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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.34 by root, Wed Aug 5 23:50:46 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	37
		38	# monitoring
		39	mon $port, $cb->(@msg) # callback is invoked on death
		40	mon $port, $otherport # kill otherport on abnormal death
		41	mon $port, $otherport, @msg # send message on death
		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		46	AnyEvent::MP::Intro - outdated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.
27		51
28	=head1 DESCRIPTION	52	=head1 DESCRIPTION
29		53
30	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
31		55
…		…
35	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>
36	manual page.	60	manual page.
37		61
38	At the moment, this module family is severly broken and underdocumented,	62	At the moment, this module family is severly broken and underdocumented,
39	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 -
40	stay tuned! The basic API should be finished, however.	64	stay tuned!
41		65
42	=head1 CONCEPTS	66	=head1 CONCEPTS
43		67
44	=over 4	68	=over 4
45		69
…		…
90		114
91	=cut	115	=cut
92		116
93	package AnyEvent::MP;	117	package AnyEvent::MP;
94		118
95	use AnyEvent::MP::Base;	119	use AnyEvent::MP::Kernel;
96		120
97	use common::sense;	121	use common::sense;
98		122
99	use Carp ();	123	use Carp ();
100		124
101	use AE ();	125	use AE ();
102		126
103	use base "Exporter";	127	use base "Exporter";
104		128
105	our $VERSION = '0.1';	129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		130
106	our @EXPORT = qw(	131	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	132	NODE $NODE *SELF node_of _any_
108	resolve_node initialise_node	133	resolve_node initialise_node
109	snd rcv mon kil reg psub	134	snd rcv mon kil reg psub spawn
110	port	135	port
111	);	136	);
112		137
113	our $SELF;	138	our $SELF;
114		139
…		…
138	it should know the noderefs of some other nodes in the network.	163	it should know the noderefs of some other nodes in the network.
139		164
140	This function initialises a node - it must be called exactly once (or	165	This function initialises a node - it must be called exactly once (or
141	never) before calling other AnyEvent::MP functions.	166	never) before calling other AnyEvent::MP functions.
142		167
143	All arguments are noderefs, which can be either resolved or unresolved.	168	All arguments (optionally except for the first) are noderefs, which can be
		169	either resolved or unresolved.
		170
		171	The first argument will be looked up in the configuration database first
		172	(if it is C<undef> then the current nodename will be used instead) to find
		173	the relevant configuration profile (see L<aemp>). If none is found then
		174	the default configuration is used. The configuration supplies additional
		175	seed/master nodes and can override the actual noderef.
144		176
145	There are two types of networked nodes, public nodes and slave nodes:	177	There are two types of networked nodes, public nodes and slave nodes:
146		178
147	=over 4	179	=over 4
148		180
149	=item public nodes	181	=item public nodes
150		182
151	For public nodes, C<$noderef> must either be a (possibly unresolved)	183	For public nodes, C<$noderef> (supplied either directly to
152	noderef, in which case it will be resolved, or C<undef> (or missing), in	184	C<initialise_node> or indirectly via a profile or the nodename) must be a
153	which case the noderef will be guessed.	185	noderef (possibly unresolved, in which case it will be resolved).
154		186
155	Afterwards, the node will bind itself on all endpoints and try to connect	187	After resolving, the node will bind itself on all endpoints and try to
156	to all additional C<$seednodes> that are specified. Seednodes are optional	188	connect to all additional C<$seednodes> that are specified. Seednodes are
157	and can be used to quickly bootstrap the node into an existing network.	189	optional and can be used to quickly bootstrap the node into an existing
		190	network.
158		191
159	=item slave nodes	192	=item slave nodes
160		193
161	When the C<$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
162	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
163	route most of their traffic to the master node that they attach to.	197	their traffic to the master node that they attach to.
164		198
165	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
166	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
167	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.
168		203
169	=back	204	=back
170		205
171	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
172	nodes, until it has successfully established a connection to a master	207	nodes, until it has successfully established a connection to a master
173	server.	208	server.
174		209
175	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.
176		213
177	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";
178		225
179	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
180	servers to become part of the network.	227	servers to become part of the network.
181		228
182	initialise_node undef, "master1", "master2";	229	initialise_node undef, "master1", "master2";
…		…
185		232
186	initialise_node 4041;	233	initialise_node 4041;
187		234
188	Example: become a public node, only visible on localhost port 4044.	235	Example: become a public node, only visible on localhost port 4044.
189		236
190	initialise_node "locahost:4044";	237	initialise_node "localhost:4044";
191
192	Example: become a slave node to any of the specified master servers.
193
194	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
195		238
196	=item $cv = resolve_node $noderef	239	=item $cv = resolve_node $noderef
197		240
198	Takes an unresolved node reference that may contain hostnames and	241	Takes an unresolved node reference that may contain hostnames and
199	abbreviated IDs, resolves all of them and returns a resolved node	242	abbreviated IDs, resolves all of them and returns a resolved node
…		…
255	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
256	node, anything can be passed.	299	node, anything can be passed.
257		300
258	=item $local_port = port	301	=item $local_port = port
259		302
260	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
261	matching port ("full port") or a single-callback port ("miniport"),	304	no callbacks set and will throw an error when it receives messages.
262	depending on how C<rcv> callbacks are bound to the object.
263		305
264	=item $port = port { my @msg = @_; $finished }	306	=item $local_port = port { my @msg = @_ }
265		307
266	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
267	matching behind it, and returns its ID. Semantically the same as creating
268	a port and calling C<rcv $port, $callback> on it.	309	creating a port and calling C<rcv $port, $callback> on it.
269		310
270	The block will be called for every message received on the port. When the	311	The block will be called for every message received on the port, with the
271	callback returns a true value its job is considered "done" and the port	312	global variable C<$SELF> set to the port ID. Runtime errors will cause the
272	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.
273		315
274	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:
275	be passed to the callback.
276		317
277	If you need the local port id in the callback, this works nicely:	318	my $port = port {
278		319	my @msg = @_;
279	my $port; $port = port {	320	...
280	snd $otherport, reply => $port;	321	kil $SELF;
281	};	322	};
282		323
283	=cut	324	=cut
284		325
285	sub rcv($@);	326	sub rcv($@);
		327
		328	sub _kilme {
		329	die "received message on port without callback";
		330	}
286		331
287	sub port(;&) {	332	sub port(;&) {
288	my $id = "$UNIQ." . $ID++;	333	my $id = "$UNIQ." . $ID++;
289	my $port = "$NODE#$id";	334	my $port = "$NODE#$id";
290		335
291	if (@_) {	336	rcv $port, shift \|\| \&_kilme;
292	rcv $port, shift;
293	} else {
294	$PORT{$id} = sub { }; # nop
295	}
296		337
297	$port	338	$port
298	}	339	}
299		340
300	=item reg $port, $name
301
302	Registers the given port under the name C<$name>. If the name already
303	exists it is replaced.
304
305	A port can only be registered under one well known name.
306
307	A port automatically becomes unregistered when it is killed.
308
309	=cut
310
311	sub reg(@) {
312	my ($port, $name) = @_;
313
314	$REG{$name} = $port;
315	}
316
317	=item rcv $port, $callback->(@msg)	341	=item rcv $local_port, $callback->(@msg)
318		342
319	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
320	one if required).	344	remove the default callback: use C<sub { }> to disable it, or better
321		345	C<kil> the port when it is no longer needed.
322	=item rcv $port, tagstring => $callback->(@msg), ...
323
324	=item rcv $port, $smartmatch => $callback->(@msg), ...
325
326	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
327
328	Register callbacks to be called on matching messages on the given full
329	port (after converting it to one if required).
330
331	The callback has to return a true value when its work is done, after
332	which is will be removed, or a false value in which case it will stay
333	registered.
334		346
335	The global C<$SELF> (exported by this module) contains C<$port> while	347	The global C<$SELF> (exported by this module) contains C<$port> while
336	executing the callback.	348	executing the callback. Runtime errors during callback execution will
		349	result in the port being C<kil>ed.
337		350
338	Runtime errors wdurign callback execution will result in the port being	351	The default callback received all messages not matched by a more specific
339	C<kil>ed.	352	C<tag> match.
340		353
341	If the match is an array reference, then it will be matched against the	354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
342	first elements of the message, otherwise only the first element is being
343	matched.
