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Revision 1.22 by root, Sat May 24 17:58:33 2008 UTC vs.
Revision 1.41 by root, Fri Jun 26 06:33:17 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).	468	as if it were a callback, read about the caveats in the description for
		469	the "->send" method).
309		470
310	Condition variables are similar to callbacks, except that you can	471	Condition variables are similar to callbacks, except that you can
311	optionally wait for them. They can also be called merge points - points	472	optionally wait for them. They can also be called merge points - points
312	in time where multiple outstanding events have been processed. And yet	473	in time where multiple outstanding events have been processed. And yet
313	another way to call them is transactions - each condition variable can	474	another way to call them is transactions - each condition variable can
…		…
364		525
365	my $done = AnyEvent->condvar;	526	my $done = AnyEvent->condvar;
366	my $delay = AnyEvent->timer (after => 5, cb => $done);	527	my $delay = AnyEvent->timer (after => 5, cb => $done);
367	$done->recv;	528	$done->recv;
368		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
369	METHODS FOR PRODUCERS	547	METHODS FOR PRODUCERS
370	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
371	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
372	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
373	uncommon for the consumer to create it as well.	551	uncommon for the consumer to create it as well.
…		…
383	Any arguments passed to the "send" call will be returned by all	561	Any arguments passed to the "send" call will be returned by all
384	future "->recv" calls.	562	future "->recv" calls.
385		563
386	Condition variables are overloaded so one can call them directly (as	564	Condition variables are overloaded so one can call them directly (as
387	a code reference). Calling them directly is the same as calling	565	a code reference). Calling them directly is the same as calling
388	"send".	566	"send". Note, however, that many C-based event loops do not handle
		567	overloading, so as tempting as it may be, passing a condition
		568	variable instead of a callback does not work. Both the pure perl and
		569	EV loops support overloading, however, as well as all functions that
		570	use perl to invoke a callback (as in AnyEvent::Socket and
		571	AnyEvent::DNS for example).
389		572
390	$cv->croak ($error)	573	$cv->croak ($error)
391	Similar to send, but causes all call's to "->recv" to invoke	574	Similar to send, but causes all call's to "->recv" to invoke
392	"Carp::croak" with the given error message/object/scalar.	575	"Carp::croak" with the given error message/object/scalar.
393		576
…		…
488		671
489	$bool = $cv->ready	672	$bool = $cv->ready
490	Returns true when the condition is "true", i.e. whether "send" or	673	Returns true when the condition is "true", i.e. whether "send" or
491	"croak" have been called.	674	"croak" have been called.
492		675
493	$cb = $cv->cb ([new callback])	676	$cb = $cv->cb ($cb->($cv))
494	This is a mutator function that returns the callback set and	677	This is a mutator function that returns the callback set and
495	optionally replaces it before doing so.	678	optionally replaces it before doing so.
496		679
497	The callback will be called when the condition becomes "true", i.e.	680	The callback will be called when the condition becomes "true", i.e.
498	when "send" or "croak" are called. Calling "recv" inside the	681	when "send" or "croak" are called, with the only argument being the
		682	condition variable itself. Calling "recv" inside the callback or at
499	callback or at any later time is guaranteed not to block.	683	any later time is guaranteed not to block.
500		684
501	GLOBAL VARIABLES AND FUNCTIONS	685	GLOBAL VARIABLES AND FUNCTIONS
502	$AnyEvent::MODEL	686	$AnyEvent::MODEL
503	Contains "undef" until the first watcher is being created. Then it	687	Contains "undef" until the first watcher is being created. Then it
504	contains the event model that is being used, which is the name of	688	contains the event model that is being used, which is the name of
…		…
515	AnyEvent::Impl::Tk based on Tk, very bad choice.	699	AnyEvent::Impl::Tk based on Tk, very bad choice.
516	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	700	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
517	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	701	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
518	AnyEvent::Impl::POE based on POE, not generic enough for full support.	702	AnyEvent::Impl::POE based on POE, not generic enough for full support.
519		703
		704	# warning, support for IO::Async is only partial, as it is too broken
		705	# and limited toe ven support the AnyEvent API. See AnyEvent::Impl::Async.
		706	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed (see its docs).
