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Revision 1.253 by root, Tue Jul 21 06:00:47 2009 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - events independent of event loop implementation
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
		6	event loops.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores 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	Respository>, 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<Tk>. The first one found is used. If none are found,	122	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	the module tries to load these modules in the stated order. The first one	123	L<POE>. The first one found is used. If none are found, the module tries
		124	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
		125	adaptor should always succeed) in the order given. The first one that can
87	that can be successfully loaded will be used. If, after this, still none	126	be successfully loaded will be used. If, after this, still none could be
88	could be found, AnyEvent will fall back to a pure-perl event loop, which	127	found, AnyEvent will fall back to a pure-perl event loop, which is not
89	is not very efficient, but should work everywhere.	128	very efficient, but should work everywhere.
90		129
91	Because AnyEvent first checks for modules that are already loaded, loading	130	Because AnyEvent first checks for modules that are already loaded, loading
92	an event model explicitly before first using AnyEvent will likely make	131	an event model explicitly before first using AnyEvent will likely make
93	that model the default. For example:	132	that model the default. For example:
94		133
…		…
101	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
102	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
103		142
104	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
105	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
106	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
107		146
108	=head1 WATCHERS	147	=head1 WATCHERS
109		148
110	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
111	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
112	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
113		152
114	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
115	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
116	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
117	is in control).	156	is in control).
118		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
119	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
120	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
121	to it).	166	to it).
122		167
123	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.
…		…
125	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
126	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.
127		172
128	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
129		174
130	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
131	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
132	undef $w;	177	undef $w;
133	});	178	});
134		179
135	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,
136	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
137	declared.	182	declared.
138		183
139	=head2 IO WATCHERS	184	=head2 I/O WATCHERS
140		185
141	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	186	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
142	with the following mandatory key-value pairs as arguments:	187	with the following mandatory key-value pairs as arguments:
143		188
144	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	189	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		190	for events (AnyEvent might or might not keep a reference to this file
		191	handle). Note that only file handles pointing to things for which
		192	non-blocking operation makes sense are allowed. This includes sockets,
		193	most character devices, pipes, fifos and so on, but not for example files
		194	or block devices.
		195
145	events. C<poll> must be a string that is either C<r> or C<w>, which	196	C<poll> must be a string that is either C<r> or C<w>, which creates a
146	creates a watcher waiting for "r"eadable or "w"ritable events,	197	watcher waiting for "r"eadable or "w"ritable events, respectively.
		198
147	respectively. C<cb> is the callback to invoke each time the file handle	199	C<cb> is the callback to invoke each time the file handle becomes ready.
148	becomes ready.
149		200
150	File handles will be kept alive, so as long as the watcher exists, the	201	Although the callback might get passed parameters, their value and
151	file handle exists, too.	202	presence is undefined and you cannot rely on them. Portable AnyEvent
		203	callbacks cannot use arguments passed to I/O watcher callbacks.
152		204
		205	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	206	You must not close a file handle as long as any watcher is active on the
154	on the underlying file descriptor.	207	underlying file descriptor.
155		208
156	Some event loops issue spurious readyness notifications, so you should	209	Some event loops issue spurious readyness notifications, so you should
157	always use non-blocking calls when reading/writing from/to your file	210	always use non-blocking calls when reading/writing from/to your file
158	handles.	211	handles.
159		212
160	Example:
161
162	# wait for readability of STDIN, then read a line and disable the watcher	213	Example: wait for readability of STDIN, then read a line and disable the
		214	watcher.
		215
163	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	216	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
164	chomp (my $input = <STDIN>);	217	chomp (my $input = <STDIN>);
165	warn "read: $input\n";	218	warn "read: $input\n";
166	undef $w;	219	undef $w;
167	});	220	});
…		…
170		223
171	You can create a time watcher by calling the C<< AnyEvent->timer >>	224	You can create a time watcher by calling the C<< AnyEvent->timer >>
172	method with the following mandatory arguments:	225	method with the following mandatory arguments:
173		226
174	C<after> specifies after how many seconds (fractional values are	227	C<after> specifies after how many seconds (fractional values are
175	supported) should the timer activate. C<cb> the callback to invoke in that	228	supported) the callback should be invoked. C<cb> is the callback to invoke
176	case.	229	in that case.
177		230
178	The timer callback will be invoked at most once: if you want a repeating	231	Although the callback might get passed parameters, their value and
179	timer you have to create a new watcher (this is a limitation by both Tk	232	presence is undefined and you cannot rely on them. Portable AnyEvent
180	and Glib).	233	callbacks cannot use arguments passed to time watcher callbacks.
181		234
182	Example:	235	The callback will normally be invoked once only. If you specify another
		236	parameter, C<interval>, as a strictly positive number (> 0), then the
		237	callback will be invoked regularly at that interval (in fractional
		238	seconds) after the first invocation. If C<interval> is specified with a
		239	false value, then it is treated as if it were missing.
183		240
		241	The callback will be rescheduled before invoking the callback, but no
		242	attempt is done to avoid timer drift in most backends, so the interval is
		243	only approximate.
		244
184	# fire an event after 7.7 seconds	245	Example: fire an event after 7.7 seconds.
		246
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	247	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	248	warn "timeout\n";
187	});	249	});
188		250
189	# to cancel the timer:	251	# to cancel the timer:
190	undef $w;	252	undef $w;
191		253
192	Example 2:
193
194	# fire an event after 0.5 seconds, then roughly every second	254	Example 2: fire an event after 0.5 seconds, then roughly every second.
195	my $w;
196		255
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	256	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		257	warn "timeout\n";
200	};	258	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		259
205	=head3 TIMING ISSUES	260	=head3 TIMING ISSUES
206		261
207	There are two ways to handle timers: based on real time (relative, "fire	262	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	263	in 10 seconds") and based on wallclock time (absolute, "fire at 12
209	o'clock").	264	o'clock").
210		265
211	While most event loops expect timers to specified in a relative way, they use	266	While most event loops expect timers to specified in a relative way, they
212	absolute time internally. This makes a difference when your clock "jumps",	267	use absolute time internally. This makes a difference when your clock
213	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to	268	"jumps", for example, when ntp decides to set your clock backwards from
214	2008-01-01, a watcher that you created to fire "after" a second might actually take	269	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
215	six years to finally fire.	270	fire "after" a second might actually take six years to finally fire.
216		271
217	AnyEvent cannot compensate for this. The only event loop that is conscious	272	AnyEvent cannot compensate for this. The only event loop that is conscious
218	about these issues is L<EV>, which offers both relative (ev_timer) and	273	about these issues is L<EV>, which offers both relative (ev_timer, based
219	absolute (ev_periodic) timers.	274	on true relative time) and absolute (ev_periodic, based on wallclock time)
		275	timers.
220		276
221	AnyEvent always prefers relative timers, if available, matching the	277	AnyEvent always prefers relative timers, if available, matching the
222	AnyEvent API.	278	AnyEvent API.
223		279
		280	AnyEvent has two additional methods that return the "current time":
		281
		282	=over 4
		283
		284	=item AnyEvent->time
		285
		286	This returns the "current wallclock time" as a fractional number of
		287	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		288	return, and the result is guaranteed to be compatible with those).
		289
		290	It progresses independently of any event loop processing, i.e. each call
		291	will check the system clock, which usually gets updated frequently.
		292
		293	=item AnyEvent->now
		294
		295	This also returns the "current wallclock time", but unlike C<time>, above,
		296	this value might change only once per event loop iteration, depending on
		297	the event loop (most return the same time as C<time>, above). This is the
		298	time that AnyEvent's timers get scheduled against.
		299
		300	I<In almost all cases (in all cases if you don't care), this is the
		301	function to call when you want to know the current time.>
		302
		303	This function is also often faster then C<< AnyEvent->time >>, and
		304	thus the preferred method if you want some timestamp (for example,
		305	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		306
		307	The rest of this section is only of relevance if you try to be very exact
		308	with your timing, you can skip it without bad conscience.
		309
		310	For a practical example of when these times differ, consider L<Event::Lib>
		311	and L<EV> and the following set-up:
		312
		313	The event loop is running and has just invoked one of your callback at
		314	time=500 (assume no other callbacks delay processing). In your callback,
		315	you wait a second by executing C<sleep 1> (blocking the process for a
		316	second) and then (at time=501) you create a relative timer that fires
		317	after three seconds.
		318
		319	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		320	both return C<501>, because that is the current time, and the timer will
		321	be scheduled to fire at time=504 (C<501> + C<3>).
		322
		323	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		324	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		325	last event processing phase started. With L<EV>, your timer gets scheduled
		326	to run at time=503 (C<500> + C<3>).
		327
		328	In one sense, L<Event::Lib> is more exact, as it uses the current time
		329	regardless of any delays introduced by event processing. However, most
		330	callbacks do not expect large delays in processing, so this causes a
		331	higher drift (and a lot more system calls to get the current time).
		332
		333	In another sense, L<EV> is more exact, as your timer will be scheduled at
		334	the same time, regardless of how long event processing actually took.
		335
		336	In either case, if you care (and in most cases, you don't), then you
		337	can get whatever behaviour you want with any event loop, by taking the
		338	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		339	account.
		340
		341	=item AnyEvent->now_update
		342
		343	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		344	the current time for each loop iteration (see the discussion of L<<
		345	AnyEvent->now >>, above).
		346
		347	When a callback runs for a long time (or when the process sleeps), then
		348	this "current" time will differ substantially from the real time, which
		349	might affect timers and time-outs.
		350
		351	When this is the case, you can call this method, which will update the
		352	event loop's idea of "current time".
		353
		354	Note that updating the time I<might> cause some events to be handled.
		355
		356	=back
		357
224	=head2 SIGNAL WATCHERS	358	=head2 SIGNAL WATCHERS
225		359
226	You can watch for signals using a signal watcher, C<signal> is the signal	360	You can watch for signals using a signal watcher, C<signal> is the signal
227	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	361	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
228	be invoked whenever a signal occurs.	362	callback to be invoked whenever a signal occurs.
229		363
		364	Although the callback might get passed parameters, their value and
		365	presence is undefined and you cannot rely on them. Portable AnyEvent
		366	callbacks cannot use arguments passed to signal watcher callbacks.
		367
230	Multiple signals occurances can be clumped together into one callback	368	Multiple signal occurrences can be clumped together into one callback
231	invocation, and callback invocation will be synchronous. synchronous means	369	invocation, and callback invocation will be synchronous. Synchronous means
232	that it might take a while until the signal gets handled by the process,	370	that it might take a while until the signal gets handled by the process,
233	but it is guarenteed not to interrupt any other callbacks.	371	but it is guaranteed not to interrupt any other callbacks.
