[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 1.73 by root, Fri Apr 25 07:47:12 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
80	module.	80	module.
81		81
82	During the first call of any watcher-creation method, the module tries	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	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>,	84	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,	85	L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,
86	the module tries to load these modules in the stated order. The first one	86	L<POE>. The first one found is used. If none are found, the module tries
		87	to load these modules (excluding Event::Lib, Qt and POE as the pure perl
		88	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	89	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	90	found, AnyEvent will fall back to a pure-perl event loop, which is not
89	is not very efficient, but should work everywhere.	91	very efficient, but should work everywhere.
90		92
91	Because AnyEvent first checks for modules that are already loaded, loading	93	Because AnyEvent first checks for modules that are already loaded, loading
92	an event model explicitly before first using AnyEvent will likely make	94	an event model explicitly before first using AnyEvent will likely make
93	that model the default. For example:	95	that model the default. For example:
94		96
…		…
145	events. C<poll> must be a string that is either C<r> or C<w>, which	147	events. C<poll> must be a string that is either C<r> or C<w>, which
146	creates a watcher waiting for "r"eadable or "w"ritable events,	148	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	149	respectively. C<cb> is the callback to invoke each time the file handle
148	becomes ready.	150	becomes ready.
149		151
150	File handles will be kept alive, so as long as the watcher exists, the	152	As long as the I/O watcher exists it will keep the file descriptor or a
151	file handle exists, too.	153	copy of it alive/open.
152		154
153	It is not allowed to close a file handle as long as any watcher is active	155	It is not allowed to close a file handle as long as any watcher is active
154	on the underlying file descriptor.	156	on the underlying file descriptor.
155		157
156	Some event loops issue spurious readyness notifications, so you should	158	Some event loops issue spurious readyness notifications, so you should
…		…
206		208
207	There are two ways to handle timers: based on real time (relative, "fire	209	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	210	in 10 seconds") and based on wallclock time (absolute, "fire at 12
209	o'clock").	211	o'clock").
210		212
211	While most event loops expect timers to specified in a relative way, they use	213	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",	214	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	215	"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	216	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
215	six years to finally fire.	217	fire "after" a second might actually take six years to finally fire.
216		218
217	AnyEvent cannot compensate for this. The only event loop that is conscious	219	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	220	about these issues is L<EV>, which offers both relative (ev_timer, based
219	absolute (ev_periodic) timers.	221	on true relative time) and absolute (ev_periodic, based on wallclock time)
		222	timers.
220		223
221	AnyEvent always prefers relative timers, if available, matching the	224	AnyEvent always prefers relative timers, if available, matching the
222	AnyEvent API.	225	AnyEvent API.
223		226
224	=head2 SIGNAL WATCHERS	227	=head2 SIGNAL WATCHERS
225		228
226	You can watch for signals using a signal watcher, C<signal> is the signal	229	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	230	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
228	be invoked whenever a signal occurs.	231	be invoked whenever a signal occurs.
229		232
230	Multiple signals occurances can be clumped together into one callback	233	Multiple signal occurances can be clumped together into one callback
231	invocation, and callback invocation will be synchronous. synchronous means	234	invocation, and callback invocation will be synchronous. synchronous means
232	that it might take a while until the signal gets handled by the process,	235	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.	236	but it is guarenteed not to interrupt any other callbacks.
234		237
235	The main advantage of using these watchers is that you can share a signal	238	The main advantage of using these watchers is that you can share a signal
…		…
353		356
354	The known classes so far are:	357	The known classes so far are:
355		358
356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.	359	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.	360	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
358	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).	361	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
359	AnyEvent::Impl::Event based on Event, also second best choice :)	362	AnyEvent::Impl::Event based on Event, second best choice.
360	AnyEvent::Impl::Glib based on Glib, third-best choice.	363	AnyEvent::Impl::Glib based on Glib, third-best choice.
361	AnyEvent::Impl::Tk based on Tk, very bad choice.	364	AnyEvent::Impl::Tk based on Tk, very bad choice.
362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.	365	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
		366	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		367	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		368	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		369
		370	There is no support for WxWidgets, as WxWidgets has no support for
		371	watching file handles. However, you can use WxWidgets through the
		372	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		373	second, which was considered to be too horrible to even consider for
		374	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		375	it's adaptor.