		707
520	There is no support for WxWidgets, as WxWidgets has no support for	708	There is no support for WxWidgets, as WxWidgets has no support for
521	watching file handles. However, you can use WxWidgets through the	709	watching file handles. However, you can use WxWidgets through the
522	POE Adaptor, as POE has a Wx backend that simply polls 20 times per	710	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
523	second, which was considered to be too horrible to even consider for	711	second, which was considered to be too horrible to even consider for
524	AnyEvent. Likewise, other POE backends can be used by AnyEvent by	712	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
…		…
578	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	766	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
579	do anything special (it does not need to be event-based) and let	767	do anything special (it does not need to be event-based) and let
580	AnyEvent decide which implementation to chose if some module relies on	768	AnyEvent decide which implementation to chose if some module relies on
581	it.	769	it.
582		770
583	If the main program relies on a specific event model. For example, in	771	If the main program relies on a specific event model - for example, in
584	Gtk2 programs you have to rely on the Glib module. You should load the	772	Gtk2 programs you have to rely on the Glib module - you should load the
585	event module before loading AnyEvent or any module that uses it:	773	event module before loading AnyEvent or any module that uses it:
586	generally speaking, you should load it as early as possible. The reason	774	generally speaking, you should load it as early as possible. The reason
587	is that modules might create watchers when they are loaded, and AnyEvent	775	is that modules might create watchers when they are loaded, and AnyEvent
588	will decide on the event model to use as soon as it creates watchers,	776	will decide on the event model to use as soon as it creates watchers,
589	and it might chose the wrong one unless you load the correct one	777	and it might chose the wrong one unless you load the correct one
590	yourself.	778	yourself.
591		779
592	You can chose to use a rather inefficient pure-perl implementation by	780	You can chose to use a pure-perl implementation by loading the
593	loading the "AnyEvent::Impl::Perl" module, which gives you similar	781	"AnyEvent::Impl::Perl" module, which gives you similar behaviour
594	behaviour everywhere, but letting AnyEvent chose is generally better.	782	everywhere, but letting AnyEvent chose the model is generally better.
		783
		784	MAINLOOP EMULATION
		785	Sometimes (often for short test scripts, or even standalone programs who
		786	only want to use AnyEvent), you do not want to run a specific event
		787	loop.
		788
		789	In that case, you can use a condition variable like this:
		790
		791	AnyEvent->condvar->recv;
		792
		793	This has the effect of entering the event loop and looping forever.
		794
		795	Note that usually your program has some exit condition, in which case it
		796	is better to use the "traditional" approach of storing a condition
		797	variable somewhere, waiting for it, and sending it when the program
		798	should exit cleanly.
595		799
596	OTHER MODULES	800	OTHER MODULES
597	The following is a non-exhaustive list of additional modules that use	801	The following is a non-exhaustive list of additional modules that use
598	AnyEvent and can therefore be mixed easily with other AnyEvent modules	802	AnyEvent and can therefore be mixed easily with other AnyEvent modules
599	in the same program. Some of the modules come with AnyEvent, some are	803	in the same program. Some of the modules come with AnyEvent, some are
…		…
602	AnyEvent::Util	806	AnyEvent::Util
603	Contains various utility functions that replace often-used but	807	Contains various utility functions that replace often-used but
604	blocking functions such as "inet_aton" by event-/callback-based	808	blocking functions such as "inet_aton" by event-/callback-based
605	versions.	809	versions.
606		810
607	AnyEvent::Handle
608	Provide read and write buffers and manages watchers for reads and
609	writes.
610
611	AnyEvent::Socket	811	AnyEvent::Socket
612	Provides various utility functions for (internet protocol) sockets,	812	Provides various utility functions for (internet protocol) sockets,
613	addresses and name resolution. Also functions to create non-blocking	813	addresses and name resolution. Also functions to create non-blocking
614	tcp connections or tcp servers, with IPv6 and SRV record support and	814	tcp connections or tcp servers, with IPv6 and SRV record support and
615	more.	815	more.
616		816
		817	AnyEvent::Handle
		818	Provide read and write buffers, manages watchers for reads and
		819	writes, supports raw and formatted I/O, I/O queued and fully
		820	transparent and non-blocking SSL/TLS.
