[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.55 by root, Mon Sep 14 05:05:09 2009 UTC vs.
Revision 1.74 by root, Sat May 2 14:39:31 2015 UTC

…		…
1	NAME	1	NAME
2	AnyEvent - the DBI of event loop programming	2	AnyEvent - the DBI of event loop programming
3		3
4	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,	4	EV, Event, Glib, Tk, UV, Perl, Event::Lib, Irssi, rxvt-unicode,
5	Qt and POE are various supported event loops/environments.	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
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.
42		46
43	SUPPORT	47	SUPPORT
		48	An FAQ document is available as AnyEvent::FAQ.
		49
44	There is a mailinglist for discussing all things AnyEvent, and an IRC	50	There also is a mailinglist for discussing all things AnyEvent, and an
45	channel, too.	51	IRC channel, too.
46		52
47	See the AnyEvent project page at the Schmorpforge Ta-Sa Software	53	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
48	Repository, at <http://anyevent.schmorp.de>, for more info.	54	Repository, at <http://anyevent.schmorp.de>, for more info.
49		55
50	WHY YOU SHOULD USE THIS MODULE (OR NOT)	56	WHY YOU SHOULD USE THIS MODULE (OR NOT)
…		…
68	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
69	model you use.	75	model you use.
70		76
71	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
72	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
73	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
74	cannot use anything else, as they are simply incompatible to everything	80	cannot use anything else, as they are simply incompatible to everything
75	that isn't them. What's worse, all the potential users of your module	81	that isn't them. What's worse, all the potential users of your module
76	are also forced to use the same event loop you use.	82	are also forced to use the same event loop you use.
77		83
78	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	84	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
79	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
80	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
81	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
82	But if your module uses AnyEvent, it works transparently with all event	88	your module uses AnyEvent, it works transparently with all event models
83	models it supports (including stuff like IO::Async, as long as those use	89	it supports (including stuff like IO::Async, as long as those use one of
84	one of the supported event loops. It is trivial to add new event loops	90	the supported event loops. It is easy to add new event loops to
85	to AnyEvent, too, so it is future-proof).	91	AnyEvent, too, so it is future-proof).
86		92
87	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
88	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
89	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
90	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
91	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
92	wrapper as technically possible.	98	technically possible.
93		99
94	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
95	useful functionality, such as an asynchronous DNS resolver, 100%	101	useful functionality, such as an asynchronous DNS resolver, 100%
96	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
97	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
…		…
100	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
101	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
102	model, you should not use this module.	108	model, you should not use this module.
103		109
104	DESCRIPTION	110	DESCRIPTION
105	AnyEvent provides an identical interface to multiple event loops. This	111	AnyEvent provides a uniform interface to various event loops. This
106	allows module authors to utilise an event loop without forcing module	112	allows module authors to use event loop functionality without forcing
107	users to use the same event loop (as only a single event loop can	113	module users to use a specific event loop implementation (since more
108	coexist peacefully at any one time).	114	than one event loop cannot coexist peacefully).
109		115
110	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
111	module.	117	module.
112		118
113	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
114	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
115	following modules is already loaded: EV, Event, Glib,	121	following modules is already loaded: EV, AnyEvent::Loop, Event, Glib,
116	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
117	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
118	(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
119	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
120	successfully loaded will be used. If, after this, still none could be	126	tried.
121	found, AnyEvent will fall back to a pure-perl event loop, which is not
122	very efficient, but should work everywhere.
123		127
124	Because AnyEvent first checks for modules that are already loaded,	128	Because AnyEvent first checks for modules that are already loaded,
125	loading an event model explicitly before first using AnyEvent will	129	loading an event model explicitly before first using AnyEvent will
126	likely make that model the default. For example:	130	likely make that model the default. For example:
127		131
…		…
129	use AnyEvent;	133	use AnyEvent;
130		134
131	# .. AnyEvent will likely default to Tk	135	# .. AnyEvent will likely default to Tk
132		136
133	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
134	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
135	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.
136		141
137	The pure-perl implementation of AnyEvent is called	142	The pure-perl implementation of AnyEvent is called "AnyEvent::Loop".
138	"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
139	explicitly and enjoy the high availability of that event loop :)	144	availability of that event loop :)
140		145
141	WATCHERS	146	WATCHERS
142	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
143	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
144	the callback to call, the file handle to watch, etc.	149	the callback to call, the file handle to watch, etc.
…		…
148	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
149	in control).	154	in control).
150		155
151	Note that callbacks must not permanently change global variables	156	Note that callbacks must not permanently change global variables
152	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
153	callbacks must not "die". The former is good programming practise in	158	callbacks must not "die". The former is good programming practice in
154	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
155	widely between event loops.	160	widely between event loops.
156		161
157	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
158	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
159	to it).	164	to it).
160		165
161	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.
162		167
163	Many watchers either are used with "recursion" (repeating timers for	168	Many watchers either are used with "recursion" (repeating timers for
164	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.
165		170
166	An any way to achieve that is this pattern:	171	One way to achieve that is this pattern:
167		172
168	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	173	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
169	# you can use $w here, for example to undef it	174	# you can use $w here, for example to undef it
170	undef $w;	175	undef $w;
171	});	176	});
…		…
202		207
203	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
204	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
205	the underlying file descriptor.	210	the underlying file descriptor.
206		211
207	Some event loops issue spurious readyness notifications, so you should	212	Some event loops issue spurious readiness notifications, so you should
208	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
209	handles.	214	handles.
210		215
211	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
212	watcher.	217	watcher.
…		…
235		240
236	Although the callback might get passed parameters, their value and	241	Although the callback might get passed parameters, their value and
237	presence is undefined and you cannot rely on them. Portable AnyEvent	242	presence is undefined and you cannot rely on them. Portable AnyEvent
238	callbacks cannot use arguments passed to time watcher callbacks.	243	callbacks cannot use arguments passed to time watcher callbacks.
239		244
240	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
241	parameter, "interval", as a strictly positive number (> 0), then the	246	parameter, "interval", as a strictly positive number (> 0), then the
242	callback will be invoked regularly at that interval (in fractional	247	callback will be invoked regularly at that interval (in fractional
243	seconds) after the first invocation. If "interval" is specified with a	248	seconds) after the first invocation. If "interval" is specified with a
244	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.
245		250
246	The callback will be rescheduled before invoking the callback, but no	251	The callback will be rescheduled before invoking the callback, but no
247	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
248	is only approximate.	253	is only approximate.
249		254
250	Example: fire an event after 7.7 seconds.	255	Example: fire an event after 7.7 seconds.
251		256
252	my $w = AnyEvent->timer (after => 7.7, cb => sub {	257	my $w = AnyEvent->timer (after => 7.7, cb => sub {
…		…
258		263
259	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.
260		265
261	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {	266	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
262	warn "timeout\n";	267	warn "timeout\n";
263	};	268	});
264		269
265	TIMING ISSUES	270	TIMING ISSUES
266	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
267	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
268	o'clock").	273	o'clock").
269		274
270	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,
271	they use absolute time internally. This makes a difference when your	276	they use absolute time internally. This makes a difference when your
272	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
273	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
274	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
275	finally fire.	280	finally fire.
276		281
277	AnyEvent cannot compensate for this. The only event loop that is	282	AnyEvent cannot compensate for this. The only event loop that is
278	conscious about these issues is EV, which offers both relative	283	conscious of these issues is EV, which offers both relative (ev_timer,
279	(ev_timer, based on true relative time) and absolute (ev_periodic, based	284	based on true relative time) and absolute (ev_periodic, based on
280	on wallclock time) timers.	285	wallclock time) timers.
281		286
282	AnyEvent always prefers relative timers, if available, matching the	287	AnyEvent always prefers relative timers, if available, matching the
283	AnyEvent API.	288	AnyEvent API.
284		289
285	AnyEvent has two additional methods that return the "current time":	290	AnyEvent has two additional methods that return the "current time":
…		…
304	*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
305	function to call when you want to know the current time.*	310	function to call when you want to know the current time.*
306		311
307	This function is also often faster then "AnyEvent->time", and thus	312	This function is also often faster then "AnyEvent->time", and thus
308	the preferred method if you want some timestamp (for example,	313	the preferred method if you want some timestamp (for example,
309	AnyEvent::Handle uses this to update it's activity timeouts).	314	AnyEvent::Handle uses this to update its activity timeouts).
310		315
311	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
312	exact with your timing, you can skip it without bad conscience.	317	exact with your timing; you can skip it without a bad conscience.
313		318
314	For a practical example of when these times differ, consider	319	For a practical example of when these times differ, consider
315	Event::Lib and EV and the following set-up:	320	Event::Lib and EV and the following set-up:
316		321
317	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
318	at time=500 (assume no other callbacks delay processing). In your	323	at time=500 (assume no other callbacks delay processing). In your
319	callback, you wait a second by executing "sleep 1" (blocking the	324	callback, you wait a second by executing "sleep 1" (blocking the
320	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
321	timer that fires after three seconds.	326	timer that fires after three seconds.
322		327
…		…
343	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
344	the difference between "AnyEvent->time" and "AnyEvent->now" into	349	the difference between "AnyEvent->time" and "AnyEvent->now" into
345	account.	350	account.
346		351
347	AnyEvent->now_update	352	AnyEvent->now_update
348	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
349	current time for each loop iteration (see the discussion of	354	time for each loop iteration (see the discussion of AnyEvent->now,
350	AnyEvent->now, above).	355	above).
351		356
352	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),
353	then this "current" time will differ substantially from the real	358	then this "current" time will differ substantially from the real
354	time, which might affect timers and time-outs.	359	time, which might affect timers and time-outs.
355		360
356	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
357	the event loop's idea of "current time".	362	the event loop's idea of "current time".
		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).
358		371
359	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.
360		373
361	SIGNAL WATCHERS	374	SIGNAL WATCHERS
362	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);	375	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
…		…
384		397
385	Example: exit on SIGINT	398	Example: exit on SIGINT
386		399
387	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	400	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
388		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
389	Signal Races, Delays and Workarounds	417	Signal Races, Delays and Workarounds
390	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching	418	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
391	callbacks to signals in a generic way, which is a pity, as you cannot do	419	callbacks to signals in a generic way, which is a pity, as you cannot do
392	race-free signal handling in perl, requiring C libraries for this.	420	race-free signal handling in perl, requiring C libraries for this.
393	AnyEvent will try to do it's best, which means in some cases, signals	421	AnyEvent will try to do its best, which means in some cases, signals
394	will be delayed. The maximum time a signal might be delayed is specified	422	will be delayed. The maximum time a signal might be delayed is 10
395	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable	423	seconds by default, but can be overriden via
396	can be changed only before the first signal watcher is created, and	424	$ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} or $AnyEvent::MAX_SIGNAL_LATENCY
397	should be left alone otherwise. This variable determines how often	425	- see the "ENVIRONMENT VARIABLES" section for details.
398	AnyEvent polls for signals (in case a wake-up was missed). Higher values
399	will cause fewer spurious wake-ups, which is better for power and CPU
400	saving.
401		426
402	All these problems can be avoided by installing the optional	427	All these problems can be avoided by installing the optional
403	Async::Interrupt module, which works with most event loops. It will not	428	Async::Interrupt module, which works with most event loops. It will not
404	work with inherently broken event loops such as Event or Event::Lib (and	429	work with inherently broken event loops such as Event or Event::Lib (and
405	not with POE currently, as POE does it's own workaround with one-second
406	latency). For those, you just have to suffer the delays.	430	not with POE currently). For those, you just have to suffer the delays.
407		431
408	CHILD PROCESS WATCHERS	432	CHILD PROCESS WATCHERS
409	$w = AnyEvent->child (pid => <process id>, cb => <callback>);	433	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
410		434
411	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.
412		436
413	The child process is specified by the "pid" argument (one some backends,	437	The child process is specified by the "pid" argument (on some backends,
414	using 0 watches for any child process exit, on others this will croak).	438	using 0 watches for any child process exit, on others this will croak).
415	The watcher will be triggered only when the child process has finished	439	The watcher will be triggered only when the child process has finished
416	and an exit status is available, not on any trace events	440	and an exit status is available, not on any trace events
417	(stopped/continued).	441	(stopped/continued).
418		442
…		…
439	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
440	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
441	you "fork" the child (alternatively, you can call "AnyEvent::detect").	465	you "fork" the child (alternatively, you can call "AnyEvent::detect").
442		466
443	As most event loops do not support waiting for child events, they will	467	As most event loops do not support waiting for child events, they will
444	be emulated by AnyEvent in most cases, in which the latency and race	468	be emulated by AnyEvent in most cases, in which case the latency and
445	problems mentioned in the description of signal watchers apply.	469	race problems mentioned in the description of signal watchers apply.
446		470
447	Example: fork a process and wait for it	471	Example: fork a process and wait for it
448		472
449	my $done = AnyEvent->condvar;	473	my $done = AnyEvent->condvar;
450		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.
451	my $pid = fork or exit 5;	479	my $pid = fork or exit 5;
452		480
453	my $w = AnyEvent->child (	481	my $w = AnyEvent->child (
454	pid => $pid,	482	pid => $pid,
455	cb => sub {	483	cb => sub {
…		…
463	$done->recv;	491	$done->recv;
464		492
465	IDLE WATCHERS	493	IDLE WATCHERS
466	$w = AnyEvent->idle (cb => <callback>);	494	$w = AnyEvent->idle (cb => <callback>);
467		495
468	Sometimes there is a need to do something, but it is not so important to	496	This will repeatedly invoke the callback after the process becomes idle,
469	do it instantly, but only when there is nothing better to do. This	497	until either the watcher is destroyed or new events have been detected.
470	"nothing better to do" is usually defined to be "no other events need
471	attention by the event loop".
472		498
473	Idle watchers ideally get invoked when the event loop has nothing better	499	Idle watchers are useful when there is a need to do something, but it is
474	to do, just before it would block the process to wait for new events.	500	not so important (or wise) to do it instantly. The callback will be
475	Instead of blocking, the idle watcher is invoked.	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.
476		507
477	Most event loops unfortunately do not really support idle watchers (only	508	Unfortunately, most event loops do not really support idle watchers
478	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,
479	will simply call the callback "from time to time".	510	AnyEvent will simply call the callback "from time to time".
480		511
481	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
482	is otherwise idle:	513	is otherwise idle:
483		514
484	my @lines; # read data	515	my @lines; # read data
…		…
510		541
511	AnyEvent is slightly different: it expects somebody else to run the	542	AnyEvent is slightly different: it expects somebody else to run the
512	event loop and will only block when necessary (usually when told by the	543	event loop and will only block when necessary (usually when told by the
513	user).	544	user).
514		545
515	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
516	because they represent a condition that must become true.	547	they represent a condition that must become true.
517		548
518	Now is probably a good time to look at the examples further below.	549	Now is probably a good time to look at the examples further below.
519		550
520	Condition variables can be created by calling the "AnyEvent->condvar"	551	Condition variables can be created by calling the "AnyEvent->condvar"
521	method, usually without arguments. The only argument pair allowed is	552	method, usually without arguments. The only argument pair allowed is
…		…
526	After creation, the condition variable is "false" until it becomes	557	After creation, the condition variable is "false" until it becomes
527	"true" by calling the "send" method (or calling the condition variable	558	"true" by calling the "send" method (or calling the condition variable
528	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
529	the "->send" method).	560	the "->send" method).
530		561
531	Condition variables are similar to callbacks, except that you can	562	Since condition variables are the most complex part of the AnyEvent API,
532	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
533	in time where multiple outstanding events have been processed. And yet	564	you can connect to:
534	another way to call them is transactions - each condition variable can	565
535	be used to represent a transaction, which finishes at some point and	566	* Condition variables are like callbacks - you can call them (and pass
536	delivers a result. And yet some people know them as "futures" - a	567	them instead of callbacks). Unlike callbacks however, you can also
537	promise to compute/deliver something that you can wait for.	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.
538		583
539	Condition variables are very useful to signal that something has	584	Condition variables are very useful to signal that something has
540	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
541	requests, then a condition variable would be the ideal candidate to	586	requests, then a condition variable would be the ideal candidate to
542	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
…		…
555		600
556	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
557	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
558	(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
559	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	604	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
560	it's "new" method in your own "new" method.	605	its "new" method in your own "new" method.
561		606
562	There are two "sides" to a condition variable - the "producer side"	607	There are two "sides" to a condition variable - the "producer side"
563	which eventually calls "-> send", and the "consumer side", which waits	608	which eventually calls "-> send", and the "consumer side", which waits
564	for the send to occur.	609	for the send to occur.
565		610
566	Example: wait for a timer.	611	Example: wait for a timer.
567		612
568	# wait till the result is ready	613	# condition: "wait till the timer is fired"
569	my $result_ready = AnyEvent->condvar;	614	my $timer_fired = AnyEvent->condvar;
570		615
571	# do something such as adding a timer	616	# create the timer - we could wait for, say
572	# or socket watcher the calls $result_ready->send	617	# a handle becomign ready, or even an
573	# when the "result" is ready.	618	# AnyEvent::HTTP request to finish, but
574	# in this case, we simply use a timer:	619	# in this case, we simply use a timer:
575	my $w = AnyEvent->timer (	620	my $w = AnyEvent->timer (
576	after => 1,	621	after => 1,
577	cb => sub { $result_ready->send },	622	cb => sub { $timer_fired->send },
578	);	623	);
579		624
580	# this "blocks" (while handling events) till the callback	625	# this "blocks" (while handling events) till the callback
581	# calls ->send	626	# calls ->send
582	$result_ready->recv;	627	$timer_fired->recv;
583		628
584	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
585	variables are also callable directly.	630	variables are also callable directly.
