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Comparing AnyEvent/README (file contents):
Revision 1.23 by root, Mon May 26 06:04:38 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 });
		37
		38	INTRODUCTION/TUTORIAL
		39	This manpage is mainly a reference manual. If you are interested in a
		40	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
		41	manpage.
21		42
22	WHY YOU SHOULD USE THIS MODULE (OR NOT)	43	WHY YOU SHOULD USE THIS MODULE (OR NOT)
23	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	44	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
24	nowadays. So what is different about AnyEvent?	45	nowadays. So what is different about AnyEvent?
25		46
26	Executive Summary: AnyEvent is compatible, AnyEvent is *free of	47	Executive Summary: AnyEvent is compatible, AnyEvent is *free of
27	policy* and AnyEvent is small and efficient.	48	policy* and AnyEvent is small and efficient.
28		49
29	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
30	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
31	pragmatic way. For event models and certain classes of immortals alike,	52	pragmatic way. For event models and certain classes of immortals alike,
32	the statement "there can only be one" is a bitter reality: In general,	53	the statement "there can only be one" is a bitter reality: In general,
33	only one event loop can be active at the same time in a process.	54	only one event loop can be active at the same time in a process.
34	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.
35		57
36	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
37	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
38	religion, a way of living, and most importantly: without forcing your	60	religion, a way of living, and most importantly: without forcing your
39	module users into the same thing by forcing them to use the same event	61	module users into the same thing by forcing them to use the same event
40	model you use.	62	model you use.
41		63
42	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
43	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
44	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
45	cannot use anything else, as it is simply incompatible to everything	67	cannot use anything else, as they are simply incompatible to everything
46	that isn't itself. What's worse, all the potential users of your module	68	that isn't them. What's worse, all the potential users of your module
47	are also forced to use the same event loop you use.	69	are also forced to use the same event loop you use.
48		70
49	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	71	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50	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
51	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
52	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.
53	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
54	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
55	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
56	event loops to AnyEvent, too, so it is future-proof).	78	to AnyEvent, too, so it is future-proof).
57		79
58	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
59	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
60	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
61	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
62	only offering the functionality that is necessary, in as thin as a	84	only offering the functionality that is necessary, in as thin as a
63	wrapper as technically possible.	85	wrapper as technically possible.
64		86
		87	Of course, AnyEvent comes with a big (and fully optional!) toolbox of
		88	useful functionality, such as an asynchronous DNS resolver, 100%
		89	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		90	such as Windows) and lots of real-world knowledge and workarounds for
		91	platform bugs and differences.
		92
65	Of course, if you want lots of policy (this can arguably be somewhat	93	Now, if you do want lots of policy (this can arguably be somewhat
66	useful) and you want to force your users to use the one and only event	94	useful) and you want to force your users to use the one and only event
67	model, you should not use this module.	95	model, you should not use this module.
68		96
69	DESCRIPTION	97	DESCRIPTION
70	AnyEvent provides an identical interface to multiple event loops. This	98	AnyEvent provides an identical interface to multiple event loops. This
99	starts using it, all bets are off. Maybe you should tell their authors	127	starts using it, all bets are off. Maybe you should tell their authors
100	to use AnyEvent so their modules work together with others seamlessly...	128	to use AnyEvent so their modules work together with others seamlessly...
101		129
102	The pure-perl implementation of AnyEvent is called	130	The pure-perl implementation of AnyEvent is called
103	"AnyEvent::Impl::Perl". Like other event modules you can load it	131	"AnyEvent::Impl::Perl". Like other event modules you can load it
104	explicitly.	132	explicitly and enjoy the high availability of that event loop :)
105		133
106	WATCHERS	134	WATCHERS
107	AnyEvent has the central concept of a watcher, which is an object that	135	AnyEvent has the central concept of a watcher, which is an object that
108	stores relevant data for each kind of event you are waiting for, such as	136	stores relevant data for each kind of event you are waiting for, such as
109	the callback to call, the file handle to watch, etc.	137	the callback to call, the file handle to watch, etc.
…		…
111	These watchers are normal Perl objects with normal Perl lifetime. After	139	These watchers are normal Perl objects with normal Perl lifetime. After
112	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
113	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
114	in control).	142	in control).
