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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.31 by root, Sat Apr 6 09:29:26 2013 UTC vs.
Revision 1.64 by root, Wed Nov 26 13:37:40 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
…		…
140		178
141	=back	179	=back
142		180
143	=head1 EXAMPLES	181	=head1 EXAMPLES
144		182
		183	This is where the wall of text ends and code speaks.
		184
145	=head2 Create a single new process, tell it to run your worker function.	185	=head2 Create a single new process, tell it to run your worker function.
146		186
147	AnyEvent::Fork	187	AnyEvent::Fork
148	->new	188	->new
149	->require ("MyModule")	189	->require ("MyModule")
…		…
152		192
153	# now $master_filehandle is connected to the	193	# now $master_filehandle is connected to the
154	# $slave_filehandle in the new process.	194	# $slave_filehandle in the new process.
155	});	195	});
156		196
157	MyModule might look like this:	197	C<MyModule> might look like this:
158		198
159	package MyModule;	199	package MyModule;
160		200
161	sub worker {	201	sub worker {
162	my ($slave_filehandle) = @_;	202	my ($slave_filehandle) = @_;
…		…
185	}	225	}
186		226
187	# now do other things - maybe use the filehandle provided by run	227	# now do other things - maybe use the filehandle provided by run
188	# to wait for the processes to die. or whatever.	228	# to wait for the processes to die. or whatever.
189		229
190	My::Server might look like this:	230	C<My::Server> might look like this:
191		231
192	package My::Server;	232	package My::Server;
193		233
194	sub run {	234	sub run {
195	my ($slave, $listener, $id) = @_;	235	my ($slave, $listener, $id) = @_;
…		…
203	}	243	}
204	}	244	}
205		245
206	=head2 use AnyEvent::Fork as a faster fork+exec	246	=head2 use AnyEvent::Fork as a faster fork+exec
207		247
208	This runs /bin/echo hi, with stdout redirected to /tmp/log and stderr to	248	This runs C</bin/echo hi>, with standard output redirected to F</tmp/log>
209	the communications socket. It is usually faster than fork+exec, but still	249	and standard error redirected to the communications socket. It is usually
210	let's you prepare the environment.	250	faster than fork+exec, but still lets you prepare the environment.
211		251
212	open my $output, ">/tmp/log" or die "$!";	252	open my $output, ">/tmp/log" or die "$!";
213		253
214	AnyEvent::Fork	254	AnyEvent::Fork
215	->new	255	->new
216	->eval ('	256	->eval ('
		257	# compile a helper function for later use
217	sub run {	258	sub run {
218	my ($fh, $output, @cmd) = @_;	259	my ($fh, $output, @cmd) = @_;
219		260
220	# perl will clear close-on-exec on STDOUT/STDERR	261	# perl will clear close-on-exec on STDOUT/STDERR
221	open STDOUT, ">&", $output or die;	262	open STDOUT, ">&", $output or die;
…		…
228	->send_arg ("/bin/echo", "hi")	269	->send_arg ("/bin/echo", "hi")
229	->run ("run", my $cv = AE::cv);	270	->run ("run", my $cv = AE::cv);
230		271
231	my $stderr = $cv->recv;	272	my $stderr = $cv->recv;
232		273
		274	=head2 For stingy users: put the worker code into a C<DATA> section.
		275
		276	When you want to be stingy with files, you can put your code into the
		277	C<DATA> section of your module (or program):
		278
		279	use AnyEvent::Fork;
		280
		281	AnyEvent::Fork
		282	->new
		283	->eval (do { local $/; <DATA> })
		284	->run ("doit", sub { ... });
		285
		286	__DATA__
		287
		288	sub doit {
		289	... do something!
		290	}
		291
		292	=head2 For stingy standalone programs: do not rely on external files at
		293	all.
		294
		295	For single-file scripts it can be inconvenient to rely on external
		296	files - even when using a C<DATA> section, you still need to C<exec> an
		297	external perl interpreter, which might not be available when using
		298	L<App::Staticperl>, L<Urlader> or L<PAR::Packer> for example.
		299
		300	Two modules help here - L<AnyEvent::Fork::Early> forks a template process
		301	for all further calls to C<new_exec>, and L<AnyEvent::Fork::Template>
		302	forks the main program as a template process.
