avoid making a blocking wait yourself, at least in callbacks,	414	you should avoid making a blocking wait yourself, at least in callbacks,
289	as this asks for trouble.	415	as this asks for trouble.
290		416
291	This object has two methods:	417	Condition variables are represented by hash refs in perl, and the keys
		418	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		419	easy (it is often useful to build your own transaction class on top of
		420	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		421	it's C<new> method in your own C<new> method.
		422
		423	There are two "sides" to a condition variable - the "producer side" which
		424	eventually calls C<< -> send >>, and the "consumer side", which waits
		425	for the send to occur.
		426
		427	Example: wait for a timer.
		428
		429	# wait till the result is ready
		430	my $result_ready = AnyEvent->condvar;
		431
		432	# do something such as adding a timer
		433	# or socket watcher the calls $result_ready->send
		434	# when the "result" is ready.
		435	# in this case, we simply use a timer:
		436	my $w = AnyEvent->timer (
		437	after => 1,
		438	cb => sub { $result_ready->send },
		439	);
		440
		441	# this "blocks" (while handling events) till the callback
		442	# calls send
		443	$result_ready->recv;
		444
		445	Example: wait for a timer, but take advantage of the fact that
		446	condition variables are also code references.
		447
		448	my $done = AnyEvent->condvar;
		449	my $delay = AnyEvent->timer (after => 5, cb => $done);
		450	$done->recv;
		451
		452	=head3 METHODS FOR PRODUCERS
		453
		454	These methods should only be used by the producing side, i.e. the
		455	code/module that eventually sends the signal. Note that it is also
		456	the producer side which creates the condvar in most cases, but it isn't
		457	uncommon for the consumer to create it as well.
292		458
293	=over 4	459	=over 4
294		460
		461	=item $cv->send (...)
		462
		463	Flag the condition as ready - a running C<< ->recv >> and all further
		464	calls to C<recv> will (eventually) return after this method has been
		465	called. If nobody is waiting the send will be remembered.
		466
		467	If a callback has been set on the condition variable, it is called
		468	immediately from within send.
		469
		470	Any arguments passed to the C<send> call will be returned by all
		471	future C<< ->recv >> calls.
		472
		473	Condition variables are overloaded so one can call them directly
		474	(as a code reference). Calling them directly is the same as calling
		475	C<send>. Note, however, that many C-based event loops do not handle
		476	overloading, so as tempting as it may be, passing a condition variable
		477	instead of a callback does not work. Both the pure perl and EV loops
		478	support overloading, however, as well as all functions that use perl to
		479	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		480	example).
		481
		482	=item $cv->croak ($error)
		483
		484	Similar to send, but causes all call's to C<< ->recv >> to invoke
		485	C<Carp::croak> with the given error message/object/scalar.
		486
		487	This can be used to signal any errors to the condition variable
		488	user/consumer.
		489
		490	=item $cv->begin ([group callback])
		491
295	=item $cv->wait	492	=item $cv->end
296		493
297	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	494	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		495
		496	These two methods can be used to combine many transactions/events into
		497	one. For example, a function that pings many hosts in parallel might want
		498	to use a condition variable for the whole process.
		499
		500	Every call to C<< ->begin >> will increment a counter, and every call to
		501	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		502	>>, the (last) callback passed to C<begin> will be executed. That callback
		503	is I<supposed> to call C<< ->send >>, but that is not required. If no
		504	callback was set, C<send> will be called without any arguments.
		505
		506	Let's clarify this with the ping example:
		507
		508	my $cv = AnyEvent->condvar;
		509
		510	my %result;
		511	$cv->begin (sub { $cv->send (\%result) });
		512
		513	for my $host (@list_of_hosts) {
		514	$cv->begin;
		515	ping_host_then_call_callback $host, sub {
		516	$result{$host} = ...;
		517	$cv->end;
		518	};
		519	}
		520
		521	$cv->end;
		522
		523	This code fragment supposedly pings a number of hosts and calls
		524	C<send> after results for all then have have been gathered - in any
		525	order. To achieve this, the code issues a call to C<begin> when it starts
		526	each ping request and calls C<end> when it has received some result for
		527	it. Since C<begin> and C<end> only maintain a counter, the order in which
		528	results arrive is not relevant.
		529
		530	There is an additional bracketing call to C<begin> and C<end> outside the
		531	loop, which serves two important purposes: first, it sets the callback
		532	to be called once the counter reaches C<0>, and second, it ensures that
		533	C<send> is called even when C<no> hosts are being pinged (the loop
		534	doesn't execute once).
		535
		536	This is the general pattern when you "fan out" into multiple subrequests:
		537	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		538	is called at least once, and then, for each subrequest you start, call
		539	C<begin> and for each subrequest you finish, call C<end>.
		540
		541	=back
		542
		543	=head3 METHODS FOR CONSUMERS
		544
		545	These methods should only be used by the consuming side, i.e. the
		546	code awaits the condition.
		547
		548	=over 4
		549
		550	=item $cv->recv
		551
		552	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
298	called on c<$cv>, while servicing other watchers normally.	553	>> methods have been called on c<$cv>, while servicing other watchers
		554	normally.
299		555
300	You can only wait once on a condition - additional calls will return	556	You can only wait once on a condition - additional calls are valid but
301	immediately.	557	will return immediately.
		558
		559	If an error condition has been set by calling C<< ->croak >>, then this
		560	function will call C<croak>.
		561
		562	In list context, all parameters passed to C<send> will be returned,
		563	in scalar context only the first one will be returned.
