[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.24 by root, Thu May 29 03:46:04 2008 UTC vs.
Revision 1.56 by root, Thu Nov 19 01:55:57 2009 UTC

…		…
1	=> NAME	1	NAME
2	AnyEvent - provide framework for multiple event loops	2	AnyEvent - the DBI of event loop programming
3		3
4	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event	4	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
5	loops	5	Qt and POE are various supported event loops/environments.
6		6
7	SYNOPSIS	7	SYNOPSIS
8	use AnyEvent;	8	use AnyEvent;
9		9
		10	# file descriptor readable
10	my $w = AnyEvent->io (fh => $fh, poll => "r\|w", cb => sub {	11	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		12
		13	# one-shot or repeating timers
		14	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		15	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		16
		17	print AnyEvent->now; # prints current event loop time
		18	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		19
		20	# POSIX signal
		21	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		22
		23	# child process exit
		24	my $w = AnyEvent->child (pid => $pid, cb => sub {
		25	my ($pid, $status) = @_;
11	...	26	...
12	});	27	});
13		28
14	my $w = AnyEvent->timer (after => $seconds, cb => sub {	29	# called when event loop idle (if applicable)
15	...	30	my $w = AnyEvent->idle (cb => sub { ... });
16	});
17		31
18	my $w = AnyEvent->condvar; # stores whether a condition was flagged	32	my $w = AnyEvent->condvar; # stores whether a condition was flagged
19	$w->send; # wake up current and all future recv's	33	$w->send; # wake up current and all future recv's
20	$w->recv; # enters "main loop" till $condvar gets ->send	34	$w->recv; # enters "main loop" till $condvar gets ->send
		35	# use a condvar in callback mode:
		36	$w->cb (sub { $_[0]->recv });
		37
		38	INTRODUCTION/TUTORIAL
		39	This manpage is mainly a reference manual. If you are interested in a
		40	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
		41	manpage.
		42
		43	SUPPORT
		44	There is a mailinglist for discussing all things AnyEvent, and an IRC
		45	channel, too.
		46
		47	See the AnyEvent project page at the Schmorpforge Ta-Sa Software
		48	Repository, at <http://anyevent.schmorp.de>, for more info.
21		49
22	WHY YOU SHOULD USE THIS MODULE (OR NOT)	50	WHY YOU SHOULD USE THIS MODULE (OR NOT)
23	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	51	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
24	nowadays. So what is different about AnyEvent?	52	nowadays. So what is different about AnyEvent?
25		53
26	Executive Summary: AnyEvent is compatible, AnyEvent is *free of	54	Executive Summary: AnyEvent is compatible, AnyEvent is *free of
27	policy* and AnyEvent is small and efficient.	55	policy* and AnyEvent is small and efficient.
28		56
29	First and foremost, AnyEvent is not an event model itself, it only	57	First and foremost, AnyEvent is not an event model itself, it only
30	interfaces to whatever event model the main program happens to use in a	58	interfaces to whatever event model the main program happens to use, in a
31	pragmatic way. For event models and certain classes of immortals alike,	59	pragmatic way. For event models and certain classes of immortals alike,
32	the statement "there can only be one" is a bitter reality: In general,	60	the statement "there can only be one" is a bitter reality: In general,
33	only one event loop can be active at the same time in a process.	61	only one event loop can be active at the same time in a process.
34	AnyEvent helps hiding the differences between those event loops.	62	AnyEvent cannot change this, but it can hide the differences between
		63	those event loops.
35		64
36	The goal of AnyEvent is to offer module authors the ability to do event	65	The goal of AnyEvent is to offer module authors the ability to do event
37	programming (waiting for I/O or timer events) without subscribing to a	66	programming (waiting for I/O or timer events) without subscribing to a
38	religion, a way of living, and most importantly: without forcing your	67	religion, a way of living, and most importantly: without forcing your
39	module users into the same thing by forcing them to use the same event	68	module users into the same thing by forcing them to use the same event
40	model you use.	69	model you use.
41		70
42	For modules like POE or IO::Async (which is a total misnomer as it is	71	For modules like POE or IO::Async (which is a total misnomer as it is
43	actually doing all I/O synchronously...), using them in your module is	72	actually doing all I/O synchronously...), using them in your module is
44	like joining a cult: After you joined, you are dependent on them and you	73	like joining a cult: After you joined, you are dependent on them and you
45	cannot use anything else, as it is simply incompatible to everything	74	cannot use anything else, as they are simply incompatible to everything
46	that isn't itself. What's worse, all the potential users of your module	75	that isn't them. What's worse, all the potential users of your module
47	are also forced to use the same event loop you use.	76	are also forced to use the same event loop you use.
48		77
49	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	78	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	79	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
51	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your	80	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your
52	module uses one of those, every user of your module has to use it, too.	81	module uses one of those, every user of your module has to use it, too.
53	But if your module uses AnyEvent, it works transparently with all event	82	But if your module uses AnyEvent, it works transparently with all event
54	models it supports (including stuff like POE and IO::Async, as long as	83	models it supports (including stuff like IO::Async, as long as those use
55	those use one of the supported event loops. It is trivial to add new	84	one of the supported event loops. It is trivial to add new event loops
56	event loops to AnyEvent, too, so it is future-proof).	85	to AnyEvent, too, so it is future-proof).
57		86
58	In addition to being free of having to use *the one and only true event	87	In addition to being free of having to use *the one and only true event
59	model*, AnyEvent also is free of bloat and policy: with POE or similar	88	model*, AnyEvent also is free of bloat and policy: with POE or similar
60	modules, you get an enormous amount of code and strict rules you have to	89	modules, you get an enormous amount of code and strict rules you have to
61	follow. AnyEvent, on the other hand, is lean and up to the point, by	90	follow. AnyEvent, on the other hand, is lean and up to the point, by
117	These watchers are normal Perl objects with normal Perl lifetime. After	146	These watchers are normal Perl objects with normal Perl lifetime. After
118	creating a watcher it will immediately "watch" for events and invoke the	147	creating a watcher it will immediately "watch" for events and invoke the
119	callback when the event occurs (of course, only when the event model is	148	callback when the event occurs (of course, only when the event model is
120	in control).	149	in control).
121		150
		151	Note that callbacks must not permanently change global variables
		152	potentially in use by the event loop (such as $_ or $[) and that
		153	callbacks must not "die". The former is good programming practise in
		154	Perl and the latter stems from the fact that exception handling differs
		155	widely between event loops.
		156
122	To disable the watcher you have to destroy it (e.g. by setting the	157	To disable the watcher you have to destroy it (e.g. by setting the
123	variable you store it in to "undef" or otherwise deleting all references	158	variable you store it in to "undef" or otherwise deleting all references
124	to it).	159	to it).
125		160
126	All watchers are created by calling a method on the "AnyEvent" class.	161	All watchers are created by calling a method on the "AnyEvent" class.
…		…
128	Many watchers either are used with "recursion" (repeating timers for	163	Many watchers either are used with "recursion" (repeating timers for
129	example), or need to refer to their watcher object in other ways.	164	example), or need to refer to their watcher object in other ways.
130		165
131	An any way to achieve that is this pattern:	166	An any way to achieve that is this pattern:
132		167
133	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	168	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
134	# you can use $w here, for example to undef it	169	# you can use $w here, for example to undef it
135	undef $w;	170	undef $w;
136	});	171	});
137		172
138	Note that "my $w; $w =" combination. This is necessary because in Perl,	173	Note that "my $w; $w =" combination. This is necessary because in Perl,
139	my variables are only visible after the statement in which they are	174	my variables are only visible after the statement in which they are
140	declared.	175	declared.
141		176
142	I/O WATCHERS	177	I/O WATCHERS
		178	$w = AnyEvent->io (
		179	fh => <filehandle_or_fileno>,
		180	poll => <"r" or "w">,
		181	cb => <callback>,
		182	);
		183
143	You can create an I/O watcher by calling the "AnyEvent->io" method with	184	You can create an I/O watcher by calling the "AnyEvent->io" method with
144	the following mandatory key-value pairs as arguments:	185	the following mandatory key-value pairs as arguments:
145		186
146	"fh" the Perl file handle (not file descriptor) to watch for events.	187	"fh" is the Perl file handle (or a naked file descriptor) to watch for
		188	events (AnyEvent might or might not keep a reference to this file
		189	handle). Note that only file handles pointing to things for which
		190	non-blocking operation makes sense are allowed. This includes sockets,
		191	most character devices, pipes, fifos and so on, but not for example
		192	files or block devices.
		193
147	"poll" must be a string that is either "r" or "w", which creates a	194	"poll" must be a string that is either "r" or "w", which creates a
148	watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"	195	watcher waiting for "r"eadable or "w"ritable events, respectively.
		196
149	is the callback to invoke each time the file handle becomes ready.	197	"cb" is the callback to invoke each time the file handle becomes ready.
150		198
151	Although the callback might get passed parameters, their value and	199	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	200	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	201	callbacks cannot use arguments passed to I/O watcher callbacks.
154		202
…		…
158		206
159	Some event loops issue spurious readyness notifications, so you should	207	Some event loops issue spurious readyness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	208	always use non-blocking calls when reading/writing from/to your file
161	handles.	209	handles.
162		210
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	211	Example: wait for readability of STDIN, then read a line and disable the
		212	watcher.
