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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.49 by root, Fri Apr 19 12:56:53 2013 UTC vs.
Revision 1.63 by root, Wed Nov 26 13:36:18 2014 UTC

…		…
38		38
39	If you need some form of RPC, you could use the L<AnyEvent::Fork::RPC>	39	If you need some form of RPC, you could use the L<AnyEvent::Fork::RPC>
40	companion module, which adds simple RPC/job queueing to a process created	40	companion module, which adds simple RPC/job queueing to a process created
41	by this module.	41	by this module.
42		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
43	Or you can implement it yourself in whatever way you like, use some	47	Or you can implement it yourself in whatever way you like: use some
44	message-passing module such as L<AnyEvent::MP>, some pipe such as	48	message-passing module such as L<AnyEvent::MP>, some pipe such as
45	L<AnyEvent::ZeroMQ>, use L<AnyEvent::Handle> on both sides to send	49	L<AnyEvent::ZeroMQ>, use L<AnyEvent::Handle> on both sides to send
46	e.g. JSON or Storable messages, and so on.	50	e.g. JSON or Storable messages, and so on.
47		51
48	=head2 COMPARISON TO OTHER MODULES	52	=head2 COMPARISON TO OTHER MODULES
…		…
52	or L<AnyEvent::Subprocess>. There are modules that implement their own	56	or L<AnyEvent::Subprocess>. There are modules that implement their own
53	process management, such as L<AnyEvent::DBI>.	57	process management, such as L<AnyEvent::DBI>.
54		58
55	The problems that all these modules try to solve are real, however, none	59	The problems that all these modules try to solve are real, however, none
56	of them (from what I have seen) tackle the very real problems of unwanted	60	of them (from what I have seen) tackle the very real problems of unwanted
57	memory sharing, efficiency, not being able to use event processing or	61	memory sharing, efficiency or not being able to use event processing, GUI
58	similar modules in the processes they create.	62	toolkits or similar modules in the processes they create.
59		63
60	This module doesn't try to replace any of them - instead it tries to solve	64	This module doesn't try to replace any of them - instead it tries to solve
61	the problem of creating processes with a minimum of fuss and overhead (and	65	the problem of creating processes with a minimum of fuss and overhead (and
62	also luxury). Ideally, most of these would use AnyEvent::Fork internally,	66	also luxury). Ideally, most of these would use AnyEvent::Fork internally,
63	except they were written before AnyEvent:Fork was available, so obviously	67	except they were written before AnyEvent:Fork was available, so obviously
…		…
85		89
86	=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
87	process.	91	process.
88		92
89	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
90	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
91	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
92	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
93	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
94	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
95	increase memory usage when freeing memory.	101	unexpectedly increase memory usage when freeing memory.
96		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
97	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
98	bad), and no sharing with exec.	113	bad), and no sharing with exec.
99		114
100	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
101	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
102	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
…		…
107	shared and what isn't, at all times.	122	shared and what isn't, at all times.
108		123
109	=item Exec'ing a new perl process might be difficult.	124	=item Exec'ing a new perl process might be difficult.
110		125
111	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
112	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.
113		129
114	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
115	interpreter. With a cooperative main program, exec'ing the interpreter	131	interpreter. With a cooperative main program, exec'ing the interpreter
116	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,
117	it will still work when used from a module.	133	it will still work when used from a module.
…		…
123	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
124	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
125	loaded.	141	loaded.
126		142
127	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
128	a template for new processes.	144	a template for new processes at a later time, e.g. for use in a process
		145	pool.
129		146
130	=item Forking might be impossible when a program is running.	147	=item Forking might be impossible when a program is running.
131		148
132	For example, POSIX makes it almost impossible to fork from a	149	For example, POSIX makes it almost impossible to fork from a
133	multi-threaded program while doing anything useful in the child - in	150	multi-threaded program while doing anything useful in the child - in
134	fact, if your perl program uses POSIX threads (even indirectly via	151	fact, if your perl program uses POSIX threads (even indirectly via
135	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
136	anymore without risking corruption issues on a number of operating	153	anymore without risking memory corruption or worse on a number of
137	systems.	154	operating systems.
138		155
139	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
140	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>).
141		158
142	=item Parallel processing with fork might be inconvenient or difficult	159	=item Parallel processing with fork might be inconvenient or difficult
…		…
250	->send_arg ("/bin/echo", "hi")	267	->send_arg ("/bin/echo", "hi")
251	->run ("run", my $cv = AE::cv);	268	->run ("run", my $cv = AE::cv);
252		269
253	my $stderr = $cv->recv;	270	my $stderr = $cv->recv;
254		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
255	=head1 CONCEPTS	341	=head1 CONCEPTS
256		342
257	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
258	process, or by forking from an existing "template" process.	344	process, or by forking from an existing "template" process.
