[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.44 by root, Fri Jul 10 22:35:27 2009 UTC vs.
Revision 1.63 by root, Wed Oct 13 19:49:46 2010 UTC

…		…
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 + IO::Async? No go. Tk + Event? No go. Again: if your
74	module uses one of those, every user of your module has to use it, too.	86	module uses one of those, every user of your module has to use it, too.
75	But if your module uses AnyEvent, it works transparently with all event	87	But if your module uses AnyEvent, it works transparently with all event
76	models it supports (including stuff like IO::Async, as long as those use	88	models it supports (including stuff like IO::Async, as long as those use
77	one of the supported event loops. It is trivial to add new event loops	89	one of 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 (or a naked 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
…		…
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
…		…
390	of when you start the watcher.	464	of when you start the watcher.
391		465
392	This means you cannot create a child watcher as the very first thing in	466	This means you cannot create a child watcher as the very first thing in
393	an AnyEvent program, you have to create at least one watcher before	467	an AnyEvent program, you have to create at least one watcher before
394	you "fork" the child (alternatively, you can call "AnyEvent::detect").	468	you "fork" the child (alternatively, you can call "AnyEvent::detect").
		469
		470	As most event loops do not support waiting for child events, they will
		471	be emulated by AnyEvent in most cases, in which the latency and race
		472	problems mentioned in the description of signal watchers apply.
395		473
396	Example: fork a process and wait for it	474	Example: fork a process and wait for it
397		475
398	my $done = AnyEvent->condvar;	476	my $done = AnyEvent->condvar;
399		477
…		…
410		488
411	# do something else, then wait for process exit	489	# do something else, then wait for process exit
412	$done->recv;	490	$done->recv;
413		491
414	IDLE WATCHERS	492	IDLE WATCHERS
415	Sometimes there is a need to do something, but it is not so important to	493	$w = AnyEvent->idle (cb => <callback>);
416	do it instantly, but only when there is nothing better to do. This
417	"nothing better to do" is usually defined to be "no other events need
418	attention by the event loop".
419		494
420	Idle watchers ideally get invoked when the event loop has nothing better	495	This will repeatedly invoke the callback after the process becomes idle,
421	to do, just before it would block the process to wait for new events.	496	until either the watcher is destroyed or new events have been detected.
422	Instead of blocking, the idle watcher is invoked.
423		497
424	Most event loops unfortunately do not really support idle watchers (only	498	Idle watchers are useful when there is a need to do something, but it is
		499	not so important (or wise) to do it instantly. The callback will be
		500	invoked only when there is "nothing better to do", which is usually
		501	defined as "all outstanding events have been handled and no new events
		502	have been detected". That means that idle watchers ideally get invoked
		503	when the event loop has just polled for new events but none have been
		504	detected. Instead of blocking to wait for more events, the idle watchers
		505	will be invoked.
		506
		507	Unfortunately, most event loops do not really support idle watchers
425	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent	508	(only EV, Event and Glib do it in a usable fashion) - for the rest,
426	will simply call the callback "from time to time".	509	AnyEvent will simply call the callback "from time to time".
427		510
428	Example: read lines from STDIN, but only process them when the program	511	Example: read lines from STDIN, but only process them when the program
429	is otherwise idle:	512	is otherwise idle:
430		513
431	my @lines; # read data	514	my @lines; # read data
…		…
444	}	527	}
445	});	528	});
446	});	529	});
447		530
448	CONDITION VARIABLES	531	CONDITION VARIABLES
		532	$cv = AnyEvent->condvar;
		533
		534	$cv->send (<list>);
		535	my @res = $cv->recv;
		536
449	If you are familiar with some event loops you will know that all of them	537	If you are familiar with some event loops you will know that all of them
450	require you to run some blocking "loop", "run" or similar function that	538	require you to run some blocking "loop", "run" or similar function that
451	will actively watch for new events and call your callbacks.	539	will actively watch for new events and call your callbacks.
452		540
453	AnyEvent is different, it expects somebody else to run the event loop	541	AnyEvent is slightly different: it expects somebody else to run the
454	and will only block when necessary (usually when told by the user).	542	event loop and will only block when necessary (usually when told by the
		543	user).
455		544
456	The instrument to do that is called a "condition variable", so called	545	The tool to do that is called a "condition variable", so called because
457	because they represent a condition that must become true.	546	they represent a condition that must become true.
		547
		548	Now is probably a good time to look at the examples further below.
458		549
459	Condition variables can be created by calling the "AnyEvent->condvar"	550	Condition variables can be created by calling the "AnyEvent->condvar"
460	method, usually without arguments. The only argument pair allowed is	551	method, usually without arguments. The only argument pair allowed is
461
462	"cb", which specifies a callback to be called when the condition	552	"cb", which specifies a callback to be called when the condition
463	variable becomes true, with the condition variable as the first argument	553	variable becomes true, with the condition variable as the first argument
464	(but not the results).	554	(but not the results).
465		555
466	After creation, the condition variable is "false" until it becomes	556	After creation, the condition variable is "false" until it becomes
467	"true" by calling the "send" method (or calling the condition variable	557	"true" by calling the "send" method (or calling the condition variable
468	as if it were a callback, read about the caveats in the description for	558	as if it were a callback, read about the caveats in the description for
469	the "->send" method).	559	the "->send" method).
470		560
471	Condition variables are similar to callbacks, except that you can	561	Since condition variables are the most complex part of the AnyEvent API,
472	optionally wait for them. They can also be called merge points - points	562	here are some different mental models of what they are - pick the ones
473	in time where multiple outstanding events have been processed. And yet	563	you can connect to:
474	another way to call them is transactions - each condition variable can	564
475	be used to represent a transaction, which finishes at some point and	565	* Condition variables are like callbacks - you can call them (and pass
476	delivers a result.	566	them instead of callbacks). Unlike callbacks however, you can also
		567	wait for them to be called.
		568
		569	* Condition variables are signals - one side can emit or send them,
		570	the other side can wait for them, or install a handler that is
		571	called when the signal fires.
		572
		573	* Condition variables are like "Merge Points" - points in your program
		574	where you merge multiple independent results/control flows into one.
		575
		576	* Condition variables represent a transaction - functions that start
		577	some kind of transaction can return them, leaving the caller the
		578	choice between waiting in a blocking fashion, or setting a callback.
		579
		580	* Condition variables represent future values, or promises to deliver
		581	some result, long before the result is available.
