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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.36 by root, Thu Aug 6 10:46:48 2009 UTC vs.
Revision 1.106 by root, Wed Dec 9 14:00:49 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
		12	$SELF # receiving/own port id in rcv callbacks
		13
		14	# initialise the node so it can send/receive messages
		15	configure;
		16
		17	# ports are message destinations
		18
		19	# sending messages
13	snd $port, type => data...;	20	snd $port, type => data...;
		21	snd $port, @msg;
		22	snd @msg_with_first_element_being_a_port;
14		23
15	$SELF # receiving/own port id in rcv callbacks	24	# creating/using ports, the simple way
		25	my $simple_port = port { my @msg = @_ };
16		26
17	rcv $port, smartmatch => $cb->($port, @msg);	27	# creating/using ports, tagged message matching
18		28	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
21	rcv $port1, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
22	snd $port2, ping => $port1;
23		31
24	# more, smarter, matches (_any_ is exported by this module)	32	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	33	my $port = spawn $node, $initfunc, @initdata;
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
27		34
28	# linking two ports, so they both crash together	35	# destroy a prot again
29	lnk $port1, $port2;	36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
30		38
31	# monitoring	39	# monitoring
32	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
33	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
34	mon $port, $otherport, @msg # send message on death	42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
		51
		52	=head1 CURRENT STATUS
		53
		54	bin/aemp - stable.
		55	AnyEvent::MP - stable API, should work.
		56	AnyEvent::MP::Intro - explains most concepts.
		57	AnyEvent::MP::Kernel - mostly stable API.
		58	AnyEvent::MP::Global - stable API.
35		59
36	=head1 DESCRIPTION	60	=head1 DESCRIPTION
37		61
38	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
39		63
40	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
41	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
42		66
43	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
44	manual page.	68	manual page and the examples under F<eg/>.
45
46	At the moment, this module family is severly broken and underdocumented,
47	so do not use. This was uploaded mainly to reserve the CPAN namespace -
48	stay tuned! The basic API should be finished, however.
49		69
50	=head1 CONCEPTS	70	=head1 CONCEPTS
51		71
52	=over 4	72	=over 4
53		73
54	=item port	74	=item port
55		75
56	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
57		78
58	Some ports allow you to register C<rcv> handlers that can match specific	79	Ports allow you to register C<rcv> handlers that can match all or just
59	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
60	will not be queued.	81	anything was listening for them or not.
61		82
62	=item port id - C<noderef#portname>	83	=item port ID - C<nodeid#portname>
63		84
64	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	85	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
65	separator, and a port name (a printable string of unspecified format). An	86	separator, and a port name (a printable string of unspecified format).
66	exception is the the node port, whose ID is identical to its node
67	reference.
68		87
69	=item node	88	=item node
70		89
71	A node is a single process containing at least one port - the node	90	A node is a single process containing at least one port - the node port,
72	port. You can send messages to node ports to find existing ports or to	91	which enables nodes to manage each other remotely, and to create new
73	create new ports, among other things.	92	ports.
74		93
75	Nodes are either private (single-process only), slaves (connected to a	94	Nodes are either public (have one or more listening ports) or private
76	master node only) or public nodes (connectable from unrelated nodes).	95	(no listening ports). Private nodes cannot talk to other private nodes
		96	currently.
77		97
78	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	98	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
79		99
80	A node reference is a string that either simply identifies the node (for	100	A node ID is a string that uniquely identifies the node within a
81	private and slave nodes), or contains a recipe on how to reach a given	101	network. Depending on the configuration used, node IDs can look like a
82	node (for public nodes).	102	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		103	doesn't interpret node IDs in any way.
83		104
84	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	=item binds - C<ip:port>
85	TCP/IP, other protocols might look different).
86		106
87	Node references come in two flavours: resolved (containing only numerical	107	Nodes can only talk to each other by creating some kind of connection to
88	addresses) or unresolved (where hostnames are used instead of addresses).	108	each other. To do this, nodes should listen on one or more local transport
		109	endpoints - binds. Currently, only standard C<ip:port> specifications can
		110	be used, which specify TCP ports to listen on.
89		111
90	Before using an unresolved node reference in a message you first have to	112	=item seed nodes
91	resolve it.	113
		114	When a node starts, it knows nothing about the network. To teach the node
		115	about the network it first has to contact some other node within the
		116	network. This node is called a seed.
		117
		118	Apart from the fact that other nodes know them as seed nodes and they have
		119	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		120	any node can function as a seed node for others.
		121
		122	In addition to discovering the network, seed nodes are also used to
		123	maintain the network and to connect nodes that otherwise would have
		124	trouble connecting. They form the backbone of an AnyEvent::MP network.
		125
		126	Seed nodes are expected to be long-running, and at least one seed node
		127	should always be available. They should also be relatively responsive - a
		128	seed node that blocks for long periods will slow down everybody else.
		129
		130	=item seeds - C<host:port>
		131
		132	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		133	TCP port) of nodes that should be used as seed nodes.
		134
		135	The nodes listening on those endpoints are expected to be long-running,
		136	and at least one of those should always be available. When nodes run out
		137	of connections (e.g. due to a network error), they try to re-establish
		138	connections to some seednodes again to join the network.
92		139
93	=back	140	=back
94		141
95	=head1 VARIABLES/FUNCTIONS	142	=head1 VARIABLES/FUNCTIONS
96		143
98		145
99	=cut	146	=cut
100		147
101	package AnyEvent::MP;	148	package AnyEvent::MP;
102		149
103	use AnyEvent::MP::Base;	150	use AnyEvent::MP::Kernel;
104		151
105	use common::sense;	152	use common::sense;
106		153
107	use Carp ();	154	use Carp ();
108		155
109	use AE ();	156	use AE ();
110		157
111	use base "Exporter";	158	use base "Exporter";
112		159
113	our $VERSION = '0.1';	160	our $VERSION = 1.24;
		161
114	our @EXPORT = qw(	162	our @EXPORT = qw(
115	NODE $NODE *SELF node_of _any_	163	NODE $NODE *SELF node_of after
116	resolve_node initialise_node	164	configure
117	snd rcv mon kil reg psub	165	snd rcv mon mon_guard kil psub peval spawn cal
118	port	166	port
119	);	167	);
120		168
121	our $SELF;	169	our $SELF;
122		170
…		…
126	kil $SELF, die => $msg;	174	kil $SELF, die => $msg;
127	}	175	}
128		176
129	=item $thisnode = NODE / $NODE	177	=item $thisnode = NODE / $NODE
130		178
131	The C<NODE> function returns, and the C<$NODE> variable contains	179	The C<NODE> function returns, and the C<$NODE> variable contains, the node
132	the noderef of the local node. The value is initialised by a call	180	ID of the node running in the current process. This value is initialised by
133	to C<become_public> or C<become_slave>, after which all local port	181	a call to C<configure>.