302		564
303	Not all event models support a blocking wait - some die in that case	565	Not all event models support a blocking wait - some die in that case
304	(programs might want to do that to stay interactive), so I<if you are	566	(programs might want to do that to stay interactive), so I<if you are
305	using this from a module, never require a blocking wait>, but let the	567	using this from a module, never require a blocking wait>, but let the
306	caller decide whether the call will block or not (for example, by coupling	568	caller decide whether the call will block or not (for example, by coupling
307	condition variables with some kind of request results and supporting	569	condition variables with some kind of request results and supporting
308	callbacks so the caller knows that getting the result will not block,	570	callbacks so the caller knows that getting the result will not block,
309	while still suppporting blocking waits if the caller so desires).	571	while still supporting blocking waits if the caller so desires).
310		572
311	Another reason I<never> to C<< ->wait >> in a module is that you cannot	573	Another reason I<never> to C<< ->recv >> in a module is that you cannot
312	sensibly have two C<< ->wait >>'s in parallel, as that would require	574	sensibly have two C<< ->recv >>'s in parallel, as that would require
313	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	575	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
314	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	576	can supply.
315	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
316	from different coroutines, however).
317		577
318	=item $cv->broadcast	578	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		579	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		580	versions and also integrates coroutines into AnyEvent, making blocking
		581	C<< ->recv >> calls perfectly safe as long as they are done from another
		582	coroutine (one that doesn't run the event loop).
319		583
320	Flag the condition as ready - a running C<< ->wait >> and all further	584	You can ensure that C<< -recv >> never blocks by setting a callback and
321	calls to C<wait> will (eventually) return after this method has been	585	only calling C<< ->recv >> from within that callback (or at a later
322	called. If nobody is waiting the broadcast will be remembered..	586	time). This will work even when the event loop does not support blocking
		587	waits otherwise.
		588
		589	=item $bool = $cv->ready
		590
		591	Returns true when the condition is "true", i.e. whether C<send> or
		592	C<croak> have been called.
		593
		594	=item $cb = $cv->cb ([new callback])
		595
		596	This is a mutator function that returns the callback set and optionally
		597	replaces it before doing so.
		598
		599	The callback will be called when the condition becomes "true", i.e. when
		600	C<send> or C<croak> are called, with the only argument being the condition
		601	variable itself. Calling C<recv> inside the callback or at any later time
		602	is guaranteed not to block.
323		603
324	=back	604	=back
325
326	Example:
327
328	# wait till the result is ready
329	my $result_ready = AnyEvent->condvar;
330
331	# do something such as adding a timer
332	# or socket watcher the calls $result_ready->broadcast
333	# when the "result" is ready.
334	# in this case, we simply use a timer:
335	my $w = AnyEvent->timer (
336	after => 1,
337	cb => sub { $result_ready->broadcast },
338	);
339
340	# this "blocks" (while handling events) till the watcher
341	# calls broadcast
342	$result_ready->wait;
343		605
344	=head1 GLOBAL VARIABLES AND FUNCTIONS	606	=head1 GLOBAL VARIABLES AND FUNCTIONS
345		607
346	=over 4	608	=over 4
347		609
…		…
353	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	615	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
354	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	616	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
355		617
356	The known classes so far are:	618	The known classes so far are:
357		619
358	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
359	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
360	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	620	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
361	AnyEvent::Impl::Event based on Event, second best choice.	621	AnyEvent::Impl::Event based on Event, second best choice.
		622	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
362	AnyEvent::Impl::Glib based on Glib, third-best choice.	623	AnyEvent::Impl::Glib based on Glib, third-best choice.
363	AnyEvent::Impl::Tk based on Tk, very bad choice.	624	AnyEvent::Impl::Tk based on Tk, very bad choice.
364	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
365	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	625	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
366	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	626	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		627	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		628
		629	There is no support for WxWidgets, as WxWidgets has no support for
		630	watching file handles. However, you can use WxWidgets through the
		631	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		632	second, which was considered to be too horrible to even consider for
		633	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		634	it's adaptor.
		635
		636	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		637	autodetecting them.
367		638
368	=item AnyEvent::detect	639	=item AnyEvent::detect
369		640
370	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	641	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
371	if necessary. You should only call this function right before you would	642	if necessary. You should only call this function right before you would
372	have created an AnyEvent watcher anyway, that is, as late as possible at	643	have created an AnyEvent watcher anyway, that is, as late as possible at
373	runtime.	644	runtime.
374		645
		646	=item $guard = AnyEvent::post_detect { BLOCK }
		647
		648	Arranges for the code block to be executed as soon as the event model is
		649	autodetected (or immediately if this has already happened).
		650
		651	If called in scalar or list context, then it creates and returns an object
		652	that automatically removes the callback again when it is destroyed. See
		653	L<Coro::BDB> for a case where this is useful.
		654
		655	=item @AnyEvent::post_detect
		656
		657	If there are any code references in this array (you can C<push> to it
		658	before or after loading AnyEvent), then they will called directly after
		659	the event loop has been chosen.
		660
		661	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		662	if it contains a true value then the event loop has already been detected,
		663	and the array will be ignored.
		664
		665	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		666
375	=back	667	=back
376		668
377	=head1 WHAT TO DO IN A MODULE	669	=head1 WHAT TO DO IN A MODULE
378		670
379	As a module author, you should C<use AnyEvent> and call AnyEvent methods	671	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
382	Be careful when you create watchers in the module body - AnyEvent will	674	Be careful when you create watchers in the module body - AnyEvent will
383	decide which event module to use as soon as the first method is called, so	675	decide which event module to use as soon as the first method is called, so
384	by calling AnyEvent in your module body you force the user of your module	676	by calling AnyEvent in your module body you force the user of your module
385	to load the event module first.	677	to load the event module first.
