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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.48 by root, Thu Aug 13 02:59:42 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
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using miniports	24	# creating/using ports, the simple way
28	my $miniport = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using full ports	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, smartmatch => $cb->(@msg);
33	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
34	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
35
36	# more, smarter, matches (_any_ is exported by this module)
37	rcv $port, [child_died => $pid] => sub { ...
38	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
39		31
40	# create a port on another node	32	# create a port on another node
41	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
42		34
		35	# destroy a prot again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
43	# monitoring	39	# monitoring
44	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
45	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
46	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	};
47		51
48	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
49		53
		54	bin/aemp - stable.
50	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
51	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
52	AnyEvent::MP::Kernel - WIP
53	AnyEvent::MP::Transport - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
54		58	AnyEvent::MP::Global - stable API.
55	stay tuned.
56		59
57	=head1 DESCRIPTION	60	=head1 DESCRIPTION
58		61
59	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
60		63
61	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
62	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
63		66
64	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>
65	manual page.	68	manual page and the examples under F<eg/>.
66
67	At the moment, this module family is severly broken and underdocumented,
68	so do not use. This was uploaded mainly to reserve the CPAN namespace -
69	stay tuned!
70		69
71	=head1 CONCEPTS	70	=head1 CONCEPTS
72		71
73	=over 4	72	=over 4
74		73
75	=item port	74	=item port
76		75
77	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).
78		78
79	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
80	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
81	will not be queued.	81	anything was listening for them or not.
82		82
83	=item port id - C<noderef#portname>	83	=item port ID - C<nodeid#portname>
84		84
85	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
86	separator, and a port name (a printable string of unspecified format). An	86	separator, and a port name (a printable string of unspecified format).
87	exception is the the node port, whose ID is identical to its node
88	reference.
89		87
90	=item node	88	=item node
91		89
92	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,
93	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
94	create new ports, among other things.	92	ports.
95		93
96	Nodes are either private (single-process only), slaves (connected to a	94	Nodes are either public (have one or more listening ports) or private
97	master node only) or public nodes (connectable from unrelated nodes).	95	(no listening ports). Private nodes cannot talk to other private nodes
		96	currently.
98		97
99	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	98	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
100		99
101	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
102	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
103	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.
104		104
105	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	=item binds - C<ip:port>
106	TCP/IP, other protocols might look different).
107		106
108	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
109	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.
110		111
111	Before using an unresolved node reference in a message you first have to	112	=item seed nodes
112	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.
113		139
114	=back	140	=back
115		141
116	=head1 VARIABLES/FUNCTIONS	142	=head1 VARIABLES/FUNCTIONS
117		143
129		155
130	use AE ();	156	use AE ();
131		157
132	use base "Exporter";	158	use base "Exporter";
133		159
134	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	160	our $VERSION = 1.24;
135		161
136	our @EXPORT = qw(	162	our @EXPORT = qw(
137	NODE $NODE *SELF node_of _any_	163	NODE $NODE *SELF node_of after
138	resolve_node initialise_node	164	configure
139	snd rcv mon kil reg psub spawn	165	snd rcv mon mon_guard kil psub peval spawn cal
140	port	166	port
141	);	167	);
142		168
143	our $SELF;	169	our $SELF;
144		170
…		…
148	kil $SELF, die => $msg;	174	kil $SELF, die => $msg;
149	}	175	}
150		176
151	=item $thisnode = NODE / $NODE	177	=item $thisnode = NODE / $NODE
152		178
153	The C<NODE> function returns, and the C<$NODE> variable contains	179	The C<NODE> function returns, and the C<$NODE> variable contains, the node
154	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
155	to C<become_public> or C<become_slave>, after which all local port	181	a call to C<configure>.
156	identifiers become invalid.
157		182
158	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
159		184
160	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.
161		186
162	=item initialise_node $noderef, $seednode, $seednode...	187	=item configure $profile, key => value...
163		188
164	=item initialise_node "slave/", $master, $master...	189	=item configure key => value...
165		190
166	Before a node can talk to other nodes on the network it has to initialise	191	Before a node can talk to other nodes on the network (i.e. enter
167	itself - the minimum a node needs to know is it's own name, and optionally	192	"distributed mode") it has to configure itself - the minimum a node needs
168	it should know the noderefs of some other nodes in the network.	193	to know is its own name, and optionally it should know the addresses of
		194	some other nodes in the network to discover other nodes.
