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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.44 by root, Wed Aug 12 21:39:58 2009 UTC vs.
Revision 1.105 by root, Sun Nov 8 23:58:02 2009 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
		14	# initialise the node so it can send/receive messages
		15	configure;
		16
15	# ports are message endpoints	17	# ports are message destinations
16		18
17	# sending messages	19	# sending messages
18	snd $port, type => data...;	20	snd $port, type => data...;
19	snd $port, @msg;	21	snd $port, @msg;
20	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
21		23
22	# miniports	24	# creating/using ports, the simple way
23	my $miniport = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
24		26
25	# full ports	27	# creating/using ports, tagged message matching
26	my $port = port;	28	my $port = port;
27	rcv $port, smartmatch => $cb->(@msg);
28	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
29	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
30		31
31	# remote ports	32	# create a port on another node
32	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
33		34
34	# more, smarter, matches (_any_ is exported by this module)	35	# destroy a prot again
35	rcv $port, [child_died => $pid] => sub { ...	36	kil $port; # "normal" kill
36	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	37	kil $port, my_error => "everything is broken"; # error kill
37		38
38	# monitoring	39	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
41	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.
42		59
43	=head1 DESCRIPTION	60	=head1 DESCRIPTION
44		61
45	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
46		63
47	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
48	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
49		66
50	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>
51	manual page.	68	manual page and the examples under F<eg/>.
52
53	At the moment, this module family is severly broken and underdocumented,
54	so do not use. This was uploaded mainly to reserve the CPAN namespace -
55	stay tuned! The basic API should be finished, however.
56		69
57	=head1 CONCEPTS	70	=head1 CONCEPTS
58		71
59	=over 4	72	=over 4
60		73
61	=item port	74	=item port
62		75
63	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).
64		78
65	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
66	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
67	will not be queued.	81	anything was listening for them or not.
68		82
69	=item port id - C<noderef#portname>	83	=item port ID - C<nodeid#portname>
70		84
71	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
72	separator, and a port name (a printable string of unspecified format). An	86	separator, and a port name (a printable string of unspecified format).
73	exception is the the node port, whose ID is identical to its node
74	reference.
75		87
76	=item node	88	=item node
77		89
78	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,
79	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
80	create new ports, among other things.	92	ports.
81		93
82	Nodes are either private (single-process only), slaves (connected to a	94	Nodes are either public (have one or more listening ports) or private
83	master node only) or public nodes (connectable from unrelated nodes).	95	(no listening ports). Private nodes cannot talk to other private nodes
		96	currently.
84		97
85	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	98	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
86		99
87	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
88	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
89	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.
90		104
91	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	=item binds - C<ip:port>
92	TCP/IP, other protocols might look different).
93		106
94	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
95	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.
96		111
97	Before using an unresolved node reference in a message you first have to	112	=item seed nodes
98	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.
99		139
100	=back	140	=back
101		141
102	=head1 VARIABLES/FUNCTIONS	142	=head1 VARIABLES/FUNCTIONS
103		143
115		155
116	use AE ();	156	use AE ();
117		157
118	use base "Exporter";	158	use base "Exporter";
119		159
120	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	160	our $VERSION = 1.23;
121		161
122	our @EXPORT = qw(	162	our @EXPORT = qw(
123	NODE $NODE *SELF node_of _any_	163	NODE $NODE *SELF node_of after
124	resolve_node initialise_node	164	configure
125	snd rcv mon kil reg psub spawn	165	snd rcv mon mon_guard kil psub peval spawn cal
126	port	166	port
127	);	167	);
128		168
129	our $SELF;	169	our $SELF;
130		170
…		…
134	kil $SELF, die => $msg;	174	kil $SELF, die => $msg;
135	}	175	}
136		176
137	=item $thisnode = NODE / $NODE	177	=item $thisnode = NODE / $NODE
138		178
139	The C<NODE> function returns, and the C<$NODE> variable contains	179	The C<NODE> function returns, and the C<$NODE> variable contains, the node
140	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
141	to C<become_public> or C<become_slave>, after which all local port	181	a call to C<configure>.
142	identifiers become invalid.
143		182
144	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
145		184
146	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.
147		186
148	=item initialise_node $noderef, $seednode, $seednode...	187	=item configure $profile, key => value...
149		188
150	=item initialise_node "slave/", $master, $master...	189	=item configure key => value...
151		190
152	Before a node can talk to other nodes on the network it has to initialise	191	Before a node can talk to other nodes on the network (i.e. enter
153	itself - the minimum a node needs to know is it's own name, and optionally	192	"distributed mode") it has to configure itself - the minimum a node needs
154	it should know the noderefs of some other nodes in the network.	193	to know is its own name, and optionally it should know the addresses of
		194	some other nodes in the network to discover other nodes.
155		195
156	This function initialises a node - it must be called exactly once (or	196	This function configures a node - it must be called exactly once (or
157	never) before calling other AnyEvent::MP functions.	197	never) before calling other AnyEvent::MP functions.
158		198
159	All arguments are noderefs, which can be either resolved or unresolved.
160
161	There are two types of networked nodes, public nodes and slave nodes:
162
163	=over 4	199	=over 4
164		200
165	=item public nodes	201	=item step 1, gathering configuration from profiles
166		202
167	For public nodes, C<$noderef> must either be a (possibly unresolved)	203	The function first looks up a profile in the aemp configuration (see the
168	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
169	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.
170		207
171	Afterwards, the node will bind itself on all endpoints and try to connect	208	The profile data is then gathered as follows:
172	to all additional C<$seednodes> that are specified. Seednodes are optional
173	and can be used to quickly bootstrap the node into an existing network.
174		209
175	=item slave nodes	210	First, all remaining key => value pairs (all of which are conveniently
		211	undocumented at the moment) will be interpreted as configuration
		212	data. Then they will be overwritten by any values specified in the global
		213	default configuration (see the F<aemp> utility), then the chain of
		214	profiles chosen by the profile name (and any C<parent> attributes).
176		215
177	When the C<$noderef> is the special string C<slave/>, then the node will	216	That means that the values specified in the profile have highest priority
178	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,
179	route most of their traffic to the master node that they attach to.	218	and can only be used to specify defaults.
180		219
181	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
182	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
183	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.
184		241
185	=back	242	=back
186		243
187	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.
188	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.
189	server.
190		246
191	Example: become a public node listening on the default node.	247	configure
192		248
193	initialise_node;	249	Example: become an anonymous node. This form is often used for commandline
		250	clients.
194		251
195	Example: become a public node, and try to contact some well-known master	252	configure nodeid => "anon/";
196	servers to become part of the network.
197		253
198	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).
199		257
200	Example: become a public node listening on port C<4041>.	258	# use the aemp commandline utility
		259	# aemp profile seed nodeid anon/ binds '*:4040'
201		260
202	initialise_node 4041;	261	# then use it
		262	configure profile => "seed";
203		263
204	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
205		266
206	initialise_node "locahost:4044";	267	# or provide a nicer-to-remember nodeid
207		268	# aemp run profile seed nodeid "$(hostname)"
208	Example: become a slave node to any of the specified master servers.
209
210	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
211
212	=item $cv = resolve_node $noderef
213
214	Takes an unresolved node reference that may contain hostnames and
215	abbreviated IDs, resolves all of them and returns a resolved node
216	reference.
217
218	In addition to C<address:port> pairs allowed in resolved noderefs, the
219	following forms are supported:
220
221	=over 4
222
223	=item the empty string
224
225	An empty-string component gets resolved as if the default port (4040) was
226	specified.
227
228	=item naked port numbers (e.g. C<1234>)
229
230	These are resolved by prepending the local nodename and a colon, to be
231	further resolved.
232
233	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
234
235	These are resolved by using AnyEvent::DNS to resolve them, optionally
236	looking up SRV records for the C<aemp=4040> port, if no port was
237	specified.
238
239	=back
240		269
241	=item $SELF	270	=item $SELF
242		271
243	Contains the current port id while executing C<rcv> callbacks or C<psub>	272	Contains the current port id while executing C<rcv> callbacks or C<psub>
244	blocks.	273	blocks.
245		274
246	=item SELF, %SELF, @SELF...	275	=item *SELF, SELF, %SELF, @SELF...
247		276
248	Due to some quirks in how perl exports variables, it is impossible to	277	Due to some quirks in how perl exports variables, it is impossible to
249	just export C<$SELF>, all the symbols called C<SELF> are exported by this	278	just export C<$SELF>, all the symbols named C<SELF> are exported by this
250	module, but only C<$SELF> is currently used.	279	module, but only C<$SELF> is currently used.
251		280
252	=item snd $port, type => @data	281	=item snd $port, type => @data
253		282
254	=item snd $port, @msg	283	=item snd $port, @msg
255		284
256	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
257	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.
258	stringifies a sa port ID (such as a port object :).
259		287
260	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
261	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
262	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.
263		292
264	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
265	function: modifying any argument is not allowed and can cause many	294	function: modifying any argument (or values referenced by them) is
266	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.
267		299
268	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
269	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
270	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
271	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
272	node, anything can be passed.	304	node, anything can be passed. Best rely only on the common denominator of
		305	these.
273		306
274	=item $local_port = port	307	=item $local_port = port
275		308
276	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
277	matching port ("full port") or a single-callback port ("miniport"),	310	no callbacks set and will throw an error when it receives messages.
278	depending on how C<rcv> callbacks are bound to the object.
279		311
280	=item $port = port { my @msg = @_; $finished }	312	=item $local_port = port { my @msg = @_ }
281		313
282	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
283	matching behind it, and returns its ID. Semantically the same as creating
284	a port and calling C<rcv $port, $callback> on it.	315	creating a port and calling C<rcv $port, $callback> on it.
285		316
286	The block will be called for every message received on the port. When the	317	The block will be called for every message received on the port, with the
287	callback returns a true value its job is considered "done" and the port	318	global variable C<$SELF> set to the port ID. Runtime errors will cause the
288	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.
289		321
290	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:
291	be passed to the callback.
292		323
293	If you need the local port id in the callback, this works nicely:	324	my $port = port {
294		325	my @msg = @_;
295	my $port; $port = port {	326	...
296	snd $otherport, reply => $port;	327	kil $SELF;
297	};	328	};
298		329
299	=cut	330	=cut
300		331
301	sub rcv($@);	332	sub rcv($@);
		333
		334	sub _kilme {
		335	die "received message on port without callback";
		336	}
302		337
303	sub port(;&) {	338	sub port(;&) {
304	my $id = "$UNIQ." . $ID++;	339	my $id = "$UNIQ." . $ID++;
305	my $port = "$NODE#$id";	340	my $port = "$NODE#$id";
306		341
307	if (@_) {	342	rcv $port, shift \|\| \&_kilme;
308	rcv $port, shift;
309	} else {
310	$PORT{$id} = sub { }; # nop
311	}
312		343
313	$port	344	$port
314	}	345	}
315		346
316	=item reg $port, $name
317
318	=item reg $name
319
320	Registers the given port (or C<$SELF><<< if missing) under the name
321	C<$name>. If the name already exists it is replaced.
322
323	A port can only be registered under one well known name.
324
325	A port automatically becomes unregistered when it is killed.
326
327	=cut
328
329	sub reg(@) {
330	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
331
332	$REG{$_[0]} = $port;
333	}
334
335	=item rcv $port, $callback->(@msg)	347	=item rcv $local_port, $callback->(@msg)
336		348
337	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
338	one if required).	350	remove the default callback: use C<sub { }> to disable it, or better
339		351	C<kil> the port when it is no longer needed.
340	=item rcv $port, tagstring => $callback->(@msg), ...
341
342	=item rcv $port, $smartmatch => $callback->(@msg), ...
343
344	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
345
346	Register callbacks to be called on matching messages on the given full
347	port (after converting it to one if required) and return the port.
348
349	The callback has to return a true value when its work is done, after
350	which is will be removed, or a false value in which case it will stay
351	registered.
352		352
353	The global C<$SELF> (exported by this module) contains C<$port> while	353	The global C<$SELF> (exported by this module) contains C<$port> while
354	executing the callback.	354	executing the callback. Runtime errors during callback execution will
		355	result in the port being C<kil>ed.
355		356
356	Runtime errors during callback execution will result in the port being	357	The default callback received all messages not matched by a more specific
357	C<kil>ed.	358	C<tag> match.
358		359
359	If the match is an array reference, then it will be matched against the	360	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
360	first elements of the message, otherwise only the first element is being
361	matched.
362		361
363	Any element in the match that is specified as C<_any_> (a function	362	Register (or replace) callbacks to be called on messages starting with the
364	exported by this module) matches any single element of the message.	363	given tag on the given port (and return the port), or unregister it (when
		364	C<$callback> is C<$undef> or missing). There can only be one callback
		365	registered for each tag.
365		366
366	While not required, it is highly recommended that the first matching	367	The original message will be passed to the callback, after the first
367	element is a string identifying the message. The one-string-only match is	368	element (the tag) has been removed. The callback will use the same
368	also the most efficient match (by far).	369	environment as the default callback (see above).
369		370
370	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.
371		372
372	my $port = rcv port,	373	my $port = rcv port,
373	msg1 => sub { ...; 0 },	374	msg1 => sub { ... },
374	msg2 => sub { ...; 0 },	375	msg2 => sub { ... },
375	;	376	;
376		377
377	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
378	in one go:	379	in one go:
379		380
380	snd $otherport, reply =>	381	snd $otherport, reply =>
381	rcv port,	382	rcv port,
382	msg1 => sub { ...; 0 },	383	msg1 => sub { ... },
383	...	384	...
384	;	385	;
385		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, $otherport;
		394	};
		395
386	=cut	396	=cut
387		397
388	sub rcv($@) {	398	sub rcv($@) {
389	my $port = shift;	399	my $port = shift;
390	my ($noderef, $portid) = split /#/, $port, 2;	400	my ($nodeid, $portid) = split /#/, $port, 2;
391		401
392	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	402	$NODE{$nodeid} == $NODE{""}
393	or Carp::croak "$port: rcv can only be called on local ports, caught";	403	or Carp::croak "$port: rcv can only be called on local ports, caught";
394		404
395	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 {
396	my $cb = shift;	413	my $cb = shift;
397	delete $PORT_DATA{$portid};
398	$PORT{$portid} = sub {	414	$PORT{$portid} = sub {
399	local $SELF = $port;	415	local $SELF = $port;
400	eval {	416	eval { &$cb }; _self_die if $@;
401	&$cb	417	};
402	and kil $port;
403	};	418	}
404	_self_die if $@;	419	} elsif (defined $_[0]) {
405	};
406	} else {
407	my $self = $PORT_DATA{$portid} \|\|= do {	420	my $self = $PORT_DATA{$portid} \|\|= do {
408	my $self = bless {	421	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
409	id => $port,
410	}, "AnyEvent::MP::Port";
411		422
412	$PORT{$portid} = sub {	423	$PORT{$portid} = sub {
413	local $SELF = $port;	424	local $SELF = $port;
414		425
415	eval {
416	for (@{ $self->{rc0}{$_[0]} }) {	426	if (my $cb = $self->[1]{$_[0]}) {
417	$_ && &{$_->[0]}	427	shift;
418	&& undef $_;	428	eval { &$cb }; _self_die if $@;
419	}	429	} else {
420
421	for (@{ $self->{rcv}{$_[0]} }) {
422	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
423	&& &{$_->[0]}	430	&{ $self->[0] };
424	&& undef $_;
425	}
426
427	for (@{ $self->{any} }) {
428	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
429	&& &{$_->[0]}
430	&& undef $_;
431	}	431	}
432	};	432	};
433	_self_die if $@;	433
		434	$self
434	};	435	};
435		436
436	$self
437	};
438
439	"AnyEvent::MP::Port" eq ref $self	437	"AnyEvent::MP::Port" eq ref $self
440	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	438	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
441		439
442	while (@_) {
443	my ($match, $cb) = splice @_, 0, 2;	440	my ($tag, $cb) = splice @_, 0, 2;
444		441
445	if (!ref $match) {	442	if (defined $cb) {
446	push @{ $self->{rc0}{$match} }, [$cb];	443	$self->[1]{$tag} = $cb;
447	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
448	my ($type, @match) = @$match;
449	@match
450	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
451	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
452	} else {	444	} else {
453	push @{ $self->{any} }, [$cb, $match];	445	delete $self->[1]{$tag};