		821
		822	AnyEvent::DNS
		823	Provides rich asynchronous DNS resolver capabilities.
		824
		825	AnyEvent::HTTP
		826	A simple-to-use HTTP library that is capable of making a lot of
		827	concurrent HTTP requests.
		828
617	AnyEvent::HTTPD	829	AnyEvent::HTTPD
618	Provides a simple web application server framework.	830	Provides a simple web application server framework.
619		831
620	AnyEvent::DNS
621	Provides rich asynchronous DNS resolver capabilities.
622
623	AnyEvent::FastPing	832	AnyEvent::FastPing
624	The fastest ping in the west.	833	The fastest ping in the west.
625		834
		835	AnyEvent::DBI
		836	Executes DBI requests asynchronously in a proxy process.
		837
		838	AnyEvent::AIO
		839	Truly asynchronous I/O, should be in the toolbox of every event
		840	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		841	together.
		842
		843	AnyEvent::BDB
		844	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
		845	fuses BDB and AnyEvent together.
		846
		847	AnyEvent::GPSD
		848	A non-blocking interface to gpsd, a daemon delivering GPS
		849	information.
		850
		851	AnyEvent::IGS
		852	A non-blocking interface to the Internet Go Server protocol (used by
		853	App::IGS).
		854
		855	AnyEvent::IRC
		856	AnyEvent based IRC client module family (replacing the older
626	Net::IRC3	857	Net::IRC3).
627	AnyEvent based IRC client module family.
628		858
629	Net::XMPP2	859	Net::XMPP2
630	AnyEvent based XMPP (Jabber protocol) module family.	860	AnyEvent based XMPP (Jabber protocol) module family.
631		861
632	Net::FCP	862	Net::FCP
…		…
637	High level API for event-based execution flow control.	867	High level API for event-based execution flow control.
638		868
639	Coro	869	Coro
640	Has special support for AnyEvent via Coro::AnyEvent.	870	Has special support for AnyEvent via Coro::AnyEvent.
641		871
642	AnyEvent::AIO, IO::AIO
643	Truly asynchronous I/O, should be in the toolbox of every event
644	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
645	together.
646
647	AnyEvent::BDB, BDB
648	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
649	fuses IO::AIO and AnyEvent together.
650
651	IO::Lambda	872	IO::Lambda
652	The lambda approach to I/O - don't ask, look there. Can use	873	The lambda approach to I/O - don't ask, look there. Can use
653	AnyEvent.	874	AnyEvent.
654		875
655	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	876	ERROR AND EXCEPTION HANDLING
656	This is an advanced topic that you do not normally need to use AnyEvent	877	In general, AnyEvent does not do any error handling - it relies on the
657	in a module. This section is only of use to event loop authors who want	878	caller to do that if required. The AnyEvent::Strict module (see also the
658	to provide AnyEvent compatibility.	879	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
		880	checking of all AnyEvent methods, however, which is highly useful during
		881	development.
659		882
660	If you need to support another event library which isn't directly	883	As for exception handling (i.e. runtime errors and exceptions thrown
661	supported by AnyEvent, you can supply your own interface to it by	884	while executing a callback), this is not only highly event-loop
662	pushing, before the first watcher gets created, the package name of the	885	specific, but also not in any way wrapped by this module, as this is the
663	event module and the package name of the interface to use onto	886	job of the main program.
664	@AnyEvent::REGISTRY. You can do that before and even without loading
665	AnyEvent, so it is reasonably cheap.
666		887
667	Example:	888	The pure perl event loop simply re-throws the exception (usually within
668		889	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
669	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	890	Glib uses "install_exception_handler" and so on.
670
671	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
672	package/class when it finds the "urxvt" package/module is already
673	loaded.
674
675	When AnyEvent is loaded and asked to find a suitable event model, it
676	will first check for the presence of urxvt by trying to "use" the
677	"urxvt::anyevent" module.
678
679	The class should provide implementations for all watcher types. See
680	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
681	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
682	the sources.
683
684	If you don't provide "signal" and "child" watchers than AnyEvent will
685	provide suitable (hopefully) replacements.
686
687	The above example isn't fictitious, the rxvt-unicode (a.k.a. urxvt)
688	terminal emulator uses the above line as-is. An interface isn't included
689	in AnyEvent because it doesn't make sense outside the embedded
690	interpreter inside rxvt-unicode, and it is updated and maintained as
691	part of the rxvt-unicode distribution.
692
693	rxvt-unicode also cheats a bit by not providing blocking access to
694	condition variables: code blocking while waiting for a condition will
695	"die". This still works with most modules/usages, and blocking calls
696	must not be done in an interactive application, so it makes sense.
697		891
698	ENVIRONMENT VARIABLES	892	ENVIRONMENT VARIABLES
699	The following environment variables are used by this module:	893	The following environment variables are used by this module or its
		894	submodules.
		895
		896	Note that AnyEvent will remove all environment variables starting with
		897	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		898	enabled.
700		899
701	"PERL_ANYEVENT_VERBOSE"	900	"PERL_ANYEVENT_VERBOSE"
702	By default, AnyEvent will be completely silent except in fatal	901	By default, AnyEvent will be completely silent except in fatal
703	conditions. You can set this environment variable to make AnyEvent	902	conditions. You can set this environment variable to make AnyEvent
704	more talkative.	903	more talkative.
…		…
707	conditions, such as not being able to load the event model specified	906	conditions, such as not being able to load the event model specified
708	by "PERL_ANYEVENT_MODEL".	907	by "PERL_ANYEVENT_MODEL".
709		908
710	When set to 2 or higher, cause AnyEvent to report to STDERR which	909	When set to 2 or higher, cause AnyEvent to report to STDERR which
711	event model it chooses.	910	event model it chooses.
		911
		912	"PERL_ANYEVENT_STRICT"
		913	AnyEvent does not do much argument checking by default, as thorough
		914	argument checking is very costly. Setting this variable to a true
		915	value will cause AnyEvent to load "AnyEvent::Strict" and then to
		916	thoroughly check the arguments passed to most method calls. If it
		917	finds any problems, it will croak.
		918
		919	In other words, enables "strict" mode.
		920
		921	Unlike "use strict", it is definitely recommended to keep it off in
		922	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
		923	while developing programs can be very useful, however.
712		924
713	"PERL_ANYEVENT_MODEL"	925	"PERL_ANYEVENT_MODEL"
714	This can be used to specify the event model to be used by AnyEvent,	926	This can be used to specify the event model to be used by AnyEvent,
715	before auto detection and -probing kicks in. It must be a string	927	before auto detection and -probing kicks in. It must be a string
716	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	928	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
721	This functionality might change in future versions.	933	This functionality might change in future versions.
722		934
723	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	935	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
724	could start your program like this:	936	could start your program like this:
725		937
726	PERL_ANYEVENT_MODEL=Perl perl ...	938	PERL_ANYEVENT_MODEL=Perl perl ...
727		939
728	"PERL_ANYEVENT_PROTOCOLS"	940	"PERL_ANYEVENT_PROTOCOLS"
729	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	941	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
730	preferences for IPv4 or IPv6. The default is unspecified (and might	942	preferences for IPv4 or IPv6. The default is unspecified (and might
731	change, or be the result of auto probing).	943	change, or be the result of auto probing).
…		…
735	mentioned will be used, and preference will be given to protocols	947	mentioned will be used, and preference will be given to protocols
736	mentioned earlier in the list.	948	mentioned earlier in the list.
737		949
738	This variable can effectively be used for denial-of-service attacks	950	This variable can effectively be used for denial-of-service attacks
739	against local programs (e.g. when setuid), although the impact is	951	against local programs (e.g. when setuid), although the impact is
740	likely small, as the program has to handle connection errors	952	likely small, as the program has to handle conenction and other
741	already-	953	failures anyways.
742		954
743	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	955	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
744	IPv6, but support both and try to use both.	956	IPv6, but support both and try to use both.
745	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	957	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
746	resolve or contact IPv6 addresses.	958	resolve or contact IPv6 addresses.
…		…
753	but some (broken) firewalls drop such DNS packets, which is why it	965	but some (broken) firewalls drop such DNS packets, which is why it
754	is off by default.	966	is off by default.
755		967
756	Setting this variable to 1 will cause AnyEvent::DNS to announce	968	Setting this variable to 1 will cause AnyEvent::DNS to announce
757	EDNS0 in its DNS requests.	969	EDNS0 in its DNS requests.
		970
		971	"PERL_ANYEVENT_MAX_FORKS"
		972	The maximum number of child processes that
		973	"AnyEvent::Util::fork_call" will create in parallel.
