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

Comparing AnyEvent-Fork-RPC/RPC.pm (file contents):
Revision 1.8 by root, Wed Apr 17 20:24:36 2013 UTC vs.
Revision 1.27 by root, Sun Apr 28 14:34:40 2013 UTC

…		…
2		2
3	AnyEvent::Fork::RPC - simple RPC extension for AnyEvent::Fork	3	AnyEvent::Fork::RPC - simple RPC extension for AnyEvent::Fork
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
		7	use AnyEvent::Fork;
7	use AnyEvent::Fork::RPC;	8	use AnyEvent::Fork::RPC;
8	# use AnyEvent::Fork is not needed
9		9
10	my $rpc = AnyEvent::Fork	10	my $rpc = AnyEvent::Fork
11	->new	11	->new
12	->require ("MyModule")	12	->require ("MyModule")
13	->AnyEvent::Fork::RPC::run (	13	->AnyEvent::Fork::RPC::run (
14	"MyModule::server",	14	"MyModule::server",
15	);	15	);
16		16
		17	use AnyEvent;
		18
17	my $cv = AE::cv;	19	my $cv = AE::cv;
18		20
19	$rpc->(1, 2, 3, sub {	21	$rpc->(1, 2, 3, sub {
20	print "MyModule::server returned @_\n";	22	print "MyModule::server returned @_\n";
21	$cv->send;	23	$cv->send;
…		…
24	$cv->recv;	26	$cv->recv;
25		27
26	=head1 DESCRIPTION	28	=head1 DESCRIPTION
27		29
28	This module implements a simple RPC protocol and backend for processes	30	This module implements a simple RPC protocol and backend for processes
29	created via L<AnyEvent::Fork>, allowing you to call a function in the	31	created via L<AnyEvent::Fork> (or L<AnyEvent::Fork::Remote>), allowing you
30	child process and receive its return values (up to 4GB serialised).	32	to call a function in the child process and receive its return values (up
		33	to 4GB serialised).
31		34
32	It implements two different backends: a synchronous one that works like a	35	It implements two different backends: a synchronous one that works like a
33	normal function call, and an asynchronous one that can run multiple jobs	36	normal function call, and an asynchronous one that can run multiple jobs
34	concurrently in the child, using AnyEvent.	37	concurrently in the child, using AnyEvent.
35		38
36	It also implements an asynchronous event mechanism from the child to the	39	It also implements an asynchronous event mechanism from the child to the
37	parent, that could be used for progress indications or other information.	40	parent, that could be used for progress indications or other information.
38		41
39	Loading this module also always loads L<AnyEvent::Fork>, so you can make a
40	separate C<use AnyEvent::Fork> if you wish, but you don't have to.
41
42	=head1 EXAMPLES	42	=head1 EXAMPLES
43		43
44	=head2 Synchronous Backend	44	=head2 Example 1: Synchronous Backend
45		45
46	Here is a simple example that implements a backend that executes C<unlink>	46	Here is a simple example that implements a backend that executes C<unlink>
47	and C<rmdir> calls, and reports their status back. It also reports the	47	and C<rmdir> calls, and reports their status back. It also reports the
48	number of requests it has processed every three requests, which is clearly	48	number of requests it has processed every three requests, which is clearly
49	silly, but illustrates the use of events.	49	silly, but illustrates the use of events.
…		…
137		137
138	And as a final remark, there is a fine module on CPAN that can	138	And as a final remark, there is a fine module on CPAN that can
139	asynchronously C<rmdir> and C<unlink> and a lot more, and more efficiently	139	asynchronously C<rmdir> and C<unlink> and a lot more, and more efficiently
140	than this example, namely L<IO::AIO>.	140	than this example, namely L<IO::AIO>.
141		141
		142	=head3 Example 1a: the same with the asynchronous backend
		143
		144	This example only shows what needs to be changed to use the async backend
		145	instead. Doing this is not very useful, the purpose of this example is
		146	to show the minimum amount of change that is required to go from the
		147	synchronous to the asynchronous backend.
