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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 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::Impl::Perl, Event,
109	AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is	121	Glib, 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::Impl::Perl should always work, so the other two are not
113	successfully loaded will be used. If, after this, still none could be	125	normally 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
131	"AnyEvent::Impl::Perl". Like other event modules you can load it	142	"AnyEvent::Impl::Perl". Like other event modules you can load it
132	explicitly and enjoy the high availability of that event loop :)	143	explicitly and enjoy the high availability of that event loop :)
133		144
…		…
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
…		…
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
…		…
380		454
381	There is a slight catch to child watchers, however: you usually start	455	There is a slight catch to child watchers, however: you usually start
382	them *after* the child process was created, and this means the process	456	them *after* the child process was created, and this means the process
383	could have exited already (and no SIGCHLD will be sent anymore).	457	could have exited already (and no SIGCHLD will be sent anymore).
384		458
385	Not all event models handle this correctly (POE doesn't), but even for	459	Not all event models handle this correctly (neither POE nor IO::Async
		460	do, see their AnyEvent::Impl manpages for details), but even for event
386	event models that *do* handle this correctly, they usually need to be	461	models that *do* handle this correctly, they usually need to be loaded
387	loaded before the process exits (i.e. before you fork in the first	462	before the process exits (i.e. before you fork in the first place).
388	place).	463	AnyEvent's pure perl event loop handles all cases correctly regardless
		464	of when you start the watcher.
389		465
390	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
391	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
392	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 the latency and race
		472	problems mentioned in the description of signal watchers apply.
393		473
394	Example: fork a process and wait for it	474	Example: fork a process and wait for it
395		475
396	my $done = AnyEvent->condvar;	476	my $done = AnyEvent->condvar;
397		477
…		…
408		488
409	# do something else, then wait for process exit	489	# do something else, then wait for process exit
410	$done->recv;	490	$done->recv;
411		491
412	IDLE WATCHERS	492	IDLE WATCHERS
413	Sometimes there is a need to do something, but it is not so important to	493	$w = AnyEvent->idle (cb => <callback>);
414	do it instantly, but only when there is nothing better to do. This
415	"nothing better to do" is usually defined to be "no other events need
416	attention by the event loop".
417		494
418	Idle watchers ideally get invoked when the event loop has nothing better	495	This will repeatedly invoke the callback after the process becomes idle,
419	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.
420	Instead of blocking, the idle watcher is invoked.
421		497
422	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
423	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,
424	will simply call the callback "from time to time".	509	AnyEvent will simply call the callback "from time to time".
425		510
426	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
427	is otherwise idle:	512	is otherwise idle:
428		513
429	my @lines; # read data	514	my @lines; # read data
…		…
442	}	527	}
443	});	528	});
444	});	529	});
445		530
446	CONDITION VARIABLES	531	CONDITION VARIABLES
		532	$cv = AnyEvent->condvar;
		533
		534	$cv->send (<list>);
		535	my @res = $cv->recv;
		536
447	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
448	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
449	will actively watch for new events and call your callbacks.	539	will actively watch for new events and call your callbacks.
450		540
451	AnyEvent is different, it expects somebody else to run the event loop	541	AnyEvent is slightly different: it expects somebody else to run the
452	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).
453		544
454	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
455	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.
456		549
457	Condition variables can be created by calling the "AnyEvent->condvar"	550	Condition variables can be created by calling the "AnyEvent->condvar"
458	method, usually without arguments. The only argument pair allowed is	551	method, usually without arguments. The only argument pair allowed is
459
460	"cb", which specifies a callback to be called when the condition	552	"cb", which specifies a callback to be called when the condition
461	variable becomes true, with the condition variable as the first argument	553	variable becomes true, with the condition variable as the first argument
462	(but not the results).	554	(but not the results).
463		555
464	After creation, the condition variable is "false" until it becomes	556	After creation, the condition variable is "false" until it becomes
465	"true" by calling the "send" method (or calling the condition variable	557	"true" by calling the "send" method (or calling the condition variable
466	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
467	the "->send" method).	559	the "->send" method).
468		560
469	Condition variables are similar to callbacks, except that you can	561	Since condition variables are the most complex part of the AnyEvent API,
470	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
471	in time where multiple outstanding events have been processed. And yet	563	you can connect to:
472	another way to call them is transactions - each condition variable can	564
473	be used to represent a transaction, which finishes at some point and	565	* Condition variables are like callbacks - you can call them (and pass
474	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.
475		582
476	Condition variables are very useful to signal that something has	583	Condition variables are very useful to signal that something has
477	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
478	requests, then a condition variable would be the ideal candidate to	585	requests, then a condition variable would be the ideal candidate to
479	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
…		…
492		599
493	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
494	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
495	(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
496	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	603	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
497	it's "new" method in your own "new" method.	604	its "new" method in your own "new" method.
498		605
499	There are two "sides" to a condition variable - the "producer side"	606	There are two "sides" to a condition variable - the "producer side"
500	which eventually calls "-> send", and the "consumer side", which waits	607	which eventually calls "-> send", and the "consumer side", which waits
501	for the send to occur.	608	for the send to occur.
502		609
503	Example: wait for a timer.	610	Example: wait for a timer.
504		611
505	# wait till the result is ready	612	# condition: "wait till the timer is fired"
506	my $result_ready = AnyEvent->condvar;	613	my $timer_fired = AnyEvent->condvar;
507		614
508	# do something such as adding a timer	615	# create the timer - we could wait for, say
509	# or socket watcher the calls $result_ready->send	616	# a handle becomign ready, or even an
510	# when the "result" is ready.	617	# AnyEvent::HTTP request to finish, but
511	# in this case, we simply use a timer:	618	# in this case, we simply use a timer:
512	my $w = AnyEvent->timer (	619	my $w = AnyEvent->timer (
513	after => 1,	620	after => 1,
514	cb => sub { $result_ready->send },	621	cb => sub { $timer_fired->send },
515	);	622	);
516		623
517	# this "blocks" (while handling events) till the callback	624	# this "blocks" (while handling events) till the callback
518	# calls send	625	# calls ->send
519	$result_ready->recv;	626	$timer_fired->recv;
520		627
521	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
522	variables are also code references.	629	variables are also callable directly.
523		630
524	my $done = AnyEvent->condvar;	631	my $done = AnyEvent->condvar;
525	my $delay = AnyEvent->timer (after => 5, cb => $done);	632	my $delay = AnyEvent->timer (after => 5, cb => $done);
526	$done->recv;	633	$done->recv;
527		634
…		…
533		640
534	...	641	...
535		642
536	my @info = $couchdb->info->recv;	643	my @info = $couchdb->info->recv;
537		644
538	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
539	results are available:	646	results are available:
540		647
541	$couchdb->info->cb (sub {	648	$couchdb->info->cb (sub {
542	my @info = $_[0]->recv;	649	my @info = $_[0]->recv;
543	});	650	});
…		…
558		665
559	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
560	future "->recv" calls.	667	future "->recv" calls.
561		668
562	Condition variables are overloaded so one can call them directly (as	669	Condition variables are overloaded so one can call them directly (as
563	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
564	"send". Note, however, that many C-based event loops do not handle	671	calling "send".
565	overloading, so as tempting as it may be, passing a condition
566	variable instead of a callback does not work. Both the pure perl and
567	EV loops support overloading, however, as well as all functions that
568	use perl to invoke a callback (as in AnyEvent::Socket and
569	AnyEvent::DNS for example).
570		672
571	$cv->croak ($error)	673	$cv->croak ($error)
572	Similar to send, but causes all call's to "->recv" to invoke	674	Similar to send, but causes all calls to "->recv" to invoke
573	"Carp::croak" with the given error message/object/scalar.	675	"Carp::croak" with the given error message/object/scalar.
574		676
575	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
576	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.
577		683
578	$cv->begin ([group callback])	684	$cv->begin ([group callback])
579	$cv->end	685	$cv->end
580	These two methods are EXPERIMENTAL and MIGHT CHANGE.
581
582	These two methods can be used to combine many transactions/events	686	These two methods can be used to combine many transactions/events
583	into one. For example, a function that pings many hosts in parallel	687	into one. For example, a function that pings many hosts in parallel
584	might want to use a condition variable for the whole process.	688	might want to use a condition variable for the whole process.
585		689
586	Every call to "->begin" will increment a counter, and every call to	690	Every call to "->begin" will increment a counter, and every call to
587	"->end" will decrement it. If the counter reaches 0 in "->end", the	691	"->end" will decrement it. If the counter reaches 0 in "->end", the
588	(last) callback passed to "begin" will be executed. That callback is	692	(last) callback passed to "begin" will be executed, passing the
589	*supposed* to call "->send", but that is not required. If no	693	condvar as first argument. That callback is *supposed* to call
		694	"->send", but that is not required. If no group callback was set,
590	callback was set, "send" will be called without any arguments.	695	"send" will be called without any arguments.
591		696
592	Let's clarify this with the ping example:	697	You can think of "$cv->send" giving you an OR condition (one call
		698	sends), while "$cv->begin" and "$cv->end" giving you an AND
		699	condition (all "begin" calls must be "end"'ed before the condvar
		700	sends).
		701
		702	Let's start with a simple example: you have two I/O watchers (for
		703	example, STDOUT and STDERR for a program), and you want to wait for
		704	both streams to close before activating a condvar:
593		705
594	my $cv = AnyEvent->condvar;	706	my $cv = AnyEvent->condvar;
595		707
		708	$cv->begin; # first watcher
		709	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		710	defined sysread $fh1, my $buf, 4096
		711	or $cv->end;
		712	});
		713
		714	$cv->begin; # second watcher
		715	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		716	defined sysread $fh2, my $buf, 4096
		717	or $cv->end;
		718	});
		719
		720	$cv->recv;
		721
		722	This works because for every event source (EOF on file handle),
		723	there is one call to "begin", so the condvar waits for all calls to
		724	"end" before sending.
		725
		726	The ping example mentioned above is slightly more complicated, as
		727	the there are results to be passwd back, and the number of tasks
		728	that are begun can potentially be zero:
		729
		730	my $cv = AnyEvent->condvar;
		731
596	my %result;	732	my %result;
597	$cv->begin (sub { $cv->send (\%result) });	733	$cv->begin (sub { shift->send (\%result) });
598		734
599	for my $host (@list_of_hosts) {	735	for my $host (@list_of_hosts) {
600	$cv->begin;	736	$cv->begin;
601	ping_host_then_call_callback $host, sub {	737	ping_host_then_call_callback $host, sub {
602	$result{$host} = ...;	738	$result{$host} = ...;
…		…
617	the loop, which serves two important purposes: first, it sets the	753	the loop, which serves two important purposes: first, it sets the
618	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
619	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
620	(the loop doesn't execute once).	756	(the loop doesn't execute once).
621		757
622	This is the general pattern when you "fan out" into multiple	758	This is the general pattern when you "fan out" into multiple (but
623	subrequests: use an outer "begin"/"end" pair to set the callback and	759	potentially zero) subrequests: use an outer "begin"/"end" pair to
624	ensure "end" is called at least once, and then, for each subrequest	760	set the callback and ensure "end" is called at least once, and then,
625	you start, call "begin" and for each subrequest you finish, call	761	for each subrequest you start, call "begin" and for each subrequest
626	"end".	762	you finish, call "end".
627		763
628	METHODS FOR CONSUMERS	764	METHODS FOR CONSUMERS
629	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
630	awaits the condition.	766	awaits the condition.
631		767
632	$cv->recv	768	$cv->recv
633	Wait (blocking if necessary) until the "->send" or "->croak" methods	769	Wait (blocking if necessary) until the "->send" or "->croak" methods
634	have been called on c<$cv>, while servicing other watchers normally.	770	have been called on $cv, while servicing other watchers normally.
635		771
636	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
637	but will return immediately.	773	but will return immediately.
638		774
639	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
640	function will call "croak".	776	function will call "croak".
641		777
642	In list context, all parameters passed to "send" will be returned,	778	In list context, all parameters passed to "send" will be returned,
643	in scalar context only the first one will be returned.	779	in scalar context only the first one will be returned.
644		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
645	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
646	(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
647	using this from a module, never require a blocking wait*, but let	790	using this from a module, never require a blocking wait*. Instead,
648	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
649	by coupling condition variables with some kind of request results	792	example, by coupling condition variables with some kind of request
650	and supporting callbacks so the caller knows that getting the result	793	results and supporting callbacks so the caller knows that getting
651	will not block, while still supporting blocking waits if the caller	794	the result will not block, while still supporting blocking waits if
652	so desires).	795	the caller so desires).
653		796
654	Another reason *never* to "->recv" in a module is that you cannot
655	sensibly have two "->recv"'s in parallel, as that would require
656	multiple interpreters or coroutines/threads, none of which
657	"AnyEvent" can supply.
658
659	The Coro module, however, *can* and *does* supply coroutines and, in
660	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
661	versions and also integrates coroutines into AnyEvent, making
662	blocking "->recv" calls perfectly safe as long as they are done from
663	another coroutine (one that doesn't run the event loop).
664
665	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
666	only calling "->recv" from within that callback (or at a later	798	only calling "->recv" from within that callback (or at a later
667	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
668	blocking waits otherwise.	800	blocking waits otherwise.
