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Revision 1.54 by root, Tue Apr 22 05:12:19 2008 UTC vs.
Revision 1.164 by root, Tue Jul 8 19:50:25 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 - 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>. The first one found is used. If none are found,	96	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	the module tries to load these modules in the stated order. The first one	97	L<POE>. The first one found is used. If none are found, the module tries
		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
87	that can be successfully loaded will be used. If, after this, still none	100	be successfully loaded will be used. If, after this, still none could be
88	could be found, AnyEvent will fall back to a pure-perl event loop, which	101	found, AnyEvent will fall back to a pure-perl event loop, which is not
89	is not very efficient, but should work everywhere.	102	very efficient, but should work everywhere.
90		103
91	Because AnyEvent first checks for modules that are already loaded, loading	104	Because AnyEvent first checks for modules that are already loaded, loading
92	an event model explicitly before first using AnyEvent will likely make	105	an event model explicitly before first using AnyEvent will likely make
93	that model the default. For example:	106	that model the default. For example:
94		107
…		…
101	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
102	use AnyEvent so their modules work together with others seamlessly...	115	use AnyEvent so their modules work together with others seamlessly...
103		116
104	The pure-perl implementation of AnyEvent is called	117	The pure-perl implementation of AnyEvent is called
105	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
106	explicitly.	119	explicitly and enjoy the high availability of that event loop :)
107		120
108	=head1 WATCHERS	121	=head1 WATCHERS
109		122
110	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
111	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
112	the callback to call, the filehandle to watch, etc.	125	the callback to call, the file handle to watch, etc.
113		126
114	These watchers are normal Perl objects with normal Perl lifetime. After	127	These watchers are normal Perl objects with normal Perl lifetime. After
115	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
116	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
117	is in control).	130	is in control).
…		…
125	Many watchers either are used with "recursion" (repeating timers for	138	Many watchers either are used with "recursion" (repeating timers for
126	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.
127		140
128	An any way to achieve that is this pattern:	141	An any way to achieve that is this pattern:
129		142
130	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	143	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
131	# you can use $w here, for example to undef it	144	# you can use $w here, for example to undef it
132	undef $w;	145	undef $w;
133	});	146	});
134		147
135	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,
136	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
137	declared.	150	declared.
138		151
139	=head2 IO WATCHERS	152	=head2 I/O WATCHERS
140		153
141	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
142	with the following mandatory key-value pairs as arguments:	155	with the following mandatory key-value pairs as arguments:
143		156
144	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
145	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>,
146	creates a watcher waiting for "r"eadable or "w"ritable events,	159	which creates a watcher waiting for "r"eadable or "w"ritable events,
147	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
148	becomes ready.	161	becomes ready.
149		162
150	File handles will be kept alive, so as long as the watcher exists, the	163	Although the callback might get passed parameters, their value and
151	file handle exists, too.	164	presence is undefined and you cannot rely on them. Portable AnyEvent
		165	callbacks cannot use arguments passed to I/O watcher callbacks.
152		166
		167	The I/O watcher might use the underlying file descriptor or a copy of it.
153	It is not allowed to close a file handle as long as any watcher is active	168	You must not close a file handle as long as any watcher is active on the
154	on the underlying file descriptor.	169	underlying file descriptor.
155		170
156	Some event loops issue spurious readyness notifications, so you should	171	Some event loops issue spurious readyness notifications, so you should
157	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
158	handles.	173	handles.
159		174
160	Example:
161
162	# wait for readability of STDIN, then read a line and disable the watcher	175	Example: wait for readability of STDIN, then read a line and disable the
		176	watcher.
		177
163	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	178	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
164	chomp (my $input = <STDIN>);	179	chomp (my $input = <STDIN>);
165	warn "read: $input\n";	180	warn "read: $input\n";
166	undef $w;	181	undef $w;
167	});	182	});
…		…
170		185
171	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 >>
172	method with the following mandatory arguments:	187	method with the following mandatory arguments:
173		188
174	C<after> specifies after how many seconds (fractional values are	189	C<after> specifies after how many seconds (fractional values are
175	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
176	case.	191	in that case.
177		192
178	The timer callback will be invoked at most once: if you want a repeating	193	Although the callback might get passed parameters, their value and
179	timer you have to create a new watcher (this is a limitation by both Tk	194	presence is undefined and you cannot rely on them. Portable AnyEvent
180	and Glib).	195	callbacks cannot use arguments passed to time watcher callbacks.
181		196
182	Example:	197	The callback will normally be invoked once only. If you specify another
		198	parameter, C<interval>, as a positive number, then the callback will be
		199	invoked regularly at that interval (in fractional seconds) after the first
		200	invocation.
183		201
		202	The callback will be rescheduled before invoking the callback, but no
		203	attempt is done to avoid timer drift in most backends, so the interval is
		204	only approximate.
		205
184	# fire an event after 7.7 seconds	206	Example: fire an event after 7.7 seconds.
		207
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	208	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	209	warn "timeout\n";
187	});	210	});
188		211
189	# to cancel the timer:	212	# to cancel the timer:
190	undef $w;	213	undef $w;
191		214
192	Example 2:
193
194	# fire an event after 0.5 seconds, then roughly every second	215	Example 2: fire an event after 0.5 seconds, then roughly every second.
195	my $w;
196		216
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	217	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		218	warn "timeout\n";
200	};	219	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		220
205	=head3 TIMING ISSUES	221	=head3 TIMING ISSUES
206		222
207	There are two ways to handle timers: based on real time (relative, "fire	223	There are two ways to handle timers: based on real time (relative, "fire
208	in 10 seconds") and based on wallclock time (absolute, "fire at 12	224	in 10 seconds") and based on wallclock time (absolute, "fire at 12
209	o'clock").	225	o'clock").
210		226
211	While most event loops expect timers to specified in a relative way, they use	227	While most event loops expect timers to specified in a relative way, they
212	absolute time internally. This makes a difference when your clock "jumps",	228	use absolute time internally. This makes a difference when your clock
213	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to	229	"jumps", for example, when ntp decides to set your clock backwards from
214	2008-01-01, a watcher that you created to fire "after" a second might actually take	230	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
215	six years to finally fire.	231	fire "after" a second might actually take six years to finally fire.
216		232
217	AnyEvent cannot compensate for this. The only event loop that is conscious	233	AnyEvent cannot compensate for this. The only event loop that is conscious
218	about these issues is L<EV>, which offers both relative (ev_timer) and	234	about these issues is L<EV>, which offers both relative (ev_timer, based
219	absolute (ev_periodic) timers.	235	on true relative time) and absolute (ev_periodic, based on wallclock time)
		236	timers.
220		237
221	AnyEvent always prefers relative timers, if available, matching the	238	AnyEvent always prefers relative timers, if available, matching the
222	AnyEvent API.	239	AnyEvent API.
		240
		241	AnyEvent has two additional methods that return the "current time":
		242
		243	=over 4
		244
		245	=item AnyEvent->time
		246
		247	This returns the "current wallclock time" as a fractional number of
		248	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		249	return, and the result is guaranteed to be compatible with those).
		250
		251	It progresses independently of any event loop processing, i.e. each call
		252	will check the system clock, which usually gets updated frequently.
		253
		254	=item AnyEvent->now
		255
		256	This also returns the "current wallclock time", but unlike C<time>, above,
		257	this value might change only once per event loop iteration, depending on
		258	the event loop (most return the same time as C<time>, above). This is the
		259	time that AnyEvent's timers get scheduled against.