		376
		377	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		378	autodetecting them.
363		379
364	=item AnyEvent::detect	380	=item AnyEvent::detect
365		381
366	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	382	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
367	if necessary. You should only call this function right before you would	383	if necessary. You should only call this function right before you would
…		…
418	no warnings;	434	no warnings;
419	use strict;	435	use strict;
420		436
421	use Carp;	437	use Carp;
422		438
423	our $VERSION = '3.12';	439	our $VERSION = '3.3';
424	our $MODEL;	440	our $MODEL;
425		441
426	our $AUTOLOAD;	442	our $AUTOLOAD;
427	our @ISA;	443	our @ISA;
428		444
…		…
435	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],	451	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
436	[EV:: => AnyEvent::Impl::EV::],	452	[EV:: => AnyEvent::Impl::EV::],
437	[Event:: => AnyEvent::Impl::Event::],	453	[Event:: => AnyEvent::Impl::Event::],
438	[Glib:: => AnyEvent::Impl::Glib::],	454	[Glib:: => AnyEvent::Impl::Glib::],
439	[Tk:: => AnyEvent::Impl::Tk::],	455	[Tk:: => AnyEvent::Impl::Tk::],
		456	[Wx:: => AnyEvent::Impl::POE::],
		457	[Prima:: => AnyEvent::Impl::POE::],
440	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	458	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		459	# everything below here will not be autoprobed as the pureperl backend should work everywhere
		460	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		461	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		462	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
441	);	463	);
442		464
443	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	465	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
444		466
445	sub detect() {	467	sub detect() {
446	unless ($MODEL) {	468	unless ($MODEL) {
447	no strict 'refs';	469	no strict 'refs';
448		470
		471	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		472	my $model = "AnyEvent::Impl::$1";
		473	if (eval "require $model") {
		474	$MODEL = $model;
		475	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		476	} else {
		477	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
		478	}
		479	}
		480
449	# check for already loaded models	481	# check for already loaded models
		482	unless ($MODEL) {
450	for (@REGISTRY, @models) {	483	for (@REGISTRY, @models) {
451	my ($package, $model) = @$_;	484	my ($package, $model) = @$_;
452	if (${"$package\::VERSION"} > 0) {	485	if (${"$package\::VERSION"} > 0) {
453	if (eval "require $model") {	486	if (eval "require $model") {
454	$MODEL = $model;	487	$MODEL = $model;
455	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	488	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
456	last;	489	last;
		490	}
457	}	491	}
458	}	492	}
459	}
460		493
461	unless ($MODEL) {	494	unless ($MODEL) {
462	# try to load a model	495	# try to load a model
463		496
464	for (@REGISTRY, @models) {	497	for (@REGISTRY, @models) {
465	my ($package, $model) = @$_;	498	my ($package, $model) = @$_;
466	if (eval "require $package"	499	if (eval "require $package"
467	and ${"$package\::VERSION"} > 0	500	and ${"$package\::VERSION"} > 0
468	and eval "require $model") {	501	and eval "require $model") {
469	$MODEL = $model;	502	$MODEL = $model;
470	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	503	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
471	last;	504	last;
		505	}
472	}	506	}
		507
		508	$MODEL
		509	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	}	510	}
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	}	511	}
478		512
479	unshift @ISA, $MODEL;	513	unshift @ISA, $MODEL;
480	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	514	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
481	}	515	}
…		…
637		671
638	=head1 ENVIRONMENT VARIABLES	672	=head1 ENVIRONMENT VARIABLES
639		673
640	The following environment variables are used by this module:	674	The following environment variables are used by this module:
641		675
642	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, cause AnyEvent to	676	=over 4
643	report to STDERR which event model it chooses.	677
		678	=item C<PERL_ANYEVENT_VERBOSE>
		679
		680	By default, AnyEvent will be completely silent except in fatal
		681	conditions. You can set this environment variable to make AnyEvent more
		682	talkative.
