[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 1.74 by root, Mon Dec 11 05:34:15 2023 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 = 1.32;
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<$Config::Config{perlpath}>.
510		628
		629	The path to perl can also be overridden by setting the global variable
		630	C<$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<@_>
578	the strings specified by C<@args>, in the "main" package.	707	to the strings specified by C<@args>, in the "main" package (so you can
		708	access the args using C<$_[0]> and so on, but not using implicit C<shift>
		709	as the latter works on C<@ARGV>).
579		710
580	This call is meant to do any custom initialisation that might be required	711	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	712	(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.	713	to completely take over the process, use C<run> for that.
583		714
584	The code will usually be executed after this call returns, and there is no	715	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	716	way to pass anything back to the calling process. Any evaluation errors
586	will be reported to stderr and cause the process to exit.	717	will be reported to stderr and cause the process to exit.
587		718
588	If you want to execute some code to take over the process (see the	719	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	720	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	721	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.	722	C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as
		723	a faster fork+exec> example to see it in action.
592		724
593	Returns the process object for easy chaining of method calls.	725	Returns the process object for easy chaining of method calls.
		726
		727	It's common to want to call an iniitalisation function with some
		728	arguments. Make sure you actually pass C<@_> to that function (for example
		729	by using C<&name> syntax), and do not just specify a function name:
		730
		731	$proc->eval ('&MyModule::init', $string1, $string2);
594		732
595	=cut	733	=cut
596		734
597	sub eval {	735	sub eval {
598	my ($self, $code, @args) = @_;	736	my ($self, $code, @args) = @_;
…		…
622	=item $proc = $proc->send_fh ($handle, ...)	760	=item $proc = $proc->send_fh ($handle, ...)
623		761
624	Send one or more file handles (I<not> file descriptors) to the process,	762	Send one or more file handles (I<not> file descriptors) to the process,
625	to prepare a call to C<run>.	763	to prepare a call to C<run>.
626		764
627	The process object keeps a reference to the handles until this is done,	765	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	766	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	767	handles. This is most easily accomplished by simply not storing the file
630	them to this method.	768	handles anywhere after passing them to this method - when AnyEvent::Fork
		769	is finished using them, perl will automatically close them.
631		770
632	Returns the process object for easy chaining of method calls.	771	Returns the process object for easy chaining of method calls.
633		772
634	Example: pass a file handle to a process, and release it without	773	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.	774	closing. It will be closed automatically when it is no longer used.
…		…
642	sub send_fh {	781	sub send_fh {
643	my ($self, @fh) = @_;	782	my ($self, @fh) = @_;
644		783
645	for my $fh (@fh) {	784	for my $fh (@fh) {
646	$self->_cmd ("h");	785	$self->_cmd ("h");
647	push @{ $self->[2] }, \$fh;	786	push @{ $self->[QUEUE] }, \$fh;
648	}	787	}
649		788
650	$self	789	$self
651	}	790	}
652		791
653	=item $proc = $proc->send_arg ($string, ...)	792	=item $proc = $proc->send_arg ($string, ...)
654		793
655	Send one or more argument strings to the process, to prepare a call to	794	Send one or more argument strings to the process, to prepare a call to
656	C<run>. The strings can be any octet string.	795	C<run>. The strings can be any octet strings.
657		796
658	The protocol is optimised to pass a moderate number of relatively short	797	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	798	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	799	meant to pass some ID information or other startup info, not big chunks of
661	data.	800	data.
…		…
677	Enter the function specified by the function name in C<$func> in the	816	Enter the function specified by the function name in C<$func> in the
678	process. The function is called with the communication socket as first	817	process. The function is called with the communication socket as first
679	argument, followed by all file handles and string arguments sent earlier	818	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.	819	via C<send_fh> and C<send_arg> methods, in the order they were called.
681		820
		821	The process object becomes unusable on return from this function - any
		822	further method calls result in undefined behaviour.
		823
682	The function name should be fully qualified, but if it isn't, it will be	824	The function name should be fully qualified, but if it isn't, it will be
683	looked up in the main package.	825	looked up in the C<main> package.
684		826
685	If the called function returns, doesn't exist, or any error occurs, the	827	If the called function returns, doesn't exist, or any error occurs, the
686	process exits.	828	process exits.
687		829
688	Preparing the process is done in the background - when all commands have	830	Preparing the process is done in the background - when all commands have
689	been sent, the callback is invoked with the local communications socket	831	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	832	as argument. At this point you can start using the socket in any way you
691	like.	833	like.
692		834
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,	835	If the communication socket isn't used, it should be closed on both sides,
697	to save on kernel memory.	836	to save on kernel memory.
698		837
699	The socket is non-blocking in the parent, and blocking in the newly	838	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.	839	created process. The close-on-exec flag is set in both.
701		840
702	Even if not used otherwise, the socket can be a good indicator for the	841	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	842	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	843	event on it, because exiting the process closes the socket (if it didn't
705	create any children using fork).	844	create any children using fork).
		845
		846	=over 4
		847
		848	=item Compatibility to L<AnyEvent::Fork::Remote>
		849
		850	If you want to write code that works with both this module and
		851	L<AnyEvent::Fork::Remote>, you need to write your code so that it assumes
		852	there are two file handles for communications, which might not be unix
		853	domain sockets. The C<run> function should start like this:
		854
		855	sub run {
		856	my ($rfh, @args) = @_; # @args is your normal arguments
		857	my $wfh = fileno $rfh ? $rfh : *STDOUT;
		858
		859	# now use $rfh for reading and $wfh for writing
		860	}
		861
		862	This checks whether the passed file handle is, in fact, the process
		863	C<STDIN> handle. If it is, then the function was invoked visa
		864	L<AnyEvent::Fork::Remote>, so STDIN should be used for reading and
		865	C<STDOUT> should be used for writing.
		866
		867	In all other cases, the function was called via this module, and there is
		868	only one file handle that should be sued for reading and writing.
		869
		870	=back
706		871
707	Example: create a template for a process pool, pass a few strings, some	872	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.	873	file handles, then fork, pass one more string, and run some code.
709		874
710	my $pool = AnyEvent::Fork	875	my $pool = AnyEvent::Fork
…		…
738	=cut	903	=cut
739		904
740	sub run {	905	sub run {
741	my ($self, $func, $cb) = @_;	906	my ($self, $func, $cb) = @_;
742		907
743	$self->[4] = $cb;	908	$self->[CB] = $cb;
744	$self->_cmd (r => $func);	909	$self->_cmd (r => $func);
		910	}
		911
		912	=back
		913
		914
		915	=head2 CHILD PROCESS INTERFACE
		916
		917	This module has a limited API for use in child processes.
		918
		919	=over 4
		920
		921	=item @args = AnyEvent::Fork::Serve::run_args
		922
		923	This function, which only exists before the C<run> method is called,
		924	returns the arguments that would be passed to the run function, and clears
		925	them.
		926
		927	This is mainly useful to get any file handles passed via C<send_fh>, but
		928	works for any arguments passed via C<< send_I<xxx> >> methods.
		929
		930	=back
		931
		932
		933	=head2 EXPERIMENTAL METHODS
		934
		935	These methods might go away completely or change behaviour, at any time.
		936
		937	=over 4
		938
		939	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		940
		941	Flushes all commands out to the process and then calls the callback with
		942	the communications socket.
		943
		944	The process object becomes unusable on return from this function - any
		945	further method calls result in undefined behaviour.
		946
		947	The point of this method is to give you a file handle that you can pass
		948	to another process. In that other process, you can call C<new_from_fh
		949	AnyEvent::Fork $fh> to create a new C<AnyEvent::Fork> object from it,
		950	thereby effectively passing a fork object to another process.
		951
		952	=cut
		953
		954	sub to_fh {
		955	my ($self, $cb) = @_;
		956
		957	$self->[CB] = $cb;
		958
		959	unless ($self->[WW]) {
		960	$self->[CB]->($self->[FH]);
		961	@$self = ();
		962	}
		963	}
		964
		965	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		966
		967	Takes a file handle originally rceeived by the C<to_fh> method and creates
		968	a new C<AnyEvent:Fork> object. The child process itself will not change in
		969	any way, i.e. it will keep all the modifications done to it before calling
		970	C<to_fh>.
		971
		972	The new object is very much like the original object, except that the
		973	C<pid> method will return C<undef> even if the process is a direct child.
		974
		975	=cut
		976
		977	sub new_from_fh {
		978	my ($class, $fh) = @_;
		979
		980	$class->_new ($fh)
745	}	981	}
746		982
747	=back	983	=back
748		984
749	=head1 PERFORMANCE	985	=head1 PERFORMANCE
…		…
759		995
760	2079 new processes per second, using manual socketpair + fork	996	2079 new processes per second, using manual socketpair + fork
761		997
762	Then I did the same thing, but instead of calling fork, I called	998	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	999	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	1000	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	1001	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	1002	(2440kB), and the socket needs to be passed to the server at the other end
767	of the socket first.	1003	of the socket first.
768		1004
769	2307 new processes per second, using AnyEvent::Fork->new	1005	2307 new processes per second, using AnyEvent::Fork->new
…		…
774	479 vfork+execs per second, using AnyEvent::Fork->new_exec	1010	479 vfork+execs per second, using AnyEvent::Fork->new_exec
775		1011
776	So how can C<< AnyEvent->new >> be faster than a standard fork, even	1012	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?	1013	though it uses the same operations, but adds a lot of overhead?
778		1014
779	The difference is simply the process size: forking the 6MB process takes	1015	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	1016	so much longer than forking the 2.5MB template process that the extra
781	introduced is canceled out.	1017	overhead is canceled out.
782		1018
783	If the benchmark process grows, the normal fork becomes even slower:	1019	If the benchmark process grows, the normal fork becomes even slower:
784		1020
785	1340 new processes, manual fork in a 20MB process	1021	1340 new processes, manual fork of a 20MB process
786	731 new processes, manual fork in a 200MB process	1022	731 new processes, manual fork of a 200MB process
787	235 new processes, manual fork in a 2000MB process	1023	235 new processes, manual fork of a 2000MB process
788		1024
789	What that means (to me) is that I can use this module without having a	1025	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	1026	conscience because of the extra overhead required to start new processes.
