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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC vs.
Revision 1.71 by root, Sun Aug 30 19:52:56 2009 UTC

…		…
11	NODE $port # returns the noderef of the port	11	NODE $port # returns the noderef of the port
12		12
13	$SELF # receiving/own port id in rcv callbacks	13	$SELF # receiving/own port id in rcv callbacks
14		14
15	# initialise the node so it can send/receive messages	15	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	16	initialise_node;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		17
20	# ports are message endpoints	18	# ports are message endpoints
21		19
22	# sending messages	20	# sending messages
23	snd $port, type => data...;	21	snd $port, type => data...;
24	snd $port, @msg;	22	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	23	snd @msg_with_first_element_being_a_port;
26		24
27	# creating/using ports, the simple way	25	# creating/using ports, the simple way
28	my $somple_port = port { my @msg = @_; 0 };	26	my $simple_port = port { my @msg = @_; 0 };
29		27
30	# creating/using ports, tagged message matching	28	# creating/using ports, tagged message matching
31	my $port = port;	29	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	31	rcv $port, pong => sub { warn "pong received\n"; 0 };
…		…
40	mon $port, $otherport # kill otherport on abnormal death	38	mon $port, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	39	mon $port, $otherport, @msg # send message on death
42		40
43	=head1 CURRENT STATUS	41	=head1 CURRENT STATUS
44		42
		43	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	44	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	45	AnyEvent::MP::Intro - uptodate, but incomplete.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	46	AnyEvent::MP::Kernel - mostly stable.
		47	AnyEvent::MP::Global - stable API, protocol not yet final.
49		48
50	stay tuned.	49	stay tuned.
51		50
52	=head1 DESCRIPTION	51	=head1 DESCRIPTION
53		52
54	This module (-family) implements a simple message passing framework.	53	This module (-family) implements a simple message passing framework.
55		54
56	Despite its simplicity, you can securely message other processes running	55	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	56	on the same or other hosts, and you can supervise entities remotely.
58		57
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	58	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	59	manual page and the examples under F<eg/>.
61		60
62	At the moment, this module family is severly broken and underdocumented,	61	At the moment, this module family is a bit underdocumented.
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		62
66	=head1 CONCEPTS	63	=head1 CONCEPTS
67		64
68	=over 4	65	=over 4
69		66
70	=item port	67	=item port
71		68
72	A port is something you can send messages to (with the C<snd> function).	69	A port is something you can send messages to (with the C<snd> function).
73		70
74	Some ports allow you to register C<rcv> handlers that can match specific	71	Ports allow you to register C<rcv> handlers that can match all or just
75	messages. All C<rcv> handlers will receive messages they match, messages	72	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	73	anything was listening for them or not.
77		74
78	=item port id - C<noderef#portname>	75	=item port ID - C<nodeid#portname>
79		76
80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	77	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
81	separator, and a port name (a printable string of unspecified format). An	78	separator, and a port name (a printable string of unspecified format).
82	exception is the the node port, whose ID is identical to its node
83	reference.
84		79
85	=item node	80	=item node
86		81
87	A node is a single process containing at least one port - the node	82	A node is a single process containing at least one port - the node port,
88	port. You can send messages to node ports to find existing ports or to	83	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	84	ports.
90		85
91	Nodes are either private (single-process only), slaves (connected to a	86	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	87	(no listening ports). Private nodes cannot talk to other private nodes
		88	currently.
93		89
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	90	=item node ID - C<[a-za-Z0-9_\-.:]+>
95		91
96	A node reference is a string that either simply identifies the node (for	92	A node ID is a string that uniquely identifies the node within a
97	private and slave nodes), or contains a recipe on how to reach a given	93	network. Depending on the configuration used, node IDs can look like a
98	node (for public nodes).	94	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		95	doesn't interpret node IDs in any way.
99		96
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	97	=item binds - C<ip:port>
101	TCP/IP, other protocols might look different).
102		98
103	Node references come in two flavours: resolved (containing only numerical	99	Nodes can only talk to each other by creating some kind of connection to
104	addresses) or unresolved (where hostnames are used instead of addresses).	100	each other. To do this, nodes should listen on one or more local transport
		101	endpoints - binds. Currently, only standard C<ip:port> specifications can
		102	be used, which specify TCP ports to listen on.
