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Revision 1.313 by root, Sun Feb 21 09:28:18 2010 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	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		53
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		55
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
27		58
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	60	policy> and AnyEvent is I<small and efficient>.
30		61
31	First and foremost, I<AnyEvent is not an event model> itself, it only	62	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	63	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	64	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	65	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	66	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	67	cannot change this, but it can hide the differences between those event
		68	loops.
37		69
38	The goal of AnyEvent is to offer module authors the ability to do event	70	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	71	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	72	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	73	module users into the same thing by forcing them to use the same event
42	model you use.	74	model you use.
43		75
44	For modules like POE or IO::Async (which is a total misnomer as it is	76	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	77	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	78	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	79	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	80	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	81	module are I<also> forced to use the same event loop you use.
50		82
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	86	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	87	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	88	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	89	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	90	to AnyEvent, too, so it is future-proof).
59		91
60	In addition to being free of having to use I<the one and only true event	92	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	93	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	96	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	97	technically possible.
66		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		100	of useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
67	Of course, if you want lots of policy (this can arguably be somewhat	105	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	106	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	107	model, you should I<not> use this module.
70
71		108
72	=head1 DESCRIPTION	109	=head1 DESCRIPTION
73		110
74	L<AnyEvent> provides an identical interface to multiple event loops. This	111	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	112	allows module authors to utilise an event loop without forcing module
…		…
79	The interface itself is vaguely similar, but not identical to the L<Event>	116	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	117	module.
81		118
82	During the first call of any watcher-creation method, the module tries	119	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of the	120	to detect the currently loaded event loop by probing whether one of the
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	121	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	122	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	L<POE>. The first one found is used. If none are found, the module tries	123	L<POE>. The first one found is used. If none are found, the module tries
87	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	124	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
88	adaptor should always succeed) in the order given. The first one that can	125	adaptor should always succeed) in the order given. The first one that can
89	be successfully loaded will be used. If, after this, still none could be	126	be successfully loaded will be used. If, after this, still none could be
…		…
103	starts using it, all bets are off. Maybe you should tell their authors to	140	starts using it, all bets are off. Maybe you should tell their authors to
104	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
105		142
106	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	144	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
108	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
109		146
110	=head1 WATCHERS	147	=head1 WATCHERS
111		148
112	AnyEvent has the central concept of a I<watcher>, which is an object that	149	AnyEvent has the central concept of a I<watcher>, which is an object that
113	stores relevant data for each kind of event you are waiting for, such as	150	stores relevant data for each kind of event you are waiting for, such as
114	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
115		152
116	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
117	creating a watcher it will immediately "watch" for events and invoke the	154	creating a watcher it will immediately "watch" for events and invoke the
118	callback when the event occurs (of course, only when the event model	155	callback when the event occurs (of course, only when the event model
119	is in control).	156	is in control).
120		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
121	To disable the watcher you have to destroy it (e.g. by setting the	164	To disable the watcher you have to destroy it (e.g. by setting the
122	variable you store it in to C<undef> or otherwise deleting all references	165	variable you store it in to C<undef> or otherwise deleting all references
123	to it).	166	to it).
124		167
125	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
127	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
128	example), or need to refer to their watcher object in other ways.	171	example), or need to refer to their watcher object in other ways.
129		172
130	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
131		174
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
134	undef $w;	177	undef $w;
135	});	178	});
136		179
137	Note that C<my $w; $w => combination. This is necessary because in Perl,	180	Note that C<my $w; $w => combination. This is necessary because in Perl,
138	my variables are only visible after the statement in which they are	181	my variables are only visible after the statement in which they are
139	declared.	182	declared.
140		183
141	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
142		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
		191
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	192	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	193	with the following mandatory key-value pairs as arguments:
145		194
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	195	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		196	for events (AnyEvent might or might not keep a reference to this file
		197	handle). Note that only file handles pointing to things for which
		198	non-blocking operation makes sense are allowed. This includes sockets,
		199	most character devices, pipes, fifos and so on, but not for example files
		200	or block devices.
		201
147	events. C<poll> must be a string that is either C<r> or C<w>, which	202	C<poll> must be a string that is either C<r> or C<w>, which creates a
148	creates a watcher waiting for "r"eadable or "w"ritable events,	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
		204
149	respectively. C<cb> is the callback to invoke each time the file handle	205	C<cb> is the callback to invoke each time the file handle becomes ready.
150	becomes ready.	206
		207	Although the callback might get passed parameters, their value and
		208	presence is undefined and you cannot rely on them. Portable AnyEvent
		209	callbacks cannot use arguments passed to I/O watcher callbacks.
151		210
152	The I/O watcher might use the underlying file descriptor or a copy of it.	211	The I/O watcher might use the underlying file descriptor or a copy of it.
153	It is not allowed to close a file handle as long as any watcher is active	212	You must not close a file handle as long as any watcher is active on the
154	on the underlying file descriptor.	213	underlying file descriptor.
155		214
156	Some event loops issue spurious readyness notifications, so you should	215	Some event loops issue spurious readyness notifications, so you should
157	always use non-blocking calls when reading/writing from/to your file	216	always use non-blocking calls when reading/writing from/to your file
158	handles.	217	handles.
159		218
160	Example:
161
162	# wait for readability of STDIN, then read a line and disable the watcher	219	Example: wait for readability of STDIN, then read a line and disable the
		220	watcher.
		221
163	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
164	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
165	warn "read: $input\n";	224	warn "read: $input\n";
166	undef $w;	225	undef $w;
167	});	226	});
168		227
169	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
170		229
		230	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		231
		232	$w = AnyEvent->timer (
		233	after => <fractional_seconds>,
		234	interval => <fractional_seconds>,
		235	cb => <callback>,
		236	);
		237
171	You can create a time watcher by calling the C<< AnyEvent->timer >>	238	You can create a time watcher by calling the C<< AnyEvent->timer >>
172	method with the following mandatory arguments:	239	method with the following mandatory arguments:
173		240
174	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
175	supported) should the timer activate. C<cb> the callback to invoke in that	242	supported) the callback should be invoked. C<cb> is the callback to invoke
176	case.	243	in that case.
177		244
178	The timer callback will be invoked at most once: if you want a repeating	245	Although the callback might get passed parameters, their value and
179	timer you have to create a new watcher (this is a limitation by both Tk	246	presence is undefined and you cannot rely on them. Portable AnyEvent
180	and Glib).	247	callbacks cannot use arguments passed to time watcher callbacks.
181		248
182	Example:	249	The callback will normally be invoked once only. If you specify another
		250	parameter, C<interval>, as a strictly positive number (> 0), then the
		251	callback will be invoked regularly at that interval (in fractional
		252	seconds) after the first invocation. If C<interval> is specified with a
		253	false value, then it is treated as if it were missing.
183		254
		255	The callback will be rescheduled before invoking the callback, but no
		256	attempt is done to avoid timer drift in most backends, so the interval is
		257	only approximate.
		258
184	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	262	warn "timeout\n";
187	});	263	});
188		264
189	# to cancel the timer:	265	# to cancel the timer:
190	undef $w;	266	undef $w;
191		267
192	Example 2:
193
194	# fire an event after 0.5 seconds, then roughly every second	268	Example 2: fire an event after 0.5 seconds, then roughly every second.
195	my $w;
196		269
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		271	warn "timeout\n";
200	};	272	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		273
205	=head3 TIMING ISSUES	274	=head3 TIMING ISSUES
206		275
207	There are two ways to handle timers: based on real time (relative, "fire	276	There are two ways to handle timers: based on real time (relative, "fire
208	in 10 seconds") and based on wallclock time (absolute, "fire at 12	277	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
220	timers.	289	timers.
221		290
222	AnyEvent always prefers relative timers, if available, matching the	291	AnyEvent always prefers relative timers, if available, matching the
223	AnyEvent API.	292	AnyEvent API.
224		293
		294	AnyEvent has two additional methods that return the "current time":
		295
		296	=over 4
		297
		298	=item AnyEvent->time
		299
		300	This returns the "current wallclock time" as a fractional number of
		301	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		302	return, and the result is guaranteed to be compatible with those).
		303
		304	It progresses independently of any event loop processing, i.e. each call
		305	will check the system clock, which usually gets updated frequently.
		306
		307	=item AnyEvent->now
		308
		309	This also returns the "current wallclock time", but unlike C<time>, above,
		310	this value might change only once per event loop iteration, depending on
		311	the event loop (most return the same time as C<time>, above). This is the
		312	time that AnyEvent's timers get scheduled against.
		313
		314	I<In almost all cases (in all cases if you don't care), this is the
		315	function to call when you want to know the current time.>
		316
		317	This function is also often faster then C<< AnyEvent->time >>, and
		318	thus the preferred method if you want some timestamp (for example,
		319	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		320
		321	The rest of this section is only of relevance if you try to be very exact
		322	with your timing, you can skip it without bad conscience.
		323
		324	For a practical example of when these times differ, consider L<Event::Lib>
		325	and L<EV> and the following set-up:
		326
		327	The event loop is running and has just invoked one of your callback at
		328	time=500 (assume no other callbacks delay processing). In your callback,
		329	you wait a second by executing C<sleep 1> (blocking the process for a
		330	second) and then (at time=501) you create a relative timer that fires
		331	after three seconds.
		332
		333	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		334	both return C<501>, because that is the current time, and the timer will
		335	be scheduled to fire at time=504 (C<501> + C<3>).
		336
		337	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		338	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		339	last event processing phase started. With L<EV>, your timer gets scheduled
		340	to run at time=503 (C<500> + C<3>).
		341
		342	In one sense, L<Event::Lib> is more exact, as it uses the current time
		343	regardless of any delays introduced by event processing. However, most
		344	callbacks do not expect large delays in processing, so this causes a
		345	higher drift (and a lot more system calls to get the current time).
		346
		347	In another sense, L<EV> is more exact, as your timer will be scheduled at
		348	the same time, regardless of how long event processing actually took.
		349
		350	In either case, if you care (and in most cases, you don't), then you
		351	can get whatever behaviour you want with any event loop, by taking the
		352	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		353	account.
		354
		355	=item AnyEvent->now_update
		356
		357	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		358	the current time for each loop iteration (see the discussion of L<<
		359	AnyEvent->now >>, above).
		360
		361	When a callback runs for a long time (or when the process sleeps), then
		362	this "current" time will differ substantially from the real time, which
		363	might affect timers and time-outs.
		364
		365	When this is the case, you can call this method, which will update the
		366	event loop's idea of "current time".
		367
		368	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		369	when mod_perl executes the script, then the event loop will have the wrong
		370	idea about the "current time" (being potentially far in the past, when the
		371	script ran the last time). In that case you should arrange a call to C<<
		372	AnyEvent->now_update >> each time the web server process wakes up again
		373	(e.g. at the start of your script, or in a handler).
		374
		375	Note that updating the time I<might> cause some events to be handled.
		376
		377	=back
		378
225	=head2 SIGNAL WATCHERS	379	=head2 SIGNAL WATCHERS
226		380
		381	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		382
227	You can watch for signals using a signal watcher, C<signal> is the signal	383	You can watch for signals using a signal watcher, C<signal> is the signal
228	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	384	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
229	be invoked whenever a signal occurs.	385	callback to be invoked whenever a signal occurs.
230		386
		387	Although the callback might get passed parameters, their value and
		388	presence is undefined and you cannot rely on them. Portable AnyEvent
		389	callbacks cannot use arguments passed to signal watcher callbacks.
		390
231	Multiple signal occurances can be clumped together into one callback	391	Multiple signal occurrences can be clumped together into one callback
232	invocation, and callback invocation will be synchronous. synchronous means	392	invocation, and callback invocation will be synchronous. Synchronous means
233	that it might take a while until the signal gets handled by the process,	393	that it might take a while until the signal gets handled by the process,
234	but it is guarenteed not to interrupt any other callbacks.	394	but it is guaranteed not to interrupt any other callbacks.
235		395
236	The main advantage of using these watchers is that you can share a signal	396	The main advantage of using these watchers is that you can share a signal
237	between multiple watchers.	397	between multiple watchers, and AnyEvent will ensure that signals will not
		398	interrupt your program at bad times.
238		399
239	This watcher might use C<%SIG>, so programs overwriting those signals	400	This watcher might use C<%SIG> (depending on the event loop used),
240	directly will likely not work correctly.	401	so programs overwriting those signals directly will likely not work
		402	correctly.
