[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.45 by root, Fri Jul 17 14:57:03 2009 UTC vs.
Revision 1.66 by root, Sun Aug 21 03:02:32 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, FLTK and POE are various supported event loops/environments.
6		6
7	SYNOPSIS	7	SYNOPSIS
8	use AnyEvent;	8	use AnyEvent;
9		9
		10	# if you prefer function calls, look at the AE manpage for
		11	# an alternative API.
		12
10	# file descriptor readable	13	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });	14	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
12		15
13	# one-shot or repeating timers	16	# one-shot or repeating timers
14	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });	17	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
15	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...	18	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
16		19
17	print AnyEvent->now; # prints current event loop time	20	print AnyEvent->now; # prints current event loop time
18	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.	21	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
19		22
20	# POSIX signal	23	# POSIX signal
37		40
38	INTRODUCTION/TUTORIAL	41	INTRODUCTION/TUTORIAL
39	This manpage is mainly a reference manual. If you are interested in a	42	This manpage is mainly a reference manual. If you are interested in a
40	tutorial or some gentle introduction, have a look at the AnyEvent::Intro	43	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
41	manpage.	44	manpage.
		45
		46	SUPPORT
		47	An FAQ document is available as AnyEvent::FAQ.
		48
		49	There also is a mailinglist for discussing all things AnyEvent, and an
		50	IRC channel, too.
		51
		52	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
		53	Repository, at <http://anyevent.schmorp.de>, for more info.
42		54
43	WHY YOU SHOULD USE THIS MODULE (OR NOT)	55	WHY YOU SHOULD USE THIS MODULE (OR NOT)
44	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
45	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
46		58
…		…
61	module users into the same thing by forcing them to use the same event	73	module users into the same thing by forcing them to use the same event
62	model you use.	74	model you use.
63		75
64	For modules like POE or IO::Async (which is a total misnomer as it is	76	For modules like POE or IO::Async (which is a total misnomer as it is
65	actually doing all I/O synchronously...), using them in your module is	77	actually doing all I/O synchronously...), using them in your module is
66	like joining a cult: After you joined, you are dependent on them and you	78	like joining a cult: After you join, you are dependent on them and you
67	cannot use anything else, as they are simply incompatible to everything	79	cannot use anything else, as they are simply incompatible to everything
68	that isn't them. What's worse, all the potential users of your module	80	that isn't them. What's worse, all the potential users of your module
69	are also forced to use the same event loop you use.	81	are also forced to use the same event loop you use.
70		82
71	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
72	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
73	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your	85	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
74	module uses one of those, every user of your module has to use it, too.	86	uses one of those, every user of your module has to use it, too. But if
75	But if your module uses AnyEvent, it works transparently with all event	87	your module uses AnyEvent, it works transparently with all event models
76	models it supports (including stuff like IO::Async, as long as those use	88	it supports (including stuff like IO::Async, as long as those use one of
77	one of the supported event loops. It is trivial to add new event loops	89	the supported event loops. It is easy to add new event loops to
78	to AnyEvent, too, so it is future-proof).	90	AnyEvent, too, so it is future-proof).
79		91
80	In addition to being free of having to use *the one and only true event	92	In addition to being free of having to use *the one and only true event
81	model*, AnyEvent also is free of bloat and policy: with POE or similar	93	model*, AnyEvent also is free of bloat and policy: with POE or similar
82	modules, you get an enormous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
83	follow. AnyEvent, on the other hand, is lean and up to the point, by	95	follow. AnyEvent, on the other hand, is lean and to the point, by only
84	only offering the functionality that is necessary, in as thin as a	96	offering the functionality that is necessary, in as thin as a wrapper as
85	wrapper as technically possible.	97	technically possible.
86		98
87	Of course, AnyEvent comes with a big (and fully optional!) toolbox of	99	Of course, AnyEvent comes with a big (and fully optional!) toolbox of
88	useful functionality, such as an asynchronous DNS resolver, 100%	100	useful functionality, such as an asynchronous DNS resolver, 100%
89	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms	101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
90	such as Windows) and lots of real-world knowledge and workarounds for	102	such as Windows) and lots of real-world knowledge and workarounds for
…		…
93	Now, if you do want lots of policy (this can arguably be somewhat	105	Now, if you do want lots of policy (this can arguably be somewhat
94	useful) and you want to force your users to use the one and only event	106	useful) and you want to force your users to use the one and only event
95	model, you should not use this module.	107	model, you should not use this module.
96		108
97	DESCRIPTION	109	DESCRIPTION
98	AnyEvent provides an identical interface to multiple event loops. This	110	AnyEvent provides a uniform interface to various event loops. This
99	allows module authors to utilise an event loop without forcing module	111	allows module authors to use event loop functionality without forcing
100	users to use the same event loop (as only a single event loop can	112	module users to use a specific event loop implementation (since more
101	coexist peacefully at any one time).	113	than one event loop cannot coexist peacefully).
102		114
103	The interface itself is vaguely similar, but not identical to the Event	115	The interface itself is vaguely similar, but not identical to the Event
104	module.	116	module.
105		117
106	During the first call of any watcher-creation method, the module tries	118	During the first call of any watcher-creation method, the module tries
107	to detect the currently loaded event loop by probing whether one of the	119	to detect the currently loaded event loop by probing whether one of the
108	following modules is already loaded: EV, Event, Glib,	120	following modules is already loaded: EV, AnyEvent::Loop, Event, Glib,
109	AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is	121	Tk, Event::Lib, Qt, POE. The first one found is used. If none are
110	used. If none are found, the module tries to load these modules	122	detected, the module tries to load the first four modules in the order
111	(excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should	123	given; but note that if EV is not available, the pure-perl
112	always succeed) in the order given. The first one that can be	124	AnyEvent::Loop should always work, so the other two are not normally
113	successfully loaded will be used. If, after this, still none could be	125	tried.
114	found, AnyEvent will fall back to a pure-perl event loop, which is not
115	very efficient, but should work everywhere.
116		126
117	Because AnyEvent first checks for modules that are already loaded,	127	Because AnyEvent first checks for modules that are already loaded,
118	loading an event model explicitly before first using AnyEvent will	128	loading an event model explicitly before first using AnyEvent will
119	likely make that model the default. For example:	129	likely make that model the default. For example:
120		130
…		…
122	use AnyEvent;	132	use AnyEvent;
123		133
124	# .. AnyEvent will likely default to Tk	134	# .. AnyEvent will likely default to Tk
125		135
126	The likely means that, if any module loads another event model and	136	The likely means that, if any module loads another event model and
127	starts using it, all bets are off. Maybe you should tell their authors	137	starts using it, all bets are off - this case should be very rare
128	to use AnyEvent so their modules work together with others seamlessly...	138	though, as very few modules hardcode event loops without announcing this
		139	very loudly.
129		140
130	The pure-perl implementation of AnyEvent is called	141	The pure-perl implementation of AnyEvent is called "AnyEvent::Loop".
131	"AnyEvent::Impl::Perl". Like other event modules you can load it	142	Like other event modules you can load it explicitly and enjoy the high
132	explicitly and enjoy the high availability of that event loop :)	143	availability of that event loop :)
133		144
134	WATCHERS	145	WATCHERS
135	AnyEvent has the central concept of a watcher, which is an object that	146	AnyEvent has the central concept of a watcher, which is an object that
136	stores relevant data for each kind of event you are waiting for, such as	147	stores relevant data for each kind of event you are waiting for, such as
137	the callback to call, the file handle to watch, etc.	148	the callback to call, the file handle to watch, etc.
…		…
141	callback when the event occurs (of course, only when the event model is	152	callback when the event occurs (of course, only when the event model is
142	in control).	153	in control).
143		154
144	Note that callbacks must not permanently change global variables	155	Note that callbacks must not permanently change global variables
145	potentially in use by the event loop (such as $_ or $[) and that	156	potentially in use by the event loop (such as $_ or $[) and that
146	callbacks must not "die". The former is good programming practise in	157	callbacks must not "die". The former is good programming practice in
147	Perl and the latter stems from the fact that exception handling differs	158	Perl and the latter stems from the fact that exception handling differs
148	widely between event loops.	159	widely between event loops.
149		160
150	To disable the watcher you have to destroy it (e.g. by setting the	161	To disable a watcher you have to destroy it (e.g. by setting the
151	variable you store it in to "undef" or otherwise deleting all references	162	variable you store it in to "undef" or otherwise deleting all references
152	to it).	163	to it).
