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Revision 1.167 by root, Tue Jul 8 23:44:51 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<Tk>, L<AnyEvent::Impl::Perl>, 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 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
90	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
91	very efficient, but should work everywhere.	102	very efficient, but should work everywhere.
92		103
…		…
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 IO 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 for events
		158	(AnyEvent might or might not keep a reference to this file handle). C<poll>
147	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
148	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
149	respectively. C<cb> is the callback to invoke each time the file handle	161	callback to invoke each time the file handle becomes ready.
150	becomes ready.
151		162
152	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
153	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.
154		166
		167	The I/O watcher might use the underlying file descriptor or a copy of it.
155	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
156	on the underlying file descriptor.	169	underlying file descriptor.
157		170
158	Some event loops issue spurious readyness notifications, so you should	171	Some event loops issue spurious readyness notifications, so you should
159	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
160	handles.	173	handles.
161		174
162	Example:
163
164	# 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
165	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	178	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
166	chomp (my $input = <STDIN>);	179	chomp (my $input = <STDIN>);
167	warn "read: $input\n";	180	warn "read: $input\n";
168	undef $w;	181	undef $w;
169	});	182	});
…		…
172		185
173	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 >>
174	method with the following mandatory arguments:	187	method with the following mandatory arguments:
175		188
176	C<after> specifies after how many seconds (fractional values are	189	C<after> specifies after how many seconds (fractional values are
177	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
178	case.	191	in that case.
179		192
180	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
181	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
182	and Glib).	195	callbacks cannot use arguments passed to time watcher callbacks.
183		196
184	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.
185		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
186	# fire an event after 7.7 seconds	207	Example: fire an event after 7.7 seconds.
		208
187	my $w = AnyEvent->timer (after => 7.7, cb => sub {	209	my $w = AnyEvent->timer (after => 7.7, cb => sub {
188	warn "timeout\n";	210	warn "timeout\n";
189	});	211	});
190		212
191	# to cancel the timer:	213	# to cancel the timer:
192	undef $w;	214	undef $w;
193		215
194	Example 2:
195
196	# 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.
197	my $w;
198		217
199	my $cb = sub {
200	# cancel the old timer while creating a new one
201	$w = AnyEvent->timer (after => 1, cb => $cb);	218	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		219	warn "timeout\n";
202	};	220	};
203
204	# start the "loop" by creating the first watcher
205	$w = AnyEvent->timer (after => 0.5, cb => $cb);
206		221
207	=head3 TIMING ISSUES	222	=head3 TIMING ISSUES
208		223
209	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
210	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
…		…
222	timers.	237	timers.
223		238
224	AnyEvent always prefers relative timers, if available, matching the	239	AnyEvent always prefers relative timers, if available, matching the
225	AnyEvent API.	240	AnyEvent API.
226		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
227	=head2 SIGNAL WATCHERS	305	=head2 SIGNAL WATCHERS
228		306
229	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
230	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	308	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
231	be invoked whenever a signal occurs.	309	callback to be invoked whenever a signal occurs.
232		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
233	Multiple signal occurances can be clumped together into one callback	315	Multiple signal occurrences can be clumped together into one callback
234	invocation, and callback invocation will be synchronous. synchronous means	316	invocation, and callback invocation will be synchronous. Synchronous means
235	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,
236	but it is guarenteed not to interrupt any other callbacks.	318	but it is guaranteed not to interrupt any other callbacks.
237		319
238	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
239	between multiple watchers.	321	between multiple watchers.
240		322
241	This watcher might use C<%SIG>, so programs overwriting those signals	323	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
251		333
252	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
253	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
254	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
255	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
256	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.
257		340
258	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).
259		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
260	my $w = AnyEvent->child (	359	my $w = AnyEvent->child (
261	pid => 1333,	360	pid => $pid,
262	cb => sub {	361	cb => sub {
263	my ($pid, $status) = @_;	362	my ($pid, $status) = @_;
264	warn "pid $pid exited with status $status";	363	warn "pid $pid exited with status $status";
		364	$done->send;
265	},	365	},
266	);	366	);
		367
		368	# do something else, then wait for process exit
		369	$done->recv;
267		370
268	=head2 CONDITION VARIABLES	371	=head2 CONDITION VARIABLES
269		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
270	Condition variables can be created by calling the C<< AnyEvent->condvar >>	383	Condition variables can be created by calling the C<< AnyEvent->condvar
271	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.
272		387
273	A condition variable waits for a condition - precisely that the C<<	388	After creation, the condition variable is "false" until it becomes "true"
274	->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).
275		392
276	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,
277	example, if you write a module that does asynchronous http requests,	401	for example, if you write a module that does asynchronous http requests,
278	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
279	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.
280		405
281	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,
282	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
283	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
284	->broadcast >> the "quit" event.	409	button of your app, which would C<< ->send >> the "quit" event.
285		410
286	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
287	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
288	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
289	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,
290	as this asks for trouble.	415	as this asks for trouble.
291		416
292	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.
293		458
294	=over 4	459	=over 4
295		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
296	=item $cv->wait	492	=item $cv->end
297		493
298	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 $cv->recv
		551
		552	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
299	called on c<$cv>, while servicing other watchers normally.	553	>> methods have been called on c<$cv>, while servicing other watchers
		554	normally.
300		555
301	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
302	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.
