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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
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... });
		12
		13	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		14	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		15
		16	print AnyEvent->now; # prints current event loop time
		17	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		18
		19	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		20
		21	my $w = AnyEvent->child (pid => $pid, cb => sub {
		22	my ($pid, $status) = @_;
12	...	23	...
13	});	24	});
14		25
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {
16	...
17	});
18
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	26	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		27	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	28	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	29	# use a condvar in callback mode:
		30	$w->cb (sub { $_[0]->recv });
		31
		32	=head1 INTRODUCTION/TUTORIAL
		33
		34	This manpage is mainly a reference manual. If you are interested
		35	in a tutorial or some gentle introduction, have a look at the
		36	L<AnyEvent::Intro> manpage.
22		37
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	38	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		39
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	40	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	41	nowadays. So what is different about AnyEvent?
27		42
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	43	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	44	policy> and AnyEvent is I<small and efficient>.
30		45
31	First and foremost, I<AnyEvent is not an event model> itself, it only	46	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	47	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	48	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	49	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	50	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	51	cannot change this, but it can hide the differences between those event
		52	loops.
37		53
38	The goal of AnyEvent is to offer module authors the ability to do event	54	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	55	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	56	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	57	module users into the same thing by forcing them to use the same event
42	model you use.	58	model you use.
43		59
44	For modules like POE or IO::Async (which is a total misnomer as it is	60	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	61	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	62	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	63	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	64	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	65	module are I<also> forced to use the same event loop you use.
50		66
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	67	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	68	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	69	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,	70	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	71	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	72	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	73	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	74	to AnyEvent, too, so it is future-proof).
59		75
60	In addition to being free of having to use I<the one and only true event	76	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	77	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	78	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	79	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	80	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	81	technically possible.
66		82
		83	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		84	of useful functionality, such as an asynchronous DNS resolver, 100%
		85	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		86	such as Windows) and lots of real-world knowledge and workarounds for
		87	platform bugs and differences.
		88
67	Of course, if you want lots of policy (this can arguably be somewhat	89	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	90	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	91	model, you should I<not> use this module.
70
71		92
72	=head1 DESCRIPTION	93	=head1 DESCRIPTION
73		94
74	L<AnyEvent> provides an identical interface to multiple event loops. This	95	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	96	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>	100	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	101	module.
81		102
82	During the first call of any watcher-creation method, the module tries	103	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	104	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>,	105	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	106	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	107	L<POE>. The first one found is used. If none are found, the module tries
87	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	108	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	109	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	110	be successfully loaded will be used. If, after this, still none could be
…		…
103	starts using it, all bets are off. Maybe you should tell their authors to	124	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...	125	use AnyEvent so their modules work together with others seamlessly...
105		126
106	The pure-perl implementation of AnyEvent is called	127	The pure-perl implementation of AnyEvent is called
107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	128	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
108	explicitly.	129	explicitly and enjoy the high availability of that event loop :)
109		130
110	=head1 WATCHERS	131	=head1 WATCHERS
111		132
112	AnyEvent has the central concept of a I<watcher>, which is an object that	133	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	134	stores relevant data for each kind of event you are waiting for, such as
114	the callback to call, the filehandle to watch, etc.	135	the callback to call, the file handle to watch, etc.
115		136
116	These watchers are normal Perl objects with normal Perl lifetime. After	137	These watchers are normal Perl objects with normal Perl lifetime. After
117	creating a watcher it will immediately "watch" for events and invoke the	138	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	139	callback when the event occurs (of course, only when the event model
119	is in control).	140	is in control).
…		…
127	Many watchers either are used with "recursion" (repeating timers for	148	Many watchers either are used with "recursion" (repeating timers for
128	example), or need to refer to their watcher object in other ways.	149	example), or need to refer to their watcher object in other ways.
129		150
130	An any way to achieve that is this pattern:	151	An any way to achieve that is this pattern:
131		152
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	153	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	154	# you can use $w here, for example to undef it
134	undef $w;	155	undef $w;
135	});	156	});
136		157
137	Note that C<my $w; $w => combination. This is necessary because in Perl,	158	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	159	my variables are only visible after the statement in which they are
139	declared.	160	declared.
140		161
141	=head2 I/O WATCHERS	162	=head2 I/O WATCHERS
142		163
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	164	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	165	with the following mandatory key-value pairs as arguments:
145		166
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	167	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for events
147	for events. C<poll> must be a string that is either C<r> or C<w>,	168	(AnyEvent might or might not keep a reference to this file handle). C<poll>
148	which creates a watcher waiting for "r"eadable or "w"ritable events,	169	must be a string that is either C<r> or C<w>, which creates a watcher
149	respectively. C<cb> is the callback to invoke each time the file handle	170	waiting for "r"eadable or "w"ritable events, respectively. C<cb> is the
150	becomes ready.	171	callback to invoke each time the file handle becomes ready.
151		172
152	Although the callback might get passed parameters, their value and	173	Although the callback might get passed parameters, their value and
153	presence is undefined and you cannot rely on them. Portable AnyEvent	174	presence is undefined and you cannot rely on them. Portable AnyEvent
154	callbacks cannot use arguments passed to I/O watcher callbacks.	175	callbacks cannot use arguments passed to I/O watcher callbacks.
155		176
…		…
159		180
160	Some event loops issue spurious readyness notifications, so you should	181	Some event loops issue spurious readyness notifications, so you should
161	always use non-blocking calls when reading/writing from/to your file	182	always use non-blocking calls when reading/writing from/to your file
162	handles.	183	handles.
163		184
164	Example:
165
166	# wait for readability of STDIN, then read a line and disable the watcher	185	Example: wait for readability of STDIN, then read a line and disable the
		186	watcher.
		187
167	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	188	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
168	chomp (my $input = <STDIN>);	189	chomp (my $input = <STDIN>);
169	warn "read: $input\n";	190	warn "read: $input\n";
170	undef $w;	191	undef $w;
171	});	192	});
…		…
181		202
182	Although the callback might get passed parameters, their value and	203	Although the callback might get passed parameters, their value and
183	presence is undefined and you cannot rely on them. Portable AnyEvent	204	presence is undefined and you cannot rely on them. Portable AnyEvent
184	callbacks cannot use arguments passed to time watcher callbacks.	205	callbacks cannot use arguments passed to time watcher callbacks.
185		206
186	The timer callback will be invoked at most once: if you want a repeating	207	The callback will normally be invoked once only. If you specify another
187	timer you have to create a new watcher (this is a limitation by both Tk	208	parameter, C<interval>, as a strictly positive number (> 0), then the
188	and Glib).	209	callback will be invoked regularly at that interval (in fractional
		210	seconds) after the first invocation. If C<interval> is specified with a
		211	false value, then it is treated as if it were missing.
189		212
190	Example:	213	The callback will be rescheduled before invoking the callback, but no
		214	attempt is done to avoid timer drift in most backends, so the interval is
		215	only approximate.
191		216
192	# fire an event after 7.7 seconds	217	Example: fire an event after 7.7 seconds.
		218
193	my $w = AnyEvent->timer (after => 7.7, cb => sub {	219	my $w = AnyEvent->timer (after => 7.7, cb => sub {
194	warn "timeout\n";	220	warn "timeout\n";
195	});	221	});
196		222
197	# to cancel the timer:	223	# to cancel the timer:
198	undef $w;	224	undef $w;
199		225
200	Example 2:
201
202	# fire an event after 0.5 seconds, then roughly every second	226	Example 2: fire an event after 0.5 seconds, then roughly every second.
203	my $w;
204		227
205	my $cb = sub {
206	# cancel the old timer while creating a new one
207	$w = AnyEvent->timer (after => 1, cb => $cb);	228	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		229	warn "timeout\n";
208	};	230	};
209
210	# start the "loop" by creating the first watcher
211	$w = AnyEvent->timer (after => 0.5, cb => $cb);
212		231
213	=head3 TIMING ISSUES	232	=head3 TIMING ISSUES
214		233
215	There are two ways to handle timers: based on real time (relative, "fire	234	There are two ways to handle timers: based on real time (relative, "fire
216	in 10 seconds") and based on wallclock time (absolute, "fire at 12	235	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
228	timers.	247	timers.
229		248
230	AnyEvent always prefers relative timers, if available, matching the	249	AnyEvent always prefers relative timers, if available, matching the
231	AnyEvent API.	250	AnyEvent API.
232		251
		252	AnyEvent has two additional methods that return the "current time":
		253
		254	=over 4
		255
		256	=item AnyEvent->time
		257
		258	This returns the "current wallclock time" as a fractional number of
		259	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		260	return, and the result is guaranteed to be compatible with those).
		261
		262	It progresses independently of any event loop processing, i.e. each call
		263	will check the system clock, which usually gets updated frequently.
		264
		265	=item AnyEvent->now
		266
		267	This also returns the "current wallclock time", but unlike C<time>, above,
		268	this value might change only once per event loop iteration, depending on
		269	the event loop (most return the same time as C<time>, above). This is the
		270	time that AnyEvent's timers get scheduled against.
		271
		272	I<In almost all cases (in all cases if you don't care), this is the
		273	function to call when you want to know the current time.>
		274
		275	This function is also often faster then C<< AnyEvent->time >>, and
		276	thus the preferred method if you want some timestamp (for example,
		277	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		278
		279	The rest of this section is only of relevance if you try to be very exact
		280	with your timing, you can skip it without bad conscience.
		281
		282	For a practical example of when these times differ, consider L<Event::Lib>
		283	and L<EV> and the following set-up:
		284
		285	The event loop is running and has just invoked one of your callback at
		286	time=500 (assume no other callbacks delay processing). In your callback,
		287	you wait a second by executing C<sleep 1> (blocking the process for a
		288	second) and then (at time=501) you create a relative timer that fires
		289	after three seconds.
		290
		291	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		292	both return C<501>, because that is the current time, and the timer will
		293	be scheduled to fire at time=504 (C<501> + C<3>).
		294
		295	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		296	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		297	last event processing phase started. With L<EV>, your timer gets scheduled
		298	to run at time=503 (C<500> + C<3>).
		299
		300	In one sense, L<Event::Lib> is more exact, as it uses the current time
		301	regardless of any delays introduced by event processing. However, most
		302	callbacks do not expect large delays in processing, so this causes a
		303	higher drift (and a lot more system calls to get the current time).
		304
		305	In another sense, L<EV> is more exact, as your timer will be scheduled at
		306	the same time, regardless of how long event processing actually took.
		307
		308	In either case, if you care (and in most cases, you don't), then you
		309	can get whatever behaviour you want with any event loop, by taking the
		310	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		311	account.
		312
		313	=back
		314
233	=head2 SIGNAL WATCHERS	315	=head2 SIGNAL WATCHERS
234		316
235	You can watch for signals using a signal watcher, C<signal> is the signal	317	You can watch for signals using a signal watcher, C<signal> is the signal
236	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	318	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
237	be invoked whenever a signal occurs.	319	callback to be invoked whenever a signal occurs.
238		320
239	Although the callback might get passed parameters, their value and	321	Although the callback might get passed parameters, their value and
240	presence is undefined and you cannot rely on them. Portable AnyEvent	322	presence is undefined and you cannot rely on them. Portable AnyEvent
241	callbacks cannot use arguments passed to signal watcher callbacks.	323	callbacks cannot use arguments passed to signal watcher callbacks.
242		324
243	Multiple signal occurances can be clumped together into one callback	325	Multiple signal occurrences can be clumped together into one callback
244	invocation, and callback invocation will be synchronous. synchronous means	326	invocation, and callback invocation will be synchronous. Synchronous means
245	that it might take a while until the signal gets handled by the process,	327	that it might take a while until the signal gets handled by the process,
246	but it is guarenteed not to interrupt any other callbacks.	328	but it is guaranteed not to interrupt any other callbacks.
247		329
248	The main advantage of using these watchers is that you can share a signal	330	The main advantage of using these watchers is that you can share a signal
249	between multiple watchers.	331	between multiple watchers.
250		332
251	This watcher might use C<%SIG>, so programs overwriting those signals	333	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
278	AnyEvent program, you I<have> to create at least one watcher before you	360	AnyEvent program, you I<have> to create at least one watcher before you
279	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	361	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
280		362
281	Example: fork a process and wait for it	363	Example: fork a process and wait for it
282		364
283	my $done = AnyEvent->condvar;	365	my $done = AnyEvent->condvar;
284		366
285	AnyEvent::detect; # force event module to be initialised
286
287	my $pid = fork or exit 5;	367	my $pid = fork or exit 5;
288		368
289	my $w = AnyEvent->child (	369	my $w = AnyEvent->child (
290	pid => $pid,	370	pid => $pid,
291	cb => sub {	371	cb => sub {
292	my ($pid, $status) = @_;	372	my ($pid, $status) = @_;
293	warn "pid $pid exited with status $status";	373	warn "pid $pid exited with status $status";
294	$done->broadcast;	374	$done->send;
295	},	375	},
296	);	376	);
297		377
298	# do something else, then wait for process exit	378	# do something else, then wait for process exit
299	$done->wait;	379	$done->recv;
300		380
301	=head2 CONDITION VARIABLES	381	=head2 CONDITION VARIABLES
302		382
		383	If you are familiar with some event loops you will know that all of them
		384	require you to run some blocking "loop", "run" or similar function that
		385	will actively watch for new events and call your callbacks.
		386
		387	AnyEvent is different, it expects somebody else to run the event loop and
		388	will only block when necessary (usually when told by the user).
		389
		390	The instrument to do that is called a "condition variable", so called
		391	because they represent a condition that must become true.
		392
303	Condition variables can be created by calling the C<< AnyEvent->condvar >>	393	Condition variables can be created by calling the C<< AnyEvent->condvar
304	method without any arguments.	394	>> method, usually without arguments. The only argument pair allowed is
305		395
306	A condition variable waits for a condition - precisely that the C<<	396	C<cb>, which specifies a callback to be called when the condition variable
307	->broadcast >> method has been called.	397	becomes true, with the condition variable as the first argument (but not
		398	the results).
308		399
309	They are very useful to signal that a condition has been fulfilled, for	400	After creation, the condition variable is "false" until it becomes "true"
		401	by calling the C<send> method (or calling the condition variable as if it
		402	were a callback, read about the caveats in the description for the C<<
		403	->send >> method).
		404
		405	Condition variables are similar to callbacks, except that you can
		406	optionally wait for them. They can also be called merge points - points
		407	in time where multiple outstanding events have been processed. And yet
		408	another way to call them is transactions - each condition variable can be
		409	used to represent a transaction, which finishes at some point and delivers
		410	a result.
		411
		412	Condition variables are very useful to signal that something has finished,
310	example, if you write a module that does asynchronous http requests,	413	for example, if you write a module that does asynchronous http requests,
311	then a condition variable would be the ideal candidate to signal the	414	then a condition variable would be the ideal candidate to signal the
312	availability of results.	415	availability of results. The user can either act when the callback is
		416	called or can synchronously C<< ->recv >> for the results.
313		417
314	You can also use condition variables to block your main program until	418	You can also use them to simulate traditional event loops - for example,
315	an event occurs - for example, you could C<< ->wait >> in your main	419	you can block your main program until an event occurs - for example, you
316	program until the user clicks the Quit button in your app, which would C<<	420	could C<< ->recv >> in your main program until the user clicks the Quit
317	->broadcast >> the "quit" event.	421	button of your app, which would C<< ->send >> the "quit" event.
318		422
319	Note that condition variables recurse into the event loop - if you have	423	Note that condition variables recurse into the event loop - if you have
320	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	424	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
321	lose. Therefore, condition variables are good to export to your caller, but	425	lose. Therefore, condition variables are good to export to your caller, but
322	you should avoid making a blocking wait yourself, at least in callbacks,	426	you should avoid making a blocking wait yourself, at least in callbacks,
323	as this asks for trouble.	427	as this asks for trouble.