153		164
154	All watchers are created by calling a method on the "AnyEvent" class.	165	All watchers are created by calling a method on the "AnyEvent" class.
155		166
156	Many watchers either are used with "recursion" (repeating timers for	167	Many watchers either are used with "recursion" (repeating timers for
157	example), or need to refer to their watcher object in other ways.	168	example), or need to refer to their watcher object in other ways.
158		169
159	An any way to achieve that is this pattern:	170	One way to achieve that is this pattern:
160		171
161	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	172	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
162	# you can use $w here, for example to undef it	173	# you can use $w here, for example to undef it
163	undef $w;	174	undef $w;
164	});	175	});
…		…
166	Note that "my $w; $w =" combination. This is necessary because in Perl,	177	Note that "my $w; $w =" combination. This is necessary because in Perl,
167	my variables are only visible after the statement in which they are	178	my variables are only visible after the statement in which they are
168	declared.	179	declared.
169		180
170	I/O WATCHERS	181	I/O WATCHERS
		182	$w = AnyEvent->io (
		183	fh => <filehandle_or_fileno>,
		184	poll => <"r" or "w">,
		185	cb => <callback>,
		186	);
		187
171	You can create an I/O watcher by calling the "AnyEvent->io" method with	188	You can create an I/O watcher by calling the "AnyEvent->io" method with
172	the following mandatory key-value pairs as arguments:	189	the following mandatory key-value pairs as arguments:
173		190
174	"fh" is the Perl file handle (or a naked file descriptor) to watch for	191	"fh" is the Perl file handle (or a naked file descriptor) to watch for
175	events (AnyEvent might or might not keep a reference to this file	192	events (AnyEvent might or might not keep a reference to this file
…		…
189		206
190	The I/O watcher might use the underlying file descriptor or a copy of	207	The I/O watcher might use the underlying file descriptor or a copy of
191	it. You must not close a file handle as long as any watcher is active on	208	it. You must not close a file handle as long as any watcher is active on
192	the underlying file descriptor.	209	the underlying file descriptor.
193		210
194	Some event loops issue spurious readyness notifications, so you should	211	Some event loops issue spurious readiness notifications, so you should
195	always use non-blocking calls when reading/writing from/to your file	212	always use non-blocking calls when reading/writing from/to your file
196	handles.	213	handles.
197		214
198	Example: wait for readability of STDIN, then read a line and disable the	215	Example: wait for readability of STDIN, then read a line and disable the
199	watcher.	216	watcher.
…		…
203	warn "read: $input\n";	220	warn "read: $input\n";
204	undef $w;	221	undef $w;
205	});	222	});
206		223
207	TIME WATCHERS	224	TIME WATCHERS
		225	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		226
		227	$w = AnyEvent->timer (
		228	after => <fractional_seconds>,
		229	interval => <fractional_seconds>,
		230	cb => <callback>,
		231	);
		232
208	You can create a time watcher by calling the "AnyEvent->timer" method	233	You can create a time watcher by calling the "AnyEvent->timer" method
209	with the following mandatory arguments:	234	with the following mandatory arguments:
210		235
211	"after" specifies after how many seconds (fractional values are	236	"after" specifies after how many seconds (fractional values are
212	supported) the callback should be invoked. "cb" is the callback to	237	supported) the callback should be invoked. "cb" is the callback to
…		…
214		239
215	Although the callback might get passed parameters, their value and	240	Although the callback might get passed parameters, their value and
216	presence is undefined and you cannot rely on them. Portable AnyEvent	241	presence is undefined and you cannot rely on them. Portable AnyEvent
217	callbacks cannot use arguments passed to time watcher callbacks.	242	callbacks cannot use arguments passed to time watcher callbacks.
218		243
219	The callback will normally be invoked once only. If you specify another	244	The callback will normally be invoked only once. If you specify another
220	parameter, "interval", as a strictly positive number (> 0), then the	245	parameter, "interval", as a strictly positive number (> 0), then the
221	callback will be invoked regularly at that interval (in fractional	246	callback will be invoked regularly at that interval (in fractional
222	seconds) after the first invocation. If "interval" is specified with a	247	seconds) after the first invocation. If "interval" is specified with a
223	false value, then it is treated as if it were missing.	248	false value, then it is treated as if it were not specified at all.
224		249
225	The callback will be rescheduled before invoking the callback, but no	250	The callback will be rescheduled before invoking the callback, but no
226	attempt is done to avoid timer drift in most backends, so the interval	251	attempt is made to avoid timer drift in most backends, so the interval
227	is only approximate.	252	is only approximate.
228		253
229	Example: fire an event after 7.7 seconds.	254	Example: fire an event after 7.7 seconds.
230		255
231	my $w = AnyEvent->timer (after => 7.7, cb => sub {	256	my $w = AnyEvent->timer (after => 7.7, cb => sub {
…		…
248		273
249	While most event loops expect timers to specified in a relative way,	274	While most event loops expect timers to specified in a relative way,
250	they use absolute time internally. This makes a difference when your	275	they use absolute time internally. This makes a difference when your
251	clock "jumps", for example, when ntp decides to set your clock backwards	276	clock "jumps", for example, when ntp decides to set your clock backwards
252	from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is	277	from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is
253	supposed to fire "after" a second might actually take six years to	278	supposed to fire "after a second" might actually take six years to
254	finally fire.	279	finally fire.
255		280
256	AnyEvent cannot compensate for this. The only event loop that is	281	AnyEvent cannot compensate for this. The only event loop that is
257	conscious about these issues is EV, which offers both relative	282	conscious of these issues is EV, which offers both relative (ev_timer,
258	(ev_timer, based on true relative time) and absolute (ev_periodic, based	283	based on true relative time) and absolute (ev_periodic, based on
259	on wallclock time) timers.	284	wallclock time) timers.
260		285
261	AnyEvent always prefers relative timers, if available, matching the	286	AnyEvent always prefers relative timers, if available, matching the
262	AnyEvent API.	287	AnyEvent API.
263		288
264	AnyEvent has two additional methods that return the "current time":	289	AnyEvent has two additional methods that return the "current time":
…		…
283	*In almost all cases (in all cases if you don't care), this is the	308	*In almost all cases (in all cases if you don't care), this is the
284	function to call when you want to know the current time.*	309	function to call when you want to know the current time.*
285		310
286	This function is also often faster then "AnyEvent->time", and thus	311	This function is also often faster then "AnyEvent->time", and thus
287	the preferred method if you want some timestamp (for example,	312	the preferred method if you want some timestamp (for example,
288	AnyEvent::Handle uses this to update it's activity timeouts).	313	AnyEvent::Handle uses this to update its activity timeouts).
289		314
290	The rest of this section is only of relevance if you try to be very	315	The rest of this section is only of relevance if you try to be very
291	exact with your timing, you can skip it without bad conscience.	316	exact with your timing; you can skip it without a bad conscience.
292		317
293	For a practical example of when these times differ, consider	318	For a practical example of when these times differ, consider
294	Event::Lib and EV and the following set-up:	319	Event::Lib and EV and the following set-up:
295		320
296	The event loop is running and has just invoked one of your callback	321	The event loop is running and has just invoked one of your callbacks
297	at time=500 (assume no other callbacks delay processing). In your	322	at time=500 (assume no other callbacks delay processing). In your
298	callback, you wait a second by executing "sleep 1" (blocking the	323	callback, you wait a second by executing "sleep 1" (blocking the
299	process for a second) and then (at time=501) you create a relative	324	process for a second) and then (at time=501) you create a relative
300	timer that fires after three seconds.	325	timer that fires after three seconds.
301		326
…		…
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 slightly different: it expects somebody else to run the	541	AnyEvent is slightly different: it expects somebody else to run the
454	event loop and will only block when necessary (usually when told by the	542	event loop and will only block when necessary (usually when told by the
455	user).	543	user).
456		544
457	The instrument to do that is called a "condition variable", so called	545	The tool to do that is called a "condition variable", so called because
458	because they represent a condition that must become true.	546	they represent a condition that must become true.
459		547
460	Now is probably a good time to look at the examples further below.	548	Now is probably a good time to look at the examples further below.
