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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.55 by root, Wed Apr 23 11:25:42 2008 UTC vs.
Revision 1.106 by root, Thu May 1 13:45:22 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 - various supported event loops	5	EV, Event, Coro::EV, Coro::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
…		…
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 the	82	to detect the currently loaded event loop by probing whether one of the
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	83	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
85	L<Event>, L<Glib>, L<Tk>. The first one found is used. If none are found,	84	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	the module tries to load these modules in the stated order. The first one	85	L<POE>. The first one found is used. If none are found, the module tries
		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
87	that can be successfully loaded will be used. If, after this, still none	88	be successfully loaded will be used. If, after this, still none could be
88	could be found, AnyEvent will fall back to a pure-perl event loop, which	89	found, AnyEvent will fall back to a pure-perl event loop, which is not
89	is not very efficient, but should work everywhere.	90	very efficient, but should work everywhere.
90		91
91	Because AnyEvent first checks for modules that are already loaded, loading	92	Because AnyEvent first checks for modules that are already loaded, loading
92	an event model explicitly before first using AnyEvent will likely make	93	an event model explicitly before first using AnyEvent will likely make
93	that model the default. For example:	94	that model the default. For example:
94		95
…		…
134		135
135	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,
136	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
137	declared.	138	declared.
138		139
139	=head2 IO WATCHERS	140	=head2 I/O WATCHERS
140		141
141	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
142	with the following mandatory key-value pairs as arguments:	143	with the following mandatory key-value pairs as arguments:
143		144
144	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
145	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>,
146	creates a watcher waiting for "r"eadable or "w"ritable events,	147	which creates a watcher waiting for "r"eadable or "w"ritable events,
147	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
148	becomes ready.	149	becomes ready.
149		150
150	File handles will be kept alive, so as long as the watcher exists, the	151	Although the callback might get passed parameters, their value and
151	file handle exists, too.	152	presence is undefined and you cannot rely on them. Portable AnyEvent
		153	callbacks cannot use arguments passed to I/O watcher callbacks.
152		154
		155	The I/O watcher might use the underlying file descriptor or a copy of it.
153	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
154	on the underlying file descriptor.	157	underlying file descriptor.
155		158
156	Some event loops issue spurious readyness notifications, so you should	159	Some event loops issue spurious readyness notifications, so you should
157	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
158	handles.	161	handles.
159		162
…		…
170		173
171	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 >>
172	method with the following mandatory arguments:	175	method with the following mandatory arguments:
173		176
174	C<after> specifies after how many seconds (fractional values are	177	C<after> specifies after how many seconds (fractional values are
175	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
176	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.
177		184
178	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
179	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
180	and Glib).	187	and Glib).
181		188
…		…
206		213
207	There are two ways to handle timers: based on real time (relative, "fire	214	There are two ways to handle timers: based on real time (relative, "fire
208	in 10 seconds") and based on wallclock time (absolute, "fire at 12	215	in 10 seconds") and based on wallclock time (absolute, "fire at 12
209	o'clock").	216	o'clock").
210		217
211	While most event loops expect timers to specified in a relative way, they use	218	While most event loops expect timers to specified in a relative way, they
212	absolute time internally. This makes a difference when your clock "jumps",	219	use absolute time internally. This makes a difference when your clock
213	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to	220	"jumps", for example, when ntp decides to set your clock backwards from
214	2008-01-01, a watcher that you created to fire "after" a second might actually take	221	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
215	six years to finally fire.	222	fire "after" a second might actually take six years to finally fire.
216		223
217	AnyEvent cannot compensate for this. The only event loop that is conscious	224	AnyEvent cannot compensate for this. The only event loop that is conscious
218	about these issues is L<EV>, which offers both relative (ev_timer) and	225	about these issues is L<EV>, which offers both relative (ev_timer, based
219	absolute (ev_periodic) timers.	226	on true relative time) and absolute (ev_periodic, based on wallclock time)
		227	timers.
