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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.30 by root, Sat Apr 6 09:28:45 2013 UTC vs.
Revision 1.70 by root, Sat Nov 5 19:26:35 2016 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	# $slave_filehandle in the new process.
155	});	195	});
156		196
157	MyModule::worker might look like this:	197	C<MyModule> might look like this:
158		198
		199	package MyModule;
		200
159	sub MyModule::worker {	201	sub worker {
160	my ($slave_filehandle) = @_;	202	my ($slave_filehandle) = @_;
161		203
162	# now $slave_filehandle is connected to the $master_filehandle	204	# now $slave_filehandle is connected to the $master_filehandle
163	# in the original prorcess. have fun!	205	# in the original process. have fun!
164	}	206	}
165		207
166	=head2 Create a pool of server processes all accepting on the same socket.	208	=head2 Create a pool of server processes all accepting on the same socket.
167		209
168	# create listener socket	210	# create listener socket
…		…
183	}	225	}
184		226
185	# now do other things - maybe use the filehandle provided by run	227	# now do other things - maybe use the filehandle provided by run
186	# to wait for the processes to die. or whatever.	228	# to wait for the processes to die. or whatever.
187		229
188	My::Server::run might look like this:	230	C<My::Server> might look like this:
189		231
190	sub My::Server::run {	232	package My::Server;
		233
		234	sub run {
191	my ($slave, $listener, $id) = @_;	235	my ($slave, $listener, $id) = @_;
192		236
193	close $slave; # we do not use the socket, so close it to save resources	237	close $slave; # we do not use the socket, so close it to save resources
194		238
195	# we could go ballistic and use e.g. AnyEvent here, or IO::AIO,	239	# we could go ballistic and use e.g. AnyEvent here, or IO::AIO,
…		…
199	}	243	}
200	}	244	}
201		245
202	=head2 use AnyEvent::Fork as a faster fork+exec	246	=head2 use AnyEvent::Fork as a faster fork+exec
203		247
204	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>
205	the communications socket. It is usually faster than fork+exec, but still	249	and standard error redirected to the communications socket. It is usually
206	let's you prepare the environment.	250	faster than fork+exec, but still lets you prepare the environment.
207		251
208	open my $output, ">/tmp/log" or die "$!";	252	open my $output, ">/tmp/log" or die "$!";
209		253
210	AnyEvent::Fork	254	AnyEvent::Fork
211	->new	255	->new
212	->eval ('	256	->eval ('
		257	# compile a helper function for later use
213	sub run {	258	sub run {
214	my ($fh, $output, @cmd) = @_;	259	my ($fh, $output, @cmd) = @_;
215		260
216	# perl will clear close-on-exec on STDOUT/STDERR	261	# perl will clear close-on-exec on STDOUT/STDERR
217	open STDOUT, ">&", $output or die;	262	open STDOUT, ">&", $output or die;
…		…
224	->send_arg ("/bin/echo", "hi")	269	->send_arg ("/bin/echo", "hi")
225	->run ("run", my $cv = AE::cv);	270	->run ("run", my $cv = AE::cv);
226		271
227	my $stderr = $cv->recv;	272	my $stderr = $cv->recv;
228		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
229	=head1 CONCEPTS	343	=head1 CONCEPTS
230		344
231	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
232	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".
233		351
234	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
235	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,
236	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
237	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
…		…
347	use AnyEvent;	465	use AnyEvent;
348	use AnyEvent::Util ();	466	use AnyEvent::Util ();
349		467
350	use IO::FDPass;	468	use IO::FDPass;
351		469
352	our $VERSION = 0.5;	470	our $VERSION = 1.31;
353
354	our $PERL; # the path to the perl interpreter, deduces with various forms of magic
355
356	=over 4
357
358	=back
359
360	=cut
361		471
362	# the early fork template process	472	# the early fork template process
363	our $EARLY;	473	our $EARLY;
364		474
365	# the empty template process	475	# the empty template process
366	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	}
367		498
368	sub _cmd {	499	sub _cmd {
369	my $self = shift;	500	my $self = shift;
370		501
371	# 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
372	# 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
373	# it.	504	# it.