		974
		975	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		976	This is an advanced topic that you do not normally need to use AnyEvent
		977	in a module. This section is only of use to event loop authors who want
		978	to provide AnyEvent compatibility.
		979
		980	If you need to support another event library which isn't directly
		981	supported by AnyEvent, you can supply your own interface to it by
		982	pushing, before the first watcher gets created, the package name of the
		983	event module and the package name of the interface to use onto
		984	@AnyEvent::REGISTRY. You can do that before and even without loading
		985	AnyEvent, so it is reasonably cheap.
		986
		987	Example:
		988
		989	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
		990
		991	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
		992	package/class when it finds the "urxvt" package/module is already
		993	loaded.
		994
		995	When AnyEvent is loaded and asked to find a suitable event model, it
		996	will first check for the presence of urxvt by trying to "use" the
		997	"urxvt::anyevent" module.
		998
		999	The class should provide implementations for all watcher types. See
		1000	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
		1001	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
		1002	the sources.
		1003
		1004	If you don't provide "signal" and "child" watchers than AnyEvent will
		1005	provide suitable (hopefully) replacements.
		1006
		1007	The above example isn't fictitious, the rxvt-unicode (a.k.a. urxvt)
		1008	terminal emulator uses the above line as-is. An interface isn't included
		1009	in AnyEvent because it doesn't make sense outside the embedded
		1010	interpreter inside rxvt-unicode, and it is updated and maintained as
		1011	part of the rxvt-unicode distribution.
		1012
		1013	rxvt-unicode also cheats a bit by not providing blocking access to
		1014	condition variables: code blocking while waiting for a condition will
		1015	"die". This still works with most modules/usages, and blocking calls
		1016	must not be done in an interactive application, so it makes sense.
758		1017
759	EXAMPLE PROGRAM	1018	EXAMPLE PROGRAM
760	The following program uses an I/O watcher to read data from STDIN, a	1019	The following program uses an I/O watcher to read data from STDIN, a
761	timer to display a message once per second, and a condition variable to	1020	timer to display a message once per second, and a condition variable to
762	quit the program when the user enters quit:	1021	quit the program when the user enters quit:
…		…
949	destroy is the time, in microseconds, that it takes to destroy a	1208	destroy is the time, in microseconds, that it takes to destroy a
950	single watcher.	1209	single watcher.
951		1210
952	Results	1211	Results
953	name watchers bytes create invoke destroy comment	1212	name watchers bytes create invoke destroy comment
954	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1213	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
955	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1214	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
956	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1215	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
957	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1216	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
958	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1217	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
959	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1218	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1219	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1220	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
960	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1221	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
961	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1222	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
962	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1223	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
963	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1224	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
964		1225
965	Discussion	1226	Discussion
966	The benchmark does not measure scalability of the event loop very	1227	The benchmark does not measure scalability of the event loop very
967	well. For example, a select-based event loop (such as the pure perl one)	1228	well. For example, a select-based event loop (such as the pure perl one)
968	can never compete with an event loop that uses epoll when the number of	1229	can never compete with an event loop that uses epoll when the number of
…		…
993	few of them active), of course, but this was not subject of this	1254	few of them active), of course, but this was not subject of this
994	benchmark.	1255	benchmark.
995		1256
996	The "Event" module has a relatively high setup and callback invocation	1257	The "Event" module has a relatively high setup and callback invocation
997	cost, but overall scores in on the third place.	1258	cost, but overall scores in on the third place.
		1259
		1260	"IO::Async" performs admirably well, about on par with "Event", even
		1261	when using its pure perl backend.
998		1262
999	"Glib"'s memory usage is quite a bit higher, but it features a faster	1263	"Glib"'s memory usage is quite a bit higher, but it features a faster
1000	callback invocation and overall ends up in the same class as "Event".	1264	callback invocation and overall ends up in the same class as "Event".
