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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.30 by root, Sat Apr 6 09:28:45 2013 UTC vs.
Revision 1.60 by root, Wed Sep 25 11:05:30 2013 UTC

…		…
27		27
28	Special care has been taken to make this module useful from other modules,	28	Special care has been taken to make this module useful from other modules,
29	while still supporting specialised environments such as L<App::Staticperl>	29	while still supporting specialised environments such as L<App::Staticperl>
30	or L<PAR::Packer>.	30	or L<PAR::Packer>.
31		31
32	=head1 WHAT THIS MODULE IS NOT	32	=head2 WHAT THIS MODULE IS NOT
33		33
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,
43	and so on.
44		42
		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.
		51
		52	=head2 COMPARISON TO OTHER MODULES
		53
		54	There is an abundance of modules on CPAN that do "something fork", such as
		55	L<Parallel::ForkManager>, L<AnyEvent::ForkManager>, L<AnyEvent::Worker>
		56	or L<AnyEvent::Subprocess>. There are modules that implement their own
		57	process management, such as L<AnyEvent::DBI>.
		58
		59	The problems that all these modules try to solve are real, however, none
		60	of them (from what I have seen) tackle the very real problems of unwanted
		61	memory sharing, efficiency, not being able to use event processing or
		62	similar modules in the processes they create.
		63
		64	This module doesn't try to replace any of them - instead it tries to solve
		65	the problem of creating processes with a minimum of fuss and overhead (and
		66	also luxury). Ideally, most of these would use AnyEvent::Fork internally,
		67	except they were written before AnyEvent:Fork was available, so obviously
		68	had to roll their own.
		69
45	=head1 PROBLEM STATEMENT	70	=head2 PROBLEM STATEMENT
46		71
47	There are two traditional ways to implement parallel processing on UNIX	72	There are two traditional ways to implement parallel processing on UNIX
48	like operating systems - fork and process, and fork+exec and process. They	73	like operating systems - fork and process, and fork+exec and process. They
49	have different advantages and disadvantages that I describe below,	74	have different advantages and disadvantages that I describe below,
50	together with how this module tries to mitigate the disadvantages.	75	together with how this module tries to mitigate the disadvantages.
…		…
152		177
153	# now $master_filehandle is connected to the	178	# now $master_filehandle is connected to the
154	# $slave_filehandle in the new process.	179	# $slave_filehandle in the new process.
155	});	180	});
156		181
157	MyModule::worker might look like this:	182	C<MyModule> might look like this:
158		183
		184	package MyModule;
		185
159	sub MyModule::worker {	186	sub worker {
160	my ($slave_filehandle) = @_;	187	my ($slave_filehandle) = @_;
161		188
162	# now $slave_filehandle is connected to the $master_filehandle	189	# now $slave_filehandle is connected to the $master_filehandle
163	# in the original prorcess. have fun!	190	# in the original prorcess. have fun!
164	}	191	}
…		…
183	}	210	}
184		211
185	# now do other things - maybe use the filehandle provided by run	212	# now do other things - maybe use the filehandle provided by run
186	# to wait for the processes to die. or whatever.	213	# to wait for the processes to die. or whatever.
187		214
188	My::Server::run might look like this:	215	C<My::Server> might look like this:
189		216
190	sub My::Server::run {	217	package My::Server;
		218
		219	sub run {
191	my ($slave, $listener, $id) = @_;	220	my ($slave, $listener, $id) = @_;
192		221
193	close $slave; # we do not use the socket, so close it to save resources	222	close $slave; # we do not use the socket, so close it to save resources
194		223
195	# we could go ballistic and use e.g. AnyEvent here, or IO::AIO,	224	# we could go ballistic and use e.g. AnyEvent here, or IO::AIO,
…		…
199	}	228	}
200	}	229	}
201		230
202	=head2 use AnyEvent::Fork as a faster fork+exec	231	=head2 use AnyEvent::Fork as a faster fork+exec
203		232
204	This runs /bin/echo hi, with stdout redirected to /tmp/log and stderr to	233	This runs C</bin/echo hi>, with standard output redirected to F</tmp/log>
205	the communications socket. It is usually faster than fork+exec, but still	234	and standard error redirected to the communications socket. It is usually
206	let's you prepare the environment.	235	faster than fork+exec, but still lets you prepare the environment.