461		549
462	Condition variables can be created by calling the "AnyEvent->condvar"	550	Condition variables can be created by calling the "AnyEvent->condvar"
463	method, usually without arguments. The only argument pair allowed is	551	method, usually without arguments. The only argument pair allowed is
…		…
468	After creation, the condition variable is "false" until it becomes	556	After creation, the condition variable is "false" until it becomes
469	"true" by calling the "send" method (or calling the condition variable	557	"true" by calling the "send" method (or calling the condition variable
470	as if it were a callback, read about the caveats in the description for	558	as if it were a callback, read about the caveats in the description for
471	the "->send" method).	559	the "->send" method).
472		560
473	Condition variables are similar to callbacks, except that you can	561	Since condition variables are the most complex part of the AnyEvent API,
474	optionally wait for them. They can also be called merge points - points	562	here are some different mental models of what they are - pick the ones
475	in time where multiple outstanding events have been processed. And yet	563	you can connect to:
476	another way to call them is transactions - each condition variable can	564
477	be used to represent a transaction, which finishes at some point and	565	* Condition variables are like callbacks - you can call them (and pass
478	delivers a result.	566	them instead of callbacks). Unlike callbacks however, you can also
		567	wait for them to be called.
		568
		569	* Condition variables are signals - one side can emit or send them,
		570	the other side can wait for them, or install a handler that is
		571	called when the signal fires.
		572
		573	* Condition variables are like "Merge Points" - points in your program
		574	where you merge multiple independent results/control flows into one.
		575
		576	* Condition variables represent a transaction - functions that start
		577	some kind of transaction can return them, leaving the caller the
		578	choice between waiting in a blocking fashion, or setting a callback.
		579
		580	* Condition variables represent future values, or promises to deliver
		581	some result, long before the result is available.
479		582
480	Condition variables are very useful to signal that something has	583	Condition variables are very useful to signal that something has
481	finished, for example, if you write a module that does asynchronous http	584	finished, for example, if you write a module that does asynchronous http
482	requests, then a condition variable would be the ideal candidate to	585	requests, then a condition variable would be the ideal candidate to
483	signal the availability of results. The user can either act when the	586	signal the availability of results. The user can either act when the
…		…
496		599
497	Condition variables are represented by hash refs in perl, and the keys	600	Condition variables are represented by hash refs in perl, and the keys
498	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy	601	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy
499	(it is often useful to build your own transaction class on top of	602	(it is often useful to build your own transaction class on top of
500	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	603	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
501	it's "new" method in your own "new" method.	604	its "new" method in your own "new" method.
502		605
503	There are two "sides" to a condition variable - the "producer side"	606	There are two "sides" to a condition variable - the "producer side"
504	which eventually calls "-> send", and the "consumer side", which waits	607	which eventually calls "-> send", and the "consumer side", which waits
505	for the send to occur.	608	for the send to occur.
506		609
507	Example: wait for a timer.	610	Example: wait for a timer.
508		611
509	# wait till the result is ready	612	# condition: "wait till the timer is fired"
510	my $result_ready = AnyEvent->condvar;	613	my $timer_fired = AnyEvent->condvar;
511		614
512	# do something such as adding a timer	615	# create the timer - we could wait for, say
513	# or socket watcher the calls $result_ready->send	616	# a handle becomign ready, or even an
514	# when the "result" is ready.	617	# AnyEvent::HTTP request to finish, but
515	# in this case, we simply use a timer:	618	# in this case, we simply use a timer:
516	my $w = AnyEvent->timer (	619	my $w = AnyEvent->timer (
517	after => 1,	620	after => 1,
518	cb => sub { $result_ready->send },	621	cb => sub { $timer_fired->send },
519	);	622	);
520		623
521	# this "blocks" (while handling events) till the callback	624	# this "blocks" (while handling events) till the callback
522	# calls -<send	625	# calls ->send
523	$result_ready->recv;	626	$timer_fired->recv;
524		627
525	Example: wait for a timer, but take advantage of the fact that condition	628	Example: wait for a timer, but take advantage of the fact that condition
526	variables are also callable directly.	629	variables are also callable directly.
527		630
528	my $done = AnyEvent->condvar;	631	my $done = AnyEvent->condvar;
…		…
566	Condition variables are overloaded so one can call them directly (as	669	Condition variables are overloaded so one can call them directly (as
567	if they were a code reference). Calling them directly is the same as	670	if they were a code reference). Calling them directly is the same as
568	calling "send".	671	calling "send".
569		672
570	$cv->croak ($error)	673	$cv->croak ($error)
571	Similar to send, but causes all call's to "->recv" to invoke	674	Similar to send, but causes all calls to "->recv" to invoke
572	"Carp::croak" with the given error message/object/scalar.	675	"Carp::croak" with the given error message/object/scalar.
573		676
574	This can be used to signal any errors to the condition variable	677	This can be used to signal any errors to the condition variable
575	user/consumer. Doing it this way instead of calling "croak" directly	678	user/consumer. Doing it this way instead of calling "croak" directly
576	delays the error detetcion, but has the overwhelmign advantage that	679	delays the error detection, but has the overwhelming advantage that
577	it diagnoses the error at the place where the result is expected,	680	it diagnoses the error at the place where the result is expected,
578	and not deep in some event clalback without connection to the actual	681	and not deep in some event callback with no connection to the actual
579	code causing the problem.	682	code causing the problem.
580		683
581	$cv->begin ([group callback])	684	$cv->begin ([group callback])
582	$cv->end	685	$cv->end
583	These two methods can be used to combine many transactions/events	686	These two methods can be used to combine many transactions/events
584	into one. For example, a function that pings many hosts in parallel	687	into one. For example, a function that pings many hosts in parallel
585	might want to use a condition variable for the whole process.	688	might want to use a condition variable for the whole process.
586		689
587	Every call to "->begin" will increment a counter, and every call to	690	Every call to "->begin" will increment a counter, and every call to
588	"->end" will decrement it. If the counter reaches 0 in "->end", the	691	"->end" will decrement it. If the counter reaches 0 in "->end", the
589	(last) callback passed to "begin" will be executed. That callback is	692	(last) callback passed to "begin" will be executed, passing the
590	supposed to call "->send", but that is not required. If no	693	condvar as first argument. That callback is supposed to call
		694	"->send", but that is not required. If no group callback was set,
591	callback was set, "send" will be called without any arguments.	695	"send" will be called without any arguments.
592		696
593	You can think of "$cv->send" giving you an OR condition (one call	697	You can think of "$cv->send" giving you an OR condition (one call
594	sends), while "$cv->begin" and "$cv->end" giving you an AND	698	sends), while "$cv->begin" and "$cv->end" giving you an AND
595	condition (all "begin" calls must be "end"'ed before the condvar	699	condition (all "begin" calls must be "end"'ed before the condvar
596	sends).	700	sends).
…		…
619	there is one call to "begin", so the condvar waits for all calls to	723	there is one call to "begin", so the condvar waits for all calls to
620	"end" before sending.	724	"end" before sending.
621		725
622	The ping example mentioned above is slightly more complicated, as	726	The ping example mentioned above is slightly more complicated, as
623	the there are results to be passwd back, and the number of tasks	727	the there are results to be passwd back, and the number of tasks
624	that are begung can potentially be zero:	728	that are begun can potentially be zero:
625		729
626	my $cv = AnyEvent->condvar;	730	my $cv = AnyEvent->condvar;
627		731
628	my %result;	732	my %result;
629	$cv->begin (sub { $cv->send (\%result) });	733	$cv->begin (sub { shift->send (\%result) });
630		734
631	for my $host (@list_of_hosts) {	735	for my $host (@list_of_hosts) {
632	$cv->begin;	736	$cv->begin;
633	ping_host_then_call_callback $host, sub {	737	ping_host_then_call_callback $host, sub {
634	$result{$host} = ...;	738	$result{$host} = ...;
…		…
650	callback to be called once the counter reaches 0, and second, it	754	callback to be called once the counter reaches 0, and second, it
651	ensures that "send" is called even when "no" hosts are being pinged	755	ensures that "send" is called even when "no" hosts are being pinged
652	(the loop doesn't execute once).	756	(the loop doesn't execute once).
653		757
654	This is the general pattern when you "fan out" into multiple (but	758	This is the general pattern when you "fan out" into multiple (but
655	potentially none) subrequests: use an outer "begin"/"end" pair to	759	potentially zero) subrequests: use an outer "begin"/"end" pair to
656	set the callback and ensure "end" is called at least once, and then,	760	set the callback and ensure "end" is called at least once, and then,
657	for each subrequest you start, call "begin" and for each subrequest	761	for each subrequest you start, call "begin" and for each subrequest
658	you finish, call "end".	762	you finish, call "end".
