[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 1.50 by root, Fri Aug 14 14:01:05 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		46	AnyEvent::MP::Intro - outdated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	=item reg $name
311
312	Registers the given port (or C<$SELF><<< if missing) under the name
313	C<$name>. If the name already exists it is replaced.
314
315	A port can only be registered under one well known name.
316
317	A port automatically becomes unregistered when it is killed.
318
319	=cut
320
321	sub reg(@) {
322	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
323
324	$REG{$_[0]} = $port;
325	}
326
327	=item rcv $port, $callback->(@msg)	341	=item rcv $local_port, $callback->(@msg)
328		342
329	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
330	one if required).	344	remove the default callback: use C<sub { }> to disable it, or better
331		345	C<kil> the port when it is no longer needed.
332	=item rcv $port, tagstring => $callback->(@msg), ...
333
334	=item rcv $port, $smartmatch => $callback->(@msg), ...
335
336	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
337
338	Register callbacks to be called on matching messages on the given full
339	port (after converting it to one if required) and return the port.
340
341	The callback has to return a true value when its work is done, after
342	which is will be removed, or a false value in which case it will stay
343	registered.
344		346
345	The global C<$SELF> (exported by this module) contains C<$port> while	347	The global C<$SELF> (exported by this module) contains C<$port> while
346	executing the callback.	348	executing the callback. Runtime errors during callback execution will
		349	result in the port being C<kil>ed.
347		350
348	Runtime errors wdurign callback execution will result in the port being	351	The default callback received all messages not matched by a more specific
349	C<kil>ed.	352	C<tag> match.
350		353
351	If the match is an array reference, then it will be matched against the	354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
352	first elements of the message, otherwise only the first element is being
353	matched.
354		355
355	Any element in the match that is specified as C<_any_> (a function	356	Register callbacks to be called on messages starting with the given tag on
356	exported by this module) matches any single element of the message.	357	the given port (and return the port), or unregister it (when C<$callback>
		358	is C<$undef>).
357		359
358	While not required, it is highly recommended that the first matching	360	The original message will be passed to the callback, after the first
359	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
360	also the most efficient match (by far).	362	environment as the default callback (see above).
361		363
362	Example: create a port and bind receivers on it in one go.	364	Example: create a port and bind receivers on it in one go.
363		365
364	my $port = rcv port,	366	my $port = rcv port,
365	msg1 => sub { ...; 0 },	367	msg1 => sub { ... },
366	msg2 => sub { ...; 0 },	368	msg2 => sub { ... },
367	;	369	;
368		370
369	Example: create a port, bind receivers and send it in a message elsewhere	371	Example: create a port, bind receivers and send it in a message elsewhere
370	in one go:	372	in one go:
371		373
372	snd $otherport, reply =>	374	snd $otherport, reply =>
373	rcv port,	375	rcv port,
374	msg1 => sub { ...; 0 },	376	msg1 => sub { ... },
375	...	377	...
376	;	378	;
377		379
378	=cut	380	=cut
379		381
…		…
382	my ($noderef, $portid) = split /#/, $port, 2;	384	my ($noderef, $portid) = split /#/, $port, 2;
383		385
384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
385	or Carp::croak "$port: rcv can only be called on local ports, caught";	387	or Carp::croak "$port: rcv can only be called on local ports, caught";
386		388
387	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 {
388	my $cb = shift;	397	my $cb = shift;
389	delete $PORT_DATA{$portid};
390	$PORT{$portid} = sub {	398	$PORT{$portid} = sub {
391	local $SELF = $port;	399	local $SELF = $port;
392	eval {	400	eval { &$cb }; _self_die if $@;
393	&$cb	401	};
394	and kil $port;
395	};	402	}
396	_self_die if $@;	403	} elsif (defined $_[0]) {
397	};
398	} else {
399	my $self = $PORT_DATA{$portid} \|\|= do {	404	my $self = $PORT_DATA{$portid} \|\|= do {
400	my $self = bless {	405	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
401	id => $port,
402	}, "AnyEvent::MP::Port";
403		406
404	$PORT{$portid} = sub {	407	$PORT{$portid} = sub {
405	local $SELF = $port;	408	local $SELF = $port;
406		409
407	eval {
