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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.3 by root, Tue Apr 2 18:00:04 2013 UTC vs.
Revision 1.72 by root, Tue Nov 5 02:44:27 2019 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::ProcessPool - manage pools of perl worker processes, exec'ed or fork'ed	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::ProcessPool;	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 single worker processes but also worker	18	This module allows you to create new processes, without actually forking
12	pool that share memory, by forking from the main program, or exec'ing new	19	them from your current process (avoiding the problems of forking), but
13	perl interpreters from a module.	20	preserving most of the advantages of fork.
14		21
15	You create a new processes in a pool by specifying a function to call	22	It can be used to create new worker processes or new independent
16	with any combination of string values and file handles.	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.
17		27
18	A pool can have initialisation code which is executed before forking. The	28	Special care has been taken to make this module useful from other modules,
19	initialisation code is only executed once and the resulting process is	29	while still supporting specialised environments such as L<App::Staticperl>
20	cached, to be used as a template.	30	or L<PAR::Packer>.
21		31
22	Pools without such initialisation code don't cache an extra process.	32	=head2 WHAT THIS MODULE IS NOT
23		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
24	=head1 PROBLEM STATEMENT	70	=head2 PROBLEM STATEMENT
25		71
26	There are two ways to implement parallel processing on UNIX like operating	72	There are two traditional ways to implement parallel processing on UNIX
27	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
28	advantages and disadvantages that I describe below, together with how this	74	have different advantages and disadvantages that I describe below,
29	module tries to mitigate the disadvantages.	75	together with how this module tries to mitigate the disadvantages.
30		76
31	=over 4	77	=over 4
32		78
33	=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.
34	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
35	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
36	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.
37		85
38	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,
39	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.
40		89
41	=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
42	process. Memory (for example, modules or data files that have been	91	process.
43	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
44	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
45	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
46	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
47	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.
48		114
49	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
50	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
51	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
52	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
53	memory usage.	119	memory usage.
54		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
55	=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
56	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
57	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
58	might run into problems when perl is upgraded for example.	128	might not even be a perl binary installed on the system.
59		129
60	This module supports creating pre-initialised perl processes to be used
61	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
62	interpreter. With a cooperative main program, exec'ing the interpreter	131	interpreter. With a cooperative main program, exec'ing the interpreter
63	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.
64		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
65	=item Forking might be impossible when a program is running. For example,	147	=item Forking might be impossible when a program is running.
66	POSIX makes it almost impossible to fork from a multithreaded program and
67	do anything useful in the child - strictly speaking, if your perl program
68	uses posix threads (even indirectly via e.g. L<IO::AIO> or L<threads>),
69	you cannot call fork on the perl level anymore, at all.
70		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
71	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
72	fork+exec in C, in a POSIX-compatible way.	157	fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>).
73		158
74	=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
75	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
76	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
77	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
78	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
79	whether another module or the main program also does, leading to problems.	166	or the main program also does, leading to problems.
80		167
81	This module only lets the main program create pools by forking (because	168	Apart from event loops, graphical toolkits also commonly fall into the
82	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
83	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
84	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.
85		178
86	=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	$cv->recv;
87		342
88	=head1 CONCEPTS	343	=head1 CONCEPTS
89		344
90	This module can create new processes either by executing a new perl	345	This module can create new processes either by executing a new perl
91	process, or by forking from an existing "template" process.	346	process, or by forking from an existing "template" process.
		347
		348	All these processes are called "child processes" (whether they are direct
		349	children or not), while the process that manages them is called the
		350	"parent process".
92		351
93	Each such process comes with its own file handle that can be used to	352	Each such process comes with its own file handle that can be used to
94	communicate with it (it's actually a socket - one end in the new process,	353	communicate with it (it's actually a socket - one end in the new process,
95	one end in the main process), and among the things you can do in it are	354	one end in the main process), and among the things you can do in it are
96	load modules, fork new processes, send file handles to it, and execute	355	load modules, fork new processes, send file handles to it, and execute
108	needed the first time. Forking from this process shares the memory used	367	needed the first time. Forking from this process shares the memory used
109	for the perl interpreter with the new process, but loading modules takes	368	for the perl interpreter with the new process, but loading modules takes
110	time, and the memory is not shared with anything else.	369	time, and the memory is not shared with anything else.
