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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.43 by root, Sun Aug 9 16:08:16 2009 UTC vs.
Revision 1.100 by root, Fri Oct 2 20:41:56 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 that 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 = $AnyEvent::MP::Base::VERSION;	148	our $VERSION = 1.21;
121		149
122	our @EXPORT = qw(	150	our @EXPORT = qw(
123	NODE $NODE *SELF node_of _any_	151	NODE $NODE *SELF node_of after
124	resolve_node initialise_node	152	configure
125	snd rcv mon kil reg psub spawn	153	snd rcv mon mon_guard kil psub spawn cal
126	port	154	port
127	);	155	);
128		156
129	our $SELF;	157	our $SELF;
130		158
…		…
134	kil $SELF, die => $msg;	162	kil $SELF, die => $msg;
135	}	163	}
136		164
137	=item $thisnode = NODE / $NODE	165	=item $thisnode = NODE / $NODE
138		166
139	The C<NODE> function returns, and the C<$NODE> variable contains	167	The C<NODE> function returns, and the C<$NODE> variable contains, the node
140	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
141	to C<become_public> or C<become_slave>, after which all local port	169	a call to C<configure>.
142	identifiers become invalid.
143		170
144	=item $noderef = node_of $port	171	=item $nodeid = node_of $port
145		172
146	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.
147		174
148	=item initialise_node $noderef, $seednode, $seednode...	175	=item configure $profile, key => value...
149		176
150	=item initialise_node "slave/", $master, $master...	177	=item configure key => value...
151		178
152	Before a node can talk to other nodes on the network it has to initialise	179	Before a node can talk to other nodes on the network (i.e. enter
153	itself - the minimum a node needs to know is it's own name, and optionally	180	"distributed mode") it has to configure itself - the minimum a node needs
154	it should know the noderefs of some other nodes in the network.	181	to know is its own name, and optionally it should know the addresses of
		182	some other nodes in the network to discover other nodes.
155		183
156	This function initialises a node - it must be called exactly once (or	184	This function configures a node - it must be called exactly once (or
157	never) before calling other AnyEvent::MP functions.	185	never) before calling other AnyEvent::MP functions.
158		186
159	All arguments are noderefs, which can be either resolved or unresolved.
160
161	There are two types of networked nodes, public nodes and slave nodes:
162
163	=over 4	187	=over 4
164		188
165	=item public nodes	189	=item step 1, gathering configuration from profiles
166		190
167	For public nodes, C<$noderef> must either be a (possibly unresolved)	191	The function first looks up a profile in the aemp configuration (see the
168	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
169	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.
170		195
171	Afterwards, the node will bind itself on all endpoints and try to connect	196	The profile data is then gathered as follows:
172	to all additional C<$seednodes> that are specified. Seednodes are optional
173	and can be used to quickly bootstrap the node into an existing network.
174		197
175	=item slave nodes	198	First, all remaining key => value pairs (all of which are conveniently
		199	undocumented at the moment) will be interpreted as configuration
		200	data. Then they will be overwritten by any values specified in the global
		201	default configuration (see the F<aemp> utility), then the chain of
		202	profiles chosen by the profile name (and any C<parent> attributes).
176		203
177	When the C<$noderef> is the special string C<slave/>, then the node will	204	That means that the values specified in the profile have highest priority
178	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,
179	route most of their traffic to the master node that they attach to.	206	and can only be used to specify defaults.
180		207
181	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
182	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
183	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.
184		229
185	=back	230	=back
186		231
187	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.
188	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.
189	server.
190		234
191	Example: become a public node listening on the default node.	235	configure
192		236
193	initialise_node;	237	Example: become an anonymous node. This form is often used for commandline
		238	clients.
194		239
195	Example: become a public node, and try to contact some well-known master	240	configure nodeid => "anon/";
196	servers to become part of the network.
197		241
198	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).
199		245
200	Example: become a public node listening on port C<4041>.	246	# use the aemp commandline utility
		247	# aemp profile seed nodeid anon/ binds '*:4040'
201		248
202	initialise_node 4041;	249	# then use it
		250	configure profile => "seed";
203		251
204	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
205		254
206	initialise_node "locahost:4044";	255	# or provide a nicer-to-remember nodeid
207		256	# 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		257
241	=item $SELF	258	=item $SELF
242		259
243	Contains the current port id while executing C<rcv> callbacks or C<psub>	260	Contains the current port id while executing C<rcv> callbacks or C<psub>
244	blocks.	261	blocks.
