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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.32 by root, Sat Apr 6 09:30:26 2013 UTC vs.
Revision 1.63 by root, Wed Nov 26 13:36:18 2014 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 or not being able to use event processing, GUI
		62	toolkits or 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.
…		…
64		89
65	=item Forking usually creates a copy-on-write copy of the parent	90	=item Forking usually creates a copy-on-write copy of the parent
66	process.	91	process.
67		92
68	For example, modules or data files that are loaded will not use additional	93	For example, modules or data files that are loaded will not use additional
69	memory after a fork. When exec'ing a new process, modules and data files	94	memory after a fork. Exec'ing a new process, in contrast, means modules
70	might need to be loaded again, at extra CPU and memory cost. But when	95	and data files might need to be loaded again, at extra CPU and memory
71	forking, literally all data structures are copied - if the program frees	96	cost.
		97
		98	But when forking, you still create a copy of your data structures - if
72	them and replaces them by new data, the child processes will retain the	99	the program frees them and replaces them by new data, the child processes
73	old version even if it isn't used, which can suddenly and unexpectedly	100	will retain the old version even if it isn't used, which can suddenly and
74	increase memory usage when freeing memory.	101	unexpectedly increase memory usage when freeing memory.
75		102
		103	For example, L<Gtk2::CV> is an image viewer optimised for large
		104	directories (millions of pictures). It also forks subprocesses for
		105	thumbnail generation, which inherit the data structure that stores all
		106	file information. If the user changes the directory, it gets freed in
		107	the main process, leaving a copy in the thumbnailer processes. This can
		108	lead to many times the memory usage that would actually be required. The
		109	solution is to fork early (and being unable to dynamically generate more
		110	subprocesses or do this from a module)... or to use L<AnyEvent:Fork>.
		111
76	The trade-off is between more sharing with fork (which can be good or	112	There is a trade-off between more sharing with fork (which can be good or
77	bad), and no sharing with exec.	113	bad), and no sharing with exec.
78		114
79	This module allows the main program to do a controlled fork, and allows	115	This module allows the main program to do a controlled fork, and allows
80	modules to exec processes safely at any time. When creating a custom	116	modules to exec processes safely at any time. When creating a custom
81	process pool you can take advantage of data sharing via fork without	117	process pool you can take advantage of data sharing via fork without
…		…
86	shared and what isn't, at all times.	122	shared and what isn't, at all times.
87		123
88	=item Exec'ing a new perl process might be difficult.	124	=item Exec'ing a new perl process might be difficult.
89		125
90	For example, it is not easy to find the correct path to the perl	126	For example, it is not easy to find the correct path to the perl
91	interpreter - C<$^X> might not be a perl interpreter at all.	127	interpreter - C<$^X> might not be a perl interpreter at all. Worse, there
		128	might not even be a perl binary installed on the system.
92		129
93	This module tries hard to identify the correct path to the perl	130	This module tries hard to identify the correct path to the perl
94	interpreter. With a cooperative main program, exec'ing the interpreter	131	interpreter. With a cooperative main program, exec'ing the interpreter
95	might not even be necessary, but even without help from the main program,	132	might not even be necessary, but even without help from the main program,
96	it will still work when used from a module.	133	it will still work when used from a module.
…		…
102	and modules are no longer loadable because they refer to a different	139	and modules are no longer loadable because they refer to a different
103	perl version, or parts of a distribution are newer than the ones already	140	perl version, or parts of a distribution are newer than the ones already
104	loaded.	141	loaded.
105		142
106	This module supports creating pre-initialised perl processes to be used as	143	This module supports creating pre-initialised perl processes to be used as
107	a template for new processes.	144	a template for new processes at a later time, e.g. for use in a process
		145	pool.
108		146
109	=item Forking might be impossible when a program is running.	147	=item Forking might be impossible when a program is running.
110		148
111	For example, POSIX makes it almost impossible to fork from a	149	For example, POSIX makes it almost impossible to fork from a
112	multi-threaded program while doing anything useful in the child - in	150	multi-threaded program while doing anything useful in the child - in
113	fact, if your perl program uses POSIX threads (even indirectly via	151	fact, if your perl program uses POSIX threads (even indirectly via
114	e.g. L<IO::AIO> or L<threads>), you cannot call fork on the perl level	152	e.g. L<IO::AIO> or L<threads>), you cannot call fork on the perl level
115	anymore without risking corruption issues on a number of operating	153	anymore without risking memory corruption or worse on a number of
116	systems.	154	operating systems.
