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

Comparing AnyEvent-Fork-RPC/RPC.pm (file contents):
Revision 1.28 by root, Sun Apr 28 15:48:31 2013 UTC vs.
Revision 1.46 by root, Sun Sep 15 20:18:14 2019 UTC

…		…
26	$cv->recv;	26	$cv->recv;
27		27
28	=head1 DESCRIPTION	28	=head1 DESCRIPTION
29		29
30	This module implements a simple RPC protocol and backend for processes	30	This module implements a simple RPC protocol and backend for processes
31	created via L<AnyEvent::Fork> (or L<AnyEvent::Fork::Remote>), allowing you	31	created via L<AnyEvent::Fork> or L<AnyEvent::Fork::Remote>, allowing you
32	to call a function in the child process and receive its return values (up	32	to call a function in the child process and receive its return values (up
33	to 4GB serialised).	33	to 4GB serialised).
34		34
35	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
36	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
…		…
58		58
59	my $rpc = AnyEvent::Fork	59	my $rpc = AnyEvent::Fork
60	->new	60	->new
61	->require ("MyWorker")	61	->require ("MyWorker")
62	->AnyEvent::Fork::RPC::run ("MyWorker::run",	62	->AnyEvent::Fork::RPC::run ("MyWorker::run",
63	on_error => sub { warn "FATAL: $_[0]"; exit 1 },	63	on_error => sub { warn "ERROR: $_[0]"; exit 1 },
64	on_event => sub { warn "$_[0] requests handled\n" },	64	on_event => sub { warn "$_[0] requests handled\n" },
65	on_destroy => $done,	65	on_destroy => $done,
66	);	66	);
67		67
68	for my $id (1..6) {	68	for my $id (1..6) {
…		…
175	you really I<are> done.	175	you really I<are> done.
176		176
177	=head2 Example 2: Asynchronous Backend	177	=head2 Example 2: Asynchronous Backend
178		178
179	This example implements multiple count-downs in the child, using	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	180	L<AnyEvent> timers. While this is a bit silly (one could use timers in the
181	parent just as well), it illustrates the ability to use AnyEvent in the	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	182	child and the fact that responses can arrive in a different order then the
183	requests.	183	requests.
184		184
185	It also shows how to embed the actual child code into a C<__DATA__>	185	It also shows how to embed the actual child code into a C<__DATA__>
…		…
201	->new	201	->new
202	->require ("AnyEvent::Fork::RPC::Async")	202	->require ("AnyEvent::Fork::RPC::Async")
203	->eval (do { local $/; <DATA> })	203	->eval (do { local $/; <DATA> })
204	->AnyEvent::Fork::RPC::run ("run",	204	->AnyEvent::Fork::RPC::run ("run",
205	async => 1,	205	async => 1,
206	on_error => sub { warn "FATAL: $_[0]"; exit 1 },	206	on_error => sub { warn "ERROR: $_[0]"; exit 1 },
207	on_event => sub { print $_[0] },	207	on_event => sub { print $_[0] },
208	on_destroy => $done,	208	on_destroy => $done,
209	);	209	);
210		210
211	for my $count (3, 2, 1) {	211	for my $count (3, 2, 1) {
…		…
287		287
288	This concludes the async example. Since L<AnyEvent::Fork> does not	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	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.	290	L<AnyEvent>, but also L<IO::AIO>, or L<Tk> for example.
291		291
		292	=head2 Example 3: Asynchronous backend with Coro
		293
		294	With L<Coro> you can create a nice asynchronous backend implementation by
		295	defining an rpc server function that creates a new Coro thread for every
		296	request that calls a function "normally", i.e. the parameters from the
		297	parent process are passed to it, and any return values are returned to the
		298	parent process, e.g.:
		299
		300	package My::Arith;
		301
		302	sub add {
		303	return $_[0] + $_[1];
		304	}
		305
		306	sub mul {
		307	return $_[0] * $_[1];
		308	}
		309
		310	sub run {
		311	my ($done, $func, @arg) = @_;
		312
		313	Coro::async_pool {
		314	$done->($func->(@arg));
		315	};
		316	}
		317
		318	The C<run> function creates a new thread for every invocation, using the
		319	first argument as function name, and calls the C<$done> callback on it's
		320	return values. This makes it quite natural to define the C<add> and C<mul>
		321	functions to add or multiply two numbers and return the result.
