ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/AnyEvent/lib/AnyEvent.pm

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.39 by root, Mon Jan 28 12:32:20 2008 UTC vs.
Revision 1.263 by root, Wed Jul 29 12:39:21 2009 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	Event, Coro, Glib, Tk, Perl - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores wether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
		53
		54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
		55
		56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
		57	nowadays. So what is different about AnyEvent?
		58
		59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
		60	policy> and AnyEvent is I<small and efficient>.
		61
		62	First and foremost, I<AnyEvent is not an event model> itself, it only
		63	interfaces to whatever event model the main program happens to use, in a
		64	pragmatic way. For event models and certain classes of immortals alike,
		65	the statement "there can only be one" is a bitter reality: In general,
		66	only one event loop can be active at the same time in a process. AnyEvent
		67	cannot change this, but it can hide the differences between those event
		68	loops.
		69
		70	The goal of AnyEvent is to offer module authors the ability to do event
		71	programming (waiting for I/O or timer events) without subscribing to a
		72	religion, a way of living, and most importantly: without forcing your
		73	module users into the same thing by forcing them to use the same event
		74	model you use.
		75
		76	For modules like POE or IO::Async (which is a total misnomer as it is
		77	actually doing all I/O I<synchronously>...), using them in your module is
		78	like joining a cult: After you joined, you are dependent on them and you
		79	cannot use anything else, as they are simply incompatible to everything
		80	that isn't them. What's worse, all the potential users of your
		81	module are I<also> forced to use the same event loop you use.
		82
		83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
		84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
		85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
		86	your module uses one of those, every user of your module has to use it,
		87	too. But if your module uses AnyEvent, it works transparently with all
		88	event models it supports (including stuff like IO::Async, as long as those
		89	use one of the supported event loops. It is trivial to add new event loops
		90	to AnyEvent, too, so it is future-proof).
		91
		92	In addition to being free of having to use I<the one and only true event
		93	model>, AnyEvent also is free of bloat and policy: with POE or similar
		94	modules, you get an enormous amount of code and strict rules you have to
		95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
		96	offering the functionality that is necessary, in as thin as a wrapper as
		97	technically possible.
		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		100	of useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
		105	Now, if you I<do want> lots of policy (this can arguably be somewhat
		106	useful) and you want to force your users to use the one and only event
		107	model, you should I<not> use this module.
22		108
23	=head1 DESCRIPTION	109	=head1 DESCRIPTION
24		110
25	L<AnyEvent> provides an identical interface to multiple event loops. This	111	L<AnyEvent> provides an identical interface to multiple event loops. This
26	allows module authors to utilise an event loop without forcing module	112	allows module authors to utilise an event loop without forcing module
27	users to use the same event loop (as only a single event loop can coexist	113	users to use the same event loop (as only a single event loop can coexist
28	peacefully at any one time).	114	peacefully at any one time).
29		115
30	The interface itself is vaguely similar but not identical to the Event	116	The interface itself is vaguely similar, but not identical to the L<Event>
31	module.	117	module.
32		118
33	On the first call of any method, the module tries to detect the currently	119	During the first call of any watcher-creation method, the module tries
34	loaded event loop by probing wether any of the following modules is	120	to detect the currently loaded event loop by probing whether one of the
35	loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is	121	following modules is already loaded: L<EV>,
36	used. If none is found, the module tries to load these modules in the	122	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
37	order given. The first one that could be successfully loaded will be	123	L<POE>. The first one found is used. If none are found, the module tries
38	used. If still none could be found, AnyEvent will fall back to a pure-perl	124	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
39	event loop, which is also not very efficient.	125	adaptor should always succeed) in the order given. The first one that can
		126	be successfully loaded will be used. If, after this, still none could be
		127	found, AnyEvent will fall back to a pure-perl event loop, which is not
		128	very efficient, but should work everywhere.
40		129
41	Because AnyEvent first checks for modules that are already loaded, loading	130	Because AnyEvent first checks for modules that are already loaded, loading
42	an Event model explicitly before first using AnyEvent will likely make	131	an event model explicitly before first using AnyEvent will likely make
43	that model the default. For example:	132	that model the default. For example:
44		133
45	use Tk;	134	use Tk;
46	use AnyEvent;	135	use AnyEvent;
47		136
48	# .. AnyEvent will likely default to Tk	137	# .. AnyEvent will likely default to Tk
49		138
		139	The I<likely> means that, if any module loads another event model and
		140	starts using it, all bets are off. Maybe you should tell their authors to
		141	use AnyEvent so their modules work together with others seamlessly...
		142
50	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
51	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	144	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
52	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
53		146
54	=head1 WATCHERS	147	=head1 WATCHERS
55		148
56	AnyEvent has the central concept of a I<watcher>, which is an object that	149	AnyEvent has the central concept of a I<watcher>, which is an object that
57	stores relevant data for each kind of event you are waiting for, such as	150	stores relevant data for each kind of event you are waiting for, such as
58	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
59		152
60	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
61	creating a watcher it will immediately "watch" for events and invoke	154	creating a watcher it will immediately "watch" for events and invoke the
		155	callback when the event occurs (of course, only when the event model
		156	is in control).
		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
62	the callback. To disable the watcher you have to destroy it (e.g. by	164	To disable the watcher you have to destroy it (e.g. by setting the
63	setting the variable that stores it to C<undef> or otherwise deleting all	165	variable you store it in to C<undef> or otherwise deleting all references
64	references to it).	166	to it).
65		167
66	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
67		169
		170	Many watchers either are used with "recursion" (repeating timers for
		171	example), or need to refer to their watcher object in other ways.
		172
		173	An any way to achieve that is this pattern:
		174
		175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		176	# you can use $w here, for example to undef it
		177	undef $w;
		178	});
		179
		180	Note that C<my $w; $w => combination. This is necessary because in Perl,
		181	my variables are only visible after the statement in which they are
		182	declared.
		183
68	=head2 IO WATCHERS	184	=head2 I/O WATCHERS
69		185
70	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	186	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
71	the following mandatory arguments:	187	with the following mandatory key-value pairs as arguments:
72		188
73	C<fh> the Perl I<filehandle> (not filedescriptor) to watch for	189	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		190	for events (AnyEvent might or might not keep a reference to this file
		191	handle). Note that only file handles pointing to things for which
		192	non-blocking operation makes sense are allowed. This includes sockets,
		193	most character devices, pipes, fifos and so on, but not for example files
		194	or block devices.
		195
74	events. C<poll> must be a string that is either C<r> or C<w>, that creates	196	C<poll> must be a string that is either C<r> or C<w>, which creates a
75	a watcher waiting for "r"eadable or "w"ritable events. C<cb> the callback	197	watcher waiting for "r"eadable or "w"ritable events, respectively.
76	to invoke everytime the filehandle becomes ready.
77		198
78	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	199	C<cb> is the callback to invoke each time the file handle becomes ready.
79	a socket you can have one r + one w, not any more (limitation comes from
80	Tk - if you are sure you are not using Tk this limitation is gone).
81		200
82	Filehandles will be kept alive, so as long as the watcher exists, the	201	Although the callback might get passed parameters, their value and
83	filehandle exists, too.	202	presence is undefined and you cannot rely on them. Portable AnyEvent
		203	callbacks cannot use arguments passed to I/O watcher callbacks.
84		204
85	Example:	205	The I/O watcher might use the underlying file descriptor or a copy of it.
		206	You must not close a file handle as long as any watcher is active on the
		207	underlying file descriptor.
86		208
		209	Some event loops issue spurious readyness notifications, so you should
		210	always use non-blocking calls when reading/writing from/to your file
		211	handles.
		212
87	# wait for readability of STDIN, then read a line and disable the watcher	213	Example: wait for readability of STDIN, then read a line and disable the
		214	watcher.
		215
88	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	216	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
89	chomp (my $input = <STDIN>);	217	chomp (my $input = <STDIN>);
90	warn "read: $input\n";	218	warn "read: $input\n";
91	undef $w;	219	undef $w;
92	});	220	});
…		…
94	=head2 TIME WATCHERS	222	=head2 TIME WATCHERS
95		223
96	You can create a time watcher by calling the C<< AnyEvent->timer >>	224	You can create a time watcher by calling the C<< AnyEvent->timer >>
97	method with the following mandatory arguments:	225	method with the following mandatory arguments:
98		226
99	C<after> after how many seconds (fractions are supported) should the timer	227	C<after> specifies after how many seconds (fractional values are
100	activate. C<cb> the callback to invoke.	228	supported) the callback should be invoked. C<cb> is the callback to invoke
		229	in that case.
101		230
102	The timer callback will be invoked at most once: if you want a repeating	231	Although the callback might get passed parameters, their value and
103	timer you have to create a new watcher (this is a limitation by both Tk	232	presence is undefined and you cannot rely on them. Portable AnyEvent
104	and Glib).	233	callbacks cannot use arguments passed to time watcher callbacks.
105		234
106	Example:	235	The callback will normally be invoked once only. If you specify another
		236	parameter, C<interval>, as a strictly positive number (> 0), then the
		237	callback will be invoked regularly at that interval (in fractional
		238	seconds) after the first invocation. If C<interval> is specified with a
		239	false value, then it is treated as if it were missing.
107		240
		241	The callback will be rescheduled before invoking the callback, but no
		242	attempt is done to avoid timer drift in most backends, so the interval is
		243	only approximate.
		244
108	# fire an event after 7.7 seconds	245	Example: fire an event after 7.7 seconds.
		246
109	my $w = AnyEvent->timer (after => 7.7, cb => sub {	247	my $w = AnyEvent->timer (after => 7.7, cb => sub {
110	warn "timeout\n";	248	warn "timeout\n";
111	});	249	});
112		250
113	# to cancel the timer:	251	# to cancel the timer:
114	undef $w;	252	undef $w;
115		253
116	=head2 CONDITION WATCHERS	254	Example 2: fire an event after 0.5 seconds, then roughly every second.
117		255
118	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	256	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
119	method without any arguments.	257	warn "timeout\n";
		258	};
120		259
121	A condition watcher watches for a condition - precisely that the C<<	260	=head3 TIMING ISSUES
122	->broadcast >> method has been called.
123		261
124	The watcher has only two methods:	262	There are two ways to handle timers: based on real time (relative, "fire
		263	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		264	o'clock").
		265
		266	While most event loops expect timers to specified in a relative way, they
		267	use absolute time internally. This makes a difference when your clock
		268	"jumps", for example, when ntp decides to set your clock backwards from
		269	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		270	fire "after" a second might actually take six years to finally fire.
		271
		272	AnyEvent cannot compensate for this. The only event loop that is conscious
		273	about these issues is L<EV>, which offers both relative (ev_timer, based
		274	on true relative time) and absolute (ev_periodic, based on wallclock time)
		275	timers.
		276
		277	AnyEvent always prefers relative timers, if available, matching the
		278	AnyEvent API.
		279
		280	AnyEvent has two additional methods that return the "current time":
125		281
126	=over 4	282	=over 4
127		283
128	=item $cv->wait	284	=item AnyEvent->time
129		285
130	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	286	This returns the "current wallclock time" as a fractional number of
131	called on c<$cv>, while servicing other watchers normally.	287	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		288	return, and the result is guaranteed to be compatible with those).
132		289
133	Not all event models support a blocking wait - some die in that case, so	290	It progresses independently of any event loop processing, i.e. each call
134	if you are using this from a module, never require a blocking wait, but	291	will check the system clock, which usually gets updated frequently.
135	let the caller decide wether the call will block or not (for example,
136	by coupling condition variables with some kind of request results and
137	supporting callbacks so the caller knows that getting the result will not
138	block, while still suppporting blockign waits if the caller so desires).
139		292
140	You can only wait once on a condition - additional calls will return	293	=item AnyEvent->now
141	immediately.
142		294
143	=item $cv->broadcast	295	This also returns the "current wallclock time", but unlike C<time>, above,
		296	this value might change only once per event loop iteration, depending on
		297	the event loop (most return the same time as C<time>, above). This is the
		298	time that AnyEvent's timers get scheduled against.
144		299
145	Flag the condition as ready - a running C<< ->wait >> and all further	300	I<In almost all cases (in all cases if you don't care), this is the
146	calls to C<wait> will return after this method has been called. If nobody	301	function to call when you want to know the current time.>
147	is waiting the broadcast will be remembered..
148		302
149	Example:	303	This function is also often faster then C<< AnyEvent->time >>, and
		304	thus the preferred method if you want some timestamp (for example,
		305	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		306
		307	The rest of this section is only of relevance if you try to be very exact
		308	with your timing, you can skip it without bad conscience.
		309
		310	For a practical example of when these times differ, consider L<Event::Lib>
		311	and L<EV> and the following set-up:
		312
		313	The event loop is running and has just invoked one of your callback at
		314	time=500 (assume no other callbacks delay processing). In your callback,
		315	you wait a second by executing C<sleep 1> (blocking the process for a
		316	second) and then (at time=501) you create a relative timer that fires
		317	after three seconds.
		318
		319	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		320	both return C<501>, because that is the current time, and the timer will
		321	be scheduled to fire at time=504 (C<501> + C<3>).
		322
		323	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		324	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		325	last event processing phase started. With L<EV>, your timer gets scheduled
		326	to run at time=503 (C<500> + C<3>).
		327
		328	In one sense, L<Event::Lib> is more exact, as it uses the current time
		329	regardless of any delays introduced by event processing. However, most
		330	callbacks do not expect large delays in processing, so this causes a
		331	higher drift (and a lot more system calls to get the current time).
		332
		333	In another sense, L<EV> is more exact, as your timer will be scheduled at
		334	the same time, regardless of how long event processing actually took.
		335
		336	In either case, if you care (and in most cases, you don't), then you
		337	can get whatever behaviour you want with any event loop, by taking the
		338	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		339	account.
		340
		341	=item AnyEvent->now_update
		342
		343	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		344	the current time for each loop iteration (see the discussion of L<<
		345	AnyEvent->now >>, above).
		346
		347	When a callback runs for a long time (or when the process sleeps), then
		348	this "current" time will differ substantially from the real time, which
		349	might affect timers and time-outs.
		350
		351	When this is the case, you can call this method, which will update the
		352	event loop's idea of "current time".
		353
		354	Note that updating the time I<might> cause some events to be handled.
		355
		356	=back
		357
		358	=head2 SIGNAL WATCHERS
		359
		360	You can watch for signals using a signal watcher, C<signal> is the signal
		361	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
		362	callback to be invoked whenever a signal occurs.
		363
		364	Although the callback might get passed parameters, their value and
		365	presence is undefined and you cannot rely on them. Portable AnyEvent
		366	callbacks cannot use arguments passed to signal watcher callbacks.
		367
		368	Multiple signal occurrences can be clumped together into one callback
		369	invocation, and callback invocation will be synchronous. Synchronous means
		370	that it might take a while until the signal gets handled by the process,
		371	but it is guaranteed not to interrupt any other callbacks.
		372
		373	The main advantage of using these watchers is that you can share a signal
		374	between multiple watchers, and AnyEvent will ensure that signals will not
		375	interrupt your program at bad times.
		376
		377	This watcher might use C<%SIG> (depending on the event loop used),
		378	so programs overwriting those signals directly will likely not work
		379	correctly.
		380
		381	Example: exit on SIGINT
		382
		383	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		384
		385	=head3 Signal Races, Delays and Workarounds
		386
		387	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		388	callbacks to signals in a generic way, which is a pity, as you cannot do
		389	race-free signal handling in perl. AnyEvent will try to do it's best, but
		390	in some cases, signals will be delayed. The maximum time a signal might
		391	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		392	seconds). This variable can be changed only before the first signal
		393	watcher is created, and should be left alone otherwise. Higher values
		394	will cause fewer spurious wake-ups, which is better for power and CPU
		395	saving. All these problems can be avoided by installing the optional
		396	L<Async::Interrupt> module. This will not work with inherently broken
		397	event loops such as L<Event> or L<Event::Lib> (and not with L<POE>
		398	currently, as POE does it's own workaround with one-second latency). With
		399	those, you just have to suffer the delays.
		400
		401	=head2 CHILD PROCESS WATCHERS
		402
		403	You can also watch on a child process exit and catch its exit status.
		404
		405	The child process is specified by the C<pid> argument (one some backends,
		406	using C<0> watches for any child process exit, on others this will
		407	croak). The watcher will be triggered only when the child process has
		408	finished and an exit status is available, not on any trace events
		409	(stopped/continued).
		410
		411	The callback will be called with the pid and exit status (as returned by
		412	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		413	callback arguments.
		414
		415	This watcher type works by installing a signal handler for C<SIGCHLD>,
		416	and since it cannot be shared, nothing else should use SIGCHLD or reap
		417	random child processes (waiting for specific child processes, e.g. inside
		418	C<system>, is just fine).
		419
		420	There is a slight catch to child watchers, however: you usually start them
		421	I<after> the child process was created, and this means the process could
		422	have exited already (and no SIGCHLD will be sent anymore).
		423
		424	Not all event models handle this correctly (neither POE nor IO::Async do,
		425	see their AnyEvent::Impl manpages for details), but even for event models
		426	that I<do> handle this correctly, they usually need to be loaded before
		427	the process exits (i.e. before you fork in the first place). AnyEvent's
		428	pure perl event loop handles all cases correctly regardless of when you
		429	start the watcher.
		430
		431	This means you cannot create a child watcher as the very first
		432	thing in an AnyEvent program, you I<have> to create at least one
		433	watcher before you C<fork> the child (alternatively, you can call
		434	C<AnyEvent::detect>).
		435
		436	As most event loops do not support waiting for child events, they will be
		437	emulated by AnyEvent in most cases, in which the latency and race problems
		438	mentioned in the description of signal watchers apply.
		439
		440	Example: fork a process and wait for it
		441
		442	my $done = AnyEvent->condvar;
		443
		444	my $pid = fork or exit 5;
		445
		446	my $w = AnyEvent->child (
		447	pid => $pid,
		448	cb => sub {
		449	my ($pid, $status) = @_;
		450	warn "pid $pid exited with status $status";
		451	$done->send;
		452	},
		453	);
		454
		455	# do something else, then wait for process exit
		456	$done->recv;
		457
		458	=head2 IDLE WATCHERS
		459
		460	Sometimes there is a need to do something, but it is not so important
		461	to do it instantly, but only when there is nothing better to do. This
		462	"nothing better to do" is usually defined to be "no other events need
		463	attention by the event loop".
		464
		465	Idle watchers ideally get invoked when the event loop has nothing
		466	better to do, just before it would block the process to wait for new
		467	events. Instead of blocking, the idle watcher is invoked.
		468
		469	Most event loops unfortunately do not really support idle watchers (only
		470	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		471	will simply call the callback "from time to time".
		472
		473	Example: read lines from STDIN, but only process them when the
		474	program is otherwise idle:
		475
		476	my @lines; # read data
		477	my $idle_w;
		478	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		479	push @lines, scalar <STDIN>;
		480
		481	# start an idle watcher, if not already done
		482	$idle_w ||= AnyEvent->idle (cb => sub {
		483	# handle only one line, when there are lines left
		484	if (my $line = shift @lines) {
		485	print "handled when idle: $line";
		486	} else {
		487	# otherwise disable the idle watcher again
		488	undef $idle_w;
		489	}
		490	});
		491	});
		492
		493	=head2 CONDITION VARIABLES
		494
		495	If you are familiar with some event loops you will know that all of them
		496	require you to run some blocking "loop", "run" or similar function that
		497	will actively watch for new events and call your callbacks.
		498
		499	AnyEvent is slightly different: it expects somebody else to run the event
		500	loop and will only block when necessary (usually when told by the user).
		501
		502	The instrument to do that is called a "condition variable", so called
		503	because they represent a condition that must become true.
		504
		505	Now is probably a good time to look at the examples further below.
		506
		507	Condition variables can be created by calling the C<< AnyEvent->condvar
		508	>> method, usually without arguments. The only argument pair allowed is
		509	C<cb>, which specifies a callback to be called when the condition variable
		510	becomes true, with the condition variable as the first argument (but not
		511	the results).
		512
		513	After creation, the condition variable is "false" until it becomes "true"
		514	by calling the C<send> method (or calling the condition variable as if it
		515	were a callback, read about the caveats in the description for the C<<
		516	->send >> method).
		517
		518	Condition variables are similar to callbacks, except that you can
		519	optionally wait for them. They can also be called merge points - points
		520	in time where multiple outstanding events have been processed. And yet
		521	another way to call them is transactions - each condition variable can be
		522	used to represent a transaction, which finishes at some point and delivers
		523	a result. And yet some people know them as "futures" - a promise to
		524	compute/deliver something that you can wait for.
		525
		526	Condition variables are very useful to signal that something has finished,
		527	for example, if you write a module that does asynchronous http requests,
		528	then a condition variable would be the ideal candidate to signal the
		529	availability of results. The user can either act when the callback is
		530	called or can synchronously C<< ->recv >> for the results.
		531
		532	You can also use them to simulate traditional event loops - for example,
		533	you can block your main program until an event occurs - for example, you
		534	could C<< ->recv >> in your main program until the user clicks the Quit
		535	button of your app, which would C<< ->send >> the "quit" event.
		536
		537	Note that condition variables recurse into the event loop - if you have
		538	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
		539	lose. Therefore, condition variables are good to export to your caller, but
		540	you should avoid making a blocking wait yourself, at least in callbacks,
		541	as this asks for trouble.
		542
		543	Condition variables are represented by hash refs in perl, and the keys
		544	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		545	easy (it is often useful to build your own transaction class on top of
		546	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		547	it's C<new> method in your own C<new> method.
		548
		549	There are two "sides" to a condition variable - the "producer side" which
		550	eventually calls C<< -> send >>, and the "consumer side", which waits
		551	for the send to occur.
		552
		553	Example: wait for a timer.
150		554
151	# wait till the result is ready	555	# wait till the result is ready
152	my $result_ready = AnyEvent->condvar;	556	my $result_ready = AnyEvent->condvar;
153		557
154	# do something such as adding a timer	558	# do something such as adding a timer
155	# or socket watcher the calls $result_ready->broadcast	559	# or socket watcher the calls $result_ready->send
156	# when the "result" is ready.	560	# when the "result" is ready.
		561	# in this case, we simply use a timer:
		562	my $w = AnyEvent->timer (
		563	after => 1,
		564	cb => sub { $result_ready->send },
		565	);
157		566
		567	# this "blocks" (while handling events) till the callback
		568	# calls -<send
158	$result_ready->wait;	569	$result_ready->recv;
		570
		571	Example: wait for a timer, but take advantage of the fact that condition
		572	variables are also callable directly.
		573
		574	my $done = AnyEvent->condvar;
		575	my $delay = AnyEvent->timer (after => 5, cb => $done);
		576	$done->recv;
		577
		578	Example: Imagine an API that returns a condvar and doesn't support
		579	callbacks. This is how you make a synchronous call, for example from
		580	the main program:
		581
		582	use AnyEvent::CouchDB;
		583
		584	...
		585
		586	my @info = $couchdb->info->recv;
		587
		588	And this is how you would just set a callback to be called whenever the
		589	results are available:
		590
		591	$couchdb->info->cb (sub {
		592	my @info = $_[0]->recv;
		593	});
		594
		595	=head3 METHODS FOR PRODUCERS
		596
		597	These methods should only be used by the producing side, i.e. the
		598	code/module that eventually sends the signal. Note that it is also
		599	the producer side which creates the condvar in most cases, but it isn't
		600	uncommon for the consumer to create it as well.
		601
		602	=over 4
		603
		604	=item $cv->send (...)
		605
		606	Flag the condition as ready - a running C<< ->recv >> and all further
		607	calls to C<recv> will (eventually) return after this method has been
		608	called. If nobody is waiting the send will be remembered.
		609
		610	If a callback has been set on the condition variable, it is called
		611	immediately from within send.
		612
		613	Any arguments passed to the C<send> call will be returned by all
		614	future C<< ->recv >> calls.
		615
		616	Condition variables are overloaded so one can call them directly (as if
		617	they were a code reference). Calling them directly is the same as calling
		618	C<send>.
		619
		620	=item $cv->croak ($error)
		621
		622	Similar to send, but causes all call's to C<< ->recv >> to invoke
		623	C<Carp::croak> with the given error message/object/scalar.
		624
		625	This can be used to signal any errors to the condition variable
		626	user/consumer. Doing it this way instead of calling C<croak> directly
		627	delays the error detetcion, but has the overwhelmign advantage that it
		628	diagnoses the error at the place where the result is expected, and not
		629	deep in some event clalback without connection to the actual code causing
		630	the problem.
		631
		632	=item $cv->begin ([group callback])
		633
		634	=item $cv->end
		635
		636	These two methods can be used to combine many transactions/events into
		637	one. For example, a function that pings many hosts in parallel might want
		638	to use a condition variable for the whole process.
		639
		640	Every call to C<< ->begin >> will increment a counter, and every call to
		641	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		642	>>, the (last) callback passed to C<begin> will be executed. That callback
		643	is I<supposed> to call C<< ->send >>, but that is not required. If no
		644	callback was set, C<send> will be called without any arguments.
		645
		646	You can think of C<< $cv->send >> giving you an OR condition (one call
		647	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		648	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		649
		650	Let's start with a simple example: you have two I/O watchers (for example,
		651	STDOUT and STDERR for a program), and you want to wait for both streams to
		652	close before activating a condvar:
		653
		654	my $cv = AnyEvent->condvar;
		655
		656	$cv->begin; # first watcher
		657	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		658	defined sysread $fh1, my $buf, 4096
		659	or $cv->end;
		660	});
		661
		662	$cv->begin; # second watcher
		663	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		664	defined sysread $fh2, my $buf, 4096
		665	or $cv->end;
		666	});
		667
		668	$cv->recv;
		669
		670	This works because for every event source (EOF on file handle), there is
		671	one call to C<begin>, so the condvar waits for all calls to C<end> before
		672	sending.
		673
		674	The ping example mentioned above is slightly more complicated, as the
		675	there are results to be passwd back, and the number of tasks that are
		676	begung can potentially be zero:
		677
		678	my $cv = AnyEvent->condvar;
		679
		680	my %result;
		681	$cv->begin (sub { $cv->send (\%result) });
		682
		683	for my $host (@list_of_hosts) {
		684	$cv->begin;
		685	ping_host_then_call_callback $host, sub {
		686	$result{$host} = ...;
		687	$cv->end;
		688	};
		689	}
		690
		691	$cv->end;
		692
		693	This code fragment supposedly pings a number of hosts and calls
		694	C<send> after results for all then have have been gathered - in any
		695	order. To achieve this, the code issues a call to C<begin> when it starts
		696	each ping request and calls C<end> when it has received some result for
		697	it. Since C<begin> and C<end> only maintain a counter, the order in which
		698	results arrive is not relevant.
		699
		700	There is an additional bracketing call to C<begin> and C<end> outside the
		701	loop, which serves two important purposes: first, it sets the callback
		702	to be called once the counter reaches C<0>, and second, it ensures that
		703	C<send> is called even when C<no> hosts are being pinged (the loop
		704	doesn't execute once).
		705
		706	This is the general pattern when you "fan out" into multiple (but
		707	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		708	the callback and ensure C<end> is called at least once, and then, for each
		709	subrequest you start, call C<begin> and for each subrequest you finish,
		710	call C<end>.
159		711
160	=back	712	=back
161		713
162	=head2 SIGNAL WATCHERS	714	=head3 METHODS FOR CONSUMERS
163		715
164	You can listen for signals using a signal watcher, C<signal> is the signal	716	These methods should only be used by the consuming side, i.e. the
165	I<name> without any C<SIG> prefix. Multiple signals events can be clumped	717	code awaits the condition.
166	together into one callback invocation, and callback invocation might or
167	might not be asynchronous.
168
169	These watchers might use C<%SIG>, so programs overwriting those signals
170	directly will likely not work correctly.
171
172	Example: exit on SIGINT
173
174	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
175
176	=head2 CHILD PROCESS WATCHERS
177
178	You can also listen for the status of a child process specified by the
179	C<pid> argument (or any child if the pid argument is 0). The watcher will
180	trigger as often as status change for the child are received. This works
181	by installing a signal handler for C<SIGCHLD>. The callback will be called with
182	the pid and exit status (as returned by waitpid).
183
184	Example: wait for pid 1333
185
186	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
187
188	=head1 GLOBALS
189		718
190	=over 4	719	=over 4
191		720
		721	=item $cv->recv
		722
		723	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		724	>> methods have been called on c<$cv>, while servicing other watchers
		725	normally.
		726
		727	You can only wait once on a condition - additional calls are valid but
		728	will return immediately.
		729
		730	If an error condition has been set by calling C<< ->croak >>, then this
		731	function will call C<croak>.
		732
		733	In list context, all parameters passed to C<send> will be returned,
		734	in scalar context only the first one will be returned.
		735
		736	Note that doing a blocking wait in a callback is not supported by any
		737	event loop, that is, recursive invocation of a blocking C<< ->recv
		738	>> is not allowed, and the C<recv> call will C<croak> if such a
		739	condition is detected. This condition can be slightly loosened by using
		740	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		741	any thread that doesn't run the event loop itself.
		742
		743	Not all event models support a blocking wait - some die in that case
		744	(programs might want to do that to stay interactive), so I<if you are
		745	using this from a module, never require a blocking wait>. Instead, let the
		746	caller decide whether the call will block or not (for example, by coupling
		747	condition variables with some kind of request results and supporting
		748	callbacks so the caller knows that getting the result will not block,
		749	while still supporting blocking waits if the caller so desires).
		750
		751	You can ensure that C<< -recv >> never blocks by setting a callback and
		752	only calling C<< ->recv >> from within that callback (or at a later
		753	time). This will work even when the event loop does not support blocking
		754	waits otherwise.
		755
		756	=item $bool = $cv->ready
		757
		758	Returns true when the condition is "true", i.e. whether C<send> or
		759	C<croak> have been called.
		760
		761	=item $cb = $cv->cb ($cb->($cv))
		762
		763	This is a mutator function that returns the callback set and optionally
		764	replaces it before doing so.
		765
		766	The callback will be called when the condition becomes "true", i.e. when
		767	C<send> or C<croak> are called, with the only argument being the condition
		768	variable itself. Calling C<recv> inside the callback or at any later time
		769	is guaranteed not to block.
		770
		771	=back
		772
		773	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		774
		775	The available backend classes are (every class has its own manpage):
		776
		777	=over 4
		778
		779	=item Backends that are autoprobed when no other event loop can be found.
		780
		781	EV is the preferred backend when no other event loop seems to be in
		782	use. If EV is not installed, then AnyEvent will try Event, and, failing
		783	that, will fall back to its own pure-perl implementation, which is
		784	available everywhere as it comes with AnyEvent itself.
		785
		786	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		787	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		788	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		789
		790	=item Backends that are transparently being picked up when they are used.
		791
		792	These will be used when they are currently loaded when the first watcher
		793	is created, in which case it is assumed that the application is using
		794	them. This means that AnyEvent will automatically pick the right backend
		795	when the main program loads an event module before anything starts to
		796	create watchers. Nothing special needs to be done by the main program.
		797
		798	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		799	AnyEvent::Impl::Tk based on Tk, very broken.
		800	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		801	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		802	AnyEvent::Impl::Irssi used when running within irssi.
		803
		804	=item Backends with special needs.
		805
		806	Qt requires the Qt::Application to be instantiated first, but will
		807	otherwise be picked up automatically. As long as the main program
		808	instantiates the application before any AnyEvent watchers are created,
		809	everything should just work.
		810
		811	AnyEvent::Impl::Qt based on Qt.
		812
		813	Support for IO::Async can only be partial, as it is too broken and
		814	architecturally limited to even support the AnyEvent API. It also
		815	is the only event loop that needs the loop to be set explicitly, so
		816	it can only be used by a main program knowing about AnyEvent. See
		817	L<AnyEvent::Impl::Async> for the gory details.
		818
		819	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		820
		821	=item Event loops that are indirectly supported via other backends.
		822
		823	Some event loops can be supported via other modules:
		824
		825	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		826
		827	B<WxWidgets> has no support for watching file handles. However, you can
		828	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		829	polls 20 times per second, which was considered to be too horrible to even
		830	consider for AnyEvent.
		831
		832	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		833	backend, so it can be supported through POE.
		834
		835	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		836	load L<POE> when detecting them, in the hope that POE will pick them up,
		837	in which case everything will be automatic.
		838
		839	=back
		840
		841	=head1 GLOBAL VARIABLES AND FUNCTIONS
		842
		843	These are not normally required to use AnyEvent, but can be useful to
		844	write AnyEvent extension modules.
		845
		846	=over 4
		847
192	=item $AnyEvent::MODEL	848	=item $AnyEvent::MODEL
193		849
194	Contains C<undef> until the first watcher is being created. Then it	850	Contains C<undef> until the first watcher is being created, before the
		851	backend has been autodetected.
		852
195	contains the event model that is being used, which is the name of the	853	Afterwards it contains the event model that is being used, which is the
196	Perl class implementing the model. This class is usually one of the	854	name of the Perl class implementing the model. This class is usually one
197	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	855	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
198	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	856	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
199		857	will be C<urxvt::anyevent>).
200	The known classes so far are:
201
202	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
203	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
204	AnyEvent::Impl::Coro based on Coro::Event, second best choice.
205	AnyEvent::Impl::Event based on Event, also second best choice :)
206	AnyEvent::Impl::Glib based on Glib, second-best choice.
207	AnyEvent::Impl::Tk based on Tk, very bad choice.
208	AnyEvent::Impl::Perl pure-perl implementation, inefficient.
209		858
210	=item AnyEvent::detect	859	=item AnyEvent::detect
211		860
212	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	861	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
213	necessary. You should only call this function right before you would have	862	if necessary. You should only call this function right before you would
214	created an AnyEvent watcher anyway, that is, very late at runtime.	863	have created an AnyEvent watcher anyway, that is, as late as possible at
		864	runtime, and not e.g. while initialising of your module.
		865
		866	If you need to do some initialisation before AnyEvent watchers are
		867	created, use C<post_detect>.
		868
		869	=item $guard = AnyEvent::post_detect { BLOCK }
		870
		871	Arranges for the code block to be executed as soon as the event model is
		872	autodetected (or immediately if this has already happened).
		873
		874	The block will be executed I<after> the actual backend has been detected
		875	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		876	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		877	other initialisations - see the sources of L<AnyEvent::Strict> or
		878	L<AnyEvent::AIO> to see how this is used.
		879
		880	The most common usage is to create some global watchers, without forcing
		881	event module detection too early, for example, L<AnyEvent::AIO> creates
		882	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		883	avoid autodetecting the event module at load time.
		884
		885	If called in scalar or list context, then it creates and returns an object
		886	that automatically removes the callback again when it is destroyed (or
		887	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		888	a case where this is useful.
		889
		890	Example: Create a watcher for the IO::AIO module and store it in
		891	C<$WATCHER>. Only do so after the event loop is initialised, though.
		892
		893	our WATCHER;
		894
		895	my $guard = AnyEvent::post_detect {
		896	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		897	};
		898
		899	# the ||= is important in case post_detect immediately runs the block,
		900	# as to not clobber the newly-created watcher. assigning both watcher and
		901	# post_detect guard to the same variable has the advantage of users being
		902	# able to just C<undef $WATCHER> if the watcher causes them grief.
		903
		904	$WATCHER ||= $guard;
		905
		906	=item @AnyEvent::post_detect
		907
		908	If there are any code references in this array (you can C<push> to it
		909	before or after loading AnyEvent), then they will called directly after
		910	the event loop has been chosen.
		911
		912	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		913	if it is defined then the event loop has already been detected, and the
		914	array will be ignored.
		915
		916	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		917	it,as it takes care of these details.
		918
		919	This variable is mainly useful for modules that can do something useful
		920	when AnyEvent is used and thus want to know when it is initialised, but do
		921	not need to even load it by default. This array provides the means to hook
		922	into AnyEvent passively, without loading it.
215		923
216	=back	924	=back
217		925
218	=head1 WHAT TO DO IN A MODULE	926	=head1 WHAT TO DO IN A MODULE
219		927
220	As a module author, you should "use AnyEvent" and call AnyEvent methods	928	As a module author, you should C<use AnyEvent> and call AnyEvent methods
221	freely, but you should not load a specific event module or rely on it.	929	freely, but you should not load a specific event module or rely on it.
222		930
223	Be careful when you create watchers in the module body - Anyevent will	931	Be careful when you create watchers in the module body - AnyEvent will
224	decide which event module to use as soon as the first method is called, so	932	decide which event module to use as soon as the first method is called, so
225	by calling AnyEvent in your module body you force the user of your module	933	by calling AnyEvent in your module body you force the user of your module
226	to load the event module first.	934	to load the event module first.
227		935
		936	Never call C<< ->recv >> on a condition variable unless you I<know> that
		937	the C<< ->send >> method has been called on it already. This is
		938	because it will stall the whole program, and the whole point of using
		939	events is to stay interactive.
		940
		941	It is fine, however, to call C<< ->recv >> when the user of your module
		942	requests it (i.e. if you create a http request object ad have a method
		943	called C<results> that returns the results, it should call C<< ->recv >>
		944	freely, as the user of your module knows what she is doing. always).
		945
228	=head1 WHAT TO DO IN THE MAIN PROGRAM	946	=head1 WHAT TO DO IN THE MAIN PROGRAM
229		947
230	There will always be a single main program - the only place that should	948	There will always be a single main program - the only place that should
231	dictate which event model to use.	949	dictate which event model to use.
232		950
233	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	951	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
234	do anything special and let AnyEvent decide which implementation to chose.	952	do anything special (it does not need to be event-based) and let AnyEvent
		953	decide which implementation to chose if some module relies on it.
235		954
236	If the main program relies on a specific event model (for example, in Gtk2	955	If the main program relies on a specific event model - for example, in
237	programs you have to rely on either Glib or Glib::Event), you should load	956	Gtk2 programs you have to rely on the Glib module - you should load the
238	it before loading AnyEvent or any module that uses it, generally, as early	957	event module before loading AnyEvent or any module that uses it: generally
239	as possible. The reason is that modules might create watchers when they	958	speaking, you should load it as early as possible. The reason is that
240	are loaded, and AnyEvent will decide on the event model to use as soon as	959	modules might create watchers when they are loaded, and AnyEvent will
241	it creates watchers, and it might chose the wrong one unless you load the	960	decide on the event model to use as soon as it creates watchers, and it
242	correct one yourself.	961	might chose the wrong one unless you load the correct one yourself.
243		962
244	You can chose to use a rather inefficient pure-perl implementation by	963	You can chose to use a pure-perl implementation by loading the
245	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	964	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
246	generally better.	965	everywhere, but letting AnyEvent chose the model is generally better.
		966
		967	=head2 MAINLOOP EMULATION
		968
		969	Sometimes (often for short test scripts, or even standalone programs who
		970	only want to use AnyEvent), you do not want to run a specific event loop.
		971
		972	In that case, you can use a condition variable like this:
		973
		974	AnyEvent->condvar->recv;
		975
		976	This has the effect of entering the event loop and looping forever.
		977
		978	Note that usually your program has some exit condition, in which case
		979	it is better to use the "traditional" approach of storing a condition
		980	variable somewhere, waiting for it, and sending it when the program should
		981	exit cleanly.
		982
		983
		984	=head1 OTHER MODULES
		985
		986	The following is a non-exhaustive list of additional modules that use
		987	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		988	modules and other event loops in the same program. Some of the modules
		989	come with AnyEvent, most are available via CPAN.
		990
		991	=over 4
		992
		993	=item L<AnyEvent::Util>
		994
		995	Contains various utility functions that replace often-used but blocking
		996	functions such as C<inet_aton> by event-/callback-based versions.
		997
		998	=item L<AnyEvent::Socket>
		999
		1000	Provides various utility functions for (internet protocol) sockets,
		1001	addresses and name resolution. Also functions to create non-blocking tcp
		1002	connections or tcp servers, with IPv6 and SRV record support and more.
		1003
		1004	=item L<AnyEvent::Handle>
		1005
		1006	Provide read and write buffers, manages watchers for reads and writes,
		1007	supports raw and formatted I/O, I/O queued and fully transparent and
		1008	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1009
		1010	=item L<AnyEvent::DNS>
		1011
		1012	Provides rich asynchronous DNS resolver capabilities.
		1013
		1014	=item L<AnyEvent::HTTP>
		1015
		1016	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1017	HTTP requests.
		1018
		1019	=item L<AnyEvent::HTTPD>
		1020
		1021	Provides a simple web application server framework.
		1022
		1023	=item L<AnyEvent::FastPing>
		1024
		1025	The fastest ping in the west.
		1026
		1027	=item L<AnyEvent::DBI>
		1028
		1029	Executes L<DBI> requests asynchronously in a proxy process.
		1030
		1031	=item L<AnyEvent::AIO>
		1032
		1033	Truly asynchronous I/O, should be in the toolbox of every event
		1034	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1035	together.
		1036
		1037	=item L<AnyEvent::BDB>
		1038
		1039	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1040	L<BDB> and AnyEvent together.
		1041
		1042	=item L<AnyEvent::GPSD>
		1043
		1044	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1045
		1046	=item L<AnyEvent::IRC>
		1047
		1048	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1049
		1050	=item L<AnyEvent::XMPP>
		1051
		1052	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1053	Net::XMPP2>.
		1054
		1055	=item L<AnyEvent::IGS>
		1056
		1057	A non-blocking interface to the Internet Go Server protocol (used by
		1058	L<App::IGS>).
		1059
		1060	=item L<Net::FCP>
		1061
		1062	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1063	of AnyEvent.
		1064
		1065	=item L<Event::ExecFlow>
		1066
		1067	High level API for event-based execution flow control.
		1068
		1069	=item L<Coro>
		1070
		1071	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1072
		1073	=back
247		1074
248	=cut	1075	=cut
249		1076
250	package AnyEvent;	1077	package AnyEvent;
251		1078
		1079	# basically a tuned-down version of common::sense
		1080	sub common_sense {
252	no warnings;	1081	# no warnings
253	use strict;	1082	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1083	# use strict vars subs
		1084	$^H |= 0x00000600;
		1085	}
254		1086
		1087	BEGIN { AnyEvent::common_sense }
		1088
255	use Carp;	1089	use Carp ();
256		1090
257	our $VERSION = '2.9';	1091	our $VERSION = 4.881;
258	our $MODEL;	1092	our $MODEL;
259		1093
260	our $AUTOLOAD;	1094	our $AUTOLOAD;
261	our @ISA;	1095	our @ISA;
262		1096
263	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
264
265	our @REGISTRY;	1097	our @REGISTRY;
266		1098
		1099	our $WIN32;
		1100
		1101	our $VERBOSE;
		1102
		1103	BEGIN {
		1104	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1105	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1106
		1107	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1108	if ${^TAINT};
		1109
		1110	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1111
		1112	}
		1113
		1114	our $MAX_SIGNAL_LATENCY = 10;
		1115
		1116	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1117
		1118	{
		1119	my $idx;
		1120	$PROTOCOL{$_} = ++$idx
		1121	for reverse split /\s*,\s*/,
		1122	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1123	}
		1124
267	my @models = (	1125	my @models = (
268	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
269	[EV:: => AnyEvent::Impl::EV::],	1126	[EV:: => AnyEvent::Impl::EV:: , 1],
270	[Coro::Event:: => AnyEvent::Impl::Coro::],
271	[Event:: => AnyEvent::Impl::Event::],	1127	[Event:: => AnyEvent::Impl::Event::, 1],
272	[Glib:: => AnyEvent::Impl::Glib::],
273	[Tk:: => AnyEvent::Impl::Tk::],
274	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1128	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1129	# everything below here will not (normally) be autoprobed
		1130	# as the pureperl backend should work everywhere
		1131	# and is usually faster
		1132	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1133	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1134	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1135	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1136	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1137	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		1138	[Wx:: => AnyEvent::Impl::POE::],
		1139	[Prima:: => AnyEvent::Impl::POE::],
		1140	# IO::Async is just too broken - we would need workarounds for its
		1141	# byzantine signal and broken child handling, among others.
		1142	# IO::Async is rather hard to detect, as it doesn't have any
		1143	# obvious default class.
		1144	# [0, IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1145	# [0, IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1146	# [0, IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
275	);	1147	);
276		1148
277	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1149	our %method = map +($_ => 1),
		1150	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1151
		1152	our @post_detect;
		1153
		1154	sub post_detect(&) {
		1155	my ($cb) = @_;
		1156
		1157	if ($MODEL) {
		1158	$cb->();
		1159
		1160	undef
		1161	} else {
		1162	push @post_detect, $cb;
		1163
		1164	defined wantarray
		1165	? bless \$cb, "AnyEvent::Util::postdetect"
		1166	: ()
		1167	}
		1168	}
		1169
		1170	sub AnyEvent::Util::postdetect::DESTROY {
		1171	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1172	}
278		1173
279	sub detect() {	1174	sub detect() {
280	unless ($MODEL) {	1175	unless ($MODEL) {
281	no strict 'refs';	1176	local $SIG{__DIE__};
		1177
		1178	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1179	my $model = "AnyEvent::Impl::$1";
		1180	if (eval "require $model") {
		1181	$MODEL = $model;
		1182	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1183	} else {
		1184	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1185	}
		1186	}
282		1187
283	# check for already loaded models	1188	# check for already loaded models
		1189	unless ($MODEL) {
284	for (@REGISTRY, @models) {	1190	for (@REGISTRY, @models) {
285	my ($package, $model) = @$_;	1191	my ($package, $model) = @$_;
286	if (${"$package\::VERSION"} > 0) {	1192	if (${"$package\::VERSION"} > 0) {
287	if (eval "require $model") {	1193	if (eval "require $model") {
288	$MODEL = $model;	1194	$MODEL = $model;
289	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	1195	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
290	last;	1196	last;
		1197	}
291	}	1198	}
292	}	1199	}
		1200
		1201	unless ($MODEL) {
		1202	# try to autoload a model
		1203	for (@REGISTRY, @models) {
		1204	my ($package, $model, $autoload) = @$_;
		1205	if (
		1206	$autoload
		1207	and eval "require $package"
		1208	and ${"$package\::VERSION"} > 0
		1209	and eval "require $model"
		1210	) {
		1211	$MODEL = $model;
		1212	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
		1213	last;
		1214	}
		1215	}
		1216
		1217	$MODEL
		1218	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
		1219	}
293	}	1220	}
294		1221
295	unless ($MODEL) {	1222	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
296	# try to load a model
297
298	for (@REGISTRY, @models) {
299	my ($package, $model) = @$_;
300	if (eval "require $package"
301	and ${"$package\::VERSION"} > 0
302	and eval "require $model") {
303	$MODEL = $model;
304	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
305	last;
306	}
307	}
308
309	$MODEL
310	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event), Glib or Tk.";
311	}
312		1223
313	unshift @ISA, $MODEL;	1224	unshift @ISA, $MODEL;
314	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1225
		1226	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1227
		1228	(shift @post_detect)->() while @post_detect;
315	}	1229	}
316		1230
317	$MODEL	1231	$MODEL
318	}	1232	}
319		1233
320	sub AUTOLOAD {	1234	sub AUTOLOAD {
321	(my $func = $AUTOLOAD) =~ s/.*://;	1235	(my $func = $AUTOLOAD) =~ s/.*://;
322		1236
323	$method{$func}	1237	$method{$func}
324	or croak "$func: not a valid method for AnyEvent objects";	1238	or Carp::croak "$func: not a valid method for AnyEvent objects";
325		1239
326	detect unless $MODEL;	1240	detect unless $MODEL;
327		1241
328	my $class = shift;	1242	my $class = shift;
329	$class->$func (@_);	1243	$class->$func (@_);
330	}	1244	}
331		1245
		1246	# utility function to dup a filehandle. this is used by many backends
		1247	# to support binding more than one watcher per filehandle (they usually
		1248	# allow only one watcher per fd, so we dup it to get a different one).
		1249	sub _dupfh($$;$$) {
		1250	my ($poll, $fh, $r, $w) = @_;
		1251
		1252	# cygwin requires the fh mode to be matching, unix doesn't
		1253	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1254
		1255	open my $fh2, $mode, $fh
		1256	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1257
		1258	# we assume CLOEXEC is already set by perl in all important cases
		1259
		1260	($fh2, $rw)
		1261	}
		1262
332	package AnyEvent::Base;	1263	package AnyEvent::Base;
333		1264
		1265	# default implementations for many methods
		1266
		1267	sub _time {
		1268	# probe for availability of Time::HiRes
		1269	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1270	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1271	*_time = \&Time::HiRes::time;
		1272	# if (eval "use POSIX (); (POSIX::times())...
		1273	} else {
		1274	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1275	*_time = sub { time }; # epic fail
		1276	}
		1277
		1278	&_time
		1279	}
		1280
		1281	sub time { _time }
		1282	sub now { _time }
		1283	sub now_update { }
		1284
334	# default implementation for ->condvar, ->wait, ->broadcast	1285	# default implementation for ->condvar
335		1286
336	sub condvar {	1287	sub condvar {
337	bless \my $flag, "AnyEvent::Base::CondVar"	1288	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
338	}
339
340	sub AnyEvent::Base::CondVar::broadcast {
341	${$_[0]}++;
342	}
343
344	sub AnyEvent::Base::CondVar::wait {
345	AnyEvent->one_event while !${$_[0]};
346	}	1289	}
347		1290
348	# default implementation for ->signal	1291	# default implementation for ->signal
349		1292
350	our %SIG_CB;	1293	our $HAVE_ASYNC_INTERRUPT;
351		1294
		1295	sub _have_async_interrupt() {
		1296	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1297	&& eval "use Async::Interrupt 1.0 (); 1")
		1298	unless defined $HAVE_ASYNC_INTERRUPT;
		1299
		1300	$HAVE_ASYNC_INTERRUPT
		1301	}
		1302
		1303	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1304	our (%SIG_ASY, %SIG_ASY_W);
		1305	our ($SIG_COUNT, $SIG_TW);
		1306
		1307	sub _signal_exec {
		1308	$HAVE_ASYNC_INTERRUPT
		1309	? $SIGPIPE_R->drain
		1310	: sysread $SIGPIPE_R, my $dummy, 9;
		1311
		1312	while (%SIG_EV) {
		1313	for (keys %SIG_EV) {
		1314	delete $SIG_EV{$_};
		1315	$_->() for values %{ $SIG_CB{$_} || {} };
		1316	}
		1317	}
		1318	}
		1319
		1320	# install a dummy wakeup watcher to reduce signal catching latency
		1321	sub _sig_add() {
		1322	unless ($SIG_COUNT++) {
		1323	# try to align timer on a full-second boundary, if possible
		1324	my $NOW = AnyEvent->now;
		1325
		1326	$SIG_TW = AnyEvent->timer (
		1327	after => $MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1328	interval => $MAX_SIGNAL_LATENCY,
		1329	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1330	);
		1331	}
		1332	}
		1333
		1334	sub _sig_del {
		1335	undef $SIG_TW
		1336	unless --$SIG_COUNT;
		1337	}
		1338
		1339	our %SIGNAME2NUM;
		1340	our @SIGNUM2NAME;
		1341	our $_sig_name_init; $_sig_name_init = sub {
		1342	undef $_sig_name_init;
		1343
		1344	if (_have_async_interrupt) {
		1345	*sig2num = \&Async::Interrupt::sig2num;
		1346	*sig2name = \&Async::Interrupt::sig2name;
		1347	} else {
		1348	require Config;
		1349
		1350	@SIGNAME2NUM{ split ' ', $Config::Config{sig_name} }
		1351	= split ' ', $Config::Config{sig_num};
		1352	@SIGNUM2NAME[values %SIGNAME2NUM] = keys %SIGNAME2NUM;
		1353
		1354	*sig2num = sub($) {
		1355	$_[0] > 0 ? shift : $SIGNAME2NUM{+shift}
		1356	};
		1357	*sig2name = sub ($) {
		1358	$_[0] > 0 ? $SIGNUM2NAME[+shift] : shift
		1359	};
		1360	}
		1361	};
		1362
		1363	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1364	sub sig2name($) { &$_sig_name_init; &sig2name }
		1365
352	sub signal {	1366	sub _signal {
353	my (undef, %arg) = @_;	1367	my (undef, %arg) = @_;
354		1368
355	my $signal = uc $arg{signal}	1369	my $signal = uc $arg{signal}
356	or Carp::croak "required option 'signal' is missing";	1370	or Carp::croak "required option 'signal' is missing";
357		1371
		1372	if ($HAVE_ASYNC_INTERRUPT) {
		1373	# async::interrupt
		1374
		1375	$signal = sig2num $signal;
358	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1376	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1377
		1378	$SIG_ASY{$signal} ||= new Async::Interrupt
		1379	cb => sub { undef $SIG_EV{$signal} },
		1380	signal => $signal,
		1381	pipe => [$SIGPIPE_R->filenos],
		1382	pipe_autodrain => 0,
		1383	;
		1384
		1385	} else {
		1386	# pure perl
		1387
		1388	# AE::Util has been loaded in signal
		1389	$signal = sig2name $signal;
		1390	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1391
359	$SIG{$signal} ||= sub {	1392	$SIG{$signal} ||= sub {
360	$_->() for values %{ $SIG_CB{$signal} || {} };	1393	local $!;
		1394	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1395	undef $SIG_EV{$signal};
		1396	};
		1397
		1398	# can't do signal processing without introducing races in pure perl,
		1399	# so limit the signal latency.
		1400	_sig_add;
361	};	1401	}
362		1402
363	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1403	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
364	}	1404	}
365		1405
		1406	sub signal {
		1407	# probe for availability of Async::Interrupt
		1408	if (_have_async_interrupt) {
		1409	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1410
		1411	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1412	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1413
		1414	} else {
		1415	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1416
		1417	require Fcntl;
		1418
		1419	if (AnyEvent::WIN32) {
		1420	require AnyEvent::Util;
		1421
		1422	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1423	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1424	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1425	} else {
		1426	pipe $SIGPIPE_R, $SIGPIPE_W;
		1427	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1428	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1429
		1430	# not strictly required, as $^F is normally 2, but let's make sure...
		1431	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1432	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1433	}
		1434
		1435	$SIGPIPE_R
		1436	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1437
		1438	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1439	}
		1440
		1441	*signal = \&_signal;
		1442	&signal
		1443	}
		1444
366	sub AnyEvent::Base::Signal::DESTROY {	1445	sub AnyEvent::Base::signal::DESTROY {
367	my ($signal, $cb) = @{$_[0]};	1446	my ($signal, $cb) = @{$_[0]};
368		1447
		1448	_sig_del;
		1449
369	delete $SIG_CB{$signal}{$cb};	1450	delete $SIG_CB{$signal}{$cb};
370		1451
371	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1452	$HAVE_ASYNC_INTERRUPT
		1453	? delete $SIG_ASY{$signal}
		1454	: # delete doesn't work with older perls - they then
		1455	# print weird messages, or just unconditionally exit
		1456	# instead of getting the default action.
		1457	undef $SIG{$signal}
		1458	unless keys %{ $SIG_CB{$signal} };
372	}	1459	}
373		1460
374	# default implementation for ->child	1461	# default implementation for ->child
375		1462
376	our %PID_CB;	1463	our %PID_CB;
377	our $CHLD_W;	1464	our $CHLD_W;
378	our $CHLD_DELAY_W;	1465	our $CHLD_DELAY_W;
379	our $PID_IDLE;
380	our $WNOHANG;	1466	our $WNOHANG;
381		1467
382	sub _child_wait {	1468	sub _emit_childstatus($$) {
383	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1469	my (undef, $rpid, $rstatus) = @_;
		1470
		1471	$_->($rpid, $rstatus)
384	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1472	for values %{ $PID_CB{$rpid} || {} },
385	(values %{ $PID_CB{0} || {} });	1473	values %{ $PID_CB{0} || {} };
386	}
387
388	undef $PID_IDLE;
389	}	1474	}
390		1475
391	sub _sigchld {	1476	sub _sigchld {
392	# make sure we deliver these changes "synchronous" with the event loop.	1477	my $pid;
393	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1478
394	undef $CHLD_DELAY_W;	1479	AnyEvent->_emit_childstatus ($pid, $?)
