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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.42 by root, Mon Apr 8 05:44:23 2013 UTC vs.
Revision 1.64 by root, Wed Nov 26 13:37:40 2014 UTC

…		…
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,	42
43	and so on.	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.
44		51
45	=head2 COMPARISON TO OTHER MODULES	52	=head2 COMPARISON TO OTHER MODULES
46		53
47	There is an abundance of modules on CPAN that do "something fork", such as	54	There is an abundance of modules on CPAN that do "something fork", such as
48	L<Parallel::ForkManager>, L<AnyEvent::ForkManager>, L<AnyEvent::Worker>	55	L<Parallel::ForkManager>, L<AnyEvent::ForkManager>, L<AnyEvent::Worker>
49	or L<AnyEvent::Subprocess>. There are modules that implement their own	56	or L<AnyEvent::Subprocess>. There are modules that implement their own
50	process management, such as L<AnyEvent::DBI>.	57	process management, such as L<AnyEvent::DBI>.
51		58
52	The problems that all these modules try to solve are real, however, none	59	The problems that all these modules try to solve are real, however, none
53	of them (from what I have seen) tackle the very real problems of unwanted	60	of them (from what I have seen) tackle the very real problems of unwanted
54	memory sharing, efficiency, not being able to use event processing or	61	memory sharing, efficiency or not being able to use event processing, GUI
55	similar modules in the processes they create.	62	toolkits or similar modules in the processes they create.
56		63
57	This module doesn't try to replace any of them - instead it tries to solve	64	This module doesn't try to replace any of them - instead it tries to solve
58	the problem of creating processes with a minimum of fuss and overhead (and	65	the problem of creating processes with a minimum of fuss and overhead (and
59	also luxury). Ideally, most of these would use AnyEvent::Fork internally,	66	also luxury). Ideally, most of these would use AnyEvent::Fork internally,
60	except they were written before AnyEvent:Fork was available, so obviously	67	except they were written before AnyEvent:Fork was available, so obviously
…		…
82		89
83	=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
84	process.	91	process.
85		92
86	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
87	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
88	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
89	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
90	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
91	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
92	increase memory usage when freeing memory.	101	unexpectedly increase memory usage when freeing memory.
93		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
94	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
95	bad), and no sharing with exec.	113	bad), and no sharing with exec.
96		114
97	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
98	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
99	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
…		…
104	shared and what isn't, at all times.	122	shared and what isn't, at all times.
105		123
106	=item Exec'ing a new perl process might be difficult.	124	=item Exec'ing a new perl process might be difficult.
107		125
108	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
109	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.
110		129
111	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
112	interpreter. With a cooperative main program, exec'ing the interpreter	131	interpreter. With a cooperative main program, exec'ing the interpreter
113	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,
114	it will still work when used from a module.	133	it will still work when used from a module.
…		…
120	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
121	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
122	loaded.	141	loaded.
123		142
124	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
125	a template for new processes.	144	a template for new processes at a later time, e.g. for use in a process
		145	pool.
126		146
127	=item Forking might be impossible when a program is running.	147	=item Forking might be impossible when a program is running.
128		148
129	For example, POSIX makes it almost impossible to fork from a	149	For example, POSIX makes it almost impossible to fork from a
130	multi-threaded program while doing anything useful in the child - in	150	multi-threaded program while doing anything useful in the child - in
131	fact, if your perl program uses POSIX threads (even indirectly via	151	fact, if your perl program uses POSIX threads (even indirectly via
132	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
133	anymore without risking corruption issues on a number of operating	153	anymore without risking memory corruption or worse on a number of
134	systems.	154	operating systems.
135		155
136	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
137	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>).
138		158
139	=item Parallel processing with fork might be inconvenient or difficult	159	=item Parallel processing with fork might be inconvenient or difficult
…		…
157	possible to use modules such as event loops or window interfaces safely.	177	possible to use modules such as event loops or window interfaces safely.
158		178
159	=back	179	=back
160		180
161	=head1 EXAMPLES	181	=head1 EXAMPLES
		182
		183	This is where the wall of text ends and code speaks.
162		184
163	=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.
