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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.49 by root, Thu Aug 13 15:29:58 2009 UTC vs.
Revision 1.99 by root, Fri Oct 2 14:12:16 2009 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using miniports	24	# creating/using ports, the simple way
28	my $miniport = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using full ports	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, smartmatch => $cb->(@msg);
33	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
34	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
35
36	# more, smarter, matches (_any_ is exported by this module)
37	rcv $port, [child_died => $pid] => sub { ...
38	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
39		31
40	# create a port on another node	32	# create a port on another node
41	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
42		34
43	# monitoring	35	# monitoring
44	mon $port, $cb->(@msg) # callback is invoked on death	36	mon $localport, $cb->(@msg) # callback is invoked on death
45	mon $port, $otherport # kill otherport on abnormal death	37	mon $localport, $otherport # kill otherport on abnormal death
46	mon $port, $otherport, @msg # send message on death	38	mon $localport, $otherport, @msg # send message on death
47		39
48	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
49		41
		42	bin/aemp - stable.
50	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
51	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.
52	AnyEvent::MP::Kernel - WIP
53	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable API.
54		46	AnyEvent::MP::Global - stable API.
55	stay tuned.
56		47
57	=head1 DESCRIPTION	48	=head1 DESCRIPTION
58		49
59	This module (-family) implements a simple message passing framework.	50	This module (-family) implements a simple message passing framework.
60		51
61	Despite its simplicity, you can securely message other processes running	52	Despite its simplicity, you can securely message other processes running
62	on the same or other hosts.	53	on the same or other hosts, and you can supervise entities remotely.
63		54
64	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	55	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
65	manual page.	56	manual page and the examples under F<eg/>.
66
67	At the moment, this module family is severly broken and underdocumented,
68	so do not use. This was uploaded mainly to reserve the CPAN namespace -
69	stay tuned!
70		57
71	=head1 CONCEPTS	58	=head1 CONCEPTS
72		59
73	=over 4	60	=over 4
74		61
75	=item port	62	=item port
76		63
77	A port is something you can send messages to (with the C<snd> function).	64	Not to be confused with a TCP port, a "port" is something you can send
		65	messages to (with the C<snd> function).
78		66
79	Some ports allow you to register C<rcv> handlers that can match specific	67	Ports allow you to register C<rcv> handlers that can match all or just
80	messages. All C<rcv> handlers will receive messages they match, messages	68	some messages. Messages send to ports will not be queued, regardless of
81	will not be queued.	69	anything was listening for them or not.
82		70
83	=item port id - C<noderef#portname>	71	=item port ID - C<nodeid#portname>
84		72
85	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	73	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
86	separator, and a port name (a printable string of unspecified format). An	74	separator, and a port name (a printable string of unspecified format).
87	exception is the the node port, whose ID is identical to its node
88	reference.
89		75
90	=item node	76	=item node
91		77
92	A node is a single process containing at least one port - the node	78	A node is a single process containing at least one port - the node port,
93	port. You can send messages to node ports to find existing ports or to	79	which enables nodes to manage each other remotely, and to create new
94	create new ports, among other things.	80	ports.
95		81
96	Nodes are either private (single-process only), slaves (connected to a	82	Nodes are either public (have one or more listening ports) or private
97	master node only) or public nodes (connectable from unrelated nodes).	83	(no listening ports). Private nodes cannot talk to other private nodes
		84	currently.
98		85
99	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	86	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
100		87
101	A node reference is a string that either simply identifies the node (for	88	A node ID is a string that uniquely identifies the node within a
102	private and slave nodes), or contains a recipe on how to reach a given	89	network. Depending on the configuration used, node IDs can look like a
103	node (for public nodes).	90	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		91	doesn't interpret node IDs in any way.
104		92
105	This recipe is simply a comma-separated list of C<address:port> pairs (for	93	=item binds - C<ip:port>
106	TCP/IP, other protocols might look different).
107		94
108	Node references come in two flavours: resolved (containing only numerical	95	Nodes can only talk to each other by creating some kind of connection to
109	addresses) or unresolved (where hostnames are used instead of addresses).	96	each other. To do this, nodes should listen on one or more local transport
		97	endpoints - binds. Currently, only standard C<ip:port> specifications can
		98	be used, which specify TCP ports to listen on.
110		99
111	Before using an unresolved node reference in a message you first have to	100	=item seed nodes
112	resolve it.	101
		102	When a node starts, it knows nothing about the network. To teach the node
		103	about the network it first has to contact some other node within the
		104	network. This node is called a seed.
		105
		106	Apart from the fact that other nodes know them as seed nodes and they have
		107	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		108	any node can function as a seed node for others.
		109
		110	In addition to discovering the network, seed nodes are also used to
		111	maintain the network and to connect nodes that otherwise would have
		112	trouble connecting. They form the backbone of an AnyEvent::MP network.