303		564
304	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
305	(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
306	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
307	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
308	condition variables with some kind of request results and supporting	569	condition variables with some kind of request results and supporting
309	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,
310	while still suppporting blocking waits if the caller so desires).	571	while still supporting blocking waits if the caller so desires).
311		572
312	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
313	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
314	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	575	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
315	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	576	can supply.
316	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
317	from different coroutines, however).
318		577
319	=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).
320		583
321	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
322	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
323	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.
324		603
325	=back	604	=back
326
327	Example:
328
329	# wait till the result is ready
330	my $result_ready = AnyEvent->condvar;
331
332	# do something such as adding a timer
333	# or socket watcher the calls $result_ready->broadcast
334	# when the "result" is ready.
335	# in this case, we simply use a timer:
336	my $w = AnyEvent->timer (
337	after => 1,
338	cb => sub { $result_ready->broadcast },
339	);
340
341	# this "blocks" (while handling events) till the watcher
342	# calls broadcast
343	$result_ready->wait;
344		605
345	=head1 GLOBAL VARIABLES AND FUNCTIONS	606	=head1 GLOBAL VARIABLES AND FUNCTIONS
346		607
347	=over 4	608	=over 4
348		609
…		…
354	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	615	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
355	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	616	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
356		617
357	The known classes so far are:	618	The known classes so far are:
358		619
359	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
360	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
361	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	620	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
362	AnyEvent::Impl::Event based on Event, second best choice.	621	AnyEvent::Impl::Event based on Event, second best choice.
		622	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
363	AnyEvent::Impl::Glib based on Glib, third-best choice.	623	AnyEvent::Impl::Glib based on Glib, third-best choice.
364	AnyEvent::Impl::Tk based on Tk, very bad choice.	624	AnyEvent::Impl::Tk based on Tk, very bad choice.
365	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
366	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	625	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
367	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	626	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
368	AnyEvent::Impl::POE based on POE, not generic enough for full support.	627	AnyEvent::Impl::POE based on POE, not generic enough for full support.
369		628
370	There is no support for WxWidgets, as WxWidgets has no support for	629	There is no support for WxWidgets, as WxWidgets has no support for
…		…
382	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	641	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
383	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
384	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
385	runtime.	644	runtime.
386		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
387	=back	667	=back
388		668
389	=head1 WHAT TO DO IN A MODULE	669	=head1 WHAT TO DO IN A MODULE
390		670
391	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
…		…
394	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
395	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
396	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
397	to load the event module first.	677	to load the event module first.
398		678
399	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
400	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
401	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
402	events is to stay interactive.	682	events is to stay interactive.
403		683
404	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
405	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
406	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 >>
407	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).
408		688
409	=head1 WHAT TO DO IN THE MAIN PROGRAM	689	=head1 WHAT TO DO IN THE MAIN PROGRAM
410		690
411	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
…		…
413		693
414	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
415	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
416	decide which implementation to chose if some module relies on it.	696	decide which implementation to chose if some module relies on it.
417		697
418	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
419	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
420	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
421	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
422	modules might create watchers when they are loaded, and AnyEvent will	702	modules might create watchers when they are loaded, and AnyEvent will
423	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
424	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.
425		705
426	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
427	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	707	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
428	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
429		820
430	=cut	821	=cut
431		822
432	package AnyEvent;	823	package AnyEvent;
433		824
434	no warnings;	825	no warnings;
435	use strict;	826	use strict;
436		827
437	use Carp;	828	use Carp;
438		829
439	our $VERSION = '3.3';	830	our $VERSION = 4.2;
440	our $MODEL;	831	our $MODEL;
441		832
442	our $AUTOLOAD;	833	our $AUTOLOAD;
443	our @ISA;	834	our @ISA;
444		835
		836	our @REGISTRY;
