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Revision 1.118 by root, Sun May 11 18:08:36 2008 UTC vs.
Revision 1.323 by root, Thu May 20 21:22:20 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	# if you prefer function calls, look at the AE manpage for
		13	# an alternative API.
		14
		15	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	16	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		17
		18	# one-shot or repeating timers
		19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		21
		22	print AnyEvent->now; # prints current event loop time
		23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		24
		25	# POSIX signal
		26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		27
		28	# child process exit
		29	my $w = AnyEvent->child (pid => $pid, cb => sub {
		30	my ($pid, $status) = @_;
12	...	31	...
13	});	32	});
14		33
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	34	# called when event loop idle (if applicable)
16	...	35	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		36
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->send; # wake up current and all future recv's	38	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	39	$w->recv; # enters "main loop" till $condvar gets ->send
		40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
		42
		43	=head1 INTRODUCTION/TUTORIAL
		44
		45	This manpage is mainly a reference manual. If you are interested
		46	in a tutorial or some gentle introduction, have a look at the
		47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	There is a mailinglist for discussing all things AnyEvent, and an IRC
		52	channel, too.
		53
		54	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		55	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		56
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	57	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		58
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	59	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	60	nowadays. So what is different about AnyEvent?
27		61
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	62	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	63	policy> and AnyEvent is I<small and efficient>.
30		64
31	First and foremost, I<AnyEvent is not an event model> itself, it only	65	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	66	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,	67	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,	68	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	69	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	70	cannot change this, but it can hide the differences between those event
		71	loops.
37		72
38	The goal of AnyEvent is to offer module authors the ability to do event	73	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	74	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	75	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	76	module users into the same thing by forcing them to use the same event
42	model you use.	77	model you use.
43		78
44	For modules like POE or IO::Async (which is a total misnomer as it is	79	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	80	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	81	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	82	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	83	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.	84	module are I<also> forced to use the same event loop you use.
50		85
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	86	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	87	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	88	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,	89	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	90	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	91	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	92	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).	93	to AnyEvent, too, so it is future-proof).
59		94
60	In addition to being free of having to use I<the one and only true event	95	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	96	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	97	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	98	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	99	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	100	technically possible.
66		101
		102	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		103	of useful functionality, such as an asynchronous DNS resolver, 100%
		104	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		105	such as Windows) and lots of real-world knowledge and workarounds for
		106	platform bugs and differences.
		107
67	Of course, if you want lots of policy (this can arguably be somewhat	108	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	109	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	110	model, you should I<not> use this module.
70		111
71	=head1 DESCRIPTION	112	=head1 DESCRIPTION
72		113
…		…
102	starts using it, all bets are off. Maybe you should tell their authors to	143	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...	144	use AnyEvent so their modules work together with others seamlessly...
104		145
105	The pure-perl implementation of AnyEvent is called	146	The pure-perl implementation of AnyEvent is called
106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	147	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
107	explicitly.	148	explicitly and enjoy the high availability of that event loop :)
108		149
109	=head1 WATCHERS	150	=head1 WATCHERS
110		151
111	AnyEvent has the central concept of a I<watcher>, which is an object that	152	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	153	stores relevant data for each kind of event you are waiting for, such as
113	the callback to call, the filehandle to watch, etc.	154	the callback to call, the file handle to watch, etc.
114		155
115	These watchers are normal Perl objects with normal Perl lifetime. After	156	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	157	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	158	callback when the event occurs (of course, only when the event model
118	is in control).	159	is in control).
119		160
		161	Note that B<callbacks must not permanently change global variables>
		162	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		163	callbacks must not C<die> >>. The former is good programming practise in
		164	Perl and the latter stems from the fact that exception handling differs
		165	widely between event loops.
		166
120	To disable the watcher you have to destroy it (e.g. by setting the	167	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	168	variable you store it in to C<undef> or otherwise deleting all references
122	to it).	169	to it).
123		170
124	All watchers are created by calling a method on the C<AnyEvent> class.	171	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	173	Many watchers either are used with "recursion" (repeating timers for
127	example), or need to refer to their watcher object in other ways.	174	example), or need to refer to their watcher object in other ways.
128		175
129	An any way to achieve that is this pattern:	176	An any way to achieve that is this pattern:
130		177
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	178	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	179	# you can use $w here, for example to undef it
133	undef $w;	180	undef $w;
134	});	181	});
135		182
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	183	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	184	my variables are only visible after the statement in which they are
138	declared.	185	declared.
139		186
140	=head2 I/O WATCHERS	187	=head2 I/O WATCHERS
141		188
		189	$w = AnyEvent->io (
		190	fh => <filehandle_or_fileno>,
		191	poll => <"r" or "w">,
		192	cb => <callback>,
		193	);
		194
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	195	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	196	with the following mandatory key-value pairs as arguments:
144		197
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	198	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		199	for events (AnyEvent might or might not keep a reference to this file
		200	handle). Note that only file handles pointing to things for which
		201	non-blocking operation makes sense are allowed. This includes sockets,
		202	most character devices, pipes, fifos and so on, but not for example files
		203	or block devices.
		204
146	for events. C<poll> must be a string that is either C<r> or C<w>,	205	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,	206	watcher waiting for "r"eadable or "w"ritable events, respectively.
		207
148	respectively. C<cb> is the callback to invoke each time the file handle	208	C<cb> is the callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		209
151	Although the callback might get passed parameters, their value and	210	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	211	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	212	callbacks cannot use arguments passed to I/O watcher callbacks.
154		213
…		…
158		217
159	Some event loops issue spurious readyness notifications, so you should	218	Some event loops issue spurious readyness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	219	always use non-blocking calls when reading/writing from/to your file
161	handles.	220	handles.
162		221
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	222	Example: wait for readability of STDIN, then read a line and disable the
		223	watcher.
		224
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	225	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	226	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	227	warn "read: $input\n";
169	undef $w;	228	undef $w;
170	});	229	});
171		230
172	=head2 TIME WATCHERS	231	=head2 TIME WATCHERS
173		232
		233	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		234
		235	$w = AnyEvent->timer (
		236	after => <fractional_seconds>,
		237	interval => <fractional_seconds>,
		238	cb => <callback>,
		239	);
		240
174	You can create a time watcher by calling the C<< AnyEvent->timer >>	241	You can create a time watcher by calling the C<< AnyEvent->timer >>
175	method with the following mandatory arguments:	242	method with the following mandatory arguments:
176		243
177	C<after> specifies after how many seconds (fractional values are	244	C<after> specifies after how many seconds (fractional values are
178	supported) the callback should be invoked. C<cb> is the callback to invoke	245	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
180		247
181	Although the callback might get passed parameters, their value and	248	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	249	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	250	callbacks cannot use arguments passed to time watcher callbacks.
184		251
185	The timer callback will be invoked at most once: if you want a repeating	252	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	253	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	254	callback will be invoked regularly at that interval (in fractional
		255	seconds) after the first invocation. If C<interval> is specified with a
		256	false value, then it is treated as if it were missing.
188		257
189	Example:	258	The callback will be rescheduled before invoking the callback, but no
		259	attempt is done to avoid timer drift in most backends, so the interval is
		260	only approximate.
190		261
191	# fire an event after 7.7 seconds	262	Example: fire an event after 7.7 seconds.
		263
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	264	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	265	warn "timeout\n";
194	});	266	});
195		267
196	# to cancel the timer:	268	# to cancel the timer:
197	undef $w;	269	undef $w;
198		270
199	Example 2:
200
201	# fire an event after 0.5 seconds, then roughly every second	271	Example 2: fire an event after 0.5 seconds, then roughly every second.
202	my $w;
203		272
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	273	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		274	warn "timeout\n";
207	};	275	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		276
212	=head3 TIMING ISSUES	277	=head3 TIMING ISSUES
213		278
214	There are two ways to handle timers: based on real time (relative, "fire	279	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	280	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
227	timers.	292	timers.
228		293
229	AnyEvent always prefers relative timers, if available, matching the	294	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	295	AnyEvent API.
231		296
		297	AnyEvent has two additional methods that return the "current time":
		298
		299	=over 4
		300
		301	=item AnyEvent->time
		302
		303	This returns the "current wallclock time" as a fractional number of
		304	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		305	return, and the result is guaranteed to be compatible with those).
		306
		307	It progresses independently of any event loop processing, i.e. each call
		308	will check the system clock, which usually gets updated frequently.
		309
		310	=item AnyEvent->now
		311
		312	This also returns the "current wallclock time", but unlike C<time>, above,
		313	this value might change only once per event loop iteration, depending on
		314	the event loop (most return the same time as C<time>, above). This is the
		315	time that AnyEvent's timers get scheduled against.
		316
		317	I<In almost all cases (in all cases if you don't care), this is the
		318	function to call when you want to know the current time.>
		319
		320	This function is also often faster then C<< AnyEvent->time >>, and
		321	thus the preferred method if you want some timestamp (for example,
		322	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		323
		324	The rest of this section is only of relevance if you try to be very exact
		325	with your timing, you can skip it without bad conscience.
		326
		327	For a practical example of when these times differ, consider L<Event::Lib>
		328	and L<EV> and the following set-up:
		329
		330	The event loop is running and has just invoked one of your callback at
		331	time=500 (assume no other callbacks delay processing). In your callback,
		332	you wait a second by executing C<sleep 1> (blocking the process for a
		333	second) and then (at time=501) you create a relative timer that fires
		334	after three seconds.
		335
		336	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		337	both return C<501>, because that is the current time, and the timer will
		338	be scheduled to fire at time=504 (C<501> + C<3>).
		339
		340	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		341	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		342	last event processing phase started. With L<EV>, your timer gets scheduled
		343	to run at time=503 (C<500> + C<3>).
		344
		345	In one sense, L<Event::Lib> is more exact, as it uses the current time
		346	regardless of any delays introduced by event processing. However, most
		347	callbacks do not expect large delays in processing, so this causes a
		348	higher drift (and a lot more system calls to get the current time).
		349
		350	In another sense, L<EV> is more exact, as your timer will be scheduled at
		351	the same time, regardless of how long event processing actually took.
		352
		353	In either case, if you care (and in most cases, you don't), then you
		354	can get whatever behaviour you want with any event loop, by taking the
		355	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		356	account.
		357
		358	=item AnyEvent->now_update
		359
		360	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		361	the current time for each loop iteration (see the discussion of L<<
		362	AnyEvent->now >>, above).
		363
		364	When a callback runs for a long time (or when the process sleeps), then
		365	this "current" time will differ substantially from the real time, which
		366	might affect timers and time-outs.
		367
		368	When this is the case, you can call this method, which will update the
		369	event loop's idea of "current time".
		370
		371	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		372	when mod_perl executes the script, then the event loop will have the wrong
		373	idea about the "current time" (being potentially far in the past, when the
		374	script ran the last time). In that case you should arrange a call to C<<
		375	AnyEvent->now_update >> each time the web server process wakes up again
		376	(e.g. at the start of your script, or in a handler).
		377
		378	Note that updating the time I<might> cause some events to be handled.
		379
		380	=back
		381
232	=head2 SIGNAL WATCHERS	382	=head2 SIGNAL WATCHERS
233		383
		384	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		385
234	You can watch for signals using a signal watcher, C<signal> is the signal	386	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	387	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	388	callback to be invoked whenever a signal occurs.
237		389
238	Although the callback might get passed parameters, their value and	390	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	391	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	392	callbacks cannot use arguments passed to signal watcher callbacks.
241		393
242	Multiple signal occurances can be clumped together into one callback	394	Multiple signal occurrences can be clumped together into one callback
243	invocation, and callback invocation will be synchronous. synchronous means	395	invocation, and callback invocation will be synchronous. Synchronous means
244	that it might take a while until the signal gets handled by the process,	396	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.	397	but it is guaranteed not to interrupt any other callbacks.
