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Comparing AnyEvent/README (file contents):
Revision 1.26 by root, Fri Jun 6 11:13:07 2008 UTC vs.
Revision 1.42 by root, Mon Jun 29 21:00:32 2009 UTC

…		…
1	NAME	1	NAME
2	AnyEvent - provide framework for multiple event loops	2	AnyEvent - provide framework for multiple event loops
3		3
4	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event	4	EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
5	loops	5	event loops.
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.
30		46
31	Executive Summary: AnyEvent is compatible, AnyEvent is *free of	47	Executive Summary: AnyEvent is compatible, AnyEvent is *free of
32	policy* and AnyEvent is small and efficient.	48	policy* and AnyEvent is small and efficient.
33		49
34	First and foremost, AnyEvent is not an event model itself, it only	50	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	51	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,	52	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,	53	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.	54	only one event loop can be active at the same time in a process.
39	AnyEvent helps hiding the differences between those event loops.	55	AnyEvent cannot change this, but it can hide the differences between
		56	those event loops.
40		57
41	The goal of AnyEvent is to offer module authors the ability to do event	58	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	59	programming (waiting for I/O or timer events) without subscribing to a
43	religion, a way of living, and most importantly: without forcing your	60	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	61	module users into the same thing by forcing them to use the same event
45	model you use.	62	model you use.
46		63
47	For modules like POE or IO::Async (which is a total misnomer as it is	64	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	65	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	66	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	67	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	68	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.	69	are also forced to use the same event loop you use.
53		70
54	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	71	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
55	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	72	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	73	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.	74	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	75	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	76	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	77	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).	78	to AnyEvent, too, so it is future-proof).
62		79
63	In addition to being free of having to use *the one and only true event	80	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	81	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	82	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	83	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	139	These watchers are normal Perl objects with normal Perl lifetime. After
123	creating a watcher it will immediately "watch" for events and invoke the	140	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	141	callback when the event occurs (of course, only when the event model is
125	in control).	142	in control).
126		143
		144	Note that callbacks must not permanently change global variables
		145	potentially in use by the event loop (such as $_ or $[) and that
		146	callbacks must not "die". The former is good programming practise in
		147	Perl and the latter stems from the fact that exception handling differs
		148	widely between event loops.
		149
127	To disable the watcher you have to destroy it (e.g. by setting the	150	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	151	variable you store it in to "undef" or otherwise deleting all references
129	to it).	152	to it).
130		153
131	All watchers are created by calling a method on the "AnyEvent" class.	154	All watchers are created by calling a method on the "AnyEvent" class.
…		…
146		169
147	I/O WATCHERS	170	I/O WATCHERS
148	You can create an I/O watcher by calling the "AnyEvent->io" method with	171	You can create an I/O watcher by calling the "AnyEvent->io" method with
149	the following mandatory key-value pairs as arguments:	172	the following mandatory key-value pairs as arguments:
150		173
151	"fh" the Perl file handle (not file descriptor) to watch for events.	174	"fh" is the Perl file handle (not file descriptor) to watch for
		175	events (AnyEvent might or might not keep a reference to this file
		176	handle). Note that only file handles pointing to things for which
		177	non-blocking operation makes sense are allowed. This includes sockets,
		178	most character devices, pipes, fifos and so on, but not for example
		179	files or block devices.
		180
152	"poll" must be a string that is either "r" or "w", which creates a	181	"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"	182	watcher waiting for "r"eadable or "w"ritable events, respectively.
		183
154	is the callback to invoke each time the file handle becomes ready.	184	"cb" is the callback to invoke each time the file handle becomes ready.
155		185
156	Although the callback might get passed parameters, their value and	186	Although the callback might get passed parameters, their value and
157	presence is undefined and you cannot rely on them. Portable AnyEvent	187	presence is undefined and you cannot rely on them. Portable AnyEvent
158	callbacks cannot use arguments passed to I/O watcher callbacks.	188	callbacks cannot use arguments passed to I/O watcher callbacks.
159		189
…		…
163		193
164	Some event loops issue spurious readyness notifications, so you should	194	Some event loops issue spurious readyness notifications, so you should
165	always use non-blocking calls when reading/writing from/to your file	195	always use non-blocking calls when reading/writing from/to your file
166	handles.	196	handles.
167		197
168	Example:
169
170	# wait for readability of STDIN, then read a line and disable the watcher	198	Example: wait for readability of STDIN, then read a line and disable the
		199	watcher.
		200
171	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	201	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
172	chomp (my $input = <STDIN>);	202	chomp (my $input = <STDIN>);
173	warn "read: $input\n";	203	warn "read: $input\n";
174	undef $w;	204	undef $w;
175	});	205	});
…		…
184		214
185	Although the callback might get passed parameters, their value and	215	Although the callback might get passed parameters, their value and
186	presence is undefined and you cannot rely on them. Portable AnyEvent	216	presence is undefined and you cannot rely on them. Portable AnyEvent
187	callbacks cannot use arguments passed to time watcher callbacks.	217	callbacks cannot use arguments passed to time watcher callbacks.