		213
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	214	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	215	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	216	warn "read: $input\n";
169	undef $w;	217	undef $w;
170	});	218	});
171		219
172	TIME WATCHERS	220	TIME WATCHERS
		221	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		222
		223	$w = AnyEvent->timer (
		224	after => <fractional_seconds>,
		225	interval => <fractional_seconds>,
		226	cb => <callback>,
		227	);
		228
173	You can create a time watcher by calling the "AnyEvent->timer" method	229	You can create a time watcher by calling the "AnyEvent->timer" method
174	with the following mandatory arguments:	230	with the following mandatory arguments:
175		231
176	"after" specifies after how many seconds (fractional values are	232	"after" specifies after how many seconds (fractional values are
177	supported) the callback should be invoked. "cb" is the callback to	233	supported) the callback should be invoked. "cb" is the callback to
…		…
179		235
180	Although the callback might get passed parameters, their value and	236	Although the callback might get passed parameters, their value and
181	presence is undefined and you cannot rely on them. Portable AnyEvent	237	presence is undefined and you cannot rely on them. Portable AnyEvent
182	callbacks cannot use arguments passed to time watcher callbacks.	238	callbacks cannot use arguments passed to time watcher callbacks.
183		239
184	The timer callback will be invoked at most once: if you want a repeating	240	The callback will normally be invoked once only. If you specify another
185	timer you have to create a new watcher (this is a limitation by both Tk	241	parameter, "interval", as a strictly positive number (> 0), then the
186	and Glib).	242	callback will be invoked regularly at that interval (in fractional
		243	seconds) after the first invocation. If "interval" is specified with a
		244	false value, then it is treated as if it were missing.
187		245
188	Example:	246	The callback will be rescheduled before invoking the callback, but no
		247	attempt is done to avoid timer drift in most backends, so the interval
		248	is only approximate.
189		249
190	# fire an event after 7.7 seconds	250	Example: fire an event after 7.7 seconds.
		251
191	my $w = AnyEvent->timer (after => 7.7, cb => sub {	252	my $w = AnyEvent->timer (after => 7.7, cb => sub {
192	warn "timeout\n";	253	warn "timeout\n";
193	});	254	});
194		255
195	# to cancel the timer:	256	# to cancel the timer:
196	undef $w;	257	undef $w;
197		258
198	Example 2:
199
200	# fire an event after 0.5 seconds, then roughly every second	259	Example 2: fire an event after 0.5 seconds, then roughly every second.
201	my $w;
202		260
203	my $cb = sub {
204	# cancel the old timer while creating a new one
205	$w = AnyEvent->timer (after => 1, cb => $cb);	261	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		262	warn "timeout\n";
206	};	263	};
207
208	# start the "loop" by creating the first watcher
209	$w = AnyEvent->timer (after => 0.5, cb => $cb);
210		264
211	TIMING ISSUES	265	TIMING ISSUES
212	There are two ways to handle timers: based on real time (relative, "fire	266	There are two ways to handle timers: based on real time (relative, "fire
213	in 10 seconds") and based on wallclock time (absolute, "fire at 12	267	in 10 seconds") and based on wallclock time (absolute, "fire at 12
214	o'clock").	268	o'clock").
…		…
288	In either case, if you care (and in most cases, you don't), then you	342	In either case, if you care (and in most cases, you don't), then you
289	can get whatever behaviour you want with any event loop, by taking	343	can get whatever behaviour you want with any event loop, by taking
290	the difference between "AnyEvent->time" and "AnyEvent->now" into	344	the difference between "AnyEvent->time" and "AnyEvent->now" into
291	account.	345	account.
292		346
		347	AnyEvent->now_update
		348	Some event loops (such as EV or AnyEvent::Impl::Perl) cache the
		349	current time for each loop iteration (see the discussion of
		350	AnyEvent->now, above).
		351
		352	When a callback runs for a long time (or when the process sleeps),
		353	then this "current" time will differ substantially from the real
		354	time, which might affect timers and time-outs.
		355
		356	When this is the case, you can call this method, which will update
		357	the event loop's idea of "current time".
		358
		359	A typical example would be a script in a web server (e.g.
		360	"mod_perl") - when mod_perl executes the script, then the event loop
		361	will have the wrong idea about the "current time" (being potentially
		362	far in the past, when the script ran the last time). In that case
		363	you should arrange a call to "AnyEvent->now_update" each time the
		364	web server process wakes up again (e.g. at the start of your script,
		365	or in a handler).
		366
		367	Note that updating the time might cause some events to be handled.
		368
293	SIGNAL WATCHERS	369	SIGNAL WATCHERS
		370	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		371
294	You can watch for signals using a signal watcher, "signal" is the signal	372	You can watch for signals using a signal watcher, "signal" is the signal
295	name without any "SIG" prefix, "cb" is the Perl callback to be invoked	373	name in uppercase and without any "SIG" prefix, "cb" is the Perl
296	whenever a signal occurs.	374	callback to be invoked whenever a signal occurs.
297		375
298	Although the callback might get passed parameters, their value and	376	Although the callback might get passed parameters, their value and
299	presence is undefined and you cannot rely on them. Portable AnyEvent	377	presence is undefined and you cannot rely on them. Portable AnyEvent
300	callbacks cannot use arguments passed to signal watcher callbacks.	378	callbacks cannot use arguments passed to signal watcher callbacks.
301		379
…		…
303	invocation, and callback invocation will be synchronous. Synchronous	381	invocation, and callback invocation will be synchronous. Synchronous
304	means that it might take a while until the signal gets handled by the	382	means that it might take a while until the signal gets handled by the
305	process, but it is guaranteed not to interrupt any other callbacks.	383	process, but it is guaranteed not to interrupt any other callbacks.
306		384
307	The main advantage of using these watchers is that you can share a	385	The main advantage of using these watchers is that you can share a
308	signal between multiple watchers.	386	signal between multiple watchers, and AnyEvent will ensure that signals
		387	will not interrupt your program at bad times.
309		388
310	This watcher might use %SIG, so programs overwriting those signals	389	This watcher might use %SIG (depending on the event loop used), so
311	directly will likely not work correctly.	390	programs overwriting those signals directly will likely not work
		391	correctly.
312		392
313	Example: exit on SIGINT	393	Example: exit on SIGINT
314		394
315	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	395	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
316		396
		397	Signal Races, Delays and Workarounds
		398	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		399	callbacks to signals in a generic way, which is a pity, as you cannot do
		400	race-free signal handling in perl, requiring C libraries for this.
		401	AnyEvent will try to do it's best, which means in some cases, signals
		402	will be delayed. The maximum time a signal might be delayed is specified
		403	in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
		404	can be changed only before the first signal watcher is created, and
		405	should be left alone otherwise. This variable determines how often
		406	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		407	will cause fewer spurious wake-ups, which is better for power and CPU
		408	saving.
		409
		410	All these problems can be avoided by installing the optional
		411	Async::Interrupt module, which works with most event loops. It will not
		412	work with inherently broken event loops such as Event or Event::Lib (and
		413	not with POE currently, as POE does it's own workaround with one-second
		414	latency). For those, you just have to suffer the delays.
		415
317	CHILD PROCESS WATCHERS	416	CHILD PROCESS WATCHERS
		417	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		418
318	You can also watch on a child process exit and catch its exit status.	419	You can also watch on a child process exit and catch its exit status.
319		420
320	The child process is specified by the "pid" argument (if set to 0, it	421	The child process is specified by the "pid" argument (one some backends,
321	watches for any child process exit). The watcher will trigger as often	422	using 0 watches for any child process exit, on others this will croak).
322	as status change for the child are received. This works by installing a	423	The watcher will be triggered only when the child process has finished
323	signal handler for "SIGCHLD". The callback will be called with the pid	424	and an exit status is available, not on any trace events
324	and exit status (as returned by waitpid), so unlike other watcher types,	425	(stopped/continued).
325	you can rely on child watcher callback arguments.	426
		427	The callback will be called with the pid and exit status (as returned by
		428	waitpid), so unlike other watcher types, you can rely on child watcher
		429	callback arguments.
		430
		431	This watcher type works by installing a signal handler for "SIGCHLD",
		432	and since it cannot be shared, nothing else should use SIGCHLD or reap
		433	random child processes (waiting for specific child processes, e.g.
		434	inside "system", is just fine).
326		435
327	There is a slight catch to child watchers, however: you usually start	436	There is a slight catch to child watchers, however: you usually start
328	them after the child process was created, and this means the process	437	them after the child process was created, and this means the process
329	could have exited already (and no SIGCHLD will be sent anymore).	438	could have exited already (and no SIGCHLD will be sent anymore).
330		439
331	Not all event models handle this correctly (POE doesn't), but even for	440	Not all event models handle this correctly (neither POE nor IO::Async
		441	do, see their AnyEvent::Impl manpages for details), but even for event
332	event models that do handle this correctly, they usually need to be	442	models that do handle this correctly, they usually need to be loaded
333	loaded before the process exits (i.e. before you fork in the first	443	before the process exits (i.e. before you fork in the first place).
334	place).	444	AnyEvent's pure perl event loop handles all cases correctly regardless
		445	of when you start the watcher.
335		446
336	This means you cannot create a child watcher as the very first thing in	447	This means you cannot create a child watcher as the very first thing in
337	an AnyEvent program, you have to create at least one watcher before	448	an AnyEvent program, you have to create at least one watcher before
338	you "fork" the child (alternatively, you can call "AnyEvent::detect").	449	you "fork" the child (alternatively, you can call "AnyEvent::detect").
