[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 1.69 by root, Sun Aug 30 18:51:49 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 };
…		…
42		40
43	=head1 CURRENT STATUS	41	=head1 CURRENT STATUS
44		42
45	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work
46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - outdated
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable
		46	AnyEvent::MP::Global - mostly stable
		47	AnyEvent::MP::Node - mostly stable, but internal anyways
		48	AnyEvent::MP::Transport - mostly stable, but internal anyways
49		49
50	stay tuned.	50	stay tuned.
51		51
52	=head1 DESCRIPTION	52	=head1 DESCRIPTION
53		53
54	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
55		55
56	Despite its simplicity, you can securely message other processes running	56	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	57	on the same or other hosts, and you can supervise entities remotely.
58		58
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	60	manual page and the examples under F<eg/>.
61		61
62	At the moment, this module family is severly broken and underdocumented,	62	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		63
66	=head1 CONCEPTS	64	=head1 CONCEPTS
67		65
68	=over 4	66	=over 4
69		67
70	=item port	68	=item port
71		69
72	A port is something you can send messages to (with the C<snd> function).	70	A port is something you can send messages to (with the C<snd> function).
73		71
74	Some ports allow you to register C<rcv> handlers that can match specific	72	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	73	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	74	anything was listening for them or not.
77		75
78	=item port id - C<noderef#portname>	76	=item port ID - C<nodeid#portname>
79		77
80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	78	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	79	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		80
85	=item node	81	=item node
86		82
87	A node is a single process containing at least one port - the node	83	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	84	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	85	ports.
90		86
91	Nodes are either private (single-process only), slaves (connected to a	87	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	88	(no listening ports). Private nodes cannot talk to other private nodes
		89	currently.
93		90
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	91	=item node ID - C<[a-za-Z0-9_\-.:]+>
95		92
96	A node reference is a string that either simply identifies the node (for	93	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	94	network. Depending on the configuration used, node IDs can look like a
98	node (for public nodes).	95	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		96	doesn't interpret node IDs in any way.
99		97
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	98	=item binds - C<ip:port>
101	TCP/IP, other protocols might look different).
102		99
103	Node references come in two flavours: resolved (containing only numerical	100	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).	101	each other. To do this, nodes should listen on one or more local transport
		102	endpoints - binds. Currently, only standard C<ip:port> specifications can
		103	be used, which specify TCP ports to listen on.
105		104
106	Before using an unresolved node reference in a message you first have to	105	=item seeds - C<host:port>
107	resolve it.	106
		107	When a node starts, it knows nothing about the network. To teach the node
		108	about the network it first has to contact some other node within the
		109	network. This node is called a seed.
		110
		111	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		112	are expected to be long-running, and at least one of those should always
		113	be available. When nodes run out of connections (e.g. due to a network
		114	error), they try to re-establish connections to some seednodes again to
		115	join the network.
		116
		117	Apart from being sued for seeding, seednodes are not special in any way -
		118	every public node can be a seednode.
108		119
109	=back	120	=back
110		121
111	=head1 VARIABLES/FUNCTIONS	122	=head1 VARIABLES/FUNCTIONS
112		123
…		…
127	use base "Exporter";	138	use base "Exporter";
128		139
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	140	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
130		141
131	our @EXPORT = qw(	142	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	143	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	144	initialise_node
134	snd rcv mon kil reg psub spawn	145	snd rcv mon mon_guard kil reg psub spawn
135	port	146	port
136	);	147	);
137		148
138	our $SELF;	149	our $SELF;
139		150
…		…
143	kil $SELF, die => $msg;	154	kil $SELF, die => $msg;
144	}	155	}
145		156
146	=item $thisnode = NODE / $NODE	157	=item $thisnode = NODE / $NODE
147		158
148	The C<NODE> function returns, and the C<$NODE> variable contains the	159	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	160	ID of the node running in the current process. This value is initialised by
150	C<initialise_node>.	161	a call to C<initialise_node>.
151		162
152	=item $noderef = node_of $port	163	=item $nodeid = node_of $port
153		164
154	Extracts and returns the noderef from a port ID or a noderef.	165	Extracts and returns the node ID from a port ID or a node ID.