		113
		114	Seed nodes are expected to be long-running, and at least one seed node
		115	should always be available. They should also be relatively responsive - a
		116	seed node that blocks for long periods will slow down everybody else.
		117
		118	=item seeds - C<host:port>
		119
		120	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		121	TCP port) of nodes 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.
113		127
114	=back	128	=back
115		129
116	=head1 VARIABLES/FUNCTIONS	130	=head1 VARIABLES/FUNCTIONS
117		131
129		143
130	use AE ();	144	use AE ();
131		145
132	use base "Exporter";	146	use base "Exporter";
133		147
134	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	148	our $VERSION = 1.2;
135		149
136	our @EXPORT = qw(	150	our @EXPORT = qw(
137	NODE $NODE *SELF node_of _any_	151	NODE $NODE *SELF node_of after
138	resolve_node initialise_node	152	configure
139	snd rcv mon kil reg psub spawn	153	snd rcv mon mon_guard kil psub spawn cal
140	port	154	port
141	);	155	);
142		156
143	our $SELF;	157	our $SELF;
144		158
…		…
148	kil $SELF, die => $msg;	162	kil $SELF, die => $msg;
149	}	163	}
150		164
151	=item $thisnode = NODE / $NODE	165	=item $thisnode = NODE / $NODE
152		166
153	The C<NODE> function returns, and the C<$NODE> variable contains	167	The C<NODE> function returns, and the C<$NODE> variable contains, the node
154	the noderef of the local node. The value is initialised by a call	168	ID of the node running in the current process. This value is initialised by
155	to C<become_public> or C<become_slave>, after which all local port	169	a call to C<configure>.
156	identifiers become invalid.
157		170
158	=item $noderef = node_of $port	171	=item $nodeid = node_of $port
159		172
160	Extracts and returns the noderef from a portid or a noderef.	173	Extracts and returns the node ID from a port ID or a node ID.
161		174
162	=item initialise_node $noderef, $seednode, $seednode...	175	=item configure $profile, key => value...
163		176
164	=item initialise_node "slave/", $master, $master...	177	=item configure key => value...
165		178
166	Before a node can talk to other nodes on the network it has to initialise	179	Before a node can talk to other nodes on the network (i.e. enter
167	itself - the minimum a node needs to know is it's own name, and optionally	180	"distributed mode") it has to configure itself - the minimum a node needs
168	it should know the noderefs of some other nodes in the network.	181	to know is its own name, and optionally it should know the addresses of
		182	some other nodes in the network to discover other nodes.
169		183
170	This function initialises a node - it must be called exactly once (or	184	This function configures a node - it must be called exactly once (or
171	never) before calling other AnyEvent::MP functions.	185	never) before calling other AnyEvent::MP functions.
172		186
173	All arguments (optionally except for the first) are noderefs, which can be
174	either resolved or unresolved.
175
176	The first argument will be looked up in the configuration database first
177	(if it is C<undef> then the current nodename will be used instead) to find
178	the relevant configuration profile (see L<aemp>). If none is found then
179	the default configuration is used. The configuration supplies additional
180	seed/master nodes and can override the actual noderef.
181
182	There are two types of networked nodes, public nodes and slave nodes:
183
184	=over 4	187	=over 4
185		188
186	=item public nodes	189	=item step 1, gathering configuration from profiles
187		190
188	For public nodes, C<$noderef> (supplied either directly to	191	The function first looks up a profile in the aemp configuration (see the
189	C<initialise_node> or indirectly via a profile or the nodename) must be a	192	L<aemp> commandline utility). The profile name can be specified via the
190	noderef (possibly unresolved, in which case it will be resolved).	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.
191		195
192	After resolving, the node will bind itself on all endpoints and try to	196	The profile data is then gathered as follows:
193	connect to all additional C<$seednodes> that are specified. Seednodes are
194	optional and can be used to quickly bootstrap the node into an existing
195	network.
196		197
197	=item slave nodes	198	First, all remaining key => value pairs (all of which are conveniently
		199	undocumented at the moment) will be interpreted as configuration
		200	data. Then they will be overwritten by any values specified in the global
		201	default configuration (see the F<aemp> utility), then the chain of
		202	profiles chosen by the profile name (and any C<parent> attributes).
198		203
199	When the C<$noderef> (either as given or overriden by the config file)	204	That means that the values specified in the profile have highest priority
200	is the special string C<slave/>, then the node will become a slave	205	and the values specified directly via C<configure> have lowest priority,
201	node. Slave nodes cannot be contacted from outside and will route most of	206	and can only be used to specify defaults.
202	their traffic to the master node that they attach to.
