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Revision 1.100 by elmex, Sun Apr 27 19:15:43 2008 UTC vs.
Revision 1.231 by root, Wed Jul 8 13:46:46 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.
269		367
270	This watcher might use C<%SIG>, so programs overwriting those signals	368	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
277	=head2 CHILD PROCESS WATCHERS	375	=head2 CHILD PROCESS WATCHERS
278		376
279	You can also watch on a child process exit and catch its exit status.	377	You can also watch on a child process exit and catch its exit status.
280		378
281	The child process is specified by the C<pid> argument (if set to C<0>, it	379	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	380	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	381	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	382	any trace events (stopped/continued).
285	and exit status (as returned by waitpid), so unlike other watcher types,	383
286	you I<can> rely on child watcher callback arguments.	384	The callback will be called with the pid and exit status (as returned by
		385	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		386	callback arguments.
		387
		388	This watcher type works by installing a signal handler for C<SIGCHLD>,
		389	and since it cannot be shared, nothing else should use SIGCHLD or reap
		390	random child processes (waiting for specific child processes, e.g. inside
		391	C<system>, is just fine).
287		392
288	There is a slight catch to child watchers, however: you usually start them	393	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	394	I<after> the child process was created, and this means the process could
290	have exited already (and no SIGCHLD will be sent anymore).	395	have exited already (and no SIGCHLD will be sent anymore).
291		396
292	Not all event models handle this correctly (POE doesn't), but even for	397	Not all event models handle this correctly (neither POE nor IO::Async do,
		398	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	399	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).	400	the process exits (i.e. before you fork in the first place). AnyEvent's
		401	pure perl event loop handles all cases correctly regardless of when you
		402	start the watcher.
295		403
296	This means you cannot create a child watcher as the very first thing in an	404	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	405	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>).	406	watcher before you C<fork> the child (alternatively, you can call
		407	C<AnyEvent::detect>).
299		408
300	Example: fork a process and wait for it	409	Example: fork a process and wait for it
301		410
302	my $done = AnyEvent->condvar;	411	my $done = AnyEvent->condvar;
303		412
304	AnyEvent::detect; # force event module to be initialised
305
306	my $pid = fork or exit 5;	413	my $pid = fork or exit 5;
307		414
308	my $w = AnyEvent->child (	415	my $w = AnyEvent->child (
309	pid => $pid,	416	pid => $pid,
310	cb => sub {	417	cb => sub {
311	my ($pid, $status) = @_;	418	my ($pid, $status) = @_;
312	warn "pid $pid exited with status $status";	419	warn "pid $pid exited with status $status";
313	$done->broadcast;	420	$done->send;
314	},	421	},
315	);	422	);
316		423
317	# do something else, then wait for process exit	424	# do something else, then wait for process exit
318	$done->wait;	425	$done->recv;
		426
		427	=head2 IDLE WATCHERS
		428
		429	Sometimes there is a need to do something, but it is not so important
		430	to do it instantly, but only when there is nothing better to do. This
		431	"nothing better to do" is usually defined to be "no other events need
		432	attention by the event loop".
		433
		434	Idle watchers ideally get invoked when the event loop has nothing
		435	better to do, just before it would block the process to wait for new
		436	events. Instead of blocking, the idle watcher is invoked.
		437
		438	Most event loops unfortunately do not really support idle watchers (only
		439	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		440	will simply call the callback "from time to time".
		441
		442	Example: read lines from STDIN, but only process them when the
		443	program is otherwise idle:
		444
		445	my @lines; # read data
		446	my $idle_w;
		447	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		448	push @lines, scalar <STDIN>;
		449
		450	# start an idle watcher, if not already done
		451	$idle_w ||= AnyEvent->idle (cb => sub {
		452	# handle only one line, when there are lines left
		453	if (my $line = shift @lines) {
		454	print "handled when idle: $line";
		455	} else {
		456	# otherwise disable the idle watcher again
		457	undef $idle_w;
		458	}
		459	});
		460	});
319		461
320	=head2 CONDITION VARIABLES	462	=head2 CONDITION VARIABLES
321		463
		464	If you are familiar with some event loops you will know that all of them
		465	require you to run some blocking "loop", "run" or similar function that
		466	will actively watch for new events and call your callbacks.
		467
		468	AnyEvent is different, it expects somebody else to run the event loop and
		469	will only block when necessary (usually when told by the user).
		470
		471	The instrument to do that is called a "condition variable", so called
		472	because they represent a condition that must become true.
		473
322	Condition variables can be created by calling the C<< AnyEvent->condvar >>	474	Condition variables can be created by calling the C<< AnyEvent->condvar
323	method without any arguments.	475	>> method, usually without arguments. The only argument pair allowed is
324		476
325	A condition variable waits for a condition - precisely that the C<<	477	C<cb>, which specifies a callback to be called when the condition variable
326	->broadcast >> method has been called.	478	becomes true, with the condition variable as the first argument (but not
		479	the results).
327		480
328	They are very useful to signal that a condition has been fulfilled, for	481	After creation, the condition variable is "false" until it becomes "true"
		482	by calling the C<send> method (or calling the condition variable as if it
		483	were a callback, read about the caveats in the description for the C<<
		484	->send >> method).
		485
		486	Condition variables are similar to callbacks, except that you can
		487	optionally wait for them. They can also be called merge points - points
		488	in time where multiple outstanding events have been processed. And yet
		489	another way to call them is transactions - each condition variable can be
		490	used to represent a transaction, which finishes at some point and delivers
		491	a result.
		492
		493	Condition variables are very useful to signal that something has finished,
329	example, if you write a module that does asynchronous http requests,	494	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	495	then a condition variable would be the ideal candidate to signal the
331	availability of results.	496	availability of results. The user can either act when the callback is
		497	called or can synchronously C<< ->recv >> for the results.
332		498
333	You can also use condition variables to block your main program until	499	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	500	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<<	501	could C<< ->recv >> in your main program until the user clicks the Quit
336	->broadcast >> the "quit" event.	502	button of your app, which would C<< ->send >> the "quit" event.
337		503
338	Note that condition variables recurse into the event loop - if you have	504	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	505	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	506	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,	507	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	508	as this asks for trouble.
343		509
344	This object has two methods:	510	Condition variables are represented by hash refs in perl, and the keys
		511	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		512	easy (it is often useful to build your own transaction class on top of
		513	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		514	it's C<new> method in your own C<new> method.
		515
		516	There are two "sides" to a condition variable - the "producer side" which
		517	eventually calls C<< -> send >>, and the "consumer side", which waits
		518	for the send to occur.
		519
		520	Example: wait for a timer.
		521
		522	# wait till the result is ready
		523	my $result_ready = AnyEvent->condvar;
		524
		525	# do something such as adding a timer
		526	# or socket watcher the calls $result_ready->send
		527	# when the "result" is ready.
		528	# in this case, we simply use a timer:
		529	my $w = AnyEvent->timer (
		530	after => 1,
		531	cb => sub { $result_ready->send },
		532	);
		533
		534	# this "blocks" (while handling events) till the callback
		535	# calls send
		536	$result_ready->recv;
		537
		538	Example: wait for a timer, but take advantage of the fact that
		539	condition variables are also code references.
		540
		541	my $done = AnyEvent->condvar;
		542	my $delay = AnyEvent->timer (after => 5, cb => $done);
		543	$done->recv;
		544
		545	Example: Imagine an API that returns a condvar and doesn't support
		546	callbacks. This is how you make a synchronous call, for example from
		547	the main program:
		548
		549	use AnyEvent::CouchDB;
		550
		551	...
		552
		553	my @info = $couchdb->info->recv;
		554
		555	And this is how you would just ste a callback to be called whenever the
		556	results are available:
		557
		558	$couchdb->info->cb (sub {
		559	my @info = $_[0]->recv;
		560	});
		561
		562	=head3 METHODS FOR PRODUCERS
		563
		564	These methods should only be used by the producing side, i.e. the
		565	code/module that eventually sends the signal. Note that it is also
		566	the producer side which creates the condvar in most cases, but it isn't
		567	uncommon for the consumer to create it as well.
