[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.41 by root, Fri Jun 26 06:33:17 2009 UTC vs.
Revision 1.65 by root, Sat Aug 13 22:44:05 2011 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 + EV? No go. Tk + Event? No go. Again: if your module
74	module uses one of those, every user of your module has to use it, too.	86	uses one of those, every user of your module has to use it, too. But if
75	But if your module uses AnyEvent, it works transparently with all event	87	your module uses AnyEvent, it works transparently with all event models
76	models it supports (including stuff like IO::Async, as long as those use	88	it supports (including stuff like IO::Async, as long as those use one of
77	one of the supported event loops. It is trivial to add new event loops	89	the supported event loops. It is easy to add new event loops to
78	to AnyEvent, too, so it is future-proof).	90	AnyEvent, too, so it is future-proof).
79		91
80	In addition to being free of having to use *the one and only true event	92	In addition to being free of having to use *the one and only true event
81	model*, AnyEvent also is free of bloat and policy: with POE or similar	93	model*, AnyEvent also is free of bloat and policy: with POE or similar
82	modules, you get an enormous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
83	follow. AnyEvent, on the other hand, is lean and up to the point, by	95	follow. AnyEvent, on the other hand, is lean and to the point, by only
84	only offering the functionality that is necessary, in as thin as a	96	offering the functionality that is necessary, in as thin as a wrapper as
85	wrapper as technically possible.	97	technically possible.
86		98
87	Of course, AnyEvent comes with a big (and fully optional!) toolbox of	99	Of course, AnyEvent comes with a big (and fully optional!) toolbox of
88	useful functionality, such as an asynchronous DNS resolver, 100%	100	useful functionality, such as an asynchronous DNS resolver, 100%
89	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms	101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
90	such as Windows) and lots of real-world knowledge and workarounds for	102	such as Windows) and lots of real-world knowledge and workarounds for
…		…
93	Now, if you do want lots of policy (this can arguably be somewhat	105	Now, if you do want lots of policy (this can arguably be somewhat
94	useful) and you want to force your users to use the one and only event	106	useful) and you want to force your users to use the one and only event
95	model, you should not use this module.	107	model, you should not use this module.
96		108
97	DESCRIPTION	109	DESCRIPTION
98	AnyEvent provides an identical interface to multiple event loops. This	110	AnyEvent provides a uniform interface to various event loops. This
99	allows module authors to utilise an event loop without forcing module	111	allows module authors to use event loop functionality without forcing
100	users to use the same event loop (as only a single event loop can	112	module users to use a specific event loop implementation (since more
101	coexist peacefully at any one time).	113	than one event loop cannot coexist peacefully).
102		114
103	The interface itself is vaguely similar, but not identical to the Event	115	The interface itself is vaguely similar, but not identical to the Event
104	module.	116	module.
105		117
106	During the first call of any watcher-creation method, the module tries	118	During the first call of any watcher-creation method, the module tries
107	to detect the currently loaded event loop by probing whether one of the	119	to detect the currently loaded event loop by probing whether one of the
108	following modules is already loaded: EV, Event, Glib,	120	following modules is already loaded: EV, AnyEvent::Loop, Event, Glib,
109	AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is	121	Tk, Event::Lib, Qt, POE. The first one found is used. If none are
110	used. If none are found, the module tries to load these modules	122	detected, the module tries to load the first four modules in the order
111	(excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should	123	given; but note that if EV is not available, the pure-perl
112	always succeed) in the order given. The first one that can be	124	AnyEvent::Loop should always work, so the other two are not normally
113	successfully loaded will be used. If, after this, still none could be	125	tried.
114	found, AnyEvent will fall back to a pure-perl event loop, which is not
115	very efficient, but should work everywhere.
116		126
117	Because AnyEvent first checks for modules that are already loaded,	127	Because AnyEvent first checks for modules that are already loaded,
118	loading an event model explicitly before first using AnyEvent will	128	loading an event model explicitly before first using AnyEvent will
119	likely make that model the default. For example:	129	likely make that model the default. For example:
120		130
…		…
122	use AnyEvent;	132	use AnyEvent;
123		133
124	# .. AnyEvent will likely default to Tk	134	# .. AnyEvent will likely default to Tk
125		135
126	The likely means that, if any module loads another event model and	136	The likely means that, if any module loads another event model and
127	starts using it, all bets are off. Maybe you should tell their authors	137	starts using it, all bets are off - this case should be very rare
128	to use AnyEvent so their modules work together with others seamlessly...	138	though, as very few modules hardcode event loops without announcing this
		139	very loudly.
129		140
130	The pure-perl implementation of AnyEvent is called	141	The pure-perl implementation of AnyEvent is called "AnyEvent::Loop".
131	"AnyEvent::Impl::Perl". Like other event modules you can load it	142	Like other event modules you can load it explicitly and enjoy the high
132	explicitly and enjoy the high availability of that event loop :)	143	availability of that event loop :)
133		144
134	WATCHERS	145	WATCHERS
135	AnyEvent has the central concept of a watcher, which is an object that	146	AnyEvent has the central concept of a watcher, which is an object that
136	stores relevant data for each kind of event you are waiting for, such as	147	stores relevant data for each kind of event you are waiting for, such as
137	the callback to call, the file handle to watch, etc.	148	the callback to call, the file handle to watch, etc.
…		…
141	callback when the event occurs (of course, only when the event model is	152	callback when the event occurs (of course, only when the event model is
142	in control).	153	in control).
143		154
144	Note that callbacks must not permanently change global variables	155	Note that callbacks must not permanently change global variables
145	potentially in use by the event loop (such as $_ or $[) and that	156	potentially in use by the event loop (such as $_ or $[) and that
146	callbacks must not "die". The former is good programming practise in	157	callbacks must not "die". The former is good programming practice in
147	Perl and the latter stems from the fact that exception handling differs	158	Perl and the latter stems from the fact that exception handling differs
148	widely between event loops.	159	widely between event loops.
149		160
150	To disable the watcher you have to destroy it (e.g. by setting the	161	To disable a watcher you have to destroy it (e.g. by setting the
151	variable you store it in to "undef" or otherwise deleting all references	162	variable you store it in to "undef" or otherwise deleting all references
152	to it).	163	to it).
153		164
154	All watchers are created by calling a method on the "AnyEvent" class.	165	All watchers are created by calling a method on the "AnyEvent" class.
155		166
156	Many watchers either are used with "recursion" (repeating timers for	167	Many watchers either are used with "recursion" (repeating timers for
157	example), or need to refer to their watcher object in other ways.	168	example), or need to refer to their watcher object in other ways.
158		169
159	An any way to achieve that is this pattern:	170	One way to achieve that is this pattern:
160		171
161	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	172	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
162	# you can use $w here, for example to undef it	173	# you can use $w here, for example to undef it
163	undef $w;	174	undef $w;
164	});	175	});
…		…
166	Note that "my $w; $w =" combination. This is necessary because in Perl,	177	Note that "my $w; $w =" combination. This is necessary because in Perl,
167	my variables are only visible after the statement in which they are	178	my variables are only visible after the statement in which they are
168	declared.	179	declared.
169		180
170	I/O WATCHERS	181	I/O WATCHERS
		182	$w = AnyEvent->io (
		183	fh => <filehandle_or_fileno>,
		184	poll => <"r" or "w">,
		185	cb => <callback>,
		186	);
		187
171	You can create an I/O watcher by calling the "AnyEvent->io" method with	188	You can create an I/O watcher by calling the "AnyEvent->io" method with
172	the following mandatory key-value pairs as arguments:	189	the following mandatory key-value pairs as arguments:
173		190
174	"fh" is the Perl file handle (not file descriptor) to watch for	191	"fh" is the Perl file handle (or a naked file descriptor) to watch for
175	events (AnyEvent might or might not keep a reference to this file	192	events (AnyEvent might or might not keep a reference to this file
176	handle). Note that only file handles pointing to things for which	193	handle). Note that only file handles pointing to things for which
177	non-blocking operation makes sense are allowed. This includes sockets,	194	non-blocking operation makes sense are allowed. This includes sockets,
178	most character devices, pipes, fifos and so on, but not for example	195	most character devices, pipes, fifos and so on, but not for example
179	files or block devices.	196	files or block devices.
…		…
189		206
190	The I/O watcher might use the underlying file descriptor or a copy of	207	The I/O watcher might use the underlying file descriptor or a copy of
191	it. You must not close a file handle as long as any watcher is active on	208	it. You must not close a file handle as long as any watcher is active on
192	the underlying file descriptor.	209	the underlying file descriptor.
193		210
194	Some event loops issue spurious readyness notifications, so you should	211	Some event loops issue spurious readiness notifications, so you should
195	always use non-blocking calls when reading/writing from/to your file	212	always use non-blocking calls when reading/writing from/to your file
196	handles.	213	handles.
197		214
198	Example: wait for readability of STDIN, then read a line and disable the	215	Example: wait for readability of STDIN, then read a line and disable the
199	watcher.	216	watcher.
