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Revision 1.20 by root, Sat May 10 22:30:28 2008 UTC vs.
Revision 1.40 by root, Tue Jun 23 23:37:32 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 enourmous amount of code and strict rules you have	82	modules, you get an enormous amount of code and strict rules you have to
61	to 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 filehandle to watch, etc.	137	the callback to call, the file handle to watch, etc.
110		138
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
234	Multiple signal occurances can be clumped together into one callback	349	Multiple signal occurrences can be clumped together into one callback
235	invocation, and callback invocation will be synchronous. synchronous	350	invocation, and callback invocation will be synchronous. Synchronous
236	means that it might take a while until the signal gets handled by the	351	means that it might take a while until the signal gets handled by the
237	process, but it is guarenteed not to interrupt any other callbacks.	352	process, but it is guaranteed not to interrupt any other callbacks.
238		353
239	The main advantage of using these watchers is that you can share a	354	The main advantage of using these watchers is that you can share a
240	signal between multiple watchers.	355	signal between multiple watchers.
241		356
242	This watcher might use %SIG, so programs overwriting those signals	357	This watcher might use %SIG, so programs overwriting those signals
…		…
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
…		…
269	an AnyEvent program, you have to create at least one watcher before	391	an AnyEvent program, you have to create at least one watcher before
270	you "fork" the child (alternatively, you can call "AnyEvent::detect").	392	you "fork" the child (alternatively, you can call "AnyEvent::detect").
271		393
272	Example: fork a process and wait for it	394	Example: fork a process and wait for it
273		395
274	my $done = AnyEvent->condvar;	396	my $done = AnyEvent->condvar;
275		397
276	my $pid = fork or exit 5;	398	my $pid = fork or exit 5;
277		399
278	my $w = AnyEvent->child (	400	my $w = AnyEvent->child (
279	pid => $pid,	401	pid => $pid,
280	cb => sub {	402	cb => sub {
281	my ($pid, $status) = @_;	403	my ($pid, $status) = @_;
282	warn "pid $pid exited with status $status";	404	warn "pid $pid exited with status $status";
283	$done->send;	405	$done->send;
284	},	406	},
285	);	407	);
286		408
287	# do something else, then wait for process exit	409	# do something else, then wait for process exit
288	$done->recv;	410	$done->recv;
		411
		412	IDLE WATCHERS
		413	Sometimes there is a need to do something, but it is not so important to
		414	do it instantly, but only when there is nothing better to do. This
		415	"nothing better to do" is usually defined to be "no other events need
		416	attention by the event loop".
		417
		418	Idle watchers ideally get invoked when the event loop has nothing better
		419	to do, just before it would block the process to wait for new events.
		420	Instead of blocking, the idle watcher is invoked.
		421
		422	Most event loops unfortunately do not really support idle watchers (only
		423	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		424	will simply call the callback "from time to time".
		425
		426	Example: read lines from STDIN, but only process them when the program
		427	is otherwise idle:
		428
		429	my @lines; # read data
		430	my $idle_w;
		431	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		432	push @lines, scalar <STDIN>;
		433
		434	# start an idle watcher, if not already done
		435	$idle_w \|\|= AnyEvent->idle (cb => sub {
		436	# handle only one line, when there are lines left
		437	if (my $line = shift @lines) {
		438	print "handled when idle: $line";
		439	} else {
		440	# otherwise disable the idle watcher again
		441	undef $idle_w;
		442	}
		443	});
		444	});
289		445
290	CONDITION VARIABLES	446	CONDITION VARIABLES
291	If you are familiar with some event loops you will know that all of them	447	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	448	require you to run some blocking "loop", "run" or similar function that
293	will actively watch for new events and call your callbacks.	449	will actively watch for new events and call your callbacks.
…		…
298	The instrument to do that is called a "condition variable", so called	454	The instrument to do that is called a "condition variable", so called
299	because they represent a condition that must become true.	455	because they represent a condition that must become true.
300		456
301	Condition variables can be created by calling the "AnyEvent->condvar"	457	Condition variables can be created by calling the "AnyEvent->condvar"
302	method, usually without arguments. The only argument pair allowed is	458	method, usually without arguments. The only argument pair allowed is
		459
303	"cb", which specifies a callback to be called when the condition	460	"cb", which specifies a callback to be called when the condition
304	variable becomes true.	461	variable becomes true, with the condition variable as the first argument
		462	(but not the results).
305		463
306	After creation, the conditon variable is "false" until it becomes "true"	464	After creation, the condition variable is "false" until it becomes
		465	"true" by calling the "send" method (or calling the condition variable
		466	as if it were a callback, read about the caveats in the description for
307	by calling the "send" method.	467	the "->send" method).
308		468
309	Condition variables are similar to callbacks, except that you can	469	Condition variables are similar to callbacks, except that you can
310	optionally wait for them. They can also be called merge points - points	470	optionally wait for them. They can also be called merge points - points
311	in time where multiple outstandign events have been processed. And yet	471	in time where multiple outstanding events have been processed. And yet
312	another way to call them is transations - each condition variable can be	472	another way to call them is transactions - each condition variable can
313	used to represent a transaction, which finishes at some point and	473	be used to represent a transaction, which finishes at some point and
314	delivers a result.	474	delivers a result.
315		475
316	Condition variables are very useful to signal that something has	476	Condition variables are very useful to signal that something has
317	finished, for example, if you write a module that does asynchronous http	477	finished, for example, if you write a module that does asynchronous http
318	requests, then a condition variable would be the ideal candidate to	478	requests, then a condition variable would be the ideal candidate to
…		…
323	you can block your main program until an event occurs - for example, you	483	you can block your main program until an event occurs - for example, you
324	could "->recv" in your main program until the user clicks the Quit	484	could "->recv" in your main program until the user clicks the Quit
325	button of your app, which would "->send" the "quit" event.	485	button of your app, which would "->send" the "quit" event.
326		486
327	Note that condition variables recurse into the event loop - if you have	487	Note that condition variables recurse into the event loop - if you have
328	two pieces of code that call "->recv" in a round-robbin fashion, you	488	two pieces of code that call "->recv" in a round-robin fashion, you
329	lose. Therefore, condition variables are good to export to your caller,	489	lose. Therefore, condition variables are good to export to your caller,
330	but you should avoid making a blocking wait yourself, at least in	490	but you should avoid making a blocking wait yourself, at least in
331	callbacks, as this asks for trouble.	491	callbacks, as this asks for trouble.
332		492
333	Condition variables are represented by hash refs in perl, and the keys	493	Condition variables are represented by hash refs in perl, and the keys
…		…
338		498
339	There are two "sides" to a condition variable - the "producer side"	499	There are two "sides" to a condition variable - the "producer side"
340	which eventually calls "-> send", and the "consumer side", which waits	500	which eventually calls "-> send", and the "consumer side", which waits
341	for the send to occur.	501	for the send to occur.
342		502
343	Example:	503	Example: wait for a timer.
344		504
345	# wait till the result is ready	505	# wait till the result is ready
346	my $result_ready = AnyEvent->condvar;	506	my $result_ready = AnyEvent->condvar;
347		507
348	# do something such as adding a timer	508	# do something such as adding a timer
…		…
356		516
357	# this "blocks" (while handling events) till the callback	517	# this "blocks" (while handling events) till the callback
358	# calls send	518	# calls send
359	$result_ready->recv;	519	$result_ready->recv;
360		520
		521	Example: wait for a timer, but take advantage of the fact that condition
		522	variables are also code references.
		523
		524	my $done = AnyEvent->condvar;
		525	my $delay = AnyEvent->timer (after => 5, cb => $done);
		526	$done->recv;
		527
		528	Example: Imagine an API that returns a condvar and doesn't support
		529	callbacks. This is how you make a synchronous call, for example from the
		530	main program:
		531
		532	use AnyEvent::CouchDB;
		533
		534	...
		535
		536	my @info = $couchdb->info->recv;
		537
		538	And this is how you would just ste a callback to be called whenever the
		539	results are available:
		540
		541	$couchdb->info->cb (sub {
		542	my @info = $_[0]->recv;
		543	});
		544
361	METHODS FOR PRODUCERS	545	METHODS FOR PRODUCERS
362	These methods should only be used by the producing side, i.e. the	546	These methods should only be used by the producing side, i.e. the
363	code/module that eventually sends the signal. Note that it is also the	547	code/module that eventually sends the signal. Note that it is also the
364	producer side which creates the condvar in most cases, but it isn't	548	producer side which creates the condvar in most cases, but it isn't
365	uncommon for the consumer to create it as well.	549	uncommon for the consumer to create it as well.
…		…
372	If a callback has been set on the condition variable, it is called	556	If a callback has been set on the condition variable, it is called
373	immediately from within send.	557	immediately from within send.
374		558
375	Any arguments passed to the "send" call will be returned by all	559	Any arguments passed to the "send" call will be returned by all
376	future "->recv" calls.	560	future "->recv" calls.
		561
		562	Condition variables are overloaded so one can call them directly (as
		563	a code reference). Calling them directly is the same as calling
		564	"send". Note, however, that many C-based event loops do not handle
		565	overloading, so as tempting as it may be, passing a condition
		566	variable instead of a callback does not work. Both the pure perl and
		567	EV loops support overloading, however, as well as all functions that
		568	use perl to invoke a callback (as in AnyEvent::Socket and
		569	AnyEvent::DNS for example).
377		570
378	$cv->croak ($error)	571	$cv->croak ($error)
379	Similar to send, but causes all call's to "->recv" to invoke	572	Similar to send, but causes all call's to "->recv" to invoke
380	"Carp::croak" with the given error message/object/scalar.	573	"Carp::croak" with the given error message/object/scalar.
381		574
…		…
427	(the loop doesn't execute once).	620	(the loop doesn't execute once).
428		621
429	This is the general pattern when you "fan out" into multiple	622	This is the general pattern when you "fan out" into multiple
430	subrequests: use an outer "begin"/"end" pair to set the callback and	623	subrequests: use an outer "begin"/"end" pair to set the callback and
431	ensure "end" is called at least once, and then, for each subrequest	624	ensure "end" is called at least once, and then, for each subrequest
432	you start, call "begin" and for eahc subrequest you finish, call	625	you start, call "begin" and for each subrequest you finish, call
433	"end".	626	"end".
434		627
435	METHODS FOR CONSUMERS	628	METHODS FOR CONSUMERS
436	These methods should only be used by the consuming side, i.e. the code	629	These methods should only be used by the consuming side, i.e. the code
437	awaits the condition.	630	awaits the condition.
…		…
453	(programs might want to do that to stay interactive), so *if you are	646	(programs might want to do that to stay interactive), so *if you are
454	using this from a module, never require a blocking wait*, but let	647	using this from a module, never require a blocking wait*, but let
455	the caller decide whether the call will block or not (for example,	648	the caller decide whether the call will block or not (for example,
456	by coupling condition variables with some kind of request results	649	by coupling condition variables with some kind of request results
457	and supporting callbacks so the caller knows that getting the result	650	and supporting callbacks so the caller knows that getting the result
458	will not block, while still suppporting blocking waits if the caller	651	will not block, while still supporting blocking waits if the caller
459	so desires).	652	so desires).
460		653
461	Another reason never to "->recv" in a module is that you cannot	654	Another reason never to "->recv" in a module is that you cannot
462	sensibly have two "->recv"'s in parallel, as that would require	655	sensibly have two "->recv"'s in parallel, as that would require
463	multiple interpreters or coroutines/threads, none of which	656	multiple interpreters or coroutines/threads, none of which
…		…
476		669
477	$bool = $cv->ready	670	$bool = $cv->ready
478	Returns true when the condition is "true", i.e. whether "send" or	671	Returns true when the condition is "true", i.e. whether "send" or
479	"croak" have been called.	672	"croak" have been called.
480		673
481	$cb = $cv->cb ([new callback])	674	$cb = $cv->cb ($cb->($cv))
482	This is a mutator function that returns the callback set and	675	This is a mutator function that returns the callback set and
483	optionally replaces it before doing so.	676	optionally replaces it before doing so.
484		677
485	The callback will be called when the condition becomes "true", i.e.	678	The callback will be called when the condition becomes "true", i.e.
486	when "send" or "croak" are called. Calling "recv" inside the	679	when "send" or "croak" are called, with the only argument being the
		680	condition variable itself. Calling "recv" inside the callback or at
487	callback or at any later time is guaranteed not to block.	681	any later time is guaranteed not to block.
488		682
489	GLOBAL VARIABLES AND FUNCTIONS	683	GLOBAL VARIABLES AND FUNCTIONS
490	$AnyEvent::MODEL	684	$AnyEvent::MODEL
491	Contains "undef" until the first watcher is being created. Then it	685	Contains "undef" until the first watcher is being created. Then it
492	contains the event model that is being used, which is the name of	686	contains the event model that is being used, which is the name of
…		…
566	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	760	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
567	do anything special (it does not need to be event-based) and let	761	do anything special (it does not need to be event-based) and let
568	AnyEvent decide which implementation to chose if some module relies on	762	AnyEvent decide which implementation to chose if some module relies on
569	it.	763	it.
570		764
571	If the main program relies on a specific event model. For example, in	765	If the main program relies on a specific event model - for example, in
572	Gtk2 programs you have to rely on the Glib module. You should load the	766	Gtk2 programs you have to rely on the Glib module - you should load the
573	event module before loading AnyEvent or any module that uses it:	767	event module before loading AnyEvent or any module that uses it:
574	generally speaking, you should load it as early as possible. The reason	768	generally speaking, you should load it as early as possible. The reason
575	is that modules might create watchers when they are loaded, and AnyEvent	769	is that modules might create watchers when they are loaded, and AnyEvent
576	will decide on the event model to use as soon as it creates watchers,	770	will decide on the event model to use as soon as it creates watchers,
577	and it might chose the wrong one unless you load the correct one	771	and it might chose the wrong one unless you load the correct one
578	yourself.	772	yourself.
579		773
580	You can chose to use a rather inefficient pure-perl implementation by	774	You can chose to use a pure-perl implementation by loading the
581	loading the "AnyEvent::Impl::Perl" module, which gives you similar	775	"AnyEvent::Impl::Perl" module, which gives you similar behaviour
582	behaviour everywhere, but letting AnyEvent chose is generally better.	776	everywhere, but letting AnyEvent chose the model is generally better.
		777
		778	MAINLOOP EMULATION
		779	Sometimes (often for short test scripts, or even standalone programs who
		780	only want to use AnyEvent), you do not want to run a specific event
		781	loop.
		782
		783	In that case, you can use a condition variable like this:
		784
		785	AnyEvent->condvar->recv;
		786
		787	This has the effect of entering the event loop and looping forever.
		788
		789	Note that usually your program has some exit condition, in which case it
		790	is better to use the "traditional" approach of storing a condition
		791	variable somewhere, waiting for it, and sending it when the program
		792	should exit cleanly.
583		793
584	OTHER MODULES	794	OTHER MODULES
585	The following is a non-exhaustive list of additional modules that use	795	The following is a non-exhaustive list of additional modules that use
586	AnyEvent and can therefore be mixed easily with other AnyEvent modules	796	AnyEvent and can therefore be mixed easily with other AnyEvent modules
587	in the same program. Some of the modules come with AnyEvent, some are	797	in the same program. Some of the modules come with AnyEvent, some are
…		…
590	AnyEvent::Util	800	AnyEvent::Util
591	Contains various utility functions that replace often-used but	801	Contains various utility functions that replace often-used but
592	blocking functions such as "inet_aton" by event-/callback-based	802	blocking functions such as "inet_aton" by event-/callback-based
593	versions.	803	versions.
594		804
		805	AnyEvent::Socket
		806	Provides various utility functions for (internet protocol) sockets,
		807	addresses and name resolution. Also functions to create non-blocking
		808	tcp connections or tcp servers, with IPv6 and SRV record support and
		809	more.
		810
595	AnyEvent::Handle	811	AnyEvent::Handle
596	Provide read and write buffers and manages watchers for reads and	812	Provide read and write buffers, manages watchers for reads and
597	writes.	813	writes, supports raw and formatted I/O, I/O queued and fully
		814	transparent and non-blocking SSL/TLS.
		815
		816	AnyEvent::DNS
		817	Provides rich asynchronous DNS resolver capabilities.
		818
		819	AnyEvent::HTTP
		820	A simple-to-use HTTP library that is capable of making a lot of
		821	concurrent HTTP requests.
598		822
599	AnyEvent::HTTPD	823	AnyEvent::HTTPD
600	Provides a simple web application server framework.	824	Provides a simple web application server framework.
601		825
602	AnyEvent::DNS
603	Provides asynchronous DNS resolver capabilities, beyond what
604	AnyEvent::Util offers.
605
606	AnyEvent::FastPing	826	AnyEvent::FastPing
607	The fastest ping in the west.	827	The fastest ping in the west.
608		828
		829	AnyEvent::DBI
		830	Executes DBI requests asynchronously in a proxy process.
		831
		832	AnyEvent::AIO
		833	Truly asynchronous I/O, should be in the toolbox of every event
		834	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		835	together.
		836
		837	AnyEvent::BDB
		838	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
		839	fuses BDB and AnyEvent together.
		840
		841	AnyEvent::GPSD
		842	A non-blocking interface to gpsd, a daemon delivering GPS
		843	information.
		844
		845	AnyEvent::IGS
		846	A non-blocking interface to the Internet Go Server protocol (used by
		847	App::IGS).
		848
		849	AnyEvent::IRC
		850	AnyEvent based IRC client module family (replacing the older
609	Net::IRC3	851	Net::IRC3).
610	AnyEvent based IRC client module family.
611		852
612	Net::XMPP2	853	Net::XMPP2
613	AnyEvent based XMPP (Jabber protocol) module family.	854	AnyEvent based XMPP (Jabber protocol) module family.
614		855
615	Net::FCP	856	Net::FCP
…		…
620	High level API for event-based execution flow control.	861	High level API for event-based execution flow control.
621		862
622	Coro	863	Coro
623	Has special support for AnyEvent via Coro::AnyEvent.	864	Has special support for AnyEvent via Coro::AnyEvent.
624		865
625	AnyEvent::AIO, IO::AIO
626	Truly asynchronous I/O, should be in the toolbox of every event
627	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
628	together.
629
630	AnyEvent::BDB, BDB
631	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
632	fuses IO::AIO and AnyEvent together.
633
634	IO::Lambda	866	IO::Lambda
635	The lambda approach to I/O - don't ask, look there. Can use	867	The lambda approach to I/O - don't ask, look there. Can use
636	AnyEvent.	868	AnyEvent.
		869
		870	ERROR AND EXCEPTION HANDLING
		871	In general, AnyEvent does not do any error handling - it relies on the
		872	caller to do that if required. The AnyEvent::Strict module (see also the
		873	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
		874	checking of all AnyEvent methods, however, which is highly useful during
		875	development.
		876
		877	As for exception handling (i.e. runtime errors and exceptions thrown
		878	while executing a callback), this is not only highly event-loop
		879	specific, but also not in any way wrapped by this module, as this is the
		880	job of the main program.
		881
		882	The pure perl event loop simply re-throws the exception (usually within
		883	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
		884	Glib uses "install_exception_handler" and so on.
		885
		886	ENVIRONMENT VARIABLES
		887	The following environment variables are used by this module or its
		888	submodules.
		889
		890	Note that AnyEvent will remove all environment variables starting with
		891	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		892	enabled.
		893
		894	"PERL_ANYEVENT_VERBOSE"
		895	By default, AnyEvent will be completely silent except in fatal
		896	conditions. You can set this environment variable to make AnyEvent
		897	more talkative.
		898
		899	When set to 1 or higher, causes AnyEvent to warn about unexpected
		900	conditions, such as not being able to load the event model specified
		901	by "PERL_ANYEVENT_MODEL".
		902
		903	When set to 2 or higher, cause AnyEvent to report to STDERR which
		904	event model it chooses.
		905
		906	"PERL_ANYEVENT_STRICT"
		907	AnyEvent does not do much argument checking by default, as thorough
		908	argument checking is very costly. Setting this variable to a true
		909	value will cause AnyEvent to load "AnyEvent::Strict" and then to
		910	thoroughly check the arguments passed to most method calls. If it
		911	finds any problems it will croak.
		912
		913	In other words, enables "strict" mode.
		914
		915	Unlike "use strict", it is definitely recommended ot keep it off in
		916	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
		917	while developing programs can be very useful, however.
		918
		919	"PERL_ANYEVENT_MODEL"
		920	This can be used to specify the event model to be used by AnyEvent,
		921	before auto detection and -probing kicks in. It must be a string
		922	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
		923	gets prepended and the resulting module name is loaded and if the
		924	load was successful, used as event model. If it fails to load
		925	AnyEvent will proceed with auto detection and -probing.
		926
		927	This functionality might change in future versions.
		928
		929	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
		930	could start your program like this:
		931
		932	PERL_ANYEVENT_MODEL=Perl perl ...
		933
		934	"PERL_ANYEVENT_PROTOCOLS"
		935	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
		936	preferences for IPv4 or IPv6. The default is unspecified (and might
		937	change, or be the result of auto probing).
		938
		939	Must be set to a comma-separated list of protocols or address
		940	families, current supported: "ipv4" and "ipv6". Only protocols
		941	mentioned will be used, and preference will be given to protocols
		942	mentioned earlier in the list.
		943
		944	This variable can effectively be used for denial-of-service attacks
		945	against local programs (e.g. when setuid), although the impact is
		946	likely small, as the program has to handle conenction and other
		947	failures anyways.
		948
		949	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
		950	IPv6, but support both and try to use both.
		951	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
		952	resolve or contact IPv6 addresses.
		953	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
		954	prefer IPv6 over IPv4.
		955
		956	"PERL_ANYEVENT_EDNS0"
		957	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
		958	for DNS. This extension is generally useful to reduce DNS traffic,
		959	but some (broken) firewalls drop such DNS packets, which is why it
		960	is off by default.
		961
		962	Setting this variable to 1 will cause AnyEvent::DNS to announce
		963	EDNS0 in its DNS requests.
		964
		965	"PERL_ANYEVENT_MAX_FORKS"
		966	The maximum number of child processes that
		967	"AnyEvent::Util::fork_call" will create in parallel.
637		968
638	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	969	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
639	This is an advanced topic that you do not normally need to use AnyEvent	970	This is an advanced topic that you do not normally need to use AnyEvent
640	in a module. This section is only of use to event loop authors who want	971	in a module. This section is only of use to event loop authors who want
641	to provide AnyEvent compatibility.	972	to provide AnyEvent compatibility.
…		…
675		1006
676	rxvt-unicode also cheats a bit by not providing blocking access to	1007	rxvt-unicode also cheats a bit by not providing blocking access to
677	condition variables: code blocking while waiting for a condition will	1008	condition variables: code blocking while waiting for a condition will
678	"die". This still works with most modules/usages, and blocking calls	1009	"die". This still works with most modules/usages, and blocking calls
679	must not be done in an interactive application, so it makes sense.	1010	must not be done in an interactive application, so it makes sense.
680
681	ENVIRONMENT VARIABLES
682	The following environment variables are used by this module:
683
684	"PERL_ANYEVENT_VERBOSE"
685	By default, AnyEvent will be completely silent except in fatal
686	conditions. You can set this environment variable to make AnyEvent
687	more talkative.
688
689	When set to 1 or higher, causes AnyEvent to warn about unexpected
690	conditions, such as not being able to load the event model specified
691	by "PERL_ANYEVENT_MODEL".
692
693	When set to 2 or higher, cause AnyEvent to report to STDERR which
694	event model it chooses.
695
696	"PERL_ANYEVENT_MODEL"
697	This can be used to specify the event model to be used by AnyEvent,
698	before autodetection and -probing kicks in. It must be a string
699	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
700	gets prepended and the resulting module name is loaded and if the
701	load was successful, used as event model. If it fails to load
702	AnyEvent will proceed with autodetection and -probing.
703
704	This functionality might change in future versions.
705
706	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
707	could start your program like this:
708
709	PERL_ANYEVENT_MODEL=Perl perl ...
710		1011
711	EXAMPLE PROGRAM	1012	EXAMPLE PROGRAM
712	The following program uses an I/O watcher to read data from STDIN, a	1013	The following program uses an I/O watcher to read data from STDIN, a
713	timer to display a message once per second, and a condition variable to	1014	timer to display a message once per second, and a condition variable to
714	quit the program when the user enters quit:	1015	quit the program when the user enters quit:
…		…
722	poll => 'r',	1023	poll => 'r',
723	cb => sub {	1024	cb => sub {
724	warn "io event <$_[0]>\n"; # will always output <r>	1025	warn "io event <$_[0]>\n"; # will always output <r>
725	chomp (my $input = <STDIN>); # read a line	1026	chomp (my $input = <STDIN>); # read a line
726	warn "read: $input\n"; # output what has been read	1027	warn "read: $input\n"; # output what has been read
727	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1028	$cv->send if $input =~ /^q/i; # quit program if /^q/i
728	},	1029	},
729	);	1030	);
730		1031
731	my $time_watcher; # can only be used once	1032	my $time_watcher; # can only be used once
732		1033
…		…
737	});	1038	});
738	}	1039	}
739		1040
740	new_timer; # create first timer	1041	new_timer; # create first timer
741		1042
742	$cv->wait; # wait until user enters /^q/i	1043	$cv->recv; # wait until user enters /^q/i
743		1044
744	REAL-WORLD EXAMPLE	1045	REAL-WORLD EXAMPLE
745	Consider the Net::FCP module. It features (among others) the following	1046	Consider the Net::FCP module. It features (among others) the following
746	API calls, which are to freenet what HTTP GET requests are to http:	1047	API calls, which are to freenet what HTTP GET requests are to http:
747		1048
…		…
796	syswrite $txn->{fh}, $txn->{request}	1097	syswrite $txn->{fh}, $txn->{request}
797	or die "connection or write error";	1098	or die "connection or write error";
798	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1099	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
799		1100
800	Again, "fh_ready_r" waits till all data has arrived, and then stores the	1101	Again, "fh_ready_r" waits till all data has arrived, and then stores the
801	result and signals any possible waiters that the request ahs finished:	1102	result and signals any possible waiters that the request has finished:
802		1103
803	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1104	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
804		1105
805	if (end-of-file or data complete) {	1106	if (end-of-file or data complete) {
806	$txn->{result} = $txn->{buf};	1107	$txn->{result} = $txn->{buf};
807	$txn->{finished}->broadcast;	1108	$txn->{finished}->send;
808	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1109	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
809	}	1110	}
810		1111
811	The "result" method, finally, just waits for the finished signal (if the	1112	The "result" method, finally, just waits for the finished signal (if the
812	request was already finished, it doesn't wait, of course, and returns	1113	request was already finished, it doesn't wait, of course, and returns
813	the data:	1114	the data:
814		1115
815	$txn->{finished}->wait;	1116	$txn->{finished}->recv;
816	return $txn->{result};	1117	return $txn->{result};
817		1118
818	The actual code goes further and collects all errors ("die"s,	1119	The actual code goes further and collects all errors ("die"s,
819	exceptions) that occured during request processing. The "result" method	1120	exceptions) that occurred during request processing. The "result" method
820	detects whether an exception as thrown (it is stored inside the $txn	1121	detects whether an exception as thrown (it is stored inside the $txn
821	object) and just throws the exception, which means connection errors and	1122	object) and just throws the exception, which means connection errors and
822	other problems get reported tot he code that tries to use the result,	1123	other problems get reported tot he code that tries to use the result,
823	not in a random callback.	1124	not in a random callback.
824		1125
…		…
855		1156
856	my $quit = AnyEvent->condvar;	1157	my $quit = AnyEvent->condvar;
857		1158
858	$fcp->txn_client_get ($url)->cb (sub {	1159	$fcp->txn_client_get ($url)->cb (sub {
859	...	1160	...
860	$quit->broadcast;	1161	$quit->send;
861	});	1162	});
862		1163
863	$quit->wait;	1164	$quit->recv;
864		1165
865	BENCHMARKS	1166	BENCHMARKS
866	To give you an idea of the performance and overheads that AnyEvent adds	1167	To give you an idea of the performance and overheads that AnyEvent adds
867	over the event loops themselves and to give you an impression of the	1168	over the event loops themselves and to give you an impression of the
868	speed of various event loops I prepared some benchmarks.	1169	speed of various event loops I prepared some benchmarks.
869		1170
870	BENCHMARKING ANYEVENT OVERHEAD	1171	BENCHMARKING ANYEVENT OVERHEAD
871	Here is a benchmark of various supported event models used natively and	1172	Here is a benchmark of various supported event models used natively and
872	through anyevent. The benchmark creates a lot of timers (with a zero	1173	through AnyEvent. The benchmark creates a lot of timers (with a zero
873	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1174	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
874	which it is), lets them fire exactly once and destroys them again.	1175	which it is), lets them fire exactly once and destroys them again.
875		1176
876	Source code for this benchmark is found as eg/bench in the AnyEvent	1177	Source code for this benchmark is found as eg/bench in the AnyEvent
877	distribution.	1178	distribution.
…		…
893	between all watchers, to avoid adding memory overhead. That means	1194	between all watchers, to avoid adding memory overhead. That means
894	closure creation and memory usage is not included in the figures.	1195	closure creation and memory usage is not included in the figures.
895		1196
896	invoke is the time, in microseconds, used to invoke a simple callback.	1197	invoke is the time, in microseconds, used to invoke a simple callback.
897	The callback simply counts down a Perl variable and after it was invoked	1198	The callback simply counts down a Perl variable and after it was invoked
898	"watcher" times, it would "->broadcast" a condvar once to signal the end	1199	"watcher" times, it would "->send" a condvar once to signal the end of
899	of this phase.	1200	this phase.
900		1201
901	destroy is the time, in microseconds, that it takes to destroy a	1202	destroy is the time, in microseconds, that it takes to destroy a
902	single watcher.	1203	single watcher.
903		1204
904	Results	1205	Results
905	name watchers bytes create invoke destroy comment	1206	name watchers bytes create invoke destroy comment
906	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1207	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
907	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1208	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
908	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1209	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
909	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1210	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
910	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1211	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
911	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1212	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
912	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1213	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
913	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1214	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
914	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1215	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
915	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1216	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
916		1217
917	Discussion	1218	Discussion
918	The benchmark does not measure scalability of the event loop very	1219	The benchmark does not measure scalability of the event loop very
919	well. For example, a select-based event loop (such as the pure perl one)	1220	well. For example, a select-based event loop (such as the pure perl one)
920	can never compete with an event loop that uses epoll when the number of	1221	can never compete with an event loop that uses epoll when the number of
…		…
992		1293
993	* You should avoid POE like the plague if you want performance or	1294	* You should avoid POE like the plague if you want performance or
994	reasonable memory usage.	1295	reasonable memory usage.
