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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.44 by root, Wed Aug 12 21:39:58 2009 UTC vs.
Revision 1.87 by root, Fri Sep 11 02:32:23 2009 UTC

…		…
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	# 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		34
38	# monitoring	35	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	36	mon $port, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	37	mon $port, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	38	mon $port, $otherport, @msg # send message on death
42		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.
		46	AnyEvent::MP::Global - stable but incomplete, protocol not yet final.
		47
		48	stay tuned.
		49
43	=head1 DESCRIPTION	50	=head1 DESCRIPTION
44		51
45	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
46		53
47	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
48	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
49		56
50	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
51	manual page.	58	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		59
57	=head1 CONCEPTS	60	=head1 CONCEPTS
58		61
59	=over 4	62	=over 4
60		63
61	=item port	64	=item port
62		65
63	A port is something you can send messages to (with the C<snd> function).	66	Not to be confused with a TCP port, a "port" is something you can send
		67	messages to (with the C<snd> function).
64		68
65	Some ports allow you to register C<rcv> handlers that can match specific	69	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	70	some messages. Messages send to ports will not be queued, regardless of
67	will not be queued.	71	anything was listening for them or not.
68		72
69	=item port id - C<noderef#portname>	73	=item port ID - C<nodeid#portname>
70		74
71	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	75	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	76	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		77
76	=item node	78	=item node
77		79
78	A node is a single process containing at least one port - the node	80	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	81	which enables nodes to manage each other remotely, and to create new
80	create new ports, among other things.	82	ports.
81		83
82	Nodes are either private (single-process only), slaves (connected to a	84	Nodes are either public (have one or more listening ports) or private
83	master node only) or public nodes (connectable from unrelated nodes).	85	(no listening ports). Private nodes cannot talk to other private nodes
		86	currently.
84		87
85	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	88	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
86		89
87	A node reference is a string that either simply identifies the node (for	90	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	91	network. Depending on the configuration used, node IDs can look like a
89	node (for public nodes).	92	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		93	doesn't interpret node IDs in any way.
90		94
91	This recipe is simply a comma-separated list of C<address:port> pairs (for	95	=item binds - C<ip:port>
92	TCP/IP, other protocols might look different).
93		96
94	Node references come in two flavours: resolved (containing only numerical	97	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).	98	each other. To do this, nodes should listen on one or more local transport
		99	endpoints - binds. Currently, only standard C<ip:port> specifications can
		100	be used, which specify TCP ports to listen on.
96		101
97	Before using an unresolved node reference in a message you first have to	102	=item seed nodes
98	resolve it.	103
		104	When a node starts, it knows nothing about the network. To teach the node
		105	about the network it first has to contact some other node within the
		106	network. This node is called a seed.
		107
		108	Apart from the fact that other nodes know them as seed nodes and they have
		109	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		110	any node can function as a seed node for others.
		111
		112	In addition to discovering the network, seed nodes are also used to
		113	maintain the network and to connect nodes that otherwise would have
		114	trouble connecting. They form the backbone of an AnyEvent::MP network.
		115
		116	Seed nodes are expected to be long-running, and at least one seed node
		117	should always be available. They should also be relatively responsive - a
		118	seed node that blocks for long periods will slow down everybody else.
		119
		120	=item seeds - C<host:port>
		121
		122	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		123	TCP port) of nodes thta should be used as seed nodes.
		124
		125	The nodes listening on those endpoints are expected to be long-running,
		126	and at least one of those should always be available. When nodes run out
		127	of connections (e.g. due to a network error), they try to re-establish
		128	connections to some seednodes again to join the network.
99		129
100	=back	130	=back
101		131
102	=head1 VARIABLES/FUNCTIONS	132	=head1 VARIABLES/FUNCTIONS
103		133
…		…
118	use base "Exporter";	148	use base "Exporter";
119		149
120	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	150	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
121		151
122	our @EXPORT = qw(	152	our @EXPORT = qw(
123	NODE $NODE *SELF node_of _any_	153	NODE $NODE *SELF node_of after
124	resolve_node initialise_node	154	configure
125	snd rcv mon kil reg psub spawn	155	snd rcv mon mon_guard kil reg psub spawn cal
126	port	156	port
127	);	157	);
128		158
129	our $SELF;	159	our $SELF;
130		160
…		…
134	kil $SELF, die => $msg;	164	kil $SELF, die => $msg;
135	}	165	}
136		166
137	=item $thisnode = NODE / $NODE	167	=item $thisnode = NODE / $NODE
138		168
139	The C<NODE> function returns, and the C<$NODE> variable contains	169	The C<NODE> function returns, and the C<$NODE> variable contains, the node
140	the noderef of the local node. The value is initialised by a call	170	ID of the node running in the current process. This value is initialised by
141	to C<become_public> or C<become_slave>, after which all local port	171	a call to C<configure>.
142	identifiers become invalid.
143		172
144	=item $noderef = node_of $port	173	=item $nodeid = node_of $port
145		174
146	Extracts and returns the noderef from a portid or a noderef.	175	Extracts and returns the node ID from a port ID or a node ID.
147		176
148	=item initialise_node $noderef, $seednode, $seednode...	177	=item configure $profile, key => value...
149		178
150	=item initialise_node "slave/", $master, $master...	179	=item configure key => value...
151		180
152	Before a node can talk to other nodes on the network it has to initialise	181	Before a node can talk to other nodes on the network (i.e. enter
153	itself - the minimum a node needs to know is it's own name, and optionally	182	"distributed mode") it has to configure itself - the minimum a node needs
154	it should know the noderefs of some other nodes in the network.	183	to know is its own name, and optionally it should know the addresses of
		184	some other nodes in the network to discover other nodes.
