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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.12 by root, Sun Aug 2 18:11:48 2009 UTC vs.
Revision 1.35 by root, Thu Aug 6 10:21:48 2009 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	NODE # returns this node identifier
10	$NODE # contains this node identifier	9	$NODE # contains this node's noderef
		10	NODE # returns this node's noderef
		11	NODE $port # returns the noderef of the port
11		12
12	snd $port, type => data...;	13	snd $port, type => data...;
		14
		15	$SELF # receiving/own port id in rcv callbacks
13		16
14	rcv $port, smartmatch => $cb->($port, @msg);	17	rcv $port, smartmatch => $cb->($port, @msg);
15		18
16	# examples:	19	# examples:
17	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };
…		…
20		23
21	# more, smarter, matches (_any_ is exported by this module)	24	# more, smarter, matches (_any_ is exported by this module)
22	rcv $port, [child_died => $pid] => sub { ...	25	rcv $port, [child_died => $pid] => sub { ...
23	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
24		27
		28	# linking two ports, so they both crash together
		29	lnk $port1, $port2;
		30
		31	# monitoring
		32	mon $port, $cb->(@msg) # callback is invoked on death
		33	mon $port, $otherport # kill otherport on abnormal death
		34	mon $port, $otherport, @msg # send message on death
		35
25	=head1 DESCRIPTION	36	=head1 DESCRIPTION
26		37
27	This module (-family) implements a simple message passing framework.	38	This module (-family) implements a simple message passing framework.
28		39
29	Despite its simplicity, you can securely message other processes running	40	Despite its simplicity, you can securely message other processes running
30	on the same or other hosts.	41	on the same or other hosts.
31		42
		43	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
		44	manual page.
		45
32	At the moment, this module family is severly brokena nd underdocumented,	46	At the moment, this module family is severly broken and underdocumented,
33	so do not use. This was uploaded mainly to resreve the CPAN namespace -	47	so do not use. This was uploaded mainly to reserve the CPAN namespace -
34	stay tuned!	48	stay tuned! The basic API should be finished, however.
35		49
36	=head1 CONCEPTS	50	=head1 CONCEPTS
37		51
38	=over 4	52	=over 4
39		53
40	=item port	54	=item port
41		55
42	A port is something you can send messages to with the C<snd> function, and	56	A port is something you can send messages to (with the C<snd> function).
43	you can register C<rcv> handlers with. All C<rcv> handlers will receive	57
44	messages they match, messages will not be queued.	58	Some ports allow you to register C<rcv> handlers that can match specific
		59	messages. All C<rcv> handlers will receive messages they match, messages
		60	will not be queued.
45		61
46	=item port id - C<noderef#portname>	62	=item port id - C<noderef#portname>
47		63
48	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	64	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as
49	by a port name (a printable string of unspecified format).	65	separator, and a port name (a printable string of unspecified format). An
		66	exception is the the node port, whose ID is identical to its node
		67	reference.
50		68
51	=item node	69	=item node
52		70
53	A node is a single process containing at least one port - the node	71	A node is a single process containing at least one port - the node
54	port. You can send messages to node ports to let them create new ports,	72	port. You can send messages to node ports to find existing ports or to
55	among other things.	73	create new ports, among other things.
56		74
57	Initially, nodes are either private (single-process only) or hidden	75	Nodes are either private (single-process only), slaves (connected to a
58	(connected to a master node only). Only when they epxlicitly "become	76	master node only) or public nodes (connectable from unrelated nodes).
59	public" can you send them messages from unrelated other nodes.
60		77
61	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	78	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
62		79
63	A noderef is a string that either uniquely identifies a given node (for	80	A node reference is a string that either simply identifies the node (for
64	private and hidden nodes), or contains a recipe on how to reach a given	81	private and slave nodes), or contains a recipe on how to reach a given
65	node (for public nodes).	82	node (for public nodes).
66		83
		84	This recipe is simply a comma-separated list of C<address:port> pairs (for
		85	TCP/IP, other protocols might look different).
		86
		87	Node references come in two flavours: resolved (containing only numerical
		88	addresses) or unresolved (where hostnames are used instead of addresses).
