[ViewVC] Diff of: cvs/AnyEvent/lib/AnyEvent.pm

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.60 by root, Fri Apr 25 01:05:26 2008 UTC vs.
Revision 1.137 by root, Mon May 26 03:27:52 2008 UTC

…		…
1	=head1 NAME	1	=head1 => NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
6		6
7	=head1 SYNOPSIS	7	=head1 SYNOPSIS
8		8
9	use AnyEvent;	9	use AnyEvent;
10		10
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	15	my $w = AnyEvent->timer (after => $seconds, cb => sub {
16	...	16	...
17	});	17	});
18		18
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	19	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		20	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	21	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's
22		22
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		24
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	26	nowadays. So what is different about AnyEvent?
…		…
57	as those use one of the supported event loops. It is trivial to add new	57	as those use one of the supported event loops. It is trivial to add new
58	event loops to AnyEvent, too, so it is future-proof).	58	event loops to AnyEvent, too, so it is future-proof).
59		59
60	In addition to being free of having to use I<the one and only true event	60	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	61	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	62	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	63	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	64	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	65	technically possible.
66		66
67	Of course, if you want lots of policy (this can arguably be somewhat	67	Of course, if you want lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	68	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	69	model, you should I<not> use this module.
70
71		70
72	=head1 DESCRIPTION	71	=head1 DESCRIPTION
73		72
74	L<AnyEvent> provides an identical interface to multiple event loops. This	73	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	74	allows module authors to utilise an event loop without forcing module
…		…
78		77
79	The interface itself is vaguely similar, but not identical to the L<Event>	78	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	79	module.
81		80
82	During the first call of any watcher-creation method, the module tries	81	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of	82	to detect the currently loaded event loop by probing whether one of the
84	the following modules is already loaded: L<Coro::EV>, L<Coro::Event>,	83	following modules is already loaded: L<EV>,
85	L<EV>, L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>. The first one	84	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	found is used. If none are found, the module tries to load these modules	85	L<POE>. The first one found is used. If none are found, the module tries
87	(excluding Event::Lib and Qt) in the order given. The first one that can	86	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
		87	adaptor should always succeed) in the order given. The first one that can
88	be successfully loaded will be used. If, after this, still none could be	88	be successfully loaded will be used. If, after this, still none could be
89	found, AnyEvent will fall back to a pure-perl event loop, which is not	89	found, AnyEvent will fall back to a pure-perl event loop, which is not
90	very efficient, but should work everywhere.	90	very efficient, but should work everywhere.
91		91
92	Because AnyEvent first checks for modules that are already loaded, loading	92	Because AnyEvent first checks for modules that are already loaded, loading
…		…
108		108
109	=head1 WATCHERS	109	=head1 WATCHERS
110		110
111	AnyEvent has the central concept of a I<watcher>, which is an object that	111	AnyEvent has the central concept of a I<watcher>, which is an object that
112	stores relevant data for each kind of event you are waiting for, such as	112	stores relevant data for each kind of event you are waiting for, such as
113	the callback to call, the filehandle to watch, etc.	113	the callback to call, the file handle to watch, etc.
114		114
115	These watchers are normal Perl objects with normal Perl lifetime. After	115	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	116	creating a watcher it will immediately "watch" for events and invoke the
117	callback when the event occurs (of course, only when the event model	117	callback when the event occurs (of course, only when the event model
118	is in control).	118	is in control).
…		…
135		135
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	136	Note that C<my $w; $w => combination. This is necessary because in Perl,
137	my variables are only visible after the statement in which they are	137	my variables are only visible after the statement in which they are
138	declared.	138	declared.
139		139
140	=head2 IO WATCHERS	140	=head2 I/O WATCHERS
141		141
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	143	with the following mandatory key-value pairs as arguments:
144		144
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch
146	events. C<poll> must be a string that is either C<r> or C<w>, which	146	for events. C<poll> must be a string that is either C<r> or C<w>,
147	creates a watcher waiting for "r"eadable or "w"ritable events,	147	which creates a watcher waiting for "r"eadable or "w"ritable events,
148	respectively. C<cb> is the callback to invoke each time the file handle	148	respectively. C<cb> is the callback to invoke each time the file handle
149	becomes ready.	149	becomes ready.
150		150
151	As long as the I/O watcher exists it will keep the file descriptor or a	151	Although the callback might get passed parameters, their value and
152	copy of it alive/open.	152	presence is undefined and you cannot rely on them. Portable AnyEvent
		153	callbacks cannot use arguments passed to I/O watcher callbacks.
153		154
		155	The I/O watcher might use the underlying file descriptor or a copy of it.
154	It is not allowed to close a file handle as long as any watcher is active	156	You must not close a file handle as long as any watcher is active on the
155	on the underlying file descriptor.	157	underlying file descriptor.
156		158
157	Some event loops issue spurious readyness notifications, so you should	159	Some event loops issue spurious readyness notifications, so you should
158	always use non-blocking calls when reading/writing from/to your file	160	always use non-blocking calls when reading/writing from/to your file
159	handles.	161	handles.
160		162
…		…
171		173
172	You can create a time watcher by calling the C<< AnyEvent->timer >>	174	You can create a time watcher by calling the C<< AnyEvent->timer >>
173	method with the following mandatory arguments:	175	method with the following mandatory arguments:
174		176
175	C<after> specifies after how many seconds (fractional values are	177	C<after> specifies after how many seconds (fractional values are
176	supported) should the timer activate. C<cb> the callback to invoke in that	178	supported) the callback should be invoked. C<cb> is the callback to invoke
177	case.	179	in that case.
		180
		181	Although the callback might get passed parameters, their value and
		182	presence is undefined and you cannot rely on them. Portable AnyEvent
		183	callbacks cannot use arguments passed to time watcher callbacks.
178		184
179	The timer callback will be invoked at most once: if you want a repeating	185	The timer callback will be invoked at most once: if you want a repeating
180	timer you have to create a new watcher (this is a limitation by both Tk	186	timer you have to create a new watcher (this is a limitation by both Tk
181	and Glib).	187	and Glib).
182		188
…		…
227		233
228	You can watch for signals using a signal watcher, C<signal> is the signal	234	You can watch for signals using a signal watcher, C<signal> is the signal
229	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	235	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
230	be invoked whenever a signal occurs.	236	be invoked whenever a signal occurs.
231		237
		238	Although the callback might get passed parameters, their value and
		239	presence is undefined and you cannot rely on them. Portable AnyEvent
		240	callbacks cannot use arguments passed to signal watcher callbacks.