1001	However, Glib scales extremely badly, doubling the number of watchers	1265	However, Glib scales extremely badly, doubling the number of watchers
1002	increases the processing time by more than a factor of four, making it	1266	increases the processing time by more than a factor of four, making it
…		…
1073	single "request", that is, reading the token from the pipe and	1337	single "request", that is, reading the token from the pipe and
1074	forwarding it to another server. This includes deleting the old timeout	1338	forwarding it to another server. This includes deleting the old timeout
1075	and creating a new one that moves the timeout into the future.	1339	and creating a new one that moves the timeout into the future.
1076		1340
1077	Results	1341	Results
1078	name sockets create request	1342	name sockets create request
1079	EV 20000 69.01 11.16	1343	EV 20000 69.01 11.16
1080	Perl 20000 73.32 35.87	1344	Perl 20000 73.32 35.87
		1345	IOAsync 20000 157.00 98.14 epoll
		1346	IOAsync 20000 159.31 616.06 poll
1081	Event 20000 212.62 257.32	1347	Event 20000 212.62 257.32
1082	Glib 20000 651.16 1896.30	1348	Glib 20000 651.16 1896.30
1083	POE 20000 349.67 12317.24 uses POE::Loop::Event	1349	POE 20000 349.67 12317.24 uses POE::Loop::Event
1084		1350
1085	Discussion	1351	Discussion
1086	This benchmark does measure scalability and overall performance of the	1352	This benchmark does measure scalability and overall performance of the
1087	particular event loop.	1353	particular event loop.
1088		1354
1089	EV is again fastest. Since it is using epoll on my system, the setup	1355	EV is again fastest. Since it is using epoll on my system, the setup
1090	time is relatively high, though.	1356	time is relatively high, though.
1091		1357
1092	Perl surprisingly comes second. It is much faster than the C-based event	1358	Perl surprisingly comes second. It is much faster than the C-based event
1093	loops Event and Glib.	1359	loops Event and Glib.
		1360
		1361	IO::Async performs very well when using its epoll backend, and still
		1362	quite good compared to Glib when using its pure perl backend.
1094		1363
1095	Event suffers from high setup time as well (look at its code and you	1364	Event suffers from high setup time as well (look at its code and you
1096	will understand why). Callback invocation also has a high overhead	1365	will understand why). Callback invocation also has a high overhead
1097	compared to the "$_->() for .."-style loop that the Perl event loop	1366	compared to the "$_->() for .."-style loop that the Perl event loop
1098	uses. Event uses select or poll in basically all documented	1367	uses. Event uses select or poll in basically all documented
…		…
1149		1418
1150	Summary	1419	Summary
1151	* C-based event loops perform very well with small number of watchers,	1420	* C-based event loops perform very well with small number of watchers,
1152	as the management overhead dominates.	1421	as the management overhead dominates.
1153		1422
		1423	THE IO::Lambda BENCHMARK
		1424	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1425	could be misinterpreted to make AnyEvent look bad. In fact, the
		1426	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1427	better (which shouldn't come as a surprise to anybody). As such, the
		1428	benchmark is fine, and mostly shows that the AnyEvent backend from
		1429	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1430	without the extra baggage? To explore this, I wrote the equivalent
		1431	benchmark for AnyEvent.
		1432
		1433	The benchmark itself creates an echo-server, and then, for 500 times,
		1434	connects to the echo server, sends a line, waits for the reply, and then
		1435	creates the next connection. This is a rather bad benchmark, as it
		1436	doesn't test the efficiency of the framework or much non-blocking I/O,
		1437	but it is a benchmark nevertheless.
		1438
		1439	name runtime
		1440	Lambda/select 0.330 sec
		1441	+ optimized 0.122 sec
		1442	Lambda/AnyEvent 0.327 sec
		1443	+ optimized 0.138 sec
		1444	Raw sockets/select 0.077 sec
		1445	POE/select, components 0.662 sec
		1446	POE/select, raw sockets 0.226 sec
		1447	POE/select, optimized 0.404 sec
		1448
		1449	AnyEvent/select/nb 0.085 sec
		1450	AnyEvent/EV/nb 0.068 sec
		1451	+state machine 0.134 sec
		1452
		1453	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1454	benchmarks actually make blocking connects and use 100% blocking I/O,
		1455	defeating the purpose of an event-based solution. All of the newly
		1456	written AnyEvent benchmarks use 100% non-blocking connects (using
		1457	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1458	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1459	connects generally require a lot more bookkeeping and event handling
		1460	than blocking connects (which involve a single syscall only).