		683
		684	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		685	conditions, such as not being able to load the event model specified by
		686	C<PERL_ANYEVENT_MODEL>.
		687
		688	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		689	model it chooses.
		690
		691	=item C<PERL_ANYEVENT_MODEL>
		692
		693	This can be used to specify the event model to be used by AnyEvent, before
		694	autodetection and -probing kicks in. It must be a string consisting
		695	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		696	and the resulting module name is loaded and if the load was successful,
		697	used as event model. If it fails to load AnyEvent will proceed with
		698	autodetection and -probing.
		699
		700	This functionality might change in future versions.
		701
		702	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		703	could start your program like this:
		704
		705	PERL_ANYEVENT_MODEL=Perl perl ...
		706
		707	=back
644		708
645	=head1 EXAMPLE PROGRAM	709	=head1 EXAMPLE PROGRAM
646		710
647	The following program uses an IO watcher to read data from STDIN, a timer	711	The following program uses an IO watcher to read data from STDIN, a timer
648	to display a message once per second, and a condition variable to quit the	712	to display a message once per second, and a condition variable to quit the
…		…
796	$quit->broadcast;	860	$quit->broadcast;
797	});	861	});
798		862
799	$quit->wait;	863	$quit->wait;
800		864
		865
		866	=head1 BENCHMARK
		867
		868	To give you an idea of the performance and overheads that AnyEvent adds
		869	over the event loops themselves (and to give you an impression of the
		870	speed of various event loops), here is a benchmark of various supported
		871	event models natively and with anyevent. The benchmark creates a lot of
		872	timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to
		873	become writable, which it is), lets them fire exactly once and destroys
		874	them again.
		875
		876	=head2 Explanation of the columns
		877
		878	I<watcher> is the number of event watchers created/destroyed. Since
		879	different event models feature vastly different performances, each event
		880	loop was given a number of watchers so that overall runtime is acceptable
		881	and similar between tested event loop (and keep them from crashing): Glib
		882	would probably take thousands of years if asked to process the same number
		883	of watchers as EV in this benchmark.
		884
		885	I<bytes> is the number of bytes (as measured by the resident set size,
		886	RSS) consumed by each watcher. This method of measuring captures both C
		887	and Perl-based overheads.
		888
		889	I<create> is the time, in microseconds (millionths of seconds), that it
		890	takes to create a single watcher. The callback is a closure shared between
		891	all watchers, to avoid adding memory overhead. That means closure creation
		892	and memory usage is not included in the figures.
		893
		894	I<invoke> is the time, in microseconds, used to invoke a simple
		895	callback. The callback simply counts down a Perl variable and after it was
		896	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		897	signal the end of this phase.
		898
		899	I<destroy> is the time, in microseconds, that it takes to destroy a single
		900	watcher.
		901
		902	=head2 Results
		903
		904	name watcher bytes create invoke destroy comment
		905	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		906	EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers
		907	CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal
		908	Perl/Any 16000 654 4.64 1.22 0.77 pure perl implementation
		909	Event/Event 16000 523 28.05 21.38 0.86 Event native interface
		910	Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers
		911	Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour
		912	Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers
		913	POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event
		914	POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select
		915
		916	=head2 Discussion
		917
		918	The benchmark does I<not> measure scalability of the event loop very
		919	well. For example, a select-based event loop (such as the pure perl one)
		920	can never compete with an event loop that uses epoll when the number of
		921	file descriptors grows high. In this benchmark, only a single filehandle
		922	is used (although some of the AnyEvent adaptors dup() its file descriptor
		923	to worka round bugs).
		924
		925	C<EV> is the sole leader regarding speed and memory use, which are both
		926	maximal/minimal, respectively. Even when going through AnyEvent, there is
		927	only one event loop that uses less memory (the C<Event> module natively), and
		928	no faster event model, not event C<Event> natively.