203		207
204	At least one additional noderef is required (either by specifying it	208	If the profile specifies a node ID, then this will become the node ID of
205	directly or because it is part of the configuration profile): The node	209	this process. If not, then the profile name will be used as node ID. The
206	will try to connect to all of them and will become a slave attached to the	210	special node ID of C<anon/> will be replaced by a random node ID.
207	first node it can successfully connect to.	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.
208		229
209	=back	230	=back
210		231
211	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.
212	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.
213	server.
214		234
215	Example: become a public node listening on the guessed noderef, or the one	235	configure
216	specified via C<aemp> for the current node. This should be the most common
217	form of invocation for "daemon"-type nodes.
218		236
219	initialise_node;	237	Example: become an anonymous node. This form is often used for commandline
		238	clients.
220		239
221	Example: become a slave node to any of the the seednodes specified via	240	configure nodeid => "anon/";
222	C<aemp>. This form is often used for commandline clients.
223		241
224	initialise_node "slave/";	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).
225		245
226	Example: become a slave node to any of the specified master servers. This	246	# use the aemp commandline utility
227	form is also often used for commandline clients.	247	# aemp profile seed nodeid anon/ binds '*:4040'
228		248
229	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	249	# then use it
		250	configure profile => "seed";
230		251
231	Example: become a public node, and try to contact some well-known master	252	# or simply use aemp from the shell again:
232	servers to become part of the network.	253	# aemp run profile seed
233		254
234	initialise_node undef, "master1", "master2";	255	# or provide a nicer-to-remember nodeid
235		256	# aemp run profile seed nodeid "$(hostname)"
236	Example: become a public node listening on port C<4041>.
237
238	initialise_node 4041;
239
240	Example: become a public node, only visible on localhost port 4044.
241
242	initialise_node "localhost:4044";
243
244	=item $cv = resolve_node $noderef
245
246	Takes an unresolved node reference that may contain hostnames and
247	abbreviated IDs, resolves all of them and returns a resolved node
248	reference.
249
250	In addition to C<address:port> pairs allowed in resolved noderefs, the
251	following forms are supported:
252
253	=over 4
254
255	=item the empty string
256
257	An empty-string component gets resolved as if the default port (4040) was
258	specified.
259
260	=item naked port numbers (e.g. C<1234>)
261
262	These are resolved by prepending the local nodename and a colon, to be
263	further resolved.
264
265	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
266
267	These are resolved by using AnyEvent::DNS to resolve them, optionally
268	looking up SRV records for the C<aemp=4040> port, if no port was
269	specified.
270
271	=back
272		257
273	=item $SELF	258	=item $SELF
274		259
275	Contains the current port id while executing C<rcv> callbacks or C<psub>	260	Contains the current port id while executing C<rcv> callbacks or C<psub>
276	blocks.	261	blocks.
277		262
278	=item SELF, %SELF, @SELF...	263	=item *SELF, SELF, %SELF, @SELF...
279		264
280	Due to some quirks in how perl exports variables, it is impossible to	265	Due to some quirks in how perl exports variables, it is impossible to
281	just export C<$SELF>, all the symbols called C<SELF> are exported by this	266	just export C<$SELF>, all the symbols named C<SELF> are exported by this
282	module, but only C<$SELF> is currently used.	267	module, but only C<$SELF> is currently used.
283		268
284	=item snd $port, type => @data	269	=item snd $port, type => @data
285		270
286	=item snd $port, @msg	271	=item snd $port, @msg
287		272
288	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
289	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.
290	stringifies a sa port ID (such as a port object :).
291		275
292	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
293	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
294	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.
295		280
296	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
297	function: modifying any argument is not allowed and can cause many	282	function: modifying any argument (or values referenced by them) is
298	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.
299		287
300	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
301	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
302	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
303	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
304	node, anything can be passed.	292	node, anything can be passed. Best rely only on the common denominator of
		293	these.
305		294
306	=item $local_port = port	295	=item $local_port = port
307		296
308	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
309	matching port ("full port") or a single-callback port ("miniport"),	298	no callbacks set and will throw an error when it receives messages.
310	depending on how C<rcv> callbacks are bound to the object.
311		299
312	=item $port = port { my @msg = @_; $finished }	300	=item $local_port = port { my @msg = @_ }
313		301
314	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
315	matching behind it, and returns its ID. Semantically the same as creating
316	a port and calling C<rcv $port, $callback> on it.	303	creating a port and calling C<rcv $port, $callback> on it.
317		304
318	The block will be called for every message received on the port. When the	305	The block will be called for every message received on the port, with the
319	callback returns a true value its job is considered "done" and the port	306	global variable C<$SELF> set to the port ID. Runtime errors will cause the
320	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.
321		309
322	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:
323	be passed to the callback.
324		311
325	If you need the local port id in the callback, this works nicely:	312	my $port = port {
326		313	my @msg = @_;
327	my $port; $port = port {	314	...