		89
		90	Before using an unresolved node reference in a message you first have to
		91	resolve it.
		92
67	=back	93	=back
68		94
69	=head1 VARIABLES/FUNCTIONS	95	=head1 VARIABLES/FUNCTIONS
70		96
71	=over 4	97	=over 4
…		…
82		108
83	use AE ();	109	use AE ();
84		110
85	use base "Exporter";	111	use base "Exporter";
86		112
87	our $VERSION = '0.02';	113	our $VERSION = '0.1';
88	our @EXPORT = qw(	114	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv _any_	115	NODE $NODE *SELF node_of _any_
90	create_port create_port_on	116	resolve_node initialise_node
91	create_miniport	117	snd rcv mon kil reg psub
92	become_slave become_public	118	port
93	);	119	);
94		120
		121	our $SELF;
		122
		123	sub _self_die() {
		124	my $msg = $@;
		125	$msg =~ s/\n+$// unless ref $msg;
		126	kil $SELF, die => $msg;
		127	}
		128
95	=item NODE / $NODE	129	=item $thisnode = NODE / $NODE
96		130
97	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	131	The C<NODE> function returns, and the C<$NODE> variable contains
98	the local node. The value is initialised by a call to C<become_public> or	132	the noderef of the local node. The value is initialised by a call
99	C<become_slave>, after which all local port identifiers become invalid.	133	to C<become_public> or C<become_slave>, after which all local port
		134	identifiers become invalid.
100		135
		136	=item $noderef = node_of $port
		137
		138	Extracts and returns the noderef from a portid or a noderef.
		139
		140	=item initialise_node $noderef, $seednode, $seednode...
		141
		142	=item initialise_node "slave/", $master, $master...
		143
		144	Before a node can talk to other nodes on the network it has to initialise
		145	itself - the minimum a node needs to know is it's own name, and optionally
		146	it should know the noderefs of some other nodes in the network.
		147
		148	This function initialises a node - it must be called exactly once (or
		149	never) before calling other AnyEvent::MP functions.
		150
		151	All arguments are noderefs, which can be either resolved or unresolved.
		152
		153	There are two types of networked nodes, public nodes and slave nodes:
		154
		155	=over 4
		156
		157	=item public nodes
		158
		159	For public nodes, C<$noderef> must either be a (possibly unresolved)
		160	noderef, in which case it will be resolved, or C<undef> (or missing), in
		161	which case the noderef will be guessed.
		162
		163	Afterwards, the node will bind itself on all endpoints and try to connect
		164	to all additional C<$seednodes> that are specified. Seednodes are optional
		165	and can be used to quickly bootstrap the node into an existing network.
		166
		167	=item slave nodes
		168
		169	When the C<$noderef> is the special string C<slave/>, then the node will
		170	become a slave node. Slave nodes cannot be contacted from outside and will
		171	route most of their traffic to the master node that they attach to.
		172
		173	At least one additional noderef is required: The node will try to connect
		174	to all of them and will become a slave attached to the first node it can
		175	successfully connect to.
		176
		177	=back
		178
		179	This function will block until all nodes have been resolved and, for slave
		180	nodes, until it has successfully established a connection to a master
		181	server.
		182
		183	Example: become a public node listening on the default node.
		184
		185	initialise_node;
		186
		187	Example: become a public node, and try to contact some well-known master
		188	servers to become part of the network.
		189
		190	initialise_node undef, "master1", "master2";
		191
		192	Example: become a public node listening on port C<4041>.
		193
		194	initialise_node 4041;
		195
		196	Example: become a public node, only visible on localhost port 4044.
		197
		198	initialise_node "locahost:4044";
		199
		200	Example: become a slave node to any of the specified master servers.
		201
		202	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
		203
		204	=item $cv = resolve_node $noderef
		205
		206	Takes an unresolved node reference that may contain hostnames and
		207	abbreviated IDs, resolves all of them and returns a resolved node
		208	reference.