995		1296
996	BENCHMARKING THE LARGE SERVER CASE	1297	BENCHMARKING THE LARGE SERVER CASE
997	This benchmark atcually benchmarks the event loop itself. It works by	1298	This benchmark actually benchmarks the event loop itself. It works by
998	creating a number of "servers": each server consists of a socketpair, a	1299	creating a number of "servers": each server consists of a socket pair, a
999	timeout watcher that gets reset on activity (but never fires), and an	1300	timeout watcher that gets reset on activity (but never fires), and an
1000	I/O watcher waiting for input on one side of the socket. Each time the	1301	I/O watcher waiting for input on one side of the socket. Each time the
1001	socket watcher reads a byte it will write that byte to a random other	1302	socket watcher reads a byte it will write that byte to a random other
1002	"server".	1303	"server".
1003		1304
1004	The effect is that there will be a lot of I/O watchers, only part of	1305	The effect is that there will be a lot of I/O watchers, only part of
1005	which are active at any one point (so there is a constant number of	1306	which are active at any one point (so there is a constant number of
1006	active fds for each loop iterstaion, but which fds these are is random).	1307	active fds for each loop iteration, but which fds these are is random).
1007	The timeout is reset each time something is read because that reflects	1308	The timeout is reset each time something is read because that reflects
1008	how most timeouts work (and puts extra pressure on the event loops).	1309	how most timeouts work (and puts extra pressure on the event loops).
1009		1310
1010	In this benchmark, we use 10000 socketpairs (20000 sockets), of which	1311	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1011	100 (1%) are active. This mirrors the activity of large servers with	1312	100 (1%) are active. This mirrors the activity of large servers with
1012	many connections, most of which are idle at any one point in time.	1313	many connections, most of which are idle at any one point in time.
1013		1314
1014	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1315	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1015	distribution.	1316	distribution.
1016		1317
1017	Explanation of the columns	1318	Explanation of the columns
1018	sockets is the number of sockets, and twice the number of "servers"	1319	sockets is the number of sockets, and twice the number of "servers"
1019	(as each server has a read and write socket end).	1320	(as each server has a read and write socket end).
1020		1321
1021	create is the time it takes to create a socketpair (which is	1322	create is the time it takes to create a socket pair (which is
1022	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	1323	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1023		1324
1024	request, the most important value, is the time it takes to handle a	1325	request, the most important value, is the time it takes to handle a
1025	single "request", that is, reading the token from the pipe and	1326	single "request", that is, reading the token from the pipe and
1026	forwarding it to another server. This includes deleting the old timeout	1327	forwarding it to another server. This includes deleting the old timeout
…		…
1090	and speed most when you have lots of watchers, not when you only have a	1391	and speed most when you have lots of watchers, not when you only have a
1091	few of them).	1392	few of them).
1092		1393
1093	EV is again fastest.	1394	EV is again fastest.
1094		1395
1095	Perl again comes second. It is noticably faster than the C-based event	1396	Perl again comes second. It is noticeably faster than the C-based event
1096	loops Event and Glib, although the difference is too small to really	1397	loops Event and Glib, although the difference is too small to really
1097	matter.	1398	matter.
1098		1399
1099	POE also performs much better in this case, but is is still far behind	1400	POE also performs much better in this case, but is is still far behind
1100	the others.	1401	the others.
1101		1402
1102	Summary	1403	Summary
1103	* C-based event loops perform very well with small number of watchers,	1404	* C-based event loops perform very well with small number of watchers,
1104	as the management overhead dominates.	1405	as the management overhead dominates.
		1406
		1407	THE IO::Lambda BENCHMARK
		1408	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1409	could be misinterpreted to make AnyEvent look bad. In fact, the
		1410	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1411	better (which shouldn't come as a surprise to anybody). As such, the
		1412	benchmark is fine, and shows that the AnyEvent backend from IO::Lambda
		1413	isn't very optimal. But how would AnyEvent compare when used without the
		1414	extra baggage? To explore this, I wrote the equivalent benchmark for
		1415	AnyEvent.
		1416
		1417	The benchmark itself creates an echo-server, and then, for 500 times,
		1418	connects to the echo server, sends a line, waits for the reply, and then
		1419	creates the next connection. This is a rather bad benchmark, as it
		1420	doesn't test the efficiency of the framework, but it is a benchmark
		1421	nevertheless.