188		218
189	The timer callback will be invoked at most once: if you want a repeating	219	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	220	parameter, "interval", as a strictly positive number (> 0), then the
191	and Glib).	221	callback will be invoked regularly at that interval (in fractional
		222	seconds) after the first invocation. If "interval" is specified with a
		223	false value, then it is treated as if it were missing.
192		224
193	Example:	225	The callback will be rescheduled before invoking the callback, but no
		226	attempt is done to avoid timer drift in most backends, so the interval
		227	is only approximate.
194		228
195	# fire an event after 7.7 seconds	229	Example: fire an event after 7.7 seconds.
		230
196	my $w = AnyEvent->timer (after => 7.7, cb => sub {	231	my $w = AnyEvent->timer (after => 7.7, cb => sub {
197	warn "timeout\n";	232	warn "timeout\n";
198	});	233	});
199		234
200	# to cancel the timer:	235	# to cancel the timer:
201	undef $w;	236	undef $w;
202		237
203	Example 2:
204
205	# fire an event after 0.5 seconds, then roughly every second	238	Example 2: fire an event after 0.5 seconds, then roughly every second.
206	my $w;
207		239
208	my $cb = sub {
209	# cancel the old timer while creating a new one
210	$w = AnyEvent->timer (after => 1, cb => $cb);	240	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		241	warn "timeout\n";
211	};	242	};
212
213	# start the "loop" by creating the first watcher
214	$w = AnyEvent->timer (after => 0.5, cb => $cb);
215		243
216	TIMING ISSUES	244	TIMING ISSUES
217	There are two ways to handle timers: based on real time (relative, "fire	245	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	246	in 10 seconds") and based on wallclock time (absolute, "fire at 12
219	o'clock").	247	o'clock").
…		…
293	In either case, if you care (and in most cases, you don't), then you	321	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	322	can get whatever behaviour you want with any event loop, by taking
295	the difference between "AnyEvent->time" and "AnyEvent->now" into	323	the difference between "AnyEvent->time" and "AnyEvent->now" into
296	account.	324	account.
297		325
		326	AnyEvent->now_update
		327	Some event loops (such as EV or AnyEvent::Impl::Perl) cache the
		328	current time for each loop iteration (see the discussion of
		329	AnyEvent->now, above).
		330
		331	When a callback runs for a long time (or when the process sleeps),
		332	then this "current" time will differ substantially from the real
		333	time, which might affect timers and time-outs.
		334
		335	When this is the case, you can call this method, which will update
		336	the event loop's idea of "current time".
		337
		338	Note that updating the time might cause some events to be handled.
		339
298	SIGNAL WATCHERS	340	SIGNAL WATCHERS
299	You can watch for signals using a signal watcher, "signal" is the signal	341	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	342	name in uppercase and without any "SIG" prefix, "cb" is the Perl
301	whenever a signal occurs.	343	callback to be invoked whenever a signal occurs.
302		344
303	Although the callback might get passed parameters, their value and	345	Although the callback might get passed parameters, their value and
304	presence is undefined and you cannot rely on them. Portable AnyEvent	346	presence is undefined and you cannot rely on them. Portable AnyEvent
305	callbacks cannot use arguments passed to signal watcher callbacks.	347	callbacks cannot use arguments passed to signal watcher callbacks.
306		348
…		…
321		363
322	CHILD PROCESS WATCHERS	364	CHILD PROCESS WATCHERS
323	You can also watch on a child process exit and catch its exit status.	365	You can also watch on a child process exit and catch its exit status.
324		366
325	The child process is specified by the "pid" argument (if set to 0, it	367	The child process is specified by the "pid" argument (if set to 0, it
326	watches for any child process exit). The watcher will trigger as often	368	watches for any child process exit). The watcher will triggered only
327	as status change for the child are received. This works by installing a	369	when the child process has finished and an exit status is available, not
328	signal handler for "SIGCHLD". The callback will be called with the pid	370	on any trace events (stopped/continued).
329	and exit status (as returned by waitpid), so unlike other watcher types,	371
330	you can rely on child watcher callback arguments.	372	The callback will be called with the pid and exit status (as returned by
		373	waitpid), so unlike other watcher types, you can rely on child watcher
		374	callback arguments.
		375
		376	This watcher type works by installing a signal handler for "SIGCHLD",
		377	and since it cannot be shared, nothing else should use SIGCHLD or reap
		378	random child processes (waiting for specific child processes, e.g.
		379	inside "system", is just fine).
331		380
332	There is a slight catch to child watchers, however: you usually start	381	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	382	them after the child process was created, and this means the process
334	could have exited already (and no SIGCHLD will be sent anymore).	383	could have exited already (and no SIGCHLD will be sent anymore).
335		384
336	Not all event models handle this correctly (POE doesn't), but even for	385	Not all event models handle this correctly (neither POE nor IO::Async
		386	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	387	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	388	before the process exits (i.e. before you fork in the first place).
339	place).	389	AnyEvent's pure perl event loop handles all cases correctly regardless
		390	of when you start the watcher.
340		391
341	This means you cannot create a child watcher as the very first thing in	392	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	393	an AnyEvent program, you have to create at least one watcher before
343	you "fork" the child (alternatively, you can call "AnyEvent::detect").	394	you "fork" the child (alternatively, you can call "AnyEvent::detect").
