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Revision 1.137 by root, Mon May 26 03:27:52 2008 UTC vs.
Revision 1.239 by root, Thu Jul 16 20:55:38 2009 UTC

1	=head1 => NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
		6	event loops.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->send; # wake up current and all future recv's	35	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
		37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
22		45
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	46	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		47
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	48	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	49	nowadays. So what is different about AnyEvent?
27		50
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	51	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	52	policy> and AnyEvent is I<small and efficient>.
30		53
31	First and foremost, I<AnyEvent is not an event model> itself, it only	54	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	55	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	56	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	57	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	58	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	59	cannot change this, but it can hide the differences between those event
		60	loops.
37		61
38	The goal of AnyEvent is to offer module authors the ability to do event	62	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	63	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	64	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	65	module users into the same thing by forcing them to use the same event
42	model you use.	66	model you use.
43		67
44	For modules like POE or IO::Async (which is a total misnomer as it is	68	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	69	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	70	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	71	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	72	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	73	module are I<also> forced to use the same event loop you use.
50		74
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	75	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	76	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	77	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	78	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	79	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	80	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	81	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	82	to AnyEvent, too, so it is future-proof).
59		83
60	In addition to being free of having to use I<the one and only true event	84	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	85	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enormous amount of code and strict rules you have to	86	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	87	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	88	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	89	technically possible.
66		90
		91	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		92	of useful functionality, such as an asynchronous DNS resolver, 100%
		93	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		94	such as Windows) and lots of real-world knowledge and workarounds for
		95	platform bugs and differences.
		96
67	Of course, if you want lots of policy (this can arguably be somewhat	97	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	98	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	99	model, you should I<not> use this module.
70		100
71	=head1 DESCRIPTION	101	=head1 DESCRIPTION
72		102
…		…
102	starts using it, all bets are off. Maybe you should tell their authors to	132	starts using it, all bets are off. Maybe you should tell their authors to
103	use AnyEvent so their modules work together with others seamlessly...	133	use AnyEvent so their modules work together with others seamlessly...
104		134
105	The pure-perl implementation of AnyEvent is called	135	The pure-perl implementation of AnyEvent is called
106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	136	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
107	explicitly.	137	explicitly and enjoy the high availability of that event loop :)
108		138
109	=head1 WATCHERS	139	=head1 WATCHERS
110		140
111	AnyEvent has the central concept of a I<watcher>, which is an object that	141	AnyEvent has the central concept of a I<watcher>, which is an object that
112	stores relevant data for each kind of event you are waiting for, such as	142	stores relevant data for each kind of event you are waiting for, such as
…		…
115	These watchers are normal Perl objects with normal Perl lifetime. After	145	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	146	creating a watcher it will immediately "watch" for events and invoke the
117	callback when the event occurs (of course, only when the event model	147	callback when the event occurs (of course, only when the event model
118	is in control).	148	is in control).
119		149
		150	Note that B<callbacks must not permanently change global variables>
		151	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		152	callbacks must not C<die> >>. The former is good programming practise in
		153	Perl and the latter stems from the fact that exception handling differs
		154	widely between event loops.
		155
120	To disable the watcher you have to destroy it (e.g. by setting the	156	To disable the watcher you have to destroy it (e.g. by setting the
121	variable you store it in to C<undef> or otherwise deleting all references	157	variable you store it in to C<undef> or otherwise deleting all references
122	to it).	158	to it).
123		159
124	All watchers are created by calling a method on the C<AnyEvent> class.	160	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	162	Many watchers either are used with "recursion" (repeating timers for
127	example), or need to refer to their watcher object in other ways.	163	example), or need to refer to their watcher object in other ways.
128		164
129	An any way to achieve that is this pattern:	165	An any way to achieve that is this pattern:
130		166
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	167	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	168	# you can use $w here, for example to undef it
133	undef $w;	169	undef $w;
134	});	170	});
135		171
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	172	Note that C<my $w; $w => combination. This is necessary because in Perl,
137	my variables are only visible after the statement in which they are	173	my variables are only visible after the statement in which they are
138	declared.	174	declared.
139		175
140	=head2 I/O WATCHERS	176	=head2 I/O WATCHERS
141		177
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	178	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	179	with the following mandatory key-value pairs as arguments:
144		180
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	181	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		182	for events (AnyEvent might or might not keep a reference to this file
		183	handle). Note that only file handles pointing to things for which
		184	non-blocking operation makes sense are allowed. This includes sockets,
		185	most character devices, pipes, fifos and so on, but not for example files
		186	or block devices.
		187
146	for events. C<poll> must be a string that is either C<r> or C<w>,	188	C<poll> must be a string that is either C<r> or C<w>, which creates a
147	which creates a watcher waiting for "r"eadable or "w"ritable events,	189	watcher waiting for "r"eadable or "w"ritable events, respectively.
		190
148	respectively. C<cb> is the callback to invoke each time the file handle	191	C<cb> is the callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		192
151	Although the callback might get passed parameters, their value and	193	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	194	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	195	callbacks cannot use arguments passed to I/O watcher callbacks.
154		196
…		…
158		200
159	Some event loops issue spurious readyness notifications, so you should	201	Some event loops issue spurious readyness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	202	always use non-blocking calls when reading/writing from/to your file
161	handles.	203	handles.
162		204
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	205	Example: wait for readability of STDIN, then read a line and disable the
		206	watcher.
		207
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	208	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	209	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	210	warn "read: $input\n";
169	undef $w;	211	undef $w;
170	});	212	});
…		…
180		222
181	Although the callback might get passed parameters, their value and	223	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	224	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	225	callbacks cannot use arguments passed to time watcher callbacks.
184		226
185	The timer callback will be invoked at most once: if you want a repeating	227	The callback will normally be invoked once only. If you specify another
186	timer you have to create a new watcher (this is a limitation by both Tk	228	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	229	callback will be invoked regularly at that interval (in fractional
		230	seconds) after the first invocation. If C<interval> is specified with a
		231	false value, then it is treated as if it were missing.
188		232
189	Example:	233	The callback will be rescheduled before invoking the callback, but no
		234	attempt is done to avoid timer drift in most backends, so the interval is
		235	only approximate.
190		236
191	# fire an event after 7.7 seconds	237	Example: fire an event after 7.7 seconds.
		238
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	239	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	240	warn "timeout\n";
194	});	241	});
195		242
196	# to cancel the timer:	243	# to cancel the timer:
197	undef $w;	244	undef $w;
198		245
199	Example 2:
200
201	# fire an event after 0.5 seconds, then roughly every second	246	Example 2: fire an event after 0.5 seconds, then roughly every second.
202	my $w;
203		247
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	248	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		249	warn "timeout\n";
207	};	250	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		251
212	=head3 TIMING ISSUES	252	=head3 TIMING ISSUES
213		253
214	There are two ways to handle timers: based on real time (relative, "fire	254	There are two ways to handle timers: based on real time (relative, "fire
215	in 10 seconds") and based on wallclock time (absolute, "fire at 12	255	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
227	timers.	267	timers.
228		268
229	AnyEvent always prefers relative timers, if available, matching the	269	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	270	AnyEvent API.
231		271
		272	AnyEvent has two additional methods that return the "current time":
		273
		274	=over 4
		275
		276	=item AnyEvent->time
		277
		278	This returns the "current wallclock time" as a fractional number of
		279	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		280	return, and the result is guaranteed to be compatible with those).
		281
		282	It progresses independently of any event loop processing, i.e. each call
		283	will check the system clock, which usually gets updated frequently.
		284
		285	=item AnyEvent->now
		286
		287	This also returns the "current wallclock time", but unlike C<time>, above,
		288	this value might change only once per event loop iteration, depending on
		289	the event loop (most return the same time as C<time>, above). This is the
		290	time that AnyEvent's timers get scheduled against.
		291
		292	I<In almost all cases (in all cases if you don't care), this is the
		293	function to call when you want to know the current time.>
		294
		295	This function is also often faster then C<< AnyEvent->time >>, and
		296	thus the preferred method if you want some timestamp (for example,
		297	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		298
		299	The rest of this section is only of relevance if you try to be very exact
		300	with your timing, you can skip it without bad conscience.
		301
		302	For a practical example of when these times differ, consider L<Event::Lib>
		303	and L<EV> and the following set-up:
		304
		305	The event loop is running and has just invoked one of your callback at
		306	time=500 (assume no other callbacks delay processing). In your callback,
		307	you wait a second by executing C<sleep 1> (blocking the process for a
		308	second) and then (at time=501) you create a relative timer that fires
		309	after three seconds.
		310
		311	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		312	both return C<501>, because that is the current time, and the timer will
		313	be scheduled to fire at time=504 (C<501> + C<3>).
		314
		315	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		316	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		317	last event processing phase started. With L<EV>, your timer gets scheduled
		318	to run at time=503 (C<500> + C<3>).
		319
		320	In one sense, L<Event::Lib> is more exact, as it uses the current time
		321	regardless of any delays introduced by event processing. However, most
		322	callbacks do not expect large delays in processing, so this causes a
		323	higher drift (and a lot more system calls to get the current time).
		324
		325	In another sense, L<EV> is more exact, as your timer will be scheduled at
		326	the same time, regardless of how long event processing actually took.
		327
		328	In either case, if you care (and in most cases, you don't), then you
		329	can get whatever behaviour you want with any event loop, by taking the
		330	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		331	account.
		332
		333	=item AnyEvent->now_update
		334
		335	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		336	the current time for each loop iteration (see the discussion of L<<
		337	AnyEvent->now >>, above).
		338
		339	When a callback runs for a long time (or when the process sleeps), then
		340	this "current" time will differ substantially from the real time, which
		341	might affect timers and time-outs.
		342
		343	When this is the case, you can call this method, which will update the
		344	event loop's idea of "current time".
		345
		346	Note that updating the time I<might> cause some events to be handled.
		347
		348	=back
		349
232	=head2 SIGNAL WATCHERS	350	=head2 SIGNAL WATCHERS
233		351
234	You can watch for signals using a signal watcher, C<signal> is the signal	352	You can watch for signals using a signal watcher, C<signal> is the signal
235	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	353	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	354	callback to be invoked whenever a signal occurs.
237		355
238	Although the callback might get passed parameters, their value and	356	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	357	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	358	callbacks cannot use arguments passed to signal watcher callbacks.
241		359
…		…
257	=head2 CHILD PROCESS WATCHERS	375	=head2 CHILD PROCESS WATCHERS
258		376
259	You can also watch on a child process exit and catch its exit status.	377	You can also watch on a child process exit and catch its exit status.
260		378
261	The child process is specified by the C<pid> argument (if set to C<0>, it	379	The child process is specified by the C<pid> argument (if set to C<0>, it
262	watches for any child process exit). The watcher will trigger as often	380	watches for any child process exit). The watcher will triggered only when
263	as status change for the child are received. This works by installing a	381	the child process has finished and an exit status is available, not on
264	signal handler for C<SIGCHLD>. The callback will be called with the pid	382	any trace events (stopped/continued).
265	and exit status (as returned by waitpid), so unlike other watcher types,	383
266	you I<can> rely on child watcher callback arguments.	384	The callback will be called with the pid and exit status (as returned by
		385	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		386	callback arguments.
		387
		388	This watcher type works by installing a signal handler for C<SIGCHLD>,
		389	and since it cannot be shared, nothing else should use SIGCHLD or reap
		390	random child processes (waiting for specific child processes, e.g. inside
		391	C<system>, is just fine).
267		392
268	There is a slight catch to child watchers, however: you usually start them	393	There is a slight catch to child watchers, however: you usually start them
269	I<after> the child process was created, and this means the process could	394	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	395	have exited already (and no SIGCHLD will be sent anymore).
271		396
272	Not all event models handle this correctly (POE doesn't), but even for	397	Not all event models handle this correctly (neither POE nor IO::Async do,
		398	see their AnyEvent::Impl manpages for details), but even for event models
273	event models that I<do> handle this correctly, they usually need to be	399	that I<do> handle this correctly, they usually need to be loaded before
274	loaded before the process exits (i.e. before you fork in the first place).	400	the process exits (i.e. before you fork in the first place). AnyEvent's
		401	pure perl event loop handles all cases correctly regardless of when you
		402	start the watcher.
275		403
276	This means you cannot create a child watcher as the very first thing in an	404	This means you cannot create a child watcher as the very first
277	AnyEvent program, you I<have> to create at least one watcher before you	405	thing in an AnyEvent program, you I<have> to create at least one
278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	406	watcher before you C<fork> the child (alternatively, you can call
		407	C<AnyEvent::detect>).
279		408
280	Example: fork a process and wait for it	409	Example: fork a process and wait for it
281		410
282	my $done = AnyEvent->condvar;	411	my $done = AnyEvent->condvar;
283		412
284	my $pid = fork or exit 5;	413	my $pid = fork or exit 5;
285		414
286	my $w = AnyEvent->child (	415	my $w = AnyEvent->child (
287	pid => $pid,	416	pid => $pid,
288	cb => sub {	417	cb => sub {
289	my ($pid, $status) = @_;	418	my ($pid, $status) = @_;
290	warn "pid $pid exited with status $status";	419	warn "pid $pid exited with status $status";
291	$done->send;	420	$done->send;
292	},	421	},
293	);	422	);
294		423
295	# do something else, then wait for process exit	424	# do something else, then wait for process exit
296	$done->recv;	425	$done->recv;
		426
		427	=head2 IDLE WATCHERS
		428
		429	Sometimes there is a need to do something, but it is not so important
		430	to do it instantly, but only when there is nothing better to do. This
		431	"nothing better to do" is usually defined to be "no other events need
		432	attention by the event loop".
		433
		434	Idle watchers ideally get invoked when the event loop has nothing
		435	better to do, just before it would block the process to wait for new
		436	events. Instead of blocking, the idle watcher is invoked.
		437
		438	Most event loops unfortunately do not really support idle watchers (only
		439	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		440	will simply call the callback "from time to time".
		441
		442	Example: read lines from STDIN, but only process them when the
		443	program is otherwise idle:
		444
		445	my @lines; # read data
		446	my $idle_w;
		447	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		448	push @lines, scalar <STDIN>;
		449
		450	# start an idle watcher, if not already done
		451	$idle_w ||= AnyEvent->idle (cb => sub {
		452	# handle only one line, when there are lines left
		453	if (my $line = shift @lines) {
		454	print "handled when idle: $line";
		455	} else {
		456	# otherwise disable the idle watcher again
		457	undef $idle_w;
		458	}
		459	});
		460	});
297		461
298	=head2 CONDITION VARIABLES	462	=head2 CONDITION VARIABLES
299		463
300	If you are familiar with some event loops you will know that all of them	464	If you are familiar with some event loops you will know that all of them
301	require you to run some blocking "loop", "run" or similar function that	465	require you to run some blocking "loop", "run" or similar function that
302	will actively watch for new events and call your callbacks.	466	will actively watch for new events and call your callbacks.
303		467
304	AnyEvent is different, it expects somebody else to run the event loop and	468	AnyEvent is slightly different: it expects somebody else to run the event
305	will only block when necessary (usually when told by the user).	469	loop and will only block when necessary (usually when told by the user).
306		470
307	The instrument to do that is called a "condition variable", so called	471	The instrument to do that is called a "condition variable", so called
308	because they represent a condition that must become true.	472	because they represent a condition that must become true.
		473
		474	Now is probably a good time to look at the examples further below.
309		475
310	Condition variables can be created by calling the C<< AnyEvent->condvar	476	Condition variables can be created by calling the C<< AnyEvent->condvar
311	>> method, usually without arguments. The only argument pair allowed is	477	>> method, usually without arguments. The only argument pair allowed is
312	C<cb>, which specifies a callback to be called when the condition variable	478	C<cb>, which specifies a callback to be called when the condition variable
313	becomes true.	479	becomes true, with the condition variable as the first argument (but not
		480	the results).
314		481
315	After creation, the condition variable is "false" until it becomes "true"	482	After creation, the condition variable is "false" until it becomes "true"
316	by calling the C<send> method (or calling the condition variable as if it	483	by calling the C<send> method (or calling the condition variable as if it
317	were a callback, read about the caveats in the description for the C<<	484	were a callback, read about the caveats in the description for the C<<
318	->send >> method).	485	->send >> method).
…		…
364	after => 1,	531	after => 1,
365	cb => sub { $result_ready->send },	532	cb => sub { $result_ready->send },
366	);	533	);
367		534
368	# this "blocks" (while handling events) till the callback	535	# this "blocks" (while handling events) till the callback
369	# calls send	536	# calls -<send
370	$result_ready->recv;	537	$result_ready->recv;
371		538
372	Example: wait for a timer, but take advantage of the fact that	539	Example: wait for a timer, but take advantage of the fact that condition
373	condition variables are also code references.	540	variables are also callable directly.
374		541
375	my $done = AnyEvent->condvar;	542	my $done = AnyEvent->condvar;
376	my $delay = AnyEvent->timer (after => 5, cb => $done);	543	my $delay = AnyEvent->timer (after => 5, cb => $done);
377	$done->recv;	544	$done->recv;
		545
		546	Example: Imagine an API that returns a condvar and doesn't support
		547	callbacks. This is how you make a synchronous call, for example from
		548	the main program:
		549
		550	use AnyEvent::CouchDB;
		551
		552	...
		553
		554	my @info = $couchdb->info->recv;
		555
		556	And this is how you would just set a callback to be called whenever the
		557	results are available:
		558
		559	$couchdb->info->cb (sub {
		560	my @info = $_[0]->recv;
		561	});
378		562
379	=head3 METHODS FOR PRODUCERS	563	=head3 METHODS FOR PRODUCERS
380		564
381	These methods should only be used by the producing side, i.e. the	565	These methods should only be used by the producing side, i.e. the
382	code/module that eventually sends the signal. Note that it is also	566	code/module that eventually sends the signal. Note that it is also
…		…
395	immediately from within send.	579	immediately from within send.
396		580
397	Any arguments passed to the C<send> call will be returned by all	581	Any arguments passed to the C<send> call will be returned by all
398	future C<< ->recv >> calls.	582	future C<< ->recv >> calls.
399		583
400	Condition variables are overloaded so one can call them directly	584	Condition variables are overloaded so one can call them directly (as if
401	(as a code reference). Calling them directly is the same as calling	585	they were a code reference). Calling them directly is the same as calling
402	C<send>. Note, however, that many C-based event loops do not handle	586	C<send>.
403	overloading, so as tempting as it may be, passing a condition variable
404	instead of a callback does not work. Both the pure perl and EV loops
405	support overloading, however, as well as all functions that use perl to
406	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
407	example).
408		587
409	=item $cv->croak ($error)	588	=item $cv->croak ($error)
410		589
411	Similar to send, but causes all call's to C<< ->recv >> to invoke	590	Similar to send, but causes all call's to C<< ->recv >> to invoke
412	C<Carp::croak> with the given error message/object/scalar.	591	C<Carp::croak> with the given error message/object/scalar.
413		592
414	This can be used to signal any errors to the condition variable	593	This can be used to signal any errors to the condition variable
415	user/consumer.	594	user/consumer. Doing it this way instead of calling C<croak> directly
		595	delays the error detetcion, but has the overwhelmign advantage that it
		596	diagnoses the error at the place where the result is expected, and not
		597	deep in some event clalback without connection to the actual code causing
		598	the problem.
416		599
417	=item $cv->begin ([group callback])	600	=item $cv->begin ([group callback])
418		601
419	=item $cv->end	602	=item $cv->end
420
421	These two methods are EXPERIMENTAL and MIGHT CHANGE.
422		603
423	These two methods can be used to combine many transactions/events into	604	These two methods can be used to combine many transactions/events into
424	one. For example, a function that pings many hosts in parallel might want	605	one. For example, a function that pings many hosts in parallel might want
425	to use a condition variable for the whole process.	606	to use a condition variable for the whole process.
426		607
…		…
428	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	609	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
429	>>, the (last) callback passed to C<begin> will be executed. That callback	610	>>, the (last) callback passed to C<begin> will be executed. That callback
430	is I<supposed> to call C<< ->send >>, but that is not required. If no	611	is I<supposed> to call C<< ->send >>, but that is not required. If no
431	callback was set, C<send> will be called without any arguments.	612	callback was set, C<send> will be called without any arguments.
432		613
433	Let's clarify this with the ping example:	614	You can think of C<< $cv->send >> giving you an OR condition (one call
		615	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		616	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		617
		618	Let's start with a simple example: you have two I/O watchers (for example,
		619	STDOUT and STDERR for a program), and you want to wait for both streams to
		620	close before activating a condvar:
		621
		622	my $cv = AnyEvent->condvar;
		623
		624	$cv->begin; # first watcher
		625	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		626	defined sysread $fh1, my $buf, 4096
		627	or $cv->end;
		628	});
		629
		630	$cv->begin; # second watcher
		631	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		632	defined sysread $fh2, my $buf, 4096
		633	or $cv->end;
		634	});
		635
		636	$cv->recv;
		637
		638	This works because for every event source (EOF on file handle), there is
		639	one call to C<begin>, so the condvar waits for all calls to C<end> before
		640	sending.
		641
		642	The ping example mentioned above is slightly more complicated, as the
		643	there are results to be passwd back, and the number of tasks that are
		644	begung can potentially be zero:
434		645
435	my $cv = AnyEvent->condvar;	646	my $cv = AnyEvent->condvar;
436		647
437	my %result;	648	my %result;
438	$cv->begin (sub { $cv->send (\%result) });	649	$cv->begin (sub { $cv->send (\%result) });
…		…
458	loop, which serves two important purposes: first, it sets the callback	669	loop, which serves two important purposes: first, it sets the callback
459	to be called once the counter reaches C<0>, and second, it ensures that	670	to be called once the counter reaches C<0>, and second, it ensures that
460	C<send> is called even when C<no> hosts are being pinged (the loop	671	C<send> is called even when C<no> hosts are being pinged (the loop
461	doesn't execute once).	672	doesn't execute once).
462		673
463	This is the general pattern when you "fan out" into multiple subrequests:	674	This is the general pattern when you "fan out" into multiple (but
464	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	675	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
465	is called at least once, and then, for each subrequest you start, call	676	the callback and ensure C<end> is called at least once, and then, for each
466	C<begin> and for each subrequest you finish, call C<end>.	677	subrequest you start, call C<begin> and for each subrequest you finish,
		678	call C<end>.
467		679
468	=back	680	=back
469		681
470	=head3 METHODS FOR CONSUMERS	682	=head3 METHODS FOR CONSUMERS
471		683
…		…
487	function will call C<croak>.	699	function will call C<croak>.
488		700
489	In list context, all parameters passed to C<send> will be returned,	701	In list context, all parameters passed to C<send> will be returned,
490	in scalar context only the first one will be returned.	702	in scalar context only the first one will be returned.
491		703
		704	Note that doing a blocking wait in a callback is not supported by any
		705	event loop, that is, recursive invocation of a blocking C<< ->recv
		706	>> is not allowed, and the C<recv> call will C<croak> if such a
		707	condition is detected. This condition can be slightly loosened by using
		708	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		709	any thread that doesn't run the event loop itself.
		710
492	Not all event models support a blocking wait - some die in that case	711	Not all event models support a blocking wait - some die in that case
493	(programs might want to do that to stay interactive), so I<if you are	712	(programs might want to do that to stay interactive), so I<if you are
494	using this from a module, never require a blocking wait>, but let the	713	using this from a module, never require a blocking wait>. Instead, let the
495	caller decide whether the call will block or not (for example, by coupling	714	caller decide whether the call will block or not (for example, by coupling
496	condition variables with some kind of request results and supporting	715	condition variables with some kind of request results and supporting
497	callbacks so the caller knows that getting the result will not block,	716	callbacks so the caller knows that getting the result will not block,
498	while still supporting blocking waits if the caller so desires).	717	while still supporting blocking waits if the caller so desires).
499		718
500	Another reason I<never> to C<< ->recv >> in a module is that you cannot
501	sensibly have two C<< ->recv >>'s in parallel, as that would require
502	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
503	can supply.
504
505	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
506	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
507	versions and also integrates coroutines into AnyEvent, making blocking
508	C<< ->recv >> calls perfectly safe as long as they are done from another
509	coroutine (one that doesn't run the event loop).
510
511	You can ensure that C<< -recv >> never blocks by setting a callback and	719	You can ensure that C<< -recv >> never blocks by setting a callback and
512	only calling C<< ->recv >> from within that callback (or at a later	720	only calling C<< ->recv >> from within that callback (or at a later
513	time). This will work even when the event loop does not support blocking	721	time). This will work even when the event loop does not support blocking
514	waits otherwise.	722	waits otherwise.
515		723
516	=item $bool = $cv->ready	724	=item $bool = $cv->ready
517		725
518	Returns true when the condition is "true", i.e. whether C<send> or	726	Returns true when the condition is "true", i.e. whether C<send> or
519	C<croak> have been called.	727	C<croak> have been called.
520		728
521	=item $cb = $cv->cb ([new callback])	729	=item $cb = $cv->cb ($cb->($cv))
522		730
523	This is a mutator function that returns the callback set and optionally	731	This is a mutator function that returns the callback set and optionally
524	replaces it before doing so.	732	replaces it before doing so.
525		733
526	The callback will be called when the condition becomes "true", i.e. when	734	The callback will be called when the condition becomes "true", i.e. when
527	C<send> or C<croak> are called. Calling C<recv> inside the callback	735	C<send> or C<croak> are called, with the only argument being the condition
528	or at any later time is guaranteed not to block.	736	variable itself. Calling C<recv> inside the callback or at any later time
		737	is guaranteed not to block.
529		738
530	=back	739	=back
531		740
		741	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		742
		743	The available backend classes are (every class has its own manpage):
		744
		745	=over 4
		746
		747	=item Backends that are autoprobed when no other event loop can be found.
		748
		749	EV is the preferred backend when no other event loop seems to be in
		750	use. If EV is not installed, then AnyEvent will try Event, and, failing
		751	that, will fall back to its own pure-perl implementation, which is
		752	available everywhere as it comes with AnyEvent itself.
		753
		754	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		755	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		756	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		757
		758	=item Backends that are transparently being picked up when they are used.
		759
		760	These will be used when they are currently loaded when the first watcher
		761	is created, in which case it is assumed that the application is using
		762	them. This means that AnyEvent will automatically pick the right backend
		763	when the main program loads an event module before anything starts to
		764	create watchers. Nothing special needs to be done by the main program.
		765
		766	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		767	AnyEvent::Impl::Tk based on Tk, very broken.
		768	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		769	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		770
		771	=item Backends with special needs.
		772
		773	Qt requires the Qt::Application to be instantiated first, but will
		774	otherwise be picked up automatically. As long as the main program
		775	instantiates the application before any AnyEvent watchers are created,
		776	everything should just work.
		777
		778	AnyEvent::Impl::Qt based on Qt.
		779
		780	Support for IO::Async can only be partial, as it is too broken and
		781	architecturally limited to even support the AnyEvent API. It also
		782	is the only event loop that needs the loop to be set explicitly, so
		783	it can only be used by a main program knowing about AnyEvent. See
		784	L<AnyEvent::Impl::Async> for the gory details.
		785
		786	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		787
		788	=item Event loops that are indirectly supported via other backends.
		789
		790	Some event loops can be supported via other modules:
		791
		792	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		793
		794	B<WxWidgets> has no support for watching file handles. However, you can
		795	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		796	polls 20 times per second, which was considered to be too horrible to even
		797	consider for AnyEvent.
		798
		799	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		800	backend, so it can be supported through POE.
		801
		802	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		803	load L<POE> when detecting them, in the hope that POE will pick them up,
		804	in which case everything will be automatic.
		805
		806	=back
		807
532	=head1 GLOBAL VARIABLES AND FUNCTIONS	808	=head1 GLOBAL VARIABLES AND FUNCTIONS
533		809
		810	These are not normally required to use AnyEvent, but can be useful to
		811	write AnyEvent extension modules.
		812
534	=over 4	813	=over 4
535		814
536	=item $AnyEvent::MODEL	815	=item $AnyEvent::MODEL
537		816
538	Contains C<undef> until the first watcher is being created. Then it	817	Contains C<undef> until the first watcher is being created, before the
		818	backend has been autodetected.
		819
539	contains the event model that is being used, which is the name of the	820	Afterwards it contains the event model that is being used, which is the
540	Perl class implementing the model. This class is usually one of the	821	name of the Perl class implementing the model. This class is usually one
541	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	822	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
542	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	823	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
543		824	will be C<urxvt::anyevent>).
544	The known classes so far are:
545
546	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
547	AnyEvent::Impl::Event based on Event, second best choice.
548	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
549	AnyEvent::Impl::Glib based on Glib, third-best choice.
550	AnyEvent::Impl::Tk based on Tk, very bad choice.
551	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
552	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
553	AnyEvent::Impl::POE based on POE, not generic enough for full support.
554
555	There is no support for WxWidgets, as WxWidgets has no support for
556	watching file handles. However, you can use WxWidgets through the
557	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
558	second, which was considered to be too horrible to even consider for
559	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
560	it's adaptor.
561
562	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
563	autodetecting them.
564		825
565	=item AnyEvent::detect	826	=item AnyEvent::detect
566		827
567	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	828	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
568	if necessary. You should only call this function right before you would	829	if necessary. You should only call this function right before you would
569	have created an AnyEvent watcher anyway, that is, as late as possible at	830	have created an AnyEvent watcher anyway, that is, as late as possible at
570	runtime.	831	runtime, and not e.g. while initialising of your module.
		832
		833	If you need to do some initialisation before AnyEvent watchers are
		834	created, use C<post_detect>.
571		835
572	=item $guard = AnyEvent::post_detect { BLOCK }	836	=item $guard = AnyEvent::post_detect { BLOCK }
573		837
574	Arranges for the code block to be executed as soon as the event model is	838	Arranges for the code block to be executed as soon as the event model is
575	autodetected (or immediately if this has already happened).	839	autodetected (or immediately if this has already happened).
		840
		841	The block will be executed I<after> the actual backend has been detected
		842	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		843	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		844	other initialisations - see the sources of L<AnyEvent::Strict> or
		845	L<AnyEvent::AIO> to see how this is used.
		846
		847	The most common usage is to create some global watchers, without forcing
		848	event module detection too early, for example, L<AnyEvent::AIO> creates
		849	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		850	avoid autodetecting the event module at load time.
576		851
577	If called in scalar or list context, then it creates and returns an object	852	If called in scalar or list context, then it creates and returns an object
578	that automatically removes the callback again when it is destroyed. See	853	that automatically removes the callback again when it is destroyed. See
579	L<Coro::BDB> for a case where this is useful.	854	L<Coro::BDB> for a case where this is useful.
580		855
…		…
583	If there are any code references in this array (you can C<push> to it	858	If there are any code references in this array (you can C<push> to it
584	before or after loading AnyEvent), then they will called directly after	859	before or after loading AnyEvent), then they will called directly after
585	the event loop has been chosen.	860	the event loop has been chosen.
586		861
587	You should check C<$AnyEvent::MODEL> before adding to this array, though:	862	You should check C<$AnyEvent::MODEL> before adding to this array, though:
588	if it contains a true value then the event loop has already been detected,	863	if it is defined then the event loop has already been detected, and the
589	and the array will be ignored.	864	array will be ignored.
590		865
591	Best use C<AnyEvent::post_detect { BLOCK }> instead.	866	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		867	it,as it takes care of these details.
		868
		869	This variable is mainly useful for modules that can do something useful
		870	when AnyEvent is used and thus want to know when it is initialised, but do
		871	not need to even load it by default. This array provides the means to hook
		872	into AnyEvent passively, without loading it.
592		873
593	=back	874	=back
594		875
595	=head1 WHAT TO DO IN A MODULE	876	=head1 WHAT TO DO IN A MODULE
596		877
…		…
651		932
652		933
653	=head1 OTHER MODULES	934	=head1 OTHER MODULES
654		935
655	The following is a non-exhaustive list of additional modules that use	936	The following is a non-exhaustive list of additional modules that use
656	AnyEvent and can therefore be mixed easily with other AnyEvent modules	937	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
657	in the same program. Some of the modules come with AnyEvent, some are	938	modules and other event loops in the same program. Some of the modules
658	available via CPAN.	939	come with AnyEvent, most are available via CPAN.
659		940
660	=over 4	941	=over 4
661		942
662	=item L<AnyEvent::Util>	943	=item L<AnyEvent::Util>
663		944
664	Contains various utility functions that replace often-used but blocking	945	Contains various utility functions that replace often-used but blocking
665	functions such as C<inet_aton> by event-/callback-based versions.	946	functions such as C<inet_aton> by event-/callback-based versions.
666
667	=item L<AnyEvent::Handle>
668
669	Provide read and write buffers and manages watchers for reads and writes.
670		947
671	=item L<AnyEvent::Socket>	948	=item L<AnyEvent::Socket>
672		949
673	Provides various utility functions for (internet protocol) sockets,	950	Provides various utility functions for (internet protocol) sockets,
674	addresses and name resolution. Also functions to create non-blocking tcp	951	addresses and name resolution. Also functions to create non-blocking tcp
675	connections or tcp servers, with IPv6 and SRV record support and more.	952	connections or tcp servers, with IPv6 and SRV record support and more.
676		953
		954	=item L<AnyEvent::Handle>
		955
		956	Provide read and write buffers, manages watchers for reads and writes,
		957	supports raw and formatted I/O, I/O queued and fully transparent and
		958	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		959
677	=item L<AnyEvent::DNS>	960	=item L<AnyEvent::DNS>
678		961
679	Provides rich asynchronous DNS resolver capabilities.	962	Provides rich asynchronous DNS resolver capabilities.
680		963
		964	=item L<AnyEvent::HTTP>
		965
		966	A simple-to-use HTTP library that is capable of making a lot of concurrent
		967	HTTP requests.
		968
681	=item L<AnyEvent::HTTPD>	969	=item L<AnyEvent::HTTPD>
682		970
683	Provides a simple web application server framework.	971	Provides a simple web application server framework.
684		972
685	=item L<AnyEvent::FastPing>	973	=item L<AnyEvent::FastPing>
686		974
687	The fastest ping in the west.	975	The fastest ping in the west.
688		976
		977	=item L<AnyEvent::DBI>
		978
		979	Executes L<DBI> requests asynchronously in a proxy process.
		980
		981	=item L<AnyEvent::AIO>
		982
		983	Truly asynchronous I/O, should be in the toolbox of every event
		984	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		985	together.
		986
		987	=item L<AnyEvent::BDB>
		988
		989	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		990	L<BDB> and AnyEvent together.
		991
		992	=item L<AnyEvent::GPSD>
		993
		994	A non-blocking interface to gpsd, a daemon delivering GPS information.
		995
689	=item L<Net::IRC3>	996	=item L<AnyEvent::IRC>
690		997
691	AnyEvent based IRC client module family.	998	AnyEvent based IRC client module family (replacing the older Net::IRC3).
692		999
693	=item L<Net::XMPP2>	1000	=item L<AnyEvent::XMPP>
694		1001
695	AnyEvent based XMPP (Jabber protocol) module family.	1002	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1003	Net::XMPP2>.
		1004
		1005	=item L<AnyEvent::IGS>
		1006
		1007	A non-blocking interface to the Internet Go Server protocol (used by
		1008	L<App::IGS>).
696		1009
697	=item L<Net::FCP>	1010	=item L<Net::FCP>
698		1011
699	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1012	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
700	of AnyEvent.	1013	of AnyEvent.
…		…
705		1018
706	=item L<Coro>	1019	=item L<Coro>
707		1020
708	Has special support for AnyEvent via L<Coro::AnyEvent>.	1021	Has special support for AnyEvent via L<Coro::AnyEvent>.
709		1022
710	=item L<AnyEvent::AIO>, L<IO::AIO>
711
712	Truly asynchronous I/O, should be in the toolbox of every event
713	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
714	together.
715
716	=item L<AnyEvent::BDB>, L<BDB>
717
718	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
719	IO::AIO and AnyEvent together.
720
721	=item L<IO::Lambda>
722
723	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
724
725	=back	1023	=back
726		1024
727	=cut	1025	=cut
728		1026
729	package AnyEvent;	1027	package AnyEvent;
730		1028
731	no warnings;	1029	no warnings;
732	use strict;	1030	use strict qw(vars subs);
733		1031
734	use Carp;	1032	use Carp ();
735		1033
736	our $VERSION = '4.03';	1034	our $VERSION = 4.82;
737	our $MODEL;	1035	our $MODEL;
738		1036
739	our $AUTOLOAD;	1037	our $AUTOLOAD;
740	our @ISA;	1038	our @ISA;
741		1039
742	our @REGISTRY;	1040	our @REGISTRY;
		1041
		1042	our $WIN32;
		1043
		1044	BEGIN {
		1045	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1046	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1047
		1048	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1049	if ${^TAINT};
		1050	}
743		1051
744	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1052	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
745		1053
746	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred	1054	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
747		1055
…		…
757	[Event:: => AnyEvent::Impl::Event::],	1065	[Event:: => AnyEvent::Impl::Event::],
758	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1066	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
759	# everything below here will not be autoprobed	1067	# everything below here will not be autoprobed
760	# as the pureperl backend should work everywhere	1068	# as the pureperl backend should work everywhere
761	# and is usually faster	1069	# and is usually faster
762	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
763	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers	1070	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
764	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1071	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1072	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
765	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1073	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
766	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1074	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
767	[Wx:: => AnyEvent::Impl::POE::],	1075	[Wx:: => AnyEvent::Impl::POE::],
768	[Prima:: => AnyEvent::Impl::POE::],	1076	[Prima:: => AnyEvent::Impl::POE::],
		1077	# IO::Async is just too broken - we would need workarounds for its
		1078	# byzantine signal and broken child handling, among others.
		1079	# IO::Async is rather hard to detect, as it doesn't have any
		1080	# obvious default class.
		1081	# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1082	# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1083	# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
769	);	1084	);
770		1085
771	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1086	our %method = map +($_ => 1),
		1087	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
772		1088
773	our @post_detect;	1089	our @post_detect;
774		1090
775	sub post_detect(&) {	1091	sub post_detect(&) {
776	my ($cb) = @_;	1092	my ($cb) = @_;
…		…
781	1	1097	1
782	} else {	1098	} else {
783	push @post_detect, $cb;	1099	push @post_detect, $cb;
784		1100
785	defined wantarray	1101	defined wantarray
786	? bless \$cb, "AnyEvent::Util::PostDetect"	1102	? bless \$cb, "AnyEvent::Util::postdetect"
787	: ()	1103	: ()
788	}	1104	}
789	}	1105	}
790		1106
791	sub AnyEvent::Util::PostDetect::DESTROY {	1107	sub AnyEvent::Util::postdetect::DESTROY {
792	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1108	@post_detect = grep $_ != ${$_[0]}, @post_detect;
793	}	1109	}
794		1110
795	sub detect() {	1111	sub detect() {
796	unless ($MODEL) {	1112	unless ($MODEL) {
…		…
799		1115
800	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1116	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
801	my $model = "AnyEvent::Impl::$1";	1117	my $model = "AnyEvent::Impl::$1";
802	if (eval "require $model") {	1118	if (eval "require $model") {
803	$MODEL = $model;	1119	$MODEL = $model;
804	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1120	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $verbose > 1;
805	} else {	1121	} else {
806	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1122	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $verbose;
807	}	1123	}
808	}	1124	}
809		1125
810	# check for already loaded models	1126	# check for already loaded models
811	unless ($MODEL) {	1127	unless ($MODEL) {
…		…
833	last;	1149	last;
834	}	1150	}
835	}	1151	}
836		1152
837	$MODEL	1153	$MODEL
838	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1154	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
839	}	1155	}
840	}	1156	}
841		1157
		1158	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1159
842	unshift @ISA, $MODEL;	1160	unshift @ISA, $MODEL;
843	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1161
		1162	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
844		1163
845	(shift @post_detect)->() while @post_detect;	1164	(shift @post_detect)->() while @post_detect;
846	}	1165	}
847		1166
848	$MODEL	1167	$MODEL
…		…
850		1169
851	sub AUTOLOAD {	1170	sub AUTOLOAD {
852	(my $func = $AUTOLOAD) =~ s/.*://;	1171	(my $func = $AUTOLOAD) =~ s/.*://;
853		1172
854	$method{$func}	1173	$method{$func}
855	or croak "$func: not a valid method for AnyEvent objects";	1174	or Carp::croak "$func: not a valid method for AnyEvent objects";
856		1175
857	detect unless $MODEL;	1176	detect unless $MODEL;
858		1177
859	my $class = shift;	1178	my $class = shift;
860	$class->$func (@_);	1179	$class->$func (@_);
861	}	1180	}
862		1181
		1182	# utility function to dup a filehandle. this is used by many backends
		1183	# to support binding more than one watcher per filehandle (they usually
		1184	# allow only one watcher per fd, so we dup it to get a different one).
		1185	sub _dupfh($$;$$) {
		1186	my ($poll, $fh, $r, $w) = @_;
		1187
		1188	# cygwin requires the fh mode to be matching, unix doesn't
		1189	my ($rw, $mode) = $poll eq "r" ? ($r, "<") : ($w, ">");
		1190
		1191	open my $fh2, "$mode&", $fh
		1192	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1193
		1194	# we assume CLOEXEC is already set by perl in all important cases
		1195
		1196	($fh2, $rw)
		1197	}
		1198
863	package AnyEvent::Base;	1199	package AnyEvent::Base;
864		1200
		1201	# default implementations for many methods
		1202
		1203	BEGIN {
		1204	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1205	*_time = \&Time::HiRes::time;
		1206	# if (eval "use POSIX (); (POSIX::times())...
		1207	} else {
		1208	*_time = sub { time }; # epic fail
		1209	}
		1210	}
		1211
		1212	sub time { _time }
		1213	sub now { _time }
		1214	sub now_update { }
		1215
865	# default implementation for ->condvar	1216	# default implementation for ->condvar
866		1217
867	sub condvar {	1218	sub condvar {
868	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1219	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
869	}	1220	}
870		1221
871	# default implementation for ->signal	1222	# default implementation for ->signal
872		1223
873	our %SIG_CB;	1224	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1225
		1226	sub _signal_exec {
		1227	sysread $SIGPIPE_R, my $dummy, 4;
		1228
		1229	while (%SIG_EV) {
		1230	for (keys %SIG_EV) {
		1231	delete $SIG_EV{$_};
		1232	$_->() for values %{ $SIG_CB{$_} || {} };
		1233	}
		1234	}
		1235	}
874		1236
875	sub signal {	1237	sub signal {
876	my (undef, %arg) = @_;	1238	my (undef, %arg) = @_;
877		1239
		1240	unless ($SIGPIPE_R) {
		1241	require Fcntl;
		1242
		1243	if (AnyEvent::WIN32) {
		1244	require AnyEvent::Util;
		1245
		1246	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1247	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1248	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1249	} else {
		1250	pipe $SIGPIPE_R, $SIGPIPE_W;
		1251	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1252	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1253
		1254	# not strictly required, as $^F is normally 2, but let's make sure...
		1255	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1256	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1257	}
		1258
		1259	$SIGPIPE_R
		1260	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1261
		1262	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1263	}
		1264
878	my $signal = uc $arg{signal}	1265	my $signal = uc $arg{signal}
879	or Carp::croak "required option 'signal' is missing";	1266	or Carp::croak "required option 'signal' is missing";
880		1267
881	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1268	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
882	$SIG{$signal} ||= sub {	1269	$SIG{$signal} ||= sub {
883	$_->() for values %{ $SIG_CB{$signal} || {} };	1270	local $!;
		1271	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1272	undef $SIG_EV{$signal};
884	};	1273	};
885		1274
886	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1275	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
887	}	1276	}
888		1277
889	sub AnyEvent::Base::Signal::DESTROY {	1278	sub AnyEvent::Base::signal::DESTROY {
890	my ($signal, $cb) = @{$_[0]};	1279	my ($signal, $cb) = @{$_[0]};
891		1280
892	delete $SIG_CB{$signal}{$cb};	1281	delete $SIG_CB{$signal}{$cb};
893		1282
		1283	# delete doesn't work with older perls - they then
		1284	# print weird messages, or just unconditionally exit
		1285	# instead of getting the default action.
894	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1286	undef $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
895	}	1287	}
896		1288
897	# default implementation for ->child	1289	# default implementation for ->child
898		1290
899	our %PID_CB;	1291	our %PID_CB;
900	our $CHLD_W;	1292	our $CHLD_W;
901	our $CHLD_DELAY_W;	1293	our $CHLD_DELAY_W;
902	our $PID_IDLE;
903	our $WNOHANG;	1294	our $WNOHANG;
904		1295
905	sub _child_wait {	1296	sub _sigchld {
906	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1297	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
907	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1298	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),
908	(values %{ $PID_CB{0} || {} });	1299	(values %{ $PID_CB{0} || {} });
909	}	1300	}
910
911	undef $PID_IDLE;
912	}
913
914	sub _sigchld {
915	# make sure we deliver these changes "synchronous" with the event loop.
916	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
917	undef $CHLD_DELAY_W;
918	&_child_wait;
919	});
920	}	1301	}
921		1302
922	sub child {	1303	sub child {
923	my (undef, %arg) = @_;	1304	my (undef, %arg) = @_;
924		1305
925	defined (my $pid = $arg{pid} + 0)	1306	defined (my $pid = $arg{pid} + 0)
926	or Carp::croak "required option 'pid' is missing";	1307	or Carp::croak "required option 'pid' is missing";
927		1308
928	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1309	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
929		1310
930	unless ($WNOHANG) {
931	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;	1311	$WNOHANG ||= eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
932	}
933		1312
934	unless ($CHLD_W) {	1313	unless ($CHLD_W) {
935	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1314	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
936	# child could be a zombie already, so make at least one round	1315	# child could be a zombie already, so make at least one round
937	&_sigchld;	1316	&_sigchld;
938	}	1317	}
939		1318
940	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1319	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
941	}	1320	}
942		1321
943	sub AnyEvent::Base::Child::DESTROY {	1322	sub AnyEvent::Base::child::DESTROY {
944	my ($pid, $cb) = @{$_[0]};	1323	my ($pid, $cb) = @{$_[0]};
945		1324
946	delete $PID_CB{$pid}{$cb};	1325	delete $PID_CB{$pid}{$cb};
947	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1326	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
948		1327
949	undef $CHLD_W unless keys %PID_CB;	1328	undef $CHLD_W unless keys %PID_CB;
		1329	}
		1330
		1331	# idle emulation is done by simply using a timer, regardless
		1332	# of whether the process is idle or not, and not letting
		1333	# the callback use more than 50% of the time.
		1334	sub idle {
		1335	my (undef, %arg) = @_;
		1336
		1337	my ($cb, $w, $rcb) = $arg{cb};
		1338
		1339	$rcb = sub {
		1340	if ($cb) {
		1341	$w = _time;
		1342	&$cb;
		1343	$w = _time - $w;
		1344
		1345	# never use more then 50% of the time for the idle watcher,
		1346	# within some limits
		1347	$w = 0.0001 if $w < 0.0001;
		1348	$w = 5 if $w > 5;
		1349
		1350	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1351	} else {
		1352	# clean up...
		1353	undef $w;
		1354	undef $rcb;
		1355	}
		1356	};
		1357
		1358	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1359
		1360	bless \\$cb, "AnyEvent::Base::idle"
		1361	}
		1362
		1363	sub AnyEvent::Base::idle::DESTROY {
		1364	undef $${$_[0]};
950	}	1365	}
951		1366
952	package AnyEvent::CondVar;	1367	package AnyEvent::CondVar;
953		1368
954	our @ISA = AnyEvent::CondVar::Base::;	1369	our @ISA = AnyEvent::CondVar::Base::;
…		…
956	package AnyEvent::CondVar::Base;	1371	package AnyEvent::CondVar::Base;
957		1372
958	use overload	1373	use overload
959	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1374	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
960	fallback => 1;	1375	fallback => 1;
		1376
		1377	our $WAITING;
961		1378
962	sub _send {	1379	sub _send {
963	# nop	1380	# nop
964	}	1381	}
965		1382
…		…
978	sub ready {	1395	sub ready {
979	$_[0]{_ae_sent}	1396	$_[0]{_ae_sent}
980	}	1397	}
981		1398
982	sub _wait {	1399	sub _wait {
		1400	$WAITING
		1401	and !$_[0]{_ae_sent}
		1402	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1403
		1404	local $WAITING = 1;
983	AnyEvent->one_event while !$_[0]{_ae_sent};	1405	AnyEvent->one_event while !$_[0]{_ae_sent};
984	}	1406	}
985		1407
986	sub recv {	1408	sub recv {
987	$_[0]->_wait;	1409	$_[0]->_wait;
…		…
1006	}	1428	}
1007		1429
1008	# undocumented/compatibility with pre-3.4	1430	# undocumented/compatibility with pre-3.4
1009	*broadcast = \&send;	1431	*broadcast = \&send;
1010	*wait = \&_wait;	1432	*wait = \&_wait;
		1433
		1434	=head1 ERROR AND EXCEPTION HANDLING
		1435
		1436	In general, AnyEvent does not do any error handling - it relies on the
		1437	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1438	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1439	checking of all AnyEvent methods, however, which is highly useful during
		1440	development.
		1441
		1442	As for exception handling (i.e. runtime errors and exceptions thrown while
		1443	executing a callback), this is not only highly event-loop specific, but
		1444	also not in any way wrapped by this module, as this is the job of the main
		1445	program.
