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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.54 by root, Tue Apr 22 05:12:19 2008 UTC vs.
Revision 1.105 by root, Thu May 1 12:35:54 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 - 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
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->broadcast;
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<broadcast> 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<< ->broadcast >> 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.
290		349
291	=over 4	350	There are two "sides" to a condition variable - the "producer side" which
292		351	eventually calls C<< -> broadcast >>, and the "consumer side", which waits
293	=item $cv->wait	352	for the broadcast to occur.
294
295	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
296	called on c<$cv>, while servicing other watchers normally.
297
298	You can only wait once on a condition - additional calls will return
299	immediately.
300
301	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
303	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
305	condition variables with some kind of request results and supporting
306	callbacks so the caller knows that getting the result will not block,
307	while still suppporting blocking waits if the caller so desires).
308
309	Another reason I<never> to C<< ->wait >> in a module is that you cannot
310	sensibly have two C<< ->wait >>'s in parallel, as that would require
311	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
312	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
313	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
314	from different coroutines, however).
315
316	=item $cv->broadcast
317
318	Flag the condition as ready - a running C<< ->wait >> and all further
319	calls to C<wait> will (eventually) return after this method has been
320	called. If nobody is waiting the broadcast will be remembered..
321
322	=back
323		353
324	Example:	354	Example:
325		355
326	# wait till the result is ready	356	# wait till the result is ready
327	my $result_ready = AnyEvent->condvar;	357	my $result_ready = AnyEvent->condvar;
…		…
333	my $w = AnyEvent->timer (	363	my $w = AnyEvent->timer (
334	after => 1,	364	after => 1,
335	cb => sub { $result_ready->broadcast },	365	cb => sub { $result_ready->broadcast },
336	);	366	);
337		367
338	# this "blocks" (while handling events) till the watcher	368	# this "blocks" (while handling events) till the callback
339	# calls broadcast	369	# calls broadcast
340	$result_ready->wait;	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 broadcasts 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.
		378
		379	=over 4
		380
		381	=item $cv->broadcast (...)
		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 broadcast will be remembered.
		386
		387	If a callback has been set on the condition variable, it is called
		388	immediately from within broadcast.
		389
		390	Any arguments passed to the C<broadcast> call will be returned by all
		391	future C<< ->wait >> calls.
		392
		393	=item $cv->croak ($error)
		394
		395	Similar to broadcast, 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<< ->broadcast >>, but that is not required. If no
		413	callback was set, C<broadcast> 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->broadcast (\%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<broadcast> 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	broadcast 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	=item $cv->wait
		458
		459	Wait (blocking if necessary) until the C<< ->broadcast >> or C<< ->croak
		460	>> methods have been called on c<$cv>, while servicing other watchers
		461	normally.
		462
		463	You can only wait once on a condition - additional calls are valid but
		464	will return immediately.
		465
		466	If an error condition has been set by calling C<< ->croak >>, then this
		467	function will call C<croak>.
		468
		469	In list context, all parameters passed to C<broadcast> will be returned,
		470	in scalar context only the first one will be returned.
		471
		472	Not all event models support a blocking wait - some die in that case
		473	(programs might want to do that to stay interactive), so I<if you are
		474	using this from a module, never require a blocking wait>, but let the
		475	caller decide whether the call will block or not (for example, by coupling
		476	condition variables with some kind of request results and supporting
		477	callbacks so the caller knows that getting the result will not block,
		478	while still suppporting blocking waits if the caller so desires).
		479
		480	Another reason I<never> to C<< ->wait >> in a module is that you cannot
		481	sensibly have two C<< ->wait >>'s in parallel, as that would require
		482	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
		483	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
		484	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
		485	from different coroutines, however).
		486
		487	You can ensure that C<< -wait >> never blocks by setting a callback and
		488	only calling C<< ->wait >> from within that callback (or at a later
		489	time). This will work even when the event loop does not support blocking
		490	waits otherwise.