105		103
106	Before using an unresolved node reference in a message you first have to	104	=item seeds - C<host:port>
107	resolve it.	105
		106	When a node starts, it knows nothing about the network. To teach the node
		107	about the network it first has to contact some other node within the
		108	network. This node is called a seed.
		109
		110	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		111	are expected to be long-running, and at least one of those should always
		112	be available. When nodes run out of connections (e.g. due to a network
		113	error), they try to re-establish connections to some seednodes again to
		114	join the network.
		115
		116	Apart from being sued for seeding, seednodes are not special in any way -
		117	every public node can be a seednode.
108		118
109	=back	119	=back
110		120
111	=head1 VARIABLES/FUNCTIONS	121	=head1 VARIABLES/FUNCTIONS
112		122
…		…
127	use base "Exporter";	137	use base "Exporter";
128		138
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
130		140
131	our @EXPORT = qw(	141	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	142	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	143	initialise_node
134	snd rcv mon kil reg psub spawn	144	snd rcv mon mon_guard kil reg psub spawn
135	port	145	port
136	);	146	);
137		147
138	our $SELF;	148	our $SELF;
139		149
…		…
143	kil $SELF, die => $msg;	153	kil $SELF, die => $msg;
144	}	154	}
145		155
146	=item $thisnode = NODE / $NODE	156	=item $thisnode = NODE / $NODE
147		157
148	The C<NODE> function returns, and the C<$NODE> variable contains the	158	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	noderef of the local node. The value is initialised by a call to	159	ID of the node running in the current process. This value is initialised by
150	C<initialise_node>.	160	a call to C<initialise_node>.
151		161
152	=item $noderef = node_of $port	162	=item $nodeid = node_of $port
153		163
154	Extracts and returns the noderef from a port ID or a noderef.	164	Extracts and returns the node ID from a port ID or a node ID.
155		165
156	=item initialise_node $noderef, $seednode, $seednode...	166	=item initialise_node $profile_name, key => value...
157		167
158	=item initialise_node "slave/", $master, $master...
159
160	Before a node can talk to other nodes on the network it has to initialise	168	Before a node can talk to other nodes on the network (i.e. enter
161	itself - the minimum a node needs to know is it's own name, and optionally	169	"distributed mode") it has to initialise itself - the minimum a node needs
162	it should know the noderefs of some other nodes in the network.	170	to know is its own name, and optionally it should know the addresses of
		171	some other nodes in the network to discover other nodes.
163		172
164	This function initialises a node - it must be called exactly once (or	173	This function initialises a node - it must be called exactly once (or
165	never) before calling other AnyEvent::MP functions.	174	never) before calling other AnyEvent::MP functions.
166		175
167	All arguments (optionally except for the first) are noderefs, which can be	176	The first argument is a profile name. If it is C<undef> or missing, then
168	either resolved or unresolved.	177	the current nodename will be used instead (i.e. F<uname -n>).
169		178
170	The first argument will be looked up in the configuration database first	179	The function first looks up the profile in the aemp configuration (see the
171	(if it is C<undef> then the current nodename will be used instead) to find	180	L<aemp> commandline utility). the profile is calculated as follows:
172	the relevant configuration profile (see L<aemp>). If none is found then
173	the default configuration is used. The configuration supplies additional
174	seed/master nodes and can override the actual noderef.
175		181
176	There are two types of networked nodes, public nodes and slave nodes:	182	First, all remaining key => value pairs (all of which are conviniently
		183	undocumented at the moment) will be used. Then they will be overwritten by
		184	any values specified in the global default configuration (see the F<aemp>
		185	utility), then the chain of profiles selected, if any. That means that
		186	the values specified in the profile have highest priority and the values
		187	specified via C<initialise_node> have lowest priority.
177		188
178	=over 4	189	If the profile specifies a node ID, then this will become the node ID of
		190	this process. If not, then the profile name will be used as node ID. The
		191	special node ID of C<anon/> will be replaced by a random node ID.
179		192
180	=item public nodes	193	The next step is to look up the binds in the profile, followed by binding
		194	aemp protocol listeners on all binds specified (it is possible and valid
		195	to have no binds, meaning that the node cannot be contacted form the
		196	outside. This means the node cannot talk to other nodes that also have no
		197	binds, but it can still talk to all "normal" nodes).