659		763
660	METHODS FOR CONSUMERS	764	METHODS FOR CONSUMERS
661	These methods should only be used by the consuming side, i.e. the code	765	These methods should only be used by the consuming side, i.e. the code
662	awaits the condition.	766	awaits the condition.
663		767
664	$cv->recv	768	$cv->recv
665	Wait (blocking if necessary) until the "->send" or "->croak" methods	769	Wait (blocking if necessary) until the "->send" or "->croak" methods
666	have been called on c<$cv>, while servicing other watchers normally.	770	have been called on $cv, while servicing other watchers normally.
667		771
668	You can only wait once on a condition - additional calls are valid	772	You can only wait once on a condition - additional calls are valid
669	but will return immediately.	773	but will return immediately.
670		774
671	If an error condition has been set by calling "->croak", then this	775	If an error condition has been set by calling "->croak", then this
…		…
688	example, by coupling condition variables with some kind of request	792	example, by coupling condition variables with some kind of request
689	results and supporting callbacks so the caller knows that getting	793	results and supporting callbacks so the caller knows that getting
690	the result will not block, while still supporting blocking waits if	794	the result will not block, while still supporting blocking waits if
691	the caller so desires).	795	the caller so desires).
692		796
693	You can ensure that "-recv" never blocks by setting a callback and	797	You can ensure that "->recv" never blocks by setting a callback and
694	only calling "->recv" from within that callback (or at a later	798	only calling "->recv" from within that callback (or at a later
695	time). This will work even when the event loop does not support	799	time). This will work even when the event loop does not support
696	blocking waits otherwise.	800	blocking waits otherwise.
697		801
698	$bool = $cv->ready	802	$bool = $cv->ready
…		…
703	This is a mutator function that returns the callback set and	807	This is a mutator function that returns the callback set and
704	optionally replaces it before doing so.	808	optionally replaces it before doing so.
705		809
706	The callback will be called when the condition becomes "true", i.e.	810	The callback will be called when the condition becomes "true", i.e.
707	when "send" or "croak" are called, with the only argument being the	811	when "send" or "croak" are called, with the only argument being the
708	condition variable itself. Calling "recv" inside the callback or at	812	condition variable itself. If the condition is already true, the
		813	callback is called immediately when it is set. Calling "recv" inside
709	any later time is guaranteed not to block.	814	the callback or at any later time is guaranteed not to block.
710		815
711	SUPPORTED EVENT LOOPS/BACKENDS	816	SUPPORTED EVENT LOOPS/BACKENDS
712	The available backend classes are (every class has its own manpage):	817	The available backend classes are (every class has its own manpage):
713		818
714	Backends that are autoprobed when no other event loop can be found.	819	Backends that are autoprobed when no other event loop can be found.
715	EV is the preferred backend when no other event loop seems to be in	820	EV is the preferred backend when no other event loop seems to be in
716	use. If EV is not installed, then AnyEvent will try Event, and,	821	use. If EV is not installed, then AnyEvent will fall back to its own
717	failing that, will fall back to its own pure-perl implementation,	822	pure-perl implementation, which is available everywhere as it comes
718	which is available everywhere as it comes with AnyEvent itself.	823	with AnyEvent itself.
719		824
720	AnyEvent::Impl::EV based on EV (interface to libev, best choice).	825	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
721	AnyEvent::Impl::Event based on Event, very stable, few glitches.
722	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.	826	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
723		827
724	Backends that are transparently being picked up when they are used.	828	Backends that are transparently being picked up when they are used.
725	These will be used when they are currently loaded when the first	829	These will be used if they are already loaded when the first watcher
726	watcher is created, in which case it is assumed that the application	830	is created, in which case it is assumed that the application is
727	is using them. This means that AnyEvent will automatically pick the	831	using them. This means that AnyEvent will automatically pick the
728	right backend when the main program loads an event module before	832	right backend when the main program loads an event module before
729	anything starts to create watchers. Nothing special needs to be done	833	anything starts to create watchers. Nothing special needs to be done
730	by the main program.	834	by the main program.
731		835
		836	AnyEvent::Impl::Event based on Event, very stable, few glitches.
732	AnyEvent::Impl::Glib based on Glib, slow but very stable.	837	AnyEvent::Impl::Glib based on Glib, slow but very stable.
733	AnyEvent::Impl::Tk based on Tk, very broken.	838	AnyEvent::Impl::Tk based on Tk, very broken.
734	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	839	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
735	AnyEvent::Impl::POE based on POE, very slow, some limitations.	840	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		841	AnyEvent::Impl::Irssi used when running within irssi.
		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).
736		845
737	Backends with special needs.	846	Backends with special needs.
738	Qt requires the Qt::Application to be instantiated first, but will	847	Qt requires the Qt::Application to be instantiated first, but will
739	otherwise be picked up automatically. As long as the main program	848	otherwise be picked up automatically. As long as the main program
740	instantiates the application before any AnyEvent watchers are	849	instantiates the application before any AnyEvent watchers are
741	created, everything should just work.	850	created, everything should just work.
742		851
743	AnyEvent::Impl::Qt based on Qt.	852	AnyEvent::Impl::Qt based on Qt.
744		853
745	Support for IO::Async can only be partial, as it is too broken and
746	architecturally limited to even support the AnyEvent API. It also is
747	the only event loop that needs the loop to be set explicitly, so it
748	can only be used by a main program knowing about AnyEvent. See
749	AnyEvent::Impl::Async for the gory details.
750
751	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
752
753	Event loops that are indirectly supported via other backends.	854	Event loops that are indirectly supported via other backends.
754	Some event loops can be supported via other modules:	855	Some event loops can be supported via other modules:
755		856
756	There is no direct support for WxWidgets (Wx) or Prima.	857	There is no direct support for WxWidgets (Wx) or Prima.
757		858
…		…
775	Contains "undef" until the first watcher is being created, before	876	Contains "undef" until the first watcher is being created, before
776	the backend has been autodetected.	877	the backend has been autodetected.
777		878
778	Afterwards it contains the event model that is being used, which is	879	Afterwards it contains the event model that is being used, which is
779	the name of the Perl class implementing the model. This class is	880	the name of the Perl class implementing the model. This class is
780	usually one of the "AnyEvent::Impl:xxx" modules, but can be any	881	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
781	other class in the case AnyEvent has been extended at runtime (e.g.	882	other class in the case AnyEvent has been extended at runtime (e.g.
782	in rxvt-unicode it will be "urxvt::anyevent").	883	in rxvt-unicode it will be "urxvt::anyevent").
783		884
784	AnyEvent::detect	885	AnyEvent::detect
785	Returns $AnyEvent::MODEL, forcing autodetection of the event model	886	Returns $AnyEvent::MODEL, forcing autodetection of the event model
786	if necessary. You should only call this function right before you	887	if necessary. You should only call this function right before you
787	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
788	possible at runtime, and not e.g. while initialising of your module.	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).
789		895
790	If you need to do some initialisation before AnyEvent watchers are	896	If you need to do some initialisation before AnyEvent watchers are
791	created, use "post_detect".	897	created, use "post_detect".
792		898
793	$guard = AnyEvent::post_detect { BLOCK }	899	$guard = AnyEvent::post_detect { BLOCK }
794	Arranges for the code block to be executed as soon as the event	900	Arranges for the code block to be executed as soon as the event
795	model is autodetected (or immediately if this has already happened).	901	model is autodetected (or immediately if that has already happened).
796		902
797	The block will be executed after the actual backend has been	903	The block will be executed after the actual backend has been
798	detected ($AnyEvent::MODEL is set), but before any watchers have	904	detected ($AnyEvent::MODEL is set), but before any watchers have
799	been created, so it is possible to e.g. patch @AnyEvent::ISA or do	905	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
800	other initialisations - see the sources of AnyEvent::Strict or	906	other initialisations - see the sources of AnyEvent::Strict or
…		…
805	creates and installs the global IO::AIO watcher in a "post_detect"	911	creates and installs the global IO::AIO watcher in a "post_detect"
806	block to avoid autodetecting the event module at load time.	912	block to avoid autodetecting the event module at load time.
807		913
808	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
809	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
810	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;
811		934
812	@AnyEvent::post_detect	935	@AnyEvent::post_detect
813	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
814	before or after loading AnyEvent), then they will called directly	937	before or after loading AnyEvent), then they will be called directly
815	after the event loop has been chosen.	938	after the event loop has been chosen.
