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1	NAME	1	NAME
2	AnyEvent - provide framework for multiple event loops	2	AnyEvent - the DBI of event loop programming
3		3
4	EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported	4	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
5	event loops.	5	Qt, FLTK and POE are various supported event loops/environments.
6		6
7	SYNOPSIS	7	SYNOPSIS
8	use AnyEvent;	8	use AnyEvent;
9		9
		10	# if you prefer function calls, look at the AE manpage for
		11	# an alternative API.
		12
10	# file descriptor readable	13	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });	14	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
12		15
13	# one-shot or repeating timers	16	# one-shot or repeating timers
14	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });	17	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
15	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...	18	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
16		19
17	print AnyEvent->now; # prints current event loop time	20	print AnyEvent->now; # prints current event loop time
18	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.	21	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
19		22
20	# POSIX signal	23	# POSIX signal
…		…
37		40
38	INTRODUCTION/TUTORIAL	41	INTRODUCTION/TUTORIAL
39	This manpage is mainly a reference manual. If you are interested in a	42	This manpage is mainly a reference manual. If you are interested in a
40	tutorial or some gentle introduction, have a look at the AnyEvent::Intro	43	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
41	manpage.	44	manpage.
		45
		46	SUPPORT
		47	An FAQ document is available as AnyEvent::FAQ.
		48
		49	There also is a mailinglist for discussing all things AnyEvent, and an
		50	IRC channel, too.
		51
		52	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
		53	Repository, at <http://anyevent.schmorp.de>, for more info.
42		54
43	WHY YOU SHOULD USE THIS MODULE (OR NOT)	55	WHY YOU SHOULD USE THIS MODULE (OR NOT)
44	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
45	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
46		58
…		…
61	module users into the same thing by forcing them to use the same event	73	module users into the same thing by forcing them to use the same event
62	model you use.	74	model you use.
63		75
64	For modules like POE or IO::Async (which is a total misnomer as it is	76	For modules like POE or IO::Async (which is a total misnomer as it is
65	actually doing all I/O *synchronously*...), using them in your module is	77	actually doing all I/O *synchronously*...), using them in your module is
66	like joining a cult: After you joined, you are dependent on them and you	78	like joining a cult: After you join, you are dependent on them and you
67	cannot use anything else, as they are simply incompatible to everything	79	cannot use anything else, as they are simply incompatible to everything
68	that isn't them. What's worse, all the potential users of your module	80	that isn't them. What's worse, all the potential users of your module
69	are *also* forced to use the same event loop you use.	81	are *also* forced to use the same event loop you use.
70		82
71	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
72	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
73	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your	85	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
74	module uses one of those, every user of your module has to use it, too.	86	uses one of those, every user of your module has to use it, too. But if
75	But if your module uses AnyEvent, it works transparently with all event	87	your module uses AnyEvent, it works transparently with all event models
76	models it supports (including stuff like IO::Async, as long as those use	88	it supports (including stuff like IO::Async, as long as those use one of
77	one of the supported event loops. It is trivial to add new event loops	89	the supported event loops. It is easy to add new event loops to
78	to AnyEvent, too, so it is future-proof).	90	AnyEvent, too, so it is future-proof).
79		91
80	In addition to being free of having to use *the one and only true event	92	In addition to being free of having to use *the one and only true event
81	model*, AnyEvent also is free of bloat and policy: with POE or similar	93	model*, AnyEvent also is free of bloat and policy: with POE or similar
82	modules, you get an enormous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
83	follow. AnyEvent, on the other hand, is lean and up to the point, by	95	follow. AnyEvent, on the other hand, is lean and to the point, by only
84	only offering the functionality that is necessary, in as thin as a	96	offering the functionality that is necessary, in as thin as a wrapper as
85	wrapper as technically possible.	97	technically possible.
86		98
87	Of course, AnyEvent comes with a big (and fully optional!) toolbox of	99	Of course, AnyEvent comes with a big (and fully optional!) toolbox of
88	useful functionality, such as an asynchronous DNS resolver, 100%	100	useful functionality, such as an asynchronous DNS resolver, 100%
89	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms	101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
90	such as Windows) and lots of real-world knowledge and workarounds for	102	such as Windows) and lots of real-world knowledge and workarounds for
…		…
93	Now, if you *do want* lots of policy (this can arguably be somewhat	105	Now, if you *do want* lots of policy (this can arguably be somewhat
94	useful) and you want to force your users to use the one and only event	106	useful) and you want to force your users to use the one and only event
95	model, you should *not* use this module.	107	model, you should *not* use this module.
96		108
97	DESCRIPTION	109	DESCRIPTION
98	AnyEvent provides an identical interface to multiple event loops. This	110	AnyEvent provides a uniform interface to various event loops. This
99	allows module authors to utilise an event loop without forcing module	111	allows module authors to use event loop functionality without forcing
100	users to use the same event loop (as only a single event loop can	112	module users to use a specific event loop implementation (since more
101	coexist peacefully at any one time).	113	than one event loop cannot coexist peacefully).
102		114
103	The interface itself is vaguely similar, but not identical to the Event	115	The interface itself is vaguely similar, but not identical to the Event
104	module.	116	module.
105		117
106	During the first call of any watcher-creation method, the module tries	118	During the first call of any watcher-creation method, the module tries
107	to detect the currently loaded event loop by probing whether one of the	119	to detect the currently loaded event loop by probing whether one of the
108	following modules is already loaded: EV, Event, Glib,	120	following modules is already loaded: EV, AnyEvent::Loop, Event, Glib,
109	AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is	121	Tk, Event::Lib, Qt, POE. The first one found is used. If none are
110	used. If none are found, the module tries to load these modules	122	detected, the module tries to load the first four modules in the order
111	(excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should	123	given; but note that if EV is not available, the pure-perl
112	always succeed) in the order given. The first one that can be	124	AnyEvent::Loop should always work, so the other two are not normally
113	successfully loaded will be used. If, after this, still none could be	125	tried.
114	found, AnyEvent will fall back to a pure-perl event loop, which is not
115	very efficient, but should work everywhere.
116		126
117	Because AnyEvent first checks for modules that are already loaded,	127	Because AnyEvent first checks for modules that are already loaded,
118	loading an event model explicitly before first using AnyEvent will	128	loading an event model explicitly before first using AnyEvent will
119	likely make that model the default. For example:	129	likely make that model the default. For example:
120		130
…		…
122	use AnyEvent;	132	use AnyEvent;
123		133
124	# .. AnyEvent will likely default to Tk	134	# .. AnyEvent will likely default to Tk
125		135
126	The *likely* means that, if any module loads another event model and	136	The *likely* means that, if any module loads another event model and
127	starts using it, all bets are off. Maybe you should tell their authors	137	starts using it, all bets are off - this case should be very rare
128	to use AnyEvent so their modules work together with others seamlessly...	138	though, as very few modules hardcode event loops without announcing this
		139	very loudly.
129		140
130	The pure-perl implementation of AnyEvent is called	141	The pure-perl implementation of AnyEvent is called "AnyEvent::Loop".
131	"AnyEvent::Impl::Perl". Like other event modules you can load it	142	Like other event modules you can load it explicitly and enjoy the high
132	explicitly and enjoy the high availability of that event loop :)	143	availability of that event loop :)
133		144
134	WATCHERS	145	WATCHERS
135	AnyEvent has the central concept of a *watcher*, which is an object that	146	AnyEvent has the central concept of a *watcher*, which is an object that
136	stores relevant data for each kind of event you are waiting for, such as	147	stores relevant data for each kind of event you are waiting for, such as
137	the callback to call, the file handle to watch, etc.	148	the callback to call, the file handle to watch, etc.
…		…
141	callback when the event occurs (of course, only when the event model is	152	callback when the event occurs (of course, only when the event model is
142	in control).	153	in control).
143		154
144	Note that callbacks must not permanently change global variables	155	Note that callbacks must not permanently change global variables
145	potentially in use by the event loop (such as $_ or $[) and that	156	potentially in use by the event loop (such as $_ or $[) and that
146	callbacks must not "die". The former is good programming practise in	157	callbacks must not "die". The former is good programming practice in
147	Perl and the latter stems from the fact that exception handling differs	158	Perl and the latter stems from the fact that exception handling differs
148	widely between event loops.	159	widely between event loops.
149		160
150	To disable the watcher you have to destroy it (e.g. by setting the	161	To disable a watcher you have to destroy it (e.g. by setting the
151	variable you store it in to "undef" or otherwise deleting all references	162	variable you store it in to "undef" or otherwise deleting all references
152	to it).	163	to it).
153		164
154	All watchers are created by calling a method on the "AnyEvent" class.	165	All watchers are created by calling a method on the "AnyEvent" class.
155		166
156	Many watchers either are used with "recursion" (repeating timers for	167	Many watchers either are used with "recursion" (repeating timers for
157	example), or need to refer to their watcher object in other ways.	168	example), or need to refer to their watcher object in other ways.
158		169
159	An any way to achieve that is this pattern:	170	One way to achieve that is this pattern:
160		171
161	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	172	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
162	# you can use $w here, for example to undef it	173	# you can use $w here, for example to undef it
163	undef $w;	174	undef $w;
164	});	175	});
…		…
166	Note that "my $w; $w =" combination. This is necessary because in Perl,	177	Note that "my $w; $w =" combination. This is necessary because in Perl,
167	my variables are only visible after the statement in which they are	178	my variables are only visible after the statement in which they are
168	declared.	179	declared.
