[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.45 by root, Fri Jul 17 14:57:03 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 slightly different: it expects somebody else to run the	541	AnyEvent is slightly different: it expects somebody else to run the
454	event loop and will only block when necessary (usually when told by the	542	event loop and will only block when necessary (usually when told by the
455	user).	543	user).
456		544
457	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
458	because they represent a condition that must become true.	546	they represent a condition that must become true.
459		547
460	Now is probably a good time to look at the examples further below.	548	Now is probably a good time to look at the examples further below.
461		549
462	Condition variables can be created by calling the "AnyEvent->condvar"	550	Condition variables can be created by calling the "AnyEvent->condvar"
463	method, usually without arguments. The only argument pair allowed is	551	method, usually without arguments. The only argument pair allowed is
…		…
468	After creation, the condition variable is "false" until it becomes	556	After creation, the condition variable is "false" until it becomes
469	"true" by calling the "send" method (or calling the condition variable	557	"true" by calling the "send" method (or calling the condition variable
470	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
471	the "->send" method).	559	the "->send" method).
472		560
473	Condition variables are similar to callbacks, except that you can	561	Since condition variables are the most complex part of the AnyEvent API,
474	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
475	in time where multiple outstanding events have been processed. And yet	563	you can connect to:
476	another way to call them is transactions - each condition variable can	564
477	be used to represent a transaction, which finishes at some point and	565	* Condition variables are like callbacks - you can call them (and pass
478	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.
479		582
480	Condition variables are very useful to signal that something has	583	Condition variables are very useful to signal that something has
481	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
482	requests, then a condition variable would be the ideal candidate to	585	requests, then a condition variable would be the ideal candidate to
483	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
…		…
496		599
497	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
498	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
499	(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
500	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	603	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
501	it's "new" method in your own "new" method.	604	its "new" method in your own "new" method.
502		605
503	There are two "sides" to a condition variable - the "producer side"	606	There are two "sides" to a condition variable - the "producer side"
504	which eventually calls "-> send", and the "consumer side", which waits	607	which eventually calls "-> send", and the "consumer side", which waits
505	for the send to occur.	608	for the send to occur.
506		609
507	Example: wait for a timer.	610	Example: wait for a timer.
508		611
509	# wait till the result is ready	612	# condition: "wait till the timer is fired"
510	my $result_ready = AnyEvent->condvar;	613	my $timer_fired = AnyEvent->condvar;
511		614
512	# do something such as adding a timer	615	# create the timer - we could wait for, say
513	# or socket watcher the calls $result_ready->send	616	# a handle becomign ready, or even an
514	# when the "result" is ready.	617	# AnyEvent::HTTP request to finish, but
515	# in this case, we simply use a timer:	618	# in this case, we simply use a timer:
516	my $w = AnyEvent->timer (	619	my $w = AnyEvent->timer (
517	after => 1,	620	after => 1,
518	cb => sub { $result_ready->send },	621	cb => sub { $timer_fired->send },
519	);	622	);
520		623
521	# this "blocks" (while handling events) till the callback	624	# this "blocks" (while handling events) till the callback
522	# calls -<send	625	# calls ->send
523	$result_ready->recv;	626	$timer_fired->recv;
524		627
525	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
526	variables are also callable directly.	629	variables are also callable directly.
527		630
528	my $done = AnyEvent->condvar;	631	my $done = AnyEvent->condvar;
…		…
566	Condition variables are overloaded so one can call them directly (as	669	Condition variables are overloaded so one can call them directly (as
567	if they were a code reference). Calling them directly is the same as	670	if they were a code reference). Calling them directly is the same as
568	calling "send".	671	calling "send".
569		672
570	$cv->croak ($error)	673	$cv->croak ($error)
571	Similar to send, but causes all call's to "->recv" to invoke	674	Similar to send, but causes all calls to "->recv" to invoke
572	"Carp::croak" with the given error message/object/scalar.	675	"Carp::croak" with the given error message/object/scalar.
