[ViewVC] Diff of: cvs/AnyEvent/lib/AnyEvent.pm

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.22 by root, Sun Dec 31 11:54:43 2006 UTC vs.
Revision 1.239 by root, Thu Jul 16 20:55:38 2009 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	Event, Coro, Glib, Tk, Perl - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
		6	event loops.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r\|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores 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 WHY YOU SHOULD USE THIS MODULE (OR NOT)
		47
		48	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
		49	nowadays. So what is different about AnyEvent?
		50
		51	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
		52	policy> and AnyEvent is I<small and efficient>.
		53
		54	First and foremost, I<AnyEvent is not an event model> itself, it only
		55	interfaces to whatever event model the main program happens to use, in a
		56	pragmatic way. For event models and certain classes of immortals alike,
		57	the statement "there can only be one" is a bitter reality: In general,
		58	only one event loop can be active at the same time in a process. AnyEvent
		59	cannot change this, but it can hide the differences between those event
		60	loops.
		61
		62	The goal of AnyEvent is to offer module authors the ability to do event
		63	programming (waiting for I/O or timer events) without subscribing to a
		64	religion, a way of living, and most importantly: without forcing your
		65	module users into the same thing by forcing them to use the same event
		66	model you use.
		67
		68	For modules like POE or IO::Async (which is a total misnomer as it is
		69	actually doing all I/O I<synchronously>...), using them in your module is
		70	like joining a cult: After you joined, you are dependent on them and you
		71	cannot use anything else, as they are simply incompatible to everything
		72	that isn't them. What's worse, all the potential users of your
		73	module are I<also> forced to use the same event loop you use.
		74
		75	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
		76	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
		77	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
		78	your module uses one of those, every user of your module has to use it,
		79	too. But if your module uses AnyEvent, it works transparently with all
		80	event models it supports (including stuff like IO::Async, as long as those
		81	use one of the supported event loops. It is trivial to add new event loops
		82	to AnyEvent, too, so it is future-proof).
		83
		84	In addition to being free of having to use I<the one and only true event
		85	model>, AnyEvent also is free of bloat and policy: with POE or similar
		86	modules, you get an enormous amount of code and strict rules you have to
		87	follow. AnyEvent, on the other hand, is lean and up to the point, by only
		88	offering the functionality that is necessary, in as thin as a wrapper as
		89	technically possible.
		90
		91	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		92	of useful functionality, such as an asynchronous DNS resolver, 100%
		93	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		94	such as Windows) and lots of real-world knowledge and workarounds for
		95	platform bugs and differences.
		96
		97	Now, if you I<do want> lots of policy (this can arguably be somewhat
		98	useful) and you want to force your users to use the one and only event
		99	model, you should I<not> use this module.
22		100
23	=head1 DESCRIPTION	101	=head1 DESCRIPTION
24		102
25	L<AnyEvent> provides an identical interface to multiple event loops. This	103	L<AnyEvent> provides an identical interface to multiple event loops. This
26	allows module authors to utilise an event loop without forcing module	104	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	105	users to use the same event loop (as only a single event loop can coexist
28	peacefully at any one time).	106	peacefully at any one time).
29		107
30	The interface itself is vaguely similar but not identical to the Event	108	The interface itself is vaguely similar, but not identical to the L<Event>
31	module.	109	module.
32		110
33	On the first call of any method, the module tries to detect the currently	111	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	112	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	113	following modules is already loaded: L<EV>,
36	used. If none is found, the module tries to load these modules in the	114	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	115	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	116	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
39	event loop, which is also not very efficient.	117	adaptor should always succeed) in the order given. The first one that can
		118	be successfully loaded will be used. If, after this, still none could be
		119	found, AnyEvent will fall back to a pure-perl event loop, which is not
		120	very efficient, but should work everywhere.
40		121
41	Because AnyEvent first checks for modules that are already loaded, loading	122	Because AnyEvent first checks for modules that are already loaded, loading
42	an Event model explicitly before first using AnyEvent will likely make	123	an event model explicitly before first using AnyEvent will likely make
43	that model the default. For example:	124	that model the default. For example:
44		125
45	use Tk;	126	use Tk;
46	use AnyEvent;	127	use AnyEvent;
47		128
48	# .. AnyEvent will likely default to Tk	129	# .. AnyEvent will likely default to Tk
49		130
		131	The I<likely> means that, if any module loads another event model and
		132	starts using it, all bets are off. Maybe you should tell their authors to
		133	use AnyEvent so their modules work together with others seamlessly...
		134
50	The pure-perl implementation of AnyEvent is called	135	The pure-perl implementation of AnyEvent is called
51	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	136	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
52	explicitly.	137	explicitly and enjoy the high availability of that event loop :)
53		138
54	=head1 WATCHERS	139	=head1 WATCHERS
55		140
56	AnyEvent has the central concept of a I<watcher>, which is an object that	141	AnyEvent has the central concept of a I<watcher>, which is an object that
57	stores relevant data for each kind of event you are waiting for, such as	142	stores relevant data for each kind of event you are waiting for, such as
58	the callback to call, the filehandle to watch, etc.	143	the callback to call, the file handle to watch, etc.
59		144
60	These watchers are normal Perl objects with normal Perl lifetime. After	145	These watchers are normal Perl objects with normal Perl lifetime. After
61	creating a watcher it will immediately "watch" for events and invoke	146	creating a watcher it will immediately "watch" for events and invoke the
		147	callback when the event occurs (of course, only when the event model
		148	is in control).
		149
		150	Note that B<callbacks must not permanently change global variables>
		151	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		152	callbacks must not C<die> >>. The former is good programming practise in
		153	Perl and the latter stems from the fact that exception handling differs
		154	widely between event loops.
		155
62	the callback. To disable the watcher you have to destroy it (e.g. by	156	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	157	variable you store it in to C<undef> or otherwise deleting all references
64	references to it).	158	to it).
65		159
66	All watchers are created by calling a method on the C<AnyEvent> class.	160	All watchers are created by calling a method on the C<AnyEvent> class.
67		161
		162	Many watchers either are used with "recursion" (repeating timers for
		163	example), or need to refer to their watcher object in other ways.
		164
		165	An any way to achieve that is this pattern:
		166
		167	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		168	# you can use $w here, for example to undef it
		169	undef $w;
		170	});
		171
		172	Note that C<my $w; $w => combination. This is necessary because in Perl,
		173	my variables are only visible after the statement in which they are
		174	declared.
		175
68	=head2 IO WATCHERS	176	=head2 I/O WATCHERS
69		177
70	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	178	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
71	the following mandatory arguments:	179	with the following mandatory key-value pairs as arguments:
72		180
73	C<fh> the Perl I<filehandle> (not filedescriptor) to watch for	181	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		182	for events (AnyEvent might or might not keep a reference to this file
		183	handle). Note that only file handles pointing to things for which
		184	non-blocking operation makes sense are allowed. This includes sockets,
		185	most character devices, pipes, fifos and so on, but not for example files
		186	or block devices.
		187
74	events. C<poll> must be a string that is either C<r> or C<w>, that creates	188	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	189	watcher waiting for "r"eadable or "w"ritable events, respectively.
76	to invoke everytime the filehandle becomes ready.
77		190
78	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	191	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		192
82	Filehandles will be kept alive, so as long as the watcher exists, the	193	Although the callback might get passed parameters, their value and
83	filehandle exists, too.	194	presence is undefined and you cannot rely on them. Portable AnyEvent
		195	callbacks cannot use arguments passed to I/O watcher callbacks.
84		196
85	Example:	197	The I/O watcher might use the underlying file descriptor or a copy of it.
		198	You must not close a file handle as long as any watcher is active on the
		199	underlying file descriptor.
86		200
		201	Some event loops issue spurious readyness notifications, so you should
		202	always use non-blocking calls when reading/writing from/to your file
		203	handles.
		204
87	# wait for readability of STDIN, then read a line and disable the watcher	205	Example: wait for readability of STDIN, then read a line and disable the
		206	watcher.
		207
88	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	208	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
89	chomp (my $input = <STDIN>);	209	chomp (my $input = <STDIN>);
90	warn "read: $input\n";	210	warn "read: $input\n";
91	undef $w;	211	undef $w;
92	});	212	});
94	=head2 TIME WATCHERS	214	=head2 TIME WATCHERS
95		215
96	You can create a time watcher by calling the C<< AnyEvent->timer >>	216	You can create a time watcher by calling the C<< AnyEvent->timer >>
97	method with the following mandatory arguments:	217	method with the following mandatory arguments:
98		218
99	C<after> after how many seconds (fractions are supported) should the timer	219	C<after> specifies after how many seconds (fractional values are
100	activate. C<cb> the callback to invoke.	220	supported) the callback should be invoked. C<cb> is the callback to invoke
		221	in that case.
101		222
102	The timer callback will be invoked at most once: if you want a repeating	223	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	224	presence is undefined and you cannot rely on them. Portable AnyEvent
104	and Glib).	225	callbacks cannot use arguments passed to time watcher callbacks.
105		226
106	Example:	227	The callback will normally be invoked once only. If you specify another
		228	parameter, C<interval>, as a strictly positive number (> 0), then the
		229	callback will be invoked regularly at that interval (in fractional
		230	seconds) after the first invocation. If C<interval> is specified with a
		231	false value, then it is treated as if it were missing.
107		232
		233	The callback will be rescheduled before invoking the callback, but no
		234	attempt is done to avoid timer drift in most backends, so the interval is
		235	only approximate.
		236
108	# fire an event after 7.7 seconds	237	Example: fire an event after 7.7 seconds.
		238
109	my $w = AnyEvent->timer (after => 7.7, cb => sub {	239	my $w = AnyEvent->timer (after => 7.7, cb => sub {
110	warn "timeout\n";	240	warn "timeout\n";
111	});	241	});
112		242
113	# to cancel the timer:	243	# to cancel the timer:
114	undef $w	244	undef $w;
115		245
116	=head2 CONDITION WATCHERS	246	Example 2: fire an event after 0.5 seconds, then roughly every second.
117		247
118	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	248	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
119	method without any arguments.	249	warn "timeout\n";
		250	};
120		251
121	A condition watcher watches for a condition - precisely that the C<<	252	=head3 TIMING ISSUES
122	->broadcast >> method has been called.