181		198
182	For public nodes, C<$noderef> (supplied either directly to	199	If the profile does not specify a binds list, then a default of C<*> is
183	C<initialise_node> or indirectly via a profile or the nodename) must be a	200	used.
184	noderef (possibly unresolved, in which case it will be resolved).
185		201
186	After resolving, the node will bind itself on all endpoints and try to	202	Lastly, the seeds list from the profile is passed to the
187	connect to all additional C<$seednodes> that are specified. Seednodes are	203	L<AnyEvent::MP::Global> module, which will then use it to keep
188	optional and can be used to quickly bootstrap the node into an existing	204	connectivity with at least on of those seed nodes at any point in time.
189	network.
190		205
191	=item slave nodes
192
193	When the C<$noderef> (either as given or overriden by the config file)
194	is the special string C<slave/>, then the node will become a slave
195	node. Slave nodes cannot be contacted from outside and will route most of
196	their traffic to the master node that they attach to.
197
198	At least one additional noderef is required (either by specifying it
199	directly or because it is part of the configuration profile): The node
200	will try to connect to all of them and will become a slave attached to the
201	first node it can successfully connect to.
202
203	=back
204
205	This function will block until all nodes have been resolved and, for slave
206	nodes, until it has successfully established a connection to a master
207	server.
208
209	Example: become a public node listening on the guessed noderef, or the one	206	Example: become a distributed node listening on the guessed noderef, or
210	specified via C<aemp> for the current node. This should be the most common	207	the one specified via C<aemp> for the current node. This should be the
211	form of invocation for "daemon"-type nodes.	208	most common form of invocation for "daemon"-type nodes.
212		209
213	initialise_node;	210	initialise_node;
214		211
215	Example: become a slave node to any of the the seednodes specified via	212	Example: become an anonymous node. This form is often used for commandline
216	C<aemp>. This form is often used for commandline clients.	213	clients.
217		214
218	initialise_node "slave/";	215	initialise_node "anon/";
219		216
220	Example: become a slave node to any of the specified master servers. This	217	Example: become a distributed node. If there is no profile of the given
221	form is also often used for commandline clients.	218	name, or no binds list was specified, resolve C<localhost:4044> and bind
222		219	on the resulting addresses.
223	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
224
225	Example: become a public node, and try to contact some well-known master
226	servers to become part of the network.
227
228	initialise_node undef, "master1", "master2";
229
230	Example: become a public node listening on port C<4041>.
231
232	initialise_node 4041;
233
234	Example: become a public node, only visible on localhost port 4044.
235		220
236	initialise_node "localhost:4044";	221	initialise_node "localhost:4044";
237
238	=item $cv = resolve_node $noderef
239
240	Takes an unresolved node reference that may contain hostnames and
241	abbreviated IDs, resolves all of them and returns a resolved node
242	reference.
243
244	In addition to C<address:port> pairs allowed in resolved noderefs, the
245	following forms are supported:
246
247	=over 4
248
249	=item the empty string
250
251	An empty-string component gets resolved as if the default port (4040) was
252	specified.
253
254	=item naked port numbers (e.g. C<1234>)
255
256	These are resolved by prepending the local nodename and a colon, to be
257	further resolved.
258
259	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
260
261	These are resolved by using AnyEvent::DNS to resolve them, optionally
262	looking up SRV records for the C<aemp=4040> port, if no port was
263	specified.
264
265	=back
266		222
267	=item $SELF	223	=item $SELF
268		224
269	Contains the current port id while executing C<rcv> callbacks or C<psub>	225	Contains the current port id while executing C<rcv> callbacks or C<psub>
270	blocks.	226	blocks.
271		227
272	=item SELF, %SELF, @SELF...	228	=item *SELF, SELF, %SELF, @SELF...
273		229
274	Due to some quirks in how perl exports variables, it is impossible to	230	Due to some quirks in how perl exports variables, it is impossible to
275	just export C<$SELF>, all the symbols called C<SELF> are exported by this	231	just export C<$SELF>, all the symbols named C<SELF> are exported by this
276	module, but only C<$SELF> is currently used.	232	module, but only C<$SELF> is currently used.
