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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.35 by root, Thu Aug 6 10:21:48 2009 UTC vs.
Revision 1.51 by root, Fri Aug 14 14:07:44 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	# initialise the node so it can send/receive messages
		16	initialise_node; # -OR-
		17	initialise_node "localhost:4040"; # -OR-
		18	initialise_node "slave/", "localhost:4040"
		19
		20	# ports are message endpoints
		21
		22	# sending messages
13	snd $port, type => data...;	23	snd $port, type => data...;
		24	snd $port, @msg;
		25	snd @msg_with_first_element_being_a_port;
14		26
15	$SELF # receiving/own port id in rcv callbacks	27	# creating/using ports, the simple way
		28	my $somple_port = port { my @msg = @_; 0 };
16		29
17	rcv $port, smartmatch => $cb->($port, @msg);	30	# creating/using ports, type matching
18		31	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
21	rcv $port1, pong => sub { warn "pong received\n" };	33	rcv $port, pong => sub { warn "pong received\n"; 0 };
22	snd $port2, ping => $port1;
23		34
24	# more, smarter, matches (_any_ is exported by this module)	35	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	36	my $port = spawn $node, $initfunc, @initdata;
26	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		46	AnyEvent::MP::Intro - outdated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 $SELF;
122		139
…		…
146	it should know the noderefs of some other nodes in the network.	163	it should know the noderefs of some other nodes in the network.
147		164
148	This function initialises a node - it must be called exactly once (or	165	This function initialises a node - it must be called exactly once (or
149	never) before calling other AnyEvent::MP functions.	166	never) before calling other AnyEvent::MP functions.
150		167
151	All arguments are noderefs, which can be either resolved or unresolved.	168	All arguments (optionally except for the first) are noderefs, which can be
		169	either resolved or unresolved.
		170
		171	The first argument will be looked up in the configuration database first
		172	(if it is C<undef> then the current nodename will be used instead) to find
		173	the relevant configuration profile (see L<aemp>). If none is found then
		174	the default configuration is used. The configuration supplies additional
		175	seed/master nodes and can override the actual noderef.
152		176
153	There are two types of networked nodes, public nodes and slave nodes:	177	There are two types of networked nodes, public nodes and slave nodes:
154		178
155	=over 4	179	=over 4
156		180
157	=item public nodes	181	=item public nodes
158		182
159	For public nodes, C<$noderef> must either be a (possibly unresolved)	183	For public nodes, C<$noderef> (supplied either directly to
160	noderef, in which case it will be resolved, or C<undef> (or missing), in	184	C<initialise_node> or indirectly via a profile or the nodename) must be a
161	which case the noderef will be guessed.	185	noderef (possibly unresolved, in which case it will be resolved).
162		186
163	Afterwards, the node will bind itself on all endpoints and try to connect	187	After resolving, the node will bind itself on all endpoints and try to
164	to all additional C<$seednodes> that are specified. Seednodes are optional	188	connect to all additional C<$seednodes> that are specified. Seednodes are
165	and can be used to quickly bootstrap the node into an existing network.	189	optional and can be used to quickly bootstrap the node into an existing
		190	network.
166		191
167	=item slave nodes	192	=item slave nodes
168		193
169	When the C<$noderef> is the special string C<slave/>, then the node will	194	When the C<$noderef> (either as given or overriden by the config file)
		195	is the special string C<slave/>, then the node will become a slave
170	become a slave node. Slave nodes cannot be contacted from outside and will	196	node. Slave nodes cannot be contacted from outside and will route most of
171	route most of their traffic to the master node that they attach to.	197	their traffic to the master node that they attach to.
172		198
173	At least one additional noderef is required: The node will try to connect	199	At least one additional noderef is required (either by specifying it
174	to all of them and will become a slave attached to the first node it can	200	directly or because it is part of the configuration profile): The node
175	successfully connect to.	201	will try to connect to all of them and will become a slave attached to the
		202	first node it can successfully connect to.