669		801
670	$bool = $cv->ready	802	$bool = $cv->ready
…		…
675	This is a mutator function that returns the callback set and	807	This is a mutator function that returns the callback set and
676	optionally replaces it before doing so.	808	optionally replaces it before doing so.
677		809
678	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.
679	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
680	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
681	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 implementation, 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
		845	Backends with special needs.
		846	Qt requires the Qt::Application to be instantiated first, but will
		847	otherwise be picked up automatically. As long as the main program
		848	instantiates the application before any AnyEvent watchers are
		849	created, everything should just work.
		850
		851	AnyEvent::Impl::Qt based on Qt.
		852
		853	Event loops that are indirectly supported via other backends.
		854	Some event loops can be supported via other modules:
		855
		856	There is no direct support for WxWidgets (Wx) or Prima.
		857
		858	WxWidgets has no support for watching file handles. However, you can
		859	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		860	simply polls 20 times per second, which was considered to be too
		861	horrible to even consider for AnyEvent.
		862
		863	Prima is not supported as nobody seems to be using it, but it has a
		864	POE backend, so it can be supported through POE.
		865
		866	AnyEvent knows about both Prima and Wx, however, and will try to
		867	load POE when detecting them, in the hope that POE will pick them
		868	up, in which case everything will be automatic.
682		869
683	GLOBAL VARIABLES AND FUNCTIONS	870	GLOBAL VARIABLES AND FUNCTIONS
		871	These are not normally required to use AnyEvent, but can be useful to
		872	write AnyEvent extension modules.
		873
684	$AnyEvent::MODEL	874	$AnyEvent::MODEL
685	Contains "undef" until the first watcher is being created. Then it	875	Contains "undef" until the first watcher is being created, before
		876	the backend has been autodetected.
		877
686	contains the event model that is being used, which is the name of	878	Afterwards it contains the event model that is being used, which is
687	the Perl class implementing the model. This class is usually one of	879	the name of the Perl class implementing the model. This class is
688	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	880	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
689	case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*).	881	other class in the case AnyEvent has been extended at runtime (e.g.
690		882	in *rxvt-unicode* it will be "urxvt::anyevent").
691	The known classes so far are:
692
693	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
694	AnyEvent::Impl::Event based on Event, second best choice.
695	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
696	AnyEvent::Impl::Glib based on Glib, third-best choice.
697	AnyEvent::Impl::Tk based on Tk, very bad choice.
698	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
699	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
700	AnyEvent::Impl::POE based on POE, not generic enough for full support.
701
702	There is no support for WxWidgets, as WxWidgets has no support for
703	watching file handles. However, you can use WxWidgets through the
704	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
705	second, which was considered to be too horrible to even consider for
706	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
707	using it's adaptor.
708
709	AnyEvent knows about Prima and Wx and will try to use POE when
710	autodetecting them.
711		883
712	AnyEvent::detect	884	AnyEvent::detect
713	Returns $AnyEvent::MODEL, forcing autodetection of the event model	885	Returns $AnyEvent::MODEL, forcing autodetection of the event model
714	if necessary. You should only call this function right before you	886	if necessary. You should only call this function right before you
715	would have created an AnyEvent watcher anyway, that is, as late as	887	would have created an AnyEvent watcher anyway, that is, as late as
716	possible at runtime.	888	possible at runtime, and not e.g. during initialisation of your
		889	module.
		890
		891	If you need to do some initialisation before AnyEvent watchers are
		892	created, use "post_detect".
717		893
718	$guard = AnyEvent::post_detect { BLOCK }	894	$guard = AnyEvent::post_detect { BLOCK }
719	Arranges for the code block to be executed as soon as the event	895	Arranges for the code block to be executed as soon as the event
720	model is autodetected (or immediately if this has already happened).	896	model is autodetected (or immediately if that has already happened).
		897
		898	The block will be executed *after* the actual backend has been
		899	detected ($AnyEvent::MODEL is set), but *before* any watchers have
		900	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		901	other initialisations - see the sources of AnyEvent::Strict or
		902	AnyEvent::AIO to see how this is used.
		903
		904	The most common usage is to create some global watchers, without
		905	forcing event module detection too early, for example, AnyEvent::AIO
		906	creates and installs the global IO::AIO watcher in a "post_detect"
		907	block to avoid autodetecting the event module at load time.
721		908
722	If called in scalar or list context, then it creates and returns an	909	If called in scalar or list context, then it creates and returns an
723	object that automatically removes the callback again when it is	910	object that automatically removes the callback again when it is
		911	destroyed (or "undef" when the hook was immediately executed). See
724	destroyed. See Coro::BDB for a case where this is useful.	912	AnyEvent::AIO for a case where this is useful.
		913
		914	Example: Create a watcher for the IO::AIO module and store it in
		915	$WATCHER, but do so only do so after the event loop is initialised.
		916
		917	our WATCHER;
		918
		919	my $guard = AnyEvent::post_detect {
		920	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		921	};
		922
		923	# the ||= is important in case post_detect immediately runs the block,
		924	# as to not clobber the newly-created watcher. assigning both watcher and
		925	# post_detect guard to the same variable has the advantage of users being
		926	# able to just C<undef $WATCHER> if the watcher causes them grief.
		927
		928	$WATCHER ||= $guard;
725		929
726	@AnyEvent::post_detect	930	@AnyEvent::post_detect
727	If there are any code references in this array (you can "push" to it	931	If there are any code references in this array (you can "push" to it
728	before or after loading AnyEvent), then they will called directly	932	before or after loading AnyEvent), then they will be called directly
729	after the event loop has been chosen.	933	after the event loop has been chosen.
730		934
731	You should check $AnyEvent::MODEL before adding to this array,	935	You should check $AnyEvent::MODEL before adding to this array,
732	though: if it contains a true value then the event loop has already	936	though: if it is defined then the event loop has already been
733	been detected, and the array will be ignored.	937	detected, and the array will be ignored.
734		938
735	Best use "AnyEvent::post_detect { BLOCK }" instead.	939	Best use "AnyEvent::post_detect { BLOCK }" when your application
		940	allows it, as it takes care of these details.
		941
		942	This variable is mainly useful for modules that can do something
		943	useful when AnyEvent is used and thus want to know when it is
		944	initialised, but do not need to even load it by default. This array
		945	provides the means to hook into AnyEvent passively, without loading
		946	it.
		947
		948	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		949	together, you could put this into Coro (this is the actual code used
		950	by Coro to accomplish this):
		951
		952	if (defined $AnyEvent::MODEL) {
		953	# AnyEvent already initialised, so load Coro::AnyEvent
		954	require Coro::AnyEvent;
		955	} else {
		956	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		957	# as soon as it is
		958	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		959	}
736		960
737	WHAT TO DO IN A MODULE	961	WHAT TO DO IN A MODULE
738	As a module author, you should "use AnyEvent" and call AnyEvent methods	962	As a module author, you should "use AnyEvent" and call AnyEvent methods
739	freely, but you should not load a specific event module or rely on it.	963	freely, but you should not load a specific event module or rely on it.