477		582
478	Condition variables are very useful to signal that something has	583	Condition variables are very useful to signal that something has
479	finished, for example, if you write a module that does asynchronous http	584	finished, for example, if you write a module that does asynchronous http
480	requests, then a condition variable would be the ideal candidate to	585	requests, then a condition variable would be the ideal candidate to
481	signal the availability of results. The user can either act when the	586	signal the availability of results. The user can either act when the
…		…
494		599
495	Condition variables are represented by hash refs in perl, and the keys	600	Condition variables are represented by hash refs in perl, and the keys
496	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy	601	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy
497	(it is often useful to build your own transaction class on top of	602	(it is often useful to build your own transaction class on top of
498	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	603	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
499	it's "new" method in your own "new" method.	604	its "new" method in your own "new" method.
500		605
501	There are two "sides" to a condition variable - the "producer side"	606	There are two "sides" to a condition variable - the "producer side"
502	which eventually calls "-> send", and the "consumer side", which waits	607	which eventually calls "-> send", and the "consumer side", which waits
503	for the send to occur.	608	for the send to occur.
504		609
505	Example: wait for a timer.	610	Example: wait for a timer.
506		611
507	# wait till the result is ready	612	# condition: "wait till the timer is fired"
508	my $result_ready = AnyEvent->condvar;	613	my $timer_fired = AnyEvent->condvar;
509		614
510	# do something such as adding a timer	615	# create the timer - we could wait for, say
511	# or socket watcher the calls $result_ready->send	616	# a handle becomign ready, or even an
512	# when the "result" is ready.	617	# AnyEvent::HTTP request to finish, but
513	# in this case, we simply use a timer:	618	# in this case, we simply use a timer:
514	my $w = AnyEvent->timer (	619	my $w = AnyEvent->timer (
515	after => 1,	620	after => 1,
516	cb => sub { $result_ready->send },	621	cb => sub { $timer_fired->send },
517	);	622	);
518		623
519	# this "blocks" (while handling events) till the callback	624	# this "blocks" (while handling events) till the callback
520	# calls send	625	# calls ->send
521	$result_ready->recv;	626	$timer_fired->recv;
522		627
523	Example: wait for a timer, but take advantage of the fact that condition	628	Example: wait for a timer, but take advantage of the fact that condition
524	variables are also code references.	629	variables are also callable directly.
525		630
526	my $done = AnyEvent->condvar;	631	my $done = AnyEvent->condvar;
527	my $delay = AnyEvent->timer (after => 5, cb => $done);	632	my $delay = AnyEvent->timer (after => 5, cb => $done);
528	$done->recv;	633	$done->recv;
529		634
…		…
535		640
536	...	641	...
537		642
538	my @info = $couchdb->info->recv;	643	my @info = $couchdb->info->recv;
539		644
540	And this is how you would just ste a callback to be called whenever the	645	And this is how you would just set a callback to be called whenever the
541	results are available:	646	results are available:
542		647
543	$couchdb->info->cb (sub {	648	$couchdb->info->cb (sub {
544	my @info = $_[0]->recv;	649	my @info = $_[0]->recv;
545	});	650	});
…		…
560		665
561	Any arguments passed to the "send" call will be returned by all	666	Any arguments passed to the "send" call will be returned by all
562	future "->recv" calls.	667	future "->recv" calls.
563		668
564	Condition variables are overloaded so one can call them directly (as	669	Condition variables are overloaded so one can call them directly (as
565	a code reference). Calling them directly is the same as calling	670	if they were a code reference). Calling them directly is the same as
566	"send". Note, however, that many C-based event loops do not handle	671	calling "send".
567	overloading, so as tempting as it may be, passing a condition
568	variable instead of a callback does not work. Both the pure perl and
569	EV loops support overloading, however, as well as all functions that
570	use perl to invoke a callback (as in AnyEvent::Socket and
571	AnyEvent::DNS for example).
572		672
573	$cv->croak ($error)	673	$cv->croak ($error)
574	Similar to send, but causes all call's to "->recv" to invoke	674	Similar to send, but causes all calls to "->recv" to invoke
575	"Carp::croak" with the given error message/object/scalar.	675	"Carp::croak" with the given error message/object/scalar.
576		676
577	This can be used to signal any errors to the condition variable	677	This can be used to signal any errors to the condition variable
578	user/consumer.	678	user/consumer. Doing it this way instead of calling "croak" directly
		679	delays the error detection, but has the overwhelming advantage that
		680	it diagnoses the error at the place where the result is expected,
		681	and not deep in some event callback with no connection to the actual
		682	code causing the problem.
579		683
580	$cv->begin ([group callback])	684	$cv->begin ([group callback])
581	$cv->end	685	$cv->end
582	These two methods can be used to combine many transactions/events	686	These two methods can be used to combine many transactions/events
583	into one. For example, a function that pings many hosts in parallel	687	into one. For example, a function that pings many hosts in parallel
584	might want to use a condition variable for the whole process.	688	might want to use a condition variable for the whole process.
585		689
586	Every call to "->begin" will increment a counter, and every call to	690	Every call to "->begin" will increment a counter, and every call to
587	"->end" will decrement it. If the counter reaches 0 in "->end", the	691	"->end" will decrement it. If the counter reaches 0 in "->end", the
588	(last) callback passed to "begin" will be executed. That callback is	692	(last) callback passed to "begin" will be executed, passing the
589	supposed to call "->send", but that is not required. If no	693	condvar as first argument. That callback is supposed to call
		694	"->send", but that is not required. If no group callback was set,
590	callback was set, "send" will be called without any arguments.	695	"send" will be called without any arguments.
591		696
592	You can think of "$cv->send" giving you an OR condition (one call	697	You can think of "$cv->send" giving you an OR condition (one call
593	sends), while "$cv->begin" and "$cv->end" giving you an AND	698	sends), while "$cv->begin" and "$cv->end" giving you an AND
594	condition (all "begin" calls must be "end"'ed before the condvar	699	condition (all "begin" calls must be "end"'ed before the condvar
595	sends).	700	sends).
…		…
618	there is one call to "begin", so the condvar waits for all calls to	723	there is one call to "begin", so the condvar waits for all calls to
619	"end" before sending.	724	"end" before sending.
620		725
621	The ping example mentioned above is slightly more complicated, as	726	The ping example mentioned above is slightly more complicated, as
622	the there are results to be passwd back, and the number of tasks	727	the there are results to be passwd back, and the number of tasks
623	that are begung can potentially be zero:	728	that are begun can potentially be zero:
624		729
625	my $cv = AnyEvent->condvar;	730	my $cv = AnyEvent->condvar;
626		731
627	my %result;	732	my %result;
628	$cv->begin (sub { $cv->send (\%result) });	733	$cv->begin (sub { shift->send (\%result) });
629		734
630	for my $host (@list_of_hosts) {	735	for my $host (@list_of_hosts) {
631	$cv->begin;	736	$cv->begin;
632	ping_host_then_call_callback $host, sub {	737	ping_host_then_call_callback $host, sub {
633	$result{$host} = ...;	738	$result{$host} = ...;
…		…
649	callback to be called once the counter reaches 0, and second, it	754	callback to be called once the counter reaches 0, and second, it
650	ensures that "send" is called even when "no" hosts are being pinged	755	ensures that "send" is called even when "no" hosts are being pinged
651	(the loop doesn't execute once).	756	(the loop doesn't execute once).
652		757
653	This is the general pattern when you "fan out" into multiple (but	758	This is the general pattern when you "fan out" into multiple (but
654	potentially none) subrequests: use an outer "begin"/"end" pair to	759	potentially zero) subrequests: use an outer "begin"/"end" pair to
655	set the callback and ensure "end" is called at least once, and then,	760	set the callback and ensure "end" is called at least once, and then,
656	for each subrequest you start, call "begin" and for each subrequest	761	for each subrequest you start, call "begin" and for each subrequest
657	you finish, call "end".	762	you finish, call "end".
658		763
659	METHODS FOR CONSUMERS	764	METHODS FOR CONSUMERS
660	These methods should only be used by the consuming side, i.e. the code	765	These methods should only be used by the consuming side, i.e. the code
661	awaits the condition.	766	awaits the condition.
662		767
663	$cv->recv	768	$cv->recv
664	Wait (blocking if necessary) until the "->send" or "->croak" methods	769	Wait (blocking if necessary) until the "->send" or "->croak" methods
665	have been called on c<$cv>, while servicing other watchers normally.	770	have been called on $cv, while servicing other watchers normally.
666		771
667	You can only wait once on a condition - additional calls are valid	772	You can only wait once on a condition - additional calls are valid
668	but will return immediately.	773	but will return immediately.
669		774
670	If an error condition has been set by calling "->croak", then this	775	If an error condition has been set by calling "->croak", then this
671	function will call "croak".	776	function will call "croak".
672		777
673	In list context, all parameters passed to "send" will be returned,	778	In list context, all parameters passed to "send" will be returned,
674	in scalar context only the first one will be returned.	779	in scalar context only the first one will be returned.
675		780
		781	Note that doing a blocking wait in a callback is not supported by
		782	any event loop, that is, recursive invocation of a blocking "->recv"
		783	is not allowed, and the "recv" call will "croak" if such a condition
		784	is detected. This condition can be slightly loosened by using
		785	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		786	thread that doesn't run the event loop itself.
		787
676	Not all event models support a blocking wait - some die in that case	788	Not all event models support a blocking wait - some die in that case
677	(programs might want to do that to stay interactive), so *if you are	789	(programs might want to do that to stay interactive), so *if you are
678	using this from a module, never require a blocking wait*, but let	790	using this from a module, never require a blocking wait*. Instead,
679	the caller decide whether the call will block or not (for example,	791	let the caller decide whether the call will block or not (for
680	by coupling condition variables with some kind of request results	792	example, by coupling condition variables with some kind of request
681	and supporting callbacks so the caller knows that getting the result	793	results and supporting callbacks so the caller knows that getting
682	will not block, while still supporting blocking waits if the caller	794	the result will not block, while still supporting blocking waits if
683	so desires).	795	the caller so desires).
684		796
685	Another reason never to "->recv" in a module is that you cannot
686	sensibly have two "->recv"'s in parallel, as that would require
687	multiple interpreters or coroutines/threads, none of which
688	"AnyEvent" can supply.
689
690	The Coro module, however, can and does supply coroutines and, in
691	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
692	versions and also integrates coroutines into AnyEvent, making
693	blocking "->recv" calls perfectly safe as long as they are done from
694	another coroutine (one that doesn't run the event loop).
695
696	You can ensure that "-recv" never blocks by setting a callback and	797	You can ensure that "->recv" never blocks by setting a callback and
697	only calling "->recv" from within that callback (or at a later	798	only calling "->recv" from within that callback (or at a later
698	time). This will work even when the event loop does not support	799	time). This will work even when the event loop does not support
699	blocking waits otherwise.	800	blocking waits otherwise.
700		801
701	$bool = $cv->ready	802	$bool = $cv->ready
…		…
706	This is a mutator function that returns the callback set and	807	This is a mutator function that returns the callback set and
707	optionally replaces it before doing so.	808	optionally replaces it before doing so.
708		809
709	The callback will be called when the condition becomes "true", i.e.	810	The callback will be called when the condition becomes "true", i.e.
710	when "send" or "croak" are called, with the only argument being the	811	when "send" or "croak" are called, with the only argument being the
711	condition variable itself. Calling "recv" inside the callback or at	812	condition variable itself. If the condition is already true, the
		813	callback is called immediately when it is set. Calling "recv" inside
712	any later time is guaranteed not to block.	814	the callback or at any later time is guaranteed not to block.
713		815
714	SUPPORTED EVENT LOOPS/BACKENDS	816	SUPPORTED EVENT LOOPS/BACKENDS
715	The available backend classes are (every class has its own manpage):	817	The available backend classes are (every class has its own manpage):
716		818
717	Backends that are autoprobed when no other event loop can be found.	819	Backends that are autoprobed when no other event loop can be found.
718	EV is the preferred backend when no other event loop seems to be in	820	EV is the preferred backend when no other event loop seems to be in
719	use. If EV is not installed, then AnyEvent will try Event, and,	821	use. If EV is not installed, then AnyEvent will fall back to its own
720	failing that, will fall back to its own pure-perl implementation,	822	pure-perl implementation, which is available everywhere as it comes
721	which is available everywhere as it comes with AnyEvent itself.	823	with AnyEvent itself.
722		824
723	AnyEvent::Impl::EV based on EV (interface to libev, best choice).	825	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
724	AnyEvent::Impl::Event based on Event, very stable, few glitches.
725	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.	826	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
726		827
727	Backends that are transparently being picked up when they are used.	828	Backends that are transparently being picked up when they are used.
728	These will be used when they are currently loaded when the first	829	These will be used if they are already loaded when the first watcher
729	watcher is created, in which case it is assumed that the application	830	is created, in which case it is assumed that the application is
730	is using them. This means that AnyEvent will automatically pick the	831	using them. This means that AnyEvent will automatically pick the
731	right backend when the main program loads an event module before	832	right backend when the main program loads an event module before
732	anything starts to create watchers. Nothing special needs to be done	833	anything starts to create watchers. Nothing special needs to be done
733	by the main program.	834	by the main program.