259		345
…		…
377	use AnyEvent;	463	use AnyEvent;
378	use AnyEvent::Util ();	464	use AnyEvent::Util ();
379		465
380	use IO::FDPass;	466	use IO::FDPass;
381		467
382	our $VERSION = 0.7;	468	our $VERSION = 1.2;
383		469
384	# the early fork template process	470	# the early fork template process
385	our $EARLY;	471	our $EARLY;
386		472
387	# the empty template process	473	# the empty template process
…		…
435	# send string	521	# send string
436	my $len = syswrite $self->[FH], $self->[QUEUE][0];	522	my $len = syswrite $self->[FH], $self->[QUEUE][0];
437		523
438	unless ($len) {	524	unless ($len) {
439	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	525	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
440	undef $self->[3];	526	undef $self->[WW];
441	die "AnyEvent::Fork: command write failure: $!";	527	die "AnyEvent::Fork: command write failure: $!";
442	}	528	}
443		529
444	substr $self->[QUEUE][0], 0, $len, "";	530	substr $self->[QUEUE][0], 0, $len, "";
445	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];	531	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
…		…
532		618
533	You should use C<new> whenever possible, except when having a template	619	You should use C<new> whenever possible, except when having a template
534	process around is unacceptable.	620	process around is unacceptable.
535		621
536	The path to the perl interpreter is divined using various methods - first	622	The path to the perl interpreter is divined using various methods - first
537	C<$^X> is investigated to see if the path ends with something that sounds	623	C<$^X> is investigated to see if the path ends with something that looks
538	as if it were the perl interpreter. Failing this, the module falls back to	624	as if it were the perl interpreter. Failing this, the module falls back to
539	using C<$Config::Config{perlpath}>.	625	using C<$Config::Config{perlpath}>.
540		626
		627	The path to perl can also be overriden by setting the global variable
		628	C<$AnyEvent::Fork::PERL> - it's value will be used for all subsequent
		629	invocations.
		630
541	=cut	631	=cut
		632
		633	our $PERL;
542		634
543	sub new_exec {	635	sub new_exec {
544	my ($self) = @_;	636	my ($self) = @_;
545		637
546	return $EARLY->fork	638	return $EARLY->fork
547	if $EARLY;	639	if $EARLY;
548		640
		641	unless (defined $PERL) {
549	# first find path of perl	642	# first find path of perl
550	my $perl = $;	643	my $perl = $^X;
551		644
552	# first we try $^X, but the path must be absolute (always on win32), and end in sth.	645	# first we try $^X, but the path must be absolute (always on win32), and end in sth.
553	# that looks like perl. this obviously only works for posix and win32	646	# that looks like perl. this obviously only works for posix and win32
554	unless (	647	unless (
555	($^O eq "MSWin32" \|\| $perl =~ m%^/%)	648	($^O eq "MSWin32" \|\| $perl =~ m%^/%)
556	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i	649	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i
557	) {	650	) {
558	# if it doesn't look perlish enough, try Config	651	# if it doesn't look perlish enough, try Config
559	require Config;	652	require Config;
560	$perl = $Config::Config{perlpath};	653	$perl = $Config::Config{perlpath};
561	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;	654	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;
		655	}
		656
		657	$PERL = $perl;
562	}	658	}
563		659
564	require Proc::FastSpawn;	660	require Proc::FastSpawn;
565		661
566	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	662	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
574	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;	670	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;
575	my %env = %ENV;	671	my %env = %ENV;
576	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;	672	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;
577		673
578	my $pid = Proc::FastSpawn::spawn (	674	my $pid = Proc::FastSpawn::spawn (
579	$perl,	675	$PERL,
580	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],	676	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],
581	[map "$_=$env{$_}", keys %env],	677	[map "$_=$env{$_}", keys %env],
582	) or die "unable to spawn AnyEvent::Fork server: $!";	678	) or die "unable to spawn AnyEvent::Fork server: $!";
583		679
584	$self->_new ($fh, $pid)	680	$self->_new ($fh, $pid)
585	}	681	}
586		682
587	=item $pid = $proc->pid	683	=item $pid = $proc->pid
588		684
589	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
590	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.
591		690
592	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
593	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,
594	to clean up their zombies when they die.	693	you need to check whether a process is a diretc child by calling this
595		694	method, and possibly creating a child watcher or reap it manually.
596	All other processes are not direct children, and will be cleaned up by
597	AnyEvent::Fork itself.
598		695
599	=cut	696	=cut
600		697
601	sub pid {	698	sub pid {
602	$_[0][PID]	699	$_[0][PID]
…		…
733		830
734	Even if not used otherwise, the socket can be a good indicator for the	831	Even if not used otherwise, the socket can be a good indicator for the
735	existence of the process - if the other process exits, you get a readable	832	existence of the process - if the other process exits, you get a readable
736	event on it, because exiting the process closes the socket (if it didn't	833	event on it, because exiting the process closes the socket (if it didn't
737	create any children using fork).	834	create any children using fork).
		835
		836	=over 4
		837
		838	=item Compatibility to L<AnyEvent::Fork::Remote>
		839
		840	If you want to write code that works with both this module and
		841	L<AnyEvent::Fork::Remote>, you need to write your code so that it assumes
		842	there are two file handles for communications, which might not be unix
		843	domain sockets. The C<run> function should start like this:
		844
		845	sub run {
		846	my ($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
738		861
739	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
740	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.
741		864
742	my $pool = AnyEvent::Fork	865	my $pool = AnyEvent::Fork
…		…
774		897
775	$self->[CB] = $cb;	898	$self->[CB] = $cb;
776	$self->_cmd (r => $func);	899	$self->_cmd (r => $func);
777	}	900	}
778		901
779	=item $proc->to_fh ($cb->($fh))	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
780		911
781	Flushes all commands out to the process and then calls the callback with	912	Flushes all commands out to the process and then calls the callback with
782	the communications socket.	913	the communications socket.
783		914
784	The process object becomes unusable on return from this function - any	915	The process object becomes unusable on return from this function - any
785	further method calls result in undefined behaviour.	916	further method calls result in undefined behaviour.
786		917
787	The point of this method is to give you a file handle thta you cna pass	918	The point of this method is to give you a file handle that you can pass
788	to another process. In that other process, you can call C<new_from_fh	919	to another process. In that other process, you can call C<new_from_fh
789	AnyEvent::Fork::RPC> to create a new C<AnyEvent::Fork> object from it,	920	AnyEvent::Fork $fh> to create a new C<AnyEvent::Fork> object from it,
790	thereby effectively passing a fork object to another process.	921	thereby effectively passing a fork object to another process.
791		922
792	=cut	923	=cut
793		924
794	sub to_fh {	925	sub to_fh {
…		…
800	$self->[CB]->($self->[FH]);	931	$self->[CB]->($self->[FH]);
801	@$self = ();	932	@$self = ();
802	}	933	}
803	}	934	}
804		935
805	=item new_from_fh AnyEvent::Fork $fh	936	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
806		937
807	Takes a file handle originally rceeived by the C<to_fh> method and creates	938	Takes a file handle originally rceeived by the C<to_fh> method and creates
808	a new C<AnyEvent:Fork> object. The child process itself will not change in	939	a new C<AnyEvent:Fork> object. The child process itself will not change in
809	any way, i.e. it will keep all the modifications done to it before calling	940	any way, i.e. it will keep all the modifications done to it before calling
810	C<to_fh>.	941	C<to_fh>.
…		…
962	Cygwin perl is not supported at the moment due to some hilarious	1093	Cygwin perl is not supported at the moment due to some hilarious
963	shortcomings of its API - see L<IO::FDPoll> for more details. If you never	1094	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
964	use C<send_fh> and always use C<new_exec> to create processes, it should	1095	use C<send_fh> and always use C<new_exec> to create processes, it should
965	work though.	1096	work though.
966		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.
		1114
967	=head1 SEE ALSO	1115	=head1 SEE ALSO
968		1116
969	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all	1117	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
970	(part of this distribution).	1118	(part of this distribution).
971		1119
972	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
973	program at a convenient time (part of this distribution).	1121	program at a convenient time (part of this distribution).
974		1122
		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
975	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).	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).
976		1130
977	=head1 AUTHOR AND CONTACT INFORMATION	1131	=head1 AUTHOR AND CONTACT INFORMATION
978		1132
979	Marc Lehmann <schmorp@schmorp.de>	1133	Marc Lehmann <schmorp@schmorp.de>
980	http://software.schmorp.de/pkg/AnyEvent-Fork	1134	http://software.schmorp.de/pkg/AnyEvent-Fork

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.49 by root, Fri Apr 19 12:56:53 2013 UTC vs. Revision 1.63 by root, Wed Nov 26 13:36:18 2014 UTC

Diff Legend

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.49 by root, Fri Apr 19 12:56:53 2013 UTC vs.
Revision 1.63 by root, Wed Nov 26 13:36:18 2014 UTC