277		233
278	=item snd $port, type => @data	234	=item snd $port, type => @data
279		235
280	=item snd $port, @msg	236	=item snd $port, @msg
281		237
282	Send the given message to the given port ID, which can identify either	238	Send the given message to the given port, which can identify either a
283	a local or a remote port, and must be a port ID.	239	local or a remote port, and must be a port ID.
284		240
285	While the message can be about anything, it is highly recommended to use a	241	While the message can be almost anything, it is highly recommended to
286	string as first element (a port ID, or some word that indicates a request	242	use a string as first element (a port ID, or some word that indicates a
287	type etc.).	243	request type etc.) and to consist if only simple perl values (scalars,
		244	arrays, hashes) - if you think you need to pass an object, think again.
288		245
289	The message data effectively becomes read-only after a call to this	246	The message data logically becomes read-only after a call to this
290	function: modifying any argument is not allowed and can cause many	247	function: modifying any argument (or values referenced by them) is
291	problems.	248	forbidden, as there can be considerable time between the call to C<snd>
		249	and the time the message is actually being serialised - in fact, it might
		250	never be copied as within the same process it is simply handed to the
		251	receiving port.
292		252
293	The type of data you can transfer depends on the transport protocol: when	253	The type of data you can transfer depends on the transport protocol: when
294	JSON is used, then only strings, numbers and arrays and hashes consisting	254	JSON is used, then only strings, numbers and arrays and hashes consisting
295	of those are allowed (no objects). When Storable is used, then anything	255	of those are allowed (no objects). When Storable is used, then anything
296	that Storable can serialise and deserialise is allowed, and for the local	256	that Storable can serialise and deserialise is allowed, and for the local
297	node, anything can be passed.	257	node, anything can be passed. Best rely only on the common denominator of
		258	these.
298		259
299	=item $local_port = port	260	=item $local_port = port
300		261
301	Create a new local port object and returns its port ID. Initially it has	262	Create a new local port object and returns its port ID. Initially it has
302	no callbacks set and will throw an error when it receives messages.	263	no callbacks set and will throw an error when it receives messages.
…		…
349	The default callback received all messages not matched by a more specific	310	The default callback received all messages not matched by a more specific
350	C<tag> match.	311	C<tag> match.
351		312
352	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	313	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
353		314
354	Register callbacks to be called on messages starting with the given tag on	315	Register (or replace) callbacks to be called on messages starting with the
355	the given port (and return the port), or unregister it (when C<$callback>	316	given tag on the given port (and return the port), or unregister it (when
356	is C<$undef>).	317	C<$callback> is C<$undef> or missing). There can only be one callback
		318	registered for each tag.
357		319
358	The original message will be passed to the callback, after the first	320	The original message will be passed to the callback, after the first
359	element (the tag) has been removed. The callback will use the same	321	element (the tag) has been removed. The callback will use the same
360	environment as the default callback (see above).	322	environment as the default callback (see above).
361		323
…		…
373	rcv port,	335	rcv port,
374	msg1 => sub { ... },	336	msg1 => sub { ... },
375	...	337	...
376	;	338	;
377		339
		340	Example: temporarily register a rcv callback for a tag matching some port
		341	(e.g. for a rpc reply) and unregister it after a message was received.
		342
		343	rcv $port, $otherport => sub {
		344	my @reply = @_;
		345
		346	rcv $SELF, $otherport;
		347	};
		348
378	=cut	349	=cut
379		350
380	sub rcv($@) {	351	sub rcv($@) {
381	my $port = shift;	352	my $port = shift;
382	my ($noderef, $portid) = split /#/, $port, 2;	353	my ($noderef, $portid) = split /#/, $port, 2;
383		354
384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	355	$NODE{$noderef} == $NODE{""}
385	or Carp::croak "$port: rcv can only be called on local ports, caught";	356	or Carp::croak "$port: rcv can only be called on local ports, caught";
386		357
387	while (@_) {	358	while (@_) {
388	if (ref $_[0]) {	359	if (ref $_[0]) {
389	if (my $self = $PORT_DATA{$portid}) {	360	if (my $self = $PORT_DATA{$portid}) {
…		…
468	$res	439	$res
469	}	440	}
470	}	441	}
471	}	442	}
472		443
473	=item $guard = mon $port, $cb->(@reason)	444	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
474		445
475	=item $guard = mon $port, $rcvport	446	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
476		447
477	=item $guard = mon $port	448	=item $guard = mon $port # kill $SELF when $port dies
478		449
479	=item $guard = mon $port, $rcvport, @msg	450	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
480		451
481	Monitor the given port and do something when the port is killed or	452	Monitor the given port and do something when the port is killed or
482	messages to it were lost, and optionally return a guard that can be used	453	messages to it were lost, and optionally return a guard that can be used
483	to stop monitoring again.	454	to stop monitoring again.
484		455
485	C<mon> effectively guarantees that, in the absence of hardware failures,	456	C<mon> effectively guarantees that, in the absence of hardware failures,
486	that after starting the monitor, either all messages sent to the port	457	after starting the monitor, either all messages sent to the port will
487	will arrive, or the monitoring action will be invoked after possible	458	arrive, or the monitoring action will be invoked after possible message
488	message loss has been detected. No messages will be lost "in between"	459	loss has been detected. No messages will be lost "in between" (after
489	(after the first lost message no further messages will be received by the	460	the first lost message no further messages will be received by the
490	port). After the monitoring action was invoked, further messages might get	461	port). After the monitoring action was invoked, further messages might get
491	delivered again.	462	delivered again.
		463
		464	Note that monitoring-actions are one-shot: once messages are lost (and a
		465	monitoring alert was raised), they are removed and will not trigger again.
492		466
493	In the first form (callback), the callback is simply called with any	467	In the first form (callback), the callback is simply called with any
494	number of C<@reason> elements (no @reason means that the port was deleted	468	number of C<@reason> elements (no @reason means that the port was deleted
495	"normally"). Note also that I<< the callback B<must> never die >>, so use	469	"normally"). Note also that I<< the callback B<must> never die >>, so use
496	C<eval> if unsure.	470	C<eval> if unsure.
…		…
558	is killed, the references will be freed.	532	is killed, the references will be freed.
559		533
560	Optionally returns a guard that will stop the monitoring.	534	Optionally returns a guard that will stop the monitoring.
561		535
562	This function is useful when you create e.g. timers or other watchers and	536	This function is useful when you create e.g. timers or other watchers and
563	want to free them when the port gets killed:	537	want to free them when the port gets killed (note the use of C<psub>):
564		538
565	$port->rcv (start => sub {	539	$port->rcv (start => sub {
566	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	540	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
567	undef $timer if 0.9 < rand;	541	undef $timer if 0.9 < rand;
568	});	542	});
569	});	543	});
570		544
571	=cut	545	=cut
…		…
580		554
581	=item kil $port[, @reason]	555	=item kil $port[, @reason]
582		556
583	Kill the specified port with the given C<@reason>.	557	Kill the specified port with the given C<@reason>.
584		558
585	If no C<@reason> is specified, then the port is killed "normally" (linked	559	If no C<@reason> is specified, then the port is killed "normally" (ports
586	ports will not be kileld, or even notified).	560	monitoring other ports will not necessarily die because a port dies
		561	"normally").
587		562
588	Otherwise, linked ports get killed with the same reason (second form of	563	Otherwise, linked ports get killed with the same reason (second form of
589	C<mon>, see below).	564	C<mon>, see above).
590		565
591	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	566	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
592	will be reported as reason C<< die => $@ >>.	567	will be reported as reason C<< die => $@ >>.
593		568
594	Transport/communication errors are reported as C<< transport_error =>	569	Transport/communication errors are reported as C<< transport_error =>
…		…
599	=item $port = spawn $node, $initfunc[, @initdata]	574	=item $port = spawn $node, $initfunc[, @initdata]
600		575
601	Creates a port on the node C<$node> (which can also be a port ID, in which	576	Creates a port on the node C<$node> (which can also be a port ID, in which
602	case it's the node where that port resides).	577	case it's the node where that port resides).
603		578
604	The port ID of the newly created port is return immediately, and it is	579	The port ID of the newly created port is returned immediately, and it is
605	permissible to immediately start sending messages or monitor the port.	580	possible to immediately start sending messages or to monitor the port.
