[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.57 by root, Sat Dec 5 02:52:03 2009 UTC vs.
Revision 1.77 by root, Sat Sep 17 02:33:54 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
782	Returns true when the condition is "true", i.e. whether "send" or	813	Returns true when the condition is "true", i.e. whether "send" or
783	"croak" have been called.	814	"croak" have been called.
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 (or "undef"
787	optionally replaces it before doing so.	818	if not) and 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.
		825
		826	Additionally, when the callback is invoked, it is also removed from
		827	the condvar (reset to "undef"), so the condvar does not keep a
		828	reference to the callback after invocation.
794		829
795	SUPPORTED EVENT LOOPS/BACKENDS	830	SUPPORTED EVENT LOOPS/BACKENDS
796	The available backend classes are (every class has its own manpage):	831	The available backend classes are (every class has its own manpage):
797		832
798	Backends that are autoprobed when no other event loop can be found.	833	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	835	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	836	pure-perl implementation, which is available everywhere as it comes
802	with AnyEvent itself.	837	with AnyEvent itself.
803		838
804	AnyEvent::Impl::EV based on EV (interface to libev, best choice).	839	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
805	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.	840	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
806		841
807	Backends that are transparently being picked up when they are used.	842	Backends that are transparently being picked up when they are used.
808	These will be used when they are currently loaded when the first	843	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	844	is created, in which case it is assumed that the application is
810	is using them. This means that AnyEvent will automatically pick the	845	using them. This means that AnyEvent will automatically pick the
811	right backend when the main program loads an event module before	846	right backend when the main program loads an event module before
812	anything starts to create watchers. Nothing special needs to be done	847	anything starts to create watchers. Nothing special needs to be done
813	by the main program.	848	by the main program.
814		849
815	AnyEvent::Impl::Event based on Event, very stable, few glitches.	850	AnyEvent::Impl::Event based on Event, very stable, few glitches.
816	AnyEvent::Impl::Glib based on Glib, slow but very stable.	851	AnyEvent::Impl::Glib based on Glib, slow but very stable.
817	AnyEvent::Impl::Tk based on Tk, very broken.	852	AnyEvent::Impl::Tk based on Tk, very broken.
		853	AnyEvent::Impl::UV based on UV, innovated square wheels.
818	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	854	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
819	AnyEvent::Impl::POE based on POE, very slow, some limitations.	855	AnyEvent::Impl::POE based on POE, very slow, some limitations.
820	AnyEvent::Impl::Irssi used when running within irssi.	856	AnyEvent::Impl::Irssi used when running within irssi.
		857	AnyEvent::Impl::IOAsync based on IO::Async.
		858	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		859	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
821		860
822	Backends with special needs.	861	Backends with special needs.
823	Qt requires the Qt::Application to be instantiated first, but will	862	Qt requires the Qt::Application to be instantiated first, but will
824	otherwise be picked up automatically. As long as the main program	863	otherwise be picked up automatically. As long as the main program
825	instantiates the application before any AnyEvent watchers are	864	instantiates the application before any AnyEvent watchers are
826	created, everything should just work.	865	created, everything should just work.
827		866
828	AnyEvent::Impl::Qt based on Qt.	867	AnyEvent::Impl::Qt based on Qt.
829		868
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.	869	Event loops that are indirectly supported via other backends.
839	Some event loops can be supported via other modules:	870	Some event loops can be supported via other modules:
840		871
841	There is no direct support for WxWidgets (Wx) or Prima.	872	There is no direct support for WxWidgets (Wx) or Prima.
842		873
…		…
860	Contains "undef" until the first watcher is being created, before	891	Contains "undef" until the first watcher is being created, before
861	the backend has been autodetected.	892	the backend has been autodetected.
862		893
863	Afterwards it contains the event model that is being used, which is	894	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	895	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	896	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.	897	other class in the case AnyEvent has been extended at runtime (e.g.
867	in rxvt-unicode it will be "urxvt::anyevent").	898	in rxvt-unicode it will be "urxvt::anyevent").
868		899
869	AnyEvent::detect	900	AnyEvent::detect
870	Returns $AnyEvent::MODEL, forcing autodetection of the event model	901	Returns $AnyEvent::MODEL, forcing autodetection of the event model
871	if necessary. You should only call this function right before you	902	if necessary. You should only call this function right before you
872	would have created an AnyEvent watcher anyway, that is, as late as	903	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.	904	possible at runtime, and not e.g. during initialisation of your
		905	module.
		906
		907	The effect of calling this function is as if a watcher had been
		908	created (specifically, actions that happen "when the first watcher
		909	is created" happen when calling detetc as well).
874		910
875	If you need to do some initialisation before AnyEvent watchers are	911	If you need to do some initialisation before AnyEvent watchers are
876	created, use "post_detect".	912	created, use "post_detect".
877		913
878	$guard = AnyEvent::post_detect { BLOCK }	914	$guard = AnyEvent::post_detect { BLOCK }
879	Arranges for the code block to be executed as soon as the event	915	Arranges for the code block to be executed as soon as the event
880	model is autodetected (or immediately if this has already happened).	916	model is autodetected (or immediately if that has already happened).
881		917
882	The block will be executed after the actual backend has been	918	The block will be executed after the actual backend has been
883	detected ($AnyEvent::MODEL is set), but before any watchers have	919	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	920	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
885	other initialisations - see the sources of AnyEvent::Strict or	921	other initialisations - see the sources of AnyEvent::Strict or
…		…
894	object that automatically removes the callback again when it is	930	object that automatically removes the callback again when it is
895	destroyed (or "undef" when the hook was immediately executed). See	931	destroyed (or "undef" when the hook was immediately executed). See
896	AnyEvent::AIO for a case where this is useful.	932	AnyEvent::AIO for a case where this is useful.
897		933
898	Example: Create a watcher for the IO::AIO module and store it in	934	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.	935	$WATCHER, but do so only do so after the event loop is initialised.