164		186
165	AnyEvent::Fork	187	AnyEvent::Fork
166	->new	188	->new
…		…
221	}	243	}
222	}	244	}
223		245
224	=head2 use AnyEvent::Fork as a faster fork+exec	246	=head2 use AnyEvent::Fork as a faster fork+exec
225		247
226	This runs C</bin/echo hi>, with stdandard output redirected to /tmp/log	248	This runs C</bin/echo hi>, with standard output redirected to F</tmp/log>
227	and standard error redirected to the communications socket. It is usually	249	and standard error redirected to the communications socket. It is usually
228	faster than fork+exec, but still lets you prepare the environment.	250	faster than fork+exec, but still lets you prepare the environment.
229		251
230	open my $output, ">/tmp/log" or die "$!";	252	open my $output, ">/tmp/log" or die "$!";
231		253
…		…
247	->send_arg ("/bin/echo", "hi")	269	->send_arg ("/bin/echo", "hi")
248	->run ("run", my $cv = AE::cv);	270	->run ("run", my $cv = AE::cv);
249		271
250	my $stderr = $cv->recv;	272	my $stderr = $cv->recv;
251		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
252	=head1 CONCEPTS	343	=head1 CONCEPTS
253		344
254	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
255	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".
256		351
257	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
258	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,
259	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
260	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
…		…
370	use AnyEvent;	465	use AnyEvent;
371	use AnyEvent::Util ();	466	use AnyEvent::Util ();
372		467
373	use IO::FDPass;	468	use IO::FDPass;
374		469
375	our $VERSION = 0.6;	470	our $VERSION = 1.2;
376
377	=over 4
378
379	=back
380
381	=cut
382		471
383	# the early fork template process	472	# the early fork template process
384	our $EARLY;	473	our $EARLY;
385		474
386	# the empty template process	475	# the empty template process
…		…
434	# send string	523	# send string
435	my $len = syswrite $self->[FH], $self->[QUEUE][0];	524	my $len = syswrite $self->[FH], $self->[QUEUE][0];
436		525
437	unless ($len) {	526	unless ($len) {
438	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	527	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
439	undef $self->[3];	528	undef $self->[WW];
440	die "AnyEvent::Fork: command write failure: $!";	529	die "AnyEvent::Fork: command write failure: $!";
441	}	530	}
442		531
443	substr $self->[QUEUE][0], 0, $len, "";	532	substr $self->[QUEUE][0], 0, $len, "";
444	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];	533	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
…		…
447		536
448	# everything written	537	# everything written
449	undef $self->[WW];	538	undef $self->[WW];
450		539
451	# invoke run callback, if any	540	# invoke run callback, if any
		541	if ($self->[CB]) {
452	$self->[CB]->($self->[FH]) if $self->[CB];	542	$self->[CB]->($self->[FH]);
		543	@$self = ();
		544	}
453	};	545	};
454		546
455	() # make sure we don't leak the watcher	547	() # make sure we don't leak the watcher
456	}	548	}
457		549
…		…
528		620
529	You should use C<new> whenever possible, except when having a template	621	You should use C<new> whenever possible, except when having a template
530	process around is unacceptable.	622	process around is unacceptable.
531		623
532	The path to the perl interpreter is divined using various methods - first	624	The path to the perl interpreter is divined using various methods - first
533	C<$^X> is investigated to see if the path ends with something that sounds	625	C<$^X> is investigated to see if the path ends with something that looks
534	as if it were the perl interpreter. Failing this, the module falls back to	626	as if it were the perl interpreter. Failing this, the module falls back to
535	using C<$Config::Config{perlpath}>.	627	using C<$Config::Config{perlpath}>.
536		628
		629	The path to perl can also be overriden by setting the global variable
		630	C<$AnyEvent::Fork::PERL> - it's value will be used for all subsequent
		631	invocations.
		632
537	=cut	633	=cut
		634
		635	our $PERL;
538		636
539	sub new_exec {	637	sub new_exec {
540	my ($self) = @_;	638	my ($self) = @_;
541		639
542	return $EARLY->fork	640	return $EARLY->fork
543	if $EARLY;	641	if $EARLY;
544		642
		643	unless (defined $PERL) {
545	# first find path of perl	644	# first find path of perl
546	my $perl = $;	645	my $perl = $^X;
547		646
548	# first we try $^X, but the path must be absolute (always on win32), and end in sth.	647	# first we try $^X, but the path must be absolute (always on win32), and end in sth.