155		166
156	=item initialise_node $noderef, $seednode, $seednode...	167	=item initialise_node $profile_name, key => value...
157		168
158	=item initialise_node "slave/", $master, $master...
159
160	Before a node can talk to other nodes on the network it has to initialise	169	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	170	"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.	171	to know is its own name, and optionally it should know the addresses of
		172	some other nodes in the network to discover other nodes.
163		173
164	This function initialises a node - it must be called exactly once (or	174	This function initialises a node - it must be called exactly once (or
165	never) before calling other AnyEvent::MP functions.	175	never) before calling other AnyEvent::MP functions.
166		176
167	All arguments (optionally except for the first) are noderefs, which can be	177	The first argument is a profile name. If it is C<undef> or missing, then
168	either resolved or unresolved.	178	the current nodename will be used instead (i.e. F<uname -n>).
169		179
170	The first argument will be looked up in the configuration database first	180	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	181	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		182
176	There are two types of networked nodes, public nodes and slave nodes:	183	First, all remaining key => value pairs will be used. Then they will be
		184	overwritten by any values specified in the global default configuration
		185	(see the F<aemp> utility), then the chain of profiles selected, if
		186	any. That means that the values specified in the profile have highest
		187	priority and the values specified via C<initialise_node> have lowest
		188	priority.
177		189
178	=over 4	190	If the profile specifies a node ID, then this will become the node ID of
		191	this process. If not, then the profile name will be used as node ID. The
		192	special node ID of C<anon/> will be replaced by a random node ID.
179		193
180	=item public nodes	194	The next step is to look up the binds in the profile, followed by binding
		195	aemp protocol listeners on all binds specified (it is possible and valid
		196	to have no binds, meaning that the node cannot be contacted form the
		197	outside. This means the node cannot talk to other nodes that also have no
		198	binds, but it can still talk to all "normal" nodes).
181		199
182	For public nodes, C<$noderef> (supplied either directly to	200	If the profile does not specify a binds list, then the node ID will be
183	C<initialise_node> or indirectly via a profile or the nodename) must be a	201	treated as if it were of the form C<host:port>, which will be resolved and
184	noderef (possibly unresolved, in which case it will be resolved).	202	used as binds list.
185		203
186	After resolving, the node will bind itself on all endpoints and try to	204	Lastly, the seeds list from the profile is passed to the
187	connect to all additional C<$seednodes> that are specified. Seednodes are	205	L<AnyEvent::MP::Global> module, which will then use it to keep
188	optional and can be used to quickly bootstrap the node into an existing	206	connectivity with at least on of those seed nodes at any point in time.
189	network.
190		207
191	=item slave nodes
192
193	When the C<$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	208	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	209	the one specified via C<aemp> for the current node. This should be the
211	form of invocation for "daemon"-type nodes.	210	most common form of invocation for "daemon"-type nodes.
212		211
213	initialise_node;	212	initialise_node;
214		213
215	Example: become a slave node to any of the the seednodes specified via	214	Example: become an anonymous node. This form is often used for commandline
216	C<aemp>. This form is often used for commandline clients.	215	clients.
217		216
218	initialise_node "slave/";	217	initialise_node "anon/";
219		218
220	Example: become a slave node to any of the specified master servers. This	219	Example: become a distributed node. If there is no profile of the given
221	form is also often used for commandline clients.	220	name, or no binds list was specified, resolve C<localhost:4044> and bind
222		221	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		222
236	initialise_node "localhost:4044";	223	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		224
267	=item $SELF	225	=item $SELF
268		226
269	Contains the current port id while executing C<rcv> callbacks or C<psub>	227	Contains the current port id while executing C<rcv> callbacks or C<psub>
270	blocks.	228	blocks.
271		229
272	=item SELF, %SELF, @SELF...	230	=item *SELF, SELF, %SELF, @SELF...
273		231
274	Due to some quirks in how perl exports variables, it is impossible to	232	Due to some quirks in how perl exports variables, it is impossible to
275	just export C<$SELF>, all the symbols called C<SELF> are exported by this	233	just export C<$SELF>, all the symbols named C<SELF> are exported by this
276	module, but only C<$SELF> is currently used.	234	module, but only C<$SELF> is currently used.
277		235
278	=item snd $port, type => @data	236	=item snd $port, type => @data
279		237
280	=item snd $port, @msg	238	=item snd $port, @msg
281		239
282	Send the given message to the given port ID, which can identify either	240	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.	241	local or a remote port, and must be a port ID.
284		242
285	While the message can be about anything, it is highly recommended to use a	243	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	244	use a string as first element (a port ID, or some word that indicates a
287	type etc.).	245	request type etc.) and to consist if only simple perl values (scalars,
		246	arrays, hashes) - if you think you need to pass an object, think again.
288		247
289	The message data effectively becomes read-only after a call to this	248	The message data logically becomes read-only after a call to this
290	function: modifying any argument is not allowed and can cause many	249	function: modifying any argument (or values referenced by them) is
291	problems.	250	forbidden, as there can be considerable time between the call to C<snd>
		251	and the time the message is actually being serialised - in fact, it might
		252	never be copied as within the same process it is simply handed to the
		253	receiving port.
292		254
293	The type of data you can transfer depends on the transport protocol: when	255	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	256	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	257	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	258	that Storable can serialise and deserialise is allowed, and for the local
297	node, anything can be passed.	259	node, anything can be passed. Best rely only on the common denominator of
		260	these.
298		261
299	=item $local_port = port	262	=item $local_port = port
300		263
301	Create a new local port object and returns its port ID. Initially it has	264	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.	265	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	312	The default callback received all messages not matched by a more specific
350	C<tag> match.	313	C<tag> match.
351		314
352	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	315	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
353		316
354	Register callbacks to be called on messages starting with the given tag on	317	Register (or replace) callbacks to be called on messages starting with the
355	the given port (and return the port), or unregister it (when C<$callback>	318	given tag on the given port (and return the port), or unregister it (when
356	is C<$undef>).	319	C<$callback> is C<$undef> or missing). There can only be one callback
		320	registered for each tag.
357		321
358	The original message will be passed to the callback, after the first	322	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	323	element (the tag) has been removed. The callback will use the same
360	environment as the default callback (see above).	324	environment as the default callback (see above).
361		325
…		…
373	rcv port,	337	rcv port,
374	msg1 => sub { ... },	338	msg1 => sub { ... },
375	...	339	...
376	;	340	;
377		341
		342	Example: temporarily register a rcv callback for a tag matching some port
		343	(e.g. for a rpc reply) and unregister it after a message was received.
		344
		345	rcv $port, $otherport => sub {
		346	my @reply = @_;
		347
		348	rcv $SELF, $otherport;
		349	};
		350
378	=cut	351	=cut
379		352
380	sub rcv($@) {	353	sub rcv($@) {
381	my $port = shift;	354	my $port = shift;
382	my ($noderef, $portid) = split /#/, $port, 2;	355	my ($noderef, $portid) = split /#/, $port, 2;
383		356
384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	357	$NODE{$noderef} == $NODE{""}
385	or Carp::croak "$port: rcv can only be called on local ports, caught";	358	or Carp::croak "$port: rcv can only be called on local ports, caught";
386		359
387	while (@_) {	360	while (@_) {
388	if (ref $_[0]) {	361	if (ref $_[0]) {
389	if (my $self = $PORT_DATA{$portid}) {	362	if (my $self = $PORT_DATA{$portid}) {
…		…
468	$res	441	$res
469	}	442	}
470	}	443	}
471	}	444	}
472		445
473	=item $guard = mon $port, $cb->(@reason)	446	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
474		447
475	=item $guard = mon $port, $rcvport	448	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
476		449
477	=item $guard = mon $port	450	=item $guard = mon $port # kill $SELF when $port dies
478		451
479	=item $guard = mon $port, $rcvport, @msg	452	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
480		453
481	Monitor the given port and do something when the port is killed or	454	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	455	messages to it were lost, and optionally return a guard that can be used
483	to stop monitoring again.	456	to stop monitoring again.
484		457
485	C<mon> effectively guarantees that, in the absence of hardware failures,	458	C<mon> effectively guarantees that, in the absence of hardware failures,
486	that after starting the monitor, either all messages sent to the port	459	after starting the monitor, either all messages sent to the port will
487	will arrive, or the monitoring action will be invoked after possible	460	arrive, or the monitoring action will be invoked after possible message
488	message loss has been detected. No messages will be lost "in between"	461	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	462	the first lost message no further messages will be received by the
490	port). After the monitoring action was invoked, further messages might get	463	port). After the monitoring action was invoked, further messages might get
491	delivered again.	464	delivered again.