791	processes.
792		1027
793	=head1 TYPICAL PROBLEMS	1028	=head1 TYPICAL PROBLEMS
794		1029
795	This section lists typical problems that remain. I hope by recognising	1030	This section lists typical problems that remain. I hope by recognising
796	them, most can be avoided.	1031	them, most can be avoided.
797		1032
798	=over 4	1033	=over 4
799		1034
800	=item "leaked" file descriptors for exec'ed processes	1035	=item leaked file descriptors for exec'ed processes
801		1036
802	POSIX systems inherit file descriptors by default when exec'ing a new	1037	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	1038	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	1039	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.	1040	often not possible to set the flag in a race-free manner.
…		…
825	libraries or the code that leaks those file descriptors.	1060	libraries or the code that leaks those file descriptors.
826		1061
827	Fortunately, most of these leaked descriptors do no harm, other than	1062	Fortunately, most of these leaked descriptors do no harm, other than
828	sitting on some resources.	1063	sitting on some resources.
829		1064
830	=item "leaked" file descriptors for fork'ed processes	1065	=item leaked file descriptors for fork'ed processes
831		1066
832	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,	1067	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,
833	which closes file descriptors not marked for being inherited.	1068	which closes file descriptors not marked for being inherited.
834		1069
835	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer	1070	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer
…		…
844		1079
845	The solution is to either not load these modules before use'ing	1080	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	1081	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay
847	initialising them, for example, by calling C<init Gtk2> manually.	1082	initialising them, for example, by calling C<init Gtk2> manually.
848		1083
849	=item exit runs destructors	1084	=item exiting calls object destructors
850		1085
851	This only applies to users of Lc<AnyEvent::Fork:Early> and	1086	This only applies to users of L<AnyEvent::Fork:Early> and
852	L<AnyEvent::Fork::Template>.	1087	L<AnyEvent::Fork::Template>, or when initialising code creates objects
		1088	that reference external resources.
853		1089
854	When a process created by AnyEvent::Fork exits, it might do so by calling	1090	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	1091	exit, or simply letting perl reach the end of the program. At which point
856	Perl runs all destructors.	1092	Perl runs all destructors.
857		1093
…		…
876	to make it so, mostly due to the bloody broken perl that nobody seems to	1112	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	1113	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	1114	useful that you can do with it without running into memory corruption
879	issues or other braindamage. Hrrrr.	1115	issues or other braindamage. Hrrrr.
880		1116
881	Cygwin perl is not supported at the moment, as it should implement fd	1117	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	1118	work within it's documented limits) and quite obviously it's not getting
883	support enough functionality to do it.	1119	improved any time soon, the best way to proceed on windows would be to
		1120	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1121
		1122	Cygwin perl is not supported at the moment due to some hilarious
		1123	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1124	use C<send_fh> and always use C<new_exec> to create processes, it should
		1125	work though.
		1126
		1127	=head1 USING AnyEvent::Fork IN SUBPROCESSES
		1128
		1129	AnyEvent::Fork itself cannot generally be used in subprocesses. As long as
		1130	only one process ever forks new processes, sharing the template processes
		1131	is possible (you could use a pipe as a lock by writing a byte into it to
		1132	unlock, and reading the byte to lock for example)
		1133
		1134	To make concurrent calls possible after fork, you should get rid of the
		1135	template and early fork processes. AnyEvent::Fork will create a new
		1136	template process as needed.
		1137
		1138	undef $AnyEvent::Fork::EARLY;
		1139	undef $AnyEvent::Fork::TEMPLATE;
		1140
		1141	It doesn't matter whether you get rid of them in the parent or child after
		1142	a fork.
884		1143
885	=head1 SEE ALSO	1144	=head1 SEE ALSO
886		1145
887	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),	1146	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1147	(part of this distribution).
		1148
888	L<AnyEvent::Fork::Template> (to create a process by forking the main	1149	L<AnyEvent::Fork::Template>, to create a process by forking the main
889	program at a convenient time).	1150	program at a convenient time (part of this distribution).
890		1151
891	=head1 AUTHOR	1152	L<AnyEvent::Fork::Remote>, for another way to create processes that is
		1153	mostly compatible to this module and modules building on top of it, but
		1154	works better with remote processes.
		1155
		1156	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1157
		1158	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1159
		1160	=head1 AUTHOR AND CONTACT INFORMATION
892		1161
893	Marc Lehmann <schmorp@schmorp.de>	1162	Marc Lehmann <schmorp@schmorp.de>
894	http://home.schmorp.de/	1163	http://software.schmorp.de/pkg/AnyEvent-Fork
895		1164
896	=cut	1165	=cut
897		1166
898	1	1167	1
899		1168

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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 1.74 by root, Mon Dec 11 05:34:15 2023 UTC