155		185
156	This function initialises a node - it must be called exactly once (or	186	This function configures a node - it must be called exactly once (or
157	never) before calling other AnyEvent::MP functions.	187	never) before calling other AnyEvent::MP functions.
158		188
159	All arguments are noderefs, which can be either resolved or unresolved.
160
161	There are two types of networked nodes, public nodes and slave nodes:
162
163	=over 4	189	=over 4
164		190
165	=item public nodes	191	=item step 1, gathering configuration from profiles
166		192
167	For public nodes, C<$noderef> must either be a (possibly unresolved)	193	The function first looks up a profile in the aemp configuration (see the
168	noderef, in which case it will be resolved, or C<undef> (or missing), in	194	L<aemp> commandline utility). The profile name can be specified via the
169	which case the noderef will be guessed.	195	named C<profile> parameter or can simply be the first parameter). If it is
		196	missing, then the nodename (F<uname -n>) will be used as profile name.
170		197
171	Afterwards, the node will bind itself on all endpoints and try to connect	198	The profile data is then gathered as follows:
172	to all additional C<$seednodes> that are specified. Seednodes are optional
173	and can be used to quickly bootstrap the node into an existing network.
174		199
175	=item slave nodes	200	First, all remaining key => value pairs (all of which are conveniently
		201	undocumented at the moment) will be interpreted as configuration
		202	data. Then they will be overwritten by any values specified in the global
		203	default configuration (see the F<aemp> utility), then the chain of
		204	profiles chosen by the profile name (and any C<parent> attributes).
176		205
177	When the C<$noderef> is the special string C<slave/>, then the node will	206	That means that the values specified in the profile have highest priority
178	become a slave node. Slave nodes cannot be contacted from outside and will	207	and the values specified directly via C<configure> have lowest priority,
179	route most of their traffic to the master node that they attach to.	208	and can only be used to specify defaults.
180		209
181	At least one additional noderef is required: The node will try to connect	210	If the profile specifies a node ID, then this will become the node ID of
182	to all of them and will become a slave attached to the first node it can	211	this process. If not, then the profile name will be used as node ID. The
183	successfully connect to.	212	special node ID of C<anon/> will be replaced by a random node ID.
		213
		214	=item step 2, bind listener sockets
		215
		216	The next step is to look up the binds in the profile, followed by binding
		217	aemp protocol listeners on all binds specified (it is possible and valid
		218	to have no binds, meaning that the node cannot be contacted form the
		219	outside. This means the node cannot talk to other nodes that also have no
		220	binds, but it can still talk to all "normal" nodes).
		221
		222	If the profile does not specify a binds list, then a default of C<*> is
		223	used, meaning the node will bind on a dynamically-assigned port on every
		224	local IP address it finds.
		225
		226	=item step 3, connect to seed nodes
		227
		228	As the last step, the seeds list from the profile is passed to the
		229	L<AnyEvent::MP::Global> module, which will then use it to keep
		230	connectivity with at least one node at any point in time.
184		231
185	=back	232	=back
186		233
187	This function will block until all nodes have been resolved and, for slave	234	Example: become a distributed node using the local node name as profile.
188	nodes, until it has successfully established a connection to a master	235	This should be the most common form of invocation for "daemon"-type nodes.
189	server.
190		236
191	Example: become a public node listening on the default node.	237	configure
192		238
193	initialise_node;	239	Example: become an anonymous node. This form is often used for commandline
		240	clients.
194		241
195	Example: become a public node, and try to contact some well-known master	242	configure nodeid => "anon/";
196	servers to become part of the network.
197		243
198	initialise_node undef, "master1", "master2";	244	Example: configure a node using a profile called seed, which si suitable
		245	for a seed node as it binds on all local addresses on a fixed port (4040,
		246	customary for aemp).
199		247
200	Example: become a public node listening on port C<4041>.	248	# use the aemp commandline utility
		249	# aemp profile seed nodeid anon/ binds '*:4040'
201		250
202	initialise_node 4041;	251	# then use it
		252	configure profile => "seed";
203		253
204	Example: become a public node, only visible on localhost port 4044.	254	# or simply use aemp from the shell again:
		255	# aemp run profile seed
205		256
206	initialise_node "locahost:4044";	257	# or provide a nicer-to-remember nodeid
207		258	# aemp run profile seed nodeid "$(hostname)"
208	Example: become a slave node to any of the specified master servers.
209
210	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
211
212	=item $cv = resolve_node $noderef
213
214	Takes an unresolved node reference that may contain hostnames and
215	abbreviated IDs, resolves all of them and returns a resolved node
216	reference.
217
218	In addition to C<address:port> pairs allowed in resolved noderefs, the
219	following forms are supported:
220
221	=over 4
222
223	=item the empty string
224
225	An empty-string component gets resolved as if the default port (4040) was
226	specified.
227
228	=item naked port numbers (e.g. C<1234>)
229
230	These are resolved by prepending the local nodename and a colon, to be
231	further resolved.
232
233	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
234
235	These are resolved by using AnyEvent::DNS to resolve them, optionally
236	looking up SRV records for the C<aemp=4040> port, if no port was
237	specified.
238
239	=back
240		259
241	=item $SELF	260	=item $SELF
242		261
243	Contains the current port id while executing C<rcv> callbacks or C<psub>	262	Contains the current port id while executing C<rcv> callbacks or C<psub>
244	blocks.	263	blocks.