134	identifiers become invalid.
135		182
136	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
137		184
138	Extracts and returns the noderef from a portid or a noderef.	185	Extracts and returns the node ID from a port ID or a node ID.
139		186
140	=item initialise_node $noderef, $seednode, $seednode...	187	=item configure $profile, key => value...
141		188
142	=item initialise_node "slave/", $master, $master...	189	=item configure key => value...
143		190
144	Before a node can talk to other nodes on the network it has to initialise	191	Before a node can talk to other nodes on the network (i.e. enter
145	itself - the minimum a node needs to know is it's own name, and optionally	192	"distributed mode") it has to configure itself - the minimum a node needs
146	it should know the noderefs of some other nodes in the network.	193	to know is its own name, and optionally it should know the addresses of
		194	some other nodes in the network to discover other nodes.
147		195
148	This function initialises a node - it must be called exactly once (or	196	This function configures a node - it must be called exactly once (or
149	never) before calling other AnyEvent::MP functions.	197	never) before calling other AnyEvent::MP functions.
150		198
151	All arguments are noderefs, which can be either resolved or unresolved.
152
153	There are two types of networked nodes, public nodes and slave nodes:
154
155	=over 4	199	=over 4
156		200
157	=item public nodes	201	=item step 1, gathering configuration from profiles
158		202
159	For public nodes, C<$noderef> must either be a (possibly unresolved)	203	The function first looks up a profile in the aemp configuration (see the
160	noderef, in which case it will be resolved, or C<undef> (or missing), in	204	L<aemp> commandline utility). The profile name can be specified via the
161	which case the noderef will be guessed.	205	named C<profile> parameter or can simply be the first parameter). If it is
		206	missing, then the nodename (F<uname -n>) will be used as profile name.
162		207
163	Afterwards, the node will bind itself on all endpoints and try to connect	208	The profile data is then gathered as follows:
164	to all additional C<$seednodes> that are specified. Seednodes are optional
165	and can be used to quickly bootstrap the node into an existing network.
166		209
167	=item slave nodes	210	First, all remaining key => value pairs (all of which are conveniently
		211	undocumented at the moment) will be interpreted as configuration
		212	data. Then they will be overwritten by any values specified in the global
		213	default configuration (see the F<aemp> utility), then the chain of
		214	profiles chosen by the profile name (and any C<parent> attributes).
168		215
169	When the C<$noderef> is the special string C<slave/>, then the node will	216	That means that the values specified in the profile have highest priority
170	become a slave node. Slave nodes cannot be contacted from outside and will	217	and the values specified directly via C<configure> have lowest priority,
171	route most of their traffic to the master node that they attach to.	218	and can only be used to specify defaults.
172		219
173	At least one additional noderef is required: The node will try to connect	220	If the profile specifies a node ID, then this will become the node ID of
174	to all of them and will become a slave attached to the first node it can	221	this process. If not, then the profile name will be used as node ID. The
175	successfully connect to.	222	special node ID of C<anon/> will be replaced by a random node ID.
		223
		224	=item step 2, bind listener sockets
		225
		226	The next step is to look up the binds in the profile, followed by binding
		227	aemp protocol listeners on all binds specified (it is possible and valid
		228	to have no binds, meaning that the node cannot be contacted form the
		229	outside. This means the node cannot talk to other nodes that also have no
		230	binds, but it can still talk to all "normal" nodes).
		231
		232	If the profile does not specify a binds list, then a default of C<*> is
		233	used, meaning the node will bind on a dynamically-assigned port on every
		234	local IP address it finds.
		235
		236	=item step 3, connect to seed nodes
		237
		238	As the last step, the seeds list from the profile is passed to the
		239	L<AnyEvent::MP::Global> module, which will then use it to keep
		240	connectivity with at least one node at any point in time.
176		241
177	=back	242	=back
178		243
179	This function will block until all nodes have been resolved and, for slave	244	Example: become a distributed node using the local node name as profile.
180	nodes, until it has successfully established a connection to a master	245	This should be the most common form of invocation for "daemon"-type nodes.
181	server.
182		246
183	Example: become a public node listening on the default node.	247	configure
184		248
185	initialise_node;	249	Example: become an anonymous node. This form is often used for commandline
		250	clients.
186		251
187	Example: become a public node, and try to contact some well-known master	252	configure nodeid => "anon/";
188	servers to become part of the network.
189		253
190	initialise_node undef, "master1", "master2";	254	Example: configure a node using a profile called seed, which si suitable
		255	for a seed node as it binds on all local addresses on a fixed port (4040,
		256	customary for aemp).
191		257
192	Example: become a public node listening on port C<4041>.	258	# use the aemp commandline utility
		259	# aemp profile seed nodeid anon/ binds '*:4040'
193		260
194	initialise_node 4041;	261	# then use it
		262	configure profile => "seed";
195		263
196	Example: become a public node, only visible on localhost port 4044.	264	# or simply use aemp from the shell again:
		265	# aemp run profile seed
197		266
198	initialise_node "locahost:4044";	267	# or provide a nicer-to-remember nodeid
199		268	# aemp run profile seed nodeid "$(hostname)"
200	Example: become a slave node to any of the specified master servers.
201
202	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
203
204	=item $cv = resolve_node $noderef
205
206	Takes an unresolved node reference that may contain hostnames and
207	abbreviated IDs, resolves all of them and returns a resolved node
208	reference.