		322
		323	Since this is the asynchronous backend, it's quite possible to define RPC
		324	function that do I/O or wait for external events - their execution will
		325	overlap as needed.
		326
		327	The above could be used like this:
		328
		329	my $rpc = AnyEvent::Fork
		330	->new
		331	->require ("MyWorker")
		332	->AnyEvent::Fork::RPC::run ("My::Arith::run",
		333	on_error => ..., on_event => ..., on_destroy => ...,
		334	);
		335
		336	$rpc->(add => 1, 3, Coro::rouse_cb); say Coro::rouse_wait;
		337	$rpc->(mul => 3, 2, Coro::rouse_cb); say Coro::rouse_wait;
		338
		339	The C<say>'s will print C<4> and C<6>.
		340
		341	=head2 Example 4: Forward AnyEvent::Log messages using C<on_event>
		342
		343	This partial example shows how to use the C<event> function to forward
		344	L<AnyEvent::Log> messages to the parent.
		345
		346	For this, the parent needs to provide a suitable C<on_event>:
		347
		348	->AnyEvent::Fork::RPC::run (
		349	on_event => sub {
		350	if ($_[0] eq "ae_log") {
		351	my (undef, $level, $message) = @_;
		352	AE::log $level, $message;
		353	} else {
		354	# other event types
		355	}
		356	},
		357	)
		358
		359	In the child, as early as possible, the following code should reconfigure
		360	L<AnyEvent::Log> to log via C<AnyEvent::Fork::RPC::event>:
		361
		362	$AnyEvent::Log::LOG->log_cb (sub {
		363	my ($timestamp, $orig_ctx, $level, $message) = @{+shift};
		364
		365	if (defined &AnyEvent::Fork::RPC::event) {
		366	AnyEvent::Fork::RPC::event (ae_log => $level, $message);
		367	} else {
		368	warn "[$$ before init] $message\n";
		369	}
		370	});
		371
		372	There is an important twist - the C<AnyEvent::Fork::RPC::event> function
		373	is only defined when the child is fully initialised. If you redirect the
		374	log messages in your C<init> function for example, then the C<event>
		375	function might not yet be available. This is why the log callback checks
		376	whether the function is there using C<defined>, and only then uses it to
		377	log the message.
		378
292	=head1 PARENT PROCESS USAGE	379	=head1 PARENT PROCESS USAGE
293		380
294	This module exports nothing, and only implements a single function:	381	This module exports nothing, and only implements a single function:
295		382
296	=over 4	383	=over 4
…		…
304	use Errno ();	391	use Errno ();
305	use Guard ();	392	use Guard ();
306		393
307	use AnyEvent;	394	use AnyEvent;
308		395
309	our $VERSION = 1.1;	396	our $VERSION = '2.0';
310		397
311	=item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...]	398	=item my $rpc = AnyEvent::Fork::RPC::run $fork, $function, [key => value...]
312		399
313	The traditional way to call it. But it is way cooler to call it in the	400	The traditional way to call it. But it is way cooler to call it in the
314	following way:	401	following way:
…		…
334	Called on (fatal) errors, with a descriptive (hopefully) message. If	421	Called on (fatal) errors, with a descriptive (hopefully) message. If
335	this callback is not provided, but C<on_event> is, then the C<on_event>	422	this callback is not provided, but C<on_event> is, then the C<on_event>
336	callback is called with the first argument being the string C<error>,	423	callback is called with the first argument being the string C<error>,
337	followed by the error message.	424	followed by the error message.
