[ViewVC] Diff of: cvs/AnyEvent-Fork/Fork.pm

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.42 by root, Mon Apr 8 05:44:23 2013 UTC vs.
Revision 1.55 by root, Fri Apr 26 23:24:30 2013 UTC

…		…
34	This module only creates processes and lets you pass file handles and	34	This module only creates processes and lets you pass file handles and
35	strings to it, and run perl code. It does not implement any kind of RPC -	35	strings to it, and run perl code. It does not implement any kind of RPC -
36	there is no back channel from the process back to you, and there is no RPC	36	there is no back channel from the process back to you, and there is no RPC
37	or message passing going on.	37	or message passing going on.
38		38
39	If you need some form of RPC, you can either implement it yourself	39	If you need some form of RPC, you could use the L<AnyEvent::Fork::RPC>
40	in whatever way you like, use some message-passing module such	40	companion module, which adds simple RPC/job queueing to a process created
41	as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use	41	by this module.
42	L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages,	42
43	and so on.	43	And if you need some automatic process pool management on top of
		44	L<AnyEvent::Fork::RPC>, you can look at the L<AnyEvent::Fork::Pool>
		45	companion module.
		46
		47	Or you can implement it yourself in whatever way you like: use some
		48	message-passing module such as L<AnyEvent::MP>, some pipe such as
		49	L<AnyEvent::ZeroMQ>, use L<AnyEvent::Handle> on both sides to send
		50	e.g. JSON or Storable messages, and so on.
44		51
45	=head2 COMPARISON TO OTHER MODULES	52	=head2 COMPARISON TO OTHER MODULES
46		53
47	There is an abundance of modules on CPAN that do "something fork", such as	54	There is an abundance of modules on CPAN that do "something fork", such as
48	L<Parallel::ForkManager>, L<AnyEvent::ForkManager>, L<AnyEvent::Worker>	55	L<Parallel::ForkManager>, L<AnyEvent::ForkManager>, L<AnyEvent::Worker>
…		…
221	}	228	}
222	}	229	}
223		230
224	=head2 use AnyEvent::Fork as a faster fork+exec	231	=head2 use AnyEvent::Fork as a faster fork+exec
225		232
226	This runs C</bin/echo hi>, with stdandard output redirected to /tmp/log	233	This runs C</bin/echo hi>, with standard output redirected to F</tmp/log>
227	and standard error redirected to the communications socket. It is usually	234	and standard error redirected to the communications socket. It is usually
228	faster than fork+exec, but still lets you prepare the environment.	235	faster than fork+exec, but still lets you prepare the environment.
229		236
230	open my $output, ">/tmp/log" or die "$!";	237	open my $output, ">/tmp/log" or die "$!";
231		238
…		…
247	->send_arg ("/bin/echo", "hi")	254	->send_arg ("/bin/echo", "hi")
248	->run ("run", my $cv = AE::cv);	255	->run ("run", my $cv = AE::cv);
249		256
250	my $stderr = $cv->recv;	257	my $stderr = $cv->recv;
251		258
		259	=head2 For stingy users: put the worker code into a C<DATA> section.
		260
		261	When you want to be stingy with files, you cna put your code into the
		262	C<DATA> section of your module (or program):
		263
		264	use AnyEvent::Fork;
		265
		266	AnyEvent::Fork
		267	->new
		268	->eval (do { local $/; <DATA> })
		269	->run ("doit", sub { ... });
		270
		271	__DATA__
		272
		273	sub doit {
		274	... do something!
		275	}
		276
		277	=head2 For stingy standalone programs: do not rely on external files at
		278	all.
		279
		280	For single-file scripts it can be inconvenient to rely on external
		281	files - even when using < C<DATA> section, you still need to C<exec>
		282	an external perl interpreter, which might not be available when using
		283	L<App::Staticperl>, L<Urlader> or L<PAR::Packer> for example.
		284
		285	Two modules help here - L<AnyEvent::Fork::Early> forks a template process
		286	for all further calls to C<new_exec>, and L<AnyEvent::Fork::Template>
		287	forks the main program as a template process.