374	push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1];	505	push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1];
375		506
376	$self->[3] \|\|= AE::io $self->[1], 1, sub {	507	$self->[WW] \|\|= AE::io $self->[FH], 1, sub {
377	do {	508	do {
378	# 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,
379	# or a plain string.	510	# or a plain string.
380		511
381	if (ref $self->[2][0]) {	512	if (ref $self->[QUEUE][0]) {
382	# send fh	513	# send fh
383	unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) {	514	unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) {
384	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	515	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
385	undef $self->[3];	516	undef $self->[WW];
386	die "AnyEvent::Fork: file descriptor send failure: $!";	517	die "AnyEvent::Fork: file descriptor send failure: $!";
387	}	518	}
388		519
389	shift @{ $self->[2] };	520	shift @{ $self->[QUEUE] };
390		521
391	} else {	522	} else {
392	# send string	523	# send string
393	my $len = syswrite $self->[1], $self->[2][0];	524	my $len = syswrite $self->[FH], $self->[QUEUE][0];
394		525
395	unless ($len) {	526	unless ($len) {
396	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	527	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
397	undef $self->[3];	528	undef $self->[WW];
398	die "AnyEvent::Fork: command write failure: $!";	529	die "AnyEvent::Fork: command write failure: $!";
399	}	530	}
400		531
401	substr $self->[2][0], 0, $len, "";	532	substr $self->[QUEUE][0], 0, $len, "";
402	shift @{ $self->[2] } unless length $self->[2][0];	533	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
403	}	534	}
404	} while @{ $self->[2] };	535	} while @{ $self->[QUEUE] };
405		536
406	# everything written	537	# everything written
407	undef $self->[3];	538	undef $self->[WW];
408		539
409	# invoke run callback, if any	540	# invoke run callback, if any
410	$self->[4]->($self->[1]) if $self->[4];	541	if ($self->[CB]) {
		542	$self->[CB]->($self->[FH]);
		543	@$self = ();
		544	}
411	};	545	};
412		546
413	() # make sure we don't leak the watcher	547	() # make sure we don't leak the watcher
414	}
415
416	sub _new {
417	my ($self, $fh, $pid) = @_;
418
419	AnyEvent::Util::fh_nonblocking $fh, 1;
420
421	$self = bless [
422	$pid,
423	$fh,
424	[], # write queue - strings or fd's
425	undef, # AE watcher
426	], $self;
427
428	$self
429	}	548	}
430		549
431	# fork template from current process, used by AnyEvent::Fork::Early/Template	550	# fork template from current process, used by AnyEvent::Fork::Early/Template
432	sub _new_fork {	551	sub _new_fork {
433	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	552	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
437		556
438	if ($pid eq 0) {	557	if ($pid eq 0) {
439	require AnyEvent::Fork::Serve;	558	require AnyEvent::Fork::Serve;
440	$AnyEvent::Fork::Serve::OWNER = $parent;	559	$AnyEvent::Fork::Serve::OWNER = $parent;
441	close $fh;	560	close $fh;
442	$0 = "$_[1] of $parent";	561	$0 = "$parent AnyEvent::Fork/exec";
443	$SIG{CHLD} = 'IGNORE';
444	AnyEvent::Fork::Serve::serve ($slave);	562	AnyEvent::Fork::Serve::serve ($slave);
445	exit 0;	563	exit 0;
446	} elsif (!$pid) {	564	} elsif (!$pid) {
447	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";	565	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";
448	}	566	}
…		…
502		620
503	You should use C<new> whenever possible, except when having a template	621	You should use C<new> whenever possible, except when having a template
504	process around is unacceptable.	622	process around is unacceptable.
505		623
506	The path to the perl interpreter is divined using various methods - first	624	The path to the perl interpreter is divined using various methods - first
507	C<$^X> is investigated to see if the path ends with something that sounds	625	C<$^X> is investigated to see if the path ends with something that looks
508	as if it were the perl interpreter. Failing this, the module falls back to	626	as if it were the perl interpreter. Failing this, the module falls back to
509	using C<$Config::Config{perlpath}>.	627	using C<$Config::Config{perlpath}>.
510		628
		629	The path to perl can also be overriden by setting the global variable
		630	C<$AnyEvent::Fork::PERL> - it's value will be used for all subsequent
		631	invocations.
		632
511	=cut	633	=cut
		634
		635	our $PERL;
512		636
513	sub new_exec {	637	sub new_exec {
514	my ($self) = @_;	638	my ($self) = @_;
515		639
516	return $EARLY->fork	640	return $EARLY->fork
517	if $EARLY;	641	if $EARLY;
518		642
		643	unless (defined $PERL) {
519	# first find path of perl	644	# first find path of perl
520	my $perl = $;	645	my $perl = $^X;
521		646
522	# first we try $^X, but the path must be absolute (always on win32), and end in sth.	647	# first we try $^X, but the path must be absolute (always on win32), and end in sth.
523	# that looks like perl. this obviously only works for posix and win32	648	# that looks like perl. this obviously only works for posix and win32
524	unless (	649	unless (
525	($^O eq "MSWin32" \|\| $perl =~ m%^/%)	650	($^O eq "MSWin32" \|\| $perl =~ m%^/%)
526	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i	651	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i
527	) {	652	) {
528	# if it doesn't look perlish enough, try Config	653	# if it doesn't look perlish enough, try Config
529	require Config;	654	require Config;
530	$perl = $Config::Config{perlpath};	655	$perl = $Config::Config{perlpath};
531	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;	656	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;
		657	}
		658
		659	$PERL = $perl;
532	}	660	}
533		661
534	require Proc::FastSpawn;	662	require Proc::FastSpawn;
535		663
536	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	664	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
544	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;	672	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;
545	my %env = %ENV;	673	my %env = %ENV;
546	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;	674	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;
547		675
548	my $pid = Proc::FastSpawn::spawn (	676	my $pid = Proc::FastSpawn::spawn (
549	$perl,	677	$PERL,
550	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],	678	[$PERL, "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],
551	[map "$_=$env{$_}", keys %env],	679	[map "$_=$env{$_}", keys %env],
552	) or die "unable to spawn AnyEvent::Fork server: $!";	680	) or die "unable to spawn AnyEvent::Fork server: $!";
553		681
554	$self->_new ($fh, $pid)	682	$self->_new ($fh, $pid)
555	}	683	}
556		684
557	=item $pid = $proc->pid	685	=item $pid = $proc->pid
558		686
559	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
560	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.
561		692
562	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
563	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,
564	to clean up their zombies when they die.	695	you need to check whether a process is a diretc child by calling this
565		696	method, and possibly creating a child watcher or reap it manually.
566	All other processes are not direct children, and will be cleaned up by
567	AnyEvent::Fork itself.
568		697
569	=cut	698	=cut
570		699
571	sub pid {	700	sub pid {
572	$_[0][0]	701	$_[0][PID]
573	}	702	}
574		703
575	=item $proc = $proc->eval ($perlcode, @args)	704	=item $proc = $proc->eval ($perlcode, @args)
576		705
577	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
578	the strings specified by C<@args>, in the "main" package.	707	the strings specified by C<@args>, in the "main" package.
579		708
580	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
581	(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
582	to completely take over the process, use C<run> for that.	711	to completely take over the process, use C<run> for that.
583		712
584	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
585	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
586	will be reported to stderr and cause the process to exit.	715	will be reported to stderr and cause the process to exit.
587		716
588	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
589	"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
590	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
591	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.
592		722
593	Returns the process object for easy chaining of method calls.	723	Returns the process object for easy chaining of method calls.
		724
		725	It's common to want to call an iniitalisation function with some
		726	arguments. Make sure you actually pass C<@_> to that function (for example
		727	by using C<&name> syntax), and do not just specify a function name:
		728
		729	$proc->eval ('&MyModule::init', $string1, $string2);
594		730
595	=cut	731	=cut
596		732
597	sub eval {	733	sub eval {
598	my ($self, $code, @args) = @_;	734	my ($self, $code, @args) = @_;
…		…
622	=item $proc = $proc->send_fh ($handle, ...)	758	=item $proc = $proc->send_fh ($handle, ...)