386		678
387	Never call C<< ->wait >> on a condition variable unless you I<know> that	679	Never call C<< ->recv >> on a condition variable unless you I<know> that
388	the C<< ->broadcast >> method has been called on it already. This is	680	the C<< ->send >> method has been called on it already. This is
389	because it will stall the whole program, and the whole point of using	681	because it will stall the whole program, and the whole point of using
390	events is to stay interactive.	682	events is to stay interactive.
391		683
392	It is fine, however, to call C<< ->wait >> when the user of your module	684	It is fine, however, to call C<< ->recv >> when the user of your module
393	requests it (i.e. if you create a http request object ad have a method	685	requests it (i.e. if you create a http request object ad have a method
394	called C<results> that returns the results, it should call C<< ->wait >>	686	called C<results> that returns the results, it should call C<< ->recv >>
395	freely, as the user of your module knows what she is doing. always).	687	freely, as the user of your module knows what she is doing. always).
396		688
397	=head1 WHAT TO DO IN THE MAIN PROGRAM	689	=head1 WHAT TO DO IN THE MAIN PROGRAM
398		690
399	There will always be a single main program - the only place that should	691	There will always be a single main program - the only place that should
…		…
401		693
402	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	694	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
403	do anything special (it does not need to be event-based) and let AnyEvent	695	do anything special (it does not need to be event-based) and let AnyEvent
404	decide which implementation to chose if some module relies on it.	696	decide which implementation to chose if some module relies on it.
405		697
406	If the main program relies on a specific event model. For example, in	698	If the main program relies on a specific event model - for example, in
407	Gtk2 programs you have to rely on the Glib module. You should load the	699	Gtk2 programs you have to rely on the Glib module - you should load the
408	event module before loading AnyEvent or any module that uses it: generally	700	event module before loading AnyEvent or any module that uses it: generally
409	speaking, you should load it as early as possible. The reason is that	701	speaking, you should load it as early as possible. The reason is that
410	modules might create watchers when they are loaded, and AnyEvent will	702	modules might create watchers when they are loaded, and AnyEvent will
411	decide on the event model to use as soon as it creates watchers, and it	703	decide on the event model to use as soon as it creates watchers, and it
412	might chose the wrong one unless you load the correct one yourself.	704	might chose the wrong one unless you load the correct one yourself.
413		705
414	You can chose to use a rather inefficient pure-perl implementation by	706	You can chose to use a pure-perl implementation by loading the
415	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	707	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
416	behaviour everywhere, but letting AnyEvent chose is generally better.	708	everywhere, but letting AnyEvent chose the model is generally better.
		709
		710	=head2 MAINLOOP EMULATION
		711
		712	Sometimes (often for short test scripts, or even standalone programs who
		713	only want to use AnyEvent), you do not want to run a specific event loop.
		714
		715	In that case, you can use a condition variable like this:
		716
		717	AnyEvent->condvar->recv;
		718
		719	This has the effect of entering the event loop and looping forever.
		720
		721	Note that usually your program has some exit condition, in which case
		722	it is better to use the "traditional" approach of storing a condition
		723	variable somewhere, waiting for it, and sending it when the program should
		724	exit cleanly.
		725
		726
		727	=head1 OTHER MODULES
		728
		729	The following is a non-exhaustive list of additional modules that use
		730	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		731	in the same program. Some of the modules come with AnyEvent, some are
		732	available via CPAN.
		733
		734	=over 4
		735
		736	=item L<AnyEvent::Util>
		737
		738	Contains various utility functions that replace often-used but blocking
		739	functions such as C<inet_aton> by event-/callback-based versions.
		740
		741	=item L<AnyEvent::Socket>
		742
		743	Provides various utility functions for (internet protocol) sockets,
		744	addresses and name resolution. Also functions to create non-blocking tcp
		745	connections or tcp servers, with IPv6 and SRV record support and more.
		746
		747	=item L<AnyEvent::Handle>
		748
		749	Provide read and write buffers, manages watchers for reads and writes,
		750	supports raw and formatted I/O, I/O queued and fully transparent and
		751	non-blocking SSL/TLS.
		752
		753	=item L<AnyEvent::DNS>
		754
		755	Provides rich asynchronous DNS resolver capabilities.
		756
		757	=item L<AnyEvent::HTTP>
		758
		759	A simple-to-use HTTP library that is capable of making a lot of concurrent
		760	HTTP requests.
		761
		762	=item L<AnyEvent::HTTPD>
		763
		764	Provides a simple web application server framework.
		765
		766	=item L<AnyEvent::FastPing>
		767
		768	The fastest ping in the west.
		769
		770	=item L<AnyEvent::DBI>
		771
		772	Executes L<DBI> requests asynchronously in a proxy process.
		773
		774	=item L<AnyEvent::AIO>
		775
		776	Truly asynchronous I/O, should be in the toolbox of every event
		777	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		778	together.
		779
		780	=item L<AnyEvent::BDB>
		781
		782	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		783	L<BDB> and AnyEvent together.
		784
		785	=item L<AnyEvent::GPSD>
		786
		787	A non-blocking interface to gpsd, a daemon delivering GPS information.
		788
		789	=item L<AnyEvent::IGS>
		790
		791	A non-blocking interface to the Internet Go Server protocol (used by
		792	L<App::IGS>).
		793
		794	=item L<Net::IRC3>
		795
		796	AnyEvent based IRC client module family.
		797
		798	=item L<Net::XMPP2>
		799
		800	AnyEvent based XMPP (Jabber protocol) module family.
		801
		802	=item L<Net::FCP>
		803
		804	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		805	of AnyEvent.
