[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.47 by root, Mon Jul 20 22:39:57 2009 UTC vs.
Revision 1.72 by root, Tue Dec 17 16:43:15 2013 UTC

…		…
1	NAME	1	NAME
2	AnyEvent - events independent of event loop implementation	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
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.
42		45
43	SUPPORT	46	SUPPORT
		47	An FAQ document is available as AnyEvent::FAQ.
		48
44	There is a mailinglist for discussing all things AnyEvent, and an IRC	49	There also is a mailinglist for discussing all things AnyEvent, and an
45	channel, too.	50	IRC channel, too.
46		51
47	See the AnyEvent project page at the Schmorpforge Ta-Sa Software	52	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
48	Respository, at <http://anyevent.schmorp.de>, for more info.	53	Repository, at <http://anyevent.schmorp.de>, for more info.
49		54
50	WHY YOU SHOULD USE THIS MODULE (OR NOT)	55	WHY YOU SHOULD USE THIS MODULE (OR NOT)
51	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
52	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
53		58
…		…
68	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
69	model you use.	74	model you use.
70		75
71	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
72	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
73	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
74	cannot use anything else, as they are simply incompatible to everything	79	cannot use anything else, as they are simply incompatible to everything
75	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
76	are also forced to use the same event loop you use.	81	are also forced to use the same event loop you use.
77		82
78	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
79	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
80	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
81	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
82	But if your module uses AnyEvent, it works transparently with all event	87	your module uses AnyEvent, it works transparently with all event models
83	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
84	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
85	to AnyEvent, too, so it is future-proof).	90	AnyEvent, too, so it is future-proof).
86		91
87	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
88	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
89	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
90	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
91	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
92	wrapper as technically possible.	97	technically possible.
93		98
94	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
95	useful functionality, such as an asynchronous DNS resolver, 100%	100	useful functionality, such as an asynchronous DNS resolver, 100%
96	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
97	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
…		…
100	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
101	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
102	model, you should not use this module.	107	model, you should not use this module.
103		108
104	DESCRIPTION	109	DESCRIPTION
105	AnyEvent provides an identical interface to multiple event loops. This	110	AnyEvent provides a uniform interface to various event loops. This
106	allows module authors to utilise an event loop without forcing module	111	allows module authors to use event loop functionality without forcing
107	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
108	coexist peacefully at any one time).	113	than one event loop cannot coexist peacefully).
109		114
110	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
111	module.	116	module.
112		117
113	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
114	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
115	following modules is already loaded: EV, Event, Glib,	120	following modules is already loaded: EV, AnyEvent::Loop, Event, Glib,
116	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
117	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
118	(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
119	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
120	successfully loaded will be used. If, after this, still none could be	125	tried.
121	found, AnyEvent will fall back to a pure-perl event loop, which is not
122	very efficient, but should work everywhere.
123		126
124	Because AnyEvent first checks for modules that are already loaded,	127	Because AnyEvent first checks for modules that are already loaded,
125	loading an event model explicitly before first using AnyEvent will	128	loading an event model explicitly before first using AnyEvent will
126	likely make that model the default. For example:	129	likely make that model the default. For example:
127		130
…		…
129	use AnyEvent;	132	use AnyEvent;
130		133
131	# .. AnyEvent will likely default to Tk	134	# .. AnyEvent will likely default to Tk
132		135
133	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
134	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
135	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.
136		140
137	The pure-perl implementation of AnyEvent is called	141	The pure-perl implementation of AnyEvent is called "AnyEvent::Loop".
138	"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
139	explicitly and enjoy the high availability of that event loop :)	143	availability of that event loop :)
140		144
141	WATCHERS	145	WATCHERS
142	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
143	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
144	the callback to call, the file handle to watch, etc.	148	the callback to call, the file handle to watch, etc.
…		…
148	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
149	in control).	153	in control).
150		154
151	Note that callbacks must not permanently change global variables	155	Note that callbacks must not permanently change global variables
152	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
153	callbacks must not "die". The former is good programming practise in	157	callbacks must not "die". The former is good programming practice in
154	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
155	widely between event loops.	159	widely between event loops.
156		160
157	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
158	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
159	to it).	163	to it).
160		164
161	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.
162		166
163	Many watchers either are used with "recursion" (repeating timers for	167	Many watchers either are used with "recursion" (repeating timers for
164	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.
165		169
166	An any way to achieve that is this pattern:	170	One way to achieve that is this pattern:
167		171
168	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	172	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
169	# you can use $w here, for example to undef it	173	# you can use $w here, for example to undef it
170	undef $w;	174	undef $w;
171	});	175	});
…		…
173	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,
174	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
175	declared.	179	declared.
176		180
177	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
178	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
179	the following mandatory key-value pairs as arguments:	189	the following mandatory key-value pairs as arguments:
180		190
181	"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
182	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
…		…
196		206
197	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
198	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
199	the underlying file descriptor.	209	the underlying file descriptor.
200		210
201	Some event loops issue spurious readyness notifications, so you should	211	Some event loops issue spurious readiness notifications, so you should
202	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
203	handles.	213	handles.
204		214
205	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
206	watcher.	216	watcher.
…		…
210	warn "read: $input\n";	220	warn "read: $input\n";
211	undef $w;	221	undef $w;
212	});	222	});
213		223
214	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
215	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
216	with the following mandatory arguments:	234	with the following mandatory arguments:
217		235
218	"after" specifies after how many seconds (fractional values are	236	"after" specifies after how many seconds (fractional values are
219	supported) the callback should be invoked. "cb" is the callback to	237	supported) the callback should be invoked. "cb" is the callback to
…		…
221		239
222	Although the callback might get passed parameters, their value and	240	Although the callback might get passed parameters, their value and
223	presence is undefined and you cannot rely on them. Portable AnyEvent	241	presence is undefined and you cannot rely on them. Portable AnyEvent
224	callbacks cannot use arguments passed to time watcher callbacks.	242	callbacks cannot use arguments passed to time watcher callbacks.
225		243
226	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
227	parameter, "interval", as a strictly positive number (> 0), then the	245	parameter, "interval", as a strictly positive number (> 0), then the
228	callback will be invoked regularly at that interval (in fractional	246	callback will be invoked regularly at that interval (in fractional
229	seconds) after the first invocation. If "interval" is specified with a	247	seconds) after the first invocation. If "interval" is specified with a
230	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.
231		249
232	The callback will be rescheduled before invoking the callback, but no	250	The callback will be rescheduled before invoking the callback, but no
233	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
234	is only approximate.	252	is only approximate.
235		253
236	Example: fire an event after 7.7 seconds.	254	Example: fire an event after 7.7 seconds.
237		255
238	my $w = AnyEvent->timer (after => 7.7, cb => sub {	256	my $w = AnyEvent->timer (after => 7.7, cb => sub {
…		…
244		262
245	Example 2: fire an event after 0.5 seconds, then roughly every second.	263	Example 2: fire an event after 0.5 seconds, then roughly every second.
246		264
247	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {	265	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
248	warn "timeout\n";	266	warn "timeout\n";
249	};	267	});
250		268
251	TIMING ISSUES	269	TIMING ISSUES
252	There are two ways to handle timers: based on real time (relative, "fire	270	There are two ways to handle timers: based on real time (relative, "fire
253	in 10 seconds") and based on wallclock time (absolute, "fire at 12	271	in 10 seconds") and based on wallclock time (absolute, "fire at 12
254	o'clock").	272	o'clock").
255		273
256	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,
257	they use absolute time internally. This makes a difference when your	275	they use absolute time internally. This makes a difference when your
258	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
259	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
260	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
261	finally fire.	279	finally fire.
262		280
263	AnyEvent cannot compensate for this. The only event loop that is	281	AnyEvent cannot compensate for this. The only event loop that is
264	conscious about these issues is EV, which offers both relative	282	conscious of these issues is EV, which offers both relative (ev_timer,
265	(ev_timer, based on true relative time) and absolute (ev_periodic, based	283	based on true relative time) and absolute (ev_periodic, based on
266	on wallclock time) timers.	284	wallclock time) timers.
267		285
268	AnyEvent always prefers relative timers, if available, matching the	286	AnyEvent always prefers relative timers, if available, matching the
269	AnyEvent API.	287	AnyEvent API.
270		288
271	AnyEvent has two additional methods that return the "current time":	289	AnyEvent has two additional methods that return the "current time":
…		…
290	*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
291	function to call when you want to know the current time.*	309	function to call when you want to know the current time.*
292		310
293	This function is also often faster then "AnyEvent->time", and thus	311	This function is also often faster then "AnyEvent->time", and thus
294	the preferred method if you want some timestamp (for example,	312	the preferred method if you want some timestamp (for example,
295	AnyEvent::Handle uses this to update it's activity timeouts).	313	AnyEvent::Handle uses this to update its activity timeouts).
296		314
297	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
298	exact with your timing, you can skip it without bad conscience.	316	exact with your timing; you can skip it without a bad conscience.
299		317
300	For a practical example of when these times differ, consider	318	For a practical example of when these times differ, consider
301	Event::Lib and EV and the following set-up:	319	Event::Lib and EV and the following set-up:
302		320
303	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
304	at time=500 (assume no other callbacks delay processing). In your	322	at time=500 (assume no other callbacks delay processing). In your
305	callback, you wait a second by executing "sleep 1" (blocking the	323	callback, you wait a second by executing "sleep 1" (blocking the
306	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
307	timer that fires after three seconds.	325	timer that fires after three seconds.
308		326
…		…
329	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
330	the difference between "AnyEvent->time" and "AnyEvent->now" into	348	the difference between "AnyEvent->time" and "AnyEvent->now" into
331	account.	349	account.
332		350
333	AnyEvent->now_update	351	AnyEvent->now_update
334	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
335	current time for each loop iteration (see the discussion of	353	time for each loop iteration (see the discussion of AnyEvent->now,
336	AnyEvent->now, above).	354	above).
337		355
338	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),
339	then this "current" time will differ substantially from the real	357	then this "current" time will differ substantially from the real
340	time, which might affect timers and time-outs.	358	time, which might affect timers and time-outs.
