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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 - 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
…		…
78		89
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	94	to detect the currently loaded event loop by probing whether one of the
84	the following modules is already loaded: L<Coro::EV>, L<Coro::Event>,	95	following modules is already loaded: L<EV>,
85	L<EV>, L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>. The first one	96	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	found is used. If none are found, the module tries to load these modules	97	L<POE>. The first one found is used. If none are found, the module tries
87	(excluding Event::Lib and Qt) in the order given. The first one that can	98	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
		99	adaptor should always succeed) in the order given. The first one that can
88	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
89	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
90	very efficient, but should work everywhere.	102	very efficient, but should work everywhere.
91		103
92	Because AnyEvent first checks for modules that are already loaded, loading	104	Because AnyEvent first checks for modules that are already loaded, loading
…		…
102	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
103	use AnyEvent so their modules work together with others seamlessly...	115	use AnyEvent so their modules work together with others seamlessly...
104		116
105	The pure-perl implementation of AnyEvent is called	117	The pure-perl implementation of AnyEvent is called
106	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
107	explicitly.	119	explicitly and enjoy the high availability of that event loop :)
108		120
109	=head1 WATCHERS	121	=head1 WATCHERS
110		122
111	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
112	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
113	the callback to call, the filehandle to watch, etc.	125	the callback to call, the file handle to watch, etc.
114		126
115	These watchers are normal Perl objects with normal Perl lifetime. After	127	These watchers are normal Perl objects with normal Perl lifetime. After
116	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
117	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
118	is in control).	130	is in control).
…		…
126	Many watchers either are used with "recursion" (repeating timers for	138	Many watchers either are used with "recursion" (repeating timers for
127	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.
128		140
129	An any way to achieve that is this pattern:	141	An any way to achieve that is this pattern:
130		142
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	143	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	144	# you can use $w here, for example to undef it
133	undef $w;	145	undef $w;
134	});	146	});
135		147
136	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,
137	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
138	declared.	150	declared.
139		151
140	=head2 IO WATCHERS	152	=head2 I/O WATCHERS
141		153
142	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
143	with the following mandatory key-value pairs as arguments:	155	with the following mandatory key-value pairs as arguments:
144		156
145	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
146	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>,
147	creates a watcher waiting for "r"eadable or "w"ritable events,	159	which creates a watcher waiting for "r"eadable or "w"ritable events,
148	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
149	becomes ready.	161	becomes ready.
150		162
151	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
152	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.
153		166
		167	The I/O watcher might use the underlying file descriptor or a copy of it.
154	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
155	on the underlying file descriptor.	169	underlying file descriptor.
156		170
157	Some event loops issue spurious readyness notifications, so you should	171	Some event loops issue spurious readyness notifications, so you should
158	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
159	handles.	173	handles.
160		174
…		…
171		185
172	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 >>
173	method with the following mandatory arguments:	187	method with the following mandatory arguments:
174		188
175	C<after> specifies after how many seconds (fractional values are	189	C<after> specifies after how many seconds (fractional values are
176	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
177	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.
178		196
179	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
180	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
181	and Glib).	199	and Glib).
182		200
…		…
207		225
208	There are two ways to handle timers: based on real time (relative, "fire	226	There are two ways to handle timers: based on real time (relative, "fire
209	in 10 seconds") and based on wallclock time (absolute, "fire at 12	227	in 10 seconds") and based on wallclock time (absolute, "fire at 12
210	o'clock").	228	o'clock").
211		229
212	While most event loops expect timers to specified in a relative way, they use	230	While most event loops expect timers to specified in a relative way, they
213	absolute time internally. This makes a difference when your clock "jumps",	231	use absolute time internally. This makes a difference when your clock
214	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to	232	"jumps", for example, when ntp decides to set your clock backwards from
215	2008-01-01, a watcher that you created to fire "after" a second might actually take	233	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
216	six years to finally fire.	234	fire "after" a second might actually take six years to finally fire.
217		235
218	AnyEvent cannot compensate for this. The only event loop that is conscious	236	AnyEvent cannot compensate for this. The only event loop that is conscious
219	about these issues is L<EV>, which offers both relative (ev_timer) and	237	about these issues is L<EV>, which offers both relative (ev_timer, based
220	absolute (ev_periodic) timers.	238	on true relative time) and absolute (ev_periodic, based on wallclock time)
		239	timers.
221		240
222	AnyEvent always prefers relative timers, if available, matching the	241	AnyEvent always prefers relative timers, if available, matching the
223	AnyEvent API.	242	AnyEvent API.
		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
224		306
225	=head2 SIGNAL WATCHERS	307	=head2 SIGNAL WATCHERS
226		308
227	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
228	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
229	be invoked whenever a signal occurs.	311	be invoked whenever a signal occurs.
230		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
231	Multiple signals occurances can be clumped together into one callback	317	Multiple signal occurrences can be clumped together into one callback
232	invocation, and callback invocation will be synchronous. synchronous means	318	invocation, and callback invocation will be synchronous. Synchronous means
233	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,
234	but it is guarenteed not to interrupt any other callbacks.	320	but it is guaranteed not to interrupt any other callbacks.
235		321
236	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
237	between multiple watchers.	323	between multiple watchers.
238		324
239	This watcher might use C<%SIG>, so programs overwriting those signals	325	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
249		335
250	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
251	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
252	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
253	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
254	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.
255		342
256	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).
257		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
258	my $w = AnyEvent->child (	361	my $w = AnyEvent->child (
259	pid => 1333,	362	pid => $pid,
260	cb => sub {	363	cb => sub {
261	my ($pid, $status) = @_;	364	my ($pid, $status) = @_;
262	warn "pid $pid exited with status $status";	365	warn "pid $pid exited with status $status";
		366	$done->send;
263	},	367	},
264	);	368	);
		369
		370	# do something else, then wait for process exit
		371	$done->recv;
265		372
266	=head2 CONDITION VARIABLES	373	=head2 CONDITION VARIABLES
267		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
268	Condition variables can be created by calling the C<< AnyEvent->condvar >>	385	Condition variables can be created by calling the C<< AnyEvent->condvar
269	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.
270		389
271	A condition variable waits for a condition - precisely that the C<<	390	After creation, the condition variable is "false" until it becomes "true"
272	->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).
273		394
274	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,
275	example, if you write a module that does asynchronous http requests,	403	for example, if you write a module that does asynchronous http requests,
276	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
277	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.
278		407
279	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,
280	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
281	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
282	->broadcast >> the "quit" event.	411	button of your app, which would C<< ->send >> the "quit" event.
283		412
284	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
285	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
286	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
287	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,
288	as this asks for trouble.	417	as this asks for trouble.
289		418
290	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.
291		460
292	=over 4	461	=over 4
293		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
294	=item $cv->wait	494	=item $cv->end
295		495
296	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 $cv->recv
		553
		554	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
297	called on c<$cv>, while servicing other watchers normally.	555	>> methods have been called on c<$cv>, while servicing other watchers
		556	normally.
298		557
299	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
300	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.
301		566
302	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
303	(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
304	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
305	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
306	condition variables with some kind of request results and supporting	571	condition variables with some kind of request results and supporting
307	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,
308	while still suppporting blocking waits if the caller so desires).	573	while still supporting blocking waits if the caller so desires).
309		574
310	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
311	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
312	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	577	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
313	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	578	can supply.
314	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
315	from different coroutines, however).
316		579
317	=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).
318		585
319	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
320	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
321	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.
322		605
323	=back	606	=back
324
325	Example:
326
327	# wait till the result is ready
328	my $result_ready = AnyEvent->condvar;
329
330	# do something such as adding a timer
331	# or socket watcher the calls $result_ready->broadcast
332	# when the "result" is ready.
333	# in this case, we simply use a timer:
334	my $w = AnyEvent->timer (
335	after => 1,
336	cb => sub { $result_ready->broadcast },
337	);
338
339	# this "blocks" (while handling events) till the watcher
340	# calls broadcast
341	$result_ready->wait;
342		607
343	=head1 GLOBAL VARIABLES AND FUNCTIONS	608	=head1 GLOBAL VARIABLES AND FUNCTIONS
344		609
345	=over 4	610	=over 4
346		611
…		…
352	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
353	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>).
354		619
355	The known classes so far are:	620	The known classes so far are:
356		621
357	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
358	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
359	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).
360	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.
