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Revision 1.229 by root, Wed Jul 8 02:01:12 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 ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->send; # 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		100
71	=head1 DESCRIPTION	101	=head1 DESCRIPTION
72		102
…		…
78	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>
79	module.	109	module.
80		110
81	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
82	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
83	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	113	following modules is already loaded: L<EV>,
84	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>,
85	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
86	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
87	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
88	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
…		…
102	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
103	use AnyEvent so their modules work together with others seamlessly...	133	use AnyEvent so their modules work together with others seamlessly...
104		134
105	The pure-perl implementation of AnyEvent is called	135	The pure-perl implementation of AnyEvent is called
106	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
107	explicitly.	137	explicitly and enjoy the high availability of that event loop :)
108		138
109	=head1 WATCHERS	139	=head1 WATCHERS
110		140
111	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
112	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
113	the callback to call, the filehandle to watch, etc.	143	the callback to call, the file handle to watch, etc.
114		144
115	These watchers are normal Perl objects with normal Perl lifetime. After	145	These watchers are normal Perl objects with normal Perl lifetime. After
116	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
117	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
118	is in control).	148	is in control).
119		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
120	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
121	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
122	to it).	158	to it).
123		159
124	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.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	162	Many watchers either are used with "recursion" (repeating timers for
127	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.
128		164
129	An any way to achieve that is this pattern:	165	An any way to achieve that is this pattern:
130		166
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	167	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	168	# you can use $w here, for example to undef it
133	undef $w;	169	undef $w;
134	});	170	});
135		171
136	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,
137	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
138	declared.	174	declared.
139		175
140	=head2 I/O WATCHERS	176	=head2 I/O WATCHERS
141		177
142	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
143	with the following mandatory key-value pairs as arguments:	179	with the following mandatory key-value pairs as arguments:
144		180
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	181	C<fh> is the Perl I<file handle> (or a naked 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
146	for events. C<poll> must be a string that is either C<r> or C<w>,	188	C<poll> must be a string that is either C<r> or C<w>, which creates a
147	which creates a watcher waiting for "r"eadable or "w"ritable events,	189	watcher waiting for "r"eadable or "w"ritable events, respectively.
		190
148	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.
149	becomes ready.
150		192
151	Although the callback might get passed parameters, their value and	193	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	194	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	195	callbacks cannot use arguments passed to I/O watcher callbacks.
154		196
…		…
158		200
159	Some event loops issue spurious readyness notifications, so you should	201	Some event loops issue spurious readyness notifications, so you should
160	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
161	handles.	203	handles.
162		204
163	Example:
164
165	# 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
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	208	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	209	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	210	warn "read: $input\n";
169	undef $w;	211	undef $w;
170	});	212	});
…		…
180		222
181	Although the callback might get passed parameters, their value and	223	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	224	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	225	callbacks cannot use arguments passed to time watcher callbacks.
184		226
185	The timer callback will be invoked at most once: if you want a repeating	227	The callback will normally be invoked once only. If you specify another
186	timer you have to create a new watcher (this is a limitation by both Tk	228	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	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.
188		232
189	Example:	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.
190		236
191	# fire an event after 7.7 seconds	237	Example: fire an event after 7.7 seconds.
		238
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	239	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	240	warn "timeout\n";
194	});	241	});
195		242
196	# to cancel the timer:	243	# to cancel the timer:
197	undef $w;	244	undef $w;
198		245
199	Example 2:
200
201	# 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.
202	my $w;
203		247
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	248	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		249	warn "timeout\n";
207	};	250	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		251
212	=head3 TIMING ISSUES	252	=head3 TIMING ISSUES
213		253
214	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
215	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
…		…
227	timers.	267	timers.
228		268
229	AnyEvent always prefers relative timers, if available, matching the	269	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	270	AnyEvent API.
231		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
232	=head2 SIGNAL WATCHERS	350	=head2 SIGNAL WATCHERS
233		351
234	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
235	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
236	be invoked whenever a signal occurs.	354	callback to be invoked whenever a signal occurs.
237		355
238	Although the callback might get passed parameters, their value and	356	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	357	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	358	callbacks cannot use arguments passed to signal watcher callbacks.
241		359
242	Multiple signal occurances can be clumped together into one callback	360	Multiple signal occurrences can be clumped together into one callback
243	invocation, and callback invocation will be synchronous. synchronous means	361	invocation, and callback invocation will be synchronous. Synchronous means
244	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,
245	but it is guarenteed not to interrupt any other callbacks.	363	but it is guaranteed not to interrupt any other callbacks.
246		364
247	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
248	between multiple watchers.	366	between multiple watchers.
249		367
250	This watcher might use C<%SIG>, so programs overwriting those signals	368	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
257	=head2 CHILD PROCESS WATCHERS	375	=head2 CHILD PROCESS WATCHERS
258		376
259	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.
260		378
261	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
262	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
263	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
264	signal handler for C<SIGCHLD>. The callback will be called with the pid	382	any trace events (stopped/continued).
265	and exit status (as returned by waitpid), so unlike other watcher types,	383
266	you I<can> rely on child watcher callback arguments.	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).
267		392
268	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
269	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
270	have exited already (and no SIGCHLD will be sent anymore).	395	have exited already (and no SIGCHLD will be sent anymore).
271		396
272	Not all event models handle this correctly (POE doesn't), but even for	397	Not all event models handle this correctly (neither POE nor IO::Async do,
		398	see their AnyEvent::Impl manpages for details), but even for event models
273	event models that I<do> handle this correctly, they usually need to be	399	that I<do> handle this correctly, they usually need to be loaded before
274	loaded before the process exits (i.e. before you fork in the first place).	400	the process exits (i.e. before you fork in the first place). AnyEvent's
		401	pure perl event loop handles all cases correctly regardless of when you
		402	start the watcher.
275		403
276	This means you cannot create a child watcher as the very first thing in an	404	This means you cannot create a child watcher as the very first
277	AnyEvent program, you I<have> to create at least one watcher before you	405	thing in an AnyEvent program, you I<have> to create at least one
278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	406	watcher before you C<fork> the child (alternatively, you can call
		407	C<AnyEvent::detect>).
279		408
280	Example: fork a process and wait for it	409	Example: fork a process and wait for it
281		410
282	my $done = AnyEvent->condvar;	411	my $done = AnyEvent->condvar;
283		412
284	AnyEvent::detect; # force event module to be initialised
285
286	my $pid = fork or exit 5;	413	my $pid = fork or exit 5;
287		414
288	my $w = AnyEvent->child (	415	my $w = AnyEvent->child (
289	pid => $pid,	416	pid => $pid,
290	cb => sub {	417	cb => sub {
291	my ($pid, $status) = @_;	418	my ($pid, $status) = @_;
292	warn "pid $pid exited with status $status";	419	warn "pid $pid exited with status $status";
293	$done->send;	420	$done->send;
294	},	421	},
295	);	422	);
296		423
297	# do something else, then wait for process exit	424	# do something else, then wait for process exit
298	$done->wait;	425	$done->recv;
		426
		427	=head2 IDLE WATCHERS
		428
		429	Sometimes there is a need to do something, but it is not so important
		430	to do it instantly, but only when there is nothing better to do. This
		431	"nothing better to do" is usually defined to be "no other events need
		432	attention by the event loop".
		433
		434	Idle watchers ideally get invoked when the event loop has nothing
		435	better to do, just before it would block the process to wait for new
		436	events. Instead of blocking, the idle watcher is invoked.
		437
		438	Most event loops unfortunately do not really support idle watchers (only
		439	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		440	will simply call the callback "from time to time".
		441
		442	Example: read lines from STDIN, but only process them when the
		443	program is otherwise idle:
		444
		445	my @lines; # read data
		446	my $idle_w;
		447	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		448	push @lines, scalar <STDIN>;
		449
		450	# start an idle watcher, if not already done
		451	$idle_w ||= AnyEvent->idle (cb => sub {
		452	# handle only one line, when there are lines left
		453	if (my $line = shift @lines) {
		454	print "handled when idle: $line";
		455	} else {
		456	# otherwise disable the idle watcher again
		457	undef $idle_w;
		458	}
		459	});
		460	});
299		461
300	=head2 CONDITION VARIABLES	462	=head2 CONDITION VARIABLES
301		463
302	If you are familiar with some event loops you will know that all of them	464	If you are familiar with some event loops you will know that all of them
303	require you to run some blocking "loop", "run" or similar function that	465	require you to run some blocking "loop", "run" or similar function that
…		…
309	The instrument to do that is called a "condition variable", so called	471	The instrument to do that is called a "condition variable", so called
310	because they represent a condition that must become true.	472	because they represent a condition that must become true.
