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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.43 by root, Sun Aug 9 16:08:16 2009 UTC vs.
Revision 1.62 by root, Thu Aug 27 07:12:48 2009 UTC

…		…
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	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"
14		19
15	# ports are message endpoints	20	# ports are message endpoints
16		21
17	# sending messages	22	# sending messages
18	snd $port, type => data...;	23	snd $port, type => data...;
19	snd $port, @msg;	24	snd $port, @msg;
20	snd @msg_with_first_element_being_a_port;	25	snd @msg_with_first_element_being_a_port;
21		26
22	# miniports	27	# creating/using ports, the simple way
23	my $miniport = port { my @msg = @_; 0 };	28	my $simple_port = port { my @msg = @_; 0 };
24		29
25	# full ports	30	# creating/using ports, tagged message matching
26	my $port = port;	31	my $port = port;
27	rcv $port, smartmatch => $cb->(@msg);
28	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
29	rcv $port, pong => sub { warn "pong received\n"; 0 };	33	rcv $port, pong => sub { warn "pong received\n"; 0 };
30		34
31	# remote ports	35	# create a port on another node
32	my $port = spawn $node, $initfunc, @initdata;	36	my $port = spawn $node, $initfunc, @initdata;
33
34	# more, smarter, matches (_any_ is exported by this module)
35	rcv $port, [child_died => $pid] => sub { ...
36	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
37		37
38	# monitoring	38	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	39	mon $port, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	40	mon $port, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	41	mon $port, $otherport, @msg # send message on death
42		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		46	AnyEvent::MP::Intro - outdated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
43	=head1 DESCRIPTION	52	=head1 DESCRIPTION
44		53
45	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
46		55
47	Despite its simplicity, you can securely message other processes running	56	Despite its simplicity, you can securely message other processes running
…		…
50	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>
51	manual page.	60	manual page.
52		61
53	At the moment, this module family is severly broken and underdocumented,	62	At the moment, this module family is severly broken and underdocumented,
54	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 -
55	stay tuned! The basic API should be finished, however.	64	stay tuned!
56		65
57	=head1 CONCEPTS	66	=head1 CONCEPTS
58		67
59	=over 4	68	=over 4
60		69
61	=item port	70	=item port
62		71
63	A port is something you can send messages to (with the C<snd> function).	72	A port is something you can send messages to (with the C<snd> function).
64		73
65	Some ports allow you to register C<rcv> handlers that can match specific	74	Ports allow you to register C<rcv> handlers that can match all or just
66	messages. All C<rcv> handlers will receive messages they match, messages	75	some messages. Messages will not be queued.
67	will not be queued.
68		76
69	=item port id - C<noderef#portname>	77	=item port id - C<noderef#portname>
70		78
71	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	79	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as
72	separator, and a port name (a printable string of unspecified format). An	80	separator, and a port name (a printable string of unspecified format). An
73	exception is the the node port, whose ID is identical to its node	81	exception is the the node port, whose ID is identical to its node
74	reference.	82	reference.
75		83
76	=item node	84	=item node
77		85
78	A node is a single process containing at least one port - the node	86	A node is a single process containing at least one port - the node port,
79	port. You can send messages to node ports to find existing ports or to	87	which provides nodes to manage each other remotely, and to create new
80	create new ports, among other things.	88	ports.
81		89
82	Nodes are either private (single-process only), slaves (connected to a	90	Nodes are either private (single-process only), slaves (can only talk to
83	master node only) or public nodes (connectable from unrelated nodes).	91	public nodes, but do not need an open port) or public nodes (connectable
		92	from any other node).