740		964
…		…
748	stall the whole program, and the whole point of using events is to stay	972	stall the whole program, and the whole point of using events is to stay
749	interactive.	973	interactive.
750		974
751	It is fine, however, to call "->recv" when the user of your module	975	It is fine, however, to call "->recv" when the user of your module
752	requests it (i.e. if you create a http request object ad have a method	976	requests it (i.e. if you create a http request object ad have a method
753	called "results" that returns the results, it should call "->recv"	977	called "results" that returns the results, it may call "->recv" freely,
754	freely, as the user of your module knows what she is doing. always).	978	as the user of your module knows what she is doing. Always).
755		979
756	WHAT TO DO IN THE MAIN PROGRAM	980	WHAT TO DO IN THE MAIN PROGRAM
757	There will always be a single main program - the only place that should	981	There will always be a single main program - the only place that should
758	dictate which event model to use.	982	dictate which event model to use.
759		983
760	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	984	If the program is not event-based, it need not do anything special, even
761	do anything special (it does not need to be event-based) and let	985	when it depends on a module that uses an AnyEvent. If the program itself
762	AnyEvent decide which implementation to chose if some module relies on	986	uses AnyEvent, but does not care which event loop is used, all it needs
763	it.	987	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		988	available loop implementation.
764		989
765	If the main program relies on a specific event model - for example, in	990	If the main program relies on a specific event model - for example, in
766	Gtk2 programs you have to rely on the Glib module - you should load the	991	Gtk2 programs you have to rely on the Glib module - you should load the
767	event module before loading AnyEvent or any module that uses it:	992	event module before loading AnyEvent or any module that uses it:
768	generally speaking, you should load it as early as possible. The reason	993	generally speaking, you should load it as early as possible. The reason
769	is that modules might create watchers when they are loaded, and AnyEvent	994	is that modules might create watchers when they are loaded, and AnyEvent
770	will decide on the event model to use as soon as it creates watchers,	995	will decide on the event model to use as soon as it creates watchers,
771	and it might chose the wrong one unless you load the correct one	996	and it might choose the wrong one unless you load the correct one
772	yourself.	997	yourself.
773		998
774	You can chose to use a pure-perl implementation by loading the	999	You can chose to use a pure-perl implementation by loading the
775	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1000	"AnyEvent::Impl::Perl" module, which gives you similar behaviour
776	everywhere, but letting AnyEvent chose the model is generally better.	1001	everywhere, but letting AnyEvent chose the model is generally better.
…		…
791	variable somewhere, waiting for it, and sending it when the program	1016	variable somewhere, waiting for it, and sending it when the program
792	should exit cleanly.	1017	should exit cleanly.
793		1018
794	OTHER MODULES	1019	OTHER MODULES
795	The following is a non-exhaustive list of additional modules that use	1020	The following is a non-exhaustive list of additional modules that use
796	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1021	AnyEvent as a client and can therefore be mixed easily with other
797	in the same program. Some of the modules come with AnyEvent, some are	1022	AnyEvent modules and other event loops in the same program. Some of the
798	available via CPAN.	1023	modules come as part of AnyEvent, the others are available via CPAN.
799		1024
800	AnyEvent::Util	1025	AnyEvent::Util
801	Contains various utility functions that replace often-used but	1026	Contains various utility functions that replace often-used blocking
802	blocking functions such as "inet_aton" by event-/callback-based	1027	functions such as "inet_aton" with event/callback-based versions.
803	versions.
804		1028
805	AnyEvent::Socket	1029	AnyEvent::Socket
806	Provides various utility functions for (internet protocol) sockets,	1030	Provides various utility functions for (internet protocol) sockets,
807	addresses and name resolution. Also functions to create non-blocking	1031	addresses and name resolution. Also functions to create non-blocking
808	tcp connections or tcp servers, with IPv6 and SRV record support and	1032	tcp connections or tcp servers, with IPv6 and SRV record support and
809	more.	1033	more.
810		1034
811	AnyEvent::Handle	1035	AnyEvent::Handle
812	Provide read and write buffers, manages watchers for reads and	1036	Provide read and write buffers, manages watchers for reads and
813	writes, supports raw and formatted I/O, I/O queued and fully	1037	writes, supports raw and formatted I/O, I/O queued and fully
814	transparent and non-blocking SSL/TLS.	1038	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
815		1039
816	AnyEvent::DNS	1040	AnyEvent::DNS
817	Provides rich asynchronous DNS resolver capabilities.	1041	Provides rich asynchronous DNS resolver capabilities.
818		1042
		1043	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
		1044	AnyEvent::IGS, AnyEvent::FCP
		1045	Implement event-based interfaces to the protocols of the same name
		1046	(for the curious, IGS is the International Go Server and FCP is the
		1047	Freenet Client Protocol).
		1048
		1049	AnyEvent::Handle::UDP
		1050	Here be danger!
		1051
		1052	As Pauli would put it, "Not only is it not right, it's not even
		1053	wrong!" - there are so many things wrong with AnyEvent::Handle::UDP,
		1054	most notably its use of a stream-based API with a protocol that
		1055	isn't streamable, that the only way to improve it is to delete it.
		1056
		1057	It features data corruption (but typically only under load) and
		1058	general confusion. On top, the author is not only clueless about UDP
		1059	but also fact-resistant - some gems of his understanding: "connect
		1060	doesn't work with UDP", "UDP packets are not IP packets", "UDP only
		1061	has datagrams, not packets", "I don't need to implement proper error
		1062	checking as UDP doesn't support error checking" and so on - he
		1063	doesn't even understand what's wrong with his module when it is
		1064	explained to him.
		1065
819	AnyEvent::HTTP	1066	AnyEvent::DBI
820	A simple-to-use HTTP library that is capable of making a lot of	1067	Executes DBI requests asynchronously in a proxy process for you,
821	concurrent HTTP requests.	1068	notifying you in an event-based way when the operation is finished.
		1069
		1070	AnyEvent::AIO
		1071	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1072	the toolbox of every event programmer. AnyEvent::AIO transparently
		1073	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1074	event-based file I/O, and much more.
822		1075
823	AnyEvent::HTTPD	1076	AnyEvent::HTTPD
824	Provides a simple web application server framework.	1077	A simple embedded webserver.
825		1078
826	AnyEvent::FastPing	1079	AnyEvent::FastPing
827	The fastest ping in the west.	1080	The fastest ping in the west.
828		1081
829	AnyEvent::DBI
830	Executes DBI requests asynchronously in a proxy process.
831
832	AnyEvent::AIO
833	Truly asynchronous I/O, should be in the toolbox of every event
834	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
835	together.