		209
		210	In addition to C<address:port> pairs allowed in resolved noderefs, the
		211	following forms are supported:
		212
		213	=over 4
		214
		215	=item the empty string
		216
		217	An empty-string component gets resolved as if the default port (4040) was
		218	specified.
		219
		220	=item naked port numbers (e.g. C<1234>)
		221
		222	These are resolved by prepending the local nodename and a colon, to be
		223	further resolved.
		224
		225	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
		226
		227	These are resolved by using AnyEvent::DNS to resolve them, optionally
		228	looking up SRV records for the C<aemp=4040> port, if no port was
		229	specified.
		230
		231	=back
		232
		233	=item $SELF
		234
		235	Contains the current port id while executing C<rcv> callbacks or C<psub>
		236	blocks.
		237
		238	=item SELF, %SELF, @SELF...
		239
		240	Due to some quirks in how perl exports variables, it is impossible to
		241	just export C<$SELF>, all the symbols called C<SELF> are exported by this
		242	module, but only C<$SELF> is currently used.
		243
101	=item snd $portid, type => @data	244	=item snd $port, type => @data
102		245
103	=item snd $portid, @msg	246	=item snd $port, @msg
104		247
105	Send the given message to the given port ID, which can identify either	248	Send the given message to the given port ID, which can identify either
106	a local or a remote port, and can be either a string or soemthignt hat	249	a local or a remote port, and can be either a string or soemthignt hat
107	stringifies a sa port ID (such as a port object :).	250	stringifies a sa port ID (such as a port object :).
108		251
…		…
118	JSON is used, then only strings, numbers and arrays and hashes consisting	261	JSON is used, then only strings, numbers and arrays and hashes consisting
119	of those are allowed (no objects). When Storable is used, then anything	262	of those are allowed (no objects). When Storable is used, then anything
120	that Storable can serialise and deserialise is allowed, and for the local	263	that Storable can serialise and deserialise is allowed, and for the local
121	node, anything can be passed.	264	node, anything can be passed.
122		265
123	=item $local_port = create_port	266	=item $local_port = port
124		267
125	Create a new local port object. See the next section for allowed methods.	268	Create a new local port object that can be used either as a pattern
		269	matching port ("full port") or a single-callback port ("miniport"),
		270	depending on how C<rcv> callbacks are bound to the object.
126		271
127	=cut	272	=item $port = port { my @msg = @_; $finished }
128		273
129	sub create_port {	274	Creates a "miniport", that is, a very lightweight port without any pattern
130	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;	275	matching behind it, and returns its ID. Semantically the same as creating
		276	a port and calling C<rcv $port, $callback> on it.
131		277
132	my $self = bless {	278	The block will be called for every message received on the port. When the
133	id => "$NODE#$id",	279	callback returns a true value its job is considered "done" and the port
134	names => [$id],	280	will be destroyed. Otherwise it will stay alive.
135	}, "AnyEvent::MP::Port";
136		281
137	$AnyEvent::MP::Base::PORT{$id} = sub {	282	The message will be passed as-is, no extra argument (i.e. no port id) will
138	unshift @_, $self;	283	be passed to the callback.
139		284
140	for (@{ $self->{rc0}{$_[1]} }) {	285	If you need the local port id in the callback, this works nicely:
141	$_ && &{$_->[0]}
142	&& undef $_;
143	}
144		286
145	for (@{ $self->{rcv}{$_[1]} }) {	287	my $port; $port = port {
146	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	288	snd $otherport, reply => $port;
147	&& &{$_->[0]}
148	&& undef $_;
149	}
150
151	for (@{ $self->{any} }) {
152	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
153	&& &{$_->[0]}
154	&& undef $_;
155	}
156	};	289	};
157		290
158	$self	291	=cut
		292
		293	sub rcv($@);
		294
		295	sub port(;&) {
		296	my $id = "$UNIQ." . $ID++;
		297	my $port = "$NODE#$id";
		298
		299	if (@_) {
		300	rcv $port, shift;
		301	} else {
		302	$PORT{$id} = sub { }; # nop
		303	}
		304
		305	$port
159	}	306	}
160		307
161	=item $portid = create_miniport { }	308	=item reg $port, $name
162		309
163	Creates a "mini port", that is, a port without much #TODO	310	Registers the given port under the name C<$name>. If the name already
		311	exists it is replaced.