84		93
85	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
86		95
87	A node reference is a string that either simply identifies the node (for	96	A node reference is a string that either simply identifies the node (for
88	private and slave nodes), or contains a recipe on how to reach a given	97	private and slave nodes), or contains a recipe on how to reach a given
…		…
105		114
106	=cut	115	=cut
107		116
108	package AnyEvent::MP;	117	package AnyEvent::MP;
109		118
110	use AnyEvent::MP::Base;	119	use AnyEvent::MP::Kernel;
111		120
112	use common::sense;	121	use common::sense;
113		122
114	use Carp ();	123	use Carp ();
115		124
116	use AE ();	125	use AE ();
117		126
118	use base "Exporter";	127	use base "Exporter";
119		128
120	our $VERSION = $AnyEvent::MP::Base::VERSION;	129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
121		130
122	our @EXPORT = qw(	131	our @EXPORT = qw(
123	NODE $NODE *SELF node_of _any_	132	NODE $NODE *SELF node_of after
124	resolve_node initialise_node	133	resolve_node initialise_node
125	snd rcv mon kil reg psub spawn	134	snd rcv mon mon_guard kil reg psub spawn
126	port	135	port
127	);	136	);
128		137
129	our $SELF;	138	our $SELF;
130		139
…		…
134	kil $SELF, die => $msg;	143	kil $SELF, die => $msg;
135	}	144	}
136		145
137	=item $thisnode = NODE / $NODE	146	=item $thisnode = NODE / $NODE
138		147
139	The C<NODE> function returns, and the C<$NODE> variable contains	148	The C<NODE> function returns, and the C<$NODE> variable contains the
140	the noderef of the local node. The value is initialised by a call	149	noderef of the local node. The value is initialised by a call to
141	to C<become_public> or C<become_slave>, after which all local port	150	C<initialise_node>.
142	identifiers become invalid.
143		151
144	=item $noderef = node_of $port	152	=item $noderef = node_of $port
145		153
146	Extracts and returns the noderef from a portid or a noderef.	154	Extracts and returns the noderef from a port ID or a noderef.
147		155
148	=item initialise_node $noderef, $seednode, $seednode...	156	=item initialise_node $noderef, $seednode, $seednode...
149		157
150	=item initialise_node "slave/", $master, $master...	158	=item initialise_node "slave/", $master, $master...
151		159
…		…
154	it should know the noderefs of some other nodes in the network.	162	it should know the noderefs of some other nodes in the network.
155		163
156	This function initialises a node - it must be called exactly once (or	164	This function initialises a node - it must be called exactly once (or
157	never) before calling other AnyEvent::MP functions.	165	never) before calling other AnyEvent::MP functions.
158		166
159	All arguments are noderefs, which can be either resolved or unresolved.	167	All arguments (optionally except for the first) are noderefs, which can be
		168	either resolved or unresolved.
		169
		170	The first argument will be looked up in the configuration database first
		171	(if it is C<undef> then the current nodename will be used instead) to find
		172	the relevant configuration profile (see L<aemp>). If none is found then
		173	the default configuration is used. The configuration supplies additional
		174	seed/master nodes and can override the actual noderef.
160		175
161	There are two types of networked nodes, public nodes and slave nodes:	176	There are two types of networked nodes, public nodes and slave nodes:
162		177
163	=over 4	178	=over 4
164		179
165	=item public nodes	180	=item public nodes
166		181
167	For public nodes, C<$noderef> must either be a (possibly unresolved)	182	For public nodes, C<$noderef> (supplied either directly to
168	noderef, in which case it will be resolved, or C<undef> (or missing), in	183	C<initialise_node> or indirectly via a profile or the nodename) must be a
169	which case the noderef will be guessed.	184	noderef (possibly unresolved, in which case it will be resolved).
170		185
171	Afterwards, the node will bind itself on all endpoints and try to connect	186	After resolving, the node will bind itself on all endpoints.
172	to all additional C<$seednodes> that are specified. Seednodes are optional
173	and can be used to quickly bootstrap the node into an existing network.
174		187
175	=item slave nodes	188	=item slave nodes
176		189
177	When the C<$noderef> is the special string C<slave/>, then the node will	190	When the C<$noderef> (either as given or overriden by the config file)
		191	is the special string C<slave/>, then the node will become a slave
178	become a slave node. Slave nodes cannot be contacted from outside and will	192	node. Slave nodes cannot be contacted from outside, and cannot talk to
179	route most of their traffic to the master node that they attach to.	193	each other (at least in this version of AnyEvent::MP).
180		194
181	At least one additional noderef is required: The node will try to connect	195	Slave nodes work by creating connections to all public nodes, using the
182	to all of them and will become a slave attached to the first node it can	196	L<AnyEvent::MP::Global> service.
183	successfully connect to.