836
837	AnyEvent::BDB
838	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
839	fuses BDB and AnyEvent together.
840
841	AnyEvent::GPSD
842	A non-blocking interface to gpsd, a daemon delivering GPS
843	information.
844
845	AnyEvent::IGS
846	A non-blocking interface to the Internet Go Server protocol (used by
847	App::IGS).
848
849	AnyEvent::IRC
850	AnyEvent based IRC client module family (replacing the older
851	Net::IRC3).
852
853	Net::XMPP2
854	AnyEvent based XMPP (Jabber protocol) module family.
855
856	Net::FCP
857	AnyEvent-based implementation of the Freenet Client Protocol,
858	birthplace of AnyEvent.
859
860	Event::ExecFlow
861	High level API for event-based execution flow control.
862
863	Coro	1082	Coro
864	Has special support for AnyEvent via Coro::AnyEvent.	1083	Has special support for AnyEvent via Coro::AnyEvent.
865		1084
866	IO::Lambda	1085	SIMPLIFIED AE API
867	The lambda approach to I/O - don't ask, look there. Can use	1086	Starting with version 5.0, AnyEvent officially supports a second, much
868	AnyEvent.	1087	simpler, API that is designed to reduce the calling, typing and memory
		1088	overhead by using function call syntax and a fixed number of parameters.
		1089
		1090	See the AE manpage for details.
869		1091
870	ERROR AND EXCEPTION HANDLING	1092	ERROR AND EXCEPTION HANDLING
871	In general, AnyEvent does not do any error handling - it relies on the	1093	In general, AnyEvent does not do any error handling - it relies on the
872	caller to do that if required. The AnyEvent::Strict module (see also the	1094	caller to do that if required. The AnyEvent::Strict module (see also the
873	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1095	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
901	by "PERL_ANYEVENT_MODEL".	1123	by "PERL_ANYEVENT_MODEL".
902		1124
903	When set to 2 or higher, cause AnyEvent to report to STDERR which	1125	When set to 2 or higher, cause AnyEvent to report to STDERR which
904	event model it chooses.	1126	event model it chooses.
905		1127
		1128	When set to 8 or higher, then AnyEvent will report extra information
		1129	on which optional modules it loads and how it implements certain
		1130	features.
		1131
906	"PERL_ANYEVENT_STRICT"	1132	"PERL_ANYEVENT_STRICT"
907	AnyEvent does not do much argument checking by default, as thorough	1133	AnyEvent does not do much argument checking by default, as thorough
908	argument checking is very costly. Setting this variable to a true	1134	argument checking is very costly. Setting this variable to a true
909	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1135	value will cause AnyEvent to load "AnyEvent::Strict" and then to
910	thoroughly check the arguments passed to most method calls. If it	1136	thoroughly check the arguments passed to most method calls. If it
911	finds any problems it will croak.	1137	finds any problems, it will croak.
912		1138
913	In other words, enables "strict" mode.	1139	In other words, enables "strict" mode.
914		1140
915	Unlike "use strict", it is definitely recommended ot keep it off in	1141	Unlike "use strict" (or its modern cousin, "use common::sense", it
916	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1142	is definitely recommended to keep it off in production. Keeping
		1143	"PERL_ANYEVENT_STRICT=1" in your environment while developing
917	while developing programs can be very useful, however.	1144	programs can be very useful, however.
918		1145
919	"PERL_ANYEVENT_MODEL"	1146	"PERL_ANYEVENT_MODEL"
920	This can be used to specify the event model to be used by AnyEvent,	1147	This can be used to specify the event model to be used by AnyEvent,
921	before auto detection and -probing kicks in. It must be a string	1148	before auto detection and -probing kicks in. It must be a string
922	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1149	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
963	EDNS0 in its DNS requests.	1190	EDNS0 in its DNS requests.
964		1191
965	"PERL_ANYEVENT_MAX_FORKS"	1192	"PERL_ANYEVENT_MAX_FORKS"
966	The maximum number of child processes that	1193	The maximum number of child processes that
967	"AnyEvent::Util::fork_call" will create in parallel.	1194	"AnyEvent::Util::fork_call" will create in parallel.
		1195
		1196	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1197	The default value for the "max_outstanding" parameter for the
		1198	default DNS resolver - this is the maximum number of parallel DNS
		1199	requests that are sent to the DNS server.
		1200
		1201	"PERL_ANYEVENT_RESOLV_CONF"
		1202	The file to use instead of /etc/resolv.conf (or OS-specific
		1203	configuration) in the default resolver. When set to the empty
		1204	string, no default config will be used.
		1205
		1206	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1207	When neither "ca_file" nor "ca_path" was specified during
		1208	AnyEvent::TLS context creation, and either of these environment
		1209	variables exist, they will be used to specify CA certificate
		1210	locations instead of a system-dependent default.
		1211
		1212	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1213	When these are set to 1, then the respective modules are not loaded.
		1214	Mostly good for testing AnyEvent itself.
968		1215
969	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1216	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
970	This is an advanced topic that you do not normally need to use AnyEvent	1217	This is an advanced topic that you do not normally need to use AnyEvent
971	in a module. This section is only of use to event loop authors who want	1218	in a module. This section is only of use to event loop authors who want
972	to provide AnyEvent compatibility.	1219	to provide AnyEvent compatibility.
…		…
1027	warn "read: $input\n"; # output what has been read	1274	warn "read: $input\n"; # output what has been read
1028	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1275	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1029	},	1276	},
1030	);	1277	);
1031		1278
1032	my $time_watcher; # can only be used once
1033
1034	sub new_timer {
1035	$timer = AnyEvent->timer (after => 1, cb => sub {	1279	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1036	warn "timeout\n"; # print 'timeout' about every second	1280	warn "timeout\n"; # print 'timeout' at most every second
1037	&new_timer; # and restart the time
1038	});
1039	}	1281	});
1040
1041	new_timer; # create first timer
1042		1282
1043	$cv->recv; # wait until user enters /^q/i	1283	$cv->recv; # wait until user enters /^q/i
1044		1284
1045	REAL-WORLD EXAMPLE	1285	REAL-WORLD EXAMPLE
1046	Consider the Net::FCP module. It features (among others) the following	1286	Consider the Net::FCP module. It features (among others) the following
…		…
1118		1358
1119	The actual code goes further and collects all errors ("die"s,	1359	The actual code goes further and collects all errors ("die"s,
1120	exceptions) that occurred during request processing. The "result" method	1360	exceptions) that occurred during request processing. The "result" method
1121	detects whether an exception as thrown (it is stored inside the $txn	1361	detects whether an exception as thrown (it is stored inside the $txn
1122	object) and just throws the exception, which means connection errors and	1362	object) and just throws the exception, which means connection errors and
1123	other problems get reported tot he code that tries to use the result,	1363	other problems get reported to the code that tries to use the result,
1124	not in a random callback.	1364	not in a random callback.
