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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.37 by root, Fri Aug 7 16:47:23 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
		12	$SELF # receiving/own port id in rcv callbacks
		13
		14	# initialise the node so it can send/receive messages
		15	configure;
		16
		17	# ports are message destinations
		18
		19	# sending messages
13	snd $port, type => data...;	20	snd $port, type => data...;
		21	snd $port, @msg;
		22	snd @msg_with_first_element_being_a_port;
14		23
15	$SELF # receiving/own port id in rcv callbacks	24	# creating/using ports, the simple way
		25	my $simple_port = port { my @msg = @_ };
16		26
17	rcv $port, smartmatch => $cb->($port, @msg);	27	# creating/using ports, tagged message matching
18		28	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
21	rcv $port1, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
22	snd $port2, ping => $port1;
23		31
24	# more, smarter, matches (_any_ is exported by this module)	32	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	33	my $port = spawn $node, $initfunc, @initdata;
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	34
		35	# destroy a prot again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
27		38
28	# monitoring	39	# monitoring
29	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
30	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
31	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.
32		59
33	=head1 DESCRIPTION	60	=head1 DESCRIPTION
34		61
35	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
36		63
37	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
38	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
39		66
40	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>
41	manual page.	68	manual page and the examples under F<eg/>.
42
43	At the moment, this module family is severly broken and underdocumented,
44	so do not use. This was uploaded mainly to reserve the CPAN namespace -
45	stay tuned! The basic API should be finished, however.
46		69
47	=head1 CONCEPTS	70	=head1 CONCEPTS
48		71
49	=over 4	72	=over 4
50		73
51	=item port	74	=item port
52		75
53	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).
54		78
55	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
56	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
57	will not be queued.	81	anything was listening for them or not.
58		82
59	=item port id - C<noderef#portname>	83	=item port ID - C<nodeid#portname>
60		84
61	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
62	separator, and a port name (a printable string of unspecified format). An	86	separator, and a port name (a printable string of unspecified format).
63	exception is the the node port, whose ID is identical to its node
64	reference.
65		87
66	=item node	88	=item node
67		89
68	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,
69	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
70	create new ports, among other things.	92	ports.
71		93
72	Nodes are either private (single-process only), slaves (connected to a	94	Nodes are either public (have one or more listening ports) or private
73	master node only) or public nodes (connectable from unrelated nodes).	95	(no listening ports). Private nodes cannot talk to other private nodes
		96	currently.
74		97
75	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	98	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
76		99
77	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
78	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
79	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.
80		104
81	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	=item binds - C<ip:port>
82	TCP/IP, other protocols might look different).
83		106
84	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
85	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.
86		111
87	Before using an unresolved node reference in a message you first have to	112	=item seed nodes
88	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.
89		139
90	=back	140	=back
91		141
92	=head1 VARIABLES/FUNCTIONS	142	=head1 VARIABLES/FUNCTIONS
93		143
95		145
96	=cut	146	=cut
97		147
98	package AnyEvent::MP;	148	package AnyEvent::MP;
99		149
100	use AnyEvent::MP::Base;	150	use AnyEvent::MP::Kernel;
101		151
102	use common::sense;	152	use common::sense;
103		153
104	use Carp ();	154	use Carp ();
105		155
106	use AE ();	156	use AE ();
107		157
108	use base "Exporter";	158	use base "Exporter";
109		159
110	our $VERSION = '0.1';	160	our $VERSION = 1.23;
		161
111	our @EXPORT = qw(	162	our @EXPORT = qw(
112	NODE $NODE *SELF node_of _any_	163	NODE $NODE *SELF node_of after
113	resolve_node initialise_node	164	configure
114	snd rcv mon kil reg psub	165	snd rcv mon mon_guard kil psub peval spawn cal
115	port	166	port
116	);	167	);
117		168
118	our $SELF;	169	our $SELF;
119		170
…		…
123	kil $SELF, die => $msg;	174	kil $SELF, die => $msg;
124	}	175	}
125		176
126	=item $thisnode = NODE / $NODE	177	=item $thisnode = NODE / $NODE
127		178
128	The C<NODE> function returns, and the C<$NODE> variable contains	179	The C<NODE> function returns, and the C<$NODE> variable contains, the node
129	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
130	to C<become_public> or C<become_slave>, after which all local port	181	a call to C<configure>.
131	identifiers become invalid.
132		182
133	=item $noderef = node_of $port	183	=item $nodeid = node_of $port
134		184
135	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.
136		186
137	=item initialise_node $noderef, $seednode, $seednode...	187	=item configure $profile, key => value...
138		188
139	=item initialise_node "slave/", $master, $master...	189	=item configure key => value...
140		190
141	Before a node can talk to other nodes on the network it has to initialise	191	Before a node can talk to other nodes on the network (i.e. enter
142	itself - the minimum a node needs to know is it's own name, and optionally	192	"distributed mode") it has to configure itself - the minimum a node needs
143	it should know the noderefs of some other nodes in the network.	193	to know is its own name, and optionally it should know the addresses of
		194	some other nodes in the network to discover other nodes.
144		195
145	This function initialises a node - it must be called exactly once (or	196	This function configures a node - it must be called exactly once (or
146	never) before calling other AnyEvent::MP functions.	197	never) before calling other AnyEvent::MP functions.
147		198
148	All arguments are noderefs, which can be either resolved or unresolved.
149
150	There are two types of networked nodes, public nodes and slave nodes:
151
152	=over 4	199	=over 4
153		200
154	=item public nodes	201	=item step 1, gathering configuration from profiles
155		202
156	For public nodes, C<$noderef> must either be a (possibly unresolved)	203	The function first looks up a profile in the aemp configuration (see the
157	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
158	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.
159		207
160	Afterwards, the node will bind itself on all endpoints and try to connect	208	The profile data is then gathered as follows:
161	to all additional C<$seednodes> that are specified. Seednodes are optional
162	and can be used to quickly bootstrap the node into an existing network.
163		209
164	=item slave nodes	210	First, all remaining key => value pairs (all of which are conveniently
		211	undocumented at the moment) will be interpreted as configuration
		212	data. Then they will be overwritten by any values specified in the global
		213	default configuration (see the F<aemp> utility), then the chain of
		214	profiles chosen by the profile name (and any C<parent> attributes).
165		215
166	When the C<$noderef> is the special string C<slave/>, then the node will	216	That means that the values specified in the profile have highest priority
167	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,
168	route most of their traffic to the master node that they attach to.	218	and can only be used to specify defaults.
169		219
170	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
171	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
172	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.
173		241
174	=back	242	=back
175		243
176	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.
177	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.
178	server.
179		246
180	Example: become a public node listening on the default node.	247	configure
181		248
182	initialise_node;	249	Example: become an anonymous node. This form is often used for commandline
		250	clients.
183		251
184	Example: become a public node, and try to contact some well-known master	252	configure nodeid => "anon/";
185	servers to become part of the network.
186		253
187	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).
188		257
189	Example: become a public node listening on port C<4041>.	258	# use the aemp commandline utility
		259	# aemp profile seed nodeid anon/ binds '*:4040'
190		260
191	initialise_node 4041;	261	# then use it
		262	configure profile => "seed";
192		263
193	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
194		266
195	initialise_node "locahost:4044";	267	# or provide a nicer-to-remember nodeid
196		268	# aemp run profile seed nodeid "$(hostname)"
197	Example: become a slave node to any of the specified master servers.
198
199	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
200
201	=item $cv = resolve_node $noderef
202
203	Takes an unresolved node reference that may contain hostnames and
204	abbreviated IDs, resolves all of them and returns a resolved node
205	reference.
206
207	In addition to C<address:port> pairs allowed in resolved noderefs, the
208	following forms are supported:
209
210	=over 4
211
212	=item the empty string
213
214	An empty-string component gets resolved as if the default port (4040) was
215	specified.
216
217	=item naked port numbers (e.g. C<1234>)
218
219	These are resolved by prepending the local nodename and a colon, to be
220	further resolved.
221
222	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
223
224	These are resolved by using AnyEvent::DNS to resolve them, optionally
225	looking up SRV records for the C<aemp=4040> port, if no port was
226	specified.
227
228	=back
229		269
230	=item $SELF	270	=item $SELF
231		271
232	Contains the current port id while executing C<rcv> callbacks or C<psub>	272	Contains the current port id while executing C<rcv> callbacks or C<psub>
233	blocks.	273	blocks.
234		274
235	=item SELF, %SELF, @SELF...	275	=item *SELF, SELF, %SELF, @SELF...
236		276
237	Due to some quirks in how perl exports variables, it is impossible to	277	Due to some quirks in how perl exports variables, it is impossible to
238	just export C<$SELF>, all the symbols called C<SELF> are exported by this	278	just export C<$SELF>, all the symbols named C<SELF> are exported by this
239	module, but only C<$SELF> is currently used.	279	module, but only C<$SELF> is currently used.
240		280
241	=item snd $port, type => @data	281	=item snd $port, type => @data
242		282
243	=item snd $port, @msg	283	=item snd $port, @msg
244		284
245	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
246	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.
247	stringifies a sa port ID (such as a port object :).
248		287
249	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
250	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
251	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.
252		292
253	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
254	function: modifying any argument is not allowed and can cause many	294	function: modifying any argument (or values referenced by them) is
255	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.
256		299
257	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
258	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
259	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
260	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
261	node, anything can be passed.	304	node, anything can be passed. Best rely only on the common denominator of
		305	these.
262		306
263	=item $local_port = port	307	=item $local_port = port
264		308
265	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
266	matching port ("full port") or a single-callback port ("miniport"),	310	no callbacks set and will throw an error when it receives messages.
267	depending on how C<rcv> callbacks are bound to the object.
268		311
269	=item $port = port { my @msg = @_; $finished }	312	=item $local_port = port { my @msg = @_ }
270		313
271	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
272	matching behind it, and returns its ID. Semantically the same as creating
273	a port and calling C<rcv $port, $callback> on it.	315	creating a port and calling C<rcv $port, $callback> on it.
274		316
275	The block will be called for every message received on the port. When the	317	The block will be called for every message received on the port, with the
276	callback returns a true value its job is considered "done" and the port	318	global variable C<$SELF> set to the port ID. Runtime errors will cause the
277	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.
278		321
279	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:
280	be passed to the callback.
281		323
282	If you need the local port id in the callback, this works nicely:	324	my $port = port {
283		325	my @msg = @_;
284	my $port; $port = port {	326	...
285	snd $otherport, reply => $port;	327	kil $SELF;
286	};	328	};
287		329
288	=cut	330	=cut
289		331
290	sub rcv($@);	332	sub rcv($@);
		333
		334	sub _kilme {
		335	die "received message on port without callback";
		336	}
291		337
292	sub port(;&) {	338	sub port(;&) {
293	my $id = "$UNIQ." . $ID++;	339	my $id = "$UNIQ." . $ID++;
294	my $port = "$NODE#$id";	340	my $port = "$NODE#$id";
295		341
296	if (@_) {	342	rcv $port, shift \|\| \&_kilme;
297	rcv $port, shift;
298	} else {
299	$PORT{$id} = sub { }; # nop
300	}
301		343
302	$port	344	$port
303	}	345	}
304		346
305	=item reg $port, $name
306
307	=item reg $name
308
309	Registers the given port (or C<$SELF><<< if missing) under the name
310	C<$name>. If the name already exists it is replaced.
311
312	A port can only be registered under one well known name.
313
314	A port automatically becomes unregistered when it is killed.
315
316	=cut
317
318	sub reg(@) {
319	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
320
321	$REG{$_[0]} = $port;
322	}
323
324	=item rcv $port, $callback->(@msg)	347	=item rcv $local_port, $callback->(@msg)
325		348
326	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
327	one if required).	350	remove the default callback: use C<sub { }> to disable it, or better
328		351	C<kil> the port when it is no longer needed.
329	=item rcv $port, tagstring => $callback->(@msg), ...
330
331	=item rcv $port, $smartmatch => $callback->(@msg), ...
332
333	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
334
335	Register callbacks to be called on matching messages on the given full
336	port (after converting it to one if required) and return the port.
337
338	The callback has to return a true value when its work is done, after
339	which is will be removed, or a false value in which case it will stay
340	registered.
341		352
342	The global C<$SELF> (exported by this module) contains C<$port> while	353	The global C<$SELF> (exported by this module) contains C<$port> while
343	executing the callback.	354	executing the callback. Runtime errors during callback execution will
		355	result in the port being C<kil>ed.
344		356
345	Runtime errors wdurign callback execution will result in the port being	357	The default callback received all messages not matched by a more specific
346	C<kil>ed.	358	C<tag> match.
347		359
348	If the match is an array reference, then it will be matched against the	360	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
349	first elements of the message, otherwise only the first element is being
350	matched.
351		361
352	Any element in the match that is specified as C<_any_> (a function	362	Register (or replace) callbacks to be called on messages starting with the
353	exported by this module) matches any single element of the message.	363	given tag on the given port (and return the port), or unregister it (when
		364	C<$callback> is C<$undef> or missing). There can only be one callback
		365	registered for each tag.
354		366
355	While not required, it is highly recommended that the first matching	367	The original message will be passed to the callback, after the first
356	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
357	also the most efficient match (by far).	369	environment as the default callback (see above).
358		370
359	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.
360		372
361	my $port = rcv port,	373	my $port = rcv port,
362	msg1 => sub { ...; 0 },	374	msg1 => sub { ... },
363	msg2 => sub { ...; 0 },	375	msg2 => sub { ... },
364	;	376	;
365		377
366	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
367	in one go:	379	in one go:
368		380
369	snd $otherport, reply =>	381	snd $otherport, reply =>
370	rcv port,	382	rcv port,
371	msg1 => sub { ...; 0 },	383	msg1 => sub { ... },
372	...	384	...
373	;	385	;
374		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, $otherport;
		394	};
		395
375	=cut	396	=cut
376		397
377	sub rcv($@) {	398	sub rcv($@) {
378	my $port = shift;	399	my $port = shift;
379	my ($noderef, $portid) = split /#/, $port, 2;	400	my ($nodeid, $portid) = split /#/, $port, 2;
380		401
381	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	402	$NODE{$nodeid} == $NODE{""}
382	or Carp::croak "$port: rcv can only be called on local ports, caught";	403	or Carp::croak "$port: rcv can only be called on local ports, caught";
383		404
384	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 {
385	my $cb = shift;	413	my $cb = shift;
386	delete $PORT_DATA{$portid};
387	$PORT{$portid} = sub {	414	$PORT{$portid} = sub {
388	local $SELF = $port;	415	local $SELF = $port;
389	eval {	416	eval { &$cb }; _self_die if $@;
390	&$cb	417	};
391	and kil $port;
392	};	418	}
393	_self_die if $@;	419	} elsif (defined $_[0]) {
394	};
395	} else {
396	my $self = $PORT_DATA{$portid} \|\|= do {	420	my $self = $PORT_DATA{$portid} \|\|= do {
397	my $self = bless {	421	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
398	id => $port,
399	}, "AnyEvent::MP::Port";
400		422
401	$PORT{$portid} = sub {	423	$PORT{$portid} = sub {
402	local $SELF = $port;	424	local $SELF = $port;
403		425
404	eval {
405	for (@{ $self->{rc0}{$_[0]} }) {	426	if (my $cb = $self->[1]{$_[0]}) {
406	$_ && &{$_->[0]}	427	shift;
407	&& undef $_;	428	eval { &$cb }; _self_die if $@;
408	}	429	} else {
409
410	for (@{ $self->{rcv}{$_[0]} }) {
411	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
412	&& &{$_->[0]}	430	&{ $self->[0] };
413	&& undef $_;
414	}
415
416	for (@{ $self->{any} }) {
417	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
418	&& &{$_->[0]}
419	&& undef $_;
420	}	431	}
421	};	432	};
422	_self_die if $@;	433
		434	$self
423	};	435	};
424		436
425	$self
426	};
427
428	"AnyEvent::MP::Port" eq ref $self	437	"AnyEvent::MP::Port" eq ref $self
429	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	438	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
430		439
431	while (@_) {
432	my ($match, $cb) = splice @_, 0, 2;	440	my ($tag, $cb) = splice @_, 0, 2;
433		441
434	if (!ref $match) {	442	if (defined $cb) {
435	push @{ $self->{rc0}{$match} }, [$cb];	443	$self->[1]{$tag} = $cb;
436	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
437	my ($type, @match) = @$match;
438	@match
439	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
440	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
441	} else {	444	} else {
442	push @{ $self->{any} }, [$cb, $match];	445	delete $self->[1]{$tag};
443	}	446	}
444	}	447	}
445	}	448	}
446		449
447	$port	450	$port
448	}	451	}
449		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
450	=item $closure = psub { BLOCK }	490	=item $closure = psub { BLOCK }
451		491
452	Remembers C<$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
453	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>
454	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 $SELF, sub {
		497	BLOCK } } >>.
455		498
456	This is useful when you register callbacks from C<rcv> callbacks:	499	This is useful when you register callbacks from C<rcv> callbacks:
457		500
458	rcv delayed_reply => sub {	501	rcv delayed_reply => sub {
459	my ($delay, @reply) = @_;	502	my ($delay, @reply) = @_;
…		…
483	$res	526	$res
484	}	527	}
485	}	528	}
486	}	529	}
487		530
488	=item $guard = mon $port, $cb->(@reason)	531	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
489		532
490	=item $guard = mon $port, $rcvport	533	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
491		534
492	=item $guard = mon $port	535	=item $guard = mon $port # kill $SELF when $port dies
493		536
494	=item $guard = mon $port, $rcvport, @msg	537	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
495		538
496	Monitor the given port and do something when the port is killed, and	539	Monitor the given port and do something when the port is killed or
497	optionally return a guard that can be used to stop monitoring again.	540	messages to it were lost, and optionally return a guard that can be used
		541	to stop monitoring again.
498		542
499	In the first form (callback), the callback is simply called with any	543	In the first form (callback), the callback is simply called with any
500	number of C<@reason> elements (no @reason means that the port was deleted	544	number of C<@reason> elements (no @reason means that the port was deleted
501	"normally"). Note also that I<< the callback B<must> never die >>, so use	545	"normally"). Note also that I<< the callback B<must> never die >>, so use
502	C<eval> if unsure.	546	C<eval> if unsure.
503		547
504	In the second form (another port given), the other port (C<$rcvport)	548	In the second form (another port given), the other port (C<$rcvport>)
505	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	549	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
506	"normal" kils nothing happens, while under all other conditions, the other	550	"normal" kils nothing happens, while under all other conditions, the other
507	port is killed with the same reason.	551	port is killed with the same reason.
508		552
509	The third form (kill self) is the same as the second form, except that	553	The third form (kill self) is the same as the second form, except that
510	C<$rvport> defaults to C<$SELF>.	554	C<$rvport> defaults to C<$SELF>.
511		555
512	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
513	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.
514		561
515	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
516	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
517	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
518	even monitoring requests can get lost (for exmaple, when the connection	565	even monitoring requests can get lost (for example, when the connection
519	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
520	these problems do not exist.	567	these problems do not exist.
521		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
522	Example: call a given callback when C<$port> is killed.	586	Example: call a given callback when C<$port> is killed.
523		587
524	mon $port, sub { warn "port died because of <@_>\n" };	588	mon $port, sub { warn "port died because of <@_>\n" };
525		589
526	Example: kill ourselves when C<$port> is killed abnormally.	590	Example: kill ourselves when C<$port> is killed abnormally.
…		…
532	mon $port, $self => "restart";	596	mon $port, $self => "restart";
533		597
534	=cut	598	=cut
535		599
536	sub mon {	600	sub mon {
537	my ($noderef, $port) = split /#/, shift, 2;	601	my ($nodeid, $port) = split /#/, shift, 2;
538		602
539	my $node = $NODE{$noderef} \|\| add_node $noderef;	603	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
540		604
541	my $cb = @_ ? $_[0] : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	605	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
542		606
543	unless (ref $cb) {	607	unless (ref $cb) {
544	if (@_) {	608	if (@_) {
545	# send a kill info message	609	# send a kill info message
546	my (@msg) = @_;	610	my (@msg) = ($cb, @_);
547	$cb = sub { snd @msg, @_ };	611	$cb = sub { snd @msg, @_ };
548	} else {	612	} else {
549	# simply kill other port	613	# simply kill other port
550	my $port = $cb;	614	my $port = $cb;
551	$cb = sub { kil $port, @_ if @_ };	615	$cb = sub { kil $port, @_ if @_ };
…		…
553	}	617	}
554		618
555	$node->monitor ($port, $cb);	619	$node->monitor ($port, $cb);
556		620
557	defined wantarray	621	defined wantarray
558	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	622	and ($cb += 0, AnyEvent::Util::guard { $node->unmonitor ($port, $cb) })
559	}	623	}
560		624
561	=item $guard = mon_guard $port, $ref, $ref...	625	=item $guard = mon_guard $port, $ref, $ref...
562		626
563	Monitors the given C<$port> and keeps the passed references. When the port	627	Monitors the given C<$port> and keeps the passed references. When the port
564	is killed, the references will be freed.	628	is killed, the references will be freed.
565		629
566	Optionally returns a guard that will stop the monitoring.	630	Optionally returns a guard that will stop the monitoring.
567		631
568	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
569	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>):
570		634
571	$port->rcv (start => sub {	635	$port->rcv (start => sub {
572	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	636	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
573	undef $timer if 0.9 < rand;	637	undef $timer if 0.9 < rand;
574	});	638	});
575	});	639	});
576		640
577	=cut	641	=cut
…		…
586		650
587	=item kil $port[, @reason]	651	=item kil $port[, @reason]
588		652
589	Kill the specified port with the given C<@reason>.	653	Kill the specified port with the given C<@reason>.
590		654
591	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
592	ports will not be kileld, or even notified).	656	monitoring other ports will not necessarily die because a port dies
		657	"normally").
593		658
594	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
595	C<mon>, see below).	660	C<mon>, see above).
596		661
597	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
598	will be reported as reason C<< die => $@ >>.	663	will be reported as reason C<< die => $@ >>.
599		664
600	Transport/communication errors are reported as C<< transport_error =>	665	Transport/communication errors are reported as C<< transport_error =>
601	$message >>.	666	$message >>.
602		667
603	=back
604
605	=head1 NODE MESSAGES
606
607	Nodes understand the following messages sent to them. Many of them take
608	arguments called C<@reply>, which will simply be used to compose a reply
609	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
610	the remaining arguments are simply the message data.
611
612	While other messages exist, they are not public and subject to change.
613
614	=over 4
615
616	=cut	668	=cut
617		669
618	=item lookup => $name, @reply	670	=item $port = spawn $node, $initfunc[, @initdata]
619		671
620	Replies with the port ID of the specified well-known port, or C<undef>.	672	Creates a port on the node C<$node> (which can also be a port ID, in which
		673	case it's the node where that port resides).
621		674
622	=item devnull => ...	675	The port ID of the newly created port is returned immediately, and it is
		676	possible to immediately start sending messages or to monitor the port.
623		677
624	Generic data sink/CPU heat conversion.	678	After the port has been created, the init function is called on the remote
		679	node, in the same context as a C<rcv> callback. This function must be a
		680	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		681	specify a function in the main program, use C<::name>.
625		682
626	=item relay => $port, @msg	683	If the function doesn't exist, then the node tries to C<require>
		684	the package, then the package above the package and so on (e.g.
		685	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		686	exists or it runs out of package names.
627		687
628	Simply forwards the message to the given port.	688	The init function is then called with the newly-created port as context
		689	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		690	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		691	the port might not get created.
629		692
630	=item eval => $string[ @reply]	693	A common idiom is to pass a local port, immediately monitor the spawned
		694	port, and in the remote init function, immediately monitor the passed
		695	local port. This two-way monitoring ensures that both ports get cleaned up
		696	when there is a problem.
631		697
632	Evaluates the given string. If C<@reply> is given, then a message of the	698	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
633	form C<@reply, $@, @evalres> is sent.	699	caller before C<spawn> returns (by delaying invocation when spawn is
		700	called for the local node).
634		701
635	Example: crash another node.	702	Example: spawn a chat server port on C<$othernode>.
636		703
637	snd $othernode, eval => "exit";	704	# this node, executed from within a port context:
		705	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		706	mon $server;
638		707
639	=item time => @reply	708	# init function on C<$othernode>
		709	sub connect {
		710	my ($srcport) = @_;
640		711
641	Replies the the current node time to C<@reply>.	712	mon $srcport;
642		713
643	Example: tell the current node to send the current time to C<$myport> in a	714	rcv $SELF, sub {
644	C<timereply> message.	715	...
		716	};
		717	}
645		718
646	snd $NODE, time => $myport, timereply => 1, 2;	719	=cut
647	# => snd $myport, timereply => 1, 2, <time>	720
		721	sub _spawn {
		722	my $port = shift;
		723	my $init = shift;
		724
		725	# rcv will create the actual port
		726	local $SELF = "$NODE#$port";
		727	eval {
		728	&{ load_func $init }
		729	};
		730	_self_die if $@;
		731	}
		732
		733	sub spawn(@) {
		734	my ($nodeid, undef) = split /#/, shift, 2;
		735
		736	my $id = "$RUNIQ." . $ID++;
		737
		738	$_[0] =~ /::/
		739	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		740
		741	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		742
		743	"$nodeid#$id"
		744	}
		745
		746	=item after $timeout, @msg
		747
		748	=item after $timeout, $callback
		749
		750	Either sends the given message, or call the given callback, after the
		751	specified number of seconds.
		752
		753	This is simply a utility function that comes in handy at times - the
		754	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		755	so it may go away in the future.
		756
		757	=cut
		758
		759	sub after($@) {
		760	my ($timeout, @action) = @_;
		761
		762	my $t; $t = AE::timer $timeout, 0, sub {
		763	undef $t;
		764	ref $action[0]
		765	? $action[0]()
		766	: snd @action;
		767	};
		768	}
		769
		770	=item cal $port, @msg, $callback[, $timeout]
		771
		772	A simple form of RPC - sends a message to the given C<$port> with the
		773	given contents (C<@msg>), but adds a reply port to the message.
		774
		775	The reply port is created temporarily just for the purpose of receiving
		776	the reply, and will be C<kil>ed when no longer needed.
		777
		778	A reply message sent to the port is passed to the C<$callback> as-is.
		779
		780	If an optional time-out (in seconds) is given and it is not C<undef>,
		781	then the callback will be called without any arguments after the time-out
		782	elapsed and the port is C<kil>ed.
		783
		784	If no time-out is given (or it is C<undef>), then the local port will
		785	monitor the remote port instead, so it eventually gets cleaned-up.
		786
		787	Currently this function returns the temporary port, but this "feature"
		788	might go in future versions unless you can make a convincing case that
		789	this is indeed useful for something.
		790
		791	=cut
		792
		793	sub cal(@) {
		794	my $timeout = ref $_[-1] ? undef : pop;
		795	my $cb = pop;
		796
		797	my $port = port {
		798	undef $timeout;
		799	kil $SELF;
		800	&$cb;
		801	};
		802
		803	if (defined $timeout) {
		804	$timeout = AE::timer $timeout, 0, sub {
		805	undef $timeout;
		806	kil $port;
		807	$cb->();
		808	};
		809	} else {
		810	mon $_[0], sub {
		811	kil $port;
		812	$cb->();
		813	};
		814	}
		815
		816	push @_, $port;
		817	&snd;
		818
		819	$port
		820	}
648		821
649	=back	822	=back
650		823
651	=head1 AnyEvent::MP vs. Distributed Erlang	824	=head1 AnyEvent::MP vs. Distributed Erlang
652		825
653	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
654	== 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
655	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
656	sample:	829	sample:
657		830
658	http://www.Erlang.se/doc/programming_rules.shtml	831	http://www.erlang.se/doc/programming_rules.shtml
659	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
660	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
661	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
662		835
663	Despite the similarities, there are also some important differences:	836	Despite the similarities, there are also some important differences:
664		837
665	=over 4	838	=over 4
666		839
667	=item * Node references contain the recipe on how to contact them.	840	=item * Node IDs are arbitrary strings in AEMP.
668		841
669	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
670	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
671	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.
672		846
673	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
674	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.
675		861
676	=item * Erlang uses processes and a mailbox, AEMP does not queue.	862	=item * Erlang uses processes and a mailbox, AEMP does not queue.
677		863
678	Erlang uses processes that selctively receive messages, and therefore	864	Erlang uses processes that selectively receive messages, and therefore
679	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
680	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.
681		869
682	(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).
683		871
684	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	872	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
685		873
686	Sending messages in Erlang is synchronous and blocks the process. AEMP	874	Sending messages in Erlang is synchronous and blocks the process (and
687	sends are immediate, connection establishment is handled in the	875	so does not need a queue that can overflow). AEMP sends are immediate,
688	background.	876	connection establishment is handled in the background.
689		877
690	=item * Erlang can silently lose messages, AEMP cannot.	878	=item * Erlang suffers from silent message loss, AEMP does not.
691		879
692	Erlang makes few guarantees on messages delivery - messages can get lost	880	Erlang implements few guarantees on messages delivery - messages can get
693	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,
694	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).
695		883
696	AEMP guarantees correct ordering, and the guarantee that there are no	884	AEMP guarantees correct ordering, and the guarantee that after one message
697	holes in the message sequence.	885	is lost, all following ones sent to the same port are lost as well, until
698		886	monitoring raises an error, so there are no silent "holes" in the message
699	=item * In Erlang, processes can be declared dead and later be found to be	887	sequence.
700	alive.
701
702	In Erlang it can happen that a monitored process is declared dead and
703	linked processes get killed, but later it turns out that the process is
704	still alive - and can receive messages.
705
706	In AEMP, when port monitoring detects a port as dead, then that port will
707	eventually be killed - it cannot happen that a node detects a port as dead
708	and then later sends messages to it, finding it is still alive.
709		888
710	=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.
711		890
712	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
713	ID known to other nodes for a completely different process, causing	892	known to other nodes for a completely different process, causing messages
714	messages destined for that process to end up in an unrelated process.	893	destined for that process to end up in an unrelated process.
715		894
716	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
717	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.
718		897
719	=item * Erlang uses unprotected connections, AEMP uses secure	898	=item * Erlang uses unprotected connections, AEMP uses secure
720	authentication and can use TLS.	899	authentication and can use TLS.
721		900
722	AEMP can use a proven protocol - SSL/TLS - to protect connections and	901	AEMP can use a proven protocol - TLS - to protect connections and
723	securely authenticate nodes.	902	securely authenticate nodes.
724		903
725	=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
726	communications.	905	communications.
727		906
728	The AEMP protocol, unlike the Erlang protocol, supports both	907	The AEMP protocol, unlike the Erlang protocol, supports both programming
729	language-independent text-only protocols (good for debugging) and binary,	908	language independent text-only protocols (good for debugging) and binary,
730	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.
731		911
732	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
733	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
734	protocol simple.	914	protocol simple.
735		915
736	=item * AEMP has more flexible monitoring options than Erlang.	916	=item * AEMP has more flexible monitoring options than Erlang.
737		917
738	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
…		…
741	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
742	on a per-process basis.	922	on a per-process basis.
743		923
744	=item * Erlang tries to hide remote/local connections, AEMP does not.	924	=item * Erlang tries to hide remote/local connections, AEMP does not.
745		925
746	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
747	as linking is (except linking is unreliable in Erlang).	927	same way as linking is (except linking is unreliable in Erlang).
748		928
749	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
750	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
751	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
752	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
753	more reliable.	933	reliable (no need for C<spawn_link>).
754		934
755	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
756	(hard to do in Erlang).	936	(hard to do in Erlang).
757		937
758	=back	938	=back
759		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
760	=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.
761		988
762	L<AnyEvent>.	989	L<AnyEvent>.
763		990
764	=head1 AUTHOR	991	=head1 AUTHOR
765		992

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