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Comparing AnyEvent/README (file contents):
Revision 1.23 by root, Mon May 26 06:04:38 2008 UTC vs.
Revision 1.54 by root, Tue Sep 1 18:27:46 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
62	only offering the functionality that is necessary, in as thin as a	91	only offering the functionality that is necessary, in as thin as a
63	wrapper as technically possible.	92	wrapper as technically possible.
64		93
		94	Of course, AnyEvent comes with a big (and fully optional!) toolbox of
		95	useful functionality, such as an asynchronous DNS resolver, 100%
		96	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		97	such as Windows) and lots of real-world knowledge and workarounds for
		98	platform bugs and differences.
		99
65	Of course, if you want lots of policy (this can arguably be somewhat	100	Now, if you do want lots of policy (this can arguably be somewhat
66	useful) and you want to force your users to use the one and only event	101	useful) and you want to force your users to use the one and only event
67	model, you should not use this module.	102	model, you should not use this module.
68		103
69	DESCRIPTION	104	DESCRIPTION
70	AnyEvent provides an identical interface to multiple event loops. This	105	AnyEvent provides an identical interface to multiple event loops. This
99	starts using it, all bets are off. Maybe you should tell their authors	134	starts using it, all bets are off. Maybe you should tell their authors
100	to use AnyEvent so their modules work together with others seamlessly...	135	to use AnyEvent so their modules work together with others seamlessly...
101		136
102	The pure-perl implementation of AnyEvent is called	137	The pure-perl implementation of AnyEvent is called
103	"AnyEvent::Impl::Perl". Like other event modules you can load it	138	"AnyEvent::Impl::Perl". Like other event modules you can load it
104	explicitly.	139	explicitly and enjoy the high availability of that event loop :)
105		140
106	WATCHERS	141	WATCHERS
107	AnyEvent has the central concept of a watcher, which is an object that	142	AnyEvent has the central concept of a watcher, which is an object that
108	stores relevant data for each kind of event you are waiting for, such as	143	stores relevant data for each kind of event you are waiting for, such as
109	the callback to call, the file handle to watch, etc.	144	the callback to call, the file handle to watch, etc.
…		…
111	These watchers are normal Perl objects with normal Perl lifetime. After	146	These watchers are normal Perl objects with normal Perl lifetime. After
112	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
113	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
114	in control).	149	in control).
115		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
116	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
117	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
118	to it).	159	to it).
119		160
120	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.
…		…
122	Many watchers either are used with "recursion" (repeating timers for	163	Many watchers either are used with "recursion" (repeating timers for
123	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.
124		165
125	An any way to achieve that is this pattern:	166	An any way to achieve that is this pattern:
126		167
127	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	168	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
128	# you can use $w here, for example to undef it	169	# you can use $w here, for example to undef it
129	undef $w;	170	undef $w;
130	});	171	});
131		172
132	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,
133	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
134	declared.	175	declared.
135		176
136	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
137	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
138	the following mandatory key-value pairs as arguments:	185	the following mandatory key-value pairs as arguments:
139		186
140	"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
141	"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
142	watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"	195	watcher waiting for "r"eadable or "w"ritable events, respectively.
		196
143	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.
144		198
145	Although the callback might get passed parameters, their value and	199	Although the callback might get passed parameters, their value and
146	presence is undefined and you cannot rely on them. Portable AnyEvent	200	presence is undefined and you cannot rely on them. Portable AnyEvent
147	callbacks cannot use arguments passed to I/O watcher callbacks.	201	callbacks cannot use arguments passed to I/O watcher callbacks.
148		202
…		…
152		206
153	Some event loops issue spurious readyness notifications, so you should	207	Some event loops issue spurious readyness notifications, so you should
154	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
155	handles.	209	handles.
156		210
157	Example:
158
159	# 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
160	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	214	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
161	chomp (my $input = <STDIN>);	215	chomp (my $input = <STDIN>);
162	warn "read: $input\n";	216	warn "read: $input\n";
163	undef $w;	217	undef $w;
164	});	218	});
165		219
166	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
167	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
168	with the following mandatory arguments:	230	with the following mandatory arguments:
169		231
170	"after" specifies after how many seconds (fractional values are	232	"after" specifies after how many seconds (fractional values are
171	supported) the callback should be invoked. "cb" is the callback to	233	supported) the callback should be invoked. "cb" is the callback to
…		…
173		235
174	Although the callback might get passed parameters, their value and	236	Although the callback might get passed parameters, their value and
175	presence is undefined and you cannot rely on them. Portable AnyEvent	237	presence is undefined and you cannot rely on them. Portable AnyEvent
176	callbacks cannot use arguments passed to time watcher callbacks.	238	callbacks cannot use arguments passed to time watcher callbacks.
177		239
178	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
179	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
180	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.
181		245
182	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.
183		249
184	# fire an event after 7.7 seconds	250	Example: fire an event after 7.7 seconds.
		251
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	252	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	253	warn "timeout\n";
187	});	254	});
188		255
189	# to cancel the timer:	256	# to cancel the timer:
190	undef $w;	257	undef $w;
191		258
192	Example 2:
193
194	# 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.
195	my $w;
196		260
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	261	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		262	warn "timeout\n";
200	};	263	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		264
205	TIMING ISSUES	265	TIMING ISSUES
206	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
207	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
208	o'clock").	268	o'clock").
…		…
220	on wallclock time) timers.	280	on wallclock time) timers.
221		281
222	AnyEvent always prefers relative timers, if available, matching the	282	AnyEvent always prefers relative timers, if available, matching the
223	AnyEvent API.	283	AnyEvent API.
224		284
		285	AnyEvent has two additional methods that return the "current time":
		286
		287	AnyEvent->time
		288	This returns the "current wallclock time" as a fractional number of
		289	seconds since the Epoch (the same thing as "time" or
		290	"Time::HiRes::time" return, and the result is guaranteed to be
		291	compatible with those).
		292
		293	It progresses independently of any event loop processing, i.e. each
		294	call will check the system clock, which usually gets updated
		295	frequently.
		296
		297	AnyEvent->now
		298	This also returns the "current wallclock time", but unlike "time",
		299	above, this value might change only once per event loop iteration,
		300	depending on the event loop (most return the same time as "time",
		301	above). This is the time that AnyEvent's timers get scheduled
		302	against.
		303
		304	*In almost all cases (in all cases if you don't care), this is the
		305	function to call when you want to know the current time.*
		306
		307	This function is also often faster then "AnyEvent->time", and thus
		308	the preferred method if you want some timestamp (for example,
		309	AnyEvent::Handle uses this to update it's activity timeouts).
		310
		311	The rest of this section is only of relevance if you try to be very
		312	exact with your timing, you can skip it without bad conscience.
		313
		314	For a practical example of when these times differ, consider
		315	Event::Lib and EV and the following set-up:
		316
		317	The event loop is running and has just invoked one of your callback
		318	at time=500 (assume no other callbacks delay processing). In your
		319	callback, you wait a second by executing "sleep 1" (blocking the
		320	process for a second) and then (at time=501) you create a relative
		321	timer that fires after three seconds.
		322
		323	With Event::Lib, "AnyEvent->time" and "AnyEvent->now" will both
		324	return 501, because that is the current time, and the timer will be
		325	scheduled to fire at time=504 (501 + 3).
		326
		327	With EV, "AnyEvent->time" returns 501 (as that is the current time),
		328	but "AnyEvent->now" returns 500, as that is the time the last event
		329	processing phase started. With EV, your timer gets scheduled to run
		330	at time=503 (500 + 3).
		331
		332	In one sense, Event::Lib is more exact, as it uses the current time
		333	regardless of any delays introduced by event processing. However,
		334	most callbacks do not expect large delays in processing, so this
		335	causes a higher drift (and a lot more system calls to get the
		336	current time).
		337
		338	In another sense, EV is more exact, as your timer will be scheduled
		339	at the same time, regardless of how long event processing actually
		340	took.
		341
		342	In either case, if you care (and in most cases, you don't), then you
		343	can get whatever behaviour you want with any event loop, by taking
		344	the difference between "AnyEvent->time" and "AnyEvent->now" into
		345	account.
		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	Note that updating the time might cause some events to be handled.
		360
225	SIGNAL WATCHERS	361	SIGNAL WATCHERS
		362	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		363
226	You can watch for signals using a signal watcher, "signal" is the signal	364	You can watch for signals using a signal watcher, "signal" is the signal
227	name without any "SIG" prefix, "cb" is the Perl callback to be invoked	365	name in uppercase and without any "SIG" prefix, "cb" is the Perl
228	whenever a signal occurs.	366	callback to be invoked whenever a signal occurs.
229		367
230	Although the callback might get passed parameters, their value and	368	Although the callback might get passed parameters, their value and
231	presence is undefined and you cannot rely on them. Portable AnyEvent	369	presence is undefined and you cannot rely on them. Portable AnyEvent
232	callbacks cannot use arguments passed to signal watcher callbacks.	370	callbacks cannot use arguments passed to signal watcher callbacks.
233		371
…		…
235	invocation, and callback invocation will be synchronous. Synchronous	373	invocation, and callback invocation will be synchronous. Synchronous
236	means that it might take a while until the signal gets handled by the	374	means that it might take a while until the signal gets handled by the
237	process, but it is guaranteed not to interrupt any other callbacks.	375	process, but it is guaranteed not to interrupt any other callbacks.
238		376
239	The main advantage of using these watchers is that you can share a	377	The main advantage of using these watchers is that you can share a
240	signal between multiple watchers.	378	signal between multiple watchers, and AnyEvent will ensure that signals
		379	will not interrupt your program at bad times.
241		380
242	This watcher might use %SIG, so programs overwriting those signals	381	This watcher might use %SIG (depending on the event loop used), so
243	directly will likely not work correctly.	382	programs overwriting those signals directly will likely not work
		383	correctly.
244		384
245	Example: exit on SIGINT	385	Example: exit on SIGINT
246		386
247	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	387	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
248		388
		389	Signal Races, Delays and Workarounds
		390	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		391	callbacks to signals in a generic way, which is a pity, as you cannot do
		392	race-free signal handling in perl, requiring C libraries for this.
		393	AnyEvent will try to do it's best, which means in some cases, signals
		394	will be delayed. The maximum time a signal might be delayed is specified
		395	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
		396	can be changed only before the first signal watcher is created, and
		397	should be left alone otherwise. This variable determines how often
		398	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		399	will cause fewer spurious wake-ups, which is better for power and CPU
		400	saving.
		401
		402	All these problems can be avoided by installing the optional
		403	Async::Interrupt module, which works with most event loops. It will not
		404	work with inherently broken event loops such as Event or Event::Lib (and
		405	not with POE currently, as POE does it's own workaround with one-second
		406	latency). For those, you just have to suffer the delays.
		407
249	CHILD PROCESS WATCHERS	408	CHILD PROCESS WATCHERS
		409	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		410
250	You can also watch on a child process exit and catch its exit status.	411	You can also watch on a child process exit and catch its exit status.
251		412
252	The child process is specified by the "pid" argument (if set to 0, it	413	The child process is specified by the "pid" argument (one some backends,
253	watches for any child process exit). The watcher will trigger as often	414	using 0 watches for any child process exit, on others this will croak).
254	as status change for the child are received. This works by installing a	415	The watcher will be triggered only when the child process has finished
255	signal handler for "SIGCHLD". The callback will be called with the pid	416	and an exit status is available, not on any trace events
256	and exit status (as returned by waitpid), so unlike other watcher types,	417	(stopped/continued).
257	you can rely on child watcher callback arguments.	418
		419	The callback will be called with the pid and exit status (as returned by
		420	waitpid), so unlike other watcher types, you can rely on child watcher
		421	callback arguments.
		422
		423	This watcher type works by installing a signal handler for "SIGCHLD",
		424	and since it cannot be shared, nothing else should use SIGCHLD or reap
		425	random child processes (waiting for specific child processes, e.g.
		426	inside "system", is just fine).
258		427
259	There is a slight catch to child watchers, however: you usually start	428	There is a slight catch to child watchers, however: you usually start
260	them after the child process was created, and this means the process	429	them after the child process was created, and this means the process
261	could have exited already (and no SIGCHLD will be sent anymore).	430	could have exited already (and no SIGCHLD will be sent anymore).
262		431
263	Not all event models handle this correctly (POE doesn't), but even for	432	Not all event models handle this correctly (neither POE nor IO::Async
		433	do, see their AnyEvent::Impl manpages for details), but even for event
264	event models that do handle this correctly, they usually need to be	434	models that do handle this correctly, they usually need to be loaded
265	loaded before the process exits (i.e. before you fork in the first	435	before the process exits (i.e. before you fork in the first place).
266	place).	436	AnyEvent's pure perl event loop handles all cases correctly regardless
		437	of when you start the watcher.
267		438
268	This means you cannot create a child watcher as the very first thing in	439	This means you cannot create a child watcher as the very first thing in
269	an AnyEvent program, you have to create at least one watcher before	440	an AnyEvent program, you have to create at least one watcher before
270	you "fork" the child (alternatively, you can call "AnyEvent::detect").	441	you "fork" the child (alternatively, you can call "AnyEvent::detect").
271		442
		443	As most event loops do not support waiting for child events, they will
		444	be emulated by AnyEvent in most cases, in which the latency and race
		445	problems mentioned in the description of signal watchers apply.
		446
272	Example: fork a process and wait for it	447	Example: fork a process and wait for it
273		448
274	my $done = AnyEvent->condvar;	449	my $done = AnyEvent->condvar;
275		450
276	my $pid = fork or exit 5;	451	my $pid = fork or exit 5;
277		452
278	my $w = AnyEvent->child (	453	my $w = AnyEvent->child (
279	pid => $pid,	454	pid => $pid,
280	cb => sub {	455	cb => sub {
281	my ($pid, $status) = @_;	456	my ($pid, $status) = @_;
282	warn "pid $pid exited with status $status";	457	warn "pid $pid exited with status $status";
283	$done->send;	458	$done->send;
284	},	459	},
285	);	460	);
286		461
287	# do something else, then wait for process exit	462	# do something else, then wait for process exit
288	$done->recv;	463	$done->recv;
		464
		465	IDLE WATCHERS
		466	$w = AnyEvent->idle (cb => <callback>);
		467
		468	Sometimes there is a need to do something, but it is not so important to
		469	do it instantly, but only when there is nothing better to do. This
		470	"nothing better to do" is usually defined to be "no other events need
		471	attention by the event loop".
		472
		473	Idle watchers ideally get invoked when the event loop has nothing better
		474	to do, just before it would block the process to wait for new events.
		475	Instead of blocking, the idle watcher is invoked.
		476
		477	Most event loops unfortunately do not really support idle watchers (only
		478	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		479	will simply call the callback "from time to time".
		480
		481	Example: read lines from STDIN, but only process them when the program
		482	is otherwise idle:
		483
		484	my @lines; # read data
		485	my $idle_w;
		486	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		487	push @lines, scalar <STDIN>;
		488
		489	# start an idle watcher, if not already done
		490	$idle_w \|\|= AnyEvent->idle (cb => sub {
		491	# handle only one line, when there are lines left
		492	if (my $line = shift @lines) {
		493	print "handled when idle: $line";
		494	} else {
		495	# otherwise disable the idle watcher again
		496	undef $idle_w;
		497	}
		498	});
		499	});
289		500
290	CONDITION VARIABLES	501	CONDITION VARIABLES
		502	$cv = AnyEvent->condvar;
		503
		504	$cv->send (<list>);
		505	my @res = $cv->recv;
		506
291	If you are familiar with some event loops you will know that all of them	507	If you are familiar with some event loops you will know that all of them
292	require you to run some blocking "loop", "run" or similar function that	508	require you to run some blocking "loop", "run" or similar function that
293	will actively watch for new events and call your callbacks.	509	will actively watch for new events and call your callbacks.
294		510
295	AnyEvent is different, it expects somebody else to run the event loop	511	AnyEvent is slightly different: it expects somebody else to run the
296	and will only block when necessary (usually when told by the user).	512	event loop and will only block when necessary (usually when told by the
		513	user).
297		514
298	The instrument to do that is called a "condition variable", so called	515	The instrument to do that is called a "condition variable", so called
299	because they represent a condition that must become true.	516	because they represent a condition that must become true.
		517
		518	Now is probably a good time to look at the examples further below.
300		519
301	Condition variables can be created by calling the "AnyEvent->condvar"	520	Condition variables can be created by calling the "AnyEvent->condvar"
302	method, usually without arguments. The only argument pair allowed is	521	method, usually without arguments. The only argument pair allowed is
303	"cb", which specifies a callback to be called when the condition	522	"cb", which specifies a callback to be called when the condition
304	variable becomes true.	523	variable becomes true, with the condition variable as the first argument
		524	(but not the results).
305		525
306	After creation, the condition variable is "false" until it becomes	526	After creation, the condition variable is "false" until it becomes
307	"true" by calling the "send" method (or calling the condition variable	527	"true" by calling the "send" method (or calling the condition variable
308	as if it were a callback, read about the caveats in the description for	528	as if it were a callback, read about the caveats in the description for
309	the "->send" method).	529	the "->send" method).
…		…
311	Condition variables are similar to callbacks, except that you can	531	Condition variables are similar to callbacks, except that you can
312	optionally wait for them. They can also be called merge points - points	532	optionally wait for them. They can also be called merge points - points
313	in time where multiple outstanding events have been processed. And yet	533	in time where multiple outstanding events have been processed. And yet
314	another way to call them is transactions - each condition variable can	534	another way to call them is transactions - each condition variable can
315	be used to represent a transaction, which finishes at some point and	535	be used to represent a transaction, which finishes at some point and
316	delivers a result.	536	delivers a result. And yet some people know them as "futures" - a
		537	promise to compute/deliver something that you can wait for.
317		538
318	Condition variables are very useful to signal that something has	539	Condition variables are very useful to signal that something has
319	finished, for example, if you write a module that does asynchronous http	540	finished, for example, if you write a module that does asynchronous http
320	requests, then a condition variable would be the ideal candidate to	541	requests, then a condition variable would be the ideal candidate to
321	signal the availability of results. The user can either act when the	542	signal the availability of results. The user can either act when the
…		…
355	after => 1,	576	after => 1,
356	cb => sub { $result_ready->send },	577	cb => sub { $result_ready->send },
357	);	578	);
358		579
359	# this "blocks" (while handling events) till the callback	580	# this "blocks" (while handling events) till the callback
360	# calls send	581	# calls ->send
361	$result_ready->recv;	582	$result_ready->recv;
362		583
363	Example: wait for a timer, but take advantage of the fact that condition	584	Example: wait for a timer, but take advantage of the fact that condition
364	variables are also code references.	585	variables are also callable directly.
365		586
366	my $done = AnyEvent->condvar;	587	my $done = AnyEvent->condvar;
367	my $delay = AnyEvent->timer (after => 5, cb => $done);	588	my $delay = AnyEvent->timer (after => 5, cb => $done);
368	$done->recv;	589	$done->recv;
		590
		591	Example: Imagine an API that returns a condvar and doesn't support
		592	callbacks. This is how you make a synchronous call, for example from the
		593	main program:
		594
		595	use AnyEvent::CouchDB;
		596
		597	...
		598
		599	my @info = $couchdb->info->recv;
		600
		601	And this is how you would just set a callback to be called whenever the
		602	results are available:
		603
		604	$couchdb->info->cb (sub {
		605	my @info = $_[0]->recv;
		606	});
369		607
370	METHODS FOR PRODUCERS	608	METHODS FOR PRODUCERS
371	These methods should only be used by the producing side, i.e. the	609	These methods should only be used by the producing side, i.e. the
372	code/module that eventually sends the signal. Note that it is also the	610	code/module that eventually sends the signal. Note that it is also the
373	producer side which creates the condvar in most cases, but it isn't	611	producer side which creates the condvar in most cases, but it isn't
…		…
383		621
384	Any arguments passed to the "send" call will be returned by all	622	Any arguments passed to the "send" call will be returned by all
385	future "->recv" calls.	623	future "->recv" calls.
386		624
387	Condition variables are overloaded so one can call them directly (as	625	Condition variables are overloaded so one can call them directly (as
388	a code reference). Calling them directly is the same as calling	626	if they were a code reference). Calling them directly is the same as
389	"send". Note, however, that many C-based event loops do not handle	627	calling "send".
390	overloading, so as tempting as it may be, passing a condition
391	variable instead of a callback does not work. Both the pure perl and
392	EV loops support overloading, however, as well as all functions that
393	use perl to invoke a callback (as in AnyEvent::Socket and
394	AnyEvent::DNS for example).
395		628
396	$cv->croak ($error)	629	$cv->croak ($error)
397	Similar to send, but causes all call's to "->recv" to invoke	630	Similar to send, but causes all call's to "->recv" to invoke
398	"Carp::croak" with the given error message/object/scalar.	631	"Carp::croak" with the given error message/object/scalar.
399		632
400	This can be used to signal any errors to the condition variable	633	This can be used to signal any errors to the condition variable
401	user/consumer.	634	user/consumer. Doing it this way instead of calling "croak" directly
		635	delays the error detetcion, but has the overwhelmign advantage that
		636	it diagnoses the error at the place where the result is expected,
		637	and not deep in some event clalback without connection to the actual
		638	code causing the problem.
402		639
403	$cv->begin ([group callback])	640	$cv->begin ([group callback])
404	$cv->end	641	$cv->end
405	These two methods are EXPERIMENTAL and MIGHT CHANGE.
406
407	These two methods can be used to combine many transactions/events	642	These two methods can be used to combine many transactions/events
408	into one. For example, a function that pings many hosts in parallel	643	into one. For example, a function that pings many hosts in parallel
409	might want to use a condition variable for the whole process.	644	might want to use a condition variable for the whole process.
410		645
411	Every call to "->begin" will increment a counter, and every call to	646	Every call to "->begin" will increment a counter, and every call to
412	"->end" will decrement it. If the counter reaches 0 in "->end", the	647	"->end" will decrement it. If the counter reaches 0 in "->end", the
413	(last) callback passed to "begin" will be executed. That callback is	648	(last) callback passed to "begin" will be executed, passing the
414	supposed to call "->send", but that is not required. If no	649	condvar as first argument. That callback is supposed to call
		650	"->send", but that is not required. If no group callback was set,
415	callback was set, "send" will be called without any arguments.	651	"send" will be called without any arguments.
416		652
417	Let's clarify this with the ping example:	653	You can think of "$cv->send" giving you an OR condition (one call
		654	sends), while "$cv->begin" and "$cv->end" giving you an AND
		655	condition (all "begin" calls must be "end"'ed before the condvar
		656	sends).
		657
		658	Let's start with a simple example: you have two I/O watchers (for
		659	example, STDOUT and STDERR for a program), and you want to wait for
		660	both streams to close before activating a condvar:
418		661
419	my $cv = AnyEvent->condvar;	662	my $cv = AnyEvent->condvar;
420		663
		664	$cv->begin; # first watcher
		665	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		666	defined sysread $fh1, my $buf, 4096
		667	or $cv->end;
		668	});
		669
		670	$cv->begin; # second watcher
		671	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		672	defined sysread $fh2, my $buf, 4096
		673	or $cv->end;
		674	});
		675
		676	$cv->recv;
		677
		678	This works because for every event source (EOF on file handle),
		679	there is one call to "begin", so the condvar waits for all calls to
		680	"end" before sending.
		681
		682	The ping example mentioned above is slightly more complicated, as
		683	the there are results to be passwd back, and the number of tasks
		684	that are begung can potentially be zero:
		685
		686	my $cv = AnyEvent->condvar;
		687
421	my %result;	688	my %result;
422	$cv->begin (sub { $cv->send (\%result) });	689	$cv->begin (sub { shift->send (\%result) });
423		690
424	for my $host (@list_of_hosts) {	691	for my $host (@list_of_hosts) {
425	$cv->begin;	692	$cv->begin;
426	ping_host_then_call_callback $host, sub {	693	ping_host_then_call_callback $host, sub {
427	$result{$host} = ...;	694	$result{$host} = ...;
…		…
442	the loop, which serves two important purposes: first, it sets the	709	the loop, which serves two important purposes: first, it sets the
443	callback to be called once the counter reaches 0, and second, it	710	callback to be called once the counter reaches 0, and second, it
444	ensures that "send" is called even when "no" hosts are being pinged	711	ensures that "send" is called even when "no" hosts are being pinged
445	(the loop doesn't execute once).	712	(the loop doesn't execute once).
446		713
447	This is the general pattern when you "fan out" into multiple	714	This is the general pattern when you "fan out" into multiple (but
448	subrequests: use an outer "begin"/"end" pair to set the callback and	715	potentially none) subrequests: use an outer "begin"/"end" pair to
449	ensure "end" is called at least once, and then, for each subrequest	716	set the callback and ensure "end" is called at least once, and then,
450	you start, call "begin" and for each subrequest you finish, call	717	for each subrequest you start, call "begin" and for each subrequest
451	"end".	718	you finish, call "end".
452		719
453	METHODS FOR CONSUMERS	720	METHODS FOR CONSUMERS
454	These methods should only be used by the consuming side, i.e. the code	721	These methods should only be used by the consuming side, i.e. the code
455	awaits the condition.	722	awaits the condition.
456		723
…		…
465	function will call "croak".	732	function will call "croak".
466		733
467	In list context, all parameters passed to "send" will be returned,	734	In list context, all parameters passed to "send" will be returned,
468	in scalar context only the first one will be returned.	735	in scalar context only the first one will be returned.
469		736
		737	Note that doing a blocking wait in a callback is not supported by
		738	any event loop, that is, recursive invocation of a blocking "->recv"
		739	is not allowed, and the "recv" call will "croak" if such a condition
		740	is detected. This condition can be slightly loosened by using
		741	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		742	thread that doesn't run the event loop itself.
		743
470	Not all event models support a blocking wait - some die in that case	744	Not all event models support a blocking wait - some die in that case
471	(programs might want to do that to stay interactive), so *if you are	745	(programs might want to do that to stay interactive), so *if you are
472	using this from a module, never require a blocking wait*, but let	746	using this from a module, never require a blocking wait*. Instead,
473	the caller decide whether the call will block or not (for example,	747	let the caller decide whether the call will block or not (for
474	by coupling condition variables with some kind of request results	748	example, by coupling condition variables with some kind of request
475	and supporting callbacks so the caller knows that getting the result	749	results and supporting callbacks so the caller knows that getting
476	will not block, while still supporting blocking waits if the caller	750	the result will not block, while still supporting blocking waits if
477	so desires).	751	the caller so desires).
478
479	Another reason never to "->recv" in a module is that you cannot
480	sensibly have two "->recv"'s in parallel, as that would require
481	multiple interpreters or coroutines/threads, none of which
482	"AnyEvent" can supply.
483
484	The Coro module, however, can and does supply coroutines and, in
485	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
486	versions and also integrates coroutines into AnyEvent, making
487	blocking "->recv" calls perfectly safe as long as they are done from
488	another coroutine (one that doesn't run the event loop).
489		752
490	You can ensure that "-recv" never blocks by setting a callback and	753	You can ensure that "-recv" never blocks by setting a callback and
491	only calling "->recv" from within that callback (or at a later	754	only calling "->recv" from within that callback (or at a later
492	time). This will work even when the event loop does not support	755	time). This will work even when the event loop does not support
493	blocking waits otherwise.	756	blocking waits otherwise.
494		757
495	$bool = $cv->ready	758	$bool = $cv->ready
496	Returns true when the condition is "true", i.e. whether "send" or	759	Returns true when the condition is "true", i.e. whether "send" or
497	"croak" have been called.	760	"croak" have been called.
498		761
499	$cb = $cv->cb ([new callback])	762	$cb = $cv->cb ($cb->($cv))
500	This is a mutator function that returns the callback set and	763	This is a mutator function that returns the callback set and
501	optionally replaces it before doing so.	764	optionally replaces it before doing so.
502		765
503	The callback will be called when the condition becomes "true", i.e.	766	The callback will be called when the condition becomes (or already
504	when "send" or "croak" are called. Calling "recv" inside the	767	was) "true", i.e. when "send" or "croak" are called (or were
505	callback or at any later time is guaranteed not to block.	768	called), with the only argument being the condition variable itself.
		769	Calling "recv" inside the callback or at any later time is
		770	guaranteed not to block.
		771
		772	SUPPORTED EVENT LOOPS/BACKENDS
		773	The available backend classes are (every class has its own manpage):
		774
		775	Backends that are autoprobed when no other event loop can be found.
		776	EV is the preferred backend when no other event loop seems to be in
		777	use. If EV is not installed, then AnyEvent will fall back to its own
		778	pure-perl implementation, which is available everywhere as it comes
		779	with AnyEvent itself.
		780
		781	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		782	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		783
		784	Backends that are transparently being picked up when they are used.
		785	These will be used when they are currently loaded when the first
		786	watcher is created, in which case it is assumed that the application
		787	is using them. This means that AnyEvent will automatically pick the
		788	right backend when the main program loads an event module before
		789	anything starts to create watchers. Nothing special needs to be done
		790	by the main program.
		791
		792	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		793	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		794	AnyEvent::Impl::Tk based on Tk, very broken.
		795	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		796	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		797	AnyEvent::Impl::Irssi used when running within irssi.
		798
		799	Backends with special needs.
		800	Qt requires the Qt::Application to be instantiated first, but will
		801	otherwise be picked up automatically. As long as the main program
		802	instantiates the application before any AnyEvent watchers are
		803	created, everything should just work.
		804
		805	AnyEvent::Impl::Qt based on Qt.
		806
		807	Support for IO::Async can only be partial, as it is too broken and
		808	architecturally limited to even support the AnyEvent API. It also is
		809	the only event loop that needs the loop to be set explicitly, so it
		810	can only be used by a main program knowing about AnyEvent. See
		811	AnyEvent::Impl::Async for the gory details.
		812
		813	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		814
		815	Event loops that are indirectly supported via other backends.
		816	Some event loops can be supported via other modules:
		817
		818	There is no direct support for WxWidgets (Wx) or Prima.
		819
		820	WxWidgets has no support for watching file handles. However, you can
		821	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		822	simply polls 20 times per second, which was considered to be too
		823	horrible to even consider for AnyEvent.
		824
		825	Prima is not supported as nobody seems to be using it, but it has a
		826	POE backend, so it can be supported through POE.
		827
		828	AnyEvent knows about both Prima and Wx, however, and will try to
		829	load POE when detecting them, in the hope that POE will pick them
		830	up, in which case everything will be automatic.
506		831
507	GLOBAL VARIABLES AND FUNCTIONS	832	GLOBAL VARIABLES AND FUNCTIONS
		833	These are not normally required to use AnyEvent, but can be useful to
		834	write AnyEvent extension modules.
		835
508	$AnyEvent::MODEL	836	$AnyEvent::MODEL
509	Contains "undef" until the first watcher is being created. Then it	837	Contains "undef" until the first watcher is being created, before
		838	the backend has been autodetected.
		839
510	contains the event model that is being used, which is the name of	840	Afterwards it contains the event model that is being used, which is
511	the Perl class implementing the model. This class is usually one of	841	the name of the Perl class implementing the model. This class is
512	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	842	usually one of the "AnyEvent::Impl:xxx" modules, but can be any
513	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).	843	other class in the case AnyEvent has been extended at runtime (e.g.
514		844	in rxvt-unicode it will be "urxvt::anyevent").
515	The known classes so far are:
516
517	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
518	AnyEvent::Impl::Event based on Event, second best choice.
519	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
520	AnyEvent::Impl::Glib based on Glib, third-best choice.
521	AnyEvent::Impl::Tk based on Tk, very bad choice.
522	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
523	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
524	AnyEvent::Impl::POE based on POE, not generic enough for full support.
525
526	There is no support for WxWidgets, as WxWidgets has no support for
527	watching file handles. However, you can use WxWidgets through the
528	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
529	second, which was considered to be too horrible to even consider for
530	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
531	using it's adaptor.
532
533	AnyEvent knows about Prima and Wx and will try to use POE when
534	autodetecting them.
535		845
536	AnyEvent::detect	846	AnyEvent::detect
537	Returns $AnyEvent::MODEL, forcing autodetection of the event model	847	Returns $AnyEvent::MODEL, forcing autodetection of the event model
538	if necessary. You should only call this function right before you	848	if necessary. You should only call this function right before you
539	would have created an AnyEvent watcher anyway, that is, as late as	849	would have created an AnyEvent watcher anyway, that is, as late as
540	possible at runtime.	850	possible at runtime, and not e.g. while initialising of your module.
		851
		852	If you need to do some initialisation before AnyEvent watchers are
		853	created, use "post_detect".
541		854
542	$guard = AnyEvent::post_detect { BLOCK }	855	$guard = AnyEvent::post_detect { BLOCK }
543	Arranges for the code block to be executed as soon as the event	856	Arranges for the code block to be executed as soon as the event
544	model is autodetected (or immediately if this has already happened).	857	model is autodetected (or immediately if this has already happened).
545		858
		859	The block will be executed after the actual backend has been
		860	detected ($AnyEvent::MODEL is set), but before any watchers have
		861	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		862	other initialisations - see the sources of AnyEvent::Strict or
		863	AnyEvent::AIO to see how this is used.
		864
		865	The most common usage is to create some global watchers, without
		866	forcing event module detection too early, for example, AnyEvent::AIO
		867	creates and installs the global IO::AIO watcher in a "post_detect"
		868	block to avoid autodetecting the event module at load time.
		869
546	If called in scalar or list context, then it creates and returns an	870	If called in scalar or list context, then it creates and returns an
547	object that automatically removes the callback again when it is	871	object that automatically removes the callback again when it is
		872	destroyed (or "undef" when the hook was immediately executed). See
548	destroyed. See Coro::BDB for a case where this is useful.	873	AnyEvent::AIO for a case where this is useful.
		874
		875	Example: Create a watcher for the IO::AIO module and store it in
		876	$WATCHER. Only do so after the event loop is initialised, though.
		877
		878	our WATCHER;
		879
		880	my $guard = AnyEvent::post_detect {
		881	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		882	};
		883
		884	# the \|\|= is important in case post_detect immediately runs the block,
		885	# as to not clobber the newly-created watcher. assigning both watcher and
		886	# post_detect guard to the same variable has the advantage of users being
		887	# able to just C<undef $WATCHER> if the watcher causes them grief.
		888
		889	$WATCHER \|\|= $guard;
549		890
550	@AnyEvent::post_detect	891	@AnyEvent::post_detect
551	If there are any code references in this array (you can "push" to it	892	If there are any code references in this array (you can "push" to it
552	before or after loading AnyEvent), then they will called directly	893	before or after loading AnyEvent), then they will called directly
553	after the event loop has been chosen.	894	after the event loop has been chosen.
554		895
555	You should check $AnyEvent::MODEL before adding to this array,	896	You should check $AnyEvent::MODEL before adding to this array,
556	though: if it contains a true value then the event loop has already	897	though: if it is defined then the event loop has already been
557	been detected, and the array will be ignored.	898	detected, and the array will be ignored.
558		899
559	Best use "AnyEvent::post_detect { BLOCK }" instead.	900	Best use "AnyEvent::post_detect { BLOCK }" when your application
		901	allows it,as it takes care of these details.
		902
		903	This variable is mainly useful for modules that can do something
		904	useful when AnyEvent is used and thus want to know when it is
		905	initialised, but do not need to even load it by default. This array
		906	provides the means to hook into AnyEvent passively, without loading
		907	it.
560		908
561	WHAT TO DO IN A MODULE	909	WHAT TO DO IN A MODULE
562	As a module author, you should "use AnyEvent" and call AnyEvent methods	910	As a module author, you should "use AnyEvent" and call AnyEvent methods
563	freely, but you should not load a specific event module or rely on it.	911	freely, but you should not load a specific event module or rely on it.
564		912
…		…
615	variable somewhere, waiting for it, and sending it when the program	963	variable somewhere, waiting for it, and sending it when the program
616	should exit cleanly.	964	should exit cleanly.
617		965
618	OTHER MODULES	966	OTHER MODULES
619	The following is a non-exhaustive list of additional modules that use	967	The following is a non-exhaustive list of additional modules that use
620	AnyEvent and can therefore be mixed easily with other AnyEvent modules	968	AnyEvent as a client and can therefore be mixed easily with other
621	in the same program. Some of the modules come with AnyEvent, some are	969	AnyEvent modules and other event loops in the same program. Some of the
622	available via CPAN.	970	modules come with AnyEvent, most are available via CPAN.
623		971
624	AnyEvent::Util	972	AnyEvent::Util
625	Contains various utility functions that replace often-used but	973	Contains various utility functions that replace often-used but
626	blocking functions such as "inet_aton" by event-/callback-based	974	blocking functions such as "inet_aton" by event-/callback-based
627	versions.	975	versions.
628
629	AnyEvent::Handle
630	Provide read and write buffers and manages watchers for reads and
631	writes.
632		976
633	AnyEvent::Socket	977	AnyEvent::Socket
634	Provides various utility functions for (internet protocol) sockets,	978	Provides various utility functions for (internet protocol) sockets,
635	addresses and name resolution. Also functions to create non-blocking	979	addresses and name resolution. Also functions to create non-blocking
636	tcp connections or tcp servers, with IPv6 and SRV record support and	980	tcp connections or tcp servers, with IPv6 and SRV record support and
637	more.	981	more.
638		982
		983	AnyEvent::Handle
		984	Provide read and write buffers, manages watchers for reads and
		985	writes, supports raw and formatted I/O, I/O queued and fully
		986	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
		987
639	AnyEvent::DNS	988	AnyEvent::DNS
640	Provides rich asynchronous DNS resolver capabilities.	989	Provides rich asynchronous DNS resolver capabilities.
641		990
		991	AnyEvent::HTTP
		992	A simple-to-use HTTP library that is capable of making a lot of
		993	concurrent HTTP requests.
		994
642	AnyEvent::HTTPD	995	AnyEvent::HTTPD
643	Provides a simple web application server framework.	996	Provides a simple web application server framework.
644		997
645	AnyEvent::FastPing	998	AnyEvent::FastPing
646	The fastest ping in the west.	999	The fastest ping in the west.
647		1000
		1001	AnyEvent::DBI
		1002	Executes DBI requests asynchronously in a proxy process.
		1003
		1004	AnyEvent::AIO
		1005	Truly asynchronous I/O, should be in the toolbox of every event
		1006	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		1007	together.
		1008
		1009	AnyEvent::BDB
		1010	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
		1011	fuses BDB and AnyEvent together.
		1012
		1013	AnyEvent::GPSD
		1014	A non-blocking interface to gpsd, a daemon delivering GPS
		1015	information.
		1016
		1017	AnyEvent::IRC
		1018	AnyEvent based IRC client module family (replacing the older
648	Net::IRC3	1019	Net::IRC3).
649	AnyEvent based IRC client module family.
650		1020
651	Net::XMPP2	1021	AnyEvent::XMPP
652	AnyEvent based XMPP (Jabber protocol) module family.	1022	AnyEvent based XMPP (Jabber protocol) module family (replacing the
		1023	older Net::XMPP2>.
		1024
		1025	AnyEvent::IGS
		1026	A non-blocking interface to the Internet Go Server protocol (used by
		1027	App::IGS).
653		1028
654	Net::FCP	1029	Net::FCP
655	AnyEvent-based implementation of the Freenet Client Protocol,	1030	AnyEvent-based implementation of the Freenet Client Protocol,
656	birthplace of AnyEvent.	1031	birthplace of AnyEvent.
657		1032
…		…
659	High level API for event-based execution flow control.	1034	High level API for event-based execution flow control.
660		1035
661	Coro	1036	Coro
662	Has special support for AnyEvent via Coro::AnyEvent.	1037	Has special support for AnyEvent via Coro::AnyEvent.
663		1038
664	AnyEvent::AIO, IO::AIO	1039	SIMPLIFIED AE API
665	Truly asynchronous I/O, should be in the toolbox of every event	1040	Starting with version 5.0, AnyEvent officially supports a second, much
666	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent	1041	simpler, API that is designed to reduce the calling, typing and memory
667	together.	1042	overhead.
668		1043
669	AnyEvent::BDB, BDB	1044	See the AE manpage for details.
670	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
671	fuses IO::AIO and AnyEvent together.
672		1045
673	IO::Lambda	1046	ERROR AND EXCEPTION HANDLING
674	The lambda approach to I/O - don't ask, look there. Can use	1047	In general, AnyEvent does not do any error handling - it relies on the
675	AnyEvent.	1048	caller to do that if required. The AnyEvent::Strict module (see also the
		1049	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
		1050	checking of all AnyEvent methods, however, which is highly useful during
		1051	development.
676		1052
677	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1053	As for exception handling (i.e. runtime errors and exceptions thrown
678	This is an advanced topic that you do not normally need to use AnyEvent	1054	while executing a callback), this is not only highly event-loop
679	in a module. This section is only of use to event loop authors who want	1055	specific, but also not in any way wrapped by this module, as this is the
680	to provide AnyEvent compatibility.	1056	job of the main program.
681		1057
682	If you need to support another event library which isn't directly	1058	The pure perl event loop simply re-throws the exception (usually within
683	supported by AnyEvent, you can supply your own interface to it by	1059	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
684	pushing, before the first watcher gets created, the package name of the	1060	Glib uses "install_exception_handler" and so on.
685	event module and the package name of the interface to use onto
686	@AnyEvent::REGISTRY. You can do that before and even without loading
687	AnyEvent, so it is reasonably cheap.
688
689	Example:
690
691	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
692
693	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
694	package/class when it finds the "urxvt" package/module is already
695	loaded.
696
697	When AnyEvent is loaded and asked to find a suitable event model, it
698	will first check for the presence of urxvt by trying to "use" the
699	"urxvt::anyevent" module.
700
701	The class should provide implementations for all watcher types. See
702	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
703	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
704	the sources.
705
706	If you don't provide "signal" and "child" watchers than AnyEvent will
707	provide suitable (hopefully) replacements.
708
709	The above example isn't fictitious, the rxvt-unicode (a.k.a. urxvt)
710	terminal emulator uses the above line as-is. An interface isn't included
711	in AnyEvent because it doesn't make sense outside the embedded
712	interpreter inside rxvt-unicode, and it is updated and maintained as
713	part of the rxvt-unicode distribution.
714
715	rxvt-unicode also cheats a bit by not providing blocking access to
716	condition variables: code blocking while waiting for a condition will
717	"die". This still works with most modules/usages, and blocking calls
718	must not be done in an interactive application, so it makes sense.
719		1061
720	ENVIRONMENT VARIABLES	1062	ENVIRONMENT VARIABLES
721	The following environment variables are used by this module:	1063	The following environment variables are used by this module or its
		1064	submodules.
		1065
		1066	Note that AnyEvent will remove all environment variables starting with
		1067	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1068	enabled.
722		1069
723	"PERL_ANYEVENT_VERBOSE"	1070	"PERL_ANYEVENT_VERBOSE"
724	By default, AnyEvent will be completely silent except in fatal	1071	By default, AnyEvent will be completely silent except in fatal
725	conditions. You can set this environment variable to make AnyEvent	1072	conditions. You can set this environment variable to make AnyEvent
726	more talkative.	1073	more talkative.
…		…
729	conditions, such as not being able to load the event model specified	1076	conditions, such as not being able to load the event model specified
730	by "PERL_ANYEVENT_MODEL".	1077	by "PERL_ANYEVENT_MODEL".
731		1078
732	When set to 2 or higher, cause AnyEvent to report to STDERR which	1079	When set to 2 or higher, cause AnyEvent to report to STDERR which
733	event model it chooses.	1080	event model it chooses.
		1081
		1082	When set to 8 or higher, then AnyEvent will report extra information
		1083	on which optional modules it loads and how it implements certain
		1084	features.
		1085
		1086	"PERL_ANYEVENT_STRICT"
		1087	AnyEvent does not do much argument checking by default, as thorough
		1088	argument checking is very costly. Setting this variable to a true
		1089	value will cause AnyEvent to load "AnyEvent::Strict" and then to
		1090	thoroughly check the arguments passed to most method calls. If it
		1091	finds any problems, it will croak.
		1092
		1093	In other words, enables "strict" mode.
		1094
		1095	Unlike "use strict" (or it's modern cousin, "use common::sense", it
		1096	is definitely recommended to keep it off in production. Keeping
		1097	"PERL_ANYEVENT_STRICT=1" in your environment while developing
		1098	programs can be very useful, however.
734		1099
735	"PERL_ANYEVENT_MODEL"	1100	"PERL_ANYEVENT_MODEL"
736	This can be used to specify the event model to be used by AnyEvent,	1101	This can be used to specify the event model to be used by AnyEvent,
737	before auto detection and -probing kicks in. It must be a string	1102	before auto detection and -probing kicks in. It must be a string
738	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1103	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
743	This functionality might change in future versions.	1108	This functionality might change in future versions.
744		1109
745	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1110	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
746	could start your program like this:	1111	could start your program like this:
747		1112
748	PERL_ANYEVENT_MODEL=Perl perl ...	1113	PERL_ANYEVENT_MODEL=Perl perl ...
749		1114
750	"PERL_ANYEVENT_PROTOCOLS"	1115	"PERL_ANYEVENT_PROTOCOLS"
751	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1116	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
752	preferences for IPv4 or IPv6. The default is unspecified (and might	1117	preferences for IPv4 or IPv6. The default is unspecified (and might
753	change, or be the result of auto probing).	1118	change, or be the result of auto probing).
…		…
757	mentioned will be used, and preference will be given to protocols	1122	mentioned will be used, and preference will be given to protocols
758	mentioned earlier in the list.	1123	mentioned earlier in the list.
759		1124
760	This variable can effectively be used for denial-of-service attacks	1125	This variable can effectively be used for denial-of-service attacks
761	against local programs (e.g. when setuid), although the impact is	1126	against local programs (e.g. when setuid), although the impact is
762	likely small, as the program has to handle connection errors	1127	likely small, as the program has to handle conenction and other
763	already-	1128	failures anyways.
764		1129
765	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1130	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
766	IPv6, but support both and try to use both.	1131	IPv6, but support both and try to use both.
767	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1132	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
768	resolve or contact IPv6 addresses.	1133	resolve or contact IPv6 addresses.
…		…
775	but some (broken) firewalls drop such DNS packets, which is why it	1140	but some (broken) firewalls drop such DNS packets, which is why it
776	is off by default.	1141	is off by default.
777		1142
778	Setting this variable to 1 will cause AnyEvent::DNS to announce	1143	Setting this variable to 1 will cause AnyEvent::DNS to announce
779	EDNS0 in its DNS requests.	1144	EDNS0 in its DNS requests.
		1145
		1146	"PERL_ANYEVENT_MAX_FORKS"
		1147	The maximum number of child processes that
		1148	"AnyEvent::Util::fork_call" will create in parallel.
		1149
		1150	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1151	The default value for the "max_outstanding" parameter for the
		1152	default DNS resolver - this is the maximum number of parallel DNS
		1153	requests that are sent to the DNS server.
		1154
		1155	"PERL_ANYEVENT_RESOLV_CONF"
		1156	The file to use instead of /etc/resolv.conf (or OS-specific
		1157	configuration) in the default resolver. When set to the empty
		1158	string, no default config will be used.
		1159
		1160	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1161	When neither "ca_file" nor "ca_path" was specified during
		1162	AnyEvent::TLS context creation, and either of these environment
		1163	variables exist, they will be used to specify CA certificate
		1164	locations instead of a system-dependent default.
		1165
		1166	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1167	When these are set to 1, then the respective modules are not loaded.
		1168	Mostly good for testing AnyEvent itself.
		1169
		1170	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1171	This is an advanced topic that you do not normally need to use AnyEvent
		1172	in a module. This section is only of use to event loop authors who want
		1173	to provide AnyEvent compatibility.
		1174
		1175	If you need to support another event library which isn't directly
		1176	supported by AnyEvent, you can supply your own interface to it by
		1177	pushing, before the first watcher gets created, the package name of the
		1178	event module and the package name of the interface to use onto
		1179	@AnyEvent::REGISTRY. You can do that before and even without loading
		1180	AnyEvent, so it is reasonably cheap.
		1181
		1182	Example:
		1183
		1184	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
		1185
		1186	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
		1187	package/class when it finds the "urxvt" package/module is already
		1188	loaded.
		1189
		1190	When AnyEvent is loaded and asked to find a suitable event model, it
		1191	will first check for the presence of urxvt by trying to "use" the
		1192	"urxvt::anyevent" module.
		1193
		1194	The class should provide implementations for all watcher types. See
		1195	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
		1196	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
		1197	the sources.
		1198
		1199	If you don't provide "signal" and "child" watchers than AnyEvent will
		1200	provide suitable (hopefully) replacements.
		1201
		1202	The above example isn't fictitious, the rxvt-unicode (a.k.a. urxvt)
		1203	terminal emulator uses the above line as-is. An interface isn't included
		1204	in AnyEvent because it doesn't make sense outside the embedded
		1205	interpreter inside rxvt-unicode, and it is updated and maintained as
		1206	part of the rxvt-unicode distribution.
		1207
		1208	rxvt-unicode also cheats a bit by not providing blocking access to
		1209	condition variables: code blocking while waiting for a condition will
		1210	"die". This still works with most modules/usages, and blocking calls
		1211	must not be done in an interactive application, so it makes sense.
780		1212
781	EXAMPLE PROGRAM	1213	EXAMPLE PROGRAM
782	The following program uses an I/O watcher to read data from STDIN, a	1214	The following program uses an I/O watcher to read data from STDIN, a
783	timer to display a message once per second, and a condition variable to	1215	timer to display a message once per second, and a condition variable to
784	quit the program when the user enters quit:	1216	quit the program when the user enters quit:
…		…
796	warn "read: $input\n"; # output what has been read	1228	warn "read: $input\n"; # output what has been read
797	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1229	$cv->send if $input =~ /^q/i; # quit program if /^q/i
798	},	1230	},
799	);	1231	);
800		1232
801	my $time_watcher; # can only be used once
802
803	sub new_timer {
804	$timer = AnyEvent->timer (after => 1, cb => sub {	1233	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
805	warn "timeout\n"; # print 'timeout' about every second	1234	warn "timeout\n"; # print 'timeout' at most every second
806	&new_timer; # and restart the time
807	});
808	}	1235	});
809
810	new_timer; # create first timer
811		1236
812	$cv->recv; # wait until user enters /^q/i	1237	$cv->recv; # wait until user enters /^q/i
813		1238
814	REAL-WORLD EXAMPLE	1239	REAL-WORLD EXAMPLE
815	Consider the Net::FCP module. It features (among others) the following	1240	Consider the Net::FCP module. It features (among others) the following
…		…
942	through AnyEvent. The benchmark creates a lot of timers (with a zero	1367	through AnyEvent. The benchmark creates a lot of timers (with a zero
943	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1368	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
944	which it is), lets them fire exactly once and destroys them again.	1369	which it is), lets them fire exactly once and destroys them again.
945		1370
946	Source code for this benchmark is found as eg/bench in the AnyEvent	1371	Source code for this benchmark is found as eg/bench in the AnyEvent
947	distribution.	1372	distribution. It uses the AE interface, which makes a real difference
		1373	for the EV and Perl backends only.
948		1374
949	Explanation of the columns	1375	Explanation of the columns
950	watcher is the number of event watchers created/destroyed. Since	1376	watcher is the number of event watchers created/destroyed. Since
951	different event models feature vastly different performances, each event	1377	different event models feature vastly different performances, each event
952	loop was given a number of watchers so that overall runtime is	1378	loop was given a number of watchers so that overall runtime is
…		…
971	destroy is the time, in microseconds, that it takes to destroy a	1397	destroy is the time, in microseconds, that it takes to destroy a
972	single watcher.	1398	single watcher.
973		1399
974	Results	1400	Results
975	name watchers bytes create invoke destroy comment	1401	name watchers bytes create invoke destroy comment
976	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1402	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
977	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1403	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
978	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1404	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
979	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1405	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
980	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1406	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
981	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1407	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		1408	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		1409	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
982	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1410	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
983	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1411	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
984	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1412	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
985	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1413	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
986		1414
987	Discussion	1415	Discussion
988	The benchmark does not measure scalability of the event loop very	1416	The benchmark does not measure scalability of the event loop very
989	well. For example, a select-based event loop (such as the pure perl one)	1417	well. For example, a select-based event loop (such as the pure perl one)
990	can never compete with an event loop that uses epoll when the number of	1418	can never compete with an event loop that uses epoll when the number of
…		…
1001	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1429	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1002	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1430	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1003	CPU cycles with POE.	1431	CPU cycles with POE.
1004		1432
1005	"EV" is the sole leader regarding speed and memory use, which are both	1433	"EV" is the sole leader regarding speed and memory use, which are both
1006	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1434	maximal/minimal, respectively. When using the AE API there is zero
		1435	overhead (when going through the AnyEvent API create is about 5-6 times
		1436	slower, with other times being equal, so still uses far less memory than
1007	far less memory than any other event loop and is still faster than Event	1437	any other event loop and is still faster than Event natively).
1008	natively.
1009		1438
1010	The pure perl implementation is hit in a few sweet spots (both the	1439	The pure perl implementation is hit in a few sweet spots (both the
1011	constant timeout and the use of a single fd hit optimisations in the	1440	constant timeout and the use of a single fd hit optimisations in the
1012	perl interpreter and the backend itself). Nevertheless this shows that	1441	perl interpreter and the backend itself). Nevertheless this shows that
1013	it adds very little overhead in itself. Like any select-based backend	1442	it adds very little overhead in itself. Like any select-based backend
…		…
1015	few of them active), of course, but this was not subject of this	1444	few of them active), of course, but this was not subject of this
1016	benchmark.	1445	benchmark.
1017		1446
1018	The "Event" module has a relatively high setup and callback invocation	1447	The "Event" module has a relatively high setup and callback invocation
1019	cost, but overall scores in on the third place.	1448	cost, but overall scores in on the third place.
		1449
		1450	"IO::Async" performs admirably well, about on par with "Event", even
		1451	when using its pure perl backend.
1020		1452
1021	"Glib"'s memory usage is quite a bit higher, but it features a faster	1453	"Glib"'s memory usage is quite a bit higher, but it features a faster
1022	callback invocation and overall ends up in the same class as "Event".	1454	callback invocation and overall ends up in the same class as "Event".
1023	However, Glib scales extremely badly, doubling the number of watchers	1455	However, Glib scales extremely badly, doubling the number of watchers
1024	increases the processing time by more than a factor of four, making it	1456	increases the processing time by more than a factor of four, making it
…		…
1080	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1512	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1081	100 (1%) are active. This mirrors the activity of large servers with	1513	100 (1%) are active. This mirrors the activity of large servers with
1082	many connections, most of which are idle at any one point in time.	1514	many connections, most of which are idle at any one point in time.
1083		1515
1084	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1516	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1085	distribution.	1517	distribution. It uses the AE interface, which makes a real difference
		1518	for the EV and Perl backends only.
1086		1519
1087	Explanation of the columns	1520	Explanation of the columns
1088	sockets is the number of sockets, and twice the number of "servers"	1521	sockets is the number of sockets, and twice the number of "servers"
1089	(as each server has a read and write socket end).	1522	(as each server has a read and write socket end).
1090		1523
…		…
1095	single "request", that is, reading the token from the pipe and	1528	single "request", that is, reading the token from the pipe and
1096	forwarding it to another server. This includes deleting the old timeout	1529	forwarding it to another server. This includes deleting the old timeout
1097	and creating a new one that moves the timeout into the future.	1530	and creating a new one that moves the timeout into the future.
1098		1531
1099	Results	1532	Results
1100	name sockets create request	1533	name sockets create request
1101	EV 20000 69.01 11.16	1534	EV 20000 62.66 7.99
1102	Perl 20000 73.32 35.87	1535	Perl 20000 68.32 32.64
1103	Event 20000 212.62 257.32	1536	IOAsync 20000 174.06 101.15 epoll
1104	Glib 20000 651.16 1896.30	1537	IOAsync 20000 174.67 610.84 poll
		1538	Event 20000 202.69 242.91
		1539	Glib 20000 557.01 1689.52
1105	POE 20000 349.67 12317.24 uses POE::Loop::Event	1540	POE 20000 341.54 12086.32 uses POE::Loop::Event
1106		1541
1107	Discussion	1542	Discussion
1108	This benchmark does measure scalability and overall performance of the	1543	This benchmark does measure scalability and overall performance of the
1109	particular event loop.	1544	particular event loop.
1110		1545
1111	EV is again fastest. Since it is using epoll on my system, the setup	1546	EV is again fastest. Since it is using epoll on my system, the setup
1112	time is relatively high, though.	1547	time is relatively high, though.
1113		1548
1114	Perl surprisingly comes second. It is much faster than the C-based event	1549	Perl surprisingly comes second. It is much faster than the C-based event
1115	loops Event and Glib.	1550	loops Event and Glib.
		1551
		1552	IO::Async performs very well when using its epoll backend, and still
		1553	quite good compared to Glib when using its pure perl backend.
1116		1554
1117	Event suffers from high setup time as well (look at its code and you	1555	Event suffers from high setup time as well (look at its code and you
1118	will understand why). Callback invocation also has a high overhead	1556	will understand why). Callback invocation also has a high overhead
1119	compared to the "$_->() for .."-style loop that the Perl event loop	1557	compared to the "$_->() for .."-style loop that the Perl event loop
1120	uses. Event uses select or poll in basically all documented	1558	uses. Event uses select or poll in basically all documented
…		…
1171		1609
1172	Summary	1610	Summary
1173	* C-based event loops perform very well with small number of watchers,	1611	* C-based event loops perform very well with small number of watchers,
1174	as the management overhead dominates.	1612	as the management overhead dominates.
1175		1613
		1614	THE IO::Lambda BENCHMARK
		1615	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1616	could be misinterpreted to make AnyEvent look bad. In fact, the
		1617	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1618	better (which shouldn't come as a surprise to anybody). As such, the
		1619	benchmark is fine, and mostly shows that the AnyEvent backend from
		1620	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1621	without the extra baggage? To explore this, I wrote the equivalent
		1622	benchmark for AnyEvent.
		1623
		1624	The benchmark itself creates an echo-server, and then, for 500 times,
		1625	connects to the echo server, sends a line, waits for the reply, and then
		1626	creates the next connection. This is a rather bad benchmark, as it
		1627	doesn't test the efficiency of the framework or much non-blocking I/O,
		1628	but it is a benchmark nevertheless.
		1629
		1630	name runtime
		1631	Lambda/select 0.330 sec
		1632	+ optimized 0.122 sec
		1633	Lambda/AnyEvent 0.327 sec
		1634	+ optimized 0.138 sec
		1635	Raw sockets/select 0.077 sec
		1636	POE/select, components 0.662 sec
		1637	POE/select, raw sockets 0.226 sec
		1638	POE/select, optimized 0.404 sec
		1639
		1640	AnyEvent/select/nb 0.085 sec
		1641	AnyEvent/EV/nb 0.068 sec
		1642	+state machine 0.134 sec
		1643
		1644	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1645	benchmarks actually make blocking connects and use 100% blocking I/O,
		1646	defeating the purpose of an event-based solution. All of the newly
		1647	written AnyEvent benchmarks use 100% non-blocking connects (using
		1648	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1649	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1650	connects generally require a lot more bookkeeping and event handling
		1651	than blocking connects (which involve a single syscall only).
		1652
		1653	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1654	offers similar expressive power as POE and IO::Lambda, using
		1655	conventional Perl syntax. This means that both the echo server and the
		1656	client are 100% non-blocking, further placing it at a disadvantage.
		1657
		1658	As you can see, the AnyEvent + EV combination even beats the
		1659	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1660	backend easily beats IO::Lambda and POE.
		1661
		1662	And even the 100% non-blocking version written using the high-level (and
		1663	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
		1664	higher level ("unoptimised") abstractions by a large margin, even though
		1665	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		1666
		1667	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1668	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1669	part of the IO::Lambda distribution and were used without any changes.
		1670
		1671	SIGNALS
		1672	AnyEvent currently installs handlers for these signals:
		1673
		1674	SIGCHLD
		1675	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
		1676	emulation for event loops that do not support them natively. Also,
		1677	some event loops install a similar handler.
		1678
		1679	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1680	then AnyEvent will reset it to default, to avoid losing child exit
		1681	statuses.
		1682
		1683	SIGPIPE
		1684	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
		1685	"undef" when AnyEvent gets loaded.
		1686
		1687	The rationale for this is that AnyEvent users usually do not really
		1688	depend on SIGPIPE delivery (which is purely an optimisation for
		1689	shell use, or badly-written programs), but "SIGPIPE" can cause
		1690	spurious and rare program exits as a lot of people do not expect
		1691	"SIGPIPE" when writing to some random socket.
		1692
		1693	The rationale for installing a no-op handler as opposed to ignoring
		1694	it is that this way, the handler will be restored to defaults on
		1695	exec.
		1696
		1697	Feel free to install your own handler, or reset it to defaults.
		1698
		1699	RECOMMENDED/OPTIONAL MODULES
		1700	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1701	it's built-in modules) are required to use it.
		1702
		1703	That does not mean that AnyEvent won't take advantage of some additional
		1704	modules if they are installed.
		1705
		1706	This section epxlains which additional modules will be used, and how
		1707	they affect AnyEvent's operetion.
		1708
		1709	Async::Interrupt
		1710	This slightly arcane module is used to implement fast signal
		1711	handling: To my knowledge, there is no way to do completely
		1712	race-free and quick signal handling in pure perl. To ensure that
		1713	signals still get delivered, AnyEvent will start an interval timer
		1714	to wake up perl (and catch the signals) with some delay (default is
		1715	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1716
		1717	If this module is available, then it will be used to implement
		1718	signal catching, which means that signals will not be delayed, and
		1719	the event loop will not be interrupted regularly, which is more
		1720	efficient (And good for battery life on laptops).
		1721
		1722	This affects not just the pure-perl event loop, but also other event
		1723	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1724
		1725	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1726	natively, and either employ their own workarounds (POE) or use
		1727	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1728	Installing Async::Interrupt does nothing for those backends.
		1729
		1730	EV This module isn't really "optional", as it is simply one of the
		1731	backend event loops that AnyEvent can use. However, it is simply the
		1732	best event loop available in terms of features, speed and stability:
		1733	It supports the AnyEvent API optimally, implements all the watcher
		1734	types in XS, does automatic timer adjustments even when no monotonic
		1735	clock is available, can take avdantage of advanced kernel interfaces
		1736	such as "epoll" and "kqueue", and is the fastest backend by far.
		1737	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1738	Glib::EV).
		1739
		1740	Guard
		1741	The guard module, when used, will be used to implement
		1742	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1743	uses a lot less memory), but otherwise doesn't affect guard
		1744	operation much. It is purely used for performance.
		1745
		1746	JSON and JSON::XS
		1747	This module is required when you want to read or write JSON data via
		1748	AnyEvent::Handle. It is also written in pure-perl, but can take
		1749	advantage of the ultra-high-speed JSON::XS module when it is
		1750	installed.
		1751
		1752	In fact, AnyEvent::Handle will use JSON::XS by default if it is
		1753	installed.
		1754
		1755	Net::SSLeay
		1756	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1757	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1758	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1759
		1760	Time::HiRes
		1761	This module is part of perl since release 5.008. It will be used
		1762	when the chosen event library does not come with a timing source on
		1763	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1764	additionally use it to try to use a monotonic clock for timing
		1765	stability.
		1766
1176	FORK	1767	FORK
1177	Most event libraries are not fork-safe. The ones who are usually are	1768	Most event libraries are not fork-safe. The ones who are usually are
1178	because they rely on inefficient but fork-safe "select" or "poll" calls.	1769	because they rely on inefficient but fork-safe "select" or "poll" calls.
1179	Only EV is fully fork-aware.	1770	Only EV is fully fork-aware.
1180		1771
1181	If you have to fork, you must either do so before creating your first	1772	If you have to fork, you must either do so before creating your first
1182	watcher OR you must not use AnyEvent at all in the child.	1773	watcher OR you must not use AnyEvent at all in the child OR you must do
		1774	something completely out of the scope of AnyEvent.
1183		1775
1184	SECURITY CONSIDERATIONS	1776	SECURITY CONSIDERATIONS
1185	AnyEvent can be forced to load any event model via	1777	AnyEvent can be forced to load any event model via
1186	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1778	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1187	to execute arbitrary code or directly gain access, it can easily be used	1779	to execute arbitrary code or directly gain access, it can easily be used
…		…
1190	model than specified in the variable.	1782	model than specified in the variable.
1191		1783
1192	You can make AnyEvent completely ignore this variable by deleting it	1784	You can make AnyEvent completely ignore this variable by deleting it
1193	before the first watcher gets created, e.g. with a "BEGIN" block:	1785	before the first watcher gets created, e.g. with a "BEGIN" block:
1194		1786
1195	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1787	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1196		1788
1197	use AnyEvent;	1789	use AnyEvent;
1198		1790
1199	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1791	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1200	be used to probe what backend is used and gain other information (which	1792	be used to probe what backend is used and gain other information (which
1201	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	1793	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
		1794	and $ENV{PERL_ANYEVENT_STRICT}.
		1795
		1796	Note that AnyEvent will remove all environment variables starting with
		1797	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1798	enabled.
		1799
		1800	BUGS
		1801	Perl 5.8 has numerous memleaks that sometimes hit this module and are
		1802	hard to work around. If you suffer from memleaks, first upgrade to Perl
		1803	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
		1804	annoying memleaks, such as leaking on "map" and "grep" but it is usually
		1805	not as pronounced).
1202		1806
1203	SEE ALSO	1807	SEE ALSO
1204	Utility functions: AnyEvent::Util.	1808	Utility functions: AnyEvent::Util.
1205		1809
1206	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1810	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1207	Event::Lib, Qt, POE.	1811	Event::Lib, Qt, POE.
1208		1812
1209	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1813	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1210	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1814	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1211	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1815	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1816	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1212		1817
1213	Non-blocking file handles, sockets, TCP clients and servers:	1818	Non-blocking file handles, sockets, TCP clients and servers:
1214	AnyEvent::Handle, AnyEvent::Socket.	1819	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1215		1820
1216	Asynchronous DNS: AnyEvent::DNS.	1821	Asynchronous DNS: AnyEvent::DNS.
1217		1822
1218	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1823	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1219		1824
1220	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1825	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1826	AnyEvent::HTTP.
1221		1827
1222	AUTHOR	1828	AUTHOR
1223	Marc Lehmann <schmorp@schmorp.de>	1829	Marc Lehmann <schmorp@schmorp.de>
1224	http://home.schmorp.de/	1830	http://home.schmorp.de/
1225		1831

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Comparing AnyEvent/README (file contents): Revision 1.23 by root, Mon May 26 06:04:38 2008 UTC vs. Revision 1.54 by root, Tue Sep 1 18:27:46 2009 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.23 by root, Mon May 26 06:04:38 2008 UTC vs.
Revision 1.54 by root, Tue Sep 1 18:27:46 2009 UTC