408	for (@{ $self->{rc0}{$_[0]} }) {	410	if (my $cb = $self->[1]{$_[0]}) {
409	$_ && &{$_->[0]}	411	shift;
410	&& undef $_;	412	eval { &$cb }; _self_die if $@;
411	}	413	} else {
412
413	for (@{ $self->{rcv}{$_[0]} }) {
414	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
415	&& &{$_->[0]}	414	&{ $self->[0] };
416	&& undef $_;
417	}
418
419	for (@{ $self->{any} }) {
420	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
421	&& &{$_->[0]}
422	&& undef $_;
423	}	415	}
424	};	416	};
425	_self_die if $@;	417
		418	$self
426	};	419	};
427		420
428	$self
429	};
430
431	"AnyEvent::MP::Port" eq ref $self	421	"AnyEvent::MP::Port" eq ref $self
432	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	422	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
433		423
434	while (@_) {
435	my ($match, $cb) = splice @_, 0, 2;	424	my ($tag, $cb) = splice @_, 0, 2;
436		425
437	if (!ref $match) {	426	if (defined $cb) {
438	push @{ $self->{rc0}{$match} }, [$cb];	427	$self->[1]{$tag} = $cb;
439	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
440	my ($type, @match) = @$match;
441	@match
442	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
443	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
444	} else {	428	} else {
445	push @{ $self->{any} }, [$cb, $match];	429	delete $self->[1]{$tag};
446	}	430	}
447	}	431	}
448	}	432	}
449		433
450	$port	434	$port
…		…
494		478
495	=item $guard = mon $port	479	=item $guard = mon $port
496		480
497	=item $guard = mon $port, $rcvport, @msg	481	=item $guard = mon $port, $rcvport, @msg
498		482
499	Monitor the given port and do something when the port is killed, and	483	Monitor the given port and do something when the port is killed or
500	optionally return a guard that can be used to stop monitoring again.	484	messages to it were lost, and optionally return a guard that can be used
		485	to stop monitoring again.
		486
		487	C<mon> effectively guarantees that, in the absence of hardware failures,
		488	that after starting the monitor, either all messages sent to the port
		489	will arrive, or the monitoring action will be invoked after possible
		490	message loss has been detected. No messages will be lost "in between"
		491	(after the first lost message no further messages will be received by the
		492	port). After the monitoring action was invoked, further messages might get
		493	delivered again.
501		494
502	In the first form (callback), the callback is simply called with any	495	In the first form (callback), the callback is simply called with any
503	number of C<@reason> elements (no @reason means that the port was deleted	496	number of C<@reason> elements (no @reason means that the port was deleted
504	"normally"). Note also that I<< the callback B<must> never die >>, so use	497	"normally"). Note also that I<< the callback B<must> never die >>, so use
505	C<eval> if unsure.	498	C<eval> if unsure.
506		499
507	In the second form (another port given), the other port (C<$rcvport)	500	In the second form (another port given), the other port (C<$rcvport>)
508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	501	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
509	"normal" kils nothing happens, while under all other conditions, the other	502	"normal" kils nothing happens, while under all other conditions, the other
510	port is killed with the same reason.	503	port is killed with the same reason.
511		504
512	The third form (kill self) is the same as the second form, except that	505	The third form (kill self) is the same as the second form, except that
513	C<$rvport> defaults to C<$SELF>.	506	C<$rvport> defaults to C<$SELF>.
514		507
515	In the last form (message), a message of the form C<@msg, @reason> will be	508	In the last form (message), a message of the form C<@msg, @reason> will be
516	C<snd>.	509	C<snd>.
517		510
		511	As a rule of thumb, monitoring requests should always monitor a port from
		512	a local port (or callback). The reason is that kill messages might get
		513	lost, just like any other message. Another less obvious reason is that
		514	even monitoring requests can get lost (for exmaple, when the connection
		515	to the other node goes down permanently). When monitoring a port locally
		516	these problems do not exist.
		517
518	Example: call a given callback when C<$port> is killed.	518	Example: call a given callback when C<$port> is killed.
519		519
520	mon $port, sub { warn "port died because of <@_>\n" };	520	mon $port, sub { warn "port died because of <@_>\n" };
521		521
522	Example: kill ourselves when C<$port> is killed abnormally.	522	Example: kill ourselves when C<$port> is killed abnormally.
