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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.25 by root, Sat Apr 6 08:55:16 2013 UTC vs.
Revision 1.53 by root, Fri Apr 26 15:44:44 2013 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, not being able to use event processing or
		62	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.
…		…
125	becomes very hard to use the event loop from a child program, as the	150	becomes very hard to use the event loop from a child program, as the
126	watchers already exist but are only meaningful in the parent. Worse, a	151	watchers already exist but are only meaningful in the parent. Worse, a
127	module might want to use such a module, not knowing whether another module	152	module might want to use such a module, not knowing whether another module
128	or the main program also does, leading to problems.	153	or the main program also does, leading to problems.
129		154
		155	Apart from event loops, graphical toolkits also commonly fall into the
		156	"unsafe module" category, or just about anything that communicates with
		157	the external world, such as network libraries and file I/O modules, which
		158	usually don't like being copied and then allowed to continue in two
		159	processes.
		160
130	With this module only the main program is allowed to create new processes	161	With this module only the main program is allowed to create new processes
131	by forking (because only the main program can know when it is still safe	162	by forking (because only the main program can know when it is still safe
132	to do so) - all other processes are created via fork+exec, which makes it	163	to do so) - all other processes are created via fork+exec, which makes it
133	possible to use modules such as event loops or window interfaces safely.	164	possible to use modules such as event loops or window interfaces safely.
134		165
…		…
146		177
147	# now $master_filehandle is connected to the	178	# now $master_filehandle is connected to the
148	# $slave_filehandle in the new process.	179	# $slave_filehandle in the new process.
149	});	180	});
150		181
151	# MyModule::worker might look like this	182	C<MyModule> might look like this:
		183
		184	package MyModule;
		185
152	sub MyModule::worker {	186	sub worker {
153	my ($slave_filehandle) = @_;	187	my ($slave_filehandle) = @_;
154		188
155	# now $slave_filehandle is connected to the $master_filehandle	189	# now $slave_filehandle is connected to the $master_filehandle
156	# in the original prorcess. have fun!	190	# in the original prorcess. have fun!
157	}	191	}
…		…
176	}	210	}
177		211
178	# now do other things - maybe use the filehandle provided by run	212	# now do other things - maybe use the filehandle provided by run
179	# to wait for the processes to die. or whatever.	213	# to wait for the processes to die. or whatever.
180		214
181	# My::Server::run might look like this	215	C<My::Server> might look like this:
182	sub My::Server::run {	216
		217	package My::Server;
		218
		219	sub run {
183	my ($slave, $listener, $id) = @_;	220	my ($slave, $listener, $id) = @_;
184		221
185	close $slave; # we do not use the socket, so close it to save resources	222	close $slave; # we do not use the socket, so close it to save resources
186		223
187	# we could go ballistic and use e.g. AnyEvent here, or IO::AIO,	224	# we could go ballistic and use e.g. AnyEvent here, or IO::AIO,
…		…
191	}	228	}
192	}	229	}
193		230
194	=head2 use AnyEvent::Fork as a faster fork+exec	231	=head2 use AnyEvent::Fork as a faster fork+exec
195		232
196	This runs /bin/echo hi, with stdout redirected to /tmp/log and stderr to	233	This runs C</bin/echo hi>, with standard output redirected to F</tmp/log>
197	the communications socket. It is usually faster than fork+exec, but still	234	and standard error redirected to the communications socket. It is usually
198	let's you prepare the environment.	235	faster than fork+exec, but still lets you prepare the environment.
199		236
200	open my $output, ">/tmp/log" or die "$!";	237	open my $output, ">/tmp/log" or die "$!";
201		238
202	AnyEvent::Fork	239	AnyEvent::Fork
203	->new	240	->new
204	->eval ('	241	->eval ('
		242	# compile a helper function for later use
205	sub run {	243	sub run {
206	my ($fh, $output, @cmd) = @_;	244	my ($fh, $output, @cmd) = @_;
207		245
208	# perl will clear close-on-exec on STDOUT/STDERR	246	# perl will clear close-on-exec on STDOUT/STDERR
209	open STDOUT, ">&", $output or die;	247	open STDOUT, ">&", $output or die;
…		…
216	->send_arg ("/bin/echo", "hi")	254	->send_arg ("/bin/echo", "hi")
217	->run ("run", my $cv = AE::cv);	255	->run ("run", my $cv = AE::cv);
218		256
219	my $stderr = $cv->recv;	257	my $stderr = $cv->recv;
220		258
		259	=head2 For stingy users: put the worker code into a C<DATA> section.
