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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.44 by root, Wed Aug 12 21:39:58 2009 UTC vs.
Revision 1.61 by root, Mon Aug 24 08:06:49 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		46	AnyEvent::MP::Intro - outdated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 (connected to a
83	master node only) or public nodes (connectable from unrelated nodes).	91	master node only) or public nodes (connectable from unrelated nodes).
84		92
85	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
…		…
118	use base "Exporter";	126	use base "Exporter";
119		127
120	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
121		129
122	our @EXPORT = qw(	130	our @EXPORT = qw(
123	NODE $NODE *SELF node_of _any_	131	NODE $NODE *SELF node_of after
124	resolve_node initialise_node	132	resolve_node initialise_node
125	snd rcv mon kil reg psub spawn	133	snd rcv mon mon_guard kil reg psub spawn
126	port	134	port
127	);	135	);
128		136
129	our $SELF;	137	our $SELF;
130		138
…		…
134	kil $SELF, die => $msg;	142	kil $SELF, die => $msg;
135	}	143	}
136		144
137	=item $thisnode = NODE / $NODE	145	=item $thisnode = NODE / $NODE
138		146
139	The C<NODE> function returns, and the C<$NODE> variable contains	147	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	148	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	149	C<initialise_node>.
142	identifiers become invalid.
143		150
144	=item $noderef = node_of $port	151	=item $noderef = node_of $port
145		152
146	Extracts and returns the noderef from a portid or a noderef.	153	Extracts and returns the noderef from a port ID or a noderef.
147		154
148	=item initialise_node $noderef, $seednode, $seednode...	155	=item initialise_node $noderef, $seednode, $seednode...
149		156
150	=item initialise_node "slave/", $master, $master...	157	=item initialise_node "slave/", $master, $master...
151		158
…		…
154	it should know the noderefs of some other nodes in the network.	161	it should know the noderefs of some other nodes in the network.
155		162
156	This function initialises a node - it must be called exactly once (or	163	This function initialises a node - it must be called exactly once (or
157	never) before calling other AnyEvent::MP functions.	164	never) before calling other AnyEvent::MP functions.
158		165
159	All arguments are noderefs, which can be either resolved or unresolved.	166	All arguments (optionally except for the first) are noderefs, which can be
		167	either resolved or unresolved.
		168
		169	The first argument will be looked up in the configuration database first
		170	(if it is C<undef> then the current nodename will be used instead) to find
		171	the relevant configuration profile (see L<aemp>). If none is found then
		172	the default configuration is used. The configuration supplies additional
		173	seed/master nodes and can override the actual noderef.
160		174
161	There are two types of networked nodes, public nodes and slave nodes:	175	There are two types of networked nodes, public nodes and slave nodes:
162		176
163	=over 4	177	=over 4
164		178
165	=item public nodes	179	=item public nodes
166		180
167	For public nodes, C<$noderef> must either be a (possibly unresolved)	181	For public nodes, C<$noderef> (supplied either directly to
168	noderef, in which case it will be resolved, or C<undef> (or missing), in	182	C<initialise_node> or indirectly via a profile or the nodename) must be a
169	which case the noderef will be guessed.	183	noderef (possibly unresolved, in which case it will be resolved).
170		184
171	Afterwards, the node will bind itself on all endpoints and try to connect	185	After resolving, the node will bind itself on all endpoints and try to
172	to all additional C<$seednodes> that are specified. Seednodes are optional	186	connect to all additional C<$seednodes> that are specified. Seednodes are
173	and can be used to quickly bootstrap the node into an existing network.	187	optional and can be used to quickly bootstrap the node into an existing
		188	network.
174		189
175	=item slave nodes	190	=item slave nodes
176		191
177	When the C<$noderef> is the special string C<slave/>, then the node will	192	When the C<$noderef> (either as given or overriden by the config file)
		193	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	194	node. Slave nodes cannot be contacted from outside and will route most of
179	route most of their traffic to the master node that they attach to.	195	their traffic to the master node that they attach to.
180		196
181	At least one additional noderef is required: The node will try to connect	197	At least one additional noderef is required (either by specifying it
182	to all of them and will become a slave attached to the first node it can	198	directly or because it is part of the configuration profile): The node
183	successfully connect to.	199	will try to connect to all of them and will become a slave attached to the
		200	first node it can successfully connect to.
		201
		202	Note that slave nodes cannot change their name, and consequently, their
		203	master, so if the master goes down, the slave node will not function well
		204	anymore until it can re-establish conenciton to its master. This makes
		205	slave nodes unsuitable for long-term nodes or fault-tolerant networks.