207		236
208	open my $output, ">/tmp/log" or die "$!";	237	open my $output, ">/tmp/log" or die "$!";
209		238
210	AnyEvent::Fork	239	AnyEvent::Fork
211	->new	240	->new
212	->eval ('	241	->eval ('
		242	# compile a helper function for later use
213	sub run {	243	sub run {
214	my ($fh, $output, @cmd) = @_;	244	my ($fh, $output, @cmd) = @_;
215		245
216	# perl will clear close-on-exec on STDOUT/STDERR	246	# perl will clear close-on-exec on STDOUT/STDERR
217	open STDOUT, ">&", $output or die;	247	open STDOUT, ">&", $output or die;
…		…
224	->send_arg ("/bin/echo", "hi")	254	->send_arg ("/bin/echo", "hi")
225	->run ("run", my $cv = AE::cv);	255	->run ("run", my $cv = AE::cv);
226		256
227	my $stderr = $cv->recv;	257	my $stderr = $cv->recv;
228		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
229	=head1 CONCEPTS	328	=head1 CONCEPTS
230		329
231	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
232	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".
233		336
234	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
235	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,
236	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
237	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
…		…
347	use AnyEvent;	450	use AnyEvent;
348	use AnyEvent::Util ();	451	use AnyEvent::Util ();
349		452
350	use IO::FDPass;	453	use IO::FDPass;
351		454
352	our $VERSION = 0.5;	455	our $VERSION = 1.2;
353
354	our $PERL; # the path to the perl interpreter, deduces with various forms of magic
355
356	=over 4
357
358	=back
359
360	=cut
361		456
362	# the early fork template process	457	# the early fork template process
363	our $EARLY;	458	our $EARLY;
364		459
365	# the empty template process	460	# the empty template process
366	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	}
367		483
368	sub _cmd {	484	sub _cmd {
369	my $self = shift;	485	my $self = shift;
370		486
371	# 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
372	# 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
373	# it.	489	# it.
374	push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1];	490	push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1];
375		491
376	$self->[3] \|\|= AE::io $self->[1], 1, sub {	492	$self->[WW] \|\|= AE::io $self->[FH], 1, sub {
377	do {	493	do {
378	# 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,
379	# or a plain string.	495	# or a plain string.
380		496
381	if (ref $self->[2][0]) {	497	if (ref $self->[QUEUE][0]) {
382	# send fh	498	# send fh
383	unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) {	499	unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) {
384	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	500	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
385	undef $self->[3];	501	undef $self->[WW];
386	die "AnyEvent::Fork: file descriptor send failure: $!";	502	die "AnyEvent::Fork: file descriptor send failure: $!";
387	}	503	}
388		504
389	shift @{ $self->[2] };	505	shift @{ $self->[QUEUE] };
390		506
391	} else {	507	} else {
392	# send string	508	# send string
393	my $len = syswrite $self->[1], $self->[2][0];	509	my $len = syswrite $self->[FH], $self->[QUEUE][0];
394		510
395	unless ($len) {	511	unless ($len) {
396	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	512	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
397	undef $self->[3];	513	undef $self->[WW];
398	die "AnyEvent::Fork: command write failure: $!";	514	die "AnyEvent::Fork: command write failure: $!";
399	}	515	}
400		516
401	substr $self->[2][0], 0, $len, "";	517	substr $self->[QUEUE][0], 0, $len, "";
402	shift @{ $self->[2] } unless length $self->[2][0];	518	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
403	}	519	}
404	} while @{ $self->[2] };	520	} while @{ $self->[QUEUE] };
405		521
406	# everything written	522	# everything written
407	undef $self->[3];	523	undef $self->[WW];
408		524
409	# invoke run callback, if any	525	# invoke run callback, if any
410	$self->[4]->($self->[1]) if $self->[4];	526	if ($self->[CB]) {
		527	$self->[CB]->($self->[FH]);
		528	@$self = ();
		529	}
411	};	530	};
412		531
413	() # make sure we don't leak the watcher	532	() # make sure we don't leak the watcher
414	}
415
416	sub _new {
417	my ($self, $fh, $pid) = @_;
418
419	AnyEvent::Util::fh_nonblocking $fh, 1;
420
421	$self = bless [
422	$pid,
423	$fh,
424	[], # write queue - strings or fd's
425	undef, # AE watcher
426	], $self;
427
428	$self
429	}	533	}
430		534
431	# fork template from current process, used by AnyEvent::Fork::Early/Template	535	# fork template from current process, used by AnyEvent::Fork::Early/Template
432	sub _new_fork {	536	sub _new_fork {
433	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	537	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
438	if ($pid eq 0) {	542	if ($pid eq 0) {
439	require AnyEvent::Fork::Serve;	543	require AnyEvent::Fork::Serve;
440	$AnyEvent::Fork::Serve::OWNER = $parent;	544	$AnyEvent::Fork::Serve::OWNER = $parent;
441	close $fh;	545	close $fh;
442	$0 = "$_[1] of $parent";	546	$0 = "$_[1] of $parent";
443	$SIG{CHLD} = 'IGNORE';
444	AnyEvent::Fork::Serve::serve ($slave);	547	AnyEvent::Fork::Serve::serve ($slave);
445	exit 0;	548	exit 0;
446	} elsif (!$pid) {	549	} elsif (!$pid) {
447	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";	550	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";
448	}	551	}
…		…
502		605
503	You should use C<new> whenever possible, except when having a template	606	You should use C<new> whenever possible, except when having a template
504	process around is unacceptable.	607	process around is unacceptable.
