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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.6 by root, Wed Apr 3 08:47:44 2013 UTC vs.
Revision 1.68 by root, Sat May 21 07:01:58 2016 UTC

…		…
3	AnyEvent::Fork - everything you wanted to use fork() for, but couldn't	3	AnyEvent::Fork - everything you wanted to use fork() for, but couldn't
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::Fork;	7	use AnyEvent::Fork;
		8
		9	AnyEvent::Fork
		10	->new
		11	->require ("MyModule")
		12	->run ("MyModule::server", my $cv = AE::cv);
		13
		14	my $fh = $cv->recv;
8		15
9	=head1 DESCRIPTION	16	=head1 DESCRIPTION
10		17
11	This module allows you to create new processes, without actually forking	18	This module allows you to create new processes, without actually forking
12	them from your current process (avoiding the problems of forking), but	19	them from your current process (avoiding the problems of forking), but
13	preserving most of the advantages of fork.	20	preserving most of the advantages of fork.
14		21
15	It can be used to create new worker processes or new independent	22	It can be used to create new worker processes or new independent
16	subprocesses for short- and long-running jobs, process pools (e.g. for use	23	subprocesses for short- and long-running jobs, process pools (e.g. for use
17	in pre-forked servers) but also to spawn new external processes (such as	24	in pre-forked servers) but also to spawn new external processes (such as
18	CGI scripts from a webserver), which can be faster (and more well behaved)	25	CGI scripts from a web server), which can be faster (and more well behaved)
19	than using fork+exec in big processes.	26	than using fork+exec in big processes.
20		27
21	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,
22	while still supporting specialised environments such as L<App::Staticperl>	29	while still supporting specialised environments such as L<App::Staticperl>
23	or L<PAR::Packer>.	30	or L<PAR::Packer>.
24		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
25	=head1 PROBLEM STATEMENT	70	=head2 PROBLEM STATEMENT
26		71
27	There are two ways to implement parallel processing on UNIX like operating	72	There are two traditional ways to implement parallel processing on UNIX
28	systems - fork and process, and fork+exec and process. They have different	73	like operating systems - fork and process, and fork+exec and process. They
29	advantages and disadvantages that I describe below, together with how this	74	have different advantages and disadvantages that I describe below,
30	module tries to mitigate the disadvantages.	75	together with how this module tries to mitigate the disadvantages.
31		76
32	=over 4	77	=over 4
33		78
34	=item Forking from a big process can be very slow (a 5GB process needs	79	=item Forking from a big process can be very slow.
35	0.05s to fork on my 3.6GHz amd64 GNU/Linux box for example). This overhead	80
		81	A 5GB process needs 0.05s to fork on my 3.6GHz amd64 GNU/Linux box. This
36	is often shared with exec (because you have to fork first), but in some	82	overhead is often shared with exec (because you have to fork first), but
37	circumstances (e.g. when vfork is used), fork+exec can be much faster.	83	in some circumstances (e.g. when vfork is used), fork+exec can be much
		84	faster.
38		85
39	This module can help here by telling a small(er) helper process to fork,	86	This module can help here by telling a small(er) helper process to fork,
40	or fork+exec instead.	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.
41		89
42	=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
43	process. Memory (for example, modules or data files that have been	91	process.
44	will not take additional memory). When exec'ing a new process, modules	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
45	and data files might need to be loaded again, at extra cpu and memory	95	and data files might need to be loaded again, at extra CPU and memory
46	cost. Likewise when forking, all data structures are copied as well - if	96	cost.
		97
		98	But when forking, you still create a copy of your data structures - if
47	the program frees them and replaces them by new data, the child processes	99	the program frees them and replaces them by new data, the child processes
48	will retain the memory even if it isn't used.	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.
49		114
50	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
51	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
52	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
53	risking to share large dynamic data structures that will blow up child	118	risking to share large dynamic data structures that will blow up child
54	memory usage.	119	memory usage.
55		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
56	=item Exec'ing a new perl process might be difficult and slow. For	124	=item Exec'ing a new perl process might be difficult.
		125
57	example, it is not easy to find the correct path to the perl interpreter,	126	For example, it is not easy to find the correct path to the perl
58	and all modules have to be loaded from disk again. Long running processes	127	interpreter - C<$^X> might not be a perl interpreter at all. Worse, there
59	might run into problems when perl is upgraded for example.	128	might not even be a perl binary installed on the system.
60		129
61	This module supports creating pre-initialised perl processes to be used
62	as template, and also tries hard to identify the correct path to the perl	130	This module tries hard to identify the correct path to the perl
63	interpreter. With a cooperative main program, exec'ing the interpreter	131	interpreter. With a cooperative main program, exec'ing the interpreter
64	might not even be necessary.	132	might not even be necessary, but even without help from the main program,
		133	it will still work when used from a module.
65		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
66	=item Forking might be impossible when a program is running. For example,	147	=item Forking might be impossible when a program is running.
67	POSIX makes it almost impossible to fork from a multithreaded program and
68	do anything useful in the child - strictly speaking, if your perl program
69	uses posix threads (even indirectly via e.g. L<IO::AIO> or L<threads>),
70	you cannot call fork on the perl level anymore, at all.