…		…
203	warn "read: $input\n";	220	warn "read: $input\n";
204	undef $w;	221	undef $w;
205	});	222	});
206		223
207	TIME WATCHERS	224	TIME WATCHERS
		225	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		226
		227	$w = AnyEvent->timer (
		228	after => <fractional_seconds>,
		229	interval => <fractional_seconds>,
		230	cb => <callback>,
		231	);
		232
208	You can create a time watcher by calling the "AnyEvent->timer" method	233	You can create a time watcher by calling the "AnyEvent->timer" method
209	with the following mandatory arguments:	234	with the following mandatory arguments:
210		235
211	"after" specifies after how many seconds (fractional values are	236	"after" specifies after how many seconds (fractional values are
212	supported) the callback should be invoked. "cb" is the callback to	237	supported) the callback should be invoked. "cb" is the callback to
…		…
214		239
215	Although the callback might get passed parameters, their value and	240	Although the callback might get passed parameters, their value and
216	presence is undefined and you cannot rely on them. Portable AnyEvent	241	presence is undefined and you cannot rely on them. Portable AnyEvent
217	callbacks cannot use arguments passed to time watcher callbacks.	242	callbacks cannot use arguments passed to time watcher callbacks.
218		243
219	The callback will normally be invoked once only. If you specify another	244	The callback will normally be invoked only once. If you specify another
220	parameter, "interval", as a strictly positive number (> 0), then the	245	parameter, "interval", as a strictly positive number (> 0), then the
221	callback will be invoked regularly at that interval (in fractional	246	callback will be invoked regularly at that interval (in fractional
222	seconds) after the first invocation. If "interval" is specified with a	247	seconds) after the first invocation. If "interval" is specified with a
223	false value, then it is treated as if it were missing.	248	false value, then it is treated as if it were not specified at all.
224		249
225	The callback will be rescheduled before invoking the callback, but no	250	The callback will be rescheduled before invoking the callback, but no
226	attempt is done to avoid timer drift in most backends, so the interval	251	attempt is made to avoid timer drift in most backends, so the interval
227	is only approximate.	252	is only approximate.
228		253
229	Example: fire an event after 7.7 seconds.	254	Example: fire an event after 7.7 seconds.
230		255
231	my $w = AnyEvent->timer (after => 7.7, cb => sub {	256	my $w = AnyEvent->timer (after => 7.7, cb => sub {
…		…
248		273
249	While most event loops expect timers to specified in a relative way,	274	While most event loops expect timers to specified in a relative way,
250	they use absolute time internally. This makes a difference when your	275	they use absolute time internally. This makes a difference when your
251	clock "jumps", for example, when ntp decides to set your clock backwards	276	clock "jumps", for example, when ntp decides to set your clock backwards
252	from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is	277	from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is
253	supposed to fire "after" a second might actually take six years to	278	supposed to fire "after a second" might actually take six years to
254	finally fire.	279	finally fire.
255		280
256	AnyEvent cannot compensate for this. The only event loop that is	281	AnyEvent cannot compensate for this. The only event loop that is
257	conscious about these issues is EV, which offers both relative	282	conscious of these issues is EV, which offers both relative (ev_timer,
258	(ev_timer, based on true relative time) and absolute (ev_periodic, based	283	based on true relative time) and absolute (ev_periodic, based on
259	on wallclock time) timers.	284	wallclock time) timers.
260		285
261	AnyEvent always prefers relative timers, if available, matching the	286	AnyEvent always prefers relative timers, if available, matching the
262	AnyEvent API.	287	AnyEvent API.
263		288
264	AnyEvent has two additional methods that return the "current time":	289	AnyEvent has two additional methods that return the "current time":
…		…
283	*In almost all cases (in all cases if you don't care), this is the	308	*In almost all cases (in all cases if you don't care), this is the
284	function to call when you want to know the current time.*	309	function to call when you want to know the current time.*
285		310
286	This function is also often faster then "AnyEvent->time", and thus	311	This function is also often faster then "AnyEvent->time", and thus
287	the preferred method if you want some timestamp (for example,	312	the preferred method if you want some timestamp (for example,
288	AnyEvent::Handle uses this to update it's activity timeouts).	313	AnyEvent::Handle uses this to update its activity timeouts).
289		314
290	The rest of this section is only of relevance if you try to be very	315	The rest of this section is only of relevance if you try to be very
291	exact with your timing, you can skip it without bad conscience.	316	exact with your timing; you can skip it without a bad conscience.
292		317
293	For a practical example of when these times differ, consider	318	For a practical example of when these times differ, consider
294	Event::Lib and EV and the following set-up:	319	Event::Lib and EV and the following set-up:
295		320
296	The event loop is running and has just invoked one of your callback	321	The event loop is running and has just invoked one of your callbacks
297	at time=500 (assume no other callbacks delay processing). In your	322	at time=500 (assume no other callbacks delay processing). In your
298	callback, you wait a second by executing "sleep 1" (blocking the	323	callback, you wait a second by executing "sleep 1" (blocking the
299	process for a second) and then (at time=501) you create a relative	324	process for a second) and then (at time=501) you create a relative
300	timer that fires after three seconds.	325	timer that fires after three seconds.
301		326
…		…
322	can get whatever behaviour you want with any event loop, by taking	347	can get whatever behaviour you want with any event loop, by taking
323	the difference between "AnyEvent->time" and "AnyEvent->now" into	348	the difference between "AnyEvent->time" and "AnyEvent->now" into
324	account.	349	account.
325		350
326	AnyEvent->now_update	351	AnyEvent->now_update
327	Some event loops (such as EV or AnyEvent::Impl::Perl) cache the	352	Some event loops (such as EV or AnyEvent::Loop) cache the current
328	current time for each loop iteration (see the discussion of	353	time for each loop iteration (see the discussion of AnyEvent->now,
329	AnyEvent->now, above).	354	above).
330		355
331	When a callback runs for a long time (or when the process sleeps),	356	When a callback runs for a long time (or when the process sleeps),
332	then this "current" time will differ substantially from the real	357	then this "current" time will differ substantially from the real
333	time, which might affect timers and time-outs.	358	time, which might affect timers and time-outs.
334		359
335	When this is the case, you can call this method, which will update	360	When this is the case, you can call this method, which will update
336	the event loop's idea of "current time".	361	the event loop's idea of "current time".
337		362
		363	A typical example would be a script in a web server (e.g.
		364	"mod_perl") - when mod_perl executes the script, then the event loop
		365	will have the wrong idea about the "current time" (being potentially
		366	far in the past, when the script ran the last time). In that case
		367	you should arrange a call to "AnyEvent->now_update" each time the
		368	web server process wakes up again (e.g. at the start of your script,
		369	or in a handler).
		370
338	Note that updating the time might cause some events to be handled.	371	Note that updating the time might cause some events to be handled.
339		372
340	SIGNAL WATCHERS	373	SIGNAL WATCHERS
		374	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		375
341	You can watch for signals using a signal watcher, "signal" is the signal	376	You can watch for signals using a signal watcher, "signal" is the signal
342	name in uppercase and without any "SIG" prefix, "cb" is the Perl	377	name in uppercase and without any "SIG" prefix, "cb" is the Perl
343	callback to be invoked whenever a signal occurs.	378	callback to be invoked whenever a signal occurs.
344		379
345	Although the callback might get passed parameters, their value and	380	Although the callback might get passed parameters, their value and
…		…
350	invocation, and callback invocation will be synchronous. Synchronous	385	invocation, and callback invocation will be synchronous. Synchronous
351	means that it might take a while until the signal gets handled by the	386	means that it might take a while until the signal gets handled by the
352	process, but it is guaranteed not to interrupt any other callbacks.	387	process, but it is guaranteed not to interrupt any other callbacks.
353		388
354	The main advantage of using these watchers is that you can share a	389	The main advantage of using these watchers is that you can share a
355	signal between multiple watchers.	390	signal between multiple watchers, and AnyEvent will ensure that signals
		391	will not interrupt your program at bad times.
356		392
357	This watcher might use %SIG, so programs overwriting those signals	393	This watcher might use %SIG (depending on the event loop used), so
358	directly will likely not work correctly.	394	programs overwriting those signals directly will likely not work
		395	correctly.
359		396
360	Example: exit on SIGINT	397	Example: exit on SIGINT
361		398
362	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	399	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
363		400
		401	Restart Behaviour
		402	While restart behaviour is up to the event loop implementation, most
		403	will not restart syscalls (that includes Async::Interrupt and AnyEvent's
		404	pure perl implementation).
		405
		406	Safe/Unsafe Signals
		407	Perl signals can be either "safe" (synchronous to opcode handling) or
		408	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		409	latter might corrupt your memory.
		410
		411	AnyEvent signal handlers are, in addition, synchronous to the event
		412	loop, i.e. they will not interrupt your running perl program but will
		413	only be called as part of the normal event handling (just like timer,
		414	I/O etc. callbacks, too).
		415
		416	Signal Races, Delays and Workarounds
		417	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		418	callbacks to signals in a generic way, which is a pity, as you cannot do
		419	race-free signal handling in perl, requiring C libraries for this.
		420	AnyEvent will try to do its best, which means in some cases, signals
		421	will be delayed. The maximum time a signal might be delayed is specified
		422	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
		423	can be changed only before the first signal watcher is created, and
		424	should be left alone otherwise. This variable determines how often
		425	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		426	will cause fewer spurious wake-ups, which is better for power and CPU
		427	saving.
		428
		429	All these problems can be avoided by installing the optional
		430	Async::Interrupt module, which works with most event loops. It will not
		431	work with inherently broken event loops such as Event or Event::Lib (and
		432	not with POE currently, as POE does its own workaround with one-second
		433	latency). For those, you just have to suffer the delays.
		434
364	CHILD PROCESS WATCHERS	435	CHILD PROCESS WATCHERS
		436	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		437
365	You can also watch on a child process exit and catch its exit status.	438	You can also watch for a child process exit and catch its exit status.
366		439
367	The child process is specified by the "pid" argument (if set to 0, it	440	The child process is specified by the "pid" argument (on some backends,
368	watches for any child process exit). The watcher will triggered only	441	using 0 watches for any child process exit, on others this will croak).
369	when the child process has finished and an exit status is available, not	442	The watcher will be triggered only when the child process has finished
370	on any trace events (stopped/continued).	443	and an exit status is available, not on any trace events
		444	(stopped/continued).
371		445
372	The callback will be called with the pid and exit status (as returned by	446	The callback will be called with the pid and exit status (as returned by
373	waitpid), so unlike other watcher types, you can rely on child watcher	447	waitpid), so unlike other watcher types, you can rely on child watcher
374	callback arguments.	448	callback arguments.
375		449
…		…
390	of when you start the watcher.	464	of when you start the watcher.
391		465
392	This means you cannot create a child watcher as the very first thing in	466	This means you cannot create a child watcher as the very first thing in
393	an AnyEvent program, you have to create at least one watcher before	467	an AnyEvent program, you have to create at least one watcher before
394	you "fork" the child (alternatively, you can call "AnyEvent::detect").	468	you "fork" the child (alternatively, you can call "AnyEvent::detect").
		469
		470	As most event loops do not support waiting for child events, they will
		471	be emulated by AnyEvent in most cases, in which case the latency and
		472	race problems mentioned in the description of signal watchers apply.
395		473
396	Example: fork a process and wait for it	474	Example: fork a process and wait for it
397		475
398	my $done = AnyEvent->condvar;	476	my $done = AnyEvent->condvar;
399		477
…		…
410		488
411	# do something else, then wait for process exit	489	# do something else, then wait for process exit
412	$done->recv;	490	$done->recv;
413		491
414	IDLE WATCHERS	492	IDLE WATCHERS
415	Sometimes there is a need to do something, but it is not so important to	493	$w = AnyEvent->idle (cb => <callback>);
416	do it instantly, but only when there is nothing better to do. This
417	"nothing better to do" is usually defined to be "no other events need
418	attention by the event loop".
419		494
420	Idle watchers ideally get invoked when the event loop has nothing better	495	This will repeatedly invoke the callback after the process becomes idle,
421	to do, just before it would block the process to wait for new events.	496	until either the watcher is destroyed or new events have been detected.
422	Instead of blocking, the idle watcher is invoked.
423		497
424	Most event loops unfortunately do not really support idle watchers (only	498	Idle watchers are useful when there is a need to do something, but it is
		499	not so important (or wise) to do it instantly. The callback will be
		500	invoked only when there is "nothing better to do", which is usually
		501	defined as "all outstanding events have been handled and no new events
		502	have been detected". That means that idle watchers ideally get invoked
		503	when the event loop has just polled for new events but none have been
		504	detected. Instead of blocking to wait for more events, the idle watchers
		505	will be invoked.
		506
		507	Unfortunately, most event loops do not really support idle watchers
425	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent	508	(only EV, Event and Glib do it in a usable fashion) - for the rest,
426	will simply call the callback "from time to time".	509	AnyEvent will simply call the callback "from time to time".
427		510
428	Example: read lines from STDIN, but only process them when the program	511	Example: read lines from STDIN, but only process them when the program
429	is otherwise idle:	512	is otherwise idle:
430		513
431	my @lines; # read data	514	my @lines; # read data
…		…
444	}	527	}
445	});	528	});
446	});	529	});
447		530
448	CONDITION VARIABLES	531	CONDITION VARIABLES
		532	$cv = AnyEvent->condvar;
		533
		534	$cv->send (<list>);
		535	my @res = $cv->recv;
		536
449	If you are familiar with some event loops you will know that all of them	537	If you are familiar with some event loops you will know that all of them
450	require you to run some blocking "loop", "run" or similar function that	538	require you to run some blocking "loop", "run" or similar function that
451	will actively watch for new events and call your callbacks.	539	will actively watch for new events and call your callbacks.
452		540
453	AnyEvent is different, it expects somebody else to run the event loop	541	AnyEvent is slightly different: it expects somebody else to run the
454	and will only block when necessary (usually when told by the user).	542	event loop and will only block when necessary (usually when told by the
		543	user).
455		544
456	The instrument to do that is called a "condition variable", so called	545	The tool to do that is called a "condition variable", so called because
457	because they represent a condition that must become true.	546	they represent a condition that must become true.
		547
		548	Now is probably a good time to look at the examples further below.
458		549
459	Condition variables can be created by calling the "AnyEvent->condvar"	550	Condition variables can be created by calling the "AnyEvent->condvar"
460	method, usually without arguments. The only argument pair allowed is	551	method, usually without arguments. The only argument pair allowed is
461
462	"cb", which specifies a callback to be called when the condition	552	"cb", which specifies a callback to be called when the condition
463	variable becomes true, with the condition variable as the first argument	553	variable becomes true, with the condition variable as the first argument
464	(but not the results).	554	(but not the results).
465		555
466	After creation, the condition variable is "false" until it becomes	556	After creation, the condition variable is "false" until it becomes
467	"true" by calling the "send" method (or calling the condition variable	557	"true" by calling the "send" method (or calling the condition variable
468	as if it were a callback, read about the caveats in the description for	558	as if it were a callback, read about the caveats in the description for
469	the "->send" method).	559	the "->send" method).
470		560
471	Condition variables are similar to callbacks, except that you can	561	Since condition variables are the most complex part of the AnyEvent API,
472	optionally wait for them. They can also be called merge points - points	562	here are some different mental models of what they are - pick the ones
473	in time where multiple outstanding events have been processed. And yet	563	you can connect to:
474	another way to call them is transactions - each condition variable can	564
475	be used to represent a transaction, which finishes at some point and	565	* Condition variables are like callbacks - you can call them (and pass
476	delivers a result.	566	them instead of callbacks). Unlike callbacks however, you can also
		567	wait for them to be called.
		568
		569	* Condition variables are signals - one side can emit or send them,
		570	the other side can wait for them, or install a handler that is
		571	called when the signal fires.
		572
		573	* Condition variables are like "Merge Points" - points in your program
		574	where you merge multiple independent results/control flows into one.
		575
		576	* Condition variables represent a transaction - functions that start
		577	some kind of transaction can return them, leaving the caller the
		578	choice between waiting in a blocking fashion, or setting a callback.
		579
		580	* Condition variables represent future values, or promises to deliver
		581	some result, long before the result is available.
477		582
478	Condition variables are very useful to signal that something has	583	Condition variables are very useful to signal that something has
479	finished, for example, if you write a module that does asynchronous http	584	finished, for example, if you write a module that does asynchronous http
480	requests, then a condition variable would be the ideal candidate to	585	requests, then a condition variable would be the ideal candidate to
481	signal the availability of results. The user can either act when the	586	signal the availability of results. The user can either act when the
…		…
494		599
495	Condition variables are represented by hash refs in perl, and the keys	600	Condition variables are represented by hash refs in perl, and the keys
496	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy	601	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy
497	(it is often useful to build your own transaction class on top of	602	(it is often useful to build your own transaction class on top of
498	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	603	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
499	it's "new" method in your own "new" method.	604	its "new" method in your own "new" method.
500		605
501	There are two "sides" to a condition variable - the "producer side"	606	There are two "sides" to a condition variable - the "producer side"
502	which eventually calls "-> send", and the "consumer side", which waits	607	which eventually calls "-> send", and the "consumer side", which waits
503	for the send to occur.	608	for the send to occur.
504		609
505	Example: wait for a timer.	610	Example: wait for a timer.
506		611
507	# wait till the result is ready	612	# condition: "wait till the timer is fired"
508	my $result_ready = AnyEvent->condvar;	613	my $timer_fired = AnyEvent->condvar;
509		614
510	# do something such as adding a timer	615	# create the timer - we could wait for, say
511	# or socket watcher the calls $result_ready->send	616	# a handle becomign ready, or even an
512	# when the "result" is ready.	617	# AnyEvent::HTTP request to finish, but
513	# in this case, we simply use a timer:	618	# in this case, we simply use a timer:
514	my $w = AnyEvent->timer (	619	my $w = AnyEvent->timer (
515	after => 1,	620	after => 1,
516	cb => sub { $result_ready->send },	621	cb => sub { $timer_fired->send },
517	);	622	);
518		623
519	# this "blocks" (while handling events) till the callback	624	# this "blocks" (while handling events) till the callback
520	# calls send	625	# calls ->send
521	$result_ready->recv;	626	$timer_fired->recv;
522		627
523	Example: wait for a timer, but take advantage of the fact that condition	628	Example: wait for a timer, but take advantage of the fact that condition
524	variables are also code references.	629	variables are also callable directly.
525		630
526	my $done = AnyEvent->condvar;	631	my $done = AnyEvent->condvar;
527	my $delay = AnyEvent->timer (after => 5, cb => $done);	632	my $delay = AnyEvent->timer (after => 5, cb => $done);
528	$done->recv;	633	$done->recv;
529		634
…		…
535		640
536	...	641	...