		260
		261	When you want to be stingy with files, you cna put your code into the
		262	C<DATA> section of your module (or program):
		263
		264	use AnyEvent::Fork;
		265
		266	AnyEvent::Fork
		267	->new
		268	->eval (do { local $/; <DATA> })
		269	->run ("doit", sub { ... });
		270
		271	__DATA__
		272
		273	sub doit {
		274	... do something!
		275	}
		276
		277	=head2 For stingy standalone programs: do not rely on external files at
		278	all.
		279
		280	For single-file scripts it can be inconvenient to rely on external
		281	files - even when using < C<DATA> section, you still need to C<exec>
		282	an external perl interpreter, which might not be available when using
		283	L<App::Staticperl>, L<Urlader> or L<PAR::Packer> for example.
		284
		285	Two modules help here - L<AnyEvent::Fork::Early> forks a template process
		286	for all further calls to C<new_exec>, and L<AnyEvent::Fork::Template>
		287	forks the main program as a template process.
		288
		289	Here is how your main program should look like:
		290
		291	#! perl
		292
		293	# optional, as the very first thing.
		294	# in case modules want to create their own processes.
		295	use AnyEvent::Fork::Early;
		296
		297	# next, load all modules you need in your template process
		298	use Example::My::Module
		299	use Example::Whatever;
		300
		301	# next, put your run function definition and anything else you
		302	# need, but do not use code outside of BEGIN blocks.
		303	sub worker_run {
		304	my ($fh, @args) = @_;
		305	...
		306	}
		307
		308	# now preserve everything so far as AnyEvent::Fork object
		309	# in §TEMPLATE.
		310	use AnyEvent::Fork::Template;
		311
		312	# do not put code outside of BEGIN blocks until here
		313
		314	# now use the $TEMPLATE process in any way you like
		315
		316	# for example: create 10 worker processes
		317	my @worker;
		318	my $cv = AE::cv;
		319	for (1..10) {
		320	$cv->begin;
		321	$TEMPLATE->fork->send_arg ($_)->run ("worker_run", sub {
		322	push @worker, shift;
		323	$cv->end;
		324	});
		325	}
		326	$cv->recv;
		327
221	=head1 CONCEPTS	328	=head1 CONCEPTS
222		329
223	This module can create new processes either by executing a new perl	330	This module can create new processes either by executing a new perl
224	process, or by forking from an existing "template" process.	331	process, or by forking from an existing "template" process.
		332
		333	All these processes are called "child processes" (whether they are direct
		334	children or not), while the process that manages them is called the
		335	"parent process".
225		336
226	Each such process comes with its own file handle that can be used to	337	Each such process comes with its own file handle that can be used to
227	communicate with it (it's actually a socket - one end in the new process,	338	communicate with it (it's actually a socket - one end in the new process,
228	one end in the main process), and among the things you can do in it are	339	one end in the main process), and among the things you can do in it are
229	load modules, fork new processes, send file handles to it, and execute	340	load modules, fork new processes, send file handles to it, and execute
…		…
303	my ($fork_fh) = @_;	414	my ($fork_fh) = @_;
304	});	415	});
305		416
306	=back	417	=back
307		418
308	=head1 FUNCTIONS	419	=head1 THE C<AnyEvent::Fork> CLASS
		420
		421	This module exports nothing, and only implements a single class -
		422	C<AnyEvent::Fork>.
		423
		424	There are two class constructors that both create new processes - C<new>
		425	and C<new_exec>. The C<fork> method creates a new process by forking an
		426	existing one and could be considered a third constructor.
		427
		428	Most of the remaining methods deal with preparing the new process, by
		429	loading code, evaluating code and sending data to the new process. They
		430	usually return the process object, so you can chain method calls.