241		403
242	Example: exit on SIGINT	404	Example: exit on SIGINT
243		405
244	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	406	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
245		407
		408	=head3 Restart Behaviour
		409
		410	While restart behaviour is up to the event loop implementation, most will
		411	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		412	pure perl implementation).
		413
		414	=head3 Safe/Unsafe Signals
		415
		416	Perl signals can be either "safe" (synchronous to opcode handling) or
		417	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		418	latter might corrupt your memory.
		419
		420	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		421	i.e. they will not interrupt your running perl program but will only be
		422	called as part of the normal event handling (just like timer, I/O etc.
		423	callbacks, too).
		424
		425	=head3 Signal Races, Delays and Workarounds
		426
		427	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		428	callbacks to signals in a generic way, which is a pity, as you cannot
		429	do race-free signal handling in perl, requiring C libraries for
		430	this. AnyEvent will try to do it's best, which means in some cases,
		431	signals will be delayed. The maximum time a signal might be delayed is
		432	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		433	variable can be changed only before the first signal watcher is created,
		434	and should be left alone otherwise. This variable determines how often
		435	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		436	will cause fewer spurious wake-ups, which is better for power and CPU
		437	saving.
		438
		439	All these problems can be avoided by installing the optional
		440	L<Async::Interrupt> module, which works with most event loops. It will not
		441	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		442	(and not with L<POE> currently, as POE does it's own workaround with
		443	one-second latency). For those, you just have to suffer the delays.
		444
246	=head2 CHILD PROCESS WATCHERS	445	=head2 CHILD PROCESS WATCHERS
247		446
		447	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		448
248	You can also watch on a child process exit and catch its exit status.	449	You can also watch on a child process exit and catch its exit status.
249		450
250	The child process is specified by the C<pid> argument (if set to C<0>, it	451	The child process is specified by the C<pid> argument (one some backends,
251	watches for any child process exit). The watcher will trigger as often	452	using C<0> watches for any child process exit, on others this will
252	as status change for the child are received. This works by installing a	453	croak). The watcher will be triggered only when the child process has
253	signal handler for C<SIGCHLD>. The callback will be called with the pid	454	finished and an exit status is available, not on any trace events
254	and exit status (as returned by waitpid).	455	(stopped/continued).
		456
		457	The callback will be called with the pid and exit status (as returned by
		458	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		459	callback arguments.
		460
		461	This watcher type works by installing a signal handler for C<SIGCHLD>,
		462	and since it cannot be shared, nothing else should use SIGCHLD or reap
		463	random child processes (waiting for specific child processes, e.g. inside
		464	C<system>, is just fine).
255		465
256	There is a slight catch to child watchers, however: you usually start them	466	There is a slight catch to child watchers, however: you usually start them
257	I<after> the child process was created, and this means the process could	467	I<after> the child process was created, and this means the process could
258	have exited already (and no SIGCHLD will be sent anymore).	468	have exited already (and no SIGCHLD will be sent anymore).
259		469
260	Not all event models handle this correctly (POE doesn't), but even for	470	Not all event models handle this correctly (neither POE nor IO::Async do,
		471	see their AnyEvent::Impl manpages for details), but even for event models
261	event models that I<do> handle this correctly, they usually need to be	472	that I<do> handle this correctly, they usually need to be loaded before
262	loaded before the process exits (i.e. before you fork in the first place).	473	the process exits (i.e. before you fork in the first place). AnyEvent's
		474	pure perl event loop handles all cases correctly regardless of when you
		475	start the watcher.
263		476
264	This means you cannot create a child watcher as the very first thing in an	477	This means you cannot create a child watcher as the very first
265	AnyEvent program, you I<have> to create at least one watcher before you	478	thing in an AnyEvent program, you I<have> to create at least one
266	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	479	watcher before you C<fork> the child (alternatively, you can call
		480	C<AnyEvent::detect>).
		481
		482	As most event loops do not support waiting for child events, they will be
		483	emulated by AnyEvent in most cases, in which the latency and race problems
		484	mentioned in the description of signal watchers apply.
267		485
268	Example: fork a process and wait for it	486	Example: fork a process and wait for it
269		487
270	my $done = AnyEvent->condvar;	488	my $done = AnyEvent->condvar;
271		489
272	AnyEvent::detect; # force event module to be initialised
273
274	my $pid = fork or exit 5;	490	my $pid = fork or exit 5;
275		491
276	my $w = AnyEvent->child (	492	my $w = AnyEvent->child (
277	pid => $pid,	493	pid => $pid,
278	cb => sub {	494	cb => sub {
279	my ($pid, $status) = @_;	495	my ($pid, $status) = @_;
280	warn "pid $pid exited with status $status";	496	warn "pid $pid exited with status $status";
281	$done->broadcast;	497	$done->send;
282	},	498	},
283	);	499	);
284		500
285	# do something else, then wait for process exit	501	# do something else, then wait for process exit
286	$done->wait;	502	$done->recv;
		503
		504	=head2 IDLE WATCHERS
		505
		506	$w = AnyEvent->idle (cb => <callback>);
		507
		508	Repeatedly invoke the callback after the process becomes idle, until
		509	either the watcher is destroyed or new events have been detected.
		510
		511	Idle watchers are useful when there is a need to do something, but it
		512	is not so important (or wise) to do it instantly. The callback will be
		513	invoked only when there is "nothing better to do", which is usually
		514	defined as "all outstanding events have been handled and no new events
		515	have been detected". That means that idle watchers ideally get invoked
		516	when the event loop has just polled for new events but none have been
		517	detected. Instead of blocking to wait for more events, the idle watchers
		518	will be invoked.
		519
		520	Unfortunately, most event loops do not really support idle watchers (only
		521	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		522	will simply call the callback "from time to time".
		523
		524	Example: read lines from STDIN, but only process them when the
		525	program is otherwise idle:
		526
		527	my @lines; # read data
		528	my $idle_w;
		529	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		530	push @lines, scalar <STDIN>;
		531
		532	# start an idle watcher, if not already done
		533	$idle_w ||= AnyEvent->idle (cb => sub {
		534	# handle only one line, when there are lines left
		535	if (my $line = shift @lines) {
		536	print "handled when idle: $line";
		537	} else {
		538	# otherwise disable the idle watcher again
		539	undef $idle_w;
		540	}
		541	});
		542	});
287		543
288	=head2 CONDITION VARIABLES	544	=head2 CONDITION VARIABLES
289		545
		546	$cv = AnyEvent->condvar;
		547
		548	$cv->send (<list>);
		549	my @res = $cv->recv;
		550
		551	If you are familiar with some event loops you will know that all of them
		552	require you to run some blocking "loop", "run" or similar function that
		553	will actively watch for new events and call your callbacks.
		554
		555	AnyEvent is slightly different: it expects somebody else to run the event
		556	loop and will only block when necessary (usually when told by the user).
		557
		558	The instrument to do that is called a "condition variable", so called
		559	because they represent a condition that must become true.
		560
		561	Now is probably a good time to look at the examples further below.
		562
290	Condition variables can be created by calling the C<< AnyEvent->condvar >>	563	Condition variables can be created by calling the C<< AnyEvent->condvar
291	method without any arguments.	564	>> method, usually without arguments. The only argument pair allowed is
		565	C<cb>, which specifies a callback to be called when the condition variable
		566	becomes true, with the condition variable as the first argument (but not
		567	the results).
292		568
293	A condition variable waits for a condition - precisely that the C<<	569	After creation, the condition variable is "false" until it becomes "true"
294	->broadcast >> method has been called.	570	by calling the C<send> method (or calling the condition variable as if it
		571	were a callback, read about the caveats in the description for the C<<
		572	->send >> method).
295		573
296	They are very useful to signal that a condition has been fulfilled, for	574	Condition variables are similar to callbacks, except that you can
		575	optionally wait for them. They can also be called merge points - points
		576	in time where multiple outstanding events have been processed. And yet
		577	another way to call them is transactions - each condition variable can be
		578	used to represent a transaction, which finishes at some point and delivers
		579	a result. And yet some people know them as "futures" - a promise to
		580	compute/deliver something that you can wait for.
		581
		582	Condition variables are very useful to signal that something has finished,
297	example, if you write a module that does asynchronous http requests,	583	for example, if you write a module that does asynchronous http requests,
298	then a condition variable would be the ideal candidate to signal the	584	then a condition variable would be the ideal candidate to signal the
299	availability of results.	585	availability of results. The user can either act when the callback is
		586	called or can synchronously C<< ->recv >> for the results.
300		587
301	You can also use condition variables to block your main program until	588	You can also use them to simulate traditional event loops - for example,
302	an event occurs - for example, you could C<< ->wait >> in your main	589	you can block your main program until an event occurs - for example, you
303	program until the user clicks the Quit button in your app, which would C<<	590	could C<< ->recv >> in your main program until the user clicks the Quit
304	->broadcast >> the "quit" event.	591	button of your app, which would C<< ->send >> the "quit" event.
305		592
306	Note that condition variables recurse into the event loop - if you have	593	Note that condition variables recurse into the event loop - if you have
307	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	594	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
308	lose. Therefore, condition variables are good to export to your caller, but	595	lose. Therefore, condition variables are good to export to your caller, but
309	you should avoid making a blocking wait yourself, at least in callbacks,	596	you should avoid making a blocking wait yourself, at least in callbacks,
310	as this asks for trouble.	597	as this asks for trouble.
311		598
312	This object has two methods:	599	Condition variables are represented by hash refs in perl, and the keys
		600	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		601	easy (it is often useful to build your own transaction class on top of
		602	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		603	it's C<new> method in your own C<new> method.
313		604
314	=over 4	605	There are two "sides" to a condition variable - the "producer side" which
		606	eventually calls C<< -> send >>, and the "consumer side", which waits
		607	for the send to occur.
315		608
316	=item $cv->wait	609	Example: wait for a timer.
317
318	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
319	called on c<$cv>, while servicing other watchers normally.
320
321	You can only wait once on a condition - additional calls will return
322	immediately.
323
324	Not all event models support a blocking wait - some die in that case
325	(programs might want to do that to stay interactive), so I<if you are
326	using this from a module, never require a blocking wait>, but let the
327	caller decide whether the call will block or not (for example, by coupling
328	condition variables with some kind of request results and supporting
329	callbacks so the caller knows that getting the result will not block,
330	while still suppporting blocking waits if the caller so desires).
331
332	Another reason I<never> to C<< ->wait >> in a module is that you cannot
333	sensibly have two C<< ->wait >>'s in parallel, as that would require
334	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
335	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
336	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
337	from different coroutines, however).
338
339	=item $cv->broadcast
340
341	Flag the condition as ready - a running C<< ->wait >> and all further
342	calls to C<wait> will (eventually) return after this method has been
343	called. If nobody is waiting the broadcast will be remembered..
344
345	=back
346
347	Example:
348		610
349	# wait till the result is ready	611	# wait till the result is ready
350	my $result_ready = AnyEvent->condvar;	612	my $result_ready = AnyEvent->condvar;
351		613
352	# do something such as adding a timer	614	# do something such as adding a timer
353	# or socket watcher the calls $result_ready->broadcast	615	# or socket watcher the calls $result_ready->send
354	# when the "result" is ready.	616	# when the "result" is ready.
355	# in this case, we simply use a timer:	617	# in this case, we simply use a timer:
356	my $w = AnyEvent->timer (	618	my $w = AnyEvent->timer (
357	after => 1,	619	after => 1,
358	cb => sub { $result_ready->broadcast },	620	cb => sub { $result_ready->send },
359	);	621	);
360		622
361	# this "blocks" (while handling events) till the watcher	623	# this "blocks" (while handling events) till the callback
362	# calls broadcast	624	# calls ->send
363	$result_ready->wait;	625	$result_ready->recv;
		626
		627	Example: wait for a timer, but take advantage of the fact that condition
		628	variables are also callable directly.
		629
		630	my $done = AnyEvent->condvar;
		631	my $delay = AnyEvent->timer (after => 5, cb => $done);
		632	$done->recv;
		633
		634	Example: Imagine an API that returns a condvar and doesn't support
		635	callbacks. This is how you make a synchronous call, for example from
		636	the main program:
		637
		638	use AnyEvent::CouchDB;
		639
		640	...