176		203
177	=back	204	=back
178		205
179	This function will block until all nodes have been resolved and, for slave	206	This function will block until all nodes have been resolved and, for slave
180	nodes, until it has successfully established a connection to a master	207	nodes, until it has successfully established a connection to a master
181	server.	208	server.
182		209
183	Example: become a public node listening on the default node.	210	Example: become a public node listening on the guessed noderef, or the one
		211	specified via C<aemp> for the current node. This should be the most common
		212	form of invocation for "daemon"-type nodes.
184		213
185	initialise_node;	214	initialise_node;
		215
		216	Example: become a slave node to any of the the seednodes specified via
		217	C<aemp>. This form is often used for commandline clients.
		218
		219	initialise_node "slave/";
		220
		221	Example: become a slave node to any of the specified master servers. This
		222	form is also often used for commandline clients.
		223
		224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
186		225
187	Example: become a public node, and try to contact some well-known master	226	Example: become a public node, and try to contact some well-known master
188	servers to become part of the network.	227	servers to become part of the network.
189		228
190	initialise_node undef, "master1", "master2";	229	initialise_node undef, "master1", "master2";
…		…
193		232
194	initialise_node 4041;	233	initialise_node 4041;
195		234
196	Example: become a public node, only visible on localhost port 4044.	235	Example: become a public node, only visible on localhost port 4044.
197		236
198	initialise_node "locahost:4044";	237	initialise_node "localhost:4044";
199
200	Example: become a slave node to any of the specified master servers.
201
202	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
203		238
204	=item $cv = resolve_node $noderef	239	=item $cv = resolve_node $noderef
205		240
206	Takes an unresolved node reference that may contain hostnames and	241	Takes an unresolved node reference that may contain hostnames and
207	abbreviated IDs, resolves all of them and returns a resolved node	242	abbreviated IDs, resolves all of them and returns a resolved node
…		…
263	that Storable can serialise and deserialise is allowed, and for the local	298	that Storable can serialise and deserialise is allowed, and for the local
264	node, anything can be passed.	299	node, anything can be passed.
265		300
266	=item $local_port = port	301	=item $local_port = port
267		302
268	Create a new local port object that can be used either as a pattern	303	Create a new local port object and returns its port ID. Initially it has
269	matching port ("full port") or a single-callback port ("miniport"),	304	no callbacks set and will throw an error when it receives messages.
270	depending on how C<rcv> callbacks are bound to the object.
271		305
272	=item $port = port { my @msg = @_; $finished }	306	=item $local_port = port { my @msg = @_ }
273		307
274	Creates a "miniport", that is, a very lightweight port without any pattern	308	Creates a new local port, and returns its ID. Semantically the same as
275	matching behind it, and returns its ID. Semantically the same as creating
276	a port and calling C<rcv $port, $callback> on it.	309	creating a port and calling C<rcv $port, $callback> on it.
277		310
278	The block will be called for every message received on the port. When the	311	The block will be called for every message received on the port, with the
279	callback returns a true value its job is considered "done" and the port	312	global variable C<$SELF> set to the port ID. Runtime errors will cause the
280	will be destroyed. Otherwise it will stay alive.	313	port to be C<kil>ed. The message will be passed as-is, no extra argument
		314	(i.e. no port ID) will be passed to the callback.
281		315
282	The message will be passed as-is, no extra argument (i.e. no port id) will	316	If you want to stop/destroy the port, simply C<kil> it:
283	be passed to the callback.
284		317
285	If you need the local port id in the callback, this works nicely:	318	my $port = port {
286		319	my @msg = @_;
287	my $port; $port = port {	320	...