71		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
72	This module can safely fork helper processes at any time, by caling	156	This module can safely fork helper processes at any time, by calling
73	fork+exec in C, in a POSIX-compatible way.	157	fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>).
74		158
75	=item Parallel processing with fork might be inconvenient or difficult	159	=item Parallel processing with fork might be inconvenient or difficult
		160	to implement. Modules might not work in both parent and child.
		161
76	to implement. For example, when a program uses an event loop and creates	162	For example, when a program uses an event loop and creates watchers it
77	watchers it becomes very hard to use the event loop from a child	163	becomes very hard to use the event loop from a child program, as the
78	program, as the watchers already exist but are only meaningful in the	164	watchers already exist but are only meaningful in the parent. Worse, a
79	parent. Worse, a module might want to use such a system, not knowing	165	module might want to use such a module, not knowing whether another module
80	whether another module or the main program also does, leading to problems.	166	or the main program also does, leading to problems.
81		167
82	This module only lets the main program create pools by forking (because	168	Apart from event loops, graphical toolkits also commonly fall into the
83	only the main program can know when it is still safe to do so) - all other	169	"unsafe module" category, or just about anything that communicates with
84	pools are created by fork+exec, after which such modules can again be	170	the external world, such as network libraries and file I/O modules, which
85	loaded.	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.
86		178
87	=back	179	=back
		180
		181	=head1 EXAMPLES
		182
		183	This is where the wall of text ends and code speaks.
		184
		185	=head2 Create a single new process, tell it to run your worker function.
		186
		187	AnyEvent::Fork
		188	->new
		189	->require ("MyModule")
		190	->run ("MyModule::worker, sub {
		191	my ($master_filehandle) = @_;
		192
		193	# now $master_filehandle is connected to the
		194	# $slave_filehandle in the new process.
		195	});
		196
		197	C<MyModule> might look like this:
		198
		199	package MyModule;
		200
		201	sub worker {
		202	my ($slave_filehandle) = @_;
		203
		204	# now $slave_filehandle is connected to the $master_filehandle
		205	# in the original process. have fun!
		206	}
		207
		208	=head2 Create a pool of server processes all accepting on the same socket.
		209
		210	# create listener socket
		211	my $listener = ...;
		212
		213	# create a pool template, initialise it and give it the socket
		214	my $pool = AnyEvent::Fork
		215	->new
		216	->require ("Some::Stuff", "My::Server")
		217	->send_fh ($listener);
		218
		219	# now create 10 identical workers
		220	for my $id (1..10) {
		221	$pool
		222	->fork
		223	->send_arg ($id)
		224	->run ("My::Server::run");
		225	}
		226
		227	# now do other things - maybe use the filehandle provided by run
		228	# to wait for the processes to die. or whatever.
		229
		230	C<My::Server> might look like this:
		231
		232	package My::Server;
		233
		234	sub run {
		235	my ($slave, $listener, $id) = @_;
		236
		237	close $slave; # we do not use the socket, so close it to save resources
		238
		239	# we could go ballistic and use e.g. AnyEvent here, or IO::AIO,
		240	# or anything we usually couldn't do in a process forked normally.
		241	while (my $socket = $listener->accept) {
		242	# do sth. with new socket
		243	}
		244	}
		245
		246	=head2 use AnyEvent::Fork as a faster fork+exec
		247
		248	This runs C</bin/echo hi>, with standard output redirected to F</tmp/log>
		249	and standard error redirected to the communications socket. It is usually
		250	faster than fork+exec, but still lets you prepare the environment.
		251
		252	open my $output, ">/tmp/log" or die "$!";
		253
		254	AnyEvent::Fork
		255	->new
		256	->eval ('
		257	# compile a helper function for later use
		258	sub run {
		259	my ($fh, $output, @cmd) = @_;
		260
		261	# perl will clear close-on-exec on STDOUT/STDERR
		262	open STDOUT, ">&", $output or die;
		263	open STDERR, ">&", $fh or die;
		264
		265	exec @cmd;
		266	}
		267	')
		268	->send_fh ($output)
		269	->send_arg ("/bin/echo", "hi")
		270	->run ("run", my $cv = AE::cv);
		271
		272	my $stderr = $cv->recv;
		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	$cv->recv;
88		342
89	=head1 CONCEPTS	343	=head1 CONCEPTS
90		344
91	This module can create new processes either by executing a new perl	345	This module can create new processes either by executing a new perl
92	process, or by forking from an existing "template" process.	346	process, or by forking from an existing "template" process.
		347
		348	All these processes are called "child processes" (whether they are direct
		349	children or not), while the process that manages them is called the
		350	"parent process".
