[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 1.77 by root, Fri Apr 25 09:00:37 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	Rewriting the benchmark to use many different sockets instead of using
		877	the same filehandle for all io watchers results in a much longer runtime
		878	(socket creation is expensive), but qualitatively the same figures, so it
		879	was not used.
		880
		881	=head2 Explanation of the columns
		882
		883	I<watcher> is the number of event watchers created/destroyed. Since
		884	different event models feature vastly different performances, each event
		885	loop was given a number of watchers so that overall runtime is acceptable
		886	and similar between tested event loop (and keep them from crashing): Glib
		887	would probably take thousands of years if asked to process the same number
		888	of watchers as EV in this benchmark.
		889
		890	I<bytes> is the number of bytes (as measured by the resident set size,
		891	RSS) consumed by each watcher. This method of measuring captures both C
		892	and Perl-based overheads.
		893
		894	I<create> is the time, in microseconds (millionths of seconds), that it
		895	takes to create a single watcher. The callback is a closure shared between
		896	all watchers, to avoid adding memory overhead. That means closure creation
		897	and memory usage is not included in the figures.
		898
		899	I<invoke> is the time, in microseconds, used to invoke a simple
		900	callback. The callback simply counts down a Perl variable and after it was
		901	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		902	signal the end of this phase.
		903
		904	I<destroy> is the time, in microseconds, that it takes to destroy a single
		905	watcher.
		906
		907	=head2 Results
		908
		909	name watchers bytes create invoke destroy comment
		910	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		911	EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers
		912	CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal
		913	Perl/Any 100000 513 4.91 0.92 1.15 pure perl implementation
		914	Event/Event 16000 523 28.05 21.38 0.86 Event native interface
		915	Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers
		916	Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour
		917	Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers
		918	POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event
		919	POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select
		920
		921	=head2 Discussion
		922
		923	The benchmark does I<not> measure scalability of the event loop very
		924	well. For example, a select-based event loop (such as the pure perl one)
		925	can never compete with an event loop that uses epoll when the number of
		926	file descriptors grows high. In this benchmark, only a single filehandle
		927	is used (although some of the AnyEvent adaptors dup() its file descriptor
		928	to worka round bugs).
		929
		930	C<EV> is the sole leader regarding speed and memory use, which are both
		931	maximal/minimal, respectively. Even when going through AnyEvent, there are
		932	only two event loops that use slightly less memory (the C<Event> module
		933	natively and the pure perl backend), and no faster event models, not even
		934	C<Event> natively.
		935
		936	The pure perl implementation is hit in a few sweet spots (both the
		937	zero timeout and the use of a single fd hit optimisations in the perl
		938	interpreter and the backend itself, and all watchers become ready at the
		939	same time). Nevertheless this shows that it adds very little overhead in
		940	itself. Like any select-based backend its performance becomes really bad
		941	with lots of file descriptors (and few of them active), of course, but
		942	this was not subject of this benchmark.
		943
		944	The C<Event> module has a relatively high setup and callback invocation cost,
		945	but overall scores on the third place.
		946
		947	C<Glib>'s memory usage is quite a bit bit higher, but it features a
		948	faster callback invocation and overall ends up in the same class as
		949	C<Event>. However, Glib scales extremely badly, doubling the number of
		950	watchers increases the processing time by more than a factor of four,
		951	making it completely unusable when using larger numbers of watchers
		952	(note that only a single file descriptor was used in the benchmark, so
		953	inefficiencies of C<poll> do not account for this).
		954
		955	The C<Tk> adaptor works relatively well. The fact that it crashes with
		956	more than 2000 watchers is a big setback, however, as correctness takes
		957	precedence over speed. Nevertheless, its performance is surprising, as the
		958	file descriptor is dup()ed for each watcher. This shows that the dup()
		959	employed by some adaptors is not a big performance issue (it does incur a
		960	hidden memory cost inside the kernel, though, that is not reflected in the
		961	figures above).
		962
		963	C<POE>, regardless of underlying event loop (wether using its pure perl
		964	select-based backend or the Event module) shows abysmal performance and
		965	memory usage: Watchers use almost 30 times as much memory as EV watchers,
		966	and 10 times as much memory as both Event or EV via AnyEvent. Watcher
		967	invocation is almost 700 times slower than with AnyEvent's pure perl
		968	implementation. The design of the POE adaptor class in AnyEvent can not
		969	really account for this, as session creation overhead is small compared
		970	to execution of the state machine, which is coded pretty optimally within
		971	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		972
		973	=head2 Summary
		974
		975	Using EV through AnyEvent is faster than any other event loop, but most
		976	event loops have acceptable performance with or without AnyEvent.
		977
		978	The overhead AnyEvent adds is usually much smaller than the overhead of
		979	the actual event loop, only with extremely fast event loops such as the EV
		980	adds AnyEvent significant overhead.
		981
		982	And you should simply avoid POE like the plague if you want performance or
		983	reasonable memory usage.
		984
		985
		986	=head1 FORK
		987
		988	Most event libraries are not fork-safe. The ones who are usually are
		989	because they are so inefficient. Only L<EV> is fully fork-aware.
		990
		991	If you have to fork, you must either do so I<before> creating your first
		992	watcher OR you must not use AnyEvent at all in the child.
		993
		994
		995	=head1 SECURITY CONSIDERATIONS
		996
		997	AnyEvent can be forced to load any event model via
		998	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		999	execute arbitrary code or directly gain access, it can easily be used to
		1000	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		1001	will not be active when the program uses a different event model than
		1002	specified in the variable.
		1003
		1004	You can make AnyEvent completely ignore this variable by deleting it
		1005	before the first watcher gets created, e.g. with a C<BEGIN> block:
		1006
		1007	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1008
		1009	use AnyEvent;
		1010
		1011
801	=head1 SEE ALSO	1012	=head1 SEE ALSO
802		1013
803	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1014	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>.	1015	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
		1016	L<Event::Lib>, L<Qt>, L<POE>.
805		1017
806	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1018	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
		1019	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		1020	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
807	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>,	1021	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
808	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>.
809		1022
810	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1023	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
		1024
811		1025
812	=head1 AUTHOR	1026	=head1 AUTHOR
813		1027
814	Marc Lehmann <schmorp@schmorp.de>	1028	Marc Lehmann <schmorp@schmorp.de>
815	http://home.schmorp.de/	1029	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 1.77 by root, Fri Apr 25 09:00:37 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 1.77 by root, Fri Apr 25 09:00:37 2008 UTC