		465
		466	Note that monitoring-actions are one-shot: once messages are lost (and a
		467	monitoring alert was raised), they are removed and will not trigger again.
492		468
493	In the first form (callback), the callback is simply called with any	469	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	470	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	471	"normally"). Note also that I<< the callback B<must> never die >>, so use
496	C<eval> if unsure.	472	C<eval> if unsure.
…		…
558	is killed, the references will be freed.	534	is killed, the references will be freed.
559		535
560	Optionally returns a guard that will stop the monitoring.	536	Optionally returns a guard that will stop the monitoring.
561		537
562	This function is useful when you create e.g. timers or other watchers and	538	This function is useful when you create e.g. timers or other watchers and
563	want to free them when the port gets killed:	539	want to free them when the port gets killed (note the use of C<psub>):
564		540
565	$port->rcv (start => sub {	541	$port->rcv (start => sub {
566	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	542	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
567	undef $timer if 0.9 < rand;	543	undef $timer if 0.9 < rand;
568	});	544	});
569	});	545	});
570		546
571	=cut	547	=cut
…		…
580		556
581	=item kil $port[, @reason]	557	=item kil $port[, @reason]
582		558
583	Kill the specified port with the given C<@reason>.	559	Kill the specified port with the given C<@reason>.
584		560
585	If no C<@reason> is specified, then the port is killed "normally" (linked	561	If no C<@reason> is specified, then the port is killed "normally" (ports
586	ports will not be kileld, or even notified).	562	monitoring other ports will not necessarily die because a port dies
		563	"normally").
587		564
588	Otherwise, linked ports get killed with the same reason (second form of	565	Otherwise, linked ports get killed with the same reason (second form of
589	C<mon>, see below).	566	C<mon>, see above).
590		567
591	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	568	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
592	will be reported as reason C<< die => $@ >>.	569	will be reported as reason C<< die => $@ >>.
593		570
594	Transport/communication errors are reported as C<< transport_error =>	571	Transport/communication errors are reported as C<< transport_error =>
…		…
599	=item $port = spawn $node, $initfunc[, @initdata]	576	=item $port = spawn $node, $initfunc[, @initdata]
600		577
601	Creates a port on the node C<$node> (which can also be a port ID, in which	578	Creates a port on the node C<$node> (which can also be a port ID, in which
602	case it's the node where that port resides).	579	case it's the node where that port resides).
603		580
604	The port ID of the newly created port is return immediately, and it is	581	The port ID of the newly created port is returned immediately, and it is
605	permissible to immediately start sending messages or monitor the port.	582	possible to immediately start sending messages or to monitor the port.
606		583
607	After the port has been created, the init function is	584	After the port has been created, the init function is called on the remote
608	called. This function must be a fully-qualified function name	585	node, in the same context as a C<rcv> callback. This function must be a
609	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	586	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
610	program, use C<::name>.	587	specify a function in the main program, use C<::name>.
611		588
612	If the function doesn't exist, then the node tries to C<require>	589	If the function doesn't exist, then the node tries to C<require>
613	the package, then the package above the package and so on (e.g.	590	the package, then the package above the package and so on (e.g.
614	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	591	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
615	exists or it runs out of package names.	592	exists or it runs out of package names.
616		593
617	The init function is then called with the newly-created port as context	594	The init function is then called with the newly-created port as context
618	object (C<$SELF>) and the C<@initdata> values as arguments.	595	object (C<$SELF>) and the C<@initdata> values as arguments.
619		596
620	A common idiom is to pass your own port, monitor the spawned port, and	597	A common idiom is to pass a local port, immediately monitor the spawned
621	in the init function, monitor the original port. This two-way monitoring	598	port, and in the remote init function, immediately monitor the passed
622	ensures that both ports get cleaned up when there is a problem.	599	local port. This two-way monitoring ensures that both ports get cleaned up
		600	when there is a problem.