234		372
235	The main advantage of using these watchers is that you can share a signal	373	The main advantage of using these watchers is that you can share a signal
236	between multiple watchers.	374	between multiple watchers, and AnyEvent will ensure that signals will not
		375	interrupt your program at bad times.
237		376
238	This watcher might use C<%SIG>, so programs overwriting those signals	377	This watcher might use C<%SIG> (depending on the event loop used),
239	directly will likely not work correctly.	378	so programs overwriting those signals directly will likely not work
		379	correctly.
240		380
241	Example: exit on SIGINT	381	Example: exit on SIGINT
242		382
243	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	383	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
244		384
		385	=head3 Signal Races, Delays and Workarounds
		386
		387	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		388	callbacks to signals in a generic way, which is a pity, as you cannot do
		389	race-free signal handling in perl. AnyEvent will try to do it's best, but
		390	in some cases, signals will be delayed. The maximum time a signal might
		391	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		392	seconds). This variable can be changed only before the first signal
		393	watcher is created, and should be left alone otherwise. Higher values
		394	will cause fewer spurious wake-ups, which is better for power and CPU
		395	saving. All these problems can be avoided by installing the optional
		396	L<Async::Interrupt> module. This will not work with inherently broken
		397	event loops such as L<Event> or L<Event::Lib> (and not with L<POE>
		398	currently, as POE does it's own workaround with one-second latency). With
		399	those, you just have to suffer the delays.
		400
245	=head2 CHILD PROCESS WATCHERS	401	=head2 CHILD PROCESS WATCHERS
246		402
247	You can also watch on a child process exit and catch its exit status.	403	You can also watch on a child process exit and catch its exit status.
248		404
249	The child process is specified by the C<pid> argument (if set to C<0>, it	405	The child process is specified by the C<pid> argument (if set to C<0>, it
250	watches for any child process exit). The watcher will trigger as often	406	watches for any child process exit). The watcher will triggered only when
251	as status change for the child are received. This works by installing a	407	the child process has finished and an exit status is available, not on
252	signal handler for C<SIGCHLD>. The callback will be called with the pid	408	any trace events (stopped/continued).
253	and exit status (as returned by waitpid).
254		409
255	Example: wait for pid 1333	410	The callback will be called with the pid and exit status (as returned by
		411	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		412	callback arguments.
256		413
		414	This watcher type works by installing a signal handler for C<SIGCHLD>,
		415	and since it cannot be shared, nothing else should use SIGCHLD or reap
		416	random child processes (waiting for specific child processes, e.g. inside
		417	C<system>, is just fine).
		418
		419	There is a slight catch to child watchers, however: you usually start them
		420	I<after> the child process was created, and this means the process could
		421	have exited already (and no SIGCHLD will be sent anymore).
		422
		423	Not all event models handle this correctly (neither POE nor IO::Async do,
		424	see their AnyEvent::Impl manpages for details), but even for event models
		425	that I<do> handle this correctly, they usually need to be loaded before
		426	the process exits (i.e. before you fork in the first place). AnyEvent's
		427	pure perl event loop handles all cases correctly regardless of when you
		428	start the watcher.
		429
		430	This means you cannot create a child watcher as the very first
		431	thing in an AnyEvent program, you I<have> to create at least one
		432	watcher before you C<fork> the child (alternatively, you can call
		433	C<AnyEvent::detect>).
		434
		435	As most event loops do not support waiting for child events, they will be
		436	emulated by AnyEvent in most cases, in which the latency and race problems
		437	mentioned in the description of signal watchers apply.
		438
		439	Example: fork a process and wait for it
		440
		441	my $done = AnyEvent->condvar;
		442
		443	my $pid = fork or exit 5;
		444
257	my $w = AnyEvent->child (	445	my $w = AnyEvent->child (
258	pid => 1333,	446	pid => $pid,
259	cb => sub {	447	cb => sub {
260	my ($pid, $status) = @_;	448	my ($pid, $status) = @_;
261	warn "pid $pid exited with status $status";	449	warn "pid $pid exited with status $status";
		450	$done->send;
262	},	451	},
263	);	452	);
		453
		454	# do something else, then wait for process exit
		455	$done->recv;
		456
		457	=head2 IDLE WATCHERS
		458
		459	Sometimes there is a need to do something, but it is not so important
		460	to do it instantly, but only when there is nothing better to do. This
		461	"nothing better to do" is usually defined to be "no other events need
		462	attention by the event loop".
		463
		464	Idle watchers ideally get invoked when the event loop has nothing
		465	better to do, just before it would block the process to wait for new
		466	events. Instead of blocking, the idle watcher is invoked.
		467
		468	Most event loops unfortunately do not really support idle watchers (only
		469	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		470	will simply call the callback "from time to time".
		471
		472	Example: read lines from STDIN, but only process them when the
		473	program is otherwise idle:
		474
		475	my @lines; # read data
		476	my $idle_w;
		477	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		478	push @lines, scalar <STDIN>;
		479
		480	# start an idle watcher, if not already done
		481	$idle_w ||= AnyEvent->idle (cb => sub {
		482	# handle only one line, when there are lines left
		483	if (my $line = shift @lines) {
		484	print "handled when idle: $line";
		485	} else {
		486	# otherwise disable the idle watcher again
		487	undef $idle_w;
		488	}
		489	});
		490	});
264		491
265	=head2 CONDITION VARIABLES	492	=head2 CONDITION VARIABLES
266		493
		494	If you are familiar with some event loops you will know that all of them
		495	require you to run some blocking "loop", "run" or similar function that
		496	will actively watch for new events and call your callbacks.
		497
		498	AnyEvent is slightly different: it expects somebody else to run the event
		499	loop and will only block when necessary (usually when told by the user).
		500
		501	The instrument to do that is called a "condition variable", so called
		502	because they represent a condition that must become true.
		503
		504	Now is probably a good time to look at the examples further below.
		505
267	Condition variables can be created by calling the C<< AnyEvent->condvar >>	506	Condition variables can be created by calling the C<< AnyEvent->condvar
268	method without any arguments.	507	>> method, usually without arguments. The only argument pair allowed is
		508	C<cb>, which specifies a callback to be called when the condition variable
		509	becomes true, with the condition variable as the first argument (but not
		510	the results).
269		511
270	A condition variable waits for a condition - precisely that the C<<	512	After creation, the condition variable is "false" until it becomes "true"
271	->broadcast >> method has been called.	513	by calling the C<send> method (or calling the condition variable as if it
		514	were a callback, read about the caveats in the description for the C<<
		515	->send >> method).
272		516
273	They are very useful to signal that a condition has been fulfilled, for	517	Condition variables are similar to callbacks, except that you can
		518	optionally wait for them. They can also be called merge points - points
		519	in time where multiple outstanding events have been processed. And yet
		520	another way to call them is transactions - each condition variable can be
		521	used to represent a transaction, which finishes at some point and delivers
		522	a result. And yet some people know them as "futures" - a promise to
		523	compute/deliver something that you can wait for.
		524
		525	Condition variables are very useful to signal that something has finished,
274	example, if you write a module that does asynchronous http requests,	526	for example, if you write a module that does asynchronous http requests,
275	then a condition variable would be the ideal candidate to signal the	527	then a condition variable would be the ideal candidate to signal the
276	availability of results.	528	availability of results. The user can either act when the callback is
		529	called or can synchronously C<< ->recv >> for the results.
277		530
278	You can also use condition variables to block your main program until	531	You can also use them to simulate traditional event loops - for example,
279	an event occurs - for example, you could C<< ->wait >> in your main	532	you can block your main program until an event occurs - for example, you
280	program until the user clicks the Quit button in your app, which would C<<	533	could C<< ->recv >> in your main program until the user clicks the Quit
281	->broadcast >> the "quit" event.	534	button of your app, which would C<< ->send >> the "quit" event.
282		535
283	Note that condition variables recurse into the event loop - if you have	536	Note that condition variables recurse into the event loop - if you have
284	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	537	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
285	lose. Therefore, condition variables are good to export to your caller, but	538	lose. Therefore, condition variables are good to export to your caller, but
286	you should avoid making a blocking wait yourself, at least in callbacks,	539	you should avoid making a blocking wait yourself, at least in callbacks,
287	as this asks for trouble.	540	as this asks for trouble.
288		541
289	This object has two methods:	542	Condition variables are represented by hash refs in perl, and the keys
		543	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		544	easy (it is often useful to build your own transaction class on top of
		545	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		546	it's C<new> method in your own C<new> method.
290		547
291	=over 4	548	There are two "sides" to a condition variable - the "producer side" which
		549	eventually calls C<< -> send >>, and the "consumer side", which waits
		550	for the send to occur.
292		551
293	=item $cv->wait	552	Example: wait for a timer.
294
295	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
296	called on c<$cv>, while servicing other watchers normally.
297
298	You can only wait once on a condition - additional calls will return
299	immediately.
300
301	Not all event models support a blocking wait - some die in that case
302	(programs might want to do that to stay interactive), so I<if you are
303	using this from a module, never require a blocking wait>, but let the
304	caller decide whether the call will block or not (for example, by coupling
305	condition variables with some kind of request results and supporting
306	callbacks so the caller knows that getting the result will not block,
307	while still suppporting blocking waits if the caller so desires).
308
309	Another reason I<never> to C<< ->wait >> in a module is that you cannot
310	sensibly have two C<< ->wait >>'s in parallel, as that would require
311	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
312	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
313	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
314	from different coroutines, however).
315
316	=item $cv->broadcast
317
318	Flag the condition as ready - a running C<< ->wait >> and all further
319	calls to C<wait> will (eventually) return after this method has been
320	called. If nobody is waiting the broadcast will be remembered..
321
322	=back
323
324	Example:
325		553
326	# wait till the result is ready	554	# wait till the result is ready
327	my $result_ready = AnyEvent->condvar;	555	my $result_ready = AnyEvent->condvar;
328		556
329	# do something such as adding a timer	557	# do something such as adding a timer
330	# or socket watcher the calls $result_ready->broadcast	558	# or socket watcher the calls $result_ready->send
331	# when the "result" is ready.	559	# when the "result" is ready.
332	# in this case, we simply use a timer:	560	# in this case, we simply use a timer:
333	my $w = AnyEvent->timer (	561	my $w = AnyEvent->timer (
334	after => 1,	562	after => 1,
335	cb => sub { $result_ready->broadcast },	563	cb => sub { $result_ready->send },
336	);	564	);
337		565
338	# this "blocks" (while handling events) till the watcher	566	# this "blocks" (while handling events) till the callback
339	# calls broadcast	567	# calls -<send
340	$result_ready->wait;	568	$result_ready->recv;
		569
		570	Example: wait for a timer, but take advantage of the fact that condition
		571	variables are also callable directly.