115		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
116	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
117	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
118	to it).	152	to it).
119		153
120	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.
…		…
122	Many watchers either are used with "recursion" (repeating timers for	156	Many watchers either are used with "recursion" (repeating timers for
123	example), or need to refer to their watcher object in other ways.	157	example), or need to refer to their watcher object in other ways.
124		158
125	An any way to achieve that is this pattern:	159	An any way to achieve that is this pattern:
126		160
127	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	161	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
128	# you can use $w here, for example to undef it	162	# you can use $w here, for example to undef it
129	undef $w;	163	undef $w;
130	});	164	});
131		165
132	Note that "my $w; $w =" combination. This is necessary because in Perl,	166	Note that "my $w; $w =" combination. This is necessary because in Perl,
133	my variables are only visible after the statement in which they are	167	my variables are only visible after the statement in which they are
134	declared.	168	declared.
135		169
136	I/O WATCHERS	170	I/O WATCHERS
137	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
138	the following mandatory key-value pairs as arguments:	172	the following mandatory key-value pairs as arguments:
139		173
140	"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
141	"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
142	watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"	182	watcher waiting for "r"eadable or "w"ritable events, respectively.
		183
143	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.
144		185
145	Although the callback might get passed parameters, their value and	186	Although the callback might get passed parameters, their value and
146	presence is undefined and you cannot rely on them. Portable AnyEvent	187	presence is undefined and you cannot rely on them. Portable AnyEvent
147	callbacks cannot use arguments passed to I/O watcher callbacks.	188	callbacks cannot use arguments passed to I/O watcher callbacks.
148		189
…		…
152		193
153	Some event loops issue spurious readyness notifications, so you should	194	Some event loops issue spurious readyness notifications, so you should
154	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
155	handles.	196	handles.
156		197
157	Example:
158
159	# 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
160	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	201	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
161	chomp (my $input = <STDIN>);	202	chomp (my $input = <STDIN>);
162	warn "read: $input\n";	203	warn "read: $input\n";
163	undef $w;	204	undef $w;
164	});	205	});
…		…
173		214
174	Although the callback might get passed parameters, their value and	215	Although the callback might get passed parameters, their value and
175	presence is undefined and you cannot rely on them. Portable AnyEvent	216	presence is undefined and you cannot rely on them. Portable AnyEvent
176	callbacks cannot use arguments passed to time watcher callbacks.	217	callbacks cannot use arguments passed to time watcher callbacks.
177		218
178	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
179	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
180	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.
181		224
182	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.
183		228
184	# fire an event after 7.7 seconds	229	Example: fire an event after 7.7 seconds.
		230
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	231	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	232	warn "timeout\n";
187	});	233	});
188		234
189	# to cancel the timer:	235	# to cancel the timer:
190	undef $w;	236	undef $w;
191		237
192	Example 2:
193
194	# 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.
195	my $w;
196		239
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	240	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		241	warn "timeout\n";
200	};	242	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		243
205	TIMING ISSUES	244	TIMING ISSUES
206	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
207	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
208	o'clock").	247	o'clock").
…		…
220	on wallclock time) timers.	259	on wallclock time) timers.
221		260
222	AnyEvent always prefers relative timers, if available, matching the	261	AnyEvent always prefers relative timers, if available, matching the
223	AnyEvent API.	262	AnyEvent API.
224		263
		264	AnyEvent has two additional methods that return the "current time":
		265
		266	AnyEvent->time
		267	This returns the "current wallclock time" as a fractional number of
		268	seconds since the Epoch (the same thing as "time" or
		269	"Time::HiRes::time" return, and the result is guaranteed to be
		270	compatible with those).
		271
		272	It progresses independently of any event loop processing, i.e. each
		273	call will check the system clock, which usually gets updated
		274	frequently.
		275
		276	AnyEvent->now
		277	This also returns the "current wallclock time", but unlike "time",
		278	above, this value might change only once per event loop iteration,
		279	depending on the event loop (most return the same time as "time",
		280	above). This is the time that AnyEvent's timers get scheduled
		281	against.
