[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.41 by root, Fri Jun 26 06:33:17 2009 UTC vs.
Revision 1.79 by root, Tue Feb 26 02:08:34 2019 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 (not 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
176	handle). Note that only file handles pointing to things for which	194	handle). Note that only file handles pointing to things for which
177	non-blocking operation makes sense are allowed. This includes sockets,	195	non-blocking operation makes sense are allowed. This includes sockets,
178	most character devices, pipes, fifos and so on, but not for example	196	most character devices, pipes, fifos and so on, but not for example
179	files or block devices.	197	files or block devices.
…		…
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
…		…
350	invocation, and callback invocation will be synchronous. Synchronous	386	invocation, and callback invocation will be synchronous. Synchronous
351	means that it might take a while until the signal gets handled by the	387	means that it might take a while until the signal gets handled by the
352	process, but it is guaranteed not to interrupt any other callbacks.	388	process, but it is guaranteed not to interrupt any other callbacks.
353		389
354	The main advantage of using these watchers is that you can share a	390	The main advantage of using these watchers is that you can share a
355	signal between multiple watchers.	391	signal between multiple watchers, and AnyEvent will ensure that signals
		392	will not interrupt your program at bad times.
356		393
357	This watcher might use %SIG, so programs overwriting those signals	394	This watcher might use %SIG (depending on the event loop used), so
358	directly will likely not work correctly.	395	programs overwriting those signals directly will likely not work
		396	correctly.
359		397
360	Example: exit on SIGINT	398	Example: exit on SIGINT
361		399
362	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	400	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
363		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
364	CHILD PROCESS WATCHERS	432	CHILD PROCESS WATCHERS
		433	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		434
365	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.
366		436
367	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,
368	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).
369	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
370	on any trace events (stopped/continued).	440	and an exit status is available, not on any trace events
		441	(stopped/continued).
371		442
372	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
373	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
374	callback arguments.	445	callback arguments.
375		446
…		…
391		462
392	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
393	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
394	you "fork" the child (alternatively, you can call "AnyEvent::detect").	465	you "fork" the child (alternatively, you can call "AnyEvent::detect").
395		466
		467	As most event loops do not support waiting for child events, they will
		468	be emulated by AnyEvent in most cases, in which case the latency and
		469	race problems mentioned in the description of signal watchers apply.
		470
396	Example: fork a process and wait for it	471	Example: fork a process and wait for it
397		472
398	my $done = AnyEvent->condvar;	473	my $done = AnyEvent->condvar;
399		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.
400	my $pid = fork or exit 5;	479	my $pid = fork or exit 5;
401		480
402	my $w = AnyEvent->child (	481	my $w = AnyEvent->child (
403	pid => $pid,	482	pid => $pid,
404	cb => sub {	483	cb => sub {
…		…
410		489
411	# do something else, then wait for process exit	490	# do something else, then wait for process exit
412	$done->recv;	491	$done->recv;
413		492
414	IDLE WATCHERS	493	IDLE WATCHERS
415	Sometimes there is a need to do something, but it is not so important to	494	$w = AnyEvent->idle (cb => <callback>);
416	do it instantly, but only when there is nothing better to do. This
417	"nothing better to do" is usually defined to be "no other events need
418	attention by the event loop".
419		495
420	Idle watchers ideally get invoked when the event loop has nothing better	496	This will repeatedly invoke the callback after the process becomes idle,
421	to do, just before it would block the process to wait for new events.	497	until either the watcher is destroyed or new events have been detected.
422	Instead of blocking, the idle watcher is invoked.
423		498
424	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
425	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,
426	will simply call the callback "from time to time".	510	AnyEvent will simply call the callback "from time to time".
427		511
428	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
429	is otherwise idle:	513	is otherwise idle:
430		514
431	my @lines; # read data	515	my @lines; # read data
…		…
444	}	528	}
445	});	529	});
446	});	530	});
447		531
448	CONDITION VARIABLES	532	CONDITION VARIABLES
		533	$cv = AnyEvent->condvar;
		534
		535	$cv->send (<list>);
		536	my @res = $cv->recv;
		537
449	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
450	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
451	will actively watch for new events and call your callbacks.	540	will actively watch for new events and call your callbacks.
452		541
453	AnyEvent is different, it expects somebody else to run the event loop	542	AnyEvent is slightly different: it expects somebody else to run the
454	and will only block when necessary (usually when told by the user).	543	event loop and will only block when necessary (usually when told by the
		544	user).
455		545
456	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
457	because they represent a condition that must become true.	547	they represent a condition that must become true.
		548
		549	Now is probably a good time to look at the examples further below.
458		550
459	Condition variables can be created by calling the "AnyEvent->condvar"	551	Condition variables can be created by calling the "AnyEvent->condvar"
460	method, usually without arguments. The only argument pair allowed is	552	method, usually without arguments. The only argument pair allowed is
461
462	"cb", which specifies a callback to be called when the condition	553	"cb", which specifies a callback to be called when the condition
463	variable becomes true, with the condition variable as the first argument	554	variable becomes true, with the condition variable as the first argument
464	(but not the results).	555	(but not the results).
465		556
466	After creation, the condition variable is "false" until it becomes	557	After creation, the condition variable is "false" until it becomes
467	"true" by calling the "send" method (or calling the condition variable	558	"true" by calling the "send" method (or calling the condition variable
468	as if it were a callback, read about the caveats in the description for	559	as if it were a callback, read about the caveats in the description for
469	the "->send" method).	560	the "->send" method).
470		561
471	Condition variables are similar to callbacks, except that you can	562	Since condition variables are the most complex part of the AnyEvent API,
472	optionally wait for them. They can also be called merge points - points	563	here are some different mental models of what they are - pick the ones
473	in time where multiple outstanding events have been processed. And yet	564	you can connect to:
474	another way to call them is transactions - each condition variable can	565
475	be used to represent a transaction, which finishes at some point and	566	* Condition variables are like callbacks - you can call them (and pass
476	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.
477		583
478	Condition variables are very useful to signal that something has	584	Condition variables are very useful to signal that something has
479	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
480	requests, then a condition variable would be the ideal candidate to	586	requests, then a condition variable would be the ideal candidate to
481	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
…		…
494		600
495	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
496	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
497	(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
498	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	604	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
499	it's "new" method in your own "new" method.	605	its "new" method in your own "new" method.
500		606
501	There are two "sides" to a condition variable - the "producer side"	607	There are two "sides" to a condition variable - the "producer side"
502	which eventually calls "-> send", and the "consumer side", which waits	608	which eventually calls "-> send", and the "consumer side", which waits
503	for the send to occur.	609	for the send to occur.
504		610
505	Example: wait for a timer.	611	Example: wait for a timer.
506		612
507	# wait till the result is ready	613	# condition: "wait till the timer is fired"
508	my $result_ready = AnyEvent->condvar;	614	my $timer_fired = AnyEvent->condvar;
509		615
510	# do something such as adding a timer	616	# create the timer - we could wait for, say
511	# or socket watcher the calls $result_ready->send	617	# a handle becomign ready, or even an
512	# when the "result" is ready.	618	# AnyEvent::HTTP request to finish, but
513	# in this case, we simply use a timer:	619	# in this case, we simply use a timer:
514	my $w = AnyEvent->timer (	620	my $w = AnyEvent->timer (
515	after => 1,	621	after => 1,
516	cb => sub { $result_ready->send },	622	cb => sub { $timer_fired->send },
517	);	623	);
518		624
519	# this "blocks" (while handling events) till the callback	625	# this "blocks" (while handling events) till the callback
520	# calls send	626	# calls ->send
521	$result_ready->recv;	627	$timer_fired->recv;
522		628
523	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
524	variables are also code references.	630	variables are also callable directly.
525		631
526	my $done = AnyEvent->condvar;	632	my $done = AnyEvent->condvar;
527	my $delay = AnyEvent->timer (after => 5, cb => $done);	633	my $delay = AnyEvent->timer (after => 5, cb => $done);
528	$done->recv;	634	$done->recv;
529		635
…		…
535		641
536	...	642	...
537		643
538	my @info = $couchdb->info->recv;	644	my @info = $couchdb->info->recv;
539		645
540	And this is how you would just ste a callback to be called whenever the	646	And this is how you would just set a callback to be called whenever the
541	results are available:	647	results are available:
542		648
543	$couchdb->info->cb (sub {	649	$couchdb->info->cb (sub {
544	my @info = $_[0]->recv;	650	my @info = $_[0]->recv;
545	});	651	});
…		…
560		666
561	Any arguments passed to the "send" call will be returned by all	667	Any arguments passed to the "send" call will be returned by all
562	future "->recv" calls.	668	future "->recv" calls.