623		601
624	Example: spawn a chat server port on C<$othernode>.	602	Example: spawn a chat server port on C<$othernode>.
625		603
626	# this node, executed from within a port context:	604	# this node, executed from within a port context:
627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	605	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
657	my $id = "$RUNIQ." . $ID++;	635	my $id = "$RUNIQ." . $ID++;
658		636
659	$_[0] =~ /::/	637	$_[0] =~ /::/
660	or Carp::croak "spawn init function must be a fully-qualified name, caught";	638	or Carp::croak "spawn init function must be a fully-qualified name, caught";
661		639
662	($NODE{$noderef} \|\| add_node $noderef)	640	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
663	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
664		641
665	"$noderef#$id"	642	"$noderef#$id"
666	}	643	}
667		644
668	=back	645	=item after $timeout, @msg
669		646
670	=head1 NODE MESSAGES	647	=item after $timeout, $callback
671		648
672	Nodes understand the following messages sent to them. Many of them take	649	Either sends the given message, or call the given callback, after the
673	arguments called C<@reply>, which will simply be used to compose a reply	650	specified number of seconds.
674	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
675	the remaining arguments are simply the message data.
676		651
677	While other messages exist, they are not public and subject to change.	652	This is simply a utility function that comes in handy at times - the
		653	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		654	so it may go away in the future.
678		655
679	=over 4
680
681	=cut	656	=cut
682		657
683	=item lookup => $name, @reply	658	sub after($@) {
		659	my ($timeout, @action) = @_;
684		660
685	Replies with the port ID of the specified well-known port, or C<undef>.	661	my $t; $t = AE::timer $timeout, 0, sub {
686		662	undef $t;
687	=item devnull => ...	663	ref $action[0]
688		664	? $action[0]()
689	Generic data sink/CPU heat conversion.	665	: snd @action;
690		666	};
691	=item relay => $port, @msg	667	}
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		668
714	=back	669	=back
715		670
716	=head1 AnyEvent::MP vs. Distributed Erlang	671	=head1 AnyEvent::MP vs. Distributed Erlang
717		672
…		…
727		682
728	Despite the similarities, there are also some important differences:	683	Despite the similarities, there are also some important differences:
729		684
730	=over 4	685	=over 4
731		686
732	=item * Node references contain the recipe on how to contact them.	687	=item * Node IDs are arbitrary strings in AEMP.
733		688
734	Erlang relies on special naming and DNS to work everywhere in the	689	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	690	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
736	convenience functionality.	691	configuraiton or DNS), but will otherwise discover other odes itself.
737		692
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	693	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
742	uses "local ports are like remote ports".	694	uses "local ports are like remote ports".
743		695
744	The failure modes for local ports are quite different (runtime errors	696	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,	697	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	698	when a connection to another node dies, you know nothing about the other
…		…
773		725
774	Erlang makes few guarantees on messages delivery - messages can get lost	726	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,	727	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).	728	and c, and the other side only receives messages a and c).
777		729
778	AEMP guarantees correct ordering, and the guarantee that there are no	730	AEMP guarantees correct ordering, and the guarantee that after one message
779	holes in the message sequence.	731	is lost, all following ones sent to the same port are lost as well, until
780		732	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	733	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		734
792	=item * Erlang can send messages to the wrong port, AEMP does not.	735	=item * Erlang can send messages to the wrong port, AEMP does not.
793		736
794	In Erlang it is quite likely that a node that restarts reuses a process ID	737	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	738	known to other nodes for a completely different process, causing messages
…		…
799	around in the network will not be sent to an unrelated port.	742	around in the network will not be sent to an unrelated port.
800		743
801	=item * Erlang uses unprotected connections, AEMP uses secure	744	=item * Erlang uses unprotected connections, AEMP uses secure
802	authentication and can use TLS.	745	authentication and can use TLS.
803		746
804	AEMP can use a proven protocol - SSL/TLS - to protect connections and	747	AEMP can use a proven protocol - TLS - to protect connections and
805	securely authenticate nodes.	748	securely authenticate nodes.
806		749
807	=item * The AEMP protocol is optimised for both text-based and binary	750	=item * The AEMP protocol is optimised for both text-based and binary
808	communications.	751	communications.