		241
232	Multiple signal occurances can be clumped together into one callback	242	Multiple signal occurrences can be clumped together into one callback
233	invocation, and callback invocation will be synchronous. synchronous means	243	invocation, and callback invocation will be synchronous. Synchronous means
234	that it might take a while until the signal gets handled by the process,	244	that it might take a while until the signal gets handled by the process,
235	but it is guarenteed not to interrupt any other callbacks.	245	but it is guaranteed not to interrupt any other callbacks.
236		246
237	The main advantage of using these watchers is that you can share a signal	247	The main advantage of using these watchers is that you can share a signal
238	between multiple watchers.	248	between multiple watchers.
239		249
240	This watcher might use C<%SIG>, so programs overwriting those signals	250	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
250		260
251	The child process is specified by the C<pid> argument (if set to C<0>, it	261	The child process is specified by the C<pid> argument (if set to C<0>, it
252	watches for any child process exit). The watcher will trigger as often	262	watches for any child process exit). The watcher will trigger as often
253	as status change for the child are received. This works by installing a	263	as status change for the child are received. This works by installing a
254	signal handler for C<SIGCHLD>. The callback will be called with the pid	264	signal handler for C<SIGCHLD>. The callback will be called with the pid
255	and exit status (as returned by waitpid).	265	and exit status (as returned by waitpid), so unlike other watcher types,
		266	you I<can> rely on child watcher callback arguments.
256		267
257	Example: wait for pid 1333	268	There is a slight catch to child watchers, however: you usually start them
		269	I<after> the child process was created, and this means the process could
		270	have exited already (and no SIGCHLD will be sent anymore).
		271
		272	Not all event models handle this correctly (POE doesn't), but even for
		273	event models that I<do> handle this correctly, they usually need to be
		274	loaded before the process exits (i.e. before you fork in the first place).
		275
		276	This means you cannot create a child watcher as the very first thing in an
		277	AnyEvent program, you I<have> to create at least one watcher before you
		278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		279
		280	Example: fork a process and wait for it
		281
		282	my $done = AnyEvent->condvar;
		283
		284	my $pid = fork or exit 5;
258		285
259	my $w = AnyEvent->child (	286	my $w = AnyEvent->child (
260	pid => 1333,	287	pid => $pid,
261	cb => sub {	288	cb => sub {
262	my ($pid, $status) = @_;	289	my ($pid, $status) = @_;
263	warn "pid $pid exited with status $status";	290	warn "pid $pid exited with status $status";
		291	$done->send;
264	},	292	},
265	);	293	);
266		294
		295	# do something else, then wait for process exit
		296	$done->recv;
		297
267	=head2 CONDITION VARIABLES	298	=head2 CONDITION VARIABLES
268		299
		300	If you are familiar with some event loops you will know that all of them
		301	require you to run some blocking "loop", "run" or similar function that
		302	will actively watch for new events and call your callbacks.
		303
		304	AnyEvent is different, it expects somebody else to run the event loop and
		305	will only block when necessary (usually when told by the user).
		306
		307	The instrument to do that is called a "condition variable", so called
		308	because they represent a condition that must become true.
		309
269	Condition variables can be created by calling the C<< AnyEvent->condvar >>	310	Condition variables can be created by calling the C<< AnyEvent->condvar
270	method without any arguments.	311	>> method, usually without arguments. The only argument pair allowed is
		312	C<cb>, which specifies a callback to be called when the condition variable
		313	becomes true.
271		314
272	A condition variable waits for a condition - precisely that the C<<	315	After creation, the condition variable is "false" until it becomes "true"
273	->broadcast >> method has been called.	316	by calling the C<send> method (or calling the condition variable as if it
		317	were a callback, read about the caveats in the description for the C<<
		318	->send >> method).
274		319
275	They are very useful to signal that a condition has been fulfilled, for	320	Condition variables are similar to callbacks, except that you can
		321	optionally wait for them. They can also be called merge points - points
		322	in time where multiple outstanding events have been processed. And yet
		323	another way to call them is transactions - each condition variable can be
		324	used to represent a transaction, which finishes at some point and delivers
		325	a result.
		326
		327	Condition variables are very useful to signal that something has finished,
276	example, if you write a module that does asynchronous http requests,	328	for example, if you write a module that does asynchronous http requests,
277	then a condition variable would be the ideal candidate to signal the	329	then a condition variable would be the ideal candidate to signal the
278	availability of results.	330	availability of results. The user can either act when the callback is
		331	called or can synchronously C<< ->recv >> for the results.
279		332
280	You can also use condition variables to block your main program until	333	You can also use them to simulate traditional event loops - for example,
281	an event occurs - for example, you could C<< ->wait >> in your main	334	you can block your main program until an event occurs - for example, you
282	program until the user clicks the Quit button in your app, which would C<<	335	could C<< ->recv >> in your main program until the user clicks the Quit
283	->broadcast >> the "quit" event.	336	button of your app, which would C<< ->send >> the "quit" event.
284		337
285	Note that condition variables recurse into the event loop - if you have	338	Note that condition variables recurse into the event loop - if you have
286	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	339	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
287	lose. Therefore, condition variables are good to export to your caller, but	340	lose. Therefore, condition variables are good to export to your caller, but
288	you should avoid making a blocking wait yourself, at least in callbacks,	341	you should avoid making a blocking wait yourself, at least in callbacks,
289	as this asks for trouble.	342	as this asks for trouble.
290		343
291	This object has two methods:	344	Condition variables are represented by hash refs in perl, and the keys
		345	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		346	easy (it is often useful to build your own transaction class on top of
		347	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		348	it's C<new> method in your own C<new> method.
		349
		350	There are two "sides" to a condition variable - the "producer side" which
		351	eventually calls C<< -> send >>, and the "consumer side", which waits
		352	for the send to occur.
		353
		354	Example: wait for a timer.
		355
		356	# wait till the result is ready
		357	my $result_ready = AnyEvent->condvar;
		358
		359	# do something such as adding a timer
		360	# or socket watcher the calls $result_ready->send
		361	# when the "result" is ready.
		362	# in this case, we simply use a timer:
		363	my $w = AnyEvent->timer (
		364	after => 1,
		365	cb => sub { $result_ready->send },
		366	);
		367
		368	# this "blocks" (while handling events) till the callback
		369	# calls send
		370	$result_ready->recv;
		371
		372	Example: wait for a timer, but take advantage of the fact that
		373	condition variables are also code references.
		374
		375	my $done = AnyEvent->condvar;
		376	my $delay = AnyEvent->timer (after => 5, cb => $done);
		377	$done->recv;
		378
		379	=head3 METHODS FOR PRODUCERS
		380
		381	These methods should only be used by the producing side, i.e. the
		382	code/module that eventually sends the signal. Note that it is also
		383	the producer side which creates the condvar in most cases, but it isn't
		384	uncommon for the consumer to create it as well.
292		385
293	=over 4	386	=over 4
294		387
		388	=item $cv->send (...)
		389
		390	Flag the condition as ready - a running C<< ->recv >> and all further
		391	calls to C<recv> will (eventually) return after this method has been
		392	called. If nobody is waiting the send will be remembered.
		393
		394	If a callback has been set on the condition variable, it is called
		395	immediately from within send.
		396
		397	Any arguments passed to the C<send> call will be returned by all
		398	future C<< ->recv >> calls.
		399
		400	Condition variables are overloaded so one can call them directly
		401	(as a code reference). Calling them directly is the same as calling
		402	C<send>. Note, however, that many C-based event loops do not handle
		403	overloading, so as tempting as it may be, passing a condition variable
		404	instead of a callback does not work. Both the pure perl and EV loops
		405	support overloading, however, as well as all functions that use perl to
		406	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		407	example).
		408
		409	=item $cv->croak ($error)
		410
		411	Similar to send, but causes all call's to C<< ->recv >> to invoke
		412	C<Carp::croak> with the given error message/object/scalar.
		413
		414	This can be used to signal any errors to the condition variable
		415	user/consumer.
		416
		417	=item $cv->begin ([group callback])
		418
295	=item $cv->wait	419	=item $cv->end
296		420
297	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	421	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		422
		423	These two methods can be used to combine many transactions/events into
		424	one. For example, a function that pings many hosts in parallel might want
		425	to use a condition variable for the whole process.
		426
		427	Every call to C<< ->begin >> will increment a counter, and every call to
		428	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		429	>>, the (last) callback passed to C<begin> will be executed. That callback
		430	is I<supposed> to call C<< ->send >>, but that is not required. If no
		431	callback was set, C<send> will be called without any arguments.
		432
		433	Let's clarify this with the ping example:
		434
		435	my $cv = AnyEvent->condvar;
		436
		437	my %result;
		438	$cv->begin (sub { $cv->send (\%result) });
		439
		440	for my $host (@list_of_hosts) {
		441	$cv->begin;
		442	ping_host_then_call_callback $host, sub {
		443	$result{$host} = ...;
		444	$cv->end;
		445	};
		446	}
		447
		448	$cv->end;
		449
		450	This code fragment supposedly pings a number of hosts and calls
		451	C<send> after results for all then have have been gathered - in any
		452	order. To achieve this, the code issues a call to C<begin> when it starts
		453	each ping request and calls C<end> when it has received some result for
		454	it. Since C<begin> and C<end> only maintain a counter, the order in which
		455	results arrive is not relevant.
		456
		457	There is an additional bracketing call to C<begin> and C<end> outside the
		458	loop, which serves two important purposes: first, it sets the callback
		459	to be called once the counter reaches C<0>, and second, it ensures that
		460	C<send> is called even when C<no> hosts are being pinged (the loop
		461	doesn't execute once).
		462
		463	This is the general pattern when you "fan out" into multiple subrequests:
		464	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		465	is called at least once, and then, for each subrequest you start, call
		466	C<begin> and for each subrequest you finish, call C<end>.
		467
		468	=back
		469
		470	=head3 METHODS FOR CONSUMERS
		471
		472	These methods should only be used by the consuming side, i.e. the
		473	code awaits the condition.
		474
		475	=over 4
		476
		477	=item $cv->recv
		478
		479	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
298	called on c<$cv>, while servicing other watchers normally.	480	>> methods have been called on c<$cv>, while servicing other watchers
		481	normally.
299		482
300	You can only wait once on a condition - additional calls will return	483	You can only wait once on a condition - additional calls are valid but
301	immediately.	484	will return immediately.
		485
		486	If an error condition has been set by calling C<< ->croak >>, then this
		487	function will call C<croak>.
		488
		489	In list context, all parameters passed to C<send> will be returned,
		490	in scalar context only the first one will be returned.
302		491
303	Not all event models support a blocking wait - some die in that case	492	Not all event models support a blocking wait - some die in that case
304	(programs might want to do that to stay interactive), so I<if you are	493	(programs might want to do that to stay interactive), so I<if you are
305	using this from a module, never require a blocking wait>, but let the	494	using this from a module, never require a blocking wait>, but let the
306	caller decide whether the call will block or not (for example, by coupling	495	caller decide whether the call will block or not (for example, by coupling
307	condition variables with some kind of request results and supporting	496	condition variables with some kind of request results and supporting
308	callbacks so the caller knows that getting the result will not block,	497	callbacks so the caller knows that getting the result will not block,
309	while still suppporting blocking waits if the caller so desires).	498	while still supporting blocking waits if the caller so desires).
310		499
311	Another reason I<never> to C<< ->wait >> in a module is that you cannot	500	Another reason I<never> to C<< ->recv >> in a module is that you cannot
312	sensibly have two C<< ->wait >>'s in parallel, as that would require	501	sensibly have two C<< ->recv >>'s in parallel, as that would require
313	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	502	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
314	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	503	can supply.
315	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
316	from different coroutines, however).
317		504
318	=item $cv->broadcast	505	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		506	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		507	versions and also integrates coroutines into AnyEvent, making blocking
		508	C<< ->recv >> calls perfectly safe as long as they are done from another
		509	coroutine (one that doesn't run the event loop).
319		510
320	Flag the condition as ready - a running C<< ->wait >> and all further	511	You can ensure that C<< -recv >> never blocks by setting a callback and
321	calls to C<wait> will (eventually) return after this method has been	512	only calling C<< ->recv >> from within that callback (or at a later
322	called. If nobody is waiting the broadcast will be remembered..	513	time). This will work even when the event loop does not support blocking
		514	waits otherwise.
		515
		516	=item $bool = $cv->ready
		517
		518	Returns true when the condition is "true", i.e. whether C<send> or
		519	C<croak> have been called.
		520
		521	=item $cb = $cv->cb ([new callback])
		522
		523	This is a mutator function that returns the callback set and optionally
		524	replaces it before doing so.
		525
		526	The callback will be called when the condition becomes "true", i.e. when
		527	C<send> or C<croak> are called. Calling C<recv> inside the callback
		528	or at any later time is guaranteed not to block.
323		529
324	=back	530	=back
325
326	Example:
327
328	# wait till the result is ready
329	my $result_ready = AnyEvent->condvar;
330
331	# do something such as adding a timer
332	# or socket watcher the calls $result_ready->broadcast
333	# when the "result" is ready.
334	# in this case, we simply use a timer:
335	my $w = AnyEvent->timer (
336	after => 1,
337	cb => sub { $result_ready->broadcast },
338	);
339
340	# this "blocks" (while handling events) till the watcher
341	# calls broadcast
342	$result_ready->wait;
343		531
344	=head1 GLOBAL VARIABLES AND FUNCTIONS	532	=head1 GLOBAL VARIABLES AND FUNCTIONS
345		533
346	=over 4	534	=over 4
347		535
…		…
353	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	541	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
354	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	542	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
355		543
356	The known classes so far are:	544	The known classes so far are:
357		545
358	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
359	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
360	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	546	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
361	AnyEvent::Impl::Event based on Event, second best choice.	547	AnyEvent::Impl::Event based on Event, second best choice.
		548	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
362	AnyEvent::Impl::Glib based on Glib, third-best choice.	549	AnyEvent::Impl::Glib based on Glib, third-best choice.
363	AnyEvent::Impl::Tk based on Tk, very bad choice.	550	AnyEvent::Impl::Tk based on Tk, very bad choice.
364	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
365	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	551	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
366	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	552	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		553	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		554
		555	There is no support for WxWidgets, as WxWidgets has no support for
		556	watching file handles. However, you can use WxWidgets through the
		557	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		558	second, which was considered to be too horrible to even consider for
		559	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		560	it's adaptor.
		561
		562	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		563	autodetecting them.
367		564
368	=item AnyEvent::detect	565	=item AnyEvent::detect
369		566
370	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	567	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
371	if necessary. You should only call this function right before you would	568	if necessary. You should only call this function right before you would
372	have created an AnyEvent watcher anyway, that is, as late as possible at	569	have created an AnyEvent watcher anyway, that is, as late as possible at
373	runtime.	570	runtime.
374		571
		572	=item $guard = AnyEvent::post_detect { BLOCK }
		573
		574	Arranges for the code block to be executed as soon as the event model is
		575	autodetected (or immediately if this has already happened).
		576
		577	If called in scalar or list context, then it creates and returns an object
		578	that automatically removes the callback again when it is destroyed. See
		579	L<Coro::BDB> for a case where this is useful.
		580
		581	=item @AnyEvent::post_detect
		582
		583	If there are any code references in this array (you can C<push> to it
		584	before or after loading AnyEvent), then they will called directly after
		585	the event loop has been chosen.
		586
		587	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		588	if it contains a true value then the event loop has already been detected,
		589	and the array will be ignored.
		590
		591	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		592
375	=back	593	=back
376		594
377	=head1 WHAT TO DO IN A MODULE	595	=head1 WHAT TO DO IN A MODULE
378		596
379	As a module author, you should C<use AnyEvent> and call AnyEvent methods	597	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
382	Be careful when you create watchers in the module body - AnyEvent will	600	Be careful when you create watchers in the module body - AnyEvent will
383	decide which event module to use as soon as the first method is called, so	601	decide which event module to use as soon as the first method is called, so
384	by calling AnyEvent in your module body you force the user of your module	602	by calling AnyEvent in your module body you force the user of your module
385	to load the event module first.	603	to load the event module first.
386		604
387	Never call C<< ->wait >> on a condition variable unless you I<know> that	605	Never call C<< ->recv >> on a condition variable unless you I<know> that
388	the C<< ->broadcast >> method has been called on it already. This is	606	the C<< ->send >> method has been called on it already. This is
389	because it will stall the whole program, and the whole point of using	607	because it will stall the whole program, and the whole point of using
390	events is to stay interactive.	608	events is to stay interactive.
391		609
392	It is fine, however, to call C<< ->wait >> when the user of your module	610	It is fine, however, to call C<< ->recv >> when the user of your module
393	requests it (i.e. if you create a http request object ad have a method	611	requests it (i.e. if you create a http request object ad have a method
394	called C<results> that returns the results, it should call C<< ->wait >>	612	called C<results> that returns the results, it should call C<< ->recv >>
395	freely, as the user of your module knows what she is doing. always).	613	freely, as the user of your module knows what she is doing. always).
396		614
397	=head1 WHAT TO DO IN THE MAIN PROGRAM	615	=head1 WHAT TO DO IN THE MAIN PROGRAM
398		616
399	There will always be a single main program - the only place that should	617	There will always be a single main program - the only place that should
…		…
401		619
402	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	620	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
403	do anything special (it does not need to be event-based) and let AnyEvent	621	do anything special (it does not need to be event-based) and let AnyEvent
404	decide which implementation to chose if some module relies on it.	622	decide which implementation to chose if some module relies on it.
405		623
406	If the main program relies on a specific event model. For example, in	624	If the main program relies on a specific event model - for example, in
407	Gtk2 programs you have to rely on the Glib module. You should load the	625	Gtk2 programs you have to rely on the Glib module - you should load the
408	event module before loading AnyEvent or any module that uses it: generally	626	event module before loading AnyEvent or any module that uses it: generally
409	speaking, you should load it as early as possible. The reason is that	627	speaking, you should load it as early as possible. The reason is that
410	modules might create watchers when they are loaded, and AnyEvent will	628	modules might create watchers when they are loaded, and AnyEvent will
411	decide on the event model to use as soon as it creates watchers, and it	629	decide on the event model to use as soon as it creates watchers, and it
412	might chose the wrong one unless you load the correct one yourself.	630	might chose the wrong one unless you load the correct one yourself.
413		631
414	You can chose to use a rather inefficient pure-perl implementation by	632	You can chose to use a pure-perl implementation by loading the
415	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	633	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
416	behaviour everywhere, but letting AnyEvent chose is generally better.	634	everywhere, but letting AnyEvent chose the model is generally better.
		635
		636	=head2 MAINLOOP EMULATION
		637
		638	Sometimes (often for short test scripts, or even standalone programs who
		639	only want to use AnyEvent), you do not want to run a specific event loop.
		640
		641	In that case, you can use a condition variable like this:
		642
		643	AnyEvent->condvar->recv;
		644
		645	This has the effect of entering the event loop and looping forever.
		646
		647	Note that usually your program has some exit condition, in which case
		648	it is better to use the "traditional" approach of storing a condition
		649	variable somewhere, waiting for it, and sending it when the program should
		650	exit cleanly.
		651
		652
		653	=head1 OTHER MODULES
		654
		655	The following is a non-exhaustive list of additional modules that use
		656	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		657	in the same program. Some of the modules come with AnyEvent, some are
		658	available via CPAN.
		659
		660	=over 4
		661
		662	=item L<AnyEvent::Util>
		663
		664	Contains various utility functions that replace often-used but blocking
		665	functions such as C<inet_aton> by event-/callback-based versions.
		666
		667	=item L<AnyEvent::Handle>
		668
		669	Provide read and write buffers and manages watchers for reads and writes.
		670
		671	=item L<AnyEvent::Socket>
		672
		673	Provides various utility functions for (internet protocol) sockets,
		674	addresses and name resolution. Also functions to create non-blocking tcp
		675	connections or tcp servers, with IPv6 and SRV record support and more.
		676
		677	=item L<AnyEvent::DNS>
		678
		679	Provides rich asynchronous DNS resolver capabilities.
		680
		681	=item L<AnyEvent::HTTPD>
		682
		683	Provides a simple web application server framework.
		684
		685	=item L<AnyEvent::FastPing>
		686
		687	The fastest ping in the west.
		688
		689	=item L<Net::IRC3>
		690
		691	AnyEvent based IRC client module family.
		692
		693	=item L<Net::XMPP2>
		694
		695	AnyEvent based XMPP (Jabber protocol) module family.
		696
		697	=item L<Net::FCP>
		698
		699	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		700	of AnyEvent.
		701
		702	=item L<Event::ExecFlow>
		703
		704	High level API for event-based execution flow control.
		705
		706	=item L<Coro>
		707
		708	Has special support for AnyEvent via L<Coro::AnyEvent>.
		709
		710	=item L<AnyEvent::AIO>, L<IO::AIO>
		711
		712	Truly asynchronous I/O, should be in the toolbox of every event
		713	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
		714	together.
		715
		716	=item L<AnyEvent::BDB>, L<BDB>
		717
		718	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
		719	IO::AIO and AnyEvent together.
		720
		721	=item L<IO::Lambda>
		722
		723	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		724
		725	=back
417		726
418	=cut	727	=cut
419		728
420	package AnyEvent;	729	package AnyEvent;
421		730
422	no warnings;	731	no warnings;
423	use strict;	732	use strict;
424		733
425	use Carp;	734	use Carp;
426		735
427	our $VERSION = '3.2';	736	our $VERSION = '4.03';
428	our $MODEL;	737	our $MODEL;
429		738
430	our $AUTOLOAD;	739	our $AUTOLOAD;
431	our @ISA;	740	our @ISA;
432		741
		742	our @REGISTRY;
		743
433	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	744	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
434		745
435	our @REGISTRY;	746	our %PROTOCOL; # (ipv4\|ipv6) => (1\|2), higher numbers are preferred
		747
		748	{
		749	my $idx;
		750	$PROTOCOL{$_} = ++$idx
		751	for reverse split /\s,\s/,
		752	$ENV{PERL_ANYEVENT_PROTOCOLS} \|\| "ipv4,ipv6";
		753	}
436		754
437	my @models = (	755	my @models = (
438	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
439	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
440	[EV:: => AnyEvent::Impl::EV::],	756	[EV:: => AnyEvent::Impl::EV::],
441	[Event:: => AnyEvent::Impl::Event::],	757	[Event:: => AnyEvent::Impl::Event::],
442	[Glib:: => AnyEvent::Impl::Glib::],
443	[Tk:: => AnyEvent::Impl::Tk::],
444	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	758	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		759	# everything below here will not be autoprobed
		760	# as the pureperl backend should work everywhere
		761	# and is usually faster
		762	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		763	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		764	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		765	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		766	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		767	[Wx:: => AnyEvent::Impl::POE::],
		768	[Prima:: => AnyEvent::Impl::POE::],
445	);	769	);
446	my @models_detect = (
447	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
448	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
449	);
450		770
451	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	771	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);
		772
		773	our @post_detect;
		774
		775	sub post_detect(&) {
		776	my ($cb) = @_;
		777
		778	if ($MODEL) {
		779	$cb->();
		780
		781	1
		782	} else {
		783	push @post_detect, $cb;
		784
		785	defined wantarray
		786	? bless \$cb, "AnyEvent::Util::PostDetect"
		787	: ()
		788	}
		789	}
		790
		791	sub AnyEvent::Util::PostDetect::DESTROY {
		792	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		793	}
452		794
453	sub detect() {	795	sub detect() {
454	unless ($MODEL) {	796	unless ($MODEL) {
455	no strict 'refs';	797	no strict 'refs';
		798	local $SIG{__DIE__};
456		799
457	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	800	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
458	my $model = "AnyEvent::Impl::$1";	801	my $model = "AnyEvent::Impl::$1";
459	if (eval "require $model") {	802	if (eval "require $model") {
460	$MODEL = $model;	803	$MODEL = $model;
…		…
464	}	807	}
465	}	808	}
466		809
467	# check for already loaded models	810	# check for already loaded models
468	unless ($MODEL) {	811	unless ($MODEL) {
469	for (@REGISTRY, @models, @models_detect) {	812	for (@REGISTRY, @models) {
470	my ($package, $model) = @$_;	813	my ($package, $model) = @$_;
471	if (${"$package\::VERSION"} > 0) {	814	if (${"$package\::VERSION"} > 0) {
472	if (eval "require $model") {	815	if (eval "require $model") {
473	$MODEL = $model;	816	$MODEL = $model;
474	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	817	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
…		…
490	last;	833	last;
491	}	834	}
492	}	835	}
493		836
494	$MODEL	837	$MODEL
495	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	838	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
496	}	839	}
497	}	840	}
498		841
499	unshift @ISA, $MODEL;	842	unshift @ISA, $MODEL;
500	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	843	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		844
		845	(shift @post_detect)->() while @post_detect;
501	}	846	}
502		847
503	$MODEL	848	$MODEL
504	}	849	}
505		850
…		…
515	$class->$func (@_);	860	$class->$func (@_);
516	}	861	}
517		862
518	package AnyEvent::Base;	863	package AnyEvent::Base;
519		864
520	# default implementation for ->condvar, ->wait, ->broadcast	865	# default implementation for ->condvar
521		866
522	sub condvar {	867	sub condvar {
523	bless \my $flag, "AnyEvent::Base::CondVar"	868	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
524	}
525
526	sub AnyEvent::Base::CondVar::broadcast {
527	${$_[0]}++;
528	}
529
530	sub AnyEvent::Base::CondVar::wait {
531	AnyEvent->one_event while !${$_[0]};
532	}	869	}
533		870
534	# default implementation for ->signal	871	# default implementation for ->signal
535		872
536	our %SIG_CB;	873	our %SIG_CB;
…		…
589	or Carp::croak "required option 'pid' is missing";	926	or Carp::croak "required option 'pid' is missing";
590		927
591	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	928	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
592		929
593	unless ($WNOHANG) {	930	unless ($WNOHANG) {
594	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } \|\| 1;	931	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } \|\| 1;
595	}	932	}
596		933
597	unless ($CHLD_W) {	934	unless ($CHLD_W) {
598	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	935	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
599	# child could be a zombie already, so make at least one round	936	# child could be a zombie already, so make at least one round
…		…
609	delete $PID_CB{$pid}{$cb};	946	delete $PID_CB{$pid}{$cb};
610	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	947	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
611		948
612	undef $CHLD_W unless keys %PID_CB;	949	undef $CHLD_W unless keys %PID_CB;
613	}	950	}
		951
		952	package AnyEvent::CondVar;
		953
		954	our @ISA = AnyEvent::CondVar::Base::;
		955
		956	package AnyEvent::CondVar::Base;
		957
		958	use overload
		959	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		960	fallback => 1;
		961
		962	sub _send {
		963	# nop
		964	}
		965
		966	sub send {
		967	my $cv = shift;
		968	$cv->{_ae_sent} = [@_];
		969	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		970	$cv->_send;
		971	}
		972
		973	sub croak {
		974	$_[0]{_ae_croak} = $_[1];
		975	$_[0]->send;
		976	}
		977
		978	sub ready {
		979	$_[0]{_ae_sent}
		980	}
		981
		982	sub _wait {
		983	AnyEvent->one_event while !$_[0]{_ae_sent};
		984	}
		985
		986	sub recv {
		987	$_[0]->_wait;
		988
		989	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		990	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		991	}
		992
		993	sub cb {
		994	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		995	$_[0]{_ae_cb}
		996	}
		997
		998	sub begin {
		999	++$_[0]{_ae_counter};
		1000	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1001	}
		1002
		1003	sub end {
		1004	return if --$_[0]{_ae_counter};
		1005	&{ $_[0]{_ae_end_cb} \|\| sub { $_[0]->send } };
		1006	}
		1007
		1008	# undocumented/compatibility with pre-3.4
		1009	*broadcast = \&send;
		1010	*wait = \&_wait;
614		1011
615	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1012	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
616		1013
617	This is an advanced topic that you do not normally need to use AnyEvent in	1014	This is an advanced topic that you do not normally need to use AnyEvent in
618	a module. This section is only of use to event loop authors who want to	1015	a module. This section is only of use to event loop authors who want to
…		…
675	model it chooses.	1072	model it chooses.
676		1073
677	=item C<PERL_ANYEVENT_MODEL>	1074	=item C<PERL_ANYEVENT_MODEL>
678		1075
679	This can be used to specify the event model to be used by AnyEvent, before	1076	This can be used to specify the event model to be used by AnyEvent, before
680	autodetection and -probing kicks in. It must be a string consisting	1077	auto detection and -probing kicks in. It must be a string consisting
681	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended	1078	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
682	and the resulting module name is loaded and if the load was successful,	1079	and the resulting module name is loaded and if the load was successful,
683	used as event model. If it fails to load AnyEvent will proceed with	1080	used as event model. If it fails to load AnyEvent will proceed with
684	autodetection and -probing.	1081	auto detection and -probing.
685		1082
686	This functionality might change in future versions.	1083	This functionality might change in future versions.
687		1084
688	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you	1085	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
689	could start your program like this:	1086	could start your program like this:
690		1087
691	PERL_ANYEVENT_MODEL=Perl perl ...	1088	PERL_ANYEVENT_MODEL=Perl perl ...
692		1089
		1090	=item C<PERL_ANYEVENT_PROTOCOLS>
		1091
		1092	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1093	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1094	of auto probing).
		1095
		1096	Must be set to a comma-separated list of protocols or address families,
		1097	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1098	used, and preference will be given to protocols mentioned earlier in the
		1099	list.
		1100
		1101	This variable can effectively be used for denial-of-service attacks
		1102	against local programs (e.g. when setuid), although the impact is likely
		1103	small, as the program has to handle connection errors already-
		1104
		1105	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1106	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1107	- only support IPv4, never try to resolve or contact IPv6
		1108	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1109	IPv6, but prefer IPv6 over IPv4.
		1110
		1111	=item C<PERL_ANYEVENT_EDNS0>
		1112
		1113	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1114	for DNS. This extension is generally useful to reduce DNS traffic, but
		1115	some (broken) firewalls drop such DNS packets, which is why it is off by
		1116	default.
		1117
		1118	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1119	EDNS0 in its DNS requests.
		1120
693	=back	1121	=back
694		1122
695	=head1 EXAMPLE PROGRAM	1123	=head1 EXAMPLE PROGRAM
696		1124
697	The following program uses an IO watcher to read data from STDIN, a timer	1125	The following program uses an I/O watcher to read data from STDIN, a timer
698	to display a message once per second, and a condition variable to quit the	1126	to display a message once per second, and a condition variable to quit the
699	program when the user enters quit:	1127	program when the user enters quit:
700		1128
701	use AnyEvent;	1129	use AnyEvent;
702		1130
…		…
707	poll => 'r',	1135	poll => 'r',
708	cb => sub {	1136	cb => sub {
709	warn "io event <$_[0]>\n"; # will always output <r>	1137	warn "io event <$_[0]>\n"; # will always output <r>
710	chomp (my $input = <STDIN>); # read a line	1138	chomp (my $input = <STDIN>); # read a line
711	warn "read: $input\n"; # output what has been read	1139	warn "read: $input\n"; # output what has been read
712	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1140	$cv->send if $input =~ /^q/i; # quit program if /^q/i
713	},	1141	},
714	);	1142	);
715		1143
716	my $time_watcher; # can only be used once	1144	my $time_watcher; # can only be used once
717		1145
…		…
722	});	1150	});
723	}	1151	}
724		1152
725	new_timer; # create first timer	1153	new_timer; # create first timer
726		1154
727	$cv->wait; # wait until user enters /^q/i	1155	$cv->recv; # wait until user enters /^q/i
728		1156
729	=head1 REAL-WORLD EXAMPLE	1157	=head1 REAL-WORLD EXAMPLE
730		1158
731	Consider the L<Net::FCP> module. It features (among others) the following	1159	Consider the L<Net::FCP> module. It features (among others) the following
732	API calls, which are to freenet what HTTP GET requests are to http:	1160	API calls, which are to freenet what HTTP GET requests are to http:
…		…
782	syswrite $txn->{fh}, $txn->{request}	1210	syswrite $txn->{fh}, $txn->{request}
783	or die "connection or write error";	1211	or die "connection or write error";
784	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1212	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
785		1213
786	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1214	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
787	result and signals any possible waiters that the request ahs finished:	1215	result and signals any possible waiters that the request has finished:
788		1216
789	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1217	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
790		1218
791	if (end-of-file or data complete) {	1219	if (end-of-file or data complete) {
792	$txn->{result} = $txn->{buf};	1220	$txn->{result} = $txn->{buf};
793	$txn->{finished}->broadcast;	1221	$txn->{finished}->send;
794	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1222	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
795	}	1223	}
796		1224
797	The C<result> method, finally, just waits for the finished signal (if the	1225	The C<result> method, finally, just waits for the finished signal (if the
798	request was already finished, it doesn't wait, of course, and returns the	1226	request was already finished, it doesn't wait, of course, and returns the
799	data:	1227	data:
800		1228
801	$txn->{finished}->wait;	1229	$txn->{finished}->recv;
802	return $txn->{result};	1230	return $txn->{result};
803		1231
804	The actual code goes further and collects all errors (C<die>s, exceptions)	1232	The actual code goes further and collects all errors (C<die>s, exceptions)
805	that occured during request processing. The C<result> method detects	1233	that occurred during request processing. The C<result> method detects
806	whether an exception as thrown (it is stored inside the $txn object)	1234	whether an exception as thrown (it is stored inside the $txn object)
807	and just throws the exception, which means connection errors and other	1235	and just throws the exception, which means connection errors and other
808	problems get reported tot he code that tries to use the result, not in a	1236	problems get reported tot he code that tries to use the result, not in a
809	random callback.	1237	random callback.
810		1238
…		…
841		1269
842	my $quit = AnyEvent->condvar;	1270	my $quit = AnyEvent->condvar;
843		1271
844	$fcp->txn_client_get ($url)->cb (sub {	1272	$fcp->txn_client_get ($url)->cb (sub {
845	...	1273	...
846	$quit->broadcast;	1274	$quit->send;
847	});	1275	});
848		1276
849	$quit->wait;	1277	$quit->recv;
		1278
		1279
		1280	=head1 BENCHMARKS
		1281
		1282	To give you an idea of the performance and overheads that AnyEvent adds
		1283	over the event loops themselves and to give you an impression of the speed
		1284	of various event loops I prepared some benchmarks.
		1285
		1286	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1287
		1288	Here is a benchmark of various supported event models used natively and
		1289	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1290	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1291	which it is), lets them fire exactly once and destroys them again.
		1292
		1293	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1294	distribution.
		1295
		1296	=head3 Explanation of the columns
		1297
		1298	I<watcher> is the number of event watchers created/destroyed. Since
		1299	different event models feature vastly different performances, each event
		1300	loop was given a number of watchers so that overall runtime is acceptable
		1301	and similar between tested event loop (and keep them from crashing): Glib
		1302	would probably take thousands of years if asked to process the same number
		1303	of watchers as EV in this benchmark.
		1304
		1305	I<bytes> is the number of bytes (as measured by the resident set size,
		1306	RSS) consumed by each watcher. This method of measuring captures both C
		1307	and Perl-based overheads.
		1308
		1309	I<create> is the time, in microseconds (millionths of seconds), that it
		1310	takes to create a single watcher. The callback is a closure shared between
		1311	all watchers, to avoid adding memory overhead. That means closure creation
		1312	and memory usage is not included in the figures.
		1313
		1314	I<invoke> is the time, in microseconds, used to invoke a simple
		1315	callback. The callback simply counts down a Perl variable and after it was
		1316	invoked "watcher" times, it would C<< ->send >> a condvar once to
		1317	signal the end of this phase.
		1318
		1319	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1320	watcher.
		1321
		1322	=head3 Results
		1323
		1324	name watchers bytes create invoke destroy comment
		1325	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		1326	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		1327	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		1328	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		1329	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		1330	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		1331	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		1332	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		1333	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		1334	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		1335
		1336	=head3 Discussion
		1337
		1338	The benchmark does I<not> measure scalability of the event loop very
		1339	well. For example, a select-based event loop (such as the pure perl one)
		1340	can never compete with an event loop that uses epoll when the number of
		1341	file descriptors grows high. In this benchmark, all events become ready at
		1342	the same time, so select/poll-based implementations get an unnatural speed
		1343	boost.
		1344
		1345	Also, note that the number of watchers usually has a nonlinear effect on
		1346	overall speed, that is, creating twice as many watchers doesn't take twice
		1347	the time - usually it takes longer. This puts event loops tested with a
		1348	higher number of watchers at a disadvantage.
		1349
		1350	To put the range of results into perspective, consider that on the
		1351	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1352	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1353	cycles with POE.
		1354
		1355	C<EV> is the sole leader regarding speed and memory use, which are both
		1356	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1357	far less memory than any other event loop and is still faster than Event
		1358	natively.
		1359
		1360	The pure perl implementation is hit in a few sweet spots (both the
		1361	constant timeout and the use of a single fd hit optimisations in the perl
		1362	interpreter and the backend itself). Nevertheless this shows that it
		1363	adds very little overhead in itself. Like any select-based backend its
		1364	performance becomes really bad with lots of file descriptors (and few of
		1365	them active), of course, but this was not subject of this benchmark.
		1366
		1367	The C<Event> module has a relatively high setup and callback invocation
		1368	cost, but overall scores in on the third place.
		1369
		1370	C<Glib>'s memory usage is quite a bit higher, but it features a
		1371	faster callback invocation and overall ends up in the same class as
		1372	C<Event>. However, Glib scales extremely badly, doubling the number of
		1373	watchers increases the processing time by more than a factor of four,
		1374	making it completely unusable when using larger numbers of watchers
		1375	(note that only a single file descriptor was used in the benchmark, so
		1376	inefficiencies of C<poll> do not account for this).
		1377
		1378	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1379	more than 2000 watchers is a big setback, however, as correctness takes
		1380	precedence over speed. Nevertheless, its performance is surprising, as the
		1381	file descriptor is dup()ed for each watcher. This shows that the dup()
		1382	employed by some adaptors is not a big performance issue (it does incur a
		1383	hidden memory cost inside the kernel which is not reflected in the figures
		1384	above).
		1385
		1386	C<POE>, regardless of underlying event loop (whether using its pure perl
		1387	select-based backend or the Event module, the POE-EV backend couldn't
		1388	be tested because it wasn't working) shows abysmal performance and
		1389	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		1390	as EV watchers, and 10 times as much memory as Event (the high memory
		1391	requirements are caused by requiring a session for each watcher). Watcher
		1392	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1393	implementation.
		1394
		1395	The design of the POE adaptor class in AnyEvent can not really account
		1396	for the performance issues, though, as session creation overhead is
		1397	small compared to execution of the state machine, which is coded pretty
		1398	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1399	using multiple sessions is not a good approach, especially regarding
		1400	memory usage, even the author of POE could not come up with a faster
		1401	design).
		1402
		1403	=head3 Summary
		1404
		1405	=over 4
		1406
		1407	=item * Using EV through AnyEvent is faster than any other event loop
		1408	(even when used without AnyEvent), but most event loops have acceptable
		1409	performance with or without AnyEvent.
		1410
		1411	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1412	the actual event loop, only with extremely fast event loops such as EV
		1413	adds AnyEvent significant overhead.
		1414
		1415	=item * You should avoid POE like the plague if you want performance or
		1416	reasonable memory usage.
		1417
		1418	=back
		1419
		1420	=head2 BENCHMARKING THE LARGE SERVER CASE
		1421
		1422	This benchmark actually benchmarks the event loop itself. It works by
		1423	creating a number of "servers": each server consists of a socket pair, a
		1424	timeout watcher that gets reset on activity (but never fires), and an I/O
		1425	watcher waiting for input on one side of the socket. Each time the socket
		1426	watcher reads a byte it will write that byte to a random other "server".
		1427
		1428	The effect is that there will be a lot of I/O watchers, only part of which
		1429	are active at any one point (so there is a constant number of active
		1430	fds for each loop iteration, but which fds these are is random). The
		1431	timeout is reset each time something is read because that reflects how
		1432	most timeouts work (and puts extra pressure on the event loops).
		1433
		1434	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1435	(1%) are active. This mirrors the activity of large servers with many
		1436	connections, most of which are idle at any one point in time.
		1437
		1438	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1439	distribution.
		1440
		1441	=head3 Explanation of the columns
		1442
		1443	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1444	each server has a read and write socket end).
		1445
		1446	I<create> is the time it takes to create a socket pair (which is
		1447	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1448
		1449	I<request>, the most important value, is the time it takes to handle a
		1450	single "request", that is, reading the token from the pipe and forwarding
		1451	it to another server. This includes deleting the old timeout and creating
		1452	a new one that moves the timeout into the future.
		1453
		1454	=head3 Results
		1455
		1456	name sockets create request
		1457	EV 20000 69.01 11.16
		1458	Perl 20000 73.32 35.87
		1459	Event 20000 212.62 257.32
		1460	Glib 20000 651.16 1896.30
		1461	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1462
		1463	=head3 Discussion
		1464
		1465	This benchmark I<does> measure scalability and overall performance of the
		1466	particular event loop.
		1467
		1468	EV is again fastest. Since it is using epoll on my system, the setup time
		1469	is relatively high, though.
		1470
		1471	Perl surprisingly comes second. It is much faster than the C-based event
		1472	loops Event and Glib.
		1473
		1474	Event suffers from high setup time as well (look at its code and you will
		1475	understand why). Callback invocation also has a high overhead compared to
		1476	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1477	uses select or poll in basically all documented configurations.
		1478
		1479	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1480	clearly fails to perform with many filehandles or in busy servers.
		1481
		1482	POE is still completely out of the picture, taking over 1000 times as long
		1483	as EV, and over 100 times as long as the Perl implementation, even though
		1484	it uses a C-based event loop in this case.
		1485
		1486	=head3 Summary
		1487
		1488	=over 4
		1489
		1490	=item * The pure perl implementation performs extremely well.
		1491
		1492	=item * Avoid Glib or POE in large projects where performance matters.
		1493
		1494	=back
		1495
		1496	=head2 BENCHMARKING SMALL SERVERS
		1497
		1498	While event loops should scale (and select-based ones do not...) even to
		1499	large servers, most programs we (or I :) actually write have only a few
		1500	I/O watchers.
		1501
		1502	In this benchmark, I use the same benchmark program as in the large server
		1503	case, but it uses only eight "servers", of which three are active at any
		1504	one time. This should reflect performance for a small server relatively
		1505	well.
		1506
		1507	The columns are identical to the previous table.
		1508
		1509	=head3 Results
		1510
		1511	name sockets create request
		1512	EV 16 20.00 6.54
		1513	Perl 16 25.75 12.62
		1514	Event 16 81.27 35.86
		1515	Glib 16 32.63 15.48
		1516	POE 16 261.87 276.28 uses POE::Loop::Event
		1517
		1518	=head3 Discussion
		1519
		1520	The benchmark tries to test the performance of a typical small
		1521	server. While knowing how various event loops perform is interesting, keep
		1522	in mind that their overhead in this case is usually not as important, due
		1523	to the small absolute number of watchers (that is, you need efficiency and
		1524	speed most when you have lots of watchers, not when you only have a few of
		1525	them).
		1526
		1527	EV is again fastest.
		1528
		1529	Perl again comes second. It is noticeably faster than the C-based event
		1530	loops Event and Glib, although the difference is too small to really
		1531	matter.
		1532
		1533	POE also performs much better in this case, but is is still far behind the
		1534	others.
		1535
		1536	=head3 Summary
		1537
		1538	=over 4
		1539
		1540	=item * C-based event loops perform very well with small number of
		1541	watchers, as the management overhead dominates.
		1542
		1543	=back
		1544
850		1545
851	=head1 FORK	1546	=head1 FORK
852		1547
853	Most event libraries are not fork-safe. The ones who are usually are	1548	Most event libraries are not fork-safe. The ones who are usually are
854	because they are so inefficient. Only L<EV> is fully fork-aware.	1549	because they rely on inefficient but fork-safe C<select> or C<poll>
		1550	calls. Only L<EV> is fully fork-aware.
855		1551
856	If you have to fork, you must either do so I<before> creating your first	1552	If you have to fork, you must either do so I<before> creating your first
857	watcher OR you must not use AnyEvent at all in the child.	1553	watcher OR you must not use AnyEvent at all in the child.
		1554
858		1555
859	=head1 SECURITY CONSIDERATIONS	1556	=head1 SECURITY CONSIDERATIONS
860		1557
861	AnyEvent can be forced to load any event model via	1558	AnyEvent can be forced to load any event model via
862	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	1559	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
870		1567
871	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1568	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
872		1569
873	use AnyEvent;	1570	use AnyEvent;
874		1571
		1572	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1573	be used to probe what backend is used and gain other information (which is
		1574	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
		1575
		1576
875	=head1 SEE ALSO	1577	=head1 SEE ALSO
876		1578
877	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1579	Utility functions: L<AnyEvent::Util>.
878	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
879	L<Event::Lib>, L<Qt>.
880		1580
881	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1581	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
882	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1582	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
883	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1583
		1584	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		1585	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		1586	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
884	L<AnyEvent::Impl::Qt>.	1587	L<AnyEvent::Impl::POE>.
885		1588
		1589	Non-blocking file handles, sockets, TCP clients and
		1590	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1591
		1592	Asynchronous DNS: L<AnyEvent::DNS>.
		1593
		1594	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1595
886	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1596	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
		1597
887		1598
888	=head1 AUTHOR	1599	=head1 AUTHOR
889		1600
890	Marc Lehmann <schmorp@schmorp.de>	1601	Marc Lehmann <schmorp@schmorp.de>
891	http://home.schmorp.de/	1602	http://home.schmorp.de/

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Revision 1.60 by root, Fri Apr 25 01:05:26 2008 UTC vs.
Revision 1.137 by root, Mon May 26 03:27:52 2008 UTC