573		676
574	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
575	user/consumer. Doing it this way instead of calling "croak" directly	678	user/consumer. Doing it this way instead of calling "croak" directly
576	delays the error detetcion, but has the overwhelmign advantage that	679	delays the error detection, but has the overwhelming advantage that
577	it diagnoses the error at the place where the result is expected,	680	it diagnoses the error at the place where the result is expected,
578	and not deep in some event clalback without connection to the actual	681	and not deep in some event callback with no connection to the actual
579	code causing the problem.	682	code causing the problem.
580		683
581	$cv->begin ([group callback])	684	$cv->begin ([group callback])
582	$cv->end	685	$cv->end
583	These two methods can be used to combine many transactions/events	686	These two methods can be used to combine many transactions/events
584	into one. For example, a function that pings many hosts in parallel	687	into one. For example, a function that pings many hosts in parallel
585	might want to use a condition variable for the whole process.	688	might want to use a condition variable for the whole process.
586		689
587	Every call to "->begin" will increment a counter, and every call to	690	Every call to "->begin" will increment a counter, and every call to
588	"->end" will decrement it. If the counter reaches 0 in "->end", the	691	"->end" will decrement it. If the counter reaches 0 in "->end", the
589	(last) callback passed to "begin" will be executed. That callback is	692	(last) callback passed to "begin" will be executed, passing the
590	supposed to call "->send", but that is not required. If no	693	condvar as first argument. That callback is supposed to call
		694	"->send", but that is not required. If no group callback was set,
591	callback was set, "send" will be called without any arguments.	695	"send" will be called without any arguments.
592		696
593	You can think of "$cv->send" giving you an OR condition (one call	697	You can think of "$cv->send" giving you an OR condition (one call
594	sends), while "$cv->begin" and "$cv->end" giving you an AND	698	sends), while "$cv->begin" and "$cv->end" giving you an AND
595	condition (all "begin" calls must be "end"'ed before the condvar	699	condition (all "begin" calls must be "end"'ed before the condvar
596	sends).	700	sends).
…		…
619	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
620	"end" before sending.	724	"end" before sending.
621		725
622	The ping example mentioned above is slightly more complicated, as	726	The ping example mentioned above is slightly more complicated, as
623	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
624	that are begung can potentially be zero:	728	that are begun can potentially be zero:
625		729
626	my $cv = AnyEvent->condvar;	730	my $cv = AnyEvent->condvar;
627		731
628	my %result;	732	my %result;
629	$cv->begin (sub { $cv->send (\%result) });	733	$cv->begin (sub { shift->send (\%result) });
630		734
631	for my $host (@list_of_hosts) {	735	for my $host (@list_of_hosts) {
632	$cv->begin;	736	$cv->begin;
633	ping_host_then_call_callback $host, sub {	737	ping_host_then_call_callback $host, sub {
634	$result{$host} = ...;	738	$result{$host} = ...;
…		…
650	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
651	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
652	(the loop doesn't execute once).	756	(the loop doesn't execute once).
653		757
654	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
655	potentially none) subrequests: use an outer "begin"/"end" pair to	759	potentially zero) subrequests: use an outer "begin"/"end" pair to
656	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,
657	for each subrequest you start, call "begin" and for each subrequest	761	for each subrequest you start, call "begin" and for each subrequest
658	you finish, call "end".	762	you finish, call "end".
659		763
660	METHODS FOR CONSUMERS	764	METHODS FOR CONSUMERS
661	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
662	awaits the condition.	766	awaits the condition.
663		767
664	$cv->recv	768	$cv->recv
665	Wait (blocking if necessary) until the "->send" or "->croak" methods	769	Wait (blocking if necessary) until the "->send" or "->croak" methods
666	have been called on c<$cv>, while servicing other watchers normally.	770	have been called on $cv, while servicing other watchers normally.
667		771
668	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
669	but will return immediately.	773	but will return immediately.