606		581
607	After the port has been created, the init function is	582	After the port has been created, the init function is called on the remote
608	called. This function must be a fully-qualified function name	583	node, in the same context as a C<rcv> callback. This function must be a
609	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	584	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
610	program, use C<::name>.	585	specify a function in the main program, use C<::name>.
611		586
612	If the function doesn't exist, then the node tries to C<require>	587	If the function doesn't exist, then the node tries to C<require>
613	the package, then the package above the package and so on (e.g.	588	the package, then the package above the package and so on (e.g.
614	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	589	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
615	exists or it runs out of package names.	590	exists or it runs out of package names.
616		591
617	The init function is then called with the newly-created port as context	592	The init function is then called with the newly-created port as context
618	object (C<$SELF>) and the C<@initdata> values as arguments.	593	object (C<$SELF>) and the C<@initdata> values as arguments.
619		594
620	A common idiom is to pass your own port, monitor the spawned port, and	595	A common idiom is to pass a local port, immediately monitor the spawned
621	in the init function, monitor the original port. This two-way monitoring	596	port, and in the remote init function, immediately monitor the passed
622	ensures that both ports get cleaned up when there is a problem.	597	local port. This two-way monitoring ensures that both ports get cleaned up
		598	when there is a problem.
623		599
624	Example: spawn a chat server port on C<$othernode>.	600	Example: spawn a chat server port on C<$othernode>.
625		601
626	# this node, executed from within a port context:	602	# this node, executed from within a port context:
627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	603	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
657	my $id = "$RUNIQ." . $ID++;	633	my $id = "$RUNIQ." . $ID++;
658		634
659	$_[0] =~ /::/	635	$_[0] =~ /::/
660	or Carp::croak "spawn init function must be a fully-qualified name, caught";	636	or Carp::croak "spawn init function must be a fully-qualified name, caught";
661		637
662	($NODE{$noderef} \|\| add_node $noderef)	638	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
663	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
664		639
665	"$noderef#$id"	640	"$noderef#$id"
666	}	641	}
667		642
668	=back	643	=item after $timeout, @msg
669		644
670	=head1 NODE MESSAGES	645	=item after $timeout, $callback
671		646
672	Nodes understand the following messages sent to them. Many of them take	647	Either sends the given message, or call the given callback, after the
673	arguments called C<@reply>, which will simply be used to compose a reply	648	specified number of seconds.
674	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
675	the remaining arguments are simply the message data.
676		649
677	While other messages exist, they are not public and subject to change.	650	This is simply a utility function that comes in handy at times - the
		651	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		652	so it may go away in the future.
678		653
679	=over 4
680
681	=cut	654	=cut
682		655
683	=item lookup => $name, @reply	656	sub after($@) {
		657	my ($timeout, @action) = @_;
684		658
685	Replies with the port ID of the specified well-known port, or C<undef>.	659	my $t; $t = AE::timer $timeout, 0, sub {
686		660	undef $t;
687	=item devnull => ...	661	ref $action[0]
688		662	? $action[0]()
689	Generic data sink/CPU heat conversion.	663	: snd @action;
690		664	};
691	=item relay => $port, @msg	665	}
692
693	Simply forwards the message to the given port.
694
695	=item eval => $string[ @reply]
696
697	Evaluates the given string. If C<@reply> is given, then a message of the
698	form C<@reply, $@, @evalres> is sent.
699
700	Example: crash another node.
701
702	snd $othernode, eval => "exit";
703
704	=item time => @reply
705
706	Replies the the current node time to C<@reply>.
707
708	Example: tell the current node to send the current time to C<$myport> in a
709	C<timereply> message.
710
711	snd $NODE, time => $myport, timereply => 1, 2;
712	# => snd $myport, timereply => 1, 2, <time>
713		666
714	=back	667	=back
715		668
716	=head1 AnyEvent::MP vs. Distributed Erlang	669	=head1 AnyEvent::MP vs. Distributed Erlang
717		670
…		…
727		680
728	Despite the similarities, there are also some important differences:	681	Despite the similarities, there are also some important differences:
729		682
730	=over 4	683	=over 4
731		684
732	=item * Node references contain the recipe on how to contact them.	685	=item * Node IDs are arbitrary strings in AEMP.