		641
		642	my @info = $couchdb->info->recv;
		643
		644	And this is how you would just set a callback to be called whenever the
		645	results are available:
		646
		647	$couchdb->info->cb (sub {
		648	my @info = $_[0]->recv;
		649	});
		650
		651	=head3 METHODS FOR PRODUCERS
		652
		653	These methods should only be used by the producing side, i.e. the
		654	code/module that eventually sends the signal. Note that it is also
		655	the producer side which creates the condvar in most cases, but it isn't
		656	uncommon for the consumer to create it as well.
		657
		658	=over 4
		659
		660	=item $cv->send (...)
		661
		662	Flag the condition as ready - a running C<< ->recv >> and all further
		663	calls to C<recv> will (eventually) return after this method has been
		664	called. If nobody is waiting the send will be remembered.
		665
		666	If a callback has been set on the condition variable, it is called
		667	immediately from within send.
		668
		669	Any arguments passed to the C<send> call will be returned by all
		670	future C<< ->recv >> calls.
		671
		672	Condition variables are overloaded so one can call them directly (as if
		673	they were a code reference). Calling them directly is the same as calling
		674	C<send>.
		675
		676	=item $cv->croak ($error)
		677
		678	Similar to send, but causes all call's to C<< ->recv >> to invoke
		679	C<Carp::croak> with the given error message/object/scalar.
		680
		681	This can be used to signal any errors to the condition variable
		682	user/consumer. Doing it this way instead of calling C<croak> directly
		683	delays the error detetcion, but has the overwhelmign advantage that it
		684	diagnoses the error at the place where the result is expected, and not
		685	deep in some event clalback without connection to the actual code causing
		686	the problem.
		687
		688	=item $cv->begin ([group callback])
		689
		690	=item $cv->end
		691
		692	These two methods can be used to combine many transactions/events into
		693	one. For example, a function that pings many hosts in parallel might want
		694	to use a condition variable for the whole process.
		695
		696	Every call to C<< ->begin >> will increment a counter, and every call to
		697	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		698	>>, the (last) callback passed to C<begin> will be executed, passing the
		699	condvar as first argument. That callback is I<supposed> to call C<< ->send
		700	>>, but that is not required. If no group callback was set, C<send> will
		701	be called without any arguments.
		702
		703	You can think of C<< $cv->send >> giving you an OR condition (one call
		704	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		705	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		706
		707	Let's start with a simple example: you have two I/O watchers (for example,
		708	STDOUT and STDERR for a program), and you want to wait for both streams to
		709	close before activating a condvar:
		710
		711	my $cv = AnyEvent->condvar;
		712
		713	$cv->begin; # first watcher
		714	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		715	defined sysread $fh1, my $buf, 4096
		716	or $cv->end;
		717	});
		718
		719	$cv->begin; # second watcher
		720	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		721	defined sysread $fh2, my $buf, 4096
		722	or $cv->end;
		723	});
		724
		725	$cv->recv;
		726
		727	This works because for every event source (EOF on file handle), there is
		728	one call to C<begin>, so the condvar waits for all calls to C<end> before
		729	sending.
		730
		731	The ping example mentioned above is slightly more complicated, as the
		732	there are results to be passwd back, and the number of tasks that are
		733	begung can potentially be zero:
		734
		735	my $cv = AnyEvent->condvar;
		736
		737	my %result;
		738	$cv->begin (sub { shift->send (\%result) });
		739
		740	for my $host (@list_of_hosts) {
		741	$cv->begin;
		742	ping_host_then_call_callback $host, sub {
		743	$result{$host} = ...;
		744	$cv->end;
		745	};
		746	}
		747
		748	$cv->end;
		749
		750	This code fragment supposedly pings a number of hosts and calls
		751	C<send> after results for all then have have been gathered - in any
		752	order. To achieve this, the code issues a call to C<begin> when it starts
		753	each ping request and calls C<end> when it has received some result for
		754	it. Since C<begin> and C<end> only maintain a counter, the order in which
		755	results arrive is not relevant.
		756
		757	There is an additional bracketing call to C<begin> and C<end> outside the
		758	loop, which serves two important purposes: first, it sets the callback
		759	to be called once the counter reaches C<0>, and second, it ensures that
		760	C<send> is called even when C<no> hosts are being pinged (the loop
		761	doesn't execute once).
		762
		763	This is the general pattern when you "fan out" into multiple (but
		764	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		765	the callback and ensure C<end> is called at least once, and then, for each
		766	subrequest you start, call C<begin> and for each subrequest you finish,
		767	call C<end>.
		768
		769	=back
		770
		771	=head3 METHODS FOR CONSUMERS
		772
		773	These methods should only be used by the consuming side, i.e. the
		774	code awaits the condition.
		775
		776	=over 4
		777
		778	=item $cv->recv
		779
		780	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		781	>> methods have been called on c<$cv>, while servicing other watchers
		782	normally.
		783
		784	You can only wait once on a condition - additional calls are valid but
		785	will return immediately.
		786
		787	If an error condition has been set by calling C<< ->croak >>, then this
		788	function will call C<croak>.
		789
		790	In list context, all parameters passed to C<send> will be returned,
		791	in scalar context only the first one will be returned.
		792
		793	Note that doing a blocking wait in a callback is not supported by any
		794	event loop, that is, recursive invocation of a blocking C<< ->recv
		795	>> is not allowed, and the C<recv> call will C<croak> if such a
		796	condition is detected. This condition can be slightly loosened by using
		797	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		798	any thread that doesn't run the event loop itself.
		799
		800	Not all event models support a blocking wait - some die in that case
		801	(programs might want to do that to stay interactive), so I<if you are
		802	using this from a module, never require a blocking wait>. Instead, let the
		803	caller decide whether the call will block or not (for example, by coupling
		804	condition variables with some kind of request results and supporting
		805	callbacks so the caller knows that getting the result will not block,
		806	while still supporting blocking waits if the caller so desires).
		807
		808	You can ensure that C<< -recv >> never blocks by setting a callback and
		809	only calling C<< ->recv >> from within that callback (or at a later
		810	time). This will work even when the event loop does not support blocking
		811	waits otherwise.
		812
		813	=item $bool = $cv->ready
		814
		815	Returns true when the condition is "true", i.e. whether C<send> or
		816	C<croak> have been called.
		817
		818	=item $cb = $cv->cb ($cb->($cv))
		819
		820	This is a mutator function that returns the callback set and optionally
		821	replaces it before doing so.
		822
		823	The callback will be called when the condition becomes (or already was)
		824	"true", i.e. when C<send> or C<croak> are called (or were called), with
		825	the only argument being the condition variable itself. Calling C<recv>
		826	inside the callback or at any later time is guaranteed not to block.
		827
		828	=back
		829
		830	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		831
		832	The available backend classes are (every class has its own manpage):
		833
		834	=over 4
		835
		836	=item Backends that are autoprobed when no other event loop can be found.
		837
		838	EV is the preferred backend when no other event loop seems to be in
		839	use. If EV is not installed, then AnyEvent will fall back to its own
		840	pure-perl implementation, which is available everywhere as it comes with
		841	AnyEvent itself.
		842
		843	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		844	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		845
		846	=item Backends that are transparently being picked up when they are used.
		847
		848	These will be used when they are currently loaded when the first watcher
		849	is created, in which case it is assumed that the application is using
		850	them. This means that AnyEvent will automatically pick the right backend
		851	when the main program loads an event module before anything starts to
		852	create watchers. Nothing special needs to be done by the main program.
		853
		854	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		855	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		856	AnyEvent::Impl::Tk based on Tk, very broken.
		857	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		858	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		859	AnyEvent::Impl::Irssi used when running within irssi.
		860
		861	=item Backends with special needs.
		862
		863	Qt requires the Qt::Application to be instantiated first, but will
		864	otherwise be picked up automatically. As long as the main program
		865	instantiates the application before any AnyEvent watchers are created,
		866	everything should just work.
		867
		868	AnyEvent::Impl::Qt based on Qt.
		869
		870	Support for IO::Async can only be partial, as it is too broken and
		871	architecturally limited to even support the AnyEvent API. It also
		872	is the only event loop that needs the loop to be set explicitly, so
		873	it can only be used by a main program knowing about AnyEvent. See
		874	L<AnyEvent::Impl::Async> for the gory details.
		875
		876	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		877
		878	=item Event loops that are indirectly supported via other backends.
		879
		880	Some event loops can be supported via other modules:
		881
		882	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		883
		884	B<WxWidgets> has no support for watching file handles. However, you can
		885	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		886	polls 20 times per second, which was considered to be too horrible to even
		887	consider for AnyEvent.
		888
		889	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		890	backend, so it can be supported through POE.
		891
		892	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		893	load L<POE> when detecting them, in the hope that POE will pick them up,
		894	in which case everything will be automatic.
		895
		896	=back
364		897
365	=head1 GLOBAL VARIABLES AND FUNCTIONS	898	=head1 GLOBAL VARIABLES AND FUNCTIONS
366		899
		900	These are not normally required to use AnyEvent, but can be useful to
		901	write AnyEvent extension modules.
		902
367	=over 4	903	=over 4
368		904
369	=item $AnyEvent::MODEL	905	=item $AnyEvent::MODEL
370		906
371	Contains C<undef> until the first watcher is being created. Then it	907	Contains C<undef> until the first watcher is being created, before the
		908	backend has been autodetected.
		909
372	contains the event model that is being used, which is the name of the	910	Afterwards it contains the event model that is being used, which is the
373	Perl class implementing the model. This class is usually one of the	911	name of the Perl class implementing the model. This class is usually one
374	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	912	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
375	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	913	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
376		914	will be C<urxvt::anyevent>).
377	The known classes so far are:
378
379	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
380	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
381	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
382	AnyEvent::Impl::Event based on Event, second best choice.
383	AnyEvent::Impl::Glib based on Glib, third-best choice.
384	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
385	AnyEvent::Impl::Tk based on Tk, very bad choice.
386	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
387	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
388	AnyEvent::Impl::POE based on POE, not generic enough for full support.
389
390	There is no support for WxWidgets, as WxWidgets has no support for
391	watching file handles. However, you can use WxWidgets through the
392	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
393	second, which was considered to be too horrible to even consider for
394	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
395	it's adaptor.
396
397	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
398	autodetecting them.
399		915
400	=item AnyEvent::detect	916	=item AnyEvent::detect
401		917
402	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	918	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
403	if necessary. You should only call this function right before you would	919	if necessary. You should only call this function right before you would
404	have created an AnyEvent watcher anyway, that is, as late as possible at	920	have created an AnyEvent watcher anyway, that is, as late as possible at
405	runtime.	921	runtime, and not e.g. while initialising of your module.
		922
		923	If you need to do some initialisation before AnyEvent watchers are
		924	created, use C<post_detect>.
		925
		926	=item $guard = AnyEvent::post_detect { BLOCK }
		927
		928	Arranges for the code block to be executed as soon as the event model is
		929	autodetected (or immediately if this has already happened).
		930
		931	The block will be executed I<after> the actual backend has been detected
		932	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		933	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		934	other initialisations - see the sources of L<AnyEvent::Strict> or
		935	L<AnyEvent::AIO> to see how this is used.
		936
		937	The most common usage is to create some global watchers, without forcing
		938	event module detection too early, for example, L<AnyEvent::AIO> creates
		939	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		940	avoid autodetecting the event module at load time.
		941
		942	If called in scalar or list context, then it creates and returns an object
		943	that automatically removes the callback again when it is destroyed (or
		944	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		945	a case where this is useful.
		946
		947	Example: Create a watcher for the IO::AIO module and store it in
		948	C<$WATCHER>. Only do so after the event loop is initialised, though.
		949
		950	our WATCHER;
		951
		952	my $guard = AnyEvent::post_detect {
		953	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		954	};
		955
		956	# the ||= is important in case post_detect immediately runs the block,
		957	# as to not clobber the newly-created watcher. assigning both watcher and
		958	# post_detect guard to the same variable has the advantage of users being
		959	# able to just C<undef $WATCHER> if the watcher causes them grief.
		960
		961	$WATCHER ||= $guard;
		962
		963	=item @AnyEvent::post_detect
		964
		965	If there are any code references in this array (you can C<push> to it
		966	before or after loading AnyEvent), then they will called directly after
		967	the event loop has been chosen.
		968
		969	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		970	if it is defined then the event loop has already been detected, and the
		971	array will be ignored.
		972
		973	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		974	it, as it takes care of these details.
		975
		976	This variable is mainly useful for modules that can do something useful
		977	when AnyEvent is used and thus want to know when it is initialised, but do
		978	not need to even load it by default. This array provides the means to hook
		979	into AnyEvent passively, without loading it.
