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Revision 1.346 by root, Fri Jan 14 06:32:21 2011 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	# if you prefer function calls, look at the AE manpage for
		13	# an alternative API.
		14
		15	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	16	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		17
		18	# one-shot or repeating timers
		19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
		21
		22	print AnyEvent->now; # prints current event loop time
		23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		24
		25	# POSIX signal
		26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		27
		28	# child process exit
		29	my $w = AnyEvent->child (pid => $pid, cb => sub {
		30	my ($pid, $status) = @_;
12	...	31	...
13	});	32	});
14		33
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	34	# called when event loop idle (if applicable)
16	...	35	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		36
19	my $w = AnyEvent->condvar; # stores wether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		38	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	39	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
		42
		43	=head1 INTRODUCTION/TUTORIAL
		44
		45	This manpage is mainly a reference manual. If you are interested
		46	in a tutorial or some gentle introduction, have a look at the
		47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	An FAQ document is available as L<AnyEvent::FAQ>.
		52
		53	There also is a mailinglist for discussing all things AnyEvent, and an IRC
		54	channel, too.
		55
		56	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		57	Repository>, at L<http://anyevent.schmorp.de>, for more info.
		58
		59	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
		60
		61	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
		62	nowadays. So what is different about AnyEvent?
		63
		64	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
		65	policy> and AnyEvent is I<small and efficient>.
		66
		67	First and foremost, I<AnyEvent is not an event model> itself, it only
		68	interfaces to whatever event model the main program happens to use, in a
		69	pragmatic way. For event models and certain classes of immortals alike,
		70	the statement "there can only be one" is a bitter reality: In general,
		71	only one event loop can be active at the same time in a process. AnyEvent
		72	cannot change this, but it can hide the differences between those event
		73	loops.
		74
		75	The goal of AnyEvent is to offer module authors the ability to do event
		76	programming (waiting for I/O or timer events) without subscribing to a
		77	religion, a way of living, and most importantly: without forcing your
		78	module users into the same thing by forcing them to use the same event
		79	model you use.
		80
		81	For modules like POE or IO::Async (which is a total misnomer as it is
		82	actually doing all I/O I<synchronously>...), using them in your module is
		83	like joining a cult: After you join, you are dependent on them and you
		84	cannot use anything else, as they are simply incompatible to everything
		85	that isn't them. What's worse, all the potential users of your
		86	module are I<also> forced to use the same event loop you use.
		87
		88	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
		89	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
		90	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
		91	uses one of those, every user of your module has to use it, too. But if
		92	your module uses AnyEvent, it works transparently with all event models it
		93	supports (including stuff like IO::Async, as long as those use one of the
		94	supported event loops. It is easy to add new event loops to AnyEvent, too,
		95	so it is future-proof).
		96
		97	In addition to being free of having to use I<the one and only true event
		98	model>, AnyEvent also is free of bloat and policy: with POE or similar
		99	modules, you get an enormous amount of code and strict rules you have to
		100	follow. AnyEvent, on the other hand, is lean and to the point, by only
		101	offering the functionality that is necessary, in as thin as a wrapper as
		102	technically possible.
		103
		104	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		105	of useful functionality, such as an asynchronous DNS resolver, 100%
		106	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		107	such as Windows) and lots of real-world knowledge and workarounds for
		108	platform bugs and differences.
		109
		110	Now, if you I<do want> lots of policy (this can arguably be somewhat
		111	useful) and you want to force your users to use the one and only event
		112	model, you should I<not> use this module.
22		113
23	=head1 DESCRIPTION	114	=head1 DESCRIPTION
24		115
25	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
26	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
27	users to use the same event loop (as only a single event loop can coexist	118	module users to use a specific event loop implementation (since more
28	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
29		120
30	The interface itself is vaguely similar but not identical to the Event	121	The interface itself is vaguely similar, but not identical to the L<Event>
31	module.	122	module.
32		123
33	On the first call of any method, the module tries to detect the currently	124	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	125	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	126	following modules is already loaded: L<EV>, L<AnyEvent::Impl::Perl>,
36	used. If none is found, the module tries to load these modules in the	127	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
37	order given. The first one that could be successfully loaded will be	128	found is used. If none are detected, the module tries to load the first
38	used. If still none could be found, AnyEvent will fall back to a pure-perl	129	four modules in the order given; but note that if L<EV> is not
39	event loop, which is also not very efficient.	130	available, the pure-perl L<AnyEvent::Impl::Perl> should always work, so
		131	the other two are not normally tried.
40		132
41	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
42	an Event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
43	that model the default. For example:	135	that model the default. For example:
44		136
45	use Tk;	137	use Tk;
46	use AnyEvent;	138	use AnyEvent;
47		139
48	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
49		141
		142	The I<likely> means that, if any module loads another event model and
		143	starts using it, all bets are off - this case should be very rare though,
		144	as very few modules hardcode event loops without announcing this very
		145	loudly.
		146
50	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called
51	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	148	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
52	explicitly.	149	explicitly and enjoy the high availability of that event loop :)
53		150
54	=head1 WATCHERS	151	=head1 WATCHERS
55		152
56	AnyEvent has the central concept of a I<watcher>, which is an object that	153	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	154	stores relevant data for each kind of event you are waiting for, such as
58	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
59		156
60	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
61	creating a watcher it will immediately "watch" for events and invoke	158	creating a watcher it will immediately "watch" for events and invoke the
		159	callback when the event occurs (of course, only when the event model
		160	is in control).
		161
		162	Note that B<callbacks must not permanently change global variables>
		163	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		164	callbacks must not C<die> >>. The former is good programming practice in
		165	Perl and the latter stems from the fact that exception handling differs
		166	widely between event loops.
		167
62	the callback. To disable the watcher you have to destroy it (e.g. by	168	To disable a 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	169	variable you store it in to C<undef> or otherwise deleting all references
64	references to it).	170	to it).
65		171
66	All watchers are created by calling a method on the C<AnyEvent> class.	172	All watchers are created by calling a method on the C<AnyEvent> class.
67		173
		174	Many watchers either are used with "recursion" (repeating timers for
		175	example), or need to refer to their watcher object in other ways.
		176
		177	One way to achieve that is this pattern:
		178
		179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		180	# you can use $w here, for example to undef it
		181	undef $w;
		182	});
		183
		184	Note that C<my $w; $w => combination. This is necessary because in Perl,
		185	my variables are only visible after the statement in which they are
		186	declared.
		187
68	=head2 IO WATCHERS	188	=head2 I/O WATCHERS
69		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
70	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	196	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
71	the following mandatory arguments:	197	with the following mandatory key-value pairs as arguments:
72		198
73	C<fh> the Perl I<filehandle> (not filedescriptor) to watch for	199	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		200	for events (AnyEvent might or might not keep a reference to this file
		201	handle). Note that only file handles pointing to things for which
		202	non-blocking operation makes sense are allowed. This includes sockets,
		203	most character devices, pipes, fifos and so on, but not for example files
		204	or block devices.
		205
74	events. C<poll> must be a string that is either C<r> or C<w>, that creates	206	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	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
76	to invoke everytime the filehandle becomes ready.
77		208
78	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	209	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		210
82	Filehandles will be kept alive, so as long as the watcher exists, the	211	Although the callback might get passed parameters, their value and
83	filehandle exists, too.	212	presence is undefined and you cannot rely on them. Portable AnyEvent
		213	callbacks cannot use arguments passed to I/O watcher callbacks.
84		214
85	Example:	215	The I/O watcher might use the underlying file descriptor or a copy of it.
		216	You must not close a file handle as long as any watcher is active on the
		217	underlying file descriptor.
86		218
		219	Some event loops issue spurious readiness notifications, so you should
		220	always use non-blocking calls when reading/writing from/to your file
		221	handles.
		222
87	# wait for readability of STDIN, then read a line and disable the watcher	223	Example: wait for readability of STDIN, then read a line and disable the
		224	watcher.
		225
88	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
89	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
90	warn "read: $input\n";	228	warn "read: $input\n";
91	undef $w;	229	undef $w;
92	});	230	});
93		231
94	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
95		233
		234	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		235
		236	$w = AnyEvent->timer (
		237	after => <fractional_seconds>,
		238	interval => <fractional_seconds>,
		239	cb => <callback>,
		240	);
		241
96	You can create a time watcher by calling the C<< AnyEvent->timer >>	242	You can create a time watcher by calling the C<< AnyEvent->timer >>
97	method with the following mandatory arguments:	243	method with the following mandatory arguments:
98		244
99	C<after> after how many seconds (fractions are supported) should the timer	245	C<after> specifies after how many seconds (fractional values are
100	activate. C<cb> the callback to invoke.	246	supported) the callback should be invoked. C<cb> is the callback to invoke
		247	in that case.
101		248
102	The timer callback will be invoked at most once: if you want a repeating	249	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	250	presence is undefined and you cannot rely on them. Portable AnyEvent
104	and Glib).	251	callbacks cannot use arguments passed to time watcher callbacks.
105		252
106	Example:	253	The callback will normally be invoked only once. If you specify another
		254	parameter, C<interval>, as a strictly positive number (> 0), then the
		255	callback will be invoked regularly at that interval (in fractional
		256	seconds) after the first invocation. If C<interval> is specified with a
		257	false value, then it is treated as if it were not specified at all.
107		258
		259	The callback will be rescheduled before invoking the callback, but no
		260	attempt is made to avoid timer drift in most backends, so the interval is
		261	only approximate.
		262
108	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
109	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
110	warn "timeout\n";	266	warn "timeout\n";
111	});	267	});
112		268
113	# to cancel the timer:	269	# to cancel the timer:
114	undef $w	270	undef $w;
115		271
116	=head2 CONDITION WATCHERS	272	Example 2: fire an event after 0.5 seconds, then roughly every second.
117		273
118	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
119	method without any arguments.	275	warn "timeout\n";
		276	};
120		277
121	A condition watcher watches for a condition - precisely that the C<<	278	=head3 TIMING ISSUES
122	->broadcast >> method has been called.
123		279
124	The watcher has only two methods:	280	There are two ways to handle timers: based on real time (relative, "fire
		281	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		282	o'clock").
		283
		284	While most event loops expect timers to specified in a relative way, they
		285	use absolute time internally. This makes a difference when your clock
		286	"jumps", for example, when ntp decides to set your clock backwards from
		287	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		288	fire "after a second" might actually take six years to finally fire.
		289
		290	AnyEvent cannot compensate for this. The only event loop that is conscious
		291	of these issues is L<EV>, which offers both relative (ev_timer, based
		292	on true relative time) and absolute (ev_periodic, based on wallclock time)
		293	timers.
		294
		295	AnyEvent always prefers relative timers, if available, matching the
		296	AnyEvent API.
		297
		298	AnyEvent has two additional methods that return the "current time":
125		299
126	=over 4	300	=over 4
127		301
128	=item $cv->wait	302	=item AnyEvent->time
129		303
130	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	304	This returns the "current wallclock time" as a fractional number of
131	called on c<$cv>, while servicing other watchers normally.	305	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		306	return, and the result is guaranteed to be compatible with those).
132		307
133	Not all event models support a blocking wait - some die in that case, so	308	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	309	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		310
140	You can only wait once on a condition - additional calls will return	311	=item AnyEvent->now
141	immediately.
142		312
143	=item $cv->broadcast	313	This also returns the "current wallclock time", but unlike C<time>, above,
		314	this value might change only once per event loop iteration, depending on
		315	the event loop (most return the same time as C<time>, above). This is the
		316	time that AnyEvent's timers get scheduled against.
144		317
145	Flag the condition as ready - a running C<< ->wait >> and all further	318	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	319	function to call when you want to know the current time.>
147	is waiting the broadcast will be remembered..
148		320
149	Example:	321	This function is also often faster then C<< AnyEvent->time >>, and
		322	thus the preferred method if you want some timestamp (for example,
		323	L<AnyEvent::Handle> uses this to update its activity timeouts).
150		324
151	# wait till the result is ready	325	The rest of this section is only of relevance if you try to be very exact
152	my $result_ready = AnyEvent->condvar;	326	with your timing; you can skip it without a bad conscience.