245		264
246	=item SELF, %SELF, @SELF...	265	=item *SELF, SELF, %SELF, @SELF...
247		266
248	Due to some quirks in how perl exports variables, it is impossible to	267	Due to some quirks in how perl exports variables, it is impossible to
249	just export C<$SELF>, all the symbols called C<SELF> are exported by this	268	just export C<$SELF>, all the symbols named C<SELF> are exported by this
250	module, but only C<$SELF> is currently used.	269	module, but only C<$SELF> is currently used.
251		270
252	=item snd $port, type => @data	271	=item snd $port, type => @data
253		272
254	=item snd $port, @msg	273	=item snd $port, @msg
255		274
256	Send the given message to the given port ID, which can identify either	275	Send the given message to the given port, which can identify either a
257	a local or a remote port, and can be either a string or soemthignt hat	276	local or a remote port, and must be a port ID.
258	stringifies a sa port ID (such as a port object :).
259		277
260	While the message can be about anything, it is highly recommended to use a	278	While the message can be almost anything, it is highly recommended to
261	string as first element (a portid, or some word that indicates a request	279	use a string as first element (a port ID, or some word that indicates a
262	type etc.).	280	request type etc.) and to consist if only simple perl values (scalars,
		281	arrays, hashes) - if you think you need to pass an object, think again.
263		282
264	The message data effectively becomes read-only after a call to this	283	The message data logically becomes read-only after a call to this
265	function: modifying any argument is not allowed and can cause many	284	function: modifying any argument (or values referenced by them) is
266	problems.	285	forbidden, as there can be considerable time between the call to C<snd>
		286	and the time the message is actually being serialised - in fact, it might
		287	never be copied as within the same process it is simply handed to the
		288	receiving port.
267		289
268	The type of data you can transfer depends on the transport protocol: when	290	The type of data you can transfer depends on the transport protocol: when
269	JSON is used, then only strings, numbers and arrays and hashes consisting	291	JSON is used, then only strings, numbers and arrays and hashes consisting
270	of those are allowed (no objects). When Storable is used, then anything	292	of those are allowed (no objects). When Storable is used, then anything
271	that Storable can serialise and deserialise is allowed, and for the local	293	that Storable can serialise and deserialise is allowed, and for the local
272	node, anything can be passed.	294	node, anything can be passed. Best rely only on the common denominator of
		295	these.
273		296
274	=item $local_port = port	297	=item $local_port = port
275		298
276	Create a new local port object that can be used either as a pattern	299	Create a new local port object and returns its port ID. Initially it has
277	matching port ("full port") or a single-callback port ("miniport"),	300	no callbacks set and will throw an error when it receives messages.
278	depending on how C<rcv> callbacks are bound to the object.
279		301
280	=item $port = port { my @msg = @_; $finished }	302	=item $local_port = port { my @msg = @_ }
281		303
282	Creates a "miniport", that is, a very lightweight port without any pattern	304	Creates a new local port, and returns its ID. Semantically the same as
283	matching behind it, and returns its ID. Semantically the same as creating
284	a port and calling C<rcv $port, $callback> on it.	305	creating a port and calling C<rcv $port, $callback> on it.
285		306
286	The block will be called for every message received on the port. When the	307	The block will be called for every message received on the port, with the
287	callback returns a true value its job is considered "done" and the port	308	global variable C<$SELF> set to the port ID. Runtime errors will cause the
288	will be destroyed. Otherwise it will stay alive.	309	port to be C<kil>ed. The message will be passed as-is, no extra argument
		310	(i.e. no port ID) will be passed to the callback.
289		311
290	The message will be passed as-is, no extra argument (i.e. no port id) will	312	If you want to stop/destroy the port, simply C<kil> it:
291	be passed to the callback.
292		313
293	If you need the local port id in the callback, this works nicely:	314	my $port = port {
294		315	my @msg = @_;
295	my $port; $port = port {	316	...
296	snd $otherport, reply => $port;	317	kil $SELF;
297	};	318	};
298		319
299	=cut	320	=cut
300		321
301	sub rcv($@);	322	sub rcv($@);
		323
		324	sub _kilme {
		325	die "received message on port without callback";
		326	}
302		327
303	sub port(;&) {	328	sub port(;&) {
304	my $id = "$UNIQ." . $ID++;	329	my $id = "$UNIQ." . $ID++;
305	my $port = "$NODE#$id";	330	my $port = "$NODE#$id";
306		331
307	if (@_) {	332	rcv $port, shift \|\| \&_kilme;
308	rcv $port, shift;
309	} else {
310	$PORT{$id} = sub { }; # nop
311	}
312		333
313	$port	334	$port
314	}	335	}
315		336
316	=item reg $port, $name
317
318	=item reg $name
319
320	Registers the given port (or C<$SELF><<< if missing) under the name
321	C<$name>. If the name already exists it is replaced.
322
323	A port can only be registered under one well known name.
324
325	A port automatically becomes unregistered when it is killed.
326
327	=cut
328
329	sub reg(@) {
330	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
331
332	$REG{$_[0]} = $port;
333	}
334
335	=item rcv $port, $callback->(@msg)	337	=item rcv $local_port, $callback->(@msg)
336		338
337	Replaces the callback on the specified miniport (after converting it to	339	Replaces the default callback on the specified port. There is no way to
338	one if required).	340	remove the default callback: use C<sub { }> to disable it, or better
339		341	C<kil> the port when it is no longer needed.
340	=item rcv $port, tagstring => $callback->(@msg), ...
341
342	=item rcv $port, $smartmatch => $callback->(@msg), ...