164		312
165	=cut	313	A port can only be registered under one well known name.
166		314
167	sub create_miniport(&) {	315	A port automatically becomes unregistered when it is killed.
168	my $cb = shift;
169	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;
170		316
171	$AnyEvent::MP::Base::PORT{$id} = sub {	317	=cut
172	$_[0] = "$NODE#$id";
173	&$cb
174	and delete $AnyEvent::MP::Base::PORT{$id};
175	};
176		318
177	"$NODE#$id"	319	sub reg(@) {
		320	my ($port, $name) = @_;
		321
		322	$REG{$name} = $port;
178	}	323	}
179		324
180	package AnyEvent::MP::Port;	325	=item rcv $port, $callback->(@msg)
181		326
182	=back	327	Replaces the callback on the specified miniport (after converting it to
		328	one if required).
183		329
184	=head1 METHODS FOR PORT OBJECTS	330	=item rcv $port, tagstring => $callback->(@msg), ...
185		331
186	=over 4	332	=item rcv $port, $smartmatch => $callback->(@msg), ...
187		333
188	=item "$port"
189
190	A port object stringifies to its port ID, so can be used directly for
191	C<snd> operations.
192
193	=cut
194
195	use overload
196	'""' => sub { $_[0]{id} },
197	fallback => 1;
198
199	=item $port->rcv (type => $callback->($port, @msg))
200
201	=item $port->rcv ($smartmatch => $callback->($port, @msg))
202
203	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	334	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
204		335
205	Register a callback on the given port.	336	Register callbacks to be called on matching messages on the given full
		337	port (after converting it to one if required).
206		338
207	The callback has to return a true value when its work is done, after	339	The callback has to return a true value when its work is done, after
208	which is will be removed, or a false value in which case it will stay	340	which is will be removed, or a false value in which case it will stay
209	registered.	341	registered.
210		342
		343	The global C<$SELF> (exported by this module) contains C<$port> while
		344	executing the callback.
		345
		346	Runtime errors wdurign callback execution will result in the port being
		347	C<kil>ed.
		348
211	If the match is an array reference, then it will be matched against the	349	If the match is an array reference, then it will be matched against the
212	first elements of the message, otherwise only the first element is being	350	first elements of the message, otherwise only the first element is being
213	matched.	351	matched.
214		352
215	Any element in the match that is specified as C<_any_> (a function	353	Any element in the match that is specified as C<_any_> (a function
…		…
220	also the most efficient match (by far).	358	also the most efficient match (by far).