338		425
339	If neither handler is provided it prints the error to STDERR and will	426	If neither handler is provided, then the error is reported with loglevel
340	start failing badly.	427	C<error> via C<AE::log>.
341		428
342	=item on_event => $cb->(...)	429	=item on_event => $cb->(...)
343		430
344	Called for every call to the C<AnyEvent::Fork::RPC::event> function in the	431	Called for every call to the C<AnyEvent::Fork::RPC::event> function in the
345	child, with the arguments of that function passed to the callback.	432	child, with the arguments of that function passed to the callback.
…		…
352	been successfully handled. This is useful when you queue some requests and	439	been successfully handled. This is useful when you queue some requests and
353	want the child to go away after it has handled them. The problem is that	440	want the child to go away after it has handled them. The problem is that
354	the parent must not exit either until all requests have been handled, and	441	the parent must not exit either until all requests have been handled, and
355	this can be accomplished by waiting for this callback.	442	this can be accomplished by waiting for this callback.
356		443
357	=item init => $function (default none)	444	=item init => $function (default: none)
358		445
359	When specified (by name), this function is called in the child as the very	446	When specified (by name), this function is called in the child as the very
360	first thing when taking over the process, with all the arguments normally	447	first thing when taking over the process, with all the arguments normally
361	passed to the C<AnyEvent::Fork::run> function, except the communications	448	passed to the C<AnyEvent::Fork::run> function, except the communications
362	socket.	449	socket.
…		…
367	It is called very early - before the serialisers are created or the	454	It is called very early - before the serialisers are created or the
368	C<$function> name is resolved into a function reference, so it could be	455	C<$function> name is resolved into a function reference, so it could be
369	used to load any modules that provide the serialiser or function. It can	456	used to load any modules that provide the serialiser or function. It can
370	not, however, create events.	457	not, however, create events.
371		458
		459	=item done => $function (default: C<CORE::exit>)
		460
		461	The function to call when the asynchronous backend detects an end of file
		462	condition when reading from the communications socket I<and> there are no
		463	outstanding requests. It is ignored by the synchronous backend.
		464
		465	By overriding this you can prolong the life of a RPC process after e.g.
		466	the parent has exited by running the event loop in the provided function
		467	(or simply calling it, for example, when your child process uses L<EV> you
		468	could provide L<EV::run> as C<done> function).
		469
		470	Of course, in that case you are responsible for exiting at the appropriate
		471	time and not returning from
		472
372	=item async => $boolean (default: 0)	473	=item async => $boolean (default: C<0>)
373		474
374	The default server used in the child does all I/O blockingly, and only	475	The default server used in the child does all I/O blockingly, and only
375	allows a single RPC call to execute concurrently.	476	allows a single RPC call to execute concurrently.
376		477
377	Setting C<async> to a true value switches to another implementation that	478	Setting C<async> to a true value switches to another implementation that
…		…
387	synchronous, and C<AnyEvent::Fork::RPC::Async> for asynchronous mode.	488	synchronous, and C<AnyEvent::Fork::RPC::Async> for asynchronous mode.
388		489
389	If you use a template process and want to fork both sync and async	490	If you use a template process and want to fork both sync and async
390	children, then it is permissible to load both modules.	491	children, then it is permissible to load both modules.
391		492
392	=item serialiser => $string (default: $AnyEvent::Fork::RPC::STRING_SERIALISER)	493	=item serialiser => $string (default: C<$AnyEvent::Fork::RPC::STRING_SERIALISER>)
393		494
394	All arguments, result data and event data have to be serialised to be	495	All arguments, result data and event data have to be serialised to be
395	transferred between the processes. For this, they have to be frozen and	496	transferred between the processes. For this, they have to be frozen and
396	thawed in both parent and child processes.	497	thawed in both parent and child processes.