733		686
734	Erlang relies on special naming and DNS to work everywhere in the	687	Erlang relies on special naming and DNS to work everywhere in the same
735	same way. AEMP relies on each node knowing it's own address(es), with	688	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
736	convenience functionality.	689	configuraiton or DNS), but will otherwise discover other odes itself.
737		690
738	This means that AEMP requires a less tightly controlled environment at the
739	cost of longer node references and a slightly higher management overhead.
740
741	=item Erlang has a "remote ports are like local ports" philosophy, AEMP	691	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
742	uses "local ports are like remote ports".	692	uses "local ports are like remote ports".
743		693
744	The failure modes for local ports are quite different (runtime errors	694	The failure modes for local ports are quite different (runtime errors
745	only) then for remote ports - when a local port dies, you I<know> it dies,	695	only) then for remote ports - when a local port dies, you I<know> it dies,
746	when a connection to another node dies, you know nothing about the other	696	when a connection to another node dies, you know nothing about the other
…		…
773		723
774	Erlang makes few guarantees on messages delivery - messages can get lost	724	Erlang makes few guarantees on messages delivery - messages can get lost
775	without any of the processes realising it (i.e. you send messages a, b,	725	without any of the processes realising it (i.e. you send messages a, b,
776	and c, and the other side only receives messages a and c).	726	and c, and the other side only receives messages a and c).
777		727
778	AEMP guarantees correct ordering, and the guarantee that there are no	728	AEMP guarantees correct ordering, and the guarantee that after one message
779	holes in the message sequence.	729	is lost, all following ones sent to the same port are lost as well, until
780		730	monitoring raises an error, so there are no silent "holes" in the message
781	=item * In Erlang, processes can be declared dead and later be found to be	731	sequence.
782	alive.
783
784	In Erlang it can happen that a monitored process is declared dead and
785	linked processes get killed, but later it turns out that the process is
786	still alive - and can receive messages.
787
788	In AEMP, when port monitoring detects a port as dead, then that port will
789	eventually be killed - it cannot happen that a node detects a port as dead
790	and then later sends messages to it, finding it is still alive.
791		732
792	=item * Erlang can send messages to the wrong port, AEMP does not.	733	=item * Erlang can send messages to the wrong port, AEMP does not.
793		734
794	In Erlang it is quite likely that a node that restarts reuses a process ID	735	In Erlang it is quite likely that a node that restarts reuses a process ID
795	known to other nodes for a completely different process, causing messages	736	known to other nodes for a completely different process, causing messages
…		…
799	around in the network will not be sent to an unrelated port.	740	around in the network will not be sent to an unrelated port.
800		741
801	=item * Erlang uses unprotected connections, AEMP uses secure	742	=item * Erlang uses unprotected connections, AEMP uses secure
802	authentication and can use TLS.	743	authentication and can use TLS.
803		744
804	AEMP can use a proven protocol - SSL/TLS - to protect connections and	745	AEMP can use a proven protocol - TLS - to protect connections and
805	securely authenticate nodes.	746	securely authenticate nodes.
806		747
807	=item * The AEMP protocol is optimised for both text-based and binary	748	=item * The AEMP protocol is optimised for both text-based and binary
808	communications.	749	communications.
809		750
810	The AEMP protocol, unlike the Erlang protocol, supports both	751	The AEMP protocol, unlike the Erlang protocol, supports both programming
811	language-independent text-only protocols (good for debugging) and binary,	752	language independent text-only protocols (good for debugging) and binary,
812	language-specific serialisers (e.g. Storable).	753	language-specific serialisers (e.g. Storable). By default, unless TLS is
		754	used, the protocol is actually completely text-based.
813		755
814	It has also been carefully designed to be implementable in other languages	756	It has also been carefully designed to be implementable in other languages
815	with a minimum of work while gracefully degrading fucntionality to make the	757	with a minimum of work while gracefully degrading functionality to make the
816	protocol simple.	758	protocol simple.
817		759
818	=item * AEMP has more flexible monitoring options than Erlang.	760	=item * AEMP has more flexible monitoring options than Erlang.
819		761
820	In Erlang, you can chose to receive I<all> exit signals as messages	762	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
823	Erlang, as one can choose between automatic kill, exit message or callback	765	Erlang, as one can choose between automatic kill, exit message or callback
824	on a per-process basis.	766	on a per-process basis.
825		767
826	=item * Erlang tries to hide remote/local connections, AEMP does not.	768	=item * Erlang tries to hide remote/local connections, AEMP does not.
827		769
828	Monitoring in Erlang is not an indicator of process death/crashes,	770	Monitoring in Erlang is not an indicator of process death/crashes, in the
829	as linking is (except linking is unreliable in Erlang).	771	same way as linking is (except linking is unreliable in Erlang).
830		772
831	In AEMP, you don't "look up" registered port names or send to named ports	773	In AEMP, you don't "look up" registered port names or send to named ports
832	that might or might not be persistent. Instead, you normally spawn a port	774	that might or might not be persistent. Instead, you normally spawn a port
833	on the remote node. The init function monitors the you, and you monitor	775	on the remote node. The init function monitors you, and you monitor the
834	the remote port. Since both monitors are local to the node, they are much	776	remote port. Since both monitors are local to the node, they are much more
835	more reliable.	777	reliable (no need for C<spawn_link>).
836		778
837	This also saves round-trips and avoids sending messages to the wrong port	779	This also saves round-trips and avoids sending messages to the wrong port
838	(hard to do in Erlang).	780	(hard to do in Erlang).
839		781
840	=back	782	=back
841		783
842	=head1 RATIONALE	784	=head1 RATIONALE
843		785
844	=over 4	786	=over 4
845		787
846	=item Why strings for ports and noderefs, why not objects?	788	=item Why strings for port and node IDs, why not objects?
847		789
848	We considered "objects", but found that the actual number of methods	790	We considered "objects", but found that the actual number of methods
849	thatc an be called are very low. Since port IDs and noderefs travel over	791	that can be called are quite low. Since port and node IDs travel over
850	the network frequently, the serialising/deserialising would add lots of	792	the network frequently, the serialising/deserialising would add lots of
851	overhead, as well as having to keep a proxy object.	793	overhead, as well as having to keep a proxy object everywhere.
852		794
853	Strings can easily be printed, easily serialised etc. and need no special	795	Strings can easily be printed, easily serialised etc. and need no special
854	procedures to be "valid".	796	procedures to be "valid".
855		797
856	And a a miniport consists of a single closure stored in a global hash - it	798	And as a result, a miniport consists of a single closure stored in a
857	can't become much cheaper.	799	global hash - it can't become much cheaper.
858		800
859	=item Why favour JSON, why not real serialising format such as Storable?	801	=item Why favour JSON, why not a real serialising format such as Storable?
860		802
861	In fact, any AnyEvent::MP node will happily accept Storable as framing	803	In fact, any AnyEvent::MP node will happily accept Storable as framing
862	format, but currently there is no way to make a node use Storable by	804	format, but currently there is no way to make a node use Storable by
863	default.	805	default (although all nodes will accept it).
864		806
865	The default framing protocol is JSON because a) JSON::XS is many times	807	The default framing protocol is JSON because a) JSON::XS is many times
866	faster for small messages and b) most importantly, after years of	808	faster for small messages and b) most importantly, after years of
867	experience we found that object serialisation is causing more problems	809	experience we found that object serialisation is causing more problems
868	than it gains: Just like function calls, objects simply do not travel	810	than it solves: Just like function calls, objects simply do not travel
869	easily over the network, mostly because they will always be a copy, so you	811	easily over the network, mostly because they will always be a copy, so you
870	always have to re-think your design.	812	always have to re-think your design.
871		813
872	Keeping your messages simple, concentrating on data structures rather than	814	Keeping your messages simple, concentrating on data structures rather than
873	objects, will keep your messages clean, tidy and efficient.	815	objects, will keep your messages clean, tidy and efficient.
874		816
875	=back	817	=back
876		818
877	=head1 SEE ALSO	819	=head1 SEE ALSO
878		820
		821	L<AnyEvent::MP::Intro> - a gentle introduction.
		822
		823	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		824
		825	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		826	your applications.
		827
879	L<AnyEvent>.	828	L<AnyEvent>.
880		829
881	=head1 AUTHOR	830	=head1 AUTHOR
882		831
883	Marc Lehmann <schmorp@schmorp.de>	832	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.71 by root, Sun Aug 30 19:52:56 2009 UTC