220		228
221	AnyEvent always prefers relative timers, if available, matching the	229	AnyEvent always prefers relative timers, if available, matching the
222	AnyEvent API.	230	AnyEvent API.
223		231
224	=head2 SIGNAL WATCHERS	232	=head2 SIGNAL WATCHERS
225		233
226	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
227	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
228	be invoked whenever a signal occurs.	236	be invoked whenever a signal occurs.
229		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
230	Multiple signals occurances can be clumped together into one callback	242	Multiple signal occurances can be clumped together into one callback
231	invocation, and callback invocation will be synchronous. synchronous means	243	invocation, and callback invocation will be synchronous. synchronous means
232	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,
233	but it is guarenteed not to interrupt any other callbacks.	245	but it is guarenteed not to interrupt any other callbacks.
234		246
235	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
…		…
248		260
249	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
250	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
251	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
252	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
253	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.
254		267
255	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;
256		287
257	my $w = AnyEvent->child (	288	my $w = AnyEvent->child (
258	pid => 1333,	289	pid => $pid,
259	cb => sub {	290	cb => sub {
260	my ($pid, $status) = @_;	291	my ($pid, $status) = @_;
261	warn "pid $pid exited with status $status";	292	warn "pid $pid exited with status $status";
		293	$done->send;
262	},	294	},
263	);	295	);
264		296
		297	# do something else, then wait for process exit
		298	$done->wait;
		299
265	=head2 CONDITION VARIABLES	300	=head2 CONDITION VARIABLES
266		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
267	Condition variables can be created by calling the C<< AnyEvent->condvar >>	312	Condition variables can be created by calling the C<< AnyEvent->condvar
268	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.
269		316
270	A condition variable waits for a condition - precisely that the C<<	317	After creation, the conditon variable is "false" until it becomes "true"
271	->broadcast >> method has been called.	318	by calling the C<send> method.
272		319
273	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,
274	example, if you write a module that does asynchronous http requests,	328	for example, if you write a module that does asynchronous http requests,
275	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
276	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.
277		332
278	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,
279	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
280	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
281	->broadcast >> the "quit" event.	336	button of your app, which would C<< ->send >> the "quit" event.
282		337
283	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
284	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
285	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
286	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,
287	as this asks for trouble.	342	as this asks for trouble.
288		343
289	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.
290		378
291	=over 4	379	=over 4
292		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
293	=item $cv->wait	459	=item $cv->wait
294		460
295	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
296	called on c<$cv>, while servicing other watchers normally.	462	>> methods have been called on c<$cv>, while servicing other watchers
		463	normally.
297		464
298	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
299	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.
300		473
301	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
302	(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
303	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
304	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
…		…
311	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
312	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	485	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
313	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s	486	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
314	from different coroutines, however).	487	from different coroutines, however).
315		488
316	=item $cv->broadcast	489	You can ensure that C<< -wait >> never blocks by setting a callback and
		490	only calling C<< ->wait >> from within that callback (or at a later
		491	time). This will work even when the event loop does not support blocking
		492	waits otherwise.
317		493
318	Flag the condition as ready - a running C<< ->wait >> and all further	494	=item $bool = $cv->ready
319	calls to C<wait> will (eventually) return after this method has been	495
320	called. If nobody is waiting the broadcast will be remembered..	496	Returns true when the condition is "true", i.e. whether C<send> or
		497	C<croak> have been called.
		498
		499	=item $cb = $cv->cb ([new callback])
		500
		501	This is a mutator function that returns the callback set and optionally
		502	replaces it before doing so.
		503
		504	The callback will be called when the condition becomes "true", i.e. when
		505	C<send> or C<croak> are called. Calling C<wait> inside the callback
		506	or at any later time is guaranteed not to block.
321		507
322	=back	508	=back
323
324	Example:
325
326	# wait till the result is ready
327	my $result_ready = AnyEvent->condvar;
328
329	# do something such as adding a timer
330	# or socket watcher the calls $result_ready->broadcast
331	# when the "result" is ready.
332	# in this case, we simply use a timer:
333	my $w = AnyEvent->timer (
334	after => 1,
335	cb => sub { $result_ready->broadcast },
336	);
337
338	# this "blocks" (while handling events) till the watcher
339	# calls broadcast
340	$result_ready->wait;
341		509
342	=head1 GLOBAL VARIABLES AND FUNCTIONS	510	=head1 GLOBAL VARIABLES AND FUNCTIONS
343		511
344	=over 4	512	=over 4
345		513
…		…
353		521
354	The known classes so far are:	522	The known classes so far are:
355		523
356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.	524	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.	525	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
358	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).	526	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
359	AnyEvent::Impl::Event based on Event, also second best choice :)	527	AnyEvent::Impl::Event based on Event, second best choice.
		528	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
360	AnyEvent::Impl::Glib based on Glib, third-best choice.	529	AnyEvent::Impl::Glib based on Glib, third-best choice.
361	AnyEvent::Impl::Tk based on Tk, very bad choice.	530	AnyEvent::Impl::Tk based on Tk, very bad choice.
362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.	531	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
363	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	532	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		533	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		534
		535	There is no support for WxWidgets, as WxWidgets has no support for
		536	watching file handles. However, you can use WxWidgets through the
		537	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		538	second, which was considered to be too horrible to even consider for
		539	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		540	it's adaptor.
		541
		542	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		543	autodetecting them.
364		544
365	=item AnyEvent::detect	545	=item AnyEvent::detect
366		546
367	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	547	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
368	if necessary. You should only call this function right before you would	548	if necessary. You should only call this function right before you would
…		…
380	decide which event module to use as soon as the first method is called, so	560	decide which event module to use as soon as the first method is called, so
381	by calling AnyEvent in your module body you force the user of your module	561	by calling AnyEvent in your module body you force the user of your module
382	to load the event module first.	562	to load the event module first.
383		563
384	Never call C<< ->wait >> on a condition variable unless you I<know> that	564	Never call C<< ->wait >> on a condition variable unless you I<know> that
385	the C<< ->broadcast >> method has been called on it already. This is	565	the C<< ->send >> method has been called on it already. This is
386	because it will stall the whole program, and the whole point of using	566	because it will stall the whole program, and the whole point of using
387	events is to stay interactive.	567	events is to stay interactive.
388		568
389	It is fine, however, to call C<< ->wait >> when the user of your module	569	It is fine, however, to call C<< ->wait >> when the user of your module
390	requests it (i.e. if you create a http request object ad have a method	570	requests it (i.e. if you create a http request object ad have a method
…		…
410		590
411	You can chose to use a rather inefficient pure-perl implementation by	591	You can chose to use a rather inefficient pure-perl implementation by
412	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	592	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
413	behaviour everywhere, but letting AnyEvent chose is generally better.	593	behaviour everywhere, but letting AnyEvent chose is generally better.
414		594
		595	=head1 OTHER MODULES
		596
		597	The following is a non-exhaustive list of additional modules that use
		598	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		599	in the same program. Some of the modules come with AnyEvent, some are
		600	available via CPAN.
		601
		602	=over 4
		603
		604	=item L<AnyEvent::Util>
		605
		606	Contains various utility functions that replace often-used but blocking
		607	functions such as C<inet_aton> by event-/callback-based versions.
		608
		609	=item L<AnyEvent::Handle>
		610
		611	Provide read and write buffers and manages watchers for reads and writes.
		612
		613	=item L<AnyEvent::Socket>
		614
		615	Provides a means to do non-blocking connects, accepts etc.
		616
		617	=item L<AnyEvent::HTTPD>
		618
		619	Provides a simple web application server framework.
		620
		621	=item L<AnyEvent::DNS>
		622
		623	Provides asynchronous DNS resolver capabilities, beyond what
		624	L<AnyEvent::Util> offers.
		625
		626	=item L<AnyEvent::FastPing>
		627
		628	The fastest ping in the west.
		629
		630	=item L<Net::IRC3>
		631
		632	AnyEvent based IRC client module family.
		633
		634	=item L<Net::XMPP2>
		635
		636	AnyEvent based XMPP (Jabber protocol) module family.
		637
		638	=item L<Net::FCP>
		639
		640	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		641	of AnyEvent.
		642
		643	=item L<Event::ExecFlow>
		644
		645	High level API for event-based execution flow control.
		646
		647	=item L<Coro>
		648
		649	Has special support for AnyEvent.
		650
		651	=item L<IO::Lambda>
		652
		653	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		654
		655	=item L<IO::AIO>
		656
		657	Truly asynchronous I/O, should be in the toolbox of every event
		658	programmer. Can be trivially made to use AnyEvent.
		659
		660	=item L<BDB>
		661
		662	Truly asynchronous Berkeley DB access. Can be trivially made to use
		663	AnyEvent.
		664
		665	=back
		666
415	=cut	667	=cut
416		668
417	package AnyEvent;	669	package AnyEvent;
418		670
419	no warnings;	671	no warnings;
420	use strict;	672	use strict;
421		673
422	use Carp;	674	use Carp;
423		675
424	our $VERSION = '3.12';	676	our $VERSION = '3.3';
425	our $MODEL;	677	our $MODEL;
426		678
427	our $AUTOLOAD;	679	our $AUTOLOAD;
428	our @ISA;	680	our @ISA;
429		681
…		…
434	my @models = (	686	my @models = (
435	[Coro::EV:: => AnyEvent::Impl::CoroEV::],	687	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
436	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],	688	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
437	[EV:: => AnyEvent::Impl::EV::],	689	[EV:: => AnyEvent::Impl::EV::],
438	[Event:: => AnyEvent::Impl::Event::],	690	[Event:: => AnyEvent::Impl::Event::],
		691	[Tk:: => AnyEvent::Impl::Tk::],
		692	[Wx:: => AnyEvent::Impl::POE::],
		693	[Prima:: => AnyEvent::Impl::POE::],
		694	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		695	# everything below here will not be autoprobed as the pureperl backend should work everywhere
439	[Glib:: => AnyEvent::Impl::Glib::],	696	[Glib:: => AnyEvent::Impl::Glib::],
440	[Tk:: => AnyEvent::Impl::Tk::],
441	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
442	[Event::Lib:: => AnyEvent::Impl::EventLib::],	697	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		698	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		699	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
443	);	700	);
444		701
445	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	702	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);
446		703
447	sub detect() {	704	sub detect() {
448	unless ($MODEL) {	705	unless ($MODEL) {
449	no strict 'refs';	706	no strict 'refs';
450		707
451	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	708	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
452	my $model = "AnyEvent::Impl::$1";	709	my $model = "AnyEvent::Impl::$1";
453	if (eval "require $model") {	710	if (eval "require $model") {
454	$MODEL = $model;	711	$MODEL = $model;
455	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	712	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		713	} else {
		714	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
456	}	715	}
457	}	716	}
458		717
459	# check for already loaded models	718	# check for already loaded models
460	unless ($MODEL) {	719	unless ($MODEL) {
…		…
653		912
654	=over 4	913	=over 4
655		914
656	=item C<PERL_ANYEVENT_VERBOSE>	915	=item C<PERL_ANYEVENT_VERBOSE>
657		916
		917	By default, AnyEvent will be completely silent except in fatal
		918	conditions. You can set this environment variable to make AnyEvent more
		919	talkative.
		920
		921	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		922	conditions, such as not being able to load the event model specified by
		923	C<PERL_ANYEVENT_MODEL>.
		924
658	When set to C<2> or higher, cause AnyEvent to report to STDERR which event	925	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
659	model it chooses.	926	model it chooses.
660		927
661	=item C<PERL_ANYEVENT_MODEL>	928	=item C<PERL_ANYEVENT_MODEL>
662		929
…		…
676		943
677	=back	944	=back
678		945
679	=head1 EXAMPLE PROGRAM	946	=head1 EXAMPLE PROGRAM
680		947
681	The following program uses an IO watcher to read data from STDIN, a timer	948	The following program uses an I/O watcher to read data from STDIN, a timer
682	to display a message once per second, and a condition variable to quit the	949	to display a message once per second, and a condition variable to quit the
683	program when the user enters quit:	950	program when the user enters quit:
684		951
685	use AnyEvent;	952	use AnyEvent;
686		953
…		…
830	$quit->broadcast;	1097	$quit->broadcast;
831	});	1098	});
832		1099
833	$quit->wait;	1100	$quit->wait;
834		1101
		1102
		1103	=head1 BENCHMARKS
		1104
		1105	To give you an idea of the performance and overheads that AnyEvent adds
		1106	over the event loops themselves and to give you an impression of the speed
		1107	of various event loops I prepared some benchmarks.
		1108
		1109	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1110
		1111	Here is a benchmark of various supported event models used natively and
		1112	through anyevent. The benchmark creates a lot of timers (with a zero
		1113	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1114	which it is), lets them fire exactly once and destroys them again.
		1115
		1116	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1117	distribution.
		1118
		1119	=head3 Explanation of the columns
		1120
		1121	I<watcher> is the number of event watchers created/destroyed. Since
		1122	different event models feature vastly different performances, each event
		1123	loop was given a number of watchers so that overall runtime is acceptable
		1124	and similar between tested event loop (and keep them from crashing): Glib
		1125	would probably take thousands of years if asked to process the same number
		1126	of watchers as EV in this benchmark.
		1127
		1128	I<bytes> is the number of bytes (as measured by the resident set size,
		1129	RSS) consumed by each watcher. This method of measuring captures both C
		1130	and Perl-based overheads.
		1131
		1132	I<create> is the time, in microseconds (millionths of seconds), that it
		1133	takes to create a single watcher. The callback is a closure shared between
		1134	all watchers, to avoid adding memory overhead. That means closure creation
		1135	and memory usage is not included in the figures.
		1136
		1137	I<invoke> is the time, in microseconds, used to invoke a simple
		1138	callback. The callback simply counts down a Perl variable and after it was
		1139	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		1140	signal the end of this phase.
		1141
		1142	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1143	watcher.
		1144
		1145	=head3 Results
		1146
		1147	name watchers bytes create invoke destroy comment
		1148	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		1149	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		1150	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		1151	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		1152	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		1153	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		1154	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		1155	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		1156	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		1157	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		1158
		1159	=head3 Discussion
		1160
		1161	The benchmark does I<not> measure scalability of the event loop very
		1162	well. For example, a select-based event loop (such as the pure perl one)
		1163	can never compete with an event loop that uses epoll when the number of
		1164	file descriptors grows high. In this benchmark, all events become ready at
		1165	the same time, so select/poll-based implementations get an unnatural speed
		1166	boost.
		1167
		1168	Also, note that the number of watchers usually has a nonlinear effect on
		1169	overall speed, that is, creating twice as many watchers doesn't take twice
		1170	the time - usually it takes longer. This puts event loops tested with a
		1171	higher number of watchers at a disadvantage.
		1172
		1173	To put the range of results into perspective, consider that on the
		1174	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1175	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1176	cycles with POE.
		1177
		1178	C<EV> is the sole leader regarding speed and memory use, which are both
		1179	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1180	far less memory than any other event loop and is still faster than Event
		1181	natively.
		1182
		1183	The pure perl implementation is hit in a few sweet spots (both the
		1184	constant timeout and the use of a single fd hit optimisations in the perl
		1185	interpreter and the backend itself). Nevertheless this shows that it
		1186	adds very little overhead in itself. Like any select-based backend its
		1187	performance becomes really bad with lots of file descriptors (and few of
		1188	them active), of course, but this was not subject of this benchmark.
		1189
		1190	The C<Event> module has a relatively high setup and callback invocation
		1191	cost, but overall scores in on the third place.
		1192
		1193	C<Glib>'s memory usage is quite a bit higher, but it features a
		1194	faster callback invocation and overall ends up in the same class as
		1195	C<Event>. However, Glib scales extremely badly, doubling the number of
		1196	watchers increases the processing time by more than a factor of four,
		1197	making it completely unusable when using larger numbers of watchers
		1198	(note that only a single file descriptor was used in the benchmark, so
		1199	inefficiencies of C<poll> do not account for this).
		1200
		1201	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1202	more than 2000 watchers is a big setback, however, as correctness takes
		1203	precedence over speed. Nevertheless, its performance is surprising, as the
		1204	file descriptor is dup()ed for each watcher. This shows that the dup()
		1205	employed by some adaptors is not a big performance issue (it does incur a
		1206	hidden memory cost inside the kernel which is not reflected in the figures
		1207	above).
		1208
		1209	C<POE>, regardless of underlying event loop (whether using its pure perl
		1210	select-based backend or the Event module, the POE-EV backend couldn't
		1211	be tested because it wasn't working) shows abysmal performance and
		1212	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		1213	as EV watchers, and 10 times as much memory as Event (the high memory
		1214	requirements are caused by requiring a session for each watcher). Watcher
		1215	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1216	implementation.
		1217
		1218	The design of the POE adaptor class in AnyEvent can not really account
		1219	for the performance issues, though, as session creation overhead is
		1220	small compared to execution of the state machine, which is coded pretty
		1221	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1222	using multiple sessions is not a good approach, especially regarding
		1223	memory usage, even the author of POE could not come up with a faster
		1224	design).
		1225
		1226	=head3 Summary
		1227
		1228	=over 4
		1229
		1230	=item * Using EV through AnyEvent is faster than any other event loop
		1231	(even when used without AnyEvent), but most event loops have acceptable
		1232	performance with or without AnyEvent.
		1233
		1234	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1235	the actual event loop, only with extremely fast event loops such as EV
		1236	adds AnyEvent significant overhead.
		1237
		1238	=item * You should avoid POE like the plague if you want performance or
		1239	reasonable memory usage.
		1240
		1241	=back
		1242
		1243	=head2 BENCHMARKING THE LARGE SERVER CASE
		1244
		1245	This benchmark atcually benchmarks the event loop itself. It works by
		1246	creating a number of "servers": each server consists of a socketpair, a
		1247	timeout watcher that gets reset on activity (but never fires), and an I/O
		1248	watcher waiting for input on one side of the socket. Each time the socket
		1249	watcher reads a byte it will write that byte to a random other "server".
		1250
		1251	The effect is that there will be a lot of I/O watchers, only part of which
		1252	are active at any one point (so there is a constant number of active
		1253	fds for each loop iterstaion, but which fds these are is random). The
		1254	timeout is reset each time something is read because that reflects how
		1255	most timeouts work (and puts extra pressure on the event loops).
		1256
		1257	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
		1258	(1%) are active. This mirrors the activity of large servers with many
		1259	connections, most of which are idle at any one point in time.
		1260
		1261	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1262	distribution.
		1263
		1264	=head3 Explanation of the columns
		1265
		1266	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1267	each server has a read and write socket end).
		1268
		1269	I<create> is the time it takes to create a socketpair (which is
		1270	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1271
		1272	I<request>, the most important value, is the time it takes to handle a
		1273	single "request", that is, reading the token from the pipe and forwarding
		1274	it to another server. This includes deleting the old timeout and creating
		1275	a new one that moves the timeout into the future.
		1276
		1277	=head3 Results
		1278
		1279	name sockets create request
		1280	EV 20000 69.01 11.16
		1281	Perl 20000 73.32 35.87
		1282	Event 20000 212.62 257.32
		1283	Glib 20000 651.16 1896.30
		1284	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1285
		1286	=head3 Discussion
		1287
		1288	This benchmark I<does> measure scalability and overall performance of the
		1289	particular event loop.
		1290
		1291	EV is again fastest. Since it is using epoll on my system, the setup time
		1292	is relatively high, though.
		1293
		1294	Perl surprisingly comes second. It is much faster than the C-based event
		1295	loops Event and Glib.
		1296
		1297	Event suffers from high setup time as well (look at its code and you will
		1298	understand why). Callback invocation also has a high overhead compared to
		1299	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1300	uses select or poll in basically all documented configurations.
		1301
		1302	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1303	clearly fails to perform with many filehandles or in busy servers.
		1304
		1305	POE is still completely out of the picture, taking over 1000 times as long
		1306	as EV, and over 100 times as long as the Perl implementation, even though
		1307	it uses a C-based event loop in this case.
		1308
		1309	=head3 Summary
		1310
		1311	=over 4
		1312
		1313	=item * The pure perl implementation performs extremely well.
		1314
		1315	=item * Avoid Glib or POE in large projects where performance matters.
		1316
		1317	=back
		1318
		1319	=head2 BENCHMARKING SMALL SERVERS
		1320
		1321	While event loops should scale (and select-based ones do not...) even to
		1322	large servers, most programs we (or I :) actually write have only a few
		1323	I/O watchers.
		1324
		1325	In this benchmark, I use the same benchmark program as in the large server
		1326	case, but it uses only eight "servers", of which three are active at any
		1327	one time. This should reflect performance for a small server relatively
		1328	well.
		1329
		1330	The columns are identical to the previous table.
		1331
		1332	=head3 Results
		1333
		1334	name sockets create request
		1335	EV 16 20.00 6.54
		1336	Perl 16 25.75 12.62
		1337	Event 16 81.27 35.86
		1338	Glib 16 32.63 15.48
		1339	POE 16 261.87 276.28 uses POE::Loop::Event
		1340
		1341	=head3 Discussion
		1342
		1343	The benchmark tries to test the performance of a typical small
		1344	server. While knowing how various event loops perform is interesting, keep
		1345	in mind that their overhead in this case is usually not as important, due
		1346	to the small absolute number of watchers (that is, you need efficiency and
		1347	speed most when you have lots of watchers, not when you only have a few of
		1348	them).
		1349
		1350	EV is again fastest.
		1351
		1352	Perl again comes second. It is noticably faster than the C-based event
		1353	loops Event and Glib, although the difference is too small to really
		1354	matter.
		1355
		1356	POE also performs much better in this case, but is is still far behind the
		1357	others.
		1358
		1359	=head3 Summary
		1360
		1361	=over 4
		1362
		1363	=item * C-based event loops perform very well with small number of
		1364	watchers, as the management overhead dominates.
		1365
		1366	=back
		1367
		1368
835	=head1 FORK	1369	=head1 FORK
836		1370
837	Most event libraries are not fork-safe. The ones who are usually are	1371	Most event libraries are not fork-safe. The ones who are usually are
838	because they are so inefficient. Only L<EV> is fully fork-aware.	1372	because they rely on inefficient but fork-safe C<select> or C<poll>
		1373	calls. Only L<EV> is fully fork-aware.
839		1374
840	If you have to fork, you must either do so I<before> creating your first	1375	If you have to fork, you must either do so I<before> creating your first
841	watcher OR you must not use AnyEvent at all in the child.	1376	watcher OR you must not use AnyEvent at all in the child.
		1377
842		1378
843	=head1 SECURITY CONSIDERATIONS	1379	=head1 SECURITY CONSIDERATIONS
844		1380
845	AnyEvent can be forced to load any event model via	1381	AnyEvent can be forced to load any event model via
846	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	1382	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
854		1390
855	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1391	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
856		1392
857	use AnyEvent;	1393	use AnyEvent;
858		1394
		1395
859	=head1 SEE ALSO	1396	=head1 SEE ALSO
860		1397
861	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1398	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
862	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1399	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
863	L<Event::Lib>.	1400	L<Event::Lib>, L<Qt>, L<POE>.
864		1401
865	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1402	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
866	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1403	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
867	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>.	1404	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
		1405	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
868		1406
869	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1407	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
		1408
870		1409
871	=head1 AUTHOR	1410	=head1 AUTHOR
872		1411
873	Marc Lehmann <schmorp@schmorp.de>	1412	Marc Lehmann <schmorp@schmorp.de>
874	http://home.schmorp.de/	1413	http://home.schmorp.de/

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.55 by root, Wed Apr 23 11:25:42 2008 UTC vs. Revision 1.106 by root, Thu May 1 13:45:22 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.55 by root, Wed Apr 23 11:25:42 2008 UTC vs.
Revision 1.106 by root, Thu May 1 13:45:22 2008 UTC