505		608
506	The path to the perl interpreter is divined using various methods - first	609	The path to the perl interpreter is divined using various methods - first
507	C<$^X> is investigated to see if the path ends with something that sounds	610	C<$^X> is investigated to see if the path ends with something that looks
508	as if it were the perl interpreter. Failing this, the module falls back to	611	as if it were the perl interpreter. Failing this, the module falls back to
509	using C<$Config::Config{perlpath}>.	612	using C<$Config::Config{perlpath}>.
510		613
		614	The path to perl can also be overriden by setting the global variable
		615	C<$AnyEvent::Fork::PERL> - it's value will be used for all subsequent
		616	invocations.
		617
511	=cut	618	=cut
		619
		620	our $PERL;
512		621
513	sub new_exec {	622	sub new_exec {
514	my ($self) = @_;	623	my ($self) = @_;
515		624
516	return $EARLY->fork	625	return $EARLY->fork
517	if $EARLY;	626	if $EARLY;
518		627
		628	unless (defined $PERL) {
519	# first find path of perl	629	# first find path of perl
520	my $perl = $;	630	my $perl = $;
521		631
522	# first we try $^X, but the path must be absolute (always on win32), and end in sth.	632	# first we try $^X, but the path must be absolute (always on win32), and end in sth.
523	# that looks like perl. this obviously only works for posix and win32	633	# that looks like perl. this obviously only works for posix and win32
524	unless (	634	unless (
525	($^O eq "MSWin32" \|\| $perl =~ m%^/%)	635	($^O eq "MSWin32" \|\| $perl =~ m%^/%)
526	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i	636	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i
527	) {	637	) {
528	# if it doesn't look perlish enough, try Config	638	# if it doesn't look perlish enough, try Config
529	require Config;	639	require Config;
530	$perl = $Config::Config{perlpath};	640	$perl = $Config::Config{perlpath};
531	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;	641	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;
		642	}
		643
		644	$PERL = $perl;
532	}	645	}
533		646
534	require Proc::FastSpawn;	647	require Proc::FastSpawn;
535		648
536	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	649	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
544	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;	657	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;
545	my %env = %ENV;	658	my %env = %ENV;
546	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;	659	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;
547		660
548	my $pid = Proc::FastSpawn::spawn (	661	my $pid = Proc::FastSpawn::spawn (
549	$perl,	662	$PERL,
550	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],	663	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],
551	[map "$_=$env{$_}", keys %env],	664	[map "$_=$env{$_}", keys %env],
552	) or die "unable to spawn AnyEvent::Fork server: $!";	665	) or die "unable to spawn AnyEvent::Fork server: $!";
553		666
554	$self->_new ($fh, $pid)	667	$self->_new ($fh, $pid)
555	}	668	}
556		669
557	=item $pid = $proc->pid	670	=item $pid = $proc->pid
558		671
559	Returns the process id of the process I<iff it is a direct child of the	672	Returns the process id of the process I<iff it is a direct child of the
560	process> running AnyEvent::Fork, and C<undef> otherwise.	673	process running AnyEvent::Fork>, and C<undef> otherwise. As a general
		674	rule (that you cannot rely upon), processes created via C<new_exec>,
		675	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template> are direct
		676	children, while all other processes are not.