361	AnyEvent::Impl::Glib based on Glib, third-best choice.	625	AnyEvent::Impl::Glib based on Glib, third-best choice.
362	AnyEvent::Impl::Tk based on Tk, very bad choice.	626	AnyEvent::Impl::Tk based on Tk, very bad choice.
363	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
364	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).
365	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	628	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		629	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		630
		631	There is no support for WxWidgets, as WxWidgets has no support for
		632	watching file handles. However, you can use WxWidgets through the
		633	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		634	second, which was considered to be too horrible to even consider for
		635	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		636	it's adaptor.
		637
		638	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		639	autodetecting them.
366		640
367	=item AnyEvent::detect	641	=item AnyEvent::detect
368		642
369	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	643	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
370	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
371	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
372	runtime.	646	runtime.
373		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
374	=back	669	=back
375		670
376	=head1 WHAT TO DO IN A MODULE	671	=head1 WHAT TO DO IN A MODULE
377		672
378	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
…		…
381	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
382	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
383	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
384	to load the event module first.	679	to load the event module first.
385		680
386	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
387	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
388	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
389	events is to stay interactive.	684	events is to stay interactive.
390		685
391	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
392	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
393	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 >>
394	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).
395		690
396	=head1 WHAT TO DO IN THE MAIN PROGRAM	691	=head1 WHAT TO DO IN THE MAIN PROGRAM
397		692
398	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
…		…
400		695
401	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
402	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
403	decide which implementation to chose if some module relies on it.	698	decide which implementation to chose if some module relies on it.
404		699
405	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
406	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
407	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
408	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
409	modules might create watchers when they are loaded, and AnyEvent will	704	modules might create watchers when they are loaded, and AnyEvent will
410	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
411	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.
412		707
413	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
414	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	709	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
415	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
416		807
417	=cut	808	=cut
418		809
419	package AnyEvent;	810	package AnyEvent;
420		811
421	no warnings;	812	no warnings;
422	use strict;	813	use strict;
423		814
424	use Carp;	815	use Carp;
425		816
426	our $VERSION = '3.12';	817	our $VERSION = 4.14;
427	our $MODEL;	818	our $MODEL;
428		819
429	our $AUTOLOAD;	820	our $AUTOLOAD;
430	our @ISA;	821	our @ISA;
431		822
		823	our @REGISTRY;
		824
		825	our $WIN32;
		826
		827	BEGIN {
		828	my $win32 = ! ! ($^O =~ /mswin32/i);
		829	eval "sub WIN32(){ $win32 }";
		830	}
		831
432	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	832	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
433		833
434	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	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		841	}
435		842
436	my @models = (	843	my @models = (
437	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
438	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
439	[EV:: => AnyEvent::Impl::EV::],	844	[EV:: => AnyEvent::Impl::EV::],
440	[Event:: => AnyEvent::Impl::Event::],	845	[Event:: => AnyEvent::Impl::Event::],
441	[Glib:: => AnyEvent::Impl::Glib::],
442	[Tk:: => AnyEvent::Impl::Tk::],
443	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	846	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		847	# everything below here will not be autoprobed
		848	# as the pureperl backend should work everywhere
		849	# and is usually faster
		850	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		851	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		852	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		853	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		854	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		855	[Wx:: => AnyEvent::Impl::POE::],
		856	[Prima:: => AnyEvent::Impl::POE::],
444	);	857	);
445	my @models_detect = (
446	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
447	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
448	);
449		858