169		195
170	This function initialises a node - it must be called exactly once (or	196	This function configures a node - it must be called exactly once (or
171	never) before calling other AnyEvent::MP functions.	197	never) before calling other AnyEvent::MP functions.
172		198
173	All arguments are noderefs, which can be either resolved or unresolved.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176
177	=over 4	199	=over 4
178		200
179	=item public nodes	201	=item step 1, gathering configuration from profiles
180		202
181	For public nodes, C<$noderef> must either be a (possibly unresolved)	203	The function first looks up a profile in the aemp configuration (see the
182	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
183	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.
184		207
185	Afterwards, the node will bind itself on all endpoints and try to connect	208	The profile data is then gathered as follows:
186	to all additional C<$seednodes> that are specified. Seednodes are optional
187	and can be used to quickly bootstrap the node into an existing network.
188		209
189	=item slave nodes	210	First, all remaining key => value pairs (all of which are conveniently
		211	undocumented at the moment) will be interpreted as configuration
		212	data. Then they will be overwritten by any values specified in the global
		213	default configuration (see the F<aemp> utility), then the chain of
		214	profiles chosen by the profile name (and any C<parent> attributes).
190		215
191	When the C<$noderef> is the special string C<slave/>, then the node will	216	That means that the values specified in the profile have highest priority
192	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,
193	route most of their traffic to the master node that they attach to.	218	and can only be used to specify defaults.
194		219
195	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
196	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
197	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.
198		241
199	=back	242	=back
200		243
201	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.
202	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.
203	server.
204		246
205	Example: become a public node listening on the default node.	247	configure
206		248
207	initialise_node;	249	Example: become an anonymous node. This form is often used for commandline
		250	clients.
208		251
209	Example: become a public node, and try to contact some well-known master	252	configure nodeid => "anon/";
210	servers to become part of the network.
211		253
212	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).
213		257
214	Example: become a public node listening on port C<4041>.	258	# use the aemp commandline utility
		259	# aemp profile seed nodeid anon/ binds '*:4040'
215		260
216	initialise_node 4041;	261	# then use it
		262	configure profile => "seed";
217		263
218	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
219		266
220	initialise_node "locahost:4044";	267	# or provide a nicer-to-remember nodeid
221		268	# aemp run profile seed nodeid "$(hostname)"
222	Example: become a slave node to any of the specified master servers.
223
224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
225
226	=item $cv = resolve_node $noderef
227
228	Takes an unresolved node reference that may contain hostnames and
229	abbreviated IDs, resolves all of them and returns a resolved node
230	reference.
231
232	In addition to C<address:port> pairs allowed in resolved noderefs, the
233	following forms are supported:
234
235	=over 4
236
237	=item the empty string
238
239	An empty-string component gets resolved as if the default port (4040) was
240	specified.
241
242	=item naked port numbers (e.g. C<1234>)
243
244	These are resolved by prepending the local nodename and a colon, to be
245	further resolved.
246
247	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
248
249	These are resolved by using AnyEvent::DNS to resolve them, optionally
250	looking up SRV records for the C<aemp=4040> port, if no port was
251	specified.
252
253	=back
254		269
255	=item $SELF	270	=item $SELF
256		271
257	Contains the current port id while executing C<rcv> callbacks or C<psub>	272	Contains the current port id while executing C<rcv> callbacks or C<psub>
258	blocks.	273	blocks.
259		274
260	=item SELF, %SELF, @SELF...	275	=item *SELF, SELF, %SELF, @SELF...
261		276
262	Due to some quirks in how perl exports variables, it is impossible to	277	Due to some quirks in how perl exports variables, it is impossible to
263	just export C<$SELF>, all the symbols called C<SELF> are exported by this	278	just export C<$SELF>, all the symbols named C<SELF> are exported by this
264	module, but only C<$SELF> is currently used.	279	module, but only C<$SELF> is currently used.
265		280
266	=item snd $port, type => @data	281	=item snd $port, type => @data
267		282
268	=item snd $port, @msg	283	=item snd $port, @msg
269		284
270	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
271	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.
272	stringifies a sa port ID (such as a port object :).
273		287
274	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
275	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
276	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.