344		355
345	Any element in the match that is specified as C<_any_> (a function	356	Register callbacks to be called on messages starting with the given tag on
346	exported by this module) matches any single element of the message.	357	the given port (and return the port), or unregister it (when C<$callback>
		358	is C<$undef>).
347		359
348	While not required, it is highly recommended that the first matching	360	The original message will be passed to the callback, after the first
349	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
350	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 $otherport, reply =>
		375	rcv port,
		376	msg1 => sub { ... },
		377	...
		378	;
351		379
352	=cut	380	=cut
353		381
354	sub rcv($@) {	382	sub rcv($@) {
355	my $port = shift;	383	my $port = shift;
356	my ($noderef, $portid) = split /#/, $port, 2;	384	my ($noderef, $portid) = split /#/, $port, 2;
357		385
358	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
359	or Carp::croak "$port: rcv can only be called on local ports, caught";	387	or Carp::croak "$port: rcv can only be called on local ports, caught";
360		388
361	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 {
362	my $cb = shift;	397	my $cb = shift;
363	delete $PORT_DATA{$portid};
364	$PORT{$portid} = sub {	398	$PORT{$portid} = sub {
365	local $SELF = $port;	399	local $SELF = $port;
366	eval {	400	eval { &$cb }; _self_die if $@;
367	&$cb	401	};
368	and kil $port;
369	};	402	}
370	_self_die if $@;	403	} elsif (defined $_[0]) {
371	};
372	} else {
373	my $self = $PORT_DATA{$portid} \|\|= do {	404	my $self = $PORT_DATA{$portid} \|\|= do {
374	my $self = bless {	405	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
375	id => $port,
376	}, "AnyEvent::MP::Port";
377		406
378	$PORT{$portid} = sub {	407	$PORT{$portid} = sub {
379	local $SELF = $port;	408	local $SELF = $port;
380		409
381	eval {
382	for (@{ $self->{rc0}{$_[0]} }) {	410	if (my $cb = $self->[1]{$_[0]}) {
383	$_ && &{$_->[0]}	411	shift;
384	&& undef $_;	412	eval { &$cb }; _self_die if $@;
385	}	413	} else {
386
387	for (@{ $self->{rcv}{$_[0]} }) {
388	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
389	&& &{$_->[0]}	414	&{ $self->[0] };
390	&& undef $_;
391	}
392
393	for (@{ $self->{any} }) {
394	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
395	&& &{$_->[0]}
396	&& undef $_;
397	}	415	}
398	};	416	};
399	_self_die if $@;	417
		418	$self
400	};	419	};
401		420
402	$self
403	};
404
405	"AnyEvent::MP::Port" eq ref $self	421	"AnyEvent::MP::Port" eq ref $self
406	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	422	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
407		423
408	while (@_) {
409	my ($match, $cb) = splice @_, 0, 2;	424	my ($tag, $cb) = splice @_, 0, 2;
410		425
411	if (!ref $match) {	426	if (defined $cb) {
412	push @{ $self->{rc0}{$match} }, [$cb];	427	$self->[1]{$tag} = $cb;
413	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
414	my ($type, @match) = @$match;
415	@match
416	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
417	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
418	} else {	428	} else {
419	push @{ $self->{any} }, [$cb, $match];	429	delete $self->[1]{$tag};
420	}	430	}
421	}	431	}
422	}	432	}
423		433
424	$port	434	$port
…		…
462	}	472	}
463	}	473	}
464		474
465	=item $guard = mon $port, $cb->(@reason)	475	=item $guard = mon $port, $cb->(@reason)
466		476
467	=item $guard = mon $port, $otherport	477	=item $guard = mon $port, $rcvport
468		478
		479	=item $guard = mon $port
		480
469	=item $guard = mon $port, $otherport, @msg	481	=item $guard = mon $port, $rcvport, @msg
470		482
471	Monitor the given port and do something when the port is killed.	483	Monitor the given port and do something when the port is killed or
		484	messages to it were lost, and optionally return a guard that can be used
		485	to stop monitoring again.