900		936
901	our WATCHER;	937	our WATCHER;
902		938
903	my $guard = AnyEvent::post_detect {	939	my $guard = AnyEvent::post_detect {
904	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);	940	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
…		…
911		947
912	$WATCHER \|\|= $guard;	948	$WATCHER \|\|= $guard;
913		949
914	@AnyEvent::post_detect	950	@AnyEvent::post_detect
915	If there are any code references in this array (you can "push" to it	951	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	952	before or after loading AnyEvent), then they will be called directly
917	after the event loop has been chosen.	953	after the event loop has been chosen.
918		954
919	You should check $AnyEvent::MODEL before adding to this array,	955	You should check $AnyEvent::MODEL before adding to this array,
920	though: if it is defined then the event loop has already been	956	though: if it is defined then the event loop has already been
921	detected, and the array will be ignored.	957	detected, and the array will be ignored.
922		958
923	Best use "AnyEvent::post_detect { BLOCK }" when your application	959	Best use "AnyEvent::post_detect { BLOCK }" when your application
924	allows it,as it takes care of these details.	960	allows it, as it takes care of these details.
925		961
926	This variable is mainly useful for modules that can do something	962	This variable is mainly useful for modules that can do something
927	useful when AnyEvent is used and thus want to know when it is	963	useful when AnyEvent is used and thus want to know when it is
928	initialised, but do not need to even load it by default. This array	964	initialised, but do not need to even load it by default. This array
929	provides the means to hook into AnyEvent passively, without loading	965	provides the means to hook into AnyEvent passively, without loading
930	it.	966	it.
931		967
		968	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		969	together, you could put this into Coro (this is the actual code used
		970	by Coro to accomplish this):
		971
		972	if (defined $AnyEvent::MODEL) {
		973	# AnyEvent already initialised, so load Coro::AnyEvent
		974	require Coro::AnyEvent;
		975	} else {
		976	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		977	# as soon as it is
		978	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		979	}
		980
		981	AnyEvent::postpone { BLOCK }
		982	Arranges for the block to be executed as soon as possible, but not
		983	before the call itself returns. In practise, the block will be
		984	executed just before the event loop polls for new events, or shortly
		985	afterwards.
		986
		987	This function never returns anything (to make the "return postpone {
		988	... }" idiom more useful.
		989
		990	To understand the usefulness of this function, consider a function
		991	that asynchronously does something for you and returns some
		992	transaction object or guard to let you cancel the operation. For
		993	example, "AnyEvent::Socket::tcp_connect":
		994
		995	# start a connection attempt unless one is active
		996	$self->{connect_guard} \|\|= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		997	delete $self->{connect_guard};
		998	...
		999	};
		1000
		1001	Imagine that this function could instantly call the callback, for
		1002	example, because it detects an obvious error such as a negative port
		1003	number. Invoking the callback before the function returns causes
		1004	problems however: the callback will be called and will try to delete
		1005	the guard object. But since the function hasn't returned yet, there
		1006	is nothing to delete. When the function eventually returns it will
		1007	assign the guard object to "$self->{connect_guard}", where it will
		1008	likely never be deleted, so the program thinks it is still trying to
		1009	connect.
		1010
		1011	This is where "AnyEvent::postpone" should be used. Instead of
		1012	calling the callback directly on error:
		1013
		1014	$cb->(undef), return # signal error to callback, BAD!
		1015	if $some_error_condition;
		1016
		1017	It should use "postpone":
		1018
		1019	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1020	if $some_error_condition;
		1021
		1022	AnyEvent::log $level, $msg[, @args]
		1023	Log the given $msg at the given $level.
		1024
		1025	If AnyEvent::Log is not loaded then this function makes a simple
		1026	test to see whether the message will be logged. If the test succeeds
		1027	it will load AnyEvent::Log and call "AnyEvent::Log::log" -
		1028	consequently, look at the AnyEvent::Log documentation for details.
		1029
		1030	If the test fails it will simply return. Right now this happens when
		1031	a numerical loglevel is used and it is larger than the level
		1032	specified via $ENV{PERL_ANYEVENT_VERBOSE}.
		1033
		1034	If you want to sprinkle loads of logging calls around your code,
		1035	consider creating a logger callback with the "AnyEvent::Log::logger"
		1036	function, which can reduce typing, codesize and can reduce the
		1037	logging overhead enourmously.
		1038
		1039	AnyEvent::fh_block $filehandle
		1040	AnyEvent::fh_unblock $filehandle
		1041	Sets blocking or non-blocking behaviour for the given filehandle.
		1042
932	WHAT TO DO IN A MODULE	1043	WHAT TO DO IN A MODULE
933	As a module author, you should "use AnyEvent" and call AnyEvent methods	1044	As a module author, you should "use AnyEvent" and call AnyEvent methods
934	freely, but you should not load a specific event module or rely on it.	1045	freely, but you should not load a specific event module or rely on it.
935		1046
936	Be careful when you create watchers in the module body - AnyEvent will	1047	Be careful when you create watchers in the module body - AnyEvent will
…		…
943	stall the whole program, and the whole point of using events is to stay	1054	stall the whole program, and the whole point of using events is to stay
944	interactive.	1055	interactive.
945		1056
946	It is fine, however, to call "->recv" when the user of your module	1057	It is fine, however, to call "->recv" when the user of your module
947	requests it (i.e. if you create a http request object ad have a method	1058	requests it (i.e. if you create a http request object ad have a method
948	called "results" that returns the results, it should call "->recv"	1059	called "results" that returns the results, it may call "->recv" freely,
949	freely, as the user of your module knows what she is doing. always).	1060	as the user of your module knows what she is doing. Always).
950		1061
951	WHAT TO DO IN THE MAIN PROGRAM	1062	WHAT TO DO IN THE MAIN PROGRAM
952	There will always be a single main program - the only place that should	1063	There will always be a single main program - the only place that should
953	dictate which event model to use.	1064	dictate which event model to use.
954		1065
955	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1066	If the program is not event-based, it need not do anything special, even
956	do anything special (it does not need to be event-based) and let	1067	when it depends on a module that uses an AnyEvent. If the program itself
957	AnyEvent decide which implementation to chose if some module relies on	1068	uses AnyEvent, but does not care which event loop is used, all it needs
958	it.	1069	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1070	available loop implementation.
959		1071
960	If the main program relies on a specific event model - for example, in	1072	If the main program relies on a specific event model - for example, in
961	Gtk2 programs you have to rely on the Glib module - you should load the	1073	Gtk2 programs you have to rely on the Glib module - you should load the
962	event module before loading AnyEvent or any module that uses it:	1074	event module before loading AnyEvent or any module that uses it:
963	generally speaking, you should load it as early as possible. The reason	1075	generally speaking, you should load it as early as possible. The reason
964	is that modules might create watchers when they are loaded, and AnyEvent	1076	is that modules might create watchers when they are loaded, and AnyEvent
965	will decide on the event model to use as soon as it creates watchers,	1077	will decide on the event model to use as soon as it creates watchers,
966	and it might chose the wrong one unless you load the correct one	1078	and it might choose the wrong one unless you load the correct one
967	yourself.	1079	yourself.
968		1080
969	You can chose to use a pure-perl implementation by loading the	1081	You can chose to use a pure-perl implementation by loading the
970	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1082	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
971	everywhere, but letting AnyEvent chose the model is generally better.	1083	but letting AnyEvent chose the model is generally better.
972		1084
973	MAINLOOP EMULATION	1085	MAINLOOP EMULATION
974	Sometimes (often for short test scripts, or even standalone programs who	1086	Sometimes (often for short test scripts, or even standalone programs who
975	only want to use AnyEvent), you do not want to run a specific event	1087	only want to use AnyEvent), you do not want to run a specific event
976	loop.	1088	loop.
…		…
988		1100
989	OTHER MODULES	1101	OTHER MODULES
990	The following is a non-exhaustive list of additional modules that use	1102	The following is a non-exhaustive list of additional modules that use
991	AnyEvent as a client and can therefore be mixed easily with other	1103	AnyEvent as a client and can therefore be mixed easily with other
992	AnyEvent modules and other event loops in the same program. Some of the	1104	AnyEvent modules and other event loops in the same program. Some of the
993	modules come with AnyEvent, most are available via CPAN.	1105	modules come as part of AnyEvent, the others are available via CPAN (see
		1106	<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
		1107	non-exhaustive list), and the list is heavily biased towards modules of
		1108	the AnyEvent author himself :)
994		1109
995	AnyEvent::Util	1110	AnyEvent::Util (part of the AnyEvent distribution)
996	Contains various utility functions that replace often-used but	1111	Contains various utility functions that replace often-used blocking
997	blocking functions such as "inet_aton" by event-/callback-based	1112	functions such as "inet_aton" with event/callback-based versions.
998	versions.
999		1113
1000	AnyEvent::Socket	1114	AnyEvent::Socket (part of the AnyEvent distribution)
1001	Provides various utility functions for (internet protocol) sockets,	1115	Provides various utility functions for (internet protocol) sockets,
1002	addresses and name resolution. Also functions to create non-blocking	1116	addresses and name resolution. Also functions to create non-blocking
1003	tcp connections or tcp servers, with IPv6 and SRV record support and	1117	tcp connections or tcp servers, with IPv6 and SRV record support and
1004	more.	1118	more.
1005		1119
1006	AnyEvent::Handle	1120	AnyEvent::Handle (part of the AnyEvent distribution)
1007	Provide read and write buffers, manages watchers for reads and	1121	Provide read and write buffers, manages watchers for reads and
1008	writes, supports raw and formatted I/O, I/O queued and fully	1122	writes, supports raw and formatted I/O, I/O queued and fully
1009	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.	1123	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
1010		1124
1011	AnyEvent::DNS	1125	AnyEvent::DNS (part of the AnyEvent distribution)
1012	Provides rich asynchronous DNS resolver capabilities.	1126	Provides rich asynchronous DNS resolver capabilities.
1013		1127
1014	AnyEvent::HTTP	1128	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
1015	A simple-to-use HTTP library that is capable of making a lot of	1129	AnyEvent::IGS, AnyEvent::FCP
1016	concurrent HTTP requests.	1130	Implement event-based interfaces to the protocols of the same name
		1131	(for the curious, IGS is the International Go Server and FCP is the
		1132	Freenet Client Protocol).
1017		1133
		1134	AnyEvent::AIO (part of the AnyEvent distribution)
		1135	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1136	the toolbox of every event programmer. AnyEvent::AIO transparently
		1137	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1138	event-based file I/O, and much more.
		1139
		1140	AnyEvent::Fork, AnyEvent::Fork::RPC, AnyEvent::Fork::Pool,
		1141	AnyEvent::Fork::Remote
		1142	These let you safely fork new subprocesses, either locally or
		1143	remotely (e.g.v ia ssh), using some RPC protocol or not, without the
		1144	limitations normally imposed by fork (AnyEvent works fine for
		1145	example). Dynamically-resized worker pools are obviously included as
		1146	well.
		1147
		1148	And they are quite tiny and fast as well - "abusing" AnyEvent::Fork
		1149	just to exec external programs can easily beat using "fork" and
		1150	"exec" (or even "system") in most programs.
		1151
		1152	AnyEvent::Filesys::Notify
		1153	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1154	path changes (e.g. "watch this directory for new files", "watch this
		1155	file for changes"). The AnyEvent::Filesys::Notify module promises to
		1156	do just that in a portbale fashion, supporting inotify on GNU/Linux
		1157	and some weird, without doubt broken, stuff on OS X to monitor
		1158	files. It can fall back to blocking scans at regular intervals
		1159	transparently on other platforms, so it's about as portable as it
		1160	gets.
		1161
		1162	(I haven't used it myself, but it seems the biggest problem with it
		1163	is it quite bad performance).
		1164
1018	AnyEvent::HTTPD	1165	AnyEvent::DBI
1019	Provides a simple web application server framework.	1166	Executes DBI requests asynchronously in a proxy process for you,
		1167	notifying you in an event-based way when the operation is finished.
1020		1168
1021	AnyEvent::FastPing	1169	AnyEvent::FastPing
1022	The fastest ping in the west.	1170	The fastest ping in the west.
1023		1171
1024	AnyEvent::DBI
1025	Executes DBI requests asynchronously in a proxy process.
1026
1027	AnyEvent::AIO
1028	Truly asynchronous I/O, should be in the toolbox of every event
1029	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
1030	together.
1031
1032	AnyEvent::BDB
1033	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
1034	fuses BDB and AnyEvent together.
1035
1036	AnyEvent::GPSD
1037	A non-blocking interface to gpsd, a daemon delivering GPS
1038	information.
1039
1040	AnyEvent::IRC
1041	AnyEvent based IRC client module family (replacing the older
1042	Net::IRC3).
1043
1044	AnyEvent::XMPP
1045	AnyEvent based XMPP (Jabber protocol) module family (replacing the
1046	older Net::XMPP2>.
1047
1048	AnyEvent::IGS
1049	A non-blocking interface to the Internet Go Server protocol (used by
1050	App::IGS).
1051
1052	Net::FCP
1053	AnyEvent-based implementation of the Freenet Client Protocol,
1054	birthplace of AnyEvent.
1055
1056	Event::ExecFlow
1057	High level API for event-based execution flow control.
1058
1059	Coro	1172	Coro
1060	Has special support for AnyEvent via Coro::AnyEvent.	1173	Has special support for AnyEvent via Coro::AnyEvent, which allows
		1174	you to simply invert the flow control - don't call us, we will call
		1175	you:
		1176
		1177	async {
		1178	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1179	print "5 seconds later!\n";
		1180
		1181	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1182	my $line = <STDIN>; # works for ttys
		1183
		1184	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1185	my ($body, $hdr) = Coro::rouse_wait;
		1186	};
1061		1187
1062	SIMPLIFIED AE API	1188	SIMPLIFIED AE API
1063	Starting with version 5.0, AnyEvent officially supports a second, much	1189	Starting with version 5.0, AnyEvent officially supports a second, much
1064	simpler, API that is designed to reduce the calling, typing and memory	1190	simpler, API that is designed to reduce the calling, typing and memory
1065	overhead.	1191	overhead by using function call syntax and a fixed number of parameters.
1066		1192
1067	See the AE manpage for details.	1193	See the AE manpage for details.
1068		1194
1069	ERROR AND EXCEPTION HANDLING	1195	ERROR AND EXCEPTION HANDLING
1070	In general, AnyEvent does not do any error handling - it relies on the	1196	In general, AnyEvent does not do any error handling - it relies on the
…		…
1081	The pure perl event loop simply re-throws the exception (usually within	1207	The pure perl event loop simply re-throws the exception (usually within
1082	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1208	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
1083	Glib uses "install_exception_handler" and so on.	1209	Glib uses "install_exception_handler" and so on.
1084		1210
1085	ENVIRONMENT VARIABLES	1211	ENVIRONMENT VARIABLES
1086	The following environment variables are used by this module or its	1212	AnyEvent supports a number of environment variables that tune the
1087	submodules.	1213	runtime behaviour. They are usually evaluated when AnyEvent is loaded,
		1214	initialised, or a submodule that uses them is loaded. Many of them also
		1215	cause AnyEvent to load additional modules - for example,
		1216	"PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be
		1217	loaded.
1088		1218
1089	Note that AnyEvent will remove all environment variables starting with	1219	All the environment variables documented here start with
1090	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is	1220	"PERL_ANYEVENT_", which is what AnyEvent considers its own namespace.
1091	enabled.	1221	Other modules are encouraged (but by no means required) to use
		1222	"PERL_ANYEVENT_SUBMODULE" if they have registered the
		1223	AnyEvent::Submodule namespace on CPAN, for any submodule. For example,
		1224	AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it
		1225	should not access env variables starting with "AE_", see below).
		1226
		1227	All variables can also be set via the "AE_" prefix, that is, instead of
		1228	setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case
		1229	there is a clash btween anyevent and another program that uses
		1230	"AE_something" you can set the corresponding "PERL_ANYEVENT_something"
		1231	variable to the empty string, as those variables take precedence.
		1232
		1233	When AnyEvent is first loaded, it copies all "AE_xxx" env variables to
		1234	their "PERL_ANYEVENT_xxx" counterpart unless that variable already
		1235	exists. If taint mode is on, then AnyEvent will remove all environment
		1236	variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with
		1237	"undef" or the empty string, if the corresaponding "AE_" variable is
		1238	set).
		1239
		1240	The exact algorithm is currently:
		1241
		1242	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		1243	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		1244	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		1245
		1246	This ensures that child processes will not see the "AE_" variables.
		1247
		1248	The following environment variables are currently known to AnyEvent:
1092		1249
1093	"PERL_ANYEVENT_VERBOSE"	1250	"PERL_ANYEVENT_VERBOSE"
1094	By default, AnyEvent will be completely silent except in fatal	1251	By default, AnyEvent will log messages with loglevel 4 ("error") or
1095	conditions. You can set this environment variable to make AnyEvent	1252	higher (see AnyEvent::Log). You can set this environment variable to
1096	more talkative.	1253	a numerical loglevel to make AnyEvent more (or less) talkative.
1097		1254
		1255	If you want to do more than just set the global logging level you
		1256	should have a look at "PERL_ANYEVENT_LOG", which allows much more
		1257	complex specifications.
		1258
		1259	When set to 0 ("off"), then no messages whatsoever will be logged
		1260	with everything else at defaults.
		1261
1098	When set to 1 or higher, causes AnyEvent to warn about unexpected	1262	When set to 5 or higher ("warn"), AnyEvent warns about unexpected
1099	conditions, such as not being able to load the event model specified	1263	conditions, such as not being able to load the event model specified
1100	by "PERL_ANYEVENT_MODEL".	1264	by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception
		1265	- this is the minimum recommended level for use during development.
1101		1266
1102	When set to 2 or higher, cause AnyEvent to report to STDERR which	1267	When set to 7 or higher (info), AnyEvent reports which event model
1103	event model it chooses.	1268	it chooses.
1104		1269
1105	When set to 8 or higher, then AnyEvent will report extra information	1270	When set to 8 or higher (debug), then AnyEvent will report extra
1106	on which optional modules it loads and how it implements certain	1271	information on which optional modules it loads and how it implements
1107	features.	1272	certain features.
		1273
		1274	"PERL_ANYEVENT_LOG"
		1275	Accepts rather complex logging specifications. For example, you
		1276	could log all "debug" messages of some module to stderr, warnings
		1277	and above to stderr, and errors and above to syslog, with:
		1278
		1279	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		1280
		1281	For the rather extensive details, see AnyEvent::Log.
		1282
		1283	This variable is evaluated when AnyEvent (or AnyEvent::Log) is
		1284	loaded, so will take effect even before AnyEvent has initialised
		1285	itself.
		1286
		1287	Note that specifying this environment variable causes the
		1288	AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE"
		1289	does not, so only using the latter saves a few hundred kB of memory
		1290	unless a module explicitly needs the extra features of
		1291	AnyEvent::Log.
1108		1292
1109	"PERL_ANYEVENT_STRICT"	1293	"PERL_ANYEVENT_STRICT"
1110	AnyEvent does not do much argument checking by default, as thorough	1294	AnyEvent does not do much argument checking by default, as thorough
1111	argument checking is very costly. Setting this variable to a true	1295	argument checking is very costly. Setting this variable to a true
1112	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1296	value will cause AnyEvent to load "AnyEvent::Strict" and then to
1113	thoroughly check the arguments passed to most method calls. If it	1297	thoroughly check the arguments passed to most method calls. If it
1114	finds any problems, it will croak.	1298	finds any problems, it will croak.
1115		1299
1116	In other words, enables "strict" mode.	1300	In other words, enables "strict" mode.
1117		1301
1118	Unlike "use strict" (or it's modern cousin, "use common::sense", it	1302	Unlike "use strict" (or its modern cousin, "use common::sense", it
1119	is definitely recommended to keep it off in production. Keeping	1303	is definitely recommended to keep it off in production. Keeping
1120	"PERL_ANYEVENT_STRICT=1" in your environment while developing	1304	"PERL_ANYEVENT_STRICT=1" in your environment while developing
1121	programs can be very useful, however.	1305	programs can be very useful, however.
1122		1306
		1307	"PERL_ANYEVENT_DEBUG_SHELL"
		1308	If this env variable is nonempty, then its contents will be
		1309	interpreted by "AnyEvent::Socket::parse_hostport" and
		1310	"AnyEvent::Debug::shell" (after replacing every occurance of $$ by
		1311	the process pid). The shell object is saved in
		1312	$AnyEvent::Debug::SHELL.
		1313
		1314	This happens when the first watcher is created.
		1315
		1316	For example, to bind a debug shell on a unix domain socket in
		1317	/tmp/debug<pid>.sock, you could use this:
		1318
		1319	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		1320	# connect with e.g.: socat readline /tmp/debug123.sock
		1321
		1322	Or to bind to tcp port 4545 on localhost:
		1323
		1324	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		1325	# connect with e.g.: telnet localhost 4545
		1326
		1327	Note that creating sockets in /tmp or on localhost is very unsafe on
		1328	multiuser systems.
		1329
		1330	"PERL_ANYEVENT_DEBUG_WRAP"
		1331	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1332	debugging purposes. See "AnyEvent::Debug::wrap" for details.
		1333
1123	"PERL_ANYEVENT_MODEL"	1334	"PERL_ANYEVENT_MODEL"
1124	This can be used to specify the event model to be used by AnyEvent,	1335	This can be used to specify the event model to be used by AnyEvent,
1125	before auto detection and -probing kicks in. It must be a string	1336	before auto detection and -probing kicks in.
1126	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1337
1127	gets prepended and the resulting module name is loaded and if the	1338	It normally is a string consisting entirely of ASCII letters (e.g.
1128	load was successful, used as event model. If it fails to load	1339	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1340	the resulting module name is loaded and - if the load was successful
		1341	- used as event model backend. If it fails to load then AnyEvent
1129	AnyEvent will proceed with auto detection and -probing.	1342	will proceed with auto detection and -probing.
1130		1343
1131	This functionality might change in future versions.	1344	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1345	then nothing gets prepended and the module name is used as-is (hint:
		1346	"::" at the end of a string designates a module name and quotes it
		1347	appropriately).
1132		1348
1133	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1349	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
1134	could start your program like this:	1350	could start your program like this:
1135		1351
1136	PERL_ANYEVENT_MODEL=Perl perl ...	1352	PERL_ANYEVENT_MODEL=Perl perl ...
		1353
		1354	"PERL_ANYEVENT_IO_MODEL"
		1355	The current file I/O model - see AnyEvent::IO for more info.
		1356
		1357	At the moment, only "Perl" (small, pure-perl, synchronous) and
		1358	"IOAIO" (truly asynchronous) are supported. The default is "IOAIO"
		1359	if AnyEvent::AIO can be loaded, otherwise it is "Perl".
1137		1360
1138	"PERL_ANYEVENT_PROTOCOLS"	1361	"PERL_ANYEVENT_PROTOCOLS"
1139	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1362	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
1140	preferences for IPv4 or IPv6. The default is unspecified (and might	1363	preferences for IPv4 or IPv6. The default is unspecified (and might
1141	change, or be the result of auto probing).	1364	change, or be the result of auto probing).
…		…
1145	mentioned will be used, and preference will be given to protocols	1368	mentioned will be used, and preference will be given to protocols
1146	mentioned earlier in the list.	1369	mentioned earlier in the list.
1147		1370
1148	This variable can effectively be used for denial-of-service attacks	1371	This variable can effectively be used for denial-of-service attacks
1149	against local programs (e.g. when setuid), although the impact is	1372	against local programs (e.g. when setuid), although the impact is
1150	likely small, as the program has to handle conenction and other	1373	likely small, as the program has to handle connection and other
1151	failures anyways.	1374	failures anyways.
1152		1375
1153	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1376	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
1154	IPv6, but support both and try to use both.	1377	IPv6, but support both and try to use both.
1155	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1378	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
1156	resolve or contact IPv6 addresses.	1379	resolve or contact IPv6 addresses.
1157	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but	1380	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
1158	prefer IPv6 over IPv4.	1381	prefer IPv6 over IPv4.
1159		1382
		1383	"PERL_ANYEVENT_HOSTS"
		1384	This variable, if specified, overrides the /etc/hosts file used by
		1385	AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be
		1386	read from that file instead.
		1387
1160	"PERL_ANYEVENT_EDNS0"	1388	"PERL_ANYEVENT_EDNS0"
1161	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension	1389	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
1162	for DNS. This extension is generally useful to reduce DNS traffic,	1390	for DNS. This extension is generally useful to reduce DNS traffic,
1163	but some (broken) firewalls drop such DNS packets, which is why it	1391	especially when DNSSEC is involved, but some (broken) firewalls drop
1164	is off by default.	1392	such DNS packets, which is why it is off by default.
1165		1393
1166	Setting this variable to 1 will cause AnyEvent::DNS to announce	1394	Setting this variable to 1 will cause AnyEvent::DNS to announce
1167	EDNS0 in its DNS requests.	1395	EDNS0 in its DNS requests.
1168		1396
1169	"PERL_ANYEVENT_MAX_FORKS"	1397	"PERL_ANYEVENT_MAX_FORKS"
…		…
1173	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"	1401	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
1174	The default value for the "max_outstanding" parameter for the	1402	The default value for the "max_outstanding" parameter for the
1175	default DNS resolver - this is the maximum number of parallel DNS	1403	default DNS resolver - this is the maximum number of parallel DNS
1176	requests that are sent to the DNS server.	1404	requests that are sent to the DNS server.
1177		1405
		1406	"PERL_ANYEVENT_MAX_SIGNAL_LATENCY"
		1407	Perl has inherently racy signal handling (you can basically choose
		1408	between losing signals and memory corruption) - pure perl event
		1409	loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't
		1410	available) therefore have to poll regularly to avoid losing signals.
		1411
		1412	Some event loops are racy, but don't poll regularly, and some event
		1413	loops are written in C but are still racy. For those event loops,
		1414	AnyEvent installs a timer that regularly wakes up the event loop.
		1415
		1416	By default, the interval for this timer is 10 seconds, but you can
		1417	override this delay with this environment variable (or by setting
		1418	the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal
		1419	watchers).
		1420
		1421	Lower values increase CPU (and energy) usage, higher values can
		1422	introduce long delays when reaping children or waiting for signals.
		1423
		1424	The AnyEvent::Async module, if available, will be used to avoid this
		1425	polling (with most event loops).
		1426
1178	"PERL_ANYEVENT_RESOLV_CONF"	1427	"PERL_ANYEVENT_RESOLV_CONF"
1179	The file to use instead of /etc/resolv.conf (or OS-specific	1428	The absolute path to a resolv.conf-style file to use instead of
1180	configuration) in the default resolver. When set to the empty	1429	/etc/resolv.conf (or the OS-specific configuration) in the default
1181	string, no default config will be used.	1430	resolver, or the empty string to select the default configuration.
1182		1431
1183	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".	1432	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1184	When neither "ca_file" nor "ca_path" was specified during	1433	When neither "ca_file" nor "ca_path" was specified during
1185	AnyEvent::TLS context creation, and either of these environment	1434	AnyEvent::TLS context creation, and either of these environment
1186	variables exist, they will be used to specify CA certificate	1435	variables are nonempty, they will be used to specify CA certificate
1187	locations instead of a system-dependent default.	1436	locations instead of a system-dependent default.
1188		1437
1189	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"	1438	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
1190	When these are set to 1, then the respective modules are not loaded.	1439	When these are set to 1, then the respective modules are not loaded.
1191	Mostly good for testing AnyEvent itself.	1440	Mostly good for testing AnyEvent itself.
…		…
1335		1584
1336	The actual code goes further and collects all errors ("die"s,	1585	The actual code goes further and collects all errors ("die"s,
1337	exceptions) that occurred during request processing. The "result" method	1586	exceptions) that occurred during request processing. The "result" method
1338	detects whether an exception as thrown (it is stored inside the $txn	1587	detects whether an exception as thrown (it is stored inside the $txn
1339	object) and just throws the exception, which means connection errors and	1588	object) and just throws the exception, which means connection errors and
1340	other problems get reported tot he code that tries to use the result,	1589	other problems get reported to the code that tries to use the result,
1341	not in a random callback.	1590	not in a random callback.
1342		1591
1343	All of this enables the following usage styles:	1592	All of this enables the following usage styles:
1344		1593
1345	1. Blocking:	1594	1. Blocking:
…		…
1363	my $txn = shift;	1612	my $txn = shift;
1364	my $data = $txn->result;	1613	my $data = $txn->result;
1365	...	1614	...
1366	});	1615	});
1367		1616
1368	EV::loop;	1617	EV::run;
1369		1618
1370	3b. The module user could use AnyEvent, too:	1619	3b. The module user could use AnyEvent, too:
1371		1620
1372	use AnyEvent;	1621	use AnyEvent;
1373		1622
…		…
1511	when used without AnyEvent), but most event loops have acceptable	1760	when used without AnyEvent), but most event loops have acceptable
1512	performance with or without AnyEvent.	1761	performance with or without AnyEvent.
1513		1762
1514	* The overhead AnyEvent adds is usually much smaller than the overhead	1763	* The overhead AnyEvent adds is usually much smaller than the overhead
1515	of the actual event loop, only with extremely fast event loops such	1764	of the actual event loop, only with extremely fast event loops such
1516	as EV adds AnyEvent significant overhead.	1765	as EV does AnyEvent add significant overhead.
1517		1766
1518	* You should avoid POE like the plague if you want performance or	1767	* You should avoid POE like the plague if you want performance or
1519	reasonable memory usage.	1768	reasonable memory usage.
1520		1769
1521	BENCHMARKING THE LARGE SERVER CASE	1770	BENCHMARKING THE LARGE SERVER CASE
…		…
1719		1968
1720	Feel free to install your own handler, or reset it to defaults.	1969	Feel free to install your own handler, or reset it to defaults.
1721		1970
1722	RECOMMENDED/OPTIONAL MODULES	1971	RECOMMENDED/OPTIONAL MODULES
1723	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and	1972	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
1724	it's built-in modules) are required to use it.	1973	its built-in modules) are required to use it.
1725		1974
1726	That does not mean that AnyEvent won't take advantage of some additional	1975	That does not mean that AnyEvent won't take advantage of some additional
1727	modules if they are installed.	1976	modules if they are installed.
1728		1977
1729	This section explains which additional modules will be used, and how	1978	This section explains which additional modules will be used, and how
…		…
1758	clock is available, can take avdantage of advanced kernel interfaces	2007	clock is available, can take avdantage of advanced kernel interfaces
1759	such as "epoll" and "kqueue", and is the fastest backend by far.	2008	such as "epoll" and "kqueue", and is the fastest backend by far.
1760	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and	2009	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
1761	Glib::EV).	2010	Glib::EV).
1762		2011
		2012	If you only use backends that rely on another event loop (e.g.
		2013	"Tk"), then this module will do nothing for you.
		2014
1763	Guard	2015	Guard
1764	The guard module, when used, will be used to implement	2016	The guard module, when used, will be used to implement
1765	"AnyEvent::Util::guard". This speeds up guards considerably (and	2017	"AnyEvent::Util::guard". This speeds up guards considerably (and
1766	uses a lot less memory), but otherwise doesn't affect guard	2018	uses a lot less memory), but otherwise doesn't affect guard
1767	operation much. It is purely used for performance.	2019	operation much. It is purely used for performance.
1768		2020
1769	JSON and JSON::XS	2021	JSON and JSON::XS
1770	One of these modules is required when you want to read or write JSON	2022	One of these modules is required when you want to read or write JSON
1771	data via AnyEvent::Handle. It is also written in pure-perl, but can	2023	data via AnyEvent::Handle. JSON is also written in pure-perl, but
1772	take advantage of the ultra-high-speed JSON::XS module when it is	2024	can take advantage of the ultra-high-speed JSON::XS module when it
1773	installed.	2025	is installed.
1774
1775	In fact, AnyEvent::Handle will use JSON::XS by default if it is
1776	installed.
1777		2026
1778	Net::SSLeay	2027	Net::SSLeay
1779	Implementing TLS/SSL in Perl is certainly interesting, but not very	2028	Implementing TLS/SSL in Perl is certainly interesting, but not very
1780	worthwhile: If this module is installed, then AnyEvent::Handle (with	2029	worthwhile: If this module is installed, then AnyEvent::Handle (with
1781	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.	2030	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
1782		2031
1783	Time::HiRes	2032	Time::HiRes
1784	This module is part of perl since release 5.008. It will be used	2033	This module is part of perl since release 5.008. It will be used
1785	when the chosen event library does not come with a timing source on	2034	when the chosen event library does not come with a timing source of
1786	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will	2035	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
1787	additionally use it to try to use a monotonic clock for timing	2036	load it to try to use a monotonic clock for timing stability.
1788	stability.	2037
		2038	AnyEvent::AIO (and IO::AIO)
		2039	The default implementation of AnyEvent::IO is to do I/O
		2040	synchronously, stopping programs while they access the disk, which
		2041	is fine for a lot of programs.
		2042
		2043	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it
		2044	switch to a true asynchronous implementation, so event processing
		2045	can continue even while waiting for disk I/O.
1789		2046
1790	FORK	2047	FORK
1791	Most event libraries are not fork-safe. The ones who are usually are	2048	Most event libraries are not fork-safe. The ones who are usually are
1792	because they rely on inefficient but fork-safe "select" or "poll" calls.	2049	because they rely on inefficient but fork-safe "select" or "poll" calls
1793	Only EV is fully fork-aware.	2050	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		2051	epoll are usually badly thought-out hacks that are incompatible with
		2052	fork in one way or another. Only EV is fully fork-aware and ensures that
		2053	you continue event-processing in both parent and child (or both, if you
		2054	know what you are doing).
1794		2055
1795	This means that, in general, you cannot fork and do event processing in	2056	This means that, in general, you cannot fork and do event processing in
1796	the child if a watcher was created before the fork (which in turn	2057	the child if the event library was initialised before the fork (which
1797	initialises the event library).	2058	usually happens when the first AnyEvent watcher is created, or the
		2059	library is loaded).
1798		2060
1799	If you have to fork, you must either do so before creating your first	2061	If you have to fork, you must either do so before creating your first
1800	watcher OR you must not use AnyEvent at all in the child OR you must do	2062	watcher OR you must not use AnyEvent at all in the child OR you must do
1801	something completely out of the scope of AnyEvent.	2063	something completely out of the scope of AnyEvent (see below).
1802		2064
1803	The problem of doing event processing in the parent and the child is	2065	The problem of doing event processing in the parent and the child is
1804	much more complicated: even for backends that are fork-aware or	2066	much more complicated: even for backends that are fork-aware or
1805	fork-safe, their behaviour is not usually what you want: fork clones all	2067	fork-safe, their behaviour is not usually what you want: fork clones all
1806	watchers, that means all timers, I/O watchers etc. are active in both	2068	watchers, that means all timers, I/O watchers etc. are active in both
1807	parent and child, which is almost never what you want.	2069	parent and child, which is almost never what you want. Using "exec" to
		2070	start worker children from some kind of manage prrocess is usually
		2071	preferred, because it is much easier and cleaner, at the expense of
		2072	having to have another binary.
		2073
		2074	In addition to logical problems with fork, there are also implementation
		2075	problems. For example, on POSIX systems, you cannot fork at all in Perl
		2076	code if a thread (I am talking of pthreads here) was ever created in the
		2077	process, and this is just the tip of the iceberg. In general, using fork
		2078	from Perl is difficult, and attempting to use fork without an exec to
		2079	implement some kind of parallel processing is almost certainly doomed.
		2080
		2081	To safely fork and exec, you should use a module such as Proc::FastSpawn
		2082	that let's you safely fork and exec new processes.
		2083
		2084	If you want to do multiprocessing using processes, you can look at the
		2085	AnyEvent::Fork module (and some related modules such as
		2086	AnyEvent::Fork::RPC, AnyEvent::Fork::Pool and AnyEvent::Fork::Remote).
		2087	This module allows you to safely create subprocesses without any
		2088	limitations - you can use X11 toolkits or AnyEvent in the children
		2089	created by AnyEvent::Fork safely and without any special precautions.
1808		2090
1809	SECURITY CONSIDERATIONS	2091	SECURITY CONSIDERATIONS
1810	AnyEvent can be forced to load any event model via	2092	AnyEvent can be forced to load any event model via
1811	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	2093	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1812	to execute arbitrary code or directly gain access, it can easily be used	2094	to execute arbitrary code or directly gain access, it can easily be used
…		…
1836	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	2118	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1837	annoying memleaks, such as leaking on "map" and "grep" but it is usually	2119	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1838	not as pronounced).	2120	not as pronounced).
1839		2121
1840	SEE ALSO	2122	SEE ALSO
1841	Utility functions: AnyEvent::Util.	2123	Tutorial/Introduction: AnyEvent::Intro.
1842		2124
1843	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	2125	FAQ: AnyEvent::FAQ.
1844	Event::Lib, Qt, POE.	2126
		2127	Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log
		2128	(simply logging).
		2129
		2130	Development/Debugging: AnyEvent::Strict (stricter checking),
		2131	AnyEvent::Debug (interactive shell, watcher tracing).
		2132
		2133	Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
		2134	Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK, Cocoa::EventLoop, UV.
1845		2135
1846	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	2136	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1847	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	2137	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1848	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,	2138	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		2139	AnyEvent::Impl::IOAsync, AnyEvent::Impl::Irssi, AnyEvent::Impl::FLTK,
1849	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.	2140	AnyEvent::Impl::Cocoa, AnyEvent::Impl::UV.
1850		2141
1851	Non-blocking file handles, sockets, TCP clients and servers:	2142	Non-blocking handles, pipes, stream sockets, TCP clients and servers:
1852	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.	2143	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1853		2144
		2145	Asynchronous File I/O: AnyEvent::IO.
		2146
1854	Asynchronous DNS: AnyEvent::DNS.	2147	Asynchronous DNS: AnyEvent::DNS.
1855		2148
1856	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	2149	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1857		2150
1858	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,	2151	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
1859	AnyEvent::HTTP.	2152	AnyEvent::HTTP.
1860		2153
1861	AUTHOR	2154	AUTHOR
1862	Marc Lehmann <schmorp@schmorp.de>	2155	Marc Lehmann <schmorp@schmorp.de>
1863	http://home.schmorp.de/	2156	http://anyevent.schmorp.de
1864		2157

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Comparing AnyEvent/README (file contents): Revision 1.57 by root, Sat Dec 5 02:52:03 2009 UTC vs. Revision 1.77 by root, Sat Sep 17 02:33:54 2016 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.57 by root, Sat Dec 5 02:52:03 2009 UTC vs.
Revision 1.77 by root, Sat Sep 17 02:33:54 2016 UTC