537		642
538	my @info = $couchdb->info->recv;	643	my @info = $couchdb->info->recv;
539		644
540	And this is how you would just ste a callback to be called whenever the	645	And this is how you would just set a callback to be called whenever the
541	results are available:	646	results are available:
542		647
543	$couchdb->info->cb (sub {	648	$couchdb->info->cb (sub {
544	my @info = $_[0]->recv;	649	my @info = $_[0]->recv;
545	});	650	});
…		…
560		665
561	Any arguments passed to the "send" call will be returned by all	666	Any arguments passed to the "send" call will be returned by all
562	future "->recv" calls.	667	future "->recv" calls.
563		668
564	Condition variables are overloaded so one can call them directly (as	669	Condition variables are overloaded so one can call them directly (as
565	a code reference). Calling them directly is the same as calling	670	if they were a code reference). Calling them directly is the same as
566	"send". Note, however, that many C-based event loops do not handle	671	calling "send".
567	overloading, so as tempting as it may be, passing a condition
568	variable instead of a callback does not work. Both the pure perl and
569	EV loops support overloading, however, as well as all functions that
570	use perl to invoke a callback (as in AnyEvent::Socket and
571	AnyEvent::DNS for example).
572		672
573	$cv->croak ($error)	673	$cv->croak ($error)
574	Similar to send, but causes all call's to "->recv" to invoke	674	Similar to send, but causes all calls to "->recv" to invoke
575	"Carp::croak" with the given error message/object/scalar.	675	"Carp::croak" with the given error message/object/scalar.
576		676
577	This can be used to signal any errors to the condition variable	677	This can be used to signal any errors to the condition variable
578	user/consumer.	678	user/consumer. Doing it this way instead of calling "croak" directly
		679	delays the error detection, but has the overwhelming advantage that
		680	it diagnoses the error at the place where the result is expected,
		681	and not deep in some event callback with no connection to the actual
		682	code causing the problem.
579		683
580	$cv->begin ([group callback])	684	$cv->begin ([group callback])
581	$cv->end	685	$cv->end
582	These two methods are EXPERIMENTAL and MIGHT CHANGE.
583
584	These two methods can be used to combine many transactions/events	686	These two methods can be used to combine many transactions/events
585	into one. For example, a function that pings many hosts in parallel	687	into one. For example, a function that pings many hosts in parallel
586	might want to use a condition variable for the whole process.	688	might want to use a condition variable for the whole process.
587		689
588	Every call to "->begin" will increment a counter, and every call to	690	Every call to "->begin" will increment a counter, and every call to
589	"->end" will decrement it. If the counter reaches 0 in "->end", the	691	"->end" will decrement it. If the counter reaches 0 in "->end", the
590	(last) callback passed to "begin" will be executed. That callback is	692	(last) callback passed to "begin" will be executed, passing the
591	supposed to call "->send", but that is not required. If no	693	condvar as first argument. That callback is supposed to call
		694	"->send", but that is not required. If no group callback was set,
592	callback was set, "send" will be called without any arguments.	695	"send" will be called without any arguments.
593		696
594	Let's clarify this with the ping example:	697	You can think of "$cv->send" giving you an OR condition (one call
		698	sends), while "$cv->begin" and "$cv->end" giving you an AND
		699	condition (all "begin" calls must be "end"'ed before the condvar
		700	sends).
		701
		702	Let's start with a simple example: you have two I/O watchers (for
		703	example, STDOUT and STDERR for a program), and you want to wait for
		704	both streams to close before activating a condvar:
595		705
596	my $cv = AnyEvent->condvar;	706	my $cv = AnyEvent->condvar;
597		707
		708	$cv->begin; # first watcher
		709	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		710	defined sysread $fh1, my $buf, 4096
		711	or $cv->end;
		712	});
		713
		714	$cv->begin; # second watcher
		715	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		716	defined sysread $fh2, my $buf, 4096
		717	or $cv->end;
		718	});
		719
		720	$cv->recv;
		721
		722	This works because for every event source (EOF on file handle),
		723	there is one call to "begin", so the condvar waits for all calls to
		724	"end" before sending.
		725
		726	The ping example mentioned above is slightly more complicated, as
		727	the there are results to be passwd back, and the number of tasks
		728	that are begun can potentially be zero:
		729
		730	my $cv = AnyEvent->condvar;
		731
598	my %result;	732	my %result;
599	$cv->begin (sub { $cv->send (\%result) });	733	$cv->begin (sub { shift->send (\%result) });
600		734
601	for my $host (@list_of_hosts) {	735	for my $host (@list_of_hosts) {
602	$cv->begin;	736	$cv->begin;
603	ping_host_then_call_callback $host, sub {	737	ping_host_then_call_callback $host, sub {
604	$result{$host} = ...;	738	$result{$host} = ...;
…		…
619	the loop, which serves two important purposes: first, it sets the	753	the loop, which serves two important purposes: first, it sets the
620	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
621	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
622	(the loop doesn't execute once).	756	(the loop doesn't execute once).
623		757
624	This is the general pattern when you "fan out" into multiple	758	This is the general pattern when you "fan out" into multiple (but
625	subrequests: use an outer "begin"/"end" pair to set the callback and	759	potentially zero) subrequests: use an outer "begin"/"end" pair to
626	ensure "end" is called at least once, and then, for each subrequest	760	set the callback and ensure "end" is called at least once, and then,
627	you start, call "begin" and for each subrequest you finish, call	761	for each subrequest you start, call "begin" and for each subrequest
628	"end".	762	you finish, call "end".
629		763
630	METHODS FOR CONSUMERS	764	METHODS FOR CONSUMERS
631	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
632	awaits the condition.	766	awaits the condition.
633		767
634	$cv->recv	768	$cv->recv
635	Wait (blocking if necessary) until the "->send" or "->croak" methods	769	Wait (blocking if necessary) until the "->send" or "->croak" methods
636	have been called on c<$cv>, while servicing other watchers normally.	770	have been called on $cv, while servicing other watchers normally.
637		771
638	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
639	but will return immediately.	773	but will return immediately.
640		774
641	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
642	function will call "croak".	776	function will call "croak".
643		777
644	In list context, all parameters passed to "send" will be returned,	778	In list context, all parameters passed to "send" will be returned,
645	in scalar context only the first one will be returned.	779	in scalar context only the first one will be returned.
646		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
647	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
648	(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
649	using this from a module, never require a blocking wait*, but let	790	using this from a module, never require a blocking wait*. Instead,
650	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
651	by coupling condition variables with some kind of request results	792	example, by coupling condition variables with some kind of request
652	and supporting callbacks so the caller knows that getting the result	793	results and supporting callbacks so the caller knows that getting
653	will not block, while still supporting blocking waits if the caller	794	the result will not block, while still supporting blocking waits if
654	so desires).	795	the caller so desires).
655		796
656	Another reason never to "->recv" in a module is that you cannot
657	sensibly have two "->recv"'s in parallel, as that would require
658	multiple interpreters or coroutines/threads, none of which
659	"AnyEvent" can supply.
660
661	The Coro module, however, can and does supply coroutines and, in
662	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
663	versions and also integrates coroutines into AnyEvent, making
664	blocking "->recv" calls perfectly safe as long as they are done from
665	another coroutine (one that doesn't run the event loop).
666
667	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
668	only calling "->recv" from within that callback (or at a later	798	only calling "->recv" from within that callback (or at a later
669	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
670	blocking waits otherwise.	800	blocking waits otherwise.
671		801
672	$bool = $cv->ready	802	$bool = $cv->ready
…		…
677	This is a mutator function that returns the callback set and	807	This is a mutator function that returns the callback set and
678	optionally replaces it before doing so.	808	optionally replaces it before doing so.
679		809
680	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.
681	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
682	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
683	any later time is guaranteed not to block.	814	the callback or at any later time is guaranteed not to block.
		815
		816	SUPPORTED EVENT LOOPS/BACKENDS
		817	The available backend classes are (every class has its own manpage):
		818
		819	Backends that are autoprobed when no other event loop can be found.
		820	EV is the preferred backend when no other event loop seems to be in
		821	use. If EV is not installed, then AnyEvent will fall back to its own
		822	pure-perl implementation, which is available everywhere as it comes
		823	with AnyEvent itself.
		824
		825	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		826	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		827
		828	Backends that are transparently being picked up when they are used.
		829	These will be used if they are already loaded when the first watcher
		830	is created, in which case it is assumed that the application is
		831	using them. This means that AnyEvent will automatically pick the
		832	right backend when the main program loads an event module before
		833	anything starts to create watchers. Nothing special needs to be done
		834	by the main program.
		835
		836	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		837	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		838	AnyEvent::Impl::Tk based on Tk, very broken.
		839	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		840	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		841	AnyEvent::Impl::Irssi used when running within irssi.
		842	AnyEvent::Impl::IOAsync based on IO::Async.
		843	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		844	AnyEvent::Impl::FLTK2 based on FLTK (fltk 2 binding).
		845
		846	Backends with special needs.
		847	Qt requires the Qt::Application to be instantiated first, but will
		848	otherwise be picked up automatically. As long as the main program
		849	instantiates the application before any AnyEvent watchers are
		850	created, everything should just work.
		851
		852	AnyEvent::Impl::Qt based on Qt.
		853
		854	Event loops that are indirectly supported via other backends.
		855	Some event loops can be supported via other modules:
		856
		857	There is no direct support for WxWidgets (Wx) or Prima.
		858
		859	WxWidgets has no support for watching file handles. However, you can
		860	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		861	simply polls 20 times per second, which was considered to be too
		862	horrible to even consider for AnyEvent.
		863
		864	Prima is not supported as nobody seems to be using it, but it has a
		865	POE backend, so it can be supported through POE.
		866
		867	AnyEvent knows about both Prima and Wx, however, and will try to
		868	load POE when detecting them, in the hope that POE will pick them
		869	up, in which case everything will be automatic.
684		870
685	GLOBAL VARIABLES AND FUNCTIONS	871	GLOBAL VARIABLES AND FUNCTIONS
		872	These are not normally required to use AnyEvent, but can be useful to
		873	write AnyEvent extension modules.
		874
686	$AnyEvent::MODEL	875	$AnyEvent::MODEL
687	Contains "undef" until the first watcher is being created. Then it	876	Contains "undef" until the first watcher is being created, before
		877	the backend has been autodetected.
		878
688	contains the event model that is being used, which is the name of	879	Afterwards it contains the event model that is being used, which is
689	the Perl class implementing the model. This class is usually one of	880	the name of the Perl class implementing the model. This class is
690	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	881	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
691	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).	882	other class in the case AnyEvent has been extended at runtime (e.g.
692		883	in rxvt-unicode it will be "urxvt::anyevent").
693	The known classes so far are:
694
695	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
696	AnyEvent::Impl::Event based on Event, second best choice.
697	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
698	AnyEvent::Impl::Glib based on Glib, third-best choice.
699	AnyEvent::Impl::Tk based on Tk, very bad choice.
700	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
701	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
702	AnyEvent::Impl::POE based on POE, not generic enough for full support.
703
704	# warning, support for IO::Async is only partial, as it is too broken
705	# and limited toe ven support the AnyEvent API. See AnyEvent::Impl::Async.
706	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed (see its docs).
707
708	There is no support for WxWidgets, as WxWidgets has no support for
709	watching file handles. However, you can use WxWidgets through the
710	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
711	second, which was considered to be too horrible to even consider for
712	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
713	using it's adaptor.
714
715	AnyEvent knows about Prima and Wx and will try to use POE when
716	autodetecting them.
717		884
718	AnyEvent::detect	885	AnyEvent::detect
719	Returns $AnyEvent::MODEL, forcing autodetection of the event model	886	Returns $AnyEvent::MODEL, forcing autodetection of the event model
720	if necessary. You should only call this function right before you	887	if necessary. You should only call this function right before you
721	would have created an AnyEvent watcher anyway, that is, as late as	888	would have created an AnyEvent watcher anyway, that is, as late as
722	possible at runtime.	889	possible at runtime, and not e.g. during initialisation of your
		890	module.
		891
		892	The effect of calling this function is as if a watcher had been
		893	created (specifically, actions that happen "when the first watcher
		894	is created" happen when calling detetc as well).
		895
		896	If you need to do some initialisation before AnyEvent watchers are
		897	created, use "post_detect".
723		898
724	$guard = AnyEvent::post_detect { BLOCK }	899	$guard = AnyEvent::post_detect { BLOCK }
725	Arranges for the code block to be executed as soon as the event	900	Arranges for the code block to be executed as soon as the event
726	model is autodetected (or immediately if this has already happened).	901	model is autodetected (or immediately if that has already happened).
		902
		903	The block will be executed after the actual backend has been
		904	detected ($AnyEvent::MODEL is set), but before any watchers have
		905	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		906	other initialisations - see the sources of AnyEvent::Strict or
		907	AnyEvent::AIO to see how this is used.
		908
		909	The most common usage is to create some global watchers, without
		910	forcing event module detection too early, for example, AnyEvent::AIO
		911	creates and installs the global IO::AIO watcher in a "post_detect"
		912	block to avoid autodetecting the event module at load time.
727		913
728	If called in scalar or list context, then it creates and returns an	914	If called in scalar or list context, then it creates and returns an
729	object that automatically removes the callback again when it is	915	object that automatically removes the callback again when it is
		916	destroyed (or "undef" when the hook was immediately executed). See
730	destroyed. See Coro::BDB for a case where this is useful.	917	AnyEvent::AIO for a case where this is useful.
		918
		919	Example: Create a watcher for the IO::AIO module and store it in
		920	$WATCHER, but do so only do so after the event loop is initialised.
		921
		922	our WATCHER;
		923
		924	my $guard = AnyEvent::post_detect {
		925	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		926	};
		927
		928	# the \|\|= is important in case post_detect immediately runs the block,
		929	# as to not clobber the newly-created watcher. assigning both watcher and
		930	# post_detect guard to the same variable has the advantage of users being
		931	# able to just C<undef $WATCHER> if the watcher causes them grief.
		932
		933	$WATCHER \|\|= $guard;
731		934
732	@AnyEvent::post_detect	935	@AnyEvent::post_detect
733	If there are any code references in this array (you can "push" to it	936	If there are any code references in this array (you can "push" to it
734	before or after loading AnyEvent), then they will called directly	937	before or after loading AnyEvent), then they will be called directly
735	after the event loop has been chosen.	938	after the event loop has been chosen.
736		939
737	You should check $AnyEvent::MODEL before adding to this array,	940	You should check $AnyEvent::MODEL before adding to this array,
738	though: if it contains a true value then the event loop has already	941	though: if it is defined then the event loop has already been
739	been detected, and the array will be ignored.	942	detected, and the array will be ignored.
740		943
741	Best use "AnyEvent::post_detect { BLOCK }" instead.	944	Best use "AnyEvent::post_detect { BLOCK }" when your application
		945	allows it, as it takes care of these details.
		946
		947	This variable is mainly useful for modules that can do something
		948	useful when AnyEvent is used and thus want to know when it is
		949	initialised, but do not need to even load it by default. This array
		950	provides the means to hook into AnyEvent passively, without loading
		951	it.
		952
		953	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		954	together, you could put this into Coro (this is the actual code used
		955	by Coro to accomplish this):
		956
		957	if (defined $AnyEvent::MODEL) {
		958	# AnyEvent already initialised, so load Coro::AnyEvent
		959	require Coro::AnyEvent;
		960	} else {
		961	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		962	# as soon as it is
		963	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		964	}
		965
		966	AnyEvent::postpone { BLOCK }
		967	Arranges for the block to be executed as soon as possible, but not
		968	before the call itself returns. In practise, the block will be
		969	executed just before the event loop polls for new events, or shortly
		970	afterwards.
		971
		972	This function never returns anything (to make the "return postpone {
		973	... }" idiom more useful.
		974
		975	To understand the usefulness of this function, consider a function
		976	that asynchronously does something for you and returns some
		977	transaction object or guard to let you cancel the operation. For
		978	example, "AnyEvent::Socket::tcp_connect":
		979
		980	# start a conenction attempt unless one is active
		981	$self->{connect_guard} \|\|= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		982	delete $self->{connect_guard};
		983	...
		984	};
		985
		986	Imagine that this function could instantly call the callback, for
		987	example, because it detects an obvious error such as a negative port
		988	number. Invoking the callback before the function returns causes
		989	problems however: the callback will be called and will try to delete
		990	the guard object. But since the function hasn't returned yet, there
		991	is nothing to delete. When the function eventually returns it will
		992	assign the guard object to "$self->{connect_guard}", where it will
		993	likely never be deleted, so the program thinks it is still trying to
		994	connect.
		995
		996	This is where "AnyEvent::postpone" should be used. Instead of
		997	calling the callback directly on error:
		998
		999	$cb->(undef), return # signal error to callback, BAD!
		1000	if $some_error_condition;
		1001
		1002	It should use "postpone":
		1003
		1004	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1005	if $some_error_condition;
742		1006
743	WHAT TO DO IN A MODULE	1007	WHAT TO DO IN A MODULE
744	As a module author, you should "use AnyEvent" and call AnyEvent methods	1008	As a module author, you should "use AnyEvent" and call AnyEvent methods
745	freely, but you should not load a specific event module or rely on it.	1009	freely, but you should not load a specific event module or rely on it.
746		1010
…		…
754	stall the whole program, and the whole point of using events is to stay	1018	stall the whole program, and the whole point of using events is to stay
755	interactive.	1019	interactive.
756		1020
757	It is fine, however, to call "->recv" when the user of your module	1021	It is fine, however, to call "->recv" when the user of your module
758	requests it (i.e. if you create a http request object ad have a method	1022	requests it (i.e. if you create a http request object ad have a method
759	called "results" that returns the results, it should call "->recv"	1023	called "results" that returns the results, it may call "->recv" freely,
760	freely, as the user of your module knows what she is doing. always).	1024	as the user of your module knows what she is doing. Always).
761		1025
762	WHAT TO DO IN THE MAIN PROGRAM	1026	WHAT TO DO IN THE MAIN PROGRAM
763	There will always be a single main program - the only place that should	1027	There will always be a single main program - the only place that should
764	dictate which event model to use.	1028	dictate which event model to use.
765		1029
766	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1030	If the program is not event-based, it need not do anything special, even
767	do anything special (it does not need to be event-based) and let	1031	when it depends on a module that uses an AnyEvent. If the program itself
768	AnyEvent decide which implementation to chose if some module relies on	1032	uses AnyEvent, but does not care which event loop is used, all it needs
769	it.	1033	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1034	available loop implementation.