184		197
185	=back	198	=back
186		199
187	This function will block until all nodes have been resolved and, for slave	200	After initialising itself, the node will connect to all additional
188	nodes, until it has successfully established a connection to a master	201	C<$seednodes> that are specified diretcly or via a profile. Seednodes are
189	server.	202	optional and can be used to quickly bootstrap the node into an existing
		203	network.
190		204
		205	All the seednodes will also be specially marked to automatically retry
		206	connecting to them indefinitely, so make sure that seednodes are really
		207	reliable and up (this might also change in the future).
		208
191	Example: become a public node listening on the default node.	209	Example: become a public node listening on the guessed noderef, or the one
		210	specified via C<aemp> for the current node. This should be the most common
		211	form of invocation for "daemon"-type nodes.
192		212
193	initialise_node;	213	initialise_node;
		214
		215	Example: become a slave node to any of the the seednodes specified via
		216	C<aemp>. This form is often used for commandline clients.
		217
		218	initialise_node "slave/";
194		219
195	Example: become a public node, and try to contact some well-known master	220	Example: become a public node, and try to contact some well-known master
196	servers to become part of the network.	221	servers to become part of the network.
197		222
198	initialise_node undef, "master1", "master2";	223	initialise_node undef, "master1", "master2";
…		…
201		226
202	initialise_node 4041;	227	initialise_node 4041;
203		228
204	Example: become a public node, only visible on localhost port 4044.	229	Example: become a public node, only visible on localhost port 4044.
205		230
206	initialise_node "locahost:4044";	231	initialise_node "localhost:4044";
207
208	Example: become a slave node to any of the specified master servers.
209
210	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
211		232
212	=item $cv = resolve_node $noderef	233	=item $cv = resolve_node $noderef
213		234
214	Takes an unresolved node reference that may contain hostnames and	235	Takes an unresolved node reference that may contain hostnames and
215	abbreviated IDs, resolves all of them and returns a resolved node	236	abbreviated IDs, resolves all of them and returns a resolved node
…		…
252	=item snd $port, type => @data	273	=item snd $port, type => @data
253		274
254	=item snd $port, @msg	275	=item snd $port, @msg
255		276
256	Send the given message to the given port ID, which can identify either	277	Send the given message to the given port ID, which can identify either
257	a local or a remote port, and can be either a string or soemthignt hat	278	a local or a remote port, and must be a port ID.
258	stringifies a sa port ID (such as a port object :).
259		279
260	While the message can be about anything, it is highly recommended to use a	280	While the message can be about anything, it is highly recommended to use a
261	string as first element (a portid, or some word that indicates a request	281	string as first element (a port ID, or some word that indicates a request
262	type etc.).	282	type etc.).
263		283
264	The message data effectively becomes read-only after a call to this	284	The message data effectively becomes read-only after a call to this
265	function: modifying any argument is not allowed and can cause many	285	function: modifying any argument is not allowed and can cause many
266	problems.	286	problems.
…		…
271	that Storable can serialise and deserialise is allowed, and for the local	291	that Storable can serialise and deserialise is allowed, and for the local
272	node, anything can be passed.	292	node, anything can be passed.
273		293
274	=item $local_port = port	294	=item $local_port = port
275		295
276	Create a new local port object that can be used either as a pattern	296	Create a new local port object and returns its port ID. Initially it has
277	matching port ("full port") or a single-callback port ("miniport"),	297	no callbacks set and will throw an error when it receives messages.
278	depending on how C<rcv> callbacks are bound to the object.
279		298
280	=item $port = port { my @msg = @_; $finished }	299	=item $local_port = port { my @msg = @_ }
281		300
282	Creates a "miniport", that is, a very lightweight port without any pattern	301	Creates a new local port, and returns its ID. Semantically the same as
283	matching behind it, and returns its ID. Semantically the same as creating
284	a port and calling C<rcv $port, $callback> on it.	302	creating a port and calling C<rcv $port, $callback> on it.
285		303
286	The block will be called for every message received on the port. When the	304	The block will be called for every message received on the port, with the
287	callback returns a true value its job is considered "done" and the port	305	global variable C<$SELF> set to the port ID. Runtime errors will cause the
288	will be destroyed. Otherwise it will stay alive.	306	port to be C<kil>ed. The message will be passed as-is, no extra argument
		307	(i.e. no port ID) will be passed to the callback.