1125		1365
1126	All of this enables the following usage styles:	1366	All of this enables the following usage styles:
1127		1367
1128	1. Blocking:	1368	1. Blocking:
…		…
1173	through AnyEvent. The benchmark creates a lot of timers (with a zero	1413	through AnyEvent. The benchmark creates a lot of timers (with a zero
1174	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1414	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1175	which it is), lets them fire exactly once and destroys them again.	1415	which it is), lets them fire exactly once and destroys them again.
1176		1416
1177	Source code for this benchmark is found as eg/bench in the AnyEvent	1417	Source code for this benchmark is found as eg/bench in the AnyEvent
1178	distribution.	1418	distribution. It uses the AE interface, which makes a real difference
		1419	for the EV and Perl backends only.
1179		1420
1180	Explanation of the columns	1421	Explanation of the columns
1181	*watcher* is the number of event watchers created/destroyed. Since	1422	*watcher* is the number of event watchers created/destroyed. Since
1182	different event models feature vastly different performances, each event	1423	different event models feature vastly different performances, each event
1183	loop was given a number of watchers so that overall runtime is	1424	loop was given a number of watchers so that overall runtime is
…		…
1202	*destroy* is the time, in microseconds, that it takes to destroy a	1443	*destroy* is the time, in microseconds, that it takes to destroy a
1203	single watcher.	1444	single watcher.
1204		1445
1205	Results	1446	Results
1206	name watchers bytes create invoke destroy comment	1447	name watchers bytes create invoke destroy comment
1207	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1448	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1208	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1449	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1209	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1450	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1210	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1451	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1211	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1452	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1212	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1453	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		1454	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		1455	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1213	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1456	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1214	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1457	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1215	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1458	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1216	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1459	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1217		1460
1218	Discussion	1461	Discussion
1219	The benchmark does *not* measure scalability of the event loop very	1462	The benchmark does *not* measure scalability of the event loop very
1220	well. For example, a select-based event loop (such as the pure perl one)	1463	well. For example, a select-based event loop (such as the pure perl one)
1221	can never compete with an event loop that uses epoll when the number of	1464	can never compete with an event loop that uses epoll when the number of
…		…
1232	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1475	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1233	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1476	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1234	CPU cycles with POE.	1477	CPU cycles with POE.
1235		1478
1236	"EV" is the sole leader regarding speed and memory use, which are both	1479	"EV" is the sole leader regarding speed and memory use, which are both
1237	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1480	maximal/minimal, respectively. When using the AE API there is zero
		1481	overhead (when going through the AnyEvent API create is about 5-6 times
		1482	slower, with other times being equal, so still uses far less memory than
1238	far less memory than any other event loop and is still faster than Event	1483	any other event loop and is still faster than Event natively).
1239	natively.
1240		1484
1241	The pure perl implementation is hit in a few sweet spots (both the	1485	The pure perl implementation is hit in a few sweet spots (both the
1242	constant timeout and the use of a single fd hit optimisations in the	1486	constant timeout and the use of a single fd hit optimisations in the
1243	perl interpreter and the backend itself). Nevertheless this shows that	1487	perl interpreter and the backend itself). Nevertheless this shows that
1244	it adds very little overhead in itself. Like any select-based backend	1488	it adds very little overhead in itself. Like any select-based backend
…		…
1246	few of them active), of course, but this was not subject of this	1490	few of them active), of course, but this was not subject of this
1247	benchmark.	1491	benchmark.
1248		1492
1249	The "Event" module has a relatively high setup and callback invocation	1493	The "Event" module has a relatively high setup and callback invocation
1250	cost, but overall scores in on the third place.	1494	cost, but overall scores in on the third place.
		1495
		1496	"IO::Async" performs admirably well, about on par with "Event", even
		1497	when using its pure perl backend.
1251		1498
1252	"Glib"'s memory usage is quite a bit higher, but it features a faster	1499	"Glib"'s memory usage is quite a bit higher, but it features a faster
1253	callback invocation and overall ends up in the same class as "Event".	1500	callback invocation and overall ends up in the same class as "Event".
1254	However, Glib scales extremely badly, doubling the number of watchers	1501	However, Glib scales extremely badly, doubling the number of watchers
1255	increases the processing time by more than a factor of four, making it	1502	increases the processing time by more than a factor of four, making it
…		…
1311	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1558	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1312	100 (1%) are active. This mirrors the activity of large servers with	1559	100 (1%) are active. This mirrors the activity of large servers with
1313	many connections, most of which are idle at any one point in time.	1560	many connections, most of which are idle at any one point in time.
1314		1561
1315	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1562	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1316	distribution.	1563	distribution. It uses the AE interface, which makes a real difference
		1564	for the EV and Perl backends only.
1317		1565
1318	Explanation of the columns	1566	Explanation of the columns
1319	*sockets* is the number of sockets, and twice the number of "servers"	1567	*sockets* is the number of sockets, and twice the number of "servers"
1320	(as each server has a read and write socket end).	1568	(as each server has a read and write socket end).
1321		1569
…		…
1326	single "request", that is, reading the token from the pipe and	1574	single "request", that is, reading the token from the pipe and
1327	forwarding it to another server. This includes deleting the old timeout	1575	forwarding it to another server. This includes deleting the old timeout
1328	and creating a new one that moves the timeout into the future.	1576	and creating a new one that moves the timeout into the future.
1329		1577
1330	Results	1578	Results
1331	name sockets create request	1579	name sockets create request
1332	EV 20000 69.01 11.16	1580	EV 20000 62.66 7.99
1333	Perl 20000 73.32 35.87	1581	Perl 20000 68.32 32.64
1334	Event 20000 212.62 257.32	1582	IOAsync 20000 174.06 101.15 epoll
1335	Glib 20000 651.16 1896.30	1583	IOAsync 20000 174.67 610.84 poll
		1584	Event 20000 202.69 242.91
		1585	Glib 20000 557.01 1689.52
1336	POE 20000 349.67 12317.24 uses POE::Loop::Event	1586	POE 20000 341.54 12086.32 uses POE::Loop::Event
1337		1587
1338	Discussion	1588	Discussion
1339	This benchmark *does* measure scalability and overall performance of the	1589	This benchmark *does* measure scalability and overall performance of the
1340	particular event loop.	1590	particular event loop.