277		292
278	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
279	function: modifying any argument is not allowed and can cause many	294	function: modifying any argument (or values referenced by them) is
280	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.
281		299
282	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
283	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
284	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
285	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
286	node, anything can be passed.	304	node, anything can be passed. Best rely only on the common denominator of
		305	these.
287		306
288	=item $local_port = port	307	=item $local_port = port
289		308
290	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
291	matching port ("full port") or a single-callback port ("miniport"),	310	no callbacks set and will throw an error when it receives messages.
292	depending on how C<rcv> callbacks are bound to the object.
293		311
294	=item $port = port { my @msg = @_; $finished }	312	=item $local_port = port { my @msg = @_ }
295		313
296	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
297	matching behind it, and returns its ID. Semantically the same as creating
298	a port and calling C<rcv $port, $callback> on it.	315	creating a port and calling C<rcv $port, $callback> on it.
299		316
300	The block will be called for every message received on the port. When the	317	The block will be called for every message received on the port, with the
301	callback returns a true value its job is considered "done" and the port	318	global variable C<$SELF> set to the port ID. Runtime errors will cause the
302	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.
303		321
304	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:
305	be passed to the callback.
306		323
307	If you need the local port id in the callback, this works nicely:	324	my $port = port {
308		325	my @msg = @_;
309	my $port; $port = port {	326	...
310	snd $otherport, reply => $port;	327	kil $SELF;
311	};	328	};
312		329
313	=cut	330	=cut
314		331
315	sub rcv($@);	332	sub rcv($@);
		333
		334	sub _kilme {
		335	die "received message on port without callback";
		336	}
316		337
317	sub port(;&) {	338	sub port(;&) {
318	my $id = "$UNIQ." . $ID++;	339	my $id = "$UNIQ." . $ID++;
319	my $port = "$NODE#$id";	340	my $port = "$NODE#$id";
320		341
321	if (@_) {	342	rcv $port, shift \|\| \&_kilme;
322	rcv $port, shift;
323	} else {
324	$PORT{$id} = sub { }; # nop
325	}
326		343
327	$port	344	$port
328	}	345	}
329		346
330	=item reg $port, $name
331
332	=item reg $name
333
334	Registers the given port (or C<$SELF><<< if missing) under the name
335	C<$name>. If the name already exists it is replaced.
336
337	A port can only be registered under one well known name.
338
339	A port automatically becomes unregistered when it is killed.
340
341	=cut
342
343	sub reg(@) {
344	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
345
346	$REG{$_[0]} = $port;
347	}
348
349	=item rcv $port, $callback->(@msg)	347	=item rcv $local_port, $callback->(@msg)
350		348
351	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
352	one if required).	350	remove the default callback: use C<sub { }> to disable it, or better
353		351	C<kil> the port when it is no longer needed.
354	=item rcv $port, tagstring => $callback->(@msg), ...
355
356	=item rcv $port, $smartmatch => $callback->(@msg), ...
357
358	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
359
360	Register callbacks to be called on matching messages on the given full
361	port (after converting it to one if required) and return the port.
362
363	The callback has to return a true value when its work is done, after
364	which is will be removed, or a false value in which case it will stay
365	registered.
366		352
367	The global C<$SELF> (exported by this module) contains C<$port> while	353	The global C<$SELF> (exported by this module) contains C<$port> while
368	executing the callback.	354	executing the callback. Runtime errors during callback execution will
		355	result in the port being C<kil>ed.
369		356
370	Runtime errors during callback execution will result in the port being	357	The default callback received all messages not matched by a more specific
371	C<kil>ed.	358	C<tag> match.
372		359
373	If the match is an array reference, then it will be matched against the	360	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
374	first elements of the message, otherwise only the first element is being
375	matched.
376		361
377	Any element in the match that is specified as C<_any_> (a function	362	Register (or replace) callbacks to be called on messages starting with the
378	exported by this module) matches any single element of the message.	363	given tag on the given port (and return the port), or unregister it (when
		364	C<$callback> is C<$undef> or missing). There can only be one callback
		365	registered for each tag.
379		366
380	While not required, it is highly recommended that the first matching	367	The original message will be passed to the callback, after the first
381	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
382	also the most efficient match (by far).	369	environment as the default callback (see above).
383		370
384	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.