311		473
312	Condition variables can be created by calling the C<< AnyEvent->condvar	474	Condition variables can be created by calling the C<< AnyEvent->condvar
313	>> method, usually without arguments. The only argument pair allowed is	475	>> method, usually without arguments. The only argument pair allowed is
		476
314	C<cb>, which specifies a callback to be called when the condition variable	477	C<cb>, which specifies a callback to be called when the condition variable
315	becomes true.	478	becomes true, with the condition variable as the first argument (but not
		479	the results).
316		480
317	After creation, the conditon variable is "false" until it becomes "true"	481	After creation, the condition variable is "false" until it becomes "true"
318	by calling the C<send> method.	482	by calling the C<send> method (or calling the condition variable as if it
		483	were a callback, read about the caveats in the description for the C<<
		484	->send >> method).
319		485
320	Condition variables are similar to callbacks, except that you can	486	Condition variables are similar to callbacks, except that you can
321	optionally wait for them. They can also be called merge points - points	487	optionally wait for them. They can also be called merge points - points
322	in time where multiple outstandign events have been processed. And yet	488	in time where multiple outstanding events have been processed. And yet
323	another way to call them is transations - each condition variable can be	489	another way to call them is transactions - each condition variable can be
324	used to represent a transaction, which finishes at some point and delivers	490	used to represent a transaction, which finishes at some point and delivers
325	a result.	491	a result.
326		492
327	Condition variables are very useful to signal that something has finished,	493	Condition variables are very useful to signal that something has finished,
328	for example, if you write a module that does asynchronous http requests,	494	for example, if you write a module that does asynchronous http requests,
329	then a condition variable would be the ideal candidate to signal the	495	then a condition variable would be the ideal candidate to signal the
330	availability of results. The user can either act when the callback is	496	availability of results. The user can either act when the callback is
331	called or can synchronously C<< ->wait >> for the results.	497	called or can synchronously C<< ->recv >> for the results.
332		498
333	You can also use them to simulate traditional event loops - for example,	499	You can also use them to simulate traditional event loops - for example,
334	you can block your main program until an event occurs - for example, you	500	you can block your main program until an event occurs - for example, you
335	could C<< ->wait >> in your main program until the user clicks the Quit	501	could C<< ->recv >> in your main program until the user clicks the Quit
336	button of your app, which would C<< ->send >> the "quit" event.	502	button of your app, which would C<< ->send >> the "quit" event.
337		503
338	Note that condition variables recurse into the event loop - if you have	504	Note that condition variables recurse into the event loop - if you have
339	two pieces of code that call C<< ->wait >> in a round-robbin fashion, you	505	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
340	lose. Therefore, condition variables are good to export to your caller, but	506	lose. Therefore, condition variables are good to export to your caller, but
341	you should avoid making a blocking wait yourself, at least in callbacks,	507	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	508	as this asks for trouble.
343		509
344	Condition variables are represented by hash refs in perl, and the keys	510	Condition variables are represented by hash refs in perl, and the keys
…		…
349		515
350	There are two "sides" to a condition variable - the "producer side" which	516	There are two "sides" to a condition variable - the "producer side" which
351	eventually calls C<< -> send >>, and the "consumer side", which waits	517	eventually calls C<< -> send >>, and the "consumer side", which waits
352	for the send to occur.	518	for the send to occur.
353		519
354	Example:	520	Example: wait for a timer.
355		521
356	# wait till the result is ready	522	# wait till the result is ready
357	my $result_ready = AnyEvent->condvar;	523	my $result_ready = AnyEvent->condvar;
358		524
359	# do something such as adding a timer	525	# do something such as adding a timer
…		…
365	cb => sub { $result_ready->send },	531	cb => sub { $result_ready->send },
366	);	532	);
367		533
368	# this "blocks" (while handling events) till the callback	534	# this "blocks" (while handling events) till the callback
369	# calls send	535	# calls send
370	$result_ready->wait;	536	$result_ready->recv;
		537
		538	Example: wait for a timer, but take advantage of the fact that
		539	condition variables are also code references.
		540
		541	my $done = AnyEvent->condvar;
		542	my $delay = AnyEvent->timer (after => 5, cb => $done);
		543	$done->recv;
		544
		545	Example: Imagine an API that returns a condvar and doesn't support
		546	callbacks. This is how you make a synchronous call, for example from
		547	the main program:
		548
		549	use AnyEvent::CouchDB;
		550
		551	...
		552
		553	my @info = $couchdb->info->recv;
		554
		555	And this is how you would just ste a callback to be called whenever the
		556	results are available:
		557
		558	$couchdb->info->cb (sub {
		559	my @info = $_[0]->recv;
		560	});
371		561
372	=head3 METHODS FOR PRODUCERS	562	=head3 METHODS FOR PRODUCERS
373		563
374	These methods should only be used by the producing side, i.e. the	564	These methods should only be used by the producing side, i.e. the
375	code/module that eventually sends the signal. Note that it is also	565	code/module that eventually sends the signal. Note that it is also
…		…
378		568
379	=over 4	569	=over 4
380		570
381	=item $cv->send (...)	571	=item $cv->send (...)
382		572
383	Flag the condition as ready - a running C<< ->wait >> and all further	573	Flag the condition as ready - a running C<< ->recv >> and all further
384	calls to C<wait> will (eventually) return after this method has been	574	calls to C<recv> will (eventually) return after this method has been
385	called. If nobody is waiting the send will be remembered.	575	called. If nobody is waiting the send will be remembered.
386		576
387	If a callback has been set on the condition variable, it is called	577	If a callback has been set on the condition variable, it is called
388	immediately from within send.	578	immediately from within send.
389		579
390	Any arguments passed to the C<send> call will be returned by all	580	Any arguments passed to the C<send> call will be returned by all
391	future C<< ->wait >> calls.	581	future C<< ->recv >> calls.
		582
		583	Condition variables are overloaded so one can call them directly
		584	(as a code reference). Calling them directly is the same as calling
		585	C<send>. Note, however, that many C-based event loops do not handle
		586	overloading, so as tempting as it may be, passing a condition variable
		587	instead of a callback does not work. Both the pure perl and EV loops
		588	support overloading, however, as well as all functions that use perl to
		589	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		590	example).
392		591
393	=item $cv->croak ($error)	592	=item $cv->croak ($error)
394		593
395	Similar to send, but causes all call's wait C<< ->wait >> to invoke	594	Similar to send, but causes all call's to C<< ->recv >> to invoke
396	C<Carp::croak> with the given error message/object/scalar.	595	C<Carp::croak> with the given error message/object/scalar.
397		596
398	This can be used to signal any errors to the condition variable	597	This can be used to signal any errors to the condition variable
399	user/consumer.	598	user/consumer.
400		599
…		…
410	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	609	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
411	>>, the (last) callback passed to C<begin> will be executed. That callback	610	>>, the (last) callback passed to C<begin> will be executed. That callback
412	is I<supposed> to call C<< ->send >>, but that is not required. If no	611	is I<supposed> to call C<< ->send >>, but that is not required. If no
413	callback was set, C<send> will be called without any arguments.	612	callback was set, C<send> will be called without any arguments.
414		613
415	Let's clarify this with the ping example:	614	You can think of C<< $cv->send >> giving you an OR condition (one call
		615	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		616	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		617
		618	Let's start with a simple example: you have two I/O watchers (for example,
		619	STDOUT and STDERR for a program), and you want to wait for both streams to
		620	close before activating a condvar:
		621
		622	my $cv = AnyEvent->condvar;
		623
		624	$cv->begin; # first watcher
		625	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		626	defined sysread $fh1, my $buf, 4096
		627	or $cv->end;
		628	});
		629
		630	$cv->begin; # second watcher
		631	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		632	defined sysread $fh2, my $buf, 4096
		633	or $cv->end;
		634	});
		635
		636	$cv->recv;
		637
		638	This works because for every event source (EOF on file handle), there is
		639	one call to C<begin>, so the condvar waits for all calls to C<end> before
		640	sending.
		641
		642	The ping example mentioned above is slightly more complicated, as the
		643	there are results to be passwd back, and the number of tasks that are
		644	begung can potentially be zero:
416		645
417	my $cv = AnyEvent->condvar;	646	my $cv = AnyEvent->condvar;
418		647
419	my %result;	648	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	649	$cv->begin (sub { $cv->send (\%result) });
…		…
440	loop, which serves two important purposes: first, it sets the callback	669	loop, which serves two important purposes: first, it sets the callback
441	to be called once the counter reaches C<0>, and second, it ensures that	670	to be called once the counter reaches C<0>, and second, it ensures that
442	C<send> is called even when C<no> hosts are being pinged (the loop	671	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	672	doesn't execute once).
444		673
445	This is the general pattern when you "fan out" into multiple subrequests:	674	This is the general pattern when you "fan out" into multiple (but
446	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	675	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
447	is called at least once, and then, for each subrequest you start, call	676	the callback and ensure C<end> is called at least once, and then, for each
448	C<begin> and for eahc subrequest you finish, call C<end>.	677	subrequest you start, call C<begin> and for each subrequest you finish,
		678	call C<end>.
449		679
450	=back	680	=back
451		681
452	=head3 METHODS FOR CONSUMERS	682	=head3 METHODS FOR CONSUMERS
453		683
454	These methods should only be used by the consuming side, i.e. the	684	These methods should only be used by the consuming side, i.e. the
455	code awaits the condition.	685	code awaits the condition.
456		686
457	=over 4	687	=over 4
458		688
459	=item $cv->wait	689	=item $cv->recv
460		690
461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	691	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
462	>> methods have been called on c<$cv>, while servicing other watchers	692	>> methods have been called on c<$cv>, while servicing other watchers
463	normally.	693	normally.
464		694
…		…
475	(programs might want to do that to stay interactive), so I<if you are	705	(programs might want to do that to stay interactive), so I<if you are
476	using this from a module, never require a blocking wait>, but let the	706	using this from a module, never require a blocking wait>, but let the
477	caller decide whether the call will block or not (for example, by coupling	707	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	708	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	709	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	710	while still supporting blocking waits if the caller so desires).
481		711
482	Another reason I<never> to C<< ->wait >> in a module is that you cannot	712	Another reason I<never> to C<< ->recv >> in a module is that you cannot
483	sensibly have two C<< ->wait >>'s in parallel, as that would require	713	sensibly have two C<< ->recv >>'s in parallel, as that would require
484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	714	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	715	can supply.
486	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
487	from different coroutines, however).
488		716
		717	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		718	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		719	versions and also integrates coroutines into AnyEvent, making blocking
		720	C<< ->recv >> calls perfectly safe as long as they are done from another
		721	coroutine (one that doesn't run the event loop).
		722
489	You can ensure that C<< -wait >> never blocks by setting a callback and	723	You can ensure that C<< -recv >> never blocks by setting a callback and
490	only calling C<< ->wait >> from within that callback (or at a later	724	only calling C<< ->recv >> from within that callback (or at a later
491	time). This will work even when the event loop does not support blocking	725	time). This will work even when the event loop does not support blocking
492	waits otherwise.	726	waits otherwise.
493		727
494	=item $bool = $cv->ready	728	=item $bool = $cv->ready
495		729
496	Returns true when the condition is "true", i.e. whether C<send> or	730	Returns true when the condition is "true", i.e. whether C<send> or
497	C<croak> have been called.	731	C<croak> have been called.
498		732
499	=item $cb = $cv->cb ([new callback])	733	=item $cb = $cv->cb ($cb->($cv))
500		734
501	This is a mutator function that returns the callback set and optionally	735	This is a mutator function that returns the callback set and optionally
502	replaces it before doing so.	736	replaces it before doing so.
503		737
504	The callback will be called when the condition becomes "true", i.e. when	738	The callback will be called when the condition becomes "true", i.e. when
505	C<send> or C<croak> are called. Calling C<wait> inside the callback	739	C<send> or C<croak> are called, with the only argument being the condition
506	or at any later time is guaranteed not to block.	740	variable itself. Calling C<recv> inside the callback or at any later time
		741	is guaranteed not to block.
507		742
508	=back	743	=back
509		744
510	=head1 GLOBAL VARIABLES AND FUNCTIONS	745	=head1 GLOBAL VARIABLES AND FUNCTIONS
511		746
…		…
519	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	754	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
520	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	755	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
521		756
522	The known classes so far are:	757	The known classes so far are:
523		758
524	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
525	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
526	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	759	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
527	AnyEvent::Impl::Event based on Event, second best choice.	760	AnyEvent::Impl::Event based on Event, second best choice.
528	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.	761	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
529	AnyEvent::Impl::Glib based on Glib, third-best choice.	762	AnyEvent::Impl::Glib based on Glib, third-best choice.
530	AnyEvent::Impl::Tk based on Tk, very bad choice.	763	AnyEvent::Impl::Tk based on Tk, very bad choice.
531	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	764	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
532	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	765	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
533	AnyEvent::Impl::POE based on POE, not generic enough for full support.	766	AnyEvent::Impl::POE based on POE, not generic enough for full support.
534		767
		768	# warning, support for IO::Async is only partial, as it is too broken
		769	# and limited toe ven support the AnyEvent API. See AnyEvent::Impl::Async.
		770	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed (see its docs).
		771
535	There is no support for WxWidgets, as WxWidgets has no support for	772	There is no support for WxWidgets, as WxWidgets has no support for
536	watching file handles. However, you can use WxWidgets through the	773	watching file handles. However, you can use WxWidgets through the
537	POE Adaptor, as POE has a Wx backend that simply polls 20 times per	774	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
538	second, which was considered to be too horrible to even consider for	775	second, which was considered to be too horrible to even consider for
539	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using	776	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
…		…
547	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	784	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
548	if necessary. You should only call this function right before you would	785	if necessary. You should only call this function right before you would
549	have created an AnyEvent watcher anyway, that is, as late as possible at	786	have created an AnyEvent watcher anyway, that is, as late as possible at
550	runtime.	787	runtime.
551		788
		789	=item $guard = AnyEvent::post_detect { BLOCK }
		790
		791	Arranges for the code block to be executed as soon as the event model is
		792	autodetected (or immediately if this has already happened).
		793
		794	If called in scalar or list context, then it creates and returns an object
		795	that automatically removes the callback again when it is destroyed. See
		796	L<Coro::BDB> for a case where this is useful.
		797
		798	=item @AnyEvent::post_detect
		799
		800	If there are any code references in this array (you can C<push> to it
		801	before or after loading AnyEvent), then they will called directly after
		802	the event loop has been chosen.
		803
		804	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		805	if it contains a true value then the event loop has already been detected,
		806	and the array will be ignored.
		807
		808	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		809
552	=back	810	=back
553		811
554	=head1 WHAT TO DO IN A MODULE	812	=head1 WHAT TO DO IN A MODULE
555		813
556	As a module author, you should C<use AnyEvent> and call AnyEvent methods	814	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
559	Be careful when you create watchers in the module body - AnyEvent will	817	Be careful when you create watchers in the module body - AnyEvent will
560	decide which event module to use as soon as the first method is called, so	818	decide which event module to use as soon as the first method is called, so
561	by calling AnyEvent in your module body you force the user of your module	819	by calling AnyEvent in your module body you force the user of your module
562	to load the event module first.	820	to load the event module first.
563		821
564	Never call C<< ->wait >> on a condition variable unless you I<know> that	822	Never call C<< ->recv >> on a condition variable unless you I<know> that
565	the C<< ->send >> method has been called on it already. This is	823	the C<< ->send >> method has been called on it already. This is
566	because it will stall the whole program, and the whole point of using	824	because it will stall the whole program, and the whole point of using
567	events is to stay interactive.	825	events is to stay interactive.
568		826
569	It is fine, however, to call C<< ->wait >> when the user of your module	827	It is fine, however, to call C<< ->recv >> when the user of your module
570	requests it (i.e. if you create a http request object ad have a method	828	requests it (i.e. if you create a http request object ad have a method
571	called C<results> that returns the results, it should call C<< ->wait >>	829	called C<results> that returns the results, it should call C<< ->recv >>
572	freely, as the user of your module knows what she is doing. always).	830	freely, as the user of your module knows what she is doing. always).
573		831
574	=head1 WHAT TO DO IN THE MAIN PROGRAM	832	=head1 WHAT TO DO IN THE MAIN PROGRAM
575		833
576	There will always be a single main program - the only place that should	834	There will always be a single main program - the only place that should
…		…
578		836
579	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	837	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
580	do anything special (it does not need to be event-based) and let AnyEvent	838	do anything special (it does not need to be event-based) and let AnyEvent
581	decide which implementation to chose if some module relies on it.	839	decide which implementation to chose if some module relies on it.
582		840
583	If the main program relies on a specific event model. For example, in	841	If the main program relies on a specific event model - for example, in
584	Gtk2 programs you have to rely on the Glib module. You should load the	842	Gtk2 programs you have to rely on the Glib module - you should load the
585	event module before loading AnyEvent or any module that uses it: generally	843	event module before loading AnyEvent or any module that uses it: generally
586	speaking, you should load it as early as possible. The reason is that	844	speaking, you should load it as early as possible. The reason is that
587	modules might create watchers when they are loaded, and AnyEvent will	845	modules might create watchers when they are loaded, and AnyEvent will
588	decide on the event model to use as soon as it creates watchers, and it	846	decide on the event model to use as soon as it creates watchers, and it
589	might chose the wrong one unless you load the correct one yourself.	847	might chose the wrong one unless you load the correct one yourself.
590		848
591	You can chose to use a rather inefficient pure-perl implementation by	849	You can chose to use a pure-perl implementation by loading the
592	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	850	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
593	behaviour everywhere, but letting AnyEvent chose is generally better.	851	everywhere, but letting AnyEvent chose the model is generally better.
		852
		853	=head2 MAINLOOP EMULATION
		854
		855	Sometimes (often for short test scripts, or even standalone programs who
		856	only want to use AnyEvent), you do not want to run a specific event loop.
		857
		858	In that case, you can use a condition variable like this:
		859
		860	AnyEvent->condvar->recv;
		861
		862	This has the effect of entering the event loop and looping forever.
		863
		864	Note that usually your program has some exit condition, in which case
		865	it is better to use the "traditional" approach of storing a condition
		866	variable somewhere, waiting for it, and sending it when the program should
		867	exit cleanly.
		868
594		869
595	=head1 OTHER MODULES	870	=head1 OTHER MODULES
596		871
597	The following is a non-exhaustive list of additional modules that use	872	The following is a non-exhaustive list of additional modules that use
598	AnyEvent and can therefore be mixed easily with other AnyEvent modules	873	AnyEvent and can therefore be mixed easily with other AnyEvent modules
…		…
604	=item L<AnyEvent::Util>	879	=item L<AnyEvent::Util>
605		880
606	Contains various utility functions that replace often-used but blocking	881	Contains various utility functions that replace often-used but blocking
607	functions such as C<inet_aton> by event-/callback-based versions.	882	functions such as C<inet_aton> by event-/callback-based versions.
608		883
		884	=item L<AnyEvent::Socket>
		885
		886	Provides various utility functions for (internet protocol) sockets,
		887	addresses and name resolution. Also functions to create non-blocking tcp
		888	connections or tcp servers, with IPv6 and SRV record support and more.
		889
609	=item L<AnyEvent::Handle>	890	=item L<AnyEvent::Handle>
610		891
611	Provide read and write buffers and manages watchers for reads and writes.	892	Provide read and write buffers, manages watchers for reads and writes,
		893	supports raw and formatted I/O, I/O queued and fully transparent and
		894	non-blocking SSL/TLS.
612		895
613	=item L<AnyEvent::Socket>	896	=item L<AnyEvent::DNS>
614		897
615	Provides a means to do non-blocking connects, accepts etc.	898	Provides rich asynchronous DNS resolver capabilities.
		899
		900	=item L<AnyEvent::HTTP>
		901
		902	A simple-to-use HTTP library that is capable of making a lot of concurrent
		903	HTTP requests.
616		904
617	=item L<AnyEvent::HTTPD>	905	=item L<AnyEvent::HTTPD>
618		906
619	Provides a simple web application server framework.	907	Provides a simple web application server framework.
620		908
621	=item L<AnyEvent::DNS>
622
623	Provides asynchronous DNS resolver capabilities, beyond what
624	L<AnyEvent::Util> offers.
625
626	=item L<AnyEvent::FastPing>	909	=item L<AnyEvent::FastPing>
627		910
628	The fastest ping in the west.	911	The fastest ping in the west.
629		912
		913	=item L<AnyEvent::DBI>
		914
		915	Executes L<DBI> requests asynchronously in a proxy process.
		916
		917	=item L<AnyEvent::AIO>
		918
		919	Truly asynchronous I/O, should be in the toolbox of every event
		920	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		921	together.
		922
		923	=item L<AnyEvent::BDB>
		924
		925	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		926	L<BDB> and AnyEvent together.
		927
		928	=item L<AnyEvent::GPSD>
		929
		930	A non-blocking interface to gpsd, a daemon delivering GPS information.
		931
		932	=item L<AnyEvent::IGS>
		933
		934	A non-blocking interface to the Internet Go Server protocol (used by
		935	L<App::IGS>).
		936
630	=item L<Net::IRC3>	937	=item L<AnyEvent::IRC>
631		938
632	AnyEvent based IRC client module family.	939	AnyEvent based IRC client module family (replacing the older Net::IRC3).
633		940
634	=item L<Net::XMPP2>	941	=item L<Net::XMPP2>
635		942
636	AnyEvent based XMPP (Jabber protocol) module family.	943	AnyEvent based XMPP (Jabber protocol) module family.
637		944
…		…
644		951
645	High level API for event-based execution flow control.	952	High level API for event-based execution flow control.
646		953
647	=item L<Coro>	954	=item L<Coro>
648		955
649	Has special support for AnyEvent.	956	Has special support for AnyEvent via L<Coro::AnyEvent>.
650		957
651	=item L<IO::Lambda>	958	=item L<IO::Lambda>
652		959
653	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.	960	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
654		961
655	=item L<IO::AIO>
656
657	Truly asynchronous I/O, should be in the toolbox of every event
658	programmer. Can be trivially made to use AnyEvent.
659
660	=item L<BDB>
661
662	Truly asynchronous Berkeley DB access. Can be trivially made to use
663	AnyEvent.
664
665	=back	962	=back
666		963
667	=cut	964	=cut
668		965
669	package AnyEvent;	966	package AnyEvent;
670		967
671	no warnings;	968	no warnings;
672	use strict;	969	use strict qw(vars subs);
673		970
674	use Carp;	971	use Carp;
675		972
676	our $VERSION = '3.3';	973	our $VERSION = 4.8;
677	our $MODEL;	974	our $MODEL;
678		975
679	our $AUTOLOAD;	976	our $AUTOLOAD;
680	our @ISA;	977	our @ISA;
681		978
		979	our @REGISTRY;
		980
		981	our $WIN32;
		982
		983	BEGIN {
		984	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		985	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		986
		987	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		988	if ${^TAINT};
		989	}
		990
682	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	991	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
683		992
684	our @REGISTRY;	993	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		994
		995	{
		996	my $idx;
		997	$PROTOCOL{$_} = ++$idx
		998	for reverse split /\s*,\s*/,
		999	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1000	}
685		1001
686	my @models = (	1002	my @models = (
687	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
688	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
689	[EV:: => AnyEvent::Impl::EV::],	1003	[EV:: => AnyEvent::Impl::EV::],
690	[Event:: => AnyEvent::Impl::Event::],	1004	[Event:: => AnyEvent::Impl::Event::],
691	[Tk:: => AnyEvent::Impl::Tk::],
692	[Wx:: => AnyEvent::Impl::POE::],
693	[Prima:: => AnyEvent::Impl::POE::],
694	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1005	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
695	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1006	# everything below here will not be autoprobed
696	[Glib:: => AnyEvent::Impl::Glib::],	1007	# as the pureperl backend should work everywhere
		1008	# and is usually faster
		1009	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1010	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
697	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1011	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
698	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1012	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
699	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1013	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		1014	[Wx:: => AnyEvent::Impl::POE::],
		1015	[Prima:: => AnyEvent::Impl::POE::],
		1016	# IO::Async is just too broken - we would need workaorunds for its
		1017	# byzantine signal and broken child handling, among others.
		1018	# IO::Async is rather hard to detect, as it doesn't have any
		1019	# obvious default class.
		1020	# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1021	# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1022	# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
700	);	1023	);
701		1024
702	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1025	our %method = map +($_ => 1),
		1026	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1027
		1028	our @post_detect;
		1029
		1030	sub post_detect(&) {
		1031	my ($cb) = @_;
		1032
		1033	if ($MODEL) {
		1034	$cb->();
		1035
		1036	1
		1037	} else {
		1038	push @post_detect, $cb;
		1039
		1040	defined wantarray
		1041	? bless \$cb, "AnyEvent::Util::postdetect"
		1042	: ()
		1043	}
		1044	}
		1045
		1046	sub AnyEvent::Util::postdetect::DESTROY {
		1047	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1048	}
703		1049
704	sub detect() {	1050	sub detect() {
705	unless ($MODEL) {	1051	unless ($MODEL) {
706	no strict 'refs';	1052	no strict 'refs';
		1053	local $SIG{__DIE__};
707		1054
708	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1055	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
709	my $model = "AnyEvent::Impl::$1";	1056	my $model = "AnyEvent::Impl::$1";
710	if (eval "require $model") {	1057	if (eval "require $model") {
711	$MODEL = $model;	1058	$MODEL = $model;
…		…
741	last;	1088	last;
742	}	1089	}
743	}	1090	}
744		1091
745	$MODEL	1092	$MODEL
746	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1093	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
747	}	1094	}
748	}	1095	}
749		1096
		1097	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1098
750	unshift @ISA, $MODEL;	1099	unshift @ISA, $MODEL;
751	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1100
		1101	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1102
		1103	(shift @post_detect)->() while @post_detect;
752	}	1104	}
753		1105
754	$MODEL	1106	$MODEL
755	}	1107	}
756		1108
…		…
764		1116
765	my $class = shift;	1117	my $class = shift;
766	$class->$func (@_);	1118	$class->$func (@_);
767	}	1119	}
768		1120
		1121	# utility function to dup a filehandle. this is used by many backends
		1122	# to support binding more than one watcher per filehandle (they usually
		1123	# allow only one watcher per fd, so we dup it to get a different one).
		1124	sub _dupfh($$;$$) {
		1125	my ($poll, $fh, $r, $w) = @_;
		1126
		1127	# cygwin requires the fh mode to be matching, unix doesn't
		1128	my ($rw, $mode) = $poll eq "r" ? ($r, "<") : ($w, ">");
		1129
		1130	open my $fh2, "$mode&", $fh
		1131	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1132
		1133	# we assume CLOEXEC is already set by perl in all important cases
		1134
		1135	($fh2, $rw)
		1136	}
		1137
769	package AnyEvent::Base;	1138	package AnyEvent::Base;
770		1139
		1140	# default implementations for many methods
		1141
		1142	BEGIN {
		1143	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1144	*_time = \&Time::HiRes::time;
		1145	# if (eval "use POSIX (); (POSIX::times())...
		1146	} else {
		1147	*_time = sub { time }; # epic fail
		1148	}
		1149	}
		1150
		1151	sub time { _time }
		1152	sub now { _time }
		1153	sub now_update { }
		1154
771	# default implementation for ->condvar, ->wait, ->broadcast	1155	# default implementation for ->condvar
772		1156
773	sub condvar {	1157	sub condvar {
774	bless \my $flag, "AnyEvent::Base::CondVar"	1158	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
775	}
776
777	sub AnyEvent::Base::CondVar::broadcast {
778	${$_[0]}++;
779	}
780
781	sub AnyEvent::Base::CondVar::wait {
782	AnyEvent->one_event while !${$_[0]};
783	}	1159	}
784		1160
785	# default implementation for ->signal	1161	# default implementation for ->signal
786		1162
787	our %SIG_CB;	1163	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1164
		1165	sub _signal_exec {
		1166	sysread $SIGPIPE_R, my $dummy, 4;
		1167
		1168	while (%SIG_EV) {
		1169	for (keys %SIG_EV) {
		1170	delete $SIG_EV{$_};
		1171	$_->() for values %{ $SIG_CB{$_} || {} };
		1172	}
		1173	}
		1174	}
788		1175
789	sub signal {	1176	sub signal {
790	my (undef, %arg) = @_;	1177	my (undef, %arg) = @_;
791		1178
		1179	unless ($SIGPIPE_R) {
		1180	require Fcntl;
		1181
		1182	if (AnyEvent::WIN32) {
		1183	require AnyEvent::Util;
		1184
		1185	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1186	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1187	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1188	} else {
		1189	pipe $SIGPIPE_R, $SIGPIPE_W;
		1190	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1191	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1192
		1193	# not strictly required, as $^F is normally 2, but let's make sure...
		1194	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1195	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1196	}
		1197
		1198	$SIGPIPE_R
		1199	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1200
		1201	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1202	}
		1203
792	my $signal = uc $arg{signal}	1204	my $signal = uc $arg{signal}
793	or Carp::croak "required option 'signal' is missing";	1205	or Carp::croak "required option 'signal' is missing";
794		1206
795	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1207	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
796	$SIG{$signal} ||= sub {	1208	$SIG{$signal} ||= sub {
797	$_->() for values %{ $SIG_CB{$signal} || {} };	1209	local $!;
		1210	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1211	undef $SIG_EV{$signal};
798	};	1212	};
799		1213
800	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1214	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
801	}	1215	}
802		1216
803	sub AnyEvent::Base::Signal::DESTROY {	1217	sub AnyEvent::Base::signal::DESTROY {
804	my ($signal, $cb) = @{$_[0]};	1218	my ($signal, $cb) = @{$_[0]};
805		1219
806	delete $SIG_CB{$signal}{$cb};	1220	delete $SIG_CB{$signal}{$cb};
807		1221
		1222	# delete doesn't work with older perls - they then
		1223	# print weird messages, or just unconditionally exit
		1224	# instead of getting the default action.
808	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1225	undef $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
809	}	1226	}
810		1227
811	# default implementation for ->child	1228	# default implementation for ->child
812		1229
813	our %PID_CB;	1230	our %PID_CB;
814	our $CHLD_W;	1231	our $CHLD_W;
815	our $CHLD_DELAY_W;	1232	our $CHLD_DELAY_W;
816	our $PID_IDLE;
817	our $WNOHANG;	1233	our $WNOHANG;
818		1234
819	sub _child_wait {	1235	sub _sigchld {
820	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1236	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
821	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1237	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),
822	(values %{ $PID_CB{0} || {} });	1238	(values %{ $PID_CB{0} || {} });
823	}	1239	}
824
825	undef $PID_IDLE;
826	}
827
828	sub _sigchld {
829	# make sure we deliver these changes "synchronous" with the event loop.
830	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
831	undef $CHLD_DELAY_W;
832	&_child_wait;
833	});
834	}	1240	}
835		1241
836	sub child {	1242	sub child {
837	my (undef, %arg) = @_;	1243	my (undef, %arg) = @_;
838		1244
839	defined (my $pid = $arg{pid} + 0)	1245	defined (my $pid = $arg{pid} + 0)
840	or Carp::croak "required option 'pid' is missing";	1246	or Carp::croak "required option 'pid' is missing";
841		1247
842	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1248	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
843		1249
844	unless ($WNOHANG) {
845	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1250	$WNOHANG ||= eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
846	}
847		1251
848	unless ($CHLD_W) {	1252	unless ($CHLD_W) {
849	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1253	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
850	# child could be a zombie already, so make at least one round	1254	# child could be a zombie already, so make at least one round
851	&_sigchld;	1255	&_sigchld;
852	}	1256	}
853		1257
854	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1258	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
855	}	1259	}
856		1260
857	sub AnyEvent::Base::Child::DESTROY {	1261	sub AnyEvent::Base::child::DESTROY {
858	my ($pid, $cb) = @{$_[0]};	1262	my ($pid, $cb) = @{$_[0]};
859		1263
860	delete $PID_CB{$pid}{$cb};	1264	delete $PID_CB{$pid}{$cb};
861	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1265	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
862		1266
863	undef $CHLD_W unless keys %PID_CB;	1267	undef $CHLD_W unless keys %PID_CB;
864	}	1268	}
		1269
		1270	# idle emulation is done by simply using a timer, regardless
		1271	# of whether the process is idle or not, and not letting
		1272	# the callback use more than 50% of the time.
		1273	sub idle {
		1274	my (undef, %arg) = @_;
		1275
		1276	my ($cb, $w, $rcb) = $arg{cb};
		1277
		1278	$rcb = sub {
		1279	if ($cb) {
		1280	$w = _time;
		1281	&$cb;
		1282	$w = _time - $w;
		1283
		1284	# never use more then 50% of the time for the idle watcher,
		1285	# within some limits
		1286	$w = 0.0001 if $w < 0.0001;
		1287	$w = 5 if $w > 5;
		1288
		1289	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1290	} else {
		1291	# clean up...
		1292	undef $w;
		1293	undef $rcb;
		1294	}
		1295	};
		1296
		1297	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1298
		1299	bless \\$cb, "AnyEvent::Base::idle"
		1300	}
		1301
		1302	sub AnyEvent::Base::idle::DESTROY {
		1303	undef $${$_[0]};
		1304	}
		1305
		1306	package AnyEvent::CondVar;
		1307
		1308	our @ISA = AnyEvent::CondVar::Base::;
		1309
		1310	package AnyEvent::CondVar::Base;
		1311
		1312	use overload
		1313	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1314	fallback => 1;
		1315
		1316	sub _send {
		1317	# nop
		1318	}
		1319
		1320	sub send {
		1321	my $cv = shift;
		1322	$cv->{_ae_sent} = [@_];
		1323	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1324	$cv->_send;
		1325	}
		1326
		1327	sub croak {
		1328	$_[0]{_ae_croak} = $_[1];
		1329	$_[0]->send;
		1330	}
		1331
		1332	sub ready {
		1333	$_[0]{_ae_sent}
		1334	}
		1335
		1336	sub _wait {
		1337	AnyEvent->one_event while !$_[0]{_ae_sent};
		1338	}
		1339
		1340	sub recv {
		1341	$_[0]->_wait;
		1342
		1343	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1344	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1345	}
		1346
		1347	sub cb {
		1348	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1349	$_[0]{_ae_cb}
		1350	}
		1351
		1352	sub begin {
		1353	++$_[0]{_ae_counter};
		1354	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1355	}
		1356
		1357	sub end {
		1358	return if --$_[0]{_ae_counter};
		1359	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1360	}
		1361
		1362	# undocumented/compatibility with pre-3.4
		1363	*broadcast = \&send;
		1364	*wait = \&_wait;
		1365
		1366	=head1 ERROR AND EXCEPTION HANDLING
		1367
		1368	In general, AnyEvent does not do any error handling - it relies on the
		1369	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1370	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1371	checking of all AnyEvent methods, however, which is highly useful during
		1372	development.
		1373
		1374	As for exception handling (i.e. runtime errors and exceptions thrown while
		1375	executing a callback), this is not only highly event-loop specific, but
		1376	also not in any way wrapped by this module, as this is the job of the main
		1377	program.
		1378
		1379	The pure perl event loop simply re-throws the exception (usually
		1380	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1381	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1382	so on.
		1383
		1384	=head1 ENVIRONMENT VARIABLES
		1385
		1386	The following environment variables are used by this module or its
		1387	submodules.
		1388
		1389	Note that AnyEvent will remove I<all> environment variables starting with
		1390	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1391	enabled.
		1392
		1393	=over 4
		1394
		1395	=item C<PERL_ANYEVENT_VERBOSE>
		1396
		1397	By default, AnyEvent will be completely silent except in fatal
		1398	conditions. You can set this environment variable to make AnyEvent more
		1399	talkative.
		1400
		1401	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1402	conditions, such as not being able to load the event model specified by
		1403	C<PERL_ANYEVENT_MODEL>.
		1404
		1405	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1406	model it chooses.
		1407
		1408	=item C<PERL_ANYEVENT_STRICT>
		1409
		1410	AnyEvent does not do much argument checking by default, as thorough
		1411	argument checking is very costly. Setting this variable to a true value
		1412	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1413	check the arguments passed to most method calls. If it finds any problems,
		1414	it will croak.
		1415
		1416	In other words, enables "strict" mode.
		1417
		1418	Unlike C<use strict>, it is definitely recommended to keep it off in
		1419	production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
		1420	developing programs can be very useful, however.
		1421
		1422	=item C<PERL_ANYEVENT_MODEL>
		1423
		1424	This can be used to specify the event model to be used by AnyEvent, before
		1425	auto detection and -probing kicks in. It must be a string consisting
		1426	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1427	and the resulting module name is loaded and if the load was successful,
		1428	used as event model. If it fails to load AnyEvent will proceed with
		1429	auto detection and -probing.
		1430
		1431	This functionality might change in future versions.
		1432
		1433	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1434	could start your program like this:
		1435
		1436	PERL_ANYEVENT_MODEL=Perl perl ...
		1437
		1438	=item C<PERL_ANYEVENT_PROTOCOLS>
		1439
		1440	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1441	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1442	of auto probing).
		1443
		1444	Must be set to a comma-separated list of protocols or address families,
		1445	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1446	used, and preference will be given to protocols mentioned earlier in the
		1447	list.
		1448
		1449	This variable can effectively be used for denial-of-service attacks
		1450	against local programs (e.g. when setuid), although the impact is likely
		1451	small, as the program has to handle conenction and other failures anyways.
		1452
		1453	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1454	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1455	- only support IPv4, never try to resolve or contact IPv6
		1456	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1457	IPv6, but prefer IPv6 over IPv4.
		1458
		1459	=item C<PERL_ANYEVENT_EDNS0>
		1460
		1461	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1462	for DNS. This extension is generally useful to reduce DNS traffic, but
		1463	some (broken) firewalls drop such DNS packets, which is why it is off by
		1464	default.
		1465
		1466	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1467	EDNS0 in its DNS requests.
		1468
		1469	=item C<PERL_ANYEVENT_MAX_FORKS>
		1470
		1471	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1472	will create in parallel.
		1473
		1474	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1475
		1476	The default value for the C<max_outstanding> parameter for the default DNS
		1477	resolver - this is the maximum number of parallel DNS requests that are
		1478	sent to the DNS server.
		1479
		1480	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1481
		1482	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1483	configuration) in the default resolver. When set to the empty string, no
		1484	default config will be used.
		1485
		1486	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1487
		1488	When neither C<ca_file> nor C<ca_path> was specified during
		1489	L<AnyEvent::TLS> context creation, and either of these environment
		1490	variables exist, they will be used to specify CA certificate locations
		1491	instead of a system-dependent default.
		1492
		1493	=back
865		1494
866	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1495	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
867		1496
868	This is an advanced topic that you do not normally need to use AnyEvent in	1497	This is an advanced topic that you do not normally need to use AnyEvent in
869	a module. This section is only of use to event loop authors who want to	1498	a module. This section is only of use to event loop authors who want to
…		…
903		1532
904	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1533	I<rxvt-unicode> also cheats a bit by not providing blocking access to
905	condition variables: code blocking while waiting for a condition will	1534	condition variables: code blocking while waiting for a condition will
906	C<die>. This still works with most modules/usages, and blocking calls must	1535	C<die>. This still works with most modules/usages, and blocking calls must
907	not be done in an interactive application, so it makes sense.	1536	not be done in an interactive application, so it makes sense.
908
909	=head1 ENVIRONMENT VARIABLES
910
911	The following environment variables are used by this module:
912
913	=over 4
914
915	=item C<PERL_ANYEVENT_VERBOSE>
916
917	By default, AnyEvent will be completely silent except in fatal
918	conditions. You can set this environment variable to make AnyEvent more
919	talkative.
920
921	When set to C<1> or higher, causes AnyEvent to warn about unexpected
922	conditions, such as not being able to load the event model specified by
923	C<PERL_ANYEVENT_MODEL>.
924
925	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
926	model it chooses.
927
928	=item C<PERL_ANYEVENT_MODEL>
929
930	This can be used to specify the event model to be used by AnyEvent, before
931	autodetection and -probing kicks in. It must be a string consisting
932	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
933	and the resulting module name is loaded and if the load was successful,
934	used as event model. If it fails to load AnyEvent will proceed with
935	autodetection and -probing.
936
937	This functionality might change in future versions.
938
939	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
940	could start your program like this:
941
942	PERL_ANYEVENT_MODEL=Perl perl ...
943
944	=back
945		1537
946	=head1 EXAMPLE PROGRAM	1538	=head1 EXAMPLE PROGRAM
947		1539
948	The following program uses an I/O watcher to read data from STDIN, a timer	1540	The following program uses an I/O watcher to read data from STDIN, a timer
949	to display a message once per second, and a condition variable to quit the	1541	to display a message once per second, and a condition variable to quit the
…		…
958	poll => 'r',	1550	poll => 'r',
959	cb => sub {	1551	cb => sub {
960	warn "io event <$_[0]>\n"; # will always output <r>	1552	warn "io event <$_[0]>\n"; # will always output <r>
961	chomp (my $input = <STDIN>); # read a line	1553	chomp (my $input = <STDIN>); # read a line
962	warn "read: $input\n"; # output what has been read	1554	warn "read: $input\n"; # output what has been read
963	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1555	$cv->send if $input =~ /^q/i; # quit program if /^q/i
964	},	1556	},
965	);	1557	);
966		1558
967	my $time_watcher; # can only be used once	1559	my $time_watcher; # can only be used once
968		1560
…		…
973	});	1565	});
974	}	1566	}
975		1567
976	new_timer; # create first timer	1568	new_timer; # create first timer
977		1569
978	$cv->wait; # wait until user enters /^q/i	1570	$cv->recv; # wait until user enters /^q/i
979		1571
980	=head1 REAL-WORLD EXAMPLE	1572	=head1 REAL-WORLD EXAMPLE
981		1573
982	Consider the L<Net::FCP> module. It features (among others) the following	1574	Consider the L<Net::FCP> module. It features (among others) the following
983	API calls, which are to freenet what HTTP GET requests are to http:	1575	API calls, which are to freenet what HTTP GET requests are to http:
…		…
1033	syswrite $txn->{fh}, $txn->{request}	1625	syswrite $txn->{fh}, $txn->{request}
1034	or die "connection or write error";	1626	or die "connection or write error";
1035	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1627	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1036		1628
1037	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1629	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1038	result and signals any possible waiters that the request ahs finished:	1630	result and signals any possible waiters that the request has finished:
1039		1631
1040	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1632	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1041		1633
1042	if (end-of-file or data complete) {	1634	if (end-of-file or data complete) {
1043	$txn->{result} = $txn->{buf};	1635	$txn->{result} = $txn->{buf};
1044	$txn->{finished}->broadcast;	1636	$txn->{finished}->send;
1045	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1637	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
1046	}	1638	}
1047		1639
1048	The C<result> method, finally, just waits for the finished signal (if the	1640	The C<result> method, finally, just waits for the finished signal (if the
1049	request was already finished, it doesn't wait, of course, and returns the	1641	request was already finished, it doesn't wait, of course, and returns the
1050	data:	1642	data:
1051		1643
1052	$txn->{finished}->wait;	1644	$txn->{finished}->recv;
1053	return $txn->{result};	1645	return $txn->{result};
1054		1646
1055	The actual code goes further and collects all errors (C<die>s, exceptions)	1647	The actual code goes further and collects all errors (C<die>s, exceptions)
1056	that occured during request processing. The C<result> method detects	1648	that occurred during request processing. The C<result> method detects
1057	whether an exception as thrown (it is stored inside the $txn object)	1649	whether an exception as thrown (it is stored inside the $txn object)
1058	and just throws the exception, which means connection errors and other	1650	and just throws the exception, which means connection errors and other
1059	problems get reported tot he code that tries to use the result, not in a	1651	problems get reported tot he code that tries to use the result, not in a
1060	random callback.	1652	random callback.
1061		1653
…		…
1092		1684
1093	my $quit = AnyEvent->condvar;	1685	my $quit = AnyEvent->condvar;
1094		1686
1095	$fcp->txn_client_get ($url)->cb (sub {	1687	$fcp->txn_client_get ($url)->cb (sub {
1096	...	1688	...
1097	$quit->broadcast;	1689	$quit->send;
1098	});	1690	});
1099		1691
1100	$quit->wait;	1692	$quit->recv;
1101		1693
1102		1694
1103	=head1 BENCHMARKS	1695	=head1 BENCHMARKS
1104		1696
1105	To give you an idea of the performance and overheads that AnyEvent adds	1697	To give you an idea of the performance and overheads that AnyEvent adds
…		…
1107	of various event loops I prepared some benchmarks.	1699	of various event loops I prepared some benchmarks.
1108		1700
1109	=head2 BENCHMARKING ANYEVENT OVERHEAD	1701	=head2 BENCHMARKING ANYEVENT OVERHEAD
1110		1702
1111	Here is a benchmark of various supported event models used natively and	1703	Here is a benchmark of various supported event models used natively and
1112	through anyevent. The benchmark creates a lot of timers (with a zero	1704	through AnyEvent. The benchmark creates a lot of timers (with a zero
1113	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1705	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1114	which it is), lets them fire exactly once and destroys them again.	1706	which it is), lets them fire exactly once and destroys them again.
1115		1707
1116	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	1708	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1117	distribution.	1709	distribution.
…		…
1134	all watchers, to avoid adding memory overhead. That means closure creation	1726	all watchers, to avoid adding memory overhead. That means closure creation
1135	and memory usage is not included in the figures.	1727	and memory usage is not included in the figures.
1136		1728
1137	I<invoke> is the time, in microseconds, used to invoke a simple	1729	I<invoke> is the time, in microseconds, used to invoke a simple
1138	callback. The callback simply counts down a Perl variable and after it was	1730	callback. The callback simply counts down a Perl variable and after it was
1139	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1731	invoked "watcher" times, it would C<< ->send >> a condvar once to
1140	signal the end of this phase.	1732	signal the end of this phase.
1141		1733
1142	I<destroy> is the time, in microseconds, that it takes to destroy a single	1734	I<destroy> is the time, in microseconds, that it takes to destroy a single
1143	watcher.	1735	watcher.
1144		1736
1145	=head3 Results	1737	=head3 Results
1146		1738
1147	name watchers bytes create invoke destroy comment	1739	name watchers bytes create invoke destroy comment
1148	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1740	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1149	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1741	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1150	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1742	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1151	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1743	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1152	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1744	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1153	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1745	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1746	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1747	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1154	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1748	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1155	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1749	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1156	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1750	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1157	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1751	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1158		1752
1159	=head3 Discussion	1753	=head3 Discussion
1160		1754
1161	The benchmark does I<not> measure scalability of the event loop very	1755	The benchmark does I<not> measure scalability of the event loop very
1162	well. For example, a select-based event loop (such as the pure perl one)	1756	well. For example, a select-based event loop (such as the pure perl one)
…		…
1187	performance becomes really bad with lots of file descriptors (and few of	1781	performance becomes really bad with lots of file descriptors (and few of
1188	them active), of course, but this was not subject of this benchmark.	1782	them active), of course, but this was not subject of this benchmark.
1189		1783
1190	The C<Event> module has a relatively high setup and callback invocation	1784	The C<Event> module has a relatively high setup and callback invocation
1191	cost, but overall scores in on the third place.	1785	cost, but overall scores in on the third place.
		1786
		1787	C<IO::Async> performs admirably well, about on par with C<Event>, even
		1788	when using its pure perl backend.
1192		1789
1193	C<Glib>'s memory usage is quite a bit higher, but it features a	1790	C<Glib>'s memory usage is quite a bit higher, but it features a
1194	faster callback invocation and overall ends up in the same class as	1791	faster callback invocation and overall ends up in the same class as
1195	C<Event>. However, Glib scales extremely badly, doubling the number of	1792	C<Event>. However, Glib scales extremely badly, doubling the number of
1196	watchers increases the processing time by more than a factor of four,	1793	watchers increases the processing time by more than a factor of four,
…		…
1240		1837
1241	=back	1838	=back
1242		1839
1243	=head2 BENCHMARKING THE LARGE SERVER CASE	1840	=head2 BENCHMARKING THE LARGE SERVER CASE
1244		1841
1245	This benchmark atcually benchmarks the event loop itself. It works by	1842	This benchmark actually benchmarks the event loop itself. It works by
1246	creating a number of "servers": each server consists of a socketpair, a	1843	creating a number of "servers": each server consists of a socket pair, a
1247	timeout watcher that gets reset on activity (but never fires), and an I/O	1844	timeout watcher that gets reset on activity (but never fires), and an I/O
1248	watcher waiting for input on one side of the socket. Each time the socket	1845	watcher waiting for input on one side of the socket. Each time the socket
1249	watcher reads a byte it will write that byte to a random other "server".	1846	watcher reads a byte it will write that byte to a random other "server".
1250		1847
1251	The effect is that there will be a lot of I/O watchers, only part of which	1848	The effect is that there will be a lot of I/O watchers, only part of which
1252	are active at any one point (so there is a constant number of active	1849	are active at any one point (so there is a constant number of active
1253	fds for each loop iterstaion, but which fds these are is random). The	1850	fds for each loop iteration, but which fds these are is random). The
1254	timeout is reset each time something is read because that reflects how	1851	timeout is reset each time something is read because that reflects how
1255	most timeouts work (and puts extra pressure on the event loops).	1852	most timeouts work (and puts extra pressure on the event loops).
1256		1853
1257	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	1854	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1258	(1%) are active. This mirrors the activity of large servers with many	1855	(1%) are active. This mirrors the activity of large servers with many
1259	connections, most of which are idle at any one point in time.	1856	connections, most of which are idle at any one point in time.
1260		1857
1261	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	1858	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1262	distribution.	1859	distribution.
…		…
1264	=head3 Explanation of the columns	1861	=head3 Explanation of the columns
1265		1862
1266	I<sockets> is the number of sockets, and twice the number of "servers" (as	1863	I<sockets> is the number of sockets, and twice the number of "servers" (as
1267	each server has a read and write socket end).	1864	each server has a read and write socket end).
1268		1865
1269	I<create> is the time it takes to create a socketpair (which is	1866	I<create> is the time it takes to create a socket pair (which is
1270	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	1867	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1271		1868
1272	I<request>, the most important value, is the time it takes to handle a	1869	I<request>, the most important value, is the time it takes to handle a
1273	single "request", that is, reading the token from the pipe and forwarding	1870	single "request", that is, reading the token from the pipe and forwarding
1274	it to another server. This includes deleting the old timeout and creating	1871	it to another server. This includes deleting the old timeout and creating
1275	a new one that moves the timeout into the future.	1872	a new one that moves the timeout into the future.
1276		1873
1277	=head3 Results	1874	=head3 Results
1278		1875
1279	name sockets create request	1876	name sockets create request
1280	EV 20000 69.01 11.16	1877	EV 20000 69.01 11.16
1281	Perl 20000 73.32 35.87	1878	Perl 20000 73.32 35.87
		1879	IOAsync 20000 157.00 98.14 epoll
		1880	IOAsync 20000 159.31 616.06 poll
1282	Event 20000 212.62 257.32	1881	Event 20000 212.62 257.32
1283	Glib 20000 651.16 1896.30	1882	Glib 20000 651.16 1896.30
1284	POE 20000 349.67 12317.24 uses POE::Loop::Event	1883	POE 20000 349.67 12317.24 uses POE::Loop::Event
1285		1884
1286	=head3 Discussion	1885	=head3 Discussion
1287		1886
1288	This benchmark I<does> measure scalability and overall performance of the	1887	This benchmark I<does> measure scalability and overall performance of the
1289	particular event loop.	1888	particular event loop.
…		…
1291	EV is again fastest. Since it is using epoll on my system, the setup time	1890	EV is again fastest. Since it is using epoll on my system, the setup time
1292	is relatively high, though.	1891	is relatively high, though.
1293		1892
1294	Perl surprisingly comes second. It is much faster than the C-based event	1893	Perl surprisingly comes second. It is much faster than the C-based event
1295	loops Event and Glib.	1894	loops Event and Glib.
		1895
		1896	IO::Async performs very well when using its epoll backend, and still quite
		1897	good compared to Glib when using its pure perl backend.
1296		1898
1297	Event suffers from high setup time as well (look at its code and you will	1899	Event suffers from high setup time as well (look at its code and you will
1298	understand why). Callback invocation also has a high overhead compared to	1900	understand why). Callback invocation also has a high overhead compared to
1299	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	1901	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1300	uses select or poll in basically all documented configurations.	1902	uses select or poll in basically all documented configurations.
…		…
1347	speed most when you have lots of watchers, not when you only have a few of	1949	speed most when you have lots of watchers, not when you only have a few of
1348	them).	1950	them).
1349		1951
1350	EV is again fastest.	1952	EV is again fastest.
1351		1953
1352	Perl again comes second. It is noticably faster than the C-based event	1954	Perl again comes second. It is noticeably faster than the C-based event
1353	loops Event and Glib, although the difference is too small to really	1955	loops Event and Glib, although the difference is too small to really
1354	matter.	1956	matter.
1355		1957
1356	POE also performs much better in this case, but is is still far behind the	1958	POE also performs much better in this case, but is is still far behind the
1357	others.	1959	others.
…		…
1363	=item * C-based event loops perform very well with small number of	1965	=item * C-based event loops perform very well with small number of
1364	watchers, as the management overhead dominates.	1966	watchers, as the management overhead dominates.
1365		1967
1366	=back	1968	=back
1367		1969
		1970	=head2 THE IO::Lambda BENCHMARK
		1971
		1972	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1973	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		1974	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		1975	shouldn't come as a surprise to anybody). As such, the benchmark is
		1976	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		1977	very optimal. But how would AnyEvent compare when used without the extra
		1978	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		1979
		1980	The benchmark itself creates an echo-server, and then, for 500 times,
		1981	connects to the echo server, sends a line, waits for the reply, and then
		1982	creates the next connection. This is a rather bad benchmark, as it doesn't
		1983	test the efficiency of the framework or much non-blocking I/O, but it is a
		1984	benchmark nevertheless.
		1985
		1986	name runtime
		1987	Lambda/select 0.330 sec
		1988	+ optimized 0.122 sec
		1989	Lambda/AnyEvent 0.327 sec
		1990	+ optimized 0.138 sec
		1991	Raw sockets/select 0.077 sec
		1992	POE/select, components 0.662 sec
		1993	POE/select, raw sockets 0.226 sec
		1994	POE/select, optimized 0.404 sec
		1995
		1996	AnyEvent/select/nb 0.085 sec
		1997	AnyEvent/EV/nb 0.068 sec
		1998	+state machine 0.134 sec
		1999
		2000	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2001	benchmarks actually make blocking connects and use 100% blocking I/O,
		2002	defeating the purpose of an event-based solution. All of the newly
		2003	written AnyEvent benchmarks use 100% non-blocking connects (using
		2004	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2005	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2006	generally require a lot more bookkeeping and event handling than blocking
		2007	connects (which involve a single syscall only).
		2008
		2009	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2010	offers similar expressive power as POE and IO::Lambda, using conventional
		2011	Perl syntax. This means that both the echo server and the client are 100%
		2012	non-blocking, further placing it at a disadvantage.
		2013
		2014	As you can see, the AnyEvent + EV combination even beats the
		2015	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2016	backend easily beats IO::Lambda and POE.
		2017
		2018	And even the 100% non-blocking version written using the high-level (and
		2019	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2020	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2021	in a non-blocking way.
		2022
		2023	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2024	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2025	part of the IO::lambda distribution and were used without any changes.
		2026
		2027
		2028	=head1 SIGNALS
		2029
		2030	AnyEvent currently installs handlers for these signals:
		2031
		2032	=over 4
		2033
		2034	=item SIGCHLD
		2035
		2036	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2037	emulation for event loops that do not support them natively. Also, some
		2038	event loops install a similar handler.
		2039
		2040	If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent will
		2041	reset it to default, to avoid losing child exit statuses.
		2042
		2043	=item SIGPIPE
		2044
		2045	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2046	when AnyEvent gets loaded.
		2047
		2048	The rationale for this is that AnyEvent users usually do not really depend
		2049	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2050	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2051	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2052	some random socket.
		2053
		2054	The rationale for installing a no-op handler as opposed to ignoring it is
		2055	that this way, the handler will be restored to defaults on exec.
		2056
		2057	Feel free to install your own handler, or reset it to defaults.
		2058
		2059	=back
		2060
		2061	=cut
		2062
		2063	undef $SIG{CHLD}
		2064	if $SIG{CHLD} eq 'IGNORE';
		2065
		2066	$SIG{PIPE} = sub { }
		2067	unless defined $SIG{PIPE};
1368		2068
1369	=head1 FORK	2069	=head1 FORK
1370		2070
1371	Most event libraries are not fork-safe. The ones who are usually are	2071	Most event libraries are not fork-safe. The ones who are usually are
1372	because they rely on inefficient but fork-safe C<select> or C<poll>	2072	because they rely on inefficient but fork-safe C<select> or C<poll>
…		…
1386	specified in the variable.	2086	specified in the variable.
1387		2087
1388	You can make AnyEvent completely ignore this variable by deleting it	2088	You can make AnyEvent completely ignore this variable by deleting it
1389	before the first watcher gets created, e.g. with a C<BEGIN> block:	2089	before the first watcher gets created, e.g. with a C<BEGIN> block:
1390		2090
1391	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2091	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1392		2092
1393	use AnyEvent;	2093	use AnyEvent;
1394		2094
1395	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2095	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1396	be used to probe what backend is used and gain other information (which is	2096	be used to probe what backend is used and gain other information (which is
1397	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2097	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2098	$ENV{PERL_ANYEVENT_STRICT}.
		2099
		2100	Note that AnyEvent will remove I<all> environment variables starting with
		2101	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2102	enabled.
		2103
		2104
		2105	=head1 BUGS
		2106
		2107	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2108	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2109	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2110	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2111	pronounced).
1398		2112
1399		2113
1400	=head1 SEE ALSO	2114	=head1 SEE ALSO
1401		2115
1402	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2116	Utility functions: L<AnyEvent::Util>.
1403	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	2117
		2118	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1404	L<Event::Lib>, L<Qt>, L<POE>.	2119	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1405		2120
1406	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2121	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1407	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2122	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1408	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	2123	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1409	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	2124	L<AnyEvent::Impl::POE>.
1410		2125
		2126	Non-blocking file handles, sockets, TCP clients and
		2127	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		2128
		2129	Asynchronous DNS: L<AnyEvent::DNS>.
		2130
		2131	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		2132
1411	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2133	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1412		2134
1413		2135
1414	=head1 AUTHOR	2136	=head1 AUTHOR
1415		2137
1416	Marc Lehmann <schmorp@schmorp.de>	2138	Marc Lehmann <schmorp@schmorp.de>
1417	http://home.schmorp.de/	2139	http://home.schmorp.de/
1418		2140
1419	=cut	2141	=cut
1420		2142
1421	1	2143	1
1422		2144

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