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Revision 1.169 by root, Wed Jul 9 10:36:22 2008 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
6		6
7	=head1 SYNOPSIS	7	=head1 SYNOPSIS
8		8
9	use AnyEvent;	9	use AnyEvent;
10		10
…		…
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	15	my $w = AnyEvent->timer (after => $seconds, cb => sub {
16	...	16	...
17	});	17	});
18		18
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	19	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		20	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	21	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	22
		23	=head1 INTRODUCTION/TUTORIAL
		24
		25	This manpage is mainly a reference manual. If you are interested
		26	in a tutorial or some gentle introduction, have a look at the
		27	L<AnyEvent::Intro> manpage.
22		28
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	29	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		30
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	31	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	32	nowadays. So what is different about AnyEvent?
27		33
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	34	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	35	policy> and AnyEvent is I<small and efficient>.
30		36
31	First and foremost, I<AnyEvent is not an event model> itself, it only	37	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	38	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,	39	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,	40	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	41	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	42	cannot change this, but it can hide the differences between those event
		43	loops.
37		44
38	The goal of AnyEvent is to offer module authors the ability to do event	45	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	46	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	47	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	48	module users into the same thing by forcing them to use the same event
42	model you use.	49	model you use.
43		50
44	For modules like POE or IO::Async (which is a total misnomer as it is	51	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	52	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	53	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	54	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	55	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.	56	module are I<also> forced to use the same event loop you use.
50		57
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	58	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	59	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	60	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,	61	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	62	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	63	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	64	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).	65	to AnyEvent, too, so it is future-proof).
59		66
60	In addition to being free of having to use I<the one and only true event	67	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	68	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	69	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	70	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	71	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	72	technically possible.
66		73
		74	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		75	of useful functionality, such as an asynchronous DNS resolver, 100%
		76	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		77	such as Windows) and lots of real-world knowledge and workarounds for
		78	platform bugs and differences.
		79
67	Of course, if you want lots of policy (this can arguably be somewhat	80	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	81	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	82	model, you should I<not> use this module.
70
71		83
72	=head1 DESCRIPTION	84	=head1 DESCRIPTION
73		85
74	L<AnyEvent> provides an identical interface to multiple event loops. This	86	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	87	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>	91	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	92	module.
81		93
82	During the first call of any watcher-creation method, the module tries	94	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	95	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>,	96	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,	97	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	L<POE>. The first one found is used. If none are found, the module tries	98	L<POE>. The first one found is used. If none are found, the module tries
87	to load these modules (excluding Event::Lib, Qt and POE as the pure perl	99	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
88	adaptor should always succeed) in the order given. The first one that can	100	adaptor should always succeed) in the order given. The first one that can
89	be successfully loaded will be used. If, after this, still none could be	101	be successfully loaded will be used. If, after this, still none could be
90	found, AnyEvent will fall back to a pure-perl event loop, which is not	102	found, AnyEvent will fall back to a pure-perl event loop, which is not
91	very efficient, but should work everywhere.	103	very efficient, but should work everywhere.
92		104
…		…
103	starts using it, all bets are off. Maybe you should tell their authors to	115	starts using it, all bets are off. Maybe you should tell their authors to
104	use AnyEvent so their modules work together with others seamlessly...	116	use AnyEvent so their modules work together with others seamlessly...
105		117
106	The pure-perl implementation of AnyEvent is called	118	The pure-perl implementation of AnyEvent is called
107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	119	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
108	explicitly.	120	explicitly and enjoy the high availability of that event loop :)
109		121
110	=head1 WATCHERS	122	=head1 WATCHERS
111		123
112	AnyEvent has the central concept of a I<watcher>, which is an object that	124	AnyEvent has the central concept of a I<watcher>, which is an object that
113	stores relevant data for each kind of event you are waiting for, such as	125	stores relevant data for each kind of event you are waiting for, such as
114	the callback to call, the filehandle to watch, etc.	126	the callback to call, the file handle to watch, etc.
115		127
116	These watchers are normal Perl objects with normal Perl lifetime. After	128	These watchers are normal Perl objects with normal Perl lifetime. After
117	creating a watcher it will immediately "watch" for events and invoke the	129	creating a watcher it will immediately "watch" for events and invoke the
118	callback when the event occurs (of course, only when the event model	130	callback when the event occurs (of course, only when the event model
119	is in control).	131	is in control).
…		…
127	Many watchers either are used with "recursion" (repeating timers for	139	Many watchers either are used with "recursion" (repeating timers for
128	example), or need to refer to their watcher object in other ways.	140	example), or need to refer to their watcher object in other ways.
129		141
130	An any way to achieve that is this pattern:	142	An any way to achieve that is this pattern:
131		143
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	144	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	145	# you can use $w here, for example to undef it
134	undef $w;	146	undef $w;
135	});	147	});
136		148
137	Note that C<my $w; $w => combination. This is necessary because in Perl,	149	Note that C<my $w; $w => combination. This is necessary because in Perl,
138	my variables are only visible after the statement in which they are	150	my variables are only visible after the statement in which they are
139	declared.	151	declared.
140		152
141	=head2 IO WATCHERS	153	=head2 I/O WATCHERS
142		154
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	155	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	156	with the following mandatory key-value pairs as arguments:
145		157
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	158	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for events
		159	(AnyEvent might or might not keep a reference to this file handle). C<poll>
147	events. C<poll> must be a string that is either C<r> or C<w>, which	160	must be a string that is either C<r> or C<w>, which creates a watcher
148	creates a watcher waiting for "r"eadable or "w"ritable events,	161	waiting for "r"eadable or "w"ritable events, respectively. C<cb> is the
149	respectively. C<cb> is the callback to invoke each time the file handle	162	callback to invoke each time the file handle becomes ready.
150	becomes ready.
151		163
152	As long as the I/O watcher exists it will keep the file descriptor or a	164	Although the callback might get passed parameters, their value and
153	copy of it alive/open.	165	presence is undefined and you cannot rely on them. Portable AnyEvent
		166	callbacks cannot use arguments passed to I/O watcher callbacks.
154		167
		168	The I/O watcher might use the underlying file descriptor or a copy of it.
155	It is not allowed to close a file handle as long as any watcher is active	169	You must not close a file handle as long as any watcher is active on the
156	on the underlying file descriptor.	170	underlying file descriptor.
157		171
158	Some event loops issue spurious readyness notifications, so you should	172	Some event loops issue spurious readyness notifications, so you should
159	always use non-blocking calls when reading/writing from/to your file	173	always use non-blocking calls when reading/writing from/to your file
160	handles.	174	handles.
161		175
162	Example:
163
164	# wait for readability of STDIN, then read a line and disable the watcher	176	Example: wait for readability of STDIN, then read a line and disable the
		177	watcher.
		178
165	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	179	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
166	chomp (my $input = <STDIN>);	180	chomp (my $input = <STDIN>);
167	warn "read: $input\n";	181	warn "read: $input\n";
168	undef $w;	182	undef $w;
169	});	183	});
…		…
172		186
173	You can create a time watcher by calling the C<< AnyEvent->timer >>	187	You can create a time watcher by calling the C<< AnyEvent->timer >>
174	method with the following mandatory arguments:	188	method with the following mandatory arguments:
175		189
176	C<after> specifies after how many seconds (fractional values are	190	C<after> specifies after how many seconds (fractional values are
177	supported) should the timer activate. C<cb> the callback to invoke in that	191	supported) the callback should be invoked. C<cb> is the callback to invoke
178	case.	192	in that case.
179		193
180	The timer callback will be invoked at most once: if you want a repeating	194	Although the callback might get passed parameters, their value and
181	timer you have to create a new watcher (this is a limitation by both Tk	195	presence is undefined and you cannot rely on them. Portable AnyEvent
182	and Glib).	196	callbacks cannot use arguments passed to time watcher callbacks.
183		197
184	Example:	198	The callback will normally be invoked once only. If you specify another
		199	parameter, C<interval>, as a strictly positive number (> 0), then the
		200	callback will be invoked regularly at that interval (in fractional
		201	seconds) after the first invocation. If C<interval> is specified with a
		202	false value, then it is treated as if it were missing.
185		203
		204	The callback will be rescheduled before invoking the callback, but no
		205	attempt is done to avoid timer drift in most backends, so the interval is
		206	only approximate.