1341		1591
1342	EV is again fastest. Since it is using epoll on my system, the setup	1592	EV is again fastest. Since it is using epoll on my system, the setup
1343	time is relatively high, though.	1593	time is relatively high, though.
1344		1594
1345	Perl surprisingly comes second. It is much faster than the C-based event	1595	Perl surprisingly comes second. It is much faster than the C-based event
1346	loops Event and Glib.	1596	loops Event and Glib.
		1597
		1598	IO::Async performs very well when using its epoll backend, and still
		1599	quite good compared to Glib when using its pure perl backend.
1347		1600
1348	Event suffers from high setup time as well (look at its code and you	1601	Event suffers from high setup time as well (look at its code and you
1349	will understand why). Callback invocation also has a high overhead	1602	will understand why). Callback invocation also has a high overhead
1350	compared to the "$_->() for .."-style loop that the Perl event loop	1603	compared to the "$_->() for .."-style loop that the Perl event loop
1351	uses. Event uses select or poll in basically all documented	1604	uses. Event uses select or poll in basically all documented
…		…
1407	THE IO::Lambda BENCHMARK	1660	THE IO::Lambda BENCHMARK
1408	Recently I was told about the benchmark in the IO::Lambda manpage, which	1661	Recently I was told about the benchmark in the IO::Lambda manpage, which
1409	could be misinterpreted to make AnyEvent look bad. In fact, the	1662	could be misinterpreted to make AnyEvent look bad. In fact, the
1410	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks	1663	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
1411	better (which shouldn't come as a surprise to anybody). As such, the	1664	better (which shouldn't come as a surprise to anybody). As such, the
1412	benchmark is fine, and shows that the AnyEvent backend from IO::Lambda	1665	benchmark is fine, and mostly shows that the AnyEvent backend from
1413	isn't very optimal. But how would AnyEvent compare when used without the	1666	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
1414	extra baggage? To explore this, I wrote the equivalent benchmark for	1667	without the extra baggage? To explore this, I wrote the equivalent
1415	AnyEvent.	1668	benchmark for AnyEvent.
1416		1669
1417	The benchmark itself creates an echo-server, and then, for 500 times,	1670	The benchmark itself creates an echo-server, and then, for 500 times,
1418	connects to the echo server, sends a line, waits for the reply, and then	1671	connects to the echo server, sends a line, waits for the reply, and then
1419	creates the next connection. This is a rather bad benchmark, as it	1672	creates the next connection. This is a rather bad benchmark, as it
1420	doesn't test the efficiency of the framework, but it is a benchmark	1673	doesn't test the efficiency of the framework or much non-blocking I/O,
1421	nevertheless.	1674	but it is a benchmark nevertheless.
1422		1675
1423	name runtime	1676	name runtime
1424	Lambda/select 0.330 sec	1677	Lambda/select 0.330 sec
1425	+ optimized 0.122 sec	1678	+ optimized 0.122 sec
1426	Lambda/AnyEvent 0.327 sec	1679	Lambda/AnyEvent 0.327 sec
…		…
1432		1685
1433	AnyEvent/select/nb 0.085 sec	1686	AnyEvent/select/nb 0.085 sec
1434	AnyEvent/EV/nb 0.068 sec	1687	AnyEvent/EV/nb 0.068 sec
1435	+state machine 0.134 sec	1688	+state machine 0.134 sec
1436		1689
1437	The benchmark is also a bit unfair (my fault) - the IO::Lambda	1690	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
1438	benchmarks actually make blocking connects and use 100% blocking I/O,	1691	benchmarks actually make blocking connects and use 100% blocking I/O,
1439	defeating the purpose of an event-based solution. All of the newly	1692	defeating the purpose of an event-based solution. All of the newly
1440	written AnyEvent benchmarks use 100% non-blocking connects (using	1693	written AnyEvent benchmarks use 100% non-blocking connects (using
1441	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS	1694	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
1442	resolver), so AnyEvent is at a disadvantage here as non-blocking	1695	resolver), so AnyEvent is at a disadvantage here, as non-blocking
1443	connects generally require a lot more bookkeeping and event handling	1696	connects generally require a lot more bookkeeping and event handling
1444	than blocking connects (which involve a single syscall only).	1697	than blocking connects (which involve a single syscall only).
1445		1698
1446	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which	1699	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
1447	offers similar expressive power as POE and IO::Lambda (using	1700	offers similar expressive power as POE and IO::Lambda, using
1448	conventional Perl syntax), which means both the echo server and the	1701	conventional Perl syntax. This means that both the echo server and the
1449	client are 100% non-blocking w.r.t. I/O, further placing it at a	1702	client are 100% non-blocking, further placing it at a disadvantage.
1450	disadvantage.
1451		1703
1452	As you can see, AnyEvent + EV even beats the hand-optimised "raw sockets	1704	As you can see, the AnyEvent + EV combination even beats the
1453	benchmark", while AnyEvent + its pure perl backend easily beats	1705	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1454	IO::Lambda and POE.	1706	backend easily beats IO::Lambda and POE.
1455		1707
1456	And even the 100% non-blocking version written using the high-level (and	1708	And even the 100% non-blocking version written using the high-level (and
1457	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda, even	1709	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
		1710	higher level ("unoptimised") abstractions by a large margin, even though
1458	thought it does all of DNS, tcp-connect and socket I/O in a non-blocking	1711	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
1459	way.
1460		1712
1461	The two AnyEvent benchmarks can be found as eg/ae0.pl and eg/ae2.pl in	1713	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
1462	the AnyEvent distribution, the remaining benchmarks are part of the	1714	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1463	IO::lambda distribution and were used without any changes.	1715	part of the IO::Lambda distribution and were used without any changes.
1464		1716
1465	SIGNALS	1717	SIGNALS
1466	AnyEvent currently installs handlers for these signals:	1718	AnyEvent currently installs handlers for these signals:
1467		1719
1468	SIGCHLD	1720	SIGCHLD
1469	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1721	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1470	emulation for event loops that do not support them natively. Also,	1722	emulation for event loops that do not support them natively. Also,
1471	some event loops install a similar handler.	1723	some event loops install a similar handler.
		1724
		1725	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1726	then AnyEvent will reset it to default, to avoid losing child exit
		1727	statuses.
1472		1728
1473	SIGPIPE	1729	SIGPIPE
1474	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is	1730	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1475	"undef" when AnyEvent gets loaded.	1731	"undef" when AnyEvent gets loaded.
1476		1732
…		…
1484	it is that this way, the handler will be restored to defaults on	1740	it is that this way, the handler will be restored to defaults on
1485	exec.	1741	exec.
1486		1742
1487	Feel free to install your own handler, or reset it to defaults.	1743	Feel free to install your own handler, or reset it to defaults.
