[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 1.71 by root, Wed Aug 21 08:40:28 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
…		…
438		484
439	# do something else, then wait for process exit	485	# do something else, then wait for process exit
440	$done->recv;	486	$done->recv;
441		487
442	IDLE WATCHERS	488	IDLE WATCHERS
443	Sometimes there is a need to do something, but it is not so important to	489	$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		490
448	Idle watchers ideally get invoked when the event loop has nothing better	491	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.	492	until either the watcher is destroyed or new events have been detected.
450	Instead of blocking, the idle watcher is invoked.
451		493
452	Most event loops unfortunately do not really support idle watchers (only	494	Idle watchers are useful when there is a need to do something, but it is
		495	not so important (or wise) to do it instantly. The callback will be
		496	invoked only when there is "nothing better to do", which is usually
		497	defined as "all outstanding events have been handled and no new events
		498	have been detected". That means that idle watchers ideally get invoked
		499	when the event loop has just polled for new events but none have been
		500	detected. Instead of blocking to wait for more events, the idle watchers
		501	will be invoked.
		502
		503	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	504	(only EV, Event and Glib do it in a usable fashion) - for the rest,
454	will simply call the callback "from time to time".	505	AnyEvent will simply call the callback "from time to time".
455		506
456	Example: read lines from STDIN, but only process them when the program	507	Example: read lines from STDIN, but only process them when the program
457	is otherwise idle:	508	is otherwise idle:
458		509
459	my @lines; # read data	510	my @lines; # read data
…		…
472	}	523	}
473	});	524	});
474	});	525	});
475		526
476	CONDITION VARIABLES	527	CONDITION VARIABLES
		528	$cv = AnyEvent->condvar;
		529
		530	$cv->send (<list>);
		531	my @res = $cv->recv;
		532
477	If you are familiar with some event loops you will know that all of them	533	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	534	require you to run some blocking "loop", "run" or similar function that
479	will actively watch for new events and call your callbacks.	535	will actively watch for new events and call your callbacks.
480		536
481	AnyEvent is slightly different: it expects somebody else to run the	537	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	538	event loop and will only block when necessary (usually when told by the
483	user).	539	user).
484		540
485	The instrument to do that is called a "condition variable", so called	541	The tool to do that is called a "condition variable", so called because
486	because they represent a condition that must become true.	542	they represent a condition that must become true.
487		543
488	Now is probably a good time to look at the examples further below.	544	Now is probably a good time to look at the examples further below.
489		545
490	Condition variables can be created by calling the "AnyEvent->condvar"	546	Condition variables can be created by calling the "AnyEvent->condvar"
491	method, usually without arguments. The only argument pair allowed is	547	method, usually without arguments. The only argument pair allowed is
…		…
496	After creation, the condition variable is "false" until it becomes	552	After creation, the condition variable is "false" until it becomes
497	"true" by calling the "send" method (or calling the condition variable	553	"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	554	as if it were a callback, read about the caveats in the description for
499	the "->send" method).	555	the "->send" method).
500		556
501	Condition variables are similar to callbacks, except that you can	557	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	558	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	559	you can connect to:
504	another way to call them is transactions - each condition variable can	560
505	be used to represent a transaction, which finishes at some point and	561	* Condition variables are like callbacks - you can call them (and pass
506	delivers a result. And yet some people know them as "futures" - a	562	them instead of callbacks). Unlike callbacks however, you can also
507	promise to compute/deliver something that you can wait for.	563	wait for them to be called.
		564
		565	* Condition variables are signals - one side can emit or send them,
		566	the other side can wait for them, or install a handler that is
		567	called when the signal fires.
		568
		569	* Condition variables are like "Merge Points" - points in your program
		570	where you merge multiple independent results/control flows into one.
		571
		572	* Condition variables represent a transaction - functions that start
		573	some kind of transaction can return them, leaving the caller the
		574	choice between waiting in a blocking fashion, or setting a callback.
		575
		576	* Condition variables represent future values, or promises to deliver
		577	some result, long before the result is available.
508		578
509	Condition variables are very useful to signal that something has	579	Condition variables are very useful to signal that something has
510	finished, for example, if you write a module that does asynchronous http	580	finished, for example, if you write a module that does asynchronous http
511	requests, then a condition variable would be the ideal candidate to	581	requests, then a condition variable would be the ideal candidate to
512	signal the availability of results. The user can either act when the	582	signal the availability of results. The user can either act when the
…		…
525		595
526	Condition variables are represented by hash refs in perl, and the keys	596	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	597	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	598	(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	599	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
530	it's "new" method in your own "new" method.	600	its "new" method in your own "new" method.
531		601
532	There are two "sides" to a condition variable - the "producer side"	602	There are two "sides" to a condition variable - the "producer side"
533	which eventually calls "-> send", and the "consumer side", which waits	603	which eventually calls "-> send", and the "consumer side", which waits
534	for the send to occur.	604	for the send to occur.
535		605
536	Example: wait for a timer.	606	Example: wait for a timer.
537		607
538	# wait till the result is ready	608	# condition: "wait till the timer is fired"
539	my $result_ready = AnyEvent->condvar;	609	my $timer_fired = AnyEvent->condvar;
540		610
541	# do something such as adding a timer	611	# create the timer - we could wait for, say
542	# or socket watcher the calls $result_ready->send	612	# a handle becomign ready, or even an
543	# when the "result" is ready.	613	# AnyEvent::HTTP request to finish, but
544	# in this case, we simply use a timer:	614	# in this case, we simply use a timer:
545	my $w = AnyEvent->timer (	615	my $w = AnyEvent->timer (
546	after => 1,	616	after => 1,
547	cb => sub { $result_ready->send },	617	cb => sub { $timer_fired->send },
548	);	618	);
549		619
550	# this "blocks" (while handling events) till the callback	620	# this "blocks" (while handling events) till the callback
551	# calls -<send	621	# calls ->send
552	$result_ready->recv;	622	$timer_fired->recv;
553		623
554	Example: wait for a timer, but take advantage of the fact that condition	624	Example: wait for a timer, but take advantage of the fact that condition
555	variables are also callable directly.	625	variables are also callable directly.
556		626
557	my $done = AnyEvent->condvar;	627	my $done = AnyEvent->condvar;
…		…
595	Condition variables are overloaded so one can call them directly (as	665	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	666	if they were a code reference). Calling them directly is the same as
597	calling "send".	667	calling "send".
598		668
599	$cv->croak ($error)	669	$cv->croak ($error)
600	Similar to send, but causes all call's to "->recv" to invoke	670	Similar to send, but causes all calls to "->recv" to invoke
601	"Carp::croak" with the given error message/object/scalar.	671	"Carp::croak" with the given error message/object/scalar.
602		672
603	This can be used to signal any errors to the condition variable	673	This can be used to signal any errors to the condition variable
604	user/consumer. Doing it this way instead of calling "croak" directly	674	user/consumer. Doing it this way instead of calling "croak" directly
605	delays the error detetcion, but has the overwhelmign advantage that	675	delays the error detection, but has the overwhelming advantage that
606	it diagnoses the error at the place where the result is expected,	676	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	677	and not deep in some event callback with no connection to the actual
608	code causing the problem.	678	code causing the problem.