734		835
		836	AnyEvent::Impl::Event based on Event, very stable, few glitches.
735	AnyEvent::Impl::Glib based on Glib, slow but very stable.	837	AnyEvent::Impl::Glib based on Glib, slow but very stable.
736	AnyEvent::Impl::Tk based on Tk, very broken.	838	AnyEvent::Impl::Tk based on Tk, very broken.
737	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	839	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
738	AnyEvent::Impl::POE based on POE, very slow, some limitations.	840	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		841	AnyEvent::Impl::Irssi used when running within irssi.
739		842
740	Backends with special needs.	843	Backends with special needs.
741	Qt requires the Qt::Application to be instantiated first, but will	844	Qt requires the Qt::Application to be instantiated first, but will
742	otherwise be picked up automatically. As long as the main program	845	otherwise be picked up automatically. As long as the main program
743	instantiates the application before any AnyEvent watchers are	846	instantiates the application before any AnyEvent watchers are
…		…
747		850
748	Support for IO::Async can only be partial, as it is too broken and	851	Support for IO::Async can only be partial, as it is too broken and
749	architecturally limited to even support the AnyEvent API. It also is	852	architecturally limited to even support the AnyEvent API. It also is
750	the only event loop that needs the loop to be set explicitly, so it	853	the only event loop that needs the loop to be set explicitly, so it
751	can only be used by a main program knowing about AnyEvent. See	854	can only be used by a main program knowing about AnyEvent. See
752	AnyEvent::Impl::Async for the gory details.	855	AnyEvent::Impl::IOAsync for the gory details.
753		856
754	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.	857	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
755		858
756	Event loops that are indirectly supported via other backends.	859	Event loops that are indirectly supported via other backends.
757	Some event loops can be supported via other modules:	860	Some event loops can be supported via other modules:
…		…
778	Contains "undef" until the first watcher is being created, before	881	Contains "undef" until the first watcher is being created, before
779	the backend has been autodetected.	882	the backend has been autodetected.
780		883
781	Afterwards it contains the event model that is being used, which is	884	Afterwards it contains the event model that is being used, which is
782	the name of the Perl class implementing the model. This class is	885	the name of the Perl class implementing the model. This class is
783	usually one of the "AnyEvent::Impl:xxx" modules, but can be any	886	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
784	other class in the case AnyEvent has been extended at runtime (e.g.	887	other class in the case AnyEvent has been extended at runtime (e.g.
785	in rxvt-unicode it will be "urxvt::anyevent").	888	in rxvt-unicode it will be "urxvt::anyevent").
786		889
787	AnyEvent::detect	890	AnyEvent::detect
788	Returns $AnyEvent::MODEL, forcing autodetection of the event model	891	Returns $AnyEvent::MODEL, forcing autodetection of the event model
789	if necessary. You should only call this function right before you	892	if necessary. You should only call this function right before you
790	would have created an AnyEvent watcher anyway, that is, as late as	893	would have created an AnyEvent watcher anyway, that is, as late as
791	possible at runtime, and not e.g. while initialising of your module.	894	possible at runtime, and not e.g. during initialisation of your
		895	module.
792		896
793	If you need to do some initialisation before AnyEvent watchers are	897	If you need to do some initialisation before AnyEvent watchers are
794	created, use "post_detect".	898	created, use "post_detect".
795		899
796	$guard = AnyEvent::post_detect { BLOCK }	900	$guard = AnyEvent::post_detect { BLOCK }
797	Arranges for the code block to be executed as soon as the event	901	Arranges for the code block to be executed as soon as the event
798	model is autodetected (or immediately if this has already happened).	902	model is autodetected (or immediately if that has already happened).
799		903
800	The block will be executed after the actual backend has been	904	The block will be executed after the actual backend has been
801	detected ($AnyEvent::MODEL is set), but before any watchers have	905	detected ($AnyEvent::MODEL is set), but before any watchers have
802	been created, so it is possible to e.g. patch @AnyEvent::ISA or do	906	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
803	other initialisations - see the sources of AnyEvent::Strict or	907	other initialisations - see the sources of AnyEvent::Strict or
…		…
808	creates and installs the global IO::AIO watcher in a "post_detect"	912	creates and installs the global IO::AIO watcher in a "post_detect"
809	block to avoid autodetecting the event module at load time.	913	block to avoid autodetecting the event module at load time.
810		914
811	If called in scalar or list context, then it creates and returns an	915	If called in scalar or list context, then it creates and returns an
812	object that automatically removes the callback again when it is	916	object that automatically removes the callback again when it is
		917	destroyed (or "undef" when the hook was immediately executed). See
813	destroyed. See Coro::BDB for a case where this is useful.	918	AnyEvent::AIO for a case where this is useful.
		919
		920	Example: Create a watcher for the IO::AIO module and store it in
		921	$WATCHER, but do so only do so after the event loop is initialised.
		922
		923	our WATCHER;
		924
		925	my $guard = AnyEvent::post_detect {
		926	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		927	};
		928
		929	# the \|\|= is important in case post_detect immediately runs the block,
		930	# as to not clobber the newly-created watcher. assigning both watcher and
		931	# post_detect guard to the same variable has the advantage of users being
		932	# able to just C<undef $WATCHER> if the watcher causes them grief.
		933
		934	$WATCHER \|\|= $guard;
814		935
815	@AnyEvent::post_detect	936	@AnyEvent::post_detect
816	If there are any code references in this array (you can "push" to it	937	If there are any code references in this array (you can "push" to it
817	before or after loading AnyEvent), then they will called directly	938	before or after loading AnyEvent), then they will be called directly
818	after the event loop has been chosen.	939	after the event loop has been chosen.
819		940
820	You should check $AnyEvent::MODEL before adding to this array,	941	You should check $AnyEvent::MODEL before adding to this array,
821	though: if it is defined then the event loop has already been	942	though: if it is defined then the event loop has already been
822	detected, and the array will be ignored.	943	detected, and the array will be ignored.
823		944
824	Best use "AnyEvent::post_detect { BLOCK }" when your application	945	Best use "AnyEvent::post_detect { BLOCK }" when your application
825	allows it,as it takes care of these details.	946	allows it, as it takes care of these details.
826		947
827	This variable is mainly useful for modules that can do something	948	This variable is mainly useful for modules that can do something
828	useful when AnyEvent is used and thus want to know when it is	949	useful when AnyEvent is used and thus want to know when it is
829	initialised, but do not need to even load it by default. This array	950	initialised, but do not need to even load it by default. This array
830	provides the means to hook into AnyEvent passively, without loading	951	provides the means to hook into AnyEvent passively, without loading
831	it.	952	it.
