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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.36 by root, Thu Aug 6 10:46:48 2009 UTC vs.
Revision 1.47 by root, Thu Aug 13 01:57:10 2009 UTC

…		…
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's noderef
10	NODE # returns this node's noderef	10	NODE # returns this node's noderef
11	NODE $port # returns the noderef of the port	11	NODE $port # returns the noderef of the port
12		12
		13	$SELF # receiving/own port id in rcv callbacks
		14
		15	# ports are message endpoints
		16
		17	# sending messages
13	snd $port, type => data...;	18	snd $port, type => data...;
		19	snd $port, @msg;
		20	snd @msg_with_first_element_being_a_port;
14		21
15	$SELF # receiving/own port id in rcv callbacks	22	# miniports
		23	my $miniport = port { my @msg = @_; 0 };
16		24
		25	# full ports
		26	my $port = port;
17	rcv $port, smartmatch => $cb->($port, @msg);	27	rcv $port, smartmatch => $cb->(@msg);
18
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	28	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
21	rcv $port1, pong => sub { warn "pong received\n" };	29	rcv $port, pong => sub { warn "pong received\n"; 0 };
22	snd $port2, ping => $port1;	30
		31	# remote ports
		32	my $port = spawn $node, $initfunc, @initdata;
23		33
24	# more, smarter, matches (_any_ is exported by this module)	34	# more, smarter, matches (_any_ is exported by this module)
25	rcv $port, [child_died => $pid] => sub { ...	35	rcv $port, [child_died => $pid] => sub { ...
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	36	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
27
28	# linking two ports, so they both crash together
29	lnk $port1, $port2;
30		37
31	# monitoring	38	# monitoring
32	mon $port, $cb->(@msg) # callback is invoked on death	39	mon $port, $cb->(@msg) # callback is invoked on death
33	mon $port, $otherport # kill otherport on abnormal death	40	mon $port, $otherport # kill otherport on abnormal death
34	mon $port, $otherport, @msg # send message on death	41	mon $port, $otherport, @msg # send message on death
35		42
		43	=head1 CURRENT STATUS
		44
		45	AnyEvent::MP - stable API, should work
		46	AnyEvent::MP::Intro - outdated
		47	AnyEvent::MP::Kernel - WIP
		48	AnyEvent::MP::Transport - mostly stable
		49
		50	stay tuned.
		51
36	=head1 DESCRIPTION	52	=head1 DESCRIPTION
37		53
38	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
39		55
40	Despite its simplicity, you can securely message other processes running	56	Despite its simplicity, you can securely message other processes running
…		…
43	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
44	manual page.	60	manual page.
45		61
46	At the moment, this module family is severly broken and underdocumented,	62	At the moment, this module family is severly broken and underdocumented,
47	so do not use. This was uploaded mainly to reserve the CPAN namespace -	63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
48	stay tuned! The basic API should be finished, however.	64	stay tuned!
49		65
50	=head1 CONCEPTS	66	=head1 CONCEPTS
51		67
52	=over 4	68	=over 4
53		69
…		…
98		114
99	=cut	115	=cut
100		116
101	package AnyEvent::MP;	117	package AnyEvent::MP;
102		118
103	use AnyEvent::MP::Base;	119	use AnyEvent::MP::Kernel;
104		120
105	use common::sense;	121	use common::sense;
106		122
107	use Carp ();	123	use Carp ();
108		124
109	use AE ();	125	use AE ();
110		126
111	use base "Exporter";	127	use base "Exporter";
112		128
113	our $VERSION = '0.1';	129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		130
114	our @EXPORT = qw(	131	our @EXPORT = qw(
115	NODE $NODE *SELF node_of _any_	132	NODE $NODE *SELF node_of _any_
116	resolve_node initialise_node	133	resolve_node initialise_node
117	snd rcv mon kil reg psub	134	snd rcv mon kil reg psub spawn
118	port	135	port
119	);	136	);
120		137
121	our $SELF;	138	our $SELF;
122		139
…		…
343	registered.	360	registered.
344		361
345	The global C<$SELF> (exported by this module) contains C<$port> while	362	The global C<$SELF> (exported by this module) contains C<$port> while
346	executing the callback.	363	executing the callback.
347		364
348	Runtime errors wdurign callback execution will result in the port being	365	Runtime errors during callback execution will result in the port being
349	C<kil>ed.	366	C<kil>ed.
350		367
351	If the match is an array reference, then it will be matched against the	368	If the match is an array reference, then it will be matched against the
352	first elements of the message, otherwise only the first element is being	369	first elements of the message, otherwise only the first element is being
353	matched.	370	matched.
…		…
494		511
495	=item $guard = mon $port	512	=item $guard = mon $port
496		513
497	=item $guard = mon $port, $rcvport, @msg	514	=item $guard = mon $port, $rcvport, @msg
498		515
499	Monitor the given port and do something when the port is killed, and	516	Monitor the given port and do something when the port is killed or
500	optionally return a guard that can be used to stop monitoring again.	517	messages to it were lost, and optionally return a guard that can be used
		518	to stop monitoring again.