		806
		807	=item L<Event::ExecFlow>
		808
		809	High level API for event-based execution flow control.
		810
		811	=item L<Coro>
		812
		813	Has special support for AnyEvent via L<Coro::AnyEvent>.
		814
		815	=item L<IO::Lambda>
		816
		817	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		818
		819	=back
417		820
418	=cut	821	=cut
419		822
420	package AnyEvent;	823	package AnyEvent;
421		824
422	no warnings;	825	no warnings;
423	use strict;	826	use strict;
424		827
425	use Carp;	828	use Carp;
426		829
427	our $VERSION = '3.2';	830	our $VERSION = 4.2;
428	our $MODEL;	831	our $MODEL;
429		832
430	our $AUTOLOAD;	833	our $AUTOLOAD;
431	our @ISA;	834	our @ISA;
432		835
		836	our @REGISTRY;
		837
		838	our $WIN32;
		839
		840	BEGIN {
		841	my $win32 = ! ! ($^O =~ /mswin32/i);
		842	eval "sub WIN32(){ $win32 }";
		843	}
		844
433	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	845	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
434		846
435	our @REGISTRY;	847	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		848
		849	{
		850	my $idx;
		851	$PROTOCOL{$_} = ++$idx
		852	for reverse split /\s*,\s*/,
		853	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		854	}
436		855
437	my @models = (	856	my @models = (
438	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
439	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
440	[EV:: => AnyEvent::Impl::EV::],	857	[EV:: => AnyEvent::Impl::EV::],
441	[Event:: => AnyEvent::Impl::Event::],	858	[Event:: => AnyEvent::Impl::Event::],
442	[Glib:: => AnyEvent::Impl::Glib::],
443	[Tk:: => AnyEvent::Impl::Tk::],
444	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	859	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		860	# everything below here will not be autoprobed
		861	# as the pureperl backend should work everywhere
		862	# and is usually faster
		863	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		864	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		865	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		866	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		867	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		868	[Wx:: => AnyEvent::Impl::POE::],
		869	[Prima:: => AnyEvent::Impl::POE::],
445	);	870	);
446	my @models_detect = (
447	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
448	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
449	);
450		871
451	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	872	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);
		873
		874	our @post_detect;
		875
		876	sub post_detect(&) {
		877	my ($cb) = @_;
		878
		879	if ($MODEL) {
		880	$cb->();
		881
		882	1
		883	} else {
		884	push @post_detect, $cb;
		885
		886	defined wantarray
		887	? bless \$cb, "AnyEvent::Util::PostDetect"
		888	: ()
		889	}
		890	}
		891
		892	sub AnyEvent::Util::PostDetect::DESTROY {
		893	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		894	}
452		895
453	sub detect() {	896	sub detect() {
454	unless ($MODEL) {	897	unless ($MODEL) {
455	no strict 'refs';	898	no strict 'refs';
		899	local $SIG{__DIE__};
456		900
457	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	901	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
458	my $model = "AnyEvent::Impl::$1";	902	my $model = "AnyEvent::Impl::$1";
459	if (eval "require $model") {	903	if (eval "require $model") {
460	$MODEL = $model;	904	$MODEL = $model;
461	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	905	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		906	} else {
		907	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
462	}	908	}
463	}	909	}
464		910
465	# check for already loaded models	911	# check for already loaded models
466	unless ($MODEL) {	912	unless ($MODEL) {
467	for (@REGISTRY, @models, @models_detect) {	913	for (@REGISTRY, @models) {
468	my ($package, $model) = @$_;	914	my ($package, $model) = @$_;
469	if (${"$package\::VERSION"} > 0) {	915	if (${"$package\::VERSION"} > 0) {
470	if (eval "require $model") {	916	if (eval "require $model") {
471	$MODEL = $model;	917	$MODEL = $model;
472	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	918	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
…		…
488	last;	934	last;
489	}	935	}
490	}	936	}
491		937
492	$MODEL	938	$MODEL
493	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.";	939	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
494	}	940	}
495	}	941	}
496		942
497	unshift @ISA, $MODEL;	943	unshift @ISA, $MODEL;
498	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	944	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		945
		946	(shift @post_detect)->() while @post_detect;
499	}	947	}
500		948
501	$MODEL	949	$MODEL
502	}	950	}
503		951
…		…
513	$class->$func (@_);	961	$class->$func (@_);
514	}	962	}
515		963
516	package AnyEvent::Base;	964	package AnyEvent::Base;
517		965
		966	# default implementation for now and time
		967
		968	use Time::HiRes ();
		969
		970	sub time { Time::HiRes::time }
		971	sub now { Time::HiRes::time }
		972
518	# default implementation for ->condvar, ->wait, ->broadcast	973	# default implementation for ->condvar
519		974
520	sub condvar {	975	sub condvar {
521	bless \my $flag, "AnyEvent::Base::CondVar"	976	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
522	}
523
524	sub AnyEvent::Base::CondVar::broadcast {
525	${$_[0]}++;
526	}
527
528	sub AnyEvent::Base::CondVar::wait {
529	AnyEvent->one_event while !${$_[0]};
530	}	977	}
531		978
532	# default implementation for ->signal	979	# default implementation for ->signal
533		980
534	our %SIG_CB;	981	our %SIG_CB;
…		…
550	sub AnyEvent::Base::Signal::DESTROY {	997	sub AnyEvent::Base::Signal::DESTROY {
551	my ($signal, $cb) = @{$_[0]};	998	my ($signal, $cb) = @{$_[0]};
552		999
553	delete $SIG_CB{$signal}{$cb};	1000	delete $SIG_CB{$signal}{$cb};
554		1001
555	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1002	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
556	}	1003	}
557		1004
558	# default implementation for ->child	1005	# default implementation for ->child
559		1006
560	our %PID_CB;	1007	our %PID_CB;
…		…