450	our %method = map +($_ => 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	}
451		882
452	sub detect() {	883	sub detect() {
453	unless ($MODEL) {	884	unless ($MODEL) {
454	no strict 'refs';	885	no strict 'refs';
		886	local $SIG{__DIE__};
455		887
456	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	888	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
457	my $model = "AnyEvent::Impl::$1";	889	my $model = "AnyEvent::Impl::$1";
458	if (eval "require $model") {	890	if (eval "require $model") {
459	$MODEL = $model;	891	$MODEL = $model;
460	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	892	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		893	} else {
		894	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
461	}	895	}
462	}	896	}
463		897
464	# check for already loaded models	898	# check for already loaded models
465	unless ($MODEL) {	899	unless ($MODEL) {
466	for (@REGISTRY, @models, @models_detect) {	900	for (@REGISTRY, @models) {
467	my ($package, $model) = @$_;	901	my ($package, $model) = @$_;
468	if (${"$package\::VERSION"} > 0) {	902	if (${"$package\::VERSION"} > 0) {
469	if (eval "require $model") {	903	if (eval "require $model") {
470	$MODEL = $model;	904	$MODEL = $model;
471	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	905	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
…		…
487	last;	921	last;
488	}	922	}
489	}	923	}
490		924
491	$MODEL	925	$MODEL
492	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.";
493	}	927	}
494	}	928	}
495		929
496	unshift @ISA, $MODEL;	930	unshift @ISA, $MODEL;
497	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	931	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		932
		933	(shift @post_detect)->() while @post_detect;
498	}	934	}
499		935
500	$MODEL	936	$MODEL
501	}	937	}
502		938
…		…
512	$class->$func (@_);	948	$class->$func (@_);
513	}	949	}
514		950
515	package AnyEvent::Base;	951	package AnyEvent::Base;
516		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
517	# default implementation for ->condvar, ->wait, ->broadcast	960	# default implementation for ->condvar
518		961
519	sub condvar {	962	sub condvar {
520	bless \my $flag, "AnyEvent::Base::CondVar"	963	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
521	}
522
523	sub AnyEvent::Base::CondVar::broadcast {
524	${$_[0]}++;
525	}
526
527	sub AnyEvent::Base::CondVar::wait {
528	AnyEvent->one_event while !${$_[0]};
529	}	964	}
530		965
531	# default implementation for ->signal	966	# default implementation for ->signal
532		967
533	our %SIG_CB;	968	our %SIG_CB;
…		…
586	or Carp::croak "required option 'pid' is missing";	1021	or Carp::croak "required option 'pid' is missing";
587		1022
588	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1023	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
589		1024
590	unless ($WNOHANG) {	1025	unless ($WNOHANG) {
591	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1026	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
592	}	1027	}
593		1028
594	unless ($CHLD_W) {	1029	unless ($CHLD_W) {
595	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1030	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
596	# 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
…		…
606	delete $PID_CB{$pid}{$cb};	1041	delete $PID_CB{$pid}{$cb};
607	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1042	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
608		1043
609	undef $CHLD_W unless keys %PID_CB;	1044	undef $CHLD_W unless keys %PID_CB;
610	}	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;
611		1106
612	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1107	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
613		1108
614	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
615	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
…		…
658		1153
659	=over 4	1154	=over 4
660		1155
661	=item C<PERL_ANYEVENT_VERBOSE>	1156	=item C<PERL_ANYEVENT_VERBOSE>
662		1157
		1158	By default, AnyEvent will be completely silent except in fatal
		1159	conditions. You can set this environment variable to make AnyEvent more
		1160	talkative.
		1161
		1162	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1163	conditions, such as not being able to load the event model specified by
		1164	C<PERL_ANYEVENT_MODEL>.
		1165
663	When set to C<2> or higher, cause AnyEvent to report to STDERR which event	1166	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
664	model it chooses.	1167	model it chooses.
665		1168
666	=item C<PERL_ANYEVENT_MODEL>	1169	=item C<PERL_ANYEVENT_MODEL>
667		1170
668	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
669	autodetection and -probing kicks in. It must be a string consisting	1172	auto detection and -probing kicks in. It must be a string consisting
670	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended	1173	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
671	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,
672	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
673	autodetection and -probing.	1176	auto detection and -probing.
674		1177
675	This functionality might change in future versions.	1178	This functionality might change in future versions.
676		1179
677	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
678	could start your program like this:	1181	could start your program like this:
679		1182
680	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.
