[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.22 by root, Sat May 24 17:58:33 2008 UTC vs.
Revision 1.65 by root, Sat Aug 13 22:44:05 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, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event	4	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
5	loops	5	Qt and POE are various supported event loops/environments.
6		6
7	SYNOPSIS	7	SYNOPSIS
8	use AnyEvent;	8	use AnyEvent;
9		9
		10	# 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
19	$w->send; # wake up current and all future recv's	36	$w->send; # wake up current and all future recv's
20	$w->recv; # enters "main loop" till $condvar gets ->send	37	$w->recv; # enters "main loop" till $condvar gets ->send
		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 enormous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
61	follow. AnyEvent, on the other hand, is lean and up to the point, by	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: EV, Event, Glib,	120	following modules is already loaded: EV, AnyEvent::Loop, Event, Glib,
81	AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is	121	Tk, Event::Lib, Qt, POE. The first one found is used. If none are
82	used. If none are found, the module tries to load these modules	122	detected, the module tries to load the first four modules in the order
83	(excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should	123	given; but note that if EV is not available, the pure-perl
84	always succeed) in the order given. The first one that can be	124	AnyEvent::Loop should always work, so the other two are not normally
85	successfully loaded will be used. If, after this, still none could be	125	tried.
86	found, AnyEvent will fall back to a pure-perl event loop, which is not
87	very efficient, but should work everywhere.
88		126
89	Because AnyEvent first checks for modules that are already loaded,	127	Because AnyEvent first checks for modules that are already loaded,
90	loading an event model explicitly before first using AnyEvent will	128	loading an event model explicitly before first using AnyEvent will
91	likely make that model the default. For example:	129	likely make that model the default. For example:
92		130
94	use AnyEvent;	132	use AnyEvent;
95		133
96	# .. AnyEvent will likely default to Tk	134	# .. AnyEvent will likely default to Tk
97		135
98	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
99	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
100	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.
101		140
102	The pure-perl implementation of AnyEvent is called	141	The pure-perl implementation of AnyEvent is called "AnyEvent::Loop".
103	"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
104	explicitly.	143	availability of that event loop :)
105		144
106	WATCHERS	145	WATCHERS
107	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
108	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
109	the callback to call, the file handle to watch, etc.	148	the callback to call, the file handle to watch, etc.
…		…
111	These watchers are normal Perl objects with normal Perl lifetime. After	150	These watchers are normal Perl objects with normal Perl lifetime. After
112	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
113	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
114	in control).	153	in control).
115		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
116	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
117	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
118	to it).	163	to it).
119		164
120	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.
121		166
122	Many watchers either are used with "recursion" (repeating timers for	167	Many watchers either are used with "recursion" (repeating timers for
123	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.
124		169
125	An any way to achieve that is this pattern:	170	One way to achieve that is this pattern:
126		171
127	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	172	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
128	# you can use $w here, for example to undef it	173	# you can use $w here, for example to undef it
129	undef $w;	174	undef $w;
130	});	175	});
131		176
132	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,
133	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
134	declared.	179	declared.
135		180
136	I/O WATCHERS	181	I/O WATCHERS
		182	$w = AnyEvent->io (
		183	fh => <filehandle_or_fileno>,
		184	poll => <"r" or "w">,
		185	cb => <callback>,
		186	);
		187
137	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
138	the following mandatory key-value pairs as arguments:	189	the following mandatory key-value pairs as arguments:
139		190
140	"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
141	"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
142	watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"	199	watcher waiting for "r"eadable or "w"ritable events, respectively.
		200
143	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.
144		202
145	Although the callback might get passed parameters, their value and	203	Although the callback might get passed parameters, their value and
146	presence is undefined and you cannot rely on them. Portable AnyEvent	204	presence is undefined and you cannot rely on them. Portable AnyEvent
147	callbacks cannot use arguments passed to I/O watcher callbacks.	205	callbacks cannot use arguments passed to I/O watcher callbacks.
148		206
149	The I/O watcher might use the underlying file descriptor or a copy of	207	The I/O watcher might use the underlying file descriptor or a copy of
150	it. You must not close a file handle as long as any watcher is active on	208	it. You must not close a file handle as long as any watcher is active on
151	the underlying file descriptor.	209	the underlying file descriptor.
152		210
153	Some event loops issue spurious readyness notifications, so you should	211	Some event loops issue spurious readiness notifications, so you should
154	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
155	handles.	213	handles.
156		214
157	Example:
158
159	# 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
160	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	218	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
161	chomp (my $input = <STDIN>);	219	chomp (my $input = <STDIN>);
162	warn "read: $input\n";	220	warn "read: $input\n";
163	undef $w;	221	undef $w;
164	});	222	});
165		223
166	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
167	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
168	with the following mandatory arguments:	234	with the following mandatory arguments:
169		235
170	"after" specifies after how many seconds (fractional values are	236	"after" specifies after how many seconds (fractional values are
171	supported) the callback should be invoked. "cb" is the callback to	237	supported) the callback should be invoked. "cb" is the callback to
…		…
173		239
174	Although the callback might get passed parameters, their value and	240	Although the callback might get passed parameters, their value and
175	presence is undefined and you cannot rely on them. Portable AnyEvent	241	presence is undefined and you cannot rely on them. Portable AnyEvent
176	callbacks cannot use arguments passed to time watcher callbacks.	242	callbacks cannot use arguments passed to time watcher callbacks.
177		243
178	The timer callback will be invoked at most once: if you want a repeating	244	The callback will normally be invoked only once. If you specify another
179	timer you have to create a new watcher (this is a limitation by both Tk	245	parameter, "interval", as a strictly positive number (> 0), then the
180	and Glib).	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.
181		249
182	Example:	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.
183		253
184	# fire an event after 7.7 seconds	254	Example: fire an event after 7.7 seconds.
		255
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	256	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	257	warn "timeout\n";
187	});	258	});
188		259
189	# to cancel the timer:	260	# to cancel the timer:
190	undef $w;	261	undef $w;
191		262
192	Example 2:
193
194	# 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.
195	my $w;
196		264
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	265	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		266	warn "timeout\n";
200	};	267	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		268
205	TIMING ISSUES	269	TIMING ISSUES
206	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
207	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
208	o'clock").	272	o'clock").
209		273
210	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,
211	they use absolute time internally. This makes a difference when your	275	they use absolute time internally. This makes a difference when your
212	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
213	from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is	277	from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is
214	supposed to fire "after" a second might actually take six years to	278	supposed to fire "after a second" might actually take six years to
215	finally fire.	279	finally fire.
216		280
217	AnyEvent cannot compensate for this. The only event loop that is	281	AnyEvent cannot compensate for this. The only event loop that is
218	conscious about these issues is EV, which offers both relative	282	conscious of these issues is EV, which offers both relative (ev_timer,
219	(ev_timer, based on true relative time) and absolute (ev_periodic, based	283	based on true relative time) and absolute (ev_periodic, based on
220	on wallclock time) timers.	284	wallclock time) timers.
221		285
222	AnyEvent always prefers relative timers, if available, matching the	286	AnyEvent always prefers relative timers, if available, matching the
223	AnyEvent API.	287	AnyEvent API.
224		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
225	SIGNAL WATCHERS	373	SIGNAL WATCHERS
		374	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		375
226	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
227	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
228	whenever a signal occurs.	378	callback to be invoked whenever a signal occurs.
229		379
230	Although the callback might get passed parameters, their value and	380	Although the callback might get passed parameters, their value and
231	presence is undefined and you cannot rely on them. Portable AnyEvent	381	presence is undefined and you cannot rely on them. Portable AnyEvent
232	callbacks cannot use arguments passed to signal watcher callbacks.	382	callbacks cannot use arguments passed to signal watcher callbacks.
233		383
…		…
235	invocation, and callback invocation will be synchronous. Synchronous	385	invocation, and callback invocation will be synchronous. Synchronous
236	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
237	process, but it is guaranteed not to interrupt any other callbacks.	387	process, but it is guaranteed not to interrupt any other callbacks.
238		388
239	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
240	signal between multiple watchers.	390	signal between multiple watchers, and AnyEvent will ensure that signals
		391	will not interrupt your program at bad times.
241		392
242	This watcher might use %SIG, so programs overwriting those signals	393	This watcher might use %SIG (depending on the event loop used), so
243	directly will likely not work correctly.	394	programs overwriting those signals directly will likely not work
		395	correctly.
244		396
245	Example: exit on SIGINT	397	Example: exit on SIGINT
246		398
247	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	399	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
248		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
249	CHILD PROCESS WATCHERS	435	CHILD PROCESS WATCHERS
		436	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		437
250	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.
251		439
252	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,
253	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).
254	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
255	signal handler for "SIGCHLD". The callback will be called with the pid	443	and an exit status is available, not on any trace events
256	and exit status (as returned by waitpid), so unlike other watcher types,	444	(stopped/continued).
257	you can rely on child watcher callback arguments.	445
		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.
		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).
258		454
259	There is a slight catch to child watchers, however: you usually start	455	There is a slight catch to child watchers, however: you usually start
260	them after the child process was created, and this means the process	456	them after the child process was created, and this means the process
261	could have exited already (and no SIGCHLD will be sent anymore).	457	could have exited already (and no SIGCHLD will be sent anymore).
262		458
263	Not all event models handle this correctly (POE doesn't), but even for	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
264	event models that do handle this correctly, they usually need to be	461	models that do handle this correctly, they usually need to be loaded
265	loaded before the process exits (i.e. before you fork in the first	462	before the process exits (i.e. before you fork in the first place).
266	place).	463	AnyEvent's pure perl event loop handles all cases correctly regardless
		464	of when you start the watcher.
267		465
268	This means you cannot create a child watcher as the very first thing in	466	This means you cannot create a child watcher as the very first thing in
269	an AnyEvent program, you have to create at least one watcher before	467	an AnyEvent program, you have to create at least one watcher before
270	you "fork" the child (alternatively, you can call "AnyEvent::detect").	468	you "fork" the child (alternatively, you can call "AnyEvent::detect").
271		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
272	Example: fork a process and wait for it	474	Example: fork a process and wait for it
273		475
274	my $done = AnyEvent->condvar;	476	my $done = AnyEvent->condvar;
275		477
276	my $pid = fork or exit 5;	478	my $pid = fork or exit 5;
277		479
278	my $w = AnyEvent->child (	480	my $w = AnyEvent->child (
279	pid => $pid,	481	pid => $pid,
280	cb => sub {	482	cb => sub {
281	my ($pid, $status) = @_;	483	my ($pid, $status) = @_;
282	warn "pid $pid exited with status $status";	484	warn "pid $pid exited with status $status";
283	$done->send;	485	$done->send;
284	},	486	},
285	);	487	);
286		488
287	# do something else, then wait for process exit	489	# do something else, then wait for process exit
288	$done->recv;	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	});
289		530
290	CONDITION VARIABLES	531	CONDITION VARIABLES
		532	$cv = AnyEvent->condvar;
		533
		534	$cv->send (<list>);
		535	my @res = $cv->recv;
		536
291	If you are familiar with some event loops you will know that all of them	537	If you are familiar with some event loops you will know that all of them
292	require you to run some blocking "loop", "run" or similar function that	538	require you to run some blocking "loop", "run" or similar function that
293	will actively watch for new events and call your callbacks.	539	will actively watch for new events and call your callbacks.
294		540
295	AnyEvent is different, it expects somebody else to run the event loop	541	AnyEvent is slightly different: it expects somebody else to run the
296	and will only block when necessary (usually when told by the user).	542	event loop and will only block when necessary (usually when told by the
		543	user).
297		544
298	The instrument to do that is called a "condition variable", so called	545	The tool to do that is called a "condition variable", so called because
299	because they represent a condition that must become true.	546	they represent a condition that must become true.
		547
		548	Now is probably a good time to look at the examples further below.
300		549
301	Condition variables can be created by calling the "AnyEvent->condvar"	550	Condition variables can be created by calling the "AnyEvent->condvar"
302	method, usually without arguments. The only argument pair allowed is	551	method, usually without arguments. The only argument pair allowed is
303	"cb", which specifies a callback to be called when the condition	552	"cb", which specifies a callback to be called when the condition
304	variable becomes true.	553	variable becomes true, with the condition variable as the first argument
		554	(but not the results).
305		555
306	After creation, the condition variable is "false" until it becomes	556	After creation, the condition variable is "false" until it becomes
307	"true" by calling the "send" method (or calling the condition variable	557	"true" by calling the "send" method (or calling the condition variable
308	as if it were a callback).	558	as if it were a callback, read about the caveats in the description for
		559	the "->send" method).
309		560
310	Condition variables are similar to callbacks, except that you can	561	Since condition variables are the most complex part of the AnyEvent API,
311	optionally wait for them. They can also be called merge points - points	562	here are some different mental models of what they are - pick the ones
312	in time where multiple outstanding events have been processed. And yet	563	you can connect to:
313	another way to call them is transactions - each condition variable can	564
314	be used to represent a transaction, which finishes at some point and	565	* Condition variables are like callbacks - you can call them (and pass
315	delivers a result.	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.
316		582
317	Condition variables are very useful to signal that something has	583	Condition variables are very useful to signal that something has
318	finished, for example, if you write a module that does asynchronous http	584	finished, for example, if you write a module that does asynchronous http
319	requests, then a condition variable would be the ideal candidate to	585	requests, then a condition variable would be the ideal candidate to
320	signal the availability of results. The user can either act when the	586	signal the availability of results. The user can either act when the
…		…
333		599
334	Condition variables are represented by hash refs in perl, and the keys	600	Condition variables are represented by hash refs in perl, and the keys
335	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy	601	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy
336	(it is often useful to build your own transaction class on top of	602	(it is often useful to build your own transaction class on top of
337	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	603	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
338	it's "new" method in your own "new" method.	604	its "new" method in your own "new" method.
339		605
340	There are two "sides" to a condition variable - the "producer side"	606	There are two "sides" to a condition variable - the "producer side"
341	which eventually calls "-> send", and the "consumer side", which waits	607	which eventually calls "-> send", and the "consumer side", which waits
342	for the send to occur.	608	for the send to occur.
343		609
344	Example: wait for a timer.	610	Example: wait for a timer.
345		611
346	# wait till the result is ready	612	# condition: "wait till the timer is fired"
347	my $result_ready = AnyEvent->condvar;	613	my $timer_fired = AnyEvent->condvar;
348		614
349	# do something such as adding a timer	615	# create the timer - we could wait for, say
350	# or socket watcher the calls $result_ready->send	616	# a handle becomign ready, or even an
351	# when the "result" is ready.	617	# AnyEvent::HTTP request to finish, but
352	# in this case, we simply use a timer:	618	# in this case, we simply use a timer:
353	my $w = AnyEvent->timer (	619	my $w = AnyEvent->timer (
354	after => 1,	620	after => 1,
355	cb => sub { $result_ready->send },	621	cb => sub { $timer_fired->send },
356	);	622	);
357		623
358	# this "blocks" (while handling events) till the callback	624	# this "blocks" (while handling events) till the callback
359	# calls send	625	# calls ->send
360	$result_ready->recv;	626	$timer_fired->recv;
361		627
362	Example: wait for a timer, but take advantage of the fact that condition	628	Example: wait for a timer, but take advantage of the fact that condition
363	variables are also code references.	629	variables are also callable directly.
364		630
365	my $done = AnyEvent->condvar;	631	my $done = AnyEvent->condvar;
366	my $delay = AnyEvent->timer (after => 5, cb => $done);	632	my $delay = AnyEvent->timer (after => 5, cb => $done);
367	$done->recv;	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	});
368		651
369	METHODS FOR PRODUCERS	652	METHODS FOR PRODUCERS
370	These methods should only be used by the producing side, i.e. the	653	These methods should only be used by the producing side, i.e. the
371	code/module that eventually sends the signal. Note that it is also the	654	code/module that eventually sends the signal. Note that it is also the
372	producer side which creates the condvar in most cases, but it isn't	655	producer side which creates the condvar in most cases, but it isn't
…		…
382		665
383	Any arguments passed to the "send" call will be returned by all	666	Any arguments passed to the "send" call will be returned by all
384	future "->recv" calls.	667	future "->recv" calls.
385		668
386	Condition variables are overloaded so one can call them directly (as	669	Condition variables are overloaded so one can call them directly (as
387	a code reference). Calling them directly is the same as calling	670	if they were a code reference). Calling them directly is the same as
388	"send".	671	calling "send".
389		672
390	$cv->croak ($error)	673	$cv->croak ($error)
391	Similar to send, but causes all call's to "->recv" to invoke	674	Similar to send, but causes all calls to "->recv" to invoke
392	"Carp::croak" with the given error message/object/scalar.	675	"Carp::croak" with the given error message/object/scalar.
393		676
394	This can be used to signal any errors to the condition variable	677	This can be used to signal any errors to the condition variable
395	user/consumer.	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.
396		683
397	$cv->begin ([group callback])	684	$cv->begin ([group callback])
398	$cv->end	685	$cv->end
399	These two methods are EXPERIMENTAL and MIGHT CHANGE.
400
401	These two methods can be used to combine many transactions/events	686	These two methods can be used to combine many transactions/events
402	into one. For example, a function that pings many hosts in parallel	687	into one. For example, a function that pings many hosts in parallel
403	might want to use a condition variable for the whole process.	688	might want to use a condition variable for the whole process.
404		689
405	Every call to "->begin" will increment a counter, and every call to	690	Every call to "->begin" will increment a counter, and every call to
406	"->end" will decrement it. If the counter reaches 0 in "->end", the	691	"->end" will decrement it. If the counter reaches 0 in "->end", the
407	(last) callback passed to "begin" will be executed. That callback is	692	(last) callback passed to "begin" will be executed, passing the
408	supposed to call "->send", but that is not required. If no	693	condvar as first argument. That callback is supposed to call
		694	"->send", but that is not required. If no group callback was set,
409	callback was set, "send" will be called without any arguments.	695	"send" will be called without any arguments.
410		696
411	Let's clarify this with the ping example:	697	You can think of "$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:
412		705
413	my $cv = AnyEvent->condvar;	706	my $cv = AnyEvent->condvar;
414		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
415	my %result;	732	my %result;
416	$cv->begin (sub { $cv->send (\%result) });	733	$cv->begin (sub { shift->send (\%result) });
417		734
418	for my $host (@list_of_hosts) {	735	for my $host (@list_of_hosts) {
419	$cv->begin;	736	$cv->begin;
420	ping_host_then_call_callback $host, sub {	737	ping_host_then_call_callback $host, sub {
421	$result{$host} = ...;	738	$result{$host} = ...;
…		…
436	the loop, which serves two important purposes: first, it sets the	753	the loop, which serves two important purposes: first, it sets the
437	callback to be called once the counter reaches 0, and second, it	754	callback to be called once the counter reaches 0, and second, it
438	ensures that "send" is called even when "no" hosts are being pinged	755	ensures that "send" is called even when "no" hosts are being pinged
439	(the loop doesn't execute once).	756	(the loop doesn't execute once).
440		757
441	This is the general pattern when you "fan out" into multiple	758	This is the general pattern when you "fan out" into multiple (but
442	subrequests: use an outer "begin"/"end" pair to set the callback and	759	potentially zero) subrequests: use an outer "begin"/"end" pair to
443	ensure "end" is called at least once, and then, for each subrequest	760	set the callback and ensure "end" is called at least once, and then,
444	you start, call "begin" and for each subrequest you finish, call	761	for each subrequest you start, call "begin" and for each subrequest
445	"end".	762	you finish, call "end".
446		763
447	METHODS FOR CONSUMERS	764	METHODS FOR CONSUMERS
448	These methods should only be used by the consuming side, i.e. the code	765	These methods should only be used by the consuming side, i.e. the code
449	awaits the condition.	766	awaits the condition.
450		767
451	$cv->recv	768	$cv->recv
452	Wait (blocking if necessary) until the "->send" or "->croak" methods	769	Wait (blocking if necessary) until the "->send" or "->croak" methods
453	have been called on c<$cv>, while servicing other watchers normally.	770	have been called on $cv, while servicing other watchers normally.
454		771
455	You can only wait once on a condition - additional calls are valid	772	You can only wait once on a condition - additional calls are valid
456	but will return immediately.	773	but will return immediately.
457		774
458	If an error condition has been set by calling "->croak", then this	775	If an error condition has been set by calling "->croak", then this
459	function will call "croak".	776	function will call "croak".
460		777
461	In list context, all parameters passed to "send" will be returned,	778	In list context, all parameters passed to "send" will be returned,
462	in scalar context only the first one will be returned.	779	in scalar context only the first one will be returned.
463		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
464	Not all event models support a blocking wait - some die in that case	788	Not all event models support a blocking wait - some die in that case
465	(programs might want to do that to stay interactive), so *if you are	789	(programs might want to do that to stay interactive), so *if you are
466	using this from a module, never require a blocking wait*, but let	790	using this from a module, never require a blocking wait*. Instead,
467	the caller decide whether the call will block or not (for example,	791	let the caller decide whether the call will block or not (for
468	by coupling condition variables with some kind of request results	792	example, by coupling condition variables with some kind of request
469	and supporting callbacks so the caller knows that getting the result	793	results and supporting callbacks so the caller knows that getting
470	will not block, while still supporting blocking waits if the caller	794	the result will not block, while still supporting blocking waits if
471	so desires).	795	the caller so desires).
472		796
473	Another reason never to "->recv" in a module is that you cannot
474	sensibly have two "->recv"'s in parallel, as that would require
475	multiple interpreters or coroutines/threads, none of which
476	"AnyEvent" can supply.
477
478	The Coro module, however, can and does supply coroutines and, in
479	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
480	versions and also integrates coroutines into AnyEvent, making
481	blocking "->recv" calls perfectly safe as long as they are done from
482	another coroutine (one that doesn't run the event loop).
483
484	You can ensure that "-recv" never blocks by setting a callback and	797	You can ensure that "->recv" never blocks by setting a callback and
485	only calling "->recv" from within that callback (or at a later	798	only calling "->recv" from within that callback (or at a later
486	time). This will work even when the event loop does not support	799	time). This will work even when the event loop does not support
487	blocking waits otherwise.	800	blocking waits otherwise.
488		801
489	$bool = $cv->ready	802	$bool = $cv->ready
490	Returns true when the condition is "true", i.e. whether "send" or	803	Returns true when the condition is "true", i.e. whether "send" or
491	"croak" have been called.	804	"croak" have been called.
492		805
493	$cb = $cv->cb ([new callback])	806	$cb = $cv->cb ($cb->($cv))
494	This is a mutator function that returns the callback set and	807	This is a mutator function that returns the callback set and
495	optionally replaces it before doing so.	808	optionally replaces it before doing so.
496		809
497	The callback will be called when the condition becomes "true", i.e.	810	The callback will be called when the condition becomes "true", i.e.
498	when "send" or "croak" are called. Calling "recv" inside the	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
499	callback or at any later time is guaranteed not to block.	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.
500		870
501	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
502	$AnyEvent::MODEL	875	$AnyEvent::MODEL
503	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
504	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
505	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
506	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
507	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.
508		883	in rxvt-unicode it will be "urxvt::anyevent").
509	The known classes so far are:
510
511	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
512	AnyEvent::Impl::Event based on Event, second best choice.
513	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
514	AnyEvent::Impl::Glib based on Glib, third-best choice.
515	AnyEvent::Impl::Tk based on Tk, very bad choice.
516	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
517	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
518	AnyEvent::Impl::POE based on POE, not generic enough for full support.
519
520	There is no support for WxWidgets, as WxWidgets has no support for
521	watching file handles. However, you can use WxWidgets through the
522	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
523	second, which was considered to be too horrible to even consider for
524	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
525	using it's adaptor.
526
527	AnyEvent knows about Prima and Wx and will try to use POE when
528	autodetecting them.
529		884
530	AnyEvent::detect	885	AnyEvent::detect
531	Returns $AnyEvent::MODEL, forcing autodetection of the event model	886	Returns $AnyEvent::MODEL, forcing autodetection of the event model
532	if necessary. You should only call this function right before you	887	if necessary. You should only call this function right before you
533	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
534	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".
535		898
536	$guard = AnyEvent::post_detect { BLOCK }	899	$guard = AnyEvent::post_detect { BLOCK }
537	Arranges for the code block to be executed as soon as the event	900	Arranges for the code block to be executed as soon as the event
538	model is autodetected (or immediately if this has already happened).	901	model is autodetected (or immediately if that has already happened).
		902
		903	The block will be executed after the actual backend has been
		904	detected ($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.
539		913
540	If called in scalar or list context, then it creates and returns an	914	If called in scalar or list context, then it creates and returns an
541	object that automatically removes the callback again when it is	915	object that automatically removes the callback again when it is
		916	destroyed (or "undef" when the hook was immediately executed). See
542	destroyed. See Coro::BDB for a case where this is useful.	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;
543		934
544	@AnyEvent::post_detect	935	@AnyEvent::post_detect
545	If there are any code references in this array (you can "push" to it	936	If there are any code references in this array (you can "push" to it
546	before or after loading AnyEvent), then they will called directly	937	before or after loading AnyEvent), then they will be called directly
547	after the event loop has been chosen.	938	after the event loop has been chosen.
548		939
549	You should check $AnyEvent::MODEL before adding to this array,	940	You should check $AnyEvent::MODEL before adding to this array,
550	though: if it contains a true value then the event loop has already	941	though: if it is defined then the event loop has already been
551	been detected, and the array will be ignored.	942	detected, and the array will be ignored.
552		943
553	Best use "AnyEvent::post_detect { BLOCK }" instead.	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;
554		1006
555	WHAT TO DO IN A MODULE	1007	WHAT TO DO IN A MODULE
556	As a module author, you should "use AnyEvent" and call AnyEvent methods	1008	As a module author, you should "use AnyEvent" and call AnyEvent methods
557	freely, but you should not load a specific event module or rely on it.	1009	freely, but you should not load a specific event module or rely on it.
558		1010
…		…
566	stall the whole program, and the whole point of using events is to stay	1018	stall the whole program, and the whole point of using events is to stay
567	interactive.	1019	interactive.
568		1020
569	It is fine, however, to call "->recv" when the user of your module	1021	It is fine, however, to call "->recv" when the user of your module
570	requests it (i.e. if you create a http request object ad have a method	1022	requests it (i.e. if you create a http request object ad have a method
571	called "results" that returns the results, it should call "->recv"	1023	called "results" that returns the results, it may call "->recv" freely,
572	freely, as the user of your module knows what she is doing. always).	1024	as the user of your module knows what she is doing. Always).
573		1025
574	WHAT TO DO IN THE MAIN PROGRAM	1026	WHAT TO DO IN THE MAIN PROGRAM
575	There will always be a single main program - the only place that should	1027	There will always be a single main program - the only place that should
576	dictate which event model to use.	1028	dictate which event model to use.
577		1029
578	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1030	If the program is not event-based, it need not do anything special, even
579	do anything special (it does not need to be event-based) and let	1031	when it depends on a module that uses an AnyEvent. If the program itself
580	AnyEvent decide which implementation to chose if some module relies on	1032	uses AnyEvent, but does not care which event loop is used, all it needs
581	it.	1033	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1034	available loop implementation.
582		1035
583	If the main program relies on a specific event model. For example, in	1036	If the main program relies on a specific event model - for example, in
584	Gtk2 programs you have to rely on the Glib module. You should load the	1037	Gtk2 programs you have to rely on the Glib module - you should load the
585	event module before loading AnyEvent or any module that uses it:	1038	event module before loading AnyEvent or any module that uses it:
586	generally speaking, you should load it as early as possible. The reason	1039	generally speaking, you should load it as early as possible. The reason
587	is that modules might create watchers when they are loaded, and AnyEvent	1040	is that modules might create watchers when they are loaded, and AnyEvent
588	will decide on the event model to use as soon as it creates watchers,	1041	will decide on the event model to use as soon as it creates watchers,
589	and it might chose the wrong one unless you load the correct one	1042	and it might choose the wrong one unless you load the correct one
590	yourself.	1043	yourself.
591		1044
592	You can chose to use a rather inefficient pure-perl implementation by	1045	You can chose to use a pure-perl implementation by loading the
593	loading the "AnyEvent::Impl::Perl" module, which gives you similar	1046	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
594	behaviour everywhere, but letting AnyEvent chose is generally better.	1047	but letting AnyEvent chose the model is generally better.
		1048
		1049	MAINLOOP EMULATION
		1050	Sometimes (often for short test scripts, or even standalone programs who
		1051	only want to use AnyEvent), you do not want to run a specific event
		1052	loop.
		1053
		1054	In that case, you can use a condition variable like this:
		1055
		1056	AnyEvent->condvar->recv;
		1057
		1058	This has the effect of entering the event loop and looping forever.
		1059
		1060	Note that usually your program has some exit condition, in which case it
		1061	is better to use the "traditional" approach of storing a condition
		1062	variable somewhere, waiting for it, and sending it when the program
		1063	should exit cleanly.
595		1064
596	OTHER MODULES	1065	OTHER MODULES
597	The following is a non-exhaustive list of additional modules that use	1066	The following is a non-exhaustive list of additional modules that use
598	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1067	AnyEvent as a client and can therefore be mixed easily with other
599	in the same program. Some of the modules come with AnyEvent, some are	1068	AnyEvent modules and other event loops in the same program. Some of the
600	available via CPAN.	1069	modules come as part of AnyEvent, the others are available via CPAN.
601		1070
602	AnyEvent::Util	1071	AnyEvent::Util
603	Contains various utility functions that replace often-used but	1072	Contains various utility functions that replace often-used blocking
604	blocking functions such as "inet_aton" by event-/callback-based	1073	functions such as "inet_aton" with event/callback-based versions.
605	versions.
606
607	AnyEvent::Handle
608	Provide read and write buffers and manages watchers for reads and
609	writes.
610		1074
611	AnyEvent::Socket	1075	AnyEvent::Socket
612	Provides various utility functions for (internet protocol) sockets,	1076	Provides various utility functions for (internet protocol) sockets,
613	addresses and name resolution. Also functions to create non-blocking	1077	addresses and name resolution. Also functions to create non-blocking
614	tcp connections or tcp servers, with IPv6 and SRV record support and	1078	tcp connections or tcp servers, with IPv6 and SRV record support and
615	more.	1079	more.
616		1080
617	AnyEvent::HTTPD	1081	AnyEvent::Handle
618	Provides a simple web application server framework.	1082	Provide read and write buffers, manages watchers for reads and
		1083	writes, supports raw and formatted I/O, I/O queued and fully
		1084	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
619		1085
620	AnyEvent::DNS	1086	AnyEvent::DNS
621	Provides rich asynchronous DNS resolver capabilities.	1087	Provides rich asynchronous DNS resolver capabilities.
622		1088
		1089	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
		1090	AnyEvent::IGS, AnyEvent::FCP
		1091	Implement event-based interfaces to the protocols of the same name
		1092	(for the curious, IGS is the International Go Server and FCP is the
		1093	Freenet Client Protocol).
		1094
		1095	AnyEvent::Handle::UDP
		1096	Here be danger!
		1097
		1098	As Pauli would put it, "Not only is it not right, it's not even
		1099	wrong!" - there are so many things wrong with AnyEvent::Handle::UDP,
		1100	most notably its use of a stream-based API with a protocol that
		1101	isn't streamable, that the only way to improve it is to delete it.
		1102
		1103	It features data corruption (but typically only under load) and
		1104	general confusion. On top, the author is not only clueless about UDP
		1105	but also fact-resistant - some gems of his understanding: "connect
		1106	doesn't work with UDP", "UDP packets are not IP packets", "UDP only
		1107	has datagrams, not packets", "I don't need to implement proper error
		1108	checking as UDP doesn't support error checking" and so on - he
		1109	doesn't even understand what's wrong with his module when it is
		1110	explained to him.
		1111
		1112	AnyEvent::DBI
		1113	Executes DBI requests asynchronously in a proxy process for you,
		1114	notifying you in an event-based way when the operation is finished.
		1115
		1116	AnyEvent::AIO
		1117	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1118	the toolbox of every event programmer. AnyEvent::AIO transparently
		1119	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1120	event-based file I/O, and much more.
		1121
		1122	AnyEvent::HTTPD
		1123	A simple embedded webserver.
		1124
623	AnyEvent::FastPing	1125	AnyEvent::FastPing
624	The fastest ping in the west.	1126	The fastest ping in the west.
625		1127
626	Net::IRC3
627	AnyEvent based IRC client module family.
628
629	Net::XMPP2
630	AnyEvent based XMPP (Jabber protocol) module family.
631
632	Net::FCP
633	AnyEvent-based implementation of the Freenet Client Protocol,
634	birthplace of AnyEvent.
635
636	Event::ExecFlow
637	High level API for event-based execution flow control.
638
639	Coro	1128	Coro
640	Has special support for AnyEvent via Coro::AnyEvent.	1129	Has special support for AnyEvent via Coro::AnyEvent.
641		1130
642	AnyEvent::AIO, IO::AIO	1131	SIMPLIFIED AE API
643	Truly asynchronous I/O, should be in the toolbox of every event	1132	Starting with version 5.0, AnyEvent officially supports a second, much
644	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent	1133	simpler, API that is designed to reduce the calling, typing and memory
645	together.	1134	overhead by using function call syntax and a fixed number of parameters.
646		1135
647	AnyEvent::BDB, BDB	1136	See the AE manpage for details.
648	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
649	fuses IO::AIO and AnyEvent together.
650		1137
651	IO::Lambda	1138	ERROR AND EXCEPTION HANDLING
652	The lambda approach to I/O - don't ask, look there. Can use	1139	In general, AnyEvent does not do any error handling - it relies on the
653	AnyEvent.	1140	caller to do that if required. The AnyEvent::Strict module (see also the
		1141	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
		1142	checking of all AnyEvent methods, however, which is highly useful during
		1143	development.
		1144
		1145	As for exception handling (i.e. runtime errors and exceptions thrown
		1146	while executing a callback), this is not only highly event-loop
		1147	specific, but also not in any way wrapped by this module, as this is the
		1148	job of the main program.
		1149
		1150	The pure perl event loop simply re-throws the exception (usually within
		1151	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
		1152	Glib uses "install_exception_handler" and so on.
		1153
		1154	ENVIRONMENT VARIABLES
		1155	The following environment variables are used by this module or its
		1156	submodules.
		1157
		1158	Note that AnyEvent will remove all environment variables starting with
		1159	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1160	enabled.
		1161
		1162	"PERL_ANYEVENT_VERBOSE"
		1163	By default, AnyEvent will be completely silent except in fatal
		1164	conditions. You can set this environment variable to make AnyEvent
		1165	more talkative.
		1166
		1167	When set to 1 or higher, causes AnyEvent to warn about unexpected
		1168	conditions, such as not being able to load the event model specified
		1169	by "PERL_ANYEVENT_MODEL".
		1170
		1171	When set to 2 or higher, cause AnyEvent to report to STDERR which
		1172	event model it chooses.
		1173
		1174	When set to 8 or higher, then AnyEvent will report extra information
		1175	on which optional modules it loads and how it implements certain
		1176	features.
		1177
		1178	"PERL_ANYEVENT_STRICT"
		1179	AnyEvent does not do much argument checking by default, as thorough
		1180	argument checking is very costly. Setting this variable to a true
		1181	value will cause AnyEvent to load "AnyEvent::Strict" and then to
		1182	thoroughly check the arguments passed to most method calls. If it
		1183	finds any problems, it will croak.
		1184
		1185	In other words, enables "strict" mode.
		1186
		1187	Unlike "use strict" (or its modern cousin, "use common::sense", it
		1188	is definitely recommended to keep it off in production. Keeping
		1189	"PERL_ANYEVENT_STRICT=1" in your environment while developing
		1190	programs can be very useful, however.
		1191
		1192	"PERL_ANYEVENT_DEBUG_SHELL"
		1193	If this env variable is set, then its contents will be interpreted
		1194	by "AnyEvent::Socket::parse_hostport" (after replacing every
		1195	occurance of $$ by the process pid) and an "AnyEvent::Debug::shell"
		1196	is bound on that port. The shell object is saved in
		1197	$AnyEvent::Debug::SHELL.
		1198
		1199	This takes place when the first watcher is created.
		1200
		1201	For example, to bind a debug shell on a unix domain socket in
		1202	/tmp/debug<pid>.sock, you could use this:
		1203
		1204	PERL_ANYEVENT_DEBUG_SHELL=unix/:/tmp/debug\$\$.sock perlprog
		1205
		1206	Note that creating sockets in /tmp is very unsafe on multiuser
		1207	systems.
		1208
		1209	"PERL_ANYEVENT_DEBUG_WRAP"
		1210	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1211	debugging purposes. See "AnyEvent::Debug::wrap" for details.
		1212
		1213	"PERL_ANYEVENT_MODEL"
		1214	This can be used to specify the event model to be used by AnyEvent,
		1215	before auto detection and -probing kicks in.
		1216
		1217	It normally is a string consisting entirely of ASCII letters (e.g.
		1218	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1219	the resulting module name is loaded and - if the load was successful
		1220	- used as event model backend. If it fails to load then AnyEvent
		1221	will proceed with auto detection and -probing.
		1222
		1223	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1224	then nothing gets prepended and the module name is used as-is (hint:
		1225	"::" at the end of a string designates a module name and quotes it
		1226	appropriately).
		1227
		1228	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
		1229	could start your program like this:
		1230
		1231	PERL_ANYEVENT_MODEL=Perl perl ...
		1232
		1233	"PERL_ANYEVENT_PROTOCOLS"
		1234	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
		1235	preferences for IPv4 or IPv6. The default is unspecified (and might
		1236	change, or be the result of auto probing).
		1237
		1238	Must be set to a comma-separated list of protocols or address
		1239	families, current supported: "ipv4" and "ipv6". Only protocols
		1240	mentioned will be used, and preference will be given to protocols
		1241	mentioned earlier in the list.
		1242
		1243	This variable can effectively be used for denial-of-service attacks
		1244	against local programs (e.g. when setuid), although the impact is
		1245	likely small, as the program has to handle conenction and other
		1246	failures anyways.
		1247
		1248	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
		1249	IPv6, but support both and try to use both.
		1250	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
		1251	resolve or contact IPv6 addresses.
		1252	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
		1253	prefer IPv6 over IPv4.
		1254
		1255	"PERL_ANYEVENT_EDNS0"
		1256	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
		1257	for DNS. This extension is generally useful to reduce DNS traffic,
		1258	but some (broken) firewalls drop such DNS packets, which is why it
		1259	is off by default.
		1260
		1261	Setting this variable to 1 will cause AnyEvent::DNS to announce
		1262	EDNS0 in its DNS requests.
		1263
		1264	"PERL_ANYEVENT_MAX_FORKS"
		1265	The maximum number of child processes that
		1266	"AnyEvent::Util::fork_call" will create in parallel.
		1267
		1268	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1269	The default value for the "max_outstanding" parameter for the
		1270	default DNS resolver - this is the maximum number of parallel DNS
		1271	requests that are sent to the DNS server.
		1272
		1273	"PERL_ANYEVENT_RESOLV_CONF"
		1274	The file to use instead of /etc/resolv.conf (or OS-specific
		1275	configuration) in the default resolver. When set to the empty
		1276	string, no default config will be used.
		1277
		1278	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1279	When neither "ca_file" nor "ca_path" was specified during
		1280	AnyEvent::TLS context creation, and either of these environment
		1281	variables exist, they will be used to specify CA certificate
		1282	locations instead of a system-dependent default.
		1283
		1284	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1285	When these are set to 1, then the respective modules are not loaded.
		1286	Mostly good for testing AnyEvent itself.
654		1287
655	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1288	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
656	This is an advanced topic that you do not normally need to use AnyEvent	1289	This is an advanced topic that you do not normally need to use AnyEvent
657	in a module. This section is only of use to event loop authors who want	1290	in a module. This section is only of use to event loop authors who want
658	to provide AnyEvent compatibility.	1291	to provide AnyEvent compatibility.
…		…
692		1325
693	rxvt-unicode also cheats a bit by not providing blocking access to	1326	rxvt-unicode also cheats a bit by not providing blocking access to
694	condition variables: code blocking while waiting for a condition will	1327	condition variables: code blocking while waiting for a condition will
695	"die". This still works with most modules/usages, and blocking calls	1328	"die". This still works with most modules/usages, and blocking calls
696	must not be done in an interactive application, so it makes sense.	1329	must not be done in an interactive application, so it makes sense.
697
698	ENVIRONMENT VARIABLES
699	The following environment variables are used by this module:
700
701	"PERL_ANYEVENT_VERBOSE"
702	By default, AnyEvent will be completely silent except in fatal
703	conditions. You can set this environment variable to make AnyEvent
704	more talkative.
705
706	When set to 1 or higher, causes AnyEvent to warn about unexpected
707	conditions, such as not being able to load the event model specified
708	by "PERL_ANYEVENT_MODEL".
709
710	When set to 2 or higher, cause AnyEvent to report to STDERR which
711	event model it chooses.
712
713	"PERL_ANYEVENT_MODEL"
714	This can be used to specify the event model to be used by AnyEvent,
715	before auto detection and -probing kicks in. It must be a string
716	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
717	gets prepended and the resulting module name is loaded and if the
718	load was successful, used as event model. If it fails to load
719	AnyEvent will proceed with auto detection and -probing.
720
721	This functionality might change in future versions.
722
723	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
724	could start your program like this:
725
726	PERL_ANYEVENT_MODEL=Perl perl ...
727
728	"PERL_ANYEVENT_PROTOCOLS"
729	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
730	preferences for IPv4 or IPv6. The default is unspecified (and might
731	change, or be the result of auto probing).
732
733	Must be set to a comma-separated list of protocols or address
734	families, current supported: "ipv4" and "ipv6". Only protocols
735	mentioned will be used, and preference will be given to protocols
736	mentioned earlier in the list.
737
738	This variable can effectively be used for denial-of-service attacks
739	against local programs (e.g. when setuid), although the impact is
740	likely small, as the program has to handle connection errors
741	already-
742
743	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
744	IPv6, but support both and try to use both.
745	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
746	resolve or contact IPv6 addresses.
747	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
748	prefer IPv6 over IPv4.
749
750	"PERL_ANYEVENT_EDNS0"
751	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
752	for DNS. This extension is generally useful to reduce DNS traffic,
753	but some (broken) firewalls drop such DNS packets, which is why it
754	is off by default.
755
756	Setting this variable to 1 will cause AnyEvent::DNS to announce
757	EDNS0 in its DNS requests.
758		1330
759	EXAMPLE PROGRAM	1331	EXAMPLE PROGRAM
760	The following program uses an I/O watcher to read data from STDIN, a	1332	The following program uses an I/O watcher to read data from STDIN, a
761	timer to display a message once per second, and a condition variable to	1333	timer to display a message once per second, and a condition variable to
762	quit the program when the user enters quit:	1334	quit the program when the user enters quit:
…		…
774	warn "read: $input\n"; # output what has been read	1346	warn "read: $input\n"; # output what has been read
775	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1347	$cv->send if $input =~ /^q/i; # quit program if /^q/i
776	},	1348	},
777	);	1349	);
778		1350
779	my $time_watcher; # can only be used once
780
781	sub new_timer {
782	$timer = AnyEvent->timer (after => 1, cb => sub {	1351	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
783	warn "timeout\n"; # print 'timeout' about every second	1352	warn "timeout\n"; # print 'timeout' at most every second
784	&new_timer; # and restart the time
785	});
786	}	1353	});
787
788	new_timer; # create first timer
789		1354
790	$cv->recv; # wait until user enters /^q/i	1355	$cv->recv; # wait until user enters /^q/i
791		1356
792	REAL-WORLD EXAMPLE	1357	REAL-WORLD EXAMPLE
793	Consider the Net::FCP module. It features (among others) the following	1358	Consider the Net::FCP module. It features (among others) the following
…		…
865		1430
866	The actual code goes further and collects all errors ("die"s,	1431	The actual code goes further and collects all errors ("die"s,
867	exceptions) that occurred during request processing. The "result" method	1432	exceptions) that occurred during request processing. The "result" method
868	detects whether an exception as thrown (it is stored inside the $txn	1433	detects whether an exception as thrown (it is stored inside the $txn
869	object) and just throws the exception, which means connection errors and	1434	object) and just throws the exception, which means connection errors and
870	other problems get reported tot he code that tries to use the result,	1435	other problems get reported to the code that tries to use the result,
871	not in a random callback.	1436	not in a random callback.
872		1437
873	All of this enables the following usage styles:	1438	All of this enables the following usage styles:
874		1439
875	1. Blocking:	1440	1. Blocking:
…		…
920	through AnyEvent. The benchmark creates a lot of timers (with a zero	1485	through AnyEvent. The benchmark creates a lot of timers (with a zero
921	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1486	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
922	which it is), lets them fire exactly once and destroys them again.	1487	which it is), lets them fire exactly once and destroys them again.
923		1488
924	Source code for this benchmark is found as eg/bench in the AnyEvent	1489	Source code for this benchmark is found as eg/bench in the AnyEvent
925	distribution.	1490	distribution. It uses the AE interface, which makes a real difference
		1491	for the EV and Perl backends only.
926		1492
927	Explanation of the columns	1493	Explanation of the columns
928	watcher is the number of event watchers created/destroyed. Since	1494	watcher is the number of event watchers created/destroyed. Since
929	different event models feature vastly different performances, each event	1495	different event models feature vastly different performances, each event
930	loop was given a number of watchers so that overall runtime is	1496	loop was given a number of watchers so that overall runtime is
…		…
949	destroy is the time, in microseconds, that it takes to destroy a	1515	destroy is the time, in microseconds, that it takes to destroy a
950	single watcher.	1516	single watcher.
951		1517
952	Results	1518	Results
953	name watchers bytes create invoke destroy comment	1519	name watchers bytes create invoke destroy comment
954	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1520	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
955	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1521	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
956	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1522	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
957	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1523	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
958	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1524	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
959	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1525	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		1526	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		1527	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
960	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1528	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
961	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1529	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
962	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1530	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
963	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1531	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
964		1532
965	Discussion	1533	Discussion
966	The benchmark does not measure scalability of the event loop very	1534	The benchmark does not measure scalability of the event loop very
967	well. For example, a select-based event loop (such as the pure perl one)	1535	well. For example, a select-based event loop (such as the pure perl one)
968	can never compete with an event loop that uses epoll when the number of	1536	can never compete with an event loop that uses epoll when the number of
…		…
979	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1547	benchmark machine, handling an event takes roughly 1600 CPU cycles with
980	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1548	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
981	CPU cycles with POE.	1549	CPU cycles with POE.
982		1550
983	"EV" is the sole leader regarding speed and memory use, which are both	1551	"EV" is the sole leader regarding speed and memory use, which are both
984	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1552	maximal/minimal, respectively. When using the AE API there is zero
		1553	overhead (when going through the AnyEvent API create is about 5-6 times
		1554	slower, with other times being equal, so still uses far less memory than
985	far less memory than any other event loop and is still faster than Event	1555	any other event loop and is still faster than Event natively).
986	natively.
987		1556
988	The pure perl implementation is hit in a few sweet spots (both the	1557	The pure perl implementation is hit in a few sweet spots (both the
989	constant timeout and the use of a single fd hit optimisations in the	1558	constant timeout and the use of a single fd hit optimisations in the
990	perl interpreter and the backend itself). Nevertheless this shows that	1559	perl interpreter and the backend itself). Nevertheless this shows that
991	it adds very little overhead in itself. Like any select-based backend	1560	it adds very little overhead in itself. Like any select-based backend
…		…
993	few of them active), of course, but this was not subject of this	1562	few of them active), of course, but this was not subject of this
994	benchmark.	1563	benchmark.
995		1564
996	The "Event" module has a relatively high setup and callback invocation	1565	The "Event" module has a relatively high setup and callback invocation
997	cost, but overall scores in on the third place.	1566	cost, but overall scores in on the third place.
		1567
		1568	"IO::Async" performs admirably well, about on par with "Event", even
		1569	when using its pure perl backend.
998		1570
999	"Glib"'s memory usage is quite a bit higher, but it features a faster	1571	"Glib"'s memory usage is quite a bit higher, but it features a faster
1000	callback invocation and overall ends up in the same class as "Event".	1572	callback invocation and overall ends up in the same class as "Event".
1001	However, Glib scales extremely badly, doubling the number of watchers	1573	However, Glib scales extremely badly, doubling the number of watchers
1002	increases the processing time by more than a factor of four, making it	1574	increases the processing time by more than a factor of four, making it
…		…
1058	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1630	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1059	100 (1%) are active. This mirrors the activity of large servers with	1631	100 (1%) are active. This mirrors the activity of large servers with
1060	many connections, most of which are idle at any one point in time.	1632	many connections, most of which are idle at any one point in time.
1061		1633
1062	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1634	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1063	distribution.	1635	distribution. It uses the AE interface, which makes a real difference
		1636	for the EV and Perl backends only.
1064		1637
1065	Explanation of the columns	1638	Explanation of the columns
1066	sockets is the number of sockets, and twice the number of "servers"	1639	sockets is the number of sockets, and twice the number of "servers"
1067	(as each server has a read and write socket end).	1640	(as each server has a read and write socket end).
1068		1641
…		…
1073	single "request", that is, reading the token from the pipe and	1646	single "request", that is, reading the token from the pipe and
1074	forwarding it to another server. This includes deleting the old timeout	1647	forwarding it to another server. This includes deleting the old timeout
1075	and creating a new one that moves the timeout into the future.	1648	and creating a new one that moves the timeout into the future.
1076		1649
1077	Results	1650	Results
1078	name sockets create request	1651	name sockets create request
1079	EV 20000 69.01 11.16	1652	EV 20000 62.66 7.99
1080	Perl 20000 73.32 35.87	1653	Perl 20000 68.32 32.64
1081	Event 20000 212.62 257.32	1654	IOAsync 20000 174.06 101.15 epoll
1082	Glib 20000 651.16 1896.30	1655	IOAsync 20000 174.67 610.84 poll
		1656	Event 20000 202.69 242.91
		1657	Glib 20000 557.01 1689.52
1083	POE 20000 349.67 12317.24 uses POE::Loop::Event	1658	POE 20000 341.54 12086.32 uses POE::Loop::Event
1084		1659
1085	Discussion	1660	Discussion
1086	This benchmark does measure scalability and overall performance of the	1661	This benchmark does measure scalability and overall performance of the
1087	particular event loop.	1662	particular event loop.
1088		1663
1089	EV is again fastest. Since it is using epoll on my system, the setup	1664	EV is again fastest. Since it is using epoll on my system, the setup
1090	time is relatively high, though.	1665	time is relatively high, though.
1091		1666
1092	Perl surprisingly comes second. It is much faster than the C-based event	1667	Perl surprisingly comes second. It is much faster than the C-based event
1093	loops Event and Glib.	1668	loops Event and Glib.
		1669
		1670	IO::Async performs very well when using its epoll backend, and still
		1671	quite good compared to Glib when using its pure perl backend.
1094		1672
1095	Event suffers from high setup time as well (look at its code and you	1673	Event suffers from high setup time as well (look at its code and you
1096	will understand why). Callback invocation also has a high overhead	1674	will understand why). Callback invocation also has a high overhead
1097	compared to the "$_->() for .."-style loop that the Perl event loop	1675	compared to the "$_->() for .."-style loop that the Perl event loop
1098	uses. Event uses select or poll in basically all documented	1676	uses. Event uses select or poll in basically all documented
…		…
1149		1727
1150	Summary	1728	Summary
1151	* C-based event loops perform very well with small number of watchers,	1729	* C-based event loops perform very well with small number of watchers,
1152	as the management overhead dominates.	1730	as the management overhead dominates.
1153		1731
		1732	THE IO::Lambda BENCHMARK
		1733	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1734	could be misinterpreted to make AnyEvent look bad. In fact, the
		1735	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1736	better (which shouldn't come as a surprise to anybody). As such, the
		1737	benchmark is fine, and mostly shows that the AnyEvent backend from
		1738	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1739	without the extra baggage? To explore this, I wrote the equivalent
		1740	benchmark for AnyEvent.
		1741
		1742	The benchmark itself creates an echo-server, and then, for 500 times,
		1743	connects to the echo server, sends a line, waits for the reply, and then
		1744	creates the next connection. This is a rather bad benchmark, as it
		1745	doesn't test the efficiency of the framework or much non-blocking I/O,
		1746	but it is a benchmark nevertheless.
		1747
		1748	name runtime
		1749	Lambda/select 0.330 sec
		1750	+ optimized 0.122 sec
		1751	Lambda/AnyEvent 0.327 sec
		1752	+ optimized 0.138 sec
		1753	Raw sockets/select 0.077 sec
		1754	POE/select, components 0.662 sec
		1755	POE/select, raw sockets 0.226 sec
		1756	POE/select, optimized 0.404 sec
		1757
		1758	AnyEvent/select/nb 0.085 sec
		1759	AnyEvent/EV/nb 0.068 sec
		1760	+state machine 0.134 sec
		1761
		1762	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1763	benchmarks actually make blocking connects and use 100% blocking I/O,
		1764	defeating the purpose of an event-based solution. All of the newly
		1765	written AnyEvent benchmarks use 100% non-blocking connects (using
		1766	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1767	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1768	connects generally require a lot more bookkeeping and event handling
		1769	than blocking connects (which involve a single syscall only).
		1770
		1771	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1772	offers similar expressive power as POE and IO::Lambda, using
		1773	conventional Perl syntax. This means that both the echo server and the
		1774	client are 100% non-blocking, further placing it at a disadvantage.
		1775
		1776	As you can see, the AnyEvent + EV combination even beats the
		1777	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1778	backend easily beats IO::Lambda and POE.
		1779
		1780	And even the 100% non-blocking version written using the high-level (and
		1781	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
		1782	higher level ("unoptimised") abstractions by a large margin, even though
		1783	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		1784
		1785	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1786	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1787	part of the IO::Lambda distribution and were used without any changes.
		1788
		1789	SIGNALS
		1790	AnyEvent currently installs handlers for these signals:
		1791
		1792	SIGCHLD
		1793	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
		1794	emulation for event loops that do not support them natively. Also,
		1795	some event loops install a similar handler.
		1796
		1797	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1798	then AnyEvent will reset it to default, to avoid losing child exit
		1799	statuses.
		1800
		1801	SIGPIPE
		1802	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
		1803	"undef" when AnyEvent gets loaded.
		1804
		1805	The rationale for this is that AnyEvent users usually do not really
		1806	depend on SIGPIPE delivery (which is purely an optimisation for
		1807	shell use, or badly-written programs), but "SIGPIPE" can cause
		1808	spurious and rare program exits as a lot of people do not expect
		1809	"SIGPIPE" when writing to some random socket.
		1810
		1811	The rationale for installing a no-op handler as opposed to ignoring
		1812	it is that this way, the handler will be restored to defaults on
		1813	exec.
		1814
		1815	Feel free to install your own handler, or reset it to defaults.
		1816
		1817	RECOMMENDED/OPTIONAL MODULES
		1818	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1819	its built-in modules) are required to use it.
		1820
		1821	That does not mean that AnyEvent won't take advantage of some additional
		1822	modules if they are installed.
		1823
		1824	This section explains which additional modules will be used, and how
		1825	they affect AnyEvent's operation.
		1826
		1827	Async::Interrupt
		1828	This slightly arcane module is used to implement fast signal
		1829	handling: To my knowledge, there is no way to do completely
		1830	race-free and quick signal handling in pure perl. To ensure that
		1831	signals still get delivered, AnyEvent will start an interval timer
		1832	to wake up perl (and catch the signals) with some delay (default is
		1833	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1834
		1835	If this module is available, then it will be used to implement
		1836	signal catching, which means that signals will not be delayed, and
		1837	the event loop will not be interrupted regularly, which is more
		1838	efficient (and good for battery life on laptops).
		1839
		1840	This affects not just the pure-perl event loop, but also other event
		1841	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1842
		1843	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1844	natively, and either employ their own workarounds (POE) or use
		1845	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1846	Installing Async::Interrupt does nothing for those backends.
		1847
		1848	EV This module isn't really "optional", as it is simply one of the
		1849	backend event loops that AnyEvent can use. However, it is simply the
		1850	best event loop available in terms of features, speed and stability:
		1851	It supports the AnyEvent API optimally, implements all the watcher
		1852	types in XS, does automatic timer adjustments even when no monotonic
		1853	clock is available, can take avdantage of advanced kernel interfaces
		1854	such as "epoll" and "kqueue", and is the fastest backend by far.
		1855	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1856	Glib::EV).
		1857
		1858	If you only use backends that rely on another event loop (e.g.
		1859	"Tk"), then this module will do nothing for you.
		1860
		1861	Guard
		1862	The guard module, when used, will be used to implement
		1863	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1864	uses a lot less memory), but otherwise doesn't affect guard
		1865	operation much. It is purely used for performance.
		1866
		1867	JSON and JSON::XS
		1868	One of these modules is required when you want to read or write JSON
		1869	data via AnyEvent::Handle. JSON is also written in pure-perl, but
		1870	can take advantage of the ultra-high-speed JSON::XS module when it
		1871	is installed.
		1872
		1873	Net::SSLeay
		1874	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1875	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1876	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1877
		1878	Time::HiRes
		1879	This module is part of perl since release 5.008. It will be used
		1880	when the chosen event library does not come with a timing source of
		1881	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
		1882	load it to try to use a monotonic clock for timing stability.
		1883
1154	FORK	1884	FORK
1155	Most event libraries are not fork-safe. The ones who are usually are	1885	Most event libraries are not fork-safe. The ones who are usually are
1156	because they rely on inefficient but fork-safe "select" or "poll" calls.	1886	because they rely on inefficient but fork-safe "select" or "poll" calls
1157	Only EV is fully fork-aware.	1887	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		1888	epoll are usually badly thought-out hacks that are incompatible with
		1889	fork in one way or another. Only EV is fully fork-aware and ensures that
		1890	you continue event-processing in both parent and child (or both, if you
		1891	know what you are doing).
		1892
		1893	This means that, in general, you cannot fork and do event processing in
		1894	the child if the event library was initialised before the fork (which
		1895	usually happens when the first AnyEvent watcher is created, or the
		1896	library is loaded).
1158		1897
1159	If you have to fork, you must either do so before creating your first	1898	If you have to fork, you must either do so before creating your first
1160	watcher OR you must not use AnyEvent at all in the child.	1899	watcher OR you must not use AnyEvent at all in the child OR you must do
		1900	something completely out of the scope of AnyEvent.
		1901
		1902	The problem of doing event processing in the parent and the child is
		1903	much more complicated: even for backends that are fork-aware or
		1904	fork-safe, their behaviour is not usually what you want: fork clones all
		1905	watchers, that means all timers, I/O watchers etc. are active in both
		1906	parent and child, which is almost never what you want. USing "exec" to
		1907	start worker children from some kind of manage rprocess is usually
		1908	preferred, because it is much easier and cleaner, at the expense of
		1909	having to have another binary.
1161		1910
1162	SECURITY CONSIDERATIONS	1911	SECURITY CONSIDERATIONS
1163	AnyEvent can be forced to load any event model via	1912	AnyEvent can be forced to load any event model via
1164	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1913	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1165	to execute arbitrary code or directly gain access, it can easily be used	1914	to execute arbitrary code or directly gain access, it can easily be used
…		…
1168	model than specified in the variable.	1917	model than specified in the variable.
1169		1918
1170	You can make AnyEvent completely ignore this variable by deleting it	1919	You can make AnyEvent completely ignore this variable by deleting it
1171	before the first watcher gets created, e.g. with a "BEGIN" block:	1920	before the first watcher gets created, e.g. with a "BEGIN" block:
1172		1921
1173	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1922	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1174		1923
1175	use AnyEvent;	1924	use AnyEvent;
1176		1925
1177	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1926	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1178	be used to probe what backend is used and gain other information (which	1927	be used to probe what backend is used and gain other information (which
1179	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	1928	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
		1929	and $ENV{PERL_ANYEVENT_STRICT}.
		1930
		1931	Note that AnyEvent will remove all environment variables starting with
		1932	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1933	enabled.
		1934
		1935	BUGS
		1936	Perl 5.8 has numerous memleaks that sometimes hit this module and are
		1937	hard to work around. If you suffer from memleaks, first upgrade to Perl
		1938	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
		1939	annoying memleaks, such as leaking on "map" and "grep" but it is usually
		1940	not as pronounced).
1180		1941
1181	SEE ALSO	1942	SEE ALSO
		1943	Tutorial/Introduction: AnyEvent::Intro.
		1944
		1945	FAQ: AnyEvent::FAQ.
		1946
1182	Utility functions: AnyEvent::Util.	1947	Utility functions: AnyEvent::Util.
1183		1948
1184	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1949	Event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
1185	Event::Lib, Qt, POE.	1950	Glib::Event, Glib, Tk, Event::Lib, Qt, POE.
1186		1951
1187	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1952	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1188	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1953	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1189	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1954	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1955	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1190		1956
1191	Non-blocking file handles, sockets, TCP clients and servers:	1957	Non-blocking file handles, sockets, TCP clients and servers:
1192	AnyEvent::Handle, AnyEvent::Socket.	1958	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1193		1959
1194	Asynchronous DNS: AnyEvent::DNS.	1960	Asynchronous DNS: AnyEvent::DNS.
1195		1961
1196	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1962	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1197		1963
1198	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1964	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
		1965	AnyEvent::HTTP.
1199		1966
1200	AUTHOR	1967	AUTHOR
1201	Marc Lehmann <schmorp@schmorp.de>	1968	Marc Lehmann <schmorp@schmorp.de>
1202	http://home.schmorp.de/	1969	http://home.schmorp.de/
1203		1970

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Comparing AnyEvent/README (file contents): Revision 1.22 by root, Sat May 24 17:58:33 2008 UTC vs. Revision 1.65 by root, Sat Aug 13 22:44:05 2011 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.22 by root, Sat May 24 17:58:33 2008 UTC vs.
Revision 1.65 by root, Sat Aug 13 22:44:05 2011 UTC