		260
		261	I<In almost all cases (in all cases if you don't care), this is the
		262	function to call when you want to know the current time.>
		263
		264	This function is also often faster then C<< AnyEvent->time >>, and
		265	thus the preferred method if you want some timestamp (for example,
		266	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		267
		268	The rest of this section is only of relevance if you try to be very exact
		269	with your timing, you can skip it without bad conscience.
		270
		271	For a practical example of when these times differ, consider L<Event::Lib>
		272	and L<EV> and the following set-up:
		273
		274	The event loop is running and has just invoked one of your callback at
		275	time=500 (assume no other callbacks delay processing). In your callback,
		276	you wait a second by executing C<sleep 1> (blocking the process for a
		277	second) and then (at time=501) you create a relative timer that fires
		278	after three seconds.
		279
		280	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		281	both return C<501>, because that is the current time, and the timer will
		282	be scheduled to fire at time=504 (C<501> + C<3>).
		283
		284	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		285	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		286	last event processing phase started. With L<EV>, your timer gets scheduled
		287	to run at time=503 (C<500> + C<3>).
		288
		289	In one sense, L<Event::Lib> is more exact, as it uses the current time
		290	regardless of any delays introduced by event processing. However, most
		291	callbacks do not expect large delays in processing, so this causes a
		292	higher drift (and a lot more system calls to get the current time).
		293
		294	In another sense, L<EV> is more exact, as your timer will be scheduled at
		295	the same time, regardless of how long event processing actually took.
		296
		297	In either case, if you care (and in most cases, you don't), then you
		298	can get whatever behaviour you want with any event loop, by taking the
		299	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		300	account.
		301
		302	=back
223		303
224	=head2 SIGNAL WATCHERS	304	=head2 SIGNAL WATCHERS
225		305
226	You can watch for signals using a signal watcher, C<signal> is the signal	306	You can watch for signals using a signal watcher, C<signal> is the signal
227	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	307	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
228	be invoked whenever a signal occurs.	308	be invoked whenever a signal occurs.
229		309
		310	Although the callback might get passed parameters, their value and
		311	presence is undefined and you cannot rely on them. Portable AnyEvent
		312	callbacks cannot use arguments passed to signal watcher callbacks.
		313
230	Multiple signals occurances can be clumped together into one callback	314	Multiple signal occurrences can be clumped together into one callback
231	invocation, and callback invocation will be synchronous. synchronous means	315	invocation, and callback invocation will be synchronous. Synchronous means
232	that it might take a while until the signal gets handled by the process,	316	that it might take a while until the signal gets handled by the process,
233	but it is guarenteed not to interrupt any other callbacks.	317	but it is guaranteed not to interrupt any other callbacks.
234		318
235	The main advantage of using these watchers is that you can share a signal	319	The main advantage of using these watchers is that you can share a signal
236	between multiple watchers.	320	between multiple watchers.
237		321
238	This watcher might use C<%SIG>, so programs overwriting those signals	322	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
248		332
249	The child process is specified by the C<pid> argument (if set to C<0>, it	333	The child process is specified by the C<pid> argument (if set to C<0>, it
250	watches for any child process exit). The watcher will trigger as often	334	watches for any child process exit). The watcher will trigger as often
251	as status change for the child are received. This works by installing a	335	as status change for the child are received. This works by installing a
252	signal handler for C<SIGCHLD>. The callback will be called with the pid	336	signal handler for C<SIGCHLD>. The callback will be called with the pid
253	and exit status (as returned by waitpid).	337	and exit status (as returned by waitpid), so unlike other watcher types,
		338	you I<can> rely on child watcher callback arguments.
254		339
255	Example: wait for pid 1333	340	There is a slight catch to child watchers, however: you usually start them
		341	I<after> the child process was created, and this means the process could
		342	have exited already (and no SIGCHLD will be sent anymore).
256		343
		344	Not all event models handle this correctly (POE doesn't), but even for
		345	event models that I<do> handle this correctly, they usually need to be
		346	loaded before the process exits (i.e. before you fork in the first place).
		347
		348	This means you cannot create a child watcher as the very first thing in an
		349	AnyEvent program, you I<have> to create at least one watcher before you
		350	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		351
		352	Example: fork a process and wait for it
		353
		354	my $done = AnyEvent->condvar;
		355
		356	my $pid = fork or exit 5;
		357
257	my $w = AnyEvent->child (	358	my $w = AnyEvent->child (
258	pid => 1333,	359	pid => $pid,
259	cb => sub {	360	cb => sub {
260	my ($pid, $status) = @_;	361	my ($pid, $status) = @_;
261	warn "pid $pid exited with status $status";	362	warn "pid $pid exited with status $status";
		363	$done->send;
262	},	364	},
263	);	365	);
		366
		367	# do something else, then wait for process exit
		368	$done->recv;
264		369
265	=head2 CONDITION VARIABLES	370	=head2 CONDITION VARIABLES
266		371
		372	If you are familiar with some event loops you will know that all of them
		373	require you to run some blocking "loop", "run" or similar function that
		374	will actively watch for new events and call your callbacks.
		375
		376	AnyEvent is different, it expects somebody else to run the event loop and
		377	will only block when necessary (usually when told by the user).
		378
		379	The instrument to do that is called a "condition variable", so called
		380	because they represent a condition that must become true.
		381
267	Condition variables can be created by calling the C<< AnyEvent->condvar >>	382	Condition variables can be created by calling the C<< AnyEvent->condvar
268	method without any arguments.	383	>> method, usually without arguments. The only argument pair allowed is
		384	C<cb>, which specifies a callback to be called when the condition variable
		385	becomes true.
269		386
270	A condition variable waits for a condition - precisely that the C<<	387	After creation, the condition variable is "false" until it becomes "true"
271	->broadcast >> method has been called.	388	by calling the C<send> method (or calling the condition variable as if it
		389	were a callback, read about the caveats in the description for the C<<
		390	->send >> method).
272		391
273	They are very useful to signal that a condition has been fulfilled, for	392	Condition variables are similar to callbacks, except that you can
		393	optionally wait for them. They can also be called merge points - points
		394	in time where multiple outstanding events have been processed. And yet
		395	another way to call them is transactions - each condition variable can be
		396	used to represent a transaction, which finishes at some point and delivers
		397	a result.
		398
		399	Condition variables are very useful to signal that something has finished,
274	example, if you write a module that does asynchronous http requests,	400	for example, if you write a module that does asynchronous http requests,
275	then a condition variable would be the ideal candidate to signal the	401	then a condition variable would be the ideal candidate to signal the
276	availability of results.	402	availability of results. The user can either act when the callback is
		403	called or can synchronously C<< ->recv >> for the results.
277		404
278	You can also use condition variables to block your main program until	405	You can also use them to simulate traditional event loops - for example,
279	an event occurs - for example, you could C<< ->wait >> in your main	406	you can block your main program until an event occurs - for example, you
280	program until the user clicks the Quit button in your app, which would C<<	407	could C<< ->recv >> in your main program until the user clicks the Quit
281	->broadcast >> the "quit" event.	408	button of your app, which would C<< ->send >> the "quit" event.