		207
186	# fire an event after 7.7 seconds	208	Example: fire an event after 7.7 seconds.
		209
187	my $w = AnyEvent->timer (after => 7.7, cb => sub {	210	my $w = AnyEvent->timer (after => 7.7, cb => sub {
188	warn "timeout\n";	211	warn "timeout\n";
189	});	212	});
190		213
191	# to cancel the timer:	214	# to cancel the timer:
192	undef $w;	215	undef $w;
193		216
194	Example 2:
195
196	# fire an event after 0.5 seconds, then roughly every second	217	Example 2: fire an event after 0.5 seconds, then roughly every second.
197	my $w;
198		218
199	my $cb = sub {
200	# cancel the old timer while creating a new one
201	$w = AnyEvent->timer (after => 1, cb => $cb);	219	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		220	warn "timeout\n";
202	};	221	};
203
204	# start the "loop" by creating the first watcher
205	$w = AnyEvent->timer (after => 0.5, cb => $cb);
206		222
207	=head3 TIMING ISSUES	223	=head3 TIMING ISSUES
208		224
209	There are two ways to handle timers: based on real time (relative, "fire	225	There are two ways to handle timers: based on real time (relative, "fire
210	in 10 seconds") and based on wallclock time (absolute, "fire at 12	226	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
222	timers.	238	timers.
223		239
224	AnyEvent always prefers relative timers, if available, matching the	240	AnyEvent always prefers relative timers, if available, matching the
225	AnyEvent API.	241	AnyEvent API.
226		242
		243	AnyEvent has two additional methods that return the "current time":
		244
		245	=over 4
		246
		247	=item AnyEvent->time
		248
		249	This returns the "current wallclock time" as a fractional number of
		250	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		251	return, and the result is guaranteed to be compatible with those).
		252
		253	It progresses independently of any event loop processing, i.e. each call
		254	will check the system clock, which usually gets updated frequently.
		255
		256	=item AnyEvent->now
		257
		258	This also returns the "current wallclock time", but unlike C<time>, above,
		259	this value might change only once per event loop iteration, depending on
		260	the event loop (most return the same time as C<time>, above). This is the
		261	time that AnyEvent's timers get scheduled against.
		262
		263	I<In almost all cases (in all cases if you don't care), this is the
		264	function to call when you want to know the current time.>
		265
		266	This function is also often faster then C<< AnyEvent->time >>, and
		267	thus the preferred method if you want some timestamp (for example,
		268	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		269
		270	The rest of this section is only of relevance if you try to be very exact
		271	with your timing, you can skip it without bad conscience.
		272
		273	For a practical example of when these times differ, consider L<Event::Lib>
		274	and L<EV> and the following set-up:
		275
		276	The event loop is running and has just invoked one of your callback at
		277	time=500 (assume no other callbacks delay processing). In your callback,
		278	you wait a second by executing C<sleep 1> (blocking the process for a
		279	second) and then (at time=501) you create a relative timer that fires
		280	after three seconds.
		281
		282	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		283	both return C<501>, because that is the current time, and the timer will
		284	be scheduled to fire at time=504 (C<501> + C<3>).
		285
		286	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		287	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		288	last event processing phase started. With L<EV>, your timer gets scheduled
		289	to run at time=503 (C<500> + C<3>).
		290
		291	In one sense, L<Event::Lib> is more exact, as it uses the current time
		292	regardless of any delays introduced by event processing. However, most
		293	callbacks do not expect large delays in processing, so this causes a
		294	higher drift (and a lot more system calls to get the current time).
		295
		296	In another sense, L<EV> is more exact, as your timer will be scheduled at
		297	the same time, regardless of how long event processing actually took.
		298
		299	In either case, if you care (and in most cases, you don't), then you
		300	can get whatever behaviour you want with any event loop, by taking the
		301	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		302	account.
		303
		304	=back
		305
227	=head2 SIGNAL WATCHERS	306	=head2 SIGNAL WATCHERS
228		307
229	You can watch for signals using a signal watcher, C<signal> is the signal	308	You can watch for signals using a signal watcher, C<signal> is the signal
230	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	309	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
231	be invoked whenever a signal occurs.	310	callback to be invoked whenever a signal occurs.
232		311
		312	Although the callback might get passed parameters, their value and
		313	presence is undefined and you cannot rely on them. Portable AnyEvent
		314	callbacks cannot use arguments passed to signal watcher callbacks.
		315
233	Multiple signal occurances can be clumped together into one callback	316	Multiple signal occurrences can be clumped together into one callback
234	invocation, and callback invocation will be synchronous. synchronous means	317	invocation, and callback invocation will be synchronous. Synchronous means
235	that it might take a while until the signal gets handled by the process,	318	that it might take a while until the signal gets handled by the process,
236	but it is guarenteed not to interrupt any other callbacks.	319	but it is guaranteed not to interrupt any other callbacks.
237		320
238	The main advantage of using these watchers is that you can share a signal	321	The main advantage of using these watchers is that you can share a signal
239	between multiple watchers.	322	between multiple watchers.
240		323
241	This watcher might use C<%SIG>, so programs overwriting those signals	324	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
251		334
252	The child process is specified by the C<pid> argument (if set to C<0>, it	335	The child process is specified by the C<pid> argument (if set to C<0>, it
253	watches for any child process exit). The watcher will trigger as often	336	watches for any child process exit). The watcher will trigger as often
254	as status change for the child are received. This works by installing a	337	as status change for the child are received. This works by installing a
255	signal handler for C<SIGCHLD>. The callback will be called with the pid	338	signal handler for C<SIGCHLD>. The callback will be called with the pid
256	and exit status (as returned by waitpid).	339	and exit status (as returned by waitpid), so unlike other watcher types,
		340	you I<can> rely on child watcher callback arguments.
257		341
258	Example: wait for pid 1333	342	There is a slight catch to child watchers, however: you usually start them
		343	I<after> the child process was created, and this means the process could
		344	have exited already (and no SIGCHLD will be sent anymore).
259		345
		346	Not all event models handle this correctly (POE doesn't), but even for
		347	event models that I<do> handle this correctly, they usually need to be
		348	loaded before the process exits (i.e. before you fork in the first place).
		349
		350	This means you cannot create a child watcher as the very first thing in an
		351	AnyEvent program, you I<have> to create at least one watcher before you
		352	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		353
		354	Example: fork a process and wait for it
		355
		356	my $done = AnyEvent->condvar;
		357
		358	my $pid = fork or exit 5;
		359
260	my $w = AnyEvent->child (	360	my $w = AnyEvent->child (
261	pid => 1333,	361	pid => $pid,
262	cb => sub {	362	cb => sub {
263	my ($pid, $status) = @_;	363	my ($pid, $status) = @_;
264	warn "pid $pid exited with status $status";	364	warn "pid $pid exited with status $status";
		365	$done->send;
265	},	366	},
266	);	367	);
		368
		369	# do something else, then wait for process exit
		370	$done->recv;
267		371
268	=head2 CONDITION VARIABLES	372	=head2 CONDITION VARIABLES
269		373
		374	If you are familiar with some event loops you will know that all of them
		375	require you to run some blocking "loop", "run" or similar function that
		376	will actively watch for new events and call your callbacks.
		377
		378	AnyEvent is different, it expects somebody else to run the event loop and
		379	will only block when necessary (usually when told by the user).
		380
		381	The instrument to do that is called a "condition variable", so called
		382	because they represent a condition that must become true.
		383
270	Condition variables can be created by calling the C<< AnyEvent->condvar >>	384	Condition variables can be created by calling the C<< AnyEvent->condvar
271	method without any arguments.	385	>> method, usually without arguments. The only argument pair allowed is
		386	C<cb>, which specifies a callback to be called when the condition variable
		387	becomes true.
272		388
273	A condition variable waits for a condition - precisely that the C<<	389	After creation, the condition variable is "false" until it becomes "true"
274	->broadcast >> method has been called.	390	by calling the C<send> method (or calling the condition variable as if it
		391	were a callback, read about the caveats in the description for the C<<
		392	->send >> method).
275		393
276	They are very useful to signal that a condition has been fulfilled, for	394	Condition variables are similar to callbacks, except that you can
		395	optionally wait for them. They can also be called merge points - points
		396	in time where multiple outstanding events have been processed. And yet
		397	another way to call them is transactions - each condition variable can be
		398	used to represent a transaction, which finishes at some point and delivers
		399	a result.