623		759
624	Send one or more file handles (I<not> file descriptors) to the process,	760	Send one or more file handles (I<not> file descriptors) to the process,
625	to prepare a call to C<run>.	761	to prepare a call to C<run>.
626		762
627	The process object keeps a reference to the handles until this is done,	763	The process object keeps a reference to the handles until they have
628	so you must not explicitly close the handles. This is most easily	764	been passed over to the process, so you must not explicitly close the
629	accomplished by simply not storing the file handles anywhere after passing	765	handles. This is most easily accomplished by simply not storing the file
630	them to this method.	766	handles anywhere after passing them to this method - when AnyEvent::Fork
		767	is finished using them, perl will automatically close them.
631		768
632	Returns the process object for easy chaining of method calls.	769	Returns the process object for easy chaining of method calls.
633		770
634	Example: pass a file handle to a process, and release it without	771	Example: pass a file handle to a process, and release it without
635	closing. It will be closed automatically when it is no longer used.	772	closing. It will be closed automatically when it is no longer used.
…		…
642	sub send_fh {	779	sub send_fh {
643	my ($self, @fh) = @_;	780	my ($self, @fh) = @_;
644		781
645	for my $fh (@fh) {	782	for my $fh (@fh) {
646	$self->_cmd ("h");	783	$self->_cmd ("h");
647	push @{ $self->[2] }, \$fh;	784	push @{ $self->[QUEUE] }, \$fh;
648	}	785	}
649		786
650	$self	787	$self
651	}	788	}
652		789
653	=item $proc = $proc->send_arg ($string, ...)	790	=item $proc = $proc->send_arg ($string, ...)
654		791
655	Send one or more argument strings to the process, to prepare a call to	792	Send one or more argument strings to the process, to prepare a call to
656	C<run>. The strings can be any octet string.	793	C<run>. The strings can be any octet strings.
657		794
658	The protocol is optimised to pass a moderate number of relatively short	795	The protocol is optimised to pass a moderate number of relatively short
659	strings - while you can pass up to 4GB of data in one go, this is more	796	strings - while you can pass up to 4GB of data in one go, this is more
660	meant to pass some ID information or other startup info, not big chunks of	797	meant to pass some ID information or other startup info, not big chunks of
661	data.	798	data.
…		…
677	Enter the function specified by the function name in C<$func> in the	814	Enter the function specified by the function name in C<$func> in the
678	process. The function is called with the communication socket as first	815	process. The function is called with the communication socket as first
679	argument, followed by all file handles and string arguments sent earlier	816	argument, followed by all file handles and string arguments sent earlier
680	via C<send_fh> and C<send_arg> methods, in the order they were called.	817	via C<send_fh> and C<send_arg> methods, in the order they were called.
681		818
		819	The process object becomes unusable on return from this function - any
		820	further method calls result in undefined behaviour.
		821
682	The function name should be fully qualified, but if it isn't, it will be	822	The function name should be fully qualified, but if it isn't, it will be
683	looked up in the main package.	823	looked up in the C<main> package.
684		824
685	If the called function returns, doesn't exist, or any error occurs, the	825	If the called function returns, doesn't exist, or any error occurs, the
686	process exits.	826	process exits.
687		827
688	Preparing the process is done in the background - when all commands have	828	Preparing the process is done in the background - when all commands have
689	been sent, the callback is invoked with the local communications socket	829	been sent, the callback is invoked with the local communications socket
690	as argument. At this point you can start using the socket in any way you	830	as argument. At this point you can start using the socket in any way you
691	like.	831	like.
692		832
693	The process object becomes unusable on return from this function - any
694	further method calls result in undefined behaviour.
695
696	If the communication socket isn't used, it should be closed on both sides,	833	If the communication socket isn't used, it should be closed on both sides,
697	to save on kernel memory.	834	to save on kernel memory.
698		835
699	The socket is non-blocking in the parent, and blocking in the newly	836	The socket is non-blocking in the parent, and blocking in the newly
700	created process. The close-on-exec flag is set in both.	837	created process. The close-on-exec flag is set in both.