184		206
185	=back	207	=back
186		208
187	This function will block until all nodes have been resolved and, for slave	209	This function will block until all nodes have been resolved and, for slave
188	nodes, until it has successfully established a connection to a master	210	nodes, until it has successfully established a connection to a master
189	server.	211	server.
190		212
		213	All the seednodes will also be specially marked to automatically retry
		214	connecting to them infinitely.
		215
191	Example: become a public node listening on the default node.	216	Example: become a public node listening on the guessed noderef, or the one
		217	specified via C<aemp> for the current node. This should be the most common
		218	form of invocation for "daemon"-type nodes.
192		219
193	initialise_node;	220	initialise_node;
		221
		222	Example: become a slave node to any of the the seednodes specified via
		223	C<aemp>. This form is often used for commandline clients.
		224
		225	initialise_node "slave/";
		226
		227	Example: become a slave node to any of the specified master servers. This
		228	form is also often used for commandline clients.
		229
		230	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
194		231
195	Example: become a public node, and try to contact some well-known master	232	Example: become a public node, and try to contact some well-known master
196	servers to become part of the network.	233	servers to become part of the network.
197		234
198	initialise_node undef, "master1", "master2";	235	initialise_node undef, "master1", "master2";
…		…
201		238
202	initialise_node 4041;	239	initialise_node 4041;
203		240
204	Example: become a public node, only visible on localhost port 4044.	241	Example: become a public node, only visible on localhost port 4044.
205		242
206	initialise_node "locahost:4044";	243	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		244
212	=item $cv = resolve_node $noderef	245	=item $cv = resolve_node $noderef
213		246
214	Takes an unresolved node reference that may contain hostnames and	247	Takes an unresolved node reference that may contain hostnames and
215	abbreviated IDs, resolves all of them and returns a resolved node	248	abbreviated IDs, resolves all of them and returns a resolved node
…		…
252	=item snd $port, type => @data	285	=item snd $port, type => @data
253		286
254	=item snd $port, @msg	287	=item snd $port, @msg
255		288
256	Send the given message to the given port ID, which can identify either	289	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	290	a local or a remote port, and must be a port ID.
258	stringifies a sa port ID (such as a port object :).
259		291
260	While the message can be about anything, it is highly recommended to use a	292	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	293	string as first element (a port ID, or some word that indicates a request
262	type etc.).	294	type etc.).
263		295
264	The message data effectively becomes read-only after a call to this	296	The message data effectively becomes read-only after a call to this
265	function: modifying any argument is not allowed and can cause many	297	function: modifying any argument is not allowed and can cause many
266	problems.	298	problems.
…		…
271	that Storable can serialise and deserialise is allowed, and for the local	303	that Storable can serialise and deserialise is allowed, and for the local
272	node, anything can be passed.	304	node, anything can be passed.
273		305
274	=item $local_port = port	306	=item $local_port = port
275		307
276	Create a new local port object that can be used either as a pattern	308	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"),	309	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		310
280	=item $port = port { my @msg = @_; $finished }	311	=item $local_port = port { my @msg = @_ }
281		312
282	Creates a "miniport", that is, a very lightweight port without any pattern	313	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.	314	creating a port and calling C<rcv $port, $callback> on it.
285		315
286	The block will be called for every message received on the port. When the	316	The block will be called for every message received on the port, with the
287	callback returns a true value its job is considered "done" and the port	317	global variable C<$SELF> set to the port ID. Runtime errors will cause the
288	will be destroyed. Otherwise it will stay alive.	318	port to be C<kil>ed. The message will be passed as-is, no extra argument
		319	(i.e. no port ID) will be passed to the callback.
289		320
290	The message will be passed as-is, no extra argument (i.e. no port id) will	321	If you want to stop/destroy the port, simply C<kil> it:
291	be passed to the callback.
292		322
293	If you need the local port id in the callback, this works nicely:	323	my $port = port {
294		324	my @msg = @_;
295	my $port; $port = port {	325	...