		572
		573	my $done = AnyEvent->condvar;
		574	my $delay = AnyEvent->timer (after => 5, cb => $done);
		575	$done->recv;
		576
		577	Example: Imagine an API that returns a condvar and doesn't support
		578	callbacks. This is how you make a synchronous call, for example from
		579	the main program:
		580
		581	use AnyEvent::CouchDB;
		582
		583	...
		584
		585	my @info = $couchdb->info->recv;
		586
		587	And this is how you would just set a callback to be called whenever the
		588	results are available:
		589
		590	$couchdb->info->cb (sub {
		591	my @info = $_[0]->recv;
		592	});
		593
		594	=head3 METHODS FOR PRODUCERS
		595
		596	These methods should only be used by the producing side, i.e. the
		597	code/module that eventually sends the signal. Note that it is also
		598	the producer side which creates the condvar in most cases, but it isn't
		599	uncommon for the consumer to create it as well.
		600
		601	=over 4
		602
		603	=item $cv->send (...)
		604
		605	Flag the condition as ready - a running C<< ->recv >> and all further
		606	calls to C<recv> will (eventually) return after this method has been
		607	called. If nobody is waiting the send will be remembered.
		608
		609	If a callback has been set on the condition variable, it is called
		610	immediately from within send.
		611
		612	Any arguments passed to the C<send> call will be returned by all
		613	future C<< ->recv >> calls.
		614
		615	Condition variables are overloaded so one can call them directly (as if
		616	they were a code reference). Calling them directly is the same as calling
		617	C<send>.
		618
		619	=item $cv->croak ($error)
		620
		621	Similar to send, but causes all call's to C<< ->recv >> to invoke
		622	C<Carp::croak> with the given error message/object/scalar.
		623
		624	This can be used to signal any errors to the condition variable
		625	user/consumer. Doing it this way instead of calling C<croak> directly
		626	delays the error detetcion, but has the overwhelmign advantage that it
		627	diagnoses the error at the place where the result is expected, and not
		628	deep in some event clalback without connection to the actual code causing
		629	the problem.
		630
		631	=item $cv->begin ([group callback])
		632
		633	=item $cv->end
		634
		635	These two methods can be used to combine many transactions/events into
		636	one. For example, a function that pings many hosts in parallel might want
		637	to use a condition variable for the whole process.
		638
		639	Every call to C<< ->begin >> will increment a counter, and every call to
		640	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		641	>>, the (last) callback passed to C<begin> will be executed. That callback
		642	is I<supposed> to call C<< ->send >>, but that is not required. If no
		643	callback was set, C<send> will be called without any arguments.
		644
		645	You can think of C<< $cv->send >> giving you an OR condition (one call
		646	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		647	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		648
		649	Let's start with a simple example: you have two I/O watchers (for example,
		650	STDOUT and STDERR for a program), and you want to wait for both streams to
		651	close before activating a condvar:
		652
		653	my $cv = AnyEvent->condvar;
		654
		655	$cv->begin; # first watcher
		656	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		657	defined sysread $fh1, my $buf, 4096
		658	or $cv->end;
		659	});
		660
		661	$cv->begin; # second watcher
		662	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		663	defined sysread $fh2, my $buf, 4096
		664	or $cv->end;
		665	});
		666
		667	$cv->recv;
		668
		669	This works because for every event source (EOF on file handle), there is
		670	one call to C<begin>, so the condvar waits for all calls to C<end> before
		671	sending.
		672
		673	The ping example mentioned above is slightly more complicated, as the
		674	there are results to be passwd back, and the number of tasks that are
		675	begung can potentially be zero:
		676
		677	my $cv = AnyEvent->condvar;
		678
		679	my %result;
		680	$cv->begin (sub { $cv->send (\%result) });
		681
		682	for my $host (@list_of_hosts) {
		683	$cv->begin;
		684	ping_host_then_call_callback $host, sub {
		685	$result{$host} = ...;
		686	$cv->end;
		687	};
		688	}
		689
		690	$cv->end;
		691
		692	This code fragment supposedly pings a number of hosts and calls
		693	C<send> after results for all then have have been gathered - in any
		694	order. To achieve this, the code issues a call to C<begin> when it starts
		695	each ping request and calls C<end> when it has received some result for
		696	it. Since C<begin> and C<end> only maintain a counter, the order in which
		697	results arrive is not relevant.
		698
		699	There is an additional bracketing call to C<begin> and C<end> outside the
		700	loop, which serves two important purposes: first, it sets the callback
		701	to be called once the counter reaches C<0>, and second, it ensures that
		702	C<send> is called even when C<no> hosts are being pinged (the loop
		703	doesn't execute once).
		704
		705	This is the general pattern when you "fan out" into multiple (but
		706	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		707	the callback and ensure C<end> is called at least once, and then, for each
		708	subrequest you start, call C<begin> and for each subrequest you finish,
		709	call C<end>.
		710
		711	=back
		712
		713	=head3 METHODS FOR CONSUMERS
		714
		715	These methods should only be used by the consuming side, i.e. the
		716	code awaits the condition.
		717
		718	=over 4
		719
		720	=item $cv->recv
		721
		722	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		723	>> methods have been called on c<$cv>, while servicing other watchers
		724	normally.
		725
		726	You can only wait once on a condition - additional calls are valid but
		727	will return immediately.
		728
		729	If an error condition has been set by calling C<< ->croak >>, then this
		730	function will call C<croak>.
		731
		732	In list context, all parameters passed to C<send> will be returned,
		733	in scalar context only the first one will be returned.
		734
		735	Note that doing a blocking wait in a callback is not supported by any
		736	event loop, that is, recursive invocation of a blocking C<< ->recv
		737	>> is not allowed, and the C<recv> call will C<croak> if such a
		738	condition is detected. This condition can be slightly loosened by using
		739	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		740	any thread that doesn't run the event loop itself.
		741
		742	Not all event models support a blocking wait - some die in that case
		743	(programs might want to do that to stay interactive), so I<if you are
		744	using this from a module, never require a blocking wait>. Instead, let the
		745	caller decide whether the call will block or not (for example, by coupling
		746	condition variables with some kind of request results and supporting
		747	callbacks so the caller knows that getting the result will not block,
		748	while still supporting blocking waits if the caller so desires).
		749
		750	You can ensure that C<< -recv >> never blocks by setting a callback and
		751	only calling C<< ->recv >> from within that callback (or at a later
		752	time). This will work even when the event loop does not support blocking
		753	waits otherwise.
		754
		755	=item $bool = $cv->ready
		756
		757	Returns true when the condition is "true", i.e. whether C<send> or
		758	C<croak> have been called.
		759
		760	=item $cb = $cv->cb ($cb->($cv))
		761
		762	This is a mutator function that returns the callback set and optionally
		763	replaces it before doing so.
		764
		765	The callback will be called when the condition becomes "true", i.e. when
		766	C<send> or C<croak> are called, with the only argument being the condition
		767	variable itself. Calling C<recv> inside the callback or at any later time
		768	is guaranteed not to block.
		769
		770	=back
		771
		772	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		773
		774	The available backend classes are (every class has its own manpage):
		775
		776	=over 4
		777
		778	=item Backends that are autoprobed when no other event loop can be found.
		779
		780	EV is the preferred backend when no other event loop seems to be in
		781	use. If EV is not installed, then AnyEvent will try Event, and, failing
		782	that, will fall back to its own pure-perl implementation, which is
		783	available everywhere as it comes with AnyEvent itself.
		784
		785	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		786	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		787	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		788
		789	=item Backends that are transparently being picked up when they are used.
		790
		791	These will be used when they are currently loaded when the first watcher
		792	is created, in which case it is assumed that the application is using
		793	them. This means that AnyEvent will automatically pick the right backend
		794	when the main program loads an event module before anything starts to
		795	create watchers. Nothing special needs to be done by the main program.
		796
		797	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		798	AnyEvent::Impl::Tk based on Tk, very broken.
		799	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		800	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		801
		802	=item Backends with special needs.
		803
		804	Qt requires the Qt::Application to be instantiated first, but will
		805	otherwise be picked up automatically. As long as the main program
		806	instantiates the application before any AnyEvent watchers are created,
		807	everything should just work.
		808
		809	AnyEvent::Impl::Qt based on Qt.
		810
		811	Support for IO::Async can only be partial, as it is too broken and
		812	architecturally limited to even support the AnyEvent API. It also
		813	is the only event loop that needs the loop to be set explicitly, so
		814	it can only be used by a main program knowing about AnyEvent. See
		815	L<AnyEvent::Impl::Async> for the gory details.
		816
		817	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		818
		819	=item Event loops that are indirectly supported via other backends.
		820
		821	Some event loops can be supported via other modules:
		822
		823	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		824
		825	B<WxWidgets> has no support for watching file handles. However, you can
		826	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		827	polls 20 times per second, which was considered to be too horrible to even
		828	consider for AnyEvent.
		829
		830	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		831	backend, so it can be supported through POE.
		832
		833	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		834	load L<POE> when detecting them, in the hope that POE will pick them up,
		835	in which case everything will be automatic.
		836
		837	=back
341		838
342	=head1 GLOBAL VARIABLES AND FUNCTIONS	839	=head1 GLOBAL VARIABLES AND FUNCTIONS
343		840
		841	These are not normally required to use AnyEvent, but can be useful to
		842	write AnyEvent extension modules.
		843
344	=over 4	844	=over 4
345		845
346	=item $AnyEvent::MODEL	846	=item $AnyEvent::MODEL
347		847
348	Contains C<undef> until the first watcher is being created. Then it	848	Contains C<undef> until the first watcher is being created, before the
		849	backend has been autodetected.
		850
349	contains the event model that is being used, which is the name of the	851	Afterwards it contains the event model that is being used, which is the
350	Perl class implementing the model. This class is usually one of the	852	name of the Perl class implementing the model. This class is usually one
351	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	853	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
352	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	854	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
353		855	will be C<urxvt::anyevent>).
354	The known classes so far are:
355
356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
358	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
359	AnyEvent::Impl::Event based on Event, also second best choice :)
360	AnyEvent::Impl::Glib based on Glib, third-best choice.
361	AnyEvent::Impl::Tk based on Tk, very bad choice.
362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
363	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
364		856
365	=item AnyEvent::detect	857	=item AnyEvent::detect
366		858
367	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	859	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
368	if necessary. You should only call this function right before you would	860	if necessary. You should only call this function right before you would
369	have created an AnyEvent watcher anyway, that is, as late as possible at	861	have created an AnyEvent watcher anyway, that is, as late as possible at
370	runtime.	862	runtime, and not e.g. while initialising of your module.
		863
		864	If you need to do some initialisation before AnyEvent watchers are
		865	created, use C<post_detect>.
		866
		867	=item $guard = AnyEvent::post_detect { BLOCK }
		868
		869	Arranges for the code block to be executed as soon as the event model is
		870	autodetected (or immediately if this has already happened).