563		669
564	Condition variables are overloaded so one can call them directly (as	670	Condition variables are overloaded so one can call them directly (as
565	a code reference). Calling them directly is the same as calling	671	if they were a code reference). Calling them directly is the same as
566	"send". Note, however, that many C-based event loops do not handle	672	calling "send".
567	overloading, so as tempting as it may be, passing a condition
568	variable instead of a callback does not work. Both the pure perl and
569	EV loops support overloading, however, as well as all functions that
570	use perl to invoke a callback (as in AnyEvent::Socket and
571	AnyEvent::DNS for example).
572		673
573	$cv->croak ($error)	674	$cv->croak ($error)
574	Similar to send, but causes all call's to "->recv" to invoke	675	Similar to send, but causes all calls to "->recv" to invoke
575	"Carp::croak" with the given error message/object/scalar.	676	"Carp::croak" with the given error message/object/scalar.
576		677
577	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
578	user/consumer.	679	user/consumer. Doing it this way instead of calling "croak" directly
		680	delays the error detection, but has the overwhelming advantage that
		681	it diagnoses the error at the place where the result is expected,
		682	and not deep in some event callback with no connection to the actual
		683	code causing the problem.
579		684
580	$cv->begin ([group callback])	685	$cv->begin ([group callback])
581	$cv->end	686	$cv->end
582	These two methods are EXPERIMENTAL and MIGHT CHANGE.
583
584	These two methods can be used to combine many transactions/events	687	These two methods can be used to combine many transactions/events
585	into one. For example, a function that pings many hosts in parallel	688	into one. For example, a function that pings many hosts in parallel
586	might want to use a condition variable for the whole process.	689	might want to use a condition variable for the whole process.
587		690
588	Every call to "->begin" will increment a counter, and every call to	691	Every call to "->begin" will increment a counter, and every call to
589	"->end" will decrement it. If the counter reaches 0 in "->end", the	692	"->end" will decrement it. If the counter reaches 0 in "->end", the
590	(last) callback passed to "begin" will be executed. That callback is	693	(last) callback passed to "begin" will be executed, passing the
591	supposed to call "->send", but that is not required. If no	694	condvar as first argument. That callback is supposed to call
		695	"->send", but that is not required. If no group callback was set,
592	callback was set, "send" will be called without any arguments.	696	"send" will be called without any arguments.
593		697
594	Let's clarify this with the ping example:	698	You can think of "$cv->send" giving you an OR condition (one call
		699	sends), while "$cv->begin" and "$cv->end" giving you an AND
		700	condition (all "begin" calls must be "end"'ed before the condvar
		701	sends).
		702
		703	Let's start with a simple example: you have two I/O watchers (for
		704	example, STDOUT and STDERR for a program), and you want to wait for
		705	both streams to close before activating a condvar:
595		706
596	my $cv = AnyEvent->condvar;	707	my $cv = AnyEvent->condvar;
597		708
		709	$cv->begin; # first watcher
		710	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		711	defined sysread $fh1, my $buf, 4096
		712	or $cv->end;
		713	});
		714
		715	$cv->begin; # second watcher
		716	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		717	defined sysread $fh2, my $buf, 4096
		718	or $cv->end;
		719	});
		720
		721	$cv->recv;
		722
		723	This works because for every event source (EOF on file handle),
		724	there is one call to "begin", so the condvar waits for all calls to
		725	"end" before sending.
		726
		727	The ping example mentioned above is slightly more complicated, as
		728	the there are results to be passed back, and the number of tasks
		729	that are begun can potentially be zero:
		730
		731	my $cv = AnyEvent->condvar;
		732
598	my %result;	733	my %result;
599	$cv->begin (sub { $cv->send (\%result) });	734	$cv->begin (sub { shift->send (\%result) });
600		735
601	for my $host (@list_of_hosts) {	736	for my $host (@list_of_hosts) {
602	$cv->begin;	737	$cv->begin;
603	ping_host_then_call_callback $host, sub {	738	ping_host_then_call_callback $host, sub {
604	$result{$host} = ...;	739	$result{$host} = ...;
…		…
606	};	741	};
607	}	742	}
608		743
609	$cv->end;	744	$cv->end;
610		745
		746	...
		747
		748	my $results = $cv->recv;
		749
611	This code fragment supposedly pings a number of hosts and calls	750	This code fragment supposedly pings a number of hosts and calls
612	"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
613	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
614	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
615	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
…		…
619	the loop, which serves two important purposes: first, it sets the	758	the loop, which serves two important purposes: first, it sets the
620	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
621	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
622	(the loop doesn't execute once).	761	(the loop doesn't execute once).
623		762
624	This is the general pattern when you "fan out" into multiple	763	This is the general pattern when you "fan out" into multiple (but
625	subrequests: use an outer "begin"/"end" pair to set the callback and	764	potentially zero) subrequests: use an outer "begin"/"end" pair to
626	ensure "end" is called at least once, and then, for each subrequest	765	set the callback and ensure "end" is called at least once, and then,
627	you start, call "begin" and for each subrequest you finish, call	766	for each subrequest you start, call "begin" and for each subrequest
628	"end".	767	you finish, call "end".
629		768
630	METHODS FOR CONSUMERS	769	METHODS FOR CONSUMERS
631	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
632	awaits the condition.	771	awaits the condition.
633		772
634	$cv->recv	773	$cv->recv
635	Wait (blocking if necessary) until the "->send" or "->croak" methods	774	Wait (blocking if necessary) until the "->send" or "->croak" methods
636	have been called on c<$cv>, while servicing other watchers normally.	775	have been called on $cv, while servicing other watchers normally.
637		776
638	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
639	but will return immediately.	778	but will return immediately.
640		779
641	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
642	function will call "croak".	781	function will call "croak".
643		782
644	In list context, all parameters passed to "send" will be returned,	783	In list context, all parameters passed to "send" will be returned,
645	in scalar context only the first one will be returned.	784	in scalar context only the first one will be returned.
646		785
		786	Note that doing a blocking wait in a callback is not supported by
		787	any event loop, that is, recursive invocation of a blocking "->recv"
		788	is not allowed and the "recv" call will "croak" if such a condition
		789	is detected. This requirement can be dropped by relying on
		790	Coro::AnyEvent , which allows you to do a blocking "->recv" from any
		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.
		797
647	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
648	(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
649	using this from a module, never require a blocking wait*, but let	800	using this from a module, never require a blocking wait*. Instead,
650	the caller decide whether the call will block or not (for example,	801	let the caller decide whether the call will block or not (for
651	by coupling condition variables with some kind of request results	802	example, by coupling condition variables with some kind of request
652	and supporting callbacks so the caller knows that getting the result	803	results and supporting callbacks so the caller knows that getting
653	will not block, while still supporting blocking waits if the caller	804	the result will not block, while still supporting blocking waits if
654	so desires).	805	the caller so desires).
655		806
656	Another reason never to "->recv" in a module is that you cannot
657	sensibly have two "->recv"'s in parallel, as that would require
658	multiple interpreters or coroutines/threads, none of which
659	"AnyEvent" can supply.
660
661	The Coro module, however, can and does supply coroutines and, in
662	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
663	versions and also integrates coroutines into AnyEvent, making
664	blocking "->recv" calls perfectly safe as long as they are done from
665	another coroutine (one that doesn't run the event loop).
666
667	You can ensure that "-recv" never blocks by setting a callback and	807	You can ensure that "->recv" never blocks by setting a callback and
668	only calling "->recv" from within that callback (or at a later	808	only calling "->recv" from within that callback (or at a later
669	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
670	blocking waits otherwise.	810	blocking waits otherwise.
671		811
672	$bool = $cv->ready	812	$bool = $cv->ready
673	Returns true when the condition is "true", i.e. whether "send" or	813	Returns true when the condition is "true", i.e. whether "send" or
674	"croak" have been called.	814	"croak" have been called.
675		815
676	$cb = $cv->cb ($cb->($cv))	816	$cb = $cv->cb ($cb->($cv))
677	This is a mutator function that returns the callback set and	817	This is a mutator function that returns the callback set (or "undef"
678	optionally replaces it before doing so.	818	if not) and optionally replaces it before doing so.
679		819
680	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.
681	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
682	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
683	any later time is guaranteed not to block.	824	the callback or at any later time is guaranteed not to block.
		825
		826	Additionally, when the callback is invoked, it is also removed from
		827	the condvar (reset to "undef"), so the condvar does not keep a
		828	reference to the callback after invocation.
		829
		830	SUPPORTED EVENT LOOPS/BACKENDS
		831	The following backend classes are part of the AnyEvent distribution
		832	(every class has its own manpage):
		833
		834	Backends that are autoprobed when no other event loop can be found.
		835	EV is the preferred backend when no other event loop seems to be in
		836	use. If EV is not installed, then AnyEvent will fall back to its own
		837	pure-perl implementation, which is available everywhere as it comes
		838	with AnyEvent itself.
		839
		840	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		841	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		842
		843	Backends that are transparently being picked up when they are used.
		844	These will be used if they are already loaded when the first watcher
		845	is created, in which case it is assumed that the application is
		846	using them. This means that AnyEvent will automatically pick the
		847	right backend when the main program loads an event module before
		848	anything starts to create watchers. Nothing special needs to be done
		849	by the main program.
		850
		851	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		852	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		853	AnyEvent::Impl::Tk based on Tk, very broken.
		854	AnyEvent::Impl::UV based on UV, innovated square wheels.
		855	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		856	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		857	AnyEvent::Impl::Irssi used when running within irssi.
		858	AnyEvent::Impl::IOAsync based on IO::Async.
		859	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		860	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
		861
		862	Backends with special needs.
		863	Qt requires the Qt::Application to be instantiated first, but will
		864	otherwise be picked up automatically. As long as the main program
		865	instantiates the application before any AnyEvent watchers are
		866	created, everything should just work.
		867
		868	AnyEvent::Impl::Qt based on Qt.
		869
		870	Event loops that are indirectly supported via other backends.
		871	Some event loops can be supported via other modules:
		872
		873	There is no direct support for WxWidgets (Wx) or Prima.
		874
		875	WxWidgets has no support for watching file handles. However, you can
		876	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		877	simply polls 20 times per second, which was considered to be too
		878	horrible to even consider for AnyEvent.
		879
		880	Prima is not supported as nobody seems to be using it, but it has a
		881	POE backend, so it can be supported through POE.
		882
		883	AnyEvent knows about both Prima and Wx, however, and will try to
		884	load POE when detecting them, in the hope that POE will pick them
		885	up, in which case everything will be automatic.
		886
		887	Known event loops outside the AnyEvent distribution
		888	The following event loops or programs support AnyEvent by providing
		889	their own AnyEvent backend. They will be picked up automatically.
		890
		891	urxvt::anyevent available to rxvt-unicode extensions
684		892
685	GLOBAL VARIABLES AND FUNCTIONS	893	GLOBAL VARIABLES AND FUNCTIONS
		894	These are not normally required to use AnyEvent, but can be useful to
		895	write AnyEvent extension modules.
		896
686	$AnyEvent::MODEL	897	$AnyEvent::MODEL
687	Contains "undef" until the first watcher is being created. Then it	898	Contains "undef" until the first watcher is being created, before
		899	the backend has been autodetected.
		900
688	contains the event model that is being used, which is the name of	901	Afterwards it contains the event model that is being used, which is
689	the Perl class implementing the model. This class is usually one of	902	the name of the Perl class implementing the model. This class is
690	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	903	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
691	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).	904	other class in the case AnyEvent has been extended at runtime (e.g.
692		905	in rxvt-unicode it will be "urxvt::anyevent").
693	The known classes so far are:
694
695	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
696	AnyEvent::Impl::Event based on Event, second best choice.
697	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
698	AnyEvent::Impl::Glib based on Glib, third-best choice.
699	AnyEvent::Impl::Tk based on Tk, very bad choice.
700	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
701	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
702	AnyEvent::Impl::POE based on POE, not generic enough for full support.
703
704	# warning, support for IO::Async is only partial, as it is too broken
705	# and limited toe ven support the AnyEvent API. See AnyEvent::Impl::Async.
706	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed (see its docs).
707
708	There is no support for WxWidgets, as WxWidgets has no support for
709	watching file handles. However, you can use WxWidgets through the
710	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
711	second, which was considered to be too horrible to even consider for
712	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
713	using it's adaptor.
714
715	AnyEvent knows about Prima and Wx and will try to use POE when
716	autodetecting them.
717		906
718	AnyEvent::detect	907	AnyEvent::detect
719	Returns $AnyEvent::MODEL, forcing autodetection of the event model	908	Returns $AnyEvent::MODEL, forcing autodetection of the event model
720	if necessary. You should only call this function right before you	909	if necessary. You should only call this function right before you
721	would have created an AnyEvent watcher anyway, that is, as late as	910	would have created an AnyEvent watcher anyway, that is, as late as
722	possible at runtime.	911	possible at runtime, and not e.g. during initialisation of your
		912	module.
		913
		914	The effect of calling this function is as if a watcher had been
		915	created (specifically, actions that happen "when the first watcher
		916	is created" happen when calling detetc as well).
		917
		918	If you need to do some initialisation before AnyEvent watchers are
		919	created, use "post_detect".
723		920
724	$guard = AnyEvent::post_detect { BLOCK }	921	$guard = AnyEvent::post_detect { BLOCK }
725	Arranges for the code block to be executed as soon as the event	922	Arranges for the code block to be executed as soon as the event
726	model is autodetected (or immediately if this has already happened).	923	model is autodetected (or immediately if that has already happened).
		924
		925	The block will be executed after the actual backend has been
		926	detected ($AnyEvent::MODEL is set), so it is possible to do some
		927	initialisation only when AnyEvent is actually initialised - see the
		928	sources of AnyEvent::AIO to see how this is used.
		929
		930	The most common usage is to create some global watchers, without
		931	forcing event module detection too early. For example, AnyEvent::AIO
		932	creates and installs the global IO::AIO watcher in a "post_detect"
		933	block to avoid autodetecting the event module at load time.
727		934
728	If called in scalar or list context, then it creates and returns an	935	If called in scalar or list context, then it creates and returns an
729	object that automatically removes the callback again when it is	936	object that automatically removes the callback again when it is
		937	destroyed (or "undef" when the hook was immediately executed). See
730	destroyed. See Coro::BDB for a case where this is useful.	938	AnyEvent::AIO for a case where this is useful.
		939
		940	Example: Create a watcher for the IO::AIO module and store it in
		941	$WATCHER, but do so only do so after the event loop is initialised.
		942
		943	our WATCHER;
		944
		945	my $guard = AnyEvent::post_detect {
		946	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		947	};
		948
		949	# the \|\|= is important in case post_detect immediately runs the block,
		950	# as to not clobber the newly-created watcher. assigning both watcher and
		951	# post_detect guard to the same variable has the advantage of users being
		952	# able to just C<undef $WATCHER> if the watcher causes them grief.
		953
		954	$WATCHER \|\|= $guard;
731		955
732	@AnyEvent::post_detect	956	@AnyEvent::post_detect
733	If there are any code references in this array (you can "push" to it	957	This is a lower level interface then "AnyEvent::post_detect" (the
734	before or after loading AnyEvent), then they will called directly	958	function). This variable is mainly useful for modules that can do
		959	something useful when AnyEvent is used and thus want to know when it
		960	is initialised, but do not need to even load it by default. This
		961	array provides the means to hook into AnyEvent passively, without
		962	loading it.
		963
		964	Here is how it works: If there are any code references in this array
		965	(you can "push" to it before or after loading AnyEvent), then they
735	after the event loop has been chosen.	966	will be called directly after the event loop has been chosen.
736		967
737	You should check $AnyEvent::MODEL before adding to this array,	968	You should check $AnyEvent::MODEL before adding to this array,
738	though: if it contains a true value then the event loop has already	969	though: if it is defined then the event loop has already been
739	been detected, and the array will be ignored.	970	detected, and the array will be ignored.
740		971
741	Best use "AnyEvent::post_detect { BLOCK }" instead.	972	Best use "AnyEvent::post_detect { BLOCK }" when your application
		973	allows it, as it takes care of these details.
		974
		975	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		976	together, you could put this into Coro (this is the actual code used
		977	by Coro to accomplish this):
		978
		979	if (defined $AnyEvent::MODEL) {
		980	# AnyEvent already initialised, so load Coro::AnyEvent
		981	require Coro::AnyEvent;
		982	} else {
		983	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		984	# as soon as it is
		985	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		986	}
		987
		988	AnyEvent::postpone { BLOCK }
		989	Arranges for the block to be executed as soon as possible, but not
		990	before the call itself returns. In practise, the block will be
		991	executed just before the event loop polls for new events, or shortly
		992	afterwards.
		993
		994	This function never returns anything (to make the "return postpone {
		995	... }" idiom more useful.
		996
		997	To understand the usefulness of this function, consider a function
		998	that asynchronously does something for you and returns some
		999	transaction object or guard to let you cancel the operation. For
		1000	example, "AnyEvent::Socket::tcp_connect":
		1001
		1002	# start a connection attempt unless one is active
		1003	$self->{connect_guard} \|\|= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1004	delete $self->{connect_guard};
		1005	...
		1006	};
		1007
		1008	Imagine that this function could instantly call the callback, for
		1009	example, because it detects an obvious error such as a negative port
		1010	number. Invoking the callback before the function returns causes
		1011	problems however: the callback will be called and will try to delete
		1012	the guard object. But since the function hasn't returned yet, there
		1013	is nothing to delete. When the function eventually returns it will
		1014	assign the guard object to "$self->{connect_guard}", where it will
		1015	likely never be deleted, so the program thinks it is still trying to
		1016	connect.
		1017
		1018	This is where "AnyEvent::postpone" should be used. Instead of
		1019	calling the callback directly on error:
		1020
		1021	$cb->(undef), return # signal error to callback, BAD!
		1022	if $some_error_condition;
		1023
		1024	It should use "postpone":
		1025
		1026	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1027	if $some_error_condition;
		1028
		1029	AnyEvent::log $level, $msg[, @args]
		1030	Log the given $msg at the given $level.
		1031
		1032	If AnyEvent::Log is not loaded then this function makes a simple
		1033	test to see whether the message will be logged. If the test succeeds
		1034	it will load AnyEvent::Log and call "AnyEvent::Log::log" -
		1035	consequently, look at the AnyEvent::Log documentation for details.
		1036
		1037	If the test fails it will simply return. Right now this happens when
		1038	a numerical loglevel is used and it is larger than the level
		1039	specified via $ENV{PERL_ANYEVENT_VERBOSE}.
		1040
		1041	If you want to sprinkle loads of logging calls around your code,
		1042	consider creating a logger callback with the "AnyEvent::Log::logger"
		1043	function, which can reduce typing, codesize and can reduce the
		1044	logging overhead enourmously.
		1045
		1046	AnyEvent::fh_block $filehandle
		1047	AnyEvent::fh_unblock $filehandle
		1048	Sets blocking or non-blocking behaviour for the given filehandle.
742		1049
743	WHAT TO DO IN A MODULE	1050	WHAT TO DO IN A MODULE
744	As a module author, you should "use AnyEvent" and call AnyEvent methods	1051	As a module author, you should "use AnyEvent" and call AnyEvent methods
745	freely, but you should not load a specific event module or rely on it.	1052	freely, but you should not load a specific event module or rely on it.
746		1053
…		…
754	stall the whole program, and the whole point of using events is to stay	1061	stall the whole program, and the whole point of using events is to stay
755	interactive.	1062	interactive.
756		1063
757	It is fine, however, to call "->recv" when the user of your module	1064	It is fine, however, to call "->recv" when the user of your module
758	requests it (i.e. if you create a http request object ad have a method	1065	requests it (i.e. if you create a http request object ad have a method
759	called "results" that returns the results, it should call "->recv"	1066	called "results" that returns the results, it may call "->recv" freely,
760	freely, as the user of your module knows what she is doing. always).	1067	as the user of your module knows what she is doing. Always).
761		1068
762	WHAT TO DO IN THE MAIN PROGRAM	1069	WHAT TO DO IN THE MAIN PROGRAM
763	There will always be a single main program - the only place that should	1070	There will always be a single main program - the only place that should
764	dictate which event model to use.	1071	dictate which event model to use.
765		1072
766	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1073	If the program is not event-based, it need not do anything special, even
767	do anything special (it does not need to be event-based) and let	1074	when it depends on a module that uses an AnyEvent. If the program itself
768	AnyEvent decide which implementation to chose if some module relies on	1075	uses AnyEvent, but does not care which event loop is used, all it needs
769	it.	1076	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1077	available loop implementation.
770		1078
771	If the main program relies on a specific event model - for example, in	1079	If the main program relies on a specific event model - for example, in
772	Gtk2 programs you have to rely on the Glib module - you should load the	1080	Gtk2 programs you have to rely on the Glib module - you should load the
773	event module before loading AnyEvent or any module that uses it:	1081	event module before loading AnyEvent or any module that uses it:
774	generally speaking, you should load it as early as possible. The reason	1082	generally speaking, you should load it as early as possible. The reason
775	is that modules might create watchers when they are loaded, and AnyEvent	1083	is that modules might create watchers when they are loaded, and AnyEvent
776	will decide on the event model to use as soon as it creates watchers,	1084	will decide on the event model to use as soon as it creates watchers,
777	and it might chose the wrong one unless you load the correct one	1085	and it might choose the wrong one unless you load the correct one
778	yourself.	1086	yourself.
779		1087
780	You can chose to use a pure-perl implementation by loading the	1088	You can chose to use a pure-perl implementation by loading the
781	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1089	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
782	everywhere, but letting AnyEvent chose the model is generally better.	1090	but letting AnyEvent chose the model is generally better.
783		1091
784	MAINLOOP EMULATION	1092	MAINLOOP EMULATION
785	Sometimes (often for short test scripts, or even standalone programs who	1093	Sometimes (often for short test scripts, or even standalone programs who
786	only want to use AnyEvent), you do not want to run a specific event	1094	only want to use AnyEvent), you do not want to run a specific event
787	loop.	1095	loop.
…		…
797	variable somewhere, waiting for it, and sending it when the program	1105	variable somewhere, waiting for it, and sending it when the program
798	should exit cleanly.	1106	should exit cleanly.
799		1107
800	OTHER MODULES	1108	OTHER MODULES
801	The following is a non-exhaustive list of additional modules that use	1109	The following is a non-exhaustive list of additional modules that use
802	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1110	AnyEvent as a client and can therefore be mixed easily with other
803	in the same program. Some of the modules come with AnyEvent, some are	1111	AnyEvent modules and other event loops in the same program. Some of the
804	available via CPAN.	1112	modules come as part of AnyEvent, the others are available via CPAN (see
		1113	<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
		1114	non-exhaustive list), and the list is heavily biased towards modules of
		1115	the AnyEvent author himself :)
805		1116
806	AnyEvent::Util	1117	AnyEvent::Util (part of the AnyEvent distribution)
807	Contains various utility functions that replace often-used but	1118	Contains various utility functions that replace often-used blocking
808	blocking functions such as "inet_aton" by event-/callback-based	1119	functions such as "inet_aton" with event/callback-based versions.
809	versions.
810		1120
811	AnyEvent::Socket	1121	AnyEvent::Socket (part of the AnyEvent distribution)
812	Provides various utility functions for (internet protocol) sockets,	1122	Provides various utility functions for (internet protocol) sockets,
813	addresses and name resolution. Also functions to create non-blocking	1123	addresses and name resolution. Also functions to create non-blocking
814	tcp connections or tcp servers, with IPv6 and SRV record support and	1124	tcp connections or tcp servers, with IPv6 and SRV record support and
815	more.	1125	more.
816		1126
817	AnyEvent::Handle	1127	AnyEvent::Handle (part of the AnyEvent distribution)
818	Provide read and write buffers, manages watchers for reads and	1128	Provide read and write buffers, manages watchers for reads and
819	writes, supports raw and formatted I/O, I/O queued and fully	1129	writes, supports raw and formatted I/O, I/O queued and fully
820	transparent and non-blocking SSL/TLS.	1130	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
821		1131
822	AnyEvent::DNS	1132	AnyEvent::DNS (part of the AnyEvent distribution)
823	Provides rich asynchronous DNS resolver capabilities.	1133	Provides rich asynchronous DNS resolver capabilities.
824		1134
825	AnyEvent::HTTP	1135	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
826	A simple-to-use HTTP library that is capable of making a lot of	1136	AnyEvent::IGS, AnyEvent::FCP
827	concurrent HTTP requests.	1137	Implement event-based interfaces to the protocols of the same name
		1138	(for the curious, IGS is the International Go Server and FCP is the
		1139	Freenet Client Protocol).
828		1140
		1141	AnyEvent::AIO (part of the AnyEvent distribution)
		1142	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1143	the toolbox of every event programmer. AnyEvent::AIO transparently
		1144	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1145	event-based file I/O, and much more.
		1146
		1147	AnyEvent::Fork, AnyEvent::Fork::RPC, AnyEvent::Fork::Pool,
		1148	AnyEvent::Fork::Remote
		1149	These let you safely fork new subprocesses, either locally or
		1150	remotely (e.g.v ia ssh), using some RPC protocol or not, without the
		1151	limitations normally imposed by fork (AnyEvent works fine for
		1152	example). Dynamically-resized worker pools are obviously included as
		1153	well.
		1154
		1155	And they are quite tiny and fast as well - "abusing" AnyEvent::Fork
		1156	just to exec external programs can easily beat using "fork" and
		1157	"exec" (or even "system") in most programs.
		1158
		1159	AnyEvent::Filesys::Notify
		1160	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1161	path changes (e.g. "watch this directory for new files", "watch this
		1162	file for changes"). The AnyEvent::Filesys::Notify module promises to
		1163	do just that in a portbale fashion, supporting inotify on GNU/Linux
		1164	and some weird, without doubt broken, stuff on OS X to monitor
		1165	files. It can fall back to blocking scans at regular intervals
		1166	transparently on other platforms, so it's about as portable as it
		1167	gets.
		1168
		1169	(I haven't used it myself, but it seems the biggest problem with it
		1170	is it quite bad performance).
		1171
829	AnyEvent::HTTPD	1172	AnyEvent::DBI
830	Provides a simple web application server framework.	1173	Executes DBI requests asynchronously in a proxy process for you,
		1174	notifying you in an event-based way when the operation is finished.
831		1175
832	AnyEvent::FastPing	1176	AnyEvent::FastPing
833	The fastest ping in the west.	1177	The fastest ping in the west.
834		1178
835	AnyEvent::DBI
836	Executes DBI requests asynchronously in a proxy process.
837
838	AnyEvent::AIO
839	Truly asynchronous I/O, should be in the toolbox of every event
840	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
841	together.
842
843	AnyEvent::BDB
844	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
845	fuses BDB and AnyEvent together.
846
847	AnyEvent::GPSD
848	A non-blocking interface to gpsd, a daemon delivering GPS
849	information.
850
851	AnyEvent::IGS
852	A non-blocking interface to the Internet Go Server protocol (used by
853	App::IGS).
854
855	AnyEvent::IRC
856	AnyEvent based IRC client module family (replacing the older
857	Net::IRC3).
858
859	Net::XMPP2
860	AnyEvent based XMPP (Jabber protocol) module family.
861
862	Net::FCP
863	AnyEvent-based implementation of the Freenet Client Protocol,
864	birthplace of AnyEvent.
865
866	Event::ExecFlow
867	High level API for event-based execution flow control.
868
869	Coro	1179	Coro
870	Has special support for AnyEvent via Coro::AnyEvent.	1180	Has special support for AnyEvent via Coro::AnyEvent, which allows
		1181	you to simply invert the flow control - don't call us, we will call
		1182	you:
871		1183
872	IO::Lambda	1184	async {
873	The lambda approach to I/O - don't ask, look there. Can use	1185	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
874	AnyEvent.	1186	print "5 seconds later!\n";
		1187
		1188	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1189	my $line = <STDIN>; # works for ttys
		1190
		1191	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1192	my ($body, $hdr) = Coro::rouse_wait;
		1193	};
		1194
		1195	SIMPLIFIED AE API
		1196	Starting with version 5.0, AnyEvent officially supports a second, much
		1197	simpler, API that is designed to reduce the calling, typing and memory
		1198	overhead by using function call syntax and a fixed number of parameters.
		1199
		1200	See the AE manpage for details.
875		1201
876	ERROR AND EXCEPTION HANDLING	1202	ERROR AND EXCEPTION HANDLING
877	In general, AnyEvent does not do any error handling - it relies on the	1203	In general, AnyEvent does not do any error handling - it relies on the
878	caller to do that if required. The AnyEvent::Strict module (see also the	1204	caller to do that if required. The AnyEvent::Strict module (see also the
879	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1205	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
888	The pure perl event loop simply re-throws the exception (usually within	1214	The pure perl event loop simply re-throws the exception (usually within
889	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1215	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
890	Glib uses "install_exception_handler" and so on.	1216	Glib uses "install_exception_handler" and so on.
891		1217
892	ENVIRONMENT VARIABLES	1218	ENVIRONMENT VARIABLES
893	The following environment variables are used by this module or its	1219	AnyEvent supports a number of environment variables that tune the
894	submodules.	1220	runtime behaviour. They are usually evaluated when AnyEvent is loaded,
		1221	initialised, or a submodule that uses them is loaded. Many of them also
		1222	cause AnyEvent to load additional modules - for example,
		1223	"PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be
		1224	loaded.
895		1225
896	Note that AnyEvent will remove all environment variables starting with	1226	All the environment variables documented here start with
897	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is	1227	"PERL_ANYEVENT_", which is what AnyEvent considers its own namespace.
898	enabled.	1228	Other modules are encouraged (but by no means required) to use
		1229	"PERL_ANYEVENT_SUBMODULE" if they have registered the
		1230	AnyEvent::Submodule namespace on CPAN, for any submodule. For example,
		1231	AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it
		1232	should not access env variables starting with "AE_", see below).
		1233
		1234	All variables can also be set via the "AE_" prefix, that is, instead of
		1235	setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case
		1236	there is a clash btween anyevent and another program that uses
		1237	"AE_something" you can set the corresponding "PERL_ANYEVENT_something"
		1238	variable to the empty string, as those variables take precedence.
		1239
		1240	When AnyEvent is first loaded, it copies all "AE_xxx" env variables to
		1241	their "PERL_ANYEVENT_xxx" counterpart unless that variable already
		1242	exists. If taint mode is on, then AnyEvent will remove all environment
		1243	variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with
		1244	"undef" or the empty string, if the corresaponding "AE_" variable is
		1245	set).
		1246
		1247	The exact algorithm is currently:
		1248
		1249	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		1250	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		1251	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		1252
		1253	This ensures that child processes will not see the "AE_" variables.
		1254
		1255	The following environment variables are currently known to AnyEvent:
899		1256
900	"PERL_ANYEVENT_VERBOSE"	1257	"PERL_ANYEVENT_VERBOSE"
901	By default, AnyEvent will be completely silent except in fatal	1258	By default, AnyEvent will log messages with loglevel 4 ("error") or
902	conditions. You can set this environment variable to make AnyEvent	1259	higher (see AnyEvent::Log). You can set this environment variable to
903	more talkative.	1260	a numerical loglevel to make AnyEvent more (or less) talkative.
904		1261
		1262	If you want to do more than just set the global logging level you
		1263	should have a look at "PERL_ANYEVENT_LOG", which allows much more
		1264	complex specifications.
		1265
		1266	When set to 0 ("off"), then no messages whatsoever will be logged
		1267	with everything else at defaults.
		1268
905	When set to 1 or higher, causes AnyEvent to warn about unexpected	1269	When set to 5 or higher ("warn"), AnyEvent warns about unexpected
906	conditions, such as not being able to load the event model specified	1270	conditions, such as not being able to load the event model specified
907	by "PERL_ANYEVENT_MODEL".	1271	by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception
		1272	- this is the minimum recommended level for use during development.
908		1273
909	When set to 2 or higher, cause AnyEvent to report to STDERR which	1274	When set to 7 or higher (info), AnyEvent reports which event model
910	event model it chooses.	1275	it chooses.
		1276
		1277	When set to 8 or higher (debug), then AnyEvent will report extra
		1278	information on which optional modules it loads and how it implements
		1279	certain features.
		1280
		1281	"PERL_ANYEVENT_LOG"
		1282	Accepts rather complex logging specifications. For example, you
		1283	could log all "debug" messages of some module to stderr, warnings
		1284	and above to stderr, and errors and above to syslog, with:
		1285
		1286	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		1287
		1288	For the rather extensive details, see AnyEvent::Log.
		1289
		1290	This variable is evaluated when AnyEvent (or AnyEvent::Log) is
		1291	loaded, so will take effect even before AnyEvent has initialised
		1292	itself.
		1293
		1294	Note that specifying this environment variable causes the
		1295	AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE"
		1296	does not, so only using the latter saves a few hundred kB of memory
		1297	unless a module explicitly needs the extra features of
		1298	AnyEvent::Log.
911		1299
912	"PERL_ANYEVENT_STRICT"	1300	"PERL_ANYEVENT_STRICT"
913	AnyEvent does not do much argument checking by default, as thorough	1301	AnyEvent does not do much argument checking by default, as thorough
914	argument checking is very costly. Setting this variable to a true	1302	argument checking is very costly. Setting this variable to a true
915	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1303	value will cause AnyEvent to load "AnyEvent::Strict" and then to
916	thoroughly check the arguments passed to most method calls. If it	1304	thoroughly check the arguments passed to most method calls. If it
917	finds any problems, it will croak.	1305	finds any problems, it will croak.
918		1306
919	In other words, enables "strict" mode.	1307	In other words, enables "strict" mode.
920		1308
921	Unlike "use strict", it is definitely recommended to keep it off in	1309	Unlike "use strict" (or its modern cousin, "use common::sense", it
922	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1310	is definitely recommended to keep it off in production. Keeping
		1311	"PERL_ANYEVENT_STRICT=1" in your environment while developing
923	while developing programs can be very useful, however.	1312	programs can be very useful, however.
		1313
		1314	"PERL_ANYEVENT_DEBUG_SHELL"
		1315	If this env variable is nonempty, then its contents will be
		1316	interpreted by "AnyEvent::Socket::parse_hostport" and
		1317	"AnyEvent::Debug::shell" (after replacing every occurance of $$ by
		1318	the process pid). The shell object is saved in
		1319	$AnyEvent::Debug::SHELL.
		1320
		1321	This happens when the first watcher is created.
		1322
		1323	For example, to bind a debug shell on a unix domain socket in
		1324	/tmp/debug<pid>.sock, you could use this:
		1325
		1326	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		1327	# connect with e.g.: socat readline /tmp/debug123.sock
		1328
		1329	Or to bind to tcp port 4545 on localhost:
		1330
		1331	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		1332	# connect with e.g.: telnet localhost 4545
		1333
		1334	Note that creating sockets in /tmp or on localhost is very unsafe on
		1335	multiuser systems.
		1336
		1337	"PERL_ANYEVENT_DEBUG_WRAP"
		1338	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1339	debugging purposes. See "AnyEvent::Debug::wrap" for details.
924		1340
925	"PERL_ANYEVENT_MODEL"	1341	"PERL_ANYEVENT_MODEL"
926	This can be used to specify the event model to be used by AnyEvent,	1342	This can be used to specify the event model to be used by AnyEvent,
927	before auto detection and -probing kicks in. It must be a string	1343	before auto detection and -probing kicks in.
928	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1344
929	gets prepended and the resulting module name is loaded and if the	1345	It normally is a string consisting entirely of ASCII letters (e.g.
930	load was successful, used as event model. If it fails to load	1346	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1347	the resulting module name is loaded and - if the load was successful
		1348	- used as event model backend. If it fails to load then AnyEvent
931	AnyEvent will proceed with auto detection and -probing.	1349	will proceed with auto detection and -probing.
932		1350
933	This functionality might change in future versions.	1351	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1352	then nothing gets prepended and the module name is used as-is (hint:
		1353	"::" at the end of a string designates a module name and quotes it
		1354	appropriately).
934		1355
935	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1356	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
936	could start your program like this:	1357	could start your program like this:
937		1358
938	PERL_ANYEVENT_MODEL=Perl perl ...	1359	PERL_ANYEVENT_MODEL=Perl perl ...
		1360
		1361	"PERL_ANYEVENT_IO_MODEL"
		1362	The current file I/O model - see AnyEvent::IO for more info.
		1363
		1364	At the moment, only "Perl" (small, pure-perl, synchronous) and
		1365	"IOAIO" (truly asynchronous) are supported. The default is "IOAIO"
		1366	if AnyEvent::AIO can be loaded, otherwise it is "Perl".
939		1367
940	"PERL_ANYEVENT_PROTOCOLS"	1368	"PERL_ANYEVENT_PROTOCOLS"
941	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1369	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
942	preferences for IPv4 or IPv6. The default is unspecified (and might	1370	preferences for IPv4 or IPv6. The default is unspecified (and might
943	change, or be the result of auto probing).	1371	change, or be the result of auto probing).
…		…
947	mentioned will be used, and preference will be given to protocols	1375	mentioned will be used, and preference will be given to protocols
948	mentioned earlier in the list.	1376	mentioned earlier in the list.
949		1377
950	This variable can effectively be used for denial-of-service attacks	1378	This variable can effectively be used for denial-of-service attacks
951	against local programs (e.g. when setuid), although the impact is	1379	against local programs (e.g. when setuid), although the impact is
952	likely small, as the program has to handle conenction and other	1380	likely small, as the program has to handle connection and other
953	failures anyways.	1381	failures anyways.
954		1382
955	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1383	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
956	IPv6, but support both and try to use both.	1384	IPv6, but support both and try to use both.
957	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1385	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
958	resolve or contact IPv6 addresses.	1386	resolve or contact IPv6 addresses.
959	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but	1387	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
960	prefer IPv6 over IPv4.	1388	prefer IPv6 over IPv4.
961		1389
		1390	"PERL_ANYEVENT_HOSTS"
		1391	This variable, if specified, overrides the /etc/hosts file used by
		1392	AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be
		1393	read from that file instead.
		1394
962	"PERL_ANYEVENT_EDNS0"	1395	"PERL_ANYEVENT_EDNS0"
963	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension	1396	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
964	for DNS. This extension is generally useful to reduce DNS traffic,	1397	for DNS. This extension is generally useful to reduce DNS traffic,
965	but some (broken) firewalls drop such DNS packets, which is why it	1398	especially when DNSSEC is involved, but some (broken) firewalls drop
966	is off by default.	1399	such DNS packets, which is why it is off by default.
967		1400
968	Setting this variable to 1 will cause AnyEvent::DNS to announce	1401	Setting this variable to 1 will cause AnyEvent::DNS to announce
969	EDNS0 in its DNS requests.	1402	EDNS0 in its DNS requests.
970		1403
971	"PERL_ANYEVENT_MAX_FORKS"	1404	"PERL_ANYEVENT_MAX_FORKS"
972	The maximum number of child processes that	1405	The maximum number of child processes that
973	"AnyEvent::Util::fork_call" will create in parallel.	1406	"AnyEvent::Util::fork_call" will create in parallel.
		1407
		1408	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1409	The default value for the "max_outstanding" parameter for the
		1410	default DNS resolver - this is the maximum number of parallel DNS
		1411	requests that are sent to the DNS server.
		1412
		1413	"PERL_ANYEVENT_MAX_SIGNAL_LATENCY"
		1414	Perl has inherently racy signal handling (you can basically choose
		1415	between losing signals and memory corruption) - pure perl event
		1416	loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't
		1417	available) therefore have to poll regularly to avoid losing signals.
		1418
		1419	Some event loops are racy, but don't poll regularly, and some event
		1420	loops are written in C but are still racy. For those event loops,
		1421	AnyEvent installs a timer that regularly wakes up the event loop.
		1422
		1423	By default, the interval for this timer is 10 seconds, but you can
		1424	override this delay with this environment variable (or by setting
		1425	the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal
		1426	watchers).
		1427
		1428	Lower values increase CPU (and energy) usage, higher values can
		1429	introduce long delays when reaping children or waiting for signals.
		1430
		1431	The AnyEvent::Async module, if available, will be used to avoid this
		1432	polling (with most event loops).
		1433
		1434	"PERL_ANYEVENT_RESOLV_CONF"
		1435	The absolute path to a resolv.conf-style file to use instead of
		1436	/etc/resolv.conf (or the OS-specific configuration) in the default
		1437	resolver, or the empty string to select the default configuration.
		1438
		1439	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1440	When neither "ca_file" nor "ca_path" was specified during
		1441	AnyEvent::TLS context creation, and either of these environment
		1442	variables are nonempty, they will be used to specify CA certificate
		1443	locations instead of a system-dependent default.
		1444
		1445	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1446	When these are set to 1, then the respective modules are not loaded.
		1447	Mostly good for testing AnyEvent itself.
974		1448
975	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1449	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
976	This is an advanced topic that you do not normally need to use AnyEvent	1450	This is an advanced topic that you do not normally need to use AnyEvent
977	in a module. This section is only of use to event loop authors who want	1451	in a module. This section is only of use to event loop authors who want
978	to provide AnyEvent compatibility.	1452	to provide AnyEvent compatibility.
…		…
1033	warn "read: $input\n"; # output what has been read	1507	warn "read: $input\n"; # output what has been read
1034	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1508	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1035	},	1509	},
1036	);	1510	);
1037		1511
1038	my $time_watcher; # can only be used once
1039
1040	sub new_timer {
1041	$timer = AnyEvent->timer (after => 1, cb => sub {	1512	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1042	warn "timeout\n"; # print 'timeout' about every second	1513	warn "timeout\n"; # print 'timeout' at most every second
1043	&new_timer; # and restart the time
1044	});
1045	}	1514	});
1046
1047	new_timer; # create first timer
1048		1515
1049	$cv->recv; # wait until user enters /^q/i	1516	$cv->recv; # wait until user enters /^q/i
1050		1517
1051	REAL-WORLD EXAMPLE	1518	REAL-WORLD EXAMPLE
1052	Consider the Net::FCP module. It features (among others) the following	1519	Consider the Net::FCP module. It features (among others) the following
…		…
1124		1591
1125	The actual code goes further and collects all errors ("die"s,	1592	The actual code goes further and collects all errors ("die"s,
1126	exceptions) that occurred during request processing. The "result" method	1593	exceptions) that occurred during request processing. The "result" method
1127	detects whether an exception as thrown (it is stored inside the $txn	1594	detects whether an exception as thrown (it is stored inside the $txn
1128	object) and just throws the exception, which means connection errors and	1595	object) and just throws the exception, which means connection errors and
1129	other problems get reported tot he code that tries to use the result,	1596	other problems get reported to the code that tries to use the result,
1130	not in a random callback.	1597	not in a random callback.
1131		1598
1132	All of this enables the following usage styles:	1599	All of this enables the following usage styles:
1133		1600
1134	1. Blocking:	1601	1. Blocking:
…		…
1152	my $txn = shift;	1619	my $txn = shift;
1153	my $data = $txn->result;	1620	my $data = $txn->result;
1154	...	1621	...
1155	});	1622	});
1156		1623
1157	EV::loop;	1624	EV::run;
1158		1625
1159	3b. The module user could use AnyEvent, too:	1626	3b. The module user could use AnyEvent, too:
1160		1627
1161	use AnyEvent;	1628	use AnyEvent;
1162		1629
…		…
1179	through AnyEvent. The benchmark creates a lot of timers (with a zero	1646	through AnyEvent. The benchmark creates a lot of timers (with a zero
1180	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1647	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1181	which it is), lets them fire exactly once and destroys them again.	1648	which it is), lets them fire exactly once and destroys them again.
1182		1649
1183	Source code for this benchmark is found as eg/bench in the AnyEvent	1650	Source code for this benchmark is found as eg/bench in the AnyEvent
1184	distribution.	1651	distribution. It uses the AE interface, which makes a real difference
		1652	for the EV and Perl backends only.
1185		1653
1186	Explanation of the columns	1654	Explanation of the columns
1187	watcher is the number of event watchers created/destroyed. Since	1655	watcher is the number of event watchers created/destroyed. Since
1188	different event models feature vastly different performances, each event	1656	different event models feature vastly different performances, each event
1189	loop was given a number of watchers so that overall runtime is	1657	loop was given a number of watchers so that overall runtime is
…		…
1208	destroy is the time, in microseconds, that it takes to destroy a	1676	destroy is the time, in microseconds, that it takes to destroy a
1209	single watcher.	1677	single watcher.
1210		1678
1211	Results	1679	Results
1212	name watchers bytes create invoke destroy comment	1680	name watchers bytes create invoke destroy comment
1213	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1681	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1214	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1682	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1215	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1683	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1216	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1684	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1217	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1685	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1218	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1686	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
1219	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll	1687	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
1220	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll	1688	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1221	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1689	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1222	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1690	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1223	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1691	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1224	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1692	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1225		1693
1226	Discussion	1694	Discussion
1227	The benchmark does not measure scalability of the event loop very	1695	The benchmark does not measure scalability of the event loop very
1228	well. For example, a select-based event loop (such as the pure perl one)	1696	well. For example, a select-based event loop (such as the pure perl one)
1229	can never compete with an event loop that uses epoll when the number of	1697	can never compete with an event loop that uses epoll when the number of
…		…
1240	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1708	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1241	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1709	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1242	CPU cycles with POE.	1710	CPU cycles with POE.
1243		1711
1244	"EV" is the sole leader regarding speed and memory use, which are both	1712	"EV" is the sole leader regarding speed and memory use, which are both
1245	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1713	maximal/minimal, respectively. When using the AE API there is zero
		1714	overhead (when going through the AnyEvent API create is about 5-6 times
		1715	slower, with other times being equal, so still uses far less memory than
1246	far less memory than any other event loop and is still faster than Event	1716	any other event loop and is still faster than Event natively).
1247	natively.
1248		1717
1249	The pure perl implementation is hit in a few sweet spots (both the	1718	The pure perl implementation is hit in a few sweet spots (both the
1250	constant timeout and the use of a single fd hit optimisations in the	1719	constant timeout and the use of a single fd hit optimisations in the
1251	perl interpreter and the backend itself). Nevertheless this shows that	1720	perl interpreter and the backend itself). Nevertheless this shows that
1252	it adds very little overhead in itself. Like any select-based backend	1721	it adds very little overhead in itself. Like any select-based backend
…		…
1298	when used without AnyEvent), but most event loops have acceptable	1767	when used without AnyEvent), but most event loops have acceptable
1299	performance with or without AnyEvent.	1768	performance with or without AnyEvent.
1300		1769
1301	* The overhead AnyEvent adds is usually much smaller than the overhead	1770	* The overhead AnyEvent adds is usually much smaller than the overhead
1302	of the actual event loop, only with extremely fast event loops such	1771	of the actual event loop, only with extremely fast event loops such
1303	as EV adds AnyEvent significant overhead.	1772	as EV does AnyEvent add significant overhead.
1304		1773
1305	* You should avoid POE like the plague if you want performance or	1774	* You should avoid POE like the plague if you want performance or
1306	reasonable memory usage.	1775	reasonable memory usage.
1307		1776
1308	BENCHMARKING THE LARGE SERVER CASE	1777	BENCHMARKING THE LARGE SERVER CASE
…		…
1322	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1791	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1323	100 (1%) are active. This mirrors the activity of large servers with	1792	100 (1%) are active. This mirrors the activity of large servers with
1324	many connections, most of which are idle at any one point in time.	1793	many connections, most of which are idle at any one point in time.
1325		1794
1326	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1795	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1327	distribution.	1796	distribution. It uses the AE interface, which makes a real difference
		1797	for the EV and Perl backends only.
1328		1798
1329	Explanation of the columns	1799	Explanation of the columns
1330	sockets is the number of sockets, and twice the number of "servers"	1800	sockets is the number of sockets, and twice the number of "servers"
1331	(as each server has a read and write socket end).	1801	(as each server has a read and write socket end).
1332		1802
…		…
1338	forwarding it to another server. This includes deleting the old timeout	1808	forwarding it to another server. This includes deleting the old timeout
1339	and creating a new one that moves the timeout into the future.	1809	and creating a new one that moves the timeout into the future.
1340		1810
1341	Results	1811	Results
1342	name sockets create request	1812	name sockets create request
1343	EV 20000 69.01 11.16	1813	EV 20000 62.66 7.99
1344	Perl 20000 73.32 35.87	1814	Perl 20000 68.32 32.64
1345	IOAsync 20000 157.00 98.14 epoll	1815	IOAsync 20000 174.06 101.15 epoll
1346	IOAsync 20000 159.31 616.06 poll	1816	IOAsync 20000 174.67 610.84 poll
1347	Event 20000 212.62 257.32	1817	Event 20000 202.69 242.91
1348	Glib 20000 651.16 1896.30	1818	Glib 20000 557.01 1689.52
1349	POE 20000 349.67 12317.24 uses POE::Loop::Event	1819	POE 20000 341.54 12086.32 uses POE::Loop::Event
1350		1820
1351	Discussion	1821	Discussion
1352	This benchmark does measure scalability and overall performance of the	1822	This benchmark does measure scalability and overall performance of the
1353	particular event loop.	1823	particular event loop.
1354		1824
…		…
1467	As you can see, the AnyEvent + EV combination even beats the	1937	As you can see, the AnyEvent + EV combination even beats the
1468	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl	1938	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1469	backend easily beats IO::Lambda and POE.	1939	backend easily beats IO::Lambda and POE.
1470		1940
1471	And even the 100% non-blocking version written using the high-level (and	1941	And even the 100% non-blocking version written using the high-level (and
1472	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a	1942	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
1473	large margin, even though it does all of DNS, tcp-connect and socket I/O	1943	higher level ("unoptimised") abstractions by a large margin, even though
1474	in a non-blocking way.	1944	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
1475		1945
1476	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and	1946	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
1477	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are	1947	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1478	part of the IO::lambda distribution and were used without any changes.	1948	part of the IO::Lambda distribution and were used without any changes.
1479		1949
1480	SIGNALS	1950	SIGNALS
1481	AnyEvent currently installs handlers for these signals:	1951	AnyEvent currently installs handlers for these signals:
1482		1952
1483	SIGCHLD	1953	SIGCHLD
1484	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1954	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1485	emulation for event loops that do not support them natively. Also,	1955	emulation for event loops that do not support them natively. Also,
1486	some event loops install a similar handler.	1956	some event loops install a similar handler.
1487		1957
1488	If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent	1958	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
1489	will reset it to default, to avoid losing child exit statuses.	1959	then AnyEvent will reset it to default, to avoid losing child exit
		1960	statuses.
1490		1961
1491	SIGPIPE	1962	SIGPIPE
1492	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is	1963	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1493	"undef" when AnyEvent gets loaded.	1964	"undef" when AnyEvent gets loaded.
1494		1965
…		…
1502	it is that this way, the handler will be restored to defaults on	1973	it is that this way, the handler will be restored to defaults on
1503	exec.	1974	exec.
1504		1975
1505	Feel free to install your own handler, or reset it to defaults.	1976	Feel free to install your own handler, or reset it to defaults.
1506		1977
		1978	RECOMMENDED/OPTIONAL MODULES
		1979	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1980	its built-in modules) are required to use it.
		1981
		1982	That does not mean that AnyEvent won't take advantage of some additional
		1983	modules if they are installed.
		1984
		1985	This section explains which additional modules will be used, and how
		1986	they affect AnyEvent's operation.
		1987
		1988	Async::Interrupt
		1989	This slightly arcane module is used to implement fast signal
		1990	handling: To my knowledge, there is no way to do completely
		1991	race-free and quick signal handling in pure perl. To ensure that
		1992	signals still get delivered, AnyEvent will start an interval timer
		1993	to wake up perl (and catch the signals) with some delay (default is
		1994	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1995
		1996	If this module is available, then it will be used to implement
		1997	signal catching, which means that signals will not be delayed, and
		1998	the event loop will not be interrupted regularly, which is more
		1999	efficient (and good for battery life on laptops).
		2000
		2001	This affects not just the pure-perl event loop, but also other event
		2002	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2003
		2004	Some event loops (POE, Event, Event::Lib) offer signal watchers
		2005	natively, and either employ their own workarounds (POE) or use
		2006	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		2007	Installing Async::Interrupt does nothing for those backends.
		2008
		2009	EV This module isn't really "optional", as it is simply one of the
		2010	backend event loops that AnyEvent can use. However, it is simply the
		2011	best event loop available in terms of features, speed and stability:
		2012	It supports the AnyEvent API optimally, implements all the watcher
		2013	types in XS, does automatic timer adjustments even when no monotonic
		2014	clock is available, can take avdantage of advanced kernel interfaces
		2015	such as "epoll" and "kqueue", and is the fastest backend by far.
		2016	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		2017	Glib::EV).
		2018
		2019	If you only use backends that rely on another event loop (e.g.
		2020	"Tk"), then this module will do nothing for you.
		2021
		2022	Guard
		2023	The guard module, when used, will be used to implement
		2024	"AnyEvent::Util::guard". This speeds up guards considerably (and
		2025	uses a lot less memory), but otherwise doesn't affect guard
		2026	operation much. It is purely used for performance.
		2027
		2028	JSON and JSON::XS
		2029	One of these modules is required when you want to read or write JSON
		2030	data via AnyEvent::Handle. JSON is also written in pure-perl, but
		2031	can take advantage of the ultra-high-speed JSON::XS module when it
		2032	is installed.
		2033
		2034	Net::SSLeay
		2035	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2036	worthwhile: If this module is installed, then AnyEvent::Handle (with
		2037	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		2038
		2039	Time::HiRes
		2040	This module is part of perl since release 5.008. It will be used
		2041	when the chosen event library does not come with a timing source of
		2042	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
		2043	load it to try to use a monotonic clock for timing stability.
		2044
		2045	AnyEvent::AIO (and IO::AIO)
		2046	The default implementation of AnyEvent::IO is to do I/O
		2047	synchronously, stopping programs while they access the disk, which
		2048	is fine for a lot of programs.
		2049
		2050	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it
		2051	switch to a true asynchronous implementation, so event processing
		2052	can continue even while waiting for disk I/O.
		2053
1507	FORK	2054	FORK
1508	Most event libraries are not fork-safe. The ones who are usually are	2055	Most event libraries are not fork-safe. The ones who are usually are
1509	because they rely on inefficient but fork-safe "select" or "poll" calls.	2056	because they rely on inefficient but fork-safe "select" or "poll" calls
1510	Only EV is fully fork-aware.	2057	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		2058	epoll are usually badly thought-out hacks that are incompatible with
		2059	fork in one way or another. Only EV is fully fork-aware and ensures that
		2060	you continue event-processing in both parent and child (or both, if you
		2061	know what you are doing).
		2062
		2063	This means that, in general, you cannot fork and do event processing in
		2064	the child if the event library was initialised before the fork (which
		2065	usually happens when the first AnyEvent watcher is created, or the
		2066	library is loaded).
1511		2067
1512	If you have to fork, you must either do so before creating your first	2068	If you have to fork, you must either do so before creating your first
1513	watcher OR you must not use AnyEvent at all in the child.	2069	watcher OR you must not use AnyEvent at all in the child OR you must do
		2070	something completely out of the scope of AnyEvent (see below).
		2071
		2072	The problem of doing event processing in the parent and the child is
		2073	much more complicated: even for backends that are fork-aware or
		2074	fork-safe, their behaviour is not usually what you want: fork clones all
		2075	watchers, that means all timers, I/O watchers etc. are active in both
		2076	parent and child, which is almost never what you want. Using "exec" to
		2077	start worker children from some kind of manage prrocess is usually
		2078	preferred, because it is much easier and cleaner, at the expense of
		2079	having to have another binary.
		2080
		2081	In addition to logical problems with fork, there are also implementation
		2082	problems. For example, on POSIX systems, you cannot fork at all in Perl
		2083	code if a thread (I am talking of pthreads here) was ever created in the
		2084	process, and this is just the tip of the iceberg. In general, using fork
		2085	from Perl is difficult, and attempting to use fork without an exec to
		2086	implement some kind of parallel processing is almost certainly doomed.
		2087
		2088	To safely fork and exec, you should use a module such as Proc::FastSpawn
		2089	that let's you safely fork and exec new processes.
		2090
		2091	If you want to do multiprocessing using processes, you can look at the
		2092	AnyEvent::Fork module (and some related modules such as
		2093	AnyEvent::Fork::RPC, AnyEvent::Fork::Pool and AnyEvent::Fork::Remote).
		2094	This module allows you to safely create subprocesses without any
		2095	limitations - you can use X11 toolkits or AnyEvent in the children
		2096	created by AnyEvent::Fork safely and without any special precautions.
1514		2097
1515	SECURITY CONSIDERATIONS	2098	SECURITY CONSIDERATIONS
1516	AnyEvent can be forced to load any event model via	2099	AnyEvent can be forced to load any event model via
1517	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	2100	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1518	to execute arbitrary code or directly gain access, it can easily be used	2101	to execute arbitrary code or directly gain access, it can easily be used
…		…
1542	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	2125	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1543	annoying memleaks, such as leaking on "map" and "grep" but it is usually	2126	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1544	not as pronounced).	2127	not as pronounced).
1545		2128
1546	SEE ALSO	2129	SEE ALSO
1547	Utility functions: AnyEvent::Util.	2130	Tutorial/Introduction: AnyEvent::Intro.
1548		2131
1549	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	2132	FAQ: AnyEvent::FAQ.
1550	Event::Lib, Qt, POE.	2133
		2134	Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log
		2135	(simply logging).
		2136
		2137	Development/Debugging: AnyEvent::Strict (stricter checking),
		2138	AnyEvent::Debug (interactive shell, watcher tracing).
		2139
		2140	Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
		2141	Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK, Cocoa::EventLoop, UV.
1551		2142
1552	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	2143	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1553	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	2144	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1554	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	2145	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		2146	AnyEvent::Impl::IOAsync, AnyEvent::Impl::Irssi, AnyEvent::Impl::FLTK,
		2147	AnyEvent::Impl::Cocoa, AnyEvent::Impl::UV.
1555		2148
1556	Non-blocking file handles, sockets, TCP clients and servers:	2149	Non-blocking handles, pipes, stream sockets, TCP clients and servers:
1557	AnyEvent::Handle, AnyEvent::Socket.	2150	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
		2151
		2152	Asynchronous File I/O: AnyEvent::IO.
1558		2153
1559	Asynchronous DNS: AnyEvent::DNS.	2154	Asynchronous DNS: AnyEvent::DNS.
1560		2155
1561	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	2156	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1562		2157
1563	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	2158	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
		2159	AnyEvent::HTTP.
1564		2160
1565	AUTHOR	2161	AUTHOR
1566	Marc Lehmann <schmorp@schmorp.de>	2162	Marc Lehmann <schmorp@schmorp.de>
1567	http://home.schmorp.de/	2163	http://anyevent.schmorp.de
1568		2164

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Comparing AnyEvent/README (file contents): Revision 1.41 by root, Fri Jun 26 06:33:17 2009 UTC vs. Revision 1.79 by root, Tue Feb 26 02:08:34 2019 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.41 by root, Fri Jun 26 06:33:17 2009 UTC vs.
Revision 1.79 by root, Tue Feb 26 02:08:34 2019 UTC