328	snd $otherport, reply => $port;	315	kil $SELF;
329	};	316	};
330		317
331	=cut	318	=cut
332		319
333	sub rcv($@);	320	sub rcv($@);
		321
		322	sub _kilme {
		323	die "received message on port without callback";
		324	}
334		325
335	sub port(;&) {	326	sub port(;&) {
336	my $id = "$UNIQ." . $ID++;	327	my $id = "$UNIQ." . $ID++;
337	my $port = "$NODE#$id";	328	my $port = "$NODE#$id";
338		329
339	if (@_) {	330	rcv $port, shift \|\| \&_kilme;
340	rcv $port, shift;
341	} else {
342	$PORT{$id} = sub { }; # nop
343	}
344		331
345	$port	332	$port
346	}	333	}
347		334
348	=item reg $port, $name
349
350	=item reg $name
351
352	Registers the given port (or C<$SELF><<< if missing) under the name
353	C<$name>. If the name already exists it is replaced.
354
355	A port can only be registered under one well known name.
356
357	A port automatically becomes unregistered when it is killed.
358
359	=cut
360
361	sub reg(@) {
362	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
363
364	$REG{$_[0]} = $port;
365	}
366
367	=item rcv $port, $callback->(@msg)	335	=item rcv $local_port, $callback->(@msg)
368		336
369	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
370	one if required).	338	remove the default callback: use C<sub { }> to disable it, or better
371		339	C<kil> the port when it is no longer needed.
372	=item rcv $port, tagstring => $callback->(@msg), ...
373
374	=item rcv $port, $smartmatch => $callback->(@msg), ...
375
376	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
377
378	Register callbacks to be called on matching messages on the given full
379	port (after converting it to one if required) and return the port.
380
381	The callback has to return a true value when its work is done, after
382	which is will be removed, or a false value in which case it will stay
383	registered.
384		340
385	The global C<$SELF> (exported by this module) contains C<$port> while	341	The global C<$SELF> (exported by this module) contains C<$port> while
386	executing the callback.	342	executing the callback. Runtime errors during callback execution will
		343	result in the port being C<kil>ed.
387		344
388	Runtime errors during callback execution will result in the port being	345	The default callback received all messages not matched by a more specific
389	C<kil>ed.	346	C<tag> match.
390		347
391	If the match is an array reference, then it will be matched against the	348	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
392	first elements of the message, otherwise only the first element is being
393	matched.
394		349
395	Any element in the match that is specified as C<_any_> (a function	350	Register (or replace) callbacks to be called on messages starting with the
396	exported by this module) matches any single element of the message.	351	given tag on the given port (and return the port), or unregister it (when
		352	C<$callback> is C<$undef> or missing). There can only be one callback
		353	registered for each tag.
397		354
398	While not required, it is highly recommended that the first matching	355	The original message will be passed to the callback, after the first
399	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
400	also the most efficient match (by far).	357	environment as the default callback (see above).
401		358
402	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.
403		360
404	my $port = rcv port,	361	my $port = rcv port,
405	msg1 => sub { ...; 0 },	362	msg1 => sub { ... },
406	msg2 => sub { ...; 0 },	363	msg2 => sub { ... },
407	;	364	;
408		365
409	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
410	in one go:	367	in one go:
411		368
412	snd $otherport, reply =>	369	snd $otherport, reply =>
413	rcv port,	370	rcv port,
414	msg1 => sub { ...; 0 },	371	msg1 => sub { ... },
415	...	372	...