		980
		981	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		982	together, you could put this into Coro (this is the actual code used by
		983	Coro to accomplish this):
		984
		985	if (defined $AnyEvent::MODEL) {
		986	# AnyEvent already initialised, so load Coro::AnyEvent
		987	require Coro::AnyEvent;
		988	} else {
		989	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		990	# as soon as it is
		991	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		992	}
406		993
407	=back	994	=back
408		995
409	=head1 WHAT TO DO IN A MODULE	996	=head1 WHAT TO DO IN A MODULE
410		997
…		…
414	Be careful when you create watchers in the module body - AnyEvent will	1001	Be careful when you create watchers in the module body - AnyEvent will
415	decide which event module to use as soon as the first method is called, so	1002	decide which event module to use as soon as the first method is called, so
416	by calling AnyEvent in your module body you force the user of your module	1003	by calling AnyEvent in your module body you force the user of your module
417	to load the event module first.	1004	to load the event module first.
418		1005
419	Never call C<< ->wait >> on a condition variable unless you I<know> that	1006	Never call C<< ->recv >> on a condition variable unless you I<know> that
420	the C<< ->broadcast >> method has been called on it already. This is	1007	the C<< ->send >> method has been called on it already. This is
421	because it will stall the whole program, and the whole point of using	1008	because it will stall the whole program, and the whole point of using
422	events is to stay interactive.	1009	events is to stay interactive.
423		1010
424	It is fine, however, to call C<< ->wait >> when the user of your module	1011	It is fine, however, to call C<< ->recv >> when the user of your module
425	requests it (i.e. if you create a http request object ad have a method	1012	requests it (i.e. if you create a http request object ad have a method
426	called C<results> that returns the results, it should call C<< ->wait >>	1013	called C<results> that returns the results, it should call C<< ->recv >>
427	freely, as the user of your module knows what she is doing. always).	1014	freely, as the user of your module knows what she is doing. always).
428		1015
429	=head1 WHAT TO DO IN THE MAIN PROGRAM	1016	=head1 WHAT TO DO IN THE MAIN PROGRAM
430		1017
431	There will always be a single main program - the only place that should	1018	There will always be a single main program - the only place that should
…		…
433		1020
434	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1021	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
435	do anything special (it does not need to be event-based) and let AnyEvent	1022	do anything special (it does not need to be event-based) and let AnyEvent
436	decide which implementation to chose if some module relies on it.	1023	decide which implementation to chose if some module relies on it.
437		1024
438	If the main program relies on a specific event model. For example, in	1025	If the main program relies on a specific event model - for example, in
439	Gtk2 programs you have to rely on the Glib module. You should load the	1026	Gtk2 programs you have to rely on the Glib module - you should load the
440	event module before loading AnyEvent or any module that uses it: generally	1027	event module before loading AnyEvent or any module that uses it: generally
441	speaking, you should load it as early as possible. The reason is that	1028	speaking, you should load it as early as possible. The reason is that
442	modules might create watchers when they are loaded, and AnyEvent will	1029	modules might create watchers when they are loaded, and AnyEvent will
443	decide on the event model to use as soon as it creates watchers, and it	1030	decide on the event model to use as soon as it creates watchers, and it
444	might chose the wrong one unless you load the correct one yourself.	1031	might chose the wrong one unless you load the correct one yourself.
445		1032
446	You can chose to use a rather inefficient pure-perl implementation by	1033	You can chose to use a pure-perl implementation by loading the
447	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1034	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
448	behaviour everywhere, but letting AnyEvent chose is generally better.	1035	everywhere, but letting AnyEvent chose the model is generally better.
		1036
		1037	=head2 MAINLOOP EMULATION
		1038
		1039	Sometimes (often for short test scripts, or even standalone programs who
		1040	only want to use AnyEvent), you do not want to run a specific event loop.
		1041
		1042	In that case, you can use a condition variable like this:
		1043
		1044	AnyEvent->condvar->recv;
		1045
		1046	This has the effect of entering the event loop and looping forever.
		1047
		1048	Note that usually your program has some exit condition, in which case
		1049	it is better to use the "traditional" approach of storing a condition
		1050	variable somewhere, waiting for it, and sending it when the program should
		1051	exit cleanly.
		1052
		1053
		1054	=head1 OTHER MODULES
		1055
		1056	The following is a non-exhaustive list of additional modules that use
		1057	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1058	modules and other event loops in the same program. Some of the modules
		1059	come with AnyEvent, most are available via CPAN.
		1060
		1061	=over 4
		1062
		1063	=item L<AnyEvent::Util>
		1064
		1065	Contains various utility functions that replace often-used but blocking
		1066	functions such as C<inet_aton> by event-/callback-based versions.
		1067
		1068	=item L<AnyEvent::Socket>
		1069
		1070	Provides various utility functions for (internet protocol) sockets,
		1071	addresses and name resolution. Also functions to create non-blocking tcp
		1072	connections or tcp servers, with IPv6 and SRV record support and more.
		1073
		1074	=item L<AnyEvent::Handle>
		1075
		1076	Provide read and write buffers, manages watchers for reads and writes,
		1077	supports raw and formatted I/O, I/O queued and fully transparent and
		1078	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1079
		1080	=item L<AnyEvent::DNS>
		1081
		1082	Provides rich asynchronous DNS resolver capabilities.
		1083
		1084	=item L<AnyEvent::HTTP>
		1085
		1086	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1087	HTTP requests.
		1088
		1089	=item L<AnyEvent::HTTPD>
		1090
		1091	Provides a simple web application server framework.
		1092
		1093	=item L<AnyEvent::FastPing>
		1094
		1095	The fastest ping in the west.
		1096
		1097	=item L<AnyEvent::DBI>
		1098
		1099	Executes L<DBI> requests asynchronously in a proxy process.
		1100
		1101	=item L<AnyEvent::AIO>
		1102
		1103	Truly asynchronous I/O, should be in the toolbox of every event
		1104	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1105	together.
		1106
		1107	=item L<AnyEvent::BDB>
		1108
		1109	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1110	L<BDB> and AnyEvent together.
		1111
		1112	=item L<AnyEvent::GPSD>
		1113
		1114	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1115
		1116	=item L<AnyEvent::IRC>
		1117
		1118	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1119
		1120	=item L<AnyEvent::XMPP>
		1121
		1122	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1123	Net::XMPP2>.
		1124
		1125	=item L<AnyEvent::IGS>
		1126
		1127	A non-blocking interface to the Internet Go Server protocol (used by
		1128	L<App::IGS>).
		1129
		1130	=item L<Net::FCP>
		1131
		1132	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1133	of AnyEvent.
		1134
		1135	=item L<Event::ExecFlow>
		1136
		1137	High level API for event-based execution flow control.
		1138
		1139	=item L<Coro>
		1140
		1141	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1142
		1143	=back
449		1144
450	=cut	1145	=cut
451		1146
452	package AnyEvent;	1147	package AnyEvent;
453		1148
454	no warnings;	1149	# basically a tuned-down version of common::sense
455	use strict;	1150	sub common_sense {
		1151	# from common:.sense 1.0
		1152	${^WARNING_BITS} = "\xfc\x3f\x33\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x00";
		1153	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1154	$^H |= 0x00000600;
		1155	}
456		1156
		1157	BEGIN { AnyEvent::common_sense }
		1158
457	use Carp;	1159	use Carp ();
458		1160
459	our $VERSION = '3.3';	1161	our $VERSION = '5.24';
460	our $MODEL;	1162	our $MODEL;
461		1163
462	our $AUTOLOAD;	1164	our $AUTOLOAD;
463	our @ISA;	1165	our @ISA;
464		1166
465	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
466
467	our @REGISTRY;	1167	our @REGISTRY;
468		1168
		1169	our $VERBOSE;
		1170
		1171	BEGIN {
		1172	require "AnyEvent/constants.pl";
		1173
		1174	eval "sub TAINT (){" . (${^TAINT} *1) . "}";
		1175
		1176	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1177	if ${^TAINT};
		1178
		1179	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1180
		1181	}
		1182
		1183	our $MAX_SIGNAL_LATENCY = 10;
		1184
		1185	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1186
		1187	{
		1188	my $idx;
		1189	$PROTOCOL{$_} = ++$idx
		1190	for reverse split /\s*,\s*/,
		1191	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1192	}
		1193
469	my @models = (	1194	my @models = (
470	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
471	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
472	[EV:: => AnyEvent::Impl::EV::],	1195	[EV:: => AnyEvent::Impl::EV:: , 1],
		1196	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1197	# everything below here will not (normally) be autoprobed
		1198	# as the pureperl backend should work everywhere
		1199	# and is usually faster
473	[Event:: => AnyEvent::Impl::Event::],	1200	[Event:: => AnyEvent::Impl::Event::, 1],
474	[Glib:: => AnyEvent::Impl::Glib::],	1201	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1202	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1203	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
475	[Tk:: => AnyEvent::Impl::Tk::],	1204	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1205	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1206	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
476	[Wx:: => AnyEvent::Impl::POE::],	1207	[Wx:: => AnyEvent::Impl::POE::],
477	[Prima:: => AnyEvent::Impl::POE::],	1208	[Prima:: => AnyEvent::Impl::POE::],
478	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1209	# IO::Async is just too broken - we would need workarounds for its
479	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1210	# byzantine signal and broken child handling, among others.
480	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1211	# IO::Async is rather hard to detect, as it doesn't have any
		1212	# obvious default class.
481	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1213	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
482	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1214	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1215	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1216	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
483	);	1217	);
484		1218
485	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1219	our %method = map +($_ => 1),
		1220	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1221
		1222	our @post_detect;
		1223
		1224	sub post_detect(&) {
		1225	my ($cb) = @_;
		1226
		1227	if ($MODEL) {
		1228	$cb->();
		1229
		1230	undef
		1231	} else {
		1232	push @post_detect, $cb;
		1233
		1234	defined wantarray
		1235	? bless \$cb, "AnyEvent::Util::postdetect"
		1236	: ()
		1237	}
		1238	}
		1239
		1240	sub AnyEvent::Util::postdetect::DESTROY {
		1241	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1242	}
486		1243
487	sub detect() {	1244	sub detect() {
		1245	# free some memory
		1246	*detect = sub () { $MODEL };
		1247
		1248	local $!; # for good measure
		1249	local $SIG{__DIE__};
		1250
		1251	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1252	my $model = "AnyEvent::Impl::$1";
		1253	if (eval "require $model") {
		1254	$MODEL = $model;
		1255	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1256	} else {
		1257	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1258	}
		1259	}
		1260
		1261	# check for already loaded models
488	unless ($MODEL) {	1262	unless ($MODEL) {
489	no strict 'refs';	1263	for (@REGISTRY, @models) {
490		1264	my ($package, $model) = @$_;
491	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1265	if (${"$package\::VERSION"} > 0) {
492	my $model = "AnyEvent::Impl::$1";
493	if (eval "require $model") {	1266	if (eval "require $model") {
494	$MODEL = $model;	1267	$MODEL = $model;
495	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1268	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
496	} else {	1269	last;
497	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1270	}
498	}	1271	}
499	}	1272	}
500		1273
501	# check for already loaded models
502	unless ($MODEL) {	1274	unless ($MODEL) {
		1275	# try to autoload a model
503	for (@REGISTRY, @models) {	1276	for (@REGISTRY, @models) {
504	my ($package, $model) = @$_;	1277	my ($package, $model, $autoload) = @$_;
		1278	if (
		1279	$autoload
		1280	and eval "require $package"
505	if (${"$package\::VERSION"} > 0) {	1281	and ${"$package\::VERSION"} > 0
506	if (eval "require $model") {	1282	and eval "require $model"
		1283	) {
507	$MODEL = $model;	1284	$MODEL = $model;
508	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1285	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
509	last;	1286	last;
510	}
511	}	1287	}
512	}	1288	}
513		1289
514	unless ($MODEL) {
515	# try to load a model
516
517	for (@REGISTRY, @models) {
518	my ($package, $model) = @$_;
519	if (eval "require $package"
520	and ${"$package\::VERSION"} > 0
521	and eval "require $model") {
522	$MODEL = $model;
523	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
524	last;
525	}
526	}
527
528	$MODEL	1290	$MODEL
529	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) or Glib.";	1291	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
530	}
531	}	1292	}
532
533	unshift @ISA, $MODEL;
534	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
535	}	1293	}
		1294
		1295	@models = (); # free probe data
		1296
		1297	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1298	unshift @ISA, $MODEL;
		1299
		1300	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1301
		1302	(shift @post_detect)->() while @post_detect;
536		1303
537	$MODEL	1304	$MODEL
538	}	1305	}
539		1306
540	sub AUTOLOAD {	1307	sub AUTOLOAD {
541	(my $func = $AUTOLOAD) =~ s/.*://;	1308	(my $func = $AUTOLOAD) =~ s/.*://;
542		1309
543	$method{$func}	1310	$method{$func}
544	or croak "$func: not a valid method for AnyEvent objects";	1311	or Carp::croak "$func: not a valid AnyEvent class method";
545		1312
546	detect unless $MODEL;	1313	detect;
547		1314
548	my $class = shift;	1315	my $class = shift;
549	$class->$func (@_);	1316	$class->$func (@_);
550	}	1317	}
551		1318
		1319	# utility function to dup a filehandle. this is used by many backends
		1320	# to support binding more than one watcher per filehandle (they usually
		1321	# allow only one watcher per fd, so we dup it to get a different one).