345		568
346	=over 4	569	=over 4
347		570
		571	=item $cv->send (...)
		572
		573	Flag the condition as ready - a running C<< ->recv >> and all further
		574	calls to C<recv> will (eventually) return after this method has been
		575	called. If nobody is waiting the send will be remembered.
		576
		577	If a callback has been set on the condition variable, it is called
		578	immediately from within send.
		579
		580	Any arguments passed to the C<send> call will be returned by all
		581	future C<< ->recv >> calls.
		582
		583	Condition variables are overloaded so one can call them directly
		584	(as a code reference). Calling them directly is the same as calling
		585	C<send>. Note, however, that many C-based event loops do not handle
		586	overloading, so as tempting as it may be, passing a condition variable
		587	instead of a callback does not work. Both the pure perl and EV loops
		588	support overloading, however, as well as all functions that use perl to
		589	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		590	example).
		591
		592	=item $cv->croak ($error)
		593
		594	Similar to send, but causes all call's to C<< ->recv >> to invoke
		595	C<Carp::croak> with the given error message/object/scalar.
		596
		597	This can be used to signal any errors to the condition variable
		598	user/consumer.
		599
		600	=item $cv->begin ([group callback])
		601
348	=item $cv->wait	602	=item $cv->end
349		603
350	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	604	These two methods can be used to combine many transactions/events into
		605	one. For example, a function that pings many hosts in parallel might want
		606	to use a condition variable for the whole process.
		607
		608	Every call to C<< ->begin >> will increment a counter, and every call to
		609	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		610	>>, the (last) callback passed to C<begin> will be executed. That callback
		611	is I<supposed> to call C<< ->send >>, but that is not required. If no
		612	callback was set, C<send> will be called without any arguments.
		613
		614	You can think of C<< $cv->send >> giving you an OR condition (one call
		615	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		616	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		617
		618	Let's start with a simple example: you have two I/O watchers (for example,
		619	STDOUT and STDERR for a program), and you want to wait for both streams to
		620	close before activating a condvar:
		621
		622	my $cv = AnyEvent->condvar;
		623
		624	$cv->begin; # first watcher
		625	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		626	defined sysread $fh1, my $buf, 4096
		627	or $cv->end;
		628	});
		629
		630	$cv->begin; # second watcher
		631	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		632	defined sysread $fh2, my $buf, 4096
		633	or $cv->end;
		634	});
		635
		636	$cv->recv;
		637
		638	This works because for every event source (EOF on file handle), there is
		639	one call to C<begin>, so the condvar waits for all calls to C<end> before
		640	sending.
		641
		642	The ping example mentioned above is slightly more complicated, as the
		643	there are results to be passwd back, and the number of tasks that are
		644	begung can potentially be zero:
		645
		646	my $cv = AnyEvent->condvar;
		647
		648	my %result;
		649	$cv->begin (sub { $cv->send (\%result) });
		650
		651	for my $host (@list_of_hosts) {
		652	$cv->begin;
		653	ping_host_then_call_callback $host, sub {
		654	$result{$host} = ...;
		655	$cv->end;
		656	};
		657	}
		658
		659	$cv->end;
		660
		661	This code fragment supposedly pings a number of hosts and calls
		662	C<send> after results for all then have have been gathered - in any
		663	order. To achieve this, the code issues a call to C<begin> when it starts
		664	each ping request and calls C<end> when it has received some result for
		665	it. Since C<begin> and C<end> only maintain a counter, the order in which
		666	results arrive is not relevant.
		667
		668	There is an additional bracketing call to C<begin> and C<end> outside the
		669	loop, which serves two important purposes: first, it sets the callback
		670	to be called once the counter reaches C<0>, and second, it ensures that
		671	C<send> is called even when C<no> hosts are being pinged (the loop
		672	doesn't execute once).
		673
		674	This is the general pattern when you "fan out" into multiple (but
		675	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		676	the callback and ensure C<end> is called at least once, and then, for each
		677	subrequest you start, call C<begin> and for each subrequest you finish,
		678	call C<end>.
		679
		680	=back
		681
		682	=head3 METHODS FOR CONSUMERS
		683
		684	These methods should only be used by the consuming side, i.e. the
		685	code awaits the condition.
		686
		687	=over 4
		688
		689	=item $cv->recv
		690
		691	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
351	called on c<$cv>, while servicing other watchers normally.	692	>> methods have been called on c<$cv>, while servicing other watchers
		693	normally.
352		694
353	You can only wait once on a condition - additional calls will return	695	You can only wait once on a condition - additional calls are valid but
354	immediately.	696	will return immediately.
		697
		698	If an error condition has been set by calling C<< ->croak >>, then this
		699	function will call C<croak>.
		700
		701	In list context, all parameters passed to C<send> will be returned,
		702	in scalar context only the first one will be returned.
355		703
356	Not all event models support a blocking wait - some die in that case	704	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	705	(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	706	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	707	caller decide whether the call will block or not (for example, by coupling
360	condition variables with some kind of request results and supporting	708	condition variables with some kind of request results and supporting
361	callbacks so the caller knows that getting the result will not block,	709	callbacks so the caller knows that getting the result will not block,
362	while still suppporting blocking waits if the caller so desires).	710	while still supporting blocking waits if the caller so desires).
363		711
364	Another reason I<never> to C<< ->wait >> in a module is that you cannot	712	Another reason I<never> to C<< ->recv >> in a module is that you cannot
365	sensibly have two C<< ->wait >>'s in parallel, as that would require	713	sensibly have two C<< ->recv >>'s in parallel, as that would require
366	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	714	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
367	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	715	can supply.
368	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
369	from different coroutines, however).
370		716
371	=item $cv->broadcast	717	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		718	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		719	versions and also integrates coroutines into AnyEvent, making blocking
		720	C<< ->recv >> calls perfectly safe as long as they are done from another
		721	coroutine (one that doesn't run the event loop).
372		722
373	Flag the condition as ready - a running C<< ->wait >> and all further	723	You can ensure that C<< -recv >> never blocks by setting a callback and
374	calls to C<wait> will (eventually) return after this method has been	724	only calling C<< ->recv >> from within that callback (or at a later
375	called. If nobody is waiting the broadcast will be remembered..	725	time). This will work even when the event loop does not support blocking
		726	waits otherwise.
		727
		728	=item $bool = $cv->ready
		729
		730	Returns true when the condition is "true", i.e. whether C<send> or
		731	C<croak> have been called.
		732
		733	=item $cb = $cv->cb ($cb->($cv))
		734
		735	This is a mutator function that returns the callback set and optionally
		736	replaces it before doing so.
		737
		738	The callback will be called when the condition becomes "true", i.e. when
		739	C<send> or C<croak> are called, with the only argument being the condition
		740	variable itself. Calling C<recv> inside the callback or at any later time
		741	is guaranteed not to block.
376		742
377	=back	743	=back
378
379	Example:
380
381	# wait till the result is ready
382	my $result_ready = AnyEvent->condvar;
383
384	# do something such as adding a timer
385	# or socket watcher the calls $result_ready->broadcast
386	# when the "result" is ready.
387	# in this case, we simply use a timer:
388	my $w = AnyEvent->timer (
389	after => 1,
390	cb => sub { $result_ready->broadcast },
391	);
392
393	# this "blocks" (while handling events) till the watcher
394	# calls broadcast
395	$result_ready->wait;
396		744
397	=head1 GLOBAL VARIABLES AND FUNCTIONS	745	=head1 GLOBAL VARIABLES AND FUNCTIONS
398		746
399	=over 4	747	=over 4
400		748
…		…
406	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	754	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
407	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	755	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
408		756
409	The known classes so far are:	757	The known classes so far are:
410		758
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).	759	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
414	AnyEvent::Impl::Event based on Event, second best choice.	760	AnyEvent::Impl::Event based on Event, second best choice.
