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

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.24 by root, Sat Apr 6 08:32:23 2013 UTC vs.
Revision 1.42 by root, Mon Apr 8 05:44:23 2013 UTC

…		…
27		27
28	Special care has been taken to make this module useful from other modules,	28	Special care has been taken to make this module useful from other modules,
29	while still supporting specialised environments such as L<App::Staticperl>	29	while still supporting specialised environments such as L<App::Staticperl>
30	or L<PAR::Packer>.	30	or L<PAR::Packer>.
31		31
32	=head1 WHAT THIS MODULE IS NOT	32	=head2 WHAT THIS MODULE IS NOT
33		33
34	This module only creates processes and lets you pass file handles and	34	This module only creates processes and lets you pass file handles and
35	strings to it, and run perl code. It does not implement any kind of RPC -	35	strings to it, and run perl code. It does not implement any kind of RPC -
36	there is no back channel from the process back to you, and there is no RPC	36	there is no back channel from the process back to you, and there is no RPC
37	or message passing going on.	37	or message passing going on.
…		…
40	in whatever way you like, use some message-passing module such	40	in whatever way you like, use some message-passing module such
41	as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use	41	as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use
42	L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages,	42	L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages,
43	and so on.	43	and so on.
44		44
		45	=head2 COMPARISON TO OTHER MODULES
		46
		47	There is an abundance of modules on CPAN that do "something fork", such as
		48	L<Parallel::ForkManager>, L<AnyEvent::ForkManager>, L<AnyEvent::Worker>
		49	or L<AnyEvent::Subprocess>. There are modules that implement their own
		50	process management, such as L<AnyEvent::DBI>.
		51
		52	The problems that all these modules try to solve are real, however, none
		53	of them (from what I have seen) tackle the very real problems of unwanted
		54	memory sharing, efficiency, not being able to use event processing or
		55	similar modules in the processes they create.
		56
		57	This module doesn't try to replace any of them - instead it tries to solve
		58	the problem of creating processes with a minimum of fuss and overhead (and
		59	also luxury). Ideally, most of these would use AnyEvent::Fork internally,
		60	except they were written before AnyEvent:Fork was available, so obviously
		61	had to roll their own.
		62
		63	=head2 PROBLEM STATEMENT
		64
		65	There are two traditional ways to implement parallel processing on UNIX
		66	like operating systems - fork and process, and fork+exec and process. They
		67	have different advantages and disadvantages that I describe below,
		68	together with how this module tries to mitigate the disadvantages.
		69
		70	=over 4
		71
		72	=item Forking from a big process can be very slow.
		73
		74	A 5GB process needs 0.05s to fork on my 3.6GHz amd64 GNU/Linux box. This
		75	overhead is often shared with exec (because you have to fork first), but
		76	in some circumstances (e.g. when vfork is used), fork+exec can be much
		77	faster.
		78
		79	This module can help here by telling a small(er) helper process to fork,
		80	which is faster then forking the main process, and also uses vfork where
		81	possible. This gives the speed of vfork, with the flexibility of fork.
		82
		83	=item Forking usually creates a copy-on-write copy of the parent
		84	process.
		85
		86	For example, modules or data files that are loaded will not use additional
		87	memory after a fork. When exec'ing a new process, modules and data files
		88	might need to be loaded again, at extra CPU and memory cost. But when
		89	forking, literally all data structures are copied - if the program frees
		90	them and replaces them by new data, the child processes will retain the
		91	old version even if it isn't used, which can suddenly and unexpectedly
		92	increase memory usage when freeing memory.
		93
		94	The trade-off is between more sharing with fork (which can be good or
		95	bad), and no sharing with exec.
		96
		97	This module allows the main program to do a controlled fork, and allows
		98	modules to exec processes safely at any time. When creating a custom
		99	process pool you can take advantage of data sharing via fork without
		100	risking to share large dynamic data structures that will blow up child
		101	memory usage.
		102
		103	In other words, this module puts you into control over what is being
		104	shared and what isn't, at all times.