		303
		304	Here is how your main program should look like:
		305
		306	#! perl
		307
		308	# optional, as the very first thing.
		309	# in case modules want to create their own processes.
		310	use AnyEvent::Fork::Early;
		311
		312	# next, load all modules you need in your template process
		313	use Example::My::Module
		314	use Example::Whatever;
		315
		316	# next, put your run function definition and anything else you
		317	# need, but do not use code outside of BEGIN blocks.
		318	sub worker_run {
		319	my ($fh, @args) = @_;
		320	...
		321	}
		322
		323	# now preserve everything so far as AnyEvent::Fork object
		324	# in $TEMPLATE.
		325	use AnyEvent::Fork::Template;
		326
		327	# do not put code outside of BEGIN blocks until here
		328
		329	# now use the $TEMPLATE process in any way you like
		330
		331	# for example: create 10 worker processes
		332	my @worker;
		333	my $cv = AE::cv;
		334	for (1..10) {
		335	$cv->begin;
		336	$TEMPLATE->fork->send_arg ($_)->run ("worker_run", sub {
		337	push @worker, shift;
		338	$cv->end;
		339	});
		340	}
		341	$cv->recv;
		342
233	=head1 CONCEPTS	343	=head1 CONCEPTS
234		344
235	This module can create new processes either by executing a new perl	345	This module can create new processes either by executing a new perl
236	process, or by forking from an existing "template" process.	346	process, or by forking from an existing "template" process.
		347
		348	All these processes are called "child processes" (whether they are direct
		349	children or not), while the process that manages them is called the
		350	"parent process".
237		351
238	Each such process comes with its own file handle that can be used to	352	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,	353	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	354	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	355	load modules, fork new processes, send file handles to it, and execute
…		…
351	use AnyEvent;	465	use AnyEvent;
352	use AnyEvent::Util ();	466	use AnyEvent::Util ();
353		467
354	use IO::FDPass;	468	use IO::FDPass;
355		469
356	our $VERSION = 0.5;	470	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		471
366	# the early fork template process	472	# the early fork template process
367	our $EARLY;	473	our $EARLY;
368		474
369	# the empty template process	475	# the empty template process
370	our $TEMPLATE;	476	our $TEMPLATE;
		477
		478	sub QUEUE() { 0 }
		479	sub FH() { 1 }
		480	sub WW() { 2 }
		481	sub PID() { 3 }
		482	sub CB() { 4 }
		483
		484	sub _new {
		485	my ($self, $fh, $pid) = @_;
		486
		487	AnyEvent::Util::fh_nonblocking $fh, 1;
		488
		489	$self = bless [
		490	[], # write queue - strings or fd's
		491	$fh,
		492	undef, # AE watcher
		493	$pid,
		494	], $self;
		495
		496	$self
		497	}
371		498
372	sub _cmd {	499	sub _cmd {
373	my $self = shift;	500	my $self = shift;
374		501
375	# ideally, we would want to use "a (w/a)*" as format string, but perl	502	# 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	503	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack
377	# it.	504	# it.
378	push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1];	505	push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1];
379		506
380	$self->[3] \|\|= AE::io $self->[1], 1, sub {	507	$self->[WW] \|\|= AE::io $self->[FH], 1, sub {
381	do {	508	do {
382	# send the next "thing" in the queue - either a reference to an fh,	509	# send the next "thing" in the queue - either a reference to an fh,
383	# or a plain string.	510	# or a plain string.
