[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.46 by root, Sat Jul 18 05:19:09 2009 UTC vs.
Revision 1.76 by root, Wed Jan 27 18:15:21 2016 UTC

…		…
1	NAME	1	NAME
2	AnyEvent - provide framework for multiple event loops	2	AnyEvent - the DBI of event loop programming
3		3
4	EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported	4	EV, Event, Glib, Tk, UV, Perl, Event::Lib, Irssi, rxvt-unicode,
5	event loops.	5	IO::Async, Qt, FLTK and POE are various supported event
		6	loops/environments.
6		7
7	SYNOPSIS	8	SYNOPSIS
8	use AnyEvent;	9	use AnyEvent;
9		10
		11	# if you prefer function calls, look at the AE manpage for
		12	# an alternative API.
		13
10	# file descriptor readable	14	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });	15	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
12		16
13	# one-shot or repeating timers	17	# one-shot or repeating timers
14	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });	18	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
15	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...	19	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
16		20
17	print AnyEvent->now; # prints current event loop time	21	print AnyEvent->now; # prints current event loop time
18	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.	22	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
19		23
20	# POSIX signal	24	# POSIX signal
37		41
38	INTRODUCTION/TUTORIAL	42	INTRODUCTION/TUTORIAL
39	This manpage is mainly a reference manual. If you are interested in a	43	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	44	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
41	manpage.	45	manpage.
		46
		47	SUPPORT
		48	An FAQ document is available as AnyEvent::FAQ.
		49
		50	There also is a mailinglist for discussing all things AnyEvent, and an
		51	IRC channel, too.
		52
		53	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
		54	Repository, at <http://anyevent.schmorp.de>, for more info.
42		55
43	WHY YOU SHOULD USE THIS MODULE (OR NOT)	56	WHY YOU SHOULD USE THIS MODULE (OR NOT)
44	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	57	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
45	nowadays. So what is different about AnyEvent?	58	nowadays. So what is different about AnyEvent?
46		59
…		…
61	module users into the same thing by forcing them to use the same event	74	module users into the same thing by forcing them to use the same event
62	model you use.	75	model you use.
63		76
64	For modules like POE or IO::Async (which is a total misnomer as it is	77	For modules like POE or IO::Async (which is a total misnomer as it is
65	actually doing all I/O synchronously...), using them in your module is	78	actually doing all I/O synchronously...), using them in your module is
66	like joining a cult: After you joined, you are dependent on them and you	79	like joining a cult: After you join, you are dependent on them and you
67	cannot use anything else, as they are simply incompatible to everything	80	cannot use anything else, as they are simply incompatible to everything
68	that isn't them. What's worse, all the potential users of your module	81	that isn't them. What's worse, all the potential users of your module
69	are also forced to use the same event loop you use.	82	are also forced to use the same event loop you use.
70		83
71	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	84	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
72	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	85	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
73	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your	86	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
74	module uses one of those, every user of your module has to use it, too.	87	uses one of those, every user of your module has to use it, too. But if
75	But if your module uses AnyEvent, it works transparently with all event	88	your module uses AnyEvent, it works transparently with all event models
76	models it supports (including stuff like IO::Async, as long as those use	89	it supports (including stuff like IO::Async, as long as those use one of
77	one of the supported event loops. It is trivial to add new event loops	90	the supported event loops. It is easy to add new event loops to
78	to AnyEvent, too, so it is future-proof).	91	AnyEvent, too, so it is future-proof).
79		92
80	In addition to being free of having to use *the one and only true event	93	In addition to being free of having to use *the one and only true event
81	model*, AnyEvent also is free of bloat and policy: with POE or similar	94	model*, AnyEvent also is free of bloat and policy: with POE or similar
82	modules, you get an enormous amount of code and strict rules you have to	95	modules, you get an enormous amount of code and strict rules you have to
83	follow. AnyEvent, on the other hand, is lean and up to the point, by	96	follow. AnyEvent, on the other hand, is lean and to the point, by only
84	only offering the functionality that is necessary, in as thin as a	97	offering the functionality that is necessary, in as thin as a wrapper as
85	wrapper as technically possible.	98	technically possible.
86		99
87	Of course, AnyEvent comes with a big (and fully optional!) toolbox of	100	Of course, AnyEvent comes with a big (and fully optional!) toolbox of
88	useful functionality, such as an asynchronous DNS resolver, 100%	101	useful functionality, such as an asynchronous DNS resolver, 100%
89	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms	102	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
90	such as Windows) and lots of real-world knowledge and workarounds for	103	such as Windows) and lots of real-world knowledge and workarounds for
…		…
93	Now, if you do want lots of policy (this can arguably be somewhat	106	Now, if you do want lots of policy (this can arguably be somewhat
94	useful) and you want to force your users to use the one and only event	107	useful) and you want to force your users to use the one and only event
95	model, you should not use this module.	108	model, you should not use this module.
96		109
97	DESCRIPTION	110	DESCRIPTION
98	AnyEvent provides an identical interface to multiple event loops. This	111	AnyEvent provides a uniform interface to various event loops. This
99	allows module authors to utilise an event loop without forcing module	112	allows module authors to use event loop functionality without forcing
100	users to use the same event loop (as only a single event loop can	113	module users to use a specific event loop implementation (since more
101	coexist peacefully at any one time).	114	than one event loop cannot coexist peacefully).
102		115
103	The interface itself is vaguely similar, but not identical to the Event	116	The interface itself is vaguely similar, but not identical to the Event
104	module.	117	module.
105		118
106	During the first call of any watcher-creation method, the module tries	119	During the first call of any watcher-creation method, the module tries
107	to detect the currently loaded event loop by probing whether one of the	120	to detect the currently loaded event loop by probing whether one of the
108	following modules is already loaded: EV, Event, Glib,	121	following modules is already loaded: EV, AnyEvent::Loop, Event, Glib,
109	AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is	122	Tk, Event::Lib, Qt, POE. The first one found is used. If none are
110	used. If none are found, the module tries to load these modules	123	detected, the module tries to load the first four modules in the order
111	(excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should	124	given; but note that if EV is not available, the pure-perl
112	always succeed) in the order given. The first one that can be	125	AnyEvent::Loop should always work, so the other two are not normally
113	successfully loaded will be used. If, after this, still none could be	126	tried.
114	found, AnyEvent will fall back to a pure-perl event loop, which is not
115	very efficient, but should work everywhere.
116		127
117	Because AnyEvent first checks for modules that are already loaded,	128	Because AnyEvent first checks for modules that are already loaded,
118	loading an event model explicitly before first using AnyEvent will	129	loading an event model explicitly before first using AnyEvent will
119	likely make that model the default. For example:	130	likely make that model the default. For example:
120		131
…		…
122	use AnyEvent;	133	use AnyEvent;
123		134
124	# .. AnyEvent will likely default to Tk	135	# .. AnyEvent will likely default to Tk
125		136
126	The likely means that, if any module loads another event model and	137	The likely means that, if any module loads another event model and
127	starts using it, all bets are off. Maybe you should tell their authors	138	starts using it, all bets are off - this case should be very rare
128	to use AnyEvent so their modules work together with others seamlessly...	139	though, as very few modules hardcode event loops without announcing this
		140	very loudly.
129		141
130	The pure-perl implementation of AnyEvent is called	142	The pure-perl implementation of AnyEvent is called "AnyEvent::Loop".
131	"AnyEvent::Impl::Perl". Like other event modules you can load it	143	Like other event modules you can load it explicitly and enjoy the high
132	explicitly and enjoy the high availability of that event loop :)	144	availability of that event loop :)
133		145
134	WATCHERS	146	WATCHERS
135	AnyEvent has the central concept of a watcher, which is an object that	147	AnyEvent has the central concept of a watcher, which is an object that
136	stores relevant data for each kind of event you are waiting for, such as	148	stores relevant data for each kind of event you are waiting for, such as
137	the callback to call, the file handle to watch, etc.	149	the callback to call, the file handle to watch, etc.
…		…
141	callback when the event occurs (of course, only when the event model is	153	callback when the event occurs (of course, only when the event model is
142	in control).	154	in control).
143		155
144	Note that callbacks must not permanently change global variables	156	Note that callbacks must not permanently change global variables
145	potentially in use by the event loop (such as $_ or $[) and that	157	potentially in use by the event loop (such as $_ or $[) and that
146	callbacks must not "die". The former is good programming practise in	158	callbacks must not "die". The former is good programming practice in
147	Perl and the latter stems from the fact that exception handling differs	159	Perl and the latter stems from the fact that exception handling differs
148	widely between event loops.	160	widely between event loops.
149		161
150	To disable the watcher you have to destroy it (e.g. by setting the	162	To disable a watcher you have to destroy it (e.g. by setting the
151	variable you store it in to "undef" or otherwise deleting all references	163	variable you store it in to "undef" or otherwise deleting all references
152	to it).	164	to it).
153		165
154	All watchers are created by calling a method on the "AnyEvent" class.	166	All watchers are created by calling a method on the "AnyEvent" class.
155		167
156	Many watchers either are used with "recursion" (repeating timers for	168	Many watchers either are used with "recursion" (repeating timers for
157	example), or need to refer to their watcher object in other ways.	169	example), or need to refer to their watcher object in other ways.
158		170
159	An any way to achieve that is this pattern:	171	One way to achieve that is this pattern:
160		172
161	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	173	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
162	# you can use $w here, for example to undef it	174	# you can use $w here, for example to undef it
163	undef $w;	175	undef $w;
164	});	176	});
…		…
166	Note that "my $w; $w =" combination. This is necessary because in Perl,	178	Note that "my $w; $w =" combination. This is necessary because in Perl,
167	my variables are only visible after the statement in which they are	179	my variables are only visible after the statement in which they are
168	declared.	180	declared.
169		181
170	I/O WATCHERS	182	I/O WATCHERS
		183	$w = AnyEvent->io (
		184	fh => <filehandle_or_fileno>,
		185	poll => <"r" or "w">,
		186	cb => <callback>,
		187	);
		188
171	You can create an I/O watcher by calling the "AnyEvent->io" method with	189	You can create an I/O watcher by calling the "AnyEvent->io" method with
172	the following mandatory key-value pairs as arguments:	190	the following mandatory key-value pairs as arguments:
173		191
174	"fh" is the Perl file handle (or a naked file descriptor) to watch for	192	"fh" is the Perl file handle (or a naked file descriptor) to watch for
175	events (AnyEvent might or might not keep a reference to this file	193	events (AnyEvent might or might not keep a reference to this file
…		…
189		207
190	The I/O watcher might use the underlying file descriptor or a copy of	208	The I/O watcher might use the underlying file descriptor or a copy of
191	it. You must not close a file handle as long as any watcher is active on	209	it. You must not close a file handle as long as any watcher is active on
192	the underlying file descriptor.	210	the underlying file descriptor.
193		211
194	Some event loops issue spurious readyness notifications, so you should	212	Some event loops issue spurious readiness notifications, so you should
195	always use non-blocking calls when reading/writing from/to your file	213	always use non-blocking calls when reading/writing from/to your file
196	handles.	214	handles.
197		215
198	Example: wait for readability of STDIN, then read a line and disable the	216	Example: wait for readability of STDIN, then read a line and disable the
199	watcher.	217	watcher.
…		…
203	warn "read: $input\n";	221	warn "read: $input\n";
204	undef $w;	222	undef $w;
205	});	223	});
206		224
207	TIME WATCHERS	225	TIME WATCHERS
		226	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		227
		228	$w = AnyEvent->timer (
		229	after => <fractional_seconds>,
		230	interval => <fractional_seconds>,
		231	cb => <callback>,
		232	);
		233
208	You can create a time watcher by calling the "AnyEvent->timer" method	234	You can create a time watcher by calling the "AnyEvent->timer" method
209	with the following mandatory arguments:	235	with the following mandatory arguments:
210		236
211	"after" specifies after how many seconds (fractional values are	237	"after" specifies after how many seconds (fractional values are
212	supported) the callback should be invoked. "cb" is the callback to	238	supported) the callback should be invoked. "cb" is the callback to
…		…
214		240
215	Although the callback might get passed parameters, their value and	241	Although the callback might get passed parameters, their value and
216	presence is undefined and you cannot rely on them. Portable AnyEvent	242	presence is undefined and you cannot rely on them. Portable AnyEvent
217	callbacks cannot use arguments passed to time watcher callbacks.	243	callbacks cannot use arguments passed to time watcher callbacks.
218		244
219	The callback will normally be invoked once only. If you specify another	245	The callback will normally be invoked only once. If you specify another
220	parameter, "interval", as a strictly positive number (> 0), then the	246	parameter, "interval", as a strictly positive number (> 0), then the
221	callback will be invoked regularly at that interval (in fractional	247	callback will be invoked regularly at that interval (in fractional
222	seconds) after the first invocation. If "interval" is specified with a	248	seconds) after the first invocation. If "interval" is specified with a
223	false value, then it is treated as if it were missing.	249	false value, then it is treated as if it were not specified at all.
224		250
225	The callback will be rescheduled before invoking the callback, but no	251	The callback will be rescheduled before invoking the callback, but no
226	attempt is done to avoid timer drift in most backends, so the interval	252	attempt is made to avoid timer drift in most backends, so the interval
227	is only approximate.	253	is only approximate.
228		254
229	Example: fire an event after 7.7 seconds.	255	Example: fire an event after 7.7 seconds.
230		256
231	my $w = AnyEvent->timer (after => 7.7, cb => sub {	257	my $w = AnyEvent->timer (after => 7.7, cb => sub {
…		…
237		263
238	Example 2: fire an event after 0.5 seconds, then roughly every second.	264	Example 2: fire an event after 0.5 seconds, then roughly every second.
239		265
240	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {	266	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
241	warn "timeout\n";	267	warn "timeout\n";
242	};	268	});
243		269
244	TIMING ISSUES	270	TIMING ISSUES
245	There are two ways to handle timers: based on real time (relative, "fire	271	There are two ways to handle timers: based on real time (relative, "fire
246	in 10 seconds") and based on wallclock time (absolute, "fire at 12	272	in 10 seconds") and based on wallclock time (absolute, "fire at 12
247	o'clock").	273	o'clock").
248		274
249	While most event loops expect timers to specified in a relative way,	275	While most event loops expect timers to specified in a relative way,
250	they use absolute time internally. This makes a difference when your	276	they use absolute time internally. This makes a difference when your
251	clock "jumps", for example, when ntp decides to set your clock backwards	277	clock "jumps", for example, when ntp decides to set your clock backwards
252	from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is	278	from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is
253	supposed to fire "after" a second might actually take six years to	279	supposed to fire "after a second" might actually take six years to
254	finally fire.	280	finally fire.
255		281
256	AnyEvent cannot compensate for this. The only event loop that is	282	AnyEvent cannot compensate for this. The only event loop that is
257	conscious about these issues is EV, which offers both relative	283	conscious of these issues is EV, which offers both relative (ev_timer,
258	(ev_timer, based on true relative time) and absolute (ev_periodic, based	284	based on true relative time) and absolute (ev_periodic, based on
259	on wallclock time) timers.	285	wallclock time) timers.
260		286
261	AnyEvent always prefers relative timers, if available, matching the	287	AnyEvent always prefers relative timers, if available, matching the
262	AnyEvent API.	288	AnyEvent API.
263		289
264	AnyEvent has two additional methods that return the "current time":	290	AnyEvent has two additional methods that return the "current time":
…		…
283	*In almost all cases (in all cases if you don't care), this is the	309	*In almost all cases (in all cases if you don't care), this is the
284	function to call when you want to know the current time.*	310	function to call when you want to know the current time.*
285		311
286	This function is also often faster then "AnyEvent->time", and thus	312	This function is also often faster then "AnyEvent->time", and thus
287	the preferred method if you want some timestamp (for example,	313	the preferred method if you want some timestamp (for example,
288	AnyEvent::Handle uses this to update it's activity timeouts).	314	AnyEvent::Handle uses this to update its activity timeouts).
289		315
290	The rest of this section is only of relevance if you try to be very	316	The rest of this section is only of relevance if you try to be very
291	exact with your timing, you can skip it without bad conscience.	317	exact with your timing; you can skip it without a bad conscience.
292		318
293	For a practical example of when these times differ, consider	319	For a practical example of when these times differ, consider
294	Event::Lib and EV and the following set-up:	320	Event::Lib and EV and the following set-up:
295		321
296	The event loop is running and has just invoked one of your callback	322	The event loop is running and has just invoked one of your callbacks
297	at time=500 (assume no other callbacks delay processing). In your	323	at time=500 (assume no other callbacks delay processing). In your
298	callback, you wait a second by executing "sleep 1" (blocking the	324	callback, you wait a second by executing "sleep 1" (blocking the
299	process for a second) and then (at time=501) you create a relative	325	process for a second) and then (at time=501) you create a relative
300	timer that fires after three seconds.	326	timer that fires after three seconds.
301		327
…		…
322	can get whatever behaviour you want with any event loop, by taking	348	can get whatever behaviour you want with any event loop, by taking
323	the difference between "AnyEvent->time" and "AnyEvent->now" into	349	the difference between "AnyEvent->time" and "AnyEvent->now" into
324	account.	350	account.
325		351
326	AnyEvent->now_update	352	AnyEvent->now_update
327	Some event loops (such as EV or AnyEvent::Impl::Perl) cache the	353	Some event loops (such as EV or AnyEvent::Loop) cache the current
328	current time for each loop iteration (see the discussion of	354	time for each loop iteration (see the discussion of AnyEvent->now,
329	AnyEvent->now, above).	355	above).
330		356
331	When a callback runs for a long time (or when the process sleeps),	357	When a callback runs for a long time (or when the process sleeps),
332	then this "current" time will differ substantially from the real	358	then this "current" time will differ substantially from the real
333	time, which might affect timers and time-outs.	359	time, which might affect timers and time-outs.
334		360
335	When this is the case, you can call this method, which will update	361	When this is the case, you can call this method, which will update
336	the event loop's idea of "current time".	362	the event loop's idea of "current time".
337		363
		364	A typical example would be a script in a web server (e.g.
		365	"mod_perl") - when mod_perl executes the script, then the event loop
		366	will have the wrong idea about the "current time" (being potentially
		367	far in the past, when the script ran the last time). In that case
		368	you should arrange a call to "AnyEvent->now_update" each time the
		369	web server process wakes up again (e.g. at the start of your script,
		370	or in a handler).
		371
338	Note that updating the time might cause some events to be handled.	372	Note that updating the time might cause some events to be handled.
339		373
340	SIGNAL WATCHERS	374	SIGNAL WATCHERS
		375	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		376
341	You can watch for signals using a signal watcher, "signal" is the signal	377	You can watch for signals using a signal watcher, "signal" is the signal
342	name in uppercase and without any "SIG" prefix, "cb" is the Perl	378	name in uppercase and without any "SIG" prefix, "cb" is the Perl
343	callback to be invoked whenever a signal occurs.	379	callback to be invoked whenever a signal occurs.
344		380
345	Although the callback might get passed parameters, their value and	381	Although the callback might get passed parameters, their value and
…		…
357		393
358	This watcher might use %SIG (depending on the event loop used), so	394	This watcher might use %SIG (depending on the event loop used), so
359	programs overwriting those signals directly will likely not work	395	programs overwriting those signals directly will likely not work
360	correctly.	396	correctly.
361		397
362	Also note that many event loops (e.g. Glib, Tk, Qt, IO::Async) do not
363	support attaching callbacks to signals, which is a pity, as you cannot
364	do race-free signal handling in perl. AnyEvent will try to do it's best,
365	but in some cases, signals will be delayed. The maximum time a signal
366	might be delayed is specified in $AnyEvent::MAX_SIGNAL_LATENCY (default:
367	10 seconds). This variable can be changed only before the first signal
368	watcher is created, and should be left alone otherwise. Higher values
369	will cause fewer spurious wake-ups, which is better for power and CPU
370	saving. All these problems can be avoided by installing the optional
371	Async::Interrupt module.
372
373	Example: exit on SIGINT	398	Example: exit on SIGINT
374		399
375	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	400	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
376		401
		402	Restart Behaviour
		403	While restart behaviour is up to the event loop implementation, most
		404	will not restart syscalls (that includes Async::Interrupt and AnyEvent's
		405	pure perl implementation).
		406
		407	Safe/Unsafe Signals
		408	Perl signals can be either "safe" (synchronous to opcode handling) or
		409	"unsafe" (asynchronous) - the former might delay signal delivery
		410	indefinitely, the latter might corrupt your memory.
		411
		412	AnyEvent signal handlers are, in addition, synchronous to the event
		413	loop, i.e. they will not interrupt your running perl program but will
		414	only be called as part of the normal event handling (just like timer,
		415	I/O etc. callbacks, too).
		416
		417	Signal Races, Delays and Workarounds
		418	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		419	callbacks to signals in a generic way, which is a pity, as you cannot do
		420	race-free signal handling in perl, requiring C libraries for this.
		421	AnyEvent will try to do its best, which means in some cases, signals
		422	will be delayed. The maximum time a signal might be delayed is 10
		423	seconds by default, but can be overriden via
		424	$ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} or $AnyEvent::MAX_SIGNAL_LATENCY
		425	- see the "ENVIRONMENT VARIABLES" section for details.
		426
		427	All these problems can be avoided by installing the optional
		428	Async::Interrupt module, which works with most event loops. It will not
		429	work with inherently broken event loops such as Event or Event::Lib (and
		430	not with POE currently). For those, you just have to suffer the delays.
		431
377	CHILD PROCESS WATCHERS	432	CHILD PROCESS WATCHERS
		433	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		434
378	You can also watch on a child process exit and catch its exit status.	435	You can also watch for a child process exit and catch its exit status.
379		436
380	The child process is specified by the "pid" argument (if set to 0, it	437	The child process is specified by the "pid" argument (on some backends,
381	watches for any child process exit). The watcher will triggered only	438	using 0 watches for any child process exit, on others this will croak).
382	when the child process has finished and an exit status is available, not	439	The watcher will be triggered only when the child process has finished
383	on any trace events (stopped/continued).	440	and an exit status is available, not on any trace events
		441	(stopped/continued).
384		442
385	The callback will be called with the pid and exit status (as returned by	443	The callback will be called with the pid and exit status (as returned by
386	waitpid), so unlike other watcher types, you can rely on child watcher	444	waitpid), so unlike other watcher types, you can rely on child watcher
387	callback arguments.	445	callback arguments.
388		446
…		…
405	This means you cannot create a child watcher as the very first thing in	463	This means you cannot create a child watcher as the very first thing in
406	an AnyEvent program, you have to create at least one watcher before	464	an AnyEvent program, you have to create at least one watcher before
407	you "fork" the child (alternatively, you can call "AnyEvent::detect").	465	you "fork" the child (alternatively, you can call "AnyEvent::detect").
408		466
409	As most event loops do not support waiting for child events, they will	467	As most event loops do not support waiting for child events, they will
410	be emulated by AnyEvent in most cases, in which the latency and race	468	be emulated by AnyEvent in most cases, in which case the latency and
411	problems mentioned in the description of signal watchers apply.	469	race problems mentioned in the description of signal watchers apply.
412		470
413	Example: fork a process and wait for it	471	Example: fork a process and wait for it
414		472
415	my $done = AnyEvent->condvar;	473	my $done = AnyEvent->condvar;
416		474
		475	# this forks and immediately calls exit in the child. this
		476	# normally has all sorts of bad consequences for your parent,
		477	# so take this as an example only. always fork and exec,
		478	# or call POSIX::_exit, in real code.
417	my $pid = fork or exit 5;	479	my $pid = fork or exit 5;
418		480
419	my $w = AnyEvent->child (	481	my $w = AnyEvent->child (
420	pid => $pid,	482	pid => $pid,
421	cb => sub {	483	cb => sub {
…		…
427		489
428	# do something else, then wait for process exit	490	# do something else, then wait for process exit
429	$done->recv;	491	$done->recv;
430		492
431	IDLE WATCHERS	493	IDLE WATCHERS
432	Sometimes there is a need to do something, but it is not so important to	494	$w = AnyEvent->idle (cb => <callback>);
433	do it instantly, but only when there is nothing better to do. This
434	"nothing better to do" is usually defined to be "no other events need
435	attention by the event loop".
436		495
437	Idle watchers ideally get invoked when the event loop has nothing better	496	This will repeatedly invoke the callback after the process becomes idle,
438	to do, just before it would block the process to wait for new events.	497	until either the watcher is destroyed or new events have been detected.
439	Instead of blocking, the idle watcher is invoked.
440		498
441	Most event loops unfortunately do not really support idle watchers (only	499	Idle watchers are useful when there is a need to do something, but it is
		500	not so important (or wise) to do it instantly. The callback will be
		501	invoked only when there is "nothing better to do", which is usually
		502	defined as "all outstanding events have been handled and no new events
		503	have been detected". That means that idle watchers ideally get invoked
		504	when the event loop has just polled for new events but none have been
		505	detected. Instead of blocking to wait for more events, the idle watchers
		506	will be invoked.
		507
		508	Unfortunately, most event loops do not really support idle watchers
442	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent	509	(only EV, Event and Glib do it in a usable fashion) - for the rest,
443	will simply call the callback "from time to time".	510	AnyEvent will simply call the callback "from time to time".
444		511
445	Example: read lines from STDIN, but only process them when the program	512	Example: read lines from STDIN, but only process them when the program
446	is otherwise idle:	513	is otherwise idle:
447		514
448	my @lines; # read data	515	my @lines; # read data
…		…
461	}	528	}
462	});	529	});
463	});	530	});
464		531
465	CONDITION VARIABLES	532	CONDITION VARIABLES
		533	$cv = AnyEvent->condvar;
		534
		535	$cv->send (<list>);
		536	my @res = $cv->recv;
		537
466	If you are familiar with some event loops you will know that all of them	538	If you are familiar with some event loops you will know that all of them
467	require you to run some blocking "loop", "run" or similar function that	539	require you to run some blocking "loop", "run" or similar function that
468	will actively watch for new events and call your callbacks.	540	will actively watch for new events and call your callbacks.
469		541
470	AnyEvent is slightly different: it expects somebody else to run the	542	AnyEvent is slightly different: it expects somebody else to run the
471	event loop and will only block when necessary (usually when told by the	543	event loop and will only block when necessary (usually when told by the
472	user).	544	user).
473		545
474	The instrument to do that is called a "condition variable", so called	546	The tool to do that is called a "condition variable", so called because
475	because they represent a condition that must become true.	547	they represent a condition that must become true.
476		548
477	Now is probably a good time to look at the examples further below.	549	Now is probably a good time to look at the examples further below.
478		550
479	Condition variables can be created by calling the "AnyEvent->condvar"	551	Condition variables can be created by calling the "AnyEvent->condvar"
480	method, usually without arguments. The only argument pair allowed is	552	method, usually without arguments. The only argument pair allowed is
…		…
485	After creation, the condition variable is "false" until it becomes	557	After creation, the condition variable is "false" until it becomes
486	"true" by calling the "send" method (or calling the condition variable	558	"true" by calling the "send" method (or calling the condition variable
487	as if it were a callback, read about the caveats in the description for	559	as if it were a callback, read about the caveats in the description for
488	the "->send" method).	560	the "->send" method).
489		561
490	Condition variables are similar to callbacks, except that you can	562	Since condition variables are the most complex part of the AnyEvent API,
491	optionally wait for them. They can also be called merge points - points	563	here are some different mental models of what they are - pick the ones
492	in time where multiple outstanding events have been processed. And yet	564	you can connect to:
493	another way to call them is transactions - each condition variable can	565
494	be used to represent a transaction, which finishes at some point and	566	* Condition variables are like callbacks - you can call them (and pass
495	delivers a result.	567	them instead of callbacks). Unlike callbacks however, you can also
		568	wait for them to be called.
		569
		570	* Condition variables are signals - one side can emit or send them,
		571	the other side can wait for them, or install a handler that is
		572	called when the signal fires.
		573
		574	* Condition variables are like "Merge Points" - points in your program
		575	where you merge multiple independent results/control flows into one.
		576
		577	* Condition variables represent a transaction - functions that start
		578	some kind of transaction can return them, leaving the caller the
		579	choice between waiting in a blocking fashion, or setting a callback.
		580
		581	* Condition variables represent future values, or promises to deliver
		582	some result, long before the result is available.
496		583
497	Condition variables are very useful to signal that something has	584	Condition variables are very useful to signal that something has
498	finished, for example, if you write a module that does asynchronous http	585	finished, for example, if you write a module that does asynchronous http
499	requests, then a condition variable would be the ideal candidate to	586	requests, then a condition variable would be the ideal candidate to
500	signal the availability of results. The user can either act when the	587	signal the availability of results. The user can either act when the
…		…
513		600
514	Condition variables are represented by hash refs in perl, and the keys	601	Condition variables are represented by hash refs in perl, and the keys
515	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy	602	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy
516	(it is often useful to build your own transaction class on top of	603	(it is often useful to build your own transaction class on top of
517	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	604	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
518	it's "new" method in your own "new" method.	605	its "new" method in your own "new" method.
519		606
520	There are two "sides" to a condition variable - the "producer side"	607	There are two "sides" to a condition variable - the "producer side"
521	which eventually calls "-> send", and the "consumer side", which waits	608	which eventually calls "-> send", and the "consumer side", which waits
522	for the send to occur.	609	for the send to occur.
523		610
524	Example: wait for a timer.	611	Example: wait for a timer.
525		612
526	# wait till the result is ready	613	# condition: "wait till the timer is fired"
527	my $result_ready = AnyEvent->condvar;	614	my $timer_fired = AnyEvent->condvar;
528		615
529	# do something such as adding a timer	616	# create the timer - we could wait for, say
530	# or socket watcher the calls $result_ready->send	617	# a handle becomign ready, or even an
531	# when the "result" is ready.	618	# AnyEvent::HTTP request to finish, but
532	# in this case, we simply use a timer:	619	# in this case, we simply use a timer:
533	my $w = AnyEvent->timer (	620	my $w = AnyEvent->timer (
534	after => 1,	621	after => 1,
535	cb => sub { $result_ready->send },	622	cb => sub { $timer_fired->send },
536	);	623	);
537		624
538	# this "blocks" (while handling events) till the callback	625	# this "blocks" (while handling events) till the callback
539	# calls -<send	626	# calls ->send
540	$result_ready->recv;	627	$timer_fired->recv;
541		628
542	Example: wait for a timer, but take advantage of the fact that condition	629	Example: wait for a timer, but take advantage of the fact that condition
543	variables are also callable directly.	630	variables are also callable directly.
544		631
545	my $done = AnyEvent->condvar;	632	my $done = AnyEvent->condvar;
…		…
583	Condition variables are overloaded so one can call them directly (as	670	Condition variables are overloaded so one can call them directly (as
584	if they were a code reference). Calling them directly is the same as	671	if they were a code reference). Calling them directly is the same as
585	calling "send".	672	calling "send".
586		673
587	$cv->croak ($error)	674	$cv->croak ($error)
588	Similar to send, but causes all call's to "->recv" to invoke	675	Similar to send, but causes all calls to "->recv" to invoke
589	"Carp::croak" with the given error message/object/scalar.	676	"Carp::croak" with the given error message/object/scalar.
590		677
591	This can be used to signal any errors to the condition variable	678	This can be used to signal any errors to the condition variable
592	user/consumer. Doing it this way instead of calling "croak" directly	679	user/consumer. Doing it this way instead of calling "croak" directly
593	delays the error detetcion, but has the overwhelmign advantage that	680	delays the error detection, but has the overwhelming advantage that
594	it diagnoses the error at the place where the result is expected,	681	it diagnoses the error at the place where the result is expected,
595	and not deep in some event clalback without connection to the actual	682	and not deep in some event callback with no connection to the actual
596	code causing the problem.	683	code causing the problem.
597		684
598	$cv->begin ([group callback])	685	$cv->begin ([group callback])
599	$cv->end	686	$cv->end
600	These two methods can be used to combine many transactions/events	687	These two methods can be used to combine many transactions/events
601	into one. For example, a function that pings many hosts in parallel	688	into one. For example, a function that pings many hosts in parallel
602	might want to use a condition variable for the whole process.	689	might want to use a condition variable for the whole process.
603		690
604	Every call to "->begin" will increment a counter, and every call to	691	Every call to "->begin" will increment a counter, and every call to
605	"->end" will decrement it. If the counter reaches 0 in "->end", the	692	"->end" will decrement it. If the counter reaches 0 in "->end", the
606	(last) callback passed to "begin" will be executed. That callback is	693	(last) callback passed to "begin" will be executed, passing the
607	supposed to call "->send", but that is not required. If no	694	condvar as first argument. That callback is supposed to call
		695	"->send", but that is not required. If no group callback was set,
608	callback was set, "send" will be called without any arguments.	696	"send" will be called without any arguments.
609		697
610	You can think of "$cv->send" giving you an OR condition (one call	698	You can think of "$cv->send" giving you an OR condition (one call
611	sends), while "$cv->begin" and "$cv->end" giving you an AND	699	sends), while "$cv->begin" and "$cv->end" giving you an AND
612	condition (all "begin" calls must be "end"'ed before the condvar	700	condition (all "begin" calls must be "end"'ed before the condvar
613	sends).	701	sends).
…		…
635	This works because for every event source (EOF on file handle),	723	This works because for every event source (EOF on file handle),
636	there is one call to "begin", so the condvar waits for all calls to	724	there is one call to "begin", so the condvar waits for all calls to
637	"end" before sending.	725	"end" before sending.
638		726
639	The ping example mentioned above is slightly more complicated, as	727	The ping example mentioned above is slightly more complicated, as
640	the there are results to be passwd back, and the number of tasks	728	the there are results to be passed back, and the number of tasks
641	that are begung can potentially be zero:	729	that are begun can potentially be zero:
642		730
643	my $cv = AnyEvent->condvar;	731	my $cv = AnyEvent->condvar;
644		732
645	my %result;	733	my %result;
646	$cv->begin (sub { $cv->send (\%result) });	734	$cv->begin (sub { shift->send (\%result) });
647		735
648	for my $host (@list_of_hosts) {	736	for my $host (@list_of_hosts) {
649	$cv->begin;	737	$cv->begin;
650	ping_host_then_call_callback $host, sub {	738	ping_host_then_call_callback $host, sub {
651	$result{$host} = ...;	739	$result{$host} = ...;
…		…
653	};	741	};
654	}	742	}
655		743
656	$cv->end;	744	$cv->end;
657		745
		746	...
		747
		748	my $results = $cv->recv;
		749
658	This code fragment supposedly pings a number of hosts and calls	750	This code fragment supposedly pings a number of hosts and calls
659	"send" after results for all then have have been gathered - in any	751	"send" after results for all then have have been gathered - in any
660	order. To achieve this, the code issues a call to "begin" when it	752	order. To achieve this, the code issues a call to "begin" when it
661	starts each ping request and calls "end" when it has received some	753	starts each ping request and calls "end" when it has received some
662	result for it. Since "begin" and "end" only maintain a counter, the	754	result for it. Since "begin" and "end" only maintain a counter, the
…		…
667	callback to be called once the counter reaches 0, and second, it	759	callback to be called once the counter reaches 0, and second, it
668	ensures that "send" is called even when "no" hosts are being pinged	760	ensures that "send" is called even when "no" hosts are being pinged
669	(the loop doesn't execute once).	761	(the loop doesn't execute once).
670		762
671	This is the general pattern when you "fan out" into multiple (but	763	This is the general pattern when you "fan out" into multiple (but
672	potentially none) subrequests: use an outer "begin"/"end" pair to	764	potentially zero) subrequests: use an outer "begin"/"end" pair to
673	set the callback and ensure "end" is called at least once, and then,	765	set the callback and ensure "end" is called at least once, and then,
674	for each subrequest you start, call "begin" and for each subrequest	766	for each subrequest you start, call "begin" and for each subrequest
675	you finish, call "end".	767	you finish, call "end".
676		768
677	METHODS FOR CONSUMERS	769	METHODS FOR CONSUMERS
678	These methods should only be used by the consuming side, i.e. the code	770	These methods should only be used by the consuming side, i.e. the code
679	awaits the condition.	771	awaits the condition.
680		772
681	$cv->recv	773	$cv->recv
682	Wait (blocking if necessary) until the "->send" or "->croak" methods	774	Wait (blocking if necessary) until the "->send" or "->croak" methods
683	have been called on c<$cv>, while servicing other watchers normally.	775	have been called on $cv, while servicing other watchers normally.
684		776
685	You can only wait once on a condition - additional calls are valid	777	You can only wait once on a condition - additional calls are valid
686	but will return immediately.	778	but will return immediately.
687		779
688	If an error condition has been set by calling "->croak", then this	780	If an error condition has been set by calling "->croak", then this
…		…
691	In list context, all parameters passed to "send" will be returned,	783	In list context, all parameters passed to "send" will be returned,
692	in scalar context only the first one will be returned.	784	in scalar context only the first one will be returned.
693		785
694	Note that doing a blocking wait in a callback is not supported by	786	Note that doing a blocking wait in a callback is not supported by
695	any event loop, that is, recursive invocation of a blocking "->recv"	787	any event loop, that is, recursive invocation of a blocking "->recv"
696	is not allowed, and the "recv" call will "croak" if such a condition	788	is not allowed and the "recv" call will "croak" if such a condition
697	is detected. This condition can be slightly loosened by using	789	is detected. This requirement can be dropped by relying on
698	Coro::AnyEvent, which allows you to do a blocking "->recv" from any	790	Coro::AnyEvent , which allows you to do a blocking "->recv" from any
699	thread that doesn't run the event loop itself.	791	thread that doesn't run the event loop itself. Coro::AnyEvent is
		792	loaded automatically when Coro is used with AnyEvent, so code does
		793	not need to do anything special to take advantage of that: any code
		794	that would normally block your program because it calls "recv", be
		795	executed in an "async" thread instead without blocking other
		796	threads.
700		797
701	Not all event models support a blocking wait - some die in that case	798	Not all event models support a blocking wait - some die in that case
702	(programs might want to do that to stay interactive), so *if you are	799	(programs might want to do that to stay interactive), so *if you are
703	using this from a module, never require a blocking wait*. Instead,	800	using this from a module, never require a blocking wait*. Instead,
704	let the caller decide whether the call will block or not (for	801	let the caller decide whether the call will block or not (for
705	example, by coupling condition variables with some kind of request	802	example, by coupling condition variables with some kind of request
706	results and supporting callbacks so the caller knows that getting	803	results and supporting callbacks so the caller knows that getting
707	the result will not block, while still supporting blocking waits if	804	the result will not block, while still supporting blocking waits if
708	the caller so desires).	805	the caller so desires).
709		806
710	You can ensure that "-recv" never blocks by setting a callback and	807	You can ensure that "->recv" never blocks by setting a callback and
711	only calling "->recv" from within that callback (or at a later	808	only calling "->recv" from within that callback (or at a later
712	time). This will work even when the event loop does not support	809	time). This will work even when the event loop does not support
713	blocking waits otherwise.	810	blocking waits otherwise.
714		811
715	$bool = $cv->ready	812	$bool = $cv->ready
…		…
720	This is a mutator function that returns the callback set and	817	This is a mutator function that returns the callback set and
721	optionally replaces it before doing so.	818	optionally replaces it before doing so.
722		819
723	The callback will be called when the condition becomes "true", i.e.	820	The callback will be called when the condition becomes "true", i.e.
724	when "send" or "croak" are called, with the only argument being the	821	when "send" or "croak" are called, with the only argument being the
725	condition variable itself. Calling "recv" inside the callback or at	822	condition variable itself. If the condition is already true, the
		823	callback is called immediately when it is set. Calling "recv" inside
726	any later time is guaranteed not to block.	824	the callback or at any later time is guaranteed not to block.
727		825
728	SUPPORTED EVENT LOOPS/BACKENDS	826	SUPPORTED EVENT LOOPS/BACKENDS
729	The available backend classes are (every class has its own manpage):	827	The available backend classes are (every class has its own manpage):
730		828
731	Backends that are autoprobed when no other event loop can be found.	829	Backends that are autoprobed when no other event loop can be found.
732	EV is the preferred backend when no other event loop seems to be in	830	EV is the preferred backend when no other event loop seems to be in
733	use. If EV is not installed, then AnyEvent will try Event, and,	831	use. If EV is not installed, then AnyEvent will fall back to its own
734	failing that, will fall back to its own pure-perl implementation,	832	pure-perl implementation, which is available everywhere as it comes
735	which is available everywhere as it comes with AnyEvent itself.	833	with AnyEvent itself.
736		834
737	AnyEvent::Impl::EV based on EV (interface to libev, best choice).	835	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
738	AnyEvent::Impl::Event based on Event, very stable, few glitches.
739	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.	836	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
740		837
741	Backends that are transparently being picked up when they are used.	838	Backends that are transparently being picked up when they are used.
742	These will be used when they are currently loaded when the first	839	These will be used if they are already loaded when the first watcher
743	watcher is created, in which case it is assumed that the application	840	is created, in which case it is assumed that the application is
744	is using them. This means that AnyEvent will automatically pick the	841	using them. This means that AnyEvent will automatically pick the
745	right backend when the main program loads an event module before	842	right backend when the main program loads an event module before
746	anything starts to create watchers. Nothing special needs to be done	843	anything starts to create watchers. Nothing special needs to be done
747	by the main program.	844	by the main program.
748		845
		846	AnyEvent::Impl::Event based on Event, very stable, few glitches.
749	AnyEvent::Impl::Glib based on Glib, slow but very stable.	847	AnyEvent::Impl::Glib based on Glib, slow but very stable.
750	AnyEvent::Impl::Tk based on Tk, very broken.	848	AnyEvent::Impl::Tk based on Tk, very broken.
		849	AnyEvent::Impl::UV based on UV, innovated square wheels.
751	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	850	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
752	AnyEvent::Impl::POE based on POE, very slow, some limitations.	851	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		852	AnyEvent::Impl::Irssi used when running within irssi.
		853	AnyEvent::Impl::IOAsync based on IO::Async.
		854	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		855	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
753		856
754	Backends with special needs.	857	Backends with special needs.
755	Qt requires the Qt::Application to be instantiated first, but will	858	Qt requires the Qt::Application to be instantiated first, but will
756	otherwise be picked up automatically. As long as the main program	859	otherwise be picked up automatically. As long as the main program
757	instantiates the application before any AnyEvent watchers are	860	instantiates the application before any AnyEvent watchers are
758	created, everything should just work.	861	created, everything should just work.
759		862
760	AnyEvent::Impl::Qt based on Qt.	863	AnyEvent::Impl::Qt based on Qt.
761		864
762	Support for IO::Async can only be partial, as it is too broken and
763	architecturally limited to even support the AnyEvent API. It also is
764	the only event loop that needs the loop to be set explicitly, so it
765	can only be used by a main program knowing about AnyEvent. See
766	AnyEvent::Impl::Async for the gory details.
767
768	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
769
770	Event loops that are indirectly supported via other backends.	865	Event loops that are indirectly supported via other backends.
771	Some event loops can be supported via other modules:	866	Some event loops can be supported via other modules:
772		867
773	There is no direct support for WxWidgets (Wx) or Prima.	868	There is no direct support for WxWidgets (Wx) or Prima.
774		869
…		…
792	Contains "undef" until the first watcher is being created, before	887	Contains "undef" until the first watcher is being created, before
793	the backend has been autodetected.	888	the backend has been autodetected.
794		889
795	Afterwards it contains the event model that is being used, which is	890	Afterwards it contains the event model that is being used, which is
796	the name of the Perl class implementing the model. This class is	891	the name of the Perl class implementing the model. This class is
797	usually one of the "AnyEvent::Impl:xxx" modules, but can be any	892	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
798	other class in the case AnyEvent has been extended at runtime (e.g.	893	other class in the case AnyEvent has been extended at runtime (e.g.
799	in rxvt-unicode it will be "urxvt::anyevent").	894	in rxvt-unicode it will be "urxvt::anyevent").
800		895
801	AnyEvent::detect	896	AnyEvent::detect
802	Returns $AnyEvent::MODEL, forcing autodetection of the event model	897	Returns $AnyEvent::MODEL, forcing autodetection of the event model
803	if necessary. You should only call this function right before you	898	if necessary. You should only call this function right before you
804	would have created an AnyEvent watcher anyway, that is, as late as	899	would have created an AnyEvent watcher anyway, that is, as late as
805	possible at runtime, and not e.g. while initialising of your module.	900	possible at runtime, and not e.g. during initialisation of your
		901	module.
		902
		903	The effect of calling this function is as if a watcher had been
		904	created (specifically, actions that happen "when the first watcher
		905	is created" happen when calling detetc as well).
806		906
807	If you need to do some initialisation before AnyEvent watchers are	907	If you need to do some initialisation before AnyEvent watchers are
808	created, use "post_detect".	908	created, use "post_detect".
809		909
810	$guard = AnyEvent::post_detect { BLOCK }	910	$guard = AnyEvent::post_detect { BLOCK }
811	Arranges for the code block to be executed as soon as the event	911	Arranges for the code block to be executed as soon as the event
812	model is autodetected (or immediately if this has already happened).	912	model is autodetected (or immediately if that has already happened).
813		913
814	The block will be executed after the actual backend has been	914	The block will be executed after the actual backend has been
815	detected ($AnyEvent::MODEL is set), but before any watchers have	915	detected ($AnyEvent::MODEL is set), but before any watchers have
816	been created, so it is possible to e.g. patch @AnyEvent::ISA or do	916	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
817	other initialisations - see the sources of AnyEvent::Strict or	917	other initialisations - see the sources of AnyEvent::Strict or
…		…
822	creates and installs the global IO::AIO watcher in a "post_detect"	922	creates and installs the global IO::AIO watcher in a "post_detect"
823	block to avoid autodetecting the event module at load time.	923	block to avoid autodetecting the event module at load time.
824		924
825	If called in scalar or list context, then it creates and returns an	925	If called in scalar or list context, then it creates and returns an
826	object that automatically removes the callback again when it is	926	object that automatically removes the callback again when it is
		927	destroyed (or "undef" when the hook was immediately executed). See
827	destroyed. See Coro::BDB for a case where this is useful.	928	AnyEvent::AIO for a case where this is useful.
		929
		930	Example: Create a watcher for the IO::AIO module and store it in
		931	$WATCHER, but do so only do so after the event loop is initialised.
		932
		933	our WATCHER;
		934
		935	my $guard = AnyEvent::post_detect {
		936	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		937	};
		938
		939	# the \|\|= is important in case post_detect immediately runs the block,
		940	# as to not clobber the newly-created watcher. assigning both watcher and
		941	# post_detect guard to the same variable has the advantage of users being
		942	# able to just C<undef $WATCHER> if the watcher causes them grief.
		943
		944	$WATCHER \|\|= $guard;
828		945
829	@AnyEvent::post_detect	946	@AnyEvent::post_detect
830	If there are any code references in this array (you can "push" to it	947	If there are any code references in this array (you can "push" to it
831	before or after loading AnyEvent), then they will called directly	948	before or after loading AnyEvent), then they will be called directly
832	after the event loop has been chosen.	949	after the event loop has been chosen.
833		950
834	You should check $AnyEvent::MODEL before adding to this array,	951	You should check $AnyEvent::MODEL before adding to this array,
835	though: if it is defined then the event loop has already been	952	though: if it is defined then the event loop has already been
836	detected, and the array will be ignored.	953	detected, and the array will be ignored.
837		954
838	Best use "AnyEvent::post_detect { BLOCK }" when your application	955	Best use "AnyEvent::post_detect { BLOCK }" when your application
839	allows it,as it takes care of these details.	956	allows it, as it takes care of these details.
840		957
841	This variable is mainly useful for modules that can do something	958	This variable is mainly useful for modules that can do something
842	useful when AnyEvent is used and thus want to know when it is	959	useful when AnyEvent is used and thus want to know when it is
843	initialised, but do not need to even load it by default. This array	960	initialised, but do not need to even load it by default. This array
844	provides the means to hook into AnyEvent passively, without loading	961	provides the means to hook into AnyEvent passively, without loading
845	it.	962	it.
846		963
		964	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		965	together, you could put this into Coro (this is the actual code used
		966	by Coro to accomplish this):
		967
		968	if (defined $AnyEvent::MODEL) {
		969	# AnyEvent already initialised, so load Coro::AnyEvent
		970	require Coro::AnyEvent;
		971	} else {
		972	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		973	# as soon as it is
		974	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		975	}
		976
		977	AnyEvent::postpone { BLOCK }
		978	Arranges for the block to be executed as soon as possible, but not
		979	before the call itself returns. In practise, the block will be
		980	executed just before the event loop polls for new events, or shortly
		981	afterwards.
		982
		983	This function never returns anything (to make the "return postpone {
		984	... }" idiom more useful.
		985
		986	To understand the usefulness of this function, consider a function
		987	that asynchronously does something for you and returns some
		988	transaction object or guard to let you cancel the operation. For
		989	example, "AnyEvent::Socket::tcp_connect":
		990
		991	# start a connection attempt unless one is active
		992	$self->{connect_guard} \|\|= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		993	delete $self->{connect_guard};
		994	...
		995	};
		996
		997	Imagine that this function could instantly call the callback, for
		998	example, because it detects an obvious error such as a negative port
		999	number. Invoking the callback before the function returns causes
		1000	problems however: the callback will be called and will try to delete
		1001	the guard object. But since the function hasn't returned yet, there
		1002	is nothing to delete. When the function eventually returns it will
		1003	assign the guard object to "$self->{connect_guard}", where it will
		1004	likely never be deleted, so the program thinks it is still trying to
		1005	connect.
		1006
		1007	This is where "AnyEvent::postpone" should be used. Instead of
		1008	calling the callback directly on error:
		1009
		1010	$cb->(undef), return # signal error to callback, BAD!
		1011	if $some_error_condition;
		1012
		1013	It should use "postpone":
		1014
		1015	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1016	if $some_error_condition;
		1017
		1018	AnyEvent::log $level, $msg[, @args]
		1019	Log the given $msg at the given $level.
		1020
		1021	If AnyEvent::Log is not loaded then this function makes a simple
		1022	test to see whether the message will be logged. If the test succeeds
		1023	it will load AnyEvent::Log and call "AnyEvent::Log::log" -
		1024	consequently, look at the AnyEvent::Log documentation for details.
		1025
		1026	If the test fails it will simply return. Right now this happens when
		1027	a numerical loglevel is used and it is larger than the level
		1028	specified via $ENV{PERL_ANYEVENT_VERBOSE}.
		1029
		1030	If you want to sprinkle loads of logging calls around your code,
		1031	consider creating a logger callback with the "AnyEvent::Log::logger"
		1032	function, which can reduce typing, codesize and can reduce the
		1033	logging overhead enourmously.
		1034
		1035	AnyEvent::fh_block $filehandle
		1036	AnyEvent::fh_unblock $filehandle
		1037	Sets blocking or non-blocking behaviour for the given filehandle.
		1038
847	WHAT TO DO IN A MODULE	1039	WHAT TO DO IN A MODULE
848	As a module author, you should "use AnyEvent" and call AnyEvent methods	1040	As a module author, you should "use AnyEvent" and call AnyEvent methods
849	freely, but you should not load a specific event module or rely on it.	1041	freely, but you should not load a specific event module or rely on it.
850		1042
851	Be careful when you create watchers in the module body - AnyEvent will	1043	Be careful when you create watchers in the module body - AnyEvent will
…		…
858	stall the whole program, and the whole point of using events is to stay	1050	stall the whole program, and the whole point of using events is to stay
859	interactive.	1051	interactive.
860		1052
861	It is fine, however, to call "->recv" when the user of your module	1053	It is fine, however, to call "->recv" when the user of your module
862	requests it (i.e. if you create a http request object ad have a method	1054	requests it (i.e. if you create a http request object ad have a method
863	called "results" that returns the results, it should call "->recv"	1055	called "results" that returns the results, it may call "->recv" freely,
864	freely, as the user of your module knows what she is doing. always).	1056	as the user of your module knows what she is doing. Always).
865		1057
866	WHAT TO DO IN THE MAIN PROGRAM	1058	WHAT TO DO IN THE MAIN PROGRAM
867	There will always be a single main program - the only place that should	1059	There will always be a single main program - the only place that should
868	dictate which event model to use.	1060	dictate which event model to use.
869		1061
870	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1062	If the program is not event-based, it need not do anything special, even
871	do anything special (it does not need to be event-based) and let	1063	when it depends on a module that uses an AnyEvent. If the program itself
872	AnyEvent decide which implementation to chose if some module relies on	1064	uses AnyEvent, but does not care which event loop is used, all it needs
873	it.	1065	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1066	available loop implementation.
874		1067
875	If the main program relies on a specific event model - for example, in	1068	If the main program relies on a specific event model - for example, in
876	Gtk2 programs you have to rely on the Glib module - you should load the	1069	Gtk2 programs you have to rely on the Glib module - you should load the
877	event module before loading AnyEvent or any module that uses it:	1070	event module before loading AnyEvent or any module that uses it:
878	generally speaking, you should load it as early as possible. The reason	1071	generally speaking, you should load it as early as possible. The reason
879	is that modules might create watchers when they are loaded, and AnyEvent	1072	is that modules might create watchers when they are loaded, and AnyEvent
880	will decide on the event model to use as soon as it creates watchers,	1073	will decide on the event model to use as soon as it creates watchers,
881	and it might chose the wrong one unless you load the correct one	1074	and it might choose the wrong one unless you load the correct one
882	yourself.	1075	yourself.
883		1076
884	You can chose to use a pure-perl implementation by loading the	1077	You can chose to use a pure-perl implementation by loading the
885	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1078	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
886	everywhere, but letting AnyEvent chose the model is generally better.	1079	but letting AnyEvent chose the model is generally better.
887		1080
888	MAINLOOP EMULATION	1081	MAINLOOP EMULATION
889	Sometimes (often for short test scripts, or even standalone programs who	1082	Sometimes (often for short test scripts, or even standalone programs who
890	only want to use AnyEvent), you do not want to run a specific event	1083	only want to use AnyEvent), you do not want to run a specific event
891	loop.	1084	loop.
…		…
903		1096
904	OTHER MODULES	1097	OTHER MODULES
905	The following is a non-exhaustive list of additional modules that use	1098	The following is a non-exhaustive list of additional modules that use
906	AnyEvent as a client and can therefore be mixed easily with other	1099	AnyEvent as a client and can therefore be mixed easily with other
907	AnyEvent modules and other event loops in the same program. Some of the	1100	AnyEvent modules and other event loops in the same program. Some of the
908	modules come with AnyEvent, most are available via CPAN.	1101	modules come as part of AnyEvent, the others are available via CPAN (see
		1102	<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
		1103	non-exhaustive list), and the list is heavily biased towards modules of
		1104	the AnyEvent author himself :)
909		1105
910	AnyEvent::Util	1106	AnyEvent::Util (part of the AnyEvent distribution)
911	Contains various utility functions that replace often-used but	1107	Contains various utility functions that replace often-used blocking
912	blocking functions such as "inet_aton" by event-/callback-based	1108	functions such as "inet_aton" with event/callback-based versions.
913	versions.
914		1109
915	AnyEvent::Socket	1110	AnyEvent::Socket (part of the AnyEvent distribution)
916	Provides various utility functions for (internet protocol) sockets,	1111	Provides various utility functions for (internet protocol) sockets,
917	addresses and name resolution. Also functions to create non-blocking	1112	addresses and name resolution. Also functions to create non-blocking
918	tcp connections or tcp servers, with IPv6 and SRV record support and	1113	tcp connections or tcp servers, with IPv6 and SRV record support and
919	more.	1114	more.
920		1115
921	AnyEvent::Handle	1116	AnyEvent::Handle (part of the AnyEvent distribution)
922	Provide read and write buffers, manages watchers for reads and	1117	Provide read and write buffers, manages watchers for reads and
923	writes, supports raw and formatted I/O, I/O queued and fully	1118	writes, supports raw and formatted I/O, I/O queued and fully
924	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.	1119	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
925		1120
926	AnyEvent::DNS	1121	AnyEvent::DNS (part of the AnyEvent distribution)
927	Provides rich asynchronous DNS resolver capabilities.	1122	Provides rich asynchronous DNS resolver capabilities.
928		1123
929	AnyEvent::HTTP	1124	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
930	A simple-to-use HTTP library that is capable of making a lot of	1125	AnyEvent::IGS, AnyEvent::FCP
931	concurrent HTTP requests.	1126	Implement event-based interfaces to the protocols of the same name
		1127	(for the curious, IGS is the International Go Server and FCP is the
		1128	Freenet Client Protocol).
932		1129
		1130	AnyEvent::AIO (part of the AnyEvent distribution)
		1131	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1132	the toolbox of every event programmer. AnyEvent::AIO transparently
		1133	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1134	event-based file I/O, and much more.
		1135
		1136	AnyEvent::Fork, AnyEvent::Fork::RPC, AnyEvent::Fork::Pool,
		1137	AnyEvent::Fork::Remote
		1138	These let you safely fork new subprocesses, either locally or
		1139	remotely (e.g.v ia ssh), using some RPC protocol or not, without the
		1140	limitations normally imposed by fork (AnyEvent works fine for
		1141	example). Dynamically-resized worker pools are obviously included as
		1142	well.
		1143
		1144	And they are quite tiny and fast as well - "abusing" AnyEvent::Fork
		1145	just to exec external programs can easily beat using "fork" and
		1146	"exec" (or even "system") in most programs.
		1147
		1148	AnyEvent::Filesys::Notify
		1149	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1150	path changes (e.g. "watch this directory for new files", "watch this
		1151	file for changes"). The AnyEvent::Filesys::Notify module promises to
		1152	do just that in a portbale fashion, supporting inotify on GNU/Linux
		1153	and some weird, without doubt broken, stuff on OS X to monitor
		1154	files. It can fall back to blocking scans at regular intervals
		1155	transparently on other platforms, so it's about as portable as it
		1156	gets.
		1157
		1158	(I haven't used it myself, but it seems the biggest problem with it
		1159	is it quite bad performance).
		1160
933	AnyEvent::HTTPD	1161	AnyEvent::DBI
934	Provides a simple web application server framework.	1162	Executes DBI requests asynchronously in a proxy process for you,
		1163	notifying you in an event-based way when the operation is finished.
935		1164
936	AnyEvent::FastPing	1165	AnyEvent::FastPing
937	The fastest ping in the west.	1166	The fastest ping in the west.
938		1167
939	AnyEvent::DBI
940	Executes DBI requests asynchronously in a proxy process.
941
942	AnyEvent::AIO
943	Truly asynchronous I/O, should be in the toolbox of every event
944	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
945	together.
946
947	AnyEvent::BDB
948	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
949	fuses BDB and AnyEvent together.
950
951	AnyEvent::GPSD
952	A non-blocking interface to gpsd, a daemon delivering GPS
953	information.
954
955	AnyEvent::IRC
956	AnyEvent based IRC client module family (replacing the older
957	Net::IRC3).
958
959	AnyEvent::XMPP
960	AnyEvent based XMPP (Jabber protocol) module family (replacing the
961	older Net::XMPP2>.
962
963	AnyEvent::IGS
964	A non-blocking interface to the Internet Go Server protocol (used by
965	App::IGS).
966
967	Net::FCP
968	AnyEvent-based implementation of the Freenet Client Protocol,
969	birthplace of AnyEvent.
970
971	Event::ExecFlow
972	High level API for event-based execution flow control.
973
974	Coro	1168	Coro
975	Has special support for AnyEvent via Coro::AnyEvent.	1169	Has special support for AnyEvent via Coro::AnyEvent, which allows
		1170	you to simply invert the flow control - don't call us, we will call
		1171	you:
		1172
		1173	async {
		1174	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1175	print "5 seconds later!\n";
		1176
		1177	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1178	my $line = <STDIN>; # works for ttys
		1179
		1180	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1181	my ($body, $hdr) = Coro::rouse_wait;
		1182	};
		1183
		1184	SIMPLIFIED AE API
		1185	Starting with version 5.0, AnyEvent officially supports a second, much
		1186	simpler, API that is designed to reduce the calling, typing and memory
		1187	overhead by using function call syntax and a fixed number of parameters.
		1188
		1189	See the AE manpage for details.
976		1190
977	ERROR AND EXCEPTION HANDLING	1191	ERROR AND EXCEPTION HANDLING
978	In general, AnyEvent does not do any error handling - it relies on the	1192	In general, AnyEvent does not do any error handling - it relies on the
979	caller to do that if required. The AnyEvent::Strict module (see also the	1193	caller to do that if required. The AnyEvent::Strict module (see also the
980	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1194	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
989	The pure perl event loop simply re-throws the exception (usually within	1203	The pure perl event loop simply re-throws the exception (usually within
990	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1204	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
991	Glib uses "install_exception_handler" and so on.	1205	Glib uses "install_exception_handler" and so on.
992		1206
993	ENVIRONMENT VARIABLES	1207	ENVIRONMENT VARIABLES
994	The following environment variables are used by this module or its	1208	AnyEvent supports a number of environment variables that tune the
995	submodules.	1209	runtime behaviour. They are usually evaluated when AnyEvent is loaded,
		1210	initialised, or a submodule that uses them is loaded. Many of them also
		1211	cause AnyEvent to load additional modules - for example,
		1212	"PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be
		1213	loaded.
996		1214
997	Note that AnyEvent will remove all environment variables starting with	1215	All the environment variables documented here start with
998	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is	1216	"PERL_ANYEVENT_", which is what AnyEvent considers its own namespace.
999	enabled.	1217	Other modules are encouraged (but by no means required) to use
		1218	"PERL_ANYEVENT_SUBMODULE" if they have registered the
		1219	AnyEvent::Submodule namespace on CPAN, for any submodule. For example,
		1220	AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it
		1221	should not access env variables starting with "AE_", see below).
		1222
		1223	All variables can also be set via the "AE_" prefix, that is, instead of
		1224	setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case
		1225	there is a clash btween anyevent and another program that uses
		1226	"AE_something" you can set the corresponding "PERL_ANYEVENT_something"
		1227	variable to the empty string, as those variables take precedence.
		1228
		1229	When AnyEvent is first loaded, it copies all "AE_xxx" env variables to
		1230	their "PERL_ANYEVENT_xxx" counterpart unless that variable already
		1231	exists. If taint mode is on, then AnyEvent will remove all environment
		1232	variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with
		1233	"undef" or the empty string, if the corresaponding "AE_" variable is
		1234	set).
		1235
		1236	The exact algorithm is currently:
		1237
		1238	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		1239	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		1240	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		1241
		1242	This ensures that child processes will not see the "AE_" variables.
		1243
		1244	The following environment variables are currently known to AnyEvent:
1000		1245
1001	"PERL_ANYEVENT_VERBOSE"	1246	"PERL_ANYEVENT_VERBOSE"
1002	By default, AnyEvent will be completely silent except in fatal	1247	By default, AnyEvent will log messages with loglevel 4 ("error") or
1003	conditions. You can set this environment variable to make AnyEvent	1248	higher (see AnyEvent::Log). You can set this environment variable to
1004	more talkative.	1249	a numerical loglevel to make AnyEvent more (or less) talkative.
1005		1250
		1251	If you want to do more than just set the global logging level you
		1252	should have a look at "PERL_ANYEVENT_LOG", which allows much more
		1253	complex specifications.
		1254
		1255	When set to 0 ("off"), then no messages whatsoever will be logged
		1256	with everything else at defaults.
		1257
1006	When set to 1 or higher, causes AnyEvent to warn about unexpected	1258	When set to 5 or higher ("warn"), AnyEvent warns about unexpected
1007	conditions, such as not being able to load the event model specified	1259	conditions, such as not being able to load the event model specified
1008	by "PERL_ANYEVENT_MODEL".	1260	by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception
		1261	- this is the minimum recommended level for use during development.
1009		1262
1010	When set to 2 or higher, cause AnyEvent to report to STDERR which	1263	When set to 7 or higher (info), AnyEvent reports which event model
1011	event model it chooses.	1264	it chooses.
1012		1265
1013	When set to 8 or higher, then AnyEvent will report extra information	1266	When set to 8 or higher (debug), then AnyEvent will report extra
1014	on which optional modules it loads and how it implements certain	1267	information on which optional modules it loads and how it implements
1015	features.	1268	certain features.
		1269
		1270	"PERL_ANYEVENT_LOG"
		1271	Accepts rather complex logging specifications. For example, you
		1272	could log all "debug" messages of some module to stderr, warnings
		1273	and above to stderr, and errors and above to syslog, with:
		1274
		1275	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		1276
		1277	For the rather extensive details, see AnyEvent::Log.
		1278
		1279	This variable is evaluated when AnyEvent (or AnyEvent::Log) is
		1280	loaded, so will take effect even before AnyEvent has initialised
		1281	itself.
		1282
		1283	Note that specifying this environment variable causes the
		1284	AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE"
		1285	does not, so only using the latter saves a few hundred kB of memory
		1286	unless a module explicitly needs the extra features of
		1287	AnyEvent::Log.
1016		1288
1017	"PERL_ANYEVENT_STRICT"	1289	"PERL_ANYEVENT_STRICT"
1018	AnyEvent does not do much argument checking by default, as thorough	1290	AnyEvent does not do much argument checking by default, as thorough
1019	argument checking is very costly. Setting this variable to a true	1291	argument checking is very costly. Setting this variable to a true
1020	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1292	value will cause AnyEvent to load "AnyEvent::Strict" and then to
1021	thoroughly check the arguments passed to most method calls. If it	1293	thoroughly check the arguments passed to most method calls. If it
1022	finds any problems, it will croak.	1294	finds any problems, it will croak.
1023		1295
1024	In other words, enables "strict" mode.	1296	In other words, enables "strict" mode.
1025		1297
1026	Unlike "use strict" (or it's modern cousin, "use common::sense", it	1298	Unlike "use strict" (or its modern cousin, "use common::sense", it
1027	is definitely recommended to keep it off in production. Keeping	1299	is definitely recommended to keep it off in production. Keeping
1028	"PERL_ANYEVENT_STRICT=1" in your environment while developing	1300	"PERL_ANYEVENT_STRICT=1" in your environment while developing
1029	programs can be very useful, however.	1301	programs can be very useful, however.
1030		1302
		1303	"PERL_ANYEVENT_DEBUG_SHELL"
		1304	If this env variable is nonempty, then its contents will be
		1305	interpreted by "AnyEvent::Socket::parse_hostport" and
		1306	"AnyEvent::Debug::shell" (after replacing every occurance of $$ by
		1307	the process pid). The shell object is saved in
		1308	$AnyEvent::Debug::SHELL.
		1309
		1310	This happens when the first watcher is created.
		1311
		1312	For example, to bind a debug shell on a unix domain socket in
		1313	/tmp/debug<pid>.sock, you could use this:
		1314
		1315	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		1316	# connect with e.g.: socat readline /tmp/debug123.sock
		1317
		1318	Or to bind to tcp port 4545 on localhost:
		1319
		1320	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		1321	# connect with e.g.: telnet localhost 4545
		1322
		1323	Note that creating sockets in /tmp or on localhost is very unsafe on
		1324	multiuser systems.
		1325
		1326	"PERL_ANYEVENT_DEBUG_WRAP"
		1327	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1328	debugging purposes. See "AnyEvent::Debug::wrap" for details.
		1329
1031	"PERL_ANYEVENT_MODEL"	1330	"PERL_ANYEVENT_MODEL"
1032	This can be used to specify the event model to be used by AnyEvent,	1331	This can be used to specify the event model to be used by AnyEvent,
1033	before auto detection and -probing kicks in. It must be a string	1332	before auto detection and -probing kicks in.
1034	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1333
1035	gets prepended and the resulting module name is loaded and if the	1334	It normally is a string consisting entirely of ASCII letters (e.g.
1036	load was successful, used as event model. If it fails to load	1335	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1336	the resulting module name is loaded and - if the load was successful
		1337	- used as event model backend. If it fails to load then AnyEvent
1037	AnyEvent will proceed with auto detection and -probing.	1338	will proceed with auto detection and -probing.
1038		1339
1039	This functionality might change in future versions.	1340	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1341	then nothing gets prepended and the module name is used as-is (hint:
		1342	"::" at the end of a string designates a module name and quotes it
		1343	appropriately).
1040		1344
1041	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1345	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
1042	could start your program like this:	1346	could start your program like this:
1043		1347
1044	PERL_ANYEVENT_MODEL=Perl perl ...	1348	PERL_ANYEVENT_MODEL=Perl perl ...
		1349
		1350	"PERL_ANYEVENT_IO_MODEL"
		1351	The current file I/O model - see AnyEvent::IO for more info.
		1352
		1353	At the moment, only "Perl" (small, pure-perl, synchronous) and
		1354	"IOAIO" (truly asynchronous) are supported. The default is "IOAIO"
		1355	if AnyEvent::AIO can be loaded, otherwise it is "Perl".
1045		1356
1046	"PERL_ANYEVENT_PROTOCOLS"	1357	"PERL_ANYEVENT_PROTOCOLS"
1047	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1358	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
1048	preferences for IPv4 or IPv6. The default is unspecified (and might	1359	preferences for IPv4 or IPv6. The default is unspecified (and might
1049	change, or be the result of auto probing).	1360	change, or be the result of auto probing).
…		…
1053	mentioned will be used, and preference will be given to protocols	1364	mentioned will be used, and preference will be given to protocols
1054	mentioned earlier in the list.	1365	mentioned earlier in the list.
1055		1366
1056	This variable can effectively be used for denial-of-service attacks	1367	This variable can effectively be used for denial-of-service attacks
1057	against local programs (e.g. when setuid), although the impact is	1368	against local programs (e.g. when setuid), although the impact is
1058	likely small, as the program has to handle conenction and other	1369	likely small, as the program has to handle connection and other
1059	failures anyways.	1370	failures anyways.
1060		1371
1061	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1372	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
1062	IPv6, but support both and try to use both.	1373	IPv6, but support both and try to use both.
1063	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1374	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
1064	resolve or contact IPv6 addresses.	1375	resolve or contact IPv6 addresses.
1065	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but	1376	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
1066	prefer IPv6 over IPv4.	1377	prefer IPv6 over IPv4.
1067		1378
		1379	"PERL_ANYEVENT_HOSTS"
		1380	This variable, if specified, overrides the /etc/hosts file used by
		1381	AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be
		1382	read from that file instead.
		1383
1068	"PERL_ANYEVENT_EDNS0"	1384	"PERL_ANYEVENT_EDNS0"
1069	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension	1385	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
1070	for DNS. This extension is generally useful to reduce DNS traffic,	1386	for DNS. This extension is generally useful to reduce DNS traffic,
1071	but some (broken) firewalls drop such DNS packets, which is why it	1387	especially when DNSSEC is involved, but some (broken) firewalls drop
1072	is off by default.	1388	such DNS packets, which is why it is off by default.
1073		1389
1074	Setting this variable to 1 will cause AnyEvent::DNS to announce	1390	Setting this variable to 1 will cause AnyEvent::DNS to announce
1075	EDNS0 in its DNS requests.	1391	EDNS0 in its DNS requests.
1076		1392
1077	"PERL_ANYEVENT_MAX_FORKS"	1393	"PERL_ANYEVENT_MAX_FORKS"
…		…
1081	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"	1397	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
1082	The default value for the "max_outstanding" parameter for the	1398	The default value for the "max_outstanding" parameter for the
1083	default DNS resolver - this is the maximum number of parallel DNS	1399	default DNS resolver - this is the maximum number of parallel DNS
1084	requests that are sent to the DNS server.	1400	requests that are sent to the DNS server.
1085		1401
		1402	"PERL_ANYEVENT_MAX_SIGNAL_LATENCY"
		1403	Perl has inherently racy signal handling (you can basically choose
		1404	between losing signals and memory corruption) - pure perl event
		1405	loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't
		1406	available) therefore have to poll regularly to avoid losing signals.
		1407
		1408	Some event loops are racy, but don't poll regularly, and some event
		1409	loops are written in C but are still racy. For those event loops,
		1410	AnyEvent installs a timer that regularly wakes up the event loop.
		1411
		1412	By default, the interval for this timer is 10 seconds, but you can
		1413	override this delay with this environment variable (or by setting
		1414	the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal
		1415	watchers).
		1416
		1417	Lower values increase CPU (and energy) usage, higher values can
		1418	introduce long delays when reaping children or waiting for signals.
		1419
		1420	The AnyEvent::Async module, if available, will be used to avoid this
		1421	polling (with most event loops).
		1422
1086	"PERL_ANYEVENT_RESOLV_CONF"	1423	"PERL_ANYEVENT_RESOLV_CONF"
1087	The file to use instead of /etc/resolv.conf (or OS-specific	1424	The absolute path to a resolv.conf-style file to use instead of
1088	configuration) in the default resolver. When set to the empty	1425	/etc/resolv.conf (or the OS-specific configuration) in the default
1089	string, no default config will be used.	1426	resolver, or the empty string to select the default configuration.
1090		1427
1091	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".	1428	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1092	When neither "ca_file" nor "ca_path" was specified during	1429	When neither "ca_file" nor "ca_path" was specified during
1093	AnyEvent::TLS context creation, and either of these environment	1430	AnyEvent::TLS context creation, and either of these environment
1094	variables exist, they will be used to specify CA certificate	1431	variables are nonempty, they will be used to specify CA certificate
1095	locations instead of a system-dependent default.	1432	locations instead of a system-dependent default.
1096		1433
1097	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"	1434	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
1098	When these are set to 1, then the respective modules are not loaded.	1435	When these are set to 1, then the respective modules are not loaded.
1099	Mostly good for testing AnyEvent itself.	1436	Mostly good for testing AnyEvent itself.
…		…
1159	warn "read: $input\n"; # output what has been read	1496	warn "read: $input\n"; # output what has been read
1160	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1497	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1161	},	1498	},
1162	);	1499	);
1163		1500
1164	my $time_watcher; # can only be used once
1165
1166	sub new_timer {
1167	$timer = AnyEvent->timer (after => 1, cb => sub {	1501	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1168	warn "timeout\n"; # print 'timeout' about every second	1502	warn "timeout\n"; # print 'timeout' at most every second
1169	&new_timer; # and restart the time
1170	});
1171	}	1503	});
1172
1173	new_timer; # create first timer
1174		1504
1175	$cv->recv; # wait until user enters /^q/i	1505	$cv->recv; # wait until user enters /^q/i
1176		1506
1177	REAL-WORLD EXAMPLE	1507	REAL-WORLD EXAMPLE
1178	Consider the Net::FCP module. It features (among others) the following	1508	Consider the Net::FCP module. It features (among others) the following
…		…
1250		1580
1251	The actual code goes further and collects all errors ("die"s,	1581	The actual code goes further and collects all errors ("die"s,
1252	exceptions) that occurred during request processing. The "result" method	1582	exceptions) that occurred during request processing. The "result" method
1253	detects whether an exception as thrown (it is stored inside the $txn	1583	detects whether an exception as thrown (it is stored inside the $txn
1254	object) and just throws the exception, which means connection errors and	1584	object) and just throws the exception, which means connection errors and
1255	other problems get reported tot he code that tries to use the result,	1585	other problems get reported to the code that tries to use the result,
1256	not in a random callback.	1586	not in a random callback.
1257		1587
1258	All of this enables the following usage styles:	1588	All of this enables the following usage styles:
1259		1589
1260	1. Blocking:	1590	1. Blocking:
…		…
1278	my $txn = shift;	1608	my $txn = shift;
1279	my $data = $txn->result;	1609	my $data = $txn->result;
1280	...	1610	...
1281	});	1611	});
1282		1612
1283	EV::loop;	1613	EV::run;
1284		1614
1285	3b. The module user could use AnyEvent, too:	1615	3b. The module user could use AnyEvent, too:
1286		1616
1287	use AnyEvent;	1617	use AnyEvent;
1288		1618
…		…
1305	through AnyEvent. The benchmark creates a lot of timers (with a zero	1635	through AnyEvent. The benchmark creates a lot of timers (with a zero
1306	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1636	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1307	which it is), lets them fire exactly once and destroys them again.	1637	which it is), lets them fire exactly once and destroys them again.
1308		1638
1309	Source code for this benchmark is found as eg/bench in the AnyEvent	1639	Source code for this benchmark is found as eg/bench in the AnyEvent
1310	distribution.	1640	distribution. It uses the AE interface, which makes a real difference
		1641	for the EV and Perl backends only.
1311		1642
1312	Explanation of the columns	1643	Explanation of the columns
1313	watcher is the number of event watchers created/destroyed. Since	1644	watcher is the number of event watchers created/destroyed. Since
1314	different event models feature vastly different performances, each event	1645	different event models feature vastly different performances, each event
1315	loop was given a number of watchers so that overall runtime is	1646	loop was given a number of watchers so that overall runtime is
…		…
1334	destroy is the time, in microseconds, that it takes to destroy a	1665	destroy is the time, in microseconds, that it takes to destroy a
1335	single watcher.	1666	single watcher.
1336		1667
1337	Results	1668	Results
1338	name watchers bytes create invoke destroy comment	1669	name watchers bytes create invoke destroy comment
1339	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1670	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1340	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1671	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1341	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1672	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1342	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1673	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1343	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1674	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1344	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1675	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
1345	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll	1676	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
1346	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll	1677	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1347	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1678	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1348	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1679	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1349	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1680	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1350	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1681	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1351		1682
1352	Discussion	1683	Discussion
1353	The benchmark does not measure scalability of the event loop very	1684	The benchmark does not measure scalability of the event loop very
1354	well. For example, a select-based event loop (such as the pure perl one)	1685	well. For example, a select-based event loop (such as the pure perl one)
1355	can never compete with an event loop that uses epoll when the number of	1686	can never compete with an event loop that uses epoll when the number of
…		…
1366	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1697	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1367	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1698	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1368	CPU cycles with POE.	1699	CPU cycles with POE.
1369		1700
1370	"EV" is the sole leader regarding speed and memory use, which are both	1701	"EV" is the sole leader regarding speed and memory use, which are both
1371	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1702	maximal/minimal, respectively. When using the AE API there is zero
		1703	overhead (when going through the AnyEvent API create is about 5-6 times
		1704	slower, with other times being equal, so still uses far less memory than
1372	far less memory than any other event loop and is still faster than Event	1705	any other event loop and is still faster than Event natively).
1373	natively.
1374		1706
1375	The pure perl implementation is hit in a few sweet spots (both the	1707	The pure perl implementation is hit in a few sweet spots (both the
1376	constant timeout and the use of a single fd hit optimisations in the	1708	constant timeout and the use of a single fd hit optimisations in the
1377	perl interpreter and the backend itself). Nevertheless this shows that	1709	perl interpreter and the backend itself). Nevertheless this shows that
1378	it adds very little overhead in itself. Like any select-based backend	1710	it adds very little overhead in itself. Like any select-based backend
…		…
1424	when used without AnyEvent), but most event loops have acceptable	1756	when used without AnyEvent), but most event loops have acceptable
1425	performance with or without AnyEvent.	1757	performance with or without AnyEvent.
1426		1758
1427	* The overhead AnyEvent adds is usually much smaller than the overhead	1759	* The overhead AnyEvent adds is usually much smaller than the overhead
1428	of the actual event loop, only with extremely fast event loops such	1760	of the actual event loop, only with extremely fast event loops such
1429	as EV adds AnyEvent significant overhead.	1761	as EV does AnyEvent add significant overhead.
1430		1762
1431	* You should avoid POE like the plague if you want performance or	1763	* You should avoid POE like the plague if you want performance or
1432	reasonable memory usage.	1764	reasonable memory usage.
1433		1765
1434	BENCHMARKING THE LARGE SERVER CASE	1766	BENCHMARKING THE LARGE SERVER CASE
…		…
1448	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1780	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1449	100 (1%) are active. This mirrors the activity of large servers with	1781	100 (1%) are active. This mirrors the activity of large servers with
1450	many connections, most of which are idle at any one point in time.	1782	many connections, most of which are idle at any one point in time.
1451		1783
1452	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1784	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1453	distribution.	1785	distribution. It uses the AE interface, which makes a real difference
		1786	for the EV and Perl backends only.
1454		1787
1455	Explanation of the columns	1788	Explanation of the columns
1456	sockets is the number of sockets, and twice the number of "servers"	1789	sockets is the number of sockets, and twice the number of "servers"
1457	(as each server has a read and write socket end).	1790	(as each server has a read and write socket end).
1458		1791
…		…
1464	forwarding it to another server. This includes deleting the old timeout	1797	forwarding it to another server. This includes deleting the old timeout
1465	and creating a new one that moves the timeout into the future.	1798	and creating a new one that moves the timeout into the future.
1466		1799
1467	Results	1800	Results
1468	name sockets create request	1801	name sockets create request
1469	EV 20000 69.01 11.16	1802	EV 20000 62.66 7.99
1470	Perl 20000 73.32 35.87	1803	Perl 20000 68.32 32.64
1471	IOAsync 20000 157.00 98.14 epoll	1804	IOAsync 20000 174.06 101.15 epoll
1472	IOAsync 20000 159.31 616.06 poll	1805	IOAsync 20000 174.67 610.84 poll
1473	Event 20000 212.62 257.32	1806	Event 20000 202.69 242.91
1474	Glib 20000 651.16 1896.30	1807	Glib 20000 557.01 1689.52
1475	POE 20000 349.67 12317.24 uses POE::Loop::Event	1808	POE 20000 341.54 12086.32 uses POE::Loop::Event
1476		1809
1477	Discussion	1810	Discussion
1478	This benchmark does measure scalability and overall performance of the	1811	This benchmark does measure scalability and overall performance of the
1479	particular event loop.	1812	particular event loop.
1480		1813
…		…
1593	As you can see, the AnyEvent + EV combination even beats the	1926	As you can see, the AnyEvent + EV combination even beats the
1594	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl	1927	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1595	backend easily beats IO::Lambda and POE.	1928	backend easily beats IO::Lambda and POE.
1596		1929
1597	And even the 100% non-blocking version written using the high-level (and	1930	And even the 100% non-blocking version written using the high-level (and
1598	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a	1931	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
1599	large margin, even though it does all of DNS, tcp-connect and socket I/O	1932	higher level ("unoptimised") abstractions by a large margin, even though
1600	in a non-blocking way.	1933	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
1601		1934
1602	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and	1935	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
1603	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are	1936	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1604	part of the IO::lambda distribution and were used without any changes.	1937	part of the IO::Lambda distribution and were used without any changes.
1605		1938
1606	SIGNALS	1939	SIGNALS
1607	AnyEvent currently installs handlers for these signals:	1940	AnyEvent currently installs handlers for these signals:
1608		1941
1609	SIGCHLD	1942	SIGCHLD
…		…
1631		1964
1632	Feel free to install your own handler, or reset it to defaults.	1965	Feel free to install your own handler, or reset it to defaults.
1633		1966
1634	RECOMMENDED/OPTIONAL MODULES	1967	RECOMMENDED/OPTIONAL MODULES
1635	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and	1968	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
1636	it's built-in modules) are required to use it.	1969	its built-in modules) are required to use it.
1637		1970
1638	That does not mean that AnyEvent won't take advantage of some additional	1971	That does not mean that AnyEvent won't take advantage of some additional
1639	modules if they are installed.	1972	modules if they are installed.
1640		1973
1641	This section epxlains which additional modules will be used, and how	1974	This section explains which additional modules will be used, and how
1642	they affect AnyEvent's operetion.	1975	they affect AnyEvent's operation.
1643		1976
1644	Async::Interrupt	1977	Async::Interrupt
1645	This slightly arcane module is used to implement fast signal	1978	This slightly arcane module is used to implement fast signal
1646	handling: To my knowledge, there is no way to do completely	1979	handling: To my knowledge, there is no way to do completely
1647	race-free and quick signal handling in pure perl. To ensure that	1980	race-free and quick signal handling in pure perl. To ensure that
1648	signals still get delivered, AnyEvent will start an interval timer	1981	signals still get delivered, AnyEvent will start an interval timer
1649	to wake up perl (and catch the signals) with soemd elay (default is	1982	to wake up perl (and catch the signals) with some delay (default is
1650	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).	1983	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
1651		1984
1652	If this module is available, then it will be used to implement	1985	If this module is available, then it will be used to implement
1653	signal catching, which means that signals will not be delayed, and	1986	signal catching, which means that signals will not be delayed, and
1654	the event loop will not be interrupted regularly, which is more	1987	the event loop will not be interrupted regularly, which is more
1655	efficient (And good for battery life on laptops).	1988	efficient (and good for battery life on laptops).
1656		1989
1657	This affects not just the pure-perl event loop, but also other event	1990	This affects not just the pure-perl event loop, but also other event
1658	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).	1991	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1992
		1993	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1994	natively, and either employ their own workarounds (POE) or use
		1995	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1996	Installing Async::Interrupt does nothing for those backends.
1659		1997
1660	EV This module isn't really "optional", as it is simply one of the	1998	EV This module isn't really "optional", as it is simply one of the
1661	backend event loops that AnyEvent can use. However, it is simply the	1999	backend event loops that AnyEvent can use. However, it is simply the
1662	best event loop available in terms of features, speed and stability:	2000	best event loop available in terms of features, speed and stability:
1663	It supports the AnyEvent API optimally, implements all the watcher	2001	It supports the AnyEvent API optimally, implements all the watcher
…		…
1665	clock is available, can take avdantage of advanced kernel interfaces	2003	clock is available, can take avdantage of advanced kernel interfaces
1666	such as "epoll" and "kqueue", and is the fastest backend by far.	2004	such as "epoll" and "kqueue", and is the fastest backend by far.
1667	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and	2005	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
1668	Glib::EV).	2006	Glib::EV).
1669		2007
		2008	If you only use backends that rely on another event loop (e.g.
		2009	"Tk"), then this module will do nothing for you.
		2010
1670	Guard	2011	Guard
1671	The guard module, when used, will be used to implement	2012	The guard module, when used, will be used to implement
1672	"AnyEvent::Util::guard". This speeds up guards considerably (and	2013	"AnyEvent::Util::guard". This speeds up guards considerably (and
1673	uses a lot less memory), but otherwise doesn't affect guard	2014	uses a lot less memory), but otherwise doesn't affect guard
1674	operation much. It is purely used for performance.	2015	operation much. It is purely used for performance.
1675		2016
1676	JSON and JSON::XS	2017	JSON and JSON::XS
1677	This module is required when you want to read or write JSON data via	2018	One of these modules is required when you want to read or write JSON
1678	AnyEvent::Handle. It is also written in pure-perl, but can take	2019	data via AnyEvent::Handle. JSON is also written in pure-perl, but
1679	advantage of the ulta-high-speed JSON::XS module when it is	2020	can take advantage of the ultra-high-speed JSON::XS module when it
1680	installed.	2021	is installed.
1681
1682	In fact, AnyEvent::Handle will use JSON::XS by default if it is
1683	installed.
1684		2022
1685	Net::SSLeay	2023	Net::SSLeay
1686	Implementing TLS/SSL in Perl is certainly interesting, but not very	2024	Implementing TLS/SSL in Perl is certainly interesting, but not very
1687	worthwhile: If this module is installed, then AnyEvent::Handle (with	2025	worthwhile: If this module is installed, then AnyEvent::Handle (with
1688	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.	2026	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
1689		2027
1690	Time::HiRes	2028	Time::HiRes
1691	This module is part of perl since release 5.008. It will be used	2029	This module is part of perl since release 5.008. It will be used
1692	when the chosen event library does not come with a timing source on	2030	when the chosen event library does not come with a timing source of
1693	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will	2031	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
1694	additionally use it to try to use a monotonic clock for timing	2032	load it to try to use a monotonic clock for timing stability.
1695	stability.	2033
		2034	AnyEvent::AIO (and IO::AIO)
		2035	The default implementation of AnyEvent::IO is to do I/O
		2036	synchronously, stopping programs while they access the disk, which
		2037	is fine for a lot of programs.
		2038
		2039	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it
		2040	switch to a true asynchronous implementation, so event processing
		2041	can continue even while waiting for disk I/O.
1696		2042
1697	FORK	2043	FORK
1698	Most event libraries are not fork-safe. The ones who are usually are	2044	Most event libraries are not fork-safe. The ones who are usually are
1699	because they rely on inefficient but fork-safe "select" or "poll" calls.	2045	because they rely on inefficient but fork-safe "select" or "poll" calls
1700	Only EV is fully fork-aware.	2046	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		2047	epoll are usually badly thought-out hacks that are incompatible with
		2048	fork in one way or another. Only EV is fully fork-aware and ensures that
		2049	you continue event-processing in both parent and child (or both, if you
		2050	know what you are doing).
		2051
		2052	This means that, in general, you cannot fork and do event processing in
		2053	the child if the event library was initialised before the fork (which
		2054	usually happens when the first AnyEvent watcher is created, or the
		2055	library is loaded).
1701		2056
1702	If you have to fork, you must either do so before creating your first	2057	If you have to fork, you must either do so before creating your first
1703	watcher OR you must not use AnyEvent at all in the child OR you must do	2058	watcher OR you must not use AnyEvent at all in the child OR you must do
1704	something completely out of the scope of AnyEvent.	2059	something completely out of the scope of AnyEvent (see below).
		2060
		2061	The problem of doing event processing in the parent and the child is
		2062	much more complicated: even for backends that are fork-aware or
		2063	fork-safe, their behaviour is not usually what you want: fork clones all
		2064	watchers, that means all timers, I/O watchers etc. are active in both
		2065	parent and child, which is almost never what you want. Using "exec" to
		2066	start worker children from some kind of manage prrocess is usually
		2067	preferred, because it is much easier and cleaner, at the expense of
		2068	having to have another binary.
		2069
		2070	In addition to logical problems with fork, there are also implementation
		2071	problems. For example, on POSIX systems, you cannot fork at all in Perl
		2072	code if a thread (I am talking of pthreads here) was ever created in the
		2073	process, and this is just the tip of the iceberg. In general, using fork
		2074	from Perl is difficult, and attempting to use fork without an exec to
		2075	implement some kind of parallel processing is almost certainly doomed.
		2076
		2077	To safely fork and exec, you should use a module such as Proc::FastSpawn
		2078	that let's you safely fork and exec new processes.
		2079
		2080	If you want to do multiprocessing using processes, you can look at the
		2081	AnyEvent::Fork module (and some related modules such as
		2082	AnyEvent::Fork::RPC, AnyEvent::Fork::Pool and AnyEvent::Fork::Remote).
		2083	This module allows you to safely create subprocesses without any
		2084	limitations - you can use X11 toolkits or AnyEvent in the children
		2085	created by AnyEvent::Fork safely and without any special precautions.
1705		2086
1706	SECURITY CONSIDERATIONS	2087	SECURITY CONSIDERATIONS
1707	AnyEvent can be forced to load any event model via	2088	AnyEvent can be forced to load any event model via
1708	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	2089	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1709	to execute arbitrary code or directly gain access, it can easily be used	2090	to execute arbitrary code or directly gain access, it can easily be used
…		…
1733	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	2114	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1734	annoying memleaks, such as leaking on "map" and "grep" but it is usually	2115	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1735	not as pronounced).	2116	not as pronounced).
1736		2117
1737	SEE ALSO	2118	SEE ALSO
1738	Utility functions: AnyEvent::Util.	2119	Tutorial/Introduction: AnyEvent::Intro.
1739		2120
1740	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	2121	FAQ: AnyEvent::FAQ.
1741	Event::Lib, Qt, POE.	2122
		2123	Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log
		2124	(simply logging).
		2125
		2126	Development/Debugging: AnyEvent::Strict (stricter checking),
		2127	AnyEvent::Debug (interactive shell, watcher tracing).
		2128
		2129	Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
		2130	Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK, Cocoa::EventLoop, UV.
1742		2131
1743	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	2132	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1744	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	2133	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1745	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,	2134	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1746	AnyEvent::Impl::IOAsync.	2135	AnyEvent::Impl::IOAsync, AnyEvent::Impl::Irssi, AnyEvent::Impl::FLTK,
		2136	AnyEvent::Impl::Cocoa, AnyEvent::Impl::UV.
1747		2137
1748	Non-blocking file handles, sockets, TCP clients and servers:	2138	Non-blocking handles, pipes, stream sockets, TCP clients and servers:
1749	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.	2139	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1750		2140
		2141	Asynchronous File I/O: AnyEvent::IO.
		2142
1751	Asynchronous DNS: AnyEvent::DNS.	2143	Asynchronous DNS: AnyEvent::DNS.
1752		2144
1753	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	2145	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1754		2146
1755	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,	2147	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
1756	AnyEvent::HTTP.	2148	AnyEvent::HTTP.
1757		2149
1758	AUTHOR	2150	AUTHOR
1759	Marc Lehmann <schmorp@schmorp.de>	2151	Marc Lehmann <schmorp@schmorp.de>
1760	http://home.schmorp.de/	2152	http://anyevent.schmorp.de
1761		2153

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Comparing AnyEvent/README (file contents):
Revision 1.46 by root, Sat Jul 18 05:19:09 2009 UTC vs.
Revision 1.76 by root, Wed Jan 27 18:15:21 2016 UTC