		282
		283	*In almost all cases (in all cases if you don't care), this is the
		284	function to call when you want to know the current time.*
		285
		286	This function is also often faster then "AnyEvent->time", and thus
		287	the preferred method if you want some timestamp (for example,
		288	AnyEvent::Handle uses this to update it's activity timeouts).
		289
		290	The rest of this section is only of relevance if you try to be very
		291	exact with your timing, you can skip it without bad conscience.
		292
		293	For a practical example of when these times differ, consider
		294	Event::Lib and EV and the following set-up:
		295
		296	The event loop is running and has just invoked one of your callback
		297	at time=500 (assume no other callbacks delay processing). In your
		298	callback, you wait a second by executing "sleep 1" (blocking the
		299	process for a second) and then (at time=501) you create a relative
		300	timer that fires after three seconds.
		301
		302	With Event::Lib, "AnyEvent->time" and "AnyEvent->now" will both
		303	return 501, because that is the current time, and the timer will be
		304	scheduled to fire at time=504 (501 + 3).
		305
		306	With EV, "AnyEvent->time" returns 501 (as that is the current time),
		307	but "AnyEvent->now" returns 500, as that is the time the last event
		308	processing phase started. With EV, your timer gets scheduled to run
		309	at time=503 (500 + 3).
		310
		311	In one sense, Event::Lib is more exact, as it uses the current time
		312	regardless of any delays introduced by event processing. However,
		313	most callbacks do not expect large delays in processing, so this
		314	causes a higher drift (and a lot more system calls to get the
		315	current time).
		316
		317	In another sense, EV is more exact, as your timer will be scheduled
		318	at the same time, regardless of how long event processing actually
		319	took.
		320
		321	In either case, if you care (and in most cases, you don't), then you
		322	can get whatever behaviour you want with any event loop, by taking
		323	the difference between "AnyEvent->time" and "AnyEvent->now" into
		324	account.
		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
225	SIGNAL WATCHERS	340	SIGNAL WATCHERS
226	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
227	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
228	whenever a signal occurs.	343	callback to be invoked whenever a signal occurs.
229		344
230	Although the callback might get passed parameters, their value and	345	Although the callback might get passed parameters, their value and
231	presence is undefined and you cannot rely on them. Portable AnyEvent	346	presence is undefined and you cannot rely on them. Portable AnyEvent
232	callbacks cannot use arguments passed to signal watcher callbacks.	347	callbacks cannot use arguments passed to signal watcher callbacks.
233		348
…		…
248		363
249	CHILD PROCESS WATCHERS	364	CHILD PROCESS WATCHERS
250	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.
251		366
252	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
253	watches for any child process exit). The watcher will trigger as often	368	watches for any child process exit). The watcher will triggered only
254	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
255	signal handler for "SIGCHLD". The callback will be called with the pid	370	on any trace events (stopped/continued).
256	and exit status (as returned by waitpid), so unlike other watcher types,	371
257	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).
258		380
259	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
260	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
261	could have exited already (and no SIGCHLD will be sent anymore).	383	could have exited already (and no SIGCHLD will be sent anymore).
262		384
263	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
264	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
265	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).
266	place).	389	AnyEvent's pure perl event loop handles all cases correctly regardless
		390	of when you start the watcher.
267		391
268	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
269	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
270	you "fork" the child (alternatively, you can call "AnyEvent::detect").	394	you "fork" the child (alternatively, you can call "AnyEvent::detect").
271		395
272	Example: fork a process and wait for it	396	Example: fork a process and wait for it
273		397
274	my $done = AnyEvent->condvar;	398	my $done = AnyEvent->condvar;
275		399
276	my $pid = fork or exit 5;	400	my $pid = fork or exit 5;
277		401
278	my $w = AnyEvent->child (	402	my $w = AnyEvent->child (
279	pid => $pid,	403	pid => $pid,
280	cb => sub {	404	cb => sub {
281	my ($pid, $status) = @_;	405	my ($pid, $status) = @_;
282	warn "pid $pid exited with status $status";	406	warn "pid $pid exited with status $status";
283	$done->send;	407	$done->send;
284	},	408	},
285	);	409	);
286		410
287	# do something else, then wait for process exit	411	# do something else, then wait for process exit
288	$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	});
289		447
290	CONDITION VARIABLES	448	CONDITION VARIABLES
291	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
292	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
293	will actively watch for new events and call your callbacks.	451	will actively watch for new events and call your callbacks.