385		372
386	my $port = rcv port,	373	my $port = rcv port,
387	msg1 => sub { ...; 0 },	374	msg1 => sub { ... },
388	msg2 => sub { ...; 0 },	375	msg2 => sub { ... },
389	;	376	;
390		377
391	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
392	in one go:	379	in one go:
393		380
394	snd $otherport, reply =>	381	snd $otherport, reply =>
395	rcv port,	382	rcv port,
396	msg1 => sub { ...; 0 },	383	msg1 => sub { ... },
397	...	384	...
398	;	385	;
399		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, $otherport;
		394	};
		395
400	=cut	396	=cut
401		397
402	sub rcv($@) {	398	sub rcv($@) {
403	my $port = shift;	399	my $port = shift;
404	my ($noderef, $portid) = split /#/, $port, 2;	400	my ($nodeid, $portid) = split /#/, $port, 2;
405		401
406	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	402	$NODE{$nodeid} == $NODE{""}
407	or Carp::croak "$port: rcv can only be called on local ports, caught";	403	or Carp::croak "$port: rcv can only be called on local ports, caught";
408		404
409	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 {
410	my $cb = shift;	413	my $cb = shift;
411	delete $PORT_DATA{$portid};
412	$PORT{$portid} = sub {	414	$PORT{$portid} = sub {
413	local $SELF = $port;	415	local $SELF = $port;
414	eval {	416	eval { &$cb }; _self_die if $@;
415	&$cb	417	};
416	and kil $port;
417	};	418	}
418	_self_die if $@;	419	} elsif (defined $_[0]) {
419	};
420	} else {
421	my $self = $PORT_DATA{$portid} \|\|= do {	420	my $self = $PORT_DATA{$portid} \|\|= do {
422	my $self = bless {	421	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
423	id => $port,
424	}, "AnyEvent::MP::Port";
425		422
426	$PORT{$portid} = sub {	423	$PORT{$portid} = sub {
427	local $SELF = $port;	424	local $SELF = $port;
428		425
429	eval {
430	for (@{ $self->{rc0}{$_[0]} }) {	426	if (my $cb = $self->[1]{$_[0]}) {
431	$_ && &{$_->[0]}	427	shift;
432	&& undef $_;	428	eval { &$cb }; _self_die if $@;
433	}	429	} else {
434
435	for (@{ $self->{rcv}{$_[0]} }) {
436	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
437	&& &{$_->[0]}	430	&{ $self->[0] };
438	&& undef $_;
439	}
440
441	for (@{ $self->{any} }) {
442	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
443	&& &{$_->[0]}
444	&& undef $_;
445	}	431	}
446	};	432	};
447	_self_die if $@;	433
		434	$self
448	};	435	};
449		436
450	$self
451	};
452
453	"AnyEvent::MP::Port" eq ref $self	437	"AnyEvent::MP::Port" eq ref $self
454	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	438	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
455		439
456	while (@_) {
457	my ($match, $cb) = splice @_, 0, 2;	440	my ($tag, $cb) = splice @_, 0, 2;
458		441
459	if (!ref $match) {	442	if (defined $cb) {
460	push @{ $self->{rc0}{$match} }, [$cb];	443	$self->[1]{$tag} = $cb;
461	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
462	my ($type, @match) = @$match;
463	@match
464	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
465	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
466	} else {	444	} else {
467	push @{ $self->{any} }, [$cb, $match];	445	delete $self->[1]{$tag};
468	}	446	}
469	}	447	}
470	}	448	}
471		449
472	$port	450	$port
473	}	451	}
474		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
475	=item $closure = psub { BLOCK }	490	=item $closure = psub { BLOCK }
476		491
477	Remembers C<$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
478	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>
479	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 $SELF, sub {
		497	BLOCK } } >>.
480		498
481	This is useful when you register callbacks from C<rcv> callbacks:	499	This is useful when you register callbacks from C<rcv> callbacks:
482		500
483	rcv delayed_reply => sub {	501	rcv delayed_reply => sub {
484	my ($delay, @reply) = @_;	502	my ($delay, @reply) = @_;
…		…
508	$res	526	$res
509	}	527	}
510	}	528	}
511	}	529	}
512		530
513	=item $guard = mon $port, $cb->(@reason)	531	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
514		532
515	=item $guard = mon $port, $rcvport	533	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
516		534
517	=item $guard = mon $port	535	=item $guard = mon $port # kill $SELF when $port dies
518		536
519	=item $guard = mon $port, $rcvport, @msg	537	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
520		538
521	Monitor the given port and do something when the port is killed or	539	Monitor the given port and do something when the port is killed or
522	messages to it were lost, and optionally return a guard that can be used	540	messages to it were lost, and optionally return a guard that can be used
523	to stop monitoring again.	541	to stop monitoring again.