288	snd $otherport, reply => $port;	321	kil $SELF;
289	};	322	};
290		323
291	=cut	324	=cut
292		325
293	sub rcv($@);	326	sub rcv($@);
		327
		328	sub _kilme {
		329	die "received message on port without callback";
		330	}
294		331
295	sub port(;&) {	332	sub port(;&) {
296	my $id = "$UNIQ." . $ID++;	333	my $id = "$UNIQ." . $ID++;
297	my $port = "$NODE#$id";	334	my $port = "$NODE#$id";
298		335
299	if (@_) {	336	rcv $port, shift \|\| \&_kilme;
300	rcv $port, shift;
301	} else {
302	$PORT{$id} = sub { }; # nop
303	}
304		337
305	$port	338	$port
306	}	339	}
307		340
308	=item reg $port, $name
309
310	Registers the given port under the name C<$name>. If the name already
311	exists it is replaced.
312
313	A port can only be registered under one well known name.
314
315	A port automatically becomes unregistered when it is killed.
316
317	=cut
318
319	sub reg(@) {
320	my ($port, $name) = @_;
321
322	$REG{$name} = $port;
323	}
324
325	=item rcv $port, $callback->(@msg)	341	=item rcv $local_port, $callback->(@msg)
326		342
327	Replaces the callback on the specified miniport (after converting it to	343	Replaces the default callback on the specified port. There is no way to
328	one if required).	344	remove the default callback: use C<sub { }> to disable it, or better
329		345	C<kil> the port when it is no longer needed.
330	=item rcv $port, tagstring => $callback->(@msg), ...
331
332	=item rcv $port, $smartmatch => $callback->(@msg), ...
333
334	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
335
336	Register callbacks to be called on matching messages on the given full
337	port (after converting it to one if required).
338
339	The callback has to return a true value when its work is done, after
340	which is will be removed, or a false value in which case it will stay
341	registered.
342		346
343	The global C<$SELF> (exported by this module) contains C<$port> while	347	The global C<$SELF> (exported by this module) contains C<$port> while
344	executing the callback.	348	executing the callback. Runtime errors during callback execution will
		349	result in the port being C<kil>ed.
345		350
346	Runtime errors wdurign callback execution will result in the port being	351	The default callback received all messages not matched by a more specific
347	C<kil>ed.	352	C<tag> match.
348		353
349	If the match is an array reference, then it will be matched against the	354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
350	first elements of the message, otherwise only the first element is being
351	matched.
352		355
353	Any element in the match that is specified as C<_any_> (a function	356	Register callbacks to be called on messages starting with the given tag on
354	exported by this module) matches any single element of the message.	357	the given port (and return the port), or unregister it (when C<$callback>
		358	is C<$undef>).
355		359
356	While not required, it is highly recommended that the first matching	360	The original message will be passed to the callback, after the first
357	element is a string identifying the message. The one-string-only match is	361	element (the tag) has been removed. The callback will use the same
358	also the most efficient match (by far).	362	environment as the default callback (see above).
		363
		364	Example: create a port and bind receivers on it in one go.
		365
		366	my $port = rcv port,
		367	msg1 => sub { ... },
		368	msg2 => sub { ... },
		369	;
		370
		371	Example: create a port, bind receivers and send it in a message elsewhere
		372	in one go:
		373
		374	snd $otherport, reply =>
		375	rcv port,
		376	msg1 => sub { ... },
		377	...
