[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 1.87 by root, Fri Sep 11 02:32:23 2009 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using miniports	24	# creating/using ports, the simple way
28	my $miniport = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using full ports	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, smartmatch => $cb->(@msg);
33	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
34	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
35
36	# more, smarter, matches (_any_ is exported by this module)
37	rcv $port, [child_died => $pid] => sub { ...
38	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
39		31
40	# create a port on another node	32	# create a port on another node
41	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
42		34
43	# monitoring	35	# monitoring
…		…
45	mon $port, $otherport # kill otherport on abnormal death	37	mon $port, $otherport # kill otherport on abnormal death
46	mon $port, $otherport, @msg # send message on death	38	mon $port, $otherport, @msg # send message on death
47		39
48	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
49		41
		42	bin/aemp - stable.
50	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
51	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.
52	AnyEvent::MP::Kernel - WIP
53	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable but incomplete, protocol not yet final.
54		47
55	stay tuned.	48	stay tuned.
56		49
57	=head1 DESCRIPTION	50	=head1 DESCRIPTION
58		51
59	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
60		53
61	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
62	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
63		56
64	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
65	manual page.	58	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		59
71	=head1 CONCEPTS	60	=head1 CONCEPTS
72		61
73	=over 4	62	=over 4
74		63
75	=item port	64	=item port
76		65
77	A port is something you can send messages to (with the C<snd> function).	66	Not to be confused with a TCP port, a "port" is something you can send
		67	messages to (with the C<snd> function).
78		68
79	Some ports allow you to register C<rcv> handlers that can match specific	69	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	70	some messages. Messages send to ports will not be queued, regardless of
81	will not be queued.	71	anything was listening for them or not.
82		72
83	=item port id - C<noderef#portname>	73	=item port ID - C<nodeid#portname>
84		74
85	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	75	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	76	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		77
90	=item node	78	=item node
91		79
92	A node is a single process containing at least one port - the node	80	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	81	which enables nodes to manage each other remotely, and to create new
94	create new ports, among other things.	82	ports.
95		83
96	Nodes are either private (single-process only), slaves (connected to a	84	Nodes are either public (have one or more listening ports) or private
97	master node only) or public nodes (connectable from unrelated nodes).	85	(no listening ports). Private nodes cannot talk to other private nodes
		86	currently.
98		87
99	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	88	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
100		89
101	A node reference is a string that either simply identifies the node (for	90	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	91	network. Depending on the configuration used, node IDs can look like a
103	node (for public nodes).	92	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		93	doesn't interpret node IDs in any way.
104		94
105	This recipe is simply a comma-separated list of C<address:port> pairs (for	95	=item binds - C<ip:port>
106	TCP/IP, other protocols might look different).
107		96
108	Node references come in two flavours: resolved (containing only numerical	97	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).	98	each other. To do this, nodes should listen on one or more local transport
		99	endpoints - binds. Currently, only standard C<ip:port> specifications can
		100	be used, which specify TCP ports to listen on.
110		101
111	Before using an unresolved node reference in a message you first have to	102	=item seed nodes
112	resolve it.	103
		104	When a node starts, it knows nothing about the network. To teach the node
		105	about the network it first has to contact some other node within the
		106	network. This node is called a seed.
		107
		108	Apart from the fact that other nodes know them as seed nodes and they have
		109	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		110	any node can function as a seed node for others.
		111
		112	In addition to discovering the network, seed nodes are also used to
		113	maintain the network and to connect nodes that otherwise would have
		114	trouble connecting. They form the backbone of an AnyEvent::MP network.
		115
		116	Seed nodes are expected to be long-running, and at least one seed node
		117	should always be available. They should also be relatively responsive - a
		118	seed node that blocks for long periods will slow down everybody else.
		119
		120	=item seeds - C<host:port>
		121
		122	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		123	TCP port) of nodes thta should be used as seed nodes.
		124
		125	The nodes listening on those endpoints are expected to be long-running,
		126	and at least one of those should always be available. When nodes run out
		127	of connections (e.g. due to a network error), they try to re-establish
		128	connections to some seednodes again to join the network.
113		129
114	=back	130	=back
115		131
116	=head1 VARIABLES/FUNCTIONS	132	=head1 VARIABLES/FUNCTIONS
117		133
…		…
132	use base "Exporter";	148	use base "Exporter";
133		149
134	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	150	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
135		151
136	our @EXPORT = qw(	152	our @EXPORT = qw(
137	NODE $NODE *SELF node_of _any_	153	NODE $NODE *SELF node_of after
138	resolve_node initialise_node	154	configure
139	snd rcv mon kil reg psub spawn	155	snd rcv mon mon_guard kil reg psub spawn cal
140	port	156	port
141	);	157	);
142		158
143	our $SELF;	159	our $SELF;
144		160
…		…
148	kil $SELF, die => $msg;	164	kil $SELF, die => $msg;
149	}	165	}
150		166
151	=item $thisnode = NODE / $NODE	167	=item $thisnode = NODE / $NODE
152		168
153	The C<NODE> function returns, and the C<$NODE> variable contains	169	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	170	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	171	a call to C<configure>.
156	identifiers become invalid.
157		172
158	=item $noderef = node_of $port	173	=item $nodeid = node_of $port
159		174
160	Extracts and returns the noderef from a portid or a noderef.	175	Extracts and returns the node ID from a port ID or a node ID.
161		176
162	=item initialise_node $noderef, $seednode, $seednode...	177	=item configure $profile, key => value...
163		178
164	=item initialise_node "slave/", $master, $master...	179	=item configure key => value...
165		180
166	Before a node can talk to other nodes on the network it has to initialise	181	Before a node can talk to other nodes on the network (i.e. enter
167	itself - the minimum a node needs to know is it's own name, and optionally	182	"distributed mode") it has to configure itself - the minimum a node needs
168	it should know the noderefs of some other nodes in the network.	183	to know is its own name, and optionally it should know the addresses of
		184	some other nodes in the network to discover other nodes.
169		185
170	This function initialises a node - it must be called exactly once (or	186	This function configures a node - it must be called exactly once (or
171	never) before calling other AnyEvent::MP functions.	187	never) before calling other AnyEvent::MP functions.
172		188
173	All arguments are noderefs, which can be either resolved or unresolved.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176
177	=over 4	189	=over 4
178		190
179	=item public nodes	191	=item step 1, gathering configuration from profiles
180		192
181	For public nodes, C<$noderef> must either be a (possibly unresolved)	193	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	194	L<aemp> commandline utility). The profile name can be specified via the
183	which case the noderef will be guessed.	195	named C<profile> parameter or can simply be the first parameter). If it is
		196	missing, then the nodename (F<uname -n>) will be used as profile name.
184		197
185	Afterwards, the node will bind itself on all endpoints and try to connect	198	The profile data is then gathered as follows:
186	to all additional C<$seednodes> that are specified. Seednodes are optional
187	and can be used to quickly bootstrap the node into an existing network.
188		199
189	=item slave nodes	200	First, all remaining key => value pairs (all of which are conveniently
		201	undocumented at the moment) will be interpreted as configuration
		202	data. Then they will be overwritten by any values specified in the global
		203	default configuration (see the F<aemp> utility), then the chain of
		204	profiles chosen by the profile name (and any C<parent> attributes).
190		205
191	When the C<$noderef> is the special string C<slave/>, then the node will	206	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	207	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.	208	and can only be used to specify defaults.
194		209
195	At least one additional noderef is required: The node will try to connect	210	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	211	this process. If not, then the profile name will be used as node ID. The
197	successfully connect to.	212	special node ID of C<anon/> will be replaced by a random node ID.
		213
		214	=item step 2, bind listener sockets
		215
		216	The next step is to look up the binds in the profile, followed by binding
		217	aemp protocol listeners on all binds specified (it is possible and valid
		218	to have no binds, meaning that the node cannot be contacted form the
		219	outside. This means the node cannot talk to other nodes that also have no
		220	binds, but it can still talk to all "normal" nodes).
		221
		222	If the profile does not specify a binds list, then a default of C<*> is
		223	used, meaning the node will bind on a dynamically-assigned port on every
		224	local IP address it finds.
		225
		226	=item step 3, connect to seed nodes
		227
		228	As the last step, the seeds list from the profile is passed to the
		229	L<AnyEvent::MP::Global> module, which will then use it to keep
		230	connectivity with at least one node at any point in time.
198		231
199	=back	232	=back
200		233
201	This function will block until all nodes have been resolved and, for slave	234	Example: become a distributed node using the local node name as profile.
202	nodes, until it has successfully established a connection to a master	235	This should be the most common form of invocation for "daemon"-type nodes.
203	server.
204		236
205	Example: become a public node listening on the default node.	237	configure
206		238
207	initialise_node;	239	Example: become an anonymous node. This form is often used for commandline
		240	clients.
208		241
209	Example: become a public node, and try to contact some well-known master	242	configure nodeid => "anon/";
210	servers to become part of the network.
211		243
212	initialise_node undef, "master1", "master2";	244	Example: configure a node using a profile called seed, which si suitable
		245	for a seed node as it binds on all local addresses on a fixed port (4040,
		246	customary for aemp).
213		247
214	Example: become a public node listening on port C<4041>.	248	# use the aemp commandline utility
		249	# aemp profile seed nodeid anon/ binds '*:4040'
215		250
216	initialise_node 4041;	251	# then use it
		252	configure profile => "seed";
217		253
218	Example: become a public node, only visible on localhost port 4044.	254	# or simply use aemp from the shell again:
		255	# aemp run profile seed
219		256
220	initialise_node "locahost:4044";	257	# or provide a nicer-to-remember nodeid
221		258	# 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		259
255	=item $SELF	260	=item $SELF
256		261
257	Contains the current port id while executing C<rcv> callbacks or C<psub>	262	Contains the current port id while executing C<rcv> callbacks or C<psub>
258	blocks.	263	blocks.
259		264
260	=item SELF, %SELF, @SELF...	265	=item *SELF, SELF, %SELF, @SELF...