397		498
398	By default, only octet strings can be passed between the processes, which	499	By default, only octet strings can be passed between the processes,
399	is reasonably fast and efficient and requires no extra modules.	500	which is reasonably fast and efficient and requires no extra modules
		501	(the C<AnyEvent::Fork::RPC> distribution does not provide these extra
		502	serialiser modules).
400		503
401	For more complicated use cases, you can provide your own freeze and thaw	504	For more complicated use cases, you can provide your own freeze and thaw
402	functions, by specifying a string with perl source code. It's supposed to	505	functions, by specifying a string with perl source code. It's supposed to
403	return two code references when evaluated: the first receives a list of	506	return two code references when evaluated: the first receives a list of
404	perl values and must return an octet string. The second receives the octet	507	perl values and must return an octet string. The second receives the octet
…		…
406		509
407	If you need an external module for serialisation, then you can either	510	If you need an external module for serialisation, then you can either
408	pre-load it into your L<AnyEvent::Fork> process, or you can add a C<use>	511	pre-load it into your L<AnyEvent::Fork> process, or you can add a C<use>
409	or C<require> statement into the serialiser string. Or both.	512	or C<require> statement into the serialiser string. Or both.
410		513
411	Here are some examples - some of them are also available as global	514	Here are some examples - all of them are also available as global
412	variables that make them easier to use.	515	variables that make them easier to use.
413		516
414	=over 4	517	=over 4
415		518
416	=item octet strings - C<$AnyEvent::Fork::RPC::STRING_SERIALISER>	519	=item C<$AnyEvent::Fork::RPC::STRING_SERIALISER> - octet strings only
417		520
418	This serialiser concatenates length-prefixes octet strings, and is the	521	This serialiser (currently the default) concatenates length-prefixes octet
419	default.	522	strings, and is the default. That means you can only pass (and return)
		523	strings containing character codes 0-255.
		524
		525	The main advantages of this serialiser are the high speed and that it
		526	doesn't need another module. The main disadvantage is that you are very
		527	limited in what you can pass - only octet strings.
420		528
421	Implementation:	529	Implementation:
422		530
423	(	531	(
424	sub { pack "(w/a)", @_ },	532	sub { pack "(w/a)", @_ },
425	sub { unpack "(w/a)", shift }	533	sub { unpack "(w/a)", shift }
426	)	534	)
427		535
428	=item json - C<$AnyEvent::Fork::RPC::JSON_SERIALISER>	536	=item C<$AnyEvent::Fork::RPC::CBOR_XS_SERIALISER> - uses L<CBOR::XS>
		537
		538	This serialiser creates CBOR::XS arrays - you have to make sure the
		539	L<CBOR::XS> module is installed for this serialiser to work. It can be
		540	beneficial for sharing when you preload the L<CBOR::XS> module in a template
		541	process.
		542
		543	L<CBOR::XS> is about as fast as the octet string serialiser, but supports
		544	complex data structures (similar to JSON) and is faster than any of the
		545	other serialisers. If you have the L<CBOR::XS> module available, it's the
		546	best choice.
		547
		548	The encoder enables C<allow_sharing> (so this serialisation method can
		549	encode cyclic and self-referencing data structures).
		550
		551	Implementation:
		552
		553	use CBOR::XS ();
		554	(
		555	sub { CBOR::XS::encode_cbor_sharing \@_ },
		556	sub { @{ CBOR::XS::decode_cbor shift } }
		557	)
		558
		559	=item C<$AnyEvent::Fork::RPC::JSON_SERIALISER> - uses L<JSON::XS> or L<JSON>
429		560
430	This serialiser creates JSON arrays - you have to make sure the L<JSON>	561	This serialiser creates JSON arrays - you have to make sure the L<JSON>
431	module is installed for this serialiser to work. It can be beneficial for	562	module is installed for this serialiser to work. It can be beneficial for
432	sharing when you preload the L<JSON> module in a template process.	563	sharing when you preload the L<JSON> module in a template process.