472		486
		487	C<mon> effectively guarantees that, in the absence of hardware failures,
		488	that after starting the monitor, either all messages sent to the port
		489	will arrive, or the monitoring action will be invoked after possible
		490	message loss has been detected. No messages will be lost "in between"
		491	(after the first lost message no further messages will be received by the
		492	port). After the monitoring action was invoked, further messages might get
		493	delivered again.
		494
473	In the first form, the callback is simply called with any number	495	In the first form (callback), the callback is simply called with any
474	of C<@reason> elements (no @reason means that the port was deleted	496	number of C<@reason> elements (no @reason means that the port was deleted
475	"normally"). Note also that I<< the callback B<must> never die >>, so use	497	"normally"). Note also that I<< the callback B<must> never die >>, so use
476	C<eval> if unsure.	498	C<eval> if unsure.
477		499
478	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	500	In the second form (another port given), the other port (C<$rcvport>)
479	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
480	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.
481		504
		505	The third form (kill self) is the same as the second form, except that
		506	C<$rvport> defaults to C<$SELF>.
		507
482	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.
483		517
484	Example: call a given callback when C<$port> is killed.	518	Example: call a given callback when C<$port> is killed.
485		519
486	mon $port, sub { warn "port died because of <@_>\n" };	520	mon $port, sub { warn "port died because of <@_>\n" };
487		521
488	Example: kill ourselves when C<$port> is killed abnormally.	522	Example: kill ourselves when C<$port> is killed abnormally.
489		523
490	mon $port, $self;	524	mon $port;
491		525
492	Example: send us a restart message another C<$port> is killed.	526	Example: send us a restart message when another C<$port> is killed.
493		527
494	mon $port, $self => "restart";	528	mon $port, $self => "restart";
495		529
496	=cut	530	=cut
497		531
498	sub mon {	532	sub mon {
499	my ($noderef, $port) = split /#/, shift, 2;	533	my ($noderef, $port) = split /#/, shift, 2;
500		534
501	my $node = $NODE{$noderef} \|\| add_node $noderef;	535	my $node = $NODE{$noderef} \|\| add_node $noderef;
502		536
503	my $cb = shift;	537	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
504		538
505	unless (ref $cb) {	539	unless (ref $cb) {
506	if (@_) {	540	if (@_) {
507	# send a kill info message	541	# send a kill info message
508	my (@msg) = ($cb, @_);	542	my (@msg) = ($cb, @_);
…		…
539	=cut	573	=cut
540		574
541	sub mon_guard {	575	sub mon_guard {
542	my ($port, @refs) = @_;	576	my ($port, @refs) = @_;
543		577
		578	#TODO: mon-less form?
		579
544	mon $port, sub { 0 && @refs }	580	mon $port, sub { 0 && @refs }
545	}	581	}
546		582
547	=item lnk $port1, $port2
548
549	Link two ports. This is simply a shorthand for:
550
551	mon $port1, $port2;
552	mon $port2, $port1;
553
554	It means that if either one is killed abnormally, the other one gets
555	killed as well.
556
557	=item kil $port[, @reason]	583	=item kil $port[, @reason]
558		584
559	Kill the specified port with the given C<@reason>.	585	Kill the specified port with the given C<@reason>.
560		586
561	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
…		…
567	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
568	will be reported as reason C<< die => $@ >>.	594	will be reported as reason C<< die => $@ >>.
569		595
570	Transport/communication errors are reported as C<< transport_error =>	596	Transport/communication errors are reported as C<< transport_error =>
571	$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	}
572		669
573	=back	670	=back
574		671
575	=head1 NODE MESSAGES	672	=head1 NODE MESSAGES
576		673
…		…
618		715
619	=back	716	=back
620		717
621	=head1 AnyEvent::MP vs. Distributed Erlang	718	=head1 AnyEvent::MP vs. Distributed Erlang
622		719
623	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	720	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
624	== aemp node, erlang process == aemp port), so many of the documents and	721	== aemp node, Erlang process == aemp port), so many of the documents and
625	programming techniques employed by erlang apply to AnyEvent::MP. Here is a	722	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
626	sample:	723	sample:
627		724
628	http://www.erlang.se/doc/programming_rules.shtml	725	http://www.Erlang.se/doc/programming_rules.shtml
629	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	726	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
630	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6	727	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
631	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	728	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
632		729
633	Despite the similarities, there are also some important differences:	730	Despite the similarities, there are also some important differences:
634		731
635	=over 4	732	=over 4
636		733
…		…
641	convenience functionality.	738	convenience functionality.