282		409
283	Note that condition variables recurse into the event loop - if you have	410	Note that condition variables recurse into the event loop - if you have
284	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	411	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
285	lose. Therefore, condition variables are good to export to your caller, but	412	lose. Therefore, condition variables are good to export to your caller, but
286	you should avoid making a blocking wait yourself, at least in callbacks,	413	you should avoid making a blocking wait yourself, at least in callbacks,
287	as this asks for trouble.	414	as this asks for trouble.
288		415
289	This object has two methods:	416	Condition variables are represented by hash refs in perl, and the keys
		417	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		418	easy (it is often useful to build your own transaction class on top of
		419	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		420	it's C<new> method in your own C<new> method.
		421
		422	There are two "sides" to a condition variable - the "producer side" which
		423	eventually calls C<< -> send >>, and the "consumer side", which waits
		424	for the send to occur.
		425
		426	Example: wait for a timer.
		427
		428	# wait till the result is ready
		429	my $result_ready = AnyEvent->condvar;
		430
		431	# do something such as adding a timer
		432	# or socket watcher the calls $result_ready->send
		433	# when the "result" is ready.
		434	# in this case, we simply use a timer:
		435	my $w = AnyEvent->timer (
		436	after => 1,
		437	cb => sub { $result_ready->send },
		438	);
		439
		440	# this "blocks" (while handling events) till the callback
		441	# calls send
		442	$result_ready->recv;
		443
		444	Example: wait for a timer, but take advantage of the fact that
		445	condition variables are also code references.
		446
		447	my $done = AnyEvent->condvar;
		448	my $delay = AnyEvent->timer (after => 5, cb => $done);
		449	$done->recv;
		450
		451	=head3 METHODS FOR PRODUCERS
		452
		453	These methods should only be used by the producing side, i.e. the
		454	code/module that eventually sends the signal. Note that it is also
		455	the producer side which creates the condvar in most cases, but it isn't
		456	uncommon for the consumer to create it as well.
290		457
291	=over 4	458	=over 4
292		459
		460	=item $cv->send (...)
		461
		462	Flag the condition as ready - a running C<< ->recv >> and all further
		463	calls to C<recv> will (eventually) return after this method has been
		464	called. If nobody is waiting the send will be remembered.
		465
		466	If a callback has been set on the condition variable, it is called
		467	immediately from within send.
		468
		469	Any arguments passed to the C<send> call will be returned by all
		470	future C<< ->recv >> calls.
		471
		472	Condition variables are overloaded so one can call them directly
		473	(as a code reference). Calling them directly is the same as calling
		474	C<send>. Note, however, that many C-based event loops do not handle
		475	overloading, so as tempting as it may be, passing a condition variable
		476	instead of a callback does not work. Both the pure perl and EV loops
		477	support overloading, however, as well as all functions that use perl to
		478	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		479	example).
		480
		481	=item $cv->croak ($error)
		482
		483	Similar to send, but causes all call's to C<< ->recv >> to invoke
		484	C<Carp::croak> with the given error message/object/scalar.
		485
		486	This can be used to signal any errors to the condition variable
		487	user/consumer.
		488
		489	=item $cv->begin ([group callback])
		490
293	=item $cv->wait	491	=item $cv->end
294		492
295	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	493	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		494
		495	These two methods can be used to combine many transactions/events into
		496	one. For example, a function that pings many hosts in parallel might want
		497	to use a condition variable for the whole process.
		498
		499	Every call to C<< ->begin >> will increment a counter, and every call to
		500	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		501	>>, the (last) callback passed to C<begin> will be executed. That callback
		502	is I<supposed> to call C<< ->send >>, but that is not required. If no
		503	callback was set, C<send> will be called without any arguments.
		504
		505	Let's clarify this with the ping example:
		506
		507	my $cv = AnyEvent->condvar;
		508
		509	my %result;
		510	$cv->begin (sub { $cv->send (\%result) });
		511
		512	for my $host (@list_of_hosts) {
		513	$cv->begin;
		514	ping_host_then_call_callback $host, sub {
		515	$result{$host} = ...;
		516	$cv->end;
		517	};
		518	}
		519
		520	$cv->end;
		521
		522	This code fragment supposedly pings a number of hosts and calls
		523	C<send> after results for all then have have been gathered - in any
		524	order. To achieve this, the code issues a call to C<begin> when it starts
		525	each ping request and calls C<end> when it has received some result for
		526	it. Since C<begin> and C<end> only maintain a counter, the order in which
		527	results arrive is not relevant.
		528
		529	There is an additional bracketing call to C<begin> and C<end> outside the
		530	loop, which serves two important purposes: first, it sets the callback
		531	to be called once the counter reaches C<0>, and second, it ensures that
		532	C<send> is called even when C<no> hosts are being pinged (the loop
		533	doesn't execute once).
		534
		535	This is the general pattern when you "fan out" into multiple subrequests:
		536	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		537	is called at least once, and then, for each subrequest you start, call
		538	C<begin> and for each subrequest you finish, call C<end>.
		539
		540	=back
		541
		542	=head3 METHODS FOR CONSUMERS
		543
		544	These methods should only be used by the consuming side, i.e. the
		545	code awaits the condition.
		546
		547	=over 4
		548
		549	=item $cv->recv
		550
		551	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
296	called on c<$cv>, while servicing other watchers normally.	552	>> methods have been called on c<$cv>, while servicing other watchers
		553	normally.
297		554
298	You can only wait once on a condition - additional calls will return	555	You can only wait once on a condition - additional calls are valid but
299	immediately.	556	will return immediately.
		557
		558	If an error condition has been set by calling C<< ->croak >>, then this
		559	function will call C<croak>.
		560
		561	In list context, all parameters passed to C<send> will be returned,
		562	in scalar context only the first one will be returned.
300		563
301	Not all event models support a blocking wait - some die in that case	564	Not all event models support a blocking wait - some die in that case
302	(programs might want to do that to stay interactive), so I<if you are	565	(programs might want to do that to stay interactive), so I<if you are
303	using this from a module, never require a blocking wait>, but let the	566	using this from a module, never require a blocking wait>, but let the
304	caller decide whether the call will block or not (for example, by coupling	567	caller decide whether the call will block or not (for example, by coupling
305	condition variables with some kind of request results and supporting	568	condition variables with some kind of request results and supporting
306	callbacks so the caller knows that getting the result will not block,	569	callbacks so the caller knows that getting the result will not block,
307	while still suppporting blocking waits if the caller so desires).	570	while still supporting blocking waits if the caller so desires).
308		571
309	Another reason I<never> to C<< ->wait >> in a module is that you cannot	572	Another reason I<never> to C<< ->recv >> in a module is that you cannot
310	sensibly have two C<< ->wait >>'s in parallel, as that would require	573	sensibly have two C<< ->recv >>'s in parallel, as that would require
311	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	574	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
312	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	575	can supply.
313	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
314	from different coroutines, however).
315		576
316	=item $cv->broadcast	577	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		578	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		579	versions and also integrates coroutines into AnyEvent, making blocking
		580	C<< ->recv >> calls perfectly safe as long as they are done from another
		581	coroutine (one that doesn't run the event loop).
317		582
318	Flag the condition as ready - a running C<< ->wait >> and all further	583	You can ensure that C<< -recv >> never blocks by setting a callback and
319	calls to C<wait> will (eventually) return after this method has been	584	only calling C<< ->recv >> from within that callback (or at a later
320	called. If nobody is waiting the broadcast will be remembered..	585	time). This will work even when the event loop does not support blocking
		586	waits otherwise.
