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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.39 by root, Sat Apr 6 22:39:37 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
232	AnyEvent::Fork	239	AnyEvent::Fork
233	->new	240	->new
234	->eval ('	241	->eval ('
		242	# compile a helper function for later use
235	sub run {	243	sub run {
236	my ($fh, $output, @cmd) = @_;	244	my ($fh, $output, @cmd) = @_;
237		245
238	# perl will clear close-on-exec on STDOUT/STDERR	246	# perl will clear close-on-exec on STDOUT/STDERR
239	open STDOUT, ">&", $output or die;	247	open STDOUT, ">&", $output or die;
…		…
246	->send_arg ("/bin/echo", "hi")	254	->send_arg ("/bin/echo", "hi")
247	->run ("run", my $cv = AE::cv);	255	->run ("run", my $cv = AE::cv);
248		256
249	my $stderr = $cv->recv;	257	my $stderr = $cv->recv;
250		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
251	=head1 CONCEPTS	328	=head1 CONCEPTS
252		329
253	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
254	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".
255		336
256	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
257	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,
258	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
259	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
…		…
369	use AnyEvent;	450	use AnyEvent;
370	use AnyEvent::Util ();	451	use AnyEvent::Util ();
371		452
372	use IO::FDPass;	453	use IO::FDPass;
373		454
374	our $VERSION = 0.5;	455	our $VERSION = '1.0';
375
376	our $PERL; # the path to the perl interpreter, deduces with various forms of magic
377
378	=over 4
379
380	=back
381
382	=cut
383		456
384	# the early fork template process	457	# the early fork template process
385	our $EARLY;	458	our $EARLY;
386		459
387	# the empty template process	460	# the empty template process
388	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	}
389		483
390	sub _cmd {	484	sub _cmd {
391	my $self = shift;	485	my $self = shift;
392		486
393	# 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
394	# 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
395	# it.	489	# it.
396	push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1];	490	push @{ $self->[QUEUE] }, pack "a N/a*", $_[0], $_[1];
397		491
398	$self->[3] \|\|= AE::io $self->[1], 1, sub {	492	$self->[WW] \|\|= AE::io $self->[FH], 1, sub {
399	do {	493	do {
400	# 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,
401	# or a plain string.	495	# or a plain string.
402		496
403	if (ref $self->[2][0]) {	497	if (ref $self->[QUEUE][0]) {
404	# send fh	498	# send fh
405	unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) {	499	unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) {
406	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	500	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
407	undef $self->[3];	501	undef $self->[WW];
408	die "AnyEvent::Fork: file descriptor send failure: $!";	502	die "AnyEvent::Fork: file descriptor send failure: $!";
409	}	503	}
410		504
411	shift @{ $self->[2] };	505	shift @{ $self->[QUEUE] };
412		506
413	} else {	507	} else {
414	# send string	508	# send string
415	my $len = syswrite $self->[1], $self->[2][0];	509	my $len = syswrite $self->[FH], $self->[QUEUE][0];
416		510
417	unless ($len) {	511	unless ($len) {
418	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	512	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
419	undef $self->[3];	513	undef $self->[WW];
420	die "AnyEvent::Fork: command write failure: $!";	514	die "AnyEvent::Fork: command write failure: $!";
421	}	515	}
422		516
423	substr $self->[2][0], 0, $len, "";	517	substr $self->[QUEUE][0], 0, $len, "";
424	shift @{ $self->[2] } unless length $self->[2][0];	518	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
425	}	519	}
426	} while @{ $self->[2] };	520	} while @{ $self->[QUEUE] };
427		521
428	# everything written	522	# everything written
429	undef $self->[3];	523	undef $self->[WW];
430		524
431	# invoke run callback, if any	525	# invoke run callback, if any
432	$self->[4]->($self->[1]) if $self->[4];	526	if ($self->[CB]) {
		527	$self->[CB]->($self->[FH]);
		528	@$self = ();
		529	}
433	};	530	};
434		531
435	() # make sure we don't leak the watcher	532	() # make sure we don't leak the watcher
436	}
437
438	sub _new {
439	my ($self, $fh, $pid) = @_;
440
441	AnyEvent::Util::fh_nonblocking $fh, 1;
442
443	$self = bless [
444	$pid,
445	$fh,
446	[], # write queue - strings or fd's
447	undef, # AE watcher
448	], $self;
449
450	$self
451	}	533	}
452		534
453	# fork template from current process, used by AnyEvent::Fork::Early/Template	535	# fork template from current process, used by AnyEvent::Fork::Early/Template
454	sub _new_fork {	536	sub _new_fork {
455	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	537	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
460	if ($pid eq 0) {	542	if ($pid eq 0) {
461	require AnyEvent::Fork::Serve;	543	require AnyEvent::Fork::Serve;
462	$AnyEvent::Fork::Serve::OWNER = $parent;	544	$AnyEvent::Fork::Serve::OWNER = $parent;
463	close $fh;	545	close $fh;
464	$0 = "$_[1] of $parent";	546	$0 = "$_[1] of $parent";
465	$SIG{CHLD} = 'IGNORE';
466	AnyEvent::Fork::Serve::serve ($slave);	547	AnyEvent::Fork::Serve::serve ($slave);
467	exit 0;	548	exit 0;
468	} elsif (!$pid) {	549	} elsif (!$pid) {
469	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";	550	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";