		378	;
359		379
360	=cut	380	=cut
361		381
362	sub rcv($@) {	382	sub rcv($@) {
363	my $port = shift;	383	my $port = shift;
364	my ($noderef, $portid) = split /#/, $port, 2;	384	my ($noderef, $portid) = split /#/, $port, 2;
365		385
366	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
367	or Carp::croak "$port: rcv can only be called on local ports, caught";	387	or Carp::croak "$port: rcv can only be called on local ports, caught";
368		388
369	if (@_ == 1) {	389	while (@_) {
		390	if (ref $_[0]) {
		391	if (my $self = $PORT_DATA{$portid}) {
		392	"AnyEvent::MP::Port" eq ref $self
		393	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		394
		395	$self->[2] = shift;
		396	} else {
370	my $cb = shift;	397	my $cb = shift;
371	delete $PORT_DATA{$portid};
372	$PORT{$portid} = sub {	398	$PORT{$portid} = sub {
373	local $SELF = $port;	399	local $SELF = $port;
374	eval {	400	eval { &$cb }; _self_die if $@;
375	&$cb	401	};
376	and kil $port;
377	};	402	}
378	_self_die if $@;	403	} elsif (defined $_[0]) {
379	};
380	} else {
381	my $self = $PORT_DATA{$portid} \|\|= do {	404	my $self = $PORT_DATA{$portid} \|\|= do {
382	my $self = bless {	405	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
383	id => $port,
384	}, "AnyEvent::MP::Port";
385		406
386	$PORT{$portid} = sub {	407	$PORT{$portid} = sub {
387	local $SELF = $port;	408	local $SELF = $port;
388		409
389	eval {
390	for (@{ $self->{rc0}{$_[0]} }) {	410	if (my $cb = $self->[1]{$_[0]}) {
391	$_ && &{$_->[0]}	411	shift;
392	&& undef $_;	412	eval { &$cb }; _self_die if $@;
393	}	413	} else {
394
395	for (@{ $self->{rcv}{$_[0]} }) {
396	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
397	&& &{$_->[0]}	414	&{ $self->[0] };
398	&& undef $_;
399	}
400
401	for (@{ $self->{any} }) {
402	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
403	&& &{$_->[0]}
404	&& undef $_;
405	}	415	}
406	};	416	};
407	_self_die if $@;	417
		418	$self
408	};	419	};
409		420
410	$self
411	};
412
413	"AnyEvent::MP::Port" eq ref $self	421	"AnyEvent::MP::Port" eq ref $self
414	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	422	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
415		423
416	while (@_) {
417	my ($match, $cb) = splice @_, 0, 2;	424	my ($tag, $cb) = splice @_, 0, 2;
418		425
419	if (!ref $match) {	426	if (defined $cb) {
420	push @{ $self->{rc0}{$match} }, [$cb];	427	$self->[1]{$tag} = $cb;
421	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
422	my ($type, @match) = @$match;
423	@match
424	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
425	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
426	} else {	428	} else {
427	push @{ $self->{any} }, [$cb, $match];	429	delete $self->[1]{$tag};
428	}	430	}
429	}	431	}
430	}	432	}
431		433
432	$port	434	$port
…		…
470	}	472	}
471	}	473	}
472		474
473	=item $guard = mon $port, $cb->(@reason)	475	=item $guard = mon $port, $cb->(@reason)
474		476
475	=item $guard = mon $port, $otherport	477	=item $guard = mon $port, $rcvport
476		478
		479	=item $guard = mon $port
		480
477	=item $guard = mon $port, $otherport, @msg	481	=item $guard = mon $port, $rcvport, @msg
478		482
479	Monitor the given port and do something when the port is killed.	483	Monitor the given port and do something when the port is killed or
		484	messages to it were lost, and optionally return a guard that can be used
		485	to stop monitoring again.
480		486
		487	C<mon> effectively guarantees that, in the absence of hardware failures,
		488	that after starting the monitor, either all messages sent to the port
		489	will arrive, or the monitoring action will be invoked after possible
		490	message loss has been detected. No messages will be lost "in between"
		491	(after the first lost message no further messages will be received by the
		492	port). After the monitoring action was invoked, further messages might get
		493	delivered again.
		494
481	In the first form, the callback is simply called with any number	495	In the first form (callback), the callback is simply called with any
482	of C<@reason> elements (no @reason means that the port was deleted	496	number of C<@reason> elements (no @reason means that the port was deleted
483	"normally"). Note also that I<< the callback B<must> never die >>, so use	497	"normally"). Note also that I<< the callback B<must> never die >>, so use
484	C<eval> if unsure.	498	C<eval> if unsure.
485		499
486	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	500	In the second form (another port given), the other port (C<$rcvport>)
487	a @reason was specified, i.e. on "normal" kils nothing happens, while	501	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
488	under all other conditions, the other port is killed with the same reason.	502	"normal" kils nothing happens, while under all other conditions, the other
		503	port is killed with the same reason.
