[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.58 by root, Sun Dec 20 22:49:52 2009 UTC vs.
Revision 1.76 by root, Wed Jan 27 18:15:21 2016 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	Sometimes there is a need to do something, but it is not so important to	496	This will repeatedly invoke the callback after the process becomes idle,
492	do it instantly, but only when there is nothing better to do. This	497	until either the watcher is destroyed or new events have been detected.
493	"nothing better to do" is usually defined to be "no other events need
494	attention by the event loop".
495		498
496	Idle watchers ideally get invoked when the event loop has nothing better	499	Idle watchers are useful when there is a need to do something, but it is
497	to do, just before it would block the process to wait for new events.	500	not so important (or wise) to do it instantly. The callback will be
498	Instead of blocking, the idle watcher is invoked.	501	invoked only when there is "nothing better to do", which is usually
		502	defined as "all outstanding events have been handled and no new events
		503	have been detected". That means that idle watchers ideally get invoked
		504	when the event loop has just polled for new events but none have been
		505	detected. Instead of blocking to wait for more events, the idle watchers
		506	will be invoked.
499		507
500	Most event loops unfortunately do not really support idle watchers (only	508	Unfortunately, most event loops do not really support idle watchers
501	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent	509	(only EV, Event and Glib do it in a usable fashion) - for the rest,
502	will simply call the callback "from time to time".	510	AnyEvent will simply call the callback "from time to time".
503		511
504	Example: read lines from STDIN, but only process them when the program	512	Example: read lines from STDIN, but only process them when the program
505	is otherwise idle:	513	is otherwise idle:
506		514
507	my @lines; # read data	515	my @lines; # read data
…		…
533		541
534	AnyEvent is slightly different: it expects somebody else to run the	542	AnyEvent is slightly different: it expects somebody else to run the
535	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
536	user).	544	user).
537		545
538	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
539	because they represent a condition that must become true.	547	they represent a condition that must become true.
540		548
541	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.
542		550
543	Condition variables can be created by calling the "AnyEvent->condvar"	551	Condition variables can be created by calling the "AnyEvent->condvar"
544	method, usually without arguments. The only argument pair allowed is	552	method, usually without arguments. The only argument pair allowed is
…		…
549	After creation, the condition variable is "false" until it becomes	557	After creation, the condition variable is "false" until it becomes
550	"true" by calling the "send" method (or calling the condition variable	558	"true" by calling the "send" method (or calling the condition variable
551	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
552	the "->send" method).	560	the "->send" method).
553		561
554	Condition variables are similar to callbacks, except that you can	562	Since condition variables are the most complex part of the AnyEvent API,
555	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
556	in time where multiple outstanding events have been processed. And yet	564	you can connect to:
557	another way to call them is transactions - each condition variable can	565
558	be used to represent a transaction, which finishes at some point and	566	* Condition variables are like callbacks - you can call them (and pass
559	delivers a result. And yet some people know them as "futures" - a	567	them instead of callbacks). Unlike callbacks however, you can also
560	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.
561		583
562	Condition variables are very useful to signal that something has	584	Condition variables are very useful to signal that something has
563	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
564	requests, then a condition variable would be the ideal candidate to	586	requests, then a condition variable would be the ideal candidate to
565	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
…		…
578		600
579	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
580	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
581	(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
582	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	604	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
583	it's "new" method in your own "new" method.	605	its "new" method in your own "new" method.
584		606
585	There are two "sides" to a condition variable - the "producer side"	607	There are two "sides" to a condition variable - the "producer side"
586	which eventually calls "-> send", and the "consumer side", which waits	608	which eventually calls "-> send", and the "consumer side", which waits
587	for the send to occur.	609	for the send to occur.
588		610
589	Example: wait for a timer.	611	Example: wait for a timer.
590		612
591	# wait till the result is ready	613	# condition: "wait till the timer is fired"
592	my $result_ready = AnyEvent->condvar;	614	my $timer_fired = AnyEvent->condvar;
593		615
594	# do something such as adding a timer	616	# create the timer - we could wait for, say
595	# or socket watcher the calls $result_ready->send	617	# a handle becomign ready, or even an
596	# when the "result" is ready.	618	# AnyEvent::HTTP request to finish, but
597	# in this case, we simply use a timer:	619	# in this case, we simply use a timer:
598	my $w = AnyEvent->timer (	620	my $w = AnyEvent->timer (
599	after => 1,	621	after => 1,
600	cb => sub { $result_ready->send },	622	cb => sub { $timer_fired->send },
601	);	623	);
602		624
603	# this "blocks" (while handling events) till the callback	625	# this "blocks" (while handling events) till the callback
604	# calls ->send	626	# calls ->send
605	$result_ready->recv;	627	$timer_fired->recv;
606		628
607	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
608	variables are also callable directly.	630	variables are also callable directly.
609		631
610	my $done = AnyEvent->condvar;	632	my $done = AnyEvent->condvar;
…		…
648	Condition variables are overloaded so one can call them directly (as	670	Condition variables are overloaded so one can call them directly (as
649	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
650	calling "send".	672	calling "send".
651		673
652	$cv->croak ($error)	674	$cv->croak ($error)
653	Similar to send, but causes all call's to "->recv" to invoke	675	Similar to send, but causes all calls to "->recv" to invoke
654	"Carp::croak" with the given error message/object/scalar.	676	"Carp::croak" with the given error message/object/scalar.
655		677
656	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
657	user/consumer. Doing it this way instead of calling "croak" directly	679	user/consumer. Doing it this way instead of calling "croak" directly
658	delays the error detetcion, but has the overwhelmign advantage that	680	delays the error detection, but has the overwhelming advantage that
659	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,
660	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
661	code causing the problem.	683	code causing the problem.
662		684
663	$cv->begin ([group callback])	685	$cv->begin ([group callback])
664	$cv->end	686	$cv->end
665	These two methods can be used to combine many transactions/events	687	These two methods can be used to combine many transactions/events
…		…
701	This works because for every event source (EOF on file handle),	723	This works because for every event source (EOF on file handle),
702	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
703	"end" before sending.	725	"end" before sending.
704		726
705	The ping example mentioned above is slightly more complicated, as	727	The ping example mentioned above is slightly more complicated, as
706	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
707	that are begung can potentially be zero:	729	that are begun can potentially be zero:
708		730
709	my $cv = AnyEvent->condvar;	731	my $cv = AnyEvent->condvar;
710		732
711	my %result;	733	my %result;
712	$cv->begin (sub { shift->send (\%result) });	734	$cv->begin (sub { shift->send (\%result) });
…		…
719	};	741	};
720	}	742	}
721		743
722	$cv->end;	744	$cv->end;
723		745
		746	...
		747
		748	my $results = $cv->recv;
		749
724	This code fragment supposedly pings a number of hosts and calls	750	This code fragment supposedly pings a number of hosts and calls
725	"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
726	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
727	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
728	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
…		…
733	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
734	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
735	(the loop doesn't execute once).	761	(the loop doesn't execute once).
736		762
737	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
738	potentially none) subrequests: use an outer "begin"/"end" pair to	764	potentially zero) subrequests: use an outer "begin"/"end" pair to
739	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,
740	for each subrequest you start, call "begin" and for each subrequest	766	for each subrequest you start, call "begin" and for each subrequest
741	you finish, call "end".	767	you finish, call "end".
742		768
743	METHODS FOR CONSUMERS	769	METHODS FOR CONSUMERS
744	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
745	awaits the condition.	771	awaits the condition.
746		772
747	$cv->recv	773	$cv->recv
748	Wait (blocking if necessary) until the "->send" or "->croak" methods	774	Wait (blocking if necessary) until the "->send" or "->croak" methods
749	have been called on c<$cv>, while servicing other watchers normally.	775	have been called on $cv, while servicing other watchers normally.
750		776
751	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
752	but will return immediately.	778	but will return immediately.
753		779
754	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
…		…
757	In list context, all parameters passed to "send" will be returned,	783	In list context, all parameters passed to "send" will be returned,
758	in scalar context only the first one will be returned.	784	in scalar context only the first one will be returned.
759		785
760	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
761	any event loop, that is, recursive invocation of a blocking "->recv"	787	any event loop, that is, recursive invocation of a blocking "->recv"
762	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
763	is detected. This condition can be slightly loosened by using	789	is detected. This requirement can be dropped by relying on
764	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
765	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.
766		797
767	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
768	(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
769	using this from a module, never require a blocking wait*. Instead,	800	using this from a module, never require a blocking wait*. Instead,
770	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
771	example, by coupling condition variables with some kind of request	802	example, by coupling condition variables with some kind of request
772	results and supporting callbacks so the caller knows that getting	803	results and supporting callbacks so the caller knows that getting
773	the result will not block, while still supporting blocking waits if	804	the result will not block, while still supporting blocking waits if
774	the caller so desires).	805	the caller so desires).
775		806
776	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
777	only calling "->recv" from within that callback (or at a later	808	only calling "->recv" from within that callback (or at a later
778	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
779	blocking waits otherwise.	810	blocking waits otherwise.
780		811
781	$bool = $cv->ready	812	$bool = $cv->ready
…		…
784		815
785	$cb = $cv->cb ($cb->($cv))	816	$cb = $cv->cb ($cb->($cv))
786	This is a mutator function that returns the callback set and	817	This is a mutator function that returns the callback set and
787	optionally replaces it before doing so.	818	optionally replaces it before doing so.
788		819
789	The callback will be called when the condition becomes (or already	820	The callback will be called when the condition becomes "true", i.e.
790	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
791	called), with the only argument being the condition variable itself.	822	condition variable itself. If the condition is already true, the
792	Calling "recv" inside the callback or at any later time is	823	callback is called immediately when it is set. Calling "recv" inside
793	guaranteed not to block.	824	the callback or at any later time is guaranteed not to block.
794		825
795	SUPPORTED EVENT LOOPS/BACKENDS	826	SUPPORTED EVENT LOOPS/BACKENDS
796	The available backend classes are (every class has its own manpage):	827	The available backend classes are (every class has its own manpage):
797		828
798	Backends that are autoprobed when no other event loop can be found.	829	Backends that are autoprobed when no other event loop can be found.
…		…
800	use. If EV is not installed, then AnyEvent will fall back to its own	831	use. If EV is not installed, then AnyEvent will fall back to its own
801	pure-perl implementation, which is available everywhere as it comes	832	pure-perl implementation, which is available everywhere as it comes
802	with AnyEvent itself.	833	with AnyEvent itself.
803		834
804	AnyEvent::Impl::EV based on EV (interface to libev, best choice).	835	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
805	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.	836	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
806		837
807	Backends that are transparently being picked up when they are used.	838	Backends that are transparently being picked up when they are used.
808	These will be used when they are currently loaded when the first	839	These will be used if they are already loaded when the first watcher
809	watcher is created, in which case it is assumed that the application	840	is created, in which case it is assumed that the application is
810	is using them. This means that AnyEvent will automatically pick the	841	using them. This means that AnyEvent will automatically pick the
811	right backend when the main program loads an event module before	842	right backend when the main program loads an event module before
812	anything starts to create watchers. Nothing special needs to be done	843	anything starts to create watchers. Nothing special needs to be done
813	by the main program.	844	by the main program.
814		845
815	AnyEvent::Impl::Event based on Event, very stable, few glitches.	846	AnyEvent::Impl::Event based on Event, very stable, few glitches.
816	AnyEvent::Impl::Glib based on Glib, slow but very stable.	847	AnyEvent::Impl::Glib based on Glib, slow but very stable.
817	AnyEvent::Impl::Tk based on Tk, very broken.	848	AnyEvent::Impl::Tk based on Tk, very broken.
		849	AnyEvent::Impl::UV based on UV, innovated square wheels.
818	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	850	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
819	AnyEvent::Impl::POE based on POE, very slow, some limitations.	851	AnyEvent::Impl::POE based on POE, very slow, some limitations.
820	AnyEvent::Impl::Irssi used when running within irssi.	852	AnyEvent::Impl::Irssi used when running within irssi.
		853	AnyEvent::Impl::IOAsync based on IO::Async.
		854	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		855	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
821		856
822	Backends with special needs.	857	Backends with special needs.
823	Qt requires the Qt::Application to be instantiated first, but will	858	Qt requires the Qt::Application to be instantiated first, but will
824	otherwise be picked up automatically. As long as the main program	859	otherwise be picked up automatically. As long as the main program
825	instantiates the application before any AnyEvent watchers are	860	instantiates the application before any AnyEvent watchers are
826	created, everything should just work.	861	created, everything should just work.
827		862
828	AnyEvent::Impl::Qt based on Qt.	863	AnyEvent::Impl::Qt based on Qt.
829		864
830	Support for IO::Async can only be partial, as it is too broken and
831	architecturally limited to even support the AnyEvent API. It also is
832	the only event loop that needs the loop to be set explicitly, so it
833	can only be used by a main program knowing about AnyEvent. See
834	AnyEvent::Impl::Async for the gory details.
835
836	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
837
838	Event loops that are indirectly supported via other backends.	865	Event loops that are indirectly supported via other backends.
839	Some event loops can be supported via other modules:	866	Some event loops can be supported via other modules:
840		867
841	There is no direct support for WxWidgets (Wx) or Prima.	868	There is no direct support for WxWidgets (Wx) or Prima.
842		869
…		…
860	Contains "undef" until the first watcher is being created, before	887	Contains "undef" until the first watcher is being created, before
861	the backend has been autodetected.	888	the backend has been autodetected.
862		889
863	Afterwards it contains the event model that is being used, which is	890	Afterwards it contains the event model that is being used, which is
864	the name of the Perl class implementing the model. This class is	891	the name of the Perl class implementing the model. This class is
865	usually one of the "AnyEvent::Impl:xxx" modules, but can be any	892	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
866	other class in the case AnyEvent has been extended at runtime (e.g.	893	other class in the case AnyEvent has been extended at runtime (e.g.
867	in rxvt-unicode it will be "urxvt::anyevent").	894	in rxvt-unicode it will be "urxvt::anyevent").
868		895
869	AnyEvent::detect	896	AnyEvent::detect
870	Returns $AnyEvent::MODEL, forcing autodetection of the event model	897	Returns $AnyEvent::MODEL, forcing autodetection of the event model
871	if necessary. You should only call this function right before you	898	if necessary. You should only call this function right before you
872	would have created an AnyEvent watcher anyway, that is, as late as	899	would have created an AnyEvent watcher anyway, that is, as late as
873	possible at runtime, and not e.g. while initialising of your module.	900	possible at runtime, and not e.g. during initialisation of your
		901	module.
		902
		903	The effect of calling this function is as if a watcher had been
		904	created (specifically, actions that happen "when the first watcher
		905	is created" happen when calling detetc as well).
874		906
875	If you need to do some initialisation before AnyEvent watchers are	907	If you need to do some initialisation before AnyEvent watchers are
876	created, use "post_detect".	908	created, use "post_detect".
877		909
878	$guard = AnyEvent::post_detect { BLOCK }	910	$guard = AnyEvent::post_detect { BLOCK }
879	Arranges for the code block to be executed as soon as the event	911	Arranges for the code block to be executed as soon as the event
880	model is autodetected (or immediately if this has already happened).	912	model is autodetected (or immediately if that has already happened).
881		913
882	The block will be executed after the actual backend has been	914	The block will be executed after the actual backend has been
883	detected ($AnyEvent::MODEL is set), but before any watchers have	915	detected ($AnyEvent::MODEL is set), but before any watchers have
884	been created, so it is possible to e.g. patch @AnyEvent::ISA or do	916	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
885	other initialisations - see the sources of AnyEvent::Strict or	917	other initialisations - see the sources of AnyEvent::Strict or
…		…
894	object that automatically removes the callback again when it is	926	object that automatically removes the callback again when it is
895	destroyed (or "undef" when the hook was immediately executed). See	927	destroyed (or "undef" when the hook was immediately executed). See
896	AnyEvent::AIO for a case where this is useful.	928	AnyEvent::AIO for a case where this is useful.
897		929
898	Example: Create a watcher for the IO::AIO module and store it in	930	Example: Create a watcher for the IO::AIO module and store it in
899	$WATCHER. Only do so after the event loop is initialised, though.	931	$WATCHER, but do so only do so after the event loop is initialised.
900		932
901	our WATCHER;	933	our WATCHER;
902		934
903	my $guard = AnyEvent::post_detect {	935	my $guard = AnyEvent::post_detect {
904	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);	936	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
…		…
911		943
912	$WATCHER \|\|= $guard;	944	$WATCHER \|\|= $guard;
913		945
914	@AnyEvent::post_detect	946	@AnyEvent::post_detect
915	If there are any code references in this array (you can "push" to it	947	If there are any code references in this array (you can "push" to it
916	before or after loading AnyEvent), then they will called directly	948	before or after loading AnyEvent), then they will be called directly
917	after the event loop has been chosen.	949	after the event loop has been chosen.
918		950
919	You should check $AnyEvent::MODEL before adding to this array,	951	You should check $AnyEvent::MODEL before adding to this array,
920	though: if it is defined then the event loop has already been	952	though: if it is defined then the event loop has already been
921	detected, and the array will be ignored.	953	detected, and the array will be ignored.
…		…
940	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent	972	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
941	# as soon as it is	973	# as soon as it is
942	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };	974	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
943	}	975	}
944		976
		977	AnyEvent::postpone { BLOCK }
		978	Arranges for the block to be executed as soon as possible, but not
		979	before the call itself returns. In practise, the block will be
		980	executed just before the event loop polls for new events, or shortly
		981	afterwards.
		982
		983	This function never returns anything (to make the "return postpone {
		984	... }" idiom more useful.
		985
		986	To understand the usefulness of this function, consider a function
		987	that asynchronously does something for you and returns some
		988	transaction object or guard to let you cancel the operation. For
		989	example, "AnyEvent::Socket::tcp_connect":
		990
		991	# start a connection attempt unless one is active
		992	$self->{connect_guard} \|\|= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		993	delete $self->{connect_guard};
		994	...
		995	};
		996
		997	Imagine that this function could instantly call the callback, for
		998	example, because it detects an obvious error such as a negative port
		999	number. Invoking the callback before the function returns causes
		1000	problems however: the callback will be called and will try to delete
		1001	the guard object. But since the function hasn't returned yet, there
		1002	is nothing to delete. When the function eventually returns it will
		1003	assign the guard object to "$self->{connect_guard}", where it will
		1004	likely never be deleted, so the program thinks it is still trying to
		1005	connect.
		1006
		1007	This is where "AnyEvent::postpone" should be used. Instead of
		1008	calling the callback directly on error:
		1009
		1010	$cb->(undef), return # signal error to callback, BAD!
		1011	if $some_error_condition;
		1012
		1013	It should use "postpone":
		1014
		1015	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1016	if $some_error_condition;
		1017
		1018	AnyEvent::log $level, $msg[, @args]
		1019	Log the given $msg at the given $level.
		1020
		1021	If AnyEvent::Log is not loaded then this function makes a simple
		1022	test to see whether the message will be logged. If the test succeeds
		1023	it will load AnyEvent::Log and call "AnyEvent::Log::log" -
		1024	consequently, look at the AnyEvent::Log documentation for details.
		1025
		1026	If the test fails it will simply return. Right now this happens when
		1027	a numerical loglevel is used and it is larger than the level
		1028	specified via $ENV{PERL_ANYEVENT_VERBOSE}.
		1029
		1030	If you want to sprinkle loads of logging calls around your code,
		1031	consider creating a logger callback with the "AnyEvent::Log::logger"
		1032	function, which can reduce typing, codesize and can reduce the
		1033	logging overhead enourmously.
		1034
		1035	AnyEvent::fh_block $filehandle
		1036	AnyEvent::fh_unblock $filehandle
		1037	Sets blocking or non-blocking behaviour for the given filehandle.
		1038
945	WHAT TO DO IN A MODULE	1039	WHAT TO DO IN A MODULE
946	As a module author, you should "use AnyEvent" and call AnyEvent methods	1040	As a module author, you should "use AnyEvent" and call AnyEvent methods
947	freely, but you should not load a specific event module or rely on it.	1041	freely, but you should not load a specific event module or rely on it.
948		1042
949	Be careful when you create watchers in the module body - AnyEvent will	1043	Be careful when you create watchers in the module body - AnyEvent will
…		…
956	stall the whole program, and the whole point of using events is to stay	1050	stall the whole program, and the whole point of using events is to stay
957	interactive.	1051	interactive.
958		1052
959	It is fine, however, to call "->recv" when the user of your module	1053	It is fine, however, to call "->recv" when the user of your module
960	requests it (i.e. if you create a http request object ad have a method	1054	requests it (i.e. if you create a http request object ad have a method
961	called "results" that returns the results, it should call "->recv"	1055	called "results" that returns the results, it may call "->recv" freely,
962	freely, as the user of your module knows what she is doing. always).	1056	as the user of your module knows what she is doing. Always).
963		1057
964	WHAT TO DO IN THE MAIN PROGRAM	1058	WHAT TO DO IN THE MAIN PROGRAM
965	There will always be a single main program - the only place that should	1059	There will always be a single main program - the only place that should
966	dictate which event model to use.	1060	dictate which event model to use.
967		1061
968	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1062	If the program is not event-based, it need not do anything special, even
969	do anything special (it does not need to be event-based) and let	1063	when it depends on a module that uses an AnyEvent. If the program itself
970	AnyEvent decide which implementation to chose if some module relies on	1064	uses AnyEvent, but does not care which event loop is used, all it needs
971	it.	1065	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1066	available loop implementation.
972		1067
973	If the main program relies on a specific event model - for example, in	1068	If the main program relies on a specific event model - for example, in
974	Gtk2 programs you have to rely on the Glib module - you should load the	1069	Gtk2 programs you have to rely on the Glib module - you should load the
975	event module before loading AnyEvent or any module that uses it:	1070	event module before loading AnyEvent or any module that uses it:
976	generally speaking, you should load it as early as possible. The reason	1071	generally speaking, you should load it as early as possible. The reason
977	is that modules might create watchers when they are loaded, and AnyEvent	1072	is that modules might create watchers when they are loaded, and AnyEvent
978	will decide on the event model to use as soon as it creates watchers,	1073	will decide on the event model to use as soon as it creates watchers,
979	and it might chose the wrong one unless you load the correct one	1074	and it might choose the wrong one unless you load the correct one
980	yourself.	1075	yourself.
981		1076
982	You can chose to use a pure-perl implementation by loading the	1077	You can chose to use a pure-perl implementation by loading the
983	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1078	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
984	everywhere, but letting AnyEvent chose the model is generally better.	1079	but letting AnyEvent chose the model is generally better.
985		1080
986	MAINLOOP EMULATION	1081	MAINLOOP EMULATION
987	Sometimes (often for short test scripts, or even standalone programs who	1082	Sometimes (often for short test scripts, or even standalone programs who
988	only want to use AnyEvent), you do not want to run a specific event	1083	only want to use AnyEvent), you do not want to run a specific event
989	loop.	1084	loop.
…		…
1001		1096
1002	OTHER MODULES	1097	OTHER MODULES
1003	The following is a non-exhaustive list of additional modules that use	1098	The following is a non-exhaustive list of additional modules that use
1004	AnyEvent as a client and can therefore be mixed easily with other	1099	AnyEvent as a client and can therefore be mixed easily with other
1005	AnyEvent modules and other event loops in the same program. Some of the	1100	AnyEvent modules and other event loops in the same program. Some of the
1006	modules come with AnyEvent, most are available via CPAN.	1101	modules come as part of AnyEvent, the others are available via CPAN (see
		1102	<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
		1103	non-exhaustive list), and the list is heavily biased towards modules of
		1104	the AnyEvent author himself :)
1007		1105
1008	AnyEvent::Util	1106	AnyEvent::Util (part of the AnyEvent distribution)
1009	Contains various utility functions that replace often-used but	1107	Contains various utility functions that replace often-used blocking
1010	blocking functions such as "inet_aton" by event-/callback-based	1108	functions such as "inet_aton" with event/callback-based versions.
1011	versions.
1012		1109
1013	AnyEvent::Socket	1110	AnyEvent::Socket (part of the AnyEvent distribution)
1014	Provides various utility functions for (internet protocol) sockets,	1111	Provides various utility functions for (internet protocol) sockets,
1015	addresses and name resolution. Also functions to create non-blocking	1112	addresses and name resolution. Also functions to create non-blocking
1016	tcp connections or tcp servers, with IPv6 and SRV record support and	1113	tcp connections or tcp servers, with IPv6 and SRV record support and
1017	more.	1114	more.
1018		1115
1019	AnyEvent::Handle	1116	AnyEvent::Handle (part of the AnyEvent distribution)
1020	Provide read and write buffers, manages watchers for reads and	1117	Provide read and write buffers, manages watchers for reads and
1021	writes, supports raw and formatted I/O, I/O queued and fully	1118	writes, supports raw and formatted I/O, I/O queued and fully
1022	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.	1119	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
1023		1120
1024	AnyEvent::DNS	1121	AnyEvent::DNS (part of the AnyEvent distribution)
1025	Provides rich asynchronous DNS resolver capabilities.	1122	Provides rich asynchronous DNS resolver capabilities.
1026		1123
1027	AnyEvent::HTTP	1124	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
1028	A simple-to-use HTTP library that is capable of making a lot of	1125	AnyEvent::IGS, AnyEvent::FCP
1029	concurrent HTTP requests.	1126	Implement event-based interfaces to the protocols of the same name
		1127	(for the curious, IGS is the International Go Server and FCP is the
		1128	Freenet Client Protocol).
1030		1129
		1130	AnyEvent::AIO (part of the AnyEvent distribution)
		1131	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1132	the toolbox of every event programmer. AnyEvent::AIO transparently
		1133	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1134	event-based file I/O, and much more.
		1135
		1136	AnyEvent::Fork, AnyEvent::Fork::RPC, AnyEvent::Fork::Pool,
		1137	AnyEvent::Fork::Remote
		1138	These let you safely fork new subprocesses, either locally or
		1139	remotely (e.g.v ia ssh), using some RPC protocol or not, without the
		1140	limitations normally imposed by fork (AnyEvent works fine for
		1141	example). Dynamically-resized worker pools are obviously included as
		1142	well.
		1143
		1144	And they are quite tiny and fast as well - "abusing" AnyEvent::Fork
		1145	just to exec external programs can easily beat using "fork" and
		1146	"exec" (or even "system") in most programs.
		1147
		1148	AnyEvent::Filesys::Notify
		1149	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1150	path changes (e.g. "watch this directory for new files", "watch this
		1151	file for changes"). The AnyEvent::Filesys::Notify module promises to
		1152	do just that in a portbale fashion, supporting inotify on GNU/Linux
		1153	and some weird, without doubt broken, stuff on OS X to monitor
		1154	files. It can fall back to blocking scans at regular intervals
		1155	transparently on other platforms, so it's about as portable as it
		1156	gets.
		1157
		1158	(I haven't used it myself, but it seems the biggest problem with it
		1159	is it quite bad performance).
		1160
1031	AnyEvent::HTTPD	1161	AnyEvent::DBI
1032	Provides a simple web application server framework.	1162	Executes DBI requests asynchronously in a proxy process for you,
		1163	notifying you in an event-based way when the operation is finished.
1033		1164
1034	AnyEvent::FastPing	1165	AnyEvent::FastPing
1035	The fastest ping in the west.	1166	The fastest ping in the west.
1036		1167
1037	AnyEvent::DBI
1038	Executes DBI requests asynchronously in a proxy process.
1039
1040	AnyEvent::AIO
1041	Truly asynchronous I/O, should be in the toolbox of every event
1042	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
1043	together.
1044
1045	AnyEvent::BDB
1046	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
1047	fuses BDB and AnyEvent together.
1048
1049	AnyEvent::GPSD
1050	A non-blocking interface to gpsd, a daemon delivering GPS
1051	information.
1052
1053	AnyEvent::IRC
1054	AnyEvent based IRC client module family (replacing the older
1055	Net::IRC3).
1056
1057	AnyEvent::XMPP
1058	AnyEvent based XMPP (Jabber protocol) module family (replacing the
1059	older Net::XMPP2>.
1060
1061	AnyEvent::IGS
1062	A non-blocking interface to the Internet Go Server protocol (used by
1063	App::IGS).
1064
1065	Net::FCP
1066	AnyEvent-based implementation of the Freenet Client Protocol,
1067	birthplace of AnyEvent.
1068
1069	Event::ExecFlow
1070	High level API for event-based execution flow control.
1071
1072	Coro	1168	Coro
1073	Has special support for AnyEvent via Coro::AnyEvent.	1169	Has special support for AnyEvent via Coro::AnyEvent, which allows
		1170	you to simply invert the flow control - don't call us, we will call
		1171	you:
		1172
		1173	async {
		1174	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1175	print "5 seconds later!\n";
		1176
		1177	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1178	my $line = <STDIN>; # works for ttys
		1179
		1180	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1181	my ($body, $hdr) = Coro::rouse_wait;
		1182	};
1074		1183
1075	SIMPLIFIED AE API	1184	SIMPLIFIED AE API
1076	Starting with version 5.0, AnyEvent officially supports a second, much	1185	Starting with version 5.0, AnyEvent officially supports a second, much
1077	simpler, API that is designed to reduce the calling, typing and memory	1186	simpler, API that is designed to reduce the calling, typing and memory
1078	overhead.	1187	overhead by using function call syntax and a fixed number of parameters.
1079		1188
1080	See the AE manpage for details.	1189	See the AE manpage for details.
1081		1190
1082	ERROR AND EXCEPTION HANDLING	1191	ERROR AND EXCEPTION HANDLING
1083	In general, AnyEvent does not do any error handling - it relies on the	1192	In general, AnyEvent does not do any error handling - it relies on the
…		…
1094	The pure perl event loop simply re-throws the exception (usually within	1203	The pure perl event loop simply re-throws the exception (usually within
1095	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1204	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
1096	Glib uses "install_exception_handler" and so on.	1205	Glib uses "install_exception_handler" and so on.
1097		1206
1098	ENVIRONMENT VARIABLES	1207	ENVIRONMENT VARIABLES
1099	The following environment variables are used by this module or its	1208	AnyEvent supports a number of environment variables that tune the
1100	submodules.	1209	runtime behaviour. They are usually evaluated when AnyEvent is loaded,
		1210	initialised, or a submodule that uses them is loaded. Many of them also
		1211	cause AnyEvent to load additional modules - for example,
		1212	"PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be
		1213	loaded.
1101		1214
1102	Note that AnyEvent will remove all environment variables starting with	1215	All the environment variables documented here start with
1103	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is	1216	"PERL_ANYEVENT_", which is what AnyEvent considers its own namespace.
1104	enabled.	1217	Other modules are encouraged (but by no means required) to use
		1218	"PERL_ANYEVENT_SUBMODULE" if they have registered the
		1219	AnyEvent::Submodule namespace on CPAN, for any submodule. For example,
		1220	AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it
		1221	should not access env variables starting with "AE_", see below).
		1222
		1223	All variables can also be set via the "AE_" prefix, that is, instead of
		1224	setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case
		1225	there is a clash btween anyevent and another program that uses
		1226	"AE_something" you can set the corresponding "PERL_ANYEVENT_something"
		1227	variable to the empty string, as those variables take precedence.
		1228
		1229	When AnyEvent is first loaded, it copies all "AE_xxx" env variables to
		1230	their "PERL_ANYEVENT_xxx" counterpart unless that variable already
		1231	exists. If taint mode is on, then AnyEvent will remove all environment
		1232	variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with
		1233	"undef" or the empty string, if the corresaponding "AE_" variable is
		1234	set).
		1235
		1236	The exact algorithm is currently:
		1237
		1238	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		1239	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		1240	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		1241
		1242	This ensures that child processes will not see the "AE_" variables.
		1243
		1244	The following environment variables are currently known to AnyEvent:
1105		1245
1106	"PERL_ANYEVENT_VERBOSE"	1246	"PERL_ANYEVENT_VERBOSE"
1107	By default, AnyEvent will be completely silent except in fatal	1247	By default, AnyEvent will log messages with loglevel 4 ("error") or
1108	conditions. You can set this environment variable to make AnyEvent	1248	higher (see AnyEvent::Log). You can set this environment variable to
1109	more talkative.	1249	a numerical loglevel to make AnyEvent more (or less) talkative.
1110		1250
		1251	If you want to do more than just set the global logging level you
		1252	should have a look at "PERL_ANYEVENT_LOG", which allows much more
		1253	complex specifications.
		1254
		1255	When set to 0 ("off"), then no messages whatsoever will be logged
		1256	with everything else at defaults.
		1257
1111	When set to 1 or higher, causes AnyEvent to warn about unexpected	1258	When set to 5 or higher ("warn"), AnyEvent warns about unexpected
1112	conditions, such as not being able to load the event model specified	1259	conditions, such as not being able to load the event model specified
1113	by "PERL_ANYEVENT_MODEL".	1260	by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception
		1261	- this is the minimum recommended level for use during development.
1114		1262
1115	When set to 2 or higher, cause AnyEvent to report to STDERR which	1263	When set to 7 or higher (info), AnyEvent reports which event model
1116	event model it chooses.	1264	it chooses.
1117		1265
1118	When set to 8 or higher, then AnyEvent will report extra information	1266	When set to 8 or higher (debug), then AnyEvent will report extra
1119	on which optional modules it loads and how it implements certain	1267	information on which optional modules it loads and how it implements
1120	features.	1268	certain features.
		1269
		1270	"PERL_ANYEVENT_LOG"
		1271	Accepts rather complex logging specifications. For example, you
		1272	could log all "debug" messages of some module to stderr, warnings
		1273	and above to stderr, and errors and above to syslog, with:
		1274
		1275	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		1276
		1277	For the rather extensive details, see AnyEvent::Log.
		1278
		1279	This variable is evaluated when AnyEvent (or AnyEvent::Log) is
		1280	loaded, so will take effect even before AnyEvent has initialised
		1281	itself.
		1282
		1283	Note that specifying this environment variable causes the
		1284	AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE"
		1285	does not, so only using the latter saves a few hundred kB of memory
		1286	unless a module explicitly needs the extra features of
		1287	AnyEvent::Log.
1121		1288
1122	"PERL_ANYEVENT_STRICT"	1289	"PERL_ANYEVENT_STRICT"
1123	AnyEvent does not do much argument checking by default, as thorough	1290	AnyEvent does not do much argument checking by default, as thorough
1124	argument checking is very costly. Setting this variable to a true	1291	argument checking is very costly. Setting this variable to a true
1125	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1292	value will cause AnyEvent to load "AnyEvent::Strict" and then to
1126	thoroughly check the arguments passed to most method calls. If it	1293	thoroughly check the arguments passed to most method calls. If it
1127	finds any problems, it will croak.	1294	finds any problems, it will croak.
1128		1295
1129	In other words, enables "strict" mode.	1296	In other words, enables "strict" mode.
1130		1297
1131	Unlike "use strict" (or it's modern cousin, "use common::sense", it	1298	Unlike "use strict" (or its modern cousin, "use common::sense", it
1132	is definitely recommended to keep it off in production. Keeping	1299	is definitely recommended to keep it off in production. Keeping
1133	"PERL_ANYEVENT_STRICT=1" in your environment while developing	1300	"PERL_ANYEVENT_STRICT=1" in your environment while developing
1134	programs can be very useful, however.	1301	programs can be very useful, however.
1135		1302
		1303	"PERL_ANYEVENT_DEBUG_SHELL"
		1304	If this env variable is nonempty, then its contents will be
		1305	interpreted by "AnyEvent::Socket::parse_hostport" and
		1306	"AnyEvent::Debug::shell" (after replacing every occurance of $$ by
		1307	the process pid). The shell object is saved in
		1308	$AnyEvent::Debug::SHELL.
		1309
		1310	This happens when the first watcher is created.
		1311
		1312	For example, to bind a debug shell on a unix domain socket in
		1313	/tmp/debug<pid>.sock, you could use this:
		1314
		1315	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		1316	# connect with e.g.: socat readline /tmp/debug123.sock
		1317
		1318	Or to bind to tcp port 4545 on localhost:
		1319
		1320	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		1321	# connect with e.g.: telnet localhost 4545
		1322
		1323	Note that creating sockets in /tmp or on localhost is very unsafe on
		1324	multiuser systems.
		1325
		1326	"PERL_ANYEVENT_DEBUG_WRAP"
		1327	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1328	debugging purposes. See "AnyEvent::Debug::wrap" for details.
		1329
1136	"PERL_ANYEVENT_MODEL"	1330	"PERL_ANYEVENT_MODEL"
1137	This can be used to specify the event model to be used by AnyEvent,	1331	This can be used to specify the event model to be used by AnyEvent,
1138	before auto detection and -probing kicks in. It must be a string	1332	before auto detection and -probing kicks in.
1139	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1333
1140	gets prepended and the resulting module name is loaded and if the	1334	It normally is a string consisting entirely of ASCII letters (e.g.
1141	load was successful, used as event model. If it fails to load	1335	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1336	the resulting module name is loaded and - if the load was successful
		1337	- used as event model backend. If it fails to load then AnyEvent
1142	AnyEvent will proceed with auto detection and -probing.	1338	will proceed with auto detection and -probing.
1143		1339
1144	This functionality might change in future versions.	1340	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1341	then nothing gets prepended and the module name is used as-is (hint:
		1342	"::" at the end of a string designates a module name and quotes it
		1343	appropriately).
1145		1344
1146	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1345	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
1147	could start your program like this:	1346	could start your program like this:
1148		1347
1149	PERL_ANYEVENT_MODEL=Perl perl ...	1348	PERL_ANYEVENT_MODEL=Perl perl ...
		1349
		1350	"PERL_ANYEVENT_IO_MODEL"
		1351	The current file I/O model - see AnyEvent::IO for more info.
		1352
		1353	At the moment, only "Perl" (small, pure-perl, synchronous) and
		1354	"IOAIO" (truly asynchronous) are supported. The default is "IOAIO"
		1355	if AnyEvent::AIO can be loaded, otherwise it is "Perl".
1150		1356
1151	"PERL_ANYEVENT_PROTOCOLS"	1357	"PERL_ANYEVENT_PROTOCOLS"
1152	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1358	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
1153	preferences for IPv4 or IPv6. The default is unspecified (and might	1359	preferences for IPv4 or IPv6. The default is unspecified (and might
1154	change, or be the result of auto probing).	1360	change, or be the result of auto probing).
…		…
1158	mentioned will be used, and preference will be given to protocols	1364	mentioned will be used, and preference will be given to protocols
1159	mentioned earlier in the list.	1365	mentioned earlier in the list.
1160		1366
1161	This variable can effectively be used for denial-of-service attacks	1367	This variable can effectively be used for denial-of-service attacks
1162	against local programs (e.g. when setuid), although the impact is	1368	against local programs (e.g. when setuid), although the impact is
1163	likely small, as the program has to handle conenction and other	1369	likely small, as the program has to handle connection and other
1164	failures anyways.	1370	failures anyways.
1165		1371
1166	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1372	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
1167	IPv6, but support both and try to use both.	1373	IPv6, but support both and try to use both.
1168	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1374	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
1169	resolve or contact IPv6 addresses.	1375	resolve or contact IPv6 addresses.
1170	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but	1376	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
1171	prefer IPv6 over IPv4.	1377	prefer IPv6 over IPv4.
1172		1378
		1379	"PERL_ANYEVENT_HOSTS"
		1380	This variable, if specified, overrides the /etc/hosts file used by
		1381	AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be
		1382	read from that file instead.
		1383
1173	"PERL_ANYEVENT_EDNS0"	1384	"PERL_ANYEVENT_EDNS0"
1174	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension	1385	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
1175	for DNS. This extension is generally useful to reduce DNS traffic,	1386	for DNS. This extension is generally useful to reduce DNS traffic,
1176	but some (broken) firewalls drop such DNS packets, which is why it	1387	especially when DNSSEC is involved, but some (broken) firewalls drop
1177	is off by default.	1388	such DNS packets, which is why it is off by default.
1178		1389
1179	Setting this variable to 1 will cause AnyEvent::DNS to announce	1390	Setting this variable to 1 will cause AnyEvent::DNS to announce
1180	EDNS0 in its DNS requests.	1391	EDNS0 in its DNS requests.
1181		1392
1182	"PERL_ANYEVENT_MAX_FORKS"	1393	"PERL_ANYEVENT_MAX_FORKS"
…		…
1186	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"	1397	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
1187	The default value for the "max_outstanding" parameter for the	1398	The default value for the "max_outstanding" parameter for the
1188	default DNS resolver - this is the maximum number of parallel DNS	1399	default DNS resolver - this is the maximum number of parallel DNS
1189	requests that are sent to the DNS server.	1400	requests that are sent to the DNS server.
1190		1401
		1402	"PERL_ANYEVENT_MAX_SIGNAL_LATENCY"
		1403	Perl has inherently racy signal handling (you can basically choose
		1404	between losing signals and memory corruption) - pure perl event
		1405	loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't
		1406	available) therefore have to poll regularly to avoid losing signals.
		1407
		1408	Some event loops are racy, but don't poll regularly, and some event
		1409	loops are written in C but are still racy. For those event loops,
		1410	AnyEvent installs a timer that regularly wakes up the event loop.
		1411
		1412	By default, the interval for this timer is 10 seconds, but you can
		1413	override this delay with this environment variable (or by setting
		1414	the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal
		1415	watchers).
		1416
		1417	Lower values increase CPU (and energy) usage, higher values can
		1418	introduce long delays when reaping children or waiting for signals.
		1419
		1420	The AnyEvent::Async module, if available, will be used to avoid this
		1421	polling (with most event loops).
		1422
1191	"PERL_ANYEVENT_RESOLV_CONF"	1423	"PERL_ANYEVENT_RESOLV_CONF"
1192	The file to use instead of /etc/resolv.conf (or OS-specific	1424	The absolute path to a resolv.conf-style file to use instead of
1193	configuration) in the default resolver. When set to the empty	1425	/etc/resolv.conf (or the OS-specific configuration) in the default
1194	string, no default config will be used.	1426	resolver, or the empty string to select the default configuration.
1195		1427
1196	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".	1428	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1197	When neither "ca_file" nor "ca_path" was specified during	1429	When neither "ca_file" nor "ca_path" was specified during
1198	AnyEvent::TLS context creation, and either of these environment	1430	AnyEvent::TLS context creation, and either of these environment
1199	variables exist, they will be used to specify CA certificate	1431	variables are nonempty, they will be used to specify CA certificate
1200	locations instead of a system-dependent default.	1432	locations instead of a system-dependent default.
1201		1433
1202	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"	1434	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
1203	When these are set to 1, then the respective modules are not loaded.	1435	When these are set to 1, then the respective modules are not loaded.
1204	Mostly good for testing AnyEvent itself.	1436	Mostly good for testing AnyEvent itself.
…		…
1348		1580
1349	The actual code goes further and collects all errors ("die"s,	1581	The actual code goes further and collects all errors ("die"s,
1350	exceptions) that occurred during request processing. The "result" method	1582	exceptions) that occurred during request processing. The "result" method
1351	detects whether an exception as thrown (it is stored inside the $txn	1583	detects whether an exception as thrown (it is stored inside the $txn
1352	object) and just throws the exception, which means connection errors and	1584	object) and just throws the exception, which means connection errors and
1353	other problems get reported tot he code that tries to use the result,	1585	other problems get reported to the code that tries to use the result,
1354	not in a random callback.	1586	not in a random callback.
1355		1587
1356	All of this enables the following usage styles:	1588	All of this enables the following usage styles:
1357		1589
1358	1. Blocking:	1590	1. Blocking:
…		…
1376	my $txn = shift;	1608	my $txn = shift;
1377	my $data = $txn->result;	1609	my $data = $txn->result;
1378	...	1610	...
1379	});	1611	});
1380		1612
1381	EV::loop;	1613	EV::run;
1382		1614
1383	3b. The module user could use AnyEvent, too:	1615	3b. The module user could use AnyEvent, too:
1384		1616
1385	use AnyEvent;	1617	use AnyEvent;
1386		1618
…		…
1524	when used without AnyEvent), but most event loops have acceptable	1756	when used without AnyEvent), but most event loops have acceptable
1525	performance with or without AnyEvent.	1757	performance with or without AnyEvent.
1526		1758
1527	* The overhead AnyEvent adds is usually much smaller than the overhead	1759	* The overhead AnyEvent adds is usually much smaller than the overhead
1528	of the actual event loop, only with extremely fast event loops such	1760	of the actual event loop, only with extremely fast event loops such
1529	as EV adds AnyEvent significant overhead.	1761	as EV does AnyEvent add significant overhead.
1530		1762
1531	* You should avoid POE like the plague if you want performance or	1763	* You should avoid POE like the plague if you want performance or
1532	reasonable memory usage.	1764	reasonable memory usage.
1533		1765
1534	BENCHMARKING THE LARGE SERVER CASE	1766	BENCHMARKING THE LARGE SERVER CASE
…		…
1732		1964
1733	Feel free to install your own handler, or reset it to defaults.	1965	Feel free to install your own handler, or reset it to defaults.
1734		1966
1735	RECOMMENDED/OPTIONAL MODULES	1967	RECOMMENDED/OPTIONAL MODULES
1736	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and	1968	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
1737	it's built-in modules) are required to use it.	1969	its built-in modules) are required to use it.
1738		1970
1739	That does not mean that AnyEvent won't take advantage of some additional	1971	That does not mean that AnyEvent won't take advantage of some additional
1740	modules if they are installed.	1972	modules if they are installed.
1741		1973
1742	This section explains which additional modules will be used, and how	1974	This section explains which additional modules will be used, and how
…		…
1771	clock is available, can take avdantage of advanced kernel interfaces	2003	clock is available, can take avdantage of advanced kernel interfaces
1772	such as "epoll" and "kqueue", and is the fastest backend by far.	2004	such as "epoll" and "kqueue", and is the fastest backend by far.
1773	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and	2005	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
1774	Glib::EV).	2006	Glib::EV).
1775		2007
		2008	If you only use backends that rely on another event loop (e.g.
		2009	"Tk"), then this module will do nothing for you.
		2010
1776	Guard	2011	Guard
1777	The guard module, when used, will be used to implement	2012	The guard module, when used, will be used to implement
1778	"AnyEvent::Util::guard". This speeds up guards considerably (and	2013	"AnyEvent::Util::guard". This speeds up guards considerably (and
1779	uses a lot less memory), but otherwise doesn't affect guard	2014	uses a lot less memory), but otherwise doesn't affect guard
1780	operation much. It is purely used for performance.	2015	operation much. It is purely used for performance.
1781		2016
1782	JSON and JSON::XS	2017	JSON and JSON::XS
1783	One of these modules is required when you want to read or write JSON	2018	One of these modules is required when you want to read or write JSON
1784	data via AnyEvent::Handle. It is also written in pure-perl, but can	2019	data via AnyEvent::Handle. JSON is also written in pure-perl, but
1785	take advantage of the ultra-high-speed JSON::XS module when it is	2020	can take advantage of the ultra-high-speed JSON::XS module when it
1786	installed.	2021	is installed.
1787
1788	In fact, AnyEvent::Handle will use JSON::XS by default if it is
1789	installed.
1790		2022
1791	Net::SSLeay	2023	Net::SSLeay
1792	Implementing TLS/SSL in Perl is certainly interesting, but not very	2024	Implementing TLS/SSL in Perl is certainly interesting, but not very
1793	worthwhile: If this module is installed, then AnyEvent::Handle (with	2025	worthwhile: If this module is installed, then AnyEvent::Handle (with
1794	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.	2026	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
1795		2027
1796	Time::HiRes	2028	Time::HiRes
1797	This module is part of perl since release 5.008. It will be used	2029	This module is part of perl since release 5.008. It will be used
1798	when the chosen event library does not come with a timing source on	2030	when the chosen event library does not come with a timing source of
1799	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will	2031	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
1800	additionally use it to try to use a monotonic clock for timing	2032	load it to try to use a monotonic clock for timing stability.
1801	stability.	2033
		2034	AnyEvent::AIO (and IO::AIO)
		2035	The default implementation of AnyEvent::IO is to do I/O
		2036	synchronously, stopping programs while they access the disk, which
		2037	is fine for a lot of programs.
		2038
		2039	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it
		2040	switch to a true asynchronous implementation, so event processing
		2041	can continue even while waiting for disk I/O.
1802		2042
1803	FORK	2043	FORK
1804	Most event libraries are not fork-safe. The ones who are usually are	2044	Most event libraries are not fork-safe. The ones who are usually are
1805	because they rely on inefficient but fork-safe "select" or "poll" calls.	2045	because they rely on inefficient but fork-safe "select" or "poll" calls
1806	Only EV is fully fork-aware.	2046	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		2047	epoll are usually badly thought-out hacks that are incompatible with
		2048	fork in one way or another. Only EV is fully fork-aware and ensures that
		2049	you continue event-processing in both parent and child (or both, if you
		2050	know what you are doing).
1807		2051
1808	This means that, in general, you cannot fork and do event processing in	2052	This means that, in general, you cannot fork and do event processing in
1809	the child if a watcher was created before the fork (which in turn	2053	the child if the event library was initialised before the fork (which
1810	initialises the event library).	2054	usually happens when the first AnyEvent watcher is created, or the
		2055	library is loaded).
1811		2056
1812	If you have to fork, you must either do so before creating your first	2057	If you have to fork, you must either do so before creating your first
1813	watcher OR you must not use AnyEvent at all in the child OR you must do	2058	watcher OR you must not use AnyEvent at all in the child OR you must do
1814	something completely out of the scope of AnyEvent.	2059	something completely out of the scope of AnyEvent (see below).
1815		2060
1816	The problem of doing event processing in the parent and the child is	2061	The problem of doing event processing in the parent and the child is
1817	much more complicated: even for backends that are fork-aware or	2062	much more complicated: even for backends that are fork-aware or
1818	fork-safe, their behaviour is not usually what you want: fork clones all	2063	fork-safe, their behaviour is not usually what you want: fork clones all
1819	watchers, that means all timers, I/O watchers etc. are active in both	2064	watchers, that means all timers, I/O watchers etc. are active in both
1820	parent and child, which is almost never what you want.	2065	parent and child, which is almost never what you want. Using "exec" to
		2066	start worker children from some kind of manage prrocess is usually
		2067	preferred, because it is much easier and cleaner, at the expense of
		2068	having to have another binary.
		2069
		2070	In addition to logical problems with fork, there are also implementation
		2071	problems. For example, on POSIX systems, you cannot fork at all in Perl
		2072	code if a thread (I am talking of pthreads here) was ever created in the
		2073	process, and this is just the tip of the iceberg. In general, using fork
		2074	from Perl is difficult, and attempting to use fork without an exec to
		2075	implement some kind of parallel processing is almost certainly doomed.
		2076
		2077	To safely fork and exec, you should use a module such as Proc::FastSpawn
		2078	that let's you safely fork and exec new processes.
		2079
		2080	If you want to do multiprocessing using processes, you can look at the
		2081	AnyEvent::Fork module (and some related modules such as
		2082	AnyEvent::Fork::RPC, AnyEvent::Fork::Pool and AnyEvent::Fork::Remote).
		2083	This module allows you to safely create subprocesses without any
		2084	limitations - you can use X11 toolkits or AnyEvent in the children
		2085	created by AnyEvent::Fork safely and without any special precautions.
1821		2086
1822	SECURITY CONSIDERATIONS	2087	SECURITY CONSIDERATIONS
1823	AnyEvent can be forced to load any event model via	2088	AnyEvent can be forced to load any event model via
1824	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	2089	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1825	to execute arbitrary code or directly gain access, it can easily be used	2090	to execute arbitrary code or directly gain access, it can easily be used
…		…
1849	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	2114	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1850	annoying memleaks, such as leaking on "map" and "grep" but it is usually	2115	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1851	not as pronounced).	2116	not as pronounced).
1852		2117
1853	SEE ALSO	2118	SEE ALSO
1854	Utility functions: AnyEvent::Util.	2119	Tutorial/Introduction: AnyEvent::Intro.
1855		2120
1856	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	2121	FAQ: AnyEvent::FAQ.
1857	Event::Lib, Qt, POE.	2122
		2123	Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log
		2124	(simply logging).
		2125
		2126	Development/Debugging: AnyEvent::Strict (stricter checking),
		2127	AnyEvent::Debug (interactive shell, watcher tracing).
		2128
		2129	Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
		2130	Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK, Cocoa::EventLoop, UV.
1858		2131
1859	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	2132	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1860	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	2133	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1861	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,	2134	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		2135	AnyEvent::Impl::IOAsync, AnyEvent::Impl::Irssi, AnyEvent::Impl::FLTK,
1862	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.	2136	AnyEvent::Impl::Cocoa, AnyEvent::Impl::UV.
1863		2137
1864	Non-blocking file handles, sockets, TCP clients and servers:	2138	Non-blocking handles, pipes, stream sockets, TCP clients and servers:
1865	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.	2139	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1866		2140
		2141	Asynchronous File I/O: AnyEvent::IO.
		2142
1867	Asynchronous DNS: AnyEvent::DNS.	2143	Asynchronous DNS: AnyEvent::DNS.
1868		2144
1869	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	2145	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1870		2146
1871	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,	2147	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
1872	AnyEvent::HTTP.	2148	AnyEvent::HTTP.
1873		2149
1874	AUTHOR	2150	AUTHOR
1875	Marc Lehmann <schmorp@schmorp.de>	2151	Marc Lehmann <schmorp@schmorp.de>
1876	http://home.schmorp.de/	2152	http://anyevent.schmorp.de
1877		2153

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Comparing AnyEvent/README (file contents):
Revision 1.58 by root, Sun Dec 20 22:49:52 2009 UTC vs.
Revision 1.76 by root, Wed Jan 27 18:15:21 2016 UTC