289		308
290	The message will be passed as-is, no extra argument (i.e. no port id) will	309	If you want to stop/destroy the port, simply C<kil> it:
291	be passed to the callback.
292		310
293	If you need the local port id in the callback, this works nicely:	311	my $port = port {
294		312	my @msg = @_;
295	my $port; $port = port {	313	...
296	snd $otherport, reply => $port;	314	kil $SELF;
297	};	315	};
298		316
299	=cut	317	=cut
300		318
301	sub rcv($@);	319	sub rcv($@);
		320
		321	sub _kilme {
		322	die "received message on port without callback";
		323	}
302		324
303	sub port(;&) {	325	sub port(;&) {
304	my $id = "$UNIQ." . $ID++;	326	my $id = "$UNIQ." . $ID++;
305	my $port = "$NODE#$id";	327	my $port = "$NODE#$id";
306		328
307	if (@_) {	329	rcv $port, shift \|\| \&_kilme;
308	rcv $port, shift;
309	} else {
310	$PORT{$id} = sub { }; # nop
311	}
312		330
313	$port	331	$port
314	}	332	}
315		333
316	=item reg $port, $name
317
318	=item reg $name
319
320	Registers the given port (or C<$SELF><<< if missing) under the name
321	C<$name>. If the name already exists it is replaced.
322
323	A port can only be registered under one well known name.
324
325	A port automatically becomes unregistered when it is killed.
326
327	=cut
328
329	sub reg(@) {
330	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
331
332	$REG{$_[0]} = $port;
333	}
334
335	=item rcv $port, $callback->(@msg)	334	=item rcv $local_port, $callback->(@msg)
336		335
337	Replaces the callback on the specified miniport (after converting it to	336	Replaces the default callback on the specified port. There is no way to
338	one if required).	337	remove the default callback: use C<sub { }> to disable it, or better
339		338	C<kil> the port when it is no longer needed.
340	=item rcv $port, tagstring => $callback->(@msg), ...
341
342	=item rcv $port, $smartmatch => $callback->(@msg), ...
343
344	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
345
346	Register callbacks to be called on matching messages on the given full
347	port (after converting it to one if required) and return the port.
348
349	The callback has to return a true value when its work is done, after
350	which is will be removed, or a false value in which case it will stay
351	registered.
352		339
353	The global C<$SELF> (exported by this module) contains C<$port> while	340	The global C<$SELF> (exported by this module) contains C<$port> while
354	executing the callback.	341	executing the callback. Runtime errors during callback execution will
		342	result in the port being C<kil>ed.
355		343
356	Runtime errors during callback execution will result in the port being	344	The default callback received all messages not matched by a more specific
357	C<kil>ed.	345	C<tag> match.
358		346
359	If the match is an array reference, then it will be matched against the	347	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
360	first elements of the message, otherwise only the first element is being
361	matched.
362		348
363	Any element in the match that is specified as C<_any_> (a function	349	Register (or replace) callbacks to be called on messages starting with the
364	exported by this module) matches any single element of the message.	350	given tag on the given port (and return the port), or unregister it (when
		351	C<$callback> is C<$undef> or missing). There can only be one callback
		352	registered for each tag.
365		353
366	While not required, it is highly recommended that the first matching	354	The original message will be passed to the callback, after the first
367	element is a string identifying the message. The one-string-only match is	355	element (the tag) has been removed. The callback will use the same
368	also the most efficient match (by far).	356	environment as the default callback (see above).
369		357
370	Example: create a port and bind receivers on it in one go.	358	Example: create a port and bind receivers on it in one go.
371		359
372	my $port = rcv port,	360	my $port = rcv port,
373	msg1 => sub { ...; 0 },	361	msg1 => sub { ... },
374	msg2 => sub { ...; 0 },	362	msg2 => sub { ... },
375	;	363	;
376		364
377	Example: create a port, bind receivers and send it in a message elsewhere	365	Example: create a port, bind receivers and send it in a message elsewhere
378	in one go:	366	in one go:
379		367
380	snd $otherport, reply =>	368	snd $otherport, reply =>
381	rcv port,	369	rcv port,
382	msg1 => sub { ...; 0 },	370	msg1 => sub { ... },
383	...	371	...