384		511
385	if (ref $self->[2][0]) {	512	if (ref $self->[QUEUE][0]) {
386	# send fh	513	# send fh
387	unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) {	514	unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) {
388	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	515	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
389	undef $self->[3];	516	undef $self->[WW];
390	die "AnyEvent::Fork: file descriptor send failure: $!";	517	die "AnyEvent::Fork: file descriptor send failure: $!";
391	}	518	}
392		519
393	shift @{ $self->[2] };	520	shift @{ $self->[QUEUE] };
394		521
395	} else {	522	} else {
396	# send string	523	# send string
397	my $len = syswrite $self->[1], $self->[2][0];	524	my $len = syswrite $self->[FH], $self->[QUEUE][0];
398		525
399	unless ($len) {	526	unless ($len) {
400	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	527	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
401	undef $self->[3];	528	undef $self->[WW];
402	die "AnyEvent::Fork: command write failure: $!";	529	die "AnyEvent::Fork: command write failure: $!";
403	}	530	}
404		531
405	substr $self->[2][0], 0, $len, "";	532	substr $self->[QUEUE][0], 0, $len, "";
406	shift @{ $self->[2] } unless length $self->[2][0];	533	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
407	}	534	}
408	} while @{ $self->[2] };	535	} while @{ $self->[QUEUE] };
409		536
410	# everything written	537	# everything written
411	undef $self->[3];	538	undef $self->[WW];
412		539
413	# invoke run callback, if any	540	# invoke run callback, if any
414	$self->[4]->($self->[1]) if $self->[4];	541	if ($self->[CB]) {
		542	$self->[CB]->($self->[FH]);
		543	@$self = ();
		544	}
415	};	545	};
416		546
417	() # make sure we don't leak the watcher	547	() # make sure we don't leak the watcher
418	}
419
420	sub _new {
421	my ($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	$self
433	}	548	}
434		549
435	# fork template from current process, used by AnyEvent::Fork::Early/Template	550	# fork template from current process, used by AnyEvent::Fork::Early/Template
436	sub _new_fork {	551	sub _new_fork {
437	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	552	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
442	if ($pid eq 0) {	557	if ($pid eq 0) {
443	require AnyEvent::Fork::Serve;	558	require AnyEvent::Fork::Serve;
444	$AnyEvent::Fork::Serve::OWNER = $parent;	559	$AnyEvent::Fork::Serve::OWNER = $parent;
445	close $fh;	560	close $fh;
446	$0 = "$_[1] of $parent";	561	$0 = "$_[1] of $parent";
447	$SIG{CHLD} = 'IGNORE';
448	AnyEvent::Fork::Serve::serve ($slave);	562	AnyEvent::Fork::Serve::serve ($slave);
449	exit 0;	563	exit 0;
450	} elsif (!$pid) {	564	} elsif (!$pid) {
451	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";	565	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";
452	}	566	}
…		…
506		620
507	You should use C<new> whenever possible, except when having a template	621	You should use C<new> whenever possible, except when having a template
508	process around is unacceptable.	622	process around is unacceptable.
509		623
510	The path to the perl interpreter is divined using various methods - first	624	The path to the perl interpreter is divined using various methods - first
511	C<$^X> is investigated to see if the path ends with something that sounds	625	C<$^X> is investigated to see if the path ends with something that looks
512	as if it were the perl interpreter. Failing this, the module falls back to	626	as if it were the perl interpreter. Failing this, the module falls back to
513	using C<$Config::Config{perlpath}>.	627	using C<$Config::Config{perlpath}>.
514		628
		629	The path to perl can also be overriden by setting the global variable
		630	C<$AnyEvent::Fork::PERL> - it's value will be used for all subsequent
		631	invocations.
		632
515	=cut	633	=cut
		634
		635	our $PERL;
516		636
517	sub new_exec {	637	sub new_exec {
518	my ($self) = @_;	638	my ($self) = @_;
519		639
520	return $EARLY->fork	640	return $EARLY->fork
521	if $EARLY;	641	if $EARLY;
522		642
		643	unless (defined $PERL) {
523	# first find path of perl	644	# first find path of perl
524	my $perl = $;	645	my $perl = $^X;
525		646
526	# first we try $^X, but the path must be absolute (always on win32), and end in sth.	647	# first we try $^X, but the path must be absolute (always on win32), and end in sth.
