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Revision 1.24 by root, Thu May 29 03:46:04 2008 UTC vs.
Revision 1.57 by root, Sat Dec 5 02:52:03 2009 UTC

1	=> NAME	1	NAME
2	AnyEvent - provide framework for multiple event loops	2	AnyEvent - the DBI of event loop programming
3		3
4	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event	4	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
5	loops	5	Qt and POE are various supported event loops/environments.
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.
		42
		43	SUPPORT
		44	There is a mailinglist for discussing all things AnyEvent, and an IRC
		45	channel, too.
		46
		47	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
		48	Repository, at <http://anyevent.schmorp.de>, for more info.
21		49
22	WHY YOU SHOULD USE THIS MODULE (OR NOT)	50	WHY YOU SHOULD USE THIS MODULE (OR NOT)
23	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	51	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
24	nowadays. So what is different about AnyEvent?	52	nowadays. So what is different about AnyEvent?
25		53
26	Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of	54	Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of
27	policy* and AnyEvent is *small and efficient*.	55	policy* and AnyEvent is *small and efficient*.
28		56
29	First and foremost, *AnyEvent is not an event model* itself, it only	57	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	58	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,	59	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,	60	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.	61	only one event loop can be active at the same time in a process.
34	AnyEvent helps hiding the differences between those event loops.	62	AnyEvent cannot change this, but it can hide the differences between
		63	those event loops.
35		64
36	The goal of AnyEvent is to offer module authors the ability to do event	65	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	66	programming (waiting for I/O or timer events) without subscribing to a
38	religion, a way of living, and most importantly: without forcing your	67	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	68	module users into the same thing by forcing them to use the same event
40	model you use.	69	model you use.
41		70
42	For modules like POE or IO::Async (which is a total misnomer as it is	71	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	72	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	73	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	74	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	75	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.	76	are *also* forced to use the same event loop you use.
48		77
49	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	78	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	79	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	80	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.	81	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	82	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	83	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	84	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).	85	to AnyEvent, too, so it is future-proof).
57		86
58	In addition to being free of having to use *the one and only true event	87	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	88	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	89	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	90	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	146	These watchers are normal Perl objects with normal Perl lifetime. After
118	creating a watcher it will immediately "watch" for events and invoke the	147	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	148	callback when the event occurs (of course, only when the event model is
120	in control).	149	in control).
121		150
		151	Note that callbacks must not permanently change global variables
		152	potentially in use by the event loop (such as $_ or $[) and that
		153	callbacks must not "die". The former is good programming practise in
		154	Perl and the latter stems from the fact that exception handling differs
		155	widely between event loops.
		156
122	To disable the watcher you have to destroy it (e.g. by setting the	157	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	158	variable you store it in to "undef" or otherwise deleting all references
124	to it).	159	to it).
125		160
126	All watchers are created by calling a method on the "AnyEvent" class.	161	All watchers are created by calling a method on the "AnyEvent" class.
…		…
128	Many watchers either are used with "recursion" (repeating timers for	163	Many watchers either are used with "recursion" (repeating timers for
129	example), or need to refer to their watcher object in other ways.	164	example), or need to refer to their watcher object in other ways.
130		165
131	An any way to achieve that is this pattern:	166	An any way to achieve that is this pattern:
132		167
133	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	168	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
134	# you can use $w here, for example to undef it	169	# you can use $w here, for example to undef it
135	undef $w;	170	undef $w;
136	});	171	});
137		172
138	Note that "my $w; $w =" combination. This is necessary because in Perl,	173	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	174	my variables are only visible after the statement in which they are
140	declared.	175	declared.
141		176
142	I/O WATCHERS	177	I/O WATCHERS
		178	$w = AnyEvent->io (
		179	fh => <filehandle_or_fileno>,
		180	poll => <"r" or "w">,
		181	cb => <callback>,
		182	);
		183
143	You can create an I/O watcher by calling the "AnyEvent->io" method with	184	You can create an I/O watcher by calling the "AnyEvent->io" method with
144	the following mandatory key-value pairs as arguments:	185	the following mandatory key-value pairs as arguments:
145		186
146	"fh" the Perl *file handle* (*not* file descriptor) to watch for events.	187	"fh" is the Perl *file handle* (or a naked file descriptor) to watch for
		188	events (AnyEvent might or might not keep a reference to this file
		189	handle). Note that only file handles pointing to things for which
		190	non-blocking operation makes sense are allowed. This includes sockets,
		191	most character devices, pipes, fifos and so on, but not for example
		192	files or block devices.
		193
147	"poll" must be a string that is either "r" or "w", which creates a	194	"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"	195	watcher waiting for "r"eadable or "w"ritable events, respectively.
		196
149	is the callback to invoke each time the file handle becomes ready.	197	"cb" is the callback to invoke each time the file handle becomes ready.
150		198
151	Although the callback might get passed parameters, their value and	199	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	200	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	201	callbacks cannot use arguments passed to I/O watcher callbacks.
154		202
…		…
158		206
159	Some event loops issue spurious readyness notifications, so you should	207	Some event loops issue spurious readyness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	208	always use non-blocking calls when reading/writing from/to your file
161	handles.	209	handles.
162		210
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	211	Example: wait for readability of STDIN, then read a line and disable the
		212	watcher.
		213
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	214	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	215	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	216	warn "read: $input\n";
169	undef $w;	217	undef $w;
170	});	218	});
171		219
172	TIME WATCHERS	220	TIME WATCHERS
		221	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		222
		223	$w = AnyEvent->timer (
		224	after => <fractional_seconds>,
		225	interval => <fractional_seconds>,
		226	cb => <callback>,
		227	);
		228
173	You can create a time watcher by calling the "AnyEvent->timer" method	229	You can create a time watcher by calling the "AnyEvent->timer" method
174	with the following mandatory arguments:	230	with the following mandatory arguments:
175		231
176	"after" specifies after how many seconds (fractional values are	232	"after" specifies after how many seconds (fractional values are
177	supported) the callback should be invoked. "cb" is the callback to	233	supported) the callback should be invoked. "cb" is the callback to
…		…
179		235
180	Although the callback might get passed parameters, their value and	236	Although the callback might get passed parameters, their value and
181	presence is undefined and you cannot rely on them. Portable AnyEvent	237	presence is undefined and you cannot rely on them. Portable AnyEvent
182	callbacks cannot use arguments passed to time watcher callbacks.	238	callbacks cannot use arguments passed to time watcher callbacks.
183		239
184	The timer callback will be invoked at most once: if you want a repeating	240	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	241	parameter, "interval", as a strictly positive number (> 0), then the
186	and Glib).	242	callback will be invoked regularly at that interval (in fractional
		243	seconds) after the first invocation. If "interval" is specified with a
		244	false value, then it is treated as if it were missing.
187		245
188	Example:	246	The callback will be rescheduled before invoking the callback, but no
		247	attempt is done to avoid timer drift in most backends, so the interval
		248	is only approximate.
189		249
190	# fire an event after 7.7 seconds	250	Example: fire an event after 7.7 seconds.
		251
191	my $w = AnyEvent->timer (after => 7.7, cb => sub {	252	my $w = AnyEvent->timer (after => 7.7, cb => sub {
192	warn "timeout\n";	253	warn "timeout\n";
193	});	254	});
194		255
195	# to cancel the timer:	256	# to cancel the timer:
196	undef $w;	257	undef $w;
197		258
198	Example 2:
199
200	# fire an event after 0.5 seconds, then roughly every second	259	Example 2: fire an event after 0.5 seconds, then roughly every second.
201	my $w;
202		260
203	my $cb = sub {
204	# cancel the old timer while creating a new one
205	$w = AnyEvent->timer (after => 1, cb => $cb);	261	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		262	warn "timeout\n";
206	};	263	};
207
208	# start the "loop" by creating the first watcher
209	$w = AnyEvent->timer (after => 0.5, cb => $cb);
210		264
211	TIMING ISSUES	265	TIMING ISSUES
212	There are two ways to handle timers: based on real time (relative, "fire	266	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	267	in 10 seconds") and based on wallclock time (absolute, "fire at 12
214	o'clock").	268	o'clock").
