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Comparing AnyEvent/README (file contents):
Revision 1.19 by root, Mon Apr 28 08:02:14 2008 UTC vs.
Revision 1.28 by root, Sat Jul 12 20:45:27 2008 UTC

…		…
1	NAME	1	NAME
2	AnyEvent - provide framework for multiple event loops	2	AnyEvent - provide framework for multiple event loops
3		3
4	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE -	4	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event
5	various supported event loops	5	loops
6		6
7	SYNOPSIS	7	SYNOPSIS
8	use AnyEvent;	8	use AnyEvent;
9		9
10	my $w = AnyEvent->io (fh => $fh, poll => "r\|w", cb => sub {	10	my $w = AnyEvent->io (fh => $fh, poll => "r\|w", cb => sub {
14	my $w = AnyEvent->timer (after => $seconds, cb => sub {	14	my $w = AnyEvent->timer (after => $seconds, cb => sub {
15	...	15	...
16	});	16	});
17		17
18	my $w = AnyEvent->condvar; # stores whether a condition was flagged	18	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		19	$w->send; # wake up current and all future recv's
19	$w->wait; # enters "main loop" till $condvar gets ->broadcast	20	$w->recv; # enters "main loop" till $condvar gets ->send
20	$w->broadcast; # wake up current and all future wait's	21
		22	INTRODUCTION/TUTORIAL
		23	This manpage is mainly a reference manual. If you are interested in a
		24	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
		25	manpage.
21		26
22	WHY YOU SHOULD USE THIS MODULE (OR NOT)	27	WHY YOU SHOULD USE THIS MODULE (OR NOT)
23	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	28	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
24	nowadays. So what is different about AnyEvent?	29	nowadays. So what is different about AnyEvent?
25		30
26	Executive Summary: AnyEvent is compatible, AnyEvent is *free of	31	Executive Summary: AnyEvent is compatible, AnyEvent is *free of
27	policy* and AnyEvent is small and efficient.	32	policy* and AnyEvent is small and efficient.
28		33
29	First and foremost, AnyEvent is not an event model itself, it only	34	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	35	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,	36	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,	37	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.	38	only one event loop can be active at the same time in a process.
34	AnyEvent helps hiding the differences between those event loops.	39	AnyEvent cannot change this, but it can hide the differences between
		40	those event loops.
35		41
36	The goal of AnyEvent is to offer module authors the ability to do event	42	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	43	programming (waiting for I/O or timer events) without subscribing to a
38	religion, a way of living, and most importantly: without forcing your	44	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	45	module users into the same thing by forcing them to use the same event
40	model you use.	46	model you use.
41		47
42	For modules like POE or IO::Async (which is a total misnomer as it is	48	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	49	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	50	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	51	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	52	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.	53	are also forced to use the same event loop you use.
48		54
49	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	55	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	56	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	57	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.	58	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	59	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	60	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	61	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).	62	to AnyEvent, too, so it is future-proof).
57		63
58	In addition to being free of having to use *the one and only true event	64	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	65	model*, AnyEvent also is free of bloat and policy: with POE or similar
60	modules, you get an enourmous amount of code and strict rules you have	66	modules, you get an enormous amount of code and strict rules you have to
61	to follow. AnyEvent, on the other hand, is lean and up to the point, by	67	follow. AnyEvent, on the other hand, is lean and up to the point, by
62	only offering the functionality that is necessary, in as thin as a	68	only offering the functionality that is necessary, in as thin as a
63	wrapper as technically possible.	69	wrapper as technically possible.
64		70
		71	Of course, AnyEvent comes with a big (and fully optional!) toolbox of
		72	useful functionality, such as an asynchronous DNS resolver, 100%
		73	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		74	such as Windows) and lots of real-world knowledge and workarounds for
		75	platform bugs and differences.
		76
65	Of course, if you want lots of policy (this can arguably be somewhat	77	Now, if you do want lots of policy (this can arguably be somewhat
66	useful) and you want to force your users to use the one and only event	78	useful) and you want to force your users to use the one and only event
67	model, you should not use this module.	79	model, you should not use this module.
68		80
69	DESCRIPTION	81	DESCRIPTION
70	AnyEvent provides an identical interface to multiple event loops. This	82	AnyEvent provides an identical interface to multiple event loops. This
…		…
75	The interface itself is vaguely similar, but not identical to the Event	87	The interface itself is vaguely similar, but not identical to the Event
76	module.	88	module.
77		89
78	During the first call of any watcher-creation method, the module tries	90	During the first call of any watcher-creation method, the module tries
79	to detect the currently loaded event loop by probing whether one of the	91	to detect the currently loaded event loop by probing whether one of the
80	following modules is already loaded: Coro::EV, Coro::Event, EV, Event,	92	following modules is already loaded: EV, Event, Glib,
81	Glib, AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found	93	AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is
82	is used. If none are found, the module tries to load these modules	94	used. If none are found, the module tries to load these modules
83	(excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should	95	(excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should
84	always succeed) in the order given. The first one that can be	96	always succeed) in the order given. The first one that can be
85	successfully loaded will be used. If, after this, still none could be	97	successfully loaded will be used. If, after this, still none could be
86	found, AnyEvent will fall back to a pure-perl event loop, which is not	98	found, AnyEvent will fall back to a pure-perl event loop, which is not
87	very efficient, but should work everywhere.	99	very efficient, but should work everywhere.
…		…
99	starts using it, all bets are off. Maybe you should tell their authors	111	starts using it, all bets are off. Maybe you should tell their authors
100	to use AnyEvent so their modules work together with others seamlessly...	112	to use AnyEvent so their modules work together with others seamlessly...
101		113
102	The pure-perl implementation of AnyEvent is called	114	The pure-perl implementation of AnyEvent is called
103	"AnyEvent::Impl::Perl". Like other event modules you can load it	115	"AnyEvent::Impl::Perl". Like other event modules you can load it
104	explicitly.	116	explicitly and enjoy the high availability of that event loop :)
105		117
106	WATCHERS	118	WATCHERS
107	AnyEvent has the central concept of a watcher, which is an object that	119	AnyEvent has the central concept of a watcher, which is an object that
108	stores relevant data for each kind of event you are waiting for, such as	120	stores relevant data for each kind of event you are waiting for, such as
109	the callback to call, the filehandle to watch, etc.	121	the callback to call, the file handle to watch, etc.
110		122
111	These watchers are normal Perl objects with normal Perl lifetime. After	123	These watchers are normal Perl objects with normal Perl lifetime. After
112	creating a watcher it will immediately "watch" for events and invoke the	124	creating a watcher it will immediately "watch" for events and invoke the
113	callback when the event occurs (of course, only when the event model is	125	callback when the event occurs (of course, only when the event model is
114	in control).	126	in control).
…		…
122	Many watchers either are used with "recursion" (repeating timers for	134	Many watchers either are used with "recursion" (repeating timers for
123	example), or need to refer to their watcher object in other ways.	135	example), or need to refer to their watcher object in other ways.
124		136
125	An any way to achieve that is this pattern:	137	An any way to achieve that is this pattern:
126		138
127	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	139	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
128	# you can use $w here, for example to undef it	140	# you can use $w here, for example to undef it
129	undef $w;	141	undef $w;
130	});	142	});
131		143
132	Note that "my $w; $w =" combination. This is necessary because in Perl,	144	Note that "my $w; $w =" combination. This is necessary because in Perl,
133	my variables are only visible after the statement in which they are	145	my variables are only visible after the statement in which they are
134	declared.	146	declared.
135		147
136	I/O WATCHERS	148	I/O WATCHERS
137	You can create an I/O watcher by calling the "AnyEvent->io" method with	149	You can create an I/O watcher by calling the "AnyEvent->io" method with
138	the following mandatory key-value pairs as arguments:	150	the following mandatory key-value pairs as arguments:
139		151
140	"fh" the Perl file handle (not file descriptor) to watch for events.	152	"fh" the Perl file handle (not file descriptor) to watch for events
		153	(AnyEvent might or might not keep a reference to this file handle).
141	"poll" must be a string that is either "r" or "w", which creates a	154	"poll" must be a string that is either "r" or "w", which creates a
142	watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"	155	watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"
143	is the callback to invoke each time the file handle becomes ready.	156	is the callback to invoke each time the file handle becomes ready.
144		157
145	Although the callback might get passed parameters, their value and	158	Although the callback might get passed parameters, their value and
…		…
152		165
153	Some event loops issue spurious readyness notifications, so you should	166	Some event loops issue spurious readyness notifications, so you should
154	always use non-blocking calls when reading/writing from/to your file	167	always use non-blocking calls when reading/writing from/to your file
155	handles.	168	handles.
156		169
157	Example:
158
159	# wait for readability of STDIN, then read a line and disable the watcher	170	Example: wait for readability of STDIN, then read a line and disable the
		171	watcher.
		172
160	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	173	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
161	chomp (my $input = <STDIN>);	174	chomp (my $input = <STDIN>);
162	warn "read: $input\n";	175	warn "read: $input\n";
163	undef $w;	176	undef $w;
164	});	177	});
…		…
173		186
174	Although the callback might get passed parameters, their value and	187	Although the callback might get passed parameters, their value and
175	presence is undefined and you cannot rely on them. Portable AnyEvent	188	presence is undefined and you cannot rely on them. Portable AnyEvent
176	callbacks cannot use arguments passed to time watcher callbacks.	189	callbacks cannot use arguments passed to time watcher callbacks.
177		190
178	The timer callback will be invoked at most once: if you want a repeating	191	The callback will normally be invoked once only. If you specify another
179	timer you have to create a new watcher (this is a limitation by both Tk	192	parameter, "interval", as a strictly positive number (> 0), then the
180	and Glib).	193	callback will be invoked regularly at that interval (in fractional
		194	seconds) after the first invocation. If "interval" is specified with a
		195	false value, then it is treated as if it were missing.
181		196
182	Example:	197	The callback will be rescheduled before invoking the callback, but no
		198	attempt is done to avoid timer drift in most backends, so the interval
		199	is only approximate.
183		200
184	# fire an event after 7.7 seconds	201	Example: fire an event after 7.7 seconds.
		202
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	203	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	204	warn "timeout\n";
187	});	205	});
188		206
189	# to cancel the timer:	207	# to cancel the timer:
190	undef $w;	208	undef $w;
191		209
192	Example 2:
193
194	# fire an event after 0.5 seconds, then roughly every second	210	Example 2: fire an event after 0.5 seconds, then roughly every second.
195	my $w;
196		211
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	212	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		213	warn "timeout\n";
200	};	214	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		215
205	TIMING ISSUES	216	TIMING ISSUES
206	There are two ways to handle timers: based on real time (relative, "fire	217	There are two ways to handle timers: based on real time (relative, "fire
207	in 10 seconds") and based on wallclock time (absolute, "fire at 12	218	in 10 seconds") and based on wallclock time (absolute, "fire at 12
208	o'clock").	219	o'clock").
…		…
220	on wallclock time) timers.	231	on wallclock time) timers.
221		232
222	AnyEvent always prefers relative timers, if available, matching the	233	AnyEvent always prefers relative timers, if available, matching the
223	AnyEvent API.	234	AnyEvent API.
224		235
		236	AnyEvent has two additional methods that return the "current time":
		237
		238	AnyEvent->time
		239	This returns the "current wallclock time" as a fractional number of
		240	seconds since the Epoch (the same thing as "time" or
		241	"Time::HiRes::time" return, and the result is guaranteed to be
		242	compatible with those).
		243
		244	It progresses independently of any event loop processing, i.e. each
		245	call will check the system clock, which usually gets updated
		246	frequently.
		247
		248	AnyEvent->now
		249	This also returns the "current wallclock time", but unlike "time",
		250	above, this value might change only once per event loop iteration,
		251	depending on the event loop (most return the same time as "time",
		252	above). This is the time that AnyEvent's timers get scheduled
		253	against.
		254
		255	*In almost all cases (in all cases if you don't care), this is the
		256	function to call when you want to know the current time.*
		257
		258	This function is also often faster then "AnyEvent->time", and thus
		259	the preferred method if you want some timestamp (for example,
		260	AnyEvent::Handle uses this to update it's activity timeouts).
		261
		262	The rest of this section is only of relevance if you try to be very
		263	exact with your timing, you can skip it without bad conscience.
		264
		265	For a practical example of when these times differ, consider
		266	Event::Lib and EV and the following set-up:
		267
		268	The event loop is running and has just invoked one of your callback
		269	at time=500 (assume no other callbacks delay processing). In your
		270	callback, you wait a second by executing "sleep 1" (blocking the
		271	process for a second) and then (at time=501) you create a relative
		272	timer that fires after three seconds.
		273
		274	With Event::Lib, "AnyEvent->time" and "AnyEvent->now" will both
		275	return 501, because that is the current time, and the timer will be
		276	scheduled to fire at time=504 (501 + 3).
		277
		278	With EV, "AnyEvent->time" returns 501 (as that is the current time),
		279	but "AnyEvent->now" returns 500, as that is the time the last event
		280	processing phase started. With EV, your timer gets scheduled to run
		281	at time=503 (500 + 3).
		282
		283	In one sense, Event::Lib is more exact, as it uses the current time
		284	regardless of any delays introduced by event processing. However,
		285	most callbacks do not expect large delays in processing, so this
		286	causes a higher drift (and a lot more system calls to get the
		287	current time).
		288
		289	In another sense, EV is more exact, as your timer will be scheduled
		290	at the same time, regardless of how long event processing actually
		291	took.
		292
		293	In either case, if you care (and in most cases, you don't), then you
		294	can get whatever behaviour you want with any event loop, by taking
		295	the difference between "AnyEvent->time" and "AnyEvent->now" into
		296	account.
		297
225	SIGNAL WATCHERS	298	SIGNAL WATCHERS
226	You can watch for signals using a signal watcher, "signal" is the signal	299	You can watch for signals using a signal watcher, "signal" is the signal
227	name without any "SIG" prefix, "cb" is the Perl callback to be invoked	300	name in uppercase and without any "SIG" prefix, "cb" is the Perl
228	whenever a signal occurs.	301	callback to be invoked whenever a signal occurs.
229		302
230	Although the callback might get passed parameters, their value and	303	Although the callback might get passed parameters, their value and
231	presence is undefined and you cannot rely on them. Portable AnyEvent	304	presence is undefined and you cannot rely on them. Portable AnyEvent
232	callbacks cannot use arguments passed to signal watcher callbacks.	305	callbacks cannot use arguments passed to signal watcher callbacks.
233		306
234	Multiple signal occurances can be clumped together into one callback	307	Multiple signal occurrences can be clumped together into one callback
235	invocation, and callback invocation will be synchronous. synchronous	308	invocation, and callback invocation will be synchronous. Synchronous
236	means that it might take a while until the signal gets handled by the	309	means that it might take a while until the signal gets handled by the
237	process, but it is guarenteed not to interrupt any other callbacks.	310	process, but it is guaranteed not to interrupt any other callbacks.
238		311
239	The main advantage of using these watchers is that you can share a	312	The main advantage of using these watchers is that you can share a
240	signal between multiple watchers.	313	signal between multiple watchers.
241		314
242	This watcher might use %SIG, so programs overwriting those signals	315	This watcher might use %SIG, so programs overwriting those signals
…		…
269	an AnyEvent program, you have to create at least one watcher before	342	an AnyEvent program, you have to create at least one watcher before
270	you "fork" the child (alternatively, you can call "AnyEvent::detect").	343	you "fork" the child (alternatively, you can call "AnyEvent::detect").
271		344
272	Example: fork a process and wait for it	345	Example: fork a process and wait for it
273		346
274	my $done = AnyEvent->condvar;	347	my $done = AnyEvent->condvar;
275		348
276	AnyEvent::detect; # force event module to be initialised
277
278	my $pid = fork or exit 5;	349	my $pid = fork or exit 5;
279		350
280	my $w = AnyEvent->child (	351	my $w = AnyEvent->child (
281	pid => $pid,	352	pid => $pid,
282	cb => sub {	353	cb => sub {
283	my ($pid, $status) = @_;	354	my ($pid, $status) = @_;
284	warn "pid $pid exited with status $status";	355	warn "pid $pid exited with status $status";
285	$done->broadcast;	356	$done->send;
286	},	357	},
287	);	358	);
288		359
289	# do something else, then wait for process exit	360	# do something else, then wait for process exit
290	$done->wait;	361	$done->recv;
291		362
292	CONDITION VARIABLES	363	CONDITION VARIABLES
		364	If you are familiar with some event loops you will know that all of them
		365	require you to run some blocking "loop", "run" or similar function that
		366	will actively watch for new events and call your callbacks.
		367
		368	AnyEvent is different, it expects somebody else to run the event loop
		369	and will only block when necessary (usually when told by the user).
		370
		371	The instrument to do that is called a "condition variable", so called
		372	because they represent a condition that must become true.
		373
293	Condition variables can be created by calling the "AnyEvent->condvar"	374	Condition variables can be created by calling the "AnyEvent->condvar"
294	method without any arguments.	375	method, usually without arguments. The only argument pair allowed is
		376	"cb", which specifies a callback to be called when the condition
		377	variable becomes true.
295		378
296	A condition variable waits for a condition - precisely that the	379	After creation, the condition variable is "false" until it becomes
297	"->broadcast" method has been called.	380	"true" by calling the "send" method (or calling the condition variable
		381	as if it were a callback, read about the caveats in the description for
		382	the "->send" method).
298		383
299	They are very useful to signal that a condition has been fulfilled, for	384	Condition variables are similar to callbacks, except that you can
		385	optionally wait for them. They can also be called merge points - points
		386	in time where multiple outstanding events have been processed. And yet
		387	another way to call them is transactions - each condition variable can
		388	be used to represent a transaction, which finishes at some point and
		389	delivers a result.
		390
		391	Condition variables are very useful to signal that something has
300	example, if you write a module that does asynchronous http requests,	392	finished, for example, if you write a module that does asynchronous http
301	then a condition variable would be the ideal candidate to signal the	393	requests, then a condition variable would be the ideal candidate to
302	availability of results.	394	signal the availability of results. The user can either act when the
		395	callback is called or can synchronously "->recv" for the results.
303		396
304	You can also use condition variables to block your main program until an	397	You can also use them to simulate traditional event loops - for example,
305	event occurs - for example, you could "->wait" in your main program	398	you can block your main program until an event occurs - for example, you
306	until the user clicks the Quit button in your app, which would	399	could "->recv" in your main program until the user clicks the Quit
307	"->broadcast" the "quit" event.	400	button of your app, which would "->send" the "quit" event.
308		401
309	Note that condition variables recurse into the event loop - if you have	402	Note that condition variables recurse into the event loop - if you have
310	two pirces of code that call "->wait" in a round-robbin fashion, you	403	two pieces of code that call "->recv" in a round-robin fashion, you
311	lose. Therefore, condition variables are good to export to your caller,	404	lose. Therefore, condition variables are good to export to your caller,
312	but you should avoid making a blocking wait yourself, at least in	405	but you should avoid making a blocking wait yourself, at least in
313	callbacks, as this asks for trouble.	406	callbacks, as this asks for trouble.
314		407
315	This object has two methods:	408	Condition variables are represented by hash refs in perl, and the keys
		409	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy
		410	(it is often useful to build your own transaction class on top of
		411	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
		412	it's "new" method in your own "new" method.
316		413
317	$cv->wait	414	There are two "sides" to a condition variable - the "producer side"
		415	which eventually calls "-> send", and the "consumer side", which waits
		416	for the send to occur.
		417
		418	Example: wait for a timer.
		419
		420	# wait till the result is ready
		421	my $result_ready = AnyEvent->condvar;
		422
		423	# do something such as adding a timer
		424	# or socket watcher the calls $result_ready->send
		425	# when the "result" is ready.
		426	# in this case, we simply use a timer:
		427	my $w = AnyEvent->timer (
		428	after => 1,
		429	cb => sub { $result_ready->send },
		430	);
		431
		432	# this "blocks" (while handling events) till the callback
		433	# calls send
		434	$result_ready->recv;
		435
		436	Example: wait for a timer, but take advantage of the fact that condition
		437	variables are also code references.
		438
		439	my $done = AnyEvent->condvar;
		440	my $delay = AnyEvent->timer (after => 5, cb => $done);
		441	$done->recv;
		442
		443	METHODS FOR PRODUCERS
		444	These methods should only be used by the producing side, i.e. the
		445	code/module that eventually sends the signal. Note that it is also the
		446	producer side which creates the condvar in most cases, but it isn't
		447	uncommon for the consumer to create it as well.
		448
		449	$cv->send (...)
		450	Flag the condition as ready - a running "->recv" and all further
		451	calls to "recv" will (eventually) return after this method has been
		452	called. If nobody is waiting the send will be remembered.
		453
		454	If a callback has been set on the condition variable, it is called
		455	immediately from within send.
		456
		457	Any arguments passed to the "send" call will be returned by all
		458	future "->recv" calls.
		459
		460	Condition variables are overloaded so one can call them directly (as
		461	a code reference). Calling them directly is the same as calling
		462	"send". Note, however, that many C-based event loops do not handle
		463	overloading, so as tempting as it may be, passing a condition
		464	variable instead of a callback does not work. Both the pure perl and
		465	EV loops support overloading, however, as well as all functions that
		466	use perl to invoke a callback (as in AnyEvent::Socket and
		467	AnyEvent::DNS for example).
		468
		469	$cv->croak ($error)
		470	Similar to send, but causes all call's to "->recv" to invoke
		471	"Carp::croak" with the given error message/object/scalar.
		472
		473	This can be used to signal any errors to the condition variable
		474	user/consumer.
		475
		476	$cv->begin ([group callback])
		477	$cv->end
		478	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		479
		480	These two methods can be used to combine many transactions/events
		481	into one. For example, a function that pings many hosts in parallel
		482	might want to use a condition variable for the whole process.
		483
		484	Every call to "->begin" will increment a counter, and every call to
		485	"->end" will decrement it. If the counter reaches 0 in "->end", the
		486	(last) callback passed to "begin" will be executed. That callback is
		487	supposed to call "->send", but that is not required. If no
		488	callback was set, "send" will be called without any arguments.
		489
		490	Let's clarify this with the ping example:
		491
		492	my $cv = AnyEvent->condvar;
		493
		494	my %result;
		495	$cv->begin (sub { $cv->send (\%result) });
		496
		497	for my $host (@list_of_hosts) {
		498	$cv->begin;
		499	ping_host_then_call_callback $host, sub {
		500	$result{$host} = ...;
		501	$cv->end;
		502	};
		503	}
		504
		505	$cv->end;
		506
		507	This code fragment supposedly pings a number of hosts and calls
		508	"send" after results for all then have have been gathered - in any
		509	order. To achieve this, the code issues a call to "begin" when it
		510	starts each ping request and calls "end" when it has received some
		511	result for it. Since "begin" and "end" only maintain a counter, the
		512	order in which results arrive is not relevant.
		513
		514	There is an additional bracketing call to "begin" and "end" outside
		515	the loop, which serves two important purposes: first, it sets the
		516	callback to be called once the counter reaches 0, and second, it
		517	ensures that "send" is called even when "no" hosts are being pinged
		518	(the loop doesn't execute once).
		519
		520	This is the general pattern when you "fan out" into multiple
		521	subrequests: use an outer "begin"/"end" pair to set the callback and
		522	ensure "end" is called at least once, and then, for each subrequest
		523	you start, call "begin" and for each subrequest you finish, call
		524	"end".
		525
		526	METHODS FOR CONSUMERS
		527	These methods should only be used by the consuming side, i.e. the code
		528	awaits the condition.
		529
		530	$cv->recv
318	Wait (blocking if necessary) until the "->broadcast" method has been	531	Wait (blocking if necessary) until the "->send" or "->croak" methods
319	called on c<$cv>, while servicing other watchers normally.	532	have been called on c<$cv>, while servicing other watchers normally.
320		533
321	You can only wait once on a condition - additional calls will return	534	You can only wait once on a condition - additional calls are valid
322	immediately.	535	but will return immediately.
		536
		537	If an error condition has been set by calling "->croak", then this
		538	function will call "croak".
		539
		540	In list context, all parameters passed to "send" will be returned,
		541	in scalar context only the first one will be returned.
323		542
324	Not all event models support a blocking wait - some die in that case	543	Not all event models support a blocking wait - some die in that case
325	(programs might want to do that to stay interactive), so *if you are	544	(programs might want to do that to stay interactive), so *if you are
326	using this from a module, never require a blocking wait*, but let	545	using this from a module, never require a blocking wait*, but let
327	the caller decide whether the call will block or not (for example,	546	the caller decide whether the call will block or not (for example,
328	by coupling condition variables with some kind of request results	547	by coupling condition variables with some kind of request results
329	and supporting callbacks so the caller knows that getting the result	548	and supporting callbacks so the caller knows that getting the result
330	will not block, while still suppporting blocking waits if the caller	549	will not block, while still supporting blocking waits if the caller
331	so desires).	550	so desires).
332		551
333	Another reason never to "->wait" in a module is that you cannot	552	Another reason never to "->recv" in a module is that you cannot
334	sensibly have two "->wait"'s in parallel, as that would require	553	sensibly have two "->recv"'s in parallel, as that would require
335	multiple interpreters or coroutines/threads, none of which	554	multiple interpreters or coroutines/threads, none of which
336	"AnyEvent" can supply (the coroutine-aware backends	555	"AnyEvent" can supply.
337	AnyEvent::Impl::CoroEV and AnyEvent::Impl::CoroEvent explicitly
338	support concurrent "->wait"'s from different coroutines, however).
339		556
340	$cv->broadcast	557	The Coro module, however, can and does supply coroutines and, in
341	Flag the condition as ready - a running "->wait" and all further	558	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
342	calls to "wait" will (eventually) return after this method has been	559	versions and also integrates coroutines into AnyEvent, making
343	called. If nobody is waiting the broadcast will be remembered..	560	blocking "->recv" calls perfectly safe as long as they are done from
		561	another coroutine (one that doesn't run the event loop).
344		562
345	Example:	563	You can ensure that "-recv" never blocks by setting a callback and
		564	only calling "->recv" from within that callback (or at a later
		565	time). This will work even when the event loop does not support
		566	blocking waits otherwise.
346		567
347	# wait till the result is ready	568	$bool = $cv->ready
348	my $result_ready = AnyEvent->condvar;	569	Returns true when the condition is "true", i.e. whether "send" or
		570	"croak" have been called.
349		571
350	# do something such as adding a timer	572	$cb = $cv->cb ([new callback])
351	# or socket watcher the calls $result_ready->broadcast	573	This is a mutator function that returns the callback set and
352	# when the "result" is ready.	574	optionally replaces it before doing so.
353	# in this case, we simply use a timer:
354	my $w = AnyEvent->timer (
355	after => 1,
356	cb => sub { $result_ready->broadcast },
357	);
358		575
359	# this "blocks" (while handling events) till the watcher	576	The callback will be called when the condition becomes "true", i.e.
360	# calls broadcast	577	when "send" or "croak" are called, with the only argument being the
361	$result_ready->wait;	578	condition variable itself. Calling "recv" inside the callback or at
		579	any later time is guaranteed not to block.
362		580
363	GLOBAL VARIABLES AND FUNCTIONS	581	GLOBAL VARIABLES AND FUNCTIONS
364	$AnyEvent::MODEL	582	$AnyEvent::MODEL
365	Contains "undef" until the first watcher is being created. Then it	583	Contains "undef" until the first watcher is being created. Then it
366	contains the event model that is being used, which is the name of	584	contains the event model that is being used, which is the name of
…		…
368	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	586	the "AnyEvent::Impl:xxx" modules, but can be any other class in the
369	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).	587	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).
370		588
371	The known classes so far are:	589	The known classes so far are:
372		590
373	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
374	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
375	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	591	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
376	AnyEvent::Impl::Event based on Event, second best choice.	592	AnyEvent::Impl::Event based on Event, second best choice.
		593	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
377	AnyEvent::Impl::Glib based on Glib, third-best choice.	594	AnyEvent::Impl::Glib based on Glib, third-best choice.
378	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
379	AnyEvent::Impl::Tk based on Tk, very bad choice.	595	AnyEvent::Impl::Tk based on Tk, very bad choice.
380	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	596	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
381	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	597	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
382	AnyEvent::Impl::POE based on POE, not generic enough for full support.	598	AnyEvent::Impl::POE based on POE, not generic enough for full support.
383		599
…		…
395	Returns $AnyEvent::MODEL, forcing autodetection of the event model	611	Returns $AnyEvent::MODEL, forcing autodetection of the event model
396	if necessary. You should only call this function right before you	612	if necessary. You should only call this function right before you
397	would have created an AnyEvent watcher anyway, that is, as late as	613	would have created an AnyEvent watcher anyway, that is, as late as
398	possible at runtime.	614	possible at runtime.
399		615
		616	$guard = AnyEvent::post_detect { BLOCK }
		617	Arranges for the code block to be executed as soon as the event
		618	model is autodetected (or immediately if this has already happened).
		619
		620	If called in scalar or list context, then it creates and returns an
		621	object that automatically removes the callback again when it is
		622	destroyed. See Coro::BDB for a case where this is useful.
		623
		624	@AnyEvent::post_detect
		625	If there are any code references in this array (you can "push" to it
		626	before or after loading AnyEvent), then they will called directly
		627	after the event loop has been chosen.
		628
		629	You should check $AnyEvent::MODEL before adding to this array,
		630	though: if it contains a true value then the event loop has already
		631	been detected, and the array will be ignored.
		632
		633	Best use "AnyEvent::post_detect { BLOCK }" instead.
		634
400	WHAT TO DO IN A MODULE	635	WHAT TO DO IN A MODULE
401	As a module author, you should "use AnyEvent" and call AnyEvent methods	636	As a module author, you should "use AnyEvent" and call AnyEvent methods
402	freely, but you should not load a specific event module or rely on it.	637	freely, but you should not load a specific event module or rely on it.
403		638
404	Be careful when you create watchers in the module body - AnyEvent will	639	Be careful when you create watchers in the module body - AnyEvent will
405	decide which event module to use as soon as the first method is called,	640	decide which event module to use as soon as the first method is called,
406	so by calling AnyEvent in your module body you force the user of your	641	so by calling AnyEvent in your module body you force the user of your
407	module to load the event module first.	642	module to load the event module first.
408		643
409	Never call "->wait" on a condition variable unless you know that the	644	Never call "->recv" on a condition variable unless you know that the
410	"->broadcast" method has been called on it already. This is because it	645	"->send" method has been called on it already. This is because it will
411	will stall the whole program, and the whole point of using events is to	646	stall the whole program, and the whole point of using events is to stay
412	stay interactive.	647	interactive.
413		648
414	It is fine, however, to call "->wait" when the user of your module	649	It is fine, however, to call "->recv" when the user of your module
415	requests it (i.e. if you create a http request object ad have a method	650	requests it (i.e. if you create a http request object ad have a method
416	called "results" that returns the results, it should call "->wait"	651	called "results" that returns the results, it should call "->recv"
417	freely, as the user of your module knows what she is doing. always).	652	freely, as the user of your module knows what she is doing. always).
418		653
419	WHAT TO DO IN THE MAIN PROGRAM	654	WHAT TO DO IN THE MAIN PROGRAM
420	There will always be a single main program - the only place that should	655	There will always be a single main program - the only place that should
421	dictate which event model to use.	656	dictate which event model to use.
…		…
423	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	658	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
424	do anything special (it does not need to be event-based) and let	659	do anything special (it does not need to be event-based) and let
425	AnyEvent decide which implementation to chose if some module relies on	660	AnyEvent decide which implementation to chose if some module relies on
426	it.	661	it.
427		662
428	If the main program relies on a specific event model. For example, in	663	If the main program relies on a specific event model - for example, in
429	Gtk2 programs you have to rely on the Glib module. You should load the	664	Gtk2 programs you have to rely on the Glib module - you should load the
430	event module before loading AnyEvent or any module that uses it:	665	event module before loading AnyEvent or any module that uses it:
431	generally speaking, you should load it as early as possible. The reason	666	generally speaking, you should load it as early as possible. The reason
432	is that modules might create watchers when they are loaded, and AnyEvent	667	is that modules might create watchers when they are loaded, and AnyEvent
433	will decide on the event model to use as soon as it creates watchers,	668	will decide on the event model to use as soon as it creates watchers,
434	and it might chose the wrong one unless you load the correct one	669	and it might chose the wrong one unless you load the correct one
435	yourself.	670	yourself.
436		671
437	You can chose to use a rather inefficient pure-perl implementation by	672	You can chose to use a pure-perl implementation by loading the
438	loading the "AnyEvent::Impl::Perl" module, which gives you similar	673	"AnyEvent::Impl::Perl" module, which gives you similar behaviour
439	behaviour everywhere, but letting AnyEvent chose is generally better.	674	everywhere, but letting AnyEvent chose the model is generally better.
		675
		676	MAINLOOP EMULATION
		677	Sometimes (often for short test scripts, or even standalone programs who
		678	only want to use AnyEvent), you do not want to run a specific event
		679	loop.
		680
		681	In that case, you can use a condition variable like this:
		682
		683	AnyEvent->condvar->recv;
		684
		685	This has the effect of entering the event loop and looping forever.
		686
		687	Note that usually your program has some exit condition, in which case it
		688	is better to use the "traditional" approach of storing a condition
		689	variable somewhere, waiting for it, and sending it when the program
		690	should exit cleanly.
440		691
441	OTHER MODULES	692	OTHER MODULES
442	The following is a non-exhaustive list of additional modules that use	693	The following is a non-exhaustive list of additional modules that use
443	AnyEvent and can therefore be mixed easily with other AnyEvent modules	694	AnyEvent and can therefore be mixed easily with other AnyEvent modules
444	in the same program. Some of the modules come with AnyEvent, some are	695	in the same program. Some of the modules come with AnyEvent, some are
…		…
447	AnyEvent::Util	698	AnyEvent::Util
448	Contains various utility functions that replace often-used but	699	Contains various utility functions that replace often-used but
449	blocking functions such as "inet_aton" by event-/callback-based	700	blocking functions such as "inet_aton" by event-/callback-based
450	versions.	701	versions.
451		702
		703	AnyEvent::Socket
		704	Provides various utility functions for (internet protocol) sockets,
		705	addresses and name resolution. Also functions to create non-blocking
		706	tcp connections or tcp servers, with IPv6 and SRV record support and
		707	more.
		708
452	AnyEvent::Handle	709	AnyEvent::Handle
453	Provide read and write buffers and manages watchers for reads and	710	Provide read and write buffers, manages watchers for reads and
454	writes.	711	writes, supports raw and formatted I/O, I/O queued and fully
		712	transparent and non-blocking SSL/TLS.
455		713
456	AnyEvent::Socket	714	AnyEvent::DNS
457	Provides a means to do non-blocking connects, accepts etc.	715	Provides rich asynchronous DNS resolver capabilities.
		716
		717	AnyEvent::HTTP
		718	A simple-to-use HTTP library that is capable of making a lot of
		719	concurrent HTTP requests.
458		720
459	AnyEvent::HTTPD	721	AnyEvent::HTTPD
460	Provides a simple web application server framework.	722	Provides a simple web application server framework.
461		723
462	AnyEvent::DNS
463	Provides asynchronous DNS resolver capabilities, beyond what
464	AnyEvent::Util offers.
465
466	AnyEvent::FastPing	724	AnyEvent::FastPing
467	The fastest ping in the west.	725	The fastest ping in the west.
		726
		727	AnyEvent::DBI
		728	Executes DBI requests asynchronously in a proxy process.
		729
		730	AnyEvent::AIO
		731	Truly asynchronous I/O, should be in the toolbox of every event
		732	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		733	together.
		734
		735	AnyEvent::BDB
		736	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
		737	fuses BDB and AnyEvent together.
		738
		739	AnyEvent::GPSD
		740	A non-blocking interface to gpsd, a daemon delivering GPS
		741	information.
		742
		743	AnyEvent::IGS
		744	A non-blocking interface to the Internet Go Server protocol (used by
		745	App::IGS).
468		746
469	Net::IRC3	747	Net::IRC3
470	AnyEvent based IRC client module family.	748	AnyEvent based IRC client module family.
471		749
472	Net::XMPP2	750	Net::XMPP2
…		…
478		756
479	Event::ExecFlow	757	Event::ExecFlow
480	High level API for event-based execution flow control.	758	High level API for event-based execution flow control.
481		759
482	Coro	760	Coro
483	Has special support for AnyEvent.	761	Has special support for AnyEvent via Coro::AnyEvent.
484		762
485	IO::Lambda	763	IO::Lambda
486	The lambda approach to I/O - don't ask, look there. Can use	764	The lambda approach to I/O - don't ask, look there. Can use
487	AnyEvent.
488
489	IO::AIO
490	Truly asynchronous I/O, should be in the toolbox of every event
491	programmer. Can be trivially made to use AnyEvent.
492
493	BDB Truly asynchronous Berkeley DB access. Can be trivially made to use
494	AnyEvent.	765	AnyEvent.
495		766
496	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	767	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
497	This is an advanced topic that you do not normally need to use AnyEvent	768	This is an advanced topic that you do not normally need to use AnyEvent
498	in a module. This section is only of use to event loop authors who want	769	in a module. This section is only of use to event loop authors who want
…		…
549	by "PERL_ANYEVENT_MODEL".	820	by "PERL_ANYEVENT_MODEL".
550		821
551	When set to 2 or higher, cause AnyEvent to report to STDERR which	822	When set to 2 or higher, cause AnyEvent to report to STDERR which
552	event model it chooses.	823	event model it chooses.
553		824
		825	"PERL_ANYEVENT_STRICT"
		826	AnyEvent does not do much argument checking by default, as thorough
		827	argument checking is very costly. Setting this variable to a true
		828	value will cause AnyEvent to load "AnyEvent::Strict" and then to
		829	thoroughly check the arguments passed to most method calls. If it
		830	finds any problems it will croak.
		831
		832	In other words, enables "strict" mode.
		833
		834	Unlike "use strict" it is definitely recommended ot keep it off in
		835	production.
		836
554	"PERL_ANYEVENT_MODEL"	837	"PERL_ANYEVENT_MODEL"
555	This can be used to specify the event model to be used by AnyEvent,	838	This can be used to specify the event model to be used by AnyEvent,
556	before autodetection and -probing kicks in. It must be a string	839	before auto detection and -probing kicks in. It must be a string
557	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	840	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
558	gets prepended and the resulting module name is loaded and if the	841	gets prepended and the resulting module name is loaded and if the
559	load was successful, used as event model. If it fails to load	842	load was successful, used as event model. If it fails to load
560	AnyEvent will proceed with autodetection and -probing.	843	AnyEvent will proceed with auto detection and -probing.
561		844
562	This functionality might change in future versions.	845	This functionality might change in future versions.
563		846
564	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	847	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
565	could start your program like this:	848	could start your program like this:
566		849
567	PERL_ANYEVENT_MODEL=Perl perl ...	850	PERL_ANYEVENT_MODEL=Perl perl ...
		851
		852	"PERL_ANYEVENT_PROTOCOLS"
		853	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
		854	preferences for IPv4 or IPv6. The default is unspecified (and might
		855	change, or be the result of auto probing).
		856
		857	Must be set to a comma-separated list of protocols or address
		858	families, current supported: "ipv4" and "ipv6". Only protocols
		859	mentioned will be used, and preference will be given to protocols
		860	mentioned earlier in the list.
		861
		862	This variable can effectively be used for denial-of-service attacks
		863	against local programs (e.g. when setuid), although the impact is
		864	likely small, as the program has to handle connection errors
		865	already-
		866
		867	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
		868	IPv6, but support both and try to use both.
		869	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
		870	resolve or contact IPv6 addresses.
		871	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
		872	prefer IPv6 over IPv4.
		873
		874	"PERL_ANYEVENT_EDNS0"
		875	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
		876	for DNS. This extension is generally useful to reduce DNS traffic,
		877	but some (broken) firewalls drop such DNS packets, which is why it
		878	is off by default.
		879
		880	Setting this variable to 1 will cause AnyEvent::DNS to announce
		881	EDNS0 in its DNS requests.
		882
		883	"PERL_ANYEVENT_MAX_FORKS"
		884	The maximum number of child processes that
		885	"AnyEvent::Util::fork_call" will create in parallel.
568		886
569	EXAMPLE PROGRAM	887	EXAMPLE PROGRAM
570	The following program uses an I/O watcher to read data from STDIN, a	888	The following program uses an I/O watcher to read data from STDIN, a
571	timer to display a message once per second, and a condition variable to	889	timer to display a message once per second, and a condition variable to
572	quit the program when the user enters quit:	890	quit the program when the user enters quit:
…		…
580	poll => 'r',	898	poll => 'r',
581	cb => sub {	899	cb => sub {
582	warn "io event <$_[0]>\n"; # will always output <r>	900	warn "io event <$_[0]>\n"; # will always output <r>
583	chomp (my $input = <STDIN>); # read a line	901	chomp (my $input = <STDIN>); # read a line
584	warn "read: $input\n"; # output what has been read	902	warn "read: $input\n"; # output what has been read
585	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	903	$cv->send if $input =~ /^q/i; # quit program if /^q/i
586	},	904	},
587	);	905	);
588		906
589	my $time_watcher; # can only be used once	907	my $time_watcher; # can only be used once
590		908
…		…
595	});	913	});
596	}	914	}
597		915
598	new_timer; # create first timer	916	new_timer; # create first timer
599		917
600	$cv->wait; # wait until user enters /^q/i	918	$cv->recv; # wait until user enters /^q/i
601		919
602	REAL-WORLD EXAMPLE	920	REAL-WORLD EXAMPLE
603	Consider the Net::FCP module. It features (among others) the following	921	Consider the Net::FCP module. It features (among others) the following
604	API calls, which are to freenet what HTTP GET requests are to http:	922	API calls, which are to freenet what HTTP GET requests are to http:
605		923
…		…
654	syswrite $txn->{fh}, $txn->{request}	972	syswrite $txn->{fh}, $txn->{request}
655	or die "connection or write error";	973	or die "connection or write error";
656	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	974	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
657		975
658	Again, "fh_ready_r" waits till all data has arrived, and then stores the	976	Again, "fh_ready_r" waits till all data has arrived, and then stores the
659	result and signals any possible waiters that the request ahs finished:	977	result and signals any possible waiters that the request has finished:
660		978
661	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	979	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
662		980
663	if (end-of-file or data complete) {	981	if (end-of-file or data complete) {
664	$txn->{result} = $txn->{buf};	982	$txn->{result} = $txn->{buf};
665	$txn->{finished}->broadcast;	983	$txn->{finished}->send;
666	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	984	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
667	}	985	}
668		986
669	The "result" method, finally, just waits for the finished signal (if the	987	The "result" method, finally, just waits for the finished signal (if the
670	request was already finished, it doesn't wait, of course, and returns	988	request was already finished, it doesn't wait, of course, and returns
671	the data:	989	the data:
672		990
673	$txn->{finished}->wait;	991	$txn->{finished}->recv;
674	return $txn->{result};	992	return $txn->{result};
675		993
676	The actual code goes further and collects all errors ("die"s,	994	The actual code goes further and collects all errors ("die"s,
677	exceptions) that occured during request processing. The "result" method	995	exceptions) that occurred during request processing. The "result" method
678	detects whether an exception as thrown (it is stored inside the $txn	996	detects whether an exception as thrown (it is stored inside the $txn
679	object) and just throws the exception, which means connection errors and	997	object) and just throws the exception, which means connection errors and
680	other problems get reported tot he code that tries to use the result,	998	other problems get reported tot he code that tries to use the result,
681	not in a random callback.	999	not in a random callback.
682		1000
…		…
713		1031
714	my $quit = AnyEvent->condvar;	1032	my $quit = AnyEvent->condvar;
715		1033
716	$fcp->txn_client_get ($url)->cb (sub {	1034	$fcp->txn_client_get ($url)->cb (sub {
717	...	1035	...
718	$quit->broadcast;	1036	$quit->send;
719	});	1037	});
720		1038
721	$quit->wait;	1039	$quit->recv;
722		1040
723	BENCHMARKS	1041	BENCHMARKS
724	To give you an idea of the performance and overheads that AnyEvent adds	1042	To give you an idea of the performance and overheads that AnyEvent adds
725	over the event loops themselves and to give you an impression of the	1043	over the event loops themselves and to give you an impression of the
726	speed of various event loops I prepared some benchmarks.	1044	speed of various event loops I prepared some benchmarks.
727		1045
728	BENCHMARKING ANYEVENT OVERHEAD	1046	BENCHMARKING ANYEVENT OVERHEAD
729	Here is a benchmark of various supported event models used natively and	1047	Here is a benchmark of various supported event models used natively and
730	through anyevent. The benchmark creates a lot of timers (with a zero	1048	through AnyEvent. The benchmark creates a lot of timers (with a zero
731	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1049	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
732	which it is), lets them fire exactly once and destroys them again.	1050	which it is), lets them fire exactly once and destroys them again.
733		1051
734	Source code for this benchmark is found as eg/bench in the AnyEvent	1052	Source code for this benchmark is found as eg/bench in the AnyEvent
735	distribution.	1053	distribution.
…		…
751	between all watchers, to avoid adding memory overhead. That means	1069	between all watchers, to avoid adding memory overhead. That means
752	closure creation and memory usage is not included in the figures.	1070	closure creation and memory usage is not included in the figures.
753		1071
754	invoke is the time, in microseconds, used to invoke a simple callback.	1072	invoke is the time, in microseconds, used to invoke a simple callback.
755	The callback simply counts down a Perl variable and after it was invoked	1073	The callback simply counts down a Perl variable and after it was invoked
756	"watcher" times, it would "->broadcast" a condvar once to signal the end	1074	"watcher" times, it would "->send" a condvar once to signal the end of
757	of this phase.	1075	this phase.
758		1076
759	destroy is the time, in microseconds, that it takes to destroy a	1077	destroy is the time, in microseconds, that it takes to destroy a
760	single watcher.	1078	single watcher.
761		1079
762	Results	1080	Results
…		…
823	the figures above).	1141	the figures above).
824		1142
825	"POE", regardless of underlying event loop (whether using its pure perl	1143	"POE", regardless of underlying event loop (whether using its pure perl
826	select-based backend or the Event module, the POE-EV backend couldn't be	1144	select-based backend or the Event module, the POE-EV backend couldn't be
827	tested because it wasn't working) shows abysmal performance and memory	1145	tested because it wasn't working) shows abysmal performance and memory
828	usage: Watchers use almost 30 times as much memory as EV watchers, and	1146	usage with AnyEvent: Watchers use almost 30 times as much memory as EV
829	10 times as much memory as Event (the high memory requirements are	1147	watchers, and 10 times as much memory as Event (the high memory
830	caused by requiring a session for each watcher). Watcher invocation	1148	requirements are caused by requiring a session for each watcher).
831	speed is almost 900 times slower than with AnyEvent's pure perl	1149	Watcher invocation speed is almost 900 times slower than with AnyEvent's
		1150	pure perl implementation.
		1151
832	implementation. The design of the POE adaptor class in AnyEvent can not	1152	The design of the POE adaptor class in AnyEvent can not really account
833	really account for this, as session creation overhead is small compared	1153	for the performance issues, though, as session creation overhead is
834	to execution of the state machine, which is coded pretty optimally	1154	small compared to execution of the state machine, which is coded pretty
835	within AnyEvent::Impl::POE. POE simply seems to be abysmally slow.	1155	optimally within AnyEvent::Impl::POE (and while everybody agrees that
		1156	using multiple sessions is not a good approach, especially regarding
		1157	memory usage, even the author of POE could not come up with a faster
		1158	design).
836		1159
837	Summary	1160	Summary
838	* Using EV through AnyEvent is faster than any other event loop (even	1161	* Using EV through AnyEvent is faster than any other event loop (even
839	when used without AnyEvent), but most event loops have acceptable	1162	when used without AnyEvent), but most event loops have acceptable
840	performance with or without AnyEvent.	1163	performance with or without AnyEvent.
…		…
845		1168
846	* You should avoid POE like the plague if you want performance or	1169	* You should avoid POE like the plague if you want performance or
847	reasonable memory usage.	1170	reasonable memory usage.
848		1171
849	BENCHMARKING THE LARGE SERVER CASE	1172	BENCHMARKING THE LARGE SERVER CASE
850	This benchmark atcually benchmarks the event loop itself. It works by	1173	This benchmark actually benchmarks the event loop itself. It works by
851	creating a number of "servers": each server consists of a socketpair, a	1174	creating a number of "servers": each server consists of a socket pair, a
852	timeout watcher that gets reset on activity (but never fires), and an	1175	timeout watcher that gets reset on activity (but never fires), and an
853	I/O watcher waiting for input on one side of the socket. Each time the	1176	I/O watcher waiting for input on one side of the socket. Each time the
854	socket watcher reads a byte it will write that byte to a random other	1177	socket watcher reads a byte it will write that byte to a random other
855	"server".	1178	"server".
856		1179
857	The effect is that there will be a lot of I/O watchers, only part of	1180	The effect is that there will be a lot of I/O watchers, only part of
858	which are active at any one point (so there is a constant number of	1181	which are active at any one point (so there is a constant number of
859	active fds for each loop iterstaion, but which fds these are is random).	1182	active fds for each loop iteration, but which fds these are is random).
860	The timeout is reset each time something is read because that reflects	1183	The timeout is reset each time something is read because that reflects
861	how most timeouts work (and puts extra pressure on the event loops).	1184	how most timeouts work (and puts extra pressure on the event loops).
862		1185
863	In this benchmark, we use 10000 socketpairs (20000 sockets), of which	1186	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
864	100 (1%) are active. This mirrors the activity of large servers with	1187	100 (1%) are active. This mirrors the activity of large servers with
865	many connections, most of which are idle at any one point in time.	1188	many connections, most of which are idle at any one point in time.
866		1189
867	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1190	Source code for this benchmark is found as eg/bench2 in the AnyEvent
868	distribution.	1191	distribution.
869		1192
870	Explanation of the columns	1193	Explanation of the columns
871	sockets is the number of sockets, and twice the number of "servers"	1194	sockets is the number of sockets, and twice the number of "servers"
872	(as each server has a read and write socket end).	1195	(as each server has a read and write socket end).
873		1196
874	create is the time it takes to create a socketpair (which is	1197	create is the time it takes to create a socket pair (which is
875	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	1198	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
876		1199
877	request, the most important value, is the time it takes to handle a	1200	request, the most important value, is the time it takes to handle a
878	single "request", that is, reading the token from the pipe and	1201	single "request", that is, reading the token from the pipe and
879	forwarding it to another server. This includes deleting the old timeout	1202	forwarding it to another server. This includes deleting the old timeout
…		…
909	POE is still completely out of the picture, taking over 1000 times as	1232	POE is still completely out of the picture, taking over 1000 times as
910	long as EV, and over 100 times as long as the Perl implementation, even	1233	long as EV, and over 100 times as long as the Perl implementation, even
911	though it uses a C-based event loop in this case.	1234	though it uses a C-based event loop in this case.
912		1235
913	Summary	1236	Summary
914	* The pure perl implementation performs extremely well, considering	1237	* The pure perl implementation performs extremely well.
915	that it uses select.
916		1238
917	* Avoid Glib or POE in large projects where performance matters.	1239	* Avoid Glib or POE in large projects where performance matters.
918		1240
919	BENCHMARKING SMALL SERVERS	1241	BENCHMARKING SMALL SERVERS
920	While event loops should scale (and select-based ones do not...) even to	1242	While event loops should scale (and select-based ones do not...) even to
…		…
944	and speed most when you have lots of watchers, not when you only have a	1266	and speed most when you have lots of watchers, not when you only have a
945	few of them).	1267	few of them).
946		1268
947	EV is again fastest.	1269	EV is again fastest.
948		1270
949	Perl again comes second. It is noticably faster than the C-based event	1271	Perl again comes second. It is noticeably faster than the C-based event
950	loops Event and Glib, although the difference is too small to really	1272	loops Event and Glib, although the difference is too small to really
951	matter.	1273	matter.
952		1274
953	POE also performs much better in this case, but is is still far behind	1275	POE also performs much better in this case, but is is still far behind
954	the others.	1276	the others.
…		…
957	* C-based event loops perform very well with small number of watchers,	1279	* C-based event loops perform very well with small number of watchers,
958	as the management overhead dominates.	1280	as the management overhead dominates.
959		1281
960	FORK	1282	FORK
961	Most event libraries are not fork-safe. The ones who are usually are	1283	Most event libraries are not fork-safe. The ones who are usually are
962	because they are so inefficient. Only EV is fully fork-aware.	1284	because they rely on inefficient but fork-safe "select" or "poll" calls.
		1285	Only EV is fully fork-aware.
963		1286
964	If you have to fork, you must either do so before creating your first	1287	If you have to fork, you must either do so before creating your first
965	watcher OR you must not use AnyEvent at all in the child.	1288	watcher OR you must not use AnyEvent at all in the child.
966		1289
967	SECURITY CONSIDERATIONS	1290	SECURITY CONSIDERATIONS
…		…
973	model than specified in the variable.	1296	model than specified in the variable.
974		1297
975	You can make AnyEvent completely ignore this variable by deleting it	1298	You can make AnyEvent completely ignore this variable by deleting it
976	before the first watcher gets created, e.g. with a "BEGIN" block:	1299	before the first watcher gets created, e.g. with a "BEGIN" block:
977		1300
978	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1301	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
979		1302
980	use AnyEvent;	1303	use AnyEvent;
		1304
		1305	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1306	be used to probe what backend is used and gain other information (which
		1307	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
		1308	and $ENV{PERL_ANYEGENT_STRICT}.
		1309
		1310	BUGS
		1311	Perl 5.8 has numerous memleaks that sometimes hit this module and are
		1312	hard to work around. If you suffer from memleaks, first upgrade to Perl
		1313	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
		1314	annoying mamleaks, such as leaking on "map" and "grep" but it is usually
		1315	not as pronounced).
981		1316
982	SEE ALSO	1317	SEE ALSO
983	Event modules: Coro::EV, EV, EV::Glib, Glib::EV, Coro::Event, Event,	1318	Utility functions: AnyEvent::Util.
984	Glib::Event, Glib, Coro, Tk, Event::Lib, Qt, POE.
985		1319
986	Implementations: AnyEvent::Impl::CoroEV, AnyEvent::Impl::EV,	1320	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
987	AnyEvent::Impl::CoroEvent, AnyEvent::Impl::Event, AnyEvent::Impl::Glib,	1321	Event::Lib, Qt, POE.
988	AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, AnyEvent::Impl::EventLib,	1322
		1323	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
		1324	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
989	AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1325	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.
990		1326
		1327	Non-blocking file handles, sockets, TCP clients and servers:
		1328	AnyEvent::Handle, AnyEvent::Socket.
		1329
		1330	Asynchronous DNS: AnyEvent::DNS.
		1331
		1332	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
		1333
991	Nontrivial usage examples: Net::FCP, Net::XMPP2.	1334	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.
992		1335
993	AUTHOR	1336	AUTHOR
994	Marc Lehmann <schmorp@schmorp.de>	1337	Marc Lehmann <schmorp@schmorp.de>
995	http://home.schmorp.de/	1338	http://home.schmorp.de/
996		1339

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Comparing AnyEvent/README (file contents): Revision 1.19 by root, Mon Apr 28 08:02:14 2008 UTC vs. Revision 1.28 by root, Sat Jul 12 20:45:27 2008 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.19 by root, Mon Apr 28 08:02:14 2008 UTC vs.
Revision 1.28 by root, Sat Jul 12 20:45:27 2008 UTC