		761	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
415	AnyEvent::Impl::Glib based on Glib, third-best choice.	762	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.	763	AnyEvent::Impl::Tk based on Tk, very bad choice.
418	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	764	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
419	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	765	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
420	AnyEvent::Impl::POE based on POE, not generic enough for full support.	766	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		767
		768	# warning, support for IO::Async is only partial, as it is too broken
		769	# and limited toe ven support the AnyEvent API. See AnyEvent::Impl::Async.
		770	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed (see its docs).
421		771
422	There is no support for WxWidgets, as WxWidgets has no support for	772	There is no support for WxWidgets, as WxWidgets has no support for
423	watching file handles. However, you can use WxWidgets through the	773	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	774	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	775	second, which was considered to be too horrible to even consider for
…		…
434	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	784	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
435	if necessary. You should only call this function right before you would	785	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	786	have created an AnyEvent watcher anyway, that is, as late as possible at
437	runtime.	787	runtime.
438		788
		789	=item $guard = AnyEvent::post_detect { BLOCK }
		790
		791	Arranges for the code block to be executed as soon as the event model is
		792	autodetected (or immediately if this has already happened).
		793
		794	If called in scalar or list context, then it creates and returns an object
		795	that automatically removes the callback again when it is destroyed. See
		796	L<Coro::BDB> for a case where this is useful.
		797
		798	=item @AnyEvent::post_detect
		799
		800	If there are any code references in this array (you can C<push> to it
		801	before or after loading AnyEvent), then they will called directly after
		802	the event loop has been chosen.
		803
		804	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		805	if it contains a true value then the event loop has already been detected,
		806	and the array will be ignored.
		807
		808	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		809
439	=back	810	=back
440		811
441	=head1 WHAT TO DO IN A MODULE	812	=head1 WHAT TO DO IN A MODULE
442		813
443	As a module author, you should C<use AnyEvent> and call AnyEvent methods	814	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
446	Be careful when you create watchers in the module body - AnyEvent will	817	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	818	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	819	by calling AnyEvent in your module body you force the user of your module
449	to load the event module first.	820	to load the event module first.
450		821
451	Never call C<< ->wait >> on a condition variable unless you I<know> that	822	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	823	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	824	because it will stall the whole program, and the whole point of using
454	events is to stay interactive.	825	events is to stay interactive.
455		826
456	It is fine, however, to call C<< ->wait >> when the user of your module	827	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	828	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 >>	829	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).	830	freely, as the user of your module knows what she is doing. always).
460		831
461	=head1 WHAT TO DO IN THE MAIN PROGRAM	832	=head1 WHAT TO DO IN THE MAIN PROGRAM
462		833
463	There will always be a single main program - the only place that should	834	There will always be a single main program - the only place that should
…		…
465		836
466	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	837	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	838	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.	839	decide which implementation to chose if some module relies on it.
469		840
470	If the main program relies on a specific event model. For example, in	841	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	842	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	843	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	844	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	845	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	846	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.	847	might chose the wrong one unless you load the correct one yourself.
477		848
478	You can chose to use a rather inefficient pure-perl implementation by	849	You can chose to use a pure-perl implementation by loading the
479	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	850	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
480	behaviour everywhere, but letting AnyEvent chose is generally better.	851	everywhere, but letting AnyEvent chose the model is generally better.
		852
		853	=head2 MAINLOOP EMULATION
		854
		855	Sometimes (often for short test scripts, or even standalone programs who
		856	only want to use AnyEvent), you do not want to run a specific event loop.
		857
		858	In that case, you can use a condition variable like this:
		859
		860	AnyEvent->condvar->recv;
		861
		862	This has the effect of entering the event loop and looping forever.
		863
		864	Note that usually your program has some exit condition, in which case
		865	it is better to use the "traditional" approach of storing a condition
		866	variable somewhere, waiting for it, and sending it when the program should
		867	exit cleanly.
		868
481		869
482	=head1 OTHER MODULES	870	=head1 OTHER MODULES
483		871
484	L<AnyEvent> itself comes with useful utility modules:	872	The following is a non-exhaustive list of additional modules that use
485		873	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
486	To make it easier to do non-blocking IO the modules L<AnyEvent::Handle>	874	modules and other event loops in the same program. Some of the modules
487	and L<AnyEvent::Socket> are provided. L<AnyEvent::Handle> provides	875	come with AnyEvent, most are available via CPAN.
488	read and write buffers and manages watchers for reads and writes.
489	L<AnyEvent::Socket> provides means to do non-blocking connects.
490
491	Aside from those there are these modules that support AnyEvent (and use it
492	for non-blocking IO):
493		876
494	=over 4	877	=over 4
495		878
		879	=item L<AnyEvent::Util>
		880
		881	Contains various utility functions that replace often-used but blocking
		882	functions such as C<inet_aton> by event-/callback-based versions.
		883
		884	=item L<AnyEvent::Socket>
		885
		886	Provides various utility functions for (internet protocol) sockets,
		887	addresses and name resolution. Also functions to create non-blocking tcp
		888	connections or tcp servers, with IPv6 and SRV record support and more.
		889
		890	=item L<AnyEvent::Handle>
		891
		892	Provide read and write buffers, manages watchers for reads and writes,
		893	supports raw and formatted I/O, I/O queued and fully transparent and
		894	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		895
		896	=item L<AnyEvent::DNS>
		897
		898	Provides rich asynchronous DNS resolver capabilities.
		899
		900	=item L<AnyEvent::HTTP>
		901
		902	A simple-to-use HTTP library that is capable of making a lot of concurrent
		903	HTTP requests.
		904
		905	=item L<AnyEvent::HTTPD>
		906
		907	Provides a simple web application server framework.
		908
496	=item L<AnyEvent::FastPing>	909	=item L<AnyEvent::FastPing>
497		910
		911	The fastest ping in the west.
		912
		913	=item L<AnyEvent::DBI>
		914
		915	Executes L<DBI> requests asynchronously in a proxy process.
		916
		917	=item L<AnyEvent::AIO>
		918
		919	Truly asynchronous I/O, should be in the toolbox of every event
		920	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		921	together.
		922
		923	=item L<AnyEvent::BDB>
		924
		925	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		926	L<BDB> and AnyEvent together.
		927
		928	=item L<AnyEvent::GPSD>
		929
		930	A non-blocking interface to gpsd, a daemon delivering GPS information.
		931
		932	=item L<AnyEvent::IRC>
		933
		934	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		935
		936	=item L<AnyEvent::XMPP>
		937
		938	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		939	Net::XMPP2>.
		940
		941	=item L<AnyEvent::IGS>
		942
		943	A non-blocking interface to the Internet Go Server protocol (used by
		944	L<App::IGS>).
		945
498	=item L<Net::IRC3>	946	=item L<Net::FCP>
499		947
500	=item L<Net::XMPP2>	948	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		949	of AnyEvent.
