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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.48 by root, Thu Aug 13 02:59:42 2009 UTC vs.
Revision 1.94 by root, Tue Sep 22 14:14:43 2009 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using miniports	24	# creating/using ports, the simple way
28	my $miniport = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using full ports	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, smartmatch => $cb->(@msg);
33	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
34	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
35
36	# more, smarter, matches (_any_ is exported by this module)
37	rcv $port, [child_died => $pid] => sub { ...
38	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
39		31
40	# create a port on another node	32	# create a port on another node
41	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
42		34
43	# monitoring	35	# monitoring
44	mon $port, $cb->(@msg) # callback is invoked on death	36	mon $localport, $cb->(@msg) # callback is invoked on death
45	mon $port, $otherport # kill otherport on abnormal death	37	mon $localport, $otherport # kill otherport on abnormal death
46	mon $port, $otherport, @msg # send message on death	38	mon $localport, $otherport, @msg # send message on death
47		39
48	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
49		41
		42	bin/aemp - stable.
50	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
51	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.
52	AnyEvent::MP::Kernel - WIP
53	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable API.
54		46	AnyEvent::MP::Global - stable API.
55	stay tuned.
56		47
57	=head1 DESCRIPTION	48	=head1 DESCRIPTION
58		49
59	This module (-family) implements a simple message passing framework.	50	This module (-family) implements a simple message passing framework.
60		51
61	Despite its simplicity, you can securely message other processes running	52	Despite its simplicity, you can securely message other processes running
62	on the same or other hosts.	53	on the same or other hosts, and you can supervise entities remotely.
63		54
64	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	55	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
65	manual page.	56	manual page and the examples under F<eg/>.
66
67	At the moment, this module family is severly broken and underdocumented,
68	so do not use. This was uploaded mainly to reserve the CPAN namespace -
69	stay tuned!
70		57
71	=head1 CONCEPTS	58	=head1 CONCEPTS
72		59
73	=over 4	60	=over 4
74		61
75	=item port	62	=item port
76		63
77	A port is something you can send messages to (with the C<snd> function).	64	Not to be confused with a TCP port, a "port" is something you can send
		65	messages to (with the C<snd> function).
78		66
79	Some ports allow you to register C<rcv> handlers that can match specific	67	Ports allow you to register C<rcv> handlers that can match all or just
80	messages. All C<rcv> handlers will receive messages they match, messages	68	some messages. Messages send to ports will not be queued, regardless of
81	will not be queued.	69	anything was listening for them or not.
82		70
83	=item port id - C<noderef#portname>	71	=item port ID - C<nodeid#portname>
84		72
85	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	73	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
86	separator, and a port name (a printable string of unspecified format). An	74	separator, and a port name (a printable string of unspecified format).
87	exception is the the node port, whose ID is identical to its node
88	reference.
89		75
90	=item node	76	=item node
91		77
92	A node is a single process containing at least one port - the node	78	A node is a single process containing at least one port - the node port,
93	port. You can send messages to node ports to find existing ports or to	79	which enables nodes to manage each other remotely, and to create new
94	create new ports, among other things.	80	ports.
95		81
96	Nodes are either private (single-process only), slaves (connected to a	82	Nodes are either public (have one or more listening ports) or private
97	master node only) or public nodes (connectable from unrelated nodes).	83	(no listening ports). Private nodes cannot talk to other private nodes
		84	currently.
98		85
99	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	86	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
100		87
101	A node reference is a string that either simply identifies the node (for	88	A node ID is a string that uniquely identifies the node within a
102	private and slave nodes), or contains a recipe on how to reach a given	89	network. Depending on the configuration used, node IDs can look like a
103	node (for public nodes).	90	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		91	doesn't interpret node IDs in any way.
104		92
105	This recipe is simply a comma-separated list of C<address:port> pairs (for	93	=item binds - C<ip:port>
106	TCP/IP, other protocols might look different).
107		94
108	Node references come in two flavours: resolved (containing only numerical	95	Nodes can only talk to each other by creating some kind of connection to
109	addresses) or unresolved (where hostnames are used instead of addresses).	96	each other. To do this, nodes should listen on one or more local transport
		97	endpoints - binds. Currently, only standard C<ip:port> specifications can
		98	be used, which specify TCP ports to listen on.
110		99
111	Before using an unresolved node reference in a message you first have to	100	=item seed nodes
112	resolve it.	101
		102	When a node starts, it knows nothing about the network. To teach the node
		103	about the network it first has to contact some other node within the
		104	network. This node is called a seed.
		105
		106	Apart from the fact that other nodes know them as seed nodes and they have
		107	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		108	any node can function as a seed node for others.
		109
		110	In addition to discovering the network, seed nodes are also used to
		111	maintain the network and to connect nodes that otherwise would have
		112	trouble connecting. They form the backbone of an AnyEvent::MP network.
		113
		114	Seed nodes are expected to be long-running, and at least one seed node
		115	should always be available. They should also be relatively responsive - a
		116	seed node that blocks for long periods will slow down everybody else.
		117
		118	=item seeds - C<host:port>
		119
		120	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		121	TCP port) of nodes thta should be used as seed nodes.
		122
		123	The nodes listening on those endpoints are expected to be long-running,
		124	and at least one of those should always be available. When nodes run out
		125	of connections (e.g. due to a network error), they try to re-establish
		126	connections to some seednodes again to join the network.