169		180
170	I/O WATCHERS	181	I/O WATCHERS
		182	$w = AnyEvent->io (
		183	fh => <filehandle_or_fileno>,
		184	poll => <"r" or "w">,
		185	cb => <callback>,
		186	);
		187
171	You can create an I/O watcher by calling the "AnyEvent->io" method with	188	You can create an I/O watcher by calling the "AnyEvent->io" method with
172	the following mandatory key-value pairs as arguments:	189	the following mandatory key-value pairs as arguments:
173		190
174	"fh" is the Perl *file handle* (*not* file descriptor) to watch for	191	"fh" is the Perl *file handle* (or a naked file descriptor) to watch for
175	events (AnyEvent might or might not keep a reference to this file	192	events (AnyEvent might or might not keep a reference to this file
176	handle). Note that only file handles pointing to things for which	193	handle). Note that only file handles pointing to things for which
177	non-blocking operation makes sense are allowed. This includes sockets,	194	non-blocking operation makes sense are allowed. This includes sockets,
178	most character devices, pipes, fifos and so on, but not for example	195	most character devices, pipes, fifos and so on, but not for example
179	files or block devices.	196	files or block devices.
…		…
189		206
190	The I/O watcher might use the underlying file descriptor or a copy of	207	The I/O watcher might use the underlying file descriptor or a copy of
191	it. You must not close a file handle as long as any watcher is active on	208	it. You must not close a file handle as long as any watcher is active on
192	the underlying file descriptor.	209	the underlying file descriptor.
193		210
194	Some event loops issue spurious readyness notifications, so you should	211	Some event loops issue spurious readiness notifications, so you should
195	always use non-blocking calls when reading/writing from/to your file	212	always use non-blocking calls when reading/writing from/to your file
196	handles.	213	handles.
197		214
198	Example: wait for readability of STDIN, then read a line and disable the	215	Example: wait for readability of STDIN, then read a line and disable the
199	watcher.	216	watcher.
…		…
203	warn "read: $input\n";	220	warn "read: $input\n";
204	undef $w;	221	undef $w;
205	});	222	});
206		223
207	TIME WATCHERS	224	TIME WATCHERS
		225	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		226
		227	$w = AnyEvent->timer (
		228	after => <fractional_seconds>,
		229	interval => <fractional_seconds>,
		230	cb => <callback>,
		231	);
		232
208	You can create a time watcher by calling the "AnyEvent->timer" method	233	You can create a time watcher by calling the "AnyEvent->timer" method
209	with the following mandatory arguments:	234	with the following mandatory arguments:
210		235
211	"after" specifies after how many seconds (fractional values are	236	"after" specifies after how many seconds (fractional values are
212	supported) the callback should be invoked. "cb" is the callback to	237	supported) the callback should be invoked. "cb" is the callback to
…		…
214		239
215	Although the callback might get passed parameters, their value and	240	Although the callback might get passed parameters, their value and
216	presence is undefined and you cannot rely on them. Portable AnyEvent	241	presence is undefined and you cannot rely on them. Portable AnyEvent
217	callbacks cannot use arguments passed to time watcher callbacks.	242	callbacks cannot use arguments passed to time watcher callbacks.
218		243
219	The callback will normally be invoked once only. If you specify another	244	The callback will normally be invoked only once. If you specify another
220	parameter, "interval", as a strictly positive number (> 0), then the	245	parameter, "interval", as a strictly positive number (> 0), then the
221	callback will be invoked regularly at that interval (in fractional	246	callback will be invoked regularly at that interval (in fractional
222	seconds) after the first invocation. If "interval" is specified with a	247	seconds) after the first invocation. If "interval" is specified with a
223	false value, then it is treated as if it were missing.	248	false value, then it is treated as if it were not specified at all.
224		249
225	The callback will be rescheduled before invoking the callback, but no	250	The callback will be rescheduled before invoking the callback, but no
226	attempt is done to avoid timer drift in most backends, so the interval	251	attempt is made to avoid timer drift in most backends, so the interval
227	is only approximate.	252	is only approximate.
228		253
229	Example: fire an event after 7.7 seconds.	254	Example: fire an event after 7.7 seconds.
230		255
231	my $w = AnyEvent->timer (after => 7.7, cb => sub {	256	my $w = AnyEvent->timer (after => 7.7, cb => sub {
…		…
248		273
249	While most event loops expect timers to specified in a relative way,	274	While most event loops expect timers to specified in a relative way,
250	they use absolute time internally. This makes a difference when your	275	they use absolute time internally. This makes a difference when your
251	clock "jumps", for example, when ntp decides to set your clock backwards	276	clock "jumps", for example, when ntp decides to set your clock backwards
252	from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is	277	from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is
253	supposed to fire "after" a second might actually take six years to	278	supposed to fire "after a second" might actually take six years to
254	finally fire.	279	finally fire.
255		280
256	AnyEvent cannot compensate for this. The only event loop that is	281	AnyEvent cannot compensate for this. The only event loop that is
257	conscious about these issues is EV, which offers both relative	282	conscious of these issues is EV, which offers both relative (ev_timer,
258	(ev_timer, based on true relative time) and absolute (ev_periodic, based	283	based on true relative time) and absolute (ev_periodic, based on
259	on wallclock time) timers.	284	wallclock time) timers.
260		285
261	AnyEvent always prefers relative timers, if available, matching the	286	AnyEvent always prefers relative timers, if available, matching the
262	AnyEvent API.	287	AnyEvent API.
263		288
264	AnyEvent has two additional methods that return the "current time":	289	AnyEvent has two additional methods that return the "current time":
…		…
283	*In almost all cases (in all cases if you don't care), this is the	308	*In almost all cases (in all cases if you don't care), this is the
284	function to call when you want to know the current time.*	309	function to call when you want to know the current time.*
285		310
286	This function is also often faster then "AnyEvent->time", and thus	311	This function is also often faster then "AnyEvent->time", and thus
287	the preferred method if you want some timestamp (for example,	312	the preferred method if you want some timestamp (for example,
288	AnyEvent::Handle uses this to update it's activity timeouts).	313	AnyEvent::Handle uses this to update its activity timeouts).
289		314
290	The rest of this section is only of relevance if you try to be very	315	The rest of this section is only of relevance if you try to be very
291	exact with your timing, you can skip it without bad conscience.	316	exact with your timing; you can skip it without a bad conscience.
292		317
293	For a practical example of when these times differ, consider	318	For a practical example of when these times differ, consider
294	Event::Lib and EV and the following set-up:	319	Event::Lib and EV and the following set-up:
295		320
296	The event loop is running and has just invoked one of your callback	321	The event loop is running and has just invoked one of your callbacks
297	at time=500 (assume no other callbacks delay processing). In your	322	at time=500 (assume no other callbacks delay processing). In your
298	callback, you wait a second by executing "sleep 1" (blocking the	323	callback, you wait a second by executing "sleep 1" (blocking the
299	process for a second) and then (at time=501) you create a relative	324	process for a second) and then (at time=501) you create a relative
300	timer that fires after three seconds.	325	timer that fires after three seconds.
301		326
…		…
322	can get whatever behaviour you want with any event loop, by taking	347	can get whatever behaviour you want with any event loop, by taking
323	the difference between "AnyEvent->time" and "AnyEvent->now" into	348	the difference between "AnyEvent->time" and "AnyEvent->now" into
324	account.	349	account.
325		350
326	AnyEvent->now_update	351	AnyEvent->now_update
327	Some event loops (such as EV or AnyEvent::Impl::Perl) cache the	352	Some event loops (such as EV or AnyEvent::Loop) cache the current
328	current time for each loop iteration (see the discussion of	353	time for each loop iteration (see the discussion of AnyEvent->now,
329	AnyEvent->now, above).	354	above).
330		355
331	When a callback runs for a long time (or when the process sleeps),	356	When a callback runs for a long time (or when the process sleeps),
332	then this "current" time will differ substantially from the real	357	then this "current" time will differ substantially from the real
333	time, which might affect timers and time-outs.	358	time, which might affect timers and time-outs.
334		359
335	When this is the case, you can call this method, which will update	360	When this is the case, you can call this method, which will update
336	the event loop's idea of "current time".	361	the event loop's idea of "current time".
337		362
		363	A typical example would be a script in a web server (e.g.
		364	"mod_perl") - when mod_perl executes the script, then the event loop
		365	will have the wrong idea about the "current time" (being potentially
		366	far in the past, when the script ran the last time). In that case
		367	you should arrange a call to "AnyEvent->now_update" each time the
		368	web server process wakes up again (e.g. at the start of your script,
		369	or in a handler).
		370
338	Note that updating the time *might* cause some events to be handled.	371	Note that updating the time *might* cause some events to be handled.
339		372
340	SIGNAL WATCHERS	373	SIGNAL WATCHERS
		374	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		375
341	You can watch for signals using a signal watcher, "signal" is the signal	376	You can watch for signals using a signal watcher, "signal" is the signal
342	*name* in uppercase and without any "SIG" prefix, "cb" is the Perl	377	*name* in uppercase and without any "SIG" prefix, "cb" is the Perl
343	callback to be invoked whenever a signal occurs.	378	callback to be invoked whenever a signal occurs.
344		379
345	Although the callback might get passed parameters, their value and	380	Although the callback might get passed parameters, their value and
…		…
350	invocation, and callback invocation will be synchronous. Synchronous	385	invocation, and callback invocation will be synchronous. Synchronous
351	means that it might take a while until the signal gets handled by the	386	means that it might take a while until the signal gets handled by the
352	process, but it is guaranteed not to interrupt any other callbacks.	387	process, but it is guaranteed not to interrupt any other callbacks.
353		388
354	The main advantage of using these watchers is that you can share a	389	The main advantage of using these watchers is that you can share a
355	signal between multiple watchers.	390	signal between multiple watchers, and AnyEvent will ensure that signals
		391	will not interrupt your program at bad times.
356		392
357	This watcher might use %SIG, so programs overwriting those signals	393	This watcher might use %SIG (depending on the event loop used), so
358	directly will likely not work correctly.	394	programs overwriting those signals directly will likely not work
		395	correctly.
359		396
360	Example: exit on SIGINT	397	Example: exit on SIGINT
361		398
362	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	399	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
363		400
		401	Restart Behaviour
		402	While restart behaviour is up to the event loop implementation, most
		403	will not restart syscalls (that includes Async::Interrupt and AnyEvent's
		404	pure perl implementation).
		405
		406	Safe/Unsafe Signals
		407	Perl signals can be either "safe" (synchronous to opcode handling) or
		408	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		409	latter might corrupt your memory.
