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Revision 1.205 by root, Sun Apr 19 12:09:46 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, POE - various supported event loops
6		6
7	=head1 SYNOPSIS	7	=head1 SYNOPSIS
8		8
9	use AnyEvent;	9	use AnyEvent;
10		10
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... });
		12
		13	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		14	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		15
		16	print AnyEvent->now; # prints current event loop time
		17	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		18
		19	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		20
		21	my $w = AnyEvent->child (pid => $pid, cb => sub {
		22	my ($pid, $status) = @_;
12	...	23	...
13	});	24	});
14		25
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {
16	...
17	});
18
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	26	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		27	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	28	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	29	# use a condvar in callback mode:
		30	$w->cb (sub { $_[0]->recv });
		31
		32	=head1 INTRODUCTION/TUTORIAL
		33
		34	This manpage is mainly a reference manual. If you are interested
		35	in a tutorial or some gentle introduction, have a look at the
		36	L<AnyEvent::Intro> manpage.
22		37
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	38	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		39
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	40	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	41	nowadays. So what is different about AnyEvent?
27		42
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	43	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	44	policy> and AnyEvent is I<small and efficient>.
30		45
31	First and foremost, I<AnyEvent is not an event model> itself, it only	46	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	47	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,	48	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,	49	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	50	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	51	cannot change this, but it can hide the differences between those event
		52	loops.
37		53
38	The goal of AnyEvent is to offer module authors the ability to do event	54	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	55	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	56	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	57	module users into the same thing by forcing them to use the same event
42	model you use.	58	model you use.
43		59
44	For modules like POE or IO::Async (which is a total misnomer as it is	60	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	61	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	62	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	63	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	64	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.	65	module are I<also> forced to use the same event loop you use.
50		66
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	67	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	68	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	69	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,	70	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	71	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	72	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	73	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).	74	to AnyEvent, too, so it is future-proof).
59		75
60	In addition to being free of having to use I<the one and only true event	76	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	77	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	78	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	79	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	80	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	81	technically possible.
66		82
		83	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		84	of useful functionality, such as an asynchronous DNS resolver, 100%
		85	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		86	such as Windows) and lots of real-world knowledge and workarounds for
		87	platform bugs and differences.
		88
67	Of course, if you want lots of policy (this can arguably be somewhat	89	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	90	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	91	model, you should I<not> use this module.
70
71		92
72	=head1 DESCRIPTION	93	=head1 DESCRIPTION
73		94
74	L<AnyEvent> provides an identical interface to multiple event loops. This	95	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	96	allows module authors to utilise an event loop without forcing module
…		…
79	The interface itself is vaguely similar, but not identical to the L<Event>	100	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	101	module.
81		102
82	During the first call of any watcher-creation method, the module tries	103	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of the	104	to detect the currently loaded event loop by probing whether one of the
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	105	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	106	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	L<POE>. The first one found is used. If none are found, the module tries	107	L<POE>. The first one found is used. If none are found, the module tries
87	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	108	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
88	adaptor should always succeed) in the order given. The first one that can	109	adaptor should always succeed) in the order given. The first one that can
89	be successfully loaded will be used. If, after this, still none could be	110	be successfully loaded will be used. If, after this, still none could be
…		…
103	starts using it, all bets are off. Maybe you should tell their authors to	124	starts using it, all bets are off. Maybe you should tell their authors to
104	use AnyEvent so their modules work together with others seamlessly...	125	use AnyEvent so their modules work together with others seamlessly...
105		126
106	The pure-perl implementation of AnyEvent is called	127	The pure-perl implementation of AnyEvent is called
107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	128	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
108	explicitly.	129	explicitly and enjoy the high availability of that event loop :)
109		130
110	=head1 WATCHERS	131	=head1 WATCHERS
111		132
112	AnyEvent has the central concept of a I<watcher>, which is an object that	133	AnyEvent has the central concept of a I<watcher>, which is an object that
113	stores relevant data for each kind of event you are waiting for, such as	134	stores relevant data for each kind of event you are waiting for, such as
114	the callback to call, the filehandle to watch, etc.	135	the callback to call, the file handle to watch, etc.
115		136
116	These watchers are normal Perl objects with normal Perl lifetime. After	137	These watchers are normal Perl objects with normal Perl lifetime. After
117	creating a watcher it will immediately "watch" for events and invoke the	138	creating a watcher it will immediately "watch" for events and invoke the
118	callback when the event occurs (of course, only when the event model	139	callback when the event occurs (of course, only when the event model
119	is in control).	140	is in control).
120		141
		142	Note that B<callbacks must not permanently change global variables>
		143	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		144	callbacks must not C<die> >>. The former is good programming practise in
		145	Perl and the latter stems from the fact that exception handling differs
		146	widely between event loops.
		147
121	To disable the watcher you have to destroy it (e.g. by setting the	148	To disable the watcher you have to destroy it (e.g. by setting the
122	variable you store it in to C<undef> or otherwise deleting all references	149	variable you store it in to C<undef> or otherwise deleting all references
123	to it).	150	to it).
124		151
125	All watchers are created by calling a method on the C<AnyEvent> class.	152	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
127	Many watchers either are used with "recursion" (repeating timers for	154	Many watchers either are used with "recursion" (repeating timers for
128	example), or need to refer to their watcher object in other ways.	155	example), or need to refer to their watcher object in other ways.
129		156
130	An any way to achieve that is this pattern:	157	An any way to achieve that is this pattern:
131		158
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	159	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	160	# you can use $w here, for example to undef it
134	undef $w;	161	undef $w;
135	});	162	});
136		163
137	Note that C<my $w; $w => combination. This is necessary because in Perl,	164	Note that C<my $w; $w => combination. This is necessary because in Perl,
138	my variables are only visible after the statement in which they are	165	my variables are only visible after the statement in which they are
139	declared.	166	declared.
140		167
141	=head2 I/O WATCHERS	168	=head2 I/O WATCHERS
142		169
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	170	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	171	with the following mandatory key-value pairs as arguments:
145		172
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	173	C<fh> is the Perl I<file handle> (I<not> file descriptor) to watch
		174	for events (AnyEvent might or might not keep a reference to this file
		175	handle). Note that only file handles pointing to things for which
		176	non-blocking operation makes sense are allowed. This includes sockets,
		177	most character devices, pipes, fifos and so on, but not for example files
		178	or block devices.
		179
147	events. C<poll> must be a string that is either C<r> or C<w>, which	180	C<poll> must be a string that is either C<r> or C<w>, which creates a
148	creates a watcher waiting for "r"eadable or "w"ritable events,	181	watcher waiting for "r"eadable or "w"ritable events, respectively.
		182
149	respectively. C<cb> is the callback to invoke each time the file handle	183	C<cb> is the callback to invoke each time the file handle becomes ready.
150	becomes ready.	184
		185	Although the callback might get passed parameters, their value and
		186	presence is undefined and you cannot rely on them. Portable AnyEvent
		187	callbacks cannot use arguments passed to I/O watcher callbacks.
151		188
152	The I/O watcher might use the underlying file descriptor or a copy of it.	189	The I/O watcher might use the underlying file descriptor or a copy of it.
153	It is not allowed to close a file handle as long as any watcher is active	190	You must not close a file handle as long as any watcher is active on the
154	on the underlying file descriptor.	191	underlying file descriptor.
155		192
156	Some event loops issue spurious readyness notifications, so you should	193	Some event loops issue spurious readyness notifications, so you should
157	always use non-blocking calls when reading/writing from/to your file	194	always use non-blocking calls when reading/writing from/to your file
158	handles.	195	handles.
159		196
160	Example:
161
162	# wait for readability of STDIN, then read a line and disable the watcher	197	Example: wait for readability of STDIN, then read a line and disable the
		198	watcher.
		199
163	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	200	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
164	chomp (my $input = <STDIN>);	201	chomp (my $input = <STDIN>);
165	warn "read: $input\n";	202	warn "read: $input\n";
166	undef $w;	203	undef $w;
167	});	204	});
…		…
170		207
171	You can create a time watcher by calling the C<< AnyEvent->timer >>	208	You can create a time watcher by calling the C<< AnyEvent->timer >>
172	method with the following mandatory arguments:	209	method with the following mandatory arguments:
173		210
174	C<after> specifies after how many seconds (fractional values are	211	C<after> specifies after how many seconds (fractional values are
175	supported) should the timer activate. C<cb> the callback to invoke in that	212	supported) the callback should be invoked. C<cb> is the callback to invoke
176	case.	213	in that case.
177		214
178	The timer callback will be invoked at most once: if you want a repeating	215	Although the callback might get passed parameters, their value and
179	timer you have to create a new watcher (this is a limitation by both Tk	216	presence is undefined and you cannot rely on them. Portable AnyEvent
180	and Glib).	217	callbacks cannot use arguments passed to time watcher callbacks.
181		218
182	Example:	219	The callback will normally be invoked once only. If you specify another
		220	parameter, C<interval>, as a strictly positive number (> 0), then the
		221	callback will be invoked regularly at that interval (in fractional
		222	seconds) after the first invocation. If C<interval> is specified with a
		223	false value, then it is treated as if it were missing.