344		395
345	Example: fork a process and wait for it	396	Example: fork a process and wait for it
346		397
347	my $done = AnyEvent->condvar;	398	my $done = AnyEvent->condvar;
348		399
349	my $pid = fork or exit 5;	400	my $pid = fork or exit 5;
350		401
351	my $w = AnyEvent->child (	402	my $w = AnyEvent->child (
352	pid => $pid,	403	pid => $pid,
353	cb => sub {	404	cb => sub {
354	my ($pid, $status) = @_;	405	my ($pid, $status) = @_;
355	warn "pid $pid exited with status $status";	406	warn "pid $pid exited with status $status";
356	$done->send;	407	$done->send;
357	},	408	},
358	);	409	);
359		410
360	# do something else, then wait for process exit	411	# do something else, then wait for process exit
361	$done->recv;	412	$done->recv;
		413
		414	IDLE WATCHERS
		415	Sometimes there is a need to do something, but it is not so important to
		416	do it instantly, but only when there is nothing better to do. This
		417	"nothing better to do" is usually defined to be "no other events need
		418	attention by the event loop".
		419
		420	Idle watchers ideally get invoked when the event loop has nothing better
		421	to do, just before it would block the process to wait for new events.
		422	Instead of blocking, the idle watcher is invoked.
		423
		424	Most event loops unfortunately do not really support idle watchers (only
		425	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		426	will simply call the callback "from time to time".
		427
		428	Example: read lines from STDIN, but only process them when the program
		429	is otherwise idle:
		430
		431	my @lines; # read data
		432	my $idle_w;
		433	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		434	push @lines, scalar <STDIN>;
		435
		436	# start an idle watcher, if not already done
		437	$idle_w \|\|= AnyEvent->idle (cb => sub {
		438	# handle only one line, when there are lines left
		439	if (my $line = shift @lines) {
		440	print "handled when idle: $line";
		441	} else {
		442	# otherwise disable the idle watcher again
		443	undef $idle_w;
		444	}
		445	});
		446	});
362		447
363	CONDITION VARIABLES	448	CONDITION VARIABLES
364	If you are familiar with some event loops you will know that all of them	449	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	450	require you to run some blocking "loop", "run" or similar function that
366	will actively watch for new events and call your callbacks.	451	will actively watch for new events and call your callbacks.
…		…
371	The instrument to do that is called a "condition variable", so called	456	The instrument to do that is called a "condition variable", so called
372	because they represent a condition that must become true.	457	because they represent a condition that must become true.
373		458
374	Condition variables can be created by calling the "AnyEvent->condvar"	459	Condition variables can be created by calling the "AnyEvent->condvar"
375	method, usually without arguments. The only argument pair allowed is	460	method, usually without arguments. The only argument pair allowed is
		461
376	"cb", which specifies a callback to be called when the condition	462	"cb", which specifies a callback to be called when the condition
377	variable becomes true.	463	variable becomes true, with the condition variable as the first argument
		464	(but not the results).
378		465
379	After creation, the condition variable is "false" until it becomes	466	After creation, the condition variable is "false" until it becomes
380	"true" by calling the "send" method (or calling the condition variable	467	"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	468	as if it were a callback, read about the caveats in the description for
382	the "->send" method).	469	the "->send" method).
…		…
438		525
439	my $done = AnyEvent->condvar;	526	my $done = AnyEvent->condvar;
440	my $delay = AnyEvent->timer (after => 5, cb => $done);	527	my $delay = AnyEvent->timer (after => 5, cb => $done);
441	$done->recv;	528	$done->recv;
442		529
		530	Example: Imagine an API that returns a condvar and doesn't support
		531	callbacks. This is how you make a synchronous call, for example from the
		532	main program:
		533
		534	use AnyEvent::CouchDB;
		535
		536	...
		537
		538	my @info = $couchdb->info->recv;
		539
		540	And this is how you would just ste a callback to be called whenever the
		541	results are available:
		542
		543	$couchdb->info->cb (sub {
		544	my @info = $_[0]->recv;
		545	});
		546
443	METHODS FOR PRODUCERS	547	METHODS FOR PRODUCERS
444	These methods should only be used by the producing side, i.e. the	548	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	549	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	550	producer side which creates the condvar in most cases, but it isn't
447	uncommon for the consumer to create it as well.	551	uncommon for the consumer to create it as well.
…		…
473	This can be used to signal any errors to the condition variable	577	This can be used to signal any errors to the condition variable
474	user/consumer.	578	user/consumer.
475		579
476	$cv->begin ([group callback])	580	$cv->begin ([group callback])
477	$cv->end	581	$cv->end
478	These two methods are EXPERIMENTAL and MIGHT CHANGE.
479
480	These two methods can be used to combine many transactions/events	582	These two methods can be used to combine many transactions/events
481	into one. For example, a function that pings many hosts in parallel	583	into one. For example, a function that pings many hosts in parallel
482	might want to use a condition variable for the whole process.	584	might want to use a condition variable for the whole process.
483		585
484	Every call to "->begin" will increment a counter, and every call to	586	Every call to "->begin" will increment a counter, and every call to
485	"->end" will decrement it. If the counter reaches 0 in "->end", the	587	"->end" will decrement it. If the counter reaches 0 in "->end", the
486	(last) callback passed to "begin" will be executed. That callback is	588	(last) callback passed to "begin" will be executed. That callback is
487	supposed to call "->send", but that is not required. If no	589	supposed to call "->send", but that is not required. If no
488	callback was set, "send" will be called without any arguments.	590	callback was set, "send" will be called without any arguments.
489		591
490	Let's clarify this with the ping example:	592	You can think of "$cv->send" giving you an OR condition (one call
		593	sends), while "$cv->begin" and "$cv->end" giving you an AND
		594	condition (all "begin" calls must be "end"'ed before the condvar
		595	sends).
		596
		597	Let's start with a simple example: you have two I/O watchers (for
		598	example, STDOUT and STDERR for a program), and you want to wait for
		599	both streams to close before activating a condvar:
		600
		601	my $cv = AnyEvent->condvar;
		602
		603	$cv->begin; # first watcher
		604	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		605	defined sysread $fh1, my $buf, 4096
		606	or $cv->end;
		607	});
		608
		609	$cv->begin; # second watcher
		610	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		611	defined sysread $fh2, my $buf, 4096
		612	or $cv->end;
		613	});
		614
		615	$cv->recv;
		616
		617	This works because for every event source (EOF on file handle),
		618	there is one call to "begin", so the condvar waits for all calls to
		619	"end" before sending.
		620
		621	The ping example mentioned above is slightly more complicated, as
		622	the there are results to be passwd back, and the number of tasks
		623	that are begung can potentially be zero:
491		624
492	my $cv = AnyEvent->condvar;	625	my $cv = AnyEvent->condvar;
493		626
494	my %result;	627	my %result;
495	$cv->begin (sub { $cv->send (\%result) });	628	$cv->begin (sub { $cv->send (\%result) });
…		…
515	the loop, which serves two important purposes: first, it sets the	648	the loop, which serves two important purposes: first, it sets the
516	callback to be called once the counter reaches 0, and second, it	649	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	650	ensures that "send" is called even when "no" hosts are being pinged
518	(the loop doesn't execute once).	651	(the loop doesn't execute once).
519		652
520	This is the general pattern when you "fan out" into multiple	653	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	654	potentially none) subrequests: use an outer "begin"/"end" pair to
522	ensure "end" is called at least once, and then, for each subrequest	655	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	656	for each subrequest you start, call "begin" and for each subrequest
524	"end".	657	you finish, call "end".
525		658
526	METHODS FOR CONSUMERS	659	METHODS FOR CONSUMERS
527	These methods should only be used by the consuming side, i.e. the code	660	These methods should only be used by the consuming side, i.e. the code
528	awaits the condition.	661	awaits the condition.
529		662
…		…
567		700
568	$bool = $cv->ready	701	$bool = $cv->ready
569	Returns true when the condition is "true", i.e. whether "send" or	702	Returns true when the condition is "true", i.e. whether "send" or
570	"croak" have been called.	703	"croak" have been called.
571		704
572	$cb = $cv->cb ([new callback])	705	$cb = $cv->cb ($cb->($cv))
573	This is a mutator function that returns the callback set and	706	This is a mutator function that returns the callback set and
574	optionally replaces it before doing so.	707	optionally replaces it before doing so.
575		708
576	The callback will be called when the condition becomes "true", i.e.	709	The callback will be called when the condition becomes "true", i.e.
577	when "send" or "croak" are called, with the only argument being the	710	when "send" or "croak" are called, with the only argument being the
…		…
595	AnyEvent::Impl::Tk based on Tk, very bad choice.	728	AnyEvent::Impl::Tk based on Tk, very bad choice.
596	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	729	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
597	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	730	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
598	AnyEvent::Impl::POE based on POE, not generic enough for full support.	731	AnyEvent::Impl::POE based on POE, not generic enough for full support.
599		732
		733	# warning, support for IO::Async is only partial, as it is too broken
		734	# and limited toe ven support the AnyEvent API. See AnyEvent::Impl::Async.
		735	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed (see its docs).
		736
600	There is no support for WxWidgets, as WxWidgets has no support for	737	There is no support for WxWidgets, as WxWidgets has no support for
601	watching file handles. However, you can use WxWidgets through the	738	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	739	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	740	second, which was considered to be too horrible to even consider for
604	AnyEvent. Likewise, other POE backends can be used by AnyEvent by	741	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
…		…
698	AnyEvent::Util	835	AnyEvent::Util
699	Contains various utility functions that replace often-used but	836	Contains various utility functions that replace often-used but
700	blocking functions such as "inet_aton" by event-/callback-based	837	blocking functions such as "inet_aton" by event-/callback-based
701	versions.	838	versions.
702		839
703	AnyEvent::Handle
704	Provide read and write buffers and manages watchers for reads and
705	writes.
706
707	AnyEvent::Socket	840	AnyEvent::Socket
708	Provides various utility functions for (internet protocol) sockets,	841	Provides various utility functions for (internet protocol) sockets,
709	addresses and name resolution. Also functions to create non-blocking	842	addresses and name resolution. Also functions to create non-blocking
710	tcp connections or tcp servers, with IPv6 and SRV record support and	843	tcp connections or tcp servers, with IPv6 and SRV record support and
711	more.	844	more.
712		845
		846	AnyEvent::Handle
		847	Provide read and write buffers, manages watchers for reads and
		848	writes, supports raw and formatted I/O, I/O queued and fully
		849	transparent and non-blocking SSL/TLS.
		850
713	AnyEvent::DNS	851	AnyEvent::DNS
714	Provides rich asynchronous DNS resolver capabilities.	852	Provides rich asynchronous DNS resolver capabilities.
715		853
716	AnyEvent::HTTP	854	AnyEvent::HTTP
717	A simple-to-use HTTP library that is capable of making a lot of	855	A simple-to-use HTTP library that is capable of making a lot of
…		…
721	Provides a simple web application server framework.	859	Provides a simple web application server framework.
722		860
723	AnyEvent::FastPing	861	AnyEvent::FastPing
724	The fastest ping in the west.	862	The fastest ping in the west.
725		863
		864	AnyEvent::DBI
		865	Executes DBI requests asynchronously in a proxy process.
		866
		867	AnyEvent::AIO
		868	Truly asynchronous I/O, should be in the toolbox of every event
		869	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		870	together.
		871
		872	AnyEvent::BDB
		873	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
		874	fuses BDB and AnyEvent together.
		875
		876	AnyEvent::GPSD
		877	A non-blocking interface to gpsd, a daemon delivering GPS
		878	information.
		879
		880	AnyEvent::IGS
		881	A non-blocking interface to the Internet Go Server protocol (used by
		882	App::IGS).
		883
		884	AnyEvent::IRC
		885	AnyEvent based IRC client module family (replacing the older
726	Net::IRC3	886	Net::IRC3).
727	AnyEvent based IRC client module family.
728		887
729	Net::XMPP2	888	Net::XMPP2
730	AnyEvent based XMPP (Jabber protocol) module family.	889	AnyEvent based XMPP (Jabber protocol) module family.
731		890
732	Net::FCP	891	Net::FCP
…		…
737	High level API for event-based execution flow control.	896	High level API for event-based execution flow control.
738		897
739	Coro	898	Coro
740	Has special support for AnyEvent via Coro::AnyEvent.	899	Has special support for AnyEvent via Coro::AnyEvent.
741		900
742	AnyEvent::AIO, IO::AIO
743	Truly asynchronous I/O, should be in the toolbox of every event
744	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
745	together.
746
747	AnyEvent::BDB, BDB
748	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
749	fuses IO::AIO and AnyEvent together.
750
751	IO::Lambda	901	IO::Lambda
752	The lambda approach to I/O - don't ask, look there. Can use	902	The lambda approach to I/O - don't ask, look there. Can use
753	AnyEvent.	903	AnyEvent.
754		904
755	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	905	ERROR AND EXCEPTION HANDLING
756	This is an advanced topic that you do not normally need to use AnyEvent	906	In general, AnyEvent does not do any error handling - it relies on the
757	in a module. This section is only of use to event loop authors who want	907	caller to do that if required. The AnyEvent::Strict module (see also the
758	to provide AnyEvent compatibility.	908	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
		909	checking of all AnyEvent methods, however, which is highly useful during
		910	development.
759		911
760	If you need to support another event library which isn't directly	912	As for exception handling (i.e. runtime errors and exceptions thrown
761	supported by AnyEvent, you can supply your own interface to it by	913	while executing a callback), this is not only highly event-loop
762	pushing, before the first watcher gets created, the package name of the	914	specific, but also not in any way wrapped by this module, as this is the
763	event module and the package name of the interface to use onto	915	job of the main program.
764	@AnyEvent::REGISTRY. You can do that before and even without loading
765	AnyEvent, so it is reasonably cheap.
766		916
767	Example:	917	The pure perl event loop simply re-throws the exception (usually within
768		918	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
769	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	919	Glib uses "install_exception_handler" and so on.
770
771	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
772	package/class when it finds the "urxvt" package/module is already
773	loaded.
774
775	When AnyEvent is loaded and asked to find a suitable event model, it
776	will first check for the presence of urxvt by trying to "use" the
777	"urxvt::anyevent" module.
778
779	The class should provide implementations for all watcher types. See
780	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
781	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
782	the sources.
783
784	If you don't provide "signal" and "child" watchers than AnyEvent will
785	provide suitable (hopefully) replacements.
786
787	The above example isn't fictitious, the rxvt-unicode (a.k.a. urxvt)
788	terminal emulator uses the above line as-is. An interface isn't included
789	in AnyEvent because it doesn't make sense outside the embedded
790	interpreter inside rxvt-unicode, and it is updated and maintained as
791	part of the rxvt-unicode distribution.
792
793	rxvt-unicode also cheats a bit by not providing blocking access to
794	condition variables: code blocking while waiting for a condition will
795	"die". This still works with most modules/usages, and blocking calls
796	must not be done in an interactive application, so it makes sense.
797		920
798	ENVIRONMENT VARIABLES	921	ENVIRONMENT VARIABLES
799	The following environment variables are used by this module:	922	The following environment variables are used by this module or its
		923	submodules.
		924
		925	Note that AnyEvent will remove all environment variables starting with
		926	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		927	enabled.
800		928
801	"PERL_ANYEVENT_VERBOSE"	929	"PERL_ANYEVENT_VERBOSE"
802	By default, AnyEvent will be completely silent except in fatal	930	By default, AnyEvent will be completely silent except in fatal
803	conditions. You can set this environment variable to make AnyEvent	931	conditions. You can set this environment variable to make AnyEvent
804	more talkative.	932	more talkative.
…		…
807	conditions, such as not being able to load the event model specified	935	conditions, such as not being able to load the event model specified
808	by "PERL_ANYEVENT_MODEL".	936	by "PERL_ANYEVENT_MODEL".
809		937
810	When set to 2 or higher, cause AnyEvent to report to STDERR which	938	When set to 2 or higher, cause AnyEvent to report to STDERR which
811	event model it chooses.	939	event model it chooses.
		940
		941	"PERL_ANYEVENT_STRICT"
		942	AnyEvent does not do much argument checking by default, as thorough
		943	argument checking is very costly. Setting this variable to a true
		944	value will cause AnyEvent to load "AnyEvent::Strict" and then to
		945	thoroughly check the arguments passed to most method calls. If it
		946	finds any problems, it will croak.
		947
		948	In other words, enables "strict" mode.
		949
		950	Unlike "use strict", it is definitely recommended to keep it off in
		951	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
		952	while developing programs can be very useful, however.
812		953
813	"PERL_ANYEVENT_MODEL"	954	"PERL_ANYEVENT_MODEL"
814	This can be used to specify the event model to be used by AnyEvent,	955	This can be used to specify the event model to be used by AnyEvent,
815	before auto detection and -probing kicks in. It must be a string	956	before auto detection and -probing kicks in. It must be a string
816	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	957	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
835	mentioned will be used, and preference will be given to protocols	976	mentioned will be used, and preference will be given to protocols
836	mentioned earlier in the list.	977	mentioned earlier in the list.
837		978
838	This variable can effectively be used for denial-of-service attacks	979	This variable can effectively be used for denial-of-service attacks
839	against local programs (e.g. when setuid), although the impact is	980	against local programs (e.g. when setuid), although the impact is
840	likely small, as the program has to handle connection errors	981	likely small, as the program has to handle conenction and other
841	already-	982	failures anyways.
842		983
843	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	984	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
844	IPv6, but support both and try to use both.	985	IPv6, but support both and try to use both.
845	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	986	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
846	resolve or contact IPv6 addresses.	987	resolve or contact IPv6 addresses.
…		…
857	EDNS0 in its DNS requests.	998	EDNS0 in its DNS requests.
858		999
859	"PERL_ANYEVENT_MAX_FORKS"	1000	"PERL_ANYEVENT_MAX_FORKS"
860	The maximum number of child processes that	1001	The maximum number of child processes that
861	"AnyEvent::Util::fork_call" will create in parallel.	1002	"AnyEvent::Util::fork_call" will create in parallel.
		1003
		1004	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1005	This is an advanced topic that you do not normally need to use AnyEvent
		1006	in a module. This section is only of use to event loop authors who want
		1007	to provide AnyEvent compatibility.
		1008
		1009	If you need to support another event library which isn't directly
		1010	supported by AnyEvent, you can supply your own interface to it by
		1011	pushing, before the first watcher gets created, the package name of the
		1012	event module and the package name of the interface to use onto
		1013	@AnyEvent::REGISTRY. You can do that before and even without loading
		1014	AnyEvent, so it is reasonably cheap.
		1015
		1016	Example:
		1017
		1018	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
		1019
		1020	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
		1021	package/class when it finds the "urxvt" package/module is already
		1022	loaded.
		1023
		1024	When AnyEvent is loaded and asked to find a suitable event model, it
		1025	will first check for the presence of urxvt by trying to "use" the
		1026	"urxvt::anyevent" module.
		1027
		1028	The class should provide implementations for all watcher types. See
		1029	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
		1030	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
		1031	the sources.
		1032
		1033	If you don't provide "signal" and "child" watchers than AnyEvent will
		1034	provide suitable (hopefully) replacements.
		1035
		1036	The above example isn't fictitious, the rxvt-unicode (a.k.a. urxvt)
		1037	terminal emulator uses the above line as-is. An interface isn't included
		1038	in AnyEvent because it doesn't make sense outside the embedded
		1039	interpreter inside rxvt-unicode, and it is updated and maintained as
		1040	part of the rxvt-unicode distribution.
		1041
		1042	rxvt-unicode also cheats a bit by not providing blocking access to
		1043	condition variables: code blocking while waiting for a condition will
		1044	"die". This still works with most modules/usages, and blocking calls
		1045	must not be done in an interactive application, so it makes sense.
862		1046
863	EXAMPLE PROGRAM	1047	EXAMPLE PROGRAM
864	The following program uses an I/O watcher to read data from STDIN, a	1048	The following program uses an I/O watcher to read data from STDIN, a
865	timer to display a message once per second, and a condition variable to	1049	timer to display a message once per second, and a condition variable to
866	quit the program when the user enters quit:	1050	quit the program when the user enters quit:
…		…
1053	destroy is the time, in microseconds, that it takes to destroy a	1237	destroy is the time, in microseconds, that it takes to destroy a
1054	single watcher.	1238	single watcher.
1055		1239
1056	Results	1240	Results
1057	name watchers bytes create invoke destroy comment	1241	name watchers bytes create invoke destroy comment
1058	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1242	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1059	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1243	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1060	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1244	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1061	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1245	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1062	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1246	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1063	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1247	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1248	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1249	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1064	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1250	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1065	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1251	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1066	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1252	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1067	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1253	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1068		1254
1069	Discussion	1255	Discussion
1070	The benchmark does not measure scalability of the event loop very	1256	The benchmark does not measure scalability of the event loop very
1071	well. For example, a select-based event loop (such as the pure perl one)	1257	well. For example, a select-based event loop (such as the pure perl one)
1072	can never compete with an event loop that uses epoll when the number of	1258	can never compete with an event loop that uses epoll when the number of
…		…
1097	few of them active), of course, but this was not subject of this	1283	few of them active), of course, but this was not subject of this
1098	benchmark.	1284	benchmark.
1099		1285
1100	The "Event" module has a relatively high setup and callback invocation	1286	The "Event" module has a relatively high setup and callback invocation
1101	cost, but overall scores in on the third place.	1287	cost, but overall scores in on the third place.
		1288
		1289	"IO::Async" performs admirably well, about on par with "Event", even
		1290	when using its pure perl backend.
1102		1291
1103	"Glib"'s memory usage is quite a bit higher, but it features a faster	1292	"Glib"'s memory usage is quite a bit higher, but it features a faster
1104	callback invocation and overall ends up in the same class as "Event".	1293	callback invocation and overall ends up in the same class as "Event".
1105	However, Glib scales extremely badly, doubling the number of watchers	1294	However, Glib scales extremely badly, doubling the number of watchers
1106	increases the processing time by more than a factor of four, making it	1295	increases the processing time by more than a factor of four, making it
…		…
1177	single "request", that is, reading the token from the pipe and	1366	single "request", that is, reading the token from the pipe and
1178	forwarding it to another server. This includes deleting the old timeout	1367	forwarding it to another server. This includes deleting the old timeout
1179	and creating a new one that moves the timeout into the future.	1368	and creating a new one that moves the timeout into the future.
1180		1369
1181	Results	1370	Results
1182	name sockets create request	1371	name sockets create request
1183	EV 20000 69.01 11.16	1372	EV 20000 69.01 11.16
1184	Perl 20000 73.32 35.87	1373	Perl 20000 73.32 35.87
		1374	IOAsync 20000 157.00 98.14 epoll
		1375	IOAsync 20000 159.31 616.06 poll
1185	Event 20000 212.62 257.32	1376	Event 20000 212.62 257.32
1186	Glib 20000 651.16 1896.30	1377	Glib 20000 651.16 1896.30
1187	POE 20000 349.67 12317.24 uses POE::Loop::Event	1378	POE 20000 349.67 12317.24 uses POE::Loop::Event
1188		1379
1189	Discussion	1380	Discussion
1190	This benchmark does measure scalability and overall performance of the	1381	This benchmark does measure scalability and overall performance of the
1191	particular event loop.	1382	particular event loop.
1192		1383
1193	EV is again fastest. Since it is using epoll on my system, the setup	1384	EV is again fastest. Since it is using epoll on my system, the setup
1194	time is relatively high, though.	1385	time is relatively high, though.
1195		1386
1196	Perl surprisingly comes second. It is much faster than the C-based event	1387	Perl surprisingly comes second. It is much faster than the C-based event
1197	loops Event and Glib.	1388	loops Event and Glib.
		1389
		1390	IO::Async performs very well when using its epoll backend, and still
		1391	quite good compared to Glib when using its pure perl backend.
1198		1392
1199	Event suffers from high setup time as well (look at its code and you	1393	Event suffers from high setup time as well (look at its code and you
1200	will understand why). Callback invocation also has a high overhead	1394	will understand why). Callback invocation also has a high overhead
1201	compared to the "$_->() for .."-style loop that the Perl event loop	1395	compared to the "$_->() for .."-style loop that the Perl event loop
1202	uses. Event uses select or poll in basically all documented	1396	uses. Event uses select or poll in basically all documented
…		…
1253		1447
1254	Summary	1448	Summary
1255	* C-based event loops perform very well with small number of watchers,	1449	* C-based event loops perform very well with small number of watchers,
1256	as the management overhead dominates.	1450	as the management overhead dominates.
1257		1451
		1452	THE IO::Lambda BENCHMARK
		1453	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1454	could be misinterpreted to make AnyEvent look bad. In fact, the
		1455	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1456	better (which shouldn't come as a surprise to anybody). As such, the
		1457	benchmark is fine, and mostly shows that the AnyEvent backend from
		1458	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1459	without the extra baggage? To explore this, I wrote the equivalent
		1460	benchmark for AnyEvent.