527	# that looks like perl. this obviously only works for posix and win32	648	# that looks like perl. this obviously only works for posix and win32
528	unless (	649	unless (
529	($^O eq "MSWin32" \|\| $perl =~ m%^/%)	650	($^O eq "MSWin32" \|\| $perl =~ m%^/%)
530	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i	651	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i
531	) {	652	) {
532	# if it doesn't look perlish enough, try Config	653	# if it doesn't look perlish enough, try Config
533	require Config;	654	require Config;
534	$perl = $Config::Config{perlpath};	655	$perl = $Config::Config{perlpath};
535	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;	656	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;
		657	}
		658
		659	$PERL = $perl;
536	}	660	}
537		661
538	require Proc::FastSpawn;	662	require Proc::FastSpawn;
539		663
540	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	664	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
548	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;	672	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;
549	my %env = %ENV;	673	my %env = %ENV;
550	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;	674	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;
551		675
552	my $pid = Proc::FastSpawn::spawn (	676	my $pid = Proc::FastSpawn::spawn (
553	$perl,	677	$PERL,
554	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],	678	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],
555	[map "$_=$env{$_}", keys %env],	679	[map "$_=$env{$_}", keys %env],
556	) or die "unable to spawn AnyEvent::Fork server: $!";	680	) or die "unable to spawn AnyEvent::Fork server: $!";
557		681
558	$self->_new ($fh, $pid)	682	$self->_new ($fh, $pid)
559	}	683	}
560		684
561	=item $pid = $proc->pid	685	=item $pid = $proc->pid
562		686
563	Returns the process id of the process I<iff it is a direct child of the	687	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.	688	process running AnyEvent::Fork>, and C<undef> otherwise. As a general
		689	rule (that you cannot rely upon), processes created via C<new_exec>,
		690	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template> are direct
		691	children, while all other processes are not.
565		692
566	Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and	693	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	694	processes created via C<new>, but when in doubt, or zombies are a problem,
568	to clean up their zombies when they die.	695	you need to check whether a process is a diretc child by calling this
569		696	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		697
573	=cut	698	=cut
574		699
575	sub pid {	700	sub pid {
576	$_[0][0]	701	$_[0][PID]
577	}	702	}
578		703
579	=item $proc = $proc->eval ($perlcode, @args)	704	=item $proc = $proc->eval ($perlcode, @args)
580		705
581	Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to	706	Evaluates the given C<$perlcode> as ... Perl code, while setting C<@_> to
582	the strings specified by C<@args>, in the "main" package.	707	the strings specified by C<@args>, in the "main" package.
583		708
584	This call is meant to do any custom initialisation that might be required	709	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	710	(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.	711	to completely take over the process, use C<run> for that.
587		712
588	The code will usually be executed after this call returns, and there is no	713	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	714	way to pass anything back to the calling process. Any evaluation errors
590	will be reported to stderr and cause the process to exit.	715	will be reported to stderr and cause the process to exit.
591		716
592	If you want to execute some code to take over the process (see the	717	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	718	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	719	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.	720	C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as
		721	a faster fork+exec> example to see it in action.
596		722
597	Returns the process object for easy chaining of method calls.	723	Returns the process object for easy chaining of method calls.
598		724
599	=cut	725	=cut
600		726
…		…
626	=item $proc = $proc->send_fh ($handle, ...)	752	=item $proc = $proc->send_fh ($handle, ...)
627		753
628	Send one or more file handles (I<not> file descriptors) to the process,	754	Send one or more file handles (I<not> file descriptors) to the process,
629	to prepare a call to C<run>.	755	to prepare a call to C<run>.
630		756
631	The process object keeps a reference to the handles until this is done,	757	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	758	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	759	handles. This is most easily accomplished by simply not storing the file
634	them to this method.	760	handles anywhere after passing them to this method - when AnyEvent::Fork
		761	is finished using them, perl will automatically close them.
635		762
636	Returns the process object for easy chaining of method calls.	763	Returns the process object for easy chaining of method calls.
637		764
638	Example: pass a file handle to a process, and release it without	765	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.	766	closing. It will be closed automatically when it is no longer used.
…		…
646	sub send_fh {	773	sub send_fh {
647	my ($self, @fh) = @_;	774	my ($self, @fh) = @_;
648		775
649	for my $fh (@fh) {	776	for my $fh (@fh) {
650	$self->_cmd ("h");	777	$self->_cmd ("h");
651	push @{ $self->[2] }, \$fh;	778	push @{ $self->[QUEUE] }, \$fh;
652	}	779	}
653		780
654	$self	781	$self
655	}	782	}
656		783
657	=item $proc = $proc->send_arg ($string, ...)	784	=item $proc = $proc->send_arg ($string, ...)
658		785
659	Send one or more argument strings to the process, to prepare a call to	786	Send one or more argument strings to the process, to prepare a call to
660	C<run>. The strings can be any octet string.	787	C<run>. The strings can be any octet strings.
661		788
662	The protocol is optimised to pass a moderate number of relatively short	789	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	790	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	791	meant to pass some ID information or other startup info, not big chunks of
665	data.	792	data.
…		…
681	Enter the function specified by the function name in C<$func> in the	808	Enter the function specified by the function name in C<$func> in the
682	process. The function is called with the communication socket as first	809	process. The function is called with the communication socket as first
683	argument, followed by all file handles and string arguments sent earlier	810	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.	811	via C<send_fh> and C<send_arg> methods, in the order they were called.
685		812
		813	The process object becomes unusable on return from this function - any
		814	further method calls result in undefined behaviour.
		815
686	The function name should be fully qualified, but if it isn't, it will be	816	The function name should be fully qualified, but if it isn't, it will be
687	looked up in the main package.	817	looked up in the C<main> package.
688		818
689	If the called function returns, doesn't exist, or any error occurs, the	819	If the called function returns, doesn't exist, or any error occurs, the
690	process exits.	820	process exits.
691		821
692	Preparing the process is done in the background - when all commands have	822	Preparing the process is done in the background - when all commands have
693	been sent, the callback is invoked with the local communications socket	823	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	824	as argument. At this point you can start using the socket in any way you
695	like.	825	like.
696		826
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,	827	If the communication socket isn't used, it should be closed on both sides,
701	to save on kernel memory.	828	to save on kernel memory.
702		829
703	The socket is non-blocking in the parent, and blocking in the newly	830	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.	831	created process. The close-on-exec flag is set in both.
705		832
706	Even if not used otherwise, the socket can be a good indicator for the	833	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	834	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	835	event on it, because exiting the process closes the socket (if it didn't
709	create any children using fork).	836	create any children using fork).
		837
		838	=over 4
		839
		840	=item Compatibility to L<AnyEvent::Fork::Remote>
		841
		842	If you want to write code that works with both this module and
		843	L<AnyEvent::Fork::Remote>, you need to write your code so that it assumes
		844	there are two file handles for communications, which might not be unix
		845	domain sockets. The C<run> function should start like this:
		846
		847	sub run {
		848	my ($rfh, @args) = @_; # @args is your normal arguments
		849	my $wfh = fileno $rfh ? $rfh : *STDOUT;
		850
		851	# now use $rfh for reading and $wfh for writing
		852	}
		853
		854	This checks whether the passed file handle is, in fact, the process
		855	C<STDIN> handle. If it is, then the function was invoked visa
		856	L<AnyEvent::Fork::Remote>, so STDIN should be used for reading and
		857	C<STDOUT> should be used for writing.
		858
		859	In all other cases, the function was called via this module, and there is
		860	only one file handle that should be sued for reading and writing.
		861
		862	=back
710		863
711	Example: create a template for a process pool, pass a few strings, some	864	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.	865	file handles, then fork, pass one more string, and run some code.
713		866
714	my $pool = AnyEvent::Fork	867	my $pool = AnyEvent::Fork
…		…
742	=cut	895	=cut
743		896
744	sub run {	897	sub run {
745	my ($self, $func, $cb) = @_;	898	my ($self, $func, $cb) = @_;
746		899
747	$self->[4] = $cb;	900	$self->[CB] = $cb;
748	$self->_cmd (r => $func);	901	$self->_cmd (r => $func);
		902	}
		903
		904	=back
		905
		906	=head2 EXPERIMENTAL METHODS
		907
		908	These methods might go away completely or change behaviour, at any time.
		909
		910	=over 4
		911
		912	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		913
		914	Flushes all commands out to the process and then calls the callback with
		915	the communications socket.
		916
		917	The process object becomes unusable on return from this function - any
		918	further method calls result in undefined behaviour.
		919
		920	The point of this method is to give you a file handle that you can pass
		921	to another process. In that other process, you can call C<new_from_fh
		922	AnyEvent::Fork $fh> to create a new C<AnyEvent::Fork> object from it,
		923	thereby effectively passing a fork object to another process.
		924
		925	=cut
		926
		927	sub to_fh {
		928	my ($self, $cb) = @_;
		929
		930	$self->[CB] = $cb;
		931
		932	unless ($self->[WW]) {
		933	$self->[CB]->($self->[FH]);
		934	@$self = ();
		935	}
		936	}
		937
		938	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		939
		940	Takes a file handle originally rceeived by the C<to_fh> method and creates
		941	a new C<AnyEvent:Fork> object. The child process itself will not change in
		942	any way, i.e. it will keep all the modifications done to it before calling
		943	C<to_fh>.
		944
		945	The new object is very much like the original object, except that the
		946	C<pid> method will return C<undef> even if the process is a direct child.
		947
		948	=cut
		949
		950	sub new_from_fh {
		951	my ($class, $fh) = @_;
		952
		953	$class->_new ($fh)
749	}	954	}
750		955
751	=back	956	=back
752		957
753	=head1 PERFORMANCE	958	=head1 PERFORMANCE
…		…
763		968
764	2079 new processes per second, using manual socketpair + fork	969	2079 new processes per second, using manual socketpair + fork
765		970
766	Then I did the same thing, but instead of calling fork, I called	971	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	972	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	973	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	974	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	975	(2440kB), and the socket needs to be passed to the server at the other end
771	of the socket first.	976	of the socket first.
772		977
773	2307 new processes per second, using AnyEvent::Fork->new	978	2307 new processes per second, using AnyEvent::Fork->new
…		…
778	479 vfork+execs per second, using AnyEvent::Fork->new_exec	983	479 vfork+execs per second, using AnyEvent::Fork->new_exec
779		984
780	So how can C<< AnyEvent->new >> be faster than a standard fork, even	985	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?	986	though it uses the same operations, but adds a lot of overhead?
782		987
783	The difference is simply the process size: forking the 6MB process takes	988	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	989	so much longer than forking the 2.5MB template process that the extra
785	introduced is canceled out.	990	overhead is canceled out.
786		991
787	If the benchmark process grows, the normal fork becomes even slower:	992	If the benchmark process grows, the normal fork becomes even slower:
788		993
789	1340 new processes, manual fork in a 20MB process	994	1340 new processes, manual fork of a 20MB process
790	731 new processes, manual fork in a 200MB process	995	731 new processes, manual fork of a 200MB process
791	235 new processes, manual fork in a 2000MB process	996	235 new processes, manual fork of a 2000MB process
792		997
793	What that means (to me) is that I can use this module without having a	998	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	999	conscience because of the extra overhead required to start new processes.
795	processes.
796		1000
797	=head1 TYPICAL PROBLEMS	1001	=head1 TYPICAL PROBLEMS
798		1002
799	This section lists typical problems that remain. I hope by recognising	1003	This section lists typical problems that remain. I hope by recognising
800	them, most can be avoided.	1004	them, most can be avoided.
801		1005
802	=over 4	1006	=over 4
803		1007
804	=item "leaked" file descriptors for exec'ed processes	1008	=item leaked file descriptors for exec'ed processes
805		1009
806	POSIX systems inherit file descriptors by default when exec'ing a new	1010	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	1011	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	1012	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.	1013	often not possible to set the flag in a race-free manner.
…		…
829	libraries or the code that leaks those file descriptors.	1033	libraries or the code that leaks those file descriptors.
830		1034
831	Fortunately, most of these leaked descriptors do no harm, other than	1035	Fortunately, most of these leaked descriptors do no harm, other than
832	sitting on some resources.	1036	sitting on some resources.
833		1037
834	=item "leaked" file descriptors for fork'ed processes	1038	=item leaked file descriptors for fork'ed processes
835		1039
836	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,	1040	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,
837	which closes file descriptors not marked for being inherited.	1041	which closes file descriptors not marked for being inherited.
838		1042
839	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer	1043	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer
…		…
848		1052
849	The solution is to either not load these modules before use'ing	1053	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	1054	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay
851	initialising them, for example, by calling C<init Gtk2> manually.	1055	initialising them, for example, by calling C<init Gtk2> manually.
852		1056
853	=item exit runs destructors	1057	=item exiting calls object destructors
854		1058
855	This only applies to users of Lc<AnyEvent::Fork:Early> and	1059	This only applies to users of L<AnyEvent::Fork:Early> and
856	L<AnyEvent::Fork::Template>.	1060	L<AnyEvent::Fork::Template>, or when initialising code creates objects
		1061	that reference external resources.
857		1062
858	When a process created by AnyEvent::Fork exits, it might do so by calling	1063	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	1064	exit, or simply letting perl reach the end of the program. At which point
860	Perl runs all destructors.	1065	Perl runs all destructors.
861		1066
…		…
880	to make it so, mostly due to the bloody broken perl that nobody seems to	1085	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	1086	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	1087	useful that you can do with it without running into memory corruption
883	issues or other braindamage. Hrrrr.	1088	issues or other braindamage. Hrrrr.
884		1089
885	Cygwin perl is not supported at the moment, as it should implement fd	1090	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	1091	work within it's documented limits) and quite obviously it's not getting
887	support enough functionality to do it.	1092	improved any time soon, the best way to proceed on windows would be to
		1093	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1094
		1095	Cygwin perl is not supported at the moment due to some hilarious
		1096	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1097	use C<send_fh> and always use C<new_exec> to create processes, it should
		1098	work though.
		1099
		1100	=head1 USING AnyEvent::Fork IN SUBPROCESSES
		1101
		1102	AnyEvent::Fork itself cannot generally be used in subprocesses. As long as
		1103	only one process ever forks new processes, sharing the template processes
		1104	is possible (you could use a pipe as a lock by writing a byte into it to
		1105	unlock, and reading the byte to lock for example)
		1106
		1107	To make concurrent calls possible after fork, you should get rid of the
		1108	template and early fork processes. AnyEvent::Fork will create a new
		1109	template process as needed.
		1110
		1111	undef $AnyEvent::Fork::EARLY;
		1112	undef $AnyEvent::Fork::TEMPLATE;
		1113
		1114	It doesn't matter whether you get rid of them in the parent or child after
		1115	a fork.
888		1116
889	=head1 SEE ALSO	1117	=head1 SEE ALSO
890		1118
891	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),	1119	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1120	(part of this distribution).
		1121
892	L<AnyEvent::Fork::Template> (to create a process by forking the main	1122	L<AnyEvent::Fork::Template>, to create a process by forking the main
893	program at a convenient time).	1123	program at a convenient time (part of this distribution).
894		1124
895	=head1 AUTHOR	1125	L<AnyEvent::Fork::Remote>, for another way to create processes that is
		1126	mostly compatible to this module and modules building on top of it, but
		1127	works better with remote processes.
		1128
		1129	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1130
		1131	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1132
		1133	=head1 AUTHOR AND CONTACT INFORMATION
896		1134
897	Marc Lehmann <schmorp@schmorp.de>	1135	Marc Lehmann <schmorp@schmorp.de>
898	http://home.schmorp.de/	1136	http://software.schmorp.de/pkg/AnyEvent-Fork
899		1137
900	=cut	1138	=cut
901		1139
902	1	1140	1
903		1141

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.31 by root, Sat Apr 6 09:29:26 2013 UTC vs. Revision 1.64 by root, Wed Nov 26 13:37:40 2014 UTC

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Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.31 by root, Sat Apr 6 09:29:26 2013 UTC vs.
Revision 1.64 by root, Wed Nov 26 13:37:40 2014 UTC