561		677
562	Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and	678	Or in other words, you do not normally have to take care of zombies for
563	L<AnyEvent::Fork::Template> are direct children, and you are responsible	679	processes created via C<new>, but when in doubt, or zombies are a problem,
564	to clean up their zombies when they die.	680	you need to check whether a process is a diretc child by calling this
565		681	method, and possibly creating a child watcher or reap it manually.
566	All other processes are not direct children, and will be cleaned up by
567	AnyEvent::Fork itself.
568		682
569	=cut	683	=cut
570		684
571	sub pid {	685	sub pid {
572	$_[0][0]	686	$_[0][PID]
573	}	687	}
574		688
575	=item $proc = $proc->eval ($perlcode, @args)	689	=item $proc = $proc->eval ($perlcode, @args)
576		690
577	Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to	691	Evaluates the given C<$perlcode> as ... Perl code, while setting C<@_> to
578	the strings specified by C<@args>, in the "main" package.	692	the strings specified by C<@args>, in the "main" package.
579		693
580	This call is meant to do any custom initialisation that might be required	694	This call is meant to do any custom initialisation that might be required
581	(for example, the C<require> method uses it). It's not supposed to be used	695	(for example, the C<require> method uses it). It's not supposed to be used
582	to completely take over the process, use C<run> for that.	696	to completely take over the process, use C<run> for that.
583		697
584	The code will usually be executed after this call returns, and there is no	698	The code will usually be executed after this call returns, and there is no
585	way to pass anything back to the calling process. Any evaluation errors	699	way to pass anything back to the calling process. Any evaluation errors
586	will be reported to stderr and cause the process to exit.	700	will be reported to stderr and cause the process to exit.
587		701
588	If you want to execute some code to take over the process (see the	702	If you want to execute some code (that isn't in a module) to take over the
589	"fork+exec" example in the SYNOPSIS), you should compile a function via	703	process, you should compile a function via C<eval> first, and then call
590	C<eval> first, and then call it via C<run>. This also gives you access to	704	it via C<run>. This also gives you access to any arguments passed via the
591	any arguments passed via the C<send_xxx> methods, such as file handles.	705	C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as
		706	a faster fork+exec> example to see it in action.
592		707
593	Returns the process object for easy chaining of method calls.	708	Returns the process object for easy chaining of method calls.
594		709
595	=cut	710	=cut
596		711
…		…
622	=item $proc = $proc->send_fh ($handle, ...)	737	=item $proc = $proc->send_fh ($handle, ...)
623		738
624	Send one or more file handles (I<not> file descriptors) to the process,	739	Send one or more file handles (I<not> file descriptors) to the process,
625	to prepare a call to C<run>.	740	to prepare a call to C<run>.
626		741
627	The process object keeps a reference to the handles until this is done,	742	The process object keeps a reference to the handles until they have
628	so you must not explicitly close the handles. This is most easily	743	been passed over to the process, so you must not explicitly close the
629	accomplished by simply not storing the file handles anywhere after passing	744	handles. This is most easily accomplished by simply not storing the file
630	them to this method.	745	handles anywhere after passing them to this method - when AnyEvent::Fork
		746	is finished using them, perl will automatically close them.
631		747
632	Returns the process object for easy chaining of method calls.	748	Returns the process object for easy chaining of method calls.
633		749
634	Example: pass a file handle to a process, and release it without	750	Example: pass a file handle to a process, and release it without
635	closing. It will be closed automatically when it is no longer used.	751	closing. It will be closed automatically when it is no longer used.
…		…
642	sub send_fh {	758	sub send_fh {
643	my ($self, @fh) = @_;	759	my ($self, @fh) = @_;
644		760
645	for my $fh (@fh) {	761	for my $fh (@fh) {
646	$self->_cmd ("h");	762	$self->_cmd ("h");
647	push @{ $self->[2] }, \$fh;	763	push @{ $self->[QUEUE] }, \$fh;
648	}	764	}
649		765
650	$self	766	$self
651	}	767	}
652		768
653	=item $proc = $proc->send_arg ($string, ...)	769	=item $proc = $proc->send_arg ($string, ...)
