[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 1.108 by root, Sat May 10 00:22:02 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->wait; # enters "main loop" till $condvar gets ->broadcast	20	$w->wait; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	21	$w->send; # 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?
…		…
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		70
71
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
76	users to use the same event loop (as only a single event loop can coexist	75	users to use the same event loop (as only a single event loop can coexist
…		…
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
…		…
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 occurances 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 guarenteed not to interrupt any other callbacks.
236		246
…		…
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	AnyEvent::detect; # force event module to be initialised
		285
		286	my $pid = fork or exit 5;
258		287
259	my $w = AnyEvent->child (	288	my $w = AnyEvent->child (
260	pid => 1333,	289	pid => $pid,
261	cb => sub {	290	cb => sub {
262	my ($pid, $status) = @_;	291	my ($pid, $status) = @_;
263	warn "pid $pid exited with status $status";	292	warn "pid $pid exited with status $status";
		293	$done->send;
264	},	294	},
265	);	295	);
266		296
		297	# do something else, then wait for process exit
		298	$done->wait;
		299
267	=head2 CONDITION VARIABLES	300	=head2 CONDITION VARIABLES
268		301
		302	If you are familiar with some event loops you will know that all of them
		303	require you to run some blocking "loop", "run" or similar function that
		304	will actively watch for new events and call your callbacks.
		305
		306	AnyEvent is different, it expects somebody else to run the event loop and
		307	will only block when necessary (usually when told by the user).
		308
		309	The instrument to do that is called a "condition variable", so called
		310	because they represent a condition that must become true.
		311
269	Condition variables can be created by calling the C<< AnyEvent->condvar >>	312	Condition variables can be created by calling the C<< AnyEvent->condvar
270	method without any arguments.	313	>> method, usually without arguments. The only argument pair allowed is
		314	C<cb>, which specifies a callback to be called when the condition variable
		315	becomes true.
271		316
272	A condition variable waits for a condition - precisely that the C<<	317	After creation, the conditon variable is "false" until it becomes "true"
273	->broadcast >> method has been called.	318	by calling the C<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 outstandign events have been processed. And yet
		323	another way to call them is transations - 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<< ->wait >> 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<< ->wait >> 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<< ->wait >> in a round-robbin 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:
		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->wait;
		371
		372	=head3 METHODS FOR PRODUCERS
		373
		374	These methods should only be used by the producing side, i.e. the
		375	code/module that eventually sends the signal. Note that it is also
		376	the producer side which creates the condvar in most cases, but it isn't
		377	uncommon for the consumer to create it as well.
292		378
293	=over 4	379	=over 4
294		380
		381	=item $cv->send (...)
		382
		383	Flag the condition as ready - a running C<< ->wait >> and all further
		384	calls to C<wait> will (eventually) return after this method has been
		385	called. If nobody is waiting the send will be remembered.
		386
		387	If a callback has been set on the condition variable, it is called
		388	immediately from within send.
		389
		390	Any arguments passed to the C<send> call will be returned by all
		391	future C<< ->wait >> calls.
		392
		393	=item $cv->croak ($error)
		394
		395	Similar to send, but causes all call's wait C<< ->wait >> to invoke
		396	C<Carp::croak> with the given error message/object/scalar.
		397
		398	This can be used to signal any errors to the condition variable
		399	user/consumer.
		400
		401	=item $cv->begin ([group callback])
		402
		403	=item $cv->end
		404
		405	These two methods can be used to combine many transactions/events into
		406	one. For example, a function that pings many hosts in parallel might want
		407	to use a condition variable for the whole process.
		408
		409	Every call to C<< ->begin >> will increment a counter, and every call to
		410	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		411	>>, the (last) callback passed to C<begin> will be executed. That callback
		412	is I<supposed> to call C<< ->send >>, but that is not required. If no
		413	callback was set, C<send> will be called without any arguments.
		414
		415	Let's clarify this with the ping example:
		416
		417	my $cv = AnyEvent->condvar;
		418
		419	my %result;
		420	$cv->begin (sub { $cv->send (\%result) });
		421
		422	for my $host (@list_of_hosts) {
		423	$cv->begin;
		424	ping_host_then_call_callback $host, sub {
		425	$result{$host} = ...;
		426	$cv->end;
		427	};
		428	}
		429
		430	$cv->end;
		431
		432	This code fragment supposedly pings a number of hosts and calls
		433	C<send> after results for all then have have been gathered - in any
		434	order. To achieve this, the code issues a call to C<begin> when it starts
		435	each ping request and calls C<end> when it has received some result for
		436	it. Since C<begin> and C<end> only maintain a counter, the order in which
		437	results arrive is not relevant.
		438
		439	There is an additional bracketing call to C<begin> and C<end> outside the
		440	loop, which serves two important purposes: first, it sets the callback
		441	to be called once the counter reaches C<0>, and second, it ensures that
		442	C<send> is called even when C<no> hosts are being pinged (the loop
		443	doesn't execute once).
		444
		445	This is the general pattern when you "fan out" into multiple subrequests:
		446	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		447	is called at least once, and then, for each subrequest you start, call
		448	C<begin> and for eahc subrequest you finish, call C<end>.
		449
		450	=back
		451
		452	=head3 METHODS FOR CONSUMERS
		453
		454	These methods should only be used by the consuming side, i.e. the
		455	code awaits the condition.
		456
		457	=over 4
		458
295	=item $cv->wait	459	=item $cv->wait
296		460
297	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
298	called on c<$cv>, while servicing other watchers normally.	462	>> methods have been called on c<$cv>, while servicing other watchers
		463	normally.
299		464
300	You can only wait once on a condition - additional calls will return	465	You can only wait once on a condition - additional calls are valid but
301	immediately.	466	will return immediately.
		467
		468	If an error condition has been set by calling C<< ->croak >>, then this
		469	function will call C<croak>.
		470
		471	In list context, all parameters passed to C<send> will be returned,
		472	in scalar context only the first one will be returned.
302		473
303	Not all event models support a blocking wait - some die in that case	474	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	475	(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	476	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	477	caller decide whether the call will block or not (for example, by coupling
…		…
309	while still suppporting blocking waits if the caller so desires).	480	while still suppporting blocking waits if the caller so desires).
310		481
311	Another reason I<never> to C<< ->wait >> in a module is that you cannot	482	Another reason I<never> to C<< ->wait >> in a module is that you cannot
312	sensibly have two C<< ->wait >>'s in parallel, as that would require	483	sensibly have two C<< ->wait >>'s in parallel, as that would require
313	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
314	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	485	can supply.
315	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
316	from different coroutines, however).
317		486
318	=item $cv->broadcast	487	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		488	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		489	versions and also integrates coroutines into AnyEvent, making blocking
		490	C<< ->wait >> calls perfectly safe as long as they are done from another
		491	coroutine (one that doesn't run the event loop).
319		492
320	Flag the condition as ready - a running C<< ->wait >> and all further	493	You can ensure that C<< -wait >> never blocks by setting a callback and
321	calls to C<wait> will (eventually) return after this method has been	494	only calling C<< ->wait >> from within that callback (or at a later
322	called. If nobody is waiting the broadcast will be remembered..	495	time). This will work even when the event loop does not support blocking
		496	waits otherwise.
		497
		498	=item $bool = $cv->ready
		499
		500	Returns true when the condition is "true", i.e. whether C<send> or
		501	C<croak> have been called.
		502
		503	=item $cb = $cv->cb ([new callback])
		504
		505	This is a mutator function that returns the callback set and optionally
		506	replaces it before doing so.
		507
		508	The callback will be called when the condition becomes "true", i.e. when
		509	C<send> or C<croak> are called. Calling C<wait> inside the callback
		510	or at any later time is guaranteed not to block.
