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Comparing AnyEvent/README (file contents):
Revision 1.25 by root, Tue Jun 3 09:02:46 2008 UTC vs.
Revision 1.53 by root, Fri Aug 21 11:59:24 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 });
21		37
22	INTRODUCTION/TUTORIAL	38	INTRODUCTION/TUTORIAL
23	This manpage is mainly a reference manual. If you are interested in a	39	This manpage is mainly a reference manual. If you are interested in a
24	tutorial or some gentle introduction, have a look at the AnyEvent::Intro	40	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
25	manpage.	41	manpage.
26		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.
		49
27	WHY YOU SHOULD USE THIS MODULE (OR NOT)	50	WHY YOU SHOULD USE THIS MODULE (OR NOT)
28	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
29	nowadays. So what is different about AnyEvent?	52	nowadays. So what is different about AnyEvent?
30		53
31	Executive Summary: AnyEvent is compatible, AnyEvent is *free of	54	Executive Summary: AnyEvent is compatible, AnyEvent is *free of
32	policy* and AnyEvent is small and efficient.	55	policy* and AnyEvent is small and efficient.
33		56
34	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
35	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
36	pragmatic way. For event models and certain classes of immortals alike,	59	pragmatic way. For event models and certain classes of immortals alike,
37	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,
38	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.
39	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.
40		64
41	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
42	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
43	religion, a way of living, and most importantly: without forcing your	67	religion, a way of living, and most importantly: without forcing your
44	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
45	model you use.	69	model you use.
46		70
47	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
48	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
49	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
50	cannot use anything else, as it is simply incompatible to everything	74	cannot use anything else, as they are simply incompatible to everything
51	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
52	are also forced to use the same event loop you use.	76	are also forced to use the same event loop you use.
53		77
54	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	78	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
55	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
56	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
57	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.
58	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
59	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
60	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
61	event loops to AnyEvent, too, so it is future-proof).	85	to AnyEvent, too, so it is future-proof).
62		86
63	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
64	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
65	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
66	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
122	These watchers are normal Perl objects with normal Perl lifetime. After	146	These watchers are normal Perl objects with normal Perl lifetime. After
123	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
124	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
125	in control).	149	in control).
126		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
127	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
128	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
129	to it).	159	to it).
130		160
131	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.
…		…
143	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,
144	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
145	declared.	175	declared.
146		176
147	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
148	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
149	the following mandatory key-value pairs as arguments:	185	the following mandatory key-value pairs as arguments:
150		186
151	"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
152	"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
153	watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"	195	watcher waiting for "r"eadable or "w"ritable events, respectively.
		196
154	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.
155		198
156	Although the callback might get passed parameters, their value and	199	Although the callback might get passed parameters, their value and
157	presence is undefined and you cannot rely on them. Portable AnyEvent	200	presence is undefined and you cannot rely on them. Portable AnyEvent
158	callbacks cannot use arguments passed to I/O watcher callbacks.	201	callbacks cannot use arguments passed to I/O watcher callbacks.
159		202
…		…
163		206
164	Some event loops issue spurious readyness notifications, so you should	207	Some event loops issue spurious readyness notifications, so you should
165	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
166	handles.	209	handles.
167		210
168	Example:
169
170	# 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
171	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	214	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
172	chomp (my $input = <STDIN>);	215	chomp (my $input = <STDIN>);
173	warn "read: $input\n";	216	warn "read: $input\n";
174	undef $w;	217	undef $w;
175	});	218	});
176		219
177	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
178	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
179	with the following mandatory arguments:	230	with the following mandatory arguments:
180		231
181	"after" specifies after how many seconds (fractional values are	232	"after" specifies after how many seconds (fractional values are
182	supported) the callback should be invoked. "cb" is the callback to	233	supported) the callback should be invoked. "cb" is the callback to
…		…
184		235
185	Although the callback might get passed parameters, their value and	236	Although the callback might get passed parameters, their value and
186	presence is undefined and you cannot rely on them. Portable AnyEvent	237	presence is undefined and you cannot rely on them. Portable AnyEvent
187	callbacks cannot use arguments passed to time watcher callbacks.	238	callbacks cannot use arguments passed to time watcher callbacks.
188		239
189	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
190	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
191	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.
192		245
193	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.
194		249
195	# fire an event after 7.7 seconds	250	Example: fire an event after 7.7 seconds.
		251
196	my $w = AnyEvent->timer (after => 7.7, cb => sub {	252	my $w = AnyEvent->timer (after => 7.7, cb => sub {
197	warn "timeout\n";	253	warn "timeout\n";
198	});	254	});
199		255
200	# to cancel the timer:	256	# to cancel the timer:
201	undef $w;	257	undef $w;
202		258
203	Example 2:
204
205	# 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.
206	my $w;
207		260
208	my $cb = sub {
209	# cancel the old timer while creating a new one
210	$w = AnyEvent->timer (after => 1, cb => $cb);	261	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		262	warn "timeout\n";
211	};	263	};
212
213	# start the "loop" by creating the first watcher
214	$w = AnyEvent->timer (after => 0.5, cb => $cb);
215		264
216	TIMING ISSUES	265	TIMING ISSUES
217	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
218	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
219	o'clock").	268	o'clock").
…		…
293	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
294	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
295	the difference between "AnyEvent->time" and "AnyEvent->now" into	344	the difference between "AnyEvent->time" and "AnyEvent->now" into
296	account.	345	account.
