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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.40 by root, Sat Aug 8 00:22:16 2009 UTC vs.
Revision 1.91 by root, Tue Sep 22 09:54:42 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
		14	# initialise the node so it can send/receive messages
		15	configure;
		16
15	# ports are message endpoints	17	# ports are message destinations
16		18
17	# sending messages	19	# sending messages
18	snd $port, type => data...;	20	snd $port, type => data...;
19	snd $port, @msg;	21	snd $port, @msg;
20	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
21		23
22	# miniports	24	# creating/using ports, the simple way
23	my $miniport = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
24		26
25	# full ports	27	# creating/using ports, tagged message matching
26	my $port = port;	28	my $port = port;
27	rcv $port, smartmatch => $cb->(@msg);
28	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
29	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
30		31
31	# remote ports	32	# create a port on another node
32	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
33		34
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
38	# monitoring	35	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	36	mon $localport, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	37	mon $localport, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	38	mon $localport, $otherport, @msg # send message on death
		39
		40	=head1 CURRENT STATUS
		41
		42	bin/aemp - stable.
		43	AnyEvent::MP - stable API, should work.
		44	AnyEvent::MP::Intro - explains most concepts.
		45	AnyEvent::MP::Kernel - mostly stable API.
		46	AnyEvent::MP::Global - stable API.
42		47
43	=head1 DESCRIPTION	48	=head1 DESCRIPTION
44		49
45	This module (-family) implements a simple message passing framework.	50	This module (-family) implements a simple message passing framework.
46		51
47	Despite its simplicity, you can securely message other processes running	52	Despite its simplicity, you can securely message other processes running
48	on the same or other hosts.	53	on the same or other hosts, and you can supervise entities remotely.
49		54
50	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>
51	manual page.	56	manual page and the examples under F<eg/>.
52
53	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 -
55	stay tuned! The basic API should be finished, however.
56		57
57	=head1 CONCEPTS	58	=head1 CONCEPTS
58		59
59	=over 4	60	=over 4
60		61
61	=item port	62	=item port
62		63
63	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).
64		66
65	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
66	messages. All C<rcv> handlers will receive messages they match, messages	68	some messages. Messages send to ports will not be queued, regardless of
67	will not be queued.	69	anything was listening for them or not.
68		70
69	=item port id - C<noderef#portname>	71	=item port ID - C<nodeid#portname>
70		72
71	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
72	separator, and a port name (a printable string of unspecified format). An	74	separator, and a port name (a printable string of unspecified format).
73	exception is the the node port, whose ID is identical to its node
74	reference.
75		75
76	=item node	76	=item node
77		77
78	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,
79	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
80	create new ports, among other things.	80	ports.
81		81
82	Nodes are either private (single-process only), slaves (connected to a	82	Nodes are either public (have one or more listening ports) or private
83	master node only) or public nodes (connectable from unrelated nodes).	83	(no listening ports). Private nodes cannot talk to other private nodes
		84	currently.
84		85
85	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	86	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
86		87
87	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
88	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
89	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.
90		92
91	This recipe is simply a comma-separated list of C<address:port> pairs (for	93	=item binds - C<ip:port>
92	TCP/IP, other protocols might look different).
93		94
94	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
95	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.
96		99
97	Before using an unresolved node reference in a message you first have to	100	=item seed nodes
98	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.
99		127
100	=back	128	=back
101		129
102	=head1 VARIABLES/FUNCTIONS	130	=head1 VARIABLES/FUNCTIONS
103		131
105		133
106	=cut	134	=cut
107		135
108	package AnyEvent::MP;	136	package AnyEvent::MP;
109		137
110	use AnyEvent::MP::Base;	138	use AnyEvent::MP::Kernel;
111		139
112	use common::sense;	140	use common::sense;
113		141
114	use Carp ();	142	use Carp ();
115		143
116	use AE ();	144	use AE ();
117		145
118	use base "Exporter";	146	use base "Exporter";
119		147
120	our $VERSION = '0.1';	148	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		149
121	our @EXPORT = qw(	150	our @EXPORT = qw(
122	NODE $NODE *SELF node_of _any_	151	NODE $NODE *SELF node_of after
123	resolve_node initialise_node	152	configure
124	snd rcv mon kil reg psub spawn	153	snd rcv mon mon_guard kil psub spawn cal
125	port	154	port
126	);	155	);
127		156
128	our $SELF;	157	our $SELF;
129		158
…		…
133	kil $SELF, die => $msg;	162	kil $SELF, die => $msg;
134	}	163	}
135		164
136	=item $thisnode = NODE / $NODE	165	=item $thisnode = NODE / $NODE
137		166
138	The C<NODE> function returns, and the C<$NODE> variable contains	167	The C<NODE> function returns, and the C<$NODE> variable contains, the node
139	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
140	to C<become_public> or C<become_slave>, after which all local port	169	a call to C<configure>.
141	identifiers become invalid.
142		170
143	=item $noderef = node_of $port	171	=item $nodeid = node_of $port
144		172
145	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.
146		174
147	=item initialise_node $noderef, $seednode, $seednode...	175	=item configure $profile, key => value...
148		176
149	=item initialise_node "slave/", $master, $master...	177	=item configure key => value...
150		178
151	Before a node can talk to other nodes on the network it has to initialise	179	Before a node can talk to other nodes on the network (i.e. enter
152	itself - the minimum a node needs to know is it's own name, and optionally	180	"distributed mode") it has to configure itself - the minimum a node needs
153	it should know the noderefs of some other nodes in the network.	181	to know is its own name, and optionally it should know the addresses of
		182	some other nodes in the network to discover other nodes.
154		183
155	This function initialises a node - it must be called exactly once (or	184	This function configures a node - it must be called exactly once (or
156	never) before calling other AnyEvent::MP functions.	185	never) before calling other AnyEvent::MP functions.
157		186
158	All arguments are noderefs, which can be either resolved or unresolved.
159
160	There are two types of networked nodes, public nodes and slave nodes:
161
162	=over 4	187	=over 4
163		188
164	=item public nodes	189	=item step 1, gathering configuration from profiles
165		190
166	For public nodes, C<$noderef> must either be a (possibly unresolved)	191	The function first looks up a profile in the aemp configuration (see the
167	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
168	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.
169		195
170	Afterwards, the node will bind itself on all endpoints and try to connect	196	The profile data is then gathered as follows:
171	to all additional C<$seednodes> that are specified. Seednodes are optional
172	and can be used to quickly bootstrap the node into an existing network.
173		197
174	=item slave nodes	198	First, all remaining key => value pairs (all of which are conveniently
		199	undocumented at the moment) will be interpreted as configuration
		200	data. Then they will be overwritten by any values specified in the global
		201	default configuration (see the F<aemp> utility), then the chain of
		202	profiles chosen by the profile name (and any C<parent> attributes).
175		203
176	When the C<$noderef> is the special string C<slave/>, then the node will	204	That means that the values specified in the profile have highest priority
177	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,
178	route most of their traffic to the master node that they attach to.	206	and can only be used to specify defaults.
179		207
180	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
181	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
182	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.
183		229
184	=back	230	=back
185		231
186	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.
187	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.
188	server.
189		234
190	Example: become a public node listening on the default node.	235	configure
191		236
192	initialise_node;	237	Example: become an anonymous node. This form is often used for commandline
		238	clients.
193		239
194	Example: become a public node, and try to contact some well-known master	240	configure nodeid => "anon/";
195	servers to become part of the network.
196		241
197	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).
198		245
199	Example: become a public node listening on port C<4041>.	246	# use the aemp commandline utility
		247	# aemp profile seed nodeid anon/ binds '*:4040'
200		248
201	initialise_node 4041;	249	# then use it
		250	configure profile => "seed";
202		251
203	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
204		254
205	initialise_node "locahost:4044";	255	# or provide a nicer-to-remember nodeid
206		256	# aemp run profile seed nodeid "$(hostname)"
207	Example: become a slave node to any of the specified master servers.
208
209	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
210
211	=item $cv = resolve_node $noderef
212
213	Takes an unresolved node reference that may contain hostnames and
214	abbreviated IDs, resolves all of them and returns a resolved node
215	reference.
216
217	In addition to C<address:port> pairs allowed in resolved noderefs, the
218	following forms are supported:
219
220	=over 4
221
222	=item the empty string
223
224	An empty-string component gets resolved as if the default port (4040) was
225	specified.
226
227	=item naked port numbers (e.g. C<1234>)
228
229	These are resolved by prepending the local nodename and a colon, to be
230	further resolved.
231
232	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
233
234	These are resolved by using AnyEvent::DNS to resolve them, optionally
235	looking up SRV records for the C<aemp=4040> port, if no port was
236	specified.
237
238	=back
239		257
240	=item $SELF	258	=item $SELF
241		259
242	Contains the current port id while executing C<rcv> callbacks or C<psub>	260	Contains the current port id while executing C<rcv> callbacks or C<psub>
243	blocks.	261	blocks.
244		262
245	=item SELF, %SELF, @SELF...	263	=item *SELF, SELF, %SELF, @SELF...
246		264
247	Due to some quirks in how perl exports variables, it is impossible to	265	Due to some quirks in how perl exports variables, it is impossible to
248	just export C<$SELF>, all the symbols called C<SELF> are exported by this	266	just export C<$SELF>, all the symbols named C<SELF> are exported by this
249	module, but only C<$SELF> is currently used.	267	module, but only C<$SELF> is currently used.
250		268
251	=item snd $port, type => @data	269	=item snd $port, type => @data
252		270
253	=item snd $port, @msg	271	=item snd $port, @msg
254		272
255	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
256	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.
257	stringifies a sa port ID (such as a port object :).
258		275
259	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
260	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
261	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.
262		280
263	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
264	function: modifying any argument is not allowed and can cause many	282	function: modifying any argument (or values referenced by them) is
265	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.
266		287
267	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
268	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
269	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
270	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
271	node, anything can be passed.	292	node, anything can be passed. Best rely only on the common denominator of
		293	these.
272		294
273	=item $local_port = port	295	=item $local_port = port
274		296
275	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
276	matching port ("full port") or a single-callback port ("miniport"),	298	no callbacks set and will throw an error when it receives messages.
277	depending on how C<rcv> callbacks are bound to the object.
278		299
279	=item $port = port { my @msg = @_; $finished }	300	=item $local_port = port { my @msg = @_ }
280		301
281	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
282	matching behind it, and returns its ID. Semantically the same as creating
283	a port and calling C<rcv $port, $callback> on it.	303	creating a port and calling C<rcv $port, $callback> on it.
284		304
285	The block will be called for every message received on the port. When the	305	The block will be called for every message received on the port, with the
286	callback returns a true value its job is considered "done" and the port	306	global variable C<$SELF> set to the port ID. Runtime errors will cause the
287	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.
288		309
289	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:
290	be passed to the callback.
291		311
292	If you need the local port id in the callback, this works nicely:	312	my $port = port {
293		313	my @msg = @_;
294	my $port; $port = port {	314	...
295	snd $otherport, reply => $port;	315	kil $SELF;
296	};	316	};
297		317
298	=cut	318	=cut
299		319
300	sub rcv($@);	320	sub rcv($@);
		321
		322	sub _kilme {
		323	die "received message on port without callback";
		324	}
301		325
302	sub port(;&) {	326	sub port(;&) {
303	my $id = "$UNIQ." . $ID++;	327	my $id = "$UNIQ." . $ID++;
304	my $port = "$NODE#$id";	328	my $port = "$NODE#$id";
305		329
306	if (@_) {	330	rcv $port, shift \|\| \&_kilme;
307	rcv $port, shift;
308	} else {
309	$PORT{$id} = sub { }; # nop
310	}
311		331
312	$port	332	$port
313	}	333	}
314		334
315	=item reg $port, $name
316
317	=item reg $name
318
319	Registers the given port (or C<$SELF><<< if missing) under the name
320	C<$name>. If the name already exists it is replaced.
321
322	A port can only be registered under one well known name.
323
324	A port automatically becomes unregistered when it is killed.
325
326	=cut
327
328	sub reg(@) {
329	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
330
331	$REG{$_[0]} = $port;
332	}
333
334	=item rcv $port, $callback->(@msg)	335	=item rcv $local_port, $callback->(@msg)
335		336
336	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
337	one if required).	338	remove the default callback: use C<sub { }> to disable it, or better
338		339	C<kil> the port when it is no longer needed.
339	=item rcv $port, tagstring => $callback->(@msg), ...
340
341	=item rcv $port, $smartmatch => $callback->(@msg), ...
342
343	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
344
345	Register callbacks to be called on matching messages on the given full
346	port (after converting it to one if required) and return the port.
347
348	The callback has to return a true value when its work is done, after
349	which is will be removed, or a false value in which case it will stay
350	registered.
351		340
352	The global C<$SELF> (exported by this module) contains C<$port> while	341	The global C<$SELF> (exported by this module) contains C<$port> while
353	executing the callback.	342	executing the callback. Runtime errors during callback execution will
		343	result in the port being C<kil>ed.
354		344
355	Runtime errors during callback execution will result in the port being	345	The default callback received all messages not matched by a more specific
356	C<kil>ed.	346	C<tag> match.
357		347
358	If the match is an array reference, then it will be matched against the	348	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
359	first elements of the message, otherwise only the first element is being
360	matched.
361		349
362	Any element in the match that is specified as C<_any_> (a function	350	Register (or replace) callbacks to be called on messages starting with the
363	exported by this module) matches any single element of the message.	351	given tag on the given port (and return the port), or unregister it (when
		352	C<$callback> is C<$undef> or missing). There can only be one callback
		353	registered for each tag.
364		354
365	While not required, it is highly recommended that the first matching	355	The original message will be passed to the callback, after the first
366	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
367	also the most efficient match (by far).	357	environment as the default callback (see above).
368		358
369	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.
370		360
371	my $port = rcv port,	361	my $port = rcv port,
372	msg1 => sub { ...; 0 },	362	msg1 => sub { ... },
373	msg2 => sub { ...; 0 },	363	msg2 => sub { ... },
374	;	364	;
375		365
376	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
377	in one go:	367	in one go:
378		368
379	snd $otherport, reply =>	369	snd $otherport, reply =>
380	rcv port,	370	rcv port,
381	msg1 => sub { ...; 0 },	371	msg1 => sub { ... },
382	...	372	...
383	;	373	;
384		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, $otherport;
		382	};
		383
385	=cut	384	=cut
386		385
387	sub rcv($@) {	386	sub rcv($@) {
388	my $port = shift;	387	my $port = shift;
389	my ($noderef, $portid) = split /#/, $port, 2;	388	my ($nodeid, $portid) = split /#/, $port, 2;
390		389
391	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	390	$NODE{$nodeid} == $NODE{""}
392	or Carp::croak "$port: rcv can only be called on local ports, caught";	391	or Carp::croak "$port: rcv can only be called on local ports, caught";
393		392
394	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 {
395	my $cb = shift;	401	my $cb = shift;
396	delete $PORT_DATA{$portid};
397	$PORT{$portid} = sub {	402	$PORT{$portid} = sub {
398	local $SELF = $port;	403	local $SELF = $port;
399	eval {	404	eval { &$cb }; _self_die if $@;
400	&$cb	405	};
401	and kil $port;
402	};	406	}
403	_self_die if $@;	407	} elsif (defined $_[0]) {
404	};
405	} else {
406	my $self = $PORT_DATA{$portid} \|\|= do {	408	my $self = $PORT_DATA{$portid} \|\|= do {
407	my $self = bless {	409	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
408	id => $port,
409	}, "AnyEvent::MP::Port";
410		410
411	$PORT{$portid} = sub {	411	$PORT{$portid} = sub {
412	local $SELF = $port;	412	local $SELF = $port;
413		413
414	eval {
415	for (@{ $self->{rc0}{$_[0]} }) {	414	if (my $cb = $self->[1]{$_[0]}) {
416	$_ && &{$_->[0]}	415	shift;
417	&& undef $_;	416	eval { &$cb }; _self_die if $@;
418	}	417	} else {
419
420	for (@{ $self->{rcv}{$_[0]} }) {
421	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
422	&& &{$_->[0]}	418	&{ $self->[0] };
423	&& undef $_;
424	}
425
426	for (@{ $self->{any} }) {
427	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
428	&& &{$_->[0]}
429	&& undef $_;
430	}	419	}
431	};	420	};
432	_self_die if $@;	421
		422	$self
433	};	423	};
434		424
435	$self
436	};
437
438	"AnyEvent::MP::Port" eq ref $self	425	"AnyEvent::MP::Port" eq ref $self
439	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	426	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
440		427
441	while (@_) {
442	my ($match, $cb) = splice @_, 0, 2;	428	my ($tag, $cb) = splice @_, 0, 2;
443		429
444	if (!ref $match) {	430	if (defined $cb) {
445	push @{ $self->{rc0}{$match} }, [$cb];	431	$self->[1]{$tag} = $cb;
446	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
447	my ($type, @match) = @$match;
448	@match
449	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
450	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
451	} else {	432	} else {
452	push @{ $self->{any} }, [$cb, $match];	433	delete $self->[1]{$tag};
453	}	434	}
454	}	435	}
455	}	436	}
456		437
457	$port	438	$port
…		…
493	$res	474	$res
494	}	475	}
495	}	476	}
496	}	477	}
497		478
498	=item $guard = mon $port, $cb->(@reason)	479	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
499		480
500	=item $guard = mon $port, $rcvport	481	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
501		482
502	=item $guard = mon $port	483	=item $guard = mon $port # kill $SELF when $port dies
503		484
504	=item $guard = mon $port, $rcvport, @msg	485	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
505		486
506	Monitor the given port and do something when the port is killed, and	487	Monitor the given port and do something when the port is killed or
507	optionally return a guard that can be used to stop monitoring again.	488	messages to it were lost, and optionally return a guard that can be used
		489	to stop monitoring again.
508		490
509	In the first form (callback), the callback is simply called with any	491	In the first form (callback), the callback is simply called with any
510	number of C<@reason> elements (no @reason means that the port was deleted	492	number of C<@reason> elements (no @reason means that the port was deleted
511	"normally"). Note also that I<< the callback B<must> never die >>, so use	493	"normally"). Note also that I<< the callback B<must> never die >>, so use
512	C<eval> if unsure.	494	C<eval> if unsure.
513		495
514	In the second form (another port given), the other port (C<$rcvport)	496	In the second form (another port given), the other port (C<$rcvport>)
515	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	497	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
516	"normal" kils nothing happens, while under all other conditions, the other	498	"normal" kils nothing happens, while under all other conditions, the other
517	port is killed with the same reason.	499	port is killed with the same reason.
518		500
519	The third form (kill self) is the same as the second form, except that	501	The third form (kill self) is the same as the second form, except that
520	C<$rvport> defaults to C<$SELF>.	502	C<$rvport> defaults to C<$SELF>.
521		503
522	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
523	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.
524		509
525	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
526	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
527	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
528	even monitoring requests can get lost (for exmaple, when the connection	513	even monitoring requests can get lost (for example, when the connection
529	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
530	these problems do not exist.	515	these problems do not exist.
531		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
532	Example: call a given callback when C<$port> is killed.	534	Example: call a given callback when C<$port> is killed.
533		535
534	mon $port, sub { warn "port died because of <@_>\n" };	536	mon $port, sub { warn "port died because of <@_>\n" };
535		537
536	Example: kill ourselves when C<$port> is killed abnormally.	538	Example: kill ourselves when C<$port> is killed abnormally.
…		…
542	mon $port, $self => "restart";	544	mon $port, $self => "restart";
543		545
544	=cut	546	=cut
545		547
546	sub mon {	548	sub mon {
547	my ($noderef, $port) = split /#/, shift, 2;	549	my ($nodeid, $port) = split /#/, shift, 2;
548		550
549	my $node = $NODE{$noderef} \|\| add_node $noderef;	551	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
550		552
551	my $cb = @_ ? $_[0] : $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,';
552		554
553	unless (ref $cb) {	555	unless (ref $cb) {
554	if (@_) {	556	if (@_) {
555	# send a kill info message	557	# send a kill info message
556	my (@msg) = @_;	558	my (@msg) = ($cb, @_);
557	$cb = sub { snd @msg, @_ };	559	$cb = sub { snd @msg, @_ };
558	} else {	560	} else {
559	# simply kill other port	561	# simply kill other port
560	my $port = $cb;	562	my $port = $cb;
561	$cb = sub { kil $port, @_ if @_ };	563	$cb = sub { kil $port, @_ if @_ };
…		…
574	is killed, the references will be freed.	576	is killed, the references will be freed.
575		577
576	Optionally returns a guard that will stop the monitoring.	578	Optionally returns a guard that will stop the monitoring.
577		579
578	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
579	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>):
580		582
581	$port->rcv (start => sub {	583	$port->rcv (start => sub {
582	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	584	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
583	undef $timer if 0.9 < rand;	585	undef $timer if 0.9 < rand;
584	});	586	});
585	});	587	});
586		588
587	=cut	589	=cut
…		…
596		598
597	=item kil $port[, @reason]	599	=item kil $port[, @reason]
598		600
599	Kill the specified port with the given C<@reason>.	601	Kill the specified port with the given C<@reason>.
600		602
601	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
602	ports will not be kileld, or even notified).	604	monitoring other ports will not necessarily die because a port dies
		605	"normally").
603		606
604	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
605	C<mon>, see below).	608	C<mon>, see above).
606		609
607	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
608	will be reported as reason C<< die => $@ >>.	611	will be reported as reason C<< die => $@ >>.
609		612
610	Transport/communication errors are reported as C<< transport_error =>	613	Transport/communication errors are reported as C<< transport_error =>
…		…
615	=item $port = spawn $node, $initfunc[, @initdata]	618	=item $port = spawn $node, $initfunc[, @initdata]
616		619
617	Creates a port on the node C<$node> (which can also be a port ID, in which	620	Creates a port on the node C<$node> (which can also be a port ID, in which
618	case it's the node where that port resides).	621	case it's the node where that port resides).
619		622
620	The port ID of the newly created port is return immediately, and it is	623	The port ID of the newly created port is returned immediately, and it is
621	permissible to immediately start sending messages or monitor the port.	624	possible to immediately start sending messages or to monitor the port.
622		625
623	After the port has been created, the init function is	626	After the port has been created, the init function is called on the remote
624	called. This function must be a fully-qualified function name	627	node, in the same context as a C<rcv> callback. This function must be a
625	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	628	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
626	program, use C<::name>.	629	specify a function in the main program, use C<::name>.
627		630
628	If the function doesn't exist, then the node tries to C<require>	631	If the function doesn't exist, then the node tries to C<require>
629	the package, then the package above the package and so on (e.g.	632	the package, then the package above the package and so on (e.g.
630	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	633	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
631	exists or it runs out of package names.	634	exists or it runs out of package names.
632		635
633	The init function is then called with the newly-created port as context	636	The init function is then called with the newly-created port as context
634	object (C<$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.
635		640
636	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
637	in the init function, monitor the original port. This two-way monitoring	642	port, and in the remote init function, immediately monitor the passed
638	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<$initfunc> has no visible effects on the
		647	caller before C<spawn> returns (by delaying invocation when spawn is
		648	called for the local node).
639		649
640	Example: spawn a chat server port on C<$othernode>.	650	Example: spawn a chat server port on C<$othernode>.
641		651
642	# this node, executed from within a port context:	652	# this node, executed from within a port context:
643	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
658		668
659	sub _spawn {	669	sub _spawn {
660	my $port = shift;	670	my $port = shift;
661	my $init = shift;	671	my $init = shift;
662		672
		673	# rcv will create the actual port
663	local $SELF = "$NODE#$port";	674	local $SELF = "$NODE#$port";
664	eval {	675	eval {
665	&{ load_func $init }	676	&{ load_func $init }
666	};	677	};
667	_self_die if $@;	678	_self_die if $@;
668	}	679	}
669		680
670	sub spawn(@) {	681	sub spawn(@) {
671	my ($noderef, undef) = split /#/, shift, 2;	682	my ($nodeid, undef) = split /#/, shift, 2;
672		683
673	my $id = "$RUNIQ." . $ID++;	684	my $id = "$RUNIQ." . $ID++;
674		685
675	$_[0] =~ /::/	686	$_[0] =~ /::/
676	or Carp::croak "spawn init function must be a fully-qualified name, caught";	687	or Carp::croak "spawn init function must be a fully-qualified name, caught";
677		688
678	($NODE{$noderef} \|\| add_node $noderef)	689	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
679	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
680		690
681	"$noderef#$id"	691	"$nodeid#$id"
682	}	692	}
683		693
684	=back	694	=item after $timeout, @msg
685		695
686	=head1 NODE MESSAGES	696	=item after $timeout, $callback
687		697
688	Nodes understand the following messages sent to them. Many of them take	698	Either sends the given message, or call the given callback, after the
689	arguments called C<@reply>, which will simply be used to compose a reply	699	specified number of seconds.
690	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
691	the remaining arguments are simply the message data.
692		700
693	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.
694		704
695	=over 4
696
697	=cut	705	=cut
698		706
699	=item lookup => $name, @reply	707	sub after($@) {
		708	my ($timeout, @action) = @_;
700		709
701	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	}
702		717
703	=item devnull => ...	718	=item cal $port, @msg, $callback[, $timeout]
704		719
705	Generic data sink/CPU heat conversion.	720	A simple form of RPC - sends a message to the given C<$port> with the
		721	given contents (C<@msg>), but adds a reply port to the message.
706		722
707	=item relay => $port, @msg	723	The reply port is created temporarily just for the purpose of receiving
		724	the reply, and will be C<kil>ed when no longer needed.
708		725
709	Simply forwards the message to the given port.	726	A reply message sent to the port is passed to the C<$callback> as-is.
710		727
711	=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.
712		731
713	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
714	form C<@reply, $@, @evalres> is sent.	733	instead, so it eventually gets cleaned-up.
715		734
716	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.
717		738
718	snd $othernode, eval => "exit";	739	=cut
719		740
720	=item time => @reply	741	sub cal(@) {
		742	my $timeout = ref $_[-1] ? undef : pop;
		743	my $cb = pop;
721		744
722	Replies the the current node time to C<@reply>.	745	my $port = port {
		746	undef $timeout;
		747	kil $SELF;
		748	&$cb;
		749	};
723		750
724	Example: tell the current node to send the current time to C<$myport> in a	751	if (defined $timeout) {
725	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	}
726		763
727	snd $NODE, time => $myport, timereply => 1, 2;	764	push @_, $port;
728	# => snd $myport, timereply => 1, 2, <time>	765	&snd;
		766
		767	$port
		768	}
729		769
730	=back	770	=back
731		771
732	=head1 AnyEvent::MP vs. Distributed Erlang	772	=head1 AnyEvent::MP vs. Distributed Erlang
733		773
…		…
743		783
744	Despite the similarities, there are also some important differences:	784	Despite the similarities, there are also some important differences:
745		785
746	=over 4	786	=over 4
747		787
748	=item * Node references contain the recipe on how to contact them.	788	=item * Node IDs are arbitrary strings in AEMP.
749		789
750	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
751	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
752	convenience functionality.	792	configuration or DNS), but will otherwise discover other odes itself.
753		793
754	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
755	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.
756		808
757	=item * Erlang uses processes and a mailbox, AEMP does not queue.	809	=item * Erlang uses processes and a mailbox, AEMP does not queue.
758		810
759	Erlang uses processes that selctively receive messages, and therefore	811	Erlang uses processes that selectively receive messages, and therefore
760	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
761	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.
762		816
763	(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).
764		818
765	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	819	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
766		820
767	Sending messages in Erlang is synchronous and blocks the process. AEMP	821	Sending messages in Erlang is synchronous and blocks the process (and
768	sends are immediate, connection establishment is handled in the	822	so does not need a queue that can overflow). AEMP sends are immediate,
769	background.	823	connection establishment is handled in the background.
770		824
771	=item * Erlang can silently lose messages, AEMP cannot.	825	=item * Erlang suffers from silent message loss, AEMP does not.
772		826
773	Erlang makes few guarantees on messages delivery - messages can get lost	827	Erlang makes few guarantees on messages delivery - messages can get lost
774	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,
775	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).
776		830
777	AEMP guarantees correct ordering, and the guarantee that there are no	831	AEMP guarantees correct ordering, and the guarantee that after one message
778	holes in the message sequence.	832	is lost, all following ones sent to the same port are lost as well, until
779		833	monitoring raises an error, so there are no silent "holes" in the message
780	=item * In Erlang, processes can be declared dead and later be found to be	834	sequence.
781	alive.
782
783	In Erlang it can happen that a monitored process is declared dead and
784	linked processes get killed, but later it turns out that the process is
785	still alive - and can receive messages.
786
787	In AEMP, when port monitoring detects a port as dead, then that port will
788	eventually be killed - it cannot happen that a node detects a port as dead
789	and then later sends messages to it, finding it is still alive.
790		835
791	=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.
792		837
793	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
794	ID known to other nodes for a completely different process, causing	839	known to other nodes for a completely different process, causing messages
795	messages destined for that process to end up in an unrelated process.	840	destined for that process to end up in an unrelated process.
796		841
797	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
798	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.
799		844
800	=item * Erlang uses unprotected connections, AEMP uses secure	845	=item * Erlang uses unprotected connections, AEMP uses secure
801	authentication and can use TLS.	846	authentication and can use TLS.
802		847
803	AEMP can use a proven protocol - SSL/TLS - to protect connections and	848	AEMP can use a proven protocol - TLS - to protect connections and
804	securely authenticate nodes.	849	securely authenticate nodes.
805		850
806	=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
807	communications.	852	communications.
808		853
809	The AEMP protocol, unlike the Erlang protocol, supports both	854	The AEMP protocol, unlike the Erlang protocol, supports both programming
810	language-independent text-only protocols (good for debugging) and binary,	855	language independent text-only protocols (good for debugging) and binary,
811	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.
812		858
813	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
814	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
815	protocol simple.	861	protocol simple.
816		862
817	=item * AEMP has more flexible monitoring options than Erlang.	863	=item * AEMP has more flexible monitoring options than Erlang.
818		864
819	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
…		…
822	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
823	on a per-process basis.	869	on a per-process basis.
824		870
825	=item * Erlang tries to hide remote/local connections, AEMP does not.	871	=item * Erlang tries to hide remote/local connections, AEMP does not.
826		872
827	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
828	as linking is (except linking is unreliable in Erlang).	874	same way as linking is (except linking is unreliable in Erlang).
829		875
830	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
831	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
832	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
833	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
834	more reliable.	880	reliable (no need for C<spawn_link>).
835		881
836	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
837	(hard to do in Erlang).	883	(hard to do in Erlang).
838		884
839	=back	885	=back
840		886
		887	=head1 RATIONALE
		888
		889	=over 4
		890
		891	=item Why strings for port and node IDs, why not objects?
		892
		893	We considered "objects", but found that the actual number of methods
		894	that can be called are quite low. Since port and node IDs travel over
		895	the network frequently, the serialising/deserialising would add lots of
		896	overhead, as well as having to keep a proxy object everywhere.
		897
		898	Strings can easily be printed, easily serialised etc. and need no special
		899	procedures to be "valid".
		900
		901	And as a result, a miniport consists of a single closure stored in a
		902	global hash - it can't become much cheaper.
		903
		904	=item Why favour JSON, why not a real serialising format such as Storable?
		905
		906	In fact, any AnyEvent::MP node will happily accept Storable as framing
		907	format, but currently there is no way to make a node use Storable by
		908	default (although all nodes will accept it).
		909
		910	The default framing protocol is JSON because a) JSON::XS is many times
		911	faster for small messages and b) most importantly, after years of
		912	experience we found that object serialisation is causing more problems
		913	than it solves: Just like function calls, objects simply do not travel
		914	easily over the network, mostly because they will always be a copy, so you
		915	always have to re-think your design.
		916
		917	Keeping your messages simple, concentrating on data structures rather than
		918	objects, will keep your messages clean, tidy and efficient.
		919
		920	=back
		921
841	=head1 SEE ALSO	922	=head1 SEE ALSO
		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.
842		933
843	L<AnyEvent>.	934	L<AnyEvent>.
844		935
845	=head1 AUTHOR	936	=head1 AUTHOR
846		937

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Revision 1.40 by root, Sat Aug 8 00:22:16 2009 UTC vs.
Revision 1.91 by root, Tue Sep 22 09:54:42 2009 UTC