261		266
262	Due to some quirks in how perl exports variables, it is impossible to	267	Due to some quirks in how perl exports variables, it is impossible to
263	just export C<$SELF>, all the symbols called C<SELF> are exported by this	268	just export C<$SELF>, all the symbols named C<SELF> are exported by this
264	module, but only C<$SELF> is currently used.	269	module, but only C<$SELF> is currently used.
265		270
266	=item snd $port, type => @data	271	=item snd $port, type => @data
267		272
268	=item snd $port, @msg	273	=item snd $port, @msg
269		274
270	Send the given message to the given port ID, which can identify either	275	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	276	local or a remote port, and must be a port ID.
272	stringifies a sa port ID (such as a port object :).
273		277
274	While the message can be about anything, it is highly recommended to use a	278	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	279	use a string as first element (a port ID, or some word that indicates a
276	type etc.).	280	request type etc.) and to consist if only simple perl values (scalars,
		281	arrays, hashes) - if you think you need to pass an object, think again.
277		282
278	The message data effectively becomes read-only after a call to this	283	The message data logically becomes read-only after a call to this
279	function: modifying any argument is not allowed and can cause many	284	function: modifying any argument (or values referenced by them) is
280	problems.	285	forbidden, as there can be considerable time between the call to C<snd>
		286	and the time the message is actually being serialised - in fact, it might
		287	never be copied as within the same process it is simply handed to the
		288	receiving port.
281		289
282	The type of data you can transfer depends on the transport protocol: when	290	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	291	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	292	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	293	that Storable can serialise and deserialise is allowed, and for the local
286	node, anything can be passed.	294	node, anything can be passed. Best rely only on the common denominator of
		295	these.
287		296
288	=item $local_port = port	297	=item $local_port = port
289		298
290	Create a new local port object that can be used either as a pattern	299	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"),	300	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		301
294	=item $port = port { my @msg = @_; $finished }	302	=item $local_port = port { my @msg = @_ }
295		303
296	Creates a "miniport", that is, a very lightweight port without any pattern	304	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.	305	creating a port and calling C<rcv $port, $callback> on it.
299		306
300	The block will be called for every message received on the port. When the	307	The block will be called for every message received on the port, with the
301	callback returns a true value its job is considered "done" and the port	308	global variable C<$SELF> set to the port ID. Runtime errors will cause the
302	will be destroyed. Otherwise it will stay alive.	309	port to be C<kil>ed. The message will be passed as-is, no extra argument
		310	(i.e. no port ID) will be passed to the callback.
303		311
304	The message will be passed as-is, no extra argument (i.e. no port id) will	312	If you want to stop/destroy the port, simply C<kil> it:
305	be passed to the callback.
306		313
307	If you need the local port id in the callback, this works nicely:	314	my $port = port {
308		315	my @msg = @_;
309	my $port; $port = port {	316	...
310	snd $otherport, reply => $port;	317	kil $SELF;
311	};	318	};
312		319
313	=cut	320	=cut
314		321
315	sub rcv($@);	322	sub rcv($@);
		323
		324	sub _kilme {
		325	die "received message on port without callback";
		326	}
316		327
317	sub port(;&) {	328	sub port(;&) {
318	my $id = "$UNIQ." . $ID++;	329	my $id = "$UNIQ." . $ID++;
319	my $port = "$NODE#$id";	330	my $port = "$NODE#$id";
320		331
321	if (@_) {	332	rcv $port, shift \|\| \&_kilme;
322	rcv $port, shift;
323	} else {
324	$PORT{$id} = sub { }; # nop
325	}
326		333
327	$port	334	$port
328	}	335	}
329		336
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)	337	=item rcv $local_port, $callback->(@msg)
350		338
351	Replaces the callback on the specified miniport (after converting it to	339	Replaces the default callback on the specified port. There is no way to
352	one if required).	340	remove the default callback: use C<sub { }> to disable it, or better
353		341	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...] => $callback->(@msg), ...
359
360	Register callbacks to be called on matching messages on the given full
361	port (after converting it to one if required) and return the port.
362
363	The callback has to return a true value when its work is done, after
364	which is will be removed, or a false value in which case it will stay
365	registered.
366		342
367	The global C<$SELF> (exported by this module) contains C<$port> while	343	The global C<$SELF> (exported by this module) contains C<$port> while
368	executing the callback.	344	executing the callback. Runtime errors during callback execution will
		345	result in the port being C<kil>ed.
369		346
370	Runtime errors during callback execution will result in the port being	347	The default callback received all messages not matched by a more specific
371	C<kil>ed.	348	C<tag> match.
372		349
373	If the match is an array reference, then it will be matched against the	350	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
374	first elements of the message, otherwise only the first element is being
375	matched.
376		351
377	Any element in the match that is specified as C<_any_> (a function	352	Register (or replace) callbacks to be called on messages starting with the
378	exported by this module) matches any single element of the message.	353	given tag on the given port (and return the port), or unregister it (when
		354	C<$callback> is C<$undef> or missing). There can only be one callback
		355	registered for each tag.