183		224
		225	The callback will be rescheduled before invoking the callback, but no
		226	attempt is done to avoid timer drift in most backends, so the interval is
		227	only approximate.
		228
184	# fire an event after 7.7 seconds	229	Example: fire an event after 7.7 seconds.
		230
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	231	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	232	warn "timeout\n";
187	});	233	});
188		234
189	# to cancel the timer:	235	# to cancel the timer:
190	undef $w;	236	undef $w;
191		237
192	Example 2:
193
194	# fire an event after 0.5 seconds, then roughly every second	238	Example 2: fire an event after 0.5 seconds, then roughly every second.
195	my $w;
196		239
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	240	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		241	warn "timeout\n";
200	};	242	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		243
205	=head3 TIMING ISSUES	244	=head3 TIMING ISSUES
206		245
207	There are two ways to handle timers: based on real time (relative, "fire	246	There are two ways to handle timers: based on real time (relative, "fire
208	in 10 seconds") and based on wallclock time (absolute, "fire at 12	247	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
220	timers.	259	timers.
221		260
222	AnyEvent always prefers relative timers, if available, matching the	261	AnyEvent always prefers relative timers, if available, matching the
223	AnyEvent API.	262	AnyEvent API.
224		263
		264	AnyEvent has two additional methods that return the "current time":
		265
		266	=over 4
		267
		268	=item AnyEvent->time
		269
		270	This returns the "current wallclock time" as a fractional number of
		271	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		272	return, and the result is guaranteed to be compatible with those).
		273
		274	It progresses independently of any event loop processing, i.e. each call
		275	will check the system clock, which usually gets updated frequently.
		276
		277	=item AnyEvent->now
		278
		279	This also returns the "current wallclock time", but unlike C<time>, above,
		280	this value might change only once per event loop iteration, depending on
		281	the event loop (most return the same time as C<time>, above). This is the
		282	time that AnyEvent's timers get scheduled against.
		283
		284	I<In almost all cases (in all cases if you don't care), this is the
		285	function to call when you want to know the current time.>
		286
		287	This function is also often faster then C<< AnyEvent->time >>, and
		288	thus the preferred method if you want some timestamp (for example,
		289	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		290
		291	The rest of this section is only of relevance if you try to be very exact
		292	with your timing, you can skip it without bad conscience.
		293
		294	For a practical example of when these times differ, consider L<Event::Lib>
		295	and L<EV> and the following set-up:
		296
		297	The event loop is running and has just invoked one of your callback at
		298	time=500 (assume no other callbacks delay processing). In your callback,
		299	you wait a second by executing C<sleep 1> (blocking the process for a
		300	second) and then (at time=501) you create a relative timer that fires
		301	after three seconds.
		302
		303	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		304	both return C<501>, because that is the current time, and the timer will
		305	be scheduled to fire at time=504 (C<501> + C<3>).
		306
		307	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		308	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		309	last event processing phase started. With L<EV>, your timer gets scheduled
		310	to run at time=503 (C<500> + C<3>).
		311
		312	In one sense, L<Event::Lib> is more exact, as it uses the current time
		313	regardless of any delays introduced by event processing. However, most
		314	callbacks do not expect large delays in processing, so this causes a
		315	higher drift (and a lot more system calls to get the current time).
		316
		317	In another sense, L<EV> is more exact, as your timer will be scheduled at
		318	the same time, regardless of how long event processing actually took.
		319
		320	In either case, if you care (and in most cases, you don't), then you
		321	can get whatever behaviour you want with any event loop, by taking the
		322	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		323	account.
		324
		325	=item AnyEvent->now_update
		326
		327	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		328	the current time for each loop iteration (see the discussion of L<<
		329	AnyEvent->now >>, above).
		330
		331	When a callback runs for a long time (or when the process sleeps), then
		332	this "current" time will differ substantially from the real time, which
		333	might affect timers and time-outs.
		334
		335	When this is the case, you can call this method, which will update the
		336	event loop's idea of "current time".
		337
		338	Note that updating the time I<might> cause some events to be handled.
		339
		340	=back
		341
225	=head2 SIGNAL WATCHERS	342	=head2 SIGNAL WATCHERS
226		343
227	You can watch for signals using a signal watcher, C<signal> is the signal	344	You can watch for signals using a signal watcher, C<signal> is the signal
228	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	345	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
229	be invoked whenever a signal occurs.	346	callback to be invoked whenever a signal occurs.
230		347
		348	Although the callback might get passed parameters, their value and
		349	presence is undefined and you cannot rely on them. Portable AnyEvent
		350	callbacks cannot use arguments passed to signal watcher callbacks.
		351
231	Multiple signal occurances can be clumped together into one callback	352	Multiple signal occurrences can be clumped together into one callback
232	invocation, and callback invocation will be synchronous. synchronous means	353	invocation, and callback invocation will be synchronous. Synchronous means
233	that it might take a while until the signal gets handled by the process,	354	that it might take a while until the signal gets handled by the process,
234	but it is guarenteed not to interrupt any other callbacks.	355	but it is guaranteed not to interrupt any other callbacks.
235		356
236	The main advantage of using these watchers is that you can share a signal	357	The main advantage of using these watchers is that you can share a signal
237	between multiple watchers.	358	between multiple watchers.
238		359
239	This watcher might use C<%SIG>, so programs overwriting those signals	360	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
246	=head2 CHILD PROCESS WATCHERS	367	=head2 CHILD PROCESS WATCHERS
247		368
248	You can also watch on a child process exit and catch its exit status.	369	You can also watch on a child process exit and catch its exit status.
249		370
250	The child process is specified by the C<pid> argument (if set to C<0>, it	371	The child process is specified by the C<pid> argument (if set to C<0>, it
251	watches for any child process exit). The watcher will trigger as often	372	watches for any child process exit). The watcher will triggered only when
252	as status change for the child are received. This works by installing a	373	the child process has finished and an exit status is available, not on
253	signal handler for C<SIGCHLD>. The callback will be called with the pid	374	any trace events (stopped/continued).
254	and exit status (as returned by waitpid).	375
		376	The callback will be called with the pid and exit status (as returned by
		377	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		378	callback arguments.
		379
		380	This watcher type works by installing a signal handler for C<SIGCHLD>,
		381	and since it cannot be shared, nothing else should use SIGCHLD or reap
		382	random child processes (waiting for specific child processes, e.g. inside
		383	C<system>, is just fine).
255		384
256	There is a slight catch to child watchers, however: you usually start them	385	There is a slight catch to child watchers, however: you usually start them
257	I<after> the child process was created, and this means the process could	386	I<after> the child process was created, and this means the process could
258	have exited already (and no SIGCHLD will be sent anymore).	387	have exited already (and no SIGCHLD will be sent anymore).
259		388
…		…
265	AnyEvent program, you I<have> to create at least one watcher before you	394	AnyEvent program, you I<have> to create at least one watcher before you
266	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	395	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
267		396
268	Example: fork a process and wait for it	397	Example: fork a process and wait for it
269		398
270	my $done = AnyEvent->condvar;	399	my $done = AnyEvent->condvar;
271		400
272	AnyEvent::detect; # force event module to be initialised
273
274	my $pid = fork or exit 5;	401	my $pid = fork or exit 5;
275		402
276	my $w = AnyEvent->child (	403	my $w = AnyEvent->child (
277	pid => $pid,	404	pid => $pid,
278	cb => sub {	405	cb => sub {
279	my ($pid, $status) = @_;	406	my ($pid, $status) = @_;
280	warn "pid $pid exited with status $status";	407	warn "pid $pid exited with status $status";
281	$done->broadcast;	408	$done->send;
282	},	409	},
283	);	410	);
284		411
285	# do something else, then wait for process exit	412	# do something else, then wait for process exit
286	$done->wait;	413	$done->recv;
287		414
288	=head2 CONDITION VARIABLES	415	=head2 CONDITION VARIABLES
289		416
		417	If you are familiar with some event loops you will know that all of them
		418	require you to run some blocking "loop", "run" or similar function that
		419	will actively watch for new events and call your callbacks.
		420
		421	AnyEvent is different, it expects somebody else to run the event loop and
		422	will only block when necessary (usually when told by the user).
		423
		424	The instrument to do that is called a "condition variable", so called
		425	because they represent a condition that must become true.
		426
290	Condition variables can be created by calling the C<< AnyEvent->condvar >>	427	Condition variables can be created by calling the C<< AnyEvent->condvar
291	method without any arguments.	428	>> method, usually without arguments. The only argument pair allowed is
292		429
293	A condition variable waits for a condition - precisely that the C<<	430	C<cb>, which specifies a callback to be called when the condition variable
294	->broadcast >> method has been called.	431	becomes true, with the condition variable as the first argument (but not
		432	the results).
295		433
296	They are very useful to signal that a condition has been fulfilled, for	434	After creation, the condition variable is "false" until it becomes "true"
		435	by calling the C<send> method (or calling the condition variable as if it
		436	were a callback, read about the caveats in the description for the C<<
		437	->send >> method).
		438
		439	Condition variables are similar to callbacks, except that you can
		440	optionally wait for them. They can also be called merge points - points
		441	in time where multiple outstanding events have been processed. And yet
		442	another way to call them is transactions - each condition variable can be
		443	used to represent a transaction, which finishes at some point and delivers
		444	a result.