		837
		838	our $WIN32;
		839
		840	BEGIN {
		841	my $win32 = ! ! ($^O =~ /mswin32/i);
		842	eval "sub WIN32(){ $win32 }";
		843	}
		844
445	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	845	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
446		846
447	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	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		854	}
448		855
449	my @models = (	856	my @models = (
450	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
451	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
452	[EV:: => AnyEvent::Impl::EV::],	857	[EV:: => AnyEvent::Impl::EV::],
453	[Event:: => AnyEvent::Impl::Event::],	858	[Event:: => AnyEvent::Impl::Event::],
454	[Glib:: => AnyEvent::Impl::Glib::],
455	[Tk:: => AnyEvent::Impl::Tk::],
456	[Wx:: => AnyEvent::Impl::POE::],
457	[Prima:: => AnyEvent::Impl::POE::],
458	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	859	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
459	# everything below here will not be autoprobed as the pureperl backend should work everywhere	860	# everything below here will not be autoprobed
		861	# as the pureperl backend should work everywhere
		862	# and is usually faster
		863	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		864	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
460	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	865	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
461	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	866	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
462	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	867	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		868	[Wx:: => AnyEvent::Impl::POE::],
		869	[Prima:: => AnyEvent::Impl::POE::],
463	);	870	);
464		871
465	our %method = map +($_ => 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	}
466		895
467	sub detect() {	896	sub detect() {
468	unless ($MODEL) {	897	unless ($MODEL) {
469	no strict 'refs';	898	no strict 'refs';
		899	local $SIG{__DIE__};
470		900
471	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	901	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
472	my $model = "AnyEvent::Impl::$1";	902	my $model = "AnyEvent::Impl::$1";
473	if (eval "require $model") {	903	if (eval "require $model") {
474	$MODEL = $model;	904	$MODEL = $model;
…		…
504	last;	934	last;
505	}	935	}
506	}	936	}
507		937
508	$MODEL	938	$MODEL
509	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.";
510	}	940	}
511	}	941	}
512		942
513	unshift @ISA, $MODEL;
514	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	943	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		944
		945	if ($ENV{PERL_ANYEVENT_STRICT}) {
		946	unshift @AnyEvent::Base::Strict::ISA, $MODEL;
		947	unshift @ISA, AnyEvent::Base::Strict::
		948	} else {
		949	unshift @ISA, $MODEL;
		950	}
		951
		952	(shift @post_detect)->() while @post_detect;
515	}	953	}
516		954
517	$MODEL	955	$MODEL
518	}	956	}
519		957
…		…
529	$class->$func (@_);	967	$class->$func (@_);
530	}	968	}
531		969
532	package AnyEvent::Base;	970	package AnyEvent::Base;
533		971
		972	# default implementation for now and time
		973
		974	use Time::HiRes ();
		975
		976	sub time { Time::HiRes::time }
		977	sub now { Time::HiRes::time }
		978
534	# default implementation for ->condvar, ->wait, ->broadcast	979	# default implementation for ->condvar
535		980
536	sub condvar {	981	sub condvar {
537	bless \my $flag, "AnyEvent::Base::CondVar"	982	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
538	}
539
540	sub AnyEvent::Base::CondVar::broadcast {
541	${$_[0]}++;
542	}
543
544	sub AnyEvent::Base::CondVar::wait {
545	AnyEvent->one_event while !${$_[0]};
546	}	983	}
547		984
548	# default implementation for ->signal	985	# default implementation for ->signal
549		986
550	our %SIG_CB;	987	our %SIG_CB;
…		…
566	sub AnyEvent::Base::Signal::DESTROY {	1003	sub AnyEvent::Base::Signal::DESTROY {
567	my ($signal, $cb) = @{$_[0]};	1004	my ($signal, $cb) = @{$_[0]};
568		1005
569	delete $SIG_CB{$signal}{$cb};	1006	delete $SIG_CB{$signal}{$cb};
570		1007
571	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1008	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
572	}	1009	}
573		1010
574	# default implementation for ->child	1011	# default implementation for ->child
575		1012
576	our %PID_CB;	1013	our %PID_CB;
…		…
603	or Carp::croak "required option 'pid' is missing";	1040	or Carp::croak "required option 'pid' is missing";
604		1041
605	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1042	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
606		1043
607	unless ($WNOHANG) {	1044	unless ($WNOHANG) {
608	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1045	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
609	}	1046	}
610		1047
611	unless ($CHLD_W) {	1048	unless ($CHLD_W) {
612	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1049	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
613	# child could be a zombie already, so make at least one round	1050	# child could be a zombie already, so make at least one round
…		…
622		1059
623	delete $PID_CB{$pid}{$cb};	1060	delete $PID_CB{$pid}{$cb};
624	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1061	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
625		1062
626	undef $CHLD_W unless keys %PID_CB;	1063	undef $CHLD_W unless keys %PID_CB;
		1064	}
		1065
		1066	package AnyEvent::CondVar;
		1067
		1068	our @ISA = AnyEvent::CondVar::Base::;
		1069
		1070	package AnyEvent::CondVar::Base;
		1071
		1072	use overload
		1073	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1074	fallback => 1;
		1075
		1076	sub _send {
		1077	# nop
		1078	}
		1079
		1080	sub send {
		1081	my $cv = shift;
		1082	$cv->{_ae_sent} = [@_];
		1083	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1084	$cv->_send;
		1085	}
		1086
		1087	sub croak {
		1088	$_[0]{_ae_croak} = $_[1];
		1089	$_[0]->send;
		1090	}
		1091
		1092	sub ready {
		1093	$_[0]{_ae_sent}
		1094	}
		1095
		1096	sub _wait {
		1097	AnyEvent->one_event while !$_[0]{_ae_sent};
		1098	}
		1099
		1100	sub recv {
		1101	$_[0]->_wait;
		1102
		1103	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1104	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1105	}
		1106
		1107	sub cb {