117		155
118	This module can safely fork helper processes at any time, by calling	156	This module can safely fork helper processes at any time, by calling
119	fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>).	157	fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>).
120		158
121	=item Parallel processing with fork might be inconvenient or difficult	159	=item Parallel processing with fork might be inconvenient or difficult
…		…
203	}	241	}
204	}	242	}
205		243
206	=head2 use AnyEvent::Fork as a faster fork+exec	244	=head2 use AnyEvent::Fork as a faster fork+exec
207		245
208	This runs C</bin/echo hi>, with stdandard output redirected to /tmp/log	246	This runs C</bin/echo hi>, with standard output redirected to F</tmp/log>
209	and standard error redirected to the communications socket. It is usually	247	and standard error redirected to the communications socket. It is usually
210	faster than fork+exec, but still lets you prepare the environment.	248	faster than fork+exec, but still lets you prepare the environment.
211		249
212	open my $output, ">/tmp/log" or die "$!";	250	open my $output, ">/tmp/log" or die "$!";
213		251
214	AnyEvent::Fork	252	AnyEvent::Fork
215	->new	253	->new
216	->eval ('	254	->eval ('
		255	# compile a helper function for later use
217	sub run {	256	sub run {
218	my ($fh, $output, @cmd) = @_;	257	my ($fh, $output, @cmd) = @_;
219		258
220	# perl will clear close-on-exec on STDOUT/STDERR	259	# perl will clear close-on-exec on STDOUT/STDERR
221	open STDOUT, ">&", $output or die;	260	open STDOUT, ">&", $output or die;
…		…
228	->send_arg ("/bin/echo", "hi")	267	->send_arg ("/bin/echo", "hi")
229	->run ("run", my $cv = AE::cv);	268	->run ("run", my $cv = AE::cv);
230		269
231	my $stderr = $cv->recv;	270	my $stderr = $cv->recv;
232		271
		272	=head2 For stingy users: put the worker code into a C<DATA> section.
		273
		274	When you want to be stingy with files, you can put your code into the
		275	C<DATA> section of your module (or program):
		276
		277	use AnyEvent::Fork;
		278
		279	AnyEvent::Fork
		280	->new
		281	->eval (do { local $/; <DATA> })
		282	->run ("doit", sub { ... });
		283
		284	__DATA__
		285
		286	sub doit {
		287	... do something!
		288	}
		289
		290	=head2 For stingy standalone programs: do not rely on external files at
		291	all.
		292
		293	For single-file scripts it can be inconvenient to rely on external
		294	files - even when using a C<DATA> section, you still need to C<exec> an
		295	external perl interpreter, which might not be available when using
		296	L<App::Staticperl>, L<Urlader> or L<PAR::Packer> for example.
		297
		298	Two modules help here - L<AnyEvent::Fork::Early> forks a template process
		299	for all further calls to C<new_exec>, and L<AnyEvent::Fork::Template>
		300	forks the main program as a template process.
		301
		302	Here is how your main program should look like:
		303
		304	#! perl
		305
		306	# optional, as the very first thing.
		307	# in case modules want to create their own processes.
		308	use AnyEvent::Fork::Early;
		309
		310	# next, load all modules you need in your template process
		311	use Example::My::Module
		312	use Example::Whatever;
		313
		314	# next, put your run function definition and anything else you
		315	# need, but do not use code outside of BEGIN blocks.
		316	sub worker_run {
		317	my ($fh, @args) = @_;
		318	...
		319	}
		320
		321	# now preserve everything so far as AnyEvent::Fork object
		322	# in $TEMPLATE.
		323	use AnyEvent::Fork::Template;
		324
		325	# do not put code outside of BEGIN blocks until here
		326
		327	# now use the $TEMPLATE process in any way you like
		328
		329	# for example: create 10 worker processes
		330	my @worker;
		331	my $cv = AE::cv;
		332	for (1..10) {
		333	$cv->begin;
		334	$TEMPLATE->fork->send_arg ($_)->run ("worker_run", sub {
		335	push @worker, shift;
		336	$cv->end;
		337	});
		338	}
		339	$cv->recv;
		340
233	=head1 CONCEPTS	341	=head1 CONCEPTS
234		342
235	This module can create new processes either by executing a new perl	343	This module can create new processes either by executing a new perl
236	process, or by forking from an existing "template" process.	344	process, or by forking from an existing "template" process.
		345
		346	All these processes are called "child processes" (whether they are direct
		347	children or not), while the process that manages them is called the
		348	"parent process".