524
525	C<mon> effectively guarantees that, in the absence of hardware failures,
526	that after starting the monitor, either all messages sent to the port
527	will arrive, or the monitoring action will be invoked after possible
528	message loss has been detected. No messages will be lost "in between"
529	(after the first lost message no further messages will be received by the
530	port). After the monitoring action was invoked, further messages might get
531	delivered again.
532		542
533	In the first form (callback), the callback is simply called with any	543	In the first form (callback), the callback is simply called with any
534	number of C<@reason> elements (no @reason means that the port was deleted	544	number of C<@reason> elements (no @reason means that the port was deleted
535	"normally"). Note also that I<< the callback B<must> never die >>, so use	545	"normally"). Note also that I<< the callback B<must> never die >>, so use
536	C<eval> if unsure.	546	C<eval> if unsure.
537		547
538	In the second form (another port given), the other port (C<$rcvport>)	548	In the second form (another port given), the other port (C<$rcvport>)
539	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	549	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
540	"normal" kils nothing happens, while under all other conditions, the other	550	"normal" kils nothing happens, while under all other conditions, the other
541	port is killed with the same reason.	551	port is killed with the same reason.
542		552
543	The third form (kill self) is the same as the second form, except that	553	The third form (kill self) is the same as the second form, except that
544	C<$rvport> defaults to C<$SELF>.	554	C<$rvport> defaults to C<$SELF>.
545		555
546	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
547	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.
548		561
549	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
550	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
551	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
552	even monitoring requests can get lost (for exmaple, when the connection	565	even monitoring requests can get lost (for example, when the connection
553	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
554	these problems do not exist.	567	these problems do not exist.
555		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
556	Example: call a given callback when C<$port> is killed.	586	Example: call a given callback when C<$port> is killed.
557		587
558	mon $port, sub { warn "port died because of <@_>\n" };	588	mon $port, sub { warn "port died because of <@_>\n" };
559		589
560	Example: kill ourselves when C<$port> is killed abnormally.	590	Example: kill ourselves when C<$port> is killed abnormally.
…		…
566	mon $port, $self => "restart";	596	mon $port, $self => "restart";
567		597
568	=cut	598	=cut
569		599
570	sub mon {	600	sub mon {
571	my ($noderef, $port) = split /#/, shift, 2;	601	my ($nodeid, $port) = split /#/, shift, 2;
572		602
573	my $node = $NODE{$noderef} \|\| add_node $noderef;	603	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
574		604
575	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,';
576		606
577	unless (ref $cb) {	607	unless (ref $cb) {
578	if (@_) {	608	if (@_) {
…		…
587	}	617	}
588		618
589	$node->monitor ($port, $cb);	619	$node->monitor ($port, $cb);
590		620
591	defined wantarray	621	defined wantarray
592	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	622	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
593	}	623	}
594		624
595	=item $guard = mon_guard $port, $ref, $ref...	625	=item $guard = mon_guard $port, $ref, $ref...
596		626
597	Monitors the given C<$port> and keeps the passed references. When the port	627	Monitors the given C<$port> and keeps the passed references. When the port
598	is killed, the references will be freed.	628	is killed, the references will be freed.
599		629
600	Optionally returns a guard that will stop the monitoring.	630	Optionally returns a guard that will stop the monitoring.
601		631
602	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
603	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>):
604		634
605	$port->rcv (start => sub {	635	$port->rcv (start => sub {
606	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	636	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
607	undef $timer if 0.9 < rand;	637	undef $timer if 0.9 < rand;
608	});	638	});
609	});	639	});
610		640
611	=cut	641	=cut
…		…
620		650
621	=item kil $port[, @reason]	651	=item kil $port[, @reason]
622		652
623	Kill the specified port with the given C<@reason>.	653	Kill the specified port with the given C<@reason>.
624		654
625	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
626	ports will not be kileld, or even notified).	656	monitoring other ports will not necessarily die because a port dies
		657	"normally").