832		953
		954	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		955	together, you could put this into Coro (this is the actual code used
		956	by Coro to accomplish this):
		957
		958	if (defined $AnyEvent::MODEL) {
		959	# AnyEvent already initialised, so load Coro::AnyEvent
		960	require Coro::AnyEvent;
		961	} else {
		962	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		963	# as soon as it is
		964	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		965	}
		966
833	WHAT TO DO IN A MODULE	967	WHAT TO DO IN A MODULE
834	As a module author, you should "use AnyEvent" and call AnyEvent methods	968	As a module author, you should "use AnyEvent" and call AnyEvent methods
835	freely, but you should not load a specific event module or rely on it.	969	freely, but you should not load a specific event module or rely on it.
836		970
837	Be careful when you create watchers in the module body - AnyEvent will	971	Be careful when you create watchers in the module body - AnyEvent will
…		…
844	stall the whole program, and the whole point of using events is to stay	978	stall the whole program, and the whole point of using events is to stay
845	interactive.	979	interactive.
846		980
847	It is fine, however, to call "->recv" when the user of your module	981	It is fine, however, to call "->recv" when the user of your module
848	requests it (i.e. if you create a http request object ad have a method	982	requests it (i.e. if you create a http request object ad have a method
849	called "results" that returns the results, it should call "->recv"	983	called "results" that returns the results, it may call "->recv" freely,
850	freely, as the user of your module knows what she is doing. always).	984	as the user of your module knows what she is doing. Always).
851		985
852	WHAT TO DO IN THE MAIN PROGRAM	986	WHAT TO DO IN THE MAIN PROGRAM
853	There will always be a single main program - the only place that should	987	There will always be a single main program - the only place that should
854	dictate which event model to use.	988	dictate which event model to use.
855		989
856	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	990	If the program is not event-based, it need not do anything special, even
857	do anything special (it does not need to be event-based) and let	991	when it depends on a module that uses an AnyEvent. If the program itself
858	AnyEvent decide which implementation to chose if some module relies on	992	uses AnyEvent, but does not care which event loop is used, all it needs
859	it.	993	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		994	available loop implementation.
860		995
861	If the main program relies on a specific event model - for example, in	996	If the main program relies on a specific event model - for example, in
862	Gtk2 programs you have to rely on the Glib module - you should load the	997	Gtk2 programs you have to rely on the Glib module - you should load the
863	event module before loading AnyEvent or any module that uses it:	998	event module before loading AnyEvent or any module that uses it:
864	generally speaking, you should load it as early as possible. The reason	999	generally speaking, you should load it as early as possible. The reason
865	is that modules might create watchers when they are loaded, and AnyEvent	1000	is that modules might create watchers when they are loaded, and AnyEvent
866	will decide on the event model to use as soon as it creates watchers,	1001	will decide on the event model to use as soon as it creates watchers,
867	and it might chose the wrong one unless you load the correct one	1002	and it might choose the wrong one unless you load the correct one
868	yourself.	1003	yourself.
869		1004
870	You can chose to use a pure-perl implementation by loading the	1005	You can chose to use a pure-perl implementation by loading the
871	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1006	"AnyEvent::Impl::Perl" module, which gives you similar behaviour
872	everywhere, but letting AnyEvent chose the model is generally better.	1007	everywhere, but letting AnyEvent chose the model is generally better.
…		…
889		1024
890	OTHER MODULES	1025	OTHER MODULES
891	The following is a non-exhaustive list of additional modules that use	1026	The following is a non-exhaustive list of additional modules that use
892	AnyEvent as a client and can therefore be mixed easily with other	1027	AnyEvent as a client and can therefore be mixed easily with other
893	AnyEvent modules and other event loops in the same program. Some of the	1028	AnyEvent modules and other event loops in the same program. Some of the
894	modules come with AnyEvent, most are available via CPAN.	1029	modules come as part of AnyEvent, the others are available via CPAN.
895		1030
896	AnyEvent::Util	1031	AnyEvent::Util
897	Contains various utility functions that replace often-used but	1032	Contains various utility functions that replace often-used blocking
898	blocking functions such as "inet_aton" by event-/callback-based	1033	functions such as "inet_aton" with event/callback-based versions.
899	versions.
900		1034
901	AnyEvent::Socket	1035	AnyEvent::Socket
902	Provides various utility functions for (internet protocol) sockets,	1036	Provides various utility functions for (internet protocol) sockets,
903	addresses and name resolution. Also functions to create non-blocking	1037	addresses and name resolution. Also functions to create non-blocking
904	tcp connections or tcp servers, with IPv6 and SRV record support and	1038	tcp connections or tcp servers, with IPv6 and SRV record support and
905	more.	1039	more.
906		1040
907	AnyEvent::Handle	1041	AnyEvent::Handle
908	Provide read and write buffers, manages watchers for reads and	1042	Provide read and write buffers, manages watchers for reads and
909	writes, supports raw and formatted I/O, I/O queued and fully	1043	writes, supports raw and formatted I/O, I/O queued and fully
910	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.	1044	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
911		1045
912	AnyEvent::DNS	1046	AnyEvent::DNS
913	Provides rich asynchronous DNS resolver capabilities.	1047	Provides rich asynchronous DNS resolver capabilities.
914		1048
		1049	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
		1050	AnyEvent::IGS, AnyEvent::FCP
		1051	Implement event-based interfaces to the protocols of the same name
		1052	(for the curious, IGS is the International Go Server and FCP is the
		1053	Freenet Client Protocol).
		1054
		1055	AnyEvent::Handle::UDP
		1056	Here be danger!
		1057
		1058	As Pauli would put it, "Not only is it not right, it's not even
		1059	wrong!" - there are so many things wrong with AnyEvent::Handle::UDP,
		1060	most notably its use of a stream-based API with a protocol that
		1061	isn't streamable, that the only way to improve it is to delete it.
		1062
		1063	It features data corruption (but typically only under load) and
		1064	general confusion. On top, the author is not only clueless about UDP
		1065	but also fact-resistant - some gems of his understanding: "connect
		1066	doesn't work with UDP", "UDP packets are not IP packets", "UDP only
		1067	has datagrams, not packets", "I don't need to implement proper error
		1068	checking as UDP doesn't support error checking" and so on - he
		1069	doesn't even understand what's wrong with his module when it is
		1070	explained to him.
		1071
915	AnyEvent::HTTP	1072	AnyEvent::DBI
916	A simple-to-use HTTP library that is capable of making a lot of	1073	Executes DBI requests asynchronously in a proxy process for you,
917	concurrent HTTP requests.	1074	notifying you in an event-based way when the operation is finished.
		1075
		1076	AnyEvent::AIO
		1077	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1078	the toolbox of every event programmer. AnyEvent::AIO transparently
		1079	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1080	event-based file I/O, and much more.