587	or Carp::croak "required option 'pid' is missing";	1034	or Carp::croak "required option 'pid' is missing";
588		1035
589	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1036	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
590		1037
591	unless ($WNOHANG) {	1038	unless ($WNOHANG) {
592	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1039	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
593	}	1040	}
594		1041
595	unless ($CHLD_W) {	1042	unless ($CHLD_W) {
596	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1043	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
597	# child could be a zombie already, so make at least one round	1044	# child could be a zombie already, so make at least one round
…		…
607	delete $PID_CB{$pid}{$cb};	1054	delete $PID_CB{$pid}{$cb};
608	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1055	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
609		1056
610	undef $CHLD_W unless keys %PID_CB;	1057	undef $CHLD_W unless keys %PID_CB;
611	}	1058	}
		1059
		1060	package AnyEvent::CondVar;
		1061
		1062	our @ISA = AnyEvent::CondVar::Base::;
		1063
		1064	package AnyEvent::CondVar::Base;
		1065
		1066	use overload
		1067	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1068	fallback => 1;
		1069
		1070	sub _send {
		1071	# nop
		1072	}
		1073
		1074	sub send {
		1075	my $cv = shift;
		1076	$cv->{_ae_sent} = [@_];
		1077	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1078	$cv->_send;
		1079	}
		1080
		1081	sub croak {
		1082	$_[0]{_ae_croak} = $_[1];
		1083	$_[0]->send;
		1084	}
		1085
		1086	sub ready {
		1087	$_[0]{_ae_sent}
		1088	}
		1089
		1090	sub _wait {
		1091	AnyEvent->one_event while !$_[0]{_ae_sent};
		1092	}
		1093
		1094	sub recv {
		1095	$_[0]->_wait;
		1096
		1097	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1098	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1099	}
		1100
		1101	sub cb {
		1102	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1103	$_[0]{_ae_cb}
		1104	}
		1105
		1106	sub begin {
		1107	++$_[0]{_ae_counter};
		1108	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1109	}
		1110
		1111	sub end {
		1112	return if --$_[0]{_ae_counter};
		1113	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1114	}
		1115
		1116	# undocumented/compatibility with pre-3.4
		1117	*broadcast = \&send;
		1118	*wait = \&_wait;
612		1119
613	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1120	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
614		1121
615	This is an advanced topic that you do not normally need to use AnyEvent in	1122	This is an advanced topic that you do not normally need to use AnyEvent in
616	a module. This section is only of use to event loop authors who want to	1123	a module. This section is only of use to event loop authors who want to
…		…
659		1166
660	=over 4	1167	=over 4
661		1168
662	=item C<PERL_ANYEVENT_VERBOSE>	1169	=item C<PERL_ANYEVENT_VERBOSE>
663		1170
		1171	By default, AnyEvent will be completely silent except in fatal
		1172	conditions. You can set this environment variable to make AnyEvent more
		1173	talkative.
		1174
		1175	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1176	conditions, such as not being able to load the event model specified by
		1177	C<PERL_ANYEVENT_MODEL>.
		1178
664	When set to C<2> or higher, cause AnyEvent to report to STDERR which event	1179	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
665	model it chooses.	1180	model it chooses.
666		1181
667	=item C<PERL_ANYEVENT_MODEL>	1182	=item C<PERL_ANYEVENT_MODEL>
668		1183
669	This can be used to specify the event model to be used by AnyEvent, before	1184	This can be used to specify the event model to be used by AnyEvent, before
670	autodetection and -probing kicks in. It must be a string consisting	1185	auto detection and -probing kicks in. It must be a string consisting
671	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended	1186	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
672	and the resulting module name is loaded and if the load was successful,	1187	and the resulting module name is loaded and if the load was successful,
673	used as event model. If it fails to load AnyEvent will proceed with	1188	used as event model. If it fails to load AnyEvent will proceed with
674	autodetection and -probing.	1189	auto detection and -probing.
675		1190
676	This functionality might change in future versions.	1191	This functionality might change in future versions.
677		1192
678	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you	1193	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
679	could start your program like this:	1194	could start your program like this:
680		1195
681	PERL_ANYEVENT_MODEL=Perl perl ...	1196	PERL_ANYEVENT_MODEL=Perl perl ...
		1197
		1198	=item C<PERL_ANYEVENT_PROTOCOLS>
		1199
		1200	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1201	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1202	of auto probing).
		1203
		1204	Must be set to a comma-separated list of protocols or address families,
		1205	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1206	used, and preference will be given to protocols mentioned earlier in the
		1207	list.
		1208
		1209	This variable can effectively be used for denial-of-service attacks
		1210	against local programs (e.g. when setuid), although the impact is likely
		1211	small, as the program has to handle connection errors already-
		1212
		1213	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1214	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1215	- only support IPv4, never try to resolve or contact IPv6
		1216	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1217	IPv6, but prefer IPv6 over IPv4.
		1218
		1219	=item C<PERL_ANYEVENT_EDNS0>
		1220
		1221	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1222	for DNS. This extension is generally useful to reduce DNS traffic, but
		1223	some (broken) firewalls drop such DNS packets, which is why it is off by
		1224	default.
		1225
		1226	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1227	EDNS0 in its DNS requests.