586		631
587	my $done = AnyEvent->condvar;	632	my $done = AnyEvent->condvar;
…		…
625	Condition variables are overloaded so one can call them directly (as	670	Condition variables are overloaded so one can call them directly (as
626	if they were a code reference). Calling them directly is the same as	671	if they were a code reference). Calling them directly is the same as
627	calling "send".	672	calling "send".
628		673
629	$cv->croak ($error)	674	$cv->croak ($error)
630	Similar to send, but causes all call's to "->recv" to invoke	675	Similar to send, but causes all calls to "->recv" to invoke
631	"Carp::croak" with the given error message/object/scalar.	676	"Carp::croak" with the given error message/object/scalar.
632		677
633	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
634	user/consumer. Doing it this way instead of calling "croak" directly	679	user/consumer. Doing it this way instead of calling "croak" directly
635	delays the error detetcion, but has the overwhelmign advantage that	680	delays the error detection, but has the overwhelming advantage that
636	it diagnoses the error at the place where the result is expected,	681	it diagnoses the error at the place where the result is expected,
637	and not deep in some event clalback without connection to the actual	682	and not deep in some event callback with no connection to the actual
638	code causing the problem.	683	code causing the problem.
639		684
640	$cv->begin ([group callback])	685	$cv->begin ([group callback])
641	$cv->end	686	$cv->end
642	These two methods can be used to combine many transactions/events	687	These two methods can be used to combine many transactions/events
…		…
678	This works because for every event source (EOF on file handle),	723	This works because for every event source (EOF on file handle),
679	there is one call to "begin", so the condvar waits for all calls to	724	there is one call to "begin", so the condvar waits for all calls to
680	"end" before sending.	725	"end" before sending.
681		726
682	The ping example mentioned above is slightly more complicated, as	727	The ping example mentioned above is slightly more complicated, as
683	the there are results to be passwd back, and the number of tasks	728	the there are results to be passed back, and the number of tasks
684	that are begung can potentially be zero:	729	that are begun can potentially be zero:
685		730
686	my $cv = AnyEvent->condvar;	731	my $cv = AnyEvent->condvar;
687		732
688	my %result;	733	my %result;
689	$cv->begin (sub { shift->send (\%result) });	734	$cv->begin (sub { shift->send (\%result) });
…		…
696	};	741	};
697	}	742	}
698		743
699	$cv->end;	744	$cv->end;
700		745
		746	...
		747
		748	my $results = $cv->recv;
		749
701	This code fragment supposedly pings a number of hosts and calls	750	This code fragment supposedly pings a number of hosts and calls
702	"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
703	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
704	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
705	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
…		…
710	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
711	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
712	(the loop doesn't execute once).	761	(the loop doesn't execute once).
713		762
714	This is the general pattern when you "fan out" into multiple (but	763	This is the general pattern when you "fan out" into multiple (but
715	potentially none) subrequests: use an outer "begin"/"end" pair to	764	potentially zero) subrequests: use an outer "begin"/"end" pair to
716	set the callback and ensure "end" is called at least once, and then,	765	set the callback and ensure "end" is called at least once, and then,
717	for each subrequest you start, call "begin" and for each subrequest	766	for each subrequest you start, call "begin" and for each subrequest
718	you finish, call "end".	767	you finish, call "end".
719		768
720	METHODS FOR CONSUMERS	769	METHODS FOR CONSUMERS
721	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
722	awaits the condition.	771	awaits the condition.
723		772
724	$cv->recv	773	$cv->recv
725	Wait (blocking if necessary) until the "->send" or "->croak" methods	774	Wait (blocking if necessary) until the "->send" or "->croak" methods
726	have been called on c<$cv>, while servicing other watchers normally.	775	have been called on $cv, while servicing other watchers normally.
727		776
728	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
729	but will return immediately.	778	but will return immediately.
730		779
731	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
…		…
734	In list context, all parameters passed to "send" will be returned,	783	In list context, all parameters passed to "send" will be returned,
735	in scalar context only the first one will be returned.	784	in scalar context only the first one will be returned.
736		785
737	Note that doing a blocking wait in a callback is not supported by	786	Note that doing a blocking wait in a callback is not supported by
738	any event loop, that is, recursive invocation of a blocking "->recv"	787	any event loop, that is, recursive invocation of a blocking "->recv"
739	is not allowed, and the "recv" call will "croak" if such a condition	788	is not allowed and the "recv" call will "croak" if such a condition
740	is detected. This condition can be slightly loosened by using	789	is detected. This requirement can be dropped by relying on
741	Coro::AnyEvent, which allows you to do a blocking "->recv" from any	790	Coro::AnyEvent , which allows you to do a blocking "->recv" from any
742	thread that doesn't run the event loop itself.	791	thread that doesn't run the event loop itself. Coro::AnyEvent is
		792	loaded automatically when Coro is used with AnyEvent, so code does
		793	not need to do anything special to take advantage of that: any code
		794	that would normally block your program because it calls "recv", be
		795	executed in an "async" thread instead without blocking other
		796	threads.
743		797
744	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
745	(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
746	using this from a module, never require a blocking wait*. Instead,	800	using this from a module, never require a blocking wait*. Instead,
747	let the caller decide whether the call will block or not (for	801	let the caller decide whether the call will block or not (for
748	example, by coupling condition variables with some kind of request	802	example, by coupling condition variables with some kind of request
749	results and supporting callbacks so the caller knows that getting	803	results and supporting callbacks so the caller knows that getting
750	the result will not block, while still supporting blocking waits if	804	the result will not block, while still supporting blocking waits if
751	the caller so desires).	805	the caller so desires).
752		806
753	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
754	only calling "->recv" from within that callback (or at a later	808	only calling "->recv" from within that callback (or at a later
755	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
756	blocking waits otherwise.	810	blocking waits otherwise.
757		811
758	$bool = $cv->ready	812	$bool = $cv->ready
…		…
761		815
762	$cb = $cv->cb ($cb->($cv))	816	$cb = $cv->cb ($cb->($cv))
763	This is a mutator function that returns the callback set and	817	This is a mutator function that returns the callback set and
764	optionally replaces it before doing so.	818	optionally replaces it before doing so.
765		819
766	The callback will be called when the condition becomes (or already	820	The callback will be called when the condition becomes "true", i.e.
767	was) "true", i.e. when "send" or "croak" are called (or were	821	when "send" or "croak" are called, with the only argument being the
768	called), with the only argument being the condition variable itself.	822	condition variable itself. If the condition is already true, the
769	Calling "recv" inside the callback or at any later time is	823	callback is called immediately when it is set. Calling "recv" inside
770	guaranteed not to block.	824	the callback or at any later time is guaranteed not to block.
771		825
772	SUPPORTED EVENT LOOPS/BACKENDS	826	SUPPORTED EVENT LOOPS/BACKENDS
773	The available backend classes are (every class has its own manpage):	827	The available backend classes are (every class has its own manpage):
774		828
775	Backends that are autoprobed when no other event loop can be found.	829	Backends that are autoprobed when no other event loop can be found.
…		…
777	use. If EV is not installed, then AnyEvent will fall back to its own	831	use. If EV is not installed, then AnyEvent will fall back to its own
778	pure-perl implementation, which is available everywhere as it comes	832	pure-perl implementation, which is available everywhere as it comes
779	with AnyEvent itself.	833	with AnyEvent itself.
780		834
781	AnyEvent::Impl::EV based on EV (interface to libev, best choice).	835	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
782	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.	836	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
783		837
784	Backends that are transparently being picked up when they are used.	838	Backends that are transparently being picked up when they are used.
785	These will be used when they are currently loaded when the first	839	These will be used if they are already loaded when the first watcher
786	watcher is created, in which case it is assumed that the application	840	is created, in which case it is assumed that the application is
787	is using them. This means that AnyEvent will automatically pick the	841	using them. This means that AnyEvent will automatically pick the
788	right backend when the main program loads an event module before	842	right backend when the main program loads an event module before
789	anything starts to create watchers. Nothing special needs to be done	843	anything starts to create watchers. Nothing special needs to be done
790	by the main program.	844	by the main program.
791		845
792	AnyEvent::Impl::Event based on Event, very stable, few glitches.	846	AnyEvent::Impl::Event based on Event, very stable, few glitches.
793	AnyEvent::Impl::Glib based on Glib, slow but very stable.	847	AnyEvent::Impl::Glib based on Glib, slow but very stable.
794	AnyEvent::Impl::Tk based on Tk, very broken.	848	AnyEvent::Impl::Tk based on Tk, very broken.
		849	AnyEvent::Impl::UV based on UV, innovated square wheels.
795	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	850	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
796	AnyEvent::Impl::POE based on POE, very slow, some limitations.	851	AnyEvent::Impl::POE based on POE, very slow, some limitations.
797	AnyEvent::Impl::Irssi used when running within irssi.	852	AnyEvent::Impl::Irssi used when running within irssi.
		853	AnyEvent::Impl::IOAsync based on IO::Async.
		854	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		855	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
798		856
799	Backends with special needs.	857	Backends with special needs.
800	Qt requires the Qt::Application to be instantiated first, but will	858	Qt requires the Qt::Application to be instantiated first, but will
801	otherwise be picked up automatically. As long as the main program	859	otherwise be picked up automatically. As long as the main program
802	instantiates the application before any AnyEvent watchers are	860	instantiates the application before any AnyEvent watchers are
803	created, everything should just work.	861	created, everything should just work.
804		862
805	AnyEvent::Impl::Qt based on Qt.	863	AnyEvent::Impl::Qt based on Qt.
806		864
807	Support for IO::Async can only be partial, as it is too broken and
808	architecturally limited to even support the AnyEvent API. It also is
809	the only event loop that needs the loop to be set explicitly, so it
810	can only be used by a main program knowing about AnyEvent. See
811	AnyEvent::Impl::Async for the gory details.
812
813	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
814
815	Event loops that are indirectly supported via other backends.	865	Event loops that are indirectly supported via other backends.
816	Some event loops can be supported via other modules:	866	Some event loops can be supported via other modules:
817		867
818	There is no direct support for WxWidgets (Wx) or Prima.	868	There is no direct support for WxWidgets (Wx) or Prima.
819		869
…		…
837	Contains "undef" until the first watcher is being created, before	887	Contains "undef" until the first watcher is being created, before
838	the backend has been autodetected.	888	the backend has been autodetected.
839		889
840	Afterwards it contains the event model that is being used, which is	890	Afterwards it contains the event model that is being used, which is
841	the name of the Perl class implementing the model. This class is	891	the name of the Perl class implementing the model. This class is
842	usually one of the "AnyEvent::Impl:xxx" modules, but can be any	892	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
843	other class in the case AnyEvent has been extended at runtime (e.g.	893	other class in the case AnyEvent has been extended at runtime (e.g.
844	in rxvt-unicode it will be "urxvt::anyevent").	894	in rxvt-unicode it will be "urxvt::anyevent").
845		895
846	AnyEvent::detect	896	AnyEvent::detect
847	Returns $AnyEvent::MODEL, forcing autodetection of the event model	897	Returns $AnyEvent::MODEL, forcing autodetection of the event model
848	if necessary. You should only call this function right before you	898	if necessary. You should only call this function right before you
849	would have created an AnyEvent watcher anyway, that is, as late as	899	would have created an AnyEvent watcher anyway, that is, as late as
850	possible at runtime, and not e.g. while initialising of your module.	900	possible at runtime, and not e.g. during initialisation of your
		901	module.
		902
		903	The effect of calling this function is as if a watcher had been
		904	created (specifically, actions that happen "when the first watcher
		905	is created" happen when calling detetc as well).
851		906
852	If you need to do some initialisation before AnyEvent watchers are	907	If you need to do some initialisation before AnyEvent watchers are
853	created, use "post_detect".	908	created, use "post_detect".
854		909
855	$guard = AnyEvent::post_detect { BLOCK }	910	$guard = AnyEvent::post_detect { BLOCK }
856	Arranges for the code block to be executed as soon as the event	911	Arranges for the code block to be executed as soon as the event
857	model is autodetected (or immediately if this has already happened).	912	model is autodetected (or immediately if that has already happened).
858		913
859	The block will be executed after the actual backend has been	914	The block will be executed after the actual backend has been
860	detected ($AnyEvent::MODEL is set), but before any watchers have	915	detected ($AnyEvent::MODEL is set), but before any watchers have
861	been created, so it is possible to e.g. patch @AnyEvent::ISA or do	916	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
862	other initialisations - see the sources of AnyEvent::Strict or	917	other initialisations - see the sources of AnyEvent::Strict or
…		…
871	object that automatically removes the callback again when it is	926	object that automatically removes the callback again when it is
872	destroyed (or "undef" when the hook was immediately executed). See	927	destroyed (or "undef" when the hook was immediately executed). See
873	AnyEvent::AIO for a case where this is useful.	928	AnyEvent::AIO for a case where this is useful.
874		929
875	Example: Create a watcher for the IO::AIO module and store it in	930	Example: Create a watcher for the IO::AIO module and store it in
876	$WATCHER. Only do so after the event loop is initialised, though.	931	$WATCHER, but do so only do so after the event loop is initialised.
877		932
878	our WATCHER;	933	our WATCHER;
879		934
880	my $guard = AnyEvent::post_detect {	935	my $guard = AnyEvent::post_detect {
881	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);	936	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
…		…
888		943
889	$WATCHER \|\|= $guard;	944	$WATCHER \|\|= $guard;
890		945
891	@AnyEvent::post_detect	946	@AnyEvent::post_detect
892	If there are any code references in this array (you can "push" to it	947	If there are any code references in this array (you can "push" to it
893	before or after loading AnyEvent), then they will called directly	948	before or after loading AnyEvent), then they will be called directly
894	after the event loop has been chosen.	949	after the event loop has been chosen.
895		950
896	You should check $AnyEvent::MODEL before adding to this array,	951	You should check $AnyEvent::MODEL before adding to this array,
897	though: if it is defined then the event loop has already been	952	though: if it is defined then the event loop has already been
898	detected, and the array will be ignored.	953	detected, and the array will be ignored.
899		954
900	Best use "AnyEvent::post_detect { BLOCK }" when your application	955	Best use "AnyEvent::post_detect { BLOCK }" when your application
901	allows it,as it takes care of these details.	956	allows it, as it takes care of these details.
902		957
903	This variable is mainly useful for modules that can do something	958	This variable is mainly useful for modules that can do something
904	useful when AnyEvent is used and thus want to know when it is	959	useful when AnyEvent is used and thus want to know when it is
905	initialised, but do not need to even load it by default. This array	960	initialised, but do not need to even load it by default. This array
906	provides the means to hook into AnyEvent passively, without loading	961	provides the means to hook into AnyEvent passively, without loading
907	it.	962	it.
908		963
		964	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		965	together, you could put this into Coro (this is the actual code used
		966	by Coro to accomplish this):
		967
		968	if (defined $AnyEvent::MODEL) {
		969	# AnyEvent already initialised, so load Coro::AnyEvent
		970	require Coro::AnyEvent;
		971	} else {
		972	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		973	# as soon as it is
		974	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		975	}
		976
		977	AnyEvent::postpone { BLOCK }
		978	Arranges for the block to be executed as soon as possible, but not
		979	before the call itself returns. In practise, the block will be
		980	executed just before the event loop polls for new events, or shortly
		981	afterwards.
		982
		983	This function never returns anything (to make the "return postpone {
		984	... }" idiom more useful.
		985
		986	To understand the usefulness of this function, consider a function
		987	that asynchronously does something for you and returns some
		988	transaction object or guard to let you cancel the operation. For
		989	example, "AnyEvent::Socket::tcp_connect":
		990
		991	# start a connection attempt unless one is active
		992	$self->{connect_guard} \|\|= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		993	delete $self->{connect_guard};
		994	...
		995	};
		996
		997	Imagine that this function could instantly call the callback, for
		998	example, because it detects an obvious error such as a negative port
		999	number. Invoking the callback before the function returns causes
		1000	problems however: the callback will be called and will try to delete
		1001	the guard object. But since the function hasn't returned yet, there
		1002	is nothing to delete. When the function eventually returns it will
		1003	assign the guard object to "$self->{connect_guard}", where it will
		1004	likely never be deleted, so the program thinks it is still trying to
		1005	connect.
		1006
		1007	This is where "AnyEvent::postpone" should be used. Instead of
		1008	calling the callback directly on error:
		1009
		1010	$cb->(undef), return # signal error to callback, BAD!
		1011	if $some_error_condition;
		1012
		1013	It should use "postpone":
		1014
		1015	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1016	if $some_error_condition;
		1017
		1018	AnyEvent::log $level, $msg[, @args]
		1019	Log the given $msg at the given $level.
		1020
		1021	If AnyEvent::Log is not loaded then this function makes a simple
		1022	test to see whether the message will be logged. If the test succeeds
		1023	it will load AnyEvent::Log and call "AnyEvent::Log::log" -
		1024	consequently, look at the AnyEvent::Log documentation for details.
		1025
		1026	If the test fails it will simply return. Right now this happens when
		1027	a numerical loglevel is used and it is larger than the level
		1028	specified via $ENV{PERL_ANYEVENT_VERBOSE}.
		1029
		1030	If you want to sprinkle loads of logging calls around your code,
		1031	consider creating a logger callback with the "AnyEvent::Log::logger"
		1032	function, which can reduce typing, codesize and can reduce the
		1033	logging overhead enourmously.
		1034
909	WHAT TO DO IN A MODULE	1035	WHAT TO DO IN A MODULE
910	As a module author, you should "use AnyEvent" and call AnyEvent methods	1036	As a module author, you should "use AnyEvent" and call AnyEvent methods
911	freely, but you should not load a specific event module or rely on it.	1037	freely, but you should not load a specific event module or rely on it.
912		1038
913	Be careful when you create watchers in the module body - AnyEvent will	1039	Be careful when you create watchers in the module body - AnyEvent will
…		…
920	stall the whole program, and the whole point of using events is to stay	1046	stall the whole program, and the whole point of using events is to stay
921	interactive.	1047	interactive.
922		1048
923	It is fine, however, to call "->recv" when the user of your module	1049	It is fine, however, to call "->recv" when the user of your module
924	requests it (i.e. if you create a http request object ad have a method	1050	requests it (i.e. if you create a http request object ad have a method
925	called "results" that returns the results, it should call "->recv"	1051	called "results" that returns the results, it may call "->recv" freely,
926	freely, as the user of your module knows what she is doing. always).	1052	as the user of your module knows what she is doing. Always).
927		1053
928	WHAT TO DO IN THE MAIN PROGRAM	1054	WHAT TO DO IN THE MAIN PROGRAM
929	There will always be a single main program - the only place that should	1055	There will always be a single main program - the only place that should
930	dictate which event model to use.	1056	dictate which event model to use.
931		1057
932	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1058	If the program is not event-based, it need not do anything special, even
933	do anything special (it does not need to be event-based) and let	1059	when it depends on a module that uses an AnyEvent. If the program itself
934	AnyEvent decide which implementation to chose if some module relies on	1060	uses AnyEvent, but does not care which event loop is used, all it needs
935	it.	1061	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1062	available loop implementation.
936		1063
937	If the main program relies on a specific event model - for example, in	1064	If the main program relies on a specific event model - for example, in
938	Gtk2 programs you have to rely on the Glib module - you should load the	1065	Gtk2 programs you have to rely on the Glib module - you should load the
939	event module before loading AnyEvent or any module that uses it:	1066	event module before loading AnyEvent or any module that uses it:
940	generally speaking, you should load it as early as possible. The reason	1067	generally speaking, you should load it as early as possible. The reason
941	is that modules might create watchers when they are loaded, and AnyEvent	1068	is that modules might create watchers when they are loaded, and AnyEvent
942	will decide on the event model to use as soon as it creates watchers,	1069	will decide on the event model to use as soon as it creates watchers,
943	and it might chose the wrong one unless you load the correct one	1070	and it might choose the wrong one unless you load the correct one
944	yourself.	1071	yourself.
945		1072
946	You can chose to use a pure-perl implementation by loading the	1073	You can chose to use a pure-perl implementation by loading the
947	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1074	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
948	everywhere, but letting AnyEvent chose the model is generally better.	1075	but letting AnyEvent chose the model is generally better.
949		1076
950	MAINLOOP EMULATION	1077	MAINLOOP EMULATION
951	Sometimes (often for short test scripts, or even standalone programs who	1078	Sometimes (often for short test scripts, or even standalone programs who
952	only want to use AnyEvent), you do not want to run a specific event	1079	only want to use AnyEvent), you do not want to run a specific event
953	loop.	1080	loop.
…		…
965		1092
966	OTHER MODULES	1093	OTHER MODULES
967	The following is a non-exhaustive list of additional modules that use	1094	The following is a non-exhaustive list of additional modules that use
968	AnyEvent as a client and can therefore be mixed easily with other	1095	AnyEvent as a client and can therefore be mixed easily with other
969	AnyEvent modules and other event loops in the same program. Some of the	1096	AnyEvent modules and other event loops in the same program. Some of the
970	modules come with AnyEvent, most are available via CPAN.	1097	modules come as part of AnyEvent, the others are available via CPAN (see
		1098	<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
		1099	non-exhaustive list), and the list is heavily biased towards modules of
		1100	the AnyEvent author himself :)
971		1101
972	AnyEvent::Util	1102	AnyEvent::Util (part of the AnyEvent distribution)
973	Contains various utility functions that replace often-used but	1103	Contains various utility functions that replace often-used blocking
974	blocking functions such as "inet_aton" by event-/callback-based	1104	functions such as "inet_aton" with event/callback-based versions.
975	versions.
976		1105
977	AnyEvent::Socket	1106	AnyEvent::Socket (part of the AnyEvent distribution)
978	Provides various utility functions for (internet protocol) sockets,	1107	Provides various utility functions for (internet protocol) sockets,
979	addresses and name resolution. Also functions to create non-blocking	1108	addresses and name resolution. Also functions to create non-blocking
980	tcp connections or tcp servers, with IPv6 and SRV record support and	1109	tcp connections or tcp servers, with IPv6 and SRV record support and
981	more.	1110	more.
982		1111
983	AnyEvent::Handle	1112	AnyEvent::Handle (part of the AnyEvent distribution)
984	Provide read and write buffers, manages watchers for reads and	1113	Provide read and write buffers, manages watchers for reads and
985	writes, supports raw and formatted I/O, I/O queued and fully	1114	writes, supports raw and formatted I/O, I/O queued and fully
986	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.	1115	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
987		1116
988	AnyEvent::DNS	1117	AnyEvent::DNS (part of the AnyEvent distribution)
989	Provides rich asynchronous DNS resolver capabilities.	1118	Provides rich asynchronous DNS resolver capabilities.
990		1119
991	AnyEvent::HTTP	1120	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
992	A simple-to-use HTTP library that is capable of making a lot of	1121	AnyEvent::IGS, AnyEvent::FCP
993	concurrent HTTP requests.	1122	Implement event-based interfaces to the protocols of the same name
		1123	(for the curious, IGS is the International Go Server and FCP is the
		1124	Freenet Client Protocol).
994		1125
		1126	AnyEvent::AIO (part of the AnyEvent distribution)
		1127	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1128	the toolbox of every event programmer. AnyEvent::AIO transparently
		1129	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1130	event-based file I/O, and much more.
		1131
		1132	AnyEvent::Fork, AnyEvent::Fork::RPC, AnyEvent::Fork::Pool,
		1133	AnyEvent::Fork::Remote
		1134	These let you safely fork new subprocesses, either locally or
		1135	remotely (e.g.v ia ssh), using some RPC protocol or not, without the
		1136	limitations normally imposed by fork (AnyEvent works fine for
		1137	example). Dynamically-resized worker pools are obviously included as
		1138	well.
		1139
		1140	And they are quite tiny and fast as well - "abusing" AnyEvent::Fork
		1141	just to exec external programs can easily beat using "fork" and
		1142	"exec" (or even "system") in most programs.
		1143
		1144	AnyEvent::Filesys::Notify
		1145	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1146	path changes (e.g. "watch this directory for new files", "watch this
		1147	file for changes"). The AnyEvent::Filesys::Notify module promises to
		1148	do just that in a portbale fashion, supporting inotify on GNU/Linux
		1149	and some weird, without doubt broken, stuff on OS X to monitor
		1150	files. It can fall back to blocking scans at regular intervals
		1151	transparently on other platforms, so it's about as portable as it
		1152	gets.
		1153
		1154	(I haven't used it myself, but it seems the biggest problem with it
		1155	is it quite bad performance).
		1156
995	AnyEvent::HTTPD	1157	AnyEvent::DBI
996	Provides a simple web application server framework.	1158	Executes DBI requests asynchronously in a proxy process for you,
		1159	notifying you in an event-based way when the operation is finished.
997		1160
998	AnyEvent::FastPing	1161	AnyEvent::FastPing
999	The fastest ping in the west.	1162	The fastest ping in the west.
1000		1163
1001	AnyEvent::DBI
1002	Executes DBI requests asynchronously in a proxy process.
1003
1004	AnyEvent::AIO
1005	Truly asynchronous I/O, should be in the toolbox of every event
1006	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
1007	together.
1008
1009	AnyEvent::BDB
1010	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
1011	fuses BDB and AnyEvent together.
1012
1013	AnyEvent::GPSD
1014	A non-blocking interface to gpsd, a daemon delivering GPS
1015	information.
1016
1017	AnyEvent::IRC
1018	AnyEvent based IRC client module family (replacing the older
1019	Net::IRC3).
1020
1021	AnyEvent::XMPP
1022	AnyEvent based XMPP (Jabber protocol) module family (replacing the
1023	older Net::XMPP2>.
1024
1025	AnyEvent::IGS
1026	A non-blocking interface to the Internet Go Server protocol (used by
1027	App::IGS).
1028
1029	Net::FCP
1030	AnyEvent-based implementation of the Freenet Client Protocol,
1031	birthplace of AnyEvent.
1032
1033	Event::ExecFlow
1034	High level API for event-based execution flow control.
1035
1036	Coro	1164	Coro
1037	Has special support for AnyEvent via Coro::AnyEvent.	1165	Has special support for AnyEvent via Coro::AnyEvent, which allows
		1166	you to simply invert the flow control - don't call us, we will call
		1167	you:
		1168
		1169	async {
		1170	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1171	print "5 seconds later!\n";
		1172
		1173	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1174	my $line = <STDIN>; # works for ttys
		1175
		1176	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1177	my ($body, $hdr) = Coro::rouse_wait;
		1178	};
1038		1179
1039	SIMPLIFIED AE API	1180	SIMPLIFIED AE API
1040	Starting with version 5.0, AnyEvent officially supports a second, much	1181	Starting with version 5.0, AnyEvent officially supports a second, much
1041	simpler, API that is designed to reduce the calling, typing and memory	1182	simpler, API that is designed to reduce the calling, typing and memory
1042	overhead.	1183	overhead by using function call syntax and a fixed number of parameters.
1043		1184
1044	See the AE manpage for details.	1185	See the AE manpage for details.
1045		1186
1046	ERROR AND EXCEPTION HANDLING	1187	ERROR AND EXCEPTION HANDLING
1047	In general, AnyEvent does not do any error handling - it relies on the	1188	In general, AnyEvent does not do any error handling - it relies on the
…		…
1058	The pure perl event loop simply re-throws the exception (usually within	1199	The pure perl event loop simply re-throws the exception (usually within
1059	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1200	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
1060	Glib uses "install_exception_handler" and so on.	1201	Glib uses "install_exception_handler" and so on.
1061		1202
1062	ENVIRONMENT VARIABLES	1203	ENVIRONMENT VARIABLES
1063	The following environment variables are used by this module or its	1204	AnyEvent supports a number of environment variables that tune the
1064	submodules.	1205	runtime behaviour. They are usually evaluated when AnyEvent is loaded,
		1206	initialised, or a submodule that uses them is loaded. Many of them also
		1207	cause AnyEvent to load additional modules - for example,
		1208	"PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be
		1209	loaded.
1065		1210
1066	Note that AnyEvent will remove all environment variables starting with	1211	All the environment variables documented here start with
1067	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is	1212	"PERL_ANYEVENT_", which is what AnyEvent considers its own namespace.
1068	enabled.	1213	Other modules are encouraged (but by no means required) to use
		1214	"PERL_ANYEVENT_SUBMODULE" if they have registered the
		1215	AnyEvent::Submodule namespace on CPAN, for any submodule. For example,
		1216	AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it
		1217	should not access env variables starting with "AE_", see below).
		1218
		1219	All variables can also be set via the "AE_" prefix, that is, instead of
		1220	setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case
		1221	there is a clash btween anyevent and another program that uses
		1222	"AE_something" you can set the corresponding "PERL_ANYEVENT_something"
		1223	variable to the empty string, as those variables take precedence.
		1224
		1225	When AnyEvent is first loaded, it copies all "AE_xxx" env variables to
		1226	their "PERL_ANYEVENT_xxx" counterpart unless that variable already
		1227	exists. If taint mode is on, then AnyEvent will remove all environment
		1228	variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with
		1229	"undef" or the empty string, if the corresaponding "AE_" variable is
		1230	set).
		1231
		1232	The exact algorithm is currently:
		1233
		1234	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		1235	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		1236	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		1237
		1238	This ensures that child processes will not see the "AE_" variables.
		1239
		1240	The following environment variables are currently known to AnyEvent:
1069		1241
1070	"PERL_ANYEVENT_VERBOSE"	1242	"PERL_ANYEVENT_VERBOSE"
1071	By default, AnyEvent will be completely silent except in fatal	1243	By default, AnyEvent will log messages with loglevel 4 ("error") or
1072	conditions. You can set this environment variable to make AnyEvent	1244	higher (see AnyEvent::Log). You can set this environment variable to
1073	more talkative.	1245	a numerical loglevel to make AnyEvent more (or less) talkative.
1074		1246
		1247	If you want to do more than just set the global logging level you
		1248	should have a look at "PERL_ANYEVENT_LOG", which allows much more
		1249	complex specifications.
		1250
		1251	When set to 0 ("off"), then no messages whatsoever will be logged
		1252	with everything else at defaults.
		1253
1075	When set to 1 or higher, causes AnyEvent to warn about unexpected	1254	When set to 5 or higher ("warn"), AnyEvent warns about unexpected
1076	conditions, such as not being able to load the event model specified	1255	conditions, such as not being able to load the event model specified
1077	by "PERL_ANYEVENT_MODEL".	1256	by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception
		1257	- this is the minimum recommended level for use during development.
1078		1258
1079	When set to 2 or higher, cause AnyEvent to report to STDERR which	1259	When set to 7 or higher (info), AnyEvent reports which event model
1080	event model it chooses.	1260	it chooses.
1081		1261
1082	When set to 8 or higher, then AnyEvent will report extra information	1262	When set to 8 or higher (debug), then AnyEvent will report extra
1083	on which optional modules it loads and how it implements certain	1263	information on which optional modules it loads and how it implements
1084	features.	1264	certain features.
		1265
		1266	"PERL_ANYEVENT_LOG"
		1267	Accepts rather complex logging specifications. For example, you
		1268	could log all "debug" messages of some module to stderr, warnings
		1269	and above to stderr, and errors and above to syslog, with:
		1270
		1271	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		1272
		1273	For the rather extensive details, see AnyEvent::Log.
		1274
		1275	This variable is evaluated when AnyEvent (or AnyEvent::Log) is
		1276	loaded, so will take effect even before AnyEvent has initialised
		1277	itself.
		1278
		1279	Note that specifying this environment variable causes the
		1280	AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE"
		1281	does not, so only using the latter saves a few hundred kB of memory
		1282	unless a module explicitly needs the extra features of
		1283	AnyEvent::Log.
1085		1284
1086	"PERL_ANYEVENT_STRICT"	1285	"PERL_ANYEVENT_STRICT"
1087	AnyEvent does not do much argument checking by default, as thorough	1286	AnyEvent does not do much argument checking by default, as thorough
1088	argument checking is very costly. Setting this variable to a true	1287	argument checking is very costly. Setting this variable to a true
1089	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1288	value will cause AnyEvent to load "AnyEvent::Strict" and then to
1090	thoroughly check the arguments passed to most method calls. If it	1289	thoroughly check the arguments passed to most method calls. If it
1091	finds any problems, it will croak.	1290	finds any problems, it will croak.
1092		1291
1093	In other words, enables "strict" mode.	1292	In other words, enables "strict" mode.
1094		1293
1095	Unlike "use strict" (or it's modern cousin, "use common::sense", it	1294	Unlike "use strict" (or its modern cousin, "use common::sense", it
1096	is definitely recommended to keep it off in production. Keeping	1295	is definitely recommended to keep it off in production. Keeping
1097	"PERL_ANYEVENT_STRICT=1" in your environment while developing	1296	"PERL_ANYEVENT_STRICT=1" in your environment while developing
1098	programs can be very useful, however.	1297	programs can be very useful, however.
1099		1298
		1299	"PERL_ANYEVENT_DEBUG_SHELL"
		1300	If this env variable is nonempty, then its contents will be
		1301	interpreted by "AnyEvent::Socket::parse_hostport" and
		1302	"AnyEvent::Debug::shell" (after replacing every occurance of $$ by
		1303	the process pid). The shell object is saved in
		1304	$AnyEvent::Debug::SHELL.
		1305
		1306	This happens when the first watcher is created.
		1307
		1308	For example, to bind a debug shell on a unix domain socket in
		1309	/tmp/debug<pid>.sock, you could use this:
		1310
		1311	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		1312	# connect with e.g.: socat readline /tmp/debug123.sock
		1313
		1314	Or to bind to tcp port 4545 on localhost:
		1315
		1316	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		1317	# connect with e.g.: telnet localhost 4545
		1318
		1319	Note that creating sockets in /tmp or on localhost is very unsafe on
		1320	multiuser systems.
		1321
		1322	"PERL_ANYEVENT_DEBUG_WRAP"
		1323	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1324	debugging purposes. See "AnyEvent::Debug::wrap" for details.
		1325
1100	"PERL_ANYEVENT_MODEL"	1326	"PERL_ANYEVENT_MODEL"
1101	This can be used to specify the event model to be used by AnyEvent,	1327	This can be used to specify the event model to be used by AnyEvent,
1102	before auto detection and -probing kicks in. It must be a string	1328	before auto detection and -probing kicks in.
1103	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1329
1104	gets prepended and the resulting module name is loaded and if the	1330	It normally is a string consisting entirely of ASCII letters (e.g.
1105	load was successful, used as event model. If it fails to load	1331	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1332	the resulting module name is loaded and - if the load was successful
		1333	- used as event model backend. If it fails to load then AnyEvent
1106	AnyEvent will proceed with auto detection and -probing.	1334	will proceed with auto detection and -probing.
1107		1335
1108	This functionality might change in future versions.	1336	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1337	then nothing gets prepended and the module name is used as-is (hint:
		1338	"::" at the end of a string designates a module name and quotes it
		1339	appropriately).
1109		1340
1110	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1341	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
1111	could start your program like this:	1342	could start your program like this:
1112		1343
1113	PERL_ANYEVENT_MODEL=Perl perl ...	1344	PERL_ANYEVENT_MODEL=Perl perl ...
		1345
		1346	"PERL_ANYEVENT_IO_MODEL"
		1347	The current file I/O model - see AnyEvent::IO for more info.
		1348
		1349	At the moment, only "Perl" (small, pure-perl, synchronous) and
		1350	"IOAIO" (truly asynchronous) are supported. The default is "IOAIO"
		1351	if AnyEvent::AIO can be loaded, otherwise it is "Perl".
1114		1352
1115	"PERL_ANYEVENT_PROTOCOLS"	1353	"PERL_ANYEVENT_PROTOCOLS"
1116	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1354	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
1117	preferences for IPv4 or IPv6. The default is unspecified (and might	1355	preferences for IPv4 or IPv6. The default is unspecified (and might
1118	change, or be the result of auto probing).	1356	change, or be the result of auto probing).
…		…
1122	mentioned will be used, and preference will be given to protocols	1360	mentioned will be used, and preference will be given to protocols
1123	mentioned earlier in the list.	1361	mentioned earlier in the list.
1124		1362
1125	This variable can effectively be used for denial-of-service attacks	1363	This variable can effectively be used for denial-of-service attacks
1126	against local programs (e.g. when setuid), although the impact is	1364	against local programs (e.g. when setuid), although the impact is
1127	likely small, as the program has to handle conenction and other	1365	likely small, as the program has to handle connection and other
1128	failures anyways.	1366	failures anyways.
1129		1367
1130	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1368	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
1131	IPv6, but support both and try to use both.	1369	IPv6, but support both and try to use both.
1132	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1370	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
1133	resolve or contact IPv6 addresses.	1371	resolve or contact IPv6 addresses.
1134	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but	1372	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
1135	prefer IPv6 over IPv4.	1373	prefer IPv6 over IPv4.
1136		1374
		1375	"PERL_ANYEVENT_HOSTS"
		1376	This variable, if specified, overrides the /etc/hosts file used by
		1377	AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be
		1378	read from that file instead.
		1379
1137	"PERL_ANYEVENT_EDNS0"	1380	"PERL_ANYEVENT_EDNS0"
1138	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension	1381	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
1139	for DNS. This extension is generally useful to reduce DNS traffic,	1382	for DNS. This extension is generally useful to reduce DNS traffic,
1140	but some (broken) firewalls drop such DNS packets, which is why it	1383	especially when DNSSEC is involved, but some (broken) firewalls drop
1141	is off by default.	1384	such DNS packets, which is why it is off by default.
1142		1385
1143	Setting this variable to 1 will cause AnyEvent::DNS to announce	1386	Setting this variable to 1 will cause AnyEvent::DNS to announce
1144	EDNS0 in its DNS requests.	1387	EDNS0 in its DNS requests.
1145		1388
1146	"PERL_ANYEVENT_MAX_FORKS"	1389	"PERL_ANYEVENT_MAX_FORKS"
…		…
1150	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"	1393	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
1151	The default value for the "max_outstanding" parameter for the	1394	The default value for the "max_outstanding" parameter for the
1152	default DNS resolver - this is the maximum number of parallel DNS	1395	default DNS resolver - this is the maximum number of parallel DNS
1153	requests that are sent to the DNS server.	1396	requests that are sent to the DNS server.
1154		1397
		1398	"PERL_ANYEVENT_MAX_SIGNAL_LATENCY"
		1399	Perl has inherently racy signal handling (you can basically choose
		1400	between losing signals and memory corruption) - pure perl event
		1401	loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't
		1402	available) therefore have to poll regularly to avoid losing signals.
		1403
		1404	Some event loops are racy, but don't poll regularly, and some event
		1405	loops are written in C but are still racy. For those event loops,
		1406	AnyEvent installs a timer that regularly wakes up the event loop.
		1407
		1408	By default, the interval for this timer is 10 seconds, but you can
		1409	override this delay with this environment variable (or by setting
		1410	the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal
		1411	watchers).
		1412
		1413	Lower values increase CPU (and energy) usage, higher values can
		1414	introduce long delays when reaping children or waiting for signals.
		1415
		1416	The AnyEvent::Async module, if available, will be used to avoid this
		1417	polling (with most event loops).
		1418
1155	"PERL_ANYEVENT_RESOLV_CONF"	1419	"PERL_ANYEVENT_RESOLV_CONF"
1156	The file to use instead of /etc/resolv.conf (or OS-specific	1420	The absolute path to a resolv.conf-style file to use instead of
1157	configuration) in the default resolver. When set to the empty	1421	/etc/resolv.conf (or the OS-specific configuration) in the default
1158	string, no default config will be used.	1422	resolver, or the empty string to select the default configuration.
1159		1423
1160	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".	1424	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1161	When neither "ca_file" nor "ca_path" was specified during	1425	When neither "ca_file" nor "ca_path" was specified during
1162	AnyEvent::TLS context creation, and either of these environment	1426	AnyEvent::TLS context creation, and either of these environment
1163	variables exist, they will be used to specify CA certificate	1427	variables are nonempty, they will be used to specify CA certificate
1164	locations instead of a system-dependent default.	1428	locations instead of a system-dependent default.
1165		1429
1166	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"	1430	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
1167	When these are set to 1, then the respective modules are not loaded.	1431	When these are set to 1, then the respective modules are not loaded.
1168	Mostly good for testing AnyEvent itself.	1432	Mostly good for testing AnyEvent itself.
…		…
1312		1576
1313	The actual code goes further and collects all errors ("die"s,	1577	The actual code goes further and collects all errors ("die"s,
1314	exceptions) that occurred during request processing. The "result" method	1578	exceptions) that occurred during request processing. The "result" method
1315	detects whether an exception as thrown (it is stored inside the $txn	1579	detects whether an exception as thrown (it is stored inside the $txn
1316	object) and just throws the exception, which means connection errors and	1580	object) and just throws the exception, which means connection errors and
1317	other problems get reported tot he code that tries to use the result,	1581	other problems get reported to the code that tries to use the result,
1318	not in a random callback.	1582	not in a random callback.
1319		1583
1320	All of this enables the following usage styles:	1584	All of this enables the following usage styles:
1321		1585
1322	1. Blocking:	1586	1. Blocking:
…		…
1488	when used without AnyEvent), but most event loops have acceptable	1752	when used without AnyEvent), but most event loops have acceptable
1489	performance with or without AnyEvent.	1753	performance with or without AnyEvent.
1490		1754
1491	* The overhead AnyEvent adds is usually much smaller than the overhead	1755	* The overhead AnyEvent adds is usually much smaller than the overhead
1492	of the actual event loop, only with extremely fast event loops such	1756	of the actual event loop, only with extremely fast event loops such
1493	as EV adds AnyEvent significant overhead.	1757	as EV does AnyEvent add significant overhead.
1494		1758
1495	* You should avoid POE like the plague if you want performance or	1759	* You should avoid POE like the plague if you want performance or
1496	reasonable memory usage.	1760	reasonable memory usage.
1497		1761
1498	BENCHMARKING THE LARGE SERVER CASE	1762	BENCHMARKING THE LARGE SERVER CASE
…		…
1696		1960
1697	Feel free to install your own handler, or reset it to defaults.	1961	Feel free to install your own handler, or reset it to defaults.
1698		1962
1699	RECOMMENDED/OPTIONAL MODULES	1963	RECOMMENDED/OPTIONAL MODULES
1700	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and	1964	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
1701	it's built-in modules) are required to use it.	1965	its built-in modules) are required to use it.
1702		1966
1703	That does not mean that AnyEvent won't take advantage of some additional	1967	That does not mean that AnyEvent won't take advantage of some additional
1704	modules if they are installed.	1968	modules if they are installed.
1705		1969
1706	This section epxlains which additional modules will be used, and how	1970	This section explains which additional modules will be used, and how
1707	they affect AnyEvent's operetion.	1971	they affect AnyEvent's operation.
1708		1972
1709	Async::Interrupt	1973	Async::Interrupt
1710	This slightly arcane module is used to implement fast signal	1974	This slightly arcane module is used to implement fast signal
1711	handling: To my knowledge, there is no way to do completely	1975	handling: To my knowledge, there is no way to do completely
1712	race-free and quick signal handling in pure perl. To ensure that	1976	race-free and quick signal handling in pure perl. To ensure that
…		…
1715	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).	1979	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
1716		1980
1717	If this module is available, then it will be used to implement	1981	If this module is available, then it will be used to implement
1718	signal catching, which means that signals will not be delayed, and	1982	signal catching, which means that signals will not be delayed, and
1719	the event loop will not be interrupted regularly, which is more	1983	the event loop will not be interrupted regularly, which is more
1720	efficient (And good for battery life on laptops).	1984	efficient (and good for battery life on laptops).
1721		1985
1722	This affects not just the pure-perl event loop, but also other event	1986	This affects not just the pure-perl event loop, but also other event
1723	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).	1987	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
1724		1988
1725	Some event loops (POE, Event, Event::Lib) offer signal watchers	1989	Some event loops (POE, Event, Event::Lib) offer signal watchers
…		…
1735	clock is available, can take avdantage of advanced kernel interfaces	1999	clock is available, can take avdantage of advanced kernel interfaces
1736	such as "epoll" and "kqueue", and is the fastest backend by far.	2000	such as "epoll" and "kqueue", and is the fastest backend by far.
1737	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and	2001	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
1738	Glib::EV).	2002	Glib::EV).
1739		2003
		2004	If you only use backends that rely on another event loop (e.g.
		2005	"Tk"), then this module will do nothing for you.
		2006
1740	Guard	2007	Guard
1741	The guard module, when used, will be used to implement	2008	The guard module, when used, will be used to implement
1742	"AnyEvent::Util::guard". This speeds up guards considerably (and	2009	"AnyEvent::Util::guard". This speeds up guards considerably (and
1743	uses a lot less memory), but otherwise doesn't affect guard	2010	uses a lot less memory), but otherwise doesn't affect guard
1744	operation much. It is purely used for performance.	2011	operation much. It is purely used for performance.
1745		2012
1746	JSON and JSON::XS	2013	JSON and JSON::XS
1747	One of these modules is required when you want to read or write JSON	2014	One of these modules is required when you want to read or write JSON
1748	data via AnyEvent::Handle. It is also written in pure-perl, but can	2015	data via AnyEvent::Handle. JSON is also written in pure-perl, but
1749	take advantage of the ultra-high-speed JSON::XS module when it is	2016	can take advantage of the ultra-high-speed JSON::XS module when it
1750	installed.	2017	is installed.
1751
1752	In fact, AnyEvent::Handle will use JSON::XS by default if it is
1753	installed.
1754		2018
1755	Net::SSLeay	2019	Net::SSLeay
1756	Implementing TLS/SSL in Perl is certainly interesting, but not very	2020	Implementing TLS/SSL in Perl is certainly interesting, but not very
1757	worthwhile: If this module is installed, then AnyEvent::Handle (with	2021	worthwhile: If this module is installed, then AnyEvent::Handle (with
1758	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.	2022	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
1759		2023
1760	Time::HiRes	2024	Time::HiRes
1761	This module is part of perl since release 5.008. It will be used	2025	This module is part of perl since release 5.008. It will be used
1762	when the chosen event library does not come with a timing source on	2026	when the chosen event library does not come with a timing source of
1763	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will	2027	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
1764	additionally use it to try to use a monotonic clock for timing	2028	load it to try to use a monotonic clock for timing stability.
1765	stability.	2029
		2030	AnyEvent::AIO (and IO::AIO)
		2031	The default implementation of AnyEvent::IO is to do I/O
		2032	synchronously, stopping programs while they access the disk, which
		2033	is fine for a lot of programs.
		2034
		2035	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it
		2036	switch to a true asynchronous implementation, so event processing
		2037	can continue even while waiting for disk I/O.
1766		2038
1767	FORK	2039	FORK
1768	Most event libraries are not fork-safe. The ones who are usually are	2040	Most event libraries are not fork-safe. The ones who are usually are
1769	because they rely on inefficient but fork-safe "select" or "poll" calls.	2041	because they rely on inefficient but fork-safe "select" or "poll" calls
1770	Only EV is fully fork-aware.	2042	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		2043	epoll are usually badly thought-out hacks that are incompatible with
		2044	fork in one way or another. Only EV is fully fork-aware and ensures that
		2045	you continue event-processing in both parent and child (or both, if you
		2046	know what you are doing).
		2047
		2048	This means that, in general, you cannot fork and do event processing in
		2049	the child if the event library was initialised before the fork (which
		2050	usually happens when the first AnyEvent watcher is created, or the
		2051	library is loaded).
1771		2052
1772	If you have to fork, you must either do so before creating your first	2053	If you have to fork, you must either do so before creating your first
1773	watcher OR you must not use AnyEvent at all in the child OR you must do	2054	watcher OR you must not use AnyEvent at all in the child OR you must do
1774	something completely out of the scope of AnyEvent.	2055	something completely out of the scope of AnyEvent (see below).
		2056
		2057	The problem of doing event processing in the parent and the child is
		2058	much more complicated: even for backends that are fork-aware or
		2059	fork-safe, their behaviour is not usually what you want: fork clones all
		2060	watchers, that means all timers, I/O watchers etc. are active in both
		2061	parent and child, which is almost never what you want. Using "exec" to
		2062	start worker children from some kind of manage prrocess is usually
		2063	preferred, because it is much easier and cleaner, at the expense of
		2064	having to have another binary.
		2065
		2066	In addition to logical problems with fork, there are also implementation
		2067	problems. For example, on POSIX systems, you cannot fork at all in Perl
		2068	code if a thread (I am talking of pthreads here) was ever created in the
		2069	process, and this is just the tip of the iceberg. In general, using fork
		2070	from Perl is difficult, and attempting to use fork without an exec to
		2071	implement some kind of parallel processing is almost certainly doomed.
		2072
		2073	To safely fork and exec, you should use a module such as Proc::FastSpawn
		2074	that let's you safely fork and exec new processes.
		2075
		2076	If you want to do multiprocessing using processes, you can look at the
		2077	AnyEvent::Fork module (and some related modules such as
		2078	AnyEvent::Fork::RPC, AnyEvent::Fork::Pool and AnyEvent::Fork::Remote).
		2079	This module allows you to safely create subprocesses without any
		2080	limitations - you can use X11 toolkits or AnyEvent in the children
		2081	created by AnyEvent::Fork safely and without any special precautions.
1775		2082
1776	SECURITY CONSIDERATIONS	2083	SECURITY CONSIDERATIONS
1777	AnyEvent can be forced to load any event model via	2084	AnyEvent can be forced to load any event model via
1778	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	2085	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1779	to execute arbitrary code or directly gain access, it can easily be used	2086	to execute arbitrary code or directly gain access, it can easily be used
…		…
1803	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	2110	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1804	annoying memleaks, such as leaking on "map" and "grep" but it is usually	2111	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1805	not as pronounced).	2112	not as pronounced).
1806		2113
1807	SEE ALSO	2114	SEE ALSO
1808	Utility functions: AnyEvent::Util.	2115	Tutorial/Introduction: AnyEvent::Intro.
1809		2116
1810	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	2117	FAQ: AnyEvent::FAQ.
1811	Event::Lib, Qt, POE.	2118
		2119	Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log
		2120	(simply logging).
		2121
		2122	Development/Debugging: AnyEvent::Strict (stricter checking),
		2123	AnyEvent::Debug (interactive shell, watcher tracing).
		2124
		2125	Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
		2126	Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK, Cocoa::EventLoop, UV.
1812		2127
1813	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	2128	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1814	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	2129	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1815	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,	2130	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		2131	AnyEvent::Impl::IOAsync, AnyEvent::Impl::Irssi, AnyEvent::Impl::FLTK,
1816	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.	2132	AnyEvent::Impl::Cocoa, AnyEvent::Impl::UV.
1817		2133
1818	Non-blocking file handles, sockets, TCP clients and servers:	2134	Non-blocking handles, pipes, stream sockets, TCP clients and servers:
1819	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.	2135	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1820		2136
		2137	Asynchronous File I/O: AnyEvent::IO.
		2138
1821	Asynchronous DNS: AnyEvent::DNS.	2139	Asynchronous DNS: AnyEvent::DNS.
1822		2140
1823	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	2141	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1824		2142
1825	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,	2143	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
1826	AnyEvent::HTTP.	2144	AnyEvent::HTTP.
1827		2145
1828	AUTHOR	2146	AUTHOR
1829	Marc Lehmann <schmorp@schmorp.de>	2147	Marc Lehmann <schmorp@schmorp.de>
1830	http://home.schmorp.de/	2148	http://anyevent.schmorp.de
1831		2149

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Comparing AnyEvent/README (file contents): Revision 1.55 by root, Mon Sep 14 05:05:09 2009 UTC vs. Revision 1.74 by root, Sat May 2 14:39:31 2015 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.55 by root, Mon Sep 14 05:05:09 2009 UTC vs.
Revision 1.74 by root, Sat May 2 14:39:31 2015 UTC