		950
		951	=item L<Event::ExecFlow>
		952
		953	High level API for event-based execution flow control.
		954
		955	=item L<Coro>
		956
		957	Has special support for AnyEvent via L<Coro::AnyEvent>.
501		958
502	=back	959	=back
503		960
504	=cut	961	=cut
505		962
506	package AnyEvent;	963	package AnyEvent;
507		964
508	no warnings;	965	no warnings;
509	use strict;	966	use strict qw(vars subs);
510		967
511	use Carp;	968	use Carp;
512		969
513	our $VERSION = '3.3';	970	our $VERSION = 4.801;
514	our $MODEL;	971	our $MODEL;
515		972
516	our $AUTOLOAD;	973	our $AUTOLOAD;
517	our @ISA;	974	our @ISA;
518		975
		976	our @REGISTRY;
		977
		978	our $WIN32;
		979
		980	BEGIN {
		981	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		982	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		983
		984	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		985	if ${^TAINT};
		986	}
		987
519	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	988	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
520		989
521	our @REGISTRY;	990	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		991
		992	{
		993	my $idx;
		994	$PROTOCOL{$_} = ++$idx
		995	for reverse split /\s*,\s*/,
		996	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		997	}
522		998
523	my @models = (	999	my @models = (
524	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
525	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
526	[EV:: => AnyEvent::Impl::EV::],	1000	[EV:: => AnyEvent::Impl::EV::],
527	[Event:: => AnyEvent::Impl::Event::],	1001	[Event:: => AnyEvent::Impl::Event::],
528	[Glib:: => AnyEvent::Impl::Glib::],
529	[Tk:: => AnyEvent::Impl::Tk::],
530	[Wx:: => AnyEvent::Impl::POE::],
531	[Prima:: => AnyEvent::Impl::POE::],
532	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1002	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
533	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1003	# everything below here will not be autoprobed
		1004	# as the pureperl backend should work everywhere
		1005	# and is usually faster
		1006	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1007	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
534	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1008	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
535	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1009	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
536	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1010	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		1011	[Wx:: => AnyEvent::Impl::POE::],
		1012	[Prima:: => AnyEvent::Impl::POE::],
		1013	# IO::Async is just too broken - we would need workaorunds for its
		1014	# byzantine signal and broken child handling, among others.
		1015	# IO::Async is rather hard to detect, as it doesn't have any
		1016	# obvious default class.
		1017	# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1018	# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1019	# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
537	);	1020	);
538		1021
539	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1022	our %method = map +($_ => 1),
		1023	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1024
		1025	our @post_detect;
		1026
		1027	sub post_detect(&) {
		1028	my ($cb) = @_;
		1029
		1030	if ($MODEL) {
		1031	$cb->();
		1032
		1033	1
		1034	} else {
		1035	push @post_detect, $cb;
		1036
		1037	defined wantarray
		1038	? bless \$cb, "AnyEvent::Util::postdetect"
		1039	: ()
		1040	}
		1041	}
		1042
		1043	sub AnyEvent::Util::postdetect::DESTROY {
		1044	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1045	}
540		1046
541	sub detect() {	1047	sub detect() {
542	unless ($MODEL) {	1048	unless ($MODEL) {
543	no strict 'refs';	1049	no strict 'refs';
		1050	local $SIG{__DIE__};
544		1051
545	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1052	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
546	my $model = "AnyEvent::Impl::$1";	1053	my $model = "AnyEvent::Impl::$1";
547	if (eval "require $model") {	1054	if (eval "require $model") {
548	$MODEL = $model;	1055	$MODEL = $model;
…		…
578	last;	1085	last;
579	}	1086	}
580	}	1087	}
581		1088
582	$MODEL	1089	$MODEL
583	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1090	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
584	}	1091	}
585	}	1092	}
586		1093
		1094	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1095
587	unshift @ISA, $MODEL;	1096	unshift @ISA, $MODEL;
588	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1097
		1098	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1099
		1100	(shift @post_detect)->() while @post_detect;
589	}	1101	}
590		1102
591	$MODEL	1103	$MODEL
592	}	1104	}
593		1105
…		…
601		1113
602	my $class = shift;	1114	my $class = shift;
603	$class->$func (@_);	1115	$class->$func (@_);
604	}	1116	}
605		1117
		1118	# utility function to dup a filehandle. this is used by many backends
		1119	# to support binding more than one watcher per filehandle (they usually
		1120	# allow only one watcher per fd, so we dup it to get a different one).
		1121	sub _dupfh($$;$$) {
		1122	my ($poll, $fh, $r, $w) = @_;
		1123
		1124	# cygwin requires the fh mode to be matching, unix doesn't
		1125	my ($rw, $mode) = $poll eq "r" ? ($r, "<") : ($w, ">");
		1126
		1127	open my $fh2, "$mode&", $fh
		1128	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1129
		1130	# we assume CLOEXEC is already set by perl in all important cases
		1131
		1132	($fh2, $rw)
		1133	}
		1134
606	package AnyEvent::Base;	1135	package AnyEvent::Base;
607		1136
		1137	# default implementations for many methods
		1138
		1139	BEGIN {
		1140	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1141	*_time = \&Time::HiRes::time;
		1142	# if (eval "use POSIX (); (POSIX::times())...
		1143	} else {
		1144	*_time = sub { time }; # epic fail
		1145	}
		1146	}
		1147
		1148	sub time { _time }
		1149	sub now { _time }
		1150	sub now_update { }
		1151
608	# default implementation for ->condvar, ->wait, ->broadcast	1152	# default implementation for ->condvar
609		1153
610	sub condvar {	1154	sub condvar {
611	bless \my $flag, "AnyEvent::Base::CondVar"	1155	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
612	}
613
614	sub AnyEvent::Base::CondVar::broadcast {
615	${$_[0]}++;
616	}
617
618	sub AnyEvent::Base::CondVar::wait {
619	AnyEvent->one_event while !${$_[0]};
620	}	1156	}
621		1157
622	# default implementation for ->signal	1158	# default implementation for ->signal
623		1159
624	our %SIG_CB;	1160	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1161
		1162	sub _signal_exec {
		1163	sysread $SIGPIPE_R, my $dummy, 4;
		1164
		1165	while (%SIG_EV) {
		1166	for (keys %SIG_EV) {
		1167	delete $SIG_EV{$_};
		1168	$_->() for values %{ $SIG_CB{$_} || {} };
		1169	}
		1170	}
		1171	}
625		1172
626	sub signal {	1173	sub signal {
627	my (undef, %arg) = @_;	1174	my (undef, %arg) = @_;
628		1175
		1176	unless ($SIGPIPE_R) {
		1177	require Fcntl;
		1178
		1179	if (AnyEvent::WIN32) {
		1180	require AnyEvent::Util;
		1181
		1182	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1183	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1184	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1185	} else {
		1186	pipe $SIGPIPE_R, $SIGPIPE_W;
		1187	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1188	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1189
		1190	# not strictly required, as $^F is normally 2, but let's make sure...
		1191	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1192	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1193	}
		1194
		1195	$SIGPIPE_R
		1196	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1197
		1198	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1199	}
		1200
629	my $signal = uc $arg{signal}	1201	my $signal = uc $arg{signal}
630	or Carp::croak "required option 'signal' is missing";	1202	or Carp::croak "required option 'signal' is missing";
631		1203
632	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1204	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
633	$SIG{$signal} ||= sub {	1205	$SIG{$signal} ||= sub {
634	$_->() for values %{ $SIG_CB{$signal} || {} };	1206	local $!;
		1207	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1208	undef $SIG_EV{$signal};
635	};	1209	};
636		1210
637	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1211	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
638	}	1212	}
639		1213
640	sub AnyEvent::Base::Signal::DESTROY {	1214	sub AnyEvent::Base::signal::DESTROY {
641	my ($signal, $cb) = @{$_[0]};	1215	my ($signal, $cb) = @{$_[0]};
642		1216
643	delete $SIG_CB{$signal}{$cb};	1217	delete $SIG_CB{$signal}{$cb};
644		1218
		1219	# delete doesn't work with older perls - they then
		1220	# print weird messages, or just unconditionally exit
		1221	# instead of getting the default action.
645	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1222	undef $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
646	}	1223	}
647		1224
648	# default implementation for ->child	1225	# default implementation for ->child
649		1226
650	our %PID_CB;	1227	our %PID_CB;
651	our $CHLD_W;	1228	our $CHLD_W;
652	our $CHLD_DELAY_W;	1229	our $CHLD_DELAY_W;
653	our $PID_IDLE;
654	our $WNOHANG;	1230	our $WNOHANG;
655		1231
656	sub _child_wait {	1232	sub _sigchld {
657	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1233	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
658	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1234	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),
659	(values %{ $PID_CB{0} || {} });	1235	(values %{ $PID_CB{0} || {} });
660	}	1236	}
661
662	undef $PID_IDLE;
663	}
664
665	sub _sigchld {
666	# make sure we deliver these changes "synchronous" with the event loop.
