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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, UV, Perl, Event::Lib, Irssi, rxvt-unicode,
5	loops	5	IO::Async, Qt, FLTK and POE are various supported event
		6	loops/environments.
6		7
7	SYNOPSIS	8	SYNOPSIS
8	use AnyEvent;	9	use AnyEvent;
9		10
		11	# if you prefer function calls, look at the AE manpage for
		12	# an alternative API.
		13
		14	# file handle or descriptor readable
10	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... });	15	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
11		16
		17	# one-shot or repeating timers
12	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });	18	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
13	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...	19	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
14		20
15	print AnyEvent->now; # prints current event loop time	21	print AnyEvent->now; # prints current event loop time
16	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.	22	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
17		23
		24	# POSIX signal
18	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });	25	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
19		26
		27	# child process exit
20	my $w = AnyEvent->child (pid => $pid, cb => sub {	28	my $w = AnyEvent->child (pid => $pid, cb => sub {
21	my ($pid, $status) = @_;	29	my ($pid, $status) = @_;
22	...	30	...
23	});	31	});
		32
		33	# called when event loop idle (if applicable)
		34	my $w = AnyEvent->idle (cb => sub { ... });
24		35
25	my $w = AnyEvent->condvar; # stores whether a condition was flagged	36	my $w = AnyEvent->condvar; # stores whether a condition was flagged
26	$w->send; # wake up current and all future recv's	37	$w->send; # wake up current and all future recv's
27	$w->recv; # enters "main loop" till $condvar gets ->send	38	$w->recv; # enters "main loop" till $condvar gets ->send
28	# use a condvar in callback mode:	39	# use a condvar in callback mode:
…		…
30		41
31	INTRODUCTION/TUTORIAL	42	INTRODUCTION/TUTORIAL
32	This manpage is mainly a reference manual. If you are interested in a	43	This manpage is mainly a reference manual. If you are interested in a
33	tutorial or some gentle introduction, have a look at the AnyEvent::Intro	44	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
34	manpage.	45	manpage.
		46
		47	SUPPORT
		48	An FAQ document is available as AnyEvent::FAQ.
		49
		50	There also is a mailinglist for discussing all things AnyEvent, and an
		51	IRC channel, too.
		52
		53	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
		54	Repository, at <http://anyevent.schmorp.de>, for more info.
35		55
36	WHY YOU SHOULD USE THIS MODULE (OR NOT)	56	WHY YOU SHOULD USE THIS MODULE (OR NOT)
37	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	57	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
38	nowadays. So what is different about AnyEvent?	58	nowadays. So what is different about AnyEvent?
39		59
…		…
54	module users into the same thing by forcing them to use the same event	74	module users into the same thing by forcing them to use the same event
55	model you use.	75	model you use.
56		76
57	For modules like POE or IO::Async (which is a total misnomer as it is	77	For modules like POE or IO::Async (which is a total misnomer as it is
58	actually doing all I/O *synchronously*...), using them in your module is	78	actually doing all I/O *synchronously*...), using them in your module is
59	like joining a cult: After you joined, you are dependent on them and you	79	like joining a cult: After you join, you are dependent on them and you
60	cannot use anything else, as they are simply incompatible to everything	80	cannot use anything else, as they are simply incompatible to everything
61	that isn't them. What's worse, all the potential users of your module	81	that isn't them. What's worse, all the potential users of your module
62	are *also* forced to use the same event loop you use.	82	are *also* forced to use the same event loop you use.
63		83
64	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	84	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
65	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	85	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
66	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your	86	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
67	module uses one of those, every user of your module has to use it, too.	87	uses one of those, every user of your module has to use it, too. But if
68	But if your module uses AnyEvent, it works transparently with all event	88	your module uses AnyEvent, it works transparently with all event models
69	models it supports (including stuff like IO::Async, as long as those use	89	it supports (including stuff like IO::Async, as long as those use one of
70	one of the supported event loops. It is trivial to add new event loops	90	the supported event loops. It is easy to add new event loops to
71	to AnyEvent, too, so it is future-proof).	91	AnyEvent, too, so it is future-proof).
72		92
73	In addition to being free of having to use *the one and only true event	93	In addition to being free of having to use *the one and only true event
74	model*, AnyEvent also is free of bloat and policy: with POE or similar	94	model*, AnyEvent also is free of bloat and policy: with POE or similar
75	modules, you get an enormous amount of code and strict rules you have to	95	modules, you get an enormous amount of code and strict rules you have to
76	follow. AnyEvent, on the other hand, is lean and up to the point, by	96	follow. AnyEvent, on the other hand, is lean and to the point, by only
77	only offering the functionality that is necessary, in as thin as a	97	offering the functionality that is necessary, in as thin as a wrapper as
78	wrapper as technically possible.	98	technically possible.
79		99
80	Of course, AnyEvent comes with a big (and fully optional!) toolbox of	100	Of course, AnyEvent comes with a big (and fully optional!) toolbox of
81	useful functionality, such as an asynchronous DNS resolver, 100%	101	useful functionality, such as an asynchronous DNS resolver, 100%
82	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms	102	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
83	such as Windows) and lots of real-world knowledge and workarounds for	103	such as Windows) and lots of real-world knowledge and workarounds for
…		…
86	Now, if you *do want* lots of policy (this can arguably be somewhat	106	Now, if you *do want* lots of policy (this can arguably be somewhat
87	useful) and you want to force your users to use the one and only event	107	useful) and you want to force your users to use the one and only event
88	model, you should *not* use this module.	108	model, you should *not* use this module.
89		109
90	DESCRIPTION	110	DESCRIPTION
91	AnyEvent provides an identical interface to multiple event loops. This	111	AnyEvent provides a uniform interface to various event loops. This
92	allows module authors to utilise an event loop without forcing module	112	allows module authors to use event loop functionality without forcing
93	users to use the same event loop (as only a single event loop can	113	module users to use a specific event loop implementation (since more
94	coexist peacefully at any one time).	114	than one event loop cannot coexist peacefully).
95		115
96	The interface itself is vaguely similar, but not identical to the Event	116	The interface itself is vaguely similar, but not identical to the Event
97	module.	117	module.
98		118
99	During the first call of any watcher-creation method, the module tries	119	During the first call of any watcher-creation method, the module tries
100	to detect the currently loaded event loop by probing whether one of the	120	to detect the currently loaded event loop by probing whether one of the
101	following modules is already loaded: EV, Event, Glib,	121	following modules is already loaded: EV, AnyEvent::Loop, Event, Glib,
102	AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is	122	Tk, Event::Lib, Qt, POE. The first one found is used. If none are
103	used. If none are found, the module tries to load these modules	123	detected, the module tries to load the first four modules in the order
104	(excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should	124	given; but note that if EV is not available, the pure-perl
105	always succeed) in the order given. The first one that can be	125	AnyEvent::Loop should always work, so the other two are not normally
106	successfully loaded will be used. If, after this, still none could be	126	tried.
107	found, AnyEvent will fall back to a pure-perl event loop, which is not
108	very efficient, but should work everywhere.
109		127
110	Because AnyEvent first checks for modules that are already loaded,	128	Because AnyEvent first checks for modules that are already loaded,
111	loading an event model explicitly before first using AnyEvent will	129	loading an event model explicitly before first using AnyEvent will
112	likely make that model the default. For example:	130	likely make that model the default. For example:
113		131
…		…
115	use AnyEvent;	133	use AnyEvent;
116		134
117	# .. AnyEvent will likely default to Tk	135	# .. AnyEvent will likely default to Tk
118		136
119	The *likely* means that, if any module loads another event model and	137	The *likely* means that, if any module loads another event model and
120	starts using it, all bets are off. Maybe you should tell their authors	138	starts using it, all bets are off - this case should be very rare
121	to use AnyEvent so their modules work together with others seamlessly...	139	though, as very few modules hardcode event loops without announcing this
		140	very loudly.
122		141
123	The pure-perl implementation of AnyEvent is called	142	The pure-perl implementation of AnyEvent is called "AnyEvent::Loop".
124	"AnyEvent::Impl::Perl". Like other event modules you can load it	143	Like other event modules you can load it explicitly and enjoy the high
125	explicitly and enjoy the high availability of that event loop :)	144	availability of that event loop :)
126		145
127	WATCHERS	146	WATCHERS
128	AnyEvent has the central concept of a *watcher*, which is an object that	147	AnyEvent has the central concept of a *watcher*, which is an object that
129	stores relevant data for each kind of event you are waiting for, such as	148	stores relevant data for each kind of event you are waiting for, such as
130	the callback to call, the file handle to watch, etc.	149	the callback to call, the file handle to watch, etc.
…		…
134	callback when the event occurs (of course, only when the event model is	153	callback when the event occurs (of course, only when the event model is
135	in control).	154	in control).
136		155
137	Note that callbacks must not permanently change global variables	156	Note that callbacks must not permanently change global variables
138	potentially in use by the event loop (such as $_ or $[) and that	157	potentially in use by the event loop (such as $_ or $[) and that
139	callbacks must not "die". The former is good programming practise in	158	callbacks must not "die". The former is good programming practice in
140	Perl and the latter stems from the fact that exception handling differs	159	Perl and the latter stems from the fact that exception handling differs
141	widely between event loops.	160	widely between event loops.
142		161
143	To disable the watcher you have to destroy it (e.g. by setting the	162	To disable a watcher you have to destroy it (e.g. by setting the
144	variable you store it in to "undef" or otherwise deleting all references	163	variable you store it in to "undef" or otherwise deleting all references
145	to it).	164	to it).
146		165
147	All watchers are created by calling a method on the "AnyEvent" class.	166	All watchers are created by calling a method on the "AnyEvent" class.
148		167
149	Many watchers either are used with "recursion" (repeating timers for	168	Many watchers either are used with "recursion" (repeating timers for
150	example), or need to refer to their watcher object in other ways.	169	example), or need to refer to their watcher object in other ways.
151		170
152	An any way to achieve that is this pattern:	171	One way to achieve that is this pattern:
153		172
154	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	173	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
155	# you can use $w here, for example to undef it	174	# you can use $w here, for example to undef it
156	undef $w;	175	undef $w;
157	});	176	});
…		…
159	Note that "my $w; $w =" combination. This is necessary because in Perl,	178	Note that "my $w; $w =" combination. This is necessary because in Perl,
160	my variables are only visible after the statement in which they are	179	my variables are only visible after the statement in which they are
161	declared.	180	declared.
162		181
163	I/O WATCHERS	182	I/O WATCHERS
		183	$w = AnyEvent->io (
		184	fh => <filehandle_or_fileno>,
		185	poll => <"r" or "w">,
		186	cb => <callback>,
		187	);
		188
164	You can create an I/O watcher by calling the "AnyEvent->io" method with	189	You can create an I/O watcher by calling the "AnyEvent->io" method with
165	the following mandatory key-value pairs as arguments:	190	the following mandatory key-value pairs as arguments:
166		191
167	"fh" is the Perl *file handle* (*not* file descriptor) to watch for	192	"fh" is the Perl *file handle* (or a naked file descriptor) to watch for
168	events (AnyEvent might or might not keep a reference to this file	193	events (AnyEvent might or might not keep a reference to this file
169	handle). Note that only file handles pointing to things for which	194	handle). Note that only file handles pointing to things for which
170	non-blocking operation makes sense are allowed. This includes sockets,	195	non-blocking operation makes sense are allowed. This includes sockets,
171	most character devices, pipes, fifos and so on, but not for example	196	most character devices, pipes, fifos and so on, but not for example
172	files or block devices.	197	files or block devices.
…		…
182		207
183	The I/O watcher might use the underlying file descriptor or a copy of	208	The I/O watcher might use the underlying file descriptor or a copy of
184	it. You must not close a file handle as long as any watcher is active on	209	it. You must not close a file handle as long as any watcher is active on
185	the underlying file descriptor.	210	the underlying file descriptor.
186		211
187	Some event loops issue spurious readyness notifications, so you should	212	Some event loops issue spurious readiness notifications, so you should
188	always use non-blocking calls when reading/writing from/to your file	213	always use non-blocking calls when reading/writing from/to your file
189	handles.	214	handles.
190		215
191	Example: wait for readability of STDIN, then read a line and disable the	216	Example: wait for readability of STDIN, then read a line and disable the
192	watcher.	217	watcher.
…		…
196	warn "read: $input\n";	221	warn "read: $input\n";
197	undef $w;	222	undef $w;
198	});	223	});
199		224
200	TIME WATCHERS	225	TIME WATCHERS
		226	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		227
		228	$w = AnyEvent->timer (
		229	after => <fractional_seconds>,
		230	interval => <fractional_seconds>,
		231	cb => <callback>,
		232	);
		233
201	You can create a time watcher by calling the "AnyEvent->timer" method	234	You can create a time watcher by calling the "AnyEvent->timer" method
202	with the following mandatory arguments:	235	with the following mandatory arguments:
203		236
204	"after" specifies after how many seconds (fractional values are	237	"after" specifies after how many seconds (fractional values are
205	supported) the callback should be invoked. "cb" is the callback to	238	supported) the callback should be invoked. "cb" is the callback to
…		…
207		240
208	Although the callback might get passed parameters, their value and	241	Although the callback might get passed parameters, their value and
209	presence is undefined and you cannot rely on them. Portable AnyEvent	242	presence is undefined and you cannot rely on them. Portable AnyEvent
210	callbacks cannot use arguments passed to time watcher callbacks.	243	callbacks cannot use arguments passed to time watcher callbacks.
211		244
212	The callback will normally be invoked once only. If you specify another	245	The callback will normally be invoked only once. If you specify another
213	parameter, "interval", as a strictly positive number (> 0), then the	246	parameter, "interval", as a strictly positive number (> 0), then the
214	callback will be invoked regularly at that interval (in fractional	247	callback will be invoked regularly at that interval (in fractional
215	seconds) after the first invocation. If "interval" is specified with a	248	seconds) after the first invocation. If "interval" is specified with a
216	false value, then it is treated as if it were missing.	249	false value, then it is treated as if it were not specified at all.
217		250
218	The callback will be rescheduled before invoking the callback, but no	251	The callback will be rescheduled before invoking the callback, but no
219	attempt is done to avoid timer drift in most backends, so the interval	252	attempt is made to avoid timer drift in most backends, so the interval
220	is only approximate.	253	is only approximate.
221		254
222	Example: fire an event after 7.7 seconds.	255	Example: fire an event after 7.7 seconds.
223		256
224	my $w = AnyEvent->timer (after => 7.7, cb => sub {	257	my $w = AnyEvent->timer (after => 7.7, cb => sub {
…		…
230		263
231	Example 2: fire an event after 0.5 seconds, then roughly every second.	264	Example 2: fire an event after 0.5 seconds, then roughly every second.
232		265
233	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {	266	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
234	warn "timeout\n";	267	warn "timeout\n";
235	};	268	});
236		269
237	TIMING ISSUES	270	TIMING ISSUES
238	There are two ways to handle timers: based on real time (relative, "fire	271	There are two ways to handle timers: based on real time (relative, "fire
239	in 10 seconds") and based on wallclock time (absolute, "fire at 12	272	in 10 seconds") and based on wallclock time (absolute, "fire at 12
240	o'clock").	273	o'clock").
241		274
242	While most event loops expect timers to specified in a relative way,	275	While most event loops expect timers to specified in a relative way,
243	they use absolute time internally. This makes a difference when your	276	they use absolute time internally. This makes a difference when your
244	clock "jumps", for example, when ntp decides to set your clock backwards	277	clock "jumps", for example, when ntp decides to set your clock backwards
245	from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is	278	from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is
246	supposed to fire "after" a second might actually take six years to	279	supposed to fire "after a second" might actually take six years to
247	finally fire.	280	finally fire.
248		281
249	AnyEvent cannot compensate for this. The only event loop that is	282	AnyEvent cannot compensate for this. The only event loop that is
250	conscious about these issues is EV, which offers both relative	283	conscious of these issues is EV, which offers both relative (ev_timer,
251	(ev_timer, based on true relative time) and absolute (ev_periodic, based	284	based on true relative time) and absolute (ev_periodic, based on
252	on wallclock time) timers.	285	wallclock time) timers.
253		286
254	AnyEvent always prefers relative timers, if available, matching the	287	AnyEvent always prefers relative timers, if available, matching the
255	AnyEvent API.	288	AnyEvent API.
256		289
257	AnyEvent has two additional methods that return the "current time":	290	AnyEvent has two additional methods that return the "current time":
…		…
276	*In almost all cases (in all cases if you don't care), this is the	309	*In almost all cases (in all cases if you don't care), this is the
277	function to call when you want to know the current time.*	310	function to call when you want to know the current time.*
278		311
279	This function is also often faster then "AnyEvent->time", and thus	312	This function is also often faster then "AnyEvent->time", and thus
280	the preferred method if you want some timestamp (for example,	313	the preferred method if you want some timestamp (for example,
281	AnyEvent::Handle uses this to update it's activity timeouts).	314	AnyEvent::Handle uses this to update its activity timeouts).
282		315
283	The rest of this section is only of relevance if you try to be very	316	The rest of this section is only of relevance if you try to be very
284	exact with your timing, you can skip it without bad conscience.	317	exact with your timing; you can skip it without a bad conscience.
285		318
286	For a practical example of when these times differ, consider	319	For a practical example of when these times differ, consider
287	Event::Lib and EV and the following set-up:	320	Event::Lib and EV and the following set-up:
288		321
289	The event loop is running and has just invoked one of your callback	322	The event loop is running and has just invoked one of your callbacks
290	at time=500 (assume no other callbacks delay processing). In your	323	at time=500 (assume no other callbacks delay processing). In your
291	callback, you wait a second by executing "sleep 1" (blocking the	324	callback, you wait a second by executing "sleep 1" (blocking the
292	process for a second) and then (at time=501) you create a relative	325	process for a second) and then (at time=501) you create a relative
293	timer that fires after three seconds.	326	timer that fires after three seconds.
294		327
…		…
314	In either case, if you care (and in most cases, you don't), then you	347	In either case, if you care (and in most cases, you don't), then you
315	can get whatever behaviour you want with any event loop, by taking	348	can get whatever behaviour you want with any event loop, by taking
316	the difference between "AnyEvent->time" and "AnyEvent->now" into	349	the difference between "AnyEvent->time" and "AnyEvent->now" into
317	account.	350	account.
318		351
		352	AnyEvent->now_update
		353	Some event loops (such as EV or AnyEvent::Loop) cache the current
		354	time for each loop iteration (see the discussion of AnyEvent->now,
		355	above).
		356
		357	When a callback runs for a long time (or when the process sleeps),
		358	then this "current" time will differ substantially from the real
		359	time, which might affect timers and time-outs.
		360
		361	When this is the case, you can call this method, which will update
		362	the event loop's idea of "current time".
		363
		364	A typical example would be a script in a web server (e.g.
		365	"mod_perl") - when mod_perl executes the script, then the event loop
		366	will have the wrong idea about the "current time" (being potentially
		367	far in the past, when the script ran the last time). In that case
		368	you should arrange a call to "AnyEvent->now_update" each time the
		369	web server process wakes up again (e.g. at the start of your script,
		370	or in a handler).
		371
		372	Note that updating the time *might* cause some events to be handled.
		373
319	SIGNAL WATCHERS	374	SIGNAL WATCHERS
		375	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		376
320	You can watch for signals using a signal watcher, "signal" is the signal	377	You can watch for signals using a signal watcher, "signal" is the signal
321	*name* in uppercase and without any "SIG" prefix, "cb" is the Perl	378	*name* in uppercase and without any "SIG" prefix, "cb" is the Perl
322	callback to be invoked whenever a signal occurs.	379	callback to be invoked whenever a signal occurs.
323		380
324	Although the callback might get passed parameters, their value and	381	Although the callback might get passed parameters, their value and
…		…
329	invocation, and callback invocation will be synchronous. Synchronous	386	invocation, and callback invocation will be synchronous. Synchronous
330	means that it might take a while until the signal gets handled by the	387	means that it might take a while until the signal gets handled by the
331	process, but it is guaranteed not to interrupt any other callbacks.	388	process, but it is guaranteed not to interrupt any other callbacks.
332		389
333	The main advantage of using these watchers is that you can share a	390	The main advantage of using these watchers is that you can share a
334	signal between multiple watchers.	391	signal between multiple watchers, and AnyEvent will ensure that signals
		392	will not interrupt your program at bad times.
335		393
336	This watcher might use %SIG, so programs overwriting those signals	394	This watcher might use %SIG (depending on the event loop used), so
337	directly will likely not work correctly.	395	programs overwriting those signals directly will likely not work
		396	correctly.
338		397
339	Example: exit on SIGINT	398	Example: exit on SIGINT
340		399
341	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	400	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
342		401
		402	Restart Behaviour
		403	While restart behaviour is up to the event loop implementation, most
		404	will not restart syscalls (that includes Async::Interrupt and AnyEvent's
		405	pure perl implementation).
		406
		407	Safe/Unsafe Signals
		408	Perl signals can be either "safe" (synchronous to opcode handling) or
		409	"unsafe" (asynchronous) - the former might delay signal delivery
		410	indefinitely, the latter might corrupt your memory.
		411
		412	AnyEvent signal handlers are, in addition, synchronous to the event
		413	loop, i.e. they will not interrupt your running perl program but will
		414	only be called as part of the normal event handling (just like timer,
		415	I/O etc. callbacks, too).
		416
		417	Signal Races, Delays and Workarounds
		418	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		419	callbacks to signals in a generic way, which is a pity, as you cannot do
		420	race-free signal handling in perl, requiring C libraries for this.
		421	AnyEvent will try to do its best, which means in some cases, signals
		422	will be delayed. The maximum time a signal might be delayed is 10
		423	seconds by default, but can be overriden via
		424	$ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} or $AnyEvent::MAX_SIGNAL_LATENCY
		425	- see the "ENVIRONMENT VARIABLES" section for details.
		426
		427	All these problems can be avoided by installing the optional
		428	Async::Interrupt module, which works with most event loops. It will not
		429	work with inherently broken event loops such as Event or Event::Lib (and
		430	not with POE currently). For those, you just have to suffer the delays.
		431
343	CHILD PROCESS WATCHERS	432	CHILD PROCESS WATCHERS
		433	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		434
344	You can also watch on a child process exit and catch its exit status.	435	You can also watch for a child process exit and catch its exit status.
345		436
346	The child process is specified by the "pid" argument (if set to 0, it	437	The child process is specified by the "pid" argument (on some backends,
347	watches for any child process exit). The watcher will triggered only	438	using 0 watches for any child process exit, on others this will croak).
348	when the child process has finished and an exit status is available, not	439	The watcher will be triggered only when the child process has finished
349	on any trace events (stopped/continued).	440	and an exit status is available, not on any trace events
		441	(stopped/continued).
350		442
351	The callback will be called with the pid and exit status (as returned by	443	The callback will be called with the pid and exit status (as returned by
352	waitpid), so unlike other watcher types, you *can* rely on child watcher	444	waitpid), so unlike other watcher types, you *can* rely on child watcher
353	callback arguments.	445	callback arguments.
354		446
…		…
359		451
360	There is a slight catch to child watchers, however: you usually start	452	There is a slight catch to child watchers, however: you usually start
361	them *after* the child process was created, and this means the process	453	them *after* the child process was created, and this means the process
362	could have exited already (and no SIGCHLD will be sent anymore).	454	could have exited already (and no SIGCHLD will be sent anymore).
363		455
364	Not all event models handle this correctly (POE doesn't), but even for	456	Not all event models handle this correctly (neither POE nor IO::Async
		457	do, see their AnyEvent::Impl manpages for details), but even for event
365	event models that *do* handle this correctly, they usually need to be	458	models that *do* handle this correctly, they usually need to be loaded
366	loaded before the process exits (i.e. before you fork in the first	459	before the process exits (i.e. before you fork in the first place).
367	place).	460	AnyEvent's pure perl event loop handles all cases correctly regardless
		461	of when you start the watcher.
368		462
369	This means you cannot create a child watcher as the very first thing in	463	This means you cannot create a child watcher as the very first thing in
370	an AnyEvent program, you *have* to create at least one watcher before	464	an AnyEvent program, you *have* to create at least one watcher before
371	you "fork" the child (alternatively, you can call "AnyEvent::detect").	465	you "fork" the child (alternatively, you can call "AnyEvent::detect").
372		466
		467	As most event loops do not support waiting for child events, they will
		468	be emulated by AnyEvent in most cases, in which case the latency and
		469	race problems mentioned in the description of signal watchers apply.
		470
373	Example: fork a process and wait for it	471	Example: fork a process and wait for it
374		472
375	my $done = AnyEvent->condvar;	473	my $done = AnyEvent->condvar;
376		474
		475	# this forks and immediately calls exit in the child. this
		476	# normally has all sorts of bad consequences for your parent,
		477	# so take this as an example only. always fork and exec,
		478	# or call POSIX::_exit, in real code.
377	my $pid = fork or exit 5;	479	my $pid = fork or exit 5;
378		480
379	my $w = AnyEvent->child (	481	my $w = AnyEvent->child (
380	pid => $pid,	482	pid => $pid,
381	cb => sub {	483	cb => sub {
382	my ($pid, $status) = @_;	484	my ($pid, $status) = @_;
383	warn "pid $pid exited with status $status";	485	warn "pid $pid exited with status $status";
384	$done->send;	486	$done->send;
385	},	487	},
386	);	488	);
387		489
388	# do something else, then wait for process exit	490	# do something else, then wait for process exit
389	$done->recv;	491	$done->recv;
390		492
		493	IDLE WATCHERS
		494	$w = AnyEvent->idle (cb => <callback>);
		495
		496	This will repeatedly invoke the callback after the process becomes idle,
		497	until either the watcher is destroyed or new events have been detected.
		498
		499	Idle watchers are useful when there is a need to do something, but it is
		500	not so important (or wise) to do it instantly. The callback will be
		501	invoked only when there is "nothing better to do", which is usually
		502	defined as "all outstanding events have been handled and no new events
		503	have been detected". That means that idle watchers ideally get invoked
		504	when the event loop has just polled for new events but none have been
		505	detected. Instead of blocking to wait for more events, the idle watchers
		506	will be invoked.
		507
		508	Unfortunately, most event loops do not really support idle watchers
		509	(only EV, Event and Glib do it in a usable fashion) - for the rest,
		510	AnyEvent will simply call the callback "from time to time".
		511
		512	Example: read lines from STDIN, but only process them when the program
		513	is otherwise idle:
		514
		515	my @lines; # read data
		516	my $idle_w;
		517	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		518	push @lines, scalar <STDIN>;
		519
		520	# start an idle watcher, if not already done
		521	$idle_w ||= AnyEvent->idle (cb => sub {
		522	# handle only one line, when there are lines left
		523	if (my $line = shift @lines) {
		524	print "handled when idle: $line";
		525	} else {
		526	# otherwise disable the idle watcher again
		527	undef $idle_w;
		528	}
		529	});
		530	});
		531
391	CONDITION VARIABLES	532	CONDITION VARIABLES
		533	$cv = AnyEvent->condvar;
		534
		535	$cv->send (<list>);
		536	my @res = $cv->recv;
		537
392	If you are familiar with some event loops you will know that all of them	538	If you are familiar with some event loops you will know that all of them
393	require you to run some blocking "loop", "run" or similar function that	539	require you to run some blocking "loop", "run" or similar function that
394	will actively watch for new events and call your callbacks.	540	will actively watch for new events and call your callbacks.
395		541
396	AnyEvent is different, it expects somebody else to run the event loop	542	AnyEvent is slightly different: it expects somebody else to run the
397	and will only block when necessary (usually when told by the user).	543	event loop and will only block when necessary (usually when told by the
		544	user).
398		545
399	The instrument to do that is called a "condition variable", so called	546	The tool to do that is called a "condition variable", so called because
400	because they represent a condition that must become true.	547	they represent a condition that must become true.
		548
		549	Now is probably a good time to look at the examples further below.
401		550
402	Condition variables can be created by calling the "AnyEvent->condvar"	551	Condition variables can be created by calling the "AnyEvent->condvar"
403	method, usually without arguments. The only argument pair allowed is	552	method, usually without arguments. The only argument pair allowed is
404
405	"cb", which specifies a callback to be called when the condition	553	"cb", which specifies a callback to be called when the condition
406	variable becomes true, with the condition variable as the first argument	554	variable becomes true, with the condition variable as the first argument
407	(but not the results).	555	(but not the results).
408		556
409	After creation, the condition variable is "false" until it becomes	557	After creation, the condition variable is "false" until it becomes
410	"true" by calling the "send" method (or calling the condition variable	558	"true" by calling the "send" method (or calling the condition variable
411	as if it were a callback, read about the caveats in the description for	559	as if it were a callback, read about the caveats in the description for
412	the "->send" method).	560	the "->send" method).
413		561
414	Condition variables are similar to callbacks, except that you can	562	Since condition variables are the most complex part of the AnyEvent API,
415	optionally wait for them. They can also be called merge points - points	563	here are some different mental models of what they are - pick the ones
416	in time where multiple outstanding events have been processed. And yet	564	you can connect to:
417	another way to call them is transactions - each condition variable can	565
418	be used to represent a transaction, which finishes at some point and	566	* Condition variables are like callbacks - you can call them (and pass
419	delivers a result.	567	them instead of callbacks). Unlike callbacks however, you can also
		568	wait for them to be called.
		569
		570	* Condition variables are signals - one side can emit or send them,
		571	the other side can wait for them, or install a handler that is
		572	called when the signal fires.
		573
		574	* Condition variables are like "Merge Points" - points in your program
		575	where you merge multiple independent results/control flows into one.
		576
		577	* Condition variables represent a transaction - functions that start
		578	some kind of transaction can return them, leaving the caller the
		579	choice between waiting in a blocking fashion, or setting a callback.
		580
		581	* Condition variables represent future values, or promises to deliver
		582	some result, long before the result is available.
420		583
421	Condition variables are very useful to signal that something has	584	Condition variables are very useful to signal that something has
422	finished, for example, if you write a module that does asynchronous http	585	finished, for example, if you write a module that does asynchronous http
423	requests, then a condition variable would be the ideal candidate to	586	requests, then a condition variable would be the ideal candidate to
424	signal the availability of results. The user can either act when the	587	signal the availability of results. The user can either act when the
…		…
437		600
438	Condition variables are represented by hash refs in perl, and the keys	601	Condition variables are represented by hash refs in perl, and the keys
439	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy	602	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy
440	(it is often useful to build your own transaction class on top of	603	(it is often useful to build your own transaction class on top of
441	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call	604	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
442	it's "new" method in your own "new" method.	605	its "new" method in your own "new" method.
443		606
444	There are two "sides" to a condition variable - the "producer side"	607	There are two "sides" to a condition variable - the "producer side"
445	which eventually calls "-> send", and the "consumer side", which waits	608	which eventually calls "-> send", and the "consumer side", which waits
446	for the send to occur.	609	for the send to occur.
447		610
448	Example: wait for a timer.	611	Example: wait for a timer.
449		612
450	# wait till the result is ready	613	# condition: "wait till the timer is fired"
451	my $result_ready = AnyEvent->condvar;	614	my $timer_fired = AnyEvent->condvar;
452		615
453	# do something such as adding a timer	616	# create the timer - we could wait for, say
454	# or socket watcher the calls $result_ready->send	617	# a handle becomign ready, or even an
455	# when the "result" is ready.	618	# AnyEvent::HTTP request to finish, but
456	# in this case, we simply use a timer:	619	# in this case, we simply use a timer:
457	my $w = AnyEvent->timer (	620	my $w = AnyEvent->timer (
458	after => 1,	621	after => 1,
459	cb => sub { $result_ready->send },	622	cb => sub { $timer_fired->send },
460	);	623	);
461		624
462	# this "blocks" (while handling events) till the callback	625	# this "blocks" (while handling events) till the callback
463	# calls send	626	# calls ->send
464	$result_ready->recv;	627	$timer_fired->recv;
465		628
466	Example: wait for a timer, but take advantage of the fact that condition	629	Example: wait for a timer, but take advantage of the fact that condition
467	variables are also code references.	630	variables are also callable directly.
468		631
469	my $done = AnyEvent->condvar;	632	my $done = AnyEvent->condvar;
470	my $delay = AnyEvent->timer (after => 5, cb => $done);	633	my $delay = AnyEvent->timer (after => 5, cb => $done);
471	$done->recv;	634	$done->recv;
472		635
…		…
478		641
479	...	642	...
480		643
481	my @info = $couchdb->info->recv;	644	my @info = $couchdb->info->recv;
482		645
483	And this is how you would just ste a callback to be called whenever the	646	And this is how you would just set a callback to be called whenever the
484	results are available:	647	results are available:
485		648
486	$couchdb->info->cb (sub {	649	$couchdb->info->cb (sub {
487	my @info = $_[0]->recv;	650	my @info = $_[0]->recv;
488	});	651	});
…		…
503		666
504	Any arguments passed to the "send" call will be returned by all	667	Any arguments passed to the "send" call will be returned by all
505	future "->recv" calls.	668	future "->recv" calls.
506		669
507	Condition variables are overloaded so one can call them directly (as	670	Condition variables are overloaded so one can call them directly (as
508	a code reference). Calling them directly is the same as calling	671	if they were a code reference). Calling them directly is the same as
509	"send". Note, however, that many C-based event loops do not handle	672	calling "send".
510	overloading, so as tempting as it may be, passing a condition
511	variable instead of a callback does not work. Both the pure perl and
512	EV loops support overloading, however, as well as all functions that
513	use perl to invoke a callback (as in AnyEvent::Socket and
514	AnyEvent::DNS for example).
515		673
516	$cv->croak ($error)	674	$cv->croak ($error)
517	Similar to send, but causes all call's to "->recv" to invoke	675	Similar to send, but causes all calls to "->recv" to invoke
518	"Carp::croak" with the given error message/object/scalar.	676	"Carp::croak" with the given error message/object/scalar.
519		677
520	This can be used to signal any errors to the condition variable	678	This can be used to signal any errors to the condition variable
521	user/consumer.	679	user/consumer. Doing it this way instead of calling "croak" directly
		680	delays the error detection, but has the overwhelming advantage that
		681	it diagnoses the error at the place where the result is expected,
		682	and not deep in some event callback with no connection to the actual
		683	code causing the problem.
522		684
523	$cv->begin ([group callback])	685	$cv->begin ([group callback])
524	$cv->end	686	$cv->end
525	These two methods are EXPERIMENTAL and MIGHT CHANGE.
526
527	These two methods can be used to combine many transactions/events	687	These two methods can be used to combine many transactions/events
528	into one. For example, a function that pings many hosts in parallel	688	into one. For example, a function that pings many hosts in parallel
529	might want to use a condition variable for the whole process.	689	might want to use a condition variable for the whole process.
530		690
531	Every call to "->begin" will increment a counter, and every call to	691	Every call to "->begin" will increment a counter, and every call to
532	"->end" will decrement it. If the counter reaches 0 in "->end", the	692	"->end" will decrement it. If the counter reaches 0 in "->end", the
533	(last) callback passed to "begin" will be executed. That callback is	693	(last) callback passed to "begin" will be executed, passing the
534	*supposed* to call "->send", but that is not required. If no	694	condvar as first argument. That callback is *supposed* to call
		695	"->send", but that is not required. If no group callback was set,
535	callback was set, "send" will be called without any arguments.	696	"send" will be called without any arguments.
536		697
537	Let's clarify this with the ping example:	698	You can think of "$cv->send" giving you an OR condition (one call
		699	sends), while "$cv->begin" and "$cv->end" giving you an AND
		700	condition (all "begin" calls must be "end"'ed before the condvar
		701	sends).
		702
		703	Let's start with a simple example: you have two I/O watchers (for
		704	example, STDOUT and STDERR for a program), and you want to wait for
		705	both streams to close before activating a condvar:
538		706
539	my $cv = AnyEvent->condvar;	707	my $cv = AnyEvent->condvar;
540		708
		709	$cv->begin; # first watcher
		710	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		711	defined sysread $fh1, my $buf, 4096
		712	or $cv->end;
		713	});
		714
		715	$cv->begin; # second watcher
		716	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		717	defined sysread $fh2, my $buf, 4096
		718	or $cv->end;
		719	});
		720
		721	$cv->recv;
		722
		723	This works because for every event source (EOF on file handle),
		724	there is one call to "begin", so the condvar waits for all calls to
		725	"end" before sending.
		726
		727	The ping example mentioned above is slightly more complicated, as
		728	the there are results to be passed back, and the number of tasks
		729	that are begun can potentially be zero:
		730
		731	my $cv = AnyEvent->condvar;
		732
541	my %result;	733	my %result;
542	$cv->begin (sub { $cv->send (\%result) });	734	$cv->begin (sub { shift->send (\%result) });
543		735
544	for my $host (@list_of_hosts) {	736	for my $host (@list_of_hosts) {
545	$cv->begin;	737	$cv->begin;
546	ping_host_then_call_callback $host, sub {	738	ping_host_then_call_callback $host, sub {
547	$result{$host} = ...;	739	$result{$host} = ...;
…		…
549	};	741	};
550	}	742	}
551		743
552	$cv->end;	744	$cv->end;
553		745
		746	...
		747
		748	my $results = $cv->recv;
		749
554	This code fragment supposedly pings a number of hosts and calls	750	This code fragment supposedly pings a number of hosts and calls
555	"send" after results for all then have have been gathered - in any	751	"send" after results for all then have have been gathered - in any
556	order. To achieve this, the code issues a call to "begin" when it	752	order. To achieve this, the code issues a call to "begin" when it
557	starts each ping request and calls "end" when it has received some	753	starts each ping request and calls "end" when it has received some
558	result for it. Since "begin" and "end" only maintain a counter, the	754	result for it. Since "begin" and "end" only maintain a counter, the
…		…
562	the loop, which serves two important purposes: first, it sets the	758	the loop, which serves two important purposes: first, it sets the
563	callback to be called once the counter reaches 0, and second, it	759	callback to be called once the counter reaches 0, and second, it
564	ensures that "send" is called even when "no" hosts are being pinged	760	ensures that "send" is called even when "no" hosts are being pinged
565	(the loop doesn't execute once).	761	(the loop doesn't execute once).
566		762
567	This is the general pattern when you "fan out" into multiple	763	This is the general pattern when you "fan out" into multiple (but
568	subrequests: use an outer "begin"/"end" pair to set the callback and	764	potentially zero) subrequests: use an outer "begin"/"end" pair to
569	ensure "end" is called at least once, and then, for each subrequest	765	set the callback and ensure "end" is called at least once, and then,
570	you start, call "begin" and for each subrequest you finish, call	766	for each subrequest you start, call "begin" and for each subrequest
571	"end".	767	you finish, call "end".
572		768
573	METHODS FOR CONSUMERS	769	METHODS FOR CONSUMERS
574	These methods should only be used by the consuming side, i.e. the code	770	These methods should only be used by the consuming side, i.e. the code
575	awaits the condition.	771	awaits the condition.
576		772
577	$cv->recv	773	$cv->recv
578	Wait (blocking if necessary) until the "->send" or "->croak" methods	774	Wait (blocking if necessary) until the "->send" or "->croak" methods
579	have been called on c<$cv>, while servicing other watchers normally.	775	have been called on $cv, while servicing other watchers normally.
580		776
581	You can only wait once on a condition - additional calls are valid	777	You can only wait once on a condition - additional calls are valid
582	but will return immediately.	778	but will return immediately.
583		779
584	If an error condition has been set by calling "->croak", then this	780	If an error condition has been set by calling "->croak", then this
585	function will call "croak".	781	function will call "croak".
586		782
587	In list context, all parameters passed to "send" will be returned,	783	In list context, all parameters passed to "send" will be returned,
588	in scalar context only the first one will be returned.	784	in scalar context only the first one will be returned.
589		785
		786	Note that doing a blocking wait in a callback is not supported by
		787	any event loop, that is, recursive invocation of a blocking "->recv"
		788	is not allowed and the "recv" call will "croak" if such a condition
		789	is detected. This requirement can be dropped by relying on
		790	Coro::AnyEvent , which allows you to do a blocking "->recv" from any
		791	thread that doesn't run the event loop itself. Coro::AnyEvent is
		792	loaded automatically when Coro is used with AnyEvent, so code does
		793	not need to do anything special to take advantage of that: any code
		794	that would normally block your program because it calls "recv", be
		795	executed in an "async" thread instead without blocking other
		796	threads.
		797
590	Not all event models support a blocking wait - some die in that case	798	Not all event models support a blocking wait - some die in that case
591	(programs might want to do that to stay interactive), so *if you are	799	(programs might want to do that to stay interactive), so *if you are
592	using this from a module, never require a blocking wait*, but let	800	using this from a module, never require a blocking wait*. Instead,
593	the caller decide whether the call will block or not (for example,	801	let the caller decide whether the call will block or not (for
594	by coupling condition variables with some kind of request results	802	example, by coupling condition variables with some kind of request
595	and supporting callbacks so the caller knows that getting the result	803	results and supporting callbacks so the caller knows that getting
596	will not block, while still supporting blocking waits if the caller	804	the result will not block, while still supporting blocking waits if
597	so desires).	805	the caller so desires).
598		806
599	Another reason *never* to "->recv" in a module is that you cannot
600	sensibly have two "->recv"'s in parallel, as that would require
601	multiple interpreters or coroutines/threads, none of which
602	"AnyEvent" can supply.
603
604	The Coro module, however, *can* and *does* supply coroutines and, in
605	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
606	versions and also integrates coroutines into AnyEvent, making
607	blocking "->recv" calls perfectly safe as long as they are done from
608	another coroutine (one that doesn't run the event loop).
609
610	You can ensure that "-recv" never blocks by setting a callback and	807	You can ensure that "->recv" never blocks by setting a callback and
611	only calling "->recv" from within that callback (or at a later	808	only calling "->recv" from within that callback (or at a later
612	time). This will work even when the event loop does not support	809	time). This will work even when the event loop does not support
613	blocking waits otherwise.	810	blocking waits otherwise.
614		811
615	$bool = $cv->ready	812	$bool = $cv->ready
616	Returns true when the condition is "true", i.e. whether "send" or	813	Returns true when the condition is "true", i.e. whether "send" or
617	"croak" have been called.	814	"croak" have been called.
618		815
619	$cb = $cv->cb ($cb->($cv))	816	$cb = $cv->cb ($cb->($cv))
620	This is a mutator function that returns the callback set and	817	This is a mutator function that returns the callback set (or "undef"
621	optionally replaces it before doing so.	818	if not) and optionally replaces it before doing so.
622		819
623	The callback will be called when the condition becomes "true", i.e.	820	The callback will be called when the condition becomes "true", i.e.
624	when "send" or "croak" are called, with the only argument being the	821	when "send" or "croak" are called, with the only argument being the
625	condition variable itself. Calling "recv" inside the callback or at	822	condition variable itself. If the condition is already true, the
		823	callback is called immediately when it is set. Calling "recv" inside
626	any later time is guaranteed not to block.	824	the callback or at any later time is guaranteed not to block.
		825
		826	Additionally, when the callback is invoked, it is also removed from
		827	the condvar (reset to "undef"), so the condvar does not keep a
		828	reference to the callback after invocation.
		829
		830	SUPPORTED EVENT LOOPS/BACKENDS
		831	The available backend classes are (every class has its own manpage):
		832
		833	Backends that are autoprobed when no other event loop can be found.
		834	EV is the preferred backend when no other event loop seems to be in
		835	use. If EV is not installed, then AnyEvent will fall back to its own
		836	pure-perl implementation, which is available everywhere as it comes
		837	with AnyEvent itself.
		838
		839	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		840	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		841
		842	Backends that are transparently being picked up when they are used.
		843	These will be used if they are already loaded when the first watcher
		844	is created, in which case it is assumed that the application is
		845	using them. This means that AnyEvent will automatically pick the
		846	right backend when the main program loads an event module before
		847	anything starts to create watchers. Nothing special needs to be done
		848	by the main program.
		849
		850	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		851	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		852	AnyEvent::Impl::Tk based on Tk, very broken.
		853	AnyEvent::Impl::UV based on UV, innovated square wheels.
		854	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		855	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		856	AnyEvent::Impl::Irssi used when running within irssi.
		857	AnyEvent::Impl::IOAsync based on IO::Async.
		858	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		859	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
		860
		861	Backends with special needs.
		862	Qt requires the Qt::Application to be instantiated first, but will
		863	otherwise be picked up automatically. As long as the main program
		864	instantiates the application before any AnyEvent watchers are
		865	created, everything should just work.
		866
		867	AnyEvent::Impl::Qt based on Qt.
		868
		869	Event loops that are indirectly supported via other backends.
		870	Some event loops can be supported via other modules:
		871
		872	There is no direct support for WxWidgets (Wx) or Prima.
		873
		874	WxWidgets has no support for watching file handles. However, you can
		875	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		876	simply polls 20 times per second, which was considered to be too
		877	horrible to even consider for AnyEvent.
		878
		879	Prima is not supported as nobody seems to be using it, but it has a
		880	POE backend, so it can be supported through POE.
		881
		882	AnyEvent knows about both Prima and Wx, however, and will try to
		883	load POE when detecting them, in the hope that POE will pick them
		884	up, in which case everything will be automatic.
627		885
628	GLOBAL VARIABLES AND FUNCTIONS	886	GLOBAL VARIABLES AND FUNCTIONS
		887	These are not normally required to use AnyEvent, but can be useful to
		888	write AnyEvent extension modules.
		889
629	$AnyEvent::MODEL	890	$AnyEvent::MODEL
630	Contains "undef" until the first watcher is being created. Then it	891	Contains "undef" until the first watcher is being created, before
		892	the backend has been autodetected.
		893
631	contains the event model that is being used, which is the name of	894	Afterwards it contains the event model that is being used, which is
632	the Perl class implementing the model. This class is usually one of	895	the name of the Perl class implementing the model. This class is
633	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	896	usually one of the "AnyEvent::Impl::xxx" modules, but can be any
634	case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*).	897	other class in the case AnyEvent has been extended at runtime (e.g.
635		898	in *rxvt-unicode* it will be "urxvt::anyevent").
636	The known classes so far are:
637
638	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
639	AnyEvent::Impl::Event based on Event, second best choice.
640	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
641	AnyEvent::Impl::Glib based on Glib, third-best choice.
642	AnyEvent::Impl::Tk based on Tk, very bad choice.
643	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
644	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
645	AnyEvent::Impl::POE based on POE, not generic enough for full support.
646
647	There is no support for WxWidgets, as WxWidgets has no support for
648	watching file handles. However, you can use WxWidgets through the
649	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
650	second, which was considered to be too horrible to even consider for
651	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
652	using it's adaptor.
653
654	AnyEvent knows about Prima and Wx and will try to use POE when
655	autodetecting them.
656		899
657	AnyEvent::detect	900	AnyEvent::detect
658	Returns $AnyEvent::MODEL, forcing autodetection of the event model	901	Returns $AnyEvent::MODEL, forcing autodetection of the event model
659	if necessary. You should only call this function right before you	902	if necessary. You should only call this function right before you
660	would have created an AnyEvent watcher anyway, that is, as late as	903	would have created an AnyEvent watcher anyway, that is, as late as
661	possible at runtime.	904	possible at runtime, and not e.g. during initialisation of your
		905	module.
		906
		907	The effect of calling this function is as if a watcher had been
		908	created (specifically, actions that happen "when the first watcher
		909	is created" happen when calling detetc as well).
		910
		911	If you need to do some initialisation before AnyEvent watchers are
		912	created, use "post_detect".
662		913
663	$guard = AnyEvent::post_detect { BLOCK }	914	$guard = AnyEvent::post_detect { BLOCK }
664	Arranges for the code block to be executed as soon as the event	915	Arranges for the code block to be executed as soon as the event
665	model is autodetected (or immediately if this has already happened).	916	model is autodetected (or immediately if that has already happened).
		917
		918	The block will be executed *after* the actual backend has been
		919	detected ($AnyEvent::MODEL is set), but *before* any watchers have
		920	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		921	other initialisations - see the sources of AnyEvent::Strict or
		922	AnyEvent::AIO to see how this is used.
		923
		924	The most common usage is to create some global watchers, without
		925	forcing event module detection too early, for example, AnyEvent::AIO
		926	creates and installs the global IO::AIO watcher in a "post_detect"
		927	block to avoid autodetecting the event module at load time.
666		928
667	If called in scalar or list context, then it creates and returns an	929	If called in scalar or list context, then it creates and returns an
668	object that automatically removes the callback again when it is	930	object that automatically removes the callback again when it is
		931	destroyed (or "undef" when the hook was immediately executed). See
669	destroyed. See Coro::BDB for a case where this is useful.	932	AnyEvent::AIO for a case where this is useful.
		933
		934	Example: Create a watcher for the IO::AIO module and store it in
		935	$WATCHER, but do so only do so after the event loop is initialised.
		936
		937	our WATCHER;
		938
		939	my $guard = AnyEvent::post_detect {
		940	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		941	};
		942
		943	# the ||= is important in case post_detect immediately runs the block,
		944	# as to not clobber the newly-created watcher. assigning both watcher and
		945	# post_detect guard to the same variable has the advantage of users being
		946	# able to just C<undef $WATCHER> if the watcher causes them grief.
		947
		948	$WATCHER ||= $guard;
670		949
671	@AnyEvent::post_detect	950	@AnyEvent::post_detect
672	If there are any code references in this array (you can "push" to it	951	If there are any code references in this array (you can "push" to it
673	before or after loading AnyEvent), then they will called directly	952	before or after loading AnyEvent), then they will be called directly
674	after the event loop has been chosen.	953	after the event loop has been chosen.
675		954
676	You should check $AnyEvent::MODEL before adding to this array,	955	You should check $AnyEvent::MODEL before adding to this array,
677	though: if it contains a true value then the event loop has already	956	though: if it is defined then the event loop has already been
678	been detected, and the array will be ignored.	957	detected, and the array will be ignored.
679		958
680	Best use "AnyEvent::post_detect { BLOCK }" instead.	959	Best use "AnyEvent::post_detect { BLOCK }" when your application
		960	allows it, as it takes care of these details.
		961
		962	This variable is mainly useful for modules that can do something
		963	useful when AnyEvent is used and thus want to know when it is
		964	initialised, but do not need to even load it by default. This array
		965	provides the means to hook into AnyEvent passively, without loading
		966	it.
		967
		968	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		969	together, you could put this into Coro (this is the actual code used
		970	by Coro to accomplish this):
		971
		972	if (defined $AnyEvent::MODEL) {
		973	# AnyEvent already initialised, so load Coro::AnyEvent
		974	require Coro::AnyEvent;
		975	} else {
		976	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		977	# as soon as it is
		978	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		979	}
		980
		981	AnyEvent::postpone { BLOCK }
		982	Arranges for the block to be executed as soon as possible, but not
		983	before the call itself returns. In practise, the block will be
		984	executed just before the event loop polls for new events, or shortly
		985	afterwards.
		986
		987	This function never returns anything (to make the "return postpone {
		988	... }" idiom more useful.
		989
		990	To understand the usefulness of this function, consider a function
		991	that asynchronously does something for you and returns some
		992	transaction object or guard to let you cancel the operation. For
		993	example, "AnyEvent::Socket::tcp_connect":
		994
		995	# start a connection attempt unless one is active
		996	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		997	delete $self->{connect_guard};
		998	...
		999	};
		1000
		1001	Imagine that this function could instantly call the callback, for
		1002	example, because it detects an obvious error such as a negative port
		1003	number. Invoking the callback before the function returns causes
		1004	problems however: the callback will be called and will try to delete
		1005	the guard object. But since the function hasn't returned yet, there
		1006	is nothing to delete. When the function eventually returns it will
		1007	assign the guard object to "$self->{connect_guard}", where it will
		1008	likely never be deleted, so the program thinks it is still trying to
		1009	connect.
		1010
		1011	This is where "AnyEvent::postpone" should be used. Instead of
		1012	calling the callback directly on error:
		1013
		1014	$cb->(undef), return # signal error to callback, BAD!
		1015	if $some_error_condition;
		1016
		1017	It should use "postpone":
		1018
		1019	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1020	if $some_error_condition;
		1021
		1022	AnyEvent::log $level, $msg[, @args]
		1023	Log the given $msg at the given $level.
		1024
		1025	If AnyEvent::Log is not loaded then this function makes a simple
		1026	test to see whether the message will be logged. If the test succeeds
		1027	it will load AnyEvent::Log and call "AnyEvent::Log::log" -
		1028	consequently, look at the AnyEvent::Log documentation for details.
		1029
		1030	If the test fails it will simply return. Right now this happens when
		1031	a numerical loglevel is used and it is larger than the level
		1032	specified via $ENV{PERL_ANYEVENT_VERBOSE}.
		1033
		1034	If you want to sprinkle loads of logging calls around your code,
		1035	consider creating a logger callback with the "AnyEvent::Log::logger"
		1036	function, which can reduce typing, codesize and can reduce the
		1037	logging overhead enourmously.
		1038
		1039	AnyEvent::fh_block $filehandle
		1040	AnyEvent::fh_unblock $filehandle
		1041	Sets blocking or non-blocking behaviour for the given filehandle.
681		1042
682	WHAT TO DO IN A MODULE	1043	WHAT TO DO IN A MODULE
683	As a module author, you should "use AnyEvent" and call AnyEvent methods	1044	As a module author, you should "use AnyEvent" and call AnyEvent methods
684	freely, but you should not load a specific event module or rely on it.	1045	freely, but you should not load a specific event module or rely on it.
685		1046
…		…
693	stall the whole program, and the whole point of using events is to stay	1054	stall the whole program, and the whole point of using events is to stay
694	interactive.	1055	interactive.
695		1056
696	It is fine, however, to call "->recv" when the user of your module	1057	It is fine, however, to call "->recv" when the user of your module
697	requests it (i.e. if you create a http request object ad have a method	1058	requests it (i.e. if you create a http request object ad have a method
698	called "results" that returns the results, it should call "->recv"	1059	called "results" that returns the results, it may call "->recv" freely,
699	freely, as the user of your module knows what she is doing. always).	1060	as the user of your module knows what she is doing. Always).
700		1061
701	WHAT TO DO IN THE MAIN PROGRAM	1062	WHAT TO DO IN THE MAIN PROGRAM
702	There will always be a single main program - the only place that should	1063	There will always be a single main program - the only place that should
703	dictate which event model to use.	1064	dictate which event model to use.
704		1065
705	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1066	If the program is not event-based, it need not do anything special, even
706	do anything special (it does not need to be event-based) and let	1067	when it depends on a module that uses an AnyEvent. If the program itself
707	AnyEvent decide which implementation to chose if some module relies on	1068	uses AnyEvent, but does not care which event loop is used, all it needs
708	it.	1069	to do is "use AnyEvent". In either case, AnyEvent will choose the best
		1070	available loop implementation.
709		1071
710	If the main program relies on a specific event model - for example, in	1072	If the main program relies on a specific event model - for example, in
711	Gtk2 programs you have to rely on the Glib module - you should load the	1073	Gtk2 programs you have to rely on the Glib module - you should load the
712	event module before loading AnyEvent or any module that uses it:	1074	event module before loading AnyEvent or any module that uses it:
713	generally speaking, you should load it as early as possible. The reason	1075	generally speaking, you should load it as early as possible. The reason
714	is that modules might create watchers when they are loaded, and AnyEvent	1076	is that modules might create watchers when they are loaded, and AnyEvent
715	will decide on the event model to use as soon as it creates watchers,	1077	will decide on the event model to use as soon as it creates watchers,
716	and it might chose the wrong one unless you load the correct one	1078	and it might choose the wrong one unless you load the correct one
717	yourself.	1079	yourself.
718		1080
719	You can chose to use a pure-perl implementation by loading the	1081	You can chose to use a pure-perl implementation by loading the
720	"AnyEvent::Impl::Perl" module, which gives you similar behaviour	1082	"AnyEvent::Loop" module, which gives you similar behaviour everywhere,
721	everywhere, but letting AnyEvent chose the model is generally better.	1083	but letting AnyEvent chose the model is generally better.
722		1084
723	MAINLOOP EMULATION	1085	MAINLOOP EMULATION
724	Sometimes (often for short test scripts, or even standalone programs who	1086	Sometimes (often for short test scripts, or even standalone programs who
725	only want to use AnyEvent), you do not want to run a specific event	1087	only want to use AnyEvent), you do not want to run a specific event
726	loop.	1088	loop.
…		…
736	variable somewhere, waiting for it, and sending it when the program	1098	variable somewhere, waiting for it, and sending it when the program
737	should exit cleanly.	1099	should exit cleanly.
738		1100
739	OTHER MODULES	1101	OTHER MODULES
740	The following is a non-exhaustive list of additional modules that use	1102	The following is a non-exhaustive list of additional modules that use
741	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1103	AnyEvent as a client and can therefore be mixed easily with other
742	in the same program. Some of the modules come with AnyEvent, some are	1104	AnyEvent modules and other event loops in the same program. Some of the
743	available via CPAN.	1105	modules come as part of AnyEvent, the others are available via CPAN (see
		1106	<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for a longer
		1107	non-exhaustive list), and the list is heavily biased towards modules of
		1108	the AnyEvent author himself :)
744		1109
745	AnyEvent::Util	1110	AnyEvent::Util (part of the AnyEvent distribution)
746	Contains various utility functions that replace often-used but	1111	Contains various utility functions that replace often-used blocking
747	blocking functions such as "inet_aton" by event-/callback-based	1112	functions such as "inet_aton" with event/callback-based versions.
748	versions.
749		1113
750	AnyEvent::Socket	1114	AnyEvent::Socket (part of the AnyEvent distribution)
751	Provides various utility functions for (internet protocol) sockets,	1115	Provides various utility functions for (internet protocol) sockets,
752	addresses and name resolution. Also functions to create non-blocking	1116	addresses and name resolution. Also functions to create non-blocking
753	tcp connections or tcp servers, with IPv6 and SRV record support and	1117	tcp connections or tcp servers, with IPv6 and SRV record support and
754	more.	1118	more.
755		1119
756	AnyEvent::Handle	1120	AnyEvent::Handle (part of the AnyEvent distribution)
757	Provide read and write buffers, manages watchers for reads and	1121	Provide read and write buffers, manages watchers for reads and
758	writes, supports raw and formatted I/O, I/O queued and fully	1122	writes, supports raw and formatted I/O, I/O queued and fully
759	transparent and non-blocking SSL/TLS.	1123	transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
760		1124
761	AnyEvent::DNS	1125	AnyEvent::DNS (part of the AnyEvent distribution)
762	Provides rich asynchronous DNS resolver capabilities.	1126	Provides rich asynchronous DNS resolver capabilities.
763		1127
764	AnyEvent::HTTP	1128	AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
765	A simple-to-use HTTP library that is capable of making a lot of	1129	AnyEvent::IGS, AnyEvent::FCP
766	concurrent HTTP requests.	1130	Implement event-based interfaces to the protocols of the same name
		1131	(for the curious, IGS is the International Go Server and FCP is the
		1132	Freenet Client Protocol).
767		1133
		1134	AnyEvent::AIO (part of the AnyEvent distribution)
		1135	Truly asynchronous (as opposed to non-blocking) I/O, should be in
		1136	the toolbox of every event programmer. AnyEvent::AIO transparently
		1137	fuses IO::AIO and AnyEvent together, giving AnyEvent access to
		1138	event-based file I/O, and much more.
		1139
		1140	AnyEvent::Fork, AnyEvent::Fork::RPC, AnyEvent::Fork::Pool,
		1141	AnyEvent::Fork::Remote
		1142	These let you safely fork new subprocesses, either locally or
		1143	remotely (e.g.v ia ssh), using some RPC protocol or not, without the
		1144	limitations normally imposed by fork (AnyEvent works fine for
		1145	example). Dynamically-resized worker pools are obviously included as
		1146	well.
		1147
		1148	And they are quite tiny and fast as well - "abusing" AnyEvent::Fork
		1149	just to exec external programs can easily beat using "fork" and
		1150	"exec" (or even "system") in most programs.
		1151
		1152	AnyEvent::Filesys::Notify
		1153	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1154	path changes (e.g. "watch this directory for new files", "watch this
		1155	file for changes"). The AnyEvent::Filesys::Notify module promises to
		1156	do just that in a portbale fashion, supporting inotify on GNU/Linux
		1157	and some weird, without doubt broken, stuff on OS X to monitor
		1158	files. It can fall back to blocking scans at regular intervals
		1159	transparently on other platforms, so it's about as portable as it
		1160	gets.
		1161
		1162	(I haven't used it myself, but it seems the biggest problem with it
		1163	is it quite bad performance).
		1164
768	AnyEvent::HTTPD	1165	AnyEvent::DBI
769	Provides a simple web application server framework.	1166	Executes DBI requests asynchronously in a proxy process for you,
		1167	notifying you in an event-based way when the operation is finished.
770		1168
771	AnyEvent::FastPing	1169	AnyEvent::FastPing
772	The fastest ping in the west.	1170	The fastest ping in the west.
773		1171
774	AnyEvent::DBI
775	Executes DBI requests asynchronously in a proxy process.
776
777	AnyEvent::AIO
778	Truly asynchronous I/O, should be in the toolbox of every event
779	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
780	together.
781
782	AnyEvent::BDB
783	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
784	fuses BDB and AnyEvent together.
785
786	AnyEvent::GPSD
787	A non-blocking interface to gpsd, a daemon delivering GPS
788	information.
789
790	AnyEvent::IGS
791	A non-blocking interface to the Internet Go Server protocol (used by
792	App::IGS).
793
794	AnyEvent::IRC
795	AnyEvent based IRC client module family (replacing the older
796	Net::IRC3).
797
798	Net::XMPP2
799	AnyEvent based XMPP (Jabber protocol) module family.
800
801	Net::FCP
802	AnyEvent-based implementation of the Freenet Client Protocol,
803	birthplace of AnyEvent.
804
805	Event::ExecFlow
806	High level API for event-based execution flow control.
807
808	Coro	1172	Coro
809	Has special support for AnyEvent via Coro::AnyEvent.	1173	Has special support for AnyEvent via Coro::AnyEvent, which allows
		1174	you to simply invert the flow control - don't call us, we will call
		1175	you:
810		1176
811	IO::Lambda	1177	async {
812	The lambda approach to I/O - don't ask, look there. Can use	1178	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
813	AnyEvent.	1179	print "5 seconds later!\n";
		1180
		1181	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1182	my $line = <STDIN>; # works for ttys
		1183
		1184	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1185	my ($body, $hdr) = Coro::rouse_wait;
		1186	};
		1187
		1188	SIMPLIFIED AE API
		1189	Starting with version 5.0, AnyEvent officially supports a second, much
		1190	simpler, API that is designed to reduce the calling, typing and memory
		1191	overhead by using function call syntax and a fixed number of parameters.
		1192
		1193	See the AE manpage for details.
814		1194
815	ERROR AND EXCEPTION HANDLING	1195	ERROR AND EXCEPTION HANDLING
816	In general, AnyEvent does not do any error handling - it relies on the	1196	In general, AnyEvent does not do any error handling - it relies on the
817	caller to do that if required. The AnyEvent::Strict module (see also the	1197	caller to do that if required. The AnyEvent::Strict module (see also the
818	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	1198	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
827	The pure perl event loop simply re-throws the exception (usually within	1207	The pure perl event loop simply re-throws the exception (usually within
828	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	1208	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
829	Glib uses "install_exception_handler" and so on.	1209	Glib uses "install_exception_handler" and so on.
830		1210
831	ENVIRONMENT VARIABLES	1211	ENVIRONMENT VARIABLES
832	The following environment variables are used by this module or its	1212	AnyEvent supports a number of environment variables that tune the
833	submodules:	1213	runtime behaviour. They are usually evaluated when AnyEvent is loaded,
		1214	initialised, or a submodule that uses them is loaded. Many of them also
		1215	cause AnyEvent to load additional modules - for example,
		1216	"PERL_ANYEVENT_DEBUG_WRAP" causes the AnyEvent::Debug module to be
		1217	loaded.
		1218
		1219	All the environment variables documented here start with
		1220	"PERL_ANYEVENT_", which is what AnyEvent considers its own namespace.
		1221	Other modules are encouraged (but by no means required) to use
		1222	"PERL_ANYEVENT_SUBMODULE" if they have registered the
		1223	AnyEvent::Submodule namespace on CPAN, for any submodule. For example,
		1224	AnyEvent::HTTP could be expected to use "PERL_ANYEVENT_HTTP_PROXY" (it
		1225	should not access env variables starting with "AE_", see below).
		1226
		1227	All variables can also be set via the "AE_" prefix, that is, instead of
		1228	setting "PERL_ANYEVENT_VERBOSE" you can also set "AE_VERBOSE". In case
		1229	there is a clash btween anyevent and another program that uses
		1230	"AE_something" you can set the corresponding "PERL_ANYEVENT_something"
		1231	variable to the empty string, as those variables take precedence.
		1232
		1233	When AnyEvent is first loaded, it copies all "AE_xxx" env variables to
		1234	their "PERL_ANYEVENT_xxx" counterpart unless that variable already
		1235	exists. If taint mode is on, then AnyEvent will remove *all* environment
		1236	variables starting with "PERL_ANYEVENT_" from %ENV (or replace them with
		1237	"undef" or the empty string, if the corresaponding "AE_" variable is
		1238	set).
		1239
		1240	The exact algorithm is currently:
		1241
		1242	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		1243	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		1244	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		1245
		1246	This ensures that child processes will not see the "AE_" variables.
		1247
		1248	The following environment variables are currently known to AnyEvent:
834		1249
835	"PERL_ANYEVENT_VERBOSE"	1250	"PERL_ANYEVENT_VERBOSE"
836	By default, AnyEvent will be completely silent except in fatal	1251	By default, AnyEvent will log messages with loglevel 4 ("error") or
837	conditions. You can set this environment variable to make AnyEvent	1252	higher (see AnyEvent::Log). You can set this environment variable to
838	more talkative.	1253	a numerical loglevel to make AnyEvent more (or less) talkative.
839		1254
		1255	If you want to do more than just set the global logging level you
		1256	should have a look at "PERL_ANYEVENT_LOG", which allows much more
		1257	complex specifications.
		1258
		1259	When set to 0 ("off"), then no messages whatsoever will be logged
		1260	with everything else at defaults.
		1261
840	When set to 1 or higher, causes AnyEvent to warn about unexpected	1262	When set to 5 or higher ("warn"), AnyEvent warns about unexpected
841	conditions, such as not being able to load the event model specified	1263	conditions, such as not being able to load the event model specified
842	by "PERL_ANYEVENT_MODEL".	1264	by "PERL_ANYEVENT_MODEL", or a guard callback throwing an exception
		1265	- this is the minimum recommended level for use during development.
843		1266
844	When set to 2 or higher, cause AnyEvent to report to STDERR which	1267	When set to 7 or higher (info), AnyEvent reports which event model
845	event model it chooses.	1268	it chooses.
		1269
		1270	When set to 8 or higher (debug), then AnyEvent will report extra
		1271	information on which optional modules it loads and how it implements
		1272	certain features.
		1273
		1274	"PERL_ANYEVENT_LOG"
		1275	Accepts rather complex logging specifications. For example, you
		1276	could log all "debug" messages of some module to stderr, warnings
		1277	and above to stderr, and errors and above to syslog, with:
		1278
		1279	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		1280
		1281	For the rather extensive details, see AnyEvent::Log.
		1282
		1283	This variable is evaluated when AnyEvent (or AnyEvent::Log) is
		1284	loaded, so will take effect even before AnyEvent has initialised
		1285	itself.
		1286
		1287	Note that specifying this environment variable causes the
		1288	AnyEvent::Log module to be loaded, while "PERL_ANYEVENT_VERBOSE"
		1289	does not, so only using the latter saves a few hundred kB of memory
		1290	unless a module explicitly needs the extra features of
		1291	AnyEvent::Log.
846		1292
847	"PERL_ANYEVENT_STRICT"	1293	"PERL_ANYEVENT_STRICT"
848	AnyEvent does not do much argument checking by default, as thorough	1294	AnyEvent does not do much argument checking by default, as thorough
849	argument checking is very costly. Setting this variable to a true	1295	argument checking is very costly. Setting this variable to a true
850	value will cause AnyEvent to load "AnyEvent::Strict" and then to	1296	value will cause AnyEvent to load "AnyEvent::Strict" and then to
851	thoroughly check the arguments passed to most method calls. If it	1297	thoroughly check the arguments passed to most method calls. If it
852	finds any problems it will croak.	1298	finds any problems, it will croak.
853		1299
854	In other words, enables "strict" mode.	1300	In other words, enables "strict" mode.
855		1301
856	Unlike "use strict", it is definitely recommended ot keep it off in	1302	Unlike "use strict" (or its modern cousin, "use common::sense", it
857	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1303	is definitely recommended to keep it off in production. Keeping
		1304	"PERL_ANYEVENT_STRICT=1" in your environment while developing
858	while developing programs can be very useful, however.	1305	programs can be very useful, however.
		1306
		1307	"PERL_ANYEVENT_DEBUG_SHELL"
		1308	If this env variable is nonempty, then its contents will be
		1309	interpreted by "AnyEvent::Socket::parse_hostport" and
		1310	"AnyEvent::Debug::shell" (after replacing every occurance of $$ by
		1311	the process pid). The shell object is saved in
		1312	$AnyEvent::Debug::SHELL.
		1313
		1314	This happens when the first watcher is created.
		1315
		1316	For example, to bind a debug shell on a unix domain socket in
		1317	/tmp/debug<pid>.sock, you could use this:
		1318
		1319	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		1320	# connect with e.g.: socat readline /tmp/debug123.sock
		1321
		1322	Or to bind to tcp port 4545 on localhost:
		1323
		1324	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		1325	# connect with e.g.: telnet localhost 4545
		1326
		1327	Note that creating sockets in /tmp or on localhost is very unsafe on
		1328	multiuser systems.
		1329
		1330	"PERL_ANYEVENT_DEBUG_WRAP"
		1331	Can be set to 0, 1 or 2 and enables wrapping of all watchers for
		1332	debugging purposes. See "AnyEvent::Debug::wrap" for details.
859		1333
860	"PERL_ANYEVENT_MODEL"	1334	"PERL_ANYEVENT_MODEL"
861	This can be used to specify the event model to be used by AnyEvent,	1335	This can be used to specify the event model to be used by AnyEvent,
862	before auto detection and -probing kicks in. It must be a string	1336	before auto detection and -probing kicks in.
863	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1337
864	gets prepended and the resulting module name is loaded and if the	1338	It normally is a string consisting entirely of ASCII letters (e.g.
865	load was successful, used as event model. If it fails to load	1339	"EV" or "IOAsync"). The string "AnyEvent::Impl::" gets prepended and
		1340	the resulting module name is loaded and - if the load was successful
		1341	- used as event model backend. If it fails to load then AnyEvent
866	AnyEvent will proceed with auto detection and -probing.	1342	will proceed with auto detection and -probing.
867		1343
868	This functionality might change in future versions.	1344	If the string ends with "::" instead (e.g. "AnyEvent::Impl::EV::")
		1345	then nothing gets prepended and the module name is used as-is (hint:
		1346	"::" at the end of a string designates a module name and quotes it
		1347	appropriately).
869		1348
870	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1349	For example, to force the pure perl model (AnyEvent::Loop::Perl) you
871	could start your program like this:	1350	could start your program like this:
872		1351
873	PERL_ANYEVENT_MODEL=Perl perl ...	1352	PERL_ANYEVENT_MODEL=Perl perl ...
		1353
		1354	"PERL_ANYEVENT_IO_MODEL"
		1355	The current file I/O model - see AnyEvent::IO for more info.
		1356
		1357	At the moment, only "Perl" (small, pure-perl, synchronous) and
		1358	"IOAIO" (truly asynchronous) are supported. The default is "IOAIO"
		1359	if AnyEvent::AIO can be loaded, otherwise it is "Perl".
874		1360
875	"PERL_ANYEVENT_PROTOCOLS"	1361	"PERL_ANYEVENT_PROTOCOLS"
876	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1362	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
877	preferences for IPv4 or IPv6. The default is unspecified (and might	1363	preferences for IPv4 or IPv6. The default is unspecified (and might
878	change, or be the result of auto probing).	1364	change, or be the result of auto probing).
…		…
882	mentioned will be used, and preference will be given to protocols	1368	mentioned will be used, and preference will be given to protocols
883	mentioned earlier in the list.	1369	mentioned earlier in the list.
884		1370
885	This variable can effectively be used for denial-of-service attacks	1371	This variable can effectively be used for denial-of-service attacks
886	against local programs (e.g. when setuid), although the impact is	1372	against local programs (e.g. when setuid), although the impact is
887	likely small, as the program has to handle conenction and other	1373	likely small, as the program has to handle connection and other
888	failures anyways.	1374	failures anyways.
889		1375
890	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1376	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
891	IPv6, but support both and try to use both.	1377	IPv6, but support both and try to use both.
892	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1378	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
893	resolve or contact IPv6 addresses.	1379	resolve or contact IPv6 addresses.
894	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but	1380	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
895	prefer IPv6 over IPv4.	1381	prefer IPv6 over IPv4.
896		1382
		1383	"PERL_ANYEVENT_HOSTS"
		1384	This variable, if specified, overrides the /etc/hosts file used by
		1385	AnyEvent::Socket"::resolve_sockaddr", i.e. hosts aliases will be
		1386	read from that file instead.
		1387
897	"PERL_ANYEVENT_EDNS0"	1388	"PERL_ANYEVENT_EDNS0"
898	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension	1389	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
899	for DNS. This extension is generally useful to reduce DNS traffic,	1390	for DNS. This extension is generally useful to reduce DNS traffic,
900	but some (broken) firewalls drop such DNS packets, which is why it	1391	especially when DNSSEC is involved, but some (broken) firewalls drop
901	is off by default.	1392	such DNS packets, which is why it is off by default.
902		1393
903	Setting this variable to 1 will cause AnyEvent::DNS to announce	1394	Setting this variable to 1 will cause AnyEvent::DNS to announce
904	EDNS0 in its DNS requests.	1395	EDNS0 in its DNS requests.
905		1396
906	"PERL_ANYEVENT_MAX_FORKS"	1397	"PERL_ANYEVENT_MAX_FORKS"
907	The maximum number of child processes that	1398	The maximum number of child processes that
908	"AnyEvent::Util::fork_call" will create in parallel.	1399	"AnyEvent::Util::fork_call" will create in parallel.
		1400
		1401	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1402	The default value for the "max_outstanding" parameter for the
		1403	default DNS resolver - this is the maximum number of parallel DNS
		1404	requests that are sent to the DNS server.
		1405
		1406	"PERL_ANYEVENT_MAX_SIGNAL_LATENCY"
		1407	Perl has inherently racy signal handling (you can basically choose
		1408	between losing signals and memory corruption) - pure perl event
		1409	loops (including "AnyEvent::Loop", when "Async::Interrupt" isn't
		1410	available) therefore have to poll regularly to avoid losing signals.
		1411
		1412	Some event loops are racy, but don't poll regularly, and some event
		1413	loops are written in C but are still racy. For those event loops,
		1414	AnyEvent installs a timer that regularly wakes up the event loop.
		1415
		1416	By default, the interval for this timer is 10 seconds, but you can
		1417	override this delay with this environment variable (or by setting
		1418	the $AnyEvent::MAX_SIGNAL_LATENCY variable before creating signal
		1419	watchers).
		1420
		1421	Lower values increase CPU (and energy) usage, higher values can
		1422	introduce long delays when reaping children or waiting for signals.
		1423
		1424	The AnyEvent::Async module, if available, will be used to avoid this
		1425	polling (with most event loops).
		1426
		1427	"PERL_ANYEVENT_RESOLV_CONF"
		1428	The absolute path to a resolv.conf-style file to use instead of
		1429	/etc/resolv.conf (or the OS-specific configuration) in the default
		1430	resolver, or the empty string to select the default configuration.
		1431
		1432	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1433	When neither "ca_file" nor "ca_path" was specified during
		1434	AnyEvent::TLS context creation, and either of these environment
		1435	variables are nonempty, they will be used to specify CA certificate
		1436	locations instead of a system-dependent default.
		1437
		1438	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1439	When these are set to 1, then the respective modules are not loaded.
		1440	Mostly good for testing AnyEvent itself.
909		1441
910	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1442	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
911	This is an advanced topic that you do not normally need to use AnyEvent	1443	This is an advanced topic that you do not normally need to use AnyEvent
912	in a module. This section is only of use to event loop authors who want	1444	in a module. This section is only of use to event loop authors who want
913	to provide AnyEvent compatibility.	1445	to provide AnyEvent compatibility.
…		…
968	warn "read: $input\n"; # output what has been read	1500	warn "read: $input\n"; # output what has been read
969	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1501	$cv->send if $input =~ /^q/i; # quit program if /^q/i
970	},	1502	},
971	);	1503	);
972		1504
973	my $time_watcher; # can only be used once
974
975	sub new_timer {
976	$timer = AnyEvent->timer (after => 1, cb => sub {	1505	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
977	warn "timeout\n"; # print 'timeout' about every second	1506	warn "timeout\n"; # print 'timeout' at most every second
978	&new_timer; # and restart the time
979	});
980	}	1507	});
981
982	new_timer; # create first timer
983		1508
984	$cv->recv; # wait until user enters /^q/i	1509	$cv->recv; # wait until user enters /^q/i
985		1510
986	REAL-WORLD EXAMPLE	1511	REAL-WORLD EXAMPLE
987	Consider the Net::FCP module. It features (among others) the following	1512	Consider the Net::FCP module. It features (among others) the following
…		…
1059		1584
1060	The actual code goes further and collects all errors ("die"s,	1585	The actual code goes further and collects all errors ("die"s,
1061	exceptions) that occurred during request processing. The "result" method	1586	exceptions) that occurred during request processing. The "result" method
1062	detects whether an exception as thrown (it is stored inside the $txn	1587	detects whether an exception as thrown (it is stored inside the $txn
1063	object) and just throws the exception, which means connection errors and	1588	object) and just throws the exception, which means connection errors and
1064	other problems get reported tot he code that tries to use the result,	1589	other problems get reported to the code that tries to use the result,
1065	not in a random callback.	1590	not in a random callback.
1066		1591
1067	All of this enables the following usage styles:	1592	All of this enables the following usage styles:
1068		1593
1069	1. Blocking:	1594	1. Blocking:
…		…
1087	my $txn = shift;	1612	my $txn = shift;
1088	my $data = $txn->result;	1613	my $data = $txn->result;
1089	...	1614	...
1090	});	1615	});
1091		1616
1092	EV::loop;	1617	EV::run;
1093		1618
1094	3b. The module user could use AnyEvent, too:	1619	3b. The module user could use AnyEvent, too:
1095		1620
1096	use AnyEvent;	1621	use AnyEvent;
1097		1622
…		…
1114	through AnyEvent. The benchmark creates a lot of timers (with a zero	1639	through AnyEvent. The benchmark creates a lot of timers (with a zero
1115	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1640	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1116	which it is), lets them fire exactly once and destroys them again.	1641	which it is), lets them fire exactly once and destroys them again.
1117		1642
1118	Source code for this benchmark is found as eg/bench in the AnyEvent	1643	Source code for this benchmark is found as eg/bench in the AnyEvent
1119	distribution.	1644	distribution. It uses the AE interface, which makes a real difference
		1645	for the EV and Perl backends only.
1120		1646
1121	Explanation of the columns	1647	Explanation of the columns
1122	*watcher* is the number of event watchers created/destroyed. Since	1648	*watcher* is the number of event watchers created/destroyed. Since
1123	different event models feature vastly different performances, each event	1649	different event models feature vastly different performances, each event
1124	loop was given a number of watchers so that overall runtime is	1650	loop was given a number of watchers so that overall runtime is
…		…
1143	*destroy* is the time, in microseconds, that it takes to destroy a	1669	*destroy* is the time, in microseconds, that it takes to destroy a
1144	single watcher.	1670	single watcher.
1145		1671
1146	Results	1672	Results
1147	name watchers bytes create invoke destroy comment	1673	name watchers bytes create invoke destroy comment
1148	EV/EV 400000 224 0.47 0.35 0.27 EV native interface	1674	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1149	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1675	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1150	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1676	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1151	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1677	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1152	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1678	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1153	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1679	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		1680	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		1681	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1154	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1682	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1155	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1683	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1156	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1684	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1157	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1685	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1158		1686
1159	Discussion	1687	Discussion
1160	The benchmark does *not* measure scalability of the event loop very	1688	The benchmark does *not* measure scalability of the event loop very
1161	well. For example, a select-based event loop (such as the pure perl one)	1689	well. For example, a select-based event loop (such as the pure perl one)
1162	can never compete with an event loop that uses epoll when the number of	1690	can never compete with an event loop that uses epoll when the number of
…		…
1173	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1701	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1174	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1702	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1175	CPU cycles with POE.	1703	CPU cycles with POE.
1176		1704
1177	"EV" is the sole leader regarding speed and memory use, which are both	1705	"EV" is the sole leader regarding speed and memory use, which are both
1178	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1706	maximal/minimal, respectively. When using the AE API there is zero
		1707	overhead (when going through the AnyEvent API create is about 5-6 times
		1708	slower, with other times being equal, so still uses far less memory than
1179	far less memory than any other event loop and is still faster than Event	1709	any other event loop and is still faster than Event natively).
1180	natively.
1181		1710
1182	The pure perl implementation is hit in a few sweet spots (both the	1711	The pure perl implementation is hit in a few sweet spots (both the
1183	constant timeout and the use of a single fd hit optimisations in the	1712	constant timeout and the use of a single fd hit optimisations in the
1184	perl interpreter and the backend itself). Nevertheless this shows that	1713	perl interpreter and the backend itself). Nevertheless this shows that
1185	it adds very little overhead in itself. Like any select-based backend	1714	it adds very little overhead in itself. Like any select-based backend
…		…
1187	few of them active), of course, but this was not subject of this	1716	few of them active), of course, but this was not subject of this
1188	benchmark.	1717	benchmark.
1189		1718
1190	The "Event" module has a relatively high setup and callback invocation	1719	The "Event" module has a relatively high setup and callback invocation
1191	cost, but overall scores in on the third place.	1720	cost, but overall scores in on the third place.
		1721
		1722	"IO::Async" performs admirably well, about on par with "Event", even
		1723	when using its pure perl backend.
1192		1724
1193	"Glib"'s memory usage is quite a bit higher, but it features a faster	1725	"Glib"'s memory usage is quite a bit higher, but it features a faster
1194	callback invocation and overall ends up in the same class as "Event".	1726	callback invocation and overall ends up in the same class as "Event".
1195	However, Glib scales extremely badly, doubling the number of watchers	1727	However, Glib scales extremely badly, doubling the number of watchers
1196	increases the processing time by more than a factor of four, making it	1728	increases the processing time by more than a factor of four, making it
…		…
1228	when used without AnyEvent), but most event loops have acceptable	1760	when used without AnyEvent), but most event loops have acceptable
1229	performance with or without AnyEvent.	1761	performance with or without AnyEvent.
1230		1762
1231	* The overhead AnyEvent adds is usually much smaller than the overhead	1763	* The overhead AnyEvent adds is usually much smaller than the overhead
1232	of the actual event loop, only with extremely fast event loops such	1764	of the actual event loop, only with extremely fast event loops such
1233	as EV adds AnyEvent significant overhead.	1765	as EV does AnyEvent add significant overhead.
1234		1766
1235	* You should avoid POE like the plague if you want performance or	1767	* You should avoid POE like the plague if you want performance or
1236	reasonable memory usage.	1768	reasonable memory usage.
1237		1769
1238	BENCHMARKING THE LARGE SERVER CASE	1770	BENCHMARKING THE LARGE SERVER CASE
…		…
1252	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1784	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1253	100 (1%) are active. This mirrors the activity of large servers with	1785	100 (1%) are active. This mirrors the activity of large servers with
1254	many connections, most of which are idle at any one point in time.	1786	many connections, most of which are idle at any one point in time.
1255		1787
1256	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1788	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1257	distribution.	1789	distribution. It uses the AE interface, which makes a real difference
		1790	for the EV and Perl backends only.
1258		1791
1259	Explanation of the columns	1792	Explanation of the columns
1260	*sockets* is the number of sockets, and twice the number of "servers"	1793	*sockets* is the number of sockets, and twice the number of "servers"
1261	(as each server has a read and write socket end).	1794	(as each server has a read and write socket end).
1262		1795
…		…
1267	single "request", that is, reading the token from the pipe and	1800	single "request", that is, reading the token from the pipe and
1268	forwarding it to another server. This includes deleting the old timeout	1801	forwarding it to another server. This includes deleting the old timeout
1269	and creating a new one that moves the timeout into the future.	1802	and creating a new one that moves the timeout into the future.
1270		1803
1271	Results	1804	Results
1272	name sockets create request	1805	name sockets create request
1273	EV 20000 69.01 11.16	1806	EV 20000 62.66 7.99
1274	Perl 20000 73.32 35.87	1807	Perl 20000 68.32 32.64
1275	Event 20000 212.62 257.32	1808	IOAsync 20000 174.06 101.15 epoll
1276	Glib 20000 651.16 1896.30	1809	IOAsync 20000 174.67 610.84 poll
		1810	Event 20000 202.69 242.91
		1811	Glib 20000 557.01 1689.52
1277	POE 20000 349.67 12317.24 uses POE::Loop::Event	1812	POE 20000 341.54 12086.32 uses POE::Loop::Event
1278		1813
1279	Discussion	1814	Discussion
1280	This benchmark *does* measure scalability and overall performance of the	1815	This benchmark *does* measure scalability and overall performance of the
1281	particular event loop.	1816	particular event loop.
1282		1817
1283	EV is again fastest. Since it is using epoll on my system, the setup	1818	EV is again fastest. Since it is using epoll on my system, the setup
1284	time is relatively high, though.	1819	time is relatively high, though.
1285		1820
1286	Perl surprisingly comes second. It is much faster than the C-based event	1821	Perl surprisingly comes second. It is much faster than the C-based event
1287	loops Event and Glib.	1822	loops Event and Glib.
		1823
		1824	IO::Async performs very well when using its epoll backend, and still
		1825	quite good compared to Glib when using its pure perl backend.
1288		1826
1289	Event suffers from high setup time as well (look at its code and you	1827	Event suffers from high setup time as well (look at its code and you
1290	will understand why). Callback invocation also has a high overhead	1828	will understand why). Callback invocation also has a high overhead
1291	compared to the "$_->() for .."-style loop that the Perl event loop	1829	compared to the "$_->() for .."-style loop that the Perl event loop
1292	uses. Event uses select or poll in basically all documented	1830	uses. Event uses select or poll in basically all documented
…		…
1343		1881
1344	Summary	1882	Summary
1345	* C-based event loops perform very well with small number of watchers,	1883	* C-based event loops perform very well with small number of watchers,
1346	as the management overhead dominates.	1884	as the management overhead dominates.
1347		1885
		1886	THE IO::Lambda BENCHMARK
		1887	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1888	could be misinterpreted to make AnyEvent look bad. In fact, the
		1889	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1890	better (which shouldn't come as a surprise to anybody). As such, the
		1891	benchmark is fine, and mostly shows that the AnyEvent backend from
		1892	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1893	without the extra baggage? To explore this, I wrote the equivalent
		1894	benchmark for AnyEvent.
		1895
		1896	The benchmark itself creates an echo-server, and then, for 500 times,
		1897	connects to the echo server, sends a line, waits for the reply, and then
		1898	creates the next connection. This is a rather bad benchmark, as it
		1899	doesn't test the efficiency of the framework or much non-blocking I/O,
		1900	but it is a benchmark nevertheless.
		1901
		1902	name runtime
		1903	Lambda/select 0.330 sec
		1904	+ optimized 0.122 sec
		1905	Lambda/AnyEvent 0.327 sec
		1906	+ optimized 0.138 sec
		1907	Raw sockets/select 0.077 sec
		1908	POE/select, components 0.662 sec
		1909	POE/select, raw sockets 0.226 sec
		1910	POE/select, optimized 0.404 sec
		1911
		1912	AnyEvent/select/nb 0.085 sec
		1913	AnyEvent/EV/nb 0.068 sec
		1914	+state machine 0.134 sec
		1915
		1916	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1917	benchmarks actually make blocking connects and use 100% blocking I/O,
		1918	defeating the purpose of an event-based solution. All of the newly
		1919	written AnyEvent benchmarks use 100% non-blocking connects (using
		1920	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1921	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1922	connects generally require a lot more bookkeeping and event handling
		1923	than blocking connects (which involve a single syscall only).
		1924
		1925	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1926	offers similar expressive power as POE and IO::Lambda, using
		1927	conventional Perl syntax. This means that both the echo server and the
		1928	client are 100% non-blocking, further placing it at a disadvantage.
		1929
		1930	As you can see, the AnyEvent + EV combination even beats the
		1931	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1932	backend easily beats IO::Lambda and POE.
		1933
		1934	And even the 100% non-blocking version written using the high-level (and
		1935	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
		1936	higher level ("unoptimised") abstractions by a large margin, even though
		1937	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		1938
		1939	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1940	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1941	part of the IO::Lambda distribution and were used without any changes.
		1942
1348	SIGNALS	1943	SIGNALS
1349	AnyEvent currently installs handlers for these signals:	1944	AnyEvent currently installs handlers for these signals:
1350		1945
1351	SIGCHLD	1946	SIGCHLD
1352	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1947	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1353	emulation for event loops that do not support them natively. Also,	1948	emulation for event loops that do not support them natively. Also,
1354	some event loops install a similar handler.	1949	some event loops install a similar handler.
		1950
		1951	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1952	then AnyEvent will reset it to default, to avoid losing child exit
		1953	statuses.
1355		1954
1356	SIGPIPE	1955	SIGPIPE
1357	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is	1956	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1358	"undef" when AnyEvent gets loaded.	1957	"undef" when AnyEvent gets loaded.
1359		1958
…		…
1367	it is that this way, the handler will be restored to defaults on	1966	it is that this way, the handler will be restored to defaults on
1368	exec.	1967	exec.
1369		1968
1370	Feel free to install your own handler, or reset it to defaults.	1969	Feel free to install your own handler, or reset it to defaults.
1371		1970
		1971	RECOMMENDED/OPTIONAL MODULES
		1972	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1973	its built-in modules) are required to use it.
		1974
		1975	That does not mean that AnyEvent won't take advantage of some additional
		1976	modules if they are installed.
		1977
		1978	This section explains which additional modules will be used, and how
		1979	they affect AnyEvent's operation.
		1980
		1981	Async::Interrupt
		1982	This slightly arcane module is used to implement fast signal
		1983	handling: To my knowledge, there is no way to do completely
		1984	race-free and quick signal handling in pure perl. To ensure that
		1985	signals still get delivered, AnyEvent will start an interval timer
		1986	to wake up perl (and catch the signals) with some delay (default is
		1987	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1988
		1989	If this module is available, then it will be used to implement
		1990	signal catching, which means that signals will not be delayed, and
		1991	the event loop will not be interrupted regularly, which is more
		1992	efficient (and good for battery life on laptops).
		1993
		1994	This affects not just the pure-perl event loop, but also other event
		1995	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1996
		1997	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1998	natively, and either employ their own workarounds (POE) or use
		1999	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		2000	Installing Async::Interrupt does nothing for those backends.
		2001
		2002	EV This module isn't really "optional", as it is simply one of the
		2003	backend event loops that AnyEvent can use. However, it is simply the
		2004	best event loop available in terms of features, speed and stability:
		2005	It supports the AnyEvent API optimally, implements all the watcher
		2006	types in XS, does automatic timer adjustments even when no monotonic
		2007	clock is available, can take avdantage of advanced kernel interfaces
		2008	such as "epoll" and "kqueue", and is the fastest backend *by far*.
		2009	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		2010	Glib::EV).
		2011
		2012	If you only use backends that rely on another event loop (e.g.
		2013	"Tk"), then this module will do nothing for you.
		2014
		2015	Guard
		2016	The guard module, when used, will be used to implement
		2017	"AnyEvent::Util::guard". This speeds up guards considerably (and
		2018	uses a lot less memory), but otherwise doesn't affect guard
		2019	operation much. It is purely used for performance.
		2020
		2021	JSON and JSON::XS
		2022	One of these modules is required when you want to read or write JSON
		2023	data via AnyEvent::Handle. JSON is also written in pure-perl, but
		2024	can take advantage of the ultra-high-speed JSON::XS module when it
		2025	is installed.
		2026
		2027	Net::SSLeay
		2028	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2029	worthwhile: If this module is installed, then AnyEvent::Handle (with
		2030	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		2031
		2032	Time::HiRes
		2033	This module is part of perl since release 5.008. It will be used
		2034	when the chosen event library does not come with a timing source of
		2035	its own. The pure-perl event loop (AnyEvent::Loop) will additionally
		2036	load it to try to use a monotonic clock for timing stability.
		2037
		2038	AnyEvent::AIO (and IO::AIO)
		2039	The default implementation of AnyEvent::IO is to do I/O
		2040	synchronously, stopping programs while they access the disk, which
		2041	is fine for a lot of programs.
		2042
		2043	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it
		2044	switch to a true asynchronous implementation, so event processing
		2045	can continue even while waiting for disk I/O.
		2046
1372	FORK	2047	FORK
1373	Most event libraries are not fork-safe. The ones who are usually are	2048	Most event libraries are not fork-safe. The ones who are usually are
1374	because they rely on inefficient but fork-safe "select" or "poll" calls.	2049	because they rely on inefficient but fork-safe "select" or "poll" calls
1375	Only EV is fully fork-aware.	2050	- higher performance APIs such as BSD's kqueue or the dreaded Linux
		2051	epoll are usually badly thought-out hacks that are incompatible with
		2052	fork in one way or another. Only EV is fully fork-aware and ensures that
		2053	you continue event-processing in both parent and child (or both, if you
		2054	know what you are doing).
		2055
		2056	This means that, in general, you cannot fork and do event processing in
		2057	the child if the event library was initialised before the fork (which
		2058	usually happens when the first AnyEvent watcher is created, or the
		2059	library is loaded).
1376		2060
1377	If you have to fork, you must either do so *before* creating your first	2061	If you have to fork, you must either do so *before* creating your first
1378	watcher OR you must not use AnyEvent at all in the child.	2062	watcher OR you must not use AnyEvent at all in the child OR you must do
		2063	something completely out of the scope of AnyEvent (see below).
		2064
		2065	The problem of doing event processing in the parent *and* the child is
		2066	much more complicated: even for backends that *are* fork-aware or
		2067	fork-safe, their behaviour is not usually what you want: fork clones all
		2068	watchers, that means all timers, I/O watchers etc. are active in both
		2069	parent and child, which is almost never what you want. Using "exec" to
		2070	start worker children from some kind of manage prrocess is usually
		2071	preferred, because it is much easier and cleaner, at the expense of
		2072	having to have another binary.
		2073
		2074	In addition to logical problems with fork, there are also implementation
		2075	problems. For example, on POSIX systems, you cannot fork at all in Perl
		2076	code if a thread (I am talking of pthreads here) was ever created in the
		2077	process, and this is just the tip of the iceberg. In general, using fork
		2078	from Perl is difficult, and attempting to use fork without an exec to
		2079	implement some kind of parallel processing is almost certainly doomed.
		2080
		2081	To safely fork and exec, you should use a module such as Proc::FastSpawn
		2082	that let's you safely fork and exec new processes.
		2083
		2084	If you want to do multiprocessing using processes, you can look at the
		2085	AnyEvent::Fork module (and some related modules such as
		2086	AnyEvent::Fork::RPC, AnyEvent::Fork::Pool and AnyEvent::Fork::Remote).
		2087	This module allows you to safely create subprocesses without any
		2088	limitations - you can use X11 toolkits or AnyEvent in the children
		2089	created by AnyEvent::Fork safely and without any special precautions.
1379		2090
1380	SECURITY CONSIDERATIONS	2091	SECURITY CONSIDERATIONS
1381	AnyEvent can be forced to load any event model via	2092	AnyEvent can be forced to load any event model via
1382	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	2093	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1383	to execute arbitrary code or directly gain access, it can easily be used	2094	to execute arbitrary code or directly gain access, it can easily be used
…		…
1387		2098
1388	You can make AnyEvent completely ignore this variable by deleting it	2099	You can make AnyEvent completely ignore this variable by deleting it
1389	before the first watcher gets created, e.g. with a "BEGIN" block:	2100	before the first watcher gets created, e.g. with a "BEGIN" block:
1390		2101
1391	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2102	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1392		2103
1393	use AnyEvent;	2104	use AnyEvent;
1394		2105
1395	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2106	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1396	be used to probe what backend is used and gain other information (which	2107	be used to probe what backend is used and gain other information (which
1397	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),	2108	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1398	and $ENV{PERL_ANYEGENT_STRICT}.	2109	and $ENV{PERL_ANYEVENT_STRICT}.
		2110
		2111	Note that AnyEvent will remove *all* environment variables starting with
		2112	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		2113	enabled.
1399		2114
1400	BUGS	2115	BUGS
1401	Perl 5.8 has numerous memleaks that sometimes hit this module and are	2116	Perl 5.8 has numerous memleaks that sometimes hit this module and are
1402	hard to work around. If you suffer from memleaks, first upgrade to Perl	2117	hard to work around. If you suffer from memleaks, first upgrade to Perl
1403	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	2118	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1404	annoying memleaks, such as leaking on "map" and "grep" but it is usually	2119	annoying memleaks, such as leaking on "map" and "grep" but it is usually
1405	not as pronounced).	2120	not as pronounced).
1406		2121
1407	SEE ALSO	2122	SEE ALSO
1408	Utility functions: AnyEvent::Util.	2123	Tutorial/Introduction: AnyEvent::Intro.
1409		2124
1410	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	2125	FAQ: AnyEvent::FAQ.
1411	Event::Lib, Qt, POE.	2126
		2127	Utility functions: AnyEvent::Util (misc. grab-bag), AnyEvent::Log
		2128	(simply logging).
		2129
		2130	Development/Debugging: AnyEvent::Strict (stricter checking),
		2131	AnyEvent::Debug (interactive shell, watcher tracing).
		2132
		2133	Supported event modules: AnyEvent::Loop, EV, EV::Glib, Glib::EV, Event,
		2134	Glib::Event, Glib, Tk, Event::Lib, Qt, POE, FLTK, Cocoa::EventLoop, UV.
1412		2135
1413	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	2136	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1414	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	2137	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1415	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	2138	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		2139	AnyEvent::Impl::IOAsync, AnyEvent::Impl::Irssi, AnyEvent::Impl::FLTK,
		2140	AnyEvent::Impl::Cocoa, AnyEvent::Impl::UV.
1416		2141
1417	Non-blocking file handles, sockets, TCP clients and servers:	2142	Non-blocking handles, pipes, stream sockets, TCP clients and servers:
1418	AnyEvent::Handle, AnyEvent::Socket.	2143	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
		2144
		2145	Asynchronous File I/O: AnyEvent::IO.
1419		2146
1420	Asynchronous DNS: AnyEvent::DNS.	2147	Asynchronous DNS: AnyEvent::DNS.
1421		2148
1422	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	2149	Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1423		2150
1424	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	2151	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
		2152	AnyEvent::HTTP.
1425		2153
1426	AUTHOR	2154	AUTHOR
1427	Marc Lehmann <schmorp@schmorp.de>	2155	Marc Lehmann <schmorp@schmorp.de>
1428	http://home.schmorp.de/	2156	http://anyevent.schmorp.de
1429		2157

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