324		428
325	This object has two methods:	429	Condition variables are represented by hash refs in perl, and the keys
		430	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		431	easy (it is often useful to build your own transaction class on top of
		432	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		433	it's C<new> method in your own C<new> method.
		434
		435	There are two "sides" to a condition variable - the "producer side" which
		436	eventually calls C<< -> send >>, and the "consumer side", which waits
		437	for the send to occur.
		438
		439	Example: wait for a timer.
		440
		441	# wait till the result is ready
		442	my $result_ready = AnyEvent->condvar;
		443
		444	# do something such as adding a timer
		445	# or socket watcher the calls $result_ready->send
		446	# when the "result" is ready.
		447	# in this case, we simply use a timer:
		448	my $w = AnyEvent->timer (
		449	after => 1,
		450	cb => sub { $result_ready->send },
		451	);
		452
		453	# this "blocks" (while handling events) till the callback
		454	# calls send
		455	$result_ready->recv;
		456
		457	Example: wait for a timer, but take advantage of the fact that
		458	condition variables are also code references.
		459
		460	my $done = AnyEvent->condvar;
		461	my $delay = AnyEvent->timer (after => 5, cb => $done);
		462	$done->recv;
		463
		464	Example: Imagine an API that returns a condvar and doesn't support
		465	callbacks. This is how you make a synchronous call, for example from
		466	the main program:
		467
		468	use AnyEvent::CouchDB;
		469
		470	...
		471
		472	my @info = $couchdb->info->recv;
		473
		474	And this is how you would just ste a callback to be called whenever the
		475	results are available:
		476
		477	$couchdb->info->cb (sub {
		478	my @info = $_[0]->recv;
		479	});
		480
		481	=head3 METHODS FOR PRODUCERS
		482
		483	These methods should only be used by the producing side, i.e. the
		484	code/module that eventually sends the signal. Note that it is also
		485	the producer side which creates the condvar in most cases, but it isn't
		486	uncommon for the consumer to create it as well.
326		487
327	=over 4	488	=over 4
328		489
		490	=item $cv->send (...)
		491
		492	Flag the condition as ready - a running C<< ->recv >> and all further
		493	calls to C<recv> will (eventually) return after this method has been
		494	called. If nobody is waiting the send will be remembered.
		495
		496	If a callback has been set on the condition variable, it is called
		497	immediately from within send.
		498
		499	Any arguments passed to the C<send> call will be returned by all
		500	future C<< ->recv >> calls.
		501
		502	Condition variables are overloaded so one can call them directly
		503	(as a code reference). Calling them directly is the same as calling
		504	C<send>. Note, however, that many C-based event loops do not handle
		505	overloading, so as tempting as it may be, passing a condition variable
		506	instead of a callback does not work. Both the pure perl and EV loops
		507	support overloading, however, as well as all functions that use perl to
		508	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		509	example).
		510
		511	=item $cv->croak ($error)
		512
		513	Similar to send, but causes all call's to C<< ->recv >> to invoke
		514	C<Carp::croak> with the given error message/object/scalar.
		515
		516	This can be used to signal any errors to the condition variable
		517	user/consumer.
		518
		519	=item $cv->begin ([group callback])
		520
329	=item $cv->wait	521	=item $cv->end
330		522
331	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	523	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		524
		525	These two methods can be used to combine many transactions/events into
		526	one. For example, a function that pings many hosts in parallel might want
		527	to use a condition variable for the whole process.
		528
		529	Every call to C<< ->begin >> will increment a counter, and every call to
		530	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		531	>>, the (last) callback passed to C<begin> will be executed. That callback
		532	is I<supposed> to call C<< ->send >>, but that is not required. If no
		533	callback was set, C<send> will be called without any arguments.
		534
		535	Let's clarify this with the ping example:
		536
		537	my $cv = AnyEvent->condvar;
		538
		539	my %result;
		540	$cv->begin (sub { $cv->send (\%result) });
		541
		542	for my $host (@list_of_hosts) {
		543	$cv->begin;
		544	ping_host_then_call_callback $host, sub {
		545	$result{$host} = ...;
		546	$cv->end;
		547	};
		548	}
		549
		550	$cv->end;
		551
		552	This code fragment supposedly pings a number of hosts and calls
		553	C<send> after results for all then have have been gathered - in any
		554	order. To achieve this, the code issues a call to C<begin> when it starts
		555	each ping request and calls C<end> when it has received some result for
		556	it. Since C<begin> and C<end> only maintain a counter, the order in which
		557	results arrive is not relevant.
		558
		559	There is an additional bracketing call to C<begin> and C<end> outside the
		560	loop, which serves two important purposes: first, it sets the callback
		561	to be called once the counter reaches C<0>, and second, it ensures that
		562	C<send> is called even when C<no> hosts are being pinged (the loop
		563	doesn't execute once).
		564
		565	This is the general pattern when you "fan out" into multiple subrequests:
		566	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		567	is called at least once, and then, for each subrequest you start, call
		568	C<begin> and for each subrequest you finish, call C<end>.
		569
		570	=back
		571
		572	=head3 METHODS FOR CONSUMERS
		573
		574	These methods should only be used by the consuming side, i.e. the
		575	code awaits the condition.
		576
		577	=over 4
		578
		579	=item $cv->recv
		580
		581	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
332	called on c<$cv>, while servicing other watchers normally.	582	>> methods have been called on c<$cv>, while servicing other watchers
		583	normally.
333		584
334	You can only wait once on a condition - additional calls will return	585	You can only wait once on a condition - additional calls are valid but
335	immediately.	586	will return immediately.
		587
		588	If an error condition has been set by calling C<< ->croak >>, then this
		589	function will call C<croak>.
		590
		591	In list context, all parameters passed to C<send> will be returned,
		592	in scalar context only the first one will be returned.
336		593
337	Not all event models support a blocking wait - some die in that case	594	Not all event models support a blocking wait - some die in that case
338	(programs might want to do that to stay interactive), so I<if you are	595	(programs might want to do that to stay interactive), so I<if you are
339	using this from a module, never require a blocking wait>, but let the	596	using this from a module, never require a blocking wait>, but let the
340	caller decide whether the call will block or not (for example, by coupling	597	caller decide whether the call will block or not (for example, by coupling
341	condition variables with some kind of request results and supporting	598	condition variables with some kind of request results and supporting
342	callbacks so the caller knows that getting the result will not block,	599	callbacks so the caller knows that getting the result will not block,
343	while still suppporting blocking waits if the caller so desires).	600	while still supporting blocking waits if the caller so desires).
344		601
345	Another reason I<never> to C<< ->wait >> in a module is that you cannot	602	Another reason I<never> to C<< ->recv >> in a module is that you cannot
346	sensibly have two C<< ->wait >>'s in parallel, as that would require	603	sensibly have two C<< ->recv >>'s in parallel, as that would require
347	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	604	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
348	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	605	can supply.
349	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
350	from different coroutines, however).
351		606
352	=item $cv->broadcast	607	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		608	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		609	versions and also integrates coroutines into AnyEvent, making blocking
		610	C<< ->recv >> calls perfectly safe as long as they are done from another
		611	coroutine (one that doesn't run the event loop).
353		612
354	Flag the condition as ready - a running C<< ->wait >> and all further	613	You can ensure that C<< -recv >> never blocks by setting a callback and
355	calls to C<wait> will (eventually) return after this method has been	614	only calling C<< ->recv >> from within that callback (or at a later
356	called. If nobody is waiting the broadcast will be remembered..	615	time). This will work even when the event loop does not support blocking
		616	waits otherwise.
		617
		618	=item $bool = $cv->ready
		619
		620	Returns true when the condition is "true", i.e. whether C<send> or
		621	C<croak> have been called.
		622
		623	=item $cb = $cv->cb ($cb->($cv))
		624
		625	This is a mutator function that returns the callback set and optionally
		626	replaces it before doing so.
		627
		628	The callback will be called when the condition becomes "true", i.e. when
		629	C<send> or C<croak> are called, with the only argument being the condition
		630	variable itself. Calling C<recv> inside the callback or at any later time
		631	is guaranteed not to block.
357		632
358	=back	633	=back
359
360	Example:
361
362	# wait till the result is ready
363	my $result_ready = AnyEvent->condvar;
364
365	# do something such as adding a timer
366	# or socket watcher the calls $result_ready->broadcast
367	# when the "result" is ready.
368	# in this case, we simply use a timer:
369	my $w = AnyEvent->timer (
370	after => 1,
371	cb => sub { $result_ready->broadcast },
372	);
373
374	# this "blocks" (while handling events) till the watcher
375	# calls broadcast
376	$result_ready->wait;
377		634
378	=head1 GLOBAL VARIABLES AND FUNCTIONS	635	=head1 GLOBAL VARIABLES AND FUNCTIONS
379		636
380	=over 4	637	=over 4
381		638
…		…
387	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	644	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
388	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	645	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
389		646
390	The known classes so far are:	647	The known classes so far are:
391		648
392	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
393	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
394	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	649	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
395	AnyEvent::Impl::Event based on Event, second best choice.	650	AnyEvent::Impl::Event based on Event, second best choice.
		651	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
396	AnyEvent::Impl::Glib based on Glib, third-best choice.	652	AnyEvent::Impl::Glib based on Glib, third-best choice.
397	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
398	AnyEvent::Impl::Tk based on Tk, very bad choice.	653	AnyEvent::Impl::Tk based on Tk, very bad choice.
399	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	654	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
400	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	655	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
401	AnyEvent::Impl::POE based on POE, not generic enough for full support.	656	AnyEvent::Impl::POE based on POE, not generic enough for full support.
402		657
…		…
415	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	670	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
416	if necessary. You should only call this function right before you would	671	if necessary. You should only call this function right before you would
417	have created an AnyEvent watcher anyway, that is, as late as possible at	672	have created an AnyEvent watcher anyway, that is, as late as possible at
418	runtime.	673	runtime.
419		674
		675	=item $guard = AnyEvent::post_detect { BLOCK }
		676
		677	Arranges for the code block to be executed as soon as the event model is
		678	autodetected (or immediately if this has already happened).
		679
		680	If called in scalar or list context, then it creates and returns an object
		681	that automatically removes the callback again when it is destroyed. See
		682	L<Coro::BDB> for a case where this is useful.
		683
		684	=item @AnyEvent::post_detect
		685
		686	If there are any code references in this array (you can C<push> to it
		687	before or after loading AnyEvent), then they will called directly after
		688	the event loop has been chosen.
		689
		690	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		691	if it contains a true value then the event loop has already been detected,
		692	and the array will be ignored.
		693
		694	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		695
420	=back	696	=back
421		697
422	=head1 WHAT TO DO IN A MODULE	698	=head1 WHAT TO DO IN A MODULE
423		699
424	As a module author, you should C<use AnyEvent> and call AnyEvent methods	700	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
427	Be careful when you create watchers in the module body - AnyEvent will	703	Be careful when you create watchers in the module body - AnyEvent will
428	decide which event module to use as soon as the first method is called, so	704	decide which event module to use as soon as the first method is called, so
429	by calling AnyEvent in your module body you force the user of your module	705	by calling AnyEvent in your module body you force the user of your module
430	to load the event module first.	706	to load the event module first.
431		707
432	Never call C<< ->wait >> on a condition variable unless you I<know> that	708	Never call C<< ->recv >> on a condition variable unless you I<know> that
433	the C<< ->broadcast >> method has been called on it already. This is	709	the C<< ->send >> method has been called on it already. This is
434	because it will stall the whole program, and the whole point of using	710	because it will stall the whole program, and the whole point of using
435	events is to stay interactive.	711	events is to stay interactive.
436		712
437	It is fine, however, to call C<< ->wait >> when the user of your module	713	It is fine, however, to call C<< ->recv >> when the user of your module
438	requests it (i.e. if you create a http request object ad have a method	714	requests it (i.e. if you create a http request object ad have a method
439	called C<results> that returns the results, it should call C<< ->wait >>	715	called C<results> that returns the results, it should call C<< ->recv >>
440	freely, as the user of your module knows what she is doing. always).	716	freely, as the user of your module knows what she is doing. always).
441		717
442	=head1 WHAT TO DO IN THE MAIN PROGRAM	718	=head1 WHAT TO DO IN THE MAIN PROGRAM
443		719
444	There will always be a single main program - the only place that should	720	There will always be a single main program - the only place that should
…		…
446		722
447	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	723	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
448	do anything special (it does not need to be event-based) and let AnyEvent	724	do anything special (it does not need to be event-based) and let AnyEvent
449	decide which implementation to chose if some module relies on it.	725	decide which implementation to chose if some module relies on it.
450		726
451	If the main program relies on a specific event model. For example, in	727	If the main program relies on a specific event model - for example, in
452	Gtk2 programs you have to rely on the Glib module. You should load the	728	Gtk2 programs you have to rely on the Glib module - you should load the
453	event module before loading AnyEvent or any module that uses it: generally	729	event module before loading AnyEvent or any module that uses it: generally
454	speaking, you should load it as early as possible. The reason is that	730	speaking, you should load it as early as possible. The reason is that
455	modules might create watchers when they are loaded, and AnyEvent will	731	modules might create watchers when they are loaded, and AnyEvent will
456	decide on the event model to use as soon as it creates watchers, and it	732	decide on the event model to use as soon as it creates watchers, and it
457	might chose the wrong one unless you load the correct one yourself.	733	might chose the wrong one unless you load the correct one yourself.
458		734
459	You can chose to use a rather inefficient pure-perl implementation by	735	You can chose to use a pure-perl implementation by loading the
460	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	736	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
461	behaviour everywhere, but letting AnyEvent chose is generally better.	737	everywhere, but letting AnyEvent chose the model is generally better.
		738
		739	=head2 MAINLOOP EMULATION
		740
		741	Sometimes (often for short test scripts, or even standalone programs who
		742	only want to use AnyEvent), you do not want to run a specific event loop.
		743
		744	In that case, you can use a condition variable like this:
		745
		746	AnyEvent->condvar->recv;
		747
		748	This has the effect of entering the event loop and looping forever.
		749
		750	Note that usually your program has some exit condition, in which case
		751	it is better to use the "traditional" approach of storing a condition
		752	variable somewhere, waiting for it, and sending it when the program should
		753	exit cleanly.
		754
		755
		756	=head1 OTHER MODULES
		757
		758	The following is a non-exhaustive list of additional modules that use
		759	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		760	in the same program. Some of the modules come with AnyEvent, some are
		761	available via CPAN.
		762
		763	=over 4
		764
		765	=item L<AnyEvent::Util>
		766
		767	Contains various utility functions that replace often-used but blocking
		768	functions such as C<inet_aton> by event-/callback-based versions.
		769
		770	=item L<AnyEvent::Socket>
		771
		772	Provides various utility functions for (internet protocol) sockets,
		773	addresses and name resolution. Also functions to create non-blocking tcp
		774	connections or tcp servers, with IPv6 and SRV record support and more.
		775
		776	=item L<AnyEvent::Handle>
		777
		778	Provide read and write buffers, manages watchers for reads and writes,
		779	supports raw and formatted I/O, I/O queued and fully transparent and
		780	non-blocking SSL/TLS.
		781
		782	=item L<AnyEvent::DNS>
		783
		784	Provides rich asynchronous DNS resolver capabilities.
		785
		786	=item L<AnyEvent::HTTP>
		787
		788	A simple-to-use HTTP library that is capable of making a lot of concurrent
		789	HTTP requests.
		790
		791	=item L<AnyEvent::HTTPD>
		792
		793	Provides a simple web application server framework.
		794
		795	=item L<AnyEvent::FastPing>
		796
		797	The fastest ping in the west.
		798
		799	=item L<AnyEvent::DBI>
		800
		801	Executes L<DBI> requests asynchronously in a proxy process.
		802
		803	=item L<AnyEvent::AIO>
		804
		805	Truly asynchronous I/O, should be in the toolbox of every event
		806	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		807	together.
		808
		809	=item L<AnyEvent::BDB>
		810
		811	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		812	L<BDB> and AnyEvent together.
		813
		814	=item L<AnyEvent::GPSD>
		815
		816	A non-blocking interface to gpsd, a daemon delivering GPS information.
		817
		818	=item L<AnyEvent::IGS>
		819
		820	A non-blocking interface to the Internet Go Server protocol (used by
		821	L<App::IGS>).
		822
		823	=item L<Net::IRC3>
		824
		825	AnyEvent based IRC client module family.
		826
		827	=item L<Net::XMPP2>
		828
		829	AnyEvent based XMPP (Jabber protocol) module family.
		830
		831	=item L<Net::FCP>
		832
		833	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		834	of AnyEvent.
		835
		836	=item L<Event::ExecFlow>
		837
		838	High level API for event-based execution flow control.
		839
		840	=item L<Coro>
		841
		842	Has special support for AnyEvent via L<Coro::AnyEvent>.
		843
		844	=item L<IO::Lambda>
		845
		846	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		847
		848	=back
462		849
463	=cut	850	=cut
464		851
465	package AnyEvent;	852	package AnyEvent;
466		853
467	no warnings;	854	no warnings;
468	use strict;	855	use strict;
469		856
470	use Carp;	857	use Carp;
471		858
472	our $VERSION = '3.3';	859	our $VERSION = 4.23;
473	our $MODEL;	860	our $MODEL;
474		861
475	our $AUTOLOAD;	862	our $AUTOLOAD;
476	our @ISA;	863	our @ISA;
477		864
		865	our @REGISTRY;
		866
		867	our $WIN32;
		868
		869	BEGIN {
		870	my $win32 = ! ! ($^O =~ /mswin32/i);
		871	eval "sub WIN32(){ $win32 }";
		872	}
		873
478	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	874	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479		875
480	our @REGISTRY;	876	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		877
		878	{
		879	my $idx;
		880	$PROTOCOL{$_} = ++$idx
		881	for reverse split /\s*,\s*/,
		882	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		883	}
481		884
482	my @models = (	885	my @models = (
483	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
484	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485	[EV:: => AnyEvent::Impl::EV::],	886	[EV:: => AnyEvent::Impl::EV::],
486	[Event:: => AnyEvent::Impl::Event::],	887	[Event:: => AnyEvent::Impl::Event::],
487	[Glib:: => AnyEvent::Impl::Glib::],
488	[Tk:: => AnyEvent::Impl::Tk::],
489	[Wx:: => AnyEvent::Impl::POE::],
490	[Prima:: => AnyEvent::Impl::POE::],
491	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	888	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
492	# everything below here will not be autoprobed as the pureperl backend should work everywhere	889	# everything below here will not be autoprobed
		890	# as the pureperl backend should work everywhere
		891	# and is usually faster
		892	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		893	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
493	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	894	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
494	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	895	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
495	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	896	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		897	[Wx:: => AnyEvent::Impl::POE::],
		898	[Prima:: => AnyEvent::Impl::POE::],
496	);	899	);
497		900
498	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	901	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);
		902
		903	our @post_detect;
		904
		905	sub post_detect(&) {
		906	my ($cb) = @_;
		907
		908	if ($MODEL) {
		909	$cb->();
		910
		911	1
		912	} else {
		913	push @post_detect, $cb;
		914
		915	defined wantarray
		916	? bless \$cb, "AnyEvent::Util::PostDetect"
		917	: ()
		918	}
		919	}
		920
		921	sub AnyEvent::Util::PostDetect::DESTROY {
		922	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		923	}
499		924
500	sub detect() {	925	sub detect() {
501	unless ($MODEL) {	926	unless ($MODEL) {
502	no strict 'refs';	927	no strict 'refs';
		928	local $SIG{__DIE__};
503		929
504	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	930	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
505	my $model = "AnyEvent::Impl::$1";	931	my $model = "AnyEvent::Impl::$1";
506	if (eval "require $model") {	932	if (eval "require $model") {
507	$MODEL = $model;	933	$MODEL = $model;
…		…
537	last;	963	last;
538	}	964	}
539	}	965	}
540		966
541	$MODEL	967	$MODEL
542	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	968	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
543	}	969	}
544	}	970	}
545		971
		972	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		973
546	unshift @ISA, $MODEL;	974	unshift @ISA, $MODEL;
547	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	975
		976	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		977
		978	(shift @post_detect)->() while @post_detect;
548	}	979	}
549		980
550	$MODEL	981	$MODEL
551	}	982	}
552		983
…		…
560		991
561	my $class = shift;	992	my $class = shift;
562	$class->$func (@_);	993	$class->$func (@_);
563	}	994	}
564		995
		996	# utility function to dup a filehandle. this is used by many backends
		997	# to support binding more than one watcher per filehandle (they usually
		998	# allow only one watcher per fd, so we dup it to get a different one).
		999	sub _dupfh($$$$) {
		1000	my ($poll, $fh, $r, $w) = @_;
		1001
		1002	require Fcntl;
		1003
		1004	# cygwin requires the fh mode to be matching, unix doesn't
		1005	my ($rw, $mode) = $poll eq "r" ? ($r, "<")
		1006	: $poll eq "w" ? ($w, ">")
		1007	: Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
		1008
		1009	open my $fh2, "$mode&" . fileno $fh
		1010	or die "cannot dup() filehandle: $!";
		1011
		1012	# we assume CLOEXEC is already set by perl in all important cases
		1013
		1014	($fh2, $rw)
		1015	}
		1016
565	package AnyEvent::Base;	1017	package AnyEvent::Base;
566		1018
		1019	# default implementation for now and time
		1020
		1021	use Time::HiRes ();
		1022
		1023	sub time { Time::HiRes::time }
		1024	sub now { Time::HiRes::time }
		1025
567	# default implementation for ->condvar, ->wait, ->broadcast	1026	# default implementation for ->condvar
568		1027
569	sub condvar {	1028	sub condvar {
570	bless \my $flag, "AnyEvent::Base::CondVar"	1029	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
571	}
572
573	sub AnyEvent::Base::CondVar::broadcast {
574	${$_[0]}++;
575	}
576
577	sub AnyEvent::Base::CondVar::wait {
578	AnyEvent->one_event while !${$_[0]};
579	}	1030	}
580		1031
581	# default implementation for ->signal	1032	# default implementation for ->signal
582		1033
583	our %SIG_CB;	1034	our %SIG_CB;
…		…
599	sub AnyEvent::Base::Signal::DESTROY {	1050	sub AnyEvent::Base::Signal::DESTROY {
600	my ($signal, $cb) = @{$_[0]};	1051	my ($signal, $cb) = @{$_[0]};
601		1052
602	delete $SIG_CB{$signal}{$cb};	1053	delete $SIG_CB{$signal}{$cb};
603		1054
604	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1055	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
605	}	1056	}
606		1057
607	# default implementation for ->child	1058	# default implementation for ->child
608		1059
609	our %PID_CB;	1060	our %PID_CB;
…		…
636	or Carp::croak "required option 'pid' is missing";	1087	or Carp::croak "required option 'pid' is missing";
637		1088
638	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1089	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
639		1090
640	unless ($WNOHANG) {	1091	unless ($WNOHANG) {
641	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1092	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
642	}	1093	}
643		1094
644	unless ($CHLD_W) {	1095	unless ($CHLD_W) {
645	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1096	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
646	# child could be a zombie already, so make at least one round	1097	# child could be a zombie already, so make at least one round
…		…
656	delete $PID_CB{$pid}{$cb};	1107	delete $PID_CB{$pid}{$cb};
657	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1108	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
658		1109
659	undef $CHLD_W unless keys %PID_CB;	1110	undef $CHLD_W unless keys %PID_CB;
660	}	1111	}
		1112
		1113	package AnyEvent::CondVar;
		1114
		1115	our @ISA = AnyEvent::CondVar::Base::;
		1116
		1117	package AnyEvent::CondVar::Base;
		1118
		1119	use overload
		1120	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1121	fallback => 1;
		1122
		1123	sub _send {
		1124	# nop
		1125	}
		1126
		1127	sub send {
		1128	my $cv = shift;
		1129	$cv->{_ae_sent} = [@_];
		1130	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1131	$cv->_send;
		1132	}
		1133
		1134	sub croak {
		1135	$_[0]{_ae_croak} = $_[1];
		1136	$_[0]->send;
		1137	}
		1138
		1139	sub ready {
		1140	$_[0]{_ae_sent}
		1141	}
		1142
		1143	sub _wait {
		1144	AnyEvent->one_event while !$_[0]{_ae_sent};
		1145	}
		1146
		1147	sub recv {
		1148	$_[0]->_wait;
		1149
		1150	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1151	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1152	}
		1153
		1154	sub cb {
		1155	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1156	$_[0]{_ae_cb}
		1157	}
		1158
		1159	sub begin {
		1160	++$_[0]{_ae_counter};
		1161	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1162	}
		1163
		1164	sub end {
		1165	return if --$_[0]{_ae_counter};
		1166	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1167	}
		1168
		1169	# undocumented/compatibility with pre-3.4
		1170	*broadcast = \&send;
		1171	*wait = \&_wait;
661		1172
662	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1173	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
663		1174
664	This is an advanced topic that you do not normally need to use AnyEvent in	1175	This is an advanced topic that you do not normally need to use AnyEvent in
665	a module. This section is only of use to event loop authors who want to	1176	a module. This section is only of use to event loop authors who want to
…		…
719	C<PERL_ANYEVENT_MODEL>.	1230	C<PERL_ANYEVENT_MODEL>.
720		1231
721	When set to C<2> or higher, cause AnyEvent to report to STDERR which event	1232	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
722	model it chooses.	1233	model it chooses.
723		1234
		1235	=item C<PERL_ANYEVENT_STRICT>
		1236
		1237	AnyEvent does not do much argument checking by default, as thorough
		1238	argument checking is very costly. Setting this variable to a true value
		1239	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1240	check the arguments passed to most method calls. If it finds any problems
		1241	it will croak.
		1242
		1243	In other words, enables "strict" mode.
		1244
		1245	Unlike C<use strict> it is definitely recommended ot keep it off in
		1246	production.
		1247
724	=item C<PERL_ANYEVENT_MODEL>	1248	=item C<PERL_ANYEVENT_MODEL>
725		1249
726	This can be used to specify the event model to be used by AnyEvent, before	1250	This can be used to specify the event model to be used by AnyEvent, before
727	autodetection and -probing kicks in. It must be a string consisting	1251	auto detection and -probing kicks in. It must be a string consisting
728	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended	1252	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
729	and the resulting module name is loaded and if the load was successful,	1253	and the resulting module name is loaded and if the load was successful,
730	used as event model. If it fails to load AnyEvent will proceed with	1254	used as event model. If it fails to load AnyEvent will proceed with
731	autodetection and -probing.	1255	auto detection and -probing.
732		1256
733	This functionality might change in future versions.	1257	This functionality might change in future versions.
734		1258
735	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you	1259	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
736	could start your program like this:	1260	could start your program like this:
737		1261
738	PERL_ANYEVENT_MODEL=Perl perl ...	1262	PERL_ANYEVENT_MODEL=Perl perl ...
		1263
		1264	=item C<PERL_ANYEVENT_PROTOCOLS>
		1265
		1266	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1267	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1268	of auto probing).
		1269
		1270	Must be set to a comma-separated list of protocols or address families,
		1271	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1272	used, and preference will be given to protocols mentioned earlier in the
		1273	list.
		1274
		1275	This variable can effectively be used for denial-of-service attacks
		1276	against local programs (e.g. when setuid), although the impact is likely
		1277	small, as the program has to handle connection errors already-
		1278
		1279	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1280	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1281	- only support IPv4, never try to resolve or contact IPv6
		1282	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1283	IPv6, but prefer IPv6 over IPv4.
		1284
		1285	=item C<PERL_ANYEVENT_EDNS0>
		1286
		1287	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1288	for DNS. This extension is generally useful to reduce DNS traffic, but
		1289	some (broken) firewalls drop such DNS packets, which is why it is off by
		1290	default.
		1291
		1292	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1293	EDNS0 in its DNS requests.
		1294
		1295	=item C<PERL_ANYEVENT_MAX_FORKS>
		1296
		1297	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1298	will create in parallel.
739		1299
740	=back	1300	=back
741		1301
742	=head1 EXAMPLE PROGRAM	1302	=head1 EXAMPLE PROGRAM
743		1303
…		…
754	poll => 'r',	1314	poll => 'r',
755	cb => sub {	1315	cb => sub {
756	warn "io event <$_[0]>\n"; # will always output <r>	1316	warn "io event <$_[0]>\n"; # will always output <r>
757	chomp (my $input = <STDIN>); # read a line	1317	chomp (my $input = <STDIN>); # read a line
758	warn "read: $input\n"; # output what has been read	1318	warn "read: $input\n"; # output what has been read
759	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1319	$cv->send if $input =~ /^q/i; # quit program if /^q/i
760	},	1320	},
761	);	1321	);
762		1322
763	my $time_watcher; # can only be used once	1323	my $time_watcher; # can only be used once
764		1324
…		…
769	});	1329	});
770	}	1330	}
771		1331
772	new_timer; # create first timer	1332	new_timer; # create first timer
773		1333
774	$cv->wait; # wait until user enters /^q/i	1334	$cv->recv; # wait until user enters /^q/i
775		1335
776	=head1 REAL-WORLD EXAMPLE	1336	=head1 REAL-WORLD EXAMPLE
777		1337
778	Consider the L<Net::FCP> module. It features (among others) the following	1338	Consider the L<Net::FCP> module. It features (among others) the following
779	API calls, which are to freenet what HTTP GET requests are to http:	1339	API calls, which are to freenet what HTTP GET requests are to http:
…		…
829	syswrite $txn->{fh}, $txn->{request}	1389	syswrite $txn->{fh}, $txn->{request}
830	or die "connection or write error";	1390	or die "connection or write error";
831	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1391	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
832		1392
833	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1393	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
834	result and signals any possible waiters that the request ahs finished:	1394	result and signals any possible waiters that the request has finished:
835		1395
836	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1396	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
837		1397
838	if (end-of-file or data complete) {	1398	if (end-of-file or data complete) {
839	$txn->{result} = $txn->{buf};	1399	$txn->{result} = $txn->{buf};
840	$txn->{finished}->broadcast;	1400	$txn->{finished}->send;
841	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1401	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
842	}	1402	}
843		1403
844	The C<result> method, finally, just waits for the finished signal (if the	1404	The C<result> method, finally, just waits for the finished signal (if the
845	request was already finished, it doesn't wait, of course, and returns the	1405	request was already finished, it doesn't wait, of course, and returns the
846	data:	1406	data:
847		1407
848	$txn->{finished}->wait;	1408	$txn->{finished}->recv;
849	return $txn->{result};	1409	return $txn->{result};
850		1410
851	The actual code goes further and collects all errors (C<die>s, exceptions)	1411	The actual code goes further and collects all errors (C<die>s, exceptions)
852	that occured during request processing. The C<result> method detects	1412	that occurred during request processing. The C<result> method detects
853	whether an exception as thrown (it is stored inside the $txn object)	1413	whether an exception as thrown (it is stored inside the $txn object)
854	and just throws the exception, which means connection errors and other	1414	and just throws the exception, which means connection errors and other
855	problems get reported tot he code that tries to use the result, not in a	1415	problems get reported tot he code that tries to use the result, not in a
856	random callback.	1416	random callback.
