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Comparing AnyEvent/README (file contents):
Revision 1.16 by root, Sat Apr 19 04:58:14 2008 UTC vs.
Revision 1.66 by root, Sun Aug 21 03:02:32 2011 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, Coro::EV, Coro::Event, Glib, Tk, Perl - various supported	4	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
5	event loops	5	Qt, FLTK and POE are various supported event loops/environments.
6		6
7	SYNOPSIS	7	SYNOPSIS
8	use AnyEvent;	8	use AnyEvent;
9		9
		10	# if you prefer function calls, look at the AE manpage for
		11	# an alternative API.
		12
		13	# file handle or descriptor readable
10	my $w = AnyEvent->io (fh => $fh, poll => "r\|w", cb => sub {	14	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		15
		16	# one-shot or repeating timers
		17	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		18	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
		19
		20	print AnyEvent->now; # prints current event loop time
		21	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		22
		23	# POSIX signal
		24	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		25
		26	# child process exit
		27	my $w = AnyEvent->child (pid => $pid, cb => sub {
		28	my ($pid, $status) = @_;
11	...	29	...
12	});	30	});
13		31
14	my $w = AnyEvent->timer (after => $seconds, cb => sub {	32	# called when event loop idle (if applicable)
15	...	33	my $w = AnyEvent->idle (cb => sub { ... });
16	});
17		34
18	my $w = AnyEvent->condvar; # stores whether a condition was flagged	35	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		36	$w->send; # wake up current and all future recv's
19	$w->wait; # enters "main loop" till $condvar gets ->broadcast	37	$w->recv; # enters "main loop" till $condvar gets ->send
20	$w->broadcast; # wake up current and all future wait's	38	# use a condvar in callback mode:
		39	$w->cb (sub { $_[0]->recv });
		40
		41	INTRODUCTION/TUTORIAL
		42	This manpage is mainly a reference manual. If you are interested in a
		43	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
		44	manpage.
		45
		46	SUPPORT
		47	An FAQ document is available as AnyEvent::FAQ.
		48
		49	There also is a mailinglist for discussing all things AnyEvent, and an
		50	IRC channel, too.
		51
		52	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
		53	Repository, at <http://anyevent.schmorp.de>, for more info.
21		54
22	WHY YOU SHOULD USE THIS MODULE (OR NOT)	55	WHY YOU SHOULD USE THIS MODULE (OR NOT)
23	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
24	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
25		58
26	Executive Summary: AnyEvent is compatible, AnyEvent is *free of	59	Executive Summary: AnyEvent is compatible, AnyEvent is *free of
27	policy* and AnyEvent is small and efficient.	60	policy* and AnyEvent is small and efficient.
28		61
29	First and foremost, AnyEvent is not an event model itself, it only	62	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	63	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,	64	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,	65	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.	66	only one event loop can be active at the same time in a process.
34	AnyEvent helps hiding the differences between those event loops.	67	AnyEvent cannot change this, but it can hide the differences between
		68	those event loops.
35		69
36	The goal of AnyEvent is to offer module authors the ability to do event	70	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	71	programming (waiting for I/O or timer events) without subscribing to a
38	religion, a way of living, and most importantly: without forcing your	72	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	73	module users into the same thing by forcing them to use the same event
40	model you use.	74	model you use.
41		75
42	For modules like POE or IO::Async (which is a total misnomer as it is	76	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	77	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	78	like joining a cult: After you join, you are dependent on them and you
45	cannot use anything else, as it is simply incompatible to everything	79	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	80	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.	81	are also forced to use the same event loop you use.
48		82
49	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	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	85	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
52	module uses one of those, every user of your module has to use it, too.	86	uses one of those, every user of your module has to use it, too. But if
53	But if your module uses AnyEvent, it works transparently with all event	87	your module uses AnyEvent, it works transparently with all event models
54	models it supports (including stuff like POE and IO::Async, as long as	88	it supports (including stuff like IO::Async, as long as those use one of
55	those use one of the supported event loops. It is trivial to add new	89	the supported event loops. It is easy to add new event loops to
56	event loops to AnyEvent, too, so it is future-proof).	90	AnyEvent, too, so it is future-proof).
57		91
58	In addition to being free of having to use *the one and only true event	92	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	93	model*, AnyEvent also is free of bloat and policy: with POE or similar
60	modules, you get an enourmous amount of code and strict rules you have	94	modules, you get an enormous amount of code and strict rules you have to
61	to follow. AnyEvent, on the other hand, is lean and up to the point, by	95	follow. AnyEvent, on the other hand, is lean and to the point, by only
62	only offering the functionality that is necessary, in as thin as a	96	offering the functionality that is necessary, in as thin as a wrapper as
63	wrapper as technically possible.	97	technically possible.
64		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox of
		100	useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
65	Of course, if you want lots of policy (this can arguably be somewhat	105	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	106	useful) and you want to force your users to use the one and only event
67	model, you should not use this module.	107	model, you should not use this module.
68		108
69	DESCRIPTION	109	DESCRIPTION
70	AnyEvent provides an identical interface to multiple event loops. This	110	AnyEvent provides a uniform interface to various event loops. This
71	allows module authors to utilise an event loop without forcing module	111	allows module authors to use event loop functionality without forcing
72	users to use the same event loop (as only a single event loop can	112	module users to use a specific event loop implementation (since more
73	coexist peacefully at any one time).	113	than one event loop cannot coexist peacefully).
74		114
75	The interface itself is vaguely similar, but not identical to the Event	115	The interface itself is vaguely similar, but not identical to the Event
76	module.	116	module.
77		117
78	During the first call of any watcher-creation method, the module tries	118	During the first call of any watcher-creation method, the module tries
79	to detect the currently loaded event loop by probing whether one of the	119	to detect the currently loaded event loop by probing whether one of the
80	following modules is already loaded: Coro::EV, Coro::Event, EV, Event,	120	following modules is already loaded: EV, AnyEvent::Loop, Event, Glib,
81	Glib, Tk. The first one found is used. If none are found, the module	121	Tk, Event::Lib, Qt, POE. The first one found is used. If none are
82	tries to load these modules in the stated order. The first one that can	122	detected, the module tries to load the first four modules in the order
83	be successfully loaded will be used. If, after this, still none could be	123	given; but note that if EV is not available, the pure-perl
84	found, AnyEvent will fall back to a pure-perl event loop, which is not	124	AnyEvent::Loop should always work, so the other two are not normally
85	very efficient, but should work everywhere.	125	tried.
86		126
87	Because AnyEvent first checks for modules that are already loaded,	127	Because AnyEvent first checks for modules that are already loaded,
88	loading an event model explicitly before first using AnyEvent will	128	loading an event model explicitly before first using AnyEvent will
89	likely make that model the default. For example:	129	likely make that model the default. For example:
90		130
92	use AnyEvent;	132	use AnyEvent;
93		133
94	# .. AnyEvent will likely default to Tk	134	# .. AnyEvent will likely default to Tk
95		135
96	The likely means that, if any module loads another event model and	136	The likely means that, if any module loads another event model and
97	starts using it, all bets are off. Maybe you should tell their authors	137	starts using it, all bets are off - this case should be very rare
98	to use AnyEvent so their modules work together with others seamlessly...	138	though, as very few modules hardcode event loops without announcing this
		139	very loudly.
99		140
100	The pure-perl implementation of AnyEvent is called	141	The pure-perl implementation of AnyEvent is called "AnyEvent::Loop".
101	"AnyEvent::Impl::Perl". Like other event modules you can load it	142	Like other event modules you can load it explicitly and enjoy the high
102	explicitly.	143	availability of that event loop :)
103		144
104	WATCHERS	145	WATCHERS
105	AnyEvent has the central concept of a watcher, which is an object that	146	AnyEvent has the central concept of a watcher, which is an object that
106	stores relevant data for each kind of event you are waiting for, such as	147	stores relevant data for each kind of event you are waiting for, such as
107	the callback to call, the filehandle to watch, etc.	148	the callback to call, the file handle to watch, etc.
108		149
109	These watchers are normal Perl objects with normal Perl lifetime. After	150	These watchers are normal Perl objects with normal Perl lifetime. After
110	creating a watcher it will immediately "watch" for events and invoke the	151	creating a watcher it will immediately "watch" for events and invoke the
111	callback when the event occurs (of course, only when the event model is	152	callback when the event occurs (of course, only when the event model is
112	in control).	153	in control).
113		154
		155	Note that callbacks must not permanently change global variables
		156	potentially in use by the event loop (such as $_ or $[) and that
		157	callbacks must not "die". The former is good programming practice in
		158	Perl and the latter stems from the fact that exception handling differs
		159	widely between event loops.
		160
114	To disable the watcher you have to destroy it (e.g. by setting the	161	To disable a watcher you have to destroy it (e.g. by setting the
115	variable you store it in to "undef" or otherwise deleting all references	162	variable you store it in to "undef" or otherwise deleting all references
116	to it).	163	to it).
117		164
118	All watchers are created by calling a method on the "AnyEvent" class.	165	All watchers are created by calling a method on the "AnyEvent" class.
119		166
120	Many watchers either are used with "recursion" (repeating timers for	167	Many watchers either are used with "recursion" (repeating timers for
121	example), or need to refer to their watcher object in other ways.	168	example), or need to refer to their watcher object in other ways.
122		169
123	An any way to achieve that is this pattern:	170	One way to achieve that is this pattern:
124		171
125	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	172	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
126	# you can use $w here, for example to undef it	173	# you can use $w here, for example to undef it
127	undef $w;	174	undef $w;
128	});	175	});
129		176
130	Note that "my $w; $w =" combination. This is necessary because in Perl,	177	Note that "my $w; $w =" combination. This is necessary because in Perl,
131	my variables are only visible after the statement in which they are	178	my variables are only visible after the statement in which they are
132	declared.	179	declared.
133		180
134	IO WATCHERS	181	I/O WATCHERS
		182	$w = AnyEvent->io (
		183	fh => <filehandle_or_fileno>,
		184	poll => <"r" or "w">,
		185	cb => <callback>,
		186	);
		187
135	You can create an I/O watcher by calling the "AnyEvent->io" method with	188	You can create an I/O watcher by calling the "AnyEvent->io" method with
136	the following mandatory key-value pairs as arguments:	189	the following mandatory key-value pairs as arguments:
137		190
138	"fh" the Perl file handle (not file descriptor) to watch for events.	191	"fh" is the Perl file handle (or a naked file descriptor) to watch for
		192	events (AnyEvent might or might not keep a reference to this file
		193	handle). Note that only file handles pointing to things for which
		194	non-blocking operation makes sense are allowed. This includes sockets,
		195	most character devices, pipes, fifos and so on, but not for example
		196	files or block devices.
		197
139	"poll" must be a string that is either "r" or "w", which creates a	198	"poll" must be a string that is either "r" or "w", which creates a
140	watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"	199	watcher waiting for "r"eadable or "w"ritable events, respectively.
		200
141	is the callback to invoke each time the file handle becomes ready.	201	"cb" is the callback to invoke each time the file handle becomes ready.
142		202
143	File handles will be kept alive, so as long as the watcher exists, the	203	Although the callback might get passed parameters, their value and
144	file handle exists, too.	204	presence is undefined and you cannot rely on them. Portable AnyEvent
		205	callbacks cannot use arguments passed to I/O watcher callbacks.
145		206
		207	The I/O watcher might use the underlying file descriptor or a copy of
146	It is not allowed to close a file handle as long as any watcher is	208	it. You must not close a file handle as long as any watcher is active on
147	active on the underlying file descriptor.	209	the underlying file descriptor.
148		210
149	Some event loops issue spurious readyness notifications, so you should	211	Some event loops issue spurious readiness notifications, so you should
150	always use non-blocking calls when reading/writing from/to your file	212	always use non-blocking calls when reading/writing from/to your file
151	handles.	213	handles.
152		214
153	Example:
154
155	# wait for readability of STDIN, then read a line and disable the watcher	215	Example: wait for readability of STDIN, then read a line and disable the
		216	watcher.
		217
156	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	218	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
157	chomp (my $input = <STDIN>);	219	chomp (my $input = <STDIN>);
158	warn "read: $input\n";	220	warn "read: $input\n";
159	undef $w;	221	undef $w;
160	});	222	});
161		223
162	TIME WATCHERS	224	TIME WATCHERS
		225	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		226
		227	$w = AnyEvent->timer (
		228	after => <fractional_seconds>,
		229	interval => <fractional_seconds>,
		230	cb => <callback>,
		231	);
		232
163	You can create a time watcher by calling the "AnyEvent->timer" method	233	You can create a time watcher by calling the "AnyEvent->timer" method
164	with the following mandatory arguments:	234	with the following mandatory arguments:
165		235
166	"after" specifies after how many seconds (fractional values are	236	"after" specifies after how many seconds (fractional values are
167	supported) should the timer activate. "cb" the callback to invoke in	237	supported) the callback should be invoked. "cb" is the callback to
168	that case.	238	invoke in that case.
169		239
170	The timer callback will be invoked at most once: if you want a repeating	240	Although the callback might get passed parameters, their value and
171	timer you have to create a new watcher (this is a limitation by both Tk	241	presence is undefined and you cannot rely on them. Portable AnyEvent
172	and Glib).	242	callbacks cannot use arguments passed to time watcher callbacks.
173		243
174	Example:	244	The callback will normally be invoked only once. If you specify another
		245	parameter, "interval", as a strictly positive number (> 0), then the
		246	callback will be invoked regularly at that interval (in fractional
		247	seconds) after the first invocation. If "interval" is specified with a
		248	false value, then it is treated as if it were not specified at all.
175		249
		250	The callback will be rescheduled before invoking the callback, but no
		251	attempt is made to avoid timer drift in most backends, so the interval
		252	is only approximate.
		253
176	# fire an event after 7.7 seconds	254	Example: fire an event after 7.7 seconds.
		255
177	my $w = AnyEvent->timer (after => 7.7, cb => sub {	256	my $w = AnyEvent->timer (after => 7.7, cb => sub {
178	warn "timeout\n";	257	warn "timeout\n";
179	});	258	});
180		259
181	# to cancel the timer:	260	# to cancel the timer:
182	undef $w;	261	undef $w;
183		262
184	Example 2:
185
186	# fire an event after 0.5 seconds, then roughly every second	263	Example 2: fire an event after 0.5 seconds, then roughly every second.
187	my $w;
188		264
189	my $cb = sub {
190	# cancel the old timer while creating a new one
191	$w = AnyEvent->timer (after => 1, cb => $cb);	265	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		266	warn "timeout\n";
192	};	267	};
193
194	# start the "loop" by creating the first watcher
195	$w = AnyEvent->timer (after => 0.5, cb => $cb);
196		268
197	TIMING ISSUES	269	TIMING ISSUES
198	There are two ways to handle timers: based on real time (relative, "fire	270	There are two ways to handle timers: based on real time (relative, "fire
199	in 10 seconds") and based on wallclock time (absolute, "fire at 12	271	in 10 seconds") and based on wallclock time (absolute, "fire at 12
200	o'clock").	272	o'clock").
201		273
202	While most event loops expect timers to specified in a relative way,	274	While most event loops expect timers to specified in a relative way,
203	they use absolute time internally. This makes a difference when your	275	they use absolute time internally. This makes a difference when your
204	clock "jumps", for example, when ntp decides to set your clock backwards	276	clock "jumps", for example, when ntp decides to set your clock backwards
205	from the wrong 2014-01-01 to 2008-01-01, a watcher that you created to	277	from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is
206	fire "after" a second might actually take six years to finally fire.	278	supposed to fire "after a second" might actually take six years to
		279	finally fire.
207		280
208	AnyEvent cannot compensate for this. The only event loop that is	281	AnyEvent cannot compensate for this. The only event loop that is
209	conscious about these issues is EV, which offers both relative	282	conscious of these issues is EV, which offers both relative (ev_timer,
210	(ev_timer) and absolute (ev_periodic) timers.	283	based on true relative time) and absolute (ev_periodic, based on
		284	wallclock time) timers.
211		285
212	AnyEvent always prefers relative timers, if available, matching the	286	AnyEvent always prefers relative timers, if available, matching the
213	AnyEvent API.	287	AnyEvent API.
214		288
		289	AnyEvent has two additional methods that return the "current time":
		290
		291	AnyEvent->time
		292	This returns the "current wallclock time" as a fractional number of
		293	seconds since the Epoch (the same thing as "time" or
		294	"Time::HiRes::time" return, and the result is guaranteed to be
		295	compatible with those).
		296
		297	It progresses independently of any event loop processing, i.e. each
		298	call will check the system clock, which usually gets updated
		299	frequently.
		300
		301	AnyEvent->now
		302	This also returns the "current wallclock time", but unlike "time",
		303	above, this value might change only once per event loop iteration,
		304	depending on the event loop (most return the same time as "time",
		305	above). This is the time that AnyEvent's timers get scheduled
		306	against.
		307
		308	*In almost all cases (in all cases if you don't care), this is the
		309	function to call when you want to know the current time.*
		310
		311	This function is also often faster then "AnyEvent->time", and thus
		312	the preferred method if you want some timestamp (for example,
		313	AnyEvent::Handle uses this to update its activity timeouts).
		314
		315	The rest of this section is only of relevance if you try to be very
		316	exact with your timing; you can skip it without a bad conscience.
		317
		318	For a practical example of when these times differ, consider
		319	Event::Lib and EV and the following set-up:
		320
		321	The event loop is running and has just invoked one of your callbacks
		322	at time=500 (assume no other callbacks delay processing). In your
		323	callback, you wait a second by executing "sleep 1" (blocking the
		324	process for a second) and then (at time=501) you create a relative
		325	timer that fires after three seconds.
		326
		327	With Event::Lib, "AnyEvent->time" and "AnyEvent->now" will both
		328	return 501, because that is the current time, and the timer will be
		329	scheduled to fire at time=504 (501 + 3).
		330
		331	With EV, "AnyEvent->time" returns 501 (as that is the current time),
		332	but "AnyEvent->now" returns 500, as that is the time the last event
		333	processing phase started. With EV, your timer gets scheduled to run
		334	at time=503 (500 + 3).
		335
		336	In one sense, Event::Lib is more exact, as it uses the current time
		337	regardless of any delays introduced by event processing. However,
		338	most callbacks do not expect large delays in processing, so this
		339	causes a higher drift (and a lot more system calls to get the
		340	current time).
		341
		342	In another sense, EV is more exact, as your timer will be scheduled
		343	at the same time, regardless of how long event processing actually
		344	took.
		345
		346	In either case, if you care (and in most cases, you don't), then you
		347	can get whatever behaviour you want with any event loop, by taking
		348	the difference between "AnyEvent->time" and "AnyEvent->now" into
		349	account.
		350
		351	AnyEvent->now_update
		352	Some event loops (such as EV or AnyEvent::Loop) cache the current
		353	time for each loop iteration (see the discussion of AnyEvent->now,
		354	above).
		355
		356	When a callback runs for a long time (or when the process sleeps),
		357	then this "current" time will differ substantially from the real
		358	time, which might affect timers and time-outs.
		359
		360	When this is the case, you can call this method, which will update
		361	the event loop's idea of "current time".
		362
		363	A typical example would be a script in a web server (e.g.
		364	"mod_perl") - when mod_perl executes the script, then the event loop
		365	will have the wrong idea about the "current time" (being potentially
		366	far in the past, when the script ran the last time). In that case
		367	you should arrange a call to "AnyEvent->now_update" each time the
		368	web server process wakes up again (e.g. at the start of your script,
		369	or in a handler).
		370
		371	Note that updating the time might cause some events to be handled.
		372
215	SIGNAL WATCHERS	373	SIGNAL WATCHERS
		374	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		375
216	You can watch for signals using a signal watcher, "signal" is the signal	376	You can watch for signals using a signal watcher, "signal" is the signal
217	name without any "SIG" prefix, "cb" is the Perl callback to be invoked	377	name in uppercase and without any "SIG" prefix, "cb" is the Perl
218	whenever a signal occurs.	378	callback to be invoked whenever a signal occurs.
219		379
		380	Although the callback might get passed parameters, their value and
		381	presence is undefined and you cannot rely on them. Portable AnyEvent
		382	callbacks cannot use arguments passed to signal watcher callbacks.
		383
220	Multiple signals occurances can be clumped together into one callback	384	Multiple signal occurrences can be clumped together into one callback
221	invocation, and callback invocation will be synchronous. synchronous	385	invocation, and callback invocation will be synchronous. Synchronous
222	means that it might take a while until the signal gets handled by the	386	means that it might take a while until the signal gets handled by the
223	process, but it is guarenteed not to interrupt any other callbacks.	387	process, but it is guaranteed not to interrupt any other callbacks.
224		388
225	The main advantage of using these watchers is that you can share a	389	The main advantage of using these watchers is that you can share a
226	signal between multiple watchers.	390	signal between multiple watchers, and AnyEvent will ensure that signals
		391	will not interrupt your program at bad times.
227		392
228	This watcher might use %SIG, so programs overwriting those signals	393	This watcher might use %SIG (depending on the event loop used), so
229	directly will likely not work correctly.	394	programs overwriting those signals directly will likely not work
		395	correctly.
230		396
231	Example: exit on SIGINT	397	Example: exit on SIGINT
232		398
233	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	399	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
234		400
		401	Restart Behaviour
		402	While restart behaviour is up to the event loop implementation, most
		403	will not restart syscalls (that includes Async::Interrupt and AnyEvent's
		404	pure perl implementation).
		405
		406	Safe/Unsafe Signals
		407	Perl signals can be either "safe" (synchronous to opcode handling) or
		408	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		409	latter might corrupt your memory.
		410
		411	AnyEvent signal handlers are, in addition, synchronous to the event
		412	loop, i.e. they will not interrupt your running perl program but will
		413	only be called as part of the normal event handling (just like timer,
		414	I/O etc. callbacks, too).
		415
		416	Signal Races, Delays and Workarounds
		417	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		418	callbacks to signals in a generic way, which is a pity, as you cannot do
		419	race-free signal handling in perl, requiring C libraries for this.
		420	AnyEvent will try to do its best, which means in some cases, signals
		421	will be delayed. The maximum time a signal might be delayed is specified
		422	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
		423	can be changed only before the first signal watcher is created, and
		424	should be left alone otherwise. This variable determines how often
		425	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		426	will cause fewer spurious wake-ups, which is better for power and CPU
		427	saving.
		428
		429	All these problems can be avoided by installing the optional
		430	Async::Interrupt module, which works with most event loops. It will not
		431	work with inherently broken event loops such as Event or Event::Lib (and
		432	not with POE currently, as POE does its own workaround with one-second
		433	latency). For those, you just have to suffer the delays.
		434
235	CHILD PROCESS WATCHERS	435	CHILD PROCESS WATCHERS
		436	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		437
236	You can also watch on a child process exit and catch its exit status.	438	You can also watch for a child process exit and catch its exit status.
237		439
238	The child process is specified by the "pid" argument (if set to 0, it	440	The child process is specified by the "pid" argument (on some backends,
239	watches for any child process exit). The watcher will trigger as often	441	using 0 watches for any child process exit, on others this will croak).
240	as status change for the child are received. This works by installing a	442	The watcher will be triggered only when the child process has finished
241	signal handler for "SIGCHLD". The callback will be called with the pid	443	and an exit status is available, not on any trace events
242	and exit status (as returned by waitpid).	444	(stopped/continued).
243		445
244	Example: wait for pid 1333	446	The callback will be called with the pid and exit status (as returned by
		447	waitpid), so unlike other watcher types, you can rely on child watcher
		448	callback arguments.
245		449
		450	This watcher type works by installing a signal handler for "SIGCHLD",
		451	and since it cannot be shared, nothing else should use SIGCHLD or reap
		452	random child processes (waiting for specific child processes, e.g.
		453	inside "system", is just fine).
		454
		455	There is a slight catch to child watchers, however: you usually start
		456	them after the child process was created, and this means the process
		457	could have exited already (and no SIGCHLD will be sent anymore).
		458
		459	Not all event models handle this correctly (neither POE nor IO::Async
		460	do, see their AnyEvent::Impl manpages for details), but even for event
		461	models that do handle this correctly, they usually need to be loaded
		462	before the process exits (i.e. before you fork in the first place).
		463	AnyEvent's pure perl event loop handles all cases correctly regardless
		464	of when you start the watcher.
		465
		466	This means you cannot create a child watcher as the very first thing in
		467	an AnyEvent program, you have to create at least one watcher before
		468	you "fork" the child (alternatively, you can call "AnyEvent::detect").
		469
		470	As most event loops do not support waiting for child events, they will
		471	be emulated by AnyEvent in most cases, in which case the latency and
		472	race problems mentioned in the description of signal watchers apply.
		473
		474	Example: fork a process and wait for it
		475
		476	my $done = AnyEvent->condvar;
		477
		478	my $pid = fork or exit 5;
		479
246	my $w = AnyEvent->child (	480	my $w = AnyEvent->child (
247	pid => 1333,	481	pid => $pid,
248	cb => sub {	482	cb => sub {
249	my ($pid, $status) = @_;	483	my ($pid, $status) = @_;
250	warn "pid $pid exited with status $status";	484	warn "pid $pid exited with status $status";
		485	$done->send;
251	},	486	},
252	);	487	);
		488
		489	# do something else, then wait for process exit
		490	$done->recv;
		491
		492	IDLE WATCHERS
		493	$w = AnyEvent->idle (cb => <callback>);
		494
		495	This will repeatedly invoke the callback after the process becomes idle,
		496	until either the watcher is destroyed or new events have been detected.
		497
		498	Idle watchers are useful when there is a need to do something, but it is
		499	not so important (or wise) to do it instantly. The callback will be
		500	invoked only when there is "nothing better to do", which is usually
		501	defined as "all outstanding events have been handled and no new events
		502	have been detected". That means that idle watchers ideally get invoked
		503	when the event loop has just polled for new events but none have been
		504	detected. Instead of blocking to wait for more events, the idle watchers
		505	will be invoked.
		506
		507	Unfortunately, most event loops do not really support idle watchers
		508	(only EV, Event and Glib do it in a usable fashion) - for the rest,
		509	AnyEvent will simply call the callback "from time to time".
		510
		511	Example: read lines from STDIN, but only process them when the program
		512	is otherwise idle:
		513
		514	my @lines; # read data
		515	my $idle_w;
		516	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		517	push @lines, scalar <STDIN>;
		518
		519	# start an idle watcher, if not already done
		520	$idle_w \|\|= AnyEvent->idle (cb => sub {
		521	# handle only one line, when there are lines left
		522	if (my $line = shift @lines) {
		523	print "handled when idle: $line";
		524	} else {
		525	# otherwise disable the idle watcher again
		526	undef $idle_w;
		527	}
		528	});
		529	});
253		530
254	CONDITION VARIABLES	531	CONDITION VARIABLES
		532	$cv = AnyEvent->condvar;
		533
		534	$cv->send (<list>);
		535	my @res = $cv->recv;
		536
		537	If you are familiar with some event loops you will know that all of them
		538	require you to run some blocking "loop", "run" or similar function that
		539	will actively watch for new events and call your callbacks.
		540
		541	AnyEvent is slightly different: it expects somebody else to run the
		542	event loop and will only block when necessary (usually when told by the
		543	user).
		544
		545	The tool to do that is called a "condition variable", so called because
		546	they represent a condition that must become true.
		547
		548	Now is probably a good time to look at the examples further below.
		549
255	Condition variables can be created by calling the "AnyEvent->condvar"	550	Condition variables can be created by calling the "AnyEvent->condvar"
256	method without any arguments.	551	method, usually without arguments. The only argument pair allowed is
		552	"cb", which specifies a callback to be called when the condition
		553	variable becomes true, with the condition variable as the first argument
		554	(but not the results).
257		555
258	A condition variable waits for a condition - precisely that the	556	After creation, the condition variable is "false" until it becomes
259	"->broadcast" method has been called.	557	"true" by calling the "send" method (or calling the condition variable
		558	as if it were a callback, read about the caveats in the description for
		559	the "->send" method).
260		560
261	They are very useful to signal that a condition has been fulfilled, for	561	Since condition variables are the most complex part of the AnyEvent API,
		562	here are some different mental models of what they are - pick the ones
		563	you can connect to:
		564
		565	* Condition variables are like callbacks - you can call them (and pass
		566	them instead of callbacks). Unlike callbacks however, you can also
		567	wait for them to be called.
		568
		569	* Condition variables are signals - one side can emit or send them,
		570	the other side can wait for them, or install a handler that is
		571	called when the signal fires.
		572
		573	* Condition variables are like "Merge Points" - points in your program
		574	where you merge multiple independent results/control flows into one.
		575
		576	* Condition variables represent a transaction - functions that start
		577	some kind of transaction can return them, leaving the caller the
		578	choice between waiting in a blocking fashion, or setting a callback.
		579
		580	* Condition variables represent future values, or promises to deliver
		581	some result, long before the result is available.
		582
		583	Condition variables are very useful to signal that something has
262	example, if you write a module that does asynchronous http requests,	584	finished, for example, if you write a module that does asynchronous http
263	then a condition variable would be the ideal candidate to signal the	585	requests, then a condition variable would be the ideal candidate to
264	availability of results.	586	signal the availability of results. The user can either act when the
		587	callback is called or can synchronously "->recv" for the results.
265		588
266	You can also use condition variables to block your main program until an	589	You can also use them to simulate traditional event loops - for example,
267	event occurs - for example, you could "->wait" in your main program	590	you can block your main program until an event occurs - for example, you
268	until the user clicks the Quit button in your app, which would	591	could "->recv" in your main program until the user clicks the Quit
269	"->broadcast" the "quit" event.	592	button of your app, which would "->send" the "quit" event.
270		593
271	Note that condition variables recurse into the event loop - if you have	594	Note that condition variables recurse into the event loop - if you have
272	two pirces of code that call "->wait" in a round-robbin fashion, you	595	two pieces of code that call "->recv" in a round-robin fashion, you
273	lose. Therefore, condition variables are good to export to your caller,	596	lose. Therefore, condition variables are good to export to your caller,
274	but you should avoid making a blocking wait yourself, at least in	597	but you should avoid making a blocking wait yourself, at least in
275	callbacks, as this asks for trouble.	598	callbacks, as this asks for trouble.
276		599
277	This object has two methods:	600	Condition variables are represented by hash refs in perl, and the keys
		601	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy
		602	(it is often useful to build your own transaction class on top of
		603	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
		604	its "new" method in your own "new" method.
278		605
279	$cv->wait	606	There are two "sides" to a condition variable - the "producer side"
280	Wait (blocking if necessary) until the "->broadcast" method has been	607	which eventually calls "-> send", and the "consumer side", which waits
281	called on c<$cv>, while servicing other watchers normally.	608	for the send to occur.
282		609
283	You can only wait once on a condition - additional calls will return	610	Example: wait for a timer.
284	immediately.
285		611
286	Not all event models support a blocking wait - some die in that case	612	# condition: "wait till the timer is fired"
287	(programs might want to do that to stay interactive), so *if you are
288	using this from a module, never require a blocking wait*, but let
289	the caller decide whether the call will block or not (for example,
290	by coupling condition variables with some kind of request results
291	and supporting callbacks so the caller knows that getting the result
292	will not block, while still suppporting blocking waits if the caller
293	so desires).
294
295	Another reason never to "->wait" in a module is that you cannot
296	sensibly have two "->wait"'s in parallel, as that would require
297	multiple interpreters or coroutines/threads, none of which
298	"AnyEvent" can supply (the coroutine-aware backends
299	AnyEvent::Impl::CoroEV and AnyEvent::Impl::CoroEvent explicitly
300	support concurrent "->wait"'s from different coroutines, however).
301
302	$cv->broadcast
303	Flag the condition as ready - a running "->wait" and all further
304	calls to "wait" will (eventually) return after this method has been
305	called. If nobody is waiting the broadcast will be remembered..
306
307	Example:
308
309	# wait till the result is ready
310	my $result_ready = AnyEvent->condvar;	613	my $timer_fired = AnyEvent->condvar;
311		614
312	# do something such as adding a timer	615	# create the timer - we could wait for, say
313	# or socket watcher the calls $result_ready->broadcast	616	# a handle becomign ready, or even an
314	# when the "result" is ready.	617	# AnyEvent::HTTP request to finish, but
315	# in this case, we simply use a timer:	618	# in this case, we simply use a timer:
316	my $w = AnyEvent->timer (	619	my $w = AnyEvent->timer (
317	after => 1,	620	after => 1,
318	cb => sub { $result_ready->broadcast },	621	cb => sub { $timer_fired->send },
319	);	622	);
320		623
321	# this "blocks" (while handling events) till the watcher	624	# this "blocks" (while handling events) till the callback
322	# calls broadcast	625	# calls ->send
323	$result_ready->wait;	626	$timer_fired->recv;
		627
		628	Example: wait for a timer, but take advantage of the fact that condition
		629	variables are also callable directly.
		630
		631	my $done = AnyEvent->condvar;
		632	my $delay = AnyEvent->timer (after => 5, cb => $done);
		633	$done->recv;
		634
		635	Example: Imagine an API that returns a condvar and doesn't support
		636	callbacks. This is how you make a synchronous call, for example from the
		637	main program:
		638
		639	use AnyEvent::CouchDB;
		640
		641	...
		642
		643	my @info = $couchdb->info->recv;
		644
		645	And this is how you would just set a callback to be called whenever the
		646	results are available:
		647
		648	$couchdb->info->cb (sub {
		649	my @info = $_[0]->recv;
		650	});
		651
		652	METHODS FOR PRODUCERS
		653	These methods should only be used by the producing side, i.e. the
		654	code/module that eventually sends the signal. Note that it is also the
		655	producer side which creates the condvar in most cases, but it isn't
		656	uncommon for the consumer to create it as well.
		657
		658	$cv->send (...)
		659	Flag the condition as ready - a running "->recv" and all further
		660	calls to "recv" will (eventually) return after this method has been
		661	called. If nobody is waiting the send will be remembered.
		662
		663	If a callback has been set on the condition variable, it is called
		664	immediately from within send.
		665
		666	Any arguments passed to the "send" call will be returned by all
		667	future "->recv" calls.
		668
		669	Condition variables are overloaded so one can call them directly (as
		670	if they were a code reference). Calling them directly is the same as
		671	calling "send".
		672
		673	$cv->croak ($error)
		674	Similar to send, but causes all calls to "->recv" to invoke
		675	"Carp::croak" with the given error message/object/scalar.
		676
		677	This can be used to signal any errors to the condition variable
		678	user/consumer. Doing it this way instead of calling "croak" directly
		679	delays the error detection, but has the overwhelming advantage that
		680	it diagnoses the error at the place where the result is expected,
		681	and not deep in some event callback with no connection to the actual
		682	code causing the problem.
		683
		684	$cv->begin ([group callback])
		685	$cv->end
		686	These two methods can be used to combine many transactions/events
		687	into one. For example, a function that pings many hosts in parallel
		688	might want to use a condition variable for the whole process.
		689
		690	Every call to "->begin" will increment a counter, and every call to
		691	"->end" will decrement it. If the counter reaches 0 in "->end", the
		692	(last) callback passed to "begin" will be executed, passing the
		693	condvar as first argument. That callback is supposed to call
		694	"->send", but that is not required. If no group callback was set,
		695	"send" will be called without any arguments.
		696
		697	You can think of "$cv->send" giving you an OR condition (one call
		698	sends), while "$cv->begin" and "$cv->end" giving you an AND
		699	condition (all "begin" calls must be "end"'ed before the condvar
		700	sends).
		701
		702	Let's start with a simple example: you have two I/O watchers (for
		703	example, STDOUT and STDERR for a program), and you want to wait for
		704	both streams to close before activating a condvar:
		705
		706	my $cv = AnyEvent->condvar;
		707
		708	$cv->begin; # first watcher
		709	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		710	defined sysread $fh1, my $buf, 4096
		711	or $cv->end;
		712	});
		713
		714	$cv->begin; # second watcher
		715	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		716	defined sysread $fh2, my $buf, 4096
		717	or $cv->end;
		718	});
		719
		720	$cv->recv;
		721
		722	This works because for every event source (EOF on file handle),
		723	there is one call to "begin", so the condvar waits for all calls to
		724	"end" before sending.
		725
		726	The ping example mentioned above is slightly more complicated, as
		727	the there are results to be passwd back, and the number of tasks
		728	that are begun can potentially be zero:
		729
		730	my $cv = AnyEvent->condvar;
		731
		732	my %result;
		733	$cv->begin (sub { shift->send (\%result) });
		734
		735	for my $host (@list_of_hosts) {
		736	$cv->begin;
		737	ping_host_then_call_callback $host, sub {
		738	$result{$host} = ...;
		739	$cv->end;
		740	};
		741	}
		742
		743	$cv->end;
		744
		745	This code fragment supposedly pings a number of hosts and calls
		746	"send" after results for all then have have been gathered - in any
		747	order. To achieve this, the code issues a call to "begin" when it
		748	starts each ping request and calls "end" when it has received some
		749	result for it. Since "begin" and "end" only maintain a counter, the
		750	order in which results arrive is not relevant.
		751
		752	There is an additional bracketing call to "begin" and "end" outside
		753	the loop, which serves two important purposes: first, it sets the
		754	callback to be called once the counter reaches 0, and second, it
		755	ensures that "send" is called even when "no" hosts are being pinged
		756	(the loop doesn't execute once).
		757
		758	This is the general pattern when you "fan out" into multiple (but
		759	potentially zero) subrequests: use an outer "begin"/"end" pair to
		760	set the callback and ensure "end" is called at least once, and then,
		761	for each subrequest you start, call "begin" and for each subrequest
		762	you finish, call "end".
		763
		764	METHODS FOR CONSUMERS
		765	These methods should only be used by the consuming side, i.e. the code
		766	awaits the condition.
		767
		768	$cv->recv
		769	Wait (blocking if necessary) until the "->send" or "->croak" methods
		770	have been called on $cv, while servicing other watchers normally.
		771
		772	You can only wait once on a condition - additional calls are valid
		773	but will return immediately.
		774
		775	If an error condition has been set by calling "->croak", then this
		776	function will call "croak".
		777
		778	In list context, all parameters passed to "send" will be returned,
		779	in scalar context only the first one will be returned.
		780
		781	Note that doing a blocking wait in a callback is not supported by
		782	any event loop, that is, recursive invocation of a blocking "->recv"
		783	is not allowed, and the "recv" call will "croak" if such a condition
		784	is detected. This condition can be slightly loosened by using
		785	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		786	thread that doesn't run the event loop itself.
		787
		788	Not all event models support a blocking wait - some die in that case
		789	(programs might want to do that to stay interactive), so *if you are
		790	using this from a module, never require a blocking wait*. Instead,
		791	let the caller decide whether the call will block or not (for
		792	example, by coupling condition variables with some kind of request
		793	results and supporting callbacks so the caller knows that getting
		794	the result will not block, while still supporting blocking waits if
		795	the caller so desires).
		796
		797	You can ensure that "->recv" never blocks by setting a callback and
		798	only calling "->recv" from within that callback (or at a later
		799	time). This will work even when the event loop does not support
		800	blocking waits otherwise.
		801
		802	$bool = $cv->ready
		803	Returns true when the condition is "true", i.e. whether "send" or
		804	"croak" have been called.
		805
		806	$cb = $cv->cb ($cb->($cv))
		807	This is a mutator function that returns the callback set and
		808	optionally replaces it before doing so.
		809
		810	The callback will be called when the condition becomes "true", i.e.
		811	when "send" or "croak" are called, with the only argument being the
		812	condition variable itself. If the condition is already true, the
		813	callback is called immediately when it is set. Calling "recv" inside
		814	the callback or at any later time is guaranteed not to block.
		815
		816	SUPPORTED EVENT LOOPS/BACKENDS
		817	The available backend classes are (every class has its own manpage):
		818
		819	Backends that are autoprobed when no other event loop can be found.
		820	EV is the preferred backend when no other event loop seems to be in
		821	use. If EV is not installed, then AnyEvent will fall back to its own
		822	pure-perl implementation, which is available everywhere as it comes
		823	with AnyEvent itself.
		824
		825	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		826	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		827
		828	Backends that are transparently being picked up when they are used.
		829	These will be used if they are already loaded when the first watcher
		830	is created, in which case it is assumed that the application is
		831	using them. This means that AnyEvent will automatically pick the
		832	right backend when the main program loads an event module before
		833	anything starts to create watchers. Nothing special needs to be done
		834	by the main program.
		835
		836	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		837	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		838	AnyEvent::Impl::Tk based on Tk, very broken.
		839	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		840	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		841	AnyEvent::Impl::Irssi used when running within irssi.
		842	AnyEvent::Impl::IOAsync based on IO::Async.
		843	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		844	AnyEvent::Impl::FLTK2 based on FLTK (fltk 2 binding).
		845
		846	Backends with special needs.
		847	Qt requires the Qt::Application to be instantiated first, but will
		848	otherwise be picked up automatically. As long as the main program
		849	instantiates the application before any AnyEvent watchers are
		850	created, everything should just work.
		851
		852	AnyEvent::Impl::Qt based on Qt.
		853
		854	Event loops that are indirectly supported via other backends.
		855	Some event loops can be supported via other modules:
		856
		857	There is no direct support for WxWidgets (Wx) or Prima.
		858
		859	WxWidgets has no support for watching file handles. However, you can
		860	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		861	simply polls 20 times per second, which was considered to be too
		862	horrible to even consider for AnyEvent.
		863
		864	Prima is not supported as nobody seems to be using it, but it has a
		865	POE backend, so it can be supported through POE.
		866
		867	AnyEvent knows about both Prima and Wx, however, and will try to
		868	load POE when detecting them, in the hope that POE will pick them
		869	up, in which case everything will be automatic.
324		870
325	GLOBAL VARIABLES AND FUNCTIONS	871	GLOBAL VARIABLES AND FUNCTIONS
		872	These are not normally required to use AnyEvent, but can be useful to
		873	write AnyEvent extension modules.
		874
326	$AnyEvent::MODEL	875	$AnyEvent::MODEL
327	Contains "undef" until the first watcher is being created. Then it	876	Contains "undef" until the first watcher is being created, before
		877	the backend has been autodetected.
		878
328	contains the event model that is being used, which is the name of	879	Afterwards it contains the event model that is being used, which is
329	the Perl class implementing the model. This class is usually one of	880	the name of the Perl class implementing the model. This class is
330	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	881	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
331	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).	882	other class in the case AnyEvent has been extended at runtime (e.g.
332		883	in rxvt-unicode it will be "urxvt::anyevent").
333	The known classes so far are:
334
335	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
336	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
337	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
338	AnyEvent::Impl::Event based on Event, also second best choice :)
339	AnyEvent::Impl::Glib based on Glib, third-best choice.
340	AnyEvent::Impl::Tk based on Tk, very bad choice.
341	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
342		884
343	AnyEvent::detect	885	AnyEvent::detect
344	Returns $AnyEvent::MODEL, forcing autodetection of the event model	886	Returns $AnyEvent::MODEL, forcing autodetection of the event model
345	if necessary. You should only call this function right before you	887	if necessary. You should only call this function right before you
346	would have created an AnyEvent watcher anyway, that is, as late as	888	would have created an AnyEvent watcher anyway, that is, as late as
347	possible at runtime.	889	possible at runtime, and not e.g. during initialisation of your
		890	module.
		891
		892	The effect of calling this function is as if a watcher had been
		893	created (specifically, actions that happen "when the first watcher
		894	is created" happen when calling detetc as well).
		895
		896	If you need to do some initialisation before AnyEvent watchers are
		897	created, use "post_detect".
		898
		899	$guard = AnyEvent::post_detect { BLOCK }
		900	Arranges for the code block to be executed as soon as the event
		901	model is autodetected (or immediately if that has already happened).
		902
		903	The block will be executed after the actual backend has been
		904	detected ($AnyEvent::MODEL is set), but before any watchers have
		905	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		906	other initialisations - see the sources of AnyEvent::Strict or
		907	AnyEvent::AIO to see how this is used.
		908
		909	The most common usage is to create some global watchers, without
		910	forcing event module detection too early, for example, AnyEvent::AIO
		911	creates and installs the global IO::AIO watcher in a "post_detect"
		912	block to avoid autodetecting the event module at load time.
		913
		914	If called in scalar or list context, then it creates and returns an
		915	object that automatically removes the callback again when it is
		916	destroyed (or "undef" when the hook was immediately executed). See
		917	AnyEvent::AIO for a case where this is useful.
		918
		919	Example: Create a watcher for the IO::AIO module and store it in
		920	$WATCHER, but do so only do so after the event loop is initialised.
		921
		922	our WATCHER;
		923
		924	my $guard = AnyEvent::post_detect {
		925	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		926	};
		927
		928	# the \|\|= is important in case post_detect immediately runs the block,
		929	# as to not clobber the newly-created watcher. assigning both watcher and
		930	# post_detect guard to the same variable has the advantage of users being
		931	# able to just C<undef $WATCHER> if the watcher causes them grief.
		932
		933	$WATCHER \|\|= $guard;
		934
		935	@AnyEvent::post_detect
		936	If there are any code references in this array (you can "push" to it
		937	before or after loading AnyEvent), then they will be called directly
		938	after the event loop has been chosen.
		939
		940	You should check $AnyEvent::MODEL before adding to this array,
		941	though: if it is defined then the event loop has already been
		942	detected, and the array will be ignored.
		943
		944	Best use "AnyEvent::post_detect { BLOCK }" when your application
		945	allows it, as it takes care of these details.
		946
		947	This variable is mainly useful for modules that can do something
		948	useful when AnyEvent is used and thus want to know when it is
		949	initialised, but do not need to even load it by default. This array
		950	provides the means to hook into AnyEvent passively, without loading
		951	it.
		952
		953	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		954	together, you could put this into Coro (this is the actual code used
		955	by Coro to accomplish this):
		956
		957	if (defined $AnyEvent::MODEL) {
		958	# AnyEvent already initialised, so load Coro::AnyEvent
		959	require Coro::AnyEvent;
		960	} else {
		961	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		962	# as soon as it is
		963	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		964	}
		965
		966	AnyEvent::postpone { BLOCK }
		967	Arranges for the block to be executed as soon as possible, but not
		968	before the call itself returns. In practise, the block will be
		969	executed just before the event loop polls for new events, or shortly
		970	afterwards.
		971
		972	This function never returns anything (to make the "return postpone {
		973	... }" idiom more useful.
		974
		975	To understand the usefulness of this function, consider a function
		976	that asynchronously does something for you and returns some
		977	transaction object or guard to let you cancel the operation. For
		978	example, "AnyEvent::Socket::tcp_connect":
		979
		980	# start a conenction attempt unless one is active
		981	$self->{connect_guard} \|\|= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		982	delete $self->{connect_guard};
		983	...
		984	};
		985
		986	Imagine that this function could instantly call the callback, for
		987	example, because it detects an obvious error such as a negative port
		988	number. Invoking the callback before the function returns causes
		989	problems however: the callback will be called and will try to delete
		990	the guard object. But since the function hasn't returned yet, there
		991	is nothing to delete. When the function eventually returns it will
		992	assign the guard object to "$self->{connect_guard}", where it will
		993	likely never be deleted, so the program thinks it is still trying to
		994	connect.
		995
		996	This is where "AnyEvent::postpone" should be used. Instead of
		997	calling the callback directly on error:
		998
		999	$cb->(undef), return # signal error to callback, BAD!
		1000	if $some_error_condition;
		1001
		1002	It should use "postpone":
		1003
		1004	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1005	if $some_error_condition;
		1006
		1007	AnyEvent::log $level, $msg[, @args]
		1008	Log the given $msg at the given $level.
		1009
		1010	Loads AnyEvent::Log on first use and calls "AnyEvent::Log::log" -
		1011	consequently, look at the AnyEvent::Log documentation for details.
		1012
		1013	If you want to sprinkle loads of logging calls around your code,
		1014	consider creating a logger callback with the "AnyEvent::Log::logger"
		1015	function.
348		1016
349	WHAT TO DO IN A MODULE	1017	WHAT TO DO IN A MODULE
350	As a module author, you should "use AnyEvent" and call AnyEvent methods	1018	As a module author, you should "use AnyEvent" and call AnyEvent methods
351	freely, but you should not load a specific event module or rely on it.	1019	freely, but you should not load a specific event module or rely on it.
352		1020
353	Be careful when you create watchers in the module body - AnyEvent will	1021	Be careful when you create watchers in the module body - AnyEvent will
354	decide which event module to use as soon as the first method is called,	1022	decide which event module to use as soon as the first method is called,
355	so by calling AnyEvent in your module body you force the user of your	1023	so by calling AnyEvent in your module body you force the user of your
356	module to load the event module first.	1024	module to load the event module first.
357		1025
358	Never call "->wait" on a condition variable unless you know that the	1026	Never call "->recv" on a condition variable unless you know that the
359	"->broadcast" method has been called on it already. This is because it	1027	"->send" method has been called on it already. This is because it will
360	will stall the whole program, and the whole point of using events is to	1028	stall the whole program, and the whole point of using events is to stay
361	stay interactive.	1029	interactive.
362		1030
363	It is fine, however, to call "->wait" when the user of your module	1031	It is fine, however, to call "->recv" when the user of your module
364	requests it (i.e. if you create a http request object ad have a method	1032	requests it (i.e. if you create a http request object ad have a method
365	called "results" that returns the results, it should call "->wait"	1033	called "results" that returns the results, it may call "->recv" freely,
366	freely, as the user of your module knows what she is doing. always).	1034	as the user of your module knows what she is doing. Always).
367		1035
368	WHAT TO DO IN THE MAIN PROGRAM	1036	WHAT TO DO IN THE MAIN PROGRAM
369	There will always be a single main program - the only place that should	1037	There will always be a single main program - the only place that should
370	dictate which event model to use.	1038	dictate which event model to use.
371		1039
372	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1040	If the program is not event-based, it need not do anything special, even
373	do anything special (it does not need to be event-based) and let	1041	when it depends on a module that uses an AnyEvent. If the program itself
374	AnyEvent decide which implementation to chose if some module relies on	1042	uses AnyEvent, but does not care which event loop is used, all it needs
375	it.	1043	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1044	available loop implementation.
376		1045
377	If the main program relies on a specific event model. For example, in	1046	If the main program relies on a specific event model - for example, in
378	Gtk2 programs you have to rely on the Glib module. You should load the	1047	Gtk2 programs you have to rely on the Glib module - you should load the
379	event module before loading AnyEvent or any module that uses it:	1048	event module before loading AnyEvent or any module that uses it:
380	generally speaking, you should load it as early as possible. The reason	1049	generally speaking, you should load it as early as possible. The reason
381	is that modules might create watchers when they are loaded, and AnyEvent	1050	is that modules might create watchers when they are loaded, and AnyEvent
382	will decide on the event model to use as soon as it creates watchers,	1051	will decide on the event model to use as soon as it creates watchers,
383	and it might chose the wrong one unless you load the correct one	1052	and it might choose the wrong one unless you load the correct one
384	yourself.	1053	yourself.
385		1054
386	You can chose to use a rather inefficient pure-perl implementation by	1055	You can chose to use a pure-perl implementation by loading the
387	loading the "AnyEvent::Impl::Perl" module, which gives you similar	1056	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
388	behaviour everywhere, but letting AnyEvent chose is generally better.	1057	but letting AnyEvent chose the model is generally better.
		1058
		1059	MAINLOOP EMULATION
		1060	Sometimes (often for short test scripts, or even standalone programs who
		1061	only want to use AnyEvent), you do not want to run a specific event
		1062	loop.
		1063
		1064	In that case, you can use a condition variable like this:
		1065
		1066	AnyEvent->condvar->recv;
		1067
		1068	This has the effect of entering the event loop and looping forever.
		1069
		1070	Note that usually your program has some exit condition, in which case it
		1071	is better to use the "traditional" approach of storing a condition
		1072	variable somewhere, waiting for it, and sending it when the program
		1073	should exit cleanly.
		1074
		1075	OTHER MODULES
		1076	The following is a non-exhaustive list of additional modules that use
		1077	AnyEvent as a client and can therefore be mixed easily with other
		1078	AnyEvent modules and other event loops in the same program. Some of the
		1079	modules come as part of AnyEvent, the others are available via CPAN (see
		1080	<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
		1081	non-exhaustive list), and the list is heavily biased towards modules of
		1082	the AnyEvent author himself :)
		1083
		1084	AnyEvent::Util
		1085	Contains various utility functions that replace often-used blocking
		1086	functions such as "inet_aton" with event/callback-based versions.
		1087
		1088	AnyEvent::Socket
		1089	Provides various utility functions for (internet protocol) sockets,
		1090	addresses and name resolution. Also functions to create non-blocking
		1091	tcp connections or tcp servers, with IPv6 and SRV record support and
		1092	more.
		1093
		1094	AnyEvent::Handle
		1095	Provide read and write buffers, manages watchers for reads and
		1096	writes, supports raw and formatted I/O, I/O queued and fully
		1097	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
		1098
		1099	AnyEvent::DNS
		1100	Provides rich asynchronous DNS resolver capabilities.
		1101
		1102	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
		1103	AnyEvent::IGS, AnyEvent::FCP
		1104	Implement event-based interfaces to the protocols of the same name
		1105	(for the curious, IGS is the International Go Server and FCP is the
		1106	Freenet Client Protocol).
		1107
		1108	AnyEvent::Handle::UDP
		1109	Here be danger!
		1110
		1111	As Pauli would put it, "Not only is it not right, it's not even
		1112	wrong!" - there are so many things wrong with AnyEvent::Handle::UDP,
		1113	most notably its use of a stream-based API with a protocol that
		1114	isn't streamable, that the only way to improve it is to delete it.
		1115
		1116	It features data corruption (but typically only under load) and
		1117	general confusion. On top, the author is not only clueless about UDP
		1118	but also fact-resistant - some gems of his understanding: "connect
		1119	doesn't work with UDP", "UDP packets are not IP packets", "UDP only
		1120	has datagrams, not packets", "I don't need to implement proper error
		1121	checking as UDP doesn't support error checking" and so on - he
		1122	doesn't even understand what's wrong with his module when it is
		1123	explained to him.
		1124
		1125	AnyEvent::DBI
		1126	Executes DBI requests asynchronously in a proxy process for you,
		1127	notifying you in an event-based way when the operation is finished.
		1128
		1129	AnyEvent::AIO
		1130	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1131	the toolbox of every event programmer. AnyEvent::AIO transparently
		1132	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1133	event-based file I/O, and much more.
		1134
		1135	AnyEvent::HTTPD
		1136	A simple embedded webserver.
		1137
		1138	AnyEvent::FastPing
		1139	The fastest ping in the west.
		1140
		1141	Coro
		1142	Has special support for AnyEvent via Coro::AnyEvent.
		1143
		1144	SIMPLIFIED AE API
		1145	Starting with version 5.0, AnyEvent officially supports a second, much
		1146	simpler, API that is designed to reduce the calling, typing and memory
		1147	overhead by using function call syntax and a fixed number of parameters.
		1148
		1149	See the AE manpage for details.
		1150
		1151	ERROR AND EXCEPTION HANDLING
		1152	In general, AnyEvent does not do any error handling - it relies on the
		1153	caller to do that if required. The AnyEvent::Strict module (see also the
		1154	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
		1155	checking of all AnyEvent methods, however, which is highly useful during
		1156	development.
		1157
		1158	As for exception handling (i.e. runtime errors and exceptions thrown
		1159	while executing a callback), this is not only highly event-loop
		1160	specific, but also not in any way wrapped by this module, as this is the
		1161	job of the main program.
		1162
		1163	The pure perl event loop simply re-throws the exception (usually within
		1164	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
		1165	Glib uses "install_exception_handler" and so on.
		1166
		1167	ENVIRONMENT VARIABLES
		1168	The following environment variables are used by this module or its
		1169	submodules.
		1170
		1171	Note that AnyEvent will remove all environment variables starting with
		1172	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1173	enabled.
		1174
		1175	"PERL_ANYEVENT_VERBOSE"
		1176	By default, AnyEvent will be completely silent except in fatal
		1177	conditions. You can set this environment variable to make AnyEvent
		1178	more talkative.
		1179
		1180	When set to 5 or higher, causes AnyEvent to warn about unexpected
		1181	conditions, such as not being able to load the event model specified
		1182	by "PERL_ANYEVENT_MODEL".
		1183
		1184	When set to 7 or higher, cause AnyEvent to report to STDERR which
		1185	event model it chooses.
		1186
		1187	When set to 8 or higher, then AnyEvent will report extra information
		1188	on which optional modules it loads and how it implements certain
		1189	features.
		1190
		1191	"PERL_ANYEVENT_STRICT"
		1192	AnyEvent does not do much argument checking by default, as thorough
		1193	argument checking is very costly. Setting this variable to a true
		1194	value will cause AnyEvent to load "AnyEvent::Strict" and then to
		1195	thoroughly check the arguments passed to most method calls. If it
		1196	finds any problems, it will croak.
		1197
		1198	In other words, enables "strict" mode.
		1199
		1200	Unlike "use strict" (or its modern cousin, "use common::sense", it
		1201	is definitely recommended to keep it off in production. Keeping
		1202	"PERL_ANYEVENT_STRICT=1" in your environment while developing
		1203	programs can be very useful, however.
		1204
		1205	"PERL_ANYEVENT_DEBUG_SHELL"
		1206	If this env variable is set, then its contents will be interpreted
		1207	by "AnyEvent::Socket::parse_hostport" (after replacing every
		1208	occurance of $$ by the process pid) and an "AnyEvent::Debug::shell"
		1209	is bound on that port. The shell object is saved in
		1210	$AnyEvent::Debug::SHELL.
		1211
		1212	This takes place when the first watcher is created.
		1213
		1214	For example, to bind a debug shell on a unix domain socket in
		1215	/tmp/debug<pid>.sock, you could use this:
		1216
		1217	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		1218
		1219	Note that creating sockets in /tmp is very unsafe on multiuser
		1220	systems.
		1221
		1222	"PERL_ANYEVENT_DEBUG_WRAP"
		1223	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1224	debugging purposes. See "AnyEvent::Debug::wrap" for details.
		1225
		1226	"PERL_ANYEVENT_MODEL"
		1227	This can be used to specify the event model to be used by AnyEvent,
		1228	before auto detection and -probing kicks in.
		1229
		1230	It normally is a string consisting entirely of ASCII letters (e.g.
		1231	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1232	the resulting module name is loaded and - if the load was successful
		1233	- used as event model backend. If it fails to load then AnyEvent
		1234	will proceed with auto detection and -probing.
		1235
		1236	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1237	then nothing gets prepended and the module name is used as-is (hint:
		1238	"::" at the end of a string designates a module name and quotes it
		1239	appropriately).
		1240
		1241	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
		1242	could start your program like this:
		1243
		1244	PERL_ANYEVENT_MODEL=Perl perl ...
		1245
		1246	"PERL_ANYEVENT_PROTOCOLS"
		1247	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
		1248	preferences for IPv4 or IPv6. The default is unspecified (and might
		1249	change, or be the result of auto probing).
		1250
		1251	Must be set to a comma-separated list of protocols or address
		1252	families, current supported: "ipv4" and "ipv6". Only protocols
		1253	mentioned will be used, and preference will be given to protocols
		1254	mentioned earlier in the list.
		1255
		1256	This variable can effectively be used for denial-of-service attacks
		1257	against local programs (e.g. when setuid), although the impact is
		1258	likely small, as the program has to handle conenction and other
		1259	failures anyways.
		1260
		1261	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
		1262	IPv6, but support both and try to use both.
		1263	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
		1264	resolve or contact IPv6 addresses.
		1265	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
		1266	prefer IPv6 over IPv4.
		1267
		1268	"PERL_ANYEVENT_EDNS0"
		1269	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
		1270	for DNS. This extension is generally useful to reduce DNS traffic,
		1271	but some (broken) firewalls drop such DNS packets, which is why it
		1272	is off by default.
		1273
		1274	Setting this variable to 1 will cause AnyEvent::DNS to announce
		1275	EDNS0 in its DNS requests.
		1276
		1277	"PERL_ANYEVENT_MAX_FORKS"
		1278	The maximum number of child processes that
		1279	"AnyEvent::Util::fork_call" will create in parallel.
		1280
		1281	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1282	The default value for the "max_outstanding" parameter for the
		1283	default DNS resolver - this is the maximum number of parallel DNS
		1284	requests that are sent to the DNS server.
		1285
		1286	"PERL_ANYEVENT_RESOLV_CONF"
		1287	The file to use instead of /etc/resolv.conf (or OS-specific
		1288	configuration) in the default resolver. When set to the empty
		1289	string, no default config will be used.
		1290
		1291	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1292	When neither "ca_file" nor "ca_path" was specified during
		1293	AnyEvent::TLS context creation, and either of these environment
		1294	variables exist, they will be used to specify CA certificate
		1295	locations instead of a system-dependent default.
		1296
		1297	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1298	When these are set to 1, then the respective modules are not loaded.
		1299	Mostly good for testing AnyEvent itself.
389		1300
390	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1301	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
391	This is an advanced topic that you do not normally need to use AnyEvent	1302	This is an advanced topic that you do not normally need to use AnyEvent
392	in a module. This section is only of use to event loop authors who want	1303	in a module. This section is only of use to event loop authors who want
393	to provide AnyEvent compatibility.	1304	to provide AnyEvent compatibility.
…		…
428	rxvt-unicode also cheats a bit by not providing blocking access to	1339	rxvt-unicode also cheats a bit by not providing blocking access to
429	condition variables: code blocking while waiting for a condition will	1340	condition variables: code blocking while waiting for a condition will
430	"die". This still works with most modules/usages, and blocking calls	1341	"die". This still works with most modules/usages, and blocking calls
431	must not be done in an interactive application, so it makes sense.	1342	must not be done in an interactive application, so it makes sense.
432		1343
433	ENVIRONMENT VARIABLES
434	The following environment variables are used by this module:
435
436	"PERL_ANYEVENT_VERBOSE" when set to 2 or higher, cause AnyEvent to
437	report to STDERR which event model it chooses.
438
439	EXAMPLE PROGRAM	1344	EXAMPLE PROGRAM
440	The following program uses an IO watcher to read data from STDIN, a	1345	The following program uses an I/O watcher to read data from STDIN, a
441	timer to display a message once per second, and a condition variable to	1346	timer to display a message once per second, and a condition variable to
442	quit the program when the user enters quit:	1347	quit the program when the user enters quit:
443		1348
444	use AnyEvent;	1349	use AnyEvent;
445		1350
…		…
450	poll => 'r',	1355	poll => 'r',
451	cb => sub {	1356	cb => sub {
452	warn "io event <$_[0]>\n"; # will always output <r>	1357	warn "io event <$_[0]>\n"; # will always output <r>
453	chomp (my $input = <STDIN>); # read a line	1358	chomp (my $input = <STDIN>); # read a line
454	warn "read: $input\n"; # output what has been read	1359	warn "read: $input\n"; # output what has been read
455	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1360	$cv->send if $input =~ /^q/i; # quit program if /^q/i
456	},	1361	},
457	);	1362	);
458		1363
459	my $time_watcher; # can only be used once
460
461	sub new_timer {
462	$timer = AnyEvent->timer (after => 1, cb => sub {	1364	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
463	warn "timeout\n"; # print 'timeout' about every second	1365	warn "timeout\n"; # print 'timeout' at most every second
464	&new_timer; # and restart the time
465	});
466	}	1366	});
467		1367
468	new_timer; # create first timer
469
470	$cv->wait; # wait until user enters /^q/i	1368	$cv->recv; # wait until user enters /^q/i
471		1369
472	REAL-WORLD EXAMPLE	1370	REAL-WORLD EXAMPLE
473	Consider the Net::FCP module. It features (among others) the following	1371	Consider the Net::FCP module. It features (among others) the following
474	API calls, which are to freenet what HTTP GET requests are to http:	1372	API calls, which are to freenet what HTTP GET requests are to http:
475		1373
…		…
524	syswrite $txn->{fh}, $txn->{request}	1422	syswrite $txn->{fh}, $txn->{request}
525	or die "connection or write error";	1423	or die "connection or write error";
526	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1424	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
527		1425
528	Again, "fh_ready_r" waits till all data has arrived, and then stores the	1426	Again, "fh_ready_r" waits till all data has arrived, and then stores the
529	result and signals any possible waiters that the request ahs finished:	1427	result and signals any possible waiters that the request has finished:
530		1428
531	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1429	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
532		1430
533	if (end-of-file or data complete) {	1431	if (end-of-file or data complete) {
534	$txn->{result} = $txn->{buf};	1432	$txn->{result} = $txn->{buf};
535	$txn->{finished}->broadcast;	1433	$txn->{finished}->send;
536	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1434	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
537	}	1435	}
538		1436
539	The "result" method, finally, just waits for the finished signal (if the	1437	The "result" method, finally, just waits for the finished signal (if the
540	request was already finished, it doesn't wait, of course, and returns	1438	request was already finished, it doesn't wait, of course, and returns
541	the data:	1439	the data:
542		1440
543	$txn->{finished}->wait;	1441	$txn->{finished}->recv;
544	return $txn->{result};	1442	return $txn->{result};
545		1443
546	The actual code goes further and collects all errors ("die"s,	1444	The actual code goes further and collects all errors ("die"s,
547	exceptions) that occured during request processing. The "result" method	1445	exceptions) that occurred during request processing. The "result" method
548	detects whether an exception as thrown (it is stored inside the $txn	1446	detects whether an exception as thrown (it is stored inside the $txn
549	object) and just throws the exception, which means connection errors and	1447	object) and just throws the exception, which means connection errors and
550	other problems get reported tot he code that tries to use the result,	1448	other problems get reported to the code that tries to use the result,
551	not in a random callback.	1449	not in a random callback.
552		1450
553	All of this enables the following usage styles:	1451	All of this enables the following usage styles:
554		1452
555	1. Blocking:	1453	1. Blocking:
…		…
583		1481
584	my $quit = AnyEvent->condvar;	1482	my $quit = AnyEvent->condvar;
585		1483
586	$fcp->txn_client_get ($url)->cb (sub {	1484	$fcp->txn_client_get ($url)->cb (sub {
587	...	1485	...
588	$quit->broadcast;	1486	$quit->send;
589	});	1487	});
590		1488
591	$quit->wait;	1489	$quit->recv;
		1490
		1491	BENCHMARKS
		1492	To give you an idea of the performance and overheads that AnyEvent adds
		1493	over the event loops themselves and to give you an impression of the
		1494	speed of various event loops I prepared some benchmarks.
		1495
		1496	BENCHMARKING ANYEVENT OVERHEAD
		1497	Here is a benchmark of various supported event models used natively and
		1498	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1499	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1500	which it is), lets them fire exactly once and destroys them again.
		1501
		1502	Source code for this benchmark is found as eg/bench in the AnyEvent
		1503	distribution. It uses the AE interface, which makes a real difference
		1504	for the EV and Perl backends only.
		1505
		1506	Explanation of the columns
		1507	watcher is the number of event watchers created/destroyed. Since
		1508	different event models feature vastly different performances, each event
		1509	loop was given a number of watchers so that overall runtime is
		1510	acceptable and similar between tested event loop (and keep them from
		1511	crashing): Glib would probably take thousands of years if asked to
		1512	process the same number of watchers as EV in this benchmark.
		1513
		1514	bytes is the number of bytes (as measured by the resident set size,
		1515	RSS) consumed by each watcher. This method of measuring captures both C
		1516	and Perl-based overheads.
		1517
		1518	create is the time, in microseconds (millionths of seconds), that it
		1519	takes to create a single watcher. The callback is a closure shared
		1520	between all watchers, to avoid adding memory overhead. That means
		1521	closure creation and memory usage is not included in the figures.
		1522
		1523	invoke is the time, in microseconds, used to invoke a simple callback.
		1524	The callback simply counts down a Perl variable and after it was invoked
		1525	"watcher" times, it would "->send" a condvar once to signal the end of
		1526	this phase.
		1527
		1528	destroy is the time, in microseconds, that it takes to destroy a
		1529	single watcher.
		1530
		1531	Results
		1532	name watchers bytes create invoke destroy comment
		1533	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
		1534	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
		1535	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
		1536	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
		1537	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
		1538	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		1539	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		1540	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
		1541	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
		1542	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
		1543	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
		1544	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
		1545
		1546	Discussion
		1547	The benchmark does not measure scalability of the event loop very
		1548	well. For example, a select-based event loop (such as the pure perl one)
		1549	can never compete with an event loop that uses epoll when the number of
		1550	file descriptors grows high. In this benchmark, all events become ready
		1551	at the same time, so select/poll-based implementations get an unnatural
		1552	speed boost.
		1553
		1554	Also, note that the number of watchers usually has a nonlinear effect on
		1555	overall speed, that is, creating twice as many watchers doesn't take
		1556	twice the time - usually it takes longer. This puts event loops tested
		1557	with a higher number of watchers at a disadvantage.
		1558
		1559	To put the range of results into perspective, consider that on the
		1560	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1561	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
		1562	CPU cycles with POE.
		1563
		1564	"EV" is the sole leader regarding speed and memory use, which are both
		1565	maximal/minimal, respectively. When using the AE API there is zero
		1566	overhead (when going through the AnyEvent API create is about 5-6 times
		1567	slower, with other times being equal, so still uses far less memory than
		1568	any other event loop and is still faster than Event natively).
		1569
		1570	The pure perl implementation is hit in a few sweet spots (both the
		1571	constant timeout and the use of a single fd hit optimisations in the
		1572	perl interpreter and the backend itself). Nevertheless this shows that
		1573	it adds very little overhead in itself. Like any select-based backend
		1574	its performance becomes really bad with lots of file descriptors (and
		1575	few of them active), of course, but this was not subject of this
		1576	benchmark.
		1577
		1578	The "Event" module has a relatively high setup and callback invocation
		1579	cost, but overall scores in on the third place.
		1580
		1581	"IO::Async" performs admirably well, about on par with "Event", even
		1582	when using its pure perl backend.
		1583
		1584	"Glib"'s memory usage is quite a bit higher, but it features a faster
		1585	callback invocation and overall ends up in the same class as "Event".
		1586	However, Glib scales extremely badly, doubling the number of watchers
		1587	increases the processing time by more than a factor of four, making it
		1588	completely unusable when using larger numbers of watchers (note that
		1589	only a single file descriptor was used in the benchmark, so
		1590	inefficiencies of "poll" do not account for this).
		1591
		1592	The "Tk" adaptor works relatively well. The fact that it crashes with
		1593	more than 2000 watchers is a big setback, however, as correctness takes
		1594	precedence over speed. Nevertheless, its performance is surprising, as
		1595	the file descriptor is dup()ed for each watcher. This shows that the
		1596	dup() employed by some adaptors is not a big performance issue (it does
		1597	incur a hidden memory cost inside the kernel which is not reflected in
		1598	the figures above).
		1599
		1600	"POE", regardless of underlying event loop (whether using its pure perl
		1601	select-based backend or the Event module, the POE-EV backend couldn't be
		1602	tested because it wasn't working) shows abysmal performance and memory
		1603	usage with AnyEvent: Watchers use almost 30 times as much memory as EV
		1604	watchers, and 10 times as much memory as Event (the high memory
		1605	requirements are caused by requiring a session for each watcher).
		1606	Watcher invocation speed is almost 900 times slower than with AnyEvent's
		1607	pure perl implementation.
		1608
		1609	The design of the POE adaptor class in AnyEvent can not really account
		1610	for the performance issues, though, as session creation overhead is
		1611	small compared to execution of the state machine, which is coded pretty
		1612	optimally within AnyEvent::Impl::POE (and while everybody agrees that
		1613	using multiple sessions is not a good approach, especially regarding
		1614	memory usage, even the author of POE could not come up with a faster
		1615	design).
		1616
		1617	Summary
		1618	* Using EV through AnyEvent is faster than any other event loop (even
		1619	when used without AnyEvent), but most event loops have acceptable
		1620	performance with or without AnyEvent.
		1621
		1622	* The overhead AnyEvent adds is usually much smaller than the overhead
		1623	of the actual event loop, only with extremely fast event loops such
		1624	as EV does AnyEvent add significant overhead.
		1625
		1626	* You should avoid POE like the plague if you want performance or
		1627	reasonable memory usage.
		1628
		1629	BENCHMARKING THE LARGE SERVER CASE
		1630	This benchmark actually benchmarks the event loop itself. It works by
		1631	creating a number of "servers": each server consists of a socket pair, a
		1632	timeout watcher that gets reset on activity (but never fires), and an
		1633	I/O watcher waiting for input on one side of the socket. Each time the
		1634	socket watcher reads a byte it will write that byte to a random other
		1635	"server".
		1636
		1637	The effect is that there will be a lot of I/O watchers, only part of
		1638	which are active at any one point (so there is a constant number of
		1639	active fds for each loop iteration, but which fds these are is random).
		1640	The timeout is reset each time something is read because that reflects
		1641	how most timeouts work (and puts extra pressure on the event loops).
		1642
		1643	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
		1644	100 (1%) are active. This mirrors the activity of large servers with
		1645	many connections, most of which are idle at any one point in time.
		1646
		1647	Source code for this benchmark is found as eg/bench2 in the AnyEvent
		1648	distribution. It uses the AE interface, which makes a real difference
		1649	for the EV and Perl backends only.
		1650
		1651	Explanation of the columns
		1652	sockets is the number of sockets, and twice the number of "servers"
		1653	(as each server has a read and write socket end).
		1654
		1655	create is the time it takes to create a socket pair (which is
		1656	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1657
		1658	request, the most important value, is the time it takes to handle a
		1659	single "request", that is, reading the token from the pipe and
		1660	forwarding it to another server. This includes deleting the old timeout
		1661	and creating a new one that moves the timeout into the future.
		1662
		1663	Results
		1664	name sockets create request
		1665	EV 20000 62.66 7.99
		1666	Perl 20000 68.32 32.64
		1667	IOAsync 20000 174.06 101.15 epoll
		1668	IOAsync 20000 174.67 610.84 poll
		1669	Event 20000 202.69 242.91
		1670	Glib 20000 557.01 1689.52
		1671	POE 20000 341.54 12086.32 uses POE::Loop::Event
		1672
		1673	Discussion
		1674	This benchmark does measure scalability and overall performance of the
		1675	particular event loop.
		1676
		1677	EV is again fastest. Since it is using epoll on my system, the setup
		1678	time is relatively high, though.
		1679
		1680	Perl surprisingly comes second. It is much faster than the C-based event
		1681	loops Event and Glib.
		1682
		1683	IO::Async performs very well when using its epoll backend, and still
		1684	quite good compared to Glib when using its pure perl backend.
		1685
		1686	Event suffers from high setup time as well (look at its code and you
		1687	will understand why). Callback invocation also has a high overhead
		1688	compared to the "$_->() for .."-style loop that the Perl event loop
		1689	uses. Event uses select or poll in basically all documented
		1690	configurations.
		1691
		1692	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1693	clearly fails to perform with many filehandles or in busy servers.
		1694
		1695	POE is still completely out of the picture, taking over 1000 times as
		1696	long as EV, and over 100 times as long as the Perl implementation, even
		1697	though it uses a C-based event loop in this case.
		1698
		1699	Summary
		1700	* The pure perl implementation performs extremely well.
		1701
		1702	* Avoid Glib or POE in large projects where performance matters.
		1703
		1704	BENCHMARKING SMALL SERVERS
		1705	While event loops should scale (and select-based ones do not...) even to
		1706	large servers, most programs we (or I :) actually write have only a few
		1707	I/O watchers.
		1708
		1709	In this benchmark, I use the same benchmark program as in the large
		1710	server case, but it uses only eight "servers", of which three are active
		1711	at any one time. This should reflect performance for a small server
		1712	relatively well.
		1713
		1714	The columns are identical to the previous table.
		1715
		1716	Results
		1717	name sockets create request
		1718	EV 16 20.00 6.54
		1719	Perl 16 25.75 12.62
		1720	Event 16 81.27 35.86
		1721	Glib 16 32.63 15.48
		1722	POE 16 261.87 276.28 uses POE::Loop::Event
		1723
		1724	Discussion
		1725	The benchmark tries to test the performance of a typical small server.
		1726	While knowing how various event loops perform is interesting, keep in
		1727	mind that their overhead in this case is usually not as important, due
		1728	to the small absolute number of watchers (that is, you need efficiency
		1729	and speed most when you have lots of watchers, not when you only have a
		1730	few of them).
		1731
		1732	EV is again fastest.
		1733
		1734	Perl again comes second. It is noticeably faster than the C-based event
		1735	loops Event and Glib, although the difference is too small to really
		1736	matter.
		1737
		1738	POE also performs much better in this case, but is is still far behind
		1739	the others.
		1740
		1741	Summary
		1742	* C-based event loops perform very well with small number of watchers,
		1743	as the management overhead dominates.
		1744
		1745	THE IO::Lambda BENCHMARK
		1746	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1747	could be misinterpreted to make AnyEvent look bad. In fact, the
		1748	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1749	better (which shouldn't come as a surprise to anybody). As such, the
		1750	benchmark is fine, and mostly shows that the AnyEvent backend from
		1751	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1752	without the extra baggage? To explore this, I wrote the equivalent
		1753	benchmark for AnyEvent.
		1754
		1755	The benchmark itself creates an echo-server, and then, for 500 times,
		1756	connects to the echo server, sends a line, waits for the reply, and then
		1757	creates the next connection. This is a rather bad benchmark, as it
		1758	doesn't test the efficiency of the framework or much non-blocking I/O,
		1759	but it is a benchmark nevertheless.
		1760
		1761	name runtime
		1762	Lambda/select 0.330 sec
		1763	+ optimized 0.122 sec
		1764	Lambda/AnyEvent 0.327 sec
		1765	+ optimized 0.138 sec
		1766	Raw sockets/select 0.077 sec
		1767	POE/select, components 0.662 sec
		1768	POE/select, raw sockets 0.226 sec
		1769	POE/select, optimized 0.404 sec
		1770
		1771	AnyEvent/select/nb 0.085 sec
		1772	AnyEvent/EV/nb 0.068 sec
		1773	+state machine 0.134 sec
		1774
		1775	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1776	benchmarks actually make blocking connects and use 100% blocking I/O,
		1777	defeating the purpose of an event-based solution. All of the newly
		1778	written AnyEvent benchmarks use 100% non-blocking connects (using
		1779	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1780	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1781	connects generally require a lot more bookkeeping and event handling
		1782	than blocking connects (which involve a single syscall only).
		1783
		1784	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1785	offers similar expressive power as POE and IO::Lambda, using
		1786	conventional Perl syntax. This means that both the echo server and the
		1787	client are 100% non-blocking, further placing it at a disadvantage.
		1788
		1789	As you can see, the AnyEvent + EV combination even beats the
		1790	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1791	backend easily beats IO::Lambda and POE.
		1792
		1793	And even the 100% non-blocking version written using the high-level (and
		1794	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
		1795	higher level ("unoptimised") abstractions by a large margin, even though
		1796	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		1797
		1798	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1799	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1800	part of the IO::Lambda distribution and were used without any changes.
		1801
		1802	SIGNALS
		1803	AnyEvent currently installs handlers for these signals:
		1804
		1805	SIGCHLD
		1806	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
		1807	emulation for event loops that do not support them natively. Also,
		1808	some event loops install a similar handler.
		1809
		1810	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1811	then AnyEvent will reset it to default, to avoid losing child exit
		1812	statuses.
		1813
		1814	SIGPIPE
		1815	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
		1816	"undef" when AnyEvent gets loaded.
		1817
		1818	The rationale for this is that AnyEvent users usually do not really
		1819	depend on SIGPIPE delivery (which is purely an optimisation for
		1820	shell use, or badly-written programs), but "SIGPIPE" can cause
		1821	spurious and rare program exits as a lot of people do not expect
		1822	"SIGPIPE" when writing to some random socket.
		1823
		1824	The rationale for installing a no-op handler as opposed to ignoring
		1825	it is that this way, the handler will be restored to defaults on
		1826	exec.
		1827
		1828	Feel free to install your own handler, or reset it to defaults.
		1829
		1830	RECOMMENDED/OPTIONAL MODULES
		1831	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1832	its built-in modules) are required to use it.
		1833
		1834	That does not mean that AnyEvent won't take advantage of some additional
		1835	modules if they are installed.
		1836
		1837	This section explains which additional modules will be used, and how
		1838	they affect AnyEvent's operation.
		1839
		1840	Async::Interrupt
		1841	This slightly arcane module is used to implement fast signal
		1842	handling: To my knowledge, there is no way to do completely
		1843	race-free and quick signal handling in pure perl. To ensure that
		1844	signals still get delivered, AnyEvent will start an interval timer
		1845	to wake up perl (and catch the signals) with some delay (default is
		1846	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1847
		1848	If this module is available, then it will be used to implement
		1849	signal catching, which means that signals will not be delayed, and
		1850	the event loop will not be interrupted regularly, which is more
		1851	efficient (and good for battery life on laptops).
		1852
		1853	This affects not just the pure-perl event loop, but also other event
		1854	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1855
		1856	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1857	natively, and either employ their own workarounds (POE) or use
		1858	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1859	Installing Async::Interrupt does nothing for those backends.
		1860
		1861	EV This module isn't really "optional", as it is simply one of the
		1862	backend event loops that AnyEvent can use. However, it is simply the
		1863	best event loop available in terms of features, speed and stability:
		1864	It supports the AnyEvent API optimally, implements all the watcher
		1865	types in XS, does automatic timer adjustments even when no monotonic
		1866	clock is available, can take avdantage of advanced kernel interfaces
		1867	such as "epoll" and "kqueue", and is the fastest backend by far.
		1868	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1869	Glib::EV).
		1870
		1871	If you only use backends that rely on another event loop (e.g.
		1872	"Tk"), then this module will do nothing for you.
		1873
		1874	Guard
		1875	The guard module, when used, will be used to implement
		1876	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1877	uses a lot less memory), but otherwise doesn't affect guard
		1878	operation much. It is purely used for performance.
		1879
		1880	JSON and JSON::XS
		1881	One of these modules is required when you want to read or write JSON
		1882	data via AnyEvent::Handle. JSON is also written in pure-perl, but
		1883	can take advantage of the ultra-high-speed JSON::XS module when it
		1884	is installed.
		1885
		1886	Net::SSLeay
		1887	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1888	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1889	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1890
		1891	Time::HiRes
		1892	This module is part of perl since release 5.008. It will be used
		1893	when the chosen event library does not come with a timing source of
		1894	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
		1895	load it to try to use a monotonic clock for timing stability.
		1896
		1897	FORK
		1898	Most event libraries are not fork-safe. The ones who are usually are
		1899	because they rely on inefficient but fork-safe "select" or "poll" calls
		1900	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		1901	epoll are usually badly thought-out hacks that are incompatible with
		1902	fork in one way or another. Only EV is fully fork-aware and ensures that
		1903	you continue event-processing in both parent and child (or both, if you
		1904	know what you are doing).
		1905
		1906	This means that, in general, you cannot fork and do event processing in
		1907	the child if the event library was initialised before the fork (which
		1908	usually happens when the first AnyEvent watcher is created, or the
		1909	library is loaded).
		1910
		1911	If you have to fork, you must either do so before creating your first
		1912	watcher OR you must not use AnyEvent at all in the child OR you must do
		1913	something completely out of the scope of AnyEvent.
		1914
		1915	The problem of doing event processing in the parent and the child is
		1916	much more complicated: even for backends that are fork-aware or
		1917	fork-safe, their behaviour is not usually what you want: fork clones all
		1918	watchers, that means all timers, I/O watchers etc. are active in both
		1919	parent and child, which is almost never what you want. USing "exec" to
		1920	start worker children from some kind of manage rprocess is usually
		1921	preferred, because it is much easier and cleaner, at the expense of
		1922	having to have another binary.
		1923
		1924	SECURITY CONSIDERATIONS
		1925	AnyEvent can be forced to load any event model via
		1926	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
		1927	to execute arbitrary code or directly gain access, it can easily be used
		1928	to make the program hang or malfunction in subtle ways, as AnyEvent
		1929	watchers will not be active when the program uses a different event
		1930	model than specified in the variable.
		1931
		1932	You can make AnyEvent completely ignore this variable by deleting it
		1933	before the first watcher gets created, e.g. with a "BEGIN" block:
		1934
		1935	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1936
		1937	use AnyEvent;
		1938
		1939	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1940	be used to probe what backend is used and gain other information (which
		1941	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
		1942	and $ENV{PERL_ANYEVENT_STRICT}.
		1943
		1944	Note that AnyEvent will remove all environment variables starting with
		1945	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1946	enabled.
		1947
		1948	BUGS
		1949	Perl 5.8 has numerous memleaks that sometimes hit this module and are
		1950	hard to work around. If you suffer from memleaks, first upgrade to Perl
		1951	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
		1952	annoying memleaks, such as leaking on "map" and "grep" but it is usually
		1953	not as pronounced).
592		1954
593	SEE ALSO	1955	SEE ALSO
594	Event modules: Coro::EV, EV, EV::Glib, Glib::EV, Coro::Event, Event,	1956	Tutorial/Introduction: AnyEvent::Intro.
595	Glib::Event, Glib, Coro, Tk.
596		1957
597	Implementations: AnyEvent::Impl::CoroEV, AnyEvent::Impl::EV,	1958	FAQ: AnyEvent::FAQ.
598	AnyEvent::Impl::CoroEvent, AnyEvent::Impl::Event, AnyEvent::Impl::Glib,	1959
		1960	Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log
		1961	(simply logging).
		1962
		1963	Development/Debugging: AnyEvent::Strict (stricter checking),
		1964	AnyEvent::Debug (interactive shell, watcher tracing).
		1965
		1966	Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
		1967	Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK.
		1968
		1969	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
599	AnyEvent::Impl::Tk, AnyEvent::Impl::Perl.	1970	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
		1971	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1972	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi, AnyEvent::Impl::FLTK.
600		1973
601	Nontrivial usage examples: Net::FCP, Net::XMPP2.	1974	Non-blocking handles, pipes, stream sockets, TCP clients and servers:
		1975	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
602		1976
		1977	Asynchronous DNS: AnyEvent::DNS.
603		1978
		1979	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
		1980
		1981	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
		1982	AnyEvent::HTTP.
		1983
		1984	AUTHOR
		1985	Marc Lehmann <schmorp@schmorp.de>
		1986	http://home.schmorp.de/
		1987

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Revision 1.66 by root, Sun Aug 21 03:02:32 2011 UTC