		148
		149	To use the async backend in the previous example, you need to add the
		150	C<async> parameter to the C<AnyEvent::Fork::RPC::run> call:
		151
		152	->AnyEvent::Fork::RPC::run ("MyWorker::run",
		153	async => 1,
		154	...
		155
		156	And since the function call protocol is now changed, you need to adopt
		157	C<MyWorker::run> to the async API.
		158
		159	First, you need to accept the extra initial C<$done> callback:
		160
		161	sub run {
		162	my ($done, $cmd, $path) = @_;
		163
		164	And since a response is now generated when C<$done> is called, as opposed
		165	to when the function returns, we need to call the C<$done> function with
		166	the status:
		167
		168	$done->($status or (0, "$!"));
		169
		170	A few remarks are in order. First, it's quite pointless to use the async
		171	backend for this example - but it I<is> possible. Second, you can call
		172	C<$done> before or after returning from the function. Third, having both
		173	returned from the function and having called the C<$done> callback, the
		174	child process may exit at any time, so you should call C<$done> only when
		175	you really I<are> done.
		176
		177	=head2 Example 2: Asynchronous Backend
		178
		179	This example implements multiple count-downs in the child, using
		180	L<AnyEvent> timers. While this is a bit silly (one could use timers in te
		181	parent just as well), it illustrates the ability to use AnyEvent in the
		182	child and the fact that responses can arrive in a different order then the
		183	requests.
		184
		185	It also shows how to embed the actual child code into a C<__DATA__>
		186	section, so it doesn't need any external files at all.
		187
		188	And when your parent process is often busy, and you have stricter timing
		189	requirements, then running timers in a child process suddenly doesn't look
		190	so silly anymore.
		191
		192	Without further ado, here is the code:
		193
		194	use AnyEvent;
		195	use AnyEvent::Fork;
		196	use AnyEvent::Fork::RPC;
		197
		198	my $done = AE::cv;
		199
		200	my $rpc = AnyEvent::Fork
		201	->new
		202	->require ("AnyEvent::Fork::RPC::Async")
		203	->eval (do { local $/; <DATA> })
		204	->AnyEvent::Fork::RPC::run ("run",
		205	async => 1,
		206	on_error => sub { warn "FATAL: $_[0]"; exit 1 },
		207	on_event => sub { print $_[0] },
		208	on_destroy => $done,
		209	);
		210
		211	for my $count (3, 2, 1) {
		212	$rpc->($count, sub {
		213	warn "job $count finished\n";
		214	});
		215	}
		216
		217	undef $rpc;
		218
		219	$done->recv;
		220
		221	__DATA__
		222
		223	# this ends up in main, as we don't use a package declaration
		224
		225	use AnyEvent;
		226
		227	sub run {
		228	my ($done, $count) = @_;
		229
		230	my $n;
		231
		232	AnyEvent::Fork::RPC::event "starting to count up to $count\n";
		233
		234	my $w; $w = AE::timer 1, 1, sub {
		235	++$n;
		236
		237	AnyEvent::Fork::RPC::event "count $n of $count\n";
		238
		239	if ($n == $count) {
		240	undef $w;
		241	$done->();
		242	}
		243	};
		244	}
		245
		246	The parent part (the one before the C<__DATA__> section) isn't very
		247	different from the earlier examples. It sets async mode, preloads
		248	the backend module (so the C<AnyEvent::Fork::RPC::event> function is
		249	declared), uses a slightly different C<on_event> handler (which we use
		250	simply for logging purposes) and then, instead of loading a module with
		251	the actual worker code, it C<eval>'s the code from the data section in the
		252	child process.
		253
		254	It then starts three countdowns, from 3 to 1 seconds downwards, destroys
		255	the rpc object so the example finishes eventually, and then just waits for
		256	the stuff to trickle in.
		257
		258	The worker code uses the event function to log some progress messages, but
		259	mostly just creates a recurring one-second timer.
		260
		261	The timer callback increments a counter, logs a message, and eventually,
		262	when the count has been reached, calls the finish callback.
		263
		264	On my system, this results in the following output. Since all timers fire
		265	at roughly the same time, the actual order isn't guaranteed, but the order
		266	shown is very likely what you would get, too.