		1322	sub _dupfh($$;$$) {
		1323	my ($poll, $fh, $r, $w) = @_;
		1324
		1325	# cygwin requires the fh mode to be matching, unix doesn't
		1326	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1327
		1328	open my $fh2, $mode, $fh
		1329	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1330
		1331	# we assume CLOEXEC is already set by perl in all important cases
		1332
		1333	($fh2, $rw)
		1334	}
		1335
		1336	=head1 SIMPLIFIED AE API
		1337
		1338	Starting with version 5.0, AnyEvent officially supports a second, much
		1339	simpler, API that is designed to reduce the calling, typing and memory
		1340	overhead.
		1341
		1342	See the L<AE> manpage for details.
		1343
		1344	=cut
		1345
		1346	package AE;
		1347
		1348	our $VERSION = $AnyEvent::VERSION;
		1349
		1350	sub io($$$) {
		1351	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1352	}
		1353
		1354	sub timer($$$) {
		1355	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1356	}
		1357
		1358	sub signal($$) {
		1359	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1360	}
		1361
		1362	sub child($$) {
		1363	AnyEvent->child (pid => $_[0], cb => $_[1])
		1364	}
		1365
		1366	sub idle($) {
		1367	AnyEvent->idle (cb => $_[0])
		1368	}
		1369
		1370	sub cv(;&) {
		1371	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1372	}
		1373
		1374	sub now() {
		1375	AnyEvent->now
		1376	}
		1377
		1378	sub now_update() {
		1379	AnyEvent->now_update
		1380	}
		1381
		1382	sub time() {
		1383	AnyEvent->time
		1384	}
		1385
552	package AnyEvent::Base;	1386	package AnyEvent::Base;
553		1387
		1388	# default implementations for many methods
		1389
		1390	sub _time() {
		1391	eval q{ # poor man's autoloading
		1392	# probe for availability of Time::HiRes
		1393	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1394	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1395	*_time = \&Time::HiRes::time;
		1396	# if (eval "use POSIX (); (POSIX::times())...
		1397	} else {
		1398	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1399	*_time = sub (){ time }; # epic fail
		1400	}
		1401	};
		1402	die if $@;
		1403
		1404	&_time
		1405	}
		1406
		1407	sub time { _time }
		1408	sub now { _time }
		1409	sub now_update { }
		1410
554	# default implementation for ->condvar, ->wait, ->broadcast	1411	# default implementation for ->condvar
555		1412
556	sub condvar {	1413	sub condvar {
557	bless \my $flag, "AnyEvent::Base::CondVar"	1414	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
558	}
559
560	sub AnyEvent::Base::CondVar::broadcast {
561	${$_[0]}++;
562	}
563
564	sub AnyEvent::Base::CondVar::wait {
565	AnyEvent->one_event while !${$_[0]};
566	}	1415	}
567		1416
568	# default implementation for ->signal	1417	# default implementation for ->signal
569		1418
570	our %SIG_CB;	1419	our $HAVE_ASYNC_INTERRUPT;
		1420
		1421	sub _have_async_interrupt() {
		1422	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1423	&& eval "use Async::Interrupt 1.02 (); 1")
		1424	unless defined $HAVE_ASYNC_INTERRUPT;
		1425
		1426	$HAVE_ASYNC_INTERRUPT
		1427	}
		1428
		1429	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1430	our (%SIG_ASY, %SIG_ASY_W);
		1431	our ($SIG_COUNT, $SIG_TW);
		1432
		1433	# install a dummy wakeup watcher to reduce signal catching latency
		1434	# used by Impls
		1435	sub _sig_add() {
		1436	unless ($SIG_COUNT++) {
		1437	# try to align timer on a full-second boundary, if possible
		1438	my $NOW = AE::now;
		1439
		1440	$SIG_TW = AE::timer
		1441	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1442	$MAX_SIGNAL_LATENCY,
		1443	sub { } # just for the PERL_ASYNC_CHECK
		1444	;
		1445	}
		1446	}
		1447
		1448	sub _sig_del {
		1449	undef $SIG_TW
		1450	unless --$SIG_COUNT;
		1451	}
		1452
		1453	our $_sig_name_init; $_sig_name_init = sub {
		1454	eval q{ # poor man's autoloading
		1455	undef $_sig_name_init;
		1456
		1457	if (_have_async_interrupt) {
		1458	*sig2num = \&Async::Interrupt::sig2num;
		1459	*sig2name = \&Async::Interrupt::sig2name;
		1460	} else {
		1461	require Config;
		1462
		1463	my %signame2num;
		1464	@signame2num{ split ' ', $Config::Config{sig_name} }
		1465	= split ' ', $Config::Config{sig_num};
		1466
		1467	my @signum2name;
		1468	@signum2name[values %signame2num] = keys %signame2num;
		1469
		1470	*sig2num = sub($) {
		1471	$_[0] > 0 ? shift : $signame2num{+shift}
		1472	};
		1473	*sig2name = sub ($) {
		1474	$_[0] > 0 ? $signum2name[+shift] : shift
		1475	};
		1476	}
		1477	};
		1478	die if $@;
		1479	};
		1480
		1481	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1482	sub sig2name($) { &$_sig_name_init; &sig2name }
571		1483
572	sub signal {	1484	sub signal {
		1485	eval q{ # poor man's autoloading {}
		1486	# probe for availability of Async::Interrupt
		1487	if (_have_async_interrupt) {
		1488	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1489
		1490	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1491	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1492
		1493	} else {
		1494	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1495
		1496	if (AnyEvent::WIN32) {
		1497	require AnyEvent::Util;
		1498
		1499	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1500	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1501	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1502	} else {
		1503	pipe $SIGPIPE_R, $SIGPIPE_W;
		1504	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1505	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1506
		1507	# not strictly required, as $^F is normally 2, but let's make sure...
		1508	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1509	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1510	}
		1511
		1512	$SIGPIPE_R
		1513	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1514
		1515	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1516	}
		1517
		1518	*signal = sub {
573	my (undef, %arg) = @_;	1519	my (undef, %arg) = @_;
574		1520
575	my $signal = uc $arg{signal}	1521	my $signal = uc $arg{signal}
576	or Carp::croak "required option 'signal' is missing";	1522	or Carp::croak "required option 'signal' is missing";
577		1523
		1524	if ($HAVE_ASYNC_INTERRUPT) {
		1525	# async::interrupt
		1526
		1527	$signal = sig2num $signal;
578	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1528	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1529
		1530	$SIG_ASY{$signal} ||= new Async::Interrupt
		1531	cb => sub { undef $SIG_EV{$signal} },
		1532	signal => $signal,
		1533	pipe => [$SIGPIPE_R->filenos],
		1534	pipe_autodrain => 0,
		1535	;
		1536
		1537	} else {
		1538	# pure perl
		1539
		1540	# AE::Util has been loaded in signal
		1541	$signal = sig2name $signal;
		1542	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1543
579	$SIG{$signal} ||= sub {	1544	$SIG{$signal} ||= sub {
		1545	local $!;
		1546	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1547	undef $SIG_EV{$signal};
		1548	};
		1549
		1550	# can't do signal processing without introducing races in pure perl,
		1551	# so limit the signal latency.
		1552	_sig_add;
		1553	}
		1554
		1555	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1556	};
		1557
		1558	*AnyEvent::Base::signal::DESTROY = sub {
		1559	my ($signal, $cb) = @{$_[0]};
		1560
		1561	_sig_del;
		1562
		1563	delete $SIG_CB{$signal}{$cb};
		1564
		1565	$HAVE_ASYNC_INTERRUPT
		1566	? delete $SIG_ASY{$signal}
		1567	: # delete doesn't work with older perls - they then
		1568	# print weird messages, or just unconditionally exit
		1569	# instead of getting the default action.
		1570	undef $SIG{$signal}
		1571	unless keys %{ $SIG_CB{$signal} };
		1572	};
		1573
		1574	*_signal_exec = sub {
		1575	$HAVE_ASYNC_INTERRUPT
		1576	? $SIGPIPE_R->drain
		1577	: sysread $SIGPIPE_R, (my $dummy), 9;
		1578
		1579	while (%SIG_EV) {
		1580	for (keys %SIG_EV) {
		1581	delete $SIG_EV{$_};
580	$_->() for values %{ $SIG_CB{$signal} || {} };	1582	$_->() for values %{ $SIG_CB{$_} || {} };
		1583	}
		1584	}
		1585	};
581	};	1586	};
		1587	die if $@;
582		1588
583	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1589	&signal
584	}
585
586	sub AnyEvent::Base::Signal::DESTROY {
587	my ($signal, $cb) = @{$_[0]};
588
589	delete $SIG_CB{$signal}{$cb};
590
591	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
592	}	1590	}
593		1591
594	# default implementation for ->child	1592	# default implementation for ->child
595		1593
596	our %PID_CB;	1594	our %PID_CB;
597	our $CHLD_W;	1595	our $CHLD_W;
598	our $CHLD_DELAY_W;	1596	our $CHLD_DELAY_W;
599	our $PID_IDLE;
600	our $WNOHANG;	1597	our $WNOHANG;
601		1598
602	sub _child_wait {	1599	# used by many Impl's
603	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1600	sub _emit_childstatus($$) {
		1601	my (undef, $rpid, $rstatus) = @_;
		1602
		1603	$_->($rpid, $rstatus)
604	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1604	for values %{ $PID_CB{$rpid} || {} },
605	(values %{ $PID_CB{0} || {} });	1605	values %{ $PID_CB{0} || {} };
606	}
607
608	undef $PID_IDLE;
609	}
610
611	sub _sigchld {
612	# make sure we deliver these changes "synchronous" with the event loop.
613	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
614	undef $CHLD_DELAY_W;
615	&_child_wait;
616	});
617	}	1606	}
618		1607
619	sub child {	1608	sub child {
		1609	eval q{ # poor man's autoloading {}
		1610	*_sigchld = sub {
		1611	my $pid;
		1612
		1613	AnyEvent->_emit_childstatus ($pid, $?)
		1614	while ($pid = waitpid -1, $WNOHANG) > 0;
		1615	};
		1616
		1617	*child = sub {
620	my (undef, %arg) = @_;	1618	my (undef, %arg) = @_;
621		1619
622	defined (my $pid = $arg{pid} + 0)	1620	defined (my $pid = $arg{pid} + 0)
623	or Carp::croak "required option 'pid' is missing";	1621	or Carp::croak "required option 'pid' is missing";
624		1622
625	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1623	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
626		1624
627	unless ($WNOHANG) {	1625	# WNOHANG is almost cetrainly 1 everywhere
628	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1626	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
629	}	1627	? 1
		1628	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
630		1629
631	unless ($CHLD_W) {	1630	unless ($CHLD_W) {
632	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1631	$CHLD_W = AE::signal CHLD => \&_sigchld;
633	# child could be a zombie already, so make at least one round	1632	# child could be a zombie already, so make at least one round
634	&_sigchld;	1633	&_sigchld;
635	}	1634	}
636		1635
637	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1636	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
638	}	1637	};
639		1638
640	sub AnyEvent::Base::Child::DESTROY {	1639	*AnyEvent::Base::child::DESTROY = sub {
641	my ($pid, $cb) = @{$_[0]};	1640	my ($pid, $cb) = @{$_[0]};
642		1641
643	delete $PID_CB{$pid}{$cb};	1642	delete $PID_CB{$pid}{$cb};
644	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1643	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
645		1644
646	undef $CHLD_W unless keys %PID_CB;	1645	undef $CHLD_W unless keys %PID_CB;
		1646	};
		1647	};
		1648	die if $@;
		1649
		1650	&child
647	}	1651	}
		1652
		1653	# idle emulation is done by simply using a timer, regardless
		1654	# of whether the process is idle or not, and not letting
		1655	# the callback use more than 50% of the time.
		1656	sub idle {
		1657	eval q{ # poor man's autoloading {}
		1658	*idle = sub {
		1659	my (undef, %arg) = @_;
		1660
		1661	my ($cb, $w, $rcb) = $arg{cb};
		1662
		1663	$rcb = sub {
		1664	if ($cb) {
		1665	$w = _time;
		1666	&$cb;
		1667	$w = _time - $w;
		1668
		1669	# never use more then 50% of the time for the idle watcher,
		1670	# within some limits
		1671	$w = 0.0001 if $w < 0.0001;
		1672	$w = 5 if $w > 5;
		1673
		1674	$w = AE::timer $w, 0, $rcb;
		1675	} else {
		1676	# clean up...
		1677	undef $w;
		1678	undef $rcb;
		1679	}
		1680	};
		1681
		1682	$w = AE::timer 0.05, 0, $rcb;
		1683
		1684	bless \\$cb, "AnyEvent::Base::idle"
		1685	};
		1686
		1687	*AnyEvent::Base::idle::DESTROY = sub {
		1688	undef $${$_[0]};
		1689	};
		1690	};
		1691	die if $@;
		1692
		1693	&idle
		1694	}
		1695
		1696	package AnyEvent::CondVar;
		1697
		1698	our @ISA = AnyEvent::CondVar::Base::;
		1699
		1700	package AnyEvent::CondVar::Base;
		1701
		1702	#use overload
		1703	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1704	# fallback => 1;
		1705
		1706	# save 300+ kilobytes by dirtily hardcoding overloading
		1707	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1708	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1709	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1710	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1711
		1712	our $WAITING;
		1713
		1714	sub _send {
		1715	# nop
		1716	}
		1717
		1718	sub send {
		1719	my $cv = shift;
		1720	$cv->{_ae_sent} = [@_];
		1721	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1722	$cv->_send;
		1723	}
		1724
		1725	sub croak {
		1726	$_[0]{_ae_croak} = $_[1];
		1727	$_[0]->send;
		1728	}
		1729
		1730	sub ready {
		1731	$_[0]{_ae_sent}
		1732	}
		1733
		1734	sub _wait {
		1735	$WAITING
		1736	and !$_[0]{_ae_sent}
		1737	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1738
		1739	local $WAITING = 1;
		1740	AnyEvent->one_event while !$_[0]{_ae_sent};
		1741	}
		1742
		1743	sub recv {
		1744	$_[0]->_wait;
		1745
		1746	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1747	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1748	}
		1749
		1750	sub cb {
		1751	my $cv = shift;
		1752
		1753	@_
		1754	and $cv->{_ae_cb} = shift
		1755	and $cv->{_ae_sent}
		1756	and (delete $cv->{_ae_cb})->($cv);
		1757
		1758	$cv->{_ae_cb}
		1759	}
		1760
		1761	sub begin {
		1762	++$_[0]{_ae_counter};
		1763	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1764	}
		1765
		1766	sub end {
		1767	return if --$_[0]{_ae_counter};
		1768	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1769	}
		1770
		1771	# undocumented/compatibility with pre-3.4
		1772	*broadcast = \&send;
		1773	*wait = \&_wait;
		1774
		1775	=head1 ERROR AND EXCEPTION HANDLING
		1776
		1777	In general, AnyEvent does not do any error handling - it relies on the
		1778	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1779	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1780	checking of all AnyEvent methods, however, which is highly useful during
		1781	development.
		1782
		1783	As for exception handling (i.e. runtime errors and exceptions thrown while
		1784	executing a callback), this is not only highly event-loop specific, but
		1785	also not in any way wrapped by this module, as this is the job of the main
		1786	program.
		1787
		1788	The pure perl event loop simply re-throws the exception (usually
		1789	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1790	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1791	so on.
		1792
		1793	=head1 ENVIRONMENT VARIABLES
		1794
		1795	The following environment variables are used by this module or its
		1796	submodules.
		1797
		1798	Note that AnyEvent will remove I<all> environment variables starting with
		1799	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1800	enabled.
		1801
		1802	=over 4
		1803
		1804	=item C<PERL_ANYEVENT_VERBOSE>
		1805
		1806	By default, AnyEvent will be completely silent except in fatal
		1807	conditions. You can set this environment variable to make AnyEvent more
		1808	talkative.
		1809
		1810	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1811	conditions, such as not being able to load the event model specified by
		1812	C<PERL_ANYEVENT_MODEL>.
		1813
		1814	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1815	model it chooses.
		1816
		1817	When set to C<8> or higher, then AnyEvent will report extra information on
		1818	which optional modules it loads and how it implements certain features.
		1819
		1820	=item C<PERL_ANYEVENT_STRICT>
		1821
		1822	AnyEvent does not do much argument checking by default, as thorough
		1823	argument checking is very costly. Setting this variable to a true value
		1824	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1825	check the arguments passed to most method calls. If it finds any problems,
		1826	it will croak.
		1827
		1828	In other words, enables "strict" mode.
		1829
		1830	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1831	>>, it is definitely recommended to keep it off in production. Keeping
		1832	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1833	can be very useful, however.
		1834
		1835	=item C<PERL_ANYEVENT_MODEL>
		1836
		1837	This can be used to specify the event model to be used by AnyEvent, before
		1838	auto detection and -probing kicks in. It must be a string consisting
		1839	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1840	and the resulting module name is loaded and if the load was successful,
		1841	used as event model. If it fails to load AnyEvent will proceed with
		1842	auto detection and -probing.
		1843
		1844	This functionality might change in future versions.
		1845
		1846	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1847	could start your program like this:
		1848
		1849	PERL_ANYEVENT_MODEL=Perl perl ...
		1850
		1851	=item C<PERL_ANYEVENT_PROTOCOLS>
		1852
		1853	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1854	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1855	of auto probing).
		1856
		1857	Must be set to a comma-separated list of protocols or address families,
		1858	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1859	used, and preference will be given to protocols mentioned earlier in the
		1860	list.
		1861
		1862	This variable can effectively be used for denial-of-service attacks
		1863	against local programs (e.g. when setuid), although the impact is likely
		1864	small, as the program has to handle conenction and other failures anyways.
		1865
		1866	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1867	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1868	- only support IPv4, never try to resolve or contact IPv6
		1869	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1870	IPv6, but prefer IPv6 over IPv4.
		1871
		1872	=item C<PERL_ANYEVENT_EDNS0>
		1873
		1874	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1875	for DNS. This extension is generally useful to reduce DNS traffic, but
		1876	some (broken) firewalls drop such DNS packets, which is why it is off by
		1877	default.
		1878
		1879	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1880	EDNS0 in its DNS requests.
		1881
		1882	=item C<PERL_ANYEVENT_MAX_FORKS>
		1883
		1884	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1885	will create in parallel.
		1886
		1887	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1888
		1889	The default value for the C<max_outstanding> parameter for the default DNS
		1890	resolver - this is the maximum number of parallel DNS requests that are
		1891	sent to the DNS server.
		1892
		1893	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1894
		1895	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1896	configuration) in the default resolver. When set to the empty string, no
		1897	default config will be used.
		1898
		1899	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1900
		1901	When neither C<ca_file> nor C<ca_path> was specified during
		1902	L<AnyEvent::TLS> context creation, and either of these environment
		1903	variables exist, they will be used to specify CA certificate locations
		1904	instead of a system-dependent default.
		1905
		1906	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1907
		1908	When these are set to C<1>, then the respective modules are not
		1909	loaded. Mostly good for testing AnyEvent itself.
		1910
		1911	=back
648		1912
649	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1913	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
650		1914
651	This is an advanced topic that you do not normally need to use AnyEvent in	1915	This is an advanced topic that you do not normally need to use AnyEvent in
652	a module. This section is only of use to event loop authors who want to	1916	a module. This section is only of use to event loop authors who want to
…		…
686		1950
687	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1951	I<rxvt-unicode> also cheats a bit by not providing blocking access to
688	condition variables: code blocking while waiting for a condition will	1952	condition variables: code blocking while waiting for a condition will
689	C<die>. This still works with most modules/usages, and blocking calls must	1953	C<die>. This still works with most modules/usages, and blocking calls must
690	not be done in an interactive application, so it makes sense.	1954	not be done in an interactive application, so it makes sense.
691
692	=head1 ENVIRONMENT VARIABLES
693
694	The following environment variables are used by this module:
695
696	=over 4
697
698	=item C<PERL_ANYEVENT_VERBOSE>
699
700	By default, AnyEvent will be completely silent except in fatal
701	conditions. You can set this environment variable to make AnyEvent more
702	talkative.
703
704	When set to C<1> or higher, causes AnyEvent to warn about unexpected
705	conditions, such as not being able to load the event model specified by
706	C<PERL_ANYEVENT_MODEL>.
707
708	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
709	model it chooses.
710
711	=item C<PERL_ANYEVENT_MODEL>
712
713	This can be used to specify the event model to be used by AnyEvent, before
714	autodetection and -probing kicks in. It must be a string consisting
715	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
716	and the resulting module name is loaded and if the load was successful,
717	used as event model. If it fails to load AnyEvent will proceed with
718	autodetection and -probing.
719
720	This functionality might change in future versions.
721
722	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
723	could start your program like this:
724
725	PERL_ANYEVENT_MODEL=Perl perl ...
726
727	=back
728		1955
729	=head1 EXAMPLE PROGRAM	1956	=head1 EXAMPLE PROGRAM
730		1957
731	The following program uses an I/O watcher to read data from STDIN, a timer	1958	The following program uses an I/O watcher to read data from STDIN, a timer
732	to display a message once per second, and a condition variable to quit the	1959	to display a message once per second, and a condition variable to quit the
…		…
741	poll => 'r',	1968	poll => 'r',
742	cb => sub {	1969	cb => sub {
743	warn "io event <$_[0]>\n"; # will always output <r>	1970	warn "io event <$_[0]>\n"; # will always output <r>
744	chomp (my $input = <STDIN>); # read a line	1971	chomp (my $input = <STDIN>); # read a line
745	warn "read: $input\n"; # output what has been read	1972	warn "read: $input\n"; # output what has been read
746	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1973	$cv->send if $input =~ /^q/i; # quit program if /^q/i
747	},	1974	},
748	);	1975	);
749		1976
750	my $time_watcher; # can only be used once
751
752	sub new_timer {
753	$timer = AnyEvent->timer (after => 1, cb => sub {	1977	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
754	warn "timeout\n"; # print 'timeout' about every second	1978	warn "timeout\n"; # print 'timeout' at most every second
755	&new_timer; # and restart the time
756	});	1979	});
757	}
758		1980
759	new_timer; # create first timer
760
761	$cv->wait; # wait until user enters /^q/i	1981	$cv->recv; # wait until user enters /^q/i
762		1982
763	=head1 REAL-WORLD EXAMPLE	1983	=head1 REAL-WORLD EXAMPLE
764		1984
765	Consider the L<Net::FCP> module. It features (among others) the following	1985	Consider the L<Net::FCP> module. It features (among others) the following
766	API calls, which are to freenet what HTTP GET requests are to http:	1986	API calls, which are to freenet what HTTP GET requests are to http:
…		…
816	syswrite $txn->{fh}, $txn->{request}	2036	syswrite $txn->{fh}, $txn->{request}
817	or die "connection or write error";	2037	or die "connection or write error";
818	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2038	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
819		2039
820	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2040	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
821	result and signals any possible waiters that the request ahs finished:	2041	result and signals any possible waiters that the request has finished:
822		2042
823	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2043	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
824		2044
825	if (end-of-file or data complete) {	2045	if (end-of-file or data complete) {
826	$txn->{result} = $txn->{buf};	2046	$txn->{result} = $txn->{buf};
827	$txn->{finished}->broadcast;	2047	$txn->{finished}->send;
828	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2048	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
829	}	2049	}
830		2050
831	The C<result> method, finally, just waits for the finished signal (if the	2051	The C<result> method, finally, just waits for the finished signal (if the
832	request was already finished, it doesn't wait, of course, and returns the	2052	request was already finished, it doesn't wait, of course, and returns the
833	data:	2053	data:
834		2054
835	$txn->{finished}->wait;	2055	$txn->{finished}->recv;
836	return $txn->{result};	2056	return $txn->{result};
837		2057
838	The actual code goes further and collects all errors (C<die>s, exceptions)	2058	The actual code goes further and collects all errors (C<die>s, exceptions)
839	that occured during request processing. The C<result> method detects	2059	that occurred during request processing. The C<result> method detects
840	whether an exception as thrown (it is stored inside the $txn object)	2060	whether an exception as thrown (it is stored inside the $txn object)
841	and just throws the exception, which means connection errors and other	2061	and just throws the exception, which means connection errors and other
842	problems get reported tot he code that tries to use the result, not in a	2062	problems get reported tot he code that tries to use the result, not in a
843	random callback.	2063	random callback.