489		504
		505	The third form (kill self) is the same as the second form, except that
		506	C<$rvport> defaults to C<$SELF>.
		507
490	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	508	In the last form (message), a message of the form C<@msg, @reason> will be
		509	C<snd>.
		510
		511	As a rule of thumb, monitoring requests should always monitor a port from
		512	a local port (or callback). The reason is that kill messages might get
		513	lost, just like any other message. Another less obvious reason is that
		514	even monitoring requests can get lost (for exmaple, when the connection
		515	to the other node goes down permanently). When monitoring a port locally
		516	these problems do not exist.
491		517
492	Example: call a given callback when C<$port> is killed.	518	Example: call a given callback when C<$port> is killed.
493		519
494	mon $port, sub { warn "port died because of <@_>\n" };	520	mon $port, sub { warn "port died because of <@_>\n" };
495		521
496	Example: kill ourselves when C<$port> is killed abnormally.	522	Example: kill ourselves when C<$port> is killed abnormally.
497		523
498	mon $port, $self;	524	mon $port;
499		525
500	Example: send us a restart message another C<$port> is killed.	526	Example: send us a restart message when another C<$port> is killed.
501		527
502	mon $port, $self => "restart";	528	mon $port, $self => "restart";
503		529
504	=cut	530	=cut
505		531
506	sub mon {	532	sub mon {
507	my ($noderef, $port) = split /#/, shift, 2;	533	my ($noderef, $port) = split /#/, shift, 2;
508		534
509	my $node = $NODE{$noderef} \|\| add_node $noderef;	535	my $node = $NODE{$noderef} \|\| add_node $noderef;
510		536
511	my $cb = shift;	537	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
512		538
513	unless (ref $cb) {	539	unless (ref $cb) {
514	if (@_) {	540	if (@_) {
515	# send a kill info message	541	# send a kill info message
516	my (@msg) = ($cb, @_);	542	my (@msg) = ($cb, @_);
…		…
547	=cut	573	=cut
548		574
549	sub mon_guard {	575	sub mon_guard {
550	my ($port, @refs) = @_;	576	my ($port, @refs) = @_;
551		577
		578	#TODO: mon-less form?
		579
552	mon $port, sub { 0 && @refs }	580	mon $port, sub { 0 && @refs }
553	}	581	}
554		582
555	=item lnk $port1, $port2
556
557	Link two ports. This is simply a shorthand for:
558
559	mon $port1, $port2;
560	mon $port2, $port1;
561
562	It means that if either one is killed abnormally, the other one gets
563	killed as well.
564
565	=item kil $port[, @reason]	583	=item kil $port[, @reason]
566		584
567	Kill the specified port with the given C<@reason>.	585	Kill the specified port with the given C<@reason>.
568		586
569	If no C<@reason> is specified, then the port is killed "normally" (linked	587	If no C<@reason> is specified, then the port is killed "normally" (linked
…		…
575	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	593	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
576	will be reported as reason C<< die => $@ >>.	594	will be reported as reason C<< die => $@ >>.
577		595
578	Transport/communication errors are reported as C<< transport_error =>	596	Transport/communication errors are reported as C<< transport_error =>
579	$message >>.	597	$message >>.
		598
		599	=cut
		600
		601	=item $port = spawn $node, $initfunc[, @initdata]
		602
		603	Creates a port on the node C<$node> (which can also be a port ID, in which
		604	case it's the node where that port resides).
		605
		606	The port ID of the newly created port is return immediately, and it is
		607	permissible to immediately start sending messages or monitor the port.
		608
		609	After the port has been created, the init function is
		610	called. This function must be a fully-qualified function name
		611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		612	program, use C<::name>.
		613
		614	If the function doesn't exist, then the node tries to C<require>
		615	the package, then the package above the package and so on (e.g.