297		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
298	SIGNAL WATCHERS	361	SIGNAL WATCHERS
		362	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		363
299	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
300	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
301	whenever a signal occurs.	366	callback to be invoked whenever a signal occurs.
302		367
303	Although the callback might get passed parameters, their value and	368	Although the callback might get passed parameters, their value and
304	presence is undefined and you cannot rely on them. Portable AnyEvent	369	presence is undefined and you cannot rely on them. Portable AnyEvent
305	callbacks cannot use arguments passed to signal watcher callbacks.	370	callbacks cannot use arguments passed to signal watcher callbacks.
306		371
…		…
308	invocation, and callback invocation will be synchronous. Synchronous	373	invocation, and callback invocation will be synchronous. Synchronous
309	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
310	process, but it is guaranteed not to interrupt any other callbacks.	375	process, but it is guaranteed not to interrupt any other callbacks.
311		376
312	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
313	signal between multiple watchers.	378	signal between multiple watchers, and AnyEvent will ensure that signals
		379	will not interrupt your program at bad times.
314		380
315	This watcher might use %SIG, so programs overwriting those signals	381	This watcher might use %SIG (depending on the event loop used), so
316	directly will likely not work correctly.	382	programs overwriting those signals directly will likely not work
		383	correctly.
317		384
318	Example: exit on SIGINT	385	Example: exit on SIGINT
319		386
320	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	387	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
321		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
322	CHILD PROCESS WATCHERS	408	CHILD PROCESS WATCHERS
		409	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		410
323	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.
324		412
325	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,
326	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).
327	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
328	signal handler for "SIGCHLD". The callback will be called with the pid	416	and an exit status is available, not on any trace events
329	and exit status (as returned by waitpid), so unlike other watcher types,	417	(stopped/continued).
330	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).
331		427
332	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
333	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
334	could have exited already (and no SIGCHLD will be sent anymore).	430	could have exited already (and no SIGCHLD will be sent anymore).
335		431
336	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
337	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
338	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).
339	place).	436	AnyEvent's pure perl event loop handles all cases correctly regardless
		437	of when you start the watcher.
340		438
341	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
342	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
343	you "fork" the child (alternatively, you can call "AnyEvent::detect").	441	you "fork" the child (alternatively, you can call "AnyEvent::detect").
344		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
345	Example: fork a process and wait for it	447	Example: fork a process and wait for it
346		448
347	my $done = AnyEvent->condvar;	449	my $done = AnyEvent->condvar;
348		450
349	my $pid = fork or exit 5;	451	my $pid = fork or exit 5;
350		452
351	my $w = AnyEvent->child (	453	my $w = AnyEvent->child (
352	pid => $pid,	454	pid => $pid,
353	cb => sub {	455	cb => sub {
354	my ($pid, $status) = @_;	456	my ($pid, $status) = @_;
355	warn "pid $pid exited with status $status";	457	warn "pid $pid exited with status $status";
356	$done->send;	458	$done->send;
357	},	459	},
358	);	460	);
359		461
360	# do something else, then wait for process exit	462	# do something else, then wait for process exit
361	$done->recv;	463	$done->recv;
362		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	});
		500
363	CONDITION VARIABLES	501	CONDITION VARIABLES
		502	$cv = AnyEvent->condvar;
		503
		504	$cv->send (<list>);
		505	my @res = $cv->recv;
		506
364	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
365	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
366	will actively watch for new events and call your callbacks.	509	will actively watch for new events and call your callbacks.
367		510
368	AnyEvent is different, it expects somebody else to run the event loop	511	AnyEvent is slightly different: it expects somebody else to run the
369	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).
370		514
371	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
372	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.
373		519
374	Condition variables can be created by calling the "AnyEvent->condvar"	520	Condition variables can be created by calling the "AnyEvent->condvar"
375	method, usually without arguments. The only argument pair allowed is	521	method, usually without arguments. The only argument pair allowed is
376	"cb", which specifies a callback to be called when the condition	522	"cb", which specifies a callback to be called when the condition
377	variable becomes true.	523	variable becomes true, with the condition variable as the first argument
		524	(but not the results).
378		525
379	After creation, the condition variable is "false" until it becomes	526	After creation, the condition variable is "false" until it becomes
380	"true" by calling the "send" method (or calling the condition variable	527	"true" by calling the "send" method (or calling the condition variable
381	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
382	the "->send" method).	529	the "->send" method).
…		…
384	Condition variables are similar to callbacks, except that you can	531	Condition variables are similar to callbacks, except that you can
385	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
386	in time where multiple outstanding events have been processed. And yet	533	in time where multiple outstanding events have been processed. And yet
387	another way to call them is transactions - each condition variable can	534	another way to call them is transactions - each condition variable can
388	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
389	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.
390		538
391	Condition variables are very useful to signal that something has	539	Condition variables are very useful to signal that something has
392	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
393	requests, then a condition variable would be the ideal candidate to	541	requests, then a condition variable would be the ideal candidate to
394	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
…		…
428	after => 1,	576	after => 1,
429	cb => sub { $result_ready->send },	577	cb => sub { $result_ready->send },
430	);	578	);
431		579
432	# this "blocks" (while handling events) till the callback	580	# this "blocks" (while handling events) till the callback
433	# calls send	581	# calls ->send
434	$result_ready->recv;	582	$result_ready->recv;
435		583
436	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
437	variables are also code references.	585	variables are also callable directly.