433		564
…		…
441	(	572	(
442	sub { JSON::encode_json \@_ },	573	sub { JSON::encode_json \@_ },
443	sub { @{ JSON::decode_json shift } }	574	sub { @{ JSON::decode_json shift } }
444	)	575	)
445		576
446	=item storable - C<$AnyEvent::Fork::RPC::STORABLE_SERIALISER>	577	=item C<$AnyEvent::Fork::RPC::STORABLE_SERIALISER> - L<Storable>
447		578
448	This serialiser uses L<Storable>, which means it has high chance of	579	This serialiser uses L<Storable>, which means it has high chance of
449	serialising just about anything you throw at it, at the cost of having	580	serialising just about anything you throw at it, at the cost of having
450	very high overhead per operation. It also comes with perl.	581	very high overhead per operation. It also comes with perl. It should be
		582	used when you need to serialise complex data structures.
451		583
452	Implementation:	584	Implementation:
453		585
454	use Storable ();	586	use Storable ();
455	(	587	(
456	sub { Storable::freeze \@_ },	588	sub { Storable::freeze \@_ },
457	sub { @{ Storable::thaw shift } }	589	sub { @{ Storable::thaw shift } }
458	)	590	)
459		591
460	=item portable storable - C<$AnyEvent::Fork::RPC::NSTORABLE_SERIALISER>	592	=item C<$AnyEvent::Fork::RPC::NSTORABLE_SERIALISER> - portable Storable
461		593
462	This serialiser also uses L<Storable>, but uses it's "network" format	594	This serialiser also uses L<Storable>, but uses it's "network" format
463	to serialise data, which makes it possible to talk to incompatible	595	to serialise data, which makes it possible to talk to different
464	perl versions (for example, when talking to a process created with	596	perl binaries (for example, when talking to a process created with
465	L<AnyEvent::Fork::Remote>).	597	L<AnyEvent::Fork::Remote>).
466		598
467	Implementation:	599	Implementation:
468		600
469	use Storable ();	601	use Storable ();
…		…
472	sub { @{ Storable::thaw shift } }	604	sub { @{ Storable::thaw shift } }
473	)	605	)
474		606
475	=back	607	=back
476		608
		609	=item buflen => $bytes (default: C<512 - 16>)
		610
		611	The starting size of the read buffer for request and response data.
		612
		613	C<AnyEvent::Fork::RPC> ensures that the buffer for reeading request and
		614	response data is large enough for at leats aingle request or response, and
		615	will dynamically enlarge the buffer if needed.
		616
		617	While this ensures that memory is not overly wasted, it typically leads
		618	to having to do one syscall per request, which can be inefficient in some
		619	cases. In such cases, it can be beneficient to increase the buffer size to
		620	hold more than one request.
		621
		622	=item buflen_req => $bytes (default: same as C<buflen>)
		623
		624	Overrides C<buflen> for request data (as read by the forked process).
		625
		626	=item buflen_res => $bytes (default: same as C<buflen>)
		627
		628	Overrides C<buflen> for response data (replies read by the parent process).
		629
477	=back	630	=back
478		631
479	See the examples section earlier in this document for some actual	632	See the examples section earlier in this document for some actual
480	examples.	633	examples.
481		634
482	=cut	635	=cut
483		636
484	our $STRING_SERIALISER = '(sub { pack "(w/a)", @_ }, sub { unpack "(w/a)", shift })';	637	our $STRING_SERIALISER = '(sub { pack "(w/a)", @_ }, sub { unpack "(w/a)", shift })';
		638	our $CBOR_XS_SERIALISER = 'use CBOR::XS (); (sub { CBOR::XS::encode_cbor_sharing \@_ }, sub { @{ CBOR::XS::decode_cbor shift } })';
485	our $JSON_SERIALISER = 'use JSON (); (sub { JSON::encode_json \@_ }, sub { @{ JSON::decode_json shift } })';	639	our $JSON_SERIALISER = 'use JSON (); (sub { JSON::encode_json \@_ }, sub { @{ JSON::decode_json shift } })';
486	our $STORABLE_SERIALISER = 'use Storable (); (sub { Storable::freeze \@_ }, sub { @{ Storable::thaw shift } })';	640	our $STORABLE_SERIALISER = 'use Storable (); (sub { Storable::freeze \@_ }, sub { @{ Storable::thaw shift } })';
487	our $NSTORABLE_SERIALISER = 'use Storable (); (sub { Storable::nfreeze \@_ }, sub { @{ Storable::thaw shift } })';	641	our $NSTORABLE_SERIALISER = 'use Storable (); (sub { Storable::nfreeze \@_ }, sub { @{ Storable::thaw shift } })';
488		642
489	sub run {	643	sub run {
490	my ($self, $function, %arg) = @_;	644	my ($self, $function, %arg) = @_;
…		…
495	my $on_destroy = delete $arg{on_destroy};	649	my $on_destroy = delete $arg{on_destroy};
496		650
497	# default for on_error is to on_event, if specified	651	# default for on_error is to on_event, if specified
498	$on_error \|\|= $on_event	652	$on_error \|\|= $on_event
499	? sub { $on_event->(error => shift) }	653	? sub { $on_event->(error => shift) }
500	: sub { die "AnyEvent::Fork::RPC: uncaught error: $_[0].\n" };	654	: sub { AE::log die => "AnyEvent::Fork::RPC: uncaught error: $_[0]." };
501		655
502	# default for on_event is to raise an error	656	# default for on_event is to raise an error
503	$on_event \|\|= sub { $on_error->("event received, but no on_event handler") };	657	$on_event \|\|= sub { $on_error->("event received, but no on_event handler") };
504		658
505	my ($f, $t) = eval $serialiser; die $@ if $@;	659	my ($f, $t) = eval $serialiser; die $@ if $@;
506		660
507	my (@rcb, %rcb, $fh, $shutdown, $wbuf, $ww);	661	my (@rcb, %rcb, $fh, $shutdown, $wbuf, $ww);
508	my ($rlen, $rbuf, $rw) = 512 - 16;	662	my ($rlen, $rbuf, $rw) = $arg{buflen_res} \|\| $arg{buflen} \|\| 512 - 16;
509		663
510	my $wcb = sub {	664	my $wcb = sub {
511	my $len = syswrite $fh, $wbuf;	665	my $len = syswrite $fh, $wbuf;
512		666
513	unless (defined $len) {	667	unless (defined $len) {
…		…
525	}	679	}
526	};	680	};
527		681
528	my $module = "AnyEvent::Fork::RPC::" . ($arg{async} ? "Async" : "Sync");	682	my $module = "AnyEvent::Fork::RPC::" . ($arg{async} ? "Async" : "Sync");
529		683
530	$self->require ($module)	684	$self->eval ("use $module 2 ()")
531	->send_arg ($function, $arg{init}, $serialiser)	685	->send_arg (
		686	function => $function,
		687	init => $arg{init},
		688	serialiser => $serialiser,
		689	done => $arg{done} \|\| "$module\::do_exit",
		690	rlen => $arg{buflen_req} \|\| $arg{buflen} \|\| 512 - 16,
		691	-10 # the above are 10 arguments
		692	)
532	->run ("$module\::run", sub {	693	->run ("$module\::run", sub {
533	$fh = shift;	694	$fh = shift
		695	or return $on_error->("connection failed");
534		696
535	my ($id, $len);	697	my ($id, $len);
536	$rw = AE::io $fh, 0, sub {	698	$rw = AE::io $fh, 0, sub {
537	$rlen = $rlen * 2 + 16 if $rlen - 128 < length $rbuf;	699	$rlen = $rlen * 2 + 16 if $rlen - 128 < length $rbuf;
538	$len = sysread $fh, $rbuf, $rlen - length $rbuf, length $rbuf;	700	$len = sysread $fh, $rbuf, $rlen - length $rbuf, length $rbuf;
…		…
639	The following function is not available in this module. They are only	801	The following function is not available in this module. They are only
640	available in the namespace of this module when the child is running,	802	available in the namespace of this module when the child is running,
641	without having to load any extra modules. They are part of the child-side	803	without having to load any extra modules. They are part of the child-side