209
210	In addition to C<address:port> pairs allowed in resolved noderefs, the
211	following forms are supported:
212
213	=over 4
214
215	=item the empty string
216
217	An empty-string component gets resolved as if the default port (4040) was
218	specified.
219
220	=item naked port numbers (e.g. C<1234>)
221
222	These are resolved by prepending the local nodename and a colon, to be
223	further resolved.
224
225	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
226
227	These are resolved by using AnyEvent::DNS to resolve them, optionally
228	looking up SRV records for the C<aemp=4040> port, if no port was
229	specified.
230
231	=back
232		269
233	=item $SELF	270	=item $SELF
234		271
235	Contains the current port id while executing C<rcv> callbacks or C<psub>	272	Contains the current port id while executing C<rcv> callbacks or C<psub>
236	blocks.	273	blocks.
237		274
238	=item SELF, %SELF, @SELF...	275	=item *SELF, SELF, %SELF, @SELF...
239		276
240	Due to some quirks in how perl exports variables, it is impossible to	277	Due to some quirks in how perl exports variables, it is impossible to
241	just export C<$SELF>, all the symbols called C<SELF> are exported by this	278	just export C<$SELF>, all the symbols named C<SELF> are exported by this
242	module, but only C<$SELF> is currently used.	279	module, but only C<$SELF> is currently used.
243		280
244	=item snd $port, type => @data	281	=item snd $port, type => @data
245		282
246	=item snd $port, @msg	283	=item snd $port, @msg
247		284
248	Send the given message to the given port ID, which can identify either	285	Send the given message to the given port, which can identify either a
249	a local or a remote port, and can be either a string or soemthignt hat	286	local or a remote port, and must be a port ID.
250	stringifies a sa port ID (such as a port object :).
251		287
252	While the message can be about anything, it is highly recommended to use a	288	While the message can be almost anything, it is highly recommended to
253	string as first element (a portid, or some word that indicates a request	289	use a string as first element (a port ID, or some word that indicates a
254	type etc.).	290	request type etc.) and to consist if only simple perl values (scalars,
		291	arrays, hashes) - if you think you need to pass an object, think again.
255		292
256	The message data effectively becomes read-only after a call to this	293	The message data logically becomes read-only after a call to this
257	function: modifying any argument is not allowed and can cause many	294	function: modifying any argument (or values referenced by them) is
258	problems.	295	forbidden, as there can be considerable time between the call to C<snd>
		296	and the time the message is actually being serialised - in fact, it might
		297	never be copied as within the same process it is simply handed to the
		298	receiving port.
259		299
260	The type of data you can transfer depends on the transport protocol: when	300	The type of data you can transfer depends on the transport protocol: when
261	JSON is used, then only strings, numbers and arrays and hashes consisting	301	JSON is used, then only strings, numbers and arrays and hashes consisting
262	of those are allowed (no objects). When Storable is used, then anything	302	of those are allowed (no objects). When Storable is used, then anything
263	that Storable can serialise and deserialise is allowed, and for the local	303	that Storable can serialise and deserialise is allowed, and for the local
264	node, anything can be passed.	304	node, anything can be passed. Best rely only on the common denominator of
		305	these.
265		306
266	=item $local_port = port	307	=item $local_port = port
267		308
268	Create a new local port object that can be used either as a pattern	309	Create a new local port object and returns its port ID. Initially it has
269	matching port ("full port") or a single-callback port ("miniport"),	310	no callbacks set and will throw an error when it receives messages.
270	depending on how C<rcv> callbacks are bound to the object.
271		311
272	=item $port = port { my @msg = @_; $finished }	312	=item $local_port = port { my @msg = @_ }
273		313
274	Creates a "miniport", that is, a very lightweight port without any pattern	314	Creates a new local port, and returns its ID. Semantically the same as
275	matching behind it, and returns its ID. Semantically the same as creating
276	a port and calling C<rcv $port, $callback> on it.	315	creating a port and calling C<rcv $port, $callback> on it.
277		316
278	The block will be called for every message received on the port. When the	317	The block will be called for every message received on the port, with the
279	callback returns a true value its job is considered "done" and the port	318	global variable C<$SELF> set to the port ID. Runtime errors will cause the
280	will be destroyed. Otherwise it will stay alive.	319	port to be C<kil>ed. The message will be passed as-is, no extra argument
		320	(i.e. no port ID) will be passed to the callback.
281		321
282	The message will be passed as-is, no extra argument (i.e. no port id) will	322	If you want to stop/destroy the port, simply C<kil> it:
283	be passed to the callback.
284		323
285	If you need the local port id in the callback, this works nicely:	324	my $port = port {
286		325	my @msg = @_;
287	my $port; $port = port {	326	...
288	snd $otherport, reply => $port;	327	kil $SELF;
289	};	328	};
290		329
291	=cut	330	=cut
292		331
293	sub rcv($@);	332	sub rcv($@);
		333
		334	sub _kilme {
		335	die "received message on port without callback";
		336	}
294		337
295	sub port(;&) {	338	sub port(;&) {
296	my $id = "$UNIQ." . $ID++;	339	my $id = "$UNIQ." . $ID++;
297	my $port = "$NODE#$id";	340	my $port = "$NODE#$id";
298		341
299	if (@_) {	342	rcv $port, shift \|\| \&_kilme;
300	rcv $port, shift;
301	} else {
302	$PORT{$id} = sub { }; # nop
303	}
304		343
305	$port	344	$port
306	}	345	}
307		346
308	=item reg $port, $name
309
310	=item reg $name
311
312	Registers the given port (or C<$SELF><<< if missing) under the name
313	C<$name>. If the name already exists it is replaced.
314
315	A port can only be registered under one well known name.
316
317	A port automatically becomes unregistered when it is killed.
318
319	=cut
320
321	sub reg(@) {
322	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
323
324	$REG{$_[0]} = $port;
325	}
326
327	=item rcv $port, $callback->(@msg)	347	=item rcv $local_port, $callback->(@msg)
328		348
329	Replaces the callback on the specified miniport (after converting it to	349	Replaces the default callback on the specified port. There is no way to
330	one if required).	350	remove the default callback: use C<sub { }> to disable it, or better
331		351	C<kil> the port when it is no longer needed.
332	=item rcv $port, tagstring => $callback->(@msg), ...
333
334	=item rcv $port, $smartmatch => $callback->(@msg), ...
335
336	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
337
338	Register callbacks to be called on matching messages on the given full
339	port (after converting it to one if required) and return the port.
340
341	The callback has to return a true value when its work is done, after
342	which is will be removed, or a false value in which case it will stay
343	registered.
344		352
345	The global C<$SELF> (exported by this module) contains C<$port> while	353	The global C<$SELF> (exported by this module) contains C<$port> while
346	executing the callback.	354	executing the callback. Runtime errors during callback execution will
		355	result in the port being C<kil>ed.
347		356
348	Runtime errors wdurign callback execution will result in the port being	357	The default callback received all messages not matched by a more specific
349	C<kil>ed.	358	C<tag> match.
350		359
351	If the match is an array reference, then it will be matched against the	360	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
352	first elements of the message, otherwise only the first element is being
353	matched.
354		361
355	Any element in the match that is specified as C<_any_> (a function	362	Register (or replace) callbacks to be called on messages starting with the
356	exported by this module) matches any single element of the message.	363	given tag on the given port (and return the port), or unregister it (when
		364	C<$callback> is C<$undef> or missing). There can only be one callback
		365	registered for each tag.
357		366
358	While not required, it is highly recommended that the first matching	367	The original message will be passed to the callback, after the first
359	element is a string identifying the message. The one-string-only match is	368	element (the tag) has been removed. The callback will use the same
360	also the most efficient match (by far).	369	environment as the default callback (see above).
361		370
362	Example: create a port and bind receivers on it in one go.	371	Example: create a port and bind receivers on it in one go.
363		372
364	my $port = rcv port,	373	my $port = rcv port,
365	msg1 => sub { ...; 0 },	374	msg1 => sub { ... },
366	msg2 => sub { ...; 0 },	375	msg2 => sub { ... },
367	;	376	;
368		377
369	Example: create a port, bind receivers and send it in a message elsewhere	378	Example: create a port, bind receivers and send it in a message elsewhere
370	in one go:	379	in one go:
371		380
372	snd $otherport, reply =>	381	snd $otherport, reply =>
373	rcv port,	382	rcv port,
374	msg1 => sub { ...; 0 },	383	msg1 => sub { ... },
375	...	384	...
376	;	385	;
377		386
		387	Example: temporarily register a rcv callback for a tag matching some port
		388	(e.g. for an rpc reply) and unregister it after a message was received.
		389
		390	rcv $port, $otherport => sub {
		391	my @reply = @_;
		392
		393	rcv $SELF, $otherport;
		394	};
		395
378	=cut	396	=cut
379		397
380	sub rcv($@) {	398	sub rcv($@) {
381	my $port = shift;	399	my $port = shift;
382	my ($noderef, $portid) = split /#/, $port, 2;	400	my ($nodeid, $portid) = split /#/, $port, 2;
383		401
384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	402	$NODE{$nodeid} == $NODE{""}
385	or Carp::croak "$port: rcv can only be called on local ports, caught";	403	or Carp::croak "$port: rcv can only be called on local ports, caught";
386		404
387	if (@_ == 1) {	405	while (@_) {
		406	if (ref $_[0]) {
		407	if (my $self = $PORT_DATA{$portid}) {
		408	"AnyEvent::MP::Port" eq ref $self
		409	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		410
		411	$self->[0] = shift;
		412	} else {
388	my $cb = shift;	413	my $cb = shift;
389	delete $PORT_DATA{$portid};
390	$PORT{$portid} = sub {	414	$PORT{$portid} = sub {
391	local $SELF = $port;	415	local $SELF = $port;
392	eval {	416	eval { &$cb }; _self_die if $@;
393	&$cb	417	};
394	and kil $port;
395	};	418	}
396	_self_die if $@;	419	} elsif (defined $_[0]) {
397	};
398	} else {
399	my $self = $PORT_DATA{$portid} \|\|= do {	420	my $self = $PORT_DATA{$portid} \|\|= do {
400	my $self = bless {	421	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
401	id => $port,
402	}, "AnyEvent::MP::Port";
403		422
404	$PORT{$portid} = sub {	423	$PORT{$portid} = sub {
405	local $SELF = $port;	424	local $SELF = $port;
406		425
407	eval {
408	for (@{ $self->{rc0}{$_[0]} }) {	426	if (my $cb = $self->[1]{$_[0]}) {
409	$_ && &{$_->[0]}	427	shift;
410	&& undef $_;	428	eval { &$cb }; _self_die if $@;
411	}	429	} else {
412
413	for (@{ $self->{rcv}{$_[0]} }) {
414	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
415	&& &{$_->[0]}	430	&{ $self->[0] };
416	&& undef $_;
417	}
418
419	for (@{ $self->{any} }) {
420	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
421	&& &{$_->[0]}
422	&& undef $_;
423	}	431	}
424	};	432	};
425	_self_die if $@;	433
		434	$self
426	};	435	};
427		436
428	$self
429	};
430
431	"AnyEvent::MP::Port" eq ref $self	437	"AnyEvent::MP::Port" eq ref $self
432	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	438	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
433		439
434	while (@_) {
435	my ($match, $cb) = splice @_, 0, 2;	440	my ($tag, $cb) = splice @_, 0, 2;
436		441
437	if (!ref $match) {	442	if (defined $cb) {
438	push @{ $self->{rc0}{$match} }, [$cb];	443	$self->[1]{$tag} = $cb;
439	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
440	my ($type, @match) = @$match;
441	@match
442	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
443	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
444	} else {	444	} else {
445	push @{ $self->{any} }, [$cb, $match];	445	delete $self->[1]{$tag};
446	}	446	}
447	}	447	}
448	}	448	}
449		449
450	$port	450	$port
451	}	451	}
452		452
		453	=item peval $port, $coderef[, @args]
		454
		455	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		456	when the code throews an exception the C<$port> will be killed.