438		586
439	my $done = AnyEvent->condvar;	587	my $done = AnyEvent->condvar;
440	my $delay = AnyEvent->timer (after => 5, cb => $done);	588	my $delay = AnyEvent->timer (after => 5, cb => $done);
441	$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	});
442		607
443	METHODS FOR PRODUCERS	608	METHODS FOR PRODUCERS
444	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
445	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
446	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
…		…
456		621
457	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
458	future "->recv" calls.	623	future "->recv" calls.
459		624
460	Condition variables are overloaded so one can call them directly (as	625	Condition variables are overloaded so one can call them directly (as
461	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
462	"send". Note, however, that many C-based event loops do not handle	627	calling "send".
463	overloading, so as tempting as it may be, passing a condition
464	variable instead of a callback does not work. Both the pure perl and
465	EV loops support overloading, however, as well as all functions that
466	use perl to invoke a callback (as in AnyEvent::Socket and
467	AnyEvent::DNS for example).
468		628
469	$cv->croak ($error)	629	$cv->croak ($error)
470	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
471	"Carp::croak" with the given error message/object/scalar.	631	"Carp::croak" with the given error message/object/scalar.
472		632
473	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
474	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.
475		639
476	$cv->begin ([group callback])	640	$cv->begin ([group callback])
477	$cv->end	641	$cv->end
478	These two methods are EXPERIMENTAL and MIGHT CHANGE.
479
480	These two methods can be used to combine many transactions/events	642	These two methods can be used to combine many transactions/events
481	into one. For example, a function that pings many hosts in parallel	643	into one. For example, a function that pings many hosts in parallel
482	might want to use a condition variable for the whole process.	644	might want to use a condition variable for the whole process.
483		645
484	Every call to "->begin" will increment a counter, and every call to	646	Every call to "->begin" will increment a counter, and every call to
485	"->end" will decrement it. If the counter reaches 0 in "->end", the	647	"->end" will decrement it. If the counter reaches 0 in "->end", the
486	(last) callback passed to "begin" will be executed. That callback is	648	(last) callback passed to "begin" will be executed, passing the
487	supposed to call "->send", but that is not required. If no	649	condvar as first argument. That callback is supposed to call
		650	"->send", but that is not required. If no group callback was set,
488	callback was set, "send" will be called without any arguments.	651	"send" will be called without any arguments.
489		652
490	Let's clarify this with the ping example:	653	You can think of "$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:
491		661
492	my $cv = AnyEvent->condvar;	662	my $cv = AnyEvent->condvar;
493		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
494	my %result;	688	my %result;
495	$cv->begin (sub { $cv->send (\%result) });	689	$cv->begin (sub { shift->send (\%result) });
496		690
497	for my $host (@list_of_hosts) {	691	for my $host (@list_of_hosts) {
498	$cv->begin;	692	$cv->begin;
499	ping_host_then_call_callback $host, sub {	693	ping_host_then_call_callback $host, sub {
500	$result{$host} = ...;	694	$result{$host} = ...;
…		…
515	the loop, which serves two important purposes: first, it sets the	709	the loop, which serves two important purposes: first, it sets the
516	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
517	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
518	(the loop doesn't execute once).	712	(the loop doesn't execute once).
519		713
520	This is the general pattern when you "fan out" into multiple	714	This is the general pattern when you "fan out" into multiple (but
521	subrequests: use an outer "begin"/"end" pair to set the callback and	715	potentially none) subrequests: use an outer "begin"/"end" pair to
522	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,
523	you start, call "begin" and for each subrequest you finish, call	717	for each subrequest you start, call "begin" and for each subrequest
524	"end".	718	you finish, call "end".
525		719
526	METHODS FOR CONSUMERS	720	METHODS FOR CONSUMERS
527	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
528	awaits the condition.	722	awaits the condition.
529		723
…		…
538	function will call "croak".	732	function will call "croak".
539		733
540	In list context, all parameters passed to "send" will be returned,	734	In list context, all parameters passed to "send" will be returned,
541	in scalar context only the first one will be returned.	735	in scalar context only the first one will be returned.
542		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
543	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
544	(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
545	using this from a module, never require a blocking wait*, but let	746	using this from a module, never require a blocking wait*. Instead,
546	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
547	by coupling condition variables with some kind of request results	748	example, by coupling condition variables with some kind of request
548	and supporting callbacks so the caller knows that getting the result	749	results and supporting callbacks so the caller knows that getting
549	will not block, while still supporting blocking waits if the caller	750	the result will not block, while still supporting blocking waits if
550	so desires).	751	the caller so desires).
551
552	Another reason never to "->recv" in a module is that you cannot
553	sensibly have two "->recv"'s in parallel, as that would require
554	multiple interpreters or coroutines/threads, none of which
555	"AnyEvent" can supply.
556
557	The Coro module, however, can and does supply coroutines and, in
558	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
559	versions and also integrates coroutines into AnyEvent, making
560	blocking "->recv" calls perfectly safe as long as they are done from
561	another coroutine (one that doesn't run the event loop).
562		752
563	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
564	only calling "->recv" from within that callback (or at a later	754	only calling "->recv" from within that callback (or at a later
565	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
566	blocking waits otherwise.	756	blocking waits otherwise.
567		757
568	$bool = $cv->ready	758	$bool = $cv->ready
569	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
570	"croak" have been called.	760	"croak" have been called.