		105
		106	=item Exec'ing a new perl process might be difficult.
		107
		108	For example, it is not easy to find the correct path to the perl
		109	interpreter - C<$^X> might not be a perl interpreter at all.
		110
		111	This module tries hard to identify the correct path to the perl
		112	interpreter. With a cooperative main program, exec'ing the interpreter
		113	might not even be necessary, but even without help from the main program,
		114	it will still work when used from a module.
		115
		116	=item Exec'ing a new perl process might be slow, as all necessary modules
		117	have to be loaded from disk again, with no guarantees of success.
		118
		119	Long running processes might run into problems when perl is upgraded
		120	and modules are no longer loadable because they refer to a different
		121	perl version, or parts of a distribution are newer than the ones already
		122	loaded.
		123
		124	This module supports creating pre-initialised perl processes to be used as
		125	a template for new processes.
		126
		127	=item Forking might be impossible when a program is running.
		128
		129	For example, POSIX makes it almost impossible to fork from a
		130	multi-threaded program while doing anything useful in the child - in
		131	fact, if your perl program uses POSIX threads (even indirectly via
		132	e.g. L<IO::AIO> or L<threads>), you cannot call fork on the perl level
		133	anymore without risking corruption issues on a number of operating
		134	systems.
		135
		136	This module can safely fork helper processes at any time, by calling
		137	fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>).
		138
		139	=item Parallel processing with fork might be inconvenient or difficult
		140	to implement. Modules might not work in both parent and child.
		141
		142	For example, when a program uses an event loop and creates watchers it
		143	becomes very hard to use the event loop from a child program, as the
		144	watchers already exist but are only meaningful in the parent. Worse, a
		145	module might want to use such a module, not knowing whether another module
		146	or the main program also does, leading to problems.
		147
		148	Apart from event loops, graphical toolkits also commonly fall into the
		149	"unsafe module" category, or just about anything that communicates with
		150	the external world, such as network libraries and file I/O modules, which
		151	usually don't like being copied and then allowed to continue in two
		152	processes.
		153
		154	With this module only the main program is allowed to create new processes
		155	by forking (because only the main program can know when it is still safe
		156	to do so) - all other processes are created via fork+exec, which makes it
		157	possible to use modules such as event loops or window interfaces safely.
		158
		159	=back
		160
45	=head1 EXAMPLES	161	=head1 EXAMPLES
46		162
47	=head2 Create a single new process, tell it to run your worker function.	163	=head2 Create a single new process, tell it to run your worker function.
48		164
49	AnyEvent::Fork	165	AnyEvent::Fork
…		…
54		170
55	# now $master_filehandle is connected to the	171	# now $master_filehandle is connected to the
56	# $slave_filehandle in the new process.	172	# $slave_filehandle in the new process.
57	});	173	});
58		174
59	# MyModule::worker might look like this	175	C<MyModule> might look like this:
		176
		177	package MyModule;
		178
60	sub MyModule::worker {	179	sub worker {
61	my ($slave_filehandle) = @_;	180	my ($slave_filehandle) = @_;
62		181
63	# now $slave_filehandle is connected to the $master_filehandle	182	# now $slave_filehandle is connected to the $master_filehandle
64	# in the original prorcess. have fun!	183	# in the original prorcess. have fun!
65	}	184	}
…		…
84	}	203	}
85		204
86	# now do other things - maybe use the filehandle provided by run	205	# now do other things - maybe use the filehandle provided by run
87	# to wait for the processes to die. or whatever.	206	# to wait for the processes to die. or whatever.