237		349
238	Each such process comes with its own file handle that can be used to	350	Each such process comes with its own file handle that can be used to
239	communicate with it (it's actually a socket - one end in the new process,	351	communicate with it (it's actually a socket - one end in the new process,
240	one end in the main process), and among the things you can do in it are	352	one end in the main process), and among the things you can do in it are
241	load modules, fork new processes, send file handles to it, and execute	353	load modules, fork new processes, send file handles to it, and execute
…		…
351	use AnyEvent;	463	use AnyEvent;
352	use AnyEvent::Util ();	464	use AnyEvent::Util ();
353		465
354	use IO::FDPass;	466	use IO::FDPass;
355		467
356	our $VERSION = 0.5;	468	our $VERSION = 1.2;
357
358	our $PERL; # the path to the perl interpreter, deduces with various forms of magic
359
360	=over 4
361
362	=back
363
364	=cut
365		469
366	# the early fork template process	470	# the early fork template process
367	our $EARLY;	471	our $EARLY;
368		472
369	# the empty template process	473	# the empty template process
370	our $TEMPLATE;	474	our $TEMPLATE;
		475
		476	sub QUEUE() { 0 }
		477	sub FH() { 1 }
		478	sub WW() { 2 }
		479	sub PID() { 3 }
		480	sub CB() { 4 }
		481
		482	sub _new {
		483	my ($self, $fh, $pid) = @_;
		484
		485	AnyEvent::Util::fh_nonblocking $fh, 1;
		486
		487	$self = bless [
		488	[], # write queue - strings or fd's
		489	$fh,
		490	undef, # AE watcher
		491	$pid,
		492	], $self;
		493
		494	$self
		495	}
371		496
372	sub _cmd {	497	sub _cmd {
373	my $self = shift;	498	my $self = shift;
374		499
375	# ideally, we would want to use "a (w/a)*" as format string, but perl	500	# ideally, we would want to use "a (w/a)*" as format string, but perl
376	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack	501	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack
377	# it.	502	# it.
378	push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1];	503	push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1];
379		504
380	$self->[3] \|\|= AE::io $self->[1], 1, sub {	505	$self->[WW] \|\|= AE::io $self->[FH], 1, sub {
381	do {	506	do {
382	# send the next "thing" in the queue - either a reference to an fh,	507	# send the next "thing" in the queue - either a reference to an fh,
383	# or a plain string.	508	# or a plain string.
384		509
385	if (ref $self->[2][0]) {	510	if (ref $self->[QUEUE][0]) {
386	# send fh	511	# send fh
387	unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) {	512	unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) {
388	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	513	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
389	undef $self->[3];	514	undef $self->[WW];
390	die "AnyEvent::Fork: file descriptor send failure: $!";	515	die "AnyEvent::Fork: file descriptor send failure: $!";
391	}	516	}
392		517
393	shift @{ $self->[2] };	518	shift @{ $self->[QUEUE] };
394		519
395	} else {	520	} else {
396	# send string	521	# send string
397	my $len = syswrite $self->[1], $self->[2][0];	522	my $len = syswrite $self->[FH], $self->[QUEUE][0];
398		523
399	unless ($len) {	524	unless ($len) {
400	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	525	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
401	undef $self->[3];	526	undef $self->[WW];
402	die "AnyEvent::Fork: command write failure: $!";	527	die "AnyEvent::Fork: command write failure: $!";
403	}	528	}
404		529
405	substr $self->[2][0], 0, $len, "";	530	substr $self->[QUEUE][0], 0, $len, "";
406	shift @{ $self->[2] } unless length $self->[2][0];	531	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
407	}	532	}
408	} while @{ $self->[2] };	533	} while @{ $self->[QUEUE] };
409		534
410	# everything written	535	# everything written
411	undef $self->[3];	536	undef $self->[WW];
412		537
413	# invoke run callback, if any	538	# invoke run callback, if any
414	$self->[4]->($self->[1]) if $self->[4];	539	if ($self->[CB]) {
		540	$self->[CB]->($self->[FH]);
		541	@$self = ();
		542	}
415	};	543	};
416		544
417	() # make sure we don't leak the watcher	545	() # make sure we don't leak the watcher
418	}
419
420	sub _new {
421	my ($self, $fh, $pid) = @_;
422
423	AnyEvent::Util::fh_nonblocking $fh, 1;
424
425	$self = bless [
426	$pid,
427	$fh,
428	[], # write queue - strings or fd's
429	undef, # AE watcher
430	], $self;
431
432	$self
433	}	546	}
434		547
435	# fork template from current process, used by AnyEvent::Fork::Early/Template	548	# fork template from current process, used by AnyEvent::Fork::Early/Template
436	sub _new_fork {	549	sub _new_fork {
437	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	550	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
442	if ($pid eq 0) {	555	if ($pid eq 0) {
443	require AnyEvent::Fork::Serve;	556	require AnyEvent::Fork::Serve;
444	$AnyEvent::Fork::Serve::OWNER = $parent;	557	$AnyEvent::Fork::Serve::OWNER = $parent;
445	close $fh;	558	close $fh;
446	$0 = "$_[1] of $parent";	559	$0 = "$_[1] of $parent";
447	$SIG{CHLD} = 'IGNORE';
448	AnyEvent::Fork::Serve::serve ($slave);	560	AnyEvent::Fork::Serve::serve ($slave);
449	exit 0;	561	exit 0;
450	} elsif (!$pid) {	562	} elsif (!$pid) {
451	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";	563	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";
452	}	564	}
…		…
506		618
507	You should use C<new> whenever possible, except when having a template	619	You should use C<new> whenever possible, except when having a template
508	process around is unacceptable.	620	process around is unacceptable.