		431
		432	If a process object is destroyed before calling its C<run> method, then
		433	the process simply exits. After C<run> is called, all responsibility is
		434	passed to the specified function.
		435
		436	As long as there is any outstanding work to be done, process objects
		437	resist being destroyed, so there is no reason to store them unless you
		438	need them later - configure and forget works just fine.
309		439
310	=over 4	440	=over 4
311		441
312	=cut	442	=cut
313		443
…		…
320	use AnyEvent;	450	use AnyEvent;
321	use AnyEvent::Util ();	451	use AnyEvent::Util ();
322		452
323	use IO::FDPass;	453	use IO::FDPass;
324		454
325	our $VERSION = 0.5;	455	our $VERSION = '1.0';
326
327	our $PERL; # the path to the perl interpreter, deduces with various forms of magic
328
329	=item my $pool = new AnyEvent::Fork key => value...
330
331	Create a new process pool. The following named parameters are supported:
332
333	=over 4
334
335	=back
336
337	=cut
338		456
339	# the early fork template process	457	# the early fork template process
340	our $EARLY;	458	our $EARLY;
341		459
342	# the empty template process	460	# the empty template process
343	our $TEMPLATE;	461	our $TEMPLATE;
		462
		463	sub QUEUE() { 0 }
		464	sub FH() { 1 }
		465	sub WW() { 2 }
		466	sub PID() { 3 }
		467	sub CB() { 4 }
		468
		469	sub _new {
		470	my ($self, $fh, $pid) = @_;
		471
		472	AnyEvent::Util::fh_nonblocking $fh, 1;
		473
		474	$self = bless [
		475	[], # write queue - strings or fd's
		476	$fh,
		477	undef, # AE watcher
		478	$pid,
		479	], $self;
		480
		481	$self
		482	}
344		483
345	sub _cmd {	484	sub _cmd {
346	my $self = shift;	485	my $self = shift;
347		486
348	# ideally, we would want to use "a (w/a)*" as format string, but perl	487	# ideally, we would want to use "a (w/a)*" as format string, but perl
349	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack	488	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack
350	# it.	489	# it.
351	push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1];	490	push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1];
352		491
353	$self->[3] \|\|= AE::io $self->[1], 1, sub {	492	$self->[WW] \|\|= AE::io $self->[FH], 1, sub {
354	do {	493	do {
355	# send the next "thing" in the queue - either a reference to an fh,	494	# send the next "thing" in the queue - either a reference to an fh,
356	# or a plain string.	495	# or a plain string.
357		496
358	if (ref $self->[2][0]) {	497	if (ref $self->[QUEUE][0]) {
359	# send fh	498	# send fh
360	unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) {	499	unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) {
361	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	500	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
362	undef $self->[3];	501	undef $self->[WW];
363	die "AnyEvent::Fork: file descriptor send failure: $!";	502	die "AnyEvent::Fork: file descriptor send failure: $!";
364	}	503	}
365		504
366	shift @{ $self->[2] };	505	shift @{ $self->[QUEUE] };
367		506
368	} else {	507	} else {
369	# send string	508	# send string
370	my $len = syswrite $self->[1], $self->[2][0];	509	my $len = syswrite $self->[FH], $self->[QUEUE][0];
371		510
372	unless ($len) {	511	unless ($len) {
373	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	512	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
374	undef $self->[3];	513	undef $self->[WW];
375	die "AnyEvent::Fork: command write failure: $!";	514	die "AnyEvent::Fork: command write failure: $!";
376	}	515	}
377		516
378	substr $self->[2][0], 0, $len, "";	517	substr $self->[QUEUE][0], 0, $len, "";
379	shift @{ $self->[2] } unless length $self->[2][0];	518	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
380	}	519	}
381	} while @{ $self->[2] };	520	} while @{ $self->[QUEUE] };
382		521
383	# everything written	522	# everything written
384	undef $self->[3];	523	undef $self->[WW];
385		524
386	# invoke run callback, if any	525	# invoke run callback, if any
387	$self->[4]->($self->[1]) if $self->[4];	526	if ($self->[CB]) {
		527	$self->[CB]->($self->[FH]);
		528	@$self = ();
		529	}
388	};	530	};
389		531
390	() # make sure we don't leak the watcher	532	() # make sure we don't leak the watcher
391	}
392
393	sub _new {
394	my ($self, $fh, $pid) = @_;
395
396	AnyEvent::Util::fh_nonblocking $fh, 1;
397
398	$self = bless [
399	$pid,
400	$fh,
401	[], # write queue - strings or fd's
402	undef, # AE watcher
403	], $self;
404
405	$self
406	}	533	}
407		534
408	# fork template from current process, used by AnyEvent::Fork::Early/Template	535	# fork template from current process, used by AnyEvent::Fork::Early/Template
409	sub _new_fork {	536	sub _new_fork {
410	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	537	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
415	if ($pid eq 0) {	542	if ($pid eq 0) {
416	require AnyEvent::Fork::Serve;	543	require AnyEvent::Fork::Serve;
417	$AnyEvent::Fork::Serve::OWNER = $parent;	544	$AnyEvent::Fork::Serve::OWNER = $parent;
418	close $fh;	545	close $fh;
419	$0 = "$_[1] of $parent";	546	$0 = "$_[1] of $parent";
420	$SIG{CHLD} = 'IGNORE';
421	AnyEvent::Fork::Serve::serve ($slave);	547	AnyEvent::Fork::Serve::serve ($slave);
422	exit 0;	548	exit 0;
423	} elsif (!$pid) {	549	} elsif (!$pid) {
424	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";	550	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";
425	}	551	}
…		…
432	Create a new "empty" perl interpreter process and returns its process	558	Create a new "empty" perl interpreter process and returns its process
433	object for further manipulation.	559	object for further manipulation.
434		560
435	The new process is forked from a template process that is kept around	561	The new process is forked from a template process that is kept around
436	for this purpose. When it doesn't exist yet, it is created by a call to	562	for this purpose. When it doesn't exist yet, it is created by a call to
437	C<new_exec> and kept around for future calls.	563	C<new_exec> first and then stays around for future calls.
438
439	When the process object is destroyed, it will release the file handle
440	that connects it with the new process. When the new process has not yet
441	called C<run>, then the process will exit. Otherwise, what happens depends
442	entirely on the code that is executed.
443		564
444	=cut	565	=cut
445		566
446	sub new {	567	sub new {
447	my $class = shift;	568	my $class = shift;
…		…
537	}	658	}
538		659
539	=item $pid = $proc->pid	660	=item $pid = $proc->pid
540		661
541	Returns the process id of the process I<iff it is a direct child of the	662	Returns the process id of the process I<iff it is a direct child of the
542	process> running AnyEvent::Fork, and C<undef> otherwise.	663	process running AnyEvent::Fork>, and C<undef> otherwise.
543		664
544	Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and	665	Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and
545	L<AnyEvent::Fork::Template> are direct children, and you are responsible	666	L<AnyEvent::Fork::Template> are direct children, and you are responsible
546	to clean up their zombies when they die.	667	to clean up their zombies when they die.
547		668
548	All other processes are not direct children, and will be cleaned up by	669	All other processes are not direct children, and will be cleaned up by
549	AnyEvent::Fork.	670	AnyEvent::Fork itself.
550		671
551	=cut	672	=cut
552		673
553	sub pid {	674	sub pid {
554	$_[0][0]	675	$_[0][PID]
555	}	676	}
556		677
557	=item $proc = $proc->eval ($perlcode, @args)	678	=item $proc = $proc->eval ($perlcode, @args)
558		679
559	Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to	680	Evaluates the given C<$perlcode> as ... Perl code, while setting C<@_> to
560	the strings specified by C<@args>, in the "main" package.	681	the strings specified by C<@args>, in the "main" package.
561		682
562	This call is meant to do any custom initialisation that might be required	683	This call is meant to do any custom initialisation that might be required
563	(for example, the C<require> method uses it). It's not supposed to be used	684	(for example, the C<require> method uses it). It's not supposed to be used
564	to completely take over the process, use C<run> for that.	685	to completely take over the process, use C<run> for that.
565		686
566	The code will usually be executed after this call returns, and there is no	687	The code will usually be executed after this call returns, and there is no
567	way to pass anything back to the calling process. Any evaluation errors	688	way to pass anything back to the calling process. Any evaluation errors
568	will be reported to stderr and cause the process to exit.	689	will be reported to stderr and cause the process to exit.
569		690
570	If you want to execute some code to take over the process (see the	691	If you want to execute some code (that isn't in a module) to take over the
571	"fork+exec" example in the SYNOPSIS), you should compile a function via	692	process, you should compile a function via C<eval> first, and then call
572	C<eval> first, and then call it via C<run>. This also gives you access to	693	it via C<run>. This also gives you access to any arguments passed via the
573	any arguments passed via the C<send_xxx> methods, such as file handles.	694	C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as
		695	a faster fork+exec> example to see it in action.
574		696
575	Returns the process object for easy chaining of method calls.	697	Returns the process object for easy chaining of method calls.
576		698
577	=cut	699	=cut
578		700
…		…
604	=item $proc = $proc->send_fh ($handle, ...)	726	=item $proc = $proc->send_fh ($handle, ...)
605		727
606	Send one or more file handles (I<not> file descriptors) to the process,	728	Send one or more file handles (I<not> file descriptors) to the process,
607	to prepare a call to C<run>.	729	to prepare a call to C<run>.
608		730
609	The process object keeps a reference to the handles until this is done,	731	The process object keeps a reference to the handles until they have
610	so you must not explicitly close the handles. This is most easily	732	been passed over to the process, so you must not explicitly close the
611	accomplished by simply not storing the file handles anywhere after passing	733	handles. This is most easily accomplished by simply not storing the file
612	them to this method.	734	handles anywhere after passing them to this method - when AnyEvent::Fork
		735	is finished using them, perl will automatically close them.
613		736
614	Returns the process object for easy chaining of method calls.	737	Returns the process object for easy chaining of method calls.
615		738
616	Example: pass a file handle to a process, and release it without	739	Example: pass a file handle to a process, and release it without
617	closing. It will be closed automatically when it is no longer used.	740	closing. It will be closed automatically when it is no longer used.
…		…
624	sub send_fh {	747	sub send_fh {
625	my ($self, @fh) = @_;	748	my ($self, @fh) = @_;
626		749
627	for my $fh (@fh) {	750	for my $fh (@fh) {
628	$self->_cmd ("h");	751	$self->_cmd ("h");
629	push @{ $self->[2] }, \$fh;	752	push @{ $self->[QUEUE] }, \$fh;
630	}	753	}
631		754
632	$self	755	$self
633	}	756	}
634		757
635	=item $proc = $proc->send_arg ($string, ...)	758	=item $proc = $proc->send_arg ($string, ...)
636		759
637	Send one or more argument strings to the process, to prepare a call to	760	Send one or more argument strings to the process, to prepare a call to
638	C<run>. The strings can be any octet string.	761	C<run>. The strings can be any octet strings.
639		762
640	The protocol is optimised to pass a moderate number of relatively short	763	The protocol is optimised to pass a moderate number of relatively short
641	strings - while you can pass up to 4GB of data in one go, this is more	764	strings - while you can pass up to 4GB of data in one go, this is more
642	meant to pass some ID information or other startup info, not big chunks of	765	meant to pass some ID information or other startup info, not big chunks of
643	data.	766	data.
…		…
659	Enter the function specified by the function name in C<$func> in the	782	Enter the function specified by the function name in C<$func> in the
660	process. The function is called with the communication socket as first	783	process. The function is called with the communication socket as first
661	argument, followed by all file handles and string arguments sent earlier	784	argument, followed by all file handles and string arguments sent earlier
662	via C<send_fh> and C<send_arg> methods, in the order they were called.	785	via C<send_fh> and C<send_arg> methods, in the order they were called.
663		786
		787	The process object becomes unusable on return from this function - any
		788	further method calls result in undefined behaviour.
		789
664	The function name should be fully qualified, but if it isn't, it will be	790	The function name should be fully qualified, but if it isn't, it will be
665	looked up in the main package.	791	looked up in the C<main> package.
666		792
667	If the called function returns, doesn't exist, or any error occurs, the	793	If the called function returns, doesn't exist, or any error occurs, the
668	process exits.	794	process exits.
669		795
670	Preparing the process is done in the background - when all commands have	796	Preparing the process is done in the background - when all commands have
671	been sent, the callback is invoked with the local communications socket	797	been sent, the callback is invoked with the local communications socket
672	as argument. At this point you can start using the socket in any way you	798	as argument. At this point you can start using the socket in any way you
673	like.	799	like.
674
675	The process object becomes unusable on return from this function - any
676	further method calls result in undefined behaviour.
677		800
678	If the communication socket isn't used, it should be closed on both sides,	801	If the communication socket isn't used, it should be closed on both sides,
679	to save on kernel memory.	802	to save on kernel memory.
680		803
681	The socket is non-blocking in the parent, and blocking in the newly	804	The socket is non-blocking in the parent, and blocking in the newly
…		…
720	=cut	843	=cut
721		844
722	sub run {	845	sub run {
723	my ($self, $func, $cb) = @_;	846	my ($self, $func, $cb) = @_;
724		847
725	$self->[4] = $cb;	848	$self->[CB] = $cb;
726	$self->_cmd (r => $func);	849	$self->_cmd (r => $func);
		850	}
		851
		852	=back
		853
		854	=head2 ADVANCED METHODS
		855
		856	=over 4
		857
		858	=item new_from_stdio AnyEvent::Fork $fh
		859
		860	Assume that you have a perl interpreter running (without any special
		861	options or a program) somewhere and it has it's STDIN and STDOUT connected
		862	to the C<$fh> somehow. I.e. exactly the state perl is in when you start it
		863	without any arguments:
		864
		865	perl
		866
		867	Then you can create an C<AnyEvent::Fork> object out of this perl
		868	interpreter with this constructor.
		869
		870	When the usefulness of this isn't immediately clear, imagine you manage to
		871	run a perl interpreter remotely (F<ssh remotemachine perl>), then you can
		872	manage it mostly like a local C<AnyEvent::Fork> child.
		873
		874	This works without any module support, i.e. the remote F<perl> does not
		875	need to have any special modules installed.
		876
		877	There are a number of limitations though: C<send_fh> will only work if the
		878	L<IO::FDPass> module is loadable by the remote perl and the two processes
		879	are connected in a way that let's L<IO::FDPass> do it's work.
		880
		881	This will therefore not work over a network conenction. From this follows
		882	that C<fork> will also not work under these circumstances, as it relies on
		883	C<send_fh> internally.
		884
		885	=cut
		886
		887	sub new_from_stdio {
		888	my ($class, $fh) = @_;
		889
		890	my $self = $class->_new ($fh);
		891
		892	# send startup code
		893	push @{ $self->[QUEUE] },
		894	(do "AnyEvent/Fork/serve.pl")
		895	. <<'EOF';
		896	{
		897	open my $fh, "+<&0"
		898	or die "AnyEvent::Fork::Serve::stdio: unable to open communications socket: $!\n";
		899	open STDIN , ">&2";
		900	open STDOUT, ">&2";
		901
		902	$OWNER = "another process";
		903	$0 = "AnyEvent::Fork/stdio of $OWNER";
		904
		905	@_ = $fh;
		906	}
		907
		908	&serve;
		909	__END__
		910	EOF
		911
		912	# the data is only sent when the user requests additional things, which
		913	# is likely early enough for our purposes.
		914
		915	$self
		916	}
		917
		918	=back
		919
		920	=head2 EXPERIMENTAL METHODS
		921
		922	These methods might go away completely or change behaviour, a any time.
		923
		924	=over 4
		925
		926	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		927
		928	Flushes all commands out to the process and then calls the callback with
		929	the communications socket.
		930
		931	The process object becomes unusable on return from this function - any
		932	further method calls result in undefined behaviour.
		933
		934	The point of this method is to give you a file handle thta you cna pass
		935	to another process. In that other process, you can call C<new_from_fh
		936	AnyEvent::Fork> to create a new C<AnyEvent::Fork> object from it, thereby
		937	effectively passing a fork object to another process.
		938
		939	=cut
		940
		941	sub to_fh {
		942	my ($self, $cb) = @_;
		943
		944	$self->[CB] = $cb;
		945
		946	unless ($self->[WW]) {
		947	$self->[CB]->($self->[FH]);
		948	@$self = ();
		949	}
		950	}
		951
		952	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		953
		954	Takes a file handle originally rceeived by the C<to_fh> method and creates
		955	a new C<AnyEvent:Fork> object. The child process itself will not change in
		956	any way, i.e. it will keep all the modifications done to it before calling
		957	C<to_fh>.
		958
		959	The new object is very much like the original object, except that the
		960	C<pid> method will return C<undef> even if the process is a direct child.
		961
		962	=cut
		963
		964	sub new_from_fh {
		965	my ($class, $fh) = @_;
		966
		967	$class->_new ($fh)
727	}	968	}
728		969
729	=back	970	=back
730		971
731	=head1 PERFORMANCE	972	=head1 PERFORMANCE
…		…
741		982
742	2079 new processes per second, using manual socketpair + fork	983	2079 new processes per second, using manual socketpair + fork
743		984
744	Then I did the same thing, but instead of calling fork, I called	985	Then I did the same thing, but instead of calling fork, I called
745	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the	986	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the
746	socket form the child to close on exit. This does the same thing as manual	987	socket from the child to close on exit. This does the same thing as manual
747	socket pair + fork, except that what is forked is the template process	988	socket pair + fork, except that what is forked is the template process
748	(2440kB), and the socket needs to be passed to the server at the other end	989	(2440kB), and the socket needs to be passed to the server at the other end
749	of the socket first.	990	of the socket first.
750		991
751	2307 new processes per second, using AnyEvent::Fork->new	992	2307 new processes per second, using AnyEvent::Fork->new
…		…
756	479 vfork+execs per second, using AnyEvent::Fork->new_exec	997	479 vfork+execs per second, using AnyEvent::Fork->new_exec
757		998
758	So how can C<< AnyEvent->new >> be faster than a standard fork, even	999	So how can C<< AnyEvent->new >> be faster than a standard fork, even
759	though it uses the same operations, but adds a lot of overhead?	1000	though it uses the same operations, but adds a lot of overhead?
760		1001
761	The difference is simply the process size: forking the 6MB process takes	1002	The difference is simply the process size: forking the 5MB process takes
762	so much longer than forking the 2.5MB template process that the overhead	1003	so much longer than forking the 2.5MB template process that the extra
763	introduced is canceled out.	1004	overhead is canceled out.
764		1005
765	If the benchmark process grows, the normal fork becomes even slower:	1006	If the benchmark process grows, the normal fork becomes even slower:
766		1007
767	1340 new processes, manual fork in a 20MB process	1008	1340 new processes, manual fork of a 20MB process
768	731 new processes, manual fork in a 200MB process	1009	731 new processes, manual fork of a 200MB process
769	235 new processes, manual fork in a 2000MB process	1010	235 new processes, manual fork of a 2000MB process
770		1011
771	What that means (to me) is that I can use this module without having a	1012	What that means (to me) is that I can use this module without having a bad
772	very bad conscience because of the extra overhead required to start new	1013	conscience because of the extra overhead required to start new processes.
773	processes.
774		1014
775	=head1 TYPICAL PROBLEMS	1015	=head1 TYPICAL PROBLEMS
776		1016
777	This section lists typical problems that remain. I hope by recognising	1017	This section lists typical problems that remain. I hope by recognising
778	them, most can be avoided.	1018	them, most can be avoided.
779		1019
780	=over 4	1020	=over 4
781		1021
782	=item "leaked" file descriptors for exec'ed processes	1022	=item leaked file descriptors for exec'ed processes
783		1023
784	POSIX systems inherit file descriptors by default when exec'ing a new	1024	POSIX systems inherit file descriptors by default when exec'ing a new
785	process. While perl itself laudably sets the close-on-exec flags on new	1025	process. While perl itself laudably sets the close-on-exec flags on new
786	file handles, most C libraries don't care, and even if all cared, it's	1026	file handles, most C libraries don't care, and even if all cared, it's
787	often not possible to set the flag in a race-free manner.	1027	often not possible to set the flag in a race-free manner.