416	;	373	;
417		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, $otherport;
		382	};
		383
418	=cut	384	=cut
419		385
420	sub rcv($@) {	386	sub rcv($@) {
421	my $port = shift;	387	my $port = shift;
422	my ($noderef, $portid) = split /#/, $port, 2;	388	my ($nodeid, $portid) = split /#/, $port, 2;
423		389
424	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	390	$NODE{$nodeid} == $NODE{""}
425	or Carp::croak "$port: rcv can only be called on local ports, caught";	391	or Carp::croak "$port: rcv can only be called on local ports, caught";
426		392
427	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 {
428	my $cb = shift;	401	my $cb = shift;
429	delete $PORT_DATA{$portid};
430	$PORT{$portid} = sub {	402	$PORT{$portid} = sub {
431	local $SELF = $port;	403	local $SELF = $port;
432	eval {	404	eval { &$cb }; _self_die if $@;
433	&$cb	405	};
434	and kil $port;
435	};	406	}
436	_self_die if $@;	407	} elsif (defined $_[0]) {
437	};
438	} else {
439	my $self = $PORT_DATA{$portid} \|\|= do {	408	my $self = $PORT_DATA{$portid} \|\|= do {
440	my $self = bless {	409	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
441	id => $port,
442	}, "AnyEvent::MP::Port";
443		410
444	$PORT{$portid} = sub {	411	$PORT{$portid} = sub {
445	local $SELF = $port;	412	local $SELF = $port;
446		413
447	eval {
448	for (@{ $self->{rc0}{$_[0]} }) {	414	if (my $cb = $self->[1]{$_[0]}) {
449	$_ && &{$_->[0]}	415	shift;
450	&& undef $_;	416	eval { &$cb }; _self_die if $@;
451	}	417	} else {
452
453	for (@{ $self->{rcv}{$_[0]} }) {
454	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
455	&& &{$_->[0]}	418	&{ $self->[0] };
456	&& undef $_;
457	}
458
459	for (@{ $self->{any} }) {
460	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
461	&& &{$_->[0]}
462	&& undef $_;
463	}	419	}
464	};	420	};
465	_self_die if $@;	421
		422	$self
466	};	423	};
467		424
468	$self
469	};
470
471	"AnyEvent::MP::Port" eq ref $self	425	"AnyEvent::MP::Port" eq ref $self
472	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	426	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
473		427
474	while (@_) {
475	my ($match, $cb) = splice @_, 0, 2;	428	my ($tag, $cb) = splice @_, 0, 2;
476		429
477	if (!ref $match) {	430	if (defined $cb) {
478	push @{ $self->{rc0}{$match} }, [$cb];	431	$self->[1]{$tag} = $cb;
479	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
480	my ($type, @match) = @$match;
481	@match
482	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
483	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
484	} else {	432	} else {
485	push @{ $self->{any} }, [$cb, $match];	433	delete $self->[1]{$tag};
486	}	434	}
487	}	435	}
488	}	436	}
489		437
490	$port	438	$port
…		…
526	$res	474	$res
527	}	475	}
528	}	476	}
529	}	477	}
530		478
531	=item $guard = mon $port, $cb->(@reason)	479	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
532		480
533	=item $guard = mon $port, $rcvport	481	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
534		482
535	=item $guard = mon $port	483	=item $guard = mon $port # kill $SELF when $port dies
536		484
537	=item $guard = mon $port, $rcvport, @msg	485	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
538		486
539	Monitor the given port and do something when the port is killed or	487	Monitor the given port and do something when the port is killed or
540	messages to it were lost, and optionally return a guard that can be used	488	messages to it were lost, and optionally return a guard that can be used
541	to stop monitoring again.	489	to stop monitoring again.
542
543	C<mon> effectively guarantees that, in the absence of hardware failures,
544	that after starting the monitor, either all messages sent to the port
545	will arrive, or the monitoring action will be invoked after possible
546	message loss has been detected. No messages will be lost "in between"
547	(after the first lost message no further messages will be received by the
548	port). After the monitoring action was invoked, further messages might get
549	delivered again.
550		490
551	In the first form (callback), the callback is simply called with any	491	In the first form (callback), the callback is simply called with any
552	number of C<@reason> elements (no @reason means that the port was deleted	492	number of C<@reason> elements (no @reason means that the port was deleted
553	"normally"). Note also that I<< the callback B<must> never die >>, so use	493	"normally"). Note also that I<< the callback B<must> never die >>, so use
554	C<eval> if unsure.	494	C<eval> if unsure.
555		495
556	In the second form (another port given), the other port (C<$rcvport>)	496	In the second form (another port given), the other port (C<$rcvport>)
557	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	497	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
558	"normal" kils nothing happens, while under all other conditions, the other	498	"normal" kils nothing happens, while under all other conditions, the other
559	port is killed with the same reason.	499	port is killed with the same reason.
560		500
561	The third form (kill self) is the same as the second form, except that	501	The third form (kill self) is the same as the second form, except that
562	C<$rvport> defaults to C<$SELF>.	502	C<$rvport> defaults to C<$SELF>.
563		503
564	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
565	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.
566		509
567	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
568	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
569	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
570	even monitoring requests can get lost (for exmaple, when the connection	513	even monitoring requests can get lost (for example, when the connection
571	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
572	these problems do not exist.	515	these problems do not exist.
573		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
574	Example: call a given callback when C<$port> is killed.	534	Example: call a given callback when C<$port> is killed.
575		535
576	mon $port, sub { warn "port died because of <@_>\n" };	536	mon $port, sub { warn "port died because of <@_>\n" };
577		537
578	Example: kill ourselves when C<$port> is killed abnormally.	538	Example: kill ourselves when C<$port> is killed abnormally.