…		…
532	sub mon {	532	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	533	my ($noderef, $port) = split /#/, shift, 2;
534		534
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	535	my $node = $NODE{$noderef} \|\| add_node $noderef;
536		536
537	my $cb = @_ ? $_[0] : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	537	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
538		538
539	unless (ref $cb) {	539	unless (ref $cb) {
540	if (@_) {	540	if (@_) {
541	# send a kill info message	541	# send a kill info message
542	my (@msg) = @_;	542	my (@msg) = ($cb, @_);
543	$cb = sub { snd @msg, @_ };	543	$cb = sub { snd @msg, @_ };
544	} else {	544	} else {
545	# simply kill other port	545	# simply kill other port
546	my $port = $cb;	546	my $port = $cb;
547	$cb = sub { kil $port, @_ if @_ };	547	$cb = sub { kil $port, @_ if @_ };
…		…
578	#TODO: mon-less form?	578	#TODO: mon-less form?
579		579
580	mon $port, sub { 0 && @refs }	580	mon $port, sub { 0 && @refs }
581	}	581	}
582		582
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]	583	=item kil $port[, @reason]
608		584
609	Kill the specified port with the given C<@reason>.	585	Kill the specified port with the given C<@reason>.
610		586
611	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
…		…
617	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
618	will be reported as reason C<< die => $@ >>.	594	will be reported as reason C<< die => $@ >>.
619		595
620	Transport/communication errors are reported as C<< transport_error =>	596	Transport/communication errors are reported as C<< transport_error =>
621	$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	}
622		669
623	=back	670	=back
624		671
625	=head1 NODE MESSAGES	672	=head1 NODE MESSAGES
626		673
…		…
759	or I<none>, there is no in-between, so monitoring single processes is	806	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	807	difficult to implement. Monitoring in AEMP is more flexible than in
761	Erlang, as one can choose between automatic kill, exit message or callback	808	Erlang, as one can choose between automatic kill, exit message or callback
762	on a per-process basis.	809	on a per-process basis.
763		810
764	=item * Erlang has different semantics for monitoring and linking, AEMP has the same.	811	=item * Erlang tries to hide remote/local connections, AEMP does not.
765		812
766	Monitoring in Erlang is not an indicator of process death/crashes,	813	Monitoring in Erlang is not an indicator of process death/crashes,
767	as linking is (except linking is unreliable in Erlang). In AEMP, the	814	as linking is (except linking is unreliable in Erlang).
768	semantics of monitoring and linking are identical, linking is simply	815
769	two-way monitoring with automatic kill.	816	In AEMP, you don't "look up" registered port names or send to named ports
		817	that might or might not be persistent. Instead, you normally spawn a port
		818	on the remote node. The init function monitors the you, and you monitor
		819	the remote port. Since both monitors are local to the node, they are much
		820	more reliable.
		821
		822	This also saves round-trips and avoids sending messages to the wrong port
		823	(hard to do in Erlang).
		824
		825	=back
		826
		827	=head1 RATIONALE
		828
		829	=over 4
		830
		831	=item Why strings for ports and noderefs, why not objects?
		832
		833	We considered "objects", but found that the actual number of methods
		834	thatc an be called are very low. Since port IDs and noderefs travel over
		835	the network frequently, the serialising/deserialising would add lots of
		836	overhead, as well as having to keep a proxy object.
		837
		838	Strings can easily be printed, easily serialised etc. and need no special
		839	procedures to be "valid".
		840
		841	And a a miniport consists of a single closure stored in a global hash - it
		842	can't become much cheaper.
		843
		844	=item Why favour JSON, why not real serialising format such as Storable?
		845
		846	In fact, any AnyEvent::MP node will happily accept Storable as framing
		847	format, but currently there is no way to make a node use Storable by
		848	default.
		849
		850	The default framing protocol is JSON because a) JSON::XS is many times
		851	faster for small messages and b) most importantly, after years of
		852	experience we found that object serialisation is causing more problems
		853	than it gains: Just like function calls, objects simply do not travel
		854	easily over the network, mostly because they will always be a copy, so you
		855	always have to re-think your design.
		856
		857	Keeping your messages simple, concentrating on data structures rather than
		858	objects, will keep your messages clean, tidy and efficient.
770		859
771	=back	860	=back
772		861
773	=head1 SEE ALSO	862	=head1 SEE ALSO
774		863

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Revision 1.36 by root, Thu Aug 6 10:46:48 2009 UTC vs.
Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC