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Revision 1.216 by root, Tue Jun 23 12:21:34 2009 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 and POE are various supported
		6	event loops.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
22		45
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	46	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		47
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	48	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	49	nowadays. So what is different about AnyEvent?
27		50
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	51	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	52	policy> and AnyEvent is I<small and efficient>.
30		53
31	First and foremost, I<AnyEvent is not an event model> itself, it only	54	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	55	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,	56	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,	57	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	58	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	59	cannot change this, but it can hide the differences between those event
		60	loops.
37		61
38	The goal of AnyEvent is to offer module authors the ability to do event	62	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	63	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	64	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	65	module users into the same thing by forcing them to use the same event
42	model you use.	66	model you use.
43		67
44	For modules like POE or IO::Async (which is a total misnomer as it is	68	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	69	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	70	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	71	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	72	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.	73	module are I<also> forced to use the same event loop you use.
50		74
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	75	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	76	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	77	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,	78	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	79	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	80	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	81	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).	82	to AnyEvent, too, so it is future-proof).
59		83
60	In addition to being free of having to use I<the one and only true event	84	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	85	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	86	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	87	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	88	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	89	technically possible.
66		90
		91	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		92	of useful functionality, such as an asynchronous DNS resolver, 100%
		93	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		94	such as Windows) and lots of real-world knowledge and workarounds for
		95	platform bugs and differences.
		96
67	Of course, if you want lots of policy (this can arguably be somewhat	97	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	98	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	99	model, you should I<not> use this module.
70
71		100
72	=head1 DESCRIPTION	101	=head1 DESCRIPTION
73		102
74	L<AnyEvent> provides an identical interface to multiple event loops. This	103	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	104	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>	108	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	109	module.
81		110
82	During the first call of any watcher-creation method, the module tries	111	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	112	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>,	113	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	114	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	115	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	116	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	117	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	118	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	132	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...	133	use AnyEvent so their modules work together with others seamlessly...
105		134
106	The pure-perl implementation of AnyEvent is called	135	The pure-perl implementation of AnyEvent is called
107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	136	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
108	explicitly.	137	explicitly and enjoy the high availability of that event loop :)
109		138
110	=head1 WATCHERS	139	=head1 WATCHERS
111		140
112	AnyEvent has the central concept of a I<watcher>, which is an object that	141	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	142	stores relevant data for each kind of event you are waiting for, such as
114	the callback to call, the filehandle to watch, etc.	143	the callback to call, the file handle to watch, etc.
115		144
116	These watchers are normal Perl objects with normal Perl lifetime. After	145	These watchers are normal Perl objects with normal Perl lifetime. After
117	creating a watcher it will immediately "watch" for events and invoke the	146	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	147	callback when the event occurs (of course, only when the event model
119	is in control).	148	is in control).
120		149
		150	Note that B<callbacks must not permanently change global variables>
		151	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		152	callbacks must not C<die> >>. The former is good programming practise in
		153	Perl and the latter stems from the fact that exception handling differs
		154	widely between event loops.
		155
121	To disable the watcher you have to destroy it (e.g. by setting the	156	To disable the watcher you have to destroy it (e.g. by setting the
122	variable you store it in to C<undef> or otherwise deleting all references	157	variable you store it in to C<undef> or otherwise deleting all references
123	to it).	158	to it).
124		159
125	All watchers are created by calling a method on the C<AnyEvent> class.	160	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
127	Many watchers either are used with "recursion" (repeating timers for	162	Many watchers either are used with "recursion" (repeating timers for
128	example), or need to refer to their watcher object in other ways.	163	example), or need to refer to their watcher object in other ways.
129		164
130	An any way to achieve that is this pattern:	165	An any way to achieve that is this pattern:
131		166
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	167	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	168	# you can use $w here, for example to undef it
134	undef $w;	169	undef $w;
135	});	170	});
136		171
137	Note that C<my $w; $w => combination. This is necessary because in Perl,	172	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	173	my variables are only visible after the statement in which they are
139	declared.	174	declared.
140		175
141	=head2 I/O WATCHERS	176	=head2 I/O WATCHERS
142		177
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	178	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	179	with the following mandatory key-value pairs as arguments:
145		180
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	181	C<fh> is the Perl I<file handle> (I<not> file descriptor) to watch
		182	for events (AnyEvent might or might not keep a reference to this file
		183	handle). Note that only file handles pointing to things for which
		184	non-blocking operation makes sense are allowed. This includes sockets,
		185	most character devices, pipes, fifos and so on, but not for example files
		186	or block devices.
		187
147	events. C<poll> must be a string that is either C<r> or C<w>, which	188	C<poll> must be a string that is either C<r> or C<w>, which creates a
148	creates a watcher waiting for "r"eadable or "w"ritable events,	189	watcher waiting for "r"eadable or "w"ritable events, respectively.
		190
149	respectively. C<cb> is the callback to invoke each time the file handle	191	C<cb> is the callback to invoke each time the file handle becomes ready.
150	becomes ready.	192
		193	Although the callback might get passed parameters, their value and
		194	presence is undefined and you cannot rely on them. Portable AnyEvent
		195	callbacks cannot use arguments passed to I/O watcher callbacks.
151		196
152	The I/O watcher might use the underlying file descriptor or a copy of it.	197	The I/O watcher might use the underlying file descriptor or a copy of it.
153	You must not close a file handle as long as any watcher is active on the	198	You must not close a file handle as long as any watcher is active on the
154	underlying file descriptor.	199	underlying file descriptor.
155		200
156	Some event loops issue spurious readyness notifications, so you should	201	Some event loops issue spurious readyness notifications, so you should
157	always use non-blocking calls when reading/writing from/to your file	202	always use non-blocking calls when reading/writing from/to your file
158	handles.	203	handles.
159		204
160	Although the callback might get passed parameters, their value and
161	presence is undefined and you cannot rely on them. Portable AnyEvent
162	callbacks cannot use arguments passed to I/O watcher callbacks.
163
164	Example:
165
166	# wait for readability of STDIN, then read a line and disable the watcher	205	Example: wait for readability of STDIN, then read a line and disable the
		206	watcher.
		207
167	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	208	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
168	chomp (my $input = <STDIN>);	209	chomp (my $input = <STDIN>);
169	warn "read: $input\n";	210	warn "read: $input\n";
170	undef $w;	211	undef $w;
171	});	212	});
…		…
174		215
175	You can create a time watcher by calling the C<< AnyEvent->timer >>	216	You can create a time watcher by calling the C<< AnyEvent->timer >>
176	method with the following mandatory arguments:	217	method with the following mandatory arguments:
177		218
178	C<after> specifies after how many seconds (fractional values are	219	C<after> specifies after how many seconds (fractional values are
179	supported) should the timer activate. C<cb> the callback to invoke in that	220	supported) the callback should be invoked. C<cb> is the callback to invoke
180	case.	221	in that case.
181
182	The timer callback will be invoked at most once: if you want a repeating
183	timer you have to create a new watcher (this is a limitation by both Tk
184	and Glib).
185		222
186	Although the callback might get passed parameters, their value and	223	Although the callback might get passed parameters, their value and
187	presence is undefined and you cannot rely on them. Portable AnyEvent	224	presence is undefined and you cannot rely on them. Portable AnyEvent
188	callbacks cannot use arguments passed to time watcher callbacks.	225	callbacks cannot use arguments passed to time watcher callbacks.
189		226
190	Example:	227	The callback will normally be invoked once only. If you specify another
		228	parameter, C<interval>, as a strictly positive number (> 0), then the
		229	callback will be invoked regularly at that interval (in fractional
		230	seconds) after the first invocation. If C<interval> is specified with a
		231	false value, then it is treated as if it were missing.
191		232
		233	The callback will be rescheduled before invoking the callback, but no
		234	attempt is done to avoid timer drift in most backends, so the interval is
		235	only approximate.
		236
192	# fire an event after 7.7 seconds	237	Example: fire an event after 7.7 seconds.
		238
193	my $w = AnyEvent->timer (after => 7.7, cb => sub {	239	my $w = AnyEvent->timer (after => 7.7, cb => sub {
194	warn "timeout\n";	240	warn "timeout\n";
195	});	241	});
196		242
197	# to cancel the timer:	243	# to cancel the timer:
198	undef $w;	244	undef $w;
199		245
200	Example 2:
201
202	# fire an event after 0.5 seconds, then roughly every second	246	Example 2: fire an event after 0.5 seconds, then roughly every second.
203	my $w;
204		247
205	my $cb = sub {
206	# cancel the old timer while creating a new one
207	$w = AnyEvent->timer (after => 1, cb => $cb);	248	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		249	warn "timeout\n";
208	};	250	};
209
210	# start the "loop" by creating the first watcher
211	$w = AnyEvent->timer (after => 0.5, cb => $cb);
212		251
213	=head3 TIMING ISSUES	252	=head3 TIMING ISSUES
214		253
215	There are two ways to handle timers: based on real time (relative, "fire	254	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	255	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
228	timers.	267	timers.
229		268
230	AnyEvent always prefers relative timers, if available, matching the	269	AnyEvent always prefers relative timers, if available, matching the
231	AnyEvent API.	270	AnyEvent API.
232		271
		272	AnyEvent has two additional methods that return the "current time":
		273
		274	=over 4
		275
		276	=item AnyEvent->time
		277
		278	This returns the "current wallclock time" as a fractional number of
		279	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		280	return, and the result is guaranteed to be compatible with those).
		281
		282	It progresses independently of any event loop processing, i.e. each call
		283	will check the system clock, which usually gets updated frequently.
		284
		285	=item AnyEvent->now
		286
		287	This also returns the "current wallclock time", but unlike C<time>, above,
		288	this value might change only once per event loop iteration, depending on
		289	the event loop (most return the same time as C<time>, above). This is the
		290	time that AnyEvent's timers get scheduled against.
		291
		292	I<In almost all cases (in all cases if you don't care), this is the
		293	function to call when you want to know the current time.>
		294
		295	This function is also often faster then C<< AnyEvent->time >>, and
		296	thus the preferred method if you want some timestamp (for example,
		297	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		298
		299	The rest of this section is only of relevance if you try to be very exact
		300	with your timing, you can skip it without bad conscience.
		301
		302	For a practical example of when these times differ, consider L<Event::Lib>
		303	and L<EV> and the following set-up:
		304
		305	The event loop is running and has just invoked one of your callback at
		306	time=500 (assume no other callbacks delay processing). In your callback,
		307	you wait a second by executing C<sleep 1> (blocking the process for a
		308	second) and then (at time=501) you create a relative timer that fires
		309	after three seconds.
		310
		311	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		312	both return C<501>, because that is the current time, and the timer will
		313	be scheduled to fire at time=504 (C<501> + C<3>).
		314
		315	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		316	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		317	last event processing phase started. With L<EV>, your timer gets scheduled
		318	to run at time=503 (C<500> + C<3>).
		319
		320	In one sense, L<Event::Lib> is more exact, as it uses the current time
		321	regardless of any delays introduced by event processing. However, most
		322	callbacks do not expect large delays in processing, so this causes a
		323	higher drift (and a lot more system calls to get the current time).
		324
		325	In another sense, L<EV> is more exact, as your timer will be scheduled at
		326	the same time, regardless of how long event processing actually took.
		327
		328	In either case, if you care (and in most cases, you don't), then you
		329	can get whatever behaviour you want with any event loop, by taking the
		330	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		331	account.
		332
		333	=item AnyEvent->now_update
		334
		335	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		336	the current time for each loop iteration (see the discussion of L<<
		337	AnyEvent->now >>, above).
		338
		339	When a callback runs for a long time (or when the process sleeps), then
		340	this "current" time will differ substantially from the real time, which
		341	might affect timers and time-outs.
		342
		343	When this is the case, you can call this method, which will update the
		344	event loop's idea of "current time".
		345
		346	Note that updating the time I<might> cause some events to be handled.
		347
		348	=back
		349
233	=head2 SIGNAL WATCHERS	350	=head2 SIGNAL WATCHERS
234		351
235	You can watch for signals using a signal watcher, C<signal> is the signal	352	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	353	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
237	be invoked whenever a signal occurs.	354	callback to be invoked whenever a signal occurs.
238		355
		356	Although the callback might get passed parameters, their value and
		357	presence is undefined and you cannot rely on them. Portable AnyEvent
		358	callbacks cannot use arguments passed to signal watcher callbacks.
		359
239	Multiple signal occurances can be clumped together into one callback	360	Multiple signal occurrences can be clumped together into one callback
240	invocation, and callback invocation will be synchronous. synchronous means	361	invocation, and callback invocation will be synchronous. Synchronous means
241	that it might take a while until the signal gets handled by the process,	362	that it might take a while until the signal gets handled by the process,
242	but it is guarenteed not to interrupt any other callbacks.	363	but it is guaranteed not to interrupt any other callbacks.
243		364
244	The main advantage of using these watchers is that you can share a signal	365	The main advantage of using these watchers is that you can share a signal
245	between multiple watchers.	366	between multiple watchers.
246		367
247	This watcher might use C<%SIG>, so programs overwriting those signals	368	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
254	=head2 CHILD PROCESS WATCHERS	375	=head2 CHILD PROCESS WATCHERS
255		376
256	You can also watch on a child process exit and catch its exit status.	377	You can also watch on a child process exit and catch its exit status.
257		378
258	The child process is specified by the C<pid> argument (if set to C<0>, it	379	The child process is specified by the C<pid> argument (if set to C<0>, it
259	watches for any child process exit). The watcher will trigger as often	380	watches for any child process exit). The watcher will triggered only when
260	as status change for the child are received. This works by installing a	381	the child process has finished and an exit status is available, not on
261	signal handler for C<SIGCHLD>. The callback will be called with the pid	382	any trace events (stopped/continued).
262	and exit status (as returned by waitpid).	383
		384	The callback will be called with the pid and exit status (as returned by
		385	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		386	callback arguments.
		387
		388	This watcher type works by installing a signal handler for C<SIGCHLD>,
		389	and since it cannot be shared, nothing else should use SIGCHLD or reap
		390	random child processes (waiting for specific child processes, e.g. inside
		391	C<system>, is just fine).
263		392
264	There is a slight catch to child watchers, however: you usually start them	393	There is a slight catch to child watchers, however: you usually start them
265	I<after> the child process was created, and this means the process could	394	I<after> the child process was created, and this means the process could
266	have exited already (and no SIGCHLD will be sent anymore).	395	have exited already (and no SIGCHLD will be sent anymore).
267		396
…		…
273	AnyEvent program, you I<have> to create at least one watcher before you	402	AnyEvent program, you I<have> to create at least one watcher before you
274	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	403	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
275		404
276	Example: fork a process and wait for it	405	Example: fork a process and wait for it
277		406
278	my $done = AnyEvent->condvar;	407	my $done = AnyEvent->condvar;
279		408
280	AnyEvent::detect; # force event module to be initialised
281
282	my $pid = fork or exit 5;	409	my $pid = fork or exit 5;
283		410
284	my $w = AnyEvent->child (	411	my $w = AnyEvent->child (
285	pid => $pid,	412	pid => $pid,
286	cb => sub {	413	cb => sub {
287	my ($pid, $status) = @_;	414	my ($pid, $status) = @_;
288	warn "pid $pid exited with status $status";	415	warn "pid $pid exited with status $status";
289	$done->broadcast;	416	$done->send;
290	},	417	},
291	);	418	);
292		419
293	# do something else, then wait for process exit	420	# do something else, then wait for process exit
294	$done->wait;	421	$done->recv;
		422
		423	=head2 IDLE WATCHERS
		424
		425	Sometimes there is a need to do something, but it is not so important
		426	to do it instantly, but only when there is nothing better to do. This
		427	"nothing better to do" is usually defined to be "no other events need
		428	attention by the event loop".
		429
		430	Idle watchers ideally get invoked when the event loop has nothing
		431	better to do, just before it would block the process to wait for new
		432	events. Instead of blocking, the idle watcher is invoked.
		433
		434	Most event loops unfortunately do not really support idle watchers (only
		435	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		436	will simply call the callback "from time to time".
		437
		438	Example: read lines from STDIN, but only process them when the
		439	program is otherwise idle:
		440
		441	my @lines; # read data
		442	my $idle_w;
		443	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		444	push @lines, scalar <STDIN>;
		445
		446	# start an idle watcher, if not already done
		447	$idle_w ||= AnyEvent->idle (cb => sub {
		448	# handle only one line, when there are lines left
		449	if (my $line = shift @lines) {
		450	print "handled when idle: $line";
		451	} else {
		452	# otherwise disable the idle watcher again
		453	undef $idle_w;
		454	}
		455	});
		456	});
295		457
296	=head2 CONDITION VARIABLES	458	=head2 CONDITION VARIABLES
297		459
		460	If you are familiar with some event loops you will know that all of them
		461	require you to run some blocking "loop", "run" or similar function that
		462	will actively watch for new events and call your callbacks.
		463
		464	AnyEvent is different, it expects somebody else to run the event loop and
		465	will only block when necessary (usually when told by the user).
		466
		467	The instrument to do that is called a "condition variable", so called
		468	because they represent a condition that must become true.
		469
298	Condition variables can be created by calling the C<< AnyEvent->condvar >>	470	Condition variables can be created by calling the C<< AnyEvent->condvar
299	method without any arguments.	471	>> method, usually without arguments. The only argument pair allowed is
300		472
301	A condition variable waits for a condition - precisely that the C<<	473	C<cb>, which specifies a callback to be called when the condition variable
302	->broadcast >> method has been called.	474	becomes true, with the condition variable as the first argument (but not
		475	the results).
303		476
304	They are very useful to signal that a condition has been fulfilled, for	477	After creation, the condition variable is "false" until it becomes "true"
		478	by calling the C<send> method (or calling the condition variable as if it
		479	were a callback, read about the caveats in the description for the C<<
		480	->send >> method).
		481
		482	Condition variables are similar to callbacks, except that you can
		483	optionally wait for them. They can also be called merge points - points
		484	in time where multiple outstanding events have been processed. And yet
		485	another way to call them is transactions - each condition variable can be
		486	used to represent a transaction, which finishes at some point and delivers
		487	a result.
		488
		489	Condition variables are very useful to signal that something has finished,
305	example, if you write a module that does asynchronous http requests,	490	for example, if you write a module that does asynchronous http requests,
306	then a condition variable would be the ideal candidate to signal the	491	then a condition variable would be the ideal candidate to signal the
307	availability of results.	492	availability of results. The user can either act when the callback is
		493	called or can synchronously C<< ->recv >> for the results.
308		494
309	You can also use condition variables to block your main program until	495	You can also use them to simulate traditional event loops - for example,
310	an event occurs - for example, you could C<< ->wait >> in your main	496	you can block your main program until an event occurs - for example, you
311	program until the user clicks the Quit button in your app, which would C<<	497	could C<< ->recv >> in your main program until the user clicks the Quit
312	->broadcast >> the "quit" event.	498	button of your app, which would C<< ->send >> the "quit" event.
313		499
314	Note that condition variables recurse into the event loop - if you have	500	Note that condition variables recurse into the event loop - if you have
315	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	501	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
316	lose. Therefore, condition variables are good to export to your caller, but	502	lose. Therefore, condition variables are good to export to your caller, but
317	you should avoid making a blocking wait yourself, at least in callbacks,	503	you should avoid making a blocking wait yourself, at least in callbacks,
318	as this asks for trouble.	504	as this asks for trouble.
319		505
320	This object has two methods:	506	Condition variables are represented by hash refs in perl, and the keys
		507	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		508	easy (it is often useful to build your own transaction class on top of
		509	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		510	it's C<new> method in your own C<new> method.
		511
		512	There are two "sides" to a condition variable - the "producer side" which
		513	eventually calls C<< -> send >>, and the "consumer side", which waits
		514	for the send to occur.
		515
		516	Example: wait for a timer.
		517
		518	# wait till the result is ready
		519	my $result_ready = AnyEvent->condvar;
		520
		521	# do something such as adding a timer
		522	# or socket watcher the calls $result_ready->send
		523	# when the "result" is ready.
		524	# in this case, we simply use a timer:
		525	my $w = AnyEvent->timer (
		526	after => 1,
		527	cb => sub { $result_ready->send },
		528	);
		529
		530	# this "blocks" (while handling events) till the callback
		531	# calls send
		532	$result_ready->recv;
		533
		534	Example: wait for a timer, but take advantage of the fact that
		535	condition variables are also code references.
		536
		537	my $done = AnyEvent->condvar;
		538	my $delay = AnyEvent->timer (after => 5, cb => $done);
		539	$done->recv;
		540
		541	Example: Imagine an API that returns a condvar and doesn't support
		542	callbacks. This is how you make a synchronous call, for example from
		543	the main program:
		544
		545	use AnyEvent::CouchDB;
		546
		547	...
		548
		549	my @info = $couchdb->info->recv;
		550
		551	And this is how you would just ste a callback to be called whenever the
		552	results are available:
		553
		554	$couchdb->info->cb (sub {
		555	my @info = $_[0]->recv;
		556	});
		557
		558	=head3 METHODS FOR PRODUCERS
		559
		560	These methods should only be used by the producing side, i.e. the
		561	code/module that eventually sends the signal. Note that it is also
		562	the producer side which creates the condvar in most cases, but it isn't
		563	uncommon for the consumer to create it as well.
321		564
322	=over 4	565	=over 4
323		566
		567	=item $cv->send (...)
		568
		569	Flag the condition as ready - a running C<< ->recv >> and all further
		570	calls to C<recv> will (eventually) return after this method has been
		571	called. If nobody is waiting the send will be remembered.
		572
		573	If a callback has been set on the condition variable, it is called
		574	immediately from within send.
		575
		576	Any arguments passed to the C<send> call will be returned by all
		577	future C<< ->recv >> calls.
		578
		579	Condition variables are overloaded so one can call them directly
		580	(as a code reference). Calling them directly is the same as calling
		581	C<send>. Note, however, that many C-based event loops do not handle
		582	overloading, so as tempting as it may be, passing a condition variable
		583	instead of a callback does not work. Both the pure perl and EV loops
		584	support overloading, however, as well as all functions that use perl to
		585	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		586	example).
		587
		588	=item $cv->croak ($error)
		589
		590	Similar to send, but causes all call's to C<< ->recv >> to invoke
		591	C<Carp::croak> with the given error message/object/scalar.
		592
		593	This can be used to signal any errors to the condition variable
		594	user/consumer.
		595
		596	=item $cv->begin ([group callback])
		597
324	=item $cv->wait	598	=item $cv->end
325		599
326	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	600	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		601
		602	These two methods can be used to combine many transactions/events into
		603	one. For example, a function that pings many hosts in parallel might want
		604	to use a condition variable for the whole process.
		605
		606	Every call to C<< ->begin >> will increment a counter, and every call to
		607	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		608	>>, the (last) callback passed to C<begin> will be executed. That callback
		609	is I<supposed> to call C<< ->send >>, but that is not required. If no
		610	callback was set, C<send> will be called without any arguments.
		611
		612	Let's clarify this with the ping example:
		613
		614	my $cv = AnyEvent->condvar;
		615
		616	my %result;
		617	$cv->begin (sub { $cv->send (\%result) });
		618
		619	for my $host (@list_of_hosts) {
		620	$cv->begin;
		621	ping_host_then_call_callback $host, sub {
		622	$result{$host} = ...;
		623	$cv->end;
		624	};
		625	}
		626
		627	$cv->end;
		628
		629	This code fragment supposedly pings a number of hosts and calls
		630	C<send> after results for all then have have been gathered - in any
		631	order. To achieve this, the code issues a call to C<begin> when it starts
		632	each ping request and calls C<end> when it has received some result for
		633	it. Since C<begin> and C<end> only maintain a counter, the order in which
		634	results arrive is not relevant.
		635
		636	There is an additional bracketing call to C<begin> and C<end> outside the
		637	loop, which serves two important purposes: first, it sets the callback
		638	to be called once the counter reaches C<0>, and second, it ensures that
		639	C<send> is called even when C<no> hosts are being pinged (the loop
		640	doesn't execute once).
		641
		642	This is the general pattern when you "fan out" into multiple subrequests:
		643	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		644	is called at least once, and then, for each subrequest you start, call
		645	C<begin> and for each subrequest you finish, call C<end>.
		646
		647	=back
		648
		649	=head3 METHODS FOR CONSUMERS
		650
		651	These methods should only be used by the consuming side, i.e. the
		652	code awaits the condition.
		653
		654	=over 4
		655
		656	=item $cv->recv
		657
		658	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
327	called on c<$cv>, while servicing other watchers normally.	659	>> methods have been called on c<$cv>, while servicing other watchers
		660	normally.
328		661
329	You can only wait once on a condition - additional calls will return	662	You can only wait once on a condition - additional calls are valid but
330	immediately.	663	will return immediately.
		664
		665	If an error condition has been set by calling C<< ->croak >>, then this
		666	function will call C<croak>.
		667
		668	In list context, all parameters passed to C<send> will be returned,
		669	in scalar context only the first one will be returned.
331		670
332	Not all event models support a blocking wait - some die in that case	671	Not all event models support a blocking wait - some die in that case
333	(programs might want to do that to stay interactive), so I<if you are	672	(programs might want to do that to stay interactive), so I<if you are
334	using this from a module, never require a blocking wait>, but let the	673	using this from a module, never require a blocking wait>, but let the
335	caller decide whether the call will block or not (for example, by coupling	674	caller decide whether the call will block or not (for example, by coupling
336	condition variables with some kind of request results and supporting	675	condition variables with some kind of request results and supporting
337	callbacks so the caller knows that getting the result will not block,	676	callbacks so the caller knows that getting the result will not block,
338	while still suppporting blocking waits if the caller so desires).	677	while still supporting blocking waits if the caller so desires).
339		678
340	Another reason I<never> to C<< ->wait >> in a module is that you cannot	679	Another reason I<never> to C<< ->recv >> in a module is that you cannot
341	sensibly have two C<< ->wait >>'s in parallel, as that would require	680	sensibly have two C<< ->recv >>'s in parallel, as that would require
342	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	681	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
343	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	682	can supply.
344	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
345	from different coroutines, however).
346		683
347	=item $cv->broadcast	684	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		685	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		686	versions and also integrates coroutines into AnyEvent, making blocking
		687	C<< ->recv >> calls perfectly safe as long as they are done from another
		688	coroutine (one that doesn't run the event loop).
348		689
349	Flag the condition as ready - a running C<< ->wait >> and all further	690	You can ensure that C<< -recv >> never blocks by setting a callback and
350	calls to C<wait> will (eventually) return after this method has been	691	only calling C<< ->recv >> from within that callback (or at a later
351	called. If nobody is waiting the broadcast will be remembered..	692	time). This will work even when the event loop does not support blocking
		693	waits otherwise.
		694
		695	=item $bool = $cv->ready
		696
		697	Returns true when the condition is "true", i.e. whether C<send> or
		698	C<croak> have been called.
		699
		700	=item $cb = $cv->cb ($cb->($cv))
		701
		702	This is a mutator function that returns the callback set and optionally
		703	replaces it before doing so.
		704
		705	The callback will be called when the condition becomes "true", i.e. when
		706	C<send> or C<croak> are called, with the only argument being the condition
		707	variable itself. Calling C<recv> inside the callback or at any later time
		708	is guaranteed not to block.
352		709
353	=back	710	=back
354
355	Example:
356
357	# wait till the result is ready
358	my $result_ready = AnyEvent->condvar;
359
360	# do something such as adding a timer
361	# or socket watcher the calls $result_ready->broadcast
362	# when the "result" is ready.
363	# in this case, we simply use a timer:
364	my $w = AnyEvent->timer (
365	after => 1,
366	cb => sub { $result_ready->broadcast },
367	);
368
369	# this "blocks" (while handling events) till the watcher
370	# calls broadcast
371	$result_ready->wait;
372		711
373	=head1 GLOBAL VARIABLES AND FUNCTIONS	712	=head1 GLOBAL VARIABLES AND FUNCTIONS
374		713
375	=over 4	714	=over 4
376		715
…		…
382	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	721	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
383	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	722	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
384		723
385	The known classes so far are:	724	The known classes so far are:
386		725
387	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
388	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
389	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	726	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
390	AnyEvent::Impl::Event based on Event, second best choice.	727	AnyEvent::Impl::Event based on Event, second best choice.
		728	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
391	AnyEvent::Impl::Glib based on Glib, third-best choice.	729	AnyEvent::Impl::Glib based on Glib, third-best choice.
392	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
393	AnyEvent::Impl::Tk based on Tk, very bad choice.	730	AnyEvent::Impl::Tk based on Tk, very bad choice.
394	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	731	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
395	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	732	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
396	AnyEvent::Impl::POE based on POE, not generic enough for full support.	733	AnyEvent::Impl::POE based on POE, not generic enough for full support.
397		734
…		…
410	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	747	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
411	if necessary. You should only call this function right before you would	748	if necessary. You should only call this function right before you would
412	have created an AnyEvent watcher anyway, that is, as late as possible at	749	have created an AnyEvent watcher anyway, that is, as late as possible at
413	runtime.	750	runtime.
414		751
		752	=item $guard = AnyEvent::post_detect { BLOCK }
		753
		754	Arranges for the code block to be executed as soon as the event model is
		755	autodetected (or immediately if this has already happened).
		756
		757	If called in scalar or list context, then it creates and returns an object
		758	that automatically removes the callback again when it is destroyed. See
		759	L<Coro::BDB> for a case where this is useful.
		760
		761	=item @AnyEvent::post_detect
		762
		763	If there are any code references in this array (you can C<push> to it
		764	before or after loading AnyEvent), then they will called directly after
		765	the event loop has been chosen.
		766
		767	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		768	if it contains a true value then the event loop has already been detected,
		769	and the array will be ignored.
		770
		771	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		772
415	=back	773	=back
416		774
417	=head1 WHAT TO DO IN A MODULE	775	=head1 WHAT TO DO IN A MODULE
418		776
419	As a module author, you should C<use AnyEvent> and call AnyEvent methods	777	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
422	Be careful when you create watchers in the module body - AnyEvent will	780	Be careful when you create watchers in the module body - AnyEvent will
423	decide which event module to use as soon as the first method is called, so	781	decide which event module to use as soon as the first method is called, so
424	by calling AnyEvent in your module body you force the user of your module	782	by calling AnyEvent in your module body you force the user of your module
425	to load the event module first.	783	to load the event module first.
426		784
427	Never call C<< ->wait >> on a condition variable unless you I<know> that	785	Never call C<< ->recv >> on a condition variable unless you I<know> that
428	the C<< ->broadcast >> method has been called on it already. This is	786	the C<< ->send >> method has been called on it already. This is
429	because it will stall the whole program, and the whole point of using	787	because it will stall the whole program, and the whole point of using
430	events is to stay interactive.	788	events is to stay interactive.
431		789
432	It is fine, however, to call C<< ->wait >> when the user of your module	790	It is fine, however, to call C<< ->recv >> when the user of your module
433	requests it (i.e. if you create a http request object ad have a method	791	requests it (i.e. if you create a http request object ad have a method
434	called C<results> that returns the results, it should call C<< ->wait >>	792	called C<results> that returns the results, it should call C<< ->recv >>
435	freely, as the user of your module knows what she is doing. always).	793	freely, as the user of your module knows what she is doing. always).
436		794
437	=head1 WHAT TO DO IN THE MAIN PROGRAM	795	=head1 WHAT TO DO IN THE MAIN PROGRAM
438		796
439	There will always be a single main program - the only place that should	797	There will always be a single main program - the only place that should
…		…
441		799
442	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	800	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
443	do anything special (it does not need to be event-based) and let AnyEvent	801	do anything special (it does not need to be event-based) and let AnyEvent
444	decide which implementation to chose if some module relies on it.	802	decide which implementation to chose if some module relies on it.
445		803
446	If the main program relies on a specific event model. For example, in	804	If the main program relies on a specific event model - for example, in
447	Gtk2 programs you have to rely on the Glib module. You should load the	805	Gtk2 programs you have to rely on the Glib module - you should load the
448	event module before loading AnyEvent or any module that uses it: generally	806	event module before loading AnyEvent or any module that uses it: generally
449	speaking, you should load it as early as possible. The reason is that	807	speaking, you should load it as early as possible. The reason is that
450	modules might create watchers when they are loaded, and AnyEvent will	808	modules might create watchers when they are loaded, and AnyEvent will
451	decide on the event model to use as soon as it creates watchers, and it	809	decide on the event model to use as soon as it creates watchers, and it
452	might chose the wrong one unless you load the correct one yourself.	810	might chose the wrong one unless you load the correct one yourself.
453		811
454	You can chose to use a rather inefficient pure-perl implementation by	812	You can chose to use a pure-perl implementation by loading the
455	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	813	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
456	behaviour everywhere, but letting AnyEvent chose is generally better.	814	everywhere, but letting AnyEvent chose the model is generally better.
		815
		816	=head2 MAINLOOP EMULATION
		817
		818	Sometimes (often for short test scripts, or even standalone programs who
		819	only want to use AnyEvent), you do not want to run a specific event loop.
		820
		821	In that case, you can use a condition variable like this:
		822
		823	AnyEvent->condvar->recv;
		824
		825	This has the effect of entering the event loop and looping forever.
		826
		827	Note that usually your program has some exit condition, in which case
		828	it is better to use the "traditional" approach of storing a condition
		829	variable somewhere, waiting for it, and sending it when the program should
		830	exit cleanly.
		831
		832
		833	=head1 OTHER MODULES
		834
		835	The following is a non-exhaustive list of additional modules that use
		836	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		837	in the same program. Some of the modules come with AnyEvent, some are
		838	available via CPAN.
		839
		840	=over 4
		841
		842	=item L<AnyEvent::Util>
		843
		844	Contains various utility functions that replace often-used but blocking
		845	functions such as C<inet_aton> by event-/callback-based versions.
		846
		847	=item L<AnyEvent::Socket>
		848
		849	Provides various utility functions for (internet protocol) sockets,
		850	addresses and name resolution. Also functions to create non-blocking tcp
		851	connections or tcp servers, with IPv6 and SRV record support and more.
		852
		853	=item L<AnyEvent::Handle>
		854
		855	Provide read and write buffers, manages watchers for reads and writes,
		856	supports raw and formatted I/O, I/O queued and fully transparent and
		857	non-blocking SSL/TLS.
		858
		859	=item L<AnyEvent::DNS>
		860
		861	Provides rich asynchronous DNS resolver capabilities.
		862
		863	=item L<AnyEvent::HTTP>
		864
		865	A simple-to-use HTTP library that is capable of making a lot of concurrent
		866	HTTP requests.
		867
		868	=item L<AnyEvent::HTTPD>
		869
		870	Provides a simple web application server framework.
		871
		872	=item L<AnyEvent::FastPing>
		873
		874	The fastest ping in the west.
		875
		876	=item L<AnyEvent::DBI>
		877
		878	Executes L<DBI> requests asynchronously in a proxy process.
		879
		880	=item L<AnyEvent::AIO>
		881
		882	Truly asynchronous I/O, should be in the toolbox of every event
		883	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		884	together.
		885
		886	=item L<AnyEvent::BDB>
		887
		888	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		889	L<BDB> and AnyEvent together.
		890
		891	=item L<AnyEvent::GPSD>
		892
		893	A non-blocking interface to gpsd, a daemon delivering GPS information.
		894
		895	=item L<AnyEvent::IGS>
		896
		897	A non-blocking interface to the Internet Go Server protocol (used by
		898	L<App::IGS>).
		899
		900	=item L<AnyEvent::IRC>
		901
		902	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		903
		904	=item L<Net::XMPP2>
		905
		906	AnyEvent based XMPP (Jabber protocol) module family.
		907
		908	=item L<Net::FCP>
		909
		910	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		911	of AnyEvent.
		912
		913	=item L<Event::ExecFlow>
		914
		915	High level API for event-based execution flow control.
		916
		917	=item L<Coro>
		918
		919	Has special support for AnyEvent via L<Coro::AnyEvent>.
		920
		921	=item L<IO::Lambda>
		922
		923	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		924
		925	=back
457		926
458	=cut	927	=cut
459		928
460	package AnyEvent;	929	package AnyEvent;
461		930
462	no warnings;	931	no warnings;
463	use strict;	932	use strict qw(vars subs);
464		933
465	use Carp;	934	use Carp;
466		935
467	our $VERSION = '3.3';	936	our $VERSION = 4.411;
468	our $MODEL;	937	our $MODEL;
469		938
470	our $AUTOLOAD;	939	our $AUTOLOAD;
471	our @ISA;	940	our @ISA;
472		941
		942	our @REGISTRY;
		943
		944	our $WIN32;
		945
		946	BEGIN {
		947	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		948	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		949
		950	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		951	if ${^TAINT};
		952	}
		953
473	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	954	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
474		955
475	our @REGISTRY;	956	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		957
		958	{
		959	my $idx;
		960	$PROTOCOL{$_} = ++$idx
		961	for reverse split /\s*,\s*/,
		962	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		963	}
476		964
477	my @models = (	965	my @models = (
478	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
479	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
480	[EV:: => AnyEvent::Impl::EV::],	966	[EV:: => AnyEvent::Impl::EV::],
481	[Event:: => AnyEvent::Impl::Event::],	967	[Event:: => AnyEvent::Impl::Event::],
482	[Glib:: => AnyEvent::Impl::Glib::],
483	[Tk:: => AnyEvent::Impl::Tk::],
484	[Wx:: => AnyEvent::Impl::POE::],
485	[Prima:: => AnyEvent::Impl::POE::],
486	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	968	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
487	# everything below here will not be autoprobed as the pureperl backend should work everywhere	969	# everything below here will not be autoprobed
		970	# as the pureperl backend should work everywhere
		971	# and is usually faster
		972	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		973	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
488	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	974	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
489	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	975	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
490	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	976	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		977	[Wx:: => AnyEvent::Impl::POE::],
		978	[Prima:: => AnyEvent::Impl::POE::],
491	);	979	);
492		980
493	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	981	our %method = map +($_ => 1),
		982	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		983
		984	our @post_detect;
		985
		986	sub post_detect(&) {
		987	my ($cb) = @_;
		988
		989	if ($MODEL) {
		990	$cb->();
		991
		992	1
		993	} else {
		994	push @post_detect, $cb;
		995
		996	defined wantarray
		997	? bless \$cb, "AnyEvent::Util::postdetect"
		998	: ()
		999	}
		1000	}
		1001
		1002	sub AnyEvent::Util::postdetect::DESTROY {
		1003	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1004	}
494		1005
495	sub detect() {	1006	sub detect() {
496	unless ($MODEL) {	1007	unless ($MODEL) {
497	no strict 'refs';	1008	no strict 'refs';
		1009	local $SIG{__DIE__};
498		1010
499	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1011	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
500	my $model = "AnyEvent::Impl::$1";	1012	my $model = "AnyEvent::Impl::$1";
501	if (eval "require $model") {	1013	if (eval "require $model") {
502	$MODEL = $model;	1014	$MODEL = $model;
…		…
532	last;	1044	last;
533	}	1045	}
534	}	1046	}
535		1047
536	$MODEL	1048	$MODEL
537	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1049	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
538	}	1050	}
539	}	1051	}
540		1052
		1053	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1054
541	unshift @ISA, $MODEL;	1055	unshift @ISA, $MODEL;
542	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1056
		1057	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1058
		1059	(shift @post_detect)->() while @post_detect;
543	}	1060	}
544		1061
545	$MODEL	1062	$MODEL
546	}	1063	}
547		1064
…		…
555		1072
556	my $class = shift;	1073	my $class = shift;
557	$class->$func (@_);	1074	$class->$func (@_);
558	}	1075	}
559		1076
		1077	# utility function to dup a filehandle. this is used by many backends
		1078	# to support binding more than one watcher per filehandle (they usually
		1079	# allow only one watcher per fd, so we dup it to get a different one).
		1080	sub _dupfh($$$$) {
		1081	my ($poll, $fh, $r, $w) = @_;
		1082
		1083	# cygwin requires the fh mode to be matching, unix doesn't
		1084	my ($rw, $mode) = $poll eq "r" ? ($r, "<")
		1085	: $poll eq "w" ? ($w, ">")
		1086	: Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
		1087
		1088	open my $fh2, "$mode&" . fileno $fh
		1089	or die "cannot dup() filehandle: $!,";
		1090
		1091	# we assume CLOEXEC is already set by perl in all important cases
		1092
		1093	($fh2, $rw)
		1094	}
		1095
560	package AnyEvent::Base;	1096	package AnyEvent::Base;
561		1097
		1098	# default implementations for many methods
		1099
		1100	BEGIN {
		1101	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1102	*_time = \&Time::HiRes::time;
		1103	# if (eval "use POSIX (); (POSIX::times())...
		1104	} else {
		1105	*_time = sub { time }; # epic fail
		1106	}
		1107	}
		1108
		1109	sub time { _time }
		1110	sub now { _time }
		1111	sub now_update { }
		1112
562	# default implementation for ->condvar, ->wait, ->broadcast	1113	# default implementation for ->condvar
563		1114
564	sub condvar {	1115	sub condvar {
565	bless \my $flag, "AnyEvent::Base::CondVar"	1116	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
566	}
567
568	sub AnyEvent::Base::CondVar::broadcast {
569	${$_[0]}++;
570	}
571
572	sub AnyEvent::Base::CondVar::wait {
573	AnyEvent->one_event while !${$_[0]};
574	}	1117	}
575		1118
576	# default implementation for ->signal	1119	# default implementation for ->signal
577		1120
578	our %SIG_CB;	1121	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1122
		1123	sub _signal_exec {
		1124	sysread $SIGPIPE_R, my $dummy, 4;
		1125
		1126	while (%SIG_EV) {
		1127	for (keys %SIG_EV) {
		1128	delete $SIG_EV{$_};
		1129	$_->() for values %{ $SIG_CB{$_} || {} };
		1130	}
		1131	}
		1132	}
579		1133
580	sub signal {	1134	sub signal {
581	my (undef, %arg) = @_;	1135	my (undef, %arg) = @_;
582		1136
		1137	unless ($SIGPIPE_R) {
		1138	require Fcntl;
		1139
		1140	if (AnyEvent::WIN32) {
		1141	require AnyEvent::Util;
		1142
		1143	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1144	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1145	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1146	} else {
		1147	pipe $SIGPIPE_R, $SIGPIPE_W;
		1148	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1149	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1150
		1151	# not strictly required, as $^F is normally 2, but let's make sure...
		1152	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1153	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1154	}
		1155
		1156	$SIGPIPE_R
		1157	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1158
		1159	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1160	}
		1161
583	my $signal = uc $arg{signal}	1162	my $signal = uc $arg{signal}
584	or Carp::croak "required option 'signal' is missing";	1163	or Carp::croak "required option 'signal' is missing";
585		1164
586	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1165	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
587	$SIG{$signal} ||= sub {	1166	$SIG{$signal} ||= sub {
588	$_->() for values %{ $SIG_CB{$signal} || {} };	1167	local $!;
		1168	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1169	undef $SIG_EV{$signal};
589	};	1170	};
590		1171
591	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1172	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
592	}	1173	}
593		1174
594	sub AnyEvent::Base::Signal::DESTROY {	1175	sub AnyEvent::Base::signal::DESTROY {
595	my ($signal, $cb) = @{$_[0]};	1176	my ($signal, $cb) = @{$_[0]};
596		1177
597	delete $SIG_CB{$signal}{$cb};	1178	delete $SIG_CB{$signal}{$cb};
598		1179
		1180	# delete doesn't work with older perls - they then
		1181	# print weird messages, or just unconditionally exit
		1182	# instead of getting the default action.
599	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1183	undef $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
600	}	1184	}
601		1185
602	# default implementation for ->child	1186	# default implementation for ->child
603		1187
604	our %PID_CB;	1188	our %PID_CB;
605	our $CHLD_W;	1189	our $CHLD_W;
606	our $CHLD_DELAY_W;	1190	our $CHLD_DELAY_W;
607	our $PID_IDLE;
608	our $WNOHANG;	1191	our $WNOHANG;
609		1192
610	sub _child_wait {	1193	sub _sigchld {
611	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1194	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
612	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1195	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),
613	(values %{ $PID_CB{0} || {} });	1196	(values %{ $PID_CB{0} || {} });
614	}	1197	}
615
616	undef $PID_IDLE;
617	}
618
619	sub _sigchld {
620	# make sure we deliver these changes "synchronous" with the event loop.
621	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
622	undef $CHLD_DELAY_W;
623	&_child_wait;
624	});
625	}	1198	}
626		1199
627	sub child {	1200	sub child {
628	my (undef, %arg) = @_;	1201	my (undef, %arg) = @_;
629		1202
630	defined (my $pid = $arg{pid} + 0)	1203	defined (my $pid = $arg{pid} + 0)
631	or Carp::croak "required option 'pid' is missing";	1204	or Carp::croak "required option 'pid' is missing";
632		1205
633	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1206	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
634		1207
635	unless ($WNOHANG) {
636	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1208	$WNOHANG ||= eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
637	}
638		1209
639	unless ($CHLD_W) {	1210	unless ($CHLD_W) {
640	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1211	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
641	# child could be a zombie already, so make at least one round	1212	# child could be a zombie already, so make at least one round
642	&_sigchld;	1213	&_sigchld;
643	}	1214	}
644		1215
645	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1216	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
646	}	1217	}
647		1218
648	sub AnyEvent::Base::Child::DESTROY {	1219	sub AnyEvent::Base::child::DESTROY {
649	my ($pid, $cb) = @{$_[0]};	1220	my ($pid, $cb) = @{$_[0]};
650		1221
651	delete $PID_CB{$pid}{$cb};	1222	delete $PID_CB{$pid}{$cb};
652	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1223	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
653		1224
654	undef $CHLD_W unless keys %PID_CB;	1225	undef $CHLD_W unless keys %PID_CB;
655	}	1226	}
		1227
		1228	# idle emulation is done by simply using a timer, regardless
		1229	# of whether the process is idle or not, and not letting
		1230	# the callback use more than 50% of the time.
		1231	sub idle {
		1232	my (undef, %arg) = @_;
		1233
		1234	my ($cb, $w, $rcb) = $arg{cb};
		1235
		1236	$rcb = sub {
		1237	if ($cb) {
		1238	$w = _time;
		1239	&$cb;
		1240	$w = _time - $w;
		1241
		1242	# never use more then 50% of the time for the idle watcher,
		1243	# within some limits
		1244	$w = 0.0001 if $w < 0.0001;
		1245	$w = 5 if $w > 5;
		1246
		1247	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1248	} else {
		1249	# clean up...
		1250	undef $w;
		1251	undef $rcb;
		1252	}
		1253	};
		1254
		1255	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1256
		1257	bless \\$cb, "AnyEvent::Base::idle"
		1258	}
		1259
		1260	sub AnyEvent::Base::idle::DESTROY {
		1261	undef $${$_[0]};
		1262	}
		1263
		1264	package AnyEvent::CondVar;
		1265
		1266	our @ISA = AnyEvent::CondVar::Base::;
		1267
		1268	package AnyEvent::CondVar::Base;
		1269
		1270	use overload
		1271	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1272	fallback => 1;
		1273
		1274	sub _send {
		1275	# nop
		1276	}
		1277
		1278	sub send {
		1279	my $cv = shift;
		1280	$cv->{_ae_sent} = [@_];
		1281	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1282	$cv->_send;
		1283	}
		1284
		1285	sub croak {
		1286	$_[0]{_ae_croak} = $_[1];
		1287	$_[0]->send;
		1288	}
		1289
		1290	sub ready {
		1291	$_[0]{_ae_sent}
		1292	}
		1293
		1294	sub _wait {
		1295	AnyEvent->one_event while !$_[0]{_ae_sent};
		1296	}
		1297
		1298	sub recv {
		1299	$_[0]->_wait;
		1300
		1301	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1302	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1303	}
		1304
		1305	sub cb {
		1306	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1307	$_[0]{_ae_cb}
		1308	}
		1309
		1310	sub begin {
		1311	++$_[0]{_ae_counter};
		1312	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1313	}
		1314
		1315	sub end {
		1316	return if --$_[0]{_ae_counter};
		1317	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1318	}
		1319
		1320	# undocumented/compatibility with pre-3.4
		1321	*broadcast = \&send;
		1322	*wait = \&_wait;
		1323
		1324	=head1 ERROR AND EXCEPTION HANDLING
		1325
		1326	In general, AnyEvent does not do any error handling - it relies on the
		1327	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1328	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1329	checking of all AnyEvent methods, however, which is highly useful during
		1330	development.
		1331
		1332	As for exception handling (i.e. runtime errors and exceptions thrown while
		1333	executing a callback), this is not only highly event-loop specific, but
		1334	also not in any way wrapped by this module, as this is the job of the main
		1335	program.
		1336
		1337	The pure perl event loop simply re-throws the exception (usually
		1338	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1339	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1340	so on.
		1341
		1342	=head1 ENVIRONMENT VARIABLES
		1343
		1344	The following environment variables are used by this module or its
		1345	submodules.
		1346
		1347	Note that AnyEvent will remove I<all> environment variables starting with
		1348	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1349	enabled.
		1350
		1351	=over 4
		1352
		1353	=item C<PERL_ANYEVENT_VERBOSE>
		1354
		1355	By default, AnyEvent will be completely silent except in fatal
		1356	conditions. You can set this environment variable to make AnyEvent more
		1357	talkative.
		1358
		1359	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1360	conditions, such as not being able to load the event model specified by
		1361	C<PERL_ANYEVENT_MODEL>.
		1362
		1363	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1364	model it chooses.
		1365
		1366	=item C<PERL_ANYEVENT_STRICT>
		1367
		1368	AnyEvent does not do much argument checking by default, as thorough
		1369	argument checking is very costly. Setting this variable to a true value
		1370	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1371	check the arguments passed to most method calls. If it finds any problems
		1372	it will croak.
		1373
		1374	In other words, enables "strict" mode.
		1375
		1376	Unlike C<use strict>, it is definitely recommended ot keep it off in
		1377	production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
		1378	developing programs can be very useful, however.
		1379
		1380	=item C<PERL_ANYEVENT_MODEL>
		1381
		1382	This can be used to specify the event model to be used by AnyEvent, before
		1383	auto detection and -probing kicks in. It must be a string consisting
		1384	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1385	and the resulting module name is loaded and if the load was successful,
		1386	used as event model. If it fails to load AnyEvent will proceed with
		1387	auto detection and -probing.
		1388
		1389	This functionality might change in future versions.
		1390
		1391	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1392	could start your program like this:
		1393
		1394	PERL_ANYEVENT_MODEL=Perl perl ...
		1395
		1396	=item C<PERL_ANYEVENT_PROTOCOLS>
		1397
		1398	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1399	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1400	of auto probing).
		1401
		1402	Must be set to a comma-separated list of protocols or address families,
		1403	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1404	used, and preference will be given to protocols mentioned earlier in the
		1405	list.
		1406
		1407	This variable can effectively be used for denial-of-service attacks
		1408	against local programs (e.g. when setuid), although the impact is likely
		1409	small, as the program has to handle conenction and other failures anyways.
		1410
		1411	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1412	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1413	- only support IPv4, never try to resolve or contact IPv6
		1414	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1415	IPv6, but prefer IPv6 over IPv4.
		1416
		1417	=item C<PERL_ANYEVENT_EDNS0>
		1418
		1419	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1420	for DNS. This extension is generally useful to reduce DNS traffic, but
		1421	some (broken) firewalls drop such DNS packets, which is why it is off by
		1422	default.
		1423
		1424	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1425	EDNS0 in its DNS requests.
		1426
		1427	=item C<PERL_ANYEVENT_MAX_FORKS>
		1428
		1429	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1430	will create in parallel.
		1431
		1432	=back
656		1433
657	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1434	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
658		1435
659	This is an advanced topic that you do not normally need to use AnyEvent in	1436	This is an advanced topic that you do not normally need to use AnyEvent in
660	a module. This section is only of use to event loop authors who want to	1437	a module. This section is only of use to event loop authors who want to
…		…
694		1471
695	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1472	I<rxvt-unicode> also cheats a bit by not providing blocking access to
696	condition variables: code blocking while waiting for a condition will	1473	condition variables: code blocking while waiting for a condition will
697	C<die>. This still works with most modules/usages, and blocking calls must	1474	C<die>. This still works with most modules/usages, and blocking calls must
698	not be done in an interactive application, so it makes sense.	1475	not be done in an interactive application, so it makes sense.
699
700	=head1 ENVIRONMENT VARIABLES
701
702	The following environment variables are used by this module:
703
704	=over 4
705
706	=item C<PERL_ANYEVENT_VERBOSE>
707
708	By default, AnyEvent will be completely silent except in fatal
709	conditions. You can set this environment variable to make AnyEvent more
710	talkative.
711
712	When set to C<1> or higher, causes AnyEvent to warn about unexpected
713	conditions, such as not being able to load the event model specified by
714	C<PERL_ANYEVENT_MODEL>.
715
716	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
717	model it chooses.
718
719	=item C<PERL_ANYEVENT_MODEL>
720
721	This can be used to specify the event model to be used by AnyEvent, before
722	autodetection and -probing kicks in. It must be a string consisting
723	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
724	and the resulting module name is loaded and if the load was successful,
725	used as event model. If it fails to load AnyEvent will proceed with
726	autodetection and -probing.
727
728	This functionality might change in future versions.
729
730	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
731	could start your program like this:
732
733	PERL_ANYEVENT_MODEL=Perl perl ...
734
735	=back
736		1476
737	=head1 EXAMPLE PROGRAM	1477	=head1 EXAMPLE PROGRAM
738		1478
739	The following program uses an I/O watcher to read data from STDIN, a timer	1479	The following program uses an I/O watcher to read data from STDIN, a timer
740	to display a message once per second, and a condition variable to quit the	1480	to display a message once per second, and a condition variable to quit the
…		…
749	poll => 'r',	1489	poll => 'r',
750	cb => sub {	1490	cb => sub {
751	warn "io event <$_[0]>\n"; # will always output <r>	1491	warn "io event <$_[0]>\n"; # will always output <r>
752	chomp (my $input = <STDIN>); # read a line	1492	chomp (my $input = <STDIN>); # read a line
753	warn "read: $input\n"; # output what has been read	1493	warn "read: $input\n"; # output what has been read
754	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1494	$cv->send if $input =~ /^q/i; # quit program if /^q/i
755	},	1495	},
756	);	1496	);
757		1497
758	my $time_watcher; # can only be used once	1498	my $time_watcher; # can only be used once
759		1499
…		…
764	});	1504	});
765	}	1505	}
766		1506
767	new_timer; # create first timer	1507	new_timer; # create first timer
768		1508
769	$cv->wait; # wait until user enters /^q/i	1509	$cv->recv; # wait until user enters /^q/i
770		1510
771	=head1 REAL-WORLD EXAMPLE	1511	=head1 REAL-WORLD EXAMPLE
772		1512
773	Consider the L<Net::FCP> module. It features (among others) the following	1513	Consider the L<Net::FCP> module. It features (among others) the following
774	API calls, which are to freenet what HTTP GET requests are to http:	1514	API calls, which are to freenet what HTTP GET requests are to http:
…		…
824	syswrite $txn->{fh}, $txn->{request}	1564	syswrite $txn->{fh}, $txn->{request}
825	or die "connection or write error";	1565	or die "connection or write error";
826	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1566	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
827		1567
828	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1568	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
829	result and signals any possible waiters that the request ahs finished:	1569	result and signals any possible waiters that the request has finished:
830		1570
831	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1571	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
832		1572
833	if (end-of-file or data complete) {	1573	if (end-of-file or data complete) {
834	$txn->{result} = $txn->{buf};	1574	$txn->{result} = $txn->{buf};
835	$txn->{finished}->broadcast;	1575	$txn->{finished}->send;
836	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1576	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
837	}	1577	}
838		1578
839	The C<result> method, finally, just waits for the finished signal (if the	1579	The C<result> method, finally, just waits for the finished signal (if the
840	request was already finished, it doesn't wait, of course, and returns the	1580	request was already finished, it doesn't wait, of course, and returns the
841	data:	1581	data:
842		1582
843	$txn->{finished}->wait;	1583	$txn->{finished}->recv;
844	return $txn->{result};	1584	return $txn->{result};
845		1585
846	The actual code goes further and collects all errors (C<die>s, exceptions)	1586	The actual code goes further and collects all errors (C<die>s, exceptions)
847	that occured during request processing. The C<result> method detects	1587	that occurred during request processing. The C<result> method detects
848	whether an exception as thrown (it is stored inside the $txn object)	1588	whether an exception as thrown (it is stored inside the $txn object)
849	and just throws the exception, which means connection errors and other	1589	and just throws the exception, which means connection errors and other
850	problems get reported tot he code that tries to use the result, not in a	1590	problems get reported tot he code that tries to use the result, not in a
851	random callback.	1591	random callback.
852		1592
…		…
883		1623
884	my $quit = AnyEvent->condvar;	1624	my $quit = AnyEvent->condvar;
885		1625
886	$fcp->txn_client_get ($url)->cb (sub {	1626	$fcp->txn_client_get ($url)->cb (sub {
887	...	1627	...
888	$quit->broadcast;	1628	$quit->send;
889	});	1629	});
890		1630
891	$quit->wait;	1631	$quit->recv;
892		1632
893		1633
894	=head1 BENCHMARK	1634	=head1 BENCHMARKS
895		1635
896	To give you an idea of the performance and overheads that AnyEvent adds	1636	To give you an idea of the performance and overheads that AnyEvent adds
897	over the event loops themselves (and to give you an impression of the	1637	over the event loops themselves and to give you an impression of the speed
898	speed of various event loops), here is a benchmark of various supported	1638	of various event loops I prepared some benchmarks.
899	event models natively and with anyevent. The benchmark creates a lot of	1639
900	timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to	1640	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1641
		1642	Here is a benchmark of various supported event models used natively and
		1643	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1644	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
901	become writable, which it is), lets them fire exactly once and destroys	1645	which it is), lets them fire exactly once and destroys them again.
902	them again.
903		1646
904	Rewriting the benchmark to use many different sockets instead of using	1647	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
905	the same filehandle for all I/O watchers results in a much longer runtime	1648	distribution.
906	(socket creation is expensive), but qualitatively the same figures, so it
907	was not used.
908		1649
909	=head2 Explanation of the columns	1650	=head3 Explanation of the columns
910		1651
911	I<watcher> is the number of event watchers created/destroyed. Since	1652	I<watcher> is the number of event watchers created/destroyed. Since
912	different event models feature vastly different performances, each event	1653	different event models feature vastly different performances, each event
913	loop was given a number of watchers so that overall runtime is acceptable	1654	loop was given a number of watchers so that overall runtime is acceptable
914	and similar between tested event loop (and keep them from crashing): Glib	1655	and similar between tested event loop (and keep them from crashing): Glib
…		…
924	all watchers, to avoid adding memory overhead. That means closure creation	1665	all watchers, to avoid adding memory overhead. That means closure creation
925	and memory usage is not included in the figures.	1666	and memory usage is not included in the figures.
926		1667
927	I<invoke> is the time, in microseconds, used to invoke a simple	1668	I<invoke> is the time, in microseconds, used to invoke a simple
928	callback. The callback simply counts down a Perl variable and after it was	1669	callback. The callback simply counts down a Perl variable and after it was
929	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1670	invoked "watcher" times, it would C<< ->send >> a condvar once to
930	signal the end of this phase.	1671	signal the end of this phase.
931		1672
932	I<destroy> is the time, in microseconds, that it takes to destroy a single	1673	I<destroy> is the time, in microseconds, that it takes to destroy a single
933	watcher.	1674	watcher.
934		1675
935	=head2 Results	1676	=head3 Results
936		1677
937	name watchers bytes create invoke destroy comment	1678	name watchers bytes create invoke destroy comment
938	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1679	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
939	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1680	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
940	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1681	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
941	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1682	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
942	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1683	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
943	Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers	1684	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
944	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1685	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
945	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1686	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
946	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1687	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
947	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1688	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
948		1689
949	=head2 Discussion	1690	=head3 Discussion
950		1691
951	The benchmark does I<not> measure scalability of the event loop very	1692	The benchmark does I<not> measure scalability of the event loop very
952	well. For example, a select-based event loop (such as the pure perl one)	1693	well. For example, a select-based event loop (such as the pure perl one)
953	can never compete with an event loop that uses epoll when the number of	1694	can never compete with an event loop that uses epoll when the number of
954	file descriptors grows high. In this benchmark, all events become ready at	1695	file descriptors grows high. In this benchmark, all events become ready at
955	the same time, so select/poll-based implementations get an unnatural speed	1696	the same time, so select/poll-based implementations get an unnatural speed
956	boost.	1697	boost.
957		1698
		1699	Also, note that the number of watchers usually has a nonlinear effect on
		1700	overall speed, that is, creating twice as many watchers doesn't take twice
		1701	the time - usually it takes longer. This puts event loops tested with a
		1702	higher number of watchers at a disadvantage.
		1703
		1704	To put the range of results into perspective, consider that on the
		1705	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1706	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1707	cycles with POE.
		1708
958	C<EV> is the sole leader regarding speed and memory use, which are both	1709	C<EV> is the sole leader regarding speed and memory use, which are both
959	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1710	maximal/minimal, respectively. Even when going through AnyEvent, it uses
960	far less memory than any other event loop and is still faster than Event	1711	far less memory than any other event loop and is still faster than Event
961	natively.	1712	natively.
962		1713
963	The pure perl implementation is hit in a few sweet spots (both the	1714	The pure perl implementation is hit in a few sweet spots (both the
964	zero timeout and the use of a single fd hit optimisations in the perl	1715	constant timeout and the use of a single fd hit optimisations in the perl
965	interpreter and the backend itself, and all watchers become ready at the	1716	interpreter and the backend itself). Nevertheless this shows that it
966	same time). Nevertheless this shows that it adds very little overhead in	1717	adds very little overhead in itself. Like any select-based backend its
967	itself. Like any select-based backend its performance becomes really bad	1718	performance becomes really bad with lots of file descriptors (and few of
968	with lots of file descriptors (and few of them active), of course, but	1719	them active), of course, but this was not subject of this benchmark.
969	this was not subject of this benchmark.
970		1720
971	The C<Event> module has a relatively high setup and callback invocation cost,	1721	The C<Event> module has a relatively high setup and callback invocation
972	but overall scores on the third place.	1722	cost, but overall scores in on the third place.
973		1723
974	C<Glib>'s memory usage is quite a bit bit higher, but it features a	1724	C<Glib>'s memory usage is quite a bit higher, but it features a
975	faster callback invocation and overall ends up in the same class as	1725	faster callback invocation and overall ends up in the same class as
976	C<Event>. However, Glib scales extremely badly, doubling the number of	1726	C<Event>. However, Glib scales extremely badly, doubling the number of
977	watchers increases the processing time by more than a factor of four,	1727	watchers increases the processing time by more than a factor of four,
978	making it completely unusable when using larger numbers of watchers	1728	making it completely unusable when using larger numbers of watchers
979	(note that only a single file descriptor was used in the benchmark, so	1729	(note that only a single file descriptor was used in the benchmark, so
…		…
982	The C<Tk> adaptor works relatively well. The fact that it crashes with	1732	The C<Tk> adaptor works relatively well. The fact that it crashes with
983	more than 2000 watchers is a big setback, however, as correctness takes	1733	more than 2000 watchers is a big setback, however, as correctness takes
984	precedence over speed. Nevertheless, its performance is surprising, as the	1734	precedence over speed. Nevertheless, its performance is surprising, as the
985	file descriptor is dup()ed for each watcher. This shows that the dup()	1735	file descriptor is dup()ed for each watcher. This shows that the dup()
986	employed by some adaptors is not a big performance issue (it does incur a	1736	employed by some adaptors is not a big performance issue (it does incur a
987	hidden memory cost inside the kernel, though, that is not reflected in the	1737	hidden memory cost inside the kernel which is not reflected in the figures
988	figures above).	1738	above).
989		1739
990	C<POE>, regardless of underlying event loop (wether using its pure perl	1740	C<POE>, regardless of underlying event loop (whether using its pure perl
991	select-based backend or the Event module) shows abysmal performance and	1741	select-based backend or the Event module, the POE-EV backend couldn't
		1742	be tested because it wasn't working) shows abysmal performance and
992	memory usage: Watchers use almost 30 times as much memory as EV watchers,	1743	memory usage with AnyEvent: Watchers use almost 30 times as much memory
993	and 10 times as much memory as both Event or EV via AnyEvent. Watcher	1744	as EV watchers, and 10 times as much memory as Event (the high memory
		1745	requirements are caused by requiring a session for each watcher). Watcher
994	invocation is almost 900 times slower than with AnyEvent's pure perl	1746	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1747	implementation.
		1748
995	implementation. The design of the POE adaptor class in AnyEvent can not	1749	The design of the POE adaptor class in AnyEvent can not really account
996	really account for this, as session creation overhead is small compared	1750	for the performance issues, though, as session creation overhead is
997	to execution of the state machine, which is coded pretty optimally within	1751	small compared to execution of the state machine, which is coded pretty
998	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1752	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1753	using multiple sessions is not a good approach, especially regarding
		1754	memory usage, even the author of POE could not come up with a faster
		1755	design).
999		1756
1000	=head2 Summary	1757	=head3 Summary
1001		1758
		1759	=over 4
		1760
1002	Using EV through AnyEvent is faster than any other event loop, but most	1761	=item * Using EV through AnyEvent is faster than any other event loop
1003	event loops have acceptable performance with or without AnyEvent.	1762	(even when used without AnyEvent), but most event loops have acceptable
		1763	performance with or without AnyEvent.
1004		1764
1005	The overhead AnyEvent adds is usually much smaller than the overhead of	1765	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
1006	the actual event loop, only with extremely fast event loops such as the EV	1766	the actual event loop, only with extremely fast event loops such as EV
1007	adds AnyEvent significant overhead.	1767	adds AnyEvent significant overhead.
1008		1768
1009	And you should simply avoid POE like the plague if you want performance or	1769	=item * You should avoid POE like the plague if you want performance or
1010	reasonable memory usage.	1770	reasonable memory usage.
1011		1771
		1772	=back
		1773
		1774	=head2 BENCHMARKING THE LARGE SERVER CASE
		1775
		1776	This benchmark actually benchmarks the event loop itself. It works by
		1777	creating a number of "servers": each server consists of a socket pair, a
		1778	timeout watcher that gets reset on activity (but never fires), and an I/O
		1779	watcher waiting for input on one side of the socket. Each time the socket
		1780	watcher reads a byte it will write that byte to a random other "server".
		1781
		1782	The effect is that there will be a lot of I/O watchers, only part of which
		1783	are active at any one point (so there is a constant number of active
		1784	fds for each loop iteration, but which fds these are is random). The
		1785	timeout is reset each time something is read because that reflects how
		1786	most timeouts work (and puts extra pressure on the event loops).
		1787
		1788	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1789	(1%) are active. This mirrors the activity of large servers with many
		1790	connections, most of which are idle at any one point in time.
		1791
		1792	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1793	distribution.
		1794
		1795	=head3 Explanation of the columns
		1796
		1797	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1798	each server has a read and write socket end).
		1799
		1800	I<create> is the time it takes to create a socket pair (which is
		1801	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1802
		1803	I<request>, the most important value, is the time it takes to handle a
		1804	single "request", that is, reading the token from the pipe and forwarding
		1805	it to another server. This includes deleting the old timeout and creating
		1806	a new one that moves the timeout into the future.
		1807
		1808	=head3 Results
		1809
		1810	name sockets create request
		1811	EV 20000 69.01 11.16
		1812	Perl 20000 73.32 35.87
		1813	Event 20000 212.62 257.32
		1814	Glib 20000 651.16 1896.30
		1815	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1816
		1817	=head3 Discussion
		1818
		1819	This benchmark I<does> measure scalability and overall performance of the
		1820	particular event loop.
		1821
		1822	EV is again fastest. Since it is using epoll on my system, the setup time
		1823	is relatively high, though.
		1824
		1825	Perl surprisingly comes second. It is much faster than the C-based event
		1826	loops Event and Glib.
		1827
		1828	Event suffers from high setup time as well (look at its code and you will
		1829	understand why). Callback invocation also has a high overhead compared to
		1830	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1831	uses select or poll in basically all documented configurations.
		1832
		1833	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1834	clearly fails to perform with many filehandles or in busy servers.
		1835
		1836	POE is still completely out of the picture, taking over 1000 times as long
		1837	as EV, and over 100 times as long as the Perl implementation, even though
		1838	it uses a C-based event loop in this case.
		1839
		1840	=head3 Summary
		1841
		1842	=over 4
		1843
		1844	=item * The pure perl implementation performs extremely well.
		1845
		1846	=item * Avoid Glib or POE in large projects where performance matters.
		1847
		1848	=back
		1849
		1850	=head2 BENCHMARKING SMALL SERVERS
		1851
		1852	While event loops should scale (and select-based ones do not...) even to
		1853	large servers, most programs we (or I :) actually write have only a few
		1854	I/O watchers.
		1855
		1856	In this benchmark, I use the same benchmark program as in the large server
		1857	case, but it uses only eight "servers", of which three are active at any
		1858	one time. This should reflect performance for a small server relatively
		1859	well.
		1860
		1861	The columns are identical to the previous table.
		1862
		1863	=head3 Results
		1864
		1865	name sockets create request
		1866	EV 16 20.00 6.54
		1867	Perl 16 25.75 12.62
		1868	Event 16 81.27 35.86
		1869	Glib 16 32.63 15.48
		1870	POE 16 261.87 276.28 uses POE::Loop::Event
		1871
		1872	=head3 Discussion
		1873
		1874	The benchmark tries to test the performance of a typical small
		1875	server. While knowing how various event loops perform is interesting, keep
		1876	in mind that their overhead in this case is usually not as important, due
		1877	to the small absolute number of watchers (that is, you need efficiency and
		1878	speed most when you have lots of watchers, not when you only have a few of
		1879	them).
		1880
		1881	EV is again fastest.
		1882
		1883	Perl again comes second. It is noticeably faster than the C-based event
		1884	loops Event and Glib, although the difference is too small to really
		1885	matter.
		1886
		1887	POE also performs much better in this case, but is is still far behind the
		1888	others.
		1889
		1890	=head3 Summary
		1891
		1892	=over 4
		1893
		1894	=item * C-based event loops perform very well with small number of
		1895	watchers, as the management overhead dominates.
		1896
		1897	=back
		1898
		1899	=head2 THE IO::Lambda BENCHMARK
		1900
		1901	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1902	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		1903	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		1904	shouldn't come as a surprise to anybody). As such, the benchmark is
		1905	fine, and shows that the AnyEvent backend from IO::Lambda isn't very
		1906	optimal. But how would AnyEvent compare when used without the extra
		1907	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		1908
		1909	The benchmark itself creates an echo-server, and then, for 500 times,
		1910	connects to the echo server, sends a line, waits for the reply, and then
		1911	creates the next connection. This is a rather bad benchmark, as it doesn't
		1912	test the efficiency of the framework, but it is a benchmark nevertheless.
		1913
		1914	name runtime
		1915	Lambda/select 0.330 sec
		1916	+ optimized 0.122 sec
		1917	Lambda/AnyEvent 0.327 sec
		1918	+ optimized 0.138 sec
		1919	Raw sockets/select 0.077 sec
		1920	POE/select, components 0.662 sec
		1921	POE/select, raw sockets 0.226 sec
		1922	POE/select, optimized 0.404 sec
		1923
		1924	AnyEvent/select/nb 0.085 sec
		1925	AnyEvent/EV/nb 0.068 sec
		1926	+state machine 0.134 sec
		1927
		1928	The benchmark is also a bit unfair (my fault) - the IO::Lambda
		1929	benchmarks actually make blocking connects and use 100% blocking I/O,
		1930	defeating the purpose of an event-based solution. All of the newly
		1931	written AnyEvent benchmarks use 100% non-blocking connects (using
		1932	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1933	resolver), so AnyEvent is at a disadvantage here as non-blocking connects
		1934	generally require a lot more bookkeeping and event handling than blocking
		1935	connects (which involve a single syscall only).
		1936
		1937	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		1938	offers similar expressive power as POE and IO::Lambda (using conventional
		1939	Perl syntax), which means both the echo server and the client are 100%
		1940	non-blocking w.r.t. I/O, further placing it at a disadvantage.
		1941
		1942	As you can see, AnyEvent + EV even beats the hand-optimised "raw sockets
		1943	benchmark", while AnyEvent + its pure perl backend easily beats
		1944	IO::Lambda and POE.
		1945
		1946	And even the 100% non-blocking version written using the high-level (and
		1947	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda,
		1948	even thought it does all of DNS, tcp-connect and socket I/O in a
		1949	non-blocking way.
		1950
		1951	The two AnyEvent benchmarks can be found as F<eg/ae0.pl> and F<eg/ae2.pl>
		1952	in the AnyEvent distribution, the remaining benchmarks are part of the
		1953	IO::lambda distribution and were used without any changes.
		1954
		1955
		1956	=head1 SIGNALS
		1957
		1958	AnyEvent currently installs handlers for these signals:
		1959
		1960	=over 4
		1961
		1962	=item SIGCHLD
		1963
		1964	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		1965	emulation for event loops that do not support them natively. Also, some
		1966	event loops install a similar handler.
		1967
		1968	=item SIGPIPE
		1969
		1970	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		1971	when AnyEvent gets loaded.
		1972
		1973	The rationale for this is that AnyEvent users usually do not really depend
		1974	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		1975	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		1976	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		1977	some random socket.
		1978
		1979	The rationale for installing a no-op handler as opposed to ignoring it is
		1980	that this way, the handler will be restored to defaults on exec.
		1981
		1982	Feel free to install your own handler, or reset it to defaults.
		1983
		1984	=back
		1985
		1986	=cut
		1987
		1988	$SIG{PIPE} = sub { }
		1989	unless defined $SIG{PIPE};
		1990
1012		1991
1013	=head1 FORK	1992	=head1 FORK
1014		1993
1015	Most event libraries are not fork-safe. The ones who are usually are	1994	Most event libraries are not fork-safe. The ones who are usually are
1016	because they are so inefficient. Only L<EV> is fully fork-aware.	1995	because they rely on inefficient but fork-safe C<select> or C<poll>
		1996	calls. Only L<EV> is fully fork-aware.
1017		1997
1018	If you have to fork, you must either do so I<before> creating your first	1998	If you have to fork, you must either do so I<before> creating your first
1019	watcher OR you must not use AnyEvent at all in the child.	1999	watcher OR you must not use AnyEvent at all in the child.
1020		2000
1021		2001
…		…
1029	specified in the variable.	2009	specified in the variable.
1030		2010
1031	You can make AnyEvent completely ignore this variable by deleting it	2011	You can make AnyEvent completely ignore this variable by deleting it
1032	before the first watcher gets created, e.g. with a C<BEGIN> block:	2012	before the first watcher gets created, e.g. with a C<BEGIN> block:
1033		2013
1034	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2014	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1035		2015
1036	use AnyEvent;	2016	use AnyEvent;
		2017
		2018	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2019	be used to probe what backend is used and gain other information (which is
		2020	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2021	$ENV{PERL_ANYEVENT_STRICT}.
		2022
		2023
		2024	=head1 BUGS
		2025
		2026	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2027	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2028	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2029	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2030	pronounced).
1037		2031
1038		2032
1039	=head1 SEE ALSO	2033	=head1 SEE ALSO
1040		2034
1041	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2035	Utility functions: L<AnyEvent::Util>.
1042	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	2036
		2037	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1043	L<Event::Lib>, L<Qt>, L<POE>.	2038	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1044		2039
1045	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2040	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1046	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2041	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1047	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	2042	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1048	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	2043	L<AnyEvent::Impl::POE>.
1049		2044
		2045	Non-blocking file handles, sockets, TCP clients and
		2046	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		2047
		2048	Asynchronous DNS: L<AnyEvent::DNS>.
		2049
		2050	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		2051
1050	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2052	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1051		2053
1052		2054
1053	=head1 AUTHOR	2055	=head1 AUTHOR
1054		2056
1055	Marc Lehmann <schmorp@schmorp.de>	2057	Marc Lehmann <schmorp@schmorp.de>
1056	http://home.schmorp.de/	2058	http://home.schmorp.de/
1057		2059
1058	=cut	2060	=cut
1059		2061
1060	1	2062	1
1061		2063

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