		457
		458	Any remaining args will be passed to the callback. Any return values will
		459	be returned to the caller.
		460
		461	This is useful when you temporarily want to execute code in the context of
		462	a port.
		463
		464	Example: create a port and run some initialisation code in it's context.
		465
		466	my $port = port { ... };
		467
		468	peval $port, sub {
		469	init
		470	or die "unable to init";
		471	};
		472
		473	=cut
		474
		475	sub peval($$) {
		476	local $SELF = shift;
		477	my $cb = shift;
		478
		479	if (wantarray) {
		480	my @res = eval { &$cb };
		481	_self_die if $@;
		482	@res
		483	} else {
		484	my $res = eval { &$cb };
		485	_self_die if $@;
		486	$res
		487	}
		488	}
		489
453	=item $closure = psub { BLOCK }	490	=item $closure = psub { BLOCK }
454		491
455	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	492	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
456	closure is executed, sets up the environment in the same way as in C<rcv>	493	closure is executed, sets up the environment in the same way as in C<rcv>
457	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	494	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		495
		496	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		497	BLOCK } } >>.
458		498
459	This is useful when you register callbacks from C<rcv> callbacks:	499	This is useful when you register callbacks from C<rcv> callbacks:
460		500
461	rcv delayed_reply => sub {	501	rcv delayed_reply => sub {
462	my ($delay, @reply) = @_;	502	my ($delay, @reply) = @_;
…		…
486	$res	526	$res
487	}	527	}
488	}	528	}
489	}	529	}
490		530
491	=item $guard = mon $port, $cb->(@reason)	531	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
492		532
493	=item $guard = mon $port, $rcvport	533	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
494		534
495	=item $guard = mon $port	535	=item $guard = mon $port # kill $SELF when $port dies
496		536
497	=item $guard = mon $port, $rcvport, @msg	537	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
498		538
499	Monitor the given port and do something when the port is killed, and	539	Monitor the given port and do something when the port is killed or
500	optionally return a guard that can be used to stop monitoring again.	540	messages to it were lost, and optionally return a guard that can be used
		541	to stop monitoring again.
501		542
502	In the first form (callback), the callback is simply called with any	543	In the first form (callback), the callback is simply called with any
503	number of C<@reason> elements (no @reason means that the port was deleted	544	number of C<@reason> elements (no @reason means that the port was deleted
504	"normally"). Note also that I<< the callback B<must> never die >>, so use	545	"normally"). Note also that I<< the callback B<must> never die >>, so use
505	C<eval> if unsure.	546	C<eval> if unsure.
506		547
507	In the second form (another port given), the other port (C<$rcvport)	548	In the second form (another port given), the other port (C<$rcvport>)
508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	549	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
509	"normal" kils nothing happens, while under all other conditions, the other	550	"normal" kils nothing happens, while under all other conditions, the other
510	port is killed with the same reason.	551	port is killed with the same reason.
511		552
512	The third form (kill self) is the same as the second form, except that	553	The third form (kill self) is the same as the second form, except that
513	C<$rvport> defaults to C<$SELF>.	554	C<$rvport> defaults to C<$SELF>.
514		555
515	In the last form (message), a message of the form C<@msg, @reason> will be	556	In the last form (message), a message of the form C<@msg, @reason> will be
516	C<snd>.	557	C<snd>.
517		558
		559	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		560	alert was raised), they are removed and will not trigger again.
		561
		562	As a rule of thumb, monitoring requests should always monitor a port from
		563	a local port (or callback). The reason is that kill messages might get
		564	lost, just like any other message. Another less obvious reason is that
		565	even monitoring requests can get lost (for example, when the connection
		566	to the other node goes down permanently). When monitoring a port locally
		567	these problems do not exist.
		568
		569	C<mon> effectively guarantees that, in the absence of hardware failures,
		570	after starting the monitor, either all messages sent to the port will
		571	arrive, or the monitoring action will be invoked after possible message
		572	loss has been detected. No messages will be lost "in between" (after
		573	the first lost message no further messages will be received by the
		574	port). After the monitoring action was invoked, further messages might get
		575	delivered again.
		576
		577	Inter-host-connection timeouts and monitoring depend on the transport
		578	used. The only transport currently implemented is TCP, and AnyEvent::MP
		579	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		580	non-idle connection, and usually around two hours for idle connections).
		581
		582	This means that monitoring is good for program errors and cleaning up
		583	stuff eventually, but they are no replacement for a timeout when you need
		584	to ensure some maximum latency.
		585
518	Example: call a given callback when C<$port> is killed.	586	Example: call a given callback when C<$port> is killed.
519		587
520	mon $port, sub { warn "port died because of <@_>\n" };	588	mon $port, sub { warn "port died because of <@_>\n" };
521		589
522	Example: kill ourselves when C<$port> is killed abnormally.	590	Example: kill ourselves when C<$port> is killed abnormally.
…		…
528	mon $port, $self => "restart";	596	mon $port, $self => "restart";
529		597
530	=cut	598	=cut
531		599
532	sub mon {	600	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	601	my ($nodeid, $port) = split /#/, shift, 2;
534		602
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	603	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
536		604
537	my $cb = @_ ? $_[0] : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	605	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
538		606
539	unless (ref $cb) {	607	unless (ref $cb) {
540	if (@_) {	608	if (@_) {
541	# send a kill info message	609	# send a kill info message
542	my (@msg) = @_;	610	my (@msg) = ($cb, @_);
543	$cb = sub { snd @msg, @_ };	611	$cb = sub { snd @msg, @_ };
544	} else {	612	} else {
545	# simply kill other port	613	# simply kill other port
546	my $port = $cb;	614	my $port = $cb;
547	$cb = sub { kil $port, @_ if @_ };	615	$cb = sub { kil $port, @_ if @_ };
…		…
549	}	617	}
550		618
551	$node->monitor ($port, $cb);	619	$node->monitor ($port, $cb);
552		620
553	defined wantarray	621	defined wantarray
554	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	622	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
555	}	623	}
556		624
557	=item $guard = mon_guard $port, $ref, $ref...	625	=item $guard = mon_guard $port, $ref, $ref...