343
344	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
345
346	Register callbacks to be called on matching messages on the given full
347	port (after converting it to one if required) and return the port.
348
349	The callback has to return a true value when its work is done, after
350	which is will be removed, or a false value in which case it will stay
351	registered.
352		342
353	The global C<$SELF> (exported by this module) contains C<$port> while	343	The global C<$SELF> (exported by this module) contains C<$port> while
354	executing the callback.	344	executing the callback. Runtime errors during callback execution will
		345	result in the port being C<kil>ed.
355		346
356	Runtime errors during callback execution will result in the port being	347	The default callback received all messages not matched by a more specific
357	C<kil>ed.	348	C<tag> match.
358		349
359	If the match is an array reference, then it will be matched against the	350	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
360	first elements of the message, otherwise only the first element is being
361	matched.
362		351
363	Any element in the match that is specified as C<_any_> (a function	352	Register (or replace) callbacks to be called on messages starting with the
364	exported by this module) matches any single element of the message.	353	given tag on the given port (and return the port), or unregister it (when
		354	C<$callback> is C<$undef> or missing). There can only be one callback
		355	registered for each tag.
365		356
366	While not required, it is highly recommended that the first matching	357	The original message will be passed to the callback, after the first
367	element is a string identifying the message. The one-string-only match is	358	element (the tag) has been removed. The callback will use the same
368	also the most efficient match (by far).	359	environment as the default callback (see above).
369		360
370	Example: create a port and bind receivers on it in one go.	361	Example: create a port and bind receivers on it in one go.
371		362
372	my $port = rcv port,	363	my $port = rcv port,
373	msg1 => sub { ...; 0 },	364	msg1 => sub { ... },
374	msg2 => sub { ...; 0 },	365	msg2 => sub { ... },
375	;	366	;
376		367
377	Example: create a port, bind receivers and send it in a message elsewhere	368	Example: create a port, bind receivers and send it in a message elsewhere
378	in one go:	369	in one go:
379		370
380	snd $otherport, reply =>	371	snd $otherport, reply =>
381	rcv port,	372	rcv port,
382	msg1 => sub { ...; 0 },	373	msg1 => sub { ... },
383	...	374	...
384	;	375	;
385		376
		377	Example: temporarily register a rcv callback for a tag matching some port
		378	(e.g. for a rpc reply) and unregister it after a message was received.
		379
		380	rcv $port, $otherport => sub {
		381	my @reply = @_;
		382
		383	rcv $SELF, $otherport;
		384	};
		385
386	=cut	386	=cut
387		387
388	sub rcv($@) {	388	sub rcv($@) {
389	my $port = shift;	389	my $port = shift;
390	my ($noderef, $portid) = split /#/, $port, 2;	390	my ($nodeid, $portid) = split /#/, $port, 2;
391		391
392	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	392	$NODE{$nodeid} == $NODE{""}
393	or Carp::croak "$port: rcv can only be called on local ports, caught";	393	or Carp::croak "$port: rcv can only be called on local ports, caught";
394		394
395	if (@_ == 1) {	395	while (@_) {
		396	if (ref $_[0]) {
		397	if (my $self = $PORT_DATA{$portid}) {
		398	"AnyEvent::MP::Port" eq ref $self
		399	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		400
		401	$self->[2] = shift;
		402	} else {
396	my $cb = shift;	403	my $cb = shift;
397	delete $PORT_DATA{$portid};
398	$PORT{$portid} = sub {	404	$PORT{$portid} = sub {
399	local $SELF = $port;	405	local $SELF = $port;
400	eval {	406	eval { &$cb }; _self_die if $@;
401	&$cb	407	};
402	and kil $port;
403	};	408	}
404	_self_die if $@;	409	} elsif (defined $_[0]) {
405	};
406	} else {
407	my $self = $PORT_DATA{$portid} \|\|= do {	410	my $self = $PORT_DATA{$portid} \|\|= do {
408	my $self = bless {	411	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
409	id => $port,
410	}, "AnyEvent::MP::Port";
411		412
412	$PORT{$portid} = sub {	413	$PORT{$portid} = sub {
413	local $SELF = $port;	414	local $SELF = $port;
414		415
415	eval {
416	for (@{ $self->{rc0}{$_[0]} }) {	416	if (my $cb = $self->[1]{$_[0]}) {
417	$_ && &{$_->[0]}	417	shift;
418	&& undef $_;	418	eval { &$cb }; _self_die if $@;
419	}	419	} else {
420
421	for (@{ $self->{rcv}{$_[0]} }) {
422	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
423	&& &{$_->[0]}	420	&{ $self->[0] };
424	&& undef $_;
425	}
426
427	for (@{ $self->{any} }) {
428	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
429	&& &{$_->[0]}
430	&& undef $_;
431	}	421	}
432	};	422	};
433	_self_die if $@;	423
		424	$self
434	};	425	};
435		426
436	$self
437	};
438
439	"AnyEvent::MP::Port" eq ref $self	427	"AnyEvent::MP::Port" eq ref $self
440	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	428	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
441		429
442	while (@_) {
443	my ($match, $cb) = splice @_, 0, 2;	430	my ($tag, $cb) = splice @_, 0, 2;
444		431
445	if (!ref $match) {	432	if (defined $cb) {
446	push @{ $self->{rc0}{$match} }, [$cb];	433	$self->[1]{$tag} = $cb;
447	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
448	my ($type, @match) = @$match;
449	@match
450	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
451	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
452	} else {	434	} else {
453	push @{ $self->{any} }, [$cb, $match];	435	delete $self->[1]{$tag};
454	}	436	}
455	}	437	}
456	}	438	}
457		439
458	$port	440	$port
…		…
494	$res	476	$res
495	}	477	}
496	}	478	}
497	}	479	}
498		480
499	=item $guard = mon $port, $cb->(@reason)	481	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
500		482
501	=item $guard = mon $port, $rcvport	483	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
502		484
503	=item $guard = mon $port	485	=item $guard = mon $port # kill $SELF when $port dies
504		486
505	=item $guard = mon $port, $rcvport, @msg	487	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
506		488
507	Monitor the given port and do something when the port is killed or	489	Monitor the given port and do something when the port is killed or
508	messages to it were lost, and optionally return a guard that can be used	490	messages to it were lost, and optionally return a guard that can be used
509	to stop monitoring again.	491	to stop monitoring again.