627		658
628	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
629	C<mon>, see below).	660	C<mon>, see above).
630		661
631	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
632	will be reported as reason C<< die => $@ >>.	663	will be reported as reason C<< die => $@ >>.
633		664
634	Transport/communication errors are reported as C<< transport_error =>	665	Transport/communication errors are reported as C<< transport_error =>
…		…
639	=item $port = spawn $node, $initfunc[, @initdata]	670	=item $port = spawn $node, $initfunc[, @initdata]
640		671
641	Creates a port on the node C<$node> (which can also be a port ID, in which	672	Creates a port on the node C<$node> (which can also be a port ID, in which
642	case it's the node where that port resides).	673	case it's the node where that port resides).
643		674
644	The port ID of the newly created port is return immediately, and it is	675	The port ID of the newly created port is returned immediately, and it is
645	permissible to immediately start sending messages or monitor the port.	676	possible to immediately start sending messages or to monitor the port.
646		677
647	After the port has been created, the init function is	678	After the port has been created, the init function is called on the remote
648	called. This function must be a fully-qualified function name	679	node, in the same context as a C<rcv> callback. This function must be a
649	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	680	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
650	program, use C<::name>.	681	specify a function in the main program, use C<::name>.
651		682
652	If the function doesn't exist, then the node tries to C<require>	683	If the function doesn't exist, then the node tries to C<require>
653	the package, then the package above the package and so on (e.g.	684	the package, then the package above the package and so on (e.g.
654	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	685	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
655	exists or it runs out of package names.	686	exists or it runs out of package names.
656		687
657	The init function is then called with the newly-created port as context	688	The init function is then called with the newly-created port as context
658	object (C<$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.
659		692
660	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
661	in the init function, monitor the original port. This two-way monitoring	694	port, and in the remote init function, immediately monitor the passed
662	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<$initfunc> has no visible effects on the
		699	caller before C<spawn> returns (by delaying invocation when spawn is
		700	called for the local node).
663		701
664	Example: spawn a chat server port on C<$othernode>.	702	Example: spawn a chat server port on C<$othernode>.
665		703
666	# this node, executed from within a port context:	704	# this node, executed from within a port context:
667	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	705	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
682		720
683	sub _spawn {	721	sub _spawn {
684	my $port = shift;	722	my $port = shift;
685	my $init = shift;	723	my $init = shift;
686		724
		725	# rcv will create the actual port
687	local $SELF = "$NODE#$port";	726	local $SELF = "$NODE#$port";
688	eval {	727	eval {
689	&{ load_func $init }	728	&{ load_func $init }
690	};	729	};
691	_self_die if $@;	730	_self_die if $@;
692	}	731	}
693		732
694	sub spawn(@) {	733	sub spawn(@) {
695	my ($noderef, undef) = split /#/, shift, 2;	734	my ($nodeid, undef) = split /#/, shift, 2;
696		735
697	my $id = "$RUNIQ." . $ID++;	736	my $id = "$RUNIQ." . $ID++;
698		737
699	$_[0] =~ /::/	738	$_[0] =~ /::/
700	or Carp::croak "spawn init function must be a fully-qualified name, caught";	739	or Carp::croak "spawn init function must be a fully-qualified name, caught";
701		740
702	($NODE{$noderef} \|\| add_node $noderef)	741	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
703	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
704		742
705	"$noderef#$id"	743	"$nodeid#$id"
706	}	744	}
707		745
708	=back	746	=item after $timeout, @msg
709		747
710	=head1 NODE MESSAGES	748	=item after $timeout, $callback
711		749
712	Nodes understand the following messages sent to them. Many of them take	750	Either sends the given message, or call the given callback, after the
713	arguments called C<@reply>, which will simply be used to compose a reply	751	specified number of seconds.
714	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
715	the remaining arguments are simply the message data.
716		752
717	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.
718		756
719	=over 4
720
721	=cut	757	=cut
722		758
723	=item lookup => $name, @reply	759	sub after($@) {
		760	my ($timeout, @action) = @_;
724		761
725	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	}
726		769
727	=item devnull => ...	770	=item cal $port, @msg, $callback[, $timeout]
728		771
729	Generic data sink/CPU heat conversion.	772	A simple form of RPC - sends a message to the given C<$port> with the
		773	given contents (C<@msg>), but adds a reply port to the message.