…		…
584	mon $port, $self => "restart";	544	mon $port, $self => "restart";
585		545
586	=cut	546	=cut
587		547
588	sub mon {	548	sub mon {
589	my ($noderef, $port) = split /#/, shift, 2;	549	my ($nodeid, $port) = split /#/, shift, 2;
590		550
591	my $node = $NODE{$noderef} \|\| add_node $noderef;	551	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
592		552
593	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,';
594		554
595	unless (ref $cb) {	555	unless (ref $cb) {
596	if (@_) {	556	if (@_) {
…		…
605	}	565	}
606		566
607	$node->monitor ($port, $cb);	567	$node->monitor ($port, $cb);
608		568
609	defined wantarray	569	defined wantarray
610	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	570	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
611	}	571	}
612		572
613	=item $guard = mon_guard $port, $ref, $ref...	573	=item $guard = mon_guard $port, $ref, $ref...
614		574
615	Monitors the given C<$port> and keeps the passed references. When the port	575	Monitors the given C<$port> and keeps the passed references. When the port
616	is killed, the references will be freed.	576	is killed, the references will be freed.
617		577
618	Optionally returns a guard that will stop the monitoring.	578	Optionally returns a guard that will stop the monitoring.
619		579
620	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
621	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>):
622		582
623	$port->rcv (start => sub {	583	$port->rcv (start => sub {
624	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	584	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
625	undef $timer if 0.9 < rand;	585	undef $timer if 0.9 < rand;
626	});	586	});
627	});	587	});
628		588
629	=cut	589	=cut
…		…
638		598
639	=item kil $port[, @reason]	599	=item kil $port[, @reason]
640		600
641	Kill the specified port with the given C<@reason>.	601	Kill the specified port with the given C<@reason>.
642		602
643	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
644	ports will not be kileld, or even notified).	604	monitoring other ports will not necessarily die because a port dies
		605	"normally").
645		606
646	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
647	C<mon>, see below).	608	C<mon>, see above).
648		609
649	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
650	will be reported as reason C<< die => $@ >>.	611	will be reported as reason C<< die => $@ >>.
651		612
652	Transport/communication errors are reported as C<< transport_error =>	613	Transport/communication errors are reported as C<< transport_error =>
…		…
657	=item $port = spawn $node, $initfunc[, @initdata]	618	=item $port = spawn $node, $initfunc[, @initdata]
658		619
659	Creates a port on the node C<$node> (which can also be a port ID, in which	620	Creates a port on the node C<$node> (which can also be a port ID, in which
660	case it's the node where that port resides).	621	case it's the node where that port resides).
661		622
662	The port ID of the newly created port is return immediately, and it is	623	The port ID of the newly created port is returned immediately, and it is
663	permissible to immediately start sending messages or monitor the port.	624	possible to immediately start sending messages or to monitor the port.
664		625
665	After the port has been created, the init function is	626	After the port has been created, the init function is called on the remote
666	called. This function must be a fully-qualified function name	627	node, in the same context as a C<rcv> callback. This function must be a
667	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	628	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
668	program, use C<::name>.	629	specify a function in the main program, use C<::name>.
669		630
670	If the function doesn't exist, then the node tries to C<require>	631	If the function doesn't exist, then the node tries to C<require>
671	the package, then the package above the package and so on (e.g.	632	the package, then the package above the package and so on (e.g.
672	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	633	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
673	exists or it runs out of package names.	634	exists or it runs out of package names.
674		635
675	The init function is then called with the newly-created port as context	636	The init function is then called with the newly-created port as context
676	object (C<$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.
677		640
678	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
679	in the init function, monitor the original port. This two-way monitoring	642	port, and in the remote init function, immediately monitor the passed
680	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<$initfunc> has no visible effects on the
		647	caller before C<spawn> returns (by delaying invocation when spawn is
		648	called for the local node).
681		649
682	Example: spawn a chat server port on C<$othernode>.	650	Example: spawn a chat server port on C<$othernode>.
683		651
684	# this node, executed from within a port context:	652	# this node, executed from within a port context:
685	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
700		668
701	sub _spawn {	669	sub _spawn {
702	my $port = shift;	670	my $port = shift;
703	my $init = shift;	671	my $init = shift;
704		672
		673	# rcv will create the actual port
705	local $SELF = "$NODE#$port";	674	local $SELF = "$NODE#$port";
706	eval {	675	eval {
707	&{ load_func $init }	676	&{ load_func $init }
708	};	677	};
709	_self_die if $@;	678	_self_die if $@;
710	}	679	}
711		680
712	sub spawn(@) {	681	sub spawn(@) {
713	my ($noderef, undef) = split /#/, shift, 2;	682	my ($nodeid, undef) = split /#/, shift, 2;
714		683
715	my $id = "$RUNIQ." . $ID++;	684	my $id = "$RUNIQ." . $ID++;
716		685
717	$_[0] =~ /::/	686	$_[0] =~ /::/
718	or Carp::croak "spawn init function must be a fully-qualified name, caught";	687	or Carp::croak "spawn init function must be a fully-qualified name, caught";
719		688
720	($NODE{$noderef} \|\| add_node $noderef)	689	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
721	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
722		690
723	"$noderef#$id"	691	"$nodeid#$id"
724	}	692	}
725		693
726	=back	694	=item after $timeout, @msg
727		695
728	=head1 NODE MESSAGES	696	=item after $timeout, $callback
729		697
730	Nodes understand the following messages sent to them. Many of them take	698	Either sends the given message, or call the given callback, after the
731	arguments called C<@reply>, which will simply be used to compose a reply	699	specified number of seconds.
732	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
733	the remaining arguments are simply the message data.
734		700
735	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.
736		704
737	=over 4
738
739	=cut	705	=cut
740		706
741	=item lookup => $name, @reply	707	sub after($@) {
		708	my ($timeout, @action) = @_;
742		709
743	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	}
744		717
745	=item devnull => ...	718	=item cal $port, @msg, $callback[, $timeout]
746		719
747	Generic data sink/CPU heat conversion.	720	A simple form of RPC - sends a message to the given C<$port> with the
		721	given contents (C<@msg>), but adds a reply port to the message.
748		722
749	=item relay => $port, @msg	723	The reply port is created temporarily just for the purpose of receiving
		724	the reply, and will be C<kil>ed when no longer needed.
750		725
751	Simply forwards the message to the given port.	726	A reply message sent to the port is passed to the C<$callback> as-is.
752		727
753	=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.
754		731
755	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
756	form C<@reply, $@, @evalres> is sent.	733	monitor the remote port instead, so it eventually gets cleaned-up.
757		734
758	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.
759		738
760	snd $othernode, eval => "exit";	739	=cut
761		740
762	=item time => @reply	741	sub cal(@) {
		742	my $timeout = ref $_[-1] ? undef : pop;
		743	my $cb = pop;
763		744
764	Replies the the current node time to C<@reply>.	745	my $port = port {
		746	undef $timeout;
		747	kil $SELF;
		748	&$cb;
		749	};
765		750
766	Example: tell the current node to send the current time to C<$myport> in a	751	if (defined $timeout) {
767	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	}
768		763
769	snd $NODE, time => $myport, timereply => 1, 2;	764	push @_, $port;
770	# => snd $myport, timereply => 1, 2, <time>	765	&snd;
		766
		767	$port
		768	}
771		769
772	=back	770	=back
773		771
774	=head1 AnyEvent::MP vs. Distributed Erlang	772	=head1 AnyEvent::MP vs. Distributed Erlang
775		773
776	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
777	== 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
778	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
779	sample:	777	sample:
780		778
781	http://www.Erlang.se/doc/programming_rules.shtml	779	http://www.erlang.se/doc/programming_rules.shtml
782	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
783	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
784	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
785		783
786	Despite the similarities, there are also some important differences:	784	Despite the similarities, there are also some important differences:
787		785
788	=over 4	786	=over 4
789		787
790	=item * Node references contain the recipe on how to contact them.	788	=item * Node IDs are arbitrary strings in AEMP.
791		789
792	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
793	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
794	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.
795		794
796	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
797	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.
798		809
799	=item * Erlang uses processes and a mailbox, AEMP does not queue.	810	=item * Erlang uses processes and a mailbox, AEMP does not queue.
800		811
801	Erlang uses processes that selctively receive messages, and therefore	812	Erlang uses processes that selectively receive messages, and therefore
802	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
803	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.
804		817
805	(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).
806		819
807	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	820	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
808		821
809	Sending messages in Erlang is synchronous and blocks the process. AEMP	822	Sending messages in Erlang is synchronous and blocks the process (and
810	sends are immediate, connection establishment is handled in the	823	so does not need a queue that can overflow). AEMP sends are immediate,
811	background.	824	connection establishment is handled in the background.
812		825
813	=item * Erlang can silently lose messages, AEMP cannot.	826	=item * Erlang suffers from silent message loss, AEMP does not.
814		827
815	Erlang makes few guarantees on messages delivery - messages can get lost	828	Erlang implements few guarantees on messages delivery - messages can get
816	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,
817	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).
818		831
819	AEMP guarantees correct ordering, and the guarantee that there are no	832	AEMP guarantees correct ordering, and the guarantee that after one message
820	holes in the message sequence.	833	is lost, all following ones sent to the same port are lost as well, until
821		834	monitoring raises an error, so there are no silent "holes" in the message
822	=item * In Erlang, processes can be declared dead and later be found to be	835	sequence.
823	alive.
824
825	In Erlang it can happen that a monitored process is declared dead and
826	linked processes get killed, but later it turns out that the process is
827	still alive - and can receive messages.
828
829	In AEMP, when port monitoring detects a port as dead, then that port will
830	eventually be killed - it cannot happen that a node detects a port as dead
831	and then later sends messages to it, finding it is still alive.
832		836
833	=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.
834		838
835	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
836	ID known to other nodes for a completely different process, causing	840	known to other nodes for a completely different process, causing messages
837	messages destined for that process to end up in an unrelated process.	841	destined for that process to end up in an unrelated process.
838		842
839	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
840	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.
841		845
842	=item * Erlang uses unprotected connections, AEMP uses secure	846	=item * Erlang uses unprotected connections, AEMP uses secure
843	authentication and can use TLS.	847	authentication and can use TLS.
844		848
845	AEMP can use a proven protocol - SSL/TLS - to protect connections and	849	AEMP can use a proven protocol - TLS - to protect connections and
846	securely authenticate nodes.	850	securely authenticate nodes.
847		851
848	=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
849	communications.	853	communications.
850		854
851	The AEMP protocol, unlike the Erlang protocol, supports both	855	The AEMP protocol, unlike the Erlang protocol, supports both programming
852	language-independent text-only protocols (good for debugging) and binary,	856	language independent text-only protocols (good for debugging) and binary,
853	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.
854		859
855	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
856	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
857	protocol simple.	862	protocol simple.
858		863
859	=item * AEMP has more flexible monitoring options than Erlang.	864	=item * AEMP has more flexible monitoring options than Erlang.
860		865
861	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
…		…
864	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
865	on a per-process basis.	870	on a per-process basis.
866		871
867	=item * Erlang tries to hide remote/local connections, AEMP does not.	872	=item * Erlang tries to hide remote/local connections, AEMP does not.
868		873
869	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
870	as linking is (except linking is unreliable in Erlang).	875	same way as linking is (except linking is unreliable in Erlang).
871		876
872	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
873	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
874	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
875	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
876	more reliable.	881	reliable (no need for C<spawn_link>).
877		882
878	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
879	(hard to do in Erlang).	884	(hard to do in Erlang).
880		885
881	=back	886	=back
882		887
883	=head1 RATIONALE	888	=head1 RATIONALE
884		889
885	=over 4	890	=over 4
886		891
887	=item Why strings for ports and noderefs, why not objects?	892	=item Why strings for port and node IDs, why not objects?
888		893
889	We considered "objects", but found that the actual number of methods	894	We considered "objects", but found that the actual number of methods
890	thatc an be called are very low. Since port IDs and noderefs travel over	895	that can be called are quite low. Since port and node IDs travel over
891	the network frequently, the serialising/deserialising would add lots of	896	the network frequently, the serialising/deserialising would add lots of
892	overhead, as well as having to keep a proxy object.	897	overhead, as well as having to keep a proxy object everywhere.
893		898
894	Strings can easily be printed, easily serialised etc. and need no special	899	Strings can easily be printed, easily serialised etc. and need no special
895	procedures to be "valid".	900	procedures to be "valid".
896		901
897	And a a miniport consists of a single closure stored in a global hash - it	902	And as a result, a miniport consists of a single closure stored in a
898	can't become much cheaper.	903	global hash - it can't become much cheaper.
899		904
900	=item Why favour JSON, why not real serialising format such as Storable?	905	=item Why favour JSON, why not a real serialising format such as Storable?
901		906
902	In fact, any AnyEvent::MP node will happily accept Storable as framing	907	In fact, any AnyEvent::MP node will happily accept Storable as framing
903	format, but currently there is no way to make a node use Storable by	908	format, but currently there is no way to make a node use Storable by
904	default.	909	default (although all nodes will accept it).
905		910
906	The default framing protocol is JSON because a) JSON::XS is many times	911	The default framing protocol is JSON because a) JSON::XS is many times
907	faster for small messages and b) most importantly, after years of	912	faster for small messages and b) most importantly, after years of
908	experience we found that object serialisation is causing more problems	913	experience we found that object serialisation is causing more problems
909	than it gains: Just like function calls, objects simply do not travel	914	than it solves: Just like function calls, objects simply do not travel
910	easily over the network, mostly because they will always be a copy, so you	915	easily over the network, mostly because they will always be a copy, so you
911	always have to re-think your design.	916	always have to re-think your design.
912		917
913	Keeping your messages simple, concentrating on data structures rather than	918	Keeping your messages simple, concentrating on data structures rather than
914	objects, will keep your messages clean, tidy and efficient.	919	objects, will keep your messages clean, tidy and efficient.
915		920
916	=back	921	=back
917		922
918	=head1 SEE ALSO	923	=head1 SEE ALSO
919		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.
		934
920	L<AnyEvent>.	935	L<AnyEvent>.
921		936
922	=head1 AUTHOR	937	=head1 AUTHOR
923		938
924	Marc Lehmann <schmorp@schmorp.de>	939	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.99 by root, Fri Oct 2 14:12:16 2009 UTC