770		1035
771	If the main program relies on a specific event model - for example, in	1036	If the main program relies on a specific event model - for example, in
772	Gtk2 programs you have to rely on the Glib module - you should load the	1037	Gtk2 programs you have to rely on the Glib module - you should load the
773	event module before loading AnyEvent or any module that uses it:	1038	event module before loading AnyEvent or any module that uses it:
774	generally speaking, you should load it as early as possible. The reason	1039	generally speaking, you should load it as early as possible. The reason
775	is that modules might create watchers when they are loaded, and AnyEvent	1040	is that modules might create watchers when they are loaded, and AnyEvent
776	will decide on the event model to use as soon as it creates watchers,	1041	will decide on the event model to use as soon as it creates watchers,
777	and it might chose the wrong one unless you load the correct one	1042	and it might choose the wrong one unless you load the correct one
778	yourself.	1043	yourself.
779		1044
780	You can chose to use a pure-perl implementation by loading the	1045	You can chose to use a pure-perl implementation by loading the
781	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1046	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
782	everywhere, but letting AnyEvent chose the model is generally better.	1047	but letting AnyEvent chose the model is generally better.
783		1048
784	MAINLOOP EMULATION	1049	MAINLOOP EMULATION
785	Sometimes (often for short test scripts, or even standalone programs who	1050	Sometimes (often for short test scripts, or even standalone programs who
786	only want to use AnyEvent), you do not want to run a specific event	1051	only want to use AnyEvent), you do not want to run a specific event
787	loop.	1052	loop.
…		…
797	variable somewhere, waiting for it, and sending it when the program	1062	variable somewhere, waiting for it, and sending it when the program
798	should exit cleanly.	1063	should exit cleanly.
799		1064
800	OTHER MODULES	1065	OTHER MODULES
801	The following is a non-exhaustive list of additional modules that use	1066	The following is a non-exhaustive list of additional modules that use
802	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1067	AnyEvent as a client and can therefore be mixed easily with other
803	in the same program. Some of the modules come with AnyEvent, some are	1068	AnyEvent modules and other event loops in the same program. Some of the
804	available via CPAN.	1069	modules come as part of AnyEvent, the others are available via CPAN.
805		1070
806	AnyEvent::Util	1071	AnyEvent::Util
807	Contains various utility functions that replace often-used but	1072	Contains various utility functions that replace often-used blocking
808	blocking functions such as "inet_aton" by event-/callback-based	1073	functions such as "inet_aton" with event/callback-based versions.
809	versions.
810		1074
811	AnyEvent::Socket	1075	AnyEvent::Socket
812	Provides various utility functions for (internet protocol) sockets,	1076	Provides various utility functions for (internet protocol) sockets,
813	addresses and name resolution. Also functions to create non-blocking	1077	addresses and name resolution. Also functions to create non-blocking
814	tcp connections or tcp servers, with IPv6 and SRV record support and	1078	tcp connections or tcp servers, with IPv6 and SRV record support and
815	more.	1079	more.
816		1080
817	AnyEvent::Handle	1081	AnyEvent::Handle
818	Provide read and write buffers, manages watchers for reads and	1082	Provide read and write buffers, manages watchers for reads and
819	writes, supports raw and formatted I/O, I/O queued and fully	1083	writes, supports raw and formatted I/O, I/O queued and fully
820	transparent and non-blocking SSL/TLS.	1084	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
821		1085
822	AnyEvent::DNS	1086	AnyEvent::DNS
823	Provides rich asynchronous DNS resolver capabilities.	1087	Provides rich asynchronous DNS resolver capabilities.
824		1088
		1089	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
		1090	AnyEvent::IGS, AnyEvent::FCP
		1091	Implement event-based interfaces to the protocols of the same name
		1092	(for the curious, IGS is the International Go Server and FCP is the
		1093	Freenet Client Protocol).
		1094
		1095	AnyEvent::Handle::UDP
		1096	Here be danger!
		1097
		1098	As Pauli would put it, "Not only is it not right, it's not even
		1099	wrong!" - there are so many things wrong with AnyEvent::Handle::UDP,
		1100	most notably its use of a stream-based API with a protocol that
		1101	isn't streamable, that the only way to improve it is to delete it.
		1102
		1103	It features data corruption (but typically only under load) and
		1104	general confusion. On top, the author is not only clueless about UDP
		1105	but also fact-resistant - some gems of his understanding: "connect
		1106	doesn't work with UDP", "UDP packets are not IP packets", "UDP only
		1107	has datagrams, not packets", "I don't need to implement proper error
		1108	checking as UDP doesn't support error checking" and so on - he
		1109	doesn't even understand what's wrong with his module when it is
		1110	explained to him.
		1111
825	AnyEvent::HTTP	1112	AnyEvent::DBI
826	A simple-to-use HTTP library that is capable of making a lot of	1113	Executes DBI requests asynchronously in a proxy process for you,
827	concurrent HTTP requests.	1114	notifying you in an event-based way when the operation is finished.
		1115
		1116	AnyEvent::AIO
		1117	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1118	the toolbox of every event programmer. AnyEvent::AIO transparently
		1119	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1120	event-based file I/O, and much more.
828		1121
829	AnyEvent::HTTPD	1122	AnyEvent::HTTPD
830	Provides a simple web application server framework.	1123	A simple embedded webserver.
831		1124
832	AnyEvent::FastPing	1125	AnyEvent::FastPing
833	The fastest ping in the west.	1126	The fastest ping in the west.
834		1127
835	AnyEvent::DBI
836	Executes DBI requests asynchronously in a proxy process.
837
838	AnyEvent::AIO
839	Truly asynchronous I/O, should be in the toolbox of every event
840	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
841	together.
842
843	AnyEvent::BDB
844	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
845	fuses BDB and AnyEvent together.
846
847	AnyEvent::GPSD
848	A non-blocking interface to gpsd, a daemon delivering GPS
849	information.
850
851	AnyEvent::IGS
852	A non-blocking interface to the Internet Go Server protocol (used by
853	App::IGS).
854
855	AnyEvent::IRC
856	AnyEvent based IRC client module family (replacing the older
857	Net::IRC3).
858
859	Net::XMPP2
860	AnyEvent based XMPP (Jabber protocol) module family.
861
862	Net::FCP
863	AnyEvent-based implementation of the Freenet Client Protocol,
864	birthplace of AnyEvent.
865
866	Event::ExecFlow
867	High level API for event-based execution flow control.
868
869	Coro	1128	Coro
870	Has special support for AnyEvent via Coro::AnyEvent.	1129	Has special support for AnyEvent via Coro::AnyEvent.
871		1130
872	IO::Lambda	1131	SIMPLIFIED AE API
873	The lambda approach to I/O - don't ask, look there. Can use	1132	Starting with version 5.0, AnyEvent officially supports a second, much
874	AnyEvent.	1133	simpler, API that is designed to reduce the calling, typing and memory
		1134	overhead by using function call syntax and a fixed number of parameters.
		1135
		1136	See the AE manpage for details.
875		1137
876	ERROR AND EXCEPTION HANDLING	1138	ERROR AND EXCEPTION HANDLING
877	In general, AnyEvent does not do any error handling - it relies on the	1139	In general, AnyEvent does not do any error handling - it relies on the
878	caller to do that if required. The AnyEvent::Strict module (see also the	1140	caller to do that if required. The AnyEvent::Strict module (see also the
879	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1141	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
907	by "PERL_ANYEVENT_MODEL".	1169	by "PERL_ANYEVENT_MODEL".
908		1170
909	When set to 2 or higher, cause AnyEvent to report to STDERR which	1171	When set to 2 or higher, cause AnyEvent to report to STDERR which
910	event model it chooses.	1172	event model it chooses.
911		1173
		1174	When set to 8 or higher, then AnyEvent will report extra information
		1175	on which optional modules it loads and how it implements certain
		1176	features.
		1177
912	"PERL_ANYEVENT_STRICT"	1178	"PERL_ANYEVENT_STRICT"
913	AnyEvent does not do much argument checking by default, as thorough	1179	AnyEvent does not do much argument checking by default, as thorough
914	argument checking is very costly. Setting this variable to a true	1180	argument checking is very costly. Setting this variable to a true
915	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1181	value will cause AnyEvent to load "AnyEvent::Strict" and then to
916	thoroughly check the arguments passed to most method calls. If it	1182	thoroughly check the arguments passed to most method calls. If it
917	finds any problems, it will croak.	1183	finds any problems, it will croak.
918		1184
919	In other words, enables "strict" mode.	1185	In other words, enables "strict" mode.
920		1186
921	Unlike "use strict", it is definitely recommended to keep it off in	1187	Unlike "use strict" (or its modern cousin, "use common::sense", it
922	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1188	is definitely recommended to keep it off in production. Keeping
		1189	"PERL_ANYEVENT_STRICT=1" in your environment while developing
923	while developing programs can be very useful, however.	1190	programs can be very useful, however.
		1191
		1192	"PERL_ANYEVENT_DEBUG_SHELL"
		1193	If this env variable is set, then its contents will be interpreted
		1194	by "AnyEvent::Socket::parse_hostport" (after replacing every
		1195	occurance of $$ by the process pid) and an "AnyEvent::Debug::shell"
		1196	is bound on that port. The shell object is saved in
		1197	$AnyEvent::Debug::SHELL.
