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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.1 by root, Wed Apr 27 01:26:44 2005 UTC vs.
Revision 1.84 by root, Fri Apr 25 13:48:42 2008 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - ???	3	AnyEvent - provide framework for multiple event loops
		4
		5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
6		8
		9	use AnyEvent;
		10
		11	my $w = AnyEvent->io (fh => $fh, poll => "r\|w", cb => sub {
		12	...
		13	});
		14
		15	my $w = AnyEvent->timer (after => $seconds, cb => sub {
		16	...
		17	});
		18
		19	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		20	$w->wait; # enters "main loop" till $condvar gets ->broadcast
		21	$w->broadcast; # wake up current and all future wait's
		22
		23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
		24
		25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
		26	nowadays. So what is different about AnyEvent?
		27
		28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
		29	policy> and AnyEvent is I<small and efficient>.
		30
		31	First and foremost, I<AnyEvent is not an event model> itself, it only
		32	interfaces to whatever event model the main program happens to use in a
		33	pragmatic way. For event models and certain classes of immortals alike,
		34	the statement "there can only be one" is a bitter reality: In general,
		35	only one event loop can be active at the same time in a process. AnyEvent
		36	helps hiding the differences between those event loops.
		37
		38	The goal of AnyEvent is to offer module authors the ability to do event
		39	programming (waiting for I/O or timer events) without subscribing to a
		40	religion, a way of living, and most importantly: without forcing your
		41	module users into the same thing by forcing them to use the same event
		42	model you use.
		43
		44	For modules like POE or IO::Async (which is a total misnomer as it is
		45	actually doing all I/O I<synchronously>...), using them in your module is
		46	like joining a cult: After you joined, you are dependent on them and you
		47	cannot use anything else, as it is simply incompatible to everything that
		48	isn't itself. What's worse, all the potential users of your module are
		49	I<also> forced to use the same event loop you use.
		50
		51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
		52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
		53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if
		54	your module uses one of those, every user of your module has to use it,
		55	too. But if your module uses AnyEvent, it works transparently with all
		56	event models it supports (including stuff like POE and IO::Async, as long
		57	as those use one of the supported event loops. It is trivial to add new
		58	event loops to AnyEvent, too, so it is future-proof).
		59
		60	In addition to being free of having to use I<the one and only true event
		61	model>, AnyEvent also is free of bloat and policy: with POE or similar
		62	modules, you get an enourmous amount of code and strict rules you have to
		63	follow. AnyEvent, on the other hand, is lean and up to the point, by only
		64	offering the functionality that is necessary, in as thin as a wrapper as
		65	technically possible.
		66
		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
		69	model, you should I<not> use this module.
		70
		71
7	=head1 DESCRIPTION	72	=head1 DESCRIPTION
8		73
		74	L<AnyEvent> provides an identical interface to multiple event loops. This
		75	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
		77	peacefully at any one time).
		78
		79	The interface itself is vaguely similar, but not identical to the L<Event>
		80	module.
		81
		82	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
		84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
		85	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
		86	L<POE>. The first one found is used. If none are found, the module tries
		87	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
		88	adaptor should always succeed) in the order given. The first one that can
		89	be successfully loaded will be used. If, after this, still none could be
		90	found, AnyEvent will fall back to a pure-perl event loop, which is not
		91	very efficient, but should work everywhere.
		92
		93	Because AnyEvent first checks for modules that are already loaded, loading
		94	an event model explicitly before first using AnyEvent will likely make
		95	that model the default. For example:
		96
		97	use Tk;
		98	use AnyEvent;
		99
		100	# .. AnyEvent will likely default to Tk
		101
		102	The I<likely> means that, if any module loads another event model and
		103	starts using it, all bets are off. Maybe you should tell their authors to
		104	use AnyEvent so their modules work together with others seamlessly...
		105
		106	The pure-perl implementation of AnyEvent is called
		107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
		108	explicitly.
		109
		110	=head1 WATCHERS
		111
		112	AnyEvent has the central concept of a I<watcher>, which is an object that
		113	stores relevant data for each kind of event you are waiting for, such as
		114	the callback to call, the filehandle to watch, etc.
		115
		116	These watchers are normal Perl objects with normal Perl lifetime. After
		117	creating a watcher it will immediately "watch" for events and invoke the
		118	callback when the event occurs (of course, only when the event model
		119	is in control).
		120
		121	To disable the watcher you have to destroy it (e.g. by setting the
		122	variable you store it in to C<undef> or otherwise deleting all references
		123	to it).
		124
		125	All watchers are created by calling a method on the C<AnyEvent> class.
		126
		127	Many watchers either are used with "recursion" (repeating timers for
		128	example), or need to refer to their watcher object in other ways.