…		…
298	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
299	because they represent a condition that must become true.	457	because they represent a condition that must become true.
300		458
301	Condition variables can be created by calling the "AnyEvent->condvar"	459	Condition variables can be created by calling the "AnyEvent->condvar"
302	method, usually without arguments. The only argument pair allowed is	460	method, usually without arguments. The only argument pair allowed is
		461
303	"cb", which specifies a callback to be called when the condition	462	"cb", which specifies a callback to be called when the condition
304	variable becomes true.	463	variable becomes true, with the condition variable as the first argument
		464	(but not the results).
305		465
306	After creation, the condition variable is "false" until it becomes	466	After creation, the condition variable is "false" until it becomes
307	"true" by calling the "send" method (or calling the condition variable	467	"true" by calling the "send" method (or calling the condition variable
308	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
309	the "->send" method).	469	the "->send" method).
…		…
365		525
366	my $done = AnyEvent->condvar;	526	my $done = AnyEvent->condvar;
367	my $delay = AnyEvent->timer (after => 5, cb => $done);	527	my $delay = AnyEvent->timer (after => 5, cb => $done);
368	$done->recv;	528	$done->recv;
369		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
370	METHODS FOR PRODUCERS	547	METHODS FOR PRODUCERS
371	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
372	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
373	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
374	uncommon for the consumer to create it as well.	551	uncommon for the consumer to create it as well.
…		…
400	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
401	user/consumer.	578	user/consumer.
402		579
403	$cv->begin ([group callback])	580	$cv->begin ([group callback])
404	$cv->end	581	$cv->end
405	These two methods are EXPERIMENTAL and MIGHT CHANGE.
406
407	These two methods can be used to combine many transactions/events	582	These two methods can be used to combine many transactions/events
408	into one. For example, a function that pings many hosts in parallel	583	into one. For example, a function that pings many hosts in parallel
409	might want to use a condition variable for the whole process.	584	might want to use a condition variable for the whole process.
410		585
411	Every call to "->begin" will increment a counter, and every call to	586	Every call to "->begin" will increment a counter, and every call to
412	"->end" will decrement it. If the counter reaches 0 in "->end", the	587	"->end" will decrement it. If the counter reaches 0 in "->end", the
413	(last) callback passed to "begin" will be executed. That callback is	588	(last) callback passed to "begin" will be executed. That callback is
414	supposed to call "->send", but that is not required. If no	589	supposed to call "->send", but that is not required. If no
415	callback was set, "send" will be called without any arguments.	590	callback was set, "send" will be called without any arguments.
416		591
417	Let's clarify this with the ping example:	592	You can think of "$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:
418		624
419	my $cv = AnyEvent->condvar;	625	my $cv = AnyEvent->condvar;
420		626
421	my %result;	627	my %result;
422	$cv->begin (sub { $cv->send (\%result) });	628	$cv->begin (sub { $cv->send (\%result) });
…		…
442	the loop, which serves two important purposes: first, it sets the	648	the loop, which serves two important purposes: first, it sets the
443	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
444	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
445	(the loop doesn't execute once).	651	(the loop doesn't execute once).
446		652
447	This is the general pattern when you "fan out" into multiple	653	This is the general pattern when you "fan out" into multiple (but
448	subrequests: use an outer "begin"/"end" pair to set the callback and	654	potentially none) subrequests: use an outer "begin"/"end" pair to
449	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,
450	you start, call "begin" and for each subrequest you finish, call	656	for each subrequest you start, call "begin" and for each subrequest
451	"end".	657	you finish, call "end".
452		658
453	METHODS FOR CONSUMERS	659	METHODS FOR CONSUMERS
454	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
455	awaits the condition.	661	awaits the condition.
456		662
…		…
494		700
495	$bool = $cv->ready	701	$bool = $cv->ready
496	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
497	"croak" have been called.	703	"croak" have been called.
498		704
499	$cb = $cv->cb ([new callback])	705	$cb = $cv->cb ($cb->($cv))
500	This is a mutator function that returns the callback set and	706	This is a mutator function that returns the callback set and
501	optionally replaces it before doing so.	707	optionally replaces it before doing so.
502		708
503	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.
504	when "send" or "croak" are called. Calling "recv" inside the	710	when "send" or "croak" are called, with the only argument being the
		711	condition variable itself. Calling "recv" inside the callback or at
505	callback or at any later time is guaranteed not to block.	712	any later time is guaranteed not to block.
506		713
507	GLOBAL VARIABLES AND FUNCTIONS	714	GLOBAL VARIABLES AND FUNCTIONS
508	$AnyEvent::MODEL	715	$AnyEvent::MODEL
509	Contains "undef" until the first watcher is being created. Then it	716	Contains "undef" until the first watcher is being created. Then it
510	contains the event model that is being used, which is the name of	717	contains the event model that is being used, which is the name of
…		…
521	AnyEvent::Impl::Tk based on Tk, very bad choice.	728	AnyEvent::Impl::Tk based on Tk, very bad choice.
522	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).
523	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	730	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
524	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.
525		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
526	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
527	watching file handles. However, you can use WxWidgets through the	738	watching file handles. However, you can use WxWidgets through the
528	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
529	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
530	AnyEvent. Likewise, other POE backends can be used by AnyEvent by	741	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
…		…
624	AnyEvent::Util	835	AnyEvent::Util
625	Contains various utility functions that replace often-used but	836	Contains various utility functions that replace often-used but
626	blocking functions such as "inet_aton" by event-/callback-based	837	blocking functions such as "inet_aton" by event-/callback-based
627	versions.	838	versions.
628		839
629	AnyEvent::Handle
630	Provide read and write buffers and manages watchers for reads and
631	writes.
632
633	AnyEvent::Socket	840	AnyEvent::Socket
634	Provides various utility functions for (internet protocol) sockets,	841	Provides various utility functions for (internet protocol) sockets,
635	addresses and name resolution. Also functions to create non-blocking	842	addresses and name resolution. Also functions to create non-blocking
636	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
637	more.	844	more.
638		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
639	AnyEvent::DNS	851	AnyEvent::DNS
640	Provides rich asynchronous DNS resolver capabilities.	852	Provides rich asynchronous DNS resolver capabilities.
641		853
		854	AnyEvent::HTTP
		855	A simple-to-use HTTP library that is capable of making a lot of
		856	concurrent HTTP requests.
		857
642	AnyEvent::HTTPD	858	AnyEvent::HTTPD
643	Provides a simple web application server framework.	859	Provides a simple web application server framework.
644		860
645	AnyEvent::FastPing	861	AnyEvent::FastPing
646	The fastest ping in the west.	862	The fastest ping in the west.
647		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
648	Net::IRC3	886	Net::IRC3).
649	AnyEvent based IRC client module family.
650		887
651	Net::XMPP2	888	Net::XMPP2
652	AnyEvent based XMPP (Jabber protocol) module family.	889	AnyEvent based XMPP (Jabber protocol) module family.
653		890
654	Net::FCP	891	Net::FCP
…		…
659	High level API for event-based execution flow control.	896	High level API for event-based execution flow control.
660		897
661	Coro	898	Coro
662	Has special support for AnyEvent via Coro::AnyEvent.	899	Has special support for AnyEvent via Coro::AnyEvent.
663		900
664	AnyEvent::AIO, IO::AIO
665	Truly asynchronous I/O, should be in the toolbox of every event
666	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
667	together.
668
669	AnyEvent::BDB, BDB
670	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
671	fuses IO::AIO and AnyEvent together.
672
673	IO::Lambda	901	IO::Lambda
674	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
675	AnyEvent.	903	AnyEvent.
676		904
677	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	905	ERROR AND EXCEPTION HANDLING
678	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
679	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
680	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.
681		911
682	If you need to support another event library which isn't directly	912	As for exception handling (i.e. runtime errors and exceptions thrown
683	supported by AnyEvent, you can supply your own interface to it by	913	while executing a callback), this is not only highly event-loop
684	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
685	event module and the package name of the interface to use onto	915	job of the main program.
686	@AnyEvent::REGISTRY. You can do that before and even without loading
687	AnyEvent, so it is reasonably cheap.
688		916
689	Example:	917	The pure perl event loop simply re-throws the exception (usually within
690		918	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
691	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	919	Glib uses "install_exception_handler" and so on.
