[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.18 by root, Thu Apr 24 09:13:26 2008 UTC vs.
Revision 1.22 by root, Sat May 24 17:58:33 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 -	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		21
22	WHY YOU SHOULD USE THIS MODULE (OR NOT)	22	WHY YOU SHOULD USE THIS MODULE (OR NOT)
23	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	23	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
24	nowadays. So what is different about AnyEvent?	24	nowadays. So what is different about AnyEvent?
25		25
…		…
55	those use one of the supported event loops. It is trivial to add new	55	those use one of the supported event loops. It is trivial to add new
56	event loops to AnyEvent, too, so it is future-proof).	56	event loops to AnyEvent, too, so it is future-proof).
57		57
58	In addition to being free of having to use *the one and only true event	58	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	59	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	60	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	61	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	62	only offering the functionality that is necessary, in as thin as a
63	wrapper as technically possible.	63	wrapper as technically possible.
64		64
65	Of course, if you want lots of policy (this can arguably be somewhat	65	Of course, if you 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	66	useful) and you want to force your users to use the one and only event
…		…
75	The interface itself is vaguely similar, but not identical to the Event	75	The interface itself is vaguely similar, but not identical to the Event
76	module.	76	module.
77		77
78	During the first call of any watcher-creation method, the module tries	78	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	79	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,	80	following modules is already loaded: EV, Event, Glib,
81	Glib, Tk, Event::Lib, Qt. The first one found is used. If none are	81	AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is
82	found, the module tries to load these modules (excluding Event::Lib and	82	used. If none are found, the module tries to load these modules
83	Qt) in the order given. The first one that can be successfully loaded	83	(excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should
84	will be used. If, after this, still none could be found, AnyEvent will	84	always succeed) in the order given. The first one that can be
85	fall back to a pure-perl event loop, which is not very efficient, but	85	successfully loaded will be used. If, after this, still none could be
86	should work everywhere.	86	found, AnyEvent will fall back to a pure-perl event loop, which is not
		87	very efficient, but should work everywhere.
87		88
88	Because AnyEvent first checks for modules that are already loaded,	89	Because AnyEvent first checks for modules that are already loaded,
89	loading an event model explicitly before first using AnyEvent will	90	loading an event model explicitly before first using AnyEvent will
90	likely make that model the default. For example:	91	likely make that model the default. For example:
91		92
…		…
103	explicitly.	104	explicitly.
104		105
105	WATCHERS	106	WATCHERS
106	AnyEvent has the central concept of a watcher, which is an object that	107	AnyEvent has the central concept of a watcher, which is an object that
107	stores relevant data for each kind of event you are waiting for, such as	108	stores relevant data for each kind of event you are waiting for, such as
108	the callback to call, the filehandle to watch, etc.	109	the callback to call, the file handle to watch, etc.
109		110
110	These watchers are normal Perl objects with normal Perl lifetime. After	111	These watchers are normal Perl objects with normal Perl lifetime. After
111	creating a watcher it will immediately "watch" for events and invoke the	112	creating a watcher it will immediately "watch" for events and invoke the
112	callback when the event occurs (of course, only when the event model is	113	callback when the event occurs (of course, only when the event model is
113	in control).	114	in control).
…		…
130		131
131	Note that "my $w; $w =" combination. This is necessary because in Perl,	132	Note that "my $w; $w =" combination. This is necessary because in Perl,
132	my variables are only visible after the statement in which they are	133	my variables are only visible after the statement in which they are
133	declared.	134	declared.
134		135
135	IO WATCHERS	136	I/O WATCHERS
136	You can create an I/O watcher by calling the "AnyEvent->io" method with	137	You can create an I/O watcher by calling the "AnyEvent->io" method with
137	the following mandatory key-value pairs as arguments:	138	the following mandatory key-value pairs as arguments:
138		139
139	"fh" the Perl file handle (not file descriptor) to watch for events.	140	"fh" the Perl file handle (not file descriptor) to watch for events.
140	"poll" must be a string that is either "r" or "w", which creates a	141	"poll" must be a string that is either "r" or "w", which creates a
141	watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"	142	watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"
142	is the callback to invoke each time the file handle becomes ready.	143	is the callback to invoke each time the file handle becomes ready.
143		144
144	As long as the I/O watcher exists it will keep the file descriptor or a	145	Although the callback might get passed parameters, their value and
145	copy of it alive/open.	146	presence is undefined and you cannot rely on them. Portable AnyEvent
		147	callbacks cannot use arguments passed to I/O watcher callbacks.
146		148
		149	The I/O watcher might use the underlying file descriptor or a copy of
147	It is not allowed to close a file handle as long as any watcher is	150	it. You must not close a file handle as long as any watcher is active on
148	active on the underlying file descriptor.	151	the underlying file descriptor.
149		152
150	Some event loops issue spurious readyness notifications, so you should	153	Some event loops issue spurious readyness notifications, so you should
151	always use non-blocking calls when reading/writing from/to your file	154	always use non-blocking calls when reading/writing from/to your file
152	handles.	155	handles.
153		156
…		…
163	TIME WATCHERS	166	TIME WATCHERS
164	You can create a time watcher by calling the "AnyEvent->timer" method	167	You can create a time watcher by calling the "AnyEvent->timer" method
165	with the following mandatory arguments:	168	with the following mandatory arguments:
166		169
167	"after" specifies after how many seconds (fractional values are	170	"after" specifies after how many seconds (fractional values are
168	supported) should the timer activate. "cb" the callback to invoke in	171	supported) the callback should be invoked. "cb" is the callback to
169	that case.	172	invoke in that case.
		173
		174	Although the callback might get passed parameters, their value and
		175	presence is undefined and you cannot rely on them. Portable AnyEvent
		176	callbacks cannot use arguments passed to time watcher callbacks.
170		177
171	The timer callback will be invoked at most once: if you want a repeating	178	The timer callback will be invoked at most once: if you want a repeating
172	timer you have to create a new watcher (this is a limitation by both Tk	179	timer you have to create a new watcher (this is a limitation by both Tk
173	and Glib).	180	and Glib).
174		181
…		…
218	SIGNAL WATCHERS	225	SIGNAL WATCHERS
219	You can watch for signals using a signal watcher, "signal" is the signal	226	You can watch for signals using a signal watcher, "signal" is the signal
220	name without any "SIG" prefix, "cb" is the Perl callback to be invoked	227	name without any "SIG" prefix, "cb" is the Perl callback to be invoked
221	whenever a signal occurs.	228	whenever a signal occurs.
222		229
		230	Although the callback might get passed parameters, their value and
		231	presence is undefined and you cannot rely on them. Portable AnyEvent
		232	callbacks cannot use arguments passed to signal watcher callbacks.
		233
223	Multiple signal occurances can be clumped together into one callback	234	Multiple signal occurrences can be clumped together into one callback
224	invocation, and callback invocation will be synchronous. synchronous	235	invocation, and callback invocation will be synchronous. Synchronous
225	means that it might take a while until the signal gets handled by the	236	means that it might take a while until the signal gets handled by the
226	process, but it is guarenteed not to interrupt any other callbacks.	237	process, but it is guaranteed not to interrupt any other callbacks.
227		238
228	The main advantage of using these watchers is that you can share a	239	The main advantage of using these watchers is that you can share a
229	signal between multiple watchers.	240	signal between multiple watchers.
230		241
231	This watcher might use %SIG, so programs overwriting those signals	242	This watcher might use %SIG, so programs overwriting those signals
…		…
240		251
241	The child process is specified by the "pid" argument (if set to 0, it	252	The child process is specified by the "pid" argument (if set to 0, it
242	watches for any child process exit). The watcher will trigger as often	253	watches for any child process exit). The watcher will trigger as often
243	as status change for the child are received. This works by installing a	254	as status change for the child are received. This works by installing a
244	signal handler for "SIGCHLD". The callback will be called with the pid	255	signal handler for "SIGCHLD". The callback will be called with the pid
245	and exit status (as returned by waitpid).	256	and exit status (as returned by waitpid), so unlike other watcher types,
		257	you can rely on child watcher callback arguments.
246		258
247	Example: wait for pid 1333	259	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
		261	could have exited already (and no SIGCHLD will be sent anymore).
		262
		263	Not all event models handle this correctly (POE doesn't), but even for
		264	event models that do handle this correctly, they usually need to be
		265	loaded before the process exits (i.e. before you fork in the first
		266	place).
		267
		268	This means you cannot create a child watcher as the very first thing in
		269	an AnyEvent program, you have to create at least one watcher before
		270	you "fork" the child (alternatively, you can call "AnyEvent::detect").
		271
		272	Example: fork a process and wait for it
		273
		274	my $done = AnyEvent->condvar;
		275
		276	my $pid = fork or exit 5;
248		277
249	my $w = AnyEvent->child (	278	my $w = AnyEvent->child (
250	pid => 1333,	279	pid => $pid,
251	cb => sub {	280	cb => sub {
252	my ($pid, $status) = @_;	281	my ($pid, $status) = @_;
253	warn "pid $pid exited with status $status";	282	warn "pid $pid exited with status $status";
		283	$done->send;
254	},	284	},
255	);	285	);
256		286
		287	# do something else, then wait for process exit
		288	$done->recv;
		289
257	CONDITION VARIABLES	290	CONDITION VARIABLES
		291	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
		293	will actively watch for new events and call your callbacks.
		294
		295	AnyEvent is different, it expects somebody else to run the event loop
		296	and will only block when necessary (usually when told by the user).
		297
		298	The instrument to do that is called a "condition variable", so called
		299	because they represent a condition that must become true.
		300
258	Condition variables can be created by calling the "AnyEvent->condvar"	301	Condition variables can be created by calling the "AnyEvent->condvar"
259	method without any arguments.	302	method, usually without arguments. The only argument pair allowed is
		303	"cb", which specifies a callback to be called when the condition
		304	variable becomes true.
260		305
261	A condition variable waits for a condition - precisely that the	306	After creation, the condition variable is "false" until it becomes
262	"->broadcast" method has been called.	307	"true" by calling the "send" method (or calling the condition variable
		308	as if it were a callback).
263		309
264	They are very useful to signal that a condition has been fulfilled, for	310	Condition variables are similar to callbacks, except that you can
		311	optionally wait for them. They can also be called merge points - points
		312	in time where multiple outstanding events have been processed. And yet
		313	another way to call them is transactions - each condition variable can
		314	be used to represent a transaction, which finishes at some point and
		315	delivers a result.
		316
		317	Condition variables are very useful to signal that something has
265	example, if you write a module that does asynchronous http requests,	318	finished, for example, if you write a module that does asynchronous http
266	then a condition variable would be the ideal candidate to signal the	319	requests, then a condition variable would be the ideal candidate to
267	availability of results.	320	signal the availability of results. The user can either act when the
		321	callback is called or can synchronously "->recv" for the results.
268		322
269	You can also use condition variables to block your main program until an	323	You can also use them to simulate traditional event loops - for example,
270	event occurs - for example, you could "->wait" in your main program	324	you can block your main program until an event occurs - for example, you
271	until the user clicks the Quit button in your app, which would	325	could "->recv" in your main program until the user clicks the Quit
272	"->broadcast" the "quit" event.	326	button of your app, which would "->send" the "quit" event.
273		327
274	Note that condition variables recurse into the event loop - if you have	328	Note that condition variables recurse into the event loop - if you have
275	two pirces of code that call "->wait" in a round-robbin fashion, you	329	two pieces of code that call "->recv" in a round-robin fashion, you
276	lose. Therefore, condition variables are good to export to your caller,	330	lose. Therefore, condition variables are good to export to your caller,
277	but you should avoid making a blocking wait yourself, at least in	331	but you should avoid making a blocking wait yourself, at least in
278	callbacks, as this asks for trouble.	332	callbacks, as this asks for trouble.
279		333
280	This object has two methods:	334	Condition variables are represented by hash refs in perl, and the keys
		335	used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy
		336	(it is often useful to build your own transaction class on top of
		337	AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
		338	it's "new" method in your own "new" method.
281		339
282	$cv->wait	340	There are two "sides" to a condition variable - the "producer side"
		341	which eventually calls "-> send", and the "consumer side", which waits
		342	for the send to occur.
		343
		344	Example: wait for a timer.
		345
		346	# wait till the result is ready
		347	my $result_ready = AnyEvent->condvar;
		348
		349	# do something such as adding a timer
		350	# or socket watcher the calls $result_ready->send
		351	# when the "result" is ready.
		352	# in this case, we simply use a timer:
		353	my $w = AnyEvent->timer (
		354	after => 1,
		355	cb => sub { $result_ready->send },
		356	);
		357
		358	# this "blocks" (while handling events) till the callback
		359	# calls send
		360	$result_ready->recv;
		361
		362	Example: wait for a timer, but take advantage of the fact that condition
		363	variables are also code references.
		364
		365	my $done = AnyEvent->condvar;
		366	my $delay = AnyEvent->timer (after => 5, cb => $done);
		367	$done->recv;
		368
		369	METHODS FOR PRODUCERS
		370	These methods should only be used by the producing side, i.e. the
		371	code/module that eventually sends the signal. Note that it is also the
		372	producer side which creates the condvar in most cases, but it isn't
		373	uncommon for the consumer to create it as well.
		374
		375	$cv->send (...)
		376	Flag the condition as ready - a running "->recv" and all further
		377	calls to "recv" will (eventually) return after this method has been
		378	called. If nobody is waiting the send will be remembered.
		379
		380	If a callback has been set on the condition variable, it is called
		381	immediately from within send.
		382
		383	Any arguments passed to the "send" call will be returned by all
		384	future "->recv" calls.
		385
		386	Condition variables are overloaded so one can call them directly (as
		387	a code reference). Calling them directly is the same as calling
		388	"send".
		389
		390	$cv->croak ($error)
		391	Similar to send, but causes all call's to "->recv" to invoke
		392	"Carp::croak" with the given error message/object/scalar.
		393
		394	This can be used to signal any errors to the condition variable
		395	user/consumer.
		396
		397	$cv->begin ([group callback])
		398	$cv->end
		399	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		400
		401	These two methods can be used to combine many transactions/events
		402	into one. For example, a function that pings many hosts in parallel
		403	might want to use a condition variable for the whole process.
		404
		405	Every call to "->begin" will increment a counter, and every call to
		406	"->end" will decrement it. If the counter reaches 0 in "->end", the
		407	(last) callback passed to "begin" will be executed. That callback is
		408	supposed to call "->send", but that is not required. If no
		409	callback was set, "send" will be called without any arguments.
		410
		411	Let's clarify this with the ping example:
		412
		413	my $cv = AnyEvent->condvar;
		414
		415	my %result;
		416	$cv->begin (sub { $cv->send (\%result) });
		417
		418	for my $host (@list_of_hosts) {
		419	$cv->begin;
		420	ping_host_then_call_callback $host, sub {
		421	$result{$host} = ...;
		422	$cv->end;
		423	};
		424	}
		425
		426	$cv->end;
		427
		428	This code fragment supposedly pings a number of hosts and calls
		429	"send" after results for all then have have been gathered - in any
		430	order. To achieve this, the code issues a call to "begin" when it
		431	starts each ping request and calls "end" when it has received some
		432	result for it. Since "begin" and "end" only maintain a counter, the
		433	order in which results arrive is not relevant.
		434
		435	There is an additional bracketing call to "begin" and "end" outside
		436	the loop, which serves two important purposes: first, it sets the
		437	callback to be called once the counter reaches 0, and second, it
		438	ensures that "send" is called even when "no" hosts are being pinged
		439	(the loop doesn't execute once).
		440
		441	This is the general pattern when you "fan out" into multiple
		442	subrequests: use an outer "begin"/"end" pair to set the callback and
		443	ensure "end" is called at least once, and then, for each subrequest
		444	you start, call "begin" and for each subrequest you finish, call
		445	"end".
		446
		447	METHODS FOR CONSUMERS
		448	These methods should only be used by the consuming side, i.e. the code
		449	awaits the condition.
		450
		451	$cv->recv
283	Wait (blocking if necessary) until the "->broadcast" method has been	452	Wait (blocking if necessary) until the "->send" or "->croak" methods
284	called on c<$cv>, while servicing other watchers normally.	453	have been called on c<$cv>, while servicing other watchers normally.
285		454
286	You can only wait once on a condition - additional calls will return	455	You can only wait once on a condition - additional calls are valid
287	immediately.	456	but will return immediately.
		457
		458	If an error condition has been set by calling "->croak", then this
		459	function will call "croak".
		460
		461	In list context, all parameters passed to "send" will be returned,
		462	in scalar context only the first one will be returned.
288		463
289	Not all event models support a blocking wait - some die in that case	464	Not all event models support a blocking wait - some die in that case
290	(programs might want to do that to stay interactive), so *if you are	465	(programs might want to do that to stay interactive), so *if you are
291	using this from a module, never require a blocking wait*, but let	466	using this from a module, never require a blocking wait*, but let
292	the caller decide whether the call will block or not (for example,	467	the caller decide whether the call will block or not (for example,
293	by coupling condition variables with some kind of request results	468	by coupling condition variables with some kind of request results
294	and supporting callbacks so the caller knows that getting the result	469	and supporting callbacks so the caller knows that getting the result
295	will not block, while still suppporting blocking waits if the caller	470	will not block, while still supporting blocking waits if the caller
296	so desires).	471	so desires).
297		472
298	Another reason never to "->wait" in a module is that you cannot	473	Another reason never to "->recv" in a module is that you cannot
299	sensibly have two "->wait"'s in parallel, as that would require	474	sensibly have two "->recv"'s in parallel, as that would require
300	multiple interpreters or coroutines/threads, none of which	475	multiple interpreters or coroutines/threads, none of which
301	"AnyEvent" can supply (the coroutine-aware backends	476	"AnyEvent" can supply.
302	AnyEvent::Impl::CoroEV and AnyEvent::Impl::CoroEvent explicitly
303	support concurrent "->wait"'s from different coroutines, however).
304		477
305	$cv->broadcast	478	The Coro module, however, can and does supply coroutines and, in
306	Flag the condition as ready - a running "->wait" and all further	479	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
307	calls to "wait" will (eventually) return after this method has been	480	versions and also integrates coroutines into AnyEvent, making
308	called. If nobody is waiting the broadcast will be remembered..	481	blocking "->recv" calls perfectly safe as long as they are done from
		482	another coroutine (one that doesn't run the event loop).
309		483
310	Example:	484	You can ensure that "-recv" never blocks by setting a callback and
		485	only calling "->recv" from within that callback (or at a later
		486	time). This will work even when the event loop does not support
		487	blocking waits otherwise.
311		488
312	# wait till the result is ready	489	$bool = $cv->ready
313	my $result_ready = AnyEvent->condvar;	490	Returns true when the condition is "true", i.e. whether "send" or
		491	"croak" have been called.
314		492
315	# do something such as adding a timer	493	$cb = $cv->cb ([new callback])
316	# or socket watcher the calls $result_ready->broadcast	494	This is a mutator function that returns the callback set and
317	# when the "result" is ready.	495	optionally replaces it before doing so.
318	# in this case, we simply use a timer:
319	my $w = AnyEvent->timer (
320	after => 1,
321	cb => sub { $result_ready->broadcast },
322	);
323		496
324	# this "blocks" (while handling events) till the watcher	497	The callback will be called when the condition becomes "true", i.e.
325	# calls broadcast	498	when "send" or "croak" are called. Calling "recv" inside the
326	$result_ready->wait;	499	callback or at any later time is guaranteed not to block.
327		500
328	GLOBAL VARIABLES AND FUNCTIONS	501	GLOBAL VARIABLES AND FUNCTIONS
329	$AnyEvent::MODEL	502	$AnyEvent::MODEL
330	Contains "undef" until the first watcher is being created. Then it	503	Contains "undef" until the first watcher is being created. Then it
331	contains the event model that is being used, which is the name of	504	contains the event model that is being used, which is the name of
…		…
333	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	506	the "AnyEvent::Impl:xxx" modules, but can be any other class in the
334	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).	507	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).
335		508
336	The known classes so far are:	509	The known classes so far are:
337		510
338	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
339	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
340	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	511	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
341	AnyEvent::Impl::Event based on Event, second best choice.	512	AnyEvent::Impl::Event based on Event, second best choice.
		513	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
342	AnyEvent::Impl::Glib based on Glib, third-best choice.	514	AnyEvent::Impl::Glib based on Glib, third-best choice.
343	AnyEvent::Impl::Tk based on Tk, very bad choice.	515	AnyEvent::Impl::Tk based on Tk, very bad choice.
344	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
345	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	516	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
346	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	517	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		518	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		519
		520	There is no support for WxWidgets, as WxWidgets has no support for
		521	watching file handles. However, you can use WxWidgets through the
		522	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		523	second, which was considered to be too horrible to even consider for
		524	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
		525	using it's adaptor.
		526
		527	AnyEvent knows about Prima and Wx and will try to use POE when
		528	autodetecting them.
347		529
348	AnyEvent::detect	530	AnyEvent::detect
349	Returns $AnyEvent::MODEL, forcing autodetection of the event model	531	Returns $AnyEvent::MODEL, forcing autodetection of the event model
350	if necessary. You should only call this function right before you	532	if necessary. You should only call this function right before you
351	would have created an AnyEvent watcher anyway, that is, as late as	533	would have created an AnyEvent watcher anyway, that is, as late as
352	possible at runtime.	534	possible at runtime.
353		535
		536	$guard = AnyEvent::post_detect { BLOCK }
		537	Arranges for the code block to be executed as soon as the event
		538	model is autodetected (or immediately if this has already happened).
		539
		540	If called in scalar or list context, then it creates and returns an
		541	object that automatically removes the callback again when it is
		542	destroyed. See Coro::BDB for a case where this is useful.
		543
		544	@AnyEvent::post_detect
		545	If there are any code references in this array (you can "push" to it
		546	before or after loading AnyEvent), then they will called directly
		547	after the event loop has been chosen.
		548
		549	You should check $AnyEvent::MODEL before adding to this array,
		550	though: if it contains a true value then the event loop has already
		551	been detected, and the array will be ignored.
		552
		553	Best use "AnyEvent::post_detect { BLOCK }" instead.
		554
354	WHAT TO DO IN A MODULE	555	WHAT TO DO IN A MODULE
355	As a module author, you should "use AnyEvent" and call AnyEvent methods	556	As a module author, you should "use AnyEvent" and call AnyEvent methods
356	freely, but you should not load a specific event module or rely on it.	557	freely, but you should not load a specific event module or rely on it.
357		558
358	Be careful when you create watchers in the module body - AnyEvent will	559	Be careful when you create watchers in the module body - AnyEvent will
359	decide which event module to use as soon as the first method is called,	560	decide which event module to use as soon as the first method is called,
360	so by calling AnyEvent in your module body you force the user of your	561	so by calling AnyEvent in your module body you force the user of your
361	module to load the event module first.	562	module to load the event module first.
362		563
363	Never call "->wait" on a condition variable unless you know that the	564	Never call "->recv" on a condition variable unless you know that the
364	"->broadcast" method has been called on it already. This is because it	565	"->send" method has been called on it already. This is because it will
365	will stall the whole program, and the whole point of using events is to	566	stall the whole program, and the whole point of using events is to stay
366	stay interactive.	567	interactive.
367		568
368	It is fine, however, to call "->wait" when the user of your module	569	It is fine, however, to call "->recv" when the user of your module
369	requests it (i.e. if you create a http request object ad have a method	570	requests it (i.e. if you create a http request object ad have a method
370	called "results" that returns the results, it should call "->wait"	571	called "results" that returns the results, it should call "->recv"
371	freely, as the user of your module knows what she is doing. always).	572	freely, as the user of your module knows what she is doing. always).
372		573
373	WHAT TO DO IN THE MAIN PROGRAM	574	WHAT TO DO IN THE MAIN PROGRAM
374	There will always be a single main program - the only place that should	575	There will always be a single main program - the only place that should
375	dictate which event model to use.	576	dictate which event model to use.
…		…
390		591
391	You can chose to use a rather inefficient pure-perl implementation by	592	You can chose to use a rather inefficient pure-perl implementation by
392	loading the "AnyEvent::Impl::Perl" module, which gives you similar	593	loading the "AnyEvent::Impl::Perl" module, which gives you similar
393	behaviour everywhere, but letting AnyEvent chose is generally better.	594	behaviour everywhere, but letting AnyEvent chose is generally better.
394		595
		596	OTHER MODULES
		597	The following is a non-exhaustive list of additional modules that use
		598	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		599	in the same program. Some of the modules come with AnyEvent, some are
		600	available via CPAN.
		601
		602	AnyEvent::Util
		603	Contains various utility functions that replace often-used but
		604	blocking functions such as "inet_aton" by event-/callback-based
		605	versions.
		606
		607	AnyEvent::Handle
		608	Provide read and write buffers and manages watchers for reads and
		609	writes.
		610
		611	AnyEvent::Socket
		612	Provides various utility functions for (internet protocol) sockets,
		613	addresses and name resolution. Also functions to create non-blocking
		614	tcp connections or tcp servers, with IPv6 and SRV record support and
		615	more.
		616
		617	AnyEvent::HTTPD
		618	Provides a simple web application server framework.
		619
		620	AnyEvent::DNS
		621	Provides rich asynchronous DNS resolver capabilities.
		622
		623	AnyEvent::FastPing
		624	The fastest ping in the west.
		625
		626	Net::IRC3
		627	AnyEvent based IRC client module family.
		628
		629	Net::XMPP2
		630	AnyEvent based XMPP (Jabber protocol) module family.
		631
		632	Net::FCP
		633	AnyEvent-based implementation of the Freenet Client Protocol,
		634	birthplace of AnyEvent.
		635
		636	Event::ExecFlow
		637	High level API for event-based execution flow control.
		638
		639	Coro
		640	Has special support for AnyEvent via Coro::AnyEvent.
		641
		642	AnyEvent::AIO, IO::AIO
		643	Truly asynchronous I/O, should be in the toolbox of every event
		644	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		645	together.
		646
		647	AnyEvent::BDB, BDB
		648	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
		649	fuses IO::AIO and AnyEvent together.
		650
		651	IO::Lambda
		652	The lambda approach to I/O - don't ask, look there. Can use
		653	AnyEvent.
		654
395	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	655	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
396	This is an advanced topic that you do not normally need to use AnyEvent	656	This is an advanced topic that you do not normally need to use AnyEvent
397	in a module. This section is only of use to event loop authors who want	657	in a module. This section is only of use to event loop authors who want
398	to provide AnyEvent compatibility.	658	to provide AnyEvent compatibility.
399		659
…		…
437		697
438	ENVIRONMENT VARIABLES	698	ENVIRONMENT VARIABLES
439	The following environment variables are used by this module:	699	The following environment variables are used by this module:
440		700
441	"PERL_ANYEVENT_VERBOSE"	701	"PERL_ANYEVENT_VERBOSE"
		702	By default, AnyEvent will be completely silent except in fatal
		703	conditions. You can set this environment variable to make AnyEvent
		704	more talkative.
		705
		706	When set to 1 or higher, causes AnyEvent to warn about unexpected
		707	conditions, such as not being able to load the event model specified
		708	by "PERL_ANYEVENT_MODEL".
		709
442	When set to 2 or higher, cause AnyEvent to report to STDERR which	710	When set to 2 or higher, cause AnyEvent to report to STDERR which
443	event model it chooses.	711	event model it chooses.
444		712
445	"PERL_ANYEVENT_MODEL"	713	"PERL_ANYEVENT_MODEL"
446	This can be used to specify the event model to be used by AnyEvent,	714	This can be used to specify the event model to be used by AnyEvent,
447	before autodetection and -probing kicks in. It must be a string	715	before auto detection and -probing kicks in. It must be a string
448	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"	716	consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
449	gets prepended and the resulting module name is loaded and if the	717	gets prepended and the resulting module name is loaded and if the
450	load was successful, used as event model. If it fails to load	718	load was successful, used as event model. If it fails to load
451	AnyEvent will proceed with autodetection and -probing.	719	AnyEvent will proceed with auto detection and -probing.
452		720
453	This functionality might change in future versions.	721	This functionality might change in future versions.
454		722
455	For example, to force the pure perl model (AnyEvent::Impl::Perl) you	723	For example, to force the pure perl model (AnyEvent::Impl::Perl) you
456	could start your program like this:	724	could start your program like this:
457		725
458	PERL_ANYEVENT_MODEL=Perl perl ...	726	PERL_ANYEVENT_MODEL=Perl perl ...
459		727
		728	"PERL_ANYEVENT_PROTOCOLS"
		729	Used by both AnyEvent::DNS and AnyEvent::Socket to determine
		730	preferences for IPv4 or IPv6. The default is unspecified (and might
		731	change, or be the result of auto probing).
		732
		733	Must be set to a comma-separated list of protocols or address
		734	families, current supported: "ipv4" and "ipv6". Only protocols
		735	mentioned will be used, and preference will be given to protocols
		736	mentioned earlier in the list.
		737
		738	This variable can effectively be used for denial-of-service attacks
		739	against local programs (e.g. when setuid), although the impact is
		740	likely small, as the program has to handle connection errors
		741	already-
		742
		743	Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
		744	IPv6, but support both and try to use both.
		745	"PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
		746	resolve or contact IPv6 addresses.
		747	"PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
		748	prefer IPv6 over IPv4.
		749
		750	"PERL_ANYEVENT_EDNS0"
		751	Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
		752	for DNS. This extension is generally useful to reduce DNS traffic,
		753	but some (broken) firewalls drop such DNS packets, which is why it
		754	is off by default.
		755
		756	Setting this variable to 1 will cause AnyEvent::DNS to announce
		757	EDNS0 in its DNS requests.
		758
460	EXAMPLE PROGRAM	759	EXAMPLE PROGRAM
461	The following program uses an IO watcher to read data from STDIN, a	760	The following program uses an I/O watcher to read data from STDIN, a
462	timer to display a message once per second, and a condition variable to	761	timer to display a message once per second, and a condition variable to
463	quit the program when the user enters quit:	762	quit the program when the user enters quit:
464		763
465	use AnyEvent;	764	use AnyEvent;
466		765
…		…
471	poll => 'r',	770	poll => 'r',
472	cb => sub {	771	cb => sub {
473	warn "io event <$_[0]>\n"; # will always output <r>	772	warn "io event <$_[0]>\n"; # will always output <r>
474	chomp (my $input = <STDIN>); # read a line	773	chomp (my $input = <STDIN>); # read a line
475	warn "read: $input\n"; # output what has been read	774	warn "read: $input\n"; # output what has been read
476	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	775	$cv->send if $input =~ /^q/i; # quit program if /^q/i
477	},	776	},
478	);	777	);
479		778
480	my $time_watcher; # can only be used once	779	my $time_watcher; # can only be used once
481		780
…		…
486	});	785	});
487	}	786	}
488		787
489	new_timer; # create first timer	788	new_timer; # create first timer
490		789
491	$cv->wait; # wait until user enters /^q/i	790	$cv->recv; # wait until user enters /^q/i
492		791
493	REAL-WORLD EXAMPLE	792	REAL-WORLD EXAMPLE
494	Consider the Net::FCP module. It features (among others) the following	793	Consider the Net::FCP module. It features (among others) the following
495	API calls, which are to freenet what HTTP GET requests are to http:	794	API calls, which are to freenet what HTTP GET requests are to http:
496		795
…		…
545	syswrite $txn->{fh}, $txn->{request}	844	syswrite $txn->{fh}, $txn->{request}
546	or die "connection or write error";	845	or die "connection or write error";
547	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	846	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
548		847
549	Again, "fh_ready_r" waits till all data has arrived, and then stores the	848	Again, "fh_ready_r" waits till all data has arrived, and then stores the
550	result and signals any possible waiters that the request ahs finished:	849	result and signals any possible waiters that the request has finished:
551		850
552	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	851	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
553		852
554	if (end-of-file or data complete) {	853	if (end-of-file or data complete) {
555	$txn->{result} = $txn->{buf};	854	$txn->{result} = $txn->{buf};
556	$txn->{finished}->broadcast;	855	$txn->{finished}->send;
557	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	856	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
558	}	857	}
559		858
560	The "result" method, finally, just waits for the finished signal (if the	859	The "result" method, finally, just waits for the finished signal (if the
561	request was already finished, it doesn't wait, of course, and returns	860	request was already finished, it doesn't wait, of course, and returns
562	the data:	861	the data:
563		862
564	$txn->{finished}->wait;	863	$txn->{finished}->recv;
565	return $txn->{result};	864	return $txn->{result};
566		865
567	The actual code goes further and collects all errors ("die"s,	866	The actual code goes further and collects all errors ("die"s,
568	exceptions) that occured during request processing. The "result" method	867	exceptions) that occurred during request processing. The "result" method
569	detects whether an exception as thrown (it is stored inside the $txn	868	detects whether an exception as thrown (it is stored inside the $txn
570	object) and just throws the exception, which means connection errors and	869	object) and just throws the exception, which means connection errors and
571	other problems get reported tot he code that tries to use the result,	870	other problems get reported tot he code that tries to use the result,
572	not in a random callback.	871	not in a random callback.
573		872
…		…
604		903
605	my $quit = AnyEvent->condvar;	904	my $quit = AnyEvent->condvar;
606		905
607	$fcp->txn_client_get ($url)->cb (sub {	906	$fcp->txn_client_get ($url)->cb (sub {
608	...	907	...
609	$quit->broadcast;	908	$quit->send;
610	});	909	});
611		910
612	$quit->wait;	911	$quit->recv;
		912
		913	BENCHMARKS
		914	To give you an idea of the performance and overheads that AnyEvent adds
		915	over the event loops themselves and to give you an impression of the
		916	speed of various event loops I prepared some benchmarks.
		917
		918	BENCHMARKING ANYEVENT OVERHEAD
		919	Here is a benchmark of various supported event models used natively and
		920	through AnyEvent. The benchmark creates a lot of timers (with a zero
		921	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		922	which it is), lets them fire exactly once and destroys them again.
		923
		924	Source code for this benchmark is found as eg/bench in the AnyEvent
		925	distribution.
		926
		927	Explanation of the columns
		928	watcher is the number of event watchers created/destroyed. Since
		929	different event models feature vastly different performances, each event
		930	loop was given a number of watchers so that overall runtime is
		931	acceptable and similar between tested event loop (and keep them from
		932	crashing): Glib would probably take thousands of years if asked to
		933	process the same number of watchers as EV in this benchmark.
		934
		935	bytes is the number of bytes (as measured by the resident set size,
		936	RSS) consumed by each watcher. This method of measuring captures both C
		937	and Perl-based overheads.
		938
		939	create is the time, in microseconds (millionths of seconds), that it
		940	takes to create a single watcher. The callback is a closure shared
		941	between all watchers, to avoid adding memory overhead. That means
		942	closure creation and memory usage is not included in the figures.
		943
		944	invoke is the time, in microseconds, used to invoke a simple callback.
		945	The callback simply counts down a Perl variable and after it was invoked
		946	"watcher" times, it would "->send" a condvar once to signal the end of
		947	this phase.
		948
		949	destroy is the time, in microseconds, that it takes to destroy a
		950	single watcher.
		951
		952	Results
		953	name watchers bytes create invoke destroy comment
		954	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		955	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		956	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		957	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		958	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		959	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		960	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		961	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		962	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		963	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		964
		965	Discussion
		966	The benchmark does not measure scalability of the event loop very
		967	well. For example, a select-based event loop (such as the pure perl one)
		968	can never compete with an event loop that uses epoll when the number of
		969	file descriptors grows high. In this benchmark, all events become ready
		970	at the same time, so select/poll-based implementations get an unnatural
		971	speed boost.
		972
		973	Also, note that the number of watchers usually has a nonlinear effect on
		974	overall speed, that is, creating twice as many watchers doesn't take
		975	twice the time - usually it takes longer. This puts event loops tested
		976	with a higher number of watchers at a disadvantage.
		977
		978	To put the range of results into perspective, consider that on the
		979	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		980	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000
		981	CPU cycles with POE.
		982
		983	"EV" is the sole leader regarding speed and memory use, which are both
		984	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		985	far less memory than any other event loop and is still faster than Event
		986	natively.
		987
		988	The pure perl implementation is hit in a few sweet spots (both the
		989	constant timeout and the use of a single fd hit optimisations in the
		990	perl interpreter and the backend itself). Nevertheless this shows that
		991	it adds very little overhead in itself. Like any select-based backend
		992	its performance becomes really bad with lots of file descriptors (and
		993	few of them active), of course, but this was not subject of this
		994	benchmark.
		995
		996	The "Event" module has a relatively high setup and callback invocation
		997	cost, but overall scores in on the third place.
		998
		999	"Glib"'s memory usage is quite a bit higher, but it features a faster
		1000	callback invocation and overall ends up in the same class as "Event".
		1001	However, Glib scales extremely badly, doubling the number of watchers
		1002	increases the processing time by more than a factor of four, making it
		1003	completely unusable when using larger numbers of watchers (note that
		1004	only a single file descriptor was used in the benchmark, so
		1005	inefficiencies of "poll" do not account for this).
		1006
		1007	The "Tk" adaptor works relatively well. The fact that it crashes with
		1008	more than 2000 watchers is a big setback, however, as correctness takes
		1009	precedence over speed. Nevertheless, its performance is surprising, as
		1010	the file descriptor is dup()ed for each watcher. This shows that the
		1011	dup() employed by some adaptors is not a big performance issue (it does
		1012	incur a hidden memory cost inside the kernel which is not reflected in
		1013	the figures above).
		1014
		1015	"POE", regardless of underlying event loop (whether using its pure perl
		1016	select-based backend or the Event module, the POE-EV backend couldn't be
		1017	tested because it wasn't working) shows abysmal performance and memory
		1018	usage with AnyEvent: Watchers use almost 30 times as much memory as EV
		1019	watchers, and 10 times as much memory as Event (the high memory
		1020	requirements are caused by requiring a session for each watcher).
		1021	Watcher invocation speed is almost 900 times slower than with AnyEvent's
		1022	pure perl implementation.
		1023
		1024	The design of the POE adaptor class in AnyEvent can not really account
		1025	for the performance issues, though, as session creation overhead is
		1026	small compared to execution of the state machine, which is coded pretty
		1027	optimally within AnyEvent::Impl::POE (and while everybody agrees that
		1028	using multiple sessions is not a good approach, especially regarding
		1029	memory usage, even the author of POE could not come up with a faster
		1030	design).
		1031
		1032	Summary
		1033	* Using EV through AnyEvent is faster than any other event loop (even
		1034	when used without AnyEvent), but most event loops have acceptable
		1035	performance with or without AnyEvent.
		1036
		1037	* The overhead AnyEvent adds is usually much smaller than the overhead
		1038	of the actual event loop, only with extremely fast event loops such
		1039	as EV adds AnyEvent significant overhead.
		1040
		1041	* You should avoid POE like the plague if you want performance or
		1042	reasonable memory usage.
		1043
		1044	BENCHMARKING THE LARGE SERVER CASE
		1045	This benchmark actually benchmarks the event loop itself. It works by
		1046	creating a number of "servers": each server consists of a socket pair, a
		1047	timeout watcher that gets reset on activity (but never fires), and an
		1048	I/O watcher waiting for input on one side of the socket. Each time the
		1049	socket watcher reads a byte it will write that byte to a random other
		1050	"server".
		1051
		1052	The effect is that there will be a lot of I/O watchers, only part of
		1053	which are active at any one point (so there is a constant number of
		1054	active fds for each loop iteration, but which fds these are is random).
		1055	The timeout is reset each time something is read because that reflects
		1056	how most timeouts work (and puts extra pressure on the event loops).
		1057
		1058	In this benchmark, we use 10000 socket pairs (20000 sockets), of which
		1059	100 (1%) are active. This mirrors the activity of large servers with
		1060	many connections, most of which are idle at any one point in time.
		1061
		1062	Source code for this benchmark is found as eg/bench2 in the AnyEvent
		1063	distribution.
		1064
		1065	Explanation of the columns
		1066	sockets is the number of sockets, and twice the number of "servers"
		1067	(as each server has a read and write socket end).
		1068
		1069	create is the time it takes to create a socket pair (which is
		1070	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1071
		1072	request, the most important value, is the time it takes to handle a
		1073	single "request", that is, reading the token from the pipe and
		1074	forwarding it to another server. This includes deleting the old timeout
		1075	and creating a new one that moves the timeout into the future.
		1076
		1077	Results
		1078	name sockets create request
		1079	EV 20000 69.01 11.16
		1080	Perl 20000 73.32 35.87
		1081	Event 20000 212.62 257.32
		1082	Glib 20000 651.16 1896.30
		1083	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1084
		1085	Discussion
		1086	This benchmark does measure scalability and overall performance of the
		1087	particular event loop.
		1088
		1089	EV is again fastest. Since it is using epoll on my system, the setup
		1090	time is relatively high, though.
		1091
		1092	Perl surprisingly comes second. It is much faster than the C-based event
		1093	loops Event and Glib.
		1094
		1095	Event suffers from high setup time as well (look at its code and you
		1096	will understand why). Callback invocation also has a high overhead
		1097	compared to the "$_->() for .."-style loop that the Perl event loop
		1098	uses. Event uses select or poll in basically all documented
		1099	configurations.
		1100
		1101	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1102	clearly fails to perform with many filehandles or in busy servers.
		1103
		1104	POE is still completely out of the picture, taking over 1000 times as
		1105	long as EV, and over 100 times as long as the Perl implementation, even
		1106	though it uses a C-based event loop in this case.
		1107
		1108	Summary
		1109	* The pure perl implementation performs extremely well.
		1110
		1111	* Avoid Glib or POE in large projects where performance matters.
		1112
		1113	BENCHMARKING SMALL SERVERS
		1114	While event loops should scale (and select-based ones do not...) even to
		1115	large servers, most programs we (or I :) actually write have only a few
		1116	I/O watchers.
		1117
		1118	In this benchmark, I use the same benchmark program as in the large
		1119	server case, but it uses only eight "servers", of which three are active
		1120	at any one time. This should reflect performance for a small server
		1121	relatively well.
		1122
		1123	The columns are identical to the previous table.
		1124
		1125	Results
		1126	name sockets create request
		1127	EV 16 20.00 6.54
		1128	Perl 16 25.75 12.62
		1129	Event 16 81.27 35.86
		1130	Glib 16 32.63 15.48
		1131	POE 16 261.87 276.28 uses POE::Loop::Event
		1132
		1133	Discussion
		1134	The benchmark tries to test the performance of a typical small server.
		1135	While knowing how various event loops perform is interesting, keep in
		1136	mind that their overhead in this case is usually not as important, due
		1137	to the small absolute number of watchers (that is, you need efficiency
		1138	and speed most when you have lots of watchers, not when you only have a
		1139	few of them).
		1140
		1141	EV is again fastest.
		1142
		1143	Perl again comes second. It is noticeably faster than the C-based event
		1144	loops Event and Glib, although the difference is too small to really
		1145	matter.
		1146
		1147	POE also performs much better in this case, but is is still far behind
		1148	the others.
		1149
		1150	Summary
		1151	* C-based event loops perform very well with small number of watchers,
		1152	as the management overhead dominates.
613		1153
614	FORK	1154	FORK
615	Most event libraries are not fork-safe. The ones who are usually are	1155	Most event libraries are not fork-safe. The ones who are usually are
616	because they are so inefficient. Only EV is fully fork-aware.	1156	because they rely on inefficient but fork-safe "select" or "poll" calls.
		1157	Only EV is fully fork-aware.
617		1158
618	If you have to fork, you must either do so before creating your first	1159	If you have to fork, you must either do so before creating your first
619	watcher OR you must not use AnyEvent at all in the child.	1160	watcher OR you must not use AnyEvent at all in the child.
620		1161
621	SECURITY CONSIDERATIONS	1162	SECURITY CONSIDERATIONS
…		…
631		1172
632	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1173	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
633		1174
634	use AnyEvent;	1175	use AnyEvent;
635		1176
		1177	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1178	be used to probe what backend is used and gain other information (which
		1179	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
		1180
636	SEE ALSO	1181	SEE ALSO
637	Event modules: Coro::EV, EV, EV::Glib, Glib::EV, Coro::Event, Event,	1182	Utility functions: AnyEvent::Util.
638	Glib::Event, Glib, Coro, Tk, Event::Lib, Qt.
639		1183
640	Implementations: AnyEvent::Impl::CoroEV, AnyEvent::Impl::EV,	1184	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
641	AnyEvent::Impl::CoroEvent, AnyEvent::Impl::Event, AnyEvent::Impl::Glib,	1185	Event::Lib, Qt, POE.
642	AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, AnyEvent::Impl::EventLib,
643	AnyEvent::Impl::Qt.
644		1186
		1187	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
		1188	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
		1189	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.
		1190
		1191	Non-blocking file handles, sockets, TCP clients and servers:
		1192	AnyEvent::Handle, AnyEvent::Socket.
		1193
		1194	Asynchronous DNS: AnyEvent::DNS.
		1195
		1196	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
		1197
645	Nontrivial usage examples: Net::FCP, Net::XMPP2.	1198	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.
646		1199
647	AUTHOR	1200	AUTHOR
648	Marc Lehmann <schmorp@schmorp.de>	1201	Marc Lehmann <schmorp@schmorp.de>
649	http://home.schmorp.de/	1202	http://home.schmorp.de/
650		1203

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Comparing AnyEvent/README (file contents): Revision 1.18 by root, Thu Apr 24 09:13:26 2008 UTC vs. Revision 1.22 by root, Sat May 24 17:58:33 2008 UTC

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Revision 1.18 by root, Thu Apr 24 09:13:26 2008 UTC vs.
Revision 1.22 by root, Sat May 24 17:58:33 2008 UTC