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Revision 1.24 by root, Thu May 29 03:46:04 2008 UTC vs.
Revision 1.55 by root, Mon Sep 14 05:05:09 2009 UTC

1	=> NAME	1	NAME
2	AnyEvent - provide framework for multiple event loops	2	AnyEvent - the DBI of event loop programming
3		3
4	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event	4	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
5	loops	5	Qt and POE are various supported event loops/environments.
6		6
7	SYNOPSIS	7	SYNOPSIS
8	use AnyEvent;	8	use AnyEvent;
9		9
		10	# file descriptor readable
10	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	11	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		12
		13	# one-shot or repeating timers
		14	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		15	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		16
		17	print AnyEvent->now; # prints current event loop time
		18	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		19
		20	# POSIX signal
		21	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		22
		23	# child process exit
		24	my $w = AnyEvent->child (pid => $pid, cb => sub {
		25	my ($pid, $status) = @_;
11	...	26	...
12	});	27	});
13		28
14	my $w = AnyEvent->timer (after => $seconds, cb => sub {	29	# called when event loop idle (if applicable)
15	...	30	my $w = AnyEvent->idle (cb => sub { ... });
16	});
17		31
18	my $w = AnyEvent->condvar; # stores whether a condition was flagged	32	my $w = AnyEvent->condvar; # stores whether a condition was flagged
19	$w->send; # wake up current and all future recv's	33	$w->send; # wake up current and all future recv's
20	$w->recv; # enters "main loop" till $condvar gets ->send	34	$w->recv; # enters "main loop" till $condvar gets ->send
		35	# use a condvar in callback mode:
		36	$w->cb (sub { $_[0]->recv });
		37
		38	INTRODUCTION/TUTORIAL
		39	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
		41	manpage.
		42
		43	SUPPORT
		44	There is a mailinglist for discussing all things AnyEvent, and an IRC
		45	channel, too.
		46
		47	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
		48	Repository, at <http://anyevent.schmorp.de>, for more info.
21		49
22	WHY YOU SHOULD USE THIS MODULE (OR NOT)	50	WHY YOU SHOULD USE THIS MODULE (OR NOT)
23	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	51	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
24	nowadays. So what is different about AnyEvent?	52	nowadays. So what is different about AnyEvent?
25		53
26	Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of	54	Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of
27	policy* and AnyEvent is *small and efficient*.	55	policy* and AnyEvent is *small and efficient*.
28		56
29	First and foremost, *AnyEvent is not an event model* itself, it only	57	First and foremost, *AnyEvent is not an event model* itself, it only
30	interfaces to whatever event model the main program happens to use in a	58	interfaces to whatever event model the main program happens to use, in a
31	pragmatic way. For event models and certain classes of immortals alike,	59	pragmatic way. For event models and certain classes of immortals alike,
32	the statement "there can only be one" is a bitter reality: In general,	60	the statement "there can only be one" is a bitter reality: In general,
33	only one event loop can be active at the same time in a process.	61	only one event loop can be active at the same time in a process.
34	AnyEvent helps hiding the differences between those event loops.	62	AnyEvent cannot change this, but it can hide the differences between
		63	those event loops.
35		64
36	The goal of AnyEvent is to offer module authors the ability to do event	65	The goal of AnyEvent is to offer module authors the ability to do event
37	programming (waiting for I/O or timer events) without subscribing to a	66	programming (waiting for I/O or timer events) without subscribing to a
38	religion, a way of living, and most importantly: without forcing your	67	religion, a way of living, and most importantly: without forcing your
39	module users into the same thing by forcing them to use the same event	68	module users into the same thing by forcing them to use the same event
40	model you use.	69	model you use.
41		70
42	For modules like POE or IO::Async (which is a total misnomer as it is	71	For modules like POE or IO::Async (which is a total misnomer as it is
43	actually doing all I/O *synchronously*...), using them in your module is	72	actually doing all I/O *synchronously*...), using them in your module is
44	like joining a cult: After you joined, you are dependent on them and you	73	like joining a cult: After you joined, you are dependent on them and you
45	cannot use anything else, as it is simply incompatible to everything	74	cannot use anything else, as they are simply incompatible to everything
46	that isn't itself. What's worse, all the potential users of your module	75	that isn't them. What's worse, all the potential users of your module
47	are *also* forced to use the same event loop you use.	76	are *also* forced to use the same event loop you use.
48		77
49	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	78	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	79	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
51	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your	80	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your
52	module uses one of those, every user of your module has to use it, too.	81	module uses one of those, every user of your module has to use it, too.
53	But if your module uses AnyEvent, it works transparently with all event	82	But if your module uses AnyEvent, it works transparently with all event
54	models it supports (including stuff like POE and IO::Async, as long as	83	models it supports (including stuff like IO::Async, as long as those use
55	those use one of the supported event loops. It is trivial to add new	84	one of the supported event loops. It is trivial to add new event loops
56	event loops to AnyEvent, too, so it is future-proof).	85	to AnyEvent, too, so it is future-proof).
57		86
58	In addition to being free of having to use *the one and only true event	87	In addition to being free of having to use *the one and only true event
59	model*, AnyEvent also is free of bloat and policy: with POE or similar	88	model*, AnyEvent also is free of bloat and policy: with POE or similar
60	modules, you get an enormous amount of code and strict rules you have to	89	modules, you get an enormous amount of code and strict rules you have to
61	follow. AnyEvent, on the other hand, is lean and up to the point, by	90	follow. AnyEvent, on the other hand, is lean and up to the point, by
…		…
117	These watchers are normal Perl objects with normal Perl lifetime. After	146	These watchers are normal Perl objects with normal Perl lifetime. After
118	creating a watcher it will immediately "watch" for events and invoke the	147	creating a watcher it will immediately "watch" for events and invoke the
119	callback when the event occurs (of course, only when the event model is	148	callback when the event occurs (of course, only when the event model is
120	in control).	149	in control).
121		150
		151	Note that callbacks must not permanently change global variables
		152	potentially in use by the event loop (such as $_ or $[) and that
		153	callbacks must not "die". The former is good programming practise in
		154	Perl and the latter stems from the fact that exception handling differs
		155	widely between event loops.
		156
122	To disable the watcher you have to destroy it (e.g. by setting the	157	To disable the watcher you have to destroy it (e.g. by setting the
123	variable you store it in to "undef" or otherwise deleting all references	158	variable you store it in to "undef" or otherwise deleting all references
124	to it).	159	to it).
125		160
126	All watchers are created by calling a method on the "AnyEvent" class.	161	All watchers are created by calling a method on the "AnyEvent" class.
…		…
128	Many watchers either are used with "recursion" (repeating timers for	163	Many watchers either are used with "recursion" (repeating timers for
129	example), or need to refer to their watcher object in other ways.	164	example), or need to refer to their watcher object in other ways.
130		165
131	An any way to achieve that is this pattern:	166	An any way to achieve that is this pattern:
132		167
133	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	168	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
134	# you can use $w here, for example to undef it	169	# you can use $w here, for example to undef it
135	undef $w;	170	undef $w;
136	});	171	});
137		172
138	Note that "my $w; $w =" combination. This is necessary because in Perl,	173	Note that "my $w; $w =" combination. This is necessary because in Perl,
139	my variables are only visible after the statement in which they are	174	my variables are only visible after the statement in which they are
140	declared.	175	declared.
141		176
142	I/O WATCHERS	177	I/O WATCHERS
		178	$w = AnyEvent->io (
		179	fh => <filehandle_or_fileno>,
		180	poll => <"r" or "w">,
		181	cb => <callback>,
		182	);
		183
143	You can create an I/O watcher by calling the "AnyEvent->io" method with	184	You can create an I/O watcher by calling the "AnyEvent->io" method with
144	the following mandatory key-value pairs as arguments:	185	the following mandatory key-value pairs as arguments:
145		186
146	"fh" the Perl *file handle* (*not* file descriptor) to watch for events.	187	"fh" is the Perl *file handle* (or a naked file descriptor) to watch for
		188	events (AnyEvent might or might not keep a reference to this file
		189	handle). Note that only file handles pointing to things for which
		190	non-blocking operation makes sense are allowed. This includes sockets,
		191	most character devices, pipes, fifos and so on, but not for example
		192	files or block devices.
		193
147	"poll" must be a string that is either "r" or "w", which creates a	194	"poll" must be a string that is either "r" or "w", which creates a
148	watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"	195	watcher waiting for "r"eadable or "w"ritable events, respectively.
		196
149	is the callback to invoke each time the file handle becomes ready.	197	"cb" is the callback to invoke each time the file handle becomes ready.
150		198
151	Although the callback might get passed parameters, their value and	199	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	200	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	201	callbacks cannot use arguments passed to I/O watcher callbacks.
154		202
…		…
158		206
159	Some event loops issue spurious readyness notifications, so you should	207	Some event loops issue spurious readyness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	208	always use non-blocking calls when reading/writing from/to your file
161	handles.	209	handles.
162		210
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	211	Example: wait for readability of STDIN, then read a line and disable the
		212	watcher.
		213
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	214	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	215	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	216	warn "read: $input\n";
169	undef $w;	217	undef $w;
170	});	218	});
171		219
172	TIME WATCHERS	220	TIME WATCHERS
		221	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		222
		223	$w = AnyEvent->timer (
		224	after => <fractional_seconds>,
		225	interval => <fractional_seconds>,
		226	cb => <callback>,
		227	);
		228
173	You can create a time watcher by calling the "AnyEvent->timer" method	229	You can create a time watcher by calling the "AnyEvent->timer" method
174	with the following mandatory arguments:	230	with the following mandatory arguments:
175		231
176	"after" specifies after how many seconds (fractional values are	232	"after" specifies after how many seconds (fractional values are
177	supported) the callback should be invoked. "cb" is the callback to	233	supported) the callback should be invoked. "cb" is the callback to
…		…
179		235
180	Although the callback might get passed parameters, their value and	236	Although the callback might get passed parameters, their value and
181	presence is undefined and you cannot rely on them. Portable AnyEvent	237	presence is undefined and you cannot rely on them. Portable AnyEvent
182	callbacks cannot use arguments passed to time watcher callbacks.	238	callbacks cannot use arguments passed to time watcher callbacks.
183		239
184	The timer callback will be invoked at most once: if you want a repeating	240	The callback will normally be invoked once only. If you specify another
185	timer you have to create a new watcher (this is a limitation by both Tk	241	parameter, "interval", as a strictly positive number (> 0), then the
186	and Glib).	242	callback will be invoked regularly at that interval (in fractional
		243	seconds) after the first invocation. If "interval" is specified with a
		244	false value, then it is treated as if it were missing.
187		245
188	Example:	246	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
		248	is only approximate.
189		249
190	# fire an event after 7.7 seconds	250	Example: fire an event after 7.7 seconds.
		251
191	my $w = AnyEvent->timer (after => 7.7, cb => sub {	252	my $w = AnyEvent->timer (after => 7.7, cb => sub {
192	warn "timeout\n";	253	warn "timeout\n";
193	});	254	});
194		255
195	# to cancel the timer:	256	# to cancel the timer:
196	undef $w;	257	undef $w;
197		258
198	Example 2:
199
200	# fire an event after 0.5 seconds, then roughly every second	259	Example 2: fire an event after 0.5 seconds, then roughly every second.
201	my $w;
202		260
203	my $cb = sub {
204	# cancel the old timer while creating a new one
205	$w = AnyEvent->timer (after => 1, cb => $cb);	261	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		262	warn "timeout\n";
206	};	263	};
207
208	# start the "loop" by creating the first watcher
209	$w = AnyEvent->timer (after => 0.5, cb => $cb);
210		264
211	TIMING ISSUES	265	TIMING ISSUES
212	There are two ways to handle timers: based on real time (relative, "fire	266	There are two ways to handle timers: based on real time (relative, "fire
213	in 10 seconds") and based on wallclock time (absolute, "fire at 12	267	in 10 seconds") and based on wallclock time (absolute, "fire at 12
214	o'clock").	268	o'clock").
…		…
288	In either case, if you care (and in most cases, you don't), then you	342	In either case, if you care (and in most cases, you don't), then you
289	can get whatever behaviour you want with any event loop, by taking	343	can get whatever behaviour you want with any event loop, by taking
290	the difference between "AnyEvent->time" and "AnyEvent->now" into	344	the difference between "AnyEvent->time" and "AnyEvent->now" into
291	account.	345	account.
292		346
		347	AnyEvent->now_update
		348	Some event loops (such as EV or AnyEvent::Impl::Perl) cache the
		349	current time for each loop iteration (see the discussion of
		350	AnyEvent->now, above).
		351
		352	When a callback runs for a long time (or when the process sleeps),
		353	then this "current" time will differ substantially from the real
		354	time, which might affect timers and time-outs.
		355
		356	When this is the case, you can call this method, which will update
		357	the event loop's idea of "current time".
		358
		359	Note that updating the time *might* cause some events to be handled.
		360
293	SIGNAL WATCHERS	361	SIGNAL WATCHERS
		362	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		363
294	You can watch for signals using a signal watcher, "signal" is the signal	364	You can watch for signals using a signal watcher, "signal" is the signal
295	*name* without any "SIG" prefix, "cb" is the Perl callback to be invoked	365	*name* in uppercase and without any "SIG" prefix, "cb" is the Perl
296	whenever a signal occurs.	366	callback to be invoked whenever a signal occurs.
297		367
298	Although the callback might get passed parameters, their value and	368	Although the callback might get passed parameters, their value and
299	presence is undefined and you cannot rely on them. Portable AnyEvent	369	presence is undefined and you cannot rely on them. Portable AnyEvent
300	callbacks cannot use arguments passed to signal watcher callbacks.	370	callbacks cannot use arguments passed to signal watcher callbacks.
301		371
…		…
303	invocation, and callback invocation will be synchronous. Synchronous	373	invocation, and callback invocation will be synchronous. Synchronous
304	means that it might take a while until the signal gets handled by the	374	means that it might take a while until the signal gets handled by the
305	process, but it is guaranteed not to interrupt any other callbacks.	375	process, but it is guaranteed not to interrupt any other callbacks.
306		376
307	The main advantage of using these watchers is that you can share a	377	The main advantage of using these watchers is that you can share a
308	signal between multiple watchers.	378	signal between multiple watchers, and AnyEvent will ensure that signals
		379	will not interrupt your program at bad times.
309		380
310	This watcher might use %SIG, so programs overwriting those signals	381	This watcher might use %SIG (depending on the event loop used), so
311	directly will likely not work correctly.	382	programs overwriting those signals directly will likely not work
		383	correctly.
312		384
313	Example: exit on SIGINT	385	Example: exit on SIGINT
314		386
315	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	387	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
316		388
		389	Signal Races, Delays and Workarounds
		390	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		391	callbacks to signals in a generic way, which is a pity, as you cannot do
		392	race-free signal handling in perl, requiring C libraries for this.
		393	AnyEvent will try to do it's best, which means in some cases, signals
		394	will be delayed. The maximum time a signal might be delayed is specified
		395	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
		396	can be changed only before the first signal watcher is created, and
		397	should be left alone otherwise. This variable determines how often
		398	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		399	will cause fewer spurious wake-ups, which is better for power and CPU
		400	saving.
		401
		402	All these problems can be avoided by installing the optional
		403	Async::Interrupt module, which works with most event loops. It will not
		404	work with inherently broken event loops such as Event or Event::Lib (and
		405	not with POE currently, as POE does it's own workaround with one-second
		406	latency). For those, you just have to suffer the delays.
		407
317	CHILD PROCESS WATCHERS	408	CHILD PROCESS WATCHERS
		409	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		410
318	You can also watch on a child process exit and catch its exit status.	411	You can also watch on a child process exit and catch its exit status.
319		412
320	The child process is specified by the "pid" argument (if set to 0, it	413	The child process is specified by the "pid" argument (one some backends,
321	watches for any child process exit). The watcher will trigger as often	414	using 0 watches for any child process exit, on others this will croak).
322	as status change for the child are received. This works by installing a	415	The watcher will be triggered only when the child process has finished
323	signal handler for "SIGCHLD". The callback will be called with the pid	416	and an exit status is available, not on any trace events
324	and exit status (as returned by waitpid), so unlike other watcher types,	417	(stopped/continued).
325	you *can* rely on child watcher callback arguments.	418
		419	The callback will be called with the pid and exit status (as returned by
		420	waitpid), so unlike other watcher types, you *can* rely on child watcher
		421	callback arguments.
		422
		423	This watcher type works by installing a signal handler for "SIGCHLD",
		424	and since it cannot be shared, nothing else should use SIGCHLD or reap
		425	random child processes (waiting for specific child processes, e.g.
		426	inside "system", is just fine).
326		427
327	There is a slight catch to child watchers, however: you usually start	428	There is a slight catch to child watchers, however: you usually start
328	them *after* the child process was created, and this means the process	429	them *after* the child process was created, and this means the process
329	could have exited already (and no SIGCHLD will be sent anymore).	430	could have exited already (and no SIGCHLD will be sent anymore).
330		431
331	Not all event models handle this correctly (POE doesn't), but even for	432	Not all event models handle this correctly (neither POE nor IO::Async
		433	do, see their AnyEvent::Impl manpages for details), but even for event
332	event models that *do* handle this correctly, they usually need to be	434	models that *do* handle this correctly, they usually need to be loaded
333	loaded before the process exits (i.e. before you fork in the first	435	before the process exits (i.e. before you fork in the first place).
334	place).	436	AnyEvent's pure perl event loop handles all cases correctly regardless
		437	of when you start the watcher.
335		438
336	This means you cannot create a child watcher as the very first thing in	439	This means you cannot create a child watcher as the very first thing in
337	an AnyEvent program, you *have* to create at least one watcher before	440	an AnyEvent program, you *have* to create at least one watcher before
338	you "fork" the child (alternatively, you can call "AnyEvent::detect").	441	you "fork" the child (alternatively, you can call "AnyEvent::detect").
339		442
		443	As most event loops do not support waiting for child events, they will
		444	be emulated by AnyEvent in most cases, in which the latency and race
		445	problems mentioned in the description of signal watchers apply.
		446
340	Example: fork a process and wait for it	447	Example: fork a process and wait for it
341		448
342	my $done = AnyEvent->condvar;	449	my $done = AnyEvent->condvar;
343		450
344	my $pid = fork or exit 5;	451	my $pid = fork or exit 5;
345		452
346	my $w = AnyEvent->child (	453	my $w = AnyEvent->child (
347	pid => $pid,	454	pid => $pid,
348	cb => sub {	455	cb => sub {
349	my ($pid, $status) = @_;	456	my ($pid, $status) = @_;
350	warn "pid $pid exited with status $status";	457	warn "pid $pid exited with status $status";
351	$done->send;	458	$done->send;
352	},	459	},
353	);	460	);
354		461
355	# do something else, then wait for process exit	462	# do something else, then wait for process exit
356	$done->recv;	463	$done->recv;
		464
		465	IDLE WATCHERS
		466	$w = AnyEvent->idle (cb => <callback>);
		467
		468	Sometimes there is a need to do something, but it is not so important to
		469	do it instantly, but only when there is nothing better to do. This
		470	"nothing better to do" is usually defined to be "no other events need
		471	attention by the event loop".
		472
		473	Idle watchers ideally get invoked when the event loop has nothing better
		474	to do, just before it would block the process to wait for new events.
		475	Instead of blocking, the idle watcher is invoked.
		476
		477	Most event loops unfortunately do not really support idle watchers (only
		478	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		479	will simply call the callback "from time to time".
		480
		481	Example: read lines from STDIN, but only process them when the program
		482	is otherwise idle:
		483
		484	my @lines; # read data
		485	my $idle_w;
		486	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		487	push @lines, scalar <STDIN>;
		488
		489	# start an idle watcher, if not already done
		490	$idle_w ||= AnyEvent->idle (cb => sub {
		491	# handle only one line, when there are lines left
		492	if (my $line = shift @lines) {
		493	print "handled when idle: $line";
		494	} else {
		495	# otherwise disable the idle watcher again
		496	undef $idle_w;
		497	}
		498	});
		499	});
357		500
358	CONDITION VARIABLES	501	CONDITION VARIABLES
		502	$cv = AnyEvent->condvar;
		503
		504	$cv->send (<list>);
		505	my @res = $cv->recv;
		506
359	If you are familiar with some event loops you will know that all of them	507	If you are familiar with some event loops you will know that all of them
360	require you to run some blocking "loop", "run" or similar function that	508	require you to run some blocking "loop", "run" or similar function that
361	will actively watch for new events and call your callbacks.	509	will actively watch for new events and call your callbacks.
362		510
363	AnyEvent is different, it expects somebody else to run the event loop	511	AnyEvent is slightly different: it expects somebody else to run the
364	and will only block when necessary (usually when told by the user).	512	event loop and will only block when necessary (usually when told by the
		513	user).
365		514
366	The instrument to do that is called a "condition variable", so called	515	The instrument to do that is called a "condition variable", so called
367	because they represent a condition that must become true.	516	because they represent a condition that must become true.
		517
		518	Now is probably a good time to look at the examples further below.
368		519
369	Condition variables can be created by calling the "AnyEvent->condvar"	520	Condition variables can be created by calling the "AnyEvent->condvar"
370	method, usually without arguments. The only argument pair allowed is	521	method, usually without arguments. The only argument pair allowed is
371	"cb", which specifies a callback to be called when the condition	522	"cb", which specifies a callback to be called when the condition
372	variable becomes true.	523	variable becomes true, with the condition variable as the first argument
		524	(but not the results).
373		525
374	After creation, the condition variable is "false" until it becomes	526	After creation, the condition variable is "false" until it becomes
375	"true" by calling the "send" method (or calling the condition variable	527	"true" by calling the "send" method (or calling the condition variable
376	as if it were a callback, read about the caveats in the description for	528	as if it were a callback, read about the caveats in the description for
377	the "->send" method).	529	the "->send" method).
…		…
379	Condition variables are similar to callbacks, except that you can	531	Condition variables are similar to callbacks, except that you can
380	optionally wait for them. They can also be called merge points - points	532	optionally wait for them. They can also be called merge points - points
381	in time where multiple outstanding events have been processed. And yet	533	in time where multiple outstanding events have been processed. And yet
382	another way to call them is transactions - each condition variable can	534	another way to call them is transactions - each condition variable can
383	be used to represent a transaction, which finishes at some point and	535	be used to represent a transaction, which finishes at some point and
384	delivers a result.	536	delivers a result. And yet some people know them as "futures" - a
		537	promise to compute/deliver something that you can wait for.
385		538
386	Condition variables are very useful to signal that something has	539	Condition variables are very useful to signal that something has
387	finished, for example, if you write a module that does asynchronous http	540	finished, for example, if you write a module that does asynchronous http
388	requests, then a condition variable would be the ideal candidate to	541	requests, then a condition variable would be the ideal candidate to
389	signal the availability of results. The user can either act when the	542	signal the availability of results. The user can either act when the
…		…
423	after => 1,	576	after => 1,
424	cb => sub { $result_ready->send },	577	cb => sub { $result_ready->send },
425	);	578	);
426		579
427	# this "blocks" (while handling events) till the callback	580	# this "blocks" (while handling events) till the callback
428	# calls send	581	# calls ->send
429	$result_ready->recv;	582	$result_ready->recv;
430		583
431	Example: wait for a timer, but take advantage of the fact that condition	584	Example: wait for a timer, but take advantage of the fact that condition
432	variables are also code references.	585	variables are also callable directly.
433		586
434	my $done = AnyEvent->condvar;	587	my $done = AnyEvent->condvar;
435	my $delay = AnyEvent->timer (after => 5, cb => $done);	588	my $delay = AnyEvent->timer (after => 5, cb => $done);
436	$done->recv;	589	$done->recv;
		590
		591	Example: Imagine an API that returns a condvar and doesn't support
		592	callbacks. This is how you make a synchronous call, for example from the
		593	main program:
		594
		595	use AnyEvent::CouchDB;
		596
		597	...
		598
		599	my @info = $couchdb->info->recv;
		600
		601	And this is how you would just set a callback to be called whenever the
		602	results are available:
		603
		604	$couchdb->info->cb (sub {
		605	my @info = $_[0]->recv;
		606	});
437		607
438	METHODS FOR PRODUCERS	608	METHODS FOR PRODUCERS
439	These methods should only be used by the producing side, i.e. the	609	These methods should only be used by the producing side, i.e. the
440	code/module that eventually sends the signal. Note that it is also the	610	code/module that eventually sends the signal. Note that it is also the
441	producer side which creates the condvar in most cases, but it isn't	611	producer side which creates the condvar in most cases, but it isn't
…		…
451		621
452	Any arguments passed to the "send" call will be returned by all	622	Any arguments passed to the "send" call will be returned by all
453	future "->recv" calls.	623	future "->recv" calls.
454		624
455	Condition variables are overloaded so one can call them directly (as	625	Condition variables are overloaded so one can call them directly (as
456	a code reference). Calling them directly is the same as calling	626	if they were a code reference). Calling them directly is the same as
457	"send". Note, however, that many C-based event loops do not handle	627	calling "send".
458	overloading, so as tempting as it may be, passing a condition
459	variable instead of a callback does not work. Both the pure perl and
460	EV loops support overloading, however, as well as all functions that
461	use perl to invoke a callback (as in AnyEvent::Socket and
462	AnyEvent::DNS for example).
463		628
464	$cv->croak ($error)	629	$cv->croak ($error)
465	Similar to send, but causes all call's to "->recv" to invoke	630	Similar to send, but causes all call's to "->recv" to invoke
466	"Carp::croak" with the given error message/object/scalar.	631	"Carp::croak" with the given error message/object/scalar.
467		632
468	This can be used to signal any errors to the condition variable	633	This can be used to signal any errors to the condition variable
469	user/consumer.	634	user/consumer. Doing it this way instead of calling "croak" directly
		635	delays the error detetcion, but has the overwhelmign advantage that
		636	it diagnoses the error at the place where the result is expected,
		637	and not deep in some event clalback without connection to the actual
		638	code causing the problem.
470		639
471	$cv->begin ([group callback])	640	$cv->begin ([group callback])
472	$cv->end	641	$cv->end
473	These two methods are EXPERIMENTAL and MIGHT CHANGE.
474
475	These two methods can be used to combine many transactions/events	642	These two methods can be used to combine many transactions/events
476	into one. For example, a function that pings many hosts in parallel	643	into one. For example, a function that pings many hosts in parallel
477	might want to use a condition variable for the whole process.	644	might want to use a condition variable for the whole process.
478		645
479	Every call to "->begin" will increment a counter, and every call to	646	Every call to "->begin" will increment a counter, and every call to
480	"->end" will decrement it. If the counter reaches 0 in "->end", the	647	"->end" will decrement it. If the counter reaches 0 in "->end", the
481	(last) callback passed to "begin" will be executed. That callback is	648	(last) callback passed to "begin" will be executed, passing the
482	*supposed* to call "->send", but that is not required. If no	649	condvar as first argument. That callback is *supposed* to call
		650	"->send", but that is not required. If no group callback was set,
483	callback was set, "send" will be called without any arguments.	651	"send" will be called without any arguments.
484		652
485	Let's clarify this with the ping example:	653	You can think of "$cv->send" giving you an OR condition (one call
		654	sends), while "$cv->begin" and "$cv->end" giving you an AND
		655	condition (all "begin" calls must be "end"'ed before the condvar
		656	sends).
		657
		658	Let's start with a simple example: you have two I/O watchers (for
		659	example, STDOUT and STDERR for a program), and you want to wait for
		660	both streams to close before activating a condvar:
486		661
487	my $cv = AnyEvent->condvar;	662	my $cv = AnyEvent->condvar;
488		663
		664	$cv->begin; # first watcher
		665	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		666	defined sysread $fh1, my $buf, 4096
		667	or $cv->end;
		668	});
		669
		670	$cv->begin; # second watcher
		671	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		672	defined sysread $fh2, my $buf, 4096
		673	or $cv->end;
		674	});
		675
		676	$cv->recv;
		677
		678	This works because for every event source (EOF on file handle),
		679	there is one call to "begin", so the condvar waits for all calls to
		680	"end" before sending.
		681
		682	The ping example mentioned above is slightly more complicated, as
		683	the there are results to be passwd back, and the number of tasks
		684	that are begung can potentially be zero:
		685
		686	my $cv = AnyEvent->condvar;
		687
489	my %result;	688	my %result;
490	$cv->begin (sub { $cv->send (\%result) });	689	$cv->begin (sub { shift->send (\%result) });
491		690
492	for my $host (@list_of_hosts) {	691	for my $host (@list_of_hosts) {
493	$cv->begin;	692	$cv->begin;
494	ping_host_then_call_callback $host, sub {	693	ping_host_then_call_callback $host, sub {
495	$result{$host} = ...;	694	$result{$host} = ...;
…		…
510	the loop, which serves two important purposes: first, it sets the	709	the loop, which serves two important purposes: first, it sets the
511	callback to be called once the counter reaches 0, and second, it	710	callback to be called once the counter reaches 0, and second, it
512	ensures that "send" is called even when "no" hosts are being pinged	711	ensures that "send" is called even when "no" hosts are being pinged
513	(the loop doesn't execute once).	712	(the loop doesn't execute once).
514		713
515	This is the general pattern when you "fan out" into multiple	714	This is the general pattern when you "fan out" into multiple (but
516	subrequests: use an outer "begin"/"end" pair to set the callback and	715	potentially none) subrequests: use an outer "begin"/"end" pair to
517	ensure "end" is called at least once, and then, for each subrequest	716	set the callback and ensure "end" is called at least once, and then,
518	you start, call "begin" and for each subrequest you finish, call	717	for each subrequest you start, call "begin" and for each subrequest
519	"end".	718	you finish, call "end".
520		719
521	METHODS FOR CONSUMERS	720	METHODS FOR CONSUMERS
522	These methods should only be used by the consuming side, i.e. the code	721	These methods should only be used by the consuming side, i.e. the code
523	awaits the condition.	722	awaits the condition.
524		723
…		…
533	function will call "croak".	732	function will call "croak".
534		733
535	In list context, all parameters passed to "send" will be returned,	734	In list context, all parameters passed to "send" will be returned,
536	in scalar context only the first one will be returned.	735	in scalar context only the first one will be returned.
537		736
		737	Note that doing a blocking wait in a callback is not supported by
		738	any event loop, that is, recursive invocation of a blocking "->recv"
		739	is not allowed, and the "recv" call will "croak" if such a condition
		740	is detected. This condition can be slightly loosened by using
		741	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		742	thread that doesn't run the event loop itself.
		743
538	Not all event models support a blocking wait - some die in that case	744	Not all event models support a blocking wait - some die in that case
539	(programs might want to do that to stay interactive), so *if you are	745	(programs might want to do that to stay interactive), so *if you are
540	using this from a module, never require a blocking wait*, but let	746	using this from a module, never require a blocking wait*. Instead,
541	the caller decide whether the call will block or not (for example,	747	let the caller decide whether the call will block or not (for
542	by coupling condition variables with some kind of request results	748	example, by coupling condition variables with some kind of request
543	and supporting callbacks so the caller knows that getting the result	749	results and supporting callbacks so the caller knows that getting
544	will not block, while still supporting blocking waits if the caller	750	the result will not block, while still supporting blocking waits if
545	so desires).	751	the caller so desires).
546
547	Another reason *never* to "->recv" in a module is that you cannot
548	sensibly have two "->recv"'s in parallel, as that would require
549	multiple interpreters or coroutines/threads, none of which
550	"AnyEvent" can supply.
551
552	The Coro module, however, *can* and *does* supply coroutines and, in
553	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
554	versions and also integrates coroutines into AnyEvent, making
555	blocking "->recv" calls perfectly safe as long as they are done from
556	another coroutine (one that doesn't run the event loop).
557		752
558	You can ensure that "-recv" never blocks by setting a callback and	753	You can ensure that "-recv" never blocks by setting a callback and
559	only calling "->recv" from within that callback (or at a later	754	only calling "->recv" from within that callback (or at a later
560	time). This will work even when the event loop does not support	755	time). This will work even when the event loop does not support
561	blocking waits otherwise.	756	blocking waits otherwise.
562		757
563	$bool = $cv->ready	758	$bool = $cv->ready
564	Returns true when the condition is "true", i.e. whether "send" or	759	Returns true when the condition is "true", i.e. whether "send" or
565	"croak" have been called.	760	"croak" have been called.
566		761
567	$cb = $cv->cb ([new callback])	762	$cb = $cv->cb ($cb->($cv))
568	This is a mutator function that returns the callback set and	763	This is a mutator function that returns the callback set and
569	optionally replaces it before doing so.	764	optionally replaces it before doing so.
570		765
571	The callback will be called when the condition becomes "true", i.e.	766	The callback will be called when the condition becomes (or already
572	when "send" or "croak" are called. Calling "recv" inside the	767	was) "true", i.e. when "send" or "croak" are called (or were
573	callback or at any later time is guaranteed not to block.	768	called), with the only argument being the condition variable itself.
		769	Calling "recv" inside the callback or at any later time is
		770	guaranteed not to block.
		771
		772	SUPPORTED EVENT LOOPS/BACKENDS
		773	The available backend classes are (every class has its own manpage):
		774
		775	Backends that are autoprobed when no other event loop can be found.
		776	EV is the preferred backend when no other event loop seems to be in
		777	use. If EV is not installed, then AnyEvent will fall back to its own
		778	pure-perl implementation, which is available everywhere as it comes
		779	with AnyEvent itself.
		780
		781	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		782	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		783
		784	Backends that are transparently being picked up when they are used.
		785	These will be used when they are currently loaded when the first
		786	watcher is created, in which case it is assumed that the application
		787	is using them. This means that AnyEvent will automatically pick the
		788	right backend when the main program loads an event module before
		789	anything starts to create watchers. Nothing special needs to be done
		790	by the main program.
		791
		792	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		793	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		794	AnyEvent::Impl::Tk based on Tk, very broken.
		795	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		796	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		797	AnyEvent::Impl::Irssi used when running within irssi.
		798
		799	Backends with special needs.
		800	Qt requires the Qt::Application to be instantiated first, but will
		801	otherwise be picked up automatically. As long as the main program
		802	instantiates the application before any AnyEvent watchers are
		803	created, everything should just work.
		804
		805	AnyEvent::Impl::Qt based on Qt.
		806
		807	Support for IO::Async can only be partial, as it is too broken and
		808	architecturally limited to even support the AnyEvent API. It also is
		809	the only event loop that needs the loop to be set explicitly, so it
		810	can only be used by a main program knowing about AnyEvent. See
		811	AnyEvent::Impl::Async for the gory details.
		812
		813	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		814
		815	Event loops that are indirectly supported via other backends.
		816	Some event loops can be supported via other modules:
		817
		818	There is no direct support for WxWidgets (Wx) or Prima.
		819
		820	WxWidgets has no support for watching file handles. However, you can
		821	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		822	simply polls 20 times per second, which was considered to be too
		823	horrible to even consider for AnyEvent.
		824
		825	Prima is not supported as nobody seems to be using it, but it has a
		826	POE backend, so it can be supported through POE.
		827
		828	AnyEvent knows about both Prima and Wx, however, and will try to
		829	load POE when detecting them, in the hope that POE will pick them
		830	up, in which case everything will be automatic.
574		831
575	GLOBAL VARIABLES AND FUNCTIONS	832	GLOBAL VARIABLES AND FUNCTIONS
		833	These are not normally required to use AnyEvent, but can be useful to
		834	write AnyEvent extension modules.
		835
576	$AnyEvent::MODEL	836	$AnyEvent::MODEL
577	Contains "undef" until the first watcher is being created. Then it	837	Contains "undef" until the first watcher is being created, before
		838	the backend has been autodetected.
		839
578	contains the event model that is being used, which is the name of	840	Afterwards it contains the event model that is being used, which is
579	the Perl class implementing the model. This class is usually one of	841	the name of the Perl class implementing the model. This class is
580	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	842	usually one of the "AnyEvent::Impl:xxx" modules, but can be any
581	case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*).	843	other class in the case AnyEvent has been extended at runtime (e.g.
582		844	in *rxvt-unicode* it will be "urxvt::anyevent").
583	The known classes so far are:
584
585	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
586	AnyEvent::Impl::Event based on Event, second best choice.
587	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
588	AnyEvent::Impl::Glib based on Glib, third-best choice.
589	AnyEvent::Impl::Tk based on Tk, very bad choice.
590	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
591	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
592	AnyEvent::Impl::POE based on POE, not generic enough for full support.
593
594	There is no support for WxWidgets, as WxWidgets has no support for
595	watching file handles. However, you can use WxWidgets through the
596	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
597	second, which was considered to be too horrible to even consider for
598	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
599	using it's adaptor.
600
601	AnyEvent knows about Prima and Wx and will try to use POE when
602	autodetecting them.
603		845
604	AnyEvent::detect	846	AnyEvent::detect
605	Returns $AnyEvent::MODEL, forcing autodetection of the event model	847	Returns $AnyEvent::MODEL, forcing autodetection of the event model
606	if necessary. You should only call this function right before you	848	if necessary. You should only call this function right before you
607	would have created an AnyEvent watcher anyway, that is, as late as	849	would have created an AnyEvent watcher anyway, that is, as late as
608	possible at runtime.	850	possible at runtime, and not e.g. while initialising of your module.
		851
		852	If you need to do some initialisation before AnyEvent watchers are
		853	created, use "post_detect".
609		854
610	$guard = AnyEvent::post_detect { BLOCK }	855	$guard = AnyEvent::post_detect { BLOCK }
611	Arranges for the code block to be executed as soon as the event	856	Arranges for the code block to be executed as soon as the event
612	model is autodetected (or immediately if this has already happened).	857	model is autodetected (or immediately if this has already happened).
613		858
		859	The block will be executed *after* the actual backend has been
		860	detected ($AnyEvent::MODEL is set), but *before* any watchers have
		861	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		862	other initialisations - see the sources of AnyEvent::Strict or
		863	AnyEvent::AIO to see how this is used.
		864
		865	The most common usage is to create some global watchers, without
		866	forcing event module detection too early, for example, AnyEvent::AIO
		867	creates and installs the global IO::AIO watcher in a "post_detect"
		868	block to avoid autodetecting the event module at load time.
		869
614	If called in scalar or list context, then it creates and returns an	870	If called in scalar or list context, then it creates and returns an
615	object that automatically removes the callback again when it is	871	object that automatically removes the callback again when it is
		872	destroyed (or "undef" when the hook was immediately executed). See
616	destroyed. See Coro::BDB for a case where this is useful.	873	AnyEvent::AIO for a case where this is useful.
		874
		875	Example: Create a watcher for the IO::AIO module and store it in
		876	$WATCHER. Only do so after the event loop is initialised, though.
		877
		878	our WATCHER;
		879
		880	my $guard = AnyEvent::post_detect {
		881	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		882	};
		883
		884	# the ||= is important in case post_detect immediately runs the block,
		885	# as to not clobber the newly-created watcher. assigning both watcher and
		886	# post_detect guard to the same variable has the advantage of users being
		887	# able to just C<undef $WATCHER> if the watcher causes them grief.
		888
		889	$WATCHER ||= $guard;
617		890
618	@AnyEvent::post_detect	891	@AnyEvent::post_detect
619	If there are any code references in this array (you can "push" to it	892	If there are any code references in this array (you can "push" to it
620	before or after loading AnyEvent), then they will called directly	893	before or after loading AnyEvent), then they will called directly
621	after the event loop has been chosen.	894	after the event loop has been chosen.
622		895
623	You should check $AnyEvent::MODEL before adding to this array,	896	You should check $AnyEvent::MODEL before adding to this array,
624	though: if it contains a true value then the event loop has already	897	though: if it is defined then the event loop has already been
625	been detected, and the array will be ignored.	898	detected, and the array will be ignored.
626		899
627	Best use "AnyEvent::post_detect { BLOCK }" instead.	900	Best use "AnyEvent::post_detect { BLOCK }" when your application
		901	allows it,as it takes care of these details.
		902
		903	This variable is mainly useful for modules that can do something
		904	useful when AnyEvent is used and thus want to know when it is
		905	initialised, but do not need to even load it by default. This array
		906	provides the means to hook into AnyEvent passively, without loading
		907	it.
628		908
629	WHAT TO DO IN A MODULE	909	WHAT TO DO IN A MODULE
630	As a module author, you should "use AnyEvent" and call AnyEvent methods	910	As a module author, you should "use AnyEvent" and call AnyEvent methods
631	freely, but you should not load a specific event module or rely on it.	911	freely, but you should not load a specific event module or rely on it.
632		912
…		…
683	variable somewhere, waiting for it, and sending it when the program	963	variable somewhere, waiting for it, and sending it when the program
684	should exit cleanly.	964	should exit cleanly.
685		965
686	OTHER MODULES	966	OTHER MODULES
687	The following is a non-exhaustive list of additional modules that use	967	The following is a non-exhaustive list of additional modules that use
688	AnyEvent and can therefore be mixed easily with other AnyEvent modules	968	AnyEvent as a client and can therefore be mixed easily with other
689	in the same program. Some of the modules come with AnyEvent, some are	969	AnyEvent modules and other event loops in the same program. Some of the
690	available via CPAN.	970	modules come with AnyEvent, most are available via CPAN.
691		971
692	AnyEvent::Util	972	AnyEvent::Util
693	Contains various utility functions that replace often-used but	973	Contains various utility functions that replace often-used but
694	blocking functions such as "inet_aton" by event-/callback-based	974	blocking functions such as "inet_aton" by event-/callback-based
695	versions.	975	versions.
696
697	AnyEvent::Handle
698	Provide read and write buffers and manages watchers for reads and
699	writes.
700		976
701	AnyEvent::Socket	977	AnyEvent::Socket
702	Provides various utility functions for (internet protocol) sockets,	978	Provides various utility functions for (internet protocol) sockets,
703	addresses and name resolution. Also functions to create non-blocking	979	addresses and name resolution. Also functions to create non-blocking
704	tcp connections or tcp servers, with IPv6 and SRV record support and	980	tcp connections or tcp servers, with IPv6 and SRV record support and
705	more.	981	more.
706		982
		983	AnyEvent::Handle
		984	Provide read and write buffers, manages watchers for reads and
		985	writes, supports raw and formatted I/O, I/O queued and fully
		986	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
		987
707	AnyEvent::DNS	988	AnyEvent::DNS
708	Provides rich asynchronous DNS resolver capabilities.	989	Provides rich asynchronous DNS resolver capabilities.
709		990
		991	AnyEvent::HTTP
		992	A simple-to-use HTTP library that is capable of making a lot of
		993	concurrent HTTP requests.
		994
710	AnyEvent::HTTPD	995	AnyEvent::HTTPD
711	Provides a simple web application server framework.	996	Provides a simple web application server framework.
712		997
713	AnyEvent::FastPing	998	AnyEvent::FastPing
714	The fastest ping in the west.	999	The fastest ping in the west.
715		1000
		1001	AnyEvent::DBI
		1002	Executes DBI requests asynchronously in a proxy process.
		1003
		1004	AnyEvent::AIO
		1005	Truly asynchronous I/O, should be in the toolbox of every event
		1006	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		1007	together.
		1008
		1009	AnyEvent::BDB
		1010	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
		1011	fuses BDB and AnyEvent together.
		1012
		1013	AnyEvent::GPSD
		1014	A non-blocking interface to gpsd, a daemon delivering GPS
		1015	information.
		1016
		1017	AnyEvent::IRC
		1018	AnyEvent based IRC client module family (replacing the older
716	Net::IRC3	1019	Net::IRC3).
717	AnyEvent based IRC client module family.
718		1020
719	Net::XMPP2	1021	AnyEvent::XMPP
720	AnyEvent based XMPP (Jabber protocol) module family.	1022	AnyEvent based XMPP (Jabber protocol) module family (replacing the
		1023	older Net::XMPP2>.
		1024
		1025	AnyEvent::IGS
		1026	A non-blocking interface to the Internet Go Server protocol (used by
		1027	App::IGS).
721		1028
722	Net::FCP	1029	Net::FCP
723	AnyEvent-based implementation of the Freenet Client Protocol,	1030	AnyEvent-based implementation of the Freenet Client Protocol,
724	birthplace of AnyEvent.	1031	birthplace of AnyEvent.
725		1032
…		…
727	High level API for event-based execution flow control.	1034	High level API for event-based execution flow control.
728		1035
729	Coro	1036	Coro
730	Has special support for AnyEvent via Coro::AnyEvent.	1037	Has special support for AnyEvent via Coro::AnyEvent.
731		1038
732	AnyEvent::AIO, IO::AIO	1039	SIMPLIFIED AE API
733	Truly asynchronous I/O, should be in the toolbox of every event	1040	Starting with version 5.0, AnyEvent officially supports a second, much
734	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent	1041	simpler, API that is designed to reduce the calling, typing and memory
735	together.	1042	overhead.
736		1043
737	AnyEvent::BDB, BDB	1044	See the AE manpage for details.
738	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
739	fuses IO::AIO and AnyEvent together.
740		1045
741	IO::Lambda	1046	ERROR AND EXCEPTION HANDLING
742	The lambda approach to I/O - don't ask, look there. Can use	1047	In general, AnyEvent does not do any error handling - it relies on the
743	AnyEvent.	1048	caller to do that if required. The AnyEvent::Strict module (see also the
		1049	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
		1050	checking of all AnyEvent methods, however, which is highly useful during
		1051	development.
744		1052
745	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1053	As for exception handling (i.e. runtime errors and exceptions thrown
746	This is an advanced topic that you do not normally need to use AnyEvent	1054	while executing a callback), this is not only highly event-loop
747	in a module. This section is only of use to event loop authors who want	1055	specific, but also not in any way wrapped by this module, as this is the
748	to provide AnyEvent compatibility.	1056	job of the main program.
749		1057
750	If you need to support another event library which isn't directly	1058	The pure perl event loop simply re-throws the exception (usually within
751	supported by AnyEvent, you can supply your own interface to it by	1059	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
752	pushing, before the first watcher gets created, the package name of the	1060	Glib uses "install_exception_handler" and so on.
753	event module and the package name of the interface to use onto
754	@AnyEvent::REGISTRY. You can do that before and even without loading
755	AnyEvent, so it is reasonably cheap.
756
757	Example:
758
759	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
760
761	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
762	package/class when it finds the "urxvt" package/module is already
763	loaded.
764
765	When AnyEvent is loaded and asked to find a suitable event model, it
766	will first check for the presence of urxvt by trying to "use" the
767	"urxvt::anyevent" module.
768
769	The class should provide implementations for all watcher types. See
770	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
771	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
772	the sources.
773
774	If you don't provide "signal" and "child" watchers than AnyEvent will
775	provide suitable (hopefully) replacements.
776
777	The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt)
778	terminal emulator uses the above line as-is. An interface isn't included
779	in AnyEvent because it doesn't make sense outside the embedded
780	interpreter inside *rxvt-unicode*, and it is updated and maintained as
781	part of the *rxvt-unicode* distribution.
782
783	*rxvt-unicode* also cheats a bit by not providing blocking access to
784	condition variables: code blocking while waiting for a condition will
785	"die". This still works with most modules/usages, and blocking calls
786	must not be done in an interactive application, so it makes sense.
787		1061
788	ENVIRONMENT VARIABLES	1062	ENVIRONMENT VARIABLES
789	The following environment variables are used by this module:	1063	The following environment variables are used by this module or its
		1064	submodules.
		1065
		1066	Note that AnyEvent will remove *all* environment variables starting with
		1067	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1068	enabled.
790		1069
791	"PERL_ANYEVENT_VERBOSE"	1070	"PERL_ANYEVENT_VERBOSE"
792	By default, AnyEvent will be completely silent except in fatal	1071	By default, AnyEvent will be completely silent except in fatal
793	conditions. You can set this environment variable to make AnyEvent	1072	conditions. You can set this environment variable to make AnyEvent
794	more talkative.	1073	more talkative.
…		…
797	conditions, such as not being able to load the event model specified	1076	conditions, such as not being able to load the event model specified
798	by "PERL_ANYEVENT_MODEL".	1077	by "PERL_ANYEVENT_MODEL".
799		1078
800	When set to 2 or higher, cause AnyEvent to report to STDERR which	1079	When set to 2 or higher, cause AnyEvent to report to STDERR which
801	event model it chooses.	1080	event model it chooses.
		1081
		1082	When set to 8 or higher, then AnyEvent will report extra information
		1083	on which optional modules it loads and how it implements certain
		1084	features.
		1085
		1086	"PERL_ANYEVENT_STRICT"
		1087	AnyEvent does not do much argument checking by default, as thorough
		1088	argument checking is very costly. Setting this variable to a true
		1089	value will cause AnyEvent to load "AnyEvent::Strict" and then to
		1090	thoroughly check the arguments passed to most method calls. If it
		1091	finds any problems, it will croak.
		1092
		1093	In other words, enables "strict" mode.
		1094
		1095	Unlike "use strict" (or it's modern cousin, "use common::sense", it
		1096	is definitely recommended to keep it off in production. Keeping
		1097	"PERL_ANYEVENT_STRICT=1" in your environment while developing
		1098	programs can be very useful, however.
802		1099
803	"PERL_ANYEVENT_MODEL"	1100	"PERL_ANYEVENT_MODEL"
804	This can be used to specify the event model to be used by AnyEvent,	1101	This can be used to specify the event model to be used by AnyEvent,
805	before auto detection and -probing kicks in. It must be a string	1102	before auto detection and -probing kicks in. It must be a string
806	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1103	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
811	This functionality might change in future versions.	1108	This functionality might change in future versions.
812		1109
813	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1110	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
814	could start your program like this:	1111	could start your program like this:
815		1112
816	PERL_ANYEVENT_MODEL=Perl perl ...	1113	PERL_ANYEVENT_MODEL=Perl perl ...
817		1114
818	"PERL_ANYEVENT_PROTOCOLS"	1115	"PERL_ANYEVENT_PROTOCOLS"
819	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1116	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
820	preferences for IPv4 or IPv6. The default is unspecified (and might	1117	preferences for IPv4 or IPv6. The default is unspecified (and might
821	change, or be the result of auto probing).	1118	change, or be the result of auto probing).
…		…
825	mentioned will be used, and preference will be given to protocols	1122	mentioned will be used, and preference will be given to protocols
826	mentioned earlier in the list.	1123	mentioned earlier in the list.
827		1124
828	This variable can effectively be used for denial-of-service attacks	1125	This variable can effectively be used for denial-of-service attacks
829	against local programs (e.g. when setuid), although the impact is	1126	against local programs (e.g. when setuid), although the impact is
830	likely small, as the program has to handle connection errors	1127	likely small, as the program has to handle conenction and other
831	already-	1128	failures anyways.
832		1129
833	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1130	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
834	IPv6, but support both and try to use both.	1131	IPv6, but support both and try to use both.
835	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1132	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
836	resolve or contact IPv6 addresses.	1133	resolve or contact IPv6 addresses.
…		…
847	EDNS0 in its DNS requests.	1144	EDNS0 in its DNS requests.
848		1145
849	"PERL_ANYEVENT_MAX_FORKS"	1146	"PERL_ANYEVENT_MAX_FORKS"
850	The maximum number of child processes that	1147	The maximum number of child processes that
851	"AnyEvent::Util::fork_call" will create in parallel.	1148	"AnyEvent::Util::fork_call" will create in parallel.
		1149
		1150	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1151	The default value for the "max_outstanding" parameter for the
		1152	default DNS resolver - this is the maximum number of parallel DNS
		1153	requests that are sent to the DNS server.
		1154
		1155	"PERL_ANYEVENT_RESOLV_CONF"
		1156	The file to use instead of /etc/resolv.conf (or OS-specific
		1157	configuration) in the default resolver. When set to the empty
		1158	string, no default config will be used.
		1159
		1160	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1161	When neither "ca_file" nor "ca_path" was specified during
		1162	AnyEvent::TLS context creation, and either of these environment
		1163	variables exist, they will be used to specify CA certificate
		1164	locations instead of a system-dependent default.
		1165
		1166	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1167	When these are set to 1, then the respective modules are not loaded.
		1168	Mostly good for testing AnyEvent itself.
		1169
		1170	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1171	This is an advanced topic that you do not normally need to use AnyEvent
		1172	in a module. This section is only of use to event loop authors who want
		1173	to provide AnyEvent compatibility.
		1174
		1175	If you need to support another event library which isn't directly
		1176	supported by AnyEvent, you can supply your own interface to it by
		1177	pushing, before the first watcher gets created, the package name of the
		1178	event module and the package name of the interface to use onto
		1179	@AnyEvent::REGISTRY. You can do that before and even without loading
		1180	AnyEvent, so it is reasonably cheap.
		1181
		1182	Example:
		1183
		1184	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
		1185
		1186	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
		1187	package/class when it finds the "urxvt" package/module is already
		1188	loaded.
		1189
		1190	When AnyEvent is loaded and asked to find a suitable event model, it
		1191	will first check for the presence of urxvt by trying to "use" the
		1192	"urxvt::anyevent" module.
		1193
		1194	The class should provide implementations for all watcher types. See
		1195	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
		1196	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
		1197	the sources.
		1198
		1199	If you don't provide "signal" and "child" watchers than AnyEvent will
		1200	provide suitable (hopefully) replacements.
		1201
		1202	The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt)
		1203	terminal emulator uses the above line as-is. An interface isn't included
		1204	in AnyEvent because it doesn't make sense outside the embedded
		1205	interpreter inside *rxvt-unicode*, and it is updated and maintained as
		1206	part of the *rxvt-unicode* distribution.
		1207
		1208	*rxvt-unicode* also cheats a bit by not providing blocking access to
		1209	condition variables: code blocking while waiting for a condition will
		1210	"die". This still works with most modules/usages, and blocking calls
		1211	must not be done in an interactive application, so it makes sense.
852		1212
853	EXAMPLE PROGRAM	1213	EXAMPLE PROGRAM
854	The following program uses an I/O watcher to read data from STDIN, a	1214	The following program uses an I/O watcher to read data from STDIN, a
855	timer to display a message once per second, and a condition variable to	1215	timer to display a message once per second, and a condition variable to
856	quit the program when the user enters quit:	1216	quit the program when the user enters quit:
…		…
868	warn "read: $input\n"; # output what has been read	1228	warn "read: $input\n"; # output what has been read
869	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1229	$cv->send if $input =~ /^q/i; # quit program if /^q/i
870	},	1230	},
871	);	1231	);
872		1232
873	my $time_watcher; # can only be used once
874
875	sub new_timer {
876	$timer = AnyEvent->timer (after => 1, cb => sub {	1233	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
877	warn "timeout\n"; # print 'timeout' about every second	1234	warn "timeout\n"; # print 'timeout' at most every second
878	&new_timer; # and restart the time
879	});
880	}	1235	});
881
882	new_timer; # create first timer
883		1236
884	$cv->recv; # wait until user enters /^q/i	1237	$cv->recv; # wait until user enters /^q/i
885		1238
886	REAL-WORLD EXAMPLE	1239	REAL-WORLD EXAMPLE
887	Consider the Net::FCP module. It features (among others) the following	1240	Consider the Net::FCP module. It features (among others) the following
…		…
1014	through AnyEvent. The benchmark creates a lot of timers (with a zero	1367	through AnyEvent. The benchmark creates a lot of timers (with a zero
1015	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1368	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1016	which it is), lets them fire exactly once and destroys them again.	1369	which it is), lets them fire exactly once and destroys them again.
1017		1370
1018	Source code for this benchmark is found as eg/bench in the AnyEvent	1371	Source code for this benchmark is found as eg/bench in the AnyEvent
1019	distribution.	1372	distribution. It uses the AE interface, which makes a real difference
		1373	for the EV and Perl backends only.
1020		1374
1021	Explanation of the columns	1375	Explanation of the columns
1022	*watcher* is the number of event watchers created/destroyed. Since	1376	*watcher* is the number of event watchers created/destroyed. Since
1023	different event models feature vastly different performances, each event	1377	different event models feature vastly different performances, each event
1024	loop was given a number of watchers so that overall runtime is	1378	loop was given a number of watchers so that overall runtime is
…		…
1043	*destroy* is the time, in microseconds, that it takes to destroy a	1397	*destroy* is the time, in microseconds, that it takes to destroy a
1044	single watcher.	1398	single watcher.
1045		1399
1046	Results	1400	Results
1047	name watchers bytes create invoke destroy comment	1401	name watchers bytes create invoke destroy comment
1048	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1402	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1049	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1403	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1050	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1404	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1051	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1405	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1052	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1406	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1053	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1407	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		1408	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		1409	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1054	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1410	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1055	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1411	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1056	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1412	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1057	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1413	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1058		1414
1059	Discussion	1415	Discussion
1060	The benchmark does *not* measure scalability of the event loop very	1416	The benchmark does *not* measure scalability of the event loop very
1061	well. For example, a select-based event loop (such as the pure perl one)	1417	well. For example, a select-based event loop (such as the pure perl one)
1062	can never compete with an event loop that uses epoll when the number of	1418	can never compete with an event loop that uses epoll when the number of
…		…
1073	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1429	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1074	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1430	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1075	CPU cycles with POE.	1431	CPU cycles with POE.
1076		1432
1077	"EV" is the sole leader regarding speed and memory use, which are both	1433	"EV" is the sole leader regarding speed and memory use, which are both
1078	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1434	maximal/minimal, respectively. When using the AE API there is zero
		1435	overhead (when going through the AnyEvent API create is about 5-6 times
		1436	slower, with other times being equal, so still uses far less memory than
1079	far less memory than any other event loop and is still faster than Event	1437	any other event loop and is still faster than Event natively).
1080	natively.
1081		1438
1082	The pure perl implementation is hit in a few sweet spots (both the	1439	The pure perl implementation is hit in a few sweet spots (both the
1083	constant timeout and the use of a single fd hit optimisations in the	1440	constant timeout and the use of a single fd hit optimisations in the
1084	perl interpreter and the backend itself). Nevertheless this shows that	1441	perl interpreter and the backend itself). Nevertheless this shows that
1085	it adds very little overhead in itself. Like any select-based backend	1442	it adds very little overhead in itself. Like any select-based backend
…		…
1087	few of them active), of course, but this was not subject of this	1444	few of them active), of course, but this was not subject of this
1088	benchmark.	1445	benchmark.
1089		1446
1090	The "Event" module has a relatively high setup and callback invocation	1447	The "Event" module has a relatively high setup and callback invocation
1091	cost, but overall scores in on the third place.	1448	cost, but overall scores in on the third place.
		1449
		1450	"IO::Async" performs admirably well, about on par with "Event", even
		1451	when using its pure perl backend.
1092		1452
1093	"Glib"'s memory usage is quite a bit higher, but it features a faster	1453	"Glib"'s memory usage is quite a bit higher, but it features a faster
1094	callback invocation and overall ends up in the same class as "Event".	1454	callback invocation and overall ends up in the same class as "Event".
1095	However, Glib scales extremely badly, doubling the number of watchers	1455	However, Glib scales extremely badly, doubling the number of watchers
1096	increases the processing time by more than a factor of four, making it	1456	increases the processing time by more than a factor of four, making it
…		…
1152	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1512	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1153	100 (1%) are active. This mirrors the activity of large servers with	1513	100 (1%) are active. This mirrors the activity of large servers with
1154	many connections, most of which are idle at any one point in time.	1514	many connections, most of which are idle at any one point in time.
1155		1515
1156	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1516	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1157	distribution.	1517	distribution. It uses the AE interface, which makes a real difference
		1518	for the EV and Perl backends only.
1158		1519
1159	Explanation of the columns	1520	Explanation of the columns
1160	*sockets* is the number of sockets, and twice the number of "servers"	1521	*sockets* is the number of sockets, and twice the number of "servers"
1161	(as each server has a read and write socket end).	1522	(as each server has a read and write socket end).
1162		1523
…		…
1167	single "request", that is, reading the token from the pipe and	1528	single "request", that is, reading the token from the pipe and
1168	forwarding it to another server. This includes deleting the old timeout	1529	forwarding it to another server. This includes deleting the old timeout
1169	and creating a new one that moves the timeout into the future.	1530	and creating a new one that moves the timeout into the future.
1170		1531
1171	Results	1532	Results
1172	name sockets create request	1533	name sockets create request
1173	EV 20000 69.01 11.16	1534	EV 20000 62.66 7.99
1174	Perl 20000 73.32 35.87	1535	Perl 20000 68.32 32.64
1175	Event 20000 212.62 257.32	1536	IOAsync 20000 174.06 101.15 epoll
1176	Glib 20000 651.16 1896.30	1537	IOAsync 20000 174.67 610.84 poll
		1538	Event 20000 202.69 242.91
		1539	Glib 20000 557.01 1689.52
1177	POE 20000 349.67 12317.24 uses POE::Loop::Event	1540	POE 20000 341.54 12086.32 uses POE::Loop::Event
1178		1541
1179	Discussion	1542	Discussion
1180	This benchmark *does* measure scalability and overall performance of the	1543	This benchmark *does* measure scalability and overall performance of the
1181	particular event loop.	1544	particular event loop.
1182		1545
1183	EV is again fastest. Since it is using epoll on my system, the setup	1546	EV is again fastest. Since it is using epoll on my system, the setup
1184	time is relatively high, though.	1547	time is relatively high, though.
1185		1548
1186	Perl surprisingly comes second. It is much faster than the C-based event	1549	Perl surprisingly comes second. It is much faster than the C-based event
1187	loops Event and Glib.	1550	loops Event and Glib.
		1551
		1552	IO::Async performs very well when using its epoll backend, and still
		1553	quite good compared to Glib when using its pure perl backend.
1188		1554
1189	Event suffers from high setup time as well (look at its code and you	1555	Event suffers from high setup time as well (look at its code and you
1190	will understand why). Callback invocation also has a high overhead	1556	will understand why). Callback invocation also has a high overhead
1191	compared to the "$_->() for .."-style loop that the Perl event loop	1557	compared to the "$_->() for .."-style loop that the Perl event loop
1192	uses. Event uses select or poll in basically all documented	1558	uses. Event uses select or poll in basically all documented
…		…
1243		1609
1244	Summary	1610	Summary
1245	* C-based event loops perform very well with small number of watchers,	1611	* C-based event loops perform very well with small number of watchers,
1246	as the management overhead dominates.	1612	as the management overhead dominates.
1247		1613
		1614	THE IO::Lambda BENCHMARK
		1615	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1616	could be misinterpreted to make AnyEvent look bad. In fact, the
		1617	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1618	better (which shouldn't come as a surprise to anybody). As such, the
		1619	benchmark is fine, and mostly shows that the AnyEvent backend from
		1620	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1621	without the extra baggage? To explore this, I wrote the equivalent
		1622	benchmark for AnyEvent.
		1623
		1624	The benchmark itself creates an echo-server, and then, for 500 times,
		1625	connects to the echo server, sends a line, waits for the reply, and then
		1626	creates the next connection. This is a rather bad benchmark, as it
		1627	doesn't test the efficiency of the framework or much non-blocking I/O,
		1628	but it is a benchmark nevertheless.
		1629
		1630	name runtime
		1631	Lambda/select 0.330 sec
		1632	+ optimized 0.122 sec
		1633	Lambda/AnyEvent 0.327 sec
		1634	+ optimized 0.138 sec
		1635	Raw sockets/select 0.077 sec
		1636	POE/select, components 0.662 sec
		1637	POE/select, raw sockets 0.226 sec
		1638	POE/select, optimized 0.404 sec
		1639
		1640	AnyEvent/select/nb 0.085 sec
		1641	AnyEvent/EV/nb 0.068 sec
		1642	+state machine 0.134 sec
		1643
		1644	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1645	benchmarks actually make blocking connects and use 100% blocking I/O,
		1646	defeating the purpose of an event-based solution. All of the newly
		1647	written AnyEvent benchmarks use 100% non-blocking connects (using
		1648	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1649	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1650	connects generally require a lot more bookkeeping and event handling
		1651	than blocking connects (which involve a single syscall only).
		1652
		1653	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1654	offers similar expressive power as POE and IO::Lambda, using
		1655	conventional Perl syntax. This means that both the echo server and the
		1656	client are 100% non-blocking, further placing it at a disadvantage.
		1657
		1658	As you can see, the AnyEvent + EV combination even beats the
		1659	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1660	backend easily beats IO::Lambda and POE.
		1661
		1662	And even the 100% non-blocking version written using the high-level (and
		1663	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
		1664	higher level ("unoptimised") abstractions by a large margin, even though
		1665	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		1666
		1667	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1668	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1669	part of the IO::Lambda distribution and were used without any changes.
		1670
		1671	SIGNALS
		1672	AnyEvent currently installs handlers for these signals:
		1673
		1674	SIGCHLD
		1675	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
		1676	emulation for event loops that do not support them natively. Also,
		1677	some event loops install a similar handler.
		1678
		1679	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1680	then AnyEvent will reset it to default, to avoid losing child exit
		1681	statuses.
		1682
		1683	SIGPIPE
		1684	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
		1685	"undef" when AnyEvent gets loaded.
		1686
		1687	The rationale for this is that AnyEvent users usually do not really
		1688	depend on SIGPIPE delivery (which is purely an optimisation for
		1689	shell use, or badly-written programs), but "SIGPIPE" can cause
		1690	spurious and rare program exits as a lot of people do not expect
		1691	"SIGPIPE" when writing to some random socket.
		1692
		1693	The rationale for installing a no-op handler as opposed to ignoring
		1694	it is that this way, the handler will be restored to defaults on
		1695	exec.
		1696
		1697	Feel free to install your own handler, or reset it to defaults.
		1698
		1699	RECOMMENDED/OPTIONAL MODULES
		1700	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1701	it's built-in modules) are required to use it.
		1702
		1703	That does not mean that AnyEvent won't take advantage of some additional
		1704	modules if they are installed.
		1705
		1706	This section epxlains which additional modules will be used, and how
		1707	they affect AnyEvent's operetion.
		1708
		1709	Async::Interrupt
		1710	This slightly arcane module is used to implement fast signal
		1711	handling: To my knowledge, there is no way to do completely
		1712	race-free and quick signal handling in pure perl. To ensure that
		1713	signals still get delivered, AnyEvent will start an interval timer
		1714	to wake up perl (and catch the signals) with some delay (default is
		1715	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1716
		1717	If this module is available, then it will be used to implement
		1718	signal catching, which means that signals will not be delayed, and
		1719	the event loop will not be interrupted regularly, which is more
		1720	efficient (And good for battery life on laptops).
		1721
		1722	This affects not just the pure-perl event loop, but also other event
		1723	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1724
		1725	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1726	natively, and either employ their own workarounds (POE) or use
		1727	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1728	Installing Async::Interrupt does nothing for those backends.
		1729
		1730	EV This module isn't really "optional", as it is simply one of the
		1731	backend event loops that AnyEvent can use. However, it is simply the
		1732	best event loop available in terms of features, speed and stability:
		1733	It supports the AnyEvent API optimally, implements all the watcher
		1734	types in XS, does automatic timer adjustments even when no monotonic
		1735	clock is available, can take avdantage of advanced kernel interfaces
		1736	such as "epoll" and "kqueue", and is the fastest backend *by far*.
		1737	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1738	Glib::EV).
		1739
		1740	Guard
		1741	The guard module, when used, will be used to implement
		1742	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1743	uses a lot less memory), but otherwise doesn't affect guard
		1744	operation much. It is purely used for performance.
		1745
		1746	JSON and JSON::XS
		1747	One of these modules is required when you want to read or write JSON
		1748	data via AnyEvent::Handle. It is also written in pure-perl, but can
		1749	take advantage of the ultra-high-speed JSON::XS module when it is
		1750	installed.
		1751
		1752	In fact, AnyEvent::Handle will use JSON::XS by default if it is
		1753	installed.
		1754
		1755	Net::SSLeay
		1756	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1757	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1758	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1759
		1760	Time::HiRes
		1761	This module is part of perl since release 5.008. It will be used
		1762	when the chosen event library does not come with a timing source on
		1763	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1764	additionally use it to try to use a monotonic clock for timing
		1765	stability.
		1766
1248	FORK	1767	FORK
1249	Most event libraries are not fork-safe. The ones who are usually are	1768	Most event libraries are not fork-safe. The ones who are usually are
1250	because they rely on inefficient but fork-safe "select" or "poll" calls.	1769	because they rely on inefficient but fork-safe "select" or "poll" calls.
1251	Only EV is fully fork-aware.	1770	Only EV is fully fork-aware.
1252		1771
1253	If you have to fork, you must either do so *before* creating your first	1772	If you have to fork, you must either do so *before* creating your first
1254	watcher OR you must not use AnyEvent at all in the child.	1773	watcher OR you must not use AnyEvent at all in the child OR you must do
		1774	something completely out of the scope of AnyEvent.
1255		1775
1256	SECURITY CONSIDERATIONS	1776	SECURITY CONSIDERATIONS
1257	AnyEvent can be forced to load any event model via	1777	AnyEvent can be forced to load any event model via
1258	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1778	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1259	to execute arbitrary code or directly gain access, it can easily be used	1779	to execute arbitrary code or directly gain access, it can easily be used
…		…
1262	model than specified in the variable.	1782	model than specified in the variable.
1263		1783
1264	You can make AnyEvent completely ignore this variable by deleting it	1784	You can make AnyEvent completely ignore this variable by deleting it
1265	before the first watcher gets created, e.g. with a "BEGIN" block:	1785	before the first watcher gets created, e.g. with a "BEGIN" block:
1266		1786
1267	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1787	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1268		1788
1269	use AnyEvent;	1789	use AnyEvent;
1270		1790
1271	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1791	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1272	be used to probe what backend is used and gain other information (which	1792	be used to probe what backend is used and gain other information (which
1273	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	1793	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
		1794	and $ENV{PERL_ANYEVENT_STRICT}.
		1795
		1796	Note that AnyEvent will remove *all* environment variables starting with
		1797	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1798	enabled.
		1799
		1800	BUGS
		1801	Perl 5.8 has numerous memleaks that sometimes hit this module and are
		1802	hard to work around. If you suffer from memleaks, first upgrade to Perl
		1803	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
		1804	annoying memleaks, such as leaking on "map" and "grep" but it is usually
		1805	not as pronounced).
1274		1806
1275	SEE ALSO	1807	SEE ALSO
1276	Utility functions: AnyEvent::Util.	1808	Utility functions: AnyEvent::Util.
1277		1809
1278	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1810	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1279	Event::Lib, Qt, POE.	1811	Event::Lib, Qt, POE.
1280		1812
1281	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1813	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1282	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1814	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1283	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1815	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1816	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1284		1817
1285	Non-blocking file handles, sockets, TCP clients and servers:	1818	Non-blocking file handles, sockets, TCP clients and servers:
1286	AnyEvent::Handle, AnyEvent::Socket.	1819	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1287		1820
1288	Asynchronous DNS: AnyEvent::DNS.	1821	Asynchronous DNS: AnyEvent::DNS.
1289		1822
1290	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1823	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1291		1824
1292	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1825	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1826	AnyEvent::HTTP.
1293		1827
1294	AUTHOR	1828	AUTHOR
1295	Marc Lehmann <schmorp@schmorp.de>	1829	Marc Lehmann <schmorp@schmorp.de>
1296	http://home.schmorp.de/	1830	http://home.schmorp.de/
1297		1831

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