384	;	372	;
		373
		374	Example: temporarily register a rcv callback for a tag matching some port
		375	(e.g. for a rpc reply) and unregister it after a message was received.
		376
		377	rcv $port, $otherport => sub {
		378	my @reply = @_;
		379
		380	rcv $SELF, $otherport;
		381	};
385		382
386	=cut	383	=cut
387		384
388	sub rcv($@) {	385	sub rcv($@) {
389	my $port = shift;	386	my $port = shift;
390	my ($noderef, $portid) = split /#/, $port, 2;	387	my ($noderef, $portid) = split /#/, $port, 2;
391		388
392	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	389	$NODE{$noderef} == $NODE{""}
393	or Carp::croak "$port: rcv can only be called on local ports, caught";	390	or Carp::croak "$port: rcv can only be called on local ports, caught";
394		391
395	if (@_ == 1) {	392	while (@_) {
		393	if (ref $_[0]) {
		394	if (my $self = $PORT_DATA{$portid}) {
		395	"AnyEvent::MP::Port" eq ref $self
		396	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		397
		398	$self->[2] = shift;
		399	} else {
396	my $cb = shift;	400	my $cb = shift;
397	delete $PORT_DATA{$portid};
398	$PORT{$portid} = sub {	401	$PORT{$portid} = sub {
399	local $SELF = $port;	402	local $SELF = $port;
400	eval {	403	eval { &$cb }; _self_die if $@;
401	&$cb	404	};
402	and kil $port;
403	};	405	}
404	_self_die if $@;	406	} elsif (defined $_[0]) {
405	};
406	} else {
407	my $self = $PORT_DATA{$portid} \|\|= do {	407	my $self = $PORT_DATA{$portid} \|\|= do {
408	my $self = bless {	408	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
409	id => $port,
410	}, "AnyEvent::MP::Port";
411		409
412	$PORT{$portid} = sub {	410	$PORT{$portid} = sub {
413	local $SELF = $port;	411	local $SELF = $port;
414		412
415	eval {
416	for (@{ $self->{rc0}{$_[0]} }) {	413	if (my $cb = $self->[1]{$_[0]}) {
417	$_ && &{$_->[0]}	414	shift;
418	&& undef $_;	415	eval { &$cb }; _self_die if $@;
419	}	416	} else {
420
421	for (@{ $self->{rcv}{$_[0]} }) {
422	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
423	&& &{$_->[0]}	417	&{ $self->[0] };
424	&& undef $_;
425	}
426
427	for (@{ $self->{any} }) {
428	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
429	&& &{$_->[0]}
430	&& undef $_;
431	}	418	}
432	};	419	};
433	_self_die if $@;	420
		421	$self
434	};	422	};
435		423
436	$self
437	};
438
439	"AnyEvent::MP::Port" eq ref $self	424	"AnyEvent::MP::Port" eq ref $self
440	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	425	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
441		426
442	while (@_) {
443	my ($match, $cb) = splice @_, 0, 2;	427	my ($tag, $cb) = splice @_, 0, 2;
444		428
445	if (!ref $match) {	429	if (defined $cb) {
446	push @{ $self->{rc0}{$match} }, [$cb];	430	$self->[1]{$tag} = $cb;
447	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
448	my ($type, @match) = @$match;
449	@match
450	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
451	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
452	} else {	431	} else {
453	push @{ $self->{any} }, [$cb, $match];	432	delete $self->[1]{$tag};
454	}	433	}
455	}	434	}
456	}	435	}
457		436
458	$port	437	$port
…		…
513	will arrive, or the monitoring action will be invoked after possible	492	will arrive, or the monitoring action will be invoked after possible
514	message loss has been detected. No messages will be lost "in between"	493	message loss has been detected. No messages will be lost "in between"
515	(after the first lost message no further messages will be received by the	494	(after the first lost message no further messages will be received by the
516	port). After the monitoring action was invoked, further messages might get	495	port). After the monitoring action was invoked, further messages might get
517	delivered again.	496	delivered again.