857		1417
…		…
888		1448
889	my $quit = AnyEvent->condvar;	1449	my $quit = AnyEvent->condvar;
890		1450
891	$fcp->txn_client_get ($url)->cb (sub {	1451	$fcp->txn_client_get ($url)->cb (sub {
892	...	1452	...
893	$quit->broadcast;	1453	$quit->send;
894	});	1454	});
895		1455
896	$quit->wait;	1456	$quit->recv;
897		1457
898		1458
899	=head1 BENCHMARK	1459	=head1 BENCHMARKS
900		1460
901	To give you an idea of the performance and overheads that AnyEvent adds	1461	To give you an idea of the performance and overheads that AnyEvent adds
902	over the event loops themselves (and to give you an impression of the	1462	over the event loops themselves and to give you an impression of the speed
903	speed of various event loops), here is a benchmark of various supported	1463	of various event loops I prepared some benchmarks.
904	event models natively and with anyevent. The benchmark creates a lot of	1464
905	timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to	1465	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1466
		1467	Here is a benchmark of various supported event models used natively and
		1468	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1469	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
906	become writable, which it is), lets them fire exactly once and destroys	1470	which it is), lets them fire exactly once and destroys them again.
907	them again.
908		1471
909	Rewriting the benchmark to use many different sockets instead of using	1472	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
910	the same filehandle for all I/O watchers results in a much longer runtime	1473	distribution.
911	(socket creation is expensive), but qualitatively the same figures, so it
912	was not used.
913		1474
914	=head2 Explanation of the columns	1475	=head3 Explanation of the columns
915		1476
916	I<watcher> is the number of event watchers created/destroyed. Since	1477	I<watcher> is the number of event watchers created/destroyed. Since
917	different event models feature vastly different performances, each event	1478	different event models feature vastly different performances, each event
918	loop was given a number of watchers so that overall runtime is acceptable	1479	loop was given a number of watchers so that overall runtime is acceptable
919	and similar between tested event loop (and keep them from crashing): Glib	1480	and similar between tested event loop (and keep them from crashing): Glib
…		…
929	all watchers, to avoid adding memory overhead. That means closure creation	1490	all watchers, to avoid adding memory overhead. That means closure creation
930	and memory usage is not included in the figures.	1491	and memory usage is not included in the figures.
931		1492
932	I<invoke> is the time, in microseconds, used to invoke a simple	1493	I<invoke> is the time, in microseconds, used to invoke a simple
933	callback. The callback simply counts down a Perl variable and after it was	1494	callback. The callback simply counts down a Perl variable and after it was
934	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1495	invoked "watcher" times, it would C<< ->send >> a condvar once to
935	signal the end of this phase.	1496	signal the end of this phase.
936		1497
937	I<destroy> is the time, in microseconds, that it takes to destroy a single	1498	I<destroy> is the time, in microseconds, that it takes to destroy a single
938	watcher.	1499	watcher.
939		1500
940	=head2 Results	1501	=head3 Results
941		1502
942	name watchers bytes create invoke destroy comment	1503	name watchers bytes create invoke destroy comment
943	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1504	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
944	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1505	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
945	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1506	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
946	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1507	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
947	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1508	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
948	Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers	1509	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
949	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1510	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
950	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1511	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
951	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1512	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
952	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1513	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
953		1514
954	=head2 Discussion	1515	=head3 Discussion
955		1516
956	The benchmark does I<not> measure scalability of the event loop very	1517	The benchmark does I<not> measure scalability of the event loop very
957	well. For example, a select-based event loop (such as the pure perl one)	1518	well. For example, a select-based event loop (such as the pure perl one)
958	can never compete with an event loop that uses epoll when the number of	1519	can never compete with an event loop that uses epoll when the number of
959	file descriptors grows high. In this benchmark, all events become ready at	1520	file descriptors grows high. In this benchmark, all events become ready at
960	the same time, so select/poll-based implementations get an unnatural speed	1521	the same time, so select/poll-based implementations get an unnatural speed
961	boost.	1522	boost.
962		1523
		1524	Also, note that the number of watchers usually has a nonlinear effect on
		1525	overall speed, that is, creating twice as many watchers doesn't take twice
		1526	the time - usually it takes longer. This puts event loops tested with a
		1527	higher number of watchers at a disadvantage.
		1528
		1529	To put the range of results into perspective, consider that on the
		1530	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1531	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1532	cycles with POE.
		1533
963	C<EV> is the sole leader regarding speed and memory use, which are both	1534	C<EV> is the sole leader regarding speed and memory use, which are both
964	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1535	maximal/minimal, respectively. Even when going through AnyEvent, it uses
965	far less memory than any other event loop and is still faster than Event	1536	far less memory than any other event loop and is still faster than Event
966	natively.	1537	natively.
967		1538
…		…
970	interpreter and the backend itself). Nevertheless this shows that it	1541	interpreter and the backend itself). Nevertheless this shows that it
971	adds very little overhead in itself. Like any select-based backend its	1542	adds very little overhead in itself. Like any select-based backend its
972	performance becomes really bad with lots of file descriptors (and few of	1543	performance becomes really bad with lots of file descriptors (and few of
973	them active), of course, but this was not subject of this benchmark.	1544	them active), of course, but this was not subject of this benchmark.
974		1545
975	The C<Event> module has a relatively high setup and callback invocation cost,	1546	The C<Event> module has a relatively high setup and callback invocation
976	but overall scores on the third place.	1547	cost, but overall scores in on the third place.
977		1548
978	C<Glib>'s memory usage is quite a bit bit higher, but it features a	1549	C<Glib>'s memory usage is quite a bit higher, but it features a
979	faster callback invocation and overall ends up in the same class as	1550	faster callback invocation and overall ends up in the same class as
980	C<Event>. However, Glib scales extremely badly, doubling the number of	1551	C<Event>. However, Glib scales extremely badly, doubling the number of
981	watchers increases the processing time by more than a factor of four,	1552	watchers increases the processing time by more than a factor of four,
982	making it completely unusable when using larger numbers of watchers	1553	making it completely unusable when using larger numbers of watchers
983	(note that only a single file descriptor was used in the benchmark, so	1554	(note that only a single file descriptor was used in the benchmark, so
…		…
989	file descriptor is dup()ed for each watcher. This shows that the dup()	1560	file descriptor is dup()ed for each watcher. This shows that the dup()
990	employed by some adaptors is not a big performance issue (it does incur a	1561	employed by some adaptors is not a big performance issue (it does incur a
991	hidden memory cost inside the kernel which is not reflected in the figures	1562	hidden memory cost inside the kernel which is not reflected in the figures
992	above).	1563	above).
993		1564
994	C<POE>, regardless of underlying event loop (whether using its pure	1565	C<POE>, regardless of underlying event loop (whether using its pure perl
995	perl select-based backend or the Event module, the POE-EV backend	1566	select-based backend or the Event module, the POE-EV backend couldn't
996	couldn't be tested because it wasn't working) shows abysmal performance	1567	be tested because it wasn't working) shows abysmal performance and
997	and memory usage: Watchers use almost 30 times as much memory as	1568	memory usage with AnyEvent: Watchers use almost 30 times as much memory
998	EV watchers, and 10 times as much memory as Event (the high memory	1569	as EV watchers, and 10 times as much memory as Event (the high memory
999	requirements are caused by requiring a session for each watcher). Watcher	1570	requirements are caused by requiring a session for each watcher). Watcher
1000	invocation speed is almost 900 times slower than with AnyEvent's pure perl	1571	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1572	implementation.
		1573
1001	implementation. The design of the POE adaptor class in AnyEvent can not	1574	The design of the POE adaptor class in AnyEvent can not really account
1002	really account for this, as session creation overhead is small compared	1575	for the performance issues, though, as session creation overhead is
1003	to execution of the state machine, which is coded pretty optimally within	1576	small compared to execution of the state machine, which is coded pretty
1004	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1577	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1578	using multiple sessions is not a good approach, especially regarding
		1579	memory usage, even the author of POE could not come up with a faster
		1580	design).
1005		1581
1006	=head2 Summary	1582	=head3 Summary
1007		1583
1008	=over 4	1584	=over 4
1009		1585
1010	=item * Using EV through AnyEvent is faster than any other event loop, but most	1586	=item * Using EV through AnyEvent is faster than any other event loop
1011	event loops have acceptable performance with or without AnyEvent.	1587	(even when used without AnyEvent), but most event loops have acceptable
		1588	performance with or without AnyEvent.
1012		1589
1013	=item * The overhead AnyEvent adds is usually much smaller than the overhead of	1590	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
1014	the actual event loop, only with extremely fast event loops such as the EV	1591	the actual event loop, only with extremely fast event loops such as EV
1015	adds AnyEvent significant overhead.	1592	adds AnyEvent significant overhead.
1016		1593
1017	=item * And you should simply avoid POE like the plague if you want performance or	1594	=item * You should avoid POE like the plague if you want performance or
1018	reasonable memory usage.	1595	reasonable memory usage.
1019		1596
1020	=back	1597	=back
1021		1598
		1599	=head2 BENCHMARKING THE LARGE SERVER CASE
		1600
		1601	This benchmark actually benchmarks the event loop itself. It works by
		1602	creating a number of "servers": each server consists of a socket pair, a
		1603	timeout watcher that gets reset on activity (but never fires), and an I/O
		1604	watcher waiting for input on one side of the socket. Each time the socket
		1605	watcher reads a byte it will write that byte to a random other "server".
		1606
		1607	The effect is that there will be a lot of I/O watchers, only part of which
		1608	are active at any one point (so there is a constant number of active
		1609	fds for each loop iteration, but which fds these are is random). The
		1610	timeout is reset each time something is read because that reflects how
		1611	most timeouts work (and puts extra pressure on the event loops).
		1612
		1613	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1614	(1%) are active. This mirrors the activity of large servers with many
		1615	connections, most of which are idle at any one point in time.
		1616
		1617	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1618	distribution.
		1619
		1620	=head3 Explanation of the columns
		1621
		1622	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1623	each server has a read and write socket end).
		1624
		1625	I<create> is the time it takes to create a socket pair (which is
		1626	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1627
		1628	I<request>, the most important value, is the time it takes to handle a
		1629	single "request", that is, reading the token from the pipe and forwarding
		1630	it to another server. This includes deleting the old timeout and creating
		1631	a new one that moves the timeout into the future.
		1632
		1633	=head3 Results
		1634
		1635	name sockets create request
		1636	EV 20000 69.01 11.16
		1637	Perl 20000 73.32 35.87
		1638	Event 20000 212.62 257.32
		1639	Glib 20000 651.16 1896.30
		1640	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1641
		1642	=head3 Discussion
		1643
		1644	This benchmark I<does> measure scalability and overall performance of the
		1645	particular event loop.
		1646
		1647	EV is again fastest. Since it is using epoll on my system, the setup time
		1648	is relatively high, though.
		1649
		1650	Perl surprisingly comes second. It is much faster than the C-based event
		1651	loops Event and Glib.
		1652
		1653	Event suffers from high setup time as well (look at its code and you will
		1654	understand why). Callback invocation also has a high overhead compared to
		1655	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1656	uses select or poll in basically all documented configurations.
		1657
		1658	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1659	clearly fails to perform with many filehandles or in busy servers.
		1660
		1661	POE is still completely out of the picture, taking over 1000 times as long
		1662	as EV, and over 100 times as long as the Perl implementation, even though
		1663	it uses a C-based event loop in this case.
		1664
		1665	=head3 Summary
		1666
		1667	=over 4
		1668
		1669	=item * The pure perl implementation performs extremely well.
		1670
		1671	=item * Avoid Glib or POE in large projects where performance matters.
		1672
		1673	=back
		1674
		1675	=head2 BENCHMARKING SMALL SERVERS
		1676
		1677	While event loops should scale (and select-based ones do not...) even to
		1678	large servers, most programs we (or I :) actually write have only a few
		1679	I/O watchers.
		1680
		1681	In this benchmark, I use the same benchmark program as in the large server
		1682	case, but it uses only eight "servers", of which three are active at any
		1683	one time. This should reflect performance for a small server relatively
		1684	well.
		1685
		1686	The columns are identical to the previous table.
		1687
		1688	=head3 Results
		1689
		1690	name sockets create request
		1691	EV 16 20.00 6.54
		1692	Perl 16 25.75 12.62
		1693	Event 16 81.27 35.86
		1694	Glib 16 32.63 15.48
		1695	POE 16 261.87 276.28 uses POE::Loop::Event
		1696
		1697	=head3 Discussion
		1698
		1699	The benchmark tries to test the performance of a typical small
		1700	server. While knowing how various event loops perform is interesting, keep
		1701	in mind that their overhead in this case is usually not as important, due
		1702	to the small absolute number of watchers (that is, you need efficiency and
		1703	speed most when you have lots of watchers, not when you only have a few of
		1704	them).
		1705
		1706	EV is again fastest.
		1707
		1708	Perl again comes second. It is noticeably faster than the C-based event
		1709	loops Event and Glib, although the difference is too small to really
		1710	matter.
		1711
		1712	POE also performs much better in this case, but is is still far behind the
		1713	others.
		1714
		1715	=head3 Summary
		1716
		1717	=over 4
		1718
		1719	=item * C-based event loops perform very well with small number of
		1720	watchers, as the management overhead dominates.
		1721
		1722	=back
		1723
1022		1724
1023	=head1 FORK	1725	=head1 FORK
1024		1726
1025	Most event libraries are not fork-safe. The ones who are usually are	1727	Most event libraries are not fork-safe. The ones who are usually are
1026	because they are so inefficient. Only L<EV> is fully fork-aware.	1728	because they rely on inefficient but fork-safe C<select> or C<poll>
		1729	calls. Only L<EV> is fully fork-aware.
1027		1730
1028	If you have to fork, you must either do so I<before> creating your first	1731	If you have to fork, you must either do so I<before> creating your first
1029	watcher OR you must not use AnyEvent at all in the child.	1732	watcher OR you must not use AnyEvent at all in the child.
1030		1733
1031		1734
…		…
1039	specified in the variable.	1742	specified in the variable.
1040		1743
1041	You can make AnyEvent completely ignore this variable by deleting it	1744	You can make AnyEvent completely ignore this variable by deleting it
1042	before the first watcher gets created, e.g. with a C<BEGIN> block:	1745	before the first watcher gets created, e.g. with a C<BEGIN> block:
1043		1746
1044	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1747	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1045		1748
1046	use AnyEvent;	1749	use AnyEvent;
		1750
		1751	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1752	be used to probe what backend is used and gain other information (which is
		1753	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		1754	$ENV{PERL_ANYEGENT_STRICT}.
		1755
		1756
		1757	=head1 BUGS
		1758
		1759	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		1760	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		1761	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		1762	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as
		1763	pronounced).
1047		1764
1048		1765
1049	=head1 SEE ALSO	1766	=head1 SEE ALSO
1050		1767
1051	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1768	Utility functions: L<AnyEvent::Util>.
1052	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1769
		1770	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1053	L<Event::Lib>, L<Qt>, L<POE>.	1771	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1054		1772
1055	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1773	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1056	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1774	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1057	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1775	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1058	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1776	L<AnyEvent::Impl::POE>.
1059		1777
		1778	Non-blocking file handles, sockets, TCP clients and
		1779	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1780
		1781	Asynchronous DNS: L<AnyEvent::DNS>.
		1782
		1783	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1784
1060	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1785	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1061		1786
1062		1787
1063	=head1 AUTHOR	1788	=head1 AUTHOR
1064		1789
1065	Marc Lehmann <schmorp@schmorp.de>	1790	Marc Lehmann <schmorp@schmorp.de>
1066	http://home.schmorp.de/	1791	http://home.schmorp.de/
1067		1792
1068	=cut	1793	=cut
1069		1794
1070	1	1795	1
1071		1796

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