341		359
342	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
343	the event loop's idea of "current time".	361	the event loop's idea of "current time".
344		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
345	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.
346		372
347	SIGNAL WATCHERS	373	SIGNAL WATCHERS
		374	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		375
348	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
349	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
350	callback to be invoked whenever a signal occurs.	378	callback to be invoked whenever a signal occurs.
351		379
352	Although the callback might get passed parameters, their value and	380	Although the callback might get passed parameters, their value and
…		…
368		396
369	Example: exit on SIGINT	397	Example: exit on SIGINT
370		398
371	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	399	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
372		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 delay signal delivery
		409	indefinitely, the 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
373	Signal Races, Delays and Workarounds	416	Signal Races, Delays and Workarounds
374	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching	417	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
375	callbacks to signals in a generic way, which is a pity, as you cannot do	418	callbacks to signals in a generic way, which is a pity, as you cannot do
376	race-free signal handling in perl. AnyEvent will try to do it's best,	419	race-free signal handling in perl, requiring C libraries for this.
377	but in some cases, signals will be delayed. The maximum time a signal	420	AnyEvent will try to do its best, which means in some cases, signals
378	might be delayed is specified in $AnyEvent::MAX_SIGNAL_LATENCY (default:	421	will be delayed. The maximum time a signal might be delayed is 10
379	10 seconds). This variable can be changed only before the first signal	422	seconds by default, but can be overriden via
380	watcher is created, and should be left alone otherwise. Higher values	423	$ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} or $AnyEvent::MAX_SIGNAL_LATENCY
381	will cause fewer spurious wake-ups, which is better for power and CPU	424	- see the "ENVIRONMENT VARIABLES" section for details.
		425
382	saving. All these problems can be avoided by installing the optional	426	All these problems can be avoided by installing the optional
383	Async::Interrupt module. This will not work with inherently broken event	427	Async::Interrupt module, which works with most event loops. It will not
384	loops such as Event or Event::Lib (and not with POE currently, as POE	428	work with inherently broken event loops such as Event or Event::Lib (and
385	does it's own workaround with one-second latency). With those, you just	429	not with POE currently). For those, you just have to suffer the delays.
386	have to suffer the delays.
387		430
388	CHILD PROCESS WATCHERS	431	CHILD PROCESS WATCHERS
		432	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		433
389	You can also watch on a child process exit and catch its exit status.	434	You can also watch for a child process exit and catch its exit status.
390		435
391	The child process is specified by the "pid" argument (if set to 0, it	436	The child process is specified by the "pid" argument (on some backends,
392	watches for any child process exit). The watcher will triggered only	437	using 0 watches for any child process exit, on others this will croak).
393	when the child process has finished and an exit status is available, not	438	The watcher will be triggered only when the child process has finished
394	on any trace events (stopped/continued).	439	and an exit status is available, not on any trace events
		440	(stopped/continued).
395		441
396	The callback will be called with the pid and exit status (as returned by	442	The callback will be called with the pid and exit status (as returned by
397	waitpid), so unlike other watcher types, you can rely on child watcher	443	waitpid), so unlike other watcher types, you can rely on child watcher
398	callback arguments.	444	callback arguments.
399		445
…		…
416	This means you cannot create a child watcher as the very first thing in	462	This means you cannot create a child watcher as the very first thing in
417	an AnyEvent program, you have to create at least one watcher before	463	an AnyEvent program, you have to create at least one watcher before
418	you "fork" the child (alternatively, you can call "AnyEvent::detect").	464	you "fork" the child (alternatively, you can call "AnyEvent::detect").
419		465
420	As most event loops do not support waiting for child events, they will	466	As most event loops do not support waiting for child events, they will
421	be emulated by AnyEvent in most cases, in which the latency and race	467	be emulated by AnyEvent in most cases, in which case the latency and
422	problems mentioned in the description of signal watchers apply.	468	race problems mentioned in the description of signal watchers apply.
423		469
424	Example: fork a process and wait for it	470	Example: fork a process and wait for it
425		471
426	my $done = AnyEvent->condvar;	472	my $done = AnyEvent->condvar;
427		473
		474	# this forks and immediately calls exit in the child. this
		475	# normally has all sorts of bad consequences for your parent,
		476	# so take this as an example only. always fork and exec,
		477	# or call POSIX::_exit, in real code.
428	my $pid = fork or exit 5;	478	my $pid = fork or exit 5;
429		479
430	my $w = AnyEvent->child (	480	my $w = AnyEvent->child (
431	pid => $pid,	481	pid => $pid,
432	cb => sub {	482	cb => sub {
…		…
438		488
439	# do something else, then wait for process exit	489	# do something else, then wait for process exit
440	$done->recv;	490	$done->recv;
441		491
442	IDLE WATCHERS	492	IDLE WATCHERS
443	Sometimes there is a need to do something, but it is not so important to	493	$w = AnyEvent->idle (cb => <callback>);
444	do it instantly, but only when there is nothing better to do. This
445	"nothing better to do" is usually defined to be "no other events need
446	attention by the event loop".
447		494
448	Idle watchers ideally get invoked when the event loop has nothing better	495	This will repeatedly invoke the callback after the process becomes idle,
449	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.
450	Instead of blocking, the idle watcher is invoked.
451		497
452	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
453	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,
454	will simply call the callback "from time to time".	509	AnyEvent will simply call the callback "from time to time".
455		510
456	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
457	is otherwise idle:	512	is otherwise idle:
458		513
459	my @lines; # read data	514	my @lines; # read data
…		…
472	}	527	}
473	});	528	});
474	});	529	});
475		530
476	CONDITION VARIABLES	531	CONDITION VARIABLES
		532	$cv = AnyEvent->condvar;
		533
		534	$cv->send (<list>);
		535	my @res = $cv->recv;
		536
477	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
478	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
479	will actively watch for new events and call your callbacks.	539	will actively watch for new events and call your callbacks.
480		540
481	AnyEvent is slightly different: it expects somebody else to run the	541	AnyEvent is slightly different: it expects somebody else to run the
482	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
483	user).	543	user).
484		544
485	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
486	because they represent a condition that must become true.	546	they represent a condition that must become true.
487		547
488	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.
489		549
490	Condition variables can be created by calling the "AnyEvent->condvar"	550	Condition variables can be created by calling the "AnyEvent->condvar"
491	method, usually without arguments. The only argument pair allowed is	551	method, usually without arguments. The only argument pair allowed is
…		…
496	After creation, the condition variable is "false" until it becomes	556	After creation, the condition variable is "false" until it becomes
497	"true" by calling the "send" method (or calling the condition variable	557	"true" by calling the "send" method (or calling the condition variable
498	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
499	the "->send" method).	559	the "->send" method).
500		560
501	Condition variables are similar to callbacks, except that you can	561	Since condition variables are the most complex part of the AnyEvent API,
502	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
503	in time where multiple outstanding events have been processed. And yet	563	you can connect to:
504	another way to call them is transactions - each condition variable can	564
505	be used to represent a transaction, which finishes at some point and	565	* Condition variables are like callbacks - you can call them (and pass
506	delivers a result. And yet some people know them as "futures" - a	566	them instead of callbacks). Unlike callbacks however, you can also
507	promise to compute/deliver something that you can wait for.	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.
508		582
509	Condition variables are very useful to signal that something has	583	Condition variables are very useful to signal that something has
510	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
511	requests, then a condition variable would be the ideal candidate to	585	requests, then a condition variable would be the ideal candidate to
512	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
…		…
525		599
526	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
527	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
528	(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
529	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	603	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
530	it's "new" method in your own "new" method.	604	its "new" method in your own "new" method.
531		605
532	There are two "sides" to a condition variable - the "producer side"	606	There are two "sides" to a condition variable - the "producer side"
533	which eventually calls "-> send", and the "consumer side", which waits	607	which eventually calls "-> send", and the "consumer side", which waits
534	for the send to occur.	608	for the send to occur.
535		609
536	Example: wait for a timer.	610	Example: wait for a timer.
537		611
538	# wait till the result is ready	612	# condition: "wait till the timer is fired"
539	my $result_ready = AnyEvent->condvar;	613	my $timer_fired = AnyEvent->condvar;
540		614
541	# do something such as adding a timer	615	# create the timer - we could wait for, say
542	# or socket watcher the calls $result_ready->send	616	# a handle becomign ready, or even an
543	# when the "result" is ready.	617	# AnyEvent::HTTP request to finish, but
544	# in this case, we simply use a timer:	618	# in this case, we simply use a timer:
545	my $w = AnyEvent->timer (	619	my $w = AnyEvent->timer (
546	after => 1,	620	after => 1,
547	cb => sub { $result_ready->send },	621	cb => sub { $timer_fired->send },
548	);	622	);
549		623
550	# this "blocks" (while handling events) till the callback	624	# this "blocks" (while handling events) till the callback
551	# calls -<send	625	# calls ->send
552	$result_ready->recv;	626	$timer_fired->recv;
553		627
554	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
555	variables are also callable directly.	629	variables are also callable directly.
556		630
557	my $done = AnyEvent->condvar;	631	my $done = AnyEvent->condvar;
…		…
595	Condition variables are overloaded so one can call them directly (as	669	Condition variables are overloaded so one can call them directly (as
596	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
597	calling "send".	671	calling "send".
598		672
599	$cv->croak ($error)	673	$cv->croak ($error)
600	Similar to send, but causes all call's to "->recv" to invoke	674	Similar to send, but causes all calls to "->recv" to invoke
601	"Carp::croak" with the given error message/object/scalar.	675	"Carp::croak" with the given error message/object/scalar.
602		676
603	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
604	user/consumer. Doing it this way instead of calling "croak" directly	678	user/consumer. Doing it this way instead of calling "croak" directly
605	delays the error detetcion, but has the overwhelmign advantage that	679	delays the error detection, but has the overwhelming advantage that
606	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,
607	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
608	code causing the problem.	682	code causing the problem.
609		683
610	$cv->begin ([group callback])	684	$cv->begin ([group callback])
611	$cv->end	685	$cv->end
612	These two methods can be used to combine many transactions/events	686	These two methods can be used to combine many transactions/events
613	into one. For example, a function that pings many hosts in parallel	687	into one. For example, a function that pings many hosts in parallel
614	might want to use a condition variable for the whole process.	688	might want to use a condition variable for the whole process.
615		689
616	Every call to "->begin" will increment a counter, and every call to	690	Every call to "->begin" will increment a counter, and every call to
617	"->end" will decrement it. If the counter reaches 0 in "->end", the	691	"->end" will decrement it. If the counter reaches 0 in "->end", the
618	(last) callback passed to "begin" will be executed. That callback is	692	(last) callback passed to "begin" will be executed, passing the
619	supposed to call "->send", but that is not required. If no	693	condvar as first argument. That callback is supposed to call
		694	"->send", but that is not required. If no group callback was set,
620	callback was set, "send" will be called without any arguments.	695	"send" will be called without any arguments.
621		696
622	You can think of "$cv->send" giving you an OR condition (one call	697	You can think of "$cv->send" giving you an OR condition (one call
623	sends), while "$cv->begin" and "$cv->end" giving you an AND	698	sends), while "$cv->begin" and "$cv->end" giving you an AND
624	condition (all "begin" calls must be "end"'ed before the condvar	699	condition (all "begin" calls must be "end"'ed before the condvar
625	sends).	700	sends).
…		…
647	This works because for every event source (EOF on file handle),	722	This works because for every event source (EOF on file handle),
648	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
649	"end" before sending.	724	"end" before sending.
650		725
651	The ping example mentioned above is slightly more complicated, as	726	The ping example mentioned above is slightly more complicated, as
652	the there are results to be passwd back, and the number of tasks	727	the there are results to be passed back, and the number of tasks
653	that are begung can potentially be zero:	728	that are begun can potentially be zero:
654		729
655	my $cv = AnyEvent->condvar;	730	my $cv = AnyEvent->condvar;
656		731
657	my %result;	732	my %result;
658	$cv->begin (sub { $cv->send (\%result) });	733	$cv->begin (sub { shift->send (\%result) });
659		734
660	for my $host (@list_of_hosts) {	735	for my $host (@list_of_hosts) {
661	$cv->begin;	736	$cv->begin;
662	ping_host_then_call_callback $host, sub {	737	ping_host_then_call_callback $host, sub {
663	$result{$host} = ...;	738	$result{$host} = ...;
…		…
665	};	740	};
666	}	741	}
667		742
668	$cv->end;	743	$cv->end;
669		744
		745	...
		746
		747	my $results = $cv->recv;
		748
670	This code fragment supposedly pings a number of hosts and calls	749	This code fragment supposedly pings a number of hosts and calls
671	"send" after results for all then have have been gathered - in any	750	"send" after results for all then have have been gathered - in any
672	order. To achieve this, the code issues a call to "begin" when it	751	order. To achieve this, the code issues a call to "begin" when it
673	starts each ping request and calls "end" when it has received some	752	starts each ping request and calls "end" when it has received some
674	result for it. Since "begin" and "end" only maintain a counter, the	753	result for it. Since "begin" and "end" only maintain a counter, the
…		…
679	callback to be called once the counter reaches 0, and second, it	758	callback to be called once the counter reaches 0, and second, it
680	ensures that "send" is called even when "no" hosts are being pinged	759	ensures that "send" is called even when "no" hosts are being pinged
681	(the loop doesn't execute once).	760	(the loop doesn't execute once).
682		761
683	This is the general pattern when you "fan out" into multiple (but	762	This is the general pattern when you "fan out" into multiple (but
684	potentially none) subrequests: use an outer "begin"/"end" pair to	763	potentially zero) subrequests: use an outer "begin"/"end" pair to
685	set the callback and ensure "end" is called at least once, and then,	764	set the callback and ensure "end" is called at least once, and then,
686	for each subrequest you start, call "begin" and for each subrequest	765	for each subrequest you start, call "begin" and for each subrequest
687	you finish, call "end".	766	you finish, call "end".
688		767
689	METHODS FOR CONSUMERS	768	METHODS FOR CONSUMERS
690	These methods should only be used by the consuming side, i.e. the code	769	These methods should only be used by the consuming side, i.e. the code
691	awaits the condition.	770	awaits the condition.
692		771
693	$cv->recv	772	$cv->recv
694	Wait (blocking if necessary) until the "->send" or "->croak" methods	773	Wait (blocking if necessary) until the "->send" or "->croak" methods
695	have been called on c<$cv>, while servicing other watchers normally.	774	have been called on $cv, while servicing other watchers normally.
696		775
697	You can only wait once on a condition - additional calls are valid	776	You can only wait once on a condition - additional calls are valid
698	but will return immediately.	777	but will return immediately.
699		778
700	If an error condition has been set by calling "->croak", then this	779	If an error condition has been set by calling "->croak", then this
…		…
703	In list context, all parameters passed to "send" will be returned,	782	In list context, all parameters passed to "send" will be returned,
704	in scalar context only the first one will be returned.	783	in scalar context only the first one will be returned.
705		784
706	Note that doing a blocking wait in a callback is not supported by	785	Note that doing a blocking wait in a callback is not supported by
707	any event loop, that is, recursive invocation of a blocking "->recv"	786	any event loop, that is, recursive invocation of a blocking "->recv"
708	is not allowed, and the "recv" call will "croak" if such a condition	787	is not allowed and the "recv" call will "croak" if such a condition
709	is detected. This condition can be slightly loosened by using	788	is detected. This requirement can be dropped by relying on
710	Coro::AnyEvent, which allows you to do a blocking "->recv" from any	789	Coro::AnyEvent , which allows you to do a blocking "->recv" from any
711	thread that doesn't run the event loop itself.	790	thread that doesn't run the event loop itself. Coro::AnyEvent is
		791	loaded automatically when Coro is used with AnyEvent, so code does
		792	not need to do anything special to take advantage of that: any code
		793	that would normally block your program because it calls "recv", be
		794	executed in an "async" thread instead without blocking other
		795	threads.
712		796
713	Not all event models support a blocking wait - some die in that case	797	Not all event models support a blocking wait - some die in that case
714	(programs might want to do that to stay interactive), so *if you are	798	(programs might want to do that to stay interactive), so *if you are
715	using this from a module, never require a blocking wait*. Instead,	799	using this from a module, never require a blocking wait*. Instead,
716	let the caller decide whether the call will block or not (for	800	let the caller decide whether the call will block or not (for
717	example, by coupling condition variables with some kind of request	801	example, by coupling condition variables with some kind of request
718	results and supporting callbacks so the caller knows that getting	802	results and supporting callbacks so the caller knows that getting
719	the result will not block, while still supporting blocking waits if	803	the result will not block, while still supporting blocking waits if
720	the caller so desires).	804	the caller so desires).
721		805
722	You can ensure that "-recv" never blocks by setting a callback and	806	You can ensure that "->recv" never blocks by setting a callback and
723	only calling "->recv" from within that callback (or at a later	807	only calling "->recv" from within that callback (or at a later
724	time). This will work even when the event loop does not support	808	time). This will work even when the event loop does not support
725	blocking waits otherwise.	809	blocking waits otherwise.
726		810
727	$bool = $cv->ready	811	$bool = $cv->ready
…		…
732	This is a mutator function that returns the callback set and	816	This is a mutator function that returns the callback set and
733	optionally replaces it before doing so.	817	optionally replaces it before doing so.
734		818
735	The callback will be called when the condition becomes "true", i.e.	819	The callback will be called when the condition becomes "true", i.e.
736	when "send" or "croak" are called, with the only argument being the	820	when "send" or "croak" are called, with the only argument being the
737	condition variable itself. Calling "recv" inside the callback or at	821	condition variable itself. If the condition is already true, the
		822	callback is called immediately when it is set. Calling "recv" inside
738	any later time is guaranteed not to block.	823	the callback or at any later time is guaranteed not to block.
739		824
740	SUPPORTED EVENT LOOPS/BACKENDS	825	SUPPORTED EVENT LOOPS/BACKENDS
741	The available backend classes are (every class has its own manpage):	826	The available backend classes are (every class has its own manpage):
742		827
743	Backends that are autoprobed when no other event loop can be found.	828	Backends that are autoprobed when no other event loop can be found.
744	EV is the preferred backend when no other event loop seems to be in	829	EV is the preferred backend when no other event loop seems to be in
745	use. If EV is not installed, then AnyEvent will try Event, and,	830	use. If EV is not installed, then AnyEvent will fall back to its own
746	failing that, will fall back to its own pure-perl implementation,	831	pure-perl implementation, which is available everywhere as it comes
747	which is available everywhere as it comes with AnyEvent itself.	832	with AnyEvent itself.
748		833
749	AnyEvent::Impl::EV based on EV (interface to libev, best choice).	834	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
750	AnyEvent::Impl::Event based on Event, very stable, few glitches.
751	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.	835	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
752		836
753	Backends that are transparently being picked up when they are used.	837	Backends that are transparently being picked up when they are used.
754	These will be used when they are currently loaded when the first	838	These will be used if they are already loaded when the first watcher
755	watcher is created, in which case it is assumed that the application	839	is created, in which case it is assumed that the application is
756	is using them. This means that AnyEvent will automatically pick the	840	using them. This means that AnyEvent will automatically pick the
757	right backend when the main program loads an event module before	841	right backend when the main program loads an event module before
758	anything starts to create watchers. Nothing special needs to be done	842	anything starts to create watchers. Nothing special needs to be done
759	by the main program.	843	by the main program.
760		844
		845	AnyEvent::Impl::Event based on Event, very stable, few glitches.
761	AnyEvent::Impl::Glib based on Glib, slow but very stable.	846	AnyEvent::Impl::Glib based on Glib, slow but very stable.
762	AnyEvent::Impl::Tk based on Tk, very broken.	847	AnyEvent::Impl::Tk based on Tk, very broken.
763	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	848	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
764	AnyEvent::Impl::POE based on POE, very slow, some limitations.	849	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		850	AnyEvent::Impl::Irssi used when running within irssi.
		851	AnyEvent::Impl::IOAsync based on IO::Async.
		852	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		853	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
765		854
766	Backends with special needs.	855	Backends with special needs.
767	Qt requires the Qt::Application to be instantiated first, but will	856	Qt requires the Qt::Application to be instantiated first, but will
768	otherwise be picked up automatically. As long as the main program	857	otherwise be picked up automatically. As long as the main program
769	instantiates the application before any AnyEvent watchers are	858	instantiates the application before any AnyEvent watchers are
770	created, everything should just work.	859	created, everything should just work.
771		860
772	AnyEvent::Impl::Qt based on Qt.	861	AnyEvent::Impl::Qt based on Qt.
773		862
774	Support for IO::Async can only be partial, as it is too broken and
775	architecturally limited to even support the AnyEvent API. It also is
776	the only event loop that needs the loop to be set explicitly, so it
777	can only be used by a main program knowing about AnyEvent. See
778	AnyEvent::Impl::Async for the gory details.
779
780	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
781
782	Event loops that are indirectly supported via other backends.	863	Event loops that are indirectly supported via other backends.
783	Some event loops can be supported via other modules:	864	Some event loops can be supported via other modules:
784		865
785	There is no direct support for WxWidgets (Wx) or Prima.	866	There is no direct support for WxWidgets (Wx) or Prima.
786		867
…		…
804	Contains "undef" until the first watcher is being created, before	885	Contains "undef" until the first watcher is being created, before
805	the backend has been autodetected.	886	the backend has been autodetected.
806		887
807	Afterwards it contains the event model that is being used, which is	888	Afterwards it contains the event model that is being used, which is
808	the name of the Perl class implementing the model. This class is	889	the name of the Perl class implementing the model. This class is
809	usually one of the "AnyEvent::Impl:xxx" modules, but can be any	890	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
810	other class in the case AnyEvent has been extended at runtime (e.g.	891	other class in the case AnyEvent has been extended at runtime (e.g.
811	in rxvt-unicode it will be "urxvt::anyevent").	892	in rxvt-unicode it will be "urxvt::anyevent").
812		893
813	AnyEvent::detect	894	AnyEvent::detect
814	Returns $AnyEvent::MODEL, forcing autodetection of the event model	895	Returns $AnyEvent::MODEL, forcing autodetection of the event model
815	if necessary. You should only call this function right before you	896	if necessary. You should only call this function right before you
816	would have created an AnyEvent watcher anyway, that is, as late as	897	would have created an AnyEvent watcher anyway, that is, as late as
817	possible at runtime, and not e.g. while initialising of your module.	898	possible at runtime, and not e.g. during initialisation of your
		899	module.
		900
		901	The effect of calling this function is as if a watcher had been
		902	created (specifically, actions that happen "when the first watcher
		903	is created" happen when calling detetc as well).
818		904
819	If you need to do some initialisation before AnyEvent watchers are	905	If you need to do some initialisation before AnyEvent watchers are
820	created, use "post_detect".	906	created, use "post_detect".
821		907
822	$guard = AnyEvent::post_detect { BLOCK }	908	$guard = AnyEvent::post_detect { BLOCK }
823	Arranges for the code block to be executed as soon as the event	909	Arranges for the code block to be executed as soon as the event
824	model is autodetected (or immediately if this has already happened).	910	model is autodetected (or immediately if that has already happened).
825		911
826	The block will be executed after the actual backend has been	912	The block will be executed after the actual backend has been
827	detected ($AnyEvent::MODEL is set), but before any watchers have	913	detected ($AnyEvent::MODEL is set), but before any watchers have
828	been created, so it is possible to e.g. patch @AnyEvent::ISA or do	914	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
829	other initialisations - see the sources of AnyEvent::Strict or	915	other initialisations - see the sources of AnyEvent::Strict or
…		…
834	creates and installs the global IO::AIO watcher in a "post_detect"	920	creates and installs the global IO::AIO watcher in a "post_detect"
835	block to avoid autodetecting the event module at load time.	921	block to avoid autodetecting the event module at load time.
836		922
837	If called in scalar or list context, then it creates and returns an	923	If called in scalar or list context, then it creates and returns an
838	object that automatically removes the callback again when it is	924	object that automatically removes the callback again when it is
		925	destroyed (or "undef" when the hook was immediately executed). See
839	destroyed. See Coro::BDB for a case where this is useful.	926	AnyEvent::AIO for a case where this is useful.
		927
		928	Example: Create a watcher for the IO::AIO module and store it in
		929	$WATCHER, but do so only do so after the event loop is initialised.
		930
		931	our WATCHER;
		932
		933	my $guard = AnyEvent::post_detect {
		934	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		935	};
		936
		937	# the \|\|= is important in case post_detect immediately runs the block,
		938	# as to not clobber the newly-created watcher. assigning both watcher and
		939	# post_detect guard to the same variable has the advantage of users being
		940	# able to just C<undef $WATCHER> if the watcher causes them grief.
		941
		942	$WATCHER \|\|= $guard;
840		943
841	@AnyEvent::post_detect	944	@AnyEvent::post_detect
842	If there are any code references in this array (you can "push" to it	945	If there are any code references in this array (you can "push" to it
843	before or after loading AnyEvent), then they will called directly	946	before or after loading AnyEvent), then they will be called directly
844	after the event loop has been chosen.	947	after the event loop has been chosen.
845		948
846	You should check $AnyEvent::MODEL before adding to this array,	949	You should check $AnyEvent::MODEL before adding to this array,
847	though: if it is defined then the event loop has already been	950	though: if it is defined then the event loop has already been
848	detected, and the array will be ignored.	951	detected, and the array will be ignored.
849		952
850	Best use "AnyEvent::post_detect { BLOCK }" when your application	953	Best use "AnyEvent::post_detect { BLOCK }" when your application
851	allows it,as it takes care of these details.	954	allows it, as it takes care of these details.
852		955
853	This variable is mainly useful for modules that can do something	956	This variable is mainly useful for modules that can do something
854	useful when AnyEvent is used and thus want to know when it is	957	useful when AnyEvent is used and thus want to know when it is
855	initialised, but do not need to even load it by default. This array	958	initialised, but do not need to even load it by default. This array
856	provides the means to hook into AnyEvent passively, without loading	959	provides the means to hook into AnyEvent passively, without loading
857	it.	960	it.
858		961
		962	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		963	together, you could put this into Coro (this is the actual code used
		964	by Coro to accomplish this):
		965
		966	if (defined $AnyEvent::MODEL) {
		967	# AnyEvent already initialised, so load Coro::AnyEvent
		968	require Coro::AnyEvent;
		969	} else {
		970	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		971	# as soon as it is
		972	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		973	}
		974
		975	AnyEvent::postpone { BLOCK }
		976	Arranges for the block to be executed as soon as possible, but not
		977	before the call itself returns. In practise, the block will be
		978	executed just before the event loop polls for new events, or shortly
		979	afterwards.
		980
		981	This function never returns anything (to make the "return postpone {
		982	... }" idiom more useful.
		983
		984	To understand the usefulness of this function, consider a function
		985	that asynchronously does something for you and returns some
		986	transaction object or guard to let you cancel the operation. For
		987	example, "AnyEvent::Socket::tcp_connect":
		988
		989	# start a conenction attempt unless one is active
		990	$self->{connect_guard} \|\|= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		991	delete $self->{connect_guard};
		992	...
		993	};
		994
		995	Imagine that this function could instantly call the callback, for
		996	example, because it detects an obvious error such as a negative port
		997	number. Invoking the callback before the function returns causes
		998	problems however: the callback will be called and will try to delete
		999	the guard object. But since the function hasn't returned yet, there
		1000	is nothing to delete. When the function eventually returns it will
		1001	assign the guard object to "$self->{connect_guard}", where it will
		1002	likely never be deleted, so the program thinks it is still trying to
		1003	connect.
		1004
		1005	This is where "AnyEvent::postpone" should be used. Instead of
		1006	calling the callback directly on error:
		1007
		1008	$cb->(undef), return # signal error to callback, BAD!
		1009	if $some_error_condition;
		1010
		1011	It should use "postpone":
		1012
		1013	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1014	if $some_error_condition;
		1015
		1016	AnyEvent::log $level, $msg[, @args]
		1017	Log the given $msg at the given $level.
		1018
		1019	If AnyEvent::Log is not loaded then this function makes a simple
		1020	test to see whether the message will be logged. If the test succeeds
		1021	it will load AnyEvent::Log and call "AnyEvent::Log::log" -
		1022	consequently, look at the AnyEvent::Log documentation for details.
		1023
		1024	If the test fails it will simply return. Right now this happens when
		1025	a numerical loglevel is used and it is larger than the level
		1026	specified via $ENV{PERL_ANYEVENT_VERBOSE}.
		1027
		1028	If you want to sprinkle loads of logging calls around your code,
		1029	consider creating a logger callback with the "AnyEvent::Log::logger"
		1030	function, which can reduce typing, codesize and can reduce the
		1031	logging overhead enourmously.
		1032
859	WHAT TO DO IN A MODULE	1033	WHAT TO DO IN A MODULE
860	As a module author, you should "use AnyEvent" and call AnyEvent methods	1034	As a module author, you should "use AnyEvent" and call AnyEvent methods
861	freely, but you should not load a specific event module or rely on it.	1035	freely, but you should not load a specific event module or rely on it.
862		1036
863	Be careful when you create watchers in the module body - AnyEvent will	1037	Be careful when you create watchers in the module body - AnyEvent will
…		…
870	stall the whole program, and the whole point of using events is to stay	1044	stall the whole program, and the whole point of using events is to stay
871	interactive.	1045	interactive.
872		1046
873	It is fine, however, to call "->recv" when the user of your module	1047	It is fine, however, to call "->recv" when the user of your module
874	requests it (i.e. if you create a http request object ad have a method	1048	requests it (i.e. if you create a http request object ad have a method
875	called "results" that returns the results, it should call "->recv"	1049	called "results" that returns the results, it may call "->recv" freely,
876	freely, as the user of your module knows what she is doing. always).	1050	as the user of your module knows what she is doing. Always).
877		1051
878	WHAT TO DO IN THE MAIN PROGRAM	1052	WHAT TO DO IN THE MAIN PROGRAM
879	There will always be a single main program - the only place that should	1053	There will always be a single main program - the only place that should
880	dictate which event model to use.	1054	dictate which event model to use.
881		1055
882	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1056	If the program is not event-based, it need not do anything special, even
883	do anything special (it does not need to be event-based) and let	1057	when it depends on a module that uses an AnyEvent. If the program itself
884	AnyEvent decide which implementation to chose if some module relies on	1058	uses AnyEvent, but does not care which event loop is used, all it needs
885	it.	1059	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1060	available loop implementation.
886		1061
887	If the main program relies on a specific event model - for example, in	1062	If the main program relies on a specific event model - for example, in
888	Gtk2 programs you have to rely on the Glib module - you should load the	1063	Gtk2 programs you have to rely on the Glib module - you should load the
889	event module before loading AnyEvent or any module that uses it:	1064	event module before loading AnyEvent or any module that uses it:
890	generally speaking, you should load it as early as possible. The reason	1065	generally speaking, you should load it as early as possible. The reason
891	is that modules might create watchers when they are loaded, and AnyEvent	1066	is that modules might create watchers when they are loaded, and AnyEvent
892	will decide on the event model to use as soon as it creates watchers,	1067	will decide on the event model to use as soon as it creates watchers,
893	and it might chose the wrong one unless you load the correct one	1068	and it might choose the wrong one unless you load the correct one
894	yourself.	1069	yourself.
895		1070
896	You can chose to use a pure-perl implementation by loading the	1071	You can chose to use a pure-perl implementation by loading the
897	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1072	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
898	everywhere, but letting AnyEvent chose the model is generally better.	1073	but letting AnyEvent chose the model is generally better.
899		1074
900	MAINLOOP EMULATION	1075	MAINLOOP EMULATION
901	Sometimes (often for short test scripts, or even standalone programs who	1076	Sometimes (often for short test scripts, or even standalone programs who
902	only want to use AnyEvent), you do not want to run a specific event	1077	only want to use AnyEvent), you do not want to run a specific event
903	loop.	1078	loop.
…		…
915		1090
916	OTHER MODULES	1091	OTHER MODULES
917	The following is a non-exhaustive list of additional modules that use	1092	The following is a non-exhaustive list of additional modules that use
918	AnyEvent as a client and can therefore be mixed easily with other	1093	AnyEvent as a client and can therefore be mixed easily with other
919	AnyEvent modules and other event loops in the same program. Some of the	1094	AnyEvent modules and other event loops in the same program. Some of the
920	modules come with AnyEvent, most are available via CPAN.	1095	modules come as part of AnyEvent, the others are available via CPAN (see
		1096	<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
		1097	non-exhaustive list), and the list is heavily biased towards modules of
		1098	the AnyEvent author himself :)
921		1099
922	AnyEvent::Util	1100	AnyEvent::Util (part of the AnyEvent distribution)
923	Contains various utility functions that replace often-used but	1101	Contains various utility functions that replace often-used blocking
924	blocking functions such as "inet_aton" by event-/callback-based	1102	functions such as "inet_aton" with event/callback-based versions.
925	versions.
926		1103
927	AnyEvent::Socket	1104	AnyEvent::Socket (part of the AnyEvent distribution)
928	Provides various utility functions for (internet protocol) sockets,	1105	Provides various utility functions for (internet protocol) sockets,
929	addresses and name resolution. Also functions to create non-blocking	1106	addresses and name resolution. Also functions to create non-blocking
930	tcp connections or tcp servers, with IPv6 and SRV record support and	1107	tcp connections or tcp servers, with IPv6 and SRV record support and
931	more.	1108	more.
932		1109
933	AnyEvent::Handle	1110	AnyEvent::Handle (part of the AnyEvent distribution)
934	Provide read and write buffers, manages watchers for reads and	1111	Provide read and write buffers, manages watchers for reads and
935	writes, supports raw and formatted I/O, I/O queued and fully	1112	writes, supports raw and formatted I/O, I/O queued and fully
936	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.	1113	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
937		1114
938	AnyEvent::DNS	1115	AnyEvent::DNS (part of the AnyEvent distribution)
939	Provides rich asynchronous DNS resolver capabilities.	1116	Provides rich asynchronous DNS resolver capabilities.
940		1117
941	AnyEvent::HTTP	1118	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
942	A simple-to-use HTTP library that is capable of making a lot of	1119	AnyEvent::IGS, AnyEvent::FCP
943	concurrent HTTP requests.	1120	Implement event-based interfaces to the protocols of the same name
		1121	(for the curious, IGS is the International Go Server and FCP is the
		1122	Freenet Client Protocol).
944		1123
		1124	AnyEvent::AIO (part of the AnyEvent distribution)
		1125	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1126	the toolbox of every event programmer. AnyEvent::AIO transparently
		1127	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1128	event-based file I/O, and much more.
		1129
		1130	AnyEvent::Fork, AnyEvent::Fork::RPC, AnyEvent::Fork::Pool,
		1131	AnyEvent::Fork::Remote
		1132	These let you safely fork new subprocesses, either locally or
		1133	remotely (e.g.v ia ssh), using some RPC protocol or not, without the
		1134	limitations normally imposed by fork (AnyEvent works fine for
		1135	example). Dynamically-resized worker pools are obviously included as
		1136	well.
		1137
		1138	And they are quite tiny and fast as well - "abusing" AnyEvent::Fork
		1139	just to exec external programs can easily beat using "fork" and
		1140	"exec" (or even "system") in most programs.
		1141
		1142	AnyEvent::Filesys::Notify
		1143	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1144	path changes (e.g. "watch this directory for new files", "watch this
		1145	file for changes"). The AnyEvent::Filesys::Notify module promises to
		1146	do just that in a portbale fashion, supporting inotify on GNU/Linux
		1147	and some weird, without doubt broken, stuff on OS X to monitor
		1148	files. It can fall back to blocking scans at regular intervals
		1149	transparently on other platforms, so it's about as portable as it
		1150	gets.
		1151
		1152	(I haven't used it myself, but it seems the biggest problem with it
		1153	is it quite bad performance).
		1154
945	AnyEvent::HTTPD	1155	AnyEvent::DBI
946	Provides a simple web application server framework.	1156	Executes DBI requests asynchronously in a proxy process for you,
		1157	notifying you in an event-based way when the operation is finished.
947		1158
948	AnyEvent::FastPing	1159	AnyEvent::FastPing
949	The fastest ping in the west.	1160	The fastest ping in the west.
950		1161
951	AnyEvent::DBI
952	Executes DBI requests asynchronously in a proxy process.
953
954	AnyEvent::AIO
955	Truly asynchronous I/O, should be in the toolbox of every event
956	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
957	together.
958
959	AnyEvent::BDB
960	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
961	fuses BDB and AnyEvent together.
962
963	AnyEvent::GPSD
964	A non-blocking interface to gpsd, a daemon delivering GPS
965	information.
966
967	AnyEvent::IRC
968	AnyEvent based IRC client module family (replacing the older
969	Net::IRC3).
970
971	AnyEvent::XMPP
972	AnyEvent based XMPP (Jabber protocol) module family (replacing the
973	older Net::XMPP2>.
974
975	AnyEvent::IGS
976	A non-blocking interface to the Internet Go Server protocol (used by
977	App::IGS).
978
979	Net::FCP
980	AnyEvent-based implementation of the Freenet Client Protocol,
981	birthplace of AnyEvent.
982
983	Event::ExecFlow
984	High level API for event-based execution flow control.
985
986	Coro	1162	Coro
987	Has special support for AnyEvent via Coro::AnyEvent.	1163	Has special support for AnyEvent via Coro::AnyEvent, which allows
		1164	you to simply invert the flow control - don't call us, we will call
		1165	you:
		1166
		1167	async {
		1168	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1169	print "5 seconds later!\n";
		1170
		1171	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1172	my $line = <STDIN>; # works for ttys
		1173
		1174	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1175	my ($body, $hdr) = Coro::rouse_wait;
		1176	};
		1177
		1178	SIMPLIFIED AE API
		1179	Starting with version 5.0, AnyEvent officially supports a second, much
		1180	simpler, API that is designed to reduce the calling, typing and memory
		1181	overhead by using function call syntax and a fixed number of parameters.
		1182
		1183	See the AE manpage for details.
988		1184
989	ERROR AND EXCEPTION HANDLING	1185	ERROR AND EXCEPTION HANDLING
990	In general, AnyEvent does not do any error handling - it relies on the	1186	In general, AnyEvent does not do any error handling - it relies on the
991	caller to do that if required. The AnyEvent::Strict module (see also the	1187	caller to do that if required. The AnyEvent::Strict module (see also the
992	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1188	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
1001	The pure perl event loop simply re-throws the exception (usually within	1197	The pure perl event loop simply re-throws the exception (usually within
1002	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1198	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
1003	Glib uses "install_exception_handler" and so on.	1199	Glib uses "install_exception_handler" and so on.
1004		1200
1005	ENVIRONMENT VARIABLES	1201	ENVIRONMENT VARIABLES
1006	The following environment variables are used by this module or its	1202	AnyEvent supports a number of environment variables that tune the
1007	submodules.	1203	runtime behaviour. They are usually evaluated when AnyEvent is loaded,
		1204	initialised, or a submodule that uses them is loaded. Many of them also
		1205	cause AnyEvent to load additional modules - for example,
		1206	"PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be
		1207	loaded.
1008		1208
1009	Note that AnyEvent will remove all environment variables starting with	1209	All the environment variables documented here start with
1010	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is	1210	"PERL_ANYEVENT_", which is what AnyEvent considers its own namespace.
1011	enabled.	1211	Other modules are encouraged (but by no means required) to use
		1212	"PERL_ANYEVENT_SUBMODULE" if they have registered the
		1213	AnyEvent::Submodule namespace on CPAN, for any submodule. For example,
		1214	AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it
		1215	should not access env variables starting with "AE_", see below).
		1216
		1217	All variables can also be set via the "AE_" prefix, that is, instead of
		1218	setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case
		1219	there is a clash btween anyevent and another program that uses
		1220	"AE_something" you can set the corresponding "PERL_ANYEVENT_something"
		1221	variable to the empty string, as those variables take precedence.
		1222
		1223	When AnyEvent is first loaded, it copies all "AE_xxx" env variables to
		1224	their "PERL_ANYEVENT_xxx" counterpart unless that variable already
		1225	exists. If taint mode is on, then AnyEvent will remove all environment
		1226	variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with
		1227	"undef" or the empty string, if the corresaponding "AE_" variable is
		1228	set).
		1229
		1230	The exact algorithm is currently:
		1231
		1232	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		1233	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		1234	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		1235
		1236	This ensures that child processes will not see the "AE_" variables.
		1237
		1238	The following environment variables are currently known to AnyEvent:
1012		1239
1013	"PERL_ANYEVENT_VERBOSE"	1240	"PERL_ANYEVENT_VERBOSE"
1014	By default, AnyEvent will be completely silent except in fatal	1241	By default, AnyEvent will log messages with loglevel 4 ("error") or
1015	conditions. You can set this environment variable to make AnyEvent	1242	higher (see AnyEvent::Log). You can set this environment variable to
1016	more talkative.	1243	a numerical loglevel to make AnyEvent more (or less) talkative.
1017		1244
		1245	If you want to do more than just set the global logging level you
		1246	should have a look at "PERL_ANYEVENT_LOG", which allows much more
		1247	complex specifications.
		1248
		1249	When set to 0 ("off"), then no messages whatsoever will be logged
		1250	with everything else at defaults.
		1251
1018	When set to 1 or higher, causes AnyEvent to warn about unexpected	1252	When set to 5 or higher ("warn"), AnyEvent warns about unexpected
1019	conditions, such as not being able to load the event model specified	1253	conditions, such as not being able to load the event model specified
1020	by "PERL_ANYEVENT_MODEL".	1254	by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception
		1255	- this is the minimum recommended level for use during development.
1021		1256
1022	When set to 2 or higher, cause AnyEvent to report to STDERR which	1257	When set to 7 or higher (info), AnyEvent reports which event model
1023	event model it chooses.	1258	it chooses.
1024		1259
1025	When set to 8 or higher, then AnyEvent will report extra information	1260	When set to 8 or higher (debug), then AnyEvent will report extra
1026	on which optional modules it loads and how it implements certain	1261	information on which optional modules it loads and how it implements
1027	features.	1262	certain features.
		1263
		1264	"PERL_ANYEVENT_LOG"
		1265	Accepts rather complex logging specifications. For example, you
		1266	could log all "debug" messages of some module to stderr, warnings
		1267	and above to stderr, and errors and above to syslog, with:
		1268
		1269	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		1270
		1271	For the rather extensive details, see AnyEvent::Log.
		1272
		1273	This variable is evaluated when AnyEvent (or AnyEvent::Log) is
		1274	loaded, so will take effect even before AnyEvent has initialised
		1275	itself.
		1276
		1277	Note that specifying this environment variable causes the
		1278	AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE"
		1279	does not, so only using the latter saves a few hundred kB of memory
		1280	unless a module explicitly needs the extra features of
		1281	AnyEvent::Log.
1028		1282
1029	"PERL_ANYEVENT_STRICT"	1283	"PERL_ANYEVENT_STRICT"
1030	AnyEvent does not do much argument checking by default, as thorough	1284	AnyEvent does not do much argument checking by default, as thorough
1031	argument checking is very costly. Setting this variable to a true	1285	argument checking is very costly. Setting this variable to a true
1032	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1286	value will cause AnyEvent to load "AnyEvent::Strict" and then to
1033	thoroughly check the arguments passed to most method calls. If it	1287	thoroughly check the arguments passed to most method calls. If it
1034	finds any problems, it will croak.	1288	finds any problems, it will croak.
1035		1289
1036	In other words, enables "strict" mode.	1290	In other words, enables "strict" mode.
1037		1291
1038	Unlike "use strict" (or it's modern cousin, "use common::sense", it	1292	Unlike "use strict" (or its modern cousin, "use common::sense", it
1039	is definitely recommended to keep it off in production. Keeping	1293	is definitely recommended to keep it off in production. Keeping
1040	"PERL_ANYEVENT_STRICT=1" in your environment while developing	1294	"PERL_ANYEVENT_STRICT=1" in your environment while developing
1041	programs can be very useful, however.	1295	programs can be very useful, however.
1042		1296
		1297	"PERL_ANYEVENT_DEBUG_SHELL"
		1298	If this env variable is nonempty, then its contents will be
		1299	interpreted by "AnyEvent::Socket::parse_hostport" and
		1300	"AnyEvent::Debug::shell" (after replacing every occurance of $$ by
		1301	the process pid). The shell object is saved in
		1302	$AnyEvent::Debug::SHELL.
		1303
		1304	This happens when the first watcher is created.
		1305
		1306	For example, to bind a debug shell on a unix domain socket in
		1307	/tmp/debug<pid>.sock, you could use this:
		1308
		1309	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		1310	# connect with e.g.: socat readline /tmp/debug123.sock
		1311
		1312	Or to bind to tcp port 4545 on localhost:
		1313
		1314	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		1315	# connect with e.g.: telnet localhost 4545
		1316
		1317	Note that creating sockets in /tmp or on localhost is very unsafe on
		1318	multiuser systems.
		1319
		1320	"PERL_ANYEVENT_DEBUG_WRAP"
		1321	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1322	debugging purposes. See "AnyEvent::Debug::wrap" for details.
		1323
1043	"PERL_ANYEVENT_MODEL"	1324	"PERL_ANYEVENT_MODEL"
1044	This can be used to specify the event model to be used by AnyEvent,	1325	This can be used to specify the event model to be used by AnyEvent,
1045	before auto detection and -probing kicks in. It must be a string	1326	before auto detection and -probing kicks in.
1046	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1327
1047	gets prepended and the resulting module name is loaded and if the	1328	It normally is a string consisting entirely of ASCII letters (e.g.
1048	load was successful, used as event model. If it fails to load	1329	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1330	the resulting module name is loaded and - if the load was successful
		1331	- used as event model backend. If it fails to load then AnyEvent
1049	AnyEvent will proceed with auto detection and -probing.	1332	will proceed with auto detection and -probing.
1050		1333
1051	This functionality might change in future versions.	1334	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1335	then nothing gets prepended and the module name is used as-is (hint:
		1336	"::" at the end of a string designates a module name and quotes it
		1337	appropriately).
1052		1338
1053	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1339	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
1054	could start your program like this:	1340	could start your program like this:
1055		1341
1056	PERL_ANYEVENT_MODEL=Perl perl ...	1342	PERL_ANYEVENT_MODEL=Perl perl ...
		1343
		1344	"PERL_ANYEVENT_IO_MODEL"
		1345	The current file I/O model - see AnyEvent::IO for more info.
		1346
		1347	At the moment, only "Perl" (small, pure-perl, synchronous) and
		1348	"IOAIO" (truly asynchronous) are supported. The default is "IOAIO"
		1349	if AnyEvent::AIO can be loaded, otherwise it is "Perl".
1057		1350
1058	"PERL_ANYEVENT_PROTOCOLS"	1351	"PERL_ANYEVENT_PROTOCOLS"
1059	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1352	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
1060	preferences for IPv4 or IPv6. The default is unspecified (and might	1353	preferences for IPv4 or IPv6. The default is unspecified (and might
1061	change, or be the result of auto probing).	1354	change, or be the result of auto probing).
…		…
1075	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1368	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
1076	resolve or contact IPv6 addresses.	1369	resolve or contact IPv6 addresses.
1077	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but	1370	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
1078	prefer IPv6 over IPv4.	1371	prefer IPv6 over IPv4.
1079		1372
		1373	"PERL_ANYEVENT_HOSTS"
		1374	This variable, if specified, overrides the /etc/hosts file used by
		1375	AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be
		1376	read from that file instead.
		1377
1080	"PERL_ANYEVENT_EDNS0"	1378	"PERL_ANYEVENT_EDNS0"
1081	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension	1379	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
1082	for DNS. This extension is generally useful to reduce DNS traffic,	1380	for DNS. This extension is generally useful to reduce DNS traffic,
1083	but some (broken) firewalls drop such DNS packets, which is why it	1381	especially when DNSSEC is involved, but some (broken) firewalls drop
1084	is off by default.	1382	such DNS packets, which is why it is off by default.
1085		1383
1086	Setting this variable to 1 will cause AnyEvent::DNS to announce	1384	Setting this variable to 1 will cause AnyEvent::DNS to announce
1087	EDNS0 in its DNS requests.	1385	EDNS0 in its DNS requests.
1088		1386
1089	"PERL_ANYEVENT_MAX_FORKS"	1387	"PERL_ANYEVENT_MAX_FORKS"
…		…
1093	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"	1391	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
1094	The default value for the "max_outstanding" parameter for the	1392	The default value for the "max_outstanding" parameter for the
1095	default DNS resolver - this is the maximum number of parallel DNS	1393	default DNS resolver - this is the maximum number of parallel DNS
1096	requests that are sent to the DNS server.	1394	requests that are sent to the DNS server.
1097		1395
		1396	"PERL_ANYEVENT_MAX_SIGNAL_LATENCY"
		1397	Perl has inherently racy signal handling (you can basically choose
		1398	between losing signals and memory corruption) - pure perl event
		1399	loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't
		1400	available) therefore have to poll regularly to avoid losing signals.
		1401
		1402	Some event loops are racy, but don't poll regularly, and some event
		1403	loops are written in C but are still racy. For those event loops,
		1404	AnyEvent installs a timer that regularly wakes up the event loop.
		1405
		1406	By default, the interval for this timer is 10 seconds, but you can
		1407	override this delay with this environment variable (or by setting
		1408	the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal
		1409	watchers).
		1410
		1411	Lower values increase CPU (and energy) usage, higher values can
		1412	introduce long delays when reaping children or waiting for signals.
		1413
		1414	The AnyEvent::Async module, if available, will be used to avoid this
		1415	polling (with most event loops).
		1416
1098	"PERL_ANYEVENT_RESOLV_CONF"	1417	"PERL_ANYEVENT_RESOLV_CONF"
1099	The file to use instead of /etc/resolv.conf (or OS-specific	1418	The absolute path to a resolv.conf-style file to use instead of
1100	configuration) in the default resolver. When set to the empty	1419	/etc/resolv.conf (or the OS-specific configuration) in the default
1101	string, no default config will be used.	1420	resolver, or the empty string to select the default configuration.
1102		1421
1103	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".	1422	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1104	When neither "ca_file" nor "ca_path" was specified during	1423	When neither "ca_file" nor "ca_path" was specified during
1105	AnyEvent::TLS context creation, and either of these environment	1424	AnyEvent::TLS context creation, and either of these environment
1106	variables exist, they will be used to specify CA certificate	1425	variables are nonempty, they will be used to specify CA certificate
1107	locations instead of a system-dependent default.	1426	locations instead of a system-dependent default.
1108		1427
1109	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"	1428	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
1110	When these are set to 1, then the respective modules are not loaded.	1429	When these are set to 1, then the respective modules are not loaded.
1111	Mostly good for testing AnyEvent itself.	1430	Mostly good for testing AnyEvent itself.
…		…
1171	warn "read: $input\n"; # output what has been read	1490	warn "read: $input\n"; # output what has been read
1172	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1491	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1173	},	1492	},
1174	);	1493	);
1175		1494
1176	my $time_watcher; # can only be used once
1177
1178	sub new_timer {
1179	$timer = AnyEvent->timer (after => 1, cb => sub {	1495	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1180	warn "timeout\n"; # print 'timeout' about every second	1496	warn "timeout\n"; # print 'timeout' at most every second
1181	&new_timer; # and restart the time
1182	});
1183	}	1497	});
1184
1185	new_timer; # create first timer
1186		1498
1187	$cv->recv; # wait until user enters /^q/i	1499	$cv->recv; # wait until user enters /^q/i
1188		1500
1189	REAL-WORLD EXAMPLE	1501	REAL-WORLD EXAMPLE
1190	Consider the Net::FCP module. It features (among others) the following	1502	Consider the Net::FCP module. It features (among others) the following
…		…
1262		1574
1263	The actual code goes further and collects all errors ("die"s,	1575	The actual code goes further and collects all errors ("die"s,
1264	exceptions) that occurred during request processing. The "result" method	1576	exceptions) that occurred during request processing. The "result" method
1265	detects whether an exception as thrown (it is stored inside the $txn	1577	detects whether an exception as thrown (it is stored inside the $txn
1266	object) and just throws the exception, which means connection errors and	1578	object) and just throws the exception, which means connection errors and
1267	other problems get reported tot he code that tries to use the result,	1579	other problems get reported to the code that tries to use the result,
1268	not in a random callback.	1580	not in a random callback.
1269		1581
1270	All of this enables the following usage styles:	1582	All of this enables the following usage styles:
1271		1583
1272	1. Blocking:	1584	1. Blocking:
…		…
1317	through AnyEvent. The benchmark creates a lot of timers (with a zero	1629	through AnyEvent. The benchmark creates a lot of timers (with a zero
1318	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1630	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1319	which it is), lets them fire exactly once and destroys them again.	1631	which it is), lets them fire exactly once and destroys them again.
1320		1632
1321	Source code for this benchmark is found as eg/bench in the AnyEvent	1633	Source code for this benchmark is found as eg/bench in the AnyEvent
1322	distribution.	1634	distribution. It uses the AE interface, which makes a real difference
		1635	for the EV and Perl backends only.
1323		1636
1324	Explanation of the columns	1637	Explanation of the columns
1325	watcher is the number of event watchers created/destroyed. Since	1638	watcher is the number of event watchers created/destroyed. Since
1326	different event models feature vastly different performances, each event	1639	different event models feature vastly different performances, each event
1327	loop was given a number of watchers so that overall runtime is	1640	loop was given a number of watchers so that overall runtime is
…		…
1346	destroy is the time, in microseconds, that it takes to destroy a	1659	destroy is the time, in microseconds, that it takes to destroy a
1347	single watcher.	1660	single watcher.
1348		1661
1349	Results	1662	Results
1350	name watchers bytes create invoke destroy comment	1663	name watchers bytes create invoke destroy comment
1351	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1664	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1352	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1665	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1353	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1666	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1354	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1667	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1355	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1668	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1356	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1669	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
1357	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll	1670	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
1358	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll	1671	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1359	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1672	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1360	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1673	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1361	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1674	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1362	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1675	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1363		1676
1364	Discussion	1677	Discussion
1365	The benchmark does not measure scalability of the event loop very	1678	The benchmark does not measure scalability of the event loop very
1366	well. For example, a select-based event loop (such as the pure perl one)	1679	well. For example, a select-based event loop (such as the pure perl one)
1367	can never compete with an event loop that uses epoll when the number of	1680	can never compete with an event loop that uses epoll when the number of
…		…
1378	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1691	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1379	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1692	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1380	CPU cycles with POE.	1693	CPU cycles with POE.
1381		1694
1382	"EV" is the sole leader regarding speed and memory use, which are both	1695	"EV" is the sole leader regarding speed and memory use, which are both
1383	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1696	maximal/minimal, respectively. When using the AE API there is zero
		1697	overhead (when going through the AnyEvent API create is about 5-6 times
		1698	slower, with other times being equal, so still uses far less memory than
1384	far less memory than any other event loop and is still faster than Event	1699	any other event loop and is still faster than Event natively).
1385	natively.
1386		1700
1387	The pure perl implementation is hit in a few sweet spots (both the	1701	The pure perl implementation is hit in a few sweet spots (both the
1388	constant timeout and the use of a single fd hit optimisations in the	1702	constant timeout and the use of a single fd hit optimisations in the
1389	perl interpreter and the backend itself). Nevertheless this shows that	1703	perl interpreter and the backend itself). Nevertheless this shows that
1390	it adds very little overhead in itself. Like any select-based backend	1704	it adds very little overhead in itself. Like any select-based backend
…		…
1436	when used without AnyEvent), but most event loops have acceptable	1750	when used without AnyEvent), but most event loops have acceptable
1437	performance with or without AnyEvent.	1751	performance with or without AnyEvent.
1438		1752
1439	* The overhead AnyEvent adds is usually much smaller than the overhead	1753	* The overhead AnyEvent adds is usually much smaller than the overhead
1440	of the actual event loop, only with extremely fast event loops such	1754	of the actual event loop, only with extremely fast event loops such
1441	as EV adds AnyEvent significant overhead.	1755	as EV does AnyEvent add significant overhead.
1442		1756
1443	* You should avoid POE like the plague if you want performance or	1757	* You should avoid POE like the plague if you want performance or
1444	reasonable memory usage.	1758	reasonable memory usage.
1445		1759
1446	BENCHMARKING THE LARGE SERVER CASE	1760	BENCHMARKING THE LARGE SERVER CASE
…		…
1460	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1774	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1461	100 (1%) are active. This mirrors the activity of large servers with	1775	100 (1%) are active. This mirrors the activity of large servers with
1462	many connections, most of which are idle at any one point in time.	1776	many connections, most of which are idle at any one point in time.
1463		1777
1464	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1778	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1465	distribution.	1779	distribution. It uses the AE interface, which makes a real difference
		1780	for the EV and Perl backends only.
1466		1781
1467	Explanation of the columns	1782	Explanation of the columns
1468	sockets is the number of sockets, and twice the number of "servers"	1783	sockets is the number of sockets, and twice the number of "servers"
1469	(as each server has a read and write socket end).	1784	(as each server has a read and write socket end).
1470		1785
…		…
1476	forwarding it to another server. This includes deleting the old timeout	1791	forwarding it to another server. This includes deleting the old timeout
1477	and creating a new one that moves the timeout into the future.	1792	and creating a new one that moves the timeout into the future.
1478		1793
1479	Results	1794	Results
1480	name sockets create request	1795	name sockets create request
1481	EV 20000 69.01 11.16	1796	EV 20000 62.66 7.99
1482	Perl 20000 73.32 35.87	1797	Perl 20000 68.32 32.64
1483	IOAsync 20000 157.00 98.14 epoll	1798	IOAsync 20000 174.06 101.15 epoll
1484	IOAsync 20000 159.31 616.06 poll	1799	IOAsync 20000 174.67 610.84 poll
1485	Event 20000 212.62 257.32	1800	Event 20000 202.69 242.91
1486	Glib 20000 651.16 1896.30	1801	Glib 20000 557.01 1689.52
1487	POE 20000 349.67 12317.24 uses POE::Loop::Event	1802	POE 20000 341.54 12086.32 uses POE::Loop::Event
1488		1803
1489	Discussion	1804	Discussion
1490	This benchmark does measure scalability and overall performance of the	1805	This benchmark does measure scalability and overall performance of the
1491	particular event loop.	1806	particular event loop.
1492		1807
…		…
1605	As you can see, the AnyEvent + EV combination even beats the	1920	As you can see, the AnyEvent + EV combination even beats the
1606	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl	1921	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1607	backend easily beats IO::Lambda and POE.	1922	backend easily beats IO::Lambda and POE.
1608		1923
1609	And even the 100% non-blocking version written using the high-level (and	1924	And even the 100% non-blocking version written using the high-level (and
1610	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a	1925	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
1611	large margin, even though it does all of DNS, tcp-connect and socket I/O	1926	higher level ("unoptimised") abstractions by a large margin, even though
1612	in a non-blocking way.	1927	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
1613		1928
1614	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and	1929	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
1615	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are	1930	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1616	part of the IO::lambda distribution and were used without any changes.	1931	part of the IO::Lambda distribution and were used without any changes.
1617		1932
1618	SIGNALS	1933	SIGNALS
1619	AnyEvent currently installs handlers for these signals:	1934	AnyEvent currently installs handlers for these signals:
1620		1935
1621	SIGCHLD	1936	SIGCHLD
…		…
1643		1958
1644	Feel free to install your own handler, or reset it to defaults.	1959	Feel free to install your own handler, or reset it to defaults.
1645		1960
1646	RECOMMENDED/OPTIONAL MODULES	1961	RECOMMENDED/OPTIONAL MODULES
1647	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and	1962	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
1648	it's built-in modules) are required to use it.	1963	its built-in modules) are required to use it.
1649		1964
1650	That does not mean that AnyEvent won't take advantage of some additional	1965	That does not mean that AnyEvent won't take advantage of some additional
1651	modules if they are installed.	1966	modules if they are installed.
1652		1967
1653	This section epxlains which additional modules will be used, and how	1968	This section explains which additional modules will be used, and how
1654	they affect AnyEvent's operetion.	1969	they affect AnyEvent's operation.
1655		1970
1656	Async::Interrupt	1971	Async::Interrupt
1657	This slightly arcane module is used to implement fast signal	1972	This slightly arcane module is used to implement fast signal
1658	handling: To my knowledge, there is no way to do completely	1973	handling: To my knowledge, there is no way to do completely
1659	race-free and quick signal handling in pure perl. To ensure that	1974	race-free and quick signal handling in pure perl. To ensure that
…		…
1662	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).	1977	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
1663		1978
1664	If this module is available, then it will be used to implement	1979	If this module is available, then it will be used to implement
1665	signal catching, which means that signals will not be delayed, and	1980	signal catching, which means that signals will not be delayed, and
1666	the event loop will not be interrupted regularly, which is more	1981	the event loop will not be interrupted regularly, which is more
1667	efficient (And good for battery life on laptops).	1982	efficient (and good for battery life on laptops).
1668		1983
1669	This affects not just the pure-perl event loop, but also other event	1984	This affects not just the pure-perl event loop, but also other event
1670	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).	1985	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
1671		1986
1672	Some event loops (POE, Event, Event::Lib) offer signal watchers	1987	Some event loops (POE, Event, Event::Lib) offer signal watchers
…		…
1682	clock is available, can take avdantage of advanced kernel interfaces	1997	clock is available, can take avdantage of advanced kernel interfaces
1683	such as "epoll" and "kqueue", and is the fastest backend by far.	1998	such as "epoll" and "kqueue", and is the fastest backend by far.
1684	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and	1999	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
1685	Glib::EV).	2000	Glib::EV).
1686		2001
		2002	If you only use backends that rely on another event loop (e.g.
		2003	"Tk"), then this module will do nothing for you.
		2004
1687	Guard	2005	Guard
1688	The guard module, when used, will be used to implement	2006	The guard module, when used, will be used to implement
1689	"AnyEvent::Util::guard". This speeds up guards considerably (and	2007	"AnyEvent::Util::guard". This speeds up guards considerably (and
1690	uses a lot less memory), but otherwise doesn't affect guard	2008	uses a lot less memory), but otherwise doesn't affect guard
1691	operation much. It is purely used for performance.	2009	operation much. It is purely used for performance.
1692		2010
1693	JSON and JSON::XS	2011	JSON and JSON::XS
1694	This module is required when you want to read or write JSON data via	2012	One of these modules is required when you want to read or write JSON
1695	AnyEvent::Handle. It is also written in pure-perl, but can take	2013	data via AnyEvent::Handle. JSON is also written in pure-perl, but
1696	advantage of the ultra-high-speed JSON::XS module when it is	2014	can take advantage of the ultra-high-speed JSON::XS module when it
1697	installed.	2015	is installed.
1698
1699	In fact, AnyEvent::Handle will use JSON::XS by default if it is
1700	installed.
1701		2016
1702	Net::SSLeay	2017	Net::SSLeay
1703	Implementing TLS/SSL in Perl is certainly interesting, but not very	2018	Implementing TLS/SSL in Perl is certainly interesting, but not very
1704	worthwhile: If this module is installed, then AnyEvent::Handle (with	2019	worthwhile: If this module is installed, then AnyEvent::Handle (with
1705	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.	2020	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
1706		2021
1707	Time::HiRes	2022	Time::HiRes
1708	This module is part of perl since release 5.008. It will be used	2023	This module is part of perl since release 5.008. It will be used
1709	when the chosen event library does not come with a timing source on	2024	when the chosen event library does not come with a timing source of
1710	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will	2025	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
1711	additionally use it to try to use a monotonic clock for timing	2026	load it to try to use a monotonic clock for timing stability.
1712	stability.	2027
		2028	AnyEvent::AIO (and IO::AIO)
		2029	The default implementation of AnyEvent::IO is to do I/O
		2030	synchronously, stopping programs while they access the disk, which
		2031	is fine for a lot of programs.
		2032
		2033	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it
		2034	switch to a true asynchronous implementation, so event processing
		2035	can continue even while waiting for disk I/O.
1713		2036
1714	FORK	2037	FORK
1715	Most event libraries are not fork-safe. The ones who are usually are	2038	Most event libraries are not fork-safe. The ones who are usually are
1716	because they rely on inefficient but fork-safe "select" or "poll" calls.	2039	because they rely on inefficient but fork-safe "select" or "poll" calls
1717	Only EV is fully fork-aware.	2040	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		2041	epoll are usually badly thought-out hacks that are incompatible with
		2042	fork in one way or another. Only EV is fully fork-aware and ensures that
		2043	you continue event-processing in both parent and child (or both, if you
		2044	know what you are doing).
		2045
		2046	This means that, in general, you cannot fork and do event processing in
		2047	the child if the event library was initialised before the fork (which
		2048	usually happens when the first AnyEvent watcher is created, or the
		2049	library is loaded).
1718		2050
1719	If you have to fork, you must either do so before creating your first	2051	If you have to fork, you must either do so before creating your first
1720	watcher OR you must not use AnyEvent at all in the child OR you must do	2052	watcher OR you must not use AnyEvent at all in the child OR you must do
1721	something completely out of the scope of AnyEvent.	2053	something completely out of the scope of AnyEvent (see below).
		2054
		2055	The problem of doing event processing in the parent and the child is
		2056	much more complicated: even for backends that are fork-aware or
		2057	fork-safe, their behaviour is not usually what you want: fork clones all
		2058	watchers, that means all timers, I/O watchers etc. are active in both
		2059	parent and child, which is almost never what you want. Using "exec" to
		2060	start worker children from some kind of manage prrocess is usually
		2061	preferred, because it is much easier and cleaner, at the expense of
		2062	having to have another binary.
		2063
		2064	In addition to logical problems with fork, there are also implementation
		2065	problems. For example, on POSIX systems, you cannot fork at all in Perl
		2066	code if a thread (I am talking of pthreads here) was ever created in the
		2067	process, and this is just the tip of the iceberg. In general, using fork
		2068	from Perl is difficult, and attempting to use fork without an exec to
		2069	implement some kind of parallel processing is almost certainly doomed.
		2070
		2071	To safely fork and exec, you should use a module such as Proc::FastSpawn
		2072	that let's you safely fork and exec new processes.
		2073
		2074	If you want to do multiprocessing using processes, you can look at the
		2075	AnyEvent::Fork module (and some related modules such as
		2076	AnyEvent::Fork::RPC, AnyEvent::Fork::Pool and AnyEvent::Fork::Remote).
		2077	This module allows you to safely create subprocesses without any
		2078	limitations - you can use X11 toolkits or AnyEvent in the children
		2079	created by AnyEvent::Fork safely and without any special precautions.
1722		2080
1723	SECURITY CONSIDERATIONS	2081	SECURITY CONSIDERATIONS
1724	AnyEvent can be forced to load any event model via	2082	AnyEvent can be forced to load any event model via
1725	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	2083	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1726	to execute arbitrary code or directly gain access, it can easily be used	2084	to execute arbitrary code or directly gain access, it can easily be used
…		…
1750	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	2108	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1751	annoying memleaks, such as leaking on "map" and "grep" but it is usually	2109	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1752	not as pronounced).	2110	not as pronounced).
1753		2111
1754	SEE ALSO	2112	SEE ALSO
1755	Utility functions: AnyEvent::Util.	2113	Tutorial/Introduction: AnyEvent::Intro.
1756		2114
1757	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	2115	FAQ: AnyEvent::FAQ.
1758	Event::Lib, Qt, POE.	2116
		2117	Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log
		2118	(simply logging).
		2119
		2120	Development/Debugging: AnyEvent::Strict (stricter checking),
		2121	AnyEvent::Debug (interactive shell, watcher tracing).
		2122
		2123	Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
		2124	Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK.
1759		2125
1760	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	2126	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1761	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	2127	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1762	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,	2128	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1763	AnyEvent::Impl::IOAsync.	2129	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi, AnyEvent::Impl::FLTK.
1764		2130
1765	Non-blocking file handles, sockets, TCP clients and servers:	2131	Non-blocking handles, pipes, stream sockets, TCP clients and servers:
1766	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.	2132	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1767		2133
		2134	Asynchronous File I/O: AnyEvent::IO.
		2135
1768	Asynchronous DNS: AnyEvent::DNS.	2136	Asynchronous DNS: AnyEvent::DNS.
1769		2137
1770	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	2138	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1771		2139
1772	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,	2140	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
1773	AnyEvent::HTTP.	2141	AnyEvent::HTTP.
1774		2142
1775	AUTHOR	2143	AUTHOR
1776	Marc Lehmann <schmorp@schmorp.de>	2144	Marc Lehmann <schmorp@schmorp.de>
1777	http://home.schmorp.de/	2145	http://anyevent.schmorp.de
1778		2146

Diff Legend

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

Comparing AnyEvent/README (file contents): Revision 1.47 by root, Mon Jul 20 22:39:57 2009 UTC vs. Revision 1.72 by root, Tue Dec 17 16:43:15 2013 UTC

Diff Legend

Comparing AnyEvent/README (file contents):
Revision 1.47 by root, Mon Jul 20 22:39:57 2009 UTC vs.
Revision 1.72 by root, Tue Dec 17 16:43:15 2013 UTC