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Revision 1.155 by root, Fri Jun 6 07:07:01 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?
…		…
48	isn't itself. What's worse, all the potential users of your module are	54	isn't itself. What's worse, all the potential users of your module are
49	I<also> forced to use the same event loop you use.	55	I<also> forced to use the same event loop you use.
50		56
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	57	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	58	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	59	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,	60	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	61	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	62	event models it supports (including stuff like POE and IO::Async, as long
57	as those use one of the supported event loops. It is trivial to add new	63	as those use one of the supported event loops. It is trivial to add new
58	event loops to AnyEvent, too, so it is future-proof).	64	event loops to AnyEvent, too, so it is future-proof).
59		65
60	In addition to being free of having to use I<the one and only true event	66	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	67	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	68	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	69	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	70	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	71	technically possible.
66		72
		73	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		74	of useful functionality, such as an asynchronous DNS resolver, 100%
		75	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		76	such as Windows) and lots of real-world knowledge and workarounds for
		77	platform bugs and differences.
		78
67	Of course, if you want lots of policy (this can arguably be somewhat	79	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	80	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	81	model, you should I<not> use this module.
70
71		82
72	=head1 DESCRIPTION	83	=head1 DESCRIPTION
73		84
74	L<AnyEvent> provides an identical interface to multiple event loops. This	85	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	86	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>	90	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	91	module.
81		92
82	During the first call of any watcher-creation method, the module tries	93	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	94	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>,	95	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,	96	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	97	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	98	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	99	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	100	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	101	found, AnyEvent will fall back to a pure-perl event loop, which is not
91	very efficient, but should work everywhere.	102	very efficient, but should work everywhere.
92		103
…		…
103	starts using it, all bets are off. Maybe you should tell their authors to	114	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...	115	use AnyEvent so their modules work together with others seamlessly...
105		116
106	The pure-perl implementation of AnyEvent is called	117	The pure-perl implementation of AnyEvent is called
107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	118	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
108	explicitly.	119	explicitly and enjoy the high availability of that event loop :)
109		120
110	=head1 WATCHERS	121	=head1 WATCHERS
111		122
112	AnyEvent has the central concept of a I<watcher>, which is an object that	123	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	124	stores relevant data for each kind of event you are waiting for, such as
114	the callback to call, the filehandle to watch, etc.	125	the callback to call, the file handle to watch, etc.
115		126
116	These watchers are normal Perl objects with normal Perl lifetime. After	127	These watchers are normal Perl objects with normal Perl lifetime. After
117	creating a watcher it will immediately "watch" for events and invoke the	128	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	129	callback when the event occurs (of course, only when the event model
119	is in control).	130	is in control).
…		…
127	Many watchers either are used with "recursion" (repeating timers for	138	Many watchers either are used with "recursion" (repeating timers for
128	example), or need to refer to their watcher object in other ways.	139	example), or need to refer to their watcher object in other ways.
129		140
130	An any way to achieve that is this pattern:	141	An any way to achieve that is this pattern:
131		142
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	143	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	144	# you can use $w here, for example to undef it
134	undef $w;	145	undef $w;
135	});	146	});
136		147
137	Note that C<my $w; $w => combination. This is necessary because in Perl,	148	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	149	my variables are only visible after the statement in which they are
139	declared.	150	declared.
140		151
141	=head2 IO WATCHERS	152	=head2 I/O WATCHERS
142		153
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	154	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	155	with the following mandatory key-value pairs as arguments:
145		156
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	157	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch
147	events. C<poll> must be a string that is either C<r> or C<w>, which	158	for events. C<poll> must be a string that is either C<r> or C<w>,
148	creates a watcher waiting for "r"eadable or "w"ritable events,	159	which creates a watcher waiting for "r"eadable or "w"ritable events,
149	respectively. C<cb> is the callback to invoke each time the file handle	160	respectively. C<cb> is the callback to invoke each time the file handle
150	becomes ready.	161	becomes ready.
151		162
152	As long as the I/O watcher exists it will keep the file descriptor or a	163	Although the callback might get passed parameters, their value and
153	copy of it alive/open.	164	presence is undefined and you cannot rely on them. Portable AnyEvent
		165	callbacks cannot use arguments passed to I/O watcher callbacks.
154		166
		167	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	168	You must not close a file handle as long as any watcher is active on the
156	on the underlying file descriptor.	169	underlying file descriptor.
157		170
158	Some event loops issue spurious readyness notifications, so you should	171	Some event loops issue spurious readyness notifications, so you should
159	always use non-blocking calls when reading/writing from/to your file	172	always use non-blocking calls when reading/writing from/to your file
160	handles.	173	handles.
161		174
…		…
172		185
173	You can create a time watcher by calling the C<< AnyEvent->timer >>	186	You can create a time watcher by calling the C<< AnyEvent->timer >>
174	method with the following mandatory arguments:	187	method with the following mandatory arguments:
175		188
176	C<after> specifies after how many seconds (fractional values are	189	C<after> specifies after how many seconds (fractional values are
177	supported) should the timer activate. C<cb> the callback to invoke in that	190	supported) the callback should be invoked. C<cb> is the callback to invoke
178	case.	191	in that case.
		192
		193	Although the callback might get passed parameters, their value and
		194	presence is undefined and you cannot rely on them. Portable AnyEvent
		195	callbacks cannot use arguments passed to time watcher callbacks.
179		196
180	The timer callback will be invoked at most once: if you want a repeating	197	The timer callback will be invoked at most once: if you want a repeating
181	timer you have to create a new watcher (this is a limitation by both Tk	198	timer you have to create a new watcher (this is a limitation by both Tk
182	and Glib).	199	and Glib).
183		200
…		…
222	timers.	239	timers.
223		240
224	AnyEvent always prefers relative timers, if available, matching the	241	AnyEvent always prefers relative timers, if available, matching the
225	AnyEvent API.	242	AnyEvent API.
226		243
		244	AnyEvent has two additional methods that return the "current time":
		245
		246	=over 4
		247
		248	=item AnyEvent->time
		249
		250	This returns the "current wallclock time" as a fractional number of
		251	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		252	return, and the result is guaranteed to be compatible with those).
		253
		254	It progresses independently of any event loop processing, i.e. each call
		255	will check the system clock, which usually gets updated frequently.
		256
		257	=item AnyEvent->now
		258
		259	This also returns the "current wallclock time", but unlike C<time>, above,
		260	this value might change only once per event loop iteration, depending on
		261	the event loop (most return the same time as C<time>, above). This is the
		262	time that AnyEvent's timers get scheduled against.