395	&_child_wait;	1480	while ($pid = waitpid -1, $WNOHANG) > 0;
396	});
397	}	1481	}
398		1482
399	sub child {	1483	sub child {
400	my (undef, %arg) = @_;	1484	my (undef, %arg) = @_;
401		1485
402	defined (my $pid = $arg{pid} + 0)	1486	defined (my $pid = $arg{pid} + 0)
403	or Carp::croak "required option 'pid' is missing";	1487	or Carp::croak "required option 'pid' is missing";
404		1488
405	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1489	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
406		1490
407	unless ($WNOHANG) {	1491	# WNOHANG is almost cetrainly 1 everywhere
408	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1492	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
409	}	1493	? 1
		1494	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
410		1495
411	unless ($CHLD_W) {	1496	unless ($CHLD_W) {
412	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1497	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
413	# child could be a zombie already, so make at least one round	1498	# child could be a zombie already, so make at least one round
414	&_sigchld;	1499	&_sigchld;
415	}	1500	}
416		1501
417	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1502	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
418	}	1503	}
419		1504
420	sub AnyEvent::Base::Child::DESTROY {	1505	sub AnyEvent::Base::child::DESTROY {
421	my ($pid, $cb) = @{$_[0]};	1506	my ($pid, $cb) = @{$_[0]};
422		1507
423	delete $PID_CB{$pid}{$cb};	1508	delete $PID_CB{$pid}{$cb};
424	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1509	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
425		1510
426	undef $CHLD_W unless keys %PID_CB;	1511	undef $CHLD_W unless keys %PID_CB;
427	}	1512	}
428		1513
		1514	# idle emulation is done by simply using a timer, regardless
		1515	# of whether the process is idle or not, and not letting
		1516	# the callback use more than 50% of the time.
		1517	sub idle {
		1518	my (undef, %arg) = @_;
		1519
		1520	my ($cb, $w, $rcb) = $arg{cb};
		1521
		1522	$rcb = sub {
		1523	if ($cb) {
		1524	$w = _time;
		1525	&$cb;
		1526	$w = _time - $w;
		1527
		1528	# never use more then 50% of the time for the idle watcher,
		1529	# within some limits
		1530	$w = 0.0001 if $w < 0.0001;
		1531	$w = 5 if $w > 5;
		1532
		1533	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1534	} else {
		1535	# clean up...
		1536	undef $w;
		1537	undef $rcb;
		1538	}
		1539	};
		1540
		1541	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1542
		1543	bless \\$cb, "AnyEvent::Base::idle"
		1544	}
		1545
		1546	sub AnyEvent::Base::idle::DESTROY {
		1547	undef $${$_[0]};
		1548	}
		1549
		1550	package AnyEvent::CondVar;
		1551
		1552	our @ISA = AnyEvent::CondVar::Base::;
		1553
		1554	package AnyEvent::CondVar::Base;
		1555
		1556	#use overload
		1557	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1558	# fallback => 1;
		1559
		1560	# save 300+ kilobytes by dirtily hardcoding overloading
		1561	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1562	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1563	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1564	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1565
		1566	our $WAITING;
		1567
		1568	sub _send {
		1569	# nop
		1570	}
		1571
		1572	sub send {
		1573	my $cv = shift;
		1574	$cv->{_ae_sent} = [@_];
		1575	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1576	$cv->_send;
		1577	}
		1578
		1579	sub croak {
		1580	$_[0]{_ae_croak} = $_[1];
		1581	$_[0]->send;
		1582	}
		1583
		1584	sub ready {
		1585	$_[0]{_ae_sent}
		1586	}
		1587
		1588	sub _wait {
		1589	$WAITING
		1590	and !$_[0]{_ae_sent}
		1591	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1592
		1593	local $WAITING = 1;
		1594	AnyEvent->one_event while !$_[0]{_ae_sent};
		1595	}
		1596
		1597	sub recv {
		1598	$_[0]->_wait;
		1599
		1600	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1601	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1602	}
		1603
		1604	sub cb {
		1605	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1606	$_[0]{_ae_cb}
		1607	}
		1608
		1609	sub begin {
		1610	++$_[0]{_ae_counter};
		1611	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1612	}
		1613
		1614	sub end {
		1615	return if --$_[0]{_ae_counter};
		1616	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1617	}
		1618
		1619	# undocumented/compatibility with pre-3.4
		1620	*broadcast = \&send;
		1621	*wait = \&_wait;
		1622
		1623	=head1 ERROR AND EXCEPTION HANDLING
		1624
		1625	In general, AnyEvent does not do any error handling - it relies on the
		1626	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1627	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1628	checking of all AnyEvent methods, however, which is highly useful during
		1629	development.
		1630
		1631	As for exception handling (i.e. runtime errors and exceptions thrown while
		1632	executing a callback), this is not only highly event-loop specific, but
		1633	also not in any way wrapped by this module, as this is the job of the main
		1634	program.
		1635
		1636	The pure perl event loop simply re-throws the exception (usually
		1637	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1638	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1639	so on.
		1640
		1641	=head1 ENVIRONMENT VARIABLES
		1642
		1643	The following environment variables are used by this module or its
		1644	submodules.
		1645
		1646	Note that AnyEvent will remove I<all> environment variables starting with
		1647	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1648	enabled.
		1649
		1650	=over 4
		1651
		1652	=item C<PERL_ANYEVENT_VERBOSE>
		1653
		1654	By default, AnyEvent will be completely silent except in fatal
		1655	conditions. You can set this environment variable to make AnyEvent more
		1656	talkative.
		1657
		1658	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1659	conditions, such as not being able to load the event model specified by
		1660	C<PERL_ANYEVENT_MODEL>.
		1661
		1662	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1663	model it chooses.
		1664
		1665	When set to C<8> or higher, then AnyEvent will report extra information on
		1666	which optional modules it loads and how it implements certain features.
		1667
		1668	=item C<PERL_ANYEVENT_STRICT>
		1669
		1670	AnyEvent does not do much argument checking by default, as thorough
		1671	argument checking is very costly. Setting this variable to a true value
		1672	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1673	check the arguments passed to most method calls. If it finds any problems,
		1674	it will croak.
		1675
		1676	In other words, enables "strict" mode.
		1677
		1678	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1679	>>, it is definitely recommended to keep it off in production. Keeping
		1680	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1681	can be very useful, however.
		1682
		1683	=item C<PERL_ANYEVENT_MODEL>
		1684
		1685	This can be used to specify the event model to be used by AnyEvent, before
		1686	auto detection and -probing kicks in. It must be a string consisting
		1687	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1688	and the resulting module name is loaded and if the load was successful,
		1689	used as event model. If it fails to load AnyEvent will proceed with
		1690	auto detection and -probing.
		1691
		1692	This functionality might change in future versions.
		1693
		1694	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1695	could start your program like this:
		1696
		1697	PERL_ANYEVENT_MODEL=Perl perl ...
		1698
		1699	=item C<PERL_ANYEVENT_PROTOCOLS>
		1700
		1701	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1702	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1703	of auto probing).
		1704
		1705	Must be set to a comma-separated list of protocols or address families,
		1706	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1707	used, and preference will be given to protocols mentioned earlier in the
		1708	list.
		1709
		1710	This variable can effectively be used for denial-of-service attacks
		1711	against local programs (e.g. when setuid), although the impact is likely
		1712	small, as the program has to handle conenction and other failures anyways.
		1713
		1714	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1715	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1716	- only support IPv4, never try to resolve or contact IPv6
		1717	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1718	IPv6, but prefer IPv6 over IPv4.
		1719
		1720	=item C<PERL_ANYEVENT_EDNS0>
		1721
		1722	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1723	for DNS. This extension is generally useful to reduce DNS traffic, but
		1724	some (broken) firewalls drop such DNS packets, which is why it is off by
		1725	default.
		1726
		1727	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1728	EDNS0 in its DNS requests.
		1729
		1730	=item C<PERL_ANYEVENT_MAX_FORKS>
		1731
		1732	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1733	will create in parallel.
		1734
		1735	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1736
		1737	The default value for the C<max_outstanding> parameter for the default DNS
		1738	resolver - this is the maximum number of parallel DNS requests that are
		1739	sent to the DNS server.
		1740
		1741	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1742
		1743	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1744	configuration) in the default resolver. When set to the empty string, no
		1745	default config will be used.
		1746
		1747	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1748
		1749	When neither C<ca_file> nor C<ca_path> was specified during
		1750	L<AnyEvent::TLS> context creation, and either of these environment
		1751	variables exist, they will be used to specify CA certificate locations
		1752	instead of a system-dependent default.
		1753
		1754	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1755
		1756	When these are set to C<1>, then the respective modules are not
		1757	loaded. Mostly good for testing AnyEvent itself.
		1758
		1759	=back
		1760
429	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1761	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1762
		1763	This is an advanced topic that you do not normally need to use AnyEvent in
		1764	a module. This section is only of use to event loop authors who want to
		1765	provide AnyEvent compatibility.
430		1766
431	If you need to support another event library which isn't directly	1767	If you need to support another event library which isn't directly
432	supported by AnyEvent, you can supply your own interface to it by	1768	supported by AnyEvent, you can supply your own interface to it by
433	pushing, before the first watcher gets created, the package name of	1769	pushing, before the first watcher gets created, the package name of
434	the event module and the package name of the interface to use onto	1770	the event module and the package name of the interface to use onto
435	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	1771	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
436	AnyEvent.	1772	AnyEvent, so it is reasonably cheap.
437		1773
438	Example:	1774	Example:
439		1775
440	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	1776	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
441		1777
442	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	1778	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
443	package/class when it finds the C<urxvt> package/module is loaded. When	1779	package/class when it finds the C<urxvt> package/module is already loaded.
		1780
444	AnyEvent is loaded and asked to find a suitable event model, it will	1781	When AnyEvent is loaded and asked to find a suitable event model, it
445	first check for the presence of urxvt.	1782	will first check for the presence of urxvt by trying to C<use> the
		1783	C<urxvt::anyevent> module.
446		1784
447	The class should provide implementations for all watcher types (see	1785	The class should provide implementations for all watcher types. See
448	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	1786	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
449	(Source code) and so on for actual examples, use C<perldoc -m	1787	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
450	AnyEvent::Impl::Glib> to see the sources).	1788	see the sources.
451		1789
		1790	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		1791	provide suitable (hopefully) replacements.
		1792
452	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	1793	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
453	uses the above line as-is. An interface isn't included in AnyEvent	1794	terminal emulator uses the above line as-is. An interface isn't included
454	because it doesn't make sense outside the embedded interpreter inside	1795	in AnyEvent because it doesn't make sense outside the embedded interpreter
455	I<rxvt-unicode>, and it is updated and maintained as part of the	1796	inside I<rxvt-unicode>, and it is updated and maintained as part of the
456	I<rxvt-unicode> distribution.	1797	I<rxvt-unicode> distribution.
457		1798
458	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1799	I<rxvt-unicode> also cheats a bit by not providing blocking access to
459	condition variables: code blocking while waiting for a condition will	1800	condition variables: code blocking while waiting for a condition will
460	C<die>. This still works with most modules/usages, and blocking calls must	1801	C<die>. This still works with most modules/usages, and blocking calls must
461	not be in an interactive application, so it makes sense.	1802	not be done in an interactive application, so it makes sense.
462		1803
463	=head1 ENVIRONMENT VARIABLES
464
465	The following environment variables are used by this module:
466
467	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
468	model gets used.