670		774
671	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
…		…
688	example, by coupling condition variables with some kind of request	792	example, by coupling condition variables with some kind of request
689	results and supporting callbacks so the caller knows that getting	793	results and supporting callbacks so the caller knows that getting
690	the result will not block, while still supporting blocking waits if	794	the result will not block, while still supporting blocking waits if
691	the caller so desires).	795	the caller so desires).
692		796
693	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
694	only calling "->recv" from within that callback (or at a later	798	only calling "->recv" from within that callback (or at a later
695	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
696	blocking waits otherwise.	800	blocking waits otherwise.
697		801
698	$bool = $cv->ready	802	$bool = $cv->ready
…		…
703	This is a mutator function that returns the callback set and	807	This is a mutator function that returns the callback set and
704	optionally replaces it before doing so.	808	optionally replaces it before doing so.
705		809
706	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.
707	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
708	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
709	any later time is guaranteed not to block.	814	the callback or at any later time is guaranteed not to block.
710		815
711	SUPPORTED EVENT LOOPS/BACKENDS	816	SUPPORTED EVENT LOOPS/BACKENDS
712	The available backend classes are (every class has its own manpage):	817	The available backend classes are (every class has its own manpage):
713		818
714	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.
715	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
716	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
717	failing that, will fall back to its own pure-perl implementation,	822	pure-perl implementation, which is available everywhere as it comes
718	which is available everywhere as it comes with AnyEvent itself.	823	with AnyEvent itself.
719		824
720	AnyEvent::Impl::EV based on EV (interface to libev, best choice).	825	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
721	AnyEvent::Impl::Event based on Event, very stable, few glitches.
722	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.	826	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
723		827
724	Backends that are transparently being picked up when they are used.	828	Backends that are transparently being picked up when they are used.
725	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
726	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
727	is using them. This means that AnyEvent will automatically pick the	831	using them. This means that AnyEvent will automatically pick the
728	right backend when the main program loads an event module before	832	right backend when the main program loads an event module before
729	anything starts to create watchers. Nothing special needs to be done	833	anything starts to create watchers. Nothing special needs to be done
730	by the main program.	834	by the main program.
731		835
		836	AnyEvent::Impl::Event based on Event, very stable, few glitches.
732	AnyEvent::Impl::Glib based on Glib, slow but very stable.	837	AnyEvent::Impl::Glib based on Glib, slow but very stable.
733	AnyEvent::Impl::Tk based on Tk, very broken.	838	AnyEvent::Impl::Tk based on Tk, very broken.
734	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	839	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
735	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.
736		842
737	Backends with special needs.	843	Backends with special needs.
738	Qt requires the Qt::Application to be instantiated first, but will	844	Qt requires the Qt::Application to be instantiated first, but will
739	otherwise be picked up automatically. As long as the main program	845	otherwise be picked up automatically. As long as the main program
740	instantiates the application before any AnyEvent watchers are	846	instantiates the application before any AnyEvent watchers are
…		…
744		850
745	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
746	architecturally limited to even support the AnyEvent API. It also is	852	architecturally limited to even support the AnyEvent API. It also is
747	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
748	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
749	AnyEvent::Impl::Async for the gory details.	855	AnyEvent::Impl::IOAsync for the gory details.
750		856
751	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.	857	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
752		858
753	Event loops that are indirectly supported via other backends.	859	Event loops that are indirectly supported via other backends.
754	Some event loops can be supported via other modules:	860	Some event loops can be supported via other modules:
…		…
775	Contains "undef" until the first watcher is being created, before	881	Contains "undef" until the first watcher is being created, before
776	the backend has been autodetected.	882	the backend has been autodetected.
777		883
778	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
779	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
780	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
781	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.
782	in rxvt-unicode it will be "urxvt::anyevent").	888	in rxvt-unicode it will be "urxvt::anyevent").
783		889
784	AnyEvent::detect	890	AnyEvent::detect
785	Returns $AnyEvent::MODEL, forcing autodetection of the event model	891	Returns $AnyEvent::MODEL, forcing autodetection of the event model
786	if necessary. You should only call this function right before you	892	if necessary. You should only call this function right before you
787	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
788	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.