		1108	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1109	$_[0]{_ae_cb}
		1110	}
		1111
		1112	sub begin {
		1113	++$_[0]{_ae_counter};
		1114	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1115	}
		1116
		1117	sub end {
		1118	return if --$_[0]{_ae_counter};
		1119	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1120	}
		1121
		1122	# undocumented/compatibility with pre-3.4
		1123	*broadcast = \&send;
		1124	*wait = \&_wait;
		1125
		1126	package AnyEvent::Base::Strict;
		1127
		1128	use Carp qw(croak);
		1129
		1130	# supply checks for argument validity for many functions
		1131
		1132	sub io {
		1133	my $class = shift;
		1134	my %arg = @_;
		1135
		1136	ref $arg{cb}
		1137	or croak "AnyEvent->io called with illegal cb argument '$arg{cb}'";
		1138	delete $arg{cb};
		1139
		1140	fileno $arg{fh}
		1141	or croak "AnyEvent->io called with illegal fh argument '$arg{fh}'";
		1142	delete $arg{fh};
		1143
		1144	$arg{poll} =~ /^[rw]$/
		1145	or croak "AnyEvent->io called with illegal poll argument '$arg{poll}'";
		1146	delete $arg{poll};
		1147
		1148	croak "AnyEvent->io called with unsupported parameter(s) " . join ", ", keys %arg
		1149	if keys %arg;
		1150
		1151	$class->SUPER::io (@_)
		1152	}
		1153
		1154	sub timer {
		1155	my $class = shift;
		1156	my %arg = @_;
		1157
		1158	ref $arg{cb}
		1159	or croak "AnyEvent->timer called with illegal cb argument '$arg{cb}'";
		1160	delete $arg{cb};
		1161
		1162	exists $arg{after}
		1163	or croak "AnyEvent->timer called without mandatory 'after' parameter";
		1164	delete $arg{after};
		1165
		1166	$arg{interval} > 0 || !$arg{interval}
		1167	or croak "AnyEvent->timer called with illegal interval argument '$arg{interval}'";
		1168	delete $arg{interval};
		1169
		1170	croak "AnyEvent->timer called with unsupported parameter(s) " . join ", ", keys %arg
		1171	if keys %arg;
		1172
		1173	$class->SUPER::timer (@_)
		1174	}
		1175
		1176	sub signal {
		1177	my $class = shift;
		1178	my %arg = @_;
		1179
		1180	ref $arg{cb}
		1181	or croak "AnyEvent->signal called with illegal cb argument '$arg{cb}'";
		1182	delete $arg{cb};
		1183
		1184	eval "require POSIX; defined &POSIX::SIG$arg{signal}"
		1185	or croak "AnyEvent->signal called with illegal signal name '$arg{signal}'";
		1186	delete $arg{signal};
		1187
		1188	croak "AnyEvent->signal called with unsupported parameter(s) " . join ", ", keys %arg
		1189	if keys %arg;
		1190
		1191	$class->SUPER::signal (@_)
		1192	}
		1193
		1194	sub child {
		1195	my $class = shift;
		1196	my %arg = @_;
		1197
		1198	ref $arg{cb}
		1199	or croak "AnyEvent->signal called with illegal cb argument '$arg{cb}'";
		1200	delete $arg{cb};
		1201
		1202	$arg{pid} =~ /^-?\d+$/
		1203	or croak "AnyEvent->signal called with illegal pid value '$arg{pid}'";
		1204	delete $arg{pid};
		1205
		1206	croak "AnyEvent->signal called with unsupported parameter(s) " . join ", ", keys %arg
		1207	if keys %arg;
		1208
		1209	$class->SUPER::child (@_)
		1210	}
		1211
		1212	sub condvar {
		1213	my $class = shift;
		1214	my %arg = @_;
		1215
		1216	!exists $arg{cb} or ref $arg{cb}
		1217	or croak "AnyEvent->condvar called with illegal cb argument '$arg{cb}'";
		1218	delete $arg{cb};
		1219
		1220	croak "AnyEvent->condvar called with unsupported parameter(s) " . join ", ", keys %arg
		1221	if keys %arg;
		1222
		1223	$class->SUPER::condvar (@_)
		1224	}
		1225
		1226	sub time {
		1227	my $class = shift;
		1228
		1229	@_
		1230	and croak "AnyEvent->time wrongly called with paramaters";
		1231
		1232	$class->SUPER::time (@_)
		1233	}
		1234
		1235	sub now {
		1236	my $class = shift;
		1237
		1238	@_
		1239	and croak "AnyEvent->now wrongly called with paramaters";
		1240
		1241	$class->SUPER::now (@_)
627	}	1242	}
628		1243
629	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1244	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
630		1245
631	This is an advanced topic that you do not normally need to use AnyEvent in	1246	This is an advanced topic that you do not normally need to use AnyEvent in
…		…
686	C<PERL_ANYEVENT_MODEL>.	1301	C<PERL_ANYEVENT_MODEL>.
687		1302
688	When set to C<2> or higher, cause AnyEvent to report to STDERR which event	1303	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
689	model it chooses.	1304	model it chooses.
690		1305
		1306	=item C<PERL_ANYEVENT_STRICT>
		1307
		1308	AnyEvent does not do much argument checking by default, as thorough
		1309	argument checking is very costly. Setting this variable to a true value
		1310	will cause AnyEvent to thoroughly check the arguments passed to most
		1311	method calls and croaks if it finds any problems. In other words, enables
		1312	"strict" mode. Unlike C<use strict> it is definitely recommended ot keep
		1313	it off in production.
		1314
691	=item C<PERL_ANYEVENT_MODEL>	1315	=item C<PERL_ANYEVENT_MODEL>
692		1316
693	This can be used to specify the event model to be used by AnyEvent, before	1317	This can be used to specify the event model to be used by AnyEvent, before
694	autodetection and -probing kicks in. It must be a string consisting	1318	auto detection and -probing kicks in. It must be a string consisting
695	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended	1319	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
696	and the resulting module name is loaded and if the load was successful,	1320	and the resulting module name is loaded and if the load was successful,
697	used as event model. If it fails to load AnyEvent will proceed with	1321	used as event model. If it fails to load AnyEvent will proceed with
698	autodetection and -probing.	1322	auto detection and -probing.
699		1323
700	This functionality might change in future versions.	1324	This functionality might change in future versions.
701		1325
702	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you	1326	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
703	could start your program like this:	1327	could start your program like this:
704		1328
705	PERL_ANYEVENT_MODEL=Perl perl ...	1329	PERL_ANYEVENT_MODEL=Perl perl ...
		1330
		1331	=item C<PERL_ANYEVENT_PROTOCOLS>
		1332
		1333	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1334	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1335	of auto probing).