571		761
572	$cb = $cv->cb ([new callback])	762	$cb = $cv->cb ($cb->($cv))
573	This is a mutator function that returns the callback set and	763	This is a mutator function that returns the callback set and
574	optionally replaces it before doing so.	764	optionally replaces it before doing so.
575		765
576	The callback will be called when the condition becomes "true", i.e.	766	The callback will be called when the condition becomes (or already
577	when "send" or "croak" are called, with the only argument being the	767	was) "true", i.e. when "send" or "croak" are called (or were
578	condition variable itself. Calling "recv" inside the callback or at	768	called), with the only argument being the condition variable itself.
		769	Calling "recv" inside the callback or at any later time is
579	any later time is guaranteed not to block.	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.
580		831
581	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
582	$AnyEvent::MODEL	836	$AnyEvent::MODEL
583	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
584	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
585	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
586	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
587	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.
588		844	in rxvt-unicode it will be "urxvt::anyevent").
589	The known classes so far are:
590
591	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
592	AnyEvent::Impl::Event based on Event, second best choice.
593	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
594	AnyEvent::Impl::Glib based on Glib, third-best choice.
595	AnyEvent::Impl::Tk based on Tk, very bad choice.
596	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
597	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
598	AnyEvent::Impl::POE based on POE, not generic enough for full support.
599
600	There is no support for WxWidgets, as WxWidgets has no support for
601	watching file handles. However, you can use WxWidgets through the
602	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
603	second, which was considered to be too horrible to even consider for
604	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
605	using it's adaptor.
606
607	AnyEvent knows about Prima and Wx and will try to use POE when
608	autodetecting them.
609		845
610	AnyEvent::detect	846	AnyEvent::detect
611	Returns $AnyEvent::MODEL, forcing autodetection of the event model	847	Returns $AnyEvent::MODEL, forcing autodetection of the event model
612	if necessary. You should only call this function right before you	848	if necessary. You should only call this function right before you
613	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
614	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".
615		854
616	$guard = AnyEvent::post_detect { BLOCK }	855	$guard = AnyEvent::post_detect { BLOCK }
617	Arranges for the code block to be executed as soon as the event	856	Arranges for the code block to be executed as soon as the event
618	model is autodetected (or immediately if this has already happened).	857	model is autodetected (or immediately if this has already happened).
619		858
		859	The block will be executed after the actual backend has been
		860	detected ($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
620	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
621	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
622	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;
623		890
624	@AnyEvent::post_detect	891	@AnyEvent::post_detect
625	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
626	before or after loading AnyEvent), then they will called directly	893	before or after loading AnyEvent), then they will called directly
627	after the event loop has been chosen.	894	after the event loop has been chosen.
628		895
629	You should check $AnyEvent::MODEL before adding to this array,	896	You should check $AnyEvent::MODEL before adding to this array,
630	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
631	been detected, and the array will be ignored.	898	detected, and the array will be ignored.
632		899
633	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.
634		908
635	WHAT TO DO IN A MODULE	909	WHAT TO DO IN A MODULE
636	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
637	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.
638		912
…		…
689	variable somewhere, waiting for it, and sending it when the program	963	variable somewhere, waiting for it, and sending it when the program
690	should exit cleanly.	964	should exit cleanly.
691		965
692	OTHER MODULES	966	OTHER MODULES
693	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
694	AnyEvent and can therefore be mixed easily with other AnyEvent modules	968	AnyEvent as a client and can therefore be mixed easily with other
695	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
696	available via CPAN.	970	modules come with AnyEvent, most are available via CPAN.
697		971
698	AnyEvent::Util	972	AnyEvent::Util
699	Contains various utility functions that replace often-used but	973	Contains various utility functions that replace often-used but
700	blocking functions such as "inet_aton" by event-/callback-based	974	blocking functions such as "inet_aton" by event-/callback-based
701	versions.	975	versions.
702
703	AnyEvent::Handle
704	Provide read and write buffers and manages watchers for reads and
705	writes.
706		976
707	AnyEvent::Socket	977	AnyEvent::Socket
708	Provides various utility functions for (internet protocol) sockets,	978	Provides various utility functions for (internet protocol) sockets,
709	addresses and name resolution. Also functions to create non-blocking	979	addresses and name resolution. Also functions to create non-blocking
710	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
711	more.	981	more.
712		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
713	AnyEvent::DNS	988	AnyEvent::DNS
714	Provides rich asynchronous DNS resolver capabilities.	989	Provides rich asynchronous DNS resolver capabilities.
715		990
		991	AnyEvent::HTTP
		992	A simple-to-use HTTP library that is capable of making a lot of
		993	concurrent HTTP requests.
		994
716	AnyEvent::HTTPD	995	AnyEvent::HTTPD
717	Provides a simple web application server framework.	996	Provides a simple web application server framework.
718		997
719	AnyEvent::FastPing	998	AnyEvent::FastPing
720	The fastest ping in the west.	999	The fastest ping in the west.
721		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
722	Net::IRC3	1019	Net::IRC3).
723	AnyEvent based IRC client module family.
724		1020
725	Net::XMPP2	1021	AnyEvent::XMPP
726	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).
727		1028
728	Net::FCP	1029	Net::FCP
729	AnyEvent-based implementation of the Freenet Client Protocol,	1030	AnyEvent-based implementation of the Freenet Client Protocol,
730	birthplace of AnyEvent.	1031	birthplace of AnyEvent.
731		1032
…		…
733	High level API for event-based execution flow control.	1034	High level API for event-based execution flow control.
734		1035
735	Coro	1036	Coro
736	Has special support for AnyEvent via Coro::AnyEvent.	1037	Has special support for AnyEvent via Coro::AnyEvent.
737		1038
738	AnyEvent::AIO, IO::AIO	1039	SIMPLIFIED AE API
739	Truly asynchronous I/O, should be in the toolbox of every event	1040	Starting with version 5.0, AnyEvent officially supports a second, much
740	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent	1041	simpler, API that is designed to reduce the calling, typing and memory
741	together.	1042	overhead.
742		1043
743	AnyEvent::BDB, BDB	1044	See the AE manpage for details.
744	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
745	fuses IO::AIO and AnyEvent together.
746		1045
747	IO::Lambda	1046	ERROR AND EXCEPTION HANDLING
748	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
749	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.
750		1052
751	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1053	As for exception handling (i.e. runtime errors and exceptions thrown
752	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
753	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
754	to provide AnyEvent compatibility.	1056	job of the main program.
755		1057
756	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
757	supported by AnyEvent, you can supply your own interface to it by	1059	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
758	pushing, before the first watcher gets created, the package name of the	1060	Glib uses "install_exception_handler" and so on.
759	event module and the package name of the interface to use onto
760	@AnyEvent::REGISTRY. You can do that before and even without loading
761	AnyEvent, so it is reasonably cheap.
762
763	Example:
764
765	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
766
767	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
768	package/class when it finds the "urxvt" package/module is already
769	loaded.
770
771	When AnyEvent is loaded and asked to find a suitable event model, it
772	will first check for the presence of urxvt by trying to "use" the
773	"urxvt::anyevent" module.
774
775	The class should provide implementations for all watcher types. See
776	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
777	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
778	the sources.
779
780	If you don't provide "signal" and "child" watchers than AnyEvent will
781	provide suitable (hopefully) replacements.
782
783	The above example isn't fictitious, the rxvt-unicode (a.k.a. urxvt)
784	terminal emulator uses the above line as-is. An interface isn't included
785	in AnyEvent because it doesn't make sense outside the embedded
786	interpreter inside rxvt-unicode, and it is updated and maintained as
787	part of the rxvt-unicode distribution.
788
789	rxvt-unicode also cheats a bit by not providing blocking access to
790	condition variables: code blocking while waiting for a condition will
791	"die". This still works with most modules/usages, and blocking calls
792	must not be done in an interactive application, so it makes sense.
793		1061
794	ENVIRONMENT VARIABLES	1062	ENVIRONMENT VARIABLES
795	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.
796		1069
797	"PERL_ANYEVENT_VERBOSE"	1070	"PERL_ANYEVENT_VERBOSE"
798	By default, AnyEvent will be completely silent except in fatal	1071	By default, AnyEvent will be completely silent except in fatal
799	conditions. You can set this environment variable to make AnyEvent	1072	conditions. You can set this environment variable to make AnyEvent
800	more talkative.	1073	more talkative.
…		…
803	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
804	by "PERL_ANYEVENT_MODEL".	1077	by "PERL_ANYEVENT_MODEL".
805		1078
806	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
807	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.
808		1099
809	"PERL_ANYEVENT_MODEL"	1100	"PERL_ANYEVENT_MODEL"
810	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,
811	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
812	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1103	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
831	mentioned will be used, and preference will be given to protocols	1122	mentioned will be used, and preference will be given to protocols
832	mentioned earlier in the list.	1123	mentioned earlier in the list.
833		1124
834	This variable can effectively be used for denial-of-service attacks	1125	This variable can effectively be used for denial-of-service attacks
835	against local programs (e.g. when setuid), although the impact is	1126	against local programs (e.g. when setuid), although the impact is
836	likely small, as the program has to handle connection errors	1127	likely small, as the program has to handle conenction and other
837	already-	1128	failures anyways.
838		1129
839	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1130	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
840	IPv6, but support both and try to use both.	1131	IPv6, but support both and try to use both.
841	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1132	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
842	resolve or contact IPv6 addresses.	1133	resolve or contact IPv6 addresses.
…		…
853	EDNS0 in its DNS requests.	1144	EDNS0 in its DNS requests.
854		1145
855	"PERL_ANYEVENT_MAX_FORKS"	1146	"PERL_ANYEVENT_MAX_FORKS"
856	The maximum number of child processes that	1147	The maximum number of child processes that
857	"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.
858		1212
859	EXAMPLE PROGRAM	1213	EXAMPLE PROGRAM
860	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
861	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
862	quit the program when the user enters quit:	1216	quit the program when the user enters quit:
…		…
1020	through AnyEvent. The benchmark creates a lot of timers (with a zero	1374	through AnyEvent. The benchmark creates a lot of timers (with a zero
1021	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1375	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1022	which it is), lets them fire exactly once and destroys them again.	1376	which it is), lets them fire exactly once and destroys them again.
1023		1377
1024	Source code for this benchmark is found as eg/bench in the AnyEvent	1378	Source code for this benchmark is found as eg/bench in the AnyEvent
1025	distribution.	1379	distribution. It uses the AE interface, which makes a real difference
		1380	for the EV and Perl backends only.
1026		1381
1027	Explanation of the columns	1382	Explanation of the columns
1028	watcher is the number of event watchers created/destroyed. Since	1383	watcher is the number of event watchers created/destroyed. Since
1029	different event models feature vastly different performances, each event	1384	different event models feature vastly different performances, each event
1030	loop was given a number of watchers so that overall runtime is	1385	loop was given a number of watchers so that overall runtime is
…		…
1049	destroy is the time, in microseconds, that it takes to destroy a	1404	destroy is the time, in microseconds, that it takes to destroy a
1050	single watcher.	1405	single watcher.
1051		1406
1052	Results	1407	Results
1053	name watchers bytes create invoke destroy comment	1408	name watchers bytes create invoke destroy comment
1054	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1409	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1055	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1410	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1056	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1411	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1057	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1412	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1058	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1413	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1059	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1414	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		1415	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		1416	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1060	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1417	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1061	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1418	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1062	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1419	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1063	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1420	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1064		1421
1065	Discussion	1422	Discussion
1066	The benchmark does not measure scalability of the event loop very	1423	The benchmark does not measure scalability of the event loop very
1067	well. For example, a select-based event loop (such as the pure perl one)	1424	well. For example, a select-based event loop (such as the pure perl one)
1068	can never compete with an event loop that uses epoll when the number of	1425	can never compete with an event loop that uses epoll when the number of
…		…
1079	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1436	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1080	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1437	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1081	CPU cycles with POE.	1438	CPU cycles with POE.
1082		1439
1083	"EV" is the sole leader regarding speed and memory use, which are both	1440	"EV" is the sole leader regarding speed and memory use, which are both
1084	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1441	maximal/minimal, respectively. When using the AE API there is zero
		1442	overhead (when going through the AnyEvent API create is about 5-6 times
		1443	slower, with other times being equal, so still uses far less memory than
1085	far less memory than any other event loop and is still faster than Event	1444	any other event loop and is still faster than Event natively).
1086	natively.
1087		1445
1088	The pure perl implementation is hit in a few sweet spots (both the	1446	The pure perl implementation is hit in a few sweet spots (both the
1089	constant timeout and the use of a single fd hit optimisations in the	1447	constant timeout and the use of a single fd hit optimisations in the
1090	perl interpreter and the backend itself). Nevertheless this shows that	1448	perl interpreter and the backend itself). Nevertheless this shows that
1091	it adds very little overhead in itself. Like any select-based backend	1449	it adds very little overhead in itself. Like any select-based backend
…		…
1093	few of them active), of course, but this was not subject of this	1451	few of them active), of course, but this was not subject of this
1094	benchmark.	1452	benchmark.
1095		1453
1096	The "Event" module has a relatively high setup and callback invocation	1454	The "Event" module has a relatively high setup and callback invocation
1097	cost, but overall scores in on the third place.	1455	cost, but overall scores in on the third place.
		1456
		1457	"IO::Async" performs admirably well, about on par with "Event", even
		1458	when using its pure perl backend.
1098		1459
1099	"Glib"'s memory usage is quite a bit higher, but it features a faster	1460	"Glib"'s memory usage is quite a bit higher, but it features a faster
1100	callback invocation and overall ends up in the same class as "Event".	1461	callback invocation and overall ends up in the same class as "Event".
1101	However, Glib scales extremely badly, doubling the number of watchers	1462	However, Glib scales extremely badly, doubling the number of watchers
1102	increases the processing time by more than a factor of four, making it	1463	increases the processing time by more than a factor of four, making it
…		…
1158	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1519	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1159	100 (1%) are active. This mirrors the activity of large servers with	1520	100 (1%) are active. This mirrors the activity of large servers with
1160	many connections, most of which are idle at any one point in time.	1521	many connections, most of which are idle at any one point in time.
1161		1522
1162	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1523	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1163	distribution.	1524	distribution. It uses the AE interface, which makes a real difference
		1525	for the EV and Perl backends only.
1164		1526
1165	Explanation of the columns	1527	Explanation of the columns
1166	sockets is the number of sockets, and twice the number of "servers"	1528	sockets is the number of sockets, and twice the number of "servers"
1167	(as each server has a read and write socket end).	1529	(as each server has a read and write socket end).
1168		1530
…		…
1173	single "request", that is, reading the token from the pipe and	1535	single "request", that is, reading the token from the pipe and
1174	forwarding it to another server. This includes deleting the old timeout	1536	forwarding it to another server. This includes deleting the old timeout
1175	and creating a new one that moves the timeout into the future.	1537	and creating a new one that moves the timeout into the future.
1176		1538
1177	Results	1539	Results
1178	name sockets create request	1540	name sockets create request
1179	EV 20000 69.01 11.16	1541	EV 20000 62.66 7.99
1180	Perl 20000 73.32 35.87	1542	Perl 20000 68.32 32.64
1181	Event 20000 212.62 257.32	1543	IOAsync 20000 174.06 101.15 epoll
1182	Glib 20000 651.16 1896.30	1544	IOAsync 20000 174.67 610.84 poll
		1545	Event 20000 202.69 242.91
		1546	Glib 20000 557.01 1689.52
1183	POE 20000 349.67 12317.24 uses POE::Loop::Event	1547	POE 20000 341.54 12086.32 uses POE::Loop::Event
1184		1548
1185	Discussion	1549	Discussion
1186	This benchmark does measure scalability and overall performance of the	1550	This benchmark does measure scalability and overall performance of the
1187	particular event loop.	1551	particular event loop.
1188		1552
1189	EV is again fastest. Since it is using epoll on my system, the setup	1553	EV is again fastest. Since it is using epoll on my system, the setup
1190	time is relatively high, though.	1554	time is relatively high, though.
1191		1555
1192	Perl surprisingly comes second. It is much faster than the C-based event	1556	Perl surprisingly comes second. It is much faster than the C-based event
1193	loops Event and Glib.	1557	loops Event and Glib.
		1558
		1559	IO::Async performs very well when using its epoll backend, and still
		1560	quite good compared to Glib when using its pure perl backend.
1194		1561
1195	Event suffers from high setup time as well (look at its code and you	1562	Event suffers from high setup time as well (look at its code and you
1196	will understand why). Callback invocation also has a high overhead	1563	will understand why). Callback invocation also has a high overhead
1197	compared to the "$_->() for .."-style loop that the Perl event loop	1564	compared to the "$_->() for .."-style loop that the Perl event loop
1198	uses. Event uses select or poll in basically all documented	1565	uses. Event uses select or poll in basically all documented
…		…
1249		1616
1250	Summary	1617	Summary
1251	* C-based event loops perform very well with small number of watchers,	1618	* C-based event loops perform very well with small number of watchers,
1252	as the management overhead dominates.	1619	as the management overhead dominates.
1253		1620
		1621	THE IO::Lambda BENCHMARK
		1622	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1623	could be misinterpreted to make AnyEvent look bad. In fact, the
		1624	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1625	better (which shouldn't come as a surprise to anybody). As such, the
		1626	benchmark is fine, and mostly shows that the AnyEvent backend from
		1627	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1628	without the extra baggage? To explore this, I wrote the equivalent
		1629	benchmark for AnyEvent.
		1630
		1631	The benchmark itself creates an echo-server, and then, for 500 times,
		1632	connects to the echo server, sends a line, waits for the reply, and then
		1633	creates the next connection. This is a rather bad benchmark, as it
		1634	doesn't test the efficiency of the framework or much non-blocking I/O,
		1635	but it is a benchmark nevertheless.
		1636
		1637	name runtime
		1638	Lambda/select 0.330 sec
		1639	+ optimized 0.122 sec
		1640	Lambda/AnyEvent 0.327 sec
		1641	+ optimized 0.138 sec
		1642	Raw sockets/select 0.077 sec
		1643	POE/select, components 0.662 sec
		1644	POE/select, raw sockets 0.226 sec
		1645	POE/select, optimized 0.404 sec
		1646
		1647	AnyEvent/select/nb 0.085 sec
		1648	AnyEvent/EV/nb 0.068 sec
		1649	+state machine 0.134 sec
		1650
		1651	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1652	benchmarks actually make blocking connects and use 100% blocking I/O,
		1653	defeating the purpose of an event-based solution. All of the newly
		1654	written AnyEvent benchmarks use 100% non-blocking connects (using
		1655	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1656	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1657	connects generally require a lot more bookkeeping and event handling
		1658	than blocking connects (which involve a single syscall only).
		1659
		1660	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1661	offers similar expressive power as POE and IO::Lambda, using
		1662	conventional Perl syntax. This means that both the echo server and the
		1663	client are 100% non-blocking, further placing it at a disadvantage.
		1664
		1665	As you can see, the AnyEvent + EV combination even beats the
		1666	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1667	backend easily beats IO::Lambda and POE.
		1668
		1669	And even the 100% non-blocking version written using the high-level (and
		1670	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a
		1671	large margin, even though it does all of DNS, tcp-connect and socket I/O
		1672	in a non-blocking way.
		1673
		1674	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1675	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1676	part of the IO::lambda distribution and were used without any changes.
		1677
		1678	SIGNALS
		1679	AnyEvent currently installs handlers for these signals:
		1680
		1681	SIGCHLD
		1682	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
		1683	emulation for event loops that do not support them natively. Also,
		1684	some event loops install a similar handler.
		1685
		1686	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1687	then AnyEvent will reset it to default, to avoid losing child exit
		1688	statuses.
		1689
		1690	SIGPIPE
		1691	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
		1692	"undef" when AnyEvent gets loaded.
		1693
		1694	The rationale for this is that AnyEvent users usually do not really
		1695	depend on SIGPIPE delivery (which is purely an optimisation for
		1696	shell use, or badly-written programs), but "SIGPIPE" can cause
		1697	spurious and rare program exits as a lot of people do not expect
		1698	"SIGPIPE" when writing to some random socket.
		1699
		1700	The rationale for installing a no-op handler as opposed to ignoring
		1701	it is that this way, the handler will be restored to defaults on
		1702	exec.
		1703
		1704	Feel free to install your own handler, or reset it to defaults.
		1705
		1706	RECOMMENDED/OPTIONAL MODULES
		1707	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1708	it's built-in modules) are required to use it.
		1709
		1710	That does not mean that AnyEvent won't take advantage of some additional
		1711	modules if they are installed.
		1712
		1713	This section epxlains which additional modules will be used, and how
		1714	they affect AnyEvent's operetion.