		587
		588	=item $bool = $cv->ready
		589
		590	Returns true when the condition is "true", i.e. whether C<send> or
		591	C<croak> have been called.
		592
		593	=item $cb = $cv->cb ([new callback])
		594
		595	This is a mutator function that returns the callback set and optionally
		596	replaces it before doing so.
		597
		598	The callback will be called when the condition becomes "true", i.e. when
		599	C<send> or C<croak> are called, with the only argument being the condition
		600	variable itself. Calling C<recv> inside the callback or at any later time
		601	is guaranteed not to block.
321		602
322	=back	603	=back
323
324	Example:
325
326	# wait till the result is ready
327	my $result_ready = AnyEvent->condvar;
328
329	# do something such as adding a timer
330	# or socket watcher the calls $result_ready->broadcast
331	# when the "result" is ready.
332	# in this case, we simply use a timer:
333	my $w = AnyEvent->timer (
334	after => 1,
335	cb => sub { $result_ready->broadcast },
336	);
337
338	# this "blocks" (while handling events) till the watcher
339	# calls broadcast
340	$result_ready->wait;
341		604
342	=head1 GLOBAL VARIABLES AND FUNCTIONS	605	=head1 GLOBAL VARIABLES AND FUNCTIONS
343		606
344	=over 4	607	=over 4
345		608
…		…
351	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	614	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
352	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	615	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
353		616
354	The known classes so far are:	617	The known classes so far are:
355		618
356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
358	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).	619	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
359	AnyEvent::Impl::Event based on Event, also second best choice :)	620	AnyEvent::Impl::Event based on Event, second best choice.
		621	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
360	AnyEvent::Impl::Glib based on Glib, third-best choice.	622	AnyEvent::Impl::Glib based on Glib, third-best choice.
361	AnyEvent::Impl::Tk based on Tk, very bad choice.	623	AnyEvent::Impl::Tk based on Tk, very bad choice.
362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.	624	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		625	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		626	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		627
		628	There is no support for WxWidgets, as WxWidgets has no support for
		629	watching file handles. However, you can use WxWidgets through the
		630	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		631	second, which was considered to be too horrible to even consider for
		632	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		633	it's adaptor.
		634
		635	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		636	autodetecting them.
363		637
364	=item AnyEvent::detect	638	=item AnyEvent::detect
365		639
366	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	640	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
367	if necessary. You should only call this function right before you would	641	if necessary. You should only call this function right before you would
368	have created an AnyEvent watcher anyway, that is, as late as possible at	642	have created an AnyEvent watcher anyway, that is, as late as possible at
369	runtime.	643	runtime.
370		644
		645	=item $guard = AnyEvent::post_detect { BLOCK }
		646
		647	Arranges for the code block to be executed as soon as the event model is
		648	autodetected (or immediately if this has already happened).
		649
		650	If called in scalar or list context, then it creates and returns an object
		651	that automatically removes the callback again when it is destroyed. See
		652	L<Coro::BDB> for a case where this is useful.
		653
		654	=item @AnyEvent::post_detect
		655
		656	If there are any code references in this array (you can C<push> to it
		657	before or after loading AnyEvent), then they will called directly after
		658	the event loop has been chosen.
		659
		660	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		661	if it contains a true value then the event loop has already been detected,
		662	and the array will be ignored.
		663
		664	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		665
371	=back	666	=back
372		667
373	=head1 WHAT TO DO IN A MODULE	668	=head1 WHAT TO DO IN A MODULE
374		669
375	As a module author, you should C<use AnyEvent> and call AnyEvent methods	670	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
378	Be careful when you create watchers in the module body - AnyEvent will	673	Be careful when you create watchers in the module body - AnyEvent will
379	decide which event module to use as soon as the first method is called, so	674	decide which event module to use as soon as the first method is called, so
380	by calling AnyEvent in your module body you force the user of your module	675	by calling AnyEvent in your module body you force the user of your module
381	to load the event module first.	676	to load the event module first.
382		677
383	Never call C<< ->wait >> on a condition variable unless you I<know> that	678	Never call C<< ->recv >> on a condition variable unless you I<know> that
384	the C<< ->broadcast >> method has been called on it already. This is	679	the C<< ->send >> method has been called on it already. This is
385	because it will stall the whole program, and the whole point of using	680	because it will stall the whole program, and the whole point of using
386	events is to stay interactive.	681	events is to stay interactive.
387		682
388	It is fine, however, to call C<< ->wait >> when the user of your module	683	It is fine, however, to call C<< ->recv >> when the user of your module
389	requests it (i.e. if you create a http request object ad have a method	684	requests it (i.e. if you create a http request object ad have a method
390	called C<results> that returns the results, it should call C<< ->wait >>	685	called C<results> that returns the results, it should call C<< ->recv >>
391	freely, as the user of your module knows what she is doing. always).	686	freely, as the user of your module knows what she is doing. always).
392		687
393	=head1 WHAT TO DO IN THE MAIN PROGRAM	688	=head1 WHAT TO DO IN THE MAIN PROGRAM
394		689
395	There will always be a single main program - the only place that should	690	There will always be a single main program - the only place that should
…		…
397		692
398	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	693	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
399	do anything special (it does not need to be event-based) and let AnyEvent	694	do anything special (it does not need to be event-based) and let AnyEvent
400	decide which implementation to chose if some module relies on it.	695	decide which implementation to chose if some module relies on it.
401		696
402	If the main program relies on a specific event model. For example, in	697	If the main program relies on a specific event model - for example, in
403	Gtk2 programs you have to rely on the Glib module. You should load the	698	Gtk2 programs you have to rely on the Glib module - you should load the
404	event module before loading AnyEvent or any module that uses it: generally	699	event module before loading AnyEvent or any module that uses it: generally
405	speaking, you should load it as early as possible. The reason is that	700	speaking, you should load it as early as possible. The reason is that
406	modules might create watchers when they are loaded, and AnyEvent will	701	modules might create watchers when they are loaded, and AnyEvent will
407	decide on the event model to use as soon as it creates watchers, and it	702	decide on the event model to use as soon as it creates watchers, and it
408	might chose the wrong one unless you load the correct one yourself.	703	might chose the wrong one unless you load the correct one yourself.
409		704
410	You can chose to use a rather inefficient pure-perl implementation by	705	You can chose to use a pure-perl implementation by loading the
411	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	706	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
412	behaviour everywhere, but letting AnyEvent chose is generally better.	707	everywhere, but letting AnyEvent chose the model is generally better.
		708
		709	=head2 MAINLOOP EMULATION
		710
		711	Sometimes (often for short test scripts, or even standalone programs who
		712	only want to use AnyEvent), you do not want to run a specific event loop.
		713
		714	In that case, you can use a condition variable like this:
		715
		716	AnyEvent->condvar->recv;
		717
		718	This has the effect of entering the event loop and looping forever.
		719
		720	Note that usually your program has some exit condition, in which case
		721	it is better to use the "traditional" approach of storing a condition
		722	variable somewhere, waiting for it, and sending it when the program should
		723	exit cleanly.
		724
		725
		726	=head1 OTHER MODULES
		727
		728	The following is a non-exhaustive list of additional modules that use
		729	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		730	in the same program. Some of the modules come with AnyEvent, some are
		731	available via CPAN.