		129
		130	An any way to achieve that is this pattern:
		131
		132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		133	# you can use $w here, for example to undef it
		134	undef $w;
		135	});
		136
		137	Note that C<my $w; $w => combination. This is necessary because in Perl,
		138	my variables are only visible after the statement in which they are
		139	declared.
		140
		141	=head2 I/O WATCHERS
		142
		143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
		144	with the following mandatory key-value pairs as arguments:
		145
		146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for
		147	events. C<poll> must be a string that is either C<r> or C<w>, which
		148	creates a watcher waiting for "r"eadable or "w"ritable events,
		149	respectively. C<cb> is the callback to invoke each time the file handle
		150	becomes ready.
		151
		152	The I/O watcher might use the underlying file descriptor or a copy of it.
		153	You must not close a file handle as long as any watcher is active on the
		154	underlying file descriptor.
		155
		156	Some event loops issue spurious readyness notifications, so you should
		157	always use non-blocking calls when reading/writing from/to your file
		158	handles.
		159
		160	Although the callback might get passed parameters, their value and
		161	presence is undefined and you cannot rely on them. Portable AnyEvent
		162	callbacks cannot use arguments passed to I/O watcher callbacks.
		163
		164	Example:
		165
		166	# wait for readability of STDIN, then read a line and disable the watcher
		167	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		168	chomp (my $input = <STDIN>);
		169	warn "read: $input\n";
		170	undef $w;
		171	});
		172
		173	=head2 TIME WATCHERS
		174
		175	You can create a time watcher by calling the C<< AnyEvent->timer >>
		176	method with the following mandatory arguments:
		177
		178	C<after> specifies after how many seconds (fractional values are
		179	supported) should the timer activate. C<cb> the callback to invoke in that
		180	case.
		181
		182	The timer callback will be invoked at most once: if you want a repeating
		183	timer you have to create a new watcher (this is a limitation by both Tk
		184	and Glib).
		185
		186	Although the callback might get passed parameters, their value and
		187	presence is undefined and you cannot rely on them. Portable AnyEvent
		188	callbacks cannot use arguments passed to time watcher callbacks.
		189
		190	Example:
		191
		192	# fire an event after 7.7 seconds
		193	my $w = AnyEvent->timer (after => 7.7, cb => sub {
		194	warn "timeout\n";
		195	});
		196
		197	# to cancel the timer:
		198	undef $w;
		199
		200	Example 2:
		201
		202	# fire an event after 0.5 seconds, then roughly every second
		203	my $w;
		204
		205	my $cb = sub {
		206	# cancel the old timer while creating a new one
		207	$w = AnyEvent->timer (after => 1, cb => $cb);
		208	};
		209
		210	# start the "loop" by creating the first watcher
		211	$w = AnyEvent->timer (after => 0.5, cb => $cb);
		212
		213	=head3 TIMING ISSUES
		214
		215	There are two ways to handle timers: based on real time (relative, "fire
		216	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		217	o'clock").
		218
		219	While most event loops expect timers to specified in a relative way, they
		220	use absolute time internally. This makes a difference when your clock
		221	"jumps", for example, when ntp decides to set your clock backwards from
		222	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		223	fire "after" a second might actually take six years to finally fire.
		224
		225	AnyEvent cannot compensate for this. The only event loop that is conscious
		226	about these issues is L<EV>, which offers both relative (ev_timer, based
		227	on true relative time) and absolute (ev_periodic, based on wallclock time)
		228	timers.
		229
		230	AnyEvent always prefers relative timers, if available, matching the
		231	AnyEvent API.
		232
		233	=head2 SIGNAL WATCHERS
		234
		235	You can watch for signals using a signal watcher, C<signal> is the signal
		236	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
		237	be invoked whenever a signal occurs.
		238
		239	Multiple signal occurances can be clumped together into one callback
		240	invocation, and callback invocation will be synchronous. synchronous means
		241	that it might take a while until the signal gets handled by the process,
		242	but it is guarenteed not to interrupt any other callbacks.
		243
		244	The main advantage of using these watchers is that you can share a signal
		245	between multiple watchers.
		246
		247	This watcher might use C<%SIG>, so programs overwriting those signals
		248	directly will likely not work correctly.
		249
		250	Example: exit on SIGINT
		251
		252	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		253
		254	=head2 CHILD PROCESS WATCHERS
		255
		256	You can also watch on a child process exit and catch its exit status.
		257
		258	The child process is specified by the C<pid> argument (if set to C<0>, it
		259	watches for any child process exit). The watcher will trigger as often
		260	as status change for the child are received. This works by installing a
		261	signal handler for C<SIGCHLD>. The callback will be called with the pid
		262	and exit status (as returned by waitpid).