816		939
817	You should check $AnyEvent::MODEL before adding to this array,	940	You should check $AnyEvent::MODEL before adding to this array,
818	though: if it is defined then the event loop has already been	941	though: if it is defined then the event loop has already been
819	detected, and the array will be ignored.	942	detected, and the array will be ignored.
820		943
821	Best use "AnyEvent::post_detect { BLOCK }" when your application	944	Best use "AnyEvent::post_detect { BLOCK }" when your application
822	allows it,as it takes care of these details.	945	allows it, as it takes care of these details.
823		946
824	This variable is mainly useful for modules that can do something	947	This variable is mainly useful for modules that can do something
825	useful when AnyEvent is used and thus want to know when it is	948	useful when AnyEvent is used and thus want to know when it is
826	initialised, but do not need to even load it by default. This array	949	initialised, but do not need to even load it by default. This array
827	provides the means to hook into AnyEvent passively, without loading	950	provides the means to hook into AnyEvent passively, without loading
828	it.	951	it.
829		952
		953	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		954	together, you could put this into Coro (this is the actual code used
		955	by Coro to accomplish this):
		956
		957	if (defined $AnyEvent::MODEL) {
		958	# AnyEvent already initialised, so load Coro::AnyEvent
		959	require Coro::AnyEvent;
		960	} else {
		961	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		962	# as soon as it is
		963	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		964	}
		965
		966	AnyEvent::postpone { BLOCK }
		967	Arranges for the block to be executed as soon as possible, but not
		968	before the call itself returns. In practise, the block will be
		969	executed just before the event loop polls for new events, or shortly
		970	afterwards.
		971
		972	This function never returns anything (to make the "return postpone {
		973	... }" idiom more useful.
		974
		975	To understand the usefulness of this function, consider a function
		976	that asynchronously does something for you and returns some
		977	transaction object or guard to let you cancel the operation. For
		978	example, "AnyEvent::Socket::tcp_connect":
		979
		980	# start a conenction attempt unless one is active
		981	$self->{connect_guard} \|\|= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		982	delete $self->{connect_guard};
		983	...
		984	};
		985
		986	Imagine that this function could instantly call the callback, for
		987	example, because it detects an obvious error such as a negative port
		988	number. Invoking the callback before the function returns causes
		989	problems however: the callback will be called and will try to delete
		990	the guard object. But since the function hasn't returned yet, there
		991	is nothing to delete. When the function eventually returns it will
		992	assign the guard object to "$self->{connect_guard}", where it will
		993	likely never be deleted, so the program thinks it is still trying to
		994	connect.
		995
		996	This is where "AnyEvent::postpone" should be used. Instead of
		997	calling the callback directly on error:
		998
		999	$cb->(undef), return # signal error to callback, BAD!
		1000	if $some_error_condition;
		1001
		1002	It should use "postpone":
		1003
		1004	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1005	if $some_error_condition;
		1006
		1007	AnyEvent::log $level, $msg[, @args]
		1008	Log the given $msg at the given $level.
		1009
		1010	Loads AnyEvent::Log on first use and calls "AnyEvent::Log::log" -
		1011	consequently, look at the AnyEvent::Log documentation for details.
		1012
		1013	If you want to sprinkle loads of logging calls around your code,
		1014	consider creating a logger callback with the "AnyEvent::Log::logger"
		1015	function.
		1016
830	WHAT TO DO IN A MODULE	1017	WHAT TO DO IN A MODULE
831	As a module author, you should "use AnyEvent" and call AnyEvent methods	1018	As a module author, you should "use AnyEvent" and call AnyEvent methods
832	freely, but you should not load a specific event module or rely on it.	1019	freely, but you should not load a specific event module or rely on it.
833		1020
834	Be careful when you create watchers in the module body - AnyEvent will	1021	Be careful when you create watchers in the module body - AnyEvent will
…		…
841	stall the whole program, and the whole point of using events is to stay	1028	stall the whole program, and the whole point of using events is to stay
842	interactive.	1029	interactive.
843		1030
844	It is fine, however, to call "->recv" when the user of your module	1031	It is fine, however, to call "->recv" when the user of your module
845	requests it (i.e. if you create a http request object ad have a method	1032	requests it (i.e. if you create a http request object ad have a method
846	called "results" that returns the results, it should call "->recv"	1033	called "results" that returns the results, it may call "->recv" freely,
847	freely, as the user of your module knows what she is doing. always).	1034	as the user of your module knows what she is doing. Always).
848		1035
849	WHAT TO DO IN THE MAIN PROGRAM	1036	WHAT TO DO IN THE MAIN PROGRAM
850	There will always be a single main program - the only place that should	1037	There will always be a single main program - the only place that should
851	dictate which event model to use.	1038	dictate which event model to use.
852		1039
853	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1040	If the program is not event-based, it need not do anything special, even
854	do anything special (it does not need to be event-based) and let	1041	when it depends on a module that uses an AnyEvent. If the program itself
855	AnyEvent decide which implementation to chose if some module relies on	1042	uses AnyEvent, but does not care which event loop is used, all it needs
856	it.	1043	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1044	available loop implementation.
857		1045
858	If the main program relies on a specific event model - for example, in	1046	If the main program relies on a specific event model - for example, in
859	Gtk2 programs you have to rely on the Glib module - you should load the	1047	Gtk2 programs you have to rely on the Glib module - you should load the
860	event module before loading AnyEvent or any module that uses it:	1048	event module before loading AnyEvent or any module that uses it:
861	generally speaking, you should load it as early as possible. The reason	1049	generally speaking, you should load it as early as possible. The reason
862	is that modules might create watchers when they are loaded, and AnyEvent	1050	is that modules might create watchers when they are loaded, and AnyEvent
863	will decide on the event model to use as soon as it creates watchers,	1051	will decide on the event model to use as soon as it creates watchers,
864	and it might chose the wrong one unless you load the correct one	1052	and it might choose the wrong one unless you load the correct one
865	yourself.	1053	yourself.
866		1054
867	You can chose to use a pure-perl implementation by loading the	1055	You can chose to use a pure-perl implementation by loading the
868	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1056	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
869	everywhere, but letting AnyEvent chose the model is generally better.	1057	but letting AnyEvent chose the model is generally better.
870		1058
871	MAINLOOP EMULATION	1059	MAINLOOP EMULATION
872	Sometimes (often for short test scripts, or even standalone programs who	1060	Sometimes (often for short test scripts, or even standalone programs who
873	only want to use AnyEvent), you do not want to run a specific event	1061	only want to use AnyEvent), you do not want to run a specific event
874	loop.	1062	loop.
…		…
886		1074
887	OTHER MODULES	1075	OTHER MODULES
888	The following is a non-exhaustive list of additional modules that use	1076	The following is a non-exhaustive list of additional modules that use
889	AnyEvent as a client and can therefore be mixed easily with other	1077	AnyEvent as a client and can therefore be mixed easily with other
890	AnyEvent modules and other event loops in the same program. Some of the	1078	AnyEvent modules and other event loops in the same program. Some of the
891	modules come with AnyEvent, most are available via CPAN.	1079	modules come as part of AnyEvent, the others are available via CPAN (see
		1080	<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
		1081	non-exhaustive list), and the list is heavily biased towards modules of
		1082	the AnyEvent author himself :)
892		1083
893	AnyEvent::Util	1084	AnyEvent::Util
894	Contains various utility functions that replace often-used but	1085	Contains various utility functions that replace often-used blocking
895	blocking functions such as "inet_aton" by event-/callback-based	1086	functions such as "inet_aton" with event/callback-based versions.
896	versions.
897		1087
898	AnyEvent::Socket	1088	AnyEvent::Socket
899	Provides various utility functions for (internet protocol) sockets,	1089	Provides various utility functions for (internet protocol) sockets,
900	addresses and name resolution. Also functions to create non-blocking	1090	addresses and name resolution. Also functions to create non-blocking
901	tcp connections or tcp servers, with IPv6 and SRV record support and	1091	tcp connections or tcp servers, with IPv6 and SRV record support and
902	more.	1092	more.