510
511	C<mon> effectively guarantees that, in the absence of hardware failures,
512	that after starting the monitor, either all messages sent to the port
513	will arrive, or the monitoring action will be invoked after possible
514	message loss has been detected. No messages will be lost "in between"
515	(after the first lost message no further messages will be received by the
516	port). After the monitoring action was invoked, further messages might get
517	delivered again.
518		492
519	In the first form (callback), the callback is simply called with any	493	In the first form (callback), the callback is simply called with any
520	number of C<@reason> elements (no @reason means that the port was deleted	494	number of C<@reason> elements (no @reason means that the port was deleted
521	"normally"). Note also that I<< the callback B<must> never die >>, so use	495	"normally"). Note also that I<< the callback B<must> never die >>, so use
522	C<eval> if unsure.	496	C<eval> if unsure.
523		497
524	In the second form (another port given), the other port (C<$rcvport>)	498	In the second form (another port given), the other port (C<$rcvport>)
525	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	499	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
526	"normal" kils nothing happens, while under all other conditions, the other	500	"normal" kils nothing happens, while under all other conditions, the other
527	port is killed with the same reason.	501	port is killed with the same reason.
528		502
529	The third form (kill self) is the same as the second form, except that	503	The third form (kill self) is the same as the second form, except that
530	C<$rvport> defaults to C<$SELF>.	504	C<$rvport> defaults to C<$SELF>.
531		505
532	In the last form (message), a message of the form C<@msg, @reason> will be	506	In the last form (message), a message of the form C<@msg, @reason> will be
533	C<snd>.	507	C<snd>.
		508
		509	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		510	alert was raised), they are removed and will not trigger again.
534		511
535	As a rule of thumb, monitoring requests should always monitor a port from	512	As a rule of thumb, monitoring requests should always monitor a port from
536	a local port (or callback). The reason is that kill messages might get	513	a local port (or callback). The reason is that kill messages might get
537	lost, just like any other message. Another less obvious reason is that	514	lost, just like any other message. Another less obvious reason is that
538	even monitoring requests can get lost (for exmaple, when the connection	515	even monitoring requests can get lost (for example, when the connection
539	to the other node goes down permanently). When monitoring a port locally	516	to the other node goes down permanently). When monitoring a port locally
540	these problems do not exist.	517	these problems do not exist.
541		518
		519	C<mon> effectively guarantees that, in the absence of hardware failures,
		520	after starting the monitor, either all messages sent to the port will
		521	arrive, or the monitoring action will be invoked after possible message
		522	loss has been detected. No messages will be lost "in between" (after
		523	the first lost message no further messages will be received by the
		524	port). After the monitoring action was invoked, further messages might get
		525	delivered again.
		526
		527	Inter-host-connection timeouts and monitoring depend on the transport
		528	used. The only transport currently implemented is TCP, and AnyEvent::MP
		529	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		530	non-idle connection, and usually around two hours for idle conenctions).
		531
		532	This means that monitoring is good for program errors and cleaning up
		533	stuff eventually, but they are no replacement for a timeout when you need
		534	to ensure some maximum latency.
		535
542	Example: call a given callback when C<$port> is killed.	536	Example: call a given callback when C<$port> is killed.
543		537
544	mon $port, sub { warn "port died because of <@_>\n" };	538	mon $port, sub { warn "port died because of <@_>\n" };
545		539
546	Example: kill ourselves when C<$port> is killed abnormally.	540	Example: kill ourselves when C<$port> is killed abnormally.
…		…
552	mon $port, $self => "restart";	546	mon $port, $self => "restart";
553		547
554	=cut	548	=cut
555		549
556	sub mon {	550	sub mon {
557	my ($noderef, $port) = split /#/, shift, 2;	551	my ($nodeid, $port) = split /#/, shift, 2;
558		552
559	my $node = $NODE{$noderef} \|\| add_node $noderef;	553	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
560		554
561	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	555	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
562		556
563	unless (ref $cb) {	557	unless (ref $cb) {
564	if (@_) {	558	if (@_) {
…		…
584	is killed, the references will be freed.	578	is killed, the references will be freed.
585		579
586	Optionally returns a guard that will stop the monitoring.	580	Optionally returns a guard that will stop the monitoring.
587		581
588	This function is useful when you create e.g. timers or other watchers and	582	This function is useful when you create e.g. timers or other watchers and
589	want to free them when the port gets killed:	583	want to free them when the port gets killed (note the use of C<psub>):
590		584
591	$port->rcv (start => sub {	585	$port->rcv (start => sub {
592	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	586	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
593	undef $timer if 0.9 < rand;	587	undef $timer if 0.9 < rand;
594	});	588	});
595	});	589	});
596		590
597	=cut	591	=cut
…		…
606		600
607	=item kil $port[, @reason]	601	=item kil $port[, @reason]
608		602
609	Kill the specified port with the given C<@reason>.	603	Kill the specified port with the given C<@reason>.
610		604
611	If no C<@reason> is specified, then the port is killed "normally" (linked	605	If no C<@reason> is specified, then the port is killed "normally" (ports
612	ports will not be kileld, or even notified).	606	monitoring other ports will not necessarily die because a port dies
		607	"normally").
613		608
614	Otherwise, linked ports get killed with the same reason (second form of	609	Otherwise, linked ports get killed with the same reason (second form of
615	C<mon>, see below).	610	C<mon>, see above).
616		611
617	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	612	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
618	will be reported as reason C<< die => $@ >>.	613	will be reported as reason C<< die => $@ >>.
619		614
620	Transport/communication errors are reported as C<< transport_error =>	615	Transport/communication errors are reported as C<< transport_error =>
…		…
625	=item $port = spawn $node, $initfunc[, @initdata]	620	=item $port = spawn $node, $initfunc[, @initdata]
626		621
627	Creates a port on the node C<$node> (which can also be a port ID, in which	622	Creates a port on the node C<$node> (which can also be a port ID, in which
628	case it's the node where that port resides).	623	case it's the node where that port resides).
629		624
630	The port ID of the newly created port is return immediately, and it is	625	The port ID of the newly created port is returned immediately, and it is
631	permissible to immediately start sending messages or monitor the port.	626	possible to immediately start sending messages or to monitor the port.
632		627
633	After the port has been created, the init function is	628	After the port has been created, the init function is called on the remote
634	called. This function must be a fully-qualified function name	629	node, in the same context as a C<rcv> callback. This function must be a
635	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	630	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
636	program, use C<::name>.	631	specify a function in the main program, use C<::name>.
637		632
638	If the function doesn't exist, then the node tries to C<require>	633	If the function doesn't exist, then the node tries to C<require>
639	the package, then the package above the package and so on (e.g.	634	the package, then the package above the package and so on (e.g.
640	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	635	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
641	exists or it runs out of package names.	636	exists or it runs out of package names.
642		637
643	The init function is then called with the newly-created port as context	638	The init function is then called with the newly-created port as context
644	object (C<$SELF>) and the C<@initdata> values as arguments.	639	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		640	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		641	the port might not get created.
645		642
646	A common idiom is to pass your own port, monitor the spawned port, and	643	A common idiom is to pass a local port, immediately monitor the spawned
647	in the init function, monitor the original port. This two-way monitoring	644	port, and in the remote init function, immediately monitor the passed
648	ensures that both ports get cleaned up when there is a problem.	645	local port. This two-way monitoring ensures that both ports get cleaned up
		646	when there is a problem.
		647
		648	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		649	caller before C<spawn> returns (by delaying invocation when spawn is
		650	called for the local node).
649		651
650	Example: spawn a chat server port on C<$othernode>.	652	Example: spawn a chat server port on C<$othernode>.
651		653
652	# this node, executed from within a port context:	654	# this node, executed from within a port context:
653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	655	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
668		670
669	sub _spawn {	671	sub _spawn {
670	my $port = shift;	672	my $port = shift;
671	my $init = shift;	673	my $init = shift;
672		674
		675	# rcv will create the actual port
673	local $SELF = "$NODE#$port";	676	local $SELF = "$NODE#$port";
674	eval {	677	eval {
675	&{ load_func $init }	678	&{ load_func $init }
676	};	679	};
677	_self_die if $@;	680	_self_die if $@;
678	}	681	}
679		682
680	sub spawn(@) {	683	sub spawn(@) {
681	my ($noderef, undef) = split /#/, shift, 2;	684	my ($nodeid, undef) = split /#/, shift, 2;
682		685
683	my $id = "$RUNIQ." . $ID++;	686	my $id = "$RUNIQ." . $ID++;
684		687
685	$_[0] =~ /::/	688	$_[0] =~ /::/
686	or Carp::croak "spawn init function must be a fully-qualified name, caught";	689	or Carp::croak "spawn init function must be a fully-qualified name, caught";
687		690
688	($NODE{$noderef} \|\| add_node $noderef)	691	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
689	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
690		692
691	"$noderef#$id"	693	"$nodeid#$id"
692	}	694	}
693		695
694	=back	696	=item after $timeout, @msg
695		697
696	=head1 NODE MESSAGES	698	=item after $timeout, $callback
697		699
698	Nodes understand the following messages sent to them. Many of them take	700	Either sends the given message, or call the given callback, after the
699	arguments called C<@reply>, which will simply be used to compose a reply	701	specified number of seconds.
700	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
701	the remaining arguments are simply the message data.
702		702
703	While other messages exist, they are not public and subject to change.	703	This is simply a utility function that comes in handy at times - the
		704	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		705	so it may go away in the future.
704		706
705	=over 4
706
707	=cut	707	=cut
708		708
709	=item lookup => $name, @reply	709	sub after($@) {
		710	my ($timeout, @action) = @_;
710		711
711	Replies with the port ID of the specified well-known port, or C<undef>.	712	my $t; $t = AE::timer $timeout, 0, sub {
		713	undef $t;
		714	ref $action[0]
		715	? $action[0]()
		716	: snd @action;
		717	};
		718	}
712		719
713	=item devnull => ...	720	=item cal $port, @msg, $callback[, $timeout]
714		721
715	Generic data sink/CPU heat conversion.	722	A simple form of RPC - sends a message to the given C<$port> with the
		723	given contents (C<@msg>), but adds a reply port to the message.
716		724
717	=item relay => $port, @msg	725	The reply port is created temporarily just for the purpose of receiving
		726	the reply, and will be C<kil>ed when no longer needed.
718		727
719	Simply forwards the message to the given port.	728	A reply message sent to the port is passed to the C<$callback> as-is.
720		729
721	=item eval => $string[ @reply]	730	If an optional time-out (in seconds) is given and it is not C<undef>,
		731	then the callback will be called without any arguments after the time-out
		732	elapsed and the port is C<kil>ed.
722		733
723	Evaluates the given string. If C<@reply> is given, then a message of the	734	If no time-out is given, then the local port will monitor the remote port
724	form C<@reply, $@, @evalres> is sent.	735	instead, so it eventually gets cleaned-up.
725		736
726	Example: crash another node.	737	Currently this function returns the temporary port, but this "feature"
		738	might go in future versions unless you can make a convincing case that
		739	this is indeed useful for something.
727		740
728	snd $othernode, eval => "exit";	741	=cut
729		742
730	=item time => @reply	743	sub cal(@) {
		744	my $timeout = ref $_[-1] ? undef : pop;
		745	my $cb = pop;
731		746
732	Replies the the current node time to C<@reply>.	747	my $port = port {
		748	undef $timeout;
		749	kil $SELF;
		750	&$cb;
		751	};
733		752
734	Example: tell the current node to send the current time to C<$myport> in a	753	if (defined $timeout) {
735	C<timereply> message.	754	$timeout = AE::timer $timeout, 0, sub {
		755	undef $timeout;
		756	kil $port;
		757	$cb->();
		758	};
		759	} else {
		760	mon $_[0], sub {
		761	kil $port;
		762	$cb->();
		763	};
		764	}
736		765
737	snd $NODE, time => $myport, timereply => 1, 2;	766	push @_, $port;
738	# => snd $myport, timereply => 1, 2, <time>	767	&snd;
		768
		769	$port
		770	}
739		771
740	=back	772	=back
741		773
742	=head1 AnyEvent::MP vs. Distributed Erlang	774	=head1 AnyEvent::MP vs. Distributed Erlang
743		775
…		…
753		785
754	Despite the similarities, there are also some important differences:	786	Despite the similarities, there are also some important differences:
755		787
756	=over 4	788	=over 4
757		789
758	=item * Node references contain the recipe on how to contact them.	790	=item * Node IDs are arbitrary strings in AEMP.
759		791
760	Erlang relies on special naming and DNS to work everywhere in the	792	Erlang relies on special naming and DNS to work everywhere in the same
761	same way. AEMP relies on each node knowing it's own address(es), with	793	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
762	convenience functionality.	794	configuration or DNS), but will otherwise discover other odes itself.
763		795
764	This means that AEMP requires a less tightly controlled environment at the	796	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
765	cost of longer node references and a slightly higher management overhead.	797	uses "local ports are like remote ports".
		798
		799	The failure modes for local ports are quite different (runtime errors
		800	only) then for remote ports - when a local port dies, you I<know> it dies,
		801	when a connection to another node dies, you know nothing about the other
		802	port.
		803
		804	Erlang pretends remote ports are as reliable as local ports, even when
		805	they are not.
		806
		807	AEMP encourages a "treat remote ports differently" philosophy, with local
		808	ports being the special case/exception, where transport errors cannot
		809	occur.
766		810
767	=item * Erlang uses processes and a mailbox, AEMP does not queue.	811	=item * Erlang uses processes and a mailbox, AEMP does not queue.
768		812
769	Erlang uses processes that selctively receive messages, and therefore	813	Erlang uses processes that selectively receive messages, and therefore
770	needs a queue. AEMP is event based, queuing messages would serve no useful	814	needs a queue. AEMP is event based, queuing messages would serve no
771	purpose.	815	useful purpose. For the same reason the pattern-matching abilities of
		816	AnyEvent::MP are more limited, as there is little need to be able to
		817	filter messages without dequeuing them.
772		818
773	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	819	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
774		820
775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	821	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
776		822
777	Sending messages in Erlang is synchronous and blocks the process. AEMP	823	Sending messages in Erlang is synchronous and blocks the process (and
778	sends are immediate, connection establishment is handled in the	824	so does not need a queue that can overflow). AEMP sends are immediate,
779	background.	825	connection establishment is handled in the background.
780		826
781	=item * Erlang can silently lose messages, AEMP cannot.	827	=item * Erlang suffers from silent message loss, AEMP does not.
782		828
783	Erlang makes few guarantees on messages delivery - messages can get lost	829	Erlang makes few guarantees on messages delivery - messages can get lost
784	without any of the processes realising it (i.e. you send messages a, b,	830	without any of the processes realising it (i.e. you send messages a, b,
785	and c, and the other side only receives messages a and c).	831	and c, and the other side only receives messages a and c).
786		832
787	AEMP guarantees correct ordering, and the guarantee that there are no	833	AEMP guarantees correct ordering, and the guarantee that after one message
788	holes in the message sequence.	834	is lost, all following ones sent to the same port are lost as well, until
789		835	monitoring raises an error, so there are no silent "holes" in the message
790	=item * In Erlang, processes can be declared dead and later be found to be	836	sequence.
791	alive.
792
793	In Erlang it can happen that a monitored process is declared dead and
794	linked processes get killed, but later it turns out that the process is
795	still alive - and can receive messages.
796
797	In AEMP, when port monitoring detects a port as dead, then that port will
798	eventually be killed - it cannot happen that a node detects a port as dead
799	and then later sends messages to it, finding it is still alive.