667	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
668	undef $CHLD_DELAY_W;
669	&_child_wait;
670	});
671	}	1237	}
672		1238
673	sub child {	1239	sub child {
674	my (undef, %arg) = @_;	1240	my (undef, %arg) = @_;
675		1241
676	defined (my $pid = $arg{pid} + 0)	1242	defined (my $pid = $arg{pid} + 0)
677	or Carp::croak "required option 'pid' is missing";	1243	or Carp::croak "required option 'pid' is missing";
678		1244
679	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1245	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
680		1246
681	unless ($WNOHANG) {
682	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1247	$WNOHANG ||= eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
683	}
684		1248
685	unless ($CHLD_W) {	1249	unless ($CHLD_W) {
686	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1250	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
687	# child could be a zombie already, so make at least one round	1251	# child could be a zombie already, so make at least one round
688	&_sigchld;	1252	&_sigchld;
689	}	1253	}
690		1254
691	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1255	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
692	}	1256	}
693		1257
694	sub AnyEvent::Base::Child::DESTROY {	1258	sub AnyEvent::Base::child::DESTROY {
695	my ($pid, $cb) = @{$_[0]};	1259	my ($pid, $cb) = @{$_[0]};
696		1260
697	delete $PID_CB{$pid}{$cb};	1261	delete $PID_CB{$pid}{$cb};
698	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1262	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
699		1263
700	undef $CHLD_W unless keys %PID_CB;	1264	undef $CHLD_W unless keys %PID_CB;
701	}	1265	}
		1266
		1267	# idle emulation is done by simply using a timer, regardless
		1268	# of whether the process is idle or not, and not letting
		1269	# the callback use more than 50% of the time.
		1270	sub idle {
		1271	my (undef, %arg) = @_;
		1272
		1273	my ($cb, $w, $rcb) = $arg{cb};
		1274
		1275	$rcb = sub {
		1276	if ($cb) {
		1277	$w = _time;
		1278	&$cb;
		1279	$w = _time - $w;
		1280
		1281	# never use more then 50% of the time for the idle watcher,
		1282	# within some limits
		1283	$w = 0.0001 if $w < 0.0001;
		1284	$w = 5 if $w > 5;
		1285
		1286	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1287	} else {
		1288	# clean up...
		1289	undef $w;
		1290	undef $rcb;
		1291	}
		1292	};
		1293
		1294	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1295
		1296	bless \\$cb, "AnyEvent::Base::idle"
		1297	}
		1298
		1299	sub AnyEvent::Base::idle::DESTROY {
		1300	undef $${$_[0]};
		1301	}
		1302
		1303	package AnyEvent::CondVar;
		1304
		1305	our @ISA = AnyEvent::CondVar::Base::;
		1306
		1307	package AnyEvent::CondVar::Base;
		1308
		1309	use overload
		1310	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1311	fallback => 1;
		1312
		1313	sub _send {
		1314	# nop
		1315	}
		1316
		1317	sub send {
		1318	my $cv = shift;
		1319	$cv->{_ae_sent} = [@_];
		1320	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1321	$cv->_send;
		1322	}
		1323
		1324	sub croak {
		1325	$_[0]{_ae_croak} = $_[1];
		1326	$_[0]->send;
		1327	}
		1328
		1329	sub ready {
		1330	$_[0]{_ae_sent}
		1331	}
		1332
		1333	sub _wait {
		1334	AnyEvent->one_event while !$_[0]{_ae_sent};
		1335	}
		1336
		1337	sub recv {
		1338	$_[0]->_wait;
		1339
		1340	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1341	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1342	}
		1343
		1344	sub cb {
		1345	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1346	$_[0]{_ae_cb}
		1347	}
		1348
		1349	sub begin {
		1350	++$_[0]{_ae_counter};
		1351	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1352	}
		1353
		1354	sub end {
		1355	return if --$_[0]{_ae_counter};
		1356	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1357	}
		1358
		1359	# undocumented/compatibility with pre-3.4
		1360	*broadcast = \&send;
		1361	*wait = \&_wait;
		1362
		1363	=head1 ERROR AND EXCEPTION HANDLING
		1364
		1365	In general, AnyEvent does not do any error handling - it relies on the
		1366	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1367	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1368	checking of all AnyEvent methods, however, which is highly useful during
		1369	development.
		1370
		1371	As for exception handling (i.e. runtime errors and exceptions thrown while
		1372	executing a callback), this is not only highly event-loop specific, but
		1373	also not in any way wrapped by this module, as this is the job of the main
		1374	program.
		1375
		1376	The pure perl event loop simply re-throws the exception (usually
		1377	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1378	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1379	so on.
		1380
		1381	=head1 ENVIRONMENT VARIABLES
		1382
		1383	The following environment variables are used by this module or its
		1384	submodules.
		1385
		1386	Note that AnyEvent will remove I<all> environment variables starting with
		1387	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1388	enabled.
		1389
		1390	=over 4
		1391
		1392	=item C<PERL_ANYEVENT_VERBOSE>
		1393
		1394	By default, AnyEvent will be completely silent except in fatal
		1395	conditions. You can set this environment variable to make AnyEvent more
		1396	talkative.
		1397
		1398	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1399	conditions, such as not being able to load the event model specified by
		1400	C<PERL_ANYEVENT_MODEL>.
		1401
		1402	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1403	model it chooses.
		1404
		1405	=item C<PERL_ANYEVENT_STRICT>
		1406
		1407	AnyEvent does not do much argument checking by default, as thorough
		1408	argument checking is very costly. Setting this variable to a true value
		1409	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1410	check the arguments passed to most method calls. If it finds any problems,
		1411	it will croak.
		1412
		1413	In other words, enables "strict" mode.
		1414
		1415	Unlike C<use strict>, it is definitely recommended to keep it off in
		1416	production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
		1417	developing programs can be very useful, however.
		1418
		1419	=item C<PERL_ANYEVENT_MODEL>
		1420
		1421	This can be used to specify the event model to be used by AnyEvent, before
		1422	auto detection and -probing kicks in. It must be a string consisting
		1423	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1424	and the resulting module name is loaded and if the load was successful,
		1425	used as event model. If it fails to load AnyEvent will proceed with
		1426	auto detection and -probing.
		1427
		1428	This functionality might change in future versions.
		1429
		1430	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1431	could start your program like this:
		1432
		1433	PERL_ANYEVENT_MODEL=Perl perl ...
		1434
		1435	=item C<PERL_ANYEVENT_PROTOCOLS>
		1436
		1437	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1438	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1439	of auto probing).
		1440
		1441	Must be set to a comma-separated list of protocols or address families,
		1442	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1443	used, and preference will be given to protocols mentioned earlier in the
		1444	list.
		1445
		1446	This variable can effectively be used for denial-of-service attacks
		1447	against local programs (e.g. when setuid), although the impact is likely
		1448	small, as the program has to handle conenction and other failures anyways.
		1449
		1450	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1451	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1452	- only support IPv4, never try to resolve or contact IPv6
		1453	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1454	IPv6, but prefer IPv6 over IPv4.
		1455
		1456	=item C<PERL_ANYEVENT_EDNS0>
		1457
		1458	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1459	for DNS. This extension is generally useful to reduce DNS traffic, but
		1460	some (broken) firewalls drop such DNS packets, which is why it is off by
		1461	default.
		1462
		1463	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1464	EDNS0 in its DNS requests.
		1465
		1466	=item C<PERL_ANYEVENT_MAX_FORKS>
		1467
		1468	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1469	will create in parallel.
		1470
		1471	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1472
		1473	The default value for the C<max_outstanding> parameter for the default DNS
		1474	resolver - this is the maximum number of parallel DNS requests that are
		1475	sent to the DNS server.
		1476
		1477	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1478
		1479	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1480	configuration) in the default resolver. When set to the empty string, no
		1481	default config will be used.
		1482
		1483	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1484
		1485	When neither C<ca_file> nor C<ca_path> was specified during
		1486	L<AnyEvent::TLS> context creation, and either of these environment
		1487	variables exist, they will be used to specify CA certificate locations
		1488	instead of a system-dependent default.