		519
		520	C<mon> effectively guarantees that, in the absence of hardware failures,
		521	that after starting the monitor, either all messages sent to the port
		522	will arrive, or the monitoring action will be invoked after possible
		523	message loss has been detected. No messages will be lost "in between"
		524	(after the first lost message no further messages will be received by the
		525	port). After the monitoring action was invoked, further messages might get
		526	delivered again.
501		527
502	In the first form (callback), the callback is simply called with any	528	In the first form (callback), the callback is simply called with any
503	number of C<@reason> elements (no @reason means that the port was deleted	529	number of C<@reason> elements (no @reason means that the port was deleted
504	"normally"). Note also that I<< the callback B<must> never die >>, so use	530	"normally"). Note also that I<< the callback B<must> never die >>, so use
505	C<eval> if unsure.	531	C<eval> if unsure.
506		532
507	In the second form (another port given), the other port (C<$rcvport)	533	In the second form (another port given), the other port (C<$rcvport>)
508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	534	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
509	"normal" kils nothing happens, while under all other conditions, the other	535	"normal" kils nothing happens, while under all other conditions, the other
510	port is killed with the same reason.	536	port is killed with the same reason.
511		537
512	The third form (kill self) is the same as the second form, except that	538	The third form (kill self) is the same as the second form, except that
513	C<$rvport> defaults to C<$SELF>.	539	C<$rvport> defaults to C<$SELF>.
514		540
515	In the last form (message), a message of the form C<@msg, @reason> will be	541	In the last form (message), a message of the form C<@msg, @reason> will be
516	C<snd>.	542	C<snd>.
517		543
		544	As a rule of thumb, monitoring requests should always monitor a port from
		545	a local port (or callback). The reason is that kill messages might get
		546	lost, just like any other message. Another less obvious reason is that
		547	even monitoring requests can get lost (for exmaple, when the connection
		548	to the other node goes down permanently). When monitoring a port locally
		549	these problems do not exist.
		550
518	Example: call a given callback when C<$port> is killed.	551	Example: call a given callback when C<$port> is killed.
519		552
520	mon $port, sub { warn "port died because of <@_>\n" };	553	mon $port, sub { warn "port died because of <@_>\n" };
521		554
522	Example: kill ourselves when C<$port> is killed abnormally.	555	Example: kill ourselves when C<$port> is killed abnormally.
…		…
532	sub mon {	565	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	566	my ($noderef, $port) = split /#/, shift, 2;
534		567
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	568	my $node = $NODE{$noderef} \|\| add_node $noderef;
536		569
537	my $cb = @_ ? $_[0] : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	570	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
538		571
539	unless (ref $cb) {	572	unless (ref $cb) {
540	if (@_) {	573	if (@_) {
541	# send a kill info message	574	# send a kill info message
542	my (@msg) = @_;	575	my (@msg) = ($cb, @_);
543	$cb = sub { snd @msg, @_ };	576	$cb = sub { snd @msg, @_ };
544	} else {	577	} else {
545	# simply kill other port	578	# simply kill other port
546	my $port = $cb;	579	my $port = $cb;
547	$cb = sub { kil $port, @_ if @_ };	580	$cb = sub { kil $port, @_ if @_ };
…		…
578	#TODO: mon-less form?	611	#TODO: mon-less form?
579		612
580	mon $port, sub { 0 && @refs }	613	mon $port, sub { 0 && @refs }
581	}	614	}
582		615
583	=item lnk $port1, $port2
584
585	=item lnk $otherport
586
587	Link two ports. This is simply a shorthand for:
588
589	mon $port1, $port2;
590	mon $port2, $port1;
591
592	It means that if either one is killed abnormally, the other one gets
593	killed as well.
594
595	The one-argument form assumes that one port is C<$SELF>.
596
597	=cut
598
599	sub lnk {
600	my $port1 = shift;
601	my $port2 = @_ ? shift : $SELF \|\| Carp::croak 'lnk: called with one argument only, but $SELF not set,';
602
603	mon $port1, $port2;
604	mon $port2, $port1;
605	}
606
607	=item kil $port[, @reason]	616	=item kil $port[, @reason]
608		617
609	Kill the specified port with the given C<@reason>.	618	Kill the specified port with the given C<@reason>.
610		619
611	If no C<@reason> is specified, then the port is killed "normally" (linked	620	If no C<@reason> is specified, then the port is killed "normally" (linked
…		…
617	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	626	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
618	will be reported as reason C<< die => $@ >>.	627	will be reported as reason C<< die => $@ >>.
619		628
620	Transport/communication errors are reported as C<< transport_error =>	629	Transport/communication errors are reported as C<< transport_error =>
621	$message >>.	630	$message >>.
		631
		632	=cut
		633
		634	=item $port = spawn $node, $initfunc[, @initdata]
		635
		636	Creates a port on the node C<$node> (which can also be a port ID, in which
		637	case it's the node where that port resides).