654		770
655	Send one or more argument strings to the process, to prepare a call to	771	Send one or more argument strings to the process, to prepare a call to
656	C<run>. The strings can be any octet string.	772	C<run>. The strings can be any octet strings.
657		773
658	The protocol is optimised to pass a moderate number of relatively short	774	The protocol is optimised to pass a moderate number of relatively short
659	strings - while you can pass up to 4GB of data in one go, this is more	775	strings - while you can pass up to 4GB of data in one go, this is more
660	meant to pass some ID information or other startup info, not big chunks of	776	meant to pass some ID information or other startup info, not big chunks of
661	data.	777	data.
…		…
677	Enter the function specified by the function name in C<$func> in the	793	Enter the function specified by the function name in C<$func> in the
678	process. The function is called with the communication socket as first	794	process. The function is called with the communication socket as first
679	argument, followed by all file handles and string arguments sent earlier	795	argument, followed by all file handles and string arguments sent earlier
680	via C<send_fh> and C<send_arg> methods, in the order they were called.	796	via C<send_fh> and C<send_arg> methods, in the order they were called.
681		797
		798	The process object becomes unusable on return from this function - any
		799	further method calls result in undefined behaviour.
		800
682	The function name should be fully qualified, but if it isn't, it will be	801	The function name should be fully qualified, but if it isn't, it will be
683	looked up in the main package.	802	looked up in the C<main> package.
684		803
685	If the called function returns, doesn't exist, or any error occurs, the	804	If the called function returns, doesn't exist, or any error occurs, the
686	process exits.	805	process exits.
687		806
688	Preparing the process is done in the background - when all commands have	807	Preparing the process is done in the background - when all commands have
689	been sent, the callback is invoked with the local communications socket	808	been sent, the callback is invoked with the local communications socket
690	as argument. At this point you can start using the socket in any way you	809	as argument. At this point you can start using the socket in any way you
691	like.	810	like.
692		811
693	The process object becomes unusable on return from this function - any
694	further method calls result in undefined behaviour.
695
696	If the communication socket isn't used, it should be closed on both sides,	812	If the communication socket isn't used, it should be closed on both sides,
697	to save on kernel memory.	813	to save on kernel memory.
698		814
699	The socket is non-blocking in the parent, and blocking in the newly	815	The socket is non-blocking in the parent, and blocking in the newly
700	created process. The close-on-exec flag is set in both.	816	created process. The close-on-exec flag is set in both.
701		817
702	Even if not used otherwise, the socket can be a good indicator for the	818	Even if not used otherwise, the socket can be a good indicator for the
703	existence of the process - if the other process exits, you get a readable	819	existence of the process - if the other process exits, you get a readable
704	event on it, because exiting the process closes the socket (if it didn't	820	event on it, because exiting the process closes the socket (if it didn't
705	create any children using fork).	821	create any children using fork).
		822
		823	=over 4
		824
		825	=item Compatibility to L<AnyEvent::Fork::Remote>
		826
		827	If you want to write code that works with both this module and
		828	L<AnyEvent::Fork::Remote>, you need to write your code so that it assumes
		829	there are two file handles for communications, which might not be unix
		830	domain sockets. The C<run> function should start like this:
		831
		832	sub run {
		833	my ($rfh, @args) = @_; # @args is your normal arguments
		834	my $wfh = fileno $rfh ? $rfh : *STDOUT;
		835
		836	# now use $rfh for reading and $wfh for writing
		837	}
		838
		839	This checks whether the passed file handle is, in fact, the process
		840	C<STDIN> handle. If it is, then the function was invoked visa
		841	L<AnyEvent::Fork::Remote>, so STDIN should be used for reading and
		842	C<STDOUT> should be used for writing.
		843
		844	In all other cases, the function was called via this module, and there is
		845	only one file handle that should be sued for reading and writing.
		846
		847	=back
706		848
707	Example: create a template for a process pool, pass a few strings, some	849	Example: create a template for a process pool, pass a few strings, some
708	file handles, then fork, pass one more string, and run some code.	850	file handles, then fork, pass one more string, and run some code.
709		851
710	my $pool = AnyEvent::Fork	852	my $pool = AnyEvent::Fork
…		…
738	=cut	880	=cut
739		881
740	sub run {	882	sub run {
741	my ($self, $func, $cb) = @_;	883	my ($self, $func, $cb) = @_;
742		884
743	$self->[4] = $cb;	885	$self->[CB] = $cb;
744	$self->_cmd (r => $func);	886	$self->_cmd (r => $func);
		887	}
		888
		889	=back
		890
		891	=head2 EXPERIMENTAL METHODS
		892
		893	These methods might go away completely or change behaviour, at any time.
		894
		895	=over 4
		896
		897	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		898
		899	Flushes all commands out to the process and then calls the callback with
		900	the communications socket.