		1489
		1490	=back
702		1491
703	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1492	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
704		1493
705	This is an advanced topic that you do not normally need to use AnyEvent in	1494	This is an advanced topic that you do not normally need to use AnyEvent in
706	a module. This section is only of use to event loop authors who want to	1495	a module. This section is only of use to event loop authors who want to
…		…
740		1529
741	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1530	I<rxvt-unicode> also cheats a bit by not providing blocking access to
742	condition variables: code blocking while waiting for a condition will	1531	condition variables: code blocking while waiting for a condition will
743	C<die>. This still works with most modules/usages, and blocking calls must	1532	C<die>. This still works with most modules/usages, and blocking calls must
744	not be done in an interactive application, so it makes sense.	1533	not be done in an interactive application, so it makes sense.
745
746	=head1 ENVIRONMENT VARIABLES
747
748	The following environment variables are used by this module:
749
750	=over 4
751
752	=item C<PERL_ANYEVENT_VERBOSE>
753
754	By default, AnyEvent will be completely silent except in fatal
755	conditions. You can set this environment variable to make AnyEvent more
756	talkative.
757
758	When set to C<1> or higher, causes AnyEvent to warn about unexpected
759	conditions, such as not being able to load the event model specified by
760	C<PERL_ANYEVENT_MODEL>.
761
762	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
763	model it chooses.
764
765	=item C<PERL_ANYEVENT_MODEL>
766
767	This can be used to specify the event model to be used by AnyEvent, before
768	autodetection and -probing kicks in. It must be a string consisting
769	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
770	and the resulting module name is loaded and if the load was successful,
771	used as event model. If it fails to load AnyEvent will proceed with
772	autodetection and -probing.
773
774	This functionality might change in future versions.
775
776	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
777	could start your program like this:
778
779	PERL_ANYEVENT_MODEL=Perl perl ...
780
781	=back
782		1534
783	=head1 EXAMPLE PROGRAM	1535	=head1 EXAMPLE PROGRAM
784		1536
785	The following program uses an I/O watcher to read data from STDIN, a timer	1537	The following program uses an I/O watcher to read data from STDIN, a timer
786	to display a message once per second, and a condition variable to quit the	1538	to display a message once per second, and a condition variable to quit the
…		…
795	poll => 'r',	1547	poll => 'r',
796	cb => sub {	1548	cb => sub {
797	warn "io event <$_[0]>\n"; # will always output <r>	1549	warn "io event <$_[0]>\n"; # will always output <r>
798	chomp (my $input = <STDIN>); # read a line	1550	chomp (my $input = <STDIN>); # read a line
799	warn "read: $input\n"; # output what has been read	1551	warn "read: $input\n"; # output what has been read
800	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1552	$cv->send if $input =~ /^q/i; # quit program if /^q/i
801	},	1553	},
802	);	1554	);
803		1555
804	my $time_watcher; # can only be used once	1556	my $time_watcher; # can only be used once
805		1557
…		…
810	});	1562	});
811	}	1563	}
812		1564
813	new_timer; # create first timer	1565	new_timer; # create first timer
814		1566
815	$cv->wait; # wait until user enters /^q/i	1567	$cv->recv; # wait until user enters /^q/i
816		1568
817	=head1 REAL-WORLD EXAMPLE	1569	=head1 REAL-WORLD EXAMPLE
818		1570
819	Consider the L<Net::FCP> module. It features (among others) the following	1571	Consider the L<Net::FCP> module. It features (among others) the following
820	API calls, which are to freenet what HTTP GET requests are to http:	1572	API calls, which are to freenet what HTTP GET requests are to http:
…		…
870	syswrite $txn->{fh}, $txn->{request}	1622	syswrite $txn->{fh}, $txn->{request}
871	or die "connection or write error";	1623	or die "connection or write error";
872	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1624	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
873		1625
874	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1626	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
875	result and signals any possible waiters that the request ahs finished:	1627	result and signals any possible waiters that the request has finished:
876		1628
877	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1629	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
878		1630
879	if (end-of-file or data complete) {	1631	if (end-of-file or data complete) {
880	$txn->{result} = $txn->{buf};	1632	$txn->{result} = $txn->{buf};
881	$txn->{finished}->broadcast;	1633	$txn->{finished}->send;
882	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1634	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
883	}	1635	}
884		1636
885	The C<result> method, finally, just waits for the finished signal (if the	1637	The C<result> method, finally, just waits for the finished signal (if the
886	request was already finished, it doesn't wait, of course, and returns the	1638	request was already finished, it doesn't wait, of course, and returns the
887	data:	1639	data:
888		1640
889	$txn->{finished}->wait;	1641	$txn->{finished}->recv;
890	return $txn->{result};	1642	return $txn->{result};
891		1643
892	The actual code goes further and collects all errors (C<die>s, exceptions)	1644	The actual code goes further and collects all errors (C<die>s, exceptions)
893	that occured during request processing. The C<result> method detects	1645	that occurred during request processing. The C<result> method detects
894	whether an exception as thrown (it is stored inside the $txn object)	1646	whether an exception as thrown (it is stored inside the $txn object)
895	and just throws the exception, which means connection errors and other	1647	and just throws the exception, which means connection errors and other
896	problems get reported tot he code that tries to use the result, not in a	1648	problems get reported tot he code that tries to use the result, not in a
897	random callback.	1649	random callback.
898		1650
…		…
929		1681
930	my $quit = AnyEvent->condvar;	1682	my $quit = AnyEvent->condvar;
931		1683
932	$fcp->txn_client_get ($url)->cb (sub {	1684	$fcp->txn_client_get ($url)->cb (sub {
933	...	1685	...
934	$quit->broadcast;	1686	$quit->send;
935	});	1687	});
936		1688
937	$quit->wait;	1689	$quit->recv;
938		1690
939		1691
940	=head1 BENCHMARKS	1692	=head1 BENCHMARKS
941		1693
942	To give you an idea of the performance and overheads that AnyEvent adds	1694	To give you an idea of the performance and overheads that AnyEvent adds
…		…
944	of various event loops I prepared some benchmarks.	1696	of various event loops I prepared some benchmarks.
945		1697
946	=head2 BENCHMARKING ANYEVENT OVERHEAD	1698	=head2 BENCHMARKING ANYEVENT OVERHEAD
947		1699
948	Here is a benchmark of various supported event models used natively and	1700	Here is a benchmark of various supported event models used natively and
949	through anyevent. The benchmark creates a lot of timers (with a zero	1701	through AnyEvent. The benchmark creates a lot of timers (with a zero
950	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1702	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
951	which it is), lets them fire exactly once and destroys them again.	1703	which it is), lets them fire exactly once and destroys them again.
952		1704
953	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	1705	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
954	distribution.	1706	distribution.
…		…
971	all watchers, to avoid adding memory overhead. That means closure creation	1723	all watchers, to avoid adding memory overhead. That means closure creation
972	and memory usage is not included in the figures.	1724	and memory usage is not included in the figures.
973		1725
974	I<invoke> is the time, in microseconds, used to invoke a simple	1726	I<invoke> is the time, in microseconds, used to invoke a simple
975	callback. The callback simply counts down a Perl variable and after it was	1727	callback. The callback simply counts down a Perl variable and after it was
976	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1728	invoked "watcher" times, it would C<< ->send >> a condvar once to
977	signal the end of this phase.	1729	signal the end of this phase.
978		1730
979	I<destroy> is the time, in microseconds, that it takes to destroy a single	1731	I<destroy> is the time, in microseconds, that it takes to destroy a single
980	watcher.	1732	watcher.