		929
		930	The pure perl implementation is hit in a few sweet spots (both the
		931	zero timeout and the use of a single fd hit optimisations in the perl
		932	interpreter and the backend itself). Nevertheless tis shows that it
		933	adds very little overhead in itself. Like any select-based backend its
		934	performance becomes really bad with lots of file descriptors, of course,
		935	but this was not subjetc of this benchmark.
		936
		937	The C<Event> module has a relatively high setup and callback invocation cost,
		938	but overall scores on the third place.
		939
		940	C<Glib>'s memory usage is quite a bit bit higher, but it features a
		941	faster callback invocation and overall ends up in the same class as
		942	C<Event>. However, Glib scales extremely badly, doubling the number of
		943	watchers increases the processing time by more than a factor of four,
		944	making it completely unusable when using larger numbers of watchers
		945	(note that only a single file descriptor was used in the benchmark, so
		946	inefficiencies of C<poll> do not account for this).
		947
		948	The C<Tk> adaptor works relatively well. The fact that it crashes with
		949	more than 2000 watchers is a big setback, however, as correctness takes
		950	precedence over speed. Nevertheless, its performance is surprising, as the
		951	file descriptor is dup()ed for each watcher. This shows that the dup()
		952	employed by some adaptors is not a big performance issue (it does incur a
		953	hidden memory cost inside the kernel, though).
		954
		955	C<POE>, regardless of underlying event loop (wether using its pure perl
		956	select-based backend or the Event module) shows abysmal performance and
		957	memory usage: Watchers use almost 30 times as much memory as EV watchers,
		958	and 10 times as much memory as both Event or EV via AnyEvent. Watcher
		959	invocation is almost 700 times slower than with AnyEvent's pure perl
		960	implementation. The design of the POE adaptor class in AnyEvent can not
		961	really account for this, as session creation overhead is small compared
		962	to execution of the state machine, which is coded pretty optimally within
		963	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		964
		965	=head2 Summary
		966
		967	Using EV through AnyEvent is faster than any other event loop, but most
		968	event loops have acceptable performance with or without AnyEvent.
		969
		970	The overhead AnyEvent adds is usually much smaller than the overhead of
		971	the actual event loop, only with extremely fast event loops such as the EV
		972	adds AnyEvent significant overhead.
		973
		974	And you should simply avoid POE like the plague if you want performance or
		975	reasonable memory usage.
		976
		977
		978	=head1 FORK
		979
		980	Most event libraries are not fork-safe. The ones who are usually are
		981	because they are so inefficient. Only L<EV> is fully fork-aware.
		982
		983	If you have to fork, you must either do so I<before> creating your first
		984	watcher OR you must not use AnyEvent at all in the child.
		985
		986
		987	=head1 SECURITY CONSIDERATIONS
		988
		989	AnyEvent can be forced to load any event model via
		990	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		991	execute arbitrary code or directly gain access, it can easily be used to
		992	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		993	will not be active when the program uses a different event model than
		994	specified in the variable.
		995
		996	You can make AnyEvent completely ignore this variable by deleting it
		997	before the first watcher gets created, e.g. with a C<BEGIN> block:
		998
		999	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1000
		1001	use AnyEvent;
		1002
		1003
801	=head1 SEE ALSO	1004	=head1 SEE ALSO
802		1005
803	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1006	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>.	1007	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
		1008	L<Event::Lib>, L<Qt>, L<POE>.
805		1009
806	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1010	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
		1011	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		1012	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
807	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>,	1013	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
808	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>.
809		1014
810	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1015	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
		1016
811		1017
812	=head1 AUTHOR	1018	=head1 AUTHOR
813		1019
814	Marc Lehmann <schmorp@schmorp.de>	1020	Marc Lehmann <schmorp@schmorp.de>
815	http://home.schmorp.de/	1021	http://home.schmorp.de/

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.54 by root, Tue Apr 22 05:12:19 2008 UTC vs. Revision 1.73 by root, Fri Apr 25 07:47:12 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.54 by root, Tue Apr 22 05:12:19 2008 UTC vs.
Revision 1.73 by root, Fri Apr 25 07:47:12 2008 UTC