509		621
510	The path to the perl interpreter is divined using various methods - first	622	The path to the perl interpreter is divined using various methods - first
511	C<$^X> is investigated to see if the path ends with something that sounds	623	C<$^X> is investigated to see if the path ends with something that looks
512	as if it were the perl interpreter. Failing this, the module falls back to	624	as if it were the perl interpreter. Failing this, the module falls back to
513	using C<$Config::Config{perlpath}>.	625	using C<$Config::Config{perlpath}>.
514		626
		627	The path to perl can also be overriden by setting the global variable
		628	C<$AnyEvent::Fork::PERL> - it's value will be used for all subsequent
		629	invocations.
		630
515	=cut	631	=cut
		632
		633	our $PERL;
516		634
517	sub new_exec {	635	sub new_exec {
518	my ($self) = @_;	636	my ($self) = @_;
519		637
520	return $EARLY->fork	638	return $EARLY->fork
521	if $EARLY;	639	if $EARLY;
522		640
		641	unless (defined $PERL) {
523	# first find path of perl	642	# first find path of perl
524	my $perl = $;	643	my $perl = $^X;
525		644
526	# first we try $^X, but the path must be absolute (always on win32), and end in sth.	645	# first we try $^X, but the path must be absolute (always on win32), and end in sth.
527	# that looks like perl. this obviously only works for posix and win32	646	# that looks like perl. this obviously only works for posix and win32
528	unless (	647	unless (
529	($^O eq "MSWin32" \|\| $perl =~ m%^/%)	648	($^O eq "MSWin32" \|\| $perl =~ m%^/%)
530	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i	649	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i
531	) {	650	) {
532	# if it doesn't look perlish enough, try Config	651	# if it doesn't look perlish enough, try Config
533	require Config;	652	require Config;
534	$perl = $Config::Config{perlpath};	653	$perl = $Config::Config{perlpath};
535	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;	654	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;
		655	}
		656
		657	$PERL = $perl;
536	}	658	}
537		659
538	require Proc::FastSpawn;	660	require Proc::FastSpawn;
539		661
540	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	662	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
548	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;	670	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;
549	my %env = %ENV;	671	my %env = %ENV;
550	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;	672	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;
551		673
552	my $pid = Proc::FastSpawn::spawn (	674	my $pid = Proc::FastSpawn::spawn (
553	$perl,	675	$PERL,
554	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],	676	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],
555	[map "$_=$env{$_}", keys %env],	677	[map "$_=$env{$_}", keys %env],
556	) or die "unable to spawn AnyEvent::Fork server: $!";	678	) or die "unable to spawn AnyEvent::Fork server: $!";
557		679
558	$self->_new ($fh, $pid)	680	$self->_new ($fh, $pid)
559	}	681	}
560		682
561	=item $pid = $proc->pid	683	=item $pid = $proc->pid
562		684
563	Returns the process id of the process I<iff it is a direct child of the	685	Returns the process id of the process I<iff it is a direct child of the
564	process> running AnyEvent::Fork, and C<undef> otherwise.	686	process running AnyEvent::Fork>, and C<undef> otherwise. As a general
		687	rule (that you cannot rely upon), processes created via C<new_exec>,
		688	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template> are direct
		689	children, while all other processes are not.
565		690
566	Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and	691	Or in other words, you do not normally have to take care of zombies for
567	L<AnyEvent::Fork::Template> are direct children, and you are responsible	692	processes created via C<new>, but when in doubt, or zombies are a problem,
568	to clean up their zombies when they die.	693	you need to check whether a process is a diretc child by calling this
569		694	method, and possibly creating a child watcher or reap it manually.