		267
		268	starting to count up to 3
		269	starting to count up to 2
		270	starting to count up to 1
		271	count 1 of 3
		272	count 1 of 2
		273	count 1 of 1
		274	job 1 finished
		275	count 2 of 2
		276	job 2 finished
		277	count 2 of 3
		278	count 3 of 3
		279	job 3 finished
		280
		281	While the overall ordering isn't guaranteed, the async backend still
		282	guarantees that events and responses are delivered to the parent process
		283	in the exact same ordering as they were generated in the child process.
		284
		285	And unless your system is I<very> busy, it should clearly show that the
		286	job started last will finish first, as it has the lowest count.
		287
		288	This concludes the async example. Since L<AnyEvent::Fork> does not
		289	actually fork, you are free to use about any module in the child, not just
		290	L<AnyEvent>, but also L<IO::AIO>, or L<Tk> for example.
		291
142	=head1 PARENT PROCESS USAGE	292	=head1 PARENT PROCESS USAGE
143		293
144	This module exports nothing, and only implements a single function:	294	This module exports nothing, and only implements a single function:
145		295
146	=over 4	296	=over 4
…		…
153		303
154	use Errno ();	304	use Errno ();
155	use Guard ();	305	use Guard ();
156		306
157	use AnyEvent;	307	use AnyEvent;
158	use AnyEvent::Fork; # we don't actually depend on it, this is for convenience
159		308
160	our $VERSION = 0.1;	309	our $VERSION = 1.1;
161		310
162	=item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...]	311	=item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...]
163		312
164	The traditional way to call it. But it is way cooler to call it in the	313	The traditional way to call it. But it is way cooler to call it in the
165	following way:	314	following way:
…		…
224		373
225	The default server used in the child does all I/O blockingly, and only	374	The default server used in the child does all I/O blockingly, and only
226	allows a single RPC call to execute concurrently.	375	allows a single RPC call to execute concurrently.
227		376
228	Setting C<async> to a true value switches to another implementation that	377	Setting C<async> to a true value switches to another implementation that
229	uses L<AnyEvent> in the child and allows multiple concurrent RPC calls.	378	uses L<AnyEvent> in the child and allows multiple concurrent RPC calls (it
		379	does not support recursion in the event loop however, blocking condvar
		380	calls will fail).
230		381
231	The actual API in the child is documented in the section that describes	382	The actual API in the child is documented in the section that describes
232	the calling semantics of the returned C<$rpc> function.	383	the calling semantics of the returned C<$rpc> function.
233		384
234	If you want to pre-load the actual back-end modules to enable memory	385	If you want to pre-load the actual back-end modules to enable memory
…		…
236	synchronous, and C<AnyEvent::Fork::RPC::Async> for asynchronous mode.	387	synchronous, and C<AnyEvent::Fork::RPC::Async> for asynchronous mode.
237		388
238	If you use a template process and want to fork both sync and async	389	If you use a template process and want to fork both sync and async
239	children, then it is permissible to load both modules.	390	children, then it is permissible to load both modules.
240		391
241	=item serialiser => $string (default: '(sub { pack "(w/a)", @_ }, sub { unpack "(w/a)", shift })')	392	=item serialiser => $string (default: $AnyEvent::Fork::RPC::STRING_SERIALISER)
242		393
243	All arguments, result data and event data have to be serialised to be	394	All arguments, result data and event data have to be serialised to be
244	transferred between the processes. For this, they have to be frozen and	395	transferred between the processes. For this, they have to be frozen and
245	thawed in both parent and child processes.	396	thawed in both parent and child processes.
246		397
247	By default, only octet strings can be passed between the processes, which	398	By default, only octet strings can be passed between the processes, which
248	is reasonably fast and efficient.	399	is reasonably fast and efficient and requires no extra modules.