454	}	446	}
455	}	447	}
456	}	448	}
457		449
458	$port	450	$port
459	}	451	}
460		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
461	=item $closure = psub { BLOCK }	490	=item $closure = psub { BLOCK }
462		491
463	Remembers C<$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
464	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>
465	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 $SELF, sub {
		497	BLOCK } } >>.
466		498
467	This is useful when you register callbacks from C<rcv> callbacks:	499	This is useful when you register callbacks from C<rcv> callbacks:
468		500
469	rcv delayed_reply => sub {	501	rcv delayed_reply => sub {
470	my ($delay, @reply) = @_;	502	my ($delay, @reply) = @_;
…		…
494	$res	526	$res
495	}	527	}
496	}	528	}
497	}	529	}
498		530
499	=item $guard = mon $port, $cb->(@reason)	531	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
500		532
501	=item $guard = mon $port, $rcvport	533	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
502		534
503	=item $guard = mon $port	535	=item $guard = mon $port # kill $SELF when $port dies
504		536
505	=item $guard = mon $port, $rcvport, @msg	537	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
506		538
507	Monitor the given port and do something when the port is killed or	539	Monitor the given port and do something when the port is killed or
508	messages to it were lost, and optionally return a guard that can be used	540	messages to it were lost, and optionally return a guard that can be used
509	to stop monitoring again.	541	to stop monitoring again.
510
511	C<mon> effectively guarantees that, in the absence of hardware failures,
512	that after starting the monitor, either all messages sent to the port
513	will arrive, or the monitoring action will be invoked after possible
514	message loss has been detected. No messages will be lost "in between"
515	(after the first lost message no further messages will be received by the
516	port). After the monitoring action was invoked, further messages might get
517	delivered again.
518		542
519	In the first form (callback), the callback is simply called with any	543	In the first form (callback), the callback is simply called with any
520	number of C<@reason> elements (no @reason means that the port was deleted	544	number of C<@reason> elements (no @reason means that the port was deleted
521	"normally"). Note also that I<< the callback B<must> never die >>, so use	545	"normally"). Note also that I<< the callback B<must> never die >>, so use
522	C<eval> if unsure.	546	C<eval> if unsure.
523		547
524	In the second form (another port given), the other port (C<$rcvport>)	548	In the second form (another port given), the other port (C<$rcvport>)
525	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	549	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
526	"normal" kils nothing happens, while under all other conditions, the other	550	"normal" kils nothing happens, while under all other conditions, the other
527	port is killed with the same reason.	551	port is killed with the same reason.
528		552
529	The third form (kill self) is the same as the second form, except that	553	The third form (kill self) is the same as the second form, except that
530	C<$rvport> defaults to C<$SELF>.	554	C<$rvport> defaults to C<$SELF>.
531		555
532	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
533	C<snd>.	557	C<snd>.
		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.
534		561
535	As a rule of thumb, monitoring requests should always monitor a port from	562	As a rule of thumb, monitoring requests should always monitor a port from
536	a local port (or callback). The reason is that kill messages might get	563	a local port (or callback). The reason is that kill messages might get
537	lost, just like any other message. Another less obvious reason is that	564	lost, just like any other message. Another less obvious reason is that
538	even monitoring requests can get lost (for exmaple, when the connection	565	even monitoring requests can get lost (for example, when the connection
539	to the other node goes down permanently). When monitoring a port locally	566	to the other node goes down permanently). When monitoring a port locally
540	these problems do not exist.	567	these problems do not exist.
541		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
542	Example: call a given callback when C<$port> is killed.	586	Example: call a given callback when C<$port> is killed.
543		587
544	mon $port, sub { warn "port died because of <@_>\n" };	588	mon $port, sub { warn "port died because of <@_>\n" };
545		589
546	Example: kill ourselves when C<$port> is killed abnormally.	590	Example: kill ourselves when C<$port> is killed abnormally.
…		…
552	mon $port, $self => "restart";	596	mon $port, $self => "restart";
553		597
554	=cut	598	=cut
555		599
556	sub mon {	600	sub mon {
557	my ($noderef, $port) = split /#/, shift, 2;	601	my ($nodeid, $port) = split /#/, shift, 2;
558		602
559	my $node = $NODE{$noderef} \|\| add_node $noderef;	603	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
560		604
561	my $cb = @_ ? shift : $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,';
562		606
563	unless (ref $cb) {	607	unless (ref $cb) {
564	if (@_) {	608	if (@_) {
…		…
573	}	617	}
574		618
575	$node->monitor ($port, $cb);	619	$node->monitor ($port, $cb);
576		620
577	defined wantarray	621	defined wantarray
578	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	622	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
579	}	623	}
580		624
581	=item $guard = mon_guard $port, $ref, $ref...	625	=item $guard = mon_guard $port, $ref, $ref...
582		626
583	Monitors the given C<$port> and keeps the passed references. When the port	627	Monitors the given C<$port> and keeps the passed references. When the port
584	is killed, the references will be freed.	628	is killed, the references will be freed.
585		629
586	Optionally returns a guard that will stop the monitoring.	630	Optionally returns a guard that will stop the monitoring.
587		631
588	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
589	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>):
590		634
591	$port->rcv (start => sub {	635	$port->rcv (start => sub {
592	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	636	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
593	undef $timer if 0.9 < rand;	637	undef $timer if 0.9 < rand;
594	});	638	});
595	});	639	});
596		640
597	=cut	641	=cut
…		…
606		650
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 =>
…		…
625	=item $port = spawn $node, $initfunc[, @initdata]	670	=item $port = spawn $node, $initfunc[, @initdata]
626		671
627	Creates a port on the node C<$node> (which can also be a port ID, in which	672	Creates a port on the node C<$node> (which can also be a port ID, in which
628	case it's the node where that port resides).	673	case it's the node where that port resides).
629		674
630	The port ID of the newly created port is return immediately, and it is	675	The port ID of the newly created port is returned immediately, and it is
631	permissible to immediately start sending messages or monitor the port.	676	possible to immediately start sending messages or to monitor the port.
632		677
633	After the port has been created, the init function is	678	After the port has been created, the init function is called on the remote
634	called. This function must be a fully-qualified function name	679	node, in the same context as a C<rcv> callback. This function must be a
635	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	680	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
636	program, use C<::name>.	681	specify a function in the main program, use C<::name>.
637		682
638	If the function doesn't exist, then the node tries to C<require>	683	If the function doesn't exist, then the node tries to C<require>
639	the package, then the package above the package and so on (e.g.	684	the package, then the package above the package and so on (e.g.
640	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	685	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
641	exists or it runs out of package names.	686	exists or it runs out of package names.
642		687
643	The init function is then called with the newly-created port as context	688	The init function is then called with the newly-created port as context
644	object (C<$SELF>) and the C<@initdata> values as arguments.	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.
645		692
646	A common idiom is to pass your own port, monitor the spawned port, and	693	A common idiom is to pass a local port, immediately monitor the spawned
647	in the init function, monitor the original port. This two-way monitoring	694	port, and in the remote init function, immediately monitor the passed
648	ensures that both ports get cleaned up when there is a problem.	695	local port. This two-way monitoring ensures that both ports get cleaned up
		696	when there is a problem.
		697
		698	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		699	caller before C<spawn> returns (by delaying invocation when spawn is
		700	called for the local node).
649		701
650	Example: spawn a chat server port on C<$othernode>.	702	Example: spawn a chat server port on C<$othernode>.
651		703
652	# this node, executed from within a port context:	704	# this node, executed from within a port context:
653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	705	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
668		720
669	sub _spawn {	721	sub _spawn {
670	my $port = shift;	722	my $port = shift;
671	my $init = shift;	723	my $init = shift;
672		724
		725	# rcv will create the actual port
673	local $SELF = "$NODE#$port";	726	local $SELF = "$NODE#$port";
674	eval {	727	eval {
675	&{ load_func $init }	728	&{ load_func $init }
676	};	729	};
677	_self_die if $@;	730	_self_die if $@;
678	}	731	}
679		732
680	sub spawn(@) {	733	sub spawn(@) {
681	my ($noderef, undef) = split /#/, shift, 2;	734	my ($nodeid, undef) = split /#/, shift, 2;
682		735
683	my $id = "$RUNIQ." . $ID++;	736	my $id = "$RUNIQ." . $ID++;
684		737
685	$_[0] =~ /::/	738	$_[0] =~ /::/
686	or Carp::croak "spawn init function must be a fully-qualified name, caught";	739	or Carp::croak "spawn init function must be a fully-qualified name, caught";
687		740
688	($NODE{$noderef} \|\| add_node $noderef)	741	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
689	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
690		742
691	"$noderef#$id"	743	"$nodeid#$id"
692	}	744	}
693		745
694	=back	746	=item after $timeout, @msg
695		747
696	=head1 NODE MESSAGES	748	=item after $timeout, $callback
697		749
698	Nodes understand the following messages sent to them. Many of them take	750	Either sends the given message, or call the given callback, after the
699	arguments called C<@reply>, which will simply be used to compose a reply	751	specified number of seconds.
700	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
701	the remaining arguments are simply the message data.
702		752
703	While other messages exist, they are not public and subject to change.	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.
704		756
705	=over 4
706
707	=cut	757	=cut
708		758
709	=item lookup => $name, @reply	759	sub after($@) {
		760	my ($timeout, @action) = @_;
710		761
711	Replies with the port ID of the specified well-known port, or C<undef>.	762	my $t; $t = AE::timer $timeout, 0, sub {
		763	undef $t;
		764	ref $action[0]
		765	? $action[0]()
		766	: snd @action;
		767	};
		768	}
712		769
713	=item devnull => ...	770	=item cal $port, @msg, $callback[, $timeout]
714		771
715	Generic data sink/CPU heat conversion.	772	A simple form of RPC - sends a message to the given C<$port> with the
		773	given contents (C<@msg>), but adds a reply port to the message.
716		774
717	=item relay => $port, @msg	775	The reply port is created temporarily just for the purpose of receiving
		776	the reply, and will be C<kil>ed when no longer needed.
718		777
719	Simply forwards the message to the given port.	778	A reply message sent to the port is passed to the C<$callback> as-is.
720		779
721	=item eval => $string[ @reply]	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.
722		783
723	Evaluates the given string. If C<@reply> is given, then a message of the	784	If no time-out is given (or it is C<undef>), then the local port will
724	form C<@reply, $@, @evalres> is sent.	785	monitor the remote port instead, so it eventually gets cleaned-up.
725		786
726	Example: crash another node.	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.
727		790
728	snd $othernode, eval => "exit";	791	=cut
729		792
730	=item time => @reply	793	sub cal(@) {
		794	my $timeout = ref $_[-1] ? undef : pop;
		795	my $cb = pop;
731		796
732	Replies the the current node time to C<@reply>.	797	my $port = port {
		798	undef $timeout;
		799	kil $SELF;
		800	&$cb;
		801	};
733		802
734	Example: tell the current node to send the current time to C<$myport> in a	803	if (defined $timeout) {
735	C<timereply> message.	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	}
736		815
737	snd $NODE, time => $myport, timereply => 1, 2;	816	push @_, $port;
738	# => snd $myport, timereply => 1, 2, <time>	817	&snd;
		818
		819	$port
		820	}
739		821
740	=back	822	=back
741		823
742	=head1 AnyEvent::MP vs. Distributed Erlang	824	=head1 AnyEvent::MP vs. Distributed Erlang
743		825
744	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
745	== 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
746	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
747	sample:	829	sample:
748		830
749	http://www.Erlang.se/doc/programming_rules.shtml	831	http://www.erlang.se/doc/programming_rules.shtml
750	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
751	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
752	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
753		835
754	Despite the similarities, there are also some important differences:	836	Despite the similarities, there are also some important differences:
755		837
756	=over 4	838	=over 4
757		839
758	=item * Node references contain the recipe on how to contact them.	840	=item * Node IDs are arbitrary strings in AEMP.
759		841
760	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
761	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
762	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.
763		846
764	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
765	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.
766		861
767	=item * Erlang uses processes and a mailbox, AEMP does not queue.	862	=item * Erlang uses processes and a mailbox, AEMP does not queue.
768		863
769	Erlang uses processes that selctively receive messages, and therefore	864	Erlang uses processes that selectively receive messages, and therefore
770	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
771	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.
772		869
773	(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).
774		871
775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	872	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
776		873
777	Sending messages in Erlang is synchronous and blocks the process. AEMP	874	Sending messages in Erlang is synchronous and blocks the process (and
778	sends are immediate, connection establishment is handled in the	875	so does not need a queue that can overflow). AEMP sends are immediate,
779	background.	876	connection establishment is handled in the background.
780		877
781	=item * Erlang can silently lose messages, AEMP cannot.	878	=item * Erlang suffers from silent message loss, AEMP does not.
782		879
783	Erlang makes few guarantees on messages delivery - messages can get lost	880	Erlang implements few guarantees on messages delivery - messages can get
784	without any of the processes realising it (i.e. you send messages a, b,	881	lost without any of the processes realising it (i.e. you send messages a,
785	and c, and the other side only receives messages a and c).	882	b, and c, and the other side only receives messages a and c).
786		883
787	AEMP guarantees correct ordering, and the guarantee that there are no	884	AEMP guarantees correct ordering, and the guarantee that after one message
788	holes in the message sequence.	885	is lost, all following ones sent to the same port are lost as well, until
789		886	monitoring raises an error, so there are no silent "holes" in the message
790	=item * In Erlang, processes can be declared dead and later be found to be	887	sequence.
791	alive.
792
793	In Erlang it can happen that a monitored process is declared dead and
794	linked processes get killed, but later it turns out that the process is
795	still alive - and can receive messages.
796
797	In AEMP, when port monitoring detects a port as dead, then that port will
798	eventually be killed - it cannot happen that a node detects a port as dead
799	and then later sends messages to it, finding it is still alive.
800		888
801	=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.
802		890
803	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
804	ID known to other nodes for a completely different process, causing	892	known to other nodes for a completely different process, causing messages
805	messages destined for that process to end up in an unrelated process.	893	destined for that process to end up in an unrelated process.
806		894
807	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
808	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.
809		897
810	=item * Erlang uses unprotected connections, AEMP uses secure	898	=item * Erlang uses unprotected connections, AEMP uses secure
811	authentication and can use TLS.	899	authentication and can use TLS.
812		900
813	AEMP can use a proven protocol - SSL/TLS - to protect connections and	901	AEMP can use a proven protocol - TLS - to protect connections and
814	securely authenticate nodes.	902	securely authenticate nodes.
815		903
816	=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
817	communications.	905	communications.
818		906
819	The AEMP protocol, unlike the Erlang protocol, supports both	907	The AEMP protocol, unlike the Erlang protocol, supports both programming
820	language-independent text-only protocols (good for debugging) and binary,	908	language independent text-only protocols (good for debugging) and binary,
821	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.
822		911
823	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
824	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
825	protocol simple.	914	protocol simple.
826		915
827	=item * AEMP has more flexible monitoring options than Erlang.	916	=item * AEMP has more flexible monitoring options than Erlang.
828		917
829	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
…		…
832	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
833	on a per-process basis.	922	on a per-process basis.
834		923
835	=item * Erlang tries to hide remote/local connections, AEMP does not.	924	=item * Erlang tries to hide remote/local connections, AEMP does not.
836		925
837	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
838	as linking is (except linking is unreliable in Erlang).	927	same way as linking is (except linking is unreliable in Erlang).
839		928
840	In AEMP, you don't "look up" registered port names or send to named ports	929	In AEMP, you don't "look up" registered port names or send to named ports
841	that might or might not be persistent. Instead, you normally spawn a port	930	that might or might not be persistent. Instead, you normally spawn a port
842	on the remote node. The init function monitors the you, and you monitor	931	on the remote node. The init function monitors you, and you monitor the
843	the remote port. Since both monitors are local to the node, they are much	932	remote port. Since both monitors are local to the node, they are much more
844	more reliable.	933	reliable (no need for C<spawn_link>).
845		934
846	This also saves round-trips and avoids sending messages to the wrong port	935	This also saves round-trips and avoids sending messages to the wrong port
847	(hard to do in Erlang).	936	(hard to do in Erlang).
848		937
849	=back	938	=back
850		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
851	=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.
852		988
853	L<AnyEvent>.	989	L<AnyEvent>.
854		990
855	=head1 AUTHOR	991	=head1 AUTHOR
856		992

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Revision 1.105 by root, Sun Nov 8 23:58:02 2009 UTC