		616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		617	exists or it runs out of package names.
		618
		619	The init function is then called with the newly-created port as context
		620	object (C<$SELF>) and the C<@initdata> values as arguments.
		621
		622	A common idiom is to pass your own port, monitor the spawned port, and
		623	in the init function, monitor the original port. This two-way monitoring
		624	ensures that both ports get cleaned up when there is a problem.
		625
		626	Example: spawn a chat server port on C<$othernode>.
		627
		628	# this node, executed from within a port context:
		629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		630	mon $server;
		631
		632	# init function on C<$othernode>
		633	sub connect {
		634	my ($srcport) = @_;
		635
		636	mon $srcport;
		637
		638	rcv $SELF, sub {
		639	...
		640	};
		641	}
		642
		643	=cut
		644
		645	sub _spawn {
		646	my $port = shift;
		647	my $init = shift;
		648
		649	local $SELF = "$NODE#$port";
		650	eval {
		651	&{ load_func $init }
		652	};
		653	_self_die if $@;
		654	}
		655
		656	sub spawn(@) {
		657	my ($noderef, undef) = split /#/, shift, 2;
		658
		659	my $id = "$RUNIQ." . $ID++;
		660
		661	$_[0] =~ /::/
		662	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		663
		664	($NODE{$noderef} \|\| add_node $noderef)
		665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
		666
		667	"$noderef#$id"
		668	}
580		669
581	=back	670	=back
582		671
583	=head1 NODE MESSAGES	672	=head1 NODE MESSAGES
584		673
…		…
649	convenience functionality.	738	convenience functionality.
650		739
651	This means that AEMP requires a less tightly controlled environment at the	740	This means that AEMP requires a less tightly controlled environment at the
652	cost of longer node references and a slightly higher management overhead.	741	cost of longer node references and a slightly higher management overhead.
653		742
		743	=item Erlang has a "remote ports are like local ports" philosophy, AEMP
		744	uses "local ports are like remote ports".
		745
		746	The failure modes for local ports are quite different (runtime errors
		747	only) then for remote ports - when a local port dies, you I<know> it dies,
		748	when a connection to another node dies, you know nothing about the other
		749	port.
		750
		751	Erlang pretends remote ports are as reliable as local ports, even when
		752	they are not.
		753
		754	AEMP encourages a "treat remote ports differently" philosophy, with local
		755	ports being the special case/exception, where transport errors cannot
		756	occur.
		757
654	=item * Erlang uses processes and a mailbox, AEMP does not queue.	758	=item * Erlang uses processes and a mailbox, AEMP does not queue.
655		759
656	Erlang uses processes that selctively receive messages, and therefore	760	Erlang uses processes that selectively receive messages, and therefore
657	needs a queue. AEMP is event based, queuing messages would serve no useful	761	needs a queue. AEMP is event based, queuing messages would serve no
658	purpose.	762	useful purpose. For the same reason the pattern-matching abilities of
		763	AnyEvent::MP are more limited, as there is little need to be able to
		764	filter messages without dequeing them.
659		765
660	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
661		767
662	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
663		769
664	Sending messages in Erlang is synchronous and blocks the process. AEMP	770	Sending messages in Erlang is synchronous and blocks the process (and
665	sends are immediate, connection establishment is handled in the	771	so does not need a queue that can overflow). AEMP sends are immediate,
666	background.	772	connection establishment is handled in the background.
667		773
668	=item * Erlang can silently lose messages, AEMP cannot.	774	=item * Erlang suffers from silent message loss, AEMP does not.
669		775
670	Erlang makes few guarantees on messages delivery - messages can get lost	776	Erlang makes few guarantees on messages delivery - messages can get lost
671	without any of the processes realising it (i.e. you send messages a, b,	777	without any of the processes realising it (i.e. you send messages a, b,
672	and c, and the other side only receives messages a and c).	778	and c, and the other side only receives messages a and c).