113		127
114	=back	128	=back
115		129
116	=head1 VARIABLES/FUNCTIONS	130	=head1 VARIABLES/FUNCTIONS
117		131
132	use base "Exporter";	146	use base "Exporter";
133		147
134	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	148	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
135		149
136	our @EXPORT = qw(	150	our @EXPORT = qw(
137	NODE $NODE *SELF node_of _any_	151	NODE $NODE *SELF node_of after
138	resolve_node initialise_node	152	configure
139	snd rcv mon kil reg psub spawn	153	snd rcv mon mon_guard kil psub spawn cal
140	port	154	port
141	);	155	);
142		156
143	our $SELF;	157	our $SELF;
144		158
…		…
148	kil $SELF, die => $msg;	162	kil $SELF, die => $msg;
149	}	163	}
150		164
151	=item $thisnode = NODE / $NODE	165	=item $thisnode = NODE / $NODE
152		166
153	The C<NODE> function returns, and the C<$NODE> variable contains	167	The C<NODE> function returns, and the C<$NODE> variable contains, the node
154	the noderef of the local node. The value is initialised by a call	168	ID of the node running in the current process. This value is initialised by
155	to C<become_public> or C<become_slave>, after which all local port	169	a call to C<configure>.
156	identifiers become invalid.
157		170
158	=item $noderef = node_of $port	171	=item $nodeid = node_of $port
159		172
160	Extracts and returns the noderef from a portid or a noderef.	173	Extracts and returns the node ID from a port ID or a node ID.
161		174
162	=item initialise_node $noderef, $seednode, $seednode...	175	=item configure $profile, key => value...
163		176
164	=item initialise_node "slave/", $master, $master...	177	=item configure key => value...
165		178
166	Before a node can talk to other nodes on the network it has to initialise	179	Before a node can talk to other nodes on the network (i.e. enter
167	itself - the minimum a node needs to know is it's own name, and optionally	180	"distributed mode") it has to configure itself - the minimum a node needs
168	it should know the noderefs of some other nodes in the network.	181	to know is its own name, and optionally it should know the addresses of
		182	some other nodes in the network to discover other nodes.
169		183
170	This function initialises a node - it must be called exactly once (or	184	This function configures a node - it must be called exactly once (or
171	never) before calling other AnyEvent::MP functions.	185	never) before calling other AnyEvent::MP functions.
172		186
173	All arguments are noderefs, which can be either resolved or unresolved.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176
177	=over 4	187	=over 4
178		188
179	=item public nodes	189	=item step 1, gathering configuration from profiles
180		190
181	For public nodes, C<$noderef> must either be a (possibly unresolved)	191	The function first looks up a profile in the aemp configuration (see the
182	noderef, in which case it will be resolved, or C<undef> (or missing), in	192	L<aemp> commandline utility). The profile name can be specified via the
183	which case the noderef will be guessed.	193	named C<profile> parameter or can simply be the first parameter). If it is
		194	missing, then the nodename (F<uname -n>) will be used as profile name.
184		195
185	Afterwards, the node will bind itself on all endpoints and try to connect	196	The profile data is then gathered as follows:
186	to all additional C<$seednodes> that are specified. Seednodes are optional
187	and can be used to quickly bootstrap the node into an existing network.
188		197
189	=item slave nodes	198	First, all remaining key => value pairs (all of which are conveniently
		199	undocumented at the moment) will be interpreted as configuration
		200	data. Then they will be overwritten by any values specified in the global
		201	default configuration (see the F<aemp> utility), then the chain of
		202	profiles chosen by the profile name (and any C<parent> attributes).
190		203
191	When the C<$noderef> is the special string C<slave/>, then the node will	204	That means that the values specified in the profile have highest priority
192	become a slave node. Slave nodes cannot be contacted from outside and will	205	and the values specified directly via C<configure> have lowest priority,
193	route most of their traffic to the master node that they attach to.	206	and can only be used to specify defaults.
194		207
195	At least one additional noderef is required: The node will try to connect	208	If the profile specifies a node ID, then this will become the node ID of
196	to all of them and will become a slave attached to the first node it can	209	this process. If not, then the profile name will be used as node ID. The
197	successfully connect to.	210	special node ID of C<anon/> will be replaced by a random node ID.
		211
		212	=item step 2, bind listener sockets
		213
		214	The next step is to look up the binds in the profile, followed by binding
		215	aemp protocol listeners on all binds specified (it is possible and valid
		216	to have no binds, meaning that the node cannot be contacted form the
		217	outside. This means the node cannot talk to other nodes that also have no
		218	binds, but it can still talk to all "normal" nodes).
		219
		220	If the profile does not specify a binds list, then a default of C<*> is
		221	used, meaning the node will bind on a dynamically-assigned port on every
		222	local IP address it finds.
		223
		224	=item step 3, connect to seed nodes
		225
		226	As the last step, the seeds list from the profile is passed to the
		227	L<AnyEvent::MP::Global> module, which will then use it to keep
		228	connectivity with at least one node at any point in time.
198		229
199	=back	230	=back
200		231
201	This function will block until all nodes have been resolved and, for slave	232	Example: become a distributed node using the local node name as profile.
202	nodes, until it has successfully established a connection to a master	233	This should be the most common form of invocation for "daemon"-type nodes.
203	server.
204		234
205	Example: become a public node listening on the default node.	235	configure
206		236
207	initialise_node;	237	Example: become an anonymous node. This form is often used for commandline
		238	clients.
208		239
209	Example: become a public node, and try to contact some well-known master	240	configure nodeid => "anon/";
210	servers to become part of the network.
211		241
212	initialise_node undef, "master1", "master2";	242	Example: configure a node using a profile called seed, which si suitable
		243	for a seed node as it binds on all local addresses on a fixed port (4040,
		244	customary for aemp).
213		245
214	Example: become a public node listening on port C<4041>.	246	# use the aemp commandline utility
		247	# aemp profile seed nodeid anon/ binds '*:4040'
215		248
216	initialise_node 4041;	249	# then use it
		250	configure profile => "seed";
217		251
218	Example: become a public node, only visible on localhost port 4044.	252	# or simply use aemp from the shell again:
		253	# aemp run profile seed
219		254
220	initialise_node "locahost:4044";	255	# or provide a nicer-to-remember nodeid
221		256	# aemp run profile seed nodeid "$(hostname)"
222	Example: become a slave node to any of the specified master servers.
223
224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
225
226	=item $cv = resolve_node $noderef
227
228	Takes an unresolved node reference that may contain hostnames and
229	abbreviated IDs, resolves all of them and returns a resolved node
230	reference.