809		752
810	The AEMP protocol, unlike the Erlang protocol, supports both	753	The AEMP protocol, unlike the Erlang protocol, supports both programming
811	language-independent text-only protocols (good for debugging) and binary,	754	language independent text-only protocols (good for debugging) and binary,
812	language-specific serialisers (e.g. Storable).	755	language-specific serialisers (e.g. Storable). By default, unless TLS is
		756	used, the protocol is actually completely text-based.
813		757
814	It has also been carefully designed to be implementable in other languages	758	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	759	with a minimum of work while gracefully degrading functionality to make the
816	protocol simple.	760	protocol simple.
817		761
818	=item * AEMP has more flexible monitoring options than Erlang.	762	=item * AEMP has more flexible monitoring options than Erlang.
819		763
820	In Erlang, you can chose to receive I<all> exit signals as messages	764	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	767	Erlang, as one can choose between automatic kill, exit message or callback
824	on a per-process basis.	768	on a per-process basis.
825		769
826	=item * Erlang tries to hide remote/local connections, AEMP does not.	770	=item * Erlang tries to hide remote/local connections, AEMP does not.
827		771
828	Monitoring in Erlang is not an indicator of process death/crashes,	772	Monitoring in Erlang is not an indicator of process death/crashes, in the
829	as linking is (except linking is unreliable in Erlang).	773	same way as linking is (except linking is unreliable in Erlang).
830		774
831	In AEMP, you don't "look up" registered port names or send to named ports	775	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	776	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	777	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	778	remote port. Since both monitors are local to the node, they are much more
835	more reliable.	779	reliable (no need for C<spawn_link>).
836		780
837	This also saves round-trips and avoids sending messages to the wrong port	781	This also saves round-trips and avoids sending messages to the wrong port
838	(hard to do in Erlang).	782	(hard to do in Erlang).
839		783
840	=back	784	=back
841		785
842	=head1 RATIONALE	786	=head1 RATIONALE
843		787
844	=over 4	788	=over 4
845		789
846	=item Why strings for ports and noderefs, why not objects?	790	=item Why strings for port and node IDs, why not objects?
847		791
848	We considered "objects", but found that the actual number of methods	792	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	793	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	794	the network frequently, the serialising/deserialising would add lots of
851	overhead, as well as having to keep a proxy object.	795	overhead, as well as having to keep a proxy object everywhere.
852		796
853	Strings can easily be printed, easily serialised etc. and need no special	797	Strings can easily be printed, easily serialised etc. and need no special
854	procedures to be "valid".	798	procedures to be "valid".
855		799
856	And a a miniport consists of a single closure stored in a global hash - it	800	And as a result, a miniport consists of a single closure stored in a
857	can't become much cheaper.	801	global hash - it can't become much cheaper.
858		802
859	=item Why favour JSON, why not real serialising format such as Storable?	803	=item Why favour JSON, why not a real serialising format such as Storable?
860		804
861	In fact, any AnyEvent::MP node will happily accept Storable as framing	805	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	806	format, but currently there is no way to make a node use Storable by
863	default.	807	default (although all nodes will accept it).
864		808
865	The default framing protocol is JSON because a) JSON::XS is many times	809	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	810	faster for small messages and b) most importantly, after years of
867	experience we found that object serialisation is causing more problems	811	experience we found that object serialisation is causing more problems
868	than it gains: Just like function calls, objects simply do not travel	812	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	813	easily over the network, mostly because they will always be a copy, so you
870	always have to re-think your design.	814	always have to re-think your design.
871		815
872	Keeping your messages simple, concentrating on data structures rather than	816	Keeping your messages simple, concentrating on data structures rather than
873	objects, will keep your messages clean, tidy and efficient.	817	objects, will keep your messages clean, tidy and efficient.
874		818
875	=back	819	=back
876		820
877	=head1 SEE ALSO	821	=head1 SEE ALSO
878		822
		823	L<AnyEvent::MP::Intro> - a gentle introduction.
		824
		825	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		826
		827	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		828	your applications.
		829
879	L<AnyEvent>.	830	L<AnyEvent>.
880		831
881	=head1 AUTHOR	832	=head1 AUTHOR
882		833
883	Marc Lehmann <schmorp@schmorp.de>	834	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.69 by root, Sun Aug 30 18:51:49 2009 UTC