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Revision 1.111 by root, Sat May 10 01:02:25 2008 UTC vs.
Revision 1.311 by root, Wed Feb 10 13:33:44 2010 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
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.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		53
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		55
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
27		58
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	60	policy> and AnyEvent is I<small and efficient>.
30		61
31	First and foremost, I<AnyEvent is not an event model> itself, it only	62	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	63	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,	64	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,	65	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	66	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	67	cannot change this, but it can hide the differences between those event
		68	loops.
37		69
38	The goal of AnyEvent is to offer module authors the ability to do event	70	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	71	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	72	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	73	module users into the same thing by forcing them to use the same event
42	model you use.	74	model you use.
43		75
44	For modules like POE or IO::Async (which is a total misnomer as it is	76	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	77	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	78	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	79	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	80	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.	81	module are I<also> forced to use the same event loop you use.
50		82
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	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	85	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,	86	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	87	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	88	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	89	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).	90	to AnyEvent, too, so it is future-proof).
59		91
60	In addition to being free of having to use I<the one and only true event	92	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	93	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	94	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	95	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	96	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	97	technically possible.
66		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		100	of useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
67	Of course, if you want lots of policy (this can arguably be somewhat	105	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	106	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	107	model, you should I<not> use this module.
70		108
71	=head1 DESCRIPTION	109	=head1 DESCRIPTION
72		110
…		…
102	starts using it, all bets are off. Maybe you should tell their authors to	140	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...	141	use AnyEvent so their modules work together with others seamlessly...
104		142
105	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	144	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
107	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
108		146
109	=head1 WATCHERS	147	=head1 WATCHERS
110		148
111	AnyEvent has the central concept of a I<watcher>, which is an object that	149	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	150	stores relevant data for each kind of event you are waiting for, such as
113	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
114		152
115	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	154	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	155	callback when the event occurs (of course, only when the event model
118	is in control).	156	is in control).
119		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
120	To disable the watcher you have to destroy it (e.g. by setting the	164	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	165	variable you store it in to C<undef> or otherwise deleting all references
122	to it).	166	to it).
123		167
124	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
127	example), or need to refer to their watcher object in other ways.	171	example), or need to refer to their watcher object in other ways.
128		172
129	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
130		174
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
133	undef $w;	177	undef $w;
134	});	178	});
135		179
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	180	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	181	my variables are only visible after the statement in which they are
138	declared.	182	declared.
139		183
140	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
141		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
		191
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	192	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	193	with the following mandatory key-value pairs as arguments:
144		194
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	195	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		196	for events (AnyEvent might or might not keep a reference to this file
		197	handle). Note that only file handles pointing to things for which
		198	non-blocking operation makes sense are allowed. This includes sockets,
		199	most character devices, pipes, fifos and so on, but not for example files
		200	or block devices.
		201
146	for events. C<poll> must be a string that is either C<r> or C<w>,	202	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,	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
		204
148	respectively. C<cb> is the callback to invoke each time the file handle	205	C<cb> is the callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		206
151	Although the callback might get passed parameters, their value and	207	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	208	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	209	callbacks cannot use arguments passed to I/O watcher callbacks.
154		210
…		…
158		214
159	Some event loops issue spurious readyness notifications, so you should	215	Some event loops issue spurious readyness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	216	always use non-blocking calls when reading/writing from/to your file
161	handles.	217	handles.
162		218
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	219	Example: wait for readability of STDIN, then read a line and disable the
		220	watcher.
		221
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	224	warn "read: $input\n";
169	undef $w;	225	undef $w;
170	});	226	});
171		227
172	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
173		229
		230	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		231
		232	$w = AnyEvent->timer (
		233	after => <fractional_seconds>,
		234	interval => <fractional_seconds>,
		235	cb => <callback>,
		236	);
		237
174	You can create a time watcher by calling the C<< AnyEvent->timer >>	238	You can create a time watcher by calling the C<< AnyEvent->timer >>
175	method with the following mandatory arguments:	239	method with the following mandatory arguments:
176		240
177	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
178	supported) the callback should be invoked. C<cb> is the callback to invoke	242	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
180		244
181	Although the callback might get passed parameters, their value and	245	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	246	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	247	callbacks cannot use arguments passed to time watcher callbacks.
184		248
185	The timer callback will be invoked at most once: if you want a repeating	249	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	250	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	251	callback will be invoked regularly at that interval (in fractional
		252	seconds) after the first invocation. If C<interval> is specified with a
		253	false value, then it is treated as if it were missing.
188		254
189	Example:	255	The callback will be rescheduled before invoking the callback, but no
		256	attempt is done to avoid timer drift in most backends, so the interval is
		257	only approximate.
190		258
191	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	262	warn "timeout\n";
194	});	263	});
195		264
196	# to cancel the timer:	265	# to cancel the timer:
197	undef $w;	266	undef $w;
198		267
199	Example 2:
200
201	# fire an event after 0.5 seconds, then roughly every second	268	Example 2: fire an event after 0.5 seconds, then roughly every second.
202	my $w;
203		269
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		271	warn "timeout\n";
207	};	272	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		273
212	=head3 TIMING ISSUES	274	=head3 TIMING ISSUES
213		275
214	There are two ways to handle timers: based on real time (relative, "fire	276	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	277	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
227	timers.	289	timers.
228		290
229	AnyEvent always prefers relative timers, if available, matching the	291	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	292	AnyEvent API.
231		293
		294	AnyEvent has two additional methods that return the "current time":
		295
		296	=over 4
		297
		298	=item AnyEvent->time
		299
		300	This returns the "current wallclock time" as a fractional number of
		301	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		302	return, and the result is guaranteed to be compatible with those).
		303
		304	It progresses independently of any event loop processing, i.e. each call
		305	will check the system clock, which usually gets updated frequently.
		306
		307	=item AnyEvent->now
		308
		309	This also returns the "current wallclock time", but unlike C<time>, above,
		310	this value might change only once per event loop iteration, depending on
		311	the event loop (most return the same time as C<time>, above). This is the
		312	time that AnyEvent's timers get scheduled against.
		313
		314	I<In almost all cases (in all cases if you don't care), this is the
		315	function to call when you want to know the current time.>
		316
		317	This function is also often faster then C<< AnyEvent->time >>, and
		318	thus the preferred method if you want some timestamp (for example,
		319	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		320
		321	The rest of this section is only of relevance if you try to be very exact
		322	with your timing, you can skip it without bad conscience.
		323
		324	For a practical example of when these times differ, consider L<Event::Lib>
		325	and L<EV> and the following set-up:
		326
		327	The event loop is running and has just invoked one of your callback at
		328	time=500 (assume no other callbacks delay processing). In your callback,
		329	you wait a second by executing C<sleep 1> (blocking the process for a
		330	second) and then (at time=501) you create a relative timer that fires
		331	after three seconds.
		332
		333	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		334	both return C<501>, because that is the current time, and the timer will
		335	be scheduled to fire at time=504 (C<501> + C<3>).
		336
		337	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		338	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		339	last event processing phase started. With L<EV>, your timer gets scheduled
		340	to run at time=503 (C<500> + C<3>).
		341
		342	In one sense, L<Event::Lib> is more exact, as it uses the current time
		343	regardless of any delays introduced by event processing. However, most
		344	callbacks do not expect large delays in processing, so this causes a
		345	higher drift (and a lot more system calls to get the current time).
		346
		347	In another sense, L<EV> is more exact, as your timer will be scheduled at
		348	the same time, regardless of how long event processing actually took.
		349
		350	In either case, if you care (and in most cases, you don't), then you
		351	can get whatever behaviour you want with any event loop, by taking the
		352	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		353	account.
		354
		355	=item AnyEvent->now_update
		356
		357	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		358	the current time for each loop iteration (see the discussion of L<<
		359	AnyEvent->now >>, above).
		360
		361	When a callback runs for a long time (or when the process sleeps), then
		362	this "current" time will differ substantially from the real time, which
		363	might affect timers and time-outs.
		364
		365	When this is the case, you can call this method, which will update the
		366	event loop's idea of "current time".
		367
		368	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		369	when mod_perl executes the script, then the event loop will have the wrong
		370	idea about the "current time" (being potentially far in the past, when the
		371	script ran the last time). In that case you should arrange a call to C<<
		372	AnyEvent->now_update >> each time the web server process wakes up again
		373	(e.g. at the start of your script, or in a handler).
		374
		375	Note that updating the time I<might> cause some events to be handled.
		376
		377	=back
		378
232	=head2 SIGNAL WATCHERS	379	=head2 SIGNAL WATCHERS
233		380
		381	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		382
234	You can watch for signals using a signal watcher, C<signal> is the signal	383	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	384	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	385	callback to be invoked whenever a signal occurs.
237		386
238	Although the callback might get passed parameters, their value and	387	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	388	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	389	callbacks cannot use arguments passed to signal watcher callbacks.
241		390
242	Multiple signal occurances can be clumped together into one callback	391	Multiple signal occurrences can be clumped together into one callback
243	invocation, and callback invocation will be synchronous. synchronous means	392	invocation, and callback invocation will be synchronous. Synchronous means
244	that it might take a while until the signal gets handled by the process,	393	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.	394	but it is guaranteed not to interrupt any other callbacks.
246		395
247	The main advantage of using these watchers is that you can share a signal	396	The main advantage of using these watchers is that you can share a signal
248	between multiple watchers.	397	between multiple watchers, and AnyEvent will ensure that signals will not
		398	interrupt your program at bad times.
249		399
250	This watcher might use C<%SIG>, so programs overwriting those signals	400	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	401	so programs overwriting those signals directly will likely not work
		402	correctly.
252		403
253	Example: exit on SIGINT	404	Example: exit on SIGINT
254		405
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	406	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		407
		408	=head3 Restart Behaviour
		409
		410	While restart behaviour is up to the event loop implementation, most will
		411	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		412	pure perl implementation).
		413
		414	=head3 Safe/Unsafe Signals
		415
		416	Perl signals can be either "safe" (synchronous to opcode handling) or
		417	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		418	latter might corrupt your memory.
		419
		420	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		421	i.e. they will not interrupt your running perl program but will only be
		422	called as part of the normal event handling (just like timer, I/O etc.
		423	callbacks, too).
		424
		425	=head3 Signal Races, Delays and Workarounds
		426
		427	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		428	callbacks to signals in a generic way, which is a pity, as you cannot
		429	do race-free signal handling in perl, requiring C libraries for
		430	this. AnyEvent will try to do it's best, which means in some cases,
		431	signals will be delayed. The maximum time a signal might be delayed is
		432	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		433	variable can be changed only before the first signal watcher is created,
		434	and should be left alone otherwise. This variable determines how often
		435	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		436	will cause fewer spurious wake-ups, which is better for power and CPU
		437	saving.
		438
		439	All these problems can be avoided by installing the optional
		440	L<Async::Interrupt> module, which works with most event loops. It will not
		441	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		442	(and not with L<POE> currently, as POE does it's own workaround with
		443	one-second latency). For those, you just have to suffer the delays.
		444
257	=head2 CHILD PROCESS WATCHERS	445	=head2 CHILD PROCESS WATCHERS
258		446
		447	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		448
259	You can also watch on a child process exit and catch its exit status.	449	You can also watch on a child process exit and catch its exit status.
260		450
261	The child process is specified by the C<pid> argument (if set to C<0>, it	451	The child process is specified by the C<pid> argument (one some backends,
262	watches for any child process exit). The watcher will trigger as often	452	using C<0> watches for any child process exit, on others this will
263	as status change for the child are received. This works by installing a	453	croak). The watcher will be triggered only when the child process has
264	signal handler for C<SIGCHLD>. The callback will be called with the pid	454	finished and an exit status is available, not on any trace events
265	and exit status (as returned by waitpid), so unlike other watcher types,	455	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	456
		457	The callback will be called with the pid and exit status (as returned by
		458	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		459	callback arguments.
		460
		461	This watcher type works by installing a signal handler for C<SIGCHLD>,
		462	and since it cannot be shared, nothing else should use SIGCHLD or reap
		463	random child processes (waiting for specific child processes, e.g. inside
		464	C<system>, is just fine).
267		465
268	There is a slight catch to child watchers, however: you usually start them	466	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	467	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	468	have exited already (and no SIGCHLD will be sent anymore).
271		469
272	Not all event models handle this correctly (POE doesn't), but even for	470	Not all event models handle this correctly (neither POE nor IO::Async do,
		471	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	472	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).	473	the process exits (i.e. before you fork in the first place). AnyEvent's
		474	pure perl event loop handles all cases correctly regardless of when you
		475	start the watcher.
275		476
276	This means you cannot create a child watcher as the very first thing in an	477	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	478	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>).	479	watcher before you C<fork> the child (alternatively, you can call
		480	C<AnyEvent::detect>).
		481
		482	As most event loops do not support waiting for child events, they will be
		483	emulated by AnyEvent in most cases, in which the latency and race problems
		484	mentioned in the description of signal watchers apply.
279		485
280	Example: fork a process and wait for it	486	Example: fork a process and wait for it
281		487
282	my $done = AnyEvent->condvar;	488	my $done = AnyEvent->condvar;
283		489
284	AnyEvent::detect; # force event module to be initialised
285
286	my $pid = fork or exit 5;	490	my $pid = fork or exit 5;
287		491
288	my $w = AnyEvent->child (	492	my $w = AnyEvent->child (
289	pid => $pid,	493	pid => $pid,
290	cb => sub {	494	cb => sub {
291	my ($pid, $status) = @_;	495	my ($pid, $status) = @_;
292	warn "pid $pid exited with status $status";	496	warn "pid $pid exited with status $status";
293	$done->send;	497	$done->send;
294	},	498	},
295	);	499	);
296		500
297	# do something else, then wait for process exit	501	# do something else, then wait for process exit
298	$done->wait;	502	$done->recv;
		503
		504	=head2 IDLE WATCHERS
		505
		506	$w = AnyEvent->idle (cb => <callback>);
		507
		508	Repeatedly invoke the callback after the process becomes idle, until
		509	either the watcher is destroyed or new events have been detected.
		510
		511	Idle watchers are useful when there is a need to do something, but it
		512	is not so important (or wise) to do it instantly. The callback will be
		513	invoked only when there is "nothing better to do", which is usually
		514	defined as "all outstanding events have been handled and no new events
		515	have been detected". That means that idle watchers ideally get invoked
		516	when the event loop has just polled for new events but none have been
		517	detected. Instead of blocking to wait for more events, the idle watchers
		518	will be invoked.
		519
		520	Unfortunately, most event loops do not really support idle watchers (only
		521	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		522	will simply call the callback "from time to time".
		523
		524	Example: read lines from STDIN, but only process them when the
		525	program is otherwise idle:
		526
		527	my @lines; # read data
		528	my $idle_w;
		529	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		530	push @lines, scalar <STDIN>;
		531
		532	# start an idle watcher, if not already done
		533	$idle_w ||= AnyEvent->idle (cb => sub {
		534	# handle only one line, when there are lines left
		535	if (my $line = shift @lines) {
		536	print "handled when idle: $line";
		537	} else {
		538	# otherwise disable the idle watcher again
		539	undef $idle_w;
		540	}
		541	});
		542	});
299		543
300	=head2 CONDITION VARIABLES	544	=head2 CONDITION VARIABLES
		545
		546	$cv = AnyEvent->condvar;
		547
		548	$cv->send (<list>);
		549	my @res = $cv->recv;
301		550
302	If you are familiar with some event loops you will know that all of them	551	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	552	require you to run some blocking "loop", "run" or similar function that
304	will actively watch for new events and call your callbacks.	553	will actively watch for new events and call your callbacks.
305		554
306	AnyEvent is different, it expects somebody else to run the event loop and	555	AnyEvent is slightly different: it expects somebody else to run the event
307	will only block when necessary (usually when told by the user).	556	loop and will only block when necessary (usually when told by the user).
308		557
309	The instrument to do that is called a "condition variable", so called	558	The instrument to do that is called a "condition variable", so called
310	because they represent a condition that must become true.	559	because they represent a condition that must become true.
		560
		561	Now is probably a good time to look at the examples further below.
311		562
312	Condition variables can be created by calling the C<< AnyEvent->condvar	563	Condition variables can be created by calling the C<< AnyEvent->condvar
313	>> method, usually without arguments. The only argument pair allowed is	564	>> method, usually without arguments. The only argument pair allowed is
314	C<cb>, which specifies a callback to be called when the condition variable	565	C<cb>, which specifies a callback to be called when the condition variable
315	becomes true.	566	becomes true, with the condition variable as the first argument (but not
		567	the results).
316		568
317	After creation, the conditon variable is "false" until it becomes "true"	569	After creation, the condition variable is "false" until it becomes "true"
318	by calling the C<send> method.	570	by calling the C<send> method (or calling the condition variable as if it
		571	were a callback, read about the caveats in the description for the C<<
		572	->send >> method).
319		573
320	Condition variables are similar to callbacks, except that you can	574	Condition variables are similar to callbacks, except that you can
321	optionally wait for them. They can also be called merge points - points	575	optionally wait for them. They can also be called merge points - points
322	in time where multiple outstandign events have been processed. And yet	576	in time where multiple outstanding events have been processed. And yet
323	another way to call them is transations - each condition variable can be	577	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	578	used to represent a transaction, which finishes at some point and delivers
325	a result.	579	a result. And yet some people know them as "futures" - a promise to
		580	compute/deliver something that you can wait for.
326		581
327	Condition variables are very useful to signal that something has finished,	582	Condition variables are very useful to signal that something has finished,
328	for example, if you write a module that does asynchronous http requests,	583	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	584	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	585	availability of results. The user can either act when the callback is
331	called or can synchronously C<< ->wait >> for the results.	586	called or can synchronously C<< ->recv >> for the results.
332		587
333	You can also use them to simulate traditional event loops - for example,	588	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	589	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	590	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.	591	button of your app, which would C<< ->send >> the "quit" event.
337		592
338	Note that condition variables recurse into the event loop - if you have	593	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	594	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	595	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,	596	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	597	as this asks for trouble.
343		598
344	Condition variables are represented by hash refs in perl, and the keys	599	Condition variables are represented by hash refs in perl, and the keys
…		…
349		604
350	There are two "sides" to a condition variable - the "producer side" which	605	There are two "sides" to a condition variable - the "producer side" which
351	eventually calls C<< -> send >>, and the "consumer side", which waits	606	eventually calls C<< -> send >>, and the "consumer side", which waits
352	for the send to occur.	607	for the send to occur.
353		608
354	Example:	609	Example: wait for a timer.
355		610
356	# wait till the result is ready	611	# wait till the result is ready
357	my $result_ready = AnyEvent->condvar;	612	my $result_ready = AnyEvent->condvar;
358		613
359	# do something such as adding a timer	614	# do something such as adding a timer
…		…
364	after => 1,	619	after => 1,
365	cb => sub { $result_ready->send },	620	cb => sub { $result_ready->send },
366	);	621	);
367		622
368	# this "blocks" (while handling events) till the callback	623	# this "blocks" (while handling events) till the callback
369	# calls send	624	# calls ->send
370	$result_ready->wait;	625	$result_ready->recv;
		626
		627	Example: wait for a timer, but take advantage of the fact that condition
		628	variables are also callable directly.
		629
		630	my $done = AnyEvent->condvar;
		631	my $delay = AnyEvent->timer (after => 5, cb => $done);
		632	$done->recv;
		633
		634	Example: Imagine an API that returns a condvar and doesn't support
		635	callbacks. This is how you make a synchronous call, for example from
		636	the main program:
		637
		638	use AnyEvent::CouchDB;
		639
		640	...
		641
		642	my @info = $couchdb->info->recv;
		643
		644	And this is how you would just set a callback to be called whenever the
		645	results are available:
		646
		647	$couchdb->info->cb (sub {
		648	my @info = $_[0]->recv;
		649	});
371		650
372	=head3 METHODS FOR PRODUCERS	651	=head3 METHODS FOR PRODUCERS
373		652
374	These methods should only be used by the producing side, i.e. the	653	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	654	code/module that eventually sends the signal. Note that it is also
…		…
378		657
379	=over 4	658	=over 4
380		659
381	=item $cv->send (...)	660	=item $cv->send (...)
382		661
383	Flag the condition as ready - a running C<< ->wait >> and all further	662	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	663	calls to C<recv> will (eventually) return after this method has been
385	called. If nobody is waiting the send will be remembered.	664	called. If nobody is waiting the send will be remembered.
386		665
387	If a callback has been set on the condition variable, it is called	666	If a callback has been set on the condition variable, it is called
388	immediately from within send.	667	immediately from within send.
389		668
390	Any arguments passed to the C<send> call will be returned by all	669	Any arguments passed to the C<send> call will be returned by all
391	future C<< ->wait >> calls.	670	future C<< ->recv >> calls.
		671
		672	Condition variables are overloaded so one can call them directly (as if
		673	they were a code reference). Calling them directly is the same as calling
		674	C<send>.
392		675
393	=item $cv->croak ($error)	676	=item $cv->croak ($error)
394		677
395	Similar to send, but causes all call's wait C<< ->wait >> to invoke	678	Similar to send, but causes all call's to C<< ->recv >> to invoke
396	C<Carp::croak> with the given error message/object/scalar.	679	C<Carp::croak> with the given error message/object/scalar.
397		680
398	This can be used to signal any errors to the condition variable	681	This can be used to signal any errors to the condition variable
399	user/consumer.	682	user/consumer. Doing it this way instead of calling C<croak> directly
		683	delays the error detetcion, but has the overwhelmign advantage that it
		684	diagnoses the error at the place where the result is expected, and not
		685	deep in some event clalback without connection to the actual code causing
		686	the problem.
400		687
401	=item $cv->begin ([group callback])	688	=item $cv->begin ([group callback])
402		689
403	=item $cv->end	690	=item $cv->end
404		691
…		…
406	one. For example, a function that pings many hosts in parallel might want	693	one. For example, a function that pings many hosts in parallel might want
407	to use a condition variable for the whole process.	694	to use a condition variable for the whole process.
408		695
409	Every call to C<< ->begin >> will increment a counter, and every call to	696	Every call to C<< ->begin >> will increment a counter, and every call to
410	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	697	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	698	>>, the (last) callback passed to C<begin> will be executed, passing the
412	is I<supposed> to call C<< ->send >>, but that is not required. If no	699	condvar as first argument. That callback is I<supposed> to call C<< ->send
413	callback was set, C<send> will be called without any arguments.	700	>>, but that is not required. If no group callback was set, C<send> will
		701	be called without any arguments.
414		702
415	Let's clarify this with the ping example:	703	You can think of C<< $cv->send >> giving you an OR condition (one call
		704	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		705	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		706
		707	Let's start with a simple example: you have two I/O watchers (for example,
		708	STDOUT and STDERR for a program), and you want to wait for both streams to
		709	close before activating a condvar:
416		710
417	my $cv = AnyEvent->condvar;	711	my $cv = AnyEvent->condvar;
418		712
		713	$cv->begin; # first watcher
		714	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		715	defined sysread $fh1, my $buf, 4096
		716	or $cv->end;
		717	});
		718
		719	$cv->begin; # second watcher
		720	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		721	defined sysread $fh2, my $buf, 4096
		722	or $cv->end;
		723	});
		724
		725	$cv->recv;
		726
		727	This works because for every event source (EOF on file handle), there is
		728	one call to C<begin>, so the condvar waits for all calls to C<end> before
		729	sending.