		1422
		1423	name runtime
		1424	Lambda/select 0.330 sec
		1425	+ optimized 0.122 sec
		1426	Lambda/AnyEvent 0.327 sec
		1427	+ optimized 0.138 sec
		1428	Raw sockets/select 0.077 sec
		1429	POE/select, components 0.662 sec
		1430	POE/select, raw sockets 0.226 sec
		1431	POE/select, optimized 0.404 sec
		1432
		1433	AnyEvent/select/nb 0.085 sec
		1434	AnyEvent/EV/nb 0.068 sec
		1435	+state machine 0.134 sec
		1436
		1437	The benchmark is also a bit unfair (my fault) - the IO::Lambda
		1438	benchmarks actually make blocking connects and use 100% blocking I/O,
		1439	defeating the purpose of an event-based solution. All of the newly
		1440	written AnyEvent benchmarks use 100% non-blocking connects (using
		1441	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1442	resolver), so AnyEvent is at a disadvantage here as non-blocking
		1443	connects generally require a lot more bookkeeping and event handling
		1444	than blocking connects (which involve a single syscall only).
		1445
		1446	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1447	offers similar expressive power as POE and IO::Lambda (using
		1448	conventional Perl syntax), which means both the echo server and the
		1449	client are 100% non-blocking w.r.t. I/O, further placing it at a
		1450	disadvantage.
		1451
		1452	As you can see, AnyEvent + EV even beats the hand-optimised "raw sockets
		1453	benchmark", while AnyEvent + its pure perl backend easily beats
		1454	IO::Lambda and POE.
		1455
		1456	And even the 100% non-blocking version written using the high-level (and
		1457	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda, even
		1458	thought it does all of DNS, tcp-connect and socket I/O in a non-blocking
		1459	way.
		1460
		1461	The two AnyEvent benchmarks can be found as eg/ae0.pl and eg/ae2.pl in
		1462	the AnyEvent distribution, the remaining benchmarks are part of the
		1463	IO::lambda distribution and were used without any changes.
		1464
		1465	SIGNALS
		1466	AnyEvent currently installs handlers for these signals:
		1467
		1468	SIGCHLD
		1469	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
		1470	emulation for event loops that do not support them natively. Also,
		1471	some event loops install a similar handler.
		1472
		1473	SIGPIPE
		1474	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
		1475	"undef" when AnyEvent gets loaded.
		1476
		1477	The rationale for this is that AnyEvent users usually do not really
		1478	depend on SIGPIPE delivery (which is purely an optimisation for
		1479	shell use, or badly-written programs), but "SIGPIPE" can cause
		1480	spurious and rare program exits as a lot of people do not expect
		1481	"SIGPIPE" when writing to some random socket.
		1482
		1483	The rationale for installing a no-op handler as opposed to ignoring
		1484	it is that this way, the handler will be restored to defaults on
		1485	exec.
		1486
		1487	Feel free to install your own handler, or reset it to defaults.
1105		1488
1106	FORK	1489	FORK
1107	Most event libraries are not fork-safe. The ones who are usually are	1490	Most event libraries are not fork-safe. The ones who are usually are
1108	because they rely on inefficient but fork-safe "select" or "poll" calls.	1491	because they rely on inefficient but fork-safe "select" or "poll" calls.
1109	Only EV is fully fork-aware.	1492	Only EV is fully fork-aware.
…		…
1120	model than specified in the variable.	1503	model than specified in the variable.
1121		1504
1122	You can make AnyEvent completely ignore this variable by deleting it	1505	You can make AnyEvent completely ignore this variable by deleting it
1123	before the first watcher gets created, e.g. with a "BEGIN" block:	1506	before the first watcher gets created, e.g. with a "BEGIN" block:
1124		1507
1125	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1508	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1126		1509
1127	use AnyEvent;	1510	use AnyEvent;
1128		1511
1129	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1512	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1130	be used to probe what backend is used and gain other information (which	1513	be used to probe what backend is used and gain other information (which
1131	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	1514	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
		1515	and $ENV{PERL_ANYEVENT_STRICT}.
		1516
		1517	BUGS
		1518	Perl 5.8 has numerous memleaks that sometimes hit this module and are
		1519	hard to work around. If you suffer from memleaks, first upgrade to Perl
		1520	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
		1521	annoying memleaks, such as leaking on "map" and "grep" but it is usually
		1522	not as pronounced).
1132		1523
1133	SEE ALSO	1524	SEE ALSO
		1525	Utility functions: AnyEvent::Util.
		1526
1134	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1527	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1135	Event::Lib, Qt, POE.	1528	Event::Lib, Qt, POE.
1136		1529
1137	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1530	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1138	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1531	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1139	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1532	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.
1140		1533
		1534	Non-blocking file handles, sockets, TCP clients and servers:
		1535	AnyEvent::Handle, AnyEvent::Socket.
		1536
		1537	Asynchronous DNS: AnyEvent::DNS.
		1538
1141	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1539	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1142		1540
1143	Nontrivial usage examples: Net::FCP, Net::XMPP2.	1541	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.
1144		1542
1145	AUTHOR	1543	AUTHOR
1146	Marc Lehmann <schmorp@schmorp.de>	1544	Marc Lehmann <schmorp@schmorp.de>
1147	http://home.schmorp.de/	1545	http://home.schmorp.de/
1148		1546

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Comparing AnyEvent/README (file contents): Revision 1.20 by root, Sat May 10 22:30:28 2008 UTC vs. Revision 1.40 by root, Tue Jun 23 23:37:32 2009 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.20 by root, Sat May 10 22:30:28 2008 UTC vs.
Revision 1.40 by root, Tue Jun 23 23:37:32 2009 UTC