		732
		733	=over 4
		734
		735	=item L<AnyEvent::Util>
		736
		737	Contains various utility functions that replace often-used but blocking
		738	functions such as C<inet_aton> by event-/callback-based versions.
		739
		740	=item L<AnyEvent::Socket>
		741
		742	Provides various utility functions for (internet protocol) sockets,
		743	addresses and name resolution. Also functions to create non-blocking tcp
		744	connections or tcp servers, with IPv6 and SRV record support and more.
		745
		746	=item L<AnyEvent::Handle>
		747
		748	Provide read and write buffers, manages watchers for reads and writes,
		749	supports raw and formatted I/O, I/O queued and fully transparent and
		750	non-blocking SSL/TLS.
		751
		752	=item L<AnyEvent::DNS>
		753
		754	Provides rich asynchronous DNS resolver capabilities.
		755
		756	=item L<AnyEvent::HTTP>
		757
		758	A simple-to-use HTTP library that is capable of making a lot of concurrent
		759	HTTP requests.
		760
		761	=item L<AnyEvent::HTTPD>
		762
		763	Provides a simple web application server framework.
		764
		765	=item L<AnyEvent::FastPing>
		766
		767	The fastest ping in the west.
		768
		769	=item L<AnyEvent::DBI>
		770
		771	Executes L<DBI> requests asynchronously in a proxy process.
		772
		773	=item L<AnyEvent::AIO>
		774
		775	Truly asynchronous I/O, should be in the toolbox of every event
		776	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		777	together.
		778
		779	=item L<AnyEvent::BDB>
		780
		781	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		782	L<BDB> and AnyEvent together.
		783
		784	=item L<AnyEvent::GPSD>
		785
		786	A non-blocking interface to gpsd, a daemon delivering GPS information.
		787
		788	=item L<AnyEvent::IGS>
		789
		790	A non-blocking interface to the Internet Go Server protocol (used by
		791	L<App::IGS>).
		792
		793	=item L<Net::IRC3>
		794
		795	AnyEvent based IRC client module family.
		796
		797	=item L<Net::XMPP2>
		798
		799	AnyEvent based XMPP (Jabber protocol) module family.
		800
		801	=item L<Net::FCP>
		802
		803	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		804	of AnyEvent.
		805
		806	=item L<Event::ExecFlow>
		807
		808	High level API for event-based execution flow control.
		809
		810	=item L<Coro>
		811
		812	Has special support for AnyEvent via L<Coro::AnyEvent>.
		813
		814	=item L<IO::Lambda>
		815
		816	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		817
		818	=back
413		819
414	=cut	820	=cut
415		821
416	package AnyEvent;	822	package AnyEvent;
417		823
418	no warnings;	824	no warnings;
419	use strict;	825	use strict;
420		826
421	use Carp;	827	use Carp;
422		828
423	our $VERSION = '3.12';	829	our $VERSION = 4.2;
424	our $MODEL;	830	our $MODEL;
425		831
426	our $AUTOLOAD;	832	our $AUTOLOAD;
427	our @ISA;	833	our @ISA;
428		834
		835	our @REGISTRY;
		836
		837	our $WIN32;
		838
		839	BEGIN {
		840	my $win32 = ! ! ($^O =~ /mswin32/i);
		841	eval "sub WIN32(){ $win32 }";
		842	}
		843
429	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	844	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
430		845
431	our @REGISTRY;	846	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		847
		848	{
		849	my $idx;
		850	$PROTOCOL{$_} = ++$idx
		851	for reverse split /\s*,\s*/,
		852	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		853	}
432		854
433	my @models = (	855	my @models = (
434	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
435	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
436	[EV:: => AnyEvent::Impl::EV::],	856	[EV:: => AnyEvent::Impl::EV::],
437	[Event:: => AnyEvent::Impl::Event::],	857	[Event:: => AnyEvent::Impl::Event::],
438	[Glib:: => AnyEvent::Impl::Glib::],
439	[Tk:: => AnyEvent::Impl::Tk::],
440	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	858	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		859	# everything below here will not be autoprobed
		860	# as the pureperl backend should work everywhere
		861	# and is usually faster
		862	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		863	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		864	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		865	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		866	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		867	[Wx:: => AnyEvent::Impl::POE::],
		868	[Prima:: => AnyEvent::Impl::POE::],
441	);	869	);
442		870
443	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	871	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);
		872
		873	our @post_detect;
		874
		875	sub post_detect(&) {
		876	my ($cb) = @_;
		877
		878	if ($MODEL) {
		879	$cb->();
		880
		881	1
		882	} else {
		883	push @post_detect, $cb;
		884
		885	defined wantarray
		886	? bless \$cb, "AnyEvent::Util::PostDetect"
		887	: ()
		888	}
		889	}
		890
		891	sub AnyEvent::Util::PostDetect::DESTROY {
		892	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		893	}
444		894
445	sub detect() {	895	sub detect() {
446	unless ($MODEL) {	896	unless ($MODEL) {
447	no strict 'refs';	897	no strict 'refs';
		898	local $SIG{__DIE__};
		899
		900	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		901	my $model = "AnyEvent::Impl::$1";
		902	if (eval "require $model") {
		903	$MODEL = $model;
		904	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		905	} else {
		906	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
		907	}
		908	}
448		909
449	# check for already loaded models	910	# check for already loaded models
		911	unless ($MODEL) {
450	for (@REGISTRY, @models) {	912	for (@REGISTRY, @models) {
451	my ($package, $model) = @$_;	913	my ($package, $model) = @$_;
452	if (${"$package\::VERSION"} > 0) {	914	if (${"$package\::VERSION"} > 0) {
453	if (eval "require $model") {	915	if (eval "require $model") {
454	$MODEL = $model;	916	$MODEL = $model;
455	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	917	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
456	last;	918	last;
		919	}
457	}	920	}
458	}	921	}
459	}
460		922
461	unless ($MODEL) {	923	unless ($MODEL) {
462	# try to load a model	924	# try to load a model
463		925
464	for (@REGISTRY, @models) {	926	for (@REGISTRY, @models) {
465	my ($package, $model) = @$_;	927	my ($package, $model) = @$_;
466	if (eval "require $package"	928	if (eval "require $package"
467	and ${"$package\::VERSION"} > 0	929	and ${"$package\::VERSION"} > 0
468	and eval "require $model") {	930	and eval "require $model") {
469	$MODEL = $model;	931	$MODEL = $model;
470	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	932	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
471	last;	933	last;
		934	}
472	}	935	}
		936
		937	$MODEL
		938	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
473	}	939	}
474
475	$MODEL
476	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), Glib or Tk.";
477	}	940	}
478		941
479	unshift @ISA, $MODEL;	942	unshift @ISA, $MODEL;
480	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	943	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		944
		945	(shift @post_detect)->() while @post_detect;
481	}	946	}
482		947
483	$MODEL	948	$MODEL
484	}	949	}
485		950
…		…
495	$class->$func (@_);	960	$class->$func (@_);