245		262
246	=item SELF, %SELF, @SELF...	263	=item *SELF, SELF, %SELF, @SELF...
247		264
248	Due to some quirks in how perl exports variables, it is impossible to	265	Due to some quirks in how perl exports variables, it is impossible to
249	just export C<$SELF>, all the symbols called C<SELF> are exported by this	266	just export C<$SELF>, all the symbols named C<SELF> are exported by this
250	module, but only C<$SELF> is currently used.	267	module, but only C<$SELF> is currently used.
251		268
252	=item snd $port, type => @data	269	=item snd $port, type => @data
253		270
254	=item snd $port, @msg	271	=item snd $port, @msg
255		272
256	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
257	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.
258	stringifies a sa port ID (such as a port object :).
259		275
260	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
261	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
262	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.
263		280
264	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
265	function: modifying any argument is not allowed and can cause many	282	function: modifying any argument (or values referenced by them) is
266	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.
267		287
268	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
269	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
270	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
271	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
272	node, anything can be passed.	292	node, anything can be passed. Best rely only on the common denominator of
		293	these.
273		294
274	=item $local_port = port	295	=item $local_port = port
275		296
276	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
277	matching port ("full port") or a single-callback port ("miniport"),	298	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		299
280	=item $port = port { my @msg = @_; $finished }	300	=item $local_port = port { my @msg = @_ }
281		301
282	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
283	matching behind it, and returns its ID. Semantically the same as creating
284	a port and calling C<rcv $port, $callback> on it.	303	creating a port and calling C<rcv $port, $callback> on it.
285		304
286	The block will be called for every message received on the port. When the	305	The block will be called for every message received on the port, with the
287	callback returns a true value its job is considered "done" and the port	306	global variable C<$SELF> set to the port ID. Runtime errors will cause the
288	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.
289		309
290	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:
291	be passed to the callback.
292		311
293	If you need the local port id in the callback, this works nicely:	312	my $port = port {
294		313	my @msg = @_;
295	my $port; $port = port {	314	...
296	snd $otherport, reply => $port;	315	kil $SELF;
297	};	316	};
298		317
299	=cut	318	=cut
300		319
301	sub rcv($@);	320	sub rcv($@);
		321
		322	sub _kilme {
		323	die "received message on port without callback";
		324	}
302		325
303	sub port(;&) {	326	sub port(;&) {
304	my $id = "$UNIQ." . $ID++;	327	my $id = "$UNIQ." . $ID++;
305	my $port = "$NODE#$id";	328	my $port = "$NODE#$id";
306		329
307	if (@_) {	330	rcv $port, shift \|\| \&_kilme;
308	rcv $port, shift;
309	} else {
310	$PORT{$id} = sub { }; # nop
311	}
312		331
313	$port	332	$port
314	}	333	}
315		334
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)	335	=item rcv $local_port, $callback->(@msg)
336		336
337	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
338	one if required).	338	remove the default callback: use C<sub { }> to disable it, or better
339		339	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...] => $callback->(@msg), ...
345
346	Register callbacks to be called on matching messages on the given full
347	port (after converting it to one if required) and return the port.
348
349	The callback has to return a true value when its work is done, after
350	which is will be removed, or a false value in which case it will stay
351	registered.
352		340
353	The global C<$SELF> (exported by this module) contains C<$port> while	341	The global C<$SELF> (exported by this module) contains C<$port> while
354	executing the callback.	342	executing the callback. Runtime errors during callback execution will
		343	result in the port being C<kil>ed.
355		344
356	Runtime errors during callback execution will result in the port being	345	The default callback received all messages not matched by a more specific
357	C<kil>ed.	346	C<tag> match.
358		347
359	If the match is an array reference, then it will be matched against the	348	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
360	first elements of the message, otherwise only the first element is being
361	matched.
362		349
363	Any element in the match that is specified as C<_any_> (a function	350	Register (or replace) callbacks to be called on messages starting with the
364	exported by this module) matches any single element of the message.	351	given tag on the given port (and return the port), or unregister it (when
		352	C<$callback> is C<$undef> or missing). There can only be one callback
		353	registered for each tag.
365		354
366	While not required, it is highly recommended that the first matching	355	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	356	element (the tag) has been removed. The callback will use the same
368	also the most efficient match (by far).	357	environment as the default callback (see above).
369		358
370	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.