111		370
112	This is ideal for when you only need one extra process of a kind, with the	371	This is ideal for when you only need one extra process of a kind, with the
113	option of starting and stipping it on demand.	372	option of starting and stopping it on demand.
		373
		374	Example:
		375
		376	AnyEvent::Fork
		377	->new
		378	->require ("Some::Module")
		379	->run ("Some::Module::run", sub {
		380	my ($fork_fh) = @_;
		381	});
114		382
115	=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
116	it and run the code	384	it and run the code
117		385
118	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
…		…
124	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
125	consumes relatively little memory of its own.	393	consumes relatively little memory of its own.
126		394
127	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
128	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
129	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
130	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 $template around to fork new processes
		411	# later, or you can destroy it, which causes it to vanish.
131		412
132	=item execute a new perl interpreter, load some code, run it	413	=item execute a new perl interpreter, load some code, run it
133		414
134	This is relatively slow, and doesn't allow you to share memory between	415	This is relatively slow, and doesn't allow you to share memory between
135	multiple processes.	416	multiple processes.
…		…
137	The only advantage is that you don't have to have a template process	418	The only advantage is that you don't have to have a template process
138	hanging around all the time to fork off some new processes, which might be	419	hanging around all the time to fork off some new processes, which might be
139	an advantage when there are long time spans where no extra processes are	420	an advantage when there are long time spans where no extra processes are
140	needed.	421	needed.
141		422
		423	Example:
		424
		425	AnyEvent::Fork
		426	->new_exec
		427	->require ("Some::Module")
		428	->run ("Some::Module::run", sub {
		429	my ($fork_fh) = @_;
		430	});
		431
142	=back	432	=back
143		433
144	=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.
145		454
146	=over 4	455	=over 4
147		456
148	=cut	457	=cut
149		458
150	package AnyEvent::ProcessPool;	459	package AnyEvent::Fork;
151		460
152	use common::sense;	461	use common::sense;
153		462
154	use Socket ();	463	use Errno ();
155		464
156	use Proc::FastSpawn;
157	use AnyEvent;	465	use AnyEvent;
158	use AnyEvent::ProcessPool::Util;
159	use AnyEvent::Util ();	466	use AnyEvent::Util ();
160		467
161	BEGIN {	468	use IO::FDPass;
162	# require Exporter;
163	}
164		469
165	=item my $pool = new AnyEvent::ProcessPool key => value...	470	our $VERSION = 1.31;
166		471
167	Create a new process pool. The following named parameters are supported:	472	# the early fork template process
		473	our $EARLY;
168		474
169	=over 4
170
171	=back
172
173	=cut
174
175	# the template process	475	# the empty template process
176	our $template;	476	our $TEMPLATE;
177		477
178	sub _queue {	478	sub QUEUE() { 0 }
179	my ($pid, $fh) = @_;	479	sub FH() { 1 }
		480	sub WW() { 2 }
		481	sub PID() { 3 }
		482	sub CB() { 4 }
180		483
181	[	484	sub _new {
		485	my ($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
182	$pid,	493	$pid,
183	$fh,	494	], $self;
184	[],
185	undef
186	]
187	}
188		495
		496	$self
		497	}
		498
189	sub queue_cmd {	499	sub _cmd {
190	my $queue = shift;	500	my $self = shift;
191		501
192	push @{ $queue->[2] }, pack "N/a", pack "a (w/a)*", @_;	502	# ideally, we would want to use "a (w/a)*" as format string, but perl
		503	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack
		504	# it.