730		774
731	=item relay => $port, @msg	775	The reply port is created temporarily just for the purpose of receiving
		776	the reply, and will be C<kil>ed when no longer needed.
732		777
733	Simply forwards the message to the given port.	778	A reply message sent to the port is passed to the C<$callback> as-is.
734		779
735	=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.
736		783
737	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
738	form C<@reply, $@, @evalres> is sent.	785	monitor the remote port instead, so it eventually gets cleaned-up.
739		786
740	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.
741		790
742	snd $othernode, eval => "exit";	791	=cut
743		792
744	=item time => @reply	793	sub cal(@) {
		794	my $timeout = ref $_[-1] ? undef : pop;
		795	my $cb = pop;
745		796
746	Replies the the current node time to C<@reply>.	797	my $port = port {
		798	undef $timeout;
		799	kil $SELF;
		800	&$cb;
		801	};
747		802
748	Example: tell the current node to send the current time to C<$myport> in a	803	if (defined $timeout) {
749	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	}
750		815
751	snd $NODE, time => $myport, timereply => 1, 2;	816	push @_, $port;
752	# => snd $myport, timereply => 1, 2, <time>	817	&snd;
		818
		819	$port
		820	}
753		821
754	=back	822	=back
755		823
756	=head1 AnyEvent::MP vs. Distributed Erlang	824	=head1 AnyEvent::MP vs. Distributed Erlang
757		825
758	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
759	== 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
760	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
761	sample:	829	sample:
762		830
763	http://www.Erlang.se/doc/programming_rules.shtml	831	http://www.erlang.se/doc/programming_rules.shtml
764	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
765	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
766	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
767		835
768	Despite the similarities, there are also some important differences:	836	Despite the similarities, there are also some important differences:
769		837
770	=over 4	838	=over 4
771		839
772	=item * Node references contain the recipe on how to contact them.	840	=item * Node IDs are arbitrary strings in AEMP.
773		841
774	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
775	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
776	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.
777		846
778	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
779	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.
780		861
781	=item * Erlang uses processes and a mailbox, AEMP does not queue.	862	=item * Erlang uses processes and a mailbox, AEMP does not queue.
782		863
783	Erlang uses processes that selctively receive messages, and therefore	864	Erlang uses processes that selectively receive messages, and therefore
784	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
785	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.
786		869
787	(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).
788		871
789	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	872	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
790		873
791	Sending messages in Erlang is synchronous and blocks the process. AEMP	874	Sending messages in Erlang is synchronous and blocks the process (and
792	sends are immediate, connection establishment is handled in the	875	so does not need a queue that can overflow). AEMP sends are immediate,
793	background.	876	connection establishment is handled in the background.
794		877
795	=item * Erlang can silently lose messages, AEMP cannot.	878	=item * Erlang suffers from silent message loss, AEMP does not.
796		879
797	Erlang makes few guarantees on messages delivery - messages can get lost	880	Erlang implements few guarantees on messages delivery - messages can get
798	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,
799	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).
800		883
801	AEMP guarantees correct ordering, and the guarantee that there are no	884	AEMP guarantees correct ordering, and the guarantee that after one message
802	holes in the message sequence.	885	is lost, all following ones sent to the same port are lost as well, until
803		886	monitoring raises an error, so there are no silent "holes" in the message
804	=item * In Erlang, processes can be declared dead and later be found to be	887	sequence.
805	alive.
806
807	In Erlang it can happen that a monitored process is declared dead and
808	linked processes get killed, but later it turns out that the process is
809	still alive - and can receive messages.
810
811	In AEMP, when port monitoring detects a port as dead, then that port will
812	eventually be killed - it cannot happen that a node detects a port as dead
813	and then later sends messages to it, finding it is still alive.
814		888
815	=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.
816		890
817	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
818	ID known to other nodes for a completely different process, causing	892	known to other nodes for a completely different process, causing messages
819	messages destined for that process to end up in an unrelated process.	893	destined for that process to end up in an unrelated process.
820		894
821	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
822	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.
823		897
824	=item * Erlang uses unprotected connections, AEMP uses secure	898	=item * Erlang uses unprotected connections, AEMP uses secure
825	authentication and can use TLS.	899	authentication and can use TLS.