642		739
643	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
644	cost of longer node references and a slightly higher management overhead.	741	cost of longer node references and a slightly higher management overhead.
645		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
646	=item * Erlang uses processes and a mailbox, AEMP does not queue.	758	=item * Erlang uses processes and a mailbox, AEMP does not queue.
647		759
648	Erlang uses processes that selctively receive messages, and therefore	760	Erlang uses processes that selectively receive messages, and therefore
649	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
650	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.
651		765
652	(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).
653		767
654	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
655		769
656	Sending messages in erlang is synchronous and blocks the process. AEMP	770	Sending messages in Erlang is synchronous and blocks the process (and
657	sends are immediate, connection establishment is handled in the	771	so does not need a queue that can overflow). AEMP sends are immediate,
658	background.	772	connection establishment is handled in the background.
659		773
660	=item * Erlang can silently lose messages, AEMP cannot.	774	=item * Erlang suffers from silent message loss, AEMP does not.
661		775
662	Erlang makes few guarantees on messages delivery - messages can get lost	776	Erlang makes few guarantees on messages delivery - messages can get lost
663	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,
664	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).
665		779
666	AEMP guarantees correct ordering, and the guarantee that there are no	780	AEMP guarantees correct ordering, and the guarantee that there are no
667	holes in the message sequence.	781	holes in the message sequence.
668		782
669	=item * In erlang, processes can be declared dead and later be found to be	783	=item * In Erlang, processes can be declared dead and later be found to be
670	alive.	784	alive.
671		785
672	In erlang it can happen that a monitored process is declared dead and	786	In Erlang it can happen that a monitored process is declared dead and
673	linked processes get killed, but later it turns out that the process is	787	linked processes get killed, but later it turns out that the process is
674	still alive - and can receive messages.	788	still alive - and can receive messages.
675		789
676	In AEMP, when port monitoring detects a port as dead, then that port will	790	In AEMP, when port monitoring detects a port as dead, then that port will
677	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
678	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.
679		793
680	=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.
681		795
682	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
683	ID known to other nodes for a completely different process, causing	797	known to other nodes for a completely different process, causing messages
684	messages destined for that process to end up in an unrelated process.	798	destined for that process to end up in an unrelated process.
685		799
686	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
687	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.
688		802
689	=item * Erlang uses unprotected connections, AEMP uses secure	803	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
693	securely authenticate nodes.	807	securely authenticate nodes.
694		808
695	=item * The AEMP protocol is optimised for both text-based and binary	809	=item * The AEMP protocol is optimised for both text-based and binary
696	communications.	810	communications.
697		811
698	The AEMP protocol, unlike the erlang protocol, supports both	812	The AEMP protocol, unlike the Erlang protocol, supports both
699	language-independent text-only protocols (good for debugging) and binary,	813	language-independent text-only protocols (good for debugging) and binary,
700	language-specific serialisers (e.g. Storable).	814	language-specific serialisers (e.g. Storable).
701		815
702	It has also been carefully designed to be implementable in other languages	816	It has also been carefully designed to be implementable in other languages
703	with a minimum of work while gracefully degrading fucntionality to make the	817	with a minimum of work while gracefully degrading fucntionality to make the
704	protocol simple.	818	protocol simple.
705		819
		820	=item * AEMP has more flexible monitoring options than Erlang.
		821
		822	In Erlang, you can chose to receive I<all> exit signals as messages
		823	or I<none>, there is no in-between, so monitoring single processes is
		824	difficult to implement. Monitoring in AEMP is more flexible than in
		825	Erlang, as one can choose between automatic kill, exit message or callback
		826	on a per-process basis.
		827
		828	=item * Erlang tries to hide remote/local connections, AEMP does not.
		829
		830	Monitoring in Erlang is not an indicator of process death/crashes,
		831	as linking is (except linking is unreliable in Erlang).
		832
		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.
		876
706	=back	877	=back
707		878
708	=head1 SEE ALSO	879	=head1 SEE ALSO
709		880
710	L<AnyEvent>.	881	L<AnyEvent>.

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