		638
		639	The port ID of the newly created port is return immediately, and it is
		640	permissible to immediately start sending messages or monitor the port.
		641
		642	After the port has been created, the init function is
		643	called. This function must be a fully-qualified function name
		644	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		645	program, use C<::name>.
		646
		647	If the function doesn't exist, then the node tries to C<require>
		648	the package, then the package above the package and so on (e.g.
		649	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		650	exists or it runs out of package names.
		651
		652	The init function is then called with the newly-created port as context
		653	object (C<$SELF>) and the C<@initdata> values as arguments.
		654
		655	A common idiom is to pass your own port, monitor the spawned port, and
		656	in the init function, monitor the original port. This two-way monitoring
		657	ensures that both ports get cleaned up when there is a problem.
		658
		659	Example: spawn a chat server port on C<$othernode>.
		660
		661	# this node, executed from within a port context:
		662	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		663	mon $server;
		664
		665	# init function on C<$othernode>
		666	sub connect {
		667	my ($srcport) = @_;
		668
		669	mon $srcport;
		670
		671	rcv $SELF, sub {
		672	...
		673	};
		674	}
		675
		676	=cut
		677
		678	sub _spawn {
		679	my $port = shift;
		680	my $init = shift;
		681
		682	local $SELF = "$NODE#$port";
		683	eval {
		684	&{ load_func $init }
		685	};
		686	_self_die if $@;
		687	}
		688
		689	sub spawn(@) {
		690	my ($noderef, undef) = split /#/, shift, 2;
		691
		692	my $id = "$RUNIQ." . $ID++;
		693
		694	$_[0] =~ /::/
		695	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		696
		697	($NODE{$noderef} \|\| add_node $noderef)
		698	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
		699
		700	"$noderef#$id"
		701	}
622		702
623	=back	703	=back
624		704
625	=head1 NODE MESSAGES	705	=head1 NODE MESSAGES
626		706
…		…
759	or I<none>, there is no in-between, so monitoring single processes is	839	or I<none>, there is no in-between, so monitoring single processes is
760	difficult to implement. Monitoring in AEMP is more flexible than in	840	difficult to implement. Monitoring in AEMP is more flexible than in
761	Erlang, as one can choose between automatic kill, exit message or callback	841	Erlang, as one can choose between automatic kill, exit message or callback
762	on a per-process basis.	842	on a per-process basis.
763		843
764	=item * Erlang has different semantics for monitoring and linking, AEMP has the same.	844	=item * Erlang tries to hide remote/local connections, AEMP does not.
765		845
766	Monitoring in Erlang is not an indicator of process death/crashes,	846	Monitoring in Erlang is not an indicator of process death/crashes,
767	as linking is (except linking is unreliable in Erlang). In AEMP, the	847	as linking is (except linking is unreliable in Erlang).
768	semantics of monitoring and linking are identical, linking is simply	848
769	two-way monitoring with automatic kill.	849	In AEMP, you don't "look up" registered port names or send to named ports
		850	that might or might not be persistent. Instead, you normally spawn a port
		851	on the remote node. The init function monitors the you, and you monitor
		852	the remote port. Since both monitors are local to the node, they are much
		853	more reliable.
		854
		855	This also saves round-trips and avoids sending messages to the wrong port
		856	(hard to do in Erlang).
		857
		858	=back
		859
		860	=head1 RATIONALE
		861
		862	=over 4
		863
		864	=item Why strings for ports and noderefs, why not objects?
		865
		866	We considered "objects", but found that the actual number of methods
		867	thatc an be called are very low. Since port IDs and noderefs travel over
		868	the network frequently, the serialising/deserialising would add lots of
		869	overhead, as well as having to keep a proxy object.
		870
		871	Strings can easily be printed, easily serialised etc. and need no special
		872	procedures to be "valid".
		873
		874	And a a miniport consists of a single closure stored in a global hash - it
		875	can't become much cheaper.
		876
		877	=item Why favour JSON, why not real serialising format such as Storable?
		878
		879	In fact, any AnyEvent::MP node will happily accept Storable as framing
		880	format, but currently there is no way to make a node use Storable by
		881	default.
		882
		883	The default framing protocol is JSON because a) JSON::XS is many times
		884	faster for small messages and b) most importantly, after years of
		885	experience we found that object serialisation is causing more problems
		886	than it gains: Just like function calls, objects simply do not travel
		887	easily over the network, mostly because they will always be a copy, so you
		888	always have to re-think your design.
		889
		890	Keeping your messages simple, concentrating on data structures rather than
		891	objects, will keep your messages clean, tidy and efficient.
770		892
771	=back	893	=back
772		894
773	=head1 SEE ALSO	895	=head1 SEE ALSO
774		896

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.36 by root, Thu Aug 6 10:46:48 2009 UTC vs. Revision 1.47 by root, Thu Aug 13 01:57:10 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.36 by root, Thu Aug 6 10:46:48 2009 UTC vs.
Revision 1.47 by root, Thu Aug 13 01:57:10 2009 UTC