379		356
380	While not required, it is highly recommended that the first matching	357	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	358	element (the tag) has been removed. The callback will use the same
382	also the most efficient match (by far).	359	environment as the default callback (see above).
383		360
384	Example: create a port and bind receivers on it in one go.	361	Example: create a port and bind receivers on it in one go.
385		362
386	my $port = rcv port,	363	my $port = rcv port,
387	msg1 => sub { ...; 0 },	364	msg1 => sub { ... },
388	msg2 => sub { ...; 0 },	365	msg2 => sub { ... },
389	;	366	;
390		367
391	Example: create a port, bind receivers and send it in a message elsewhere	368	Example: create a port, bind receivers and send it in a message elsewhere
392	in one go:	369	in one go:
393		370
394	snd $otherport, reply =>	371	snd $otherport, reply =>
395	rcv port,	372	rcv port,
396	msg1 => sub { ...; 0 },	373	msg1 => sub { ... },
397	...	374	...
398	;	375	;
399		376
		377	Example: temporarily register a rcv callback for a tag matching some port
		378	(e.g. for a rpc reply) and unregister it after a message was received.
		379
		380	rcv $port, $otherport => sub {
		381	my @reply = @_;
		382
		383	rcv $SELF, $otherport;
		384	};
		385
400	=cut	386	=cut
401		387
402	sub rcv($@) {	388	sub rcv($@) {
403	my $port = shift;	389	my $port = shift;
404	my ($noderef, $portid) = split /#/, $port, 2;	390	my ($nodeid, $portid) = split /#/, $port, 2;
405		391
406	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	392	$NODE{$nodeid} == $NODE{""}
407	or Carp::croak "$port: rcv can only be called on local ports, caught";	393	or Carp::croak "$port: rcv can only be called on local ports, caught";
408		394
409	if (@_ == 1) {	395	while (@_) {
		396	if (ref $_[0]) {
		397	if (my $self = $PORT_DATA{$portid}) {
		398	"AnyEvent::MP::Port" eq ref $self
		399	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		400
		401	$self->[2] = shift;
		402	} else {
410	my $cb = shift;	403	my $cb = shift;
411	delete $PORT_DATA{$portid};
412	$PORT{$portid} = sub {	404	$PORT{$portid} = sub {
413	local $SELF = $port;	405	local $SELF = $port;
414	eval {	406	eval { &$cb }; _self_die if $@;
415	&$cb	407	};
416	and kil $port;
417	};	408	}
418	_self_die if $@;	409	} elsif (defined $_[0]) {
419	};
420	} else {
421	my $self = $PORT_DATA{$portid} \|\|= do {	410	my $self = $PORT_DATA{$portid} \|\|= do {
422	my $self = bless {	411	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
423	id => $port,
424	}, "AnyEvent::MP::Port";
425		412
426	$PORT{$portid} = sub {	413	$PORT{$portid} = sub {
427	local $SELF = $port;	414	local $SELF = $port;
428		415
429	eval {
430	for (@{ $self->{rc0}{$_[0]} }) {	416	if (my $cb = $self->[1]{$_[0]}) {
431	$_ && &{$_->[0]}	417	shift;
432	&& undef $_;	418	eval { &$cb }; _self_die if $@;
433	}	419	} else {
434
435	for (@{ $self->{rcv}{$_[0]} }) {
436	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
437	&& &{$_->[0]}	420	&{ $self->[0] };
438	&& undef $_;
439	}
440
441	for (@{ $self->{any} }) {
442	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
443	&& &{$_->[0]}
444	&& undef $_;
445	}	421	}
446	};	422	};
447	_self_die if $@;	423
		424	$self
448	};	425	};
449		426
450	$self
451	};
452
453	"AnyEvent::MP::Port" eq ref $self	427	"AnyEvent::MP::Port" eq ref $self
454	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	428	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
455		429
456	while (@_) {
457	my ($match, $cb) = splice @_, 0, 2;	430	my ($tag, $cb) = splice @_, 0, 2;
458		431
459	if (!ref $match) {	432	if (defined $cb) {
460	push @{ $self->{rc0}{$match} }, [$cb];	433	$self->[1]{$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 {	434	} else {
467	push @{ $self->{any} }, [$cb, $match];	435	delete $self->[1]{$tag};
468	}	436	}
469	}	437	}
470	}	438	}
471		439
472	$port	440	$port
…		…
508	$res	476	$res
509	}	477	}
510	}	478	}
511	}	479	}
512		480
513	=item $guard = mon $port, $cb->(@reason)	481	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
514		482
515	=item $guard = mon $port, $rcvport	483	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
516		484
517	=item $guard = mon $port	485	=item $guard = mon $port # kill $SELF when $port dies
518		486
519	=item $guard = mon $port, $rcvport, @msg	487	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
520		488
521	Monitor the given port and do something when the port is killed or	489	Monitor the given port and do something when the port is killed or
522	messages to it were lost, and optionally return a guard that can be used	490	messages to it were lost, and optionally return a guard that can be used
523	to stop monitoring again.	491	to stop monitoring again.