		410
		411	AnyEvent signal handlers are, in addition, synchronous to the event
		412	loop, i.e. they will not interrupt your running perl program but will
		413	only be called as part of the normal event handling (just like timer,
		414	I/O etc. callbacks, too).
		415
		416	Signal Races, Delays and Workarounds
		417	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		418	callbacks to signals in a generic way, which is a pity, as you cannot do
		419	race-free signal handling in perl, requiring C libraries for this.
		420	AnyEvent will try to do its best, which means in some cases, signals
		421	will be delayed. The maximum time a signal might be delayed is specified
		422	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
		423	can be changed only before the first signal watcher is created, and
		424	should be left alone otherwise. This variable determines how often
		425	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		426	will cause fewer spurious wake-ups, which is better for power and CPU
		427	saving.
		428
		429	All these problems can be avoided by installing the optional
		430	Async::Interrupt module, which works with most event loops. It will not
		431	work with inherently broken event loops such as Event or Event::Lib (and
		432	not with POE currently, as POE does its own workaround with one-second
		433	latency). For those, you just have to suffer the delays.
		434
364	CHILD PROCESS WATCHERS	435	CHILD PROCESS WATCHERS
		436	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		437
365	You can also watch on a child process exit and catch its exit status.	438	You can also watch for a child process exit and catch its exit status.
366		439
367	The child process is specified by the "pid" argument (if set to 0, it	440	The child process is specified by the "pid" argument (on some backends,
368	watches for any child process exit). The watcher will triggered only	441	using 0 watches for any child process exit, on others this will croak).
369	when the child process has finished and an exit status is available, not	442	The watcher will be triggered only when the child process has finished
370	on any trace events (stopped/continued).	443	and an exit status is available, not on any trace events
		444	(stopped/continued).
371		445
372	The callback will be called with the pid and exit status (as returned by	446	The callback will be called with the pid and exit status (as returned by
373	waitpid), so unlike other watcher types, you *can* rely on child watcher	447	waitpid), so unlike other watcher types, you *can* rely on child watcher
374	callback arguments.	448	callback arguments.
375		449
…		…
390	of when you start the watcher.	464	of when you start the watcher.
391		465
392	This means you cannot create a child watcher as the very first thing in	466	This means you cannot create a child watcher as the very first thing in
393	an AnyEvent program, you *have* to create at least one watcher before	467	an AnyEvent program, you *have* to create at least one watcher before
394	you "fork" the child (alternatively, you can call "AnyEvent::detect").	468	you "fork" the child (alternatively, you can call "AnyEvent::detect").
		469
		470	As most event loops do not support waiting for child events, they will
		471	be emulated by AnyEvent in most cases, in which case the latency and
		472	race problems mentioned in the description of signal watchers apply.
395		473
396	Example: fork a process and wait for it	474	Example: fork a process and wait for it
397		475
398	my $done = AnyEvent->condvar;	476	my $done = AnyEvent->condvar;
399		477
…		…
410		488
411	# do something else, then wait for process exit	489	# do something else, then wait for process exit
412	$done->recv;	490	$done->recv;
413		491
414	IDLE WATCHERS	492	IDLE WATCHERS
415	Sometimes there is a need to do something, but it is not so important to	493	$w = AnyEvent->idle (cb => <callback>);
416	do it instantly, but only when there is nothing better to do. This
417	"nothing better to do" is usually defined to be "no other events need
418	attention by the event loop".
419		494
420	Idle watchers ideally get invoked when the event loop has nothing better	495	This will repeatedly invoke the callback after the process becomes idle,
421	to do, just before it would block the process to wait for new events.	496	until either the watcher is destroyed or new events have been detected.
422	Instead of blocking, the idle watcher is invoked.
423		497
424	Most event loops unfortunately do not really support idle watchers (only	498	Idle watchers are useful when there is a need to do something, but it is
		499	not so important (or wise) to do it instantly. The callback will be
		500	invoked only when there is "nothing better to do", which is usually
		501	defined as "all outstanding events have been handled and no new events
		502	have been detected". That means that idle watchers ideally get invoked
		503	when the event loop has just polled for new events but none have been
		504	detected. Instead of blocking to wait for more events, the idle watchers
		505	will be invoked.
		506
		507	Unfortunately, most event loops do not really support idle watchers
425	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent	508	(only EV, Event and Glib do it in a usable fashion) - for the rest,
426	will simply call the callback "from time to time".	509	AnyEvent will simply call the callback "from time to time".
427		510
428	Example: read lines from STDIN, but only process them when the program	511	Example: read lines from STDIN, but only process them when the program
429	is otherwise idle:	512	is otherwise idle:
430		513
431	my @lines; # read data	514	my @lines; # read data
…		…
444	}	527	}
445	});	528	});
446	});	529	});
447		530
448	CONDITION VARIABLES	531	CONDITION VARIABLES
		532	$cv = AnyEvent->condvar;
		533
		534	$cv->send (<list>);
		535	my @res = $cv->recv;
		536
449	If you are familiar with some event loops you will know that all of them	537	If you are familiar with some event loops you will know that all of them
450	require you to run some blocking "loop", "run" or similar function that	538	require you to run some blocking "loop", "run" or similar function that
451	will actively watch for new events and call your callbacks.	539	will actively watch for new events and call your callbacks.
452		540
453	AnyEvent is different, it expects somebody else to run the event loop	541	AnyEvent is slightly different: it expects somebody else to run the
454	and will only block when necessary (usually when told by the user).	542	event loop and will only block when necessary (usually when told by the
		543	user).
455		544
456	The instrument to do that is called a "condition variable", so called	545	The tool to do that is called a "condition variable", so called because
457	because they represent a condition that must become true.	546	they represent a condition that must become true.
		547
		548	Now is probably a good time to look at the examples further below.
458		549
459	Condition variables can be created by calling the "AnyEvent->condvar"	550	Condition variables can be created by calling the "AnyEvent->condvar"
460	method, usually without arguments. The only argument pair allowed is	551	method, usually without arguments. The only argument pair allowed is
461
462	"cb", which specifies a callback to be called when the condition	552	"cb", which specifies a callback to be called when the condition
463	variable becomes true, with the condition variable as the first argument	553	variable becomes true, with the condition variable as the first argument
464	(but not the results).	554	(but not the results).
465		555
466	After creation, the condition variable is "false" until it becomes	556	After creation, the condition variable is "false" until it becomes
467	"true" by calling the "send" method (or calling the condition variable	557	"true" by calling the "send" method (or calling the condition variable
468	as if it were a callback, read about the caveats in the description for	558	as if it were a callback, read about the caveats in the description for
469	the "->send" method).	559	the "->send" method).
470		560
471	Condition variables are similar to callbacks, except that you can	561	Since condition variables are the most complex part of the AnyEvent API,
472	optionally wait for them. They can also be called merge points - points	562	here are some different mental models of what they are - pick the ones
473	in time where multiple outstanding events have been processed. And yet	563	you can connect to:
474	another way to call them is transactions - each condition variable can	564
475	be used to represent a transaction, which finishes at some point and	565	* Condition variables are like callbacks - you can call them (and pass
476	delivers a result.	566	them instead of callbacks). Unlike callbacks however, you can also
		567	wait for them to be called.
		568
		569	* Condition variables are signals - one side can emit or send them,
		570	the other side can wait for them, or install a handler that is
		571	called when the signal fires.
		572
		573	* Condition variables are like "Merge Points" - points in your program
		574	where you merge multiple independent results/control flows into one.
		575
		576	* Condition variables represent a transaction - functions that start
		577	some kind of transaction can return them, leaving the caller the
		578	choice between waiting in a blocking fashion, or setting a callback.
		579
		580	* Condition variables represent future values, or promises to deliver
		581	some result, long before the result is available.
477		582
478	Condition variables are very useful to signal that something has	583	Condition variables are very useful to signal that something has
479	finished, for example, if you write a module that does asynchronous http	584	finished, for example, if you write a module that does asynchronous http
480	requests, then a condition variable would be the ideal candidate to	585	requests, then a condition variable would be the ideal candidate to
481	signal the availability of results. The user can either act when the	586	signal the availability of results. The user can either act when the
…		…
494		599
495	Condition variables are represented by hash refs in perl, and the keys	600	Condition variables are represented by hash refs in perl, and the keys
496	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy	601	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy
497	(it is often useful to build your own transaction class on top of	602	(it is often useful to build your own transaction class on top of
498	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	603	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
499	it's "new" method in your own "new" method.	604	its "new" method in your own "new" method.
500		605
501	There are two "sides" to a condition variable - the "producer side"	606	There are two "sides" to a condition variable - the "producer side"
502	which eventually calls "-> send", and the "consumer side", which waits	607	which eventually calls "-> send", and the "consumer side", which waits
503	for the send to occur.	608	for the send to occur.
504		609
505	Example: wait for a timer.	610	Example: wait for a timer.
506		611
507	# wait till the result is ready	612	# condition: "wait till the timer is fired"
508	my $result_ready = AnyEvent->condvar;	613	my $timer_fired = AnyEvent->condvar;
509		614
510	# do something such as adding a timer	615	# create the timer - we could wait for, say
511	# or socket watcher the calls $result_ready->send	616	# a handle becomign ready, or even an
512	# when the "result" is ready.	617	# AnyEvent::HTTP request to finish, but
513	# in this case, we simply use a timer:	618	# in this case, we simply use a timer:
514	my $w = AnyEvent->timer (	619	my $w = AnyEvent->timer (
515	after => 1,	620	after => 1,
516	cb => sub { $result_ready->send },	621	cb => sub { $timer_fired->send },
517	);	622	);
518		623
519	# this "blocks" (while handling events) till the callback	624	# this "blocks" (while handling events) till the callback
520	# calls send	625	# calls ->send
521	$result_ready->recv;	626	$timer_fired->recv;
522		627
523	Example: wait for a timer, but take advantage of the fact that condition	628	Example: wait for a timer, but take advantage of the fact that condition
524	variables are also code references.	629	variables are also callable directly.