123		253
124	The watcher has only two methods:	254	There are two ways to handle timers: based on real time (relative, "fire
		255	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		256	o'clock").
		257
		258	While most event loops expect timers to specified in a relative way, they
		259	use absolute time internally. This makes a difference when your clock
		260	"jumps", for example, when ntp decides to set your clock backwards from
		261	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		262	fire "after" a second might actually take six years to finally fire.
		263
		264	AnyEvent cannot compensate for this. The only event loop that is conscious
		265	about these issues is L<EV>, which offers both relative (ev_timer, based
		266	on true relative time) and absolute (ev_periodic, based on wallclock time)
		267	timers.
		268
		269	AnyEvent always prefers relative timers, if available, matching the
		270	AnyEvent API.
		271
		272	AnyEvent has two additional methods that return the "current time":
125		273
126	=over 4	274	=over 4
127		275
128	=item $cv->wait	276	=item AnyEvent->time
129		277
130	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	278	This returns the "current wallclock time" as a fractional number of
131	called on c<$cv>, while servicing other watchers normally.	279	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		280	return, and the result is guaranteed to be compatible with those).
132		281
133	Not all event models support a blocking wait - some die in that case, so	282	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	283	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		284
140	You can only wait once on a condition - additional calls will return	285	=item AnyEvent->now
141	immediately.
142		286
143	=item $cv->broadcast	287	This also returns the "current wallclock time", but unlike C<time>, above,
		288	this value might change only once per event loop iteration, depending on
		289	the event loop (most return the same time as C<time>, above). This is the
		290	time that AnyEvent's timers get scheduled against.
144		291
145	Flag the condition as ready - a running C<< ->wait >> and all further	292	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	293	function to call when you want to know the current time.>
147	is waiting the broadcast will be remembered..
148		294
149	Example:	295	This function is also often faster then C<< AnyEvent->time >>, and
		296	thus the preferred method if you want some timestamp (for example,
		297	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		298
		299	The rest of this section is only of relevance if you try to be very exact
		300	with your timing, you can skip it without bad conscience.
		301
		302	For a practical example of when these times differ, consider L<Event::Lib>
		303	and L<EV> and the following set-up:
		304
		305	The event loop is running and has just invoked one of your callback at
		306	time=500 (assume no other callbacks delay processing). In your callback,
		307	you wait a second by executing C<sleep 1> (blocking the process for a
		308	second) and then (at time=501) you create a relative timer that fires
		309	after three seconds.
		310
		311	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		312	both return C<501>, because that is the current time, and the timer will
		313	be scheduled to fire at time=504 (C<501> + C<3>).
		314
		315	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		316	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		317	last event processing phase started. With L<EV>, your timer gets scheduled
		318	to run at time=503 (C<500> + C<3>).
		319
		320	In one sense, L<Event::Lib> is more exact, as it uses the current time
		321	regardless of any delays introduced by event processing. However, most
		322	callbacks do not expect large delays in processing, so this causes a
		323	higher drift (and a lot more system calls to get the current time).
		324
		325	In another sense, L<EV> is more exact, as your timer will be scheduled at
		326	the same time, regardless of how long event processing actually took.
		327
		328	In either case, if you care (and in most cases, you don't), then you
		329	can get whatever behaviour you want with any event loop, by taking the
		330	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		331	account.
		332
		333	=item AnyEvent->now_update
		334
		335	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		336	the current time for each loop iteration (see the discussion of L<<
		337	AnyEvent->now >>, above).
		338
		339	When a callback runs for a long time (or when the process sleeps), then
		340	this "current" time will differ substantially from the real time, which
		341	might affect timers and time-outs.
		342
		343	When this is the case, you can call this method, which will update the
		344	event loop's idea of "current time".
		345
		346	Note that updating the time I<might> cause some events to be handled.
		347
		348	=back
		349
		350	=head2 SIGNAL WATCHERS
		351
		352	You can watch for signals using a signal watcher, C<signal> is the signal
		353	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
		354	callback to be invoked whenever a signal occurs.
		355
		356	Although the callback might get passed parameters, their value and
		357	presence is undefined and you cannot rely on them. Portable AnyEvent
		358	callbacks cannot use arguments passed to signal watcher callbacks.
		359
		360	Multiple signal occurrences can be clumped together into one callback
		361	invocation, and callback invocation will be synchronous. Synchronous means
		362	that it might take a while until the signal gets handled by the process,
		363	but it is guaranteed not to interrupt any other callbacks.
		364
		365	The main advantage of using these watchers is that you can share a signal
		366	between multiple watchers.
		367
		368	This watcher might use C<%SIG>, so programs overwriting those signals
		369	directly will likely not work correctly.
		370
		371	Example: exit on SIGINT
		372
		373	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		374
		375	=head2 CHILD PROCESS WATCHERS
		376
		377	You can also watch on a child process exit and catch its exit status.
		378
		379	The child process is specified by the C<pid> argument (if set to C<0>, it
		380	watches for any child process exit). The watcher will triggered only when
		381	the child process has finished and an exit status is available, not on
		382	any trace events (stopped/continued).
		383
		384	The callback will be called with the pid and exit status (as returned by
		385	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		386	callback arguments.
		387
		388	This watcher type works by installing a signal handler for C<SIGCHLD>,
		389	and since it cannot be shared, nothing else should use SIGCHLD or reap
		390	random child processes (waiting for specific child processes, e.g. inside
		391	C<system>, is just fine).
		392
		393	There is a slight catch to child watchers, however: you usually start them
		394	I<after> the child process was created, and this means the process could
		395	have exited already (and no SIGCHLD will be sent anymore).
		396
		397	Not all event models handle this correctly (neither POE nor IO::Async do,
		398	see their AnyEvent::Impl manpages for details), but even for event models
		399	that I<do> handle this correctly, they usually need to be loaded before
		400	the process exits (i.e. before you fork in the first place). AnyEvent's
		401	pure perl event loop handles all cases correctly regardless of when you
		402	start the watcher.
		403
		404	This means you cannot create a child watcher as the very first
		405	thing in an AnyEvent program, you I<have> to create at least one
		406	watcher before you C<fork> the child (alternatively, you can call
		407	C<AnyEvent::detect>).
		408
		409	Example: fork a process and wait for it
		410
		411	my $done = AnyEvent->condvar;
		412
		413	my $pid = fork or exit 5;
		414
		415	my $w = AnyEvent->child (
		416	pid => $pid,
		417	cb => sub {
		418	my ($pid, $status) = @_;
		419	warn "pid $pid exited with status $status";
		420	$done->send;
		421	},
		422	);
		423
		424	# do something else, then wait for process exit
		425	$done->recv;
		426
		427	=head2 IDLE WATCHERS
		428
		429	Sometimes there is a need to do something, but it is not so important
		430	to do it instantly, but only when there is nothing better to do. This
		431	"nothing better to do" is usually defined to be "no other events need
		432	attention by the event loop".
		433
		434	Idle watchers ideally get invoked when the event loop has nothing
		435	better to do, just before it would block the process to wait for new
		436	events. Instead of blocking, the idle watcher is invoked.
		437
		438	Most event loops unfortunately do not really support idle watchers (only
		439	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		440	will simply call the callback "from time to time".
		441
		442	Example: read lines from STDIN, but only process them when the
		443	program is otherwise idle:
		444
		445	my @lines; # read data
		446	my $idle_w;
		447	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		448	push @lines, scalar <STDIN>;
		449
		450	# start an idle watcher, if not already done
		451	$idle_w \|\|= AnyEvent->idle (cb => sub {
		452	# handle only one line, when there are lines left
		453	if (my $line = shift @lines) {
		454	print "handled when idle: $line";
		455	} else {
		456	# otherwise disable the idle watcher again
		457	undef $idle_w;
		458	}
		459	});
		460	});
		461
		462	=head2 CONDITION VARIABLES
		463
		464	If you are familiar with some event loops you will know that all of them
		465	require you to run some blocking "loop", "run" or similar function that
		466	will actively watch for new events and call your callbacks.
		467
		468	AnyEvent is slightly different: it expects somebody else to run the event
		469	loop and will only block when necessary (usually when told by the user).
		470
		471	The instrument to do that is called a "condition variable", so called
		472	because they represent a condition that must become true.
		473
		474	Now is probably a good time to look at the examples further below.
		475
		476	Condition variables can be created by calling the C<< AnyEvent->condvar
		477	>> method, usually without arguments. The only argument pair allowed is
		478	C<cb>, which specifies a callback to be called when the condition variable
		479	becomes true, with the condition variable as the first argument (but not
		480	the results).
		481
		482	After creation, the condition variable is "false" until it becomes "true"
		483	by calling the C<send> method (or calling the condition variable as if it
		484	were a callback, read about the caveats in the description for the C<<
		485	->send >> method).
		486
		487	Condition variables are similar to callbacks, except that you can
		488	optionally wait for them. They can also be called merge points - points
		489	in time where multiple outstanding events have been processed. And yet
		490	another way to call them is transactions - each condition variable can be
		491	used to represent a transaction, which finishes at some point and delivers
		492	a result.
		493
		494	Condition variables are very useful to signal that something has finished,
		495	for example, if you write a module that does asynchronous http requests,
		496	then a condition variable would be the ideal candidate to signal the
		497	availability of results. The user can either act when the callback is
		498	called or can synchronously C<< ->recv >> for the results.
		499
		500	You can also use them to simulate traditional event loops - for example,
		501	you can block your main program until an event occurs - for example, you
		502	could C<< ->recv >> in your main program until the user clicks the Quit
		503	button of your app, which would C<< ->send >> the "quit" event.
		504
		505	Note that condition variables recurse into the event loop - if you have
		506	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
		507	lose. Therefore, condition variables are good to export to your caller, but
		508	you should avoid making a blocking wait yourself, at least in callbacks,
		509	as this asks for trouble.
		510
		511	Condition variables are represented by hash refs in perl, and the keys
		512	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		513	easy (it is often useful to build your own transaction class on top of
		514	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		515	it's C<new> method in your own C<new> method.
		516
		517	There are two "sides" to a condition variable - the "producer side" which
		518	eventually calls C<< -> send >>, and the "consumer side", which waits
		519	for the send to occur.