		263
		264	There is a slight catch to child watchers, however: you usually start them
		265	I<after> the child process was created, and this means the process could
		266	have exited already (and no SIGCHLD will be sent anymore).
		267
		268	Not all event models handle this correctly (POE doesn't), but even for
		269	event models that I<do> handle this correctly, they usually need to be
		270	loaded before the process exits (i.e. before you fork in the first place).
		271
		272	This means you cannot create a child watcher as the very first thing in an
		273	AnyEvent program, you I<have> to create at least one watcher before you
		274	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		275
		276	Example: fork a process and wait for it
		277
		278	my $done = AnyEvent->condvar;
		279
		280	AnyEvent::detect; # force event module to be initialised
		281
		282	my $pid = fork or exit 5;
		283
		284	my $w = AnyEvent->child (
		285	pid => $pid,
		286	cb => sub {
		287	my ($pid, $status) = @_;
		288	warn "pid $pid exited with status $status";
		289	$done->broadcast;
		290	},
		291	);
		292
		293	# do something else, then wait for process exit
		294	$done->wait;
		295
		296	=head2 CONDITION VARIABLES
		297
		298	Condition variables can be created by calling the C<< AnyEvent->condvar >>
		299	method without any arguments.
		300
		301	A condition variable waits for a condition - precisely that the C<<
		302	->broadcast >> method has been called.
		303
		304	They are very useful to signal that a condition has been fulfilled, for
		305	example, if you write a module that does asynchronous http requests,
		306	then a condition variable would be the ideal candidate to signal the
		307	availability of results.
		308
		309	You can also use condition variables to block your main program until
		310	an event occurs - for example, you could C<< ->wait >> in your main
		311	program until the user clicks the Quit button in your app, which would C<<
		312	->broadcast >> the "quit" event.
		313
		314	Note that condition variables recurse into the event loop - if you have
		315	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
		316	lose. Therefore, condition variables are good to export to your caller, but
		317	you should avoid making a blocking wait yourself, at least in callbacks,
		318	as this asks for trouble.
		319
		320	This object has two methods:
		321
9	=over 4	322	=over 4
10		323
		324	=item $cv->wait
		325
		326	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
		327	called on c<$cv>, while servicing other watchers normally.
		328
		329	You can only wait once on a condition - additional calls will return
		330	immediately.
		331
		332	Not all event models support a blocking wait - some die in that case
		333	(programs might want to do that to stay interactive), so I<if you are
		334	using this from a module, never require a blocking wait>, but let the
		335	caller decide whether the call will block or not (for example, by coupling
		336	condition variables with some kind of request results and supporting
		337	callbacks so the caller knows that getting the result will not block,
		338	while still suppporting blocking waits if the caller so desires).
		339
		340	Another reason I<never> to C<< ->wait >> in a module is that you cannot
		341	sensibly have two C<< ->wait >>'s in parallel, as that would require
		342	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
		343	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
		344	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
		345	from different coroutines, however).
		346
		347	=item $cv->broadcast
		348
		349	Flag the condition as ready - a running C<< ->wait >> and all further
		350	calls to C<wait> will (eventually) return after this method has been
		351	called. If nobody is waiting the broadcast will be remembered..
		352
		353	=back
		354
		355	Example:
		356
		357	# wait till the result is ready
		358	my $result_ready = AnyEvent->condvar;
		359
		360	# do something such as adding a timer
		361	# or socket watcher the calls $result_ready->broadcast
		362	# when the "result" is ready.
		363	# in this case, we simply use a timer:
		364	my $w = AnyEvent->timer (
		365	after => 1,
		366	cb => sub { $result_ready->broadcast },
		367	);
		368
		369	# this "blocks" (while handling events) till the watcher
		370	# calls broadcast
		371	$result_ready->wait;
		372
		373	=head1 GLOBAL VARIABLES AND FUNCTIONS
		374
		375	=over 4
		376
		377	=item $AnyEvent::MODEL
		378
		379	Contains C<undef> until the first watcher is being created. Then it
		380	contains the event model that is being used, which is the name of the
		381	Perl class implementing the model. This class is usually one of the
		382	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
		383	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
		384
		385	The known classes so far are:
		386
		387	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
		388	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
		389	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
		390	AnyEvent::Impl::Event based on Event, second best choice.
		391	AnyEvent::Impl::Glib based on Glib, third-best choice.
		392	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
		393	AnyEvent::Impl::Tk based on Tk, very bad choice.
		394	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		395	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		396	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		397
		398	There is no support for WxWidgets, as WxWidgets has no support for
		399	watching file handles. However, you can use WxWidgets through the
		400	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		401	second, which was considered to be too horrible to even consider for
		402	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		403	it's adaptor.
		404
		405	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		406	autodetecting them.
		407
		408	=item AnyEvent::detect
		409
		410	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
		411	if necessary. You should only call this function right before you would
		412	have created an AnyEvent watcher anyway, that is, as late as possible at
		413	runtime.
		414
		415	=back
		416
		417	=head1 WHAT TO DO IN A MODULE
		418
		419	As a module author, you should C<use AnyEvent> and call AnyEvent methods
		420	freely, but you should not load a specific event module or rely on it.
		421
		422	Be careful when you create watchers in the module body - AnyEvent will
		423	decide which event module to use as soon as the first method is called, so
		424	by calling AnyEvent in your module body you force the user of your module
		425	to load the event module first.
		426
		427	Never call C<< ->wait >> on a condition variable unless you I<know> that
		428	the C<< ->broadcast >> method has been called on it already. This is
		429	because it will stall the whole program, and the whole point of using
		430	events is to stay interactive.
		431
		432	It is fine, however, to call C<< ->wait >> when the user of your module
		433	requests it (i.e. if you create a http request object ad have a method
		434	called C<results> that returns the results, it should call C<< ->wait >>
		435	freely, as the user of your module knows what she is doing. always).
		436
		437	=head1 WHAT TO DO IN THE MAIN PROGRAM
		438
		439	There will always be a single main program - the only place that should
		440	dictate which event model to use.
		441
		442	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
		443	do anything special (it does not need to be event-based) and let AnyEvent
		444	decide which implementation to chose if some module relies on it.
		445
		446	If the main program relies on a specific event model. For example, in
		447	Gtk2 programs you have to rely on the Glib module. You should load the
		448	event module before loading AnyEvent or any module that uses it: generally
		449	speaking, you should load it as early as possible. The reason is that
		450	modules might create watchers when they are loaded, and AnyEvent will
		451	decide on the event model to use as soon as it creates watchers, and it
		452	might chose the wrong one unless you load the correct one yourself.
		453
		454	You can chose to use a rather inefficient pure-perl implementation by
		455	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
		456	behaviour everywhere, but letting AnyEvent chose is generally better.
		457
11	=cut	458	=cut
12		459
13	package AnyEvent;	460	package AnyEvent;
14		461
		462	no warnings;
		463	use strict;
		464
15	use Carp;	465	use Carp;
16		466
17	$VERSION = 0.1;	467	our $VERSION = '3.3';
		468	our $MODEL;
18		469
19	no warnings;	470	our $AUTOLOAD;
		471	our @ISA;
		472
		473	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		474
		475	our @REGISTRY;
20		476
21	my @models = (	477	my @models = (
22	[Coro => Coro::Event::],	478	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
23	[Event => Event::],	479	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
24	[Glib => Glib::],	480	[EV:: => AnyEvent::Impl::EV::],
25	[Tk => Tk::],	481	[Event:: => AnyEvent::Impl::Event::],
		482	[Glib:: => AnyEvent::Impl::Glib::],
		483	[Tk:: => AnyEvent::Impl::Tk::],
		484	[Wx:: => AnyEvent::Impl::POE::],
		485	[Prima:: => AnyEvent::Impl::POE::],
		486	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		487	# everything below here will not be autoprobed as the pureperl backend should work everywhere
		488	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		489	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		490	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
26	);	491	);
27		492
		493	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
		494
		495	sub detect() {
		496	unless ($MODEL) {
		497	no strict 'refs';
		498
		499	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		500	my $model = "AnyEvent::Impl::$1";
		501	if (eval "require $model") {
		502	$MODEL = $model;
		503	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		504	} else {
		505	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
		506	}
		507	}
		508
		509	# check for already loaded models
		510	unless ($MODEL) {
		511	for (@REGISTRY, @models) {
		512	my ($package, $model) = @$_;
		513	if (${"$package\::VERSION"} > 0) {
		514	if (eval "require $model") {
		515	$MODEL = $model;
		516	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
		517	last;
		518	}
		519	}
		520	}
		521
		522	unless ($MODEL) {
		523	# try to load a model
		524
		525	for (@REGISTRY, @models) {
		526	my ($package, $model) = @$_;
		527	if (eval "require $package"
		528	and ${"$package\::VERSION"} > 0
		529	and eval "require $model") {
		530	$MODEL = $model;
		531	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
		532	last;
		533	}
		534	}
		535
		536	$MODEL
		537	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.";
		538	}
		539	}
		540
		541	unshift @ISA, $MODEL;
		542	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		543	}
		544
		545	$MODEL
		546	}
		547
28	sub AUTOLOAD {	548	sub AUTOLOAD {
29	$AUTOLOAD =~ s/.*://;	549	(my $func = $AUTOLOAD) =~ s/.*://;
30		550
31	for (@models) {	551	$method{$func}
32	my ($model, $package) = @$_;	552	or croak "$func: not a valid method for AnyEvent objects";
33	if (defined ${"$package\::VERSION"}) {	553
34	$EVENT = "AnyEvent::Impl::$model";	554	detect unless $MODEL;
35	eval "require $EVENT"; die if $@;	555
36	goto &{"$EVENT\::$AUTOLOAD"};	556	my $class = shift;
37	}	557	$class->$func (@_);
		558	}
		559
		560	package AnyEvent::Base;
		561
		562	# default implementation for ->condvar, ->wait, ->broadcast
		563
		564	sub condvar {
		565	bless \my $flag, "AnyEvent::Base::CondVar"
		566	}
		567
		568	sub AnyEvent::Base::CondVar::broadcast {
		569	${$_[0]}++;
		570	}
		571
		572	sub AnyEvent::Base::CondVar::wait {
		573	AnyEvent->one_event while !${$_[0]};
		574	}
		575
		576	# default implementation for ->signal
		577
		578	our %SIG_CB;
		579
		580	sub signal {
		581	my (undef, %arg) = @_;
		582
		583	my $signal = uc $arg{signal}
		584	or Carp::croak "required option 'signal' is missing";
		585
		586	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		587	$SIG{$signal} \|\|= sub {
		588	$_->() for values %{ $SIG_CB{$signal} \|\| {} };
		589	};
		590
		591	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"
		592	}
		593
		594	sub AnyEvent::Base::Signal::DESTROY {
		595	my ($signal, $cb) = @{$_[0]};
		596
		597	delete $SIG_CB{$signal}{$cb};
		598
		599	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
		600	}
		601
		602	# default implementation for ->child
		603
		604	our %PID_CB;
		605	our $CHLD_W;
		606	our $CHLD_DELAY_W;
		607	our $PID_IDLE;
		608	our $WNOHANG;
		609
		610	sub _child_wait {
		611	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
		612	$_->($pid, $?) for (values %{ $PID_CB{$pid} \|\| {} }),
		613	(values %{ $PID_CB{0} \|\| {} });
38	}	614	}
39		615
40	for (@models) {	616	undef $PID_IDLE;
41	my ($model, $package) = @$_;	617	}
42	$EVENT = "AnyEvent::Impl::$model";	618
43	if (eval "require $EVENT") {	619	sub _sigchld {
44	goto &{"$EVENT\::$AUTOLOAD"};	620	# make sure we deliver these changes "synchronous" with the event loop.
45	}	621	$CHLD_DELAY_W \|\|= AnyEvent->timer (after => 0, cb => sub {
		622	undef $CHLD_DELAY_W;
		623	&_child_wait;
		624	});
		625	}
		626
		627	sub child {
		628	my (undef, %arg) = @_;
		629
		630	defined (my $pid = $arg{pid} + 0)
		631	or Carp::croak "required option 'pid' is missing";
		632
		633	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
		634
		635	unless ($WNOHANG) {
		636	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } \|\| 1;
46	}	637	}
47		638
48	die "No event module selected for AnyEvent and autodetect failed. Install any of these: Coro, Event, Glib or Tk.";	639	unless ($CHLD_W) {
		640	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
		641	# child could be a zombie already, so make at least one round
		642	&_sigchld;
		643	}
		644
		645	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
49	}	646	}
50		647
51	1;	648	sub AnyEvent::Base::Child::DESTROY {
		649	my ($pid, $cb) = @{$_[0]};
52		650
		651	delete $PID_CB{$pid}{$cb};
		652	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		653
		654	undef $CHLD_W unless keys %PID_CB;
		655	}
		656
		657	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		658
		659	This is an advanced topic that you do not normally need to use AnyEvent in
		660	a module. This section is only of use to event loop authors who want to
		661	provide AnyEvent compatibility.
		662
		663	If you need to support another event library which isn't directly
		664	supported by AnyEvent, you can supply your own interface to it by
		665	pushing, before the first watcher gets created, the package name of
		666	the event module and the package name of the interface to use onto
		667	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
		668	AnyEvent, so it is reasonably cheap.
		669
		670	Example:
		671
		672	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
		673
		674	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
		675	package/class when it finds the C<urxvt> package/module is already loaded.
		676
		677	When AnyEvent is loaded and asked to find a suitable event model, it
		678	will first check for the presence of urxvt by trying to C<use> the
		679	C<urxvt::anyevent> module.
		680
		681	The class should provide implementations for all watcher types. See
		682	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
		683	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
		684	see the sources.
		685
		686	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		687	provide suitable (hopefully) replacements.
		688
		689	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
		690	terminal emulator uses the above line as-is. An interface isn't included
		691	in AnyEvent because it doesn't make sense outside the embedded interpreter
		692	inside I<rxvt-unicode>, and it is updated and maintained as part of the
		693	I<rxvt-unicode> distribution.
		694
		695	I<rxvt-unicode> also cheats a bit by not providing blocking access to
		696	condition variables: code blocking while waiting for a condition will
		697	C<die>. This still works with most modules/usages, and blocking calls must
		698	not be done in an interactive application, so it makes sense.
		699
		700	=head1 ENVIRONMENT VARIABLES
		701
		702	The following environment variables are used by this module:
		703
		704	=over 4
		705
		706	=item C<PERL_ANYEVENT_VERBOSE>
		707
		708	By default, AnyEvent will be completely silent except in fatal
		709	conditions. You can set this environment variable to make AnyEvent more
		710	talkative.
		711
		712	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		713	conditions, such as not being able to load the event model specified by
		714	C<PERL_ANYEVENT_MODEL>.
		715
		716	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		717	model it chooses.
		718
		719	=item C<PERL_ANYEVENT_MODEL>
		720
		721	This can be used to specify the event model to be used by AnyEvent, before
		722	autodetection and -probing kicks in. It must be a string consisting
		723	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		724	and the resulting module name is loaded and if the load was successful,
		725	used as event model. If it fails to load AnyEvent will proceed with
		726	autodetection and -probing.
		727
		728	This functionality might change in future versions.
		729
		730	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		731	could start your program like this:
		732
		733	PERL_ANYEVENT_MODEL=Perl perl ...
		734
		735	=back
		736
		737	=head1 EXAMPLE PROGRAM
		738
		739	The following program uses an I/O watcher to read data from STDIN, a timer
		740	to display a message once per second, and a condition variable to quit the
		741	program when the user enters quit:
		742
		743	use AnyEvent;
		744
		745	my $cv = AnyEvent->condvar;
		746
		747	my $io_watcher = AnyEvent->io (
		748	fh => \*STDIN,
		749	poll => 'r',
		750	cb => sub {
		751	warn "io event <$_[0]>\n"; # will always output <r>
		752	chomp (my $input = <STDIN>); # read a line
		753	warn "read: $input\n"; # output what has been read
		754	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
		755	},
		756	);
		757
		758	my $time_watcher; # can only be used once
		759
		760	sub new_timer {
		761	$timer = AnyEvent->timer (after => 1, cb => sub {
		762	warn "timeout\n"; # print 'timeout' about every second
		763	&new_timer; # and restart the time
		764	});
		765	}
		766
		767	new_timer; # create first timer
		768
		769	$cv->wait; # wait until user enters /^q/i
		770
		771	=head1 REAL-WORLD EXAMPLE
		772
		773	Consider the L<Net::FCP> module. It features (among others) the following
		774	API calls, which are to freenet what HTTP GET requests are to http:
		775
		776	my $data = $fcp->client_get ($url); # blocks
		777
		778	my $transaction = $fcp->txn_client_get ($url); # does not block
		779	$transaction->cb ( sub { ... } ); # set optional result callback
		780	my $data = $transaction->result; # possibly blocks
		781
		782	The C<client_get> method works like C<LWP::Simple::get>: it requests the
		783	given URL and waits till the data has arrived. It is defined to be:
		784
		785	sub client_get { $_[0]->txn_client_get ($_[1])->result }
		786
		787	And in fact is automatically generated. This is the blocking API of
		788	L<Net::FCP>, and it works as simple as in any other, similar, module.
		789
		790	More complicated is C<txn_client_get>: It only creates a transaction
		791	(completion, result, ...) object and initiates the transaction.
		792
		793	my $txn = bless { }, Net::FCP::Txn::;
		794
		795	It also creates a condition variable that is used to signal the completion
		796	of the request:
		797
		798	$txn->{finished} = AnyAvent->condvar;
		799
		800	It then creates a socket in non-blocking mode.
		801
		802	socket $txn->{fh}, ...;
		803	fcntl $txn->{fh}, F_SETFL, O_NONBLOCK;
		804	connect $txn->{fh}, ...
		805	and !$!{EWOULDBLOCK}
		806	and !$!{EINPROGRESS}
		807	and Carp::croak "unable to connect: $!\n";
		808
		809	Then it creates a write-watcher which gets called whenever an error occurs
		810	or the connection succeeds:
		811
		812	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });
		813
		814	And returns this transaction object. The C<fh_ready_w> callback gets
		815	called as soon as the event loop detects that the socket is ready for
		816	writing.
		817
		818	The C<fh_ready_w> method makes the socket blocking again, writes the
		819	request data and replaces the watcher by a read watcher (waiting for reply
		820	data). The actual code is more complicated, but that doesn't matter for
		821	this example:
		822
		823	fcntl $txn->{fh}, F_SETFL, 0;
		824	syswrite $txn->{fh}, $txn->{request}
		825	or die "connection or write error";
		826	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
		827
		828	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
		829	result and signals any possible waiters that the request ahs finished:
		830
		831	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
		832
		833	if (end-of-file or data complete) {
		834	$txn->{result} = $txn->{buf};
		835	$txn->{finished}->broadcast;
		836	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
		837	}
		838
		839	The C<result> method, finally, just waits for the finished signal (if the
		840	request was already finished, it doesn't wait, of course, and returns the
		841	data:
		842
		843	$txn->{finished}->wait;
		844	return $txn->{result};
		845
		846	The actual code goes further and collects all errors (C<die>s, exceptions)
		847	that occured during request processing. The C<result> method detects
		848	whether an exception as thrown (it is stored inside the $txn object)
		849	and just throws the exception, which means connection errors and other
		850	problems get reported tot he code that tries to use the result, not in a
		851	random callback.
		852
		853	All of this enables the following usage styles:
		854
		855	1. Blocking:
		856
		857	my $data = $fcp->client_get ($url);
		858
		859	2. Blocking, but running in parallel:
		860
		861	my @datas = map $_->result,
		862	map $fcp->txn_client_get ($_),
		863	@urls;
		864
		865	Both blocking examples work without the module user having to know
		866	anything about events.
		867
		868	3a. Event-based in a main program, using any supported event module:
		869
		870	use EV;
		871
		872	$fcp->txn_client_get ($url)->cb (sub {
		873	my $txn = shift;
		874	my $data = $txn->result;
		875	...
		876	});
		877
		878	EV::loop;
		879
		880	3b. The module user could use AnyEvent, too:
		881
		882	use AnyEvent;
		883
		884	my $quit = AnyEvent->condvar;
		885
		886	$fcp->txn_client_get ($url)->cb (sub {
		887	...
		888	$quit->broadcast;
		889	});
		890
		891	$quit->wait;
		892
		893
		894	=head1 BENCHMARK
		895
		896	To give you an idea of the performance and overheads that AnyEvent adds
		897	over the event loops themselves (and to give you an impression of the
		898	speed of various event loops), here is a benchmark of various supported
		899	event models natively and with anyevent. The benchmark creates a lot of
		900	timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to
		901	become writable, which it is), lets them fire exactly once and destroys
		902	them again.
		903
		904	Rewriting the benchmark to use many different sockets instead of using
		905	the same filehandle for all I/O watchers results in a much longer runtime
		906	(socket creation is expensive), but qualitatively the same figures, so it
		907	was not used.
		908
		909	=head2 Explanation of the columns
		910
		911	I<watcher> is the number of event watchers created/destroyed. Since
		912	different event models feature vastly different performances, each event
		913	loop was given a number of watchers so that overall runtime is acceptable
		914	and similar between tested event loop (and keep them from crashing): Glib
		915	would probably take thousands of years if asked to process the same number
		916	of watchers as EV in this benchmark.
		917
		918	I<bytes> is the number of bytes (as measured by the resident set size,
		919	RSS) consumed by each watcher. This method of measuring captures both C
		920	and Perl-based overheads.
		921
		922	I<create> is the time, in microseconds (millionths of seconds), that it
		923	takes to create a single watcher. The callback is a closure shared between
		924	all watchers, to avoid adding memory overhead. That means closure creation
		925	and memory usage is not included in the figures.
		926
		927	I<invoke> is the time, in microseconds, used to invoke a simple
		928	callback. The callback simply counts down a Perl variable and after it was
		929	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		930	signal the end of this phase.
		931
		932	I<destroy> is the time, in microseconds, that it takes to destroy a single
		933	watcher.
		934
		935	=head2 Results
		936
		937	name watchers bytes create invoke destroy comment
		938	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		939	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		940	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		941	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		942	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		943	Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers
		944	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		945	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		946	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		947	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		948
		949	=head2 Discussion
		950
		951	The benchmark does I<not> measure scalability of the event loop very
		952	well. For example, a select-based event loop (such as the pure perl one)
		953	can never compete with an event loop that uses epoll when the number of
		954	file descriptors grows high. In this benchmark, all events become ready at
		955	the same time, so select/poll-based implementations get an unnatural speed
		956	boost.
		957
		958	C<EV> is the sole leader regarding speed and memory use, which are both
		959	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		960	far less memory than any other event loop and is still faster than Event
		961	natively.
		962
		963	The pure perl implementation is hit in a few sweet spots (both the
		964	zero timeout and the use of a single fd hit optimisations in the perl
		965	interpreter and the backend itself, and all watchers become ready at the
		966	same time). Nevertheless this shows that it adds very little overhead in
		967	itself. Like any select-based backend its performance becomes really bad
		968	with lots of file descriptors (and few of them active), of course, but
		969	this was not subject of this benchmark.
		970
		971	The C<Event> module has a relatively high setup and callback invocation cost,
		972	but overall scores on the third place.
		973
		974	C<Glib>'s memory usage is quite a bit bit higher, but it features a
		975	faster callback invocation and overall ends up in the same class as
		976	C<Event>. However, Glib scales extremely badly, doubling the number of
		977	watchers increases the processing time by more than a factor of four,
		978	making it completely unusable when using larger numbers of watchers
		979	(note that only a single file descriptor was used in the benchmark, so
		980	inefficiencies of C<poll> do not account for this).
		981
		982	The C<Tk> adaptor works relatively well. The fact that it crashes with
		983	more than 2000 watchers is a big setback, however, as correctness takes
		984	precedence over speed. Nevertheless, its performance is surprising, as the
		985	file descriptor is dup()ed for each watcher. This shows that the dup()
		986	employed by some adaptors is not a big performance issue (it does incur a
		987	hidden memory cost inside the kernel, though, that is not reflected in the
		988	figures above).
		989
		990	C<POE>, regardless of underlying event loop (wether using its pure perl
		991	select-based backend or the Event module) shows abysmal performance and
		992	memory usage: Watchers use almost 30 times as much memory as EV watchers,
		993	and 10 times as much memory as both Event or EV via AnyEvent. Watcher
		994	invocation is almost 900 times slower than with AnyEvent's pure perl
		995	implementation. The design of the POE adaptor class in AnyEvent can not
		996	really account for this, as session creation overhead is small compared
		997	to execution of the state machine, which is coded pretty optimally within
		998	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		999
		1000	=head2 Summary
		1001
		1002	Using EV through AnyEvent is faster than any other event loop, but most
		1003	event loops have acceptable performance with or without AnyEvent.
		1004
		1005	The overhead AnyEvent adds is usually much smaller than the overhead of
		1006	the actual event loop, only with extremely fast event loops such as the EV
		1007	adds AnyEvent significant overhead.
		1008
		1009	And you should simply avoid POE like the plague if you want performance or
		1010	reasonable memory usage.
		1011
		1012
		1013	=head1 FORK
		1014
		1015	Most event libraries are not fork-safe. The ones who are usually are
		1016	because they are so inefficient. Only L<EV> is fully fork-aware.
		1017
		1018	If you have to fork, you must either do so I<before> creating your first
		1019	watcher OR you must not use AnyEvent at all in the child.
		1020
		1021
		1022	=head1 SECURITY CONSIDERATIONS
		1023
		1024	AnyEvent can be forced to load any event model via
		1025	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		1026	execute arbitrary code or directly gain access, it can easily be used to
		1027	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		1028	will not be active when the program uses a different event model than
		1029	specified in the variable.
		1030
		1031	You can make AnyEvent completely ignore this variable by deleting it
		1032	before the first watcher gets created, e.g. with a C<BEGIN> block:
		1033
		1034	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1035
		1036	use AnyEvent;
		1037
		1038
		1039	=head1 SEE ALSO
		1040
		1041	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
		1042	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
		1043	L<Event::Lib>, L<Qt>, L<POE>.
		1044
		1045	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
		1046	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		1047	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
		1048	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
		1049
		1050	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
		1051
		1052
		1053	=head1 AUTHOR
		1054
		1055	Marc Lehmann <schmorp@schmorp.de>
		1056	http://home.schmorp.de/
		1057
		1058	=cut
		1059
		1060	1
		1061

Diff Legend

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

Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.1 by root, Wed Apr 27 01:26:44 2005 UTC vs. Revision 1.84 by root, Fri Apr 25 13:48:42 2008 UTC

Diff Legend

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.1 by root, Wed Apr 27 01:26:44 2005 UTC vs.
Revision 1.84 by root, Fri Apr 25 13:48:42 2008 UTC