246		398
247	The main advantage of using these watchers is that you can share a signal	399	The main advantage of using these watchers is that you can share a signal
248	between multiple watchers.	400	between multiple watchers, and AnyEvent will ensure that signals will not
		401	interrupt your program at bad times.
249		402
250	This watcher might use C<%SIG>, so programs overwriting those signals	403	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	404	so programs overwriting those signals directly will likely not work
		405	correctly.
252		406
253	Example: exit on SIGINT	407	Example: exit on SIGINT
254		408
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	409	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		410
		411	=head3 Restart Behaviour
		412
		413	While restart behaviour is up to the event loop implementation, most will
		414	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		415	pure perl implementation).
		416
		417	=head3 Safe/Unsafe Signals
		418
		419	Perl signals can be either "safe" (synchronous to opcode handling) or
		420	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		421	latter might corrupt your memory.
		422
		423	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		424	i.e. they will not interrupt your running perl program but will only be
		425	called as part of the normal event handling (just like timer, I/O etc.
		426	callbacks, too).
		427
		428	=head3 Signal Races, Delays and Workarounds
		429
		430	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		431	callbacks to signals in a generic way, which is a pity, as you cannot
		432	do race-free signal handling in perl, requiring C libraries for
		433	this. AnyEvent will try to do it's best, which means in some cases,
		434	signals will be delayed. The maximum time a signal might be delayed is
		435	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		436	variable can be changed only before the first signal watcher is created,
		437	and should be left alone otherwise. This variable determines how often
		438	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		439	will cause fewer spurious wake-ups, which is better for power and CPU
		440	saving.
		441
		442	All these problems can be avoided by installing the optional
		443	L<Async::Interrupt> module, which works with most event loops. It will not
		444	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		445	(and not with L<POE> currently, as POE does it's own workaround with
		446	one-second latency). For those, you just have to suffer the delays.
		447
257	=head2 CHILD PROCESS WATCHERS	448	=head2 CHILD PROCESS WATCHERS
258		449
		450	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		451
259	You can also watch on a child process exit and catch its exit status.	452	You can also watch on a child process exit and catch its exit status.
260		453
261	The child process is specified by the C<pid> argument (if set to C<0>, it	454	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	455	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	456	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	457	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,	458	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	459
		460	The callback will be called with the pid and exit status (as returned by
		461	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		462	callback arguments.
		463
		464	This watcher type works by installing a signal handler for C<SIGCHLD>,
		465	and since it cannot be shared, nothing else should use SIGCHLD or reap
		466	random child processes (waiting for specific child processes, e.g. inside
		467	C<system>, is just fine).
267		468
268	There is a slight catch to child watchers, however: you usually start them	469	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	470	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	471	have exited already (and no SIGCHLD will be sent anymore).
271		472
272	Not all event models handle this correctly (POE doesn't), but even for	473	Not all event models handle this correctly (neither POE nor IO::Async do,
		474	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	475	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).	476	the process exits (i.e. before you fork in the first place). AnyEvent's
		477	pure perl event loop handles all cases correctly regardless of when you
		478	start the watcher.
275		479
276	This means you cannot create a child watcher as the very first thing in an	480	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	481	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>).	482	watcher before you C<fork> the child (alternatively, you can call
		483	C<AnyEvent::detect>).
		484
		485	As most event loops do not support waiting for child events, they will be
		486	emulated by AnyEvent in most cases, in which the latency and race problems
		487	mentioned in the description of signal watchers apply.
279		488
280	Example: fork a process and wait for it	489	Example: fork a process and wait for it
281		490
282	my $done = AnyEvent->condvar;	491	my $done = AnyEvent->condvar;
283		492
284	my $pid = fork or exit 5;	493	my $pid = fork or exit 5;
285		494
286	my $w = AnyEvent->child (	495	my $w = AnyEvent->child (
287	pid => $pid,	496	pid => $pid,
288	cb => sub {	497	cb => sub {
289	my ($pid, $status) = @_;	498	my ($pid, $status) = @_;
290	warn "pid $pid exited with status $status";	499	warn "pid $pid exited with status $status";
291	$done->send;	500	$done->send;
292	},	501	},
293	);	502	);
294		503
295	# do something else, then wait for process exit	504	# do something else, then wait for process exit
296	$done->recv;	505	$done->recv;
		506
		507	=head2 IDLE WATCHERS
		508
		509	$w = AnyEvent->idle (cb => <callback>);
		510
		511	Repeatedly invoke the callback after the process becomes idle, until
		512	either the watcher is destroyed or new events have been detected.
		513
		514	Idle watchers are useful when there is a need to do something, but it
		515	is not so important (or wise) to do it instantly. The callback will be
		516	invoked only when there is "nothing better to do", which is usually
		517	defined as "all outstanding events have been handled and no new events
		518	have been detected". That means that idle watchers ideally get invoked
		519	when the event loop has just polled for new events but none have been
		520	detected. Instead of blocking to wait for more events, the idle watchers
		521	will be invoked.
		522
		523	Unfortunately, most event loops do not really support idle watchers (only
		524	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		525	will simply call the callback "from time to time".
		526
		527	Example: read lines from STDIN, but only process them when the
		528	program is otherwise idle:
		529
		530	my @lines; # read data
		531	my $idle_w;
		532	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		533	push @lines, scalar <STDIN>;
		534
		535	# start an idle watcher, if not already done
		536	$idle_w ||= AnyEvent->idle (cb => sub {
		537	# handle only one line, when there are lines left
		538	if (my $line = shift @lines) {
		539	print "handled when idle: $line";
		540	} else {
		541	# otherwise disable the idle watcher again
		542	undef $idle_w;
		543	}
		544	});
		545	});
297		546
298	=head2 CONDITION VARIABLES	547	=head2 CONDITION VARIABLES
		548
		549	$cv = AnyEvent->condvar;
		550
		551	$cv->send (<list>);
		552	my @res = $cv->recv;
299		553
300	If you are familiar with some event loops you will know that all of them	554	If you are familiar with some event loops you will know that all of them
301	require you to run some blocking "loop", "run" or similar function that	555	require you to run some blocking "loop", "run" or similar function that
302	will actively watch for new events and call your callbacks.	556	will actively watch for new events and call your callbacks.
303		557
304	AnyEvent is different, it expects somebody else to run the event loop and	558	AnyEvent is slightly different: it expects somebody else to run the event
305	will only block when necessary (usually when told by the user).	559	loop and will only block when necessary (usually when told by the user).
306		560
307	The instrument to do that is called a "condition variable", so called	561	The instrument to do that is called a "condition variable", so called
308	because they represent a condition that must become true.	562	because they represent a condition that must become true.
		563
		564	Now is probably a good time to look at the examples further below.
309		565
310	Condition variables can be created by calling the C<< AnyEvent->condvar	566	Condition variables can be created by calling the C<< AnyEvent->condvar
311	>> method, usually without arguments. The only argument pair allowed is	567	>> method, usually without arguments. The only argument pair allowed is
312	C<cb>, which specifies a callback to be called when the condition variable	568	C<cb>, which specifies a callback to be called when the condition variable
313	becomes true.	569	becomes true, with the condition variable as the first argument (but not
		570	the results).
314		571
315	After creation, the conditon variable is "false" until it becomes "true"	572	After creation, the condition variable is "false" until it becomes "true"
316	by calling the C<send> method.	573	by calling the C<send> method (or calling the condition variable as if it
		574	were a callback, read about the caveats in the description for the C<<
		575	->send >> method).
317		576
318	Condition variables are similar to callbacks, except that you can	577	Condition variables are similar to callbacks, except that you can
319	optionally wait for them. They can also be called merge points - points	578	optionally wait for them. They can also be called merge points - points
320	in time where multiple outstandign events have been processed. And yet	579	in time where multiple outstanding events have been processed. And yet
321	another way to call them is transations - each condition variable can be	580	another way to call them is transactions - each condition variable can be
322	used to represent a transaction, which finishes at some point and delivers	581	used to represent a transaction, which finishes at some point and delivers
323	a result.	582	a result. And yet some people know them as "futures" - a promise to
		583	compute/deliver something that you can wait for.
324		584
325	Condition variables are very useful to signal that something has finished,	585	Condition variables are very useful to signal that something has finished,
326	for example, if you write a module that does asynchronous http requests,	586	for example, if you write a module that does asynchronous http requests,
327	then a condition variable would be the ideal candidate to signal the	587	then a condition variable would be the ideal candidate to signal the
328	availability of results. The user can either act when the callback is	588	availability of results. The user can either act when the callback is
…		…
332	you can block your main program until an event occurs - for example, you	592	you can block your main program until an event occurs - for example, you
333	could C<< ->recv >> in your main program until the user clicks the Quit	593	could C<< ->recv >> in your main program until the user clicks the Quit
334	button of your app, which would C<< ->send >> the "quit" event.	594	button of your app, which would C<< ->send >> the "quit" event.
335		595
336	Note that condition variables recurse into the event loop - if you have	596	Note that condition variables recurse into the event loop - if you have
337	two pieces of code that call C<< ->recv >> in a round-robbin fashion, you	597	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
338	lose. Therefore, condition variables are good to export to your caller, but	598	lose. Therefore, condition variables are good to export to your caller, but
339	you should avoid making a blocking wait yourself, at least in callbacks,	599	you should avoid making a blocking wait yourself, at least in callbacks,
340	as this asks for trouble.	600	as this asks for trouble.
341		601
342	Condition variables are represented by hash refs in perl, and the keys	602	Condition variables are represented by hash refs in perl, and the keys
…		…
347		607
348	There are two "sides" to a condition variable - the "producer side" which	608	There are two "sides" to a condition variable - the "producer side" which
349	eventually calls C<< -> send >>, and the "consumer side", which waits	609	eventually calls C<< -> send >>, and the "consumer side", which waits
350	for the send to occur.	610	for the send to occur.
351		611
352	Example:	612	Example: wait for a timer.
353		613
354	# wait till the result is ready	614	# condition: "wait till the timer is fired"
355	my $result_ready = AnyEvent->condvar;	615	my $timer_fired = AnyEvent->condvar;
356		616
357	# do something such as adding a timer	617	# create the timer - we could wait for, say
358	# or socket watcher the calls $result_ready->send	618	# a handle becomign ready, or even an
359	# when the "result" is ready.	619	# AnyEvent::HTTP request to finish, but
360	# in this case, we simply use a timer:	620	# in this case, we simply use a timer:
361	my $w = AnyEvent->timer (	621	my $w = AnyEvent->timer (
362	after => 1,	622	after => 1,
363	cb => sub { $result_ready->send },	623	cb => sub { $timer_fired->send },
364	);	624	);
365		625
366	# this "blocks" (while handling events) till the callback	626	# this "blocks" (while handling events) till the callback
367	# calls send	627	# calls ->send
368	$result_ready->recv;	628	$timer_fired->recv;
		629
		630	Example: wait for a timer, but take advantage of the fact that condition
		631	variables are also callable directly.
		632
		633	my $done = AnyEvent->condvar;
		634	my $delay = AnyEvent->timer (after => 5, cb => $done);
		635	$done->recv;
		636
		637	Example: Imagine an API that returns a condvar and doesn't support
		638	callbacks. This is how you make a synchronous call, for example from
		639	the main program:
		640
		641	use AnyEvent::CouchDB;
		642
		643	...
		644
		645	my @info = $couchdb->info->recv;
		646
		647	And this is how you would just set a callback to be called whenever the
		648	results are available:
		649
		650	$couchdb->info->cb (sub {
		651	my @info = $_[0]->recv;
		652	});
369		653
370	=head3 METHODS FOR PRODUCERS	654	=head3 METHODS FOR PRODUCERS
371		655
372	These methods should only be used by the producing side, i.e. the	656	These methods should only be used by the producing side, i.e. the
373	code/module that eventually sends the signal. Note that it is also	657	code/module that eventually sends the signal. Note that it is also
…		…
386	immediately from within send.	670	immediately from within send.
387		671
388	Any arguments passed to the C<send> call will be returned by all	672	Any arguments passed to the C<send> call will be returned by all
389	future C<< ->recv >> calls.	673	future C<< ->recv >> calls.
390		674
		675	Condition variables are overloaded so one can call them directly (as if
		676	they were a code reference). Calling them directly is the same as calling
		677	C<send>.
		678
391	=item $cv->croak ($error)	679	=item $cv->croak ($error)
392		680
393	Similar to send, but causes all call's to C<< ->recv >> to invoke	681	Similar to send, but causes all call's to C<< ->recv >> to invoke
394	C<Carp::croak> with the given error message/object/scalar.	682	C<Carp::croak> with the given error message/object/scalar.
395		683
396	This can be used to signal any errors to the condition variable	684	This can be used to signal any errors to the condition variable
397	user/consumer.	685	user/consumer. Doing it this way instead of calling C<croak> directly
		686	delays the error detetcion, but has the overwhelmign advantage that it
		687	diagnoses the error at the place where the result is expected, and not
		688	deep in some event clalback without connection to the actual code causing
		689	the problem.
398		690
399	=item $cv->begin ([group callback])	691	=item $cv->begin ([group callback])
400		692
401	=item $cv->end	693	=item $cv->end
402
403	These two methods are EXPERIMENTAL and MIGHT CHANGE.
404		694
405	These two methods can be used to combine many transactions/events into	695	These two methods can be used to combine many transactions/events into
406	one. For example, a function that pings many hosts in parallel might want	696	one. For example, a function that pings many hosts in parallel might want
407	to use a condition variable for the whole process.	697	to use a condition variable for the whole process.
408		698
409	Every call to C<< ->begin >> will increment a counter, and every call to	699	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	700	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	701	>>, 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	702	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.	703	>>, but that is not required. If no group callback was set, C<send> will
		704	be called without any arguments.
414		705
415	Let's clarify this with the ping example:	706	You can think of C<< $cv->send >> giving you an OR condition (one call
		707	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		708	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		709
		710	Let's start with a simple example: you have two I/O watchers (for example,
		711	STDOUT and STDERR for a program), and you want to wait for both streams to
		712	close before activating a condvar:
416		713
417	my $cv = AnyEvent->condvar;	714	my $cv = AnyEvent->condvar;
418		715
		716	$cv->begin; # first watcher
		717	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		718	defined sysread $fh1, my $buf, 4096
		719	or $cv->end;
		720	});
		721
		722	$cv->begin; # second watcher
		723	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		724	defined sysread $fh2, my $buf, 4096
		725	or $cv->end;
		726	});
		727
		728	$cv->recv;
		729
		730	This works because for every event source (EOF on file handle), there is
		731	one call to C<begin>, so the condvar waits for all calls to C<end> before
		732	sending.
		733
		734	The ping example mentioned above is slightly more complicated, as the
		735	there are results to be passwd back, and the number of tasks that are
		736	begung can potentially be zero:
		737
		738	my $cv = AnyEvent->condvar;
		739
419	my %result;	740	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	741	$cv->begin (sub { shift->send (\%result) });
421		742
422	for my $host (@list_of_hosts) {	743	for my $host (@list_of_hosts) {
423	$cv->begin;	744	$cv->begin;
424	ping_host_then_call_callback $host, sub {	745	ping_host_then_call_callback $host, sub {
425	$result{$host} = ...;	746	$result{$host} = ...;
…		…
440	loop, which serves two important purposes: first, it sets the callback	761	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	762	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	763	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	764	doesn't execute once).
444		765
445	This is the general pattern when you "fan out" into multiple subrequests:	766	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>	767	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	768	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>.	769	subrequest you start, call C<begin> and for each subrequest you finish,
		770	call C<end>.
449		771
450	=back	772	=back
451		773
452	=head3 METHODS FOR CONSUMERS	774	=head3 METHODS FOR CONSUMERS
453		775
…		…
469	function will call C<croak>.	791	function will call C<croak>.
470		792
471	In list context, all parameters passed to C<send> will be returned,	793	In list context, all parameters passed to C<send> will be returned,
472	in scalar context only the first one will be returned.	794	in scalar context only the first one will be returned.
473		795
		796	Note that doing a blocking wait in a callback is not supported by any
		797	event loop, that is, recursive invocation of a blocking C<< ->recv
		798	>> is not allowed, and the C<recv> call will C<croak> if such a
		799	condition is detected. This condition can be slightly loosened by using
		800	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		801	any thread that doesn't run the event loop itself.
		802
474	Not all event models support a blocking wait - some die in that case	803	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	804	(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	805	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	806	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	807	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	808	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	809	while still supporting blocking waits if the caller so desires).
481
482	Another reason I<never> to C<< ->recv >> in a module is that you cannot
483	sensibly have two C<< ->recv >>'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<< ->recv >> calls perfectly safe as long as they are done from another
491	coroutine (one that doesn't run the event loop).
492		810
493	You can ensure that C<< -recv >> never blocks by setting a callback and	811	You can ensure that C<< -recv >> never blocks by setting a callback and
494	only calling C<< ->recv >> from within that callback (or at a later	812	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	813	time). This will work even when the event loop does not support blocking
496	waits otherwise.	814	waits otherwise.
…		…
498	=item $bool = $cv->ready	816	=item $bool = $cv->ready
499		817
500	Returns true when the condition is "true", i.e. whether C<send> or	818	Returns true when the condition is "true", i.e. whether C<send> or
501	C<croak> have been called.	819	C<croak> have been called.
502		820
503	=item $cb = $cv->cb ([new callback])	821	=item $cb = $cv->cb ($cb->($cv))
504		822
505	This is a mutator function that returns the callback set and optionally	823	This is a mutator function that returns the callback set and optionally
506	replaces it before doing so.	824	replaces it before doing so.
507		825
508	The callback will be called when the condition becomes "true", i.e. when	826	The callback will be called when the condition becomes (or already was)
509	C<send> or C<croak> are called. Calling C<recv> inside the callback	827	"true", i.e. when C<send> or C<croak> are called (or were called), with
		828	the only argument being the condition variable itself. Calling C<recv>
510	or at any later time is guaranteed not to block.	829	inside the callback or at any later time is guaranteed not to block.
511		830
512	=back	831	=back
513		832
		833	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		834
		835	The available backend classes are (every class has its own manpage):
		836
		837	=over 4
		838
		839	=item Backends that are autoprobed when no other event loop can be found.
		840
		841	EV is the preferred backend when no other event loop seems to be in
		842	use. If EV is not installed, then AnyEvent will fall back to its own
		843	pure-perl implementation, which is available everywhere as it comes with
		844	AnyEvent itself.
		845
		846	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		847	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		848
		849	=item Backends that are transparently being picked up when they are used.
		850
		851	These will be used when they are currently loaded when the first watcher
		852	is created, in which case it is assumed that the application is using
		853	them. This means that AnyEvent will automatically pick the right backend
		854	when the main program loads an event module before anything starts to
		855	create watchers. Nothing special needs to be done by the main program.
		856
		857	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		858	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		859	AnyEvent::Impl::Tk based on Tk, very broken.
		860	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		861	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		862	AnyEvent::Impl::Irssi used when running within irssi.
		863
		864	=item Backends with special needs.
		865
		866	Qt requires the Qt::Application to be instantiated first, but will
		867	otherwise be picked up automatically. As long as the main program
		868	instantiates the application before any AnyEvent watchers are created,
		869	everything should just work.
		870
		871	AnyEvent::Impl::Qt based on Qt.
		872
		873	Support for IO::Async can only be partial, as it is too broken and
		874	architecturally limited to even support the AnyEvent API. It also
		875	is the only event loop that needs the loop to be set explicitly, so
		876	it can only be used by a main program knowing about AnyEvent. See
		877	L<AnyEvent::Impl::Async> for the gory details.
		878
		879	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		880
		881	=item Event loops that are indirectly supported via other backends.
		882
		883	Some event loops can be supported via other modules:
		884
		885	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		886
		887	B<WxWidgets> has no support for watching file handles. However, you can
		888	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		889	polls 20 times per second, which was considered to be too horrible to even
		890	consider for AnyEvent.
		891
		892	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		893	backend, so it can be supported through POE.
		894
		895	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		896	load L<POE> when detecting them, in the hope that POE will pick them up,
		897	in which case everything will be automatic.
		898
		899	=back
		900
514	=head1 GLOBAL VARIABLES AND FUNCTIONS	901	=head1 GLOBAL VARIABLES AND FUNCTIONS
515		902
		903	These are not normally required to use AnyEvent, but can be useful to
		904	write AnyEvent extension modules.
		905
516	=over 4	906	=over 4
517		907
518	=item $AnyEvent::MODEL	908	=item $AnyEvent::MODEL
519		909
520	Contains C<undef> until the first watcher is being created. Then it	910	Contains C<undef> until the first watcher is being created, before the
		911	backend has been autodetected.
		912
521	contains the event model that is being used, which is the name of the	913	Afterwards it contains the event model that is being used, which is the
522	Perl class implementing the model. This class is usually one of the	914	name of the Perl class implementing the model. This class is usually one
523	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	915	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
524	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	916	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
525		917	will be C<urxvt::anyevent>).
526	The known classes so far are:
527
528	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
529	AnyEvent::Impl::Event based on Event, second best choice.
530	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
531	AnyEvent::Impl::Glib based on Glib, third-best choice.
532	AnyEvent::Impl::Tk based on Tk, very bad choice.
533	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
534	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
535	AnyEvent::Impl::POE based on POE, not generic enough for full support.
536
537	There is no support for WxWidgets, as WxWidgets has no support for
538	watching file handles. However, you can use WxWidgets through the
539	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
540	second, which was considered to be too horrible to even consider for
541	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
542	it's adaptor.
543
544	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
545	autodetecting them.
546		918
547	=item AnyEvent::detect	919	=item AnyEvent::detect
548		920
549	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	921	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
550	if necessary. You should only call this function right before you would	922	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	923	have created an AnyEvent watcher anyway, that is, as late as possible at
552	runtime.	924	runtime, and not e.g. while initialising of your module.
		925
		926	If you need to do some initialisation before AnyEvent watchers are
		927	created, use C<post_detect>.
553		928
554	=item $guard = AnyEvent::post_detect { BLOCK }	929	=item $guard = AnyEvent::post_detect { BLOCK }
555		930
556	Arranges for the code block to be executed as soon as the event model is	931	Arranges for the code block to be executed as soon as the event model is
557	autodetected (or immediately if this has already happened).	932	autodetected (or immediately if this has already happened).
558		933
		934	The block will be executed I<after> the actual backend has been detected
		935	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		936	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		937	other initialisations - see the sources of L<AnyEvent::Strict> or
		938	L<AnyEvent::AIO> to see how this is used.
		939
		940	The most common usage is to create some global watchers, without forcing
		941	event module detection too early, for example, L<AnyEvent::AIO> creates
		942	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		943	avoid autodetecting the event module at load time.
		944
559	If called in scalar or list context, then it creates and returns an object	945	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. See	946	that automatically removes the callback again when it is destroyed (or
		947	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
561	L<Coro::BDB> for a case where this is useful.	948	a case where this is useful.
		949
		950	Example: Create a watcher for the IO::AIO module and store it in
		951	C<$WATCHER>. Only do so after the event loop is initialised, though.
		952
		953	our WATCHER;
		954
		955	my $guard = AnyEvent::post_detect {
		956	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		957	};
		958
		959	# the ||= is important in case post_detect immediately runs the block,
		960	# as to not clobber the newly-created watcher. assigning both watcher and
		961	# post_detect guard to the same variable has the advantage of users being
		962	# able to just C<undef $WATCHER> if the watcher causes them grief.
