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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.41 by root, Mon Apr 8 03:20:53 2013 UTC vs.
Revision 1.54 by root, Fri Apr 26 17:24:05 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
387	our $TEMPLATE;	461	our $TEMPLATE;
		462
		463	sub QUEUE() { 0 }
		464	sub FH() { 1 }
		465	sub WW() { 2 }
		466	sub PID() { 3 }
		467	sub CB() { 4 }
		468
		469	sub _new {
		470	my ($self, $fh, $pid) = @_;
		471
		472	AnyEvent::Util::fh_nonblocking $fh, 1;
		473
		474	$self = bless [
		475	[], # write queue - strings or fd's
		476	$fh,
		477	undef, # AE watcher
		478	$pid,
		479	], $self;
		480
		481	$self
		482	}
388		483
389	sub _cmd {	484	sub _cmd {
390	my $self = shift;	485	my $self = shift;
391		486
392	# ideally, we would want to use "a (w/a)*" as format string, but perl	487	# ideally, we would want to use "a (w/a)*" as format string, but perl
393	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack	488	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack
394	# it.	489	# it.
395	push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1];	490	push @{ $self->[QUEUE] }, pack "a N/a*", $_[0], $_[1];
396		491
397	$self->[3] \|\|= AE::io $self->[1], 1, sub {	492	$self->[WW] \|\|= AE::io $self->[FH], 1, sub {
398	do {	493	do {
399	# send the next "thing" in the queue - either a reference to an fh,	494	# send the next "thing" in the queue - either a reference to an fh,
400	# or a plain string.	495	# or a plain string.
401		496
402	if (ref $self->[2][0]) {	497	if (ref $self->[QUEUE][0]) {
403	# send fh	498	# send fh
404	unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) {	499	unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) {
405	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	500	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
406	undef $self->[3];	501	undef $self->[WW];
407	die "AnyEvent::Fork: file descriptor send failure: $!";	502	die "AnyEvent::Fork: file descriptor send failure: $!";
408	}	503	}
409		504
410	shift @{ $self->[2] };	505	shift @{ $self->[QUEUE] };
411		506
412	} else {	507	} else {
413	# send string	508	# send string
414	my $len = syswrite $self->[1], $self->[2][0];	509	my $len = syswrite $self->[FH], $self->[QUEUE][0];
415		510
416	unless ($len) {	511	unless ($len) {
417	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	512	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
418	undef $self->[3];	513	undef $self->[WW];
419	die "AnyEvent::Fork: command write failure: $!";	514	die "AnyEvent::Fork: command write failure: $!";
420	}	515	}
421		516
422	substr $self->[2][0], 0, $len, "";	517	substr $self->[QUEUE][0], 0, $len, "";
423	shift @{ $self->[2] } unless length $self->[2][0];	518	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
424	}	519	}
425	} while @{ $self->[2] };	520	} while @{ $self->[QUEUE] };
426		521
427	# everything written	522	# everything written
428	undef $self->[3];	523	undef $self->[WW];
429		524
430	# invoke run callback, if any	525	# invoke run callback, if any
431	$self->[4]->($self->[1]) if $self->[4];	526	if ($self->[CB]) {
		527	$self->[CB]->($self->[FH]);
		528	@$self = ();
		529	}
432	};	530	};
433		531
434	() # make sure we don't leak the watcher	532	() # make sure we don't leak the watcher
435	}
436
437	sub _new {
438	my ($self, $fh, $pid) = @_;
439
440	AnyEvent::Util::fh_nonblocking $fh, 1;
441
442	$self = bless [
443	$pid,
444	$fh,
445	[], # write queue - strings or fd's
446	undef, # AE watcher
447	], $self;
448
449	$self
450	}	533	}
451		534
452	# fork template from current process, used by AnyEvent::Fork::Early/Template	535	# fork template from current process, used by AnyEvent::Fork::Early/Template
453	sub _new_fork {	536	sub _new_fork {
454	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	537	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
587	AnyEvent::Fork itself.	670	AnyEvent::Fork itself.
588		671
589	=cut	672	=cut
590		673
591	sub pid {	674	sub pid {
592	$_[0][0]	675	$_[0][PID]
593	}	676	}
594		677
595	=item $proc = $proc->eval ($perlcode, @args)	678	=item $proc = $proc->eval ($perlcode, @args)
596		679
597	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
598	the strings specified by C<@args>, in the "main" package.	681	the strings specified by C<@args>, in the "main" package.
599		682
600	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
601	(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
602	to completely take over the process, use C<run> for that.	685	to completely take over the process, use C<run> for that.
…		…
664	sub send_fh {	747	sub send_fh {
665	my ($self, @fh) = @_;	748	my ($self, @fh) = @_;
666		749
667	for my $fh (@fh) {	750	for my $fh (@fh) {
668	$self->_cmd ("h");	751	$self->_cmd ("h");
669	push @{ $self->[2] }, \$fh;	752	push @{ $self->[QUEUE] }, \$fh;
670	}	753	}
671		754
672	$self	755	$self
673	}	756	}
674		757
…		…
760	=cut	843	=cut
761		844
762	sub run {	845	sub run {
763	my ($self, $func, $cb) = @_;	846	my ($self, $func, $cb) = @_;
764		847
765	$self->[4] = $cb;	848	$self->[CB] = $cb;
766	$self->_cmd (r => $func);	849	$self->_cmd (r => $func);
		850	}
		851
		852	=back
		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 connection. 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	Although not a limitation of this module, keep in mind that the
		886	"communications socket" is simply C<STDIN>, and depending on how you
		887	started F<perl> (e.g. via F<ssh>), it might only be half-duplex. This is
		888	fine for C<AnyEvent::Fork>, but your C<run> function might want to use
		889	C<STDIN> (or the "communications socket") for input and C<STDOUT> for
		890	output.
		891
		892	You can support both cases by checking the C<fileno> of the handle passed
		893	to your run function:
		894
		895	sub run {
		896	my ($rfh) = @_;
		897
		898	my $wfh = fileno $rfh ? $rfh : *STDOUT;
		899
		900	# now use $rfh for reading and $wfh for writing
		901	}
		902
		903	=cut
		904
		905	sub new_from_stdio {
		906	my ($class, $fh) = @_;
		907
		908	my $self = $class->_new ($fh);
		909
		910	# send startup code
		911	push @{ $self->[QUEUE] },
		912	(do "AnyEvent/Fork/serve.pl")
		913	. <<'EOF';
		914
		915	$OWNER = "another process";
		916	$0 = "AnyEvent::Fork/stdio of $OWNER";
		917
		918	serve *STDIN;
		919	__END__
		920	EOF
		921
		922	# the data is only sent when the user requests additional things, which
		923	# is likely early enough for our purposes.
		924
		925	$self
		926	}
		927
		928	=back
		929
		930	=head2 EXPERIMENTAL METHODS
		931
		932	These methods might go away completely or change behaviour, a any time.
		933
		934	=over 4
		935
		936	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		937
		938	Flushes all commands out to the process and then calls the callback with
		939	the communications socket.
		940
		941	The process object becomes unusable on return from this function - any
		942	further method calls result in undefined behaviour.
		943
		944	The point of this method is to give you a file handle thta you cna pass
		945	to another process. In that other process, you can call C<new_from_fh
		946	AnyEvent::Fork> to create a new C<AnyEvent::Fork> object from it, thereby
		947	effectively passing a fork object to another process.
		948
		949	=cut
		950
		951	sub to_fh {
		952	my ($self, $cb) = @_;
		953
		954	$self->[CB] = $cb;
		955
		956	unless ($self->[WW]) {
		957	$self->[CB]->($self->[FH]);
		958	@$self = ();
		959	}
		960	}
		961
		962	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		963
		964	Takes a file handle originally rceeived by the C<to_fh> method and creates
		965	a new C<AnyEvent:Fork> object. The child process itself will not change in
		966	any way, i.e. it will keep all the modifications done to it before calling
		967	C<to_fh>.
		968
		969	The new object is very much like the original object, except that the
		970	C<pid> method will return C<undef> even if the process is a direct child.
		971
		972	=cut
		973
		974	sub new_from_fh {
		975	my ($class, $fh) = @_;
		976
		977	$class->_new ($fh)
767	}	978	}
768		979
769	=back	980	=back
770		981
771	=head1 PERFORMANCE	982	=head1 PERFORMANCE
…		…
781		992
782	2079 new processes per second, using manual socketpair + fork	993	2079 new processes per second, using manual socketpair + fork
783		994
784	Then I did the same thing, but instead of calling fork, I called	995	Then I did the same thing, but instead of calling fork, I called
785	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the	996	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the
786	socket form the child to close on exit. This does the same thing as manual	997	socket from the child to close on exit. This does the same thing as manual
787	socket pair + fork, except that what is forked is the template process	998	socket pair + fork, except that what is forked is the template process
788	(2440kB), and the socket needs to be passed to the server at the other end	999	(2440kB), and the socket needs to be passed to the server at the other end
789	of the socket first.	1000	of the socket first.
