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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.19 by root, Sat Apr 6 02:31:26 2013 UTC vs.
Revision 1.57 by root, Sun Aug 25 17:38:43 2013 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::Fork;	7	use AnyEvent::Fork;
8		8
9	##################################################################	9	AnyEvent::Fork
		10	->new
		11	->require ("MyModule")
		12	->run ("MyModule::server", my $cv = AE::cv);
		13
		14	my $fh = $cv->recv;
		15
		16	=head1 DESCRIPTION
		17
		18	This module allows you to create new processes, without actually forking
		19	them from your current process (avoiding the problems of forking), but
		20	preserving most of the advantages of fork.
		21
		22	It can be used to create new worker processes or new independent
		23	subprocesses for short- and long-running jobs, process pools (e.g. for use
		24	in pre-forked servers) but also to spawn new external processes (such as
		25	CGI scripts from a web server), which can be faster (and more well behaved)
		26	than using fork+exec in big processes.
		27
		28	Special care has been taken to make this module useful from other modules,
		29	while still supporting specialised environments such as L<App::Staticperl>
		30	or L<PAR::Packer>.
		31
		32	=head2 WHAT THIS MODULE IS NOT
		33
		34	This module only creates processes and lets you pass file handles and
		35	strings to it, and run perl code. It does not implement any kind of RPC -
		36	there is no back channel from the process back to you, and there is no RPC
		37	or message passing going on.
		38
		39	If you need some form of RPC, you could use the L<AnyEvent::Fork::RPC>
		40	companion module, which adds simple RPC/job queueing to a process created
		41	by this module.
		42
		43	And if you need some automatic process pool management on top of
		44	L<AnyEvent::Fork::RPC>, you can look at the L<AnyEvent::Fork::Pool>
		45	companion module.
		46
		47	Or you can implement it yourself in whatever way you like: use some
		48	message-passing module such as L<AnyEvent::MP>, some pipe such as
		49	L<AnyEvent::ZeroMQ>, use L<AnyEvent::Handle> on both sides to send
		50	e.g. JSON or Storable messages, and so on.
		51
		52	=head2 COMPARISON TO OTHER MODULES
		53
		54	There is an abundance of modules on CPAN that do "something fork", such as
		55	L<Parallel::ForkManager>, L<AnyEvent::ForkManager>, L<AnyEvent::Worker>
		56	or L<AnyEvent::Subprocess>. There are modules that implement their own
		57	process management, such as L<AnyEvent::DBI>.
		58
		59	The problems that all these modules try to solve are real, however, none
		60	of them (from what I have seen) tackle the very real problems of unwanted
		61	memory sharing, efficiency, not being able to use event processing or
		62	similar modules in the processes they create.
		63
		64	This module doesn't try to replace any of them - instead it tries to solve
		65	the problem of creating processes with a minimum of fuss and overhead (and
		66	also luxury). Ideally, most of these would use AnyEvent::Fork internally,
		67	except they were written before AnyEvent:Fork was available, so obviously
		68	had to roll their own.
		69
		70	=head2 PROBLEM STATEMENT
		71
		72	There are two traditional ways to implement parallel processing on UNIX
		73	like operating systems - fork and process, and fork+exec and process. They
		74	have different advantages and disadvantages that I describe below,
		75	together with how this module tries to mitigate the disadvantages.
		76
		77	=over 4
		78
		79	=item Forking from a big process can be very slow.
		80
		81	A 5GB process needs 0.05s to fork on my 3.6GHz amd64 GNU/Linux box. This
		82	overhead is often shared with exec (because you have to fork first), but
		83	in some circumstances (e.g. when vfork is used), fork+exec can be much
		84	faster.
		85
		86	This module can help here by telling a small(er) helper process to fork,
		87	which is faster then forking the main process, and also uses vfork where
		88	possible. This gives the speed of vfork, with the flexibility of fork.
		89
		90	=item Forking usually creates a copy-on-write copy of the parent
		91	process.
		92
		93	For example, modules or data files that are loaded will not use additional
		94	memory after a fork. When exec'ing a new process, modules and data files
		95	might need to be loaded again, at extra CPU and memory cost. But when
		96	forking, literally all data structures are copied - if the program frees
		97	them and replaces them by new data, the child processes will retain the
		98	old version even if it isn't used, which can suddenly and unexpectedly
		99	increase memory usage when freeing memory.
		100
		101	The trade-off is between more sharing with fork (which can be good or
		102	bad), and no sharing with exec.
		103
		104	This module allows the main program to do a controlled fork, and allows
		105	modules to exec processes safely at any time. When creating a custom
		106	process pool you can take advantage of data sharing via fork without
		107	risking to share large dynamic data structures that will blow up child
		108	memory usage.
		109
		110	In other words, this module puts you into control over what is being
		111	shared and what isn't, at all times.
		112
		113	=item Exec'ing a new perl process might be difficult.
		114
		115	For example, it is not easy to find the correct path to the perl
		116	interpreter - C<$^X> might not be a perl interpreter at all.
		117
		118	This module tries hard to identify the correct path to the perl
		119	interpreter. With a cooperative main program, exec'ing the interpreter
		120	might not even be necessary, but even without help from the main program,
		121	it will still work when used from a module.
		122
		123	=item Exec'ing a new perl process might be slow, as all necessary modules
		124	have to be loaded from disk again, with no guarantees of success.
		125
		126	Long running processes might run into problems when perl is upgraded
		127	and modules are no longer loadable because they refer to a different
		128	perl version, or parts of a distribution are newer than the ones already
		129	loaded.
		130
		131	This module supports creating pre-initialised perl processes to be used as
		132	a template for new processes.
		133
		134	=item Forking might be impossible when a program is running.
		135
		136	For example, POSIX makes it almost impossible to fork from a
		137	multi-threaded program while doing anything useful in the child - in
		138	fact, if your perl program uses POSIX threads (even indirectly via
		139	e.g. L<IO::AIO> or L<threads>), you cannot call fork on the perl level
		140	anymore without risking corruption issues on a number of operating
		141	systems.
		142
		143	This module can safely fork helper processes at any time, by calling
		144	fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>).
		145
		146	=item Parallel processing with fork might be inconvenient or difficult
		147	to implement. Modules might not work in both parent and child.
		148
		149	For example, when a program uses an event loop and creates watchers it
		150	becomes very hard to use the event loop from a child program, as the
		151	watchers already exist but are only meaningful in the parent. Worse, a
		152	module might want to use such a module, not knowing whether another module
		153	or the main program also does, leading to problems.
		154
		155	Apart from event loops, graphical toolkits also commonly fall into the
		156	"unsafe module" category, or just about anything that communicates with
		157	the external world, such as network libraries and file I/O modules, which
		158	usually don't like being copied and then allowed to continue in two
		159	processes.
		160
		161	With this module only the main program is allowed to create new processes
		162	by forking (because only the main program can know when it is still safe
		163	to do so) - all other processes are created via fork+exec, which makes it
		164	possible to use modules such as event loops or window interfaces safely.
		165
		166	=back
		167
		168	=head1 EXAMPLES
		169
10	# create a single new process, tell it to run your worker function	170	=head2 Create a single new process, tell it to run your worker function.
11		171
12	AnyEvent::Fork	172	AnyEvent::Fork
13	->new	173	->new
14	->require ("MyModule")	174	->require ("MyModule")
15	->run ("MyModule::worker, sub {	175	->run ("MyModule::worker, sub {
…		…
17		177
18	# now $master_filehandle is connected to the	178	# now $master_filehandle is connected to the
19	# $slave_filehandle in the new process.	179	# $slave_filehandle in the new process.
20	});	180	});
21		181
22	# MyModule::worker might look like this	182	C<MyModule> might look like this:
		183
		184	package MyModule;
		185
23	sub MyModule::worker {	186	sub worker {
24	my ($slave_filehandle) = @_;	187	my ($slave_filehandle) = @_;
25		188
26	# now $slave_filehandle is connected to the $master_filehandle	189	# now $slave_filehandle is connected to the $master_filehandle
27	# in the original prorcess. have fun!	190	# in the original prorcess. have fun!
28	}	191	}
29		192
30	##################################################################
31	# create a pool of server processes all accepting on the same socket	193	=head2 Create a pool of server processes all accepting on the same socket.
32		194
33	# create listener socket	195	# create listener socket
34	my $listener = ...;	196	my $listener = ...;
35		197
36	# create a pool template, initialise it and give it the socket	198	# create a pool template, initialise it and give it the socket
…		…
48	}	210	}
49		211
50	# now do other things - maybe use the filehandle provided by run	212	# now do other things - maybe use the filehandle provided by run
51	# to wait for the processes to die. or whatever.	213	# to wait for the processes to die. or whatever.
52		214
53	# My::Server::run might look like this	215	C<My::Server> might look like this:
54	sub My::Server::run {	216
		217	package My::Server;
		218
		219	sub run {
55	my ($slave, $listener, $id) = @_;	220	my ($slave, $listener, $id) = @_;
56		221
57	close $slave; # we do not use the socket, so close it to save resources	222	close $slave; # we do not use the socket, so close it to save resources
58		223
59	# we could go ballistic and use e.g. AnyEvent here, or IO::AIO,	224	# we could go ballistic and use e.g. AnyEvent here, or IO::AIO,
…		…
61	while (my $socket = $listener->accept) {	226	while (my $socket = $listener->accept) {
62	# do sth. with new socket	227	# do sth. with new socket
63	}	228	}
64	}	229	}
65		230
66	=head1 DESCRIPTION	231	=head2 use AnyEvent::Fork as a faster fork+exec
67		232
68	This module allows you to create new processes, without actually forking	233	This runs C</bin/echo hi>, with standard output redirected to F</tmp/log>
69	them from your current process (avoiding the problems of forking), but	234	and standard error redirected to the communications socket. It is usually
70	preserving most of the advantages of fork.	235	faster than fork+exec, but still lets you prepare the environment.
71		236
72	It can be used to create new worker processes or new independent	237	open my $output, ">/tmp/log" or die "$!";
73	subprocesses for short- and long-running jobs, process pools (e.g. for use
74	in pre-forked servers) but also to spawn new external processes (such as
75	CGI scripts from a web server), which can be faster (and more well behaved)
76	than using fork+exec in big processes.
77		238
78	Special care has been taken to make this module useful from other modules,	239	AnyEvent::Fork
79	while still supporting specialised environments such as L<App::Staticperl>	240	->new
80	or L<PAR::Packer>.	241	->eval ('
		242	# compile a helper function for later use
		243	sub run {
		244	my ($fh, $output, @cmd) = @_;
81		245
82	=head1 WHAT THIS MODULE IS NOT	246	# perl will clear close-on-exec on STDOUT/STDERR
		247	open STDOUT, ">&", $output or die;
		248	open STDERR, ">&", $fh or die;
83		249
84	This module only creates processes and lets you pass file handles and	250	exec @cmd;
85	strings to it, and run perl code. It does not implement any kind of RPC -	251	}
86	there is no back channel from the process back to you, and there is no RPC	252	')
87	or message passing going on.	253	->send_fh ($output)
		254	->send_arg ("/bin/echo", "hi")
		255	->run ("run", my $cv = AE::cv);
88		256
89	If you need some form of RPC, you can either implement it yourself	257	my $stderr = $cv->recv;
90	in whatever way you like, use some message-passing module such
91	as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use
92	L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages,
93	and so on.
94		258
95	=head1 PROBLEM STATEMENT	259	=head2 For stingy users: put the worker code into a C<DATA> section.
96		260
97	There are two ways to implement parallel processing on UNIX like operating	261	When you want to be stingy with files, you cna put your code into the
98	systems - fork and process, and fork+exec and process. They have different	262	C<DATA> section of your module (or program):
99	advantages and disadvantages that I describe below, together with how this
100	module tries to mitigate the disadvantages.
101		263
102	=over 4	264	use AnyEvent::Fork;
103		265
104	=item Forking from a big process can be very slow (a 5GB process needs	266	AnyEvent::Fork
105	0.05s to fork on my 3.6GHz amd64 GNU/Linux box for example). This overhead	267	->new
106	is often shared with exec (because you have to fork first), but in some	268	->eval (do { local $/; <DATA> })
107	circumstances (e.g. when vfork is used), fork+exec can be much faster.	269	->run ("doit", sub { ... });
108		270
109	This module can help here by telling a small(er) helper process to fork,	271	__DATA__
110	or fork+exec instead.
111		272
112	=item Forking usually creates a copy-on-write copy of the parent	273	sub doit {
113	process. Memory (for example, modules or data files that have been	274	... do something!
114	will not take additional memory). When exec'ing a new process, modules	275	}
115	and data files might need to be loaded again, at extra CPU and memory
116	cost. Likewise when forking, all data structures are copied as well - if
117	the program frees them and replaces them by new data, the child processes
118	will retain the memory even if it isn't used.
119		276
120	This module allows the main program to do a controlled fork, and allows	277	=head2 For stingy standalone programs: do not rely on external files at
121	modules to exec processes safely at any time. When creating a custom	278	all.
122	process pool you can take advantage of data sharing via fork without
123	risking to share large dynamic data structures that will blow up child
124	memory usage.
125		279
126	=item Exec'ing a new perl process might be difficult and slow. For	280	For single-file scripts it can be inconvenient to rely on external
127	example, it is not easy to find the correct path to the perl interpreter,	281	files - even when using < C<DATA> section, you still need to C<exec>
128	and all modules have to be loaded from disk again. Long running processes	282	an external perl interpreter, which might not be available when using
129	might run into problems when perl is upgraded for example.	283	L<App::Staticperl>, L<Urlader> or L<PAR::Packer> for example.
130		284
131	This module supports creating pre-initialised perl processes to be used	285	Two modules help here - L<AnyEvent::Fork::Early> forks a template process
132	as template, and also tries hard to identify the correct path to the perl	286	for all further calls to C<new_exec>, and L<AnyEvent::Fork::Template>
133	interpreter. With a cooperative main program, exec'ing the interpreter	287	forks the main program as a template process.
134	might not even be necessary.
135		288
136	=item Forking might be impossible when a program is running. For example,	289	Here is how your main program should look like:
137	POSIX makes it almost impossible to fork from a multi-threaded program and
138	do anything useful in the child - strictly speaking, if your perl program
139	uses posix threads (even indirectly via e.g. L<IO::AIO> or L<threads>),
140	you cannot call fork on the perl level anymore, at all.
141		290
142	This module can safely fork helper processes at any time, by calling	291	#! perl
143	fork+exec in C, in a POSIX-compatible way.
144		292
145	=item Parallel processing with fork might be inconvenient or difficult	293	# optional, as the very first thing.
146	to implement. For example, when a program uses an event loop and creates	294	# in case modules want to create their own processes.
147	watchers it becomes very hard to use the event loop from a child	295	use AnyEvent::Fork::Early;
148	program, as the watchers already exist but are only meaningful in the
149	parent. Worse, a module might want to use such a system, not knowing
150	whether another module or the main program also does, leading to problems.
151		296
152	This module only lets the main program create pools by forking (because	297	# next, load all modules you need in your template process
153	only the main program can know when it is still safe to do so) - all other	298	use Example::My::Module
154	pools are created by fork+exec, after which such modules can again be	299	use Example::Whatever;
155	loaded.
156		300
157	=back	301	# next, put your run function definition and anything else you
		302	# need, but do not use code outside of BEGIN blocks.
		303	sub worker_run {
		304	my ($fh, @args) = @_;
		305	...
		306	}
		307
		308	# now preserve everything so far as AnyEvent::Fork object
		309	# in §TEMPLATE.
		310	use AnyEvent::Fork::Template;
		311
		312	# do not put code outside of BEGIN blocks until here
		313
		314	# now use the $TEMPLATE process in any way you like
		315
		316	# for example: create 10 worker processes
		317	my @worker;
		318	my $cv = AE::cv;
		319	for (1..10) {
		320	$cv->begin;
		321	$TEMPLATE->fork->send_arg ($_)->run ("worker_run", sub {
		322	push @worker, shift;
		323	$cv->end;
		324	});
		325	}
		326	$cv->recv;
158		327
159	=head1 CONCEPTS	328	=head1 CONCEPTS
160		329
161	This module can create new processes either by executing a new perl	330	This module can create new processes either by executing a new perl
162	process, or by forking from an existing "template" process.	331	process, or by forking from an existing "template" process.
		332
		333	All these processes are called "child processes" (whether they are direct
		334	children or not), while the process that manages them is called the
		335	"parent process".
163		336
164	Each such process comes with its own file handle that can be used to	337	Each such process comes with its own file handle that can be used to
165	communicate with it (it's actually a socket - one end in the new process,	338	communicate with it (it's actually a socket - one end in the new process,
166	one end in the main process), and among the things you can do in it are	339	one end in the main process), and among the things you can do in it are
167	load modules, fork new processes, send file handles to it, and execute	340	load modules, fork new processes, send file handles to it, and execute
…		…
241	my ($fork_fh) = @_;	414	my ($fork_fh) = @_;
242	});	415	});
243		416
244	=back	417	=back
245		418
246	=head1 FUNCTIONS	419	=head1 THE C<AnyEvent::Fork> CLASS
		420
		421	This module exports nothing, and only implements a single class -
		422	C<AnyEvent::Fork>.
		423
		424	There are two class constructors that both create new processes - C<new>
		425	and C<new_exec>. The C<fork> method creates a new process by forking an
		426	existing one and could be considered a third constructor.
		427
		428	Most of the remaining methods deal with preparing the new process, by
		429	loading code, evaluating code and sending data to the new process. They
		430	usually return the process object, so you can chain method calls.
		431
		432	If a process object is destroyed before calling its C<run> method, then
		433	the process simply exits. After C<run> is called, all responsibility is
		434	passed to the specified function.
		435
		436	As long as there is any outstanding work to be done, process objects
		437	resist being destroyed, so there is no reason to store them unless you
		438	need them later - configure and forget works just fine.
247		439
248	=over 4	440	=over 4
249		441
250	=cut	442	=cut
251		443
…		…
258	use AnyEvent;	450	use AnyEvent;
259	use AnyEvent::Util ();	451	use AnyEvent::Util ();
260		452
261	use IO::FDPass;	453	use IO::FDPass;
262		454
263	our $VERSION = 0.2;	455	our $VERSION = 1.1;
264
265	our $PERL; # the path to the perl interpreter, deduces with various forms of magic
266
267	=item my $pool = new AnyEvent::Fork key => value...
268
269	Create a new process pool. The following named parameters are supported:
270
271	=over 4
272
273	=back
274
275	=cut
276		456
277	# the early fork template process	457	# the early fork template process
278	our $EARLY;	458	our $EARLY;
279		459
280	# the empty template process	460	# the empty template process
281	our $TEMPLATE;	461	our $TEMPLATE;
		462
		463	sub QUEUE() { 0 }
		464	sub FH() { 1 }
		465	sub WW() { 2 }
		466	sub PID() { 3 }
		467	sub CB() { 4 }
		468
		469	sub _new {
		470	my ($self, $fh, $pid) = @_;
		471
		472	AnyEvent::Util::fh_nonblocking $fh, 1;
		473
		474	$self = bless [
		475	[], # write queue - strings or fd's
		476	$fh,
		477	undef, # AE watcher
		478	$pid,
		479	], $self;
		480
		481	$self
		482	}
282		483
283	sub _cmd {	484	sub _cmd {
284	my $self = shift;	485	my $self = shift;
285		486
286	# ideally, we would want to use "a (w/a)*" as format string, but perl	487	# ideally, we would want to use "a (w/a)*" as format string, but perl
287	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack	488	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack
288	# it.	489	# it.
289	push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1];	490	push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1];
290		491
291	$self->[3] \|\|= AE::io $self->[1], 1, sub {	492	$self->[WW] \|\|= AE::io $self->[FH], 1, sub {
292	do {	493	do {
293	# send the next "thing" in the queue - either a reference to an fh,	494	# send the next "thing" in the queue - either a reference to an fh,
294	# or a plain string.	495	# or a plain string.
295		496
296	if (ref $self->[2][0]) {	497	if (ref $self->[QUEUE][0]) {
297	# send fh	498	# send fh
298	unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) {	499	unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) {
299	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	500	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
300	undef $self->[3];	501	undef $self->[WW];
301	die "AnyEvent::Fork: file descriptor send failure: $!";	502	die "AnyEvent::Fork: file descriptor send failure: $!";
302	}	503	}
303		504
304	shift @{ $self->[2] };	505	shift @{ $self->[QUEUE] };
305		506
306	} else {	507	} else {
307	# send string	508	# send string
308	my $len = syswrite $self->[1], $self->[2][0];	509	my $len = syswrite $self->[FH], $self->[QUEUE][0];
309		510
310	unless ($len) {	511	unless ($len) {
311	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	512	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
312	undef $self->[3];	513	undef $self->[WW];
313	die "AnyEvent::Fork: command write failure: $!";	514	die "AnyEvent::Fork: command write failure: $!";
314	}	515	}
315		516
316	substr $self->[2][0], 0, $len, "";	517	substr $self->[QUEUE][0], 0, $len, "";
317	shift @{ $self->[2] } unless length $self->[2][0];	518	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
318	}	519	}
319	} while @{ $self->[2] };	520	} while @{ $self->[QUEUE] };
320		521
321	# everything written	522	# everything written
322	undef $self->[3];	523	undef $self->[WW];
323		524
324	# invoke run callback, if any	525	# invoke run callback, if any
325	$self->[0]->($self->[1]) if $self->[0];	526	if ($self->[CB]) {
		527	$self->[CB]->($self->[FH]);
		528	@$self = ();
		529	}
326	};	530	};
327		531
328	() # make sure we don't leak the watcher	532	() # make sure we don't leak the watcher
329	}
330
331	sub _new {
332	my ($self, $fh, $pid) = @_;
333
334	AnyEvent::Util::fh_nonblocking $fh, 1;
335
336	$self = bless [
337	undef, # run callback
338	$fh,
339	[], # write queue - strings or fd's
340	undef, # AE watcher
341	$pid,
342	], $self;
343
344	$self
345	}	533	}
346		534
347	# fork template from current process, used by AnyEvent::Fork::Early/Template	535	# fork template from current process, used by AnyEvent::Fork::Early/Template
348	sub _new_fork {	536	sub _new_fork {
349	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	537	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
354	if ($pid eq 0) {	542	if ($pid eq 0) {
355	require AnyEvent::Fork::Serve;	543	require AnyEvent::Fork::Serve;
356	$AnyEvent::Fork::Serve::OWNER = $parent;	544	$AnyEvent::Fork::Serve::OWNER = $parent;
357	close $fh;	545	close $fh;
358	$0 = "$_[1] of $parent";	546	$0 = "$_[1] of $parent";
359	$SIG{CHLD} = 'IGNORE';
360	AnyEvent::Fork::Serve::serve ($slave);	547	AnyEvent::Fork::Serve::serve ($slave);
361	exit 0;	548	exit 0;
362	} elsif (!$pid) {	549	} elsif (!$pid) {
363	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";	550	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";
364	}	551	}
…		…
371	Create a new "empty" perl interpreter process and returns its process	558	Create a new "empty" perl interpreter process and returns its process
372	object for further manipulation.	559	object for further manipulation.
373		560
374	The new process is forked from a template process that is kept around	561	The new process is forked from a template process that is kept around
375	for this purpose. When it doesn't exist yet, it is created by a call to	562	for this purpose. When it doesn't exist yet, it is created by a call to
376	C<new_exec> and kept around for future calls.	563	C<new_exec> first and then stays around for future calls.
377
378	When the process object is destroyed, it will release the file handle
379	that connects it with the new process. When the new process has not yet
380	called C<run>, then the process will exit. Otherwise, what happens depends
381	entirely on the code that is executed.
382		564
383	=cut	565	=cut
384		566
385	sub new {	567	sub new {
386	my $class = shift;	568	my $class = shift;
…		…
423		605
424	You should use C<new> whenever possible, except when having a template	606	You should use C<new> whenever possible, except when having a template
425	process around is unacceptable.	607	process around is unacceptable.
426		608
427	The path to the perl interpreter is divined using various methods - first	609	The path to the perl interpreter is divined using various methods - first
428	C<$^X> is investigated to see if the path ends with something that sounds	610	C<$^X> is investigated to see if the path ends with something that looks
429	as if it were the perl interpreter. Failing this, the module falls back to	611	as if it were the perl interpreter. Failing this, the module falls back to
430	using C<$Config::Config{perlpath}>.	612	using C<$Config::Config{perlpath}>.
431		613
		614	The path to perl can also be overriden by setting the global variable
		615	C<$AnyEvent::Fork::PERL> - it's value will be used for all subsequent
		616	invocations.
		617
432	=cut	618	=cut
		619
		620	our $PERL;
433		621
434	sub new_exec {	622	sub new_exec {
435	my ($self) = @_;	623	my ($self) = @_;
436		624
437	return $EARLY->fork	625	return $EARLY->fork
438	if $EARLY;	626	if $EARLY;
439		627
		628	unless (defined $PERL) {
440	# first find path of perl	629	# first find path of perl
441	my $perl = $;	630	my $perl = $;
442		631
443	# first we try $^X, but the path must be absolute (always on win32), and end in sth.	632	# first we try $^X, but the path must be absolute (always on win32), and end in sth.
444	# that looks like perl. this obviously only works for posix and win32	633	# that looks like perl. this obviously only works for posix and win32
445	unless (	634	unless (
446	($^O eq "MSWin32" \|\| $perl =~ m%^/%)	635	($^O eq "MSWin32" \|\| $perl =~ m%^/%)
447	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i	636	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i
448	) {	637	) {
449	# if it doesn't look perlish enough, try Config	638	# if it doesn't look perlish enough, try Config
450	require Config;	639	require Config;
451	$perl = $Config::Config{perlpath};	640	$perl = $Config::Config{perlpath};
452	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;	641	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;
		642	}
		643
		644	$PERL = $perl;
453	}	645	}
454		646
455	require Proc::FastSpawn;	647	require Proc::FastSpawn;
456		648
457	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	649	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
465	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;	657	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;
466	my %env = %ENV;	658	my %env = %ENV;
467	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;	659	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;
468		660
469	my $pid = Proc::FastSpawn::spawn (	661	my $pid = Proc::FastSpawn::spawn (
470	$perl,	662	$PERL,
471	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],	663	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],
472	[map "$_=$env{$_}", keys %env],	664	[map "$_=$env{$_}", keys %env],
473	) or die "unable to spawn AnyEvent::Fork server: $!";	665	) or die "unable to spawn AnyEvent::Fork server: $!";
474		666
475	$self->_new ($fh, $pid)	667	$self->_new ($fh, $pid)
476	}	668	}
477		669
		670	=item $pid = $proc->pid
		671
		672	Returns the process id of the process I<iff it is a direct child of the
		673	process running AnyEvent::Fork>, and C<undef> otherwise.
		674
		675	Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and
		676	L<AnyEvent::Fork::Template> are direct children, and you are responsible
		677	to clean up their zombies when they die.
		678
		679	All other processes are not direct children, and will be cleaned up by
		680	AnyEvent::Fork itself.
		681
		682	=cut
		683
		684	sub pid {
		685	$_[0][PID]
		686	}
		687
478	=item $proc = $proc->eval ($perlcode, @args)	688	=item $proc = $proc->eval ($perlcode, @args)
479		689
480	Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to	690	Evaluates the given C<$perlcode> as ... Perl code, while setting C<@_> to
481	the strings specified by C<@args>.	691	the strings specified by C<@args>, in the "main" package.
482		692
483	This call is meant to do any custom initialisation that might be required	693	This call is meant to do any custom initialisation that might be required
484	(for example, the C<require> method uses it). It's not supposed to be used	694	(for example, the C<require> method uses it). It's not supposed to be used
485	to completely take over the process, use C<run> for that.	695	to completely take over the process, use C<run> for that.
486		696
487	The code will usually be executed after this call returns, and there is no	697	The code will usually be executed after this call returns, and there is no
488	way to pass anything back to the calling process. Any evaluation errors	698	way to pass anything back to the calling process. Any evaluation errors
489	will be reported to stderr and cause the process to exit.	699	will be reported to stderr and cause the process to exit.
490		700
		701	If you want to execute some code (that isn't in a module) to take over the
		702	process, you should compile a function via C<eval> first, and then call
		703	it via C<run>. This also gives you access to any arguments passed via the
		704	C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as
		705	a faster fork+exec> example to see it in action.
		706
491	Returns the process object for easy chaining of method calls.	707	Returns the process object for easy chaining of method calls.
492		708
493	=cut	709	=cut
494		710
495	sub eval {	711	sub eval {
…		…
520	=item $proc = $proc->send_fh ($handle, ...)	736	=item $proc = $proc->send_fh ($handle, ...)
521		737
522	Send one or more file handles (I<not> file descriptors) to the process,	738	Send one or more file handles (I<not> file descriptors) to the process,
523	to prepare a call to C<run>.	739	to prepare a call to C<run>.
524		740
525	The process object keeps a reference to the handles until this is done,	741	The process object keeps a reference to the handles until they have
526	so you must not explicitly close the handles. This is most easily	742	been passed over to the process, so you must not explicitly close the
527	accomplished by simply not storing the file handles anywhere after passing	743	handles. This is most easily accomplished by simply not storing the file
528	them to this method.	744	handles anywhere after passing them to this method - when AnyEvent::Fork
		745	is finished using them, perl will automatically close them.
529		746
530	Returns the process object for easy chaining of method calls.	747	Returns the process object for easy chaining of method calls.
531		748
532	Example: pass a file handle to a process, and release it without	749	Example: pass a file handle to a process, and release it without
533	closing. It will be closed automatically when it is no longer used.	750	closing. It will be closed automatically when it is no longer used.
…		…
540	sub send_fh {	757	sub send_fh {
541	my ($self, @fh) = @_;	758	my ($self, @fh) = @_;
542		759
543	for my $fh (@fh) {	760	for my $fh (@fh) {
544	$self->_cmd ("h");	761	$self->_cmd ("h");
545	push @{ $self->[2] }, \$fh;	762	push @{ $self->[QUEUE] }, \$fh;
546	}	763	}
547		764
548	$self	765	$self
549	}	766	}
550		767
551	=item $proc = $proc->send_arg ($string, ...)	768	=item $proc = $proc->send_arg ($string, ...)
552		769
553	Send one or more argument strings to the process, to prepare a call to	770	Send one or more argument strings to the process, to prepare a call to
554	C<run>. The strings can be any octet string.	771	C<run>. The strings can be any octet strings.
555		772
556	The protocol is optimised to pass a moderate number of relatively short	773	The protocol is optimised to pass a moderate number of relatively short
557	strings - while you can pass up to 4GB of data in one go, this is more	774	strings - while you can pass up to 4GB of data in one go, this is more
558	meant to pass some ID information or other startup info, not big chunks of	775	meant to pass some ID information or other startup info, not big chunks of
559	data.	776	data.
…		…
570	$self	787	$self
571	}	788	}
572		789
573	=item $proc->run ($func, $cb->($fh))	790	=item $proc->run ($func, $cb->($fh))
574		791
575	Enter the function specified by the fully qualified name in C<$func> in	792	Enter the function specified by the function name in C<$func> in the
576	the process. The function is called with the communication socket as first	793	process. The function is called with the communication socket as first
577	argument, followed by all file handles and string arguments sent earlier	794	argument, followed by all file handles and string arguments sent earlier
578	via C<send_fh> and C<send_arg> methods, in the order they were called.	795	via C<send_fh> and C<send_arg> methods, in the order they were called.
579		796
580	If the called function returns, the process exits.
581
582	Preparing the process can take time - when the process is ready, the
583	callback is invoked with the local communications socket as argument.
584
585	The process object becomes unusable on return from this function.	797	The process object becomes unusable on return from this function - any
		798	further method calls result in undefined behaviour.
		799
		800	The function name should be fully qualified, but if it isn't, it will be
		801	looked up in the C<main> package.
		802
		803	If the called function returns, doesn't exist, or any error occurs, the
		804	process exits.
		805
		806	Preparing the process is done in the background - when all commands have
		807	been sent, the callback is invoked with the local communications socket
		808	as argument. At this point you can start using the socket in any way you
		809	like.
586		810
587	If the communication socket isn't used, it should be closed on both sides,	811	If the communication socket isn't used, it should be closed on both sides,
588	to save on kernel memory.	812	to save on kernel memory.
589		813
590	The socket is non-blocking in the parent, and blocking in the newly	814	The socket is non-blocking in the parent, and blocking in the newly
591	created process. The close-on-exec flag is set on both. Even if not used	815	created process. The close-on-exec flag is set in both.
		816
592	otherwise, the socket can be a good indicator for the existence of the	817	Even if not used otherwise, the socket can be a good indicator for the
593	process - if the other process exits, you get a readable event on it,	818	existence of the process - if the other process exits, you get a readable
594	because exiting the process closes the socket (if it didn't create any	819	event on it, because exiting the process closes the socket (if it didn't
595	children using fork).	820	create any children using fork).
596		821
597	Example: create a template for a process pool, pass a few strings, some	822	Example: create a template for a process pool, pass a few strings, some
598	file handles, then fork, pass one more string, and run some code.	823	file handles, then fork, pass one more string, and run some code.
599		824
600	my $pool = AnyEvent::Fork	825	my $pool = AnyEvent::Fork
…		…
608	->send_arg ("str3")	833	->send_arg ("str3")
609	->run ("Some::function", sub {	834	->run ("Some::function", sub {
610	my ($fh) = @_;	835	my ($fh) = @_;
611		836
612	# fh is nonblocking, but we trust that the OS can accept these	837	# fh is nonblocking, but we trust that the OS can accept these
613	# extra 3 octets anyway.	838	# few octets anyway.
614	syswrite $fh, "hi #$_\n";	839	syswrite $fh, "hi #$_\n";
615		840
616	# $fh is being closed here, as we don't store it anywhere	841	# $fh is being closed here, as we don't store it anywhere
617	});	842	});
618	}	843	}
…		…
620	# Some::function might look like this - all parameters passed before fork	845	# Some::function might look like this - all parameters passed before fork
621	# and after will be passed, in order, after the communications socket.	846	# and after will be passed, in order, after the communications socket.
622	sub Some::function {	847	sub Some::function {
623	my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_;	848	my ($fh, $str1, $str2, $fh1, $fh2, $str3) = @_;
624		849
625	print scalar <$fh>; # prints "hi 1\n" and "hi 2\n"	850	print scalar <$fh>; # prints "hi #1\n" and "hi #2\n" in any order
626	}	851	}
627		852
628	=cut	853	=cut
629		854
630	sub run {	855	sub run {
631	my ($self, $func, $cb) = @_;	856	my ($self, $func, $cb) = @_;
632		857
633	$self->[0] = $cb;	858	$self->[CB] = $cb;
634	$self->_cmd (r => $func);	859	$self->_cmd (r => $func);
		860	}
		861
		862	=back
		863
		864	=head2 EXPERIMENTAL METHODS
		865
		866	These methods might go away completely or change behaviour, at any time.
		867
		868	=over 4
		869
		870	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		871
		872	Flushes all commands out to the process and then calls the callback with
		873	the communications socket.
		874
		875	The process object becomes unusable on return from this function - any
		876	further method calls result in undefined behaviour.
		877
		878	The point of this method is to give you a file handle thta you cna pass
		879	to another process. In that other process, you can call C<new_from_fh
		880	AnyEvent::Fork> to create a new C<AnyEvent::Fork> object from it, thereby
		881	effectively passing a fork object to another process.
		882
		883	=cut
		884
		885	sub to_fh {
		886	my ($self, $cb) = @_;
		887
		888	$self->[CB] = $cb;
		889
		890	unless ($self->[WW]) {
		891	$self->[CB]->($self->[FH]);
		892	@$self = ();
		893	}
		894	}
		895
		896	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		897
		898	Takes a file handle originally rceeived by the C<to_fh> method and creates
		899	a new C<AnyEvent:Fork> object. The child process itself will not change in
		900	any way, i.e. it will keep all the modifications done to it before calling
		901	C<to_fh>.
		902
		903	The new object is very much like the original object, except that the
		904	C<pid> method will return C<undef> even if the process is a direct child.
		905
		906	=cut
		907
		908	sub new_from_fh {
		909	my ($class, $fh) = @_;
		910
		911	$class->_new ($fh)
635	}	912	}
636		913
637	=back	914	=back
638		915
639	=head1 PERFORMANCE	916	=head1 PERFORMANCE
…		…
649		926
650	2079 new processes per second, using manual socketpair + fork	927	2079 new processes per second, using manual socketpair + fork
651		928
652	Then I did the same thing, but instead of calling fork, I called	929	Then I did the same thing, but instead of calling fork, I called
653	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the	930	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the
654	socket form the child to close on exit. This does the same thing as manual	931	socket from the child to close on exit. This does the same thing as manual
655	socket pair + fork, except that what is forked is the template process	932	socket pair + fork, except that what is forked is the template process
656	(2440kB), and the socket needs to be passed to the server at the other end	933	(2440kB), and the socket needs to be passed to the server at the other end
657	of the socket first.	934	of the socket first.
658		935
659	2307 new processes per second, using AnyEvent::Fork->new	936	2307 new processes per second, using AnyEvent::Fork->new
…		…
664	479 vfork+execs per second, using AnyEvent::Fork->new_exec	941	479 vfork+execs per second, using AnyEvent::Fork->new_exec
665		942
666	So how can C<< AnyEvent->new >> be faster than a standard fork, even	943	So how can C<< AnyEvent->new >> be faster than a standard fork, even
667	though it uses the same operations, but adds a lot of overhead?	944	though it uses the same operations, but adds a lot of overhead?
668		945
669	The difference is simply the process size: forking the 6MB process takes	946	The difference is simply the process size: forking the 5MB process takes
670	so much longer than forking the 2.5MB template process that the overhead	947	so much longer than forking the 2.5MB template process that the extra
671	introduced is canceled out.	948	overhead is canceled out.
672		949
673	If the benchmark process grows, the normal fork becomes even slower:	950	If the benchmark process grows, the normal fork becomes even slower:
674		951
675	1340 new processes, manual fork in a 20MB process	952	1340 new processes, manual fork of a 20MB process
676	731 new processes, manual fork in a 200MB process	953	731 new processes, manual fork of a 200MB process
677	235 new processes, manual fork in a 2000MB process	954	235 new processes, manual fork of a 2000MB process
678		955
679	What that means (to me) is that I can use this module without having a	956	What that means (to me) is that I can use this module without having a bad
680	very bad conscience because of the extra overhead required to start new	957	conscience because of the extra overhead required to start new processes.
681	processes.
682		958
683	=head1 TYPICAL PROBLEMS	959	=head1 TYPICAL PROBLEMS
684		960
685	This section lists typical problems that remain. I hope by recognising	961	This section lists typical problems that remain. I hope by recognising
686	them, most can be avoided.	962	them, most can be avoided.
687		963
688	=over 4	964	=over 4
689		965
690	=item "leaked" file descriptors for exec'ed processes	966	=item leaked file descriptors for exec'ed processes
691		967
692	POSIX systems inherit file descriptors by default when exec'ing a new	968	POSIX systems inherit file descriptors by default when exec'ing a new
693	process. While perl itself laudably sets the close-on-exec flags on new	969	process. While perl itself laudably sets the close-on-exec flags on new
694	file handles, most C libraries don't care, and even if all cared, it's	970	file handles, most C libraries don't care, and even if all cared, it's
695	often not possible to set the flag in a race-free manner.	971	often not possible to set the flag in a race-free manner.
…		…
715	libraries or the code that leaks those file descriptors.	991	libraries or the code that leaks those file descriptors.
716		992
717	Fortunately, most of these leaked descriptors do no harm, other than	993	Fortunately, most of these leaked descriptors do no harm, other than
718	sitting on some resources.	994	sitting on some resources.
719		995
720	=item "leaked" file descriptors for fork'ed processes	996	=item leaked file descriptors for fork'ed processes
721		997
722	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,	998	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,
723	which closes file descriptors not marked for being inherited.	999	which closes file descriptors not marked for being inherited.
724		1000
725	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer	1001	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer
…		…
734		1010
735	The solution is to either not load these modules before use'ing	1011	The solution is to either not load these modules before use'ing
736	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay	1012	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay
737	initialising them, for example, by calling C<init Gtk2> manually.	1013	initialising them, for example, by calling C<init Gtk2> manually.
738		1014
739	=item exit runs destructors	1015	=item exiting calls object destructors
740		1016
741	This only applies to users of Lc<AnyEvent::Fork:Early> and	1017	This only applies to users of L<AnyEvent::Fork:Early> and
742	L<AnyEvent::Fork::Template>.	1018	L<AnyEvent::Fork::Template>, or when initialising code creates objects
		1019	that reference external resources.
743		1020
744	When a process created by AnyEvent::Fork exits, it might do so by calling	1021	When a process created by AnyEvent::Fork exits, it might do so by calling
745	exit, or simply letting perl reach the end of the program. At which point	1022	exit, or simply letting perl reach the end of the program. At which point
746	Perl runs all destructors.	1023	Perl runs all destructors.
747		1024
…		…
766	to make it so, mostly due to the bloody broken perl that nobody seems to	1043	to make it so, mostly due to the bloody broken perl that nobody seems to
767	care about. The fork emulation is a bad joke - I have yet to see something	1044	care about. The fork emulation is a bad joke - I have yet to see something
768	useful that you can do with it without running into memory corruption	1045	useful that you can do with it without running into memory corruption
769	issues or other braindamage. Hrrrr.	1046	issues or other braindamage. Hrrrr.
770		1047
771	Cygwin perl is not supported at the moment, as it should implement fd	1048	Since fork is endlessly broken on win32 perls (it doesn't even remotely
772	passing, but doesn't, and rolling my own is hard, as cygwin doesn't	1049	work within it's documented limits) and quite obviously it's not getting
773	support enough functionality to do it.	1050	improved any time soon, the best way to proceed on windows would be to
		1051	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1052
		1053	Cygwin perl is not supported at the moment due to some hilarious
		1054	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1055	use C<send_fh> and always use C<new_exec> to create processes, it should
		1056	work though.
774		1057
775	=head1 SEE ALSO	1058	=head1 SEE ALSO
776		1059
777	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),	1060	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1061	(part of this distribution).
		1062
778	L<AnyEvent::Fork::Template> (to create a process by forking the main	1063	L<AnyEvent::Fork::Template>, to create a process by forking the main
779	program at a convenient time).	1064	program at a convenient time (part of this distribution).
780		1065
781	=head1 AUTHOR	1066	L<AnyEvent::Fork::Remote>, for another way to create processes that is
		1067	mostly compatible to this module and modules building on top of it, but
		1068	works better with remote processes.
		1069
		1070	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1071
		1072	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1073
		1074	=head1 AUTHOR AND CONTACT INFORMATION
782		1075
783	Marc Lehmann <schmorp@schmorp.de>	1076	Marc Lehmann <schmorp@schmorp.de>
784	http://home.schmorp.de/	1077	http://software.schmorp.de/pkg/AnyEvent-Fork
785		1078
786	=cut	1079	=cut
787		1080
788	1	1081	1
789		1082

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.19 by root, Sat Apr 6 02:31:26 2013 UTC vs. Revision 1.57 by root, Sun Aug 25 17:38:43 2013 UTC

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Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.19 by root, Sat Apr 6 02:31:26 2013 UTC vs.
Revision 1.57 by root, Sun Aug 25 17:38:43 2013 UTC