231
232	In addition to C<address:port> pairs allowed in resolved noderefs, the
233	following forms are supported:
234
235	=over 4
236
237	=item the empty string
238
239	An empty-string component gets resolved as if the default port (4040) was
240	specified.
241
242	=item naked port numbers (e.g. C<1234>)
243
244	These are resolved by prepending the local nodename and a colon, to be
245	further resolved.
246
247	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
248
249	These are resolved by using AnyEvent::DNS to resolve them, optionally
250	looking up SRV records for the C<aemp=4040> port, if no port was
251	specified.
252
253	=back
254		257
255	=item $SELF	258	=item $SELF
256		259
257	Contains the current port id while executing C<rcv> callbacks or C<psub>	260	Contains the current port id while executing C<rcv> callbacks or C<psub>
258	blocks.	261	blocks.
259		262
260	=item SELF, %SELF, @SELF...	263	=item *SELF, SELF, %SELF, @SELF...
261		264
262	Due to some quirks in how perl exports variables, it is impossible to	265	Due to some quirks in how perl exports variables, it is impossible to
263	just export C<$SELF>, all the symbols called C<SELF> are exported by this	266	just export C<$SELF>, all the symbols named C<SELF> are exported by this
264	module, but only C<$SELF> is currently used.	267	module, but only C<$SELF> is currently used.
265		268
266	=item snd $port, type => @data	269	=item snd $port, type => @data
267		270
268	=item snd $port, @msg	271	=item snd $port, @msg
269		272
270	Send the given message to the given port ID, which can identify either	273	Send the given message to the given port, which can identify either a
271	a local or a remote port, and can be either a string or soemthignt hat	274	local or a remote port, and must be a port ID.
272	stringifies a sa port ID (such as a port object :).
273		275
274	While the message can be about anything, it is highly recommended to use a	276	While the message can be almost anything, it is highly recommended to
275	string as first element (a portid, or some word that indicates a request	277	use a string as first element (a port ID, or some word that indicates a
276	type etc.).	278	request type etc.) and to consist if only simple perl values (scalars,
		279	arrays, hashes) - if you think you need to pass an object, think again.
277		280
278	The message data effectively becomes read-only after a call to this	281	The message data logically becomes read-only after a call to this
279	function: modifying any argument is not allowed and can cause many	282	function: modifying any argument (or values referenced by them) is
280	problems.	283	forbidden, as there can be considerable time between the call to C<snd>
		284	and the time the message is actually being serialised - in fact, it might
		285	never be copied as within the same process it is simply handed to the
		286	receiving port.
281		287
282	The type of data you can transfer depends on the transport protocol: when	288	The type of data you can transfer depends on the transport protocol: when
283	JSON is used, then only strings, numbers and arrays and hashes consisting	289	JSON is used, then only strings, numbers and arrays and hashes consisting
284	of those are allowed (no objects). When Storable is used, then anything	290	of those are allowed (no objects). When Storable is used, then anything
285	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
286	node, anything can be passed.	292	node, anything can be passed. Best rely only on the common denominator of
		293	these.
287		294
288	=item $local_port = port	295	=item $local_port = port
289		296
290	Create a new local port object that can be used either as a pattern	297	Create a new local port object and returns its port ID. Initially it has
291	matching port ("full port") or a single-callback port ("miniport"),	298	no callbacks set and will throw an error when it receives messages.
292	depending on how C<rcv> callbacks are bound to the object.
293		299
294	=item $port = port { my @msg = @_; $finished }	300	=item $local_port = port { my @msg = @_ }
295		301
296	Creates a "miniport", that is, a very lightweight port without any pattern	302	Creates a new local port, and returns its ID. Semantically the same as
297	matching behind it, and returns its ID. Semantically the same as creating
298	a port and calling C<rcv $port, $callback> on it.	303	creating a port and calling C<rcv $port, $callback> on it.
299		304
300	The block will be called for every message received on the port. When the	305	The block will be called for every message received on the port, with the
301	callback returns a true value its job is considered "done" and the port	306	global variable C<$SELF> set to the port ID. Runtime errors will cause the
302	will be destroyed. Otherwise it will stay alive.	307	port to be C<kil>ed. The message will be passed as-is, no extra argument
		308	(i.e. no port ID) will be passed to the callback.
303		309
304	The message will be passed as-is, no extra argument (i.e. no port id) will	310	If you want to stop/destroy the port, simply C<kil> it:
305	be passed to the callback.
306		311
307	If you need the local port id in the callback, this works nicely:	312	my $port = port {
308		313	my @msg = @_;
309	my $port; $port = port {	314	...
310	snd $otherport, reply => $port;	315	kil $SELF;
311	};	316	};
312		317
313	=cut	318	=cut
314		319
315	sub rcv($@);	320	sub rcv($@);
		321
		322	sub _kilme {
		323	die "received message on port without callback";
		324	}
316		325
317	sub port(;&) {	326	sub port(;&) {
318	my $id = "$UNIQ." . $ID++;	327	my $id = "$UNIQ." . $ID++;
319	my $port = "$NODE#$id";	328	my $port = "$NODE#$id";
320		329
321	if (@_) {	330	rcv $port, shift \|\| \&_kilme;
322	rcv $port, shift;
323	} else {
324	$PORT{$id} = sub { }; # nop
325	}
326		331
327	$port	332	$port
328	}	333	}
329		334
330	=item reg $port, $name
331
332	=item reg $name
333
334	Registers the given port (or C<$SELF><<< if missing) under the name
335	C<$name>. If the name already exists it is replaced.
336
337	A port can only be registered under one well known name.
338
339	A port automatically becomes unregistered when it is killed.
340
341	=cut
342
343	sub reg(@) {
344	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
345
346	$REG{$_[0]} = $port;
347	}
348
349	=item rcv $port, $callback->(@msg)	335	=item rcv $local_port, $callback->(@msg)
350		336
351	Replaces the callback on the specified miniport (after converting it to	337	Replaces the default callback on the specified port. There is no way to
352	one if required).	338	remove the default callback: use C<sub { }> to disable it, or better
353		339	C<kil> the port when it is no longer needed.
354	=item rcv $port, tagstring => $callback->(@msg), ...
355
356	=item rcv $port, $smartmatch => $callback->(@msg), ...
357
358	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
359
360	Register callbacks to be called on matching messages on the given full
361	port (after converting it to one if required) and return the port.
362
363	The callback has to return a true value when its work is done, after
364	which is will be removed, or a false value in which case it will stay
365	registered.
366		340
367	The global C<$SELF> (exported by this module) contains C<$port> while	341	The global C<$SELF> (exported by this module) contains C<$port> while
368	executing the callback.	342	executing the callback. Runtime errors during callback execution will
		343	result in the port being C<kil>ed.
369		344
370	Runtime errors during callback execution will result in the port being	345	The default callback received all messages not matched by a more specific
371	C<kil>ed.	346	C<tag> match.
372		347
373	If the match is an array reference, then it will be matched against the	348	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
374	first elements of the message, otherwise only the first element is being
375	matched.
376		349
377	Any element in the match that is specified as C<_any_> (a function	350	Register (or replace) callbacks to be called on messages starting with the
378	exported by this module) matches any single element of the message.	351	given tag on the given port (and return the port), or unregister it (when
		352	C<$callback> is C<$undef> or missing). There can only be one callback
		353	registered for each tag.
379		354
380	While not required, it is highly recommended that the first matching	355	The original message will be passed to the callback, after the first
381	element is a string identifying the message. The one-string-only match is	356	element (the tag) has been removed. The callback will use the same
382	also the most efficient match (by far).	357	environment as the default callback (see above).
383		358
384	Example: create a port and bind receivers on it in one go.	359	Example: create a port and bind receivers on it in one go.
385		360
386	my $port = rcv port,	361	my $port = rcv port,
387	msg1 => sub { ...; 0 },	362	msg1 => sub { ... },
388	msg2 => sub { ...; 0 },	363	msg2 => sub { ... },
389	;	364	;
390		365
391	Example: create a port, bind receivers and send it in a message elsewhere	366	Example: create a port, bind receivers and send it in a message elsewhere
392	in one go:	367	in one go:
393		368
394	snd $otherport, reply =>	369	snd $otherport, reply =>
395	rcv port,	370	rcv port,
396	msg1 => sub { ...; 0 },	371	msg1 => sub { ... },
397	...	372	...
398	;	373	;
399		374
		375	Example: temporarily register a rcv callback for a tag matching some port
		376	(e.g. for a rpc reply) and unregister it after a message was received.
		377
		378	rcv $port, $otherport => sub {
		379	my @reply = @_;
		380
		381	rcv $SELF, $otherport;
		382	};
		383
400	=cut	384	=cut
401		385
402	sub rcv($@) {	386	sub rcv($@) {
403	my $port = shift;	387	my $port = shift;
404	my ($noderef, $portid) = split /#/, $port, 2;	388	my ($nodeid, $portid) = split /#/, $port, 2;
405		389
406	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	390	$NODE{$nodeid} == $NODE{""}
407	or Carp::croak "$port: rcv can only be called on local ports, caught";	391	or Carp::croak "$port: rcv can only be called on local ports, caught";
408		392
409	if (@_ == 1) {	393	while (@_) {
		394	if (ref $_[0]) {
		395	if (my $self = $PORT_DATA{$portid}) {
		396	"AnyEvent::MP::Port" eq ref $self
		397	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		398
		399	$self->[2] = shift;
		400	} else {
410	my $cb = shift;	401	my $cb = shift;
411	delete $PORT_DATA{$portid};
412	$PORT{$portid} = sub {	402	$PORT{$portid} = sub {
413	local $SELF = $port;	403	local $SELF = $port;
414	eval {	404	eval { &$cb }; _self_die if $@;
415	&$cb	405	};
416	and kil $port;
417	};	406	}
418	_self_die if $@;	407	} elsif (defined $_[0]) {
419	};
420	} else {
421	my $self = $PORT_DATA{$portid} \|\|= do {	408	my $self = $PORT_DATA{$portid} \|\|= do {
422	my $self = bless {	409	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
423	id => $port,
424	}, "AnyEvent::MP::Port";
425		410
426	$PORT{$portid} = sub {	411	$PORT{$portid} = sub {
427	local $SELF = $port;	412	local $SELF = $port;
428		413
429	eval {
430	for (@{ $self->{rc0}{$_[0]} }) {	414	if (my $cb = $self->[1]{$_[0]}) {
431	$_ && &{$_->[0]}	415	shift;
432	&& undef $_;	416	eval { &$cb }; _self_die if $@;
433	}	417	} else {
434
435	for (@{ $self->{rcv}{$_[0]} }) {
436	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
437	&& &{$_->[0]}	418	&{ $self->[0] };
438	&& undef $_;
439	}
440
441	for (@{ $self->{any} }) {
442	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
443	&& &{$_->[0]}
444	&& undef $_;
445	}	419	}
446	};	420	};
447	_self_die if $@;	421
		422	$self
448	};	423	};
449		424
450	$self
451	};
452
453	"AnyEvent::MP::Port" eq ref $self	425	"AnyEvent::MP::Port" eq ref $self
454	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	426	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
455		427
456	while (@_) {
457	my ($match, $cb) = splice @_, 0, 2;	428	my ($tag, $cb) = splice @_, 0, 2;
458		429
459	if (!ref $match) {	430	if (defined $cb) {
460	push @{ $self->{rc0}{$match} }, [$cb];	431	$self->[1]{$tag} = $cb;
461	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
462	my ($type, @match) = @$match;
463	@match
464	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
465	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
466	} else {	432	} else {
467	push @{ $self->{any} }, [$cb, $match];	433	delete $self->[1]{$tag};
468	}	434	}
469	}	435	}
470	}	436	}
471		437
472	$port	438	$port
…		…
508	$res	474	$res
509	}	475	}
510	}	476	}
511	}	477	}
512		478
513	=item $guard = mon $port, $cb->(@reason)	479	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
514		480
515	=item $guard = mon $port, $rcvport	481	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
516		482
517	=item $guard = mon $port	483	=item $guard = mon $port # kill $SELF when $port dies
518		484
519	=item $guard = mon $port, $rcvport, @msg	485	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
520		486
521	Monitor the given port and do something when the port is killed or	487	Monitor the given port and do something when the port is killed or
522	messages to it were lost, and optionally return a guard that can be used	488	messages to it were lost, and optionally return a guard that can be used
523	to stop monitoring again.	489	to stop monitoring again.
524
525	C<mon> effectively guarantees that, in the absence of hardware failures,
526	that after starting the monitor, either all messages sent to the port
527	will arrive, or the monitoring action will be invoked after possible
528	message loss has been detected. No messages will be lost "in between"
529	(after the first lost message no further messages will be received by the
530	port). After the monitoring action was invoked, further messages might get
531	delivered again.
532		490
533	In the first form (callback), the callback is simply called with any	491	In the first form (callback), the callback is simply called with any
534	number of C<@reason> elements (no @reason means that the port was deleted	492	number of C<@reason> elements (no @reason means that the port was deleted
535	"normally"). Note also that I<< the callback B<must> never die >>, so use	493	"normally"). Note also that I<< the callback B<must> never die >>, so use
536	C<eval> if unsure.	494	C<eval> if unsure.
537		495
538	In the second form (another port given), the other port (C<$rcvport>)	496	In the second form (another port given), the other port (C<$rcvport>)
539	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	497	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
540	"normal" kils nothing happens, while under all other conditions, the other	498	"normal" kils nothing happens, while under all other conditions, the other
541	port is killed with the same reason.	499	port is killed with the same reason.
542		500
543	The third form (kill self) is the same as the second form, except that	501	The third form (kill self) is the same as the second form, except that
544	C<$rvport> defaults to C<$SELF>.	502	C<$rvport> defaults to C<$SELF>.
545		503
546	In the last form (message), a message of the form C<@msg, @reason> will be	504	In the last form (message), a message of the form C<@msg, @reason> will be
547	C<snd>.	505	C<snd>.
		506
		507	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		508	alert was raised), they are removed and will not trigger again.
548		509
549	As a rule of thumb, monitoring requests should always monitor a port from	510	As a rule of thumb, monitoring requests should always monitor a port from
550	a local port (or callback). The reason is that kill messages might get	511	a local port (or callback). The reason is that kill messages might get
551	lost, just like any other message. Another less obvious reason is that	512	lost, just like any other message. Another less obvious reason is that
552	even monitoring requests can get lost (for exmaple, when the connection	513	even monitoring requests can get lost (for example, when the connection
553	to the other node goes down permanently). When monitoring a port locally	514	to the other node goes down permanently). When monitoring a port locally
554	these problems do not exist.	515	these problems do not exist.
555		516
		517	C<mon> effectively guarantees that, in the absence of hardware failures,
		518	after starting the monitor, either all messages sent to the port will
		519	arrive, or the monitoring action will be invoked after possible message
		520	loss has been detected. No messages will be lost "in between" (after
		521	the first lost message no further messages will be received by the
		522	port). After the monitoring action was invoked, further messages might get
		523	delivered again.
		524
		525	Inter-host-connection timeouts and monitoring depend on the transport
		526	used. The only transport currently implemented is TCP, and AnyEvent::MP
		527	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		528	non-idle connection, and usually around two hours for idle conenctions).
		529
		530	This means that monitoring is good for program errors and cleaning up
		531	stuff eventually, but they are no replacement for a timeout when you need
		532	to ensure some maximum latency.
		533
556	Example: call a given callback when C<$port> is killed.	534	Example: call a given callback when C<$port> is killed.
557		535
558	mon $port, sub { warn "port died because of <@_>\n" };	536	mon $port, sub { warn "port died because of <@_>\n" };
559		537
560	Example: kill ourselves when C<$port> is killed abnormally.	538	Example: kill ourselves when C<$port> is killed abnormally.
…		…
566	mon $port, $self => "restart";	544	mon $port, $self => "restart";
567		545
568	=cut	546	=cut
569		547
570	sub mon {	548	sub mon {
571	my ($noderef, $port) = split /#/, shift, 2;	549	my ($nodeid, $port) = split /#/, shift, 2;
572		550
573	my $node = $NODE{$noderef} \|\| add_node $noderef;	551	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
574		552
575	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	553	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
576		554
577	unless (ref $cb) {	555	unless (ref $cb) {
578	if (@_) {	556	if (@_) {
…		…
587	}	565	}
588		566
589	$node->monitor ($port, $cb);	567	$node->monitor ($port, $cb);
590		568
591	defined wantarray	569	defined wantarray
592	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	570	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
593	}	571	}
594		572
595	=item $guard = mon_guard $port, $ref, $ref...	573	=item $guard = mon_guard $port, $ref, $ref...
596		574
597	Monitors the given C<$port> and keeps the passed references. When the port	575	Monitors the given C<$port> and keeps the passed references. When the port
598	is killed, the references will be freed.	576	is killed, the references will be freed.
599		577
600	Optionally returns a guard that will stop the monitoring.	578	Optionally returns a guard that will stop the monitoring.
601		579
602	This function is useful when you create e.g. timers or other watchers and	580	This function is useful when you create e.g. timers or other watchers and
603	want to free them when the port gets killed:	581	want to free them when the port gets killed (note the use of C<psub>):
604		582
605	$port->rcv (start => sub {	583	$port->rcv (start => sub {
606	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	584	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
607	undef $timer if 0.9 < rand;	585	undef $timer if 0.9 < rand;
608	});	586	});
609	});	587	});
610		588
611	=cut	589	=cut
…		…
620		598
621	=item kil $port[, @reason]	599	=item kil $port[, @reason]
622		600
623	Kill the specified port with the given C<@reason>.	601	Kill the specified port with the given C<@reason>.
624		602
625	If no C<@reason> is specified, then the port is killed "normally" (linked	603	If no C<@reason> is specified, then the port is killed "normally" (ports
626	ports will not be kileld, or even notified).	604	monitoring other ports will not necessarily die because a port dies
		605	"normally").
627		606
628	Otherwise, linked ports get killed with the same reason (second form of	607	Otherwise, linked ports get killed with the same reason (second form of
629	C<mon>, see below).	608	C<mon>, see above).
630		609
631	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	610	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
632	will be reported as reason C<< die => $@ >>.	611	will be reported as reason C<< die => $@ >>.
633		612
634	Transport/communication errors are reported as C<< transport_error =>	613	Transport/communication errors are reported as C<< transport_error =>
…		…
639	=item $port = spawn $node, $initfunc[, @initdata]	618	=item $port = spawn $node, $initfunc[, @initdata]
640		619
641	Creates a port on the node C<$node> (which can also be a port ID, in which	620	Creates a port on the node C<$node> (which can also be a port ID, in which
642	case it's the node where that port resides).	621	case it's the node where that port resides).
643		622
644	The port ID of the newly created port is return immediately, and it is	623	The port ID of the newly created port is returned immediately, and it is
645	permissible to immediately start sending messages or monitor the port.	624	possible to immediately start sending messages or to monitor the port.
646		625
647	After the port has been created, the init function is	626	After the port has been created, the init function is called on the remote
648	called. This function must be a fully-qualified function name	627	node, in the same context as a C<rcv> callback. This function must be a
649	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	628	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
650	program, use C<::name>.	629	specify a function in the main program, use C<::name>.
651		630
652	If the function doesn't exist, then the node tries to C<require>	631	If the function doesn't exist, then the node tries to C<require>
653	the package, then the package above the package and so on (e.g.	632	the package, then the package above the package and so on (e.g.
654	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	633	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
655	exists or it runs out of package names.	634	exists or it runs out of package names.
656		635
657	The init function is then called with the newly-created port as context	636	The init function is then called with the newly-created port as context
658	object (C<$SELF>) and the C<@initdata> values as arguments.	637	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		638	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		639	the port might not get created.
659		640
660	A common idiom is to pass your own port, monitor the spawned port, and	641	A common idiom is to pass a local port, immediately monitor the spawned
661	in the init function, monitor the original port. This two-way monitoring	642	port, and in the remote init function, immediately monitor the passed
662	ensures that both ports get cleaned up when there is a problem.	643	local port. This two-way monitoring ensures that both ports get cleaned up
		644	when there is a problem.
		645
		646	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		647	caller before C<spawn> returns (by delaying invocation when spawn is
		648	called for the local node).
663		649
664	Example: spawn a chat server port on C<$othernode>.	650	Example: spawn a chat server port on C<$othernode>.
665		651
666	# this node, executed from within a port context:	652	# this node, executed from within a port context:
667	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
682		668
683	sub _spawn {	669	sub _spawn {
684	my $port = shift;	670	my $port = shift;
685	my $init = shift;	671	my $init = shift;
686		672
		673	# rcv will create the actual port
687	local $SELF = "$NODE#$port";	674	local $SELF = "$NODE#$port";
688	eval {	675	eval {
689	&{ load_func $init }	676	&{ load_func $init }
690	};	677	};
691	_self_die if $@;	678	_self_die if $@;
692	}	679	}
693		680
694	sub spawn(@) {	681	sub spawn(@) {
695	my ($noderef, undef) = split /#/, shift, 2;	682	my ($nodeid, undef) = split /#/, shift, 2;
696		683
697	my $id = "$RUNIQ." . $ID++;	684	my $id = "$RUNIQ." . $ID++;
698		685
699	$_[0] =~ /::/	686	$_[0] =~ /::/
700	or Carp::croak "spawn init function must be a fully-qualified name, caught";	687	or Carp::croak "spawn init function must be a fully-qualified name, caught";
701		688
702	($NODE{$noderef} \|\| add_node $noderef)	689	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
703	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
704		690
705	"$noderef#$id"	691	"$nodeid#$id"
706	}	692	}
707		693
708	=back	694	=item after $timeout, @msg
709		695
710	=head1 NODE MESSAGES	696	=item after $timeout, $callback
711		697
712	Nodes understand the following messages sent to them. Many of them take	698	Either sends the given message, or call the given callback, after the
713	arguments called C<@reply>, which will simply be used to compose a reply	699	specified number of seconds.
714	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
715	the remaining arguments are simply the message data.
716		700
717	While other messages exist, they are not public and subject to change.	701	This is simply a utility function that comes in handy at times - the
		702	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		703	so it may go away in the future.
718		704
719	=over 4
720
721	=cut	705	=cut
722		706
723	=item lookup => $name, @reply	707	sub after($@) {
		708	my ($timeout, @action) = @_;
724		709
725	Replies with the port ID of the specified well-known port, or C<undef>.	710	my $t; $t = AE::timer $timeout, 0, sub {
		711	undef $t;
		712	ref $action[0]
		713	? $action[0]()
		714	: snd @action;
		715	};
		716	}
726		717
727	=item devnull => ...	718	=item cal $port, @msg, $callback[, $timeout]
728		719
729	Generic data sink/CPU heat conversion.	720	A simple form of RPC - sends a message to the given C<$port> with the
		721	given contents (C<@msg>), but adds a reply port to the message.
730		722
731	=item relay => $port, @msg	723	The reply port is created temporarily just for the purpose of receiving
		724	the reply, and will be C<kil>ed when no longer needed.
732		725
733	Simply forwards the message to the given port.	726	A reply message sent to the port is passed to the C<$callback> as-is.
734		727
735	=item eval => $string[ @reply]	728	If an optional time-out (in seconds) is given and it is not C<undef>,
		729	then the callback will be called without any arguments after the time-out
		730	elapsed and the port is C<kil>ed.
736		731
737	Evaluates the given string. If C<@reply> is given, then a message of the	732	If no time-out is given, then the local port will monitor the remote port
738	form C<@reply, $@, @evalres> is sent.	733	instead, so it eventually gets cleaned-up.
739		734
740	Example: crash another node.	735	Currently this function returns the temporary port, but this "feature"
		736	might go in future versions unless you can make a convincing case that
		737	this is indeed useful for something.
741		738
742	snd $othernode, eval => "exit";	739	=cut
743		740
744	=item time => @reply	741	sub cal(@) {
		742	my $timeout = ref $_[-1] ? undef : pop;
		743	my $cb = pop;
745		744
746	Replies the the current node time to C<@reply>.	745	my $port = port {
		746	undef $timeout;
		747	kil $SELF;
		748	&$cb;
		749	};
747		750
748	Example: tell the current node to send the current time to C<$myport> in a	751	if (defined $timeout) {
749	C<timereply> message.	752	$timeout = AE::timer $timeout, 0, sub {
		753	undef $timeout;
		754	kil $port;
		755	$cb->();
		756	};
		757	} else {
		758	mon $_[0], sub {
		759	kil $port;
		760	$cb->();
		761	};
		762	}
750		763
751	snd $NODE, time => $myport, timereply => 1, 2;	764	push @_, $port;
752	# => snd $myport, timereply => 1, 2, <time>	765	&snd;
		766
		767	$port
		768	}
753		769
754	=back	770	=back
755		771
756	=head1 AnyEvent::MP vs. Distributed Erlang	772	=head1 AnyEvent::MP vs. Distributed Erlang
757		773
…		…
767		783
768	Despite the similarities, there are also some important differences:	784	Despite the similarities, there are also some important differences:
769		785
770	=over 4	786	=over 4
771		787
772	=item * Node references contain the recipe on how to contact them.	788	=item * Node IDs are arbitrary strings in AEMP.
773		789
774	Erlang relies on special naming and DNS to work everywhere in the	790	Erlang relies on special naming and DNS to work everywhere in the same
775	same way. AEMP relies on each node knowing it's own address(es), with	791	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
776	convenience functionality.	792	configuration or DNS), but will otherwise discover other odes itself.
777		793
778	This means that AEMP requires a less tightly controlled environment at the	794	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
779	cost of longer node references and a slightly higher management overhead.	795	uses "local ports are like remote ports".
		796
		797	The failure modes for local ports are quite different (runtime errors
		798	only) then for remote ports - when a local port dies, you I<know> it dies,
		799	when a connection to another node dies, you know nothing about the other
		800	port.
		801
		802	Erlang pretends remote ports are as reliable as local ports, even when
		803	they are not.
		804
		805	AEMP encourages a "treat remote ports differently" philosophy, with local
		806	ports being the special case/exception, where transport errors cannot
		807	occur.
780		808
781	=item * Erlang uses processes and a mailbox, AEMP does not queue.	809	=item * Erlang uses processes and a mailbox, AEMP does not queue.
782		810
783	Erlang uses processes that selctively receive messages, and therefore	811	Erlang uses processes that selectively receive messages, and therefore
784	needs a queue. AEMP is event based, queuing messages would serve no useful	812	needs a queue. AEMP is event based, queuing messages would serve no
785	purpose.	813	useful purpose. For the same reason the pattern-matching abilities of
		814	AnyEvent::MP are more limited, as there is little need to be able to
		815	filter messages without dequeuing them.
786		816
787	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	817	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
788		818
789	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	819	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
790		820
791	Sending messages in Erlang is synchronous and blocks the process. AEMP	821	Sending messages in Erlang is synchronous and blocks the process (and
792	sends are immediate, connection establishment is handled in the	822	so does not need a queue that can overflow). AEMP sends are immediate,
793	background.	823	connection establishment is handled in the background.
794		824
795	=item * Erlang can silently lose messages, AEMP cannot.	825	=item * Erlang suffers from silent message loss, AEMP does not.
796		826
797	Erlang makes few guarantees on messages delivery - messages can get lost	827	Erlang makes few guarantees on messages delivery - messages can get lost
798	without any of the processes realising it (i.e. you send messages a, b,	828	without any of the processes realising it (i.e. you send messages a, b,
799	and c, and the other side only receives messages a and c).	829	and c, and the other side only receives messages a and c).
800		830
801	AEMP guarantees correct ordering, and the guarantee that there are no	831	AEMP guarantees correct ordering, and the guarantee that after one message
802	holes in the message sequence.	832	is lost, all following ones sent to the same port are lost as well, until
803		833	monitoring raises an error, so there are no silent "holes" in the message
804	=item * In Erlang, processes can be declared dead and later be found to be	834	sequence.
805	alive.
806
807	In Erlang it can happen that a monitored process is declared dead and
808	linked processes get killed, but later it turns out that the process is
809	still alive - and can receive messages.
810
811	In AEMP, when port monitoring detects a port as dead, then that port will
812	eventually be killed - it cannot happen that a node detects a port as dead
813	and then later sends messages to it, finding it is still alive.
814		835
815	=item * Erlang can send messages to the wrong port, AEMP does not.	836	=item * Erlang can send messages to the wrong port, AEMP does not.
816		837
817	In Erlang it is quite possible that a node that restarts reuses a process	838	In Erlang it is quite likely that a node that restarts reuses a process ID
818	ID known to other nodes for a completely different process, causing	839	known to other nodes for a completely different process, causing messages
819	messages destined for that process to end up in an unrelated process.	840	destined for that process to end up in an unrelated process.
820		841
821	AEMP never reuses port IDs, so old messages or old port IDs floating	842	AEMP never reuses port IDs, so old messages or old port IDs floating
822	around in the network will not be sent to an unrelated port.	843	around in the network will not be sent to an unrelated port.