609		679
610	$cv->begin ([group callback])	680	$cv->begin ([group callback])
611	$cv->end	681	$cv->end
612	These two methods can be used to combine many transactions/events	682	These two methods can be used to combine many transactions/events
613	into one. For example, a function that pings many hosts in parallel	683	into one. For example, a function that pings many hosts in parallel
614	might want to use a condition variable for the whole process.	684	might want to use a condition variable for the whole process.
615		685
616	Every call to "->begin" will increment a counter, and every call to	686	Every call to "->begin" will increment a counter, and every call to
617	"->end" will decrement it. If the counter reaches 0 in "->end", the	687	"->end" will decrement it. If the counter reaches 0 in "->end", the
618	(last) callback passed to "begin" will be executed. That callback is	688	(last) callback passed to "begin" will be executed, passing the
619	supposed to call "->send", but that is not required. If no	689	condvar as first argument. That callback is supposed to call
		690	"->send", but that is not required. If no group callback was set,
620	callback was set, "send" will be called without any arguments.	691	"send" will be called without any arguments.
621		692
622	You can think of "$cv->send" giving you an OR condition (one call	693	You can think of "$cv->send" giving you an OR condition (one call
623	sends), while "$cv->begin" and "$cv->end" giving you an AND	694	sends), while "$cv->begin" and "$cv->end" giving you an AND
624	condition (all "begin" calls must be "end"'ed before the condvar	695	condition (all "begin" calls must be "end"'ed before the condvar
625	sends).	696	sends).
…		…
648	there is one call to "begin", so the condvar waits for all calls to	719	there is one call to "begin", so the condvar waits for all calls to
649	"end" before sending.	720	"end" before sending.
650		721
651	The ping example mentioned above is slightly more complicated, as	722	The ping example mentioned above is slightly more complicated, as
652	the there are results to be passwd back, and the number of tasks	723	the there are results to be passwd back, and the number of tasks
653	that are begung can potentially be zero:	724	that are begun can potentially be zero:
654		725
655	my $cv = AnyEvent->condvar;	726	my $cv = AnyEvent->condvar;
656		727
657	my %result;	728	my %result;
658	$cv->begin (sub { $cv->send (\%result) });	729	$cv->begin (sub { shift->send (\%result) });
659		730
660	for my $host (@list_of_hosts) {	731	for my $host (@list_of_hosts) {
661	$cv->begin;	732	$cv->begin;
662	ping_host_then_call_callback $host, sub {	733	ping_host_then_call_callback $host, sub {
663	$result{$host} = ...;	734	$result{$host} = ...;
…		…
665	};	736	};
666	}	737	}
667		738
668	$cv->end;	739	$cv->end;
669		740
		741	...
		742
		743	my $results = $cv->recv;
		744
670	This code fragment supposedly pings a number of hosts and calls	745	This code fragment supposedly pings a number of hosts and calls
671	"send" after results for all then have have been gathered - in any	746	"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	747	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	748	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	749	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	754	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	755	ensures that "send" is called even when "no" hosts are being pinged
681	(the loop doesn't execute once).	756	(the loop doesn't execute once).
682		757
683	This is the general pattern when you "fan out" into multiple (but	758	This is the general pattern when you "fan out" into multiple (but
684	potentially none) subrequests: use an outer "begin"/"end" pair to	759	potentially zero) subrequests: use an outer "begin"/"end" pair to
685	set the callback and ensure "end" is called at least once, and then,	760	set the callback and ensure "end" is called at least once, and then,
686	for each subrequest you start, call "begin" and for each subrequest	761	for each subrequest you start, call "begin" and for each subrequest
687	you finish, call "end".	762	you finish, call "end".
688		763
689	METHODS FOR CONSUMERS	764	METHODS FOR CONSUMERS
690	These methods should only be used by the consuming side, i.e. the code	765	These methods should only be used by the consuming side, i.e. the code
691	awaits the condition.	766	awaits the condition.
692		767
693	$cv->recv	768	$cv->recv
694	Wait (blocking if necessary) until the "->send" or "->croak" methods	769	Wait (blocking if necessary) until the "->send" or "->croak" methods
695	have been called on c<$cv>, while servicing other watchers normally.	770	have been called on $cv, while servicing other watchers normally.
696		771
697	You can only wait once on a condition - additional calls are valid	772	You can only wait once on a condition - additional calls are valid
698	but will return immediately.	773	but will return immediately.
699		774
700	If an error condition has been set by calling "->croak", then this	775	If an error condition has been set by calling "->croak", then this
…		…
703	In list context, all parameters passed to "send" will be returned,	778	In list context, all parameters passed to "send" will be returned,
704	in scalar context only the first one will be returned.	779	in scalar context only the first one will be returned.
705		780
706	Note that doing a blocking wait in a callback is not supported by	781	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"	782	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	783	is not allowed and the "recv" call will "croak" if such a condition
709	is detected. This condition can be slightly loosened by using	784	is detected. This requirement can be dropped by relying on
710	Coro::AnyEvent, which allows you to do a blocking "->recv" from any	785	Coro::AnyEvent , which allows you to do a blocking "->recv" from any
711	thread that doesn't run the event loop itself.	786	thread that doesn't run the event loop itself. Coro::AnyEvent is
		787	loaded automatically when Coro is used with AnyEvent, so code does
		788	not need to do anything special to take advantage of that: any code
		789	that would normally block your program because it calls "recv", be
		790	executed in an "async" thread instead without blocking other
		791	threads.
712		792
713	Not all event models support a blocking wait - some die in that case	793	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	794	(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,	795	using this from a module, never require a blocking wait*. Instead,
716	let the caller decide whether the call will block or not (for	796	let the caller decide whether the call will block or not (for
717	example, by coupling condition variables with some kind of request	797	example, by coupling condition variables with some kind of request
718	results and supporting callbacks so the caller knows that getting	798	results and supporting callbacks so the caller knows that getting
719	the result will not block, while still supporting blocking waits if	799	the result will not block, while still supporting blocking waits if
720	the caller so desires).	800	the caller so desires).
721		801
722	You can ensure that "-recv" never blocks by setting a callback and	802	You can ensure that "->recv" never blocks by setting a callback and
723	only calling "->recv" from within that callback (or at a later	803	only calling "->recv" from within that callback (or at a later
724	time). This will work even when the event loop does not support	804	time). This will work even when the event loop does not support
725	blocking waits otherwise.	805	blocking waits otherwise.
726		806
727	$bool = $cv->ready	807	$bool = $cv->ready
…		…
732	This is a mutator function that returns the callback set and	812	This is a mutator function that returns the callback set and
733	optionally replaces it before doing so.	813	optionally replaces it before doing so.
734		814
735	The callback will be called when the condition becomes "true", i.e.	815	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	816	when "send" or "croak" are called, with the only argument being the
737	condition variable itself. Calling "recv" inside the callback or at	817	condition variable itself. If the condition is already true, the
		818	callback is called immediately when it is set. Calling "recv" inside
738	any later time is guaranteed not to block.	819	the callback or at any later time is guaranteed not to block.
739		820
740	SUPPORTED EVENT LOOPS/BACKENDS	821	SUPPORTED EVENT LOOPS/BACKENDS
741	The available backend classes are (every class has its own manpage):	822	The available backend classes are (every class has its own manpage):
742		823
743	Backends that are autoprobed when no other event loop can be found.	824	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	825	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,	826	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,	827	pure-perl implementation, which is available everywhere as it comes
747	which is available everywhere as it comes with AnyEvent itself.	828	with AnyEvent itself.
748		829
749	AnyEvent::Impl::EV based on EV (interface to libev, best choice).	830	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.	831	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
752		832
753	Backends that are transparently being picked up when they are used.	833	Backends that are transparently being picked up when they are used.
754	These will be used when they are currently loaded when the first	834	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	835	is created, in which case it is assumed that the application is
756	is using them. This means that AnyEvent will automatically pick the	836	using them. This means that AnyEvent will automatically pick the
757	right backend when the main program loads an event module before	837	right backend when the main program loads an event module before
758	anything starts to create watchers. Nothing special needs to be done	838	anything starts to create watchers. Nothing special needs to be done
759	by the main program.	839	by the main program.
760		840
		841	AnyEvent::Impl::Event based on Event, very stable, few glitches.
761	AnyEvent::Impl::Glib based on Glib, slow but very stable.	842	AnyEvent::Impl::Glib based on Glib, slow but very stable.
762	AnyEvent::Impl::Tk based on Tk, very broken.	843	AnyEvent::Impl::Tk based on Tk, very broken.
763	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	844	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
764	AnyEvent::Impl::POE based on POE, very slow, some limitations.	845	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		846	AnyEvent::Impl::Irssi used when running within irssi.
		847	AnyEvent::Impl::IOAsync based on IO::Async.
		848	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		849	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
765		850
766	Backends with special needs.	851	Backends with special needs.
767	Qt requires the Qt::Application to be instantiated first, but will	852	Qt requires the Qt::Application to be instantiated first, but will
768	otherwise be picked up automatically. As long as the main program	853	otherwise be picked up automatically. As long as the main program
769	instantiates the application before any AnyEvent watchers are	854	instantiates the application before any AnyEvent watchers are
770	created, everything should just work.	855	created, everything should just work.
771		856
772	AnyEvent::Impl::Qt based on Qt.	857	AnyEvent::Impl::Qt based on Qt.
773		858
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.	859	Event loops that are indirectly supported via other backends.
783	Some event loops can be supported via other modules:	860	Some event loops can be supported via other modules:
784		861
785	There is no direct support for WxWidgets (Wx) or Prima.	862	There is no direct support for WxWidgets (Wx) or Prima.
786		863
…		…
804	Contains "undef" until the first watcher is being created, before	881	Contains "undef" until the first watcher is being created, before
805	the backend has been autodetected.	882	the backend has been autodetected.
806		883
807	Afterwards it contains the event model that is being used, which is	884	Afterwards it contains the event model that is being used, which is
808	the name of the Perl class implementing the model. This class is	885	the name of the Perl class implementing the model. This class is
809	usually one of the "AnyEvent::Impl:xxx" modules, but can be any	886	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
810	other class in the case AnyEvent has been extended at runtime (e.g.	887	other class in the case AnyEvent has been extended at runtime (e.g.
811	in rxvt-unicode it will be "urxvt::anyevent").	888	in rxvt-unicode it will be "urxvt::anyevent").
812		889
813	AnyEvent::detect	890	AnyEvent::detect
814	Returns $AnyEvent::MODEL, forcing autodetection of the event model	891	Returns $AnyEvent::MODEL, forcing autodetection of the event model
815	if necessary. You should only call this function right before you	892	if necessary. You should only call this function right before you
816	would have created an AnyEvent watcher anyway, that is, as late as	893	would have created an AnyEvent watcher anyway, that is, as late as
817	possible at runtime, and not e.g. while initialising of your module.	894	possible at runtime, and not e.g. during initialisation of your
		895	module.
		896
		897	The effect of calling this function is as if a watcher had been
		898	created (specifically, actions that happen "when the first watcher
		899	is created" happen when calling detetc as well).
818		900
819	If you need to do some initialisation before AnyEvent watchers are	901	If you need to do some initialisation before AnyEvent watchers are
820	created, use "post_detect".	902	created, use "post_detect".
821		903
822	$guard = AnyEvent::post_detect { BLOCK }	904	$guard = AnyEvent::post_detect { BLOCK }
823	Arranges for the code block to be executed as soon as the event	905	Arranges for the code block to be executed as soon as the event
824	model is autodetected (or immediately if this has already happened).	906	model is autodetected (or immediately if that has already happened).
825		907
826	The block will be executed after the actual backend has been	908	The block will be executed after the actual backend has been
827	detected ($AnyEvent::MODEL is set), but before any watchers have	909	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	910	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
829	other initialisations - see the sources of AnyEvent::Strict or	911	other initialisations - see the sources of AnyEvent::Strict or
…		…
834	creates and installs the global IO::AIO watcher in a "post_detect"	916	creates and installs the global IO::AIO watcher in a "post_detect"
835	block to avoid autodetecting the event module at load time.	917	block to avoid autodetecting the event module at load time.
836		918
837	If called in scalar or list context, then it creates and returns an	919	If called in scalar or list context, then it creates and returns an
838	object that automatically removes the callback again when it is	920	object that automatically removes the callback again when it is
		921	destroyed (or "undef" when the hook was immediately executed). See
839	destroyed. See Coro::BDB for a case where this is useful.	922	AnyEvent::AIO for a case where this is useful.
		923
		924	Example: Create a watcher for the IO::AIO module and store it in
		925	$WATCHER, but do so only do so after the event loop is initialised.
		926
		927	our WATCHER;
		928
		929	my $guard = AnyEvent::post_detect {
		930	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		931	};
		932
		933	# the \|\|= is important in case post_detect immediately runs the block,
		934	# as to not clobber the newly-created watcher. assigning both watcher and
		935	# post_detect guard to the same variable has the advantage of users being
		936	# able to just C<undef $WATCHER> if the watcher causes them grief.
		937
		938	$WATCHER \|\|= $guard;
840		939
841	@AnyEvent::post_detect	940	@AnyEvent::post_detect
842	If there are any code references in this array (you can "push" to it	941	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	942	before or after loading AnyEvent), then they will be called directly
844	after the event loop has been chosen.	943	after the event loop has been chosen.
845		944
846	You should check $AnyEvent::MODEL before adding to this array,	945	You should check $AnyEvent::MODEL before adding to this array,
847	though: if it is defined then the event loop has already been	946	though: if it is defined then the event loop has already been
848	detected, and the array will be ignored.	947	detected, and the array will be ignored.
849		948
850	Best use "AnyEvent::post_detect { BLOCK }" when your application	949	Best use "AnyEvent::post_detect { BLOCK }" when your application
851	allows it,as it takes care of these details.	950	allows it, as it takes care of these details.
852		951
853	This variable is mainly useful for modules that can do something	952	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	953	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	954	initialised, but do not need to even load it by default. This array
856	provides the means to hook into AnyEvent passively, without loading	955	provides the means to hook into AnyEvent passively, without loading
857	it.	956	it.
858		957
		958	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		959	together, you could put this into Coro (this is the actual code used
		960	by Coro to accomplish this):
		961
		962	if (defined $AnyEvent::MODEL) {
		963	# AnyEvent already initialised, so load Coro::AnyEvent
		964	require Coro::AnyEvent;
		965	} else {
		966	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		967	# as soon as it is
		968	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		969	}
		970
		971	AnyEvent::postpone { BLOCK }
		972	Arranges for the block to be executed as soon as possible, but not
		973	before the call itself returns. In practise, the block will be
		974	executed just before the event loop polls for new events, or shortly
		975	afterwards.
		976
		977	This function never returns anything (to make the "return postpone {
		978	... }" idiom more useful.
		979
		980	To understand the usefulness of this function, consider a function
		981	that asynchronously does something for you and returns some
		982	transaction object or guard to let you cancel the operation. For
		983	example, "AnyEvent::Socket::tcp_connect":
		984
		985	# start a conenction attempt unless one is active
		986	$self->{connect_guard} \|\|= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		987	delete $self->{connect_guard};
		988	...
		989	};
		990
		991	Imagine that this function could instantly call the callback, for
		992	example, because it detects an obvious error such as a negative port
		993	number. Invoking the callback before the function returns causes
		994	problems however: the callback will be called and will try to delete
		995	the guard object. But since the function hasn't returned yet, there
		996	is nothing to delete. When the function eventually returns it will
		997	assign the guard object to "$self->{connect_guard}", where it will
		998	likely never be deleted, so the program thinks it is still trying to
		999	connect.
		1000
		1001	This is where "AnyEvent::postpone" should be used. Instead of
		1002	calling the callback directly on error:
		1003
		1004	$cb->(undef), return # signal error to callback, BAD!
		1005	if $some_error_condition;
		1006
		1007	It should use "postpone":
		1008
		1009	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1010	if $some_error_condition;
		1011
		1012	AnyEvent::log $level, $msg[, @args]
		1013	Log the given $msg at the given $level.
		1014
		1015	If AnyEvent::Log is not loaded then this function makes a simple
		1016	test to see whether the message will be logged. If the test succeeds
		1017	it will load AnyEvent::Log and call "AnyEvent::Log::log" -
		1018	consequently, look at the AnyEvent::Log documentation for details.
		1019
		1020	If the test fails it will simply return. Right now this happens when
		1021	a numerical loglevel is used and it is larger than the level
		1022	specified via $ENV{PERL_ANYEVENT_VERBOSE}.
		1023
		1024	If you want to sprinkle loads of logging calls around your code,
		1025	consider creating a logger callback with the "AnyEvent::Log::logger"
		1026	function, which can reduce typing, codesize and can reduce the
		1027	logging overhead enourmously.
		1028
859	WHAT TO DO IN A MODULE	1029	WHAT TO DO IN A MODULE
860	As a module author, you should "use AnyEvent" and call AnyEvent methods	1030	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.	1031	freely, but you should not load a specific event module or rely on it.
862		1032
863	Be careful when you create watchers in the module body - AnyEvent will	1033	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	1040	stall the whole program, and the whole point of using events is to stay
871	interactive.	1041	interactive.
872		1042
873	It is fine, however, to call "->recv" when the user of your module	1043	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	1044	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"	1045	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).	1046	as the user of your module knows what she is doing. Always).
877		1047
878	WHAT TO DO IN THE MAIN PROGRAM	1048	WHAT TO DO IN THE MAIN PROGRAM
879	There will always be a single main program - the only place that should	1049	There will always be a single main program - the only place that should
880	dictate which event model to use.	1050	dictate which event model to use.
881		1051
882	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1052	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	1053	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	1054	uses AnyEvent, but does not care which event loop is used, all it needs
885	it.	1055	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1056	available loop implementation.
886		1057
887	If the main program relies on a specific event model - for example, in	1058	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	1059	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:	1060	event module before loading AnyEvent or any module that uses it:
890	generally speaking, you should load it as early as possible. The reason	1061	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	1062	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,	1063	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	1064	and it might choose the wrong one unless you load the correct one
894	yourself.	1065	yourself.
895		1066
896	You can chose to use a pure-perl implementation by loading the	1067	You can chose to use a pure-perl implementation by loading the
897	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1068	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
898	everywhere, but letting AnyEvent chose the model is generally better.	1069	but letting AnyEvent chose the model is generally better.
899		1070
900	MAINLOOP EMULATION	1071	MAINLOOP EMULATION
901	Sometimes (often for short test scripts, or even standalone programs who	1072	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	1073	only want to use AnyEvent), you do not want to run a specific event
903	loop.	1074	loop.
…		…
915		1086
916	OTHER MODULES	1087	OTHER MODULES
917	The following is a non-exhaustive list of additional modules that use	1088	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	1089	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	1090	AnyEvent modules and other event loops in the same program. Some of the
920	modules come with AnyEvent, most are available via CPAN.	1091	modules come as part of AnyEvent, the others are available via CPAN (see
		1092	<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
		1093	non-exhaustive list), and the list is heavily biased towards modules of
		1094	the AnyEvent author himself :)
921		1095
922	AnyEvent::Util	1096	AnyEvent::Util (part of the AnyEvent distribution)
923	Contains various utility functions that replace often-used but	1097	Contains various utility functions that replace often-used blocking
924	blocking functions such as "inet_aton" by event-/callback-based	1098	functions such as "inet_aton" with event/callback-based versions.
925	versions.
926		1099
927	AnyEvent::Socket	1100	AnyEvent::Socket (part of the AnyEvent distribution)
928	Provides various utility functions for (internet protocol) sockets,	1101	Provides various utility functions for (internet protocol) sockets,
929	addresses and name resolution. Also functions to create non-blocking	1102	addresses and name resolution. Also functions to create non-blocking
930	tcp connections or tcp servers, with IPv6 and SRV record support and	1103	tcp connections or tcp servers, with IPv6 and SRV record support and
931	more.	1104	more.
932		1105
933	AnyEvent::Handle	1106	AnyEvent::Handle (part of the AnyEvent distribution)
934	Provide read and write buffers, manages watchers for reads and	1107	Provide read and write buffers, manages watchers for reads and
935	writes, supports raw and formatted I/O, I/O queued and fully	1108	writes, supports raw and formatted I/O, I/O queued and fully
936	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.	1109	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
937		1110
938	AnyEvent::DNS	1111	AnyEvent::DNS (part of the AnyEvent distribution)
939	Provides rich asynchronous DNS resolver capabilities.	1112	Provides rich asynchronous DNS resolver capabilities.
940		1113
		1114	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
		1115	AnyEvent::IGS, AnyEvent::FCP
		1116	Implement event-based interfaces to the protocols of the same name
		1117	(for the curious, IGS is the International Go Server and FCP is the
		1118	Freenet Client Protocol).
		1119
		1120	AnyEvent::AIO (part of the AnyEvent distribution)
		1121	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1122	the toolbox of every event programmer. AnyEvent::AIO transparently
		1123	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1124	event-based file I/O, and much more.
		1125
		1126	AnyEvent::Filesys::Notify
		1127	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1128	path changes (e.g. "watch this directory for new files", "watch this
		1129	file for changes"). The AnyEvent::Filesys::Notify module promises to
		1130	do just that in a portbale fashion, supporting inotify on GNU/Linux
		1131	and some weird, without doubt broken, stuff on OS X to monitor
		1132	files. It can fall back to blocking scans at regular intervals
		1133	transparently on other platforms, so it's about as portable as it
		1134	gets.
		1135
		1136	(I haven't used it myself, but I haven't heard anybody complaining
		1137	about it yet).
		1138
941	AnyEvent::HTTP	1139	AnyEvent::DBI
942	A simple-to-use HTTP library that is capable of making a lot of	1140	Executes DBI requests asynchronously in a proxy process for you,
943	concurrent HTTP requests.	1141	notifying you in an event-based way when the operation is finished.
944		1142
945	AnyEvent::HTTPD	1143	AnyEvent::HTTPD
946	Provides a simple web application server framework.	1144	A simple embedded webserver.
947		1145
948	AnyEvent::FastPing	1146	AnyEvent::FastPing
949	The fastest ping in the west.	1147	The fastest ping in the west.
950		1148
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	1149	Coro
987	Has special support for AnyEvent via Coro::AnyEvent.	1150	Has special support for AnyEvent via Coro::AnyEvent, which allows
		1151	you to simply invert the flow control - don't call us, we will call
		1152	you:
		1153
		1154	async {
		1155	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1156	print "5 seconds later!\n";
		1157
		1158	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1159	my $line = <STDIN>; # works for ttys
		1160
		1161	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1162	my ($body, $hdr) = Coro::rouse_wait;
		1163	};
		1164
		1165	SIMPLIFIED AE API
		1166	Starting with version 5.0, AnyEvent officially supports a second, much
		1167	simpler, API that is designed to reduce the calling, typing and memory
		1168	overhead by using function call syntax and a fixed number of parameters.
		1169
		1170	See the AE manpage for details.
988		1171
989	ERROR AND EXCEPTION HANDLING	1172	ERROR AND EXCEPTION HANDLING
990	In general, AnyEvent does not do any error handling - it relies on the	1173	In general, AnyEvent does not do any error handling - it relies on the
991	caller to do that if required. The AnyEvent::Strict module (see also the	1174	caller to do that if required. The AnyEvent::Strict module (see also the
992	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1175	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
1001	The pure perl event loop simply re-throws the exception (usually within	1184	The pure perl event loop simply re-throws the exception (usually within
1002	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1185	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
1003	Glib uses "install_exception_handler" and so on.	1186	Glib uses "install_exception_handler" and so on.
1004		1187
1005	ENVIRONMENT VARIABLES	1188	ENVIRONMENT VARIABLES
1006	The following environment variables are used by this module or its	1189	AnyEvent supports a number of environment variables that tune the
1007	submodules.	1190	runtime behaviour. They are usually evaluated when AnyEvent is loaded,
		1191	initialised, or a submodule that uses them is loaded. Many of them also
		1192	cause AnyEvent to load additional modules - for example,
		1193	"PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be
		1194	loaded.
1008		1195
1009	Note that AnyEvent will remove all environment variables starting with	1196	All the environment variables documented here start with
1010	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is	1197	"PERL_ANYEVENT_", which is what AnyEvent considers its own namespace.
1011	enabled.	1198	Other modules are encouraged (but by no means required) to use
		1199	"PERL_ANYEVENT_SUBMODULE" if they have registered the
		1200	AnyEvent::Submodule namespace on CPAN, for any submodule. For example,
		1201	AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it
		1202	should not access env variables starting with "AE_", see below).
		1203
		1204	All variables can also be set via the "AE_" prefix, that is, instead of
		1205	setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case
		1206	there is a clash btween anyevent and another program that uses
		1207	"AE_something" you can set the corresponding "PERL_ANYEVENT_something"
		1208	variable to the empty string, as those variables take precedence.
		1209
		1210	When AnyEvent is first loaded, it copies all "AE_xxx" env variables to
		1211	their "PERL_ANYEVENT_xxx" counterpart unless that variable already
		1212	exists. If taint mode is on, then AnyEvent will remove all environment
		1213	variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with
		1214	"undef" or the empty string, if the corresaponding "AE_" variable is
		1215	set).
		1216
		1217	The exact algorithm is currently:
		1218
		1219	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		1220	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		1221	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		1222
		1223	This ensures that child processes will not see the "AE_" variables.
		1224
		1225	The following environment variables are currently known to AnyEvent:
1012		1226
1013	"PERL_ANYEVENT_VERBOSE"	1227	"PERL_ANYEVENT_VERBOSE"
1014	By default, AnyEvent will be completely silent except in fatal	1228	By default, AnyEvent will log messages with loglevel 4 ("error") or
1015	conditions. You can set this environment variable to make AnyEvent	1229	higher (see AnyEvent::Log). You can set this environment variable to
1016	more talkative.	1230	a numerical loglevel to make AnyEvent more (or less) talkative.
1017		1231
		1232	If you want to do more than just set the global logging level you
		1233	should have a look at "PERL_ANYEVENT_LOG", which allows much more
		1234	complex specifications.
		1235
		1236	When set to 0 ("off"), then no messages whatsoever will be logged
		1237	with everything else at defaults.
		1238
1018	When set to 1 or higher, causes AnyEvent to warn about unexpected	1239	When set to 5 or higher ("warn"), AnyEvent warns about unexpected
1019	conditions, such as not being able to load the event model specified	1240	conditions, such as not being able to load the event model specified
1020	by "PERL_ANYEVENT_MODEL".	1241	by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception
		1242	- this is the minimum recommended level for use during development.
1021		1243
1022	When set to 2 or higher, cause AnyEvent to report to STDERR which	1244	When set to 7 or higher (info), AnyEvent reports which event model
1023	event model it chooses.	1245	it chooses.
1024		1246
1025	When set to 8 or higher, then AnyEvent will report extra information	1247	When set to 8 or higher (debug), then AnyEvent will report extra
1026	on which optional modules it loads and how it implements certain	1248	information on which optional modules it loads and how it implements
1027	features.	1249	certain features.
		1250
		1251	"PERL_ANYEVENT_LOG"
		1252	Accepts rather complex logging specifications. For example, you
		1253	could log all "debug" messages of some module to stderr, warnings
		1254	and above to stderr, and errors and above to syslog, with:
		1255
		1256	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		1257
		1258	For the rather extensive details, see AnyEvent::Log.
		1259
		1260	This variable is evaluated when AnyEvent (or AnyEvent::Log) is
		1261	loaded, so will take effect even before AnyEvent has initialised
		1262	itself.
		1263
		1264	Note that specifying this environment variable causes the
		1265	AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE"
		1266	does not, so only using the latter saves a few hundred kB of memory
		1267	unless a module explicitly needs the extra features of
		1268	AnyEvent::Log.
1028		1269
1029	"PERL_ANYEVENT_STRICT"	1270	"PERL_ANYEVENT_STRICT"
1030	AnyEvent does not do much argument checking by default, as thorough	1271	AnyEvent does not do much argument checking by default, as thorough
1031	argument checking is very costly. Setting this variable to a true	1272	argument checking is very costly. Setting this variable to a true
1032	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1273	value will cause AnyEvent to load "AnyEvent::Strict" and then to
1033	thoroughly check the arguments passed to most method calls. If it	1274	thoroughly check the arguments passed to most method calls. If it
1034	finds any problems, it will croak.	1275	finds any problems, it will croak.
1035		1276
1036	In other words, enables "strict" mode.	1277	In other words, enables "strict" mode.
1037		1278
1038	Unlike "use strict" (or it's modern cousin, "use common::sense", it	1279	Unlike "use strict" (or its modern cousin, "use common::sense", it
1039	is definitely recommended to keep it off in production. Keeping	1280	is definitely recommended to keep it off in production. Keeping
1040	"PERL_ANYEVENT_STRICT=1" in your environment while developing	1281	"PERL_ANYEVENT_STRICT=1" in your environment while developing
1041	programs can be very useful, however.	1282	programs can be very useful, however.
1042		1283
		1284	"PERL_ANYEVENT_DEBUG_SHELL"
		1285	If this env variable is nonempty, then its contents will be
		1286	interpreted by "AnyEvent::Socket::parse_hostport" and
		1287	"AnyEvent::Debug::shell" (after replacing every occurance of $$ by
		1288	the process pid). The shell object is saved in
		1289	$AnyEvent::Debug::SHELL.
		1290
		1291	This happens when the first watcher is created.
		1292
		1293	For example, to bind a debug shell on a unix domain socket in
		1294	/tmp/debug<pid>.sock, you could use this:
		1295
		1296	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		1297	# connect with e.g.: socat readline /tmp/debug123.sock
		1298
		1299	Or to bind to tcp port 4545 on localhost:
		1300
		1301	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		1302	# connect with e.g.: telnet localhost 4545
		1303
		1304	Note that creating sockets in /tmp or on localhost is very unsafe on
		1305	multiuser systems.
		1306
		1307	"PERL_ANYEVENT_DEBUG_WRAP"
		1308	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1309	debugging purposes. See "AnyEvent::Debug::wrap" for details.
		1310
1043	"PERL_ANYEVENT_MODEL"	1311	"PERL_ANYEVENT_MODEL"
1044	This can be used to specify the event model to be used by AnyEvent,	1312	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	1313	before auto detection and -probing kicks in.
1046	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1314
1047	gets prepended and the resulting module name is loaded and if the	1315	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	1316	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1317	the resulting module name is loaded and - if the load was successful
		1318	- used as event model backend. If it fails to load then AnyEvent
1049	AnyEvent will proceed with auto detection and -probing.	1319	will proceed with auto detection and -probing.
1050		1320
1051	This functionality might change in future versions.	1321	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1322	then nothing gets prepended and the module name is used as-is (hint:
		1323	"::" at the end of a string designates a module name and quotes it
		1324	appropriately).
1052		1325
1053	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1326	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
1054	could start your program like this:	1327	could start your program like this:
1055		1328
1056	PERL_ANYEVENT_MODEL=Perl perl ...	1329	PERL_ANYEVENT_MODEL=Perl perl ...
		1330
		1331	"PERL_ANYEVENT_IO_MODEL"
		1332	The current file I/O model - see AnyEvent::IO for more info.
		1333
		1334	At the moment, only "Perl" (small, pure-perl, synchronous) and
		1335	"IOAIO" (truly asynchronous) are supported. The default is "IOAIO"
		1336	if AnyEvent::AIO can be loaded, otherwise it is "Perl".
1057		1337
1058	"PERL_ANYEVENT_PROTOCOLS"	1338	"PERL_ANYEVENT_PROTOCOLS"
1059	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1339	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
1060	preferences for IPv4 or IPv6. The default is unspecified (and might	1340	preferences for IPv4 or IPv6. The default is unspecified (and might
1061	change, or be the result of auto probing).	1341	change, or be the result of auto probing).
…		…
1075	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1355	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
1076	resolve or contact IPv6 addresses.	1356	resolve or contact IPv6 addresses.
1077	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but	1357	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
1078	prefer IPv6 over IPv4.	1358	prefer IPv6 over IPv4.
1079		1359
		1360	"PERL_ANYEVENT_HOSTS"
		1361	This variable, if specified, overrides the /etc/hosts file used by
		1362	AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be
		1363	read from that file instead.
		1364
1080	"PERL_ANYEVENT_EDNS0"	1365	"PERL_ANYEVENT_EDNS0"
1081	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension	1366	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
1082	for DNS. This extension is generally useful to reduce DNS traffic,	1367	for DNS. This extension is generally useful to reduce DNS traffic,
1083	but some (broken) firewalls drop such DNS packets, which is why it	1368	especially when DNSSEC is involved, but some (broken) firewalls drop
1084	is off by default.	1369	such DNS packets, which is why it is off by default.
1085		1370
1086	Setting this variable to 1 will cause AnyEvent::DNS to announce	1371	Setting this variable to 1 will cause AnyEvent::DNS to announce
1087	EDNS0 in its DNS requests.	1372	EDNS0 in its DNS requests.
1088		1373
1089	"PERL_ANYEVENT_MAX_FORKS"	1374	"PERL_ANYEVENT_MAX_FORKS"
…		…
1093	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"	1378	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
1094	The default value for the "max_outstanding" parameter for the	1379	The default value for the "max_outstanding" parameter for the
1095	default DNS resolver - this is the maximum number of parallel DNS	1380	default DNS resolver - this is the maximum number of parallel DNS
1096	requests that are sent to the DNS server.	1381	requests that are sent to the DNS server.
1097		1382
		1383	"PERL_ANYEVENT_MAX_SIGNAL_LATENCY"
		1384	Perl has inherently racy signal handling (you can basically choose
		1385	between losing signals and memory corruption) - pure perl event
		1386	loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't
		1387	available) therefore have to poll regularly to avoid losing signals.
		1388
		1389	Some event loops are racy, but don't poll regularly, and some event
		1390	loops are written in C but are still racy. For those event loops,
		1391	AnyEvent installs a timer that regularly wakes up the event loop.
		1392
		1393	By default, the interval for this timer is 10 seconds, but you can
		1394	override this delay with this environment variable (or by setting
		1395	the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal
		1396	watchers).
		1397
		1398	Lower values increase CPU (and energy) usage, higher values can
		1399	introduce long delays when reaping children or waiting for signals.
		1400
		1401	The AnyEvent::Async module, if available, will be used to avoid this
		1402	polling (with most event loops).
		1403
1098	"PERL_ANYEVENT_RESOLV_CONF"	1404	"PERL_ANYEVENT_RESOLV_CONF"
1099	The file to use instead of /etc/resolv.conf (or OS-specific	1405	The absolute path to a resolv.conf-style file to use instead of
1100	configuration) in the default resolver. When set to the empty	1406	/etc/resolv.conf (or the OS-specific configuration) in the default
1101	string, no default config will be used.	1407	resolver, or the empty string to select the default configuration.
1102		1408
1103	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".	1409	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1104	When neither "ca_file" nor "ca_path" was specified during	1410	When neither "ca_file" nor "ca_path" was specified during
1105	AnyEvent::TLS context creation, and either of these environment	1411	AnyEvent::TLS context creation, and either of these environment
1106	variables exist, they will be used to specify CA certificate	1412	variables are nonempty, they will be used to specify CA certificate
1107	locations instead of a system-dependent default.	1413	locations instead of a system-dependent default.
1108		1414
1109	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"	1415	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
1110	When these are set to 1, then the respective modules are not loaded.	1416	When these are set to 1, then the respective modules are not loaded.
1111	Mostly good for testing AnyEvent itself.	1417	Mostly good for testing AnyEvent itself.
…		…
1171	warn "read: $input\n"; # output what has been read	1477	warn "read: $input\n"; # output what has been read
1172	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1478	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1173	},	1479	},
1174	);	1480	);
1175		1481
1176	my $time_watcher; # can only be used once
1177
1178	sub new_timer {
1179	$timer = AnyEvent->timer (after => 1, cb => sub {	1482	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1180	warn "timeout\n"; # print 'timeout' about every second	1483	warn "timeout\n"; # print 'timeout' at most every second
1181	&new_timer; # and restart the time
1182	});
1183	}	1484	});
1184
1185	new_timer; # create first timer
1186		1485
1187	$cv->recv; # wait until user enters /^q/i	1486	$cv->recv; # wait until user enters /^q/i
1188		1487
1189	REAL-WORLD EXAMPLE	1488	REAL-WORLD EXAMPLE
1190	Consider the Net::FCP module. It features (among others) the following	1489	Consider the Net::FCP module. It features (among others) the following
…		…
1262		1561
1263	The actual code goes further and collects all errors ("die"s,	1562	The actual code goes further and collects all errors ("die"s,
1264	exceptions) that occurred during request processing. The "result" method	1563	exceptions) that occurred during request processing. The "result" method
1265	detects whether an exception as thrown (it is stored inside the $txn	1564	detects whether an exception as thrown (it is stored inside the $txn
1266	object) and just throws the exception, which means connection errors and	1565	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,	1566	other problems get reported to the code that tries to use the result,
1268	not in a random callback.	1567	not in a random callback.
1269		1568
1270	All of this enables the following usage styles:	1569	All of this enables the following usage styles:
1271		1570
1272	1. Blocking:	1571	1. Blocking:
…		…
1317	through AnyEvent. The benchmark creates a lot of timers (with a zero	1616	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,	1617	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.	1618	which it is), lets them fire exactly once and destroys them again.
1320		1619
1321	Source code for this benchmark is found as eg/bench in the AnyEvent	1620	Source code for this benchmark is found as eg/bench in the AnyEvent
1322	distribution.	1621	distribution. It uses the AE interface, which makes a real difference
		1622	for the EV and Perl backends only.
1323		1623
1324	Explanation of the columns	1624	Explanation of the columns
1325	watcher is the number of event watchers created/destroyed. Since	1625	watcher is the number of event watchers created/destroyed. Since
1326	different event models feature vastly different performances, each event	1626	different event models feature vastly different performances, each event
1327	loop was given a number of watchers so that overall runtime is	1627	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	1646	destroy is the time, in microseconds, that it takes to destroy a
1347	single watcher.	1647	single watcher.
1348		1648
1349	Results	1649	Results
1350	name watchers bytes create invoke destroy comment	1650	name watchers bytes create invoke destroy comment
1351	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1651	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	1652	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	1653	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	1654	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	1655	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	1656	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	1657	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	1658	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	1659	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	1660	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	1661	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	1662	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1363		1663
1364	Discussion	1664	Discussion
1365	The benchmark does not measure scalability of the event loop very	1665	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)	1666	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	1667	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	1678	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	1679	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1380	CPU cycles with POE.	1680	CPU cycles with POE.
1381		1681
1382	"EV" is the sole leader regarding speed and memory use, which are both	1682	"EV" is the sole leader regarding speed and memory use, which are both
1383	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1683	maximal/minimal, respectively. When using the AE API there is zero
		1684	overhead (when going through the AnyEvent API create is about 5-6 times
		1685	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	1686	any other event loop and is still faster than Event natively).
1385	natively.
1386		1687
1387	The pure perl implementation is hit in a few sweet spots (both the	1688	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	1689	constant timeout and the use of a single fd hit optimisations in the
1389	perl interpreter and the backend itself). Nevertheless this shows that	1690	perl interpreter and the backend itself). Nevertheless this shows that
1390	it adds very little overhead in itself. Like any select-based backend	1691	it adds very little overhead in itself. Like any select-based backend
…		…
1436	when used without AnyEvent), but most event loops have acceptable	1737	when used without AnyEvent), but most event loops have acceptable
1437	performance with or without AnyEvent.	1738	performance with or without AnyEvent.
1438		1739
1439	* The overhead AnyEvent adds is usually much smaller than the overhead	1740	* The overhead AnyEvent adds is usually much smaller than the overhead
1440	of the actual event loop, only with extremely fast event loops such	1741	of the actual event loop, only with extremely fast event loops such
1441	as EV adds AnyEvent significant overhead.	1742	as EV does AnyEvent add significant overhead.
1442		1743
1443	* You should avoid POE like the plague if you want performance or	1744	* You should avoid POE like the plague if you want performance or
1444	reasonable memory usage.	1745	reasonable memory usage.
1445		1746
1446	BENCHMARKING THE LARGE SERVER CASE	1747	BENCHMARKING THE LARGE SERVER CASE
…		…
1460	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1761	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	1762	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.	1763	many connections, most of which are idle at any one point in time.
1463		1764
1464	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1765	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1465	distribution.	1766	distribution. It uses the AE interface, which makes a real difference
		1767	for the EV and Perl backends only.
1466		1768
1467	Explanation of the columns	1769	Explanation of the columns
1468	sockets is the number of sockets, and twice the number of "servers"	1770	sockets is the number of sockets, and twice the number of "servers"
1469	(as each server has a read and write socket end).	1771	(as each server has a read and write socket end).
1470		1772
…		…
1476	forwarding it to another server. This includes deleting the old timeout	1778	forwarding it to another server. This includes deleting the old timeout
1477	and creating a new one that moves the timeout into the future.	1779	and creating a new one that moves the timeout into the future.
1478		1780
1479	Results	1781	Results
1480	name sockets create request	1782	name sockets create request
1481	EV 20000 69.01 11.16	1783	EV 20000 62.66 7.99
1482	Perl 20000 73.32 35.87	1784	Perl 20000 68.32 32.64
1483	IOAsync 20000 157.00 98.14 epoll	1785	IOAsync 20000 174.06 101.15 epoll
1484	IOAsync 20000 159.31 616.06 poll	1786	IOAsync 20000 174.67 610.84 poll
1485	Event 20000 212.62 257.32	1787	Event 20000 202.69 242.91
1486	Glib 20000 651.16 1896.30	1788	Glib 20000 557.01 1689.52
1487	POE 20000 349.67 12317.24 uses POE::Loop::Event	1789	POE 20000 341.54 12086.32 uses POE::Loop::Event
1488		1790
1489	Discussion	1791	Discussion
1490	This benchmark does measure scalability and overall performance of the	1792	This benchmark does measure scalability and overall performance of the
1491	particular event loop.	1793	particular event loop.
1492		1794
…		…
1605	As you can see, the AnyEvent + EV combination even beats the	1907	As you can see, the AnyEvent + EV combination even beats the
1606	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl	1908	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1607	backend easily beats IO::Lambda and POE.	1909	backend easily beats IO::Lambda and POE.
1608		1910
1609	And even the 100% non-blocking version written using the high-level (and	1911	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	1912	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	1913	higher level ("unoptimised") abstractions by a large margin, even though
1612	in a non-blocking way.	1914	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
1613		1915
1614	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and	1916	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	1917	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1616	part of the IO::lambda distribution and were used without any changes.	1918	part of the IO::Lambda distribution and were used without any changes.
1617		1919
1618	SIGNALS	1920	SIGNALS
1619	AnyEvent currently installs handlers for these signals:	1921	AnyEvent currently installs handlers for these signals:
1620		1922
1621	SIGCHLD	1923	SIGCHLD
…		…
1643		1945
1644	Feel free to install your own handler, or reset it to defaults.	1946	Feel free to install your own handler, or reset it to defaults.
1645		1947
1646	RECOMMENDED/OPTIONAL MODULES	1948	RECOMMENDED/OPTIONAL MODULES
1647	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and	1949	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.	1950	its built-in modules) are required to use it.
1649		1951
1650	That does not mean that AnyEvent won't take advantage of some additional	1952	That does not mean that AnyEvent won't take advantage of some additional
1651	modules if they are installed.	1953	modules if they are installed.
1652		1954
1653	This section epxlains which additional modules will be used, and how	1955	This section explains which additional modules will be used, and how
1654	they affect AnyEvent's operetion.	1956	they affect AnyEvent's operation.
1655		1957
1656	Async::Interrupt	1958	Async::Interrupt
1657	This slightly arcane module is used to implement fast signal	1959	This slightly arcane module is used to implement fast signal
1658	handling: To my knowledge, there is no way to do completely	1960	handling: To my knowledge, there is no way to do completely
1659	race-free and quick signal handling in pure perl. To ensure that	1961	race-free and quick signal handling in pure perl. To ensure that
…		…
1662	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).	1964	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
1663		1965
1664	If this module is available, then it will be used to implement	1966	If this module is available, then it will be used to implement
1665	signal catching, which means that signals will not be delayed, and	1967	signal catching, which means that signals will not be delayed, and
1666	the event loop will not be interrupted regularly, which is more	1968	the event loop will not be interrupted regularly, which is more
1667	efficient (And good for battery life on laptops).	1969	efficient (and good for battery life on laptops).
1668		1970
1669	This affects not just the pure-perl event loop, but also other event	1971	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).	1972	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
1671		1973
1672	Some event loops (POE, Event, Event::Lib) offer signal watchers	1974	Some event loops (POE, Event, Event::Lib) offer signal watchers
…		…
1682	clock is available, can take avdantage of advanced kernel interfaces	1984	clock is available, can take avdantage of advanced kernel interfaces
1683	such as "epoll" and "kqueue", and is the fastest backend by far.	1985	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	1986	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
1685	Glib::EV).	1987	Glib::EV).
1686		1988
		1989	If you only use backends that rely on another event loop (e.g.
		1990	"Tk"), then this module will do nothing for you.
		1991
1687	Guard	1992	Guard
1688	The guard module, when used, will be used to implement	1993	The guard module, when used, will be used to implement
1689	"AnyEvent::Util::guard". This speeds up guards considerably (and	1994	"AnyEvent::Util::guard". This speeds up guards considerably (and
1690	uses a lot less memory), but otherwise doesn't affect guard	1995	uses a lot less memory), but otherwise doesn't affect guard
1691	operation much. It is purely used for performance.	1996	operation much. It is purely used for performance.
1692		1997
1693	JSON and JSON::XS	1998	JSON and JSON::XS
1694	This module is required when you want to read or write JSON data via	1999	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	2000	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	2001	can take advantage of the ultra-high-speed JSON::XS module when it
1697	installed.	2002	is installed.
1698
1699	In fact, AnyEvent::Handle will use JSON::XS by default if it is
1700	installed.
1701		2003
1702	Net::SSLeay	2004	Net::SSLeay
1703	Implementing TLS/SSL in Perl is certainly interesting, but not very	2005	Implementing TLS/SSL in Perl is certainly interesting, but not very
1704	worthwhile: If this module is installed, then AnyEvent::Handle (with	2006	worthwhile: If this module is installed, then AnyEvent::Handle (with
1705	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.	2007	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
1706		2008
1707	Time::HiRes	2009	Time::HiRes
1708	This module is part of perl since release 5.008. It will be used	2010	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	2011	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	2012	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
1711	additionally use it to try to use a monotonic clock for timing	2013	load it to try to use a monotonic clock for timing stability.
1712	stability.	2014
		2015	AnyEvent::AIO (and IO::AIO)
		2016	The default implementation of AnyEvent::IO is to do I/O
		2017	synchronously, stopping programs while they access the disk, which
		2018	is fine for a lot of programs.
		2019
		2020	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it
		2021	switch to a true asynchronous implementation, so event processing
		2022	can continue even while waiting for disk I/O.
1713		2023
1714	FORK	2024	FORK
1715	Most event libraries are not fork-safe. The ones who are usually are	2025	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.	2026	because they rely on inefficient but fork-safe "select" or "poll" calls
1717	Only EV is fully fork-aware.	2027	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		2028	epoll are usually badly thought-out hacks that are incompatible with
		2029	fork in one way or another. Only EV is fully fork-aware and ensures that
		2030	you continue event-processing in both parent and child (or both, if you
		2031	know what you are doing).
		2032
		2033	This means that, in general, you cannot fork and do event processing in
		2034	the child if the event library was initialised before the fork (which
		2035	usually happens when the first AnyEvent watcher is created, or the
		2036	library is loaded).
1718		2037
1719	If you have to fork, you must either do so before creating your first	2038	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	2039	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.	2040	something completely out of the scope of AnyEvent.
		2041
		2042	The problem of doing event processing in the parent and the child is
		2043	much more complicated: even for backends that are fork-aware or
		2044	fork-safe, their behaviour is not usually what you want: fork clones all
		2045	watchers, that means all timers, I/O watchers etc. are active in both
		2046	parent and child, which is almost never what you want. USing "exec" to
		2047	start worker children from some kind of manage rprocess is usually
		2048	preferred, because it is much easier and cleaner, at the expense of
		2049	having to have another binary.
1722		2050
1723	SECURITY CONSIDERATIONS	2051	SECURITY CONSIDERATIONS
1724	AnyEvent can be forced to load any event model via	2052	AnyEvent can be forced to load any event model via
1725	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	2053	$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	2054	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	2078	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	2079	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1752	not as pronounced).	2080	not as pronounced).
1753		2081
1754	SEE ALSO	2082	SEE ALSO
1755	Utility functions: AnyEvent::Util.	2083	Tutorial/Introduction: AnyEvent::Intro.
1756		2084
1757	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	2085	FAQ: AnyEvent::FAQ.
1758	Event::Lib, Qt, POE.	2086
		2087	Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log
		2088	(simply logging).
		2089
		2090	Development/Debugging: AnyEvent::Strict (stricter checking),
		2091	AnyEvent::Debug (interactive shell, watcher tracing).
		2092
		2093	Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
		2094	Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK.
1759		2095
1760	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	2096	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1761	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	2097	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1762	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,	2098	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1763	AnyEvent::Impl::IOAsync.	2099	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi, AnyEvent::Impl::FLTK.
1764		2100
1765	Non-blocking file handles, sockets, TCP clients and servers:	2101	Non-blocking handles, pipes, stream sockets, TCP clients and servers:
1766	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.	2102	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1767		2103
		2104	Asynchronous File I/O: AnyEvent::IO.
		2105
1768	Asynchronous DNS: AnyEvent::DNS.	2106	Asynchronous DNS: AnyEvent::DNS.
1769		2107
1770	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	2108	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1771		2109
1772	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,	2110	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
1773	AnyEvent::HTTP.	2111	AnyEvent::HTTP.
1774		2112
1775	AUTHOR	2113	AUTHOR
1776	Marc Lehmann <schmorp@schmorp.de>	2114	Marc Lehmann <schmorp@schmorp.de>
1777	http://home.schmorp.de/	2115	http://anyevent.schmorp.de
1778		2116

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 1.71 by root, Wed Aug 21 08:40:28 2013 UTC

Diff Legend

Comparing AnyEvent/README (file contents):
Revision 1.47 by root, Mon Jul 20 22:39:57 2009 UTC vs.
Revision 1.71 by root, Wed Aug 21 08:40:28 2013 UTC