903		1093
904	AnyEvent::Handle	1094	AnyEvent::Handle
905	Provide read and write buffers, manages watchers for reads and	1095	Provide read and write buffers, manages watchers for reads and
906	writes, supports raw and formatted I/O, I/O queued and fully	1096	writes, supports raw and formatted I/O, I/O queued and fully
907	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.	1097	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
908		1098
909	AnyEvent::DNS	1099	AnyEvent::DNS
910	Provides rich asynchronous DNS resolver capabilities.	1100	Provides rich asynchronous DNS resolver capabilities.
911		1101
		1102	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
		1103	AnyEvent::IGS, AnyEvent::FCP
		1104	Implement event-based interfaces to the protocols of the same name
		1105	(for the curious, IGS is the International Go Server and FCP is the
		1106	Freenet Client Protocol).
		1107
		1108	AnyEvent::Handle::UDP
		1109	Here be danger!
		1110
		1111	As Pauli would put it, "Not only is it not right, it's not even
		1112	wrong!" - there are so many things wrong with AnyEvent::Handle::UDP,
		1113	most notably its use of a stream-based API with a protocol that
		1114	isn't streamable, that the only way to improve it is to delete it.
		1115
		1116	It features data corruption (but typically only under load) and
		1117	general confusion. On top, the author is not only clueless about UDP
		1118	but also fact-resistant - some gems of his understanding: "connect
		1119	doesn't work with UDP", "UDP packets are not IP packets", "UDP only
		1120	has datagrams, not packets", "I don't need to implement proper error
		1121	checking as UDP doesn't support error checking" and so on - he
		1122	doesn't even understand what's wrong with his module when it is
		1123	explained to him.
		1124
912	AnyEvent::HTTP	1125	AnyEvent::DBI
913	A simple-to-use HTTP library that is capable of making a lot of	1126	Executes DBI requests asynchronously in a proxy process for you,
914	concurrent HTTP requests.	1127	notifying you in an event-based way when the operation is finished.
		1128
		1129	AnyEvent::AIO
		1130	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1131	the toolbox of every event programmer. AnyEvent::AIO transparently
		1132	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1133	event-based file I/O, and much more.
915		1134
916	AnyEvent::HTTPD	1135	AnyEvent::HTTPD
917	Provides a simple web application server framework.	1136	A simple embedded webserver.
918		1137
919	AnyEvent::FastPing	1138	AnyEvent::FastPing
920	The fastest ping in the west.	1139	The fastest ping in the west.
921		1140
922	AnyEvent::DBI
923	Executes DBI requests asynchronously in a proxy process.
924
925	AnyEvent::AIO
926	Truly asynchronous I/O, should be in the toolbox of every event
927	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
928	together.
929
930	AnyEvent::BDB
931	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
932	fuses BDB and AnyEvent together.
933
934	AnyEvent::GPSD
935	A non-blocking interface to gpsd, a daemon delivering GPS
936	information.
937
938	AnyEvent::IRC
939	AnyEvent based IRC client module family (replacing the older
940	Net::IRC3).
941
942	AnyEvent::XMPP
943	AnyEvent based XMPP (Jabber protocol) module family (replacing the
944	older Net::XMPP2>.
945
946	AnyEvent::IGS
947	A non-blocking interface to the Internet Go Server protocol (used by
948	App::IGS).
949
950	Net::FCP
951	AnyEvent-based implementation of the Freenet Client Protocol,
952	birthplace of AnyEvent.
953
954	Event::ExecFlow
955	High level API for event-based execution flow control.
956
957	Coro	1141	Coro
958	Has special support for AnyEvent via Coro::AnyEvent.	1142	Has special support for AnyEvent via Coro::AnyEvent.
		1143
		1144	SIMPLIFIED AE API
		1145	Starting with version 5.0, AnyEvent officially supports a second, much
		1146	simpler, API that is designed to reduce the calling, typing and memory
		1147	overhead by using function call syntax and a fixed number of parameters.
		1148
		1149	See the AE manpage for details.
959		1150
960	ERROR AND EXCEPTION HANDLING	1151	ERROR AND EXCEPTION HANDLING
961	In general, AnyEvent does not do any error handling - it relies on the	1152	In general, AnyEvent does not do any error handling - it relies on the
962	caller to do that if required. The AnyEvent::Strict module (see also the	1153	caller to do that if required. The AnyEvent::Strict module (see also the
963	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1154	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
984	"PERL_ANYEVENT_VERBOSE"	1175	"PERL_ANYEVENT_VERBOSE"
985	By default, AnyEvent will be completely silent except in fatal	1176	By default, AnyEvent will be completely silent except in fatal
986	conditions. You can set this environment variable to make AnyEvent	1177	conditions. You can set this environment variable to make AnyEvent
987	more talkative.	1178	more talkative.
988		1179
989	When set to 1 or higher, causes AnyEvent to warn about unexpected	1180	When set to 5 or higher, causes AnyEvent to warn about unexpected
990	conditions, such as not being able to load the event model specified	1181	conditions, such as not being able to load the event model specified
991	by "PERL_ANYEVENT_MODEL".	1182	by "PERL_ANYEVENT_MODEL".
992		1183
993	When set to 2 or higher, cause AnyEvent to report to STDERR which	1184	When set to 7 or higher, cause AnyEvent to report to STDERR which
994	event model it chooses.	1185	event model it chooses.
		1186
		1187	When set to 8 or higher, then AnyEvent will report extra information
		1188	on which optional modules it loads and how it implements certain
		1189	features.
995		1190
996	"PERL_ANYEVENT_STRICT"	1191	"PERL_ANYEVENT_STRICT"
997	AnyEvent does not do much argument checking by default, as thorough	1192	AnyEvent does not do much argument checking by default, as thorough
998	argument checking is very costly. Setting this variable to a true	1193	argument checking is very costly. Setting this variable to a true
999	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1194	value will cause AnyEvent to load "AnyEvent::Strict" and then to
1000	thoroughly check the arguments passed to most method calls. If it	1195	thoroughly check the arguments passed to most method calls. If it
1001	finds any problems, it will croak.	1196	finds any problems, it will croak.
1002		1197
1003	In other words, enables "strict" mode.	1198	In other words, enables "strict" mode.
1004		1199
1005	Unlike "use strict", it is definitely recommended to keep it off in	1200	Unlike "use strict" (or its modern cousin, "use common::sense", it
1006	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1201	is definitely recommended to keep it off in production. Keeping
		1202	"PERL_ANYEVENT_STRICT=1" in your environment while developing
1007	while developing programs can be very useful, however.	1203	programs can be very useful, however.
		1204
		1205	"PERL_ANYEVENT_DEBUG_SHELL"
		1206	If this env variable is set, then its contents will be interpreted
		1207	by "AnyEvent::Socket::parse_hostport" (after replacing every
		1208	occurance of $$ by the process pid) and an "AnyEvent::Debug::shell"
		1209	is bound on that port. The shell object is saved in
		1210	$AnyEvent::Debug::SHELL.
		1211
		1212	This takes place when the first watcher is created.
		1213
		1214	For example, to bind a debug shell on a unix domain socket in
		1215	/tmp/debug<pid>.sock, you could use this:
		1216
		1217	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		1218
		1219	Note that creating sockets in /tmp is very unsafe on multiuser
		1220	systems.
		1221
		1222	"PERL_ANYEVENT_DEBUG_WRAP"
		1223	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1224	debugging purposes. See "AnyEvent::Debug::wrap" for details.
1008		1225
1009	"PERL_ANYEVENT_MODEL"	1226	"PERL_ANYEVENT_MODEL"
1010	This can be used to specify the event model to be used by AnyEvent,	1227	This can be used to specify the event model to be used by AnyEvent,
1011	before auto detection and -probing kicks in. It must be a string	1228	before auto detection and -probing kicks in.
1012	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1229
1013	gets prepended and the resulting module name is loaded and if the	1230	It normally is a string consisting entirely of ASCII letters (e.g.
1014	load was successful, used as event model. If it fails to load	1231	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1232	the resulting module name is loaded and - if the load was successful
		1233	- used as event model backend. If it fails to load then AnyEvent
1015	AnyEvent will proceed with auto detection and -probing.	1234	will proceed with auto detection and -probing.
1016		1235
1017	This functionality might change in future versions.	1236	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1237	then nothing gets prepended and the module name is used as-is (hint:
		1238	"::" at the end of a string designates a module name and quotes it
		1239	appropriately).