		1446
		1447	The pure perl event loop simply re-throws the exception (usually
		1448	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1449	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1450	so on.
		1451
		1452	=head1 ENVIRONMENT VARIABLES
		1453
		1454	The following environment variables are used by this module or its
		1455	submodules.
		1456
		1457	Note that AnyEvent will remove I<all> environment variables starting with
		1458	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1459	enabled.
		1460
		1461	=over 4
		1462
		1463	=item C<PERL_ANYEVENT_VERBOSE>
		1464
		1465	By default, AnyEvent will be completely silent except in fatal
		1466	conditions. You can set this environment variable to make AnyEvent more
		1467	talkative.
		1468
		1469	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1470	conditions, such as not being able to load the event model specified by
		1471	C<PERL_ANYEVENT_MODEL>.
		1472
		1473	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1474	model it chooses.
		1475
		1476	=item C<PERL_ANYEVENT_STRICT>
		1477
		1478	AnyEvent does not do much argument checking by default, as thorough
		1479	argument checking is very costly. Setting this variable to a true value
		1480	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1481	check the arguments passed to most method calls. If it finds any problems,
		1482	it will croak.
		1483
		1484	In other words, enables "strict" mode.
		1485
		1486	Unlike C<use strict>, it is definitely recommended to keep it off in
		1487	production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
		1488	developing programs can be very useful, however.
		1489
		1490	=item C<PERL_ANYEVENT_MODEL>
		1491
		1492	This can be used to specify the event model to be used by AnyEvent, before
		1493	auto detection and -probing kicks in. It must be a string consisting
		1494	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1495	and the resulting module name is loaded and if the load was successful,
		1496	used as event model. If it fails to load AnyEvent will proceed with
		1497	auto detection and -probing.
		1498
		1499	This functionality might change in future versions.
		1500
		1501	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1502	could start your program like this:
		1503
		1504	PERL_ANYEVENT_MODEL=Perl perl ...
		1505
		1506	=item C<PERL_ANYEVENT_PROTOCOLS>
		1507
		1508	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1509	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1510	of auto probing).
		1511
		1512	Must be set to a comma-separated list of protocols or address families,
		1513	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1514	used, and preference will be given to protocols mentioned earlier in the
		1515	list.
		1516
		1517	This variable can effectively be used for denial-of-service attacks
		1518	against local programs (e.g. when setuid), although the impact is likely
		1519	small, as the program has to handle conenction and other failures anyways.
		1520
		1521	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1522	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1523	- only support IPv4, never try to resolve or contact IPv6
		1524	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1525	IPv6, but prefer IPv6 over IPv4.
		1526
		1527	=item C<PERL_ANYEVENT_EDNS0>
		1528
		1529	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1530	for DNS. This extension is generally useful to reduce DNS traffic, but
		1531	some (broken) firewalls drop such DNS packets, which is why it is off by
		1532	default.
		1533
		1534	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1535	EDNS0 in its DNS requests.
		1536
		1537	=item C<PERL_ANYEVENT_MAX_FORKS>
		1538
		1539	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1540	will create in parallel.
		1541
		1542	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1543
		1544	The default value for the C<max_outstanding> parameter for the default DNS
		1545	resolver - this is the maximum number of parallel DNS requests that are
		1546	sent to the DNS server.
		1547
		1548	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1549
		1550	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1551	configuration) in the default resolver. When set to the empty string, no
		1552	default config will be used.
		1553
		1554	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1555
		1556	When neither C<ca_file> nor C<ca_path> was specified during
		1557	L<AnyEvent::TLS> context creation, and either of these environment
		1558	variables exist, they will be used to specify CA certificate locations
		1559	instead of a system-dependent default.
		1560
		1561	=back
1011		1562
1012	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1563	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1013		1564
1014	This is an advanced topic that you do not normally need to use AnyEvent in	1565	This is an advanced topic that you do not normally need to use AnyEvent in
1015	a module. This section is only of use to event loop authors who want to	1566	a module. This section is only of use to event loop authors who want to
…		…
1049		1600
1050	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1601	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1051	condition variables: code blocking while waiting for a condition will	1602	condition variables: code blocking while waiting for a condition will
1052	C<die>. This still works with most modules/usages, and blocking calls must	1603	C<die>. This still works with most modules/usages, and blocking calls must
1053	not be done in an interactive application, so it makes sense.	1604	not be done in an interactive application, so it makes sense.
1054
1055	=head1 ENVIRONMENT VARIABLES
1056
1057	The following environment variables are used by this module:
1058
1059	=over 4
1060
1061	=item C<PERL_ANYEVENT_VERBOSE>
1062
1063	By default, AnyEvent will be completely silent except in fatal
1064	conditions. You can set this environment variable to make AnyEvent more
1065	talkative.
1066
1067	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1068	conditions, such as not being able to load the event model specified by
1069	C<PERL_ANYEVENT_MODEL>.
1070
1071	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1072	model it chooses.
1073
1074	=item C<PERL_ANYEVENT_MODEL>
1075
1076	This can be used to specify the event model to be used by AnyEvent, before
1077	auto detection and -probing kicks in. It must be a string consisting
1078	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1079	and the resulting module name is loaded and if the load was successful,
1080	used as event model. If it fails to load AnyEvent will proceed with
1081	auto detection and -probing.
1082
1083	This functionality might change in future versions.
1084
1085	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1086	could start your program like this:
1087
1088	PERL_ANYEVENT_MODEL=Perl perl ...
1089
1090	=item C<PERL_ANYEVENT_PROTOCOLS>
1091
1092	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1093	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1094	of auto probing).
1095
1096	Must be set to a comma-separated list of protocols or address families,
1097	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1098	used, and preference will be given to protocols mentioned earlier in the
1099	list.
1100
1101	This variable can effectively be used for denial-of-service attacks
1102	against local programs (e.g. when setuid), although the impact is likely
1103	small, as the program has to handle connection errors already-
1104
1105	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1106	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1107	- only support IPv4, never try to resolve or contact IPv6
1108	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1109	IPv6, but prefer IPv6 over IPv4.
1110
1111	=item C<PERL_ANYEVENT_EDNS0>
1112
1113	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1114	for DNS. This extension is generally useful to reduce DNS traffic, but
1115	some (broken) firewalls drop such DNS packets, which is why it is off by
1116	default.
1117
1118	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1119	EDNS0 in its DNS requests.
1120
1121	=back
1122		1605
1123	=head1 EXAMPLE PROGRAM	1606	=head1 EXAMPLE PROGRAM
1124		1607
1125	The following program uses an I/O watcher to read data from STDIN, a timer	1608	The following program uses an I/O watcher to read data from STDIN, a timer
1126	to display a message once per second, and a condition variable to quit the	1609	to display a message once per second, and a condition variable to quit the
…		…
1320	watcher.	1803	watcher.
1321		1804
1322	=head3 Results	1805	=head3 Results
1323		1806
1324	name watchers bytes create invoke destroy comment	1807	name watchers bytes create invoke destroy comment
1325	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1808	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1326	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1809	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1327	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1810	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1328	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1811	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1329	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1812	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1330	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1813	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1814	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1815	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1331	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1816	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1332	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1817	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1333	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1818	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1334	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1819	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1335		1820
1336	=head3 Discussion	1821	=head3 Discussion
1337		1822
1338	The benchmark does I<not> measure scalability of the event loop very	1823	The benchmark does I<not> measure scalability of the event loop very
1339	well. For example, a select-based event loop (such as the pure perl one)	1824	well. For example, a select-based event loop (such as the pure perl one)
…		…
1364	performance becomes really bad with lots of file descriptors (and few of	1849	performance becomes really bad with lots of file descriptors (and few of
1365	them active), of course, but this was not subject of this benchmark.	1850	them active), of course, but this was not subject of this benchmark.
1366		1851
1367	The C<Event> module has a relatively high setup and callback invocation	1852	The C<Event> module has a relatively high setup and callback invocation
1368	cost, but overall scores in on the third place.	1853	cost, but overall scores in on the third place.
		1854
		1855	C<IO::Async> performs admirably well, about on par with C<Event>, even
		1856	when using its pure perl backend.
1369		1857
1370	C<Glib>'s memory usage is quite a bit higher, but it features a	1858	C<Glib>'s memory usage is quite a bit higher, but it features a
1371	faster callback invocation and overall ends up in the same class as	1859	faster callback invocation and overall ends up in the same class as
1372	C<Event>. However, Glib scales extremely badly, doubling the number of	1860	C<Event>. However, Glib scales extremely badly, doubling the number of
1373	watchers increases the processing time by more than a factor of four,	1861	watchers increases the processing time by more than a factor of four,
…		…
1451	it to another server. This includes deleting the old timeout and creating	1939	it to another server. This includes deleting the old timeout and creating
1452	a new one that moves the timeout into the future.	1940	a new one that moves the timeout into the future.
1453		1941
1454	=head3 Results	1942	=head3 Results
1455		1943
1456	name sockets create request	1944	name sockets create request
1457	EV 20000 69.01 11.16	1945	EV 20000 69.01 11.16
1458	Perl 20000 73.32 35.87	1946	Perl 20000 73.32 35.87
		1947	IOAsync 20000 157.00 98.14 epoll
		1948	IOAsync 20000 159.31 616.06 poll
1459	Event 20000 212.62 257.32	1949	Event 20000 212.62 257.32
1460	Glib 20000 651.16 1896.30	1950	Glib 20000 651.16 1896.30
1461	POE 20000 349.67 12317.24 uses POE::Loop::Event	1951	POE 20000 349.67 12317.24 uses POE::Loop::Event
1462		1952
1463	=head3 Discussion	1953	=head3 Discussion
1464		1954
1465	This benchmark I<does> measure scalability and overall performance of the	1955	This benchmark I<does> measure scalability and overall performance of the
1466	particular event loop.	1956	particular event loop.
…		…
1468	EV is again fastest. Since it is using epoll on my system, the setup time	1958	EV is again fastest. Since it is using epoll on my system, the setup time
1469	is relatively high, though.	1959	is relatively high, though.
1470		1960
1471	Perl surprisingly comes second. It is much faster than the C-based event	1961	Perl surprisingly comes second. It is much faster than the C-based event
1472	loops Event and Glib.	1962	loops Event and Glib.
		1963
		1964	IO::Async performs very well when using its epoll backend, and still quite
		1965	good compared to Glib when using its pure perl backend.
1473		1966
1474	Event suffers from high setup time as well (look at its code and you will	1967	Event suffers from high setup time as well (look at its code and you will
1475	understand why). Callback invocation also has a high overhead compared to	1968	understand why). Callback invocation also has a high overhead compared to
1476	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	1969	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1477	uses select or poll in basically all documented configurations.	1970	uses select or poll in basically all documented configurations.
…		…
1540	=item * C-based event loops perform very well with small number of	2033	=item * C-based event loops perform very well with small number of
1541	watchers, as the management overhead dominates.	2034	watchers, as the management overhead dominates.
1542		2035
1543	=back	2036	=back
1544		2037
		2038	=head2 THE IO::Lambda BENCHMARK
		2039
		2040	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2041	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2042	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2043	shouldn't come as a surprise to anybody). As such, the benchmark is
		2044	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2045	very optimal. But how would AnyEvent compare when used without the extra
		2046	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2047
		2048	The benchmark itself creates an echo-server, and then, for 500 times,
		2049	connects to the echo server, sends a line, waits for the reply, and then
		2050	creates the next connection. This is a rather bad benchmark, as it doesn't
		2051	test the efficiency of the framework or much non-blocking I/O, but it is a
		2052	benchmark nevertheless.
		2053
		2054	name runtime
		2055	Lambda/select 0.330 sec
		2056	+ optimized 0.122 sec
		2057	Lambda/AnyEvent 0.327 sec
		2058	+ optimized 0.138 sec
		2059	Raw sockets/select 0.077 sec
		2060	POE/select, components 0.662 sec
		2061	POE/select, raw sockets 0.226 sec
		2062	POE/select, optimized 0.404 sec
		2063
		2064	AnyEvent/select/nb 0.085 sec
		2065	AnyEvent/EV/nb 0.068 sec
		2066	+state machine 0.134 sec
		2067
		2068	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2069	benchmarks actually make blocking connects and use 100% blocking I/O,
		2070	defeating the purpose of an event-based solution. All of the newly
		2071	written AnyEvent benchmarks use 100% non-blocking connects (using
		2072	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2073	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2074	generally require a lot more bookkeeping and event handling than blocking
		2075	connects (which involve a single syscall only).
		2076
		2077	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2078	offers similar expressive power as POE and IO::Lambda, using conventional
		2079	Perl syntax. This means that both the echo server and the client are 100%
		2080	non-blocking, further placing it at a disadvantage.
		2081
		2082	As you can see, the AnyEvent + EV combination even beats the
		2083	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2084	backend easily beats IO::Lambda and POE.
		2085
		2086	And even the 100% non-blocking version written using the high-level (and
		2087	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2088	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2089	in a non-blocking way.
		2090
		2091	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2092	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2093	part of the IO::lambda distribution and were used without any changes.
		2094
		2095
		2096	=head1 SIGNALS
		2097
		2098	AnyEvent currently installs handlers for these signals:
		2099
		2100	=over 4
		2101
		2102	=item SIGCHLD
		2103
		2104	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2105	emulation for event loops that do not support them natively. Also, some
		2106	event loops install a similar handler.
		2107
		2108	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2109	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2110
		2111	=item SIGPIPE
		2112
		2113	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2114	when AnyEvent gets loaded.
		2115
		2116	The rationale for this is that AnyEvent users usually do not really depend
		2117	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2118	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2119	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2120	some random socket.
		2121
		2122	The rationale for installing a no-op handler as opposed to ignoring it is
		2123	that this way, the handler will be restored to defaults on exec.
		2124
		2125	Feel free to install your own handler, or reset it to defaults.
		2126
		2127	=back
		2128
		2129	=cut
		2130
		2131	undef $SIG{CHLD}
		2132	if $SIG{CHLD} eq 'IGNORE';
		2133
		2134	$SIG{PIPE} = sub { }
		2135	unless defined $SIG{PIPE};
1545		2136
1546	=head1 FORK	2137	=head1 FORK
1547		2138
1548	Most event libraries are not fork-safe. The ones who are usually are	2139	Most event libraries are not fork-safe. The ones who are usually are
1549	because they rely on inefficient but fork-safe C<select> or C<poll>	2140	because they rely on inefficient but fork-safe C<select> or C<poll>
…		…
1563	specified in the variable.	2154	specified in the variable.
1564		2155
1565	You can make AnyEvent completely ignore this variable by deleting it	2156	You can make AnyEvent completely ignore this variable by deleting it
1566	before the first watcher gets created, e.g. with a C<BEGIN> block:	2157	before the first watcher gets created, e.g. with a C<BEGIN> block:
1567		2158
1568	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2159	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1569		2160
1570	use AnyEvent;	2161	use AnyEvent;
1571		2162
1572	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2163	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1573	be used to probe what backend is used and gain other information (which is	2164	be used to probe what backend is used and gain other information (which is
1574	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2165	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2166	$ENV{PERL_ANYEVENT_STRICT}.
		2167
		2168	Note that AnyEvent will remove I<all> environment variables starting with
		2169	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2170	enabled.
		2171
		2172
		2173	=head1 BUGS
		2174
		2175	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2176	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2177	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2178	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2179	pronounced).
1575		2180
1576		2181
1577	=head1 SEE ALSO	2182	=head1 SEE ALSO
1578		2183
1579	Utility functions: L<AnyEvent::Util>.	2184	Utility functions: L<AnyEvent::Util>.
…		…
1582	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2187	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1583		2188
1584	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2189	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1585	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2190	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1586	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2191	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1587	L<AnyEvent::Impl::POE>.	2192	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>.
1588		2193
1589	Non-blocking file handles, sockets, TCP clients and	2194	Non-blocking file handles, sockets, TCP clients and
1590	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2195	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1591		2196
1592	Asynchronous DNS: L<AnyEvent::DNS>.	2197	Asynchronous DNS: L<AnyEvent::DNS>.
1593		2198
1594	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2199	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2200	L<Coro::Event>,
1595		2201
1596	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2202	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2203	L<AnyEvent::HTTP>.
1597		2204
1598		2205
1599	=head1 AUTHOR	2206	=head1 AUTHOR
1600		2207
1601	Marc Lehmann <schmorp@schmorp.de>	2208	Marc Lehmann <schmorp@schmorp.de>
1602	http://home.schmorp.de/	2209	http://home.schmorp.de/
1603		2210
1604	=cut	2211	=cut
1605		2212
1606	1	2213	1
1607		2214

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