		288
		289	Here is how your main program should look like:
		290
		291	#! perl
		292
		293	# optional, as the very first thing.
		294	# in case modules want to create their own processes.
		295	use AnyEvent::Fork::Early;
		296
		297	# next, load all modules you need in your template process
		298	use Example::My::Module
		299	use Example::Whatever;
		300
		301	# next, put your run function definition and anything else you
		302	# need, but do not use code outside of BEGIN blocks.
		303	sub worker_run {
		304	my ($fh, @args) = @_;
		305	...
		306	}
		307
		308	# now preserve everything so far as AnyEvent::Fork object
		309	# in §TEMPLATE.
		310	use AnyEvent::Fork::Template;
		311
		312	# do not put code outside of BEGIN blocks until here
		313
		314	# now use the $TEMPLATE process in any way you like
		315
		316	# for example: create 10 worker processes
		317	my @worker;
		318	my $cv = AE::cv;
		319	for (1..10) {
		320	$cv->begin;
		321	$TEMPLATE->fork->send_arg ($_)->run ("worker_run", sub {
		322	push @worker, shift;
		323	$cv->end;
		324	});
		325	}
		326	$cv->recv;
		327
252	=head1 CONCEPTS	328	=head1 CONCEPTS
253		329
254	This module can create new processes either by executing a new perl	330	This module can create new processes either by executing a new perl
255	process, or by forking from an existing "template" process.	331	process, or by forking from an existing "template" process.
		332
		333	All these processes are called "child processes" (whether they are direct
		334	children or not), while the process that manages them is called the
		335	"parent process".
256		336
257	Each such process comes with its own file handle that can be used to	337	Each such process comes with its own file handle that can be used to
258	communicate with it (it's actually a socket - one end in the new process,	338	communicate with it (it's actually a socket - one end in the new process,
259	one end in the main process), and among the things you can do in it are	339	one end in the main process), and among the things you can do in it are
260	load modules, fork new processes, send file handles to it, and execute	340	load modules, fork new processes, send file handles to it, and execute
…		…
370	use AnyEvent;	450	use AnyEvent;
371	use AnyEvent::Util ();	451	use AnyEvent::Util ();
372		452
373	use IO::FDPass;	453	use IO::FDPass;
374		454
375	our $VERSION = 0.6;	455	our $VERSION = '1.0';
376
377	=over 4
378
379	=back
380
381	=cut
382		456
383	# the early fork template process	457	# the early fork template process
384	our $EARLY;	458	our $EARLY;
385		459
386	# the empty template process	460	# the empty template process
…		…
434	# send string	508	# send string
435	my $len = syswrite $self->[FH], $self->[QUEUE][0];	509	my $len = syswrite $self->[FH], $self->[QUEUE][0];
436		510
437	unless ($len) {	511	unless ($len) {
438	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	512	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
439	undef $self->[3];	513	undef $self->[WW];
440	die "AnyEvent::Fork: command write failure: $!";	514	die "AnyEvent::Fork: command write failure: $!";
441	}	515	}
442		516
443	substr $self->[QUEUE][0], 0, $len, "";	517	substr $self->[QUEUE][0], 0, $len, "";
444	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];	518	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
…		…
447		521
448	# everything written	522	# everything written
449	undef $self->[WW];	523	undef $self->[WW];
450		524
451	# invoke run callback, if any	525	# invoke run callback, if any
		526	if ($self->[CB]) {
452	$self->[CB]->($self->[FH]) if $self->[CB];	527	$self->[CB]->($self->[FH]);
		528	@$self = ();
		529	}
453	};	530	};
454		531
455	() # make sure we don't leak the watcher	532	() # make sure we don't leak the watcher
456	}	533	}
457		534
…		…
598	$_[0][PID]	675	$_[0][PID]
599	}	676	}
600		677
601	=item $proc = $proc->eval ($perlcode, @args)	678	=item $proc = $proc->eval ($perlcode, @args)
602		679
603	Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to	680	Evaluates the given C<$perlcode> as ... Perl code, while setting C<@_> to
604	the strings specified by C<@args>, in the "main" package.	681	the strings specified by C<@args>, in the "main" package.