701		838
702	Even if not used otherwise, the socket can be a good indicator for the	839	Even if not used otherwise, the socket can be a good indicator for the
703	existence of the process - if the other process exits, you get a readable	840	existence of the process - if the other process exits, you get a readable
704	event on it, because exiting the process closes the socket (if it didn't	841	event on it, because exiting the process closes the socket (if it didn't
705	create any children using fork).	842	create any children using fork).
		843
		844	=over 4
		845
		846	=item Compatibility to L<AnyEvent::Fork::Remote>
		847
		848	If you want to write code that works with both this module and
		849	L<AnyEvent::Fork::Remote>, you need to write your code so that it assumes
		850	there are two file handles for communications, which might not be unix
		851	domain sockets. The C<run> function should start like this:
		852
		853	sub run {
		854	my ($rfh, @args) = @_; # @args is your normal arguments
		855	my $wfh = fileno $rfh ? $rfh : *STDOUT;
		856
		857	# now use $rfh for reading and $wfh for writing
		858	}
		859
		860	This checks whether the passed file handle is, in fact, the process
		861	C<STDIN> handle. If it is, then the function was invoked visa
		862	L<AnyEvent::Fork::Remote>, so STDIN should be used for reading and
		863	C<STDOUT> should be used for writing.
		864
		865	In all other cases, the function was called via this module, and there is
		866	only one file handle that should be sued for reading and writing.
		867
		868	=back
706		869
707	Example: create a template for a process pool, pass a few strings, some	870	Example: create a template for a process pool, pass a few strings, some
708	file handles, then fork, pass one more string, and run some code.	871	file handles, then fork, pass one more string, and run some code.
709		872
710	my $pool = AnyEvent::Fork	873	my $pool = AnyEvent::Fork
…		…
738	=cut	901	=cut
739		902
740	sub run {	903	sub run {
741	my ($self, $func, $cb) = @_;	904	my ($self, $func, $cb) = @_;
742		905
743	$self->[4] = $cb;	906	$self->[CB] = $cb;
744	$self->_cmd (r => $func);	907	$self->_cmd (r => $func);
		908	}
		909
		910	=back
		911
		912
		913	=head2 CHILD PROCESS INTERFACE
		914
		915	This module has a limited API for use in child processes.
		916
		917	=over 4
		918
		919	=item @args = AnyEvent::Fork::Serve::run_args
		920
		921	This function, which only exists before the C<run> method is called,
		922	returns the arguments that would be passed to the run function, and clears
		923	them.
		924
		925	This is mainly useful to get any file handles passed via C<send_fh>, but
		926	works for any arguments passed via C<< send_I<xxx> >> methods.
		927
		928	=back
		929
		930
		931	=head2 EXPERIMENTAL METHODS
		932
		933	These methods might go away completely or change behaviour, at any time.
		934
		935	=over 4
		936
		937	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		938
		939	Flushes all commands out to the process and then calls the callback with
		940	the communications socket.
		941
		942	The process object becomes unusable on return from this function - any
		943	further method calls result in undefined behaviour.
		944
		945	The point of this method is to give you a file handle that you can pass
		946	to another process. In that other process, you can call C<new_from_fh
		947	AnyEvent::Fork $fh> to create a new C<AnyEvent::Fork> object from it,
		948	thereby effectively passing a fork object to another process.
		949
		950	=cut
		951
		952	sub to_fh {
		953	my ($self, $cb) = @_;
		954
		955	$self->[CB] = $cb;
		956
		957	unless ($self->[WW]) {
		958	$self->[CB]->($self->[FH]);
		959	@$self = ();