		1228
		1229	=item C<PERL_ANYEVENT_MAX_FORKS>
		1230
		1231	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1232	will create in parallel.
682		1233
683	=back	1234	=back
684		1235
685	=head1 EXAMPLE PROGRAM	1236	=head1 EXAMPLE PROGRAM
686		1237
687	The following program uses an IO watcher to read data from STDIN, a timer	1238	The following program uses an I/O watcher to read data from STDIN, a timer
688	to display a message once per second, and a condition variable to quit the	1239	to display a message once per second, and a condition variable to quit the
689	program when the user enters quit:	1240	program when the user enters quit:
690		1241
691	use AnyEvent;	1242	use AnyEvent;
692		1243
…		…
697	poll => 'r',	1248	poll => 'r',
698	cb => sub {	1249	cb => sub {
699	warn "io event <$_[0]>\n"; # will always output <r>	1250	warn "io event <$_[0]>\n"; # will always output <r>
700	chomp (my $input = <STDIN>); # read a line	1251	chomp (my $input = <STDIN>); # read a line
701	warn "read: $input\n"; # output what has been read	1252	warn "read: $input\n"; # output what has been read
702	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1253	$cv->send if $input =~ /^q/i; # quit program if /^q/i
703	},	1254	},
704	);	1255	);
705		1256
706	my $time_watcher; # can only be used once	1257	my $time_watcher; # can only be used once
707		1258
…		…
712	});	1263	});
713	}	1264	}
714		1265
715	new_timer; # create first timer	1266	new_timer; # create first timer
716		1267
717	$cv->wait; # wait until user enters /^q/i	1268	$cv->recv; # wait until user enters /^q/i
718		1269
719	=head1 REAL-WORLD EXAMPLE	1270	=head1 REAL-WORLD EXAMPLE
720		1271
721	Consider the L<Net::FCP> module. It features (among others) the following	1272	Consider the L<Net::FCP> module. It features (among others) the following
722	API calls, which are to freenet what HTTP GET requests are to http:	1273	API calls, which are to freenet what HTTP GET requests are to http:
…		…
772	syswrite $txn->{fh}, $txn->{request}	1323	syswrite $txn->{fh}, $txn->{request}
773	or die "connection or write error";	1324	or die "connection or write error";
774	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1325	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
775		1326
776	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1327	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
777	result and signals any possible waiters that the request ahs finished:	1328	result and signals any possible waiters that the request has finished:
778		1329
779	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1330	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
780		1331
781	if (end-of-file or data complete) {	1332	if (end-of-file or data complete) {
782	$txn->{result} = $txn->{buf};	1333	$txn->{result} = $txn->{buf};
783	$txn->{finished}->broadcast;	1334	$txn->{finished}->send;
784	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1335	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
785	}	1336	}
786		1337
787	The C<result> method, finally, just waits for the finished signal (if the	1338	The C<result> method, finally, just waits for the finished signal (if the
788	request was already finished, it doesn't wait, of course, and returns the	1339	request was already finished, it doesn't wait, of course, and returns the
789	data:	1340	data:
790		1341
791	$txn->{finished}->wait;	1342	$txn->{finished}->recv;
792	return $txn->{result};	1343	return $txn->{result};
793		1344
794	The actual code goes further and collects all errors (C<die>s, exceptions)	1345	The actual code goes further and collects all errors (C<die>s, exceptions)
795	that occured during request processing. The C<result> method detects	1346	that occurred during request processing. The C<result> method detects
796	whether an exception as thrown (it is stored inside the $txn object)	1347	whether an exception as thrown (it is stored inside the $txn object)
797	and just throws the exception, which means connection errors and other	1348	and just throws the exception, which means connection errors and other
798	problems get reported tot he code that tries to use the result, not in a	1349	problems get reported tot he code that tries to use the result, not in a
799	random callback.	1350	random callback.
800		1351
…		…
831		1382
832	my $quit = AnyEvent->condvar;	1383	my $quit = AnyEvent->condvar;
833		1384
834	$fcp->txn_client_get ($url)->cb (sub {	1385	$fcp->txn_client_get ($url)->cb (sub {
835	...	1386	...
836	$quit->broadcast;	1387	$quit->send;
837	});	1388	});
838		1389
839	$quit->wait;	1390	$quit->recv;
		1391
		1392
		1393	=head1 BENCHMARKS
		1394
		1395	To give you an idea of the performance and overheads that AnyEvent adds
		1396	over the event loops themselves and to give you an impression of the speed
		1397	of various event loops I prepared some benchmarks.
		1398
		1399	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1400
		1401	Here is a benchmark of various supported event models used natively and
		1402	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1403	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1404	which it is), lets them fire exactly once and destroys them again.
		1405
		1406	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1407	distribution.
		1408
		1409	=head3 Explanation of the columns
		1410
		1411	I<watcher> is the number of event watchers created/destroyed. Since
		1412	different event models feature vastly different performances, each event
		1413	loop was given a number of watchers so that overall runtime is acceptable
		1414	and similar between tested event loop (and keep them from crashing): Glib
		1415	would probably take thousands of years if asked to process the same number
		1416	of watchers as EV in this benchmark.
		1417
		1418	I<bytes> is the number of bytes (as measured by the resident set size,
		1419	RSS) consumed by each watcher. This method of measuring captures both C
		1420	and Perl-based overheads.
		1421
		1422	I<create> is the time, in microseconds (millionths of seconds), that it
		1423	takes to create a single watcher. The callback is a closure shared between
		1424	all watchers, to avoid adding memory overhead. That means closure creation
		1425	and memory usage is not included in the figures.