789		896
790	If you need to do some initialisation before AnyEvent watchers are	897	If you need to do some initialisation before AnyEvent watchers are
791	created, use "post_detect".	898	created, use "post_detect".
792		899
793	$guard = AnyEvent::post_detect { BLOCK }	900	$guard = AnyEvent::post_detect { BLOCK }
794	Arranges for the code block to be executed as soon as the event	901	Arranges for the code block to be executed as soon as the event
795	model is autodetected (or immediately if this has already happened).	902	model is autodetected (or immediately if that has already happened).
796		903
797	The block will be executed after the actual backend has been	904	The block will be executed after the actual backend has been
798	detected ($AnyEvent::MODEL is set), but before any watchers have	905	detected ($AnyEvent::MODEL is set), but before any watchers have
799	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
800	other initialisations - see the sources of AnyEvent::Strict or	907	other initialisations - see the sources of AnyEvent::Strict or
…		…
805	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"
806	block to avoid autodetecting the event module at load time.	913	block to avoid autodetecting the event module at load time.
807		914
808	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
809	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
810	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;
811		935
812	@AnyEvent::post_detect	936	@AnyEvent::post_detect
813	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
814	before or after loading AnyEvent), then they will called directly	938	before or after loading AnyEvent), then they will be called directly
815	after the event loop has been chosen.	939	after the event loop has been chosen.
816		940
817	You should check $AnyEvent::MODEL before adding to this array,	941	You should check $AnyEvent::MODEL before adding to this array,
818	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
819	detected, and the array will be ignored.	943	detected, and the array will be ignored.
820		944
821	Best use "AnyEvent::post_detect { BLOCK }" when your application	945	Best use "AnyEvent::post_detect { BLOCK }" when your application
822	allows it,as it takes care of these details.	946	allows it, as it takes care of these details.
823		947
824	This variable is mainly useful for modules that can do something	948	This variable is mainly useful for modules that can do something
825	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
826	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
827	provides the means to hook into AnyEvent passively, without loading	951	provides the means to hook into AnyEvent passively, without loading
828	it.	952	it.
829		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
830	WHAT TO DO IN A MODULE	967	WHAT TO DO IN A MODULE
831	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
832	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.
833		970
834	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
…		…
841	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
842	interactive.	979	interactive.
843		980
844	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
845	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
846	called "results" that returns the results, it should call "->recv"	983	called "results" that returns the results, it may call "->recv" freely,
847	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).
848		985
849	WHAT TO DO IN THE MAIN PROGRAM	986	WHAT TO DO IN THE MAIN PROGRAM
850	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
851	dictate which event model to use.	988	dictate which event model to use.
852		989
853	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
854	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
855	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
856	it.	993	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		994	available loop implementation.
857		995
858	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
859	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
860	event module before loading AnyEvent or any module that uses it:	998	event module before loading AnyEvent or any module that uses it:
861	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
862	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
863	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,
864	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
865	yourself.	1003	yourself.
866		1004
867	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
868	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1006	"AnyEvent::Impl::Perl" module, which gives you similar behaviour
869	everywhere, but letting AnyEvent chose the model is generally better.	1007	everywhere, but letting AnyEvent chose the model is generally better.
…		…
886		1024
887	OTHER MODULES	1025	OTHER MODULES
888	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
889	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
890	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
891	modules come with AnyEvent, most are available via CPAN.	1029	modules come as part of AnyEvent, the others are available via CPAN.
892		1030
893	AnyEvent::Util	1031	AnyEvent::Util
894	Contains various utility functions that replace often-used but	1032	Contains various utility functions that replace often-used blocking
895	blocking functions such as "inet_aton" by event-/callback-based	1033	functions such as "inet_aton" with event/callback-based versions.
896	versions.
897		1034
898	AnyEvent::Socket	1035	AnyEvent::Socket
899	Provides various utility functions for (internet protocol) sockets,	1036	Provides various utility functions for (internet protocol) sockets,
900	addresses and name resolution. Also functions to create non-blocking	1037	addresses and name resolution. Also functions to create non-blocking
901	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
902	more.	1039	more.
903		1040
904	AnyEvent::Handle	1041	AnyEvent::Handle
905	Provide read and write buffers, manages watchers for reads and	1042	Provide read and write buffers, manages watchers for reads and
906	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
907	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.	1044	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
908		1045
909	AnyEvent::DNS	1046	AnyEvent::DNS
910	Provides rich asynchronous DNS resolver capabilities.	1047	Provides rich asynchronous DNS resolver capabilities.
911		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
912	AnyEvent::HTTP	1072	AnyEvent::DBI
913	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,
914	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.
915		1081
916	AnyEvent::HTTPD	1082	AnyEvent::HTTPD
917	Provides a simple web application server framework.	1083	A simple embedded webserver.
918		1084
919	AnyEvent::FastPing	1085	AnyEvent::FastPing
920	The fastest ping in the west.	1086	The fastest ping in the west.
921		1087
922	AnyEvent::DBI
923	Executes DBI requests asynchronously in a proxy process.
924
925	AnyEvent::AIO
926	Truly asynchronous I/O, should be in the toolbox of every event
927	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
928	together.
929
930	AnyEvent::BDB
931	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
932	fuses BDB and AnyEvent together.
933
934	AnyEvent::GPSD
935	A non-blocking interface to gpsd, a daemon delivering GPS
936	information.
937
938	AnyEvent::IRC
939	AnyEvent based IRC client module family (replacing the older
940	Net::IRC3).
941
942	AnyEvent::XMPP
943	AnyEvent based XMPP (Jabber protocol) module family (replacing the
944	older Net::XMPP2>.
945
946	AnyEvent::IGS
947	A non-blocking interface to the Internet Go Server protocol (used by
948	App::IGS).
949
950	Net::FCP
951	AnyEvent-based implementation of the Freenet Client Protocol,
952	birthplace of AnyEvent.
953
954	Event::ExecFlow
955	High level API for event-based execution flow control.
956
957	Coro	1088	Coro
958	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.
959		1097
960	ERROR AND EXCEPTION HANDLING	1098	ERROR AND EXCEPTION HANDLING
961	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
962	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
963	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1101	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
991	by "PERL_ANYEVENT_MODEL".	1129	by "PERL_ANYEVENT_MODEL".
992		1130
993	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
994	event model it chooses.	1132	event model it chooses.
995		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
996	"PERL_ANYEVENT_STRICT"	1138	"PERL_ANYEVENT_STRICT"
997	AnyEvent does not do much argument checking by default, as thorough	1139	AnyEvent does not do much argument checking by default, as thorough
998	argument checking is very costly. Setting this variable to a true	1140	argument checking is very costly. Setting this variable to a true
999	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1141	value will cause AnyEvent to load "AnyEvent::Strict" and then to
1000	thoroughly check the arguments passed to most method calls. If it	1142	thoroughly check the arguments passed to most method calls. If it
1001	finds any problems, it will croak.	1143	finds any problems, it will croak.
1002		1144
1003	In other words, enables "strict" mode.	1145	In other words, enables "strict" mode.
1004		1146
1005	Unlike "use strict", it is definitely recommended to keep it off in	1147	Unlike "use strict" (or its modern cousin, "use common::sense", it
1006	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
1007	while developing programs can be very useful, however.	1150	programs can be very useful, however.
1008		1151
1009	"PERL_ANYEVENT_MODEL"	1152	"PERL_ANYEVENT_MODEL"
1010	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,
1011	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
1012	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1155	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
1069	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".	1212	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1070	When neither "ca_file" nor "ca_path" was specified during	1213	When neither "ca_file" nor "ca_path" was specified during
1071	AnyEvent::TLS context creation, and either of these environment	1214	AnyEvent::TLS context creation, and either of these environment
1072	variables exist, they will be used to specify CA certificate	1215	variables exist, they will be used to specify CA certificate
1073	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.