		263
		264	I<In almost all cases (in all cases if you don't care), this is the
		265	function to call when you want to know the current time.>
		266
		267	This function is also often faster then C<< AnyEvent->time >>, and
		268	thus the preferred method if you want some timestamp (for example,
		269	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		270
		271	The rest of this section is only of relevance if you try to be very exact
		272	with your timing, you can skip it without bad conscience.
		273
		274	For a practical example of when these times differ, consider L<Event::Lib>
		275	and L<EV> and the following set-up:
		276
		277	The event loop is running and has just invoked one of your callback at
		278	time=500 (assume no other callbacks delay processing). In your callback,
		279	you wait a second by executing C<sleep 1> (blocking the process for a
		280	second) and then (at time=501) you create a relative timer that fires
		281	after three seconds.
		282
		283	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		284	both return C<501>, because that is the current time, and the timer will
		285	be scheduled to fire at time=504 (C<501> + C<3>).
		286
		287	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		288	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		289	last event processing phase started. With L<EV>, your timer gets scheduled
		290	to run at time=503 (C<500> + C<3>).
		291
		292	In one sense, L<Event::Lib> is more exact, as it uses the current time
		293	regardless of any delays introduced by event processing. However, most
		294	callbacks do not expect large delays in processing, so this causes a
		295	higher drift (and a lot more system calls to get the current time).
		296
		297	In another sense, L<EV> is more exact, as your timer will be scheduled at
		298	the same time, regardless of how long event processing actually took.
		299
		300	In either case, if you care (and in most cases, you don't), then you
		301	can get whatever behaviour you want with any event loop, by taking the
		302	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		303	account.
		304
		305	=back
		306
227	=head2 SIGNAL WATCHERS	307	=head2 SIGNAL WATCHERS
228		308
229	You can watch for signals using a signal watcher, C<signal> is the signal	309	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	310	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
231	be invoked whenever a signal occurs.	311	be invoked whenever a signal occurs.
232		312
		313	Although the callback might get passed parameters, their value and
		314	presence is undefined and you cannot rely on them. Portable AnyEvent
		315	callbacks cannot use arguments passed to signal watcher callbacks.
		316
233	Multiple signal occurances can be clumped together into one callback	317	Multiple signal occurrences can be clumped together into one callback
234	invocation, and callback invocation will be synchronous. synchronous means	318	invocation, and callback invocation will be synchronous. Synchronous means
235	that it might take a while until the signal gets handled by the process,	319	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.	320	but it is guaranteed not to interrupt any other callbacks.
237		321
238	The main advantage of using these watchers is that you can share a signal	322	The main advantage of using these watchers is that you can share a signal
239	between multiple watchers.	323	between multiple watchers.
240		324
241	This watcher might use C<%SIG>, so programs overwriting those signals	325	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
251		335
252	The child process is specified by the C<pid> argument (if set to C<0>, it	336	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	337	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	338	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	339	signal handler for C<SIGCHLD>. The callback will be called with the pid
256	and exit status (as returned by waitpid).	340	and exit status (as returned by waitpid), so unlike other watcher types,
		341	you I<can> rely on child watcher callback arguments.
257		342
258	Example: wait for pid 1333	343	There is a slight catch to child watchers, however: you usually start them
		344	I<after> the child process was created, and this means the process could
		345	have exited already (and no SIGCHLD will be sent anymore).
259		346
		347	Not all event models handle this correctly (POE doesn't), but even for
		348	event models that I<do> handle this correctly, they usually need to be
		349	loaded before the process exits (i.e. before you fork in the first place).
		350
		351	This means you cannot create a child watcher as the very first thing in an
		352	AnyEvent program, you I<have> to create at least one watcher before you
		353	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		354
		355	Example: fork a process and wait for it
		356
		357	my $done = AnyEvent->condvar;
		358
		359	my $pid = fork or exit 5;
		360
260	my $w = AnyEvent->child (	361	my $w = AnyEvent->child (
261	pid => 1333,	362	pid => $pid,
262	cb => sub {	363	cb => sub {
263	my ($pid, $status) = @_;	364	my ($pid, $status) = @_;
264	warn "pid $pid exited with status $status";	365	warn "pid $pid exited with status $status";
		366	$done->send;
265	},	367	},
266	);	368	);
		369
		370	# do something else, then wait for process exit
		371	$done->recv;
267		372
268	=head2 CONDITION VARIABLES	373	=head2 CONDITION VARIABLES
269		374
		375	If you are familiar with some event loops you will know that all of them
		376	require you to run some blocking "loop", "run" or similar function that
		377	will actively watch for new events and call your callbacks.
		378
		379	AnyEvent is different, it expects somebody else to run the event loop and
		380	will only block when necessary (usually when told by the user).
		381
		382	The instrument to do that is called a "condition variable", so called
		383	because they represent a condition that must become true.
		384
270	Condition variables can be created by calling the C<< AnyEvent->condvar >>	385	Condition variables can be created by calling the C<< AnyEvent->condvar
271	method without any arguments.	386	>> method, usually without arguments. The only argument pair allowed is
		387	C<cb>, which specifies a callback to be called when the condition variable
		388	becomes true.
272		389
273	A condition variable waits for a condition - precisely that the C<<	390	After creation, the condition variable is "false" until it becomes "true"
274	->broadcast >> method has been called.	391	by calling the C<send> method (or calling the condition variable as if it
		392	were a callback, read about the caveats in the description for the C<<
		393	->send >> method).
275		394
276	They are very useful to signal that a condition has been fulfilled, for	395	Condition variables are similar to callbacks, except that you can
		396	optionally wait for them. They can also be called merge points - points
		397	in time where multiple outstanding events have been processed. And yet
		398	another way to call them is transactions - each condition variable can be
		399	used to represent a transaction, which finishes at some point and delivers
		400	a result.
		401
		402	Condition variables are very useful to signal that something has finished,
277	example, if you write a module that does asynchronous http requests,	403	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	404	then a condition variable would be the ideal candidate to signal the
279	availability of results.	405	availability of results. The user can either act when the callback is
		406	called or can synchronously C<< ->recv >> for the results.
280		407
281	You can also use condition variables to block your main program until	408	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	409	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<<	410	could C<< ->recv >> in your main program until the user clicks the Quit
284	->broadcast >> the "quit" event.	411	button of your app, which would C<< ->send >> the "quit" event.
285		412
286	Note that condition variables recurse into the event loop - if you have	413	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	414	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	415	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,	416	you should avoid making a blocking wait yourself, at least in callbacks,
290	as this asks for trouble.	417	as this asks for trouble.
291		418
292	This object has two methods:	419	Condition variables are represented by hash refs in perl, and the keys
		420	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		421	easy (it is often useful to build your own transaction class on top of
		422	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		423	it's C<new> method in your own C<new> method.
