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Revision 1.29 by root, Wed Oct 31 14:17:43 2007 UTC vs.
Revision 1.262 by root, Tue Jul 28 13:08:17 2009 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	Event, Coro, Glib, Tk, Perl - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores wether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
		53
		54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
		55
		56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
		57	nowadays. So what is different about AnyEvent?
		58
		59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
		60	policy> and AnyEvent is I<small and efficient>.
		61
		62	First and foremost, I<AnyEvent is not an event model> itself, it only
		63	interfaces to whatever event model the main program happens to use, in a
		64	pragmatic way. For event models and certain classes of immortals alike,
		65	the statement "there can only be one" is a bitter reality: In general,
		66	only one event loop can be active at the same time in a process. AnyEvent
		67	cannot change this, but it can hide the differences between those event
		68	loops.
		69
		70	The goal of AnyEvent is to offer module authors the ability to do event
		71	programming (waiting for I/O or timer events) without subscribing to a
		72	religion, a way of living, and most importantly: without forcing your
		73	module users into the same thing by forcing them to use the same event
		74	model you use.
		75
		76	For modules like POE or IO::Async (which is a total misnomer as it is
		77	actually doing all I/O I<synchronously>...), using them in your module is
		78	like joining a cult: After you joined, you are dependent on them and you
		79	cannot use anything else, as they are simply incompatible to everything
		80	that isn't them. What's worse, all the potential users of your
		81	module are I<also> forced to use the same event loop you use.
		82
		83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
		84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
		85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
		86	your module uses one of those, every user of your module has to use it,
		87	too. But if your module uses AnyEvent, it works transparently with all
		88	event models it supports (including stuff like IO::Async, as long as those
		89	use one of the supported event loops. It is trivial to add new event loops
		90	to AnyEvent, too, so it is future-proof).
		91
		92	In addition to being free of having to use I<the one and only true event
		93	model>, AnyEvent also is free of bloat and policy: with POE or similar
		94	modules, you get an enormous amount of code and strict rules you have to
		95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
		96	offering the functionality that is necessary, in as thin as a wrapper as
		97	technically possible.
		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		100	of useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
		105	Now, if you I<do want> lots of policy (this can arguably be somewhat
		106	useful) and you want to force your users to use the one and only event
		107	model, you should I<not> use this module.
22		108
23	=head1 DESCRIPTION	109	=head1 DESCRIPTION
24		110
25	L<AnyEvent> provides an identical interface to multiple event loops. This	111	L<AnyEvent> provides an identical interface to multiple event loops. This
26	allows module authors to utilise an event loop without forcing module	112	allows module authors to utilise an event loop without forcing module
27	users to use the same event loop (as only a single event loop can coexist	113	users to use the same event loop (as only a single event loop can coexist
28	peacefully at any one time).	114	peacefully at any one time).
29		115
30	The interface itself is vaguely similar but not identical to the Event	116	The interface itself is vaguely similar, but not identical to the L<Event>
31	module.	117	module.
32		118
33	On the first call of any method, the module tries to detect the currently	119	During the first call of any watcher-creation method, the module tries
34	loaded event loop by probing wether any of the following modules is	120	to detect the currently loaded event loop by probing whether one of the
35	loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is	121	following modules is already loaded: L<EV>,
36	used. If none is found, the module tries to load these modules in the	122	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
37	order given. The first one that could be successfully loaded will be	123	L<POE>. The first one found is used. If none are found, the module tries
38	used. If still none could be found, AnyEvent will fall back to a pure-perl	124	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
39	event loop, which is also not very efficient.	125	adaptor should always succeed) in the order given. The first one that can
		126	be successfully loaded will be used. If, after this, still none could be
		127	found, AnyEvent will fall back to a pure-perl event loop, which is not
		128	very efficient, but should work everywhere.
40		129
41	Because AnyEvent first checks for modules that are already loaded, loading	130	Because AnyEvent first checks for modules that are already loaded, loading
42	an Event model explicitly before first using AnyEvent will likely make	131	an event model explicitly before first using AnyEvent will likely make
43	that model the default. For example:	132	that model the default. For example:
44		133
45	use Tk;	134	use Tk;
46	use AnyEvent;	135	use AnyEvent;
47		136
48	# .. AnyEvent will likely default to Tk	137	# .. AnyEvent will likely default to Tk
49		138
		139	The I<likely> means that, if any module loads another event model and
		140	starts using it, all bets are off. Maybe you should tell their authors to
		141	use AnyEvent so their modules work together with others seamlessly...
		142
50	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
51	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	144	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
52	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
53		146
54	=head1 WATCHERS	147	=head1 WATCHERS
55		148
56	AnyEvent has the central concept of a I<watcher>, which is an object that	149	AnyEvent has the central concept of a I<watcher>, which is an object that
57	stores relevant data for each kind of event you are waiting for, such as	150	stores relevant data for each kind of event you are waiting for, such as
58	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
59		152
60	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
61	creating a watcher it will immediately "watch" for events and invoke	154	creating a watcher it will immediately "watch" for events and invoke the
		155	callback when the event occurs (of course, only when the event model
		156	is in control).
		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
62	the callback. To disable the watcher you have to destroy it (e.g. by	164	To disable the watcher you have to destroy it (e.g. by setting the
63	setting the variable that stores it to C<undef> or otherwise deleting all	165	variable you store it in to C<undef> or otherwise deleting all references
64	references to it).	166	to it).
65		167
66	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
67		169
		170	Many watchers either are used with "recursion" (repeating timers for
		171	example), or need to refer to their watcher object in other ways.
		172
		173	An any way to achieve that is this pattern:
		174
		175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		176	# you can use $w here, for example to undef it
		177	undef $w;
		178	});
		179
		180	Note that C<my $w; $w => combination. This is necessary because in Perl,
		181	my variables are only visible after the statement in which they are
		182	declared.
		183
68	=head2 IO WATCHERS	184	=head2 I/O WATCHERS
69		185
70	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	186	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
71	the following mandatory arguments:	187	with the following mandatory key-value pairs as arguments:
72		188
73	C<fh> the Perl I<filehandle> (not filedescriptor) to watch for	189	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		190	for events (AnyEvent might or might not keep a reference to this file
		191	handle). Note that only file handles pointing to things for which
		192	non-blocking operation makes sense are allowed. This includes sockets,
		193	most character devices, pipes, fifos and so on, but not for example files
		194	or block devices.
		195
74	events. C<poll> must be a string that is either C<r> or C<w>, that creates	196	C<poll> must be a string that is either C<r> or C<w>, which creates a
75	a watcher waiting for "r"eadable or "w"ritable events. C<cb> teh callback	197	watcher waiting for "r"eadable or "w"ritable events, respectively.
76	to invoke everytime the filehandle becomes ready.
77		198
78	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	199	C<cb> is the callback to invoke each time the file handle becomes ready.
79	a socket you can have one r + one w, not any more (limitation comes from
80	Tk - if you are sure you are not using Tk this limitation is gone).
81		200
82	Filehandles will be kept alive, so as long as the watcher exists, the	201	Although the callback might get passed parameters, their value and
83	filehandle exists, too.	202	presence is undefined and you cannot rely on them. Portable AnyEvent
		203	callbacks cannot use arguments passed to I/O watcher callbacks.
84		204
85	Example:	205	The I/O watcher might use the underlying file descriptor or a copy of it.
		206	You must not close a file handle as long as any watcher is active on the
		207	underlying file descriptor.
86		208
		209	Some event loops issue spurious readyness notifications, so you should
		210	always use non-blocking calls when reading/writing from/to your file
		211	handles.
		212
87	# wait for readability of STDIN, then read a line and disable the watcher	213	Example: wait for readability of STDIN, then read a line and disable the
		214	watcher.
		215
88	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	216	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
89	chomp (my $input = <STDIN>);	217	chomp (my $input = <STDIN>);
90	warn "read: $input\n";	218	warn "read: $input\n";
91	undef $w;	219	undef $w;
92	});	220	});
…		…
94	=head2 TIME WATCHERS	222	=head2 TIME WATCHERS
95		223
96	You can create a time watcher by calling the C<< AnyEvent->timer >>	224	You can create a time watcher by calling the C<< AnyEvent->timer >>
97	method with the following mandatory arguments:	225	method with the following mandatory arguments:
98		226
99	C<after> after how many seconds (fractions are supported) should the timer	227	C<after> specifies after how many seconds (fractional values are
100	activate. C<cb> the callback to invoke.	228	supported) the callback should be invoked. C<cb> is the callback to invoke
		229	in that case.
101		230
102	The timer callback will be invoked at most once: if you want a repeating	231	Although the callback might get passed parameters, their value and
103	timer you have to create a new watcher (this is a limitation by both Tk	232	presence is undefined and you cannot rely on them. Portable AnyEvent
104	and Glib).	233	callbacks cannot use arguments passed to time watcher callbacks.
105		234
106	Example:	235	The callback will normally be invoked once only. If you specify another
		236	parameter, C<interval>, as a strictly positive number (> 0), then the
		237	callback will be invoked regularly at that interval (in fractional
		238	seconds) after the first invocation. If C<interval> is specified with a
		239	false value, then it is treated as if it were missing.
107		240
		241	The callback will be rescheduled before invoking the callback, but no
		242	attempt is done to avoid timer drift in most backends, so the interval is
		243	only approximate.
		244
108	# fire an event after 7.7 seconds	245	Example: fire an event after 7.7 seconds.
		246
109	my $w = AnyEvent->timer (after => 7.7, cb => sub {	247	my $w = AnyEvent->timer (after => 7.7, cb => sub {
110	warn "timeout\n";	248	warn "timeout\n";
111	});	249	});
112		250
113	# to cancel the timer:	251	# to cancel the timer:
114	undef $w	252	undef $w;
115		253
116	=head2 CONDITION WATCHERS	254	Example 2: fire an event after 0.5 seconds, then roughly every second.
117		255
118	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	256	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
119	method without any arguments.	257	warn "timeout\n";
		258	};
120		259
121	A condition watcher watches for a condition - precisely that the C<<	260	=head3 TIMING ISSUES
122	->broadcast >> method has been called.
123		261
124	The watcher has only two methods:	262	There are two ways to handle timers: based on real time (relative, "fire
		263	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		264	o'clock").
		265
		266	While most event loops expect timers to specified in a relative way, they
		267	use absolute time internally. This makes a difference when your clock
		268	"jumps", for example, when ntp decides to set your clock backwards from
		269	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		270	fire "after" a second might actually take six years to finally fire.
		271
		272	AnyEvent cannot compensate for this. The only event loop that is conscious
		273	about these issues is L<EV>, which offers both relative (ev_timer, based
		274	on true relative time) and absolute (ev_periodic, based on wallclock time)
		275	timers.
		276
		277	AnyEvent always prefers relative timers, if available, matching the
		278	AnyEvent API.
		279
		280	AnyEvent has two additional methods that return the "current time":
125		281
126	=over 4	282	=over 4
127		283
128	=item $cv->wait	284	=item AnyEvent->time
129		285
130	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	286	This returns the "current wallclock time" as a fractional number of
131	called on c<$cv>, while servicing other watchers normally.	287	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		288	return, and the result is guaranteed to be compatible with those).
132		289
133	Not all event models support a blocking wait - some die in that case, so	290	It progresses independently of any event loop processing, i.e. each call
134	if you are using this from a module, never require a blocking wait, but	291	will check the system clock, which usually gets updated frequently.