		871
		872	The block will be executed I<after> the actual backend has been detected
		873	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		874	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		875	other initialisations - see the sources of L<AnyEvent::Strict> or
		876	L<AnyEvent::AIO> to see how this is used.
		877
		878	The most common usage is to create some global watchers, without forcing
		879	event module detection too early, for example, L<AnyEvent::AIO> creates
		880	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		881	avoid autodetecting the event module at load time.
		882
		883	If called in scalar or list context, then it creates and returns an object
		884	that automatically removes the callback again when it is destroyed (or
		885	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		886	a case where this is useful.
		887
		888	Example: Create a watcher for the IO::AIO module and store it in
		889	C<$WATCHER>. Only do so after the event loop is initialised, though.
		890
		891	our WATCHER;
		892
		893	my $guard = AnyEvent::post_detect {
		894	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		895	};
		896
		897	# the ||= is important in case post_detect immediately runs the block,
		898	# as to not clobber the newly-created watcher. assigning both watcher and
		899	# post_detect guard to the same variable has the advantage of users being
		900	# able to just C<undef $WATCHER> if the watcher causes them grief.
		901
		902	$WATCHER ||= $guard;
		903
		904	=item @AnyEvent::post_detect
		905
		906	If there are any code references in this array (you can C<push> to it
		907	before or after loading AnyEvent), then they will called directly after
		908	the event loop has been chosen.
		909
		910	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		911	if it is defined then the event loop has already been detected, and the
		912	array will be ignored.
		913
		914	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		915	it,as it takes care of these details.
		916
		917	This variable is mainly useful for modules that can do something useful
		918	when AnyEvent is used and thus want to know when it is initialised, but do
		919	not need to even load it by default. This array provides the means to hook
		920	into AnyEvent passively, without loading it.
371		921
372	=back	922	=back
373		923
374	=head1 WHAT TO DO IN A MODULE	924	=head1 WHAT TO DO IN A MODULE
375		925
…		…
379	Be careful when you create watchers in the module body - AnyEvent will	929	Be careful when you create watchers in the module body - AnyEvent will
380	decide which event module to use as soon as the first method is called, so	930	decide which event module to use as soon as the first method is called, so
381	by calling AnyEvent in your module body you force the user of your module	931	by calling AnyEvent in your module body you force the user of your module
382	to load the event module first.	932	to load the event module first.
383		933
384	Never call C<< ->wait >> on a condition variable unless you I<know> that	934	Never call C<< ->recv >> on a condition variable unless you I<know> that
385	the C<< ->broadcast >> method has been called on it already. This is	935	the C<< ->send >> method has been called on it already. This is
386	because it will stall the whole program, and the whole point of using	936	because it will stall the whole program, and the whole point of using
387	events is to stay interactive.	937	events is to stay interactive.
388		938
389	It is fine, however, to call C<< ->wait >> when the user of your module	939	It is fine, however, to call C<< ->recv >> when the user of your module
390	requests it (i.e. if you create a http request object ad have a method	940	requests it (i.e. if you create a http request object ad have a method
391	called C<results> that returns the results, it should call C<< ->wait >>	941	called C<results> that returns the results, it should call C<< ->recv >>
392	freely, as the user of your module knows what she is doing. always).	942	freely, as the user of your module knows what she is doing. always).
393		943
394	=head1 WHAT TO DO IN THE MAIN PROGRAM	944	=head1 WHAT TO DO IN THE MAIN PROGRAM
395		945
396	There will always be a single main program - the only place that should	946	There will always be a single main program - the only place that should
…		…
398		948
399	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	949	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
400	do anything special (it does not need to be event-based) and let AnyEvent	950	do anything special (it does not need to be event-based) and let AnyEvent
401	decide which implementation to chose if some module relies on it.	951	decide which implementation to chose if some module relies on it.
402		952
403	If the main program relies on a specific event model. For example, in	953	If the main program relies on a specific event model - for example, in
404	Gtk2 programs you have to rely on the Glib module. You should load the	954	Gtk2 programs you have to rely on the Glib module - you should load the
405	event module before loading AnyEvent or any module that uses it: generally	955	event module before loading AnyEvent or any module that uses it: generally
406	speaking, you should load it as early as possible. The reason is that	956	speaking, you should load it as early as possible. The reason is that
407	modules might create watchers when they are loaded, and AnyEvent will	957	modules might create watchers when they are loaded, and AnyEvent will
408	decide on the event model to use as soon as it creates watchers, and it	958	decide on the event model to use as soon as it creates watchers, and it
409	might chose the wrong one unless you load the correct one yourself.	959	might chose the wrong one unless you load the correct one yourself.
410		960
411	You can chose to use a rather inefficient pure-perl implementation by	961	You can chose to use a pure-perl implementation by loading the
412	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	962	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
413	behaviour everywhere, but letting AnyEvent chose is generally better.	963	everywhere, but letting AnyEvent chose the model is generally better.
		964
		965	=head2 MAINLOOP EMULATION
		966
		967	Sometimes (often for short test scripts, or even standalone programs who
		968	only want to use AnyEvent), you do not want to run a specific event loop.
		969
		970	In that case, you can use a condition variable like this:
		971
		972	AnyEvent->condvar->recv;
		973
		974	This has the effect of entering the event loop and looping forever.
		975
		976	Note that usually your program has some exit condition, in which case
		977	it is better to use the "traditional" approach of storing a condition
		978	variable somewhere, waiting for it, and sending it when the program should
		979	exit cleanly.
		980
		981
		982	=head1 OTHER MODULES
		983
		984	The following is a non-exhaustive list of additional modules that use
		985	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		986	modules and other event loops in the same program. Some of the modules
		987	come with AnyEvent, most are available via CPAN.
		988
		989	=over 4
		990
		991	=item L<AnyEvent::Util>
		992
		993	Contains various utility functions that replace often-used but blocking
		994	functions such as C<inet_aton> by event-/callback-based versions.
		995
		996	=item L<AnyEvent::Socket>
		997
		998	Provides various utility functions for (internet protocol) sockets,
		999	addresses and name resolution. Also functions to create non-blocking tcp
		1000	connections or tcp servers, with IPv6 and SRV record support and more.
		1001
		1002	=item L<AnyEvent::Handle>
		1003
		1004	Provide read and write buffers, manages watchers for reads and writes,
		1005	supports raw and formatted I/O, I/O queued and fully transparent and
		1006	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1007
		1008	=item L<AnyEvent::DNS>
		1009
		1010	Provides rich asynchronous DNS resolver capabilities.
		1011
		1012	=item L<AnyEvent::HTTP>
		1013
		1014	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1015	HTTP requests.
		1016
		1017	=item L<AnyEvent::HTTPD>
		1018
		1019	Provides a simple web application server framework.
		1020
		1021	=item L<AnyEvent::FastPing>
		1022
		1023	The fastest ping in the west.
		1024
		1025	=item L<AnyEvent::DBI>
		1026
		1027	Executes L<DBI> requests asynchronously in a proxy process.
		1028
		1029	=item L<AnyEvent::AIO>
		1030
		1031	Truly asynchronous I/O, should be in the toolbox of every event
		1032	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1033	together.
		1034
		1035	=item L<AnyEvent::BDB>
		1036
		1037	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1038	L<BDB> and AnyEvent together.
		1039
		1040	=item L<AnyEvent::GPSD>
		1041
		1042	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1043
		1044	=item L<AnyEvent::IRC>
		1045
		1046	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1047
		1048	=item L<AnyEvent::XMPP>
		1049
		1050	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1051	Net::XMPP2>.
		1052
		1053	=item L<AnyEvent::IGS>
		1054
		1055	A non-blocking interface to the Internet Go Server protocol (used by
		1056	L<App::IGS>).
		1057
		1058	=item L<Net::FCP>
		1059
		1060	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1061	of AnyEvent.
		1062
		1063	=item L<Event::ExecFlow>
		1064
		1065	High level API for event-based execution flow control.
		1066
		1067	=item L<Coro>
		1068
		1069	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1070
		1071	=back
414		1072
415	=cut	1073	=cut
416		1074
417	package AnyEvent;	1075	package AnyEvent;
418		1076
		1077	# basically a tuned-down version of common::sense
		1078	sub common_sense {
419	no warnings;	1079	# no warnings
420	use strict;	1080	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1081	# use strict vars subs
		1082	$^H |= 0x00000600;
		1083	}
421		1084
		1085	BEGIN { AnyEvent::common_sense }
		1086
422	use Carp;	1087	use Carp ();
423		1088
424	our $VERSION = '3.12';	1089	our $VERSION = 4.86;
425	our $MODEL;	1090	our $MODEL;
426		1091
427	our $AUTOLOAD;	1092	our $AUTOLOAD;
428	our @ISA;	1093	our @ISA;
429		1094
430	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
431
432	our @REGISTRY;	1095	our @REGISTRY;
433		1096
		1097	our $WIN32;
		1098
		1099	our $VERBOSE;
		1100
		1101	BEGIN {
		1102	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1103	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1104
		1105	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1106	if ${^TAINT};
		1107
		1108	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1109
		1110	}
		1111
		1112	our $MAX_SIGNAL_LATENCY = 10;
		1113
		1114	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1115
		1116	{
		1117	my $idx;
		1118	$PROTOCOL{$_} = ++$idx
		1119	for reverse split /\s*,\s*/,
		1120	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1121	}
		1122
434	my @models = (	1123	my @models = (
435	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
436	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
437	[EV:: => AnyEvent::Impl::EV::],	1124	[EV:: => AnyEvent::Impl::EV::],
438	[Event:: => AnyEvent::Impl::Event::],	1125	[Event:: => AnyEvent::Impl::Event::],
439	[Glib:: => AnyEvent::Impl::Glib::],
440	[Tk:: => AnyEvent::Impl::Tk::],
441	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1126	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		1127	# everything below here will not be autoprobed
		1128	# as the pureperl backend should work everywhere
		1129	# and is usually faster
		1130	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
442	[Event::Lib:: => AnyEvent::Impl::EventLib::],	1131	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1132	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1133	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1134	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		1135	[Wx:: => AnyEvent::Impl::POE::],
		1136	[Prima:: => AnyEvent::Impl::POE::],
		1137	# IO::Async is just too broken - we would need workarounds for its
		1138	# byzantine signal and broken child handling, among others.
		1139	# IO::Async is rather hard to detect, as it doesn't have any
		1140	# obvious default class.