605		682
606	This call is meant to do any custom initialisation that might be required	683	This call is meant to do any custom initialisation that might be required
607	(for example, the C<require> method uses it). It's not supposed to be used	684	(for example, the C<require> method uses it). It's not supposed to be used
608	to completely take over the process, use C<run> for that.	685	to completely take over the process, use C<run> for that.
…		…
772	$self->_cmd (r => $func);	849	$self->_cmd (r => $func);
773	}	850	}
774		851
775	=back	852	=back
776		853
		854	=head2 EXPERIMENTAL METHODS
		855
		856	These methods might go away completely or change behaviour, at any time.
		857
		858	=over 4
		859
		860	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		861
		862	Flushes all commands out to the process and then calls the callback with
		863	the communications socket.
		864
		865	The process object becomes unusable on return from this function - any
		866	further method calls result in undefined behaviour.
		867
		868	The point of this method is to give you a file handle thta you cna pass
		869	to another process. In that other process, you can call C<new_from_fh
		870	AnyEvent::Fork> to create a new C<AnyEvent::Fork> object from it, thereby
		871	effectively passing a fork object to another process.
		872
		873	=cut
		874
		875	sub to_fh {
		876	my ($self, $cb) = @_;
		877
		878	$self->[CB] = $cb;
		879
		880	unless ($self->[WW]) {
		881	$self->[CB]->($self->[FH]);
		882	@$self = ();
		883	}
		884	}
		885
		886	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		887
		888	Takes a file handle originally rceeived by the C<to_fh> method and creates
		889	a new C<AnyEvent:Fork> object. The child process itself will not change in
		890	any way, i.e. it will keep all the modifications done to it before calling
		891	C<to_fh>.
		892
		893	The new object is very much like the original object, except that the
		894	C<pid> method will return C<undef> even if the process is a direct child.
		895
		896	=cut
		897
		898	sub new_from_fh {
		899	my ($class, $fh) = @_;
		900
		901	$class->_new ($fh)
		902	}
		903
		904	=back
		905
777	=head1 PERFORMANCE	906	=head1 PERFORMANCE
778		907
779	Now for some unscientific benchmark numbers (all done on an amd64	908	Now for some unscientific benchmark numbers (all done on an amd64
780	GNU/Linux box). These are intended to give you an idea of the relative	909	GNU/Linux box). These are intended to give you an idea of the relative
781	performance you can expect, they are not meant to be absolute performance	910	performance you can expect, they are not meant to be absolute performance
…		…
787		916
788	2079 new processes per second, using manual socketpair + fork	917	2079 new processes per second, using manual socketpair + fork
789		918
790	Then I did the same thing, but instead of calling fork, I called	919	Then I did the same thing, but instead of calling fork, I called
791	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the	920	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the
792	socket form the child to close on exit. This does the same thing as manual	921	socket from the child to close on exit. This does the same thing as manual
793	socket pair + fork, except that what is forked is the template process	922	socket pair + fork, except that what is forked is the template process
794	(2440kB), and the socket needs to be passed to the server at the other end	923	(2440kB), and the socket needs to be passed to the server at the other end
795	of the socket first.	924	of the socket first.
796		925
797	2307 new processes per second, using AnyEvent::Fork->new	926	2307 new processes per second, using AnyEvent::Fork->new
…		…
804	So how can C<< AnyEvent->new >> be faster than a standard fork, even	933	So how can C<< AnyEvent->new >> be faster than a standard fork, even
805	though it uses the same operations, but adds a lot of overhead?	934	though it uses the same operations, but adds a lot of overhead?