		497
		498	Note that monitoring-actions are one-shot: once released, they are removed
		499	and will not trigger again.
518		500
519	In the first form (callback), the callback is simply called with any	501	In the first form (callback), the callback is simply called with any
520	number of C<@reason> elements (no @reason means that the port was deleted	502	number of C<@reason> elements (no @reason means that the port was deleted
521	"normally"). Note also that I<< the callback B<must> never die >>, so use	503	"normally"). Note also that I<< the callback B<must> never die >>, so use
522	C<eval> if unsure.	504	C<eval> if unsure.
…		…
683	my $id = "$RUNIQ." . $ID++;	665	my $id = "$RUNIQ." . $ID++;
684		666
685	$_[0] =~ /::/	667	$_[0] =~ /::/
686	or Carp::croak "spawn init function must be a fully-qualified name, caught";	668	or Carp::croak "spawn init function must be a fully-qualified name, caught";
687		669
688	($NODE{$noderef} \|\| add_node $noderef)	670	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
689	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
690		671
691	"$noderef#$id"	672	"$noderef#$id"
692	}	673	}
693		674
694	=back	675	=item after $timeout, @msg
695		676
696	=head1 NODE MESSAGES	677	=item after $timeout, $callback
697		678
698	Nodes understand the following messages sent to them. Many of them take	679	Either sends the given message, or call the given callback, after the
699	arguments called C<@reply>, which will simply be used to compose a reply	680	specified number of seconds.
700	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
701	the remaining arguments are simply the message data.
702		681
703	While other messages exist, they are not public and subject to change.	682	This is simply a utility function that come sin handy at times.
704		683
705	=over 4
706
707	=cut	684	=cut
708		685
709	=item lookup => $name, @reply	686	sub after($@) {
		687	my ($timeout, @action) = @_;
710		688
711	Replies with the port ID of the specified well-known port, or C<undef>.	689	my $t; $t = AE::timer $timeout, 0, sub {
712		690	undef $t;
713	=item devnull => ...	691	ref $action[0]
714		692	? $action[0]()
715	Generic data sink/CPU heat conversion.	693	: snd @action;
716		694	};
717	=item relay => $port, @msg	695	}
718
719	Simply forwards the message to the given port.
720
721	=item eval => $string[ @reply]
722
723	Evaluates the given string. If C<@reply> is given, then a message of the
724	form C<@reply, $@, @evalres> is sent.
725
726	Example: crash another node.
727
728	snd $othernode, eval => "exit";
729
730	=item time => @reply
731
732	Replies the the current node time to C<@reply>.
733
734	Example: tell the current node to send the current time to C<$myport> in a
735	C<timereply> message.
736
737	snd $NODE, time => $myport, timereply => 1, 2;
738	# => snd $myport, timereply => 1, 2, <time>
739		696
740	=back	697	=back
741		698
742	=head1 AnyEvent::MP vs. Distributed Erlang	699	=head1 AnyEvent::MP vs. Distributed Erlang
743		700
…		…
762	convenience functionality.	719	convenience functionality.
763		720
764	This means that AEMP requires a less tightly controlled environment at the	721	This means that AEMP requires a less tightly controlled environment at the
765	cost of longer node references and a slightly higher management overhead.	722	cost of longer node references and a slightly higher management overhead.
766		723
		724	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		725	uses "local ports are like remote ports".
		726
		727	The failure modes for local ports are quite different (runtime errors
		728	only) then for remote ports - when a local port dies, you I<know> it dies,
		729	when a connection to another node dies, you know nothing about the other
		730	port.
		731
		732	Erlang pretends remote ports are as reliable as local ports, even when
		733	they are not.
		734
		735	AEMP encourages a "treat remote ports differently" philosophy, with local
		736	ports being the special case/exception, where transport errors cannot
		737	occur.
		738
767	=item * Erlang uses processes and a mailbox, AEMP does not queue.	739	=item * Erlang uses processes and a mailbox, AEMP does not queue.