339		450
		451	As most event loops do not support waiting for child events, they will
		452	be emulated by AnyEvent in most cases, in which the latency and race
		453	problems mentioned in the description of signal watchers apply.
		454
340	Example: fork a process and wait for it	455	Example: fork a process and wait for it
341		456
342	my $done = AnyEvent->condvar;	457	my $done = AnyEvent->condvar;
343		458
344	my $pid = fork or exit 5;	459	my $pid = fork or exit 5;
345		460
346	my $w = AnyEvent->child (	461	my $w = AnyEvent->child (
347	pid => $pid,	462	pid => $pid,
348	cb => sub {	463	cb => sub {
349	my ($pid, $status) = @_;	464	my ($pid, $status) = @_;
350	warn "pid $pid exited with status $status";	465	warn "pid $pid exited with status $status";
351	$done->send;	466	$done->send;
352	},	467	},
353	);	468	);
354		469
355	# do something else, then wait for process exit	470	# do something else, then wait for process exit
356	$done->recv;	471	$done->recv;
		472
		473	IDLE WATCHERS
		474	$w = AnyEvent->idle (cb => <callback>);
		475
		476	Sometimes there is a need to do something, but it is not so important to
		477	do it instantly, but only when there is nothing better to do. This
		478	"nothing better to do" is usually defined to be "no other events need
		479	attention by the event loop".
		480
		481	Idle watchers ideally get invoked when the event loop has nothing better
		482	to do, just before it would block the process to wait for new events.
		483	Instead of blocking, the idle watcher is invoked.
		484
		485	Most event loops unfortunately do not really support idle watchers (only
		486	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		487	will simply call the callback "from time to time".
		488
		489	Example: read lines from STDIN, but only process them when the program
		490	is otherwise idle:
		491
		492	my @lines; # read data
		493	my $idle_w;
		494	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		495	push @lines, scalar <STDIN>;
		496
		497	# start an idle watcher, if not already done
		498	$idle_w \|\|= AnyEvent->idle (cb => sub {
		499	# handle only one line, when there are lines left
		500	if (my $line = shift @lines) {
		501	print "handled when idle: $line";
		502	} else {
		503	# otherwise disable the idle watcher again
		504	undef $idle_w;
		505	}
		506	});
		507	});
357		508
358	CONDITION VARIABLES	509	CONDITION VARIABLES
		510	$cv = AnyEvent->condvar;
		511
		512	$cv->send (<list>);
		513	my @res = $cv->recv;
		514
359	If you are familiar with some event loops you will know that all of them	515	If you are familiar with some event loops you will know that all of them
360	require you to run some blocking "loop", "run" or similar function that	516	require you to run some blocking "loop", "run" or similar function that
361	will actively watch for new events and call your callbacks.	517	will actively watch for new events and call your callbacks.
362		518
363	AnyEvent is different, it expects somebody else to run the event loop	519	AnyEvent is slightly different: it expects somebody else to run the
364	and will only block when necessary (usually when told by the user).	520	event loop and will only block when necessary (usually when told by the
		521	user).
365		522
366	The instrument to do that is called a "condition variable", so called	523	The instrument to do that is called a "condition variable", so called
367	because they represent a condition that must become true.	524	because they represent a condition that must become true.
		525
		526	Now is probably a good time to look at the examples further below.
368		527
369	Condition variables can be created by calling the "AnyEvent->condvar"	528	Condition variables can be created by calling the "AnyEvent->condvar"
370	method, usually without arguments. The only argument pair allowed is	529	method, usually without arguments. The only argument pair allowed is
371	"cb", which specifies a callback to be called when the condition	530	"cb", which specifies a callback to be called when the condition
372	variable becomes true.	531	variable becomes true, with the condition variable as the first argument
		532	(but not the results).
373		533
374	After creation, the condition variable is "false" until it becomes	534	After creation, the condition variable is "false" until it becomes
375	"true" by calling the "send" method (or calling the condition variable	535	"true" by calling the "send" method (or calling the condition variable
376	as if it were a callback, read about the caveats in the description for	536	as if it were a callback, read about the caveats in the description for
377	the "->send" method).	537	the "->send" method).
…		…
379	Condition variables are similar to callbacks, except that you can	539	Condition variables are similar to callbacks, except that you can
380	optionally wait for them. They can also be called merge points - points	540	optionally wait for them. They can also be called merge points - points
381	in time where multiple outstanding events have been processed. And yet	541	in time where multiple outstanding events have been processed. And yet
382	another way to call them is transactions - each condition variable can	542	another way to call them is transactions - each condition variable can
383	be used to represent a transaction, which finishes at some point and	543	be used to represent a transaction, which finishes at some point and
384	delivers a result.	544	delivers a result. And yet some people know them as "futures" - a
		545	promise to compute/deliver something that you can wait for.
385		546
386	Condition variables are very useful to signal that something has	547	Condition variables are very useful to signal that something has
387	finished, for example, if you write a module that does asynchronous http	548	finished, for example, if you write a module that does asynchronous http
388	requests, then a condition variable would be the ideal candidate to	549	requests, then a condition variable would be the ideal candidate to
389	signal the availability of results. The user can either act when the	550	signal the availability of results. The user can either act when the
…		…
423	after => 1,	584	after => 1,
424	cb => sub { $result_ready->send },	585	cb => sub { $result_ready->send },
425	);	586	);
426		587
427	# this "blocks" (while handling events) till the callback	588	# this "blocks" (while handling events) till the callback
428	# calls send	589	# calls ->send
429	$result_ready->recv;	590	$result_ready->recv;
430		591
431	Example: wait for a timer, but take advantage of the fact that condition	592	Example: wait for a timer, but take advantage of the fact that condition
432	variables are also code references.	593	variables are also callable directly.
433		594
434	my $done = AnyEvent->condvar;	595	my $done = AnyEvent->condvar;
435	my $delay = AnyEvent->timer (after => 5, cb => $done);	596	my $delay = AnyEvent->timer (after => 5, cb => $done);
436	$done->recv;	597	$done->recv;
		598
		599	Example: Imagine an API that returns a condvar and doesn't support
		600	callbacks. This is how you make a synchronous call, for example from the
		601	main program:
		602
		603	use AnyEvent::CouchDB;
		604
		605	...
		606
		607	my @info = $couchdb->info->recv;
		608
		609	And this is how you would just set a callback to be called whenever the
		610	results are available:
		611
		612	$couchdb->info->cb (sub {
		613	my @info = $_[0]->recv;
		614	});
437		615
438	METHODS FOR PRODUCERS	616	METHODS FOR PRODUCERS
439	These methods should only be used by the producing side, i.e. the	617	These methods should only be used by the producing side, i.e. the
440	code/module that eventually sends the signal. Note that it is also the	618	code/module that eventually sends the signal. Note that it is also the
441	producer side which creates the condvar in most cases, but it isn't	619	producer side which creates the condvar in most cases, but it isn't
…		…
451		629
452	Any arguments passed to the "send" call will be returned by all	630	Any arguments passed to the "send" call will be returned by all
453	future "->recv" calls.	631	future "->recv" calls.
454		632
455	Condition variables are overloaded so one can call them directly (as	633	Condition variables are overloaded so one can call them directly (as
456	a code reference). Calling them directly is the same as calling	634	if they were a code reference). Calling them directly is the same as
457	"send". Note, however, that many C-based event loops do not handle	635	calling "send".
458	overloading, so as tempting as it may be, passing a condition
459	variable instead of a callback does not work. Both the pure perl and
460	EV loops support overloading, however, as well as all functions that
461	use perl to invoke a callback (as in AnyEvent::Socket and
462	AnyEvent::DNS for example).
463		636
464	$cv->croak ($error)	637	$cv->croak ($error)
465	Similar to send, but causes all call's to "->recv" to invoke	638	Similar to send, but causes all call's to "->recv" to invoke
466	"Carp::croak" with the given error message/object/scalar.	639	"Carp::croak" with the given error message/object/scalar.
467		640
468	This can be used to signal any errors to the condition variable	641	This can be used to signal any errors to the condition variable
469	user/consumer.	642	user/consumer. Doing it this way instead of calling "croak" directly
		643	delays the error detetcion, but has the overwhelmign advantage that
		644	it diagnoses the error at the place where the result is expected,
		645	and not deep in some event clalback without connection to the actual
		646	code causing the problem.
470		647
471	$cv->begin ([group callback])	648	$cv->begin ([group callback])
472	$cv->end	649	$cv->end
473	These two methods are EXPERIMENTAL and MIGHT CHANGE.
474
475	These two methods can be used to combine many transactions/events	650	These two methods can be used to combine many transactions/events
476	into one. For example, a function that pings many hosts in parallel	651	into one. For example, a function that pings many hosts in parallel
477	might want to use a condition variable for the whole process.	652	might want to use a condition variable for the whole process.
478		653
479	Every call to "->begin" will increment a counter, and every call to	654	Every call to "->begin" will increment a counter, and every call to
480	"->end" will decrement it. If the counter reaches 0 in "->end", the	655	"->end" will decrement it. If the counter reaches 0 in "->end", the
481	(last) callback passed to "begin" will be executed. That callback is	656	(last) callback passed to "begin" will be executed, passing the
482	supposed to call "->send", but that is not required. If no	657	condvar as first argument. That callback is supposed to call
		658	"->send", but that is not required. If no group callback was set,
483	callback was set, "send" will be called without any arguments.	659	"send" will be called without any arguments.