558		626
559	Monitors the given C<$port> and keeps the passed references. When the port	627	Monitors the given C<$port> and keeps the passed references. When the port
560	is killed, the references will be freed.	628	is killed, the references will be freed.
561		629
562	Optionally returns a guard that will stop the monitoring.	630	Optionally returns a guard that will stop the monitoring.
563		631
564	This function is useful when you create e.g. timers or other watchers and	632	This function is useful when you create e.g. timers or other watchers and
565	want to free them when the port gets killed:	633	want to free them when the port gets killed (note the use of C<psub>):
566		634
567	$port->rcv (start => sub {	635	$port->rcv (start => sub {
568	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	636	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
569	undef $timer if 0.9 < rand;	637	undef $timer if 0.9 < rand;
570	});	638	});
571	});	639	});
572		640
573	=cut	641	=cut
…		…
578	#TODO: mon-less form?	646	#TODO: mon-less form?
579		647
580	mon $port, sub { 0 && @refs }	648	mon $port, sub { 0 && @refs }
581	}	649	}
582		650
583	=item lnk $port1, $port2
584
585	=item lnk $otherport
586
587	Link two ports. This is simply a shorthand for:
588
589	mon $port1, $port2;
590	mon $port2, $port1;
591
592	It means that if either one is killed abnormally, the other one gets
593	killed as well.
594
595	The one-argument form assumes that one port is C<$SELF>.
596
597	=cut
598
599	sub lnk {
600	my $port1 = shift;
601	my $port2 = @_ ? shift : $SELF \|\| Carp::croak 'lnk: called with one argument only, but $SELF not set,';
602
603	mon $port1, $port2;
604	mon $port2, $port1;
605	}
606
607	=item kil $port[, @reason]	651	=item kil $port[, @reason]
608		652
609	Kill the specified port with the given C<@reason>.	653	Kill the specified port with the given C<@reason>.
610		654
611	If no C<@reason> is specified, then the port is killed "normally" (linked	655	If no C<@reason> is specified, then the port is killed "normally" (ports
612	ports will not be kileld, or even notified).	656	monitoring other ports will not necessarily die because a port dies
		657	"normally").
613		658
614	Otherwise, linked ports get killed with the same reason (second form of	659	Otherwise, linked ports get killed with the same reason (second form of
615	C<mon>, see below).	660	C<mon>, see above).
616		661
617	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	662	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
618	will be reported as reason C<< die => $@ >>.	663	will be reported as reason C<< die => $@ >>.
619		664
620	Transport/communication errors are reported as C<< transport_error =>	665	Transport/communication errors are reported as C<< transport_error =>
621	$message >>.	666	$message >>.
622		667
623	=back
624
625	=head1 NODE MESSAGES
626
627	Nodes understand the following messages sent to them. Many of them take
628	arguments called C<@reply>, which will simply be used to compose a reply
629	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
630	the remaining arguments are simply the message data.
631
632	While other messages exist, they are not public and subject to change.
633
634	=over 4
635
636	=cut	668	=cut
637		669
638	=item lookup => $name, @reply	670	=item $port = spawn $node, $initfunc[, @initdata]
639		671
640	Replies with the port ID of the specified well-known port, or C<undef>.	672	Creates a port on the node C<$node> (which can also be a port ID, in which
		673	case it's the node where that port resides).
641		674
642	=item devnull => ...	675	The port ID of the newly created port is returned immediately, and it is
		676	possible to immediately start sending messages or to monitor the port.
643		677
644	Generic data sink/CPU heat conversion.	678	After the port has been created, the init function is called on the remote
		679	node, in the same context as a C<rcv> callback. This function must be a
		680	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		681	specify a function in the main program, use C<::name>.
645		682
646	=item relay => $port, @msg	683	If the function doesn't exist, then the node tries to C<require>
		684	the package, then the package above the package and so on (e.g.
		685	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		686	exists or it runs out of package names.
647		687
648	Simply forwards the message to the given port.	688	The init function is then called with the newly-created port as context
		689	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		690	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		691	the port might not get created.
649		692
650	=item eval => $string[ @reply]	693	A common idiom is to pass a local port, immediately monitor the spawned
		694	port, and in the remote init function, immediately monitor the passed
		695	local port. This two-way monitoring ensures that both ports get cleaned up
		696	when there is a problem.
651		697
652	Evaluates the given string. If C<@reply> is given, then a message of the	698	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
653	form C<@reply, $@, @evalres> is sent.	699	caller before C<spawn> returns (by delaying invocation when spawn is
		700	called for the local node).
654		701
655	Example: crash another node.	702	Example: spawn a chat server port on C<$othernode>.
656		703
657	snd $othernode, eval => "exit";	704	# this node, executed from within a port context:
		705	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		706	mon $server;
658		707
659	=item time => @reply	708	# init function on C<$othernode>
		709	sub connect {
		710	my ($srcport) = @_;
660		711
661	Replies the the current node time to C<@reply>.	712	mon $srcport;
662		713
663	Example: tell the current node to send the current time to C<$myport> in a	714	rcv $SELF, sub {
664	C<timereply> message.	715	...
		716	};
		717	}
665		718
666	snd $NODE, time => $myport, timereply => 1, 2;	719	=cut
667	# => snd $myport, timereply => 1, 2, <time>	720
		721	sub _spawn {
		722	my $port = shift;
		723	my $init = shift;
		724
		725	# rcv will create the actual port
		726	local $SELF = "$NODE#$port";
		727	eval {
		728	&{ load_func $init }
		729	};
		730	_self_die if $@;
		731	}
		732
		733	sub spawn(@) {
		734	my ($nodeid, undef) = split /#/, shift, 2;
		735
		736	my $id = "$RUNIQ." . $ID++;
		737
		738	$_[0] =~ /::/
		739	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		740
		741	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		742
		743	"$nodeid#$id"
		744	}
		745
		746	=item after $timeout, @msg
		747
		748	=item after $timeout, $callback
		749
		750	Either sends the given message, or call the given callback, after the
		751	specified number of seconds.
		752
		753	This is simply a utility function that comes in handy at times - the
		754	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		755	so it may go away in the future.
		756
		757	=cut
		758
		759	sub after($@) {
		760	my ($timeout, @action) = @_;
		761
		762	my $t; $t = AE::timer $timeout, 0, sub {
		763	undef $t;
		764	ref $action[0]
		765	? $action[0]()
		766	: snd @action;
		767	};
		768	}
		769
		770	=item cal $port, @msg, $callback[, $timeout]
		771
		772	A simple form of RPC - sends a message to the given C<$port> with the
		773	given contents (C<@msg>), but adds a reply port to the message.
		774
		775	The reply port is created temporarily just for the purpose of receiving
		776	the reply, and will be C<kil>ed when no longer needed.
		777
		778	A reply message sent to the port is passed to the C<$callback> as-is.
		779
		780	If an optional time-out (in seconds) is given and it is not C<undef>,
		781	then the callback will be called without any arguments after the time-out
		782	elapsed and the port is C<kil>ed.
		783
		784	If no time-out is given (or it is C<undef>), then the local port will
		785	monitor the remote port instead, so it eventually gets cleaned-up.
		786
		787	Currently this function returns the temporary port, but this "feature"
		788	might go in future versions unless you can make a convincing case that
		789	this is indeed useful for something.
		790
		791	=cut
		792
		793	sub cal(@) {
		794	my $timeout = ref $_[-1] ? undef : pop;
		795	my $cb = pop;
		796
		797	my $port = port {
		798	undef $timeout;
		799	kil $SELF;
		800	&$cb;
		801	};
		802
		803	if (defined $timeout) {
		804	$timeout = AE::timer $timeout, 0, sub {
		805	undef $timeout;
		806	kil $port;
		807	$cb->();
		808	};
		809	} else {
		810	mon $_[0], sub {
		811	kil $port;
		812	$cb->();
		813	};
		814	}
		815
		816	push @_, $port;
		817	&snd;
		818
		819	$port
		820	}
668		821
669	=back	822	=back
670		823
671	=head1 AnyEvent::MP vs. Distributed Erlang	824	=head1 AnyEvent::MP vs. Distributed Erlang
672		825
673	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	826	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
674	== aemp node, Erlang process == aemp port), so many of the documents and	827	== aemp node, Erlang process == aemp port), so many of the documents and
675	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	828	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
676	sample:	829	sample:
677		830
678	http://www.Erlang.se/doc/programming_rules.shtml	831	http://www.erlang.se/doc/programming_rules.shtml
679	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	832	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
680	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	833	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
681	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	834	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
682		835
683	Despite the similarities, there are also some important differences:	836	Despite the similarities, there are also some important differences:
684		837
685	=over 4	838	=over 4
686		839
687	=item * Node references contain the recipe on how to contact them.	840	=item * Node IDs are arbitrary strings in AEMP.
688		841
689	Erlang relies on special naming and DNS to work everywhere in the	842	Erlang relies on special naming and DNS to work everywhere in the same
690	same way. AEMP relies on each node knowing it's own address(es), with	843	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
691	convenience functionality.	844	configuration or DNS), and possibly the addresses of some seed nodes, but
		845	will otherwise discover other nodes (and their IDs) itself.
692		846
693	This means that AEMP requires a less tightly controlled environment at the	847	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
694	cost of longer node references and a slightly higher management overhead.	848	uses "local ports are like remote ports".
		849
		850	The failure modes for local ports are quite different (runtime errors
		851	only) then for remote ports - when a local port dies, you I<know> it dies,
		852	when a connection to another node dies, you know nothing about the other
		853	port.
		854
		855	Erlang pretends remote ports are as reliable as local ports, even when
		856	they are not.
		857
		858	AEMP encourages a "treat remote ports differently" philosophy, with local
		859	ports being the special case/exception, where transport errors cannot
		860	occur.
695		861
696	=item * Erlang uses processes and a mailbox, AEMP does not queue.	862	=item * Erlang uses processes and a mailbox, AEMP does not queue.
697		863
698	Erlang uses processes that selctively receive messages, and therefore	864	Erlang uses processes that selectively receive messages, and therefore
699	needs a queue. AEMP is event based, queuing messages would serve no useful	865	needs a queue. AEMP is event based, queuing messages would serve no
700	purpose.	866	useful purpose. For the same reason the pattern-matching abilities of
		867	AnyEvent::MP are more limited, as there is little need to be able to
		868	filter messages without dequeuing them.
701		869
702	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	870	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
703		871
704	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	872	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
705		873
706	Sending messages in Erlang is synchronous and blocks the process. AEMP	874	Sending messages in Erlang is synchronous and blocks the process (and
707	sends are immediate, connection establishment is handled in the	875	so does not need a queue that can overflow). AEMP sends are immediate,
708	background.	876	connection establishment is handled in the background.
709		877
710	=item * Erlang can silently lose messages, AEMP cannot.	878	=item * Erlang suffers from silent message loss, AEMP does not.
711		879
712	Erlang makes few guarantees on messages delivery - messages can get lost	880	Erlang implements few guarantees on messages delivery - messages can get
713	without any of the processes realising it (i.e. you send messages a, b,	881	lost without any of the processes realising it (i.e. you send messages a,
714	and c, and the other side only receives messages a and c).	882	b, and c, and the other side only receives messages a and c).
715		883
716	AEMP guarantees correct ordering, and the guarantee that there are no	884	AEMP guarantees correct ordering, and the guarantee that after one message
717	holes in the message sequence.	885	is lost, all following ones sent to the same port are lost as well, until
718		886	monitoring raises an error, so there are no silent "holes" in the message
719	=item * In Erlang, processes can be declared dead and later be found to be	887	sequence.
720	alive.
721
722	In Erlang it can happen that a monitored process is declared dead and
723	linked processes get killed, but later it turns out that the process is
724	still alive - and can receive messages.
725
726	In AEMP, when port monitoring detects a port as dead, then that port will
727	eventually be killed - it cannot happen that a node detects a port as dead
728	and then later sends messages to it, finding it is still alive.
729		888
730	=item * Erlang can send messages to the wrong port, AEMP does not.	889	=item * Erlang can send messages to the wrong port, AEMP does not.
731		890
732	In Erlang it is quite possible that a node that restarts reuses a process	891	In Erlang it is quite likely that a node that restarts reuses a process ID
733	ID known to other nodes for a completely different process, causing	892	known to other nodes for a completely different process, causing messages
734	messages destined for that process to end up in an unrelated process.	893	destined for that process to end up in an unrelated process.
735		894
736	AEMP never reuses port IDs, so old messages or old port IDs floating	895	AEMP never reuses port IDs, so old messages or old port IDs floating
737	around in the network will not be sent to an unrelated port.	896	around in the network will not be sent to an unrelated port.
738		897
739	=item * Erlang uses unprotected connections, AEMP uses secure	898	=item * Erlang uses unprotected connections, AEMP uses secure
740	authentication and can use TLS.	899	authentication and can use TLS.
741		900
742	AEMP can use a proven protocol - SSL/TLS - to protect connections and	901	AEMP can use a proven protocol - TLS - to protect connections and
743	securely authenticate nodes.	902	securely authenticate nodes.
744		903
745	=item * The AEMP protocol is optimised for both text-based and binary	904	=item * The AEMP protocol is optimised for both text-based and binary
746	communications.	905	communications.
747		906
748	The AEMP protocol, unlike the Erlang protocol, supports both	907	The AEMP protocol, unlike the Erlang protocol, supports both programming
749	language-independent text-only protocols (good for debugging) and binary,	908	language independent text-only protocols (good for debugging) and binary,
750	language-specific serialisers (e.g. Storable).	909	language-specific serialisers (e.g. Storable). By default, unless TLS is
		910	used, the protocol is actually completely text-based.
751		911
752	It has also been carefully designed to be implementable in other languages	912	It has also been carefully designed to be implementable in other languages
753	with a minimum of work while gracefully degrading fucntionality to make the	913	with a minimum of work while gracefully degrading functionality to make the
754	protocol simple.	914	protocol simple.
755		915
756	=item * AEMP has more flexible monitoring options than Erlang.	916	=item * AEMP has more flexible monitoring options than Erlang.
757		917
758	In Erlang, you can chose to receive I<all> exit signals as messages	918	In Erlang, you can chose to receive I<all> exit signals as messages
759	or I<none>, there is no in-between, so monitoring single processes is	919	or I<none>, there is no in-between, so monitoring single processes is
760	difficult to implement. Monitoring in AEMP is more flexible than in	920	difficult to implement. Monitoring in AEMP is more flexible than in
761	Erlang, as one can choose between automatic kill, exit message or callback	921	Erlang, as one can choose between automatic kill, exit message or callback
762	on a per-process basis.	922	on a per-process basis.
763		923
764	=item * Erlang has different semantics for monitoring and linking, AEMP has the same.	924	=item * Erlang tries to hide remote/local connections, AEMP does not.
765		925
766	Monitoring in Erlang is not an indicator of process death/crashes,	926	Monitoring in Erlang is not an indicator of process death/crashes, in the
767	as linking is (except linking is unreliable in Erlang). In AEMP, the	927	same way as linking is (except linking is unreliable in Erlang).
768	semantics of monitoring and linking are identical, linking is simply	928
769	two-way monitoring with automatic kill.	929	In AEMP, you don't "look up" registered port names or send to named ports
		930	that might or might not be persistent. Instead, you normally spawn a port
		931	on the remote node. The init function monitors you, and you monitor the
		932	remote port. Since both monitors are local to the node, they are much more
		933	reliable (no need for C<spawn_link>).
		934
		935	This also saves round-trips and avoids sending messages to the wrong port
		936	(hard to do in Erlang).
770		937
771	=back	938	=back
772		939
		940	=head1 RATIONALE
		941
		942	=over 4
		943
		944	=item Why strings for port and node IDs, why not objects?
		945
		946	We considered "objects", but found that the actual number of methods
		947	that can be called are quite low. Since port and node IDs travel over
		948	the network frequently, the serialising/deserialising would add lots of
		949	overhead, as well as having to keep a proxy object everywhere.
		950
		951	Strings can easily be printed, easily serialised etc. and need no special
		952	procedures to be "valid".
		953
		954	And as a result, a miniport consists of a single closure stored in a
		955	global hash - it can't become much cheaper.
		956
		957	=item Why favour JSON, why not a real serialising format such as Storable?
		958
		959	In fact, any AnyEvent::MP node will happily accept Storable as framing
		960	format, but currently there is no way to make a node use Storable by
		961	default (although all nodes will accept it).
		962
		963	The default framing protocol is JSON because a) JSON::XS is many times
		964	faster for small messages and b) most importantly, after years of
		965	experience we found that object serialisation is causing more problems
		966	than it solves: Just like function calls, objects simply do not travel
		967	easily over the network, mostly because they will always be a copy, so you
		968	always have to re-think your design.
		969
		970	Keeping your messages simple, concentrating on data structures rather than
		971	objects, will keep your messages clean, tidy and efficient.
		972
		973	=back
		974
773	=head1 SEE ALSO	975	=head1 SEE ALSO
		976
		977	L<AnyEvent::MP::Intro> - a gentle introduction.
		978
		979	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		980
		981	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		982	your applications.
		983
		984	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		985
		986	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		987	all nodes.
774		988
775	L<AnyEvent>.	989	L<AnyEvent>.
776		990
777	=head1 AUTHOR	991	=head1 AUTHOR
778		992

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Revision 1.106 by root, Wed Dec 9 14:00:49 2009 UTC