135	let the caller decide wether the call will block or not (for example,
136	by coupling condition variables with some kind of request results and
137	supporting callbacks so the caller knows that getting the result will not
138	block, while still suppporting blockign waits if the caller so desires).
139		292
140	You can only wait once on a condition - additional calls will return	293	=item AnyEvent->now
141	immediately.
142		294
143	=item $cv->broadcast	295	This also returns the "current wallclock time", but unlike C<time>, above,
		296	this value might change only once per event loop iteration, depending on
		297	the event loop (most return the same time as C<time>, above). This is the
		298	time that AnyEvent's timers get scheduled against.
144		299
145	Flag the condition as ready - a running C<< ->wait >> and all further	300	I<In almost all cases (in all cases if you don't care), this is the
146	calls to C<wait> will return after this method has been called. If nobody	301	function to call when you want to know the current time.>
147	is waiting the broadcast will be remembered..
148		302
149	Example:	303	This function is also often faster then C<< AnyEvent->time >>, and
		304	thus the preferred method if you want some timestamp (for example,
		305	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		306
		307	The rest of this section is only of relevance if you try to be very exact
		308	with your timing, you can skip it without bad conscience.
		309
		310	For a practical example of when these times differ, consider L<Event::Lib>
		311	and L<EV> and the following set-up:
		312
		313	The event loop is running and has just invoked one of your callback at
		314	time=500 (assume no other callbacks delay processing). In your callback,
		315	you wait a second by executing C<sleep 1> (blocking the process for a
		316	second) and then (at time=501) you create a relative timer that fires
		317	after three seconds.
		318
		319	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		320	both return C<501>, because that is the current time, and the timer will
		321	be scheduled to fire at time=504 (C<501> + C<3>).
		322
		323	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		324	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		325	last event processing phase started. With L<EV>, your timer gets scheduled
		326	to run at time=503 (C<500> + C<3>).
		327
		328	In one sense, L<Event::Lib> is more exact, as it uses the current time
		329	regardless of any delays introduced by event processing. However, most
		330	callbacks do not expect large delays in processing, so this causes a
		331	higher drift (and a lot more system calls to get the current time).
		332
		333	In another sense, L<EV> is more exact, as your timer will be scheduled at
		334	the same time, regardless of how long event processing actually took.
		335
		336	In either case, if you care (and in most cases, you don't), then you
		337	can get whatever behaviour you want with any event loop, by taking the
		338	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		339	account.
		340
		341	=item AnyEvent->now_update
		342
		343	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		344	the current time for each loop iteration (see the discussion of L<<
		345	AnyEvent->now >>, above).
		346
		347	When a callback runs for a long time (or when the process sleeps), then
		348	this "current" time will differ substantially from the real time, which
		349	might affect timers and time-outs.
		350
		351	When this is the case, you can call this method, which will update the
		352	event loop's idea of "current time".
		353
		354	Note that updating the time I<might> cause some events to be handled.
		355
		356	=back
		357
		358	=head2 SIGNAL WATCHERS
		359
		360	You can watch for signals using a signal watcher, C<signal> is the signal
		361	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
		362	callback to be invoked whenever a signal occurs.
		363
		364	Although the callback might get passed parameters, their value and
		365	presence is undefined and you cannot rely on them. Portable AnyEvent
		366	callbacks cannot use arguments passed to signal watcher callbacks.
		367
		368	Multiple signal occurrences can be clumped together into one callback
		369	invocation, and callback invocation will be synchronous. Synchronous means
		370	that it might take a while until the signal gets handled by the process,
		371	but it is guaranteed not to interrupt any other callbacks.
		372
		373	The main advantage of using these watchers is that you can share a signal
		374	between multiple watchers, and AnyEvent will ensure that signals will not
		375	interrupt your program at bad times.
		376
		377	This watcher might use C<%SIG> (depending on the event loop used),
		378	so programs overwriting those signals directly will likely not work
		379	correctly.
		380
		381	Example: exit on SIGINT
		382
		383	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		384
		385	=head3 Signal Races, Delays and Workarounds
		386
		387	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		388	callbacks to signals in a generic way, which is a pity, as you cannot do
		389	race-free signal handling in perl. AnyEvent will try to do it's best, but
		390	in some cases, signals will be delayed. The maximum time a signal might
		391	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		392	seconds). This variable can be changed only before the first signal
		393	watcher is created, and should be left alone otherwise. Higher values
		394	will cause fewer spurious wake-ups, which is better for power and CPU
		395	saving. All these problems can be avoided by installing the optional
		396	L<Async::Interrupt> module. This will not work with inherently broken
		397	event loops such as L<Event> or L<Event::Lib> (and not with L<POE>
		398	currently, as POE does it's own workaround with one-second latency). With
		399	those, you just have to suffer the delays.
		400
		401	=head2 CHILD PROCESS WATCHERS
		402
		403	You can also watch on a child process exit and catch its exit status.
		404
		405	The child process is specified by the C<pid> argument (one some backends,
		406	using C<0> watches for any child process exit, on others this will
		407	croak). The watcher will be triggered only when the child process has
		408	finished and an exit status is available, not on any trace events
		409	(stopped/continued).
		410
		411	The callback will be called with the pid and exit status (as returned by
		412	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		413	callback arguments.
		414
		415	This watcher type works by installing a signal handler for C<SIGCHLD>,
		416	and since it cannot be shared, nothing else should use SIGCHLD or reap
		417	random child processes (waiting for specific child processes, e.g. inside
		418	C<system>, is just fine).
		419
		420	There is a slight catch to child watchers, however: you usually start them
		421	I<after> the child process was created, and this means the process could
		422	have exited already (and no SIGCHLD will be sent anymore).
		423
		424	Not all event models handle this correctly (neither POE nor IO::Async do,
		425	see their AnyEvent::Impl manpages for details), but even for event models
		426	that I<do> handle this correctly, they usually need to be loaded before
		427	the process exits (i.e. before you fork in the first place). AnyEvent's
		428	pure perl event loop handles all cases correctly regardless of when you
		429	start the watcher.
		430
		431	This means you cannot create a child watcher as the very first
		432	thing in an AnyEvent program, you I<have> to create at least one
		433	watcher before you C<fork> the child (alternatively, you can call
		434	C<AnyEvent::detect>).
		435
		436	As most event loops do not support waiting for child events, they will be
		437	emulated by AnyEvent in most cases, in which the latency and race problems
		438	mentioned in the description of signal watchers apply.
		439
		440	Example: fork a process and wait for it
		441
		442	my $done = AnyEvent->condvar;
		443
		444	my $pid = fork or exit 5;
		445
		446	my $w = AnyEvent->child (
		447	pid => $pid,
		448	cb => sub {
		449	my ($pid, $status) = @_;
		450	warn "pid $pid exited with status $status";
		451	$done->send;
		452	},
		453	);
		454
		455	# do something else, then wait for process exit
		456	$done->recv;
		457
		458	=head2 IDLE WATCHERS
		459
		460	Sometimes there is a need to do something, but it is not so important
		461	to do it instantly, but only when there is nothing better to do. This
		462	"nothing better to do" is usually defined to be "no other events need
		463	attention by the event loop".
		464
		465	Idle watchers ideally get invoked when the event loop has nothing
		466	better to do, just before it would block the process to wait for new
		467	events. Instead of blocking, the idle watcher is invoked.
		468
		469	Most event loops unfortunately do not really support idle watchers (only
		470	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		471	will simply call the callback "from time to time".
		472
		473	Example: read lines from STDIN, but only process them when the
		474	program is otherwise idle:
		475
		476	my @lines; # read data
		477	my $idle_w;
		478	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		479	push @lines, scalar <STDIN>;
		480
		481	# start an idle watcher, if not already done
		482	$idle_w ||= AnyEvent->idle (cb => sub {
		483	# handle only one line, when there are lines left
		484	if (my $line = shift @lines) {
		485	print "handled when idle: $line";
		486	} else {
		487	# otherwise disable the idle watcher again
		488	undef $idle_w;
		489	}
		490	});
		491	});
		492
		493	=head2 CONDITION VARIABLES
		494
		495	If you are familiar with some event loops you will know that all of them
		496	require you to run some blocking "loop", "run" or similar function that
		497	will actively watch for new events and call your callbacks.
		498
		499	AnyEvent is slightly different: it expects somebody else to run the event
		500	loop and will only block when necessary (usually when told by the user).
		501
		502	The instrument to do that is called a "condition variable", so called
		503	because they represent a condition that must become true.
		504
		505	Now is probably a good time to look at the examples further below.
		506
		507	Condition variables can be created by calling the C<< AnyEvent->condvar
		508	>> method, usually without arguments. The only argument pair allowed is
		509	C<cb>, which specifies a callback to be called when the condition variable
		510	becomes true, with the condition variable as the first argument (but not
		511	the results).
		512
		513	After creation, the condition variable is "false" until it becomes "true"
		514	by calling the C<send> method (or calling the condition variable as if it
		515	were a callback, read about the caveats in the description for the C<<
		516	->send >> method).
		517
		518	Condition variables are similar to callbacks, except that you can
		519	optionally wait for them. They can also be called merge points - points
		520	in time where multiple outstanding events have been processed. And yet
		521	another way to call them is transactions - each condition variable can be
		522	used to represent a transaction, which finishes at some point and delivers
		523	a result. And yet some people know them as "futures" - a promise to
		524	compute/deliver something that you can wait for.
		525
		526	Condition variables are very useful to signal that something has finished,
		527	for example, if you write a module that does asynchronous http requests,
		528	then a condition variable would be the ideal candidate to signal the
		529	availability of results. The user can either act when the callback is
		530	called or can synchronously C<< ->recv >> for the results.
		531
		532	You can also use them to simulate traditional event loops - for example,
		533	you can block your main program until an event occurs - for example, you
		534	could C<< ->recv >> in your main program until the user clicks the Quit
		535	button of your app, which would C<< ->send >> the "quit" event.
		536
		537	Note that condition variables recurse into the event loop - if you have
		538	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
		539	lose. Therefore, condition variables are good to export to your caller, but
		540	you should avoid making a blocking wait yourself, at least in callbacks,
		541	as this asks for trouble.
		542
		543	Condition variables are represented by hash refs in perl, and the keys
		544	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		545	easy (it is often useful to build your own transaction class on top of
		546	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		547	it's C<new> method in your own C<new> method.
		548
		549	There are two "sides" to a condition variable - the "producer side" which
		550	eventually calls C<< -> send >>, and the "consumer side", which waits
		551	for the send to occur.
		552
		553	Example: wait for a timer.
150		554
151	# wait till the result is ready	555	# wait till the result is ready
152	my $result_ready = AnyEvent->condvar;	556	my $result_ready = AnyEvent->condvar;
153		557
154	# do something such as adding a timer	558	# do something such as adding a timer
155	# or socket watcher the calls $result_ready->broadcast	559	# or socket watcher the calls $result_ready->send
156	# when the "result" is ready.	560	# when the "result" is ready.
		561	# in this case, we simply use a timer:
		562	my $w = AnyEvent->timer (
		563	after => 1,
		564	cb => sub { $result_ready->send },
		565	);
157		566
		567	# this "blocks" (while handling events) till the callback
		568	# calls -<send
158	$result_ready->wait;	569	$result_ready->recv;
		570
		571	Example: wait for a timer, but take advantage of the fact that condition
		572	variables are also callable directly.
		573
		574	my $done = AnyEvent->condvar;
		575	my $delay = AnyEvent->timer (after => 5, cb => $done);
		576	$done->recv;
		577
		578	Example: Imagine an API that returns a condvar and doesn't support
		579	callbacks. This is how you make a synchronous call, for example from
		580	the main program:
		581
		582	use AnyEvent::CouchDB;
		583
		584	...
		585
		586	my @info = $couchdb->info->recv;
		587
		588	And this is how you would just set a callback to be called whenever the
		589	results are available:
		590
		591	$couchdb->info->cb (sub {
		592	my @info = $_[0]->recv;
		593	});
		594
		595	=head3 METHODS FOR PRODUCERS
		596
		597	These methods should only be used by the producing side, i.e. the
		598	code/module that eventually sends the signal. Note that it is also
		599	the producer side which creates the condvar in most cases, but it isn't
		600	uncommon for the consumer to create it as well.
		601
		602	=over 4
		603
		604	=item $cv->send (...)
		605
		606	Flag the condition as ready - a running C<< ->recv >> and all further
		607	calls to C<recv> will (eventually) return after this method has been
		608	called. If nobody is waiting the send will be remembered.
		609
		610	If a callback has been set on the condition variable, it is called
		611	immediately from within send.
		612
		613	Any arguments passed to the C<send> call will be returned by all
		614	future C<< ->recv >> calls.
		615
		616	Condition variables are overloaded so one can call them directly (as if
		617	they were a code reference). Calling them directly is the same as calling
		618	C<send>.
		619
		620	=item $cv->croak ($error)
		621
		622	Similar to send, but causes all call's to C<< ->recv >> to invoke
		623	C<Carp::croak> with the given error message/object/scalar.
		624
		625	This can be used to signal any errors to the condition variable
		626	user/consumer. Doing it this way instead of calling C<croak> directly
		627	delays the error detetcion, but has the overwhelmign advantage that it
		628	diagnoses the error at the place where the result is expected, and not
		629	deep in some event clalback without connection to the actual code causing
		630	the problem.
		631
		632	=item $cv->begin ([group callback])
		633
		634	=item $cv->end
		635
		636	These two methods can be used to combine many transactions/events into
		637	one. For example, a function that pings many hosts in parallel might want
		638	to use a condition variable for the whole process.
		639
		640	Every call to C<< ->begin >> will increment a counter, and every call to
		641	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		642	>>, the (last) callback passed to C<begin> will be executed. That callback
		643	is I<supposed> to call C<< ->send >>, but that is not required. If no
		644	callback was set, C<send> will be called without any arguments.
		645
		646	You can think of C<< $cv->send >> giving you an OR condition (one call
		647	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		648	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		649
		650	Let's start with a simple example: you have two I/O watchers (for example,
		651	STDOUT and STDERR for a program), and you want to wait for both streams to
		652	close before activating a condvar:
		653
		654	my $cv = AnyEvent->condvar;
		655
		656	$cv->begin; # first watcher
		657	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		658	defined sysread $fh1, my $buf, 4096
		659	or $cv->end;
		660	});
		661
		662	$cv->begin; # second watcher
		663	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		664	defined sysread $fh2, my $buf, 4096
		665	or $cv->end;
		666	});
		667
		668	$cv->recv;
		669
		670	This works because for every event source (EOF on file handle), there is
		671	one call to C<begin>, so the condvar waits for all calls to C<end> before
		672	sending.
		673
		674	The ping example mentioned above is slightly more complicated, as the
		675	there are results to be passwd back, and the number of tasks that are
		676	begung can potentially be zero:
		677
		678	my $cv = AnyEvent->condvar;
		679
		680	my %result;
		681	$cv->begin (sub { $cv->send (\%result) });
		682
		683	for my $host (@list_of_hosts) {
		684	$cv->begin;
		685	ping_host_then_call_callback $host, sub {
		686	$result{$host} = ...;
		687	$cv->end;
		688	};
		689	}
		690
		691	$cv->end;
		692
		693	This code fragment supposedly pings a number of hosts and calls
		694	C<send> after results for all then have have been gathered - in any
		695	order. To achieve this, the code issues a call to C<begin> when it starts
		696	each ping request and calls C<end> when it has received some result for
		697	it. Since C<begin> and C<end> only maintain a counter, the order in which
		698	results arrive is not relevant.
		699
		700	There is an additional bracketing call to C<begin> and C<end> outside the
		701	loop, which serves two important purposes: first, it sets the callback
		702	to be called once the counter reaches C<0>, and second, it ensures that
		703	C<send> is called even when C<no> hosts are being pinged (the loop
		704	doesn't execute once).
		705
		706	This is the general pattern when you "fan out" into multiple (but
		707	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		708	the callback and ensure C<end> is called at least once, and then, for each
		709	subrequest you start, call C<begin> and for each subrequest you finish,
		710	call C<end>.
159		711
160	=back	712	=back
161		713
162	=head2 SIGNAL WATCHERS	714	=head3 METHODS FOR CONSUMERS
163		715
164	You can listen for signals using a signal watcher, C<signal> is the signal	716	These methods should only be used by the consuming side, i.e. the
165	I<name> without any C<SIG> prefix. Multiple signals events can be clumped	717	code awaits the condition.
166	together into one callback invocation, and callback invocation might or
167	might not be asynchronous.
168
169	These watchers might use C<%SIG>, so programs overwriting those signals
170	directly will likely not work correctly.
171
172	Example: exit on SIGINT
173
174	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
175
176	=head2 CHILD PROCESS WATCHERS
177
178	You can also listen for the status of a child process specified by the
179	C<pid> argument. The watcher will only trigger once. This works by
180	installing a signal handler for C<SIGCHLD>.
181
182	Example: wait for pid 1333
183
184	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
185
186	=head1 GLOBALS
187		718
188	=over 4	719	=over 4
189		720
		721	=item $cv->recv
		722
		723	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		724	>> methods have been called on c<$cv>, while servicing other watchers
		725	normally.
		726
		727	You can only wait once on a condition - additional calls are valid but
		728	will return immediately.
		729
		730	If an error condition has been set by calling C<< ->croak >>, then this
		731	function will call C<croak>.
		732
		733	In list context, all parameters passed to C<send> will be returned,
		734	in scalar context only the first one will be returned.
		735
		736	Note that doing a blocking wait in a callback is not supported by any
		737	event loop, that is, recursive invocation of a blocking C<< ->recv
		738	>> is not allowed, and the C<recv> call will C<croak> if such a
		739	condition is detected. This condition can be slightly loosened by using
		740	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		741	any thread that doesn't run the event loop itself.
		742
		743	Not all event models support a blocking wait - some die in that case
		744	(programs might want to do that to stay interactive), so I<if you are
		745	using this from a module, never require a blocking wait>. Instead, let the
		746	caller decide whether the call will block or not (for example, by coupling
		747	condition variables with some kind of request results and supporting
		748	callbacks so the caller knows that getting the result will not block,
		749	while still supporting blocking waits if the caller so desires).
		750
		751	You can ensure that C<< -recv >> never blocks by setting a callback and
		752	only calling C<< ->recv >> from within that callback (or at a later
		753	time). This will work even when the event loop does not support blocking
		754	waits otherwise.
		755
		756	=item $bool = $cv->ready
		757
		758	Returns true when the condition is "true", i.e. whether C<send> or
		759	C<croak> have been called.
		760
		761	=item $cb = $cv->cb ($cb->($cv))
		762
		763	This is a mutator function that returns the callback set and optionally
		764	replaces it before doing so.
		765
		766	The callback will be called when the condition becomes "true", i.e. when
		767	C<send> or C<croak> are called, with the only argument being the condition
		768	variable itself. Calling C<recv> inside the callback or at any later time
		769	is guaranteed not to block.
		770
		771	=back
		772
		773	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		774
		775	The available backend classes are (every class has its own manpage):
		776
		777	=over 4
		778
		779	=item Backends that are autoprobed when no other event loop can be found.
		780
		781	EV is the preferred backend when no other event loop seems to be in
		782	use. If EV is not installed, then AnyEvent will try Event, and, failing
		783	that, will fall back to its own pure-perl implementation, which is
		784	available everywhere as it comes with AnyEvent itself.
		785
		786	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		787	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		788	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		789
		790	=item Backends that are transparently being picked up when they are used.
		791
		792	These will be used when they are currently loaded when the first watcher
		793	is created, in which case it is assumed that the application is using
		794	them. This means that AnyEvent will automatically pick the right backend
		795	when the main program loads an event module before anything starts to
		796	create watchers. Nothing special needs to be done by the main program.
		797
		798	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		799	AnyEvent::Impl::Tk based on Tk, very broken.
		800	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		801	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		802	AnyEvent::Impl::Irssi used when running within irssi.
		803
		804	=item Backends with special needs.
		805
		806	Qt requires the Qt::Application to be instantiated first, but will
		807	otherwise be picked up automatically. As long as the main program
		808	instantiates the application before any AnyEvent watchers are created,
		809	everything should just work.
		810
		811	AnyEvent::Impl::Qt based on Qt.
		812
		813	Support for IO::Async can only be partial, as it is too broken and
		814	architecturally limited to even support the AnyEvent API. It also
		815	is the only event loop that needs the loop to be set explicitly, so
		816	it can only be used by a main program knowing about AnyEvent. See
		817	L<AnyEvent::Impl::Async> for the gory details.
		818
		819	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		820
		821	=item Event loops that are indirectly supported via other backends.
		822
		823	Some event loops can be supported via other modules:
		824
		825	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		826
		827	B<WxWidgets> has no support for watching file handles. However, you can
		828	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		829	polls 20 times per second, which was considered to be too horrible to even
		830	consider for AnyEvent.
		831
		832	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		833	backend, so it can be supported through POE.
		834
		835	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		836	load L<POE> when detecting them, in the hope that POE will pick them up,
		837	in which case everything will be automatic.
		838
		839	=back
		840
		841	=head1 GLOBAL VARIABLES AND FUNCTIONS
		842
		843	These are not normally required to use AnyEvent, but can be useful to
		844	write AnyEvent extension modules.
		845
		846	=over 4
		847
190	=item $AnyEvent::MODEL	848	=item $AnyEvent::MODEL
191		849
192	Contains C<undef> until the first watcher is being created. Then it	850	Contains C<undef> until the first watcher is being created, before the
		851	backend has been autodetected.
		852
193	contains the event model that is being used, which is the name of the	853	Afterwards it contains the event model that is being used, which is the
194	Perl class implementing the model. This class is usually one of the	854	name of the Perl class implementing the model. This class is usually one
195	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	855	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
196	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	856	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
197		857	will be C<urxvt::anyevent>).
198	The known classes so far are:
199
200	EV::AnyEvent based on EV (an interface to libev, best choice)
201	AnyEvent::Impl::Coro based on Coro::Event, second best choice.
202	AnyEvent::Impl::Event based on Event, also second best choice :)
203	AnyEvent::Impl::Glib based on Glib, second-best choice.
204	AnyEvent::Impl::Tk based on Tk, very bad choice.
205	AnyEvent::Impl::Perl pure-perl implementation, inefficient.
206		858
207	=item AnyEvent::detect	859	=item AnyEvent::detect
208		860
209	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	861	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
210	necessary. You should only call this function right before you would have	862	if necessary. You should only call this function right before you would
211	created an AnyEvent watcher anyway, that is, very late at runtime.	863	have created an AnyEvent watcher anyway, that is, as late as possible at
		864	runtime, and not e.g. while initialising of your module.
		865
		866	If you need to do some initialisation before AnyEvent watchers are
		867	created, use C<post_detect>.
		868
		869	=item $guard = AnyEvent::post_detect { BLOCK }
		870
		871	Arranges for the code block to be executed as soon as the event model is
		872	autodetected (or immediately if this has already happened).
		873
		874	The block will be executed I<after> the actual backend has been detected
		875	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		876	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		877	other initialisations - see the sources of L<AnyEvent::Strict> or
		878	L<AnyEvent::AIO> to see how this is used.
		879
		880	The most common usage is to create some global watchers, without forcing
		881	event module detection too early, for example, L<AnyEvent::AIO> creates
		882	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		883	avoid autodetecting the event module at load time.
		884
		885	If called in scalar or list context, then it creates and returns an object
		886	that automatically removes the callback again when it is destroyed (or
		887	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		888	a case where this is useful.
		889
		890	Example: Create a watcher for the IO::AIO module and store it in
		891	C<$WATCHER>. Only do so after the event loop is initialised, though.
		892
		893	our WATCHER;
		894
		895	my $guard = AnyEvent::post_detect {
		896	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		897	};
		898
		899	# the ||= is important in case post_detect immediately runs the block,
		900	# as to not clobber the newly-created watcher. assigning both watcher and
		901	# post_detect guard to the same variable has the advantage of users being
		902	# able to just C<undef $WATCHER> if the watcher causes them grief.
		903
		904	$WATCHER ||= $guard;
		905
		906	=item @AnyEvent::post_detect
		907
		908	If there are any code references in this array (you can C<push> to it
		909	before or after loading AnyEvent), then they will called directly after
		910	the event loop has been chosen.
		911
		912	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		913	if it is defined then the event loop has already been detected, and the
		914	array will be ignored.
		915
		916	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		917	it,as it takes care of these details.
		918
		919	This variable is mainly useful for modules that can do something useful
		920	when AnyEvent is used and thus want to know when it is initialised, but do
		921	not need to even load it by default. This array provides the means to hook
		922	into AnyEvent passively, without loading it.
212		923
213	=back	924	=back
214		925
215	=head1 WHAT TO DO IN A MODULE	926	=head1 WHAT TO DO IN A MODULE
216		927
217	As a module author, you should "use AnyEvent" and call AnyEvent methods	928	As a module author, you should C<use AnyEvent> and call AnyEvent methods
218	freely, but you should not load a specific event module or rely on it.	929	freely, but you should not load a specific event module or rely on it.
219		930
220	Be careful when you create watchers in the module body - Anyevent will	931	Be careful when you create watchers in the module body - AnyEvent will
221	decide which event module to use as soon as the first method is called, so	932	decide which event module to use as soon as the first method is called, so
222	by calling AnyEvent in your module body you force the user of your module	933	by calling AnyEvent in your module body you force the user of your module
223	to load the event module first.	934	to load the event module first.
224		935
		936	Never call C<< ->recv >> on a condition variable unless you I<know> that
		937	the C<< ->send >> method has been called on it already. This is
		938	because it will stall the whole program, and the whole point of using
		939	events is to stay interactive.
		940
		941	It is fine, however, to call C<< ->recv >> when the user of your module
		942	requests it (i.e. if you create a http request object ad have a method
		943	called C<results> that returns the results, it should call C<< ->recv >>
		944	freely, as the user of your module knows what she is doing. always).
		945
225	=head1 WHAT TO DO IN THE MAIN PROGRAM	946	=head1 WHAT TO DO IN THE MAIN PROGRAM
226		947
227	There will always be a single main program - the only place that should	948	There will always be a single main program - the only place that should
228	dictate which event model to use.	949	dictate which event model to use.
229		950
230	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	951	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
231	do anything special and let AnyEvent decide which implementation to chose.	952	do anything special (it does not need to be event-based) and let AnyEvent
		953	decide which implementation to chose if some module relies on it.
232		954
233	If the main program relies on a specific event model (for example, in Gtk2	955	If the main program relies on a specific event model - for example, in
234	programs you have to rely on either Glib or Glib::Event), you should load	956	Gtk2 programs you have to rely on the Glib module - you should load the
235	it before loading AnyEvent or any module that uses it, generally, as early	957	event module before loading AnyEvent or any module that uses it: generally
236	as possible. The reason is that modules might create watchers when they	958	speaking, you should load it as early as possible. The reason is that
237	are loaded, and AnyEvent will decide on the event model to use as soon as	959	modules might create watchers when they are loaded, and AnyEvent will
238	it creates watchers, and it might chose the wrong one unless you load the	960	decide on the event model to use as soon as it creates watchers, and it
239	correct one yourself.	961	might chose the wrong one unless you load the correct one yourself.
240		962
241	You can chose to use a rather inefficient pure-perl implementation by	963	You can chose to use a pure-perl implementation by loading the
242	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	964	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
243	generally better.	965	everywhere, but letting AnyEvent chose the model is generally better.
		966
		967	=head2 MAINLOOP EMULATION
		968
		969	Sometimes (often for short test scripts, or even standalone programs who
		970	only want to use AnyEvent), you do not want to run a specific event loop.
		971
		972	In that case, you can use a condition variable like this:
		973
		974	AnyEvent->condvar->recv;
		975
		976	This has the effect of entering the event loop and looping forever.
		977
		978	Note that usually your program has some exit condition, in which case
		979	it is better to use the "traditional" approach of storing a condition
		980	variable somewhere, waiting for it, and sending it when the program should
		981	exit cleanly.
		982
		983
		984	=head1 OTHER MODULES
		985
		986	The following is a non-exhaustive list of additional modules that use
		987	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		988	modules and other event loops in the same program. Some of the modules
		989	come with AnyEvent, most are available via CPAN.
		990
		991	=over 4
		992
		993	=item L<AnyEvent::Util>
		994
		995	Contains various utility functions that replace often-used but blocking
		996	functions such as C<inet_aton> by event-/callback-based versions.
		997
		998	=item L<AnyEvent::Socket>
		999
		1000	Provides various utility functions for (internet protocol) sockets,
		1001	addresses and name resolution. Also functions to create non-blocking tcp
		1002	connections or tcp servers, with IPv6 and SRV record support and more.
		1003
		1004	=item L<AnyEvent::Handle>
		1005
		1006	Provide read and write buffers, manages watchers for reads and writes,
		1007	supports raw and formatted I/O, I/O queued and fully transparent and
		1008	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1009
		1010	=item L<AnyEvent::DNS>
		1011
		1012	Provides rich asynchronous DNS resolver capabilities.
		1013
		1014	=item L<AnyEvent::HTTP>
		1015
		1016	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1017	HTTP requests.
		1018
		1019	=item L<AnyEvent::HTTPD>
		1020
		1021	Provides a simple web application server framework.
		1022
		1023	=item L<AnyEvent::FastPing>
		1024
		1025	The fastest ping in the west.
		1026
		1027	=item L<AnyEvent::DBI>
		1028
		1029	Executes L<DBI> requests asynchronously in a proxy process.
		1030
		1031	=item L<AnyEvent::AIO>
		1032
		1033	Truly asynchronous I/O, should be in the toolbox of every event
		1034	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1035	together.
		1036
		1037	=item L<AnyEvent::BDB>
		1038
		1039	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1040	L<BDB> and AnyEvent together.
		1041
		1042	=item L<AnyEvent::GPSD>
		1043
		1044	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1045
		1046	=item L<AnyEvent::IRC>
		1047
		1048	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1049
		1050	=item L<AnyEvent::XMPP>
		1051
		1052	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1053	Net::XMPP2>.
		1054
		1055	=item L<AnyEvent::IGS>
		1056
		1057	A non-blocking interface to the Internet Go Server protocol (used by
		1058	L<App::IGS>).
		1059
		1060	=item L<Net::FCP>
		1061
		1062	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1063	of AnyEvent.
		1064
		1065	=item L<Event::ExecFlow>
		1066
		1067	High level API for event-based execution flow control.
		1068
		1069	=item L<Coro>
		1070
		1071	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1072
		1073	=back
244		1074
245	=cut	1075	=cut
246		1076
247	package AnyEvent;	1077	package AnyEvent;
248		1078
		1079	# basically a tuned-down version of common::sense
		1080	sub common_sense {
249	no warnings;	1081	# no warnings
250	use strict;	1082	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1083	# use strict vars subs
		1084	$^H |= 0x00000600;
		1085	}
251		1086
		1087	BEGIN { AnyEvent::common_sense }
		1088
252	use Carp;	1089	use Carp ();
253		1090
254	our $VERSION = '2.55';	1091	our $VERSION = 4.881;
255	our $MODEL;	1092	our $MODEL;
256		1093
257	our $AUTOLOAD;	1094	our $AUTOLOAD;
258	our @ISA;	1095	our @ISA;
259		1096
260	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
261
262	our @REGISTRY;	1097	our @REGISTRY;
263		1098
		1099	our $WIN32;
		1100
		1101	our $VERBOSE;
		1102
		1103	BEGIN {
		1104	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1105	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1106
		1107	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1108	if ${^TAINT};
		1109
		1110	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1111
		1112	}
		1113
		1114	our $MAX_SIGNAL_LATENCY = 10;
		1115
		1116	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1117
		1118	{
		1119	my $idx;
		1120	$PROTOCOL{$_} = ++$idx
		1121	for reverse split /\s*,\s*/,
		1122	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1123	}
		1124
264	my @models = (	1125	my @models = (
265	[Coro::Event:: => AnyEvent::Impl::Coro::],
266	[EV:: => EV::AnyEvent::],	1126	[EV:: => AnyEvent::Impl::EV:: , 1],
267	[Event:: => AnyEvent::Impl::Event::],	1127	[Event:: => AnyEvent::Impl::Event::, 1],
268	[Glib:: => AnyEvent::Impl::Glib::],
269	[Tk:: => AnyEvent::Impl::Tk::],
270	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1128	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1129	# everything below here will not (normally) be autoprobed
		1130	# as the pureperl backend should work everywhere
		1131	# and is usually faster
		1132	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1133	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1134	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1135	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1136	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1137	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		1138	[Wx:: => AnyEvent::Impl::POE::],
		1139	[Prima:: => AnyEvent::Impl::POE::],
		1140	# IO::Async is just too broken - we would need workarounds for its
		1141	# byzantine signal and broken child handling, among others.
		1142	# IO::Async is rather hard to detect, as it doesn't have any
		1143	# obvious default class.
		1144	# [0, IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1145	# [0, IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1146	# [0, IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
271	);	1147	);
272		1148
273	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1149	our %method = map +($_ => 1),
		1150	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1151
		1152	our @post_detect;
		1153
		1154	sub post_detect(&) {
		1155	my ($cb) = @_;
		1156
		1157	if ($MODEL) {
		1158	$cb->();
		1159
		1160	undef
		1161	} else {
		1162	push @post_detect, $cb;
		1163
		1164	defined wantarray
		1165	? bless \$cb, "AnyEvent::Util::postdetect"
		1166	: ()
		1167	}
		1168	}
		1169
		1170	sub AnyEvent::Util::postdetect::DESTROY {
		1171	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1172	}
274		1173
275	sub detect() {	1174	sub detect() {
276	unless ($MODEL) {	1175	unless ($MODEL) {
277	no strict 'refs';	1176	local $SIG{__DIE__};
		1177
		1178	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1179	my $model = "AnyEvent::Impl::$1";
		1180	if (eval "require $model") {
		1181	$MODEL = $model;
		1182	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1183	} else {
		1184	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1185	}
		1186	}
278		1187
279	# check for already loaded models	1188	# check for already loaded models
		1189	unless ($MODEL) {
280	for (@REGISTRY, @models) {	1190	for (@REGISTRY, @models) {
281	my ($package, $model) = @$_;	1191	my ($package, $model) = @$_;
282	if (${"$package\::VERSION"} > 0) {	1192	if (${"$package\::VERSION"} > 0) {
283	if (eval "require $model") {	1193	if (eval "require $model") {
284	$MODEL = $model;	1194	$MODEL = $model;
285	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	1195	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
286	last;	1196	last;
		1197	}
287	}	1198	}
288	}	1199	}
		1200
		1201	unless ($MODEL) {
		1202	# try to autoload a model
		1203	for (@REGISTRY, @models) {
		1204	my ($package, $model, $autoload) = @$_;
		1205	if (
		1206	$autoload
		1207	and eval "require $package"
		1208	and ${"$package\::VERSION"} > 0
		1209	and eval "require $model"
		1210	) {
		1211	$MODEL = $model;
		1212	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
		1213	last;
		1214	}
		1215	}
		1216
		1217	$MODEL
		1218	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
		1219	}
289	}	1220	}
290		1221
291	unless ($MODEL) {	1222	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
292	# try to load a model
293
294	for (@REGISTRY, @models) {
295	my ($package, $model) = @$_;
296	if (eval "require $package"
297	and ${"$package\::VERSION"} > 0
298	and eval "require $model") {
299	$MODEL = $model;
300	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
301	last;
302	}
303	}
304
305	$MODEL
306	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Event (or Coro+Event), Glib or Tk.";
307	}
308		1223
309	unshift @ISA, $MODEL;	1224	unshift @ISA, $MODEL;
310	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1225
		1226	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1227
		1228	(shift @post_detect)->() while @post_detect;
311	}	1229	}
312		1230
313	$MODEL	1231	$MODEL
314	}	1232	}
315		1233
316	sub AUTOLOAD {	1234	sub AUTOLOAD {
317	(my $func = $AUTOLOAD) =~ s/.*://;	1235	(my $func = $AUTOLOAD) =~ s/.*://;
318		1236
319	$method{$func}	1237	$method{$func}
320	or croak "$func: not a valid method for AnyEvent objects";	1238	or Carp::croak "$func: not a valid method for AnyEvent objects";
321		1239
322	detect unless $MODEL;	1240	detect unless $MODEL;
323		1241
324	my $class = shift;	1242	my $class = shift;
325	$class->$func (@_);	1243	$class->$func (@_);
326	}	1244	}
327		1245
		1246	# utility function to dup a filehandle. this is used by many backends
		1247	# to support binding more than one watcher per filehandle (they usually
		1248	# allow only one watcher per fd, so we dup it to get a different one).
		1249	sub _dupfh($$;$$) {
		1250	my ($poll, $fh, $r, $w) = @_;
		1251
		1252	# cygwin requires the fh mode to be matching, unix doesn't
		1253	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1254
		1255	open my $fh2, $mode, $fh
		1256	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1257
		1258	# we assume CLOEXEC is already set by perl in all important cases
		1259
		1260	($fh2, $rw)
		1261	}
		1262
328	package AnyEvent::Base;	1263	package AnyEvent::Base;
329		1264
		1265	# default implementations for many methods
		1266
		1267	sub _time {
		1268	# probe for availability of Time::HiRes
		1269	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1270	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1271	*_time = \&Time::HiRes::time;
		1272	# if (eval "use POSIX (); (POSIX::times())...
		1273	} else {
		1274	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1275	*_time = sub { time }; # epic fail
		1276	}
		1277
		1278	&_time
		1279	}
		1280
		1281	sub time { _time }
		1282	sub now { _time }
		1283	sub now_update { }
		1284
330	# default implementation for ->condvar, ->wait, ->broadcast	1285	# default implementation for ->condvar
331		1286
332	sub condvar {	1287	sub condvar {
333	bless \my $flag, "AnyEvent::Base::CondVar"	1288	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
334	}
335
336	sub AnyEvent::Base::CondVar::broadcast {
337	${$_[0]}++;
338	}
339
340	sub AnyEvent::Base::CondVar::wait {
341	AnyEvent->one_event while !${$_[0]};
342	}	1289	}
343		1290
344	# default implementation for ->signal	1291	# default implementation for ->signal
345		1292
346	our %SIG_CB;	1293	our $HAVE_ASYNC_INTERRUPT;
		1294	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1295	our (%SIG_ASY, %SIG_ASY_W);
		1296	our ($SIG_COUNT, $SIG_TW);
347		1297
		1298	sub _signal_exec {
		1299	$HAVE_ASYNC_INTERRUPT
		1300	? $SIGPIPE_R->drain
		1301	: sysread $SIGPIPE_R, my $dummy, 9;
		1302
		1303	while (%SIG_EV) {
		1304	for (keys %SIG_EV) {
		1305	delete $SIG_EV{$_};
		1306	$_->() for values %{ $SIG_CB{$_} || {} };
		1307	}
		1308	}
		1309	}
		1310
		1311	# install a dummy wakeup watcher to reduce signal catching latency
		1312	sub _sig_add() {
		1313	unless ($SIG_COUNT++) {
		1314	# try to align timer on a full-second boundary, if possible
		1315	my $NOW = AnyEvent->now;
		1316
		1317	$SIG_TW = AnyEvent->timer (
		1318	after => $MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1319	interval => $MAX_SIGNAL_LATENCY,
		1320	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1321	);
		1322	}
		1323	}
		1324
		1325	sub _sig_del {
		1326	undef $SIG_TW
		1327	unless --$SIG_COUNT;
		1328	}
		1329
348	sub signal {	1330	sub _signal {
349	my (undef, %arg) = @_;	1331	my (undef, %arg) = @_;
350		1332
351	my $signal = uc $arg{signal}	1333	my $signal = uc $arg{signal}
352	or Carp::croak "required option 'signal' is missing";	1334	or Carp::croak "required option 'signal' is missing";
353		1335
		1336	if ($HAVE_ASYNC_INTERRUPT) {
		1337	# async::interrupt
		1338
		1339	$signal = Async::Interrupt::sig2num ($signal);
354	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1340	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1341
		1342	$SIG_ASY{$signal} ||= new Async::Interrupt
		1343	cb => sub { undef $SIG_EV{$signal} },
		1344	signal => $signal,
		1345	pipe => [$SIGPIPE_R->filenos],
		1346	pipe_autodrain => 0,
		1347	;
		1348
		1349	} else {
		1350	# pure perl
		1351
		1352	# AE::Util has been loaded in signal
		1353	$signal = AnyEvent::Util::sig2name ($signal);
		1354	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1355
355	$SIG{$signal} ||= sub {	1356	$SIG{$signal} ||= sub {
356	$_->() for values %{ $SIG_CB{$signal} || {} };	1357	local $!;
		1358	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1359	undef $SIG_EV{$signal};
		1360	};
		1361
		1362	# can't do signal processing without introducing races in pure perl,
		1363	# so limit the signal latency.
		1364	_sig_add;
357	};	1365	}
358		1366
359	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1367	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
360	}	1368	}
361		1369
		1370	sub signal {
		1371	# probe for availability of Async::Interrupt
		1372	if (!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT} && eval "use Async::Interrupt 1.0 (); 1") {
		1373	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1374
		1375	$HAVE_ASYNC_INTERRUPT = 1;
		1376	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1377	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1378
		1379	} else {
		1380	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1381
		1382	require Fcntl;
		1383
		1384	if (AnyEvent::WIN32) {
		1385	require AnyEvent::Util;
		1386
		1387	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1388	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1389	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1390	} else {
		1391	pipe $SIGPIPE_R, $SIGPIPE_W;
		1392	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1393	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1394
		1395	# not strictly required, as $^F is normally 2, but let's make sure...
		1396	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1397	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1398	}
		1399
		1400	$SIGPIPE_R
		1401	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1402
		1403	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1404	}
		1405
		1406	*signal = \&_signal;
		1407	&signal
		1408	}
		1409
362	sub AnyEvent::Base::Signal::DESTROY {	1410	sub AnyEvent::Base::signal::DESTROY {
363	my ($signal, $cb) = @{$_[0]};	1411	my ($signal, $cb) = @{$_[0]};
364		1412
		1413	_sig_del;
		1414
365	delete $SIG_CB{$signal}{$cb};	1415	delete $SIG_CB{$signal}{$cb};
366		1416
367	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1417	$HAVE_ASYNC_INTERRUPT
		1418	? delete $SIG_ASY{$signal}
		1419	: # delete doesn't work with older perls - they then
		1420	# print weird messages, or just unconditionally exit
		1421	# instead of getting the default action.
		1422	undef $SIG{$signal}
		1423	unless keys %{ $SIG_CB{$signal} };
368	}	1424	}
369		1425
370	# default implementation for ->child	1426	# default implementation for ->child
371		1427
372	our %PID_CB;	1428	our %PID_CB;
373	our $CHLD_W;	1429	our $CHLD_W;
374	our $PID_IDLE;	1430	our $CHLD_DELAY_W;
375	our $WNOHANG;	1431	our $WNOHANG;
376		1432
377	sub _child_wait {	1433	sub _emit_childstatus($$) {
378	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1434	my (undef, $rpid, $rstatus) = @_;
		1435
		1436	$_->($rpid, $rstatus)
379	$_->() for values %{ (delete $PID_CB{$pid}) || {} };	1437	for values %{ $PID_CB{$rpid} || {} },
380	}	1438	values %{ $PID_CB{0} || {} };
		1439	}
381		1440
382	undef $PID_IDLE;	1441	sub _sigchld {
		1442	my $pid;
		1443
		1444	AnyEvent->_emit_childstatus ($pid, $?)
		1445	while ($pid = waitpid -1, $WNOHANG) > 0;
383	}	1446	}
384		1447
385	sub child {	1448	sub child {
386	my (undef, %arg) = @_;	1449	my (undef, %arg) = @_;
387		1450
388	my $pid = uc $arg{pid}	1451	defined (my $pid = $arg{pid} + 0)
389	or Carp::croak "required option 'pid' is missing";	1452	or Carp::croak "required option 'pid' is missing";
390		1453
391	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1454	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
392		1455
393	unless ($WNOHANG) {	1456	# WNOHANG is almost cetrainly 1 everywhere
394	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1457	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
		1458	? 1
		1459	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
		1460
		1461	unless ($CHLD_W) {
		1462	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
		1463	# child could be a zombie already, so make at least one round
		1464	&_sigchld;
395	}	1465	}
396		1466
397	unless ($CHLD_W) {
398	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_child_wait);
399	# child could be a zombie already
400	$PID_IDLE ||= AnyEvent->timer (after => 0, cb => \&_child_wait);
401	}
402
403	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1467	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
404	}	1468	}
405		1469
406	sub AnyEvent::Base::Child::DESTROY {	1470	sub AnyEvent::Base::child::DESTROY {
407	my ($pid, $cb) = @{$_[0]};	1471	my ($pid, $cb) = @{$_[0]};
408		1472
409	delete $PID_CB{$pid}{$cb};	1473	delete $PID_CB{$pid}{$cb};
410	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1474	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
411		1475
412	undef $CHLD_W unless keys %PID_CB;	1476	undef $CHLD_W unless keys %PID_CB;
413	}	1477	}
414		1478
		1479	# idle emulation is done by simply using a timer, regardless
		1480	# of whether the process is idle or not, and not letting
		1481	# the callback use more than 50% of the time.
		1482	sub idle {
		1483	my (undef, %arg) = @_;
		1484
		1485	my ($cb, $w, $rcb) = $arg{cb};
		1486
		1487	$rcb = sub {
		1488	if ($cb) {
		1489	$w = _time;
		1490	&$cb;
		1491	$w = _time - $w;
		1492
		1493	# never use more then 50% of the time for the idle watcher,
		1494	# within some limits
		1495	$w = 0.0001 if $w < 0.0001;
		1496	$w = 5 if $w > 5;
		1497
		1498	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1499	} else {
		1500	# clean up...
		1501	undef $w;
		1502	undef $rcb;
		1503	}
		1504	};
		1505
		1506	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1507
		1508	bless \\$cb, "AnyEvent::Base::idle"
		1509	}
		1510
		1511	sub AnyEvent::Base::idle::DESTROY {
		1512	undef $${$_[0]};
		1513	}
		1514
		1515	package AnyEvent::CondVar;
		1516
		1517	our @ISA = AnyEvent::CondVar::Base::;
		1518
		1519	package AnyEvent::CondVar::Base;
		1520
		1521	#use overload
		1522	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1523	# fallback => 1;
		1524
		1525	# save 300+ kilobytes by dirtily hardcoding overloading
		1526	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1527	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1528	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1529	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1530
		1531	our $WAITING;
		1532
		1533	sub _send {
		1534	# nop
		1535	}
		1536
		1537	sub send {
		1538	my $cv = shift;
		1539	$cv->{_ae_sent} = [@_];
		1540	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1541	$cv->_send;
		1542	}
		1543
		1544	sub croak {
		1545	$_[0]{_ae_croak} = $_[1];
		1546	$_[0]->send;
		1547	}
		1548
		1549	sub ready {
		1550	$_[0]{_ae_sent}
		1551	}
		1552
		1553	sub _wait {
		1554	$WAITING
		1555	and !$_[0]{_ae_sent}
		1556	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1557
		1558	local $WAITING = 1;
		1559	AnyEvent->one_event while !$_[0]{_ae_sent};
		1560	}
		1561
		1562	sub recv {
		1563	$_[0]->_wait;
		1564
		1565	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1566	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1567	}
		1568
		1569	sub cb {
		1570	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1571	$_[0]{_ae_cb}
		1572	}
		1573
		1574	sub begin {
		1575	++$_[0]{_ae_counter};
		1576	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1577	}
		1578
		1579	sub end {
		1580	return if --$_[0]{_ae_counter};
		1581	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1582	}
		1583
		1584	# undocumented/compatibility with pre-3.4
		1585	*broadcast = \&send;
		1586	*wait = \&_wait;
		1587
		1588	=head1 ERROR AND EXCEPTION HANDLING
		1589
		1590	In general, AnyEvent does not do any error handling - it relies on the
		1591	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1592	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1593	checking of all AnyEvent methods, however, which is highly useful during
		1594	development.
		1595
		1596	As for exception handling (i.e. runtime errors and exceptions thrown while
		1597	executing a callback), this is not only highly event-loop specific, but
		1598	also not in any way wrapped by this module, as this is the job of the main
		1599	program.
		1600
		1601	The pure perl event loop simply re-throws the exception (usually
		1602	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1603	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1604	so on.
		1605
		1606	=head1 ENVIRONMENT VARIABLES
		1607
		1608	The following environment variables are used by this module or its
		1609	submodules.
		1610
		1611	Note that AnyEvent will remove I<all> environment variables starting with
		1612	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1613	enabled.
		1614
		1615	=over 4
		1616
		1617	=item C<PERL_ANYEVENT_VERBOSE>
		1618
		1619	By default, AnyEvent will be completely silent except in fatal
		1620	conditions. You can set this environment variable to make AnyEvent more
		1621	talkative.
		1622
		1623	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1624	conditions, such as not being able to load the event model specified by
		1625	C<PERL_ANYEVENT_MODEL>.
		1626
		1627	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1628	model it chooses.
		1629
		1630	When set to C<8> or higher, then AnyEvent will report extra information on
		1631	which optional modules it loads and how it implements certain features.
		1632
		1633	=item C<PERL_ANYEVENT_STRICT>
		1634
		1635	AnyEvent does not do much argument checking by default, as thorough
		1636	argument checking is very costly. Setting this variable to a true value
		1637	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1638	check the arguments passed to most method calls. If it finds any problems,
		1639	it will croak.
		1640
		1641	In other words, enables "strict" mode.
		1642
		1643	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1644	>>, it is definitely recommended to keep it off in production. Keeping
		1645	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1646	can be very useful, however.
		1647
		1648	=item C<PERL_ANYEVENT_MODEL>
		1649
		1650	This can be used to specify the event model to be used by AnyEvent, before
		1651	auto detection and -probing kicks in. It must be a string consisting
		1652	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1653	and the resulting module name is loaded and if the load was successful,
		1654	used as event model. If it fails to load AnyEvent will proceed with
		1655	auto detection and -probing.
		1656
		1657	This functionality might change in future versions.
		1658
		1659	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1660	could start your program like this:
		1661
		1662	PERL_ANYEVENT_MODEL=Perl perl ...
		1663
		1664	=item C<PERL_ANYEVENT_PROTOCOLS>
		1665
		1666	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1667	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1668	of auto probing).
		1669
		1670	Must be set to a comma-separated list of protocols or address families,
		1671	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1672	used, and preference will be given to protocols mentioned earlier in the
		1673	list.
		1674
		1675	This variable can effectively be used for denial-of-service attacks
		1676	against local programs (e.g. when setuid), although the impact is likely
		1677	small, as the program has to handle conenction and other failures anyways.
		1678
		1679	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1680	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1681	- only support IPv4, never try to resolve or contact IPv6
		1682	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1683	IPv6, but prefer IPv6 over IPv4.
		1684
		1685	=item C<PERL_ANYEVENT_EDNS0>
		1686
		1687	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1688	for DNS. This extension is generally useful to reduce DNS traffic, but
		1689	some (broken) firewalls drop such DNS packets, which is why it is off by
		1690	default.
		1691
		1692	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1693	EDNS0 in its DNS requests.
		1694
		1695	=item C<PERL_ANYEVENT_MAX_FORKS>
		1696
		1697	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1698	will create in parallel.
		1699
		1700	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1701
		1702	The default value for the C<max_outstanding> parameter for the default DNS
		1703	resolver - this is the maximum number of parallel DNS requests that are
		1704	sent to the DNS server.
		1705
		1706	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1707
		1708	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1709	configuration) in the default resolver. When set to the empty string, no
		1710	default config will be used.
		1711
		1712	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1713
		1714	When neither C<ca_file> nor C<ca_path> was specified during
		1715	L<AnyEvent::TLS> context creation, and either of these environment
		1716	variables exist, they will be used to specify CA certificate locations
		1717	instead of a system-dependent default.
		1718
		1719	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1720
		1721	When these are set to C<1>, then the respective modules are not
		1722	loaded. Mostly good for testing AnyEvent itself.
		1723
		1724	=back
		1725
415	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1726	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1727
		1728	This is an advanced topic that you do not normally need to use AnyEvent in
		1729	a module. This section is only of use to event loop authors who want to
		1730	provide AnyEvent compatibility.
416		1731
417	If you need to support another event library which isn't directly	1732	If you need to support another event library which isn't directly
418	supported by AnyEvent, you can supply your own interface to it by	1733	supported by AnyEvent, you can supply your own interface to it by
419	pushing, before the first watcher gets created, the package name of	1734	pushing, before the first watcher gets created, the package name of
420	the event module and the package name of the interface to use onto	1735	the event module and the package name of the interface to use onto
421	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	1736	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
422	AnyEvent.	1737	AnyEvent, so it is reasonably cheap.
423		1738
424	Example:	1739	Example:
425		1740
426	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	1741	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
427		1742
428	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	1743	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
429	package/class when it finds the C<urxvt> package/module is loaded. When	1744	package/class when it finds the C<urxvt> package/module is already loaded.
		1745
430	AnyEvent is loaded and asked to find a suitable event model, it will	1746	When AnyEvent is loaded and asked to find a suitable event model, it
431	first check for the presence of urxvt.	1747	will first check for the presence of urxvt by trying to C<use> the
		1748	C<urxvt::anyevent> module.
432		1749
433	The class should provide implementations for all watcher types (see	1750	The class should provide implementations for all watcher types. See
434	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	1751	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
435	(Source code) and so on for actual examples, use C<perldoc -m	1752	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
436	AnyEvent::Impl::Glib> to see the sources).	1753	see the sources.
437		1754
		1755	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		1756	provide suitable (hopefully) replacements.
		1757
438	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	1758	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
439	uses the above line as-is. An interface isn't included in AnyEvent	1759	terminal emulator uses the above line as-is. An interface isn't included
440	because it doesn't make sense outside the embedded interpreter inside	1760	in AnyEvent because it doesn't make sense outside the embedded interpreter
441	I<rxvt-unicode>, and it is updated and maintained as part of the	1761	inside I<rxvt-unicode>, and it is updated and maintained as part of the
442	I<rxvt-unicode> distribution.	1762	I<rxvt-unicode> distribution.
443		1763
444	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1764	I<rxvt-unicode> also cheats a bit by not providing blocking access to
445	condition variables: code blocking while waiting for a condition will	1765	condition variables: code blocking while waiting for a condition will
446	C<die>. This still works with most modules/usages, and blocking calls must	1766	C<die>. This still works with most modules/usages, and blocking calls must
447	not be in an interactive application, so it makes sense.	1767	not be done in an interactive application, so it makes sense.
448		1768
449	=head1 ENVIRONMENT VARIABLES
450
451	The following environment variables are used by this module:
452
453	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
454	model gets used.
455
456	=head1 EXAMPLE	1769	=head1 EXAMPLE PROGRAM
457		1770
458	The following program uses an io watcher to read data from stdin, a timer	1771	The following program uses an I/O watcher to read data from STDIN, a timer
459	to display a message once per second, and a condvar to exit the program	1772	to display a message once per second, and a condition variable to quit the
460	when the user enters quit:	1773	program when the user enters quit:
461		1774
462	use AnyEvent;	1775	use AnyEvent;
463		1776
464	my $cv = AnyEvent->condvar;	1777	my $cv = AnyEvent->condvar;
465		1778
466	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	1779	my $io_watcher = AnyEvent->io (
		1780	fh => \*STDIN,
		1781	poll => 'r',
		1782	cb => sub {
467	warn "io event <$_[0]>\n"; # will always output <r>	1783	warn "io event <$_[0]>\n"; # will always output <r>
468	chomp (my $input = <STDIN>); # read a line	1784	chomp (my $input = <STDIN>); # read a line
469	warn "read: $input\n"; # output what has been read	1785	warn "read: $input\n"; # output what has been read
470	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1786	$cv->send if $input =~ /^q/i; # quit program if /^q/i
		1787	},
471	});	1788	);
472		1789
473	my $time_watcher; # can only be used once	1790	my $time_watcher; # can only be used once
474		1791
475	sub new_timer {	1792	sub new_timer {
476	$timer = AnyEvent->timer (after => 1, cb => sub {	1793	$timer = AnyEvent->timer (after => 1, cb => sub {
…		…
479	});	1796	});
480	}	1797	}
481		1798
482	new_timer; # create first timer	1799	new_timer; # create first timer
483		1800
484	$cv->wait; # wait until user enters /^q/i	1801	$cv->recv; # wait until user enters /^q/i
485		1802
486	=head1 REAL-WORLD EXAMPLE	1803	=head1 REAL-WORLD EXAMPLE
487		1804
488	Consider the L<Net::FCP> module. It features (among others) the following	1805	Consider the L<Net::FCP> module. It features (among others) the following
489	API calls, which are to freenet what HTTP GET requests are to http:	1806	API calls, which are to freenet what HTTP GET requests are to http:
…		…
539	syswrite $txn->{fh}, $txn->{request}	1856	syswrite $txn->{fh}, $txn->{request}
540	or die "connection or write error";	1857	or die "connection or write error";
541	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1858	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
542		1859
543	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1860	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
544	result and signals any possible waiters that the request ahs finished:	1861	result and signals any possible waiters that the request has finished:
545		1862
546	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1863	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
547		1864
548	if (end-of-file or data complete) {	1865	if (end-of-file or data complete) {
549	$txn->{result} = $txn->{buf};	1866	$txn->{result} = $txn->{buf};
550	$txn->{finished}->broadcast;	1867	$txn->{finished}->send;
551	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1868	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
552	}	1869	}
553		1870
554	The C<result> method, finally, just waits for the finished signal (if the	1871	The C<result> method, finally, just waits for the finished signal (if the
555	request was already finished, it doesn't wait, of course, and returns the	1872	request was already finished, it doesn't wait, of course, and returns the
556	data:	1873	data:
557		1874
558	$txn->{finished}->wait;	1875	$txn->{finished}->recv;
559	return $txn->{result};	1876	return $txn->{result};
560		1877
561	The actual code goes further and collects all errors (C<die>s, exceptions)	1878	The actual code goes further and collects all errors (C<die>s, exceptions)
562	that occured during request processing. The C<result> method detects	1879	that occurred during request processing. The C<result> method detects
563	wether an exception as thrown (it is stored inside the $txn object)	1880	whether an exception as thrown (it is stored inside the $txn object)
564	and just throws the exception, which means connection errors and other	1881	and just throws the exception, which means connection errors and other
565	problems get reported tot he code that tries to use the result, not in a	1882	problems get reported tot he code that tries to use the result, not in a
566	random callback.	1883	random callback.
567		1884
568	All of this enables the following usage styles:	1885	All of this enables the following usage styles:
569		1886
570	1. Blocking:	1887	1. Blocking:
571		1888
572	my $data = $fcp->client_get ($url);	1889	my $data = $fcp->client_get ($url);
573		1890
574	2. Blocking, but parallelizing:	1891	2. Blocking, but running in parallel:
575		1892
576	my @datas = map $_->result,	1893	my @datas = map $_->result,
577	map $fcp->txn_client_get ($_),	1894	map $fcp->txn_client_get ($_),
578	@urls;	1895	@urls;
579		1896
580	Both blocking examples work without the module user having to know	1897	Both blocking examples work without the module user having to know
581	anything about events.	1898	anything about events.
582		1899
583	3a. Event-based in a main program, using any support Event module:	1900	3a. Event-based in a main program, using any supported event module:
584		1901
585	use Event;	1902	use EV;
586		1903
587	$fcp->txn_client_get ($url)->cb (sub {	1904	$fcp->txn_client_get ($url)->cb (sub {
588	my $txn = shift;	1905	my $txn = shift;
589	my $data = $txn->result;	1906	my $data = $txn->result;
590	...	1907	...
591	});	1908	});
592		1909
593	Event::loop;	1910	EV::loop;
594		1911
595	3b. The module user could use AnyEvent, too:	1912	3b. The module user could use AnyEvent, too:
596		1913
597	use AnyEvent;	1914	use AnyEvent;
598		1915
599	my $quit = AnyEvent->condvar;	1916	my $quit = AnyEvent->condvar;
600		1917
601	$fcp->txn_client_get ($url)->cb (sub {	1918	$fcp->txn_client_get ($url)->cb (sub {
602	...	1919	...
603	$quit->broadcast;	1920	$quit->send;
604	});	1921	});
605		1922
606	$quit->wait;	1923	$quit->recv;
		1924
		1925
		1926	=head1 BENCHMARKS
		1927
		1928	To give you an idea of the performance and overheads that AnyEvent adds
		1929	over the event loops themselves and to give you an impression of the speed
		1930	of various event loops I prepared some benchmarks.
		1931
		1932	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1933
		1934	Here is a benchmark of various supported event models used natively and
		1935	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1936	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1937	which it is), lets them fire exactly once and destroys them again.
		1938
		1939	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1940	distribution.
		1941
		1942	=head3 Explanation of the columns
		1943
		1944	I<watcher> is the number of event watchers created/destroyed. Since
		1945	different event models feature vastly different performances, each event
		1946	loop was given a number of watchers so that overall runtime is acceptable
		1947	and similar between tested event loop (and keep them from crashing): Glib
		1948	would probably take thousands of years if asked to process the same number
		1949	of watchers as EV in this benchmark.
		1950
		1951	I<bytes> is the number of bytes (as measured by the resident set size,
		1952	RSS) consumed by each watcher. This method of measuring captures both C
		1953	and Perl-based overheads.
		1954
		1955	I<create> is the time, in microseconds (millionths of seconds), that it
		1956	takes to create a single watcher. The callback is a closure shared between
		1957	all watchers, to avoid adding memory overhead. That means closure creation
		1958	and memory usage is not included in the figures.
		1959
		1960	I<invoke> is the time, in microseconds, used to invoke a simple
		1961	callback. The callback simply counts down a Perl variable and after it was
		1962	invoked "watcher" times, it would C<< ->send >> a condvar once to
		1963	signal the end of this phase.
		1964
		1965	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1966	watcher.
		1967
		1968	=head3 Results
		1969
		1970	name watchers bytes create invoke destroy comment
		1971	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
		1972	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
		1973	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
		1974	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
		1975	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
		1976	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1977	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1978	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
		1979	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
		1980	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
		1981	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
		1982	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
		1983
		1984	=head3 Discussion
		1985
		1986	The benchmark does I<not> measure scalability of the event loop very
		1987	well. For example, a select-based event loop (such as the pure perl one)
		1988	can never compete with an event loop that uses epoll when the number of
		1989	file descriptors grows high. In this benchmark, all events become ready at
		1990	the same time, so select/poll-based implementations get an unnatural speed
		1991	boost.
		1992
		1993	Also, note that the number of watchers usually has a nonlinear effect on
		1994	overall speed, that is, creating twice as many watchers doesn't take twice
		1995	the time - usually it takes longer. This puts event loops tested with a
		1996	higher number of watchers at a disadvantage.
		1997
		1998	To put the range of results into perspective, consider that on the
		1999	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2000	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2001	cycles with POE.
		2002
		2003	C<EV> is the sole leader regarding speed and memory use, which are both
		2004	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		2005	far less memory than any other event loop and is still faster than Event
		2006	natively.
		2007
		2008	The pure perl implementation is hit in a few sweet spots (both the
		2009	constant timeout and the use of a single fd hit optimisations in the perl
		2010	interpreter and the backend itself). Nevertheless this shows that it
		2011	adds very little overhead in itself. Like any select-based backend its
		2012	performance becomes really bad with lots of file descriptors (and few of
		2013	them active), of course, but this was not subject of this benchmark.
		2014
		2015	The C<Event> module has a relatively high setup and callback invocation
		2016	cost, but overall scores in on the third place.
		2017
		2018	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2019	when using its pure perl backend.
		2020
		2021	C<Glib>'s memory usage is quite a bit higher, but it features a
		2022	faster callback invocation and overall ends up in the same class as
		2023	C<Event>. However, Glib scales extremely badly, doubling the number of
		2024	watchers increases the processing time by more than a factor of four,
		2025	making it completely unusable when using larger numbers of watchers
		2026	(note that only a single file descriptor was used in the benchmark, so
		2027	inefficiencies of C<poll> do not account for this).
		2028
		2029	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2030	more than 2000 watchers is a big setback, however, as correctness takes
		2031	precedence over speed. Nevertheless, its performance is surprising, as the
		2032	file descriptor is dup()ed for each watcher. This shows that the dup()
		2033	employed by some adaptors is not a big performance issue (it does incur a
		2034	hidden memory cost inside the kernel which is not reflected in the figures
		2035	above).
		2036
		2037	C<POE>, regardless of underlying event loop (whether using its pure perl
		2038	select-based backend or the Event module, the POE-EV backend couldn't
		2039	be tested because it wasn't working) shows abysmal performance and
		2040	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2041	as EV watchers, and 10 times as much memory as Event (the high memory
		2042	requirements are caused by requiring a session for each watcher). Watcher
		2043	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2044	implementation.
		2045
		2046	The design of the POE adaptor class in AnyEvent can not really account
		2047	for the performance issues, though, as session creation overhead is
		2048	small compared to execution of the state machine, which is coded pretty
		2049	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2050	using multiple sessions is not a good approach, especially regarding
		2051	memory usage, even the author of POE could not come up with a faster
		2052	design).
		2053
		2054	=head3 Summary
		2055
		2056	=over 4
		2057
		2058	=item * Using EV through AnyEvent is faster than any other event loop
		2059	(even when used without AnyEvent), but most event loops have acceptable
		2060	performance with or without AnyEvent.
		2061
		2062	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2063	the actual event loop, only with extremely fast event loops such as EV
		2064	adds AnyEvent significant overhead.
		2065
		2066	=item * You should avoid POE like the plague if you want performance or
		2067	reasonable memory usage.
		2068
		2069	=back
		2070
		2071	=head2 BENCHMARKING THE LARGE SERVER CASE
		2072
		2073	This benchmark actually benchmarks the event loop itself. It works by
		2074	creating a number of "servers": each server consists of a socket pair, a
		2075	timeout watcher that gets reset on activity (but never fires), and an I/O
		2076	watcher waiting for input on one side of the socket. Each time the socket
		2077	watcher reads a byte it will write that byte to a random other "server".
		2078
		2079	The effect is that there will be a lot of I/O watchers, only part of which
		2080	are active at any one point (so there is a constant number of active
		2081	fds for each loop iteration, but which fds these are is random). The
		2082	timeout is reset each time something is read because that reflects how
		2083	most timeouts work (and puts extra pressure on the event loops).
		2084
		2085	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2086	(1%) are active. This mirrors the activity of large servers with many
		2087	connections, most of which are idle at any one point in time.
		2088
		2089	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2090	distribution.
		2091
		2092	=head3 Explanation of the columns
		2093
		2094	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2095	each server has a read and write socket end).
		2096
		2097	I<create> is the time it takes to create a socket pair (which is
		2098	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2099
		2100	I<request>, the most important value, is the time it takes to handle a
		2101	single "request", that is, reading the token from the pipe and forwarding
		2102	it to another server. This includes deleting the old timeout and creating
		2103	a new one that moves the timeout into the future.
		2104
		2105	=head3 Results
		2106
		2107	name sockets create request
		2108	EV 20000 69.01 11.16
		2109	Perl 20000 73.32 35.87
		2110	IOAsync 20000 157.00 98.14 epoll
		2111	IOAsync 20000 159.31 616.06 poll
		2112	Event 20000 212.62 257.32
		2113	Glib 20000 651.16 1896.30
		2114	POE 20000 349.67 12317.24 uses POE::Loop::Event
		2115
		2116	=head3 Discussion
		2117
		2118	This benchmark I<does> measure scalability and overall performance of the
		2119	particular event loop.
		2120
		2121	EV is again fastest. Since it is using epoll on my system, the setup time
		2122	is relatively high, though.
		2123
		2124	Perl surprisingly comes second. It is much faster than the C-based event
		2125	loops Event and Glib.
		2126
		2127	IO::Async performs very well when using its epoll backend, and still quite
		2128	good compared to Glib when using its pure perl backend.
		2129
		2130	Event suffers from high setup time as well (look at its code and you will
		2131	understand why). Callback invocation also has a high overhead compared to
		2132	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2133	uses select or poll in basically all documented configurations.
		2134
		2135	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2136	clearly fails to perform with many filehandles or in busy servers.
		2137
		2138	POE is still completely out of the picture, taking over 1000 times as long
		2139	as EV, and over 100 times as long as the Perl implementation, even though
		2140	it uses a C-based event loop in this case.
		2141
		2142	=head3 Summary
		2143
		2144	=over 4
		2145
		2146	=item * The pure perl implementation performs extremely well.
		2147
		2148	=item * Avoid Glib or POE in large projects where performance matters.
		2149
		2150	=back
		2151
		2152	=head2 BENCHMARKING SMALL SERVERS
		2153
		2154	While event loops should scale (and select-based ones do not...) even to
		2155	large servers, most programs we (or I :) actually write have only a few
		2156	I/O watchers.
		2157
		2158	In this benchmark, I use the same benchmark program as in the large server
		2159	case, but it uses only eight "servers", of which three are active at any
		2160	one time. This should reflect performance for a small server relatively
		2161	well.
		2162
		2163	The columns are identical to the previous table.
		2164
		2165	=head3 Results
		2166
		2167	name sockets create request
		2168	EV 16 20.00 6.54
		2169	Perl 16 25.75 12.62
		2170	Event 16 81.27 35.86
		2171	Glib 16 32.63 15.48
		2172	POE 16 261.87 276.28 uses POE::Loop::Event
		2173
		2174	=head3 Discussion
		2175
		2176	The benchmark tries to test the performance of a typical small
		2177	server. While knowing how various event loops perform is interesting, keep
		2178	in mind that their overhead in this case is usually not as important, due
		2179	to the small absolute number of watchers (that is, you need efficiency and
		2180	speed most when you have lots of watchers, not when you only have a few of
		2181	them).
		2182
		2183	EV is again fastest.
		2184
		2185	Perl again comes second. It is noticeably faster than the C-based event
		2186	loops Event and Glib, although the difference is too small to really
		2187	matter.
		2188
		2189	POE also performs much better in this case, but is is still far behind the
		2190	others.
		2191
		2192	=head3 Summary
		2193
		2194	=over 4
		2195
		2196	=item * C-based event loops perform very well with small number of
		2197	watchers, as the management overhead dominates.
		2198
		2199	=back
		2200
		2201	=head2 THE IO::Lambda BENCHMARK
		2202
		2203	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2204	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2205	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2206	shouldn't come as a surprise to anybody). As such, the benchmark is
		2207	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2208	very optimal. But how would AnyEvent compare when used without the extra
		2209	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2210
		2211	The benchmark itself creates an echo-server, and then, for 500 times,
		2212	connects to the echo server, sends a line, waits for the reply, and then
		2213	creates the next connection. This is a rather bad benchmark, as it doesn't
		2214	test the efficiency of the framework or much non-blocking I/O, but it is a
		2215	benchmark nevertheless.
		2216
		2217	name runtime
		2218	Lambda/select 0.330 sec
		2219	+ optimized 0.122 sec
		2220	Lambda/AnyEvent 0.327 sec
		2221	+ optimized 0.138 sec
		2222	Raw sockets/select 0.077 sec
		2223	POE/select, components 0.662 sec
		2224	POE/select, raw sockets 0.226 sec
		2225	POE/select, optimized 0.404 sec
		2226
		2227	AnyEvent/select/nb 0.085 sec
		2228	AnyEvent/EV/nb 0.068 sec
		2229	+state machine 0.134 sec
		2230
		2231	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2232	benchmarks actually make blocking connects and use 100% blocking I/O,
		2233	defeating the purpose of an event-based solution. All of the newly
		2234	written AnyEvent benchmarks use 100% non-blocking connects (using
		2235	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2236	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2237	generally require a lot more bookkeeping and event handling than blocking
		2238	connects (which involve a single syscall only).
		2239
		2240	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2241	offers similar expressive power as POE and IO::Lambda, using conventional
		2242	Perl syntax. This means that both the echo server and the client are 100%
		2243	non-blocking, further placing it at a disadvantage.
		2244
		2245	As you can see, the AnyEvent + EV combination even beats the
		2246	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2247	backend easily beats IO::Lambda and POE.
		2248
		2249	And even the 100% non-blocking version written using the high-level (and
		2250	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2251	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2252	in a non-blocking way.
		2253
		2254	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2255	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2256	part of the IO::lambda distribution and were used without any changes.
		2257
		2258
		2259	=head1 SIGNALS
		2260
		2261	AnyEvent currently installs handlers for these signals:
		2262
		2263	=over 4
		2264
		2265	=item SIGCHLD
		2266
		2267	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2268	emulation for event loops that do not support them natively. Also, some
		2269	event loops install a similar handler.
		2270
		2271	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2272	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2273
		2274	=item SIGPIPE
		2275
		2276	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2277	when AnyEvent gets loaded.
		2278
		2279	The rationale for this is that AnyEvent users usually do not really depend
		2280	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2281	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2282	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2283	some random socket.
		2284
		2285	The rationale for installing a no-op handler as opposed to ignoring it is
		2286	that this way, the handler will be restored to defaults on exec.
		2287
		2288	Feel free to install your own handler, or reset it to defaults.
		2289
		2290	=back
		2291
		2292	=cut
		2293
		2294	undef $SIG{CHLD}
		2295	if $SIG{CHLD} eq 'IGNORE';
		2296
		2297	$SIG{PIPE} = sub { }
		2298	unless defined $SIG{PIPE};
		2299
		2300	=head1 RECOMMENDED/OPTIONAL MODULES
		2301
		2302	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2303	it's built-in modules) are required to use it.
		2304
		2305	That does not mean that AnyEvent won't take advantage of some additional
		2306	modules if they are installed.
		2307
		2308	This section epxlains which additional modules will be used, and how they
		2309	affect AnyEvent's operetion.
		2310
		2311	=over 4
		2312
		2313	=item L<Async::Interrupt>
		2314
		2315	This slightly arcane module is used to implement fast signal handling: To
		2316	my knowledge, there is no way to do completely race-free and quick
		2317	signal handling in pure perl. To ensure that signals still get
		2318	delivered, AnyEvent will start an interval timer to wake up perl (and
		2319	catch the signals) with some delay (default is 10 seconds, look for
		2320	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2321
		2322	If this module is available, then it will be used to implement signal
		2323	catching, which means that signals will not be delayed, and the event loop
		2324	will not be interrupted regularly, which is more efficient (And good for
		2325	battery life on laptops).
		2326
		2327	This affects not just the pure-perl event loop, but also other event loops
		2328	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2329
		2330	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2331	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2332	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2333	does nothing for those backends.
		2334
		2335	=item L<EV>
		2336
		2337	This module isn't really "optional", as it is simply one of the backend
		2338	event loops that AnyEvent can use. However, it is simply the best event
		2339	loop available in terms of features, speed and stability: It supports
		2340	the AnyEvent API optimally, implements all the watcher types in XS, does
		2341	automatic timer adjustments even when no monotonic clock is available,
		2342	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2343	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2344	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2345
		2346	=item L<Guard>
		2347
		2348	The guard module, when used, will be used to implement
		2349	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2350	lot less memory), but otherwise doesn't affect guard operation much. It is
		2351	purely used for performance.
		2352
		2353	=item L<JSON> and L<JSON::XS>
		2354
		2355	This module is required when you want to read or write JSON data via
		2356	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2357	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2358
		2359	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2360	installed.
		2361
		2362	=item L<Net::SSLeay>
		2363
		2364	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2365	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2366	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2367
		2368	=item L<Time::HiRes>
		2369
		2370	This module is part of perl since release 5.008. It will be used when the
		2371	chosen event library does not come with a timing source on it's own. The
		2372	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2373	try to use a monotonic clock for timing stability.
		2374
		2375	=back
		2376
		2377
		2378	=head1 FORK
		2379
		2380	Most event libraries are not fork-safe. The ones who are usually are
		2381	because they rely on inefficient but fork-safe C<select> or C<poll>
		2382	calls. Only L<EV> is fully fork-aware.
		2383
		2384	If you have to fork, you must either do so I<before> creating your first
		2385	watcher OR you must not use AnyEvent at all in the child OR you must do
		2386	something completely out of the scope of AnyEvent.
		2387
		2388
		2389	=head1 SECURITY CONSIDERATIONS
		2390
		2391	AnyEvent can be forced to load any event model via
		2392	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		2393	execute arbitrary code or directly gain access, it can easily be used to
		2394	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		2395	will not be active when the program uses a different event model than
		2396	specified in the variable.
		2397
		2398	You can make AnyEvent completely ignore this variable by deleting it
		2399	before the first watcher gets created, e.g. with a C<BEGIN> block:
		2400
		2401	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		2402
		2403	use AnyEvent;
		2404
		2405	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2406	be used to probe what backend is used and gain other information (which is
		2407	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2408	$ENV{PERL_ANYEVENT_STRICT}.
		2409
		2410	Note that AnyEvent will remove I<all> environment variables starting with
		2411	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2412	enabled.
		2413
		2414
		2415	=head1 BUGS
		2416
		2417	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2418	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2419	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2420	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2421	pronounced).
		2422
607		2423
608	=head1 SEE ALSO	2424	=head1 SEE ALSO
609		2425
610	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	2426	Utility functions: L<AnyEvent::Util>.
611		2427
612	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	2428	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		2429	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
613		2430
614	Nontrivial usage example: L<Net::FCP>.	2431	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2432	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2433	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2434	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
615		2435
616	=head1	2436	Non-blocking file handles, sockets, TCP clients and
		2437	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2438
		2439	Asynchronous DNS: L<AnyEvent::DNS>.
		2440
		2441	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2442	L<Coro::Event>,
		2443
		2444	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2445	L<AnyEvent::HTTP>.
		2446
		2447
		2448	=head1 AUTHOR
		2449
		2450	Marc Lehmann <schmorp@schmorp.de>
		2451	http://home.schmorp.de/
617		2452
618	=cut	2453	=cut
619		2454
620	1	2455	1
621		2456

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