681		1220
682	=back	1221	=back
683		1222
684	=head1 EXAMPLE PROGRAM	1223	=head1 EXAMPLE PROGRAM
685		1224
686	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
687	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
688	program when the user enters quit:	1227	program when the user enters quit:
689		1228
690	use AnyEvent;	1229	use AnyEvent;
691		1230
…		…
696	poll => 'r',	1235	poll => 'r',
697	cb => sub {	1236	cb => sub {
698	warn "io event <$_[0]>\n"; # will always output <r>	1237	warn "io event <$_[0]>\n"; # will always output <r>
699	chomp (my $input = <STDIN>); # read a line	1238	chomp (my $input = <STDIN>); # read a line
700	warn "read: $input\n"; # output what has been read	1239	warn "read: $input\n"; # output what has been read
701	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1240	$cv->send if $input =~ /^q/i; # quit program if /^q/i
702	},	1241	},
703	);	1242	);
704		1243
705	my $time_watcher; # can only be used once	1244	my $time_watcher; # can only be used once
706		1245
…		…
711	});	1250	});
712	}	1251	}
713		1252
714	new_timer; # create first timer	1253	new_timer; # create first timer
715		1254
716	$cv->wait; # wait until user enters /^q/i	1255	$cv->recv; # wait until user enters /^q/i
717		1256
718	=head1 REAL-WORLD EXAMPLE	1257	=head1 REAL-WORLD EXAMPLE
719		1258
720	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
721	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:
…		…
771	syswrite $txn->{fh}, $txn->{request}	1310	syswrite $txn->{fh}, $txn->{request}
772	or die "connection or write error";	1311	or die "connection or write error";
773	$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 });
774		1313
775	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
776	result and signals any possible waiters that the request ahs finished:	1315	result and signals any possible waiters that the request has finished:
777		1316
778	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1317	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
779		1318
780	if (end-of-file or data complete) {	1319	if (end-of-file or data complete) {
781	$txn->{result} = $txn->{buf};	1320	$txn->{result} = $txn->{buf};
782	$txn->{finished}->broadcast;	1321	$txn->{finished}->send;
783	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1322	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
784	}	1323	}
785		1324
786	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
787	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
788	data:	1327	data:
789		1328
790	$txn->{finished}->wait;	1329	$txn->{finished}->recv;
791	return $txn->{result};	1330	return $txn->{result};
792		1331
793	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)
794	that occured during request processing. The C<result> method detects	1333	that occurred during request processing. The C<result> method detects
795	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)
796	and just throws the exception, which means connection errors and other	1335	and just throws the exception, which means connection errors and other
797	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
798	random callback.	1337	random callback.
799		1338
…		…
830		1369
831	my $quit = AnyEvent->condvar;	1370	my $quit = AnyEvent->condvar;
832		1371
833	$fcp->txn_client_get ($url)->cb (sub {	1372	$fcp->txn_client_get ($url)->cb (sub {
834	...	1373	...
835	$quit->broadcast;	1374	$quit->send;
836	});	1375	});
837		1376
838	$quit->wait;	1377	$quit->recv;
		1378
		1379
		1380	=head1 BENCHMARKS
		1381
		1382	To give you an idea of the performance and overheads that AnyEvent adds
		1383	over the event loops themselves and to give you an impression of the speed
		1384	of various event loops I prepared some benchmarks.
		1385
		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,
		1391	which it is), lets them fire exactly once and destroys them again.
		1392
		1393	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1394	distribution.
		1395
		1396	=head3 Explanation of the columns
		1397
		1398	I<watcher> is the number of event watchers created/destroyed. Since
		1399	different event models feature vastly different performances, each event
		1400	loop was given a number of watchers so that overall runtime is acceptable
		1401	and similar between tested event loop (and keep them from crashing): Glib
		1402	would probably take thousands of years if asked to process the same number
		1403	of watchers as EV in this benchmark.
		1404
		1405	I<bytes> is the number of bytes (as measured by the resident set size,
		1406	RSS) consumed by each watcher. This method of measuring captures both C
		1407	and Perl-based overheads.
		1408
		1409	I<create> is the time, in microseconds (millionths of seconds), that it
		1410	takes to create a single watcher. The callback is a closure shared between
		1411	all watchers, to avoid adding memory overhead. That means closure creation
		1412	and memory usage is not included in the figures.
		1413
		1414	I<invoke> is the time, in microseconds, used to invoke a simple
		1415	callback. The callback simply counts down a Perl variable and after it was
		1416	invoked "watcher" times, it would C<< ->send >> a condvar once to
		1417	signal the end of this phase.
		1418
		1419	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1420	watcher.
		1421
		1422	=head3 Results
		1423
		1424	name watchers bytes create invoke destroy comment
		1425	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		1426	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		1427	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		1428	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		1429	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		1430	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		1431	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		1432	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		1433	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		1434	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		1435
		1436	=head3 Discussion
		1437
		1438	The benchmark does I<not> measure scalability of the event loop very
		1439	well. For example, a select-based event loop (such as the pure perl one)
		1440	can never compete with an event loop that uses epoll when the number of
		1441	file descriptors grows high. In this benchmark, all events become ready at
		1442	the same time, so select/poll-based implementations get an unnatural speed
		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.
		1454
		1455	C<EV> is the sole leader regarding speed and memory use, which are both
		1456	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1457	far less memory than any other event loop and is still faster than Event
		1458	natively.
		1459
		1460	The pure perl implementation is hit in a few sweet spots (both the
		1461	constant timeout and the use of a single fd hit optimisations in the perl
		1462	interpreter and the backend itself). Nevertheless this shows that it
		1463	adds very little overhead in itself. Like any select-based backend its
		1464	performance becomes really bad with lots of file descriptors (and few of
		1465	them active), of course, but this was not subject of this benchmark.
		1466
		1467	The C<Event> module has a relatively high setup and callback invocation
		1468	cost, but overall scores in on the third place.
		1469
		1470	C<Glib>'s memory usage is quite a bit higher, but it features a
		1471	faster callback invocation and overall ends up in the same class as
		1472	C<Event>. However, Glib scales extremely badly, doubling the number of
		1473	watchers increases the processing time by more than a factor of four,
		1474	making it completely unusable when using larger numbers of watchers
		1475	(note that only a single file descriptor was used in the benchmark, so
		1476	inefficiencies of C<poll> do not account for this).
		1477
		1478	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1479	more than 2000 watchers is a big setback, however, as correctness takes
		1480	precedence over speed. Nevertheless, its performance is surprising, as the
		1481	file descriptor is dup()ed for each watcher. This shows that the dup()
		1482	employed by some adaptors is not a big performance issue (it does incur a
		1483	hidden memory cost inside the kernel which is not reflected in the figures
		1484	above).
		1485
		1486	C<POE>, regardless of underlying event loop (whether using its pure perl
		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
		1489	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		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
		1492	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1493	implementation.
		1494
		1495	The design of the POE adaptor class in AnyEvent can not really account
		1496	for the performance issues, though, as session creation overhead is
		1497	small compared to execution of the state machine, which is coded pretty
		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).
		1502
		1503	=head3 Summary
		1504
		1505	=over 4
		1506
		1507	=item * Using EV through AnyEvent is faster than any other event loop
		1508	(even when used without AnyEvent), but most event loops have acceptable
		1509	performance with or without AnyEvent.
		1510
		1511	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1512	the actual event loop, only with extremely fast event loops such as EV
		1513	adds AnyEvent significant overhead.
		1514
		1515	=item * You should avoid POE like the plague if you want performance or
		1516	reasonable memory usage.
		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
839		1645
840	=head1 FORK	1646	=head1 FORK
841		1647
842	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
843	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.
844		1651
845	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
846	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.
		1654
847		1655
848	=head1 SECURITY CONSIDERATIONS	1656	=head1 SECURITY CONSIDERATIONS
849		1657
850	AnyEvent can be forced to load any event model via	1658	AnyEvent can be forced to load any event model via
851	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	1659	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
855	specified in the variable.	1663	specified in the variable.
856		1664
857	You can make AnyEvent completely ignore this variable by deleting it	1665	You can make AnyEvent completely ignore this variable by deleting it
858	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:
859		1667
860	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1668	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
861		1669
862	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).
		1675
863		1676
864	=head1 SEE ALSO	1677	=head1 SEE ALSO
865		1678
866	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1679	Utility functions: L<AnyEvent::Util>.
867	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
868	L<Event::Lib>, L<Qt>.
869		1680
870	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1681	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
871	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1682	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
872	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1683
		1684	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		1685	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		1686	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
873	L<AnyEvent::Impl::Qt>.	1687	L<AnyEvent::Impl::POE>.
874		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
875	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1696	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
		1697
876		1698
877	=head1 AUTHOR	1699	=head1 AUTHOR
878		1700
879	Marc Lehmann <schmorp@schmorp.de>	1701	Marc Lehmann <schmorp@schmorp.de>
880	http://home.schmorp.de/	1702	http://home.schmorp.de/
881		1703
882	=cut	1704	=cut
883		1705
884	1	1706	1
885		1707

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