1074		1221
1075	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1222	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1076	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
1077	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
1078	to provide AnyEvent compatibility.	1225	to provide AnyEvent compatibility.
…		…
1133	warn "read: $input\n"; # output what has been read	1280	warn "read: $input\n"; # output what has been read
1134	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1281	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1135	},	1282	},
1136	);	1283	);
1137		1284
1138	my $time_watcher; # can only be used once
1139
1140	sub new_timer {
1141	$timer = AnyEvent->timer (after => 1, cb => sub {	1285	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1142	warn "timeout\n"; # print 'timeout' about every second	1286	warn "timeout\n"; # print 'timeout' at most every second
1143	&new_timer; # and restart the time
1144	});
1145	}	1287	});
1146
1147	new_timer; # create first timer
1148		1288
1149	$cv->recv; # wait until user enters /^q/i	1289	$cv->recv; # wait until user enters /^q/i
1150		1290
1151	REAL-WORLD EXAMPLE	1291	REAL-WORLD EXAMPLE
1152	Consider the Net::FCP module. It features (among others) the following	1292	Consider the Net::FCP module. It features (among others) the following
…		…
1224		1364
1225	The actual code goes further and collects all errors ("die"s,	1365	The actual code goes further and collects all errors ("die"s,
1226	exceptions) that occurred during request processing. The "result" method	1366	exceptions) that occurred during request processing. The "result" method
1227	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
1228	object) and just throws the exception, which means connection errors and	1368	object) and just throws the exception, which means connection errors and
1229	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,
1230	not in a random callback.	1370	not in a random callback.
1231		1371
1232	All of this enables the following usage styles:	1372	All of this enables the following usage styles:
1233		1373
1234	1. Blocking:	1374	1. Blocking:
…		…
1279	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
1280	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,
1281	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.
1282		1422
1283	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
1284	distribution.	1424	distribution. It uses the AE interface, which makes a real difference
		1425	for the EV and Perl backends only.
1285		1426
1286	Explanation of the columns	1427	Explanation of the columns
1287	watcher is the number of event watchers created/destroyed. Since	1428	watcher is the number of event watchers created/destroyed. Since
1288	different event models feature vastly different performances, each event	1429	different event models feature vastly different performances, each event
1289	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
…		…
1308	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
1309	single watcher.	1450	single watcher.
1310		1451
1311	Results	1452	Results
1312	name watchers bytes create invoke destroy comment	1453	name watchers bytes create invoke destroy comment
1313	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
1314	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
1315	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
1316	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
1317	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
1318	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
1319	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
1320	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
1321	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
1322	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
1323	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
1324	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
1325		1466
1326	Discussion	1467	Discussion
1327	The benchmark does not measure scalability of the event loop very	1468	The benchmark does not measure scalability of the event loop very
1328	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)
1329	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
…		…
1340	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1481	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1341	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
1342	CPU cycles with POE.	1483	CPU cycles with POE.
1343		1484
1344	"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
1345	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
1346	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).
1347	natively.
1348		1490
1349	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
1350	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
1351	perl interpreter and the backend itself). Nevertheless this shows that	1493	perl interpreter and the backend itself). Nevertheless this shows that
1352	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
…		…
1422	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
1423	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
1424	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.
1425		1567
1426	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
1427	distribution.	1569	distribution. It uses the AE interface, which makes a real difference
		1570	for the EV and Perl backends only.
1428		1571
1429	Explanation of the columns	1572	Explanation of the columns
1430	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"
1431	(as each server has a read and write socket end).	1574	(as each server has a read and write socket end).
1432		1575
…		…
1438	forwarding it to another server. This includes deleting the old timeout	1581	forwarding it to another server. This includes deleting the old timeout
1439	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.