		960	}
		961	}
		962
		963	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		964
		965	Takes a file handle originally rceeived by the C<to_fh> method and creates
		966	a new C<AnyEvent:Fork> object. The child process itself will not change in
		967	any way, i.e. it will keep all the modifications done to it before calling
		968	C<to_fh>.
		969
		970	The new object is very much like the original object, except that the
		971	C<pid> method will return C<undef> even if the process is a direct child.
		972
		973	=cut
		974
		975	sub new_from_fh {
		976	my ($class, $fh) = @_;
		977
		978	$class->_new ($fh)
745	}	979	}
746		980
747	=back	981	=back
748		982
749	=head1 PERFORMANCE	983	=head1 PERFORMANCE
…		…
759		993
760	2079 new processes per second, using manual socketpair + fork	994	2079 new processes per second, using manual socketpair + fork
761		995
762	Then I did the same thing, but instead of calling fork, I called	996	Then I did the same thing, but instead of calling fork, I called
763	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the	997	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the
764	socket form the child to close on exit. This does the same thing as manual	998	socket from the child to close on exit. This does the same thing as manual
765	socket pair + fork, except that what is forked is the template process	999	socket pair + fork, except that what is forked is the template process
766	(2440kB), and the socket needs to be passed to the server at the other end	1000	(2440kB), and the socket needs to be passed to the server at the other end
767	of the socket first.	1001	of the socket first.
768		1002
769	2307 new processes per second, using AnyEvent::Fork->new	1003	2307 new processes per second, using AnyEvent::Fork->new
…		…
774	479 vfork+execs per second, using AnyEvent::Fork->new_exec	1008	479 vfork+execs per second, using AnyEvent::Fork->new_exec
775		1009
776	So how can C<< AnyEvent->new >> be faster than a standard fork, even	1010	So how can C<< AnyEvent->new >> be faster than a standard fork, even
777	though it uses the same operations, but adds a lot of overhead?	1011	though it uses the same operations, but adds a lot of overhead?
778		1012
779	The difference is simply the process size: forking the 6MB process takes	1013	The difference is simply the process size: forking the 5MB process takes
780	so much longer than forking the 2.5MB template process that the overhead	1014	so much longer than forking the 2.5MB template process that the extra
781	introduced is canceled out.	1015	overhead is canceled out.
782		1016
783	If the benchmark process grows, the normal fork becomes even slower:	1017	If the benchmark process grows, the normal fork becomes even slower:
784		1018
785	1340 new processes, manual fork in a 20MB process	1019	1340 new processes, manual fork of a 20MB process
786	731 new processes, manual fork in a 200MB process	1020	731 new processes, manual fork of a 200MB process
787	235 new processes, manual fork in a 2000MB process	1021	235 new processes, manual fork of a 2000MB process
788		1022
789	What that means (to me) is that I can use this module without having a	1023	What that means (to me) is that I can use this module without having a bad
790	very bad conscience because of the extra overhead required to start new	1024	conscience because of the extra overhead required to start new processes.
791	processes.
792		1025
793	=head1 TYPICAL PROBLEMS	1026	=head1 TYPICAL PROBLEMS
794		1027
795	This section lists typical problems that remain. I hope by recognising	1028	This section lists typical problems that remain. I hope by recognising
796	them, most can be avoided.	1029	them, most can be avoided.
797		1030
798	=over 4	1031	=over 4
799		1032
800	=item "leaked" file descriptors for exec'ed processes	1033	=item leaked file descriptors for exec'ed processes
801		1034
802	POSIX systems inherit file descriptors by default when exec'ing a new	1035	POSIX systems inherit file descriptors by default when exec'ing a new
803	process. While perl itself laudably sets the close-on-exec flags on new	1036	process. While perl itself laudably sets the close-on-exec flags on new
804	file handles, most C libraries don't care, and even if all cared, it's	1037	file handles, most C libraries don't care, and even if all cared, it's
805	often not possible to set the flag in a race-free manner.	1038	often not possible to set the flag in a race-free manner.
…		…
825	libraries or the code that leaks those file descriptors.	1058	libraries or the code that leaks those file descriptors.
826		1059
827	Fortunately, most of these leaked descriptors do no harm, other than	1060	Fortunately, most of these leaked descriptors do no harm, other than
828	sitting on some resources.	1061	sitting on some resources.
829		1062
830	=item "leaked" file descriptors for fork'ed processes	1063	=item leaked file descriptors for fork'ed processes
831		1064
832	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,	1065	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,
833	which closes file descriptors not marked for being inherited.	1066	which closes file descriptors not marked for being inherited.
834		1067
835	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer	1068	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer
…		…
844		1077
845	The solution is to either not load these modules before use'ing	1078	The solution is to either not load these modules before use'ing
846	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay	1079	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay
847	initialising them, for example, by calling C<init Gtk2> manually.	1080	initialising them, for example, by calling C<init Gtk2> manually.
