[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.59 by root, Tue Jan 5 10:45:25 2010 UTC vs.
Revision 1.79 by root, Tue Feb 26 02:08:34 2019 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
…		…
399	will not restart syscalls (that includes Async::Interrupt and AnyEvent's	404	will not restart syscalls (that includes Async::Interrupt and AnyEvent's
400	pure perl implementation).	405	pure perl implementation).
401		406
402	Safe/Unsafe Signals	407	Safe/Unsafe Signals
403	Perl signals can be either "safe" (synchronous to opcode handling) or	408	Perl signals can be either "safe" (synchronous to opcode handling) or
404	"unsafe" (asynchronous) - the former might get delayed indefinitely, the	409	"unsafe" (asynchronous) - the former might delay signal delivery
405	latter might corrupt your memory.	410	indefinitely, the latter might corrupt your memory.
406		411
407	AnyEvent signal handlers are, in addition, synchronous to the event	412	AnyEvent signal handlers are, in addition, synchronous to the event
408	loop, i.e. they will not interrupt your running perl program but will	413	loop, i.e. they will not interrupt your running perl program but will
409	only be called as part of the normal event handling (just like timer,	414	only be called as part of the normal event handling (just like timer,
410	I/O etc. callbacks, too).	415	I/O etc. callbacks, too).
411		416
412	Signal Races, Delays and Workarounds	417	Signal Races, Delays and Workarounds
413	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
414	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
415	race-free signal handling in perl, requiring C libraries for this.	420	race-free signal handling in perl, requiring C libraries for this.
416	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
417	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
418	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable	423	seconds by default, but can be overriden via
419	can be changed only before the first signal watcher is created, and	424	$ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} or $AnyEvent::MAX_SIGNAL_LATENCY
420	should be left alone otherwise. This variable determines how often	425	- see the "ENVIRONMENT VARIABLES" section for details.
421	AnyEvent polls for signals (in case a wake-up was missed). Higher values
422	will cause fewer spurious wake-ups, which is better for power and CPU
423	saving.
424		426
425	All these problems can be avoided by installing the optional	427	All these problems can be avoided by installing the optional
426	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
427	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
428	not with POE currently, as POE does it's own workaround with one-second
429	latency). For those, you just have to suffer the delays.	430	not with POE currently). For those, you just have to suffer the delays.
430		431
431	CHILD PROCESS WATCHERS	432	CHILD PROCESS WATCHERS
432	$w = AnyEvent->child (pid => <process id>, cb => <callback>);	433	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
433		434
434	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.
435		436
436	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,
437	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).
438	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
439	and an exit status is available, not on any trace events	440	and an exit status is available, not on any trace events
440	(stopped/continued).	441	(stopped/continued).
441		442
…		…
462	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
463	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
464	you "fork" the child (alternatively, you can call "AnyEvent::detect").	465	you "fork" the child (alternatively, you can call "AnyEvent::detect").
465		466
466	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
467	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
468	problems mentioned in the description of signal watchers apply.	469	race problems mentioned in the description of signal watchers apply.
469		470
470	Example: fork a process and wait for it	471	Example: fork a process and wait for it
471		472
472	my $done = AnyEvent->condvar;	473	my $done = AnyEvent->condvar;
473		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.
474	my $pid = fork or exit 5;	479	my $pid = fork or exit 5;
475		480
476	my $w = AnyEvent->child (	481	my $w = AnyEvent->child (
477	pid => $pid,	482	pid => $pid,
478	cb => sub {	483	cb => sub {
…		…
486	$done->recv;	491	$done->recv;
487		492
488	IDLE WATCHERS	493	IDLE WATCHERS
489	$w = AnyEvent->idle (cb => <callback>);	494	$w = AnyEvent->idle (cb => <callback>);
490		495
491	Repeatedly invoke the callback after the process becomes idle, until	496	This will repeatedly invoke the callback after the process becomes idle,
492	either the watcher is destroyed or new events have been detected.	497	until either the watcher is destroyed or new events have been detected.
493		498
494	Idle watchers are useful when there is a need to do something, but it is	499	Idle watchers are useful when there is a need to do something, but it is
495	not so important (or wise) to do it instantly. The callback will be	500	not so important (or wise) to do it instantly. The callback will be
496	invoked only when there is "nothing better to do", which is usually	501	invoked only when there is "nothing better to do", which is usually
497	defined as "all outstanding events have been handled and no new events	502	defined as "all outstanding events have been handled and no new events
…		…
536		541
537	AnyEvent is slightly different: it expects somebody else to run the	542	AnyEvent is slightly different: it expects somebody else to run the
538	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
539	user).	544	user).
540		545
541	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
542	because they represent a condition that must become true.	547	they represent a condition that must become true.
543		548
544	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.
545		550
546	Condition variables can be created by calling the "AnyEvent->condvar"	551	Condition variables can be created by calling the "AnyEvent->condvar"
547	method, usually without arguments. The only argument pair allowed is	552	method, usually without arguments. The only argument pair allowed is
…		…
552	After creation, the condition variable is "false" until it becomes	557	After creation, the condition variable is "false" until it becomes
553	"true" by calling the "send" method (or calling the condition variable	558	"true" by calling the "send" method (or calling the condition variable
554	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
555	the "->send" method).	560	the "->send" method).
556		561
557	Condition variables are similar to callbacks, except that you can	562	Since condition variables are the most complex part of the AnyEvent API,
558	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
559	in time where multiple outstanding events have been processed. And yet	564	you can connect to:
560	another way to call them is transactions - each condition variable can	565
561	be used to represent a transaction, which finishes at some point and	566	* Condition variables are like callbacks - you can call them (and pass
562	delivers a result. And yet some people know them as "futures" - a	567	them instead of callbacks). Unlike callbacks however, you can also
563	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.
564		583
565	Condition variables are very useful to signal that something has	584	Condition variables are very useful to signal that something has
566	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
567	requests, then a condition variable would be the ideal candidate to	586	requests, then a condition variable would be the ideal candidate to
568	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
…		…
581		600
582	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
583	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
584	(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
585	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	604	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
586	it's "new" method in your own "new" method.	605	its "new" method in your own "new" method.
587		606
588	There are two "sides" to a condition variable - the "producer side"	607	There are two "sides" to a condition variable - the "producer side"
589	which eventually calls "-> send", and the "consumer side", which waits	608	which eventually calls "-> send", and the "consumer side", which waits
590	for the send to occur.	609	for the send to occur.
591		610
592	Example: wait for a timer.	611	Example: wait for a timer.
593		612
594	# wait till the result is ready	613	# condition: "wait till the timer is fired"
595	my $result_ready = AnyEvent->condvar;	614	my $timer_fired = AnyEvent->condvar;
596		615
597	# do something such as adding a timer	616	# create the timer - we could wait for, say
598	# or socket watcher the calls $result_ready->send	617	# a handle becomign ready, or even an
599	# when the "result" is ready.	618	# AnyEvent::HTTP request to finish, but
600	# in this case, we simply use a timer:	619	# in this case, we simply use a timer:
601	my $w = AnyEvent->timer (	620	my $w = AnyEvent->timer (
602	after => 1,	621	after => 1,
603	cb => sub { $result_ready->send },	622	cb => sub { $timer_fired->send },
604	);	623	);
605		624
606	# this "blocks" (while handling events) till the callback	625	# this "blocks" (while handling events) till the callback
607	# calls ->send	626	# calls ->send
608	$result_ready->recv;	627	$timer_fired->recv;
609		628
610	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
611	variables are also callable directly.	630	variables are also callable directly.
612		631
613	my $done = AnyEvent->condvar;	632	my $done = AnyEvent->condvar;
…		…
651	Condition variables are overloaded so one can call them directly (as	670	Condition variables are overloaded so one can call them directly (as
652	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
653	calling "send".	672	calling "send".
654		673
655	$cv->croak ($error)	674	$cv->croak ($error)
656	Similar to send, but causes all call's to "->recv" to invoke	675	Similar to send, but causes all calls to "->recv" to invoke
657	"Carp::croak" with the given error message/object/scalar.	676	"Carp::croak" with the given error message/object/scalar.
658		677
659	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
660	user/consumer. Doing it this way instead of calling "croak" directly	679	user/consumer. Doing it this way instead of calling "croak" directly
661	delays the error detetcion, but has the overwhelmign advantage that	680	delays the error detection, but has the overwhelming advantage that
662	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,
663	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
664	code causing the problem.	683	code causing the problem.
665		684
666	$cv->begin ([group callback])	685	$cv->begin ([group callback])
667	$cv->end	686	$cv->end
668	These two methods can be used to combine many transactions/events	687	These two methods can be used to combine many transactions/events
…		…
704	This works because for every event source (EOF on file handle),	723	This works because for every event source (EOF on file handle),
705	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
706	"end" before sending.	725	"end" before sending.
707		726
708	The ping example mentioned above is slightly more complicated, as	727	The ping example mentioned above is slightly more complicated, as
709	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
710	that are begung can potentially be zero:	729	that are begun can potentially be zero:
711		730
712	my $cv = AnyEvent->condvar;	731	my $cv = AnyEvent->condvar;
713		732
714	my %result;	733	my %result;
715	$cv->begin (sub { shift->send (\%result) });	734	$cv->begin (sub { shift->send (\%result) });
…		…
722	};	741	};
723	}	742	}
724		743
725	$cv->end;	744	$cv->end;
726		745
		746	...
		747
		748	my $results = $cv->recv;
		749
727	This code fragment supposedly pings a number of hosts and calls	750	This code fragment supposedly pings a number of hosts and calls
728	"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
729	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
730	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
731	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
…		…
736	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
737	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
738	(the loop doesn't execute once).	761	(the loop doesn't execute once).
739		762
740	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
741	potentially none) subrequests: use an outer "begin"/"end" pair to	764	potentially zero) subrequests: use an outer "begin"/"end" pair to
742	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,
743	for each subrequest you start, call "begin" and for each subrequest	766	for each subrequest you start, call "begin" and for each subrequest
744	you finish, call "end".	767	you finish, call "end".
745		768
746	METHODS FOR CONSUMERS	769	METHODS FOR CONSUMERS
747	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
748	awaits the condition.	771	awaits the condition.
749		772
750	$cv->recv	773	$cv->recv
751	Wait (blocking if necessary) until the "->send" or "->croak" methods	774	Wait (blocking if necessary) until the "->send" or "->croak" methods
752	have been called on c<$cv>, while servicing other watchers normally.	775	have been called on $cv, while servicing other watchers normally.
753		776
754	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
755	but will return immediately.	778	but will return immediately.
756		779
757	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
…		…
760	In list context, all parameters passed to "send" will be returned,	783	In list context, all parameters passed to "send" will be returned,
761	in scalar context only the first one will be returned.	784	in scalar context only the first one will be returned.
762		785
763	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
764	any event loop, that is, recursive invocation of a blocking "->recv"	787	any event loop, that is, recursive invocation of a blocking "->recv"
765	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
766	is detected. This condition can be slightly loosened by using	789	is detected. This requirement can be dropped by relying on
767	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
768	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.
769		797
770	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
771	(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
772	using this from a module, never require a blocking wait*. Instead,	800	using this from a module, never require a blocking wait*. Instead,
773	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
774	example, by coupling condition variables with some kind of request	802	example, by coupling condition variables with some kind of request
775	results and supporting callbacks so the caller knows that getting	803	results and supporting callbacks so the caller knows that getting
776	the result will not block, while still supporting blocking waits if	804	the result will not block, while still supporting blocking waits if
777	the caller so desires).	805	the caller so desires).
778		806
779	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
780	only calling "->recv" from within that callback (or at a later	808	only calling "->recv" from within that callback (or at a later
781	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
782	blocking waits otherwise.	810	blocking waits otherwise.
783		811
784	$bool = $cv->ready	812	$bool = $cv->ready
785	Returns true when the condition is "true", i.e. whether "send" or	813	Returns true when the condition is "true", i.e. whether "send" or
786	"croak" have been called.	814	"croak" have been called.
787		815
788	$cb = $cv->cb ($cb->($cv))	816	$cb = $cv->cb ($cb->($cv))
789	This is a mutator function that returns the callback set and	817	This is a mutator function that returns the callback set (or "undef"
790	optionally replaces it before doing so.	818	if not) and optionally replaces it before doing so.
791		819
792	The callback will be called when the condition becomes (or already	820	The callback will be called when the condition becomes "true", i.e.
793	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
794	called), with the only argument being the condition variable itself.	822	condition variable itself. If the condition is already true, the
795	Calling "recv" inside the callback or at any later time is	823	callback is called immediately when it is set. Calling "recv" inside
796	guaranteed not to block.	824	the callback or at any later time is guaranteed not to block.
		825
		826	Additionally, when the callback is invoked, it is also removed from
		827	the condvar (reset to "undef"), so the condvar does not keep a
		828	reference to the callback after invocation.
797		829
798	SUPPORTED EVENT LOOPS/BACKENDS	830	SUPPORTED EVENT LOOPS/BACKENDS
799	The available backend classes are (every class has its own manpage):	831	The following backend classes are part of the AnyEvent distribution
		832	(every class has its own manpage):
800		833
801	Backends that are autoprobed when no other event loop can be found.	834	Backends that are autoprobed when no other event loop can be found.
802	EV is the preferred backend when no other event loop seems to be in	835	EV is the preferred backend when no other event loop seems to be in
803	use. If EV is not installed, then AnyEvent will fall back to its own	836	use. If EV is not installed, then AnyEvent will fall back to its own
804	pure-perl implementation, which is available everywhere as it comes	837	pure-perl implementation, which is available everywhere as it comes
805	with AnyEvent itself.	838	with AnyEvent itself.
806		839
807	AnyEvent::Impl::EV based on EV (interface to libev, best choice).	840	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
808	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.	841	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
809		842
810	Backends that are transparently being picked up when they are used.	843	Backends that are transparently being picked up when they are used.
811	These will be used when they are currently loaded when the first	844	These will be used if they are already loaded when the first watcher
812	watcher is created, in which case it is assumed that the application	845	is created, in which case it is assumed that the application is
813	is using them. This means that AnyEvent will automatically pick the	846	using them. This means that AnyEvent will automatically pick the
814	right backend when the main program loads an event module before	847	right backend when the main program loads an event module before
815	anything starts to create watchers. Nothing special needs to be done	848	anything starts to create watchers. Nothing special needs to be done
816	by the main program.	849	by the main program.
817		850
818	AnyEvent::Impl::Event based on Event, very stable, few glitches.	851	AnyEvent::Impl::Event based on Event, very stable, few glitches.
819	AnyEvent::Impl::Glib based on Glib, slow but very stable.	852	AnyEvent::Impl::Glib based on Glib, slow but very stable.
820	AnyEvent::Impl::Tk based on Tk, very broken.	853	AnyEvent::Impl::Tk based on Tk, very broken.
		854	AnyEvent::Impl::UV based on UV, innovated square wheels.
821	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	855	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
822	AnyEvent::Impl::POE based on POE, very slow, some limitations.	856	AnyEvent::Impl::POE based on POE, very slow, some limitations.
823	AnyEvent::Impl::Irssi used when running within irssi.	857	AnyEvent::Impl::Irssi used when running within irssi.
		858	AnyEvent::Impl::IOAsync based on IO::Async.
		859	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		860	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
824		861
825	Backends with special needs.	862	Backends with special needs.
826	Qt requires the Qt::Application to be instantiated first, but will	863	Qt requires the Qt::Application to be instantiated first, but will
827	otherwise be picked up automatically. As long as the main program	864	otherwise be picked up automatically. As long as the main program
828	instantiates the application before any AnyEvent watchers are	865	instantiates the application before any AnyEvent watchers are
829	created, everything should just work.	866	created, everything should just work.
830		867
831	AnyEvent::Impl::Qt based on Qt.	868	AnyEvent::Impl::Qt based on Qt.
832		869
833	Support for IO::Async can only be partial, as it is too broken and
834	architecturally limited to even support the AnyEvent API. It also is
835	the only event loop that needs the loop to be set explicitly, so it
836	can only be used by a main program knowing about AnyEvent. See
837	AnyEvent::Impl::Async for the gory details.
838
839	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
840
841	Event loops that are indirectly supported via other backends.	870	Event loops that are indirectly supported via other backends.
842	Some event loops can be supported via other modules:	871	Some event loops can be supported via other modules:
843		872
844	There is no direct support for WxWidgets (Wx) or Prima.	873	There is no direct support for WxWidgets (Wx) or Prima.
845		874
…		…
853		882
854	AnyEvent knows about both Prima and Wx, however, and will try to	883	AnyEvent knows about both Prima and Wx, however, and will try to
855	load POE when detecting them, in the hope that POE will pick them	884	load POE when detecting them, in the hope that POE will pick them
856	up, in which case everything will be automatic.	885	up, in which case everything will be automatic.
857		886
		887	Known event loops outside the AnyEvent distribution
		888	The following event loops or programs support AnyEvent by providing
		889	their own AnyEvent backend. They will be picked up automatically.
		890
		891	urxvt::anyevent available to rxvt-unicode extensions
		892
858	GLOBAL VARIABLES AND FUNCTIONS	893	GLOBAL VARIABLES AND FUNCTIONS
859	These are not normally required to use AnyEvent, but can be useful to	894	These are not normally required to use AnyEvent, but can be useful to
860	write AnyEvent extension modules.	895	write AnyEvent extension modules.
861		896
862	$AnyEvent::MODEL	897	$AnyEvent::MODEL
863	Contains "undef" until the first watcher is being created, before	898	Contains "undef" until the first watcher is being created, before
864	the backend has been autodetected.	899	the backend has been autodetected.
865		900
866	Afterwards it contains the event model that is being used, which is	901	Afterwards it contains the event model that is being used, which is
867	the name of the Perl class implementing the model. This class is	902	the name of the Perl class implementing the model. This class is
868	usually one of the "AnyEvent::Impl:xxx" modules, but can be any	903	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
869	other class in the case AnyEvent has been extended at runtime (e.g.	904	other class in the case AnyEvent has been extended at runtime (e.g.
870	in rxvt-unicode it will be "urxvt::anyevent").	905	in rxvt-unicode it will be "urxvt::anyevent").
871		906
872	AnyEvent::detect	907	AnyEvent::detect
873	Returns $AnyEvent::MODEL, forcing autodetection of the event model	908	Returns $AnyEvent::MODEL, forcing autodetection of the event model
874	if necessary. You should only call this function right before you	909	if necessary. You should only call this function right before you
875	would have created an AnyEvent watcher anyway, that is, as late as	910	would have created an AnyEvent watcher anyway, that is, as late as
876	possible at runtime, and not e.g. while initialising of your module.	911	possible at runtime, and not e.g. during initialisation of your
		912	module.
		913
		914	The effect of calling this function is as if a watcher had been
		915	created (specifically, actions that happen "when the first watcher
		916	is created" happen when calling detetc as well).
877		917
878	If you need to do some initialisation before AnyEvent watchers are	918	If you need to do some initialisation before AnyEvent watchers are
879	created, use "post_detect".	919	created, use "post_detect".
880		920
881	$guard = AnyEvent::post_detect { BLOCK }	921	$guard = AnyEvent::post_detect { BLOCK }
882	Arranges for the code block to be executed as soon as the event	922	Arranges for the code block to be executed as soon as the event
883	model is autodetected (or immediately if this has already happened).	923	model is autodetected (or immediately if that has already happened).
884		924
885	The block will be executed after the actual backend has been	925	The block will be executed after the actual backend has been
886	detected ($AnyEvent::MODEL is set), but before any watchers have	926	detected ($AnyEvent::MODEL is set), so it is possible to do some
887	been created, so it is possible to e.g. patch @AnyEvent::ISA or do	927	initialisation only when AnyEvent is actually initialised - see the
888	other initialisations - see the sources of AnyEvent::Strict or
889	AnyEvent::AIO to see how this is used.	928	sources of AnyEvent::AIO to see how this is used.
890		929
891	The most common usage is to create some global watchers, without	930	The most common usage is to create some global watchers, without
892	forcing event module detection too early, for example, AnyEvent::AIO	931	forcing event module detection too early. For example, AnyEvent::AIO
893	creates and installs the global IO::AIO watcher in a "post_detect"	932	creates and installs the global IO::AIO watcher in a "post_detect"
894	block to avoid autodetecting the event module at load time.	933	block to avoid autodetecting the event module at load time.
895		934
896	If called in scalar or list context, then it creates and returns an	935	If called in scalar or list context, then it creates and returns an
897	object that automatically removes the callback again when it is	936	object that automatically removes the callback again when it is
898	destroyed (or "undef" when the hook was immediately executed). See	937	destroyed (or "undef" when the hook was immediately executed). See
899	AnyEvent::AIO for a case where this is useful.	938	AnyEvent::AIO for a case where this is useful.
900		939
901	Example: Create a watcher for the IO::AIO module and store it in	940	Example: Create a watcher for the IO::AIO module and store it in
902	$WATCHER. Only do so after the event loop is initialised, though.	941	$WATCHER, but do so only do so after the event loop is initialised.
903		942
904	our WATCHER;	943	our WATCHER;
905		944
906	my $guard = AnyEvent::post_detect {	945	my $guard = AnyEvent::post_detect {
907	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);	946	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
…		…
913	# able to just C<undef $WATCHER> if the watcher causes them grief.	952	# able to just C<undef $WATCHER> if the watcher causes them grief.
914		953
915	$WATCHER \|\|= $guard;	954	$WATCHER \|\|= $guard;
916		955
917	@AnyEvent::post_detect	956	@AnyEvent::post_detect
918	If there are any code references in this array (you can "push" to it	957	This is a lower level interface then "AnyEvent::post_detect" (the
919	before or after loading AnyEvent), then they will called directly	958	function). This variable is mainly useful for modules that can do
		959	something useful when AnyEvent is used and thus want to know when it
		960	is initialised, but do not need to even load it by default. This
		961	array provides the means to hook into AnyEvent passively, without
		962	loading it.
		963
		964	Here is how it works: If there are any code references in this array
		965	(you can "push" to it before or after loading AnyEvent), then they
920	after the event loop has been chosen.	966	will be called directly after the event loop has been chosen.
921		967
922	You should check $AnyEvent::MODEL before adding to this array,	968	You should check $AnyEvent::MODEL before adding to this array,
923	though: if it is defined then the event loop has already been	969	though: if it is defined then the event loop has already been
924	detected, and the array will be ignored.	970	detected, and the array will be ignored.
925		971
926	Best use "AnyEvent::post_detect { BLOCK }" when your application	972	Best use "AnyEvent::post_detect { BLOCK }" when your application
927	allows it, as it takes care of these details.	973	allows it, as it takes care of these details.
928
929	This variable is mainly useful for modules that can do something
930	useful when AnyEvent is used and thus want to know when it is
931	initialised, but do not need to even load it by default. This array
932	provides the means to hook into AnyEvent passively, without loading
933	it.
934		974
935	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used	975	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
936	together, you could put this into Coro (this is the actual code used	976	together, you could put this into Coro (this is the actual code used
937	by Coro to accomplish this):	977	by Coro to accomplish this):
938		978
…		…
943	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent	983	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
944	# as soon as it is	984	# as soon as it is
945	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };	985	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
946	}	986	}
947		987
		988	AnyEvent::postpone { BLOCK }
		989	Arranges for the block to be executed as soon as possible, but not
		990	before the call itself returns. In practise, the block will be
		991	executed just before the event loop polls for new events, or shortly
		992	afterwards.
		993
		994	This function never returns anything (to make the "return postpone {
		995	... }" idiom more useful.
		996
		997	To understand the usefulness of this function, consider a function
		998	that asynchronously does something for you and returns some
		999	transaction object or guard to let you cancel the operation. For
		1000	example, "AnyEvent::Socket::tcp_connect":
		1001
		1002	# start a connection attempt unless one is active
		1003	$self->{connect_guard} \|\|= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1004	delete $self->{connect_guard};
		1005	...
		1006	};
		1007
		1008	Imagine that this function could instantly call the callback, for
		1009	example, because it detects an obvious error such as a negative port
		1010	number. Invoking the callback before the function returns causes
		1011	problems however: the callback will be called and will try to delete
		1012	the guard object. But since the function hasn't returned yet, there
		1013	is nothing to delete. When the function eventually returns it will
		1014	assign the guard object to "$self->{connect_guard}", where it will
		1015	likely never be deleted, so the program thinks it is still trying to
		1016	connect.
		1017
		1018	This is where "AnyEvent::postpone" should be used. Instead of
		1019	calling the callback directly on error:
		1020
		1021	$cb->(undef), return # signal error to callback, BAD!
		1022	if $some_error_condition;
		1023
		1024	It should use "postpone":
		1025
		1026	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1027	if $some_error_condition;
		1028
		1029	AnyEvent::log $level, $msg[, @args]
		1030	Log the given $msg at the given $level.
		1031
		1032	If AnyEvent::Log is not loaded then this function makes a simple
		1033	test to see whether the message will be logged. If the test succeeds
		1034	it will load AnyEvent::Log and call "AnyEvent::Log::log" -
		1035	consequently, look at the AnyEvent::Log documentation for details.
		1036
		1037	If the test fails it will simply return. Right now this happens when
		1038	a numerical loglevel is used and it is larger than the level
		1039	specified via $ENV{PERL_ANYEVENT_VERBOSE}.
		1040
		1041	If you want to sprinkle loads of logging calls around your code,
		1042	consider creating a logger callback with the "AnyEvent::Log::logger"
		1043	function, which can reduce typing, codesize and can reduce the
		1044	logging overhead enourmously.
		1045
		1046	AnyEvent::fh_block $filehandle
		1047	AnyEvent::fh_unblock $filehandle
		1048	Sets blocking or non-blocking behaviour for the given filehandle.
		1049
948	WHAT TO DO IN A MODULE	1050	WHAT TO DO IN A MODULE
949	As a module author, you should "use AnyEvent" and call AnyEvent methods	1051	As a module author, you should "use AnyEvent" and call AnyEvent methods
950	freely, but you should not load a specific event module or rely on it.	1052	freely, but you should not load a specific event module or rely on it.
951		1053
952	Be careful when you create watchers in the module body - AnyEvent will	1054	Be careful when you create watchers in the module body - AnyEvent will
…		…
959	stall the whole program, and the whole point of using events is to stay	1061	stall the whole program, and the whole point of using events is to stay
960	interactive.	1062	interactive.
961		1063
962	It is fine, however, to call "->recv" when the user of your module	1064	It is fine, however, to call "->recv" when the user of your module
963	requests it (i.e. if you create a http request object ad have a method	1065	requests it (i.e. if you create a http request object ad have a method
964	called "results" that returns the results, it should call "->recv"	1066	called "results" that returns the results, it may call "->recv" freely,
965	freely, as the user of your module knows what she is doing. always).	1067	as the user of your module knows what she is doing. Always).
966		1068
967	WHAT TO DO IN THE MAIN PROGRAM	1069	WHAT TO DO IN THE MAIN PROGRAM
968	There will always be a single main program - the only place that should	1070	There will always be a single main program - the only place that should
969	dictate which event model to use.	1071	dictate which event model to use.
970		1072
971	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1073	If the program is not event-based, it need not do anything special, even
972	do anything special (it does not need to be event-based) and let	1074	when it depends on a module that uses an AnyEvent. If the program itself
973	AnyEvent decide which implementation to chose if some module relies on	1075	uses AnyEvent, but does not care which event loop is used, all it needs
974	it.	1076	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1077	available loop implementation.
975		1078
976	If the main program relies on a specific event model - for example, in	1079	If the main program relies on a specific event model - for example, in
977	Gtk2 programs you have to rely on the Glib module - you should load the	1080	Gtk2 programs you have to rely on the Glib module - you should load the
978	event module before loading AnyEvent or any module that uses it:	1081	event module before loading AnyEvent or any module that uses it:
979	generally speaking, you should load it as early as possible. The reason	1082	generally speaking, you should load it as early as possible. The reason
980	is that modules might create watchers when they are loaded, and AnyEvent	1083	is that modules might create watchers when they are loaded, and AnyEvent
981	will decide on the event model to use as soon as it creates watchers,	1084	will decide on the event model to use as soon as it creates watchers,
982	and it might chose the wrong one unless you load the correct one	1085	and it might choose the wrong one unless you load the correct one
983	yourself.	1086	yourself.
984		1087
985	You can chose to use a pure-perl implementation by loading the	1088	You can chose to use a pure-perl implementation by loading the
986	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1089	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
987	everywhere, but letting AnyEvent chose the model is generally better.	1090	but letting AnyEvent chose the model is generally better.
988		1091
989	MAINLOOP EMULATION	1092	MAINLOOP EMULATION
990	Sometimes (often for short test scripts, or even standalone programs who	1093	Sometimes (often for short test scripts, or even standalone programs who
991	only want to use AnyEvent), you do not want to run a specific event	1094	only want to use AnyEvent), you do not want to run a specific event
992	loop.	1095	loop.
…		…
1004		1107
1005	OTHER MODULES	1108	OTHER MODULES
1006	The following is a non-exhaustive list of additional modules that use	1109	The following is a non-exhaustive list of additional modules that use
1007	AnyEvent as a client and can therefore be mixed easily with other	1110	AnyEvent as a client and can therefore be mixed easily with other
1008	AnyEvent modules and other event loops in the same program. Some of the	1111	AnyEvent modules and other event loops in the same program. Some of the
1009	modules come with AnyEvent, most are available via CPAN.	1112	modules come as part of AnyEvent, the others are available via CPAN (see
		1113	<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
		1114	non-exhaustive list), and the list is heavily biased towards modules of
		1115	the AnyEvent author himself :)
1010		1116
1011	AnyEvent::Util	1117	AnyEvent::Util (part of the AnyEvent distribution)
1012	Contains various utility functions that replace often-used but	1118	Contains various utility functions that replace often-used blocking
1013	blocking functions such as "inet_aton" by event-/callback-based	1119	functions such as "inet_aton" with event/callback-based versions.
1014	versions.
1015		1120
1016	AnyEvent::Socket	1121	AnyEvent::Socket (part of the AnyEvent distribution)
1017	Provides various utility functions for (internet protocol) sockets,	1122	Provides various utility functions for (internet protocol) sockets,
1018	addresses and name resolution. Also functions to create non-blocking	1123	addresses and name resolution. Also functions to create non-blocking
1019	tcp connections or tcp servers, with IPv6 and SRV record support and	1124	tcp connections or tcp servers, with IPv6 and SRV record support and
1020	more.	1125	more.
1021		1126
1022	AnyEvent::Handle	1127	AnyEvent::Handle (part of the AnyEvent distribution)
1023	Provide read and write buffers, manages watchers for reads and	1128	Provide read and write buffers, manages watchers for reads and
1024	writes, supports raw and formatted I/O, I/O queued and fully	1129	writes, supports raw and formatted I/O, I/O queued and fully
1025	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.	1130	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
1026		1131
1027	AnyEvent::DNS	1132	AnyEvent::DNS (part of the AnyEvent distribution)
1028	Provides rich asynchronous DNS resolver capabilities.	1133	Provides rich asynchronous DNS resolver capabilities.
1029		1134
1030	AnyEvent::HTTP	1135	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
1031	A simple-to-use HTTP library that is capable of making a lot of	1136	AnyEvent::IGS, AnyEvent::FCP
1032	concurrent HTTP requests.	1137	Implement event-based interfaces to the protocols of the same name
		1138	(for the curious, IGS is the International Go Server and FCP is the
		1139	Freenet Client Protocol).
1033		1140
		1141	AnyEvent::AIO (part of the AnyEvent distribution)
		1142	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1143	the toolbox of every event programmer. AnyEvent::AIO transparently
		1144	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1145	event-based file I/O, and much more.
		1146
		1147	AnyEvent::Fork, AnyEvent::Fork::RPC, AnyEvent::Fork::Pool,
		1148	AnyEvent::Fork::Remote
		1149	These let you safely fork new subprocesses, either locally or
		1150	remotely (e.g.v ia ssh), using some RPC protocol or not, without the
		1151	limitations normally imposed by fork (AnyEvent works fine for
		1152	example). Dynamically-resized worker pools are obviously included as
		1153	well.
		1154
		1155	And they are quite tiny and fast as well - "abusing" AnyEvent::Fork
		1156	just to exec external programs can easily beat using "fork" and
		1157	"exec" (or even "system") in most programs.
		1158
		1159	AnyEvent::Filesys::Notify
		1160	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1161	path changes (e.g. "watch this directory for new files", "watch this
		1162	file for changes"). The AnyEvent::Filesys::Notify module promises to
		1163	do just that in a portbale fashion, supporting inotify on GNU/Linux
		1164	and some weird, without doubt broken, stuff on OS X to monitor
		1165	files. It can fall back to blocking scans at regular intervals
		1166	transparently on other platforms, so it's about as portable as it
		1167	gets.
		1168
		1169	(I haven't used it myself, but it seems the biggest problem with it
		1170	is it quite bad performance).
		1171
1034	AnyEvent::HTTPD	1172	AnyEvent::DBI
1035	Provides a simple web application server framework.	1173	Executes DBI requests asynchronously in a proxy process for you,
		1174	notifying you in an event-based way when the operation is finished.
1036		1175
1037	AnyEvent::FastPing	1176	AnyEvent::FastPing
1038	The fastest ping in the west.	1177	The fastest ping in the west.
1039		1178
1040	AnyEvent::DBI
1041	Executes DBI requests asynchronously in a proxy process.
1042
1043	AnyEvent::AIO
1044	Truly asynchronous I/O, should be in the toolbox of every event
1045	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
1046	together.
1047
1048	AnyEvent::BDB
1049	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
1050	fuses BDB and AnyEvent together.
1051
1052	AnyEvent::GPSD
1053	A non-blocking interface to gpsd, a daemon delivering GPS
1054	information.
1055
1056	AnyEvent::IRC
1057	AnyEvent based IRC client module family (replacing the older
1058	Net::IRC3).
1059
1060	AnyEvent::XMPP
1061	AnyEvent based XMPP (Jabber protocol) module family (replacing the
1062	older Net::XMPP2>.
1063
1064	AnyEvent::IGS
1065	A non-blocking interface to the Internet Go Server protocol (used by
1066	App::IGS).
1067
1068	Net::FCP
1069	AnyEvent-based implementation of the Freenet Client Protocol,
1070	birthplace of AnyEvent.
1071
1072	Event::ExecFlow
1073	High level API for event-based execution flow control.
1074
1075	Coro	1179	Coro
1076	Has special support for AnyEvent via Coro::AnyEvent.	1180	Has special support for AnyEvent via Coro::AnyEvent, which allows
		1181	you to simply invert the flow control - don't call us, we will call
		1182	you:
		1183
		1184	async {
		1185	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1186	print "5 seconds later!\n";
		1187
		1188	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1189	my $line = <STDIN>; # works for ttys
		1190
		1191	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1192	my ($body, $hdr) = Coro::rouse_wait;
		1193	};
1077		1194
1078	SIMPLIFIED AE API	1195	SIMPLIFIED AE API
1079	Starting with version 5.0, AnyEvent officially supports a second, much	1196	Starting with version 5.0, AnyEvent officially supports a second, much
1080	simpler, API that is designed to reduce the calling, typing and memory	1197	simpler, API that is designed to reduce the calling, typing and memory
1081	overhead.	1198	overhead by using function call syntax and a fixed number of parameters.
1082		1199
1083	See the AE manpage for details.	1200	See the AE manpage for details.
1084		1201
1085	ERROR AND EXCEPTION HANDLING	1202	ERROR AND EXCEPTION HANDLING
1086	In general, AnyEvent does not do any error handling - it relies on the	1203	In general, AnyEvent does not do any error handling - it relies on the
…		…
1097	The pure perl event loop simply re-throws the exception (usually within	1214	The pure perl event loop simply re-throws the exception (usually within
1098	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1215	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
1099	Glib uses "install_exception_handler" and so on.	1216	Glib uses "install_exception_handler" and so on.
1100		1217
1101	ENVIRONMENT VARIABLES	1218	ENVIRONMENT VARIABLES
1102	The following environment variables are used by this module or its	1219	AnyEvent supports a number of environment variables that tune the
1103	submodules.	1220	runtime behaviour. They are usually evaluated when AnyEvent is loaded,
		1221	initialised, or a submodule that uses them is loaded. Many of them also
		1222	cause AnyEvent to load additional modules - for example,
		1223	"PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be
		1224	loaded.
1104		1225
1105	Note that AnyEvent will remove all environment variables starting with	1226	All the environment variables documented here start with
1106	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is	1227	"PERL_ANYEVENT_", which is what AnyEvent considers its own namespace.
1107	enabled.	1228	Other modules are encouraged (but by no means required) to use
		1229	"PERL_ANYEVENT_SUBMODULE" if they have registered the
		1230	AnyEvent::Submodule namespace on CPAN, for any submodule. For example,
		1231	AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it
		1232	should not access env variables starting with "AE_", see below).
		1233
		1234	All variables can also be set via the "AE_" prefix, that is, instead of
		1235	setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case
		1236	there is a clash btween anyevent and another program that uses
		1237	"AE_something" you can set the corresponding "PERL_ANYEVENT_something"
		1238	variable to the empty string, as those variables take precedence.
		1239
		1240	When AnyEvent is first loaded, it copies all "AE_xxx" env variables to
		1241	their "PERL_ANYEVENT_xxx" counterpart unless that variable already
		1242	exists. If taint mode is on, then AnyEvent will remove all environment
		1243	variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with
		1244	"undef" or the empty string, if the corresaponding "AE_" variable is
		1245	set).
		1246
		1247	The exact algorithm is currently:
		1248
		1249	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		1250	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		1251	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		1252
		1253	This ensures that child processes will not see the "AE_" variables.
		1254
		1255	The following environment variables are currently known to AnyEvent:
1108		1256
1109	"PERL_ANYEVENT_VERBOSE"	1257	"PERL_ANYEVENT_VERBOSE"
1110	By default, AnyEvent will be completely silent except in fatal	1258	By default, AnyEvent will log messages with loglevel 4 ("error") or
1111	conditions. You can set this environment variable to make AnyEvent	1259	higher (see AnyEvent::Log). You can set this environment variable to
1112	more talkative.	1260	a numerical loglevel to make AnyEvent more (or less) talkative.
1113		1261
		1262	If you want to do more than just set the global logging level you
		1263	should have a look at "PERL_ANYEVENT_LOG", which allows much more
		1264	complex specifications.
		1265
		1266	When set to 0 ("off"), then no messages whatsoever will be logged
		1267	with everything else at defaults.
		1268
1114	When set to 1 or higher, causes AnyEvent to warn about unexpected	1269	When set to 5 or higher ("warn"), AnyEvent warns about unexpected
1115	conditions, such as not being able to load the event model specified	1270	conditions, such as not being able to load the event model specified
1116	by "PERL_ANYEVENT_MODEL".	1271	by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception
		1272	- this is the minimum recommended level for use during development.
1117		1273
1118	When set to 2 or higher, cause AnyEvent to report to STDERR which	1274	When set to 7 or higher (info), AnyEvent reports which event model
1119	event model it chooses.	1275	it chooses.
1120		1276
1121	When set to 8 or higher, then AnyEvent will report extra information	1277	When set to 8 or higher (debug), then AnyEvent will report extra
1122	on which optional modules it loads and how it implements certain	1278	information on which optional modules it loads and how it implements
1123	features.	1279	certain features.
		1280
		1281	"PERL_ANYEVENT_LOG"
		1282	Accepts rather complex logging specifications. For example, you
		1283	could log all "debug" messages of some module to stderr, warnings
		1284	and above to stderr, and errors and above to syslog, with:
		1285
		1286	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		1287
		1288	For the rather extensive details, see AnyEvent::Log.
		1289
		1290	This variable is evaluated when AnyEvent (or AnyEvent::Log) is
		1291	loaded, so will take effect even before AnyEvent has initialised
		1292	itself.
		1293
		1294	Note that specifying this environment variable causes the
		1295	AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE"
		1296	does not, so only using the latter saves a few hundred kB of memory
		1297	unless a module explicitly needs the extra features of
		1298	AnyEvent::Log.
1124		1299
1125	"PERL_ANYEVENT_STRICT"	1300	"PERL_ANYEVENT_STRICT"
1126	AnyEvent does not do much argument checking by default, as thorough	1301	AnyEvent does not do much argument checking by default, as thorough
1127	argument checking is very costly. Setting this variable to a true	1302	argument checking is very costly. Setting this variable to a true
1128	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1303	value will cause AnyEvent to load "AnyEvent::Strict" and then to
1129	thoroughly check the arguments passed to most method calls. If it	1304	thoroughly check the arguments passed to most method calls. If it
1130	finds any problems, it will croak.	1305	finds any problems, it will croak.
1131		1306
1132	In other words, enables "strict" mode.	1307	In other words, enables "strict" mode.
1133		1308
1134	Unlike "use strict" (or it's modern cousin, "use common::sense", it	1309	Unlike "use strict" (or its modern cousin, "use common::sense", it
1135	is definitely recommended to keep it off in production. Keeping	1310	is definitely recommended to keep it off in production. Keeping
1136	"PERL_ANYEVENT_STRICT=1" in your environment while developing	1311	"PERL_ANYEVENT_STRICT=1" in your environment while developing
1137	programs can be very useful, however.	1312	programs can be very useful, however.
1138		1313
		1314	"PERL_ANYEVENT_DEBUG_SHELL"
		1315	If this env variable is nonempty, then its contents will be
		1316	interpreted by "AnyEvent::Socket::parse_hostport" and
		1317	"AnyEvent::Debug::shell" (after replacing every occurance of $$ by
		1318	the process pid). The shell object is saved in
		1319	$AnyEvent::Debug::SHELL.
		1320
		1321	This happens when the first watcher is created.
		1322
		1323	For example, to bind a debug shell on a unix domain socket in
		1324	/tmp/debug<pid>.sock, you could use this:
		1325
		1326	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		1327	# connect with e.g.: socat readline /tmp/debug123.sock
		1328
		1329	Or to bind to tcp port 4545 on localhost:
		1330
		1331	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		1332	# connect with e.g.: telnet localhost 4545
		1333
		1334	Note that creating sockets in /tmp or on localhost is very unsafe on
		1335	multiuser systems.
		1336
		1337	"PERL_ANYEVENT_DEBUG_WRAP"
		1338	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1339	debugging purposes. See "AnyEvent::Debug::wrap" for details.
		1340
1139	"PERL_ANYEVENT_MODEL"	1341	"PERL_ANYEVENT_MODEL"
1140	This can be used to specify the event model to be used by AnyEvent,	1342	This can be used to specify the event model to be used by AnyEvent,
1141	before auto detection and -probing kicks in. It must be a string	1343	before auto detection and -probing kicks in.
1142	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1344
1143	gets prepended and the resulting module name is loaded and if the	1345	It normally is a string consisting entirely of ASCII letters (e.g.
1144	load was successful, used as event model. If it fails to load	1346	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1347	the resulting module name is loaded and - if the load was successful
		1348	- used as event model backend. If it fails to load then AnyEvent
1145	AnyEvent will proceed with auto detection and -probing.	1349	will proceed with auto detection and -probing.
1146		1350
1147	This functionality might change in future versions.	1351	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1352	then nothing gets prepended and the module name is used as-is (hint:
		1353	"::" at the end of a string designates a module name and quotes it
		1354	appropriately).
1148		1355
1149	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1356	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
1150	could start your program like this:	1357	could start your program like this:
1151		1358
1152	PERL_ANYEVENT_MODEL=Perl perl ...	1359	PERL_ANYEVENT_MODEL=Perl perl ...
		1360
		1361	"PERL_ANYEVENT_IO_MODEL"
		1362	The current file I/O model - see AnyEvent::IO for more info.
		1363
		1364	At the moment, only "Perl" (small, pure-perl, synchronous) and
		1365	"IOAIO" (truly asynchronous) are supported. The default is "IOAIO"
		1366	if AnyEvent::AIO can be loaded, otherwise it is "Perl".
1153		1367
1154	"PERL_ANYEVENT_PROTOCOLS"	1368	"PERL_ANYEVENT_PROTOCOLS"
1155	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1369	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
1156	preferences for IPv4 or IPv6. The default is unspecified (and might	1370	preferences for IPv4 or IPv6. The default is unspecified (and might
1157	change, or be the result of auto probing).	1371	change, or be the result of auto probing).
…		…
1161	mentioned will be used, and preference will be given to protocols	1375	mentioned will be used, and preference will be given to protocols
1162	mentioned earlier in the list.	1376	mentioned earlier in the list.
1163		1377
1164	This variable can effectively be used for denial-of-service attacks	1378	This variable can effectively be used for denial-of-service attacks
1165	against local programs (e.g. when setuid), although the impact is	1379	against local programs (e.g. when setuid), although the impact is
1166	likely small, as the program has to handle conenction and other	1380	likely small, as the program has to handle connection and other
1167	failures anyways.	1381	failures anyways.
1168		1382
1169	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1383	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
1170	IPv6, but support both and try to use both.	1384	IPv6, but support both and try to use both.
1171	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1385	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
1172	resolve or contact IPv6 addresses.	1386	resolve or contact IPv6 addresses.
1173	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but	1387	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
1174	prefer IPv6 over IPv4.	1388	prefer IPv6 over IPv4.
1175		1389
		1390	"PERL_ANYEVENT_HOSTS"
		1391	This variable, if specified, overrides the /etc/hosts file used by
		1392	AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be
		1393	read from that file instead.
		1394
1176	"PERL_ANYEVENT_EDNS0"	1395	"PERL_ANYEVENT_EDNS0"
1177	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension	1396	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
1178	for DNS. This extension is generally useful to reduce DNS traffic,	1397	for DNS. This extension is generally useful to reduce DNS traffic,
1179	but some (broken) firewalls drop such DNS packets, which is why it	1398	especially when DNSSEC is involved, but some (broken) firewalls drop
1180	is off by default.	1399	such DNS packets, which is why it is off by default.
1181		1400
1182	Setting this variable to 1 will cause AnyEvent::DNS to announce	1401	Setting this variable to 1 will cause AnyEvent::DNS to announce
1183	EDNS0 in its DNS requests.	1402	EDNS0 in its DNS requests.
1184		1403
1185	"PERL_ANYEVENT_MAX_FORKS"	1404	"PERL_ANYEVENT_MAX_FORKS"
…		…
1189	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"	1408	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
1190	The default value for the "max_outstanding" parameter for the	1409	The default value for the "max_outstanding" parameter for the
1191	default DNS resolver - this is the maximum number of parallel DNS	1410	default DNS resolver - this is the maximum number of parallel DNS
1192	requests that are sent to the DNS server.	1411	requests that are sent to the DNS server.
1193		1412
		1413	"PERL_ANYEVENT_MAX_SIGNAL_LATENCY"
		1414	Perl has inherently racy signal handling (you can basically choose
		1415	between losing signals and memory corruption) - pure perl event
		1416	loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't
		1417	available) therefore have to poll regularly to avoid losing signals.
		1418
		1419	Some event loops are racy, but don't poll regularly, and some event
		1420	loops are written in C but are still racy. For those event loops,
		1421	AnyEvent installs a timer that regularly wakes up the event loop.
		1422
		1423	By default, the interval for this timer is 10 seconds, but you can
		1424	override this delay with this environment variable (or by setting
		1425	the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal
		1426	watchers).
		1427
		1428	Lower values increase CPU (and energy) usage, higher values can
		1429	introduce long delays when reaping children or waiting for signals.
		1430
		1431	The AnyEvent::Async module, if available, will be used to avoid this
		1432	polling (with most event loops).
		1433
1194	"PERL_ANYEVENT_RESOLV_CONF"	1434	"PERL_ANYEVENT_RESOLV_CONF"
1195	The file to use instead of /etc/resolv.conf (or OS-specific	1435	The absolute path to a resolv.conf-style file to use instead of
1196	configuration) in the default resolver. When set to the empty	1436	/etc/resolv.conf (or the OS-specific configuration) in the default
1197	string, no default config will be used.	1437	resolver, or the empty string to select the default configuration.
1198		1438
1199	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".	1439	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1200	When neither "ca_file" nor "ca_path" was specified during	1440	When neither "ca_file" nor "ca_path" was specified during
1201	AnyEvent::TLS context creation, and either of these environment	1441	AnyEvent::TLS context creation, and either of these environment
1202	variables exist, they will be used to specify CA certificate	1442	variables are nonempty, they will be used to specify CA certificate
1203	locations instead of a system-dependent default.	1443	locations instead of a system-dependent default.
1204		1444
1205	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"	1445	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
1206	When these are set to 1, then the respective modules are not loaded.	1446	When these are set to 1, then the respective modules are not loaded.
1207	Mostly good for testing AnyEvent itself.	1447	Mostly good for testing AnyEvent itself.
…		…
1351		1591
1352	The actual code goes further and collects all errors ("die"s,	1592	The actual code goes further and collects all errors ("die"s,
1353	exceptions) that occurred during request processing. The "result" method	1593	exceptions) that occurred during request processing. The "result" method
1354	detects whether an exception as thrown (it is stored inside the $txn	1594	detects whether an exception as thrown (it is stored inside the $txn
1355	object) and just throws the exception, which means connection errors and	1595	object) and just throws the exception, which means connection errors and
1356	other problems get reported tot he code that tries to use the result,	1596	other problems get reported to the code that tries to use the result,
1357	not in a random callback.	1597	not in a random callback.
1358		1598
1359	All of this enables the following usage styles:	1599	All of this enables the following usage styles:
1360		1600
1361	1. Blocking:	1601	1. Blocking:
…		…
1379	my $txn = shift;	1619	my $txn = shift;
1380	my $data = $txn->result;	1620	my $data = $txn->result;
1381	...	1621	...
1382	});	1622	});
1383		1623
1384	EV::loop;	1624	EV::run;
1385		1625
1386	3b. The module user could use AnyEvent, too:	1626	3b. The module user could use AnyEvent, too:
1387		1627
1388	use AnyEvent;	1628	use AnyEvent;
1389		1629
…		…
1527	when used without AnyEvent), but most event loops have acceptable	1767	when used without AnyEvent), but most event loops have acceptable
1528	performance with or without AnyEvent.	1768	performance with or without AnyEvent.
1529		1769
1530	* The overhead AnyEvent adds is usually much smaller than the overhead	1770	* The overhead AnyEvent adds is usually much smaller than the overhead
1531	of the actual event loop, only with extremely fast event loops such	1771	of the actual event loop, only with extremely fast event loops such
1532	as EV adds AnyEvent significant overhead.	1772	as EV does AnyEvent add significant overhead.
1533		1773
1534	* You should avoid POE like the plague if you want performance or	1774	* You should avoid POE like the plague if you want performance or
1535	reasonable memory usage.	1775	reasonable memory usage.
1536		1776
1537	BENCHMARKING THE LARGE SERVER CASE	1777	BENCHMARKING THE LARGE SERVER CASE
…		…
1735		1975
1736	Feel free to install your own handler, or reset it to defaults.	1976	Feel free to install your own handler, or reset it to defaults.
1737		1977
1738	RECOMMENDED/OPTIONAL MODULES	1978	RECOMMENDED/OPTIONAL MODULES
1739	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and	1979	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
1740	it's built-in modules) are required to use it.	1980	its built-in modules) are required to use it.
1741		1981
1742	That does not mean that AnyEvent won't take advantage of some additional	1982	That does not mean that AnyEvent won't take advantage of some additional
1743	modules if they are installed.	1983	modules if they are installed.
1744		1984
1745	This section explains which additional modules will be used, and how	1985	This section explains which additional modules will be used, and how
…		…
1774	clock is available, can take avdantage of advanced kernel interfaces	2014	clock is available, can take avdantage of advanced kernel interfaces
1775	such as "epoll" and "kqueue", and is the fastest backend by far.	2015	such as "epoll" and "kqueue", and is the fastest backend by far.
1776	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and	2016	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
1777	Glib::EV).	2017	Glib::EV).
1778		2018
		2019	If you only use backends that rely on another event loop (e.g.
		2020	"Tk"), then this module will do nothing for you.
		2021
1779	Guard	2022	Guard
1780	The guard module, when used, will be used to implement	2023	The guard module, when used, will be used to implement
1781	"AnyEvent::Util::guard". This speeds up guards considerably (and	2024	"AnyEvent::Util::guard". This speeds up guards considerably (and
1782	uses a lot less memory), but otherwise doesn't affect guard	2025	uses a lot less memory), but otherwise doesn't affect guard
1783	operation much. It is purely used for performance.	2026	operation much. It is purely used for performance.
1784		2027
1785	JSON and JSON::XS	2028	JSON and JSON::XS
1786	One of these modules is required when you want to read or write JSON	2029	One of these modules is required when you want to read or write JSON
1787	data via AnyEvent::Handle. It is also written in pure-perl, but can	2030	data via AnyEvent::Handle. JSON is also written in pure-perl, but
1788	take advantage of the ultra-high-speed JSON::XS module when it is	2031	can take advantage of the ultra-high-speed JSON::XS module when it
1789	installed.	2032	is installed.
1790
1791	In fact, AnyEvent::Handle will use JSON::XS by default if it is
1792	installed.
1793		2033
1794	Net::SSLeay	2034	Net::SSLeay
1795	Implementing TLS/SSL in Perl is certainly interesting, but not very	2035	Implementing TLS/SSL in Perl is certainly interesting, but not very
1796	worthwhile: If this module is installed, then AnyEvent::Handle (with	2036	worthwhile: If this module is installed, then AnyEvent::Handle (with
1797	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.	2037	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
1798		2038
1799	Time::HiRes	2039	Time::HiRes
1800	This module is part of perl since release 5.008. It will be used	2040	This module is part of perl since release 5.008. It will be used
1801	when the chosen event library does not come with a timing source on	2041	when the chosen event library does not come with a timing source of
1802	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will	2042	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
1803	additionally use it to try to use a monotonic clock for timing	2043	load it to try to use a monotonic clock for timing stability.
1804	stability.	2044
		2045	AnyEvent::AIO (and IO::AIO)
		2046	The default implementation of AnyEvent::IO is to do I/O
		2047	synchronously, stopping programs while they access the disk, which
		2048	is fine for a lot of programs.
		2049
		2050	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it
		2051	switch to a true asynchronous implementation, so event processing
		2052	can continue even while waiting for disk I/O.
1805		2053
1806	FORK	2054	FORK
1807	Most event libraries are not fork-safe. The ones who are usually are	2055	Most event libraries are not fork-safe. The ones who are usually are
1808	because they rely on inefficient but fork-safe "select" or "poll" calls	2056	because they rely on inefficient but fork-safe "select" or "poll" calls
1809	- higher performance APIs such as BSD's kqueue or the dreaded Linux	2057	- higher performance APIs such as BSD's kqueue or the dreaded Linux
…		…
1817	usually happens when the first AnyEvent watcher is created, or the	2065	usually happens when the first AnyEvent watcher is created, or the
1818	library is loaded).	2066	library is loaded).
1819		2067
1820	If you have to fork, you must either do so before creating your first	2068	If you have to fork, you must either do so before creating your first
1821	watcher OR you must not use AnyEvent at all in the child OR you must do	2069	watcher OR you must not use AnyEvent at all in the child OR you must do
1822	something completely out of the scope of AnyEvent.	2070	something completely out of the scope of AnyEvent (see below).
1823		2071
1824	The problem of doing event processing in the parent and the child is	2072	The problem of doing event processing in the parent and the child is
1825	much more complicated: even for backends that are fork-aware or	2073	much more complicated: even for backends that are fork-aware or
1826	fork-safe, their behaviour is not usually what you want: fork clones all	2074	fork-safe, their behaviour is not usually what you want: fork clones all
1827	watchers, that means all timers, I/O watchers etc. are active in both	2075	watchers, that means all timers, I/O watchers etc. are active in both
1828	parent and child, which is almost never what you want. USing "exec" to	2076	parent and child, which is almost never what you want. Using "exec" to
1829	start worker children from some kind of manage rprocess is usually	2077	start worker children from some kind of manage prrocess is usually
1830	preferred, because it is much easier and cleaner, at the expense of	2078	preferred, because it is much easier and cleaner, at the expense of
1831	having to have another binary.	2079	having to have another binary.
		2080
		2081	In addition to logical problems with fork, there are also implementation
		2082	problems. For example, on POSIX systems, you cannot fork at all in Perl
		2083	code if a thread (I am talking of pthreads here) was ever created in the
		2084	process, and this is just the tip of the iceberg. In general, using fork
		2085	from Perl is difficult, and attempting to use fork without an exec to
		2086	implement some kind of parallel processing is almost certainly doomed.
		2087
		2088	To safely fork and exec, you should use a module such as Proc::FastSpawn
		2089	that let's you safely fork and exec new processes.
		2090
		2091	If you want to do multiprocessing using processes, you can look at the
		2092	AnyEvent::Fork module (and some related modules such as
		2093	AnyEvent::Fork::RPC, AnyEvent::Fork::Pool and AnyEvent::Fork::Remote).
		2094	This module allows you to safely create subprocesses without any
		2095	limitations - you can use X11 toolkits or AnyEvent in the children
		2096	created by AnyEvent::Fork safely and without any special precautions.
1832		2097
1833	SECURITY CONSIDERATIONS	2098	SECURITY CONSIDERATIONS
1834	AnyEvent can be forced to load any event model via	2099	AnyEvent can be forced to load any event model via
1835	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	2100	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1836	to execute arbitrary code or directly gain access, it can easily be used	2101	to execute arbitrary code or directly gain access, it can easily be used
…		…
1860	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	2125	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1861	annoying memleaks, such as leaking on "map" and "grep" but it is usually	2126	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1862	not as pronounced).	2127	not as pronounced).
1863		2128
1864	SEE ALSO	2129	SEE ALSO
1865	Utility functions: AnyEvent::Util.	2130	Tutorial/Introduction: AnyEvent::Intro.
1866		2131
1867	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	2132	FAQ: AnyEvent::FAQ.
1868	Event::Lib, Qt, POE.	2133
		2134	Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log
		2135	(simply logging).
		2136
		2137	Development/Debugging: AnyEvent::Strict (stricter checking),
		2138	AnyEvent::Debug (interactive shell, watcher tracing).
		2139
		2140	Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
		2141	Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK, Cocoa::EventLoop, UV.
1869		2142
1870	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	2143	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1871	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	2144	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1872	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,	2145	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		2146	AnyEvent::Impl::IOAsync, AnyEvent::Impl::Irssi, AnyEvent::Impl::FLTK,
1873	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.	2147	AnyEvent::Impl::Cocoa, AnyEvent::Impl::UV.
1874		2148
1875	Non-blocking file handles, sockets, TCP clients and servers:	2149	Non-blocking handles, pipes, stream sockets, TCP clients and servers:
1876	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.	2150	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1877		2151
		2152	Asynchronous File I/O: AnyEvent::IO.
		2153
1878	Asynchronous DNS: AnyEvent::DNS.	2154	Asynchronous DNS: AnyEvent::DNS.
1879		2155
1880	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	2156	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1881		2157
1882	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,	2158	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
1883	AnyEvent::HTTP.	2159	AnyEvent::HTTP.
1884		2160
1885	AUTHOR	2161	AUTHOR
1886	Marc Lehmann <schmorp@schmorp.de>	2162	Marc Lehmann <schmorp@schmorp.de>
1887	http://home.schmorp.de/	2163	http://anyevent.schmorp.de
1888		2164

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Comparing AnyEvent/README (file contents): Revision 1.59 by root, Tue Jan 5 10:45:25 2010 UTC vs. Revision 1.79 by root, Tue Feb 26 02:08:34 2019 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.59 by root, Tue Jan 5 10:45:25 2010 UTC vs.
Revision 1.79 by root, Tue Feb 26 02:08:34 2019 UTC