469
470	=head1 EXAMPLE	1804	=head1 EXAMPLE PROGRAM
471		1805
472	The following program uses an io watcher to read data from stdin, a timer	1806	The following program uses an I/O watcher to read data from STDIN, a timer
473	to display a message once per second, and a condvar to exit the program	1807	to display a message once per second, and a condition variable to quit the
474	when the user enters quit:	1808	program when the user enters quit:
475		1809
476	use AnyEvent;	1810	use AnyEvent;
477		1811
478	my $cv = AnyEvent->condvar;	1812	my $cv = AnyEvent->condvar;
479		1813
480	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	1814	my $io_watcher = AnyEvent->io (
		1815	fh => \*STDIN,
		1816	poll => 'r',
		1817	cb => sub {
481	warn "io event <$_[0]>\n"; # will always output <r>	1818	warn "io event <$_[0]>\n"; # will always output <r>
482	chomp (my $input = <STDIN>); # read a line	1819	chomp (my $input = <STDIN>); # read a line
483	warn "read: $input\n"; # output what has been read	1820	warn "read: $input\n"; # output what has been read
484	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1821	$cv->send if $input =~ /^q/i; # quit program if /^q/i
		1822	},
485	});	1823	);
486		1824
487	my $time_watcher; # can only be used once	1825	my $time_watcher; # can only be used once
488		1826
489	sub new_timer {	1827	sub new_timer {
490	$timer = AnyEvent->timer (after => 1, cb => sub {	1828	$timer = AnyEvent->timer (after => 1, cb => sub {
…		…
493	});	1831	});
494	}	1832	}
495		1833
496	new_timer; # create first timer	1834	new_timer; # create first timer
497		1835
498	$cv->wait; # wait until user enters /^q/i	1836	$cv->recv; # wait until user enters /^q/i
499		1837
500	=head1 REAL-WORLD EXAMPLE	1838	=head1 REAL-WORLD EXAMPLE
501		1839
502	Consider the L<Net::FCP> module. It features (among others) the following	1840	Consider the L<Net::FCP> module. It features (among others) the following
503	API calls, which are to freenet what HTTP GET requests are to http:	1841	API calls, which are to freenet what HTTP GET requests are to http:
…		…
553	syswrite $txn->{fh}, $txn->{request}	1891	syswrite $txn->{fh}, $txn->{request}
554	or die "connection or write error";	1892	or die "connection or write error";
555	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1893	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
556		1894
557	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1895	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
558	result and signals any possible waiters that the request ahs finished:	1896	result and signals any possible waiters that the request has finished:
559		1897
560	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1898	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
561		1899
562	if (end-of-file or data complete) {	1900	if (end-of-file or data complete) {
563	$txn->{result} = $txn->{buf};	1901	$txn->{result} = $txn->{buf};
564	$txn->{finished}->broadcast;	1902	$txn->{finished}->send;
565	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1903	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
566	}	1904	}
567		1905
568	The C<result> method, finally, just waits for the finished signal (if the	1906	The C<result> method, finally, just waits for the finished signal (if the
569	request was already finished, it doesn't wait, of course, and returns the	1907	request was already finished, it doesn't wait, of course, and returns the
570	data:	1908	data:
571		1909
572	$txn->{finished}->wait;	1910	$txn->{finished}->recv;
573	return $txn->{result};	1911	return $txn->{result};
574		1912
575	The actual code goes further and collects all errors (C<die>s, exceptions)	1913	The actual code goes further and collects all errors (C<die>s, exceptions)
576	that occured during request processing. The C<result> method detects	1914	that occurred during request processing. The C<result> method detects
577	wether an exception as thrown (it is stored inside the $txn object)	1915	whether an exception as thrown (it is stored inside the $txn object)
578	and just throws the exception, which means connection errors and other	1916	and just throws the exception, which means connection errors and other
579	problems get reported tot he code that tries to use the result, not in a	1917	problems get reported tot he code that tries to use the result, not in a
580	random callback.	1918	random callback.
581		1919
582	All of this enables the following usage styles:	1920	All of this enables the following usage styles:
583		1921
584	1. Blocking:	1922	1. Blocking:
585		1923
586	my $data = $fcp->client_get ($url);	1924	my $data = $fcp->client_get ($url);
587		1925
588	2. Blocking, but parallelizing:	1926	2. Blocking, but running in parallel:
589		1927
590	my @datas = map $_->result,	1928	my @datas = map $_->result,
591	map $fcp->txn_client_get ($_),	1929	map $fcp->txn_client_get ($_),
592	@urls;	1930	@urls;
593		1931
594	Both blocking examples work without the module user having to know	1932	Both blocking examples work without the module user having to know
595	anything about events.	1933	anything about events.
596		1934
597	3a. Event-based in a main program, using any support Event module:	1935	3a. Event-based in a main program, using any supported event module:
598		1936
599	use Event;	1937	use EV;
600		1938
601	$fcp->txn_client_get ($url)->cb (sub {	1939	$fcp->txn_client_get ($url)->cb (sub {
602	my $txn = shift;	1940	my $txn = shift;
603	my $data = $txn->result;	1941	my $data = $txn->result;
604	...	1942	...
605	});	1943	});
606		1944
607	Event::loop;	1945	EV::loop;
608		1946
609	3b. The module user could use AnyEvent, too:	1947	3b. The module user could use AnyEvent, too:
610		1948
611	use AnyEvent;	1949	use AnyEvent;
612		1950
613	my $quit = AnyEvent->condvar;	1951	my $quit = AnyEvent->condvar;
614		1952
615	$fcp->txn_client_get ($url)->cb (sub {	1953	$fcp->txn_client_get ($url)->cb (sub {
616	...	1954	...
617	$quit->broadcast;	1955	$quit->send;
618	});	1956	});
619		1957
620	$quit->wait;	1958	$quit->recv;
		1959
		1960
		1961	=head1 BENCHMARKS
		1962
		1963	To give you an idea of the performance and overheads that AnyEvent adds
		1964	over the event loops themselves and to give you an impression of the speed
		1965	of various event loops I prepared some benchmarks.
		1966
		1967	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1968
		1969	Here is a benchmark of various supported event models used natively and
		1970	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1971	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1972	which it is), lets them fire exactly once and destroys them again.
		1973
		1974	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1975	distribution.
		1976
		1977	=head3 Explanation of the columns
		1978
		1979	I<watcher> is the number of event watchers created/destroyed. Since
		1980	different event models feature vastly different performances, each event
		1981	loop was given a number of watchers so that overall runtime is acceptable
		1982	and similar between tested event loop (and keep them from crashing): Glib
		1983	would probably take thousands of years if asked to process the same number
		1984	of watchers as EV in this benchmark.
		1985
		1986	I<bytes> is the number of bytes (as measured by the resident set size,
		1987	RSS) consumed by each watcher. This method of measuring captures both C
		1988	and Perl-based overheads.
		1989
		1990	I<create> is the time, in microseconds (millionths of seconds), that it
		1991	takes to create a single watcher. The callback is a closure shared between
		1992	all watchers, to avoid adding memory overhead. That means closure creation
		1993	and memory usage is not included in the figures.
		1994
		1995	I<invoke> is the time, in microseconds, used to invoke a simple
		1996	callback. The callback simply counts down a Perl variable and after it was
		1997	invoked "watcher" times, it would C<< ->send >> a condvar once to
		1998	signal the end of this phase.
		1999
		2000	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2001	watcher.
		2002
		2003	=head3 Results
		2004
		2005	name watchers bytes create invoke destroy comment
		2006	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
		2007	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
		2008	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
		2009	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
		2010	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
		2011	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		2012	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		2013	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
		2014	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
		2015	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
		2016	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
		2017	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
		2018
		2019	=head3 Discussion
		2020
		2021	The benchmark does I<not> measure scalability of the event loop very
		2022	well. For example, a select-based event loop (such as the pure perl one)
		2023	can never compete with an event loop that uses epoll when the number of
		2024	file descriptors grows high. In this benchmark, all events become ready at
		2025	the same time, so select/poll-based implementations get an unnatural speed
		2026	boost.
		2027
		2028	Also, note that the number of watchers usually has a nonlinear effect on
		2029	overall speed, that is, creating twice as many watchers doesn't take twice
		2030	the time - usually it takes longer. This puts event loops tested with a
		2031	higher number of watchers at a disadvantage.
		2032
		2033	To put the range of results into perspective, consider that on the
		2034	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2035	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2036	cycles with POE.
		2037
		2038	C<EV> is the sole leader regarding speed and memory use, which are both
		2039	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		2040	far less memory than any other event loop and is still faster than Event
		2041	natively.
		2042
		2043	The pure perl implementation is hit in a few sweet spots (both the
		2044	constant timeout and the use of a single fd hit optimisations in the perl
		2045	interpreter and the backend itself). Nevertheless this shows that it
		2046	adds very little overhead in itself. Like any select-based backend its
		2047	performance becomes really bad with lots of file descriptors (and few of
		2048	them active), of course, but this was not subject of this benchmark.
		2049
		2050	The C<Event> module has a relatively high setup and callback invocation
		2051	cost, but overall scores in on the third place.
		2052
		2053	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2054	when using its pure perl backend.
		2055
		2056	C<Glib>'s memory usage is quite a bit higher, but it features a
		2057	faster callback invocation and overall ends up in the same class as
		2058	C<Event>. However, Glib scales extremely badly, doubling the number of
		2059	watchers increases the processing time by more than a factor of four,
		2060	making it completely unusable when using larger numbers of watchers
		2061	(note that only a single file descriptor was used in the benchmark, so
		2062	inefficiencies of C<poll> do not account for this).
		2063
		2064	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2065	more than 2000 watchers is a big setback, however, as correctness takes
		2066	precedence over speed. Nevertheless, its performance is surprising, as the
		2067	file descriptor is dup()ed for each watcher. This shows that the dup()
		2068	employed by some adaptors is not a big performance issue (it does incur a
		2069	hidden memory cost inside the kernel which is not reflected in the figures
		2070	above).
		2071
		2072	C<POE>, regardless of underlying event loop (whether using its pure perl
		2073	select-based backend or the Event module, the POE-EV backend couldn't
		2074	be tested because it wasn't working) shows abysmal performance and
		2075	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2076	as EV watchers, and 10 times as much memory as Event (the high memory
		2077	requirements are caused by requiring a session for each watcher). Watcher
		2078	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2079	implementation.
		2080
		2081	The design of the POE adaptor class in AnyEvent can not really account
		2082	for the performance issues, though, as session creation overhead is
		2083	small compared to execution of the state machine, which is coded pretty
		2084	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2085	using multiple sessions is not a good approach, especially regarding
		2086	memory usage, even the author of POE could not come up with a faster
		2087	design).
		2088
		2089	=head3 Summary
		2090
		2091	=over 4
		2092
		2093	=item * Using EV through AnyEvent is faster than any other event loop
		2094	(even when used without AnyEvent), but most event loops have acceptable
		2095	performance with or without AnyEvent.
		2096
		2097	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2098	the actual event loop, only with extremely fast event loops such as EV
		2099	adds AnyEvent significant overhead.
		2100
		2101	=item * You should avoid POE like the plague if you want performance or
		2102	reasonable memory usage.
		2103
		2104	=back
		2105
		2106	=head2 BENCHMARKING THE LARGE SERVER CASE
		2107
		2108	This benchmark actually benchmarks the event loop itself. It works by
		2109	creating a number of "servers": each server consists of a socket pair, a
		2110	timeout watcher that gets reset on activity (but never fires), and an I/O
		2111	watcher waiting for input on one side of the socket. Each time the socket
		2112	watcher reads a byte it will write that byte to a random other "server".
		2113
		2114	The effect is that there will be a lot of I/O watchers, only part of which
		2115	are active at any one point (so there is a constant number of active
		2116	fds for each loop iteration, but which fds these are is random). The
		2117	timeout is reset each time something is read because that reflects how
		2118	most timeouts work (and puts extra pressure on the event loops).
		2119
		2120	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2121	(1%) are active. This mirrors the activity of large servers with many
		2122	connections, most of which are idle at any one point in time.
		2123
		2124	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2125	distribution.