642	API of L<AnyEvent::Fork::RPC>.	804	API of L<AnyEvent::Fork::RPC>.
643		805
		806	Note that these functions are typically not yet declared when code is
		807	compiled into the child, because the backend module is only loaded when
		808	you call C<run>, which is typically the last method you call on the fork
		809	object.
		810
		811	Therefore, you either have to explicitly pre-load the right backend module
		812	or mark calls to these functions as function calls, e.g.:
		813
		814	AnyEvent::Fork::RPC::event (0 => "five");
		815	AnyEvent::Fork::RPC::event->(0 => "five");
		816	&AnyEvent::Fork::RPC::flush;
		817
644	=over 4	818	=over 4
645		819
646	=item AnyEvent::Fork::RPC::event ...	820	=item AnyEvent::Fork::RPC::event (...)
647		821
648	Send an event to the parent. Events are a bit like RPC calls made by the	822	Send an event to the parent. Events are a bit like RPC calls made by the
649	child process to the parent, except that there is no notion of return	823	child process to the parent, except that there is no notion of return
650	values.	824	values.
651		825
652	See the examples section earlier in this document for some actual	826	See the examples section earlier in this document for some actual
653	examples.	827	examples.
		828
		829	Note: the event data, like any data send to the parent, might not be sent
		830	immediatelly but queued for later sending, so there is no guarantee that
		831	the event has been sent to the parent when the call returns - when you
		832	e.g. exit directly after calling this function, the parent might never
		833	receive the event. See the next function for a remedy.
		834
		835	=item $success = AnyEvent::Fork::RPC::flush ()
		836
		837	Synchronously wait and flush the reply data to the parent. Returns true on
		838	success and false otherwise (i.e. when the reply data cannot be written at
		839	all). Ignoring the success status is a common and healthy behaviour.
		840
		841	Only the "async" backend does something on C<flush> - the "sync" backend
		842	is not buffering reply data and always returns true from this function.
		843
		844	Normally, reply data might or might not be written to the parent
		845	immediatelly but is buffered. This can greatly improve performance and
		846	efficiency, but sometimes can get in your way: for example. when you want
		847	to send an error message just before exiting, or when you want to ensure
		848	replies timely reach the parent before starting a long blocking operation.
		849
		850	In these cases, you can call this function to flush any outstanding reply
		851	data to the parent. This is done blockingly, so no requests will be
		852	handled and no event callbacks will be called.
		853
		854	For example, you could wrap your request function in a C<eval> block and
		855	report the exception string back to the caller just before exiting:
		856
		857	sub req {
		858	...
		859
		860	eval {
		861	...
		862	};
		863
		864	if ($@) {
		865	AnyEvent::RPC::event (throw => "$@");
		866	AnyEvent::RPC::flush ();
		867	exit;
		868	}
		869
		870	...
		871	}
		872
		873	=back
		874
		875	=head2 PROCESS EXIT
		876
		877	If and when the child process exits depends on the backend and
		878	configuration. Apart from explicit exits (e.g. by calling C<exit>) or
		879	runtime conditions (uncaught exceptions, signals etc.), the backends exit
		880	under these conditions:
		881
		882	=over 4
		883
		884	=item Synchronous Backend
		885
		886	The synchronous backend is very simple: when the process waits for another
		887	request to arrive and the writing side (usually in the parent) is closed,
		888	it will exit normally, i.e. as if your main program reached the end of the
		889	file.