323		511
324	=back	512	=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		513
344	=head1 GLOBAL VARIABLES AND FUNCTIONS	514	=head1 GLOBAL VARIABLES AND FUNCTIONS
345		515
346	=over 4	516	=over 4
347		517
…		…
353	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	523	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>).	524	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
355		525
356	The known classes so far are:	526	The known classes so far are:
357		527
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).	528	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
361	AnyEvent::Impl::Event based on Event, second best choice.	529	AnyEvent::Impl::Event based on Event, second best choice.
		530	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
362	AnyEvent::Impl::Glib based on Glib, third-best choice.	531	AnyEvent::Impl::Glib based on Glib, third-best choice.
363	AnyEvent::Impl::Tk based on Tk, very bad choice.	532	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).	533	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
366	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	534	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		535	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		536
		537	There is no support for WxWidgets, as WxWidgets has no support for
		538	watching file handles. However, you can use WxWidgets through the
		539	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		540	second, which was considered to be too horrible to even consider for
		541	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		542	it's adaptor.
		543
		544	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		545	autodetecting them.
367		546
368	=item AnyEvent::detect	547	=item AnyEvent::detect
369		548
370	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	549	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
371	if necessary. You should only call this function right before you would	550	if necessary. You should only call this function right before you would
372	have created an AnyEvent watcher anyway, that is, as late as possible at	551	have created an AnyEvent watcher anyway, that is, as late as possible at
373	runtime.	552	runtime.
374		553
		554	=item @AnyEvent::detect
		555
		556	If there are any code references in this array (you can C<push> to it
		557	before or after loading AnyEvent), then they will called directly after
		558	the event loop has been chosen.
		559
		560	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		561	if it contains a true value then the event loop has already been detected,
		562	and the array will be ignored.
		563
375	=back	564	=back
376		565
377	=head1 WHAT TO DO IN A MODULE	566	=head1 WHAT TO DO IN A MODULE
378		567
379	As a module author, you should C<use AnyEvent> and call AnyEvent methods	568	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
383	decide which event module to use as soon as the first method is called, so	572	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	573	by calling AnyEvent in your module body you force the user of your module
385	to load the event module first.	574	to load the event module first.
386		575
387	Never call C<< ->wait >> on a condition variable unless you I<know> that	576	Never call C<< ->wait >> on a condition variable unless you I<know> that
388	the C<< ->broadcast >> method has been called on it already. This is	577	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	578	because it will stall the whole program, and the whole point of using
390	events is to stay interactive.	579	events is to stay interactive.
391		580
392	It is fine, however, to call C<< ->wait >> when the user of your module	581	It is fine, however, to call C<< ->wait >> when the user of your module
393	requests it (i.e. if you create a http request object ad have a method	582	requests it (i.e. if you create a http request object ad have a method
…		…
413		602
414	You can chose to use a rather inefficient pure-perl implementation by	603	You can chose to use a rather inefficient pure-perl implementation by
415	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	604	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
416	behaviour everywhere, but letting AnyEvent chose is generally better.	605	behaviour everywhere, but letting AnyEvent chose is generally better.
417		606
		607	=head1 OTHER MODULES
		608
		609	The following is a non-exhaustive list of additional modules that use
		610	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		611	in the same program. Some of the modules come with AnyEvent, some are
		612	available via CPAN.
		613
		614	=over 4
		615
		616	=item L<AnyEvent::Util>
		617
		618	Contains various utility functions that replace often-used but blocking
		619	functions such as C<inet_aton> by event-/callback-based versions.
		620
		621	=item L<AnyEvent::Handle>
		622
		623	Provide read and write buffers and manages watchers for reads and writes.
		624
		625	=item L<AnyEvent::Socket>
		626
		627	Provides a means to do non-blocking connects, accepts etc.
		628
		629	=item L<AnyEvent::HTTPD>
		630
		631	Provides a simple web application server framework.
		632
		633	=item L<AnyEvent::DNS>
		634
		635	Provides asynchronous DNS resolver capabilities, beyond what
		636	L<AnyEvent::Util> offers.
		637
		638	=item L<AnyEvent::FastPing>
		639
		640	The fastest ping in the west.
		641
		642	=item L<Net::IRC3>
		643
		644	AnyEvent based IRC client module family.
		645
		646	=item L<Net::XMPP2>
		647
		648	AnyEvent based XMPP (Jabber protocol) module family.
		649
		650	=item L<Net::FCP>
		651
		652	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		653	of AnyEvent.
		654
		655	=item L<Event::ExecFlow>
		656
		657	High level API for event-based execution flow control.
		658
		659	=item L<Coro>
		660
		661	Has special support for AnyEvent via L<Coro::AnyEvent>.
		662
		663	=item L<IO::Lambda>
		664
		665	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		666
		667	=item L<IO::AIO>
		668
		669	Truly asynchronous I/O, should be in the toolbox of every event
		670	programmer. Can be trivially made to use AnyEvent.
		671
		672	=item L<BDB>
		673
		674	Truly asynchronous Berkeley DB access. Can be trivially made to use
		675	AnyEvent.
		676
		677	=back
		678
418	=cut	679	=cut
419		680
420	package AnyEvent;	681	package AnyEvent;
421		682
422	no warnings;	683	no warnings;
423	use strict;	684	use strict;
424		685
425	use Carp;	686	use Carp;
426		687
427	our $VERSION = '3.2';	688	our $VERSION = '3.4';
428	our $MODEL;	689	our $MODEL;
429		690
430	our $AUTOLOAD;	691	our $AUTOLOAD;
431	our @ISA;	692	our @ISA;
432		693
433	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	694	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
434		695
435	our @REGISTRY;	696	our @REGISTRY;
436		697
437	my @models = (	698	my @models = (
438	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
439	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
440	[EV:: => AnyEvent::Impl::EV::],	699	[EV:: => AnyEvent::Impl::EV::],
441	[Event:: => AnyEvent::Impl::Event::],	700	[Event:: => AnyEvent::Impl::Event::],
		701	[Tk:: => AnyEvent::Impl::Tk::],
		702	[Wx:: => AnyEvent::Impl::POE::],
		703	[Prima:: => AnyEvent::Impl::POE::],
		704	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		705	# everything below here will not be autoprobed as the pureperl backend should work everywhere
442	[Glib:: => AnyEvent::Impl::Glib::],	706	[Glib:: => AnyEvent::Impl::Glib::],
443	[Tk:: => AnyEvent::Impl::Tk::],	707	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
444	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	708	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		709	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
445	);	710	);
446	my @models_detect = (
447	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
448	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
449	);
450		711
451	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	712	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);
		713
		714	our @detect;
452		715
453	sub detect() {	716	sub detect() {
454	unless ($MODEL) {	717	unless ($MODEL) {
455	no strict 'refs';	718	no strict 'refs';
456		719
…		…
464	}	727	}
465	}	728	}
466		729
467	# check for already loaded models	730	# check for already loaded models
468	unless ($MODEL) {	731	unless ($MODEL) {
469	for (@REGISTRY, @models, @models_detect) {	732	for (@REGISTRY, @models) {
470	my ($package, $model) = @$_;	733	my ($package, $model) = @$_;
471	if (${"$package\::VERSION"} > 0) {	734	if (${"$package\::VERSION"} > 0) {
472	if (eval "require $model") {	735	if (eval "require $model") {
473	$MODEL = $model;	736	$MODEL = $model;
474	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	737	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
…		…
490	last;	753	last;
491	}	754	}
492	}	755	}
493		756
494	$MODEL	757	$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.";	758	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
496	}	759	}
497	}	760	}
498		761
499	unshift @ISA, $MODEL;	762	unshift @ISA, $MODEL;
500	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	763	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		764
		765	(shift @detect)->() while @detect;
501	}	766	}
502		767
503	$MODEL	768	$MODEL
504	}	769	}
505		770
…		…
692		957
693	=back	958	=back
694		959
695	=head1 EXAMPLE PROGRAM	960	=head1 EXAMPLE PROGRAM
696		961
697	The following program uses an IO watcher to read data from STDIN, a timer	962	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	963	to display a message once per second, and a condition variable to quit the
699	program when the user enters quit:	964	program when the user enters quit:
700		965
701	use AnyEvent;	966	use AnyEvent;
702		967
…		…
846	$quit->broadcast;	1111	$quit->broadcast;
847	});	1112	});
848		1113
849	$quit->wait;	1114	$quit->wait;
850		1115
		1116
		1117	=head1 BENCHMARKS
		1118
		1119	To give you an idea of the performance and overheads that AnyEvent adds
		1120	over the event loops themselves and to give you an impression of the speed
		1121	of various event loops I prepared some benchmarks.
		1122
		1123	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1124
		1125	Here is a benchmark of various supported event models used natively and
		1126	through anyevent. The benchmark creates a lot of timers (with a zero
		1127	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1128	which it is), lets them fire exactly once and destroys them again.
		1129
		1130	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1131	distribution.
		1132
		1133	=head3 Explanation of the columns
		1134
		1135	I<watcher> is the number of event watchers created/destroyed. Since
		1136	different event models feature vastly different performances, each event
		1137	loop was given a number of watchers so that overall runtime is acceptable
		1138	and similar between tested event loop (and keep them from crashing): Glib
		1139	would probably take thousands of years if asked to process the same number
		1140	of watchers as EV in this benchmark.
		1141
		1142	I<bytes> is the number of bytes (as measured by the resident set size,
		1143	RSS) consumed by each watcher. This method of measuring captures both C
		1144	and Perl-based overheads.
		1145
		1146	I<create> is the time, in microseconds (millionths of seconds), that it
		1147	takes to create a single watcher. The callback is a closure shared between
		1148	all watchers, to avoid adding memory overhead. That means closure creation
		1149	and memory usage is not included in the figures.
		1150
		1151	I<invoke> is the time, in microseconds, used to invoke a simple
		1152	callback. The callback simply counts down a Perl variable and after it was
		1153	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		1154	signal the end of this phase.
		1155
		1156	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1157	watcher.
		1158
		1159	=head3 Results
		1160
		1161	name watchers bytes create invoke destroy comment
		1162	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		1163	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		1164	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		1165	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		1166	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		1167	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		1168	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		1169	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		1170	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		1171	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		1172
		1173	=head3 Discussion
		1174
		1175	The benchmark does I<not> measure scalability of the event loop very
		1176	well. For example, a select-based event loop (such as the pure perl one)
		1177	can never compete with an event loop that uses epoll when the number of
		1178	file descriptors grows high. In this benchmark, all events become ready at
		1179	the same time, so select/poll-based implementations get an unnatural speed
		1180	boost.
		1181
		1182	Also, note that the number of watchers usually has a nonlinear effect on
		1183	overall speed, that is, creating twice as many watchers doesn't take twice
		1184	the time - usually it takes longer. This puts event loops tested with a
		1185	higher number of watchers at a disadvantage.
		1186
		1187	To put the range of results into perspective, consider that on the
		1188	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1189	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1190	cycles with POE.
		1191
		1192	C<EV> is the sole leader regarding speed and memory use, which are both
		1193	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1194	far less memory than any other event loop and is still faster than Event
		1195	natively.
		1196
		1197	The pure perl implementation is hit in a few sweet spots (both the
		1198	constant timeout and the use of a single fd hit optimisations in the perl
		1199	interpreter and the backend itself). Nevertheless this shows that it
		1200	adds very little overhead in itself. Like any select-based backend its
		1201	performance becomes really bad with lots of file descriptors (and few of
		1202	them active), of course, but this was not subject of this benchmark.
		1203
		1204	The C<Event> module has a relatively high setup and callback invocation
		1205	cost, but overall scores in on the third place.
		1206
		1207	C<Glib>'s memory usage is quite a bit higher, but it features a
		1208	faster callback invocation and overall ends up in the same class as
		1209	C<Event>. However, Glib scales extremely badly, doubling the number of
		1210	watchers increases the processing time by more than a factor of four,
		1211	making it completely unusable when using larger numbers of watchers
		1212	(note that only a single file descriptor was used in the benchmark, so
		1213	inefficiencies of C<poll> do not account for this).
		1214
		1215	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1216	more than 2000 watchers is a big setback, however, as correctness takes
		1217	precedence over speed. Nevertheless, its performance is surprising, as the
		1218	file descriptor is dup()ed for each watcher. This shows that the dup()
		1219	employed by some adaptors is not a big performance issue (it does incur a
		1220	hidden memory cost inside the kernel which is not reflected in the figures
		1221	above).
		1222
		1223	C<POE>, regardless of underlying event loop (whether using its pure perl
		1224	select-based backend or the Event module, the POE-EV backend couldn't
		1225	be tested because it wasn't working) shows abysmal performance and
		1226	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		1227	as EV watchers, and 10 times as much memory as Event (the high memory
		1228	requirements are caused by requiring a session for each watcher). Watcher
		1229	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1230	implementation.
		1231
		1232	The design of the POE adaptor class in AnyEvent can not really account
		1233	for the performance issues, though, as session creation overhead is
		1234	small compared to execution of the state machine, which is coded pretty
		1235	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1236	using multiple sessions is not a good approach, especially regarding
		1237	memory usage, even the author of POE could not come up with a faster
		1238	design).
		1239
		1240	=head3 Summary
		1241
		1242	=over 4
		1243
		1244	=item * Using EV through AnyEvent is faster than any other event loop
		1245	(even when used without AnyEvent), but most event loops have acceptable
		1246	performance with or without AnyEvent.
		1247
		1248	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1249	the actual event loop, only with extremely fast event loops such as EV
		1250	adds AnyEvent significant overhead.
		1251
		1252	=item * You should avoid POE like the plague if you want performance or
		1253	reasonable memory usage.
		1254
		1255	=back
		1256
		1257	=head2 BENCHMARKING THE LARGE SERVER CASE
		1258
		1259	This benchmark atcually benchmarks the event loop itself. It works by
		1260	creating a number of "servers": each server consists of a socketpair, a
		1261	timeout watcher that gets reset on activity (but never fires), and an I/O
		1262	watcher waiting for input on one side of the socket. Each time the socket
		1263	watcher reads a byte it will write that byte to a random other "server".
		1264
		1265	The effect is that there will be a lot of I/O watchers, only part of which
		1266	are active at any one point (so there is a constant number of active
		1267	fds for each loop iterstaion, but which fds these are is random). The
		1268	timeout is reset each time something is read because that reflects how
		1269	most timeouts work (and puts extra pressure on the event loops).
		1270
		1271	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
		1272	(1%) are active. This mirrors the activity of large servers with many
		1273	connections, most of which are idle at any one point in time.
		1274
		1275	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1276	distribution.
		1277
		1278	=head3 Explanation of the columns
		1279
		1280	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1281	each server has a read and write socket end).
		1282
		1283	I<create> is the time it takes to create a socketpair (which is
		1284	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1285
		1286	I<request>, the most important value, is the time it takes to handle a
		1287	single "request", that is, reading the token from the pipe and forwarding
		1288	it to another server. This includes deleting the old timeout and creating
		1289	a new one that moves the timeout into the future.
		1290
		1291	=head3 Results
		1292
		1293	name sockets create request
		1294	EV 20000 69.01 11.16
		1295	Perl 20000 73.32 35.87
		1296	Event 20000 212.62 257.32
		1297	Glib 20000 651.16 1896.30
		1298	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1299
		1300	=head3 Discussion
		1301
		1302	This benchmark I<does> measure scalability and overall performance of the
		1303	particular event loop.
		1304
		1305	EV is again fastest. Since it is using epoll on my system, the setup time
		1306	is relatively high, though.
		1307
		1308	Perl surprisingly comes second. It is much faster than the C-based event
		1309	loops Event and Glib.
		1310
		1311	Event suffers from high setup time as well (look at its code and you will
		1312	understand why). Callback invocation also has a high overhead compared to
		1313	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1314	uses select or poll in basically all documented configurations.
		1315
		1316	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1317	clearly fails to perform with many filehandles or in busy servers.
		1318
		1319	POE is still completely out of the picture, taking over 1000 times as long
		1320	as EV, and over 100 times as long as the Perl implementation, even though
		1321	it uses a C-based event loop in this case.
		1322
		1323	=head3 Summary
		1324
		1325	=over 4
		1326
		1327	=item * The pure perl implementation performs extremely well.
		1328
		1329	=item * Avoid Glib or POE in large projects where performance matters.
		1330
		1331	=back
		1332
		1333	=head2 BENCHMARKING SMALL SERVERS
		1334
		1335	While event loops should scale (and select-based ones do not...) even to
		1336	large servers, most programs we (or I :) actually write have only a few
		1337	I/O watchers.
		1338
		1339	In this benchmark, I use the same benchmark program as in the large server
		1340	case, but it uses only eight "servers", of which three are active at any
		1341	one time. This should reflect performance for a small server relatively
		1342	well.
		1343
		1344	The columns are identical to the previous table.
		1345
		1346	=head3 Results
		1347
		1348	name sockets create request
		1349	EV 16 20.00 6.54
		1350	Perl 16 25.75 12.62
		1351	Event 16 81.27 35.86
		1352	Glib 16 32.63 15.48
		1353	POE 16 261.87 276.28 uses POE::Loop::Event
		1354
		1355	=head3 Discussion
		1356
		1357	The benchmark tries to test the performance of a typical small
		1358	server. While knowing how various event loops perform is interesting, keep
		1359	in mind that their overhead in this case is usually not as important, due
		1360	to the small absolute number of watchers (that is, you need efficiency and
		1361	speed most when you have lots of watchers, not when you only have a few of
		1362	them).
		1363
		1364	EV is again fastest.
		1365
		1366	Perl again comes second. It is noticably faster than the C-based event
		1367	loops Event and Glib, although the difference is too small to really
		1368	matter.
		1369
		1370	POE also performs much better in this case, but is is still far behind the
		1371	others.
		1372
		1373	=head3 Summary
		1374
		1375	=over 4
		1376
		1377	=item * C-based event loops perform very well with small number of
		1378	watchers, as the management overhead dominates.
		1379
		1380	=back
		1381
		1382
851	=head1 FORK	1383	=head1 FORK
852		1384
853	Most event libraries are not fork-safe. The ones who are usually are	1385	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.	1386	because they rely on inefficient but fork-safe C<select> or C<poll>
		1387	calls. Only L<EV> is fully fork-aware.
855		1388
856	If you have to fork, you must either do so I<before> creating your first	1389	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.	1390	watcher OR you must not use AnyEvent at all in the child.
		1391
858		1392
859	=head1 SECURITY CONSIDERATIONS	1393	=head1 SECURITY CONSIDERATIONS
860		1394
861	AnyEvent can be forced to load any event model via	1395	AnyEvent can be forced to load any event model via
862	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	1396	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
870		1404
871	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1405	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
872		1406
873	use AnyEvent;	1407	use AnyEvent;
874		1408
		1409	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1410	be used to probe what backend is used and gain other information (which is
		1411	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
		1412
		1413
875	=head1 SEE ALSO	1414	=head1 SEE ALSO
876		1415
877	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1416	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
878	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1417	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
879	L<Event::Lib>, L<Qt>.
880		1418
881	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1419	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
882	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1420	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
883	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1421	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
884	L<AnyEvent::Impl::Qt>.	1422	L<AnyEvent::Impl::POE>.
		1423
		1424	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
885		1425
886	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1426	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
		1427
887		1428
888	=head1 AUTHOR	1429	=head1 AUTHOR
889		1430
890	Marc Lehmann <schmorp@schmorp.de>	1431	Marc Lehmann <schmorp@schmorp.de>
891	http://home.schmorp.de/	1432	http://home.schmorp.de/

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.60 by root, Fri Apr 25 01:05:26 2008 UTC vs. Revision 1.108 by root, Sat May 10 00:22:02 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.60 by root, Fri Apr 25 01:05:26 2008 UTC vs.
Revision 1.108 by root, Sat May 10 00:22:02 2008 UTC