549	# that looks like perl. this obviously only works for posix and win32	648	# that looks like perl. this obviously only works for posix and win32
550	unless (	649	unless (
551	($^O eq "MSWin32" \|\| $perl =~ m%^/%)	650	($^O eq "MSWin32" \|\| $perl =~ m%^/%)
552	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i	651	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i
553	) {	652	) {
554	# if it doesn't look perlish enough, try Config	653	# if it doesn't look perlish enough, try Config
555	require Config;	654	require Config;
556	$perl = $Config::Config{perlpath};	655	$perl = $Config::Config{perlpath};
557	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;	656	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;
		657	}
		658
		659	$PERL = $perl;
558	}	660	}
559		661
560	require Proc::FastSpawn;	662	require Proc::FastSpawn;
561		663
562	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	664	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
570	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;	672	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;
571	my %env = %ENV;	673	my %env = %ENV;
572	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;	674	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;
573		675
574	my $pid = Proc::FastSpawn::spawn (	676	my $pid = Proc::FastSpawn::spawn (
575	$perl,	677	$PERL,
576	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],	678	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],
577	[map "$_=$env{$_}", keys %env],	679	[map "$_=$env{$_}", keys %env],
578	) or die "unable to spawn AnyEvent::Fork server: $!";	680	) or die "unable to spawn AnyEvent::Fork server: $!";
579		681
580	$self->_new ($fh, $pid)	682	$self->_new ($fh, $pid)
581	}	683	}
582		684
583	=item $pid = $proc->pid	685	=item $pid = $proc->pid
584		686
585	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
586	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.
587		692
588	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
589	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,
590	to clean up their zombies when they die.	695	you need to check whether a process is a diretc child by calling this
591		696	method, and possibly creating a child watcher or reap it manually.
592	All other processes are not direct children, and will be cleaned up by
593	AnyEvent::Fork itself.
594		697
595	=cut	698	=cut
596		699
597	sub pid {	700	sub pid {
598	$_[0][PID]	701	$_[0][PID]
599	}	702	}
600		703
601	=item $proc = $proc->eval ($perlcode, @args)	704	=item $proc = $proc->eval ($perlcode, @args)
602		705
603	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
604	the strings specified by C<@args>, in the "main" package.	707	the strings specified by C<@args>, in the "main" package.
605		708
606	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
607	(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
608	to completely take over the process, use C<run> for that.	711	to completely take over the process, use C<run> for that.
…		…
729		832
730	Even if not used otherwise, the socket can be a good indicator for the	833	Even if not used otherwise, the socket can be a good indicator for the
731	existence of the process - if the other process exits, you get a readable	834	existence of the process - if the other process exits, you get a readable
732	event on it, because exiting the process closes the socket (if it didn't	835	event on it, because exiting the process closes the socket (if it didn't
733	create any children using fork).	836	create any children using fork).
		837
		838	=over 4
		839
		840	=item Compatibility to L<AnyEvent::Fork::Remote>
		841
		842	If you want to write code that works with both this module and
		843	L<AnyEvent::Fork::Remote>, you need to write your code so that it assumes
		844	there are two file handles for communications, which might not be unix
		845	domain sockets. The C<run> function should start like this:
		846
		847	sub run {
		848	my ($rfh, @args) = @_; # @args is your normal arguments
		849	my $wfh = fileno $rfh ? $rfh : *STDOUT;
		850
		851	# now use $rfh for reading and $wfh for writing
		852	}
		853
		854	This checks whether the passed file handle is, in fact, the process
		855	C<STDIN> handle. If it is, then the function was invoked visa
		856	L<AnyEvent::Fork::Remote>, so STDIN should be used for reading and
		857	C<STDOUT> should be used for writing.
		858
		859	In all other cases, the function was called via this module, and there is
		860	only one file handle that should be sued for reading and writing.
		861
		862	=back
734		863
735	Example: create a template for a process pool, pass a few strings, some	864	Example: create a template for a process pool, pass a few strings, some
736	file handles, then fork, pass one more string, and run some code.	865	file handles, then fork, pass one more string, and run some code.
737		866
738	my $pool = AnyEvent::Fork	867	my $pool = AnyEvent::Fork
…		…
772	$self->_cmd (r => $func);	901	$self->_cmd (r => $func);
773	}	902	}
774		903
775	=back	904	=back
776		905
		906	=head2 EXPERIMENTAL METHODS
		907
		908	These methods might go away completely or change behaviour, at any time.
		909
		910	=over 4
		911
		912	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		913
		914	Flushes all commands out to the process and then calls the callback with
		915	the communications socket.
		916
		917	The process object becomes unusable on return from this function - any
		918	further method calls result in undefined behaviour.
		919
		920	The point of this method is to give you a file handle that you can pass
		921	to another process. In that other process, you can call C<new_from_fh
		922	AnyEvent::Fork $fh> to create a new C<AnyEvent::Fork> object from it,
		923	thereby effectively passing a fork object to another process.
		924
		925	=cut
		926
		927	sub to_fh {
		928	my ($self, $cb) = @_;
		929
		930	$self->[CB] = $cb;
		931
		932	unless ($self->[WW]) {
		933	$self->[CB]->($self->[FH]);
		934	@$self = ();
		935	}
		936	}
		937
		938	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		939
		940	Takes a file handle originally rceeived by the C<to_fh> method and creates
		941	a new C<AnyEvent:Fork> object. The child process itself will not change in
		942	any way, i.e. it will keep all the modifications done to it before calling
		943	C<to_fh>.
		944
		945	The new object is very much like the original object, except that the
		946	C<pid> method will return C<undef> even if the process is a direct child.
		947
		948	=cut
		949
		950	sub new_from_fh {
		951	my ($class, $fh) = @_;
		952
		953	$class->_new ($fh)
		954	}
		955
		956	=back
		957
777	=head1 PERFORMANCE	958	=head1 PERFORMANCE
778		959
779	Now for some unscientific benchmark numbers (all done on an amd64	960	Now for some unscientific benchmark numbers (all done on an amd64
780	GNU/Linux box). These are intended to give you an idea of the relative	961	GNU/Linux box). These are intended to give you an idea of the relative
781	performance you can expect, they are not meant to be absolute performance	962	performance you can expect, they are not meant to be absolute performance
…		…
787		968
788	2079 new processes per second, using manual socketpair + fork	969	2079 new processes per second, using manual socketpair + fork
789		970
790	Then I did the same thing, but instead of calling fork, I called	971	Then I did the same thing, but instead of calling fork, I called
791	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the	972	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the
792	socket form the child to close on exit. This does the same thing as manual	973	socket from the child to close on exit. This does the same thing as manual
793	socket pair + fork, except that what is forked is the template process	974	socket pair + fork, except that what is forked is the template process
794	(2440kB), and the socket needs to be passed to the server at the other end	975	(2440kB), and the socket needs to be passed to the server at the other end
795	of the socket first.	976	of the socket first.
796		977
797	2307 new processes per second, using AnyEvent::Fork->new	978	2307 new processes per second, using AnyEvent::Fork->new
…		…
804	So how can C<< AnyEvent->new >> be faster than a standard fork, even	985	So how can C<< AnyEvent->new >> be faster than a standard fork, even
805	though it uses the same operations, but adds a lot of overhead?	986	though it uses the same operations, but adds a lot of overhead?
806		987
807	The difference is simply the process size: forking the 5MB process takes	988	The difference is simply the process size: forking the 5MB process takes
808	so much longer than forking the 2.5MB template process that the extra	989	so much longer than forking the 2.5MB template process that the extra
809	overhead introduced is canceled out.	990	overhead is canceled out.
810		991
811	If the benchmark process grows, the normal fork becomes even slower:	992	If the benchmark process grows, the normal fork becomes even slower:
812		993
813	1340 new processes, manual fork of a 20MB process	994	1340 new processes, manual fork of a 20MB process
814	731 new processes, manual fork of a 200MB process	995	731 new processes, manual fork of a 200MB process
…		…
874	initialising them, for example, by calling C<init Gtk2> manually.	1055	initialising them, for example, by calling C<init Gtk2> manually.
875		1056
876	=item exiting calls object destructors	1057	=item exiting calls object destructors
877		1058
878	This only applies to users of L<AnyEvent::Fork:Early> and	1059	This only applies to users of L<AnyEvent::Fork:Early> and
879	L<AnyEvent::Fork::Template>, or when initialiasing code creates objects	1060	L<AnyEvent::Fork::Template>, or when initialising code creates objects
880	that reference external resources.	1061	that reference external resources.
881		1062
882	When a process created by AnyEvent::Fork exits, it might do so by calling	1063	When a process created by AnyEvent::Fork exits, it might do so by calling
883	exit, or simply letting perl reach the end of the program. At which point	1064	exit, or simply letting perl reach the end of the program. At which point
884	Perl runs all destructors.	1065	Perl runs all destructors.
…		…
904	to make it so, mostly due to the bloody broken perl that nobody seems to	1085	to make it so, mostly due to the bloody broken perl that nobody seems to
905	care about. The fork emulation is a bad joke - I have yet to see something	1086	care about. The fork emulation is a bad joke - I have yet to see something
906	useful that you can do with it without running into memory corruption	1087	useful that you can do with it without running into memory corruption
907	issues or other braindamage. Hrrrr.	1088	issues or other braindamage. Hrrrr.
908		1089
		1090	Since fork is endlessly broken on win32 perls (it doesn't even remotely
		1091	work within it's documented limits) and quite obviously it's not getting
		1092	improved any time soon, the best way to proceed on windows would be to
		1093	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1094
909	Cygwin perl is not supported at the moment due to some hilarious	1095	Cygwin perl is not supported at the moment due to some hilarious
910	shortcomings of its API - see L<IO::FDPoll> for more details.	1096	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1097	use C<send_fh> and always use C<new_exec> to create processes, it should
		1098	work though.
		1099
		1100	=head1 USING AnyEvent::Fork IN SUBPROCESSES
		1101
		1102	AnyEvent::Fork itself cannot generally be used in subprocesses. As long as
		1103	only one process ever forks new processes, sharing the template processes
		1104	is possible (you could use a pipe as a lock by writing a byte into it to
		1105	unlock, and reading the byte to lock for example)
		1106
		1107	To make concurrent calls possible after fork, you should get rid of the
		1108	template and early fork processes. AnyEvent::Fork will create a new
		1109	template process as needed.
		1110
		1111	undef $AnyEvent::Fork::EARLY;
		1112	undef $AnyEvent::Fork::TEMPLATE;
		1113
		1114	It doesn't matter whether you get rid of them in the parent or child after
		1115	a fork.
911		1116
912	=head1 SEE ALSO	1117	=head1 SEE ALSO
913		1118
914	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),	1119	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1120	(part of this distribution).
		1121
915	L<AnyEvent::Fork::Template> (to create a process by forking the main	1122	L<AnyEvent::Fork::Template>, to create a process by forking the main
916	program at a convenient time).	1123	program at a convenient time (part of this distribution).
917		1124
918	=head1 AUTHOR	1125	L<AnyEvent::Fork::Remote>, for another way to create processes that is
		1126	mostly compatible to this module and modules building on top of it, but
		1127	works better with remote processes.
		1128
		1129	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1130
		1131	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1132
		1133	=head1 AUTHOR AND CONTACT INFORMATION
919		1134
920	Marc Lehmann <schmorp@schmorp.de>	1135	Marc Lehmann <schmorp@schmorp.de>
921	http://home.schmorp.de/	1136	http://software.schmorp.de/pkg/AnyEvent-Fork
922		1137
923	=cut	1138	=cut
924		1139
925	1	1140	1
926		1141

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.42 by root, Mon Apr 8 05:44:23 2013 UTC vs. Revision 1.64 by root, Wed Nov 26 13:37:40 2014 UTC

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Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.42 by root, Mon Apr 8 05:44:23 2013 UTC vs.
Revision 1.64 by root, Wed Nov 26 13:37:40 2014 UTC