		424
		425	There are two "sides" to a condition variable - the "producer side" which
		426	eventually calls C<< -> send >>, and the "consumer side", which waits
		427	for the send to occur.
		428
		429	Example: wait for a timer.
		430
		431	# wait till the result is ready
		432	my $result_ready = AnyEvent->condvar;
		433
		434	# do something such as adding a timer
		435	# or socket watcher the calls $result_ready->send
		436	# when the "result" is ready.
		437	# in this case, we simply use a timer:
		438	my $w = AnyEvent->timer (
		439	after => 1,
		440	cb => sub { $result_ready->send },
		441	);
		442
		443	# this "blocks" (while handling events) till the callback
		444	# calls send
		445	$result_ready->recv;
		446
		447	Example: wait for a timer, but take advantage of the fact that
		448	condition variables are also code references.
		449
		450	my $done = AnyEvent->condvar;
		451	my $delay = AnyEvent->timer (after => 5, cb => $done);
		452	$done->recv;
		453
		454	=head3 METHODS FOR PRODUCERS
		455
		456	These methods should only be used by the producing side, i.e. the
		457	code/module that eventually sends the signal. Note that it is also
		458	the producer side which creates the condvar in most cases, but it isn't
		459	uncommon for the consumer to create it as well.
293		460
294	=over 4	461	=over 4
295		462
		463	=item $cv->send (...)
		464
		465	Flag the condition as ready - a running C<< ->recv >> and all further
		466	calls to C<recv> will (eventually) return after this method has been
		467	called. If nobody is waiting the send will be remembered.
		468
		469	If a callback has been set on the condition variable, it is called
		470	immediately from within send.
		471
		472	Any arguments passed to the C<send> call will be returned by all
		473	future C<< ->recv >> calls.
		474
		475	Condition variables are overloaded so one can call them directly
		476	(as a code reference). Calling them directly is the same as calling
		477	C<send>. Note, however, that many C-based event loops do not handle
		478	overloading, so as tempting as it may be, passing a condition variable
		479	instead of a callback does not work. Both the pure perl and EV loops
		480	support overloading, however, as well as all functions that use perl to
		481	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		482	example).
		483
		484	=item $cv->croak ($error)
		485
		486	Similar to send, but causes all call's to C<< ->recv >> to invoke
		487	C<Carp::croak> with the given error message/object/scalar.
		488
		489	This can be used to signal any errors to the condition variable
		490	user/consumer.
		491
		492	=item $cv->begin ([group callback])
		493
296	=item $cv->wait	494	=item $cv->end
297		495
298	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	496	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		497
		498	These two methods can be used to combine many transactions/events into
		499	one. For example, a function that pings many hosts in parallel might want
		500	to use a condition variable for the whole process.
		501
		502	Every call to C<< ->begin >> will increment a counter, and every call to
		503	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		504	>>, the (last) callback passed to C<begin> will be executed. That callback
		505	is I<supposed> to call C<< ->send >>, but that is not required. If no
		506	callback was set, C<send> will be called without any arguments.
		507
		508	Let's clarify this with the ping example:
		509
		510	my $cv = AnyEvent->condvar;
		511
		512	my %result;
		513	$cv->begin (sub { $cv->send (\%result) });
		514
		515	for my $host (@list_of_hosts) {
		516	$cv->begin;
		517	ping_host_then_call_callback $host, sub {
		518	$result{$host} = ...;
		519	$cv->end;
		520	};
		521	}
		522
		523	$cv->end;
		524
		525	This code fragment supposedly pings a number of hosts and calls
		526	C<send> after results for all then have have been gathered - in any
		527	order. To achieve this, the code issues a call to C<begin> when it starts
		528	each ping request and calls C<end> when it has received some result for
		529	it. Since C<begin> and C<end> only maintain a counter, the order in which
		530	results arrive is not relevant.
		531
		532	There is an additional bracketing call to C<begin> and C<end> outside the
		533	loop, which serves two important purposes: first, it sets the callback
		534	to be called once the counter reaches C<0>, and second, it ensures that
		535	C<send> is called even when C<no> hosts are being pinged (the loop
		536	doesn't execute once).
		537
		538	This is the general pattern when you "fan out" into multiple subrequests:
		539	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		540	is called at least once, and then, for each subrequest you start, call
		541	C<begin> and for each subrequest you finish, call C<end>.
		542
		543	=back
		544
		545	=head3 METHODS FOR CONSUMERS
		546
		547	These methods should only be used by the consuming side, i.e. the
		548	code awaits the condition.
		549
		550	=over 4
		551
		552	=item $cv->recv
		553
		554	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
299	called on c<$cv>, while servicing other watchers normally.	555	>> methods have been called on c<$cv>, while servicing other watchers
		556	normally.
300		557
301	You can only wait once on a condition - additional calls will return	558	You can only wait once on a condition - additional calls are valid but
302	immediately.	559	will return immediately.
		560
		561	If an error condition has been set by calling C<< ->croak >>, then this
		562	function will call C<croak>.
		563
		564	In list context, all parameters passed to C<send> will be returned,
		565	in scalar context only the first one will be returned.
303		566
304	Not all event models support a blocking wait - some die in that case	567	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	568	(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	569	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	570	caller decide whether the call will block or not (for example, by coupling
308	condition variables with some kind of request results and supporting	571	condition variables with some kind of request results and supporting
309	callbacks so the caller knows that getting the result will not block,	572	callbacks so the caller knows that getting the result will not block,
310	while still suppporting blocking waits if the caller so desires).	573	while still supporting blocking waits if the caller so desires).
311		574
312	Another reason I<never> to C<< ->wait >> in a module is that you cannot	575	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	576	sensibly have two C<< ->recv >>'s in parallel, as that would require
314	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	577	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
315	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	578	can supply.
316	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
317	from different coroutines, however).
318		579
319	=item $cv->broadcast	580	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		581	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		582	versions and also integrates coroutines into AnyEvent, making blocking
		583	C<< ->recv >> calls perfectly safe as long as they are done from another
		584	coroutine (one that doesn't run the event loop).
320		585
321	Flag the condition as ready - a running C<< ->wait >> and all further	586	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	587	only calling C<< ->recv >> from within that callback (or at a later
323	called. If nobody is waiting the broadcast will be remembered..	588	time). This will work even when the event loop does not support blocking
		589	waits otherwise.
		590
		591	=item $bool = $cv->ready
		592
		593	Returns true when the condition is "true", i.e. whether C<send> or
		594	C<croak> have been called.
		595
		596	=item $cb = $cv->cb ([new callback])
		597
		598	This is a mutator function that returns the callback set and optionally
		599	replaces it before doing so.
		600
		601	The callback will be called when the condition becomes "true", i.e. when
		602	C<send> or C<croak> are called, with the only argument being the condition
		603	variable itself. Calling C<recv> inside the callback or at any later time
		604	is guaranteed not to block.
324		605
325	=back	606	=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	$result_ready->wait;
344		607
345	=head1 GLOBAL VARIABLES AND FUNCTIONS	608	=head1 GLOBAL VARIABLES AND FUNCTIONS
346		609
347	=over 4	610	=over 4
348		611
…		…
354	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	617	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
355	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	618	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
356		619
357	The known classes so far are:	620	The known classes so far are:
358		621
359	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
360	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
361	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	622	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
362	AnyEvent::Impl::Event based on Event, second best choice.	623	AnyEvent::Impl::Event based on Event, second best choice.
		624	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
363	AnyEvent::Impl::Glib based on Glib, third-best choice.	625	AnyEvent::Impl::Glib based on Glib, third-best choice.
364	AnyEvent::Impl::Tk based on Tk, very bad choice.	626	AnyEvent::Impl::Tk based on Tk, very bad choice.
365	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
366	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	627	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
367	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	628	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
368	AnyEvent::Impl::POE based on POE, not generic enough for full support.	629	AnyEvent::Impl::POE based on POE, not generic enough for full support.
369		630
370	There is no support for WxWidgets, as WxWidgets has no support for	631	There is no support for WxWidgets, as WxWidgets has no support for
…		…
382	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	643	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
383	if necessary. You should only call this function right before you would	644	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	645	have created an AnyEvent watcher anyway, that is, as late as possible at
385	runtime.	646	runtime.
386		647
		648	=item $guard = AnyEvent::post_detect { BLOCK }
		649
		650	Arranges for the code block to be executed as soon as the event model is
		651	autodetected (or immediately if this has already happened).
		652
		653	If called in scalar or list context, then it creates and returns an object
		654	that automatically removes the callback again when it is destroyed. See
		655	L<Coro::BDB> for a case where this is useful.
		656
		657	=item @AnyEvent::post_detect
		658
		659	If there are any code references in this array (you can C<push> to it
		660	before or after loading AnyEvent), then they will called directly after
		661	the event loop has been chosen.
		662
		663	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		664	if it contains a true value then the event loop has already been detected,
		665	and the array will be ignored.
		666
		667	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		668
387	=back	669	=back
388		670
389	=head1 WHAT TO DO IN A MODULE	671	=head1 WHAT TO DO IN A MODULE
390		672
391	As a module author, you should C<use AnyEvent> and call AnyEvent methods	673	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	676	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	677	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	678	by calling AnyEvent in your module body you force the user of your module
397	to load the event module first.	679	to load the event module first.
398		680
399	Never call C<< ->wait >> on a condition variable unless you I<know> that	681	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	682	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	683	because it will stall the whole program, and the whole point of using
402	events is to stay interactive.	684	events is to stay interactive.
403		685
404	It is fine, however, to call C<< ->wait >> when the user of your module	686	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	687	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 >>	688	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).	689	freely, as the user of your module knows what she is doing. always).
408		690
409	=head1 WHAT TO DO IN THE MAIN PROGRAM	691	=head1 WHAT TO DO IN THE MAIN PROGRAM
410		692
411	There will always be a single main program - the only place that should	693	There will always be a single main program - the only place that should
…		…
413		695
414	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	696	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	697	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.	698	decide which implementation to chose if some module relies on it.
417		699
418	If the main program relies on a specific event model. For example, in	700	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	701	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	702	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	703	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	704	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	705	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.	706	might chose the wrong one unless you load the correct one yourself.
425		707
426	You can chose to use a rather inefficient pure-perl implementation by	708	You can chose to use a pure-perl implementation by loading the
427	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	709	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
428	behaviour everywhere, but letting AnyEvent chose is generally better.	710	everywhere, but letting AnyEvent chose the model is generally better.
		711
		712	=head2 MAINLOOP EMULATION
		713
		714	Sometimes (often for short test scripts, or even standalone programs who
		715	only want to use AnyEvent), you do not want to run a specific event loop.
		716
		717	In that case, you can use a condition variable like this:
		718
		719	AnyEvent->condvar->recv;
		720
		721	This has the effect of entering the event loop and looping forever.
		722
		723	Note that usually your program has some exit condition, in which case
		724	it is better to use the "traditional" approach of storing a condition
		725	variable somewhere, waiting for it, and sending it when the program should
		726	exit cleanly.
		727
		728
		729	=head1 OTHER MODULES
		730
		731	The following is a non-exhaustive list of additional modules that use
		732	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		733	in the same program. Some of the modules come with AnyEvent, some are
		734	available via CPAN.
		735
		736	=over 4
		737
		738	=item L<AnyEvent::Util>
		739
		740	Contains various utility functions that replace often-used but blocking
		741	functions such as C<inet_aton> by event-/callback-based versions.
		742
		743	=item L<AnyEvent::Handle>
		744
		745	Provide read and write buffers and manages watchers for reads and writes.
		746
		747	=item L<AnyEvent::Socket>
		748
		749	Provides various utility functions for (internet protocol) sockets,
		750	addresses and name resolution. Also functions to create non-blocking tcp
		751	connections or tcp servers, with IPv6 and SRV record support and more.
		752
		753	=item L<AnyEvent::DNS>
		754
		755	Provides rich asynchronous DNS resolver capabilities.
		756
		757	=item L<AnyEvent::HTTP>
		758
		759	A simple-to-use HTTP library that is capable of making a lot of concurrent
		760	HTTP requests.
		761
		762	=item L<AnyEvent::HTTPD>
		763
		764	Provides a simple web application server framework.
		765
		766	=item L<AnyEvent::FastPing>
		767
		768	The fastest ping in the west.
		769
		770	=item L<Net::IRC3>
		771
		772	AnyEvent based IRC client module family.
		773
		774	=item L<Net::XMPP2>
		775
		776	AnyEvent based XMPP (Jabber protocol) module family.
		777
		778	=item L<Net::FCP>
		779
		780	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		781	of AnyEvent.
		782
		783	=item L<Event::ExecFlow>
		784
		785	High level API for event-based execution flow control.
		786
		787	=item L<Coro>
		788
		789	Has special support for AnyEvent via L<Coro::AnyEvent>.
		790
		791	=item L<AnyEvent::AIO>, L<IO::AIO>
		792
		793	Truly asynchronous I/O, should be in the toolbox of every event
		794	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		795	together.
		796
		797	=item L<AnyEvent::BDB>, L<BDB>
		798
		799	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
		800	IO::AIO and AnyEvent together.
		801
		802	=item L<IO::Lambda>
		803
		804	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		805
		806	=back
429		807
430	=cut	808	=cut
431		809
432	package AnyEvent;	810	package AnyEvent;
433		811
434	no warnings;	812	no warnings;
435	use strict;	813	use strict;
436		814
437	use Carp;	815	use Carp;
438		816
439	our $VERSION = '3.3';	817	our $VERSION = 4.14;
440	our $MODEL;	818	our $MODEL;
441		819
442	our $AUTOLOAD;	820	our $AUTOLOAD;
443	our @ISA;	821	our @ISA;
444		822
		823	our @REGISTRY;
		824
		825	our $WIN32;
		826
		827	BEGIN {
		828	my $win32 = ! ! ($^O =~ /mswin32/i);
		829	eval "sub WIN32(){ $win32 }";
		830	}
		831
445	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	832	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
446		833
447	our @REGISTRY;	834	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		835
		836	{
		837	my $idx;
		838	$PROTOCOL{$_} = ++$idx
		839	for reverse split /\s*,\s*/,
		840	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		841	}
448		842
449	my @models = (	843	my @models = (
450	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
451	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
452	[EV:: => AnyEvent::Impl::EV::],	844	[EV:: => AnyEvent::Impl::EV::],
453	[Event:: => AnyEvent::Impl::Event::],	845	[Event:: => AnyEvent::Impl::Event::],
454	[Glib:: => AnyEvent::Impl::Glib::],
455	[Tk:: => AnyEvent::Impl::Tk::],
456	[Wx:: => AnyEvent::Impl::POE::],
457	[Prima:: => AnyEvent::Impl::POE::],
458	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	846	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
459	# everything below here will not be autoprobed as the pureperl backend should work everywhere	847	# everything below here will not be autoprobed
		848	# as the pureperl backend should work everywhere
		849	# and is usually faster
		850	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		851	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
460	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	852	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
461	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	853	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
462	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	854	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		855	[Wx:: => AnyEvent::Impl::POE::],
		856	[Prima:: => AnyEvent::Impl::POE::],
463	);	857	);
464		858
465	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	859	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);
		860
		861	our @post_detect;
		862
		863	sub post_detect(&) {
		864	my ($cb) = @_;
		865
		866	if ($MODEL) {
		867	$cb->();
		868
		869	1
		870	} else {
		871	push @post_detect, $cb;
		872
		873	defined wantarray
		874	? bless \$cb, "AnyEvent::Util::PostDetect"
		875	: ()
		876	}
		877	}
		878
		879	sub AnyEvent::Util::PostDetect::DESTROY {
		880	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		881	}
466		882
467	sub detect() {	883	sub detect() {
468	unless ($MODEL) {	884	unless ($MODEL) {
469	no strict 'refs';	885	no strict 'refs';
		886	local $SIG{__DIE__};
470		887
471	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	888	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
472	my $model = "AnyEvent::Impl::$1";	889	my $model = "AnyEvent::Impl::$1";
473	if (eval "require $model") {	890	if (eval "require $model") {
474	$MODEL = $model;	891	$MODEL = $model;
…		…
504	last;	921	last;
505	}	922	}
506	}	923	}
507		924
508	$MODEL	925	$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.";	926	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
510	}	927	}
511	}	928	}
512		929
513	unshift @ISA, $MODEL;	930	unshift @ISA, $MODEL;
514	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	931	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		932
		933	(shift @post_detect)->() while @post_detect;
515	}	934	}
516		935
517	$MODEL	936	$MODEL
518	}	937	}
519		938
…		…
529	$class->$func (@_);	948	$class->$func (@_);
530	}	949	}
531		950
532	package AnyEvent::Base;	951	package AnyEvent::Base;
533		952
		953	# default implementation for now and time
		954
		955	use Time::HiRes ();
		956
		957	sub time { Time::HiRes::time }
		958	sub now { Time::HiRes::time }
		959
534	# default implementation for ->condvar, ->wait, ->broadcast	960	# default implementation for ->condvar
535		961
536	sub condvar {	962	sub condvar {
537	bless \my $flag, "AnyEvent::Base::CondVar"	963	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	}	964	}
547		965
548	# default implementation for ->signal	966	# default implementation for ->signal
549		967
550	our %SIG_CB;	968	our %SIG_CB;
…		…
603	or Carp::croak "required option 'pid' is missing";	1021	or Carp::croak "required option 'pid' is missing";
604		1022
605	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1023	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
606		1024
607	unless ($WNOHANG) {	1025	unless ($WNOHANG) {
608	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1026	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
609	}	1027	}
610		1028
611	unless ($CHLD_W) {	1029	unless ($CHLD_W) {
612	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1030	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
613	# child could be a zombie already, so make at least one round	1031	# child could be a zombie already, so make at least one round
…		…
623	delete $PID_CB{$pid}{$cb};	1041	delete $PID_CB{$pid}{$cb};
624	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1042	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
625		1043
626	undef $CHLD_W unless keys %PID_CB;	1044	undef $CHLD_W unless keys %PID_CB;
627	}	1045	}
		1046
		1047	package AnyEvent::CondVar;
		1048
		1049	our @ISA = AnyEvent::CondVar::Base::;
		1050
		1051	package AnyEvent::CondVar::Base;
		1052
		1053	use overload
		1054	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1055	fallback => 1;
		1056
		1057	sub _send {
		1058	# nop
		1059	}
		1060
		1061	sub send {
		1062	my $cv = shift;
		1063	$cv->{_ae_sent} = [@_];
		1064	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1065	$cv->_send;
		1066	}
		1067
		1068	sub croak {
		1069	$_[0]{_ae_croak} = $_[1];
		1070	$_[0]->send;
		1071	}
		1072
		1073	sub ready {
		1074	$_[0]{_ae_sent}
		1075	}
		1076
		1077	sub _wait {
		1078	AnyEvent->one_event while !$_[0]{_ae_sent};
		1079	}
		1080
		1081	sub recv {
		1082	$_[0]->_wait;
		1083
		1084	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1085	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1086	}
		1087
		1088	sub cb {
		1089	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1090	$_[0]{_ae_cb}
		1091	}
		1092
		1093	sub begin {
		1094	++$_[0]{_ae_counter};
		1095	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1096	}
		1097
		1098	sub end {
		1099	return if --$_[0]{_ae_counter};
		1100	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1101	}
		1102
		1103	# undocumented/compatibility with pre-3.4
		1104	*broadcast = \&send;
		1105	*wait = \&_wait;
628		1106
629	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1107	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
630		1108
631	This is an advanced topic that you do not normally need to use AnyEvent in	1109	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	1110	a module. This section is only of use to event loop authors who want to
…		…
689	model it chooses.	1167	model it chooses.
690		1168
691	=item C<PERL_ANYEVENT_MODEL>	1169	=item C<PERL_ANYEVENT_MODEL>
692		1170
693	This can be used to specify the event model to be used by AnyEvent, before	1171	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	1172	auto detection and -probing kicks in. It must be a string consisting
695	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended	1173	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,	1174	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	1175	used as event model. If it fails to load AnyEvent will proceed with
698	autodetection and -probing.	1176	auto detection and -probing.
699		1177
700	This functionality might change in future versions.	1178	This functionality might change in future versions.
701		1179
702	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you	1180	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
703	could start your program like this:	1181	could start your program like this:
704		1182
705	PERL_ANYEVENT_MODEL=Perl perl ...	1183	PERL_ANYEVENT_MODEL=Perl perl ...
		1184
		1185	=item C<PERL_ANYEVENT_PROTOCOLS>
		1186
		1187	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1188	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1189	of auto probing).
		1190
		1191	Must be set to a comma-separated list of protocols or address families,
		1192	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1193	used, and preference will be given to protocols mentioned earlier in the
		1194	list.
		1195
		1196	This variable can effectively be used for denial-of-service attacks
		1197	against local programs (e.g. when setuid), although the impact is likely
		1198	small, as the program has to handle connection errors already-
		1199
		1200	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1201	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1202	- only support IPv4, never try to resolve or contact IPv6
		1203	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1204	IPv6, but prefer IPv6 over IPv4.
		1205
		1206	=item C<PERL_ANYEVENT_EDNS0>
		1207
		1208	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1209	for DNS. This extension is generally useful to reduce DNS traffic, but
		1210	some (broken) firewalls drop such DNS packets, which is why it is off by
		1211	default.
		1212
		1213	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1214	EDNS0 in its DNS requests.
		1215
		1216	=item C<PERL_ANYEVENT_MAX_FORKS>
		1217
		1218	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1219	will create in parallel.
706		1220
707	=back	1221	=back
708		1222
709	=head1 EXAMPLE PROGRAM	1223	=head1 EXAMPLE PROGRAM
710		1224
711	The following program uses an IO watcher to read data from STDIN, a timer	1225	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	1226	to display a message once per second, and a condition variable to quit the
713	program when the user enters quit:	1227	program when the user enters quit:
714		1228
715	use AnyEvent;	1229	use AnyEvent;
716		1230
…		…
721	poll => 'r',	1235	poll => 'r',
722	cb => sub {	1236	cb => sub {
723	warn "io event <$_[0]>\n"; # will always output <r>	1237	warn "io event <$_[0]>\n"; # will always output <r>
724	chomp (my $input = <STDIN>); # read a line	1238	chomp (my $input = <STDIN>); # read a line
725	warn "read: $input\n"; # output what has been read	1239	warn "read: $input\n"; # output what has been read
726	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1240	$cv->send if $input =~ /^q/i; # quit program if /^q/i
727	},	1241	},
728	);	1242	);
729		1243
730	my $time_watcher; # can only be used once	1244	my $time_watcher; # can only be used once
731		1245
…		…
736	});	1250	});
737	}	1251	}
738		1252
739	new_timer; # create first timer	1253	new_timer; # create first timer
740		1254
741	$cv->wait; # wait until user enters /^q/i	1255	$cv->recv; # wait until user enters /^q/i
742		1256
743	=head1 REAL-WORLD EXAMPLE	1257	=head1 REAL-WORLD EXAMPLE
744		1258
745	Consider the L<Net::FCP> module. It features (among others) the following	1259	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:	1260	API calls, which are to freenet what HTTP GET requests are to http:
…		…
796	syswrite $txn->{fh}, $txn->{request}	1310	syswrite $txn->{fh}, $txn->{request}
797	or die "connection or write error";	1311	or die "connection or write error";
798	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1312	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
799		1313
800	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1314	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:	1315	result and signals any possible waiters that the request has finished:
802		1316
803	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1317	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
804		1318
805	if (end-of-file or data complete) {	1319	if (end-of-file or data complete) {
806	$txn->{result} = $txn->{buf};	1320	$txn->{result} = $txn->{buf};
807	$txn->{finished}->broadcast;	1321	$txn->{finished}->send;
808	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1322	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
809	}	1323	}
810		1324
811	The C<result> method, finally, just waits for the finished signal (if the	1325	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	1326	request was already finished, it doesn't wait, of course, and returns the
813	data:	1327	data:
814		1328
815	$txn->{finished}->wait;	1329	$txn->{finished}->recv;
816	return $txn->{result};	1330	return $txn->{result};
817		1331
818	The actual code goes further and collects all errors (C<die>s, exceptions)	1332	The actual code goes further and collects all errors (C<die>s, exceptions)
819	that occured during request processing. The C<result> method detects	1333	that occurred during request processing. The C<result> method detects
820	whether an exception as thrown (it is stored inside the $txn object)	1334	whether an exception as thrown (it is stored inside the $txn object)
821	and just throws the exception, which means connection errors and other	1335	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	1336	problems get reported tot he code that tries to use the result, not in a
823	random callback.	1337	random callback.
824		1338
…		…
855		1369
856	my $quit = AnyEvent->condvar;	1370	my $quit = AnyEvent->condvar;
857		1371
858	$fcp->txn_client_get ($url)->cb (sub {	1372	$fcp->txn_client_get ($url)->cb (sub {
859	...	1373	...
860	$quit->broadcast;	1374	$quit->send;
861	});	1375	});
862		1376
863	$quit->wait;	1377	$quit->recv;
864		1378
865		1379
866	=head1 BENCHMARK	1380	=head1 BENCHMARKS
867		1381
868	To give you an idea of the performance and overheads that AnyEvent adds	1382	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	1383	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	1384	of various event loops I prepared some benchmarks.
871	event models natively and with anyevent. The benchmark creates a lot of	1385
872	timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to	1386	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1387
		1388	Here is a benchmark of various supported event models used natively and
		1389	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1390	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	1391	which it is), lets them fire exactly once and destroys them again.
874	them again.
875		1392
		1393	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1394	distribution.
		1395
876	=head2 Explanation of the columns	1396	=head3 Explanation of the columns
877		1397
878	I<watcher> is the number of event watchers created/destroyed. Since	1398	I<watcher> is the number of event watchers created/destroyed. Since
879	different event models feature vastly different performances, each event	1399	different event models feature vastly different performances, each event
880	loop was given a number of watchers so that overall runtime is acceptable	1400	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	1401	and similar between tested event loop (and keep them from crashing): Glib
…		…
891	all watchers, to avoid adding memory overhead. That means closure creation	1411	all watchers, to avoid adding memory overhead. That means closure creation
892	and memory usage is not included in the figures.	1412	and memory usage is not included in the figures.