296	snd $otherport, reply => $port;	326	kil $SELF;
297	};	327	};
298		328
299	=cut	329	=cut
300		330
301	sub rcv($@);	331	sub rcv($@);
		332
		333	sub _kilme {
		334	die "received message on port without callback";
		335	}
302		336
303	sub port(;&) {	337	sub port(;&) {
304	my $id = "$UNIQ." . $ID++;	338	my $id = "$UNIQ." . $ID++;
305	my $port = "$NODE#$id";	339	my $port = "$NODE#$id";
306		340
307	if (@_) {	341	rcv $port, shift \|\| \&_kilme;
308	rcv $port, shift;
309	} else {
310	$PORT{$id} = sub { }; # nop
311	}
312		342
313	$port	343	$port
314	}	344	}
315		345
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)	346	=item rcv $local_port, $callback->(@msg)
336		347
337	Replaces the callback on the specified miniport (after converting it to	348	Replaces the default callback on the specified port. There is no way to
338	one if required).	349	remove the default callback: use C<sub { }> to disable it, or better
339		350	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...] => $callback->(@msg), ...
345
346	Register callbacks to be called on matching messages on the given full
347	port (after converting it to one if required) and return the port.
348
349	The callback has to return a true value when its work is done, after
350	which is will be removed, or a false value in which case it will stay
351	registered.
352		351
353	The global C<$SELF> (exported by this module) contains C<$port> while	352	The global C<$SELF> (exported by this module) contains C<$port> while
354	executing the callback.	353	executing the callback. Runtime errors during callback execution will
		354	result in the port being C<kil>ed.
355		355
356	Runtime errors during callback execution will result in the port being	356	The default callback received all messages not matched by a more specific
357	C<kil>ed.	357	C<tag> match.
358		358
359	If the match is an array reference, then it will be matched against the	359	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
360	first elements of the message, otherwise only the first element is being
361	matched.
362		360
363	Any element in the match that is specified as C<_any_> (a function	361	Register (or replace) callbacks to be called on messages starting with the
364	exported by this module) matches any single element of the message.	362	given tag on the given port (and return the port), or unregister it (when
		363	C<$callback> is C<$undef> or missing). There can only be one callback
		364	registered for each tag.
365		365
366	While not required, it is highly recommended that the first matching	366	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	367	element (the tag) has been removed. The callback will use the same
368	also the most efficient match (by far).	368	environment as the default callback (see above).
369		369
370	Example: create a port and bind receivers on it in one go.	370	Example: create a port and bind receivers on it in one go.
371		371
372	my $port = rcv port,	372	my $port = rcv port,
373	msg1 => sub { ...; 0 },	373	msg1 => sub { ... },
374	msg2 => sub { ...; 0 },	374	msg2 => sub { ... },
375	;	375	;
376		376
377	Example: create a port, bind receivers and send it in a message elsewhere	377	Example: create a port, bind receivers and send it in a message elsewhere
378	in one go:	378	in one go:
379		379
380	snd $otherport, reply =>	380	snd $otherport, reply =>
381	rcv port,	381	rcv port,
382	msg1 => sub { ...; 0 },	382	msg1 => sub { ... },
383	...	383	...
384	;	384	;
		385
		386	Example: temporarily register a rcv callback for a tag matching some port
		387	(e.g. for a rpc reply) and unregister it after a message was received.
		388
		389	rcv $port, $otherport => sub {
		390	my @reply = @_;
		391
		392	rcv $SELF, $otherport;
		393	};
385		394
386	=cut	395	=cut
387		396
388	sub rcv($@) {	397	sub rcv($@) {
389	my $port = shift;	398	my $port = shift;
390	my ($noderef, $portid) = split /#/, $port, 2;	399	my ($noderef, $portid) = split /#/, $port, 2;
391		400
392	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	401	$NODE{$noderef} == $NODE{""}
393	or Carp::croak "$port: rcv can only be called on local ports, caught";	402	or Carp::croak "$port: rcv can only be called on local ports, caught";
394		403
395	if (@_ == 1) {	404	while (@_) {
		405	if (ref $_[0]) {
		406	if (my $self = $PORT_DATA{$portid}) {
		407	"AnyEvent::MP::Port" eq ref $self
		408	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		409
		410	$self->[2] = shift;
		411	} else {
396	my $cb = shift;	412	my $cb = shift;
397	delete $PORT_DATA{$portid};
398	$PORT{$portid} = sub {	413	$PORT{$portid} = sub {
399	local $SELF = $port;	414	local $SELF = $port;
400	eval {	415	eval { &$cb }; _self_die if $@;
401	&$cb	416	};
402	and kil $port;
403	};	417	}
404	_self_die if $@;	418	} elsif (defined $_[0]) {