844		2064
…		…
875		2095
876	my $quit = AnyEvent->condvar;	2096	my $quit = AnyEvent->condvar;
877		2097
878	$fcp->txn_client_get ($url)->cb (sub {	2098	$fcp->txn_client_get ($url)->cb (sub {
879	...	2099	...
880	$quit->broadcast;	2100	$quit->send;
881	});	2101	});
882		2102
883	$quit->wait;	2103	$quit->recv;
884		2104
885		2105
886	=head1 BENCHMARK	2106	=head1 BENCHMARKS
887		2107
888	To give you an idea of the performance and overheads that AnyEvent adds	2108	To give you an idea of the performance and overheads that AnyEvent adds
889	over the event loops themselves (and to give you an impression of the	2109	over the event loops themselves and to give you an impression of the speed
890	speed of various event loops), here is a benchmark of various supported	2110	of various event loops I prepared some benchmarks.
891	event models natively and with anyevent. The benchmark creates a lot of	2111
892	timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to	2112	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2113
		2114	Here is a benchmark of various supported event models used natively and
		2115	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2116	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
893	become writable, which it is), lets them fire exactly once and destroys	2117	which it is), lets them fire exactly once and destroys them again.
894	them again.
895		2118
896	Rewriting the benchmark to use many different sockets instead of using	2119	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
897	the same filehandle for all I/O watchers results in a much longer runtime	2120	distribution. It uses the L<AE> interface, which makes a real difference
898	(socket creation is expensive), but qualitatively the same figures, so it	2121	for the EV and Perl backends only.
899	was not used.
900		2122
901	=head2 Explanation of the columns	2123	=head3 Explanation of the columns
902		2124
903	I<watcher> is the number of event watchers created/destroyed. Since	2125	I<watcher> is the number of event watchers created/destroyed. Since
904	different event models feature vastly different performances, each event	2126	different event models feature vastly different performances, each event
905	loop was given a number of watchers so that overall runtime is acceptable	2127	loop was given a number of watchers so that overall runtime is acceptable
906	and similar between tested event loop (and keep them from crashing): Glib	2128	and similar between tested event loop (and keep them from crashing): Glib
…		…
916	all watchers, to avoid adding memory overhead. That means closure creation	2138	all watchers, to avoid adding memory overhead. That means closure creation
917	and memory usage is not included in the figures.	2139	and memory usage is not included in the figures.
918		2140
919	I<invoke> is the time, in microseconds, used to invoke a simple	2141	I<invoke> is the time, in microseconds, used to invoke a simple
920	callback. The callback simply counts down a Perl variable and after it was	2142	callback. The callback simply counts down a Perl variable and after it was
921	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2143	invoked "watcher" times, it would C<< ->send >> a condvar once to
922	signal the end of this phase.	2144	signal the end of this phase.
923		2145
924	I<destroy> is the time, in microseconds, that it takes to destroy a single	2146	I<destroy> is the time, in microseconds, that it takes to destroy a single
925	watcher.	2147	watcher.
926		2148
927	=head2 Results	2149	=head3 Results
928		2150
929	name watchers bytes create invoke destroy comment	2151	name watchers bytes create invoke destroy comment
930	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2152	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
931	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2153	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
932	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2154	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
933	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2155	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
934	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2156	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
935	Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers	2157	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2158	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2159	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
936	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2160	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
937	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2161	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
938	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2162	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
939	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2163	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
940		2164
941	=head2 Discussion	2165	=head3 Discussion
942		2166
943	The benchmark does I<not> measure scalability of the event loop very	2167	The benchmark does I<not> measure scalability of the event loop very
944	well. For example, a select-based event loop (such as the pure perl one)	2168	well. For example, a select-based event loop (such as the pure perl one)
945	can never compete with an event loop that uses epoll when the number of	2169	can never compete with an event loop that uses epoll when the number of
946	file descriptors grows high. In this benchmark, all events become ready at	2170	file descriptors grows high. In this benchmark, all events become ready at
947	the same time, so select/poll-based implementations get an unnatural speed	2171	the same time, so select/poll-based implementations get an unnatural speed
948	boost.	2172	boost.
949		2173
		2174	Also, note that the number of watchers usually has a nonlinear effect on
		2175	overall speed, that is, creating twice as many watchers doesn't take twice
		2176	the time - usually it takes longer. This puts event loops tested with a
		2177	higher number of watchers at a disadvantage.
		2178
		2179	To put the range of results into perspective, consider that on the
		2180	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2181	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2182	cycles with POE.
		2183
950	C<EV> is the sole leader regarding speed and memory use, which are both	2184	C<EV> is the sole leader regarding speed and memory use, which are both
951	maximal/minimal, respectively. Even when going through AnyEvent, there are	2185	maximal/minimal, respectively. When using the L<AE> API there is zero
952	only two event loops that use slightly less memory (the C<Event> module	2186	overhead (when going through the AnyEvent API create is about 5-6 times
953	natively and the pure perl backend), and no faster event models, not even	2187	slower, with other times being equal, so still uses far less memory than
954	C<Event> natively.	2188	any other event loop and is still faster than Event natively).
955		2189
956	The pure perl implementation is hit in a few sweet spots (both the	2190	The pure perl implementation is hit in a few sweet spots (both the
957	zero timeout and the use of a single fd hit optimisations in the perl	2191	constant timeout and the use of a single fd hit optimisations in the perl
958	interpreter and the backend itself, and all watchers become ready at the	2192	interpreter and the backend itself). Nevertheless this shows that it
959	same time). Nevertheless this shows that it adds very little overhead in	2193	adds very little overhead in itself. Like any select-based backend its
960	itself. Like any select-based backend its performance becomes really bad	2194	performance becomes really bad with lots of file descriptors (and few of
961	with lots of file descriptors (and few of them active), of course, but	2195	them active), of course, but this was not subject of this benchmark.
962	this was not subject of this benchmark.
963		2196
964	The C<Event> module has a relatively high setup and callback invocation cost,	2197	The C<Event> module has a relatively high setup and callback invocation
965	but overall scores on the third place.	2198	cost, but overall scores in on the third place.
966		2199
		2200	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2201	when using its pure perl backend.
		2202
967	C<Glib>'s memory usage is quite a bit bit higher, but it features a	2203	C<Glib>'s memory usage is quite a bit higher, but it features a
968	faster callback invocation and overall ends up in the same class as	2204	faster callback invocation and overall ends up in the same class as
969	C<Event>. However, Glib scales extremely badly, doubling the number of	2205	C<Event>. However, Glib scales extremely badly, doubling the number of
970	watchers increases the processing time by more than a factor of four,	2206	watchers increases the processing time by more than a factor of four,
971	making it completely unusable when using larger numbers of watchers	2207	making it completely unusable when using larger numbers of watchers
972	(note that only a single file descriptor was used in the benchmark, so	2208	(note that only a single file descriptor was used in the benchmark, so
…		…
975	The C<Tk> adaptor works relatively well. The fact that it crashes with	2211	The C<Tk> adaptor works relatively well. The fact that it crashes with
976	more than 2000 watchers is a big setback, however, as correctness takes	2212	more than 2000 watchers is a big setback, however, as correctness takes
977	precedence over speed. Nevertheless, its performance is surprising, as the	2213	precedence over speed. Nevertheless, its performance is surprising, as the
978	file descriptor is dup()ed for each watcher. This shows that the dup()	2214	file descriptor is dup()ed for each watcher. This shows that the dup()
979	employed by some adaptors is not a big performance issue (it does incur a	2215	employed by some adaptors is not a big performance issue (it does incur a
980	hidden memory cost inside the kernel, though, that is not reflected in the	2216	hidden memory cost inside the kernel which is not reflected in the figures
981	figures above).	2217	above).
982		2218
983	C<POE>, regardless of underlying event loop (wether using its pure perl	2219	C<POE>, regardless of underlying event loop (whether using its pure perl
984	select-based backend or the Event module) shows abysmal performance and	2220	select-based backend or the Event module, the POE-EV backend couldn't
		2221	be tested because it wasn't working) shows abysmal performance and
985	memory usage: Watchers use almost 30 times as much memory as EV watchers,	2222	memory usage with AnyEvent: Watchers use almost 30 times as much memory
986	and 10 times as much memory as both Event or EV via AnyEvent. Watcher	2223	as EV watchers, and 10 times as much memory as Event (the high memory
		2224	requirements are caused by requiring a session for each watcher). Watcher
987	invocation is almost 900 times slower than with AnyEvent's pure perl	2225	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2226	implementation.
		2227
988	implementation. The design of the POE adaptor class in AnyEvent can not	2228	The design of the POE adaptor class in AnyEvent can not really account
989	really account for this, as session creation overhead is small compared	2229	for the performance issues, though, as session creation overhead is
990	to execution of the state machine, which is coded pretty optimally within	2230	small compared to execution of the state machine, which is coded pretty
991	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	2231	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2232	using multiple sessions is not a good approach, especially regarding
		2233	memory usage, even the author of POE could not come up with a faster
		2234	design).
992		2235
993	=head2 Summary	2236	=head3 Summary
994		2237
		2238	=over 4
		2239
995	Using EV through AnyEvent is faster than any other event loop, but most	2240	=item * Using EV through AnyEvent is faster than any other event loop
996	event loops have acceptable performance with or without AnyEvent.	2241	(even when used without AnyEvent), but most event loops have acceptable
		2242	performance with or without AnyEvent.
997		2243
998	The overhead AnyEvent adds is usually much smaller than the overhead of	2244	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
999	the actual event loop, only with extremely fast event loops such as the EV	2245	the actual event loop, only with extremely fast event loops such as EV
1000	adds AnyEvent significant overhead.	2246	adds AnyEvent significant overhead.
1001		2247
1002	And you should simply avoid POE like the plague if you want performance or	2248	=item * You should avoid POE like the plague if you want performance or
1003	reasonable memory usage.	2249	reasonable memory usage.
1004		2250
		2251	=back
		2252
		2253	=head2 BENCHMARKING THE LARGE SERVER CASE
		2254
		2255	This benchmark actually benchmarks the event loop itself. It works by
		2256	creating a number of "servers": each server consists of a socket pair, a
		2257	timeout watcher that gets reset on activity (but never fires), and an I/O
		2258	watcher waiting for input on one side of the socket. Each time the socket
		2259	watcher reads a byte it will write that byte to a random other "server".
		2260
		2261	The effect is that there will be a lot of I/O watchers, only part of which
		2262	are active at any one point (so there is a constant number of active
		2263	fds for each loop iteration, but which fds these are is random). The
		2264	timeout is reset each time something is read because that reflects how
		2265	most timeouts work (and puts extra pressure on the event loops).
		2266
		2267	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2268	(1%) are active. This mirrors the activity of large servers with many
		2269	connections, most of which are idle at any one point in time.
		2270
		2271	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2272	distribution. It uses the L<AE> interface, which makes a real difference
		2273	for the EV and Perl backends only.
		2274
		2275	=head3 Explanation of the columns
		2276
		2277	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2278	each server has a read and write socket end).
		2279
		2280	I<create> is the time it takes to create a socket pair (which is
		2281	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2282
		2283	I<request>, the most important value, is the time it takes to handle a
		2284	single "request", that is, reading the token from the pipe and forwarding
		2285	it to another server. This includes deleting the old timeout and creating
		2286	a new one that moves the timeout into the future.