249		400
250	For more complicated use cases, you can provide your own freeze and thaw	401	For more complicated use cases, you can provide your own freeze and thaw
251	functions, by specifying a string with perl source code. It's supposed to	402	functions, by specifying a string with perl source code. It's supposed to
252	return two code references when evaluated: the first receives a list of	403	return two code references when evaluated: the first receives a list of
253	perl values and must return an octet string. The second receives the octet	404	perl values and must return an octet string. The second receives the octet
…		…
255		406
256	If you need an external module for serialisation, then you can either	407	If you need an external module for serialisation, then you can either
257	pre-load it into your L<AnyEvent::Fork> process, or you can add a C<use>	408	pre-load it into your L<AnyEvent::Fork> process, or you can add a C<use>
258	or C<require> statement into the serialiser string. Or both.	409	or C<require> statement into the serialiser string. Or both.
259		410
		411	Here are some examples - some of them are also available as global
		412	variables that make them easier to use.
		413
		414	=over 4
		415
		416	=item octet strings - C<$AnyEvent::Fork::RPC::STRING_SERIALISER>
		417
		418	This serialiser concatenates length-prefixes octet strings, and is the
		419	default.
		420
		421	Implementation:
		422
		423	(
		424	sub { pack "(w/a)", @_ },
		425	sub { unpack "(w/a)", shift }
		426	)
		427
		428	=item json - C<$AnyEvent::Fork::RPC::JSON_SERIALISER>
		429
		430	This serialiser creates JSON arrays - you have to make sure the L<JSON>
		431	module is installed for this serialiser to work. It can be beneficial for
		432	sharing when you preload the L<JSON> module in a template process.
		433
		434	L<JSON> (with L<JSON::XS> installed) is slower than the octet string
		435	serialiser, but usually much faster than L<Storable>, unless big chunks of
		436	binary data need to be transferred.
		437
		438	Implementation:
		439
		440	use JSON ();
		441	(
		442	sub { JSON::encode_json \@_ },
		443	sub { @{ JSON::decode_json shift } }
		444	)
		445
		446	=item storable - C<$AnyEvent::Fork::RPC::STORABLE_SERIALISER>
		447
		448	This serialiser uses L<Storable>, which means it has high chance of
		449	serialising just about anything you throw at it, at the cost of having
		450	very high overhead per operation. It also comes with perl.
		451
		452	Implementation:
		453
		454	use Storable ();
		455	(
		456	sub { Storable::freeze \@_ },
		457	sub { @{ Storable::thaw shift } }
		458	)
		459
260	=back	460	=back
261		461
		462	=back
		463
262	See the examples section earlier in this document for some actual examples.	464	See the examples section earlier in this document for some actual
		465	examples.
263		466
264	=cut	467	=cut
265		468
266	our $STRING_SERIALISER = '(sub { pack "(w/a)", @_ }, sub { unpack "(w/a)", shift })';	469	our $STRING_SERIALISER = '(sub { pack "(w/a)", @_ }, sub { unpack "(w/a)", shift })';
		470	our $JSON_SERIALISER = 'use JSON (); (sub { JSON::encode_json \@_ }, sub { @{ JSON::decode_json shift } })';
		471	our $STORABLE_SERIALISER = 'use Storable (); (sub { Storable::freeze \@_ }, sub { @{ Storable::thaw shift } })';
267		472
268	sub run {	473	sub run {
269	my ($self, $function, %arg) = @_;	474	my ($self, $function, %arg) = @_;
270		475
271	my $serialiser = delete $arg{serialiser} \|\| $STRING_SERIALISER;	476	my $serialiser = delete $arg{serialiser} \|\| $STRING_SERIALISER;
…		…
281	# default for on_event is to raise an error	486	# default for on_event is to raise an error
282	$on_event \|\|= sub { $on_error->("event received, but no on_event handler") };	487	$on_event \|\|= sub { $on_error->("event received, but no on_event handler") };
283		488
284	my ($f, $t) = eval $serialiser; die $@ if $@;	489	my ($f, $t) = eval $serialiser; die $@ if $@;
285		490
286	my (@rcb, $fh, $shutdown, $wbuf, $ww, $rw);	491	my (@rcb, %rcb, $fh, $shutdown, $wbuf, $ww);
287	my ($rlen, $rbuf) = 512 - 16;	492	my ($rlen, $rbuf, $rw) = 512 - 16;
288		493
289	my $wcb = sub {	494	my $wcb = sub {
290	my $len = syswrite $fh, $wbuf;	495	my $len = syswrite $fh, $wbuf;
291		496
292	if (!defined $len) {	497	unless (defined $len) {
293	if ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) {	498	if ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) {
294	undef $rw; undef $ww; # it ends here	499	undef $rw; undef $ww; # it ends here
295	$on_error->("$!");	500	$on_error->("$!");
296	}	501	}
297	}	502	}
…		…
308		513
309	$self->require ($module)	514	$self->require ($module)
310	->send_arg ($function, $arg{init}, $serialiser)	515	->send_arg ($function, $arg{init}, $serialiser)
311	->run ("$module\::run", sub {	516	->run ("$module\::run", sub {
312	$fh = shift;	517	$fh = shift;
		518
		519	my ($id, $len);
313	$rw = AE::io $fh, 0, sub {	520	$rw = AE::io $fh, 0, sub {
314	$rlen = $rlen * 2 + 16 if $rlen - 128 < length $rbuf;	521	$rlen = $rlen * 2 + 16 if $rlen - 128 < length $rbuf;
315	my $len = sysread $fh, $rbuf, $rlen - length $rbuf, length $rbuf;	522	$len = sysread $fh, $rbuf, $rlen - length $rbuf, length $rbuf;
316		523
317	if ($len) {	524	if ($len) {
318	while (4 <= length $rbuf) {	525	while (8 <= length $rbuf) {
319	$len = unpack "L", $rbuf;	526	($id, $len) = unpack "NN", $rbuf;
320	4 + $len <= length $rbuf	527	8 + $len <= length $rbuf
321	or last;	528	or last;
322		529
323	my @r = $t->(substr $rbuf, 4, $len);	530	my @r = $t->(substr $rbuf, 8, $len);
324	substr $rbuf, 0, $len + 4, "";	531	substr $rbuf, 0, 8 + $len, "";
		532
		533	if ($id) {
		534	if (@rcb) {
		535	(shift @rcb)->(@r);
		536	} elsif (my $cb = delete $rcb{$id}) {
		537	$cb->(@r);
		538	} else {
		539	undef $rw; undef $ww;
		540	$on_error->("unexpected data from child");
325		541	}
326	if (pop @r) {	542	} else {
327	$on_event->(@r);	543	$on_event->(@r);
328	} elsif (@rcb) {
329	(shift @rcb)->(@r);
330	} else {
331	undef $rw; undef $ww;
332	$on_error->("unexpected data from child");
333	}	544	}
334	}	545	}
335	} elsif (defined $len) {	546	} elsif (defined $len) {
336	undef $rw; undef $ww; # it ends here	547	undef $rw; undef $ww; # it ends here
337		548
338	if (@rcb) {	549	if (@rcb \|\| %rcb) {
339	$on_error->("unexpected eof");	550	$on_error->("unexpected eof");
340	} else {	551	} else {
341	$on_destroy->();	552	$on_destroy->()
		553	if $on_destroy;
342	}	554	}
343	} elsif ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) {	555	} elsif ($! != Errno::EAGAIN && $! != Errno::EWOULDBLOCK) {
344	undef $rw; undef $ww; # it ends here	556	undef $rw; undef $ww; # it ends here
345	$on_error->("read: $!");	557	$on_error->("read: $!");
346	}	558	}
…		…
349	$ww \|\|= AE::io $fh, 1, $wcb;	561	$ww \|\|= AE::io $fh, 1, $wcb;
350	});	562	});
351		563
352	my $guard = Guard::guard {	564	my $guard = Guard::guard {
353	$shutdown = 1;	565	$shutdown = 1;
354	$ww \|\|= $fh && AE::io $fh, 1, $wcb;	566
		567	shutdown $fh, 1 if $fh && !$ww;
355	};	568	};
356		569
		570	my $id;
		571
		572	$arg{async}
357	sub {	573	? sub {
358	push @rcb, pop;	574	$id = ($id == 0xffffffff ? 0 : $id) + 1;
		575	$id = ($id == 0xffffffff ? 0 : $id) + 1 while exists $rcb{$id}; # rarely loops
359		576
		577	$rcb{$id} = pop;
		578
360	$guard; # keep it alive	579	$guard if 0; # keep it alive
361		580
362	$wbuf .= pack "L/a*", &$f;	581	$wbuf .= pack "NN/a*", $id, &$f;
363	$ww \|\|= $fh && AE::io $fh, 1, $wcb;	582	$ww \|\|= $fh && AE::io $fh, 1, $wcb;
364	}	583	}
		584	: sub {
		585	push @rcb, pop;
		586
		587	$guard; # keep it alive
		588
		589	$wbuf .= pack "N/a*", &$f;
		590	$ww \|\|= $fh && AE::io $fh, 1, $wcb;
		591	}
365	}	592	}
366		593
367	=item $rpc->(..., $cb->(...))	594	=item $rpc->(..., $cb->(...))
368		595
369	The RPC object returned by C<AnyEvent::Fork::RPC::run> is actually a code	596	The RPC object returned by C<AnyEvent::Fork::RPC::run> is actually a code
…		…
409	See the examples section earlier in this document for some actual	636	See the examples section earlier in this document for some actual
410	examples.	637	examples.
411		638
412	=back	639	=back
413		640
		641	=head1 ADVANCED TOPICS
		642
		643	=head2 Choosing a backend
		644
		645	So how do you decide which backend to use? Well, that's your problem to
		646	solve, but here are some thoughts on the matter:
		647
		648	=over 4
		649
		650	=item Synchronous
		651
		652	The synchronous backend does not rely on any external modules (well,
		653	except L<common::sense>, which works around a bug in how perl's warning
		654	system works). This keeps the process very small, for example, on my
		655	system, an empty perl interpreter uses 1492kB RSS, which becomes 2020kB
		656	after C<use warnings; use strict> (for people who grew up with C64s around
		657	them this is probably shocking every single time they see it). The worker
		658	process in the first example in this document uses 1792kB.
		659
		660	Since the calls are done synchronously, slow jobs will keep newer jobs
		661	from executing.
		662
		663	The synchronous backend also has no overhead due to running an event loop
		664	- reading requests is therefore very efficient, while writing responses is
		665	less so, as every response results in a write syscall.
		666
		667	If the parent process is busy and a bit slow reading responses, the child
		668	waits instead of processing further requests. This also limits the amount
		669	of memory needed for buffering, as never more than one response has to be
		670	buffered.
		671
		672	The API in the child is simple - you just have to define a function that
		673	does something and returns something.
		674
		675	It's hard to use modules or code that relies on an event loop, as the
		676	child cannot execute anything while it waits for more input.
		677
		678	=item Asynchronous
		679
		680	The asynchronous backend relies on L<AnyEvent>, which tries to be small,
		681	but still comes at a price: On my system, the worker from example 1a uses
		682	3420kB RSS (for L<AnyEvent>, which loads L<EV>, which needs L<XSLoader>
		683	which in turn loads a lot of other modules such as L<warnings>, L<strict>,
		684	L<vars>, L<Exporter>...).
		685
		686	It batches requests and responses reasonably efficiently, doing only as
		687	few reads and writes as needed, but needs to poll for events via the event
		688	loop.
		689
		690	Responses are queued when the parent process is busy. This means the child
		691	can continue to execute any queued requests. It also means that a child
		692	might queue a lot of responses in memory when it generates them and the
		693	parent process is slow accepting them.
		694
		695	The API is not a straightforward RPC pattern - you have to call a
		696	"done" callback to pass return values and signal completion. Also, more
		697	importantly, the API starts jobs as fast as possible - when 1000 jobs
		698	are queued and the jobs are slow, they will all run concurrently. The
		699	child must implement some queueing/limiting mechanism if this causes
		700	problems. Alternatively, the parent could limit the amount of rpc calls
		701	that are outstanding.
		702
		703	Blocking use of condvars is not supported.
		704
		705	Using event-based modules such as L<IO::AIO>, L<Gtk2>, L<Tk> and so on is
		706	easy.
		707
		708	=back
		709
		710	=head2 Passing file descriptors
		711
		712	Unlike L<AnyEvent::Fork>, this module has no in-built file handle or file
		713	descriptor passing abilities.
		714
		715	The reason is that passing file descriptors is extraordinary tricky
		716	business, and conflicts with efficient batching of messages.
		717
		718	There still is a method you can use: Create a
		719	C<AnyEvent::Util::portable_socketpair> and C<send_fh> one half of it to
		720	the process before you pass control to C<AnyEvent::Fork::RPC::run>.
		721
		722	Whenever you want to pass a file descriptor, send an rpc request to the
		723	child process (so it expects the descriptor), then send it over the other
		724	half of the socketpair. The child should fetch the descriptor from the
		725	half it has passed earlier.
		726
		727	Here is some (untested) pseudocode to that effect:
		728
		729	use AnyEvent::Util;
		730	use AnyEvent::Fork;
		731	use AnyEvent::Fork::RPC;
		732	use IO::FDPass;
		733
		734	my ($s1, $s2) = AnyEvent::Util::portable_socketpair;
		735
		736	my $rpc = AnyEvent::Fork
		737	->new
		738	->send_fh ($s2)
		739	->require ("MyWorker")
		740	->AnyEvent::Fork::RPC::run ("MyWorker::run"
		741	init => "MyWorker::init",
		742	);
		743
		744	undef $s2; # no need to keep it around
		745
		746	# pass an fd
		747	$rpc->("i'll send some fd now, please expect it!", my $cv = AE::cv);
		748
		749	IO::FDPass fileno $s1, fileno $handle_to_pass;
		750
		751	$cv->recv;
		752
		753	The MyWorker module could look like this:
		754
		755	package MyWorker;
		756
		757	use IO::FDPass;
		758
		759	my $s2;
		760
		761	sub init {
		762	$s2 = $_[0];
		763	}
		764
		765	sub run {
		766	if ($_[0] eq "i'll send some fd now, please expect it!") {
		767	my $fd = IO::FDPass::recv fileno $s2;
		768	...
		769	}
		770	}
		771
		772	Of course, this might be blocking if you pass a lot of file descriptors,
		773	so you might want to look into L<AnyEvent::FDpasser> which can handle the
		774	gory details.
		775
		776	=head1 EXCEPTIONS
		777
		778	There are no provisions whatsoever for catching exceptions at this time -
		779	in the child, exeptions might kill the process, causing calls to be lost
		780	and the parent encountering a fatal error. In the parent, exceptions in
		781	the result callback will not be caught and cause undefined behaviour.
		782
414	=head1 SEE ALSO	783	=head1 SEE ALSO
415		784
416	L<AnyEvent::Fork> (to create the processes in the first place),	785	L<AnyEvent::Fork>, to create the processes in the first place.
		786
		787	L<AnyEvent::Fork::Remote>, likewise, but helpful for remote processes.
		788
417	L<AnyEvent::Fork::Pool> (to manage whole pools of processes).	789	L<AnyEvent::Fork::Pool>, to manage whole pools of processes.
418		790
419	=head1 AUTHOR AND CONTACT INFORMATION	791	=head1 AUTHOR AND CONTACT INFORMATION
420		792
421	Marc Lehmann <schmorp@schmorp.de>	793	Marc Lehmann <schmorp@schmorp.de>
422	http://software.schmorp.de/pkg/AnyEvent-Fork-RPC	794	http://software.schmorp.de/pkg/AnyEvent-Fork-RPC

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Comparing AnyEvent-Fork-RPC/RPC.pm (file contents): Revision 1.8 by root, Wed Apr 17 20:24:36 2013 UTC vs. Revision 1.27 by root, Sun Apr 28 14:34:40 2013 UTC

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Comparing AnyEvent-Fork-RPC/RPC.pm (file contents):
Revision 1.8 by root, Wed Apr 17 20:24:36 2013 UTC vs.
Revision 1.27 by root, Sun Apr 28 14:34:40 2013 UTC