823		844
824	=item * Erlang uses unprotected connections, AEMP uses secure	845	=item * Erlang uses unprotected connections, AEMP uses secure
825	authentication and can use TLS.	846	authentication and can use TLS.
826		847
827	AEMP can use a proven protocol - SSL/TLS - to protect connections and	848	AEMP can use a proven protocol - TLS - to protect connections and
828	securely authenticate nodes.	849	securely authenticate nodes.
829		850
830	=item * The AEMP protocol is optimised for both text-based and binary	851	=item * The AEMP protocol is optimised for both text-based and binary
831	communications.	852	communications.
832		853
833	The AEMP protocol, unlike the Erlang protocol, supports both	854	The AEMP protocol, unlike the Erlang protocol, supports both programming
834	language-independent text-only protocols (good for debugging) and binary,	855	language independent text-only protocols (good for debugging) and binary,
835	language-specific serialisers (e.g. Storable).	856	language-specific serialisers (e.g. Storable). By default, unless TLS is
		857	used, the protocol is actually completely text-based.
836		858
837	It has also been carefully designed to be implementable in other languages	859	It has also been carefully designed to be implementable in other languages
838	with a minimum of work while gracefully degrading fucntionality to make the	860	with a minimum of work while gracefully degrading functionality to make the
839	protocol simple.	861	protocol simple.
840		862
841	=item * AEMP has more flexible monitoring options than Erlang.	863	=item * AEMP has more flexible monitoring options than Erlang.
842		864
843	In Erlang, you can chose to receive I<all> exit signals as messages	865	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
846	Erlang, as one can choose between automatic kill, exit message or callback	868	Erlang, as one can choose between automatic kill, exit message or callback
847	on a per-process basis.	869	on a per-process basis.
848		870
849	=item * Erlang tries to hide remote/local connections, AEMP does not.	871	=item * Erlang tries to hide remote/local connections, AEMP does not.
850		872
851	Monitoring in Erlang is not an indicator of process death/crashes,	873	Monitoring in Erlang is not an indicator of process death/crashes, in the
852	as linking is (except linking is unreliable in Erlang).	874	same way as linking is (except linking is unreliable in Erlang).
853		875
854	In AEMP, you don't "look up" registered port names or send to named ports	876	In AEMP, you don't "look up" registered port names or send to named ports
855	that might or might not be persistent. Instead, you normally spawn a port	877	that might or might not be persistent. Instead, you normally spawn a port
856	on the remote node. The init function monitors the you, and you monitor	878	on the remote node. The init function monitors you, and you monitor the
857	the remote port. Since both monitors are local to the node, they are much	879	remote port. Since both monitors are local to the node, they are much more
858	more reliable.	880	reliable (no need for C<spawn_link>).
859		881
860	This also saves round-trips and avoids sending messages to the wrong port	882	This also saves round-trips and avoids sending messages to the wrong port
861	(hard to do in Erlang).	883	(hard to do in Erlang).
862		884
863	=back	885	=back
864		886
865	=head1 RATIONALE	887	=head1 RATIONALE
866		888
867	=over 4	889	=over 4
868		890
869	=item Why strings for ports and noderefs, why not objects?	891	=item Why strings for port and node IDs, why not objects?
870		892
871	We considered "objects", but found that the actual number of methods	893	We considered "objects", but found that the actual number of methods
872	thatc an be called are very low. Since port IDs and noderefs travel over	894	that can be called are quite low. Since port and node IDs travel over
873	the network frequently, the serialising/deserialising would add lots of	895	the network frequently, the serialising/deserialising would add lots of
874	overhead, as well as having to keep a proxy object.	896	overhead, as well as having to keep a proxy object everywhere.
875		897
876	Strings can easily be printed, easily serialised etc. and need no special	898	Strings can easily be printed, easily serialised etc. and need no special
877	procedures to be "valid".	899	procedures to be "valid".
878		900
879	And a a miniport consists of a single closure stored in a global hash - it	901	And as a result, a miniport consists of a single closure stored in a
880	can't become much cheaper.	902	global hash - it can't become much cheaper.
881		903
882	=item Why favour JSON, why not real serialising format such as Storable?	904	=item Why favour JSON, why not a real serialising format such as Storable?
883		905
884	In fact, any AnyEvent::MP node will happily accept Storable as framing	906	In fact, any AnyEvent::MP node will happily accept Storable as framing
885	format, but currently there is no way to make a node use Storable by	907	format, but currently there is no way to make a node use Storable by
886	default.	908	default (although all nodes will accept it).
887		909
888	The default framing protocol is JSON because a) JSON::XS is many times	910	The default framing protocol is JSON because a) JSON::XS is many times
889	faster for small messages and b) most importantly, after years of	911	faster for small messages and b) most importantly, after years of
890	experience we found that object serialisation is causing more problems	912	experience we found that object serialisation is causing more problems
891	than it gains: Just like function calls, objects simply do not travel	913	than it solves: Just like function calls, objects simply do not travel
892	easily over the network, mostly because they will always be a copy, so you	914	easily over the network, mostly because they will always be a copy, so you
893	always have to re-think your design.	915	always have to re-think your design.
894		916
895	Keeping your messages simple, concentrating on data structures rather than	917	Keeping your messages simple, concentrating on data structures rather than
896	objects, will keep your messages clean, tidy and efficient.	918	objects, will keep your messages clean, tidy and efficient.
897		919
898	=back	920	=back
899		921
900	=head1 SEE ALSO	922	=head1 SEE ALSO
901		923
		924	L<AnyEvent::MP::Intro> - a gentle introduction.
		925
		926	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		927
		928	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		929	your applications.
		930
		931	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		932	all nodes.
		933
902	L<AnyEvent>.	934	L<AnyEvent>.
903		935
904	=head1 AUTHOR	936	=head1 AUTHOR
905		937
906	Marc Lehmann <schmorp@schmorp.de>	938	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.94 by root, Tue Sep 22 14:14:43 2009 UTC