		445
		446	Condition variables are very useful to signal that something has finished,
297	example, if you write a module that does asynchronous http requests,	447	for example, if you write a module that does asynchronous http requests,
298	then a condition variable would be the ideal candidate to signal the	448	then a condition variable would be the ideal candidate to signal the
299	availability of results.	449	availability of results. The user can either act when the callback is
		450	called or can synchronously C<< ->recv >> for the results.
300		451
301	You can also use condition variables to block your main program until	452	You can also use them to simulate traditional event loops - for example,
302	an event occurs - for example, you could C<< ->wait >> in your main	453	you can block your main program until an event occurs - for example, you
303	program until the user clicks the Quit button in your app, which would C<<	454	could C<< ->recv >> in your main program until the user clicks the Quit
304	->broadcast >> the "quit" event.	455	button of your app, which would C<< ->send >> the "quit" event.
305		456
306	Note that condition variables recurse into the event loop - if you have	457	Note that condition variables recurse into the event loop - if you have
307	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	458	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
308	lose. Therefore, condition variables are good to export to your caller, but	459	lose. Therefore, condition variables are good to export to your caller, but
309	you should avoid making a blocking wait yourself, at least in callbacks,	460	you should avoid making a blocking wait yourself, at least in callbacks,
310	as this asks for trouble.	461	as this asks for trouble.
311		462
312	This object has two methods:	463	Condition variables are represented by hash refs in perl, and the keys
		464	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		465	easy (it is often useful to build your own transaction class on top of
		466	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		467	it's C<new> method in your own C<new> method.
		468
		469	There are two "sides" to a condition variable - the "producer side" which
		470	eventually calls C<< -> send >>, and the "consumer side", which waits
		471	for the send to occur.
		472
		473	Example: wait for a timer.
		474
		475	# wait till the result is ready
		476	my $result_ready = AnyEvent->condvar;
		477
		478	# do something such as adding a timer
		479	# or socket watcher the calls $result_ready->send
		480	# when the "result" is ready.
		481	# in this case, we simply use a timer:
		482	my $w = AnyEvent->timer (
		483	after => 1,
		484	cb => sub { $result_ready->send },
		485	);
		486
		487	# this "blocks" (while handling events) till the callback
		488	# calls send
		489	$result_ready->recv;
		490
		491	Example: wait for a timer, but take advantage of the fact that
		492	condition variables are also code references.
		493
		494	my $done = AnyEvent->condvar;
		495	my $delay = AnyEvent->timer (after => 5, cb => $done);
		496	$done->recv;
		497
		498	Example: Imagine an API that returns a condvar and doesn't support
		499	callbacks. This is how you make a synchronous call, for example from
		500	the main program:
		501
		502	use AnyEvent::CouchDB;
		503
		504	...
		505
		506	my @info = $couchdb->info->recv;
		507
		508	And this is how you would just ste a callback to be called whenever the
		509	results are available:
		510
		511	$couchdb->info->cb (sub {
		512	my @info = $_[0]->recv;
		513	});
		514
		515	=head3 METHODS FOR PRODUCERS
		516
		517	These methods should only be used by the producing side, i.e. the
		518	code/module that eventually sends the signal. Note that it is also
		519	the producer side which creates the condvar in most cases, but it isn't
		520	uncommon for the consumer to create it as well.
313		521
314	=over 4	522	=over 4
315		523
		524	=item $cv->send (...)
		525
		526	Flag the condition as ready - a running C<< ->recv >> and all further
		527	calls to C<recv> will (eventually) return after this method has been
		528	called. If nobody is waiting the send will be remembered.
		529
		530	If a callback has been set on the condition variable, it is called
		531	immediately from within send.
		532
		533	Any arguments passed to the C<send> call will be returned by all
		534	future C<< ->recv >> calls.
		535
		536	Condition variables are overloaded so one can call them directly
		537	(as a code reference). Calling them directly is the same as calling
		538	C<send>. Note, however, that many C-based event loops do not handle
		539	overloading, so as tempting as it may be, passing a condition variable
		540	instead of a callback does not work. Both the pure perl and EV loops
		541	support overloading, however, as well as all functions that use perl to
		542	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		543	example).
		544
		545	=item $cv->croak ($error)
		546
		547	Similar to send, but causes all call's to C<< ->recv >> to invoke
		548	C<Carp::croak> with the given error message/object/scalar.
		549
		550	This can be used to signal any errors to the condition variable
		551	user/consumer.
		552
		553	=item $cv->begin ([group callback])
		554
316	=item $cv->wait	555	=item $cv->end
317		556
318	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	557	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		558
		559	These two methods can be used to combine many transactions/events into
		560	one. For example, a function that pings many hosts in parallel might want
		561	to use a condition variable for the whole process.
		562
		563	Every call to C<< ->begin >> will increment a counter, and every call to
		564	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		565	>>, the (last) callback passed to C<begin> will be executed. That callback
		566	is I<supposed> to call C<< ->send >>, but that is not required. If no
		567	callback was set, C<send> will be called without any arguments.
		568
		569	Let's clarify this with the ping example:
		570
		571	my $cv = AnyEvent->condvar;
		572
		573	my %result;
		574	$cv->begin (sub { $cv->send (\%result) });
		575
		576	for my $host (@list_of_hosts) {
		577	$cv->begin;
		578	ping_host_then_call_callback $host, sub {
		579	$result{$host} = ...;
		580	$cv->end;
		581	};
		582	}
		583
		584	$cv->end;
		585
		586	This code fragment supposedly pings a number of hosts and calls
		587	C<send> after results for all then have have been gathered - in any
		588	order. To achieve this, the code issues a call to C<begin> when it starts
		589	each ping request and calls C<end> when it has received some result for
		590	it. Since C<begin> and C<end> only maintain a counter, the order in which
		591	results arrive is not relevant.
		592
		593	There is an additional bracketing call to C<begin> and C<end> outside the
		594	loop, which serves two important purposes: first, it sets the callback
		595	to be called once the counter reaches C<0>, and second, it ensures that
		596	C<send> is called even when C<no> hosts are being pinged (the loop
		597	doesn't execute once).
		598
		599	This is the general pattern when you "fan out" into multiple subrequests:
		600	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		601	is called at least once, and then, for each subrequest you start, call
		602	C<begin> and for each subrequest you finish, call C<end>.
		603
		604	=back
		605
		606	=head3 METHODS FOR CONSUMERS
		607
		608	These methods should only be used by the consuming side, i.e. the
		609	code awaits the condition.
		610
		611	=over 4
		612
		613	=item $cv->recv
		614
		615	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
319	called on c<$cv>, while servicing other watchers normally.	616	>> methods have been called on c<$cv>, while servicing other watchers
		617	normally.
320		618
321	You can only wait once on a condition - additional calls will return	619	You can only wait once on a condition - additional calls are valid but
322	immediately.	620	will return immediately.
		621
		622	If an error condition has been set by calling C<< ->croak >>, then this
		623	function will call C<croak>.
		624
		625	In list context, all parameters passed to C<send> will be returned,
		626	in scalar context only the first one will be returned.
323		627
324	Not all event models support a blocking wait - some die in that case	628	Not all event models support a blocking wait - some die in that case
325	(programs might want to do that to stay interactive), so I<if you are	629	(programs might want to do that to stay interactive), so I<if you are
326	using this from a module, never require a blocking wait>, but let the	630	using this from a module, never require a blocking wait>, but let the
327	caller decide whether the call will block or not (for example, by coupling	631	caller decide whether the call will block or not (for example, by coupling
328	condition variables with some kind of request results and supporting	632	condition variables with some kind of request results and supporting
329	callbacks so the caller knows that getting the result will not block,	633	callbacks so the caller knows that getting the result will not block,
330	while still suppporting blocking waits if the caller so desires).	634	while still supporting blocking waits if the caller so desires).
331		635
332	Another reason I<never> to C<< ->wait >> in a module is that you cannot	636	Another reason I<never> to C<< ->recv >> in a module is that you cannot
333	sensibly have two C<< ->wait >>'s in parallel, as that would require	637	sensibly have two C<< ->recv >>'s in parallel, as that would require
334	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	638	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
335	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	639	can supply.
336	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
337	from different coroutines, however).
338		640
339	=item $cv->broadcast	641	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		642	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		643	versions and also integrates coroutines into AnyEvent, making blocking
		644	C<< ->recv >> calls perfectly safe as long as they are done from another
		645	coroutine (one that doesn't run the event loop).
340		646
341	Flag the condition as ready - a running C<< ->wait >> and all further	647	You can ensure that C<< -recv >> never blocks by setting a callback and
342	calls to C<wait> will (eventually) return after this method has been	648	only calling C<< ->recv >> from within that callback (or at a later
343	called. If nobody is waiting the broadcast will be remembered..	649	time). This will work even when the event loop does not support blocking
		650	waits otherwise.
		651
		652	=item $bool = $cv->ready
		653
		654	Returns true when the condition is "true", i.e. whether C<send> or
		655	C<croak> have been called.
		656
		657	=item $cb = $cv->cb ($cb->($cv))
		658
		659	This is a mutator function that returns the callback set and optionally
		660	replaces it before doing so.
		661
		662	The callback will be called when the condition becomes "true", i.e. when
		663	C<send> or C<croak> are called, with the only argument being the condition
		664	variable itself. Calling C<recv> inside the callback or at any later time
		665	is guaranteed not to block.
344		666
345	=back	667	=back
346
347	Example:
348
349	# wait till the result is ready
350	my $result_ready = AnyEvent->condvar;
351
352	# do something such as adding a timer
353	# or socket watcher the calls $result_ready->broadcast
354	# when the "result" is ready.
355	# in this case, we simply use a timer:
356	my $w = AnyEvent->timer (
357	after => 1,
358	cb => sub { $result_ready->broadcast },
359	);
360
361	# this "blocks" (while handling events) till the watcher
362	# calls broadcast
363	$result_ready->wait;
364		668
365	=head1 GLOBAL VARIABLES AND FUNCTIONS	669	=head1 GLOBAL VARIABLES AND FUNCTIONS
366		670
367	=over 4	671	=over 4
368		672
…		…
374	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	678	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
375	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	679	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
376		680
377	The known classes so far are:	681	The known classes so far are:
378		682
379	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
380	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
381	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	683	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
382	AnyEvent::Impl::Event based on Event, second best choice.	684	AnyEvent::Impl::Event based on Event, second best choice.
		685	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
383	AnyEvent::Impl::Glib based on Glib, third-best choice.	686	AnyEvent::Impl::Glib based on Glib, third-best choice.
384	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
385	AnyEvent::Impl::Tk based on Tk, very bad choice.	687	AnyEvent::Impl::Tk based on Tk, very bad choice.
386	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	688	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
387	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	689	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
388	AnyEvent::Impl::POE based on POE, not generic enough for full support.	690	AnyEvent::Impl::POE based on POE, not generic enough for full support.
389		691
…		…
402	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	704	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
403	if necessary. You should only call this function right before you would	705	if necessary. You should only call this function right before you would
404	have created an AnyEvent watcher anyway, that is, as late as possible at	706	have created an AnyEvent watcher anyway, that is, as late as possible at
405	runtime.	707	runtime.
406		708
		709	=item $guard = AnyEvent::post_detect { BLOCK }
		710
		711	Arranges for the code block to be executed as soon as the event model is
		712	autodetected (or immediately if this has already happened).
		713
		714	If called in scalar or list context, then it creates and returns an object
		715	that automatically removes the callback again when it is destroyed. See
		716	L<Coro::BDB> for a case where this is useful.
		717
		718	=item @AnyEvent::post_detect
		719
		720	If there are any code references in this array (you can C<push> to it
		721	before or after loading AnyEvent), then they will called directly after
		722	the event loop has been chosen.
		723
		724	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		725	if it contains a true value then the event loop has already been detected,
		726	and the array will be ignored.
		727
		728	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		729
407	=back	730	=back
408		731
409	=head1 WHAT TO DO IN A MODULE	732	=head1 WHAT TO DO IN A MODULE
410		733
411	As a module author, you should C<use AnyEvent> and call AnyEvent methods	734	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
414	Be careful when you create watchers in the module body - AnyEvent will	737	Be careful when you create watchers in the module body - AnyEvent will
415	decide which event module to use as soon as the first method is called, so	738	decide which event module to use as soon as the first method is called, so
416	by calling AnyEvent in your module body you force the user of your module	739	by calling AnyEvent in your module body you force the user of your module
417	to load the event module first.	740	to load the event module first.
418		741
419	Never call C<< ->wait >> on a condition variable unless you I<know> that	742	Never call C<< ->recv >> on a condition variable unless you I<know> that
420	the C<< ->broadcast >> method has been called on it already. This is	743	the C<< ->send >> method has been called on it already. This is
421	because it will stall the whole program, and the whole point of using	744	because it will stall the whole program, and the whole point of using
422	events is to stay interactive.	745	events is to stay interactive.
423		746
424	It is fine, however, to call C<< ->wait >> when the user of your module	747	It is fine, however, to call C<< ->recv >> when the user of your module
425	requests it (i.e. if you create a http request object ad have a method	748	requests it (i.e. if you create a http request object ad have a method
426	called C<results> that returns the results, it should call C<< ->wait >>	749	called C<results> that returns the results, it should call C<< ->recv >>
427	freely, as the user of your module knows what she is doing. always).	750	freely, as the user of your module knows what she is doing. always).
428		751
429	=head1 WHAT TO DO IN THE MAIN PROGRAM	752	=head1 WHAT TO DO IN THE MAIN PROGRAM
430		753
431	There will always be a single main program - the only place that should	754	There will always be a single main program - the only place that should
…		…
433		756
434	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	757	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
435	do anything special (it does not need to be event-based) and let AnyEvent	758	do anything special (it does not need to be event-based) and let AnyEvent
436	decide which implementation to chose if some module relies on it.	759	decide which implementation to chose if some module relies on it.
437		760
438	If the main program relies on a specific event model. For example, in	761	If the main program relies on a specific event model - for example, in
439	Gtk2 programs you have to rely on the Glib module. You should load the	762	Gtk2 programs you have to rely on the Glib module - you should load the
440	event module before loading AnyEvent or any module that uses it: generally	763	event module before loading AnyEvent or any module that uses it: generally
441	speaking, you should load it as early as possible. The reason is that	764	speaking, you should load it as early as possible. The reason is that
442	modules might create watchers when they are loaded, and AnyEvent will	765	modules might create watchers when they are loaded, and AnyEvent will
443	decide on the event model to use as soon as it creates watchers, and it	766	decide on the event model to use as soon as it creates watchers, and it
444	might chose the wrong one unless you load the correct one yourself.	767	might chose the wrong one unless you load the correct one yourself.
445		768
446	You can chose to use a rather inefficient pure-perl implementation by	769	You can chose to use a pure-perl implementation by loading the
447	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	770	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
448	behaviour everywhere, but letting AnyEvent chose is generally better.	771	everywhere, but letting AnyEvent chose the model is generally better.
		772
		773	=head2 MAINLOOP EMULATION
		774
		775	Sometimes (often for short test scripts, or even standalone programs who
		776	only want to use AnyEvent), you do not want to run a specific event loop.
		777
		778	In that case, you can use a condition variable like this:
		779
		780	AnyEvent->condvar->recv;
		781
		782	This has the effect of entering the event loop and looping forever.
		783
		784	Note that usually your program has some exit condition, in which case
		785	it is better to use the "traditional" approach of storing a condition
		786	variable somewhere, waiting for it, and sending it when the program should
		787	exit cleanly.
		788
		789
		790	=head1 OTHER MODULES
		791
		792	The following is a non-exhaustive list of additional modules that use
		793	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		794	in the same program. Some of the modules come with AnyEvent, some are
		795	available via CPAN.
		796
		797	=over 4
		798
		799	=item L<AnyEvent::Util>
		800
		801	Contains various utility functions that replace often-used but blocking
		802	functions such as C<inet_aton> by event-/callback-based versions.
		803
		804	=item L<AnyEvent::Socket>
		805
		806	Provides various utility functions for (internet protocol) sockets,
		807	addresses and name resolution. Also functions to create non-blocking tcp
		808	connections or tcp servers, with IPv6 and SRV record support and more.
		809
		810	=item L<AnyEvent::Handle>
		811
		812	Provide read and write buffers, manages watchers for reads and writes,
		813	supports raw and formatted I/O, I/O queued and fully transparent and
		814	non-blocking SSL/TLS.
		815
		816	=item L<AnyEvent::DNS>
		817
		818	Provides rich asynchronous DNS resolver capabilities.
		819
		820	=item L<AnyEvent::HTTP>
		821
		822	A simple-to-use HTTP library that is capable of making a lot of concurrent
		823	HTTP requests.
		824
		825	=item L<AnyEvent::HTTPD>
		826
		827	Provides a simple web application server framework.
		828
		829	=item L<AnyEvent::FastPing>
		830
		831	The fastest ping in the west.
		832
		833	=item L<AnyEvent::DBI>
		834
		835	Executes L<DBI> requests asynchronously in a proxy process.
		836
		837	=item L<AnyEvent::AIO>
		838
		839	Truly asynchronous I/O, should be in the toolbox of every event
		840	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		841	together.
		842
		843	=item L<AnyEvent::BDB>
		844
		845	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		846	L<BDB> and AnyEvent together.
		847
		848	=item L<AnyEvent::GPSD>
		849
		850	A non-blocking interface to gpsd, a daemon delivering GPS information.
		851
		852	=item L<AnyEvent::IGS>
		853
		854	A non-blocking interface to the Internet Go Server protocol (used by
		855	L<App::IGS>).
		856
		857	=item L<AnyEvent::IRC>
		858
		859	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		860
		861	=item L<Net::XMPP2>
		862
		863	AnyEvent based XMPP (Jabber protocol) module family.
		864
		865	=item L<Net::FCP>
		866
		867	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		868	of AnyEvent.
		869
		870	=item L<Event::ExecFlow>
		871
		872	High level API for event-based execution flow control.
		873
		874	=item L<Coro>
		875
		876	Has special support for AnyEvent via L<Coro::AnyEvent>.
		877
		878	=item L<IO::Lambda>
		879
		880	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		881
		882	=back
449		883
450	=cut	884	=cut
451		885
452	package AnyEvent;	886	package AnyEvent;
453		887
454	no warnings;	888	no warnings;
455	use strict;	889	use strict qw(vars subs);
456		890
457	use Carp;	891	use Carp;
458		892
459	our $VERSION = '3.3';	893	our $VERSION = 4.351;
460	our $MODEL;	894	our $MODEL;
461		895
462	our $AUTOLOAD;	896	our $AUTOLOAD;
463	our @ISA;	897	our @ISA;
464		898
		899	our @REGISTRY;
		900
		901	our $WIN32;
		902
		903	BEGIN {
		904	my $win32 = ! ! ($^O =~ /mswin32/i);
		905	eval "sub WIN32(){ $win32 }";
		906	}
		907
465	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	908	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
466		909
467	our @REGISTRY;	910	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		911
		912	{
		913	my $idx;
		914	$PROTOCOL{$_} = ++$idx
		915	for reverse split /\s*,\s*/,
		916	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		917	}
468		918
469	my @models = (	919	my @models = (
470	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
471	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
472	[EV:: => AnyEvent::Impl::EV::],	920	[EV:: => AnyEvent::Impl::EV::],
473	[Event:: => AnyEvent::Impl::Event::],	921	[Event:: => AnyEvent::Impl::Event::],
474	[Glib:: => AnyEvent::Impl::Glib::],
475	[Tk:: => AnyEvent::Impl::Tk::],
476	[Wx:: => AnyEvent::Impl::POE::],
477	[Prima:: => AnyEvent::Impl::POE::],
478	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	922	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
479	# everything below here will not be autoprobed as the pureperl backend should work everywhere	923	# everything below here will not be autoprobed
		924	# as the pureperl backend should work everywhere
		925	# and is usually faster
		926	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		927	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
480	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	928	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
481	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	929	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
482	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	930	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		931	[Wx:: => AnyEvent::Impl::POE::],
		932	[Prima:: => AnyEvent::Impl::POE::],
483	);	933	);
484		934
485	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	935	our %method = map +($_ => 1),
		936	qw(io timer time now now_update signal child condvar one_event DESTROY);
		937
		938	our @post_detect;
		939
		940	sub post_detect(&) {
		941	my ($cb) = @_;
		942
		943	if ($MODEL) {
		944	$cb->();
		945
		946	1
		947	} else {
		948	push @post_detect, $cb;
		949
		950	defined wantarray
		951	? bless \$cb, "AnyEvent::Util::PostDetect"
		952	: ()
		953	}
		954	}
		955
		956	sub AnyEvent::Util::PostDetect::DESTROY {
		957	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		958	}
486		959
487	sub detect() {	960	sub detect() {
488	unless ($MODEL) {	961	unless ($MODEL) {
489	no strict 'refs';	962	no strict 'refs';
		963	local $SIG{__DIE__};
490		964
491	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	965	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
492	my $model = "AnyEvent::Impl::$1";	966	my $model = "AnyEvent::Impl::$1";
493	if (eval "require $model") {	967	if (eval "require $model") {
494	$MODEL = $model;	968	$MODEL = $model;
…		…
524	last;	998	last;
525	}	999	}
526	}	1000	}
527		1001
528	$MODEL	1002	$MODEL
529	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1003	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
530	}	1004	}
531	}	1005	}
532		1006
		1007	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1008
533	unshift @ISA, $MODEL;	1009	unshift @ISA, $MODEL;
534	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1010
		1011	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1012
		1013	(shift @post_detect)->() while @post_detect;
535	}	1014	}
536		1015
537	$MODEL	1016	$MODEL
538	}	1017	}
539		1018
…		…
547		1026
548	my $class = shift;	1027	my $class = shift;
549	$class->$func (@_);	1028	$class->$func (@_);
550	}	1029	}
551		1030
		1031	# utility function to dup a filehandle. this is used by many backends
		1032	# to support binding more than one watcher per filehandle (they usually
		1033	# allow only one watcher per fd, so we dup it to get a different one).
		1034	sub _dupfh($$$$) {
		1035	my ($poll, $fh, $r, $w) = @_;
		1036
		1037	# cygwin requires the fh mode to be matching, unix doesn't
		1038	my ($rw, $mode) = $poll eq "r" ? ($r, "<")
		1039	: $poll eq "w" ? ($w, ">")
		1040	: Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
		1041
		1042	open my $fh2, "$mode&" . fileno $fh
		1043	or die "cannot dup() filehandle: $!,";
		1044
		1045	# we assume CLOEXEC is already set by perl in all important cases
		1046
		1047	($fh2, $rw)
		1048	}
		1049
552	package AnyEvent::Base;	1050	package AnyEvent::Base;
553		1051
		1052	# default implementations for many methods
		1053
		1054	BEGIN {
		1055	if (eval "use Time::HiRes (); time (); 1") {
		1056	*_time = \&Time::HiRes::time;
		1057	# if (eval "use POSIX (); (POSIX::times())...
		1058	} else {
		1059	*_time = sub { time }; # epic fail
		1060	}
		1061	}
		1062
		1063	sub time { _time }
		1064	sub now { _time }
		1065	sub now_update { }
		1066
554	# default implementation for ->condvar, ->wait, ->broadcast	1067	# default implementation for ->condvar
555		1068
556	sub condvar {	1069	sub condvar {
557	bless \my $flag, "AnyEvent::Base::CondVar"	1070	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
558	}
559
560	sub AnyEvent::Base::CondVar::broadcast {
561	${$_[0]}++;
562	}
563
564	sub AnyEvent::Base::CondVar::wait {
565	AnyEvent->one_event while !${$_[0]};
566	}	1071	}
567		1072
568	# default implementation for ->signal	1073	# default implementation for ->signal
569		1074
570	our %SIG_CB;	1075	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1076
		1077	sub _signal_exec {
		1078	sysread $SIGPIPE_R, my $dummy, 4;
		1079
		1080	while (%SIG_EV) {
		1081	for (keys %SIG_EV) {
		1082	delete $SIG_EV{$_};
		1083	$_->() for values %{ $SIG_CB{$_} || {} };
		1084	}
		1085	}
		1086	}
571		1087
572	sub signal {	1088	sub signal {
573	my (undef, %arg) = @_;	1089	my (undef, %arg) = @_;
574		1090
		1091	unless ($SIGPIPE_R) {
		1092	require Fcntl;
		1093
		1094	if (AnyEvent::WIN32) {
		1095	require AnyEvent::Util;
		1096
		1097	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1098	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1099	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1100	} else {
		1101	pipe $SIGPIPE_R, $SIGPIPE_W;
		1102	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1103	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1104	}
		1105
		1106	$SIGPIPE_R
		1107	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1108
		1109	# not strictly required, as $^F is normally 2, but let's make sure...
		1110	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1111	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1112
		1113	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1114	}
		1115
575	my $signal = uc $arg{signal}	1116	my $signal = uc $arg{signal}
576	or Carp::croak "required option 'signal' is missing";	1117	or Carp::croak "required option 'signal' is missing";
577		1118
578	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1119	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
579	$SIG{$signal} ||= sub {	1120	$SIG{$signal} ||= sub {
580	$_->() for values %{ $SIG_CB{$signal} || {} };	1121	local $!;
		1122	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1123	undef $SIG_EV{$signal};
581	};	1124	};
582		1125
583	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1126	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"
584	}	1127	}
585		1128
586	sub AnyEvent::Base::Signal::DESTROY {	1129	sub AnyEvent::Base::Signal::DESTROY {
587	my ($signal, $cb) = @{$_[0]};	1130	my ($signal, $cb) = @{$_[0]};
588		1131
589	delete $SIG_CB{$signal}{$cb};	1132	delete $SIG_CB{$signal}{$cb};
590		1133
591	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1134	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
592	}	1135	}
593		1136
594	# default implementation for ->child	1137	# default implementation for ->child
595		1138
596	our %PID_CB;	1139	our %PID_CB;
…		…
623	or Carp::croak "required option 'pid' is missing";	1166	or Carp::croak "required option 'pid' is missing";
624		1167
625	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1168	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
626		1169
627	unless ($WNOHANG) {	1170	unless ($WNOHANG) {
628	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1171	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
629	}	1172	}
630		1173
631	unless ($CHLD_W) {	1174	unless ($CHLD_W) {
632	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1175	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
633	# child could be a zombie already, so make at least one round	1176	# child could be a zombie already, so make at least one round
…		…
643	delete $PID_CB{$pid}{$cb};	1186	delete $PID_CB{$pid}{$cb};
644	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1187	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
645		1188
646	undef $CHLD_W unless keys %PID_CB;	1189	undef $CHLD_W unless keys %PID_CB;
647	}	1190	}
		1191
		1192	package AnyEvent::CondVar;
		1193
		1194	our @ISA = AnyEvent::CondVar::Base::;
		1195
		1196	package AnyEvent::CondVar::Base;
		1197
		1198	use overload
		1199	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1200	fallback => 1;
		1201
		1202	sub _send {
		1203	# nop
		1204	}
		1205
		1206	sub send {
		1207	my $cv = shift;
		1208	$cv->{_ae_sent} = [@_];
		1209	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1210	$cv->_send;
		1211	}
		1212
		1213	sub croak {
		1214	$_[0]{_ae_croak} = $_[1];
		1215	$_[0]->send;
		1216	}
		1217
		1218	sub ready {
		1219	$_[0]{_ae_sent}
		1220	}
		1221
		1222	sub _wait {
		1223	AnyEvent->one_event while !$_[0]{_ae_sent};
		1224	}
		1225
		1226	sub recv {
		1227	$_[0]->_wait;
		1228
		1229	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1230	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1231	}
		1232
		1233	sub cb {
		1234	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1235	$_[0]{_ae_cb}
		1236	}
		1237
		1238	sub begin {
		1239	++$_[0]{_ae_counter};
		1240	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1241	}
		1242
		1243	sub end {
		1244	return if --$_[0]{_ae_counter};
		1245	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1246	}
		1247
		1248	# undocumented/compatibility with pre-3.4
		1249	*broadcast = \&send;
		1250	*wait = \&_wait;
		1251
		1252	=head1 ERROR AND EXCEPTION HANDLING
		1253
		1254	In general, AnyEvent does not do any error handling - it relies on the
		1255	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1256	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1257	checking of all AnyEvent methods, however, which is highly useful during
		1258	development.
		1259
		1260	As for exception handling (i.e. runtime errors and exceptions thrown while
		1261	executing a callback), this is not only highly event-loop specific, but
		1262	also not in any way wrapped by this module, as this is the job of the main
		1263	program.
		1264
		1265	The pure perl event loop simply re-throws the exception (usually
		1266	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1267	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1268	so on.
		1269
		1270	=head1 ENVIRONMENT VARIABLES
		1271
		1272	The following environment variables are used by this module or its
		1273	submodules:
		1274
		1275	=over 4
		1276
		1277	=item C<PERL_ANYEVENT_VERBOSE>
		1278
		1279	By default, AnyEvent will be completely silent except in fatal
		1280	conditions. You can set this environment variable to make AnyEvent more
		1281	talkative.
		1282
		1283	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1284	conditions, such as not being able to load the event model specified by
		1285	C<PERL_ANYEVENT_MODEL>.
		1286
		1287	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1288	model it chooses.
		1289
		1290	=item C<PERL_ANYEVENT_STRICT>
		1291
		1292	AnyEvent does not do much argument checking by default, as thorough
		1293	argument checking is very costly. Setting this variable to a true value
		1294	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1295	check the arguments passed to most method calls. If it finds any problems
		1296	it will croak.
		1297
		1298	In other words, enables "strict" mode.
		1299
		1300	Unlike C<use strict>, it is definitely recommended ot keep it off in
		1301	production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
		1302	developing programs can be very useful, however.
		1303
		1304	=item C<PERL_ANYEVENT_MODEL>
		1305
		1306	This can be used to specify the event model to be used by AnyEvent, before
		1307	auto detection and -probing kicks in. It must be a string consisting
		1308	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1309	and the resulting module name is loaded and if the load was successful,
		1310	used as event model. If it fails to load AnyEvent will proceed with
		1311	auto detection and -probing.
		1312
		1313	This functionality might change in future versions.
		1314
		1315	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1316	could start your program like this:
		1317
		1318	PERL_ANYEVENT_MODEL=Perl perl ...
		1319
		1320	=item C<PERL_ANYEVENT_PROTOCOLS>
		1321
		1322	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1323	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1324	of auto probing).
		1325
		1326	Must be set to a comma-separated list of protocols or address families,
		1327	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1328	used, and preference will be given to protocols mentioned earlier in the
		1329	list.
		1330
		1331	This variable can effectively be used for denial-of-service attacks
		1332	against local programs (e.g. when setuid), although the impact is likely
		1333	small, as the program has to handle conenction and other failures anyways.
		1334
		1335	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1336	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1337	- only support IPv4, never try to resolve or contact IPv6
		1338	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1339	IPv6, but prefer IPv6 over IPv4.
		1340
		1341	=item C<PERL_ANYEVENT_EDNS0>
		1342
		1343	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1344	for DNS. This extension is generally useful to reduce DNS traffic, but
		1345	some (broken) firewalls drop such DNS packets, which is why it is off by
		1346	default.
		1347
		1348	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1349	EDNS0 in its DNS requests.
		1350
		1351	=item C<PERL_ANYEVENT_MAX_FORKS>
		1352
		1353	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1354	will create in parallel.
		1355
		1356	=back
648		1357
649	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1358	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
650		1359
651	This is an advanced topic that you do not normally need to use AnyEvent in	1360	This is an advanced topic that you do not normally need to use AnyEvent in
652	a module. This section is only of use to event loop authors who want to	1361	a module. This section is only of use to event loop authors who want to
…		…
686		1395
687	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1396	I<rxvt-unicode> also cheats a bit by not providing blocking access to
688	condition variables: code blocking while waiting for a condition will	1397	condition variables: code blocking while waiting for a condition will
689	C<die>. This still works with most modules/usages, and blocking calls must	1398	C<die>. This still works with most modules/usages, and blocking calls must
690	not be done in an interactive application, so it makes sense.	1399	not be done in an interactive application, so it makes sense.
691
692	=head1 ENVIRONMENT VARIABLES
693
694	The following environment variables are used by this module:
695
696	=over 4
697
698	=item C<PERL_ANYEVENT_VERBOSE>
699
700	By default, AnyEvent will be completely silent except in fatal
701	conditions. You can set this environment variable to make AnyEvent more
702	talkative.
703
704	When set to C<1> or higher, causes AnyEvent to warn about unexpected
705	conditions, such as not being able to load the event model specified by
706	C<PERL_ANYEVENT_MODEL>.
707
708	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
709	model it chooses.
710
711	=item C<PERL_ANYEVENT_MODEL>
712
713	This can be used to specify the event model to be used by AnyEvent, before
714	autodetection and -probing kicks in. It must be a string consisting
715	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
716	and the resulting module name is loaded and if the load was successful,
717	used as event model. If it fails to load AnyEvent will proceed with
718	autodetection and -probing.
719
720	This functionality might change in future versions.
721
722	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
723	could start your program like this:
724
725	PERL_ANYEVENT_MODEL=Perl perl ...
726
727	=back
728		1400
729	=head1 EXAMPLE PROGRAM	1401	=head1 EXAMPLE PROGRAM
730		1402
731	The following program uses an I/O watcher to read data from STDIN, a timer	1403	The following program uses an I/O watcher to read data from STDIN, a timer
732	to display a message once per second, and a condition variable to quit the	1404	to display a message once per second, and a condition variable to quit the
…		…
741	poll => 'r',	1413	poll => 'r',
742	cb => sub {	1414	cb => sub {
743	warn "io event <$_[0]>\n"; # will always output <r>	1415	warn "io event <$_[0]>\n"; # will always output <r>
744	chomp (my $input = <STDIN>); # read a line	1416	chomp (my $input = <STDIN>); # read a line
745	warn "read: $input\n"; # output what has been read	1417	warn "read: $input\n"; # output what has been read
746	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1418	$cv->send if $input =~ /^q/i; # quit program if /^q/i
747	},	1419	},
748	);	1420	);
749		1421
750	my $time_watcher; # can only be used once	1422	my $time_watcher; # can only be used once
751		1423
…		…
756	});	1428	});
757	}	1429	}
758		1430
759	new_timer; # create first timer	1431	new_timer; # create first timer
760		1432
761	$cv->wait; # wait until user enters /^q/i	1433	$cv->recv; # wait until user enters /^q/i
762		1434
763	=head1 REAL-WORLD EXAMPLE	1435	=head1 REAL-WORLD EXAMPLE
764		1436
765	Consider the L<Net::FCP> module. It features (among others) the following	1437	Consider the L<Net::FCP> module. It features (among others) the following
766	API calls, which are to freenet what HTTP GET requests are to http:	1438	API calls, which are to freenet what HTTP GET requests are to http:
…		…
816	syswrite $txn->{fh}, $txn->{request}	1488	syswrite $txn->{fh}, $txn->{request}
817	or die "connection or write error";	1489	or die "connection or write error";
818	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1490	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
819		1491
820	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1492	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
821	result and signals any possible waiters that the request ahs finished:	1493	result and signals any possible waiters that the request has finished:
822		1494
823	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1495	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
824		1496
825	if (end-of-file or data complete) {	1497	if (end-of-file or data complete) {
826	$txn->{result} = $txn->{buf};	1498	$txn->{result} = $txn->{buf};
827	$txn->{finished}->broadcast;	1499	$txn->{finished}->send;
828	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1500	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
829	}	1501	}
830		1502
831	The C<result> method, finally, just waits for the finished signal (if the	1503	The C<result> method, finally, just waits for the finished signal (if the
832	request was already finished, it doesn't wait, of course, and returns the	1504	request was already finished, it doesn't wait, of course, and returns the
833	data:	1505	data:
834		1506
835	$txn->{finished}->wait;	1507	$txn->{finished}->recv;
836	return $txn->{result};	1508	return $txn->{result};
837		1509
838	The actual code goes further and collects all errors (C<die>s, exceptions)	1510	The actual code goes further and collects all errors (C<die>s, exceptions)
839	that occured during request processing. The C<result> method detects	1511	that occurred during request processing. The C<result> method detects
840	whether an exception as thrown (it is stored inside the $txn object)	1512	whether an exception as thrown (it is stored inside the $txn object)
841	and just throws the exception, which means connection errors and other	1513	and just throws the exception, which means connection errors and other
842	problems get reported tot he code that tries to use the result, not in a	1514	problems get reported tot he code that tries to use the result, not in a
843	random callback.	1515	random callback.
844		1516
…		…
875		1547
876	my $quit = AnyEvent->condvar;	1548	my $quit = AnyEvent->condvar;
877		1549
878	$fcp->txn_client_get ($url)->cb (sub {	1550	$fcp->txn_client_get ($url)->cb (sub {
879	...	1551	...
880	$quit->broadcast;	1552	$quit->send;
881	});	1553	});
882		1554
883	$quit->wait;	1555	$quit->recv;
884		1556
885		1557
886	=head1 BENCHMARK	1558	=head1 BENCHMARKS
887		1559
888	To give you an idea of the performance and overheads that AnyEvent adds	1560	To give you an idea of the performance and overheads that AnyEvent adds
889	over the event loops themselves (and to give you an impression of the	1561	over the event loops themselves and to give you an impression of the speed
890	speed of various event loops), here is a benchmark of various supported	1562	of various event loops I prepared some benchmarks.
891	event models natively and with anyevent. The benchmark creates a lot of	1563
892	timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to	1564	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1565
		1566	Here is a benchmark of various supported event models used natively and
		1567	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1568	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
893	become writable, which it is), lets them fire exactly once and destroys	1569	which it is), lets them fire exactly once and destroys them again.
894	them again.
895		1570
896	Rewriting the benchmark to use many different sockets instead of using	1571	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
897	the same filehandle for all I/O watchers results in a much longer runtime	1572	distribution.
898	(socket creation is expensive), but qualitatively the same figures, so it
899	was not used.
900		1573
901	=head2 Explanation of the columns	1574	=head3 Explanation of the columns
902		1575
903	I<watcher> is the number of event watchers created/destroyed. Since	1576	I<watcher> is the number of event watchers created/destroyed. Since
904	different event models feature vastly different performances, each event	1577	different event models feature vastly different performances, each event
905	loop was given a number of watchers so that overall runtime is acceptable	1578	loop was given a number of watchers so that overall runtime is acceptable
906	and similar between tested event loop (and keep them from crashing): Glib	1579	and similar between tested event loop (and keep them from crashing): Glib
…		…
916	all watchers, to avoid adding memory overhead. That means closure creation	1589	all watchers, to avoid adding memory overhead. That means closure creation
917	and memory usage is not included in the figures.	1590	and memory usage is not included in the figures.
918		1591
919	I<invoke> is the time, in microseconds, used to invoke a simple	1592	I<invoke> is the time, in microseconds, used to invoke a simple
920	callback. The callback simply counts down a Perl variable and after it was	1593	callback. The callback simply counts down a Perl variable and after it was
921	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1594	invoked "watcher" times, it would C<< ->send >> a condvar once to
922	signal the end of this phase.	1595	signal the end of this phase.
923		1596
924	I<destroy> is the time, in microseconds, that it takes to destroy a single	1597	I<destroy> is the time, in microseconds, that it takes to destroy a single
925	watcher.	1598	watcher.
926		1599
927	=head2 Results	1600	=head3 Results
928		1601
929	name watchers bytes create invoke destroy comment	1602	name watchers bytes create invoke destroy comment
930	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1603	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
931	EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers	1604	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
932	CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal	1605	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
933	Perl/Any 100000 513 4.91 0.92 1.15 pure perl implementation	1606	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
934	Event/Event 16000 523 28.05 21.38 0.86 Event native interface	1607	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
935	Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers	1608	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
936	Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour	1609	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
937	Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers	1610	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
938	POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event	1611	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
939	POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select	1612	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
940		1613
941	=head2 Discussion	1614	=head3 Discussion
942		1615
943	The benchmark does I<not> measure scalability of the event loop very	1616	The benchmark does I<not> measure scalability of the event loop very
944	well. For example, a select-based event loop (such as the pure perl one)	1617	well. For example, a select-based event loop (such as the pure perl one)
945	can never compete with an event loop that uses epoll when the number of	1618	can never compete with an event loop that uses epoll when the number of
946	file descriptors grows high. In this benchmark, all events become ready at	1619	file descriptors grows high. In this benchmark, all events become ready at
947	the same time, so select/poll-based implementations get an unnatural speed	1620	the same time, so select/poll-based implementations get an unnatural speed
948	boost.	1621	boost.
949		1622
		1623	Also, note that the number of watchers usually has a nonlinear effect on
		1624	overall speed, that is, creating twice as many watchers doesn't take twice
		1625	the time - usually it takes longer. This puts event loops tested with a
		1626	higher number of watchers at a disadvantage.
		1627
		1628	To put the range of results into perspective, consider that on the
		1629	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1630	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1631	cycles with POE.
		1632
950	C<EV> is the sole leader regarding speed and memory use, which are both	1633	C<EV> is the sole leader regarding speed and memory use, which are both
951	maximal/minimal, respectively. Even when going through AnyEvent, there are	1634	maximal/minimal, respectively. Even when going through AnyEvent, it uses
952	only two event loops that use slightly less memory (the C<Event> module	1635	far less memory than any other event loop and is still faster than Event
953	natively and the pure perl backend), and no faster event models, not even	1636	natively.
954	C<Event> natively.
955		1637
956	The pure perl implementation is hit in a few sweet spots (both the	1638	The pure perl implementation is hit in a few sweet spots (both the
957	zero timeout and the use of a single fd hit optimisations in the perl	1639	constant timeout and the use of a single fd hit optimisations in the perl
958	interpreter and the backend itself, and all watchers become ready at the	1640	interpreter and the backend itself). Nevertheless this shows that it
959	same time). Nevertheless this shows that it adds very little overhead in	1641	adds very little overhead in itself. Like any select-based backend its
960	itself. Like any select-based backend its performance becomes really bad	1642	performance becomes really bad with lots of file descriptors (and few of
961	with lots of file descriptors (and few of them active), of course, but	1643	them active), of course, but this was not subject of this benchmark.
962	this was not subject of this benchmark.
963		1644
964	The C<Event> module has a relatively high setup and callback invocation cost,	1645	The C<Event> module has a relatively high setup and callback invocation
965	but overall scores on the third place.	1646	cost, but overall scores in on the third place.
966		1647
967	C<Glib>'s memory usage is quite a bit bit higher, but it features a	1648	C<Glib>'s memory usage is quite a bit higher, but it features a
968	faster callback invocation and overall ends up in the same class as	1649	faster callback invocation and overall ends up in the same class as
969	C<Event>. However, Glib scales extremely badly, doubling the number of	1650	C<Event>. However, Glib scales extremely badly, doubling the number of
970	watchers increases the processing time by more than a factor of four,	1651	watchers increases the processing time by more than a factor of four,
971	making it completely unusable when using larger numbers of watchers	1652	making it completely unusable when using larger numbers of watchers
972	(note that only a single file descriptor was used in the benchmark, so	1653	(note that only a single file descriptor was used in the benchmark, so
…		…
975	The C<Tk> adaptor works relatively well. The fact that it crashes with	1656	The C<Tk> adaptor works relatively well. The fact that it crashes with
976	more than 2000 watchers is a big setback, however, as correctness takes	1657	more than 2000 watchers is a big setback, however, as correctness takes
977	precedence over speed. Nevertheless, its performance is surprising, as the	1658	precedence over speed. Nevertheless, its performance is surprising, as the
978	file descriptor is dup()ed for each watcher. This shows that the dup()	1659	file descriptor is dup()ed for each watcher. This shows that the dup()
979	employed by some adaptors is not a big performance issue (it does incur a	1660	employed by some adaptors is not a big performance issue (it does incur a
980	hidden memory cost inside the kernel, though, that is not reflected in the	1661	hidden memory cost inside the kernel which is not reflected in the figures
981	figures above).	1662	above).
982		1663
983	C<POE>, regardless of underlying event loop (wether using its pure perl	1664	C<POE>, regardless of underlying event loop (whether using its pure perl
984	select-based backend or the Event module) shows abysmal performance and	1665	select-based backend or the Event module, the POE-EV backend couldn't
		1666	be tested because it wasn't working) shows abysmal performance and
985	memory usage: Watchers use almost 30 times as much memory as EV watchers,	1667	memory usage with AnyEvent: Watchers use almost 30 times as much memory
986	and 10 times as much memory as both Event or EV via AnyEvent. Watcher	1668	as EV watchers, and 10 times as much memory as Event (the high memory
		1669	requirements are caused by requiring a session for each watcher). Watcher
987	invocation is almost 900 times slower than with AnyEvent's pure perl	1670	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1671	implementation.
		1672
988	implementation. The design of the POE adaptor class in AnyEvent can not	1673	The design of the POE adaptor class in AnyEvent can not really account
989	really account for this, as session creation overhead is small compared	1674	for the performance issues, though, as session creation overhead is
990	to execution of the state machine, which is coded pretty optimally within	1675	small compared to execution of the state machine, which is coded pretty
991	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1676	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1677	using multiple sessions is not a good approach, especially regarding
		1678	memory usage, even the author of POE could not come up with a faster
		1679	design).
992		1680
993	=head2 Summary	1681	=head3 Summary
994		1682
		1683	=over 4
		1684
995	Using EV through AnyEvent is faster than any other event loop, but most	1685	=item * Using EV through AnyEvent is faster than any other event loop
996	event loops have acceptable performance with or without AnyEvent.	1686	(even when used without AnyEvent), but most event loops have acceptable
		1687	performance with or without AnyEvent.
997		1688
998	The overhead AnyEvent adds is usually much smaller than the overhead of	1689	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
999	the actual event loop, only with extremely fast event loops such as the EV	1690	the actual event loop, only with extremely fast event loops such as EV
1000	adds AnyEvent significant overhead.	1691	adds AnyEvent significant overhead.
1001		1692
1002	And you should simply avoid POE like the plague if you want performance or	1693	=item * You should avoid POE like the plague if you want performance or
1003	reasonable memory usage.	1694	reasonable memory usage.
1004		1695
		1696	=back
		1697
		1698	=head2 BENCHMARKING THE LARGE SERVER CASE
		1699
		1700	This benchmark actually benchmarks the event loop itself. It works by
		1701	creating a number of "servers": each server consists of a socket pair, a
		1702	timeout watcher that gets reset on activity (but never fires), and an I/O
		1703	watcher waiting for input on one side of the socket. Each time the socket
		1704	watcher reads a byte it will write that byte to a random other "server".
		1705
		1706	The effect is that there will be a lot of I/O watchers, only part of which
		1707	are active at any one point (so there is a constant number of active
		1708	fds for each loop iteration, but which fds these are is random). The
		1709	timeout is reset each time something is read because that reflects how
		1710	most timeouts work (and puts extra pressure on the event loops).
		1711
		1712	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1713	(1%) are active. This mirrors the activity of large servers with many
		1714	connections, most of which are idle at any one point in time.
		1715
		1716	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1717	distribution.
		1718
		1719	=head3 Explanation of the columns
		1720
		1721	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1722	each server has a read and write socket end).
		1723
		1724	I<create> is the time it takes to create a socket pair (which is
		1725	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1726
		1727	I<request>, the most important value, is the time it takes to handle a
		1728	single "request", that is, reading the token from the pipe and forwarding
		1729	it to another server. This includes deleting the old timeout and creating
		1730	a new one that moves the timeout into the future.
		1731
		1732	=head3 Results
		1733
		1734	name sockets create request
		1735	EV 20000 69.01 11.16
		1736	Perl 20000 73.32 35.87
		1737	Event 20000 212.62 257.32
		1738	Glib 20000 651.16 1896.30
		1739	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1740
		1741	=head3 Discussion
		1742
		1743	This benchmark I<does> measure scalability and overall performance of the
		1744	particular event loop.
		1745
		1746	EV is again fastest. Since it is using epoll on my system, the setup time
		1747	is relatively high, though.
		1748
		1749	Perl surprisingly comes second. It is much faster than the C-based event
		1750	loops Event and Glib.
		1751
		1752	Event suffers from high setup time as well (look at its code and you will
		1753	understand why). Callback invocation also has a high overhead compared to
		1754	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1755	uses select or poll in basically all documented configurations.
		1756
		1757	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1758	clearly fails to perform with many filehandles or in busy servers.
		1759
		1760	POE is still completely out of the picture, taking over 1000 times as long
		1761	as EV, and over 100 times as long as the Perl implementation, even though
		1762	it uses a C-based event loop in this case.
		1763
		1764	=head3 Summary
		1765
		1766	=over 4
		1767
		1768	=item * The pure perl implementation performs extremely well.
		1769
		1770	=item * Avoid Glib or POE in large projects where performance matters.
		1771
		1772	=back
		1773
		1774	=head2 BENCHMARKING SMALL SERVERS
		1775
		1776	While event loops should scale (and select-based ones do not...) even to
		1777	large servers, most programs we (or I :) actually write have only a few
		1778	I/O watchers.
		1779
		1780	In this benchmark, I use the same benchmark program as in the large server
		1781	case, but it uses only eight "servers", of which three are active at any
		1782	one time. This should reflect performance for a small server relatively
		1783	well.
		1784
		1785	The columns are identical to the previous table.
		1786
		1787	=head3 Results
		1788
		1789	name sockets create request
		1790	EV 16 20.00 6.54
		1791	Perl 16 25.75 12.62
		1792	Event 16 81.27 35.86
		1793	Glib 16 32.63 15.48
		1794	POE 16 261.87 276.28 uses POE::Loop::Event
		1795
		1796	=head3 Discussion
		1797
		1798	The benchmark tries to test the performance of a typical small
		1799	server. While knowing how various event loops perform is interesting, keep
		1800	in mind that their overhead in this case is usually not as important, due
		1801	to the small absolute number of watchers (that is, you need efficiency and
		1802	speed most when you have lots of watchers, not when you only have a few of
		1803	them).
		1804
		1805	EV is again fastest.
		1806
		1807	Perl again comes second. It is noticeably faster than the C-based event
		1808	loops Event and Glib, although the difference is too small to really
		1809	matter.
		1810
		1811	POE also performs much better in this case, but is is still far behind the
		1812	others.
		1813
		1814	=head3 Summary
		1815
		1816	=over 4
		1817
		1818	=item * C-based event loops perform very well with small number of
		1819	watchers, as the management overhead dominates.
		1820
		1821	=back
		1822
		1823
		1824	=head1 SIGNALS
		1825
		1826	AnyEvent currently installs handlers for these signals:
		1827
		1828	=over 4
		1829
		1830	=item SIGCHLD
		1831
		1832	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		1833	emulation for event loops that do not support them natively. Also, some
		1834	event loops install a similar handler.
		1835
		1836	=item SIGPIPE
		1837
		1838	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		1839	when AnyEvent gets loaded.
		1840
		1841	The rationale for this is that AnyEvent users usually do not really depend
		1842	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		1843	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		1844	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		1845	some random socket.
		1846
		1847	The rationale for installing a no-op handler as opposed to ignoring it is
		1848	that this way, the handler will be restored to defaults on exec.
		1849
		1850	Feel free to install your own handler, or reset it to defaults.
		1851
		1852	=back
		1853
		1854	=cut
		1855
		1856	$SIG{PIPE} = sub { }
		1857	unless defined $SIG{PIPE};
		1858
1005		1859
1006	=head1 FORK	1860	=head1 FORK
1007		1861
1008	Most event libraries are not fork-safe. The ones who are usually are	1862	Most event libraries are not fork-safe. The ones who are usually are
1009	because they are so inefficient. Only L<EV> is fully fork-aware.	1863	because they rely on inefficient but fork-safe C<select> or C<poll>
		1864	calls. Only L<EV> is fully fork-aware.
1010		1865
1011	If you have to fork, you must either do so I<before> creating your first	1866	If you have to fork, you must either do so I<before> creating your first
1012	watcher OR you must not use AnyEvent at all in the child.	1867	watcher OR you must not use AnyEvent at all in the child.
1013		1868
1014		1869
…		…
1022	specified in the variable.	1877	specified in the variable.
1023		1878
1024	You can make AnyEvent completely ignore this variable by deleting it	1879	You can make AnyEvent completely ignore this variable by deleting it
1025	before the first watcher gets created, e.g. with a C<BEGIN> block:	1880	before the first watcher gets created, e.g. with a C<BEGIN> block:
1026		1881
1027	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1882	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1028		1883
1029	use AnyEvent;	1884	use AnyEvent;
		1885
		1886	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1887	be used to probe what backend is used and gain other information (which is
		1888	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		1889	$ENV{PERL_ANYEGENT_STRICT}.
		1890
		1891
		1892	=head1 BUGS
		1893
		1894	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		1895	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		1896	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		1897	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		1898	pronounced).
1030		1899
1031		1900
1032	=head1 SEE ALSO	1901	=head1 SEE ALSO
1033		1902
1034	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1903	Utility functions: L<AnyEvent::Util>.
1035	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1904
		1905	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1036	L<Event::Lib>, L<Qt>, L<POE>.	1906	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1037		1907
1038	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1908	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1039	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1909	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1040	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1910	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1041	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1911	L<AnyEvent::Impl::POE>.
1042		1912
		1913	Non-blocking file handles, sockets, TCP clients and
		1914	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1915
		1916	Asynchronous DNS: L<AnyEvent::DNS>.
		1917
		1918	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1919
1043	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1920	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1044		1921
1045		1922
1046	=head1 AUTHOR	1923	=head1 AUTHOR
1047		1924
1048	Marc Lehmann <schmorp@schmorp.de>	1925	Marc Lehmann <schmorp@schmorp.de>
1049	http://home.schmorp.de/	1926	http://home.schmorp.de/
1050		1927
1051	=cut	1928	=cut
1052		1929
1053	1	1930	1
1054		1931

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