496	}	961	}
497		962
498	package AnyEvent::Base;	963	package AnyEvent::Base;
499		964
		965	# default implementation for now and time
		966
		967	use Time::HiRes ();
		968
		969	sub time { Time::HiRes::time }
		970	sub now { Time::HiRes::time }
		971
500	# default implementation for ->condvar, ->wait, ->broadcast	972	# default implementation for ->condvar
501		973
502	sub condvar {	974	sub condvar {
503	bless \my $flag, "AnyEvent::Base::CondVar"	975	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
504	}
505
506	sub AnyEvent::Base::CondVar::broadcast {
507	${$_[0]}++;
508	}
509
510	sub AnyEvent::Base::CondVar::wait {
511	AnyEvent->one_event while !${$_[0]};
512	}	976	}
513		977
514	# default implementation for ->signal	978	# default implementation for ->signal
515		979
516	our %SIG_CB;	980	our %SIG_CB;
…		…
532	sub AnyEvent::Base::Signal::DESTROY {	996	sub AnyEvent::Base::Signal::DESTROY {
533	my ($signal, $cb) = @{$_[0]};	997	my ($signal, $cb) = @{$_[0]};
534		998
535	delete $SIG_CB{$signal}{$cb};	999	delete $SIG_CB{$signal}{$cb};
536		1000
537	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1001	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
538	}	1002	}
539		1003
540	# default implementation for ->child	1004	# default implementation for ->child
541		1005
542	our %PID_CB;	1006	our %PID_CB;
…		…
569	or Carp::croak "required option 'pid' is missing";	1033	or Carp::croak "required option 'pid' is missing";
570		1034
571	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1035	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
572		1036
573	unless ($WNOHANG) {	1037	unless ($WNOHANG) {
574	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1038	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
575	}	1039	}
576		1040
577	unless ($CHLD_W) {	1041	unless ($CHLD_W) {
578	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1042	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
579	# child could be a zombie already, so make at least one round	1043	# child could be a zombie already, so make at least one round
…		…
589	delete $PID_CB{$pid}{$cb};	1053	delete $PID_CB{$pid}{$cb};
590	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1054	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
591		1055
592	undef $CHLD_W unless keys %PID_CB;	1056	undef $CHLD_W unless keys %PID_CB;
593	}	1057	}
		1058
		1059	package AnyEvent::CondVar;
		1060
		1061	our @ISA = AnyEvent::CondVar::Base::;
		1062
		1063	package AnyEvent::CondVar::Base;
		1064
		1065	use overload
		1066	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1067	fallback => 1;
		1068
		1069	sub _send {
		1070	# nop
		1071	}
		1072
		1073	sub send {
		1074	my $cv = shift;
		1075	$cv->{_ae_sent} = [@_];
		1076	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1077	$cv->_send;
		1078	}
		1079
		1080	sub croak {
		1081	$_[0]{_ae_croak} = $_[1];
		1082	$_[0]->send;
		1083	}
		1084
		1085	sub ready {
		1086	$_[0]{_ae_sent}
		1087	}
		1088
		1089	sub _wait {
		1090	AnyEvent->one_event while !$_[0]{_ae_sent};
		1091	}
		1092
		1093	sub recv {
		1094	$_[0]->_wait;
		1095
		1096	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1097	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1098	}
		1099
		1100	sub cb {
		1101	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1102	$_[0]{_ae_cb}
		1103	}
		1104
		1105	sub begin {
		1106	++$_[0]{_ae_counter};
		1107	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1108	}
		1109
		1110	sub end {
		1111	return if --$_[0]{_ae_counter};
		1112	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1113	}
		1114
		1115	# undocumented/compatibility with pre-3.4
		1116	*broadcast = \&send;
		1117	*wait = \&_wait;
594		1118
595	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1119	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
596		1120
597	This is an advanced topic that you do not normally need to use AnyEvent in	1121	This is an advanced topic that you do not normally need to use AnyEvent in
598	a module. This section is only of use to event loop authors who want to	1122	a module. This section is only of use to event loop authors who want to
…		…
637		1161
638	=head1 ENVIRONMENT VARIABLES	1162	=head1 ENVIRONMENT VARIABLES
639		1163
640	The following environment variables are used by this module:	1164	The following environment variables are used by this module:
641		1165
642	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, cause AnyEvent to	1166	=over 4
643	report to STDERR which event model it chooses.	1167
		1168	=item C<PERL_ANYEVENT_VERBOSE>
		1169
		1170	By default, AnyEvent will be completely silent except in fatal
		1171	conditions. You can set this environment variable to make AnyEvent more
		1172	talkative.
		1173
		1174	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1175	conditions, such as not being able to load the event model specified by
		1176	C<PERL_ANYEVENT_MODEL>.
		1177
		1178	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1179	model it chooses.
		1180
		1181	=item C<PERL_ANYEVENT_MODEL>
		1182
		1183	This can be used to specify the event model to be used by AnyEvent, before
		1184	auto detection and -probing kicks in. It must be a string consisting
		1185	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1186	and the resulting module name is loaded and if the load was successful,
		1187	used as event model. If it fails to load AnyEvent will proceed with
		1188	auto detection and -probing.
		1189
		1190	This functionality might change in future versions.
		1191
		1192	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1193	could start your program like this:
		1194
		1195	PERL_ANYEVENT_MODEL=Perl perl ...
		1196
		1197	=item C<PERL_ANYEVENT_PROTOCOLS>
		1198
		1199	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1200	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1201	of auto probing).
		1202
		1203	Must be set to a comma-separated list of protocols or address families,
		1204	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1205	used, and preference will be given to protocols mentioned earlier in the
		1206	list.
		1207
		1208	This variable can effectively be used for denial-of-service attacks
		1209	against local programs (e.g. when setuid), although the impact is likely
		1210	small, as the program has to handle connection errors already-
		1211
		1212	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1213	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1214	- only support IPv4, never try to resolve or contact IPv6
		1215	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1216	IPv6, but prefer IPv6 over IPv4.
		1217
		1218	=item C<PERL_ANYEVENT_EDNS0>
		1219
		1220	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1221	for DNS. This extension is generally useful to reduce DNS traffic, but
		1222	some (broken) firewalls drop such DNS packets, which is why it is off by
		1223	default.
		1224
		1225	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1226	EDNS0 in its DNS requests.
		1227
		1228	=item C<PERL_ANYEVENT_MAX_FORKS>
		1229
		1230	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1231	will create in parallel.