484		660
485	Let's clarify this with the ping example:	661	You can think of "$cv->send" giving you an OR condition (one call
		662	sends), while "$cv->begin" and "$cv->end" giving you an AND
		663	condition (all "begin" calls must be "end"'ed before the condvar
		664	sends).
		665
		666	Let's start with a simple example: you have two I/O watchers (for
		667	example, STDOUT and STDERR for a program), and you want to wait for
		668	both streams to close before activating a condvar:
486		669
487	my $cv = AnyEvent->condvar;	670	my $cv = AnyEvent->condvar;
488		671
		672	$cv->begin; # first watcher
		673	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		674	defined sysread $fh1, my $buf, 4096
		675	or $cv->end;
		676	});
		677
		678	$cv->begin; # second watcher
		679	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		680	defined sysread $fh2, my $buf, 4096
		681	or $cv->end;
		682	});
		683
		684	$cv->recv;
		685
		686	This works because for every event source (EOF on file handle),
		687	there is one call to "begin", so the condvar waits for all calls to
		688	"end" before sending.
		689
		690	The ping example mentioned above is slightly more complicated, as
		691	the there are results to be passwd back, and the number of tasks
		692	that are begung can potentially be zero:
		693
		694	my $cv = AnyEvent->condvar;
		695
489	my %result;	696	my %result;
490	$cv->begin (sub { $cv->send (\%result) });	697	$cv->begin (sub { shift->send (\%result) });
491		698
492	for my $host (@list_of_hosts) {	699	for my $host (@list_of_hosts) {
493	$cv->begin;	700	$cv->begin;
494	ping_host_then_call_callback $host, sub {	701	ping_host_then_call_callback $host, sub {
495	$result{$host} = ...;	702	$result{$host} = ...;
…		…
510	the loop, which serves two important purposes: first, it sets the	717	the loop, which serves two important purposes: first, it sets the
511	callback to be called once the counter reaches 0, and second, it	718	callback to be called once the counter reaches 0, and second, it
512	ensures that "send" is called even when "no" hosts are being pinged	719	ensures that "send" is called even when "no" hosts are being pinged
513	(the loop doesn't execute once).	720	(the loop doesn't execute once).
514		721
515	This is the general pattern when you "fan out" into multiple	722	This is the general pattern when you "fan out" into multiple (but
516	subrequests: use an outer "begin"/"end" pair to set the callback and	723	potentially none) subrequests: use an outer "begin"/"end" pair to
517	ensure "end" is called at least once, and then, for each subrequest	724	set the callback and ensure "end" is called at least once, and then,
518	you start, call "begin" and for each subrequest you finish, call	725	for each subrequest you start, call "begin" and for each subrequest
519	"end".	726	you finish, call "end".
520		727
521	METHODS FOR CONSUMERS	728	METHODS FOR CONSUMERS
522	These methods should only be used by the consuming side, i.e. the code	729	These methods should only be used by the consuming side, i.e. the code
523	awaits the condition.	730	awaits the condition.
524		731
…		…
533	function will call "croak".	740	function will call "croak".
534		741
535	In list context, all parameters passed to "send" will be returned,	742	In list context, all parameters passed to "send" will be returned,
536	in scalar context only the first one will be returned.	743	in scalar context only the first one will be returned.
537		744
		745	Note that doing a blocking wait in a callback is not supported by
		746	any event loop, that is, recursive invocation of a blocking "->recv"
		747	is not allowed, and the "recv" call will "croak" if such a condition
		748	is detected. This condition can be slightly loosened by using
		749	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		750	thread that doesn't run the event loop itself.
		751
538	Not all event models support a blocking wait - some die in that case	752	Not all event models support a blocking wait - some die in that case
539	(programs might want to do that to stay interactive), so *if you are	753	(programs might want to do that to stay interactive), so *if you are
540	using this from a module, never require a blocking wait*, but let	754	using this from a module, never require a blocking wait*. Instead,
541	the caller decide whether the call will block or not (for example,	755	let the caller decide whether the call will block or not (for
542	by coupling condition variables with some kind of request results	756	example, by coupling condition variables with some kind of request
543	and supporting callbacks so the caller knows that getting the result	757	results and supporting callbacks so the caller knows that getting
544	will not block, while still supporting blocking waits if the caller	758	the result will not block, while still supporting blocking waits if
545	so desires).	759	the caller so desires).
546
547	Another reason never to "->recv" in a module is that you cannot
548	sensibly have two "->recv"'s in parallel, as that would require
549	multiple interpreters or coroutines/threads, none of which
550	"AnyEvent" can supply.
551
552	The Coro module, however, can and does supply coroutines and, in
553	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
554	versions and also integrates coroutines into AnyEvent, making
555	blocking "->recv" calls perfectly safe as long as they are done from
556	another coroutine (one that doesn't run the event loop).
557		760
558	You can ensure that "-recv" never blocks by setting a callback and	761	You can ensure that "-recv" never blocks by setting a callback and
559	only calling "->recv" from within that callback (or at a later	762	only calling "->recv" from within that callback (or at a later
560	time). This will work even when the event loop does not support	763	time). This will work even when the event loop does not support
561	blocking waits otherwise.	764	blocking waits otherwise.
562		765
563	$bool = $cv->ready	766	$bool = $cv->ready
564	Returns true when the condition is "true", i.e. whether "send" or	767	Returns true when the condition is "true", i.e. whether "send" or
565	"croak" have been called.	768	"croak" have been called.
566		769
567	$cb = $cv->cb ([new callback])	770	$cb = $cv->cb ($cb->($cv))
568	This is a mutator function that returns the callback set and	771	This is a mutator function that returns the callback set and
569	optionally replaces it before doing so.	772	optionally replaces it before doing so.
570		773
571	The callback will be called when the condition becomes "true", i.e.	774	The callback will be called when the condition becomes (or already
572	when "send" or "croak" are called. Calling "recv" inside the	775	was) "true", i.e. when "send" or "croak" are called (or were
573	callback or at any later time is guaranteed not to block.	776	called), with the only argument being the condition variable itself.
		777	Calling "recv" inside the callback or at any later time is
		778	guaranteed not to block.
		779
		780	SUPPORTED EVENT LOOPS/BACKENDS
		781	The available backend classes are (every class has its own manpage):
		782
		783	Backends that are autoprobed when no other event loop can be found.
		784	EV is the preferred backend when no other event loop seems to be in
		785	use. If EV is not installed, then AnyEvent will fall back to its own
		786	pure-perl implementation, which is available everywhere as it comes
		787	with AnyEvent itself.
		788
		789	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		790	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		791
		792	Backends that are transparently being picked up when they are used.
		793	These will be used when they are currently loaded when the first
		794	watcher is created, in which case it is assumed that the application
		795	is using them. This means that AnyEvent will automatically pick the
		796	right backend when the main program loads an event module before
		797	anything starts to create watchers. Nothing special needs to be done
		798	by the main program.
		799
		800	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		801	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		802	AnyEvent::Impl::Tk based on Tk, very broken.
		803	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		804	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		805	AnyEvent::Impl::Irssi used when running within irssi.
		806
		807	Backends with special needs.
		808	Qt requires the Qt::Application to be instantiated first, but will
		809	otherwise be picked up automatically. As long as the main program
		810	instantiates the application before any AnyEvent watchers are
		811	created, everything should just work.
		812
		813	AnyEvent::Impl::Qt based on Qt.
		814
		815	Support for IO::Async can only be partial, as it is too broken and
		816	architecturally limited to even support the AnyEvent API. It also is
		817	the only event loop that needs the loop to be set explicitly, so it
		818	can only be used by a main program knowing about AnyEvent. See
		819	AnyEvent::Impl::Async for the gory details.
		820
		821	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		822
		823	Event loops that are indirectly supported via other backends.
		824	Some event loops can be supported via other modules:
		825
		826	There is no direct support for WxWidgets (Wx) or Prima.
		827
		828	WxWidgets has no support for watching file handles. However, you can
		829	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		830	simply polls 20 times per second, which was considered to be too
		831	horrible to even consider for AnyEvent.
		832
		833	Prima is not supported as nobody seems to be using it, but it has a
		834	POE backend, so it can be supported through POE.
		835
		836	AnyEvent knows about both Prima and Wx, however, and will try to
		837	load POE when detecting them, in the hope that POE will pick them
		838	up, in which case everything will be automatic.
574		839
575	GLOBAL VARIABLES AND FUNCTIONS	840	GLOBAL VARIABLES AND FUNCTIONS
		841	These are not normally required to use AnyEvent, but can be useful to
		842	write AnyEvent extension modules.
		843
576	$AnyEvent::MODEL	844	$AnyEvent::MODEL
577	Contains "undef" until the first watcher is being created. Then it	845	Contains "undef" until the first watcher is being created, before
		846	the backend has been autodetected.
		847
578	contains the event model that is being used, which is the name of	848	Afterwards it contains the event model that is being used, which is
579	the Perl class implementing the model. This class is usually one of	849	the name of the Perl class implementing the model. This class is
580	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	850	usually one of the "AnyEvent::Impl:xxx" modules, but can be any
581	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).	851	other class in the case AnyEvent has been extended at runtime (e.g.
582		852	in rxvt-unicode it will be "urxvt::anyevent").
583	The known classes so far are:
584
585	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
586	AnyEvent::Impl::Event based on Event, second best choice.
587	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
588	AnyEvent::Impl::Glib based on Glib, third-best choice.
589	AnyEvent::Impl::Tk based on Tk, very bad choice.
590	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
591	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
592	AnyEvent::Impl::POE based on POE, not generic enough for full support.
593
594	There is no support for WxWidgets, as WxWidgets has no support for
595	watching file handles. However, you can use WxWidgets through the
596	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
597	second, which was considered to be too horrible to even consider for
598	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
599	using it's adaptor.
600
601	AnyEvent knows about Prima and Wx and will try to use POE when
602	autodetecting them.
603		853
604	AnyEvent::detect	854	AnyEvent::detect
605	Returns $AnyEvent::MODEL, forcing autodetection of the event model	855	Returns $AnyEvent::MODEL, forcing autodetection of the event model
606	if necessary. You should only call this function right before you	856	if necessary. You should only call this function right before you
607	would have created an AnyEvent watcher anyway, that is, as late as	857	would have created an AnyEvent watcher anyway, that is, as late as
608	possible at runtime.	858	possible at runtime, and not e.g. while initialising of your module.
		859
		860	If you need to do some initialisation before AnyEvent watchers are
		861	created, use "post_detect".
609		862
610	$guard = AnyEvent::post_detect { BLOCK }	863	$guard = AnyEvent::post_detect { BLOCK }
611	Arranges for the code block to be executed as soon as the event	864	Arranges for the code block to be executed as soon as the event
612	model is autodetected (or immediately if this has already happened).	865	model is autodetected (or immediately if this has already happened).
613		866
		867	The block will be executed after the actual backend has been
		868	detected ($AnyEvent::MODEL is set), but before any watchers have
		869	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		870	other initialisations - see the sources of AnyEvent::Strict or
		871	AnyEvent::AIO to see how this is used.
		872
		873	The most common usage is to create some global watchers, without
		874	forcing event module detection too early, for example, AnyEvent::AIO
		875	creates and installs the global IO::AIO watcher in a "post_detect"
		876	block to avoid autodetecting the event module at load time.
		877
614	If called in scalar or list context, then it creates and returns an	878	If called in scalar or list context, then it creates and returns an
615	object that automatically removes the callback again when it is	879	object that automatically removes the callback again when it is
		880	destroyed (or "undef" when the hook was immediately executed). See
616	destroyed. See Coro::BDB for a case where this is useful.	881	AnyEvent::AIO for a case where this is useful.
		882
		883	Example: Create a watcher for the IO::AIO module and store it in
		884	$WATCHER. Only do so after the event loop is initialised, though.
		885
		886	our WATCHER;
		887
		888	my $guard = AnyEvent::post_detect {
		889	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		890	};
		891
		892	# the \|\|= is important in case post_detect immediately runs the block,
		893	# as to not clobber the newly-created watcher. assigning both watcher and
		894	# post_detect guard to the same variable has the advantage of users being
		895	# able to just C<undef $WATCHER> if the watcher causes them grief.
		896
		897	$WATCHER \|\|= $guard;
617		898
618	@AnyEvent::post_detect	899	@AnyEvent::post_detect
619	If there are any code references in this array (you can "push" to it	900	If there are any code references in this array (you can "push" to it
620	before or after loading AnyEvent), then they will called directly	901	before or after loading AnyEvent), then they will called directly
621	after the event loop has been chosen.	902	after the event loop has been chosen.
622		903
623	You should check $AnyEvent::MODEL before adding to this array,	904	You should check $AnyEvent::MODEL before adding to this array,
624	though: if it contains a true value then the event loop has already	905	though: if it is defined then the event loop has already been
625	been detected, and the array will be ignored.	906	detected, and the array will be ignored.
626		907
627	Best use "AnyEvent::post_detect { BLOCK }" instead.	908	Best use "AnyEvent::post_detect { BLOCK }" when your application
		909	allows it,as it takes care of these details.
		910
		911	This variable is mainly useful for modules that can do something
		912	useful when AnyEvent is used and thus want to know when it is
		913	initialised, but do not need to even load it by default. This array
		914	provides the means to hook into AnyEvent passively, without loading
		915	it.
628		916
629	WHAT TO DO IN A MODULE	917	WHAT TO DO IN A MODULE
630	As a module author, you should "use AnyEvent" and call AnyEvent methods	918	As a module author, you should "use AnyEvent" and call AnyEvent methods
631	freely, but you should not load a specific event module or rely on it.	919	freely, but you should not load a specific event module or rely on it.
632		920
…		…
683	variable somewhere, waiting for it, and sending it when the program	971	variable somewhere, waiting for it, and sending it when the program
684	should exit cleanly.	972	should exit cleanly.
685		973
686	OTHER MODULES	974	OTHER MODULES
687	The following is a non-exhaustive list of additional modules that use	975	The following is a non-exhaustive list of additional modules that use
688	AnyEvent and can therefore be mixed easily with other AnyEvent modules	976	AnyEvent as a client and can therefore be mixed easily with other
689	in the same program. Some of the modules come with AnyEvent, some are	977	AnyEvent modules and other event loops in the same program. Some of the
690	available via CPAN.	978	modules come with AnyEvent, most are available via CPAN.
691		979
692	AnyEvent::Util	980	AnyEvent::Util
693	Contains various utility functions that replace often-used but	981	Contains various utility functions that replace often-used but
694	blocking functions such as "inet_aton" by event-/callback-based	982	blocking functions such as "inet_aton" by event-/callback-based
695	versions.	983	versions.
696
697	AnyEvent::Handle
698	Provide read and write buffers and manages watchers for reads and
699	writes.
700		984
701	AnyEvent::Socket	985	AnyEvent::Socket
702	Provides various utility functions for (internet protocol) sockets,	986	Provides various utility functions for (internet protocol) sockets,
703	addresses and name resolution. Also functions to create non-blocking	987	addresses and name resolution. Also functions to create non-blocking
704	tcp connections or tcp servers, with IPv6 and SRV record support and	988	tcp connections or tcp servers, with IPv6 and SRV record support and
705	more.	989	more.
706		990
		991	AnyEvent::Handle
		992	Provide read and write buffers, manages watchers for reads and
		993	writes, supports raw and formatted I/O, I/O queued and fully
		994	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
		995
707	AnyEvent::DNS	996	AnyEvent::DNS
708	Provides rich asynchronous DNS resolver capabilities.	997	Provides rich asynchronous DNS resolver capabilities.
709		998
		999	AnyEvent::HTTP
		1000	A simple-to-use HTTP library that is capable of making a lot of
		1001	concurrent HTTP requests.
		1002
710	AnyEvent::HTTPD	1003	AnyEvent::HTTPD
711	Provides a simple web application server framework.	1004	Provides a simple web application server framework.
712		1005
713	AnyEvent::FastPing	1006	AnyEvent::FastPing
714	The fastest ping in the west.	1007	The fastest ping in the west.
715		1008
		1009	AnyEvent::DBI
		1010	Executes DBI requests asynchronously in a proxy process.
		1011
		1012	AnyEvent::AIO
		1013	Truly asynchronous I/O, should be in the toolbox of every event
		1014	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		1015	together.
		1016
		1017	AnyEvent::BDB
		1018	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
		1019	fuses BDB and AnyEvent together.
		1020
		1021	AnyEvent::GPSD
		1022	A non-blocking interface to gpsd, a daemon delivering GPS
		1023	information.
		1024
		1025	AnyEvent::IRC
		1026	AnyEvent based IRC client module family (replacing the older
716	Net::IRC3	1027	Net::IRC3).
717	AnyEvent based IRC client module family.
718		1028
719	Net::XMPP2	1029	AnyEvent::XMPP
720	AnyEvent based XMPP (Jabber protocol) module family.	1030	AnyEvent based XMPP (Jabber protocol) module family (replacing the
		1031	older Net::XMPP2>.
		1032
		1033	AnyEvent::IGS
		1034	A non-blocking interface to the Internet Go Server protocol (used by
		1035	App::IGS).
721		1036
722	Net::FCP	1037	Net::FCP
723	AnyEvent-based implementation of the Freenet Client Protocol,	1038	AnyEvent-based implementation of the Freenet Client Protocol,
724	birthplace of AnyEvent.	1039	birthplace of AnyEvent.
725		1040
…		…
727	High level API for event-based execution flow control.	1042	High level API for event-based execution flow control.
728		1043
729	Coro	1044	Coro
730	Has special support for AnyEvent via Coro::AnyEvent.	1045	Has special support for AnyEvent via Coro::AnyEvent.
731		1046
732	AnyEvent::AIO, IO::AIO	1047	SIMPLIFIED AE API
733	Truly asynchronous I/O, should be in the toolbox of every event	1048	Starting with version 5.0, AnyEvent officially supports a second, much
734	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent	1049	simpler, API that is designed to reduce the calling, typing and memory
735	together.	1050	overhead.
736		1051
737	AnyEvent::BDB, BDB	1052	See the AE manpage for details.
738	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
739	fuses IO::AIO and AnyEvent together.
740		1053
741	IO::Lambda	1054	ERROR AND EXCEPTION HANDLING
742	The lambda approach to I/O - don't ask, look there. Can use	1055	In general, AnyEvent does not do any error handling - it relies on the
743	AnyEvent.	1056	caller to do that if required. The AnyEvent::Strict module (see also the
		1057	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
		1058	checking of all AnyEvent methods, however, which is highly useful during
		1059	development.
744		1060
745	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1061	As for exception handling (i.e. runtime errors and exceptions thrown
746	This is an advanced topic that you do not normally need to use AnyEvent	1062	while executing a callback), this is not only highly event-loop
747	in a module. This section is only of use to event loop authors who want	1063	specific, but also not in any way wrapped by this module, as this is the
748	to provide AnyEvent compatibility.	1064	job of the main program.
749		1065
750	If you need to support another event library which isn't directly	1066	The pure perl event loop simply re-throws the exception (usually within
751	supported by AnyEvent, you can supply your own interface to it by	1067	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
752	pushing, before the first watcher gets created, the package name of the	1068	Glib uses "install_exception_handler" and so on.
753	event module and the package name of the interface to use onto
754	@AnyEvent::REGISTRY. You can do that before and even without loading
755	AnyEvent, so it is reasonably cheap.
756
757	Example:
758
759	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
760
761	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
762	package/class when it finds the "urxvt" package/module is already
763	loaded.
764
765	When AnyEvent is loaded and asked to find a suitable event model, it
766	will first check for the presence of urxvt by trying to "use" the
767	"urxvt::anyevent" module.
768
769	The class should provide implementations for all watcher types. See
770	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
771	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
772	the sources.
773
774	If you don't provide "signal" and "child" watchers than AnyEvent will
775	provide suitable (hopefully) replacements.
776
777	The above example isn't fictitious, the rxvt-unicode (a.k.a. urxvt)
778	terminal emulator uses the above line as-is. An interface isn't included
779	in AnyEvent because it doesn't make sense outside the embedded
780	interpreter inside rxvt-unicode, and it is updated and maintained as
781	part of the rxvt-unicode distribution.
782
783	rxvt-unicode also cheats a bit by not providing blocking access to
784	condition variables: code blocking while waiting for a condition will
785	"die". This still works with most modules/usages, and blocking calls
786	must not be done in an interactive application, so it makes sense.
787		1069
788	ENVIRONMENT VARIABLES	1070	ENVIRONMENT VARIABLES
789	The following environment variables are used by this module:	1071	The following environment variables are used by this module or its
		1072	submodules.
		1073
		1074	Note that AnyEvent will remove all environment variables starting with
		1075	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1076	enabled.
790		1077
791	"PERL_ANYEVENT_VERBOSE"	1078	"PERL_ANYEVENT_VERBOSE"
792	By default, AnyEvent will be completely silent except in fatal	1079	By default, AnyEvent will be completely silent except in fatal
793	conditions. You can set this environment variable to make AnyEvent	1080	conditions. You can set this environment variable to make AnyEvent
794	more talkative.	1081	more talkative.
…		…
797	conditions, such as not being able to load the event model specified	1084	conditions, such as not being able to load the event model specified
798	by "PERL_ANYEVENT_MODEL".	1085	by "PERL_ANYEVENT_MODEL".
799		1086
800	When set to 2 or higher, cause AnyEvent to report to STDERR which	1087	When set to 2 or higher, cause AnyEvent to report to STDERR which
801	event model it chooses.	1088	event model it chooses.
		1089
		1090	When set to 8 or higher, then AnyEvent will report extra information
		1091	on which optional modules it loads and how it implements certain
		1092	features.
		1093
		1094	"PERL_ANYEVENT_STRICT"
		1095	AnyEvent does not do much argument checking by default, as thorough
		1096	argument checking is very costly. Setting this variable to a true
		1097	value will cause AnyEvent to load "AnyEvent::Strict" and then to
		1098	thoroughly check the arguments passed to most method calls. If it
		1099	finds any problems, it will croak.
		1100
		1101	In other words, enables "strict" mode.
		1102
		1103	Unlike "use strict" (or it's modern cousin, "use common::sense", it
		1104	is definitely recommended to keep it off in production. Keeping
		1105	"PERL_ANYEVENT_STRICT=1" in your environment while developing
		1106	programs can be very useful, however.
802		1107
803	"PERL_ANYEVENT_MODEL"	1108	"PERL_ANYEVENT_MODEL"
804	This can be used to specify the event model to be used by AnyEvent,	1109	This can be used to specify the event model to be used by AnyEvent,
805	before auto detection and -probing kicks in. It must be a string	1110	before auto detection and -probing kicks in. It must be a string
806	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	1111	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
…		…
811	This functionality might change in future versions.	1116	This functionality might change in future versions.
812		1117
813	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	1118	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
814	could start your program like this:	1119	could start your program like this:
815		1120
816	PERL_ANYEVENT_MODEL=Perl perl ...	1121	PERL_ANYEVENT_MODEL=Perl perl ...
817		1122
818	"PERL_ANYEVENT_PROTOCOLS"	1123	"PERL_ANYEVENT_PROTOCOLS"
819	Used by both AnyEvent::DNS and AnyEvent::Socket to determine	1124	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
820	preferences for IPv4 or IPv6. The default is unspecified (and might	1125	preferences for IPv4 or IPv6. The default is unspecified (and might
821	change, or be the result of auto probing).	1126	change, or be the result of auto probing).
…		…
825	mentioned will be used, and preference will be given to protocols	1130	mentioned will be used, and preference will be given to protocols
826	mentioned earlier in the list.	1131	mentioned earlier in the list.
827		1132
828	This variable can effectively be used for denial-of-service attacks	1133	This variable can effectively be used for denial-of-service attacks
829	against local programs (e.g. when setuid), although the impact is	1134	against local programs (e.g. when setuid), although the impact is
830	likely small, as the program has to handle connection errors	1135	likely small, as the program has to handle conenction and other
831	already-	1136	failures anyways.
832		1137
833	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over	1138	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
834	IPv6, but support both and try to use both.	1139	IPv6, but support both and try to use both.
835	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to	1140	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
836	resolve or contact IPv6 addresses.	1141	resolve or contact IPv6 addresses.
…		…
847	EDNS0 in its DNS requests.	1152	EDNS0 in its DNS requests.
848		1153
849	"PERL_ANYEVENT_MAX_FORKS"	1154	"PERL_ANYEVENT_MAX_FORKS"
850	The maximum number of child processes that	1155	The maximum number of child processes that
851	"AnyEvent::Util::fork_call" will create in parallel.	1156	"AnyEvent::Util::fork_call" will create in parallel.
		1157
		1158	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1159	The default value for the "max_outstanding" parameter for the
		1160	default DNS resolver - this is the maximum number of parallel DNS
		1161	requests that are sent to the DNS server.
		1162
		1163	"PERL_ANYEVENT_RESOLV_CONF"
		1164	The file to use instead of /etc/resolv.conf (or OS-specific
		1165	configuration) in the default resolver. When set to the empty
		1166	string, no default config will be used.
		1167
		1168	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1169	When neither "ca_file" nor "ca_path" was specified during
		1170	AnyEvent::TLS context creation, and either of these environment
		1171	variables exist, they will be used to specify CA certificate
		1172	locations instead of a system-dependent default.
		1173
		1174	"PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
		1175	When these are set to 1, then the respective modules are not loaded.
		1176	Mostly good for testing AnyEvent itself.
		1177
		1178	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1179	This is an advanced topic that you do not normally need to use AnyEvent
		1180	in a module. This section is only of use to event loop authors who want
		1181	to provide AnyEvent compatibility.
		1182
		1183	If you need to support another event library which isn't directly
		1184	supported by AnyEvent, you can supply your own interface to it by
		1185	pushing, before the first watcher gets created, the package name of the
		1186	event module and the package name of the interface to use onto
		1187	@AnyEvent::REGISTRY. You can do that before and even without loading
		1188	AnyEvent, so it is reasonably cheap.
		1189
		1190	Example:
		1191
		1192	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
		1193
		1194	This tells AnyEvent to (literally) use the "urxvt::anyevent::"
		1195	package/class when it finds the "urxvt" package/module is already
		1196	loaded.
		1197
		1198	When AnyEvent is loaded and asked to find a suitable event model, it
		1199	will first check for the presence of urxvt by trying to "use" the
		1200	"urxvt::anyevent" module.
		1201
		1202	The class should provide implementations for all watcher types. See
		1203	AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
		1204	so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
		1205	the sources.
		1206
		1207	If you don't provide "signal" and "child" watchers than AnyEvent will
		1208	provide suitable (hopefully) replacements.
		1209
		1210	The above example isn't fictitious, the rxvt-unicode (a.k.a. urxvt)
		1211	terminal emulator uses the above line as-is. An interface isn't included
		1212	in AnyEvent because it doesn't make sense outside the embedded
		1213	interpreter inside rxvt-unicode, and it is updated and maintained as
		1214	part of the rxvt-unicode distribution.
		1215
		1216	rxvt-unicode also cheats a bit by not providing blocking access to
		1217	condition variables: code blocking while waiting for a condition will
		1218	"die". This still works with most modules/usages, and blocking calls
		1219	must not be done in an interactive application, so it makes sense.
852		1220
853	EXAMPLE PROGRAM	1221	EXAMPLE PROGRAM
854	The following program uses an I/O watcher to read data from STDIN, a	1222	The following program uses an I/O watcher to read data from STDIN, a
855	timer to display a message once per second, and a condition variable to	1223	timer to display a message once per second, and a condition variable to
856	quit the program when the user enters quit:	1224	quit the program when the user enters quit:
…		…
868	warn "read: $input\n"; # output what has been read	1236	warn "read: $input\n"; # output what has been read
869	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1237	$cv->send if $input =~ /^q/i; # quit program if /^q/i
870	},	1238	},
871	);	1239	);
872		1240
873	my $time_watcher; # can only be used once
874
875	sub new_timer {
876	$timer = AnyEvent->timer (after => 1, cb => sub {	1241	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
877	warn "timeout\n"; # print 'timeout' about every second	1242	warn "timeout\n"; # print 'timeout' at most every second
878	&new_timer; # and restart the time
879	});
880	}	1243	});
881
882	new_timer; # create first timer
883		1244
884	$cv->recv; # wait until user enters /^q/i	1245	$cv->recv; # wait until user enters /^q/i
885		1246
886	REAL-WORLD EXAMPLE	1247	REAL-WORLD EXAMPLE
887	Consider the Net::FCP module. It features (among others) the following	1248	Consider the Net::FCP module. It features (among others) the following
…		…
1014	through AnyEvent. The benchmark creates a lot of timers (with a zero	1375	through AnyEvent. The benchmark creates a lot of timers (with a zero
1015	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1376	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1016	which it is), lets them fire exactly once and destroys them again.	1377	which it is), lets them fire exactly once and destroys them again.
1017		1378
1018	Source code for this benchmark is found as eg/bench in the AnyEvent	1379	Source code for this benchmark is found as eg/bench in the AnyEvent
1019	distribution.	1380	distribution. It uses the AE interface, which makes a real difference
		1381	for the EV and Perl backends only.
1020		1382
1021	Explanation of the columns	1383	Explanation of the columns
1022	watcher is the number of event watchers created/destroyed. Since	1384	watcher is the number of event watchers created/destroyed. Since
1023	different event models feature vastly different performances, each event	1385	different event models feature vastly different performances, each event
1024	loop was given a number of watchers so that overall runtime is	1386	loop was given a number of watchers so that overall runtime is
…		…
1043	destroy is the time, in microseconds, that it takes to destroy a	1405	destroy is the time, in microseconds, that it takes to destroy a
1044	single watcher.	1406	single watcher.
1045		1407
1046	Results	1408	Results
1047	name watchers bytes create invoke destroy comment	1409	name watchers bytes create invoke destroy comment
1048	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1410	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1049	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1411	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1050	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1412	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1051	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1413	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1052	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1414	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1053	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1415	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		1416	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		1417	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1054	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1418	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1055	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1419	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1056	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1420	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1057	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1421	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1058		1422
1059	Discussion	1423	Discussion
1060	The benchmark does not measure scalability of the event loop very	1424	The benchmark does not measure scalability of the event loop very
1061	well. For example, a select-based event loop (such as the pure perl one)	1425	well. For example, a select-based event loop (such as the pure perl one)
1062	can never compete with an event loop that uses epoll when the number of	1426	can never compete with an event loop that uses epoll when the number of
…		…
1073	benchmark machine, handling an event takes roughly 1600 CPU cycles with	1437	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1074	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000	1438	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
1075	CPU cycles with POE.	1439	CPU cycles with POE.
1076		1440
1077	"EV" is the sole leader regarding speed and memory use, which are both	1441	"EV" is the sole leader regarding speed and memory use, which are both
1078	maximal/minimal, respectively. Even when going through AnyEvent, it uses	1442	maximal/minimal, respectively. When using the AE API there is zero
		1443	overhead (when going through the AnyEvent API create is about 5-6 times
		1444	slower, with other times being equal, so still uses far less memory than
1079	far less memory than any other event loop and is still faster than Event	1445	any other event loop and is still faster than Event natively).
1080	natively.
1081		1446
1082	The pure perl implementation is hit in a few sweet spots (both the	1447	The pure perl implementation is hit in a few sweet spots (both the
1083	constant timeout and the use of a single fd hit optimisations in the	1448	constant timeout and the use of a single fd hit optimisations in the
1084	perl interpreter and the backend itself). Nevertheless this shows that	1449	perl interpreter and the backend itself). Nevertheless this shows that
1085	it adds very little overhead in itself. Like any select-based backend	1450	it adds very little overhead in itself. Like any select-based backend
…		…
1087	few of them active), of course, but this was not subject of this	1452	few of them active), of course, but this was not subject of this
1088	benchmark.	1453	benchmark.
1089		1454
1090	The "Event" module has a relatively high setup and callback invocation	1455	The "Event" module has a relatively high setup and callback invocation
1091	cost, but overall scores in on the third place.	1456	cost, but overall scores in on the third place.
		1457
		1458	"IO::Async" performs admirably well, about on par with "Event", even
		1459	when using its pure perl backend.
1092		1460
1093	"Glib"'s memory usage is quite a bit higher, but it features a faster	1461	"Glib"'s memory usage is quite a bit higher, but it features a faster
1094	callback invocation and overall ends up in the same class as "Event".	1462	callback invocation and overall ends up in the same class as "Event".
1095	However, Glib scales extremely badly, doubling the number of watchers	1463	However, Glib scales extremely badly, doubling the number of watchers
1096	increases the processing time by more than a factor of four, making it	1464	increases the processing time by more than a factor of four, making it
…		…
1152	In this benchmark, we use 10000 socket pairs (20000 sockets), of which	1520	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1153	100 (1%) are active. This mirrors the activity of large servers with	1521	100 (1%) are active. This mirrors the activity of large servers with
1154	many connections, most of which are idle at any one point in time.	1522	many connections, most of which are idle at any one point in time.
1155		1523
1156	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1524	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1157	distribution.	1525	distribution. It uses the AE interface, which makes a real difference
		1526	for the EV and Perl backends only.
1158		1527
1159	Explanation of the columns	1528	Explanation of the columns
1160	sockets is the number of sockets, and twice the number of "servers"	1529	sockets is the number of sockets, and twice the number of "servers"
1161	(as each server has a read and write socket end).	1530	(as each server has a read and write socket end).
1162		1531
…		…
1167	single "request", that is, reading the token from the pipe and	1536	single "request", that is, reading the token from the pipe and
1168	forwarding it to another server. This includes deleting the old timeout	1537	forwarding it to another server. This includes deleting the old timeout
1169	and creating a new one that moves the timeout into the future.	1538	and creating a new one that moves the timeout into the future.
1170		1539
1171	Results	1540	Results
1172	name sockets create request	1541	name sockets create request
1173	EV 20000 69.01 11.16	1542	EV 20000 62.66 7.99
1174	Perl 20000 73.32 35.87	1543	Perl 20000 68.32 32.64
1175	Event 20000 212.62 257.32	1544	IOAsync 20000 174.06 101.15 epoll
1176	Glib 20000 651.16 1896.30	1545	IOAsync 20000 174.67 610.84 poll
		1546	Event 20000 202.69 242.91
		1547	Glib 20000 557.01 1689.52
1177	POE 20000 349.67 12317.24 uses POE::Loop::Event	1548	POE 20000 341.54 12086.32 uses POE::Loop::Event
1178		1549
1179	Discussion	1550	Discussion
1180	This benchmark does measure scalability and overall performance of the	1551	This benchmark does measure scalability and overall performance of the
1181	particular event loop.	1552	particular event loop.
1182		1553
1183	EV is again fastest. Since it is using epoll on my system, the setup	1554	EV is again fastest. Since it is using epoll on my system, the setup
1184	time is relatively high, though.	1555	time is relatively high, though.
1185		1556
1186	Perl surprisingly comes second. It is much faster than the C-based event	1557	Perl surprisingly comes second. It is much faster than the C-based event
1187	loops Event and Glib.	1558	loops Event and Glib.
		1559
		1560	IO::Async performs very well when using its epoll backend, and still
		1561	quite good compared to Glib when using its pure perl backend.
1188		1562
1189	Event suffers from high setup time as well (look at its code and you	1563	Event suffers from high setup time as well (look at its code and you
1190	will understand why). Callback invocation also has a high overhead	1564	will understand why). Callback invocation also has a high overhead
1191	compared to the "$_->() for .."-style loop that the Perl event loop	1565	compared to the "$_->() for .."-style loop that the Perl event loop
1192	uses. Event uses select or poll in basically all documented	1566	uses. Event uses select or poll in basically all documented
…		…
1243		1617
1244	Summary	1618	Summary
1245	* C-based event loops perform very well with small number of watchers,	1619	* C-based event loops perform very well with small number of watchers,
1246	as the management overhead dominates.	1620	as the management overhead dominates.
1247		1621
		1622	THE IO::Lambda BENCHMARK
		1623	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1624	could be misinterpreted to make AnyEvent look bad. In fact, the
		1625	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1626	better (which shouldn't come as a surprise to anybody). As such, the
		1627	benchmark is fine, and mostly shows that the AnyEvent backend from
		1628	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1629	without the extra baggage? To explore this, I wrote the equivalent
		1630	benchmark for AnyEvent.
		1631
		1632	The benchmark itself creates an echo-server, and then, for 500 times,
		1633	connects to the echo server, sends a line, waits for the reply, and then
		1634	creates the next connection. This is a rather bad benchmark, as it
		1635	doesn't test the efficiency of the framework or much non-blocking I/O,
		1636	but it is a benchmark nevertheless.
		1637
		1638	name runtime
		1639	Lambda/select 0.330 sec
		1640	+ optimized 0.122 sec
		1641	Lambda/AnyEvent 0.327 sec
		1642	+ optimized 0.138 sec
		1643	Raw sockets/select 0.077 sec
		1644	POE/select, components 0.662 sec
		1645	POE/select, raw sockets 0.226 sec
		1646	POE/select, optimized 0.404 sec
		1647
		1648	AnyEvent/select/nb 0.085 sec
		1649	AnyEvent/EV/nb 0.068 sec
		1650	+state machine 0.134 sec
		1651
		1652	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1653	benchmarks actually make blocking connects and use 100% blocking I/O,
		1654	defeating the purpose of an event-based solution. All of the newly
		1655	written AnyEvent benchmarks use 100% non-blocking connects (using
		1656	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1657	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1658	connects generally require a lot more bookkeeping and event handling
		1659	than blocking connects (which involve a single syscall only).
		1660
		1661	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1662	offers similar expressive power as POE and IO::Lambda, using
		1663	conventional Perl syntax. This means that both the echo server and the
		1664	client are 100% non-blocking, further placing it at a disadvantage.
		1665
		1666	As you can see, the AnyEvent + EV combination even beats the
		1667	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1668	backend easily beats IO::Lambda and POE.
		1669
		1670	And even the 100% non-blocking version written using the high-level (and
		1671	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda
		1672	higher level ("unoptimised") abstractions by a large margin, even though
		1673	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		1674
		1675	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1676	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1677	part of the IO::Lambda distribution and were used without any changes.
		1678
		1679	SIGNALS
		1680	AnyEvent currently installs handlers for these signals:
		1681
		1682	SIGCHLD
		1683	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
		1684	emulation for event loops that do not support them natively. Also,
		1685	some event loops install a similar handler.
		1686
		1687	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1688	then AnyEvent will reset it to default, to avoid losing child exit
		1689	statuses.
		1690
		1691	SIGPIPE
		1692	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
		1693	"undef" when AnyEvent gets loaded.
		1694
		1695	The rationale for this is that AnyEvent users usually do not really
		1696	depend on SIGPIPE delivery (which is purely an optimisation for
		1697	shell use, or badly-written programs), but "SIGPIPE" can cause
		1698	spurious and rare program exits as a lot of people do not expect
		1699	"SIGPIPE" when writing to some random socket.
		1700
		1701	The rationale for installing a no-op handler as opposed to ignoring
		1702	it is that this way, the handler will be restored to defaults on
		1703	exec.
		1704
		1705	Feel free to install your own handler, or reset it to defaults.
		1706
		1707	RECOMMENDED/OPTIONAL MODULES
		1708	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		1709	it's built-in modules) are required to use it.
		1710
		1711	That does not mean that AnyEvent won't take advantage of some additional
		1712	modules if they are installed.
		1713
		1714	This section epxlains which additional modules will be used, and how
		1715	they affect AnyEvent's operetion.
		1716
		1717	Async::Interrupt
		1718	This slightly arcane module is used to implement fast signal
		1719	handling: To my knowledge, there is no way to do completely
		1720	race-free and quick signal handling in pure perl. To ensure that
		1721	signals still get delivered, AnyEvent will start an interval timer
		1722	to wake up perl (and catch the signals) with some delay (default is
		1723	10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
		1724
		1725	If this module is available, then it will be used to implement
		1726	signal catching, which means that signals will not be delayed, and
		1727	the event loop will not be interrupted regularly, which is more
		1728	efficient (And good for battery life on laptops).
		1729
		1730	This affects not just the pure-perl event loop, but also other event
		1731	loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
		1732
		1733	Some event loops (POE, Event, Event::Lib) offer signal watchers
		1734	natively, and either employ their own workarounds (POE) or use
		1735	AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
		1736	Installing Async::Interrupt does nothing for those backends.
		1737
		1738	EV This module isn't really "optional", as it is simply one of the
		1739	backend event loops that AnyEvent can use. However, it is simply the
		1740	best event loop available in terms of features, speed and stability:
		1741	It supports the AnyEvent API optimally, implements all the watcher
		1742	types in XS, does automatic timer adjustments even when no monotonic
		1743	clock is available, can take avdantage of advanced kernel interfaces
		1744	such as "epoll" and "kqueue", and is the fastest backend by far.
		1745	You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
		1746	Glib::EV).
		1747
		1748	Guard
		1749	The guard module, when used, will be used to implement
		1750	"AnyEvent::Util::guard". This speeds up guards considerably (and
		1751	uses a lot less memory), but otherwise doesn't affect guard
		1752	operation much. It is purely used for performance.
		1753
		1754	JSON and JSON::XS
		1755	One of these modules is required when you want to read or write JSON
		1756	data via AnyEvent::Handle. It is also written in pure-perl, but can
		1757	take advantage of the ultra-high-speed JSON::XS module when it is
		1758	installed.
		1759
		1760	In fact, AnyEvent::Handle will use JSON::XS by default if it is
		1761	installed.
		1762
		1763	Net::SSLeay
		1764	Implementing TLS/SSL in Perl is certainly interesting, but not very
		1765	worthwhile: If this module is installed, then AnyEvent::Handle (with
		1766	the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
		1767
		1768	Time::HiRes
		1769	This module is part of perl since release 5.008. It will be used
		1770	when the chosen event library does not come with a timing source on
		1771	it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
		1772	additionally use it to try to use a monotonic clock for timing
		1773	stability.
		1774
1248	FORK	1775	FORK
1249	Most event libraries are not fork-safe. The ones who are usually are	1776	Most event libraries are not fork-safe. The ones who are usually are
1250	because they rely on inefficient but fork-safe "select" or "poll" calls.	1777	because they rely on inefficient but fork-safe "select" or "poll" calls.
1251	Only EV is fully fork-aware.	1778	Only EV is fully fork-aware.
1252		1779
1253	If you have to fork, you must either do so before creating your first	1780	If you have to fork, you must either do so before creating your first
1254	watcher OR you must not use AnyEvent at all in the child.	1781	watcher OR you must not use AnyEvent at all in the child OR you must do
		1782	something completely out of the scope of AnyEvent.
1255		1783
1256	SECURITY CONSIDERATIONS	1784	SECURITY CONSIDERATIONS
1257	AnyEvent can be forced to load any event model via	1785	AnyEvent can be forced to load any event model via
1258	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used	1786	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1259	to execute arbitrary code or directly gain access, it can easily be used	1787	to execute arbitrary code or directly gain access, it can easily be used
…		…
1262	model than specified in the variable.	1790	model than specified in the variable.
1263		1791
1264	You can make AnyEvent completely ignore this variable by deleting it	1792	You can make AnyEvent completely ignore this variable by deleting it
1265	before the first watcher gets created, e.g. with a "BEGIN" block:	1793	before the first watcher gets created, e.g. with a "BEGIN" block:
1266		1794
1267	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1795	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1268		1796
1269	use AnyEvent;	1797	use AnyEvent;
1270		1798
1271	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1799	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1272	be used to probe what backend is used and gain other information (which	1800	be used to probe what backend is used and gain other information (which
1273	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	1801	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
		1802	and $ENV{PERL_ANYEVENT_STRICT}.
		1803
		1804	Note that AnyEvent will remove all environment variables starting with
		1805	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1806	enabled.
		1807
		1808	BUGS
		1809	Perl 5.8 has numerous memleaks that sometimes hit this module and are
		1810	hard to work around. If you suffer from memleaks, first upgrade to Perl
		1811	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
		1812	annoying memleaks, such as leaking on "map" and "grep" but it is usually
		1813	not as pronounced).
1274		1814
1275	SEE ALSO	1815	SEE ALSO
1276	Utility functions: AnyEvent::Util.	1816	Utility functions: AnyEvent::Util.
1277		1817
1278	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1818	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1279	Event::Lib, Qt, POE.	1819	Event::Lib, Qt, POE.
1280		1820
1281	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1821	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1282	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1822	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1283	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1823	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1824	AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1284		1825
1285	Non-blocking file handles, sockets, TCP clients and servers:	1826	Non-blocking file handles, sockets, TCP clients and servers:
1286	AnyEvent::Handle, AnyEvent::Socket.	1827	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1287		1828
1288	Asynchronous DNS: AnyEvent::DNS.	1829	Asynchronous DNS: AnyEvent::DNS.
1289		1830
1290	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1831	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1291		1832
1292	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1833	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1834	AnyEvent::HTTP.
1293		1835
1294	AUTHOR	1836	AUTHOR
1295	Marc Lehmann <schmorp@schmorp.de>	1837	Marc Lehmann <schmorp@schmorp.de>
1296	http://home.schmorp.de/	1838	http://home.schmorp.de/
1297		1839

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Comparing AnyEvent/README (file contents): Revision 1.24 by root, Thu May 29 03:46:04 2008 UTC vs. Revision 1.56 by root, Thu Nov 19 01:55:57 2009 UTC

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Revision 1.24 by root, Thu May 29 03:46:04 2008 UTC vs.
Revision 1.56 by root, Thu Nov 19 01:55:57 2009 UTC