		963
		964	$WATCHER ||= $guard;
562		965
563	=item @AnyEvent::post_detect	966	=item @AnyEvent::post_detect
564		967
565	If there are any code references in this array (you can C<push> to it	968	If there are any code references in this array (you can C<push> to it
566	before or after loading AnyEvent), then they will called directly after	969	before or after loading AnyEvent), then they will called directly after
567	the event loop has been chosen.	970	the event loop has been chosen.
568		971
569	You should check C<$AnyEvent::MODEL> before adding to this array, though:	972	You should check C<$AnyEvent::MODEL> before adding to this array, though:
570	if it contains a true value then the event loop has already been detected,	973	if it is defined then the event loop has already been detected, and the
571	and the array will be ignored.	974	array will be ignored.
572		975
573	Best use C<AnyEvent::post_detect { BLOCK }> instead.	976	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		977	it, as it takes care of these details.
		978
		979	This variable is mainly useful for modules that can do something useful
		980	when AnyEvent is used and thus want to know when it is initialised, but do
		981	not need to even load it by default. This array provides the means to hook
		982	into AnyEvent passively, without loading it.
		983
		984	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		985	together, you could put this into Coro (this is the actual code used by
		986	Coro to accomplish this):
		987
		988	if (defined $AnyEvent::MODEL) {
		989	# AnyEvent already initialised, so load Coro::AnyEvent
		990	require Coro::AnyEvent;
		991	} else {
		992	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		993	# as soon as it is
		994	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		995	}
574		996
575	=back	997	=back
576		998
577	=head1 WHAT TO DO IN A MODULE	999	=head1 WHAT TO DO IN A MODULE
578		1000
…		…
601		1023
602	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1024	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
603	do anything special (it does not need to be event-based) and let AnyEvent	1025	do anything special (it does not need to be event-based) and let AnyEvent
604	decide which implementation to chose if some module relies on it.	1026	decide which implementation to chose if some module relies on it.
605		1027
606	If the main program relies on a specific event model. For example, in	1028	If the main program relies on a specific event model - for example, in
607	Gtk2 programs you have to rely on the Glib module. You should load the	1029	Gtk2 programs you have to rely on the Glib module - you should load the
608	event module before loading AnyEvent or any module that uses it: generally	1030	event module before loading AnyEvent or any module that uses it: generally
609	speaking, you should load it as early as possible. The reason is that	1031	speaking, you should load it as early as possible. The reason is that
610	modules might create watchers when they are loaded, and AnyEvent will	1032	modules might create watchers when they are loaded, and AnyEvent will
611	decide on the event model to use as soon as it creates watchers, and it	1033	decide on the event model to use as soon as it creates watchers, and it
612	might chose the wrong one unless you load the correct one yourself.	1034	might chose the wrong one unless you load the correct one yourself.
613		1035
614	You can chose to use a rather inefficient pure-perl implementation by	1036	You can chose to use a pure-perl implementation by loading the
615	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1037	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
616	behaviour everywhere, but letting AnyEvent chose is generally better.	1038	everywhere, but letting AnyEvent chose the model is generally better.
		1039
		1040	=head2 MAINLOOP EMULATION
		1041
		1042	Sometimes (often for short test scripts, or even standalone programs who
		1043	only want to use AnyEvent), you do not want to run a specific event loop.
		1044
		1045	In that case, you can use a condition variable like this:
		1046
		1047	AnyEvent->condvar->recv;
		1048
		1049	This has the effect of entering the event loop and looping forever.
		1050
		1051	Note that usually your program has some exit condition, in which case
		1052	it is better to use the "traditional" approach of storing a condition
		1053	variable somewhere, waiting for it, and sending it when the program should
		1054	exit cleanly.
		1055
617		1056
618	=head1 OTHER MODULES	1057	=head1 OTHER MODULES
619		1058
620	The following is a non-exhaustive list of additional modules that use	1059	The following is a non-exhaustive list of additional modules that use
621	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1060	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
622	in the same program. Some of the modules come with AnyEvent, some are	1061	modules and other event loops in the same program. Some of the modules
623	available via CPAN.	1062	come with AnyEvent, most are available via CPAN.
624		1063
625	=over 4	1064	=over 4
626		1065
627	=item L<AnyEvent::Util>	1066	=item L<AnyEvent::Util>
628		1067
629	Contains various utility functions that replace often-used but blocking	1068	Contains various utility functions that replace often-used but blocking
630	functions such as C<inet_aton> by event-/callback-based versions.	1069	functions such as C<inet_aton> by event-/callback-based versions.
631		1070
		1071	=item L<AnyEvent::Socket>
		1072
		1073	Provides various utility functions for (internet protocol) sockets,
		1074	addresses and name resolution. Also functions to create non-blocking tcp
		1075	connections or tcp servers, with IPv6 and SRV record support and more.
		1076
632	=item L<AnyEvent::Handle>	1077	=item L<AnyEvent::Handle>
633		1078
634	Provide read and write buffers and manages watchers for reads and writes.	1079	Provide read and write buffers, manages watchers for reads and writes,
		1080	supports raw and formatted I/O, I/O queued and fully transparent and
		1081	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1082
		1083	=item L<AnyEvent::DNS>
		1084
		1085	Provides rich asynchronous DNS resolver capabilities.
		1086
		1087	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1088
		1089	Implement event-based interfaces to the protocols of the same name (for
		1090	the curious, IGS is the International Go Server and FCP is the Freenet
		1091	Client Protocol).
		1092
		1093	=item L<AnyEvent::Handle::UDP>
		1094
		1095	Here be danger!
		1096
		1097	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1098	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1099	it's use of a stream-based API with a protocol that isn't streamable, that
		1100	the only way to improve it is to delete it.
		1101
		1102	It features data corruption (but typically only under load) and general
		1103	confusion. On top, the author is not only clueless about UDP but also
		1104	fact-resistant - some gems of his understanding: "connect doesn't work
		1105	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1106	packets", "I don't need to implement proper error checking as UDP doesn't
		1107	support error checking" and so on - he doesn't even understand what's
		1108	wrong with his module when it is explained to him.
		1109
		1110	=item L<AnyEvent::DBI>
		1111
		1112	Executes L<DBI> requests asynchronously in a proxy process for you,
		1113	notifying you in an event-bnased way when the operation is finished.
		1114
		1115	=item L<AnyEvent::AIO>
		1116
		1117	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1118	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1119	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1120	file I/O, and much more.
635		1121
636	=item L<AnyEvent::HTTPD>	1122	=item L<AnyEvent::HTTPD>
637		1123
638	Provides a simple web application server framework.	1124	A simple embedded webserver.
639
640	=item L<AnyEvent::DNS>
641
642	Provides asynchronous DNS resolver capabilities, beyond what
643	L<AnyEvent::Util> offers.
644		1125
645	=item L<AnyEvent::FastPing>	1126	=item L<AnyEvent::FastPing>
646		1127
647	The fastest ping in the west.	1128	The fastest ping in the west.
648		1129
649	=item L<Net::IRC3>
650
651	AnyEvent based IRC client module family.
652
653	=item L<Net::XMPP2>
654
655	AnyEvent based XMPP (Jabber protocol) module family.
656
657	=item L<Net::FCP>
658
659	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
660	of AnyEvent.
661
662	=item L<Event::ExecFlow>
663
664	High level API for event-based execution flow control.
665
666	=item L<Coro>	1130	=item L<Coro>
667		1131
668	Has special support for AnyEvent via L<Coro::AnyEvent>.	1132	Has special support for AnyEvent via L<Coro::AnyEvent>.
669		1133
670	=item L<AnyEvent::AIO>, L<IO::AIO>
671
672	Truly asynchronous I/O, should be in the toolbox of every event
673	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
674	together.
675
676	=item L<AnyEvent::BDB>, L<BDB>
677
678	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
679	IO::AIO and AnyEvent together.
680
681	=item L<IO::Lambda>
682
683	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
684
685	=back	1134	=back
686		1135
687	=cut	1136	=cut
688		1137
689	package AnyEvent;	1138	package AnyEvent;
690		1139
691	no warnings;	1140	# basically a tuned-down version of common::sense
692	use strict;	1141	sub common_sense {
		1142	# from common:.sense 1.0
		1143	${^WARNING_BITS} = "\xfc\x3f\x33\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x00";
		1144	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1145	$^H |= 0x00000600;
		1146	}
693		1147
		1148	BEGIN { AnyEvent::common_sense }
		1149
694	use Carp;	1150	use Carp ();
695		1151
696	our $VERSION = '3.41';	1152	our $VERSION = '5.261';
697	our $MODEL;	1153	our $MODEL;
698		1154
699	our $AUTOLOAD;	1155	our $AUTOLOAD;
700	our @ISA;	1156	our @ISA;
701		1157
702	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
703
704	our @REGISTRY;	1158	our @REGISTRY;
705		1159
		1160	our $VERBOSE;
		1161
		1162	BEGIN {
		1163	require "AnyEvent/constants.pl";
		1164
		1165	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1166
		1167	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1168	if ${^TAINT};
		1169
		1170	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1171
		1172	}
		1173
		1174	our $MAX_SIGNAL_LATENCY = 10;
		1175
		1176	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1177
		1178	{
		1179	my $idx;
		1180	$PROTOCOL{$_} = ++$idx
		1181	for reverse split /\s*,\s*/,
		1182	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1183	}
		1184
706	my @models = (	1185	my @models = (
707	[EV:: => AnyEvent::Impl::EV::],	1186	[EV:: => AnyEvent::Impl::EV:: , 1],
		1187	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1188	# everything below here will not (normally) be autoprobed
		1189	# as the pureperl backend should work everywhere
		1190	# and is usually faster
708	[Event:: => AnyEvent::Impl::Event::],	1191	[Event:: => AnyEvent::Impl::Event::, 1],
		1192	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1193	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1194	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
709	[Tk:: => AnyEvent::Impl::Tk::],	1195	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1196	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1197	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
710	[Wx:: => AnyEvent::Impl::POE::],	1198	[Wx:: => AnyEvent::Impl::POE::],
711	[Prima:: => AnyEvent::Impl::POE::],	1199	[Prima:: => AnyEvent::Impl::POE::],
712	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1200	# IO::Async is just too broken - we would need workarounds for its
713	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1201	# byzantine signal and broken child handling, among others.
714	[Glib:: => AnyEvent::Impl::Glib::],	1202	# IO::Async is rather hard to detect, as it doesn't have any
715	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1203	# obvious default class.
716	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1204	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
717	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1205	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1206	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1207	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
718	);	1208	);
719		1209
720	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1210	our %method = map +($_ => 1),
		1211	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
721		1212
722	our @post_detect;	1213	our @post_detect;
723		1214
724	sub post_detect(&) {	1215	sub post_detect(&) {
725	my ($cb) = @_;	1216	my ($cb) = @_;
726		1217
727	if ($MODEL) {
728	$cb->();
729
730	1
731	} else {
732	push @post_detect, $cb;	1218	push @post_detect, $cb;
733		1219
734	defined wantarray	1220	defined wantarray
735	? bless \$cb, "AnyEvent::Util::Guard"	1221	? bless \$cb, "AnyEvent::Util::postdetect"
736	: ()	1222	: ()
		1223	}
		1224
		1225	sub AnyEvent::Util::postdetect::DESTROY {
		1226	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1227	}
		1228
		1229	sub detect() {
		1230	# free some memory
		1231	*detect = sub () { $MODEL };
		1232
		1233	local $!; # for good measure
		1234	local $SIG{__DIE__};
		1235
		1236	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1237	my $model = "AnyEvent::Impl::$1";
		1238	if (eval "require $model") {
		1239	$MODEL = $model;
		1240	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1241	} else {
		1242	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1243	}
737	}	1244	}
738	}
739		1245
740	sub AnyEvent::Util::Guard::DESTROY {	1246	# check for already loaded models
741	@post_detect = grep $_ != ${$_[0]}, @post_detect;
742	}
743
744	sub detect() {
745	unless ($MODEL) {	1247	unless ($MODEL) {
746	no strict 'refs';	1248	for (@REGISTRY, @models) {
747		1249	my ($package, $model) = @$_;
748	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1250	if (${"$package\::VERSION"} > 0) {
749	my $model = "AnyEvent::Impl::$1";
750	if (eval "require $model") {	1251	if (eval "require $model") {
751	$MODEL = $model;	1252	$MODEL = $model;
752	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1253	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
753	} else {	1254	last;
754	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1255	}
755	}	1256	}
756	}	1257	}
757		1258
758	# check for already loaded models
759	unless ($MODEL) {	1259	unless ($MODEL) {
		1260	# try to autoload a model
760	for (@REGISTRY, @models) {	1261	for (@REGISTRY, @models) {
761	my ($package, $model) = @$_;	1262	my ($package, $model, $autoload) = @$_;
		1263	if (
		1264	$autoload
		1265	and eval "require $package"
762	if (${"$package\::VERSION"} > 0) {	1266	and ${"$package\::VERSION"} > 0
763	if (eval "require $model") {	1267	and eval "require $model"
		1268	) {
764	$MODEL = $model;	1269	$MODEL = $model;
765	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1270	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
766	last;	1271	last;
767	}
768	}	1272	}
769	}	1273	}
770		1274
771	unless ($MODEL) {
772	# try to load a model
773
774	for (@REGISTRY, @models) {
775	my ($package, $model) = @$_;
776	if (eval "require $package"
777	and ${"$package\::VERSION"} > 0
778	and eval "require $model") {
779	$MODEL = $model;
780	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
781	last;
782	}
783	}
784
785	$MODEL	1275	$MODEL
786	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1276	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
787	}
788	}	1277	}
789
790	unshift @ISA, $MODEL;
791	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
792
793	(shift @post_detect)->() while @post_detect;
794	}	1278	}
		1279
		1280	@models = (); # free probe data
		1281
		1282	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1283	unshift @ISA, $MODEL;
		1284
		1285	# now nuke some methods that are overriden by the backend.
		1286	# SUPER is not allowed.
		1287	for (qw(time signal child idle)) {
		1288	undef &{"AnyEvent::Base::$_"}
		1289	if defined &{"$MODEL\::$_"};
		1290	}
		1291
		1292	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1293
		1294	(shift @post_detect)->() while @post_detect;
		1295
		1296	*post_detect = sub(&) {
		1297	shift->();
		1298
		1299	undef
		1300	};
795		1301
796	$MODEL	1302	$MODEL
797	}	1303	}
798		1304
799	sub AUTOLOAD {	1305	sub AUTOLOAD {
800	(my $func = $AUTOLOAD) =~ s/.*://;	1306	(my $func = $AUTOLOAD) =~ s/.*://;
801		1307
802	$method{$func}	1308	$method{$func}
803	or croak "$func: not a valid method for AnyEvent objects";	1309	or Carp::croak "$func: not a valid AnyEvent class method";
804		1310
805	detect unless $MODEL;	1311	detect;
806		1312
807	my $class = shift;	1313	my $class = shift;
808	$class->$func (@_);	1314	$class->$func (@_);
809	}	1315	}
810		1316
		1317	# utility function to dup a filehandle. this is used by many backends
		1318	# to support binding more than one watcher per filehandle (they usually
		1319	# allow only one watcher per fd, so we dup it to get a different one).
		1320	sub _dupfh($$;$$) {
		1321	my ($poll, $fh, $r, $w) = @_;
		1322
		1323	# cygwin requires the fh mode to be matching, unix doesn't
		1324	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1325
		1326	open my $fh2, $mode, $fh
		1327	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1328
		1329	# we assume CLOEXEC is already set by perl in all important cases
		1330
		1331	($fh2, $rw)
		1332	}
		1333
		1334	=head1 SIMPLIFIED AE API
		1335
		1336	Starting with version 5.0, AnyEvent officially supports a second, much
		1337	simpler, API that is designed to reduce the calling, typing and memory
		1338	overhead by using function call syntax and a fixed number of parameters.
		1339
		1340	See the L<AE> manpage for details.
		1341
		1342	=cut
		1343
		1344	package AE;
		1345
		1346	our $VERSION = $AnyEvent::VERSION;
		1347
		1348	# fall back to the main API by default - backends and AnyEvent::Base
		1349	# implementations can overwrite these.
		1350
		1351	sub io($$$) {
		1352	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1353	}
		1354
		1355	sub timer($$$) {
		1356	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1357	}
		1358
		1359	sub signal($$) {
		1360	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1361	}
		1362
		1363	sub child($$) {
		1364	AnyEvent->child (pid => $_[0], cb => $_[1])
		1365	}
		1366
		1367	sub idle($) {
		1368	AnyEvent->idle (cb => $_[0])
		1369	}
		1370
		1371	sub cv(;&) {
		1372	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1373	}
		1374
		1375	sub now() {
		1376	AnyEvent->now
		1377	}
		1378
		1379	sub now_update() {
		1380	AnyEvent->now_update
		1381	}
		1382
		1383	sub time() {
		1384	AnyEvent->time
		1385	}
		1386
811	package AnyEvent::Base;	1387	package AnyEvent::Base;
812		1388
		1389	# default implementations for many methods
		1390
		1391	sub time {
		1392	eval q{ # poor man's autoloading {}
		1393	# probe for availability of Time::HiRes
		1394	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1395	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1396	*AE::time = \&Time::HiRes::time;
		1397	# if (eval "use POSIX (); (POSIX::times())...
		1398	} else {
		1399	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1400	*AE::time = sub (){ time }; # epic fail
		1401	}
		1402
		1403	*time = sub { AE::time }; # different prototypes
		1404	};
		1405	die if $@;
		1406
		1407	&time
		1408	}
		1409
		1410	*now = \&time;
		1411
		1412	sub now_update { }
		1413
813	# default implementation for ->condvar	1414	# default implementation for ->condvar
814		1415
815	sub condvar {	1416	sub condvar {
816	bless {}, AnyEvent::CondVar::	1417	eval q{ # poor man's autoloading {}
		1418	*condvar = sub {
		1419	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1420	};
		1421
		1422	*AE::cv = sub (;&) {
		1423	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1424	};
		1425	};
		1426	die if $@;
		1427
		1428	&condvar
817	}	1429	}
818		1430
819	# default implementation for ->signal	1431	# default implementation for ->signal
820		1432
821	our %SIG_CB;	1433	our $HAVE_ASYNC_INTERRUPT;
		1434
		1435	sub _have_async_interrupt() {
		1436	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1437	&& eval "use Async::Interrupt 1.02 (); 1")
		1438	unless defined $HAVE_ASYNC_INTERRUPT;
		1439
		1440	$HAVE_ASYNC_INTERRUPT
		1441	}
		1442
		1443	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1444	our (%SIG_ASY, %SIG_ASY_W);
		1445	our ($SIG_COUNT, $SIG_TW);
		1446
		1447	# install a dummy wakeup watcher to reduce signal catching latency
		1448	# used by Impls
		1449	sub _sig_add() {
		1450	unless ($SIG_COUNT++) {
		1451	# try to align timer on a full-second boundary, if possible
		1452	my $NOW = AE::now;
		1453
		1454	$SIG_TW = AE::timer
		1455	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1456	$MAX_SIGNAL_LATENCY,
		1457	sub { } # just for the PERL_ASYNC_CHECK
		1458	;
		1459	}
		1460	}
		1461
		1462	sub _sig_del {
		1463	undef $SIG_TW
		1464	unless --$SIG_COUNT;
		1465	}
		1466
		1467	our $_sig_name_init; $_sig_name_init = sub {
		1468	eval q{ # poor man's autoloading {}
		1469	undef $_sig_name_init;
		1470
		1471	if (_have_async_interrupt) {
		1472	*sig2num = \&Async::Interrupt::sig2num;
		1473	*sig2name = \&Async::Interrupt::sig2name;
		1474	} else {
		1475	require Config;
		1476
		1477	my %signame2num;
		1478	@signame2num{ split ' ', $Config::Config{sig_name} }
		1479	= split ' ', $Config::Config{sig_num};
		1480
		1481	my @signum2name;
		1482	@signum2name[values %signame2num] = keys %signame2num;
		1483
		1484	*sig2num = sub($) {
		1485	$_[0] > 0 ? shift : $signame2num{+shift}
		1486	};
		1487	*sig2name = sub ($) {
		1488	$_[0] > 0 ? $signum2name[+shift] : shift
		1489	};
		1490	}
		1491	};
		1492	die if $@;
		1493	};
		1494
		1495	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1496	sub sig2name($) { &$_sig_name_init; &sig2name }
822		1497
823	sub signal {	1498	sub signal {
		1499	eval q{ # poor man's autoloading {}
		1500	# probe for availability of Async::Interrupt
		1501	if (_have_async_interrupt) {
		1502	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1503
		1504	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1505	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1506
		1507	} else {
		1508	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1509
		1510	if (AnyEvent::WIN32) {
		1511	require AnyEvent::Util;
		1512
		1513	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1514	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1515	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1516	} else {
		1517	pipe $SIGPIPE_R, $SIGPIPE_W;
		1518	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1519	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1520
		1521	# not strictly required, as $^F is normally 2, but let's make sure...
		1522	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1523	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1524	}
		1525
		1526	$SIGPIPE_R
		1527	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1528
		1529	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1530	}
		1531
		1532	*signal = $HAVE_ASYNC_INTERRUPT
		1533	? sub {
824	my (undef, %arg) = @_;	1534	my (undef, %arg) = @_;
825		1535
		1536	# async::interrupt
826	my $signal = uc $arg{signal}	1537	my $signal = sig2num $arg{signal};
827	or Carp::croak "required option 'signal' is missing";
828
829	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1538	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1539
		1540	$SIG_ASY{$signal} ||= new Async::Interrupt
		1541	cb => sub { undef $SIG_EV{$signal} },
		1542	signal => $signal,
		1543	pipe => [$SIGPIPE_R->filenos],
		1544	pipe_autodrain => 0,
		1545	;
		1546
		1547	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1548	}
		1549	: sub {
		1550	my (undef, %arg) = @_;
		1551
		1552	# pure perl
		1553	my $signal = sig2name $arg{signal};
		1554	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1555
830	$SIG{$signal} ||= sub {	1556	$SIG{$signal} ||= sub {
		1557	local $!;
		1558	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1559	undef $SIG_EV{$signal};
		1560	};
		1561
		1562	# can't do signal processing without introducing races in pure perl,
		1563	# so limit the signal latency.
		1564	_sig_add;
		1565
		1566	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1567	}
		1568	;
		1569
		1570	*AnyEvent::Base::signal::DESTROY = sub {
		1571	my ($signal, $cb) = @{$_[0]};
		1572
		1573	_sig_del;
		1574
		1575	delete $SIG_CB{$signal}{$cb};
		1576
		1577	$HAVE_ASYNC_INTERRUPT
		1578	? delete $SIG_ASY{$signal}
		1579	: # delete doesn't work with older perls - they then
		1580	# print weird messages, or just unconditionally exit
		1581	# instead of getting the default action.
		1582	undef $SIG{$signal}
		1583	unless keys %{ $SIG_CB{$signal} };
		1584	};
		1585
		1586	*_signal_exec = sub {
		1587	$HAVE_ASYNC_INTERRUPT
		1588	? $SIGPIPE_R->drain
		1589	: sysread $SIGPIPE_R, (my $dummy), 9;
		1590
		1591	while (%SIG_EV) {
		1592	for (keys %SIG_EV) {
		1593	delete $SIG_EV{$_};
831	$_->() for values %{ $SIG_CB{$signal} || {} };	1594	$_->() for values %{ $SIG_CB{$_} || {} };
		1595	}
		1596	}
		1597	};
832	};	1598	};
		1599	die if $@;
833		1600
834	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1601	&signal
835	}
836
837	sub AnyEvent::Base::Signal::DESTROY {
838	my ($signal, $cb) = @{$_[0]};
839
840	delete $SIG_CB{$signal}{$cb};
841
842	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
843	}	1602	}
844		1603
845	# default implementation for ->child	1604	# default implementation for ->child
846		1605
847	our %PID_CB;	1606	our %PID_CB;
848	our $CHLD_W;	1607	our $CHLD_W;
849	our $CHLD_DELAY_W;	1608	our $CHLD_DELAY_W;
850	our $PID_IDLE;
851	our $WNOHANG;	1609	our $WNOHANG;
852		1610
853	sub _child_wait {	1611	# used by many Impl's
854	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1612	sub _emit_childstatus($$) {
		1613	my (undef, $rpid, $rstatus) = @_;
		1614
		1615	$_->($rpid, $rstatus)
855	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1616	for values %{ $PID_CB{$rpid} || {} },
856	(values %{ $PID_CB{0} || {} });	1617	values %{ $PID_CB{0} || {} };
857	}
858
859	undef $PID_IDLE;
860	}
861
862	sub _sigchld {
863	# make sure we deliver these changes "synchronous" with the event loop.
864	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
865	undef $CHLD_DELAY_W;
866	&_child_wait;
867	});
868	}	1618	}
869		1619
870	sub child {	1620	sub child {
		1621	eval q{ # poor man's autoloading {}
		1622	*_sigchld = sub {
		1623	my $pid;
		1624
		1625	AnyEvent->_emit_childstatus ($pid, $?)
		1626	while ($pid = waitpid -1, $WNOHANG) > 0;
		1627	};
		1628
		1629	*child = sub {
871	my (undef, %arg) = @_;	1630	my (undef, %arg) = @_;
872		1631
873	defined (my $pid = $arg{pid} + 0)	1632	defined (my $pid = $arg{pid} + 0)
874	or Carp::croak "required option 'pid' is missing";	1633	or Carp::croak "required option 'pid' is missing";
875		1634
876	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1635	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
877		1636
878	unless ($WNOHANG) {	1637	# WNOHANG is almost cetrainly 1 everywhere
879	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1638	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
880	}	1639	? 1
		1640	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
881		1641
882	unless ($CHLD_W) {	1642	unless ($CHLD_W) {
883	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1643	$CHLD_W = AE::signal CHLD => \&_sigchld;
884	# child could be a zombie already, so make at least one round	1644	# child could be a zombie already, so make at least one round
885	&_sigchld;	1645	&_sigchld;
886	}	1646	}
887		1647
888	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1648	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
889	}	1649	};
890		1650
891	sub AnyEvent::Base::Child::DESTROY {	1651	*AnyEvent::Base::child::DESTROY = sub {
892	my ($pid, $cb) = @{$_[0]};	1652	my ($pid, $cb) = @{$_[0]};
893		1653
894	delete $PID_CB{$pid}{$cb};	1654	delete $PID_CB{$pid}{$cb};
895	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1655	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
896		1656
897	undef $CHLD_W unless keys %PID_CB;	1657	undef $CHLD_W unless keys %PID_CB;
		1658	};
		1659	};
		1660	die if $@;
		1661
		1662	&child
		1663	}
		1664
		1665	# idle emulation is done by simply using a timer, regardless
		1666	# of whether the process is idle or not, and not letting
		1667	# the callback use more than 50% of the time.
		1668	sub idle {
		1669	eval q{ # poor man's autoloading {}
		1670	*idle = sub {
		1671	my (undef, %arg) = @_;
		1672
		1673	my ($cb, $w, $rcb) = $arg{cb};
		1674
		1675	$rcb = sub {
		1676	if ($cb) {
		1677	$w = _time;
		1678	&$cb;
		1679	$w = _time - $w;
		1680
		1681	# never use more then 50% of the time for the idle watcher,
		1682	# within some limits
		1683	$w = 0.0001 if $w < 0.0001;
		1684	$w = 5 if $w > 5;
		1685
		1686	$w = AE::timer $w, 0, $rcb;
		1687	} else {
		1688	# clean up...
		1689	undef $w;
		1690	undef $rcb;
		1691	}
		1692	};
		1693
		1694	$w = AE::timer 0.05, 0, $rcb;
		1695
		1696	bless \\$cb, "AnyEvent::Base::idle"
		1697	};
		1698
		1699	*AnyEvent::Base::idle::DESTROY = sub {
		1700	undef $${$_[0]};
		1701	};
		1702	};
		1703	die if $@;
		1704
		1705	&idle
898	}	1706	}
899		1707
900	package AnyEvent::CondVar;	1708	package AnyEvent::CondVar;
901		1709
902	our @ISA = AnyEvent::CondVar::Base::;	1710	our @ISA = AnyEvent::CondVar::Base::;
903		1711
904	package AnyEvent::CondVar::Base;	1712	package AnyEvent::CondVar::Base;
		1713
		1714	#use overload
		1715	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1716	# fallback => 1;
		1717
		1718	# save 300+ kilobytes by dirtily hardcoding overloading
		1719	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1720	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1721	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1722	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1723
		1724	our $WAITING;
905		1725
906	sub _send {	1726	sub _send {
907	# nop	1727	# nop
908	}	1728	}
909		1729
…		…
922	sub ready {	1742	sub ready {
923	$_[0]{_ae_sent}	1743	$_[0]{_ae_sent}
924	}	1744	}
925		1745
926	sub _wait {	1746	sub _wait {
		1747	$WAITING
		1748	and !$_[0]{_ae_sent}
		1749	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1750
		1751	local $WAITING = 1;
927	AnyEvent->one_event while !$_[0]{_ae_sent};	1752	AnyEvent->one_event while !$_[0]{_ae_sent};
928	}	1753	}
929		1754
930	sub recv {	1755	sub recv {
931	$_[0]->_wait;	1756	$_[0]->_wait;
…		…
933	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};	1758	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
934	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]	1759	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
935	}	1760	}
936		1761
937	sub cb {	1762	sub cb {
938	$_[0]{_ae_cb} = $_[1] if @_ > 1;	1763	my $cv = shift;
		1764
		1765	@_
		1766	and $cv->{_ae_cb} = shift
		1767	and $cv->{_ae_sent}
		1768	and (delete $cv->{_ae_cb})->($cv);
		1769
939	$_[0]{_ae_cb}	1770	$cv->{_ae_cb}
940	}	1771	}
941		1772
942	sub begin {	1773	sub begin {
943	++$_[0]{_ae_counter};	1774	++$_[0]{_ae_counter};
944	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	1775	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
945	}	1776	}
946		1777
947	sub end {	1778	sub end {
948	return if --$_[0]{_ae_counter};	1779	return if --$_[0]{_ae_counter};
949	&{ $_[0]{_ae_end_cb} } if $_[0]{_ae_end_cb};	1780	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
950	}	1781	}
951		1782
952	# undocumented/compatibility with pre-3.4	1783	# undocumented/compatibility with pre-3.4
953	*broadcast = \&send;	1784	*broadcast = \&send;
954	*wait = \&_wait;	1785	*wait = \&_wait;
		1786
		1787	=head1 ERROR AND EXCEPTION HANDLING
		1788
		1789	In general, AnyEvent does not do any error handling - it relies on the
		1790	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1791	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1792	checking of all AnyEvent methods, however, which is highly useful during
		1793	development.
		1794
		1795	As for exception handling (i.e. runtime errors and exceptions thrown while
		1796	executing a callback), this is not only highly event-loop specific, but
		1797	also not in any way wrapped by this module, as this is the job of the main
		1798	program.
		1799
		1800	The pure perl event loop simply re-throws the exception (usually
		1801	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1802	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1803	so on.
		1804
		1805	=head1 ENVIRONMENT VARIABLES
		1806
		1807	The following environment variables are used by this module or its
		1808	submodules.
		1809
		1810	Note that AnyEvent will remove I<all> environment variables starting with
		1811	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1812	enabled.
		1813
		1814	=over 4
		1815
		1816	=item C<PERL_ANYEVENT_VERBOSE>
		1817
		1818	By default, AnyEvent will be completely silent except in fatal
		1819	conditions. You can set this environment variable to make AnyEvent more
		1820	talkative.
		1821
		1822	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1823	conditions, such as not being able to load the event model specified by
		1824	C<PERL_ANYEVENT_MODEL>.
		1825
		1826	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1827	model it chooses.
		1828
		1829	When set to C<8> or higher, then AnyEvent will report extra information on
		1830	which optional modules it loads and how it implements certain features.
		1831
		1832	=item C<PERL_ANYEVENT_STRICT>
		1833
		1834	AnyEvent does not do much argument checking by default, as thorough
		1835	argument checking is very costly. Setting this variable to a true value
		1836	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1837	check the arguments passed to most method calls. If it finds any problems,
		1838	it will croak.
		1839
		1840	In other words, enables "strict" mode.
		1841
		1842	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1843	>>, it is definitely recommended to keep it off in production. Keeping
		1844	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1845	can be very useful, however.
		1846
		1847	=item C<PERL_ANYEVENT_MODEL>
		1848
		1849	This can be used to specify the event model to be used by AnyEvent, before
		1850	auto detection and -probing kicks in. It must be a string consisting
		1851	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1852	and the resulting module name is loaded and if the load was successful,
		1853	used as event model. If it fails to load AnyEvent will proceed with
		1854	auto detection and -probing.
		1855
		1856	This functionality might change in future versions.
		1857
		1858	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1859	could start your program like this:
		1860
		1861	PERL_ANYEVENT_MODEL=Perl perl ...
		1862
		1863	=item C<PERL_ANYEVENT_PROTOCOLS>
		1864
		1865	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1866	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1867	of auto probing).
		1868
		1869	Must be set to a comma-separated list of protocols or address families,
		1870	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1871	used, and preference will be given to protocols mentioned earlier in the
		1872	list.
		1873
		1874	This variable can effectively be used for denial-of-service attacks
		1875	against local programs (e.g. when setuid), although the impact is likely
		1876	small, as the program has to handle conenction and other failures anyways.
		1877
		1878	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1879	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1880	- only support IPv4, never try to resolve or contact IPv6
		1881	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1882	IPv6, but prefer IPv6 over IPv4.
		1883
		1884	=item C<PERL_ANYEVENT_EDNS0>
		1885
		1886	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1887	for DNS. This extension is generally useful to reduce DNS traffic, but
		1888	some (broken) firewalls drop such DNS packets, which is why it is off by
		1889	default.
		1890
		1891	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1892	EDNS0 in its DNS requests.
		1893
		1894	=item C<PERL_ANYEVENT_MAX_FORKS>
		1895
		1896	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1897	will create in parallel.
		1898
		1899	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1900
		1901	The default value for the C<max_outstanding> parameter for the default DNS
		1902	resolver - this is the maximum number of parallel DNS requests that are
		1903	sent to the DNS server.
		1904
		1905	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1906
		1907	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1908	configuration) in the default resolver. When set to the empty string, no
		1909	default config will be used.
		1910
		1911	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1912
		1913	When neither C<ca_file> nor C<ca_path> was specified during
		1914	L<AnyEvent::TLS> context creation, and either of these environment
		1915	variables exist, they will be used to specify CA certificate locations
		1916	instead of a system-dependent default.
		1917
		1918	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1919
		1920	When these are set to C<1>, then the respective modules are not
		1921	loaded. Mostly good for testing AnyEvent itself.
		1922
		1923	=back
955		1924
956	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1925	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
957		1926
958	This is an advanced topic that you do not normally need to use AnyEvent in	1927	This is an advanced topic that you do not normally need to use AnyEvent in
959	a module. This section is only of use to event loop authors who want to	1928	a module. This section is only of use to event loop authors who want to
…		…
993		1962
994	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1963	I<rxvt-unicode> also cheats a bit by not providing blocking access to
995	condition variables: code blocking while waiting for a condition will	1964	condition variables: code blocking while waiting for a condition will
996	C<die>. This still works with most modules/usages, and blocking calls must	1965	C<die>. This still works with most modules/usages, and blocking calls must
997	not be done in an interactive application, so it makes sense.	1966	not be done in an interactive application, so it makes sense.
998
999	=head1 ENVIRONMENT VARIABLES
1000
1001	The following environment variables are used by this module:
1002
1003	=over 4
1004
1005	=item C<PERL_ANYEVENT_VERBOSE>
1006
1007	By default, AnyEvent will be completely silent except in fatal
1008	conditions. You can set this environment variable to make AnyEvent more
1009	talkative.
1010
1011	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1012	conditions, such as not being able to load the event model specified by
1013	C<PERL_ANYEVENT_MODEL>.
1014
1015	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1016	model it chooses.
1017
1018	=item C<PERL_ANYEVENT_MODEL>
1019
1020	This can be used to specify the event model to be used by AnyEvent, before
1021	autodetection and -probing kicks in. It must be a string consisting
1022	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1023	and the resulting module name is loaded and if the load was successful,
1024	used as event model. If it fails to load AnyEvent will proceed with
1025	autodetection and -probing.
1026
1027	This functionality might change in future versions.
1028
1029	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1030	could start your program like this:
1031
1032	PERL_ANYEVENT_MODEL=Perl perl ...
1033
1034	=back
1035		1967
1036	=head1 EXAMPLE PROGRAM	1968	=head1 EXAMPLE PROGRAM
1037		1969
1038	The following program uses an I/O watcher to read data from STDIN, a timer	1970	The following program uses an I/O watcher to read data from STDIN, a timer
1039	to display a message once per second, and a condition variable to quit the	1971	to display a message once per second, and a condition variable to quit the
…		…
1052	warn "read: $input\n"; # output what has been read	1984	warn "read: $input\n"; # output what has been read
1053	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1985	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1054	},	1986	},
1055	);	1987	);
1056		1988
1057	my $time_watcher; # can only be used once
1058
1059	sub new_timer {
1060	$timer = AnyEvent->timer (after => 1, cb => sub {	1989	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1061	warn "timeout\n"; # print 'timeout' about every second	1990	warn "timeout\n"; # print 'timeout' at most every second
1062	&new_timer; # and restart the time
1063	});	1991	});
1064	}
1065
1066	new_timer; # create first timer
1067		1992
1068	$cv->recv; # wait until user enters /^q/i	1993	$cv->recv; # wait until user enters /^q/i
1069		1994
1070	=head1 REAL-WORLD EXAMPLE	1995	=head1 REAL-WORLD EXAMPLE
1071		1996
…		…
1123	syswrite $txn->{fh}, $txn->{request}	2048	syswrite $txn->{fh}, $txn->{request}
1124	or die "connection or write error";	2049	or die "connection or write error";
1125	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2050	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1126		2051
1127	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2052	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1128	result and signals any possible waiters that the request ahs finished:	2053	result and signals any possible waiters that the request has finished:
1129		2054
1130	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2055	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1131		2056
1132	if (end-of-file or data complete) {	2057	if (end-of-file or data complete) {
1133	$txn->{result} = $txn->{buf};	2058	$txn->{result} = $txn->{buf};
…		…
1141		2066
1142	$txn->{finished}->recv;	2067	$txn->{finished}->recv;
1143	return $txn->{result};	2068	return $txn->{result};
1144		2069
1145	The actual code goes further and collects all errors (C<die>s, exceptions)	2070	The actual code goes further and collects all errors (C<die>s, exceptions)
1146	that occured during request processing. The C<result> method detects	2071	that occurred during request processing. The C<result> method detects
1147	whether an exception as thrown (it is stored inside the $txn object)	2072	whether an exception as thrown (it is stored inside the $txn object)
1148	and just throws the exception, which means connection errors and other	2073	and just throws the exception, which means connection errors and other
1149	problems get reported tot he code that tries to use the result, not in a	2074	problems get reported to the code that tries to use the result, not in a
1150	random callback.	2075	random callback.
1151		2076
1152	All of this enables the following usage styles:	2077	All of this enables the following usage styles:
1153		2078
1154	1. Blocking:	2079	1. Blocking:
…		…
1197	of various event loops I prepared some benchmarks.	2122	of various event loops I prepared some benchmarks.
1198		2123
1199	=head2 BENCHMARKING ANYEVENT OVERHEAD	2124	=head2 BENCHMARKING ANYEVENT OVERHEAD
1200		2125
1201	Here is a benchmark of various supported event models used natively and	2126	Here is a benchmark of various supported event models used natively and
1202	through anyevent. The benchmark creates a lot of timers (with a zero	2127	through AnyEvent. The benchmark creates a lot of timers (with a zero
1203	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2128	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1204	which it is), lets them fire exactly once and destroys them again.	2129	which it is), lets them fire exactly once and destroys them again.
1205		2130
1206	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2131	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1207	distribution.	2132	distribution. It uses the L<AE> interface, which makes a real difference
		2133	for the EV and Perl backends only.
1208		2134
1209	=head3 Explanation of the columns	2135	=head3 Explanation of the columns
1210		2136
1211	I<watcher> is the number of event watchers created/destroyed. Since	2137	I<watcher> is the number of event watchers created/destroyed. Since
1212	different event models feature vastly different performances, each event	2138	different event models feature vastly different performances, each event
…		…
1233	watcher.	2159	watcher.
1234		2160
1235	=head3 Results	2161	=head3 Results
1236		2162
1237	name watchers bytes create invoke destroy comment	2163	name watchers bytes create invoke destroy comment
1238	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2164	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1239	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2165	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1240	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2166	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1241	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2167	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1242	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2168	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1243	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2169	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2170	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2171	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1244	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2172	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1245	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2173	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1246	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2174	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1247	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2175	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1248		2176
1249	=head3 Discussion	2177	=head3 Discussion
1250		2178
1251	The benchmark does I<not> measure scalability of the event loop very	2179	The benchmark does I<not> measure scalability of the event loop very
1252	well. For example, a select-based event loop (such as the pure perl one)	2180	well. For example, a select-based event loop (such as the pure perl one)
…		…
1264	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2192	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1265	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2193	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1266	cycles with POE.	2194	cycles with POE.
1267		2195
1268	C<EV> is the sole leader regarding speed and memory use, which are both	2196	C<EV> is the sole leader regarding speed and memory use, which are both
1269	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2197	maximal/minimal, respectively. When using the L<AE> API there is zero
		2198	overhead (when going through the AnyEvent API create is about 5-6 times
		2199	slower, with other times being equal, so still uses far less memory than
1270	far less memory than any other event loop and is still faster than Event	2200	any other event loop and is still faster than Event natively).
1271	natively.
1272		2201
1273	The pure perl implementation is hit in a few sweet spots (both the	2202	The pure perl implementation is hit in a few sweet spots (both the
1274	constant timeout and the use of a single fd hit optimisations in the perl	2203	constant timeout and the use of a single fd hit optimisations in the perl
1275	interpreter and the backend itself). Nevertheless this shows that it	2204	interpreter and the backend itself). Nevertheless this shows that it
1276	adds very little overhead in itself. Like any select-based backend its	2205	adds very little overhead in itself. Like any select-based backend its
1277	performance becomes really bad with lots of file descriptors (and few of	2206	performance becomes really bad with lots of file descriptors (and few of
1278	them active), of course, but this was not subject of this benchmark.	2207	them active), of course, but this was not subject of this benchmark.
1279		2208
1280	The C<Event> module has a relatively high setup and callback invocation	2209	The C<Event> module has a relatively high setup and callback invocation
1281	cost, but overall scores in on the third place.	2210	cost, but overall scores in on the third place.
		2211
		2212	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2213	when using its pure perl backend.
1282		2214
1283	C<Glib>'s memory usage is quite a bit higher, but it features a	2215	C<Glib>'s memory usage is quite a bit higher, but it features a
1284	faster callback invocation and overall ends up in the same class as	2216	faster callback invocation and overall ends up in the same class as
1285	C<Event>. However, Glib scales extremely badly, doubling the number of	2217	C<Event>. However, Glib scales extremely badly, doubling the number of
1286	watchers increases the processing time by more than a factor of four,	2218	watchers increases the processing time by more than a factor of four,
…		…
1330		2262
1331	=back	2263	=back
1332		2264
1333	=head2 BENCHMARKING THE LARGE SERVER CASE	2265	=head2 BENCHMARKING THE LARGE SERVER CASE
1334		2266
1335	This benchmark atcually benchmarks the event loop itself. It works by	2267	This benchmark actually benchmarks the event loop itself. It works by
1336	creating a number of "servers": each server consists of a socketpair, a	2268	creating a number of "servers": each server consists of a socket pair, a
1337	timeout watcher that gets reset on activity (but never fires), and an I/O	2269	timeout watcher that gets reset on activity (but never fires), and an I/O
1338	watcher waiting for input on one side of the socket. Each time the socket	2270	watcher waiting for input on one side of the socket. Each time the socket
1339	watcher reads a byte it will write that byte to a random other "server".	2271	watcher reads a byte it will write that byte to a random other "server".
1340		2272
1341	The effect is that there will be a lot of I/O watchers, only part of which	2273	The effect is that there will be a lot of I/O watchers, only part of which
1342	are active at any one point (so there is a constant number of active	2274	are active at any one point (so there is a constant number of active
1343	fds for each loop iterstaion, but which fds these are is random). The	2275	fds for each loop iteration, but which fds these are is random). The
1344	timeout is reset each time something is read because that reflects how	2276	timeout is reset each time something is read because that reflects how
1345	most timeouts work (and puts extra pressure on the event loops).	2277	most timeouts work (and puts extra pressure on the event loops).
1346		2278
1347	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2279	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1348	(1%) are active. This mirrors the activity of large servers with many	2280	(1%) are active. This mirrors the activity of large servers with many
1349	connections, most of which are idle at any one point in time.	2281	connections, most of which are idle at any one point in time.
1350		2282
1351	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2283	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1352	distribution.	2284	distribution. It uses the L<AE> interface, which makes a real difference
		2285	for the EV and Perl backends only.
1353		2286
1354	=head3 Explanation of the columns	2287	=head3 Explanation of the columns
1355		2288
1356	I<sockets> is the number of sockets, and twice the number of "servers" (as	2289	I<sockets> is the number of sockets, and twice the number of "servers" (as
1357	each server has a read and write socket end).	2290	each server has a read and write socket end).
1358		2291
1359	I<create> is the time it takes to create a socketpair (which is	2292	I<create> is the time it takes to create a socket pair (which is
1360	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2293	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1361		2294
1362	I<request>, the most important value, is the time it takes to handle a	2295	I<request>, the most important value, is the time it takes to handle a
1363	single "request", that is, reading the token from the pipe and forwarding	2296	single "request", that is, reading the token from the pipe and forwarding
1364	it to another server. This includes deleting the old timeout and creating	2297	it to another server. This includes deleting the old timeout and creating
1365	a new one that moves the timeout into the future.	2298	a new one that moves the timeout into the future.
1366		2299
1367	=head3 Results	2300	=head3 Results
1368		2301
1369	name sockets create request	2302	name sockets create request
1370	EV 20000 69.01 11.16	2303	EV 20000 62.66 7.99
1371	Perl 20000 73.32 35.87	2304	Perl 20000 68.32 32.64
1372	Event 20000 212.62 257.32	2305	IOAsync 20000 174.06 101.15 epoll
1373	Glib 20000 651.16 1896.30	2306	IOAsync 20000 174.67 610.84 poll
		2307	Event 20000 202.69 242.91
		2308	Glib 20000 557.01 1689.52
1374	POE 20000 349.67 12317.24 uses POE::Loop::Event	2309	POE 20000 341.54 12086.32 uses POE::Loop::Event
1375		2310
1376	=head3 Discussion	2311	=head3 Discussion
1377		2312
1378	This benchmark I<does> measure scalability and overall performance of the	2313	This benchmark I<does> measure scalability and overall performance of the
1379	particular event loop.	2314	particular event loop.
…		…
1381	EV is again fastest. Since it is using epoll on my system, the setup time	2316	EV is again fastest. Since it is using epoll on my system, the setup time
1382	is relatively high, though.	2317	is relatively high, though.
1383		2318
1384	Perl surprisingly comes second. It is much faster than the C-based event	2319	Perl surprisingly comes second. It is much faster than the C-based event
1385	loops Event and Glib.	2320	loops Event and Glib.
		2321
		2322	IO::Async performs very well when using its epoll backend, and still quite
		2323	good compared to Glib when using its pure perl backend.
1386		2324
1387	Event suffers from high setup time as well (look at its code and you will	2325	Event suffers from high setup time as well (look at its code and you will
1388	understand why). Callback invocation also has a high overhead compared to	2326	understand why). Callback invocation also has a high overhead compared to
1389	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2327	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1390	uses select or poll in basically all documented configurations.	2328	uses select or poll in basically all documented configurations.
…		…
1437	speed most when you have lots of watchers, not when you only have a few of	2375	speed most when you have lots of watchers, not when you only have a few of
1438	them).	2376	them).
1439		2377
1440	EV is again fastest.	2378	EV is again fastest.
1441		2379
1442	Perl again comes second. It is noticably faster than the C-based event	2380	Perl again comes second. It is noticeably faster than the C-based event
1443	loops Event and Glib, although the difference is too small to really	2381	loops Event and Glib, although the difference is too small to really
1444	matter.	2382	matter.
1445		2383
1446	POE also performs much better in this case, but is is still far behind the	2384	POE also performs much better in this case, but is is still far behind the
1447	others.	2385	others.
…		…
1453	=item * C-based event loops perform very well with small number of	2391	=item * C-based event loops perform very well with small number of
1454	watchers, as the management overhead dominates.	2392	watchers, as the management overhead dominates.
1455		2393
1456	=back	2394	=back
1457		2395
		2396	=head2 THE IO::Lambda BENCHMARK
		2397
		2398	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2399	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2400	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2401	shouldn't come as a surprise to anybody). As such, the benchmark is
		2402	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2403	very optimal. But how would AnyEvent compare when used without the extra
		2404	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2405
		2406	The benchmark itself creates an echo-server, and then, for 500 times,
		2407	connects to the echo server, sends a line, waits for the reply, and then
		2408	creates the next connection. This is a rather bad benchmark, as it doesn't
		2409	test the efficiency of the framework or much non-blocking I/O, but it is a
		2410	benchmark nevertheless.
		2411
		2412	name runtime
		2413	Lambda/select 0.330 sec
		2414	+ optimized 0.122 sec
		2415	Lambda/AnyEvent 0.327 sec
		2416	+ optimized 0.138 sec
		2417	Raw sockets/select 0.077 sec
		2418	POE/select, components 0.662 sec
		2419	POE/select, raw sockets 0.226 sec
		2420	POE/select, optimized 0.404 sec
		2421
		2422	AnyEvent/select/nb 0.085 sec
		2423	AnyEvent/EV/nb 0.068 sec
		2424	+state machine 0.134 sec
		2425
		2426	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2427	benchmarks actually make blocking connects and use 100% blocking I/O,
		2428	defeating the purpose of an event-based solution. All of the newly
		2429	written AnyEvent benchmarks use 100% non-blocking connects (using
		2430	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2431	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2432	generally require a lot more bookkeeping and event handling than blocking
		2433	connects (which involve a single syscall only).
		2434
		2435	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2436	offers similar expressive power as POE and IO::Lambda, using conventional
		2437	Perl syntax. This means that both the echo server and the client are 100%
		2438	non-blocking, further placing it at a disadvantage.
		2439
		2440	As you can see, the AnyEvent + EV combination even beats the
		2441	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2442	backend easily beats IO::Lambda and POE.
		2443
		2444	And even the 100% non-blocking version written using the high-level (and
		2445	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2446	higher level ("unoptimised") abstractions by a large margin, even though
		2447	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2448
		2449	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2450	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2451	part of the IO::Lambda distribution and were used without any changes.
		2452
		2453
		2454	=head1 SIGNALS
		2455
		2456	AnyEvent currently installs handlers for these signals:
		2457
		2458	=over 4
		2459
		2460	=item SIGCHLD
		2461
		2462	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2463	emulation for event loops that do not support them natively. Also, some
		2464	event loops install a similar handler.
		2465
		2466	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2467	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2468
		2469	=item SIGPIPE
		2470
		2471	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2472	when AnyEvent gets loaded.
		2473
		2474	The rationale for this is that AnyEvent users usually do not really depend
		2475	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2476	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2477	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2478	some random socket.
		2479
		2480	The rationale for installing a no-op handler as opposed to ignoring it is
		2481	that this way, the handler will be restored to defaults on exec.
		2482
		2483	Feel free to install your own handler, or reset it to defaults.
		2484
		2485	=back
		2486
		2487	=cut
		2488
		2489	undef $SIG{CHLD}
		2490	if $SIG{CHLD} eq 'IGNORE';
		2491
		2492	$SIG{PIPE} = sub { }
		2493	unless defined $SIG{PIPE};
		2494
		2495	=head1 RECOMMENDED/OPTIONAL MODULES
		2496
		2497	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2498	it's built-in modules) are required to use it.
		2499
		2500	That does not mean that AnyEvent won't take advantage of some additional
		2501	modules if they are installed.
		2502
		2503	This section explains which additional modules will be used, and how they
		2504	affect AnyEvent's operation.
		2505
		2506	=over 4
		2507
		2508	=item L<Async::Interrupt>
		2509
		2510	This slightly arcane module is used to implement fast signal handling: To
		2511	my knowledge, there is no way to do completely race-free and quick
		2512	signal handling in pure perl. To ensure that signals still get
		2513	delivered, AnyEvent will start an interval timer to wake up perl (and
		2514	catch the signals) with some delay (default is 10 seconds, look for
		2515	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2516
		2517	If this module is available, then it will be used to implement signal
		2518	catching, which means that signals will not be delayed, and the event loop
		2519	will not be interrupted regularly, which is more efficient (and good for
		2520	battery life on laptops).
		2521
		2522	This affects not just the pure-perl event loop, but also other event loops
		2523	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2524
		2525	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2526	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2527	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2528	does nothing for those backends.
		2529
		2530	=item L<EV>
		2531
		2532	This module isn't really "optional", as it is simply one of the backend
		2533	event loops that AnyEvent can use. However, it is simply the best event
		2534	loop available in terms of features, speed and stability: It supports
		2535	the AnyEvent API optimally, implements all the watcher types in XS, does
		2536	automatic timer adjustments even when no monotonic clock is available,
		2537	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2538	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2539	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2540
		2541	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2542	then this module will do nothing for you.
		2543
		2544	=item L<Guard>
		2545
		2546	The guard module, when used, will be used to implement
		2547	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2548	lot less memory), but otherwise doesn't affect guard operation much. It is
		2549	purely used for performance.
		2550
		2551	=item L<JSON> and L<JSON::XS>
		2552
		2553	One of these modules is required when you want to read or write JSON data
		2554	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2555	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2556
		2557	=item L<Net::SSLeay>
		2558
		2559	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2560	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2561	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2562
		2563	=item L<Time::HiRes>
		2564
		2565	This module is part of perl since release 5.008. It will be used when the
		2566	chosen event library does not come with a timing source on it's own. The
		2567	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2568	try to use a monotonic clock for timing stability.
		2569
		2570	=back
		2571
1458		2572
1459	=head1 FORK	2573	=head1 FORK
1460		2574
1461	Most event libraries are not fork-safe. The ones who are usually are	2575	Most event libraries are not fork-safe. The ones who are usually are
1462	because they rely on inefficient but fork-safe C<select> or C<poll>	2576	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1463	calls. Only L<EV> is fully fork-aware.	2577	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2578	are usually badly thought-out hacks that are incompatible with fork in
		2579	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2580	continue event-processing in both parent and child (or both, if you know
		2581	what you are doing).
		2582
		2583	This means that, in general, you cannot fork and do event processing in
		2584	the child if the event library was initialised before the fork (which
		2585	usually happens when the first AnyEvent watcher is created, or the library
		2586	is loaded).
1464		2587
1465	If you have to fork, you must either do so I<before> creating your first	2588	If you have to fork, you must either do so I<before> creating your first
1466	watcher OR you must not use AnyEvent at all in the child.	2589	watcher OR you must not use AnyEvent at all in the child OR you must do
		2590	something completely out of the scope of AnyEvent.
		2591
		2592	The problem of doing event processing in the parent I<and> the child
		2593	is much more complicated: even for backends that I<are> fork-aware or
		2594	fork-safe, their behaviour is not usually what you want: fork clones all
		2595	watchers, that means all timers, I/O watchers etc. are active in both
		2596	parent and child, which is almost never what you want. USing C<exec>
		2597	to start worker children from some kind of manage rprocess is usually
		2598	preferred, because it is much easier and cleaner, at the expense of having
		2599	to have another binary.
1467		2600
1468		2601
1469	=head1 SECURITY CONSIDERATIONS	2602	=head1 SECURITY CONSIDERATIONS
1470		2603
1471	AnyEvent can be forced to load any event model via	2604	AnyEvent can be forced to load any event model via
…		…
1476	specified in the variable.	2609	specified in the variable.
1477		2610
1478	You can make AnyEvent completely ignore this variable by deleting it	2611	You can make AnyEvent completely ignore this variable by deleting it
1479	before the first watcher gets created, e.g. with a C<BEGIN> block:	2612	before the first watcher gets created, e.g. with a C<BEGIN> block:
1480		2613
1481	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2614	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1482		2615
1483	use AnyEvent;	2616	use AnyEvent;
1484		2617
1485	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2618	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1486	be used to probe what backend is used and gain other information (which is	2619	be used to probe what backend is used and gain other information (which is
1487	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2620	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2621	$ENV{PERL_ANYEVENT_STRICT}.
		2622
		2623	Note that AnyEvent will remove I<all> environment variables starting with
		2624	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2625	enabled.
		2626
		2627
		2628	=head1 BUGS
		2629
		2630	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2631	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2632	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2633	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2634	pronounced).
1488		2635
1489		2636
1490	=head1 SEE ALSO	2637	=head1 SEE ALSO
		2638
		2639	Utility functions: L<AnyEvent::Util>.
1491		2640
1492	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,	2641	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1493	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2642	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1494		2643
1495	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2644	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1496	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2645	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1497	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2646	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1498	L<AnyEvent::Impl::POE>.	2647	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1499		2648
		2649	Non-blocking file handles, sockets, TCP clients and
		2650	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2651
		2652	Asynchronous DNS: L<AnyEvent::DNS>.
		2653
1500	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2654	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2655	L<Coro::Event>,
1501		2656
1502	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2657	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2658	L<AnyEvent::HTTP>.
1503		2659
1504		2660
1505	=head1 AUTHOR	2661	=head1 AUTHOR
1506		2662
1507	Marc Lehmann <schmorp@schmorp.de>	2663	Marc Lehmann <schmorp@schmorp.de>
1508	http://home.schmorp.de/	2664	http://home.schmorp.de/
1509		2665
1510	=cut	2666	=cut
1511		2667
1512	1	2668	1
1513		2669

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