		400
		401	Condition variables are very useful to signal that something has finished,
277	example, if you write a module that does asynchronous http requests,	402	for example, if you write a module that does asynchronous http requests,
278	then a condition variable would be the ideal candidate to signal the	403	then a condition variable would be the ideal candidate to signal the
279	availability of results.	404	availability of results. The user can either act when the callback is
		405	called or can synchronously C<< ->recv >> for the results.
280		406
281	You can also use condition variables to block your main program until	407	You can also use them to simulate traditional event loops - for example,
282	an event occurs - for example, you could C<< ->wait >> in your main	408	you can block your main program until an event occurs - for example, you
283	program until the user clicks the Quit button in your app, which would C<<	409	could C<< ->recv >> in your main program until the user clicks the Quit
284	->broadcast >> the "quit" event.	410	button of your app, which would C<< ->send >> the "quit" event.
285		411
286	Note that condition variables recurse into the event loop - if you have	412	Note that condition variables recurse into the event loop - if you have
287	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	413	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
288	lose. Therefore, condition variables are good to export to your caller, but	414	lose. Therefore, condition variables are good to export to your caller, but
289	you should avoid making a blocking wait yourself, at least in callbacks,	415	you should avoid making a blocking wait yourself, at least in callbacks,
290	as this asks for trouble.	416	as this asks for trouble.
291		417
292	This object has two methods:	418	Condition variables are represented by hash refs in perl, and the keys
		419	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		420	easy (it is often useful to build your own transaction class on top of
		421	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		422	it's C<new> method in your own C<new> method.
		423
		424	There are two "sides" to a condition variable - the "producer side" which
		425	eventually calls C<< -> send >>, and the "consumer side", which waits
		426	for the send to occur.
		427
		428	Example: wait for a timer.
		429
		430	# wait till the result is ready
		431	my $result_ready = AnyEvent->condvar;
		432
		433	# do something such as adding a timer
		434	# or socket watcher the calls $result_ready->send
		435	# when the "result" is ready.
		436	# in this case, we simply use a timer:
		437	my $w = AnyEvent->timer (
		438	after => 1,
		439	cb => sub { $result_ready->send },
		440	);
		441
		442	# this "blocks" (while handling events) till the callback
		443	# calls send
		444	$result_ready->recv;
		445
		446	Example: wait for a timer, but take advantage of the fact that
		447	condition variables are also code references.
		448
		449	my $done = AnyEvent->condvar;
		450	my $delay = AnyEvent->timer (after => 5, cb => $done);
		451	$done->recv;
		452
		453	=head3 METHODS FOR PRODUCERS
		454
		455	These methods should only be used by the producing side, i.e. the
		456	code/module that eventually sends the signal. Note that it is also
		457	the producer side which creates the condvar in most cases, but it isn't
		458	uncommon for the consumer to create it as well.
293		459
294	=over 4	460	=over 4
295		461
		462	=item $cv->send (...)
		463
		464	Flag the condition as ready - a running C<< ->recv >> and all further
		465	calls to C<recv> will (eventually) return after this method has been
		466	called. If nobody is waiting the send will be remembered.
		467
		468	If a callback has been set on the condition variable, it is called
		469	immediately from within send.
		470
		471	Any arguments passed to the C<send> call will be returned by all
		472	future C<< ->recv >> calls.
		473
		474	Condition variables are overloaded so one can call them directly
		475	(as a code reference). Calling them directly is the same as calling
		476	C<send>. Note, however, that many C-based event loops do not handle
		477	overloading, so as tempting as it may be, passing a condition variable
		478	instead of a callback does not work. Both the pure perl and EV loops
		479	support overloading, however, as well as all functions that use perl to
		480	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		481	example).
		482
		483	=item $cv->croak ($error)
		484
		485	Similar to send, but causes all call's to C<< ->recv >> to invoke
		486	C<Carp::croak> with the given error message/object/scalar.
		487
		488	This can be used to signal any errors to the condition variable
		489	user/consumer.
		490
		491	=item $cv->begin ([group callback])
		492
296	=item $cv->wait	493	=item $cv->end
297		494
298	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	495	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		496
		497	These two methods can be used to combine many transactions/events into
		498	one. For example, a function that pings many hosts in parallel might want
		499	to use a condition variable for the whole process.
		500
		501	Every call to C<< ->begin >> will increment a counter, and every call to
		502	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		503	>>, the (last) callback passed to C<begin> will be executed. That callback
		504	is I<supposed> to call C<< ->send >>, but that is not required. If no
		505	callback was set, C<send> will be called without any arguments.
		506
		507	Let's clarify this with the ping example:
		508
		509	my $cv = AnyEvent->condvar;
		510
		511	my %result;
		512	$cv->begin (sub { $cv->send (\%result) });
		513
		514	for my $host (@list_of_hosts) {
		515	$cv->begin;
		516	ping_host_then_call_callback $host, sub {
		517	$result{$host} = ...;
		518	$cv->end;
		519	};
		520	}
		521
		522	$cv->end;
		523
		524	This code fragment supposedly pings a number of hosts and calls
		525	C<send> after results for all then have have been gathered - in any
		526	order. To achieve this, the code issues a call to C<begin> when it starts
		527	each ping request and calls C<end> when it has received some result for
		528	it. Since C<begin> and C<end> only maintain a counter, the order in which
		529	results arrive is not relevant.
		530
		531	There is an additional bracketing call to C<begin> and C<end> outside the
		532	loop, which serves two important purposes: first, it sets the callback
		533	to be called once the counter reaches C<0>, and second, it ensures that
		534	C<send> is called even when C<no> hosts are being pinged (the loop
		535	doesn't execute once).
		536
		537	This is the general pattern when you "fan out" into multiple subrequests:
		538	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		539	is called at least once, and then, for each subrequest you start, call
		540	C<begin> and for each subrequest you finish, call C<end>.
		541
		542	=back
		543
		544	=head3 METHODS FOR CONSUMERS
		545
		546	These methods should only be used by the consuming side, i.e. the
		547	code awaits the condition.
		548
		549	=over 4
		550
		551	=item $cv->recv
		552
		553	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
299	called on c<$cv>, while servicing other watchers normally.	554	>> methods have been called on c<$cv>, while servicing other watchers
		555	normally.
300		556
301	You can only wait once on a condition - additional calls will return	557	You can only wait once on a condition - additional calls are valid but
302	immediately.	558	will return immediately.
		559
		560	If an error condition has been set by calling C<< ->croak >>, then this
		561	function will call C<croak>.
		562
		563	In list context, all parameters passed to C<send> will be returned,
		564	in scalar context only the first one will be returned.
303		565
304	Not all event models support a blocking wait - some die in that case	566	Not all event models support a blocking wait - some die in that case
305	(programs might want to do that to stay interactive), so I<if you are	567	(programs might want to do that to stay interactive), so I<if you are
306	using this from a module, never require a blocking wait>, but let the	568	using this from a module, never require a blocking wait>, but let the
307	caller decide whether the call will block or not (for example, by coupling	569	caller decide whether the call will block or not (for example, by coupling
308	condition variables with some kind of request results and supporting	570	condition variables with some kind of request results and supporting
309	callbacks so the caller knows that getting the result will not block,	571	callbacks so the caller knows that getting the result will not block,
310	while still suppporting blocking waits if the caller so desires).	572	while still supporting blocking waits if the caller so desires).
311		573
312	Another reason I<never> to C<< ->wait >> in a module is that you cannot	574	Another reason I<never> to C<< ->recv >> in a module is that you cannot
313	sensibly have two C<< ->wait >>'s in parallel, as that would require	575	sensibly have two C<< ->recv >>'s in parallel, as that would require
314	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	576	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
315	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	577	can supply.
316	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
317	from different coroutines, however).
318		578
319	=item $cv->broadcast	579	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		580	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		581	versions and also integrates coroutines into AnyEvent, making blocking
		582	C<< ->recv >> calls perfectly safe as long as they are done from another
		583	coroutine (one that doesn't run the event loop).
320		584
321	Flag the condition as ready - a running C<< ->wait >> and all further	585	You can ensure that C<< -recv >> never blocks by setting a callback and
322	calls to C<wait> will (eventually) return after this method has been	586	only calling C<< ->recv >> from within that callback (or at a later
323	called. If nobody is waiting the broadcast will be remembered..	587	time). This will work even when the event loop does not support blocking
		588	waits otherwise.
		589
		590	=item $bool = $cv->ready
		591
		592	Returns true when the condition is "true", i.e. whether C<send> or
		593	C<croak> have been called.
		594
		595	=item $cb = $cv->cb ([new callback])
		596
		597	This is a mutator function that returns the callback set and optionally
		598	replaces it before doing so.
		599
		600	The callback will be called when the condition becomes "true", i.e. when
		601	C<send> or C<croak> are called, with the only argument being the condition
		602	variable itself. Calling C<recv> inside the callback or at any later time
		603	is guaranteed not to block.
324		604
325	=back	605	=back
326
327	Example:
328
329	# wait till the result is ready
330	my $result_ready = AnyEvent->condvar;
331
332	# do something such as adding a timer
333	# or socket watcher the calls $result_ready->broadcast
334	# when the "result" is ready.
335	# in this case, we simply use a timer:
336	my $w = AnyEvent->timer (
337	after => 1,
338	cb => sub { $result_ready->broadcast },
339	);
340
341	# this "blocks" (while handling events) till the watcher
342	# calls broadcast
343	$result_ready->wait;
344		606
345	=head1 GLOBAL VARIABLES AND FUNCTIONS	607	=head1 GLOBAL VARIABLES AND FUNCTIONS
346		608
347	=over 4	609	=over 4
348		610
…		…
354	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	616	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
355	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	617	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
356		618
357	The known classes so far are:	619	The known classes so far are:
358		620
359	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
360	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
361	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	621	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
362	AnyEvent::Impl::Event based on Event, second best choice.	622	AnyEvent::Impl::Event based on Event, second best choice.
		623	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
363	AnyEvent::Impl::Glib based on Glib, third-best choice.	624	AnyEvent::Impl::Glib based on Glib, third-best choice.
364	AnyEvent::Impl::Tk based on Tk, very bad choice.	625	AnyEvent::Impl::Tk based on Tk, very bad choice.
365	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
366	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	626	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
367	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	627	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
368	AnyEvent::Impl::POE based on POE, not generic enough for full support.	628	AnyEvent::Impl::POE based on POE, not generic enough for full support.
369		629
370	There is no support for WxWidgets, as WxWidgets has no support for	630	There is no support for WxWidgets, as WxWidgets has no support for
…		…
382	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	642	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
383	if necessary. You should only call this function right before you would	643	if necessary. You should only call this function right before you would
384	have created an AnyEvent watcher anyway, that is, as late as possible at	644	have created an AnyEvent watcher anyway, that is, as late as possible at
385	runtime.	645	runtime.
386		646
		647	=item $guard = AnyEvent::post_detect { BLOCK }
		648
		649	Arranges for the code block to be executed as soon as the event model is
		650	autodetected (or immediately if this has already happened).
		651
		652	If called in scalar or list context, then it creates and returns an object
		653	that automatically removes the callback again when it is destroyed. See
		654	L<Coro::BDB> for a case where this is useful.
		655
		656	=item @AnyEvent::post_detect
		657
		658	If there are any code references in this array (you can C<push> to it
		659	before or after loading AnyEvent), then they will called directly after
		660	the event loop has been chosen.
		661
		662	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		663	if it contains a true value then the event loop has already been detected,
		664	and the array will be ignored.
		665
		666	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		667
387	=back	668	=back
388		669
389	=head1 WHAT TO DO IN A MODULE	670	=head1 WHAT TO DO IN A MODULE
390		671
391	As a module author, you should C<use AnyEvent> and call AnyEvent methods	672	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
394	Be careful when you create watchers in the module body - AnyEvent will	675	Be careful when you create watchers in the module body - AnyEvent will
395	decide which event module to use as soon as the first method is called, so	676	decide which event module to use as soon as the first method is called, so
396	by calling AnyEvent in your module body you force the user of your module	677	by calling AnyEvent in your module body you force the user of your module
397	to load the event module first.	678	to load the event module first.
398		679
399	Never call C<< ->wait >> on a condition variable unless you I<know> that	680	Never call C<< ->recv >> on a condition variable unless you I<know> that
400	the C<< ->broadcast >> method has been called on it already. This is	681	the C<< ->send >> method has been called on it already. This is
401	because it will stall the whole program, and the whole point of using	682	because it will stall the whole program, and the whole point of using
402	events is to stay interactive.	683	events is to stay interactive.
403		684
404	It is fine, however, to call C<< ->wait >> when the user of your module	685	It is fine, however, to call C<< ->recv >> when the user of your module
405	requests it (i.e. if you create a http request object ad have a method	686	requests it (i.e. if you create a http request object ad have a method
406	called C<results> that returns the results, it should call C<< ->wait >>	687	called C<results> that returns the results, it should call C<< ->recv >>
407	freely, as the user of your module knows what she is doing. always).	688	freely, as the user of your module knows what she is doing. always).
408		689
409	=head1 WHAT TO DO IN THE MAIN PROGRAM	690	=head1 WHAT TO DO IN THE MAIN PROGRAM
410		691
411	There will always be a single main program - the only place that should	692	There will always be a single main program - the only place that should
…		…
413		694
414	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	695	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
415	do anything special (it does not need to be event-based) and let AnyEvent	696	do anything special (it does not need to be event-based) and let AnyEvent
416	decide which implementation to chose if some module relies on it.	697	decide which implementation to chose if some module relies on it.
417		698
418	If the main program relies on a specific event model. For example, in	699	If the main program relies on a specific event model - for example, in
419	Gtk2 programs you have to rely on the Glib module. You should load the	700	Gtk2 programs you have to rely on the Glib module - you should load the
420	event module before loading AnyEvent or any module that uses it: generally	701	event module before loading AnyEvent or any module that uses it: generally
421	speaking, you should load it as early as possible. The reason is that	702	speaking, you should load it as early as possible. The reason is that
422	modules might create watchers when they are loaded, and AnyEvent will	703	modules might create watchers when they are loaded, and AnyEvent will
423	decide on the event model to use as soon as it creates watchers, and it	704	decide on the event model to use as soon as it creates watchers, and it
424	might chose the wrong one unless you load the correct one yourself.	705	might chose the wrong one unless you load the correct one yourself.
425		706
426	You can chose to use a rather inefficient pure-perl implementation by	707	You can chose to use a pure-perl implementation by loading the
427	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	708	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
428	behaviour everywhere, but letting AnyEvent chose is generally better.	709	everywhere, but letting AnyEvent chose the model is generally better.
		710
		711	=head2 MAINLOOP EMULATION
		712
		713	Sometimes (often for short test scripts, or even standalone programs who
		714	only want to use AnyEvent), you do not want to run a specific event loop.
		715
		716	In that case, you can use a condition variable like this:
		717
		718	AnyEvent->condvar->recv;
		719
		720	This has the effect of entering the event loop and looping forever.
		721
		722	Note that usually your program has some exit condition, in which case
		723	it is better to use the "traditional" approach of storing a condition
		724	variable somewhere, waiting for it, and sending it when the program should
		725	exit cleanly.
		726
		727
		728	=head1 OTHER MODULES
		729
		730	The following is a non-exhaustive list of additional modules that use
		731	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		732	in the same program. Some of the modules come with AnyEvent, some are
		733	available via CPAN.
		734
		735	=over 4
		736
		737	=item L<AnyEvent::Util>
		738
		739	Contains various utility functions that replace often-used but blocking
		740	functions such as C<inet_aton> by event-/callback-based versions.
		741
		742	=item L<AnyEvent::Socket>
		743
		744	Provides various utility functions for (internet protocol) sockets,
		745	addresses and name resolution. Also functions to create non-blocking tcp
		746	connections or tcp servers, with IPv6 and SRV record support and more.
		747
		748	=item L<AnyEvent::Handle>
		749
		750	Provide read and write buffers, manages watchers for reads and writes,
		751	supports raw and formatted I/O, I/O queued and fully transparent and
		752	non-blocking SSL/TLS.
		753
		754	=item L<AnyEvent::DNS>
		755
		756	Provides rich asynchronous DNS resolver capabilities.
		757
		758	=item L<AnyEvent::HTTP>
		759
		760	A simple-to-use HTTP library that is capable of making a lot of concurrent
		761	HTTP requests.
		762
		763	=item L<AnyEvent::HTTPD>
		764
		765	Provides a simple web application server framework.
		766
		767	=item L<AnyEvent::FastPing>
		768
		769	The fastest ping in the west.
		770
		771	=item L<AnyEvent::DBI>
		772
		773	Executes L<DBI> requests asynchronously in a proxy process.
		774
		775	=item L<AnyEvent::AIO>
		776
		777	Truly asynchronous I/O, should be in the toolbox of every event
		778	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		779	together.
		780
		781	=item L<AnyEvent::BDB>
		782
		783	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		784	L<BDB> and AnyEvent together.
		785
		786	=item L<AnyEvent::GPSD>
		787
		788	A non-blocking interface to gpsd, a daemon delivering GPS information.
		789
		790	=item L<AnyEvent::IGS>
		791
		792	A non-blocking interface to the Internet Go Server protocol (used by
		793	L<App::IGS>).
		794
		795	=item L<Net::IRC3>
		796
		797	AnyEvent based IRC client module family.
		798
		799	=item L<Net::XMPP2>
		800
		801	AnyEvent based XMPP (Jabber protocol) module family.
		802
		803	=item L<Net::FCP>
		804
		805	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		806	of AnyEvent.
		807
		808	=item L<Event::ExecFlow>
		809
		810	High level API for event-based execution flow control.
		811
		812	=item L<Coro>
		813
		814	Has special support for AnyEvent via L<Coro::AnyEvent>.
		815
		816	=item L<IO::Lambda>
		817
		818	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		819
		820	=back
429		821
430	=cut	822	=cut
431		823
432	package AnyEvent;	824	package AnyEvent;
433		825
434	no warnings;	826	no warnings;
435	use strict;	827	use strict;
436		828
437	use Carp;	829	use Carp;
438		830
439	our $VERSION = '3.3';	831	our $VERSION = 4.2;
440	our $MODEL;	832	our $MODEL;
441		833
442	our $AUTOLOAD;	834	our $AUTOLOAD;
443	our @ISA;	835	our @ISA;
444		836
		837	our @REGISTRY;
		838
		839	our $WIN32;
		840
		841	BEGIN {
		842	my $win32 = ! ! ($^O =~ /mswin32/i);
		843	eval "sub WIN32(){ $win32 }";
		844	}
		845
445	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	846	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
446		847
447	our @REGISTRY;	848	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		849
		850	{
		851	my $idx;
		852	$PROTOCOL{$_} = ++$idx
		853	for reverse split /\s*,\s*/,
		854	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		855	}
448		856
449	my @models = (	857	my @models = (
450	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
451	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
452	[EV:: => AnyEvent::Impl::EV::],	858	[EV:: => AnyEvent::Impl::EV::],
453	[Event:: => AnyEvent::Impl::Event::],	859	[Event:: => AnyEvent::Impl::Event::],
454	[Glib:: => AnyEvent::Impl::Glib::],
455	[Tk:: => AnyEvent::Impl::Tk::],
456	[Wx:: => AnyEvent::Impl::POE::],
457	[Prima:: => AnyEvent::Impl::POE::],
458	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	860	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
459	# everything below here will not be autoprobed as the pureperl backend should work everywhere	861	# everything below here will not be autoprobed
		862	# as the pureperl backend should work everywhere
		863	# and is usually faster
		864	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		865	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
460	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	866	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
461	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	867	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
462	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	868	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		869	[Wx:: => AnyEvent::Impl::POE::],
		870	[Prima:: => AnyEvent::Impl::POE::],
463	);	871	);
464		872
465	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	873	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);
		874
		875	our @post_detect;
		876
		877	sub post_detect(&) {
		878	my ($cb) = @_;
		879
		880	if ($MODEL) {
		881	$cb->();
		882
		883	1
		884	} else {
		885	push @post_detect, $cb;
		886
		887	defined wantarray
		888	? bless \$cb, "AnyEvent::Util::PostDetect"
		889	: ()
		890	}
		891	}
		892
		893	sub AnyEvent::Util::PostDetect::DESTROY {
		894	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		895	}
466		896
467	sub detect() {	897	sub detect() {
468	unless ($MODEL) {	898	unless ($MODEL) {
469	no strict 'refs';	899	no strict 'refs';
		900	local $SIG{__DIE__};
470		901
471	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	902	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
472	my $model = "AnyEvent::Impl::$1";	903	my $model = "AnyEvent::Impl::$1";
473	if (eval "require $model") {	904	if (eval "require $model") {
474	$MODEL = $model;	905	$MODEL = $model;
…		…
504	last;	935	last;
505	}	936	}
506	}	937	}
507		938
508	$MODEL	939	$MODEL
509	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	940	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
510	}	941	}
511	}	942	}
512		943
		944	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		945
513	unshift @ISA, $MODEL;	946	unshift @ISA, $MODEL;
514	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	947
		948	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		949
		950	(shift @post_detect)->() while @post_detect;
515	}	951	}
516		952
517	$MODEL	953	$MODEL
518	}	954	}
519		955
…		…
527		963
528	my $class = shift;	964	my $class = shift;
529	$class->$func (@_);	965	$class->$func (@_);
530	}	966	}
531		967
		968	# utility function to dup a filehandle. this is used by many backends
		969	# to support binding more than one watcher per filehandle (they usually
		970	# allow only one watcher per fd, so we dup it to get a different one).
		971	sub _dupfh($$$$) {
		972	my ($poll, $fh, $r, $w) = @_;
		973
		974	require Fcntl;
		975
		976	# cygwin requires the fh mode to be matching, unix doesn't
		977	my ($rw, $mode) = $poll eq "r" ? ($r, "<")
		978	: $poll eq "w" ? ($w, ">")
		979	: Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
		980
		981	open my $fh2, "$mode&" . fileno $fh
		982	or die "cannot dup() filehandle: $!";
		983
		984	# we assume CLOEXEC is already set by perl in all important cases
		985
		986	($fh2, $rw)
		987	}
		988
532	package AnyEvent::Base;	989	package AnyEvent::Base;
533		990
		991	# default implementation for now and time
		992
		993	use Time::HiRes ();
		994
		995	sub time { Time::HiRes::time }
		996	sub now { Time::HiRes::time }
		997
534	# default implementation for ->condvar, ->wait, ->broadcast	998	# default implementation for ->condvar
535		999
536	sub condvar {	1000	sub condvar {
537	bless \my $flag, "AnyEvent::Base::CondVar"	1001	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
538	}
539
540	sub AnyEvent::Base::CondVar::broadcast {
541	${$_[0]}++;
542	}
543
544	sub AnyEvent::Base::CondVar::wait {
545	AnyEvent->one_event while !${$_[0]};
546	}	1002	}
547		1003
548	# default implementation for ->signal	1004	# default implementation for ->signal
549		1005
550	our %SIG_CB;	1006	our %SIG_CB;
…		…
566	sub AnyEvent::Base::Signal::DESTROY {	1022	sub AnyEvent::Base::Signal::DESTROY {
567	my ($signal, $cb) = @{$_[0]};	1023	my ($signal, $cb) = @{$_[0]};
568		1024
569	delete $SIG_CB{$signal}{$cb};	1025	delete $SIG_CB{$signal}{$cb};
570		1026
571	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1027	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
572	}	1028	}
573		1029
574	# default implementation for ->child	1030	# default implementation for ->child
575		1031
576	our %PID_CB;	1032	our %PID_CB;
…		…
603	or Carp::croak "required option 'pid' is missing";	1059	or Carp::croak "required option 'pid' is missing";
604		1060
605	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1061	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
606		1062
607	unless ($WNOHANG) {	1063	unless ($WNOHANG) {
608	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1064	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
609	}	1065	}
610		1066
611	unless ($CHLD_W) {	1067	unless ($CHLD_W) {
612	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1068	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
613	# child could be a zombie already, so make at least one round	1069	# child could be a zombie already, so make at least one round
…		…
623	delete $PID_CB{$pid}{$cb};	1079	delete $PID_CB{$pid}{$cb};
624	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1080	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
625		1081
626	undef $CHLD_W unless keys %PID_CB;	1082	undef $CHLD_W unless keys %PID_CB;
627	}	1083	}
		1084
		1085	package AnyEvent::CondVar;
		1086
		1087	our @ISA = AnyEvent::CondVar::Base::;
		1088
		1089	package AnyEvent::CondVar::Base;
		1090
		1091	use overload
		1092	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1093	fallback => 1;
		1094
		1095	sub _send {
		1096	# nop
		1097	}
		1098
		1099	sub send {
		1100	my $cv = shift;
		1101	$cv->{_ae_sent} = [@_];
		1102	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1103	$cv->_send;
		1104	}
		1105
		1106	sub croak {
		1107	$_[0]{_ae_croak} = $_[1];
		1108	$_[0]->send;
		1109	}
		1110
		1111	sub ready {
		1112	$_[0]{_ae_sent}
		1113	}
		1114
		1115	sub _wait {
		1116	AnyEvent->one_event while !$_[0]{_ae_sent};
		1117	}
		1118
		1119	sub recv {
		1120	$_[0]->_wait;
		1121
		1122	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1123	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1124	}
		1125
		1126	sub cb {
		1127	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1128	$_[0]{_ae_cb}
		1129	}
		1130
		1131	sub begin {
		1132	++$_[0]{_ae_counter};
		1133	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1134	}
		1135
		1136	sub end {
		1137	return if --$_[0]{_ae_counter};
		1138	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1139	}
		1140
		1141	# undocumented/compatibility with pre-3.4
		1142	*broadcast = \&send;
		1143	*wait = \&_wait;
628		1144
629	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1145	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
630		1146
631	This is an advanced topic that you do not normally need to use AnyEvent in	1147	This is an advanced topic that you do not normally need to use AnyEvent in
632	a module. This section is only of use to event loop authors who want to	1148	a module. This section is only of use to event loop authors who want to
…		…
686	C<PERL_ANYEVENT_MODEL>.	1202	C<PERL_ANYEVENT_MODEL>.
687		1203
688	When set to C<2> or higher, cause AnyEvent to report to STDERR which event	1204	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
689	model it chooses.	1205	model it chooses.
690		1206
		1207	=item C<PERL_ANYEVENT_STRICT>
		1208
		1209	AnyEvent does not do much argument checking by default, as thorough
		1210	argument checking is very costly. Setting this variable to a true value
		1211	will cause AnyEvent to thoroughly check the arguments passed to most
		1212	method calls and croaks if it finds any problems. In other words, enables
		1213	"strict" mode. Unlike C<use strict> it is definitely recommended ot keep
		1214	it off in production.
		1215
691	=item C<PERL_ANYEVENT_MODEL>	1216	=item C<PERL_ANYEVENT_MODEL>
692		1217
693	This can be used to specify the event model to be used by AnyEvent, before	1218	This can be used to specify the event model to be used by AnyEvent, before
694	autodetection and -probing kicks in. It must be a string consisting	1219	auto detection and -probing kicks in. It must be a string consisting
695	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended	1220	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
696	and the resulting module name is loaded and if the load was successful,	1221	and the resulting module name is loaded and if the load was successful,
697	used as event model. If it fails to load AnyEvent will proceed with	1222	used as event model. If it fails to load AnyEvent will proceed with
698	autodetection and -probing.	1223	auto detection and -probing.
699		1224
700	This functionality might change in future versions.	1225	This functionality might change in future versions.
701		1226
702	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you	1227	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
703	could start your program like this:	1228	could start your program like this:
704		1229
705	PERL_ANYEVENT_MODEL=Perl perl ...	1230	PERL_ANYEVENT_MODEL=Perl perl ...
		1231
		1232	=item C<PERL_ANYEVENT_PROTOCOLS>
		1233
		1234	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1235	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1236	of auto probing).
		1237
		1238	Must be set to a comma-separated list of protocols or address families,
		1239	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1240	used, and preference will be given to protocols mentioned earlier in the
		1241	list.
		1242
		1243	This variable can effectively be used for denial-of-service attacks
		1244	against local programs (e.g. when setuid), although the impact is likely
		1245	small, as the program has to handle connection errors already-
		1246
		1247	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1248	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1249	- only support IPv4, never try to resolve or contact IPv6
		1250	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1251	IPv6, but prefer IPv6 over IPv4.
		1252
		1253	=item C<PERL_ANYEVENT_EDNS0>
		1254
		1255	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1256	for DNS. This extension is generally useful to reduce DNS traffic, but
		1257	some (broken) firewalls drop such DNS packets, which is why it is off by
		1258	default.
		1259
		1260	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1261	EDNS0 in its DNS requests.
		1262
		1263	=item C<PERL_ANYEVENT_MAX_FORKS>
		1264
		1265	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1266	will create in parallel.
706		1267
707	=back	1268	=back
708		1269
709	=head1 EXAMPLE PROGRAM	1270	=head1 EXAMPLE PROGRAM
710		1271
711	The following program uses an IO watcher to read data from STDIN, a timer	1272	The following program uses an I/O watcher to read data from STDIN, a timer
712	to display a message once per second, and a condition variable to quit the	1273	to display a message once per second, and a condition variable to quit the
713	program when the user enters quit:	1274	program when the user enters quit:
714		1275
715	use AnyEvent;	1276	use AnyEvent;
716		1277
…		…
721	poll => 'r',	1282	poll => 'r',
722	cb => sub {	1283	cb => sub {
723	warn "io event <$_[0]>\n"; # will always output <r>	1284	warn "io event <$_[0]>\n"; # will always output <r>
724	chomp (my $input = <STDIN>); # read a line	1285	chomp (my $input = <STDIN>); # read a line
725	warn "read: $input\n"; # output what has been read	1286	warn "read: $input\n"; # output what has been read
726	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1287	$cv->send if $input =~ /^q/i; # quit program if /^q/i
727	},	1288	},
728	);	1289	);
729		1290
730	my $time_watcher; # can only be used once	1291	my $time_watcher; # can only be used once
731		1292
…		…
736	});	1297	});
737	}	1298	}
738		1299
739	new_timer; # create first timer	1300	new_timer; # create first timer
740		1301
741	$cv->wait; # wait until user enters /^q/i	1302	$cv->recv; # wait until user enters /^q/i
742		1303
743	=head1 REAL-WORLD EXAMPLE	1304	=head1 REAL-WORLD EXAMPLE
744		1305
745	Consider the L<Net::FCP> module. It features (among others) the following	1306	Consider the L<Net::FCP> module. It features (among others) the following
746	API calls, which are to freenet what HTTP GET requests are to http:	1307	API calls, which are to freenet what HTTP GET requests are to http:
…		…
796	syswrite $txn->{fh}, $txn->{request}	1357	syswrite $txn->{fh}, $txn->{request}
797	or die "connection or write error";	1358	or die "connection or write error";
798	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1359	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
799		1360
800	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1361	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
801	result and signals any possible waiters that the request ahs finished:	1362	result and signals any possible waiters that the request has finished:
802		1363
803	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1364	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
804		1365
805	if (end-of-file or data complete) {	1366	if (end-of-file or data complete) {
806	$txn->{result} = $txn->{buf};	1367	$txn->{result} = $txn->{buf};
807	$txn->{finished}->broadcast;	1368	$txn->{finished}->send;
808	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1369	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
809	}	1370	}
810		1371
811	The C<result> method, finally, just waits for the finished signal (if the	1372	The C<result> method, finally, just waits for the finished signal (if the
812	request was already finished, it doesn't wait, of course, and returns the	1373	request was already finished, it doesn't wait, of course, and returns the
813	data:	1374	data:
814		1375
815	$txn->{finished}->wait;	1376	$txn->{finished}->recv;
816	return $txn->{result};	1377	return $txn->{result};
817		1378
818	The actual code goes further and collects all errors (C<die>s, exceptions)	1379	The actual code goes further and collects all errors (C<die>s, exceptions)
819	that occured during request processing. The C<result> method detects	1380	that occurred during request processing. The C<result> method detects
820	whether an exception as thrown (it is stored inside the $txn object)	1381	whether an exception as thrown (it is stored inside the $txn object)
821	and just throws the exception, which means connection errors and other	1382	and just throws the exception, which means connection errors and other
822	problems get reported tot he code that tries to use the result, not in a	1383	problems get reported tot he code that tries to use the result, not in a
823	random callback.	1384	random callback.
824		1385
…		…
855		1416
856	my $quit = AnyEvent->condvar;	1417	my $quit = AnyEvent->condvar;
857		1418
858	$fcp->txn_client_get ($url)->cb (sub {	1419	$fcp->txn_client_get ($url)->cb (sub {
859	...	1420	...
860	$quit->broadcast;	1421	$quit->send;
861	});	1422	});
862		1423
863	$quit->wait;	1424	$quit->recv;
864		1425
865		1426
866	=head1 BENCHMARK	1427	=head1 BENCHMARKS
867		1428
868	To give you an idea of the performance and overheads that AnyEvent adds	1429	To give you an idea of the performance and overheads that AnyEvent adds
869	over the event loops themselves (and to give you an impression of the	1430	over the event loops themselves and to give you an impression of the speed
870	speed of various event loops), here is a benchmark of various supported	1431	of various event loops I prepared some benchmarks.
871	event models natively and with anyevent. The benchmark creates a lot of	1432
872	timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to	1433	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1434
		1435	Here is a benchmark of various supported event models used natively and
		1436	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1437	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
873	become writable, which it is), lets them fire exactly once and destroys	1438	which it is), lets them fire exactly once and destroys them again.
874	them again.
875		1439
		1440	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1441	distribution.
		1442
876	=head2 Explanation of the columns	1443	=head3 Explanation of the columns
877		1444
878	I<watcher> is the number of event watchers created/destroyed. Since	1445	I<watcher> is the number of event watchers created/destroyed. Since
879	different event models feature vastly different performances, each event	1446	different event models feature vastly different performances, each event
880	loop was given a number of watchers so that overall runtime is acceptable	1447	loop was given a number of watchers so that overall runtime is acceptable
881	and similar between tested event loop (and keep them from crashing): Glib	1448	and similar between tested event loop (and keep them from crashing): Glib
…		…
891	all watchers, to avoid adding memory overhead. That means closure creation	1458	all watchers, to avoid adding memory overhead. That means closure creation
892	and memory usage is not included in the figures.	1459	and memory usage is not included in the figures.
893		1460
894	I<invoke> is the time, in microseconds, used to invoke a simple	1461	I<invoke> is the time, in microseconds, used to invoke a simple
895	callback. The callback simply counts down a Perl variable and after it was	1462	callback. The callback simply counts down a Perl variable and after it was
896	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1463	invoked "watcher" times, it would C<< ->send >> a condvar once to
897	signal the end of this phase.	1464	signal the end of this phase.
898		1465
899	I<destroy> is the time, in microseconds, that it takes to destroy a single	1466	I<destroy> is the time, in microseconds, that it takes to destroy a single
900	watcher.	1467	watcher.
901		1468
902	=head2 Results	1469	=head3 Results
903		1470
904	name watchers bytes create invoke destroy comment	1471	name watchers bytes create invoke destroy comment
905	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1472	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
906	EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers	1473	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
907	CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal	1474	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
908	Perl/Any 100000 513 4.91 0.92 1.15 pure perl implementation	1475	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
909	Event/Event 16000 523 28.05 21.38 0.86 Event native interface	1476	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
910	Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers	1477	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
911	Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour	1478	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
912	Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers	1479	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
913	POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event	1480	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
914	POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select	1481	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
915		1482
916	=head2 Discussion	1483	=head3 Discussion
917		1484
918	The benchmark does I<not> measure scalability of the event loop very	1485	The benchmark does I<not> measure scalability of the event loop very
919	well. For example, a select-based event loop (such as the pure perl one)	1486	well. For example, a select-based event loop (such as the pure perl one)
920	can never compete with an event loop that uses epoll when the number of	1487	can never compete with an event loop that uses epoll when the number of
921	file descriptors grows high. In this benchmark, only a single filehandle	1488	file descriptors grows high. In this benchmark, all events become ready at
922	is used (although some of the AnyEvent adaptors dup() its file descriptor	1489	the same time, so select/poll-based implementations get an unnatural speed
923	to worka round bugs).	1490	boost.
		1491
		1492	Also, note that the number of watchers usually has a nonlinear effect on
		1493	overall speed, that is, creating twice as many watchers doesn't take twice
		1494	the time - usually it takes longer. This puts event loops tested with a
		1495	higher number of watchers at a disadvantage.
		1496
		1497	To put the range of results into perspective, consider that on the
		1498	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1499	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1500	cycles with POE.
924		1501
925	C<EV> is the sole leader regarding speed and memory use, which are both	1502	C<EV> is the sole leader regarding speed and memory use, which are both
926	maximal/minimal, respectively. Even when going through AnyEvent, there are	1503	maximal/minimal, respectively. Even when going through AnyEvent, it uses
927	only two event loops that use slightly less memory (the C<Event> module	1504	far less memory than any other event loop and is still faster than Event
928	natively and the pure perl backend), and no faster event models, not even	1505	natively.
929	C<Event> natively.
930		1506
931	The pure perl implementation is hit in a few sweet spots (both the	1507	The pure perl implementation is hit in a few sweet spots (both the
932	zero timeout and the use of a single fd hit optimisations in the perl	1508	constant timeout and the use of a single fd hit optimisations in the perl
933	interpreter and the backend itself). Nevertheless tis shows that it	1509	interpreter and the backend itself). Nevertheless this shows that it
934	adds very little overhead in itself. Like any select-based backend its	1510	adds very little overhead in itself. Like any select-based backend its
935	performance becomes really bad with lots of file descriptors, of course,	1511	performance becomes really bad with lots of file descriptors (and few of
936	but this was not subject of this benchmark.	1512	them active), of course, but this was not subject of this benchmark.
937		1513
938	The C<Event> module has a relatively high setup and callback invocation cost,	1514	The C<Event> module has a relatively high setup and callback invocation
939	but overall scores on the third place.	1515	cost, but overall scores in on the third place.
940		1516
941	C<Glib>'s memory usage is quite a bit bit higher, but it features a	1517	C<Glib>'s memory usage is quite a bit higher, but it features a
942	faster callback invocation and overall ends up in the same class as	1518	faster callback invocation and overall ends up in the same class as
943	C<Event>. However, Glib scales extremely badly, doubling the number of	1519	C<Event>. However, Glib scales extremely badly, doubling the number of
944	watchers increases the processing time by more than a factor of four,	1520	watchers increases the processing time by more than a factor of four,
945	making it completely unusable when using larger numbers of watchers	1521	making it completely unusable when using larger numbers of watchers
946	(note that only a single file descriptor was used in the benchmark, so	1522	(note that only a single file descriptor was used in the benchmark, so
…		…
949	The C<Tk> adaptor works relatively well. The fact that it crashes with	1525	The C<Tk> adaptor works relatively well. The fact that it crashes with
950	more than 2000 watchers is a big setback, however, as correctness takes	1526	more than 2000 watchers is a big setback, however, as correctness takes
951	precedence over speed. Nevertheless, its performance is surprising, as the	1527	precedence over speed. Nevertheless, its performance is surprising, as the
952	file descriptor is dup()ed for each watcher. This shows that the dup()	1528	file descriptor is dup()ed for each watcher. This shows that the dup()
953	employed by some adaptors is not a big performance issue (it does incur a	1529	employed by some adaptors is not a big performance issue (it does incur a
954	hidden memory cost inside the kernel, though, that is not reflected in the	1530	hidden memory cost inside the kernel which is not reflected in the figures
955	figures above).	1531	above).
956		1532
957	C<POE>, regardless of underlying event loop (wether using its pure perl	1533	C<POE>, regardless of underlying event loop (whether using its pure perl
958	select-based backend or the Event module) shows abysmal performance and	1534	select-based backend or the Event module, the POE-EV backend couldn't
		1535	be tested because it wasn't working) shows abysmal performance and
959	memory usage: Watchers use almost 30 times as much memory as EV watchers,	1536	memory usage with AnyEvent: Watchers use almost 30 times as much memory
960	and 10 times as much memory as both Event or EV via AnyEvent. Watcher	1537	as EV watchers, and 10 times as much memory as Event (the high memory
		1538	requirements are caused by requiring a session for each watcher). Watcher
961	invocation is almost 700 times slower than with AnyEvent's pure perl	1539	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1540	implementation.
		1541
962	implementation. The design of the POE adaptor class in AnyEvent can not	1542	The design of the POE adaptor class in AnyEvent can not really account
963	really account for this, as session creation overhead is small compared	1543	for the performance issues, though, as session creation overhead is
964	to execution of the state machine, which is coded pretty optimally within	1544	small compared to execution of the state machine, which is coded pretty
965	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1545	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1546	using multiple sessions is not a good approach, especially regarding
		1547	memory usage, even the author of POE could not come up with a faster
		1548	design).
966		1549
967	=head2 Summary	1550	=head3 Summary
968		1551
		1552	=over 4
		1553
969	Using EV through AnyEvent is faster than any other event loop, but most	1554	=item * Using EV through AnyEvent is faster than any other event loop
970	event loops have acceptable performance with or without AnyEvent.	1555	(even when used without AnyEvent), but most event loops have acceptable
		1556	performance with or without AnyEvent.
971		1557
972	The overhead AnyEvent adds is usually much smaller than the overhead of	1558	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
973	the actual event loop, only with extremely fast event loops such as the EV	1559	the actual event loop, only with extremely fast event loops such as EV
974	adds AnyEvent significant overhead.	1560	adds AnyEvent significant overhead.
975		1561
976	And you should simply avoid POE like the plague if you want performance or	1562	=item * You should avoid POE like the plague if you want performance or
977	reasonable memory usage.	1563	reasonable memory usage.
978		1564
		1565	=back
		1566
		1567	=head2 BENCHMARKING THE LARGE SERVER CASE
		1568
		1569	This benchmark actually benchmarks the event loop itself. It works by
		1570	creating a number of "servers": each server consists of a socket pair, a
		1571	timeout watcher that gets reset on activity (but never fires), and an I/O
		1572	watcher waiting for input on one side of the socket. Each time the socket
		1573	watcher reads a byte it will write that byte to a random other "server".
		1574
		1575	The effect is that there will be a lot of I/O watchers, only part of which
		1576	are active at any one point (so there is a constant number of active
		1577	fds for each loop iteration, but which fds these are is random). The
		1578	timeout is reset each time something is read because that reflects how
		1579	most timeouts work (and puts extra pressure on the event loops).
		1580
		1581	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1582	(1%) are active. This mirrors the activity of large servers with many
		1583	connections, most of which are idle at any one point in time.
		1584
		1585	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1586	distribution.
		1587
		1588	=head3 Explanation of the columns
		1589
		1590	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1591	each server has a read and write socket end).
		1592
		1593	I<create> is the time it takes to create a socket pair (which is
		1594	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1595
		1596	I<request>, the most important value, is the time it takes to handle a
		1597	single "request", that is, reading the token from the pipe and forwarding
		1598	it to another server. This includes deleting the old timeout and creating
		1599	a new one that moves the timeout into the future.
		1600
		1601	=head3 Results
		1602
		1603	name sockets create request
		1604	EV 20000 69.01 11.16
		1605	Perl 20000 73.32 35.87
		1606	Event 20000 212.62 257.32
		1607	Glib 20000 651.16 1896.30
		1608	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1609
		1610	=head3 Discussion
		1611
		1612	This benchmark I<does> measure scalability and overall performance of the
		1613	particular event loop.
		1614
		1615	EV is again fastest. Since it is using epoll on my system, the setup time
		1616	is relatively high, though.
		1617
		1618	Perl surprisingly comes second. It is much faster than the C-based event
		1619	loops Event and Glib.
		1620
		1621	Event suffers from high setup time as well (look at its code and you will
		1622	understand why). Callback invocation also has a high overhead compared to
		1623	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1624	uses select or poll in basically all documented configurations.
		1625
		1626	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1627	clearly fails to perform with many filehandles or in busy servers.
		1628
		1629	POE is still completely out of the picture, taking over 1000 times as long
		1630	as EV, and over 100 times as long as the Perl implementation, even though
		1631	it uses a C-based event loop in this case.
		1632
		1633	=head3 Summary
		1634
		1635	=over 4
		1636
		1637	=item * The pure perl implementation performs extremely well.
		1638
		1639	=item * Avoid Glib or POE in large projects where performance matters.
		1640
		1641	=back
		1642
		1643	=head2 BENCHMARKING SMALL SERVERS
		1644
		1645	While event loops should scale (and select-based ones do not...) even to
		1646	large servers, most programs we (or I :) actually write have only a few
		1647	I/O watchers.
		1648
		1649	In this benchmark, I use the same benchmark program as in the large server
		1650	case, but it uses only eight "servers", of which three are active at any
		1651	one time. This should reflect performance for a small server relatively
		1652	well.
		1653
		1654	The columns are identical to the previous table.
		1655
		1656	=head3 Results
		1657
		1658	name sockets create request
		1659	EV 16 20.00 6.54
		1660	Perl 16 25.75 12.62
		1661	Event 16 81.27 35.86
		1662	Glib 16 32.63 15.48
		1663	POE 16 261.87 276.28 uses POE::Loop::Event
		1664
		1665	=head3 Discussion
		1666
		1667	The benchmark tries to test the performance of a typical small
		1668	server. While knowing how various event loops perform is interesting, keep
		1669	in mind that their overhead in this case is usually not as important, due
		1670	to the small absolute number of watchers (that is, you need efficiency and
		1671	speed most when you have lots of watchers, not when you only have a few of
		1672	them).
		1673
		1674	EV is again fastest.
		1675
		1676	Perl again comes second. It is noticeably faster than the C-based event
		1677	loops Event and Glib, although the difference is too small to really
		1678	matter.
		1679
		1680	POE also performs much better in this case, but is is still far behind the
		1681	others.
		1682
		1683	=head3 Summary
		1684
		1685	=over 4
		1686
		1687	=item * C-based event loops perform very well with small number of
		1688	watchers, as the management overhead dominates.
		1689
		1690	=back
		1691
979		1692
980	=head1 FORK	1693	=head1 FORK
981		1694
982	Most event libraries are not fork-safe. The ones who are usually are	1695	Most event libraries are not fork-safe. The ones who are usually are
983	because they are so inefficient. Only L<EV> is fully fork-aware.	1696	because they rely on inefficient but fork-safe C<select> or C<poll>
		1697	calls. Only L<EV> is fully fork-aware.
984		1698
985	If you have to fork, you must either do so I<before> creating your first	1699	If you have to fork, you must either do so I<before> creating your first
986	watcher OR you must not use AnyEvent at all in the child.	1700	watcher OR you must not use AnyEvent at all in the child.
987		1701
988		1702
…		…
996	specified in the variable.	1710	specified in the variable.
997		1711
998	You can make AnyEvent completely ignore this variable by deleting it	1712	You can make AnyEvent completely ignore this variable by deleting it
999	before the first watcher gets created, e.g. with a C<BEGIN> block:	1713	before the first watcher gets created, e.g. with a C<BEGIN> block:
1000		1714
1001	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1715	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1002		1716
1003	use AnyEvent;	1717	use AnyEvent;
		1718
		1719	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1720	be used to probe what backend is used and gain other information (which is
		1721	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		1722	$ENV{PERL_ANYEGENT_STRICT}.
		1723
		1724
		1725	=head1 BUGS
		1726
		1727	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		1728	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		1729	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		1730	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as
		1731	pronounced).
1004		1732
1005		1733
1006	=head1 SEE ALSO	1734	=head1 SEE ALSO
1007		1735
1008	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1736	Utility functions: L<AnyEvent::Util>.
1009	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1737
		1738	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1010	L<Event::Lib>, L<Qt>, L<POE>.	1739	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1011		1740
1012	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1741	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1013	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1742	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1014	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1743	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1015	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1744	L<AnyEvent::Impl::POE>.
1016		1745
		1746	Non-blocking file handles, sockets, TCP clients and
		1747	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1748
		1749	Asynchronous DNS: L<AnyEvent::DNS>.
		1750
		1751	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1752
1017	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1753	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1018		1754
1019		1755
1020	=head1 AUTHOR	1756	=head1 AUTHOR
1021		1757
1022	Marc Lehmann <schmorp@schmorp.de>	1758	Marc Lehmann <schmorp@schmorp.de>
1023	http://home.schmorp.de/	1759	http://home.schmorp.de/
1024		1760
1025	=cut	1761	=cut
1026		1762
1027	1	1763	1
1028		1764

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