		1336
		1337	Must be set to a comma-separated list of protocols or address families,
		1338	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1339	used, and preference will be given to protocols mentioned earlier in the
		1340	list.
		1341
		1342	This variable can effectively be used for denial-of-service attacks
		1343	against local programs (e.g. when setuid), although the impact is likely
		1344	small, as the program has to handle connection errors already-
		1345
		1346	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1347	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1348	- only support IPv4, never try to resolve or contact IPv6
		1349	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1350	IPv6, but prefer IPv6 over IPv4.
		1351
		1352	=item C<PERL_ANYEVENT_EDNS0>
		1353
		1354	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1355	for DNS. This extension is generally useful to reduce DNS traffic, but
		1356	some (broken) firewalls drop such DNS packets, which is why it is off by
		1357	default.
		1358
		1359	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1360	EDNS0 in its DNS requests.
		1361
		1362	=item C<PERL_ANYEVENT_MAX_FORKS>
		1363
		1364	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1365	will create in parallel.
706		1366
707	=back	1367	=back
708		1368
709	=head1 EXAMPLE PROGRAM	1369	=head1 EXAMPLE PROGRAM
710		1370
711	The following program uses an IO watcher to read data from STDIN, a timer	1371	The following program uses an I/O watcher to read data from STDIN, a timer
712	to display a message once per second, and a condition variable to quit the	1372	to display a message once per second, and a condition variable to quit the
713	program when the user enters quit:	1373	program when the user enters quit:
714		1374
715	use AnyEvent;	1375	use AnyEvent;
716		1376
…		…
721	poll => 'r',	1381	poll => 'r',
722	cb => sub {	1382	cb => sub {
723	warn "io event <$_[0]>\n"; # will always output <r>	1383	warn "io event <$_[0]>\n"; # will always output <r>
724	chomp (my $input = <STDIN>); # read a line	1384	chomp (my $input = <STDIN>); # read a line
725	warn "read: $input\n"; # output what has been read	1385	warn "read: $input\n"; # output what has been read
726	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1386	$cv->send if $input =~ /^q/i; # quit program if /^q/i
727	},	1387	},
728	);	1388	);
729		1389
730	my $time_watcher; # can only be used once	1390	my $time_watcher; # can only be used once
731		1391
…		…
736	});	1396	});
737	}	1397	}
738		1398
739	new_timer; # create first timer	1399	new_timer; # create first timer
740		1400
741	$cv->wait; # wait until user enters /^q/i	1401	$cv->recv; # wait until user enters /^q/i
742		1402
743	=head1 REAL-WORLD EXAMPLE	1403	=head1 REAL-WORLD EXAMPLE
744		1404
745	Consider the L<Net::FCP> module. It features (among others) the following	1405	Consider the L<Net::FCP> module. It features (among others) the following
746	API calls, which are to freenet what HTTP GET requests are to http:	1406	API calls, which are to freenet what HTTP GET requests are to http:
…		…
796	syswrite $txn->{fh}, $txn->{request}	1456	syswrite $txn->{fh}, $txn->{request}
797	or die "connection or write error";	1457	or die "connection or write error";
798	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1458	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
799		1459
800	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1460	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
801	result and signals any possible waiters that the request ahs finished:	1461	result and signals any possible waiters that the request has finished:
802		1462
803	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1463	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
804		1464
805	if (end-of-file or data complete) {	1465	if (end-of-file or data complete) {
806	$txn->{result} = $txn->{buf};	1466	$txn->{result} = $txn->{buf};
807	$txn->{finished}->broadcast;	1467	$txn->{finished}->send;
808	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1468	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
809	}	1469	}
810		1470
811	The C<result> method, finally, just waits for the finished signal (if the	1471	The C<result> method, finally, just waits for the finished signal (if the
812	request was already finished, it doesn't wait, of course, and returns the	1472	request was already finished, it doesn't wait, of course, and returns the
813	data:	1473	data:
814		1474
815	$txn->{finished}->wait;	1475	$txn->{finished}->recv;
816	return $txn->{result};	1476	return $txn->{result};
817		1477
818	The actual code goes further and collects all errors (C<die>s, exceptions)	1478	The actual code goes further and collects all errors (C<die>s, exceptions)
819	that occured during request processing. The C<result> method detects	1479	that occurred during request processing. The C<result> method detects
820	whether an exception as thrown (it is stored inside the $txn object)	1480	whether an exception as thrown (it is stored inside the $txn object)
821	and just throws the exception, which means connection errors and other	1481	and just throws the exception, which means connection errors and other
822	problems get reported tot he code that tries to use the result, not in a	1482	problems get reported tot he code that tries to use the result, not in a
823	random callback.	1483	random callback.
824		1484
…		…
855		1515
856	my $quit = AnyEvent->condvar;	1516	my $quit = AnyEvent->condvar;
857		1517
858	$fcp->txn_client_get ($url)->cb (sub {	1518	$fcp->txn_client_get ($url)->cb (sub {
859	...	1519	...
860	$quit->broadcast;	1520	$quit->send;
861	});	1521	});
862		1522
863	$quit->wait;	1523	$quit->recv;
864		1524
865		1525
866	=head1 BENCHMARK	1526	=head1 BENCHMARKS
867		1527
868	To give you an idea of the performance and overheads that AnyEvent adds	1528	To give you an idea of the performance and overheads that AnyEvent adds
869	over the event loops themselves (and to give you an impression of the	1529	over the event loops themselves and to give you an impression of the speed
870	speed of various event loops), here is a benchmark of various supported	1530	of various event loops I prepared some benchmarks.
871	event models natively and with anyevent. The benchmark creates a lot of	1531
872	timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to	1532	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1533
		1534	Here is a benchmark of various supported event models used natively and
		1535	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1536	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
873	become writable, which it is), lets them fire exactly once and destroys	1537	which it is), lets them fire exactly once and destroys them again.
874	them again.
875		1538
		1539	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1540	distribution.
		1541
876	=head2 Explanation of the columns	1542	=head3 Explanation of the columns
877		1543
878	I<watcher> is the number of event watchers created/destroyed. Since	1544	I<watcher> is the number of event watchers created/destroyed. Since
879	different event models feature vastly different performances, each event	1545	different event models feature vastly different performances, each event
880	loop was given a number of watchers so that overall runtime is acceptable	1546	loop was given a number of watchers so that overall runtime is acceptable
881	and similar between tested event loop (and keep them from crashing): Glib	1547	and similar between tested event loop (and keep them from crashing): Glib
…		…
891	all watchers, to avoid adding memory overhead. That means closure creation	1557	all watchers, to avoid adding memory overhead. That means closure creation
892	and memory usage is not included in the figures.	1558	and memory usage is not included in the figures.
893		1559
894	I<invoke> is the time, in microseconds, used to invoke a simple	1560	I<invoke> is the time, in microseconds, used to invoke a simple
895	callback. The callback simply counts down a Perl variable and after it was	1561	callback. The callback simply counts down a Perl variable and after it was
896	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1562	invoked "watcher" times, it would C<< ->send >> a condvar once to
897	signal the end of this phase.	1563	signal the end of this phase.
898		1564
899	I<destroy> is the time, in microseconds, that it takes to destroy a single	1565	I<destroy> is the time, in microseconds, that it takes to destroy a single
900	watcher.	1566	watcher.
901		1567
902	=head2 Results	1568	=head3 Results
903		1569
904	name watchers bytes create invoke destroy comment	1570	name watchers bytes create invoke destroy comment
905	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1571	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
906	EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers	1572	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
907	CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal	1573	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
908	Perl/Any 100000 513 4.91 0.92 1.15 pure perl implementation	1574	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
909	Event/Event 16000 523 28.05 21.38 0.86 Event native interface	1575	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
910	Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers	1576	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
911	Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour	1577	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
912	Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers	1578	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
913	POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event	1579	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
914	POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select	1580	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
915		1581
916	=head2 Discussion	1582	=head3 Discussion
917		1583
918	The benchmark does I<not> measure scalability of the event loop very	1584	The benchmark does I<not> measure scalability of the event loop very
919	well. For example, a select-based event loop (such as the pure perl one)	1585	well. For example, a select-based event loop (such as the pure perl one)
920	can never compete with an event loop that uses epoll when the number of	1586	can never compete with an event loop that uses epoll when the number of
921	file descriptors grows high. In this benchmark, only a single filehandle	1587	file descriptors grows high. In this benchmark, all events become ready at
922	is used (although some of the AnyEvent adaptors dup() its file descriptor	1588	the same time, so select/poll-based implementations get an unnatural speed
923	to worka round bugs).	1589	boost.
		1590
		1591	Also, note that the number of watchers usually has a nonlinear effect on
		1592	overall speed, that is, creating twice as many watchers doesn't take twice
		1593	the time - usually it takes longer. This puts event loops tested with a
		1594	higher number of watchers at a disadvantage.
		1595
		1596	To put the range of results into perspective, consider that on the
		1597	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1598	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1599	cycles with POE.
924		1600
925	C<EV> is the sole leader regarding speed and memory use, which are both	1601	C<EV> is the sole leader regarding speed and memory use, which are both
926	maximal/minimal, respectively. Even when going through AnyEvent, there are	1602	maximal/minimal, respectively. Even when going through AnyEvent, it uses
927	only two event loops that use slightly less memory (the C<Event> module	1603	far less memory than any other event loop and is still faster than Event
928	natively and the pure perl backend), and no faster event models, not even	1604	natively.
929	C<Event> natively.
930		1605
931	The pure perl implementation is hit in a few sweet spots (both the	1606	The pure perl implementation is hit in a few sweet spots (both the
932	zero timeout and the use of a single fd hit optimisations in the perl	1607	constant timeout and the use of a single fd hit optimisations in the perl
933	interpreter and the backend itself). Nevertheless tis shows that it	1608	interpreter and the backend itself). Nevertheless this shows that it
934	adds very little overhead in itself. Like any select-based backend its	1609	adds very little overhead in itself. Like any select-based backend its
935	performance becomes really bad with lots of file descriptors, of course,	1610	performance becomes really bad with lots of file descriptors (and few of
936	but this was not subject of this benchmark.	1611	them active), of course, but this was not subject of this benchmark.
937		1612
938	The C<Event> module has a relatively high setup and callback invocation cost,	1613	The C<Event> module has a relatively high setup and callback invocation
939	but overall scores on the third place.	1614	cost, but overall scores in on the third place.
940		1615
941	C<Glib>'s memory usage is quite a bit bit higher, but it features a	1616	C<Glib>'s memory usage is quite a bit higher, but it features a
942	faster callback invocation and overall ends up in the same class as	1617	faster callback invocation and overall ends up in the same class as
943	C<Event>. However, Glib scales extremely badly, doubling the number of	1618	C<Event>. However, Glib scales extremely badly, doubling the number of
944	watchers increases the processing time by more than a factor of four,	1619	watchers increases the processing time by more than a factor of four,
945	making it completely unusable when using larger numbers of watchers	1620	making it completely unusable when using larger numbers of watchers
946	(note that only a single file descriptor was used in the benchmark, so	1621	(note that only a single file descriptor was used in the benchmark, so
…		…
949	The C<Tk> adaptor works relatively well. The fact that it crashes with	1624	The C<Tk> adaptor works relatively well. The fact that it crashes with
950	more than 2000 watchers is a big setback, however, as correctness takes	1625	more than 2000 watchers is a big setback, however, as correctness takes
951	precedence over speed. Nevertheless, its performance is surprising, as the	1626	precedence over speed. Nevertheless, its performance is surprising, as the
952	file descriptor is dup()ed for each watcher. This shows that the dup()	1627	file descriptor is dup()ed for each watcher. This shows that the dup()
953	employed by some adaptors is not a big performance issue (it does incur a	1628	employed by some adaptors is not a big performance issue (it does incur a
954	hidden memory cost inside the kernel, though, that is not reflected in the	1629	hidden memory cost inside the kernel which is not reflected in the figures
955	figures above).	1630	above).
956		1631
957	C<POE>, regardless of underlying event loop (wether using its pure perl	1632	C<POE>, regardless of underlying event loop (whether using its pure perl
958	select-based backend or the Event module) shows abysmal performance and	1633	select-based backend or the Event module, the POE-EV backend couldn't
		1634	be tested because it wasn't working) shows abysmal performance and
959	memory usage: Watchers use almost 30 times as much memory as EV watchers,	1635	memory usage with AnyEvent: Watchers use almost 30 times as much memory
960	and 10 times as much memory as both Event or EV via AnyEvent. Watcher	1636	as EV watchers, and 10 times as much memory as Event (the high memory
		1637	requirements are caused by requiring a session for each watcher). Watcher
961	invocation is almost 700 times slower than with AnyEvent's pure perl	1638	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1639	implementation.
		1640
962	implementation. The design of the POE adaptor class in AnyEvent can not	1641	The design of the POE adaptor class in AnyEvent can not really account
963	really account for this, as session creation overhead is small compared	1642	for the performance issues, though, as session creation overhead is
964	to execution of the state machine, which is coded pretty optimally within	1643	small compared to execution of the state machine, which is coded pretty
965	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1644	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1645	using multiple sessions is not a good approach, especially regarding
		1646	memory usage, even the author of POE could not come up with a faster
		1647	design).
966		1648
967	=head2 Summary	1649	=head3 Summary
968		1650
		1651	=over 4
		1652
969	Using EV through AnyEvent is faster than any other event loop, but most	1653	=item * Using EV through AnyEvent is faster than any other event loop
970	event loops have acceptable performance with or without AnyEvent.	1654	(even when used without AnyEvent), but most event loops have acceptable
		1655	performance with or without AnyEvent.
971		1656
972	The overhead AnyEvent adds is usually much smaller than the overhead of	1657	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
973	the actual event loop, only with extremely fast event loops such as the EV	1658	the actual event loop, only with extremely fast event loops such as EV
974	adds AnyEvent significant overhead.	1659	adds AnyEvent significant overhead.
975		1660
976	And you should simply avoid POE like the plague if you want performance or	1661	=item * You should avoid POE like the plague if you want performance or
977	reasonable memory usage.	1662	reasonable memory usage.
978		1663
		1664	=back
		1665
		1666	=head2 BENCHMARKING THE LARGE SERVER CASE
		1667
		1668	This benchmark actually benchmarks the event loop itself. It works by
		1669	creating a number of "servers": each server consists of a socket pair, a
		1670	timeout watcher that gets reset on activity (but never fires), and an I/O
		1671	watcher waiting for input on one side of the socket. Each time the socket
		1672	watcher reads a byte it will write that byte to a random other "server".
		1673
		1674	The effect is that there will be a lot of I/O watchers, only part of which
		1675	are active at any one point (so there is a constant number of active
		1676	fds for each loop iteration, but which fds these are is random). The
		1677	timeout is reset each time something is read because that reflects how
		1678	most timeouts work (and puts extra pressure on the event loops).
		1679
		1680	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1681	(1%) are active. This mirrors the activity of large servers with many
		1682	connections, most of which are idle at any one point in time.
		1683
		1684	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1685	distribution.
		1686
		1687	=head3 Explanation of the columns
		1688
		1689	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1690	each server has a read and write socket end).
		1691
		1692	I<create> is the time it takes to create a socket pair (which is
		1693	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1694
		1695	I<request>, the most important value, is the time it takes to handle a
		1696	single "request", that is, reading the token from the pipe and forwarding
		1697	it to another server. This includes deleting the old timeout and creating
		1698	a new one that moves the timeout into the future.
		1699
		1700	=head3 Results
		1701
		1702	name sockets create request
		1703	EV 20000 69.01 11.16
		1704	Perl 20000 73.32 35.87
		1705	Event 20000 212.62 257.32
		1706	Glib 20000 651.16 1896.30
		1707	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1708
		1709	=head3 Discussion
		1710
		1711	This benchmark I<does> measure scalability and overall performance of the
		1712	particular event loop.
		1713
		1714	EV is again fastest. Since it is using epoll on my system, the setup time
		1715	is relatively high, though.
		1716
		1717	Perl surprisingly comes second. It is much faster than the C-based event
		1718	loops Event and Glib.
		1719
		1720	Event suffers from high setup time as well (look at its code and you will
		1721	understand why). Callback invocation also has a high overhead compared to
		1722	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1723	uses select or poll in basically all documented configurations.
		1724
		1725	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1726	clearly fails to perform with many filehandles or in busy servers.
		1727
		1728	POE is still completely out of the picture, taking over 1000 times as long
		1729	as EV, and over 100 times as long as the Perl implementation, even though
		1730	it uses a C-based event loop in this case.
		1731
		1732	=head3 Summary
		1733
		1734	=over 4
		1735
		1736	=item * The pure perl implementation performs extremely well.
		1737
		1738	=item * Avoid Glib or POE in large projects where performance matters.
		1739
		1740	=back
		1741
		1742	=head2 BENCHMARKING SMALL SERVERS
		1743
		1744	While event loops should scale (and select-based ones do not...) even to
		1745	large servers, most programs we (or I :) actually write have only a few
		1746	I/O watchers.
		1747
		1748	In this benchmark, I use the same benchmark program as in the large server
		1749	case, but it uses only eight "servers", of which three are active at any
		1750	one time. This should reflect performance for a small server relatively
		1751	well.
		1752
		1753	The columns are identical to the previous table.
		1754
		1755	=head3 Results
		1756
		1757	name sockets create request
		1758	EV 16 20.00 6.54
		1759	Perl 16 25.75 12.62
		1760	Event 16 81.27 35.86
		1761	Glib 16 32.63 15.48
		1762	POE 16 261.87 276.28 uses POE::Loop::Event
		1763
		1764	=head3 Discussion
		1765
		1766	The benchmark tries to test the performance of a typical small
		1767	server. While knowing how various event loops perform is interesting, keep
		1768	in mind that their overhead in this case is usually not as important, due
		1769	to the small absolute number of watchers (that is, you need efficiency and
		1770	speed most when you have lots of watchers, not when you only have a few of
		1771	them).
		1772
		1773	EV is again fastest.
		1774
		1775	Perl again comes second. It is noticeably faster than the C-based event
		1776	loops Event and Glib, although the difference is too small to really
		1777	matter.
		1778
		1779	POE also performs much better in this case, but is is still far behind the
		1780	others.
		1781
		1782	=head3 Summary
		1783
		1784	=over 4
		1785
		1786	=item * C-based event loops perform very well with small number of
		1787	watchers, as the management overhead dominates.
		1788
		1789	=back
		1790
979		1791
980	=head1 FORK	1792	=head1 FORK
981		1793
982	Most event libraries are not fork-safe. The ones who are usually are	1794	Most event libraries are not fork-safe. The ones who are usually are
983	because they are so inefficient. Only L<EV> is fully fork-aware.	1795	because they rely on inefficient but fork-safe C<select> or C<poll>
		1796	calls. Only L<EV> is fully fork-aware.
984		1797
985	If you have to fork, you must either do so I<before> creating your first	1798	If you have to fork, you must either do so I<before> creating your first
986	watcher OR you must not use AnyEvent at all in the child.	1799	watcher OR you must not use AnyEvent at all in the child.
987		1800
988		1801
…		…
996	specified in the variable.	1809	specified in the variable.
997		1810
998	You can make AnyEvent completely ignore this variable by deleting it	1811	You can make AnyEvent completely ignore this variable by deleting it
999	before the first watcher gets created, e.g. with a C<BEGIN> block:	1812	before the first watcher gets created, e.g. with a C<BEGIN> block:
1000		1813
1001	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1814	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1002		1815
1003	use AnyEvent;	1816	use AnyEvent;
		1817
		1818	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1819	be used to probe what backend is used and gain other information (which is
		1820	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		1821	$ENV{PERL_ANYEGENT_STRICT}.
		1822
		1823
		1824	=head1 BUGS
		1825
		1826	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		1827	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		1828	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		1829	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as
		1830	pronounced).
1004		1831
1005		1832
1006	=head1 SEE ALSO	1833	=head1 SEE ALSO
1007		1834
1008	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1835	Utility functions: L<AnyEvent::Util>.
1009	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1836
		1837	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1010	L<Event::Lib>, L<Qt>, L<POE>.	1838	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1011		1839
1012	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1840	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1013	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1841	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1014	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1842	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1015	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1843	L<AnyEvent::Impl::POE>.
1016		1844
		1845	Non-blocking file handles, sockets, TCP clients and
		1846	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1847
		1848	Asynchronous DNS: L<AnyEvent::DNS>.
		1849
		1850	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1851
1017	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1852	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1018		1853
1019		1854
1020	=head1 AUTHOR	1855	=head1 AUTHOR
1021		1856
1022	Marc Lehmann <schmorp@schmorp.de>	1857	Marc Lehmann <schmorp@schmorp.de>
1023	http://home.schmorp.de/	1858	http://home.schmorp.de/
1024		1859
1025	=cut	1860	=cut
1026		1861
1027	1	1862	1
1028		1863

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