1018		1240
1019	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1241	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
1020	could start your program like this:	1242	could start your program like this:
1021		1243
1022	PERL_ANYEVENT_MODEL=Perl perl ...	1244	PERL_ANYEVENT_MODEL=Perl perl ...
1023		1245
1024	"PERL_ANYEVENT_PROTOCOLS"	1246	"PERL_ANYEVENT_PROTOCOLS"
…		…
1069	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".	1291	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1070	When neither "ca_file" nor "ca_path" was specified during	1292	When neither "ca_file" nor "ca_path" was specified during
1071	AnyEvent::TLS context creation, and either of these environment	1293	AnyEvent::TLS context creation, and either of these environment
1072	variables exist, they will be used to specify CA certificate	1294	variables exist, they will be used to specify CA certificate
1073	locations instead of a system-dependent default.	1295	locations instead of a system-dependent default.
		1296
		1297	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1298	When these are set to 1, then the respective modules are not loaded.
		1299	Mostly good for testing AnyEvent itself.
1074		1300
1075	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1301	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1076	This is an advanced topic that you do not normally need to use AnyEvent	1302	This is an advanced topic that you do not normally need to use AnyEvent
1077	in a module. This section is only of use to event loop authors who want	1303	in a module. This section is only of use to event loop authors who want
1078	to provide AnyEvent compatibility.	1304	to provide AnyEvent compatibility.
…		…
1133	warn "read: $input\n"; # output what has been read	1359	warn "read: $input\n"; # output what has been read
1134	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1360	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1135	},	1361	},
1136	);	1362	);
1137		1363
1138	my $time_watcher; # can only be used once
1139
1140	sub new_timer {
1141	$timer = AnyEvent->timer (after => 1, cb => sub {	1364	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1142	warn "timeout\n"; # print 'timeout' about every second	1365	warn "timeout\n"; # print 'timeout' at most every second
1143	&new_timer; # and restart the time
1144	});
1145	}	1366	});
1146
1147	new_timer; # create first timer
1148		1367
1149	$cv->recv; # wait until user enters /^q/i	1368	$cv->recv; # wait until user enters /^q/i
1150		1369
1151	REAL-WORLD EXAMPLE	1370	REAL-WORLD EXAMPLE
1152	Consider the Net::FCP module. It features (among others) the following	1371	Consider the Net::FCP module. It features (among others) the following
…		…
1224		1443
1225	The actual code goes further and collects all errors ("die"s,	1444	The actual code goes further and collects all errors ("die"s,
1226	exceptions) that occurred during request processing. The "result" method	1445	exceptions) that occurred during request processing. The "result" method
1227	detects whether an exception as thrown (it is stored inside the $txn	1446	detects whether an exception as thrown (it is stored inside the $txn
1228	object) and just throws the exception, which means connection errors and	1447	object) and just throws the exception, which means connection errors and
1229	other problems get reported tot he code that tries to use the result,	1448	other problems get reported to the code that tries to use the result,
1230	not in a random callback.	1449	not in a random callback.
1231		1450
1232	All of this enables the following usage styles:	1451	All of this enables the following usage styles:
1233		1452
1234	1. Blocking:	1453	1. Blocking:
…		…
1279	through AnyEvent. The benchmark creates a lot of timers (with a zero	1498	through AnyEvent. The benchmark creates a lot of timers (with a zero
1280	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1499	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1281	which it is), lets them fire exactly once and destroys them again.	1500	which it is), lets them fire exactly once and destroys them again.
1282		1501
1283	Source code for this benchmark is found as eg/bench in the AnyEvent	1502	Source code for this benchmark is found as eg/bench in the AnyEvent
1284	distribution.	1503	distribution. It uses the AE interface, which makes a real difference
		1504	for the EV and Perl backends only.
1285		1505
1286	Explanation of the columns	1506	Explanation of the columns
1287	watcher is the number of event watchers created/destroyed. Since	1507	watcher is the number of event watchers created/destroyed. Since
1288	different event models feature vastly different performances, each event	1508	different event models feature vastly different performances, each event
1289	loop was given a number of watchers so that overall runtime is	1509	loop was given a number of watchers so that overall runtime is
…		…
1308	destroy is the time, in microseconds, that it takes to destroy a	1528	destroy is the time, in microseconds, that it takes to destroy a
1309	single watcher.	1529	single watcher.
1310		1530
1311	Results	1531	Results
1312	name watchers bytes create invoke destroy comment	1532	name watchers bytes create invoke destroy comment
1313	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1533	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1314	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1534	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1315	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1535	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1316	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1536	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1317	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1537	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1318	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1538	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
1319	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll	1539	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
1320	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll	1540	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1321	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1541	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1322	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1542	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1323	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1543	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1324	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1544	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1325		1545
1326	Discussion	1546	Discussion
1327	The benchmark does not measure scalability of the event loop very	1547	The benchmark does not measure scalability of the event loop very
1328	well. For example, a select-based event loop (such as the pure perl one)	1548	well. For example, a select-based event loop (such as the pure perl one)
1329	can never compete with an event loop that uses epoll when the number of	1549	can never compete with an event loop that uses epoll when the number of
…		…
1340	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1560	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1341	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1561	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1342	CPU cycles with POE.	1562	CPU cycles with POE.
1343		1563
1344	"EV" is the sole leader regarding speed and memory use, which are both	1564	"EV" is the sole leader regarding speed and memory use, which are both
1345	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1565	maximal/minimal, respectively. When using the AE API there is zero
		1566	overhead (when going through the AnyEvent API create is about 5-6 times
		1567	slower, with other times being equal, so still uses far less memory than
1346	far less memory than any other event loop and is still faster than Event	1568	any other event loop and is still faster than Event natively).
1347	natively.
1348		1569
1349	The pure perl implementation is hit in a few sweet spots (both the	1570	The pure perl implementation is hit in a few sweet spots (both the
1350	constant timeout and the use of a single fd hit optimisations in the	1571	constant timeout and the use of a single fd hit optimisations in the
1351	perl interpreter and the backend itself). Nevertheless this shows that	1572	perl interpreter and the backend itself). Nevertheless this shows that
1352	it adds very little overhead in itself. Like any select-based backend	1573	it adds very little overhead in itself. Like any select-based backend
…		…
1398	when used without AnyEvent), but most event loops have acceptable	1619	when used without AnyEvent), but most event loops have acceptable
1399	performance with or without AnyEvent.	1620	performance with or without AnyEvent.
1400		1621
1401	* The overhead AnyEvent adds is usually much smaller than the overhead	1622	* The overhead AnyEvent adds is usually much smaller than the overhead
1402	of the actual event loop, only with extremely fast event loops such	1623	of the actual event loop, only with extremely fast event loops such
1403	as EV adds AnyEvent significant overhead.	1624	as EV does AnyEvent add significant overhead.
1404		1625
1405	* You should avoid POE like the plague if you want performance or	1626	* You should avoid POE like the plague if you want performance or
1406	reasonable memory usage.	1627	reasonable memory usage.
1407		1628
1408	BENCHMARKING THE LARGE SERVER CASE	1629	BENCHMARKING THE LARGE SERVER CASE
…		…
1422	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1643	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1423	100 (1%) are active. This mirrors the activity of large servers with	1644	100 (1%) are active. This mirrors the activity of large servers with
1424	many connections, most of which are idle at any one point in time.	1645	many connections, most of which are idle at any one point in time.
1425		1646
1426	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1647	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1427	distribution.	1648	distribution. It uses the AE interface, which makes a real difference
		1649	for the EV and Perl backends only.
1428		1650
1429	Explanation of the columns	1651	Explanation of the columns
1430	sockets is the number of sockets, and twice the number of "servers"	1652	sockets is the number of sockets, and twice the number of "servers"
1431	(as each server has a read and write socket end).	1653	(as each server has a read and write socket end).
1432		1654
…		…
1438	forwarding it to another server. This includes deleting the old timeout	1660	forwarding it to another server. This includes deleting the old timeout
1439	and creating a new one that moves the timeout into the future.	1661	and creating a new one that moves the timeout into the future.
1440		1662
1441	Results	1663	Results
1442	name sockets create request	1664	name sockets create request
1443	EV 20000 69.01 11.16	1665	EV 20000 62.66 7.99
1444	Perl 20000 73.32 35.87	1666	Perl 20000 68.32 32.64
1445	IOAsync 20000 157.00 98.14 epoll	1667	IOAsync 20000 174.06 101.15 epoll
1446	IOAsync 20000 159.31 616.06 poll	1668	IOAsync 20000 174.67 610.84 poll
1447	Event 20000 212.62 257.32	1669	Event 20000 202.69 242.91
1448	Glib 20000 651.16 1896.30	1670	Glib 20000 557.01 1689.52
1449	POE 20000 349.67 12317.24 uses POE::Loop::Event	1671	POE 20000 341.54 12086.32 uses POE::Loop::Event
1450		1672
1451	Discussion	1673	Discussion
1452	This benchmark does measure scalability and overall performance of the	1674	This benchmark does measure scalability and overall performance of the
1453	particular event loop.	1675	particular event loop.