800		837
801	=item * Erlang can send messages to the wrong port, AEMP does not.	838	=item * Erlang can send messages to the wrong port, AEMP does not.
802		839
803	In Erlang it is quite possible that a node that restarts reuses a process	840	In Erlang it is quite likely that a node that restarts reuses a process ID
804	ID known to other nodes for a completely different process, causing	841	known to other nodes for a completely different process, causing messages
805	messages destined for that process to end up in an unrelated process.	842	destined for that process to end up in an unrelated process.
806		843
807	AEMP never reuses port IDs, so old messages or old port IDs floating	844	AEMP never reuses port IDs, so old messages or old port IDs floating
808	around in the network will not be sent to an unrelated port.	845	around in the network will not be sent to an unrelated port.
809		846
810	=item * Erlang uses unprotected connections, AEMP uses secure	847	=item * Erlang uses unprotected connections, AEMP uses secure
811	authentication and can use TLS.	848	authentication and can use TLS.
812		849
813	AEMP can use a proven protocol - SSL/TLS - to protect connections and	850	AEMP can use a proven protocol - TLS - to protect connections and
814	securely authenticate nodes.	851	securely authenticate nodes.
815		852
816	=item * The AEMP protocol is optimised for both text-based and binary	853	=item * The AEMP protocol is optimised for both text-based and binary
817	communications.	854	communications.
818		855
819	The AEMP protocol, unlike the Erlang protocol, supports both	856	The AEMP protocol, unlike the Erlang protocol, supports both programming
820	language-independent text-only protocols (good for debugging) and binary,	857	language independent text-only protocols (good for debugging) and binary,
821	language-specific serialisers (e.g. Storable).	858	language-specific serialisers (e.g. Storable). By default, unless TLS is
		859	used, the protocol is actually completely text-based.
822		860
823	It has also been carefully designed to be implementable in other languages	861	It has also been carefully designed to be implementable in other languages
824	with a minimum of work while gracefully degrading fucntionality to make the	862	with a minimum of work while gracefully degrading functionality to make the
825	protocol simple.	863	protocol simple.
826		864
827	=item * AEMP has more flexible monitoring options than Erlang.	865	=item * AEMP has more flexible monitoring options than Erlang.
828		866
829	In Erlang, you can chose to receive I<all> exit signals as messages	867	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
832	Erlang, as one can choose between automatic kill, exit message or callback	870	Erlang, as one can choose between automatic kill, exit message or callback
833	on a per-process basis.	871	on a per-process basis.
834		872
835	=item * Erlang tries to hide remote/local connections, AEMP does not.	873	=item * Erlang tries to hide remote/local connections, AEMP does not.
836		874
837	Monitoring in Erlang is not an indicator of process death/crashes,	875	Monitoring in Erlang is not an indicator of process death/crashes, in the
838	as linking is (except linking is unreliable in Erlang).	876	same way as linking is (except linking is unreliable in Erlang).
839		877
840	In AEMP, you don't "look up" registered port names or send to named ports	878	In AEMP, you don't "look up" registered port names or send to named ports
841	that might or might not be persistent. Instead, you normally spawn a port	879	that might or might not be persistent. Instead, you normally spawn a port
842	on the remote node. The init function monitors the you, and you monitor	880	on the remote node. The init function monitors you, and you monitor the
843	the remote port. Since both monitors are local to the node, they are much	881	remote port. Since both monitors are local to the node, they are much more
844	more reliable.	882	reliable (no need for C<spawn_link>).
845		883
846	This also saves round-trips and avoids sending messages to the wrong port	884	This also saves round-trips and avoids sending messages to the wrong port
847	(hard to do in Erlang).	885	(hard to do in Erlang).
848		886
849	=back	887	=back
850		888
		889	=head1 RATIONALE
		890
		891	=over 4
		892
		893	=item Why strings for port and node IDs, why not objects?
		894
		895	We considered "objects", but found that the actual number of methods
		896	that can be called are quite low. Since port and node IDs travel over
		897	the network frequently, the serialising/deserialising would add lots of
		898	overhead, as well as having to keep a proxy object everywhere.
		899
		900	Strings can easily be printed, easily serialised etc. and need no special
		901	procedures to be "valid".
		902
		903	And as a result, a miniport consists of a single closure stored in a
		904	global hash - it can't become much cheaper.
		905
		906	=item Why favour JSON, why not a real serialising format such as Storable?
		907
		908	In fact, any AnyEvent::MP node will happily accept Storable as framing
		909	format, but currently there is no way to make a node use Storable by
		910	default (although all nodes will accept it).
		911
		912	The default framing protocol is JSON because a) JSON::XS is many times
		913	faster for small messages and b) most importantly, after years of
		914	experience we found that object serialisation is causing more problems
		915	than it solves: Just like function calls, objects simply do not travel
		916	easily over the network, mostly because they will always be a copy, so you
		917	always have to re-think your design.
		918
		919	Keeping your messages simple, concentrating on data structures rather than
		920	objects, will keep your messages clean, tidy and efficient.
		921
		922	=back
		923
851	=head1 SEE ALSO	924	=head1 SEE ALSO
		925
		926	L<AnyEvent::MP::Intro> - a gentle introduction.
		927
		928	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		929
		930	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		931	your applications.
		932
		933	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		934	all nodes.
852		935
853	L<AnyEvent>.	936	L<AnyEvent>.
854		937
855	=head1 AUTHOR	938	=head1 AUTHOR
856		939

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Revision 1.44 by root, Wed Aug 12 21:39:58 2009 UTC vs.
Revision 1.87 by root, Fri Sep 11 02:32:23 2009 UTC