[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 1.53 by root, Fri Apr 26 15:44:44 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 ADVANCED METHODS
		855
		856	=over 4
		857
		858	=item new_from_stdio AnyEvent::Fork $fh
		859
		860	Assume that you have a perl interpreter running (without any special
		861	options or a program) somewhere and it has it's STDIN and STDOUT connected
		862	to the C<$fh> somehow. I.e. exactly the state perl is in when you start it
		863	without any arguments:
		864
		865	perl
		866
		867	Then you can create an C<AnyEvent::Fork> object out of this perl
		868	interpreter with this constructor.
		869
		870	When the usefulness of this isn't immediately clear, imagine you manage to
		871	run a perl interpreter remotely (F<ssh remotemachine perl>), then you can
		872	manage it mostly like a local C<AnyEvent::Fork> child.
		873
		874	This works without any module support, i.e. the remote F<perl> does not
		875	need to have any special modules installed.
		876
		877	There are a number of limitations though: C<send_fh> will only work if the
		878	L<IO::FDPass> module is loadable by the remote perl and the two processes
		879	are connected in a way that let's L<IO::FDPass> do it's work.
		880
		881	This will therefore not work over a network conenction. From this follows
		882	that C<fork> will also not work under these circumstances, as it relies on
		883	C<send_fh> internally.
		884
		885	=cut
		886
		887	sub new_from_stdio {
		888	my ($class, $fh) = @_;
		889
		890	my $self = $class->_new ($fh);
		891
		892	# send startup code
		893	push @{ $self->[QUEUE] },
		894	(do "AnyEvent/Fork/serve.pl")
		895	. <<'EOF';
		896	{
		897	open my $fh, "+<&0"
		898	or die "AnyEvent::Fork::Serve::stdio: unable to open communications socket: $!\n";
		899	open STDIN , ">&2";
		900	open STDOUT, ">&2";
		901
		902	$OWNER = "another process";
		903	$0 = "AnyEvent::Fork/stdio of $OWNER";
		904
		905	@_ = $fh;
		906	}
		907
		908	&serve;
		909	__END__
		910	EOF
		911
		912	# the data is only sent when the user requests additional things, which
		913	# is likely early enough for our purposes.
		914
		915	$self
		916	}
		917
		918	=back
		919
		920	=head2 EXPERIMENTAL METHODS
		921
		922	These methods might go away completely or change behaviour, a any time.
		923
		924	=over 4
		925
		926	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		927
		928	Flushes all commands out to the process and then calls the callback with
		929	the communications socket.
		930
		931	The process object becomes unusable on return from this function - any
		932	further method calls result in undefined behaviour.
		933
		934	The point of this method is to give you a file handle thta you cna pass
		935	to another process. In that other process, you can call C<new_from_fh
		936	AnyEvent::Fork> to create a new C<AnyEvent::Fork> object from it, thereby
		937	effectively passing a fork object to another process.
		938
		939	=cut
		940
		941	sub to_fh {
		942	my ($self, $cb) = @_;
		943
		944	$self->[CB] = $cb;
		945
		946	unless ($self->[WW]) {
		947	$self->[CB]->($self->[FH]);
		948	@$self = ();
		949	}
		950	}
		951
		952	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		953
		954	Takes a file handle originally rceeived by the C<to_fh> method and creates
		955	a new C<AnyEvent:Fork> object. The child process itself will not change in
		956	any way, i.e. it will keep all the modifications done to it before calling
		957	C<to_fh>.
		958
		959	The new object is very much like the original object, except that the
		960	C<pid> method will return C<undef> even if the process is a direct child.
		961
		962	=cut
		963
		964	sub new_from_fh {
		965	my ($class, $fh) = @_;
		966
		967	$class->_new ($fh)
		968	}
		969
		970	=back
		971
777	=head1 PERFORMANCE	972	=head1 PERFORMANCE
778		973
779	Now for some unscientific benchmark numbers (all done on an amd64	974	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	975	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	976	performance you can expect, they are not meant to be absolute performance
…		…
787		982
788	2079 new processes per second, using manual socketpair + fork	983	2079 new processes per second, using manual socketpair + fork
789		984
790	Then I did the same thing, but instead of calling fork, I called	985	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	986	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	987	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	988	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	989	(2440kB), and the socket needs to be passed to the server at the other end
795	of the socket first.	990	of the socket first.