		1198
		1199	This takes place when the first watcher is created.
		1200
		1201	For example, to bind a debug shell on a unix domain socket in
		1202	/tmp/debug<pid>.sock, you could use this:
		1203
		1204	PERL_ANYEVENT_DEBUG_SHELL=unix/:/tmp/debug\$\$.sock perlprog
		1205
		1206	Note that creating sockets in /tmp is very unsafe on multiuser
		1207	systems.
		1208
		1209	"PERL_ANYEVENT_DEBUG_WRAP"
		1210	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1211	debugging purposes. See "AnyEvent::Debug::wrap" for details.
924		1212
925	"PERL_ANYEVENT_MODEL"	1213	"PERL_ANYEVENT_MODEL"
926	This can be used to specify the event model to be used by AnyEvent,	1214	This can be used to specify the event model to be used by AnyEvent,
927	before auto detection and -probing kicks in. It must be a string	1215	before auto detection and -probing kicks in.
928	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1216
929	gets prepended and the resulting module name is loaded and if the	1217	It normally is a string consisting entirely of ASCII letters (e.g.
930	load was successful, used as event model. If it fails to load	1218	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1219	the resulting module name is loaded and - if the load was successful
		1220	- used as event model backend. If it fails to load then AnyEvent
931	AnyEvent will proceed with auto detection and -probing.	1221	will proceed with auto detection and -probing.
932		1222
933	This functionality might change in future versions.	1223	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1224	then nothing gets prepended and the module name is used as-is (hint:
		1225	"::" at the end of a string designates a module name and quotes it
		1226	appropriately).
934		1227
935	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1228	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
936	could start your program like this:	1229	could start your program like this:
937		1230
938	PERL_ANYEVENT_MODEL=Perl perl ...	1231	PERL_ANYEVENT_MODEL=Perl perl ...
939		1232
940	"PERL_ANYEVENT_PROTOCOLS"	1233	"PERL_ANYEVENT_PROTOCOLS"
…		…
969	EDNS0 in its DNS requests.	1262	EDNS0 in its DNS requests.
970		1263
971	"PERL_ANYEVENT_MAX_FORKS"	1264	"PERL_ANYEVENT_MAX_FORKS"
972	The maximum number of child processes that	1265	The maximum number of child processes that
973	"AnyEvent::Util::fork_call" will create in parallel.	1266	"AnyEvent::Util::fork_call" will create in parallel.
		1267
		1268	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1269	The default value for the "max_outstanding" parameter for the
		1270	default DNS resolver - this is the maximum number of parallel DNS
		1271	requests that are sent to the DNS server.
		1272
		1273	"PERL_ANYEVENT_RESOLV_CONF"
		1274	The file to use instead of /etc/resolv.conf (or OS-specific
		1275	configuration) in the default resolver. When set to the empty
		1276	string, no default config will be used.
		1277
		1278	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1279	When neither "ca_file" nor "ca_path" was specified during
		1280	AnyEvent::TLS context creation, and either of these environment
		1281	variables exist, they will be used to specify CA certificate
		1282	locations instead of a system-dependent default.
		1283
		1284	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1285	When these are set to 1, then the respective modules are not loaded.
		1286	Mostly good for testing AnyEvent itself.
974		1287
975	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1288	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
976	This is an advanced topic that you do not normally need to use AnyEvent	1289	This is an advanced topic that you do not normally need to use AnyEvent
977	in a module. This section is only of use to event loop authors who want	1290	in a module. This section is only of use to event loop authors who want
978	to provide AnyEvent compatibility.	1291	to provide AnyEvent compatibility.
…		…
1033	warn "read: $input\n"; # output what has been read	1346	warn "read: $input\n"; # output what has been read
1034	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1347	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1035	},	1348	},
1036	);	1349	);
1037		1350
1038	my $time_watcher; # can only be used once
1039
1040	sub new_timer {
1041	$timer = AnyEvent->timer (after => 1, cb => sub {	1351	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1042	warn "timeout\n"; # print 'timeout' about every second	1352	warn "timeout\n"; # print 'timeout' at most every second
1043	&new_timer; # and restart the time
1044	});
1045	}	1353	});
1046
1047	new_timer; # create first timer
1048		1354
1049	$cv->recv; # wait until user enters /^q/i	1355	$cv->recv; # wait until user enters /^q/i
1050		1356
1051	REAL-WORLD EXAMPLE	1357	REAL-WORLD EXAMPLE
1052	Consider the Net::FCP module. It features (among others) the following	1358	Consider the Net::FCP module. It features (among others) the following
…		…
1124		1430
1125	The actual code goes further and collects all errors ("die"s,	1431	The actual code goes further and collects all errors ("die"s,
1126	exceptions) that occurred during request processing. The "result" method	1432	exceptions) that occurred during request processing. The "result" method
1127	detects whether an exception as thrown (it is stored inside the $txn	1433	detects whether an exception as thrown (it is stored inside the $txn
1128	object) and just throws the exception, which means connection errors and	1434	object) and just throws the exception, which means connection errors and
1129	other problems get reported tot he code that tries to use the result,	1435	other problems get reported to the code that tries to use the result,
1130	not in a random callback.	1436	not in a random callback.
1131		1437
1132	All of this enables the following usage styles:	1438	All of this enables the following usage styles:
1133		1439
1134	1. Blocking:	1440	1. Blocking:
…		…
1179	through AnyEvent. The benchmark creates a lot of timers (with a zero	1485	through AnyEvent. The benchmark creates a lot of timers (with a zero
1180	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1486	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1181	which it is), lets them fire exactly once and destroys them again.	1487	which it is), lets them fire exactly once and destroys them again.
1182		1488
1183	Source code for this benchmark is found as eg/bench in the AnyEvent	1489	Source code for this benchmark is found as eg/bench in the AnyEvent
1184	distribution.	1490	distribution. It uses the AE interface, which makes a real difference
		1491	for the EV and Perl backends only.
1185		1492
1186	Explanation of the columns	1493	Explanation of the columns
1187	watcher is the number of event watchers created/destroyed. Since	1494	watcher is the number of event watchers created/destroyed. Since
1188	different event models feature vastly different performances, each event	1495	different event models feature vastly different performances, each event
1189	loop was given a number of watchers so that overall runtime is	1496	loop was given a number of watchers so that overall runtime is
…		…
1208	destroy is the time, in microseconds, that it takes to destroy a	1515	destroy is the time, in microseconds, that it takes to destroy a
1209	single watcher.	1516	single watcher.
1210		1517
1211	Results	1518	Results
1212	name watchers bytes create invoke destroy comment	1519	name watchers bytes create invoke destroy comment
1213	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1520	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1214	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1521	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1215	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1522	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1216	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1523	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1217	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1524	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1218	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1525	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
1219	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll	1526	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
1220	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll	1527	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1221	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1528	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1222	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1529	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1223	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1530	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1224	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1531	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1225		1532
1226	Discussion	1533	Discussion
1227	The benchmark does not measure scalability of the event loop very	1534	The benchmark does not measure scalability of the event loop very
1228	well. For example, a select-based event loop (such as the pure perl one)	1535	well. For example, a select-based event loop (such as the pure perl one)
1229	can never compete with an event loop that uses epoll when the number of	1536	can never compete with an event loop that uses epoll when the number of
…		…
1240	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1547	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1241	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1548	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1242	CPU cycles with POE.	1549	CPU cycles with POE.
1243		1550
1244	"EV" is the sole leader regarding speed and memory use, which are both	1551	"EV" is the sole leader regarding speed and memory use, which are both
1245	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1552	maximal/minimal, respectively. When using the AE API there is zero
		1553	overhead (when going through the AnyEvent API create is about 5-6 times
		1554	slower, with other times being equal, so still uses far less memory than
1246	far less memory than any other event loop and is still faster than Event	1555	any other event loop and is still faster than Event natively).
1247	natively.
1248		1556
1249	The pure perl implementation is hit in a few sweet spots (both the	1557	The pure perl implementation is hit in a few sweet spots (both the
1250	constant timeout and the use of a single fd hit optimisations in the	1558	constant timeout and the use of a single fd hit optimisations in the
1251	perl interpreter and the backend itself). Nevertheless this shows that	1559	perl interpreter and the backend itself). Nevertheless this shows that
1252	it adds very little overhead in itself. Like any select-based backend	1560	it adds very little overhead in itself. Like any select-based backend
…		…
1322	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1630	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1323	100 (1%) are active. This mirrors the activity of large servers with	1631	100 (1%) are active. This mirrors the activity of large servers with
1324	many connections, most of which are idle at any one point in time.	1632	many connections, most of which are idle at any one point in time.
1325		1633
1326	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1634	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1327	distribution.	1635	distribution. It uses the AE interface, which makes a real difference
		1636	for the EV and Perl backends only.
1328		1637
1329	Explanation of the columns	1638	Explanation of the columns
1330	sockets is the number of sockets, and twice the number of "servers"	1639	sockets is the number of sockets, and twice the number of "servers"
1331	(as each server has a read and write socket end).	1640	(as each server has a read and write socket end).
1332		1641
…		…
1338	forwarding it to another server. This includes deleting the old timeout	1647	forwarding it to another server. This includes deleting the old timeout
1339	and creating a new one that moves the timeout into the future.	1648	and creating a new one that moves the timeout into the future.
1340		1649
1341	Results	1650	Results
1342	name sockets create request	1651	name sockets create request
1343	EV 20000 69.01 11.16	1652	EV 20000 62.66 7.99
1344	Perl 20000 73.32 35.87	1653	Perl 20000 68.32 32.64
1345	IOAsync 20000 157.00 98.14 epoll	1654	IOAsync 20000 174.06 101.15 epoll
1346	IOAsync 20000 159.31 616.06 poll	1655	IOAsync 20000 174.67 610.84 poll
1347	Event 20000 212.62 257.32	1656	Event 20000 202.69 242.91
1348	Glib 20000 651.16 1896.30	1657	Glib 20000 557.01 1689.52
1349	POE 20000 349.67 12317.24 uses POE::Loop::Event	1658	POE 20000 341.54 12086.32 uses POE::Loop::Event
1350		1659
1351	Discussion	1660	Discussion
1352	This benchmark does measure scalability and overall performance of the	1661	This benchmark does measure scalability and overall performance of the
1353	particular event loop.	1662	particular event loop.
1354		1663
…		…
1467	As you can see, the AnyEvent + EV combination even beats the	1776	As you can see, the AnyEvent + EV combination even beats the
1468	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl	1777	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1469	backend easily beats IO::Lambda and POE.	1778	backend easily beats IO::Lambda and POE.
1470		1779
1471	And even the 100% non-blocking version written using the high-level (and	1780	And even the 100% non-blocking version written using the high-level (and
1472	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a	1781	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
1473	large margin, even though it does all of DNS, tcp-connect and socket I/O	1782	higher level ("unoptimised") abstractions by a large margin, even though
1474	in a non-blocking way.	1783	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
1475		1784
1476	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and	1785	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
1477	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are	1786	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1478	part of the IO::lambda distribution and were used without any changes.	1787	part of the IO::Lambda distribution and were used without any changes.
1479		1788
1480	SIGNALS	1789	SIGNALS
1481	AnyEvent currently installs handlers for these signals:	1790	AnyEvent currently installs handlers for these signals:
1482		1791
1483	SIGCHLD	1792	SIGCHLD
1484	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1793	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1485	emulation for event loops that do not support them natively. Also,	1794	emulation for event loops that do not support them natively. Also,
1486	some event loops install a similar handler.	1795	some event loops install a similar handler.
1487		1796
1488	If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent	1797	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
1489	will reset it to default, to avoid losing child exit statuses.	1798	then AnyEvent will reset it to default, to avoid losing child exit
		1799	statuses.
1490		1800
1491	SIGPIPE	1801	SIGPIPE
1492	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is	1802	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1493	"undef" when AnyEvent gets loaded.	1803	"undef" when AnyEvent gets loaded.
1494		1804
…		…
1502	it is that this way, the handler will be restored to defaults on	1812	it is that this way, the handler will be restored to defaults on
1503	exec.	1813	exec.
1504		1814
1505	Feel free to install your own handler, or reset it to defaults.	1815	Feel free to install your own handler, or reset it to defaults.
1506		1816
		1817	RECOMMENDED/OPTIONAL MODULES
		1818	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1819	its built-in modules) are required to use it.
		1820
		1821	That does not mean that AnyEvent won't take advantage of some additional
		1822	modules if they are installed.
		1823
		1824	This section explains which additional modules will be used, and how
		1825	they affect AnyEvent's operation.
		1826
		1827	Async::Interrupt
		1828	This slightly arcane module is used to implement fast signal
		1829	handling: To my knowledge, there is no way to do completely
		1830	race-free and quick signal handling in pure perl. To ensure that
		1831	signals still get delivered, AnyEvent will start an interval timer
		1832	to wake up perl (and catch the signals) with some delay (default is
		1833	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1834
		1835	If this module is available, then it will be used to implement
		1836	signal catching, which means that signals will not be delayed, and
		1837	the event loop will not be interrupted regularly, which is more
		1838	efficient (and good for battery life on laptops).
		1839
		1840	This affects not just the pure-perl event loop, but also other event
		1841	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1842
		1843	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1844	natively, and either employ their own workarounds (POE) or use
		1845	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1846	Installing Async::Interrupt does nothing for those backends.
		1847
		1848	EV This module isn't really "optional", as it is simply one of the
		1849	backend event loops that AnyEvent can use. However, it is simply the
		1850	best event loop available in terms of features, speed and stability:
		1851	It supports the AnyEvent API optimally, implements all the watcher
		1852	types in XS, does automatic timer adjustments even when no monotonic
		1853	clock is available, can take avdantage of advanced kernel interfaces
		1854	such as "epoll" and "kqueue", and is the fastest backend by far.
		1855	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1856	Glib::EV).
		1857
		1858	If you only use backends that rely on another event loop (e.g.
		1859	"Tk"), then this module will do nothing for you.
		1860
		1861	Guard
		1862	The guard module, when used, will be used to implement
		1863	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1864	uses a lot less memory), but otherwise doesn't affect guard
		1865	operation much. It is purely used for performance.
		1866
		1867	JSON and JSON::XS
		1868	One of these modules is required when you want to read or write JSON
		1869	data via AnyEvent::Handle. JSON is also written in pure-perl, but
		1870	can take advantage of the ultra-high-speed JSON::XS module when it
		1871	is installed.
		1872
		1873	Net::SSLeay
		1874	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1875	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1876	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1877
		1878	Time::HiRes
		1879	This module is part of perl since release 5.008. It will be used
		1880	when the chosen event library does not come with a timing source of
		1881	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
		1882	load it to try to use a monotonic clock for timing stability.
		1883
1507	FORK	1884	FORK
1508	Most event libraries are not fork-safe. The ones who are usually are	1885	Most event libraries are not fork-safe. The ones who are usually are
1509	because they rely on inefficient but fork-safe "select" or "poll" calls.	1886	because they rely on inefficient but fork-safe "select" or "poll" calls
1510	Only EV is fully fork-aware.	1887	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		1888	epoll are usually badly thought-out hacks that are incompatible with
		1889	fork in one way or another. Only EV is fully fork-aware and ensures that
		1890	you continue event-processing in both parent and child (or both, if you
		1891	know what you are doing).
		1892
		1893	This means that, in general, you cannot fork and do event processing in
		1894	the child if the event library was initialised before the fork (which
		1895	usually happens when the first AnyEvent watcher is created, or the
		1896	library is loaded).
1511		1897
1512	If you have to fork, you must either do so before creating your first	1898	If you have to fork, you must either do so before creating your first
1513	watcher OR you must not use AnyEvent at all in the child.	1899	watcher OR you must not use AnyEvent at all in the child OR you must do
		1900	something completely out of the scope of AnyEvent.
		1901
		1902	The problem of doing event processing in the parent and the child is
		1903	much more complicated: even for backends that are fork-aware or
		1904	fork-safe, their behaviour is not usually what you want: fork clones all
		1905	watchers, that means all timers, I/O watchers etc. are active in both
		1906	parent and child, which is almost never what you want. USing "exec" to
		1907	start worker children from some kind of manage rprocess is usually
		1908	preferred, because it is much easier and cleaner, at the expense of
		1909	having to have another binary.
1514		1910
1515	SECURITY CONSIDERATIONS	1911	SECURITY CONSIDERATIONS
1516	AnyEvent can be forced to load any event model via	1912	AnyEvent can be forced to load any event model via
1517	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1913	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1518	to execute arbitrary code or directly gain access, it can easily be used	1914	to execute arbitrary code or directly gain access, it can easily be used
…		…
1542	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	1938	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1543	annoying memleaks, such as leaking on "map" and "grep" but it is usually	1939	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1544	not as pronounced).	1940	not as pronounced).
1545		1941
1546	SEE ALSO	1942	SEE ALSO
		1943	Tutorial/Introduction: AnyEvent::Intro.
		1944
		1945	FAQ: AnyEvent::FAQ.
		1946
1547	Utility functions: AnyEvent::Util.	1947	Utility functions: AnyEvent::Util.
1548		1948
1549	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1949	Event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
1550	Event::Lib, Qt, POE.	1950	Glib::Event, Glib, Tk, Event::Lib, Qt, POE.
1551		1951
1552	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1952	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1553	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1953	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1554	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1954	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1955	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1555		1956
1556	Non-blocking file handles, sockets, TCP clients and servers:	1957	Non-blocking file handles, sockets, TCP clients and servers:
1557	AnyEvent::Handle, AnyEvent::Socket.	1958	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1558		1959
1559	Asynchronous DNS: AnyEvent::DNS.	1960	Asynchronous DNS: AnyEvent::DNS.
1560		1961
1561	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1962	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1562		1963
1563	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1964	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
		1965	AnyEvent::HTTP.
1564		1966
1565	AUTHOR	1967	AUTHOR
1566	Marc Lehmann <schmorp@schmorp.de>	1968	Marc Lehmann <schmorp@schmorp.de>
1567	http://home.schmorp.de/	1969	http://home.schmorp.de/
1568		1970

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Comparing AnyEvent/README (file contents): Revision 1.41 by root, Fri Jun 26 06:33:17 2009 UTC vs. Revision 1.65 by root, Sat Aug 13 22:44:05 2011 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.41 by root, Fri Jun 26 06:33:17 2009 UTC vs.
Revision 1.65 by root, Sat Aug 13 22:44:05 2011 UTC