918		1081
919	AnyEvent::HTTPD	1082	AnyEvent::HTTPD
920	Provides a simple web application server framework.	1083	A simple embedded webserver.
921		1084
922	AnyEvent::FastPing	1085	AnyEvent::FastPing
923	The fastest ping in the west.	1086	The fastest ping in the west.
924		1087
925	AnyEvent::DBI
926	Executes DBI requests asynchronously in a proxy process.
927
928	AnyEvent::AIO
929	Truly asynchronous I/O, should be in the toolbox of every event
930	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
931	together.
932
933	AnyEvent::BDB
934	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
935	fuses BDB and AnyEvent together.
936
937	AnyEvent::GPSD
938	A non-blocking interface to gpsd, a daemon delivering GPS
939	information.
940
941	AnyEvent::IRC
942	AnyEvent based IRC client module family (replacing the older
943	Net::IRC3).
944
945	AnyEvent::XMPP
946	AnyEvent based XMPP (Jabber protocol) module family (replacing the
947	older Net::XMPP2>.
948
949	AnyEvent::IGS
950	A non-blocking interface to the Internet Go Server protocol (used by
951	App::IGS).
952
953	Net::FCP
954	AnyEvent-based implementation of the Freenet Client Protocol,
955	birthplace of AnyEvent.
956
957	Event::ExecFlow
958	High level API for event-based execution flow control.
959
960	Coro	1088	Coro
961	Has special support for AnyEvent via Coro::AnyEvent.	1089	Has special support for AnyEvent via Coro::AnyEvent.
		1090
		1091	SIMPLIFIED AE API
		1092	Starting with version 5.0, AnyEvent officially supports a second, much
		1093	simpler, API that is designed to reduce the calling, typing and memory
		1094	overhead by using function call syntax and a fixed number of parameters.
		1095
		1096	See the AE manpage for details.
962		1097
963	ERROR AND EXCEPTION HANDLING	1098	ERROR AND EXCEPTION HANDLING
964	In general, AnyEvent does not do any error handling - it relies on the	1099	In general, AnyEvent does not do any error handling - it relies on the
965	caller to do that if required. The AnyEvent::Strict module (see also the	1100	caller to do that if required. The AnyEvent::Strict module (see also the
966	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1101	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
994	by "PERL_ANYEVENT_MODEL".	1129	by "PERL_ANYEVENT_MODEL".
995		1130
996	When set to 2 or higher, cause AnyEvent to report to STDERR which	1131	When set to 2 or higher, cause AnyEvent to report to STDERR which
997	event model it chooses.	1132	event model it chooses.
998		1133
		1134	When set to 8 or higher, then AnyEvent will report extra information
		1135	on which optional modules it loads and how it implements certain
		1136	features.
		1137
999	"PERL_ANYEVENT_STRICT"	1138	"PERL_ANYEVENT_STRICT"
1000	AnyEvent does not do much argument checking by default, as thorough	1139	AnyEvent does not do much argument checking by default, as thorough
1001	argument checking is very costly. Setting this variable to a true	1140	argument checking is very costly. Setting this variable to a true
1002	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1141	value will cause AnyEvent to load "AnyEvent::Strict" and then to
1003	thoroughly check the arguments passed to most method calls. If it	1142	thoroughly check the arguments passed to most method calls. If it
1004	finds any problems, it will croak.	1143	finds any problems, it will croak.
1005		1144
1006	In other words, enables "strict" mode.	1145	In other words, enables "strict" mode.
1007		1146
1008	Unlike "use strict", it is definitely recommended to keep it off in	1147	Unlike "use strict" (or its modern cousin, "use common::sense", it
1009	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1148	is definitely recommended to keep it off in production. Keeping
		1149	"PERL_ANYEVENT_STRICT=1" in your environment while developing
1010	while developing programs can be very useful, however.	1150	programs can be very useful, however.
1011		1151
1012	"PERL_ANYEVENT_MODEL"	1152	"PERL_ANYEVENT_MODEL"
1013	This can be used to specify the event model to be used by AnyEvent,	1153	This can be used to specify the event model to be used by AnyEvent,
1014	before auto detection and -probing kicks in. It must be a string	1154	before auto detection and -probing kicks in. It must be a string
1015	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1155	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
1072	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".	1212	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1073	When neither "ca_file" nor "ca_path" was specified during	1213	When neither "ca_file" nor "ca_path" was specified during
1074	AnyEvent::TLS context creation, and either of these environment	1214	AnyEvent::TLS context creation, and either of these environment
1075	variables exist, they will be used to specify CA certificate	1215	variables exist, they will be used to specify CA certificate
1076	locations instead of a system-dependent default.	1216	locations instead of a system-dependent default.
		1217
		1218	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1219	When these are set to 1, then the respective modules are not loaded.
		1220	Mostly good for testing AnyEvent itself.
1077		1221
1078	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1222	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1079	This is an advanced topic that you do not normally need to use AnyEvent	1223	This is an advanced topic that you do not normally need to use AnyEvent
1080	in a module. This section is only of use to event loop authors who want	1224	in a module. This section is only of use to event loop authors who want
1081	to provide AnyEvent compatibility.	1225	to provide AnyEvent compatibility.
…		…
1136	warn "read: $input\n"; # output what has been read	1280	warn "read: $input\n"; # output what has been read
1137	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1281	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1138	},	1282	},
1139	);	1283	);
1140		1284
1141	my $time_watcher; # can only be used once
1142
1143	sub new_timer {
1144	$timer = AnyEvent->timer (after => 1, cb => sub {	1285	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1145	warn "timeout\n"; # print 'timeout' about every second	1286	warn "timeout\n"; # print 'timeout' at most every second
1146	&new_timer; # and restart the time
1147	});
1148	}	1287	});
1149
1150	new_timer; # create first timer
1151		1288
1152	$cv->recv; # wait until user enters /^q/i	1289	$cv->recv; # wait until user enters /^q/i
1153		1290
1154	REAL-WORLD EXAMPLE	1291	REAL-WORLD EXAMPLE
1155	Consider the Net::FCP module. It features (among others) the following	1292	Consider the Net::FCP module. It features (among others) the following
…		…
1227		1364
1228	The actual code goes further and collects all errors ("die"s,	1365	The actual code goes further and collects all errors ("die"s,
1229	exceptions) that occurred during request processing. The "result" method	1366	exceptions) that occurred during request processing. The "result" method
1230	detects whether an exception as thrown (it is stored inside the $txn	1367	detects whether an exception as thrown (it is stored inside the $txn
1231	object) and just throws the exception, which means connection errors and	1368	object) and just throws the exception, which means connection errors and
1232	other problems get reported tot he code that tries to use the result,	1369	other problems get reported to the code that tries to use the result,
1233	not in a random callback.	1370	not in a random callback.
1234		1371
1235	All of this enables the following usage styles:	1372	All of this enables the following usage styles:
1236		1373
1237	1. Blocking:	1374	1. Blocking:
…		…
1282	through AnyEvent. The benchmark creates a lot of timers (with a zero	1419	through AnyEvent. The benchmark creates a lot of timers (with a zero
1283	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1420	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1284	which it is), lets them fire exactly once and destroys them again.	1421	which it is), lets them fire exactly once and destroys them again.
1285		1422
1286	Source code for this benchmark is found as eg/bench in the AnyEvent	1423	Source code for this benchmark is found as eg/bench in the AnyEvent
1287	distribution.	1424	distribution. It uses the AE interface, which makes a real difference
		1425	for the EV and Perl backends only.
1288		1426
1289	Explanation of the columns	1427	Explanation of the columns
1290	watcher is the number of event watchers created/destroyed. Since	1428	watcher is the number of event watchers created/destroyed. Since
1291	different event models feature vastly different performances, each event	1429	different event models feature vastly different performances, each event
1292	loop was given a number of watchers so that overall runtime is	1430	loop was given a number of watchers so that overall runtime is
…		…
1311	destroy is the time, in microseconds, that it takes to destroy a	1449	destroy is the time, in microseconds, that it takes to destroy a
1312	single watcher.	1450	single watcher.
1313		1451
1314	Results	1452	Results
1315	name watchers bytes create invoke destroy comment	1453	name watchers bytes create invoke destroy comment
1316	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1454	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1317	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1455	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1318	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1456	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1319	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1457	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1320	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1458	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1321	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1459	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
1322	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll	1460	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
1323	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll	1461	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1324	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1462	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1325	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1463	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1326	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1464	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1327	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1465	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1328		1466
1329	Discussion	1467	Discussion
1330	The benchmark does not measure scalability of the event loop very	1468	The benchmark does not measure scalability of the event loop very
1331	well. For example, a select-based event loop (such as the pure perl one)	1469	well. For example, a select-based event loop (such as the pure perl one)
1332	can never compete with an event loop that uses epoll when the number of	1470	can never compete with an event loop that uses epoll when the number of
…		…
1343	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1481	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1344	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1482	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1345	CPU cycles with POE.	1483	CPU cycles with POE.
1346		1484
1347	"EV" is the sole leader regarding speed and memory use, which are both	1485	"EV" is the sole leader regarding speed and memory use, which are both
1348	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1486	maximal/minimal, respectively. When using the AE API there is zero
		1487	overhead (when going through the AnyEvent API create is about 5-6 times
		1488	slower, with other times being equal, so still uses far less memory than
1349	far less memory than any other event loop and is still faster than Event	1489	any other event loop and is still faster than Event natively).
1350	natively.
1351		1490
1352	The pure perl implementation is hit in a few sweet spots (both the	1491	The pure perl implementation is hit in a few sweet spots (both the
1353	constant timeout and the use of a single fd hit optimisations in the	1492	constant timeout and the use of a single fd hit optimisations in the
1354	perl interpreter and the backend itself). Nevertheless this shows that	1493	perl interpreter and the backend itself). Nevertheless this shows that
1355	it adds very little overhead in itself. Like any select-based backend	1494	it adds very little overhead in itself. Like any select-based backend
…		…
1425	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1564	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1426	100 (1%) are active. This mirrors the activity of large servers with	1565	100 (1%) are active. This mirrors the activity of large servers with
1427	many connections, most of which are idle at any one point in time.	1566	many connections, most of which are idle at any one point in time.
1428		1567
1429	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1568	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1430	distribution.	1569	distribution. It uses the AE interface, which makes a real difference
		1570	for the EV and Perl backends only.
1431		1571
1432	Explanation of the columns	1572	Explanation of the columns
1433	sockets is the number of sockets, and twice the number of "servers"	1573	sockets is the number of sockets, and twice the number of "servers"
1434	(as each server has a read and write socket end).	1574	(as each server has a read and write socket end).
1435		1575
…		…
1441	forwarding it to another server. This includes deleting the old timeout	1581	forwarding it to another server. This includes deleting the old timeout
1442	and creating a new one that moves the timeout into the future.	1582	and creating a new one that moves the timeout into the future.
1443		1583
1444	Results	1584	Results
1445	name sockets create request	1585	name sockets create request
1446	EV 20000 69.01 11.16	1586	EV 20000 62.66 7.99
1447	Perl 20000 73.32 35.87	1587	Perl 20000 68.32 32.64
1448	IOAsync 20000 157.00 98.14 epoll	1588	IOAsync 20000 174.06 101.15 epoll
1449	IOAsync 20000 159.31 616.06 poll	1589	IOAsync 20000 174.67 610.84 poll
1450	Event 20000 212.62 257.32	1590	Event 20000 202.69 242.91
1451	Glib 20000 651.16 1896.30	1591	Glib 20000 557.01 1689.52
1452	POE 20000 349.67 12317.24 uses POE::Loop::Event	1592	POE 20000 341.54 12086.32 uses POE::Loop::Event
1453		1593
1454	Discussion	1594	Discussion
1455	This benchmark does measure scalability and overall performance of the	1595	This benchmark does measure scalability and overall performance of the
1456	particular event loop.	1596	particular event loop.
1457		1597
…		…
1570	As you can see, the AnyEvent + EV combination even beats the	1710	As you can see, the AnyEvent + EV combination even beats the
1571	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl	1711	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1572	backend easily beats IO::Lambda and POE.	1712	backend easily beats IO::Lambda and POE.
1573		1713
1574	And even the 100% non-blocking version written using the high-level (and	1714	And even the 100% non-blocking version written using the high-level (and
1575	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a	1715	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
1576	large margin, even though it does all of DNS, tcp-connect and socket I/O	1716	higher level ("unoptimised") abstractions by a large margin, even though
1577	in a non-blocking way.	1717	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
1578		1718
1579	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and	1719	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
1580	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are	1720	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1581	part of the IO::lambda distribution and were used without any changes.	1721	part of the IO::Lambda distribution and were used without any changes.
1582		1722
1583	SIGNALS	1723	SIGNALS
1584	AnyEvent currently installs handlers for these signals:	1724	AnyEvent currently installs handlers for these signals:
1585		1725
1586	SIGCHLD	1726	SIGCHLD
…		…
1606	it is that this way, the handler will be restored to defaults on	1746	it is that this way, the handler will be restored to defaults on
1607	exec.	1747	exec.
