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Revision 1.200 by root, Wed Apr 1 14:02:27 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 - 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<Tk>. The first one found is used. If none are found,	106	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	the module tries to load these modules in the stated order. The first one	107	L<POE>. The first one found is used. If none are found, the module tries
		108	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
		109	adaptor should always succeed) in the order given. The first one that can
87	that can be successfully loaded will be used. If, after this, still none	110	be successfully loaded will be used. If, after this, still none could be
88	could be found, AnyEvent will fall back to a pure-perl event loop, which	111	found, AnyEvent will fall back to a pure-perl event loop, which is not
89	is not very efficient, but should work everywhere.	112	very efficient, but should work everywhere.
90		113
91	Because AnyEvent first checks for modules that are already loaded, loading	114	Because AnyEvent first checks for modules that are already loaded, loading
92	an event model explicitly before first using AnyEvent will likely make	115	an event model explicitly before first using AnyEvent will likely make
93	that model the default. For example:	116	that model the default. For example:
94		117
…		…
101	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
102	use AnyEvent so their modules work together with others seamlessly...	125	use AnyEvent so their modules work together with others seamlessly...
103		126
104	The pure-perl implementation of AnyEvent is called	127	The pure-perl implementation of AnyEvent is called
105	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
106	explicitly.	129	explicitly and enjoy the high availability of that event loop :)
107		130
108	=head1 WATCHERS	131	=head1 WATCHERS
109		132
110	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
111	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
112	the callback to call, the filehandle to watch, etc.	135	the callback to call, the file handle to watch, etc.
113		136
114	These watchers are normal Perl objects with normal Perl lifetime. After	137	These watchers are normal Perl objects with normal Perl lifetime. After
115	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
116	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
117	is in control).	140	is in control).
118		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
119	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
120	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
121	to it).	150	to it).
122		151
123	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.
…		…
125	Many watchers either are used with "recursion" (repeating timers for	154	Many watchers either are used with "recursion" (repeating timers for
126	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.
127		156
128	An any way to achieve that is this pattern:	157	An any way to achieve that is this pattern:
129		158
130	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	159	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
131	# you can use $w here, for example to undef it	160	# you can use $w here, for example to undef it
132	undef $w;	161	undef $w;
133	});	162	});
134		163
135	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,
136	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
137	declared.	166	declared.
138		167
139	=head2 IO WATCHERS	168	=head2 I/O WATCHERS
140		169
141	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
142	with the following mandatory key-value pairs as arguments:	171	with the following mandatory key-value pairs as arguments:
143		172
144	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
145	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
146	creates a watcher waiting for "r"eadable or "w"ritable events,	181	watcher waiting for "r"eadable or "w"ritable events, respectively.
		182
147	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.
148	becomes ready.
149		184
150	As long as the I/O watcher exists it will keep the file descriptor or a	185	Although the callback might get passed parameters, their value and
151	copy of it alive/open.	186	presence is undefined and you cannot rely on them. Portable AnyEvent
		187	callbacks cannot use arguments passed to I/O watcher callbacks.
152		188
		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
209	o'clock").	248	o'clock").
210		249
211	While most event loops expect timers to specified in a relative way, they use	250	While most event loops expect timers to specified in a relative way, they
212	absolute time internally. This makes a difference when your clock "jumps",	251	use absolute time internally. This makes a difference when your clock
213	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to	252	"jumps", for example, when ntp decides to set your clock backwards from
214	2008-01-01, a watcher that you created to fire "after" a second might actually take	253	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
215	six years to finally fire.	254	fire "after" a second might actually take six years to finally fire.
216		255
217	AnyEvent cannot compensate for this. The only event loop that is conscious	256	AnyEvent cannot compensate for this. The only event loop that is conscious
218	about these issues is L<EV>, which offers both relative (ev_timer) and	257	about these issues is L<EV>, which offers both relative (ev_timer, based
219	absolute (ev_periodic) timers.	258	on true relative time) and absolute (ev_periodic, based on wallclock time)
		259	timers.
220		260
221	AnyEvent always prefers relative timers, if available, matching the	261	AnyEvent always prefers relative timers, if available, matching the
222	AnyEvent API.	262	AnyEvent API.
223		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	=back
		326
224	=head2 SIGNAL WATCHERS	327	=head2 SIGNAL WATCHERS
225		328
226	You can watch for signals using a signal watcher, C<signal> is the signal	329	You can watch for signals using a signal watcher, C<signal> is the signal
227	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	330	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
228	be invoked whenever a signal occurs.	331	callback to be invoked whenever a signal occurs.
229		332
		333	Although the callback might get passed parameters, their value and
		334	presence is undefined and you cannot rely on them. Portable AnyEvent
		335	callbacks cannot use arguments passed to signal watcher callbacks.
		336
230	Multiple signals occurances can be clumped together into one callback	337	Multiple signal occurrences can be clumped together into one callback
231	invocation, and callback invocation will be synchronous. synchronous means	338	invocation, and callback invocation will be synchronous. Synchronous means
232	that it might take a while until the signal gets handled by the process,	339	that it might take a while until the signal gets handled by the process,
233	but it is guarenteed not to interrupt any other callbacks.	340	but it is guaranteed not to interrupt any other callbacks.
234		341
235	The main advantage of using these watchers is that you can share a signal	342	The main advantage of using these watchers is that you can share a signal
236	between multiple watchers.	343	between multiple watchers.
237		344
238	This watcher might use C<%SIG>, so programs overwriting those signals	345	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
245	=head2 CHILD PROCESS WATCHERS	352	=head2 CHILD PROCESS WATCHERS
246		353
247	You can also watch on a child process exit and catch its exit status.	354	You can also watch on a child process exit and catch its exit status.
248		355
249	The child process is specified by the C<pid> argument (if set to C<0>, it	356	The child process is specified by the C<pid> argument (if set to C<0>, it
250	watches for any child process exit). The watcher will trigger as often	357	watches for any child process exit). The watcher will triggered only when
251	as status change for the child are received. This works by installing a	358	the child process has finished and an exit status is available, not on
252	signal handler for C<SIGCHLD>. The callback will be called with the pid	359	any trace events (stopped/continued).
253	and exit status (as returned by waitpid).
254		360
255	Example: wait for pid 1333	361	The callback will be called with the pid and exit status (as returned by
		362	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		363	callback arguments.
256		364
		365	This watcher type works by installing a signal handler for C<SIGCHLD>,
		366	and since it cannot be shared, nothing else should use SIGCHLD or reap
		367	random child processes (waiting for specific child processes, e.g. inside
		368	C<system>, is just fine).
		369
		370	There is a slight catch to child watchers, however: you usually start them
		371	I<after> the child process was created, and this means the process could
		372	have exited already (and no SIGCHLD will be sent anymore).
		373
		374	Not all event models handle this correctly (POE doesn't), but even for
		375	event models that I<do> handle this correctly, they usually need to be
		376	loaded before the process exits (i.e. before you fork in the first place).
		377
		378	This means you cannot create a child watcher as the very first thing in an
		379	AnyEvent program, you I<have> to create at least one watcher before you
		380	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		381
		382	Example: fork a process and wait for it
		383
		384	my $done = AnyEvent->condvar;
		385
		386	my $pid = fork or exit 5;
		387
257	my $w = AnyEvent->child (	388	my $w = AnyEvent->child (
258	pid => 1333,	389	pid => $pid,
259	cb => sub {	390	cb => sub {
260	my ($pid, $status) = @_;	391	my ($pid, $status) = @_;
261	warn "pid $pid exited with status $status";	392	warn "pid $pid exited with status $status";
		393	$done->send;
262	},	394	},
263	);	395	);
		396
		397	# do something else, then wait for process exit
		398	$done->recv;
264		399
265	=head2 CONDITION VARIABLES	400	=head2 CONDITION VARIABLES
266		401
		402	If you are familiar with some event loops you will know that all of them
		403	require you to run some blocking "loop", "run" or similar function that
		404	will actively watch for new events and call your callbacks.
		405
		406	AnyEvent is different, it expects somebody else to run the event loop and
		407	will only block when necessary (usually when told by the user).
		408
		409	The instrument to do that is called a "condition variable", so called
		410	because they represent a condition that must become true.
		411
267	Condition variables can be created by calling the C<< AnyEvent->condvar >>	412	Condition variables can be created by calling the C<< AnyEvent->condvar
268	method without any arguments.	413	>> method, usually without arguments. The only argument pair allowed is
269		414
270	A condition variable waits for a condition - precisely that the C<<	415	C<cb>, which specifies a callback to be called when the condition variable
271	->broadcast >> method has been called.	416	becomes true, with the condition variable as the first argument (but not
		417	the results).
272		418
273	They are very useful to signal that a condition has been fulfilled, for	419	After creation, the condition variable is "false" until it becomes "true"
		420	by calling the C<send> method (or calling the condition variable as if it
		421	were a callback, read about the caveats in the description for the C<<
		422	->send >> method).
		423
		424	Condition variables are similar to callbacks, except that you can
		425	optionally wait for them. They can also be called merge points - points
		426	in time where multiple outstanding events have been processed. And yet
		427	another way to call them is transactions - each condition variable can be
		428	used to represent a transaction, which finishes at some point and delivers
		429	a result.
		430
		431	Condition variables are very useful to signal that something has finished,
274	example, if you write a module that does asynchronous http requests,	432	for example, if you write a module that does asynchronous http requests,
275	then a condition variable would be the ideal candidate to signal the	433	then a condition variable would be the ideal candidate to signal the
276	availability of results.	434	availability of results. The user can either act when the callback is
		435	called or can synchronously C<< ->recv >> for the results.
277		436
278	You can also use condition variables to block your main program until	437	You can also use them to simulate traditional event loops - for example,
279	an event occurs - for example, you could C<< ->wait >> in your main	438	you can block your main program until an event occurs - for example, you
280	program until the user clicks the Quit button in your app, which would C<<	439	could C<< ->recv >> in your main program until the user clicks the Quit
281	->broadcast >> the "quit" event.	440	button of your app, which would C<< ->send >> the "quit" event.
282		441
283	Note that condition variables recurse into the event loop - if you have	442	Note that condition variables recurse into the event loop - if you have
284	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	443	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
285	lose. Therefore, condition variables are good to export to your caller, but	444	lose. Therefore, condition variables are good to export to your caller, but
286	you should avoid making a blocking wait yourself, at least in callbacks,	445	you should avoid making a blocking wait yourself, at least in callbacks,
287	as this asks for trouble.	446	as this asks for trouble.
288		447
289	This object has two methods:	448	Condition variables are represented by hash refs in perl, and the keys
		449	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		450	easy (it is often useful to build your own transaction class on top of
		451	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		452	it's C<new> method in your own C<new> method.
		453
		454	There are two "sides" to a condition variable - the "producer side" which
		455	eventually calls C<< -> send >>, and the "consumer side", which waits
		456	for the send to occur.
		457
		458	Example: wait for a timer.
		459
		460	# wait till the result is ready
		461	my $result_ready = AnyEvent->condvar;
		462
		463	# do something such as adding a timer
		464	# or socket watcher the calls $result_ready->send
		465	# when the "result" is ready.
		466	# in this case, we simply use a timer:
		467	my $w = AnyEvent->timer (
		468	after => 1,
		469	cb => sub { $result_ready->send },
		470	);
		471
		472	# this "blocks" (while handling events) till the callback
		473	# calls send
		474	$result_ready->recv;
		475
		476	Example: wait for a timer, but take advantage of the fact that
		477	condition variables are also code references.
		478
		479	my $done = AnyEvent->condvar;
		480	my $delay = AnyEvent->timer (after => 5, cb => $done);
		481	$done->recv;
		482
		483	Example: Imagine an API that returns a condvar and doesn't support
		484	callbacks. This is how you make a synchronous call, for example from
		485	the main program:
		486
		487	use AnyEvent::CouchDB;
		488
		489	...
		490
		491	my @info = $couchdb->info->recv;
		492
		493	And this is how you would just ste a callback to be called whenever the
		494	results are available:
		495
		496	$couchdb->info->cb (sub {
		497	my @info = $_[0]->recv;
		498	});
		499
		500	=head3 METHODS FOR PRODUCERS
		501
		502	These methods should only be used by the producing side, i.e. the
		503	code/module that eventually sends the signal. Note that it is also
		504	the producer side which creates the condvar in most cases, but it isn't
		505	uncommon for the consumer to create it as well.
290		506
291	=over 4	507	=over 4
292		508
		509	=item $cv->send (...)
		510
		511	Flag the condition as ready - a running C<< ->recv >> and all further
		512	calls to C<recv> will (eventually) return after this method has been
		513	called. If nobody is waiting the send will be remembered.
		514
		515	If a callback has been set on the condition variable, it is called
		516	immediately from within send.
		517
		518	Any arguments passed to the C<send> call will be returned by all
		519	future C<< ->recv >> calls.
		520
		521	Condition variables are overloaded so one can call them directly
		522	(as a code reference). Calling them directly is the same as calling
		523	C<send>. Note, however, that many C-based event loops do not handle
		524	overloading, so as tempting as it may be, passing a condition variable
		525	instead of a callback does not work. Both the pure perl and EV loops
		526	support overloading, however, as well as all functions that use perl to
		527	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		528	example).
		529
		530	=item $cv->croak ($error)
		531
		532	Similar to send, but causes all call's to C<< ->recv >> to invoke
		533	C<Carp::croak> with the given error message/object/scalar.
		534
		535	This can be used to signal any errors to the condition variable
		536	user/consumer.
		537
		538	=item $cv->begin ([group callback])
		539
293	=item $cv->wait	540	=item $cv->end
294		541
295	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	542	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		543
		544	These two methods can be used to combine many transactions/events into
		545	one. For example, a function that pings many hosts in parallel might want
		546	to use a condition variable for the whole process.
		547
		548	Every call to C<< ->begin >> will increment a counter, and every call to
		549	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		550	>>, the (last) callback passed to C<begin> will be executed. That callback
		551	is I<supposed> to call C<< ->send >>, but that is not required. If no
		552	callback was set, C<send> will be called without any arguments.
		553
		554	Let's clarify this with the ping example:
		555
		556	my $cv = AnyEvent->condvar;
		557
		558	my %result;
		559	$cv->begin (sub { $cv->send (\%result) });
		560
		561	for my $host (@list_of_hosts) {
		562	$cv->begin;
		563	ping_host_then_call_callback $host, sub {
		564	$result{$host} = ...;
		565	$cv->end;
		566	};
		567	}
		568
		569	$cv->end;
		570
		571	This code fragment supposedly pings a number of hosts and calls
		572	C<send> after results for all then have have been gathered - in any
		573	order. To achieve this, the code issues a call to C<begin> when it starts
		574	each ping request and calls C<end> when it has received some result for
		575	it. Since C<begin> and C<end> only maintain a counter, the order in which
		576	results arrive is not relevant.
		577
		578	There is an additional bracketing call to C<begin> and C<end> outside the
		579	loop, which serves two important purposes: first, it sets the callback
		580	to be called once the counter reaches C<0>, and second, it ensures that
		581	C<send> is called even when C<no> hosts are being pinged (the loop
		582	doesn't execute once).
		583
		584	This is the general pattern when you "fan out" into multiple subrequests:
		585	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		586	is called at least once, and then, for each subrequest you start, call
		587	C<begin> and for each subrequest you finish, call C<end>.
		588
		589	=back
		590
		591	=head3 METHODS FOR CONSUMERS
		592
		593	These methods should only be used by the consuming side, i.e. the
		594	code awaits the condition.
		595
		596	=over 4
		597
		598	=item $cv->recv
		599
		600	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
296	called on c<$cv>, while servicing other watchers normally.	601	>> methods have been called on c<$cv>, while servicing other watchers
		602	normally.
297		603
298	You can only wait once on a condition - additional calls will return	604	You can only wait once on a condition - additional calls are valid but
299	immediately.	605	will return immediately.
		606
		607	If an error condition has been set by calling C<< ->croak >>, then this
		608	function will call C<croak>.
		609
		610	In list context, all parameters passed to C<send> will be returned,
		611	in scalar context only the first one will be returned.
300		612
301	Not all event models support a blocking wait - some die in that case	613	Not all event models support a blocking wait - some die in that case
302	(programs might want to do that to stay interactive), so I<if you are	614	(programs might want to do that to stay interactive), so I<if you are
303	using this from a module, never require a blocking wait>, but let the	615	using this from a module, never require a blocking wait>, but let the
304	caller decide whether the call will block or not (for example, by coupling	616	caller decide whether the call will block or not (for example, by coupling
305	condition variables with some kind of request results and supporting	617	condition variables with some kind of request results and supporting
306	callbacks so the caller knows that getting the result will not block,	618	callbacks so the caller knows that getting the result will not block,
307	while still suppporting blocking waits if the caller so desires).	619	while still supporting blocking waits if the caller so desires).
308		620
309	Another reason I<never> to C<< ->wait >> in a module is that you cannot	621	Another reason I<never> to C<< ->recv >> in a module is that you cannot
310	sensibly have two C<< ->wait >>'s in parallel, as that would require	622	sensibly have two C<< ->recv >>'s in parallel, as that would require
311	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	623	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
312	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	624	can supply.
313	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
314	from different coroutines, however).
315		625
316	=item $cv->broadcast	626	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		627	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		628	versions and also integrates coroutines into AnyEvent, making blocking
		629	C<< ->recv >> calls perfectly safe as long as they are done from another
		630	coroutine (one that doesn't run the event loop).
317		631
318	Flag the condition as ready - a running C<< ->wait >> and all further	632	You can ensure that C<< -recv >> never blocks by setting a callback and
319	calls to C<wait> will (eventually) return after this method has been	633	only calling C<< ->recv >> from within that callback (or at a later
320	called. If nobody is waiting the broadcast will be remembered..	634	time). This will work even when the event loop does not support blocking
		635	waits otherwise.
		636
		637	=item $bool = $cv->ready
		638
		639	Returns true when the condition is "true", i.e. whether C<send> or
		640	C<croak> have been called.
		641
		642	=item $cb = $cv->cb ($cb->($cv))
		643
		644	This is a mutator function that returns the callback set and optionally
		645	replaces it before doing so.
		646
		647	The callback will be called when the condition becomes "true", i.e. when
		648	C<send> or C<croak> are called, with the only argument being the condition
		649	variable itself. Calling C<recv> inside the callback or at any later time
		650	is guaranteed not to block.
321		651
322	=back	652	=back
323
324	Example:
325
326	# wait till the result is ready
327	my $result_ready = AnyEvent->condvar;
328
329	# do something such as adding a timer
330	# or socket watcher the calls $result_ready->broadcast
331	# when the "result" is ready.
332	# in this case, we simply use a timer:
333	my $w = AnyEvent->timer (
334	after => 1,
335	cb => sub { $result_ready->broadcast },
336	);
337
338	# this "blocks" (while handling events) till the watcher
339	# calls broadcast
340	$result_ready->wait;
341		653
342	=head1 GLOBAL VARIABLES AND FUNCTIONS	654	=head1 GLOBAL VARIABLES AND FUNCTIONS
343		655
344	=over 4	656	=over 4
345		657
…		…
351	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	663	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
352	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	664	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
353		665
354	The known classes so far are:	666	The known classes so far are:
355		667
356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
358	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	668	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
359	AnyEvent::Impl::Event based on Event, second best choice.	669	AnyEvent::Impl::Event based on Event, second best choice.
		670	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
360	AnyEvent::Impl::Glib based on Glib, third-best choice.	671	AnyEvent::Impl::Glib based on Glib, third-best choice.
361	AnyEvent::Impl::Tk based on Tk, very bad choice.	672	AnyEvent::Impl::Tk based on Tk, very bad choice.
362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
363	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	673	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
364	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	674	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		675	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		676
		677	There is no support for WxWidgets, as WxWidgets has no support for
		678	watching file handles. However, you can use WxWidgets through the
		679	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		680	second, which was considered to be too horrible to even consider for
		681	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		682	it's adaptor.
		683
		684	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		685	autodetecting them.
365		686
366	=item AnyEvent::detect	687	=item AnyEvent::detect
367		688
368	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	689	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
369	if necessary. You should only call this function right before you would	690	if necessary. You should only call this function right before you would
370	have created an AnyEvent watcher anyway, that is, as late as possible at	691	have created an AnyEvent watcher anyway, that is, as late as possible at
371	runtime.	692	runtime.
372		693
		694	=item $guard = AnyEvent::post_detect { BLOCK }
		695
		696	Arranges for the code block to be executed as soon as the event model is
		697	autodetected (or immediately if this has already happened).
		698
		699	If called in scalar or list context, then it creates and returns an object
		700	that automatically removes the callback again when it is destroyed. See
		701	L<Coro::BDB> for a case where this is useful.
		702
		703	=item @AnyEvent::post_detect
		704
		705	If there are any code references in this array (you can C<push> to it
		706	before or after loading AnyEvent), then they will called directly after
		707	the event loop has been chosen.
		708
		709	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		710	if it contains a true value then the event loop has already been detected,
		711	and the array will be ignored.
		712
		713	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		714
373	=back	715	=back
374		716
375	=head1 WHAT TO DO IN A MODULE	717	=head1 WHAT TO DO IN A MODULE
376		718
377	As a module author, you should C<use AnyEvent> and call AnyEvent methods	719	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
380	Be careful when you create watchers in the module body - AnyEvent will	722	Be careful when you create watchers in the module body - AnyEvent will
381	decide which event module to use as soon as the first method is called, so	723	decide which event module to use as soon as the first method is called, so
382	by calling AnyEvent in your module body you force the user of your module	724	by calling AnyEvent in your module body you force the user of your module
383	to load the event module first.	725	to load the event module first.
384		726
385	Never call C<< ->wait >> on a condition variable unless you I<know> that	727	Never call C<< ->recv >> on a condition variable unless you I<know> that
386	the C<< ->broadcast >> method has been called on it already. This is	728	the C<< ->send >> method has been called on it already. This is
387	because it will stall the whole program, and the whole point of using	729	because it will stall the whole program, and the whole point of using
388	events is to stay interactive.	730	events is to stay interactive.
389		731
390	It is fine, however, to call C<< ->wait >> when the user of your module	732	It is fine, however, to call C<< ->recv >> when the user of your module
391	requests it (i.e. if you create a http request object ad have a method	733	requests it (i.e. if you create a http request object ad have a method
392	called C<results> that returns the results, it should call C<< ->wait >>	734	called C<results> that returns the results, it should call C<< ->recv >>
393	freely, as the user of your module knows what she is doing. always).	735	freely, as the user of your module knows what she is doing. always).
394		736
395	=head1 WHAT TO DO IN THE MAIN PROGRAM	737	=head1 WHAT TO DO IN THE MAIN PROGRAM
396		738
397	There will always be a single main program - the only place that should	739	There will always be a single main program - the only place that should
…		…
399		741
400	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	742	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
401	do anything special (it does not need to be event-based) and let AnyEvent	743	do anything special (it does not need to be event-based) and let AnyEvent
402	decide which implementation to chose if some module relies on it.	744	decide which implementation to chose if some module relies on it.
403		745
404	If the main program relies on a specific event model. For example, in	746	If the main program relies on a specific event model - for example, in
405	Gtk2 programs you have to rely on the Glib module. You should load the	747	Gtk2 programs you have to rely on the Glib module - you should load the
406	event module before loading AnyEvent or any module that uses it: generally	748	event module before loading AnyEvent or any module that uses it: generally
407	speaking, you should load it as early as possible. The reason is that	749	speaking, you should load it as early as possible. The reason is that
408	modules might create watchers when they are loaded, and AnyEvent will	750	modules might create watchers when they are loaded, and AnyEvent will
409	decide on the event model to use as soon as it creates watchers, and it	751	decide on the event model to use as soon as it creates watchers, and it
410	might chose the wrong one unless you load the correct one yourself.	752	might chose the wrong one unless you load the correct one yourself.
411		753
412	You can chose to use a rather inefficient pure-perl implementation by	754	You can chose to use a pure-perl implementation by loading the
413	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	755	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
414	behaviour everywhere, but letting AnyEvent chose is generally better.	756	everywhere, but letting AnyEvent chose the model is generally better.
		757
		758	=head2 MAINLOOP EMULATION
		759
		760	Sometimes (often for short test scripts, or even standalone programs who
		761	only want to use AnyEvent), you do not want to run a specific event loop.
		762
		763	In that case, you can use a condition variable like this:
		764
		765	AnyEvent->condvar->recv;
		766
		767	This has the effect of entering the event loop and looping forever.
		768
		769	Note that usually your program has some exit condition, in which case
		770	it is better to use the "traditional" approach of storing a condition
		771	variable somewhere, waiting for it, and sending it when the program should
		772	exit cleanly.
		773
		774
		775	=head1 OTHER MODULES
		776
		777	The following is a non-exhaustive list of additional modules that use
		778	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		779	in the same program. Some of the modules come with AnyEvent, some are
		780	available via CPAN.
		781
		782	=over 4
		783
		784	=item L<AnyEvent::Util>
		785
		786	Contains various utility functions that replace often-used but blocking
		787	functions such as C<inet_aton> by event-/callback-based versions.
		788
		789	=item L<AnyEvent::Socket>
		790
		791	Provides various utility functions for (internet protocol) sockets,
		792	addresses and name resolution. Also functions to create non-blocking tcp
		793	connections or tcp servers, with IPv6 and SRV record support and more.
		794
		795	=item L<AnyEvent::Handle>
		796
		797	Provide read and write buffers, manages watchers for reads and writes,
		798	supports raw and formatted I/O, I/O queued and fully transparent and
		799	non-blocking SSL/TLS.
		800
		801	=item L<AnyEvent::DNS>
		802
		803	Provides rich asynchronous DNS resolver capabilities.
		804
		805	=item L<AnyEvent::HTTP>
		806
		807	A simple-to-use HTTP library that is capable of making a lot of concurrent
		808	HTTP requests.
		809
		810	=item L<AnyEvent::HTTPD>
		811
		812	Provides a simple web application server framework.
		813
		814	=item L<AnyEvent::FastPing>
		815
		816	The fastest ping in the west.
		817
		818	=item L<AnyEvent::DBI>
		819
		820	Executes L<DBI> requests asynchronously in a proxy process.
		821
		822	=item L<AnyEvent::AIO>
		823
		824	Truly asynchronous I/O, should be in the toolbox of every event
		825	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		826	together.
		827
		828	=item L<AnyEvent::BDB>
		829
		830	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		831	L<BDB> and AnyEvent together.
		832
		833	=item L<AnyEvent::GPSD>
		834
		835	A non-blocking interface to gpsd, a daemon delivering GPS information.
		836
		837	=item L<AnyEvent::IGS>
		838
		839	A non-blocking interface to the Internet Go Server protocol (used by
		840	L<App::IGS>).
		841
		842	=item L<AnyEvent::IRC>
		843
		844	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		845
		846	=item L<Net::XMPP2>
		847
		848	AnyEvent based XMPP (Jabber protocol) module family.
		849
		850	=item L<Net::FCP>
		851
		852	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		853	of AnyEvent.
		854
		855	=item L<Event::ExecFlow>
		856
		857	High level API for event-based execution flow control.
		858
		859	=item L<Coro>
		860
		861	Has special support for AnyEvent via L<Coro::AnyEvent>.
		862
		863	=item L<IO::Lambda>
		864
		865	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		866
		867	=back
415		868
416	=cut	869	=cut
417		870
418	package AnyEvent;	871	package AnyEvent;
419		872
420	no warnings;	873	no warnings;
421	use strict;	874	use strict qw(vars subs);
422		875
423	use Carp;	876	use Carp;
424		877
425	our $VERSION = '3.12';	878	our $VERSION = 4.35;
426	our $MODEL;	879	our $MODEL;
427		880
428	our $AUTOLOAD;	881	our $AUTOLOAD;
429	our @ISA;	882	our @ISA;
430		883
		884	our @REGISTRY;
		885
		886	our $WIN32;
		887
		888	BEGIN {
		889	my $win32 = ! ! ($^O =~ /mswin32/i);
		890	eval "sub WIN32(){ $win32 }";
		891	}
		892
431	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	893	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
432		894
433	our @REGISTRY;	895	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		896
		897	{
		898	my $idx;
		899	$PROTOCOL{$_} = ++$idx
		900	for reverse split /\s*,\s*/,
		901	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		902	}
434		903
435	my @models = (	904	my @models = (
436	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
437	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
438	[EV:: => AnyEvent::Impl::EV::],	905	[EV:: => AnyEvent::Impl::EV::],
439	[Event:: => AnyEvent::Impl::Event::],	906	[Event:: => AnyEvent::Impl::Event::],
440	[Glib:: => AnyEvent::Impl::Glib::],
441	[Tk:: => AnyEvent::Impl::Tk::],
442	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	907	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		908	# everything below here will not be autoprobed
		909	# as the pureperl backend should work everywhere
		910	# and is usually faster
		911	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		912	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		913	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		914	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		915	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		916	[Wx:: => AnyEvent::Impl::POE::],
		917	[Prima:: => AnyEvent::Impl::POE::],
443	);	918	);
444	my @models_detect = (
445	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
446	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
447	);
448		919
449	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	920	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);
		921
		922	our @post_detect;
		923
		924	sub post_detect(&) {
		925	my ($cb) = @_;
		926
		927	if ($MODEL) {
		928	$cb->();
		929
		930	1
		931	} else {
		932	push @post_detect, $cb;
		933
		934	defined wantarray
		935	? bless \$cb, "AnyEvent::Util::PostDetect"
		936	: ()
		937	}
		938	}
		939
		940	sub AnyEvent::Util::PostDetect::DESTROY {
		941	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		942	}
450		943
451	sub detect() {	944	sub detect() {
452	unless ($MODEL) {	945	unless ($MODEL) {
453	no strict 'refs';	946	no strict 'refs';
		947	local $SIG{__DIE__};
454		948
455	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	949	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
456	my $model = "AnyEvent::Impl::$1";	950	my $model = "AnyEvent::Impl::$1";
457	if (eval "require $model") {	951	if (eval "require $model") {
458	$MODEL = $model;	952	$MODEL = $model;
459	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	953	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		954	} else {
		955	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
460	}	956	}
461	}	957	}
462		958
463	# check for already loaded models	959	# check for already loaded models
464	unless ($MODEL) {	960	unless ($MODEL) {
465	for (@REGISTRY, @models, @models_detect) {	961	for (@REGISTRY, @models) {
466	my ($package, $model) = @$_;	962	my ($package, $model) = @$_;
467	if (${"$package\::VERSION"} > 0) {	963	if (${"$package\::VERSION"} > 0) {
468	if (eval "require $model") {	964	if (eval "require $model") {
469	$MODEL = $model;	965	$MODEL = $model;
470	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	966	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
…		…
486	last;	982	last;
487	}	983	}
488	}	984	}
489		985
490	$MODEL	986	$MODEL
491	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	987	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
492	}	988	}
493	}	989	}
494		990
		991	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		992
495	unshift @ISA, $MODEL;	993	unshift @ISA, $MODEL;
496	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	994
		995	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		996
		997	(shift @post_detect)->() while @post_detect;
497	}	998	}
498		999
499	$MODEL	1000	$MODEL
500	}	1001	}
501		1002
…		…
509		1010
510	my $class = shift;	1011	my $class = shift;
511	$class->$func (@_);	1012	$class->$func (@_);
512	}	1013	}
513		1014
		1015	# utility function to dup a filehandle. this is used by many backends
		1016	# to support binding more than one watcher per filehandle (they usually
		1017	# allow only one watcher per fd, so we dup it to get a different one).
		1018	sub _dupfh($$$$) {
		1019	my ($poll, $fh, $r, $w) = @_;
		1020
		1021	# cygwin requires the fh mode to be matching, unix doesn't
		1022	my ($rw, $mode) = $poll eq "r" ? ($r, "<")
		1023	: $poll eq "w" ? ($w, ">")
		1024	: Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
		1025
		1026	open my $fh2, "$mode&" . fileno $fh
		1027	or die "cannot dup() filehandle: $!";
		1028
		1029	# we assume CLOEXEC is already set by perl in all important cases
		1030
		1031	($fh2, $rw)
		1032	}
		1033
514	package AnyEvent::Base;	1034	package AnyEvent::Base;
515		1035
		1036	# default implementation for now and time
		1037
		1038	BEGIN {
		1039	if (eval "use Time::HiRes (); time (); 1") {
		1040	*_time = \&Time::HiRes::time;
		1041	# if (eval "use POSIX (); (POSIX::times())...
		1042	} else {
		1043	*_time = sub { time }; # epic fail
		1044	}
		1045	}
		1046
		1047	sub time { _time }
		1048	sub now { _time }
		1049
516	# default implementation for ->condvar, ->wait, ->broadcast	1050	# default implementation for ->condvar
517		1051
518	sub condvar {	1052	sub condvar {
519	bless \my $flag, "AnyEvent::Base::CondVar"	1053	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
520	}
521
522	sub AnyEvent::Base::CondVar::broadcast {
523	${$_[0]}++;
524	}
525
526	sub AnyEvent::Base::CondVar::wait {
527	AnyEvent->one_event while !${$_[0]};
528	}	1054	}
529		1055
530	# default implementation for ->signal	1056	# default implementation for ->signal
531		1057
532	our %SIG_CB;	1058	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1059
		1060	sub _signal_exec {
		1061	sysread $SIGPIPE_R, my $dummy, 4;
		1062
		1063	while (%SIG_EV) {
		1064	for (keys %SIG_EV) {
		1065	delete $SIG_EV{$_};
		1066	$_->() for values %{ $SIG_CB{$_} || {} };
		1067	}
		1068	}
		1069	}
533		1070
534	sub signal {	1071	sub signal {
535	my (undef, %arg) = @_;	1072	my (undef, %arg) = @_;
536		1073
		1074	unless ($SIGPIPE_R) {
		1075	require Fcntl;
		1076
		1077	if (AnyEvent::WIN32) {
		1078	require AnyEvent::Util;
		1079
		1080	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1081	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1082	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1083	} else {
		1084	pipe $SIGPIPE_R, $SIGPIPE_W;
		1085	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1086	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1087	}
		1088
		1089	$SIGPIPE_R
		1090	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1091
		1092	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1093	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1094
		1095	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1096	}
		1097
537	my $signal = uc $arg{signal}	1098	my $signal = uc $arg{signal}
538	or Carp::croak "required option 'signal' is missing";	1099	or Carp::croak "required option 'signal' is missing";
539		1100
540	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1101	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
541	$SIG{$signal} ||= sub {	1102	$SIG{$signal} ||= sub {
542	$_->() for values %{ $SIG_CB{$signal} || {} };	1103	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1104	undef $SIG_EV{$signal};
543	};	1105	};
544		1106
545	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1107	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"
546	}	1108	}
547		1109
548	sub AnyEvent::Base::Signal::DESTROY {	1110	sub AnyEvent::Base::Signal::DESTROY {
549	my ($signal, $cb) = @{$_[0]};	1111	my ($signal, $cb) = @{$_[0]};
550		1112
551	delete $SIG_CB{$signal}{$cb};	1113	delete $SIG_CB{$signal}{$cb};
552		1114
553	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1115	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
554	}	1116	}
555		1117
556	# default implementation for ->child	1118	# default implementation for ->child
557		1119
558	our %PID_CB;	1120	our %PID_CB;
…		…
585	or Carp::croak "required option 'pid' is missing";	1147	or Carp::croak "required option 'pid' is missing";
586		1148
587	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1149	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
588		1150
589	unless ($WNOHANG) {	1151	unless ($WNOHANG) {
590	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1152	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
591	}	1153	}
592		1154
593	unless ($CHLD_W) {	1155	unless ($CHLD_W) {
594	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1156	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
595	# child could be a zombie already, so make at least one round	1157	# child could be a zombie already, so make at least one round
…		…
605	delete $PID_CB{$pid}{$cb};	1167	delete $PID_CB{$pid}{$cb};
606	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1168	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
607		1169
608	undef $CHLD_W unless keys %PID_CB;	1170	undef $CHLD_W unless keys %PID_CB;
609	}	1171	}
		1172
		1173	package AnyEvent::CondVar;
		1174
		1175	our @ISA = AnyEvent::CondVar::Base::;
		1176
		1177	package AnyEvent::CondVar::Base;
		1178
		1179	use overload
		1180	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1181	fallback => 1;
		1182
		1183	sub _send {
		1184	# nop
		1185	}
		1186
		1187	sub send {
		1188	my $cv = shift;
		1189	$cv->{_ae_sent} = [@_];
		1190	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1191	$cv->_send;
		1192	}
		1193
		1194	sub croak {
		1195	$_[0]{_ae_croak} = $_[1];
		1196	$_[0]->send;
		1197	}
		1198
		1199	sub ready {
		1200	$_[0]{_ae_sent}
		1201	}
		1202
		1203	sub _wait {
		1204	AnyEvent->one_event while !$_[0]{_ae_sent};
		1205	}
		1206
		1207	sub recv {
		1208	$_[0]->_wait;
		1209
		1210	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1211	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1212	}
		1213
		1214	sub cb {
		1215	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1216	$_[0]{_ae_cb}
		1217	}
		1218
		1219	sub begin {
		1220	++$_[0]{_ae_counter};
		1221	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1222	}
		1223
		1224	sub end {
		1225	return if --$_[0]{_ae_counter};
		1226	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1227	}
		1228
		1229	# undocumented/compatibility with pre-3.4
		1230	*broadcast = \&send;
		1231	*wait = \&_wait;
		1232
		1233	=head1 ERROR AND EXCEPTION HANDLING
		1234
		1235	In general, AnyEvent does not do any error handling - it relies on the
		1236	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1237	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1238	checking of all AnyEvent methods, however, which is highly useful during
		1239	development.
		1240
		1241	As for exception handling (i.e. runtime errors and exceptions thrown while
		1242	executing a callback), this is not only highly event-loop specific, but
		1243	also not in any way wrapped by this module, as this is the job of the main
		1244	program.
		1245
		1246	The pure perl event loop simply re-throws the exception (usually
		1247	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1248	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1249	so on.
		1250
		1251	=head1 ENVIRONMENT VARIABLES
		1252
		1253	The following environment variables are used by this module or its
		1254	submodules:
		1255
		1256	=over 4
		1257
		1258	=item C<PERL_ANYEVENT_VERBOSE>
		1259
		1260	By default, AnyEvent will be completely silent except in fatal
		1261	conditions. You can set this environment variable to make AnyEvent more
		1262	talkative.
		1263
		1264	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1265	conditions, such as not being able to load the event model specified by
		1266	C<PERL_ANYEVENT_MODEL>.
		1267
		1268	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1269	model it chooses.
		1270
		1271	=item C<PERL_ANYEVENT_STRICT>
		1272
		1273	AnyEvent does not do much argument checking by default, as thorough
		1274	argument checking is very costly. Setting this variable to a true value
		1275	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1276	check the arguments passed to most method calls. If it finds any problems
		1277	it will croak.
		1278
		1279	In other words, enables "strict" mode.
		1280
		1281	Unlike C<use strict>, it is definitely recommended ot keep it off in
		1282	production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
		1283	developing programs can be very useful, however.
		1284
		1285	=item C<PERL_ANYEVENT_MODEL>
		1286
		1287	This can be used to specify the event model to be used by AnyEvent, before
		1288	auto detection and -probing kicks in. It must be a string consisting
		1289	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1290	and the resulting module name is loaded and if the load was successful,
		1291	used as event model. If it fails to load AnyEvent will proceed with
		1292	auto detection and -probing.
		1293
		1294	This functionality might change in future versions.
		1295
		1296	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1297	could start your program like this:
		1298
		1299	PERL_ANYEVENT_MODEL=Perl perl ...
		1300
		1301	=item C<PERL_ANYEVENT_PROTOCOLS>
		1302
		1303	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1304	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1305	of auto probing).
		1306
		1307	Must be set to a comma-separated list of protocols or address families,
		1308	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1309	used, and preference will be given to protocols mentioned earlier in the
		1310	list.
		1311
		1312	This variable can effectively be used for denial-of-service attacks
		1313	against local programs (e.g. when setuid), although the impact is likely
		1314	small, as the program has to handle conenction and other failures anyways.
		1315
		1316	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1317	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1318	- only support IPv4, never try to resolve or contact IPv6
		1319	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1320	IPv6, but prefer IPv6 over IPv4.
		1321
		1322	=item C<PERL_ANYEVENT_EDNS0>
		1323
		1324	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1325	for DNS. This extension is generally useful to reduce DNS traffic, but
		1326	some (broken) firewalls drop such DNS packets, which is why it is off by
		1327	default.
		1328
		1329	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1330	EDNS0 in its DNS requests.
		1331
		1332	=item C<PERL_ANYEVENT_MAX_FORKS>
		1333
		1334	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1335	will create in parallel.
		1336
		1337	=back
610		1338
611	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1339	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
612		1340
613	This is an advanced topic that you do not normally need to use AnyEvent in	1341	This is an advanced topic that you do not normally need to use AnyEvent in
614	a module. This section is only of use to event loop authors who want to	1342	a module. This section is only of use to event loop authors who want to
…		…
649	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1377	I<rxvt-unicode> also cheats a bit by not providing blocking access to
650	condition variables: code blocking while waiting for a condition will	1378	condition variables: code blocking while waiting for a condition will
651	C<die>. This still works with most modules/usages, and blocking calls must	1379	C<die>. This still works with most modules/usages, and blocking calls must
652	not be done in an interactive application, so it makes sense.	1380	not be done in an interactive application, so it makes sense.
653		1381
654	=head1 ENVIRONMENT VARIABLES
655
656	The following environment variables are used by this module:
657
658	=over 4
659
660	=item C<PERL_ANYEVENT_VERBOSE>
661
662	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
663	model it chooses.
664
665	=item C<PERL_ANYEVENT_MODEL>
666
667	This can be used to specify the event model to be used by AnyEvent, before
668	autodetection and -probing kicks in. It must be a string consisting
669	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
670	and the resulting module name is loaded and if the load was successful,
671	used as event model. If it fails to load AnyEvent will proceed with
672	autodetection and -probing.
673
674	This functionality might change in future versions.
675
676	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
677	could start your program like this:
678
679	PERL_ANYEVENT_MODEL=Perl perl ...
680
681	=back
682
683	=head1 EXAMPLE PROGRAM	1382	=head1 EXAMPLE PROGRAM
684		1383
685	The following program uses an IO watcher to read data from STDIN, a timer	1384	The following program uses an I/O watcher to read data from STDIN, a timer
686	to display a message once per second, and a condition variable to quit the	1385	to display a message once per second, and a condition variable to quit the
687	program when the user enters quit:	1386	program when the user enters quit:
688		1387
689	use AnyEvent;	1388	use AnyEvent;
690		1389
…		…
695	poll => 'r',	1394	poll => 'r',
696	cb => sub {	1395	cb => sub {
697	warn "io event <$_[0]>\n"; # will always output <r>	1396	warn "io event <$_[0]>\n"; # will always output <r>
698	chomp (my $input = <STDIN>); # read a line	1397	chomp (my $input = <STDIN>); # read a line
699	warn "read: $input\n"; # output what has been read	1398	warn "read: $input\n"; # output what has been read
700	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1399	$cv->send if $input =~ /^q/i; # quit program if /^q/i
701	},	1400	},
702	);	1401	);
703		1402
704	my $time_watcher; # can only be used once	1403	my $time_watcher; # can only be used once
705		1404
…		…
710	});	1409	});
711	}	1410	}
712		1411
713	new_timer; # create first timer	1412	new_timer; # create first timer
714		1413
715	$cv->wait; # wait until user enters /^q/i	1414	$cv->recv; # wait until user enters /^q/i
716		1415
717	=head1 REAL-WORLD EXAMPLE	1416	=head1 REAL-WORLD EXAMPLE
718		1417
719	Consider the L<Net::FCP> module. It features (among others) the following	1418	Consider the L<Net::FCP> module. It features (among others) the following
720	API calls, which are to freenet what HTTP GET requests are to http:	1419	API calls, which are to freenet what HTTP GET requests are to http:
…		…
770	syswrite $txn->{fh}, $txn->{request}	1469	syswrite $txn->{fh}, $txn->{request}
771	or die "connection or write error";	1470	or die "connection or write error";
772	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1471	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
773		1472
774	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1473	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
775	result and signals any possible waiters that the request ahs finished:	1474	result and signals any possible waiters that the request has finished:
776		1475
777	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1476	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
778		1477
779	if (end-of-file or data complete) {	1478	if (end-of-file or data complete) {
780	$txn->{result} = $txn->{buf};	1479	$txn->{result} = $txn->{buf};
781	$txn->{finished}->broadcast;	1480	$txn->{finished}->send;
782	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1481	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
783	}	1482	}
784		1483
785	The C<result> method, finally, just waits for the finished signal (if the	1484	The C<result> method, finally, just waits for the finished signal (if the
786	request was already finished, it doesn't wait, of course, and returns the	1485	request was already finished, it doesn't wait, of course, and returns the
787	data:	1486	data:
788		1487
789	$txn->{finished}->wait;	1488	$txn->{finished}->recv;
790	return $txn->{result};	1489	return $txn->{result};
791		1490
792	The actual code goes further and collects all errors (C<die>s, exceptions)	1491	The actual code goes further and collects all errors (C<die>s, exceptions)
793	that occured during request processing. The C<result> method detects	1492	that occurred during request processing. The C<result> method detects
794	whether an exception as thrown (it is stored inside the $txn object)	1493	whether an exception as thrown (it is stored inside the $txn object)
795	and just throws the exception, which means connection errors and other	1494	and just throws the exception, which means connection errors and other
796	problems get reported tot he code that tries to use the result, not in a	1495	problems get reported tot he code that tries to use the result, not in a
797	random callback.	1496	random callback.
798		1497
…		…
829		1528
830	my $quit = AnyEvent->condvar;	1529	my $quit = AnyEvent->condvar;
831		1530
832	$fcp->txn_client_get ($url)->cb (sub {	1531	$fcp->txn_client_get ($url)->cb (sub {
833	...	1532	...
834	$quit->broadcast;	1533	$quit->send;
835	});	1534	});
836		1535
837	$quit->wait;	1536	$quit->recv;
		1537
		1538
		1539	=head1 BENCHMARKS
		1540
		1541	To give you an idea of the performance and overheads that AnyEvent adds
		1542	over the event loops themselves and to give you an impression of the speed
		1543	of various event loops I prepared some benchmarks.
		1544
		1545	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1546
		1547	Here is a benchmark of various supported event models used natively and
		1548	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1549	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1550	which it is), lets them fire exactly once and destroys them again.
		1551
		1552	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1553	distribution.
		1554
		1555	=head3 Explanation of the columns
		1556
		1557	I<watcher> is the number of event watchers created/destroyed. Since
		1558	different event models feature vastly different performances, each event
		1559	loop was given a number of watchers so that overall runtime is acceptable
		1560	and similar between tested event loop (and keep them from crashing): Glib
		1561	would probably take thousands of years if asked to process the same number
		1562	of watchers as EV in this benchmark.
		1563
		1564	I<bytes> is the number of bytes (as measured by the resident set size,
		1565	RSS) consumed by each watcher. This method of measuring captures both C
		1566	and Perl-based overheads.
		1567
		1568	I<create> is the time, in microseconds (millionths of seconds), that it
		1569	takes to create a single watcher. The callback is a closure shared between
		1570	all watchers, to avoid adding memory overhead. That means closure creation
		1571	and memory usage is not included in the figures.
		1572
		1573	I<invoke> is the time, in microseconds, used to invoke a simple
		1574	callback. The callback simply counts down a Perl variable and after it was
		1575	invoked "watcher" times, it would C<< ->send >> a condvar once to
		1576	signal the end of this phase.
		1577
		1578	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1579	watcher.
		1580
		1581	=head3 Results
		1582
		1583	name watchers bytes create invoke destroy comment
		1584	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
		1585	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
		1586	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
		1587	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
		1588	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
		1589	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1590	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
		1591	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
		1592	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
		1593	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
		1594
		1595	=head3 Discussion
		1596
		1597	The benchmark does I<not> measure scalability of the event loop very
		1598	well. For example, a select-based event loop (such as the pure perl one)
		1599	can never compete with an event loop that uses epoll when the number of
		1600	file descriptors grows high. In this benchmark, all events become ready at
		1601	the same time, so select/poll-based implementations get an unnatural speed
		1602	boost.
		1603
		1604	Also, note that the number of watchers usually has a nonlinear effect on
		1605	overall speed, that is, creating twice as many watchers doesn't take twice
		1606	the time - usually it takes longer. This puts event loops tested with a
		1607	higher number of watchers at a disadvantage.
		1608
		1609	To put the range of results into perspective, consider that on the
		1610	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1611	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1612	cycles with POE.
		1613
		1614	C<EV> is the sole leader regarding speed and memory use, which are both
		1615	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1616	far less memory than any other event loop and is still faster than Event
		1617	natively.
		1618
		1619	The pure perl implementation is hit in a few sweet spots (both the
		1620	constant timeout and the use of a single fd hit optimisations in the perl
		1621	interpreter and the backend itself). Nevertheless this shows that it
		1622	adds very little overhead in itself. Like any select-based backend its
		1623	performance becomes really bad with lots of file descriptors (and few of
		1624	them active), of course, but this was not subject of this benchmark.
		1625
		1626	The C<Event> module has a relatively high setup and callback invocation
		1627	cost, but overall scores in on the third place.
		1628
		1629	C<Glib>'s memory usage is quite a bit higher, but it features a
		1630	faster callback invocation and overall ends up in the same class as
		1631	C<Event>. However, Glib scales extremely badly, doubling the number of
		1632	watchers increases the processing time by more than a factor of four,
		1633	making it completely unusable when using larger numbers of watchers
		1634	(note that only a single file descriptor was used in the benchmark, so
		1635	inefficiencies of C<poll> do not account for this).
		1636
		1637	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1638	more than 2000 watchers is a big setback, however, as correctness takes
		1639	precedence over speed. Nevertheless, its performance is surprising, as the
		1640	file descriptor is dup()ed for each watcher. This shows that the dup()
		1641	employed by some adaptors is not a big performance issue (it does incur a
		1642	hidden memory cost inside the kernel which is not reflected in the figures
		1643	above).
		1644
		1645	C<POE>, regardless of underlying event loop (whether using its pure perl
		1646	select-based backend or the Event module, the POE-EV backend couldn't
		1647	be tested because it wasn't working) shows abysmal performance and
		1648	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		1649	as EV watchers, and 10 times as much memory as Event (the high memory
		1650	requirements are caused by requiring a session for each watcher). Watcher
		1651	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1652	implementation.
		1653
		1654	The design of the POE adaptor class in AnyEvent can not really account
		1655	for the performance issues, though, as session creation overhead is
		1656	small compared to execution of the state machine, which is coded pretty
		1657	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1658	using multiple sessions is not a good approach, especially regarding
		1659	memory usage, even the author of POE could not come up with a faster
		1660	design).
		1661
		1662	=head3 Summary
		1663
		1664	=over 4
		1665
		1666	=item * Using EV through AnyEvent is faster than any other event loop
		1667	(even when used without AnyEvent), but most event loops have acceptable
		1668	performance with or without AnyEvent.
		1669
		1670	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1671	the actual event loop, only with extremely fast event loops such as EV
		1672	adds AnyEvent significant overhead.
		1673
		1674	=item * You should avoid POE like the plague if you want performance or
		1675	reasonable memory usage.
		1676
		1677	=back
		1678
		1679	=head2 BENCHMARKING THE LARGE SERVER CASE
		1680
		1681	This benchmark actually benchmarks the event loop itself. It works by
		1682	creating a number of "servers": each server consists of a socket pair, a
		1683	timeout watcher that gets reset on activity (but never fires), and an I/O
		1684	watcher waiting for input on one side of the socket. Each time the socket
		1685	watcher reads a byte it will write that byte to a random other "server".
		1686
		1687	The effect is that there will be a lot of I/O watchers, only part of which
		1688	are active at any one point (so there is a constant number of active
		1689	fds for each loop iteration, but which fds these are is random). The
		1690	timeout is reset each time something is read because that reflects how
		1691	most timeouts work (and puts extra pressure on the event loops).
		1692
		1693	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1694	(1%) are active. This mirrors the activity of large servers with many
		1695	connections, most of which are idle at any one point in time.
		1696
		1697	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1698	distribution.
		1699
		1700	=head3 Explanation of the columns
		1701
		1702	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1703	each server has a read and write socket end).
		1704
		1705	I<create> is the time it takes to create a socket pair (which is
		1706	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1707
		1708	I<request>, the most important value, is the time it takes to handle a
		1709	single "request", that is, reading the token from the pipe and forwarding
		1710	it to another server. This includes deleting the old timeout and creating
		1711	a new one that moves the timeout into the future.
		1712
		1713	=head3 Results
		1714
		1715	name sockets create request
		1716	EV 20000 69.01 11.16
		1717	Perl 20000 73.32 35.87
		1718	Event 20000 212.62 257.32
		1719	Glib 20000 651.16 1896.30
		1720	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1721
		1722	=head3 Discussion
		1723
		1724	This benchmark I<does> measure scalability and overall performance of the
		1725	particular event loop.
		1726
		1727	EV is again fastest. Since it is using epoll on my system, the setup time
		1728	is relatively high, though.
		1729
		1730	Perl surprisingly comes second. It is much faster than the C-based event
		1731	loops Event and Glib.
		1732
		1733	Event suffers from high setup time as well (look at its code and you will
		1734	understand why). Callback invocation also has a high overhead compared to
		1735	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1736	uses select or poll in basically all documented configurations.
		1737
		1738	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1739	clearly fails to perform with many filehandles or in busy servers.
		1740
		1741	POE is still completely out of the picture, taking over 1000 times as long
		1742	as EV, and over 100 times as long as the Perl implementation, even though
		1743	it uses a C-based event loop in this case.
		1744
		1745	=head3 Summary
		1746
		1747	=over 4
		1748
		1749	=item * The pure perl implementation performs extremely well.
		1750
		1751	=item * Avoid Glib or POE in large projects where performance matters.
		1752
		1753	=back
		1754
		1755	=head2 BENCHMARKING SMALL SERVERS
		1756
		1757	While event loops should scale (and select-based ones do not...) even to
		1758	large servers, most programs we (or I :) actually write have only a few
		1759	I/O watchers.
		1760
		1761	In this benchmark, I use the same benchmark program as in the large server
		1762	case, but it uses only eight "servers", of which three are active at any
		1763	one time. This should reflect performance for a small server relatively
		1764	well.
		1765
		1766	The columns are identical to the previous table.
		1767
		1768	=head3 Results
		1769
		1770	name sockets create request
		1771	EV 16 20.00 6.54
		1772	Perl 16 25.75 12.62
		1773	Event 16 81.27 35.86
		1774	Glib 16 32.63 15.48
		1775	POE 16 261.87 276.28 uses POE::Loop::Event
		1776
		1777	=head3 Discussion
		1778
		1779	The benchmark tries to test the performance of a typical small
		1780	server. While knowing how various event loops perform is interesting, keep
		1781	in mind that their overhead in this case is usually not as important, due
		1782	to the small absolute number of watchers (that is, you need efficiency and
		1783	speed most when you have lots of watchers, not when you only have a few of
		1784	them).
		1785
		1786	EV is again fastest.
		1787
		1788	Perl again comes second. It is noticeably faster than the C-based event
		1789	loops Event and Glib, although the difference is too small to really
		1790	matter.
		1791
		1792	POE also performs much better in this case, but is is still far behind the
		1793	others.
		1794
		1795	=head3 Summary
		1796
		1797	=over 4
		1798
		1799	=item * C-based event loops perform very well with small number of
		1800	watchers, as the management overhead dominates.
		1801
		1802	=back
		1803
		1804
		1805	=head1 SIGNALS
		1806
		1807	AnyEvent currently installs handlers for these signals:
		1808
		1809	=over 4
		1810
		1811	=item SIGCHLD
		1812
		1813	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		1814	emulation for event loops that do not support them natively. Also, some
		1815	event loops install a similar handler.
		1816
		1817	=item SIGPIPE
		1818
		1819	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		1820	when AnyEvent gets loaded.
		1821
		1822	The rationale for this is that AnyEvent users usually do not really depend
		1823	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		1824	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		1825	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		1826	some random socket.
		1827
		1828	The rationale for installing a no-op handler as opposed to ignoring it is
		1829	that this way, the handler will be restored to defaults on exec.
		1830
		1831	Feel free to install your own handler, or reset it to defaults.
		1832
		1833	=back
		1834
		1835	=cut
		1836
		1837	$SIG{PIPE} = sub { }
		1838	unless defined $SIG{PIPE};
		1839
838		1840
839	=head1 FORK	1841	=head1 FORK
840		1842
841	Most event libraries are not fork-safe. The ones who are usually are	1843	Most event libraries are not fork-safe. The ones who are usually are
842	because they are so inefficient. Only L<EV> is fully fork-aware.	1844	because they rely on inefficient but fork-safe C<select> or C<poll>
		1845	calls. Only L<EV> is fully fork-aware.
843		1846
844	If you have to fork, you must either do so I<before> creating your first	1847	If you have to fork, you must either do so I<before> creating your first
845	watcher OR you must not use AnyEvent at all in the child.	1848	watcher OR you must not use AnyEvent at all in the child.
		1849
846		1850
847	=head1 SECURITY CONSIDERATIONS	1851	=head1 SECURITY CONSIDERATIONS
848		1852
849	AnyEvent can be forced to load any event model via	1853	AnyEvent can be forced to load any event model via
850	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	1854	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
854	specified in the variable.	1858	specified in the variable.
855		1859
856	You can make AnyEvent completely ignore this variable by deleting it	1860	You can make AnyEvent completely ignore this variable by deleting it
857	before the first watcher gets created, e.g. with a C<BEGIN> block:	1861	before the first watcher gets created, e.g. with a C<BEGIN> block:
858		1862
859	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1863	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
860		1864
861	use AnyEvent;	1865	use AnyEvent;
		1866
		1867	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1868	be used to probe what backend is used and gain other information (which is
		1869	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		1870	$ENV{PERL_ANYEGENT_STRICT}.
		1871
		1872
		1873	=head1 BUGS
		1874
		1875	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		1876	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		1877	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		1878	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		1879	pronounced).
		1880
862		1881
863	=head1 SEE ALSO	1882	=head1 SEE ALSO
864		1883
865	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1884	Utility functions: L<AnyEvent::Util>.
866	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
867	L<Event::Lib>, L<Qt>.
868		1885
869	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1886	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
870	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1887	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
871	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1888
		1889	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		1890	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		1891	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
872	L<AnyEvent::Impl::Qt>.	1892	L<AnyEvent::Impl::POE>.
873		1893
		1894	Non-blocking file handles, sockets, TCP clients and
		1895	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1896
		1897	Asynchronous DNS: L<AnyEvent::DNS>.
		1898
		1899	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1900
874	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1901	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
		1902
875		1903
876	=head1 AUTHOR	1904	=head1 AUTHOR
877		1905
878	Marc Lehmann <schmorp@schmorp.de>	1906	Marc Lehmann <schmorp@schmorp.de>
879	http://home.schmorp.de/	1907	http://home.schmorp.de/
880		1908
881	=cut	1909	=cut
882		1910
883	1	1911	1
884		1912

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