768		740
769	Erlang uses processes that selctively receive messages, and therefore	741	Erlang uses processes that selectively receive messages, and therefore
770	needs a queue. AEMP is event based, queuing messages would serve no useful	742	needs a queue. AEMP is event based, queuing messages would serve no
771	purpose.	743	useful purpose. For the same reason the pattern-matching abilities of
		744	AnyEvent::MP are more limited, as there is little need to be able to
		745	filter messages without dequeing them.
772		746
773	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	747	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
774		748
775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	749	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
776		750
777	Sending messages in Erlang is synchronous and blocks the process. AEMP	751	Sending messages in Erlang is synchronous and blocks the process (and
778	sends are immediate, connection establishment is handled in the	752	so does not need a queue that can overflow). AEMP sends are immediate,
779	background.	753	connection establishment is handled in the background.
780		754
781	=item * Erlang can silently lose messages, AEMP cannot.	755	=item * Erlang suffers from silent message loss, AEMP does not.
782		756
783	Erlang makes few guarantees on messages delivery - messages can get lost	757	Erlang makes few guarantees on messages delivery - messages can get lost
784	without any of the processes realising it (i.e. you send messages a, b,	758	without any of the processes realising it (i.e. you send messages a, b,
785	and c, and the other side only receives messages a and c).	759	and c, and the other side only receives messages a and c).
786		760
…		…
798	eventually be killed - it cannot happen that a node detects a port as dead	772	eventually be killed - it cannot happen that a node detects a port as dead
799	and then later sends messages to it, finding it is still alive.	773	and then later sends messages to it, finding it is still alive.
800		774
801	=item * Erlang can send messages to the wrong port, AEMP does not.	775	=item * Erlang can send messages to the wrong port, AEMP does not.
802		776
803	In Erlang it is quite possible that a node that restarts reuses a process	777	In Erlang it is quite likely that a node that restarts reuses a process ID
804	ID known to other nodes for a completely different process, causing	778	known to other nodes for a completely different process, causing messages
805	messages destined for that process to end up in an unrelated process.	779	destined for that process to end up in an unrelated process.
806		780
807	AEMP never reuses port IDs, so old messages or old port IDs floating	781	AEMP never reuses port IDs, so old messages or old port IDs floating
808	around in the network will not be sent to an unrelated port.	782	around in the network will not be sent to an unrelated port.
809		783
810	=item * Erlang uses unprotected connections, AEMP uses secure	784	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
846	This also saves round-trips and avoids sending messages to the wrong port	820	This also saves round-trips and avoids sending messages to the wrong port
847	(hard to do in Erlang).	821	(hard to do in Erlang).
848		822
849	=back	823	=back
850		824
		825	=head1 RATIONALE
		826
		827	=over 4
		828
		829	=item Why strings for ports and noderefs, why not objects?
		830
		831	We considered "objects", but found that the actual number of methods
		832	thatc an be called are very low. Since port IDs and noderefs travel over
		833	the network frequently, the serialising/deserialising would add lots of
		834	overhead, as well as having to keep a proxy object.
		835
		836	Strings can easily be printed, easily serialised etc. and need no special
		837	procedures to be "valid".
		838
		839	And a a miniport consists of a single closure stored in a global hash - it
		840	can't become much cheaper.
		841
		842	=item Why favour JSON, why not real serialising format such as Storable?
		843
		844	In fact, any AnyEvent::MP node will happily accept Storable as framing
		845	format, but currently there is no way to make a node use Storable by
		846	default.
		847
		848	The default framing protocol is JSON because a) JSON::XS is many times
		849	faster for small messages and b) most importantly, after years of
		850	experience we found that object serialisation is causing more problems
		851	than it gains: Just like function calls, objects simply do not travel
		852	easily over the network, mostly because they will always be a copy, so you
		853	always have to re-think your design.
		854
		855	Keeping your messages simple, concentrating on data structures rather than
		856	objects, will keep your messages clean, tidy and efficient.
		857
		858	=back
		859
851	=head1 SEE ALSO	860	=head1 SEE ALSO
852		861
853	L<AnyEvent>.	862	L<AnyEvent>.
854		863
855	=head1 AUTHOR	864	=head1 AUTHOR

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.43 by root, Sun Aug 9 16:08:16 2009 UTC vs.
Revision 1.62 by root, Thu Aug 27 07:12:48 2009 UTC