…		…
288	In either case, if you care (and in most cases, you don't), then you	342	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	343	can get whatever behaviour you want with any event loop, by taking
290	the difference between "AnyEvent->time" and "AnyEvent->now" into	344	the difference between "AnyEvent->time" and "AnyEvent->now" into
291	account.	345	account.
292		346
		347	AnyEvent->now_update
		348	Some event loops (such as EV or AnyEvent::Impl::Perl) cache the
		349	current time for each loop iteration (see the discussion of
		350	AnyEvent->now, above).
		351
		352	When a callback runs for a long time (or when the process sleeps),
		353	then this "current" time will differ substantially from the real
		354	time, which might affect timers and time-outs.
		355
		356	When this is the case, you can call this method, which will update
		357	the event loop's idea of "current time".
		358
		359	A typical example would be a script in a web server (e.g.
		360	"mod_perl") - when mod_perl executes the script, then the event loop
		361	will have the wrong idea about the "current time" (being potentially
		362	far in the past, when the script ran the last time). In that case
		363	you should arrange a call to "AnyEvent->now_update" each time the
		364	web server process wakes up again (e.g. at the start of your script,
		365	or in a handler).
		366
		367	Note that updating the time *might* cause some events to be handled.
		368
293	SIGNAL WATCHERS	369	SIGNAL WATCHERS
		370	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		371
294	You can watch for signals using a signal watcher, "signal" is the signal	372	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	373	*name* in uppercase and without any "SIG" prefix, "cb" is the Perl
296	whenever a signal occurs.	374	callback to be invoked whenever a signal occurs.
297		375
298	Although the callback might get passed parameters, their value and	376	Although the callback might get passed parameters, their value and
299	presence is undefined and you cannot rely on them. Portable AnyEvent	377	presence is undefined and you cannot rely on them. Portable AnyEvent
300	callbacks cannot use arguments passed to signal watcher callbacks.	378	callbacks cannot use arguments passed to signal watcher callbacks.
301		379
…		…
303	invocation, and callback invocation will be synchronous. Synchronous	381	invocation, and callback invocation will be synchronous. Synchronous
304	means that it might take a while until the signal gets handled by the	382	means that it might take a while until the signal gets handled by the
305	process, but it is guaranteed not to interrupt any other callbacks.	383	process, but it is guaranteed not to interrupt any other callbacks.
306		384
307	The main advantage of using these watchers is that you can share a	385	The main advantage of using these watchers is that you can share a
308	signal between multiple watchers.	386	signal between multiple watchers, and AnyEvent will ensure that signals
		387	will not interrupt your program at bad times.
309		388
310	This watcher might use %SIG, so programs overwriting those signals	389	This watcher might use %SIG (depending on the event loop used), so
311	directly will likely not work correctly.	390	programs overwriting those signals directly will likely not work
		391	correctly.
312		392
313	Example: exit on SIGINT	393	Example: exit on SIGINT
314		394
315	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	395	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
316		396
		397	Restart Behaviour
		398	While restart behaviour is up to the event loop implementation, most
		399	will not restart syscalls (that includes Async::Interrupt and AnyEvent's
		400	pure perl implementation).
		401
		402	Safe/Unsafe Signals
		403	Perl signals can be either "safe" (synchronous to opcode handling) or
		404	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		405	latter might corrupt your memory.
		406
		407	AnyEvent signal handlers are, in addition, synchronous to the event
		408	loop, i.e. they will not interrupt your running perl program but will
		409	only be called as part of the normal event handling (just like timer,
		410	I/O etc. callbacks, too).
		411
		412	Signal Races, Delays and Workarounds
		413	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		414	callbacks to signals in a generic way, which is a pity, as you cannot do
		415	race-free signal handling in perl, requiring C libraries for this.
		416	AnyEvent will try to do it's best, which means in some cases, signals
		417	will be delayed. The maximum time a signal might be delayed is specified
		418	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
		419	can be changed only before the first signal watcher is created, and
		420	should be left alone otherwise. This variable determines how often
		421	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		422	will cause fewer spurious wake-ups, which is better for power and CPU
		423	saving.
		424
		425	All these problems can be avoided by installing the optional
		426	Async::Interrupt module, which works with most event loops. It will not
		427	work with inherently broken event loops such as Event or Event::Lib (and
		428	not with POE currently, as POE does it's own workaround with one-second
		429	latency). For those, you just have to suffer the delays.
		430
317	CHILD PROCESS WATCHERS	431	CHILD PROCESS WATCHERS
		432	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		433
318	You can also watch on a child process exit and catch its exit status.	434	You can also watch on a child process exit and catch its exit status.
319		435
320	The child process is specified by the "pid" argument (if set to 0, it	436	The child process is specified by the "pid" argument (one some backends,
321	watches for any child process exit). The watcher will trigger as often	437	using 0 watches for any child process exit, on others this will croak).
322	as status change for the child are received. This works by installing a	438	The watcher will be triggered only when the child process has finished
323	signal handler for "SIGCHLD". The callback will be called with the pid	439	and an exit status is available, not on any trace events
324	and exit status (as returned by waitpid), so unlike other watcher types,	440	(stopped/continued).
325	you *can* rely on child watcher callback arguments.	441
		442	The callback will be called with the pid and exit status (as returned by
		443	waitpid), so unlike other watcher types, you *can* rely on child watcher
		444	callback arguments.
		445
		446	This watcher type works by installing a signal handler for "SIGCHLD",
		447	and since it cannot be shared, nothing else should use SIGCHLD or reap
		448	random child processes (waiting for specific child processes, e.g.
		449	inside "system", is just fine).
326		450
327	There is a slight catch to child watchers, however: you usually start	451	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	452	them *after* the child process was created, and this means the process
329	could have exited already (and no SIGCHLD will be sent anymore).	453	could have exited already (and no SIGCHLD will be sent anymore).
330		454
331	Not all event models handle this correctly (POE doesn't), but even for	455	Not all event models handle this correctly (neither POE nor IO::Async
		456	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	457	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	458	before the process exits (i.e. before you fork in the first place).
334	place).	459	AnyEvent's pure perl event loop handles all cases correctly regardless
		460	of when you start the watcher.
335		461
336	This means you cannot create a child watcher as the very first thing in	462	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	463	an AnyEvent program, you *have* to create at least one watcher before
338	you "fork" the child (alternatively, you can call "AnyEvent::detect").	464	you "fork" the child (alternatively, you can call "AnyEvent::detect").
339		465
		466	As most event loops do not support waiting for child events, they will
		467	be emulated by AnyEvent in most cases, in which the latency and race
		468	problems mentioned in the description of signal watchers apply.
		469
340	Example: fork a process and wait for it	470	Example: fork a process and wait for it
341		471
342	my $done = AnyEvent->condvar;	472	my $done = AnyEvent->condvar;
343		473
344	my $pid = fork or exit 5;	474	my $pid = fork or exit 5;
345		475
346	my $w = AnyEvent->child (	476	my $w = AnyEvent->child (
347	pid => $pid,	477	pid => $pid,
348	cb => sub {	478	cb => sub {
349	my ($pid, $status) = @_;	479	my ($pid, $status) = @_;
350	warn "pid $pid exited with status $status";	480	warn "pid $pid exited with status $status";
351	$done->send;	481	$done->send;
352	},	482	},
353	);	483	);
354		484
355	# do something else, then wait for process exit	485	# do something else, then wait for process exit
356	$done->recv;	486	$done->recv;
		487
		488	IDLE WATCHERS
		489	$w = AnyEvent->idle (cb => <callback>);
		490
		491	Sometimes there is a need to do something, but it is not so important to
		492	do it instantly, but only when there is nothing better to do. This
		493	"nothing better to do" is usually defined to be "no other events need
		494	attention by the event loop".
		495
		496	Idle watchers ideally get invoked when the event loop has nothing better
		497	to do, just before it would block the process to wait for new events.
		498	Instead of blocking, the idle watcher is invoked.
		499
		500	Most event loops unfortunately do not really support idle watchers (only
		501	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		502	will simply call the callback "from time to time".
		503
		504	Example: read lines from STDIN, but only process them when the program
		505	is otherwise idle:
		506
		507	my @lines; # read data
		508	my $idle_w;
		509	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		510	push @lines, scalar <STDIN>;
		511
		512	# start an idle watcher, if not already done
		513	$idle_w ||= AnyEvent->idle (cb => sub {
		514	# handle only one line, when there are lines left
		515	if (my $line = shift @lines) {
		516	print "handled when idle: $line";
		517	} else {
		518	# otherwise disable the idle watcher again
		519	undef $idle_w;
		520	}
		521	});
		522	});
357		523
358	CONDITION VARIABLES	524	CONDITION VARIABLES
		525	$cv = AnyEvent->condvar;
		526
		527	$cv->send (<list>);
		528	my @res = $cv->recv;
		529
359	If you are familiar with some event loops you will know that all of them	530	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	531	require you to run some blocking "loop", "run" or similar function that
361	will actively watch for new events and call your callbacks.	532	will actively watch for new events and call your callbacks.
362		533
363	AnyEvent is different, it expects somebody else to run the event loop	534	AnyEvent is slightly different: it expects somebody else to run the
364	and will only block when necessary (usually when told by the user).	535	event loop and will only block when necessary (usually when told by the
		536	user).
365		537
366	The instrument to do that is called a "condition variable", so called	538	The instrument to do that is called a "condition variable", so called
367	because they represent a condition that must become true.	539	because they represent a condition that must become true.
		540
		541	Now is probably a good time to look at the examples further below.
368		542
369	Condition variables can be created by calling the "AnyEvent->condvar"	543	Condition variables can be created by calling the "AnyEvent->condvar"
370	method, usually without arguments. The only argument pair allowed is	544	method, usually without arguments. The only argument pair allowed is
371	"cb", which specifies a callback to be called when the condition	545	"cb", which specifies a callback to be called when the condition
372	variable becomes true.	546	variable becomes true, with the condition variable as the first argument
		547	(but not the results).
373		548
374	After creation, the condition variable is "false" until it becomes	549	After creation, the condition variable is "false" until it becomes
375	"true" by calling the "send" method (or calling the condition variable	550	"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	551	as if it were a callback, read about the caveats in the description for
377	the "->send" method).	552	the "->send" method).
…		…
379	Condition variables are similar to callbacks, except that you can	554	Condition variables are similar to callbacks, except that you can
380	optionally wait for them. They can also be called merge points - points	555	optionally wait for them. They can also be called merge points - points
381	in time where multiple outstanding events have been processed. And yet	556	in time where multiple outstanding events have been processed. And yet
382	another way to call them is transactions - each condition variable can	557	another way to call them is transactions - each condition variable can
383	be used to represent a transaction, which finishes at some point and	558	be used to represent a transaction, which finishes at some point and
384	delivers a result.	559	delivers a result. And yet some people know them as "futures" - a
		560	promise to compute/deliver something that you can wait for.
385		561
386	Condition variables are very useful to signal that something has	562	Condition variables are very useful to signal that something has
387	finished, for example, if you write a module that does asynchronous http	563	finished, for example, if you write a module that does asynchronous http
388	requests, then a condition variable would be the ideal candidate to	564	requests, then a condition variable would be the ideal candidate to
389	signal the availability of results. The user can either act when the	565	signal the availability of results. The user can either act when the
…		…
423	after => 1,	599	after => 1,
424	cb => sub { $result_ready->send },	600	cb => sub { $result_ready->send },
425	);	601	);
426		602
427	# this "blocks" (while handling events) till the callback	603	# this "blocks" (while handling events) till the callback
428	# calls send	604	# calls ->send
429	$result_ready->recv;	605	$result_ready->recv;
430		606
431	Example: wait for a timer, but take advantage of the fact that condition	607	Example: wait for a timer, but take advantage of the fact that condition
432	variables are also code references.	608	variables are also callable directly.
433		609
434	my $done = AnyEvent->condvar;	610	my $done = AnyEvent->condvar;
435	my $delay = AnyEvent->timer (after => 5, cb => $done);	611	my $delay = AnyEvent->timer (after => 5, cb => $done);
436	$done->recv;	612	$done->recv;
		613
		614	Example: Imagine an API that returns a condvar and doesn't support
		615	callbacks. This is how you make a synchronous call, for example from the
		616	main program:
		617
		618	use AnyEvent::CouchDB;
		619
		620	...
		621
		622	my @info = $couchdb->info->recv;
		623
		624	And this is how you would just set a callback to be called whenever the
		625	results are available:
		626
		627	$couchdb->info->cb (sub {
		628	my @info = $_[0]->recv;
		629	});
437		630
438	METHODS FOR PRODUCERS	631	METHODS FOR PRODUCERS
439	These methods should only be used by the producing side, i.e. the	632	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	633	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	634	producer side which creates the condvar in most cases, but it isn't
…		…
451		644
452	Any arguments passed to the "send" call will be returned by all	645	Any arguments passed to the "send" call will be returned by all
453	future "->recv" calls.	646	future "->recv" calls.
454		647
455	Condition variables are overloaded so one can call them directly (as	648	Condition variables are overloaded so one can call them directly (as
456	a code reference). Calling them directly is the same as calling	649	if they were a code reference). Calling them directly is the same as
457	"send". Note, however, that many C-based event loops do not handle	650	calling "send".
458	overloading, so as tempting as it may be, passing a condition
459	variable instead of a callback does not work. Both the pure perl and
460	EV loops support overloading, however, as well as all functions that
461	use perl to invoke a callback (as in AnyEvent::Socket and
462	AnyEvent::DNS for example).
463		651
464	$cv->croak ($error)	652	$cv->croak ($error)
465	Similar to send, but causes all call's to "->recv" to invoke	653	Similar to send, but causes all call's to "->recv" to invoke
466	"Carp::croak" with the given error message/object/scalar.	654	"Carp::croak" with the given error message/object/scalar.
467		655
468	This can be used to signal any errors to the condition variable	656	This can be used to signal any errors to the condition variable
469	user/consumer.	657	user/consumer. Doing it this way instead of calling "croak" directly
		658	delays the error detetcion, but has the overwhelmign advantage that
		659	it diagnoses the error at the place where the result is expected,
		660	and not deep in some event clalback without connection to the actual
		661	code causing the problem.
470		662
471	$cv->begin ([group callback])	663	$cv->begin ([group callback])
472	$cv->end	664	$cv->end
473	These two methods are EXPERIMENTAL and MIGHT CHANGE.
474
475	These two methods can be used to combine many transactions/events	665	These two methods can be used to combine many transactions/events
476	into one. For example, a function that pings many hosts in parallel	666	into one. For example, a function that pings many hosts in parallel
477	might want to use a condition variable for the whole process.	667	might want to use a condition variable for the whole process.
478		668
479	Every call to "->begin" will increment a counter, and every call to	669	Every call to "->begin" will increment a counter, and every call to
480	"->end" will decrement it. If the counter reaches 0 in "->end", the	670	"->end" will decrement it. If the counter reaches 0 in "->end", the
481	(last) callback passed to "begin" will be executed. That callback is	671	(last) callback passed to "begin" will be executed, passing the
482	*supposed* to call "->send", but that is not required. If no	672	condvar as first argument. That callback is *supposed* to call
		673	"->send", but that is not required. If no group callback was set,
483	callback was set, "send" will be called without any arguments.	674	"send" will be called without any arguments.
484		675
485	Let's clarify this with the ping example:	676	You can think of "$cv->send" giving you an OR condition (one call
		677	sends), while "$cv->begin" and "$cv->end" giving you an AND
		678	condition (all "begin" calls must be "end"'ed before the condvar
		679	sends).
		680
		681	Let's start with a simple example: you have two I/O watchers (for
		682	example, STDOUT and STDERR for a program), and you want to wait for
		683	both streams to close before activating a condvar:
486		684
487	my $cv = AnyEvent->condvar;	685	my $cv = AnyEvent->condvar;
488		686
		687	$cv->begin; # first watcher
		688	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		689	defined sysread $fh1, my $buf, 4096
		690	or $cv->end;
		691	});
		692
		693	$cv->begin; # second watcher
		694	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		695	defined sysread $fh2, my $buf, 4096
		696	or $cv->end;
		697	});
		698
		699	$cv->recv;
		700
		701	This works because for every event source (EOF on file handle),
		702	there is one call to "begin", so the condvar waits for all calls to
		703	"end" before sending.
		704
		705	The ping example mentioned above is slightly more complicated, as
		706	the there are results to be passwd back, and the number of tasks
		707	that are begung can potentially be zero:
		708
		709	my $cv = AnyEvent->condvar;
		710
489	my %result;	711	my %result;
490	$cv->begin (sub { $cv->send (\%result) });	712	$cv->begin (sub { shift->send (\%result) });
491		713
492	for my $host (@list_of_hosts) {	714	for my $host (@list_of_hosts) {
493	$cv->begin;	715	$cv->begin;
494	ping_host_then_call_callback $host, sub {	716	ping_host_then_call_callback $host, sub {
495	$result{$host} = ...;	717	$result{$host} = ...;
…		…
510	the loop, which serves two important purposes: first, it sets the	732	the loop, which serves two important purposes: first, it sets the
511	callback to be called once the counter reaches 0, and second, it	733	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	734	ensures that "send" is called even when "no" hosts are being pinged
513	(the loop doesn't execute once).	735	(the loop doesn't execute once).
514		736
515	This is the general pattern when you "fan out" into multiple	737	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	738	potentially none) subrequests: use an outer "begin"/"end" pair to
517	ensure "end" is called at least once, and then, for each subrequest	739	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	740	for each subrequest you start, call "begin" and for each subrequest
519	"end".	741	you finish, call "end".
520		742
521	METHODS FOR CONSUMERS	743	METHODS FOR CONSUMERS
522	These methods should only be used by the consuming side, i.e. the code	744	These methods should only be used by the consuming side, i.e. the code
523	awaits the condition.	745	awaits the condition.
524		746
…		…
533	function will call "croak".	755	function will call "croak".
534		756
535	In list context, all parameters passed to "send" will be returned,	757	In list context, all parameters passed to "send" will be returned,
536	in scalar context only the first one will be returned.	758	in scalar context only the first one will be returned.
537		759
		760	Note that doing a blocking wait in a callback is not supported by
		761	any event loop, that is, recursive invocation of a blocking "->recv"
		762	is not allowed, and the "recv" call will "croak" if such a condition
		763	is detected. This condition can be slightly loosened by using
		764	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		765	thread that doesn't run the event loop itself.
		766
538	Not all event models support a blocking wait - some die in that case	767	Not all event models support a blocking wait - some die in that case
539	(programs might want to do that to stay interactive), so *if you are	768	(programs might want to do that to stay interactive), so *if you are
540	using this from a module, never require a blocking wait*, but let	769	using this from a module, never require a blocking wait*. Instead,
541	the caller decide whether the call will block or not (for example,	770	let the caller decide whether the call will block or not (for
542	by coupling condition variables with some kind of request results	771	example, by coupling condition variables with some kind of request
543	and supporting callbacks so the caller knows that getting the result	772	results and supporting callbacks so the caller knows that getting
544	will not block, while still supporting blocking waits if the caller	773	the result will not block, while still supporting blocking waits if
545	so desires).	774	the caller so desires).
546
547	Another reason *never* to "->recv" in a module is that you cannot
548	sensibly have two "->recv"'s in parallel, as that would require
549	multiple interpreters or coroutines/threads, none of which
550	"AnyEvent" can supply.
551
552	The Coro module, however, *can* and *does* supply coroutines and, in
553	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
554	versions and also integrates coroutines into AnyEvent, making
555	blocking "->recv" calls perfectly safe as long as they are done from
556	another coroutine (one that doesn't run the event loop).
557		775
558	You can ensure that "-recv" never blocks by setting a callback and	776	You can ensure that "-recv" never blocks by setting a callback and
559	only calling "->recv" from within that callback (or at a later	777	only calling "->recv" from within that callback (or at a later
560	time). This will work even when the event loop does not support	778	time). This will work even when the event loop does not support
561	blocking waits otherwise.	779	blocking waits otherwise.
562		780
563	$bool = $cv->ready	781	$bool = $cv->ready
564	Returns true when the condition is "true", i.e. whether "send" or	782	Returns true when the condition is "true", i.e. whether "send" or
565	"croak" have been called.	783	"croak" have been called.
566		784
567	$cb = $cv->cb ([new callback])	785	$cb = $cv->cb ($cb->($cv))
568	This is a mutator function that returns the callback set and	786	This is a mutator function that returns the callback set and
569	optionally replaces it before doing so.	787	optionally replaces it before doing so.
570		788
571	The callback will be called when the condition becomes "true", i.e.	789	The callback will be called when the condition becomes (or already
572	when "send" or "croak" are called. Calling "recv" inside the	790	was) "true", i.e. when "send" or "croak" are called (or were
573	callback or at any later time is guaranteed not to block.	791	called), with the only argument being the condition variable itself.
		792	Calling "recv" inside the callback or at any later time is
		793	guaranteed not to block.
		794
		795	SUPPORTED EVENT LOOPS/BACKENDS
		796	The available backend classes are (every class has its own manpage):
		797
		798	Backends that are autoprobed when no other event loop can be found.
		799	EV is the preferred backend when no other event loop seems to be in
		800	use. If EV is not installed, then AnyEvent will fall back to its own
		801	pure-perl implementation, which is available everywhere as it comes
		802	with AnyEvent itself.
		803
		804	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		805	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		806
		807	Backends that are transparently being picked up when they are used.
		808	These will be used when they are currently loaded when the first
		809	watcher is created, in which case it is assumed that the application
		810	is using them. This means that AnyEvent will automatically pick the
		811	right backend when the main program loads an event module before
		812	anything starts to create watchers. Nothing special needs to be done
		813	by the main program.
		814
		815	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		816	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		817	AnyEvent::Impl::Tk based on Tk, very broken.
		818	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		819	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		820	AnyEvent::Impl::Irssi used when running within irssi.
		821
		822	Backends with special needs.
		823	Qt requires the Qt::Application to be instantiated first, but will
		824	otherwise be picked up automatically. As long as the main program
		825	instantiates the application before any AnyEvent watchers are
		826	created, everything should just work.
		827
		828	AnyEvent::Impl::Qt based on Qt.
		829
		830	Support for IO::Async can only be partial, as it is too broken and
		831	architecturally limited to even support the AnyEvent API. It also is
		832	the only event loop that needs the loop to be set explicitly, so it
		833	can only be used by a main program knowing about AnyEvent. See
		834	AnyEvent::Impl::Async for the gory details.
		835
		836	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		837
		838	Event loops that are indirectly supported via other backends.
		839	Some event loops can be supported via other modules:
		840
		841	There is no direct support for WxWidgets (Wx) or Prima.
		842
		843	WxWidgets has no support for watching file handles. However, you can
		844	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		845	simply polls 20 times per second, which was considered to be too
		846	horrible to even consider for AnyEvent.
		847
		848	Prima is not supported as nobody seems to be using it, but it has a
		849	POE backend, so it can be supported through POE.
		850
		851	AnyEvent knows about both Prima and Wx, however, and will try to
		852	load POE when detecting them, in the hope that POE will pick them
		853	up, in which case everything will be automatic.
574		854
575	GLOBAL VARIABLES AND FUNCTIONS	855	GLOBAL VARIABLES AND FUNCTIONS
		856	These are not normally required to use AnyEvent, but can be useful to
		857	write AnyEvent extension modules.
		858
576	$AnyEvent::MODEL	859	$AnyEvent::MODEL
577	Contains "undef" until the first watcher is being created. Then it	860	Contains "undef" until the first watcher is being created, before
		861	the backend has been autodetected.
		862
578	contains the event model that is being used, which is the name of	863	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	864	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	865	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*).	866	other class in the case AnyEvent has been extended at runtime (e.g.
582		867	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		868
604	AnyEvent::detect	869	AnyEvent::detect
605	Returns $AnyEvent::MODEL, forcing autodetection of the event model	870	Returns $AnyEvent::MODEL, forcing autodetection of the event model
606	if necessary. You should only call this function right before you	871	if necessary. You should only call this function right before you
607	would have created an AnyEvent watcher anyway, that is, as late as	872	would have created an AnyEvent watcher anyway, that is, as late as
608	possible at runtime.	873	possible at runtime, and not e.g. while initialising of your module.
		874
		875	If you need to do some initialisation before AnyEvent watchers are
		876	created, use "post_detect".