		1715
		1716	Async::Interrupt
		1717	This slightly arcane module is used to implement fast signal
		1718	handling: To my knowledge, there is no way to do completely
		1719	race-free and quick signal handling in pure perl. To ensure that
		1720	signals still get delivered, AnyEvent will start an interval timer
		1721	to wake up perl (and catch the signals) with some delay (default is
		1722	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1723
		1724	If this module is available, then it will be used to implement
		1725	signal catching, which means that signals will not be delayed, and
		1726	the event loop will not be interrupted regularly, which is more
		1727	efficient (And good for battery life on laptops).
		1728
		1729	This affects not just the pure-perl event loop, but also other event
		1730	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1731
		1732	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1733	natively, and either employ their own workarounds (POE) or use
		1734	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1735	Installing Async::Interrupt does nothing for those backends.
		1736
		1737	EV This module isn't really "optional", as it is simply one of the
		1738	backend event loops that AnyEvent can use. However, it is simply the
		1739	best event loop available in terms of features, speed and stability:
		1740	It supports the AnyEvent API optimally, implements all the watcher
		1741	types in XS, does automatic timer adjustments even when no monotonic
		1742	clock is available, can take avdantage of advanced kernel interfaces
		1743	such as "epoll" and "kqueue", and is the fastest backend by far.
		1744	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1745	Glib::EV).
		1746
		1747	Guard
		1748	The guard module, when used, will be used to implement
		1749	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1750	uses a lot less memory), but otherwise doesn't affect guard
		1751	operation much. It is purely used for performance.
		1752
		1753	JSON and JSON::XS
		1754	This module is required when you want to read or write JSON data via
		1755	AnyEvent::Handle. It is also written in pure-perl, but can take
		1756	advantage of the ultra-high-speed JSON::XS module when it is
		1757	installed.
		1758
		1759	In fact, AnyEvent::Handle will use JSON::XS by default if it is
		1760	installed.
		1761
		1762	Net::SSLeay
		1763	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1764	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1765	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1766
		1767	Time::HiRes
		1768	This module is part of perl since release 5.008. It will be used
		1769	when the chosen event library does not come with a timing source on
		1770	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1771	additionally use it to try to use a monotonic clock for timing
		1772	stability.
		1773
1254	FORK	1774	FORK
1255	Most event libraries are not fork-safe. The ones who are usually are	1775	Most event libraries are not fork-safe. The ones who are usually are
1256	because they rely on inefficient but fork-safe "select" or "poll" calls.	1776	because they rely on inefficient but fork-safe "select" or "poll" calls.
1257	Only EV is fully fork-aware.	1777	Only EV is fully fork-aware.
1258		1778
1259	If you have to fork, you must either do so before creating your first	1779	If you have to fork, you must either do so before creating your first
1260	watcher OR you must not use AnyEvent at all in the child.	1780	watcher OR you must not use AnyEvent at all in the child OR you must do
		1781	something completely out of the scope of AnyEvent.
1261		1782
1262	SECURITY CONSIDERATIONS	1783	SECURITY CONSIDERATIONS
1263	AnyEvent can be forced to load any event model via	1784	AnyEvent can be forced to load any event model via
1264	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1785	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1265	to execute arbitrary code or directly gain access, it can easily be used	1786	to execute arbitrary code or directly gain access, it can easily be used
…		…
1269		1790
1270	You can make AnyEvent completely ignore this variable by deleting it	1791	You can make AnyEvent completely ignore this variable by deleting it
1271	before the first watcher gets created, e.g. with a "BEGIN" block:	1792	before the first watcher gets created, e.g. with a "BEGIN" block:
1272		1793
1273	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1794	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1274		1795
1275	use AnyEvent;	1796	use AnyEvent;
1276		1797
1277	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1798	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1278	be used to probe what backend is used and gain other information (which	1799	be used to probe what backend is used and gain other information (which
1279	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	1800	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
		1801	and $ENV{PERL_ANYEVENT_STRICT}.
		1802
		1803	Note that AnyEvent will remove all environment variables starting with
		1804	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1805	enabled.
		1806
		1807	BUGS
		1808	Perl 5.8 has numerous memleaks that sometimes hit this module and are
		1809	hard to work around. If you suffer from memleaks, first upgrade to Perl
		1810	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
		1811	annoying memleaks, such as leaking on "map" and "grep" but it is usually
		1812	not as pronounced).
1280		1813
1281	SEE ALSO	1814	SEE ALSO
1282	Utility functions: AnyEvent::Util.	1815	Utility functions: AnyEvent::Util.
1283		1816
1284	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1817	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1285	Event::Lib, Qt, POE.	1818	Event::Lib, Qt, POE.
1286		1819
1287	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1820	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1288	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1821	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1289	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1822	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1823	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1290		1824
1291	Non-blocking file handles, sockets, TCP clients and servers:	1825	Non-blocking file handles, sockets, TCP clients and servers:
1292	AnyEvent::Handle, AnyEvent::Socket.	1826	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1293		1827
1294	Asynchronous DNS: AnyEvent::DNS.	1828	Asynchronous DNS: AnyEvent::DNS.
1295		1829
1296	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1830	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1297		1831
1298	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1832	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1833	AnyEvent::HTTP.
1299		1834
1300	AUTHOR	1835	AUTHOR
1301	Marc Lehmann <schmorp@schmorp.de>	1836	Marc Lehmann <schmorp@schmorp.de>
1302	http://home.schmorp.de/	1837	http://home.schmorp.de/
1303		1838

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Revision 1.25 by root, Tue Jun 3 09:02:46 2008 UTC vs.
Revision 1.53 by root, Fri Aug 21 11:59:24 2009 UTC