1488		1744
		1745	RECOMMENDED/OPTIONAL MODULES
		1746	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1747	its built-in modules) are required to use it.
		1748
		1749	That does not mean that AnyEvent won't take advantage of some additional
		1750	modules if they are installed.
		1751
		1752	This section explains which additional modules will be used, and how
		1753	they affect AnyEvent's operation.
		1754
		1755	Async::Interrupt
		1756	This slightly arcane module is used to implement fast signal
		1757	handling: To my knowledge, there is no way to do completely
		1758	race-free and quick signal handling in pure perl. To ensure that
		1759	signals still get delivered, AnyEvent will start an interval timer
		1760	to wake up perl (and catch the signals) with some delay (default is
		1761	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1762
		1763	If this module is available, then it will be used to implement
		1764	signal catching, which means that signals will not be delayed, and
		1765	the event loop will not be interrupted regularly, which is more
		1766	efficient (and good for battery life on laptops).
		1767
		1768	This affects not just the pure-perl event loop, but also other event
		1769	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1770
		1771	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1772	natively, and either employ their own workarounds (POE) or use
		1773	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1774	Installing Async::Interrupt does nothing for those backends.
		1775
		1776	EV This module isn't really "optional", as it is simply one of the
		1777	backend event loops that AnyEvent can use. However, it is simply the
		1778	best event loop available in terms of features, speed and stability:
		1779	It supports the AnyEvent API optimally, implements all the watcher
		1780	types in XS, does automatic timer adjustments even when no monotonic
		1781	clock is available, can take avdantage of advanced kernel interfaces
		1782	such as "epoll" and "kqueue", and is the fastest backend *by far*.
		1783	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1784	Glib::EV).
		1785
		1786	If you only use backends that rely on another event loop (e.g.
		1787	"Tk"), then this module will do nothing for you.
		1788
		1789	Guard
		1790	The guard module, when used, will be used to implement
		1791	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1792	uses a lot less memory), but otherwise doesn't affect guard
		1793	operation much. It is purely used for performance.
		1794
		1795	JSON and JSON::XS
		1796	One of these modules is required when you want to read or write JSON
		1797	data via AnyEvent::Handle. JSON is also written in pure-perl, but
		1798	can take advantage of the ultra-high-speed JSON::XS module when it
		1799	is installed.
		1800
		1801	Net::SSLeay
		1802	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1803	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1804	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1805
		1806	Time::HiRes
		1807	This module is part of perl since release 5.008. It will be used
		1808	when the chosen event library does not come with a timing source of
		1809	its own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1810	additionally use it to try to use a monotonic clock for timing
		1811	stability.
		1812
1489	FORK	1813	FORK
1490	Most event libraries are not fork-safe. The ones who are usually are	1814	Most event libraries are not fork-safe. The ones who are usually are
1491	because they rely on inefficient but fork-safe "select" or "poll" calls.	1815	because they rely on inefficient but fork-safe "select" or "poll" calls
1492	Only EV is fully fork-aware.	1816	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		1817	epoll are usually badly thought-out hacks that are incompatible with
		1818	fork in one way or another. Only EV is fully fork-aware and ensures that
		1819	you continue event-processing in both parent and child (or both, if you
		1820	know what you are doing).
		1821
		1822	This means that, in general, you cannot fork and do event processing in
		1823	the child if the event library was initialised before the fork (which
		1824	usually happens when the first AnyEvent watcher is created, or the
		1825	library is loaded).
1493		1826
1494	If you have to fork, you must either do so *before* creating your first	1827	If you have to fork, you must either do so *before* creating your first
1495	watcher OR you must not use AnyEvent at all in the child.	1828	watcher OR you must not use AnyEvent at all in the child OR you must do
		1829	something completely out of the scope of AnyEvent.
		1830
		1831	The problem of doing event processing in the parent *and* the child is
		1832	much more complicated: even for backends that *are* fork-aware or
		1833	fork-safe, their behaviour is not usually what you want: fork clones all
		1834	watchers, that means all timers, I/O watchers etc. are active in both
		1835	parent and child, which is almost never what you want. USing "exec" to
		1836	start worker children from some kind of manage rprocess is usually
		1837	preferred, because it is much easier and cleaner, at the expense of
		1838	having to have another binary.
1496		1839
1497	SECURITY CONSIDERATIONS	1840	SECURITY CONSIDERATIONS
1498	AnyEvent can be forced to load any event model via	1841	AnyEvent can be forced to load any event model via
1499	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1842	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1500	to execute arbitrary code or directly gain access, it can easily be used	1843	to execute arbitrary code or directly gain access, it can easily be used
…		…
1512	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1855	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1513	be used to probe what backend is used and gain other information (which	1856	be used to probe what backend is used and gain other information (which
1514	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),	1857	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1515	and $ENV{PERL_ANYEVENT_STRICT}.	1858	and $ENV{PERL_ANYEVENT_STRICT}.
1516		1859
		1860	Note that AnyEvent will remove *all* environment variables starting with
		1861	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1862	enabled.
		1863
1517	BUGS	1864	BUGS
1518	Perl 5.8 has numerous memleaks that sometimes hit this module and are	1865	Perl 5.8 has numerous memleaks that sometimes hit this module and are
1519	hard to work around. If you suffer from memleaks, first upgrade to Perl	1866	hard to work around. If you suffer from memleaks, first upgrade to Perl
1520	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	1867	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1521	annoying memleaks, such as leaking on "map" and "grep" but it is usually	1868	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1522	not as pronounced).	1869	not as pronounced).
1523		1870
1524	SEE ALSO	1871	SEE ALSO
		1872	Tutorial/Introduction: AnyEvent::Intro.
		1873
		1874	FAQ: AnyEvent::FAQ.
		1875
1525	Utility functions: AnyEvent::Util.	1876	Utility functions: AnyEvent::Util.
1526		1877
1527	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1878	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1528	Event::Lib, Qt, POE.	1879	Event::Lib, Qt, POE.
1529		1880
1530	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1881	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1531	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1882	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1532	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1883	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1884	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1533		1885
1534	Non-blocking file handles, sockets, TCP clients and servers:	1886	Non-blocking file handles, sockets, TCP clients and servers:
1535	AnyEvent::Handle, AnyEvent::Socket.	1887	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1536		1888
1537	Asynchronous DNS: AnyEvent::DNS.	1889	Asynchronous DNS: AnyEvent::DNS.
1538		1890
1539	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1891	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1540		1892
1541	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1893	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
		1894	AnyEvent::HTTP.
1542		1895
1543	AUTHOR	1896	AUTHOR
1544	Marc Lehmann <schmorp@schmorp.de>	1897	Marc Lehmann <schmorp@schmorp.de>
1545	http://home.schmorp.de/	1898	http://home.schmorp.de/
1546		1899

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