		890
		891	That means that if your parent process exits, the RPC process will usually
		892	exit as well, either because it is idle anyway, or because it executes a
		893	request. In the latter case, you will likely get an error when the RPc
		894	process tries to send the results to the parent (because agruably, you
		895	shouldn't exit your parent while there are still outstanding requests).
		896
		897	The process is usually quiescent when it happens, so it should rarely be a
		898	problem, and C<END> handlers can be used to clean up.
		899
		900	=item Asynchronous Backend
		901
		902	For the asynchronous backend, things are more complicated: Whenever it
		903	listens for another request by the parent, it might detect that the socket
		904	was closed (e.g. because the parent exited). It will sotp listening for
		905	new requests and instead try to write out any remaining data (if any) or
		906	simply check whether the socket can be written to. After this, the RPC
		907	process is effectively done - no new requests are incoming, no outstanding
		908	request data can be written back.
		909
		910	Since chances are high that there are event watchers that the RPC server
		911	knows nothing about (why else would one use the async backend if not for
		912	the ability to register watchers?), the event loop would often happily
		913	continue.
		914
		915	This is why the asynchronous backend explicitly calls C<CORE::exit> when
		916	it is done (under other circumstances, such as when there is an I/O error
		917	and there is outstanding data to write, it will log a fatal message via
		918	L<AnyEvent::Log>, also causing the program to exit).
		919
		920	You can override this by specifying a function name to call via the C<done>
		921	parameter instead.
654		922
655	=back	923	=back
656		924
657	=head1 ADVANCED TOPICS	925	=head1 ADVANCED TOPICS
658		926
…		…
714	are queued and the jobs are slow, they will all run concurrently. The	982	are queued and the jobs are slow, they will all run concurrently. The
715	child must implement some queueing/limiting mechanism if this causes	983	child must implement some queueing/limiting mechanism if this causes
716	problems. Alternatively, the parent could limit the amount of rpc calls	984	problems. Alternatively, the parent could limit the amount of rpc calls
717	that are outstanding.	985	that are outstanding.
718		986
719	Blocking use of condvars is not supported.	987	Blocking use of condvars is not supported (in the main thread, outside of
		988	e.g. L<Coro> threads).
720		989
721	Using event-based modules such as L<IO::AIO>, L<Gtk2>, L<Tk> and so on is	990	Using event-based modules such as L<IO::AIO>, L<Gtk2>, L<Tk> and so on is
722	easy.	991	easy.
723		992
724	=back	993	=back
…		…
790	gory details.	1059	gory details.
791		1060
792	=head1 EXCEPTIONS	1061	=head1 EXCEPTIONS
793		1062
794	There are no provisions whatsoever for catching exceptions at this time -	1063	There are no provisions whatsoever for catching exceptions at this time -
795	in the child, exeptions might kill the process, causing calls to be lost	1064	in the child, exceptions might kill the process, causing calls to be lost
796	and the parent encountering a fatal error. In the parent, exceptions in	1065	and the parent encountering a fatal error. In the parent, exceptions in
797	the result callback will not be caught and cause undefined behaviour.	1066	the result callback will not be caught and cause undefined behaviour.
798		1067
799	=head1 SEE ALSO	1068	=head1 SEE ALSO
800		1069

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Comparing AnyEvent-Fork-RPC/RPC.pm (file contents): Revision 1.28 by root, Sun Apr 28 15:48:31 2013 UTC vs. Revision 1.46 by root, Sun Sep 15 20:18:14 2019 UTC

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Comparing AnyEvent-Fork-RPC/RPC.pm (file contents):
Revision 1.28 by root, Sun Apr 28 15:48:31 2013 UTC vs.
Revision 1.46 by root, Sun Sep 15 20:18:14 2019 UTC