609		877
610	$guard = AnyEvent::post_detect { BLOCK }	878	$guard = AnyEvent::post_detect { BLOCK }
611	Arranges for the code block to be executed as soon as the event	879	Arranges for the code block to be executed as soon as the event
612	model is autodetected (or immediately if this has already happened).	880	model is autodetected (or immediately if this has already happened).
613		881
		882	The block will be executed *after* the actual backend has been
		883	detected ($AnyEvent::MODEL is set), but *before* any watchers have
		884	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		885	other initialisations - see the sources of AnyEvent::Strict or
		886	AnyEvent::AIO to see how this is used.
		887
		888	The most common usage is to create some global watchers, without
		889	forcing event module detection too early, for example, AnyEvent::AIO
		890	creates and installs the global IO::AIO watcher in a "post_detect"
		891	block to avoid autodetecting the event module at load time.
		892
614	If called in scalar or list context, then it creates and returns an	893	If called in scalar or list context, then it creates and returns an
615	object that automatically removes the callback again when it is	894	object that automatically removes the callback again when it is
		895	destroyed (or "undef" when the hook was immediately executed). See
616	destroyed. See Coro::BDB for a case where this is useful.	896	AnyEvent::AIO for a case where this is useful.
		897
		898	Example: Create a watcher for the IO::AIO module and store it in
		899	$WATCHER. Only do so after the event loop is initialised, though.
		900
		901	our WATCHER;
		902
		903	my $guard = AnyEvent::post_detect {
		904	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		905	};
		906
		907	# the ||= is important in case post_detect immediately runs the block,
		908	# as to not clobber the newly-created watcher. assigning both watcher and
		909	# post_detect guard to the same variable has the advantage of users being
		910	# able to just C<undef $WATCHER> if the watcher causes them grief.
		911
		912	$WATCHER ||= $guard;
617		913
618	@AnyEvent::post_detect	914	@AnyEvent::post_detect
619	If there are any code references in this array (you can "push" to it	915	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	916	before or after loading AnyEvent), then they will called directly
621	after the event loop has been chosen.	917	after the event loop has been chosen.
622		918
623	You should check $AnyEvent::MODEL before adding to this array,	919	You should check $AnyEvent::MODEL before adding to this array,
624	though: if it contains a true value then the event loop has already	920	though: if it is defined then the event loop has already been
625	been detected, and the array will be ignored.	921	detected, and the array will be ignored.
626		922
627	Best use "AnyEvent::post_detect { BLOCK }" instead.	923	Best use "AnyEvent::post_detect { BLOCK }" when your application
		924	allows it,as it takes care of these details.
		925
		926	This variable is mainly useful for modules that can do something
		927	useful when AnyEvent is used and thus want to know when it is
		928	initialised, but do not need to even load it by default. This array
		929	provides the means to hook into AnyEvent passively, without loading
		930	it.
628		931
629	WHAT TO DO IN A MODULE	932	WHAT TO DO IN A MODULE
630	As a module author, you should "use AnyEvent" and call AnyEvent methods	933	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.	934	freely, but you should not load a specific event module or rely on it.
632		935
…		…
683	variable somewhere, waiting for it, and sending it when the program	986	variable somewhere, waiting for it, and sending it when the program
684	should exit cleanly.	987	should exit cleanly.
685		988
686	OTHER MODULES	989	OTHER MODULES
687	The following is a non-exhaustive list of additional modules that use	990	The following is a non-exhaustive list of additional modules that use
688	AnyEvent and can therefore be mixed easily with other AnyEvent modules	991	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	992	AnyEvent modules and other event loops in the same program. Some of the
690	available via CPAN.	993	modules come with AnyEvent, most are available via CPAN.
691		994
692	AnyEvent::Util	995	AnyEvent::Util
693	Contains various utility functions that replace often-used but	996	Contains various utility functions that replace often-used but
694	blocking functions such as "inet_aton" by event-/callback-based	997	blocking functions such as "inet_aton" by event-/callback-based
695	versions.	998	versions.
696
697	AnyEvent::Handle
698	Provide read and write buffers and manages watchers for reads and
699	writes.
700		999
701	AnyEvent::Socket	1000	AnyEvent::Socket
702	Provides various utility functions for (internet protocol) sockets,	1001	Provides various utility functions for (internet protocol) sockets,
703	addresses and name resolution. Also functions to create non-blocking	1002	addresses and name resolution. Also functions to create non-blocking
704	tcp connections or tcp servers, with IPv6 and SRV record support and	1003	tcp connections or tcp servers, with IPv6 and SRV record support and
705	more.	1004	more.
706		1005
		1006	AnyEvent::Handle
		1007	Provide read and write buffers, manages watchers for reads and
		1008	writes, supports raw and formatted I/O, I/O queued and fully
		1009	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
		1010
707	AnyEvent::DNS	1011	AnyEvent::DNS
708	Provides rich asynchronous DNS resolver capabilities.	1012	Provides rich asynchronous DNS resolver capabilities.
709		1013
		1014	AnyEvent::HTTP
		1015	A simple-to-use HTTP library that is capable of making a lot of
		1016	concurrent HTTP requests.
		1017
710	AnyEvent::HTTPD	1018	AnyEvent::HTTPD
711	Provides a simple web application server framework.	1019	Provides a simple web application server framework.
712		1020
713	AnyEvent::FastPing	1021	AnyEvent::FastPing
714	The fastest ping in the west.	1022	The fastest ping in the west.
715		1023
		1024	AnyEvent::DBI
		1025	Executes DBI requests asynchronously in a proxy process.
		1026
		1027	AnyEvent::AIO
		1028	Truly asynchronous I/O, should be in the toolbox of every event
		1029	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		1030	together.
		1031
		1032	AnyEvent::BDB
		1033	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
		1034	fuses BDB and AnyEvent together.
		1035
		1036	AnyEvent::GPSD
		1037	A non-blocking interface to gpsd, a daemon delivering GPS
		1038	information.
		1039
		1040	AnyEvent::IRC
		1041	AnyEvent based IRC client module family (replacing the older
716	Net::IRC3	1042	Net::IRC3).
717	AnyEvent based IRC client module family.
718		1043
719	Net::XMPP2	1044	AnyEvent::XMPP
720	AnyEvent based XMPP (Jabber protocol) module family.	1045	AnyEvent based XMPP (Jabber protocol) module family (replacing the
		1046	older Net::XMPP2>.
		1047
		1048	AnyEvent::IGS
		1049	A non-blocking interface to the Internet Go Server protocol (used by
		1050	App::IGS).
721		1051
722	Net::FCP	1052	Net::FCP
723	AnyEvent-based implementation of the Freenet Client Protocol,	1053	AnyEvent-based implementation of the Freenet Client Protocol,
724	birthplace of AnyEvent.	1054	birthplace of AnyEvent.
725		1055
…		…
727	High level API for event-based execution flow control.	1057	High level API for event-based execution flow control.
728		1058
729	Coro	1059	Coro
730	Has special support for AnyEvent via Coro::AnyEvent.	1060	Has special support for AnyEvent via Coro::AnyEvent.
731		1061
732	AnyEvent::AIO, IO::AIO	1062	SIMPLIFIED AE API
733	Truly asynchronous I/O, should be in the toolbox of every event	1063	Starting with version 5.0, AnyEvent officially supports a second, much
734	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent	1064	simpler, API that is designed to reduce the calling, typing and memory
735	together.	1065	overhead.
736		1066
737	AnyEvent::BDB, BDB	1067	See the AE manpage for details.
738	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
739	fuses IO::AIO and AnyEvent together.
740		1068
741	IO::Lambda	1069	ERROR AND EXCEPTION HANDLING
742	The lambda approach to I/O - don't ask, look there. Can use	1070	In general, AnyEvent does not do any error handling - it relies on the
743	AnyEvent.	1071	caller to do that if required. The AnyEvent::Strict module (see also the
		1072	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
		1073	checking of all AnyEvent methods, however, which is highly useful during
		1074	development.
744		1075
745	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1076	As for exception handling (i.e. runtime errors and exceptions thrown
746	This is an advanced topic that you do not normally need to use AnyEvent	1077	while executing a callback), this is not only highly event-loop
747	in a module. This section is only of use to event loop authors who want	1078	specific, but also not in any way wrapped by this module, as this is the
748	to provide AnyEvent compatibility.	1079	job of the main program.
749		1080
750	If you need to support another event library which isn't directly	1081	The pure perl event loop simply re-throws the exception (usually within
751	supported by AnyEvent, you can supply your own interface to it by	1082	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
752	pushing, before the first watcher gets created, the package name of the	1083	Glib uses "install_exception_handler" and so on.
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		1084
788	ENVIRONMENT VARIABLES	1085	ENVIRONMENT VARIABLES
789	The following environment variables are used by this module:	1086	The following environment variables are used by this module or its
		1087	submodules.
		1088
		1089	Note that AnyEvent will remove *all* environment variables starting with
		1090	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1091	enabled.
790		1092
791	"PERL_ANYEVENT_VERBOSE"	1093	"PERL_ANYEVENT_VERBOSE"
792	By default, AnyEvent will be completely silent except in fatal	1094	By default, AnyEvent will be completely silent except in fatal
793	conditions. You can set this environment variable to make AnyEvent	1095	conditions. You can set this environment variable to make AnyEvent
794	more talkative.	1096	more talkative.
…		…
797	conditions, such as not being able to load the event model specified	1099	conditions, such as not being able to load the event model specified
798	by "PERL_ANYEVENT_MODEL".	1100	by "PERL_ANYEVENT_MODEL".
799		1101
800	When set to 2 or higher, cause AnyEvent to report to STDERR which	1102	When set to 2 or higher, cause AnyEvent to report to STDERR which
801	event model it chooses.	1103	event model it chooses.
		1104
		1105	When set to 8 or higher, then AnyEvent will report extra information
		1106	on which optional modules it loads and how it implements certain
		1107	features.
		1108
		1109	"PERL_ANYEVENT_STRICT"
		1110	AnyEvent does not do much argument checking by default, as thorough
		1111	argument checking is very costly. Setting this variable to a true
		1112	value will cause AnyEvent to load "AnyEvent::Strict" and then to
		1113	thoroughly check the arguments passed to most method calls. If it
		1114	finds any problems, it will croak.
		1115
		1116	In other words, enables "strict" mode.
		1117
		1118	Unlike "use strict" (or it's modern cousin, "use common::sense", it
		1119	is definitely recommended to keep it off in production. Keeping
		1120	"PERL_ANYEVENT_STRICT=1" in your environment while developing
		1121	programs can be very useful, however.
802		1122
803	"PERL_ANYEVENT_MODEL"	1123	"PERL_ANYEVENT_MODEL"
804	This can be used to specify the event model to be used by AnyEvent,	1124	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	1125	before auto detection and -probing kicks in. It must be a string
806	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1126	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
811	This functionality might change in future versions.	1131	This functionality might change in future versions.
812		1132
813	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1133	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
814	could start your program like this:	1134	could start your program like this:
815		1135
816	PERL_ANYEVENT_MODEL=Perl perl ...	1136	PERL_ANYEVENT_MODEL=Perl perl ...
817		1137
818	"PERL_ANYEVENT_PROTOCOLS"	1138	"PERL_ANYEVENT_PROTOCOLS"
819	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1139	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
820	preferences for IPv4 or IPv6. The default is unspecified (and might	1140	preferences for IPv4 or IPv6. The default is unspecified (and might
821	change, or be the result of auto probing).	1141	change, or be the result of auto probing).
…		…
825	mentioned will be used, and preference will be given to protocols	1145	mentioned will be used, and preference will be given to protocols
826	mentioned earlier in the list.	1146	mentioned earlier in the list.
827		1147
828	This variable can effectively be used for denial-of-service attacks	1148	This variable can effectively be used for denial-of-service attacks
829	against local programs (e.g. when setuid), although the impact is	1149	against local programs (e.g. when setuid), although the impact is
830	likely small, as the program has to handle connection errors	1150	likely small, as the program has to handle conenction and other
831	already-	1151	failures anyways.
832		1152
833	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1153	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
834	IPv6, but support both and try to use both.	1154	IPv6, but support both and try to use both.
835	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1155	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
836	resolve or contact IPv6 addresses.	1156	resolve or contact IPv6 addresses.
…		…
847	EDNS0 in its DNS requests.	1167	EDNS0 in its DNS requests.
848		1168
849	"PERL_ANYEVENT_MAX_FORKS"	1169	"PERL_ANYEVENT_MAX_FORKS"
850	The maximum number of child processes that	1170	The maximum number of child processes that
851	"AnyEvent::Util::fork_call" will create in parallel.	1171	"AnyEvent::Util::fork_call" will create in parallel.
		1172
		1173	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1174	The default value for the "max_outstanding" parameter for the
		1175	default DNS resolver - this is the maximum number of parallel DNS
		1176	requests that are sent to the DNS server.
		1177
		1178	"PERL_ANYEVENT_RESOLV_CONF"
		1179	The file to use instead of /etc/resolv.conf (or OS-specific
		1180	configuration) in the default resolver. When set to the empty
		1181	string, no default config will be used.
		1182
		1183	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1184	When neither "ca_file" nor "ca_path" was specified during
		1185	AnyEvent::TLS context creation, and either of these environment
		1186	variables exist, they will be used to specify CA certificate
		1187	locations instead of a system-dependent default.
		1188
		1189	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1190	When these are set to 1, then the respective modules are not loaded.
		1191	Mostly good for testing AnyEvent itself.
		1192
		1193	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1194	This is an advanced topic that you do not normally need to use AnyEvent
		1195	in a module. This section is only of use to event loop authors who want
		1196	to provide AnyEvent compatibility.
		1197
		1198	If you need to support another event library which isn't directly
		1199	supported by AnyEvent, you can supply your own interface to it by
		1200	pushing, before the first watcher gets created, the package name of the
		1201	event module and the package name of the interface to use onto
		1202	@AnyEvent::REGISTRY. You can do that before and even without loading
		1203	AnyEvent, so it is reasonably cheap.
		1204
		1205	Example:
		1206
		1207	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
		1208
		1209	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
		1210	package/class when it finds the "urxvt" package/module is already
		1211	loaded.
		1212
		1213	When AnyEvent is loaded and asked to find a suitable event model, it
		1214	will first check for the presence of urxvt by trying to "use" the
		1215	"urxvt::anyevent" module.
		1216
		1217	The class should provide implementations for all watcher types. See
		1218	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
		1219	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
		1220	the sources.
		1221
		1222	If you don't provide "signal" and "child" watchers than AnyEvent will
		1223	provide suitable (hopefully) replacements.
		1224
		1225	The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt)
		1226	terminal emulator uses the above line as-is. An interface isn't included
		1227	in AnyEvent because it doesn't make sense outside the embedded
		1228	interpreter inside *rxvt-unicode*, and it is updated and maintained as
		1229	part of the *rxvt-unicode* distribution.
		1230
		1231	*rxvt-unicode* also cheats a bit by not providing blocking access to
		1232	condition variables: code blocking while waiting for a condition will
		1233	"die". This still works with most modules/usages, and blocking calls
		1234	must not be done in an interactive application, so it makes sense.
852		1235
853	EXAMPLE PROGRAM	1236	EXAMPLE PROGRAM
854	The following program uses an I/O watcher to read data from STDIN, a	1237	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	1238	timer to display a message once per second, and a condition variable to
856	quit the program when the user enters quit:	1239	quit the program when the user enters quit:
…		…
868	warn "read: $input\n"; # output what has been read	1251	warn "read: $input\n"; # output what has been read
869	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1252	$cv->send if $input =~ /^q/i; # quit program if /^q/i
870	},	1253	},
871	);	1254	);
872		1255
873	my $time_watcher; # can only be used once
874
875	sub new_timer {
876	$timer = AnyEvent->timer (after => 1, cb => sub {	1256	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
877	warn "timeout\n"; # print 'timeout' about every second	1257	warn "timeout\n"; # print 'timeout' at most every second
878	&new_timer; # and restart the time
879	});
880	}	1258	});
881
882	new_timer; # create first timer
883		1259
884	$cv->recv; # wait until user enters /^q/i	1260	$cv->recv; # wait until user enters /^q/i
885		1261
886	REAL-WORLD EXAMPLE	1262	REAL-WORLD EXAMPLE
887	Consider the Net::FCP module. It features (among others) the following	1263	Consider the Net::FCP module. It features (among others) the following
…		…
1014	through AnyEvent. The benchmark creates a lot of timers (with a zero	1390	through AnyEvent. The benchmark creates a lot of timers (with a zero
1015	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1391	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1016	which it is), lets them fire exactly once and destroys them again.	1392	which it is), lets them fire exactly once and destroys them again.
1017		1393
1018	Source code for this benchmark is found as eg/bench in the AnyEvent	1394	Source code for this benchmark is found as eg/bench in the AnyEvent
1019	distribution.	1395	distribution. It uses the AE interface, which makes a real difference
		1396	for the EV and Perl backends only.
1020		1397
1021	Explanation of the columns	1398	Explanation of the columns
1022	*watcher* is the number of event watchers created/destroyed. Since	1399	*watcher* is the number of event watchers created/destroyed. Since
1023	different event models feature vastly different performances, each event	1400	different event models feature vastly different performances, each event
1024	loop was given a number of watchers so that overall runtime is	1401	loop was given a number of watchers so that overall runtime is
…		…
1043	*destroy* is the time, in microseconds, that it takes to destroy a	1420	*destroy* is the time, in microseconds, that it takes to destroy a
1044	single watcher.	1421	single watcher.
1045		1422
1046	Results	1423	Results
1047	name watchers bytes create invoke destroy comment	1424	name watchers bytes create invoke destroy comment
1048	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1425	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1049	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1426	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1050	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1427	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1051	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1428	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1052	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1429	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1053	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1430	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		1431	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		1432	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1054	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1433	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1055	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1434	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1056	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1435	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1057	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1436	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1058		1437
1059	Discussion	1438	Discussion
1060	The benchmark does *not* measure scalability of the event loop very	1439	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)	1440	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	1441	can never compete with an event loop that uses epoll when the number of
…		…
1073	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1452	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1074	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1453	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1075	CPU cycles with POE.	1454	CPU cycles with POE.
1076		1455
1077	"EV" is the sole leader regarding speed and memory use, which are both	1456	"EV" is the sole leader regarding speed and memory use, which are both
1078	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1457	maximal/minimal, respectively. When using the AE API there is zero
		1458	overhead (when going through the AnyEvent API create is about 5-6 times
		1459	slower, with other times being equal, so still uses far less memory than
1079	far less memory than any other event loop and is still faster than Event	1460	any other event loop and is still faster than Event natively).
1080	natively.
1081		1461
1082	The pure perl implementation is hit in a few sweet spots (both the	1462	The pure perl implementation is hit in a few sweet spots (both the
1083	constant timeout and the use of a single fd hit optimisations in the	1463	constant timeout and the use of a single fd hit optimisations in the
1084	perl interpreter and the backend itself). Nevertheless this shows that	1464	perl interpreter and the backend itself). Nevertheless this shows that
1085	it adds very little overhead in itself. Like any select-based backend	1465	it adds very little overhead in itself. Like any select-based backend
…		…
1087	few of them active), of course, but this was not subject of this	1467	few of them active), of course, but this was not subject of this
1088	benchmark.	1468	benchmark.
1089		1469
1090	The "Event" module has a relatively high setup and callback invocation	1470	The "Event" module has a relatively high setup and callback invocation
1091	cost, but overall scores in on the third place.	1471	cost, but overall scores in on the third place.
		1472
		1473	"IO::Async" performs admirably well, about on par with "Event", even
		1474	when using its pure perl backend.
1092		1475
1093	"Glib"'s memory usage is quite a bit higher, but it features a faster	1476	"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".	1477	callback invocation and overall ends up in the same class as "Event".
1095	However, Glib scales extremely badly, doubling the number of watchers	1478	However, Glib scales extremely badly, doubling the number of watchers
1096	increases the processing time by more than a factor of four, making it	1479	increases the processing time by more than a factor of four, making it
…		…
1152	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1535	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1153	100 (1%) are active. This mirrors the activity of large servers with	1536	100 (1%) are active. This mirrors the activity of large servers with
1154	many connections, most of which are idle at any one point in time.	1537	many connections, most of which are idle at any one point in time.
1155		1538
1156	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1539	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1157	distribution.	1540	distribution. It uses the AE interface, which makes a real difference
		1541	for the EV and Perl backends only.
1158		1542
1159	Explanation of the columns	1543	Explanation of the columns
1160	*sockets* is the number of sockets, and twice the number of "servers"	1544	*sockets* is the number of sockets, and twice the number of "servers"
1161	(as each server has a read and write socket end).	1545	(as each server has a read and write socket end).
1162		1546
…		…
1167	single "request", that is, reading the token from the pipe and	1551	single "request", that is, reading the token from the pipe and
1168	forwarding it to another server. This includes deleting the old timeout	1552	forwarding it to another server. This includes deleting the old timeout
1169	and creating a new one that moves the timeout into the future.	1553	and creating a new one that moves the timeout into the future.
1170		1554
1171	Results	1555	Results
1172	name sockets create request	1556	name sockets create request
1173	EV 20000 69.01 11.16	1557	EV 20000 62.66 7.99
1174	Perl 20000 73.32 35.87	1558	Perl 20000 68.32 32.64
1175	Event 20000 212.62 257.32	1559	IOAsync 20000 174.06 101.15 epoll
1176	Glib 20000 651.16 1896.30	1560	IOAsync 20000 174.67 610.84 poll
		1561	Event 20000 202.69 242.91
		1562	Glib 20000 557.01 1689.52
1177	POE 20000 349.67 12317.24 uses POE::Loop::Event	1563	POE 20000 341.54 12086.32 uses POE::Loop::Event
1178		1564
1179	Discussion	1565	Discussion
1180	This benchmark *does* measure scalability and overall performance of the	1566	This benchmark *does* measure scalability and overall performance of the
1181	particular event loop.	1567	particular event loop.
1182		1568
1183	EV is again fastest. Since it is using epoll on my system, the setup	1569	EV is again fastest. Since it is using epoll on my system, the setup
1184	time is relatively high, though.	1570	time is relatively high, though.
1185		1571
1186	Perl surprisingly comes second. It is much faster than the C-based event	1572	Perl surprisingly comes second. It is much faster than the C-based event
1187	loops Event and Glib.	1573	loops Event and Glib.
		1574
		1575	IO::Async performs very well when using its epoll backend, and still
		1576	quite good compared to Glib when using its pure perl backend.
1188		1577
1189	Event suffers from high setup time as well (look at its code and you	1578	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	1579	will understand why). Callback invocation also has a high overhead
1191	compared to the "$_->() for .."-style loop that the Perl event loop	1580	compared to the "$_->() for .."-style loop that the Perl event loop
1192	uses. Event uses select or poll in basically all documented	1581	uses. Event uses select or poll in basically all documented
…		…
1243		1632
1244	Summary	1633	Summary
1245	* C-based event loops perform very well with small number of watchers,	1634	* C-based event loops perform very well with small number of watchers,
1246	as the management overhead dominates.	1635	as the management overhead dominates.
1247		1636
		1637	THE IO::Lambda BENCHMARK
		1638	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1639	could be misinterpreted to make AnyEvent look bad. In fact, the
		1640	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1641	better (which shouldn't come as a surprise to anybody). As such, the
		1642	benchmark is fine, and mostly shows that the AnyEvent backend from
		1643	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1644	without the extra baggage? To explore this, I wrote the equivalent
		1645	benchmark for AnyEvent.
		1646
		1647	The benchmark itself creates an echo-server, and then, for 500 times,
		1648	connects to the echo server, sends a line, waits for the reply, and then
		1649	creates the next connection. This is a rather bad benchmark, as it
		1650	doesn't test the efficiency of the framework or much non-blocking I/O,
		1651	but it is a benchmark nevertheless.
		1652
		1653	name runtime
		1654	Lambda/select 0.330 sec
		1655	+ optimized 0.122 sec
		1656	Lambda/AnyEvent 0.327 sec
		1657	+ optimized 0.138 sec
		1658	Raw sockets/select 0.077 sec
		1659	POE/select, components 0.662 sec
		1660	POE/select, raw sockets 0.226 sec
		1661	POE/select, optimized 0.404 sec
		1662
		1663	AnyEvent/select/nb 0.085 sec
		1664	AnyEvent/EV/nb 0.068 sec
		1665	+state machine 0.134 sec
		1666
		1667	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1668	benchmarks actually make blocking connects and use 100% blocking I/O,
		1669	defeating the purpose of an event-based solution. All of the newly
		1670	written AnyEvent benchmarks use 100% non-blocking connects (using
		1671	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1672	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1673	connects generally require a lot more bookkeeping and event handling
		1674	than blocking connects (which involve a single syscall only).
		1675
		1676	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1677	offers similar expressive power as POE and IO::Lambda, using
		1678	conventional Perl syntax. This means that both the echo server and the
		1679	client are 100% non-blocking, further placing it at a disadvantage.
		1680
		1681	As you can see, the AnyEvent + EV combination even beats the
		1682	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1683	backend easily beats IO::Lambda and POE.
		1684
		1685	And even the 100% non-blocking version written using the high-level (and
		1686	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
		1687	higher level ("unoptimised") abstractions by a large margin, even though
		1688	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		1689
		1690	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1691	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1692	part of the IO::Lambda distribution and were used without any changes.
		1693
		1694	SIGNALS
		1695	AnyEvent currently installs handlers for these signals:
		1696
		1697	SIGCHLD
		1698	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
		1699	emulation for event loops that do not support them natively. Also,
		1700	some event loops install a similar handler.
		1701
		1702	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1703	then AnyEvent will reset it to default, to avoid losing child exit
		1704	statuses.
		1705
		1706	SIGPIPE
		1707	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
		1708	"undef" when AnyEvent gets loaded.
		1709
		1710	The rationale for this is that AnyEvent users usually do not really
		1711	depend on SIGPIPE delivery (which is purely an optimisation for
		1712	shell use, or badly-written programs), but "SIGPIPE" can cause
		1713	spurious and rare program exits as a lot of people do not expect
		1714	"SIGPIPE" when writing to some random socket.
		1715
		1716	The rationale for installing a no-op handler as opposed to ignoring
		1717	it is that this way, the handler will be restored to defaults on
		1718	exec.
		1719
		1720	Feel free to install your own handler, or reset it to defaults.
		1721
		1722	RECOMMENDED/OPTIONAL MODULES
		1723	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1724	it's built-in modules) are required to use it.
		1725
		1726	That does not mean that AnyEvent won't take advantage of some additional
		1727	modules if they are installed.
		1728
		1729	This section explains which additional modules will be used, and how
		1730	they affect AnyEvent's operation.
		1731
		1732	Async::Interrupt
		1733	This slightly arcane module is used to implement fast signal
		1734	handling: To my knowledge, there is no way to do completely
		1735	race-free and quick signal handling in pure perl. To ensure that
		1736	signals still get delivered, AnyEvent will start an interval timer
		1737	to wake up perl (and catch the signals) with some delay (default is
		1738	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1739
		1740	If this module is available, then it will be used to implement
		1741	signal catching, which means that signals will not be delayed, and
		1742	the event loop will not be interrupted regularly, which is more
		1743	efficient (and good for battery life on laptops).
		1744
		1745	This affects not just the pure-perl event loop, but also other event
		1746	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1747
		1748	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1749	natively, and either employ their own workarounds (POE) or use
		1750	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1751	Installing Async::Interrupt does nothing for those backends.
		1752
		1753	EV This module isn't really "optional", as it is simply one of the
		1754	backend event loops that AnyEvent can use. However, it is simply the
		1755	best event loop available in terms of features, speed and stability:
		1756	It supports the AnyEvent API optimally, implements all the watcher
		1757	types in XS, does automatic timer adjustments even when no monotonic
		1758	clock is available, can take avdantage of advanced kernel interfaces
		1759	such as "epoll" and "kqueue", and is the fastest backend *by far*.
		1760	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1761	Glib::EV).
		1762
		1763	Guard
		1764	The guard module, when used, will be used to implement
		1765	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1766	uses a lot less memory), but otherwise doesn't affect guard
		1767	operation much. It is purely used for performance.
		1768
		1769	JSON and JSON::XS
		1770	One of these modules is required when you want to read or write JSON
		1771	data via AnyEvent::Handle. It is also written in pure-perl, but can
		1772	take advantage of the ultra-high-speed JSON::XS module when it is
		1773	installed.
		1774
		1775	In fact, AnyEvent::Handle will use JSON::XS by default if it is
		1776	installed.
		1777
		1778	Net::SSLeay
		1779	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1780	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1781	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1782
		1783	Time::HiRes
		1784	This module is part of perl since release 5.008. It will be used
		1785	when the chosen event library does not come with a timing source on
		1786	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1787	additionally use it to try to use a monotonic clock for timing
		1788	stability.
		1789
1248	FORK	1790	FORK
1249	Most event libraries are not fork-safe. The ones who are usually are	1791	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.	1792	because they rely on inefficient but fork-safe "select" or "poll" calls.
1251	Only EV is fully fork-aware.	1793	Only EV is fully fork-aware.
1252		1794
		1795	This means that, in general, you cannot fork and do event processing in
		1796	the child if a watcher was created before the fork (which in turn
		1797	initialises the event library).
		1798
1253	If you have to fork, you must either do so *before* creating your first	1799	If you have to fork, you must either do so *before* creating your first
1254	watcher OR you must not use AnyEvent at all in the child.	1800	watcher OR you must not use AnyEvent at all in the child OR you must do
		1801	something completely out of the scope of AnyEvent.
		1802
		1803	The problem of doing event processing in the parent *and* the child is
		1804	much more complicated: even for backends that *are* fork-aware or
		1805	fork-safe, their behaviour is not usually what you want: fork clones all
		1806	watchers, that means all timers, I/O watchers etc. are active in both
		1807	parent and child, which is almost never what you want.
1255		1808
1256	SECURITY CONSIDERATIONS	1809	SECURITY CONSIDERATIONS
1257	AnyEvent can be forced to load any event model via	1810	AnyEvent can be forced to load any event model via
1258	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1811	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1259	to execute arbitrary code or directly gain access, it can easily be used	1812	to execute arbitrary code or directly gain access, it can easily be used
…		…
1262	model than specified in the variable.	1815	model than specified in the variable.
1263		1816
1264	You can make AnyEvent completely ignore this variable by deleting it	1817	You can make AnyEvent completely ignore this variable by deleting it
1265	before the first watcher gets created, e.g. with a "BEGIN" block:	1818	before the first watcher gets created, e.g. with a "BEGIN" block:
1266		1819
1267	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1820	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1268		1821
1269	use AnyEvent;	1822	use AnyEvent;
1270		1823
1271	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1824	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	1825	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).	1826	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
		1827	and $ENV{PERL_ANYEVENT_STRICT}.
		1828
		1829	Note that AnyEvent will remove *all* environment variables starting with
		1830	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1831	enabled.
		1832
		1833	BUGS
		1834	Perl 5.8 has numerous memleaks that sometimes hit this module and are
		1835	hard to work around. If you suffer from memleaks, first upgrade to Perl
		1836	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
		1837	annoying memleaks, such as leaking on "map" and "grep" but it is usually
		1838	not as pronounced).
1274		1839
1275	SEE ALSO	1840	SEE ALSO
1276	Utility functions: AnyEvent::Util.	1841	Utility functions: AnyEvent::Util.
1277		1842
1278	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1843	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1279	Event::Lib, Qt, POE.	1844	Event::Lib, Qt, POE.
1280		1845
1281	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1846	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1282	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1847	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1283	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1848	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1849	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1284		1850
1285	Non-blocking file handles, sockets, TCP clients and servers:	1851	Non-blocking file handles, sockets, TCP clients and servers:
1286	AnyEvent::Handle, AnyEvent::Socket.	1852	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1287		1853
1288	Asynchronous DNS: AnyEvent::DNS.	1854	Asynchronous DNS: AnyEvent::DNS.
1289		1855
1290	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1856	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1291		1857
1292	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1858	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1859	AnyEvent::HTTP.
1293		1860
1294	AUTHOR	1861	AUTHOR
1295	Marc Lehmann <schmorp@schmorp.de>	1862	Marc Lehmann <schmorp@schmorp.de>
1296	http://home.schmorp.de/	1863	http://home.schmorp.de/
1297		1864

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