1440		1583
1441	Results	1584	Results
1442	name sockets create request	1585	name sockets create request
1443	EV 20000 69.01 11.16	1586	EV 20000 62.66 7.99
1444	Perl 20000 73.32 35.87	1587	Perl 20000 68.32 32.64
1445	IOAsync 20000 157.00 98.14 epoll	1588	IOAsync 20000 174.06 101.15 epoll
1446	IOAsync 20000 159.31 616.06 poll	1589	IOAsync 20000 174.67 610.84 poll
1447	Event 20000 212.62 257.32	1590	Event 20000 202.69 242.91
1448	Glib 20000 651.16 1896.30	1591	Glib 20000 557.01 1689.52
1449	POE 20000 349.67 12317.24 uses POE::Loop::Event	1592	POE 20000 341.54 12086.32 uses POE::Loop::Event
1450		1593
1451	Discussion	1594	Discussion
1452	This benchmark does measure scalability and overall performance of the	1595	This benchmark does measure scalability and overall performance of the
1453	particular event loop.	1596	particular event loop.
1454		1597
…		…
1567	As you can see, the AnyEvent + EV combination even beats the	1710	As you can see, the AnyEvent + EV combination even beats the
1568	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl	1711	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1569	backend easily beats IO::Lambda and POE.	1712	backend easily beats IO::Lambda and POE.
1570		1713
1571	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
1572	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a	1715	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
1573	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
1574	in a non-blocking way.	1717	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
1575		1718
1576	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
1577	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are	1720	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1578	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.
1579		1722
1580	SIGNALS	1723	SIGNALS
1581	AnyEvent currently installs handlers for these signals:	1724	AnyEvent currently installs handlers for these signals:
1582		1725
1583	SIGCHLD	1726	SIGCHLD
…		…
1603	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
1604	exec.	1747	exec.
1605		1748
1606	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.
1607		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
1608	FORK	1819	FORK
1609	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
1610	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
1611	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).
1612		1832
1613	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
1614	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.
1615		1845
1616	SECURITY CONSIDERATIONS	1846	SECURITY CONSIDERATIONS
1617	AnyEvent can be forced to load any event model via	1847	AnyEvent can be forced to load any event model via
1618	$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
1619	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
…		…
1643	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
1644	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
1645	not as pronounced).	1875	not as pronounced).
1646		1876
1647	SEE ALSO	1877	SEE ALSO
		1878	Tutorial/Introduction: AnyEvent::Intro.
		1879
		1880	FAQ: AnyEvent::FAQ.
		1881
1648	Utility functions: AnyEvent::Util.	1882	Utility functions: AnyEvent::Util.
1649		1883
1650	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,
1651	Event::Lib, Qt, POE.	1885	Event::Lib, Qt, POE.
1652		1886
1653	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1887	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1654	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1888	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1655	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,	1889	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1656	AnyEvent::Impl::IOAsync.	1890	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1657		1891
1658	Non-blocking file handles, sockets, TCP clients and servers:	1892	Non-blocking file handles, sockets, TCP clients and servers:
1659	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.	1893	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1660		1894
1661	Asynchronous DNS: AnyEvent::DNS.	1895	Asynchronous DNS: AnyEvent::DNS.
1662		1896
1663	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1897	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1664		1898
1665	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,	1899	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
1666	AnyEvent::HTTP.	1900	AnyEvent::HTTP.
1667		1901
1668	AUTHOR	1902	AUTHOR
1669	Marc Lehmann <schmorp@schmorp.de>	1903	Marc Lehmann <schmorp@schmorp.de>
1670	http://home.schmorp.de/	1904	http://home.schmorp.de/

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Comparing AnyEvent/README (file contents): Revision 1.45 by root, Fri Jul 17 14:57:03 2009 UTC vs. Revision 1.63 by root, Wed Oct 13 19:49:46 2010 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.45 by root, Fri Jul 17 14:57:03 2009 UTC vs.
Revision 1.63 by root, Wed Oct 13 19:49:46 2010 UTC