570	All other processes are not direct children, and will be cleaned up by
571	AnyEvent::Fork itself.
572		695
573	=cut	696	=cut
574		697
575	sub pid {	698	sub pid {
576	$_[0][0]	699	$_[0][PID]
577	}	700	}
578		701
579	=item $proc = $proc->eval ($perlcode, @args)	702	=item $proc = $proc->eval ($perlcode, @args)
580		703
581	Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to	704	Evaluates the given C<$perlcode> as ... Perl code, while setting C<@_> to
582	the strings specified by C<@args>, in the "main" package.	705	the strings specified by C<@args>, in the "main" package.
583		706
584	This call is meant to do any custom initialisation that might be required	707	This call is meant to do any custom initialisation that might be required
585	(for example, the C<require> method uses it). It's not supposed to be used	708	(for example, the C<require> method uses it). It's not supposed to be used
586	to completely take over the process, use C<run> for that.	709	to completely take over the process, use C<run> for that.
587		710
588	The code will usually be executed after this call returns, and there is no	711	The code will usually be executed after this call returns, and there is no
589	way to pass anything back to the calling process. Any evaluation errors	712	way to pass anything back to the calling process. Any evaluation errors
590	will be reported to stderr and cause the process to exit.	713	will be reported to stderr and cause the process to exit.
591		714
592	If you want to execute some code to take over the process (see the	715	If you want to execute some code (that isn't in a module) to take over the
593	"fork+exec" example in the SYNOPSIS), you should compile a function via	716	process, you should compile a function via C<eval> first, and then call
594	C<eval> first, and then call it via C<run>. This also gives you access to	717	it via C<run>. This also gives you access to any arguments passed via the
595	any arguments passed via the C<send_xxx> methods, such as file handles.	718	C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as
		719	a faster fork+exec> example to see it in action.
596		720
597	Returns the process object for easy chaining of method calls.	721	Returns the process object for easy chaining of method calls.
598		722
599	=cut	723	=cut
600		724
…		…
626	=item $proc = $proc->send_fh ($handle, ...)	750	=item $proc = $proc->send_fh ($handle, ...)
627		751
628	Send one or more file handles (I<not> file descriptors) to the process,	752	Send one or more file handles (I<not> file descriptors) to the process,
629	to prepare a call to C<run>.	753	to prepare a call to C<run>.
630		754
631	The process object keeps a reference to the handles until this is done,	755	The process object keeps a reference to the handles until they have
632	so you must not explicitly close the handles. This is most easily	756	been passed over to the process, so you must not explicitly close the
633	accomplished by simply not storing the file handles anywhere after passing	757	handles. This is most easily accomplished by simply not storing the file
634	them to this method.	758	handles anywhere after passing them to this method - when AnyEvent::Fork
		759	is finished using them, perl will automatically close them.
635		760
636	Returns the process object for easy chaining of method calls.	761	Returns the process object for easy chaining of method calls.
637		762
638	Example: pass a file handle to a process, and release it without	763	Example: pass a file handle to a process, and release it without
639	closing. It will be closed automatically when it is no longer used.	764	closing. It will be closed automatically when it is no longer used.
…		…
646	sub send_fh {	771	sub send_fh {
647	my ($self, @fh) = @_;	772	my ($self, @fh) = @_;
648		773
649	for my $fh (@fh) {	774	for my $fh (@fh) {
650	$self->_cmd ("h");	775	$self->_cmd ("h");
651	push @{ $self->[2] }, \$fh;	776	push @{ $self->[QUEUE] }, \$fh;
652	}	777	}
653		778
654	$self	779	$self
655	}	780	}
656		781
657	=item $proc = $proc->send_arg ($string, ...)	782	=item $proc = $proc->send_arg ($string, ...)
658		783
659	Send one or more argument strings to the process, to prepare a call to	784	Send one or more argument strings to the process, to prepare a call to
660	C<run>. The strings can be any octet string.	785	C<run>. The strings can be any octet strings.
661		786
662	The protocol is optimised to pass a moderate number of relatively short	787	The protocol is optimised to pass a moderate number of relatively short
663	strings - while you can pass up to 4GB of data in one go, this is more	788	strings - while you can pass up to 4GB of data in one go, this is more
664	meant to pass some ID information or other startup info, not big chunks of	789	meant to pass some ID information or other startup info, not big chunks of
665	data.	790	data.
…		…
681	Enter the function specified by the function name in C<$func> in the	806	Enter the function specified by the function name in C<$func> in the
682	process. The function is called with the communication socket as first	807	process. The function is called with the communication socket as first
683	argument, followed by all file handles and string arguments sent earlier	808	argument, followed by all file handles and string arguments sent earlier
684	via C<send_fh> and C<send_arg> methods, in the order they were called.	809	via C<send_fh> and C<send_arg> methods, in the order they were called.
685		810
		811	The process object becomes unusable on return from this function - any
		812	further method calls result in undefined behaviour.
		813
686	The function name should be fully qualified, but if it isn't, it will be	814	The function name should be fully qualified, but if it isn't, it will be
687	looked up in the main package.	815	looked up in the C<main> package.
688		816
689	If the called function returns, doesn't exist, or any error occurs, the	817	If the called function returns, doesn't exist, or any error occurs, the
690	process exits.	818	process exits.
691		819
692	Preparing the process is done in the background - when all commands have	820	Preparing the process is done in the background - when all commands have
693	been sent, the callback is invoked with the local communications socket	821	been sent, the callback is invoked with the local communications socket
694	as argument. At this point you can start using the socket in any way you	822	as argument. At this point you can start using the socket in any way you
695	like.	823	like.
696		824
697	The process object becomes unusable on return from this function - any
698	further method calls result in undefined behaviour.
699
700	If the communication socket isn't used, it should be closed on both sides,	825	If the communication socket isn't used, it should be closed on both sides,
701	to save on kernel memory.	826	to save on kernel memory.
702		827
703	The socket is non-blocking in the parent, and blocking in the newly	828	The socket is non-blocking in the parent, and blocking in the newly
704	created process. The close-on-exec flag is set in both.	829	created process. The close-on-exec flag is set in both.
705		830
706	Even if not used otherwise, the socket can be a good indicator for the	831	Even if not used otherwise, the socket can be a good indicator for the
707	existence of the process - if the other process exits, you get a readable	832	existence of the process - if the other process exits, you get a readable
708	event on it, because exiting the process closes the socket (if it didn't	833	event on it, because exiting the process closes the socket (if it didn't
709	create any children using fork).	834	create any children using fork).
		835
		836	=over 4
		837
		838	=item Compatibility to L<AnyEvent::Fork::Remote>
		839
		840	If you want to write code that works with both this module and
		841	L<AnyEvent::Fork::Remote>, you need to write your code so that it assumes
		842	there are two file handles for communications, which might not be unix
		843	domain sockets. The C<run> function should start like this:
		844
		845	sub run {
		846	my ($rfh, @args) = @_; # @args is your normal arguments
		847	my $wfh = fileno $rfh ? $rfh : *STDOUT;
		848
		849	# now use $rfh for reading and $wfh for writing
		850	}
		851
		852	This checks whether the passed file handle is, in fact, the process
		853	C<STDIN> handle. If it is, then the function was invoked visa
		854	L<AnyEvent::Fork::Remote>, so STDIN should be used for reading and
		855	C<STDOUT> should be used for writing.
		856
		857	In all other cases, the function was called via this module, and there is
		858	only one file handle that should be sued for reading and writing.
		859
		860	=back
710		861
711	Example: create a template for a process pool, pass a few strings, some	862	Example: create a template for a process pool, pass a few strings, some
712	file handles, then fork, pass one more string, and run some code.	863	file handles, then fork, pass one more string, and run some code.
713		864
714	my $pool = AnyEvent::Fork	865	my $pool = AnyEvent::Fork
…		…
742	=cut	893	=cut
743		894
744	sub run {	895	sub run {
745	my ($self, $func, $cb) = @_;	896	my ($self, $func, $cb) = @_;
746		897
747	$self->[4] = $cb;	898	$self->[CB] = $cb;
748	$self->_cmd (r => $func);	899	$self->_cmd (r => $func);
		900	}
		901
		902	=back
		903
		904	=head2 EXPERIMENTAL METHODS
		905
		906	These methods might go away completely or change behaviour, at any time.
		907
		908	=over 4
		909
		910	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		911
		912	Flushes all commands out to the process and then calls the callback with
		913	the communications socket.
		914
		915	The process object becomes unusable on return from this function - any
		916	further method calls result in undefined behaviour.
		917
		918	The point of this method is to give you a file handle that you can pass
		919	to another process. In that other process, you can call C<new_from_fh
		920	AnyEvent::Fork $fh> to create a new C<AnyEvent::Fork> object from it,
		921	thereby effectively passing a fork object to another process.
