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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.18 by root, Sat Apr 6 01:33:56 2013 UTC vs.
Revision 1.64 by root, Wed Nov 26 13:37:40 2014 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::Fork;	7	use AnyEvent::Fork;
8		8
9	##################################################################	9	AnyEvent::Fork
		10	->new
		11	->require ("MyModule")
		12	->run ("MyModule::server", my $cv = AE::cv);
		13
		14	my $fh = $cv->recv;
		15
		16	=head1 DESCRIPTION
		17
		18	This module allows you to create new processes, without actually forking
		19	them from your current process (avoiding the problems of forking), but
		20	preserving most of the advantages of fork.
		21
		22	It can be used to create new worker processes or new independent
		23	subprocesses for short- and long-running jobs, process pools (e.g. for use
		24	in pre-forked servers) but also to spawn new external processes (such as
		25	CGI scripts from a web server), which can be faster (and more well behaved)
		26	than using fork+exec in big processes.
		27
		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>
		30	or L<PAR::Packer>.
		31
		32	=head2 WHAT THIS MODULE IS NOT
		33
		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 -
		36	there is no back channel from the process back to you, and there is no RPC
		37	or message passing going on.
		38
		39	If you need some form of RPC, you could use the L<AnyEvent::Fork::RPC>
		40	companion module, which adds simple RPC/job queueing to a process created
		41	by this module.
		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
		70	=head2 PROBLEM STATEMENT
		71
		72	There are two traditional ways to implement parallel processing on UNIX
		73	like operating systems - fork and process, and fork+exec and process. They
		74	have different advantages and disadvantages that I describe below,
		75	together with how this module tries to mitigate the disadvantages.
		76
		77	=over 4
		78
		79	=item Forking from a big process can be very slow.
		80
		81	A 5GB process needs 0.05s to fork on my 3.6GHz amd64 GNU/Linux box. This
		82	overhead is often shared with exec (because you have to fork first), but
		83	in some circumstances (e.g. when vfork is used), fork+exec can be much
		84	faster.
		85
		86	This module can help here by telling a small(er) helper process to fork,
		87	which is faster then forking the main process, and also uses vfork where
		88	possible. This gives the speed of vfork, with the flexibility of fork.
		89
		90	=item Forking usually creates a copy-on-write copy of the parent
		91	process.
		92
		93	For example, modules or data files that are loaded will not use additional
		94	memory after a fork. Exec'ing a new process, in contrast, means modules
		95	and data files might need to be loaded again, at extra CPU and memory
		96	cost.
		97
		98	But when forking, you still create a copy of your data structures - if
		99	the program frees them and replaces them by new data, the child processes
		100	will retain the old version even if it isn't used, which can suddenly and
		101	unexpectedly increase memory usage when freeing memory.
		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
		112	There is a trade-off between more sharing with fork (which can be good or
		113	bad), and no sharing with exec.
		114
		115	This module allows the main program to do a controlled fork, and allows
		116	modules to exec processes safely at any time. When creating a custom
		117	process pool you can take advantage of data sharing via fork without
		118	risking to share large dynamic data structures that will blow up child
		119	memory usage.
		120
		121	In other words, this module puts you into control over what is being
		122	shared and what isn't, at all times.
		123
		124	=item Exec'ing a new perl process might be difficult.
		125
		126	For example, it is not easy to find the correct path to the perl
		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.
		129
		130	This module tries hard to identify the correct path to the perl
		131	interpreter. With a cooperative main program, exec'ing the interpreter
		132	might not even be necessary, but even without help from the main program,
		133	it will still work when used from a module.
		134
		135	=item Exec'ing a new perl process might be slow, as all necessary modules
		136	have to be loaded from disk again, with no guarantees of success.
		137
		138	Long running processes might run into problems when perl is upgraded
		139	and modules are no longer loadable because they refer to a different
		140	perl version, or parts of a distribution are newer than the ones already
		141	loaded.
		142
		143	This module supports creating pre-initialised perl processes to be used as
		144	a template for new processes at a later time, e.g. for use in a process
		145	pool.
		146
		147	=item Forking might be impossible when a program is running.
		148
		149	For example, POSIX makes it almost impossible to fork from a
		150	multi-threaded program while doing anything useful in the child - in
		151	fact, if your perl program uses POSIX threads (even indirectly via
		152	e.g. L<IO::AIO> or L<threads>), you cannot call fork on the perl level
		153	anymore without risking memory corruption or worse on a number of
		154	operating systems.
		155
		156	This module can safely fork helper processes at any time, by calling
		157	fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>).
		158
		159	=item Parallel processing with fork might be inconvenient or difficult
		160	to implement. Modules might not work in both parent and child.
		161
		162	For example, when a program uses an event loop and creates watchers it
		163	becomes very hard to use the event loop from a child program, as the
		164	watchers already exist but are only meaningful in the parent. Worse, a
		165	module might want to use such a module, not knowing whether another module
		166	or the main program also does, leading to problems.
		167
		168	Apart from event loops, graphical toolkits also commonly fall into the
		169	"unsafe module" category, or just about anything that communicates with
		170	the external world, such as network libraries and file I/O modules, which
		171	usually don't like being copied and then allowed to continue in two
		172	processes.