221		359
222	=cut	360	=cut
223		361
224	sub rcv($@) {	362	sub rcv($@) {
225	my ($self, $match, $cb) = @_;	363	my $port = shift;
		364	my ($noderef, $portid) = split /#/, $port, 2;
226		365
227	if (!ref $match) {	366	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
228	push @{ $self->{rc0}{$match} }, [$cb];	367	or Carp::croak "$port: rcv can only be called on local ports, caught";
229	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	368
230	my ($type, @match) = @$match;	369	if (@_ == 1) {
231	@match	370	my $cb = shift;
232	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	371	delete $PORT_DATA{$portid};
233	: push @{ $self->{rc0}{$match->[0]} }, [$cb];	372	$PORT{$portid} = sub {
		373	local $SELF = $port;
		374	eval {
		375	&$cb
		376	and kil $port;
		377	};
		378	_self_die if $@;
		379	};
234	} else {	380	} else {
		381	my $self = $PORT_DATA{$portid} \|\|= do {
		382	my $self = bless {
		383	id => $port,
		384	}, "AnyEvent::MP::Port";
		385
		386	$PORT{$portid} = sub {
		387	local $SELF = $port;
		388
		389	eval {
		390	for (@{ $self->{rc0}{$_[0]} }) {
		391	$_ && &{$_->[0]}
		392	&& undef $_;
		393	}
		394
		395	for (@{ $self->{rcv}{$_[0]} }) {
		396	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
		397	&& &{$_->[0]}
		398	&& undef $_;
		399	}
		400
		401	for (@{ $self->{any} }) {
		402	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
		403	&& &{$_->[0]}
		404	&& undef $_;
		405	}
		406	};
		407	_self_die if $@;
		408	};
		409
		410	$self
		411	};
		412
		413	"AnyEvent::MP::Port" eq ref $self
		414	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		415
		416	while (@_) {
		417	my ($match, $cb) = splice @_, 0, 2;
		418
		419	if (!ref $match) {
		420	push @{ $self->{rc0}{$match} }, [$cb];
		421	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
		422	my ($type, @match) = @$match;
		423	@match
		424	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
		425	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
		426	} else {
235	push @{ $self->{any} }, [$cb, $match];	427	push @{ $self->{any} }, [$cb, $match];
		428	}
		429	}
		430	}
		431
		432	$port
		433	}
		434
		435	=item $closure = psub { BLOCK }
		436
		437	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		438	closure is executed, sets up the environment in the same way as in C<rcv>
		439	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		440
		441	This is useful when you register callbacks from C<rcv> callbacks:
		442
		443	rcv delayed_reply => sub {
		444	my ($delay, @reply) = @_;
		445	my $timer = AE::timer $delay, 0, psub {
		446	snd @reply, $SELF;
		447	};
		448	};
		449
		450	=cut
		451
		452	sub psub(&) {
		453	my $cb = shift;
		454
		455	my $port = $SELF
		456	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		457
		458	sub {
		459	local $SELF = $port;
		460
		461	if (wantarray) {
		462	my @res = eval { &$cb };
		463	_self_die if $@;
		464	@res
		465	} else {
		466	my $res = eval { &$cb };
		467	_self_die if $@;
		468	$res
		469	}
236	}	470	}
237	}	471	}
238		472
239	=item $port->register ($name)	473	=item $guard = mon $port, $cb->(@reason)
240		474
241	Registers the given port under the well known name C<$name>. If the name	475	=item $guard = mon $port, $otherport
242	already exists it is replaced.
243		476
244	A port can only be registered under one well known name.	477	=item $guard = mon $port, $otherport, @msg
245		478
246	=cut	479	Monitor the given port and do something when the port is killed.
247		480
248	sub register {	481	In the first form, the callback is simply called with any number
249	my ($self, $name) = @_;	482	of C<@reason> elements (no @reason means that the port was deleted
		483	"normally"). Note also that I<< the callback B<must> never die >>, so use
		484	C<eval> if unsure.
250		485
251	$self->{wkname} = $name;	486	In the second form, the other port will be C<kil>'ed with C<@reason>, iff
252	$AnyEvent::MP::Base::WKP{$name} = "$self";	487	a @reason was specified, i.e. on "normal" kils nothing happens, while
		488	under all other conditions, the other port is killed with the same reason.
		489
		490	In the last form, a message of the form C<@msg, @reason> will be C<snd>.
		491
		492	Example: call a given callback when C<$port> is killed.
		493
		494	mon $port, sub { warn "port died because of <@_>\n" };
		495
		496	Example: kill ourselves when C<$port> is killed abnormally.
		497
		498	mon $port, $self;
		499
		500	Example: send us a restart message another C<$port> is killed.
		501
		502	mon $port, $self => "restart";
		503
		504	=cut
		505
		506	sub mon {
		507	my ($noderef, $port) = split /#/, shift, 2;
		508
		509	my $node = $NODE{$noderef} \|\| add_node $noderef;
		510
		511	my $cb = shift;
		512
		513	unless (ref $cb) {
		514	if (@_) {
		515	# send a kill info message
		516	my (@msg) = ($cb, @_);
		517	$cb = sub { snd @msg, @_ };
		518	} else {
		519	# simply kill other port
		520	my $port = $cb;
		521	$cb = sub { kil $port, @_ if @_ };
		522	}
		523	}
		524
		525	$node->monitor ($port, $cb);
		526
		527	defined wantarray
		528	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
253	}	529	}
254		530
255	=item $port->destroy	531	=item $guard = mon_guard $port, $ref, $ref...