405	};
406	} else {
407	my $self = $PORT_DATA{$portid} \|\|= do {	419	my $self = $PORT_DATA{$portid} \|\|= do {
408	my $self = bless {	420	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
409	id => $port,
410	}, "AnyEvent::MP::Port";
411		421
412	$PORT{$portid} = sub {	422	$PORT{$portid} = sub {
413	local $SELF = $port;	423	local $SELF = $port;
414		424
415	eval {
416	for (@{ $self->{rc0}{$_[0]} }) {	425	if (my $cb = $self->[1]{$_[0]}) {
417	$_ && &{$_->[0]}	426	shift;
418	&& undef $_;	427	eval { &$cb }; _self_die if $@;
419	}	428	} else {
420
421	for (@{ $self->{rcv}{$_[0]} }) {
422	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
423	&& &{$_->[0]}	429	&{ $self->[0] };
424	&& undef $_;
425	}
426
427	for (@{ $self->{any} }) {
428	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
429	&& &{$_->[0]}
430	&& undef $_;
431	}	430	}
432	};	431	};
433	_self_die if $@;	432
		433	$self
434	};	434	};
435		435
436	$self
437	};
438
439	"AnyEvent::MP::Port" eq ref $self	436	"AnyEvent::MP::Port" eq ref $self
440	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	437	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
441		438
442	while (@_) {
443	my ($match, $cb) = splice @_, 0, 2;	439	my ($tag, $cb) = splice @_, 0, 2;
444		440
445	if (!ref $match) {	441	if (defined $cb) {
446	push @{ $self->{rc0}{$match} }, [$cb];	442	$self->[1]{$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 {	443	} else {
453	push @{ $self->{any} }, [$cb, $match];	444	delete $self->[1]{$tag};
454	}	445	}
455	}	446	}
456	}	447	}
457		448
458	$port	449	$port
…		…
513	will arrive, or the monitoring action will be invoked after possible	504	will arrive, or the monitoring action will be invoked after possible
514	message loss has been detected. No messages will be lost "in between"	505	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	506	(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	507	port). After the monitoring action was invoked, further messages might get
517	delivered again.	508	delivered again.
		509
		510	Note that monitoring-actions are one-shot: once released, they are removed
		511	and will not trigger again.
518		512
519	In the first form (callback), the callback is simply called with any	513	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	514	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	515	"normally"). Note also that I<< the callback B<must> never die >>, so use
522	C<eval> if unsure.	516	C<eval> if unsure.
…		…
683	my $id = "$RUNIQ." . $ID++;	677	my $id = "$RUNIQ." . $ID++;
684		678
685	$_[0] =~ /::/	679	$_[0] =~ /::/
686	or Carp::croak "spawn init function must be a fully-qualified name, caught";	680	or Carp::croak "spawn init function must be a fully-qualified name, caught";
687		681
688	($NODE{$noderef} \|\| add_node $noderef)	682	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
689	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
690		683
691	"$noderef#$id"	684	"$noderef#$id"
692	}	685	}
693		686
694	=back	687	=item after $timeout, @msg
695		688
696	=head1 NODE MESSAGES	689	=item after $timeout, $callback
697		690
698	Nodes understand the following messages sent to them. Many of them take	691	Either sends the given message, or call the given callback, after the
699	arguments called C<@reply>, which will simply be used to compose a reply	692	specified number of seconds.
700	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
701	the remaining arguments are simply the message data.
702		693
703	While other messages exist, they are not public and subject to change.	694	This is simply a utility function that come sin handy at times.
704		695
705	=over 4
706
707	=cut	696	=cut
708		697
709	=item lookup => $name, @reply	698	sub after($@) {
		699	my ($timeout, @action) = @_;
710		700
711	Replies with the port ID of the specified well-known port, or C<undef>.	701	my $t; $t = AE::timer $timeout, 0, sub {
712		702	undef $t;
713	=item devnull => ...	703	ref $action[0]
714		704	? $action[0]()
715	Generic data sink/CPU heat conversion.	705	: snd @action;
716		706	};
717	=item relay => $port, @msg	707	}
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		708
740	=back	709	=back
741		710
742	=head1 AnyEvent::MP vs. Distributed Erlang	711	=head1 AnyEvent::MP vs. Distributed Erlang
743		712
…		…
762	convenience functionality.	731	convenience functionality.
763		732
764	This means that AEMP requires a less tightly controlled environment at the	733	This means that AEMP requires a less tightly controlled environment at the
765	cost of longer node references and a slightly higher management overhead.	734	cost of longer node references and a slightly higher management overhead.
766		735
		736	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		737	uses "local ports are like remote ports".
		738
		739	The failure modes for local ports are quite different (runtime errors
		740	only) then for remote ports - when a local port dies, you I<know> it dies,
		741	when a connection to another node dies, you know nothing about the other
		742	port.
		743
		744	Erlang pretends remote ports are as reliable as local ports, even when
		745	they are not.
		746
		747	AEMP encourages a "treat remote ports differently" philosophy, with local
		748	ports being the special case/exception, where transport errors cannot
		749	occur.
		750
767	=item * Erlang uses processes and a mailbox, AEMP does not queue.	751	=item * Erlang uses processes and a mailbox, AEMP does not queue.
768		752
769	Erlang uses processes that selctively receive messages, and therefore	753	Erlang uses processes that selectively receive messages, and therefore
770	needs a queue. AEMP is event based, queuing messages would serve no useful	754	needs a queue. AEMP is event based, queuing messages would serve no
771	purpose.	755	useful purpose. For the same reason the pattern-matching abilities of
		756	AnyEvent::MP are more limited, as there is little need to be able to
		757	filter messages without dequeing them.
772		758
773	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	759	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
774		760
775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	761	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
776		762
777	Sending messages in Erlang is synchronous and blocks the process. AEMP	763	Sending messages in Erlang is synchronous and blocks the process (and
778	sends are immediate, connection establishment is handled in the	764	so does not need a queue that can overflow). AEMP sends are immediate,
779	background.	765	connection establishment is handled in the background.
780		766
781	=item * Erlang can silently lose messages, AEMP cannot.	767	=item * Erlang suffers from silent message loss, AEMP does not.
782		768
783	Erlang makes few guarantees on messages delivery - messages can get lost	769	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,	770	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).	771	and c, and the other side only receives messages a and c).
786		772
…		…
798	eventually be killed - it cannot happen that a node detects a port as dead	784	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.	785	and then later sends messages to it, finding it is still alive.
800		786
801	=item * Erlang can send messages to the wrong port, AEMP does not.	787	=item * Erlang can send messages to the wrong port, AEMP does not.
802		788
803	In Erlang it is quite possible that a node that restarts reuses a process	789	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	790	known to other nodes for a completely different process, causing messages
805	messages destined for that process to end up in an unrelated process.	791	destined for that process to end up in an unrelated process.
806		792
807	AEMP never reuses port IDs, so old messages or old port IDs floating	793	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.	794	around in the network will not be sent to an unrelated port.
809		795
810	=item * Erlang uses unprotected connections, AEMP uses secure	796	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
846	This also saves round-trips and avoids sending messages to the wrong port	832	This also saves round-trips and avoids sending messages to the wrong port
847	(hard to do in Erlang).	833	(hard to do in Erlang).
848		834
849	=back	835	=back
850		836
		837	=head1 RATIONALE
		838
		839	=over 4
		840
		841	=item Why strings for ports and noderefs, why not objects?
		842
		843	We considered "objects", but found that the actual number of methods
		844	thatc an be called are very low. Since port IDs and noderefs travel over
		845	the network frequently, the serialising/deserialising would add lots of
		846	overhead, as well as having to keep a proxy object.
		847
		848	Strings can easily be printed, easily serialised etc. and need no special
		849	procedures to be "valid".
		850
		851	And a a miniport consists of a single closure stored in a global hash - it
		852	can't become much cheaper.
		853
		854	=item Why favour JSON, why not real serialising format such as Storable?
		855
		856	In fact, any AnyEvent::MP node will happily accept Storable as framing
		857	format, but currently there is no way to make a node use Storable by
		858	default.
		859
		860	The default framing protocol is JSON because a) JSON::XS is many times
		861	faster for small messages and b) most importantly, after years of
		862	experience we found that object serialisation is causing more problems
		863	than it gains: Just like function calls, objects simply do not travel
		864	easily over the network, mostly because they will always be a copy, so you
		865	always have to re-think your design.
		866
		867	Keeping your messages simple, concentrating on data structures rather than
		868	objects, will keep your messages clean, tidy and efficient.
		869
		870	=back
		871
851	=head1 SEE ALSO	872	=head1 SEE ALSO
852		873
853	L<AnyEvent>.	874	L<AnyEvent>.
854		875
855	=head1 AUTHOR	876	=head1 AUTHOR

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Revision 1.44 by root, Wed Aug 12 21:39:58 2009 UTC vs.
Revision 1.61 by root, Mon Aug 24 08:06:49 2009 UTC