		1232
		1233	=back
644		1234
645	=head1 EXAMPLE PROGRAM	1235	=head1 EXAMPLE PROGRAM
646		1236
647	The following program uses an IO watcher to read data from STDIN, a timer	1237	The following program uses an I/O watcher to read data from STDIN, a timer
648	to display a message once per second, and a condition variable to quit the	1238	to display a message once per second, and a condition variable to quit the
649	program when the user enters quit:	1239	program when the user enters quit:
650		1240
651	use AnyEvent;	1241	use AnyEvent;
652		1242
…		…
657	poll => 'r',	1247	poll => 'r',
658	cb => sub {	1248	cb => sub {
659	warn "io event <$_[0]>\n"; # will always output <r>	1249	warn "io event <$_[0]>\n"; # will always output <r>
660	chomp (my $input = <STDIN>); # read a line	1250	chomp (my $input = <STDIN>); # read a line
661	warn "read: $input\n"; # output what has been read	1251	warn "read: $input\n"; # output what has been read
662	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1252	$cv->send if $input =~ /^q/i; # quit program if /^q/i
663	},	1253	},
664	);	1254	);
665		1255
666	my $time_watcher; # can only be used once	1256	my $time_watcher; # can only be used once
667		1257
…		…
672	});	1262	});
673	}	1263	}
674		1264
675	new_timer; # create first timer	1265	new_timer; # create first timer
676		1266
677	$cv->wait; # wait until user enters /^q/i	1267	$cv->recv; # wait until user enters /^q/i
678		1268
679	=head1 REAL-WORLD EXAMPLE	1269	=head1 REAL-WORLD EXAMPLE
680		1270
681	Consider the L<Net::FCP> module. It features (among others) the following	1271	Consider the L<Net::FCP> module. It features (among others) the following
682	API calls, which are to freenet what HTTP GET requests are to http:	1272	API calls, which are to freenet what HTTP GET requests are to http:
…		…
732	syswrite $txn->{fh}, $txn->{request}	1322	syswrite $txn->{fh}, $txn->{request}
733	or die "connection or write error";	1323	or die "connection or write error";
734	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1324	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
735		1325
736	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1326	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
737	result and signals any possible waiters that the request ahs finished:	1327	result and signals any possible waiters that the request has finished:
738		1328
739	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1329	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
740		1330
741	if (end-of-file or data complete) {	1331	if (end-of-file or data complete) {
742	$txn->{result} = $txn->{buf};	1332	$txn->{result} = $txn->{buf};
743	$txn->{finished}->broadcast;	1333	$txn->{finished}->send;
744	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1334	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
745	}	1335	}
746		1336
747	The C<result> method, finally, just waits for the finished signal (if the	1337	The C<result> method, finally, just waits for the finished signal (if the
748	request was already finished, it doesn't wait, of course, and returns the	1338	request was already finished, it doesn't wait, of course, and returns the
749	data:	1339	data:
750		1340
751	$txn->{finished}->wait;	1341	$txn->{finished}->recv;
752	return $txn->{result};	1342	return $txn->{result};
753		1343
754	The actual code goes further and collects all errors (C<die>s, exceptions)	1344	The actual code goes further and collects all errors (C<die>s, exceptions)
755	that occured during request processing. The C<result> method detects	1345	that occurred during request processing. The C<result> method detects
756	whether an exception as thrown (it is stored inside the $txn object)	1346	whether an exception as thrown (it is stored inside the $txn object)
757	and just throws the exception, which means connection errors and other	1347	and just throws the exception, which means connection errors and other
758	problems get reported tot he code that tries to use the result, not in a	1348	problems get reported tot he code that tries to use the result, not in a
759	random callback.	1349	random callback.
760		1350
…		…
791		1381
792	my $quit = AnyEvent->condvar;	1382	my $quit = AnyEvent->condvar;
793		1383
794	$fcp->txn_client_get ($url)->cb (sub {	1384	$fcp->txn_client_get ($url)->cb (sub {
795	...	1385	...
796	$quit->broadcast;	1386	$quit->send;
797	});	1387	});
798		1388
799	$quit->wait;	1389	$quit->recv;
		1390
		1391
		1392	=head1 BENCHMARKS
		1393
		1394	To give you an idea of the performance and overheads that AnyEvent adds
		1395	over the event loops themselves and to give you an impression of the speed
		1396	of various event loops I prepared some benchmarks.
		1397
		1398	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1399
		1400	Here is a benchmark of various supported event models used natively and
		1401	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1402	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1403	which it is), lets them fire exactly once and destroys them again.
		1404
		1405	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1406	distribution.
		1407
		1408	=head3 Explanation of the columns
		1409
		1410	I<watcher> is the number of event watchers created/destroyed. Since
		1411	different event models feature vastly different performances, each event
		1412	loop was given a number of watchers so that overall runtime is acceptable
		1413	and similar between tested event loop (and keep them from crashing): Glib
		1414	would probably take thousands of years if asked to process the same number
		1415	of watchers as EV in this benchmark.
		1416
		1417	I<bytes> is the number of bytes (as measured by the resident set size,
		1418	RSS) consumed by each watcher. This method of measuring captures both C
		1419	and Perl-based overheads.
		1420
		1421	I<create> is the time, in microseconds (millionths of seconds), that it
		1422	takes to create a single watcher. The callback is a closure shared between
		1423	all watchers, to avoid adding memory overhead. That means closure creation
		1424	and memory usage is not included in the figures.
		1425
		1426	I<invoke> is the time, in microseconds, used to invoke a simple
		1427	callback. The callback simply counts down a Perl variable and after it was
		1428	invoked "watcher" times, it would C<< ->send >> a condvar once to
		1429	signal the end of this phase.
		1430
		1431	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1432	watcher.
		1433
		1434	=head3 Results
		1435
		1436	name watchers bytes create invoke destroy comment
		1437	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		1438	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		1439	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		1440	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		1441	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		1442	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		1443	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		1444	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		1445	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		1446	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		1447
		1448	=head3 Discussion
		1449
		1450	The benchmark does I<not> measure scalability of the event loop very
		1451	well. For example, a select-based event loop (such as the pure perl one)
		1452	can never compete with an event loop that uses epoll when the number of
		1453	file descriptors grows high. In this benchmark, all events become ready at
		1454	the same time, so select/poll-based implementations get an unnatural speed
		1455	boost.
		1456
		1457	Also, note that the number of watchers usually has a nonlinear effect on
		1458	overall speed, that is, creating twice as many watchers doesn't take twice
		1459	the time - usually it takes longer. This puts event loops tested with a
		1460	higher number of watchers at a disadvantage.
		1461
		1462	To put the range of results into perspective, consider that on the
		1463	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1464	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1465	cycles with POE.
		1466
		1467	C<EV> is the sole leader regarding speed and memory use, which are both
		1468	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1469	far less memory than any other event loop and is still faster than Event
		1470	natively.
		1471
		1472	The pure perl implementation is hit in a few sweet spots (both the
		1473	constant timeout and the use of a single fd hit optimisations in the perl
		1474	interpreter and the backend itself). Nevertheless this shows that it
		1475	adds very little overhead in itself. Like any select-based backend its
		1476	performance becomes really bad with lots of file descriptors (and few of
		1477	them active), of course, but this was not subject of this benchmark.
		1478
		1479	The C<Event> module has a relatively high setup and callback invocation
		1480	cost, but overall scores in on the third place.
		1481
		1482	C<Glib>'s memory usage is quite a bit higher, but it features a
		1483	faster callback invocation and overall ends up in the same class as
		1484	C<Event>. However, Glib scales extremely badly, doubling the number of
		1485	watchers increases the processing time by more than a factor of four,
		1486	making it completely unusable when using larger numbers of watchers
		1487	(note that only a single file descriptor was used in the benchmark, so
		1488	inefficiencies of C<poll> do not account for this).
		1489
		1490	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1491	more than 2000 watchers is a big setback, however, as correctness takes
		1492	precedence over speed. Nevertheless, its performance is surprising, as the
		1493	file descriptor is dup()ed for each watcher. This shows that the dup()
		1494	employed by some adaptors is not a big performance issue (it does incur a
		1495	hidden memory cost inside the kernel which is not reflected in the figures
		1496	above).
		1497
		1498	C<POE>, regardless of underlying event loop (whether using its pure perl
		1499	select-based backend or the Event module, the POE-EV backend couldn't
		1500	be tested because it wasn't working) shows abysmal performance and
		1501	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		1502	as EV watchers, and 10 times as much memory as Event (the high memory
		1503	requirements are caused by requiring a session for each watcher). Watcher
		1504	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1505	implementation.