		1141	# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1142	# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1143	# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
443	);	1144	);
444		1145
445	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1146	our %method = map +($_ => 1),
		1147	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1148
		1149	our @post_detect;
		1150
		1151	sub post_detect(&) {
		1152	my ($cb) = @_;
		1153
		1154	if ($MODEL) {
		1155	$cb->();
		1156
		1157	undef
		1158	} else {
		1159	push @post_detect, $cb;
		1160
		1161	defined wantarray
		1162	? bless \$cb, "AnyEvent::Util::postdetect"
		1163	: ()
		1164	}
		1165	}
		1166
		1167	sub AnyEvent::Util::postdetect::DESTROY {
		1168	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1169	}
446		1170
447	sub detect() {	1171	sub detect() {
448	unless ($MODEL) {	1172	unless ($MODEL) {
449	no strict 'refs';	1173	local $SIG{__DIE__};
450		1174
451	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1175	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
452	my $model = "AnyEvent::Impl::$1";	1176	my $model = "AnyEvent::Impl::$1";
453	if (eval "require $model") {	1177	if (eval "require $model") {
454	$MODEL = $model;	1178	$MODEL = $model;
455	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1179	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1180	} else {
		1181	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
456	}	1182	}
457	}	1183	}
458		1184
459	# check for already loaded models	1185	# check for already loaded models
460	unless ($MODEL) {	1186	unless ($MODEL) {
461	for (@REGISTRY, @models) {	1187	for (@REGISTRY, @models) {
462	my ($package, $model) = @$_;	1188	my ($package, $model) = @$_;
463	if (${"$package\::VERSION"} > 0) {	1189	if (${"$package\::VERSION"} > 0) {
464	if (eval "require $model") {	1190	if (eval "require $model") {
465	$MODEL = $model;	1191	$MODEL = $model;
466	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1192	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
467	last;	1193	last;
468	}	1194	}
469	}	1195	}
470	}	1196	}
471		1197
…		…
476	my ($package, $model) = @$_;	1202	my ($package, $model) = @$_;
477	if (eval "require $package"	1203	if (eval "require $package"
478	and ${"$package\::VERSION"} > 0	1204	and ${"$package\::VERSION"} > 0
479	and eval "require $model") {	1205	and eval "require $model") {
480	$MODEL = $model;	1206	$MODEL = $model;
481	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1207	warn "AnyEvent: autoprobed model '$model', using it.\n" if $VERBOSE >= 2;
482	last;	1208	last;
483	}	1209	}
484	}	1210	}
485		1211
486	$MODEL	1212	$MODEL
487	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1213	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
488	}	1214	}
489	}	1215	}
490		1216
		1217	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1218
491	unshift @ISA, $MODEL;	1219	unshift @ISA, $MODEL;
492	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1220
		1221	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1222
		1223	(shift @post_detect)->() while @post_detect;
493	}	1224	}
494		1225
495	$MODEL	1226	$MODEL
496	}	1227	}
497		1228
498	sub AUTOLOAD {	1229	sub AUTOLOAD {
499	(my $func = $AUTOLOAD) =~ s/.*://;	1230	(my $func = $AUTOLOAD) =~ s/.*://;
500		1231
501	$method{$func}	1232	$method{$func}
502	or croak "$func: not a valid method for AnyEvent objects";	1233	or Carp::croak "$func: not a valid method for AnyEvent objects";
503		1234
504	detect unless $MODEL;	1235	detect unless $MODEL;
505		1236
506	my $class = shift;	1237	my $class = shift;
507	$class->$func (@_);	1238	$class->$func (@_);
508	}	1239	}
509		1240
		1241	# utility function to dup a filehandle. this is used by many backends
		1242	# to support binding more than one watcher per filehandle (they usually
		1243	# allow only one watcher per fd, so we dup it to get a different one).
		1244	sub _dupfh($$;$$) {
		1245	my ($poll, $fh, $r, $w) = @_;
		1246
		1247	# cygwin requires the fh mode to be matching, unix doesn't
		1248	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1249
		1250	open my $fh2, $mode, $fh
		1251	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1252
		1253	# we assume CLOEXEC is already set by perl in all important cases
		1254
		1255	($fh2, $rw)
		1256	}
		1257
510	package AnyEvent::Base;	1258	package AnyEvent::Base;
511		1259
		1260	# default implementations for many methods
		1261
		1262	sub _time {
		1263	# probe for availability of Time::HiRes
		1264	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1265	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1266	*_time = \&Time::HiRes::time;
		1267	# if (eval "use POSIX (); (POSIX::times())...
		1268	} else {
		1269	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1270	*_time = sub { time }; # epic fail
		1271	}
		1272
		1273	&_time
		1274	}
		1275
		1276	sub time { _time }
		1277	sub now { _time }
		1278	sub now_update { }
		1279
512	# default implementation for ->condvar, ->wait, ->broadcast	1280	# default implementation for ->condvar
513		1281
514	sub condvar {	1282	sub condvar {
515	bless \my $flag, "AnyEvent::Base::CondVar"	1283	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
516	}
517
518	sub AnyEvent::Base::CondVar::broadcast {
519	${$_[0]}++;
520	}
521
522	sub AnyEvent::Base::CondVar::wait {
523	AnyEvent->one_event while !${$_[0]};
524	}	1284	}
525		1285
526	# default implementation for ->signal	1286	# default implementation for ->signal
527		1287
528	our %SIG_CB;	1288	our $HAVE_ASYNC_INTERRUPT;
		1289	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1290	our (%SIG_ASY, %SIG_ASY_W);
		1291	our ($SIG_COUNT, $SIG_TW);
529		1292
		1293	sub _signal_exec {
		1294	$HAVE_ASYNC_INTERRUPT
		1295	? $SIGPIPE_R->drain
		1296	: sysread $SIGPIPE_R, my $dummy, 9;
		1297
		1298	while (%SIG_EV) {
		1299	for (keys %SIG_EV) {
		1300	delete $SIG_EV{$_};
		1301	$_->() for values %{ $SIG_CB{$_} || {} };
		1302	}
		1303	}
		1304	}
		1305
		1306	# install a dumym wakeupw atcher to reduce signal catching latency
		1307	sub _sig_add() {
		1308	unless ($SIG_COUNT++) {
		1309	# try to align timer on a full-second boundary, if possible
		1310	my $NOW = AnyEvent->now;
		1311
		1312	$SIG_TW = AnyEvent->timer (
		1313	after => $MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1314	interval => $MAX_SIGNAL_LATENCY,
		1315	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1316	);
		1317	}
		1318	}
		1319
		1320	sub _sig_del {
		1321	undef $SIG_TW
		1322	unless --$SIG_COUNT;
		1323	}
		1324
530	sub signal {	1325	sub _signal {
531	my (undef, %arg) = @_;	1326	my (undef, %arg) = @_;
532		1327
533	my $signal = uc $arg{signal}	1328	my $signal = uc $arg{signal}
534	or Carp::croak "required option 'signal' is missing";	1329	or Carp::croak "required option 'signal' is missing";
535		1330
536	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1331	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1332
		1333	if ($HAVE_ASYNC_INTERRUPT) {
		1334	# async::interrupt
		1335
		1336	$SIG_ASY{$signal} ||= do {
		1337	my $asy = new Async::Interrupt
		1338	cb => sub { undef $SIG_EV{$signal} },
		1339	signal => $signal,
		1340	pipe => [$SIGPIPE_R->filenos],
		1341	;
		1342	$asy->pipe_autodrain (0);
		1343
		1344	$asy
		1345	};
		1346
		1347	} else {
		1348	# pure perl
		1349
537	$SIG{$signal} ||= sub {	1350	$SIG{$signal} ||= sub {
538	$_->() for values %{ $SIG_CB{$signal} || {} };	1351	local $!;
		1352	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1353	undef $SIG_EV{$signal};
		1354	};
		1355
		1356	# can't do signal processing without introducing races in pure perl,
		1357	# so limit the signal latency.
		1358	_sig_add;
539	};	1359	}
540		1360
541	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1361	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
542	}	1362	}
543		1363
		1364	sub signal {
		1365	# probe for availability of Async::Interrupt
		1366	if (!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT} && eval "use Async::Interrupt 0.6 (); 1") {
		1367	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1368
		1369	$HAVE_ASYNC_INTERRUPT = 1;
		1370	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1371	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1372
		1373	} else {
		1374	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1375
		1376	require Fcntl;
		1377
		1378	if (AnyEvent::WIN32) {
		1379	require AnyEvent::Util;
		1380
		1381	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1382	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1383	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1384	} else {
		1385	pipe $SIGPIPE_R, $SIGPIPE_W;
		1386	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1387	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1388
		1389	# not strictly required, as $^F is normally 2, but let's make sure...
		1390	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1391	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1392	}
		1393
		1394	$SIGPIPE_R
		1395	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1396
		1397	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1398	}
		1399
		1400	*signal = \&_signal;
		1401	&signal
		1402	}
		1403
544	sub AnyEvent::Base::Signal::DESTROY {	1404	sub AnyEvent::Base::signal::DESTROY {
545	my ($signal, $cb) = @{$_[0]};	1405	my ($signal, $cb) = @{$_[0]};
546		1406
		1407	_sig_del;
		1408
547	delete $SIG_CB{$signal}{$cb};	1409	delete $SIG_CB{$signal}{$cb};
548		1410
549	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1411	$HAVE_ASYNC_INTERRUPT
		1412	? delete $SIG_ASY{$signal}
		1413	: # delete doesn't work with older perls - they then
		1414	# print weird messages, or just unconditionally exit
		1415	# instead of getting the default action.
		1416	undef $SIG{$signal}
		1417	unless keys %{ $SIG_CB{$signal} };
550	}	1418	}
551		1419
552	# default implementation for ->child	1420	# default implementation for ->child
553		1421
554	our %PID_CB;	1422	our %PID_CB;
555	our $CHLD_W;	1423	our $CHLD_W;
556	our $CHLD_DELAY_W;	1424	our $CHLD_DELAY_W;
557	our $PID_IDLE;
558	our $WNOHANG;	1425	our $WNOHANG;
559		1426
560	sub _child_wait {	1427	sub _sigchld {
561	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1428	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
		1429	$_->($pid, $?)
562	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1430	for values %{ $PID_CB{$pid} || {} },
563	(values %{ $PID_CB{0} || {} });	1431	values %{ $PID_CB{0} || {} };
564	}	1432	}
565
566	undef $PID_IDLE;
567	}
568
569	sub _sigchld {
570	# make sure we deliver these changes "synchronous" with the event loop.
571	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
572	undef $CHLD_DELAY_W;
573	&_child_wait;
574	});
575	}	1433	}
576		1434
577	sub child {	1435	sub child {
578	my (undef, %arg) = @_;	1436	my (undef, %arg) = @_;
579		1437
580	defined (my $pid = $arg{pid} + 0)	1438	defined (my $pid = $arg{pid} + 0)
581	or Carp::croak "required option 'pid' is missing";	1439	or Carp::croak "required option 'pid' is missing";
582		1440
583	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1441	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
584		1442
585	unless ($WNOHANG) {	1443	# WNOHANG is almost cetrainly 1 everywhere
586	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1444	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
587	}	1445	? 1
		1446	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
588		1447
589	unless ($CHLD_W) {	1448	unless ($CHLD_W) {
590	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1449	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
591	# child could be a zombie already, so make at least one round	1450	# child could be a zombie already, so make at least one round
592	&_sigchld;	1451	&_sigchld;
593	}	1452	}
594		1453
595	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1454	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
596	}	1455	}
597		1456
598	sub AnyEvent::Base::Child::DESTROY {	1457	sub AnyEvent::Base::child::DESTROY {
599	my ($pid, $cb) = @{$_[0]};	1458	my ($pid, $cb) = @{$_[0]};
600		1459
601	delete $PID_CB{$pid}{$cb};	1460	delete $PID_CB{$pid}{$cb};
602	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1461	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
603		1462
604	undef $CHLD_W unless keys %PID_CB;	1463	undef $CHLD_W unless keys %PID_CB;
605	}	1464	}
		1465
		1466	# idle emulation is done by simply using a timer, regardless
		1467	# of whether the process is idle or not, and not letting
		1468	# the callback use more than 50% of the time.
		1469	sub idle {
		1470	my (undef, %arg) = @_;
		1471
		1472	my ($cb, $w, $rcb) = $arg{cb};
		1473
		1474	$rcb = sub {
		1475	if ($cb) {
		1476	$w = _time;
		1477	&$cb;
		1478	$w = _time - $w;
		1479
		1480	# never use more then 50% of the time for the idle watcher,
		1481	# within some limits
		1482	$w = 0.0001 if $w < 0.0001;
		1483	$w = 5 if $w > 5;
		1484
		1485	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1486	} else {
		1487	# clean up...
		1488	undef $w;
		1489	undef $rcb;
		1490	}
		1491	};
		1492
		1493	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1494
		1495	bless \\$cb, "AnyEvent::Base::idle"
		1496	}
		1497
		1498	sub AnyEvent::Base::idle::DESTROY {
		1499	undef $${$_[0]};
		1500	}
		1501
		1502	package AnyEvent::CondVar;
		1503
		1504	our @ISA = AnyEvent::CondVar::Base::;
		1505
		1506	package AnyEvent::CondVar::Base;
		1507
		1508	#use overload
		1509	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1510	# fallback => 1;
		1511
		1512	# save 300+ kilobytes by dirtily hardcoding overloading
		1513	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1514	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1515	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1516	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1517
		1518	our $WAITING;
		1519
		1520	sub _send {
		1521	# nop
		1522	}
		1523
		1524	sub send {
		1525	my $cv = shift;
		1526	$cv->{_ae_sent} = [@_];
		1527	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1528	$cv->_send;
		1529	}
		1530
		1531	sub croak {
		1532	$_[0]{_ae_croak} = $_[1];
		1533	$_[0]->send;
		1534	}
		1535
		1536	sub ready {
		1537	$_[0]{_ae_sent}
		1538	}
		1539
		1540	sub _wait {
		1541	$WAITING
		1542	and !$_[0]{_ae_sent}
		1543	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1544
		1545	local $WAITING = 1;
		1546	AnyEvent->one_event while !$_[0]{_ae_sent};
		1547	}
		1548
		1549	sub recv {
		1550	$_[0]->_wait;
		1551
		1552	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1553	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1554	}
		1555
		1556	sub cb {
		1557	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1558	$_[0]{_ae_cb}
		1559	}
		1560
		1561	sub begin {
		1562	++$_[0]{_ae_counter};
		1563	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1564	}
		1565
		1566	sub end {
		1567	return if --$_[0]{_ae_counter};
		1568	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1569	}
		1570
		1571	# undocumented/compatibility with pre-3.4
		1572	*broadcast = \&send;
		1573	*wait = \&_wait;
		1574
		1575	=head1 ERROR AND EXCEPTION HANDLING
		1576
		1577	In general, AnyEvent does not do any error handling - it relies on the
		1578	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1579	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1580	checking of all AnyEvent methods, however, which is highly useful during
		1581	development.
		1582
		1583	As for exception handling (i.e. runtime errors and exceptions thrown while
		1584	executing a callback), this is not only highly event-loop specific, but
		1585	also not in any way wrapped by this module, as this is the job of the main
		1586	program.
		1587
		1588	The pure perl event loop simply re-throws the exception (usually
		1589	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1590	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1591	so on.
		1592
		1593	=head1 ENVIRONMENT VARIABLES
		1594
		1595	The following environment variables are used by this module or its
		1596	submodules.
		1597
		1598	Note that AnyEvent will remove I<all> environment variables starting with
		1599	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1600	enabled.
		1601
		1602	=over 4
		1603
		1604	=item C<PERL_ANYEVENT_VERBOSE>
		1605
		1606	By default, AnyEvent will be completely silent except in fatal
		1607	conditions. You can set this environment variable to make AnyEvent more
		1608	talkative.
		1609
		1610	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1611	conditions, such as not being able to load the event model specified by
		1612	C<PERL_ANYEVENT_MODEL>.
		1613
		1614	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1615	model it chooses.
		1616
		1617	When set to C<8> or higher, then AnyEvent will report extra information on
		1618	which optional modules it loads and how it implements certain features.
		1619
		1620	=item C<PERL_ANYEVENT_STRICT>
		1621
		1622	AnyEvent does not do much argument checking by default, as thorough
		1623	argument checking is very costly. Setting this variable to a true value
		1624	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1625	check the arguments passed to most method calls. If it finds any problems,
		1626	it will croak.
		1627
		1628	In other words, enables "strict" mode.
		1629
		1630	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1631	>>, it is definitely recommended to keep it off in production. Keeping
		1632	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1633	can be very useful, however.
		1634
		1635	=item C<PERL_ANYEVENT_MODEL>
		1636
		1637	This can be used to specify the event model to be used by AnyEvent, before
		1638	auto detection and -probing kicks in. It must be a string consisting
		1639	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1640	and the resulting module name is loaded and if the load was successful,
		1641	used as event model. If it fails to load AnyEvent will proceed with
		1642	auto detection and -probing.
		1643
		1644	This functionality might change in future versions.
		1645
		1646	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1647	could start your program like this:
		1648
		1649	PERL_ANYEVENT_MODEL=Perl perl ...
		1650
		1651	=item C<PERL_ANYEVENT_PROTOCOLS>
		1652
		1653	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1654	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1655	of auto probing).
		1656
		1657	Must be set to a comma-separated list of protocols or address families,
		1658	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1659	used, and preference will be given to protocols mentioned earlier in the
		1660	list.
		1661
		1662	This variable can effectively be used for denial-of-service attacks
		1663	against local programs (e.g. when setuid), although the impact is likely
		1664	small, as the program has to handle conenction and other failures anyways.
		1665
		1666	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1667	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1668	- only support IPv4, never try to resolve or contact IPv6
		1669	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1670	IPv6, but prefer IPv6 over IPv4.
		1671
		1672	=item C<PERL_ANYEVENT_EDNS0>
		1673
		1674	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1675	for DNS. This extension is generally useful to reduce DNS traffic, but
		1676	some (broken) firewalls drop such DNS packets, which is why it is off by
		1677	default.
		1678
		1679	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1680	EDNS0 in its DNS requests.
		1681
		1682	=item C<PERL_ANYEVENT_MAX_FORKS>
		1683
		1684	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1685	will create in parallel.
		1686
		1687	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1688
		1689	The default value for the C<max_outstanding> parameter for the default DNS
		1690	resolver - this is the maximum number of parallel DNS requests that are
		1691	sent to the DNS server.
		1692
		1693	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1694
		1695	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1696	configuration) in the default resolver. When set to the empty string, no
		1697	default config will be used.
		1698
		1699	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1700
		1701	When neither C<ca_file> nor C<ca_path> was specified during
		1702	L<AnyEvent::TLS> context creation, and either of these environment
		1703	variables exist, they will be used to specify CA certificate locations
		1704	instead of a system-dependent default.
		1705
		1706	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1707
		1708	When these are set to C<1>, then the respective modules are not
		1709	loaded. Mostly good for testing AnyEvent itself.
		1710
		1711	=back
606		1712
607	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1713	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
608		1714
609	This is an advanced topic that you do not normally need to use AnyEvent in	1715	This is an advanced topic that you do not normally need to use AnyEvent in
610	a module. This section is only of use to event loop authors who want to	1716	a module. This section is only of use to event loop authors who want to
…		…
645	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1751	I<rxvt-unicode> also cheats a bit by not providing blocking access to
646	condition variables: code blocking while waiting for a condition will	1752	condition variables: code blocking while waiting for a condition will
647	C<die>. This still works with most modules/usages, and blocking calls must	1753	C<die>. This still works with most modules/usages, and blocking calls must
648	not be done in an interactive application, so it makes sense.	1754	not be done in an interactive application, so it makes sense.
649		1755
650	=head1 ENVIRONMENT VARIABLES
651
652	The following environment variables are used by this module:
653
654	=over 4
655
656	=item C<PERL_ANYEVENT_VERBOSE>
657
658	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
659	model it chooses.
660
661	=item C<PERL_ANYEVENT_MODEL>
662
663	This can be used to specify the event model to be used by AnyEvent, before
664	autodetection and -probing kicks in. It must be a string consisting
665	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
666	and the resulting module name is loaded and if the load was successful,
667	used as event model. If it fails to load AnyEvent will proceed with
668	autodetection and -probing.