371		360
372	my $port = rcv port,	361	my $port = rcv port,
373	msg1 => sub { ...; 0 },	362	msg1 => sub { ... },
374	msg2 => sub { ...; 0 },	363	msg2 => sub { ... },
375	;	364	;
376		365
377	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
378	in one go:	367	in one go:
379		368
380	snd $otherport, reply =>	369	snd $otherport, reply =>
381	rcv port,	370	rcv port,
382	msg1 => sub { ...; 0 },	371	msg1 => sub { ... },
383	...	372	...
384	;	373	;
385		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, $otherport;
		382	};
		383
386	=cut	384	=cut
387		385
388	sub rcv($@) {	386	sub rcv($@) {
389	my $port = shift;	387	my $port = shift;
390	my ($noderef, $portid) = split /#/, $port, 2;	388	my ($nodeid, $portid) = split /#/, $port, 2;
391		389
392	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	390	$NODE{$nodeid} == $NODE{""}
393	or Carp::croak "$port: rcv can only be called on local ports, caught";	391	or Carp::croak "$port: rcv can only be called on local ports, caught";
394		392
395	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 {
396	my $cb = shift;	401	my $cb = shift;
397	delete $PORT_DATA{$portid};
398	$PORT{$portid} = sub {	402	$PORT{$portid} = sub {
399	local $SELF = $port;	403	local $SELF = $port;
400	eval {	404	eval { &$cb }; _self_die if $@;
401	&$cb	405	};
402	and kil $port;
403	};	406	}
404	_self_die if $@;	407	} elsif (defined $_[0]) {
405	};
406	} else {
407	my $self = $PORT_DATA{$portid} \|\|= do {	408	my $self = $PORT_DATA{$portid} \|\|= do {
408	my $self = bless {	409	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
409	id => $port,
410	}, "AnyEvent::MP::Port";
411		410
412	$PORT{$portid} = sub {	411	$PORT{$portid} = sub {
413	local $SELF = $port;	412	local $SELF = $port;
414		413
415	eval {
416	for (@{ $self->{rc0}{$_[0]} }) {	414	if (my $cb = $self->[1]{$_[0]}) {
417	$_ && &{$_->[0]}	415	shift;
418	&& undef $_;	416	eval { &$cb }; _self_die if $@;
419	}	417	} else {
420
421	for (@{ $self->{rcv}{$_[0]} }) {
422	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
423	&& &{$_->[0]}	418	&{ $self->[0] };
424	&& undef $_;
425	}
426
427	for (@{ $self->{any} }) {
428	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
429	&& &{$_->[0]}
430	&& undef $_;
431	}	419	}
432	};	420	};
433	_self_die if $@;	421
		422	$self
434	};	423	};
435		424
436	$self
437	};
438
439	"AnyEvent::MP::Port" eq ref $self	425	"AnyEvent::MP::Port" eq ref $self
440	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	426	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
441		427
442	while (@_) {
443	my ($match, $cb) = splice @_, 0, 2;	428	my ($tag, $cb) = splice @_, 0, 2;
444		429
445	if (!ref $match) {	430	if (defined $cb) {
446	push @{ $self->{rc0}{$match} }, [$cb];	431	$self->[1]{$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 {	432	} else {
453	push @{ $self->{any} }, [$cb, $match];	433	delete $self->[1]{$tag};
454	}	434	}
455	}	435	}
456	}	436	}
457		437
458	$port	438	$port
…		…
494	$res	474	$res
495	}	475	}
496	}	476	}
497	}	477	}
498		478
499	=item $guard = mon $port, $cb->(@reason)	479	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
500		480
501	=item $guard = mon $port, $rcvport	481	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
502		482
503	=item $guard = mon $port	483	=item $guard = mon $port # kill $SELF when $port dies
504		484
505	=item $guard = mon $port, $rcvport, @msg	485	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
506		486
507	Monitor the given port and do something when the port is killed or	487	Monitor the given port and do something when the port is killed or
508	messages to it were lost, and optionally return a guard that can be used	488	messages to it were lost, and optionally return a guard that can be used
509	to stop monitoring again.	489	to stop monitoring again.
510
511	C<mon> effectively guarantees that, in the absence of hardware failures,
512	that after starting the monitor, either all messages sent to the port
513	will arrive, or the monitoring action will be invoked after possible
514	message loss has been detected. No messages will be lost "in between"
515	(after the first lost message no further messages will be received by the
516	port). After the monitoring action was invoked, further messages might get
517	delivered again.
