[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.24 by root, Thu May 29 03:46:04 2008 UTC vs.
Revision 1.43 by root, Thu Jul 9 08:37:06 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
117	These watchers are normal Perl objects with normal Perl lifetime. After	139	These watchers are normal Perl objects with normal Perl lifetime. After
118	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
119	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
120	in control).	142	in control).
121		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
122	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
123	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
124	to it).	152	to it).
125		153
126	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.
…		…
128	Many watchers either are used with "recursion" (repeating timers for	156	Many watchers either are used with "recursion" (repeating timers for
129	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.
130		158
131	An any way to achieve that is this pattern:	159	An any way to achieve that is this pattern:
132		160
133	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	161	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
134	# you can use $w here, for example to undef it	162	# you can use $w here, for example to undef it
135	undef $w;	163	undef $w;
136	});	164	});
137		165
138	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,
139	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
140	declared.	168	declared.
141		169
142	I/O WATCHERS	170	I/O WATCHERS
143	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
144	the following mandatory key-value pairs as arguments:	172	the following mandatory key-value pairs as arguments:
145		173
146	"fh" the Perl file handle (not file descriptor) to watch for events.	174	"fh" is the Perl file handle (or a naked 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
147	"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
148	watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"	182	watcher waiting for "r"eadable or "w"ritable events, respectively.
		183
149	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.
150		185
151	Although the callback might get passed parameters, their value and	186	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	187	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	188	callbacks cannot use arguments passed to I/O watcher callbacks.
154		189
…		…
158		193
159	Some event loops issue spurious readyness notifications, so you should	194	Some event loops issue spurious readyness notifications, so you should
160	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
161	handles.	196	handles.
162		197
163	Example:
164
165	# 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
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	201	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	202	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	203	warn "read: $input\n";
169	undef $w;	204	undef $w;
170	});	205	});
…		…
179		214
180	Although the callback might get passed parameters, their value and	215	Although the callback might get passed parameters, their value and
181	presence is undefined and you cannot rely on them. Portable AnyEvent	216	presence is undefined and you cannot rely on them. Portable AnyEvent
182	callbacks cannot use arguments passed to time watcher callbacks.	217	callbacks cannot use arguments passed to time watcher callbacks.
183		218
184	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
185	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
186	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.
187		224
188	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.
189		228
190	# fire an event after 7.7 seconds	229	Example: fire an event after 7.7 seconds.
		230
191	my $w = AnyEvent->timer (after => 7.7, cb => sub {	231	my $w = AnyEvent->timer (after => 7.7, cb => sub {
192	warn "timeout\n";	232	warn "timeout\n";
193	});	233	});
194		234
195	# to cancel the timer:	235	# to cancel the timer:
196	undef $w;	236	undef $w;
197		237
198	Example 2:
199
200	# 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.
201	my $w;
202		239
203	my $cb = sub {
204	# cancel the old timer while creating a new one
205	$w = AnyEvent->timer (after => 1, cb => $cb);	240	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		241	warn "timeout\n";
206	};	242	};
207
208	# start the "loop" by creating the first watcher
209	$w = AnyEvent->timer (after => 0.5, cb => $cb);
210		243
211	TIMING ISSUES	244	TIMING ISSUES
212	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
213	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
214	o'clock").	247	o'clock").
…		…
288	In either case, if you care (and in most cases, you don't), then you	321	In either case, if you care (and in most cases, you don't), then you
289	can get whatever behaviour you want with any event loop, by taking	322	can get whatever behaviour you want with any event loop, by taking
290	the difference between "AnyEvent->time" and "AnyEvent->now" into	323	the difference between "AnyEvent->time" and "AnyEvent->now" into
291	account.	324	account.
292		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
293	SIGNAL WATCHERS	340	SIGNAL WATCHERS
294	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
295	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
296	whenever a signal occurs.	343	callback to be invoked whenever a signal occurs.
297		344
298	Although the callback might get passed parameters, their value and	345	Although the callback might get passed parameters, their value and
299	presence is undefined and you cannot rely on them. Portable AnyEvent	346	presence is undefined and you cannot rely on them. Portable AnyEvent
300	callbacks cannot use arguments passed to signal watcher callbacks.	347	callbacks cannot use arguments passed to signal watcher callbacks.
301		348
…		…
316		363
317	CHILD PROCESS WATCHERS	364	CHILD PROCESS WATCHERS
318	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.
319		366
320	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
321	watches for any child process exit). The watcher will trigger as often	368	watches for any child process exit). The watcher will triggered only
322	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
323	signal handler for "SIGCHLD". The callback will be called with the pid	370	on any trace events (stopped/continued).
324	and exit status (as returned by waitpid), so unlike other watcher types,	371
325	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).
326		380
327	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
328	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
329	could have exited already (and no SIGCHLD will be sent anymore).	383	could have exited already (and no SIGCHLD will be sent anymore).
330		384
331	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
332	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
333	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).
334	place).	389	AnyEvent's pure perl event loop handles all cases correctly regardless
		390	of when you start the watcher.
335		391
336	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
337	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
338	you "fork" the child (alternatively, you can call "AnyEvent::detect").	394	you "fork" the child (alternatively, you can call "AnyEvent::detect").