256		532
257	Explicitly destroy/remove/nuke/vaporise the port.	533	Monitors the given C<$port> and keeps the passed references. When the port
		534	is killed, the references will be freed.
258		535
259	Ports are normally kept alive by there mere existance alone, and need to	536	Optionally returns a guard that will stop the monitoring.
260	be destroyed explicitly.
261		537
262	=cut	538	This function is useful when you create e.g. timers or other watchers and
		539	want to free them when the port gets killed:
263		540
264	sub destroy {	541	$port->rcv (start => sub {
265	my ($self) = @_;	542	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		543	undef $timer if 0.9 < rand;
		544	});
		545	});
266		546
267	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	547	=cut
268		548
269	delete $AnyEvent::MP::Base::PORT{$_}	549	sub mon_guard {
270	for @{ $self->{names} };	550	my ($port, @refs) = @_;
		551
		552	mon $port, sub { 0 && @refs }
271	}	553	}
272		554
273	=back	555	=item lnk $port1, $port2
274		556
275	=head1 FUNCTIONS FOR NODES	557	Link two ports. This is simply a shorthand for:
276		558
277	=over 4	559	mon $port1, $port2;
		560	mon $port2, $port1;
278		561
279	=item mon $noderef, $callback->($noderef, $status, $)	562	It means that if either one is killed abnormally, the other one gets
		563	killed as well.
280		564
281	Monitors the given noderef.	565	=item kil $port[, @reason]
282		566
283	=item become_public endpoint...	567	Kill the specified port with the given C<@reason>.
284		568
285	Tells the node to become a public node, i.e. reachable from other nodes.	569	If no C<@reason> is specified, then the port is killed "normally" (linked
		570	ports will not be kileld, or even notified).
286		571
287	If no arguments are given, or the first argument is C<undef>, then	572	Otherwise, linked ports get killed with the same reason (second form of
288	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the	573	C<mon>, see below).
289	local nodename resolves to.
290		574
291	Otherwise the first argument must be an array-reference with transport	575	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
292	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	576	will be reported as reason C<< die => $@ >>.
293	local nodename is used as hostname). The endpoints are all resolved and
294	will become the node reference.
295		577
296	=cut	578	Transport/communication errors are reported as C<< transport_error =>
		579	$message >>.
297		580
298	=back	581	=back
299		582
300	=head1 NODE MESSAGES	583	=head1 NODE MESSAGES
301		584
302	Nodes understand the following messages sent to them. Many of them take	585	Nodes understand the following messages sent to them. Many of them take
303	arguments called C<@reply>, which will simply be used to compose a reply	586	arguments called C<@reply>, which will simply be used to compose a reply
304	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	587	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
305	the remaining arguments are simply the message data.	588	the remaining arguments are simply the message data.
306		589
		590	While other messages exist, they are not public and subject to change.
		591
307	=over 4	592	=over 4
308		593
309	=cut	594	=cut
310		595
311	=item wkp => $name, @reply	596	=item lookup => $name, @reply
312		597
313	Replies with the port ID of the specified well-known port, or C<undef>.	598	Replies with the port ID of the specified well-known port, or C<undef>.
314		599
315	=item devnull => ...	600	=item devnull => ...
316		601
…		…
339	snd $NODE, time => $myport, timereply => 1, 2;	624	snd $NODE, time => $myport, timereply => 1, 2;
340	# => snd $myport, timereply => 1, 2, <time>	625	# => snd $myport, timereply => 1, 2, <time>
341		626
342	=back	627	=back
343		628
		629	=head1 AnyEvent::MP vs. Distributed Erlang
		630
		631	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		632	== aemp node, Erlang process == aemp port), so many of the documents and
		633	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		634	sample:
		635
		636	http://www.Erlang.se/doc/programming_rules.shtml
		637	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		638	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		639	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		640
		641	Despite the similarities, there are also some important differences:
		642
		643	=over 4
		644
		645	=item * Node references contain the recipe on how to contact them.