525		630
526	my $done = AnyEvent->condvar;	631	my $done = AnyEvent->condvar;
527	my $delay = AnyEvent->timer (after => 5, cb => $done);	632	my $delay = AnyEvent->timer (after => 5, cb => $done);
528	$done->recv;	633	$done->recv;
529		634
…		…
535		640
536	...	641	...
537		642
538	my @info = $couchdb->info->recv;	643	my @info = $couchdb->info->recv;
539		644
540	And this is how you would just ste a callback to be called whenever the	645	And this is how you would just set a callback to be called whenever the
541	results are available:	646	results are available:
542		647
543	$couchdb->info->cb (sub {	648	$couchdb->info->cb (sub {
544	my @info = $_[0]->recv;	649	my @info = $_[0]->recv;
545	});	650	});
…		…
560		665
561	Any arguments passed to the "send" call will be returned by all	666	Any arguments passed to the "send" call will be returned by all
562	future "->recv" calls.	667	future "->recv" calls.
563		668
564	Condition variables are overloaded so one can call them directly (as	669	Condition variables are overloaded so one can call them directly (as
565	a code reference). Calling them directly is the same as calling	670	if they were a code reference). Calling them directly is the same as
566	"send". Note, however, that many C-based event loops do not handle	671	calling "send".
567	overloading, so as tempting as it may be, passing a condition
568	variable instead of a callback does not work. Both the pure perl and
569	EV loops support overloading, however, as well as all functions that
570	use perl to invoke a callback (as in AnyEvent::Socket and
571	AnyEvent::DNS for example).
572		672
573	$cv->croak ($error)	673	$cv->croak ($error)
574	Similar to send, but causes all call's to "->recv" to invoke	674	Similar to send, but causes all calls to "->recv" to invoke
575	"Carp::croak" with the given error message/object/scalar.	675	"Carp::croak" with the given error message/object/scalar.
576		676
577	This can be used to signal any errors to the condition variable	677	This can be used to signal any errors to the condition variable
578	user/consumer.	678	user/consumer. Doing it this way instead of calling "croak" directly
		679	delays the error detection, but has the overwhelming advantage that
		680	it diagnoses the error at the place where the result is expected,
		681	and not deep in some event callback with no connection to the actual
		682	code causing the problem.
579		683
580	$cv->begin ([group callback])	684	$cv->begin ([group callback])
581	$cv->end	685	$cv->end
582	These two methods can be used to combine many transactions/events	686	These two methods can be used to combine many transactions/events
583	into one. For example, a function that pings many hosts in parallel	687	into one. For example, a function that pings many hosts in parallel
584	might want to use a condition variable for the whole process.	688	might want to use a condition variable for the whole process.
585		689
586	Every call to "->begin" will increment a counter, and every call to	690	Every call to "->begin" will increment a counter, and every call to
587	"->end" will decrement it. If the counter reaches 0 in "->end", the	691	"->end" will decrement it. If the counter reaches 0 in "->end", the
588	(last) callback passed to "begin" will be executed. That callback is	692	(last) callback passed to "begin" will be executed, passing the
589	*supposed* to call "->send", but that is not required. If no	693	condvar as first argument. That callback is *supposed* to call
		694	"->send", but that is not required. If no group callback was set,
590	callback was set, "send" will be called without any arguments.	695	"send" will be called without any arguments.
591		696
592	You can think of "$cv->send" giving you an OR condition (one call	697	You can think of "$cv->send" giving you an OR condition (one call
593	sends), while "$cv->begin" and "$cv->end" giving you an AND	698	sends), while "$cv->begin" and "$cv->end" giving you an AND
594	condition (all "begin" calls must be "end"'ed before the condvar	699	condition (all "begin" calls must be "end"'ed before the condvar
595	sends).	700	sends).
…		…
618	there is one call to "begin", so the condvar waits for all calls to	723	there is one call to "begin", so the condvar waits for all calls to
619	"end" before sending.	724	"end" before sending.
620		725
621	The ping example mentioned above is slightly more complicated, as	726	The ping example mentioned above is slightly more complicated, as
622	the there are results to be passwd back, and the number of tasks	727	the there are results to be passwd back, and the number of tasks
623	that are begung can potentially be zero:	728	that are begun can potentially be zero:
624		729
625	my $cv = AnyEvent->condvar;	730	my $cv = AnyEvent->condvar;
626		731
627	my %result;	732	my %result;
628	$cv->begin (sub { $cv->send (\%result) });	733	$cv->begin (sub { shift->send (\%result) });
629		734
630	for my $host (@list_of_hosts) {	735	for my $host (@list_of_hosts) {
631	$cv->begin;	736	$cv->begin;
632	ping_host_then_call_callback $host, sub {	737	ping_host_then_call_callback $host, sub {
633	$result{$host} = ...;	738	$result{$host} = ...;
…		…
649	callback to be called once the counter reaches 0, and second, it	754	callback to be called once the counter reaches 0, and second, it
650	ensures that "send" is called even when "no" hosts are being pinged	755	ensures that "send" is called even when "no" hosts are being pinged
651	(the loop doesn't execute once).	756	(the loop doesn't execute once).
652		757
653	This is the general pattern when you "fan out" into multiple (but	758	This is the general pattern when you "fan out" into multiple (but
654	potentially none) subrequests: use an outer "begin"/"end" pair to	759	potentially zero) subrequests: use an outer "begin"/"end" pair to
655	set the callback and ensure "end" is called at least once, and then,	760	set the callback and ensure "end" is called at least once, and then,
656	for each subrequest you start, call "begin" and for each subrequest	761	for each subrequest you start, call "begin" and for each subrequest
657	you finish, call "end".	762	you finish, call "end".
658		763
659	METHODS FOR CONSUMERS	764	METHODS FOR CONSUMERS
660	These methods should only be used by the consuming side, i.e. the code	765	These methods should only be used by the consuming side, i.e. the code
661	awaits the condition.	766	awaits the condition.
662		767
663	$cv->recv	768	$cv->recv
664	Wait (blocking if necessary) until the "->send" or "->croak" methods	769	Wait (blocking if necessary) until the "->send" or "->croak" methods
665	have been called on c<$cv>, while servicing other watchers normally.	770	have been called on $cv, while servicing other watchers normally.
666		771
667	You can only wait once on a condition - additional calls are valid	772	You can only wait once on a condition - additional calls are valid
668	but will return immediately.	773	but will return immediately.
669		774
670	If an error condition has been set by calling "->croak", then this	775	If an error condition has been set by calling "->croak", then this
671	function will call "croak".	776	function will call "croak".
672		777
673	In list context, all parameters passed to "send" will be returned,	778	In list context, all parameters passed to "send" will be returned,
674	in scalar context only the first one will be returned.	779	in scalar context only the first one will be returned.
675		780
		781	Note that doing a blocking wait in a callback is not supported by
		782	any event loop, that is, recursive invocation of a blocking "->recv"
		783	is not allowed, and the "recv" call will "croak" if such a condition
		784	is detected. This condition can be slightly loosened by using
		785	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		786	thread that doesn't run the event loop itself.
		787
676	Not all event models support a blocking wait - some die in that case	788	Not all event models support a blocking wait - some die in that case
677	(programs might want to do that to stay interactive), so *if you are	789	(programs might want to do that to stay interactive), so *if you are
678	using this from a module, never require a blocking wait*, but let	790	using this from a module, never require a blocking wait*. Instead,
679	the caller decide whether the call will block or not (for example,	791	let the caller decide whether the call will block or not (for
680	by coupling condition variables with some kind of request results	792	example, by coupling condition variables with some kind of request
681	and supporting callbacks so the caller knows that getting the result	793	results and supporting callbacks so the caller knows that getting
682	will not block, while still supporting blocking waits if the caller	794	the result will not block, while still supporting blocking waits if
683	so desires).	795	the caller so desires).
684		796
685	Another reason *never* to "->recv" in a module is that you cannot
686	sensibly have two "->recv"'s in parallel, as that would require
687	multiple interpreters or coroutines/threads, none of which
688	"AnyEvent" can supply.
689
690	The Coro module, however, *can* and *does* supply coroutines and, in
691	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
692	versions and also integrates coroutines into AnyEvent, making
693	blocking "->recv" calls perfectly safe as long as they are done from
694	another coroutine (one that doesn't run the event loop).
695
696	You can ensure that "-recv" never blocks by setting a callback and	797	You can ensure that "->recv" never blocks by setting a callback and
697	only calling "->recv" from within that callback (or at a later	798	only calling "->recv" from within that callback (or at a later
698	time). This will work even when the event loop does not support	799	time). This will work even when the event loop does not support
699	blocking waits otherwise.	800	blocking waits otherwise.
700		801
701	$bool = $cv->ready	802	$bool = $cv->ready
…		…
706	This is a mutator function that returns the callback set and	807	This is a mutator function that returns the callback set and
707	optionally replaces it before doing so.	808	optionally replaces it before doing so.
708		809
709	The callback will be called when the condition becomes "true", i.e.	810	The callback will be called when the condition becomes "true", i.e.
710	when "send" or "croak" are called, with the only argument being the	811	when "send" or "croak" are called, with the only argument being the
711	condition variable itself. Calling "recv" inside the callback or at	812	condition variable itself. If the condition is already true, the
		813	callback is called immediately when it is set. Calling "recv" inside
712	any later time is guaranteed not to block.	814	the callback or at any later time is guaranteed not to block.
		815
		816	SUPPORTED EVENT LOOPS/BACKENDS
		817	The available backend classes are (every class has its own manpage):
		818
		819	Backends that are autoprobed when no other event loop can be found.
		820	EV is the preferred backend when no other event loop seems to be in
		821	use. If EV is not installed, then AnyEvent will fall back to its own
		822	pure-perl implementation, which is available everywhere as it comes
		823	with AnyEvent itself.
		824
		825	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		826	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		827
		828	Backends that are transparently being picked up when they are used.
		829	These will be used if they are already loaded when the first watcher
		830	is created, in which case it is assumed that the application is
		831	using them. This means that AnyEvent will automatically pick the
		832	right backend when the main program loads an event module before
		833	anything starts to create watchers. Nothing special needs to be done
		834	by the main program.
		835
		836	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		837	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		838	AnyEvent::Impl::Tk based on Tk, very broken.
		839	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		840	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		841	AnyEvent::Impl::Irssi used when running within irssi.
		842	AnyEvent::Impl::IOAsync based on IO::Async.
		843	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		844	AnyEvent::Impl::FLTK2 based on FLTK (fltk 2 binding).
		845
		846	Backends with special needs.
		847	Qt requires the Qt::Application to be instantiated first, but will
		848	otherwise be picked up automatically. As long as the main program
		849	instantiates the application before any AnyEvent watchers are
		850	created, everything should just work.
		851
		852	AnyEvent::Impl::Qt based on Qt.
		853
		854	Event loops that are indirectly supported via other backends.
		855	Some event loops can be supported via other modules:
		856
		857	There is no direct support for WxWidgets (Wx) or Prima.
		858
		859	WxWidgets has no support for watching file handles. However, you can
		860	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		861	simply polls 20 times per second, which was considered to be too
		862	horrible to even consider for AnyEvent.
		863
		864	Prima is not supported as nobody seems to be using it, but it has a
		865	POE backend, so it can be supported through POE.
		866
		867	AnyEvent knows about both Prima and Wx, however, and will try to
		868	load POE when detecting them, in the hope that POE will pick them
		869	up, in which case everything will be automatic.
713		870
714	GLOBAL VARIABLES AND FUNCTIONS	871	GLOBAL VARIABLES AND FUNCTIONS
		872	These are not normally required to use AnyEvent, but can be useful to
		873	write AnyEvent extension modules.
		874
715	$AnyEvent::MODEL	875	$AnyEvent::MODEL
716	Contains "undef" until the first watcher is being created. Then it	876	Contains "undef" until the first watcher is being created, before
		877	the backend has been autodetected.
		878
717	contains the event model that is being used, which is the name of	879	Afterwards it contains the event model that is being used, which is
718	the Perl class implementing the model. This class is usually one of	880	the name of the Perl class implementing the model. This class is
719	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	881	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
720	case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*).	882	other class in the case AnyEvent has been extended at runtime (e.g.
721		883	in *rxvt-unicode* it will be "urxvt::anyevent").
722	The known classes so far are:
723
724	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
725	AnyEvent::Impl::Event based on Event, second best choice.
726	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
727	AnyEvent::Impl::Glib based on Glib, third-best choice.
728	AnyEvent::Impl::Tk based on Tk, very bad choice.
729	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
730	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
731	AnyEvent::Impl::POE based on POE, not generic enough for full support.
732
733	# warning, support for IO::Async is only partial, as it is too broken
734	# and limited toe ven support the AnyEvent API. See AnyEvent::Impl::Async.
735	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed (see its docs).
736
737	There is no support for WxWidgets, as WxWidgets has no support for
738	watching file handles. However, you can use WxWidgets through the
739	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
740	second, which was considered to be too horrible to even consider for
741	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
742	using it's adaptor.
743
744	AnyEvent knows about Prima and Wx and will try to use POE when
745	autodetecting them.
746		884
747	AnyEvent::detect	885	AnyEvent::detect
748	Returns $AnyEvent::MODEL, forcing autodetection of the event model	886	Returns $AnyEvent::MODEL, forcing autodetection of the event model
749	if necessary. You should only call this function right before you	887	if necessary. You should only call this function right before you
750	would have created an AnyEvent watcher anyway, that is, as late as	888	would have created an AnyEvent watcher anyway, that is, as late as
751	possible at runtime.	889	possible at runtime, and not e.g. during initialisation of your
		890	module.
		891
		892	The effect of calling this function is as if a watcher had been
		893	created (specifically, actions that happen "when the first watcher
		894	is created" happen when calling detetc as well).
		895
		896	If you need to do some initialisation before AnyEvent watchers are
		897	created, use "post_detect".
752		898
753	$guard = AnyEvent::post_detect { BLOCK }	899	$guard = AnyEvent::post_detect { BLOCK }
754	Arranges for the code block to be executed as soon as the event	900	Arranges for the code block to be executed as soon as the event
755	model is autodetected (or immediately if this has already happened).	901	model is autodetected (or immediately if that has already happened).
		902
		903	The block will be executed *after* the actual backend has been
		904	detected ($AnyEvent::MODEL is set), but *before* any watchers have
		905	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		906	other initialisations - see the sources of AnyEvent::Strict or
		907	AnyEvent::AIO to see how this is used.
		908
		909	The most common usage is to create some global watchers, without
		910	forcing event module detection too early, for example, AnyEvent::AIO
		911	creates and installs the global IO::AIO watcher in a "post_detect"
		912	block to avoid autodetecting the event module at load time.
756		913
757	If called in scalar or list context, then it creates and returns an	914	If called in scalar or list context, then it creates and returns an
758	object that automatically removes the callback again when it is	915	object that automatically removes the callback again when it is
		916	destroyed (or "undef" when the hook was immediately executed). See
759	destroyed. See Coro::BDB for a case where this is useful.	917	AnyEvent::AIO for a case where this is useful.
		918
		919	Example: Create a watcher for the IO::AIO module and store it in
		920	$WATCHER, but do so only do so after the event loop is initialised.
		921
		922	our WATCHER;
		923
		924	my $guard = AnyEvent::post_detect {
		925	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		926	};
		927
		928	# the ||= is important in case post_detect immediately runs the block,
		929	# as to not clobber the newly-created watcher. assigning both watcher and
		930	# post_detect guard to the same variable has the advantage of users being
		931	# able to just C<undef $WATCHER> if the watcher causes them grief.
		932
		933	$WATCHER ||= $guard;
760		934
761	@AnyEvent::post_detect	935	@AnyEvent::post_detect
762	If there are any code references in this array (you can "push" to it	936	If there are any code references in this array (you can "push" to it
763	before or after loading AnyEvent), then they will called directly	937	before or after loading AnyEvent), then they will be called directly
764	after the event loop has been chosen.	938	after the event loop has been chosen.
765		939
766	You should check $AnyEvent::MODEL before adding to this array,	940	You should check $AnyEvent::MODEL before adding to this array,
767	though: if it contains a true value then the event loop has already	941	though: if it is defined then the event loop has already been
768	been detected, and the array will be ignored.	942	detected, and the array will be ignored.
769		943
770	Best use "AnyEvent::post_detect { BLOCK }" instead.	944	Best use "AnyEvent::post_detect { BLOCK }" when your application
		945	allows it, as it takes care of these details.
		946
		947	This variable is mainly useful for modules that can do something
		948	useful when AnyEvent is used and thus want to know when it is
		949	initialised, but do not need to even load it by default. This array
		950	provides the means to hook into AnyEvent passively, without loading
		951	it.
		952
		953	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		954	together, you could put this into Coro (this is the actual code used
		955	by Coro to accomplish this):
		956
		957	if (defined $AnyEvent::MODEL) {
		958	# AnyEvent already initialised, so load Coro::AnyEvent
		959	require Coro::AnyEvent;
		960	} else {
		961	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		962	# as soon as it is
		963	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		964	}
		965
		966	AnyEvent::postpone { BLOCK }
		967	Arranges for the block to be executed as soon as possible, but not
		968	before the call itself returns. In practise, the block will be
		969	executed just before the event loop polls for new events, or shortly
		970	afterwards.
		971
		972	This function never returns anything (to make the "return postpone {
		973	... }" idiom more useful.
		974
		975	To understand the usefulness of this function, consider a function
		976	that asynchronously does something for you and returns some
		977	transaction object or guard to let you cancel the operation. For
		978	example, "AnyEvent::Socket::tcp_connect":
		979
		980	# start a conenction attempt unless one is active
		981	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		982	delete $self->{connect_guard};
		983	...
		984	};
		985
		986	Imagine that this function could instantly call the callback, for
		987	example, because it detects an obvious error such as a negative port
		988	number. Invoking the callback before the function returns causes
		989	problems however: the callback will be called and will try to delete
		990	the guard object. But since the function hasn't returned yet, there
		991	is nothing to delete. When the function eventually returns it will
		992	assign the guard object to "$self->{connect_guard}", where it will
		993	likely never be deleted, so the program thinks it is still trying to
		994	connect.
		995
		996	This is where "AnyEvent::postpone" should be used. Instead of
		997	calling the callback directly on error:
		998
		999	$cb->(undef), return # signal error to callback, BAD!
		1000	if $some_error_condition;
		1001
		1002	It should use "postpone":
		1003
		1004	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1005	if $some_error_condition;
		1006
		1007	AnyEvent::log $level, $msg[, @args]
		1008	Log the given $msg at the given $level.
		1009
		1010	Loads AnyEvent::Log on first use and calls "AnyEvent::Log::log" -
		1011	consequently, look at the AnyEvent::Log documentation for details.
		1012
		1013	If you want to sprinkle loads of logging calls around your code,
		1014	consider creating a logger callback with the "AnyEvent::Log::logger"
		1015	function.
771		1016
772	WHAT TO DO IN A MODULE	1017	WHAT TO DO IN A MODULE
773	As a module author, you should "use AnyEvent" and call AnyEvent methods	1018	As a module author, you should "use AnyEvent" and call AnyEvent methods
774	freely, but you should not load a specific event module or rely on it.	1019	freely, but you should not load a specific event module or rely on it.
775		1020
…		…
783	stall the whole program, and the whole point of using events is to stay	1028	stall the whole program, and the whole point of using events is to stay
784	interactive.	1029	interactive.
785		1030
786	It is fine, however, to call "->recv" when the user of your module	1031	It is fine, however, to call "->recv" when the user of your module
787	requests it (i.e. if you create a http request object ad have a method	1032	requests it (i.e. if you create a http request object ad have a method
788	called "results" that returns the results, it should call "->recv"	1033	called "results" that returns the results, it may call "->recv" freely,
789	freely, as the user of your module knows what she is doing. always).	1034	as the user of your module knows what she is doing. Always).