1454		1676
…		…
1567	As you can see, the AnyEvent + EV combination even beats the	1789	As you can see, the AnyEvent + EV combination even beats the
1568	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl	1790	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1569	backend easily beats IO::Lambda and POE.	1791	backend easily beats IO::Lambda and POE.
1570		1792
1571	And even the 100% non-blocking version written using the high-level (and	1793	And even the 100% non-blocking version written using the high-level (and
1572	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a	1794	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
1573	large margin, even though it does all of DNS, tcp-connect and socket I/O	1795	higher level ("unoptimised") abstractions by a large margin, even though
1574	in a non-blocking way.	1796	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
1575		1797
1576	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and	1798	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
1577	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are	1799	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1578	part of the IO::lambda distribution and were used without any changes.	1800	part of the IO::Lambda distribution and were used without any changes.
1579		1801
1580	SIGNALS	1802	SIGNALS
1581	AnyEvent currently installs handlers for these signals:	1803	AnyEvent currently installs handlers for these signals:
1582		1804
1583	SIGCHLD	1805	SIGCHLD
…		…
1603	it is that this way, the handler will be restored to defaults on	1825	it is that this way, the handler will be restored to defaults on
1604	exec.	1826	exec.
1605		1827
1606	Feel free to install your own handler, or reset it to defaults.	1828	Feel free to install your own handler, or reset it to defaults.
1607		1829
		1830	RECOMMENDED/OPTIONAL MODULES
		1831	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1832	its built-in modules) are required to use it.
		1833
		1834	That does not mean that AnyEvent won't take advantage of some additional
		1835	modules if they are installed.
		1836
		1837	This section explains which additional modules will be used, and how
		1838	they affect AnyEvent's operation.
		1839
		1840	Async::Interrupt
		1841	This slightly arcane module is used to implement fast signal
		1842	handling: To my knowledge, there is no way to do completely
		1843	race-free and quick signal handling in pure perl. To ensure that
		1844	signals still get delivered, AnyEvent will start an interval timer
		1845	to wake up perl (and catch the signals) with some delay (default is
		1846	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1847
		1848	If this module is available, then it will be used to implement
		1849	signal catching, which means that signals will not be delayed, and
		1850	the event loop will not be interrupted regularly, which is more
		1851	efficient (and good for battery life on laptops).
		1852
		1853	This affects not just the pure-perl event loop, but also other event
		1854	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1855
		1856	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1857	natively, and either employ their own workarounds (POE) or use
		1858	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1859	Installing Async::Interrupt does nothing for those backends.
		1860
		1861	EV This module isn't really "optional", as it is simply one of the
		1862	backend event loops that AnyEvent can use. However, it is simply the
		1863	best event loop available in terms of features, speed and stability:
		1864	It supports the AnyEvent API optimally, implements all the watcher
		1865	types in XS, does automatic timer adjustments even when no monotonic
		1866	clock is available, can take avdantage of advanced kernel interfaces
		1867	such as "epoll" and "kqueue", and is the fastest backend by far.
		1868	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1869	Glib::EV).
		1870
		1871	If you only use backends that rely on another event loop (e.g.
		1872	"Tk"), then this module will do nothing for you.
		1873
		1874	Guard
		1875	The guard module, when used, will be used to implement
		1876	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1877	uses a lot less memory), but otherwise doesn't affect guard
		1878	operation much. It is purely used for performance.
		1879
		1880	JSON and JSON::XS
		1881	One of these modules is required when you want to read or write JSON
		1882	data via AnyEvent::Handle. JSON is also written in pure-perl, but
		1883	can take advantage of the ultra-high-speed JSON::XS module when it
		1884	is installed.
		1885
		1886	Net::SSLeay
		1887	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1888	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1889	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1890
		1891	Time::HiRes
		1892	This module is part of perl since release 5.008. It will be used
		1893	when the chosen event library does not come with a timing source of
		1894	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
		1895	load it to try to use a monotonic clock for timing stability.
		1896
1608	FORK	1897	FORK
1609	Most event libraries are not fork-safe. The ones who are usually are	1898	Most event libraries are not fork-safe. The ones who are usually are
1610	because they rely on inefficient but fork-safe "select" or "poll" calls.	1899	because they rely on inefficient but fork-safe "select" or "poll" calls
1611	Only EV is fully fork-aware.	1900	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		1901	epoll are usually badly thought-out hacks that are incompatible with
		1902	fork in one way or another. Only EV is fully fork-aware and ensures that
		1903	you continue event-processing in both parent and child (or both, if you
		1904	know what you are doing).
		1905
		1906	This means that, in general, you cannot fork and do event processing in
		1907	the child if the event library was initialised before the fork (which
		1908	usually happens when the first AnyEvent watcher is created, or the
		1909	library is loaded).
1612		1910
1613	If you have to fork, you must either do so before creating your first	1911	If you have to fork, you must either do so before creating your first
1614	watcher OR you must not use AnyEvent at all in the child.	1912	watcher OR you must not use AnyEvent at all in the child OR you must do
		1913	something completely out of the scope of AnyEvent.
		1914
		1915	The problem of doing event processing in the parent and the child is
		1916	much more complicated: even for backends that are fork-aware or
		1917	fork-safe, their behaviour is not usually what you want: fork clones all
		1918	watchers, that means all timers, I/O watchers etc. are active in both
		1919	parent and child, which is almost never what you want. USing "exec" to
		1920	start worker children from some kind of manage rprocess is usually
		1921	preferred, because it is much easier and cleaner, at the expense of
		1922	having to have another binary.
1615		1923
1616	SECURITY CONSIDERATIONS	1924	SECURITY CONSIDERATIONS
1617	AnyEvent can be forced to load any event model via	1925	AnyEvent can be forced to load any event model via
1618	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1926	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1619	to execute arbitrary code or directly gain access, it can easily be used	1927	to execute arbitrary code or directly gain access, it can easily be used
…		…
1643	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	1951	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1644	annoying memleaks, such as leaking on "map" and "grep" but it is usually	1952	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1645	not as pronounced).	1953	not as pronounced).
1646		1954
1647	SEE ALSO	1955	SEE ALSO
1648	Utility functions: AnyEvent::Util.	1956	Tutorial/Introduction: AnyEvent::Intro.
1649		1957
1650	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1958	FAQ: AnyEvent::FAQ.
1651	Event::Lib, Qt, POE.	1959
		1960	Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log
		1961	(simply logging).
		1962
		1963	Development/Debugging: AnyEvent::Strict (stricter checking),
		1964	AnyEvent::Debug (interactive shell, watcher tracing).
		1965
		1966	Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
		1967	Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK.
1652		1968
1653	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1969	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1654	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1970	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1655	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,	1971	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1656	AnyEvent::Impl::IOAsync.	1972	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi, AnyEvent::Impl::FLTK.
1657		1973
1658	Non-blocking file handles, sockets, TCP clients and servers:	1974	Non-blocking handles, pipes, stream sockets, TCP clients and servers:
1659	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.	1975	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1660		1976
1661	Asynchronous DNS: AnyEvent::DNS.	1977	Asynchronous DNS: AnyEvent::DNS.
1662		1978
1663	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1979	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1664		1980
1665	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,	1981	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
1666	AnyEvent::HTTP.	1982	AnyEvent::HTTP.
1667		1983
1668	AUTHOR	1984	AUTHOR
1669	Marc Lehmann <schmorp@schmorp.de>	1985	Marc Lehmann <schmorp@schmorp.de>
1670	http://home.schmorp.de/	1986	http://home.schmorp.de/

Diff Legend

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

Comparing AnyEvent/README (file contents): Revision 1.45 by root, Fri Jul 17 14:57:03 2009 UTC vs. Revision 1.66 by root, Sun Aug 21 03:02:32 2011 UTC

Diff Legend

Comparing AnyEvent/README (file contents):
Revision 1.45 by root, Fri Jul 17 14:57:03 2009 UTC vs.
Revision 1.66 by root, Sun Aug 21 03:02:32 2011 UTC