790		1001
791	2307 new processes per second, using AnyEvent::Fork->new	1002	2307 new processes per second, using AnyEvent::Fork->new
…		…
798	So how can C<< AnyEvent->new >> be faster than a standard fork, even	1009	So how can C<< AnyEvent->new >> be faster than a standard fork, even
799	though it uses the same operations, but adds a lot of overhead?	1010	though it uses the same operations, but adds a lot of overhead?
800		1011
801	The difference is simply the process size: forking the 5MB process takes	1012	The difference is simply the process size: forking the 5MB process takes
802	so much longer than forking the 2.5MB template process that the extra	1013	so much longer than forking the 2.5MB template process that the extra
803	overhead introduced is canceled out.	1014	overhead is canceled out.
804		1015
805	If the benchmark process grows, the normal fork becomes even slower:	1016	If the benchmark process grows, the normal fork becomes even slower:
806		1017
807	1340 new processes, manual fork of a 20MB process	1018	1340 new processes, manual fork of a 20MB process
808	731 new processes, manual fork of a 200MB process	1019	731 new processes, manual fork of a 200MB process
…		…
868	initialising them, for example, by calling C<init Gtk2> manually.	1079	initialising them, for example, by calling C<init Gtk2> manually.
869		1080
870	=item exiting calls object destructors	1081	=item exiting calls object destructors
871		1082
872	This only applies to users of L<AnyEvent::Fork:Early> and	1083	This only applies to users of L<AnyEvent::Fork:Early> and
873	L<AnyEvent::Fork::Template>, or when initialiasing code creates objects	1084	L<AnyEvent::Fork::Template>, or when initialising code creates objects
874	that reference external resources.	1085	that reference external resources.
875		1086
876	When a process created by AnyEvent::Fork exits, it might do so by calling	1087	When a process created by AnyEvent::Fork exits, it might do so by calling
877	exit, or simply letting perl reach the end of the program. At which point	1088	exit, or simply letting perl reach the end of the program. At which point
878	Perl runs all destructors.	1089	Perl runs all destructors.
…		…
898	to make it so, mostly due to the bloody broken perl that nobody seems to	1109	to make it so, mostly due to the bloody broken perl that nobody seems to
899	care about. The fork emulation is a bad joke - I have yet to see something	1110	care about. The fork emulation is a bad joke - I have yet to see something
900	useful that you can do with it without running into memory corruption	1111	useful that you can do with it without running into memory corruption
901	issues or other braindamage. Hrrrr.	1112	issues or other braindamage. Hrrrr.
902		1113
		1114	Since fork is endlessly broken on win32 perls (it doesn't even remotely
		1115	work within it's documented limits) and quite obviously it's not getting
		1116	improved any time soon, the best way to proceed on windows would be to
		1117	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1118
903	Cygwin perl is not supported at the moment due to some hilarious	1119	Cygwin perl is not supported at the moment due to some hilarious
904	shortcomings of its API - see L<IO::FDPoll> for more details.	1120	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1121	use C<send_fh> and always use C<new_exec> to create processes, it should
		1122	work though.
905		1123
906	=head1 SEE ALSO	1124	=head1 SEE ALSO
907		1125
908	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),	1126	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1127	(part of this distribution).
		1128
909	L<AnyEvent::Fork::Template> (to create a process by forking the main	1129	L<AnyEvent::Fork::Template>, to create a process by forking the main
910	program at a convenient time).	1130	program at a convenient time (part of this distribution).
911		1131
912	=head1 AUTHOR	1132	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1133
		1134	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1135
		1136	=head1 AUTHOR AND CONTACT INFORMATION
913		1137
914	Marc Lehmann <schmorp@schmorp.de>	1138	Marc Lehmann <schmorp@schmorp.de>
915	http://home.schmorp.de/	1139	http://software.schmorp.de/pkg/AnyEvent-Fork
916		1140
917	=cut	1141	=cut
918		1142
919	1	1143	1
920		1144

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.41 by root, Mon Apr 8 03:20:53 2013 UTC vs. Revision 1.54 by root, Fri Apr 26 17:24:05 2013 UTC

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Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.41 by root, Mon Apr 8 03:20:53 2013 UTC vs.
Revision 1.54 by root, Fri Apr 26 17:24:05 2013 UTC