790		1035
791	WHAT TO DO IN THE MAIN PROGRAM	1036	WHAT TO DO IN THE MAIN PROGRAM
792	There will always be a single main program - the only place that should	1037	There will always be a single main program - the only place that should
793	dictate which event model to use.	1038	dictate which event model to use.
794		1039
795	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1040	If the program is not event-based, it need not do anything special, even
796	do anything special (it does not need to be event-based) and let	1041	when it depends on a module that uses an AnyEvent. If the program itself
797	AnyEvent decide which implementation to chose if some module relies on	1042	uses AnyEvent, but does not care which event loop is used, all it needs
798	it.	1043	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1044	available loop implementation.
799		1045
800	If the main program relies on a specific event model - for example, in	1046	If the main program relies on a specific event model - for example, in
801	Gtk2 programs you have to rely on the Glib module - you should load the	1047	Gtk2 programs you have to rely on the Glib module - you should load the
802	event module before loading AnyEvent or any module that uses it:	1048	event module before loading AnyEvent or any module that uses it:
803	generally speaking, you should load it as early as possible. The reason	1049	generally speaking, you should load it as early as possible. The reason
804	is that modules might create watchers when they are loaded, and AnyEvent	1050	is that modules might create watchers when they are loaded, and AnyEvent
805	will decide on the event model to use as soon as it creates watchers,	1051	will decide on the event model to use as soon as it creates watchers,
806	and it might chose the wrong one unless you load the correct one	1052	and it might choose the wrong one unless you load the correct one
807	yourself.	1053	yourself.
808		1054
809	You can chose to use a pure-perl implementation by loading the	1055	You can chose to use a pure-perl implementation by loading the
810	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1056	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
811	everywhere, but letting AnyEvent chose the model is generally better.	1057	but letting AnyEvent chose the model is generally better.
812		1058
813	MAINLOOP EMULATION	1059	MAINLOOP EMULATION
814	Sometimes (often for short test scripts, or even standalone programs who	1060	Sometimes (often for short test scripts, or even standalone programs who
815	only want to use AnyEvent), you do not want to run a specific event	1061	only want to use AnyEvent), you do not want to run a specific event
816	loop.	1062	loop.
…		…
826	variable somewhere, waiting for it, and sending it when the program	1072	variable somewhere, waiting for it, and sending it when the program
827	should exit cleanly.	1073	should exit cleanly.
828		1074
829	OTHER MODULES	1075	OTHER MODULES
830	The following is a non-exhaustive list of additional modules that use	1076	The following is a non-exhaustive list of additional modules that use
831	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1077	AnyEvent as a client and can therefore be mixed easily with other
832	in the same program. Some of the modules come with AnyEvent, some are	1078	AnyEvent modules and other event loops in the same program. Some of the
833	available via CPAN.	1079	modules come as part of AnyEvent, the others are available via CPAN (see
		1080	<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
		1081	non-exhaustive list), and the list is heavily biased towards modules of
		1082	the AnyEvent author himself :)
834		1083
835	AnyEvent::Util	1084	AnyEvent::Util
836	Contains various utility functions that replace often-used but	1085	Contains various utility functions that replace often-used blocking
837	blocking functions such as "inet_aton" by event-/callback-based	1086	functions such as "inet_aton" with event/callback-based versions.
838	versions.
839		1087
840	AnyEvent::Socket	1088	AnyEvent::Socket
841	Provides various utility functions for (internet protocol) sockets,	1089	Provides various utility functions for (internet protocol) sockets,
842	addresses and name resolution. Also functions to create non-blocking	1090	addresses and name resolution. Also functions to create non-blocking
843	tcp connections or tcp servers, with IPv6 and SRV record support and	1091	tcp connections or tcp servers, with IPv6 and SRV record support and
844	more.	1092	more.
845		1093
846	AnyEvent::Handle	1094	AnyEvent::Handle
847	Provide read and write buffers, manages watchers for reads and	1095	Provide read and write buffers, manages watchers for reads and
848	writes, supports raw and formatted I/O, I/O queued and fully	1096	writes, supports raw and formatted I/O, I/O queued and fully
849	transparent and non-blocking SSL/TLS.	1097	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
850		1098
851	AnyEvent::DNS	1099	AnyEvent::DNS
852	Provides rich asynchronous DNS resolver capabilities.	1100	Provides rich asynchronous DNS resolver capabilities.
853		1101
		1102	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
		1103	AnyEvent::IGS, AnyEvent::FCP
		1104	Implement event-based interfaces to the protocols of the same name
		1105	(for the curious, IGS is the International Go Server and FCP is the
		1106	Freenet Client Protocol).
		1107
		1108	AnyEvent::Handle::UDP
		1109	Here be danger!
		1110
		1111	As Pauli would put it, "Not only is it not right, it's not even
		1112	wrong!" - there are so many things wrong with AnyEvent::Handle::UDP,
		1113	most notably its use of a stream-based API with a protocol that
		1114	isn't streamable, that the only way to improve it is to delete it.
		1115
		1116	It features data corruption (but typically only under load) and
		1117	general confusion. On top, the author is not only clueless about UDP
		1118	but also fact-resistant - some gems of his understanding: "connect
		1119	doesn't work with UDP", "UDP packets are not IP packets", "UDP only
		1120	has datagrams, not packets", "I don't need to implement proper error
		1121	checking as UDP doesn't support error checking" and so on - he
		1122	doesn't even understand what's wrong with his module when it is
		1123	explained to him.
		1124
854	AnyEvent::HTTP	1125	AnyEvent::DBI
855	A simple-to-use HTTP library that is capable of making a lot of	1126	Executes DBI requests asynchronously in a proxy process for you,
856	concurrent HTTP requests.	1127	notifying you in an event-based way when the operation is finished.
		1128
		1129	AnyEvent::AIO
		1130	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1131	the toolbox of every event programmer. AnyEvent::AIO transparently
		1132	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1133	event-based file I/O, and much more.
857		1134
858	AnyEvent::HTTPD	1135	AnyEvent::HTTPD
859	Provides a simple web application server framework.	1136	A simple embedded webserver.
860		1137
861	AnyEvent::FastPing	1138	AnyEvent::FastPing
862	The fastest ping in the west.	1139	The fastest ping in the west.
863		1140
864	AnyEvent::DBI
865	Executes DBI requests asynchronously in a proxy process.
866
867	AnyEvent::AIO
868	Truly asynchronous I/O, should be in the toolbox of every event
869	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
870	together.
871
872	AnyEvent::BDB
873	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
874	fuses BDB and AnyEvent together.
875
876	AnyEvent::GPSD
877	A non-blocking interface to gpsd, a daemon delivering GPS
878	information.
879
880	AnyEvent::IGS
881	A non-blocking interface to the Internet Go Server protocol (used by
882	App::IGS).
883
884	AnyEvent::IRC
885	AnyEvent based IRC client module family (replacing the older
886	Net::IRC3).
887
888	Net::XMPP2
889	AnyEvent based XMPP (Jabber protocol) module family.
890
891	Net::FCP
892	AnyEvent-based implementation of the Freenet Client Protocol,
893	birthplace of AnyEvent.
894
895	Event::ExecFlow
896	High level API for event-based execution flow control.
897
898	Coro	1141	Coro
899	Has special support for AnyEvent via Coro::AnyEvent.	1142	Has special support for AnyEvent via Coro::AnyEvent.
900		1143
901	IO::Lambda	1144	SIMPLIFIED AE API
902	The lambda approach to I/O - don't ask, look there. Can use	1145	Starting with version 5.0, AnyEvent officially supports a second, much
903	AnyEvent.	1146	simpler, API that is designed to reduce the calling, typing and memory
		1147	overhead by using function call syntax and a fixed number of parameters.
		1148
		1149	See the AE manpage for details.
904		1150
905	ERROR AND EXCEPTION HANDLING	1151	ERROR AND EXCEPTION HANDLING
906	In general, AnyEvent does not do any error handling - it relies on the	1152	In general, AnyEvent does not do any error handling - it relies on the
907	caller to do that if required. The AnyEvent::Strict module (see also the	1153	caller to do that if required. The AnyEvent::Strict module (see also the
908	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1154	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
929	"PERL_ANYEVENT_VERBOSE"	1175	"PERL_ANYEVENT_VERBOSE"
930	By default, AnyEvent will be completely silent except in fatal	1176	By default, AnyEvent will be completely silent except in fatal
931	conditions. You can set this environment variable to make AnyEvent	1177	conditions. You can set this environment variable to make AnyEvent
932	more talkative.	1178	more talkative.
933		1179
934	When set to 1 or higher, causes AnyEvent to warn about unexpected	1180	When set to 5 or higher, causes AnyEvent to warn about unexpected
935	conditions, such as not being able to load the event model specified	1181	conditions, such as not being able to load the event model specified
936	by "PERL_ANYEVENT_MODEL".	1182	by "PERL_ANYEVENT_MODEL".
937		1183
938	When set to 2 or higher, cause AnyEvent to report to STDERR which	1184	When set to 7 or higher, cause AnyEvent to report to STDERR which
939	event model it chooses.	1185	event model it chooses.
		1186
		1187	When set to 8 or higher, then AnyEvent will report extra information
		1188	on which optional modules it loads and how it implements certain
		1189	features.
940		1190
941	"PERL_ANYEVENT_STRICT"	1191	"PERL_ANYEVENT_STRICT"
942	AnyEvent does not do much argument checking by default, as thorough	1192	AnyEvent does not do much argument checking by default, as thorough
943	argument checking is very costly. Setting this variable to a true	1193	argument checking is very costly. Setting this variable to a true
944	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1194	value will cause AnyEvent to load "AnyEvent::Strict" and then to
945	thoroughly check the arguments passed to most method calls. If it	1195	thoroughly check the arguments passed to most method calls. If it
946	finds any problems, it will croak.	1196	finds any problems, it will croak.