806		935
807	The difference is simply the process size: forking the 5MB process takes	936	The difference is simply the process size: forking the 5MB process takes
808	so much longer than forking the 2.5MB template process that the extra	937	so much longer than forking the 2.5MB template process that the extra
809	overhead introduced is canceled out.	938	overhead is canceled out.
810		939
811	If the benchmark process grows, the normal fork becomes even slower:	940	If the benchmark process grows, the normal fork becomes even slower:
812		941
813	1340 new processes, manual fork of a 20MB process	942	1340 new processes, manual fork of a 20MB process
814	731 new processes, manual fork of a 200MB process	943	731 new processes, manual fork of a 200MB process
…		…
874	initialising them, for example, by calling C<init Gtk2> manually.	1003	initialising them, for example, by calling C<init Gtk2> manually.
875		1004
876	=item exiting calls object destructors	1005	=item exiting calls object destructors
877		1006
878	This only applies to users of L<AnyEvent::Fork:Early> and	1007	This only applies to users of L<AnyEvent::Fork:Early> and
879	L<AnyEvent::Fork::Template>, or when initialiasing code creates objects	1008	L<AnyEvent::Fork::Template>, or when initialising code creates objects
880	that reference external resources.	1009	that reference external resources.
881		1010
882	When a process created by AnyEvent::Fork exits, it might do so by calling	1011	When a process created by AnyEvent::Fork exits, it might do so by calling
883	exit, or simply letting perl reach the end of the program. At which point	1012	exit, or simply letting perl reach the end of the program. At which point
884	Perl runs all destructors.	1013	Perl runs all destructors.
…		…
904	to make it so, mostly due to the bloody broken perl that nobody seems to	1033	to make it so, mostly due to the bloody broken perl that nobody seems to
905	care about. The fork emulation is a bad joke - I have yet to see something	1034	care about. The fork emulation is a bad joke - I have yet to see something
906	useful that you can do with it without running into memory corruption	1035	useful that you can do with it without running into memory corruption
907	issues or other braindamage. Hrrrr.	1036	issues or other braindamage. Hrrrr.
908		1037
		1038	Since fork is endlessly broken on win32 perls (it doesn't even remotely
		1039	work within it's documented limits) and quite obviously it's not getting
		1040	improved any time soon, the best way to proceed on windows would be to
		1041	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1042
909	Cygwin perl is not supported at the moment due to some hilarious	1043	Cygwin perl is not supported at the moment due to some hilarious
910	shortcomings of its API - see L<IO::FDPoll> for more details.	1044	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1045	use C<send_fh> and always use C<new_exec> to create processes, it should
		1046	work though.
911		1047
912	=head1 SEE ALSO	1048	=head1 SEE ALSO
913		1049
914	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),	1050	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1051	(part of this distribution).
		1052
915	L<AnyEvent::Fork::Template> (to create a process by forking the main	1053	L<AnyEvent::Fork::Template>, to create a process by forking the main
916	program at a convenient time).	1054	program at a convenient time (part of this distribution).
917		1055
918	=head1 AUTHOR	1056	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1057
		1058	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1059
		1060	=head1 AUTHOR AND CONTACT INFORMATION
919		1061
920	Marc Lehmann <schmorp@schmorp.de>	1062	Marc Lehmann <schmorp@schmorp.de>
921	http://home.schmorp.de/	1063	http://software.schmorp.de/pkg/AnyEvent-Fork
922		1064
923	=cut	1065	=cut
924		1066
925	1	1067	1
926		1068

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.42 by root, Mon Apr 8 05:44:23 2013 UTC vs. Revision 1.55 by root, Fri Apr 26 23:24:30 2013 UTC

Diff Legend

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.42 by root, Mon Apr 8 05:44:23 2013 UTC vs.
Revision 1.55 by root, Fri Apr 26 23:24:30 2013 UTC