692
693	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
694	package/class when it finds the "urxvt" package/module is already
695	loaded.
696
697	When AnyEvent is loaded and asked to find a suitable event model, it
698	will first check for the presence of urxvt by trying to "use" the
699	"urxvt::anyevent" module.
700
701	The class should provide implementations for all watcher types. See
702	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
703	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
704	the sources.
705
706	If you don't provide "signal" and "child" watchers than AnyEvent will
707	provide suitable (hopefully) replacements.
708
709	The above example isn't fictitious, the rxvt-unicode (a.k.a. urxvt)
710	terminal emulator uses the above line as-is. An interface isn't included
711	in AnyEvent because it doesn't make sense outside the embedded
712	interpreter inside rxvt-unicode, and it is updated and maintained as
713	part of the rxvt-unicode distribution.
714
715	rxvt-unicode also cheats a bit by not providing blocking access to
716	condition variables: code blocking while waiting for a condition will
717	"die". This still works with most modules/usages, and blocking calls
718	must not be done in an interactive application, so it makes sense.
719		920
720	ENVIRONMENT VARIABLES	921	ENVIRONMENT VARIABLES
721	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.
722		928
723	"PERL_ANYEVENT_VERBOSE"	929	"PERL_ANYEVENT_VERBOSE"
724	By default, AnyEvent will be completely silent except in fatal	930	By default, AnyEvent will be completely silent except in fatal
725	conditions. You can set this environment variable to make AnyEvent	931	conditions. You can set this environment variable to make AnyEvent
726	more talkative.	932	more talkative.
…		…
729	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
730	by "PERL_ANYEVENT_MODEL".	936	by "PERL_ANYEVENT_MODEL".
731		937
732	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
733	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.
734		953
735	"PERL_ANYEVENT_MODEL"	954	"PERL_ANYEVENT_MODEL"
736	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,
737	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
738	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	957	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
743	This functionality might change in future versions.	962	This functionality might change in future versions.
744		963
745	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	964	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
746	could start your program like this:	965	could start your program like this:
747		966
748	PERL_ANYEVENT_MODEL=Perl perl ...	967	PERL_ANYEVENT_MODEL=Perl perl ...
749		968
750	"PERL_ANYEVENT_PROTOCOLS"	969	"PERL_ANYEVENT_PROTOCOLS"
751	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	970	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
752	preferences for IPv4 or IPv6. The default is unspecified (and might	971	preferences for IPv4 or IPv6. The default is unspecified (and might
753	change, or be the result of auto probing).	972	change, or be the result of auto probing).
…		…
757	mentioned will be used, and preference will be given to protocols	976	mentioned will be used, and preference will be given to protocols
758	mentioned earlier in the list.	977	mentioned earlier in the list.
759		978
760	This variable can effectively be used for denial-of-service attacks	979	This variable can effectively be used for denial-of-service attacks
761	against local programs (e.g. when setuid), although the impact is	980	against local programs (e.g. when setuid), although the impact is
762	likely small, as the program has to handle connection errors	981	likely small, as the program has to handle conenction and other
763	already-	982	failures anyways.
764		983
765	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	984	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
766	IPv6, but support both and try to use both.	985	IPv6, but support both and try to use both.
767	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	986	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
768	resolve or contact IPv6 addresses.	987	resolve or contact IPv6 addresses.
…		…
775	but some (broken) firewalls drop such DNS packets, which is why it	994	but some (broken) firewalls drop such DNS packets, which is why it
776	is off by default.	995	is off by default.
777		996
778	Setting this variable to 1 will cause AnyEvent::DNS to announce	997	Setting this variable to 1 will cause AnyEvent::DNS to announce
779	EDNS0 in its DNS requests.	998	EDNS0 in its DNS requests.
		999
		1000	"PERL_ANYEVENT_MAX_FORKS"
		1001	The maximum number of child processes that
		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.
780		1046
781	EXAMPLE PROGRAM	1047	EXAMPLE PROGRAM
782	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
783	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
784	quit the program when the user enters quit:	1050	quit the program when the user enters quit:
…		…
971	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
972	single watcher.	1238	single watcher.