893		1413
894	I<invoke> is the time, in microseconds, used to invoke a simple	1414	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	1415	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	1416	invoked "watcher" times, it would C<< ->send >> a condvar once to
897	signal the end of this phase.	1417	signal the end of this phase.
898		1418
899	I<destroy> is the time, in microseconds, that it takes to destroy a single	1419	I<destroy> is the time, in microseconds, that it takes to destroy a single
900	watcher.	1420	watcher.
901		1421
902	=head2 Results	1422	=head3 Results
903		1423
904	name watcher bytes create invoke destroy comment	1424	name watchers bytes create invoke destroy comment
905	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1425	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	1426	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	1427	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
908	Perl/Any 16000 654 4.64 1.22 0.77 pure perl implementation	1428	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	1429	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	1430	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	1431	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	1432	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	1433	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	1434	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
915		1435
916	=head2 Discussion	1436	=head3 Discussion
917		1437
918	The benchmark does I<not> measure scalability of the event loop very	1438	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)	1439	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	1440	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	1441	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	1442	the same time, so select/poll-based implementations get an unnatural speed
923	to worka round bugs).	1443	boost.
		1444
		1445	Also, note that the number of watchers usually has a nonlinear effect on
		1446	overall speed, that is, creating twice as many watchers doesn't take twice
		1447	the time - usually it takes longer. This puts event loops tested with a
		1448	higher number of watchers at a disadvantage.
		1449
		1450	To put the range of results into perspective, consider that on the
		1451	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1452	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1453	cycles with POE.
924		1454
925	C<EV> is the sole leader regarding speed and memory use, which are both	1455	C<EV> is the sole leader regarding speed and memory use, which are both
926	maximal/minimal, respectively. Even when going through AnyEvent, there is	1456	maximal/minimal, respectively. Even when going through AnyEvent, it uses
927	only one event loop that uses less memory (the C<Event> module natively), and	1457	far less memory than any other event loop and is still faster than Event
928	no faster event model, not event C<Event> natively.	1458	natively.
929		1459
930	The pure perl implementation is hit in a few sweet spots (both the	1460	The pure perl implementation is hit in a few sweet spots (both the
931	zero timeout and the use of a single fd hit optimisations in the perl	1461	constant timeout and the use of a single fd hit optimisations in the perl
932	interpreter and the backend itself). Nevertheless tis shows that it	1462	interpreter and the backend itself). Nevertheless this shows that it
933	adds very little overhead in itself. Like any select-based backend its	1463	adds very little overhead in itself. Like any select-based backend its
934	performance becomes really bad with lots of file descriptors, of course,	1464	performance becomes really bad with lots of file descriptors (and few of
935	but this was not subjetc of this benchmark.	1465	them active), of course, but this was not subject of this benchmark.
936		1466
937	The C<Event> module has a relatively high setup and callback invocation cost,	1467	The C<Event> module has a relatively high setup and callback invocation
938	but overall scores on the third place.	1468	cost, but overall scores in on the third place.
939		1469
940	C<Glib>'s memory usage is quite a bit bit higher, but it features a	1470	C<Glib>'s memory usage is quite a bit higher, but it features a
941	faster callback invocation and overall ends up in the same class as	1471	faster callback invocation and overall ends up in the same class as
942	C<Event>. However, Glib scales extremely badly, doubling the number of	1472	C<Event>. However, Glib scales extremely badly, doubling the number of
943	watchers increases the processing time by more than a factor of four,	1473	watchers increases the processing time by more than a factor of four,
944	making it completely unusable when using larger numbers of watchers	1474	making it completely unusable when using larger numbers of watchers
945	(note that only a single file descriptor was used in the benchmark, so	1475	(note that only a single file descriptor was used in the benchmark, so
…		…
948	The C<Tk> adaptor works relatively well. The fact that it crashes with	1478	The C<Tk> adaptor works relatively well. The fact that it crashes with
949	more than 2000 watchers is a big setback, however, as correctness takes	1479	more than 2000 watchers is a big setback, however, as correctness takes
950	precedence over speed. Nevertheless, its performance is surprising, as the	1480	precedence over speed. Nevertheless, its performance is surprising, as the
951	file descriptor is dup()ed for each watcher. This shows that the dup()	1481	file descriptor is dup()ed for each watcher. This shows that the dup()
952	employed by some adaptors is not a big performance issue (it does incur a	1482	employed by some adaptors is not a big performance issue (it does incur a
953	hidden memory cost inside the kernel, though).	1483	hidden memory cost inside the kernel which is not reflected in the figures
		1484	above).
954		1485
955	C<POE>, regardless of underlying event loop (wether using its pure perl	1486	C<POE>, regardless of underlying event loop (whether using its pure perl
956	select-based backend or the Event module) shows abysmal performance and	1487	select-based backend or the Event module, the POE-EV backend couldn't
		1488	be tested because it wasn't working) shows abysmal performance and
957	memory usage: Watchers use almost 30 times as much memory as EV watchers,	1489	memory usage with AnyEvent: Watchers use almost 30 times as much memory
958	and 10 times as much memory as both Event or EV via AnyEvent. Watcher	1490	as EV watchers, and 10 times as much memory as Event (the high memory
		1491	requirements are caused by requiring a session for each watcher). Watcher
959	invocation is almost 700 times slower than with AnyEvent's pure perl	1492	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1493	implementation.
		1494
960	implementation. The design of the POE adaptor class in AnyEvent can not	1495	The design of the POE adaptor class in AnyEvent can not really account
961	really account for this, as session creation overhead is small compared	1496	for the performance issues, though, as session creation overhead is
962	to execution of the state machine, which is coded pretty optimally within	1497	small compared to execution of the state machine, which is coded pretty
963	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1498	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1499	using multiple sessions is not a good approach, especially regarding
		1500	memory usage, even the author of POE could not come up with a faster
		1501	design).
964		1502
965	=head2 Summary	1503	=head3 Summary
966		1504
		1505	=over 4
		1506
967	Using EV through AnyEvent is faster than any other event loop, but most	1507	=item * Using EV through AnyEvent is faster than any other event loop
968	event loops have acceptable performance with or without AnyEvent.	1508	(even when used without AnyEvent), but most event loops have acceptable
		1509	performance with or without AnyEvent.
969		1510
970	The overhead AnyEvent adds is usually much smaller than the overhead of	1511	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
971	the actual event loop, only with extremely fast event loops such as the EV	1512	the actual event loop, only with extremely fast event loops such as EV
972	adds AnyEvent significant overhead.	1513	adds AnyEvent significant overhead.
973		1514
974	And you should simply avoid POE like the plague if you want performance or	1515	=item * You should avoid POE like the plague if you want performance or
975	reasonable memory usage.	1516	reasonable memory usage.
976		1517
		1518	=back
		1519
		1520	=head2 BENCHMARKING THE LARGE SERVER CASE
		1521
		1522	This benchmark actually benchmarks the event loop itself. It works by
		1523	creating a number of "servers": each server consists of a socket pair, a
		1524	timeout watcher that gets reset on activity (but never fires), and an I/O
		1525	watcher waiting for input on one side of the socket. Each time the socket
		1526	watcher reads a byte it will write that byte to a random other "server".
		1527
		1528	The effect is that there will be a lot of I/O watchers, only part of which
		1529	are active at any one point (so there is a constant number of active
		1530	fds for each loop iteration, but which fds these are is random). The
		1531	timeout is reset each time something is read because that reflects how
		1532	most timeouts work (and puts extra pressure on the event loops).
		1533
		1534	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1535	(1%) are active. This mirrors the activity of large servers with many
		1536	connections, most of which are idle at any one point in time.
		1537
		1538	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1539	distribution.
		1540
		1541	=head3 Explanation of the columns
		1542
		1543	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1544	each server has a read and write socket end).
		1545
		1546	I<create> is the time it takes to create a socket pair (which is
		1547	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1548
		1549	I<request>, the most important value, is the time it takes to handle a
		1550	single "request", that is, reading the token from the pipe and forwarding
		1551	it to another server. This includes deleting the old timeout and creating
		1552	a new one that moves the timeout into the future.
		1553
		1554	=head3 Results
		1555
		1556	name sockets create request
		1557	EV 20000 69.01 11.16
		1558	Perl 20000 73.32 35.87
		1559	Event 20000 212.62 257.32
		1560	Glib 20000 651.16 1896.30
		1561	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1562
		1563	=head3 Discussion
		1564
		1565	This benchmark I<does> measure scalability and overall performance of the
		1566	particular event loop.
		1567
		1568	EV is again fastest. Since it is using epoll on my system, the setup time
		1569	is relatively high, though.
		1570
		1571	Perl surprisingly comes second. It is much faster than the C-based event
		1572	loops Event and Glib.
		1573
		1574	Event suffers from high setup time as well (look at its code and you will
		1575	understand why). Callback invocation also has a high overhead compared to
		1576	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1577	uses select or poll in basically all documented configurations.
		1578
		1579	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1580	clearly fails to perform with many filehandles or in busy servers.
		1581
		1582	POE is still completely out of the picture, taking over 1000 times as long
		1583	as EV, and over 100 times as long as the Perl implementation, even though
		1584	it uses a C-based event loop in this case.
		1585
		1586	=head3 Summary
		1587
		1588	=over 4
		1589
		1590	=item * The pure perl implementation performs extremely well.
		1591
		1592	=item * Avoid Glib or POE in large projects where performance matters.
		1593
		1594	=back
		1595
		1596	=head2 BENCHMARKING SMALL SERVERS
		1597
		1598	While event loops should scale (and select-based ones do not...) even to
		1599	large servers, most programs we (or I :) actually write have only a few
		1600	I/O watchers.
		1601
		1602	In this benchmark, I use the same benchmark program as in the large server
		1603	case, but it uses only eight "servers", of which three are active at any
		1604	one time. This should reflect performance for a small server relatively
		1605	well.
		1606
		1607	The columns are identical to the previous table.
		1608
		1609	=head3 Results
		1610
		1611	name sockets create request
		1612	EV 16 20.00 6.54
		1613	Perl 16 25.75 12.62
		1614	Event 16 81.27 35.86
		1615	Glib 16 32.63 15.48
		1616	POE 16 261.87 276.28 uses POE::Loop::Event
		1617
		1618	=head3 Discussion
		1619
		1620	The benchmark tries to test the performance of a typical small
		1621	server. While knowing how various event loops perform is interesting, keep
		1622	in mind that their overhead in this case is usually not as important, due
		1623	to the small absolute number of watchers (that is, you need efficiency and
		1624	speed most when you have lots of watchers, not when you only have a few of
		1625	them).
		1626
		1627	EV is again fastest.
		1628
		1629	Perl again comes second. It is noticeably faster than the C-based event
		1630	loops Event and Glib, although the difference is too small to really
		1631	matter.
		1632
		1633	POE also performs much better in this case, but is is still far behind the
		1634	others.
		1635
		1636	=head3 Summary
		1637
		1638	=over 4
		1639
		1640	=item * C-based event loops perform very well with small number of
		1641	watchers, as the management overhead dominates.
		1642
		1643	=back
		1644
977		1645
978	=head1 FORK	1646	=head1 FORK
979		1647
980	Most event libraries are not fork-safe. The ones who are usually are	1648	Most event libraries are not fork-safe. The ones who are usually are
981	because they are so inefficient. Only L<EV> is fully fork-aware.	1649	because they rely on inefficient but fork-safe C<select> or C<poll>
		1650	calls. Only L<EV> is fully fork-aware.
982		1651
983	If you have to fork, you must either do so I<before> creating your first	1652	If you have to fork, you must either do so I<before> creating your first
984	watcher OR you must not use AnyEvent at all in the child.	1653	watcher OR you must not use AnyEvent at all in the child.
985		1654
986		1655
…		…
994	specified in the variable.	1663	specified in the variable.
995		1664
996	You can make AnyEvent completely ignore this variable by deleting it	1665	You can make AnyEvent completely ignore this variable by deleting it
997	before the first watcher gets created, e.g. with a C<BEGIN> block:	1666	before the first watcher gets created, e.g. with a C<BEGIN> block:
998		1667
999	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1668	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1000		1669
1001	use AnyEvent;	1670	use AnyEvent;
		1671
		1672	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1673	be used to probe what backend is used and gain other information (which is
		1674	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
1002		1675
1003		1676
1004	=head1 SEE ALSO	1677	=head1 SEE ALSO
1005		1678
1006	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1679	Utility functions: L<AnyEvent::Util>.
1007	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1680
		1681	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1008	L<Event::Lib>, L<Qt>, L<POE>.	1682	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1009		1683
1010	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1684	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1011	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1685	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1012	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1686	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1013	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1687	L<AnyEvent::Impl::POE>.
1014		1688
		1689	Non-blocking file handles, sockets, TCP clients and
		1690	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1691
		1692	Asynchronous DNS: L<AnyEvent::DNS>.
		1693
		1694	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1695
1015	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1696	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1016		1697
1017		1698
1018	=head1 AUTHOR	1699	=head1 AUTHOR
1019		1700
1020	Marc Lehmann <schmorp@schmorp.de>	1701	Marc Lehmann <schmorp@schmorp.de>
1021	http://home.schmorp.de/	1702	http://home.schmorp.de/
1022		1703
1023	=cut	1704	=cut
1024		1705
1025	1	1706	1
1026		1707

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