		1506
		1507	The design of the POE adaptor class in AnyEvent can not really account
		1508	for the performance issues, though, as session creation overhead is
		1509	small compared to execution of the state machine, which is coded pretty
		1510	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1511	using multiple sessions is not a good approach, especially regarding
		1512	memory usage, even the author of POE could not come up with a faster
		1513	design).
		1514
		1515	=head3 Summary
		1516
		1517	=over 4
		1518
		1519	=item * Using EV through AnyEvent is faster than any other event loop
		1520	(even when used without AnyEvent), but most event loops have acceptable
		1521	performance with or without AnyEvent.
		1522
		1523	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1524	the actual event loop, only with extremely fast event loops such as EV
		1525	adds AnyEvent significant overhead.
		1526
		1527	=item * You should avoid POE like the plague if you want performance or
		1528	reasonable memory usage.
		1529
		1530	=back
		1531
		1532	=head2 BENCHMARKING THE LARGE SERVER CASE
		1533
		1534	This benchmark actually benchmarks the event loop itself. It works by
		1535	creating a number of "servers": each server consists of a socket pair, a
		1536	timeout watcher that gets reset on activity (but never fires), and an I/O
		1537	watcher waiting for input on one side of the socket. Each time the socket
		1538	watcher reads a byte it will write that byte to a random other "server".
		1539
		1540	The effect is that there will be a lot of I/O watchers, only part of which
		1541	are active at any one point (so there is a constant number of active
		1542	fds for each loop iteration, but which fds these are is random). The
		1543	timeout is reset each time something is read because that reflects how
		1544	most timeouts work (and puts extra pressure on the event loops).
		1545
		1546	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1547	(1%) are active. This mirrors the activity of large servers with many
		1548	connections, most of which are idle at any one point in time.
		1549
		1550	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1551	distribution.
		1552
		1553	=head3 Explanation of the columns
		1554
		1555	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1556	each server has a read and write socket end).
		1557
		1558	I<create> is the time it takes to create a socket pair (which is
		1559	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1560
		1561	I<request>, the most important value, is the time it takes to handle a
		1562	single "request", that is, reading the token from the pipe and forwarding
		1563	it to another server. This includes deleting the old timeout and creating
		1564	a new one that moves the timeout into the future.
		1565
		1566	=head3 Results
		1567
		1568	name sockets create request
		1569	EV 20000 69.01 11.16
		1570	Perl 20000 73.32 35.87
		1571	Event 20000 212.62 257.32
		1572	Glib 20000 651.16 1896.30
		1573	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1574
		1575	=head3 Discussion
		1576
		1577	This benchmark I<does> measure scalability and overall performance of the
		1578	particular event loop.
		1579
		1580	EV is again fastest. Since it is using epoll on my system, the setup time
		1581	is relatively high, though.
		1582
		1583	Perl surprisingly comes second. It is much faster than the C-based event
		1584	loops Event and Glib.
		1585
		1586	Event suffers from high setup time as well (look at its code and you will
		1587	understand why). Callback invocation also has a high overhead compared to
		1588	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1589	uses select or poll in basically all documented configurations.
		1590
		1591	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1592	clearly fails to perform with many filehandles or in busy servers.
		1593
		1594	POE is still completely out of the picture, taking over 1000 times as long
		1595	as EV, and over 100 times as long as the Perl implementation, even though
		1596	it uses a C-based event loop in this case.
		1597
		1598	=head3 Summary
		1599
		1600	=over 4
		1601
		1602	=item * The pure perl implementation performs extremely well.
		1603
		1604	=item * Avoid Glib or POE in large projects where performance matters.
		1605
		1606	=back
		1607
		1608	=head2 BENCHMARKING SMALL SERVERS
		1609
		1610	While event loops should scale (and select-based ones do not...) even to
		1611	large servers, most programs we (or I :) actually write have only a few
		1612	I/O watchers.
		1613
		1614	In this benchmark, I use the same benchmark program as in the large server
		1615	case, but it uses only eight "servers", of which three are active at any
		1616	one time. This should reflect performance for a small server relatively
		1617	well.
		1618
		1619	The columns are identical to the previous table.
		1620
		1621	=head3 Results
		1622
		1623	name sockets create request
		1624	EV 16 20.00 6.54
		1625	Perl 16 25.75 12.62
		1626	Event 16 81.27 35.86
		1627	Glib 16 32.63 15.48
		1628	POE 16 261.87 276.28 uses POE::Loop::Event
		1629
		1630	=head3 Discussion
		1631
		1632	The benchmark tries to test the performance of a typical small
		1633	server. While knowing how various event loops perform is interesting, keep
		1634	in mind that their overhead in this case is usually not as important, due
		1635	to the small absolute number of watchers (that is, you need efficiency and
		1636	speed most when you have lots of watchers, not when you only have a few of
		1637	them).
		1638
		1639	EV is again fastest.
		1640
		1641	Perl again comes second. It is noticeably faster than the C-based event
		1642	loops Event and Glib, although the difference is too small to really
		1643	matter.
		1644
		1645	POE also performs much better in this case, but is is still far behind the
		1646	others.
		1647
		1648	=head3 Summary
		1649
		1650	=over 4
		1651
		1652	=item * C-based event loops perform very well with small number of
		1653	watchers, as the management overhead dominates.
		1654
		1655	=back
		1656
		1657
		1658	=head1 FORK
		1659
		1660	Most event libraries are not fork-safe. The ones who are usually are
		1661	because they rely on inefficient but fork-safe C<select> or C<poll>
		1662	calls. Only L<EV> is fully fork-aware.
		1663
		1664	If you have to fork, you must either do so I<before> creating your first
		1665	watcher OR you must not use AnyEvent at all in the child.
		1666
		1667
		1668	=head1 SECURITY CONSIDERATIONS
		1669
		1670	AnyEvent can be forced to load any event model via
		1671	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		1672	execute arbitrary code or directly gain access, it can easily be used to
		1673	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		1674	will not be active when the program uses a different event model than
		1675	specified in the variable.
		1676
		1677	You can make AnyEvent completely ignore this variable by deleting it
		1678	before the first watcher gets created, e.g. with a C<BEGIN> block:
		1679
		1680	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1681
		1682	use AnyEvent;
		1683
		1684	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1685	be used to probe what backend is used and gain other information (which is
		1686	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
		1687
		1688
		1689	=head1 BUGS
		1690
		1691	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		1692	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		1693	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		1694	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as
		1695	pronounced).
		1696
800		1697
801	=head1 SEE ALSO	1698	=head1 SEE ALSO
802		1699
803	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1700	Utility functions: L<AnyEvent::Util>.
804	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>.
805		1701
806	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1702	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		1703	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
		1704
807	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>,	1705	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
808	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>.	1706	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		1707	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		1708	L<AnyEvent::Impl::POE>.
809		1709
		1710	Non-blocking file handles, sockets, TCP clients and
		1711	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1712
		1713	Asynchronous DNS: L<AnyEvent::DNS>.
		1714
		1715	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1716
810	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1717	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
		1718
811		1719
812	=head1 AUTHOR	1720	=head1 AUTHOR
813		1721
814	Marc Lehmann <schmorp@schmorp.de>	1722	Marc Lehmann <schmorp@schmorp.de>
815	http://home.schmorp.de/	1723	http://home.schmorp.de/
816		1724
817	=cut	1725	=cut
818		1726
819	1	1727	1
820		1728

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