981		1733
982	=head3 Results	1734	=head3 Results
983		1735
984	name watchers bytes create invoke destroy comment	1736	name watchers bytes create invoke destroy comment
985	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1737	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
986	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1738	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
987	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1739	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
988	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1740	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
989	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1741	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
990	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1742	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1743	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1744	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
991	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1745	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
992	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1746	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
993	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1747	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
994	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1748	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
995		1749
996	=head3 Discussion	1750	=head3 Discussion
997		1751
998	The benchmark does I<not> measure scalability of the event loop very	1752	The benchmark does I<not> measure scalability of the event loop very
999	well. For example, a select-based event loop (such as the pure perl one)	1753	well. For example, a select-based event loop (such as the pure perl one)
…		…
1024	performance becomes really bad with lots of file descriptors (and few of	1778	performance becomes really bad with lots of file descriptors (and few of
1025	them active), of course, but this was not subject of this benchmark.	1779	them active), of course, but this was not subject of this benchmark.
1026		1780
1027	The C<Event> module has a relatively high setup and callback invocation	1781	The C<Event> module has a relatively high setup and callback invocation
1028	cost, but overall scores in on the third place.	1782	cost, but overall scores in on the third place.
		1783
		1784	C<IO::Async> performs admirably well, about on par with C<Event>, even
		1785	when using its pure perl backend.
1029		1786
1030	C<Glib>'s memory usage is quite a bit higher, but it features a	1787	C<Glib>'s memory usage is quite a bit higher, but it features a
1031	faster callback invocation and overall ends up in the same class as	1788	faster callback invocation and overall ends up in the same class as
1032	C<Event>. However, Glib scales extremely badly, doubling the number of	1789	C<Event>. However, Glib scales extremely badly, doubling the number of
1033	watchers increases the processing time by more than a factor of four,	1790	watchers increases the processing time by more than a factor of four,
…		…
1041	file descriptor is dup()ed for each watcher. This shows that the dup()	1798	file descriptor is dup()ed for each watcher. This shows that the dup()
1042	employed by some adaptors is not a big performance issue (it does incur a	1799	employed by some adaptors is not a big performance issue (it does incur a
1043	hidden memory cost inside the kernel which is not reflected in the figures	1800	hidden memory cost inside the kernel which is not reflected in the figures
1044	above).	1801	above).
1045		1802
1046	C<POE>, regardless of underlying event loop (whether using its pure	1803	C<POE>, regardless of underlying event loop (whether using its pure perl
1047	perl select-based backend or the Event module, the POE-EV backend	1804	select-based backend or the Event module, the POE-EV backend couldn't
1048	couldn't be tested because it wasn't working) shows abysmal performance	1805	be tested because it wasn't working) shows abysmal performance and
1049	and memory usage: Watchers use almost 30 times as much memory as	1806	memory usage with AnyEvent: Watchers use almost 30 times as much memory
1050	EV watchers, and 10 times as much memory as Event (the high memory	1807	as EV watchers, and 10 times as much memory as Event (the high memory
1051	requirements are caused by requiring a session for each watcher). Watcher	1808	requirements are caused by requiring a session for each watcher). Watcher
1052	invocation speed is almost 900 times slower than with AnyEvent's pure perl	1809	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1810	implementation.
		1811
1053	implementation. The design of the POE adaptor class in AnyEvent can not	1812	The design of the POE adaptor class in AnyEvent can not really account
1054	really account for this, as session creation overhead is small compared	1813	for the performance issues, though, as session creation overhead is
1055	to execution of the state machine, which is coded pretty optimally within	1814	small compared to execution of the state machine, which is coded pretty
1056	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1815	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1816	using multiple sessions is not a good approach, especially regarding
		1817	memory usage, even the author of POE could not come up with a faster
		1818	design).
1057		1819
1058	=head3 Summary	1820	=head3 Summary
1059		1821
1060	=over 4	1822	=over 4
1061		1823
…		…
1072		1834
1073	=back	1835	=back
1074		1836
1075	=head2 BENCHMARKING THE LARGE SERVER CASE	1837	=head2 BENCHMARKING THE LARGE SERVER CASE
1076		1838
1077	This benchmark atcually benchmarks the event loop itself. It works by	1839	This benchmark actually benchmarks the event loop itself. It works by
1078	creating a number of "servers": each server consists of a socketpair, a	1840	creating a number of "servers": each server consists of a socket pair, a
1079	timeout watcher that gets reset on activity (but never fires), and an I/O	1841	timeout watcher that gets reset on activity (but never fires), and an I/O
1080	watcher waiting for input on one side of the socket. Each time the socket	1842	watcher waiting for input on one side of the socket. Each time the socket
1081	watcher reads a byte it will write that byte to a random other "server".	1843	watcher reads a byte it will write that byte to a random other "server".
1082		1844
1083	The effect is that there will be a lot of I/O watchers, only part of which	1845	The effect is that there will be a lot of I/O watchers, only part of which
1084	are active at any one point (so there is a constant number of active	1846	are active at any one point (so there is a constant number of active
1085	fds for each loop iterstaion, but which fds these are is random). The	1847	fds for each loop iteration, but which fds these are is random). The
1086	timeout is reset each time something is read because that reflects how	1848	timeout is reset each time something is read because that reflects how
1087	most timeouts work (and puts extra pressure on the event loops).	1849	most timeouts work (and puts extra pressure on the event loops).
1088		1850
1089	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	1851	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1090	(1%) are active. This mirrors the activity of large servers with many	1852	(1%) are active. This mirrors the activity of large servers with many
1091	connections, most of which are idle at any one point in time.	1853	connections, most of which are idle at any one point in time.
1092		1854
1093	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	1855	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1094	distribution.	1856	distribution.
…		…
1096	=head3 Explanation of the columns	1858	=head3 Explanation of the columns
1097		1859
1098	I<sockets> is the number of sockets, and twice the number of "servers" (as	1860	I<sockets> is the number of sockets, and twice the number of "servers" (as
1099	each server has a read and write socket end).	1861	each server has a read and write socket end).
1100		1862
1101	I<create> is the time it takes to create a socketpair (which is	1863	I<create> is the time it takes to create a socket pair (which is
1102	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	1864	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1103		1865
1104	I<request>, the most important value, is the time it takes to handle a	1866	I<request>, the most important value, is the time it takes to handle a
1105	single "request", that is, reading the token from the pipe and forwarding	1867	single "request", that is, reading the token from the pipe and forwarding
1106	it to another server. This includes deleting the old timeout and creating	1868	it to another server. This includes deleting the old timeout and creating
1107	a new one that moves the timeout into the future.	1869	a new one that moves the timeout into the future.
1108		1870
1109	=head3 Results	1871	=head3 Results
1110		1872
1111	name sockets create request	1873	name sockets create request
1112	EV 20000 69.01 11.16	1874	EV 20000 69.01 11.16
1113	Perl 20000 73.32 35.87	1875	Perl 20000 73.32 35.87
		1876	IOAsync 20000 157.00 98.14 epoll
		1877	IOAsync 20000 159.31 616.06 poll
1114	Event 20000 212.62 257.32	1878	Event 20000 212.62 257.32
1115	Glib 20000 651.16 1896.30	1879	Glib 20000 651.16 1896.30
1116	POE 20000 349.67 12317.24 uses POE::Loop::Event	1880	POE 20000 349.67 12317.24 uses POE::Loop::Event
1117		1881
1118	=head3 Discussion	1882	=head3 Discussion
1119		1883
1120	This benchmark I<does> measure scalability and overall performance of the	1884	This benchmark I<does> measure scalability and overall performance of the
1121	particular event loop.	1885	particular event loop.
…		…
1123	EV is again fastest. Since it is using epoll on my system, the setup time	1887	EV is again fastest. Since it is using epoll on my system, the setup time
1124	is relatively high, though.	1888	is relatively high, though.
1125		1889
1126	Perl surprisingly comes second. It is much faster than the C-based event	1890	Perl surprisingly comes second. It is much faster than the C-based event
1127	loops Event and Glib.	1891	loops Event and Glib.
		1892
		1893	IO::Async performs very well when using its epoll backend, and still quite
		1894	good compared to Glib when using its pure perl backend.