88		207
89	# My::Server::run might look like this	208	C<My::Server> might look like this:
90	sub My::Server::run {	209
		210	package My::Server;
		211
		212	sub run {
91	my ($slave, $listener, $id) = @_;	213	my ($slave, $listener, $id) = @_;
92		214
93	close $slave; # we do not use the socket, so close it to save resources	215	close $slave; # we do not use the socket, so close it to save resources
94		216
95	# we could go ballistic and use e.g. AnyEvent here, or IO::AIO,	217	# we could go ballistic and use e.g. AnyEvent here, or IO::AIO,
…		…
99	}	221	}
100	}	222	}
101		223
102	=head2 use AnyEvent::Fork as a faster fork+exec	224	=head2 use AnyEvent::Fork as a faster fork+exec
103		225
104	This runs /bin/echo hi, with stdout redirected to /tmp/log and stderr to	226	This runs C</bin/echo hi>, with stdandard output redirected to /tmp/log
105	the communications socket. It is usually faster than fork+exec, but still	227	and standard error redirected to the communications socket. It is usually
106	let's you prepare the environment.	228	faster than fork+exec, but still lets you prepare the environment.
107		229
108	open my $output, ">/tmp/log" or die "$!";	230	open my $output, ">/tmp/log" or die "$!";
109		231
110	AnyEvent::Fork	232	AnyEvent::Fork
111	->new	233	->new
112	->eval ('	234	->eval ('
		235	# compile a helper function for later use
113	sub run {	236	sub run {
114	my ($fh, $output, @cmd) = @_;	237	my ($fh, $output, @cmd) = @_;
115		238
116	# perl will clear close-on-exec on STDOUT/STDERR	239	# perl will clear close-on-exec on STDOUT/STDERR
117	open STDOUT, ">&", $output or die;	240	open STDOUT, ">&", $output or die;
…		…
123	->send_fh ($output)	246	->send_fh ($output)
124	->send_arg ("/bin/echo", "hi")	247	->send_arg ("/bin/echo", "hi")
125	->run ("run", my $cv = AE::cv);	248	->run ("run", my $cv = AE::cv);
126		249
127	my $stderr = $cv->recv;	250	my $stderr = $cv->recv;
128
129	=head1 PROBLEM STATEMENT
130
131	There are two ways to implement parallel processing on UNIX like operating
132	systems - fork and process, and fork+exec and process. They have different
133	advantages and disadvantages that I describe below, together with how this
134	module tries to mitigate the disadvantages.
135
136	=over 4
137
138	=item Forking from a big process can be very slow (a 5GB process needs
139	0.05s to fork on my 3.6GHz amd64 GNU/Linux box for example). This overhead
140	is often shared with exec (because you have to fork first), but in some
141	circumstances (e.g. when vfork is used), fork+exec can be much faster.
142
143	This module can help here by telling a small(er) helper process to fork,
144	or fork+exec instead.
145
146	=item Forking usually creates a copy-on-write copy of the parent
147	process. Memory (for example, modules or data files that have been
148	will not take additional memory). When exec'ing a new process, modules
149	and data files might need to be loaded again, at extra CPU and memory
150	cost. Likewise when forking, all data structures are copied as well - if
151	the program frees them and replaces them by new data, the child processes
152	will retain the memory even if it isn't used.
153
154	This module allows the main program to do a controlled fork, and allows
155	modules to exec processes safely at any time. When creating a custom
156	process pool you can take advantage of data sharing via fork without
157	risking to share large dynamic data structures that will blow up child
158	memory usage.
159
160	=item Exec'ing a new perl process might be difficult and slow. For
161	example, it is not easy to find the correct path to the perl interpreter,
162	and all modules have to be loaded from disk again. Long running processes
163	might run into problems when perl is upgraded for example.
164
165	This module supports creating pre-initialised perl processes to be used
166	as template, and also tries hard to identify the correct path to the perl
167	interpreter. With a cooperative main program, exec'ing the interpreter
168	might not even be necessary.
169
170	=item Forking might be impossible when a program is running. For example,
171	POSIX makes it almost impossible to fork from a multi-threaded program and
172	do anything useful in the child - strictly speaking, if your perl program
173	uses posix threads (even indirectly via e.g. L<IO::AIO> or L<threads>),
174	you cannot call fork on the perl level anymore, at all.
175
176	This module can safely fork helper processes at any time, by calling
177	fork+exec in C, in a POSIX-compatible way.
178
179	=item Parallel processing with fork might be inconvenient or difficult
180	to implement. For example, when a program uses an event loop and creates
181	watchers it becomes very hard to use the event loop from a child
182	program, as the watchers already exist but are only meaningful in the
183	parent. Worse, a module might want to use such a system, not knowing
184	whether another module or the main program also does, leading to problems.
185
186	This module only lets the main program create pools by forking (because
187	only the main program can know when it is still safe to do so) - all other
188	pools are created by fork+exec, after which such modules can again be
189	loaded.
190
191	=back
192		251
193	=head1 CONCEPTS	252	=head1 CONCEPTS
194		253
195	This module can create new processes either by executing a new perl	254	This module can create new processes either by executing a new perl
196	process, or by forking from an existing "template" process.	255	process, or by forking from an existing "template" process.
…		…
275	my ($fork_fh) = @_;	334	my ($fork_fh) = @_;
276	});	335	});
277		336
278	=back	337	=back
279		338
280	=head1 FUNCTIONS	339	=head1 THE C<AnyEvent::Fork> CLASS
		340
		341	This module exports nothing, and only implements a single class -
		342	C<AnyEvent::Fork>.
		343
		344	There are two class constructors that both create new processes - C<new>
		345	and C<new_exec>. The C<fork> method creates a new process by forking an
		346	existing one and could be considered a third constructor.
		347
		348	Most of the remaining methods deal with preparing the new process, by
		349	loading code, evaluating code and sending data to the new process. They
		350	usually return the process object, so you can chain method calls.
		351
		352	If a process object is destroyed before calling its C<run> method, then
		353	the process simply exits. After C<run> is called, all responsibility is
		354	passed to the specified function.
		355
		356	As long as there is any outstanding work to be done, process objects
		357	resist being destroyed, so there is no reason to store them unless you
		358	need them later - configure and forget works just fine.
281		359
282	=over 4	360	=over 4
283		361
284	=cut	362	=cut
285		363
…		…
292	use AnyEvent;	370	use AnyEvent;
293	use AnyEvent::Util ();	371	use AnyEvent::Util ();
294		372
295	use IO::FDPass;	373	use IO::FDPass;
296		374
297	our $VERSION = 0.5;	375	our $VERSION = 0.6;
298
299	our $PERL; # the path to the perl interpreter, deduces with various forms of magic
300
301	=item my $pool = new AnyEvent::Fork key => value...
302
303	Create a new process pool. The following named parameters are supported:
304		376
305	=over 4	377	=over 4
306		378
307	=back	379	=back
308		380
…		…
311	# the early fork template process	383	# the early fork template process
312	our $EARLY;	384	our $EARLY;
313		385
314	# the empty template process	386	# the empty template process
315	our $TEMPLATE;	387	our $TEMPLATE;
		388
		389	sub QUEUE() { 0 }
		390	sub FH() { 1 }
		391	sub WW() { 2 }
		392	sub PID() { 3 }
		393	sub CB() { 4 }
		394
		395	sub _new {
		396	my ($self, $fh, $pid) = @_;
		397
		398	AnyEvent::Util::fh_nonblocking $fh, 1;
		399
		400	$self = bless [
		401	[], # write queue - strings or fd's
		402	$fh,
		403	undef, # AE watcher
		404	$pid,
		405	], $self;
		406
		407	$self
		408	}
316		409
317	sub _cmd {	410	sub _cmd {
318	my $self = shift;	411	my $self = shift;
319		412
320	# ideally, we would want to use "a (w/a)*" as format string, but perl	413	# ideally, we would want to use "a (w/a)*" as format string, but perl
321	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack	414	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack
322	# it.	415	# it.
323	push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1];	416	push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1];
324		417
325	$self->[3] \|\|= AE::io $self->[1], 1, sub {	418	$self->[WW] \|\|= AE::io $self->[FH], 1, sub {
326	do {	419	do {
327	# send the next "thing" in the queue - either a reference to an fh,	420	# send the next "thing" in the queue - either a reference to an fh,
328	# or a plain string.	421	# or a plain string.
329		422
330	if (ref $self->[2][0]) {	423	if (ref $self->[QUEUE][0]) {
331	# send fh	424	# send fh
332	unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) {	425	unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) {
333	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	426	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
334	undef $self->[3];	427	undef $self->[WW];
335	die "AnyEvent::Fork: file descriptor send failure: $!";	428	die "AnyEvent::Fork: file descriptor send failure: $!";
336	}	429	}
337		430
338	shift @{ $self->[2] };	431	shift @{ $self->[QUEUE] };
339		432
340	} else {	433	} else {
341	# send string	434	# send string
342	my $len = syswrite $self->[1], $self->[2][0];	435	my $len = syswrite $self->[FH], $self->[QUEUE][0];
343		436
344	unless ($len) {	437	unless ($len) {
345	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	438	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
346	undef $self->[3];	439	undef $self->[3];
347	die "AnyEvent::Fork: command write failure: $!";	440	die "AnyEvent::Fork: command write failure: $!";
348	}	441	}
349		442
350	substr $self->[2][0], 0, $len, "";	443	substr $self->[QUEUE][0], 0, $len, "";
351	shift @{ $self->[2] } unless length $self->[2][0];	444	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
352	}	445	}
353	} while @{ $self->[2] };	446	} while @{ $self->[QUEUE] };
354		447
355	# everything written	448	# everything written
356	undef $self->[3];	449	undef $self->[WW];
357		450
358	# invoke run callback, if any	451	# invoke run callback, if any
359	$self->[4]->($self->[1]) if $self->[4];	452	$self->[CB]->($self->[FH]) if $self->[CB];
360	};	453	};
361		454
362	() # make sure we don't leak the watcher	455	() # make sure we don't leak the watcher
363	}
364
365	sub _new {
366	my ($self, $fh, $pid) = @_;
367
368	AnyEvent::Util::fh_nonblocking $fh, 1;
369
370	$self = bless [
371	$pid,
372	$fh,
373	[], # write queue - strings or fd's
374	undef, # AE watcher
375	], $self;
376
377	$self
378	}	456	}
379		457
380	# fork template from current process, used by AnyEvent::Fork::Early/Template	458	# fork template from current process, used by AnyEvent::Fork::Early/Template
381	sub _new_fork {	459	sub _new_fork {
382	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	460	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
387	if ($pid eq 0) {	465	if ($pid eq 0) {
388	require AnyEvent::Fork::Serve;	466	require AnyEvent::Fork::Serve;
389	$AnyEvent::Fork::Serve::OWNER = $parent;	467	$AnyEvent::Fork::Serve::OWNER = $parent;
390	close $fh;	468	close $fh;
391	$0 = "$_[1] of $parent";	469	$0 = "$_[1] of $parent";
392	$SIG{CHLD} = 'IGNORE';
393	AnyEvent::Fork::Serve::serve ($slave);	470	AnyEvent::Fork::Serve::serve ($slave);
394	exit 0;	471	exit 0;
395	} elsif (!$pid) {	472	} elsif (!$pid) {
396	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";	473	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";
397	}	474	}
…		…
404	Create a new "empty" perl interpreter process and returns its process	481	Create a new "empty" perl interpreter process and returns its process
405	object for further manipulation.	482	object for further manipulation.
406		483
407	The new process is forked from a template process that is kept around	484	The new process is forked from a template process that is kept around
408	for this purpose. When it doesn't exist yet, it is created by a call to	485	for this purpose. When it doesn't exist yet, it is created by a call to
409	C<new_exec> and kept around for future calls.	486	C<new_exec> first and then stays around for future calls.
410
411	When the process object is destroyed, it will release the file handle
412	that connects it with the new process. When the new process has not yet
413	called C<run>, then the process will exit. Otherwise, what happens depends
414	entirely on the code that is executed.
415		487
416	=cut	488	=cut
417		489
418	sub new {	490	sub new {
419	my $class = shift;	491	my $class = shift;
…		…
509	}	581	}
510		582
511	=item $pid = $proc->pid	583	=item $pid = $proc->pid
512		584
513	Returns the process id of the process I<iff it is a direct child of the	585	Returns the process id of the process I<iff it is a direct child of the
514	process> running AnyEvent::Fork, and C<undef> otherwise.	586	process running AnyEvent::Fork>, and C<undef> otherwise.
515		587
516	Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and	588	Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and
517	L<AnyEvent::Fork::Template> are direct children, and you are responsible	589	L<AnyEvent::Fork::Template> are direct children, and you are responsible
518	to clean up their zombies when they die.	590	to clean up their zombies when they die.
519		591
520	All other processes are not direct children, and will be cleaned up by	592	All other processes are not direct children, and will be cleaned up by
521	AnyEvent::Fork.	593	AnyEvent::Fork itself.
522		594
523	=cut	595	=cut
524		596
525	sub pid {	597	sub pid {
526	$_[0][0]	598	$_[0][PID]
527	}	599	}
528		600
529	=item $proc = $proc->eval ($perlcode, @args)	601	=item $proc = $proc->eval ($perlcode, @args)
530		602
531	Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to	603	Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to
…		…
537		609
538	The code will usually be executed after this call returns, and there is no	610	The code will usually be executed after this call returns, and there is no
539	way to pass anything back to the calling process. Any evaluation errors	611	way to pass anything back to the calling process. Any evaluation errors
540	will be reported to stderr and cause the process to exit.	612	will be reported to stderr and cause the process to exit.
541		613
542	If you want to execute some code to take over the process (see the	614	If you want to execute some code (that isn't in a module) to take over the
543	"fork+exec" example in the SYNOPSIS), you should compile a function via	615	process, you should compile a function via C<eval> first, and then call
544	C<eval> first, and then call it via C<run>. This also gives you access to	616	it via C<run>. This also gives you access to any arguments passed via the
545	any arguments passed via the C<send_xxx> methods, such as file handles.	617	C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as
		618	a faster fork+exec> example to see it in action.
546		619
547	Returns the process object for easy chaining of method calls.	620	Returns the process object for easy chaining of method calls.
548		621
549	=cut	622	=cut
550		623
…		…
576	=item $proc = $proc->send_fh ($handle, ...)	649	=item $proc = $proc->send_fh ($handle, ...)
577		650
578	Send one or more file handles (I<not> file descriptors) to the process,	651	Send one or more file handles (I<not> file descriptors) to the process,
579	to prepare a call to C<run>.	652	to prepare a call to C<run>.
580		653
581	The process object keeps a reference to the handles until this is done,	654	The process object keeps a reference to the handles until they have
582	so you must not explicitly close the handles. This is most easily	655	been passed over to the process, so you must not explicitly close the
583	accomplished by simply not storing the file handles anywhere after passing	656	handles. This is most easily accomplished by simply not storing the file
584	them to this method.	657	handles anywhere after passing them to this method - when AnyEvent::Fork
		658	is finished using them, perl will automatically close them.
585		659
586	Returns the process object for easy chaining of method calls.	660	Returns the process object for easy chaining of method calls.
587		661
588	Example: pass a file handle to a process, and release it without	662	Example: pass a file handle to a process, and release it without
589	closing. It will be closed automatically when it is no longer used.	663	closing. It will be closed automatically when it is no longer used.
…		…
596	sub send_fh {	670	sub send_fh {
597	my ($self, @fh) = @_;	671	my ($self, @fh) = @_;
598		672
599	for my $fh (@fh) {	673	for my $fh (@fh) {
600	$self->_cmd ("h");	674	$self->_cmd ("h");
601	push @{ $self->[2] }, \$fh;	675	push @{ $self->[QUEUE] }, \$fh;
602	}	676	}
603		677
604	$self	678	$self
605	}	679	}
606		680
607	=item $proc = $proc->send_arg ($string, ...)	681	=item $proc = $proc->send_arg ($string, ...)
608		682
609	Send one or more argument strings to the process, to prepare a call to	683	Send one or more argument strings to the process, to prepare a call to
610	C<run>. The strings can be any octet string.	684	C<run>. The strings can be any octet strings.
611		685
612	The protocol is optimised to pass a moderate number of relatively short	686	The protocol is optimised to pass a moderate number of relatively short
613	strings - while you can pass up to 4GB of data in one go, this is more	687	strings - while you can pass up to 4GB of data in one go, this is more
614	meant to pass some ID information or other startup info, not big chunks of	688	meant to pass some ID information or other startup info, not big chunks of
615	data.	689	data.
…		…
631	Enter the function specified by the function name in C<$func> in the	705	Enter the function specified by the function name in C<$func> in the
632	process. The function is called with the communication socket as first	706	process. The function is called with the communication socket as first
633	argument, followed by all file handles and string arguments sent earlier	707	argument, followed by all file handles and string arguments sent earlier
634	via C<send_fh> and C<send_arg> methods, in the order they were called.	708	via C<send_fh> and C<send_arg> methods, in the order they were called.
635		709
		710	The process object becomes unusable on return from this function - any
		711	further method calls result in undefined behaviour.
		712
636	The function name should be fully qualified, but if it isn't, it will be	713	The function name should be fully qualified, but if it isn't, it will be
637	looked up in the main package.	714	looked up in the C<main> package.
638		715
639	If the called function returns, doesn't exist, or any error occurs, the	716	If the called function returns, doesn't exist, or any error occurs, the
640	process exits.	717	process exits.
641		718
642	Preparing the process is done in the background - when all commands have	719	Preparing the process is done in the background - when all commands have
643	been sent, the callback is invoked with the local communications socket	720	been sent, the callback is invoked with the local communications socket
644	as argument. At this point you can start using the socket in any way you	721	as argument. At this point you can start using the socket in any way you
645	like.	722	like.
646
647	The process object becomes unusable on return from this function - any
648	further method calls result in undefined behaviour.
649		723
650	If the communication socket isn't used, it should be closed on both sides,	724	If the communication socket isn't used, it should be closed on both sides,
651	to save on kernel memory.	725	to save on kernel memory.
652		726
653	The socket is non-blocking in the parent, and blocking in the newly	727	The socket is non-blocking in the parent, and blocking in the newly
…		…
692	=cut	766	=cut
693		767
694	sub run {	768	sub run {
695	my ($self, $func, $cb) = @_;	769	my ($self, $func, $cb) = @_;
696		770
697	$self->[4] = $cb;	771	$self->[CB] = $cb;
698	$self->_cmd (r => $func);	772	$self->_cmd (r => $func);
699	}	773	}
700		774
701	=back	775	=back
702		776
…		…
728	479 vfork+execs per second, using AnyEvent::Fork->new_exec	802	479 vfork+execs per second, using AnyEvent::Fork->new_exec
729		803
730	So how can C<< AnyEvent->new >> be faster than a standard fork, even	804	So how can C<< AnyEvent->new >> be faster than a standard fork, even
731	though it uses the same operations, but adds a lot of overhead?	805	though it uses the same operations, but adds a lot of overhead?
732		806
733	The difference is simply the process size: forking the 6MB process takes	807	The difference is simply the process size: forking the 5MB process takes
734	so much longer than forking the 2.5MB template process that the overhead	808	so much longer than forking the 2.5MB template process that the extra
735	introduced is canceled out.	809	overhead introduced is canceled out.
736		810
737	If the benchmark process grows, the normal fork becomes even slower:	811	If the benchmark process grows, the normal fork becomes even slower:
738		812
739	1340 new processes, manual fork in a 20MB process	813	1340 new processes, manual fork of a 20MB process
740	731 new processes, manual fork in a 200MB process	814	731 new processes, manual fork of a 200MB process
741	235 new processes, manual fork in a 2000MB process	815	235 new processes, manual fork of a 2000MB process
742		816
743	What that means (to me) is that I can use this module without having a	817	What that means (to me) is that I can use this module without having a bad
744	very bad conscience because of the extra overhead required to start new	818	conscience because of the extra overhead required to start new processes.
745	processes.
746		819
747	=head1 TYPICAL PROBLEMS	820	=head1 TYPICAL PROBLEMS
748		821
749	This section lists typical problems that remain. I hope by recognising	822	This section lists typical problems that remain. I hope by recognising
750	them, most can be avoided.	823	them, most can be avoided.
751		824
752	=over 4	825	=over 4
753		826
754	=item "leaked" file descriptors for exec'ed processes	827	=item leaked file descriptors for exec'ed processes
755		828
756	POSIX systems inherit file descriptors by default when exec'ing a new	829	POSIX systems inherit file descriptors by default when exec'ing a new
757	process. While perl itself laudably sets the close-on-exec flags on new	830	process. While perl itself laudably sets the close-on-exec flags on new
758	file handles, most C libraries don't care, and even if all cared, it's	831	file handles, most C libraries don't care, and even if all cared, it's
759	often not possible to set the flag in a race-free manner.	832	often not possible to set the flag in a race-free manner.
…		…
779	libraries or the code that leaks those file descriptors.	852	libraries or the code that leaks those file descriptors.
780		853
781	Fortunately, most of these leaked descriptors do no harm, other than	854	Fortunately, most of these leaked descriptors do no harm, other than
782	sitting on some resources.	855	sitting on some resources.
783		856
784	=item "leaked" file descriptors for fork'ed processes	857	=item leaked file descriptors for fork'ed processes
785		858
786	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,	859	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,
787	which closes file descriptors not marked for being inherited.	860	which closes file descriptors not marked for being inherited.
788		861
789	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer	862	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer
…		…
798		871
799	The solution is to either not load these modules before use'ing	872	The solution is to either not load these modules before use'ing
800	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay	873	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay
801	initialising them, for example, by calling C<init Gtk2> manually.	874	initialising them, for example, by calling C<init Gtk2> manually.
802		875
803	=item exit runs destructors	876	=item exiting calls object destructors
804		877
805	This only applies to users of Lc<AnyEvent::Fork:Early> and	878	This only applies to users of L<AnyEvent::Fork:Early> and
806	L<AnyEvent::Fork::Template>.	879	L<AnyEvent::Fork::Template>, or when initialiasing code creates objects
		880	that reference external resources.
807		881
808	When a process created by AnyEvent::Fork exits, it might do so by calling	882	When a process created by AnyEvent::Fork exits, it might do so by calling
809	exit, or simply letting perl reach the end of the program. At which point	883	exit, or simply letting perl reach the end of the program. At which point
810	Perl runs all destructors.	884	Perl runs all destructors.
811		885
…		…
830	to make it so, mostly due to the bloody broken perl that nobody seems to	904	to make it so, mostly due to the bloody broken perl that nobody seems to
831	care about. The fork emulation is a bad joke - I have yet to see something	905	care about. The fork emulation is a bad joke - I have yet to see something
832	useful that you can do with it without running into memory corruption	906	useful that you can do with it without running into memory corruption
833	issues or other braindamage. Hrrrr.	907	issues or other braindamage. Hrrrr.
834		908
835	Cygwin perl is not supported at the moment, as it should implement fd	909	Cygwin perl is not supported at the moment due to some hilarious
836	passing, but doesn't, and rolling my own is hard, as cygwin doesn't	910	shortcomings of its API - see L<IO::FDPoll> for more details.
837	support enough functionality to do it.
838		911
839	=head1 SEE ALSO	912	=head1 SEE ALSO
840		913
841	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),	914	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),
842	L<AnyEvent::Fork::Template> (to create a process by forking the main	915	L<AnyEvent::Fork::Template> (to create a process by forking the main

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.24 by root, Sat Apr 6 08:32:23 2013 UTC vs. Revision 1.42 by root, Mon Apr 8 05:44:23 2013 UTC

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Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.24 by root, Sat Apr 6 08:32:23 2013 UTC vs.
Revision 1.42 by root, Mon Apr 8 05:44:23 2013 UTC