339		395
340	Example: fork a process and wait for it	396	Example: fork a process and wait for it
341		397
342	my $done = AnyEvent->condvar;	398	my $done = AnyEvent->condvar;
343		399
344	my $pid = fork or exit 5;	400	my $pid = fork or exit 5;
345		401
346	my $w = AnyEvent->child (	402	my $w = AnyEvent->child (
347	pid => $pid,	403	pid => $pid,
348	cb => sub {	404	cb => sub {
349	my ($pid, $status) = @_;	405	my ($pid, $status) = @_;
350	warn "pid $pid exited with status $status";	406	warn "pid $pid exited with status $status";
351	$done->send;	407	$done->send;
352	},	408	},
353	);	409	);
354		410
355	# do something else, then wait for process exit	411	# do something else, then wait for process exit
356	$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	});
357		447
358	CONDITION VARIABLES	448	CONDITION VARIABLES
359	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
360	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
361	will actively watch for new events and call your callbacks.	451	will actively watch for new events and call your callbacks.
…		…
366	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
367	because they represent a condition that must become true.	457	because they represent a condition that must become true.
368		458
369	Condition variables can be created by calling the "AnyEvent->condvar"	459	Condition variables can be created by calling the "AnyEvent->condvar"
370	method, usually without arguments. The only argument pair allowed is	460	method, usually without arguments. The only argument pair allowed is
		461
371	"cb", which specifies a callback to be called when the condition	462	"cb", which specifies a callback to be called when the condition
372	variable becomes true.	463	variable becomes true, with the condition variable as the first argument
		464	(but not the results).
373		465
374	After creation, the condition variable is "false" until it becomes	466	After creation, the condition variable is "false" until it becomes
375	"true" by calling the "send" method (or calling the condition variable	467	"true" by calling the "send" method (or calling the condition variable
376	as if it were a callback, read about the caveats in the description for	468	as if it were a callback, read about the caveats in the description for
377	the "->send" method).	469	the "->send" method).
…		…
433		525
434	my $done = AnyEvent->condvar;	526	my $done = AnyEvent->condvar;
435	my $delay = AnyEvent->timer (after => 5, cb => $done);	527	my $delay = AnyEvent->timer (after => 5, cb => $done);
436	$done->recv;	528	$done->recv;
437		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
438	METHODS FOR PRODUCERS	547	METHODS FOR PRODUCERS
439	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
440	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
441	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
442	uncommon for the consumer to create it as well.	551	uncommon for the consumer to create it as well.
…		…
468	This can be used to signal any errors to the condition variable	577	This can be used to signal any errors to the condition variable
469	user/consumer.	578	user/consumer.
470		579
471	$cv->begin ([group callback])	580	$cv->begin ([group callback])
472	$cv->end	581	$cv->end
473	These two methods are EXPERIMENTAL and MIGHT CHANGE.
474
475	These two methods can be used to combine many transactions/events	582	These two methods can be used to combine many transactions/events
476	into one. For example, a function that pings many hosts in parallel	583	into one. For example, a function that pings many hosts in parallel
477	might want to use a condition variable for the whole process.	584	might want to use a condition variable for the whole process.
478		585
479	Every call to "->begin" will increment a counter, and every call to	586	Every call to "->begin" will increment a counter, and every call to
480	"->end" will decrement it. If the counter reaches 0 in "->end", the	587	"->end" will decrement it. If the counter reaches 0 in "->end", the
481	(last) callback passed to "begin" will be executed. That callback is	588	(last) callback passed to "begin" will be executed. That callback is
482	supposed to call "->send", but that is not required. If no	589	supposed to call "->send", but that is not required. If no
483	callback was set, "send" will be called without any arguments.	590	callback was set, "send" will be called without any arguments.
484		591
485	Let's clarify this with the ping example:	592	You can think of "$cv->send" giving you an OR condition (one call
		593	sends), while "$cv->begin" and "$cv->end" giving you an AND
		594	condition (all "begin" calls must be "end"'ed before the condvar
		595	sends).
		596
		597	Let's start with a simple example: you have two I/O watchers (for
		598	example, STDOUT and STDERR for a program), and you want to wait for
		599	both streams to close before activating a condvar:
		600
		601	my $cv = AnyEvent->condvar;
		602
		603	$cv->begin; # first watcher
		604	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		605	defined sysread $fh1, my $buf, 4096
		606	or $cv->end;
		607	});
		608
		609	$cv->begin; # second watcher
		610	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		611	defined sysread $fh2, my $buf, 4096
		612	or $cv->end;
		613	});
		614
		615	$cv->recv;
		616
		617	This works because for every event source (EOF on file handle),
		618	there is one call to "begin", so the condvar waits for all calls to
		619	"end" before sending.
		620
		621	The ping example mentioned above is slightly more complicated, as
		622	the there are results to be passwd back, and the number of tasks
		623	that are begung can potentially be zero:
486		624
487	my $cv = AnyEvent->condvar;	625	my $cv = AnyEvent->condvar;
488		626
489	my %result;	627	my %result;
490	$cv->begin (sub { $cv->send (\%result) });	628	$cv->begin (sub { $cv->send (\%result) });
…		…
510	the loop, which serves two important purposes: first, it sets the	648	the loop, which serves two important purposes: first, it sets the
511	callback to be called once the counter reaches 0, and second, it	649	callback to be called once the counter reaches 0, and second, it
512	ensures that "send" is called even when "no" hosts are being pinged	650	ensures that "send" is called even when "no" hosts are being pinged
513	(the loop doesn't execute once).	651	(the loop doesn't execute once).
514		652
515	This is the general pattern when you "fan out" into multiple	653	This is the general pattern when you "fan out" into multiple (but
516	subrequests: use an outer "begin"/"end" pair to set the callback and	654	potentially none) subrequests: use an outer "begin"/"end" pair to
517	ensure "end" is called at least once, and then, for each subrequest	655	set the callback and ensure "end" is called at least once, and then,
518	you start, call "begin" and for each subrequest you finish, call	656	for each subrequest you start, call "begin" and for each subrequest
519	"end".	657	you finish, call "end".
520		658
521	METHODS FOR CONSUMERS	659	METHODS FOR CONSUMERS
522	These methods should only be used by the consuming side, i.e. the code	660	These methods should only be used by the consuming side, i.e. the code
523	awaits the condition.	661	awaits the condition.
524		662
…		…
562		700
563	$bool = $cv->ready	701	$bool = $cv->ready
564	Returns true when the condition is "true", i.e. whether "send" or	702	Returns true when the condition is "true", i.e. whether "send" or
565	"croak" have been called.	703	"croak" have been called.
566		704
567	$cb = $cv->cb ([new callback])	705	$cb = $cv->cb ($cb->($cv))
568	This is a mutator function that returns the callback set and	706	This is a mutator function that returns the callback set and
569	optionally replaces it before doing so.	707	optionally replaces it before doing so.
570		708
571	The callback will be called when the condition becomes "true", i.e.	709	The callback will be called when the condition becomes "true", i.e.
572	when "send" or "croak" are called. Calling "recv" inside the	710	when "send" or "croak" are called, with the only argument being the
		711	condition variable itself. Calling "recv" inside the callback or at
573	callback or at any later time is guaranteed not to block.	712	any later time is guaranteed not to block.
		713
		714	SUPPORTED EVENT LOOPS/BACKENDS
		715	The available backend classes are (every class has its own manpage):
		716
		717	Backends that are autoprobed when no other event loop can be found.
		718	EV is the preferred backend when no other event loop seems to be in
		719	use. If EV is not installed, then AnyEvent will try Event, and,
		720	failing that, will fall back to its own pure-perl implementation,
		721	which is available everywhere as it comes with AnyEvent itself.
		722
		723	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		724	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		725	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		726
		727	Backends that are transparently being picked up when they are used.
		728	These will be used when they are currently loaded when the first
		729	watcher is created, in which case it is assumed that the application
		730	is using them. This means that AnyEvent will automatically pick the
		731	right backend when the main program loads an event module before
		732	anything starts to create watchers. Nothing special needs to be done
		733	by the main program.
		734
		735	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		736	AnyEvent::Impl::Tk based on Tk, very broken.
		737	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		738	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		739
		740	Backends with special needs.
		741	Qt requires the Qt::Application to be instantiated first, but will
		742	otherwise be picked up automatically. As long as the main program
		743	instantiates the application before any AnyEvent watchers are
		744	created, everything should just work.
		745
		746	AnyEvent::Impl::Qt based on Qt.
		747
		748	Support for IO::Async can only be partial, as it is too broken and
		749	architecturally limited to even support the AnyEvent API. It also is
		750	the only event loop that needs the loop to be set explicitly, so it
		751	can only be used by a main program knowing about AnyEvent. See
		752	AnyEvent::Impl::Async for the gory details.
		753
		754	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		755
		756	Event loops that are indirectly supported via other backends.
		757	Some event loops can be supported via other modules:
		758
		759	There is no direct support for WxWidgets (Wx) or Prima.
		760
		761	WxWidgets has no support for watching file handles. However, you can
		762	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		763	simply polls 20 times per second, which was considered to be too
		764	horrible to even consider for AnyEvent.
		765
		766	Prima is not supported as nobody seems to be using it, but it has a
		767	POE backend, so it can be supported through POE.
		768
		769	AnyEvent knows about both Prima and Wx, however, and will try to
		770	load POE when detecting them, in the hope that POE will pick them
		771	up, in which case everything will be automatic.
574		772
575	GLOBAL VARIABLES AND FUNCTIONS	773	GLOBAL VARIABLES AND FUNCTIONS
		774	These are not normally required to use AnyEvent, but can be useful to
		775	write AnyEvent extension modules.
		776
576	$AnyEvent::MODEL	777	$AnyEvent::MODEL
577	Contains "undef" until the first watcher is being created. Then it	778	Contains "undef" until the first watcher is being created, before
		779	the backend has been autodetected.
		780
578	contains the event model that is being used, which is the name of	781	Afterwards it contains the event model that is being used, which is
579	the Perl class implementing the model. This class is usually one of	782	the name of the Perl class implementing the model. This class is
580	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	783	usually one of the "AnyEvent::Impl:xxx" modules, but can be any
581	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).	784	other class in the case AnyEvent has been extended at runtime (e.g.
582		785	in rxvt-unicode it will be "urxvt::anyevent").
583	The known classes so far are:
584
585	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
586	AnyEvent::Impl::Event based on Event, second best choice.
587	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
588	AnyEvent::Impl::Glib based on Glib, third-best choice.
589	AnyEvent::Impl::Tk based on Tk, very bad choice.
590	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
591	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
592	AnyEvent::Impl::POE based on POE, not generic enough for full support.
593
594	There is no support for WxWidgets, as WxWidgets has no support for
595	watching file handles. However, you can use WxWidgets through the
596	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
597	second, which was considered to be too horrible to even consider for
598	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
599	using it's adaptor.
600
601	AnyEvent knows about Prima and Wx and will try to use POE when
602	autodetecting them.