1608		1748
1609	Feel free to install your own handler, or reset it to defaults.	1749	Feel free to install your own handler, or reset it to defaults.
1610		1750
		1751	RECOMMENDED/OPTIONAL MODULES
		1752	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1753	its built-in modules) are required to use it.
		1754
		1755	That does not mean that AnyEvent won't take advantage of some additional
		1756	modules if they are installed.
		1757
		1758	This section explains which additional modules will be used, and how
		1759	they affect AnyEvent's operation.
		1760
		1761	Async::Interrupt
		1762	This slightly arcane module is used to implement fast signal
		1763	handling: To my knowledge, there is no way to do completely
		1764	race-free and quick signal handling in pure perl. To ensure that
		1765	signals still get delivered, AnyEvent will start an interval timer
		1766	to wake up perl (and catch the signals) with some delay (default is
		1767	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1768
		1769	If this module is available, then it will be used to implement
		1770	signal catching, which means that signals will not be delayed, and
		1771	the event loop will not be interrupted regularly, which is more
		1772	efficient (and good for battery life on laptops).
		1773
		1774	This affects not just the pure-perl event loop, but also other event
		1775	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1776
		1777	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1778	natively, and either employ their own workarounds (POE) or use
		1779	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1780	Installing Async::Interrupt does nothing for those backends.
		1781
		1782	EV This module isn't really "optional", as it is simply one of the
		1783	backend event loops that AnyEvent can use. However, it is simply the
		1784	best event loop available in terms of features, speed and stability:
		1785	It supports the AnyEvent API optimally, implements all the watcher
		1786	types in XS, does automatic timer adjustments even when no monotonic
		1787	clock is available, can take avdantage of advanced kernel interfaces
		1788	such as "epoll" and "kqueue", and is the fastest backend by far.
		1789	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1790	Glib::EV).
		1791
		1792	If you only use backends that rely on another event loop (e.g.
		1793	"Tk"), then this module will do nothing for you.
		1794
		1795	Guard
		1796	The guard module, when used, will be used to implement
		1797	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1798	uses a lot less memory), but otherwise doesn't affect guard
		1799	operation much. It is purely used for performance.
		1800
		1801	JSON and JSON::XS
		1802	One of these modules is required when you want to read or write JSON
		1803	data via AnyEvent::Handle. JSON is also written in pure-perl, but
		1804	can take advantage of the ultra-high-speed JSON::XS module when it
		1805	is installed.
		1806
		1807	Net::SSLeay
		1808	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1809	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1810	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1811
		1812	Time::HiRes
		1813	This module is part of perl since release 5.008. It will be used
		1814	when the chosen event library does not come with a timing source of
		1815	its own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1816	additionally use it to try to use a monotonic clock for timing
		1817	stability.
		1818
1611	FORK	1819	FORK
1612	Most event libraries are not fork-safe. The ones who are usually are	1820	Most event libraries are not fork-safe. The ones who are usually are
1613	because they rely on inefficient but fork-safe "select" or "poll" calls.	1821	because they rely on inefficient but fork-safe "select" or "poll" calls
1614	Only EV is fully fork-aware.	1822	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		1823	epoll are usually badly thought-out hacks that are incompatible with
		1824	fork in one way or another. Only EV is fully fork-aware and ensures that
		1825	you continue event-processing in both parent and child (or both, if you
		1826	know what you are doing).
		1827
		1828	This means that, in general, you cannot fork and do event processing in
		1829	the child if the event library was initialised before the fork (which
		1830	usually happens when the first AnyEvent watcher is created, or the
		1831	library is loaded).
1615		1832
1616	If you have to fork, you must either do so before creating your first	1833	If you have to fork, you must either do so before creating your first
1617	watcher OR you must not use AnyEvent at all in the child.	1834	watcher OR you must not use AnyEvent at all in the child OR you must do
		1835	something completely out of the scope of AnyEvent.
		1836
		1837	The problem of doing event processing in the parent and the child is
		1838	much more complicated: even for backends that are fork-aware or
		1839	fork-safe, their behaviour is not usually what you want: fork clones all
		1840	watchers, that means all timers, I/O watchers etc. are active in both
		1841	parent and child, which is almost never what you want. USing "exec" to
		1842	start worker children from some kind of manage rprocess is usually
		1843	preferred, because it is much easier and cleaner, at the expense of
		1844	having to have another binary.
1618		1845
1619	SECURITY CONSIDERATIONS	1846	SECURITY CONSIDERATIONS
1620	AnyEvent can be forced to load any event model via	1847	AnyEvent can be forced to load any event model via
1621	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1848	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1622	to execute arbitrary code or directly gain access, it can easily be used	1849	to execute arbitrary code or directly gain access, it can easily be used
…		…
1646	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	1873	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1647	annoying memleaks, such as leaking on "map" and "grep" but it is usually	1874	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1648	not as pronounced).	1875	not as pronounced).
1649		1876
1650	SEE ALSO	1877	SEE ALSO
		1878	Tutorial/Introduction: AnyEvent::Intro.
		1879
		1880	FAQ: AnyEvent::FAQ.
		1881
1651	Utility functions: AnyEvent::Util.	1882	Utility functions: AnyEvent::Util.
1652		1883
1653	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1884	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1654	Event::Lib, Qt, POE.	1885	Event::Lib, Qt, POE.
1655		1886
1656	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1887	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1657	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1888	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1658	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,	1889	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1659	AnyEvent::Impl::IOAsync.	1890	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1660		1891
1661	Non-blocking file handles, sockets, TCP clients and servers:	1892	Non-blocking file handles, sockets, TCP clients and servers:
1662	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.	1893	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1663		1894
1664	Asynchronous DNS: AnyEvent::DNS.	1895	Asynchronous DNS: AnyEvent::DNS.
1665		1896
1666	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1897	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1667		1898
1668	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,	1899	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
1669	AnyEvent::HTTP.	1900	AnyEvent::HTTP.
1670		1901
1671	AUTHOR	1902	AUTHOR
1672	Marc Lehmann <schmorp@schmorp.de>	1903	Marc Lehmann <schmorp@schmorp.de>
1673	http://home.schmorp.de/	1904	http://home.schmorp.de/

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent/README (file contents): Revision 1.44 by root, Fri Jul 10 22:35:27 2009 UTC vs. Revision 1.63 by root, Wed Oct 13 19:49:46 2010 UTC

Diff Legend

Comparing AnyEvent/README (file contents):
Revision 1.44 by root, Fri Jul 10 22:35:27 2009 UTC vs.
Revision 1.63 by root, Wed Oct 13 19:49:46 2010 UTC