		520
		521	Example: wait for a timer.
150		522
151	# wait till the result is ready	523	# wait till the result is ready
152	my $result_ready = AnyEvent->condvar;	524	my $result_ready = AnyEvent->condvar;
153		525
154	# do something such as adding a timer	526	# do something such as adding a timer
155	# or socket watcher the calls $result_ready->broadcast	527	# or socket watcher the calls $result_ready->send
156	# when the "result" is ready.	528	# when the "result" is ready.
		529	# in this case, we simply use a timer:
		530	my $w = AnyEvent->timer (
		531	after => 1,
		532	cb => sub { $result_ready->send },
		533	);
157		534
		535	# this "blocks" (while handling events) till the callback
		536	# calls -<send
158	$result_ready->wait;	537	$result_ready->recv;
		538
		539	Example: wait for a timer, but take advantage of the fact that condition
		540	variables are also callable directly.
		541
		542	my $done = AnyEvent->condvar;
		543	my $delay = AnyEvent->timer (after => 5, cb => $done);
		544	$done->recv;
		545
		546	Example: Imagine an API that returns a condvar and doesn't support
		547	callbacks. This is how you make a synchronous call, for example from
		548	the main program:
		549
		550	use AnyEvent::CouchDB;
		551
		552	...
		553
		554	my @info = $couchdb->info->recv;
		555
		556	And this is how you would just set a callback to be called whenever the
		557	results are available:
		558
		559	$couchdb->info->cb (sub {
		560	my @info = $_[0]->recv;
		561	});
		562
		563	=head3 METHODS FOR PRODUCERS
		564
		565	These methods should only be used by the producing side, i.e. the
		566	code/module that eventually sends the signal. Note that it is also
		567	the producer side which creates the condvar in most cases, but it isn't
		568	uncommon for the consumer to create it as well.
		569
		570	=over 4
		571
		572	=item $cv->send (...)
		573
		574	Flag the condition as ready - a running C<< ->recv >> and all further
		575	calls to C<recv> will (eventually) return after this method has been
		576	called. If nobody is waiting the send will be remembered.
		577
		578	If a callback has been set on the condition variable, it is called
		579	immediately from within send.
		580
		581	Any arguments passed to the C<send> call will be returned by all
		582	future C<< ->recv >> calls.
		583
		584	Condition variables are overloaded so one can call them directly (as if
		585	they were a code reference). Calling them directly is the same as calling
		586	C<send>.
		587
		588	=item $cv->croak ($error)
		589
		590	Similar to send, but causes all call's to C<< ->recv >> to invoke
		591	C<Carp::croak> with the given error message/object/scalar.
		592
		593	This can be used to signal any errors to the condition variable
		594	user/consumer. Doing it this way instead of calling C<croak> directly
		595	delays the error detetcion, but has the overwhelmign advantage that it
		596	diagnoses the error at the place where the result is expected, and not
		597	deep in some event clalback without connection to the actual code causing
		598	the problem.
		599
		600	=item $cv->begin ([group callback])
		601
		602	=item $cv->end
		603
		604	These two methods can be used to combine many transactions/events into
		605	one. For example, a function that pings many hosts in parallel might want
		606	to use a condition variable for the whole process.
		607
		608	Every call to C<< ->begin >> will increment a counter, and every call to
		609	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		610	>>, the (last) callback passed to C<begin> will be executed. That callback
		611	is I<supposed> to call C<< ->send >>, but that is not required. If no
		612	callback was set, C<send> will be called without any arguments.
		613
		614	You can think of C<< $cv->send >> giving you an OR condition (one call
		615	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		616	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		617
		618	Let's start with a simple example: you have two I/O watchers (for example,
		619	STDOUT and STDERR for a program), and you want to wait for both streams to
		620	close before activating a condvar:
		621
		622	my $cv = AnyEvent->condvar;
		623
		624	$cv->begin; # first watcher
		625	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		626	defined sysread $fh1, my $buf, 4096
		627	or $cv->end;
		628	});
		629
		630	$cv->begin; # second watcher
		631	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		632	defined sysread $fh2, my $buf, 4096
		633	or $cv->end;
		634	});
		635
		636	$cv->recv;
		637
		638	This works because for every event source (EOF on file handle), there is
		639	one call to C<begin>, so the condvar waits for all calls to C<end> before
		640	sending.
		641
		642	The ping example mentioned above is slightly more complicated, as the
		643	there are results to be passwd back, and the number of tasks that are
		644	begung can potentially be zero:
		645
		646	my $cv = AnyEvent->condvar;
		647
		648	my %result;
		649	$cv->begin (sub { $cv->send (\%result) });
		650
		651	for my $host (@list_of_hosts) {
		652	$cv->begin;
		653	ping_host_then_call_callback $host, sub {
		654	$result{$host} = ...;
		655	$cv->end;
		656	};
		657	}
		658
		659	$cv->end;
		660
		661	This code fragment supposedly pings a number of hosts and calls
		662	C<send> after results for all then have have been gathered - in any
		663	order. To achieve this, the code issues a call to C<begin> when it starts
		664	each ping request and calls C<end> when it has received some result for
		665	it. Since C<begin> and C<end> only maintain a counter, the order in which
		666	results arrive is not relevant.
		667
		668	There is an additional bracketing call to C<begin> and C<end> outside the
		669	loop, which serves two important purposes: first, it sets the callback
		670	to be called once the counter reaches C<0>, and second, it ensures that
		671	C<send> is called even when C<no> hosts are being pinged (the loop
		672	doesn't execute once).
		673
		674	This is the general pattern when you "fan out" into multiple (but
		675	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		676	the callback and ensure C<end> is called at least once, and then, for each
		677	subrequest you start, call C<begin> and for each subrequest you finish,
		678	call C<end>.
159		679
160	=back	680	=back
161		681
162	=head2 SIGNAL WATCHERS	682	=head3 METHODS FOR CONSUMERS
163		683
164	You can listen for signals using a signal watcher, C<signal> is the signal	684	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	685	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		686
188	=over 4	687	=over 4
189		688
		689	=item $cv->recv
		690
		691	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		692	>> methods have been called on c<$cv>, while servicing other watchers
		693	normally.
		694
		695	You can only wait once on a condition - additional calls are valid but
		696	will return immediately.
		697
		698	If an error condition has been set by calling C<< ->croak >>, then this
		699	function will call C<croak>.
		700
		701	In list context, all parameters passed to C<send> will be returned,
		702	in scalar context only the first one will be returned.
		703
		704	Note that doing a blocking wait in a callback is not supported by any
		705	event loop, that is, recursive invocation of a blocking C<< ->recv
		706	>> is not allowed, and the C<recv> call will C<croak> if such a
		707	condition is detected. This condition can be slightly loosened by using
		708	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		709	any thread that doesn't run the event loop itself.
		710
		711	Not all event models support a blocking wait - some die in that case
		712	(programs might want to do that to stay interactive), so I<if you are
		713	using this from a module, never require a blocking wait>. Instead, let the
		714	caller decide whether the call will block or not (for example, by coupling
		715	condition variables with some kind of request results and supporting
		716	callbacks so the caller knows that getting the result will not block,
		717	while still supporting blocking waits if the caller so desires).
		718
		719	You can ensure that C<< -recv >> never blocks by setting a callback and
		720	only calling C<< ->recv >> from within that callback (or at a later
		721	time). This will work even when the event loop does not support blocking
		722	waits otherwise.
		723
		724	=item $bool = $cv->ready
		725
		726	Returns true when the condition is "true", i.e. whether C<send> or
		727	C<croak> have been called.
		728
		729	=item $cb = $cv->cb ($cb->($cv))
		730
		731	This is a mutator function that returns the callback set and optionally
		732	replaces it before doing so.
		733
		734	The callback will be called when the condition becomes "true", i.e. when
		735	C<send> or C<croak> are called, with the only argument being the condition
		736	variable itself. Calling C<recv> inside the callback or at any later time
		737	is guaranteed not to block.
		738
		739	=back
		740
		741	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		742
		743	The available backend classes are (every class has its own manpage):
		744
		745	=over 4
		746
		747	=item Backends that are autoprobed when no other event loop can be found.
		748
		749	EV is the preferred backend when no other event loop seems to be in
		750	use. If EV is not installed, then AnyEvent will try Event, and, failing
		751	that, will fall back to its own pure-perl implementation, which is
		752	available everywhere as it comes with AnyEvent itself.
		753
		754	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		755	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		756	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		757
		758	=item Backends that are transparently being picked up when they are used.
		759
		760	These will be used when they are currently loaded when the first watcher
		761	is created, in which case it is assumed that the application is using
		762	them. This means that AnyEvent will automatically pick the right backend
		763	when the main program loads an event module before anything starts to
		764	create watchers. Nothing special needs to be done by the main program.
		765
		766	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		767	AnyEvent::Impl::Tk based on Tk, very broken.
		768	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		769	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		770
		771	=item Backends with special needs.
		772
		773	Qt requires the Qt::Application to be instantiated first, but will
		774	otherwise be picked up automatically. As long as the main program
		775	instantiates the application before any AnyEvent watchers are created,
		776	everything should just work.
		777
		778	AnyEvent::Impl::Qt based on Qt.
		779
		780	Support for IO::Async can only be partial, as it is too broken and
		781	architecturally limited to even support the AnyEvent API. It also
		782	is the only event loop that needs the loop to be set explicitly, so
		783	it can only be used by a main program knowing about AnyEvent. See
		784	L<AnyEvent::Impl::Async> for the gory details.
		785
		786	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		787
		788	=item Event loops that are indirectly supported via other backends.
		789
		790	Some event loops can be supported via other modules:
		791
		792	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		793
		794	B<WxWidgets> has no support for watching file handles. However, you can
		795	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		796	polls 20 times per second, which was considered to be too horrible to even
		797	consider for AnyEvent.
		798
		799	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		800	backend, so it can be supported through POE.
		801
		802	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		803	load L<POE> when detecting them, in the hope that POE will pick them up,
		804	in which case everything will be automatic.
		805
		806	=back
		807
		808	=head1 GLOBAL VARIABLES AND FUNCTIONS
		809
		810	These are not normally required to use AnyEvent, but can be useful to
		811	write AnyEvent extension modules.
		812
		813	=over 4
		814
190	=item $AnyEvent::MODEL	815	=item $AnyEvent::MODEL
191		816
192	Contains C<undef> until the first watcher is being created. Then it	817	Contains C<undef> until the first watcher is being created, before the
		818	backend has been autodetected.
		819
193	contains the event model that is being used, which is the name of the	820	Afterwards it contains the event model that is being used, which is the
194	Perl class implementing the model. This class is usually one of the	821	name of the Perl class implementing the model. This class is usually one
195	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	822	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
196	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	823	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
197		824	will be C<urxvt::anyevent>).
198	The known classes so far are:
199
200	AnyEvent::Impl::Coro based on Coro::Event, best choise.
201	AnyEvent::Impl::Event based on Event, also best choice :)
202	AnyEvent::Impl::Glib based on Glib, second-best choice.
203	AnyEvent::Impl::Tk based on Tk, very bad choice.
204	AnyEvent::Impl::Perl pure-perl implementation, inefficient.
205		825
206	=item AnyEvent::detect	826	=item AnyEvent::detect
207		827
208	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	828	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
209	necessary. You should only call this function right before you would have	829	if necessary. You should only call this function right before you would
210	created an AnyEvent watcher anyway, that is, very late at runtime.	830	have created an AnyEvent watcher anyway, that is, as late as possible at
		831	runtime, and not e.g. while initialising of your module.
		832
		833	If you need to do some initialisation before AnyEvent watchers are
		834	created, use C<post_detect>.
		835
		836	=item $guard = AnyEvent::post_detect { BLOCK }
		837
		838	Arranges for the code block to be executed as soon as the event model is
		839	autodetected (or immediately if this has already happened).
		840
		841	The block will be executed I<after> the actual backend has been detected
		842	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		843	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		844	other initialisations - see the sources of L<AnyEvent::Strict> or
		845	L<AnyEvent::AIO> to see how this is used.
		846
		847	The most common usage is to create some global watchers, without forcing
		848	event module detection too early, for example, L<AnyEvent::AIO> creates
		849	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		850	avoid autodetecting the event module at load time.
		851
		852	If called in scalar or list context, then it creates and returns an object
		853	that automatically removes the callback again when it is destroyed. See
		854	L<Coro::BDB> for a case where this is useful.
		855
		856	=item @AnyEvent::post_detect
		857
		858	If there are any code references in this array (you can C<push> to it
		859	before or after loading AnyEvent), then they will called directly after
		860	the event loop has been chosen.
		861
		862	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		863	if it is defined then the event loop has already been detected, and the
		864	array will be ignored.
		865
		866	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		867	it,as it takes care of these details.
		868
		869	This variable is mainly useful for modules that can do something useful
		870	when AnyEvent is used and thus want to know when it is initialised, but do
		871	not need to even load it by default. This array provides the means to hook
		872	into AnyEvent passively, without loading it.
211		873
212	=back	874	=back
213		875
214	=head1 WHAT TO DO IN A MODULE	876	=head1 WHAT TO DO IN A MODULE
215		877
216	As a module author, you should "use AnyEvent" and call AnyEvent methods	878	As a module author, you should C<use AnyEvent> and call AnyEvent methods
217	freely, but you should not load a specific event module or rely on it.	879	freely, but you should not load a specific event module or rely on it.
218		880
219	Be careful when you create watchers in the module body - Anyevent will	881	Be careful when you create watchers in the module body - AnyEvent will
220	decide which event module to use as soon as the first method is called, so	882	decide which event module to use as soon as the first method is called, so
221	by calling AnyEvent in your module body you force the user of your module	883	by calling AnyEvent in your module body you force the user of your module
222	to load the event module first.	884	to load the event module first.
223		885
		886	Never call C<< ->recv >> on a condition variable unless you I<know> that
		887	the C<< ->send >> method has been called on it already. This is
		888	because it will stall the whole program, and the whole point of using
		889	events is to stay interactive.
		890
		891	It is fine, however, to call C<< ->recv >> when the user of your module
		892	requests it (i.e. if you create a http request object ad have a method
		893	called C<results> that returns the results, it should call C<< ->recv >>
		894	freely, as the user of your module knows what she is doing. always).
		895
224	=head1 WHAT TO DO IN THE MAIN PROGRAM	896	=head1 WHAT TO DO IN THE MAIN PROGRAM
225		897
226	There will always be a single main program - the only place that should	898	There will always be a single main program - the only place that should
227	dictate which event model to use.	899	dictate which event model to use.
228		900
229	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	901	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
230	do anything special and let AnyEvent decide which implementation to chose.	902	do anything special (it does not need to be event-based) and let AnyEvent
		903	decide which implementation to chose if some module relies on it.
231		904
232	If the main program relies on a specific event model (for example, in Gtk2	905	If the main program relies on a specific event model - for example, in
233	programs you have to rely on either Glib or Glib::Event), you should load	906	Gtk2 programs you have to rely on the Glib module - you should load the
234	it before loading AnyEvent or any module that uses it, generally, as early	907	event module before loading AnyEvent or any module that uses it: generally
235	as possible. The reason is that modules might create watchers when they	908	speaking, you should load it as early as possible. The reason is that
236	are loaded, and AnyEvent will decide on the event model to use as soon as	909	modules might create watchers when they are loaded, and AnyEvent will
237	it creates watchers, and it might chose the wrong one unless you load the	910	decide on the event model to use as soon as it creates watchers, and it
238	correct one yourself.	911	might chose the wrong one unless you load the correct one yourself.
239		912
240	You can chose to use a rather inefficient pure-perl implementation by	913	You can chose to use a pure-perl implementation by loading the
241	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	914	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
242	generally better.	915	everywhere, but letting AnyEvent chose the model is generally better.
		916
		917	=head2 MAINLOOP EMULATION
		918
		919	Sometimes (often for short test scripts, or even standalone programs who
		920	only want to use AnyEvent), you do not want to run a specific event loop.
		921
		922	In that case, you can use a condition variable like this:
		923
		924	AnyEvent->condvar->recv;
		925
		926	This has the effect of entering the event loop and looping forever.
		927
		928	Note that usually your program has some exit condition, in which case
		929	it is better to use the "traditional" approach of storing a condition
		930	variable somewhere, waiting for it, and sending it when the program should
		931	exit cleanly.
		932
		933
		934	=head1 OTHER MODULES
		935
		936	The following is a non-exhaustive list of additional modules that use
		937	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		938	modules and other event loops in the same program. Some of the modules
		939	come with AnyEvent, most are available via CPAN.
		940
		941	=over 4
		942
		943	=item L<AnyEvent::Util>
		944
		945	Contains various utility functions that replace often-used but blocking
		946	functions such as C<inet_aton> by event-/callback-based versions.
		947
		948	=item L<AnyEvent::Socket>
		949
		950	Provides various utility functions for (internet protocol) sockets,
		951	addresses and name resolution. Also functions to create non-blocking tcp
		952	connections or tcp servers, with IPv6 and SRV record support and more.
		953
		954	=item L<AnyEvent::Handle>
		955
		956	Provide read and write buffers, manages watchers for reads and writes,
		957	supports raw and formatted I/O, I/O queued and fully transparent and
		958	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		959
		960	=item L<AnyEvent::DNS>
		961
		962	Provides rich asynchronous DNS resolver capabilities.
		963
		964	=item L<AnyEvent::HTTP>
		965
		966	A simple-to-use HTTP library that is capable of making a lot of concurrent
		967	HTTP requests.
		968
		969	=item L<AnyEvent::HTTPD>
		970
		971	Provides a simple web application server framework.
		972
		973	=item L<AnyEvent::FastPing>
		974
		975	The fastest ping in the west.
		976
		977	=item L<AnyEvent::DBI>
		978
		979	Executes L<DBI> requests asynchronously in a proxy process.
		980
		981	=item L<AnyEvent::AIO>
		982
		983	Truly asynchronous I/O, should be in the toolbox of every event
		984	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		985	together.
		986
		987	=item L<AnyEvent::BDB>
		988
		989	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		990	L<BDB> and AnyEvent together.
		991
		992	=item L<AnyEvent::GPSD>
		993
		994	A non-blocking interface to gpsd, a daemon delivering GPS information.
		995
		996	=item L<AnyEvent::IRC>
		997
		998	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		999
		1000	=item L<AnyEvent::XMPP>
		1001
		1002	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1003	Net::XMPP2>.
		1004
		1005	=item L<AnyEvent::IGS>
		1006
		1007	A non-blocking interface to the Internet Go Server protocol (used by
		1008	L<App::IGS>).
		1009
		1010	=item L<Net::FCP>
		1011
		1012	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1013	of AnyEvent.
		1014
		1015	=item L<Event::ExecFlow>
		1016
		1017	High level API for event-based execution flow control.
		1018
		1019	=item L<Coro>
		1020
		1021	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1022
		1023	=back
243		1024
244	=cut	1025	=cut
245		1026
246	package AnyEvent;	1027	package AnyEvent;
247		1028
248	no warnings;	1029	no warnings;
249	use strict;	1030	use strict qw(vars subs);
		1031
250	use Carp;	1032	use Carp ();
251		1033
252	our $VERSION = '2.51';	1034	our $VERSION = 4.82;
253	our $MODEL;	1035	our $MODEL;
254		1036
255	our $AUTOLOAD;	1037	our $AUTOLOAD;
256	our @ISA;	1038	our @ISA;
257		1039
		1040	our @REGISTRY;
		1041
		1042	our $WIN32;
		1043
		1044	BEGIN {
		1045	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1046	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1047
		1048	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1049	if ${^TAINT};
		1050	}
		1051
258	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1052	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
259		1053
260	our @REGISTRY;	1054	our %PROTOCOL; # (ipv4\|ipv6) => (1\|2), higher numbers are preferred
		1055
		1056	{
		1057	my $idx;
		1058	$PROTOCOL{$_} = ++$idx
		1059	for reverse split /\s,\s/,
		1060	$ENV{PERL_ANYEVENT_PROTOCOLS} \|\| "ipv4,ipv6";
		1061	}
261		1062
262	my @models = (	1063	my @models = (
263	[Coro::Event:: => AnyEvent::Impl::Coro::],	1064	[EV:: => AnyEvent::Impl::EV::],
264	[Event:: => AnyEvent::Impl::Event::],	1065	[Event:: => AnyEvent::Impl::Event::],
265	[Glib:: => AnyEvent::Impl::Glib::],
266	[Tk:: => AnyEvent::Impl::Tk::],
267	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1066	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		1067	# everything below here will not be autoprobed
		1068	# as the pureperl backend should work everywhere
		1069	# and is usually faster
		1070	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		1071	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1072	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1073	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1074	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		1075	[Wx:: => AnyEvent::Impl::POE::],
		1076	[Prima:: => AnyEvent::Impl::POE::],
		1077	# IO::Async is just too broken - we would need workarounds for its
		1078	# byzantine signal and broken child handling, among others.
		1079	# IO::Async is rather hard to detect, as it doesn't have any
		1080	# obvious default class.
		1081	# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1082	# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1083	# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
268	);	1084	);
269		1085
270	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1086	our %method = map +($_ => 1),
		1087	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1088
		1089	our @post_detect;
		1090
		1091	sub post_detect(&) {
		1092	my ($cb) = @_;
		1093
		1094	if ($MODEL) {
		1095	$cb->();
		1096
		1097	1
		1098	} else {
		1099	push @post_detect, $cb;
		1100
		1101	defined wantarray
		1102	? bless \$cb, "AnyEvent::Util::postdetect"
		1103	: ()
		1104	}
		1105	}
		1106
		1107	sub AnyEvent::Util::postdetect::DESTROY {
		1108	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1109	}
271		1110
272	sub detect() {	1111	sub detect() {
273	unless ($MODEL) {	1112	unless ($MODEL) {
274	no strict 'refs';	1113	no strict 'refs';
		1114	local $SIG{__DIE__};
		1115
		1116	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1117	my $model = "AnyEvent::Impl::$1";
		1118	if (eval "require $model") {
		1119	$MODEL = $model;
		1120	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $verbose > 1;
		1121	} else {
		1122	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $verbose;
		1123	}
		1124	}
275		1125
276	# check for already loaded models	1126	# check for already loaded models
		1127	unless ($MODEL) {
277	for (@REGISTRY, @models) {	1128	for (@REGISTRY, @models) {
278	my ($package, $model) = @$_;	1129	my ($package, $model) = @$_;
279	if (${"$package\::VERSION"} > 0) {	1130	if (${"$package\::VERSION"} > 0) {
280	if (eval "require $model") {	1131	if (eval "require $model") {
281	$MODEL = $model;	1132	$MODEL = $model;
282	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	1133	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
283	last;	1134	last;
		1135	}
284	}	1136	}
285	}	1137	}
		1138
		1139	unless ($MODEL) {
		1140	# try to load a model
		1141
		1142	for (@REGISTRY, @models) {
		1143	my ($package, $model) = @$_;
		1144	if (eval "require $package"
		1145	and ${"$package\::VERSION"} > 0
		1146	and eval "require $model") {
		1147	$MODEL = $model;
		1148	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
		1149	last;
		1150	}
		1151	}
		1152
		1153	$MODEL
		1154	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
		1155	}
286	}	1156	}
287		1157
288	unless ($MODEL) {	1158	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
289	# try to load a model
290
291	for (@REGISTRY, @models) {
292	my ($package, $model) = @$_;
293	if (eval "require $package"
294	and ${"$package\::VERSION"} > 0
295	and eval "require $model") {
296	$MODEL = $model;
297	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
298	last;
299	}
300	}
301
302	$MODEL
303	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Event (or Coro+Event), Glib or Tk.";
304	}
305		1159
306	unshift @ISA, $MODEL;	1160	unshift @ISA, $MODEL;
307	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1161
		1162	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1163
		1164	(shift @post_detect)->() while @post_detect;
308	}	1165	}
309		1166
310	$MODEL	1167	$MODEL
311	}	1168	}
312		1169
313	sub AUTOLOAD {	1170	sub AUTOLOAD {
314	(my $func = $AUTOLOAD) =~ s/.*://;	1171	(my $func = $AUTOLOAD) =~ s/.*://;
315		1172
316	$method{$func}	1173	$method{$func}
317	or croak "$func: not a valid method for AnyEvent objects";	1174	or Carp::croak "$func: not a valid method for AnyEvent objects";
318		1175
319	detect unless $MODEL;	1176	detect unless $MODEL;
320		1177
321	my $class = shift;	1178	my $class = shift;
322	$class->$func (@_);	1179	$class->$func (@_);
323	}	1180	}
324		1181
		1182	# utility function to dup a filehandle. this is used by many backends
		1183	# to support binding more than one watcher per filehandle (they usually
		1184	# allow only one watcher per fd, so we dup it to get a different one).
		1185	sub _dupfh($$;$$) {
		1186	my ($poll, $fh, $r, $w) = @_;
		1187
		1188	# cygwin requires the fh mode to be matching, unix doesn't
		1189	my ($rw, $mode) = $poll eq "r" ? ($r, "<") : ($w, ">");
		1190
		1191	open my $fh2, "$mode&", $fh
		1192	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1193
		1194	# we assume CLOEXEC is already set by perl in all important cases
		1195
		1196	($fh2, $rw)
		1197	}
		1198
325	package AnyEvent::Base;	1199	package AnyEvent::Base;
326		1200
		1201	# default implementations for many methods
		1202
		1203	BEGIN {
		1204	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1205	*_time = \&Time::HiRes::time;
		1206	# if (eval "use POSIX (); (POSIX::times())...
		1207	} else {
		1208	*_time = sub { time }; # epic fail
		1209	}
		1210	}
		1211
		1212	sub time { _time }
		1213	sub now { _time }
		1214	sub now_update { }
		1215
327	# default implementation for ->condvar, ->wait, ->broadcast	1216	# default implementation for ->condvar
328		1217
329	sub condvar {	1218	sub condvar {
330	bless \my $flag, "AnyEvent::Base::CondVar"	1219	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
331	}
332
333	sub AnyEvent::Base::CondVar::broadcast {
334	${$_[0]}++;
335	}
336
337	sub AnyEvent::Base::CondVar::wait {
338	AnyEvent->one_event while !${$_[0]};
339	}	1220	}
340		1221
341	# default implementation for ->signal	1222	# default implementation for ->signal
342		1223
343	our %SIG_CB;	1224	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1225
		1226	sub _signal_exec {
		1227	sysread $SIGPIPE_R, my $dummy, 4;
		1228
		1229	while (%SIG_EV) {
		1230	for (keys %SIG_EV) {
		1231	delete $SIG_EV{$_};
		1232	$_->() for values %{ $SIG_CB{$_} \|\| {} };
		1233	}
		1234	}
		1235	}
344		1236
345	sub signal {	1237	sub signal {
346	my (undef, %arg) = @_;	1238	my (undef, %arg) = @_;
347		1239
		1240	unless ($SIGPIPE_R) {
		1241	require Fcntl;
		1242
		1243	if (AnyEvent::WIN32) {
		1244	require AnyEvent::Util;
		1245
		1246	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1247	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1248	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1249	} else {
		1250	pipe $SIGPIPE_R, $SIGPIPE_W;
		1251	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1252	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1253
		1254	# not strictly required, as $^F is normally 2, but let's make sure...
		1255	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1256	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1257	}
		1258
		1259	$SIGPIPE_R
		1260	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1261
		1262	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1263	}
		1264
348	my $signal = uc $arg{signal}	1265	my $signal = uc $arg{signal}
349	or Carp::croak "required option 'signal' is missing";	1266	or Carp::croak "required option 'signal' is missing";
350		1267
351	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1268	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
352	$SIG{$signal} \|\|= sub {	1269	$SIG{$signal} \|\|= sub {
353	$_->() for values %{ $SIG_CB{$signal} \|\| {} };	1270	local $!;
		1271	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1272	undef $SIG_EV{$signal};
354	};	1273	};
355		1274
356	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1275	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
357	}	1276	}
358		1277
359	sub AnyEvent::Base::Signal::DESTROY {	1278	sub AnyEvent::Base::signal::DESTROY {
360	my ($signal, $cb) = @{$_[0]};	1279	my ($signal, $cb) = @{$_[0]};
361		1280
362	delete $SIG_CB{$signal}{$cb};	1281	delete $SIG_CB{$signal}{$cb};
363		1282
		1283	# delete doesn't work with older perls - they then
		1284	# print weird messages, or just unconditionally exit
		1285	# instead of getting the default action.
364	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1286	undef $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
365	}	1287	}
366		1288
367	# default implementation for ->child	1289	# default implementation for ->child
368		1290
369	our %PID_CB;	1291	our %PID_CB;
370	our $CHLD_W;	1292	our $CHLD_W;
371	our $PID_IDLE;	1293	our $CHLD_DELAY_W;
372	our $WNOHANG;	1294	our $WNOHANG;
373		1295
374	sub _child_wait {	1296	sub _sigchld {
375	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1297	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
376	$_->() for values %{ (delete $PID_CB{$pid}) \|\| {} };	1298	$_->($pid, $?) for (values %{ $PID_CB{$pid} \|\| {} }),
		1299	(values %{ $PID_CB{0} \|\| {} });
377	}	1300	}
378
379	undef $PID_IDLE;
380	}	1301	}
381		1302
382	sub child {	1303	sub child {
383	my (undef, %arg) = @_;	1304	my (undef, %arg) = @_;
384		1305
385	my $pid = uc $arg{pid}	1306	defined (my $pid = $arg{pid} + 0)
386	or Carp::croak "required option 'pid' is missing";	1307	or Carp::croak "required option 'pid' is missing";
387		1308
388	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1309	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
389		1310
390	unless ($WNOHANG) {	1311	$WNOHANG \|\|= eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } \|\| 1;
		1312
		1313	unless ($CHLD_W) {
391	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_child_wait);	1314	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
392	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } \|\| 1;	1315	# child could be a zombie already, so make at least one round
		1316	&_sigchld;
393	}	1317	}
394		1318
395	# child could be a zombie already
396	$PID_IDLE \|\|= AnyEvent->timer (after => 0, cb => \&_child_wait);
397
398	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1319	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
399	}	1320	}
400		1321
401	sub AnyEvent::Base::Child::DESTROY {	1322	sub AnyEvent::Base::child::DESTROY {
402	my ($pid, $cb) = @{$_[0]};	1323	my ($pid, $cb) = @{$_[0]};
403		1324
404	delete $PID_CB{$pid}{$cb};	1325	delete $PID_CB{$pid}{$cb};
405	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1326	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
406		1327
407	undef $CHLD_W unless keys %PID_CB;	1328	undef $CHLD_W unless keys %PID_CB;
408	}	1329	}
409		1330
		1331	# idle emulation is done by simply using a timer, regardless
		1332	# of whether the process is idle or not, and not letting
		1333	# the callback use more than 50% of the time.
		1334	sub idle {
		1335	my (undef, %arg) = @_;
		1336
		1337	my ($cb, $w, $rcb) = $arg{cb};
		1338
		1339	$rcb = sub {
		1340	if ($cb) {
		1341	$w = _time;
		1342	&$cb;
		1343	$w = _time - $w;
		1344
		1345	# never use more then 50% of the time for the idle watcher,
		1346	# within some limits
		1347	$w = 0.0001 if $w < 0.0001;
		1348	$w = 5 if $w > 5;
		1349
		1350	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1351	} else {
		1352	# clean up...
		1353	undef $w;
		1354	undef $rcb;
		1355	}
		1356	};
		1357
		1358	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1359
		1360	bless \\$cb, "AnyEvent::Base::idle"
		1361	}
		1362
		1363	sub AnyEvent::Base::idle::DESTROY {
		1364	undef $${$_[0]};
		1365	}
		1366
		1367	package AnyEvent::CondVar;
		1368
		1369	our @ISA = AnyEvent::CondVar::Base::;
		1370
		1371	package AnyEvent::CondVar::Base;
		1372
		1373	use overload
		1374	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1375	fallback => 1;
		1376
		1377	our $WAITING;
		1378
		1379	sub _send {
		1380	# nop
		1381	}
		1382
		1383	sub send {
		1384	my $cv = shift;
		1385	$cv->{_ae_sent} = [@_];
		1386	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1387	$cv->_send;
		1388	}
		1389
		1390	sub croak {
		1391	$_[0]{_ae_croak} = $_[1];
		1392	$_[0]->send;
		1393	}
		1394
		1395	sub ready {
		1396	$_[0]{_ae_sent}
		1397	}
		1398
		1399	sub _wait {
		1400	$WAITING
		1401	and !$_[0]{_ae_sent}
		1402	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1403
		1404	local $WAITING = 1;
		1405	AnyEvent->one_event while !$_[0]{_ae_sent};
		1406	}
		1407
		1408	sub recv {
		1409	$_[0]->_wait;
		1410
		1411	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1412	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1413	}
		1414
		1415	sub cb {
		1416	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1417	$_[0]{_ae_cb}
		1418	}
		1419
		1420	sub begin {
		1421	++$_[0]{_ae_counter};
		1422	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1423	}
		1424
		1425	sub end {
		1426	return if --$_[0]{_ae_counter};
		1427	&{ $_[0]{_ae_end_cb} \|\| sub { $_[0]->send } };
		1428	}
		1429
		1430	# undocumented/compatibility with pre-3.4
		1431	*broadcast = \&send;
		1432	*wait = \&_wait;
		1433
		1434	=head1 ERROR AND EXCEPTION HANDLING
		1435
		1436	In general, AnyEvent does not do any error handling - it relies on the
		1437	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1438	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1439	checking of all AnyEvent methods, however, which is highly useful during
		1440	development.
		1441
		1442	As for exception handling (i.e. runtime errors and exceptions thrown while
		1443	executing a callback), this is not only highly event-loop specific, but
		1444	also not in any way wrapped by this module, as this is the job of the main
		1445	program.
		1446
		1447	The pure perl event loop simply re-throws the exception (usually
		1448	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1449	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1450	so on.
		1451
		1452	=head1 ENVIRONMENT VARIABLES
		1453
		1454	The following environment variables are used by this module or its
		1455	submodules.
		1456
		1457	Note that AnyEvent will remove I<all> environment variables starting with
		1458	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1459	enabled.
		1460
		1461	=over 4
		1462
		1463	=item C<PERL_ANYEVENT_VERBOSE>
		1464
		1465	By default, AnyEvent will be completely silent except in fatal
		1466	conditions. You can set this environment variable to make AnyEvent more
		1467	talkative.
		1468
		1469	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1470	conditions, such as not being able to load the event model specified by
		1471	C<PERL_ANYEVENT_MODEL>.
		1472
		1473	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1474	model it chooses.
		1475
		1476	=item C<PERL_ANYEVENT_STRICT>
		1477
		1478	AnyEvent does not do much argument checking by default, as thorough
		1479	argument checking is very costly. Setting this variable to a true value
		1480	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1481	check the arguments passed to most method calls. If it finds any problems,
		1482	it will croak.
		1483
		1484	In other words, enables "strict" mode.
		1485
		1486	Unlike C<use strict>, it is definitely recommended to keep it off in
		1487	production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
		1488	developing programs can be very useful, however.
		1489
		1490	=item C<PERL_ANYEVENT_MODEL>
		1491
		1492	This can be used to specify the event model to be used by AnyEvent, before
		1493	auto detection and -probing kicks in. It must be a string consisting
		1494	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1495	and the resulting module name is loaded and if the load was successful,
		1496	used as event model. If it fails to load AnyEvent will proceed with
		1497	auto detection and -probing.
		1498
		1499	This functionality might change in future versions.
		1500
		1501	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1502	could start your program like this:
		1503
		1504	PERL_ANYEVENT_MODEL=Perl perl ...
		1505
		1506	=item C<PERL_ANYEVENT_PROTOCOLS>
		1507
		1508	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1509	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1510	of auto probing).
		1511
		1512	Must be set to a comma-separated list of protocols or address families,
		1513	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1514	used, and preference will be given to protocols mentioned earlier in the
		1515	list.
		1516
		1517	This variable can effectively be used for denial-of-service attacks
		1518	against local programs (e.g. when setuid), although the impact is likely
		1519	small, as the program has to handle conenction and other failures anyways.
		1520
		1521	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1522	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1523	- only support IPv4, never try to resolve or contact IPv6
		1524	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1525	IPv6, but prefer IPv6 over IPv4.
		1526
		1527	=item C<PERL_ANYEVENT_EDNS0>
		1528
		1529	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1530	for DNS. This extension is generally useful to reduce DNS traffic, but
		1531	some (broken) firewalls drop such DNS packets, which is why it is off by
		1532	default.
		1533
		1534	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1535	EDNS0 in its DNS requests.
		1536
		1537	=item C<PERL_ANYEVENT_MAX_FORKS>
		1538
		1539	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1540	will create in parallel.
		1541
		1542	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1543
		1544	The default value for the C<max_outstanding> parameter for the default DNS
		1545	resolver - this is the maximum number of parallel DNS requests that are
		1546	sent to the DNS server.
		1547
		1548	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1549
		1550	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1551	configuration) in the default resolver. When set to the empty string, no
		1552	default config will be used.
		1553
		1554	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1555
		1556	When neither C<ca_file> nor C<ca_path> was specified during
		1557	L<AnyEvent::TLS> context creation, and either of these environment
		1558	variables exist, they will be used to specify CA certificate locations
		1559	instead of a system-dependent default.
		1560
		1561	=back
		1562
410	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1563	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1564
		1565	This is an advanced topic that you do not normally need to use AnyEvent in
		1566	a module. This section is only of use to event loop authors who want to
		1567	provide AnyEvent compatibility.
411		1568
412	If you need to support another event library which isn't directly	1569	If you need to support another event library which isn't directly
413	supported by AnyEvent, you can supply your own interface to it by	1570	supported by AnyEvent, you can supply your own interface to it by
414	pushing, before the first watcher gets created, the package name of	1571	pushing, before the first watcher gets created, the package name of
415	the event module and the package name of the interface to use onto	1572	the event module and the package name of the interface to use onto
416	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	1573	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
417	AnyEvent.	1574	AnyEvent, so it is reasonably cheap.
418		1575
419	Example:	1576	Example:
420		1577
421	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	1578	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
422		1579
423	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	1580	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
424	package/class when it finds the C<urxvt> package/module is loaded. When	1581	package/class when it finds the C<urxvt> package/module is already loaded.
		1582
425	AnyEvent is loaded and asked to find a suitable event model, it will	1583	When AnyEvent is loaded and asked to find a suitable event model, it
426	first check for the presence of urxvt.	1584	will first check for the presence of urxvt by trying to C<use> the
		1585	C<urxvt::anyevent> module.
427		1586
428	The class should provide implementations for all watcher types (see	1587	The class should provide implementations for all watcher types. See
429	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	1588	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
430	(Source code) and so on for actual examples, use C<perldoc -m	1589	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
431	AnyEvent::Impl::Glib> to see the sources).	1590	see the sources.
432		1591
		1592	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		1593	provide suitable (hopefully) replacements.
		1594
433	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	1595	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
434	uses the above line as-is. An interface isn't included in AnyEvent	1596	terminal emulator uses the above line as-is. An interface isn't included
435	because it doesn't make sense outside the embedded interpreter inside	1597	in AnyEvent because it doesn't make sense outside the embedded interpreter
436	I<rxvt-unicode>, and it is updated and maintained as part of the	1598	inside I<rxvt-unicode>, and it is updated and maintained as part of the
437	I<rxvt-unicode> distribution.	1599	I<rxvt-unicode> distribution.
438		1600
439	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1601	I<rxvt-unicode> also cheats a bit by not providing blocking access to
440	condition variables: code blocking while waiting for a condition will	1602	condition variables: code blocking while waiting for a condition will
441	C<die>. This still works with most modules/usages, and blocking calls must	1603	C<die>. This still works with most modules/usages, and blocking calls must
442	not be in an interactive appliation, so it makes sense.	1604	not be done in an interactive application, so it makes sense.
443		1605
444	=head1 ENVIRONMENT VARIABLES
445
446	The following environment variables are used by this module:
447
448	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
449	model gets used.