947		1197
948	In other words, enables "strict" mode.	1198	In other words, enables "strict" mode.
949		1199
950	Unlike "use strict", it is definitely recommended to keep it off in	1200	Unlike "use strict" (or its modern cousin, "use common::sense", it
951	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1201	is definitely recommended to keep it off in production. Keeping
		1202	"PERL_ANYEVENT_STRICT=1" in your environment while developing
952	while developing programs can be very useful, however.	1203	programs can be very useful, however.
		1204
		1205	"PERL_ANYEVENT_DEBUG_SHELL"
		1206	If this env variable is set, then its contents will be interpreted
		1207	by "AnyEvent::Socket::parse_hostport" (after replacing every
		1208	occurance of $$ by the process pid) and an "AnyEvent::Debug::shell"
		1209	is bound on that port. The shell object is saved in
		1210	$AnyEvent::Debug::SHELL.
		1211
		1212	This takes place when the first watcher is created.
		1213
		1214	For example, to bind a debug shell on a unix domain socket in
		1215	/tmp/debug<pid>.sock, you could use this:
		1216
		1217	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		1218
		1219	Note that creating sockets in /tmp is very unsafe on multiuser
		1220	systems.
		1221
		1222	"PERL_ANYEVENT_DEBUG_WRAP"
		1223	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1224	debugging purposes. See "AnyEvent::Debug::wrap" for details.
953		1225
954	"PERL_ANYEVENT_MODEL"	1226	"PERL_ANYEVENT_MODEL"
955	This can be used to specify the event model to be used by AnyEvent,	1227	This can be used to specify the event model to be used by AnyEvent,
956	before auto detection and -probing kicks in. It must be a string	1228	before auto detection and -probing kicks in.
957	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1229
958	gets prepended and the resulting module name is loaded and if the	1230	It normally is a string consisting entirely of ASCII letters (e.g.
959	load was successful, used as event model. If it fails to load	1231	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1232	the resulting module name is loaded and - if the load was successful
		1233	- used as event model backend. If it fails to load then AnyEvent
960	AnyEvent will proceed with auto detection and -probing.	1234	will proceed with auto detection and -probing.
961		1235
962	This functionality might change in future versions.	1236	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1237	then nothing gets prepended and the module name is used as-is (hint:
		1238	"::" at the end of a string designates a module name and quotes it
		1239	appropriately).
963		1240
964	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1241	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
965	could start your program like this:	1242	could start your program like this:
966		1243
967	PERL_ANYEVENT_MODEL=Perl perl ...	1244	PERL_ANYEVENT_MODEL=Perl perl ...
968		1245
969	"PERL_ANYEVENT_PROTOCOLS"	1246	"PERL_ANYEVENT_PROTOCOLS"
…		…
998	EDNS0 in its DNS requests.	1275	EDNS0 in its DNS requests.
999		1276
1000	"PERL_ANYEVENT_MAX_FORKS"	1277	"PERL_ANYEVENT_MAX_FORKS"
1001	The maximum number of child processes that	1278	The maximum number of child processes that
1002	"AnyEvent::Util::fork_call" will create in parallel.	1279	"AnyEvent::Util::fork_call" will create in parallel.
		1280
		1281	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1282	The default value for the "max_outstanding" parameter for the
		1283	default DNS resolver - this is the maximum number of parallel DNS
		1284	requests that are sent to the DNS server.
		1285
		1286	"PERL_ANYEVENT_RESOLV_CONF"
		1287	The file to use instead of /etc/resolv.conf (or OS-specific
		1288	configuration) in the default resolver. When set to the empty
		1289	string, no default config will be used.
		1290
		1291	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1292	When neither "ca_file" nor "ca_path" was specified during
		1293	AnyEvent::TLS context creation, and either of these environment
		1294	variables exist, they will be used to specify CA certificate
		1295	locations instead of a system-dependent default.
		1296
		1297	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1298	When these are set to 1, then the respective modules are not loaded.
		1299	Mostly good for testing AnyEvent itself.
1003		1300
1004	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1301	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1005	This is an advanced topic that you do not normally need to use AnyEvent	1302	This is an advanced topic that you do not normally need to use AnyEvent
1006	in a module. This section is only of use to event loop authors who want	1303	in a module. This section is only of use to event loop authors who want
1007	to provide AnyEvent compatibility.	1304	to provide AnyEvent compatibility.
…		…
1062	warn "read: $input\n"; # output what has been read	1359	warn "read: $input\n"; # output what has been read
1063	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1360	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1064	},	1361	},
1065	);	1362	);
1066		1363
1067	my $time_watcher; # can only be used once
1068
1069	sub new_timer {
1070	$timer = AnyEvent->timer (after => 1, cb => sub {	1364	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1071	warn "timeout\n"; # print 'timeout' about every second	1365	warn "timeout\n"; # print 'timeout' at most every second
1072	&new_timer; # and restart the time
1073	});
1074	}	1366	});
1075
1076	new_timer; # create first timer
1077		1367
1078	$cv->recv; # wait until user enters /^q/i	1368	$cv->recv; # wait until user enters /^q/i
1079		1369
1080	REAL-WORLD EXAMPLE	1370	REAL-WORLD EXAMPLE
1081	Consider the Net::FCP module. It features (among others) the following	1371	Consider the Net::FCP module. It features (among others) the following
…		…
1153		1443
1154	The actual code goes further and collects all errors ("die"s,	1444	The actual code goes further and collects all errors ("die"s,
1155	exceptions) that occurred during request processing. The "result" method	1445	exceptions) that occurred during request processing. The "result" method
1156	detects whether an exception as thrown (it is stored inside the $txn	1446	detects whether an exception as thrown (it is stored inside the $txn
1157	object) and just throws the exception, which means connection errors and	1447	object) and just throws the exception, which means connection errors and
1158	other problems get reported tot he code that tries to use the result,	1448	other problems get reported to the code that tries to use the result,
1159	not in a random callback.	1449	not in a random callback.
1160		1450
1161	All of this enables the following usage styles:	1451	All of this enables the following usage styles:
1162		1452
1163	1. Blocking:	1453	1. Blocking:
…		…
1208	through AnyEvent. The benchmark creates a lot of timers (with a zero	1498	through AnyEvent. The benchmark creates a lot of timers (with a zero
1209	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1499	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1210	which it is), lets them fire exactly once and destroys them again.	1500	which it is), lets them fire exactly once and destroys them again.
1211		1501
1212	Source code for this benchmark is found as eg/bench in the AnyEvent	1502	Source code for this benchmark is found as eg/bench in the AnyEvent
1213	distribution.	1503	distribution. It uses the AE interface, which makes a real difference
		1504	for the EV and Perl backends only.
1214		1505
1215	Explanation of the columns	1506	Explanation of the columns
1216	*watcher* is the number of event watchers created/destroyed. Since	1507	*watcher* is the number of event watchers created/destroyed. Since
1217	different event models feature vastly different performances, each event	1508	different event models feature vastly different performances, each event
1218	loop was given a number of watchers so that overall runtime is	1509	loop was given a number of watchers so that overall runtime is
…		…
1237	*destroy* is the time, in microseconds, that it takes to destroy a	1528	*destroy* is the time, in microseconds, that it takes to destroy a
1238	single watcher.	1529	single watcher.
1239		1530
1240	Results	1531	Results
1241	name watchers bytes create invoke destroy comment	1532	name watchers bytes create invoke destroy comment
1242	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1533	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1243	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1534	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1244	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1535	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1245	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1536	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1246	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1537	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1247	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1538	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
1248	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll	1539	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
1249	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll	1540	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1250	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1541	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1251	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1542	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1252	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1543	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1253	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1544	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1254		1545
1255	Discussion	1546	Discussion
1256	The benchmark does *not* measure scalability of the event loop very	1547	The benchmark does *not* measure scalability of the event loop very
1257	well. For example, a select-based event loop (such as the pure perl one)	1548	well. For example, a select-based event loop (such as the pure perl one)
1258	can never compete with an event loop that uses epoll when the number of	1549	can never compete with an event loop that uses epoll when the number of
…		…
1269	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1560	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1270	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1561	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1271	CPU cycles with POE.	1562	CPU cycles with POE.
1272		1563
1273	"EV" is the sole leader regarding speed and memory use, which are both	1564	"EV" is the sole leader regarding speed and memory use, which are both
1274	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1565	maximal/minimal, respectively. When using the AE API there is zero
		1566	overhead (when going through the AnyEvent API create is about 5-6 times
		1567	slower, with other times being equal, so still uses far less memory than
1275	far less memory than any other event loop and is still faster than Event	1568	any other event loop and is still faster than Event natively).
1276	natively.
1277		1569
1278	The pure perl implementation is hit in a few sweet spots (both the	1570	The pure perl implementation is hit in a few sweet spots (both the
1279	constant timeout and the use of a single fd hit optimisations in the	1571	constant timeout and the use of a single fd hit optimisations in the
1280	perl interpreter and the backend itself). Nevertheless this shows that	1572	perl interpreter and the backend itself). Nevertheless this shows that
1281	it adds very little overhead in itself. Like any select-based backend	1573	it adds very little overhead in itself. Like any select-based backend
…		…
1327	when used without AnyEvent), but most event loops have acceptable	1619	when used without AnyEvent), but most event loops have acceptable
1328	performance with or without AnyEvent.	1620	performance with or without AnyEvent.
1329		1621
1330	* The overhead AnyEvent adds is usually much smaller than the overhead	1622	* The overhead AnyEvent adds is usually much smaller than the overhead
1331	of the actual event loop, only with extremely fast event loops such	1623	of the actual event loop, only with extremely fast event loops such
1332	as EV adds AnyEvent significant overhead.	1624	as EV does AnyEvent add significant overhead.
1333		1625
1334	* You should avoid POE like the plague if you want performance or	1626	* You should avoid POE like the plague if you want performance or
1335	reasonable memory usage.	1627	reasonable memory usage.
1336		1628
1337	BENCHMARKING THE LARGE SERVER CASE	1629	BENCHMARKING THE LARGE SERVER CASE
…		…
1351	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1643	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1352	100 (1%) are active. This mirrors the activity of large servers with	1644	100 (1%) are active. This mirrors the activity of large servers with
1353	many connections, most of which are idle at any one point in time.	1645	many connections, most of which are idle at any one point in time.