		2287
		2288	=head3 Results
		2289
		2290	name sockets create request
		2291	EV 20000 62.66 7.99
		2292	Perl 20000 68.32 32.64
		2293	IOAsync 20000 174.06 101.15 epoll
		2294	IOAsync 20000 174.67 610.84 poll
		2295	Event 20000 202.69 242.91
		2296	Glib 20000 557.01 1689.52
		2297	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2298
		2299	=head3 Discussion
		2300
		2301	This benchmark I<does> measure scalability and overall performance of the
		2302	particular event loop.
		2303
		2304	EV is again fastest. Since it is using epoll on my system, the setup time
		2305	is relatively high, though.
		2306
		2307	Perl surprisingly comes second. It is much faster than the C-based event
		2308	loops Event and Glib.
		2309
		2310	IO::Async performs very well when using its epoll backend, and still quite
		2311	good compared to Glib when using its pure perl backend.
		2312
		2313	Event suffers from high setup time as well (look at its code and you will
		2314	understand why). Callback invocation also has a high overhead compared to
		2315	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2316	uses select or poll in basically all documented configurations.
		2317
		2318	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2319	clearly fails to perform with many filehandles or in busy servers.
		2320
		2321	POE is still completely out of the picture, taking over 1000 times as long
		2322	as EV, and over 100 times as long as the Perl implementation, even though
		2323	it uses a C-based event loop in this case.
		2324
		2325	=head3 Summary
		2326
		2327	=over 4
		2328
		2329	=item * The pure perl implementation performs extremely well.
		2330
		2331	=item * Avoid Glib or POE in large projects where performance matters.
		2332
		2333	=back
		2334
		2335	=head2 BENCHMARKING SMALL SERVERS
		2336
		2337	While event loops should scale (and select-based ones do not...) even to
		2338	large servers, most programs we (or I :) actually write have only a few
		2339	I/O watchers.
		2340
		2341	In this benchmark, I use the same benchmark program as in the large server
		2342	case, but it uses only eight "servers", of which three are active at any
		2343	one time. This should reflect performance for a small server relatively
		2344	well.
		2345
		2346	The columns are identical to the previous table.
		2347
		2348	=head3 Results
		2349
		2350	name sockets create request
		2351	EV 16 20.00 6.54
		2352	Perl 16 25.75 12.62
		2353	Event 16 81.27 35.86
		2354	Glib 16 32.63 15.48
		2355	POE 16 261.87 276.28 uses POE::Loop::Event
		2356
		2357	=head3 Discussion
		2358
		2359	The benchmark tries to test the performance of a typical small
		2360	server. While knowing how various event loops perform is interesting, keep
		2361	in mind that their overhead in this case is usually not as important, due
		2362	to the small absolute number of watchers (that is, you need efficiency and
		2363	speed most when you have lots of watchers, not when you only have a few of
		2364	them).
		2365
		2366	EV is again fastest.
		2367
		2368	Perl again comes second. It is noticeably faster than the C-based event
		2369	loops Event and Glib, although the difference is too small to really
		2370	matter.
		2371
		2372	POE also performs much better in this case, but is is still far behind the
		2373	others.
		2374
		2375	=head3 Summary
		2376
		2377	=over 4
		2378
		2379	=item * C-based event loops perform very well with small number of
		2380	watchers, as the management overhead dominates.
		2381
		2382	=back
		2383
		2384	=head2 THE IO::Lambda BENCHMARK
		2385
		2386	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2387	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2388	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2389	shouldn't come as a surprise to anybody). As such, the benchmark is
		2390	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2391	very optimal. But how would AnyEvent compare when used without the extra
		2392	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2393
		2394	The benchmark itself creates an echo-server, and then, for 500 times,
		2395	connects to the echo server, sends a line, waits for the reply, and then
		2396	creates the next connection. This is a rather bad benchmark, as it doesn't
		2397	test the efficiency of the framework or much non-blocking I/O, but it is a
		2398	benchmark nevertheless.
		2399
		2400	name runtime
		2401	Lambda/select 0.330 sec
		2402	+ optimized 0.122 sec
		2403	Lambda/AnyEvent 0.327 sec
		2404	+ optimized 0.138 sec
		2405	Raw sockets/select 0.077 sec
		2406	POE/select, components 0.662 sec
		2407	POE/select, raw sockets 0.226 sec
		2408	POE/select, optimized 0.404 sec
		2409
		2410	AnyEvent/select/nb 0.085 sec
		2411	AnyEvent/EV/nb 0.068 sec
		2412	+state machine 0.134 sec
		2413
		2414	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2415	benchmarks actually make blocking connects and use 100% blocking I/O,
		2416	defeating the purpose of an event-based solution. All of the newly
		2417	written AnyEvent benchmarks use 100% non-blocking connects (using
		2418	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2419	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2420	generally require a lot more bookkeeping and event handling than blocking
		2421	connects (which involve a single syscall only).
		2422
		2423	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2424	offers similar expressive power as POE and IO::Lambda, using conventional
		2425	Perl syntax. This means that both the echo server and the client are 100%
		2426	non-blocking, further placing it at a disadvantage.
		2427
		2428	As you can see, the AnyEvent + EV combination even beats the
		2429	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2430	backend easily beats IO::Lambda and POE.
		2431
		2432	And even the 100% non-blocking version written using the high-level (and
		2433	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2434	higher level ("unoptimised") abstractions by a large margin, even though
		2435	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2436
		2437	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2438	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2439	part of the IO::Lambda distribution and were used without any changes.
		2440
		2441
		2442	=head1 SIGNALS
		2443
		2444	AnyEvent currently installs handlers for these signals:
		2445
		2446	=over 4
		2447
		2448	=item SIGCHLD
		2449
		2450	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2451	emulation for event loops that do not support them natively. Also, some
		2452	event loops install a similar handler.
		2453
		2454	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2455	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2456
		2457	=item SIGPIPE
		2458
		2459	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2460	when AnyEvent gets loaded.
		2461
		2462	The rationale for this is that AnyEvent users usually do not really depend
		2463	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2464	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2465	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2466	some random socket.
		2467
		2468	The rationale for installing a no-op handler as opposed to ignoring it is
		2469	that this way, the handler will be restored to defaults on exec.
		2470
		2471	Feel free to install your own handler, or reset it to defaults.
		2472
		2473	=back
		2474
		2475	=cut
		2476
		2477	undef $SIG{CHLD}
		2478	if $SIG{CHLD} eq 'IGNORE';
		2479
		2480	$SIG{PIPE} = sub { }
		2481	unless defined $SIG{PIPE};
		2482
		2483	=head1 RECOMMENDED/OPTIONAL MODULES
		2484
		2485	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2486	it's built-in modules) are required to use it.
		2487
		2488	That does not mean that AnyEvent won't take advantage of some additional
		2489	modules if they are installed.
		2490
		2491	This section explains which additional modules will be used, and how they
		2492	affect AnyEvent's operation.
		2493
		2494	=over 4
		2495
		2496	=item L<Async::Interrupt>
		2497
		2498	This slightly arcane module is used to implement fast signal handling: To
		2499	my knowledge, there is no way to do completely race-free and quick
		2500	signal handling in pure perl. To ensure that signals still get
		2501	delivered, AnyEvent will start an interval timer to wake up perl (and
		2502	catch the signals) with some delay (default is 10 seconds, look for
		2503	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2504
		2505	If this module is available, then it will be used to implement signal
		2506	catching, which means that signals will not be delayed, and the event loop
		2507	will not be interrupted regularly, which is more efficient (and good for
		2508	battery life on laptops).
		2509
		2510	This affects not just the pure-perl event loop, but also other event loops
		2511	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2512
		2513	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2514	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2515	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2516	does nothing for those backends.
		2517
		2518	=item L<EV>
		2519
		2520	This module isn't really "optional", as it is simply one of the backend
		2521	event loops that AnyEvent can use. However, it is simply the best event
		2522	loop available in terms of features, speed and stability: It supports
		2523	the AnyEvent API optimally, implements all the watcher types in XS, does
		2524	automatic timer adjustments even when no monotonic clock is available,
		2525	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2526	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2527	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2528
		2529	=item L<Guard>
		2530
		2531	The guard module, when used, will be used to implement
		2532	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2533	lot less memory), but otherwise doesn't affect guard operation much. It is
		2534	purely used for performance.
		2535
		2536	=item L<JSON> and L<JSON::XS>
		2537
		2538	One of these modules is required when you want to read or write JSON data
		2539	via L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2540	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2541
		2542	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2543	installed.
		2544
		2545	=item L<Net::SSLeay>
		2546
		2547	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2548	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2549	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2550
		2551	=item L<Time::HiRes>
		2552
		2553	This module is part of perl since release 5.008. It will be used when the
		2554	chosen event library does not come with a timing source on it's own. The
		2555	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2556	try to use a monotonic clock for timing stability.
		2557
		2558	=back
		2559
1005		2560
1006	=head1 FORK	2561	=head1 FORK
1007		2562
1008	Most event libraries are not fork-safe. The ones who are usually are	2563	Most event libraries are not fork-safe. The ones who are usually are
1009	because they are so inefficient. Only L<EV> is fully fork-aware.	2564	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2565	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2566	are usually badly thought-out hacks that are incompatible with fork in
		2567	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2568	continue event-processing in both parent and child (or both, if you know
		2569	what you are doing).
		2570
		2571	This means that, in general, you cannot fork and do event processing in
		2572	the child if the event library was initialised before the fork (which
		2573	usually happens when the first AnyEvent watcher is created, or the library
		2574	is loaded).
1010		2575
1011	If you have to fork, you must either do so I<before> creating your first	2576	If you have to fork, you must either do so I<before> creating your first
1012	watcher OR you must not use AnyEvent at all in the child.	2577	watcher OR you must not use AnyEvent at all in the child OR you must do
		2578	something completely out of the scope of AnyEvent.
		2579
		2580	The problem of doing event processing in the parent I<and> the child
		2581	is much more complicated: even for backends that I<are> fork-aware or
		2582	fork-safe, their behaviour is not usually what you want: fork clones all
		2583	watchers, that means all timers, I/O watchers etc. are active in both
		2584	parent and child, which is almost never what you want. USing C<exec>
		2585	to start worker children from some kind of manage rprocess is usually
		2586	preferred, because it is much easier and cleaner, at the expense of having
		2587	to have another binary.
1013		2588
1014		2589
1015	=head1 SECURITY CONSIDERATIONS	2590	=head1 SECURITY CONSIDERATIONS
1016		2591
1017	AnyEvent can be forced to load any event model via	2592	AnyEvent can be forced to load any event model via
…		…
1022	specified in the variable.	2597	specified in the variable.
1023		2598
1024	You can make AnyEvent completely ignore this variable by deleting it	2599	You can make AnyEvent completely ignore this variable by deleting it
1025	before the first watcher gets created, e.g. with a C<BEGIN> block:	2600	before the first watcher gets created, e.g. with a C<BEGIN> block:
1026		2601
1027	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2602	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1028		2603
1029	use AnyEvent;	2604	use AnyEvent;
		2605
		2606	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2607	be used to probe what backend is used and gain other information (which is
		2608	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2609	$ENV{PERL_ANYEVENT_STRICT}.
		2610
		2611	Note that AnyEvent will remove I<all> environment variables starting with
		2612	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2613	enabled.
		2614
		2615
		2616	=head1 BUGS
		2617
		2618	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2619	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2620	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2621	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2622	pronounced).
1030		2623
1031		2624
1032	=head1 SEE ALSO	2625	=head1 SEE ALSO
1033		2626
1034	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2627	Utility functions: L<AnyEvent::Util>.
1035	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	2628
		2629	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1036	L<Event::Lib>, L<Qt>, L<POE>.	2630	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1037		2631
1038	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2632	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2633	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2634	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1039	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2635	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1040	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
1041	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1042		2636
		2637	Non-blocking file handles, sockets, TCP clients and
		2638	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2639
		2640	Asynchronous DNS: L<AnyEvent::DNS>.
		2641
		2642	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2643	L<Coro::Event>,
		2644
1043	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2645	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2646	L<AnyEvent::HTTP>.
1044		2647
1045		2648
1046	=head1 AUTHOR	2649	=head1 AUTHOR
1047		2650
1048	Marc Lehmann <schmorp@schmorp.de>	2651	Marc Lehmann <schmorp@schmorp.de>
1049	http://home.schmorp.de/	2652	http://home.schmorp.de/
1050		2653
1051	=cut	2654	=cut
1052		2655
1053	1	2656	1
1054		2657

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