796		991
797	2307 new processes per second, using AnyEvent::Fork->new	992	2307 new processes per second, using AnyEvent::Fork->new
…		…
804	So how can C<< AnyEvent->new >> be faster than a standard fork, even	999	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?	1000	though it uses the same operations, but adds a lot of overhead?
806		1001
807	The difference is simply the process size: forking the 5MB process takes	1002	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	1003	so much longer than forking the 2.5MB template process that the extra
809	overhead introduced is canceled out.	1004	overhead is canceled out.
810		1005
811	If the benchmark process grows, the normal fork becomes even slower:	1006	If the benchmark process grows, the normal fork becomes even slower:
812		1007
813	1340 new processes, manual fork of a 20MB process	1008	1340 new processes, manual fork of a 20MB process
814	731 new processes, manual fork of a 200MB process	1009	731 new processes, manual fork of a 200MB process
…		…
874	initialising them, for example, by calling C<init Gtk2> manually.	1069	initialising them, for example, by calling C<init Gtk2> manually.
875		1070
876	=item exiting calls object destructors	1071	=item exiting calls object destructors
877		1072
878	This only applies to users of L<AnyEvent::Fork:Early> and	1073	This only applies to users of L<AnyEvent::Fork:Early> and
879	L<AnyEvent::Fork::Template>, or when initialiasing code creates objects	1074	L<AnyEvent::Fork::Template>, or when initialising code creates objects
880	that reference external resources.	1075	that reference external resources.
881		1076
882	When a process created by AnyEvent::Fork exits, it might do so by calling	1077	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	1078	exit, or simply letting perl reach the end of the program. At which point
884	Perl runs all destructors.	1079	Perl runs all destructors.
…		…
904	to make it so, mostly due to the bloody broken perl that nobody seems to	1099	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	1100	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	1101	useful that you can do with it without running into memory corruption
907	issues or other braindamage. Hrrrr.	1102	issues or other braindamage. Hrrrr.
908		1103
		1104	Since fork is endlessly broken on win32 perls (it doesn't even remotely
		1105	work within it's documented limits) and quite obviously it's not getting
		1106	improved any time soon, the best way to proceed on windows would be to
		1107	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1108
909	Cygwin perl is not supported at the moment due to some hilarious	1109	Cygwin perl is not supported at the moment due to some hilarious
910	shortcomings of its API - see L<IO::FDPoll> for more details.	1110	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1111	use C<send_fh> and always use C<new_exec> to create processes, it should
		1112	work though.
911		1113
912	=head1 SEE ALSO	1114	=head1 SEE ALSO
913		1115
914	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),	1116	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1117	(part of this distribution).
		1118
915	L<AnyEvent::Fork::Template> (to create a process by forking the main	1119	L<AnyEvent::Fork::Template>, to create a process by forking the main
916	program at a convenient time).	1120	program at a convenient time (part of this distribution).
917		1121
918	=head1 AUTHOR	1122	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1123
		1124	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1125
		1126	=head1 AUTHOR AND CONTACT INFORMATION
919		1127
920	Marc Lehmann <schmorp@schmorp.de>	1128	Marc Lehmann <schmorp@schmorp.de>
921	http://home.schmorp.de/	1129	http://software.schmorp.de/pkg/AnyEvent-Fork
922		1130
923	=cut	1131	=cut
924		1132
925	1	1133	1
926		1134

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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 1.53 by root, Fri Apr 26 15:44:44 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 1.53 by root, Fri Apr 26 15:44:44 2013 UTC