		1461
		1462	The benchmark itself creates an echo-server, and then, for 500 times,
		1463	connects to the echo server, sends a line, waits for the reply, and then
		1464	creates the next connection. This is a rather bad benchmark, as it
		1465	doesn't test the efficiency of the framework or much non-blocking I/O,
		1466	but it is a benchmark nevertheless.
		1467
		1468	name runtime
		1469	Lambda/select 0.330 sec
		1470	+ optimized 0.122 sec
		1471	Lambda/AnyEvent 0.327 sec
		1472	+ optimized 0.138 sec
		1473	Raw sockets/select 0.077 sec
		1474	POE/select, components 0.662 sec
		1475	POE/select, raw sockets 0.226 sec
		1476	POE/select, optimized 0.404 sec
		1477
		1478	AnyEvent/select/nb 0.085 sec
		1479	AnyEvent/EV/nb 0.068 sec
		1480	+state machine 0.134 sec
		1481
		1482	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1483	benchmarks actually make blocking connects and use 100% blocking I/O,
		1484	defeating the purpose of an event-based solution. All of the newly
		1485	written AnyEvent benchmarks use 100% non-blocking connects (using
		1486	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1487	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1488	connects generally require a lot more bookkeeping and event handling
		1489	than blocking connects (which involve a single syscall only).
		1490
		1491	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1492	offers similar expressive power as POE and IO::Lambda, using
		1493	conventional Perl syntax. This means that both the echo server and the
		1494	client are 100% non-blocking, further placing it at a disadvantage.
		1495
		1496	As you can see, the AnyEvent + EV combination even beats the
		1497	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1498	backend easily beats IO::Lambda and POE.
		1499
		1500	And even the 100% non-blocking version written using the high-level (and
		1501	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a
		1502	large margin, even though it does all of DNS, tcp-connect and socket I/O
		1503	in a non-blocking way.
		1504
		1505	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1506	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1507	part of the IO::lambda distribution and were used without any changes.
		1508
		1509	SIGNALS
		1510	AnyEvent currently installs handlers for these signals:
		1511
		1512	SIGCHLD
		1513	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
		1514	emulation for event loops that do not support them natively. Also,
		1515	some event loops install a similar handler.
		1516
		1517	If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent
		1518	will reset it to default, to avoid losing child exit statuses.
		1519
		1520	SIGPIPE
		1521	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
		1522	"undef" when AnyEvent gets loaded.
		1523
		1524	The rationale for this is that AnyEvent users usually do not really
		1525	depend on SIGPIPE delivery (which is purely an optimisation for
		1526	shell use, or badly-written programs), but "SIGPIPE" can cause
		1527	spurious and rare program exits as a lot of people do not expect
		1528	"SIGPIPE" when writing to some random socket.
		1529
		1530	The rationale for installing a no-op handler as opposed to ignoring
		1531	it is that this way, the handler will be restored to defaults on
		1532	exec.
		1533
		1534	Feel free to install your own handler, or reset it to defaults.
		1535
1258	FORK	1536	FORK
1259	Most event libraries are not fork-safe. The ones who are usually are	1537	Most event libraries are not fork-safe. The ones who are usually are
1260	because they rely on inefficient but fork-safe "select" or "poll" calls.	1538	because they rely on inefficient but fork-safe "select" or "poll" calls.
1261	Only EV is fully fork-aware.	1539	Only EV is fully fork-aware.
1262		1540
…		…
1273		1551
1274	You can make AnyEvent completely ignore this variable by deleting it	1552	You can make AnyEvent completely ignore this variable by deleting it
1275	before the first watcher gets created, e.g. with a "BEGIN" block:	1553	before the first watcher gets created, e.g. with a "BEGIN" block:
1276		1554
1277	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1555	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1278		1556
1279	use AnyEvent;	1557	use AnyEvent;
1280		1558
1281	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1559	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1282	be used to probe what backend is used and gain other information (which	1560	be used to probe what backend is used and gain other information (which
1283	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	1561	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
		1562	and $ENV{PERL_ANYEVENT_STRICT}.
		1563
		1564	Note that AnyEvent will remove all environment variables starting with
		1565	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1566	enabled.
1284		1567
1285	BUGS	1568	BUGS
1286	Perl 5.8 has numerous memleaks that sometimes hit this module and are	1569	Perl 5.8 has numerous memleaks that sometimes hit this module and are
1287	hard to work around. If you suffer from memleaks, first upgrade to Perl	1570	hard to work around. If you suffer from memleaks, first upgrade to Perl
1288	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	1571	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1289	annoying mamleaks, such as leaking on "map" and "grep" but it is usually	1572	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1290	not as pronounced).	1573	not as pronounced).
1291		1574
1292	SEE ALSO	1575	SEE ALSO
1293	Utility functions: AnyEvent::Util.	1576	Utility functions: AnyEvent::Util.
1294		1577

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Comparing AnyEvent/README (file contents): Revision 1.26 by root, Fri Jun 6 11:13:07 2008 UTC vs. Revision 1.42 by root, Mon Jun 29 21:00:32 2009 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.26 by root, Fri Jun 6 11:13:07 2008 UTC vs.
Revision 1.42 by root, Mon Jun 29 21:00:32 2009 UTC