1128		1895
1129	Event suffers from high setup time as well (look at its code and you will	1896	Event suffers from high setup time as well (look at its code and you will
1130	understand why). Callback invocation also has a high overhead compared to	1897	understand why). Callback invocation also has a high overhead compared to
1131	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	1898	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1132	uses select or poll in basically all documented configurations.	1899	uses select or poll in basically all documented configurations.
…		…
1140		1907
1141	=head3 Summary	1908	=head3 Summary
1142		1909
1143	=over 4	1910	=over 4
1144		1911
1145	=item * The pure perl implementation performs extremely well, considering	1912	=item * The pure perl implementation performs extremely well.
1146	that it uses select.
1147		1913
1148	=item * Avoid Glib or POE in large projects where performance matters.	1914	=item * Avoid Glib or POE in large projects where performance matters.
1149		1915
1150	=back	1916	=back
1151		1917
…		…
1180	speed most when you have lots of watchers, not when you only have a few of	1946	speed most when you have lots of watchers, not when you only have a few of
1181	them).	1947	them).
1182		1948
1183	EV is again fastest.	1949	EV is again fastest.
1184		1950
1185	The C-based event loops Event and Glib come in second this time, as the	1951	Perl again comes second. It is noticeably faster than the C-based event
1186	overhead of running an iteration is much smaller in C than in Perl (little	1952	loops Event and Glib, although the difference is too small to really
1187	code to execute in the inner loop, and perl's function calling overhead is	1953	matter.
1188	high, and updating all the data structures is costly).
1189
1190	The pure perl event loop is much slower, but still competitive.
1191		1954
1192	POE also performs much better in this case, but is is still far behind the	1955	POE also performs much better in this case, but is is still far behind the
1193	others.	1956	others.
1194		1957
1195	=head3 Summary	1958	=head3 Summary
…		…
1199	=item * C-based event loops perform very well with small number of	1962	=item * C-based event loops perform very well with small number of
1200	watchers, as the management overhead dominates.	1963	watchers, as the management overhead dominates.
1201		1964
1202	=back	1965	=back
1203		1966
		1967	=head2 THE IO::Lambda BENCHMARK
		1968
		1969	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1970	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		1971	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		1972	shouldn't come as a surprise to anybody). As such, the benchmark is
		1973	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		1974	very optimal. But how would AnyEvent compare when used without the extra
		1975	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		1976
		1977	The benchmark itself creates an echo-server, and then, for 500 times,
		1978	connects to the echo server, sends a line, waits for the reply, and then
		1979	creates the next connection. This is a rather bad benchmark, as it doesn't
		1980	test the efficiency of the framework or much non-blocking I/O, but it is a
		1981	benchmark nevertheless.
		1982
		1983	name runtime
		1984	Lambda/select 0.330 sec
		1985	+ optimized 0.122 sec
		1986	Lambda/AnyEvent 0.327 sec
		1987	+ optimized 0.138 sec
		1988	Raw sockets/select 0.077 sec
		1989	POE/select, components 0.662 sec
		1990	POE/select, raw sockets 0.226 sec
		1991	POE/select, optimized 0.404 sec
		1992
		1993	AnyEvent/select/nb 0.085 sec
		1994	AnyEvent/EV/nb 0.068 sec
		1995	+state machine 0.134 sec
		1996
		1997	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1998	benchmarks actually make blocking connects and use 100% blocking I/O,
		1999	defeating the purpose of an event-based solution. All of the newly
		2000	written AnyEvent benchmarks use 100% non-blocking connects (using
		2001	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2002	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2003	generally require a lot more bookkeeping and event handling than blocking
		2004	connects (which involve a single syscall only).
		2005
		2006	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2007	offers similar expressive power as POE and IO::Lambda, using conventional
		2008	Perl syntax. This means that both the echo server and the client are 100%
		2009	non-blocking, further placing it at a disadvantage.
		2010
		2011	As you can see, the AnyEvent + EV combination even beats the
		2012	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2013	backend easily beats IO::Lambda and POE.
		2014
		2015	And even the 100% non-blocking version written using the high-level (and
		2016	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2017	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2018	in a non-blocking way.
		2019
		2020	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2021	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2022	part of the IO::lambda distribution and were used without any changes.
		2023
		2024
		2025	=head1 SIGNALS
		2026
		2027	AnyEvent currently installs handlers for these signals:
		2028
		2029	=over 4
		2030
		2031	=item SIGCHLD
		2032
		2033	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2034	emulation for event loops that do not support them natively. Also, some
		2035	event loops install a similar handler.
		2036
		2037	If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent will
		2038	reset it to default, to avoid losing child exit statuses.
		2039
		2040	=item SIGPIPE
		2041
		2042	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2043	when AnyEvent gets loaded.
		2044
		2045	The rationale for this is that AnyEvent users usually do not really depend
		2046	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2047	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2048	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2049	some random socket.
		2050
		2051	The rationale for installing a no-op handler as opposed to ignoring it is
		2052	that this way, the handler will be restored to defaults on exec.
		2053
		2054	Feel free to install your own handler, or reset it to defaults.
		2055
		2056	=back
		2057
		2058	=cut
		2059
		2060	undef $SIG{CHLD}
		2061	if $SIG{CHLD} eq 'IGNORE';
		2062
		2063	$SIG{PIPE} = sub { }
		2064	unless defined $SIG{PIPE};
1204		2065
1205	=head1 FORK	2066	=head1 FORK
1206		2067
1207	Most event libraries are not fork-safe. The ones who are usually are	2068	Most event libraries are not fork-safe. The ones who are usually are
1208	because they are so inefficient. Only L<EV> is fully fork-aware.	2069	because they rely on inefficient but fork-safe C<select> or C<poll>
		2070	calls. Only L<EV> is fully fork-aware.
1209		2071
1210	If you have to fork, you must either do so I<before> creating your first	2072	If you have to fork, you must either do so I<before> creating your first
1211	watcher OR you must not use AnyEvent at all in the child.	2073	watcher OR you must not use AnyEvent at all in the child.
1212		2074
1213		2075
…		…
1221	specified in the variable.	2083	specified in the variable.
1222		2084
1223	You can make AnyEvent completely ignore this variable by deleting it	2085	You can make AnyEvent completely ignore this variable by deleting it
1224	before the first watcher gets created, e.g. with a C<BEGIN> block:	2086	before the first watcher gets created, e.g. with a C<BEGIN> block:
1225		2087
1226	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2088	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1227		2089
1228	use AnyEvent;	2090	use AnyEvent;
		2091
		2092	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2093	be used to probe what backend is used and gain other information (which is
		2094	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2095	$ENV{PERL_ANYEVENT_STRICT}.
		2096
		2097	Note that AnyEvent will remove I<all> environment variables starting with
		2098	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2099	enabled.
		2100
		2101
		2102	=head1 BUGS
		2103
		2104	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2105	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2106	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2107	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2108	pronounced).
1229		2109
1230		2110
1231	=head1 SEE ALSO	2111	=head1 SEE ALSO
1232		2112
1233	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2113	Utility functions: L<AnyEvent::Util>.
1234	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	2114
		2115	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1235	L<Event::Lib>, L<Qt>, L<POE>.	2116	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1236		2117
1237	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2118	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1238	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2119	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1239	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	2120	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1240	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	2121	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>.
1241		2122
		2123	Non-blocking file handles, sockets, TCP clients and
		2124	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2125
		2126	Asynchronous DNS: L<AnyEvent::DNS>.
		2127
		2128	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2129	L<Coro::Event>,
		2130
1242	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2131	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2132	L<AnyEvent::HTTP>.
1243		2133
1244		2134
1245	=head1 AUTHOR	2135	=head1 AUTHOR
1246		2136
1247	Marc Lehmann <schmorp@schmorp.de>	2137	Marc Lehmann <schmorp@schmorp.de>
1248	http://home.schmorp.de/	2138	http://home.schmorp.de/
1249		2139
1250	=cut	2140	=cut
1251		2141
1252	1	2142	1
1253		2143

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