826		900
827	AEMP can use a proven protocol - SSL/TLS - to protect connections and	901	AEMP can use a proven protocol - TLS - to protect connections and
828	securely authenticate nodes.	902	securely authenticate nodes.
829		903
830	=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
831	communications.	905	communications.
832		906
833	The AEMP protocol, unlike the Erlang protocol, supports both	907	The AEMP protocol, unlike the Erlang protocol, supports both programming
834	language-independent text-only protocols (good for debugging) and binary,	908	language independent text-only protocols (good for debugging) and binary,
835	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.
836		911
837	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
838	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
839	protocol simple.	914	protocol simple.
840		915
841	=item * AEMP has more flexible monitoring options than Erlang.	916	=item * AEMP has more flexible monitoring options than Erlang.
842		917
843	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
…		…
846	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
847	on a per-process basis.	922	on a per-process basis.
848		923
849	=item * Erlang tries to hide remote/local connections, AEMP does not.	924	=item * Erlang tries to hide remote/local connections, AEMP does not.
850		925
851	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
852	as linking is (except linking is unreliable in Erlang).	927	same way as linking is (except linking is unreliable in Erlang).
853		928
854	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
855	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
856	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
857	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
858	more reliable.	933	reliable (no need for C<spawn_link>).
859		934
860	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
861	(hard to do in Erlang).	936	(hard to do in Erlang).
862		937
863	=back	938	=back
864		939
865	=head1 RATIONALE	940	=head1 RATIONALE
866		941
867	=over 4	942	=over 4
868		943
869	=item Why strings for ports and noderefs, why not objects?	944	=item Why strings for port and node IDs, why not objects?
870		945
871	We considered "objects", but found that the actual number of methods	946	We considered "objects", but found that the actual number of methods
872	thatc an be called are very low. Since port IDs and noderefs travel over	947	that can be called are quite low. Since port and node IDs travel over
873	the network frequently, the serialising/deserialising would add lots of	948	the network frequently, the serialising/deserialising would add lots of
874	overhead, as well as having to keep a proxy object.	949	overhead, as well as having to keep a proxy object everywhere.
875		950
876	Strings can easily be printed, easily serialised etc. and need no special	951	Strings can easily be printed, easily serialised etc. and need no special
877	procedures to be "valid".	952	procedures to be "valid".
878		953
879	And a a miniport consists of a single closure stored in a global hash - it	954	And as a result, a miniport consists of a single closure stored in a
880	can't become much cheaper.	955	global hash - it can't become much cheaper.
881		956
882	=item Why favour JSON, why not real serialising format such as Storable?	957	=item Why favour JSON, why not a real serialising format such as Storable?
883		958
884	In fact, any AnyEvent::MP node will happily accept Storable as framing	959	In fact, any AnyEvent::MP node will happily accept Storable as framing
885	format, but currently there is no way to make a node use Storable by	960	format, but currently there is no way to make a node use Storable by
886	default.	961	default (although all nodes will accept it).
887		962
888	The default framing protocol is JSON because a) JSON::XS is many times	963	The default framing protocol is JSON because a) JSON::XS is many times
889	faster for small messages and b) most importantly, after years of	964	faster for small messages and b) most importantly, after years of
890	experience we found that object serialisation is causing more problems	965	experience we found that object serialisation is causing more problems
891	than it gains: Just like function calls, objects simply do not travel	966	than it solves: Just like function calls, objects simply do not travel
892	easily over the network, mostly because they will always be a copy, so you	967	easily over the network, mostly because they will always be a copy, so you
893	always have to re-think your design.	968	always have to re-think your design.
894		969
895	Keeping your messages simple, concentrating on data structures rather than	970	Keeping your messages simple, concentrating on data structures rather than
896	objects, will keep your messages clean, tidy and efficient.	971	objects, will keep your messages clean, tidy and efficient.
897		972
898	=back	973	=back
899		974
900	=head1 SEE ALSO	975	=head1 SEE ALSO
901		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.
		988
902	L<AnyEvent>.	989	L<AnyEvent>.
903		990
904	=head1 AUTHOR	991	=head1 AUTHOR
905		992
906	Marc Lehmann <schmorp@schmorp.de>	993	Marc Lehmann <schmorp@schmorp.de>

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