470	}	551	}
…		…
589	AnyEvent::Fork itself.	670	AnyEvent::Fork itself.
590		671
591	=cut	672	=cut
592		673
593	sub pid {	674	sub pid {
594	$_[0][0]	675	$_[0][PID]
595	}	676	}
596		677
597	=item $proc = $proc->eval ($perlcode, @args)	678	=item $proc = $proc->eval ($perlcode, @args)
598		679
599	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
600	the strings specified by C<@args>, in the "main" package.	681	the strings specified by C<@args>, in the "main" package.
601		682
602	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
603	(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
604	to completely take over the process, use C<run> for that.	685	to completely take over the process, use C<run> for that.
…		…
666	sub send_fh {	747	sub send_fh {
667	my ($self, @fh) = @_;	748	my ($self, @fh) = @_;
668		749
669	for my $fh (@fh) {	750	for my $fh (@fh) {
670	$self->_cmd ("h");	751	$self->_cmd ("h");
671	push @{ $self->[2] }, \$fh;	752	push @{ $self->[QUEUE] }, \$fh;
672	}	753	}
673		754
674	$self	755	$self
675	}	756	}
676		757
…		…
762	=cut	843	=cut
763		844
764	sub run {	845	sub run {
765	my ($self, $func, $cb) = @_;	846	my ($self, $func, $cb) = @_;
766		847
767	$self->[4] = $cb;	848	$self->[CB] = $cb;
768	$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)
769	}	978	}
770		979
771	=back	980	=back
772		981
773	=head1 PERFORMANCE	982	=head1 PERFORMANCE
…		…
783		992
784	2079 new processes per second, using manual socketpair + fork	993	2079 new processes per second, using manual socketpair + fork
785		994
786	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
787	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
788	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
789	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
790	(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
791	of the socket first.	1000	of the socket first.
792		1001
793	2307 new processes per second, using AnyEvent::Fork->new	1002	2307 new processes per second, using AnyEvent::Fork->new
…		…
800	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
801	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?
802		1011
803	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
804	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
805	overhead introduced is canceled out.	1014	overhead is canceled out.
806		1015
807	If the benchmark process grows, the normal fork becomes even slower:	1016	If the benchmark process grows, the normal fork becomes even slower:
808		1017
809	1340 new processes, manual fork of a 20MB process	1018	1340 new processes, manual fork of a 20MB process
810	731 new processes, manual fork of a 200MB process	1019	731 new processes, manual fork of a 200MB process
…		…
870	initialising them, for example, by calling C<init Gtk2> manually.	1079	initialising them, for example, by calling C<init Gtk2> manually.
871		1080
872	=item exiting calls object destructors	1081	=item exiting calls object destructors
873		1082
874	This only applies to users of L<AnyEvent::Fork:Early> and	1083	This only applies to users of L<AnyEvent::Fork:Early> and
875	L<AnyEvent::Fork::Template>, or when initialiasing code creates objects	1084	L<AnyEvent::Fork::Template>, or when initialising code creates objects
876	that reference external resources.	1085	that reference external resources.
877		1086
878	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
879	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
880	Perl runs all destructors.	1089	Perl runs all destructors.
…		…
900	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
901	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
902	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
903	issues or other braindamage. Hrrrr.	1112	issues or other braindamage. Hrrrr.
904		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
905	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
906	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.
907		1123
908	=head1 SEE ALSO	1124	=head1 SEE ALSO
909		1125
910	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
911	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
912	program at a convenient time).	1130	program at a convenient time (part of this distribution).
913		1131
914	=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
915		1137
916	Marc Lehmann <schmorp@schmorp.de>	1138	Marc Lehmann <schmorp@schmorp.de>
917	http://home.schmorp.de/	1139	http://software.schmorp.de/pkg/AnyEvent-Fork
918		1140
919	=cut	1141	=cut
920		1142
921	1	1143	1
922		1144

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.39 by root, Sat Apr 6 22:39:37 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 1.39 by root, Sat Apr 6 22:39:37 2013 UTC vs.
Revision 1.54 by root, Fri Apr 26 17:24:05 2013 UTC