		922
		923	=cut
		924
		925	sub to_fh {
		926	my ($self, $cb) = @_;
		927
		928	$self->[CB] = $cb;
		929
		930	unless ($self->[WW]) {
		931	$self->[CB]->($self->[FH]);
		932	@$self = ();
		933	}
		934	}
		935
		936	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		937
		938	Takes a file handle originally rceeived by the C<to_fh> method and creates
		939	a new C<AnyEvent:Fork> object. The child process itself will not change in
		940	any way, i.e. it will keep all the modifications done to it before calling
		941	C<to_fh>.
		942
		943	The new object is very much like the original object, except that the
		944	C<pid> method will return C<undef> even if the process is a direct child.
		945
		946	=cut
		947
		948	sub new_from_fh {
		949	my ($class, $fh) = @_;
		950
		951	$class->_new ($fh)
749	}	952	}
750		953
751	=back	954	=back
752		955
753	=head1 PERFORMANCE	956	=head1 PERFORMANCE
…		…
763		966
764	2079 new processes per second, using manual socketpair + fork	967	2079 new processes per second, using manual socketpair + fork
765		968
766	Then I did the same thing, but instead of calling fork, I called	969	Then I did the same thing, but instead of calling fork, I called
767	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the	970	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the
768	socket form the child to close on exit. This does the same thing as manual	971	socket from the child to close on exit. This does the same thing as manual
769	socket pair + fork, except that what is forked is the template process	972	socket pair + fork, except that what is forked is the template process
770	(2440kB), and the socket needs to be passed to the server at the other end	973	(2440kB), and the socket needs to be passed to the server at the other end
771	of the socket first.	974	of the socket first.
772		975
773	2307 new processes per second, using AnyEvent::Fork->new	976	2307 new processes per second, using AnyEvent::Fork->new
…		…
778	479 vfork+execs per second, using AnyEvent::Fork->new_exec	981	479 vfork+execs per second, using AnyEvent::Fork->new_exec
779		982
780	So how can C<< AnyEvent->new >> be faster than a standard fork, even	983	So how can C<< AnyEvent->new >> be faster than a standard fork, even
781	though it uses the same operations, but adds a lot of overhead?	984	though it uses the same operations, but adds a lot of overhead?
782		985
783	The difference is simply the process size: forking the 6MB process takes	986	The difference is simply the process size: forking the 5MB process takes
784	so much longer than forking the 2.5MB template process that the overhead	987	so much longer than forking the 2.5MB template process that the extra
785	introduced is canceled out.	988	overhead is canceled out.
786		989
787	If the benchmark process grows, the normal fork becomes even slower:	990	If the benchmark process grows, the normal fork becomes even slower:
788		991
789	1340 new processes, manual fork in a 20MB process	992	1340 new processes, manual fork of a 20MB process
790	731 new processes, manual fork in a 200MB process	993	731 new processes, manual fork of a 200MB process
791	235 new processes, manual fork in a 2000MB process	994	235 new processes, manual fork of a 2000MB process
792		995
793	What that means (to me) is that I can use this module without having a	996	What that means (to me) is that I can use this module without having a bad
794	very bad conscience because of the extra overhead required to start new	997	conscience because of the extra overhead required to start new processes.
795	processes.
796		998
797	=head1 TYPICAL PROBLEMS	999	=head1 TYPICAL PROBLEMS
798		1000
799	This section lists typical problems that remain. I hope by recognising	1001	This section lists typical problems that remain. I hope by recognising
800	them, most can be avoided.	1002	them, most can be avoided.
801		1003
802	=over 4	1004	=over 4
803		1005
804	=item "leaked" file descriptors for exec'ed processes	1006	=item leaked file descriptors for exec'ed processes
805		1007
806	POSIX systems inherit file descriptors by default when exec'ing a new	1008	POSIX systems inherit file descriptors by default when exec'ing a new
807	process. While perl itself laudably sets the close-on-exec flags on new	1009	process. While perl itself laudably sets the close-on-exec flags on new
808	file handles, most C libraries don't care, and even if all cared, it's	1010	file handles, most C libraries don't care, and even if all cared, it's
809	often not possible to set the flag in a race-free manner.	1011	often not possible to set the flag in a race-free manner.
…		…
829	libraries or the code that leaks those file descriptors.	1031	libraries or the code that leaks those file descriptors.
830		1032
831	Fortunately, most of these leaked descriptors do no harm, other than	1033	Fortunately, most of these leaked descriptors do no harm, other than
832	sitting on some resources.	1034	sitting on some resources.
833		1035
834	=item "leaked" file descriptors for fork'ed processes	1036	=item leaked file descriptors for fork'ed processes
835		1037
836	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,	1038	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,
837	which closes file descriptors not marked for being inherited.	1039	which closes file descriptors not marked for being inherited.
838		1040
839	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer	1041	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer
…		…
848		1050
849	The solution is to either not load these modules before use'ing	1051	The solution is to either not load these modules before use'ing
850	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay	1052	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay
851	initialising them, for example, by calling C<init Gtk2> manually.	1053	initialising them, for example, by calling C<init Gtk2> manually.
852		1054
853	=item exit runs destructors	1055	=item exiting calls object destructors
854		1056
855	This only applies to users of Lc<AnyEvent::Fork:Early> and	1057	This only applies to users of L<AnyEvent::Fork:Early> and
856	L<AnyEvent::Fork::Template>.	1058	L<AnyEvent::Fork::Template>, or when initialising code creates objects
		1059	that reference external resources.
857		1060
858	When a process created by AnyEvent::Fork exits, it might do so by calling	1061	When a process created by AnyEvent::Fork exits, it might do so by calling
859	exit, or simply letting perl reach the end of the program. At which point	1062	exit, or simply letting perl reach the end of the program. At which point
860	Perl runs all destructors.	1063	Perl runs all destructors.
861		1064
…		…
880	to make it so, mostly due to the bloody broken perl that nobody seems to	1083	to make it so, mostly due to the bloody broken perl that nobody seems to
881	care about. The fork emulation is a bad joke - I have yet to see something	1084	care about. The fork emulation is a bad joke - I have yet to see something
882	useful that you can do with it without running into memory corruption	1085	useful that you can do with it without running into memory corruption
883	issues or other braindamage. Hrrrr.	1086	issues or other braindamage. Hrrrr.
884		1087
885	Cygwin perl is not supported at the moment, as it should implement fd	1088	Since fork is endlessly broken on win32 perls (it doesn't even remotely
886	passing, but doesn't, and rolling my own is hard, as cygwin doesn't	1089	work within it's documented limits) and quite obviously it's not getting
887	support enough functionality to do it.	1090	improved any time soon, the best way to proceed on windows would be to
		1091	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1092
		1093	Cygwin perl is not supported at the moment due to some hilarious
		1094	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1095	use C<send_fh> and always use C<new_exec> to create processes, it should
		1096	work though.
		1097
		1098	=head1 USING AnyEvent::Fork IN SUBPROCESSES
		1099
		1100	AnyEvent::Fork itself cannot generally be used in subprocesses. As long as
		1101	only one process ever forks new processes, sharing the template processes
		1102	is possible (you could use a pipe as a lock by writing a byte into it to
		1103	unlock, and reading the byte to lock for example)
		1104
		1105	To make concurrent calls possible after fork, you should get rid of the
		1106	template and early fork processes. AnyEvent::Fork will create a new
		1107	template process as needed.
		1108
		1109	undef $AnyEvent::Fork::EARLY;
		1110	undef $AnyEvent::Fork::TEMPLATE;
		1111
		1112	It doesn't matter whether you get rid of them in the parent or child after
		1113	a fork.
888		1114
889	=head1 SEE ALSO	1115	=head1 SEE ALSO
890		1116
891	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),	1117	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1118	(part of this distribution).
		1119
892	L<AnyEvent::Fork::Template> (to create a process by forking the main	1120	L<AnyEvent::Fork::Template>, to create a process by forking the main
893	program at a convenient time).	1121	program at a convenient time (part of this distribution).
894		1122
895	=head1 AUTHOR	1123	L<AnyEvent::Fork::Remote>, for another way to create processes that is
		1124	mostly compatible to this module and modules building on top of it, but
		1125	works better with remote processes.
		1126
		1127	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1128
		1129	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1130
		1131	=head1 AUTHOR AND CONTACT INFORMATION
896		1132
897	Marc Lehmann <schmorp@schmorp.de>	1133	Marc Lehmann <schmorp@schmorp.de>
898	http://home.schmorp.de/	1134	http://software.schmorp.de/pkg/AnyEvent-Fork
899		1135
900	=cut	1136	=cut
901		1137
902	1	1138	1
903		1139

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.32 by root, Sat Apr 6 09:30:26 2013 UTC vs. Revision 1.63 by root, Wed Nov 26 13:36:18 2014 UTC

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Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.32 by root, Sat Apr 6 09:30:26 2013 UTC vs.
Revision 1.63 by root, Wed Nov 26 13:36:18 2014 UTC