153		327
154	# do something such as adding a timer	328	For a practical example of when these times differ, consider L<Event::Lib>
155	# or socket watcher the calls $result_ready->broadcast	329	and L<EV> and the following set-up:
156	# when the "result" is ready.
157		330
158	$result_ready->wait;	331	The event loop is running and has just invoked one of your callbacks at
		332	time=500 (assume no other callbacks delay processing). In your callback,
		333	you wait a second by executing C<sleep 1> (blocking the process for a
		334	second) and then (at time=501) you create a relative timer that fires
		335	after three seconds.
		336
		337	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		338	both return C<501>, because that is the current time, and the timer will
		339	be scheduled to fire at time=504 (C<501> + C<3>).
		340
		341	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		342	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		343	last event processing phase started. With L<EV>, your timer gets scheduled
		344	to run at time=503 (C<500> + C<3>).
		345
		346	In one sense, L<Event::Lib> is more exact, as it uses the current time
		347	regardless of any delays introduced by event processing. However, most
		348	callbacks do not expect large delays in processing, so this causes a
		349	higher drift (and a lot more system calls to get the current time).
		350
		351	In another sense, L<EV> is more exact, as your timer will be scheduled at
		352	the same time, regardless of how long event processing actually took.
		353
		354	In either case, if you care (and in most cases, you don't), then you
		355	can get whatever behaviour you want with any event loop, by taking the
		356	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		357	account.
		358
		359	=item AnyEvent->now_update
		360
		361	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		362	the current time for each loop iteration (see the discussion of L<<
		363	AnyEvent->now >>, above).
		364
		365	When a callback runs for a long time (or when the process sleeps), then
		366	this "current" time will differ substantially from the real time, which
		367	might affect timers and time-outs.
		368
		369	When this is the case, you can call this method, which will update the
		370	event loop's idea of "current time".
		371
		372	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		373	when mod_perl executes the script, then the event loop will have the wrong
		374	idea about the "current time" (being potentially far in the past, when the
		375	script ran the last time). In that case you should arrange a call to C<<
		376	AnyEvent->now_update >> each time the web server process wakes up again
		377	(e.g. at the start of your script, or in a handler).
		378
		379	Note that updating the time I<might> cause some events to be handled.
159		380
160	=back	381	=back
161		382
162	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
163		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
164	You can listen for signals using a signal watcher, C<signal> is the signal	387	You can watch for signals using a signal watcher, C<signal> is the signal
165	I<name> without any C<SIG> prefix. Multiple signals events can be clumped	388	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
166	together into one callback invocation, and callback invocation might or	389	callback to be invoked whenever a signal occurs.
167	might not be asynchronous.
168		390
169	These watchers might use C<%SIG>, so programs overwriting those signals	391	Although the callback might get passed parameters, their value and
170	directly will likely not work correctly.	392	presence is undefined and you cannot rely on them. Portable AnyEvent
		393	callbacks cannot use arguments passed to signal watcher callbacks.
		394
		395	Multiple signal occurrences can be clumped together into one callback
		396	invocation, and callback invocation will be synchronous. Synchronous means
		397	that it might take a while until the signal gets handled by the process,
		398	but it is guaranteed not to interrupt any other callbacks.
		399
		400	The main advantage of using these watchers is that you can share a signal
		401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
		403
		404	This watcher might use C<%SIG> (depending on the event loop used),
		405	so programs overwriting those signals directly will likely not work
		406	correctly.
171		407
172	Example: exit on SIGINT	408	Example: exit on SIGINT
173		409
174	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
175		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling) or
		421	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		422	latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		432	callbacks to signals in a generic way, which is a pity, as you cannot
		433	do race-free signal handling in perl, requiring C libraries for
		434	this. AnyEvent will try to do its best, which means in some cases,
		435	signals will be delayed. The maximum time a signal might be delayed is
		436	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		437	variable can be changed only before the first signal watcher is created,
		438	and should be left alone otherwise. This variable determines how often
		439	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		440	will cause fewer spurious wake-ups, which is better for power and CPU
		441	saving.
		442
		443	All these problems can be avoided by installing the optional
		444	L<Async::Interrupt> module, which works with most event loops. It will not
		445	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		446	(and not with L<POE> currently, as POE does its own workaround with
		447	one-second latency). For those, you just have to suffer the delays.
		448
176	=head2 CHILD PROCESS WATCHERS	449	=head2 CHILD PROCESS WATCHERS
177		450
178	You can also listen for the status of a child process specified by the	451	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
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		452
184	Example: wait for pid 1333	453	You can also watch for a child process exit and catch its exit status.
185		454
186	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });	455	The child process is specified by the C<pid> argument (on some backends,
		456	using C<0> watches for any child process exit, on others this will
		457	croak). The watcher will be triggered only when the child process has
		458	finished and an exit status is available, not on any trace events
		459	(stopped/continued).
187		460
188	=head1 GLOBALS	461	The callback will be called with the pid and exit status (as returned by
		462	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		463	callback arguments.
		464
		465	This watcher type works by installing a signal handler for C<SIGCHLD>,
		466	and since it cannot be shared, nothing else should use SIGCHLD or reap
		467	random child processes (waiting for specific child processes, e.g. inside
		468	C<system>, is just fine).
		469
		470	There is a slight catch to child watchers, however: you usually start them
		471	I<after> the child process was created, and this means the process could
		472	have exited already (and no SIGCHLD will be sent anymore).
		473
		474	Not all event models handle this correctly (neither POE nor IO::Async do,
		475	see their AnyEvent::Impl manpages for details), but even for event models
		476	that I<do> handle this correctly, they usually need to be loaded before
		477	the process exits (i.e. before you fork in the first place). AnyEvent's
		478	pure perl event loop handles all cases correctly regardless of when you
		479	start the watcher.
		480
		481	This means you cannot create a child watcher as the very first
		482	thing in an AnyEvent program, you I<have> to create at least one
		483	watcher before you C<fork> the child (alternatively, you can call
		484	C<AnyEvent::detect>).
		485
		486	As most event loops do not support waiting for child events, they will be
		487	emulated by AnyEvent in most cases, in which the latency and race problems
		488	mentioned in the description of signal watchers apply.
		489
		490	Example: fork a process and wait for it
		491
		492	my $done = AnyEvent->condvar;
		493
		494	my $pid = fork or exit 5;
		495
		496	my $w = AnyEvent->child (
		497	pid => $pid,
		498	cb => sub {
		499	my ($pid, $status) = @_;
		500	warn "pid $pid exited with status $status";
		501	$done->send;
		502	},
		503	);
		504
		505	# do something else, then wait for process exit
		506	$done->recv;
		507
		508	=head2 IDLE WATCHERS
		509
		510	$w = AnyEvent->idle (cb => <callback>);
		511
		512	This will repeatedly invoke the callback after the process becomes idle,
		513	until either the watcher is destroyed or new events have been detected.
		514
		515	Idle watchers are useful when there is a need to do something, but it
		516	is not so important (or wise) to do it instantly. The callback will be
		517	invoked only when there is "nothing better to do", which is usually
		518	defined as "all outstanding events have been handled and no new events
		519	have been detected". That means that idle watchers ideally get invoked
		520	when the event loop has just polled for new events but none have been
		521	detected. Instead of blocking to wait for more events, the idle watchers
		522	will be invoked.
		523
		524	Unfortunately, most event loops do not really support idle watchers (only
		525	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		526	will simply call the callback "from time to time".
		527
		528	Example: read lines from STDIN, but only process them when the
		529	program is otherwise idle:
		530
		531	my @lines; # read data
		532	my $idle_w;
		533	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		534	push @lines, scalar <STDIN>;
		535
		536	# start an idle watcher, if not already done
		537	$idle_w ||= AnyEvent->idle (cb => sub {
		538	# handle only one line, when there are lines left
		539	if (my $line = shift @lines) {
		540	print "handled when idle: $line";
		541	} else {
		542	# otherwise disable the idle watcher again
		543	undef $idle_w;
		544	}
		545	});
		546	});
		547
		548	=head2 CONDITION VARIABLES
		549
		550	$cv = AnyEvent->condvar;
		551
		552	$cv->send (<list>);
		553	my @res = $cv->recv;
		554
		555	If you are familiar with some event loops you will know that all of them
		556	require you to run some blocking "loop", "run" or similar function that
		557	will actively watch for new events and call your callbacks.
		558
		559	AnyEvent is slightly different: it expects somebody else to run the event
		560	loop and will only block when necessary (usually when told by the user).
		561
		562	The tool to do that is called a "condition variable", so called because
		563	they represent a condition that must become true.
		564
		565	Now is probably a good time to look at the examples further below.
		566
		567	Condition variables can be created by calling the C<< AnyEvent->condvar
		568	>> method, usually without arguments. The only argument pair allowed is
		569	C<cb>, which specifies a callback to be called when the condition variable
		570	becomes true, with the condition variable as the first argument (but not
		571	the results).
		572
		573	After creation, the condition variable is "false" until it becomes "true"
		574	by calling the C<send> method (or calling the condition variable as if it
		575	were a callback, read about the caveats in the description for the C<<
		576	->send >> method).
		577
		578	Since condition variables are the most complex part of the AnyEvent API, here are
		579	some different mental models of what they are - pick the ones you can connect to:
189		580
190	=over 4	581	=over 4
191		582
		583	=item * Condition variables are like callbacks - you can call them (and pass them instead
		584	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		585
		586	=item * Condition variables are signals - one side can emit or send them,
		587	the other side can wait for them, or install a handler that is called when
		588	the signal fires.
		589
		590	=item * Condition variables are like "Merge Points" - points in your program
		591	where you merge multiple independent results/control flows into one.
		592
		593	=item * Condition variables represent a transaction - functions that start
		594	some kind of transaction can return them, leaving the caller the choice
		595	between waiting in a blocking fashion, or setting a callback.
		596
		597	=item * Condition variables represent future values, or promises to deliver
		598	some result, long before the result is available.
		599
		600	=back
		601
		602	Condition variables are very useful to signal that something has finished,
		603	for example, if you write a module that does asynchronous http requests,
		604	then a condition variable would be the ideal candidate to signal the
		605	availability of results. The user can either act when the callback is
		606	called or can synchronously C<< ->recv >> for the results.
		607
		608	You can also use them to simulate traditional event loops - for example,
		609	you can block your main program until an event occurs - for example, you
		610	could C<< ->recv >> in your main program until the user clicks the Quit
		611	button of your app, which would C<< ->send >> the "quit" event.
		612
		613	Note that condition variables recurse into the event loop - if you have
		614	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
		615	lose. Therefore, condition variables are good to export to your caller, but
		616	you should avoid making a blocking wait yourself, at least in callbacks,
		617	as this asks for trouble.
		618
		619	Condition variables are represented by hash refs in perl, and the keys
		620	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		621	easy (it is often useful to build your own transaction class on top of
		622	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		623	its C<new> method in your own C<new> method.
		624
		625	There are two "sides" to a condition variable - the "producer side" which
		626	eventually calls C<< -> send >>, and the "consumer side", which waits
		627	for the send to occur.
		628
		629	Example: wait for a timer.
		630
		631	# condition: "wait till the timer is fired"
		632	my $timer_fired = AnyEvent->condvar;
		633
		634	# create the timer - we could wait for, say
		635	# a handle becomign ready, or even an
		636	# AnyEvent::HTTP request to finish, but
		637	# in this case, we simply use a timer:
		638	my $w = AnyEvent->timer (
		639	after => 1,
		640	cb => sub { $timer_fired->send },
		641	);
		642
		643	# this "blocks" (while handling events) till the callback
		644	# calls ->send
		645	$timer_fired->recv;
		646
		647	Example: wait for a timer, but take advantage of the fact that condition
		648	variables are also callable directly.