603		786
604	AnyEvent::detect	787	AnyEvent::detect
605	Returns $AnyEvent::MODEL, forcing autodetection of the event model	788	Returns $AnyEvent::MODEL, forcing autodetection of the event model
606	if necessary. You should only call this function right before you	789	if necessary. You should only call this function right before you
607	would have created an AnyEvent watcher anyway, that is, as late as	790	would have created an AnyEvent watcher anyway, that is, as late as
608	possible at runtime.	791	possible at runtime, and not e.g. while initialising of your module.
		792
		793	If you need to do some initialisation before AnyEvent watchers are
		794	created, use "post_detect".
609		795
610	$guard = AnyEvent::post_detect { BLOCK }	796	$guard = AnyEvent::post_detect { BLOCK }
611	Arranges for the code block to be executed as soon as the event	797	Arranges for the code block to be executed as soon as the event
612	model is autodetected (or immediately if this has already happened).	798	model is autodetected (or immediately if this has already happened).
		799
		800	The block will be executed after the actual backend has been
		801	detected ($AnyEvent::MODEL is set), but before any watchers have
		802	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		803	other initialisations - see the sources of AnyEvent::Strict or
		804	AnyEvent::AIO to see how this is used.
		805
		806	The most common usage is to create some global watchers, without
		807	forcing event module detection too early, for example, AnyEvent::AIO
		808	creates and installs the global IO::AIO watcher in a "post_detect"
		809	block to avoid autodetecting the event module at load time.
613		810
614	If called in scalar or list context, then it creates and returns an	811	If called in scalar or list context, then it creates and returns an
615	object that automatically removes the callback again when it is	812	object that automatically removes the callback again when it is
616	destroyed. See Coro::BDB for a case where this is useful.	813	destroyed. See Coro::BDB for a case where this is useful.
617		814
…		…
619	If there are any code references in this array (you can "push" to it	816	If there are any code references in this array (you can "push" to it
620	before or after loading AnyEvent), then they will called directly	817	before or after loading AnyEvent), then they will called directly
621	after the event loop has been chosen.	818	after the event loop has been chosen.
622		819
623	You should check $AnyEvent::MODEL before adding to this array,	820	You should check $AnyEvent::MODEL before adding to this array,
624	though: if it contains a true value then the event loop has already	821	though: if it is defined then the event loop has already been
625	been detected, and the array will be ignored.	822	detected, and the array will be ignored.
626		823
627	Best use "AnyEvent::post_detect { BLOCK }" instead.	824	Best use "AnyEvent::post_detect { BLOCK }" when your application
		825	allows it,as it takes care of these details.
		826
		827	This variable is mainly useful for modules that can do something
		828	useful when AnyEvent is used and thus want to know when it is
		829	initialised, but do not need to even load it by default. This array
		830	provides the means to hook into AnyEvent passively, without loading
		831	it.
628		832
629	WHAT TO DO IN A MODULE	833	WHAT TO DO IN A MODULE
630	As a module author, you should "use AnyEvent" and call AnyEvent methods	834	As a module author, you should "use AnyEvent" and call AnyEvent methods
631	freely, but you should not load a specific event module or rely on it.	835	freely, but you should not load a specific event module or rely on it.
632		836
…		…
683	variable somewhere, waiting for it, and sending it when the program	887	variable somewhere, waiting for it, and sending it when the program
684	should exit cleanly.	888	should exit cleanly.
685		889
686	OTHER MODULES	890	OTHER MODULES
687	The following is a non-exhaustive list of additional modules that use	891	The following is a non-exhaustive list of additional modules that use
688	AnyEvent and can therefore be mixed easily with other AnyEvent modules	892	AnyEvent as a client and can therefore be mixed easily with other
689	in the same program. Some of the modules come with AnyEvent, some are	893	AnyEvent modules and other event loops in the same program. Some of the
690	available via CPAN.	894	modules come with AnyEvent, most are available via CPAN.
691		895
692	AnyEvent::Util	896	AnyEvent::Util
693	Contains various utility functions that replace often-used but	897	Contains various utility functions that replace often-used but
694	blocking functions such as "inet_aton" by event-/callback-based	898	blocking functions such as "inet_aton" by event-/callback-based
695	versions.	899	versions.
696
697	AnyEvent::Handle
698	Provide read and write buffers and manages watchers for reads and
699	writes.
700		900
701	AnyEvent::Socket	901	AnyEvent::Socket
702	Provides various utility functions for (internet protocol) sockets,	902	Provides various utility functions for (internet protocol) sockets,
703	addresses and name resolution. Also functions to create non-blocking	903	addresses and name resolution. Also functions to create non-blocking
704	tcp connections or tcp servers, with IPv6 and SRV record support and	904	tcp connections or tcp servers, with IPv6 and SRV record support and
705	more.	905	more.
706		906
		907	AnyEvent::Handle
		908	Provide read and write buffers, manages watchers for reads and
		909	writes, supports raw and formatted I/O, I/O queued and fully
		910	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
		911
707	AnyEvent::DNS	912	AnyEvent::DNS
708	Provides rich asynchronous DNS resolver capabilities.	913	Provides rich asynchronous DNS resolver capabilities.
709		914
		915	AnyEvent::HTTP
		916	A simple-to-use HTTP library that is capable of making a lot of
		917	concurrent HTTP requests.
		918
710	AnyEvent::HTTPD	919	AnyEvent::HTTPD
711	Provides a simple web application server framework.	920	Provides a simple web application server framework.
712		921
713	AnyEvent::FastPing	922	AnyEvent::FastPing
714	The fastest ping in the west.	923	The fastest ping in the west.
715		924
		925	AnyEvent::DBI
		926	Executes DBI requests asynchronously in a proxy process.
		927
		928	AnyEvent::AIO
		929	Truly asynchronous I/O, should be in the toolbox of every event
		930	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		931	together.
		932
		933	AnyEvent::BDB
		934	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
		935	fuses BDB and AnyEvent together.
		936
		937	AnyEvent::GPSD
		938	A non-blocking interface to gpsd, a daemon delivering GPS
		939	information.
		940
		941	AnyEvent::IRC
		942	AnyEvent based IRC client module family (replacing the older
716	Net::IRC3	943	Net::IRC3).
717	AnyEvent based IRC client module family.
718		944
719	Net::XMPP2	945	AnyEvent::XMPP
720	AnyEvent based XMPP (Jabber protocol) module family.	946	AnyEvent based XMPP (Jabber protocol) module family (replacing the
		947	older Net::XMPP2>.
		948
		949	AnyEvent::IGS
		950	A non-blocking interface to the Internet Go Server protocol (used by
		951	App::IGS).
721		952
722	Net::FCP	953	Net::FCP
723	AnyEvent-based implementation of the Freenet Client Protocol,	954	AnyEvent-based implementation of the Freenet Client Protocol,
724	birthplace of AnyEvent.	955	birthplace of AnyEvent.
725		956
…		…
727	High level API for event-based execution flow control.	958	High level API for event-based execution flow control.
728		959
729	Coro	960	Coro
730	Has special support for AnyEvent via Coro::AnyEvent.	961	Has special support for AnyEvent via Coro::AnyEvent.
731		962
732	AnyEvent::AIO, IO::AIO	963	ERROR AND EXCEPTION HANDLING
733	Truly asynchronous I/O, should be in the toolbox of every event	964	In general, AnyEvent does not do any error handling - it relies on the
734	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent	965	caller to do that if required. The AnyEvent::Strict module (see also the
735	together.	966	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
		967	checking of all AnyEvent methods, however, which is highly useful during
		968	development.
736		969
737	AnyEvent::BDB, BDB	970	As for exception handling (i.e. runtime errors and exceptions thrown
738	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently	971	while executing a callback), this is not only highly event-loop
739	fuses IO::AIO and AnyEvent together.	972	specific, but also not in any way wrapped by this module, as this is the
		973	job of the main program.
740		974
741	IO::Lambda	975	The pure perl event loop simply re-throws the exception (usually within
742	The lambda approach to I/O - don't ask, look there. Can use	976	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
743	AnyEvent.	977	Glib uses "install_exception_handler" and so on.
744
745	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
746	This is an advanced topic that you do not normally need to use AnyEvent
747	in a module. This section is only of use to event loop authors who want
748	to provide AnyEvent compatibility.
749
750	If you need to support another event library which isn't directly
751	supported by AnyEvent, you can supply your own interface to it by
752	pushing, before the first watcher gets created, the package name of the
753	event module and the package name of the interface to use onto
754	@AnyEvent::REGISTRY. You can do that before and even without loading
755	AnyEvent, so it is reasonably cheap.
756
757	Example:
758
759	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
760
761	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
762	package/class when it finds the "urxvt" package/module is already
763	loaded.
764
765	When AnyEvent is loaded and asked to find a suitable event model, it
766	will first check for the presence of urxvt by trying to "use" the
767	"urxvt::anyevent" module.
768
769	The class should provide implementations for all watcher types. See
770	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
771	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
772	the sources.
773
774	If you don't provide "signal" and "child" watchers than AnyEvent will
775	provide suitable (hopefully) replacements.
776
777	The above example isn't fictitious, the rxvt-unicode (a.k.a. urxvt)
778	terminal emulator uses the above line as-is. An interface isn't included
779	in AnyEvent because it doesn't make sense outside the embedded
780	interpreter inside rxvt-unicode, and it is updated and maintained as
781	part of the rxvt-unicode distribution.
782
783	rxvt-unicode also cheats a bit by not providing blocking access to
784	condition variables: code blocking while waiting for a condition will
785	"die". This still works with most modules/usages, and blocking calls
786	must not be done in an interactive application, so it makes sense.
787		978
788	ENVIRONMENT VARIABLES	979	ENVIRONMENT VARIABLES
789	The following environment variables are used by this module:	980	The following environment variables are used by this module or its
		981	submodules.
		982
		983	Note that AnyEvent will remove all environment variables starting with
		984	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		985	enabled.
790		986
791	"PERL_ANYEVENT_VERBOSE"	987	"PERL_ANYEVENT_VERBOSE"
792	By default, AnyEvent will be completely silent except in fatal	988	By default, AnyEvent will be completely silent except in fatal
793	conditions. You can set this environment variable to make AnyEvent	989	conditions. You can set this environment variable to make AnyEvent
794	more talkative.	990	more talkative.
…		…
797	conditions, such as not being able to load the event model specified	993	conditions, such as not being able to load the event model specified
798	by "PERL_ANYEVENT_MODEL".	994	by "PERL_ANYEVENT_MODEL".
799		995
800	When set to 2 or higher, cause AnyEvent to report to STDERR which	996	When set to 2 or higher, cause AnyEvent to report to STDERR which
801	event model it chooses.	997	event model it chooses.
		998
		999	"PERL_ANYEVENT_STRICT"
		1000	AnyEvent does not do much argument checking by default, as thorough
		1001	argument checking is very costly. Setting this variable to a true
		1002	value will cause AnyEvent to load "AnyEvent::Strict" and then to
		1003	thoroughly check the arguments passed to most method calls. If it
		1004	finds any problems, it will croak.