		173
		174	With this module only the main program is allowed to create new processes
		175	by forking (because only the main program can know when it is still safe
		176	to do so) - all other processes are created via fork+exec, which makes it
		177	possible to use modules such as event loops or window interfaces safely.
		178
		179	=back
		180
		181	=head1 EXAMPLES
		182
		183	This is where the wall of text ends and code speaks.
		184
10	# 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.
11		186
12	AnyEvent::Fork	187	AnyEvent::Fork
13	->new	188	->new
14	->require ("MyModule")	189	->require ("MyModule")
15	->run ("MyModule::worker, sub {	190	->run ("MyModule::worker, sub {
…		…
17		192
18	# now $master_filehandle is connected to the	193	# now $master_filehandle is connected to the
19	# $slave_filehandle in the new process.	194	# $slave_filehandle in the new process.
20	});	195	});
21		196
22	# MyModule::worker might look like this	197	C<MyModule> might look like this:
		198
		199	package MyModule;
		200
23	sub MyModule::worker {	201	sub worker {
24	my ($slave_filehandle) = @_;	202	my ($slave_filehandle) = @_;
25		203
26	# now $slave_filehandle is connected to the $master_filehandle	204	# now $slave_filehandle is connected to the $master_filehandle
27	# in the original prorcess. have fun!	205	# in the original prorcess. have fun!
28	}	206	}
29		207
30	##################################################################
31	# 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.
32		209
33	# create listener socket	210	# create listener socket
34	my $listener = ...;	211	my $listener = ...;
35		212
36	# create a pool template, initialise it and give it the socket	213	# create a pool template, initialise it and give it the socket
…		…
48	}	225	}
49		226
50	# now do other things - maybe use the filehandle provided by run	227	# now do other things - maybe use the filehandle provided by run
51	# to wait for the processes to die. or whatever.	228	# to wait for the processes to die. or whatever.
52		229
53	# My::Server::run might look like this	230	C<My::Server> might look like this:
54	sub My::Server::run {	231
		232	package My::Server;
		233
		234	sub run {
55	my ($slave, $listener, $id) = @_;	235	my ($slave, $listener, $id) = @_;
56		236
57	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
58		238
59	# 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,
…		…
61	while (my $socket = $listener->accept) {	241	while (my $socket = $listener->accept) {
62	# do sth. with new socket	242	# do sth. with new socket
63	}	243	}
64	}	244	}
65		245
66	=head1 DESCRIPTION	246	=head2 use AnyEvent::Fork as a faster fork+exec
67		247
68	This module allows you to create new processes, without actually forking	248	This runs C</bin/echo hi>, with standard output redirected to F</tmp/log>
69	them from your current process (avoiding the problems of forking), but	249	and standard error redirected to the communications socket. It is usually
70	preserving most of the advantages of fork.	250	faster than fork+exec, but still lets you prepare the environment.
71		251
72	It can be used to create new worker processes or new independent	252	open my $output, ">/tmp/log" or die "$!";
73	subprocesses for short- and long-running jobs, process pools (e.g. for use
74	in pre-forked servers) but also to spawn new external processes (such as
75	CGI scripts from a web server), which can be faster (and more well behaved)
76	than using fork+exec in big processes.
77		253
78	Special care has been taken to make this module useful from other modules,	254	AnyEvent::Fork
79	while still supporting specialised environments such as L<App::Staticperl>	255	->new
80	or L<PAR::Packer>.	256	->eval ('
		257	# compile a helper function for later use
		258	sub run {
		259	my ($fh, $output, @cmd) = @_;
81		260
82	=head1 WHAT THIS MODULE IS NOT	261	# perl will clear close-on-exec on STDOUT/STDERR
		262	open STDOUT, ">&", $output or die;
		263	open STDERR, ">&", $fh or die;
83		264
84	This module only creates processes and lets you pass file handles and	265	exec @cmd;
85	strings to it, and run perl code. It does not implement any kind of RPC -	266	}
86	there is no back channel from the process back to you, and there is no RPC	267	')
87	or message passing going on.	268	->send_fh ($output)
		269	->send_arg ("/bin/echo", "hi")
		270	->run ("run", my $cv = AE::cv);
88		271
89	If you need some form of RPC, you can either implement it yourself	272	my $stderr = $cv->recv;
90	in whatever way you like, use some message-passing module such
91	as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use
92	L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages,
93	and so on.
94		273
95	=head1 PROBLEM STATEMENT	274	=head2 For stingy users: put the worker code into a C<DATA> section.
96		275
97	There are two ways to implement parallel processing on UNIX like operating	276	When you want to be stingy with files, you can put your code into the
98	systems - fork and process, and fork+exec and process. They have different	277	C<DATA> section of your module (or program):
99	advantages and disadvantages that I describe below, together with how this
100	module tries to mitigate the disadvantages.
101		278
102	=over 4	279	use AnyEvent::Fork;
103		280
104	=item Forking from a big process can be very slow (a 5GB process needs	281	AnyEvent::Fork
105	0.05s to fork on my 3.6GHz amd64 GNU/Linux box for example). This overhead	282	->new
106	is often shared with exec (because you have to fork first), but in some	283	->eval (do { local $/; <DATA> })
107	circumstances (e.g. when vfork is used), fork+exec can be much faster.	284	->run ("doit", sub { ... });
108		285
109	This module can help here by telling a small(er) helper process to fork,	286	__DATA__
110	or fork+exec instead.
111		287
112	=item Forking usually creates a copy-on-write copy of the parent	288	sub doit {
113	process. Memory (for example, modules or data files that have been	289	... do something!
114	will not take additional memory). When exec'ing a new process, modules	290	}
115	and data files might need to be loaded again, at extra CPU and memory
116	cost. Likewise when forking, all data structures are copied as well - if
117	the program frees them and replaces them by new data, the child processes
118	will retain the memory even if it isn't used.
119		291
120	This module allows the main program to do a controlled fork, and allows	292	=head2 For stingy standalone programs: do not rely on external files at
121	modules to exec processes safely at any time. When creating a custom	293	all.
122	process pool you can take advantage of data sharing via fork without
123	risking to share large dynamic data structures that will blow up child
124	memory usage.
125		294
126	=item Exec'ing a new perl process might be difficult and slow. For	295	For single-file scripts it can be inconvenient to rely on external
127	example, it is not easy to find the correct path to the perl interpreter,	296	files - even when using a C<DATA> section, you still need to C<exec> an
128	and all modules have to be loaded from disk again. Long running processes	297	external perl interpreter, which might not be available when using
129	might run into problems when perl is upgraded for example.	298	L<App::Staticperl>, L<Urlader> or L<PAR::Packer> for example.
130		299
131	This module supports creating pre-initialised perl processes to be used	300	Two modules help here - L<AnyEvent::Fork::Early> forks a template process
132	as template, and also tries hard to identify the correct path to the perl	301	for all further calls to C<new_exec>, and L<AnyEvent::Fork::Template>
133	interpreter. With a cooperative main program, exec'ing the interpreter	302	forks the main program as a template process.
134	might not even be necessary.
135		303
136	=item Forking might be impossible when a program is running. For example,	304	Here is how your main program should look like:
137	POSIX makes it almost impossible to fork from a multi-threaded program and
138	do anything useful in the child - strictly speaking, if your perl program
139	uses posix threads (even indirectly via e.g. L<IO::AIO> or L<threads>),
140	you cannot call fork on the perl level anymore, at all.
141		305
142	This module can safely fork helper processes at any time, by calling	306	#! perl
143	fork+exec in C, in a POSIX-compatible way.
144		307
145	=item Parallel processing with fork might be inconvenient or difficult	308	# optional, as the very first thing.
146	to implement. For example, when a program uses an event loop and creates	309	# in case modules want to create their own processes.
147	watchers it becomes very hard to use the event loop from a child	310	use AnyEvent::Fork::Early;
148	program, as the watchers already exist but are only meaningful in the
149	parent. Worse, a module might want to use such a system, not knowing
150	whether another module or the main program also does, leading to problems.
151		311
152	This module only lets the main program create pools by forking (because	312	# next, load all modules you need in your template process
153	only the main program can know when it is still safe to do so) - all other	313	use Example::My::Module
154	pools are created by fork+exec, after which such modules can again be	314	use Example::Whatever;
155	loaded.
156		315
157	=back	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	$cv->recv;
158		342
159	=head1 CONCEPTS	343	=head1 CONCEPTS
160		344
161	This module can create new processes either by executing a new perl	345	This module can create new processes either by executing a new perl
162	process, or by forking from an existing "template" process.	346	process, or by forking from an existing "template" process.
		347
		348	All these processes are called "child processes" (whether they are direct
		349	children or not), while the process that manages them is called the
		350	"parent process".
163		351
164	Each such process comes with its own file handle that can be used to	352	Each such process comes with its own file handle that can be used to
165	communicate with it (it's actually a socket - one end in the new process,	353	communicate with it (it's actually a socket - one end in the new process,
166	one end in the main process), and among the things you can do in it are	354	one end in the main process), and among the things you can do in it are
167	load modules, fork new processes, send file handles to it, and execute	355	load modules, fork new processes, send file handles to it, and execute
…		…
241	my ($fork_fh) = @_;	429	my ($fork_fh) = @_;
242	});	430	});
243		431
244	=back	432	=back
245		433
246	=head1 FUNCTIONS	434	=head1 THE C<AnyEvent::Fork> CLASS
		435
		436	This module exports nothing, and only implements a single class -
		437	C<AnyEvent::Fork>.
		438
		439	There are two class constructors that both create new processes - C<new>
		440	and C<new_exec>. The C<fork> method creates a new process by forking an
		441	existing one and could be considered a third constructor.
		442
		443	Most of the remaining methods deal with preparing the new process, by
		444	loading code, evaluating code and sending data to the new process. They
		445	usually return the process object, so you can chain method calls.
		446
		447	If a process object is destroyed before calling its C<run> method, then
		448	the process simply exits. After C<run> is called, all responsibility is
		449	passed to the specified function.
		450
		451	As long as there is any outstanding work to be done, process objects
		452	resist being destroyed, so there is no reason to store them unless you
		453	need them later - configure and forget works just fine.
247		454
248	=over 4	455	=over 4
249		456
250	=cut	457	=cut
251		458
…		…
258	use AnyEvent;	465	use AnyEvent;
259	use AnyEvent::Util ();	466	use AnyEvent::Util ();
260		467
261	use IO::FDPass;	468	use IO::FDPass;
262		469
263	our $VERSION = 0.2;	470	our $VERSION = 1.2;
264
265	our $PERL; # the path to the perl interpreter, deduces with various forms of magic
266
267	=item my $pool = new AnyEvent::Fork key => value...
268
269	Create a new process pool. The following named parameters are supported:
270
271	=over 4
272
273	=back
274
275	=cut
276		471
277	# the early fork template process	472	# the early fork template process
278	our $EARLY;	473	our $EARLY;
279		474
280	# the empty template process	475	# the empty template process
281	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	}
282		498
283	sub _cmd {	499	sub _cmd {
284	my $self = shift;	500	my $self = shift;
285		501
286	# 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
287	# 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
288	# it.	504	# it.
289	push @{ $self->[2] }, pack "L/a", pack "(w/a)*", @_;	505	push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1];
290		506
291	unless ($self->[3]) {	507	$self->[WW] \|\|= AE::io $self->[FH], 1, sub {
292	my $wcb = sub {
293	do {	508	do {
294	# 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,
295	# or a plain string.	510	# or a plain string.
296		511
297	if (ref $self->[2][0]) {	512	if (ref $self->[QUEUE][0]) {
298	# send fh	513	# send fh
299	unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) {	514	unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) {
300	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	515	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
301	undef $self->[3];	516	undef $self->[WW];
302	die "AnyEvent::Fork: file descriptor send failure: $!";	517	die "AnyEvent::Fork: file descriptor send failure: $!";
303	}
304
305	shift @{ $self->[2] };
306
307	} else {
308	# send string
309	my $len = syswrite $self->[1], $self->[2][0];
310
311	unless ($len) {
312	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
313	undef $self->[3];
314	die "AnyEvent::Fork: command write failure: $!";
315	}
316
317	substr $self->[2][0], 0, $len, "";
318	shift @{ $self->[2] } unless length $self->[2][0];
319	}	518	}
		519
		520	shift @{ $self->[QUEUE] };
		521
		522	} else {
		523	# send string
		524	my $len = syswrite $self->[FH], $self->[QUEUE][0];
		525
		526	unless ($len) {
		527	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
		528	undef $self->[WW];
		529	die "AnyEvent::Fork: command write failure: $!";
		530	}
		531
		532	substr $self->[QUEUE][0], 0, $len, "";
		533	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
		534	}
320	} while @{ $self->[2] };	535	} while @{ $self->[QUEUE] };
321		536
322	# everything written	537	# everything written
323	undef $self->[3];	538	undef $self->[WW];
		539
324	# invoke run callback	540	# invoke run callback, if any
		541	if ($self->[CB]) {
325	$self->[0]->($self->[1]) if $self->[0];	542	$self->[CB]->($self->[FH]);
		543	@$self = ();
326	};	544	}
327
328	$wcb->();
329
330	$self->[3] \|\|= AE::io $self->[1], 1, $wcb
331	if @{ $self->[2] };
332	}	545	};
333		546
334	() # make sure we don't leak the watcher	547	() # make sure we don't leak the watcher
335	}
336
337	sub _new {
338	my ($self, $fh) = @_;
339
340	AnyEvent::Util::fh_nonblocking $fh, 1;
341
342	$self = bless [
343	undef, # run callback
344	$fh,
345	[], # write queue - strings or fd's
346	undef, # AE watcher
347	], $self;
348
349	$self
350	}	548	}
351		549
352	# fork template from current process, used by AnyEvent::Fork::Early/Template	550	# fork template from current process, used by AnyEvent::Fork::Early/Template
353	sub _new_fork {	551	sub _new_fork {
354	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	552	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
359	if ($pid eq 0) {	557	if ($pid eq 0) {
360	require AnyEvent::Fork::Serve;	558	require AnyEvent::Fork::Serve;
361	$AnyEvent::Fork::Serve::OWNER = $parent;	559	$AnyEvent::Fork::Serve::OWNER = $parent;
362	close $fh;	560	close $fh;
363	$0 = "$_[1] of $parent";	561	$0 = "$_[1] of $parent";
364	$SIG{CHLD} = 'IGNORE';
365	AnyEvent::Fork::Serve::serve ($slave);	562	AnyEvent::Fork::Serve::serve ($slave);
366	exit 0;	563	exit 0;
367	} elsif (!$pid) {	564	} elsif (!$pid) {
368	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";	565	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";
369	}	566	}
370		567
371	AnyEvent::Fork->_new ($fh)	568	AnyEvent::Fork->_new ($fh, $pid)
372	}	569	}
373		570
374	=item my $proc = new AnyEvent::Fork	571	=item my $proc = new AnyEvent::Fork
375		572
376	Create a new "empty" perl interpreter process and returns its process	573	Create a new "empty" perl interpreter process and returns its process
377	object for further manipulation.	574	object for further manipulation.