		730
		731	The ping example mentioned above is slightly more complicated, as the
		732	there are results to be passwd back, and the number of tasks that are
		733	begung can potentially be zero:
		734
		735	my $cv = AnyEvent->condvar;
		736
419	my %result;	737	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	738	$cv->begin (sub { shift->send (\%result) });
421		739
422	for my $host (@list_of_hosts) {	740	for my $host (@list_of_hosts) {
423	$cv->begin;	741	$cv->begin;
424	ping_host_then_call_callback $host, sub {	742	ping_host_then_call_callback $host, sub {
425	$result{$host} = ...;	743	$result{$host} = ...;
…		…
440	loop, which serves two important purposes: first, it sets the callback	758	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	759	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	760	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	761	doesn't execute once).
444		762
445	This is the general pattern when you "fan out" into multiple subrequests:	763	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>	764	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	765	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>.	766	subrequest you start, call C<begin> and for each subrequest you finish,
		767	call C<end>.
449		768
450	=back	769	=back
451		770
452	=head3 METHODS FOR CONSUMERS	771	=head3 METHODS FOR CONSUMERS
453		772
454	These methods should only be used by the consuming side, i.e. the	773	These methods should only be used by the consuming side, i.e. the
455	code awaits the condition.	774	code awaits the condition.
456		775
457	=over 4	776	=over 4
458		777
459	=item $cv->wait	778	=item $cv->recv
460		779
461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	780	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
462	>> methods have been called on c<$cv>, while servicing other watchers	781	>> methods have been called on c<$cv>, while servicing other watchers
463	normally.	782	normally.
464		783
…		…
469	function will call C<croak>.	788	function will call C<croak>.
470		789
471	In list context, all parameters passed to C<send> will be returned,	790	In list context, all parameters passed to C<send> will be returned,
472	in scalar context only the first one will be returned.	791	in scalar context only the first one will be returned.
473		792
		793	Note that doing a blocking wait in a callback is not supported by any
		794	event loop, that is, recursive invocation of a blocking C<< ->recv
		795	>> is not allowed, and the C<recv> call will C<croak> if such a
		796	condition is detected. This condition can be slightly loosened by using
		797	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		798	any thread that doesn't run the event loop itself.
		799
474	Not all event models support a blocking wait - some die in that case	800	Not all event models support a blocking wait - some die in that case
475	(programs might want to do that to stay interactive), so I<if you are	801	(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	802	using this from a module, never require a blocking wait>. Instead, let the
477	caller decide whether the call will block or not (for example, by coupling	803	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	804	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	805	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	806	while still supporting blocking waits if the caller so desires).
481		807
482	Another reason I<never> to C<< ->wait >> in a module is that you cannot
483	sensibly have two C<< ->wait >>'s in parallel, as that would require
484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485	can supply.
486
487	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
488	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
489	versions and also integrates coroutines into AnyEvent, making blocking
490	C<< ->wait >> calls perfectly safe as long as they are done from another
491	coroutine (one that doesn't run the event loop).
492
493	You can ensure that C<< -wait >> never blocks by setting a callback and	808	You can ensure that C<< -recv >> never blocks by setting a callback and
494	only calling C<< ->wait >> from within that callback (or at a later	809	only calling C<< ->recv >> from within that callback (or at a later
495	time). This will work even when the event loop does not support blocking	810	time). This will work even when the event loop does not support blocking
496	waits otherwise.	811	waits otherwise.
497		812
498	=item $bool = $cv->ready	813	=item $bool = $cv->ready
499		814
500	Returns true when the condition is "true", i.e. whether C<send> or	815	Returns true when the condition is "true", i.e. whether C<send> or
501	C<croak> have been called.	816	C<croak> have been called.
502		817
503	=item $cb = $cv->cb ([new callback])	818	=item $cb = $cv->cb ($cb->($cv))
504		819
505	This is a mutator function that returns the callback set and optionally	820	This is a mutator function that returns the callback set and optionally
506	replaces it before doing so.	821	replaces it before doing so.
507		822
508	The callback will be called when the condition becomes "true", i.e. when	823	The callback will be called when the condition becomes (or already was)
509	C<send> or C<croak> are called. Calling C<wait> inside the callback	824	"true", i.e. when C<send> or C<croak> are called (or were called), with
		825	the only argument being the condition variable itself. Calling C<recv>
510	or at any later time is guaranteed not to block.	826	inside the callback or at any later time is guaranteed not to block.
511		827
512	=back	828	=back
513		829
		830	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		831
		832	The available backend classes are (every class has its own manpage):
		833
		834	=over 4
		835
		836	=item Backends that are autoprobed when no other event loop can be found.
		837
		838	EV is the preferred backend when no other event loop seems to be in
		839	use. If EV is not installed, then AnyEvent will fall back to its own
		840	pure-perl implementation, which is available everywhere as it comes with
		841	AnyEvent itself.
		842
		843	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		844	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		845
		846	=item Backends that are transparently being picked up when they are used.
		847
		848	These will be used when they are currently loaded when the first watcher
		849	is created, in which case it is assumed that the application is using
		850	them. This means that AnyEvent will automatically pick the right backend
		851	when the main program loads an event module before anything starts to
		852	create watchers. Nothing special needs to be done by the main program.
		853
		854	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		855	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		856	AnyEvent::Impl::Tk based on Tk, very broken.
		857	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		858	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		859	AnyEvent::Impl::Irssi used when running within irssi.
		860
		861	=item Backends with special needs.
		862
		863	Qt requires the Qt::Application to be instantiated first, but will
		864	otherwise be picked up automatically. As long as the main program
		865	instantiates the application before any AnyEvent watchers are created,
		866	everything should just work.
		867
		868	AnyEvent::Impl::Qt based on Qt.
		869
		870	Support for IO::Async can only be partial, as it is too broken and
		871	architecturally limited to even support the AnyEvent API. It also
		872	is the only event loop that needs the loop to be set explicitly, so
		873	it can only be used by a main program knowing about AnyEvent. See
		874	L<AnyEvent::Impl::Async> for the gory details.
		875
		876	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		877
		878	=item Event loops that are indirectly supported via other backends.
		879
		880	Some event loops can be supported via other modules:
		881
		882	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		883
		884	B<WxWidgets> has no support for watching file handles. However, you can
		885	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		886	polls 20 times per second, which was considered to be too horrible to even
		887	consider for AnyEvent.
		888
		889	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		890	backend, so it can be supported through POE.
		891
		892	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		893	load L<POE> when detecting them, in the hope that POE will pick them up,
		894	in which case everything will be automatic.
		895
		896	=back
		897
514	=head1 GLOBAL VARIABLES AND FUNCTIONS	898	=head1 GLOBAL VARIABLES AND FUNCTIONS
515		899
		900	These are not normally required to use AnyEvent, but can be useful to
		901	write AnyEvent extension modules.
		902
516	=over 4	903	=over 4
517		904
518	=item $AnyEvent::MODEL	905	=item $AnyEvent::MODEL
519		906
520	Contains C<undef> until the first watcher is being created. Then it	907	Contains C<undef> until the first watcher is being created, before the
		908	backend has been autodetected.
		909
521	contains the event model that is being used, which is the name of the	910	Afterwards it contains the event model that is being used, which is the
522	Perl class implementing the model. This class is usually one of the	911	name of the Perl class implementing the model. This class is usually one
523	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	912	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
524	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	913	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
525		914	will be C<urxvt::anyevent>).
526	The known classes so far are:
527
528	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
529	AnyEvent::Impl::Event based on Event, second best choice.
530	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
531	AnyEvent::Impl::Glib based on Glib, third-best choice.
532	AnyEvent::Impl::Tk based on Tk, very bad choice.
533	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
534	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
535	AnyEvent::Impl::POE based on POE, not generic enough for full support.
536
537	There is no support for WxWidgets, as WxWidgets has no support for
538	watching file handles. However, you can use WxWidgets through the
539	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
540	second, which was considered to be too horrible to even consider for
541	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
542	it's adaptor.
543
544	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
545	autodetecting them.
546		915
547	=item AnyEvent::detect	916	=item AnyEvent::detect
548		917
549	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	918	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
550	if necessary. You should only call this function right before you would	919	if necessary. You should only call this function right before you would
551	have created an AnyEvent watcher anyway, that is, as late as possible at	920	have created an AnyEvent watcher anyway, that is, as late as possible at
552	runtime.	921	runtime, and not e.g. while initialising of your module.
		922
		923	If you need to do some initialisation before AnyEvent watchers are
		924	created, use C<post_detect>.
553		925
554	=item $guard = AnyEvent::post_detect { BLOCK }	926	=item $guard = AnyEvent::post_detect { BLOCK }
555		927
556	Arranges for the code block to be executed as soon as the event model is	928	Arranges for the code block to be executed as soon as the event model is
557	autodetected (or immediately if this has already happened).	929	autodetected (or immediately if this has already happened).
558		930
		931	The block will be executed I<after> the actual backend has been detected
		932	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		933	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		934	other initialisations - see the sources of L<AnyEvent::Strict> or
		935	L<AnyEvent::AIO> to see how this is used.
		936
		937	The most common usage is to create some global watchers, without forcing
		938	event module detection too early, for example, L<AnyEvent::AIO> creates
		939	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		940	avoid autodetecting the event module at load time.
		941
559	If called in scalar or list context, then it creates and returns an object	942	If called in scalar or list context, then it creates and returns an object
560	that automatically removes the callback again when it is destroyed.	943	that automatically removes the callback again when it is destroyed (or
		944	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		945	a case where this is useful.
		946
		947	Example: Create a watcher for the IO::AIO module and store it in
		948	C<$WATCHER>. Only do so after the event loop is initialised, though.
		949
		950	our WATCHER;
		951
		952	my $guard = AnyEvent::post_detect {
		953	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		954	};
		955
		956	# the ||= is important in case post_detect immediately runs the block,
		957	# as to not clobber the newly-created watcher. assigning both watcher and
		958	# post_detect guard to the same variable has the advantage of users being
		959	# able to just C<undef $WATCHER> if the watcher causes them grief.
		960
		961	$WATCHER ||= $guard;
561		962
562	=item @AnyEvent::post_detect	963	=item @AnyEvent::post_detect
563		964
564	If there are any code references in this array (you can C<push> to it	965	If there are any code references in this array (you can C<push> to it
565	before or after loading AnyEvent), then they will called directly after	966	before or after loading AnyEvent), then they will called directly after
566	the event loop has been chosen.	967	the event loop has been chosen.
567		968
568	You should check C<$AnyEvent::MODEL> before adding to this array, though:	969	You should check C<$AnyEvent::MODEL> before adding to this array, though:
569	if it contains a true value then the event loop has already been detected,	970	if it is defined then the event loop has already been detected, and the
570	and the array will be ignored.	971	array will be ignored.
571		972
572	Best use C<AnyEvent::post_detect { BLOCK }> instead.	973	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		974	it, as it takes care of these details.
		975
		976	This variable is mainly useful for modules that can do something useful
		977	when AnyEvent is used and thus want to know when it is initialised, but do
		978	not need to even load it by default. This array provides the means to hook
		979	into AnyEvent passively, without loading it.
		980
		981	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		982	together, you could put this into Coro (this is the actual code used by
		983	Coro to accomplish this):
		984
		985	if (defined $AnyEvent::MODEL) {
		986	# AnyEvent already initialised, so load Coro::AnyEvent
		987	require Coro::AnyEvent;
		988	} else {
		989	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		990	# as soon as it is
		991	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		992	}
573		993
574	=back	994	=back
575		995
576	=head1 WHAT TO DO IN A MODULE	996	=head1 WHAT TO DO IN A MODULE
577		997
…		…
581	Be careful when you create watchers in the module body - AnyEvent will	1001	Be careful when you create watchers in the module body - AnyEvent will
582	decide which event module to use as soon as the first method is called, so	1002	decide which event module to use as soon as the first method is called, so
583	by calling AnyEvent in your module body you force the user of your module	1003	by calling AnyEvent in your module body you force the user of your module
584	to load the event module first.	1004	to load the event module first.
585		1005
586	Never call C<< ->wait >> on a condition variable unless you I<know> that	1006	Never call C<< ->recv >> on a condition variable unless you I<know> that
587	the C<< ->send >> method has been called on it already. This is	1007	the C<< ->send >> method has been called on it already. This is
588	because it will stall the whole program, and the whole point of using	1008	because it will stall the whole program, and the whole point of using
589	events is to stay interactive.	1009	events is to stay interactive.
590		1010
591	It is fine, however, to call C<< ->wait >> when the user of your module	1011	It is fine, however, to call C<< ->recv >> when the user of your module
592	requests it (i.e. if you create a http request object ad have a method	1012	requests it (i.e. if you create a http request object ad have a method
593	called C<results> that returns the results, it should call C<< ->wait >>	1013	called C<results> that returns the results, it should call C<< ->recv >>
594	freely, as the user of your module knows what she is doing. always).	1014	freely, as the user of your module knows what she is doing. always).
595		1015
596	=head1 WHAT TO DO IN THE MAIN PROGRAM	1016	=head1 WHAT TO DO IN THE MAIN PROGRAM
597		1017
598	There will always be a single main program - the only place that should	1018	There will always be a single main program - the only place that should
…		…
600		1020
601	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1021	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
602	do anything special (it does not need to be event-based) and let AnyEvent	1022	do anything special (it does not need to be event-based) and let AnyEvent
603	decide which implementation to chose if some module relies on it.	1023	decide which implementation to chose if some module relies on it.
604		1024
605	If the main program relies on a specific event model. For example, in	1025	If the main program relies on a specific event model - for example, in
606	Gtk2 programs you have to rely on the Glib module. You should load the	1026	Gtk2 programs you have to rely on the Glib module - you should load the
607	event module before loading AnyEvent or any module that uses it: generally	1027	event module before loading AnyEvent or any module that uses it: generally
608	speaking, you should load it as early as possible. The reason is that	1028	speaking, you should load it as early as possible. The reason is that
609	modules might create watchers when they are loaded, and AnyEvent will	1029	modules might create watchers when they are loaded, and AnyEvent will
610	decide on the event model to use as soon as it creates watchers, and it	1030	decide on the event model to use as soon as it creates watchers, and it
611	might chose the wrong one unless you load the correct one yourself.	1031	might chose the wrong one unless you load the correct one yourself.
612		1032
613	You can chose to use a rather inefficient pure-perl implementation by	1033	You can chose to use a pure-perl implementation by loading the
614	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1034	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
615	behaviour everywhere, but letting AnyEvent chose is generally better.	1035	everywhere, but letting AnyEvent chose the model is generally better.
		1036
		1037	=head2 MAINLOOP EMULATION
		1038
		1039	Sometimes (often for short test scripts, or even standalone programs who
		1040	only want to use AnyEvent), you do not want to run a specific event loop.
		1041
		1042	In that case, you can use a condition variable like this:
		1043
		1044	AnyEvent->condvar->recv;
		1045
		1046	This has the effect of entering the event loop and looping forever.
		1047
		1048	Note that usually your program has some exit condition, in which case
		1049	it is better to use the "traditional" approach of storing a condition
		1050	variable somewhere, waiting for it, and sending it when the program should
		1051	exit cleanly.
		1052
616		1053
617	=head1 OTHER MODULES	1054	=head1 OTHER MODULES
618		1055
619	The following is a non-exhaustive list of additional modules that use	1056	The following is a non-exhaustive list of additional modules that use
620	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1057	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
621	in the same program. Some of the modules come with AnyEvent, some are	1058	modules and other event loops in the same program. Some of the modules
622	available via CPAN.	1059	come with AnyEvent, most are available via CPAN.
623		1060
624	=over 4	1061	=over 4
625		1062
626	=item L<AnyEvent::Util>	1063	=item L<AnyEvent::Util>
627		1064
628	Contains various utility functions that replace often-used but blocking	1065	Contains various utility functions that replace often-used but blocking
629	functions such as C<inet_aton> by event-/callback-based versions.	1066	functions such as C<inet_aton> by event-/callback-based versions.
630		1067
		1068	=item L<AnyEvent::Socket>
		1069
		1070	Provides various utility functions for (internet protocol) sockets,
		1071	addresses and name resolution. Also functions to create non-blocking tcp
		1072	connections or tcp servers, with IPv6 and SRV record support and more.
		1073
631	=item L<AnyEvent::Handle>	1074	=item L<AnyEvent::Handle>
632		1075
633	Provide read and write buffers and manages watchers for reads and writes.	1076	Provide read and write buffers, manages watchers for reads and writes,
		1077	supports raw and formatted I/O, I/O queued and fully transparent and
		1078	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
634		1079
635	=item L<AnyEvent::Socket>	1080	=item L<AnyEvent::DNS>
636		1081
637	Provides a means to do non-blocking connects, accepts etc.	1082	Provides rich asynchronous DNS resolver capabilities.
		1083
		1084	=item L<AnyEvent::HTTP>
		1085
		1086	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1087	HTTP requests.
638		1088
639	=item L<AnyEvent::HTTPD>	1089	=item L<AnyEvent::HTTPD>
640		1090
641	Provides a simple web application server framework.	1091	Provides a simple web application server framework.
642		1092
643	=item L<AnyEvent::DNS>
644
645	Provides asynchronous DNS resolver capabilities, beyond what
646	L<AnyEvent::Util> offers.
647
648	=item L<AnyEvent::FastPing>	1093	=item L<AnyEvent::FastPing>
649		1094
650	The fastest ping in the west.	1095	The fastest ping in the west.
651		1096
		1097	=item L<AnyEvent::DBI>
		1098
		1099	Executes L<DBI> requests asynchronously in a proxy process.
		1100
		1101	=item L<AnyEvent::AIO>
		1102
		1103	Truly asynchronous I/O, should be in the toolbox of every event
		1104	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1105	together.
		1106
		1107	=item L<AnyEvent::BDB>
		1108
		1109	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1110	L<BDB> and AnyEvent together.
		1111
		1112	=item L<AnyEvent::GPSD>
		1113
		1114	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1115
652	=item L<Net::IRC3>	1116	=item L<AnyEvent::IRC>
653		1117
654	AnyEvent based IRC client module family.	1118	AnyEvent based IRC client module family (replacing the older Net::IRC3).
655		1119
656	=item L<Net::XMPP2>	1120	=item L<AnyEvent::XMPP>
657		1121
658	AnyEvent based XMPP (Jabber protocol) module family.	1122	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1123	Net::XMPP2>.
		1124
		1125	=item L<AnyEvent::IGS>
		1126
		1127	A non-blocking interface to the Internet Go Server protocol (used by
		1128	L<App::IGS>).
659		1129
660	=item L<Net::FCP>	1130	=item L<Net::FCP>
661		1131
662	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1132	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
663	of AnyEvent.	1133	of AnyEvent.
…		…
668		1138
669	=item L<Coro>	1139	=item L<Coro>
670		1140
671	Has special support for AnyEvent via L<Coro::AnyEvent>.	1141	Has special support for AnyEvent via L<Coro::AnyEvent>.
672		1142
673	=item L<IO::Lambda>
674
675	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
676
677	=item L<IO::AIO>
678
679	Truly asynchronous I/O, should be in the toolbox of every event
680	programmer. Can be trivially made to use AnyEvent.
681
682	=item L<BDB>
683
684	Truly asynchronous Berkeley DB access. Can be trivially made to use
685	AnyEvent.
686
687	=back	1143	=back
688		1144
689	=cut	1145	=cut
690		1146
691	package AnyEvent;	1147	package AnyEvent;
692		1148
693	no warnings;	1149	# basically a tuned-down version of common::sense
694	use strict;	1150	sub common_sense {
		1151	# from common:.sense 1.0
		1152	${^WARNING_BITS} = "\xfc\x3f\x33\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x00";
		1153	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1154	$^H |= 0x00000600;
		1155	}
695		1156
		1157	BEGIN { AnyEvent::common_sense }
		1158
696	use Carp;	1159	use Carp ();
697		1160
698	our $VERSION = '3.4';	1161	our $VERSION = '5.24';
699	our $MODEL;	1162	our $MODEL;
700		1163
701	our $AUTOLOAD;	1164	our $AUTOLOAD;
702	our @ISA;	1165	our @ISA;
703		1166
704	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
705
706	our @REGISTRY;	1167	our @REGISTRY;
707		1168
		1169	our $VERBOSE;
		1170
		1171	BEGIN {
		1172	eval "sub CYGWIN(){" . (($^O =~ /cygwin/i) *1) . "}";
		1173	eval "sub WIN32 (){" . (($^O =~ /mswin32/i)*1) . "}";
		1174	eval "sub TAINT (){" . (${^TAINT} *1) . "}";
		1175
		1176	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1177	if ${^TAINT};
		1178
		1179	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1180
		1181	}
		1182
		1183	our $MAX_SIGNAL_LATENCY = 10;
		1184
		1185	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1186
		1187	{
		1188	my $idx;
		1189	$PROTOCOL{$_} = ++$idx
		1190	for reverse split /\s*,\s*/,
		1191	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1192	}
		1193
708	my @models = (	1194	my @models = (
709	[EV:: => AnyEvent::Impl::EV::],	1195	[EV:: => AnyEvent::Impl::EV:: , 1],
		1196	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1197	# everything below here will not (normally) be autoprobed
		1198	# as the pureperl backend should work everywhere
		1199	# and is usually faster
710	[Event:: => AnyEvent::Impl::Event::],	1200	[Event:: => AnyEvent::Impl::Event::, 1],
		1201	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1202	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1203	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
711	[Tk:: => AnyEvent::Impl::Tk::],	1204	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1205	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1206	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
712	[Wx:: => AnyEvent::Impl::POE::],	1207	[Wx:: => AnyEvent::Impl::POE::],
713	[Prima:: => AnyEvent::Impl::POE::],	1208	[Prima:: => AnyEvent::Impl::POE::],
714	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1209	# IO::Async is just too broken - we would need workarounds for its
715	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1210	# byzantine signal and broken child handling, among others.
716	[Glib:: => AnyEvent::Impl::Glib::],	1211	# IO::Async is rather hard to detect, as it doesn't have any
717	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1212	# obvious default class.