		646
		647	Erlang relies on special naming and DNS to work everywhere in the
		648	same way. AEMP relies on each node knowing it's own address(es), with
		649	convenience functionality.
		650
		651	This means that AEMP requires a less tightly controlled environment at the
		652	cost of longer node references and a slightly higher management overhead.
		653
		654	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		655
		656	Erlang uses processes that selctively receive messages, and therefore
		657	needs a queue. AEMP is event based, queuing messages would serve no useful
		658	purpose.
		659
		660	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
		661
		662	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		663
		664	Sending messages in Erlang is synchronous and blocks the process. AEMP
		665	sends are immediate, connection establishment is handled in the
		666	background.
		667
		668	=item * Erlang can silently lose messages, AEMP cannot.
		669
		670	Erlang makes few guarantees on messages delivery - messages can get lost
		671	without any of the processes realising it (i.e. you send messages a, b,
		672	and c, and the other side only receives messages a and c).
		673
		674	AEMP guarantees correct ordering, and the guarantee that there are no
		675	holes in the message sequence.
		676
		677	=item * In Erlang, processes can be declared dead and later be found to be
		678	alive.
		679
		680	In Erlang it can happen that a monitored process is declared dead and
		681	linked processes get killed, but later it turns out that the process is
		682	still alive - and can receive messages.
		683
		684	In AEMP, when port monitoring detects a port as dead, then that port will
		685	eventually be killed - it cannot happen that a node detects a port as dead
		686	and then later sends messages to it, finding it is still alive.
		687
		688	=item * Erlang can send messages to the wrong port, AEMP does not.
		689
		690	In Erlang it is quite possible that a node that restarts reuses a process
		691	ID known to other nodes for a completely different process, causing
		692	messages destined for that process to end up in an unrelated process.
		693
		694	AEMP never reuses port IDs, so old messages or old port IDs floating
		695	around in the network will not be sent to an unrelated port.
		696
		697	=item * Erlang uses unprotected connections, AEMP uses secure
		698	authentication and can use TLS.
		699
		700	AEMP can use a proven protocol - SSL/TLS - to protect connections and
		701	securely authenticate nodes.
		702
		703	=item * The AEMP protocol is optimised for both text-based and binary
		704	communications.
		705
		706	The AEMP protocol, unlike the Erlang protocol, supports both
		707	language-independent text-only protocols (good for debugging) and binary,
		708	language-specific serialisers (e.g. Storable).
		709
		710	It has also been carefully designed to be implementable in other languages
		711	with a minimum of work while gracefully degrading fucntionality to make the
		712	protocol simple.
		713
		714	=item * AEMP has more flexible monitoring options than Erlang.
		715
		716	In Erlang, you can chose to receive I<all> exit signals as messages
		717	or I<none>, there is no in-between, so monitoring single processes is
		718	difficult to implement. Monitoring in AEMP is more flexible than in
		719	Erlang, as one can choose between automatic kill, exit message or callback
		720	on a per-process basis.
		721
		722	=item * Erlang has different semantics for monitoring and linking, AEMP has the same.
		723
		724	Monitoring in Erlang is not an indicator of process death/crashes,
		725	as linking is (except linking is unreliable in Erlang). In AEMP, the
		726	semantics of monitoring and linking are identical, linking is simply
		727	two-way monitoring with automatic kill.
		728
		729	=back
		730
344	=head1 SEE ALSO	731	=head1 SEE ALSO
345		732
346	L<AnyEvent>.	733	L<AnyEvent>.
347		734
348	=head1 AUTHOR	735	=head1 AUTHOR

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Revision 1.35 by root, Thu Aug 6 10:21:48 2009 UTC