		2126
		2127	=head3 Explanation of the columns
		2128
		2129	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2130	each server has a read and write socket end).
		2131
		2132	I<create> is the time it takes to create a socket pair (which is
		2133	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2134
		2135	I<request>, the most important value, is the time it takes to handle a
		2136	single "request", that is, reading the token from the pipe and forwarding
		2137	it to another server. This includes deleting the old timeout and creating
		2138	a new one that moves the timeout into the future.
		2139
		2140	=head3 Results
		2141
		2142	name sockets create request
		2143	EV 20000 69.01 11.16
		2144	Perl 20000 73.32 35.87
		2145	IOAsync 20000 157.00 98.14 epoll
		2146	IOAsync 20000 159.31 616.06 poll
		2147	Event 20000 212.62 257.32
		2148	Glib 20000 651.16 1896.30
		2149	POE 20000 349.67 12317.24 uses POE::Loop::Event
		2150
		2151	=head3 Discussion
		2152
		2153	This benchmark I<does> measure scalability and overall performance of the
		2154	particular event loop.
		2155
		2156	EV is again fastest. Since it is using epoll on my system, the setup time
		2157	is relatively high, though.
		2158
		2159	Perl surprisingly comes second. It is much faster than the C-based event
		2160	loops Event and Glib.
		2161
		2162	IO::Async performs very well when using its epoll backend, and still quite
		2163	good compared to Glib when using its pure perl backend.
		2164
		2165	Event suffers from high setup time as well (look at its code and you will
		2166	understand why). Callback invocation also has a high overhead compared to
		2167	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2168	uses select or poll in basically all documented configurations.
		2169
		2170	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2171	clearly fails to perform with many filehandles or in busy servers.
		2172
		2173	POE is still completely out of the picture, taking over 1000 times as long
		2174	as EV, and over 100 times as long as the Perl implementation, even though
		2175	it uses a C-based event loop in this case.
		2176
		2177	=head3 Summary
		2178
		2179	=over 4
		2180
		2181	=item * The pure perl implementation performs extremely well.
		2182
		2183	=item * Avoid Glib or POE in large projects where performance matters.
		2184
		2185	=back
		2186
		2187	=head2 BENCHMARKING SMALL SERVERS
		2188
		2189	While event loops should scale (and select-based ones do not...) even to
		2190	large servers, most programs we (or I :) actually write have only a few
		2191	I/O watchers.
		2192
		2193	In this benchmark, I use the same benchmark program as in the large server
		2194	case, but it uses only eight "servers", of which three are active at any
		2195	one time. This should reflect performance for a small server relatively
		2196	well.
		2197
		2198	The columns are identical to the previous table.
		2199
		2200	=head3 Results
		2201
		2202	name sockets create request
		2203	EV 16 20.00 6.54
		2204	Perl 16 25.75 12.62
		2205	Event 16 81.27 35.86
		2206	Glib 16 32.63 15.48
		2207	POE 16 261.87 276.28 uses POE::Loop::Event
		2208
		2209	=head3 Discussion
		2210
		2211	The benchmark tries to test the performance of a typical small
		2212	server. While knowing how various event loops perform is interesting, keep
		2213	in mind that their overhead in this case is usually not as important, due
		2214	to the small absolute number of watchers (that is, you need efficiency and
		2215	speed most when you have lots of watchers, not when you only have a few of
		2216	them).
		2217
		2218	EV is again fastest.
		2219
		2220	Perl again comes second. It is noticeably faster than the C-based event
		2221	loops Event and Glib, although the difference is too small to really
		2222	matter.
		2223
		2224	POE also performs much better in this case, but is is still far behind the
		2225	others.
		2226
		2227	=head3 Summary
		2228
		2229	=over 4
		2230
		2231	=item * C-based event loops perform very well with small number of
		2232	watchers, as the management overhead dominates.
		2233
		2234	=back
		2235
		2236	=head2 THE IO::Lambda BENCHMARK
		2237
		2238	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2239	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2240	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2241	shouldn't come as a surprise to anybody). As such, the benchmark is
		2242	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2243	very optimal. But how would AnyEvent compare when used without the extra
		2244	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2245
		2246	The benchmark itself creates an echo-server, and then, for 500 times,
		2247	connects to the echo server, sends a line, waits for the reply, and then
		2248	creates the next connection. This is a rather bad benchmark, as it doesn't
		2249	test the efficiency of the framework or much non-blocking I/O, but it is a
		2250	benchmark nevertheless.
		2251
		2252	name runtime
		2253	Lambda/select 0.330 sec
		2254	+ optimized 0.122 sec
		2255	Lambda/AnyEvent 0.327 sec
		2256	+ optimized 0.138 sec
		2257	Raw sockets/select 0.077 sec
		2258	POE/select, components 0.662 sec
		2259	POE/select, raw sockets 0.226 sec
		2260	POE/select, optimized 0.404 sec
		2261
		2262	AnyEvent/select/nb 0.085 sec
		2263	AnyEvent/EV/nb 0.068 sec
		2264	+state machine 0.134 sec
		2265
		2266	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2267	benchmarks actually make blocking connects and use 100% blocking I/O,
		2268	defeating the purpose of an event-based solution. All of the newly
		2269	written AnyEvent benchmarks use 100% non-blocking connects (using
		2270	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2271	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2272	generally require a lot more bookkeeping and event handling than blocking
		2273	connects (which involve a single syscall only).
		2274
		2275	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2276	offers similar expressive power as POE and IO::Lambda, using conventional
		2277	Perl syntax. This means that both the echo server and the client are 100%
		2278	non-blocking, further placing it at a disadvantage.
		2279
		2280	As you can see, the AnyEvent + EV combination even beats the
		2281	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2282	backend easily beats IO::Lambda and POE.
		2283
		2284	And even the 100% non-blocking version written using the high-level (and
		2285	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2286	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2287	in a non-blocking way.
		2288
		2289	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2290	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2291	part of the IO::lambda distribution and were used without any changes.
		2292
		2293
		2294	=head1 SIGNALS
		2295
		2296	AnyEvent currently installs handlers for these signals:
		2297
		2298	=over 4
		2299
		2300	=item SIGCHLD
		2301
		2302	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2303	emulation for event loops that do not support them natively. Also, some
		2304	event loops install a similar handler.
		2305
		2306	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2307	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2308
		2309	=item SIGPIPE
		2310
		2311	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2312	when AnyEvent gets loaded.
		2313
		2314	The rationale for this is that AnyEvent users usually do not really depend
		2315	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2316	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2317	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2318	some random socket.
		2319
		2320	The rationale for installing a no-op handler as opposed to ignoring it is
		2321	that this way, the handler will be restored to defaults on exec.
		2322
		2323	Feel free to install your own handler, or reset it to defaults.
		2324
		2325	=back
		2326
		2327	=cut
		2328
		2329	undef $SIG{CHLD}
		2330	if $SIG{CHLD} eq 'IGNORE';
		2331
		2332	$SIG{PIPE} = sub { }
		2333	unless defined $SIG{PIPE};
		2334
		2335	=head1 RECOMMENDED/OPTIONAL MODULES
		2336
		2337	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2338	it's built-in modules) are required to use it.
		2339
		2340	That does not mean that AnyEvent won't take advantage of some additional
		2341	modules if they are installed.
		2342
		2343	This section epxlains which additional modules will be used, and how they
		2344	affect AnyEvent's operetion.
		2345
		2346	=over 4
		2347
		2348	=item L<Async::Interrupt>
		2349
		2350	This slightly arcane module is used to implement fast signal handling: To
		2351	my knowledge, there is no way to do completely race-free and quick
		2352	signal handling in pure perl. To ensure that signals still get
		2353	delivered, AnyEvent will start an interval timer to wake up perl (and
		2354	catch the signals) with some delay (default is 10 seconds, look for
		2355	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2356
		2357	If this module is available, then it will be used to implement signal
		2358	catching, which means that signals will not be delayed, and the event loop
		2359	will not be interrupted regularly, which is more efficient (And good for
		2360	battery life on laptops).
		2361
		2362	This affects not just the pure-perl event loop, but also other event loops
		2363	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2364
		2365	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2366	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2367	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2368	does nothing for those backends.
		2369
		2370	=item L<EV>
		2371
		2372	This module isn't really "optional", as it is simply one of the backend
		2373	event loops that AnyEvent can use. However, it is simply the best event
		2374	loop available in terms of features, speed and stability: It supports
		2375	the AnyEvent API optimally, implements all the watcher types in XS, does
		2376	automatic timer adjustments even when no monotonic clock is available,
		2377	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2378	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2379	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2380
		2381	=item L<Guard>
		2382
		2383	The guard module, when used, will be used to implement
		2384	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2385	lot less memory), but otherwise doesn't affect guard operation much. It is
		2386	purely used for performance.
		2387
		2388	=item L<JSON> and L<JSON::XS>
		2389
		2390	This module is required when you want to read or write JSON data via
		2391	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2392	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2393
		2394	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2395	installed.
		2396
		2397	=item L<Net::SSLeay>
		2398
		2399	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2400	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2401	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2402
		2403	=item L<Time::HiRes>
		2404
		2405	This module is part of perl since release 5.008. It will be used when the
		2406	chosen event library does not come with a timing source on it's own. The
		2407	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2408	try to use a monotonic clock for timing stability.
		2409
		2410	=back
		2411
		2412
		2413	=head1 FORK
		2414
		2415	Most event libraries are not fork-safe. The ones who are usually are
		2416	because they rely on inefficient but fork-safe C<select> or C<poll>
		2417	calls. Only L<EV> is fully fork-aware.
		2418
		2419	If you have to fork, you must either do so I<before> creating your first
		2420	watcher OR you must not use AnyEvent at all in the child OR you must do
		2421	something completely out of the scope of AnyEvent.
		2422
		2423
		2424	=head1 SECURITY CONSIDERATIONS
		2425
		2426	AnyEvent can be forced to load any event model via
		2427	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		2428	execute arbitrary code or directly gain access, it can easily be used to
		2429	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		2430	will not be active when the program uses a different event model than
		2431	specified in the variable.
		2432
		2433	You can make AnyEvent completely ignore this variable by deleting it
		2434	before the first watcher gets created, e.g. with a C<BEGIN> block:
		2435
		2436	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		2437
		2438	use AnyEvent;
		2439
		2440	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2441	be used to probe what backend is used and gain other information (which is
		2442	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2443	$ENV{PERL_ANYEVENT_STRICT}.
		2444
		2445	Note that AnyEvent will remove I<all> environment variables starting with
		2446	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2447	enabled.
		2448
		2449
		2450	=head1 BUGS
		2451
		2452	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2453	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2454	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2455	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2456	pronounced).
		2457
621		2458
622	=head1 SEE ALSO	2459	=head1 SEE ALSO
623		2460
624	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	2461	Utility functions: L<AnyEvent::Util>.
625		2462
626	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	2463	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		2464	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
627		2465
628	Nontrivial usage example: L<Net::FCP>.	2466	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2467	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2468	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2469	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
629		2470
630	=head1	2471	Non-blocking file handles, sockets, TCP clients and
		2472	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2473
		2474	Asynchronous DNS: L<AnyEvent::DNS>.
		2475
		2476	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2477	L<Coro::Event>,
		2478
		2479	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2480	L<AnyEvent::HTTP>.
		2481
		2482
		2483	=head1 AUTHOR
		2484
		2485	Marc Lehmann <schmorp@schmorp.de>
		2486	http://home.schmorp.de/
631		2487
632	=cut	2488	=cut
633		2489
634	1	2490	1
635		2491

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines