ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/AnyEvent/lib/AnyEvent.pm

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.99 by root, Sun Apr 27 17:09:33 2008 UTC vs.
Revision 1.245 by root, Sat Jul 18 05:19:09 2009 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, 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.
22		45
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	46	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		47
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	48	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	49	nowadays. So what is different about AnyEvent?
27		50
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	51	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	52	policy> and AnyEvent is I<small and efficient>.
30		53
31	First and foremost, I<AnyEvent is not an event model> itself, it only	54	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	55	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,	56	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,	57	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	58	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	59	cannot change this, but it can hide the differences between those event
		60	loops.
37		61
38	The goal of AnyEvent is to offer module authors the ability to do event	62	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	63	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	64	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	65	module users into the same thing by forcing them to use the same event
42	model you use.	66	model you use.
43		67
44	For modules like POE or IO::Async (which is a total misnomer as it is	68	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	69	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	70	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	71	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	72	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.	73	module are I<also> forced to use the same event loop you use.
50		74
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	75	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	76	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	77	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,	78	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	79	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	80	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	81	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).	82	to AnyEvent, too, so it is future-proof).
59		83
60	In addition to being free of having to use I<the one and only true event	84	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	85	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	86	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	87	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	88	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	89	technically possible.
66		90
		91	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		92	of useful functionality, such as an asynchronous DNS resolver, 100%
		93	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		94	such as Windows) and lots of real-world knowledge and workarounds for
		95	platform bugs and differences.
		96
67	Of course, if you want lots of policy (this can arguably be somewhat	97	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	98	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	99	model, you should I<not> use this module.
70
71	#TODO#
72
73	Net::IRC3
74	AnyEvent::HTTPD
75	AnyEvent::DNS
76	IO::AnyEvent
77	Net::FPing
78	Net::XMPP2
79	Coro
80
81	AnyEvent::IRC
82	AnyEvent::HTTPD
83	AnyEvent::DNS
84	AnyEvent::Handle
85	AnyEvent::Socket
86	AnyEvent::FPing
87	AnyEvent::XMPP
88	AnyEvent::SNMP
89	Coro
90		100
91	=head1 DESCRIPTION	101	=head1 DESCRIPTION
92		102
93	L<AnyEvent> provides an identical interface to multiple event loops. This	103	L<AnyEvent> provides an identical interface to multiple event loops. This
94	allows module authors to utilise an event loop without forcing module	104	allows module authors to utilise an event loop without forcing module
…		…
98	The interface itself is vaguely similar, but not identical to the L<Event>	108	The interface itself is vaguely similar, but not identical to the L<Event>
99	module.	109	module.
100		110
101	During the first call of any watcher-creation method, the module tries	111	During the first call of any watcher-creation method, the module tries
102	to detect the currently loaded event loop by probing whether one of the	112	to detect the currently loaded event loop by probing whether one of the
103	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	113	following modules is already loaded: L<EV>,
104	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	114	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
105	L<POE>. The first one found is used. If none are found, the module tries	115	L<POE>. The first one found is used. If none are found, the module tries
106	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	116	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
107	adaptor should always succeed) in the order given. The first one that can	117	adaptor should always succeed) in the order given. The first one that can
108	be successfully loaded will be used. If, after this, still none could be	118	be successfully loaded will be used. If, after this, still none could be
…		…
122	starts using it, all bets are off. Maybe you should tell their authors to	132	starts using it, all bets are off. Maybe you should tell their authors to
123	use AnyEvent so their modules work together with others seamlessly...	133	use AnyEvent so their modules work together with others seamlessly...
124		134
125	The pure-perl implementation of AnyEvent is called	135	The pure-perl implementation of AnyEvent is called
126	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	136	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
127	explicitly.	137	explicitly and enjoy the high availability of that event loop :)
128		138
129	=head1 WATCHERS	139	=head1 WATCHERS
130		140
131	AnyEvent has the central concept of a I<watcher>, which is an object that	141	AnyEvent has the central concept of a I<watcher>, which is an object that
132	stores relevant data for each kind of event you are waiting for, such as	142	stores relevant data for each kind of event you are waiting for, such as
133	the callback to call, the filehandle to watch, etc.	143	the callback to call, the file handle to watch, etc.
134		144
135	These watchers are normal Perl objects with normal Perl lifetime. After	145	These watchers are normal Perl objects with normal Perl lifetime. After
136	creating a watcher it will immediately "watch" for events and invoke the	146	creating a watcher it will immediately "watch" for events and invoke the
137	callback when the event occurs (of course, only when the event model	147	callback when the event occurs (of course, only when the event model
138	is in control).	148	is in control).
139		149
		150	Note that B<callbacks must not permanently change global variables>
		151	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		152	callbacks must not C<die> >>. The former is good programming practise in
		153	Perl and the latter stems from the fact that exception handling differs
		154	widely between event loops.
		155
140	To disable the watcher you have to destroy it (e.g. by setting the	156	To disable the watcher you have to destroy it (e.g. by setting the
141	variable you store it in to C<undef> or otherwise deleting all references	157	variable you store it in to C<undef> or otherwise deleting all references
142	to it).	158	to it).
143		159
144	All watchers are created by calling a method on the C<AnyEvent> class.	160	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
146	Many watchers either are used with "recursion" (repeating timers for	162	Many watchers either are used with "recursion" (repeating timers for
147	example), or need to refer to their watcher object in other ways.	163	example), or need to refer to their watcher object in other ways.
148		164
149	An any way to achieve that is this pattern:	165	An any way to achieve that is this pattern:
150		166
151	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	167	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
152	# you can use $w here, for example to undef it	168	# you can use $w here, for example to undef it
153	undef $w;	169	undef $w;
154	});	170	});
155		171
156	Note that C<my $w; $w => combination. This is necessary because in Perl,	172	Note that C<my $w; $w => combination. This is necessary because in Perl,
157	my variables are only visible after the statement in which they are	173	my variables are only visible after the statement in which they are
158	declared.	174	declared.
159		175
160	=head2 I/O WATCHERS	176	=head2 I/O WATCHERS
161		177
162	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	178	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
163	with the following mandatory key-value pairs as arguments:	179	with the following mandatory key-value pairs as arguments:
164		180
165	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	181	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		182	for events (AnyEvent might or might not keep a reference to this file
		183	handle). Note that only file handles pointing to things for which
		184	non-blocking operation makes sense are allowed. This includes sockets,
		185	most character devices, pipes, fifos and so on, but not for example files
		186	or block devices.
		187
166	for events. C<poll> must be a string that is either C<r> or C<w>,	188	C<poll> must be a string that is either C<r> or C<w>, which creates a
167	which creates a watcher waiting for "r"eadable or "w"ritable events,	189	watcher waiting for "r"eadable or "w"ritable events, respectively.
		190
168	respectively. C<cb> is the callback to invoke each time the file handle	191	C<cb> is the callback to invoke each time the file handle becomes ready.
169	becomes ready.
170		192
171	Although the callback might get passed parameters, their value and	193	Although the callback might get passed parameters, their value and
172	presence is undefined and you cannot rely on them. Portable AnyEvent	194	presence is undefined and you cannot rely on them. Portable AnyEvent
173	callbacks cannot use arguments passed to I/O watcher callbacks.	195	callbacks cannot use arguments passed to I/O watcher callbacks.
174		196
…		…
178		200
179	Some event loops issue spurious readyness notifications, so you should	201	Some event loops issue spurious readyness notifications, so you should
180	always use non-blocking calls when reading/writing from/to your file	202	always use non-blocking calls when reading/writing from/to your file
181	handles.	203	handles.
182		204
183	Example:
184
185	# wait for readability of STDIN, then read a line and disable the watcher	205	Example: wait for readability of STDIN, then read a line and disable the
		206	watcher.
		207
186	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	208	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
187	chomp (my $input = <STDIN>);	209	chomp (my $input = <STDIN>);
188	warn "read: $input\n";	210	warn "read: $input\n";
189	undef $w;	211	undef $w;
190	});	212	});
…		…
200		222
201	Although the callback might get passed parameters, their value and	223	Although the callback might get passed parameters, their value and
202	presence is undefined and you cannot rely on them. Portable AnyEvent	224	presence is undefined and you cannot rely on them. Portable AnyEvent
203	callbacks cannot use arguments passed to time watcher callbacks.	225	callbacks cannot use arguments passed to time watcher callbacks.
204		226
205	The timer callback will be invoked at most once: if you want a repeating	227	The callback will normally be invoked once only. If you specify another
206	timer you have to create a new watcher (this is a limitation by both Tk	228	parameter, C<interval>, as a strictly positive number (> 0), then the
207	and Glib).	229	callback will be invoked regularly at that interval (in fractional
		230	seconds) after the first invocation. If C<interval> is specified with a
		231	false value, then it is treated as if it were missing.
208		232
209	Example:	233	The callback will be rescheduled before invoking the callback, but no
		234	attempt is done to avoid timer drift in most backends, so the interval is
		235	only approximate.
210		236
211	# fire an event after 7.7 seconds	237	Example: fire an event after 7.7 seconds.
		238
212	my $w = AnyEvent->timer (after => 7.7, cb => sub {	239	my $w = AnyEvent->timer (after => 7.7, cb => sub {
213	warn "timeout\n";	240	warn "timeout\n";
214	});	241	});
215		242
216	# to cancel the timer:	243	# to cancel the timer:
217	undef $w;	244	undef $w;
218		245
219	Example 2:
220
221	# fire an event after 0.5 seconds, then roughly every second	246	Example 2: fire an event after 0.5 seconds, then roughly every second.
222	my $w;
223		247
224	my $cb = sub {
225	# cancel the old timer while creating a new one
226	$w = AnyEvent->timer (after => 1, cb => $cb);	248	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		249	warn "timeout\n";
227	};	250	};
228
229	# start the "loop" by creating the first watcher
230	$w = AnyEvent->timer (after => 0.5, cb => $cb);
231		251
232	=head3 TIMING ISSUES	252	=head3 TIMING ISSUES
233		253
234	There are two ways to handle timers: based on real time (relative, "fire	254	There are two ways to handle timers: based on real time (relative, "fire
235	in 10 seconds") and based on wallclock time (absolute, "fire at 12	255	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
247	timers.	267	timers.
248		268
249	AnyEvent always prefers relative timers, if available, matching the	269	AnyEvent always prefers relative timers, if available, matching the
250	AnyEvent API.	270	AnyEvent API.
251		271
		272	AnyEvent has two additional methods that return the "current time":
		273
		274	=over 4
		275
		276	=item AnyEvent->time
		277
		278	This returns the "current wallclock time" as a fractional number of
		279	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		280	return, and the result is guaranteed to be compatible with those).
		281
		282	It progresses independently of any event loop processing, i.e. each call
		283	will check the system clock, which usually gets updated frequently.
		284
		285	=item AnyEvent->now
		286
		287	This also returns the "current wallclock time", but unlike C<time>, above,
		288	this value might change only once per event loop iteration, depending on
		289	the event loop (most return the same time as C<time>, above). This is the
		290	time that AnyEvent's timers get scheduled against.
		291
		292	I<In almost all cases (in all cases if you don't care), this is the
		293	function to call when you want to know the current time.>
		294
		295	This function is also often faster then C<< AnyEvent->time >>, and
		296	thus the preferred method if you want some timestamp (for example,
		297	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		298
		299	The rest of this section is only of relevance if you try to be very exact
		300	with your timing, you can skip it without bad conscience.
		301
		302	For a practical example of when these times differ, consider L<Event::Lib>
		303	and L<EV> and the following set-up:
		304
		305	The event loop is running and has just invoked one of your callback at
		306	time=500 (assume no other callbacks delay processing). In your callback,
		307	you wait a second by executing C<sleep 1> (blocking the process for a
		308	second) and then (at time=501) you create a relative timer that fires
		309	after three seconds.
		310
		311	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		312	both return C<501>, because that is the current time, and the timer will
		313	be scheduled to fire at time=504 (C<501> + C<3>).
		314
		315	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		316	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		317	last event processing phase started. With L<EV>, your timer gets scheduled
		318	to run at time=503 (C<500> + C<3>).
		319
		320	In one sense, L<Event::Lib> is more exact, as it uses the current time
		321	regardless of any delays introduced by event processing. However, most
		322	callbacks do not expect large delays in processing, so this causes a
		323	higher drift (and a lot more system calls to get the current time).
		324
		325	In another sense, L<EV> is more exact, as your timer will be scheduled at
		326	the same time, regardless of how long event processing actually took.
		327
		328	In either case, if you care (and in most cases, you don't), then you
		329	can get whatever behaviour you want with any event loop, by taking the
		330	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		331	account.
		332
		333	=item AnyEvent->now_update
		334
		335	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		336	the current time for each loop iteration (see the discussion of L<<
		337	AnyEvent->now >>, above).
		338
		339	When a callback runs for a long time (or when the process sleeps), then
		340	this "current" time will differ substantially from the real time, which
		341	might affect timers and time-outs.
		342
		343	When this is the case, you can call this method, which will update the
		344	event loop's idea of "current time".
		345
		346	Note that updating the time I<might> cause some events to be handled.
		347
		348	=back
		349
252	=head2 SIGNAL WATCHERS	350	=head2 SIGNAL WATCHERS
253		351
254	You can watch for signals using a signal watcher, C<signal> is the signal	352	You can watch for signals using a signal watcher, C<signal> is the signal
255	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	353	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
256	be invoked whenever a signal occurs.	354	callback to be invoked whenever a signal occurs.
257		355
258	Although the callback might get passed parameters, their value and	356	Although the callback might get passed parameters, their value and
259	presence is undefined and you cannot rely on them. Portable AnyEvent	357	presence is undefined and you cannot rely on them. Portable AnyEvent
260	callbacks cannot use arguments passed to signal watcher callbacks.	358	callbacks cannot use arguments passed to signal watcher callbacks.
261		359
262	Multiple signal occurances can be clumped together into one callback	360	Multiple signal occurrences can be clumped together into one callback
263	invocation, and callback invocation will be synchronous. synchronous means	361	invocation, and callback invocation will be synchronous. Synchronous means
264	that it might take a while until the signal gets handled by the process,	362	that it might take a while until the signal gets handled by the process,
265	but it is guarenteed not to interrupt any other callbacks.	363	but it is guaranteed not to interrupt any other callbacks.
266		364
267	The main advantage of using these watchers is that you can share a signal	365	The main advantage of using these watchers is that you can share a signal
268	between multiple watchers.	366	between multiple watchers, and AnyEvent will ensure that signals will not
		367	interrupt your program at bad times.
269		368
270	This watcher might use C<%SIG>, so programs overwriting those signals	369	This watcher might use C<%SIG> (depending on the event loop used),
271	directly will likely not work correctly.	370	so programs overwriting those signals directly will likely not work
		371	correctly.
		372
		373	Also note that many event loops (e.g. Glib, Tk, Qt, IO::Async) do not
		374	support attaching callbacks to signals, which is a pity, as you cannot do
		375	race-free signal handling in perl. AnyEvent will try to do it's best, but
		376	in some cases, signals will be delayed. The maximum time a signal might
		377	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		378	seconds). This variable can be changed only before the first signal
		379	watcher is created, and should be left alone otherwise. Higher values
		380	will cause fewer spurious wake-ups, which is better for power and CPU
		381	saving. All these problems can be avoided by installing the optional
		382	L<Async::Interrupt> module.
272		383
273	Example: exit on SIGINT	384	Example: exit on SIGINT
274		385
275	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	386	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
276		387
277	=head2 CHILD PROCESS WATCHERS	388	=head2 CHILD PROCESS WATCHERS
278		389
279	You can also watch on a child process exit and catch its exit status.	390	You can also watch on a child process exit and catch its exit status.
280		391
281	The child process is specified by the C<pid> argument (if set to C<0>, it	392	The child process is specified by the C<pid> argument (if set to C<0>, it
282	watches for any child process exit). The watcher will trigger as often	393	watches for any child process exit). The watcher will triggered only when
283	as status change for the child are received. This works by installing a	394	the child process has finished and an exit status is available, not on
284	signal handler for C<SIGCHLD>. The callback will be called with the pid	395	any trace events (stopped/continued).
285	and exit status (as returned by waitpid), so unlike other watcher types,	396
286	you I<can> rely on child watcher callback arguments.	397	The callback will be called with the pid and exit status (as returned by
		398	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		399	callback arguments.
		400
		401	This watcher type works by installing a signal handler for C<SIGCHLD>,
		402	and since it cannot be shared, nothing else should use SIGCHLD or reap
		403	random child processes (waiting for specific child processes, e.g. inside
		404	C<system>, is just fine).
287		405
288	There is a slight catch to child watchers, however: you usually start them	406	There is a slight catch to child watchers, however: you usually start them
289	I<after> the child process was created, and this means the process could	407	I<after> the child process was created, and this means the process could
290	have exited already (and no SIGCHLD will be sent anymore).	408	have exited already (and no SIGCHLD will be sent anymore).
291		409
292	Not all event models handle this correctly (POE doesn't), but even for	410	Not all event models handle this correctly (neither POE nor IO::Async do,
		411	see their AnyEvent::Impl manpages for details), but even for event models
293	event models that I<do> handle this correctly, they usually need to be	412	that I<do> handle this correctly, they usually need to be loaded before
294	loaded before the process exits (i.e. before you fork in the first place).	413	the process exits (i.e. before you fork in the first place). AnyEvent's
		414	pure perl event loop handles all cases correctly regardless of when you
		415	start the watcher.
295		416
296	This means you cannot create a child watcher as the very first thing in an	417	This means you cannot create a child watcher as the very first
297	AnyEvent program, you I<have> to create at least one watcher before you	418	thing in an AnyEvent program, you I<have> to create at least one
298	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	419	watcher before you C<fork> the child (alternatively, you can call
		420	C<AnyEvent::detect>).
		421
		422	As most event loops do not support waiting for child events, they will be
		423	emulated by AnyEvent in most cases, in which the latency and race problems
		424	mentioned in the description of signal watchers apply.
299		425
300	Example: fork a process and wait for it	426	Example: fork a process and wait for it
301		427
302	my $done = AnyEvent->condvar;	428	my $done = AnyEvent->condvar;
303		429
304	AnyEvent::detect; # force event module to be initialised
305
306	my $pid = fork or exit 5;	430	my $pid = fork or exit 5;
307		431
308	my $w = AnyEvent->child (	432	my $w = AnyEvent->child (
309	pid => $pid,	433	pid => $pid,
310	cb => sub {	434	cb => sub {
311	my ($pid, $status) = @_;	435	my ($pid, $status) = @_;
312	warn "pid $pid exited with status $status";	436	warn "pid $pid exited with status $status";
313	$done->broadcast;	437	$done->send;
314	},	438	},
315	);	439	);
316		440
317	# do something else, then wait for process exit	441	# do something else, then wait for process exit
318	$done->wait;	442	$done->recv;
		443
		444	=head2 IDLE WATCHERS
		445
		446	Sometimes there is a need to do something, but it is not so important
		447	to do it instantly, but only when there is nothing better to do. This
		448	"nothing better to do" is usually defined to be "no other events need
		449	attention by the event loop".
		450
		451	Idle watchers ideally get invoked when the event loop has nothing
		452	better to do, just before it would block the process to wait for new
		453	events. Instead of blocking, the idle watcher is invoked.
		454
		455	Most event loops unfortunately do not really support idle watchers (only
		456	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		457	will simply call the callback "from time to time".
		458
		459	Example: read lines from STDIN, but only process them when the
		460	program is otherwise idle:
		461
		462	my @lines; # read data
		463	my $idle_w;
		464	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		465	push @lines, scalar <STDIN>;
		466
		467	# start an idle watcher, if not already done
		468	$idle_w ||= AnyEvent->idle (cb => sub {
		469	# handle only one line, when there are lines left
		470	if (my $line = shift @lines) {
		471	print "handled when idle: $line";
		472	} else {
		473	# otherwise disable the idle watcher again
		474	undef $idle_w;
		475	}
		476	});
		477	});
319		478
320	=head2 CONDITION VARIABLES	479	=head2 CONDITION VARIABLES
321		480
		481	If you are familiar with some event loops you will know that all of them
		482	require you to run some blocking "loop", "run" or similar function that
		483	will actively watch for new events and call your callbacks.
		484
		485	AnyEvent is slightly different: it expects somebody else to run the event
		486	loop and will only block when necessary (usually when told by the user).
		487
		488	The instrument to do that is called a "condition variable", so called
		489	because they represent a condition that must become true.
		490
		491	Now is probably a good time to look at the examples further below.
		492
322	Condition variables can be created by calling the C<< AnyEvent->condvar >>	493	Condition variables can be created by calling the C<< AnyEvent->condvar
323	method without any arguments.	494	>> method, usually without arguments. The only argument pair allowed is
		495	C<cb>, which specifies a callback to be called when the condition variable
		496	becomes true, with the condition variable as the first argument (but not
		497	the results).
324		498
325	A condition variable waits for a condition - precisely that the C<<	499	After creation, the condition variable is "false" until it becomes "true"
326	->broadcast >> method has been called.	500	by calling the C<send> method (or calling the condition variable as if it
		501	were a callback, read about the caveats in the description for the C<<
		502	->send >> method).
327		503
328	They are very useful to signal that a condition has been fulfilled, for	504	Condition variables are similar to callbacks, except that you can
		505	optionally wait for them. They can also be called merge points - points
		506	in time where multiple outstanding events have been processed. And yet
		507	another way to call them is transactions - each condition variable can be
		508	used to represent a transaction, which finishes at some point and delivers
		509	a result.
		510
		511	Condition variables are very useful to signal that something has finished,
329	example, if you write a module that does asynchronous http requests,	512	for example, if you write a module that does asynchronous http requests,
330	then a condition variable would be the ideal candidate to signal the	513	then a condition variable would be the ideal candidate to signal the
331	availability of results.	514	availability of results. The user can either act when the callback is
		515	called or can synchronously C<< ->recv >> for the results.
332		516
333	You can also use condition variables to block your main program until	517	You can also use them to simulate traditional event loops - for example,
334	an event occurs - for example, you could C<< ->wait >> in your main	518	you can block your main program until an event occurs - for example, you
335	program until the user clicks the Quit button in your app, which would C<<	519	could C<< ->recv >> in your main program until the user clicks the Quit
336	->broadcast >> the "quit" event.	520	button of your app, which would C<< ->send >> the "quit" event.
337		521
338	Note that condition variables recurse into the event loop - if you have	522	Note that condition variables recurse into the event loop - if you have
339	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	523	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
340	lose. Therefore, condition variables are good to export to your caller, but	524	lose. Therefore, condition variables are good to export to your caller, but
341	you should avoid making a blocking wait yourself, at least in callbacks,	525	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	526	as this asks for trouble.
343		527
344	This object has two methods:	528	Condition variables are represented by hash refs in perl, and the keys
		529	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		530	easy (it is often useful to build your own transaction class on top of
		531	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		532	it's C<new> method in your own C<new> method.
345		533
346	=over 4	534	There are two "sides" to a condition variable - the "producer side" which
		535	eventually calls C<< -> send >>, and the "consumer side", which waits
		536	for the send to occur.
347		537
348	=item $cv->wait	538	Example: wait for a timer.
349
350	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
351	called on c<$cv>, while servicing other watchers normally.
352
353	You can only wait once on a condition - additional calls will return
354	immediately.
355
356	Not all event models support a blocking wait - some die in that case
357	(programs might want to do that to stay interactive), so I<if you are
358	using this from a module, never require a blocking wait>, but let the
359	caller decide whether the call will block or not (for example, by coupling
360	condition variables with some kind of request results and supporting
361	callbacks so the caller knows that getting the result will not block,
362	while still suppporting blocking waits if the caller so desires).
363
364	Another reason I<never> to C<< ->wait >> in a module is that you cannot
365	sensibly have two C<< ->wait >>'s in parallel, as that would require
366	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
367	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
368	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
369	from different coroutines, however).
370
371	=item $cv->broadcast
372
373	Flag the condition as ready - a running C<< ->wait >> and all further
374	calls to C<wait> will (eventually) return after this method has been
375	called. If nobody is waiting the broadcast will be remembered..
376
377	=back
378
379	Example:
380		539
381	# wait till the result is ready	540	# wait till the result is ready
382	my $result_ready = AnyEvent->condvar;	541	my $result_ready = AnyEvent->condvar;
383		542
384	# do something such as adding a timer	543	# do something such as adding a timer
385	# or socket watcher the calls $result_ready->broadcast	544	# or socket watcher the calls $result_ready->send
386	# when the "result" is ready.	545	# when the "result" is ready.
387	# in this case, we simply use a timer:	546	# in this case, we simply use a timer:
388	my $w = AnyEvent->timer (	547	my $w = AnyEvent->timer (
389	after => 1,	548	after => 1,
390	cb => sub { $result_ready->broadcast },	549	cb => sub { $result_ready->send },
391	);	550	);
392		551
393	# this "blocks" (while handling events) till the watcher	552	# this "blocks" (while handling events) till the callback
394	# calls broadcast	553	# calls -<send
395	$result_ready->wait;	554	$result_ready->recv;
		555
		556	Example: wait for a timer, but take advantage of the fact that condition
		557	variables are also callable directly.
		558
		559	my $done = AnyEvent->condvar;
		560	my $delay = AnyEvent->timer (after => 5, cb => $done);
		561	$done->recv;
		562
		563	Example: Imagine an API that returns a condvar and doesn't support
		564	callbacks. This is how you make a synchronous call, for example from
		565	the main program:
		566
		567	use AnyEvent::CouchDB;
		568
		569	...
		570
		571	my @info = $couchdb->info->recv;
		572
		573	And this is how you would just set a callback to be called whenever the
		574	results are available:
		575
		576	$couchdb->info->cb (sub {
		577	my @info = $_[0]->recv;
		578	});
		579
		580	=head3 METHODS FOR PRODUCERS
		581
		582	These methods should only be used by the producing side, i.e. the
		583	code/module that eventually sends the signal. Note that it is also
		584	the producer side which creates the condvar in most cases, but it isn't
		585	uncommon for the consumer to create it as well.
		586
		587	=over 4
		588
		589	=item $cv->send (...)
		590
		591	Flag the condition as ready - a running C<< ->recv >> and all further
		592	calls to C<recv> will (eventually) return after this method has been
		593	called. If nobody is waiting the send will be remembered.
		594
		595	If a callback has been set on the condition variable, it is called
		596	immediately from within send.
		597
		598	Any arguments passed to the C<send> call will be returned by all
		599	future C<< ->recv >> calls.
		600
		601	Condition variables are overloaded so one can call them directly (as if
		602	they were a code reference). Calling them directly is the same as calling
		603	C<send>.
		604
		605	=item $cv->croak ($error)
		606
		607	Similar to send, but causes all call's to C<< ->recv >> to invoke
		608	C<Carp::croak> with the given error message/object/scalar.
		609
		610	This can be used to signal any errors to the condition variable
		611	user/consumer. Doing it this way instead of calling C<croak> directly
		612	delays the error detetcion, but has the overwhelmign advantage that it
		613	diagnoses the error at the place where the result is expected, and not
		614	deep in some event clalback without connection to the actual code causing
		615	the problem.
		616
		617	=item $cv->begin ([group callback])
		618
		619	=item $cv->end
		620
		621	These two methods can be used to combine many transactions/events into
		622	one. For example, a function that pings many hosts in parallel might want
		623	to use a condition variable for the whole process.
		624
		625	Every call to C<< ->begin >> will increment a counter, and every call to
		626	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		627	>>, the (last) callback passed to C<begin> will be executed. That callback
		628	is I<supposed> to call C<< ->send >>, but that is not required. If no
		629	callback was set, C<send> will be called without any arguments.
		630
		631	You can think of C<< $cv->send >> giving you an OR condition (one call
		632	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		633	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		634
		635	Let's start with a simple example: you have two I/O watchers (for example,
		636	STDOUT and STDERR for a program), and you want to wait for both streams to
		637	close before activating a condvar:
		638
		639	my $cv = AnyEvent->condvar;
		640
		641	$cv->begin; # first watcher
		642	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		643	defined sysread $fh1, my $buf, 4096
		644	or $cv->end;
		645	});
		646
		647	$cv->begin; # second watcher
		648	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		649	defined sysread $fh2, my $buf, 4096
		650	or $cv->end;
		651	});
		652
		653	$cv->recv;
		654
		655	This works because for every event source (EOF on file handle), there is
		656	one call to C<begin>, so the condvar waits for all calls to C<end> before
		657	sending.
		658
		659	The ping example mentioned above is slightly more complicated, as the
		660	there are results to be passwd back, and the number of tasks that are
		661	begung can potentially be zero:
		662
		663	my $cv = AnyEvent->condvar;
		664
		665	my %result;
		666	$cv->begin (sub { $cv->send (\%result) });
		667
		668	for my $host (@list_of_hosts) {
		669	$cv->begin;
		670	ping_host_then_call_callback $host, sub {
		671	$result{$host} = ...;
		672	$cv->end;
		673	};
		674	}
		675
		676	$cv->end;
		677
		678	This code fragment supposedly pings a number of hosts and calls
		679	C<send> after results for all then have have been gathered - in any
		680	order. To achieve this, the code issues a call to C<begin> when it starts
		681	each ping request and calls C<end> when it has received some result for
		682	it. Since C<begin> and C<end> only maintain a counter, the order in which
		683	results arrive is not relevant.
		684
		685	There is an additional bracketing call to C<begin> and C<end> outside the
		686	loop, which serves two important purposes: first, it sets the callback
		687	to be called once the counter reaches C<0>, and second, it ensures that
		688	C<send> is called even when C<no> hosts are being pinged (the loop
		689	doesn't execute once).
		690
		691	This is the general pattern when you "fan out" into multiple (but
		692	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		693	the callback and ensure C<end> is called at least once, and then, for each
		694	subrequest you start, call C<begin> and for each subrequest you finish,
		695	call C<end>.
		696
		697	=back
		698
		699	=head3 METHODS FOR CONSUMERS
		700
		701	These methods should only be used by the consuming side, i.e. the
		702	code awaits the condition.
		703
		704	=over 4
		705
		706	=item $cv->recv
		707
		708	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		709	>> methods have been called on c<$cv>, while servicing other watchers
		710	normally.
		711
		712	You can only wait once on a condition - additional calls are valid but
		713	will return immediately.
		714
		715	If an error condition has been set by calling C<< ->croak >>, then this
		716	function will call C<croak>.
		717
		718	In list context, all parameters passed to C<send> will be returned,
		719	in scalar context only the first one will be returned.
		720
		721	Note that doing a blocking wait in a callback is not supported by any
		722	event loop, that is, recursive invocation of a blocking C<< ->recv
		723	>> is not allowed, and the C<recv> call will C<croak> if such a
		724	condition is detected. This condition can be slightly loosened by using
		725	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		726	any thread that doesn't run the event loop itself.
		727
		728	Not all event models support a blocking wait - some die in that case
		729	(programs might want to do that to stay interactive), so I<if you are
		730	using this from a module, never require a blocking wait>. Instead, let the
		731	caller decide whether the call will block or not (for example, by coupling
		732	condition variables with some kind of request results and supporting
		733	callbacks so the caller knows that getting the result will not block,
		734	while still supporting blocking waits if the caller so desires).
		735
		736	You can ensure that C<< -recv >> never blocks by setting a callback and
		737	only calling C<< ->recv >> from within that callback (or at a later
		738	time). This will work even when the event loop does not support blocking
		739	waits otherwise.
		740
		741	=item $bool = $cv->ready
		742
		743	Returns true when the condition is "true", i.e. whether C<send> or
		744	C<croak> have been called.
		745
		746	=item $cb = $cv->cb ($cb->($cv))
		747
		748	This is a mutator function that returns the callback set and optionally
		749	replaces it before doing so.
		750
		751	The callback will be called when the condition becomes "true", i.e. when
		752	C<send> or C<croak> are called, with the only argument being the condition
		753	variable itself. Calling C<recv> inside the callback or at any later time
		754	is guaranteed not to block.
		755
		756	=back
		757
		758	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		759
		760	The available backend classes are (every class has its own manpage):
		761
		762	=over 4
		763
		764	=item Backends that are autoprobed when no other event loop can be found.
		765
		766	EV is the preferred backend when no other event loop seems to be in
		767	use. If EV is not installed, then AnyEvent will try Event, and, failing
		768	that, will fall back to its own pure-perl implementation, which is
		769	available everywhere as it comes with AnyEvent itself.
		770
		771	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		772	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		773	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		774
		775	=item Backends that are transparently being picked up when they are used.
		776
		777	These will be used when they are currently loaded when the first watcher
		778	is created, in which case it is assumed that the application is using
		779	them. This means that AnyEvent will automatically pick the right backend
		780	when the main program loads an event module before anything starts to
		781	create watchers. Nothing special needs to be done by the main program.
		782
		783	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		784	AnyEvent::Impl::Tk based on Tk, very broken.
		785	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		786	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		787
		788	=item Backends with special needs.
		789
		790	Qt requires the Qt::Application to be instantiated first, but will
		791	otherwise be picked up automatically. As long as the main program
		792	instantiates the application before any AnyEvent watchers are created,
		793	everything should just work.
		794
		795	AnyEvent::Impl::Qt based on Qt.
		796
		797	Support for IO::Async can only be partial, as it is too broken and
		798	architecturally limited to even support the AnyEvent API. It also
		799	is the only event loop that needs the loop to be set explicitly, so
		800	it can only be used by a main program knowing about AnyEvent. See
		801	L<AnyEvent::Impl::Async> for the gory details.
		802
		803	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		804
		805	=item Event loops that are indirectly supported via other backends.
		806
		807	Some event loops can be supported via other modules:
		808
		809	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		810
		811	B<WxWidgets> has no support for watching file handles. However, you can
		812	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		813	polls 20 times per second, which was considered to be too horrible to even
		814	consider for AnyEvent.
		815
		816	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		817	backend, so it can be supported through POE.
		818
		819	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		820	load L<POE> when detecting them, in the hope that POE will pick them up,
		821	in which case everything will be automatic.
		822
		823	=back
396		824
397	=head1 GLOBAL VARIABLES AND FUNCTIONS	825	=head1 GLOBAL VARIABLES AND FUNCTIONS
398		826
		827	These are not normally required to use AnyEvent, but can be useful to
		828	write AnyEvent extension modules.
		829
399	=over 4	830	=over 4
400		831
401	=item $AnyEvent::MODEL	832	=item $AnyEvent::MODEL
402		833
403	Contains C<undef> until the first watcher is being created. Then it	834	Contains C<undef> until the first watcher is being created, before the
		835	backend has been autodetected.
		836
404	contains the event model that is being used, which is the name of the	837	Afterwards it contains the event model that is being used, which is the
405	Perl class implementing the model. This class is usually one of the	838	name of the Perl class implementing the model. This class is usually one
406	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	839	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
407	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	840	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
408		841	will be C<urxvt::anyevent>).
409	The known classes so far are:
410
411	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
412	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
413	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
414	AnyEvent::Impl::Event based on Event, second best choice.
415	AnyEvent::Impl::Glib based on Glib, third-best choice.
416	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
417	AnyEvent::Impl::Tk based on Tk, very bad choice.
418	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
419	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
420	AnyEvent::Impl::POE based on POE, not generic enough for full support.
421
422	There is no support for WxWidgets, as WxWidgets has no support for
423	watching file handles. However, you can use WxWidgets through the
424	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
425	second, which was considered to be too horrible to even consider for
426	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
427	it's adaptor.
428
429	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
430	autodetecting them.
431		842
432	=item AnyEvent::detect	843	=item AnyEvent::detect
433		844
434	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	845	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
435	if necessary. You should only call this function right before you would	846	if necessary. You should only call this function right before you would
436	have created an AnyEvent watcher anyway, that is, as late as possible at	847	have created an AnyEvent watcher anyway, that is, as late as possible at
437	runtime.	848	runtime, and not e.g. while initialising of your module.
		849
		850	If you need to do some initialisation before AnyEvent watchers are
		851	created, use C<post_detect>.
		852
		853	=item $guard = AnyEvent::post_detect { BLOCK }
		854
		855	Arranges for the code block to be executed as soon as the event model is
		856	autodetected (or immediately if this has already happened).
		857
		858	The block will be executed I<after> the actual backend has been detected
		859	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		860	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		861	other initialisations - see the sources of L<AnyEvent::Strict> or
		862	L<AnyEvent::AIO> to see how this is used.
		863
		864	The most common usage is to create some global watchers, without forcing
		865	event module detection too early, for example, L<AnyEvent::AIO> creates
		866	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		867	avoid autodetecting the event module at load time.
		868
		869	If called in scalar or list context, then it creates and returns an object
		870	that automatically removes the callback again when it is destroyed. See
		871	L<Coro::BDB> for a case where this is useful.
		872
		873	=item @AnyEvent::post_detect
		874
		875	If there are any code references in this array (you can C<push> to it
		876	before or after loading AnyEvent), then they will called directly after
		877	the event loop has been chosen.
		878
		879	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		880	if it is defined then the event loop has already been detected, and the
		881	array will be ignored.
		882
		883	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		884	it,as it takes care of these details.
		885
		886	This variable is mainly useful for modules that can do something useful
		887	when AnyEvent is used and thus want to know when it is initialised, but do
		888	not need to even load it by default. This array provides the means to hook
		889	into AnyEvent passively, without loading it.
438		890
439	=back	891	=back
440		892
441	=head1 WHAT TO DO IN A MODULE	893	=head1 WHAT TO DO IN A MODULE
442		894
…		…
446	Be careful when you create watchers in the module body - AnyEvent will	898	Be careful when you create watchers in the module body - AnyEvent will
447	decide which event module to use as soon as the first method is called, so	899	decide which event module to use as soon as the first method is called, so
448	by calling AnyEvent in your module body you force the user of your module	900	by calling AnyEvent in your module body you force the user of your module
449	to load the event module first.	901	to load the event module first.
450		902
451	Never call C<< ->wait >> on a condition variable unless you I<know> that	903	Never call C<< ->recv >> on a condition variable unless you I<know> that
452	the C<< ->broadcast >> method has been called on it already. This is	904	the C<< ->send >> method has been called on it already. This is
453	because it will stall the whole program, and the whole point of using	905	because it will stall the whole program, and the whole point of using
454	events is to stay interactive.	906	events is to stay interactive.
455		907
456	It is fine, however, to call C<< ->wait >> when the user of your module	908	It is fine, however, to call C<< ->recv >> when the user of your module
457	requests it (i.e. if you create a http request object ad have a method	909	requests it (i.e. if you create a http request object ad have a method
458	called C<results> that returns the results, it should call C<< ->wait >>	910	called C<results> that returns the results, it should call C<< ->recv >>
459	freely, as the user of your module knows what she is doing. always).	911	freely, as the user of your module knows what she is doing. always).
460		912
461	=head1 WHAT TO DO IN THE MAIN PROGRAM	913	=head1 WHAT TO DO IN THE MAIN PROGRAM
462		914
463	There will always be a single main program - the only place that should	915	There will always be a single main program - the only place that should
…		…
465		917
466	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	918	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
467	do anything special (it does not need to be event-based) and let AnyEvent	919	do anything special (it does not need to be event-based) and let AnyEvent
468	decide which implementation to chose if some module relies on it.	920	decide which implementation to chose if some module relies on it.
469		921
470	If the main program relies on a specific event model. For example, in	922	If the main program relies on a specific event model - for example, in
471	Gtk2 programs you have to rely on the Glib module. You should load the	923	Gtk2 programs you have to rely on the Glib module - you should load the
472	event module before loading AnyEvent or any module that uses it: generally	924	event module before loading AnyEvent or any module that uses it: generally
473	speaking, you should load it as early as possible. The reason is that	925	speaking, you should load it as early as possible. The reason is that
474	modules might create watchers when they are loaded, and AnyEvent will	926	modules might create watchers when they are loaded, and AnyEvent will
475	decide on the event model to use as soon as it creates watchers, and it	927	decide on the event model to use as soon as it creates watchers, and it
476	might chose the wrong one unless you load the correct one yourself.	928	might chose the wrong one unless you load the correct one yourself.
477		929
478	You can chose to use a rather inefficient pure-perl implementation by	930	You can chose to use a pure-perl implementation by loading the
479	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	931	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
480	behaviour everywhere, but letting AnyEvent chose is generally better.	932	everywhere, but letting AnyEvent chose the model is generally better.
		933
		934	=head2 MAINLOOP EMULATION
		935
		936	Sometimes (often for short test scripts, or even standalone programs who
		937	only want to use AnyEvent), you do not want to run a specific event loop.
		938
		939	In that case, you can use a condition variable like this:
		940
		941	AnyEvent->condvar->recv;
		942
		943	This has the effect of entering the event loop and looping forever.
		944
		945	Note that usually your program has some exit condition, in which case
		946	it is better to use the "traditional" approach of storing a condition
		947	variable somewhere, waiting for it, and sending it when the program should
		948	exit cleanly.
		949
		950
		951	=head1 OTHER MODULES
		952
		953	The following is a non-exhaustive list of additional modules that use
		954	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		955	modules and other event loops in the same program. Some of the modules
		956	come with AnyEvent, most are available via CPAN.
		957
		958	=over 4
		959
		960	=item L<AnyEvent::Util>
		961
		962	Contains various utility functions that replace often-used but blocking
		963	functions such as C<inet_aton> by event-/callback-based versions.
		964
		965	=item L<AnyEvent::Socket>
		966
		967	Provides various utility functions for (internet protocol) sockets,
		968	addresses and name resolution. Also functions to create non-blocking tcp
		969	connections or tcp servers, with IPv6 and SRV record support and more.
		970
		971	=item L<AnyEvent::Handle>
		972
		973	Provide read and write buffers, manages watchers for reads and writes,
		974	supports raw and formatted I/O, I/O queued and fully transparent and
		975	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		976
		977	=item L<AnyEvent::DNS>
		978
		979	Provides rich asynchronous DNS resolver capabilities.
		980
		981	=item L<AnyEvent::HTTP>
		982
		983	A simple-to-use HTTP library that is capable of making a lot of concurrent
		984	HTTP requests.
		985
		986	=item L<AnyEvent::HTTPD>
		987
		988	Provides a simple web application server framework.
		989
		990	=item L<AnyEvent::FastPing>
		991
		992	The fastest ping in the west.
		993
		994	=item L<AnyEvent::DBI>
		995
		996	Executes L<DBI> requests asynchronously in a proxy process.
		997
		998	=item L<AnyEvent::AIO>
		999
		1000	Truly asynchronous I/O, should be in the toolbox of every event
		1001	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1002	together.
		1003
		1004	=item L<AnyEvent::BDB>
		1005
		1006	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1007	L<BDB> and AnyEvent together.
		1008
		1009	=item L<AnyEvent::GPSD>
		1010
		1011	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1012
		1013	=item L<AnyEvent::IRC>
		1014
		1015	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1016
		1017	=item L<AnyEvent::XMPP>
		1018
		1019	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1020	Net::XMPP2>.
		1021
		1022	=item L<AnyEvent::IGS>
		1023
		1024	A non-blocking interface to the Internet Go Server protocol (used by
		1025	L<App::IGS>).
		1026
		1027	=item L<Net::FCP>
		1028
		1029	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1030	of AnyEvent.
		1031
		1032	=item L<Event::ExecFlow>
		1033
		1034	High level API for event-based execution flow control.
		1035
		1036	=item L<Coro>
		1037
		1038	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1039
		1040	=back
481		1041
482	=cut	1042	=cut
483		1043
484	package AnyEvent;	1044	package AnyEvent;
485		1045
		1046	# basically a tuned-down version of common::sense
		1047	sub common_sense {
486	no warnings;	1048	# no warnings
487	use strict;	1049	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1050	# use strict vars subs
		1051	$^H |= 0x00000600;
		1052	}
488		1053
		1054	BEGIN { AnyEvent::common_sense }
		1055
489	use Carp;	1056	use Carp ();
490		1057
491	our $VERSION = '3.3';	1058	our $VERSION = 4.85;
492	our $MODEL;	1059	our $MODEL;
493		1060
494	our $AUTOLOAD;	1061	our $AUTOLOAD;
495	our @ISA;	1062	our @ISA;
496		1063
497	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
498
499	our @REGISTRY;	1064	our @REGISTRY;
500		1065
		1066	our $WIN32;
		1067
		1068	our $VERBOSE;
		1069
		1070	BEGIN {
		1071	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1072	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1073
		1074	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1075	if ${^TAINT};
		1076
		1077	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1078
		1079	}
		1080
		1081	our $MAX_SIGNAL_LATENCY = 10;
		1082
		1083	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1084
		1085	{
		1086	my $idx;
		1087	$PROTOCOL{$_} = ++$idx
		1088	for reverse split /\s*,\s*/,
		1089	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1090	}
		1091
501	my @models = (	1092	my @models = (
502	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
503	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
504	[EV:: => AnyEvent::Impl::EV::],	1093	[EV:: => AnyEvent::Impl::EV::],
505	[Event:: => AnyEvent::Impl::Event::],	1094	[Event:: => AnyEvent::Impl::Event::],
506	[Glib:: => AnyEvent::Impl::Glib::],	1095	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		1096	# everything below here will not be autoprobed
		1097	# as the pureperl backend should work everywhere
		1098	# and is usually faster
		1099	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		1100	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
507	[Tk:: => AnyEvent::Impl::Tk::],	1101	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1102	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1103	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
508	[Wx:: => AnyEvent::Impl::POE::],	1104	[Wx:: => AnyEvent::Impl::POE::],
509	[Prima:: => AnyEvent::Impl::POE::],	1105	[Prima:: => AnyEvent::Impl::POE::],
510	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1106	# IO::Async is just too broken - we would need workarounds for its
511	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1107	# byzantine signal and broken child handling, among others.
512	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1108	# IO::Async is rather hard to detect, as it doesn't have any
		1109	# obvious default class.
513	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1110	# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
514	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1111	# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1112	# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
515	);	1113	);
516		1114
517	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1115	our %method = map +($_ => 1),
		1116	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1117
		1118	our @post_detect;
		1119
		1120	sub post_detect(&) {
		1121	my ($cb) = @_;
		1122
		1123	if ($MODEL) {
		1124	$cb->();
		1125
		1126	1
		1127	} else {
		1128	push @post_detect, $cb;
		1129
		1130	defined wantarray
		1131	? bless \$cb, "AnyEvent::Util::postdetect"
		1132	: ()
		1133	}
		1134	}
		1135
		1136	sub AnyEvent::Util::postdetect::DESTROY {
		1137	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1138	}
518		1139
519	sub detect() {	1140	sub detect() {
520	unless ($MODEL) {	1141	unless ($MODEL) {
521	no strict 'refs';	1142	local $SIG{__DIE__};
522		1143
523	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1144	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
524	my $model = "AnyEvent::Impl::$1";	1145	my $model = "AnyEvent::Impl::$1";
525	if (eval "require $model") {	1146	if (eval "require $model") {
526	$MODEL = $model;	1147	$MODEL = $model;
527	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1148	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
528	} else {	1149	} else {
529	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1150	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
530	}	1151	}
531	}	1152	}
532		1153
533	# check for already loaded models	1154	# check for already loaded models
534	unless ($MODEL) {	1155	unless ($MODEL) {
535	for (@REGISTRY, @models) {	1156	for (@REGISTRY, @models) {
536	my ($package, $model) = @$_;	1157	my ($package, $model) = @$_;
537	if (${"$package\::VERSION"} > 0) {	1158	if (${"$package\::VERSION"} > 0) {
538	if (eval "require $model") {	1159	if (eval "require $model") {
539	$MODEL = $model;	1160	$MODEL = $model;
540	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1161	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
541	last;	1162	last;
542	}	1163	}
543	}	1164	}
544	}	1165	}
545		1166
…		…
550	my ($package, $model) = @$_;	1171	my ($package, $model) = @$_;
551	if (eval "require $package"	1172	if (eval "require $package"
552	and ${"$package\::VERSION"} > 0	1173	and ${"$package\::VERSION"} > 0
553	and eval "require $model") {	1174	and eval "require $model") {
554	$MODEL = $model;	1175	$MODEL = $model;
555	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1176	warn "AnyEvent: autoprobed model '$model', using it.\n" if $VERBOSE >= 2;
556	last;	1177	last;
557	}	1178	}
558	}	1179	}
559		1180
560	$MODEL	1181	$MODEL
561	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1182	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
562	}	1183	}
563	}	1184	}
564		1185
		1186	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1187
565	unshift @ISA, $MODEL;	1188	unshift @ISA, $MODEL;
566	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1189
		1190	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1191
		1192	(shift @post_detect)->() while @post_detect;
567	}	1193	}
568		1194
569	$MODEL	1195	$MODEL
570	}	1196	}
571		1197
572	sub AUTOLOAD {	1198	sub AUTOLOAD {
573	(my $func = $AUTOLOAD) =~ s/.*://;	1199	(my $func = $AUTOLOAD) =~ s/.*://;
574		1200
575	$method{$func}	1201	$method{$func}
576	or croak "$func: not a valid method for AnyEvent objects";	1202	or Carp::croak "$func: not a valid method for AnyEvent objects";
577		1203
578	detect unless $MODEL;	1204	detect unless $MODEL;
579		1205
580	my $class = shift;	1206	my $class = shift;
581	$class->$func (@_);	1207	$class->$func (@_);
582	}	1208	}
583		1209
		1210	# utility function to dup a filehandle. this is used by many backends
		1211	# to support binding more than one watcher per filehandle (they usually
		1212	# allow only one watcher per fd, so we dup it to get a different one).
		1213	sub _dupfh($$;$$) {
		1214	my ($poll, $fh, $r, $w) = @_;
		1215
		1216	# cygwin requires the fh mode to be matching, unix doesn't
		1217	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1218
		1219	open my $fh2, $mode, $fh
		1220	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1221
		1222	# we assume CLOEXEC is already set by perl in all important cases
		1223
		1224	($fh2, $rw)
		1225	}
		1226
584	package AnyEvent::Base;	1227	package AnyEvent::Base;
585		1228
		1229	# default implementations for many methods
		1230
		1231	sub _time {
		1232	# probe for availability of Time::HiRes
		1233	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1234	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1235	*_time = \&Time::HiRes::time;
		1236	# if (eval "use POSIX (); (POSIX::times())...
		1237	} else {
		1238	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1239	*_time = sub { time }; # epic fail
		1240	}
		1241
		1242	&_time
		1243	}
		1244
		1245	sub time { _time }
		1246	sub now { _time }
		1247	sub now_update { }
		1248
586	# default implementation for ->condvar, ->wait, ->broadcast	1249	# default implementation for ->condvar
587		1250
588	sub condvar {	1251	sub condvar {
589	bless \my $flag, "AnyEvent::Base::CondVar"	1252	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
590	}
591
592	sub AnyEvent::Base::CondVar::broadcast {
593	${$_[0]}++;
594	}
595
596	sub AnyEvent::Base::CondVar::wait {
597	AnyEvent->one_event while !${$_[0]};
598	}	1253	}
599		1254
600	# default implementation for ->signal	1255	# default implementation for ->signal
601		1256
602	our %SIG_CB;	1257	our $HAVE_ASYNC_INTERRUPT;
		1258	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1259	our (%SIG_ASY, %SIG_ASY_W);
		1260	our ($SIG_COUNT, $SIG_TW);
603		1261
		1262	sub _signal_exec {
		1263	$HAVE_ASYNC_INTERRUPT
		1264	? $SIGPIPE_R->drain
		1265	: sysread $SIGPIPE_R, my $dummy, 9;
		1266
		1267	while (%SIG_EV) {
		1268	for (keys %SIG_EV) {
		1269	delete $SIG_EV{$_};
		1270	$_->() for values %{ $SIG_CB{$_} || {} };
		1271	}
		1272	}
		1273	}
		1274
604	sub signal {	1275	sub _signal {
605	my (undef, %arg) = @_;	1276	my (undef, %arg) = @_;
606		1277
607	my $signal = uc $arg{signal}	1278	my $signal = uc $arg{signal}
608	or Carp::croak "required option 'signal' is missing";	1279	or Carp::croak "required option 'signal' is missing";
609		1280
610	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1281	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1282
		1283	if ($HAVE_ASYNC_INTERRUPT) {
		1284	# async::interrupt
		1285
		1286	$SIG_ASY{$signal} ||= do {
		1287	my $asy = new Async::Interrupt
		1288	cb => sub { undef $SIG_EV{$signal} },
		1289	signal => $signal,
		1290	pipe => [$SIGPIPE_R->filenos],
		1291	;
		1292	$asy->pipe_autodrain (0);
		1293
		1294	$asy
		1295	};
		1296
		1297	} else {
		1298	# pure perl
		1299
611	$SIG{$signal} ||= sub {	1300	$SIG{$signal} ||= sub {
612	$_->() for values %{ $SIG_CB{$signal} || {} };	1301	local $!;
		1302	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1303	undef $SIG_EV{$signal};
		1304	};
		1305
		1306	# can't do signal processing without introducing races in pure perl,
		1307	# so limit the signal latency.
		1308	++$SIG_COUNT;
		1309	$SIG_TW ||= AnyEvent->timer (
		1310	after => $MAX_SIGNAL_LATENCY,
		1311	interval => $MAX_SIGNAL_LATENCY,
		1312	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1313	);
613	};	1314	}
614		1315
615	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1316	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
616	}	1317	}
617		1318
		1319	sub signal {
		1320	# probe for availability of Async::Interrupt
		1321	if (!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT} && eval "use Async::Interrupt 0.6 (); 1") {
		1322	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1323
		1324	$HAVE_ASYNC_INTERRUPT = 1;
		1325	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1326	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1327
		1328	} else {
		1329	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1330
		1331	require Fcntl;
		1332
		1333	if (AnyEvent::WIN32) {
		1334	require AnyEvent::Util;
		1335
		1336	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1337	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1338	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1339	} else {
		1340	pipe $SIGPIPE_R, $SIGPIPE_W;
		1341	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1342	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1343
		1344	# not strictly required, as $^F is normally 2, but let's make sure...
		1345	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1346	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1347	}
		1348
		1349	$SIGPIPE_R
		1350	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1351
		1352	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1353	}
		1354
		1355	*signal = \&_signal;
		1356	&signal
		1357	}
		1358
618	sub AnyEvent::Base::Signal::DESTROY {	1359	sub AnyEvent::Base::signal::DESTROY {
619	my ($signal, $cb) = @{$_[0]};	1360	my ($signal, $cb) = @{$_[0]};
620		1361
		1362	undef $SIG_TW
		1363	unless --$SIG_COUNT;
		1364
621	delete $SIG_CB{$signal}{$cb};	1365	delete $SIG_CB{$signal}{$cb};
622		1366
623	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1367	$HAVE_ASYNC_INTERRUPT
		1368	? delete $SIG_ASY{$signal}
		1369	: # delete doesn't work with older perls - they then
		1370	# print weird messages, or just unconditionally exit
		1371	# instead of getting the default action.
		1372	undef $SIG{$signal}
		1373	unless keys %{ $SIG_CB{$signal} };
624	}	1374	}
625		1375
626	# default implementation for ->child	1376	# default implementation for ->child
627		1377
628	our %PID_CB;	1378	our %PID_CB;
629	our $CHLD_W;	1379	our $CHLD_W;
630	our $CHLD_DELAY_W;	1380	our $CHLD_DELAY_W;
631	our $PID_IDLE;
632	our $WNOHANG;	1381	our $WNOHANG;
633		1382
634	sub _child_wait {	1383	sub _sigchld {
635	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1384	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
		1385	$_->($pid, $?)
636	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1386	for values %{ $PID_CB{$pid} || {} },
637	(values %{ $PID_CB{0} || {} });	1387	values %{ $PID_CB{0} || {} };
638	}	1388	}
639
640	undef $PID_IDLE;
641	}
642
643	sub _sigchld {
644	# make sure we deliver these changes "synchronous" with the event loop.
645	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
646	undef $CHLD_DELAY_W;
647	&_child_wait;
648	});
649	}	1389	}
650		1390
651	sub child {	1391	sub child {
652	my (undef, %arg) = @_;	1392	my (undef, %arg) = @_;
653		1393
654	defined (my $pid = $arg{pid} + 0)	1394	defined (my $pid = $arg{pid} + 0)
655	or Carp::croak "required option 'pid' is missing";	1395	or Carp::croak "required option 'pid' is missing";
656		1396
657	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1397	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
658		1398
659	unless ($WNOHANG) {	1399	# WNOHANG is almost cetrainly 1 everywhere
660	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1400	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
661	}	1401	? 1
		1402	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
662		1403
663	unless ($CHLD_W) {	1404	unless ($CHLD_W) {
664	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1405	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
665	# child could be a zombie already, so make at least one round	1406	# child could be a zombie already, so make at least one round
666	&_sigchld;	1407	&_sigchld;
667	}	1408	}
668		1409
669	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1410	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
670	}	1411	}
671		1412
672	sub AnyEvent::Base::Child::DESTROY {	1413	sub AnyEvent::Base::child::DESTROY {
673	my ($pid, $cb) = @{$_[0]};	1414	my ($pid, $cb) = @{$_[0]};
674		1415
675	delete $PID_CB{$pid}{$cb};	1416	delete $PID_CB{$pid}{$cb};
676	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1417	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
677		1418
678	undef $CHLD_W unless keys %PID_CB;	1419	undef $CHLD_W unless keys %PID_CB;
679	}	1420	}
		1421
		1422	# idle emulation is done by simply using a timer, regardless
		1423	# of whether the process is idle or not, and not letting
		1424	# the callback use more than 50% of the time.
		1425	sub idle {
		1426	my (undef, %arg) = @_;
		1427
		1428	my ($cb, $w, $rcb) = $arg{cb};
		1429
		1430	$rcb = sub {
		1431	if ($cb) {
		1432	$w = _time;
		1433	&$cb;
		1434	$w = _time - $w;
		1435
		1436	# never use more then 50% of the time for the idle watcher,
		1437	# within some limits
		1438	$w = 0.0001 if $w < 0.0001;
		1439	$w = 5 if $w > 5;
		1440
		1441	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1442	} else {
		1443	# clean up...
		1444	undef $w;
		1445	undef $rcb;
		1446	}
		1447	};
		1448
		1449	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1450
		1451	bless \\$cb, "AnyEvent::Base::idle"
		1452	}
		1453
		1454	sub AnyEvent::Base::idle::DESTROY {
		1455	undef $${$_[0]};
		1456	}
		1457
		1458	package AnyEvent::CondVar;
		1459
		1460	our @ISA = AnyEvent::CondVar::Base::;
		1461
		1462	package AnyEvent::CondVar::Base;
		1463
		1464	#use overload
		1465	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1466	# fallback => 1;
		1467
		1468	# save 300+ kilobytes by dirtily hardcoding overloading
		1469	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1470	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1471	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1472	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1473
		1474	our $WAITING;
		1475
		1476	sub _send {
		1477	# nop
		1478	}
		1479
		1480	sub send {
		1481	my $cv = shift;
		1482	$cv->{_ae_sent} = [@_];
		1483	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1484	$cv->_send;
		1485	}
		1486
		1487	sub croak {
		1488	$_[0]{_ae_croak} = $_[1];
		1489	$_[0]->send;
		1490	}
		1491
		1492	sub ready {
		1493	$_[0]{_ae_sent}
		1494	}
		1495
		1496	sub _wait {
		1497	$WAITING
		1498	and !$_[0]{_ae_sent}
		1499	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1500
		1501	local $WAITING = 1;
		1502	AnyEvent->one_event while !$_[0]{_ae_sent};
		1503	}
		1504
		1505	sub recv {
		1506	$_[0]->_wait;
		1507
		1508	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1509	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1510	}
		1511
		1512	sub cb {
		1513	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1514	$_[0]{_ae_cb}
		1515	}
		1516
		1517	sub begin {
		1518	++$_[0]{_ae_counter};
		1519	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1520	}
		1521
		1522	sub end {
		1523	return if --$_[0]{_ae_counter};
		1524	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1525	}
		1526
		1527	# undocumented/compatibility with pre-3.4
		1528	*broadcast = \&send;
		1529	*wait = \&_wait;
		1530
		1531	=head1 ERROR AND EXCEPTION HANDLING
		1532
		1533	In general, AnyEvent does not do any error handling - it relies on the
		1534	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1535	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1536	checking of all AnyEvent methods, however, which is highly useful during
		1537	development.
		1538
		1539	As for exception handling (i.e. runtime errors and exceptions thrown while
		1540	executing a callback), this is not only highly event-loop specific, but
		1541	also not in any way wrapped by this module, as this is the job of the main
		1542	program.
		1543
		1544	The pure perl event loop simply re-throws the exception (usually
		1545	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1546	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1547	so on.
		1548
		1549	=head1 ENVIRONMENT VARIABLES
		1550
		1551	The following environment variables are used by this module or its
		1552	submodules.
		1553
		1554	Note that AnyEvent will remove I<all> environment variables starting with
		1555	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1556	enabled.
		1557
		1558	=over 4
		1559
		1560	=item C<PERL_ANYEVENT_VERBOSE>
		1561
		1562	By default, AnyEvent will be completely silent except in fatal
		1563	conditions. You can set this environment variable to make AnyEvent more
		1564	talkative.
		1565
		1566	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1567	conditions, such as not being able to load the event model specified by
		1568	C<PERL_ANYEVENT_MODEL>.
		1569
		1570	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1571	model it chooses.
		1572
		1573	When set to C<8> or higher, then AnyEvent will report extra information on
		1574	which optional modules it loads and how it implements certain features.
		1575
		1576	=item C<PERL_ANYEVENT_STRICT>
		1577
		1578	AnyEvent does not do much argument checking by default, as thorough
		1579	argument checking is very costly. Setting this variable to a true value
		1580	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1581	check the arguments passed to most method calls. If it finds any problems,
		1582	it will croak.
		1583
		1584	In other words, enables "strict" mode.
		1585
		1586	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1587	>>, it is definitely recommended to keep it off in production. Keeping
		1588	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1589	can be very useful, however.
		1590
		1591	=item C<PERL_ANYEVENT_MODEL>
		1592
		1593	This can be used to specify the event model to be used by AnyEvent, before
		1594	auto detection and -probing kicks in. It must be a string consisting
		1595	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1596	and the resulting module name is loaded and if the load was successful,
		1597	used as event model. If it fails to load AnyEvent will proceed with
		1598	auto detection and -probing.
		1599
		1600	This functionality might change in future versions.
		1601
		1602	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1603	could start your program like this:
		1604
		1605	PERL_ANYEVENT_MODEL=Perl perl ...
		1606
		1607	=item C<PERL_ANYEVENT_PROTOCOLS>
		1608
		1609	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1610	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1611	of auto probing).
		1612
		1613	Must be set to a comma-separated list of protocols or address families,
		1614	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1615	used, and preference will be given to protocols mentioned earlier in the
		1616	list.
		1617
		1618	This variable can effectively be used for denial-of-service attacks
		1619	against local programs (e.g. when setuid), although the impact is likely
		1620	small, as the program has to handle conenction and other failures anyways.
		1621
		1622	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1623	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1624	- only support IPv4, never try to resolve or contact IPv6
		1625	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1626	IPv6, but prefer IPv6 over IPv4.
		1627
		1628	=item C<PERL_ANYEVENT_EDNS0>
		1629
		1630	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1631	for DNS. This extension is generally useful to reduce DNS traffic, but
		1632	some (broken) firewalls drop such DNS packets, which is why it is off by
		1633	default.
		1634
		1635	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1636	EDNS0 in its DNS requests.
		1637
		1638	=item C<PERL_ANYEVENT_MAX_FORKS>
		1639
		1640	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1641	will create in parallel.
		1642
		1643	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1644
		1645	The default value for the C<max_outstanding> parameter for the default DNS
		1646	resolver - this is the maximum number of parallel DNS requests that are
		1647	sent to the DNS server.
		1648
		1649	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1650
		1651	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1652	configuration) in the default resolver. When set to the empty string, no
		1653	default config will be used.
		1654
		1655	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1656
		1657	When neither C<ca_file> nor C<ca_path> was specified during
		1658	L<AnyEvent::TLS> context creation, and either of these environment
		1659	variables exist, they will be used to specify CA certificate locations
		1660	instead of a system-dependent default.
		1661
		1662	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1663
		1664	When these are set to C<1>, then the respective modules are not
		1665	loaded. Mostly good for testing AnyEvent itself.
		1666
		1667	=back
680		1668
681	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1669	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
682		1670
683	This is an advanced topic that you do not normally need to use AnyEvent in	1671	This is an advanced topic that you do not normally need to use AnyEvent in
684	a module. This section is only of use to event loop authors who want to	1672	a module. This section is only of use to event loop authors who want to
…		…
718		1706
719	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1707	I<rxvt-unicode> also cheats a bit by not providing blocking access to
720	condition variables: code blocking while waiting for a condition will	1708	condition variables: code blocking while waiting for a condition will
721	C<die>. This still works with most modules/usages, and blocking calls must	1709	C<die>. This still works with most modules/usages, and blocking calls must
722	not be done in an interactive application, so it makes sense.	1710	not be done in an interactive application, so it makes sense.
723
724	=head1 ENVIRONMENT VARIABLES
725
726	The following environment variables are used by this module:
727
728	=over 4
729
730	=item C<PERL_ANYEVENT_VERBOSE>
731
732	By default, AnyEvent will be completely silent except in fatal
733	conditions. You can set this environment variable to make AnyEvent more
734	talkative.
735
736	When set to C<1> or higher, causes AnyEvent to warn about unexpected
737	conditions, such as not being able to load the event model specified by
738	C<PERL_ANYEVENT_MODEL>.
739
740	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
741	model it chooses.
742
743	=item C<PERL_ANYEVENT_MODEL>
744
745	This can be used to specify the event model to be used by AnyEvent, before
746	autodetection and -probing kicks in. It must be a string consisting
747	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
748	and the resulting module name is loaded and if the load was successful,
749	used as event model. If it fails to load AnyEvent will proceed with
750	autodetection and -probing.
751
752	This functionality might change in future versions.
753
754	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
755	could start your program like this:
756
757	PERL_ANYEVENT_MODEL=Perl perl ...
758
759	=back
760		1711
761	=head1 EXAMPLE PROGRAM	1712	=head1 EXAMPLE PROGRAM
762		1713
763	The following program uses an I/O watcher to read data from STDIN, a timer	1714	The following program uses an I/O watcher to read data from STDIN, a timer
764	to display a message once per second, and a condition variable to quit the	1715	to display a message once per second, and a condition variable to quit the
…		…
773	poll => 'r',	1724	poll => 'r',
774	cb => sub {	1725	cb => sub {
775	warn "io event <$_[0]>\n"; # will always output <r>	1726	warn "io event <$_[0]>\n"; # will always output <r>
776	chomp (my $input = <STDIN>); # read a line	1727	chomp (my $input = <STDIN>); # read a line
777	warn "read: $input\n"; # output what has been read	1728	warn "read: $input\n"; # output what has been read
778	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1729	$cv->send if $input =~ /^q/i; # quit program if /^q/i
779	},	1730	},
780	);	1731	);
781		1732
782	my $time_watcher; # can only be used once	1733	my $time_watcher; # can only be used once
783		1734
…		…
788	});	1739	});
789	}	1740	}
790		1741
791	new_timer; # create first timer	1742	new_timer; # create first timer
792		1743
793	$cv->wait; # wait until user enters /^q/i	1744	$cv->recv; # wait until user enters /^q/i
794		1745
795	=head1 REAL-WORLD EXAMPLE	1746	=head1 REAL-WORLD EXAMPLE
796		1747
797	Consider the L<Net::FCP> module. It features (among others) the following	1748	Consider the L<Net::FCP> module. It features (among others) the following
798	API calls, which are to freenet what HTTP GET requests are to http:	1749	API calls, which are to freenet what HTTP GET requests are to http:
…		…
848	syswrite $txn->{fh}, $txn->{request}	1799	syswrite $txn->{fh}, $txn->{request}
849	or die "connection or write error";	1800	or die "connection or write error";
850	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1801	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
851		1802
852	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1803	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
853	result and signals any possible waiters that the request ahs finished:	1804	result and signals any possible waiters that the request has finished:
854		1805
855	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1806	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
856		1807
857	if (end-of-file or data complete) {	1808	if (end-of-file or data complete) {
858	$txn->{result} = $txn->{buf};	1809	$txn->{result} = $txn->{buf};
859	$txn->{finished}->broadcast;	1810	$txn->{finished}->send;
860	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1811	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
861	}	1812	}
862		1813
863	The C<result> method, finally, just waits for the finished signal (if the	1814	The C<result> method, finally, just waits for the finished signal (if the
864	request was already finished, it doesn't wait, of course, and returns the	1815	request was already finished, it doesn't wait, of course, and returns the
865	data:	1816	data:
866		1817
867	$txn->{finished}->wait;	1818	$txn->{finished}->recv;
868	return $txn->{result};	1819	return $txn->{result};
869		1820
870	The actual code goes further and collects all errors (C<die>s, exceptions)	1821	The actual code goes further and collects all errors (C<die>s, exceptions)
871	that occured during request processing. The C<result> method detects	1822	that occurred during request processing. The C<result> method detects
872	whether an exception as thrown (it is stored inside the $txn object)	1823	whether an exception as thrown (it is stored inside the $txn object)
873	and just throws the exception, which means connection errors and other	1824	and just throws the exception, which means connection errors and other
874	problems get reported tot he code that tries to use the result, not in a	1825	problems get reported tot he code that tries to use the result, not in a
875	random callback.	1826	random callback.
876		1827
…		…
907		1858
908	my $quit = AnyEvent->condvar;	1859	my $quit = AnyEvent->condvar;
909		1860
910	$fcp->txn_client_get ($url)->cb (sub {	1861	$fcp->txn_client_get ($url)->cb (sub {
911	...	1862	...
912	$quit->broadcast;	1863	$quit->send;
913	});	1864	});
914		1865
915	$quit->wait;	1866	$quit->recv;
916		1867
917		1868
918	=head1 BENCHMARKS	1869	=head1 BENCHMARKS
919		1870
920	To give you an idea of the performance and overheads that AnyEvent adds	1871	To give you an idea of the performance and overheads that AnyEvent adds
…		…
922	of various event loops I prepared some benchmarks.	1873	of various event loops I prepared some benchmarks.
923		1874
924	=head2 BENCHMARKING ANYEVENT OVERHEAD	1875	=head2 BENCHMARKING ANYEVENT OVERHEAD
925		1876
926	Here is a benchmark of various supported event models used natively and	1877	Here is a benchmark of various supported event models used natively and
927	through anyevent. The benchmark creates a lot of timers (with a zero	1878	through AnyEvent. The benchmark creates a lot of timers (with a zero
928	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1879	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
929	which it is), lets them fire exactly once and destroys them again.	1880	which it is), lets them fire exactly once and destroys them again.
930		1881
931	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	1882	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
932	distribution.	1883	distribution.
…		…
949	all watchers, to avoid adding memory overhead. That means closure creation	1900	all watchers, to avoid adding memory overhead. That means closure creation
950	and memory usage is not included in the figures.	1901	and memory usage is not included in the figures.
951		1902
952	I<invoke> is the time, in microseconds, used to invoke a simple	1903	I<invoke> is the time, in microseconds, used to invoke a simple
953	callback. The callback simply counts down a Perl variable and after it was	1904	callback. The callback simply counts down a Perl variable and after it was
954	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1905	invoked "watcher" times, it would C<< ->send >> a condvar once to
955	signal the end of this phase.	1906	signal the end of this phase.
956		1907
957	I<destroy> is the time, in microseconds, that it takes to destroy a single	1908	I<destroy> is the time, in microseconds, that it takes to destroy a single
958	watcher.	1909	watcher.
959		1910
960	=head3 Results	1911	=head3 Results
961		1912
962	name watchers bytes create invoke destroy comment	1913	name watchers bytes create invoke destroy comment
963	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1914	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
964	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1915	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
965	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1916	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
966	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1917	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
967	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1918	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
968	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1919	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1920	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1921	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
969	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1922	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
970	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1923	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
971	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1924	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
972	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1925	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
973		1926
974	=head3 Discussion	1927	=head3 Discussion
975		1928
976	The benchmark does I<not> measure scalability of the event loop very	1929	The benchmark does I<not> measure scalability of the event loop very
977	well. For example, a select-based event loop (such as the pure perl one)	1930	well. For example, a select-based event loop (such as the pure perl one)
…		…
1002	performance becomes really bad with lots of file descriptors (and few of	1955	performance becomes really bad with lots of file descriptors (and few of
1003	them active), of course, but this was not subject of this benchmark.	1956	them active), of course, but this was not subject of this benchmark.
1004		1957
1005	The C<Event> module has a relatively high setup and callback invocation	1958	The C<Event> module has a relatively high setup and callback invocation
1006	cost, but overall scores in on the third place.	1959	cost, but overall scores in on the third place.
		1960
		1961	C<IO::Async> performs admirably well, about on par with C<Event>, even
		1962	when using its pure perl backend.
1007		1963
1008	C<Glib>'s memory usage is quite a bit higher, but it features a	1964	C<Glib>'s memory usage is quite a bit higher, but it features a
1009	faster callback invocation and overall ends up in the same class as	1965	faster callback invocation and overall ends up in the same class as
1010	C<Event>. However, Glib scales extremely badly, doubling the number of	1966	C<Event>. However, Glib scales extremely badly, doubling the number of
1011	watchers increases the processing time by more than a factor of four,	1967	watchers increases the processing time by more than a factor of four,
…		…
1019	file descriptor is dup()ed for each watcher. This shows that the dup()	1975	file descriptor is dup()ed for each watcher. This shows that the dup()
1020	employed by some adaptors is not a big performance issue (it does incur a	1976	employed by some adaptors is not a big performance issue (it does incur a
1021	hidden memory cost inside the kernel which is not reflected in the figures	1977	hidden memory cost inside the kernel which is not reflected in the figures
1022	above).	1978	above).
1023		1979
1024	C<POE>, regardless of underlying event loop (whether using its pure	1980	C<POE>, regardless of underlying event loop (whether using its pure perl
1025	perl select-based backend or the Event module, the POE-EV backend	1981	select-based backend or the Event module, the POE-EV backend couldn't
1026	couldn't be tested because it wasn't working) shows abysmal performance	1982	be tested because it wasn't working) shows abysmal performance and
1027	and memory usage: Watchers use almost 30 times as much memory as	1983	memory usage with AnyEvent: Watchers use almost 30 times as much memory
1028	EV watchers, and 10 times as much memory as Event (the high memory	1984	as EV watchers, and 10 times as much memory as Event (the high memory
1029	requirements are caused by requiring a session for each watcher). Watcher	1985	requirements are caused by requiring a session for each watcher). Watcher
1030	invocation speed is almost 900 times slower than with AnyEvent's pure perl	1986	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1987	implementation.
		1988
1031	implementation. The design of the POE adaptor class in AnyEvent can not	1989	The design of the POE adaptor class in AnyEvent can not really account
1032	really account for this, as session creation overhead is small compared	1990	for the performance issues, though, as session creation overhead is
1033	to execution of the state machine, which is coded pretty optimally within	1991	small compared to execution of the state machine, which is coded pretty
1034	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1992	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1993	using multiple sessions is not a good approach, especially regarding
		1994	memory usage, even the author of POE could not come up with a faster
		1995	design).
1035		1996
1036	=head3 Summary	1997	=head3 Summary
1037		1998
1038	=over 4	1999	=over 4
1039		2000
…		…
1050		2011
1051	=back	2012	=back
1052		2013
1053	=head2 BENCHMARKING THE LARGE SERVER CASE	2014	=head2 BENCHMARKING THE LARGE SERVER CASE
1054		2015
1055	This benchmark atcually benchmarks the event loop itself. It works by	2016	This benchmark actually benchmarks the event loop itself. It works by
1056	creating a number of "servers": each server consists of a socketpair, a	2017	creating a number of "servers": each server consists of a socket pair, a
1057	timeout watcher that gets reset on activity (but never fires), and an I/O	2018	timeout watcher that gets reset on activity (but never fires), and an I/O
1058	watcher waiting for input on one side of the socket. Each time the socket	2019	watcher waiting for input on one side of the socket. Each time the socket
1059	watcher reads a byte it will write that byte to a random other "server".	2020	watcher reads a byte it will write that byte to a random other "server".
1060		2021
1061	The effect is that there will be a lot of I/O watchers, only part of which	2022	The effect is that there will be a lot of I/O watchers, only part of which
1062	are active at any one point (so there is a constant number of active	2023	are active at any one point (so there is a constant number of active
1063	fds for each loop iterstaion, but which fds these are is random). The	2024	fds for each loop iteration, but which fds these are is random). The
1064	timeout is reset each time something is read because that reflects how	2025	timeout is reset each time something is read because that reflects how
1065	most timeouts work (and puts extra pressure on the event loops).	2026	most timeouts work (and puts extra pressure on the event loops).
1066		2027
1067	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2028	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1068	(1%) are active. This mirrors the activity of large servers with many	2029	(1%) are active. This mirrors the activity of large servers with many
1069	connections, most of which are idle at any one point in time.	2030	connections, most of which are idle at any one point in time.
1070		2031
1071	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2032	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1072	distribution.	2033	distribution.
…		…
1074	=head3 Explanation of the columns	2035	=head3 Explanation of the columns
1075		2036
1076	I<sockets> is the number of sockets, and twice the number of "servers" (as	2037	I<sockets> is the number of sockets, and twice the number of "servers" (as
1077	each server has a read and write socket end).	2038	each server has a read and write socket end).
1078		2039
1079	I<create> is the time it takes to create a socketpair (which is	2040	I<create> is the time it takes to create a socket pair (which is
1080	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2041	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1081		2042
1082	I<request>, the most important value, is the time it takes to handle a	2043	I<request>, the most important value, is the time it takes to handle a
1083	single "request", that is, reading the token from the pipe and forwarding	2044	single "request", that is, reading the token from the pipe and forwarding
1084	it to another server. This includes deleting the old timeout and creating	2045	it to another server. This includes deleting the old timeout and creating
1085	a new one that moves the timeout into the future.	2046	a new one that moves the timeout into the future.
1086		2047
1087	=head3 Results	2048	=head3 Results
1088		2049
1089	name sockets create request	2050	name sockets create request
1090	EV 20000 69.01 11.16	2051	EV 20000 69.01 11.16
1091	Perl 20000 73.32 35.87	2052	Perl 20000 73.32 35.87
		2053	IOAsync 20000 157.00 98.14 epoll
		2054	IOAsync 20000 159.31 616.06 poll
1092	Event 20000 212.62 257.32	2055	Event 20000 212.62 257.32
1093	Glib 20000 651.16 1896.30	2056	Glib 20000 651.16 1896.30
1094	POE 20000 349.67 12317.24 uses POE::Loop::Event	2057	POE 20000 349.67 12317.24 uses POE::Loop::Event
1095		2058
1096	=head3 Discussion	2059	=head3 Discussion
1097		2060
1098	This benchmark I<does> measure scalability and overall performance of the	2061	This benchmark I<does> measure scalability and overall performance of the
1099	particular event loop.	2062	particular event loop.
…		…
1101	EV is again fastest. Since it is using epoll on my system, the setup time	2064	EV is again fastest. Since it is using epoll on my system, the setup time
1102	is relatively high, though.	2065	is relatively high, though.
1103		2066
1104	Perl surprisingly comes second. It is much faster than the C-based event	2067	Perl surprisingly comes second. It is much faster than the C-based event
1105	loops Event and Glib.	2068	loops Event and Glib.
		2069
		2070	IO::Async performs very well when using its epoll backend, and still quite
		2071	good compared to Glib when using its pure perl backend.
1106		2072
1107	Event suffers from high setup time as well (look at its code and you will	2073	Event suffers from high setup time as well (look at its code and you will
1108	understand why). Callback invocation also has a high overhead compared to	2074	understand why). Callback invocation also has a high overhead compared to
1109	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2075	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1110	uses select or poll in basically all documented configurations.	2076	uses select or poll in basically all documented configurations.
…		…
1118		2084
1119	=head3 Summary	2085	=head3 Summary
1120		2086
1121	=over 4	2087	=over 4
1122		2088
1123	=item * The pure perl implementation performs extremely well, considering	2089	=item * The pure perl implementation performs extremely well.
1124	that it uses select.
1125		2090
1126	=item * Avoid Glib or POE in large projects where performance matters.	2091	=item * Avoid Glib or POE in large projects where performance matters.
1127		2092
1128	=back	2093	=back
1129		2094
…		…
1158	speed most when you have lots of watchers, not when you only have a few of	2123	speed most when you have lots of watchers, not when you only have a few of
1159	them).	2124	them).
1160		2125
1161	EV is again fastest.	2126	EV is again fastest.
1162		2127
1163	The C-based event loops Event and Glib come in second this time, as the	2128	Perl again comes second. It is noticeably faster than the C-based event
1164	overhead of running an iteration is much smaller in C than in Perl (little	2129	loops Event and Glib, although the difference is too small to really
1165	code to execute in the inner loop, and perl's function calling overhead is	2130	matter.
1166	high, and updating all the data structures is costly).
1167
1168	The pure perl event loop is much slower, but still competitive.
1169		2131
1170	POE also performs much better in this case, but is is still far behind the	2132	POE also performs much better in this case, but is is still far behind the
1171	others.	2133	others.
1172		2134
1173	=head3 Summary	2135	=head3 Summary
…		…
1177	=item * C-based event loops perform very well with small number of	2139	=item * C-based event loops perform very well with small number of
1178	watchers, as the management overhead dominates.	2140	watchers, as the management overhead dominates.
1179		2141
1180	=back	2142	=back
1181		2143
		2144	=head2 THE IO::Lambda BENCHMARK
		2145
		2146	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2147	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2148	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2149	shouldn't come as a surprise to anybody). As such, the benchmark is
		2150	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2151	very optimal. But how would AnyEvent compare when used without the extra
		2152	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2153
		2154	The benchmark itself creates an echo-server, and then, for 500 times,
		2155	connects to the echo server, sends a line, waits for the reply, and then
		2156	creates the next connection. This is a rather bad benchmark, as it doesn't
		2157	test the efficiency of the framework or much non-blocking I/O, but it is a
		2158	benchmark nevertheless.
		2159
		2160	name runtime
		2161	Lambda/select 0.330 sec
		2162	+ optimized 0.122 sec
		2163	Lambda/AnyEvent 0.327 sec
		2164	+ optimized 0.138 sec
		2165	Raw sockets/select 0.077 sec
		2166	POE/select, components 0.662 sec
		2167	POE/select, raw sockets 0.226 sec
		2168	POE/select, optimized 0.404 sec
		2169
		2170	AnyEvent/select/nb 0.085 sec
		2171	AnyEvent/EV/nb 0.068 sec
		2172	+state machine 0.134 sec
		2173
		2174	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2175	benchmarks actually make blocking connects and use 100% blocking I/O,
		2176	defeating the purpose of an event-based solution. All of the newly
		2177	written AnyEvent benchmarks use 100% non-blocking connects (using
		2178	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2179	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2180	generally require a lot more bookkeeping and event handling than blocking
		2181	connects (which involve a single syscall only).
		2182
		2183	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2184	offers similar expressive power as POE and IO::Lambda, using conventional
		2185	Perl syntax. This means that both the echo server and the client are 100%
		2186	non-blocking, further placing it at a disadvantage.
		2187
		2188	As you can see, the AnyEvent + EV combination even beats the
		2189	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2190	backend easily beats IO::Lambda and POE.
		2191
		2192	And even the 100% non-blocking version written using the high-level (and
		2193	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2194	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2195	in a non-blocking way.
		2196
		2197	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2198	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2199	part of the IO::lambda distribution and were used without any changes.
		2200
		2201
		2202	=head1 SIGNALS
		2203
		2204	AnyEvent currently installs handlers for these signals:
		2205
		2206	=over 4
		2207
		2208	=item SIGCHLD
		2209
		2210	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2211	emulation for event loops that do not support them natively. Also, some
		2212	event loops install a similar handler.
		2213
		2214	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2215	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2216
		2217	=item SIGPIPE
		2218
		2219	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2220	when AnyEvent gets loaded.
		2221
		2222	The rationale for this is that AnyEvent users usually do not really depend
		2223	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2224	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2225	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2226	some random socket.
		2227
		2228	The rationale for installing a no-op handler as opposed to ignoring it is
		2229	that this way, the handler will be restored to defaults on exec.
		2230
		2231	Feel free to install your own handler, or reset it to defaults.
		2232
		2233	=back
		2234
		2235	=cut
		2236
		2237	undef $SIG{CHLD}
		2238	if $SIG{CHLD} eq 'IGNORE';
		2239
		2240	$SIG{PIPE} = sub { }
		2241	unless defined $SIG{PIPE};
		2242
		2243	=head1 RECOMMENDED/OPTIONAL MODULES
		2244
		2245	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2246	it's built-in modules) are required to use it.
		2247
		2248	That does not mean that AnyEvent won't take advantage of some additional
		2249	modules if they are installed.
		2250
		2251	This section epxlains which additional modules will be used, and how they
		2252	affect AnyEvent's operetion.
		2253
		2254	=over 4
		2255
		2256	=item L<Async::Interrupt>
		2257
		2258	This slightly arcane module is used to implement fast signal handling: To
		2259	my knowledge, there is no way to do completely race-free and quick
		2260	signal handling in pure perl. To ensure that signals still get
		2261	delivered, AnyEvent will start an interval timer to wake up perl (and
		2262	catch the signals) with soemd elay (default is 10 seconds, look for
		2263	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2264
		2265	If this module is available, then it will be used to implement signal
		2266	catching, which means that signals will not be delayed, and the event loop
		2267	will not be interrupted regularly, which is more efficient (And good for
		2268	battery life on laptops).
		2269
		2270	This affects not just the pure-perl event loop, but also other event loops
		2271	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2272
		2273	=item L<EV>
		2274
		2275	This module isn't really "optional", as it is simply one of the backend
		2276	event loops that AnyEvent can use. However, it is simply the best event
		2277	loop available in terms of features, speed and stability: It supports
		2278	the AnyEvent API optimally, implements all the watcher types in XS, does
		2279	automatic timer adjustments even when no monotonic clock is available,
		2280	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2281	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2282	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2283
		2284	=item L<Guard>
		2285
		2286	The guard module, when used, will be used to implement
		2287	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2288	lot less memory), but otherwise doesn't affect guard operation much. It is
		2289	purely used for performance.
		2290
		2291	=item L<JSON> and L<JSON::XS>
		2292
		2293	This module is required when you want to read or write JSON data via
		2294	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2295	advantage of the ulta-high-speed L<JSON::XS> module when it is installed.
		2296
		2297	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2298	installed.
		2299
		2300	=item L<Net::SSLeay>
		2301
		2302	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2303	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2304	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2305
		2306	=item L<Time::HiRes>
		2307
		2308	This module is part of perl since release 5.008. It will be used when the
		2309	chosen event library does not come with a timing source on it's own. The
		2310	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2311	try to use a monotonic clock for timing stability.
		2312
		2313	=back
		2314
1182		2315
1183	=head1 FORK	2316	=head1 FORK
1184		2317
1185	Most event libraries are not fork-safe. The ones who are usually are	2318	Most event libraries are not fork-safe. The ones who are usually are
1186	because they are so inefficient. Only L<EV> is fully fork-aware.	2319	because they rely on inefficient but fork-safe C<select> or C<poll>
		2320	calls. Only L<EV> is fully fork-aware.
1187		2321
1188	If you have to fork, you must either do so I<before> creating your first	2322	If you have to fork, you must either do so I<before> creating your first
1189	watcher OR you must not use AnyEvent at all in the child.	2323	watcher OR you must not use AnyEvent at all in the child OR you must do
		2324	something completely out of the scope of AnyEvent.
1190		2325
1191		2326
1192	=head1 SECURITY CONSIDERATIONS	2327	=head1 SECURITY CONSIDERATIONS
1193		2328
1194	AnyEvent can be forced to load any event model via	2329	AnyEvent can be forced to load any event model via
…		…
1199	specified in the variable.	2334	specified in the variable.
1200		2335
1201	You can make AnyEvent completely ignore this variable by deleting it	2336	You can make AnyEvent completely ignore this variable by deleting it
1202	before the first watcher gets created, e.g. with a C<BEGIN> block:	2337	before the first watcher gets created, e.g. with a C<BEGIN> block:
1203		2338
1204	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2339	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1205		2340
1206	use AnyEvent;	2341	use AnyEvent;
		2342
		2343	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2344	be used to probe what backend is used and gain other information (which is
		2345	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2346	$ENV{PERL_ANYEVENT_STRICT}.
		2347
		2348	Note that AnyEvent will remove I<all> environment variables starting with
		2349	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2350	enabled.
		2351
		2352
		2353	=head1 BUGS
		2354
		2355	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2356	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2357	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2358	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2359	pronounced).
1207		2360
1208		2361
1209	=head1 SEE ALSO	2362	=head1 SEE ALSO
1210		2363
1211	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2364	Utility functions: L<AnyEvent::Util>.
1212	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	2365
		2366	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1213	L<Event::Lib>, L<Qt>, L<POE>.	2367	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1214		2368
1215	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2369	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1216	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2370	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1217	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	2371	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1218	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	2372	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>.
1219		2373
		2374	Non-blocking file handles, sockets, TCP clients and
		2375	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2376
		2377	Asynchronous DNS: L<AnyEvent::DNS>.
		2378
		2379	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2380	L<Coro::Event>,
		2381
1220	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2382	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2383	L<AnyEvent::HTTP>.
1221		2384
1222		2385
1223	=head1 AUTHOR	2386	=head1 AUTHOR
1224		2387
1225	Marc Lehmann <schmorp@schmorp.de>	2388	Marc Lehmann <schmorp@schmorp.de>
1226	http://home.schmorp.de/	2389	http://home.schmorp.de/
1227		2390
1228	=cut	2391	=cut
1229		2392
1230	1	2393	1
1231		2394

Diff Legend

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