669
670	This functionality might change in future versions.
671
672	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
673	could start your program like this:
674
675	PERL_ANYEVENT_MODEL=Perl perl ...
676
677	=back
678
679	=head1 EXAMPLE PROGRAM	1756	=head1 EXAMPLE PROGRAM
680		1757
681	The following program uses an IO watcher to read data from STDIN, a timer	1758	The following program uses an I/O watcher to read data from STDIN, a timer
682	to display a message once per second, and a condition variable to quit the	1759	to display a message once per second, and a condition variable to quit the
683	program when the user enters quit:	1760	program when the user enters quit:
684		1761
685	use AnyEvent;	1762	use AnyEvent;
686		1763
…		…
691	poll => 'r',	1768	poll => 'r',
692	cb => sub {	1769	cb => sub {
693	warn "io event <$_[0]>\n"; # will always output <r>	1770	warn "io event <$_[0]>\n"; # will always output <r>
694	chomp (my $input = <STDIN>); # read a line	1771	chomp (my $input = <STDIN>); # read a line
695	warn "read: $input\n"; # output what has been read	1772	warn "read: $input\n"; # output what has been read
696	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1773	$cv->send if $input =~ /^q/i; # quit program if /^q/i
697	},	1774	},
698	);	1775	);
699		1776
700	my $time_watcher; # can only be used once	1777	my $time_watcher; # can only be used once
701		1778
…		…
706	});	1783	});
707	}	1784	}
708		1785
709	new_timer; # create first timer	1786	new_timer; # create first timer
710		1787
711	$cv->wait; # wait until user enters /^q/i	1788	$cv->recv; # wait until user enters /^q/i
712		1789
713	=head1 REAL-WORLD EXAMPLE	1790	=head1 REAL-WORLD EXAMPLE
714		1791
715	Consider the L<Net::FCP> module. It features (among others) the following	1792	Consider the L<Net::FCP> module. It features (among others) the following
716	API calls, which are to freenet what HTTP GET requests are to http:	1793	API calls, which are to freenet what HTTP GET requests are to http:
…		…
766	syswrite $txn->{fh}, $txn->{request}	1843	syswrite $txn->{fh}, $txn->{request}
767	or die "connection or write error";	1844	or die "connection or write error";
768	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1845	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
769		1846
770	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1847	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
771	result and signals any possible waiters that the request ahs finished:	1848	result and signals any possible waiters that the request has finished:
772		1849
773	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1850	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
774		1851
775	if (end-of-file or data complete) {	1852	if (end-of-file or data complete) {
776	$txn->{result} = $txn->{buf};	1853	$txn->{result} = $txn->{buf};
777	$txn->{finished}->broadcast;	1854	$txn->{finished}->send;
778	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1855	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
779	}	1856	}
780		1857
781	The C<result> method, finally, just waits for the finished signal (if the	1858	The C<result> method, finally, just waits for the finished signal (if the
782	request was already finished, it doesn't wait, of course, and returns the	1859	request was already finished, it doesn't wait, of course, and returns the
783	data:	1860	data:
784		1861
785	$txn->{finished}->wait;	1862	$txn->{finished}->recv;
786	return $txn->{result};	1863	return $txn->{result};
787		1864
788	The actual code goes further and collects all errors (C<die>s, exceptions)	1865	The actual code goes further and collects all errors (C<die>s, exceptions)
789	that occured during request processing. The C<result> method detects	1866	that occurred during request processing. The C<result> method detects
790	whether an exception as thrown (it is stored inside the $txn object)	1867	whether an exception as thrown (it is stored inside the $txn object)
791	and just throws the exception, which means connection errors and other	1868	and just throws the exception, which means connection errors and other
792	problems get reported tot he code that tries to use the result, not in a	1869	problems get reported tot he code that tries to use the result, not in a
793	random callback.	1870	random callback.
794		1871
…		…
825		1902
826	my $quit = AnyEvent->condvar;	1903	my $quit = AnyEvent->condvar;
827		1904
828	$fcp->txn_client_get ($url)->cb (sub {	1905	$fcp->txn_client_get ($url)->cb (sub {
829	...	1906	...
830	$quit->broadcast;	1907	$quit->send;
831	});	1908	});
832		1909
833	$quit->wait;	1910	$quit->recv;
		1911
		1912
		1913	=head1 BENCHMARKS
		1914
		1915	To give you an idea of the performance and overheads that AnyEvent adds
		1916	over the event loops themselves and to give you an impression of the speed
		1917	of various event loops I prepared some benchmarks.
		1918
		1919	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1920
		1921	Here is a benchmark of various supported event models used natively and
		1922	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1923	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1924	which it is), lets them fire exactly once and destroys them again.
		1925
		1926	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1927	distribution.
		1928
		1929	=head3 Explanation of the columns
		1930
		1931	I<watcher> is the number of event watchers created/destroyed. Since
		1932	different event models feature vastly different performances, each event
		1933	loop was given a number of watchers so that overall runtime is acceptable
		1934	and similar between tested event loop (and keep them from crashing): Glib
		1935	would probably take thousands of years if asked to process the same number
		1936	of watchers as EV in this benchmark.
		1937
		1938	I<bytes> is the number of bytes (as measured by the resident set size,
		1939	RSS) consumed by each watcher. This method of measuring captures both C
		1940	and Perl-based overheads.
		1941
		1942	I<create> is the time, in microseconds (millionths of seconds), that it
		1943	takes to create a single watcher. The callback is a closure shared between
		1944	all watchers, to avoid adding memory overhead. That means closure creation
		1945	and memory usage is not included in the figures.
		1946
		1947	I<invoke> is the time, in microseconds, used to invoke a simple
		1948	callback. The callback simply counts down a Perl variable and after it was
		1949	invoked "watcher" times, it would C<< ->send >> a condvar once to
		1950	signal the end of this phase.
		1951
		1952	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1953	watcher.
		1954
		1955	=head3 Results
		1956
		1957	name watchers bytes create invoke destroy comment
		1958	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
		1959	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
		1960	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
		1961	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
		1962	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
		1963	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1964	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1965	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
		1966	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
		1967	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
		1968	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
		1969	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
		1970
		1971	=head3 Discussion
		1972
		1973	The benchmark does I<not> measure scalability of the event loop very
		1974	well. For example, a select-based event loop (such as the pure perl one)
		1975	can never compete with an event loop that uses epoll when the number of
		1976	file descriptors grows high. In this benchmark, all events become ready at
		1977	the same time, so select/poll-based implementations get an unnatural speed
		1978	boost.
		1979
		1980	Also, note that the number of watchers usually has a nonlinear effect on
		1981	overall speed, that is, creating twice as many watchers doesn't take twice
		1982	the time - usually it takes longer. This puts event loops tested with a
		1983	higher number of watchers at a disadvantage.
		1984
		1985	To put the range of results into perspective, consider that on the
		1986	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1987	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1988	cycles with POE.
		1989
		1990	C<EV> is the sole leader regarding speed and memory use, which are both
		1991	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1992	far less memory than any other event loop and is still faster than Event
		1993	natively.
		1994
		1995	The pure perl implementation is hit in a few sweet spots (both the
		1996	constant timeout and the use of a single fd hit optimisations in the perl
		1997	interpreter and the backend itself). Nevertheless this shows that it
		1998	adds very little overhead in itself. Like any select-based backend its
		1999	performance becomes really bad with lots of file descriptors (and few of
		2000	them active), of course, but this was not subject of this benchmark.
		2001
		2002	The C<Event> module has a relatively high setup and callback invocation
		2003	cost, but overall scores in on the third place.
		2004
		2005	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2006	when using its pure perl backend.
		2007
		2008	C<Glib>'s memory usage is quite a bit higher, but it features a
		2009	faster callback invocation and overall ends up in the same class as
		2010	C<Event>. However, Glib scales extremely badly, doubling the number of
		2011	watchers increases the processing time by more than a factor of four,
		2012	making it completely unusable when using larger numbers of watchers
		2013	(note that only a single file descriptor was used in the benchmark, so
		2014	inefficiencies of C<poll> do not account for this).
		2015
		2016	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2017	more than 2000 watchers is a big setback, however, as correctness takes
		2018	precedence over speed. Nevertheless, its performance is surprising, as the
		2019	file descriptor is dup()ed for each watcher. This shows that the dup()
		2020	employed by some adaptors is not a big performance issue (it does incur a
		2021	hidden memory cost inside the kernel which is not reflected in the figures
		2022	above).
		2023
		2024	C<POE>, regardless of underlying event loop (whether using its pure perl
		2025	select-based backend or the Event module, the POE-EV backend couldn't
		2026	be tested because it wasn't working) shows abysmal performance and
		2027	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2028	as EV watchers, and 10 times as much memory as Event (the high memory
		2029	requirements are caused by requiring a session for each watcher). Watcher
		2030	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2031	implementation.
		2032
		2033	The design of the POE adaptor class in AnyEvent can not really account
		2034	for the performance issues, though, as session creation overhead is
		2035	small compared to execution of the state machine, which is coded pretty
		2036	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2037	using multiple sessions is not a good approach, especially regarding
		2038	memory usage, even the author of POE could not come up with a faster
		2039	design).
		2040
		2041	=head3 Summary
		2042
		2043	=over 4
		2044
		2045	=item * Using EV through AnyEvent is faster than any other event loop
		2046	(even when used without AnyEvent), but most event loops have acceptable
		2047	performance with or without AnyEvent.
		2048
		2049	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2050	the actual event loop, only with extremely fast event loops such as EV
		2051	adds AnyEvent significant overhead.
		2052
		2053	=item * You should avoid POE like the plague if you want performance or
		2054	reasonable memory usage.
		2055
		2056	=back
		2057
		2058	=head2 BENCHMARKING THE LARGE SERVER CASE
		2059
		2060	This benchmark actually benchmarks the event loop itself. It works by
		2061	creating a number of "servers": each server consists of a socket pair, a
		2062	timeout watcher that gets reset on activity (but never fires), and an I/O
		2063	watcher waiting for input on one side of the socket. Each time the socket
		2064	watcher reads a byte it will write that byte to a random other "server".
		2065
		2066	The effect is that there will be a lot of I/O watchers, only part of which
		2067	are active at any one point (so there is a constant number of active
		2068	fds for each loop iteration, but which fds these are is random). The
		2069	timeout is reset each time something is read because that reflects how
		2070	most timeouts work (and puts extra pressure on the event loops).
		2071
		2072	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2073	(1%) are active. This mirrors the activity of large servers with many
		2074	connections, most of which are idle at any one point in time.
		2075
		2076	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2077	distribution.
		2078
		2079	=head3 Explanation of the columns
		2080
		2081	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2082	each server has a read and write socket end).
		2083
		2084	I<create> is the time it takes to create a socket pair (which is
		2085	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2086
		2087	I<request>, the most important value, is the time it takes to handle a
		2088	single "request", that is, reading the token from the pipe and forwarding
		2089	it to another server. This includes deleting the old timeout and creating
		2090	a new one that moves the timeout into the future.
		2091
		2092	=head3 Results
		2093
		2094	name sockets create request
		2095	EV 20000 69.01 11.16
		2096	Perl 20000 73.32 35.87
		2097	IOAsync 20000 157.00 98.14 epoll
		2098	IOAsync 20000 159.31 616.06 poll
		2099	Event 20000 212.62 257.32
		2100	Glib 20000 651.16 1896.30
		2101	POE 20000 349.67 12317.24 uses POE::Loop::Event
		2102
		2103	=head3 Discussion
		2104
		2105	This benchmark I<does> measure scalability and overall performance of the
		2106	particular event loop.
		2107
		2108	EV is again fastest. Since it is using epoll on my system, the setup time
		2109	is relatively high, though.
		2110
		2111	Perl surprisingly comes second. It is much faster than the C-based event
		2112	loops Event and Glib.
		2113
		2114	IO::Async performs very well when using its epoll backend, and still quite
		2115	good compared to Glib when using its pure perl backend.