848		1081
849	=item exit runs destructors	1082	=item exiting calls object destructors
850		1083
851	This only applies to users of Lc<AnyEvent::Fork:Early> and	1084	This only applies to users of L<AnyEvent::Fork:Early> and
852	L<AnyEvent::Fork::Template>.	1085	L<AnyEvent::Fork::Template>, or when initialising code creates objects
		1086	that reference external resources.
853		1087
854	When a process created by AnyEvent::Fork exits, it might do so by calling	1088	When a process created by AnyEvent::Fork exits, it might do so by calling
855	exit, or simply letting perl reach the end of the program. At which point	1089	exit, or simply letting perl reach the end of the program. At which point
856	Perl runs all destructors.	1090	Perl runs all destructors.
857		1091
…		…
876	to make it so, mostly due to the bloody broken perl that nobody seems to	1110	to make it so, mostly due to the bloody broken perl that nobody seems to
877	care about. The fork emulation is a bad joke - I have yet to see something	1111	care about. The fork emulation is a bad joke - I have yet to see something
878	useful that you can do with it without running into memory corruption	1112	useful that you can do with it without running into memory corruption
879	issues or other braindamage. Hrrrr.	1113	issues or other braindamage. Hrrrr.
880		1114
881	Cygwin perl is not supported at the moment, as it should implement fd	1115	Since fork is endlessly broken on win32 perls (it doesn't even remotely
882	passing, but doesn't, and rolling my own is hard, as cygwin doesn't	1116	work within it's documented limits) and quite obviously it's not getting
883	support enough functionality to do it.	1117	improved any time soon, the best way to proceed on windows would be to
		1118	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1119
		1120	Cygwin perl is not supported at the moment due to some hilarious
		1121	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1122	use C<send_fh> and always use C<new_exec> to create processes, it should
		1123	work though.
		1124
		1125	=head1 USING AnyEvent::Fork IN SUBPROCESSES
		1126
		1127	AnyEvent::Fork itself cannot generally be used in subprocesses. As long as
		1128	only one process ever forks new processes, sharing the template processes
		1129	is possible (you could use a pipe as a lock by writing a byte into it to
		1130	unlock, and reading the byte to lock for example)
		1131
		1132	To make concurrent calls possible after fork, you should get rid of the
		1133	template and early fork processes. AnyEvent::Fork will create a new
		1134	template process as needed.
		1135
		1136	undef $AnyEvent::Fork::EARLY;
		1137	undef $AnyEvent::Fork::TEMPLATE;
		1138
		1139	It doesn't matter whether you get rid of them in the parent or child after
		1140	a fork.
884		1141
885	=head1 SEE ALSO	1142	=head1 SEE ALSO
886		1143
887	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),	1144	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1145	(part of this distribution).
		1146
888	L<AnyEvent::Fork::Template> (to create a process by forking the main	1147	L<AnyEvent::Fork::Template>, to create a process by forking the main
889	program at a convenient time).	1148	program at a convenient time (part of this distribution).
890		1149
891	=head1 AUTHOR	1150	L<AnyEvent::Fork::Remote>, for another way to create processes that is
		1151	mostly compatible to this module and modules building on top of it, but
		1152	works better with remote processes.
		1153
		1154	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1155
		1156	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1157
		1158	=head1 AUTHOR AND CONTACT INFORMATION
892		1159
893	Marc Lehmann <schmorp@schmorp.de>	1160	Marc Lehmann <schmorp@schmorp.de>
894	http://home.schmorp.de/	1161	http://software.schmorp.de/pkg/AnyEvent-Fork
895		1162
896	=cut	1163	=cut
897		1164
898	1	1165	1
899		1166

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.30 by root, Sat Apr 6 09:28:45 2013 UTC vs. Revision 1.70 by root, Sat Nov 5 19:26:35 2016 UTC

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Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.30 by root, Sat Apr 6 09:28:45 2013 UTC vs.
Revision 1.70 by root, Sat Nov 5 19:26:35 2016 UTC