378		575
379	The new process is forked from a template process that is kept around	576	The new process is forked from a template process that is kept around
380	for this purpose. When it doesn't exist yet, it is created by a call to	577	for this purpose. When it doesn't exist yet, it is created by a call to
381	C<new_exec> and kept around for future calls.	578	C<new_exec> first and then stays around for future calls.
382
383	When the process object is destroyed, it will release the file handle
384	that connects it with the new process. When the new process has not yet
385	called C<run>, then the process will exit. Otherwise, what happens depends
386	entirely on the code that is executed.
387		579
388	=cut	580	=cut
389		581
390	sub new {	582	sub new {
391	my $class = shift;	583	my $class = shift;
…		…
428		620
429	You should use C<new> whenever possible, except when having a template	621	You should use C<new> whenever possible, except when having a template
430	process around is unacceptable.	622	process around is unacceptable.
431		623
432	The path to the perl interpreter is divined using various methods - first	624	The path to the perl interpreter is divined using various methods - first
433	C<$^X> is investigated to see if the path ends with something that sounds	625	C<$^X> is investigated to see if the path ends with something that looks
434	as if it were the perl interpreter. Failing this, the module falls back to	626	as if it were the perl interpreter. Failing this, the module falls back to
435	using C<$Config::Config{perlpath}>.	627	using C<$Config::Config{perlpath}>.
436		628
		629	The path to perl can also be overriden by setting the global variable
		630	C<$AnyEvent::Fork::PERL> - it's value will be used for all subsequent
		631	invocations.
		632
437	=cut	633	=cut
		634
		635	our $PERL;
438		636
439	sub new_exec {	637	sub new_exec {
440	my ($self) = @_;	638	my ($self) = @_;
441		639
442	return $EARLY->fork	640	return $EARLY->fork
443	if $EARLY;	641	if $EARLY;
444		642
		643	unless (defined $PERL) {
445	# first find path of perl	644	# first find path of perl
446	my $perl = $;	645	my $perl = $^X;
447		646
448	# first we try $^X, but the path must be absolute (always on win32), and end in sth.	647	# first we try $^X, but the path must be absolute (always on win32), and end in sth.
449	# that looks like perl. this obviously only works for posix and win32	648	# that looks like perl. this obviously only works for posix and win32
450	unless (	649	unless (
451	($^O eq "MSWin32" \|\| $perl =~ m%^/%)	650	($^O eq "MSWin32" \|\| $perl =~ m%^/%)
452	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i	651	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i
453	) {	652	) {
454	# if it doesn't look perlish enough, try Config	653	# if it doesn't look perlish enough, try Config
455	require Config;	654	require Config;
456	$perl = $Config::Config{perlpath};	655	$perl = $Config::Config{perlpath};
457	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;	656	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;
		657	}
		658
		659	$PERL = $perl;
458	}	660	}
459		661
460	require Proc::FastSpawn;	662	require Proc::FastSpawn;
461		663
462	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	664	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
469	# quick. also doesn't work in win32. of course. what did you expect	671	# quick. also doesn't work in win32. of course. what did you expect
470	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;	672	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;
471	my %env = %ENV;	673	my %env = %ENV;
472	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;	674	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;
473		675
474	Proc::FastSpawn::spawn (	676	my $pid = Proc::FastSpawn::spawn (
475	$perl,	677	$PERL,
476	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],	678	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],
477	[map "$_=$env{$_}", keys %env],	679	[map "$_=$env{$_}", keys %env],
478	) or die "unable to spawn AnyEvent::Fork server: $!";	680	) or die "unable to spawn AnyEvent::Fork server: $!";
479		681
480	$self->_new ($fh)	682	$self->_new ($fh, $pid)
		683	}
		684
		685	=item $pid = $proc->pid
		686
		687	Returns the process id of the process I<iff it is a direct child of the
		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.
		692
		693	Or in other words, you do not normally have to take care of zombies for
		694	processes created via C<new>, but when in doubt, or zombies are a problem,
		695	you need to check whether a process is a diretc child by calling this
		696	method, and possibly creating a child watcher or reap it manually.
		697
		698	=cut
		699
		700	sub pid {
		701	$_[0][PID]
481	}	702	}
482		703
483	=item $proc = $proc->eval ($perlcode, @args)	704	=item $proc = $proc->eval ($perlcode, @args)
484		705
485	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
486	the strings specified by C<@args>.	707	the strings specified by C<@args>, in the "main" package.
487		708
488	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
489	(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
490	to completely take over the process, use C<run> for that.	711	to completely take over the process, use C<run> for that.
491		712
492	The code will usually be executed after this call returns, and there is no	713	The code will usually be executed after this call returns, and there is no
493	way to pass anything back to the calling process. Any evaluation errors	714	way to pass anything back to the calling process. Any evaluation errors
494	will be reported to stderr and cause the process to exit.	715	will be reported to stderr and cause the process to exit.
495		716
		717	If you want to execute some code (that isn't in a module) to take over the
		718	process, you should compile a function via C<eval> first, and then call
		719	it via C<run>. This also gives you access to any arguments passed via the
		720	C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as
		721	a faster fork+exec> example to see it in action.
		722
496	Returns the process object for easy chaining of method calls.	723	Returns the process object for easy chaining of method calls.
497		724
498	=cut	725	=cut
499		726
500	sub eval {	727	sub eval {
501	my ($self, $code, @args) = @_;	728	my ($self, $code, @args) = @_;
502		729
503	$self->_cmd (e => $code, @args);	730	$self->_cmd (e => pack "(w/a)", $code, @args);
504		731
505	$self	732	$self
506	}	733	}
507		734
508	=item $proc = $proc->require ($module, ...)	735	=item $proc = $proc->require ($module, ...)
…		…
525	=item $proc = $proc->send_fh ($handle, ...)	752	=item $proc = $proc->send_fh ($handle, ...)
526		753
527	Send one or more file handles (I<not> file descriptors) to the process,	754	Send one or more file handles (I<not> file descriptors) to the process,
528	to prepare a call to C<run>.	755	to prepare a call to C<run>.
529		756
530	The process object keeps a reference to the handles until this is done,	757	The process object keeps a reference to the handles until they have
531	so you must not explicitly close the handles. This is most easily	758	been passed over to the process, so you must not explicitly close the
532	accomplished by simply not storing the file handles anywhere after passing	759	handles. This is most easily accomplished by simply not storing the file
533	them to this method.	760	handles anywhere after passing them to this method - when AnyEvent::Fork
		761	is finished using them, perl will automatically close them.
534		762
535	Returns the process object for easy chaining of method calls.	763	Returns the process object for easy chaining of method calls.
536		764
537	Example: pass a file handle to a process, and release it without	765	Example: pass a file handle to a process, and release it without
538	closing. It will be closed automatically when it is no longer used.	766	closing. It will be closed automatically when it is no longer used.
…		…
545	sub send_fh {	773	sub send_fh {
546	my ($self, @fh) = @_;	774	my ($self, @fh) = @_;
547		775
548	for my $fh (@fh) {	776	for my $fh (@fh) {
549	$self->_cmd ("h");	777	$self->_cmd ("h");
550	push @{ $self->[2] }, \$fh;	778	push @{ $self->[QUEUE] }, \$fh;
551	}	779	}
552		780
553	$self	781	$self
554	}	782	}
555		783
556	=item $proc = $proc->send_arg ($string, ...)	784	=item $proc = $proc->send_arg ($string, ...)
557		785
558	Send one or more argument strings to the process, to prepare a call to	786	Send one or more argument strings to the process, to prepare a call to
559	C<run>. The strings can be any octet string.	787	C<run>. The strings can be any octet strings.
560		788
561	The protocol is optimised to pass a moderate number of relatively short	789	The protocol is optimised to pass a moderate number of relatively short
562	strings - while you can pass up to 4GB of data in one go, this is more	790	strings - while you can pass up to 4GB of data in one go, this is more
563	meant to pass some ID information or other startup info, not big chunks of	791	meant to pass some ID information or other startup info, not big chunks of
564	data.	792	data.
…		…
568	=cut	796	=cut
569		797
570	sub send_arg {	798	sub send_arg {
571	my ($self, @arg) = @_;	799	my ($self, @arg) = @_;
572		800
573	$self->_cmd (a => @arg);	801	$self->_cmd (a => pack "(w/a)", @arg);
574		802
575	$self	803	$self
576	}	804	}
577		805
578	=item $proc->run ($func, $cb->($fh))	806	=item $proc->run ($func, $cb->($fh))
579		807
580	Enter the function specified by the fully qualified name in C<$func> in	808	Enter the function specified by the function name in C<$func> in the
581	the process. The function is called with the communication socket as first	809	process. The function is called with the communication socket as first
582	argument, followed by all file handles and string arguments sent earlier	810	argument, followed by all file handles and string arguments sent earlier
583	via C<send_fh> and C<send_arg> methods, in the order they were called.	811	via C<send_fh> and C<send_arg> methods, in the order they were called.
584		812
585	If the called function returns, the process exits.
586
587	Preparing the process can take time - when the process is ready, the
588	callback is invoked with the local communications socket as argument.
589
590	The process object becomes unusable on return from this function.	813	The process object becomes unusable on return from this function - any
		814	further method calls result in undefined behaviour.
		815
		816	The function name should be fully qualified, but if it isn't, it will be
		817	looked up in the C<main> package.
		818
		819	If the called function returns, doesn't exist, or any error occurs, the
		820	process exits.
		821
		822	Preparing the process is done in the background - when all commands have
		823	been sent, the callback is invoked with the local communications socket
		824	as argument. At this point you can start using the socket in any way you
		825	like.
591		826
592	If the communication socket isn't used, it should be closed on both sides,	827	If the communication socket isn't used, it should be closed on both sides,
593	to save on kernel memory.	828	to save on kernel memory.
594		829
595	The socket is non-blocking in the parent, and blocking in the newly	830	The socket is non-blocking in the parent, and blocking in the newly
596	created process. The close-on-exec flag is set on both. Even if not used	831	created process. The close-on-exec flag is set in both.
		832
597	otherwise, the socket can be a good indicator for the existence of the	833	Even if not used otherwise, the socket can be a good indicator for the
598	process - if the other process exits, you get a readable event on it,	834	existence of the process - if the other process exits, you get a readable
599	because exiting the process closes the socket (if it didn't create any	835	event on it, because exiting the process closes the socket (if it didn't
600	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
601		863
602	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
603	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.
604		866
605	my $pool = AnyEvent::Fork	867	my $pool = AnyEvent::Fork
…		…
613	->send_arg ("str3")	875	->send_arg ("str3")
614	->run ("Some::function", sub {	876	->run ("Some::function", sub {
615	my ($fh) = @_;	877	my ($fh) = @_;
616		878
617	# fh is nonblocking, but we trust that the OS can accept these	879	# fh is nonblocking, but we trust that the OS can accept these
618	# extra 3 octets anyway.	880	# few octets anyway.
619	syswrite $fh, "hi #$_\n";	881	syswrite $fh, "hi #$_\n";
620		882
621	# $fh is being closed here, as we don't store it anywhere	883	# $fh is being closed here, as we don't store it anywhere
622	});	884	});
623	}	885	}
…		…
625	# Some::function might look like this - all parameters passed before fork	887	# Some::function might look like this - all parameters passed before fork
626	# and after will be passed, in order, after the communications socket.	888	# and after will be passed, in order, after the communications socket.
627	sub Some::function {	889	sub Some::function {
628	my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_;	890	my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_;
629		891
630	print scalar <$fh>; # prints "hi 1\n" and "hi 2\n"	892	print scalar <$fh>; # prints "hi #1\n" and "hi #2\n" in any order
631	}	893	}
632		894
633	=cut	895	=cut
634		896
635	sub run {	897	sub run {
636	my ($self, $func, $cb) = @_;	898	my ($self, $func, $cb) = @_;
637		899
638	$self->[0] = $cb;	900	$self->[CB] = $cb;
639	$self->_cmd (r => $func);	901	$self->_cmd (r => $func);
		902	}
		903
		904	=back
		905
		906	=head2 EXPERIMENTAL METHODS
		907
		908	These methods might go away completely or change behaviour, at any time.
		909
		910	=over 4
		911
		912	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		913
		914	Flushes all commands out to the process and then calls the callback with
		915	the communications socket.
		916
		917	The process object becomes unusable on return from this function - any
		918	further method calls result in undefined behaviour.
		919
		920	The point of this method is to give you a file handle that you can pass
		921	to another process. In that other process, you can call C<new_from_fh
		922	AnyEvent::Fork $fh> to create a new C<AnyEvent::Fork> object from it,
		923	thereby effectively passing a fork object to another process.
		924
		925	=cut
		926
		927	sub to_fh {
		928	my ($self, $cb) = @_;
		929
		930	$self->[CB] = $cb;
		931
		932	unless ($self->[WW]) {
		933	$self->[CB]->($self->[FH]);
		934	@$self = ();
		935	}
		936	}
		937
		938	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		939
		940	Takes a file handle originally rceeived by the C<to_fh> method and creates
		941	a new C<AnyEvent:Fork> object. The child process itself will not change in
		942	any way, i.e. it will keep all the modifications done to it before calling
		943	C<to_fh>.
		944
		945	The new object is very much like the original object, except that the
		946	C<pid> method will return C<undef> even if the process is a direct child.
		947
		948	=cut
		949
		950	sub new_from_fh {
		951	my ($class, $fh) = @_;
		952
		953	$class->_new ($fh)
640	}	954	}
641		955
642	=back	956	=back
643		957
644	=head1 PERFORMANCE	958	=head1 PERFORMANCE
…		…
654		968
655	2079 new processes per second, using manual socketpair + fork	969	2079 new processes per second, using manual socketpair + fork
656		970
657	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
658	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
659	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
660	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
661	(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
662	of the socket first.	976	of the socket first.
663		977
664	2307 new processes per second, using AnyEvent::Fork->new	978	2307 new processes per second, using AnyEvent::Fork->new
…		…
669	479 vfork+execs per second, using AnyEvent::Fork->new_exec	983	479 vfork+execs per second, using AnyEvent::Fork->new_exec
670		984
671	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
672	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?
673		987
674	The difference is simply the process size: forking the 6MB process takes	988	The difference is simply the process size: forking the 5MB process takes
675	so much longer than forking the 2.5MB template process that the overhead	989	so much longer than forking the 2.5MB template process that the extra
676	introduced is canceled out.	990	overhead is canceled out.
677		991
678	If the benchmark process grows, the normal fork becomes even slower:	992	If the benchmark process grows, the normal fork becomes even slower:
679		993
680	1340 new processes, manual fork in a 20MB process	994	1340 new processes, manual fork of a 20MB process
681	731 new processes, manual fork in a 200MB process	995	731 new processes, manual fork of a 200MB process
682	235 new processes, manual fork in a 2000MB process	996	235 new processes, manual fork of a 2000MB process
683		997
684	What that means (to me) is that I can use this module without having a	998	What that means (to me) is that I can use this module without having a bad
685	very bad conscience because of the extra overhead required to start new	999	conscience because of the extra overhead required to start new processes.
686	processes.
687		1000
688	=head1 TYPICAL PROBLEMS	1001	=head1 TYPICAL PROBLEMS
689		1002
690	This section lists typical problems that remain. I hope by recognising	1003	This section lists typical problems that remain. I hope by recognising
691	them, most can be avoided.	1004	them, most can be avoided.
692		1005
693	=over 4	1006	=over 4
694		1007
695	=item exit runs destructors
696
697	=item "leaked" file descriptors for exec'ed processes	1008	=item leaked file descriptors for exec'ed processes
698		1009
699	POSIX systems inherit file descriptors by default when exec'ing a new	1010	POSIX systems inherit file descriptors by default when exec'ing a new
700	process. While perl itself laudably sets the close-on-exec flags on new	1011	process. While perl itself laudably sets the close-on-exec flags on new
701	file handles, most C libraries don't care, and even if all cared, it's	1012	file handles, most C libraries don't care, and even if all cared, it's
702	often not possible to set the flag in a race-free manner.	1013	often not possible to set the flag in a race-free manner.
…		…
722	libraries or the code that leaks those file descriptors.	1033	libraries or the code that leaks those file descriptors.
723		1034
724	Fortunately, most of these leaked descriptors do no harm, other than	1035	Fortunately, most of these leaked descriptors do no harm, other than
725	sitting on some resources.	1036	sitting on some resources.
726		1037
727	=item "leaked" file descriptors for fork'ed processes	1038	=item leaked file descriptors for fork'ed processes
728		1039
729	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,	1040	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,
730	which closes file descriptors not marked for being inherited.	1041	which closes file descriptors not marked for being inherited.
731		1042
732	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer	1043	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer
…		…
740	trouble with a fork.	1051	trouble with a fork.
741		1052
742	The solution is to either not load these modules before use'ing	1053	The solution is to either not load these modules before use'ing
743	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay	1054	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay
744	initialising them, for example, by calling C<init Gtk2> manually.	1055	initialising them, for example, by calling C<init Gtk2> manually.
		1056
		1057	=item exiting calls object destructors
		1058
		1059	This only applies to users of L<AnyEvent::Fork:Early> and
		1060	L<AnyEvent::Fork::Template>, or when initialising code creates objects
		1061	that reference external resources.
		1062
		1063	When a process created by AnyEvent::Fork exits, it might do so by calling
		1064	exit, or simply letting perl reach the end of the program. At which point
		1065	Perl runs all destructors.
		1066
		1067	Not all destructors are fork-safe - for example, an object that represents
		1068	the connection to an X display might tell the X server to free resources,
		1069	which is inconvenient when the "real" object in the parent still needs to
		1070	use them.
		1071
		1072	This is obviously not a problem for L<AnyEvent::Fork::Early>, as you used
		1073	it as the very first thing, right?
		1074
		1075	It is a problem for L<AnyEvent::Fork::Template> though - and the solution
		1076	is to not create objects with nontrivial destructors that might have an
		1077	effect outside of Perl.
745		1078
746	=back	1079	=back
747		1080
748	=head1 PORTABILITY NOTES	1081	=head1 PORTABILITY NOTES
749		1082
…		…
752	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
753	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
754	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
755	issues or other braindamage. Hrrrr.	1088	issues or other braindamage. Hrrrr.
756		1089
757	Cygwin perl is not supported at the moment, as it should implement fd	1090	Since fork is endlessly broken on win32 perls (it doesn't even remotely
758	passing, but doesn't, and rolling my own is hard, as cygwin doesn't	1091	work within it's documented limits) and quite obviously it's not getting
759	support enough functionality to do it.	1092	improved any time soon, the best way to proceed on windows would be to
		1093	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1094
		1095	Cygwin perl is not supported at the moment due to some hilarious
		1096	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1097	use C<send_fh> and always use C<new_exec> to create processes, it should
		1098	work though.
		1099
		1100	=head1 USING AnyEvent::Fork IN SUBPROCESSES
		1101
		1102	AnyEvent::Fork itself cannot generally be used in subprocesses. As long as
		1103	only one process ever forks new processes, sharing the template processes
		1104	is possible (you could use a pipe as a lock by writing a byte into it to
		1105	unlock, and reading the byte to lock for example)
		1106
		1107	To make concurrent calls possible after fork, you should get rid of the
		1108	template and early fork processes. AnyEvent::Fork will create a new
		1109	template process as needed.
		1110
		1111	undef $AnyEvent::Fork::EARLY;
		1112	undef $AnyEvent::Fork::TEMPLATE;
		1113
		1114	It doesn't matter whether you get rid of them in the parent or child after
		1115	a fork.
760		1116
761	=head1 SEE ALSO	1117	=head1 SEE ALSO
762		1118
763	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
764	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
765	program at a convenient time).	1123	program at a convenient time (part of this distribution).
766		1124
767	=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
768		1134
769	Marc Lehmann <schmorp@schmorp.de>	1135	Marc Lehmann <schmorp@schmorp.de>
770	http://home.schmorp.de/	1136	http://software.schmorp.de/pkg/AnyEvent-Fork
771		1137
772	=cut	1138	=cut
773		1139
774	1	1140	1
775		1141

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.18 by root, Sat Apr 6 01:33:56 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 1.18 by root, Sat Apr 6 01:33:56 2013 UTC vs.
Revision 1.64 by root, Wed Nov 26 13:37:40 2014 UTC