		505	push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1];
193		506
194	$queue->[3] \|\|= AE::io $queue->[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
195	if (ref $queue->[2][0]) {	512	if (ref $self->[QUEUE][0]) {
196	AnyEvent::ProcessPool::Util::fd_send fileno $queue->[1], fileno ${ $queue->[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
197	and shift @{ $queue->[2] };	520	shift @{ $self->[QUEUE] };
		521
198	} else {	522	} else {
		523	# send string
199	my $len = syswrite $queue->[1], $queue->[2][0]	524	my $len = syswrite $self->[FH], $self->[QUEUE][0];
200	or do { undef $queue->[3]; die "AnyEvent::ProcessPool::queue write failure: $!" };	525
		526	unless ($len) {
		527	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
		528	undef $self->[WW];
		529	die "AnyEvent::Fork: command write failure: $!";
		530	}
		531
201	substr $queue->[2][0], 0, $len, "";	532	substr $self->[QUEUE][0], 0, $len, "";
202	shift @{ $queue->[2] } unless length $queue->[2][0];	533	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
		534	}
		535	} while @{ $self->[QUEUE] };
		536
		537	# everything written
		538	undef $self->[WW];
		539
		540	# invoke run callback, if any
		541	if ($self->[CB]) {
		542	$self->[CB]->($self->[FH]);
		543	@$self = ();
203	}	544	}
204
205	undef $queue->[3] unless @{ $queue->[2] };
206	};	545	};
207	}
208		546
209	sub run_template {	547	() # make sure we don't leak the watcher
210	return if $template;	548	}
211		549
		550	# fork template from current process, used by AnyEvent::Fork::Early/Template
		551	sub _new_fork {
212	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	552	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
213	AnyEvent::Util::fh_nonblocking $fh, 1;	553	my $parent = $$;
214	fd_inherit fileno $slave;
215		554
216	my %env = %ENV;	555	my $pid = fork;
217	$env{PERL5LIB} = join ":", grep !ref, @INC;
218		556
219	my $pid = spawn	557	if ($pid eq 0) {
220	$^X,	558	require AnyEvent::Fork::Serve;
221	["perl", "-MAnyEvent::ProcessPool::Serve", "-e", "AnyEvent::ProcessPool::Serve::me", fileno $slave],	559	$AnyEvent::Fork::Serve::OWNER = $parent;
222	[map "$_=$env{$_}", keys %env],	560	close $fh;
223	or die "unable to spawn AnyEvent::ProcessPool server: $!";	561	$0 = "$parent AnyEvent::Fork/exec";
		562	AnyEvent::Fork::Serve::serve ($slave);
		563	exit 0;
		564	} elsif (!$pid) {
		565	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";
		566	}
224		567
225	close $slave;	568	AnyEvent::Fork->_new ($fh, $pid)
226
227	$template = _queue $pid, $fh;
228
229	my ($a, $b) = AnyEvent::Util::portable_socketpair;
230
231	queue_cmd $template, "Iabc";
232	push @{ $template->[2] }, \$b;
233
234	use Coro::AnyEvent; Coro::AnyEvent::sleep 1;
235	undef $b;
236	die "x" . <$a>;
237	}	569	}
		570
		571	=item my $proc = new AnyEvent::Fork
		572
		573	Create a new "empty" perl interpreter process and returns its process
		574	object for further manipulation.
		575
		576	The new process is forked from a template process that is kept around
		577	for this purpose. When it doesn't exist yet, it is created by a call to
		578	C<new_exec> first and then stays around for future calls.
		579
		580	=cut
238		581
239	sub new {	582	sub new {
240	my $class = shift;	583	my $class = shift;
241		584
242	my $self = bless {	585	$TEMPLATE \|\|= $class->new_exec;
		586	$TEMPLATE->fork
		587	}
		588
		589	=item $new_proc = $proc->fork
		590
		591	Forks C<$proc>, creating a new process, and returns the process object
		592	of the new process.
		593
		594	If any of the C<send_> functions have been called before fork, then they
		595	will be cloned in the child. For example, in a pre-forked server, you
		596	might C<send_fh> the listening socket into the template process, and then
		597	keep calling C<fork> and C<run>.
		598
		599	=cut
		600
		601	sub fork {
		602	my ($self) = @_;
		603
		604	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
		605
		606	$self->send_fh ($slave);
		607	$self->_cmd ("f");
		608
		609	AnyEvent::Fork->_new ($fh)
		610	}
		611
		612	=item my $proc = new_exec AnyEvent::Fork
		613
		614	Create a new "empty" perl interpreter process and returns its process
		615	object for further manipulation.
		616
		617	Unlike the C<new> method, this method I<always> spawns a new perl process
		618	(except in some cases, see L<AnyEvent::Fork::Early> for details). This
		619	reduces the amount of memory sharing that is possible, and is also slower.
		620
		621	You should use C<new> whenever possible, except when having a template
		622	process around is unacceptable.
		623
		624	The path to the perl interpreter is divined using various methods - first
		625	C<$^X> is investigated to see if the path ends with something that looks
		626	as if it were the perl interpreter. Failing this, the module falls back to
		627	using C<$Config::Config{perlpath}>.
		628
		629	The path to perl can also be overridden by setting the global variable
		630	C<$AnyEvent::Fork::PERL> - it's value will be used for all subsequent
		631	invocations.
		632
		633	=cut
		634
		635	our $PERL;
		636
		637	sub new_exec {
		638	my ($self) = @_;
		639
		640	return $EARLY->fork
		641	if $EARLY;
		642
		643	unless (defined $PERL) {
		644	# first find path of perl
		645	my $perl = $^X;
		646
		647	# first we try $^X, but the path must be absolute (always on win32), and end in sth.
		648	# that looks like perl. this obviously only works for posix and win32
		649	unless (
		650	($^O eq "MSWin32" \|\| $perl =~ m%^/%)
		651	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i
		652	) {
		653	# if it doesn't look perlish enough, try Config
		654	require Config;
		655	$perl = $Config::Config{perlpath};
		656	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;
243	@_	657	}
244	}, $class;
245		658
246	run_template;	659	$PERL = $perl;
		660	}
		661
		662	require Proc::FastSpawn;
		663
		664	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
		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);
		670
		671	# quick. also doesn't work in win32. of course. what did you expect
		672	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;
		673	my %env = %ENV;
		674	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;
		675
		676	my $pid = Proc::FastSpawn::spawn (
		677	$PERL,
		678	[$PERL, "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],
		679	[map "$_=$env{$_}", keys %env],
		680	) or die "unable to spawn AnyEvent::Fork server: $!";
		681
		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<$perlcode> as ... Perl code, while setting C<@_>
		707	to the strings specified by C<@args>, in the "main" package (so you can
		708	access the args using C<$_[0]> and so on, but not using implicit C<shit>
		709	as the latter works on C<@ARGV>).
		710
		711	This call is meant to do any custom initialisation that might be required
		712	(for example, the C<require> method uses it). It's not supposed to be used
		713	to completely take over the process, use C<run> for that.
		714
		715	The code will usually be executed after this call returns, and there is no
		716	way to pass anything back to the calling process. Any evaluation errors
		717	will be reported to stderr and cause the process to exit.
		718
		719	If you want to execute some code (that isn't in a module) to take over the
		720	process, you should compile a function via C<eval> first, and then call
		721	it via C<run>. This also gives you access to any arguments passed via the
		722	C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as
		723	a faster fork+exec> example to see it in action.
		724
		725	Returns the process object for easy chaining of method calls.
		726
		727	It's common to want to call an iniitalisation function with some
		728	arguments. Make sure you actually pass C<@_> to that function (for example
		729	by using C<&name> syntax), and do not just specify a function name:
		730
		731	$proc->eval ('&MyModule::init', $string1, $string2);
		732
		733	=cut
		734
		735	sub eval {
		736	my ($self, $code, @args) = @_;
		737
		738	$self->_cmd (e => pack "(w/a)", $code, @args);
247		739
248	$self	740	$self
249	}	741	}
250		742
		743	=item $proc = $proc->require ($module, ...)
		744
		745	Tries to load the given module(s) into the process
		746
		747	Returns the process object for easy chaining of method calls.
		748
		749	=cut
		750
		751	sub require {
		752	my ($self, @modules) = @_;
		753
		754	s%::%/%g for @modules;
		755	$self->eval ('require "$_.pm" for @_', @modules);
		756
		757	$self
		758	}
		759
		760	=item $proc = $proc->send_fh ($handle, ...)
		761
		762	Send one or more file handles (I<not> file descriptors) to the process,
		763	to prepare a call to C<run>.
		764
		765	The process object keeps a reference to the handles until they have
		766	been passed over to the process, so you must not explicitly close the
		767	handles. This is most easily accomplished by simply not storing the file
		768	handles anywhere after passing them to this method - when AnyEvent::Fork
		769	is finished using them, perl will automatically close them.
		770
		771	Returns the process object for easy chaining of method calls.
		772
		773	Example: pass a file handle to a process, and release it without
		774	closing. It will be closed automatically when it is no longer used.
		775
		776	$proc->send_fh ($my_fh);
		777	undef $my_fh; # free the reference if you want, but DO NOT CLOSE IT
		778
		779	=cut
		780
		781	sub send_fh {
		782	my ($self, @fh) = @_;
		783
		784	for my $fh (@fh) {
		785	$self->_cmd ("h");
		786	push @{ $self->[QUEUE] }, \$fh;
		787	}
		788
		789	$self
		790	}
		791
		792	=item $proc = $proc->send_arg ($string, ...)
		793
		794	Send one or more argument strings to the process, to prepare a call to
		795	C<run>. The strings can be any octet strings.
		796
		797	The protocol is optimised to pass a moderate number of relatively short
		798	strings - while you can pass up to 4GB of data in one go, this is more
		799	meant to pass some ID information or other startup info, not big chunks of
		800	data.
		801
		802	Returns the process object for easy chaining of method calls.
		803
		804	=cut
		805
		806	sub send_arg {
		807	my ($self, @arg) = @_;
		808
		809	$self->_cmd (a => pack "(w/a)", @arg);
		810
		811	$self
		812	}
		813
		814	=item $proc->run ($func, $cb->($fh))
		815
		816	Enter the function specified by the function name in C<$func> in the
		817	process. The function is called with the communication socket as first
		818	argument, followed by all file handles and string arguments sent earlier
		819	via C<send_fh> and C<send_arg> methods, in the order they were called.
		820
		821	The process object becomes unusable on return from this function - any
		822	further method calls result in undefined behaviour.
		823
		824	The function name should be fully qualified, but if it isn't, it will be
		825	looked up in the C<main> package.
		826
		827	If the called function returns, doesn't exist, or any error occurs, the
		828	process exits.
		829
		830	Preparing the process is done in the background - when all commands have
		831	been sent, the callback is invoked with the local communications socket
		832	as argument. At this point you can start using the socket in any way you
		833	like.
		834
		835	If the communication socket isn't used, it should be closed on both sides,
		836	to save on kernel memory.
		837
		838	The socket is non-blocking in the parent, and blocking in the newly
		839	created process. The close-on-exec flag is set in both.
		840
		841	Even if not used otherwise, the socket can be a good indicator for the
		842	existence of the process - if the other process exits, you get a readable
		843	event on it, because exiting the process closes the socket (if it didn't
		844	create any children using fork).
		845
		846	=over 4
		847
		848	=item Compatibility to L<AnyEvent::Fork::Remote>
		849
		850	If you want to write code that works with both this module and
		851	L<AnyEvent::Fork::Remote>, you need to write your code so that it assumes
		852	there are two file handles for communications, which might not be unix
		853	domain sockets. The C<run> function should start like this:
		854
		855	sub run {
		856	my ($rfh, @args) = @_; # @args is your normal arguments
		857	my $wfh = fileno $rfh ? $rfh : *STDOUT;
		858
		859	# now use $rfh for reading and $wfh for writing
		860	}
		861
		862	This checks whether the passed file handle is, in fact, the process
		863	C<STDIN> handle. If it is, then the function was invoked visa
		864	L<AnyEvent::Fork::Remote>, so STDIN should be used for reading and
		865	C<STDOUT> should be used for writing.
		866
		867	In all other cases, the function was called via this module, and there is
		868	only one file handle that should be sued for reading and writing.
		869
251	=back	870	=back
252		871
253	=head1 AUTHOR	872	Example: create a template for a process pool, pass a few strings, some
		873	file handles, then fork, pass one more string, and run some code.
		874
		875	my $pool = AnyEvent::Fork
		876	->new
		877	->send_arg ("str1", "str2")
		878	->send_fh ($fh1, $fh2);
		879
		880	for (1..2) {
		881	$pool
		882	->fork
		883	->send_arg ("str3")
		884	->run ("Some::function", sub {
		885	my ($fh) = @_;
		886
		887	# fh is nonblocking, but we trust that the OS can accept these
		888	# few octets anyway.
		889	syswrite $fh, "hi #$_\n";
		890
		891	# $fh is being closed here, as we don't store it anywhere
		892	});
		893	}
		894
		895	# Some::function might look like this - all parameters passed before fork
		896	# and after will be passed, in order, after the communications socket.
		897	sub Some::function {
		898	my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_;
		899
		900	print scalar <$fh>; # prints "hi #1\n" and "hi #2\n" in any order
		901	}
		902
		903	=cut
		904
		905	sub run {
		906	my ($self, $func, $cb) = @_;
		907
		908	$self->[CB] = $cb;
		909	$self->_cmd (r => $func);
		910	}
		911
		912	=back
		913
		914
		915	=head2 CHILD PROCESS INTERFACE
		916
		917	This module has a limited API for use in child processes.
		918
		919	=over 4
		920
		921	=item @args = AnyEvent::Fork::Serve::run_args
		922
		923	This function, which only exists before the C<run> method is called,
		924	returns the arguments that would be passed to the run function, and clears
		925	them.
		926
		927	This is mainly useful to get any file handles passed via C<send_fh>, but
		928	works for any arguments passed via C<< send_I<xxx> >> methods.
		929
		930	=back
		931
		932
		933	=head2 EXPERIMENTAL METHODS
		934
		935	These methods might go away completely or change behaviour, at any time.
		936
		937	=over 4
		938
		939	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		940
		941	Flushes all commands out to the process and then calls the callback with
		942	the communications socket.
		943
		944	The process object becomes unusable on return from this function - any
		945	further method calls result in undefined behaviour.
		946
		947	The point of this method is to give you a file handle that you can pass
		948	to another process. In that other process, you can call C<new_from_fh
		949	AnyEvent::Fork $fh> to create a new C<AnyEvent::Fork> object from it,
		950	thereby effectively passing a fork object to another process.
		951
		952	=cut
		953
		954	sub to_fh {
		955	my ($self, $cb) = @_;
		956
		957	$self->[CB] = $cb;
		958
		959	unless ($self->[WW]) {
		960	$self->[CB]->($self->[FH]);
		961	@$self = ();
		962	}
		963	}
		964
		965	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		966
		967	Takes a file handle originally rceeived by the C<to_fh> method and creates
		968	a new C<AnyEvent:Fork> object. The child process itself will not change in
		969	any way, i.e. it will keep all the modifications done to it before calling
		970	C<to_fh>.
		971
		972	The new object is very much like the original object, except that the
		973	C<pid> method will return C<undef> even if the process is a direct child.
		974
		975	=cut
		976
		977	sub new_from_fh {
		978	my ($class, $fh) = @_;
		979
		980	$class->_new ($fh)
		981	}
		982
		983	=back
		984
		985	=head1 PERFORMANCE
		986
		987	Now for some unscientific benchmark numbers (all done on an amd64
		988	GNU/Linux box). These are intended to give you an idea of the relative
		989	performance you can expect, they are not meant to be absolute performance
		990	numbers.
		991
		992	OK, so, I ran a simple benchmark that creates a socket pair, forks, calls
		993	exit in the child and waits for the socket to close in the parent. I did
		994	load AnyEvent, EV and AnyEvent::Fork, for a total process size of 5100kB.
		995
		996	2079 new processes per second, using manual socketpair + fork
		997
		998	Then I did the same thing, but instead of calling fork, I called
		999	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the
		1000	socket from the child to close on exit. This does the same thing as manual
		1001	socket pair + fork, except that what is forked is the template process
		1002	(2440kB), and the socket needs to be passed to the server at the other end
		1003	of the socket first.
		1004
		1005	2307 new processes per second, using AnyEvent::Fork->new
		1006
		1007	And finally, using C<new_exec> instead C<new>, using vforks+execs to exec
		1008	a new perl interpreter and compile the small server each time, I get:
		1009
		1010	479 vfork+execs per second, using AnyEvent::Fork->new_exec
		1011
		1012	So how can C<< AnyEvent->new >> be faster than a standard fork, even
		1013	though it uses the same operations, but adds a lot of overhead?
		1014
		1015	The difference is simply the process size: forking the 5MB process takes
		1016	so much longer than forking the 2.5MB template process that the extra
		1017	overhead is canceled out.
		1018
		1019	If the benchmark process grows, the normal fork becomes even slower:
		1020
		1021	1340 new processes, manual fork of a 20MB process
		1022	731 new processes, manual fork of a 200MB process
		1023	235 new processes, manual fork of a 2000MB process
		1024
		1025	What that means (to me) is that I can use this module without having a bad
		1026	conscience because of the extra overhead required to start new processes.
		1027
		1028	=head1 TYPICAL PROBLEMS
		1029
		1030	This section lists typical problems that remain. I hope by recognising
		1031	them, most can be avoided.
		1032
		1033	=over 4
		1034
		1035	=item leaked file descriptors for exec'ed processes
		1036
		1037	POSIX systems inherit file descriptors by default when exec'ing a new
		1038	process. While perl itself laudably sets the close-on-exec flags on new
		1039	file handles, most C libraries don't care, and even if all cared, it's
		1040	often not possible to set the flag in a race-free manner.
		1041
		1042	That means some file descriptors can leak through. And since it isn't
		1043	possible to know which file descriptors are "good" and "necessary" (or
		1044	even to know which file descriptors are open), there is no good way to
		1045	close the ones that might harm.
		1046
		1047	As an example of what "harm" can be done consider a web server that
		1048	accepts connections and afterwards some module uses AnyEvent::Fork for the
		1049	first time, causing it to fork and exec a new process, which might inherit
		1050	the network socket. When the server closes the socket, it is still open
		1051	in the child (which doesn't even know that) and the client might conclude
		1052	that the connection is still fine.
		1053
		1054	For the main program, there are multiple remedies available -
		1055	L<AnyEvent::Fork::Early> is one, creating a process early and not using
		1056	C<new_exec> is another, as in both cases, the first process can be exec'ed
		1057	well before many random file descriptors are open.
		1058
		1059	In general, the solution for these kind of problems is to fix the
		1060	libraries or the code that leaks those file descriptors.
		1061
		1062	Fortunately, most of these leaked descriptors do no harm, other than
		1063	sitting on some resources.
		1064
		1065	=item leaked file descriptors for fork'ed processes
		1066
		1067	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,
		1068	which closes file descriptors not marked for being inherited.
		1069
		1070	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer
		1071	a way to create these processes by forking, and this leaks more file
		1072	descriptors than exec'ing them, as there is no way to mark descriptors as
		1073	"close on fork".
		1074
		1075	An example would be modules like L<EV>, L<IO::AIO> or L<Gtk2>. Both create
		1076	pipes for internal uses, and L<Gtk2> might open a connection to the X
		1077	server. L<EV> and L<IO::AIO> can deal with fork, but Gtk2 might have
		1078	trouble with a fork.
		1079
		1080	The solution is to either not load these modules before use'ing
		1081	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay
		1082	initialising them, for example, by calling C<init Gtk2> manually.
		1083
		1084	=item exiting calls object destructors
		1085
		1086	This only applies to users of L<AnyEvent::Fork:Early> and
		1087	L<AnyEvent::Fork::Template>, or when initialising code creates objects
		1088	that reference external resources.
		1089
		1090	When a process created by AnyEvent::Fork exits, it might do so by calling
		1091	exit, or simply letting perl reach the end of the program. At which point
		1092	Perl runs all destructors.
		1093
		1094	Not all destructors are fork-safe - for example, an object that represents
		1095	the connection to an X display might tell the X server to free resources,
		1096	which is inconvenient when the "real" object in the parent still needs to
		1097	use them.
		1098
		1099	This is obviously not a problem for L<AnyEvent::Fork::Early>, as you used
		1100	it as the very first thing, right?
		1101
		1102	It is a problem for L<AnyEvent::Fork::Template> though - and the solution
		1103	is to not create objects with nontrivial destructors that might have an
		1104	effect outside of Perl.
		1105
		1106	=back
		1107
		1108	=head1 PORTABILITY NOTES
		1109
		1110	Native win32 perls are somewhat supported (AnyEvent::Fork::Early is a nop,
		1111	and ::Template is not going to work), and it cost a lot of blood and sweat
		1112	to make it so, mostly due to the bloody broken perl that nobody seems to
		1113	care about. The fork emulation is a bad joke - I have yet to see something
		1114	useful that you can do with it without running into memory corruption
		1115	issues or other braindamage. Hrrrr.
		1116
		1117	Since fork is endlessly broken on win32 perls (it doesn't even remotely
		1118	work within it's documented limits) and quite obviously it's not getting
		1119	improved any time soon, the best way to proceed on windows would be to
		1120	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1121
		1122	Cygwin perl is not supported at the moment due to some hilarious
		1123	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1124	use C<send_fh> and always use C<new_exec> to create processes, it should
		1125	work though.
		1126
		1127	=head1 USING AnyEvent::Fork IN SUBPROCESSES
		1128
		1129	AnyEvent::Fork itself cannot generally be used in subprocesses. As long as
		1130	only one process ever forks new processes, sharing the template processes
		1131	is possible (you could use a pipe as a lock by writing a byte into it to
		1132	unlock, and reading the byte to lock for example)
		1133
		1134	To make concurrent calls possible after fork, you should get rid of the
		1135	template and early fork processes. AnyEvent::Fork will create a new
		1136	template process as needed.
		1137
		1138	undef $AnyEvent::Fork::EARLY;
		1139	undef $AnyEvent::Fork::TEMPLATE;
		1140
		1141	It doesn't matter whether you get rid of them in the parent or child after
		1142	a fork.
		1143
		1144	=head1 SEE ALSO
		1145
		1146	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1147	(part of this distribution).
		1148
		1149	L<AnyEvent::Fork::Template>, to create a process by forking the main
		1150	program at a convenient time (part of this distribution).
		1151
		1152	L<AnyEvent::Fork::Remote>, for another way to create processes that is
		1153	mostly compatible to this module and modules building on top of it, but
		1154	works better with remote processes.
		1155
		1156	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1157
		1158	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1159
		1160	=head1 AUTHOR AND CONTACT INFORMATION
254		1161
255	Marc Lehmann <schmorp@schmorp.de>	1162	Marc Lehmann <schmorp@schmorp.de>
256	http://home.schmorp.de/	1163	http://software.schmorp.de/pkg/AnyEvent-Fork
257		1164
258	=cut	1165	=cut
259		1166
260	1	1167	1
261		1168

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.3 by root, Tue Apr 2 18:00:04 2013 UTC vs. Revision 1.72 by root, Tue Nov 5 02:44:27 2019 UTC

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Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.3 by root, Tue Apr 2 18:00:04 2013 UTC vs.
Revision 1.72 by root, Tue Nov 5 02:44:27 2019 UTC