		1461
		1462	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1463	offers similar expressive power as POE and IO::Lambda, using
		1464	conventional Perl syntax. This means that both the echo server and the
		1465	client are 100% non-blocking, further placing it at a disadvantage.
		1466
		1467	As you can see, the AnyEvent + EV combination even beats the
		1468	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1469	backend easily beats IO::Lambda and POE.
		1470
		1471	And even the 100% non-blocking version written using the high-level (and
		1472	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a
		1473	large margin, even though it does all of DNS, tcp-connect and socket I/O
		1474	in a non-blocking way.
		1475
		1476	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1477	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1478	part of the IO::lambda distribution and were used without any changes.
		1479
		1480	SIGNALS
		1481	AnyEvent currently installs handlers for these signals:
		1482
		1483	SIGCHLD
		1484	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
		1485	emulation for event loops that do not support them natively. Also,
		1486	some event loops install a similar handler.
		1487
		1488	If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent
		1489	will reset it to default, to avoid losing child exit statuses.
		1490
		1491	SIGPIPE
		1492	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
		1493	"undef" when AnyEvent gets loaded.
		1494
		1495	The rationale for this is that AnyEvent users usually do not really
		1496	depend on SIGPIPE delivery (which is purely an optimisation for
		1497	shell use, or badly-written programs), but "SIGPIPE" can cause
		1498	spurious and rare program exits as a lot of people do not expect
		1499	"SIGPIPE" when writing to some random socket.
		1500
		1501	The rationale for installing a no-op handler as opposed to ignoring
		1502	it is that this way, the handler will be restored to defaults on
		1503	exec.
		1504
		1505	Feel free to install your own handler, or reset it to defaults.
		1506
1154	FORK	1507	FORK
1155	Most event libraries are not fork-safe. The ones who are usually are	1508	Most event libraries are not fork-safe. The ones who are usually are
1156	because they rely on inefficient but fork-safe "select" or "poll" calls.	1509	because they rely on inefficient but fork-safe "select" or "poll" calls.
1157	Only EV is fully fork-aware.	1510	Only EV is fully fork-aware.
1158		1511
…		…
1168	model than specified in the variable.	1521	model than specified in the variable.
1169		1522
1170	You can make AnyEvent completely ignore this variable by deleting it	1523	You can make AnyEvent completely ignore this variable by deleting it
1171	before the first watcher gets created, e.g. with a "BEGIN" block:	1524	before the first watcher gets created, e.g. with a "BEGIN" block:
1172		1525
1173	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1526	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1174		1527
1175	use AnyEvent;	1528	use AnyEvent;
1176		1529
1177	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1530	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1178	be used to probe what backend is used and gain other information (which	1531	be used to probe what backend is used and gain other information (which
1179	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	1532	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
		1533	and $ENV{PERL_ANYEVENT_STRICT}.
		1534
		1535	Note that AnyEvent will remove all environment variables starting with
		1536	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1537	enabled.
		1538
		1539	BUGS
		1540	Perl 5.8 has numerous memleaks that sometimes hit this module and are
		1541	hard to work around. If you suffer from memleaks, first upgrade to Perl
		1542	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
		1543	annoying memleaks, such as leaking on "map" and "grep" but it is usually
		1544	not as pronounced).
1180		1545
1181	SEE ALSO	1546	SEE ALSO
1182	Utility functions: AnyEvent::Util.	1547	Utility functions: AnyEvent::Util.
1183		1548
1184	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1549	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
…		…
1196	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1561	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1197		1562
1198	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1563	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.
1199		1564
1200	AUTHOR	1565	AUTHOR
1201	Marc Lehmann <schmorp@schmorp.de>	1566	Marc Lehmann <schmorp@schmorp.de>
1202	http://home.schmorp.de/	1567	http://home.schmorp.de/
1203		1568

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Comparing AnyEvent/README (file contents): Revision 1.22 by root, Sat May 24 17:58:33 2008 UTC vs. Revision 1.41 by root, Fri Jun 26 06:33:17 2009 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.22 by root, Sat May 24 17:58:33 2008 UTC vs.
Revision 1.41 by root, Fri Jun 26 06:33:17 2009 UTC