518		490
519	In the first form (callback), the callback is simply called with any	491	In the first form (callback), the callback is simply called with any
520	number of C<@reason> elements (no @reason means that the port was deleted	492	number of C<@reason> elements (no @reason means that the port was deleted
521	"normally"). Note also that I<< the callback B<must> never die >>, so use	493	"normally"). Note also that I<< the callback B<must> never die >>, so use
522	C<eval> if unsure.	494	C<eval> if unsure.
523		495
524	In the second form (another port given), the other port (C<$rcvport>)	496	In the second form (another port given), the other port (C<$rcvport>)
525	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	497	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
526	"normal" kils nothing happens, while under all other conditions, the other	498	"normal" kils nothing happens, while under all other conditions, the other
527	port is killed with the same reason.	499	port is killed with the same reason.
528		500
529	The third form (kill self) is the same as the second form, except that	501	The third form (kill self) is the same as the second form, except that
530	C<$rvport> defaults to C<$SELF>.	502	C<$rvport> defaults to C<$SELF>.
531		503
532	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
533	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.
534		509
535	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
536	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
537	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
538	even monitoring requests can get lost (for exmaple, when the connection	513	even monitoring requests can get lost (for example, when the connection
539	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
540	these problems do not exist.	515	these problems do not exist.
541		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 connections).
		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
542	Example: call a given callback when C<$port> is killed.	534	Example: call a given callback when C<$port> is killed.
543		535
544	mon $port, sub { warn "port died because of <@_>\n" };	536	mon $port, sub { warn "port died because of <@_>\n" };
545		537
546	Example: kill ourselves when C<$port> is killed abnormally.	538	Example: kill ourselves when C<$port> is killed abnormally.
…		…
552	mon $port, $self => "restart";	544	mon $port, $self => "restart";
553		545
554	=cut	546	=cut
555		547
556	sub mon {	548	sub mon {
557	my ($noderef, $port) = split /#/, shift, 2;	549	my ($nodeid, $port) = split /#/, shift, 2;
558		550
559	my $node = $NODE{$noderef} \|\| add_node $noderef;	551	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
560		552
561	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	553	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
562		554
563	unless (ref $cb) {	555	unless (ref $cb) {
564	if (@_) {	556	if (@_) {
…		…
573	}	565	}
574		566
575	$node->monitor ($port, $cb);	567	$node->monitor ($port, $cb);
576		568
577	defined wantarray	569	defined wantarray
578	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	570	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
579	}	571	}
580		572
581	=item $guard = mon_guard $port, $ref, $ref...	573	=item $guard = mon_guard $port, $ref, $ref...
582		574
583	Monitors the given C<$port> and keeps the passed references. When the port	575	Monitors the given C<$port> and keeps the passed references. When the port
584	is killed, the references will be freed.	576	is killed, the references will be freed.
585		577
586	Optionally returns a guard that will stop the monitoring.	578	Optionally returns a guard that will stop the monitoring.
587		579
588	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
589	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>):
590		582
591	$port->rcv (start => sub {	583	$port->rcv (start => sub {
592	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	584	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
593	undef $timer if 0.9 < rand;	585	undef $timer if 0.9 < rand;
594	});	586	});
595	});	587	});
596		588
597	=cut	589	=cut
…		…
606		598
607	=item kil $port[, @reason]	599	=item kil $port[, @reason]
608		600
609	Kill the specified port with the given C<@reason>.	601	Kill the specified port with the given C<@reason>.
610		602
611	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
612	ports will not be kileld, or even notified).	604	monitoring other ports will not necessarily die because a port dies
		605	"normally").
613		606
614	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
615	C<mon>, see below).	608	C<mon>, see above).
616		609
617	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
618	will be reported as reason C<< die => $@ >>.	611	will be reported as reason C<< die => $@ >>.
619		612
620	Transport/communication errors are reported as C<< transport_error =>	613	Transport/communication errors are reported as C<< transport_error =>
…		…
625	=item $port = spawn $node, $initfunc[, @initdata]	618	=item $port = spawn $node, $initfunc[, @initdata]
626		619
627	Creates a port on the node C<$node> (which can also be a port ID, in which	620	Creates a port on the node C<$node> (which can also be a port ID, in which
628	case it's the node where that port resides).	621	case it's the node where that port resides).