93		351
94	Each such process comes with its own file handle that can be used to	352	Each such process comes with its own file handle that can be used to
95	communicate with it (it's actually a socket - one end in the new process,	353	communicate with it (it's actually a socket - one end in the new process,
96	one end in the main process), and among the things you can do in it are	354	one end in the main process), and among the things you can do in it are
97	load modules, fork new processes, send file handles to it, and execute	355	load modules, fork new processes, send file handles to it, and execute
…		…
109	needed the first time. Forking from this process shares the memory used	367	needed the first time. Forking from this process shares the memory used
110	for the perl interpreter with the new process, but loading modules takes	368	for the perl interpreter with the new process, but loading modules takes
111	time, and the memory is not shared with anything else.	369	time, and the memory is not shared with anything else.
112		370
113	This is ideal for when you only need one extra process of a kind, with the	371	This is ideal for when you only need one extra process of a kind, with the
114	option of starting and stipping it on demand.	372	option of starting and stopping it on demand.
		373
		374	Example:
		375
		376	AnyEvent::Fork
		377	->new
		378	->require ("Some::Module")
		379	->run ("Some::Module::run", sub {
		380	my ($fork_fh) = @_;
		381	});
115		382
116	=item fork a new template process, load code, then fork processes off of	383	=item fork a new template process, load code, then fork processes off of
117	it and run the code	384	it and run the code
118		385
119	When you need to have a bunch of processes that all execute the same (or	386	When you need to have a bunch of processes that all execute the same (or
…		…
125	modules you loaded) is shared between the processes, and each new process	392	modules you loaded) is shared between the processes, and each new process
126	consumes relatively little memory of its own.	393	consumes relatively little memory of its own.
127		394
128	The disadvantage of this approach is that you need to create a template	395	The disadvantage of this approach is that you need to create a template
129	process for the sole purpose of forking new processes from it, but if you	396	process for the sole purpose of forking new processes from it, but if you
130	only need a fixed number of proceses you can create them, and then destroy	397	only need a fixed number of processes you can create them, and then destroy
131	the template process.	398	the template process.
		399
		400	Example:
		401
		402	my $template = AnyEvent::Fork->new->require ("Some::Module");
		403
		404	for (1..10) {
		405	$template->fork->run ("Some::Module::run", sub {
		406	my ($fork_fh) = @_;
		407	});
		408	}
		409
		410	# at this point, you can keep $template around to fork new processes
		411	# later, or you can destroy it, which causes it to vanish.
132		412
133	=item execute a new perl interpreter, load some code, run it	413	=item execute a new perl interpreter, load some code, run it
134		414
135	This is relatively slow, and doesn't allow you to share memory between	415	This is relatively slow, and doesn't allow you to share memory between
136	multiple processes.	416	multiple processes.
…		…
138	The only advantage is that you don't have to have a template process	418	The only advantage is that you don't have to have a template process
139	hanging around all the time to fork off some new processes, which might be	419	hanging around all the time to fork off some new processes, which might be
140	an advantage when there are long time spans where no extra processes are	420	an advantage when there are long time spans where no extra processes are
141	needed.	421	needed.
142		422
		423	Example:
		424
		425	AnyEvent::Fork
		426	->new_exec
		427	->require ("Some::Module")
		428	->run ("Some::Module::run", sub {
		429	my ($fork_fh) = @_;
		430	});
		431
143	=back	432	=back
144		433
145	=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.
146		454
147	=over 4	455	=over 4
148		456
149	=cut	457	=cut
150		458
151	package AnyEvent::Fork;	459	package AnyEvent::Fork;
152		460
153	use common::sense;	461	use common::sense;
154		462
155	use Socket ();	463	use Errno ();
156		464
157	use AnyEvent;	465	use AnyEvent;
158	use AnyEvent::Fork::Util;
159	use AnyEvent::Util ();	466	use AnyEvent::Util ();
160		467
161	our $PERL; # the path to the perl interpreter, deduces with various forms of magic	468	use IO::FDPass;
162		469
163	=item my $pool = new AnyEvent::Fork key => value...	470	our $VERSION = 1.3;
164
165	Create a new process pool. The following named parameters are supported:
166
167	=over 4
168
169	=back
170
171	=cut
172		471
173	# the early fork template process	472	# the early fork template process
174	our $EARLY;	473	our $EARLY;
175		474
176	# the empty template process	475	# the empty template process
177	our $TEMPLATE;	476	our $TEMPLATE;
178		477
		478	sub QUEUE() { 0 }
		479	sub FH() { 1 }
		480	sub WW() { 2 }
		481	sub PID() { 3 }
		482	sub CB() { 4 }
		483
		484	sub _new {
		485	my ($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	}
		498
179	sub _cmd {	499	sub _cmd {
180	my $self = shift;	500	my $self = shift;
181		501
182	# ideally, we would want to use "a (w/a)*" as format string, but perl versions	502	# ideally, we would want to use "a (w/a)*" as format string, but perl
183	# from at least 5.8.9 to 5.16.3 are all buggy and can't unpack it.	503	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack
184	push @{ $self->[2] }, pack "N/a", pack "(w/a)*", @_;	504	# it.
		505	push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1];
185		506
186	$self->[3] \|\|= AE::io $self->[1], 1, sub {	507	$self->[WW] \|\|= AE::io $self->[FH], 1, sub {
		508	do {
		509	# send the next "thing" in the queue - either a reference to an fh,
		510	# or a plain string.
		511
187	if (ref $self->[2][0]) {	512	if (ref $self->[QUEUE][0]) {
188	AnyEvent::Fork::Util::fd_send fileno $self->[1], fileno ${ $self->[2][0] }	513	# send fh
		514	unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) {
		515	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
		516	undef $self->[WW];
		517	die "AnyEvent::Fork: file descriptor send failure: $!";
		518	}
		519
189	and shift @{ $self->[2] };	520	shift @{ $self->[QUEUE] };
190		521
191	} else {	522	} else {
		523	# send string
192	my $len = syswrite $self->[1], $self->[2][0]	524	my $len = syswrite $self->[FH], $self->[QUEUE][0];
		525
		526	unless ($len) {
		527	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
		528	undef $self->[WW];
193	or do { undef $self->[3]; die "AnyEvent::Fork: command write failure: $!" };	529	die "AnyEvent::Fork: command write failure: $!";
		530	}
194		531
195	substr $self->[2][0], 0, $len, "";	532	substr $self->[QUEUE][0], 0, $len, "";
196	shift @{ $self->[2] } unless length $self->[2][0];	533	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
197	}	534	}
		535	} while @{ $self->[QUEUE] };
198		536
199	unless (@{ $self->[2] }) {	537	# everything written
200	undef $self->[3];	538	undef $self->[WW];
		539
		540	# invoke run callback, if any
		541	if ($self->[CB]) {
201	$self->[0]->($self->[1]) if $self->[0];	542	$self->[CB]->($self->[FH]);
		543	@$self = ();
202	}	544	}
203	};	545	};
204	}
205		546
206	sub _new {	547	() # make sure we don't leak the watcher
207	my ($self, $fh) = @_;
208
209	AnyEvent::Util::fh_nonblocking $fh, 1;
210
211	$self = bless [
212	undef, # run callback
213	$fh,
214	[], # write queue - strings or fd's
215	undef, # AE watcher
216	], $self;
217
218	# my ($a, $b) = AnyEvent::Util::portable_socketpair;
219
220	# queue_cmd $template, "Iabc";
221	# push @{ $template->[2] }, \$b;
222
223	# use Coro::AnyEvent; Coro::AnyEvent::sleep 1;
224	# undef $b;
225	# die "x" . <$a>;
226
227	$self
228	}	548	}
229		549
230	# fork template from current process, used by AnyEvent::Fork::Early/Template	550	# fork template from current process, used by AnyEvent::Fork::Early/Template
231	sub _new_fork {	551	sub _new_fork {
232	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	552	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
		553	my $parent = $$;
		554
233	my $pid = fork;	555	my $pid = fork;
234		556
235	if ($pid eq 0) {	557	if ($pid eq 0) {
236	require AnyEvent::Fork::Serve;	558	require AnyEvent::Fork::Serve;
		559	$AnyEvent::Fork::Serve::OWNER = $parent;
237	close $fh;	560	close $fh;
		561	$0 = "$AnyEvent::Fork::Serve::OWNER AnyEvent::Fork/exec";
238	AnyEvent::Fork::Serve::serve ($slave);	562	AnyEvent::Fork::Serve::serve ($slave);
239	AnyEvent::Fork::Util::_exit 0;	563	exit 0;
240	} elsif (!$pid) {	564	} elsif (!$pid) {
241	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";	565	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";
242	}	566	}
243		567
244	AnyEvent::Fork->_new ($fh)	568	AnyEvent::Fork->_new ($fh, $pid)
245	}	569	}
246		570
247	=item my $proc = new AnyEvent::Fork	571	=item my $proc = new AnyEvent::Fork
248		572
249	Create a new "empty" perl interpreter process and returns its process	573	Create a new "empty" perl interpreter process and returns its process
250	object for further manipulation.	574	object for further manipulation.
251		575
252	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
253	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
254	C<new_exec> and kept around for future calls.	578	C<new_exec> first and then stays around for future calls.
255		579
256	=cut	580	=cut
257		581
258	sub new {	582	sub new {
259	my $class = shift;	583	my $class = shift;
…		…
295	reduces the amount of memory sharing that is possible, and is also slower.	619	reduces the amount of memory sharing that is possible, and is also slower.
296		620
297	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
298	process around is unacceptable.	622	process around is unacceptable.
299		623
300	The path to the perl interpreter is divined usign various methods - first	624	The path to the perl interpreter is divined using various methods - first
301	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
302	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
303	using C<$Config::Config{perlpath}>.	627	using C<$Config::Config{perlpath}>.
304		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
305	=cut	633	=cut
		634
		635	our $PERL;
306		636
307	sub new_exec {	637	sub new_exec {
308	my ($self) = @_;	638	my ($self) = @_;
309		639
310	return $EARLY->fork	640	return $EARLY->fork
311	if $EARLY;	641	if $EARLY;
312		642
		643	unless (defined $PERL) {
313	# first find path of perl	644	# first find path of perl
314	my $perl = $;	645	my $perl = $^X;
315		646
316	# 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.
317	# 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
318	unless (	649	unless (
319	(AnyEvent::Fork::Util::WIN32 \|\| $perl =~ m%^/%)	650	($^O eq "MSWin32" \|\| $perl =~ m%^/%)
320	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i	651	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i
321	) {	652	) {
322	# if it doesn't look perlish enough, try Config	653	# if it doesn't look perlish enough, try Config
323	require Config;	654	require Config;
324	$perl = $Config::Config{perlpath};	655	$perl = $Config::Config{perlpath};
325	$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;
326	}	660	}
327		661
328	require Proc::FastSpawn;	662	require Proc::FastSpawn;
329		663
330	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	664	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
331	Proc::FastSpawn::fd_inherit (fileno $slave);	665	Proc::FastSpawn::fd_inherit (fileno $slave);
		666
		667	# new fh's should always be set cloexec (due to $^F),
		668	# but hey, not on win32, so we always clear the inherit flag.
		669	Proc::FastSpawn::fd_inherit (fileno $fh, 0);
332		670
333	# 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
334	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;	672	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;
335	my %env = %ENV;	673	my %env = %ENV;
336	$env{PERL5LIB} = join ":", grep !ref, @INC;	674	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;
337		675
338	Proc::FastSpawn::spawn (	676	my $pid = Proc::FastSpawn::spawn (
339	$perl,	677	$PERL,
340	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave],	678	[$PERL, "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],
341	[map "$_=$env{$_}", keys %env],	679	[map "$_=$env{$_}", keys %env],
342	) or die "unable to spawn AnyEvent::Fork server: $!";	680	) or die "unable to spawn AnyEvent::Fork server: $!";
343		681
344	$self->_new ($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]
		702	}
		703
		704	=item $proc = $proc->eval ($perlcode, @args)
		705
		706	Evaluates the given C<$perlcode> as ... Perl code, while setting C<@_> to
		707	the strings specified by C<@args>, in the "main" package.
		708
		709	This call is meant to do any custom initialisation that might be required
		710	(for example, the C<require> method uses it). It's not supposed to be used
		711	to completely take over the process, use C<run> for that.
		712
		713	The code will usually be executed after this call returns, and there is no
		714	way to pass anything back to the calling process. Any evaluation errors
		715	will be reported to stderr and cause the process to exit.
		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
		723	Returns the process object for easy chaining of method calls.
		724
		725	It's common to want to call an iniitalisation function with some
		726	arguments. Make sure you actually pass C<@_> to that function (for example
		727	by using C<&name> syntax), and do not just specify a function name:
		728
		729	$proc->eval ('&MyModule::init', $string1, $string2);
		730
		731	=cut
		732
		733	sub eval {
		734	my ($self, $code, @args) = @_;
		735
		736	$self->_cmd (e => pack "(w/a)", $code, @args);
		737
		738	$self
345	}	739	}
346		740
347	=item $proc = $proc->require ($module, ...)	741	=item $proc = $proc->require ($module, ...)
348		742
349	Tries to load the given modules into the process	743	Tries to load the given module(s) into the process
350		744
351	Returns the process object for easy chaining of method calls.	745	Returns the process object for easy chaining of method calls.
		746
		747	=cut
		748
		749	sub require {
		750	my ($self, @modules) = @_;
		751
		752	s%::%/%g for @modules;
		753	$self->eval ('require "$_.pm" for @_', @modules);
		754
		755	$self
		756	}
352		757
353	=item $proc = $proc->send_fh ($handle, ...)	758	=item $proc = $proc->send_fh ($handle, ...)
354		759
355	Send one or more file handles (I<not> file descriptors) to the process,	760	Send one or more file handles (I<not> file descriptors) to the process,
356	to prepare a call to C<run>.	761	to prepare a call to C<run>.
357		762
358	The process object keeps a reference to the handles until this is done,	763	The process object keeps a reference to the handles until they have
359	so you must not explicitly close the handles. This is most easily	764	been passed over to the process, so you must not explicitly close the
360	accomplished by simply not storing the file handles anywhere after passing	765	handles. This is most easily accomplished by simply not storing the file
361	them to this method.	766	handles anywhere after passing them to this method - when AnyEvent::Fork
		767	is finished using them, perl will automatically close them.
362		768
363	Returns the process object for easy chaining of method calls.	769	Returns the process object for easy chaining of method calls.
		770
		771	Example: pass a file handle to a process, and release it without
		772	closing. It will be closed automatically when it is no longer used.
		773
		774	$proc->send_fh ($my_fh);
		775	undef $my_fh; # free the reference if you want, but DO NOT CLOSE IT
364		776
365	=cut	777	=cut
366		778
367	sub send_fh {	779	sub send_fh {
368	my ($self, @fh) = @_;	780	my ($self, @fh) = @_;
369		781
370	for my $fh (@fh) {	782	for my $fh (@fh) {
371	$self->_cmd ("h");	783	$self->_cmd ("h");
372	push @{ $self->[2] }, \$fh;	784	push @{ $self->[QUEUE] }, \$fh;
373	}	785	}
374		786
375	$self	787	$self
376	}	788	}
377		789
378	=item $proc = $proc->send_arg ($string, ...)	790	=item $proc = $proc->send_arg ($string, ...)