		2116
		2117	Event suffers from high setup time as well (look at its code and you will
		2118	understand why). Callback invocation also has a high overhead compared to
		2119	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2120	uses select or poll in basically all documented configurations.
		2121
		2122	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2123	clearly fails to perform with many filehandles or in busy servers.
		2124
		2125	POE is still completely out of the picture, taking over 1000 times as long
		2126	as EV, and over 100 times as long as the Perl implementation, even though
		2127	it uses a C-based event loop in this case.
		2128
		2129	=head3 Summary
		2130
		2131	=over 4
		2132
		2133	=item * The pure perl implementation performs extremely well.
		2134
		2135	=item * Avoid Glib or POE in large projects where performance matters.
		2136
		2137	=back
		2138
		2139	=head2 BENCHMARKING SMALL SERVERS
		2140
		2141	While event loops should scale (and select-based ones do not...) even to
		2142	large servers, most programs we (or I :) actually write have only a few
		2143	I/O watchers.
		2144
		2145	In this benchmark, I use the same benchmark program as in the large server
		2146	case, but it uses only eight "servers", of which three are active at any
		2147	one time. This should reflect performance for a small server relatively
		2148	well.
		2149
		2150	The columns are identical to the previous table.
		2151
		2152	=head3 Results
		2153
		2154	name sockets create request
		2155	EV 16 20.00 6.54
		2156	Perl 16 25.75 12.62
		2157	Event 16 81.27 35.86
		2158	Glib 16 32.63 15.48
		2159	POE 16 261.87 276.28 uses POE::Loop::Event
		2160
		2161	=head3 Discussion
		2162
		2163	The benchmark tries to test the performance of a typical small
		2164	server. While knowing how various event loops perform is interesting, keep
		2165	in mind that their overhead in this case is usually not as important, due
		2166	to the small absolute number of watchers (that is, you need efficiency and
		2167	speed most when you have lots of watchers, not when you only have a few of
		2168	them).
		2169
		2170	EV is again fastest.
		2171
		2172	Perl again comes second. It is noticeably faster than the C-based event
		2173	loops Event and Glib, although the difference is too small to really
		2174	matter.
		2175
		2176	POE also performs much better in this case, but is is still far behind the
		2177	others.
		2178
		2179	=head3 Summary
		2180
		2181	=over 4
		2182
		2183	=item * C-based event loops perform very well with small number of
		2184	watchers, as the management overhead dominates.
		2185
		2186	=back
		2187
		2188	=head2 THE IO::Lambda BENCHMARK
		2189
		2190	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2191	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2192	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2193	shouldn't come as a surprise to anybody). As such, the benchmark is
		2194	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2195	very optimal. But how would AnyEvent compare when used without the extra
		2196	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2197
		2198	The benchmark itself creates an echo-server, and then, for 500 times,
		2199	connects to the echo server, sends a line, waits for the reply, and then
		2200	creates the next connection. This is a rather bad benchmark, as it doesn't
		2201	test the efficiency of the framework or much non-blocking I/O, but it is a
		2202	benchmark nevertheless.
		2203
		2204	name runtime
		2205	Lambda/select 0.330 sec
		2206	+ optimized 0.122 sec
		2207	Lambda/AnyEvent 0.327 sec
		2208	+ optimized 0.138 sec
		2209	Raw sockets/select 0.077 sec
		2210	POE/select, components 0.662 sec
		2211	POE/select, raw sockets 0.226 sec
		2212	POE/select, optimized 0.404 sec
		2213
		2214	AnyEvent/select/nb 0.085 sec
		2215	AnyEvent/EV/nb 0.068 sec
		2216	+state machine 0.134 sec
		2217
		2218	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2219	benchmarks actually make blocking connects and use 100% blocking I/O,
		2220	defeating the purpose of an event-based solution. All of the newly
		2221	written AnyEvent benchmarks use 100% non-blocking connects (using
		2222	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2223	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2224	generally require a lot more bookkeeping and event handling than blocking
		2225	connects (which involve a single syscall only).
		2226
		2227	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2228	offers similar expressive power as POE and IO::Lambda, using conventional
		2229	Perl syntax. This means that both the echo server and the client are 100%
		2230	non-blocking, further placing it at a disadvantage.
		2231
		2232	As you can see, the AnyEvent + EV combination even beats the
		2233	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2234	backend easily beats IO::Lambda and POE.
		2235
		2236	And even the 100% non-blocking version written using the high-level (and
		2237	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2238	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2239	in a non-blocking way.
		2240
		2241	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2242	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2243	part of the IO::lambda distribution and were used without any changes.
		2244
		2245
		2246	=head1 SIGNALS
		2247
		2248	AnyEvent currently installs handlers for these signals:
		2249
		2250	=over 4
		2251
		2252	=item SIGCHLD
		2253
		2254	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2255	emulation for event loops that do not support them natively. Also, some
		2256	event loops install a similar handler.
		2257
		2258	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2259	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2260
		2261	=item SIGPIPE
		2262
		2263	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2264	when AnyEvent gets loaded.
		2265
		2266	The rationale for this is that AnyEvent users usually do not really depend
		2267	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2268	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2269	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2270	some random socket.
		2271
		2272	The rationale for installing a no-op handler as opposed to ignoring it is
		2273	that this way, the handler will be restored to defaults on exec.
		2274
		2275	Feel free to install your own handler, or reset it to defaults.
		2276
		2277	=back
		2278
		2279	=cut
		2280
		2281	undef $SIG{CHLD}
		2282	if $SIG{CHLD} eq 'IGNORE';
		2283
		2284	$SIG{PIPE} = sub { }
		2285	unless defined $SIG{PIPE};
		2286
		2287	=head1 RECOMMENDED/OPTIONAL MODULES
		2288
		2289	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2290	it's built-in modules) are required to use it.
		2291
		2292	That does not mean that AnyEvent won't take advantage of some additional
		2293	modules if they are installed.
		2294
		2295	This section epxlains which additional modules will be used, and how they
		2296	affect AnyEvent's operetion.
		2297
		2298	=over 4
		2299
		2300	=item L<Async::Interrupt>
		2301
		2302	This slightly arcane module is used to implement fast signal handling: To
		2303	my knowledge, there is no way to do completely race-free and quick
		2304	signal handling in pure perl. To ensure that signals still get
		2305	delivered, AnyEvent will start an interval timer to wake up perl (and
		2306	catch the signals) with some delay (default is 10 seconds, look for
		2307	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2308
		2309	If this module is available, then it will be used to implement signal
		2310	catching, which means that signals will not be delayed, and the event loop
		2311	will not be interrupted regularly, which is more efficient (And good for
		2312	battery life on laptops).
		2313
		2314	This affects not just the pure-perl event loop, but also other event loops
		2315	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2316
		2317	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2318	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2319	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2320	does nothing for those backends.
		2321
		2322	=item L<EV>
		2323
		2324	This module isn't really "optional", as it is simply one of the backend
		2325	event loops that AnyEvent can use. However, it is simply the best event
		2326	loop available in terms of features, speed and stability: It supports
		2327	the AnyEvent API optimally, implements all the watcher types in XS, does
		2328	automatic timer adjustments even when no monotonic clock is available,
		2329	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2330	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2331	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2332
		2333	=item L<Guard>
		2334
		2335	The guard module, when used, will be used to implement
		2336	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2337	lot less memory), but otherwise doesn't affect guard operation much. It is
		2338	purely used for performance.
		2339
		2340	=item L<JSON> and L<JSON::XS>
		2341
		2342	This module is required when you want to read or write JSON data via
		2343	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2344	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2345
		2346	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2347	installed.
		2348
		2349	=item L<Net::SSLeay>
		2350
		2351	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2352	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2353	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2354
		2355	=item L<Time::HiRes>
		2356
		2357	This module is part of perl since release 5.008. It will be used when the
		2358	chosen event library does not come with a timing source on it's own. The
		2359	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2360	try to use a monotonic clock for timing stability.
		2361
		2362	=back
		2363
834		2364
835	=head1 FORK	2365	=head1 FORK
836		2366
837	Most event libraries are not fork-safe. The ones who are usually are	2367	Most event libraries are not fork-safe. The ones who are usually are
838	because they are so inefficient. Only L<EV> is fully fork-aware.	2368	because they rely on inefficient but fork-safe C<select> or C<poll>
		2369	calls. Only L<EV> is fully fork-aware.
839		2370
840	If you have to fork, you must either do so I<before> creating your first	2371	If you have to fork, you must either do so I<before> creating your first
841	watcher OR you must not use AnyEvent at all in the child.	2372	watcher OR you must not use AnyEvent at all in the child OR you must do
		2373	something completely out of the scope of AnyEvent.
		2374
842		2375
843	=head1 SECURITY CONSIDERATIONS	2376	=head1 SECURITY CONSIDERATIONS
844		2377
845	AnyEvent can be forced to load any event model via	2378	AnyEvent can be forced to load any event model via
846	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	2379	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
850	specified in the variable.	2383	specified in the variable.
851		2384
852	You can make AnyEvent completely ignore this variable by deleting it	2385	You can make AnyEvent completely ignore this variable by deleting it
853	before the first watcher gets created, e.g. with a C<BEGIN> block:	2386	before the first watcher gets created, e.g. with a C<BEGIN> block:
854		2387
855	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2388	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
856		2389
857	use AnyEvent;	2390	use AnyEvent;
		2391
		2392	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2393	be used to probe what backend is used and gain other information (which is
		2394	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2395	$ENV{PERL_ANYEVENT_STRICT}.
		2396
		2397	Note that AnyEvent will remove I<all> environment variables starting with
		2398	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2399	enabled.
		2400
		2401
		2402	=head1 BUGS
		2403
		2404	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2405	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2406	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2407	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2408	pronounced).
		2409
858		2410
859	=head1 SEE ALSO	2411	=head1 SEE ALSO
860		2412
861	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2413	Utility functions: L<AnyEvent::Util>.
862	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
863	L<Event::Lib>.
864		2414
865	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2415	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
866	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2416	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
867	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>.
868		2417
		2418	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2419	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2420	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2421	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>.
		2422
		2423	Non-blocking file handles, sockets, TCP clients and
		2424	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2425
		2426	Asynchronous DNS: L<AnyEvent::DNS>.
		2427
		2428	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2429	L<Coro::Event>,
		2430
869	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2431	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2432	L<AnyEvent::HTTP>.
		2433
870		2434
871	=head1 AUTHOR	2435	=head1 AUTHOR
872		2436
873	Marc Lehmann <schmorp@schmorp.de>	2437	Marc Lehmann <schmorp@schmorp.de>
874	http://home.schmorp.de/	2438	http://home.schmorp.de/
875		2439
876	=cut	2440	=cut
877		2441
878	1	2442	1
879		2443

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