		1005
		1006	In other words, enables "strict" mode.
		1007
		1008	Unlike "use strict", it is definitely recommended to keep it off in
		1009	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
		1010	while developing programs can be very useful, however.
802		1011
803	"PERL_ANYEVENT_MODEL"	1012	"PERL_ANYEVENT_MODEL"
804	This can be used to specify the event model to be used by AnyEvent,	1013	This can be used to specify the event model to be used by AnyEvent,
805	before auto detection and -probing kicks in. It must be a string	1014	before auto detection and -probing kicks in. It must be a string
806	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1015	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
811	This functionality might change in future versions.	1020	This functionality might change in future versions.
812		1021
813	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1022	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
814	could start your program like this:	1023	could start your program like this:
815		1024
816	PERL_ANYEVENT_MODEL=Perl perl ...	1025	PERL_ANYEVENT_MODEL=Perl perl ...
817		1026
818	"PERL_ANYEVENT_PROTOCOLS"	1027	"PERL_ANYEVENT_PROTOCOLS"
819	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1028	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
820	preferences for IPv4 or IPv6. The default is unspecified (and might	1029	preferences for IPv4 or IPv6. The default is unspecified (and might
821	change, or be the result of auto probing).	1030	change, or be the result of auto probing).
…		…
825	mentioned will be used, and preference will be given to protocols	1034	mentioned will be used, and preference will be given to protocols
826	mentioned earlier in the list.	1035	mentioned earlier in the list.
827		1036
828	This variable can effectively be used for denial-of-service attacks	1037	This variable can effectively be used for denial-of-service attacks
829	against local programs (e.g. when setuid), although the impact is	1038	against local programs (e.g. when setuid), although the impact is
830	likely small, as the program has to handle connection errors	1039	likely small, as the program has to handle conenction and other
831	already-	1040	failures anyways.
832		1041
833	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1042	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
834	IPv6, but support both and try to use both.	1043	IPv6, but support both and try to use both.
835	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1044	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
836	resolve or contact IPv6 addresses.	1045	resolve or contact IPv6 addresses.
…		…
847	EDNS0 in its DNS requests.	1056	EDNS0 in its DNS requests.
848		1057
849	"PERL_ANYEVENT_MAX_FORKS"	1058	"PERL_ANYEVENT_MAX_FORKS"
850	The maximum number of child processes that	1059	The maximum number of child processes that
851	"AnyEvent::Util::fork_call" will create in parallel.	1060	"AnyEvent::Util::fork_call" will create in parallel.
		1061
		1062	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1063	The default value for the "max_outstanding" parameter for the
		1064	default DNS resolver - this is the maximum number of parallel DNS
		1065	requests that are sent to the DNS server.
		1066
		1067	"PERL_ANYEVENT_RESOLV_CONF"
		1068	The file to use instead of /etc/resolv.conf (or OS-specific
		1069	configuration) in the default resolver. When set to the empty
		1070	string, no default config will be used.
		1071
		1072	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1073	When neither "ca_file" nor "ca_path" was specified during
		1074	AnyEvent::TLS context creation, and either of these environment
		1075	variables exist, they will be used to specify CA certificate
		1076	locations instead of a system-dependent default.
		1077
		1078	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1079	This is an advanced topic that you do not normally need to use AnyEvent
		1080	in a module. This section is only of use to event loop authors who want
		1081	to provide AnyEvent compatibility.
		1082
		1083	If you need to support another event library which isn't directly
		1084	supported by AnyEvent, you can supply your own interface to it by
		1085	pushing, before the first watcher gets created, the package name of the
		1086	event module and the package name of the interface to use onto
		1087	@AnyEvent::REGISTRY. You can do that before and even without loading
		1088	AnyEvent, so it is reasonably cheap.
		1089
		1090	Example:
		1091
		1092	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
		1093
		1094	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
		1095	package/class when it finds the "urxvt" package/module is already
		1096	loaded.
		1097
		1098	When AnyEvent is loaded and asked to find a suitable event model, it
		1099	will first check for the presence of urxvt by trying to "use" the
		1100	"urxvt::anyevent" module.
		1101
		1102	The class should provide implementations for all watcher types. See
		1103	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
		1104	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
		1105	the sources.
		1106
		1107	If you don't provide "signal" and "child" watchers than AnyEvent will
		1108	provide suitable (hopefully) replacements.
		1109
		1110	The above example isn't fictitious, the rxvt-unicode (a.k.a. urxvt)
		1111	terminal emulator uses the above line as-is. An interface isn't included
		1112	in AnyEvent because it doesn't make sense outside the embedded
		1113	interpreter inside rxvt-unicode, and it is updated and maintained as
		1114	part of the rxvt-unicode distribution.
		1115
		1116	rxvt-unicode also cheats a bit by not providing blocking access to
		1117	condition variables: code blocking while waiting for a condition will
		1118	"die". This still works with most modules/usages, and blocking calls
		1119	must not be done in an interactive application, so it makes sense.
852		1120
853	EXAMPLE PROGRAM	1121	EXAMPLE PROGRAM
854	The following program uses an I/O watcher to read data from STDIN, a	1122	The following program uses an I/O watcher to read data from STDIN, a
855	timer to display a message once per second, and a condition variable to	1123	timer to display a message once per second, and a condition variable to
856	quit the program when the user enters quit:	1124	quit the program when the user enters quit:
…		…
1043	destroy is the time, in microseconds, that it takes to destroy a	1311	destroy is the time, in microseconds, that it takes to destroy a
1044	single watcher.	1312	single watcher.
1045		1313
1046	Results	1314	Results
1047	name watchers bytes create invoke destroy comment	1315	name watchers bytes create invoke destroy comment
1048	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1316	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1049	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1317	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1050	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1318	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1051	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1319	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1052	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1320	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1053	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1321	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1322	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1323	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1054	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1324	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1055	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1325	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1056	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1326	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1057	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1327	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1058		1328
1059	Discussion	1329	Discussion
1060	The benchmark does not measure scalability of the event loop very	1330	The benchmark does not measure scalability of the event loop very
1061	well. For example, a select-based event loop (such as the pure perl one)	1331	well. For example, a select-based event loop (such as the pure perl one)
1062	can never compete with an event loop that uses epoll when the number of	1332	can never compete with an event loop that uses epoll when the number of
…		…
1087	few of them active), of course, but this was not subject of this	1357	few of them active), of course, but this was not subject of this
1088	benchmark.	1358	benchmark.
1089		1359
1090	The "Event" module has a relatively high setup and callback invocation	1360	The "Event" module has a relatively high setup and callback invocation
1091	cost, but overall scores in on the third place.	1361	cost, but overall scores in on the third place.
		1362
		1363	"IO::Async" performs admirably well, about on par with "Event", even
		1364	when using its pure perl backend.
1092		1365
1093	"Glib"'s memory usage is quite a bit higher, but it features a faster	1366	"Glib"'s memory usage is quite a bit higher, but it features a faster
1094	callback invocation and overall ends up in the same class as "Event".	1367	callback invocation and overall ends up in the same class as "Event".
1095	However, Glib scales extremely badly, doubling the number of watchers	1368	However, Glib scales extremely badly, doubling the number of watchers
1096	increases the processing time by more than a factor of four, making it	1369	increases the processing time by more than a factor of four, making it
…		…
1167	single "request", that is, reading the token from the pipe and	1440	single "request", that is, reading the token from the pipe and
1168	forwarding it to another server. This includes deleting the old timeout	1441	forwarding it to another server. This includes deleting the old timeout
1169	and creating a new one that moves the timeout into the future.	1442	and creating a new one that moves the timeout into the future.
1170		1443
1171	Results	1444	Results
1172	name sockets create request	1445	name sockets create request
1173	EV 20000 69.01 11.16	1446	EV 20000 69.01 11.16
1174	Perl 20000 73.32 35.87	1447	Perl 20000 73.32 35.87
		1448	IOAsync 20000 157.00 98.14 epoll
		1449	IOAsync 20000 159.31 616.06 poll
1175	Event 20000 212.62 257.32	1450	Event 20000 212.62 257.32
1176	Glib 20000 651.16 1896.30	1451	Glib 20000 651.16 1896.30
1177	POE 20000 349.67 12317.24 uses POE::Loop::Event	1452	POE 20000 349.67 12317.24 uses POE::Loop::Event
1178		1453
1179	Discussion	1454	Discussion
1180	This benchmark does measure scalability and overall performance of the	1455	This benchmark does measure scalability and overall performance of the
1181	particular event loop.	1456	particular event loop.
1182		1457
1183	EV is again fastest. Since it is using epoll on my system, the setup	1458	EV is again fastest. Since it is using epoll on my system, the setup
1184	time is relatively high, though.	1459	time is relatively high, though.
1185		1460
1186	Perl surprisingly comes second. It is much faster than the C-based event	1461	Perl surprisingly comes second. It is much faster than the C-based event
1187	loops Event and Glib.	1462	loops Event and Glib.
		1463
		1464	IO::Async performs very well when using its epoll backend, and still
		1465	quite good compared to Glib when using its pure perl backend.
1188		1466
1189	Event suffers from high setup time as well (look at its code and you	1467	Event suffers from high setup time as well (look at its code and you
1190	will understand why). Callback invocation also has a high overhead	1468	will understand why). Callback invocation also has a high overhead
1191	compared to the "$_->() for .."-style loop that the Perl event loop	1469	compared to the "$_->() for .."-style loop that the Perl event loop
1192	uses. Event uses select or poll in basically all documented	1470	uses. Event uses select or poll in basically all documented
…		…
1243		1521
1244	Summary	1522	Summary
1245	* C-based event loops perform very well with small number of watchers,	1523	* C-based event loops perform very well with small number of watchers,
1246	as the management overhead dominates.	1524	as the management overhead dominates.
1247		1525
		1526	THE IO::Lambda BENCHMARK
		1527	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1528	could be misinterpreted to make AnyEvent look bad. In fact, the
		1529	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1530	better (which shouldn't come as a surprise to anybody). As such, the
		1531	benchmark is fine, and mostly shows that the AnyEvent backend from
		1532	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1533	without the extra baggage? To explore this, I wrote the equivalent
		1534	benchmark for AnyEvent.
		1535
		1536	The benchmark itself creates an echo-server, and then, for 500 times,
		1537	connects to the echo server, sends a line, waits for the reply, and then
		1538	creates the next connection. This is a rather bad benchmark, as it
		1539	doesn't test the efficiency of the framework or much non-blocking I/O,
		1540	but it is a benchmark nevertheless.
		1541
		1542	name runtime
		1543	Lambda/select 0.330 sec
		1544	+ optimized 0.122 sec
		1545	Lambda/AnyEvent 0.327 sec
		1546	+ optimized 0.138 sec
		1547	Raw sockets/select 0.077 sec
		1548	POE/select, components 0.662 sec
		1549	POE/select, raw sockets 0.226 sec
		1550	POE/select, optimized 0.404 sec
		1551
		1552	AnyEvent/select/nb 0.085 sec
		1553	AnyEvent/EV/nb 0.068 sec
		1554	+state machine 0.134 sec
		1555
		1556	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1557	benchmarks actually make blocking connects and use 100% blocking I/O,
		1558	defeating the purpose of an event-based solution. All of the newly
		1559	written AnyEvent benchmarks use 100% non-blocking connects (using
		1560	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1561	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1562	connects generally require a lot more bookkeeping and event handling
		1563	than blocking connects (which involve a single syscall only).
		1564
		1565	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1566	offers similar expressive power as POE and IO::Lambda, using
		1567	conventional Perl syntax. This means that both the echo server and the
		1568	client are 100% non-blocking, further placing it at a disadvantage.
		1569
		1570	As you can see, the AnyEvent + EV combination even beats the
		1571	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1572	backend easily beats IO::Lambda and POE.
		1573
		1574	And even the 100% non-blocking version written using the high-level (and
		1575	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a
		1576	large margin, even though it does all of DNS, tcp-connect and socket I/O
		1577	in a non-blocking way.
		1578
		1579	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1580	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1581	part of the IO::lambda distribution and were used without any changes.
		1582
		1583	SIGNALS
		1584	AnyEvent currently installs handlers for these signals:
		1585
		1586	SIGCHLD
		1587	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
		1588	emulation for event loops that do not support them natively. Also,
		1589	some event loops install a similar handler.
		1590
		1591	If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent
		1592	will reset it to default, to avoid losing child exit statuses.
		1593
		1594	SIGPIPE
		1595	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
		1596	"undef" when AnyEvent gets loaded.
		1597
		1598	The rationale for this is that AnyEvent users usually do not really
		1599	depend on SIGPIPE delivery (which is purely an optimisation for
		1600	shell use, or badly-written programs), but "SIGPIPE" can cause
		1601	spurious and rare program exits as a lot of people do not expect
		1602	"SIGPIPE" when writing to some random socket.
		1603
		1604	The rationale for installing a no-op handler as opposed to ignoring
		1605	it is that this way, the handler will be restored to defaults on
		1606	exec.
		1607
		1608	Feel free to install your own handler, or reset it to defaults.
		1609
1248	FORK	1610	FORK
1249	Most event libraries are not fork-safe. The ones who are usually are	1611	Most event libraries are not fork-safe. The ones who are usually are
1250	because they rely on inefficient but fork-safe "select" or "poll" calls.	1612	because they rely on inefficient but fork-safe "select" or "poll" calls.
1251	Only EV is fully fork-aware.	1613	Only EV is fully fork-aware.
1252		1614
…		…
1262	model than specified in the variable.	1624	model than specified in the variable.
1263		1625
1264	You can make AnyEvent completely ignore this variable by deleting it	1626	You can make AnyEvent completely ignore this variable by deleting it
1265	before the first watcher gets created, e.g. with a "BEGIN" block:	1627	before the first watcher gets created, e.g. with a "BEGIN" block:
1266		1628
1267	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1629	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1268		1630
1269	use AnyEvent;	1631	use AnyEvent;
1270		1632
1271	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1633	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1272	be used to probe what backend is used and gain other information (which	1634	be used to probe what backend is used and gain other information (which
1273	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	1635	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
		1636	and $ENV{PERL_ANYEVENT_STRICT}.
		1637
		1638	Note that AnyEvent will remove all environment variables starting with
		1639	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1640	enabled.
		1641
		1642	BUGS
		1643	Perl 5.8 has numerous memleaks that sometimes hit this module and are
		1644	hard to work around. If you suffer from memleaks, first upgrade to Perl
		1645	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
		1646	annoying memleaks, such as leaking on "map" and "grep" but it is usually
		1647	not as pronounced).
1274		1648
1275	SEE ALSO	1649	SEE ALSO
1276	Utility functions: AnyEvent::Util.	1650	Utility functions: AnyEvent::Util.
1277		1651
1278	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1652	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1279	Event::Lib, Qt, POE.	1653	Event::Lib, Qt, POE.
1280		1654
1281	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1655	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1282	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1656	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1283	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1657	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1658	AnyEvent::Impl::IOAsync.
1284		1659
1285	Non-blocking file handles, sockets, TCP clients and servers:	1660	Non-blocking file handles, sockets, TCP clients and servers:
1286	AnyEvent::Handle, AnyEvent::Socket.	1661	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1287		1662
1288	Asynchronous DNS: AnyEvent::DNS.	1663	Asynchronous DNS: AnyEvent::DNS.
1289		1664
1290	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1665	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1291		1666
1292	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1667	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1668	AnyEvent::HTTP.
1293		1669
1294	AUTHOR	1670	AUTHOR
1295	Marc Lehmann <schmorp@schmorp.de>	1671	Marc Lehmann <schmorp@schmorp.de>
1296	http://home.schmorp.de/	1672	http://home.schmorp.de/
1297		1673

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent/README (file contents): Revision 1.24 by root, Thu May 29 03:46:04 2008 UTC vs. Revision 1.43 by root, Thu Jul 9 08:37:06 2009 UTC

Diff Legend

Comparing AnyEvent/README (file contents):
Revision 1.24 by root, Thu May 29 03:46:04 2008 UTC vs.
Revision 1.43 by root, Thu Jul 9 08:37:06 2009 UTC