		649
		650	my $done = AnyEvent->condvar;
		651	my $delay = AnyEvent->timer (after => 5, cb => $done);
		652	$done->recv;
		653
		654	Example: Imagine an API that returns a condvar and doesn't support
		655	callbacks. This is how you make a synchronous call, for example from
		656	the main program:
		657
		658	use AnyEvent::CouchDB;
		659
		660	...
		661
		662	my @info = $couchdb->info->recv;
		663
		664	And this is how you would just set a callback to be called whenever the
		665	results are available:
		666
		667	$couchdb->info->cb (sub {
		668	my @info = $_[0]->recv;
		669	});
		670
		671	=head3 METHODS FOR PRODUCERS
		672
		673	These methods should only be used by the producing side, i.e. the
		674	code/module that eventually sends the signal. Note that it is also
		675	the producer side which creates the condvar in most cases, but it isn't
		676	uncommon for the consumer to create it as well.
		677
		678	=over 4
		679
		680	=item $cv->send (...)
		681
		682	Flag the condition as ready - a running C<< ->recv >> and all further
		683	calls to C<recv> will (eventually) return after this method has been
		684	called. If nobody is waiting the send will be remembered.
		685
		686	If a callback has been set on the condition variable, it is called
		687	immediately from within send.
		688
		689	Any arguments passed to the C<send> call will be returned by all
		690	future C<< ->recv >> calls.
		691
		692	Condition variables are overloaded so one can call them directly (as if
		693	they were a code reference). Calling them directly is the same as calling
		694	C<send>.
		695
		696	=item $cv->croak ($error)
		697
		698	Similar to send, but causes all calls to C<< ->recv >> to invoke
		699	C<Carp::croak> with the given error message/object/scalar.
		700
		701	This can be used to signal any errors to the condition variable
		702	user/consumer. Doing it this way instead of calling C<croak> directly
		703	delays the error detection, but has the overwhelming advantage that it
		704	diagnoses the error at the place where the result is expected, and not
		705	deep in some event callback with no connection to the actual code causing
		706	the problem.
		707
		708	=item $cv->begin ([group callback])
		709
		710	=item $cv->end
		711
		712	These two methods can be used to combine many transactions/events into
		713	one. For example, a function that pings many hosts in parallel might want
		714	to use a condition variable for the whole process.
		715
		716	Every call to C<< ->begin >> will increment a counter, and every call to
		717	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		718	>>, the (last) callback passed to C<begin> will be executed, passing the
		719	condvar as first argument. That callback is I<supposed> to call C<< ->send
		720	>>, but that is not required. If no group callback was set, C<send> will
		721	be called without any arguments.
		722
		723	You can think of C<< $cv->send >> giving you an OR condition (one call
		724	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		725	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		726
		727	Let's start with a simple example: you have two I/O watchers (for example,
		728	STDOUT and STDERR for a program), and you want to wait for both streams to
		729	close before activating a condvar:
		730
		731	my $cv = AnyEvent->condvar;
		732
		733	$cv->begin; # first watcher
		734	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		735	defined sysread $fh1, my $buf, 4096
		736	or $cv->end;
		737	});
		738
		739	$cv->begin; # second watcher
		740	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		741	defined sysread $fh2, my $buf, 4096
		742	or $cv->end;
		743	});
		744
		745	$cv->recv;
		746
		747	This works because for every event source (EOF on file handle), there is
		748	one call to C<begin>, so the condvar waits for all calls to C<end> before
		749	sending.
		750
		751	The ping example mentioned above is slightly more complicated, as the
		752	there are results to be passwd back, and the number of tasks that are
		753	begun can potentially be zero:
		754
		755	my $cv = AnyEvent->condvar;
		756
		757	my %result;
		758	$cv->begin (sub { shift->send (\%result) });
		759
		760	for my $host (@list_of_hosts) {
		761	$cv->begin;
		762	ping_host_then_call_callback $host, sub {
		763	$result{$host} = ...;
		764	$cv->end;
		765	};
		766	}
		767
		768	$cv->end;
		769
		770	This code fragment supposedly pings a number of hosts and calls
		771	C<send> after results for all then have have been gathered - in any
		772	order. To achieve this, the code issues a call to C<begin> when it starts
		773	each ping request and calls C<end> when it has received some result for
		774	it. Since C<begin> and C<end> only maintain a counter, the order in which
		775	results arrive is not relevant.
		776
		777	There is an additional bracketing call to C<begin> and C<end> outside the
		778	loop, which serves two important purposes: first, it sets the callback
		779	to be called once the counter reaches C<0>, and second, it ensures that
		780	C<send> is called even when C<no> hosts are being pinged (the loop
		781	doesn't execute once).
		782
		783	This is the general pattern when you "fan out" into multiple (but
		784	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
		785	the callback and ensure C<end> is called at least once, and then, for each
		786	subrequest you start, call C<begin> and for each subrequest you finish,
		787	call C<end>.
		788
		789	=back
		790
		791	=head3 METHODS FOR CONSUMERS
		792
		793	These methods should only be used by the consuming side, i.e. the
		794	code awaits the condition.
		795
		796	=over 4
		797
		798	=item $cv->recv
		799
		800	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		801	>> methods have been called on C<$cv>, while servicing other watchers
		802	normally.
		803
		804	You can only wait once on a condition - additional calls are valid but
		805	will return immediately.
		806
		807	If an error condition has been set by calling C<< ->croak >>, then this
		808	function will call C<croak>.
		809
		810	In list context, all parameters passed to C<send> will be returned,
		811	in scalar context only the first one will be returned.
		812
		813	Note that doing a blocking wait in a callback is not supported by any
		814	event loop, that is, recursive invocation of a blocking C<< ->recv
		815	>> is not allowed, and the C<recv> call will C<croak> if such a
		816	condition is detected. This condition can be slightly loosened by using
		817	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		818	any thread that doesn't run the event loop itself.
		819
		820	Not all event models support a blocking wait - some die in that case
		821	(programs might want to do that to stay interactive), so I<if you are
		822	using this from a module, never require a blocking wait>. Instead, let the
		823	caller decide whether the call will block or not (for example, by coupling
		824	condition variables with some kind of request results and supporting
		825	callbacks so the caller knows that getting the result will not block,
		826	while still supporting blocking waits if the caller so desires).
		827
		828	You can ensure that C<< ->recv >> never blocks by setting a callback and
		829	only calling C<< ->recv >> from within that callback (or at a later
		830	time). This will work even when the event loop does not support blocking
		831	waits otherwise.
		832
		833	=item $bool = $cv->ready
		834
		835	Returns true when the condition is "true", i.e. whether C<send> or
		836	C<croak> have been called.
		837
		838	=item $cb = $cv->cb ($cb->($cv))
		839
		840	This is a mutator function that returns the callback set and optionally
		841	replaces it before doing so.
		842
		843	The callback will be called when the condition becomes "true", i.e. when
		844	C<send> or C<croak> are called, with the only argument being the
		845	condition variable itself. If the condition is already true, the
		846	callback is called immediately when it is set. Calling C<recv> inside
		847	the callback or at any later time is guaranteed not to block.
		848
		849	=back
		850
		851	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		852
		853	The available backend classes are (every class has its own manpage):
		854
		855	=over 4
		856
		857	=item Backends that are autoprobed when no other event loop can be found.
		858
		859	EV is the preferred backend when no other event loop seems to be in
		860	use. If EV is not installed, then AnyEvent will fall back to its own
		861	pure-perl implementation, which is available everywhere as it comes with
		862	AnyEvent itself.
		863
		864	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		865	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		866
		867	=item Backends that are transparently being picked up when they are used.
		868
		869	These will be used if they are already loaded when the first watcher
		870	is created, in which case it is assumed that the application is using
		871	them. This means that AnyEvent will automatically pick the right backend
		872	when the main program loads an event module before anything starts to
		873	create watchers. Nothing special needs to be done by the main program.
		874
		875	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		876	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		877	AnyEvent::Impl::Tk based on Tk, very broken.
		878	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		879	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		880	AnyEvent::Impl::Irssi used when running within irssi.
		881	AnyEvent::Impl::IOAsync based on IO::Async.
		882	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		883
		884	=item Backends with special needs.
		885
		886	Qt requires the Qt::Application to be instantiated first, but will
		887	otherwise be picked up automatically. As long as the main program
		888	instantiates the application before any AnyEvent watchers are created,
		889	everything should just work.
		890
		891	AnyEvent::Impl::Qt based on Qt.
		892
		893	=item Event loops that are indirectly supported via other backends.
		894
		895	Some event loops can be supported via other modules:
		896
		897	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		898
		899	B<WxWidgets> has no support for watching file handles. However, you can
		900	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		901	polls 20 times per second, which was considered to be too horrible to even
		902	consider for AnyEvent.
		903
		904	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		905	backend, so it can be supported through POE.
		906
		907	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		908	load L<POE> when detecting them, in the hope that POE will pick them up,
		909	in which case everything will be automatic.
		910
		911	=back
		912
		913	=head1 GLOBAL VARIABLES AND FUNCTIONS
		914
		915	These are not normally required to use AnyEvent, but can be useful to
		916	write AnyEvent extension modules.
		917
		918	=over 4
		919
192	=item $AnyEvent::MODEL	920	=item $AnyEvent::MODEL
193		921
194	Contains C<undef> until the first watcher is being created. Then it	922	Contains C<undef> until the first watcher is being created, before the
		923	backend has been autodetected.
		924
195	contains the event model that is being used, which is the name of the	925	Afterwards it contains the event model that is being used, which is the
196	Perl class implementing the model. This class is usually one of the	926	name of the Perl class implementing the model. This class is usually one
197	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	927	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
198	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	928	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
199		929	will be C<urxvt::anyevent>).
200	The known classes so far are:
201
202	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
203	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
204	AnyEvent::Impl::Coro based on Coro::Event, second best choice.
205	AnyEvent::Impl::Event based on Event, also second best choice :)
206	AnyEvent::Impl::Glib based on Glib, second-best choice.
207	AnyEvent::Impl::Tk based on Tk, very bad choice.
208	AnyEvent::Impl::Perl pure-perl implementation, inefficient.
209		930
210	=item AnyEvent::detect	931	=item AnyEvent::detect
211		932
212	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	933	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
213	necessary. You should only call this function right before you would have	934	if necessary. You should only call this function right before you would
214	created an AnyEvent watcher anyway, that is, very late at runtime.	935	have created an AnyEvent watcher anyway, that is, as late as possible at
		936	runtime, and not e.g. during initialisation of your module.
		937
		938	If you need to do some initialisation before AnyEvent watchers are
		939	created, use C<post_detect>.
		940
		941	=item $guard = AnyEvent::post_detect { BLOCK }
		942
		943	Arranges for the code block to be executed as soon as the event model is
		944	autodetected (or immediately if that has already happened).
		945
		946	The block will be executed I<after> the actual backend has been detected
		947	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		948	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		949	other initialisations - see the sources of L<AnyEvent::Strict> or
		950	L<AnyEvent::AIO> to see how this is used.
		951
		952	The most common usage is to create some global watchers, without forcing
		953	event module detection too early, for example, L<AnyEvent::AIO> creates
		954	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		955	avoid autodetecting the event module at load time.
		956
		957	If called in scalar or list context, then it creates and returns an object
		958	that automatically removes the callback again when it is destroyed (or
		959	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		960	a case where this is useful.
		961
		962	Example: Create a watcher for the IO::AIO module and store it in
		963	C<$WATCHER>, but do so only do so after the event loop is initialised.
		964
		965	our WATCHER;
		966
		967	my $guard = AnyEvent::post_detect {
		968	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		969	};
		970
		971	# the ||= is important in case post_detect immediately runs the block,
		972	# as to not clobber the newly-created watcher. assigning both watcher and
		973	# post_detect guard to the same variable has the advantage of users being
		974	# able to just C<undef $WATCHER> if the watcher causes them grief.
		975
		976	$WATCHER ||= $guard;
		977
		978	=item @AnyEvent::post_detect
		979
		980	If there are any code references in this array (you can C<push> to it
		981	before or after loading AnyEvent), then they will be called directly
		982	after the event loop has been chosen.
		983
		984	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		985	if it is defined then the event loop has already been detected, and the
		986	array will be ignored.
		987
		988	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		989	it, as it takes care of these details.
		990
		991	This variable is mainly useful for modules that can do something useful
		992	when AnyEvent is used and thus want to know when it is initialised, but do
		993	not need to even load it by default. This array provides the means to hook
		994	into AnyEvent passively, without loading it.
		995
		996	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		997	together, you could put this into Coro (this is the actual code used by
		998	Coro to accomplish this):
		999
		1000	if (defined $AnyEvent::MODEL) {
		1001	# AnyEvent already initialised, so load Coro::AnyEvent
		1002	require Coro::AnyEvent;
		1003	} else {
		1004	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1005	# as soon as it is
		1006	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1007	}
215		1008
216	=back	1009	=back
217		1010
218	=head1 WHAT TO DO IN A MODULE	1011	=head1 WHAT TO DO IN A MODULE
219		1012
220	As a module author, you should "use AnyEvent" and call AnyEvent methods	1013	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.	1014	freely, but you should not load a specific event module or rely on it.
222		1015
223	Be careful when you create watchers in the module body - Anyevent will	1016	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	1017	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	1018	by calling AnyEvent in your module body you force the user of your module
226	to load the event module first.	1019	to load the event module first.
227		1020
		1021	Never call C<< ->recv >> on a condition variable unless you I<know> that
		1022	the C<< ->send >> method has been called on it already. This is
		1023	because it will stall the whole program, and the whole point of using
		1024	events is to stay interactive.
		1025
		1026	It is fine, however, to call C<< ->recv >> when the user of your module
		1027	requests it (i.e. if you create a http request object ad have a method
		1028	called C<results> that returns the results, it may call C<< ->recv >>
		1029	freely, as the user of your module knows what she is doing. Always).
		1030
228	=head1 WHAT TO DO IN THE MAIN PROGRAM	1031	=head1 WHAT TO DO IN THE MAIN PROGRAM
229		1032
230	There will always be a single main program - the only place that should	1033	There will always be a single main program - the only place that should
231	dictate which event model to use.	1034	dictate which event model to use.
232		1035
233	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1036	If the program is not event-based, it need not do anything special, even
234	do anything special and let AnyEvent decide which implementation to chose.	1037	when it depends on a module that uses an AnyEvent. If the program itself
		1038	uses AnyEvent, but does not care which event loop is used, all it needs
		1039	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1040	available loop implementation.
235		1041
236	If the main program relies on a specific event model (for example, in Gtk2	1042	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	1043	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	1044	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	1045	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	1046	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	1047	decide on the event model to use as soon as it creates watchers, and it
242	correct one yourself.	1048	might choose the wrong one unless you load the correct one yourself.
243		1049
244	You can chose to use a rather inefficient pure-perl implementation by	1050	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	1051	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
246	generally better.	1052	everywhere, but letting AnyEvent chose the model is generally better.
		1053
		1054	=head2 MAINLOOP EMULATION
		1055
		1056	Sometimes (often for short test scripts, or even standalone programs who
		1057	only want to use AnyEvent), you do not want to run a specific event loop.
		1058
		1059	In that case, you can use a condition variable like this:
		1060
		1061	AnyEvent->condvar->recv;
		1062
		1063	This has the effect of entering the event loop and looping forever.
		1064
		1065	Note that usually your program has some exit condition, in which case
		1066	it is better to use the "traditional" approach of storing a condition
		1067	variable somewhere, waiting for it, and sending it when the program should
		1068	exit cleanly.
		1069
		1070
		1071	=head1 OTHER MODULES
		1072
		1073	The following is a non-exhaustive list of additional modules that use
		1074	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1075	modules and other event loops in the same program. Some of the modules
		1076	come as part of AnyEvent, the others are available via CPAN.
		1077
		1078	=over 4
		1079
		1080	=item L<AnyEvent::Util>
		1081
		1082	Contains various utility functions that replace often-used blocking
		1083	functions such as C<inet_aton> with event/callback-based versions.
		1084
		1085	=item L<AnyEvent::Socket>
		1086
		1087	Provides various utility functions for (internet protocol) sockets,
		1088	addresses and name resolution. Also functions to create non-blocking tcp
		1089	connections or tcp servers, with IPv6 and SRV record support and more.
		1090
		1091	=item L<AnyEvent::Handle>
		1092
		1093	Provide read and write buffers, manages watchers for reads and writes,
		1094	supports raw and formatted I/O, I/O queued and fully transparent and
		1095	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1096
		1097	=item L<AnyEvent::DNS>
		1098
		1099	Provides rich asynchronous DNS resolver capabilities.
		1100
		1101	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1102
		1103	Implement event-based interfaces to the protocols of the same name (for
		1104	the curious, IGS is the International Go Server and FCP is the Freenet
		1105	Client Protocol).
		1106
		1107	=item L<AnyEvent::Handle::UDP>
		1108
		1109	Here be danger!
		1110
		1111	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1112	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1113	its use of a stream-based API with a protocol that isn't streamable, that
		1114	the only way to improve it is to delete it.
		1115
		1116	It features data corruption (but typically only under load) and general
		1117	confusion. On top, the author is not only clueless about UDP but also
		1118	fact-resistant - some gems of his understanding: "connect doesn't work
		1119	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1120	packets", "I don't need to implement proper error checking as UDP doesn't
		1121	support error checking" and so on - he doesn't even understand what's
		1122	wrong with his module when it is explained to him.
		1123
		1124	=item L<AnyEvent::DBI>
		1125
		1126	Executes L<DBI> requests asynchronously in a proxy process for you,
		1127	notifying you in an event-based way when the operation is finished.
		1128
		1129	=item L<AnyEvent::AIO>
		1130
		1131	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1132	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1133	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1134	file I/O, and much more.
		1135
		1136	=item L<AnyEvent::HTTPD>
		1137
		1138	A simple embedded webserver.
		1139
		1140	=item L<AnyEvent::FastPing>
		1141
		1142	The fastest ping in the west.
		1143
		1144	=item L<Coro>
		1145
		1146	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1147
		1148	=back
247		1149
248	=cut	1150	=cut
249		1151
250	package AnyEvent;	1152	package AnyEvent;
251		1153
252	no warnings;	1154	# basically a tuned-down version of common::sense
253	use strict;	1155	sub common_sense {
		1156	# from common:.sense 3.4
		1157	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00";
		1158	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1159	$^H |= 0x00000600;
		1160	}
254		1161
		1162	BEGIN { AnyEvent::common_sense }
		1163
255	use Carp;	1164	use Carp ();
256		1165
257	our $VERSION = '2.6';	1166	our $VERSION = '5.3';
258	our $MODEL;	1167	our $MODEL;
259		1168
260	our $AUTOLOAD;	1169	our $AUTOLOAD;
261	our @ISA;	1170	our @ISA;
262		1171
263	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
264
265	our @REGISTRY;	1172	our @REGISTRY;
266		1173
		1174	our $VERBOSE;
		1175
		1176	BEGIN {
		1177	require "AnyEvent/constants.pl";
		1178
		1179	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1180
		1181	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1182	if ${^TAINT};
		1183
		1184	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1185
		1186	}
		1187
		1188	our $MAX_SIGNAL_LATENCY = 10;
		1189
		1190	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1191
		1192	{
		1193	my $idx;
		1194	$PROTOCOL{$_} = ++$idx
		1195	for reverse split /\s*,\s*/,
		1196	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1197	}
		1198
267	my @models = (	1199	my @models = (
268	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
269	[EV:: => AnyEvent::Impl::EV::],	1200	[EV:: => AnyEvent::Impl::EV:: , 1],
270	[Coro::Event:: => AnyEvent::Impl::Coro::],	1201	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1202	# everything below here will not (normally) be autoprobed
		1203	# as the pureperl backend should work everywhere
		1204	# and is usually faster
271	[Event:: => AnyEvent::Impl::Event::],	1205	[Event:: => AnyEvent::Impl::Event::, 1],
272	[Glib:: => AnyEvent::Impl::Glib::],	1206	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1207	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1208	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1209	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1210	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1211	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
273	[Tk:: => AnyEvent::Impl::Tk::],	1212	[Wx:: => AnyEvent::Impl::POE::],
274	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1213	[Prima:: => AnyEvent::Impl::POE::],
		1214	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::],
		1215	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
275	);	1216	);
276		1217
277	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1218	our %method = map +($_ => 1),
		1219	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1220
		1221	our @post_detect;
		1222
		1223	sub post_detect(&) {
		1224	my ($cb) = @_;
		1225
		1226	push @post_detect, $cb;
		1227
		1228	defined wantarray
		1229	? bless \$cb, "AnyEvent::Util::postdetect"
		1230	: ()
		1231	}
		1232
		1233	sub AnyEvent::Util::postdetect::DESTROY {
		1234	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1235	}
278		1236
279	sub detect() {	1237	sub detect() {
		1238	# free some memory
		1239	*detect = sub () { $MODEL };
		1240
		1241	local $!; # for good measure
		1242	local $SIG{__DIE__};
		1243
		1244	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1245	my $model = "AnyEvent::Impl::$1";
		1246	if (eval "require $model") {
		1247	$MODEL = $model;
		1248	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1249	} else {
		1250	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1251	}
		1252	}
		1253
		1254	# check for already loaded models
280	unless ($MODEL) {	1255	unless ($MODEL) {
281	no strict 'refs';
282
283	# check for already loaded models
284	for (@REGISTRY, @models) {	1256	for (@REGISTRY, @models) {
285	my ($package, $model) = @$_;	1257	my ($package, $model) = @$_;
286	if (${"$package\::VERSION"} > 0) {	1258	if (${"$package\::VERSION"} > 0) {
287	if (eval "require $model") {	1259	if (eval "require $model") {
288	$MODEL = $model;	1260	$MODEL = $model;
289	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	1261	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
290	last;	1262	last;
291	}	1263	}
292	}	1264	}
293	}	1265	}
294		1266
295	unless ($MODEL) {	1267	unless ($MODEL) {
296	# try to load a model	1268	# try to autoload a model
297
298	for (@REGISTRY, @models) {	1269	for (@REGISTRY, @models) {
299	my ($package, $model) = @$_;	1270	my ($package, $model, $autoload) = @$_;
		1271	if (
		1272	$autoload
300	if (eval "require $package"	1273	and eval "require $package"
301	and ${"$package\::VERSION"} > 0	1274	and ${"$package\::VERSION"} > 0
302	and eval "require $model") {	1275	and eval "require $model"
		1276	) {
303	$MODEL = $model;	1277	$MODEL = $model;
304	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	1278	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
305	last;	1279	last;
306	}	1280	}
307	}	1281	}
308		1282
309	$MODEL	1283	$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.";	1284	or die "AnyEvent: backend autodetection failed - did you properly install AnyEvent?\n";
311	}	1285	}
312
313	unshift @ISA, $MODEL;
314	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
315	}	1286	}
		1287
		1288	@models = (); # free probe data
		1289
		1290	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1291	unshift @ISA, $MODEL;
		1292
		1293	# now nuke some methods that are overridden by the backend.
		1294	# SUPER is not allowed.
		1295	for (qw(time signal child idle)) {
		1296	undef &{"AnyEvent::Base::$_"}
		1297	if defined &{"$MODEL\::$_"};
		1298	}
		1299
		1300	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1301	eval { require AnyEvent::Strict };
		1302	warn "AnyEvent: cannot load AnyEvent::Strict: $@"
		1303	if $@ && $VERBOSE;
		1304	}
		1305
		1306	(shift @post_detect)->() while @post_detect;
		1307
		1308	*post_detect = sub(&) {
		1309	shift->();
		1310
		1311	undef
		1312	};
316		1313
317	$MODEL	1314	$MODEL
318	}	1315	}
319		1316
320	sub AUTOLOAD {	1317	sub AUTOLOAD {
321	(my $func = $AUTOLOAD) =~ s/.*://;	1318	(my $func = $AUTOLOAD) =~ s/.*://;
322		1319
323	$method{$func}	1320	$method{$func}
324	or croak "$func: not a valid method for AnyEvent objects";	1321	or Carp::croak "$func: not a valid AnyEvent class method";
325		1322
326	detect unless $MODEL;	1323	detect;
327		1324
328	my $class = shift;	1325	my $class = shift;
329	$class->$func (@_);	1326	$class->$func (@_);
330	}	1327	}
331		1328
		1329	# utility function to dup a filehandle. this is used by many backends
		1330	# to support binding more than one watcher per filehandle (they usually
		1331	# allow only one watcher per fd, so we dup it to get a different one).
		1332	sub _dupfh($$;$$) {
		1333	my ($poll, $fh, $r, $w) = @_;
		1334
		1335	# cygwin requires the fh mode to be matching, unix doesn't
		1336	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1337
		1338	open my $fh2, $mode, $fh
		1339	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1340
		1341	# we assume CLOEXEC is already set by perl in all important cases
		1342
		1343	($fh2, $rw)
		1344	}
		1345
		1346	=head1 SIMPLIFIED AE API
		1347
		1348	Starting with version 5.0, AnyEvent officially supports a second, much
		1349	simpler, API that is designed to reduce the calling, typing and memory
		1350	overhead by using function call syntax and a fixed number of parameters.
		1351
		1352	See the L<AE> manpage for details.
		1353
		1354	=cut
		1355
		1356	package AE;
		1357
		1358	our $VERSION = $AnyEvent::VERSION;
		1359
		1360	# fall back to the main API by default - backends and AnyEvent::Base
		1361	# implementations can overwrite these.
		1362
		1363	sub io($$$) {
		1364	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1365	}
		1366
		1367	sub timer($$$) {
		1368	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1369	}
		1370
		1371	sub signal($$) {
		1372	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1373	}
		1374
		1375	sub child($$) {
		1376	AnyEvent->child (pid => $_[0], cb => $_[1])
		1377	}
		1378
		1379	sub idle($) {
		1380	AnyEvent->idle (cb => $_[0])
		1381	}
		1382
		1383	sub cv(;&) {
		1384	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1385	}
		1386
		1387	sub now() {
		1388	AnyEvent->now
		1389	}
		1390
		1391	sub now_update() {
		1392	AnyEvent->now_update
		1393	}
		1394
		1395	sub time() {
		1396	AnyEvent->time
		1397	}
		1398
332	package AnyEvent::Base;	1399	package AnyEvent::Base;
333		1400
		1401	# default implementations for many methods
		1402
		1403	sub time {
		1404	eval q{ # poor man's autoloading {}
		1405	# probe for availability of Time::HiRes
		1406	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1407	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1408	*AE::time = \&Time::HiRes::time;
		1409	# if (eval "use POSIX (); (POSIX::times())...
		1410	} else {
		1411	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1412	*AE::time = sub (){ time }; # epic fail
		1413	}
		1414
		1415	*time = sub { AE::time }; # different prototypes
		1416	};
		1417	die if $@;
		1418
		1419	&time
		1420	}
		1421
		1422	*now = \&time;
		1423
		1424	sub now_update { }
		1425
334	# default implementation for ->condvar, ->wait, ->broadcast	1426	# default implementation for ->condvar
335		1427
336	sub condvar {	1428	sub condvar {
337	bless \my $flag, "AnyEvent::Base::CondVar"	1429	eval q{ # poor man's autoloading {}
338	}	1430	*condvar = sub {
		1431	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1432	};
339		1433
340	sub AnyEvent::Base::CondVar::broadcast {	1434	*AE::cv = sub (;&) {
341	${$_[0]}++;	1435	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
342	}	1436	};
		1437	};
		1438	die if $@;
343		1439
344	sub AnyEvent::Base::CondVar::wait {	1440	&condvar
345	AnyEvent->one_event while !${$_[0]};
346	}	1441	}
347		1442
348	# default implementation for ->signal	1443	# default implementation for ->signal
349		1444
350	our %SIG_CB;	1445	our $HAVE_ASYNC_INTERRUPT;
		1446
		1447	sub _have_async_interrupt() {
		1448	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1449	&& eval "use Async::Interrupt 1.02 (); 1")
		1450	unless defined $HAVE_ASYNC_INTERRUPT;
		1451
		1452	$HAVE_ASYNC_INTERRUPT
		1453	}
		1454
		1455	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1456	our (%SIG_ASY, %SIG_ASY_W);
		1457	our ($SIG_COUNT, $SIG_TW);
		1458
		1459	# install a dummy wakeup watcher to reduce signal catching latency
		1460	# used by Impls
		1461	sub _sig_add() {
		1462	unless ($SIG_COUNT++) {
		1463	# try to align timer on a full-second boundary, if possible
		1464	my $NOW = AE::now;
		1465
		1466	$SIG_TW = AE::timer
		1467	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1468	$MAX_SIGNAL_LATENCY,
		1469	sub { } # just for the PERL_ASYNC_CHECK
		1470	;
		1471	}
		1472	}
		1473
		1474	sub _sig_del {
		1475	undef $SIG_TW
		1476	unless --$SIG_COUNT;
		1477	}
		1478
		1479	our $_sig_name_init; $_sig_name_init = sub {
		1480	eval q{ # poor man's autoloading {}
		1481	undef $_sig_name_init;
		1482
		1483	if (_have_async_interrupt) {
		1484	*sig2num = \&Async::Interrupt::sig2num;
		1485	*sig2name = \&Async::Interrupt::sig2name;
		1486	} else {
		1487	require Config;
		1488
		1489	my %signame2num;
		1490	@signame2num{ split ' ', $Config::Config{sig_name} }
		1491	= split ' ', $Config::Config{sig_num};
		1492
		1493	my @signum2name;
		1494	@signum2name[values %signame2num] = keys %signame2num;
		1495
		1496	*sig2num = sub($) {
		1497	$_[0] > 0 ? shift : $signame2num{+shift}
		1498	};
		1499	*sig2name = sub ($) {
		1500	$_[0] > 0 ? $signum2name[+shift] : shift
		1501	};
		1502	}
		1503	};
		1504	die if $@;
		1505	};
		1506
		1507	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1508	sub sig2name($) { &$_sig_name_init; &sig2name }
351		1509
352	sub signal {	1510	sub signal {
		1511	eval q{ # poor man's autoloading {}
		1512	# probe for availability of Async::Interrupt
		1513	if (_have_async_interrupt) {
		1514	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1515
		1516	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1517	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1518
		1519	} else {
		1520	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1521
		1522	if (AnyEvent::WIN32) {
		1523	require AnyEvent::Util;
		1524
		1525	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1526	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1527	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1528	} else {
		1529	pipe $SIGPIPE_R, $SIGPIPE_W;
		1530	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1531	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1532
		1533	# not strictly required, as $^F is normally 2, but let's make sure...
		1534	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1535	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1536	}
		1537
		1538	$SIGPIPE_R
		1539	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1540
		1541	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1542	}
		1543
		1544	*signal = $HAVE_ASYNC_INTERRUPT
		1545	? sub {
353	my (undef, %arg) = @_;	1546	my (undef, %arg) = @_;
354		1547
		1548	# async::interrupt
355	my $signal = uc $arg{signal}	1549	my $signal = sig2num $arg{signal};
356	or Carp::croak "required option 'signal' is missing";
357
358	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1550	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1551
		1552	$SIG_ASY{$signal} ||= new Async::Interrupt
		1553	cb => sub { undef $SIG_EV{$signal} },
		1554	signal => $signal,
		1555	pipe => [$SIGPIPE_R->filenos],
		1556	pipe_autodrain => 0,
		1557	;
		1558
		1559	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1560	}
		1561	: sub {
		1562	my (undef, %arg) = @_;
		1563
		1564	# pure perl
		1565	my $signal = sig2name $arg{signal};
		1566	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1567
359	$SIG{$signal} ||= sub {	1568	$SIG{$signal} ||= sub {
		1569	local $!;
		1570	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1571	undef $SIG_EV{$signal};
		1572	};
		1573
		1574	# can't do signal processing without introducing races in pure perl,
		1575	# so limit the signal latency.
		1576	_sig_add;
		1577
		1578	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1579	}
		1580	;
		1581
		1582	*AnyEvent::Base::signal::DESTROY = sub {
		1583	my ($signal, $cb) = @{$_[0]};
		1584
		1585	_sig_del;
		1586
		1587	delete $SIG_CB{$signal}{$cb};
		1588
		1589	$HAVE_ASYNC_INTERRUPT
		1590	? delete $SIG_ASY{$signal}
		1591	: # delete doesn't work with older perls - they then
		1592	# print weird messages, or just unconditionally exit
		1593	# instead of getting the default action.
		1594	undef $SIG{$signal}
		1595	unless keys %{ $SIG_CB{$signal} };
		1596	};
		1597
		1598	*_signal_exec = sub {
		1599	$HAVE_ASYNC_INTERRUPT
		1600	? $SIGPIPE_R->drain
		1601	: sysread $SIGPIPE_R, (my $dummy), 9;
		1602
		1603	while (%SIG_EV) {
		1604	for (keys %SIG_EV) {
		1605	delete $SIG_EV{$_};
360	$_->() for values %{ $SIG_CB{$signal} || {} };	1606	$_->() for values %{ $SIG_CB{$_} || {} };
		1607	}
		1608	}
		1609	};
361	};	1610	};
		1611	die if $@;
362		1612
363	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1613	&signal
364	}
365
366	sub AnyEvent::Base::Signal::DESTROY {
367	my ($signal, $cb) = @{$_[0]};
368
369	delete $SIG_CB{$signal}{$cb};
370
371	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
372	}	1614	}
373		1615
374	# default implementation for ->child	1616	# default implementation for ->child
375		1617
376	our %PID_CB;	1618	our %PID_CB;
377	our $CHLD_W;	1619	our $CHLD_W;
378	our $PID_IDLE;	1620	our $CHLD_DELAY_W;
379	our $WNOHANG;
380		1621
381	sub _child_wait {	1622	# used by many Impl's
382	while (0 <= (my $pid = waitpid -1, $WNOHANG)) {	1623	sub _emit_childstatus($$) {
		1624	my (undef, $rpid, $rstatus) = @_;
		1625
		1626	$_->($rpid, $rstatus)
383	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1627	for values %{ $PID_CB{$rpid} || {} },
384	(values %{ $PID_CB{0} || {} });	1628	values %{ $PID_CB{0} || {} };
385	}
386
387	undef $PID_IDLE;
388	}	1629	}
389		1630
390	sub child {	1631	sub child {
		1632	eval q{ # poor man's autoloading {}
		1633	*_sigchld = sub {
		1634	my $pid;
		1635
		1636	AnyEvent->_emit_childstatus ($pid, $?)
		1637	while ($pid = waitpid -1, WNOHANG) > 0;
		1638	};
		1639
		1640	*child = sub {
391	my (undef, %arg) = @_;	1641	my (undef, %arg) = @_;
392		1642
393	defined (my $pid = $arg{pid} + 0)	1643	defined (my $pid = $arg{pid} + 0)
394	or Carp::croak "required option 'pid' is missing";	1644	or Carp::croak "required option 'pid' is missing";
395		1645
396	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1646	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
397		1647
398	unless ($WNOHANG) {
399	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
400	}
401
402	unless ($CHLD_W) {	1648	unless ($CHLD_W) {
403	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_child_wait);	1649	$CHLD_W = AE::signal CHLD => \&_sigchld;
404	# child could be a zombie already	1650	# child could be a zombie already, so make at least one round
405	$PID_IDLE ||= AnyEvent->timer (after => 0, cb => \&_child_wait);	1651	&_sigchld;
406	}	1652	}
407		1653
408	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1654	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
409	}	1655	};
410		1656
411	sub AnyEvent::Base::Child::DESTROY {	1657	*AnyEvent::Base::child::DESTROY = sub {
412	my ($pid, $cb) = @{$_[0]};	1658	my ($pid, $cb) = @{$_[0]};
413		1659
414	delete $PID_CB{$pid}{$cb};	1660	delete $PID_CB{$pid}{$cb};
415	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1661	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
416		1662
417	undef $CHLD_W unless keys %PID_CB;	1663	undef $CHLD_W unless keys %PID_CB;
		1664	};
		1665	};
		1666	die if $@;
		1667
		1668	&child
418	}	1669	}
		1670
		1671	# idle emulation is done by simply using a timer, regardless
		1672	# of whether the process is idle or not, and not letting
		1673	# the callback use more than 50% of the time.
		1674	sub idle {
		1675	eval q{ # poor man's autoloading {}
		1676	*idle = sub {
		1677	my (undef, %arg) = @_;
		1678
		1679	my ($cb, $w, $rcb) = $arg{cb};
		1680
		1681	$rcb = sub {
		1682	if ($cb) {
		1683	$w = _time;
		1684	&$cb;
		1685	$w = _time - $w;
		1686
		1687	# never use more then 50% of the time for the idle watcher,
		1688	# within some limits
		1689	$w = 0.0001 if $w < 0.0001;
		1690	$w = 5 if $w > 5;
		1691
		1692	$w = AE::timer $w, 0, $rcb;
		1693	} else {
		1694	# clean up...
		1695	undef $w;
		1696	undef $rcb;
		1697	}
		1698	};
		1699
		1700	$w = AE::timer 0.05, 0, $rcb;
		1701
		1702	bless \\$cb, "AnyEvent::Base::idle"
		1703	};
		1704
		1705	*AnyEvent::Base::idle::DESTROY = sub {
		1706	undef $${$_[0]};
		1707	};
		1708	};
		1709	die if $@;
		1710
		1711	&idle
		1712	}
		1713
		1714	package AnyEvent::CondVar;
		1715
		1716	our @ISA = AnyEvent::CondVar::Base::;
		1717
		1718	# only to be used for subclassing
		1719	sub new {
		1720	my $class = shift;
		1721	bless AnyEvent->condvar (@_), $class
		1722	}
		1723
		1724	package AnyEvent::CondVar::Base;
		1725
		1726	#use overload
		1727	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1728	# fallback => 1;
		1729
		1730	# save 300+ kilobytes by dirtily hardcoding overloading
		1731	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1732	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1733	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1734	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1735
		1736	our $WAITING;
		1737
		1738	sub _send {
		1739	# nop
		1740	}
		1741
		1742	sub send {
		1743	my $cv = shift;
		1744	$cv->{_ae_sent} = [@_];
		1745	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1746	$cv->_send;
		1747	}
		1748
		1749	sub croak {
		1750	$_[0]{_ae_croak} = $_[1];
		1751	$_[0]->send;
		1752	}
		1753
		1754	sub ready {
		1755	$_[0]{_ae_sent}
		1756	}
		1757
		1758	sub _wait {
		1759	$WAITING
		1760	and !$_[0]{_ae_sent}
		1761	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1762
		1763	local $WAITING = 1;
		1764	AnyEvent->one_event while !$_[0]{_ae_sent};
		1765	}
		1766
		1767	sub recv {
		1768	$_[0]->_wait;
		1769
		1770	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1771	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1772	}
		1773
		1774	sub cb {
		1775	my $cv = shift;
		1776
		1777	@_
		1778	and $cv->{_ae_cb} = shift
		1779	and $cv->{_ae_sent}
		1780	and (delete $cv->{_ae_cb})->($cv);
		1781
		1782	$cv->{_ae_cb}
		1783	}
		1784
		1785	sub begin {
		1786	++$_[0]{_ae_counter};
		1787	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1788	}
		1789
		1790	sub end {
		1791	return if --$_[0]{_ae_counter};
		1792	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1793	}
		1794
		1795	# undocumented/compatibility with pre-3.4
		1796	*broadcast = \&send;
		1797	*wait = \&_wait;
		1798
		1799	=head1 ERROR AND EXCEPTION HANDLING
		1800
		1801	In general, AnyEvent does not do any error handling - it relies on the
		1802	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1803	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1804	checking of all AnyEvent methods, however, which is highly useful during
		1805	development.
		1806
		1807	As for exception handling (i.e. runtime errors and exceptions thrown while
		1808	executing a callback), this is not only highly event-loop specific, but
		1809	also not in any way wrapped by this module, as this is the job of the main
		1810	program.
		1811
		1812	The pure perl event loop simply re-throws the exception (usually
		1813	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1814	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1815	so on.
		1816
		1817	=head1 ENVIRONMENT VARIABLES
		1818
		1819	The following environment variables are used by this module or its
		1820	submodules.
		1821
		1822	Note that AnyEvent will remove I<all> environment variables starting with
		1823	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1824	enabled.
		1825
		1826	=over 4
		1827
		1828	=item C<PERL_ANYEVENT_VERBOSE>
		1829
		1830	By default, AnyEvent will be completely silent except in fatal
		1831	conditions. You can set this environment variable to make AnyEvent more
		1832	talkative.
		1833
		1834	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1835	conditions, such as not being able to load the event model specified by
		1836	C<PERL_ANYEVENT_MODEL>.
		1837
		1838	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1839	model it chooses.
		1840
		1841	When set to C<8> or higher, then AnyEvent will report extra information on
		1842	which optional modules it loads and how it implements certain features.
		1843
		1844	=item C<PERL_ANYEVENT_STRICT>
		1845
		1846	AnyEvent does not do much argument checking by default, as thorough
		1847	argument checking is very costly. Setting this variable to a true value
		1848	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1849	check the arguments passed to most method calls. If it finds any problems,
		1850	it will croak.
		1851
		1852	In other words, enables "strict" mode.
		1853
		1854	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		1855	>>, it is definitely recommended to keep it off in production. Keeping
		1856	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1857	can be very useful, however.
		1858
		1859	=item C<PERL_ANYEVENT_MODEL>
		1860
		1861	This can be used to specify the event model to be used by AnyEvent, before
		1862	auto detection and -probing kicks in. It must be a string consisting
		1863	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1864	and the resulting module name is loaded and if the load was successful,
		1865	used as event model. If it fails to load AnyEvent will proceed with
		1866	auto detection and -probing.
		1867
		1868	This functionality might change in future versions.
		1869
		1870	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1871	could start your program like this:
		1872
		1873	PERL_ANYEVENT_MODEL=Perl perl ...
		1874
		1875	=item C<PERL_ANYEVENT_PROTOCOLS>
		1876
		1877	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1878	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1879	of auto probing).
		1880
		1881	Must be set to a comma-separated list of protocols or address families,
		1882	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1883	used, and preference will be given to protocols mentioned earlier in the
		1884	list.
		1885
		1886	This variable can effectively be used for denial-of-service attacks
		1887	against local programs (e.g. when setuid), although the impact is likely
		1888	small, as the program has to handle conenction and other failures anyways.
		1889
		1890	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1891	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1892	- only support IPv4, never try to resolve or contact IPv6
		1893	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1894	IPv6, but prefer IPv6 over IPv4.
		1895
		1896	=item C<PERL_ANYEVENT_EDNS0>
		1897
		1898	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1899	for DNS. This extension is generally useful to reduce DNS traffic, but
		1900	some (broken) firewalls drop such DNS packets, which is why it is off by
		1901	default.
		1902
		1903	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1904	EDNS0 in its DNS requests.
		1905
		1906	=item C<PERL_ANYEVENT_MAX_FORKS>
		1907
		1908	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1909	will create in parallel.
		1910
		1911	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1912
		1913	The default value for the C<max_outstanding> parameter for the default DNS
		1914	resolver - this is the maximum number of parallel DNS requests that are
		1915	sent to the DNS server.
		1916
		1917	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1918
		1919	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1920	configuration) in the default resolver. When set to the empty string, no
		1921	default config will be used.
		1922
		1923	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1924
		1925	When neither C<ca_file> nor C<ca_path> was specified during
		1926	L<AnyEvent::TLS> context creation, and either of these environment
		1927	variables exist, they will be used to specify CA certificate locations
		1928	instead of a system-dependent default.
		1929
		1930	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1931
		1932	When these are set to C<1>, then the respective modules are not
		1933	loaded. Mostly good for testing AnyEvent itself.
		1934
		1935	=back
419		1936
420	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1937	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1938
		1939	This is an advanced topic that you do not normally need to use AnyEvent in
		1940	a module. This section is only of use to event loop authors who want to
		1941	provide AnyEvent compatibility.
421		1942
422	If you need to support another event library which isn't directly	1943	If you need to support another event library which isn't directly
423	supported by AnyEvent, you can supply your own interface to it by	1944	supported by AnyEvent, you can supply your own interface to it by
424	pushing, before the first watcher gets created, the package name of	1945	pushing, before the first watcher gets created, the package name of
425	the event module and the package name of the interface to use onto	1946	the event module and the package name of the interface to use onto
426	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	1947	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
427	AnyEvent.	1948	AnyEvent, so it is reasonably cheap.
428		1949
429	Example:	1950	Example:
430		1951
431	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	1952	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
432		1953
433	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	1954	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
434	package/class when it finds the C<urxvt> package/module is loaded. When	1955	package/class when it finds the C<urxvt> package/module is already loaded.
		1956
435	AnyEvent is loaded and asked to find a suitable event model, it will	1957	When AnyEvent is loaded and asked to find a suitable event model, it
436	first check for the presence of urxvt.	1958	will first check for the presence of urxvt by trying to C<use> the
		1959	C<urxvt::anyevent> module.
437		1960
438	The class should provide implementations for all watcher types (see	1961	The class should provide implementations for all watcher types. See
439	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	1962	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
440	(Source code) and so on for actual examples, use C<perldoc -m	1963	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
441	AnyEvent::Impl::Glib> to see the sources).	1964	see the sources.
442		1965
		1966	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		1967	provide suitable (hopefully) replacements.
		1968
443	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	1969	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
444	uses the above line as-is. An interface isn't included in AnyEvent	1970	terminal emulator uses the above line as-is. An interface isn't included
445	because it doesn't make sense outside the embedded interpreter inside	1971	in AnyEvent because it doesn't make sense outside the embedded interpreter
446	I<rxvt-unicode>, and it is updated and maintained as part of the	1972	inside I<rxvt-unicode>, and it is updated and maintained as part of the
447	I<rxvt-unicode> distribution.	1973	I<rxvt-unicode> distribution.
448		1974
449	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1975	I<rxvt-unicode> also cheats a bit by not providing blocking access to
450	condition variables: code blocking while waiting for a condition will	1976	condition variables: code blocking while waiting for a condition will
451	C<die>. This still works with most modules/usages, and blocking calls must	1977	C<die>. This still works with most modules/usages, and blocking calls must
452	not be in an interactive application, so it makes sense.	1978	not be done in an interactive application, so it makes sense.
453		1979
454	=head1 ENVIRONMENT VARIABLES
455
456	The following environment variables are used by this module:
457
458	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
459	model gets used.
460
461	=head1 EXAMPLE	1980	=head1 EXAMPLE PROGRAM
462		1981
463	The following program uses an io watcher to read data from stdin, a timer	1982	The following program uses an I/O watcher to read data from STDIN, a timer
464	to display a message once per second, and a condvar to exit the program	1983	to display a message once per second, and a condition variable to quit the
465	when the user enters quit:	1984	program when the user enters quit:
466		1985
467	use AnyEvent;	1986	use AnyEvent;
468		1987
469	my $cv = AnyEvent->condvar;	1988	my $cv = AnyEvent->condvar;
470		1989
471	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	1990	my $io_watcher = AnyEvent->io (
		1991	fh => \*STDIN,
		1992	poll => 'r',
		1993	cb => sub {
472	warn "io event <$_[0]>\n"; # will always output <r>	1994	warn "io event <$_[0]>\n"; # will always output <r>
473	chomp (my $input = <STDIN>); # read a line	1995	chomp (my $input = <STDIN>); # read a line
474	warn "read: $input\n"; # output what has been read	1996	warn "read: $input\n"; # output what has been read
475	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1997	$cv->send if $input =~ /^q/i; # quit program if /^q/i
		1998	},
		1999	);
		2000
		2001	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
		2002	warn "timeout\n"; # print 'timeout' at most every second
476	});	2003	});
477		2004
478	my $time_watcher; # can only be used once
479
480	sub new_timer {
481	$timer = AnyEvent->timer (after => 1, cb => sub {
482	warn "timeout\n"; # print 'timeout' about every second
483	&new_timer; # and restart the time
484	});
485	}
486
487	new_timer; # create first timer
488
489	$cv->wait; # wait until user enters /^q/i	2005	$cv->recv; # wait until user enters /^q/i
490		2006
491	=head1 REAL-WORLD EXAMPLE	2007	=head1 REAL-WORLD EXAMPLE
492		2008
493	Consider the L<Net::FCP> module. It features (among others) the following	2009	Consider the L<Net::FCP> module. It features (among others) the following
494	API calls, which are to freenet what HTTP GET requests are to http:	2010	API calls, which are to freenet what HTTP GET requests are to http:
…		…
544	syswrite $txn->{fh}, $txn->{request}	2060	syswrite $txn->{fh}, $txn->{request}
545	or die "connection or write error";	2061	or die "connection or write error";
546	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2062	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
547		2063
548	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2064	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
549	result and signals any possible waiters that the request ahs finished:	2065	result and signals any possible waiters that the request has finished:
550		2066
551	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2067	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
552		2068
553	if (end-of-file or data complete) {	2069	if (end-of-file or data complete) {
554	$txn->{result} = $txn->{buf};	2070	$txn->{result} = $txn->{buf};
555	$txn->{finished}->broadcast;	2071	$txn->{finished}->send;
556	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2072	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
557	}	2073	}
558		2074
559	The C<result> method, finally, just waits for the finished signal (if the	2075	The C<result> method, finally, just waits for the finished signal (if the
560	request was already finished, it doesn't wait, of course, and returns the	2076	request was already finished, it doesn't wait, of course, and returns the
561	data:	2077	data:
562		2078
563	$txn->{finished}->wait;	2079	$txn->{finished}->recv;
564	return $txn->{result};	2080	return $txn->{result};
565		2081
566	The actual code goes further and collects all errors (C<die>s, exceptions)	2082	The actual code goes further and collects all errors (C<die>s, exceptions)
567	that occured during request processing. The C<result> method detects	2083	that occurred during request processing. The C<result> method detects
568	wether an exception as thrown (it is stored inside the $txn object)	2084	whether an exception as thrown (it is stored inside the $txn object)
569	and just throws the exception, which means connection errors and other	2085	and just throws the exception, which means connection errors and other
570	problems get reported tot he code that tries to use the result, not in a	2086	problems get reported to the code that tries to use the result, not in a
571	random callback.	2087	random callback.
572		2088
573	All of this enables the following usage styles:	2089	All of this enables the following usage styles:
574		2090
575	1. Blocking:	2091	1. Blocking:
576		2092
577	my $data = $fcp->client_get ($url);	2093	my $data = $fcp->client_get ($url);
578		2094
579	2. Blocking, but parallelizing:	2095	2. Blocking, but running in parallel:
580		2096
581	my @datas = map $_->result,	2097	my @datas = map $_->result,
582	map $fcp->txn_client_get ($_),	2098	map $fcp->txn_client_get ($_),
583	@urls;	2099	@urls;
584		2100
585	Both blocking examples work without the module user having to know	2101	Both blocking examples work without the module user having to know
586	anything about events.	2102	anything about events.
587		2103
588	3a. Event-based in a main program, using any support Event module:	2104	3a. Event-based in a main program, using any supported event module:
589		2105
590	use Event;	2106	use EV;
591		2107
592	$fcp->txn_client_get ($url)->cb (sub {	2108	$fcp->txn_client_get ($url)->cb (sub {
593	my $txn = shift;	2109	my $txn = shift;
594	my $data = $txn->result;	2110	my $data = $txn->result;
595	...	2111	...
596	});	2112	});
597		2113
598	Event::loop;	2114	EV::loop;
599		2115
600	3b. The module user could use AnyEvent, too:	2116	3b. The module user could use AnyEvent, too:
601		2117
602	use AnyEvent;	2118	use AnyEvent;
603		2119
604	my $quit = AnyEvent->condvar;	2120	my $quit = AnyEvent->condvar;
605		2121
606	$fcp->txn_client_get ($url)->cb (sub {	2122	$fcp->txn_client_get ($url)->cb (sub {
607	...	2123	...
608	$quit->broadcast;	2124	$quit->send;
609	});	2125	});
610		2126
611	$quit->wait;	2127	$quit->recv;
		2128
		2129
		2130	=head1 BENCHMARKS
		2131
		2132	To give you an idea of the performance and overheads that AnyEvent adds
		2133	over the event loops themselves and to give you an impression of the speed
		2134	of various event loops I prepared some benchmarks.
		2135
		2136	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2137
		2138	Here is a benchmark of various supported event models used natively and
		2139	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2140	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		2141	which it is), lets them fire exactly once and destroys them again.
		2142
		2143	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2144	distribution. It uses the L<AE> interface, which makes a real difference
		2145	for the EV and Perl backends only.
		2146
		2147	=head3 Explanation of the columns
		2148
		2149	I<watcher> is the number of event watchers created/destroyed. Since
		2150	different event models feature vastly different performances, each event
		2151	loop was given a number of watchers so that overall runtime is acceptable
		2152	and similar between tested event loop (and keep them from crashing): Glib
		2153	would probably take thousands of years if asked to process the same number
		2154	of watchers as EV in this benchmark.
		2155
		2156	I<bytes> is the number of bytes (as measured by the resident set size,
		2157	RSS) consumed by each watcher. This method of measuring captures both C
		2158	and Perl-based overheads.
		2159
		2160	I<create> is the time, in microseconds (millionths of seconds), that it
		2161	takes to create a single watcher. The callback is a closure shared between
		2162	all watchers, to avoid adding memory overhead. That means closure creation
		2163	and memory usage is not included in the figures.
		2164
		2165	I<invoke> is the time, in microseconds, used to invoke a simple
		2166	callback. The callback simply counts down a Perl variable and after it was
		2167	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2168	signal the end of this phase.
		2169
		2170	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2171	watcher.
		2172
		2173	=head3 Results
		2174
		2175	name watchers bytes create invoke destroy comment
		2176	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
		2177	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
		2178	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
		2179	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
		2180	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
		2181	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2182	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2183	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
		2184	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
		2185	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
		2186	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
		2187	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
		2188
		2189	=head3 Discussion
		2190
		2191	The benchmark does I<not> measure scalability of the event loop very
		2192	well. For example, a select-based event loop (such as the pure perl one)
		2193	can never compete with an event loop that uses epoll when the number of
		2194	file descriptors grows high. In this benchmark, all events become ready at
		2195	the same time, so select/poll-based implementations get an unnatural speed
		2196	boost.
		2197
		2198	Also, note that the number of watchers usually has a nonlinear effect on
		2199	overall speed, that is, creating twice as many watchers doesn't take twice
		2200	the time - usually it takes longer. This puts event loops tested with a
		2201	higher number of watchers at a disadvantage.
		2202
		2203	To put the range of results into perspective, consider that on the
		2204	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2205	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2206	cycles with POE.
		2207
		2208	C<EV> is the sole leader regarding speed and memory use, which are both
		2209	maximal/minimal, respectively. When using the L<AE> API there is zero
		2210	overhead (when going through the AnyEvent API create is about 5-6 times
		2211	slower, with other times being equal, so still uses far less memory than
		2212	any other event loop and is still faster than Event natively).
		2213
		2214	The pure perl implementation is hit in a few sweet spots (both the
		2215	constant timeout and the use of a single fd hit optimisations in the perl
		2216	interpreter and the backend itself). Nevertheless this shows that it
		2217	adds very little overhead in itself. Like any select-based backend its
		2218	performance becomes really bad with lots of file descriptors (and few of
		2219	them active), of course, but this was not subject of this benchmark.
		2220
		2221	The C<Event> module has a relatively high setup and callback invocation
		2222	cost, but overall scores in on the third place.
		2223
		2224	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2225	when using its pure perl backend.
		2226
		2227	C<Glib>'s memory usage is quite a bit higher, but it features a
		2228	faster callback invocation and overall ends up in the same class as
		2229	C<Event>. However, Glib scales extremely badly, doubling the number of
		2230	watchers increases the processing time by more than a factor of four,
		2231	making it completely unusable when using larger numbers of watchers
		2232	(note that only a single file descriptor was used in the benchmark, so
		2233	inefficiencies of C<poll> do not account for this).
		2234
		2235	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2236	more than 2000 watchers is a big setback, however, as correctness takes
		2237	precedence over speed. Nevertheless, its performance is surprising, as the
		2238	file descriptor is dup()ed for each watcher. This shows that the dup()
		2239	employed by some adaptors is not a big performance issue (it does incur a
		2240	hidden memory cost inside the kernel which is not reflected in the figures
		2241	above).
		2242
		2243	C<POE>, regardless of underlying event loop (whether using its pure perl
		2244	select-based backend or the Event module, the POE-EV backend couldn't
		2245	be tested because it wasn't working) shows abysmal performance and
		2246	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2247	as EV watchers, and 10 times as much memory as Event (the high memory
		2248	requirements are caused by requiring a session for each watcher). Watcher
		2249	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2250	implementation.
		2251
		2252	The design of the POE adaptor class in AnyEvent can not really account
		2253	for the performance issues, though, as session creation overhead is
		2254	small compared to execution of the state machine, which is coded pretty
		2255	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2256	using multiple sessions is not a good approach, especially regarding
		2257	memory usage, even the author of POE could not come up with a faster
		2258	design).
		2259
		2260	=head3 Summary
		2261
		2262	=over 4
		2263
		2264	=item * Using EV through AnyEvent is faster than any other event loop
		2265	(even when used without AnyEvent), but most event loops have acceptable
		2266	performance with or without AnyEvent.
		2267
		2268	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2269	the actual event loop, only with extremely fast event loops such as EV
		2270	adds AnyEvent significant overhead.
		2271
		2272	=item * You should avoid POE like the plague if you want performance or
		2273	reasonable memory usage.
		2274
		2275	=back
		2276
		2277	=head2 BENCHMARKING THE LARGE SERVER CASE
		2278
		2279	This benchmark actually benchmarks the event loop itself. It works by
		2280	creating a number of "servers": each server consists of a socket pair, a
		2281	timeout watcher that gets reset on activity (but never fires), and an I/O
		2282	watcher waiting for input on one side of the socket. Each time the socket
		2283	watcher reads a byte it will write that byte to a random other "server".
		2284
		2285	The effect is that there will be a lot of I/O watchers, only part of which
		2286	are active at any one point (so there is a constant number of active
		2287	fds for each loop iteration, but which fds these are is random). The
		2288	timeout is reset each time something is read because that reflects how
		2289	most timeouts work (and puts extra pressure on the event loops).
		2290
		2291	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2292	(1%) are active. This mirrors the activity of large servers with many
		2293	connections, most of which are idle at any one point in time.
		2294
		2295	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2296	distribution. It uses the L<AE> interface, which makes a real difference
		2297	for the EV and Perl backends only.
		2298
		2299	=head3 Explanation of the columns
		2300
		2301	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2302	each server has a read and write socket end).
		2303
		2304	I<create> is the time it takes to create a socket pair (which is
		2305	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2306
		2307	I<request>, the most important value, is the time it takes to handle a
		2308	single "request", that is, reading the token from the pipe and forwarding
		2309	it to another server. This includes deleting the old timeout and creating
		2310	a new one that moves the timeout into the future.