		491
		492	=back
341		493
342	=head1 GLOBAL VARIABLES AND FUNCTIONS	494	=head1 GLOBAL VARIABLES AND FUNCTIONS
343		495
344	=over 4	496	=over 4
345		497
…		…
353		505
354	The known classes so far are:	506	The known classes so far are:
355		507
356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.	508	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.	509	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
358	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).	510	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
359	AnyEvent::Impl::Event based on Event, also second best choice :)	511	AnyEvent::Impl::Event based on Event, second best choice.
		512	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
360	AnyEvent::Impl::Glib based on Glib, third-best choice.	513	AnyEvent::Impl::Glib based on Glib, third-best choice.
361	AnyEvent::Impl::Tk based on Tk, very bad choice.	514	AnyEvent::Impl::Tk based on Tk, very bad choice.
362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.	515	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		516	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		517	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		518
		519	There is no support for WxWidgets, as WxWidgets has no support for
		520	watching file handles. However, you can use WxWidgets through the
		521	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		522	second, which was considered to be too horrible to even consider for
		523	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		524	it's adaptor.
		525
		526	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		527	autodetecting them.
363		528
364	=item AnyEvent::detect	529	=item AnyEvent::detect
365		530
366	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	531	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
367	if necessary. You should only call this function right before you would	532	if necessary. You should only call this function right before you would
…		…
409		574
410	You can chose to use a rather inefficient pure-perl implementation by	575	You can chose to use a rather inefficient pure-perl implementation by
411	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	576	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
412	behaviour everywhere, but letting AnyEvent chose is generally better.	577	behaviour everywhere, but letting AnyEvent chose is generally better.
413		578
		579	=head1 OTHER MODULES
		580
		581	The following is a non-exhaustive list of additional modules that use
		582	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		583	in the same program. Some of the modules come with AnyEvent, some are
		584	available via CPAN.
		585
		586	=over 4
		587
		588	=item L<AnyEvent::Util>
		589
		590	Contains various utility functions that replace often-used but blocking
		591	functions such as C<inet_aton> by event-/callback-based versions.
		592
		593	=item L<AnyEvent::Handle>
		594
		595	Provide read and write buffers and manages watchers for reads and writes.
		596
		597	=item L<AnyEvent::Socket>
		598
		599	Provides a means to do non-blocking connects, accepts etc.
		600
		601	=item L<AnyEvent::HTTPD>
		602
		603	Provides a simple web application server framework.
		604
		605	=item L<AnyEvent::DNS>
		606
		607	Provides asynchronous DNS resolver capabilities, beyond what
		608	L<AnyEvent::Util> offers.
		609
		610	=item L<AnyEvent::FastPing>
		611
		612	The fastest ping in the west.
		613
		614	=item L<Net::IRC3>
		615
		616	AnyEvent based IRC client module family.
		617
		618	=item L<Net::XMPP2>
		619
		620	AnyEvent based XMPP (Jabber protocol) module family.
		621
		622	=item L<Net::FCP>
		623
		624	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		625	of AnyEvent.
		626
		627	=item L<Event::ExecFlow>
		628
		629	High level API for event-based execution flow control.
		630
		631	=item L<Coro>
		632
		633	Has special support for AnyEvent.
		634
		635	=item L<IO::Lambda>
		636
		637	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		638
		639	=item L<IO::AIO>
		640
		641	Truly asynchronous I/O, should be in the toolbox of every event
		642	programmer. Can be trivially made to use AnyEvent.
		643
		644	=item L<BDB>
		645
		646	Truly asynchronous Berkeley DB access. Can be trivially made to use
		647	AnyEvent.
		648
		649	=back
		650
414	=cut	651	=cut
415		652
416	package AnyEvent;	653	package AnyEvent;
417		654
418	no warnings;	655	no warnings;
419	use strict;	656	use strict;
420		657
421	use Carp;	658	use Carp;
422		659
423	our $VERSION = '3.12';	660	our $VERSION = '3.3';
424	our $MODEL;	661	our $MODEL;
425		662
426	our $AUTOLOAD;	663	our $AUTOLOAD;
427	our @ISA;	664	our @ISA;
428		665
…		…
433	my @models = (	670	my @models = (
434	[Coro::EV:: => AnyEvent::Impl::CoroEV::],	671	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
435	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],	672	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
436	[EV:: => AnyEvent::Impl::EV::],	673	[EV:: => AnyEvent::Impl::EV::],
437	[Event:: => AnyEvent::Impl::Event::],	674	[Event:: => AnyEvent::Impl::Event::],
		675	[Tk:: => AnyEvent::Impl::Tk::],
		676	[Wx:: => AnyEvent::Impl::POE::],
		677	[Prima:: => AnyEvent::Impl::POE::],
		678	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		679	# everything below here will not be autoprobed as the pureperl backend should work everywhere
438	[Glib:: => AnyEvent::Impl::Glib::],	680	[Glib:: => AnyEvent::Impl::Glib::],
439	[Tk:: => AnyEvent::Impl::Tk::],	681	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
440	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	682	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		683	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
441	);	684	);
442		685
443	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	686	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
444		687
445	sub detect() {	688	sub detect() {
446	unless ($MODEL) {	689	unless ($MODEL) {
447	no strict 'refs';	690	no strict 'refs';
448		691
		692	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		693	my $model = "AnyEvent::Impl::$1";
		694	if (eval "require $model") {
		695	$MODEL = $model;
		696	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		697	} else {
		698	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
		699	}
		700	}
		701
449	# check for already loaded models	702	# check for already loaded models
		703	unless ($MODEL) {
450	for (@REGISTRY, @models) {	704	for (@REGISTRY, @models) {
451	my ($package, $model) = @$_;	705	my ($package, $model) = @$_;
452	if (${"$package\::VERSION"} > 0) {	706	if (${"$package\::VERSION"} > 0) {
453	if (eval "require $model") {	707	if (eval "require $model") {
454	$MODEL = $model;	708	$MODEL = $model;
455	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	709	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
456	last;	710	last;
		711	}
457	}	712	}
458	}	713	}
459	}
460		714
461	unless ($MODEL) {	715	unless ($MODEL) {
462	# try to load a model	716	# try to load a model
463		717
464	for (@REGISTRY, @models) {	718	for (@REGISTRY, @models) {
465	my ($package, $model) = @$_;	719	my ($package, $model) = @$_;
466	if (eval "require $package"	720	if (eval "require $package"
467	and ${"$package\::VERSION"} > 0	721	and ${"$package\::VERSION"} > 0
468	and eval "require $model") {	722	and eval "require $model") {
469	$MODEL = $model;	723	$MODEL = $model;
470	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	724	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
471	last;	725	last;
		726	}
472	}	727	}
		728
		729	$MODEL
		730	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.";
473	}	731	}
474
475	$MODEL
476	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), Glib or Tk.";
477	}	732	}
478		733
479	unshift @ISA, $MODEL;	734	unshift @ISA, $MODEL;
480	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	735	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
481	}	736	}
…		…
637		892
638	=head1 ENVIRONMENT VARIABLES	893	=head1 ENVIRONMENT VARIABLES
639		894
640	The following environment variables are used by this module:	895	The following environment variables are used by this module:
641		896
642	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, cause AnyEvent to	897	=over 4
643	report to STDERR which event model it chooses.	898
		899	=item C<PERL_ANYEVENT_VERBOSE>
		900
		901	By default, AnyEvent will be completely silent except in fatal
		902	conditions. You can set this environment variable to make AnyEvent more
		903	talkative.
		904
		905	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		906	conditions, such as not being able to load the event model specified by
		907	C<PERL_ANYEVENT_MODEL>.
		908
		909	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		910	model it chooses.
		911
		912	=item C<PERL_ANYEVENT_MODEL>
		913
		914	This can be used to specify the event model to be used by AnyEvent, before
		915	autodetection and -probing kicks in. It must be a string consisting
		916	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		917	and the resulting module name is loaded and if the load was successful,
		918	used as event model. If it fails to load AnyEvent will proceed with
		919	autodetection and -probing.
		920
		921	This functionality might change in future versions.
		922
		923	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		924	could start your program like this:
		925
		926	PERL_ANYEVENT_MODEL=Perl perl ...
		927
		928	=back
644		929
645	=head1 EXAMPLE PROGRAM	930	=head1 EXAMPLE PROGRAM
646		931
647	The following program uses an IO watcher to read data from STDIN, a timer	932	The following program uses an I/O watcher to read data from STDIN, a timer
648	to display a message once per second, and a condition variable to quit the	933	to display a message once per second, and a condition variable to quit the
649	program when the user enters quit:	934	program when the user enters quit:
650		935
651	use AnyEvent;	936	use AnyEvent;
652		937
…		…
796	$quit->broadcast;	1081	$quit->broadcast;
797	});	1082	});
798		1083
799	$quit->wait;	1084	$quit->wait;
800		1085
		1086
		1087	=head1 BENCHMARKS
		1088
		1089	To give you an idea of the performance and overheads that AnyEvent adds
		1090	over the event loops themselves and to give you an impression of the speed
		1091	of various event loops I prepared some benchmarks.
		1092
		1093	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1094
		1095	Here is a benchmark of various supported event models used natively and
		1096	through anyevent. The benchmark creates a lot of timers (with a zero
		1097	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1098	which it is), lets them fire exactly once and destroys them again.
		1099
		1100	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1101	distribution.
		1102
		1103	=head3 Explanation of the columns
		1104
		1105	I<watcher> is the number of event watchers created/destroyed. Since
		1106	different event models feature vastly different performances, each event
		1107	loop was given a number of watchers so that overall runtime is acceptable
		1108	and similar between tested event loop (and keep them from crashing): Glib
		1109	would probably take thousands of years if asked to process the same number
		1110	of watchers as EV in this benchmark.
		1111
		1112	I<bytes> is the number of bytes (as measured by the resident set size,
		1113	RSS) consumed by each watcher. This method of measuring captures both C
		1114	and Perl-based overheads.
		1115
		1116	I<create> is the time, in microseconds (millionths of seconds), that it
		1117	takes to create a single watcher. The callback is a closure shared between
		1118	all watchers, to avoid adding memory overhead. That means closure creation
		1119	and memory usage is not included in the figures.
		1120
		1121	I<invoke> is the time, in microseconds, used to invoke a simple
		1122	callback. The callback simply counts down a Perl variable and after it was
		1123	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		1124	signal the end of this phase.
		1125
		1126	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1127	watcher.
		1128
		1129	=head3 Results
		1130
		1131	name watchers bytes create invoke destroy comment
		1132	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		1133	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		1134	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		1135	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		1136	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		1137	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		1138	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		1139	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		1140	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		1141	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		1142
		1143	=head3 Discussion
		1144
		1145	The benchmark does I<not> measure scalability of the event loop very
		1146	well. For example, a select-based event loop (such as the pure perl one)
		1147	can never compete with an event loop that uses epoll when the number of
		1148	file descriptors grows high. In this benchmark, all events become ready at
		1149	the same time, so select/poll-based implementations get an unnatural speed
		1150	boost.
		1151
		1152	Also, note that the number of watchers usually has a nonlinear effect on
		1153	overall speed, that is, creating twice as many watchers doesn't take twice
		1154	the time - usually it takes longer. This puts event loops tested with a
		1155	higher number of watchers at a disadvantage.
		1156
		1157	To put the range of results into perspective, consider that on the
		1158	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1159	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1160	cycles with POE.
		1161
		1162	C<EV> is the sole leader regarding speed and memory use, which are both
		1163	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1164	far less memory than any other event loop and is still faster than Event
		1165	natively.
		1166
		1167	The pure perl implementation is hit in a few sweet spots (both the
		1168	constant timeout and the use of a single fd hit optimisations in the perl
		1169	interpreter and the backend itself). Nevertheless this shows that it
		1170	adds very little overhead in itself. Like any select-based backend its
		1171	performance becomes really bad with lots of file descriptors (and few of
		1172	them active), of course, but this was not subject of this benchmark.
		1173
		1174	The C<Event> module has a relatively high setup and callback invocation
		1175	cost, but overall scores in on the third place.
		1176
		1177	C<Glib>'s memory usage is quite a bit higher, but it features a
		1178	faster callback invocation and overall ends up in the same class as
		1179	C<Event>. However, Glib scales extremely badly, doubling the number of
		1180	watchers increases the processing time by more than a factor of four,
		1181	making it completely unusable when using larger numbers of watchers
		1182	(note that only a single file descriptor was used in the benchmark, so
		1183	inefficiencies of C<poll> do not account for this).
		1184
		1185	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1186	more than 2000 watchers is a big setback, however, as correctness takes
		1187	precedence over speed. Nevertheless, its performance is surprising, as the
		1188	file descriptor is dup()ed for each watcher. This shows that the dup()
		1189	employed by some adaptors is not a big performance issue (it does incur a
		1190	hidden memory cost inside the kernel which is not reflected in the figures
		1191	above).
		1192
		1193	C<POE>, regardless of underlying event loop (whether using its pure perl
		1194	select-based backend or the Event module, the POE-EV backend couldn't
		1195	be tested because it wasn't working) shows abysmal performance and
		1196	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		1197	as EV watchers, and 10 times as much memory as Event (the high memory
		1198	requirements are caused by requiring a session for each watcher). Watcher
		1199	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1200	implementation.
		1201
		1202	The design of the POE adaptor class in AnyEvent can not really account
		1203	for the performance issues, though, as session creation overhead is
		1204	small compared to execution of the state machine, which is coded pretty
		1205	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1206	using multiple sessions is not a good approach, especially regarding
		1207	memory usage, even the author of POE could not come up with a faster
		1208	design).
		1209
		1210	=head3 Summary
		1211
		1212	=over 4
		1213
		1214	=item * Using EV through AnyEvent is faster than any other event loop
		1215	(even when used without AnyEvent), but most event loops have acceptable
		1216	performance with or without AnyEvent.
		1217
		1218	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1219	the actual event loop, only with extremely fast event loops such as EV
		1220	adds AnyEvent significant overhead.
		1221
		1222	=item * You should avoid POE like the plague if you want performance or
		1223	reasonable memory usage.
		1224
		1225	=back
		1226
		1227	=head2 BENCHMARKING THE LARGE SERVER CASE
		1228
		1229	This benchmark atcually benchmarks the event loop itself. It works by
		1230	creating a number of "servers": each server consists of a socketpair, a
		1231	timeout watcher that gets reset on activity (but never fires), and an I/O
		1232	watcher waiting for input on one side of the socket. Each time the socket
		1233	watcher reads a byte it will write that byte to a random other "server".
		1234
		1235	The effect is that there will be a lot of I/O watchers, only part of which
		1236	are active at any one point (so there is a constant number of active
		1237	fds for each loop iterstaion, but which fds these are is random). The
		1238	timeout is reset each time something is read because that reflects how
		1239	most timeouts work (and puts extra pressure on the event loops).
		1240
		1241	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
		1242	(1%) are active. This mirrors the activity of large servers with many
		1243	connections, most of which are idle at any one point in time.
		1244
		1245	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1246	distribution.
		1247
		1248	=head3 Explanation of the columns
		1249
		1250	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1251	each server has a read and write socket end).
		1252
		1253	I<create> is the time it takes to create a socketpair (which is
		1254	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1255
		1256	I<request>, the most important value, is the time it takes to handle a
		1257	single "request", that is, reading the token from the pipe and forwarding
		1258	it to another server. This includes deleting the old timeout and creating
		1259	a new one that moves the timeout into the future.
		1260
		1261	=head3 Results
		1262
		1263	name sockets create request
		1264	EV 20000 69.01 11.16
		1265	Perl 20000 73.32 35.87
		1266	Event 20000 212.62 257.32
		1267	Glib 20000 651.16 1896.30
		1268	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1269
		1270	=head3 Discussion
		1271
		1272	This benchmark I<does> measure scalability and overall performance of the
		1273	particular event loop.
		1274
		1275	EV is again fastest. Since it is using epoll on my system, the setup time
		1276	is relatively high, though.
		1277
		1278	Perl surprisingly comes second. It is much faster than the C-based event
		1279	loops Event and Glib.
		1280
		1281	Event suffers from high setup time as well (look at its code and you will
		1282	understand why). Callback invocation also has a high overhead compared to
		1283	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1284	uses select or poll in basically all documented configurations.
		1285
		1286	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1287	clearly fails to perform with many filehandles or in busy servers.
		1288
		1289	POE is still completely out of the picture, taking over 1000 times as long
		1290	as EV, and over 100 times as long as the Perl implementation, even though
		1291	it uses a C-based event loop in this case.
		1292
		1293	=head3 Summary
		1294
		1295	=over 4
		1296
		1297	=item * The pure perl implementation performs extremely well.
		1298
		1299	=item * Avoid Glib or POE in large projects where performance matters.
		1300
		1301	=back
		1302
		1303	=head2 BENCHMARKING SMALL SERVERS
		1304
		1305	While event loops should scale (and select-based ones do not...) even to
		1306	large servers, most programs we (or I :) actually write have only a few
		1307	I/O watchers.
		1308
		1309	In this benchmark, I use the same benchmark program as in the large server
		1310	case, but it uses only eight "servers", of which three are active at any
		1311	one time. This should reflect performance for a small server relatively
		1312	well.
		1313
		1314	The columns are identical to the previous table.
		1315
		1316	=head3 Results
		1317
		1318	name sockets create request
		1319	EV 16 20.00 6.54
		1320	Perl 16 25.75 12.62
		1321	Event 16 81.27 35.86
		1322	Glib 16 32.63 15.48
		1323	POE 16 261.87 276.28 uses POE::Loop::Event
		1324
		1325	=head3 Discussion
		1326
		1327	The benchmark tries to test the performance of a typical small
		1328	server. While knowing how various event loops perform is interesting, keep
		1329	in mind that their overhead in this case is usually not as important, due
		1330	to the small absolute number of watchers (that is, you need efficiency and
		1331	speed most when you have lots of watchers, not when you only have a few of
		1332	them).
		1333
		1334	EV is again fastest.
		1335
		1336	Perl again comes second. It is noticably faster than the C-based event
		1337	loops Event and Glib, although the difference is too small to really
		1338	matter.
		1339
		1340	POE also performs much better in this case, but is is still far behind the
		1341	others.
		1342
		1343	=head3 Summary
		1344
		1345	=over 4
		1346
		1347	=item * C-based event loops perform very well with small number of
		1348	watchers, as the management overhead dominates.
		1349
		1350	=back
		1351
		1352
		1353	=head1 FORK
		1354
		1355	Most event libraries are not fork-safe. The ones who are usually are
		1356	because they rely on inefficient but fork-safe C<select> or C<poll>
		1357	calls. Only L<EV> is fully fork-aware.
		1358
		1359	If you have to fork, you must either do so I<before> creating your first
		1360	watcher OR you must not use AnyEvent at all in the child.
		1361
		1362
		1363	=head1 SECURITY CONSIDERATIONS
		1364
		1365	AnyEvent can be forced to load any event model via
		1366	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		1367	execute arbitrary code or directly gain access, it can easily be used to
		1368	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		1369	will not be active when the program uses a different event model than
		1370	specified in the variable.
		1371
		1372	You can make AnyEvent completely ignore this variable by deleting it
		1373	before the first watcher gets created, e.g. with a C<BEGIN> block:
		1374
		1375	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1376
		1377	use AnyEvent;
		1378
		1379
801	=head1 SEE ALSO	1380	=head1 SEE ALSO
802		1381
803	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1382	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
804	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>.	1383	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
		1384	L<Event::Lib>, L<Qt>, L<POE>.
805		1385
806	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1386	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
		1387	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		1388	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
807	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>,	1389	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
808	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>.
809		1390
810	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1391	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
		1392
811		1393
812	=head1 AUTHOR	1394	=head1 AUTHOR
813		1395
814	Marc Lehmann <schmorp@schmorp.de>	1396	Marc Lehmann <schmorp@schmorp.de>
815	http://home.schmorp.de/	1397	http://home.schmorp.de/

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.54 by root, Tue Apr 22 05:12:19 2008 UTC vs. Revision 1.105 by root, Thu May 1 12:35:54 2008 UTC

Diff Legend

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.54 by root, Tue Apr 22 05:12:19 2008 UTC vs.
Revision 1.105 by root, Thu May 1 12:35:54 2008 UTC