[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.21 by root, Sat May 17 21:34:15 2008 UTC vs.
Revision 1.36 by root, Fri Mar 27 10:49:50 2009 UTC

…		…
5	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 { ... });
11	...
12	});
13		11
14	my $w = AnyEvent->timer (after => $seconds, cb => sub {	12	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		13	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		14
		15	print AnyEvent->now; # prints current event loop time
		16	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		17
		18	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		19
		20	my $w = AnyEvent->child (pid => $pid, cb => sub {
		21	my ($pid, $status) = @_;
15	...	22	...
16	});	23	});
17		24
18	my $w = AnyEvent->condvar; # stores whether a condition was flagged	25	my $w = AnyEvent->condvar; # stores whether a condition was flagged
19	$w->send; # wake up current and all future recv's	26	$w->send; # wake up current and all future recv's
20	$w->recv; # enters "main loop" till $condvar gets ->send	27	$w->recv; # enters "main loop" till $condvar gets ->send
		28	# use a condvar in callback mode:
		29	$w->cb (sub { $_[0]->recv });
		30
		31	INTRODUCTION/TUTORIAL
		32	This manpage is mainly a reference manual. If you are interested in a
		33	tutorial or some gentle introduction, have a look at the AnyEvent::Intro
		34	manpage.
21		35
22	WHY YOU SHOULD USE THIS MODULE (OR NOT)	36	WHY YOU SHOULD USE THIS MODULE (OR NOT)
23	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	37	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
24	nowadays. So what is different about AnyEvent?	38	nowadays. So what is different about AnyEvent?
25		39
26	Executive Summary: AnyEvent is compatible, AnyEvent is *free of	40	Executive Summary: AnyEvent is compatible, AnyEvent is *free of
27	policy* and AnyEvent is small and efficient.	41	policy* and AnyEvent is small and efficient.
28		42
29	First and foremost, AnyEvent is not an event model itself, it only	43	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	44	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,	45	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,	46	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.	47	only one event loop can be active at the same time in a process.
34	AnyEvent helps hiding the differences between those event loops.	48	AnyEvent cannot change this, but it can hide the differences between
		49	those event loops.
35		50
36	The goal of AnyEvent is to offer module authors the ability to do event	51	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	52	programming (waiting for I/O or timer events) without subscribing to a
38	religion, a way of living, and most importantly: without forcing your	53	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	54	module users into the same thing by forcing them to use the same event
40	model you use.	55	model you use.
41		56
42	For modules like POE or IO::Async (which is a total misnomer as it is	57	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	58	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	59	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	60	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	61	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.	62	are also forced to use the same event loop you use.
48		63
49	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	64	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	65	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	66	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.	67	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	68	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	69	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	70	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).	71	to AnyEvent, too, so it is future-proof).
57		72
58	In addition to being free of having to use *the one and only true event	73	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	74	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	75	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	76	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	77	only offering the functionality that is necessary, in as thin as a
63	wrapper as technically possible.	78	wrapper as technically possible.
64		79
		80	Of course, AnyEvent comes with a big (and fully optional!) toolbox of
		81	useful functionality, such as an asynchronous DNS resolver, 100%
		82	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		83	such as Windows) and lots of real-world knowledge and workarounds for
		84	platform bugs and differences.
		85
65	Of course, if you want lots of policy (this can arguably be somewhat	86	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	87	useful) and you want to force your users to use the one and only event
67	model, you should not use this module.	88	model, you should not use this module.
68		89
69	DESCRIPTION	90	DESCRIPTION
70	AnyEvent provides an identical interface to multiple event loops. This	91	AnyEvent provides an identical interface to multiple event loops. This
…		…
99	starts using it, all bets are off. Maybe you should tell their authors	120	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...	121	to use AnyEvent so their modules work together with others seamlessly...
101		122
102	The pure-perl implementation of AnyEvent is called	123	The pure-perl implementation of AnyEvent is called
103	"AnyEvent::Impl::Perl". Like other event modules you can load it	124	"AnyEvent::Impl::Perl". Like other event modules you can load it
104	explicitly.	125	explicitly and enjoy the high availability of that event loop :)
105		126
106	WATCHERS	127	WATCHERS
107	AnyEvent has the central concept of a watcher, which is an object that	128	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	129	stores relevant data for each kind of event you are waiting for, such as
109	the callback to call, the filehandle to watch, etc.	130	the callback to call, the file handle to watch, etc.
110		131
111	These watchers are normal Perl objects with normal Perl lifetime. After	132	These watchers are normal Perl objects with normal Perl lifetime. After
112	creating a watcher it will immediately "watch" for events and invoke the	133	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	134	callback when the event occurs (of course, only when the event model is
114	in control).	135	in control).
115		136
		137	Note that callbacks must not permanently change global variables
		138	potentially in use by the event loop (such as $_ or $[) and that
		139	callbacks must not "die". The former is good programming practise in
		140	Perl and the latter stems from the fact that exception handling differs
		141	widely between event loops.
		142
116	To disable the watcher you have to destroy it (e.g. by setting the	143	To disable the watcher you have to destroy it (e.g. by setting the
117	variable you store it in to "undef" or otherwise deleting all references	144	variable you store it in to "undef" or otherwise deleting all references
118	to it).	145	to it).
119		146
120	All watchers are created by calling a method on the "AnyEvent" class.	147	All watchers are created by calling a method on the "AnyEvent" class.
…		…
122	Many watchers either are used with "recursion" (repeating timers for	149	Many watchers either are used with "recursion" (repeating timers for
123	example), or need to refer to their watcher object in other ways.	150	example), or need to refer to their watcher object in other ways.
124		151
125	An any way to achieve that is this pattern:	152	An any way to achieve that is this pattern:
126		153
127	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	154	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
128	# you can use $w here, for example to undef it	155	# you can use $w here, for example to undef it
129	undef $w;	156	undef $w;
130	});	157	});
131		158
132	Note that "my $w; $w =" combination. This is necessary because in Perl,	159	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	160	my variables are only visible after the statement in which they are
134	declared.	161	declared.
135		162
136	I/O WATCHERS	163	I/O WATCHERS
137	You can create an I/O watcher by calling the "AnyEvent->io" method with	164	You can create an I/O watcher by calling the "AnyEvent->io" method with
138	the following mandatory key-value pairs as arguments:	165	the following mandatory key-value pairs as arguments:
139		166
140	"fh" the Perl file handle (not file descriptor) to watch for events.	167	"fh" is the Perl file handle (not file descriptor) to watch for
		168	events (AnyEvent might or might not keep a reference to this file
		169	handle). Note that only file handles pointing to things for which
		170	non-blocking operation makes sense are allowed. This includes sockets,
		171	most character devices, pipes, fifos and so on, but not for example
		172	files or block devices.
		173
141	"poll" must be a string that is either "r" or "w", which creates a	174	"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"	175	watcher waiting for "r"eadable or "w"ritable events, respectively.
		176
143	is the callback to invoke each time the file handle becomes ready.	177	"cb" is the callback to invoke each time the file handle becomes ready.
144		178
145	Although the callback might get passed parameters, their value and	179	Although the callback might get passed parameters, their value and
146	presence is undefined and you cannot rely on them. Portable AnyEvent	180	presence is undefined and you cannot rely on them. Portable AnyEvent
147	callbacks cannot use arguments passed to I/O watcher callbacks.	181	callbacks cannot use arguments passed to I/O watcher callbacks.
148		182
…		…
152		186
153	Some event loops issue spurious readyness notifications, so you should	187	Some event loops issue spurious readyness notifications, so you should
154	always use non-blocking calls when reading/writing from/to your file	188	always use non-blocking calls when reading/writing from/to your file
155	handles.	189	handles.
156		190
157	Example:
158
159	# wait for readability of STDIN, then read a line and disable the watcher	191	Example: wait for readability of STDIN, then read a line and disable the
		192	watcher.
		193
160	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	194	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
161	chomp (my $input = <STDIN>);	195	chomp (my $input = <STDIN>);
162	warn "read: $input\n";	196	warn "read: $input\n";
163	undef $w;	197	undef $w;
164	});	198	});
…		…
173		207
174	Although the callback might get passed parameters, their value and	208	Although the callback might get passed parameters, their value and
175	presence is undefined and you cannot rely on them. Portable AnyEvent	209	presence is undefined and you cannot rely on them. Portable AnyEvent
176	callbacks cannot use arguments passed to time watcher callbacks.	210	callbacks cannot use arguments passed to time watcher callbacks.
177		211
178	The timer callback will be invoked at most once: if you want a repeating	212	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	213	parameter, "interval", as a strictly positive number (> 0), then the
180	and Glib).	214	callback will be invoked regularly at that interval (in fractional
		215	seconds) after the first invocation. If "interval" is specified with a
		216	false value, then it is treated as if it were missing.
181		217
182	Example:	218	The callback will be rescheduled before invoking the callback, but no
		219	attempt is done to avoid timer drift in most backends, so the interval
		220	is only approximate.
183		221
184	# fire an event after 7.7 seconds	222	Example: fire an event after 7.7 seconds.
		223
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	224	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	225	warn "timeout\n";
187	});	226	});
188		227
189	# to cancel the timer:	228	# to cancel the timer:
190	undef $w;	229	undef $w;
191		230
192	Example 2:
193
194	# fire an event after 0.5 seconds, then roughly every second	231	Example 2: fire an event after 0.5 seconds, then roughly every second.
195	my $w;
196		232
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	233	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		234	warn "timeout\n";
200	};	235	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		236
205	TIMING ISSUES	237	TIMING ISSUES
206	There are two ways to handle timers: based on real time (relative, "fire	238	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	239	in 10 seconds") and based on wallclock time (absolute, "fire at 12
208	o'clock").	240	o'clock").
…		…
220	on wallclock time) timers.	252	on wallclock time) timers.
221		253
222	AnyEvent always prefers relative timers, if available, matching the	254	AnyEvent always prefers relative timers, if available, matching the
223	AnyEvent API.	255	AnyEvent API.
224		256
		257	AnyEvent has two additional methods that return the "current time":
		258
		259	AnyEvent->time
		260	This returns the "current wallclock time" as a fractional number of
		261	seconds since the Epoch (the same thing as "time" or
		262	"Time::HiRes::time" return, and the result is guaranteed to be
		263	compatible with those).
		264
		265	It progresses independently of any event loop processing, i.e. each
		266	call will check the system clock, which usually gets updated
		267	frequently.
		268
		269	AnyEvent->now
		270	This also returns the "current wallclock time", but unlike "time",
		271	above, this value might change only once per event loop iteration,
		272	depending on the event loop (most return the same time as "time",
		273	above). This is the time that AnyEvent's timers get scheduled
		274	against.
		275
		276	*In almost all cases (in all cases if you don't care), this is the
		277	function to call when you want to know the current time.*
		278
		279	This function is also often faster then "AnyEvent->time", and thus
		280	the preferred method if you want some timestamp (for example,
		281	AnyEvent::Handle uses this to update it's activity timeouts).
		282
		283	The rest of this section is only of relevance if you try to be very
		284	exact with your timing, you can skip it without bad conscience.
		285
		286	For a practical example of when these times differ, consider
		287	Event::Lib and EV and the following set-up:
		288
		289	The event loop is running and has just invoked one of your callback
		290	at time=500 (assume no other callbacks delay processing). In your
		291	callback, you wait a second by executing "sleep 1" (blocking the
		292	process for a second) and then (at time=501) you create a relative
		293	timer that fires after three seconds.
		294
		295	With Event::Lib, "AnyEvent->time" and "AnyEvent->now" will both
		296	return 501, because that is the current time, and the timer will be
		297	scheduled to fire at time=504 (501 + 3).
		298
		299	With EV, "AnyEvent->time" returns 501 (as that is the current time),
		300	but "AnyEvent->now" returns 500, as that is the time the last event
		301	processing phase started. With EV, your timer gets scheduled to run
		302	at time=503 (500 + 3).
		303
		304	In one sense, Event::Lib is more exact, as it uses the current time
		305	regardless of any delays introduced by event processing. However,
		306	most callbacks do not expect large delays in processing, so this
		307	causes a higher drift (and a lot more system calls to get the
		308	current time).
		309
		310	In another sense, EV is more exact, as your timer will be scheduled
		311	at the same time, regardless of how long event processing actually
		312	took.
		313
		314	In either case, if you care (and in most cases, you don't), then you
		315	can get whatever behaviour you want with any event loop, by taking
		316	the difference between "AnyEvent->time" and "AnyEvent->now" into
		317	account.
		318
225	SIGNAL WATCHERS	319	SIGNAL WATCHERS
226	You can watch for signals using a signal watcher, "signal" is the signal	320	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	321	name in uppercase and without any "SIG" prefix, "cb" is the Perl
228	whenever a signal occurs.	322	callback to be invoked whenever a signal occurs.
229		323
230	Although the callback might get passed parameters, their value and	324	Although the callback might get passed parameters, their value and
231	presence is undefined and you cannot rely on them. Portable AnyEvent	325	presence is undefined and you cannot rely on them. Portable AnyEvent
232	callbacks cannot use arguments passed to signal watcher callbacks.	326	callbacks cannot use arguments passed to signal watcher callbacks.
233		327
234	Multiple signal occurances can be clumped together into one callback	328	Multiple signal occurrences can be clumped together into one callback
235	invocation, and callback invocation will be synchronous. synchronous	329	invocation, and callback invocation will be synchronous. Synchronous
236	means that it might take a while until the signal gets handled by the	330	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.	331	process, but it is guaranteed not to interrupt any other callbacks.
238		332
239	The main advantage of using these watchers is that you can share a	333	The main advantage of using these watchers is that you can share a
240	signal between multiple watchers.	334	signal between multiple watchers.
241		335
242	This watcher might use %SIG, so programs overwriting those signals	336	This watcher might use %SIG, so programs overwriting those signals
…		…
248		342
249	CHILD PROCESS WATCHERS	343	CHILD PROCESS WATCHERS
250	You can also watch on a child process exit and catch its exit status.	344	You can also watch on a child process exit and catch its exit status.
251		345
252	The child process is specified by the "pid" argument (if set to 0, it	346	The child process is specified by the "pid" argument (if set to 0, it
253	watches for any child process exit). The watcher will trigger as often	347	watches for any child process exit). The watcher will triggered only
254	as status change for the child are received. This works by installing a	348	when the child process has finished and an exit status is available, not
255	signal handler for "SIGCHLD". The callback will be called with the pid	349	on any trace events (stopped/continued).
256	and exit status (as returned by waitpid), so unlike other watcher types,	350
257	you can rely on child watcher callback arguments.	351	The callback will be called with the pid and exit status (as returned by
		352	waitpid), so unlike other watcher types, you can rely on child watcher
		353	callback arguments.
		354
		355	This watcher type works by installing a signal handler for "SIGCHLD",
		356	and since it cannot be shared, nothing else should use SIGCHLD or reap
		357	random child processes (waiting for specific child processes, e.g.
		358	inside "system", is just fine).
258		359
259	There is a slight catch to child watchers, however: you usually start	360	There is a slight catch to child watchers, however: you usually start
260	them after the child process was created, and this means the process	361	them after the child process was created, and this means the process
261	could have exited already (and no SIGCHLD will be sent anymore).	362	could have exited already (and no SIGCHLD will be sent anymore).
262		363
…		…
269	an AnyEvent program, you have to create at least one watcher before	370	an AnyEvent program, you have to create at least one watcher before
270	you "fork" the child (alternatively, you can call "AnyEvent::detect").	371	you "fork" the child (alternatively, you can call "AnyEvent::detect").
271		372
272	Example: fork a process and wait for it	373	Example: fork a process and wait for it
273		374
274	my $done = AnyEvent->condvar;	375	my $done = AnyEvent->condvar;
275		376
276	my $pid = fork or exit 5;	377	my $pid = fork or exit 5;
277		378
278	my $w = AnyEvent->child (	379	my $w = AnyEvent->child (
279	pid => $pid,	380	pid => $pid,
280	cb => sub {	381	cb => sub {
281	my ($pid, $status) = @_;	382	my ($pid, $status) = @_;
282	warn "pid $pid exited with status $status";	383	warn "pid $pid exited with status $status";
283	$done->send;	384	$done->send;
284	},	385	},
285	);	386	);
286		387
287	# do something else, then wait for process exit	388	# do something else, then wait for process exit
288	$done->recv;	389	$done->recv;
289		390
290	CONDITION VARIABLES	391	CONDITION VARIABLES
291	If you are familiar with some event loops you will know that all of them	392	If you are familiar with some event loops you will know that all of them
292	require you to run some blocking "loop", "run" or similar function that	393	require you to run some blocking "loop", "run" or similar function that
293	will actively watch for new events and call your callbacks.	394	will actively watch for new events and call your callbacks.
…		…
298	The instrument to do that is called a "condition variable", so called	399	The instrument to do that is called a "condition variable", so called
299	because they represent a condition that must become true.	400	because they represent a condition that must become true.
300		401
301	Condition variables can be created by calling the "AnyEvent->condvar"	402	Condition variables can be created by calling the "AnyEvent->condvar"
302	method, usually without arguments. The only argument pair allowed is	403	method, usually without arguments. The only argument pair allowed is
		404
303	"cb", which specifies a callback to be called when the condition	405	"cb", which specifies a callback to be called when the condition
304	variable becomes true.	406	variable becomes true, with the condition variable as the first argument
		407	(but not the results).
305		408
306	After creation, the conditon variable is "false" until it becomes "true"	409	After creation, the condition variable is "false" until it becomes
		410	"true" by calling the "send" method (or calling the condition variable
		411	as if it were a callback, read about the caveats in the description for
307	by calling the "send" method.	412	the "->send" method).
308		413
309	Condition variables are similar to callbacks, except that you can	414	Condition variables are similar to callbacks, except that you can
310	optionally wait for them. They can also be called merge points - points	415	optionally wait for them. They can also be called merge points - points
311	in time where multiple outstandign events have been processed. And yet	416	in time where multiple outstanding events have been processed. And yet
312	another way to call them is transations - each condition variable can be	417	another way to call them is transactions - each condition variable can
313	used to represent a transaction, which finishes at some point and	418	be used to represent a transaction, which finishes at some point and
314	delivers a result.	419	delivers a result.
315		420
316	Condition variables are very useful to signal that something has	421	Condition variables are very useful to signal that something has
317	finished, for example, if you write a module that does asynchronous http	422	finished, for example, if you write a module that does asynchronous http
318	requests, then a condition variable would be the ideal candidate to	423	requests, then a condition variable would be the ideal candidate to
…		…
323	you can block your main program until an event occurs - for example, you	428	you can block your main program until an event occurs - for example, you
324	could "->recv" in your main program until the user clicks the Quit	429	could "->recv" in your main program until the user clicks the Quit
325	button of your app, which would "->send" the "quit" event.	430	button of your app, which would "->send" the "quit" event.
326		431
327	Note that condition variables recurse into the event loop - if you have	432	Note that condition variables recurse into the event loop - if you have
328	two pieces of code that call "->recv" in a round-robbin fashion, you	433	two pieces of code that call "->recv" in a round-robin fashion, you
329	lose. Therefore, condition variables are good to export to your caller,	434	lose. Therefore, condition variables are good to export to your caller,
330	but you should avoid making a blocking wait yourself, at least in	435	but you should avoid making a blocking wait yourself, at least in
331	callbacks, as this asks for trouble.	436	callbacks, as this asks for trouble.
332		437
333	Condition variables are represented by hash refs in perl, and the keys	438	Condition variables are represented by hash refs in perl, and the keys
…		…
338		443
339	There are two "sides" to a condition variable - the "producer side"	444	There are two "sides" to a condition variable - the "producer side"
340	which eventually calls "-> send", and the "consumer side", which waits	445	which eventually calls "-> send", and the "consumer side", which waits
341	for the send to occur.	446	for the send to occur.
342		447
343	Example:	448	Example: wait for a timer.
344		449
345	# wait till the result is ready	450	# wait till the result is ready
346	my $result_ready = AnyEvent->condvar;	451	my $result_ready = AnyEvent->condvar;
347		452
348	# do something such as adding a timer	453	# do something such as adding a timer
…		…
356		461
357	# this "blocks" (while handling events) till the callback	462	# this "blocks" (while handling events) till the callback
358	# calls send	463	# calls send
359	$result_ready->recv;	464	$result_ready->recv;
360		465
		466	Example: wait for a timer, but take advantage of the fact that condition
		467	variables are also code references.
		468
		469	my $done = AnyEvent->condvar;
		470	my $delay = AnyEvent->timer (after => 5, cb => $done);
		471	$done->recv;
		472
		473	Example: Imagine an API that returns a condvar and doesn't support
		474	callbacks. This is how you make a synchronous call, for example from the
		475	main program:
		476
		477	use AnyEvent::CouchDB;
		478
		479	...
		480
		481	my @info = $couchdb->info->recv;
		482
		483	And this is how you would just ste a callback to be called whenever the
		484	results are available:
		485
		486	$couchdb->info->cb (sub {
		487	my @info = $_[0]->recv;
		488	});
		489
361	METHODS FOR PRODUCERS	490	METHODS FOR PRODUCERS
362	These methods should only be used by the producing side, i.e. the	491	These methods should only be used by the producing side, i.e. the
363	code/module that eventually sends the signal. Note that it is also the	492	code/module that eventually sends the signal. Note that it is also the
364	producer side which creates the condvar in most cases, but it isn't	493	producer side which creates the condvar in most cases, but it isn't
365	uncommon for the consumer to create it as well.	494	uncommon for the consumer to create it as well.
…		…
372	If a callback has been set on the condition variable, it is called	501	If a callback has been set on the condition variable, it is called
373	immediately from within send.	502	immediately from within send.
374		503
375	Any arguments passed to the "send" call will be returned by all	504	Any arguments passed to the "send" call will be returned by all
376	future "->recv" calls.	505	future "->recv" calls.
		506
		507	Condition variables are overloaded so one can call them directly (as
		508	a code reference). Calling them directly is the same as calling
		509	"send". Note, however, that many C-based event loops do not handle
		510	overloading, so as tempting as it may be, passing a condition
		511	variable instead of a callback does not work. Both the pure perl and
		512	EV loops support overloading, however, as well as all functions that
		513	use perl to invoke a callback (as in AnyEvent::Socket and
		514	AnyEvent::DNS for example).
377		515
378	$cv->croak ($error)	516	$cv->croak ($error)
379	Similar to send, but causes all call's to "->recv" to invoke	517	Similar to send, but causes all call's to "->recv" to invoke
380	"Carp::croak" with the given error message/object/scalar.	518	"Carp::croak" with the given error message/object/scalar.
381		519
…		…
427	(the loop doesn't execute once).	565	(the loop doesn't execute once).
428		566
429	This is the general pattern when you "fan out" into multiple	567	This is the general pattern when you "fan out" into multiple
430	subrequests: use an outer "begin"/"end" pair to set the callback and	568	subrequests: use an outer "begin"/"end" pair to set the callback and
431	ensure "end" is called at least once, and then, for each subrequest	569	ensure "end" is called at least once, and then, for each subrequest
432	you start, call "begin" and for eahc subrequest you finish, call	570	you start, call "begin" and for each subrequest you finish, call
433	"end".	571	"end".
434		572
435	METHODS FOR CONSUMERS	573	METHODS FOR CONSUMERS
436	These methods should only be used by the consuming side, i.e. the code	574	These methods should only be used by the consuming side, i.e. the code
437	awaits the condition.	575	awaits the condition.
…		…
453	(programs might want to do that to stay interactive), so *if you are	591	(programs might want to do that to stay interactive), so *if you are
454	using this from a module, never require a blocking wait*, but let	592	using this from a module, never require a blocking wait*, but let
455	the caller decide whether the call will block or not (for example,	593	the caller decide whether the call will block or not (for example,
456	by coupling condition variables with some kind of request results	594	by coupling condition variables with some kind of request results
457	and supporting callbacks so the caller knows that getting the result	595	and supporting callbacks so the caller knows that getting the result
458	will not block, while still suppporting blocking waits if the caller	596	will not block, while still supporting blocking waits if the caller
459	so desires).	597	so desires).
460		598
461	Another reason never to "->recv" in a module is that you cannot	599	Another reason never to "->recv" in a module is that you cannot
462	sensibly have two "->recv"'s in parallel, as that would require	600	sensibly have two "->recv"'s in parallel, as that would require
463	multiple interpreters or coroutines/threads, none of which	601	multiple interpreters or coroutines/threads, none of which
…		…
476		614
477	$bool = $cv->ready	615	$bool = $cv->ready
478	Returns true when the condition is "true", i.e. whether "send" or	616	Returns true when the condition is "true", i.e. whether "send" or
479	"croak" have been called.	617	"croak" have been called.
480		618
481	$cb = $cv->cb ([new callback])	619	$cb = $cv->cb ($cb->($cv))
482	This is a mutator function that returns the callback set and	620	This is a mutator function that returns the callback set and
483	optionally replaces it before doing so.	621	optionally replaces it before doing so.
484		622
485	The callback will be called when the condition becomes "true", i.e.	623	The callback will be called when the condition becomes "true", i.e.
486	when "send" or "croak" are called. Calling "recv" inside the	624	when "send" or "croak" are called, with the only argument being the
		625	condition variable itself. Calling "recv" inside the callback or at
487	callback or at any later time is guaranteed not to block.	626	any later time is guaranteed not to block.
488		627
489	GLOBAL VARIABLES AND FUNCTIONS	628	GLOBAL VARIABLES AND FUNCTIONS
490	$AnyEvent::MODEL	629	$AnyEvent::MODEL
491	Contains "undef" until the first watcher is being created. Then it	630	Contains "undef" until the first watcher is being created. Then it
492	contains the event model that is being used, which is the name of	631	contains the event model that is being used, which is the name of
…		…
566	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	705	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
567	do anything special (it does not need to be event-based) and let	706	do anything special (it does not need to be event-based) and let
568	AnyEvent decide which implementation to chose if some module relies on	707	AnyEvent decide which implementation to chose if some module relies on
569	it.	708	it.
570		709
571	If the main program relies on a specific event model. For example, in	710	If the main program relies on a specific event model - for example, in
572	Gtk2 programs you have to rely on the Glib module. You should load the	711	Gtk2 programs you have to rely on the Glib module - you should load the
573	event module before loading AnyEvent or any module that uses it:	712	event module before loading AnyEvent or any module that uses it:
574	generally speaking, you should load it as early as possible. The reason	713	generally speaking, you should load it as early as possible. The reason
575	is that modules might create watchers when they are loaded, and AnyEvent	714	is that modules might create watchers when they are loaded, and AnyEvent
576	will decide on the event model to use as soon as it creates watchers,	715	will decide on the event model to use as soon as it creates watchers,
577	and it might chose the wrong one unless you load the correct one	716	and it might chose the wrong one unless you load the correct one
578	yourself.	717	yourself.
579		718
580	You can chose to use a rather inefficient pure-perl implementation by	719	You can chose to use a pure-perl implementation by loading the
581	loading the "AnyEvent::Impl::Perl" module, which gives you similar	720	"AnyEvent::Impl::Perl" module, which gives you similar behaviour
582	behaviour everywhere, but letting AnyEvent chose is generally better.	721	everywhere, but letting AnyEvent chose the model is generally better.
		722
		723	MAINLOOP EMULATION
		724	Sometimes (often for short test scripts, or even standalone programs who
		725	only want to use AnyEvent), you do not want to run a specific event
		726	loop.
		727
		728	In that case, you can use a condition variable like this:
		729
		730	AnyEvent->condvar->recv;
		731
		732	This has the effect of entering the event loop and looping forever.
		733
		734	Note that usually your program has some exit condition, in which case it
		735	is better to use the "traditional" approach of storing a condition
		736	variable somewhere, waiting for it, and sending it when the program
		737	should exit cleanly.
583		738
584	OTHER MODULES	739	OTHER MODULES
585	The following is a non-exhaustive list of additional modules that use	740	The following is a non-exhaustive list of additional modules that use
586	AnyEvent and can therefore be mixed easily with other AnyEvent modules	741	AnyEvent and can therefore be mixed easily with other AnyEvent modules
587	in the same program. Some of the modules come with AnyEvent, some are	742	in the same program. Some of the modules come with AnyEvent, some are
…		…
590	AnyEvent::Util	745	AnyEvent::Util
591	Contains various utility functions that replace often-used but	746	Contains various utility functions that replace often-used but
592	blocking functions such as "inet_aton" by event-/callback-based	747	blocking functions such as "inet_aton" by event-/callback-based
593	versions.	748	versions.
594		749
		750	AnyEvent::Socket
		751	Provides various utility functions for (internet protocol) sockets,
		752	addresses and name resolution. Also functions to create non-blocking
		753	tcp connections or tcp servers, with IPv6 and SRV record support and
		754	more.
		755
595	AnyEvent::Handle	756	AnyEvent::Handle
596	Provide read and write buffers and manages watchers for reads and	757	Provide read and write buffers, manages watchers for reads and
597	writes.	758	writes, supports raw and formatted I/O, I/O queued and fully
		759	transparent and non-blocking SSL/TLS.
		760
		761	AnyEvent::DNS
		762	Provides rich asynchronous DNS resolver capabilities.
		763
		764	AnyEvent::HTTP
		765	A simple-to-use HTTP library that is capable of making a lot of
		766	concurrent HTTP requests.
598		767
599	AnyEvent::HTTPD	768	AnyEvent::HTTPD
600	Provides a simple web application server framework.	769	Provides a simple web application server framework.
601		770
602	AnyEvent::DNS
603	Provides asynchronous DNS resolver capabilities, beyond what
604	AnyEvent::Util offers.
605
606	AnyEvent::FastPing	771	AnyEvent::FastPing
607	The fastest ping in the west.	772	The fastest ping in the west.
608		773
		774	AnyEvent::DBI
		775	Executes DBI requests asynchronously in a proxy process.
		776
		777	AnyEvent::AIO
		778	Truly asynchronous I/O, should be in the toolbox of every event
		779	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		780	together.
		781
		782	AnyEvent::BDB
		783	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
		784	fuses BDB and AnyEvent together.
		785
		786	AnyEvent::GPSD
		787	A non-blocking interface to gpsd, a daemon delivering GPS
		788	information.
		789
		790	AnyEvent::IGS
		791	A non-blocking interface to the Internet Go Server protocol (used by
		792	App::IGS).
		793
		794	AnyEvent::IRC
		795	AnyEvent based IRC client module family (replacing the older
609	Net::IRC3	796	Net::IRC3).
610	AnyEvent based IRC client module family.
611		797
612	Net::XMPP2	798	Net::XMPP2
613	AnyEvent based XMPP (Jabber protocol) module family.	799	AnyEvent based XMPP (Jabber protocol) module family.
614		800
615	Net::FCP	801	Net::FCP
…		…
620	High level API for event-based execution flow control.	806	High level API for event-based execution flow control.
621		807
622	Coro	808	Coro
623	Has special support for AnyEvent via Coro::AnyEvent.	809	Has special support for AnyEvent via Coro::AnyEvent.
624		810
625	AnyEvent::AIO, IO::AIO
626	Truly asynchronous I/O, should be in the toolbox of every event
627	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
628	together.
629
630	AnyEvent::BDB, BDB
631	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
632	fuses IO::AIO and AnyEvent together.
633
634	IO::Lambda	811	IO::Lambda
635	The lambda approach to I/O - don't ask, look there. Can use	812	The lambda approach to I/O - don't ask, look there. Can use
636	AnyEvent.	813	AnyEvent.
		814
		815	ERROR AND EXCEPTION HANDLING
		816	In general, AnyEvent does not do any error handling - it relies on the
		817	caller to do that if required. The AnyEvent::Strict module (see also the
		818	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
		819	checking of all AnyEvent methods, however, which is highly useful during
		820	development.
		821
		822	As for exception handling (i.e. runtime errors and exceptions thrown
		823	while executing a callback), this is not only highly event-loop
		824	specific, but also not in any way wrapped by this module, as this is the
		825	job of the main program.
		826
		827	The pure perl event loop simply re-throws the exception (usually within
		828	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
		829	Glib uses "install_exception_handler" and so on.
		830
		831	ENVIRONMENT VARIABLES
		832	The following environment variables are used by this module or its
		833	submodules:
		834
		835	"PERL_ANYEVENT_VERBOSE"
		836	By default, AnyEvent will be completely silent except in fatal
		837	conditions. You can set this environment variable to make AnyEvent
		838	more talkative.
		839
		840	When set to 1 or higher, causes AnyEvent to warn about unexpected
		841	conditions, such as not being able to load the event model specified
		842	by "PERL_ANYEVENT_MODEL".
		843
		844	When set to 2 or higher, cause AnyEvent to report to STDERR which
		845	event model it chooses.
		846
		847	"PERL_ANYEVENT_STRICT"
		848	AnyEvent does not do much argument checking by default, as thorough
		849	argument checking is very costly. Setting this variable to a true
		850	value will cause AnyEvent to load "AnyEvent::Strict" and then to
		851	thoroughly check the arguments passed to most method calls. If it
		852	finds any problems it will croak.
		853
		854	In other words, enables "strict" mode.
		855
		856	Unlike "use strict", it is definitely recommended ot keep it off in
		857	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
		858	while developing programs can be very useful, however.
		859
		860	"PERL_ANYEVENT_MODEL"
		861	This can be used to specify the event model to be used by AnyEvent,
		862	before auto detection and -probing kicks in. It must be a string
		863	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
		864	gets prepended and the resulting module name is loaded and if the
		865	load was successful, used as event model. If it fails to load
		866	AnyEvent will proceed with auto detection and -probing.
		867
		868	This functionality might change in future versions.
		869
		870	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
		871	could start your program like this:
		872
		873	PERL_ANYEVENT_MODEL=Perl perl ...
		874
		875	"PERL_ANYEVENT_PROTOCOLS"
		876	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
		877	preferences for IPv4 or IPv6. The default is unspecified (and might
		878	change, or be the result of auto probing).
		879
		880	Must be set to a comma-separated list of protocols or address
		881	families, current supported: "ipv4" and "ipv6". Only protocols
		882	mentioned will be used, and preference will be given to protocols
		883	mentioned earlier in the list.
		884
		885	This variable can effectively be used for denial-of-service attacks
		886	against local programs (e.g. when setuid), although the impact is
		887	likely small, as the program has to handle conenction and other
		888	failures anyways.
		889
		890	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
		891	IPv6, but support both and try to use both.
		892	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
		893	resolve or contact IPv6 addresses.
		894	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
		895	prefer IPv6 over IPv4.
		896
		897	"PERL_ANYEVENT_EDNS0"
		898	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
		899	for DNS. This extension is generally useful to reduce DNS traffic,
		900	but some (broken) firewalls drop such DNS packets, which is why it
		901	is off by default.
		902
		903	Setting this variable to 1 will cause AnyEvent::DNS to announce
		904	EDNS0 in its DNS requests.
		905
		906	"PERL_ANYEVENT_MAX_FORKS"
		907	The maximum number of child processes that
		908	"AnyEvent::Util::fork_call" will create in parallel.
637		909
638	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	910	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
639	This is an advanced topic that you do not normally need to use AnyEvent	911	This is an advanced topic that you do not normally need to use AnyEvent
640	in a module. This section is only of use to event loop authors who want	912	in a module. This section is only of use to event loop authors who want
641	to provide AnyEvent compatibility.	913	to provide AnyEvent compatibility.
…		…
675		947
676	rxvt-unicode also cheats a bit by not providing blocking access to	948	rxvt-unicode also cheats a bit by not providing blocking access to
677	condition variables: code blocking while waiting for a condition will	949	condition variables: code blocking while waiting for a condition will
678	"die". This still works with most modules/usages, and blocking calls	950	"die". This still works with most modules/usages, and blocking calls
679	must not be done in an interactive application, so it makes sense.	951	must not be done in an interactive application, so it makes sense.
680
681	ENVIRONMENT VARIABLES
682	The following environment variables are used by this module:
683
684	"PERL_ANYEVENT_VERBOSE"
685	By default, AnyEvent will be completely silent except in fatal
686	conditions. You can set this environment variable to make AnyEvent
687	more talkative.
688
689	When set to 1 or higher, causes AnyEvent to warn about unexpected
690	conditions, such as not being able to load the event model specified
691	by "PERL_ANYEVENT_MODEL".
692
693	When set to 2 or higher, cause AnyEvent to report to STDERR which
694	event model it chooses.
695
696	"PERL_ANYEVENT_MODEL"
697	This can be used to specify the event model to be used by AnyEvent,
698	before autodetection and -probing kicks in. It must be a string
699	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
700	gets prepended and the resulting module name is loaded and if the
701	load was successful, used as event model. If it fails to load
702	AnyEvent will proceed with autodetection and -probing.
703
704	This functionality might change in future versions.
705
706	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
707	could start your program like this:
708
709	PERL_ANYEVENT_MODEL=Perl perl ...
710		952
711	EXAMPLE PROGRAM	953	EXAMPLE PROGRAM
712	The following program uses an I/O watcher to read data from STDIN, a	954	The following program uses an I/O watcher to read data from STDIN, a
713	timer to display a message once per second, and a condition variable to	955	timer to display a message once per second, and a condition variable to
714	quit the program when the user enters quit:	956	quit the program when the user enters quit:
…		…
796	syswrite $txn->{fh}, $txn->{request}	1038	syswrite $txn->{fh}, $txn->{request}
797	or die "connection or write error";	1039	or die "connection or write error";
798	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1040	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
799		1041
800	Again, "fh_ready_r" waits till all data has arrived, and then stores the	1042	Again, "fh_ready_r" waits till all data has arrived, and then stores the
801	result and signals any possible waiters that the request ahs finished:	1043	result and signals any possible waiters that the request has finished:
802		1044
803	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1045	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
804		1046
805	if (end-of-file or data complete) {	1047	if (end-of-file or data complete) {
806	$txn->{result} = $txn->{buf};	1048	$txn->{result} = $txn->{buf};
…		…
814		1056
815	$txn->{finished}->recv;	1057	$txn->{finished}->recv;
816	return $txn->{result};	1058	return $txn->{result};
817		1059
818	The actual code goes further and collects all errors ("die"s,	1060	The actual code goes further and collects all errors ("die"s,
819	exceptions) that occured during request processing. The "result" method	1061	exceptions) that occurred during request processing. The "result" method
820	detects whether an exception as thrown (it is stored inside the $txn	1062	detects whether an exception as thrown (it is stored inside the $txn
821	object) and just throws the exception, which means connection errors and	1063	object) and just throws the exception, which means connection errors and
822	other problems get reported tot he code that tries to use the result,	1064	other problems get reported tot he code that tries to use the result,
823	not in a random callback.	1065	not in a random callback.
824		1066
…		…
867	over the event loops themselves and to give you an impression of the	1109	over the event loops themselves and to give you an impression of the
868	speed of various event loops I prepared some benchmarks.	1110	speed of various event loops I prepared some benchmarks.
869		1111
870	BENCHMARKING ANYEVENT OVERHEAD	1112	BENCHMARKING ANYEVENT OVERHEAD
871	Here is a benchmark of various supported event models used natively and	1113	Here is a benchmark of various supported event models used natively and
872	through anyevent. The benchmark creates a lot of timers (with a zero	1114	through AnyEvent. The benchmark creates a lot of timers (with a zero
873	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1115	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
874	which it is), lets them fire exactly once and destroys them again.	1116	which it is), lets them fire exactly once and destroys them again.
875		1117
876	Source code for this benchmark is found as eg/bench in the AnyEvent	1118	Source code for this benchmark is found as eg/bench in the AnyEvent
877	distribution.	1119	distribution.
…		…
901	destroy is the time, in microseconds, that it takes to destroy a	1143	destroy is the time, in microseconds, that it takes to destroy a
902	single watcher.	1144	single watcher.
903		1145
904	Results	1146	Results
905	name watchers bytes create invoke destroy comment	1147	name watchers bytes create invoke destroy comment
906	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1148	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
907	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1149	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
908	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1150	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
909	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1151	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
910	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1152	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
911	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1153	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
912	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1154	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
913	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1155	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
914	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1156	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
915	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1157	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
916		1158
917	Discussion	1159	Discussion
918	The benchmark does not measure scalability of the event loop very	1160	The benchmark does not measure scalability of the event loop very
919	well. For example, a select-based event loop (such as the pure perl one)	1161	well. For example, a select-based event loop (such as the pure perl one)
920	can never compete with an event loop that uses epoll when the number of	1162	can never compete with an event loop that uses epoll when the number of
…		…
992		1234
993	* You should avoid POE like the plague if you want performance or	1235	* You should avoid POE like the plague if you want performance or
994	reasonable memory usage.	1236	reasonable memory usage.
995		1237
996	BENCHMARKING THE LARGE SERVER CASE	1238	BENCHMARKING THE LARGE SERVER CASE
997	This benchmark atcually benchmarks the event loop itself. It works by	1239	This benchmark actually benchmarks the event loop itself. It works by
998	creating a number of "servers": each server consists of a socketpair, a	1240	creating a number of "servers": each server consists of a socket pair, a
999	timeout watcher that gets reset on activity (but never fires), and an	1241	timeout watcher that gets reset on activity (but never fires), and an
1000	I/O watcher waiting for input on one side of the socket. Each time the	1242	I/O watcher waiting for input on one side of the socket. Each time the
1001	socket watcher reads a byte it will write that byte to a random other	1243	socket watcher reads a byte it will write that byte to a random other
1002	"server".	1244	"server".
1003		1245
1004	The effect is that there will be a lot of I/O watchers, only part of	1246	The effect is that there will be a lot of I/O watchers, only part of
1005	which are active at any one point (so there is a constant number of	1247	which are active at any one point (so there is a constant number of
1006	active fds for each loop iterstaion, but which fds these are is random).	1248	active fds for each loop iteration, but which fds these are is random).
1007	The timeout is reset each time something is read because that reflects	1249	The timeout is reset each time something is read because that reflects
1008	how most timeouts work (and puts extra pressure on the event loops).	1250	how most timeouts work (and puts extra pressure on the event loops).
1009		1251
1010	In this benchmark, we use 10000 socketpairs (20000 sockets), of which	1252	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
1011	100 (1%) are active. This mirrors the activity of large servers with	1253	100 (1%) are active. This mirrors the activity of large servers with
1012	many connections, most of which are idle at any one point in time.	1254	many connections, most of which are idle at any one point in time.
1013		1255
1014	Source code for this benchmark is found as eg/bench2 in the AnyEvent	1256	Source code for this benchmark is found as eg/bench2 in the AnyEvent
1015	distribution.	1257	distribution.
1016		1258
1017	Explanation of the columns	1259	Explanation of the columns
1018	sockets is the number of sockets, and twice the number of "servers"	1260	sockets is the number of sockets, and twice the number of "servers"
1019	(as each server has a read and write socket end).	1261	(as each server has a read and write socket end).
1020		1262
1021	create is the time it takes to create a socketpair (which is	1263	create is the time it takes to create a socket pair (which is
1022	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	1264	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1023		1265
1024	request, the most important value, is the time it takes to handle a	1266	request, the most important value, is the time it takes to handle a
1025	single "request", that is, reading the token from the pipe and	1267	single "request", that is, reading the token from the pipe and
1026	forwarding it to another server. This includes deleting the old timeout	1268	forwarding it to another server. This includes deleting the old timeout
…		…
1090	and speed most when you have lots of watchers, not when you only have a	1332	and speed most when you have lots of watchers, not when you only have a
1091	few of them).	1333	few of them).
1092		1334
1093	EV is again fastest.	1335	EV is again fastest.
1094		1336
1095	Perl again comes second. It is noticably faster than the C-based event	1337	Perl again comes second. It is noticeably faster than the C-based event
1096	loops Event and Glib, although the difference is too small to really	1338	loops Event and Glib, although the difference is too small to really
1097	matter.	1339	matter.
1098		1340
1099	POE also performs much better in this case, but is is still far behind	1341	POE also performs much better in this case, but is is still far behind
1100	the others.	1342	the others.
1101		1343
1102	Summary	1344	Summary
1103	* C-based event loops perform very well with small number of watchers,	1345	* C-based event loops perform very well with small number of watchers,
1104	as the management overhead dominates.	1346	as the management overhead dominates.
		1347
		1348	SIGNALS
		1349	AnyEvent currently installs handlers for these signals:
		1350
		1351	SIGCHLD
		1352	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
		1353	emulation for event loops that do not support them natively. Also,
		1354	some event loops install a similar handler.
		1355
		1356	SIGPIPE
		1357	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
		1358	"undef" when AnyEvent gets loaded.
		1359
		1360	The rationale for this is that AnyEvent users usually do not really
		1361	depend on SIGPIPE delivery (which is purely an optimisation for
		1362	shell use, or badly-written programs), but "SIGPIPE" can cause
		1363	spurious and rare program exits as a lot of people do not expect
		1364	"SIGPIPE" when writing to some random socket.
		1365
		1366	The rationale for installing a no-op handler as opposed to ignoring
		1367	it is that this way, the handler will be restored to defaults on
		1368	exec.
		1369
		1370	Feel free to install your own handler, or reset it to defaults.
1105		1371
1106	FORK	1372	FORK
1107	Most event libraries are not fork-safe. The ones who are usually are	1373	Most event libraries are not fork-safe. The ones who are usually are
1108	because they rely on inefficient but fork-safe "select" or "poll" calls.	1374	because they rely on inefficient but fork-safe "select" or "poll" calls.
1109	Only EV is fully fork-aware.	1375	Only EV is fully fork-aware.
…		…
1120	model than specified in the variable.	1386	model than specified in the variable.
1121		1387
1122	You can make AnyEvent completely ignore this variable by deleting it	1388	You can make AnyEvent completely ignore this variable by deleting it
1123	before the first watcher gets created, e.g. with a "BEGIN" block:	1389	before the first watcher gets created, e.g. with a "BEGIN" block:
1124		1390
1125	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1391	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1126		1392
1127	use AnyEvent;	1393	use AnyEvent;
1128		1394
1129	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1395	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1130	be used to probe what backend is used and gain other information (which	1396	be used to probe what backend is used and gain other information (which
1131	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	1397	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
		1398	and $ENV{PERL_ANYEGENT_STRICT}.
		1399
		1400	BUGS
		1401	Perl 5.8 has numerous memleaks that sometimes hit this module and are
		1402	hard to work around. If you suffer from memleaks, first upgrade to Perl
		1403	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
		1404	annoying memleaks, such as leaking on "map" and "grep" but it is usually
		1405	not as pronounced).
1132		1406
1133	SEE ALSO	1407	SEE ALSO
		1408	Utility functions: AnyEvent::Util.
		1409
1134	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1410	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1135	Event::Lib, Qt, POE.	1411	Event::Lib, Qt, POE.
1136		1412
1137	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1413	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1138	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1414	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1139	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1415	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.
1140		1416
		1417	Non-blocking file handles, sockets, TCP clients and servers:
		1418	AnyEvent::Handle, AnyEvent::Socket.
		1419
		1420	Asynchronous DNS: AnyEvent::DNS.
		1421
1141	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1422	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1142		1423
1143	Nontrivial usage examples: Net::FCP, Net::XMPP2.	1424	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.
1144		1425
1145	AUTHOR	1426	AUTHOR
1146	Marc Lehmann <schmorp@schmorp.de>	1427	Marc Lehmann <schmorp@schmorp.de>
1147	http://home.schmorp.de/	1428	http://home.schmorp.de/
1148		1429

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Comparing AnyEvent/README (file contents): Revision 1.21 by root, Sat May 17 21:34:15 2008 UTC vs. Revision 1.36 by root, Fri Mar 27 10:49:50 2009 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.21 by root, Sat May 17 21:34:15 2008 UTC vs.
Revision 1.36 by root, Fri Mar 27 10:49:50 2009 UTC