…		…
807	libraries or the code that leaks those file descriptors.	1047	libraries or the code that leaks those file descriptors.
808		1048
809	Fortunately, most of these leaked descriptors do no harm, other than	1049	Fortunately, most of these leaked descriptors do no harm, other than
810	sitting on some resources.	1050	sitting on some resources.
811		1051
812	=item "leaked" file descriptors for fork'ed processes	1052	=item leaked file descriptors for fork'ed processes
813		1053
814	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,	1054	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,
815	which closes file descriptors not marked for being inherited.	1055	which closes file descriptors not marked for being inherited.
816		1056
817	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer	1057	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer
…		…
826		1066
827	The solution is to either not load these modules before use'ing	1067	The solution is to either not load these modules before use'ing
828	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay	1068	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay
829	initialising them, for example, by calling C<init Gtk2> manually.	1069	initialising them, for example, by calling C<init Gtk2> manually.
830		1070
831	=item exit runs destructors	1071	=item exiting calls object destructors
832		1072
833	This only applies to users of Lc<AnyEvent::Fork:Early> and	1073	This only applies to users of L<AnyEvent::Fork:Early> and
834	L<AnyEvent::Fork::Template>.	1074	L<AnyEvent::Fork::Template>, or when initialising code creates objects
		1075	that reference external resources.
835		1076
836	When a process created by AnyEvent::Fork exits, it might do so by calling	1077	When a process created by AnyEvent::Fork exits, it might do so by calling
837	exit, or simply letting perl reach the end of the program. At which point	1078	exit, or simply letting perl reach the end of the program. At which point
838	Perl runs all destructors.	1079	Perl runs all destructors.
839		1080
…		…
858	to make it so, mostly due to the bloody broken perl that nobody seems to	1099	to make it so, mostly due to the bloody broken perl that nobody seems to
859	care about. The fork emulation is a bad joke - I have yet to see something	1100	care about. The fork emulation is a bad joke - I have yet to see something
860	useful that you can do with it without running into memory corruption	1101	useful that you can do with it without running into memory corruption
861	issues or other braindamage. Hrrrr.	1102	issues or other braindamage. Hrrrr.
862		1103
863	Cygwin perl is not supported at the moment, as it should implement fd	1104	Since fork is endlessly broken on win32 perls (it doesn't even remotely
864	passing, but doesn't, and rolling my own is hard, as cygwin doesn't	1105	work within it's documented limits) and quite obviously it's not getting
865	support enough functionality to do it.	1106	improved any time soon, the best way to proceed on windows would be to
		1107	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1108
		1109	Cygwin perl is not supported at the moment due to some hilarious
		1110	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1111	use C<send_fh> and always use C<new_exec> to create processes, it should
		1112	work though.
866		1113
867	=head1 SEE ALSO	1114	=head1 SEE ALSO
868		1115
869	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),	1116	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1117	(part of this distribution).
		1118
870	L<AnyEvent::Fork::Template> (to create a process by forking the main	1119	L<AnyEvent::Fork::Template>, to create a process by forking the main
871	program at a convenient time).	1120	program at a convenient time (part of this distribution).
872		1121
873	=head1 AUTHOR	1122	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1123
		1124	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1125
		1126	=head1 AUTHOR AND CONTACT INFORMATION
874		1127
875	Marc Lehmann <schmorp@schmorp.de>	1128	Marc Lehmann <schmorp@schmorp.de>
876	http://home.schmorp.de/	1129	http://software.schmorp.de/pkg/AnyEvent-Fork
877		1130
878	=cut	1131	=cut
879		1132
880	1	1133	1
881		1134

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.25 by root, Sat Apr 6 08:55:16 2013 UTC vs. Revision 1.53 by root, Fri Apr 26 15:44:44 2013 UTC

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Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.25 by root, Sat Apr 6 08:55:16 2013 UTC vs.
Revision 1.53 by root, Fri Apr 26 15:44:44 2013 UTC