		1426
		1427	I<invoke> is the time, in microseconds, used to invoke a simple
		1428	callback. The callback simply counts down a Perl variable and after it was
		1429	invoked "watcher" times, it would C<< ->send >> a condvar once to
		1430	signal the end of this phase.
		1431
		1432	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1433	watcher.
		1434
		1435	=head3 Results
		1436
		1437	name watchers bytes create invoke destroy comment
		1438	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		1439	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		1440	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		1441	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		1442	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		1443	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		1444	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		1445	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		1446	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		1447	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		1448
		1449	=head3 Discussion
		1450
		1451	The benchmark does I<not> measure scalability of the event loop very
		1452	well. For example, a select-based event loop (such as the pure perl one)
		1453	can never compete with an event loop that uses epoll when the number of
		1454	file descriptors grows high. In this benchmark, all events become ready at
		1455	the same time, so select/poll-based implementations get an unnatural speed
		1456	boost.
		1457
		1458	Also, note that the number of watchers usually has a nonlinear effect on
		1459	overall speed, that is, creating twice as many watchers doesn't take twice
		1460	the time - usually it takes longer. This puts event loops tested with a
		1461	higher number of watchers at a disadvantage.
		1462
		1463	To put the range of results into perspective, consider that on the
		1464	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1465	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1466	cycles with POE.
		1467
		1468	C<EV> is the sole leader regarding speed and memory use, which are both
		1469	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1470	far less memory than any other event loop and is still faster than Event
		1471	natively.
		1472
		1473	The pure perl implementation is hit in a few sweet spots (both the
		1474	constant timeout and the use of a single fd hit optimisations in the perl
		1475	interpreter and the backend itself). Nevertheless this shows that it
		1476	adds very little overhead in itself. Like any select-based backend its
		1477	performance becomes really bad with lots of file descriptors (and few of
		1478	them active), of course, but this was not subject of this benchmark.
		1479
		1480	The C<Event> module has a relatively high setup and callback invocation
		1481	cost, but overall scores in on the third place.
		1482
		1483	C<Glib>'s memory usage is quite a bit higher, but it features a
		1484	faster callback invocation and overall ends up in the same class as
		1485	C<Event>. However, Glib scales extremely badly, doubling the number of
		1486	watchers increases the processing time by more than a factor of four,
		1487	making it completely unusable when using larger numbers of watchers
		1488	(note that only a single file descriptor was used in the benchmark, so
		1489	inefficiencies of C<poll> do not account for this).
		1490
		1491	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1492	more than 2000 watchers is a big setback, however, as correctness takes
		1493	precedence over speed. Nevertheless, its performance is surprising, as the
		1494	file descriptor is dup()ed for each watcher. This shows that the dup()
		1495	employed by some adaptors is not a big performance issue (it does incur a
		1496	hidden memory cost inside the kernel which is not reflected in the figures
		1497	above).
		1498
		1499	C<POE>, regardless of underlying event loop (whether using its pure perl
		1500	select-based backend or the Event module, the POE-EV backend couldn't
		1501	be tested because it wasn't working) shows abysmal performance and
		1502	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		1503	as EV watchers, and 10 times as much memory as Event (the high memory
		1504	requirements are caused by requiring a session for each watcher). Watcher
		1505	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1506	implementation.
		1507
		1508	The design of the POE adaptor class in AnyEvent can not really account
		1509	for the performance issues, though, as session creation overhead is
		1510	small compared to execution of the state machine, which is coded pretty
		1511	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1512	using multiple sessions is not a good approach, especially regarding
		1513	memory usage, even the author of POE could not come up with a faster
		1514	design).
		1515
		1516	=head3 Summary
		1517
		1518	=over 4
		1519
		1520	=item * Using EV through AnyEvent is faster than any other event loop
		1521	(even when used without AnyEvent), but most event loops have acceptable
		1522	performance with or without AnyEvent.
		1523
		1524	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1525	the actual event loop, only with extremely fast event loops such as EV
		1526	adds AnyEvent significant overhead.
		1527
		1528	=item * You should avoid POE like the plague if you want performance or
		1529	reasonable memory usage.
		1530
		1531	=back
		1532
		1533	=head2 BENCHMARKING THE LARGE SERVER CASE
		1534
		1535	This benchmark actually benchmarks the event loop itself. It works by
		1536	creating a number of "servers": each server consists of a socket pair, a
		1537	timeout watcher that gets reset on activity (but never fires), and an I/O
		1538	watcher waiting for input on one side of the socket. Each time the socket
		1539	watcher reads a byte it will write that byte to a random other "server".
		1540
		1541	The effect is that there will be a lot of I/O watchers, only part of which
		1542	are active at any one point (so there is a constant number of active
		1543	fds for each loop iteration, but which fds these are is random). The
		1544	timeout is reset each time something is read because that reflects how
		1545	most timeouts work (and puts extra pressure on the event loops).
		1546
		1547	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1548	(1%) are active. This mirrors the activity of large servers with many
		1549	connections, most of which are idle at any one point in time.
		1550
		1551	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1552	distribution.
		1553
		1554	=head3 Explanation of the columns
		1555
		1556	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1557	each server has a read and write socket end).
		1558
		1559	I<create> is the time it takes to create a socket pair (which is
		1560	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1561
		1562	I<request>, the most important value, is the time it takes to handle a
		1563	single "request", that is, reading the token from the pipe and forwarding
		1564	it to another server. This includes deleting the old timeout and creating
		1565	a new one that moves the timeout into the future.
		1566
		1567	=head3 Results
		1568
		1569	name sockets create request
		1570	EV 20000 69.01 11.16
		1571	Perl 20000 73.32 35.87
		1572	Event 20000 212.62 257.32
		1573	Glib 20000 651.16 1896.30
		1574	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1575
		1576	=head3 Discussion
		1577
		1578	This benchmark I<does> measure scalability and overall performance of the
		1579	particular event loop.
		1580
		1581	EV is again fastest. Since it is using epoll on my system, the setup time
		1582	is relatively high, though.
		1583
		1584	Perl surprisingly comes second. It is much faster than the C-based event
		1585	loops Event and Glib.
		1586
		1587	Event suffers from high setup time as well (look at its code and you will
		1588	understand why). Callback invocation also has a high overhead compared to
		1589	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1590	uses select or poll in basically all documented configurations.
		1591
		1592	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1593	clearly fails to perform with many filehandles or in busy servers.
		1594
		1595	POE is still completely out of the picture, taking over 1000 times as long
		1596	as EV, and over 100 times as long as the Perl implementation, even though
		1597	it uses a C-based event loop in this case.
		1598
		1599	=head3 Summary
		1600
		1601	=over 4
		1602
		1603	=item * The pure perl implementation performs extremely well.
		1604
		1605	=item * Avoid Glib or POE in large projects where performance matters.
		1606
		1607	=back
		1608
		1609	=head2 BENCHMARKING SMALL SERVERS
		1610
		1611	While event loops should scale (and select-based ones do not...) even to
		1612	large servers, most programs we (or I :) actually write have only a few
		1613	I/O watchers.
		1614
		1615	In this benchmark, I use the same benchmark program as in the large server
		1616	case, but it uses only eight "servers", of which three are active at any
		1617	one time. This should reflect performance for a small server relatively
		1618	well.
		1619
		1620	The columns are identical to the previous table.
		1621
		1622	=head3 Results
		1623
		1624	name sockets create request
		1625	EV 16 20.00 6.54
		1626	Perl 16 25.75 12.62
		1627	Event 16 81.27 35.86
		1628	Glib 16 32.63 15.48
		1629	POE 16 261.87 276.28 uses POE::Loop::Event
		1630
		1631	=head3 Discussion
		1632
		1633	The benchmark tries to test the performance of a typical small
		1634	server. While knowing how various event loops perform is interesting, keep
		1635	in mind that their overhead in this case is usually not as important, due
		1636	to the small absolute number of watchers (that is, you need efficiency and
		1637	speed most when you have lots of watchers, not when you only have a few of
		1638	them).
		1639
		1640	EV is again fastest.
		1641
		1642	Perl again comes second. It is noticeably faster than the C-based event
		1643	loops Event and Glib, although the difference is too small to really
		1644	matter.
		1645
		1646	POE also performs much better in this case, but is is still far behind the
		1647	others.
		1648
		1649	=head3 Summary
		1650
		1651	=over 4
		1652
		1653	=item * C-based event loops perform very well with small number of
		1654	watchers, as the management overhead dominates.
		1655
		1656	=back
		1657
840		1658
841	=head1 FORK	1659	=head1 FORK
842		1660
843	Most event libraries are not fork-safe. The ones who are usually are	1661	Most event libraries are not fork-safe. The ones who are usually are
844	because they are so inefficient. Only L<EV> is fully fork-aware.	1662	because they rely on inefficient but fork-safe C<select> or C<poll>
		1663	calls. Only L<EV> is fully fork-aware.
845		1664
846	If you have to fork, you must either do so I<before> creating your first	1665	If you have to fork, you must either do so I<before> creating your first
847	watcher OR you must not use AnyEvent at all in the child.	1666	watcher OR you must not use AnyEvent at all in the child.
		1667
848		1668
849	=head1 SECURITY CONSIDERATIONS	1669	=head1 SECURITY CONSIDERATIONS
850		1670
851	AnyEvent can be forced to load any event model via	1671	AnyEvent can be forced to load any event model via
852	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	1672	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
856	specified in the variable.	1676	specified in the variable.
857		1677
858	You can make AnyEvent completely ignore this variable by deleting it	1678	You can make AnyEvent completely ignore this variable by deleting it
859	before the first watcher gets created, e.g. with a C<BEGIN> block:	1679	before the first watcher gets created, e.g. with a C<BEGIN> block:
860		1680
861	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1681	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
862		1682
863	use AnyEvent;	1683	use AnyEvent;
		1684
		1685	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1686	be used to probe what backend is used and gain other information (which is
		1687	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
		1688
		1689
		1690	=head1 BUGS
		1691
		1692	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		1693	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		1694	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		1695	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as
		1696	pronounced).
		1697
864		1698
865	=head1 SEE ALSO	1699	=head1 SEE ALSO
866		1700
867	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1701	Utility functions: L<AnyEvent::Util>.
868	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
869	L<Event::Lib>, L<Qt>.
870		1702
871	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1703	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
872	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1704	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
873	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1705
		1706	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		1707	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		1708	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
874	L<AnyEvent::Impl::Qt>.	1709	L<AnyEvent::Impl::POE>.
875		1710
		1711	Non-blocking file handles, sockets, TCP clients and
		1712	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1713
		1714	Asynchronous DNS: L<AnyEvent::DNS>.
		1715
		1716	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1717
876	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1718	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
		1719
877		1720
878	=head1 AUTHOR	1721	=head1 AUTHOR
879		1722
880	Marc Lehmann <schmorp@schmorp.de>	1723	Marc Lehmann <schmorp@schmorp.de>
881	http://home.schmorp.de/	1724	http://home.schmorp.de/
882		1725
883	=cut	1726	=cut
884		1727
885	1	1728	1
886		1729

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