1354		1646
1355	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1647	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1356	distribution.	1648	distribution. It uses the AE interface, which makes a real difference
		1649	for the EV and Perl backends only.
1357		1650
1358	Explanation of the columns	1651	Explanation of the columns
1359	*sockets* is the number of sockets, and twice the number of "servers"	1652	*sockets* is the number of sockets, and twice the number of "servers"
1360	(as each server has a read and write socket end).	1653	(as each server has a read and write socket end).
1361		1654
…		…
1367	forwarding it to another server. This includes deleting the old timeout	1660	forwarding it to another server. This includes deleting the old timeout
1368	and creating a new one that moves the timeout into the future.	1661	and creating a new one that moves the timeout into the future.
1369		1662
1370	Results	1663	Results
1371	name sockets create request	1664	name sockets create request
1372	EV 20000 69.01 11.16	1665	EV 20000 62.66 7.99
1373	Perl 20000 73.32 35.87	1666	Perl 20000 68.32 32.64
1374	IOAsync 20000 157.00 98.14 epoll	1667	IOAsync 20000 174.06 101.15 epoll
1375	IOAsync 20000 159.31 616.06 poll	1668	IOAsync 20000 174.67 610.84 poll
1376	Event 20000 212.62 257.32	1669	Event 20000 202.69 242.91
1377	Glib 20000 651.16 1896.30	1670	Glib 20000 557.01 1689.52
1378	POE 20000 349.67 12317.24 uses POE::Loop::Event	1671	POE 20000 341.54 12086.32 uses POE::Loop::Event
1379		1672
1380	Discussion	1673	Discussion
1381	This benchmark *does* measure scalability and overall performance of the	1674	This benchmark *does* measure scalability and overall performance of the
1382	particular event loop.	1675	particular event loop.
1383		1676
…		…
1496	As you can see, the AnyEvent + EV combination even beats the	1789	As you can see, the AnyEvent + EV combination even beats the
1497	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl	1790	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1498	backend easily beats IO::Lambda and POE.	1791	backend easily beats IO::Lambda and POE.
1499		1792
1500	And even the 100% non-blocking version written using the high-level (and	1793	And even the 100% non-blocking version written using the high-level (and
1501	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a	1794	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
1502	large margin, even though it does all of DNS, tcp-connect and socket I/O	1795	higher level ("unoptimised") abstractions by a large margin, even though
1503	in a non-blocking way.	1796	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
1504		1797
1505	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and	1798	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
1506	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are	1799	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1507	part of the IO::lambda distribution and were used without any changes.	1800	part of the IO::Lambda distribution and were used without any changes.
1508		1801
1509	SIGNALS	1802	SIGNALS
1510	AnyEvent currently installs handlers for these signals:	1803	AnyEvent currently installs handlers for these signals:
1511		1804
1512	SIGCHLD	1805	SIGCHLD
1513	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1806	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1514	emulation for event loops that do not support them natively. Also,	1807	emulation for event loops that do not support them natively. Also,
1515	some event loops install a similar handler.	1808	some event loops install a similar handler.
1516		1809
1517	If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent	1810	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
1518	will reset it to default, to avoid losing child exit statuses.	1811	then AnyEvent will reset it to default, to avoid losing child exit
		1812	statuses.
1519		1813
1520	SIGPIPE	1814	SIGPIPE
1521	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is	1815	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1522	"undef" when AnyEvent gets loaded.	1816	"undef" when AnyEvent gets loaded.
1523		1817
…		…
1531	it is that this way, the handler will be restored to defaults on	1825	it is that this way, the handler will be restored to defaults on
1532	exec.	1826	exec.
1533		1827
1534	Feel free to install your own handler, or reset it to defaults.	1828	Feel free to install your own handler, or reset it to defaults.
1535		1829
		1830	RECOMMENDED/OPTIONAL MODULES
		1831	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1832	its built-in modules) are required to use it.
		1833
		1834	That does not mean that AnyEvent won't take advantage of some additional
		1835	modules if they are installed.
		1836
		1837	This section explains which additional modules will be used, and how
		1838	they affect AnyEvent's operation.
		1839
		1840	Async::Interrupt
		1841	This slightly arcane module is used to implement fast signal
		1842	handling: To my knowledge, there is no way to do completely
		1843	race-free and quick signal handling in pure perl. To ensure that
		1844	signals still get delivered, AnyEvent will start an interval timer
		1845	to wake up perl (and catch the signals) with some delay (default is
		1846	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1847
		1848	If this module is available, then it will be used to implement
		1849	signal catching, which means that signals will not be delayed, and
		1850	the event loop will not be interrupted regularly, which is more
		1851	efficient (and good for battery life on laptops).
		1852
		1853	This affects not just the pure-perl event loop, but also other event
		1854	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1855
		1856	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1857	natively, and either employ their own workarounds (POE) or use
		1858	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1859	Installing Async::Interrupt does nothing for those backends.
		1860
		1861	EV This module isn't really "optional", as it is simply one of the
		1862	backend event loops that AnyEvent can use. However, it is simply the
		1863	best event loop available in terms of features, speed and stability:
		1864	It supports the AnyEvent API optimally, implements all the watcher
		1865	types in XS, does automatic timer adjustments even when no monotonic
		1866	clock is available, can take avdantage of advanced kernel interfaces
		1867	such as "epoll" and "kqueue", and is the fastest backend *by far*.
		1868	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1869	Glib::EV).
		1870
		1871	If you only use backends that rely on another event loop (e.g.
		1872	"Tk"), then this module will do nothing for you.
		1873
		1874	Guard
		1875	The guard module, when used, will be used to implement
		1876	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1877	uses a lot less memory), but otherwise doesn't affect guard
		1878	operation much. It is purely used for performance.
		1879
		1880	JSON and JSON::XS
		1881	One of these modules is required when you want to read or write JSON
		1882	data via AnyEvent::Handle. JSON is also written in pure-perl, but
		1883	can take advantage of the ultra-high-speed JSON::XS module when it
		1884	is installed.
		1885
		1886	Net::SSLeay
		1887	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1888	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1889	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1890
		1891	Time::HiRes
		1892	This module is part of perl since release 5.008. It will be used
		1893	when the chosen event library does not come with a timing source of
		1894	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
		1895	load it to try to use a monotonic clock for timing stability.
		1896
1536	FORK	1897	FORK
1537	Most event libraries are not fork-safe. The ones who are usually are	1898	Most event libraries are not fork-safe. The ones who are usually are
1538	because they rely on inefficient but fork-safe "select" or "poll" calls.	1899	because they rely on inefficient but fork-safe "select" or "poll" calls
1539	Only EV is fully fork-aware.	1900	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		1901	epoll are usually badly thought-out hacks that are incompatible with
		1902	fork in one way or another. Only EV is fully fork-aware and ensures that
		1903	you continue event-processing in both parent and child (or both, if you
		1904	know what you are doing).
		1905
		1906	This means that, in general, you cannot fork and do event processing in
		1907	the child if the event library was initialised before the fork (which
		1908	usually happens when the first AnyEvent watcher is created, or the
		1909	library is loaded).
1540		1910
1541	If you have to fork, you must either do so *before* creating your first	1911	If you have to fork, you must either do so *before* creating your first
1542	watcher OR you must not use AnyEvent at all in the child.	1912	watcher OR you must not use AnyEvent at all in the child OR you must do
		1913	something completely out of the scope of AnyEvent.
		1914
		1915	The problem of doing event processing in the parent *and* the child is
		1916	much more complicated: even for backends that *are* fork-aware or
		1917	fork-safe, their behaviour is not usually what you want: fork clones all
		1918	watchers, that means all timers, I/O watchers etc. are active in both
		1919	parent and child, which is almost never what you want. USing "exec" to
		1920	start worker children from some kind of manage rprocess is usually
		1921	preferred, because it is much easier and cleaner, at the expense of
		1922	having to have another binary.
1543		1923
1544	SECURITY CONSIDERATIONS	1924	SECURITY CONSIDERATIONS
1545	AnyEvent can be forced to load any event model via	1925	AnyEvent can be forced to load any event model via
1546	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1926	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1547	to execute arbitrary code or directly gain access, it can easily be used	1927	to execute arbitrary code or directly gain access, it can easily be used
…		…
1571	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	1951	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1572	annoying memleaks, such as leaking on "map" and "grep" but it is usually	1952	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1573	not as pronounced).	1953	not as pronounced).
1574		1954
1575	SEE ALSO	1955	SEE ALSO
1576	Utility functions: AnyEvent::Util.	1956	Tutorial/Introduction: AnyEvent::Intro.
1577		1957
1578	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1958	FAQ: AnyEvent::FAQ.
1579	Event::Lib, Qt, POE.	1959
		1960	Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log
		1961	(simply logging).
		1962
		1963	Development/Debugging: AnyEvent::Strict (stricter checking),
		1964	AnyEvent::Debug (interactive shell, watcher tracing).
		1965
		1966	Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
		1967	Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK.
1580		1968
1581	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1969	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1582	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1970	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1583	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1971	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1972	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi, AnyEvent::Impl::FLTK.
1584		1973
1585	Non-blocking file handles, sockets, TCP clients and servers:	1974	Non-blocking handles, pipes, stream sockets, TCP clients and servers:
1586	AnyEvent::Handle, AnyEvent::Socket.	1975	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1587		1976
1588	Asynchronous DNS: AnyEvent::DNS.	1977	Asynchronous DNS: AnyEvent::DNS.
1589		1978
1590	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1979	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1591		1980
1592	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1981	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
		1982	AnyEvent::HTTP.
1593		1983
1594	AUTHOR	1984	AUTHOR
1595	Marc Lehmann <schmorp@schmorp.de>	1985	Marc Lehmann <schmorp@schmorp.de>
1596	http://home.schmorp.de/	1986	http://home.schmorp.de/
1597		1987

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