973		1239
974	Results	1240	Results
975	name watchers bytes create invoke destroy comment	1241	name watchers bytes create invoke destroy comment
976	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
977	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
978	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
979	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
980	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
981	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
982	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
983	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
984	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
985	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
986		1254
987	Discussion	1255	Discussion
988	The benchmark does not measure scalability of the event loop very	1256	The benchmark does not measure scalability of the event loop very
989	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)
990	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
…		…
1015	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
1016	benchmark.	1284	benchmark.
1017		1285
1018	The "Event" module has a relatively high setup and callback invocation	1286	The "Event" module has a relatively high setup and callback invocation
1019	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.
1020		1291
1021	"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
1022	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".
1023	However, Glib scales extremely badly, doubling the number of watchers	1294	However, Glib scales extremely badly, doubling the number of watchers
1024	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
…		…
1095	single "request", that is, reading the token from the pipe and	1366	single "request", that is, reading the token from the pipe and
1096	forwarding it to another server. This includes deleting the old timeout	1367	forwarding it to another server. This includes deleting the old timeout
1097	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.
1098		1369
1099	Results	1370	Results
1100	name sockets create request	1371	name sockets create request
1101	EV 20000 69.01 11.16	1372	EV 20000 69.01 11.16
1102	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
1103	Event 20000 212.62 257.32	1376	Event 20000 212.62 257.32
1104	Glib 20000 651.16 1896.30	1377	Glib 20000 651.16 1896.30
1105	POE 20000 349.67 12317.24 uses POE::Loop::Event	1378	POE 20000 349.67 12317.24 uses POE::Loop::Event
1106		1379
1107	Discussion	1380	Discussion
1108	This benchmark does measure scalability and overall performance of the	1381	This benchmark does measure scalability and overall performance of the
1109	particular event loop.	1382	particular event loop.
1110		1383
1111	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
1112	time is relatively high, though.	1385	time is relatively high, though.
1113		1386
1114	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
1115	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.
1116		1392
1117	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
1118	will understand why). Callback invocation also has a high overhead	1394	will understand why). Callback invocation also has a high overhead
1119	compared to the "$_->() for .."-style loop that the Perl event loop	1395	compared to the "$_->() for .."-style loop that the Perl event loop
1120	uses. Event uses select or poll in basically all documented	1396	uses. Event uses select or poll in basically all documented
…		…
1171		1447
1172	Summary	1448	Summary
1173	* 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,
1174	as the management overhead dominates.	1450	as the management overhead dominates.
1175		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
1176	FORK	1536	FORK
1177	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
1178	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.
1179	Only EV is fully fork-aware.	1539	Only EV is fully fork-aware.
1180		1540
…		…
1190	model than specified in the variable.	1550	model than specified in the variable.
1191		1551
1192	You can make AnyEvent completely ignore this variable by deleting it	1552	You can make AnyEvent completely ignore this variable by deleting it
1193	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:
1194		1554
1195	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1555	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1196		1556
1197	use AnyEvent;	1557	use AnyEvent;
1198		1558
1199	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1559	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1200	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
1201	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.
		1567
		1568	BUGS
		1569	Perl 5.8 has numerous memleaks that sometimes hit this module and are
		1570	hard to work around. If you suffer from memleaks, first upgrade to Perl
		1571	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
		1572	annoying memleaks, such as leaking on "map" and "grep" but it is usually
		1573	not as pronounced).
1202		1574
1203	SEE ALSO	1575	SEE ALSO
1204	Utility functions: AnyEvent::Util.	1576	Utility functions: AnyEvent::Util.
1205		1577
1206	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1578	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
…		…
1218	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1590	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1219		1591
1220	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1592	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.
1221		1593
1222	AUTHOR	1594	AUTHOR
1223	Marc Lehmann <schmorp@schmorp.de>	1595	Marc Lehmann <schmorp@schmorp.de>
1224	http://home.schmorp.de/	1596	http://home.schmorp.de/
1225		1597

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Comparing AnyEvent/README (file contents): Revision 1.23 by root, Mon May 26 06:04:38 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 1.23 by root, Mon May 26 06:04:38 2008 UTC vs.
Revision 1.42 by root, Mon Jun 29 21:00:32 2009 UTC