524
525	C<mon> effectively guarantees that, in the absence of hardware failures,
526	that after starting the monitor, either all messages sent to the port
527	will arrive, or the monitoring action will be invoked after possible
528	message loss has been detected. No messages will be lost "in between"
529	(after the first lost message no further messages will be received by the
530	port). After the monitoring action was invoked, further messages might get
531	delivered again.
532		492
533	In the first form (callback), the callback is simply called with any	493	In the first form (callback), the callback is simply called with any
534	number of C<@reason> elements (no @reason means that the port was deleted	494	number of C<@reason> elements (no @reason means that the port was deleted
535	"normally"). Note also that I<< the callback B<must> never die >>, so use	495	"normally"). Note also that I<< the callback B<must> never die >>, so use
536	C<eval> if unsure.	496	C<eval> if unsure.
537		497
538	In the second form (another port given), the other port (C<$rcvport>)	498	In the second form (another port given), the other port (C<$rcvport>)
539	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	499	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
540	"normal" kils nothing happens, while under all other conditions, the other	500	"normal" kils nothing happens, while under all other conditions, the other
541	port is killed with the same reason.	501	port is killed with the same reason.
542		502
543	The third form (kill self) is the same as the second form, except that	503	The third form (kill self) is the same as the second form, except that
544	C<$rvport> defaults to C<$SELF>.	504	C<$rvport> defaults to C<$SELF>.
545		505
546	In the last form (message), a message of the form C<@msg, @reason> will be	506	In the last form (message), a message of the form C<@msg, @reason> will be
547	C<snd>.	507	C<snd>.
		508
		509	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		510	alert was raised), they are removed and will not trigger again.
548		511
549	As a rule of thumb, monitoring requests should always monitor a port from	512	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	513	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	514	lost, just like any other message. Another less obvious reason is that
552	even monitoring requests can get lost (for exmaple, when the connection	515	even monitoring requests can get lost (for example, when the connection
553	to the other node goes down permanently). When monitoring a port locally	516	to the other node goes down permanently). When monitoring a port locally
554	these problems do not exist.	517	these problems do not exist.
555		518
		519	C<mon> effectively guarantees that, in the absence of hardware failures,
		520	after starting the monitor, either all messages sent to the port will
		521	arrive, or the monitoring action will be invoked after possible message
		522	loss has been detected. No messages will be lost "in between" (after
		523	the first lost message no further messages will be received by the
		524	port). After the monitoring action was invoked, further messages might get
		525	delivered again.
		526
		527	Inter-host-connection timeouts and monitoring depend on the transport
		528	used. The only transport currently implemented is TCP, and AnyEvent::MP
		529	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		530	non-idle connection, and usually around two hours for idle conenctions).
		531
		532	This means that monitoring is good for program errors and cleaning up
		533	stuff eventually, but they are no replacement for a timeout when you need
		534	to ensure some maximum latency.
		535
556	Example: call a given callback when C<$port> is killed.	536	Example: call a given callback when C<$port> is killed.
557		537
558	mon $port, sub { warn "port died because of <@_>\n" };	538	mon $port, sub { warn "port died because of <@_>\n" };
559		539
560	Example: kill ourselves when C<$port> is killed abnormally.	540	Example: kill ourselves when C<$port> is killed abnormally.
…		…
566	mon $port, $self => "restart";	546	mon $port, $self => "restart";
567		547
568	=cut	548	=cut
569		549
570	sub mon {	550	sub mon {
571	my ($noderef, $port) = split /#/, shift, 2;	551	my ($nodeid, $port) = split /#/, shift, 2;
572		552
573	my $node = $NODE{$noderef} \|\| add_node $noderef;	553	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
574		554
575	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	555	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
576		556
577	unless (ref $cb) {	557	unless (ref $cb) {
578	if (@_) {	558	if (@_) {
…		…
598	is killed, the references will be freed.	578	is killed, the references will be freed.
599		579
600	Optionally returns a guard that will stop the monitoring.	580	Optionally returns a guard that will stop the monitoring.
601		581
602	This function is useful when you create e.g. timers or other watchers and	582	This function is useful when you create e.g. timers or other watchers and
603	want to free them when the port gets killed:	583	want to free them when the port gets killed (note the use of C<psub>):
604		584
605	$port->rcv (start => sub {	585	$port->rcv (start => sub {
606	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	586	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
607	undef $timer if 0.9 < rand;	587	undef $timer if 0.9 < rand;
608	});	588	});
609	});	589	});
610		590
611	=cut	591	=cut
…		…
620		600
621	=item kil $port[, @reason]	601	=item kil $port[, @reason]
622		602
623	Kill the specified port with the given C<@reason>.	603	Kill the specified port with the given C<@reason>.
624		604
625	If no C<@reason> is specified, then the port is killed "normally" (linked	605	If no C<@reason> is specified, then the port is killed "normally" (ports
626	ports will not be kileld, or even notified).	606	monitoring other ports will not necessarily die because a port dies
		607	"normally").
627		608
628	Otherwise, linked ports get killed with the same reason (second form of	609	Otherwise, linked ports get killed with the same reason (second form of
629	C<mon>, see below).	610	C<mon>, see above).
630		611
631	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	612	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
632	will be reported as reason C<< die => $@ >>.	613	will be reported as reason C<< die => $@ >>.
633		614
634	Transport/communication errors are reported as C<< transport_error =>	615	Transport/communication errors are reported as C<< transport_error =>
…		…
639	=item $port = spawn $node, $initfunc[, @initdata]	620	=item $port = spawn $node, $initfunc[, @initdata]
640		621
641	Creates a port on the node C<$node> (which can also be a port ID, in which	622	Creates a port on the node C<$node> (which can also be a port ID, in which
642	case it's the node where that port resides).	623	case it's the node where that port resides).
643		624
644	The port ID of the newly created port is return immediately, and it is	625	The port ID of the newly created port is returned immediately, and it is
645	permissible to immediately start sending messages or monitor the port.	626	possible to immediately start sending messages or to monitor the port.
646		627
647	After the port has been created, the init function is	628	After the port has been created, the init function is called on the remote
648	called. This function must be a fully-qualified function name	629	node, in the same context as a C<rcv> callback. This function must be a
649	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	630	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
650	program, use C<::name>.	631	specify a function in the main program, use C<::name>.
651		632
652	If the function doesn't exist, then the node tries to C<require>	633	If the function doesn't exist, then the node tries to C<require>
653	the package, then the package above the package and so on (e.g.	634	the package, then the package above the package and so on (e.g.
654	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	635	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
655	exists or it runs out of package names.	636	exists or it runs out of package names.
656		637
657	The init function is then called with the newly-created port as context	638	The init function is then called with the newly-created port as context
658	object (C<$SELF>) and the C<@initdata> values as arguments.	639	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		640	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		641	the port might not get created.
659		642
660	A common idiom is to pass your own port, monitor the spawned port, and	643	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	644	port, and in the remote init function, immediately monitor the passed
662	ensures that both ports get cleaned up when there is a problem.	645	local port. This two-way monitoring ensures that both ports get cleaned up
		646	when there is a problem.
		647
		648	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		649	caller before C<spawn> returns (by delaying invocation when spawn is
		650	called for the local node).
663		651
664	Example: spawn a chat server port on C<$othernode>.	652	Example: spawn a chat server port on C<$othernode>.
665		653
666	# this node, executed from within a port context:	654	# this node, executed from within a port context:
667	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	655	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
682		670
683	sub _spawn {	671	sub _spawn {
684	my $port = shift;	672	my $port = shift;
685	my $init = shift;	673	my $init = shift;
686		674
		675	# rcv will create the actual port
687	local $SELF = "$NODE#$port";	676	local $SELF = "$NODE#$port";
688	eval {	677	eval {
689	&{ load_func $init }	678	&{ load_func $init }
690	};	679	};
691	_self_die if $@;	680	_self_die if $@;
692	}	681	}
693		682
694	sub spawn(@) {	683	sub spawn(@) {
695	my ($noderef, undef) = split /#/, shift, 2;	684	my ($nodeid, undef) = split /#/, shift, 2;
696		685
697	my $id = "$RUNIQ." . $ID++;	686	my $id = "$RUNIQ." . $ID++;
698		687
699	$_[0] =~ /::/	688	$_[0] =~ /::/
700	or Carp::croak "spawn init function must be a fully-qualified name, caught";	689	or Carp::croak "spawn init function must be a fully-qualified name, caught";
701		690
702	($NODE{$noderef} \|\| add_node $noderef)	691	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
703	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
704		692
705	"$noderef#$id"	693	"$nodeid#$id"
706	}	694	}
707		695
708	=back	696	=item after $timeout, @msg
709		697
710	=head1 NODE MESSAGES	698	=item after $timeout, $callback
711		699
712	Nodes understand the following messages sent to them. Many of them take	700	Either sends the given message, or call the given callback, after the
713	arguments called C<@reply>, which will simply be used to compose a reply	701	specified number of seconds.
714	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
715	the remaining arguments are simply the message data.
716		702
717	While other messages exist, they are not public and subject to change.	703	This is simply a utility function that comes in handy at times - the
		704	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		705	so it may go away in the future.
718		706
719	=over 4
720
721	=cut	707	=cut
722		708
723	=item lookup => $name, @reply	709	sub after($@) {
		710	my ($timeout, @action) = @_;
724		711
725	Replies with the port ID of the specified well-known port, or C<undef>.	712	my $t; $t = AE::timer $timeout, 0, sub {
		713	undef $t;
		714	ref $action[0]
		715	? $action[0]()
		716	: snd @action;
		717	};
		718	}
726		719
727	=item devnull => ...	720	=item cal $port, @msg, $callback[, $timeout]
728		721
729	Generic data sink/CPU heat conversion.	722	A simple form of RPC - sends a message to the given C<$port> with the
		723	given contents (C<@msg>), but adds a reply port to the message.
730		724
731	=item relay => $port, @msg	725	The reply port is created temporarily just for the purpose of receiving
		726	the reply, and will be C<kil>ed when no longer needed.
732		727
733	Simply forwards the message to the given port.	728	A reply message sent to the port is passed to the C<$callback> as-is.
734		729
735	=item eval => $string[ @reply]	730	If an optional time-out (in seconds) is given and it is not C<undef>,
		731	then the callback will be called without any arguments after the time-out
		732	elapsed and the port is C<kil>ed.
736		733
737	Evaluates the given string. If C<@reply> is given, then a message of the	734	If no time-out is given, then the local port will monitor the remote port
738	form C<@reply, $@, @evalres> is sent.	735	instead, so it eventually gets cleaned-up.
739		736
740	Example: crash another node.	737	Currently this function returns the temporary port, but this "feature"
		738	might go in future versions unless you can make a convincing case that
		739	this is indeed useful for something.
741		740
742	snd $othernode, eval => "exit";	741	=cut
743		742
744	=item time => @reply	743	sub cal(@) {
		744	my $timeout = ref $_[-1] ? undef : pop;
		745	my $cb = pop;
745		746
746	Replies the the current node time to C<@reply>.	747	my $port = port {
		748	undef $timeout;
		749	kil $SELF;
		750	&$cb;
		751	};
747		752
748	Example: tell the current node to send the current time to C<$myport> in a	753	if (defined $timeout) {
749	C<timereply> message.	754	$timeout = AE::timer $timeout, 0, sub {
		755	undef $timeout;
		756	kil $port;
		757	$cb->();
		758	};
		759	} else {
		760	mon $_[0], sub {
		761	kil $port;
		762	$cb->();
		763	};
		764	}
750		765
751	snd $NODE, time => $myport, timereply => 1, 2;	766	push @_, $port;
752	# => snd $myport, timereply => 1, 2, <time>	767	&snd;
		768
		769	$port
		770	}
753		771
754	=back	772	=back
755		773
756	=head1 AnyEvent::MP vs. Distributed Erlang	774	=head1 AnyEvent::MP vs. Distributed Erlang
757		775
…		…
767		785
768	Despite the similarities, there are also some important differences:	786	Despite the similarities, there are also some important differences:
769		787
770	=over 4	788	=over 4
771		789
772	=item * Node references contain the recipe on how to contact them.	790	=item * Node IDs are arbitrary strings in AEMP.
773		791
774	Erlang relies on special naming and DNS to work everywhere in the	792	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	793	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
776	convenience functionality.	794	configuration or DNS), but will otherwise discover other odes itself.
777		795
778	This means that AEMP requires a less tightly controlled environment at the	796	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
779	cost of longer node references and a slightly higher management overhead.	797	uses "local ports are like remote ports".
		798
		799	The failure modes for local ports are quite different (runtime errors
		800	only) then for remote ports - when a local port dies, you I<know> it dies,
		801	when a connection to another node dies, you know nothing about the other
		802	port.
		803
		804	Erlang pretends remote ports are as reliable as local ports, even when
		805	they are not.
		806
		807	AEMP encourages a "treat remote ports differently" philosophy, with local
		808	ports being the special case/exception, where transport errors cannot
		809	occur.
780		810
781	=item * Erlang uses processes and a mailbox, AEMP does not queue.	811	=item * Erlang uses processes and a mailbox, AEMP does not queue.
782		812
783	Erlang uses processes that selctively receive messages, and therefore	813	Erlang uses processes that selectively receive messages, and therefore
784	needs a queue. AEMP is event based, queuing messages would serve no useful	814	needs a queue. AEMP is event based, queuing messages would serve no
785	purpose.	815	useful purpose. For the same reason the pattern-matching abilities of
		816	AnyEvent::MP are more limited, as there is little need to be able to
		817	filter messages without dequeuing them.
786		818
787	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	819	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
788		820
789	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	821	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
790		822
791	Sending messages in Erlang is synchronous and blocks the process. AEMP	823	Sending messages in Erlang is synchronous and blocks the process (and
792	sends are immediate, connection establishment is handled in the	824	so does not need a queue that can overflow). AEMP sends are immediate,
793	background.	825	connection establishment is handled in the background.
794		826
795	=item * Erlang can silently lose messages, AEMP cannot.	827	=item * Erlang suffers from silent message loss, AEMP does not.
796		828
797	Erlang makes few guarantees on messages delivery - messages can get lost	829	Erlang makes few guarantees on messages delivery - messages can get lost
798	without any of the processes realising it (i.e. you send messages a, b,	830	without any of the processes realising it (i.e. you send messages a, b,
799	and c, and the other side only receives messages a and c).	831	and c, and the other side only receives messages a and c).
800		832
801	AEMP guarantees correct ordering, and the guarantee that there are no	833	AEMP guarantees correct ordering, and the guarantee that after one message
802	holes in the message sequence.	834	is lost, all following ones sent to the same port are lost as well, until
803		835	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	836	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		837
815	=item * Erlang can send messages to the wrong port, AEMP does not.	838	=item * Erlang can send messages to the wrong port, AEMP does not.
816		839
817	In Erlang it is quite possible that a node that restarts reuses a process	840	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	841	known to other nodes for a completely different process, causing messages
819	messages destined for that process to end up in an unrelated process.	842	destined for that process to end up in an unrelated process.
820		843
821	AEMP never reuses port IDs, so old messages or old port IDs floating	844	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.	845	around in the network will not be sent to an unrelated port.
823		846
824	=item * Erlang uses unprotected connections, AEMP uses secure	847	=item * Erlang uses unprotected connections, AEMP uses secure
825	authentication and can use TLS.	848	authentication and can use TLS.
826		849
827	AEMP can use a proven protocol - SSL/TLS - to protect connections and	850	AEMP can use a proven protocol - TLS - to protect connections and
828	securely authenticate nodes.	851	securely authenticate nodes.
829		852
830	=item * The AEMP protocol is optimised for both text-based and binary	853	=item * The AEMP protocol is optimised for both text-based and binary
831	communications.	854	communications.
832		855
833	The AEMP protocol, unlike the Erlang protocol, supports both	856	The AEMP protocol, unlike the Erlang protocol, supports both programming
834	language-independent text-only protocols (good for debugging) and binary,	857	language independent text-only protocols (good for debugging) and binary,
835	language-specific serialisers (e.g. Storable).	858	language-specific serialisers (e.g. Storable). By default, unless TLS is
		859	used, the protocol is actually completely text-based.
836		860
837	It has also been carefully designed to be implementable in other languages	861	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	862	with a minimum of work while gracefully degrading functionality to make the
839	protocol simple.	863	protocol simple.
840		864
841	=item * AEMP has more flexible monitoring options than Erlang.	865	=item * AEMP has more flexible monitoring options than Erlang.
842		866
843	In Erlang, you can chose to receive I<all> exit signals as messages	867	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	870	Erlang, as one can choose between automatic kill, exit message or callback
847	on a per-process basis.	871	on a per-process basis.
848		872
849	=item * Erlang tries to hide remote/local connections, AEMP does not.	873	=item * Erlang tries to hide remote/local connections, AEMP does not.
850		874
851	Monitoring in Erlang is not an indicator of process death/crashes,	875	Monitoring in Erlang is not an indicator of process death/crashes, in the
852	as linking is (except linking is unreliable in Erlang).	876	same way as linking is (except linking is unreliable in Erlang).
853		877
854	In AEMP, you don't "look up" registered port names or send to named ports	878	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	879	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	880	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	881	remote port. Since both monitors are local to the node, they are much more
858	more reliable.	882	reliable (no need for C<spawn_link>).
859		883
860	This also saves round-trips and avoids sending messages to the wrong port	884	This also saves round-trips and avoids sending messages to the wrong port
861	(hard to do in Erlang).	885	(hard to do in Erlang).
862		886
863	=back	887	=back
864		888
865	=head1 RATIONALE	889	=head1 RATIONALE
866		890
867	=over 4	891	=over 4
868		892
869	=item Why strings for ports and noderefs, why not objects?	893	=item Why strings for port and node IDs, why not objects?
870		894
871	We considered "objects", but found that the actual number of methods	895	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	896	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	897	the network frequently, the serialising/deserialising would add lots of
874	overhead, as well as having to keep a proxy object.	898	overhead, as well as having to keep a proxy object everywhere.
875		899
876	Strings can easily be printed, easily serialised etc. and need no special	900	Strings can easily be printed, easily serialised etc. and need no special
877	procedures to be "valid".	901	procedures to be "valid".
878		902
879	And a a miniport consists of a single closure stored in a global hash - it	903	And as a result, a miniport consists of a single closure stored in a
880	can't become much cheaper.	904	global hash - it can't become much cheaper.
881		905
882	=item Why favour JSON, why not real serialising format such as Storable?	906	=item Why favour JSON, why not a real serialising format such as Storable?
883		907
884	In fact, any AnyEvent::MP node will happily accept Storable as framing	908	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	909	format, but currently there is no way to make a node use Storable by
886	default.	910	default (although all nodes will accept it).
887		911
888	The default framing protocol is JSON because a) JSON::XS is many times	912	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	913	faster for small messages and b) most importantly, after years of
890	experience we found that object serialisation is causing more problems	914	experience we found that object serialisation is causing more problems
891	than it gains: Just like function calls, objects simply do not travel	915	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	916	easily over the network, mostly because they will always be a copy, so you
893	always have to re-think your design.	917	always have to re-think your design.
894		918
895	Keeping your messages simple, concentrating on data structures rather than	919	Keeping your messages simple, concentrating on data structures rather than
896	objects, will keep your messages clean, tidy and efficient.	920	objects, will keep your messages clean, tidy and efficient.
897		921
898	=back	922	=back
899		923
900	=head1 SEE ALSO	924	=head1 SEE ALSO
901		925
		926	L<AnyEvent::MP::Intro> - a gentle introduction.
		927
		928	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		929
		930	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		931	your applications.
		932
		933	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		934	all nodes.
		935
902	L<AnyEvent>.	936	L<AnyEvent>.
903		937
904	=head1 AUTHOR	938	=head1 AUTHOR
905		939
906	Marc Lehmann <schmorp@schmorp.de>	940	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.87 by root, Fri Sep 11 02:32:23 2009 UTC