629		622
630	The port ID of the newly created port is return immediately, and it is	623	The port ID of the newly created port is returned immediately, and it is
631	permissible to immediately start sending messages or monitor the port.	624	possible to immediately start sending messages or to monitor the port.
632		625
633	After the port has been created, the init function is	626	After the port has been created, the init function is called on the remote
634	called. This function must be a fully-qualified function name	627	node, in the same context as a C<rcv> callback. This function must be a
635	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	628	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
636	program, use C<::name>.	629	specify a function in the main program, use C<::name>.
637		630
638	If the function doesn't exist, then the node tries to C<require>	631	If the function doesn't exist, then the node tries to C<require>
639	the package, then the package above the package and so on (e.g.	632	the package, then the package above the package and so on (e.g.
640	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	633	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
641	exists or it runs out of package names.	634	exists or it runs out of package names.
642		635
643	The init function is then called with the newly-created port as context	636	The init function is then called with the newly-created port as context
644	object (C<$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.
645		640
646	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
647	in the init function, monitor the original port. This two-way monitoring	642	port, and in the remote init function, immediately monitor the passed
648	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<$initfunc> has no visible effects on the
		647	caller before C<spawn> returns (by delaying invocation when spawn is
		648	called for the local node).
649		649
650	Example: spawn a chat server port on C<$othernode>.	650	Example: spawn a chat server port on C<$othernode>.
651		651
652	# this node, executed from within a port context:	652	# this node, executed from within a port context:
653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
668		668
669	sub _spawn {	669	sub _spawn {
670	my $port = shift;	670	my $port = shift;
671	my $init = shift;	671	my $init = shift;
672		672
		673	# rcv will create the actual port
673	local $SELF = "$NODE#$port";	674	local $SELF = "$NODE#$port";
674	eval {	675	eval {
675	&{ load_func $init }	676	&{ load_func $init }
676	};	677	};
677	_self_die if $@;	678	_self_die if $@;
678	}	679	}
679		680
680	sub spawn(@) {	681	sub spawn(@) {
681	my ($noderef, undef) = split /#/, shift, 2;	682	my ($nodeid, undef) = split /#/, shift, 2;
682		683
683	my $id = "$RUNIQ." . $ID++;	684	my $id = "$RUNIQ." . $ID++;
684		685
685	$_[0] =~ /::/	686	$_[0] =~ /::/
686	or Carp::croak "spawn init function must be a fully-qualified name, caught";	687	or Carp::croak "spawn init function must be a fully-qualified name, caught";
687		688
688	($NODE{$noderef} \|\| add_node $noderef)	689	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
689	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
690		690
691	"$noderef#$id"	691	"$nodeid#$id"
692	}	692	}
693		693
694	=back	694	=item after $timeout, @msg
695		695
696	=head1 NODE MESSAGES	696	=item after $timeout, $callback
697		697
698	Nodes understand the following messages sent to them. Many of them take	698	Either sends the given message, or call the given callback, after the
699	arguments called C<@reply>, which will simply be used to compose a reply	699	specified number of seconds.
700	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
701	the remaining arguments are simply the message data.
702		700
703	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.
704		704
705	=over 4
706
707	=cut	705	=cut
708		706
709	=item lookup => $name, @reply	707	sub after($@) {
		708	my ($timeout, @action) = @_;
710		709
711	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	}
712		717
713	=item devnull => ...	718	=item cal $port, @msg, $callback[, $timeout]
714		719
715	Generic data sink/CPU heat conversion.	720	A simple form of RPC - sends a message to the given C<$port> with the
		721	given contents (C<@msg>), but adds a reply port to the message.
716		722
717	=item relay => $port, @msg	723	The reply port is created temporarily just for the purpose of receiving
		724	the reply, and will be C<kil>ed when no longer needed.
718		725
719	Simply forwards the message to the given port.	726	A reply message sent to the port is passed to the C<$callback> as-is.
720		727
721	=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.
722		731
723	Evaluates the given string. If C<@reply> is given, then a message of the	732	If no time-out is given (or it is C<undef>), then the local port will
724	form C<@reply, $@, @evalres> is sent.	733	monitor the remote port instead, so it eventually gets cleaned-up.
725		734
726	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.
727		738
728	snd $othernode, eval => "exit";	739	=cut
729		740
730	=item time => @reply	741	sub cal(@) {
		742	my $timeout = ref $_[-1] ? undef : pop;
		743	my $cb = pop;
731		744
732	Replies the the current node time to C<@reply>.	745	my $port = port {
		746	undef $timeout;
		747	kil $SELF;
		748	&$cb;
		749	};
733		750
734	Example: tell the current node to send the current time to C<$myport> in a	751	if (defined $timeout) {
735	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	}
736		763
737	snd $NODE, time => $myport, timereply => 1, 2;	764	push @_, $port;
738	# => snd $myport, timereply => 1, 2, <time>	765	&snd;
		766
		767	$port
		768	}
739		769
740	=back	770	=back
741		771
742	=head1 AnyEvent::MP vs. Distributed Erlang	772	=head1 AnyEvent::MP vs. Distributed Erlang
743		773
744	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	774	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
745	== aemp node, Erlang process == aemp port), so many of the documents and	775	== aemp node, Erlang process == aemp port), so many of the documents and
746	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	776	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
747	sample:	777	sample:
748		778
749	http://www.Erlang.se/doc/programming_rules.shtml	779	http://www.erlang.se/doc/programming_rules.shtml
750	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	780	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
751	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	781	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
752	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	782	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
753		783
754	Despite the similarities, there are also some important differences:	784	Despite the similarities, there are also some important differences:
755		785
756	=over 4	786	=over 4
757		787
758	=item * Node references contain the recipe on how to contact them.	788	=item * Node IDs are arbitrary strings in AEMP.
759		789
760	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
761	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
762	convenience functionality.	792	configuration or DNS), and possibly the addresses of some seed nodes, but
		793	will otherwise discover other nodes (and their IDs) itself.
763		794
764	This means that AEMP requires a less tightly controlled environment at the	795	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
765	cost of longer node references and a slightly higher management overhead.	796	uses "local ports are like remote ports".
		797
		798	The failure modes for local ports are quite different (runtime errors
		799	only) then for remote ports - when a local port dies, you I<know> it dies,
		800	when a connection to another node dies, you know nothing about the other
		801	port.
		802
		803	Erlang pretends remote ports are as reliable as local ports, even when
		804	they are not.
		805
		806	AEMP encourages a "treat remote ports differently" philosophy, with local
		807	ports being the special case/exception, where transport errors cannot
		808	occur.
766		809
767	=item * Erlang uses processes and a mailbox, AEMP does not queue.	810	=item * Erlang uses processes and a mailbox, AEMP does not queue.
768		811
769	Erlang uses processes that selctively receive messages, and therefore	812	Erlang uses processes that selectively receive messages, and therefore
770	needs a queue. AEMP is event based, queuing messages would serve no useful	813	needs a queue. AEMP is event based, queuing messages would serve no
771	purpose.	814	useful purpose. For the same reason the pattern-matching abilities of
		815	AnyEvent::MP are more limited, as there is little need to be able to
		816	filter messages without dequeuing them.
772		817
773	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	818	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
774		819
775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	820	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
776		821
777	Sending messages in Erlang is synchronous and blocks the process. AEMP	822	Sending messages in Erlang is synchronous and blocks the process (and
778	sends are immediate, connection establishment is handled in the	823	so does not need a queue that can overflow). AEMP sends are immediate,
779	background.	824	connection establishment is handled in the background.
780		825
781	=item * Erlang can silently lose messages, AEMP cannot.	826	=item * Erlang suffers from silent message loss, AEMP does not.
782		827
783	Erlang makes few guarantees on messages delivery - messages can get lost	828	Erlang implements few guarantees on messages delivery - messages can get
784	without any of the processes realising it (i.e. you send messages a, b,	829	lost without any of the processes realising it (i.e. you send messages a,
785	and c, and the other side only receives messages a and c).	830	b, and c, and the other side only receives messages a and c).
786		831
787	AEMP guarantees correct ordering, and the guarantee that there are no	832	AEMP guarantees correct ordering, and the guarantee that after one message
788	holes in the message sequence.	833	is lost, all following ones sent to the same port are lost as well, until
789		834	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	835	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		836
801	=item * Erlang can send messages to the wrong port, AEMP does not.	837	=item * Erlang can send messages to the wrong port, AEMP does not.
802		838
803	In Erlang it is quite possible that a node that restarts reuses a process	839	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	840	known to other nodes for a completely different process, causing messages
805	messages destined for that process to end up in an unrelated process.	841	destined for that process to end up in an unrelated process.
806		842
807	AEMP never reuses port IDs, so old messages or old port IDs floating	843	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.	844	around in the network will not be sent to an unrelated port.
809		845
810	=item * Erlang uses unprotected connections, AEMP uses secure	846	=item * Erlang uses unprotected connections, AEMP uses secure
811	authentication and can use TLS.	847	authentication and can use TLS.
812		848
813	AEMP can use a proven protocol - SSL/TLS - to protect connections and	849	AEMP can use a proven protocol - TLS - to protect connections and
814	securely authenticate nodes.	850	securely authenticate nodes.
815		851
816	=item * The AEMP protocol is optimised for both text-based and binary	852	=item * The AEMP protocol is optimised for both text-based and binary
817	communications.	853	communications.
818		854
819	The AEMP protocol, unlike the Erlang protocol, supports both	855	The AEMP protocol, unlike the Erlang protocol, supports both programming
820	language-independent text-only protocols (good for debugging) and binary,	856	language independent text-only protocols (good for debugging) and binary,
821	language-specific serialisers (e.g. Storable).	857	language-specific serialisers (e.g. Storable). By default, unless TLS is
		858	used, the protocol is actually completely text-based.
822		859
823	It has also been carefully designed to be implementable in other languages	860	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	861	with a minimum of work while gracefully degrading functionality to make the
825	protocol simple.	862	protocol simple.
826		863
827	=item * AEMP has more flexible monitoring options than Erlang.	864	=item * AEMP has more flexible monitoring options than Erlang.
828		865
829	In Erlang, you can chose to receive I<all> exit signals as messages	866	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	869	Erlang, as one can choose between automatic kill, exit message or callback
833	on a per-process basis.	870	on a per-process basis.
834		871
835	=item * Erlang tries to hide remote/local connections, AEMP does not.	872	=item * Erlang tries to hide remote/local connections, AEMP does not.
836		873
837	Monitoring in Erlang is not an indicator of process death/crashes,	874	Monitoring in Erlang is not an indicator of process death/crashes, in the
838	as linking is (except linking is unreliable in Erlang).	875	same way as linking is (except linking is unreliable in Erlang).
839		876
840	In AEMP, you don't "look up" registered port names or send to named ports	877	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	878	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	879	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	880	remote port. Since both monitors are local to the node, they are much more
844	more reliable.	881	reliable (no need for C<spawn_link>).
845		882
846	This also saves round-trips and avoids sending messages to the wrong port	883	This also saves round-trips and avoids sending messages to the wrong port
847	(hard to do in Erlang).	884	(hard to do in Erlang).
848		885
849	=back	886	=back
850		887
		888	=head1 RATIONALE
		889
		890	=over 4
		891
		892	=item Why strings for port and node IDs, why not objects?
		893
		894	We considered "objects", but found that the actual number of methods
		895	that can be called are quite low. Since port and node IDs travel over
		896	the network frequently, the serialising/deserialising would add lots of
		897	overhead, as well as having to keep a proxy object everywhere.
		898
		899	Strings can easily be printed, easily serialised etc. and need no special
		900	procedures to be "valid".
		901
		902	And as a result, a miniport consists of a single closure stored in a
		903	global hash - it can't become much cheaper.
		904
		905	=item Why favour JSON, why not a real serialising format such as Storable?
		906
		907	In fact, any AnyEvent::MP node will happily accept Storable as framing
		908	format, but currently there is no way to make a node use Storable by
		909	default (although all nodes will accept it).
		910
		911	The default framing protocol is JSON because a) JSON::XS is many times
		912	faster for small messages and b) most importantly, after years of
		913	experience we found that object serialisation is causing more problems
		914	than it solves: Just like function calls, objects simply do not travel
		915	easily over the network, mostly because they will always be a copy, so you
		916	always have to re-think your design.
		917
		918	Keeping your messages simple, concentrating on data structures rather than
		919	objects, will keep your messages clean, tidy and efficient.
		920
		921	=back
		922
851	=head1 SEE ALSO	923	=head1 SEE ALSO
		924
		925	L<AnyEvent::MP::Intro> - a gentle introduction.
		926
		927	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		928
		929	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		930	your applications.
		931
		932	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		933	all nodes.
852		934
853	L<AnyEvent>.	935	L<AnyEvent>.
854		936
855	=head1 AUTHOR	937	=head1 AUTHOR
856		938

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Revision 1.100 by root, Fri Oct 2 20:41:56 2009 UTC