		901
		902	The process object becomes unusable on return from this function - any
		903	further method calls result in undefined behaviour.
		904
		905	The point of this method is to give you a file handle that you can pass
		906	to another process. In that other process, you can call C<new_from_fh
		907	AnyEvent::Fork $fh> to create a new C<AnyEvent::Fork> object from it,
		908	thereby effectively passing a fork object to another process.
		909
		910	=cut
		911
		912	sub to_fh {
		913	my ($self, $cb) = @_;
		914
		915	$self->[CB] = $cb;
		916
		917	unless ($self->[WW]) {
		918	$self->[CB]->($self->[FH]);
		919	@$self = ();
		920	}
		921	}
		922
		923	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		924
		925	Takes a file handle originally rceeived by the C<to_fh> method and creates
		926	a new C<AnyEvent:Fork> object. The child process itself will not change in
		927	any way, i.e. it will keep all the modifications done to it before calling
		928	C<to_fh>.
		929
		930	The new object is very much like the original object, except that the
		931	C<pid> method will return C<undef> even if the process is a direct child.
		932
		933	=cut
		934
		935	sub new_from_fh {
		936	my ($class, $fh) = @_;
		937
		938	$class->_new ($fh)
745	}	939	}
746		940
747	=back	941	=back
748		942
749	=head1 PERFORMANCE	943	=head1 PERFORMANCE
…		…
759		953
760	2079 new processes per second, using manual socketpair + fork	954	2079 new processes per second, using manual socketpair + fork
761		955
762	Then I did the same thing, but instead of calling fork, I called	956	Then I did the same thing, but instead of calling fork, I called
763	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the	957	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the
764	socket form the child to close on exit. This does the same thing as manual	958	socket from the child to close on exit. This does the same thing as manual
765	socket pair + fork, except that what is forked is the template process	959	socket pair + fork, except that what is forked is the template process
766	(2440kB), and the socket needs to be passed to the server at the other end	960	(2440kB), and the socket needs to be passed to the server at the other end
767	of the socket first.	961	of the socket first.
768		962
769	2307 new processes per second, using AnyEvent::Fork->new	963	2307 new processes per second, using AnyEvent::Fork->new
…		…
774	479 vfork+execs per second, using AnyEvent::Fork->new_exec	968	479 vfork+execs per second, using AnyEvent::Fork->new_exec
775		969
776	So how can C<< AnyEvent->new >> be faster than a standard fork, even	970	So how can C<< AnyEvent->new >> be faster than a standard fork, even
777	though it uses the same operations, but adds a lot of overhead?	971	though it uses the same operations, but adds a lot of overhead?
778		972
779	The difference is simply the process size: forking the 6MB process takes	973	The difference is simply the process size: forking the 5MB process takes
780	so much longer than forking the 2.5MB template process that the overhead	974	so much longer than forking the 2.5MB template process that the extra
781	introduced is canceled out.	975	overhead is canceled out.
782		976
783	If the benchmark process grows, the normal fork becomes even slower:	977	If the benchmark process grows, the normal fork becomes even slower:
784		978
785	1340 new processes, manual fork in a 20MB process	979	1340 new processes, manual fork of a 20MB process
786	731 new processes, manual fork in a 200MB process	980	731 new processes, manual fork of a 200MB process
787	235 new processes, manual fork in a 2000MB process	981	235 new processes, manual fork of a 2000MB process
788		982
789	What that means (to me) is that I can use this module without having a	983	What that means (to me) is that I can use this module without having a bad
790	very bad conscience because of the extra overhead required to start new	984	conscience because of the extra overhead required to start new processes.
791	processes.
792		985
793	=head1 TYPICAL PROBLEMS	986	=head1 TYPICAL PROBLEMS
794		987
795	This section lists typical problems that remain. I hope by recognising	988	This section lists typical problems that remain. I hope by recognising
796	them, most can be avoided.	989	them, most can be avoided.
797		990
798	=over 4	991	=over 4
799		992
800	=item "leaked" file descriptors for exec'ed processes	993	=item leaked file descriptors for exec'ed processes
801		994
802	POSIX systems inherit file descriptors by default when exec'ing a new	995	POSIX systems inherit file descriptors by default when exec'ing a new
803	process. While perl itself laudably sets the close-on-exec flags on new	996	process. While perl itself laudably sets the close-on-exec flags on new
804	file handles, most C libraries don't care, and even if all cared, it's	997	file handles, most C libraries don't care, and even if all cared, it's
805	often not possible to set the flag in a race-free manner.	998	often not possible to set the flag in a race-free manner.
…		…
825	libraries or the code that leaks those file descriptors.	1018	libraries or the code that leaks those file descriptors.
826		1019
827	Fortunately, most of these leaked descriptors do no harm, other than	1020	Fortunately, most of these leaked descriptors do no harm, other than
828	sitting on some resources.	1021	sitting on some resources.
829		1022
830	=item "leaked" file descriptors for fork'ed processes	1023	=item leaked file descriptors for fork'ed processes
831		1024
832	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,	1025	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,
833	which closes file descriptors not marked for being inherited.	1026	which closes file descriptors not marked for being inherited.
834		1027
835	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer	1028	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer
…		…
844		1037
845	The solution is to either not load these modules before use'ing	1038	The solution is to either not load these modules before use'ing
846	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay	1039	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay
847	initialising them, for example, by calling C<init Gtk2> manually.	1040	initialising them, for example, by calling C<init Gtk2> manually.
848		1041
849	=item exit runs destructors	1042	=item exiting calls object destructors
850		1043
851	This only applies to users of Lc<AnyEvent::Fork:Early> and	1044	This only applies to users of L<AnyEvent::Fork:Early> and
852	L<AnyEvent::Fork::Template>.	1045	L<AnyEvent::Fork::Template>, or when initialising code creates objects
		1046	that reference external resources.
853		1047
854	When a process created by AnyEvent::Fork exits, it might do so by calling	1048	When a process created by AnyEvent::Fork exits, it might do so by calling
855	exit, or simply letting perl reach the end of the program. At which point	1049	exit, or simply letting perl reach the end of the program. At which point
856	Perl runs all destructors.	1050	Perl runs all destructors.
857		1051
…		…
876	to make it so, mostly due to the bloody broken perl that nobody seems to	1070	to make it so, mostly due to the bloody broken perl that nobody seems to
877	care about. The fork emulation is a bad joke - I have yet to see something	1071	care about. The fork emulation is a bad joke - I have yet to see something
878	useful that you can do with it without running into memory corruption	1072	useful that you can do with it without running into memory corruption
879	issues or other braindamage. Hrrrr.	1073	issues or other braindamage. Hrrrr.
880		1074
881	Cygwin perl is not supported at the moment, as it should implement fd	1075	Since fork is endlessly broken on win32 perls (it doesn't even remotely
882	passing, but doesn't, and rolling my own is hard, as cygwin doesn't	1076	work within it's documented limits) and quite obviously it's not getting
883	support enough functionality to do it.	1077	improved any time soon, the best way to proceed on windows would be to
		1078	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1079
		1080	Cygwin perl is not supported at the moment due to some hilarious
		1081	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1082	use C<send_fh> and always use C<new_exec> to create processes, it should
		1083	work though.
884		1084
885	=head1 SEE ALSO	1085	=head1 SEE ALSO
886		1086
887	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),	1087	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1088	(part of this distribution).
		1089
888	L<AnyEvent::Fork::Template> (to create a process by forking the main	1090	L<AnyEvent::Fork::Template>, to create a process by forking the main
889	program at a convenient time).	1091	program at a convenient time (part of this distribution).
890		1092
891	=head1 AUTHOR	1093	L<AnyEvent::Fork::Remote>, for another way to create processes that is
		1094	mostly compatible to this module and modules building on top of it, but
		1095	works better with remote processes.
		1096
		1097	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1098
		1099	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1100
		1101	=head1 AUTHOR AND CONTACT INFORMATION
892		1102
893	Marc Lehmann <schmorp@schmorp.de>	1103	Marc Lehmann <schmorp@schmorp.de>
894	http://home.schmorp.de/	1104	http://software.schmorp.de/pkg/AnyEvent-Fork
895		1105
896	=cut	1106	=cut
897		1107
898	1	1108	1
899		1109

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.30 by root, Sat Apr 6 09:28:45 2013 UTC vs. Revision 1.60 by root, Wed Sep 25 11:05:30 2013 UTC

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Revision 1.60 by root, Wed Sep 25 11:05:30 2013 UTC