379		791
380	Send one or more argument strings to the process, to prepare a call to	792	Send one or more argument strings to the process, to prepare a call to
381	C<run>. The strings can be any octet string.	793	C<run>. The strings can be any octet strings.
382		794
		795	The protocol is optimised to pass a moderate number of relatively short
		796	strings - while you can pass up to 4GB of data in one go, this is more
		797	meant to pass some ID information or other startup info, not big chunks of
		798	data.
		799
383	Returns the process object for easy chaining of emthod calls.	800	Returns the process object for easy chaining of method calls.
384		801
385	=cut	802	=cut
386		803
387	sub send_arg {	804	sub send_arg {
388	my ($self, @arg) = @_;	805	my ($self, @arg) = @_;
389		806
390	$self->_cmd (a => @arg);	807	$self->_cmd (a => pack "(w/a)", @arg);
391		808
392	$self	809	$self
393	}	810	}
394		811
395	=item $proc->run ($func, $cb->($fh))	812	=item $proc->run ($func, $cb->($fh))
396		813
397	Enter the function specified by the fully qualified name in C<$func> in	814	Enter the function specified by the function name in C<$func> in the
398	the process. The function is called with the communication socket as first	815	process. The function is called with the communication socket as first
399	argument, followed by all file handles and string arguments sent earlier	816	argument, followed by all file handles and string arguments sent earlier
400	via C<send_fh> and C<send_arg> methods, in the order they were called.	817	via C<send_fh> and C<send_arg> methods, in the order they were called.
401		818
402	If the called function returns, the process exits.
403
404	Preparing the process can take time - when the process is ready, the
405	callback is invoked with the local communications socket as argument.
406
407	The process object becomes unusable on return from this function.	819	The process object becomes unusable on return from this function - any
		820	further method calls result in undefined behaviour.
		821
		822	The function name should be fully qualified, but if it isn't, it will be
		823	looked up in the C<main> package.
		824
		825	If the called function returns, doesn't exist, or any error occurs, the
		826	process exits.
		827
		828	Preparing the process is done in the background - when all commands have
		829	been sent, the callback is invoked with the local communications socket
		830	as argument. At this point you can start using the socket in any way you
		831	like.
408		832
409	If the communication socket isn't used, it should be closed on both sides,	833	If the communication socket isn't used, it should be closed on both sides,
410	to save on kernel memory.	834	to save on kernel memory.
411		835
412	The socket is non-blocking in the parent, and blocking in the newly	836	The socket is non-blocking in the parent, and blocking in the newly
413	created process. The close-on-exec flag is set on both. Even if not used	837	created process. The close-on-exec flag is set in both.
		838
414	otherwise, the socket can be a good indicator for the existance of the	839	Even if not used otherwise, the socket can be a good indicator for the
415	process - if the othe rprocess exits, you get a readable event on it,	840	existence of the process - if the other process exits, you get a readable
416	because exiting the process closes the socket (if it didn't create any	841	event on it, because exiting the process closes the socket (if it didn't
417	children using fork).	842	create any children using fork).
		843
		844	=over 4
		845
		846	=item Compatibility to L<AnyEvent::Fork::Remote>
		847
		848	If you want to write code that works with both this module and
		849	L<AnyEvent::Fork::Remote>, you need to write your code so that it assumes
		850	there are two file handles for communications, which might not be unix
		851	domain sockets. The C<run> function should start like this:
		852
		853	sub run {
		854	my ($rfh, @args) = @_; # @args is your normal arguments
		855	my $wfh = fileno $rfh ? $rfh : *STDOUT;
		856
		857	# now use $rfh for reading and $wfh for writing
		858	}
		859
		860	This checks whether the passed file handle is, in fact, the process
		861	C<STDIN> handle. If it is, then the function was invoked visa
		862	L<AnyEvent::Fork::Remote>, so STDIN should be used for reading and
		863	C<STDOUT> should be used for writing.
		864
		865	In all other cases, the function was called via this module, and there is
		866	only one file handle that should be sued for reading and writing.
		867
		868	=back
		869
		870	Example: create a template for a process pool, pass a few strings, some
		871	file handles, then fork, pass one more string, and run some code.
		872
		873	my $pool = AnyEvent::Fork
		874	->new
		875	->send_arg ("str1", "str2")
		876	->send_fh ($fh1, $fh2);
		877
		878	for (1..2) {
		879	$pool
		880	->fork
		881	->send_arg ("str3")
		882	->run ("Some::function", sub {
		883	my ($fh) = @_;
		884
		885	# fh is nonblocking, but we trust that the OS can accept these
		886	# few octets anyway.
		887	syswrite $fh, "hi #$_\n";
		888
		889	# $fh is being closed here, as we don't store it anywhere
		890	});
		891	}
		892
		893	# Some::function might look like this - all parameters passed before fork
		894	# and after will be passed, in order, after the communications socket.
		895	sub Some::function {
		896	my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_;
		897
		898	print scalar <$fh>; # prints "hi #1\n" and "hi #2\n" in any order
		899	}
418		900
419	=cut	901	=cut
420		902
421	sub run {	903	sub run {
422	my ($self, $func, $cb) = @_;	904	my ($self, $func, $cb) = @_;
423		905
424	$self->[0] = $cb;	906	$self->[CB] = $cb;
425	$self->_cmd ("r", $func);	907	$self->_cmd (r => $func);
426	}	908	}
427		909
428	=back	910	=back
429		911
430	=head1 AUTHOR	912	=head2 EXPERIMENTAL METHODS
		913
		914	These methods might go away completely or change behaviour, at any time.
		915
		916	=over 4
		917
		918	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		919
		920	Flushes all commands out to the process and then calls the callback with
		921	the communications socket.
		922
		923	The process object becomes unusable on return from this function - any
		924	further method calls result in undefined behaviour.
		925
		926	The point of this method is to give you a file handle that you can pass
		927	to another process. In that other process, you can call C<new_from_fh
		928	AnyEvent::Fork $fh> to create a new C<AnyEvent::Fork> object from it,
		929	thereby effectively passing a fork object to another process.
		930
		931	=cut
		932
		933	sub to_fh {
		934	my ($self, $cb) = @_;
		935
		936	$self->[CB] = $cb;
		937
		938	unless ($self->[WW]) {
		939	$self->[CB]->($self->[FH]);
		940	@$self = ();
		941	}
		942	}
		943
		944	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		945
		946	Takes a file handle originally rceeived by the C<to_fh> method and creates
		947	a new C<AnyEvent:Fork> object. The child process itself will not change in
		948	any way, i.e. it will keep all the modifications done to it before calling
		949	C<to_fh>.
		950
		951	The new object is very much like the original object, except that the
		952	C<pid> method will return C<undef> even if the process is a direct child.
		953
		954	=cut
		955
		956	sub new_from_fh {
		957	my ($class, $fh) = @_;
		958
		959	$class->_new ($fh)
		960	}
		961
		962	=back
		963
		964	=head1 PERFORMANCE
		965
		966	Now for some unscientific benchmark numbers (all done on an amd64
		967	GNU/Linux box). These are intended to give you an idea of the relative
		968	performance you can expect, they are not meant to be absolute performance
		969	numbers.
		970
		971	OK, so, I ran a simple benchmark that creates a socket pair, forks, calls
		972	exit in the child and waits for the socket to close in the parent. I did
		973	load AnyEvent, EV and AnyEvent::Fork, for a total process size of 5100kB.
		974
		975	2079 new processes per second, using manual socketpair + fork
		976
		977	Then I did the same thing, but instead of calling fork, I called
		978	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the
		979	socket from the child to close on exit. This does the same thing as manual
		980	socket pair + fork, except that what is forked is the template process
		981	(2440kB), and the socket needs to be passed to the server at the other end
		982	of the socket first.
		983
		984	2307 new processes per second, using AnyEvent::Fork->new
		985
		986	And finally, using C<new_exec> instead C<new>, using vforks+execs to exec
		987	a new perl interpreter and compile the small server each time, I get:
		988
		989	479 vfork+execs per second, using AnyEvent::Fork->new_exec
		990
		991	So how can C<< AnyEvent->new >> be faster than a standard fork, even
		992	though it uses the same operations, but adds a lot of overhead?
		993
		994	The difference is simply the process size: forking the 5MB process takes
		995	so much longer than forking the 2.5MB template process that the extra
		996	overhead is canceled out.
		997
		998	If the benchmark process grows, the normal fork becomes even slower:
		999
		1000	1340 new processes, manual fork of a 20MB process
		1001	731 new processes, manual fork of a 200MB process
		1002	235 new processes, manual fork of a 2000MB process
		1003
		1004	What that means (to me) is that I can use this module without having a bad
		1005	conscience because of the extra overhead required to start new processes.
		1006
		1007	=head1 TYPICAL PROBLEMS
		1008
		1009	This section lists typical problems that remain. I hope by recognising
		1010	them, most can be avoided.
		1011
		1012	=over 4
		1013
		1014	=item leaked file descriptors for exec'ed processes
		1015
		1016	POSIX systems inherit file descriptors by default when exec'ing a new
		1017	process. While perl itself laudably sets the close-on-exec flags on new
		1018	file handles, most C libraries don't care, and even if all cared, it's
		1019	often not possible to set the flag in a race-free manner.
		1020
		1021	That means some file descriptors can leak through. And since it isn't
		1022	possible to know which file descriptors are "good" and "necessary" (or
		1023	even to know which file descriptors are open), there is no good way to
		1024	close the ones that might harm.
		1025
		1026	As an example of what "harm" can be done consider a web server that
		1027	accepts connections and afterwards some module uses AnyEvent::Fork for the
		1028	first time, causing it to fork and exec a new process, which might inherit
		1029	the network socket. When the server closes the socket, it is still open
		1030	in the child (which doesn't even know that) and the client might conclude
		1031	that the connection is still fine.
		1032
		1033	For the main program, there are multiple remedies available -
		1034	L<AnyEvent::Fork::Early> is one, creating a process early and not using
		1035	C<new_exec> is another, as in both cases, the first process can be exec'ed
		1036	well before many random file descriptors are open.
		1037
		1038	In general, the solution for these kind of problems is to fix the
		1039	libraries or the code that leaks those file descriptors.
		1040
		1041	Fortunately, most of these leaked descriptors do no harm, other than
		1042	sitting on some resources.
		1043
		1044	=item leaked file descriptors for fork'ed processes
		1045
		1046	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,
		1047	which closes file descriptors not marked for being inherited.
		1048
		1049	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer
		1050	a way to create these processes by forking, and this leaks more file
		1051	descriptors than exec'ing them, as there is no way to mark descriptors as
		1052	"close on fork".
		1053
		1054	An example would be modules like L<EV>, L<IO::AIO> or L<Gtk2>. Both create
		1055	pipes for internal uses, and L<Gtk2> might open a connection to the X
		1056	server. L<EV> and L<IO::AIO> can deal with fork, but Gtk2 might have
		1057	trouble with a fork.
		1058
		1059	The solution is to either not load these modules before use'ing
		1060	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay
		1061	initialising them, for example, by calling C<init Gtk2> manually.
		1062
		1063	=item exiting calls object destructors
		1064
		1065	This only applies to users of L<AnyEvent::Fork:Early> and
		1066	L<AnyEvent::Fork::Template>, or when initialising code creates objects
		1067	that reference external resources.
		1068
		1069	When a process created by AnyEvent::Fork exits, it might do so by calling
		1070	exit, or simply letting perl reach the end of the program. At which point
		1071	Perl runs all destructors.
		1072
		1073	Not all destructors are fork-safe - for example, an object that represents
		1074	the connection to an X display might tell the X server to free resources,
		1075	which is inconvenient when the "real" object in the parent still needs to
		1076	use them.
		1077
		1078	This is obviously not a problem for L<AnyEvent::Fork::Early>, as you used
		1079	it as the very first thing, right?
		1080
		1081	It is a problem for L<AnyEvent::Fork::Template> though - and the solution
		1082	is to not create objects with nontrivial destructors that might have an
		1083	effect outside of Perl.
		1084
		1085	=back
		1086
		1087	=head1 PORTABILITY NOTES
		1088
		1089	Native win32 perls are somewhat supported (AnyEvent::Fork::Early is a nop,
		1090	and ::Template is not going to work), and it cost a lot of blood and sweat
		1091	to make it so, mostly due to the bloody broken perl that nobody seems to
		1092	care about. The fork emulation is a bad joke - I have yet to see something
		1093	useful that you can do with it without running into memory corruption
		1094	issues or other braindamage. Hrrrr.
		1095
		1096	Since fork is endlessly broken on win32 perls (it doesn't even remotely
		1097	work within it's documented limits) and quite obviously it's not getting
		1098	improved any time soon, the best way to proceed on windows would be to
		1099	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1100
		1101	Cygwin perl is not supported at the moment due to some hilarious
		1102	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1103	use C<send_fh> and always use C<new_exec> to create processes, it should
		1104	work though.
		1105
		1106	=head1 USING AnyEvent::Fork IN SUBPROCESSES
		1107
		1108	AnyEvent::Fork itself cannot generally be used in subprocesses. As long as
		1109	only one process ever forks new processes, sharing the template processes
		1110	is possible (you could use a pipe as a lock by writing a byte into it to
		1111	unlock, and reading the byte to lock for example)
		1112
		1113	To make concurrent calls possible after fork, you should get rid of the
		1114	template and early fork processes. AnyEvent::Fork will create a new
		1115	template process as needed.
		1116
		1117	undef $AnyEvent::Fork::EARLY;
		1118	undef $AnyEvent::Fork::TEMPLATE;
		1119
		1120	It doesn't matter whether you get rid of them in the parent or child after
		1121	a fork.
		1122
		1123	=head1 SEE ALSO
		1124
		1125	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1126	(part of this distribution).
		1127
		1128	L<AnyEvent::Fork::Template>, to create a process by forking the main
		1129	program at a convenient time (part of this distribution).
		1130
		1131	L<AnyEvent::Fork::Remote>, for another way to create processes that is
		1132	mostly compatible to this module and modules building on top of it, but
		1133	works better with remote processes.
		1134
		1135	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1136
		1137	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1138
		1139	=head1 AUTHOR AND CONTACT INFORMATION
431		1140
432	Marc Lehmann <schmorp@schmorp.de>	1141	Marc Lehmann <schmorp@schmorp.de>
433	http://home.schmorp.de/	1142	http://software.schmorp.de/pkg/AnyEvent-Fork
434		1143
435	=cut	1144	=cut
436		1145
437	1	1146	1
438		1147

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.6 by root, Wed Apr 3 08:47:44 2013 UTC vs. Revision 1.68 by root, Sat May 21 07:01:58 2016 UTC

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Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.6 by root, Wed Apr 3 08:47:44 2013 UTC vs.
Revision 1.68 by root, Sat May 21 07:01:58 2016 UTC