673		779
…		…
685	eventually be killed - it cannot happen that a node detects a port as dead	791	eventually be killed - it cannot happen that a node detects a port as dead
686	and then later sends messages to it, finding it is still alive.	792	and then later sends messages to it, finding it is still alive.
687		793
688	=item * Erlang can send messages to the wrong port, AEMP does not.	794	=item * Erlang can send messages to the wrong port, AEMP does not.
689		795
690	In Erlang it is quite possible that a node that restarts reuses a process	796	In Erlang it is quite likely that a node that restarts reuses a process ID
691	ID known to other nodes for a completely different process, causing	797	known to other nodes for a completely different process, causing messages
692	messages destined for that process to end up in an unrelated process.	798	destined for that process to end up in an unrelated process.
693		799
694	AEMP never reuses port IDs, so old messages or old port IDs floating	800	AEMP never reuses port IDs, so old messages or old port IDs floating
695	around in the network will not be sent to an unrelated port.	801	around in the network will not be sent to an unrelated port.
696		802
697	=item * Erlang uses unprotected connections, AEMP uses secure	803	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
717	or I<none>, there is no in-between, so monitoring single processes is	823	or I<none>, there is no in-between, so monitoring single processes is
718	difficult to implement. Monitoring in AEMP is more flexible than in	824	difficult to implement. Monitoring in AEMP is more flexible than in
719	Erlang, as one can choose between automatic kill, exit message or callback	825	Erlang, as one can choose between automatic kill, exit message or callback
720	on a per-process basis.	826	on a per-process basis.
721		827
722	=item * Erlang has different semantics for monitoring and linking, AEMP has the same.	828	=item * Erlang tries to hide remote/local connections, AEMP does not.
723		829
724	Monitoring in Erlang is not an indicator of process death/crashes,	830	Monitoring in Erlang is not an indicator of process death/crashes,
725	as linking is (except linking is unreliable in Erlang). In AEMP, the	831	as linking is (except linking is unreliable in Erlang).
726	semantics of monitoring and linking are identical, linking is simply	832
727	two-way monitoring with automatic kill.	833	In AEMP, you don't "look up" registered port names or send to named ports
		834	that might or might not be persistent. Instead, you normally spawn a port
		835	on the remote node. The init function monitors the you, and you monitor
		836	the remote port. Since both monitors are local to the node, they are much
		837	more reliable.
		838
		839	This also saves round-trips and avoids sending messages to the wrong port
		840	(hard to do in Erlang).
		841
		842	=back
		843
		844	=head1 RATIONALE
		845
		846	=over 4
		847
		848	=item Why strings for ports and noderefs, why not objects?
		849
		850	We considered "objects", but found that the actual number of methods
		851	thatc an be called are very low. Since port IDs and noderefs travel over
		852	the network frequently, the serialising/deserialising would add lots of
		853	overhead, as well as having to keep a proxy object.
		854
		855	Strings can easily be printed, easily serialised etc. and need no special
		856	procedures to be "valid".
		857
		858	And a a miniport consists of a single closure stored in a global hash - it
		859	can't become much cheaper.
		860
		861	=item Why favour JSON, why not real serialising format such as Storable?
		862
		863	In fact, any AnyEvent::MP node will happily accept Storable as framing
		864	format, but currently there is no way to make a node use Storable by
		865	default.
		866
		867	The default framing protocol is JSON because a) JSON::XS is many times
		868	faster for small messages and b) most importantly, after years of
		869	experience we found that object serialisation is causing more problems
		870	than it gains: Just like function calls, objects simply do not travel
		871	easily over the network, mostly because they will always be a copy, so you
		872	always have to re-think your design.
		873
		874	Keeping your messages simple, concentrating on data structures rather than
		875	objects, will keep your messages clean, tidy and efficient.
728		876
729	=back	877	=back
730		878
731	=head1 SEE ALSO	879	=head1 SEE ALSO
732		880

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Revision 1.51 by root, Fri Aug 14 14:07:44 2009 UTC