		2311
		2312	=head3 Results
		2313
		2314	name sockets create request
		2315	EV 20000 62.66 7.99
		2316	Perl 20000 68.32 32.64
		2317	IOAsync 20000 174.06 101.15 epoll
		2318	IOAsync 20000 174.67 610.84 poll
		2319	Event 20000 202.69 242.91
		2320	Glib 20000 557.01 1689.52
		2321	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2322
		2323	=head3 Discussion
		2324
		2325	This benchmark I<does> measure scalability and overall performance of the
		2326	particular event loop.
		2327
		2328	EV is again fastest. Since it is using epoll on my system, the setup time
		2329	is relatively high, though.
		2330
		2331	Perl surprisingly comes second. It is much faster than the C-based event
		2332	loops Event and Glib.
		2333
		2334	IO::Async performs very well when using its epoll backend, and still quite
		2335	good compared to Glib when using its pure perl backend.
		2336
		2337	Event suffers from high setup time as well (look at its code and you will
		2338	understand why). Callback invocation also has a high overhead compared to
		2339	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2340	uses select or poll in basically all documented configurations.
		2341
		2342	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2343	clearly fails to perform with many filehandles or in busy servers.
		2344
		2345	POE is still completely out of the picture, taking over 1000 times as long
		2346	as EV, and over 100 times as long as the Perl implementation, even though
		2347	it uses a C-based event loop in this case.
		2348
		2349	=head3 Summary
		2350
		2351	=over 4
		2352
		2353	=item * The pure perl implementation performs extremely well.
		2354
		2355	=item * Avoid Glib or POE in large projects where performance matters.
		2356
		2357	=back
		2358
		2359	=head2 BENCHMARKING SMALL SERVERS
		2360
		2361	While event loops should scale (and select-based ones do not...) even to
		2362	large servers, most programs we (or I :) actually write have only a few
		2363	I/O watchers.
		2364
		2365	In this benchmark, I use the same benchmark program as in the large server
		2366	case, but it uses only eight "servers", of which three are active at any
		2367	one time. This should reflect performance for a small server relatively
		2368	well.
		2369
		2370	The columns are identical to the previous table.
		2371
		2372	=head3 Results
		2373
		2374	name sockets create request
		2375	EV 16 20.00 6.54
		2376	Perl 16 25.75 12.62
		2377	Event 16 81.27 35.86
		2378	Glib 16 32.63 15.48
		2379	POE 16 261.87 276.28 uses POE::Loop::Event
		2380
		2381	=head3 Discussion
		2382
		2383	The benchmark tries to test the performance of a typical small
		2384	server. While knowing how various event loops perform is interesting, keep
		2385	in mind that their overhead in this case is usually not as important, due
		2386	to the small absolute number of watchers (that is, you need efficiency and
		2387	speed most when you have lots of watchers, not when you only have a few of
		2388	them).
		2389
		2390	EV is again fastest.
		2391
		2392	Perl again comes second. It is noticeably faster than the C-based event
		2393	loops Event and Glib, although the difference is too small to really
		2394	matter.
		2395
		2396	POE also performs much better in this case, but is is still far behind the
		2397	others.
		2398
		2399	=head3 Summary
		2400
		2401	=over 4
		2402
		2403	=item * C-based event loops perform very well with small number of
		2404	watchers, as the management overhead dominates.
		2405
		2406	=back
		2407
		2408	=head2 THE IO::Lambda BENCHMARK
		2409
		2410	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2411	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2412	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2413	shouldn't come as a surprise to anybody). As such, the benchmark is
		2414	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2415	very optimal. But how would AnyEvent compare when used without the extra
		2416	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2417
		2418	The benchmark itself creates an echo-server, and then, for 500 times,
		2419	connects to the echo server, sends a line, waits for the reply, and then
		2420	creates the next connection. This is a rather bad benchmark, as it doesn't
		2421	test the efficiency of the framework or much non-blocking I/O, but it is a
		2422	benchmark nevertheless.
		2423
		2424	name runtime
		2425	Lambda/select 0.330 sec
		2426	+ optimized 0.122 sec
		2427	Lambda/AnyEvent 0.327 sec
		2428	+ optimized 0.138 sec
		2429	Raw sockets/select 0.077 sec
		2430	POE/select, components 0.662 sec
		2431	POE/select, raw sockets 0.226 sec
		2432	POE/select, optimized 0.404 sec
		2433
		2434	AnyEvent/select/nb 0.085 sec
		2435	AnyEvent/EV/nb 0.068 sec
		2436	+state machine 0.134 sec
		2437
		2438	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2439	benchmarks actually make blocking connects and use 100% blocking I/O,
		2440	defeating the purpose of an event-based solution. All of the newly
		2441	written AnyEvent benchmarks use 100% non-blocking connects (using
		2442	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2443	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2444	generally require a lot more bookkeeping and event handling than blocking
		2445	connects (which involve a single syscall only).
		2446
		2447	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2448	offers similar expressive power as POE and IO::Lambda, using conventional
		2449	Perl syntax. This means that both the echo server and the client are 100%
		2450	non-blocking, further placing it at a disadvantage.
		2451
		2452	As you can see, the AnyEvent + EV combination even beats the
		2453	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2454	backend easily beats IO::Lambda and POE.
		2455
		2456	And even the 100% non-blocking version written using the high-level (and
		2457	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2458	higher level ("unoptimised") abstractions by a large margin, even though
		2459	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2460
		2461	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2462	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2463	part of the IO::Lambda distribution and were used without any changes.
		2464
		2465
		2466	=head1 SIGNALS
		2467
		2468	AnyEvent currently installs handlers for these signals:
		2469
		2470	=over 4
		2471
		2472	=item SIGCHLD
		2473
		2474	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2475	emulation for event loops that do not support them natively. Also, some
		2476	event loops install a similar handler.
		2477
		2478	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2479	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2480
		2481	=item SIGPIPE
		2482
		2483	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2484	when AnyEvent gets loaded.
		2485
		2486	The rationale for this is that AnyEvent users usually do not really depend
		2487	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2488	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2489	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2490	some random socket.
		2491
		2492	The rationale for installing a no-op handler as opposed to ignoring it is
		2493	that this way, the handler will be restored to defaults on exec.
		2494
		2495	Feel free to install your own handler, or reset it to defaults.
		2496
		2497	=back
		2498
		2499	=cut
		2500
		2501	undef $SIG{CHLD}
		2502	if $SIG{CHLD} eq 'IGNORE';
		2503
		2504	$SIG{PIPE} = sub { }
		2505	unless defined $SIG{PIPE};
		2506
		2507	=head1 RECOMMENDED/OPTIONAL MODULES
		2508
		2509	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2510	its built-in modules) are required to use it.
		2511
		2512	That does not mean that AnyEvent won't take advantage of some additional
		2513	modules if they are installed.
		2514
		2515	This section explains which additional modules will be used, and how they
		2516	affect AnyEvent's operation.
		2517
		2518	=over 4
		2519
		2520	=item L<Async::Interrupt>
		2521
		2522	This slightly arcane module is used to implement fast signal handling: To
		2523	my knowledge, there is no way to do completely race-free and quick
		2524	signal handling in pure perl. To ensure that signals still get
		2525	delivered, AnyEvent will start an interval timer to wake up perl (and
		2526	catch the signals) with some delay (default is 10 seconds, look for
		2527	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2528
		2529	If this module is available, then it will be used to implement signal
		2530	catching, which means that signals will not be delayed, and the event loop
		2531	will not be interrupted regularly, which is more efficient (and good for
		2532	battery life on laptops).
		2533
		2534	This affects not just the pure-perl event loop, but also other event loops
		2535	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2536
		2537	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2538	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2539	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2540	does nothing for those backends.
		2541
		2542	=item L<EV>
		2543
		2544	This module isn't really "optional", as it is simply one of the backend
		2545	event loops that AnyEvent can use. However, it is simply the best event
		2546	loop available in terms of features, speed and stability: It supports
		2547	the AnyEvent API optimally, implements all the watcher types in XS, does
		2548	automatic timer adjustments even when no monotonic clock is available,
		2549	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2550	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2551	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2552
		2553	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2554	then this module will do nothing for you.
		2555
		2556	=item L<Guard>
		2557
		2558	The guard module, when used, will be used to implement
		2559	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2560	lot less memory), but otherwise doesn't affect guard operation much. It is
		2561	purely used for performance.
		2562
		2563	=item L<JSON> and L<JSON::XS>
		2564
		2565	One of these modules is required when you want to read or write JSON data
		2566	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2567	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2568
		2569	=item L<Net::SSLeay>
		2570
		2571	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2572	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2573	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2574
		2575	=item L<Time::HiRes>
		2576
		2577	This module is part of perl since release 5.008. It will be used when the
		2578	chosen event library does not come with a timing source of its own. The
		2579	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2580	try to use a monotonic clock for timing stability.
		2581
		2582	=back
		2583
		2584
		2585	=head1 FORK
		2586
		2587	Most event libraries are not fork-safe. The ones who are usually are
		2588	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2589	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2590	are usually badly thought-out hacks that are incompatible with fork in
		2591	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2592	continue event-processing in both parent and child (or both, if you know
		2593	what you are doing).
		2594
		2595	This means that, in general, you cannot fork and do event processing in
		2596	the child if the event library was initialised before the fork (which
		2597	usually happens when the first AnyEvent watcher is created, or the library
		2598	is loaded).
		2599
		2600	If you have to fork, you must either do so I<before> creating your first
		2601	watcher OR you must not use AnyEvent at all in the child OR you must do
		2602	something completely out of the scope of AnyEvent.
		2603
		2604	The problem of doing event processing in the parent I<and> the child
		2605	is much more complicated: even for backends that I<are> fork-aware or
		2606	fork-safe, their behaviour is not usually what you want: fork clones all
		2607	watchers, that means all timers, I/O watchers etc. are active in both
		2608	parent and child, which is almost never what you want. USing C<exec>
		2609	to start worker children from some kind of manage rprocess is usually
		2610	preferred, because it is much easier and cleaner, at the expense of having
		2611	to have another binary.
		2612
		2613
		2614	=head1 SECURITY CONSIDERATIONS
		2615
		2616	AnyEvent can be forced to load any event model via
		2617	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		2618	execute arbitrary code or directly gain access, it can easily be used to
		2619	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		2620	will not be active when the program uses a different event model than
		2621	specified in the variable.
		2622
		2623	You can make AnyEvent completely ignore this variable by deleting it
		2624	before the first watcher gets created, e.g. with a C<BEGIN> block:
		2625
		2626	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		2627
		2628	use AnyEvent;
		2629
		2630	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2631	be used to probe what backend is used and gain other information (which is
		2632	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2633	$ENV{PERL_ANYEVENT_STRICT}.
		2634
		2635	Note that AnyEvent will remove I<all> environment variables starting with
		2636	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2637	enabled.
		2638
		2639
		2640	=head1 BUGS
		2641
		2642	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2643	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2644	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2645	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2646	pronounced).
		2647
612		2648
613	=head1 SEE ALSO	2649	=head1 SEE ALSO
614		2650
615	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	2651	Tutorial/Introduction: L<AnyEvent::Intro>.
616		2652
617	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	2653	FAQ: L<AnyEvent::FAQ>.
618		2654
619	Nontrivial usage example: L<Net::FCP>.	2655	Utility functions: L<AnyEvent::Util>.
620		2656
621	=head1	2657	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		2658	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
		2659
		2660	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2661	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2662	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2663	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
		2664
		2665	Non-blocking file handles, sockets, TCP clients and
		2666	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2667
		2668	Asynchronous DNS: L<AnyEvent::DNS>.
		2669
		2670	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		2671
		2672	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		2673	L<AnyEvent::HTTP>.
		2674
		2675
		2676	=head1 AUTHOR
		2677
		2678	Marc Lehmann <schmorp@schmorp.de>
		2679	http://home.schmorp.de/
622		2680
623	=cut	2681	=cut
624		2682
625	1	2683	1
626		2684

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