718	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1213	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
719	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1214	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1215	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1216	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
720	);	1217	);
721		1218
722	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1219	our %method = map +($_ => 1),
		1220	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
723		1221
724	our @post_detect;	1222	our @post_detect;
725		1223
726	sub post_detect(&) {	1224	sub post_detect(&) {
727	my ($cb) = @_;	1225	my ($cb) = @_;
728		1226
729	if ($MODEL) {	1227	if ($MODEL) {
730	$cb->();	1228	$cb->();
731		1229
732	1	1230	undef
733	} else {	1231	} else {
734	push @post_detect, $cb;	1232	push @post_detect, $cb;
735		1233
736	defined wantarray	1234	defined wantarray
737	? bless \$cb, "AnyEvent::Util::Guard"	1235	? bless \$cb, "AnyEvent::Util::postdetect"
738	: ()	1236	: ()
739	}	1237	}
740	}	1238	}
741		1239
742	sub AnyEvent::Util::Guard::DESTROY {	1240	sub AnyEvent::Util::postdetect::DESTROY {
743	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1241	@post_detect = grep $_ != ${$_[0]}, @post_detect;
744	}	1242	}
745		1243
746	sub detect() {	1244	sub detect() {
747	unless ($MODEL) {	1245	unless ($MODEL) {
748	no strict 'refs';	1246	local $SIG{__DIE__};
749		1247
750	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1248	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
751	my $model = "AnyEvent::Impl::$1";	1249	my $model = "AnyEvent::Impl::$1";
752	if (eval "require $model") {	1250	if (eval "require $model") {
753	$MODEL = $model;	1251	$MODEL = $model;
754	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1252	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
755	} else {	1253	} else {
756	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1254	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
757	}	1255	}
758	}	1256	}
759		1257
760	# check for already loaded models	1258	# check for already loaded models
761	unless ($MODEL) {	1259	unless ($MODEL) {
762	for (@REGISTRY, @models) {	1260	for (@REGISTRY, @models) {
763	my ($package, $model) = @$_;	1261	my ($package, $model) = @$_;
764	if (${"$package\::VERSION"} > 0) {	1262	if (${"$package\::VERSION"} > 0) {
765	if (eval "require $model") {	1263	if (eval "require $model") {
766	$MODEL = $model;	1264	$MODEL = $model;
767	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1265	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
768	last;	1266	last;
769	}	1267	}
770	}	1268	}
771	}	1269	}
772		1270
773	unless ($MODEL) {	1271	unless ($MODEL) {
774	# try to load a model	1272	# try to autoload a model
775
776	for (@REGISTRY, @models) {	1273	for (@REGISTRY, @models) {
777	my ($package, $model) = @$_;	1274	my ($package, $model, $autoload) = @$_;
		1275	if (
		1276	$autoload
778	if (eval "require $package"	1277	and eval "require $package"
779	and ${"$package\::VERSION"} > 0	1278	and ${"$package\::VERSION"} > 0
780	and eval "require $model") {	1279	and eval "require $model"
		1280	) {
781	$MODEL = $model;	1281	$MODEL = $model;
782	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1282	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
783	last;	1283	last;
784	}	1284	}
785	}	1285	}
786		1286
787	$MODEL	1287	$MODEL
788	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1288	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
789	}	1289	}
790	}	1290	}
791		1291
		1292	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1293
792	unshift @ISA, $MODEL;	1294	unshift @ISA, $MODEL;
793	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1295
		1296	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
794		1297
795	(shift @post_detect)->() while @post_detect;	1298	(shift @post_detect)->() while @post_detect;
796	}	1299	}
797		1300
798	$MODEL	1301	$MODEL
…		…
800		1303
801	sub AUTOLOAD {	1304	sub AUTOLOAD {
802	(my $func = $AUTOLOAD) =~ s/.*://;	1305	(my $func = $AUTOLOAD) =~ s/.*://;
803		1306
804	$method{$func}	1307	$method{$func}
805	or croak "$func: not a valid method for AnyEvent objects";	1308	or Carp::croak "$func: not a valid method for AnyEvent objects";
806		1309
807	detect unless $MODEL;	1310	detect unless $MODEL;
808		1311
809	my $class = shift;	1312	my $class = shift;
810	$class->$func (@_);	1313	$class->$func (@_);
811	}	1314	}
812		1315
		1316	# utility function to dup a filehandle. this is used by many backends
		1317	# to support binding more than one watcher per filehandle (they usually
		1318	# allow only one watcher per fd, so we dup it to get a different one).
		1319	sub _dupfh($$;$$) {
		1320	my ($poll, $fh, $r, $w) = @_;
		1321
		1322	# cygwin requires the fh mode to be matching, unix doesn't
		1323	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1324
		1325	open my $fh2, $mode, $fh
		1326	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1327
		1328	# we assume CLOEXEC is already set by perl in all important cases
		1329
		1330	($fh2, $rw)
		1331	}
		1332
		1333	=head1 SIMPLIFIED AE API
		1334
		1335	Starting with version 5.0, AnyEvent officially supports a second, much
		1336	simpler, API that is designed to reduce the calling, typing and memory
		1337	overhead.
		1338
		1339	See the L<AE> manpage for details.
		1340
		1341	=cut
		1342
		1343	package AE;
		1344
		1345	our $VERSION = $AnyEvent::VERSION;
		1346
		1347	sub io($$$) {
		1348	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1349	}
		1350
		1351	sub timer($$$) {
		1352	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1353	}
		1354
		1355	sub signal($$) {
		1356	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1357	}
		1358
		1359	sub child($$) {
		1360	AnyEvent->child (pid => $_[0], cb => $_[1])
		1361	}
		1362
		1363	sub idle($) {
		1364	AnyEvent->idle (cb => $_[0])
		1365	}
		1366
		1367	sub cv(;&) {
		1368	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1369	}
		1370
		1371	sub now() {
		1372	AnyEvent->now
		1373	}
		1374
		1375	sub now_update() {
		1376	AnyEvent->now_update
		1377	}
		1378
		1379	sub time() {
		1380	AnyEvent->time
		1381	}
		1382
813	package AnyEvent::Base;	1383	package AnyEvent::Base;
814		1384
		1385	# default implementations for many methods
		1386
		1387	sub _time() {
		1388	# probe for availability of Time::HiRes
		1389	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1390	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1391	*_time = \&Time::HiRes::time;
		1392	# if (eval "use POSIX (); (POSIX::times())...
		1393	} else {
		1394	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1395	*_time = sub (){ time }; # epic fail
		1396	}
		1397
		1398	&_time
		1399	}
		1400
		1401	sub time { _time }
		1402	sub now { _time }
		1403	sub now_update { }
		1404
815	# default implementation for ->condvar, ->wait, ->broadcast	1405	# default implementation for ->condvar
816		1406
817	sub condvar {	1407	sub condvar {
818	bless \my $flag, "AnyEvent::Base::CondVar"	1408	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
819	}
820
821	sub AnyEvent::Base::CondVar::broadcast {
822	${$_[0]}++;
823	}
824
825	sub AnyEvent::Base::CondVar::wait {
826	AnyEvent->one_event while !${$_[0]};
827	}	1409	}
828		1410
829	# default implementation for ->signal	1411	# default implementation for ->signal
830		1412
831	our %SIG_CB;	1413	our $HAVE_ASYNC_INTERRUPT;
		1414
		1415	sub _have_async_interrupt() {
		1416	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1417	&& eval "use Async::Interrupt 1.02 (); 1")
		1418	unless defined $HAVE_ASYNC_INTERRUPT;
		1419
		1420	$HAVE_ASYNC_INTERRUPT
		1421	}
		1422
		1423	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1424	our (%SIG_ASY, %SIG_ASY_W);
		1425	our ($SIG_COUNT, $SIG_TW);
		1426
		1427	sub _signal_exec {
		1428	$HAVE_ASYNC_INTERRUPT
		1429	? $SIGPIPE_R->drain
		1430	: sysread $SIGPIPE_R, (my $dummy), 9;
		1431
		1432	while (%SIG_EV) {
		1433	for (keys %SIG_EV) {
		1434	delete $SIG_EV{$_};
		1435	$_->() for values %{ $SIG_CB{$_} || {} };
		1436	}
		1437	}
		1438	}
		1439
		1440	# install a dummy wakeup watcher to reduce signal catching latency
		1441	sub _sig_add() {
		1442	unless ($SIG_COUNT++) {
		1443	# try to align timer on a full-second boundary, if possible
		1444	my $NOW = AE::now;
		1445
		1446	$SIG_TW = AE::timer
		1447	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1448	$MAX_SIGNAL_LATENCY,
		1449	sub { } # just for the PERL_ASYNC_CHECK
		1450	;
		1451	}
		1452	}
		1453
		1454	sub _sig_del {
		1455	undef $SIG_TW
		1456	unless --$SIG_COUNT;
		1457	}
		1458
		1459	our $_sig_name_init; $_sig_name_init = sub {
		1460	eval q{ # poor man's autoloading
		1461	undef $_sig_name_init;
		1462
		1463	if (_have_async_interrupt) {
		1464	*sig2num = \&Async::Interrupt::sig2num;
		1465	*sig2name = \&Async::Interrupt::sig2name;
		1466	} else {
		1467	require Config;
		1468
		1469	my %signame2num;
		1470	@signame2num{ split ' ', $Config::Config{sig_name} }
		1471	= split ' ', $Config::Config{sig_num};
		1472
		1473	my @signum2name;
		1474	@signum2name[values %signame2num] = keys %signame2num;
		1475
		1476	*sig2num = sub($) {
		1477	$_[0] > 0 ? shift : $signame2num{+shift}
		1478	};
		1479	*sig2name = sub ($) {
		1480	$_[0] > 0 ? $signum2name[+shift] : shift
		1481	};
		1482	}
		1483	};
		1484	die if $@;
		1485	};
		1486
		1487	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1488	sub sig2name($) { &$_sig_name_init; &sig2name }
832		1489
833	sub signal {	1490	sub signal {
		1491	eval q{ # poor man's autoloading {}
		1492	# probe for availability of Async::Interrupt
		1493	if (_have_async_interrupt) {
		1494	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1495
		1496	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1497	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1498
		1499	} else {
		1500	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1501
		1502	require Fcntl;
		1503
		1504	if (AnyEvent::WIN32) {
		1505	require AnyEvent::Util;
		1506
		1507	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1508	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1509	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1510	} else {
		1511	pipe $SIGPIPE_R, $SIGPIPE_W;
		1512	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1513	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1514
		1515	# not strictly required, as $^F is normally 2, but let's make sure...
		1516	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1517	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1518	}
		1519
		1520	$SIGPIPE_R
		1521	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1522
		1523	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1524	}
		1525
		1526	*signal = sub {
834	my (undef, %arg) = @_;	1527	my (undef, %arg) = @_;
835		1528
836	my $signal = uc $arg{signal}	1529	my $signal = uc $arg{signal}
837	or Carp::croak "required option 'signal' is missing";	1530	or Carp::croak "required option 'signal' is missing";
838		1531
		1532	if ($HAVE_ASYNC_INTERRUPT) {
		1533	# async::interrupt
		1534
		1535	$signal = sig2num $signal;
839	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1536	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1537
		1538	$SIG_ASY{$signal} ||= new Async::Interrupt
		1539	cb => sub { undef $SIG_EV{$signal} },
		1540	signal => $signal,
		1541	pipe => [$SIGPIPE_R->filenos],
		1542	pipe_autodrain => 0,
		1543	;
		1544
		1545	} else {
		1546	# pure perl
		1547
		1548	# AE::Util has been loaded in signal
		1549	$signal = sig2name $signal;
		1550	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1551
840	$SIG{$signal} ||= sub {	1552	$SIG{$signal} ||= sub {
841	$_->() for values %{ $SIG_CB{$signal} || {} };	1553	local $!;
		1554	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1555	undef $SIG_EV{$signal};
		1556	};
		1557
		1558	# can't do signal processing without introducing races in pure perl,
		1559	# so limit the signal latency.
		1560	_sig_add;
		1561	}
		1562
		1563	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1564	};
		1565
		1566	*AnyEvent::Base::signal::DESTROY = sub {
		1567	my ($signal, $cb) = @{$_[0]};
		1568
		1569	_sig_del;
		1570
		1571	delete $SIG_CB{$signal}{$cb};
		1572
		1573	$HAVE_ASYNC_INTERRUPT
		1574	? delete $SIG_ASY{$signal}
		1575	: # delete doesn't work with older perls - they then
		1576	# print weird messages, or just unconditionally exit
		1577	# instead of getting the default action.
		1578	undef $SIG{$signal}
		1579	unless keys %{ $SIG_CB{$signal} };
		1580	};
842	};	1581	};
843		1582	die if $@;
844	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1583	&signal
845	}
846
847	sub AnyEvent::Base::Signal::DESTROY {
848	my ($signal, $cb) = @{$_[0]};
849
850	delete $SIG_CB{$signal}{$cb};
851
852	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
853	}	1584	}
854		1585
855	# default implementation for ->child	1586	# default implementation for ->child
856		1587
857	our %PID_CB;	1588	our %PID_CB;
858	our $CHLD_W;	1589	our $CHLD_W;
859	our $CHLD_DELAY_W;	1590	our $CHLD_DELAY_W;
860	our $PID_IDLE;
861	our $WNOHANG;	1591	our $WNOHANG;
862		1592
863	sub _child_wait {	1593	sub _emit_childstatus($$) {
864	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1594	my (undef, $rpid, $rstatus) = @_;
		1595
		1596	$_->($rpid, $rstatus)
865	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1597	for values %{ $PID_CB{$rpid} || {} },
866	(values %{ $PID_CB{0} || {} });	1598	values %{ $PID_CB{0} || {} };
867	}
868
869	undef $PID_IDLE;
870	}	1599	}
871		1600
872	sub _sigchld {	1601	sub _sigchld {
873	# make sure we deliver these changes "synchronous" with the event loop.	1602	my $pid;
874	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1603
875	undef $CHLD_DELAY_W;	1604	AnyEvent->_emit_childstatus ($pid, $?)
876	&_child_wait;	1605	while ($pid = waitpid -1, $WNOHANG) > 0;
877	});
878	}	1606	}
879		1607
880	sub child {	1608	sub child {
881	my (undef, %arg) = @_;	1609	my (undef, %arg) = @_;
882		1610
883	defined (my $pid = $arg{pid} + 0)	1611	defined (my $pid = $arg{pid} + 0)
884	or Carp::croak "required option 'pid' is missing";	1612	or Carp::croak "required option 'pid' is missing";
885		1613
886	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1614	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
887		1615
888	unless ($WNOHANG) {	1616	# WNOHANG is almost cetrainly 1 everywhere
889	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1617	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
890	}	1618	? 1
		1619	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
891		1620
892	unless ($CHLD_W) {	1621	unless ($CHLD_W) {
893	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1622	$CHLD_W = AE::signal CHLD => \&_sigchld;
894	# child could be a zombie already, so make at least one round	1623	# child could be a zombie already, so make at least one round
895	&_sigchld;	1624	&_sigchld;
896	}	1625	}
897		1626
898	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1627	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
899	}	1628	}
900		1629
901	sub AnyEvent::Base::Child::DESTROY {	1630	sub AnyEvent::Base::child::DESTROY {
902	my ($pid, $cb) = @{$_[0]};	1631	my ($pid, $cb) = @{$_[0]};
903		1632
904	delete $PID_CB{$pid}{$cb};	1633	delete $PID_CB{$pid}{$cb};
905	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1634	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
906		1635
907	undef $CHLD_W unless keys %PID_CB;	1636	undef $CHLD_W unless keys %PID_CB;
908	}	1637	}
		1638
		1639	# idle emulation is done by simply using a timer, regardless
		1640	# of whether the process is idle or not, and not letting
		1641	# the callback use more than 50% of the time.
		1642	sub idle {
		1643	my (undef, %arg) = @_;
		1644
		1645	my ($cb, $w, $rcb) = $arg{cb};
		1646
		1647	$rcb = sub {
		1648	if ($cb) {
		1649	$w = _time;
		1650	&$cb;
		1651	$w = _time - $w;
		1652
		1653	# never use more then 50% of the time for the idle watcher,
		1654	# within some limits
		1655	$w = 0.0001 if $w < 0.0001;
		1656	$w = 5 if $w > 5;
		1657
		1658	$w = AE::timer $w, 0, $rcb;
		1659	} else {
		1660	# clean up...
		1661	undef $w;
		1662	undef $rcb;
		1663	}
		1664	};
		1665
		1666	$w = AE::timer 0.05, 0, $rcb;
		1667
		1668	bless \\$cb, "AnyEvent::Base::idle"
		1669	}
		1670
		1671	sub AnyEvent::Base::idle::DESTROY {
		1672	undef $${$_[0]};
		1673	}
		1674
		1675	package AnyEvent::CondVar;
		1676
		1677	our @ISA = AnyEvent::CondVar::Base::;
		1678
		1679	package AnyEvent::CondVar::Base;
		1680
		1681	#use overload
		1682	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1683	# fallback => 1;
		1684
		1685	# save 300+ kilobytes by dirtily hardcoding overloading
		1686	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1687	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1688	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1689	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1690
		1691	our $WAITING;
		1692
		1693	sub _send {
		1694	# nop
		1695	}
		1696
		1697	sub send {
		1698	my $cv = shift;
		1699	$cv->{_ae_sent} = [@_];
		1700	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1701	$cv->_send;
		1702	}
		1703
		1704	sub croak {
		1705	$_[0]{_ae_croak} = $_[1];
		1706	$_[0]->send;
		1707	}
		1708
		1709	sub ready {
		1710	$_[0]{_ae_sent}
		1711	}
		1712
		1713	sub _wait {
		1714	$WAITING
		1715	and !$_[0]{_ae_sent}
		1716	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1717
		1718	local $WAITING = 1;
		1719	AnyEvent->one_event while !$_[0]{_ae_sent};
		1720	}
		1721
		1722	sub recv {
		1723	$_[0]->_wait;
		1724
		1725	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1726	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1727	}
		1728
		1729	sub cb {
		1730	my $cv = shift;
		1731
		1732	@_
		1733	and $cv->{_ae_cb} = shift
		1734	and $cv->{_ae_sent}
		1735	and (delete $cv->{_ae_cb})->($cv);
		1736
		1737	$cv->{_ae_cb}
		1738	}
		1739
		1740	sub begin {
		1741	++$_[0]{_ae_counter};
		1742	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1743	}
		1744
		1745	sub end {
		1746	return if --$_[0]{_ae_counter};
		1747	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1748	}
		1749
		1750	# undocumented/compatibility with pre-3.4
		1751	*broadcast = \&send;
		1752	*wait = \&_wait;
		1753
		1754	=head1 ERROR AND EXCEPTION HANDLING
		1755
		1756	In general, AnyEvent does not do any error handling - it relies on the
		1757	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1758	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1759	checking of all AnyEvent methods, however, which is highly useful during
		1760	development.
		1761
		1762	As for exception handling (i.e. runtime errors and exceptions thrown while
		1763	executing a callback), this is not only highly event-loop specific, but
		1764	also not in any way wrapped by this module, as this is the job of the main
		1765	program.
		1766
		1767	The pure perl event loop simply re-throws the exception (usually
		1768	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1769	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1770	so on.
		1771
		1772	=head1 ENVIRONMENT VARIABLES
		1773
		1774	The following environment variables are used by this module or its
		1775	submodules.
		1776
		1777	Note that AnyEvent will remove I<all> environment variables starting with
		1778	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1779	enabled.
		1780
		1781	=over 4
		1782
		1783	=item C<PERL_ANYEVENT_VERBOSE>
		1784
		1785	By default, AnyEvent will be completely silent except in fatal
		1786	conditions. You can set this environment variable to make AnyEvent more
		1787	talkative.
		1788
		1789	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1790	conditions, such as not being able to load the event model specified by
		1791	C<PERL_ANYEVENT_MODEL>.
		1792
		1793	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1794	model it chooses.
		1795
		1796	When set to C<8> or higher, then AnyEvent will report extra information on
		1797	which optional modules it loads and how it implements certain features.
		1798
		1799	=item C<PERL_ANYEVENT_STRICT>
		1800
		1801	AnyEvent does not do much argument checking by default, as thorough
		1802	argument checking is very costly. Setting this variable to a true value
		1803	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1804	check the arguments passed to most method calls. If it finds any problems,
		1805	it will croak.
		1806
		1807	In other words, enables "strict" mode.
		1808
		1809	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1810	>>, it is definitely recommended to keep it off in production. Keeping
		1811	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1812	can be very useful, however.
		1813
		1814	=item C<PERL_ANYEVENT_MODEL>
		1815
		1816	This can be used to specify the event model to be used by AnyEvent, before
		1817	auto detection and -probing kicks in. It must be a string consisting
		1818	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1819	and the resulting module name is loaded and if the load was successful,
		1820	used as event model. If it fails to load AnyEvent will proceed with
		1821	auto detection and -probing.
		1822
		1823	This functionality might change in future versions.
		1824
		1825	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1826	could start your program like this:
		1827
		1828	PERL_ANYEVENT_MODEL=Perl perl ...
		1829
		1830	=item C<PERL_ANYEVENT_PROTOCOLS>
		1831
		1832	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1833	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1834	of auto probing).
		1835
		1836	Must be set to a comma-separated list of protocols or address families,
		1837	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1838	used, and preference will be given to protocols mentioned earlier in the
		1839	list.
		1840
		1841	This variable can effectively be used for denial-of-service attacks
		1842	against local programs (e.g. when setuid), although the impact is likely
		1843	small, as the program has to handle conenction and other failures anyways.
		1844
		1845	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1846	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1847	- only support IPv4, never try to resolve or contact IPv6
		1848	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1849	IPv6, but prefer IPv6 over IPv4.
		1850
		1851	=item C<PERL_ANYEVENT_EDNS0>
		1852
		1853	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1854	for DNS. This extension is generally useful to reduce DNS traffic, but
		1855	some (broken) firewalls drop such DNS packets, which is why it is off by
		1856	default.
		1857
		1858	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1859	EDNS0 in its DNS requests.
		1860
		1861	=item C<PERL_ANYEVENT_MAX_FORKS>
		1862
		1863	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1864	will create in parallel.
		1865
		1866	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1867
		1868	The default value for the C<max_outstanding> parameter for the default DNS
		1869	resolver - this is the maximum number of parallel DNS requests that are
		1870	sent to the DNS server.
		1871
		1872	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1873
		1874	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1875	configuration) in the default resolver. When set to the empty string, no
		1876	default config will be used.
		1877
		1878	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1879
		1880	When neither C<ca_file> nor C<ca_path> was specified during
		1881	L<AnyEvent::TLS> context creation, and either of these environment
		1882	variables exist, they will be used to specify CA certificate locations
		1883	instead of a system-dependent default.
		1884
		1885	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1886
		1887	When these are set to C<1>, then the respective modules are not
		1888	loaded. Mostly good for testing AnyEvent itself.
		1889
		1890	=back
909		1891
910	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1892	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
911		1893
912	This is an advanced topic that you do not normally need to use AnyEvent in	1894	This is an advanced topic that you do not normally need to use AnyEvent in
913	a module. This section is only of use to event loop authors who want to	1895	a module. This section is only of use to event loop authors who want to
…		…
947		1929
948	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1930	I<rxvt-unicode> also cheats a bit by not providing blocking access to
949	condition variables: code blocking while waiting for a condition will	1931	condition variables: code blocking while waiting for a condition will
950	C<die>. This still works with most modules/usages, and blocking calls must	1932	C<die>. This still works with most modules/usages, and blocking calls must
951	not be done in an interactive application, so it makes sense.	1933	not be done in an interactive application, so it makes sense.
952
953	=head1 ENVIRONMENT VARIABLES
954
955	The following environment variables are used by this module:
956
957	=over 4
958
959	=item C<PERL_ANYEVENT_VERBOSE>
960
961	By default, AnyEvent will be completely silent except in fatal
962	conditions. You can set this environment variable to make AnyEvent more
963	talkative.
964
965	When set to C<1> or higher, causes AnyEvent to warn about unexpected
966	conditions, such as not being able to load the event model specified by
967	C<PERL_ANYEVENT_MODEL>.
968
969	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
970	model it chooses.
971
972	=item C<PERL_ANYEVENT_MODEL>
973
974	This can be used to specify the event model to be used by AnyEvent, before
975	autodetection and -probing kicks in. It must be a string consisting
976	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
977	and the resulting module name is loaded and if the load was successful,
978	used as event model. If it fails to load AnyEvent will proceed with
979	autodetection and -probing.
980
981	This functionality might change in future versions.
982
983	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
984	could start your program like this:
985
986	PERL_ANYEVENT_MODEL=Perl perl ...
987
988	=back
989		1934
990	=head1 EXAMPLE PROGRAM	1935	=head1 EXAMPLE PROGRAM
991		1936
992	The following program uses an I/O watcher to read data from STDIN, a timer	1937	The following program uses an I/O watcher to read data from STDIN, a timer
993	to display a message once per second, and a condition variable to quit the	1938	to display a message once per second, and a condition variable to quit the
…		…
1002	poll => 'r',	1947	poll => 'r',
1003	cb => sub {	1948	cb => sub {
1004	warn "io event <$_[0]>\n"; # will always output <r>	1949	warn "io event <$_[0]>\n"; # will always output <r>
1005	chomp (my $input = <STDIN>); # read a line	1950	chomp (my $input = <STDIN>); # read a line
1006	warn "read: $input\n"; # output what has been read	1951	warn "read: $input\n"; # output what has been read
1007	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1952	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1008	},	1953	},
1009	);	1954	);
1010		1955
1011	my $time_watcher; # can only be used once
1012
1013	sub new_timer {
1014	$timer = AnyEvent->timer (after => 1, cb => sub {	1956	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1015	warn "timeout\n"; # print 'timeout' about every second	1957	warn "timeout\n"; # print 'timeout' at most every second
1016	&new_timer; # and restart the time
1017	});	1958	});
1018	}
1019		1959
1020	new_timer; # create first timer
1021
1022	$cv->wait; # wait until user enters /^q/i	1960	$cv->recv; # wait until user enters /^q/i
1023		1961
1024	=head1 REAL-WORLD EXAMPLE	1962	=head1 REAL-WORLD EXAMPLE
1025		1963
1026	Consider the L<Net::FCP> module. It features (among others) the following	1964	Consider the L<Net::FCP> module. It features (among others) the following
1027	API calls, which are to freenet what HTTP GET requests are to http:	1965	API calls, which are to freenet what HTTP GET requests are to http:
…		…
1077	syswrite $txn->{fh}, $txn->{request}	2015	syswrite $txn->{fh}, $txn->{request}
1078	or die "connection or write error";	2016	or die "connection or write error";
1079	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2017	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1080		2018
1081	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2019	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1082	result and signals any possible waiters that the request ahs finished:	2020	result and signals any possible waiters that the request has finished:
1083		2021
1084	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2022	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1085		2023
1086	if (end-of-file or data complete) {	2024	if (end-of-file or data complete) {
1087	$txn->{result} = $txn->{buf};	2025	$txn->{result} = $txn->{buf};
1088	$txn->{finished}->broadcast;	2026	$txn->{finished}->send;
1089	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2027	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
1090	}	2028	}
1091		2029
1092	The C<result> method, finally, just waits for the finished signal (if the	2030	The C<result> method, finally, just waits for the finished signal (if the
1093	request was already finished, it doesn't wait, of course, and returns the	2031	request was already finished, it doesn't wait, of course, and returns the
1094	data:	2032	data:
1095		2033
1096	$txn->{finished}->wait;	2034	$txn->{finished}->recv;
1097	return $txn->{result};	2035	return $txn->{result};
1098		2036
1099	The actual code goes further and collects all errors (C<die>s, exceptions)	2037	The actual code goes further and collects all errors (C<die>s, exceptions)
1100	that occured during request processing. The C<result> method detects	2038	that occurred during request processing. The C<result> method detects
1101	whether an exception as thrown (it is stored inside the $txn object)	2039	whether an exception as thrown (it is stored inside the $txn object)
1102	and just throws the exception, which means connection errors and other	2040	and just throws the exception, which means connection errors and other
1103	problems get reported tot he code that tries to use the result, not in a	2041	problems get reported tot he code that tries to use the result, not in a
1104	random callback.	2042	random callback.
1105		2043
…		…
1136		2074
1137	my $quit = AnyEvent->condvar;	2075	my $quit = AnyEvent->condvar;
1138		2076
1139	$fcp->txn_client_get ($url)->cb (sub {	2077	$fcp->txn_client_get ($url)->cb (sub {
1140	...	2078	...
1141	$quit->broadcast;	2079	$quit->send;
1142	});	2080	});
1143		2081
1144	$quit->wait;	2082	$quit->recv;
1145		2083
1146		2084
1147	=head1 BENCHMARKS	2085	=head1 BENCHMARKS
1148		2086
1149	To give you an idea of the performance and overheads that AnyEvent adds	2087	To give you an idea of the performance and overheads that AnyEvent adds
…		…
1151	of various event loops I prepared some benchmarks.	2089	of various event loops I prepared some benchmarks.
1152		2090
1153	=head2 BENCHMARKING ANYEVENT OVERHEAD	2091	=head2 BENCHMARKING ANYEVENT OVERHEAD
1154		2092
1155	Here is a benchmark of various supported event models used natively and	2093	Here is a benchmark of various supported event models used natively and
1156	through anyevent. The benchmark creates a lot of timers (with a zero	2094	through AnyEvent. The benchmark creates a lot of timers (with a zero
1157	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2095	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1158	which it is), lets them fire exactly once and destroys them again.	2096	which it is), lets them fire exactly once and destroys them again.
1159		2097
1160	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2098	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1161	distribution.	2099	distribution. It uses the L<AE> interface, which makes a real difference
		2100	for the EV and Perl backends only.
1162		2101
1163	=head3 Explanation of the columns	2102	=head3 Explanation of the columns
1164		2103
1165	I<watcher> is the number of event watchers created/destroyed. Since	2104	I<watcher> is the number of event watchers created/destroyed. Since
1166	different event models feature vastly different performances, each event	2105	different event models feature vastly different performances, each event
…		…
1178	all watchers, to avoid adding memory overhead. That means closure creation	2117	all watchers, to avoid adding memory overhead. That means closure creation
1179	and memory usage is not included in the figures.	2118	and memory usage is not included in the figures.
1180		2119
1181	I<invoke> is the time, in microseconds, used to invoke a simple	2120	I<invoke> is the time, in microseconds, used to invoke a simple
1182	callback. The callback simply counts down a Perl variable and after it was	2121	callback. The callback simply counts down a Perl variable and after it was
1183	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2122	invoked "watcher" times, it would C<< ->send >> a condvar once to
1184	signal the end of this phase.	2123	signal the end of this phase.
1185		2124
1186	I<destroy> is the time, in microseconds, that it takes to destroy a single	2125	I<destroy> is the time, in microseconds, that it takes to destroy a single
1187	watcher.	2126	watcher.
1188		2127
1189	=head3 Results	2128	=head3 Results
1190		2129
1191	name watchers bytes create invoke destroy comment	2130	name watchers bytes create invoke destroy comment
1192	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2131	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1193	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2132	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1194	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2133	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1195	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2134	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1196	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2135	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1197	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2136	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2137	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2138	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1198	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2139	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1199	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2140	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1200	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2141	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1201	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2142	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1202		2143
1203	=head3 Discussion	2144	=head3 Discussion
1204		2145
1205	The benchmark does I<not> measure scalability of the event loop very	2146	The benchmark does I<not> measure scalability of the event loop very
1206	well. For example, a select-based event loop (such as the pure perl one)	2147	well. For example, a select-based event loop (such as the pure perl one)
…		…
1218	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2159	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1219	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2160	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1220	cycles with POE.	2161	cycles with POE.
1221		2162
1222	C<EV> is the sole leader regarding speed and memory use, which are both	2163	C<EV> is the sole leader regarding speed and memory use, which are both
1223	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2164	maximal/minimal, respectively. When using the L<AE> API there is zero
		2165	overhead (when going through the AnyEvent API create is about 5-6 times
		2166	slower, with other times being equal, so still uses far less memory than
1224	far less memory than any other event loop and is still faster than Event	2167	any other event loop and is still faster than Event natively).
1225	natively.
1226		2168
1227	The pure perl implementation is hit in a few sweet spots (both the	2169	The pure perl implementation is hit in a few sweet spots (both the
1228	constant timeout and the use of a single fd hit optimisations in the perl	2170	constant timeout and the use of a single fd hit optimisations in the perl
1229	interpreter and the backend itself). Nevertheless this shows that it	2171	interpreter and the backend itself). Nevertheless this shows that it
1230	adds very little overhead in itself. Like any select-based backend its	2172	adds very little overhead in itself. Like any select-based backend its
1231	performance becomes really bad with lots of file descriptors (and few of	2173	performance becomes really bad with lots of file descriptors (and few of
1232	them active), of course, but this was not subject of this benchmark.	2174	them active), of course, but this was not subject of this benchmark.
1233		2175
1234	The C<Event> module has a relatively high setup and callback invocation	2176	The C<Event> module has a relatively high setup and callback invocation
1235	cost, but overall scores in on the third place.	2177	cost, but overall scores in on the third place.
		2178
		2179	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2180	when using its pure perl backend.
1236		2181
1237	C<Glib>'s memory usage is quite a bit higher, but it features a	2182	C<Glib>'s memory usage is quite a bit higher, but it features a
1238	faster callback invocation and overall ends up in the same class as	2183	faster callback invocation and overall ends up in the same class as
1239	C<Event>. However, Glib scales extremely badly, doubling the number of	2184	C<Event>. However, Glib scales extremely badly, doubling the number of
1240	watchers increases the processing time by more than a factor of four,	2185	watchers increases the processing time by more than a factor of four,
…		…
1284		2229
1285	=back	2230	=back
1286		2231
1287	=head2 BENCHMARKING THE LARGE SERVER CASE	2232	=head2 BENCHMARKING THE LARGE SERVER CASE
1288		2233
1289	This benchmark atcually benchmarks the event loop itself. It works by	2234	This benchmark actually benchmarks the event loop itself. It works by
1290	creating a number of "servers": each server consists of a socketpair, a	2235	creating a number of "servers": each server consists of a socket pair, a
1291	timeout watcher that gets reset on activity (but never fires), and an I/O	2236	timeout watcher that gets reset on activity (but never fires), and an I/O
1292	watcher waiting for input on one side of the socket. Each time the socket	2237	watcher waiting for input on one side of the socket. Each time the socket
1293	watcher reads a byte it will write that byte to a random other "server".	2238	watcher reads a byte it will write that byte to a random other "server".
1294		2239
1295	The effect is that there will be a lot of I/O watchers, only part of which	2240	The effect is that there will be a lot of I/O watchers, only part of which
1296	are active at any one point (so there is a constant number of active	2241	are active at any one point (so there is a constant number of active
1297	fds for each loop iterstaion, but which fds these are is random). The	2242	fds for each loop iteration, but which fds these are is random). The
1298	timeout is reset each time something is read because that reflects how	2243	timeout is reset each time something is read because that reflects how
1299	most timeouts work (and puts extra pressure on the event loops).	2244	most timeouts work (and puts extra pressure on the event loops).
1300		2245
1301	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2246	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1302	(1%) are active. This mirrors the activity of large servers with many	2247	(1%) are active. This mirrors the activity of large servers with many
1303	connections, most of which are idle at any one point in time.	2248	connections, most of which are idle at any one point in time.
1304		2249
1305	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2250	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1306	distribution.	2251	distribution. It uses the L<AE> interface, which makes a real difference
		2252	for the EV and Perl backends only.
1307		2253
1308	=head3 Explanation of the columns	2254	=head3 Explanation of the columns
1309		2255
1310	I<sockets> is the number of sockets, and twice the number of "servers" (as	2256	I<sockets> is the number of sockets, and twice the number of "servers" (as
1311	each server has a read and write socket end).	2257	each server has a read and write socket end).
1312		2258
1313	I<create> is the time it takes to create a socketpair (which is	2259	I<create> is the time it takes to create a socket pair (which is
1314	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2260	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1315		2261
1316	I<request>, the most important value, is the time it takes to handle a	2262	I<request>, the most important value, is the time it takes to handle a
1317	single "request", that is, reading the token from the pipe and forwarding	2263	single "request", that is, reading the token from the pipe and forwarding
1318	it to another server. This includes deleting the old timeout and creating	2264	it to another server. This includes deleting the old timeout and creating
1319	a new one that moves the timeout into the future.	2265	a new one that moves the timeout into the future.
1320		2266
1321	=head3 Results	2267	=head3 Results
1322		2268
1323	name sockets create request	2269	name sockets create request
1324	EV 20000 69.01 11.16	2270	EV 20000 62.66 7.99
1325	Perl 20000 73.32 35.87	2271	Perl 20000 68.32 32.64
1326	Event 20000 212.62 257.32	2272	IOAsync 20000 174.06 101.15 epoll
1327	Glib 20000 651.16 1896.30	2273	IOAsync 20000 174.67 610.84 poll
		2274	Event 20000 202.69 242.91
		2275	Glib 20000 557.01 1689.52
1328	POE 20000 349.67 12317.24 uses POE::Loop::Event	2276	POE 20000 341.54 12086.32 uses POE::Loop::Event
1329		2277
1330	=head3 Discussion	2278	=head3 Discussion
1331		2279
1332	This benchmark I<does> measure scalability and overall performance of the	2280	This benchmark I<does> measure scalability and overall performance of the
1333	particular event loop.	2281	particular event loop.
…		…
1335	EV is again fastest. Since it is using epoll on my system, the setup time	2283	EV is again fastest. Since it is using epoll on my system, the setup time
1336	is relatively high, though.	2284	is relatively high, though.
1337		2285
1338	Perl surprisingly comes second. It is much faster than the C-based event	2286	Perl surprisingly comes second. It is much faster than the C-based event
1339	loops Event and Glib.	2287	loops Event and Glib.
		2288
		2289	IO::Async performs very well when using its epoll backend, and still quite
		2290	good compared to Glib when using its pure perl backend.
1340		2291
1341	Event suffers from high setup time as well (look at its code and you will	2292	Event suffers from high setup time as well (look at its code and you will
1342	understand why). Callback invocation also has a high overhead compared to	2293	understand why). Callback invocation also has a high overhead compared to
1343	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2294	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1344	uses select or poll in basically all documented configurations.	2295	uses select or poll in basically all documented configurations.
…		…
1391	speed most when you have lots of watchers, not when you only have a few of	2342	speed most when you have lots of watchers, not when you only have a few of
1392	them).	2343	them).
1393		2344
1394	EV is again fastest.	2345	EV is again fastest.
1395		2346
1396	Perl again comes second. It is noticably faster than the C-based event	2347	Perl again comes second. It is noticeably faster than the C-based event
1397	loops Event and Glib, although the difference is too small to really	2348	loops Event and Glib, although the difference is too small to really
1398	matter.	2349	matter.
1399		2350
1400	POE also performs much better in this case, but is is still far behind the	2351	POE also performs much better in this case, but is is still far behind the
1401	others.	2352	others.
…		…
1407	=item * C-based event loops perform very well with small number of	2358	=item * C-based event loops perform very well with small number of
1408	watchers, as the management overhead dominates.	2359	watchers, as the management overhead dominates.
1409		2360
1410	=back	2361	=back
1411		2362
		2363	=head2 THE IO::Lambda BENCHMARK
		2364
		2365	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2366	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2367	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2368	shouldn't come as a surprise to anybody). As such, the benchmark is
		2369	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2370	very optimal. But how would AnyEvent compare when used without the extra
		2371	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2372
		2373	The benchmark itself creates an echo-server, and then, for 500 times,
		2374	connects to the echo server, sends a line, waits for the reply, and then
		2375	creates the next connection. This is a rather bad benchmark, as it doesn't
		2376	test the efficiency of the framework or much non-blocking I/O, but it is a
		2377	benchmark nevertheless.
		2378
		2379	name runtime
		2380	Lambda/select 0.330 sec
		2381	+ optimized 0.122 sec
		2382	Lambda/AnyEvent 0.327 sec
		2383	+ optimized 0.138 sec
		2384	Raw sockets/select 0.077 sec
		2385	POE/select, components 0.662 sec
		2386	POE/select, raw sockets 0.226 sec
		2387	POE/select, optimized 0.404 sec
		2388
		2389	AnyEvent/select/nb 0.085 sec
		2390	AnyEvent/EV/nb 0.068 sec
		2391	+state machine 0.134 sec
		2392
		2393	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2394	benchmarks actually make blocking connects and use 100% blocking I/O,
		2395	defeating the purpose of an event-based solution. All of the newly
		2396	written AnyEvent benchmarks use 100% non-blocking connects (using
		2397	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2398	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2399	generally require a lot more bookkeeping and event handling than blocking
		2400	connects (which involve a single syscall only).
		2401
		2402	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2403	offers similar expressive power as POE and IO::Lambda, using conventional
		2404	Perl syntax. This means that both the echo server and the client are 100%
		2405	non-blocking, further placing it at a disadvantage.
		2406
		2407	As you can see, the AnyEvent + EV combination even beats the
		2408	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2409	backend easily beats IO::Lambda and POE.
		2410
		2411	And even the 100% non-blocking version written using the high-level (and
		2412	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2413	higher level ("unoptimised") abstractions by a large margin, even though
		2414	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2415
		2416	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2417	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2418	part of the IO::Lambda distribution and were used without any changes.
		2419
		2420
		2421	=head1 SIGNALS
		2422
		2423	AnyEvent currently installs handlers for these signals:
		2424
		2425	=over 4
		2426
		2427	=item SIGCHLD
		2428
		2429	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2430	emulation for event loops that do not support them natively. Also, some
		2431	event loops install a similar handler.
		2432
		2433	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2434	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2435
		2436	=item SIGPIPE
		2437
		2438	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2439	when AnyEvent gets loaded.
		2440
		2441	The rationale for this is that AnyEvent users usually do not really depend
		2442	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2443	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2444	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2445	some random socket.
		2446
		2447	The rationale for installing a no-op handler as opposed to ignoring it is
		2448	that this way, the handler will be restored to defaults on exec.
		2449
		2450	Feel free to install your own handler, or reset it to defaults.
		2451
		2452	=back
		2453
		2454	=cut
		2455
		2456	undef $SIG{CHLD}
		2457	if $SIG{CHLD} eq 'IGNORE';
		2458
		2459	$SIG{PIPE} = sub { }
		2460	unless defined $SIG{PIPE};
		2461
		2462	=head1 RECOMMENDED/OPTIONAL MODULES
		2463
		2464	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2465	it's built-in modules) are required to use it.
		2466
		2467	That does not mean that AnyEvent won't take advantage of some additional
		2468	modules if they are installed.
		2469
		2470	This section explains which additional modules will be used, and how they
		2471	affect AnyEvent's operation.
		2472
		2473	=over 4
		2474
		2475	=item L<Async::Interrupt>
		2476
		2477	This slightly arcane module is used to implement fast signal handling: To
		2478	my knowledge, there is no way to do completely race-free and quick
		2479	signal handling in pure perl. To ensure that signals still get
		2480	delivered, AnyEvent will start an interval timer to wake up perl (and
		2481	catch the signals) with some delay (default is 10 seconds, look for
		2482	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2483
		2484	If this module is available, then it will be used to implement signal
		2485	catching, which means that signals will not be delayed, and the event loop
		2486	will not be interrupted regularly, which is more efficient (and good for
		2487	battery life on laptops).
		2488
		2489	This affects not just the pure-perl event loop, but also other event loops
		2490	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2491
		2492	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2493	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2494	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2495	does nothing for those backends.
		2496
		2497	=item L<EV>
		2498
		2499	This module isn't really "optional", as it is simply one of the backend
		2500	event loops that AnyEvent can use. However, it is simply the best event
		2501	loop available in terms of features, speed and stability: It supports
		2502	the AnyEvent API optimally, implements all the watcher types in XS, does
		2503	automatic timer adjustments even when no monotonic clock is available,
		2504	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2505	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2506	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2507
		2508	=item L<Guard>
		2509
		2510	The guard module, when used, will be used to implement
		2511	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2512	lot less memory), but otherwise doesn't affect guard operation much. It is
		2513	purely used for performance.
		2514
		2515	=item L<JSON> and L<JSON::XS>
		2516
		2517	One of these modules is required when you want to read or write JSON data
		2518	via L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2519	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2520
		2521	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2522	installed.
		2523
		2524	=item L<Net::SSLeay>
		2525
		2526	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2527	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2528	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2529
		2530	=item L<Time::HiRes>
		2531
		2532	This module is part of perl since release 5.008. It will be used when the
		2533	chosen event library does not come with a timing source on it's own. The
		2534	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2535	try to use a monotonic clock for timing stability.
		2536
		2537	=back
		2538
1412		2539
1413	=head1 FORK	2540	=head1 FORK
1414		2541
1415	Most event libraries are not fork-safe. The ones who are usually are	2542	Most event libraries are not fork-safe. The ones who are usually are
1416	because they rely on inefficient but fork-safe C<select> or C<poll>	2543	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1417	calls. Only L<EV> is fully fork-aware.	2544	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2545	are usually badly thought-out hacks that are incompatible with fork in
		2546	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2547	continue event-processing in both parent and child (or both, if you know
		2548	what you are doing).
		2549
		2550	This means that, in general, you cannot fork and do event processing in
		2551	the child if the event library was initialised before the fork (which
		2552	usually happens when the first AnyEvent watcher is created, or the library
		2553	is loaded).
1418		2554
1419	If you have to fork, you must either do so I<before> creating your first	2555	If you have to fork, you must either do so I<before> creating your first
1420	watcher OR you must not use AnyEvent at all in the child.	2556	watcher OR you must not use AnyEvent at all in the child OR you must do
		2557	something completely out of the scope of AnyEvent.
		2558
		2559	The problem of doing event processing in the parent I<and> the child
		2560	is much more complicated: even for backends that I<are> fork-aware or
		2561	fork-safe, their behaviour is not usually what you want: fork clones all
		2562	watchers, that means all timers, I/O watchers etc. are active in both
		2563	parent and child, which is almost never what you want. USing C<exec>
		2564	to start worker children from some kind of manage rprocess is usually
		2565	preferred, because it is much easier and cleaner, at the expense of having
		2566	to have another binary.
1421		2567
1422		2568
1423	=head1 SECURITY CONSIDERATIONS	2569	=head1 SECURITY CONSIDERATIONS
1424		2570
1425	AnyEvent can be forced to load any event model via	2571	AnyEvent can be forced to load any event model via
…		…
1430	specified in the variable.	2576	specified in the variable.
1431		2577
1432	You can make AnyEvent completely ignore this variable by deleting it	2578	You can make AnyEvent completely ignore this variable by deleting it
1433	before the first watcher gets created, e.g. with a C<BEGIN> block:	2579	before the first watcher gets created, e.g. with a C<BEGIN> block:
1434		2580
1435	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2581	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1436		2582
1437	use AnyEvent;	2583	use AnyEvent;
1438		2584
1439	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2585	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1440	be used to probe what backend is used and gain other information (which is	2586	be used to probe what backend is used and gain other information (which is
1441	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2587	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2588	$ENV{PERL_ANYEVENT_STRICT}.
		2589
		2590	Note that AnyEvent will remove I<all> environment variables starting with
		2591	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2592	enabled.
		2593
		2594
		2595	=head1 BUGS
		2596
		2597	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2598	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2599	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2600	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2601	pronounced).
1442		2602
1443		2603
1444	=head1 SEE ALSO	2604	=head1 SEE ALSO
		2605
		2606	Utility functions: L<AnyEvent::Util>.
1445		2607
1446	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,	2608	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1447	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2609	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1448		2610
1449	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2611	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1450	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2612	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1451	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2613	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1452	L<AnyEvent::Impl::POE>.	2614	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1453		2615
		2616	Non-blocking file handles, sockets, TCP clients and
		2617	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2618
		2619	Asynchronous DNS: L<AnyEvent::DNS>.
		2620
1454	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2621	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2622	L<Coro::Event>,
1455		2623
1456	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2624	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2625	L<AnyEvent::HTTP>.
1457		2626
1458		2627
1459	=head1 AUTHOR	2628	=head1 AUTHOR
1460		2629
1461	Marc Lehmann <schmorp@schmorp.de>	2630	Marc Lehmann <schmorp@schmorp.de>
1462	http://home.schmorp.de/	2631	http://home.schmorp.de/
1463		2632
1464	=cut	2633	=cut
1465		2634
1466	1	2635	1
1467		2636

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