450
451	=head1 EXAMPLE	1606	=head1 EXAMPLE PROGRAM
452		1607
453	The following program uses an io watcher to read data from stdin, a timer	1608	The following program uses an I/O watcher to read data from STDIN, a timer
454	to display a message once per second, and a condvar to exit the program	1609	to display a message once per second, and a condition variable to quit the
455	when the user enters quit:	1610	program when the user enters quit:
456		1611
457	use AnyEvent;	1612	use AnyEvent;
458		1613
459	my $cv = AnyEvent->condvar;	1614	my $cv = AnyEvent->condvar;
460		1615
461	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	1616	my $io_watcher = AnyEvent->io (
		1617	fh => \*STDIN,
		1618	poll => 'r',
		1619	cb => sub {
462	warn "io event <$_[0]>\n"; # will always output <r>	1620	warn "io event <$_[0]>\n"; # will always output <r>
463	chomp (my $input = <STDIN>); # read a line	1621	chomp (my $input = <STDIN>); # read a line
464	warn "read: $input\n"; # output what has been read	1622	warn "read: $input\n"; # output what has been read
465	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1623	$cv->send if $input =~ /^q/i; # quit program if /^q/i
		1624	},
466	});	1625	);
467		1626
468	my $time_watcher; # can only be used once	1627	my $time_watcher; # can only be used once
469		1628
470	sub new_timer {	1629	sub new_timer {
471	$timer = AnyEvent->timer (after => 1, cb => sub {	1630	$timer = AnyEvent->timer (after => 1, cb => sub {
…		…
474	});	1633	});
475	}	1634	}
476		1635
477	new_timer; # create first timer	1636	new_timer; # create first timer
478		1637
479	$cv->wait; # wait until user enters /^q/i	1638	$cv->recv; # wait until user enters /^q/i
480		1639
481	=head1 REAL-WORLD EXAMPLE	1640	=head1 REAL-WORLD EXAMPLE
482		1641
483	Consider the L<Net::FCP> module. It features (among others) the following	1642	Consider the L<Net::FCP> module. It features (among others) the following
484	API calls, which are to freenet what HTTP GET requests are to http:	1643	API calls, which are to freenet what HTTP GET requests are to http:
…		…
534	syswrite $txn->{fh}, $txn->{request}	1693	syswrite $txn->{fh}, $txn->{request}
535	or die "connection or write error";	1694	or die "connection or write error";
536	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1695	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
537		1696
538	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1697	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
539	result and signals any possible waiters that the request ahs finished:	1698	result and signals any possible waiters that the request has finished:
540		1699
541	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1700	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
542		1701
543	if (end-of-file or data complete) {	1702	if (end-of-file or data complete) {
544	$txn->{result} = $txn->{buf};	1703	$txn->{result} = $txn->{buf};
545	$txn->{finished}->broadcast;	1704	$txn->{finished}->send;
546	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1705	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
547	}	1706	}
548		1707
549	The C<result> method, finally, just waits for the finished signal (if the	1708	The C<result> method, finally, just waits for the finished signal (if the
550	request was already finished, it doesn't wait, of course, and returns the	1709	request was already finished, it doesn't wait, of course, and returns the
551	data:	1710	data:
552		1711
553	$txn->{finished}->wait;	1712	$txn->{finished}->recv;
554	return $txn->{result};	1713	return $txn->{result};
555		1714
556	The actual code goes further and collects all errors (C<die>s, exceptions)	1715	The actual code goes further and collects all errors (C<die>s, exceptions)
557	that occured during request processing. The C<result> method detects	1716	that occurred during request processing. The C<result> method detects
558	wether an exception as thrown (it is stored inside the $txn object)	1717	whether an exception as thrown (it is stored inside the $txn object)
559	and just throws the exception, which means connection errors and other	1718	and just throws the exception, which means connection errors and other
560	problems get reported tot he code that tries to use the result, not in a	1719	problems get reported tot he code that tries to use the result, not in a
561	random callback.	1720	random callback.
562		1721
563	All of this enables the following usage styles:	1722	All of this enables the following usage styles:
564		1723
565	1. Blocking:	1724	1. Blocking:
566		1725
567	my $data = $fcp->client_get ($url);	1726	my $data = $fcp->client_get ($url);
568		1727
569	2. Blocking, but parallelizing:	1728	2. Blocking, but running in parallel:
570		1729
571	my @datas = map $_->result,	1730	my @datas = map $_->result,
572	map $fcp->txn_client_get ($_),	1731	map $fcp->txn_client_get ($_),
573	@urls;	1732	@urls;
574		1733
575	Both blocking examples work without the module user having to know	1734	Both blocking examples work without the module user having to know
576	anything about events.	1735	anything about events.
577		1736
578	3a. Event-based in a main program, using any support Event module:	1737	3a. Event-based in a main program, using any supported event module:
579		1738
580	use Event;	1739	use EV;
581		1740
582	$fcp->txn_client_get ($url)->cb (sub {	1741	$fcp->txn_client_get ($url)->cb (sub {
583	my $txn = shift;	1742	my $txn = shift;
584	my $data = $txn->result;	1743	my $data = $txn->result;
585	...	1744	...
586	});	1745	});
587		1746
588	Event::loop;	1747	EV::loop;
589		1748
590	3b. The module user could use AnyEvent, too:	1749	3b. The module user could use AnyEvent, too:
591		1750
592	use AnyEvent;	1751	use AnyEvent;
593		1752
594	my $quit = AnyEvent->condvar;	1753	my $quit = AnyEvent->condvar;
595		1754
596	$fcp->txn_client_get ($url)->cb (sub {	1755	$fcp->txn_client_get ($url)->cb (sub {
597	...	1756	...
598	$quit->broadcast;	1757	$quit->send;
599	});	1758	});
600		1759
601	$quit->wait;	1760	$quit->recv;
		1761
		1762
		1763	=head1 BENCHMARKS
		1764
		1765	To give you an idea of the performance and overheads that AnyEvent adds
		1766	over the event loops themselves and to give you an impression of the speed
		1767	of various event loops I prepared some benchmarks.
		1768
		1769	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1770
		1771	Here is a benchmark of various supported event models used natively and
		1772	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1773	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1774	which it is), lets them fire exactly once and destroys them again.
		1775
		1776	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1777	distribution.
		1778
		1779	=head3 Explanation of the columns
		1780
		1781	I<watcher> is the number of event watchers created/destroyed. Since
		1782	different event models feature vastly different performances, each event
		1783	loop was given a number of watchers so that overall runtime is acceptable
		1784	and similar between tested event loop (and keep them from crashing): Glib
		1785	would probably take thousands of years if asked to process the same number
		1786	of watchers as EV in this benchmark.
		1787
		1788	I<bytes> is the number of bytes (as measured by the resident set size,
		1789	RSS) consumed by each watcher. This method of measuring captures both C
		1790	and Perl-based overheads.
		1791
		1792	I<create> is the time, in microseconds (millionths of seconds), that it
		1793	takes to create a single watcher. The callback is a closure shared between
		1794	all watchers, to avoid adding memory overhead. That means closure creation
		1795	and memory usage is not included in the figures.
		1796
		1797	I<invoke> is the time, in microseconds, used to invoke a simple
		1798	callback. The callback simply counts down a Perl variable and after it was
		1799	invoked "watcher" times, it would C<< ->send >> a condvar once to
		1800	signal the end of this phase.
		1801
		1802	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1803	watcher.
		1804
		1805	=head3 Results
		1806
		1807	name watchers bytes create invoke destroy comment
		1808	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
		1809	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
		1810	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
		1811	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
		1812	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
		1813	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1814	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1815	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
		1816	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
		1817	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
		1818	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
		1819	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
		1820
		1821	=head3 Discussion
		1822
		1823	The benchmark does I<not> measure scalability of the event loop very
		1824	well. For example, a select-based event loop (such as the pure perl one)
		1825	can never compete with an event loop that uses epoll when the number of
		1826	file descriptors grows high. In this benchmark, all events become ready at
		1827	the same time, so select/poll-based implementations get an unnatural speed
		1828	boost.
		1829
		1830	Also, note that the number of watchers usually has a nonlinear effect on
		1831	overall speed, that is, creating twice as many watchers doesn't take twice
		1832	the time - usually it takes longer. This puts event loops tested with a
		1833	higher number of watchers at a disadvantage.
		1834
		1835	To put the range of results into perspective, consider that on the
		1836	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1837	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1838	cycles with POE.
		1839
		1840	C<EV> is the sole leader regarding speed and memory use, which are both
		1841	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1842	far less memory than any other event loop and is still faster than Event
		1843	natively.
		1844
		1845	The pure perl implementation is hit in a few sweet spots (both the
		1846	constant timeout and the use of a single fd hit optimisations in the perl
		1847	interpreter and the backend itself). Nevertheless this shows that it
		1848	adds very little overhead in itself. Like any select-based backend its
		1849	performance becomes really bad with lots of file descriptors (and few of
		1850	them active), of course, but this was not subject of this benchmark.
		1851
		1852	The C<Event> module has a relatively high setup and callback invocation
		1853	cost, but overall scores in on the third place.
		1854
		1855	C<IO::Async> performs admirably well, about on par with C<Event>, even
		1856	when using its pure perl backend.
		1857
		1858	C<Glib>'s memory usage is quite a bit higher, but it features a
		1859	faster callback invocation and overall ends up in the same class as
		1860	C<Event>. However, Glib scales extremely badly, doubling the number of
		1861	watchers increases the processing time by more than a factor of four,
		1862	making it completely unusable when using larger numbers of watchers
		1863	(note that only a single file descriptor was used in the benchmark, so
		1864	inefficiencies of C<poll> do not account for this).
		1865
		1866	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1867	more than 2000 watchers is a big setback, however, as correctness takes
		1868	precedence over speed. Nevertheless, its performance is surprising, as the
		1869	file descriptor is dup()ed for each watcher. This shows that the dup()
		1870	employed by some adaptors is not a big performance issue (it does incur a
		1871	hidden memory cost inside the kernel which is not reflected in the figures
		1872	above).
		1873
		1874	C<POE>, regardless of underlying event loop (whether using its pure perl
		1875	select-based backend or the Event module, the POE-EV backend couldn't
		1876	be tested because it wasn't working) shows abysmal performance and
		1877	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		1878	as EV watchers, and 10 times as much memory as Event (the high memory
		1879	requirements are caused by requiring a session for each watcher). Watcher
		1880	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1881	implementation.
		1882
		1883	The design of the POE adaptor class in AnyEvent can not really account
		1884	for the performance issues, though, as session creation overhead is
		1885	small compared to execution of the state machine, which is coded pretty
		1886	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1887	using multiple sessions is not a good approach, especially regarding
		1888	memory usage, even the author of POE could not come up with a faster
		1889	design).
		1890
		1891	=head3 Summary
		1892
		1893	=over 4
		1894
		1895	=item * Using EV through AnyEvent is faster than any other event loop
		1896	(even when used without AnyEvent), but most event loops have acceptable
		1897	performance with or without AnyEvent.
		1898
		1899	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1900	the actual event loop, only with extremely fast event loops such as EV
		1901	adds AnyEvent significant overhead.
		1902
		1903	=item * You should avoid POE like the plague if you want performance or
		1904	reasonable memory usage.
		1905
		1906	=back
		1907
		1908	=head2 BENCHMARKING THE LARGE SERVER CASE
		1909
		1910	This benchmark actually benchmarks the event loop itself. It works by
		1911	creating a number of "servers": each server consists of a socket pair, a
		1912	timeout watcher that gets reset on activity (but never fires), and an I/O
		1913	watcher waiting for input on one side of the socket. Each time the socket
		1914	watcher reads a byte it will write that byte to a random other "server".
		1915
		1916	The effect is that there will be a lot of I/O watchers, only part of which
		1917	are active at any one point (so there is a constant number of active
		1918	fds for each loop iteration, but which fds these are is random). The
		1919	timeout is reset each time something is read because that reflects how
		1920	most timeouts work (and puts extra pressure on the event loops).
		1921
		1922	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1923	(1%) are active. This mirrors the activity of large servers with many
		1924	connections, most of which are idle at any one point in time.
		1925
		1926	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1927	distribution.
		1928
		1929	=head3 Explanation of the columns
		1930
		1931	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1932	each server has a read and write socket end).
		1933
		1934	I<create> is the time it takes to create a socket pair (which is
		1935	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1936
		1937	I<request>, the most important value, is the time it takes to handle a
		1938	single "request", that is, reading the token from the pipe and forwarding
		1939	it to another server. This includes deleting the old timeout and creating
		1940	a new one that moves the timeout into the future.
		1941
		1942	=head3 Results
		1943
		1944	name sockets create request
		1945	EV 20000 69.01 11.16
		1946	Perl 20000 73.32 35.87
		1947	IOAsync 20000 157.00 98.14 epoll
		1948	IOAsync 20000 159.31 616.06 poll
		1949	Event 20000 212.62 257.32
		1950	Glib 20000 651.16 1896.30
		1951	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1952
		1953	=head3 Discussion
		1954
		1955	This benchmark I<does> measure scalability and overall performance of the
		1956	particular event loop.
		1957
		1958	EV is again fastest. Since it is using epoll on my system, the setup time
		1959	is relatively high, though.
		1960
		1961	Perl surprisingly comes second. It is much faster than the C-based event
		1962	loops Event and Glib.
		1963
		1964	IO::Async performs very well when using its epoll backend, and still quite
		1965	good compared to Glib when using its pure perl backend.
		1966
		1967	Event suffers from high setup time as well (look at its code and you will
		1968	understand why). Callback invocation also has a high overhead compared to
		1969	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1970	uses select or poll in basically all documented configurations.
		1971
		1972	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1973	clearly fails to perform with many filehandles or in busy servers.
		1974
		1975	POE is still completely out of the picture, taking over 1000 times as long
		1976	as EV, and over 100 times as long as the Perl implementation, even though
		1977	it uses a C-based event loop in this case.
		1978
		1979	=head3 Summary
		1980
		1981	=over 4
		1982
		1983	=item * The pure perl implementation performs extremely well.
		1984
		1985	=item * Avoid Glib or POE in large projects where performance matters.
		1986
		1987	=back
		1988
		1989	=head2 BENCHMARKING SMALL SERVERS
		1990
		1991	While event loops should scale (and select-based ones do not...) even to
		1992	large servers, most programs we (or I :) actually write have only a few
		1993	I/O watchers.
		1994
		1995	In this benchmark, I use the same benchmark program as in the large server
		1996	case, but it uses only eight "servers", of which three are active at any
		1997	one time. This should reflect performance for a small server relatively
		1998	well.
		1999
		2000	The columns are identical to the previous table.
		2001
		2002	=head3 Results
		2003
		2004	name sockets create request
		2005	EV 16 20.00 6.54
		2006	Perl 16 25.75 12.62
		2007	Event 16 81.27 35.86
		2008	Glib 16 32.63 15.48
		2009	POE 16 261.87 276.28 uses POE::Loop::Event
		2010
		2011	=head3 Discussion
		2012
		2013	The benchmark tries to test the performance of a typical small
		2014	server. While knowing how various event loops perform is interesting, keep
		2015	in mind that their overhead in this case is usually not as important, due
		2016	to the small absolute number of watchers (that is, you need efficiency and
		2017	speed most when you have lots of watchers, not when you only have a few of
		2018	them).
		2019
		2020	EV is again fastest.
		2021
		2022	Perl again comes second. It is noticeably faster than the C-based event
		2023	loops Event and Glib, although the difference is too small to really
		2024	matter.
		2025
		2026	POE also performs much better in this case, but is is still far behind the
		2027	others.
		2028
		2029	=head3 Summary
		2030
		2031	=over 4
		2032
		2033	=item * C-based event loops perform very well with small number of
		2034	watchers, as the management overhead dominates.
		2035
		2036	=back
		2037
		2038	=head2 THE IO::Lambda BENCHMARK
		2039
		2040	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2041	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2042	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2043	shouldn't come as a surprise to anybody). As such, the benchmark is
		2044	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2045	very optimal. But how would AnyEvent compare when used without the extra
		2046	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2047
		2048	The benchmark itself creates an echo-server, and then, for 500 times,
		2049	connects to the echo server, sends a line, waits for the reply, and then
		2050	creates the next connection. This is a rather bad benchmark, as it doesn't
		2051	test the efficiency of the framework or much non-blocking I/O, but it is a
		2052	benchmark nevertheless.
		2053
		2054	name runtime
		2055	Lambda/select 0.330 sec
		2056	+ optimized 0.122 sec
		2057	Lambda/AnyEvent 0.327 sec
		2058	+ optimized 0.138 sec
		2059	Raw sockets/select 0.077 sec
		2060	POE/select, components 0.662 sec
		2061	POE/select, raw sockets 0.226 sec
		2062	POE/select, optimized 0.404 sec
		2063
		2064	AnyEvent/select/nb 0.085 sec
		2065	AnyEvent/EV/nb 0.068 sec
		2066	+state machine 0.134 sec
		2067
		2068	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2069	benchmarks actually make blocking connects and use 100% blocking I/O,
		2070	defeating the purpose of an event-based solution. All of the newly
		2071	written AnyEvent benchmarks use 100% non-blocking connects (using
		2072	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2073	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2074	generally require a lot more bookkeeping and event handling than blocking
		2075	connects (which involve a single syscall only).
		2076
		2077	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2078	offers similar expressive power as POE and IO::Lambda, using conventional
		2079	Perl syntax. This means that both the echo server and the client are 100%
		2080	non-blocking, further placing it at a disadvantage.
		2081
		2082	As you can see, the AnyEvent + EV combination even beats the
		2083	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2084	backend easily beats IO::Lambda and POE.
		2085
		2086	And even the 100% non-blocking version written using the high-level (and
		2087	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2088	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2089	in a non-blocking way.
		2090
		2091	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2092	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2093	part of the IO::lambda distribution and were used without any changes.
		2094
		2095
		2096	=head1 SIGNALS
		2097
		2098	AnyEvent currently installs handlers for these signals:
		2099
		2100	=over 4
		2101
		2102	=item SIGCHLD
		2103
		2104	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2105	emulation for event loops that do not support them natively. Also, some
		2106	event loops install a similar handler.
		2107
		2108	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2109	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2110
		2111	=item SIGPIPE
		2112
		2113	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2114	when AnyEvent gets loaded.
		2115
		2116	The rationale for this is that AnyEvent users usually do not really depend
		2117	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2118	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2119	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2120	some random socket.
		2121
		2122	The rationale for installing a no-op handler as opposed to ignoring it is
		2123	that this way, the handler will be restored to defaults on exec.
		2124
		2125	Feel free to install your own handler, or reset it to defaults.
		2126
		2127	=back
		2128
		2129	=cut
		2130
		2131	undef $SIG{CHLD}
		2132	if $SIG{CHLD} eq 'IGNORE';
		2133
		2134	$SIG{PIPE} = sub { }
		2135	unless defined $SIG{PIPE};
		2136
		2137	=head1 FORK
		2138
		2139	Most event libraries are not fork-safe. The ones who are usually are
		2140	because they rely on inefficient but fork-safe C<select> or C<poll>
		2141	calls. Only L<EV> is fully fork-aware.
		2142
		2143	If you have to fork, you must either do so I<before> creating your first
		2144	watcher OR you must not use AnyEvent at all in the child.
		2145
		2146
		2147	=head1 SECURITY CONSIDERATIONS
		2148
		2149	AnyEvent can be forced to load any event model via
		2150	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		2151	execute arbitrary code or directly gain access, it can easily be used to
		2152	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		2153	will not be active when the program uses a different event model than
		2154	specified in the variable.
		2155
		2156	You can make AnyEvent completely ignore this variable by deleting it
		2157	before the first watcher gets created, e.g. with a C<BEGIN> block:
		2158
		2159	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		2160
		2161	use AnyEvent;
		2162
		2163	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2164	be used to probe what backend is used and gain other information (which is
		2165	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2166	$ENV{PERL_ANYEVENT_STRICT}.
		2167
		2168	Note that AnyEvent will remove I<all> environment variables starting with
		2169	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2170	enabled.
		2171
		2172
		2173	=head1 BUGS
		2174
		2175	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2176	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2177	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2178	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2179	pronounced).
		2180
602		2181
603	=head1 SEE ALSO	2182	=head1 SEE ALSO
604		2183
605	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	2184	Utility functions: L<AnyEvent::Util>.
606		2185
607	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	2186	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		2187	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
608		2188
609	Nontrivial usage example: L<Net::FCP>.	2189	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2190	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2191	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2192	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>.
610		2193
611	=head1	2194	Non-blocking file handles, sockets, TCP clients and
		2195	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2196
		2197	Asynchronous DNS: L<AnyEvent::DNS>.
		2198
		2199	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2200	L<Coro::Event>,
		2201
		2202	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2203	L<AnyEvent::HTTP>.
		2204
		2205
		2206	=head1 AUTHOR
		2207
		2208	Marc Lehmann <schmorp@schmorp.de>
		2209	http://home.schmorp.de/
612		2210
613	=cut	2211	=cut
614		2212
615	1	2213	1
616		2214

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
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Revision 1.239 by root, Thu Jul 16 20:55:38 2009 UTC