[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 1.67 by root, Fri Aug 28 22:21:53 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46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - outdated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
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 then 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).
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	If the profile specifies a node ID, then this will become the node ID of
		184	this process. If not, then the profile name will be used as node ID. The
		185	special node ID of C<anon/> will be replaced by a random node ID.
177		186
178	=over 4	187	The next step is to look up the binds in the profile, followed by binding
		188	aemp protocol listeners on all binds specified (it is possible and valid
		189	to have no binds, meaning that the node cannot be contacted form the
		190	outside. This means the node cannot talk to other nodes that also have no
		191	binds, but it can still talk to all "normal" nodes).
179		192
180	=item public nodes	193	If the profile does not specify a binds list, then the node ID will be
		194	treated as if it were of the form C<host:port>, which will be resolved and
		195	used as binds list.
181		196
182	For public nodes, C<$noderef> (supplied either directly to	197	Lastly, the seeds list from the profile is passed to the
183	C<initialise_node> or indirectly via a profile or the nodename) must be a	198	L<AnyEvent::MP::Global> module, which will then use it to keep
184	noderef (possibly unresolved, in which case it will be resolved).	199	connectivity with at least on of those seed nodes at any point in time.
185		200
186	After resolving, the node will bind itself on all endpoints and try to
187	connect to all additional C<$seednodes> that are specified. Seednodes are
188	optional and can be used to quickly bootstrap the node into an existing
189	network.
190
191	=item slave nodes
192
193	When the C<$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	201	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	202	the one specified via C<aemp> for the current node. This should be the
211	form of invocation for "daemon"-type nodes.	203	most common form of invocation for "daemon"-type nodes.
212		204
213	initialise_node;	205	initialise_node;
214		206
215	Example: become a slave node to any of the the seednodes specified via	207	Example: become an anonymous node. This form is often used for commandline
216	C<aemp>. This form is often used for commandline clients.	208	clients.
217		209
218	initialise_node "slave/";	210	initialise_node "anon/";
219		211
220	Example: become a slave node to any of the specified master servers. This	212	Example: become a distributed node. If there is no profile of the given
221	form is also often used for commandline clients.	213	name, or no binds list was specified, resolve C<localhost:4044> and bind
222		214	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		215
236	initialise_node "localhost:4044";	216	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		217
267	=item $SELF	218	=item $SELF
268		219
269	Contains the current port id while executing C<rcv> callbacks or C<psub>	220	Contains the current port id while executing C<rcv> callbacks or C<psub>
270	blocks.	221	blocks.
271		222
272	=item SELF, %SELF, @SELF...	223	=item *SELF, SELF, %SELF, @SELF...
273		224
274	Due to some quirks in how perl exports variables, it is impossible to	225	Due to some quirks in how perl exports variables, it is impossible to
275	just export C<$SELF>, all the symbols called C<SELF> are exported by this	226	just export C<$SELF>, all the symbols named C<SELF> are exported by this
276	module, but only C<$SELF> is currently used.	227	module, but only C<$SELF> is currently used.
277		228
278	=item snd $port, type => @data	229	=item snd $port, type => @data
279		230
280	=item snd $port, @msg	231	=item snd $port, @msg
281		232
282	Send the given message to the given port ID, which can identify either	233	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.	234	local or a remote port, and must be a port ID.
284		235
285	While the message can be about anything, it is highly recommended to use a	236	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	237	use a string as first element (a port ID, or some word that indicates a
287	type etc.).	238	request type etc.) and to consist if only simple perl values (scalars,
		239	arrays, hashes) - if you think you need to pass an object, think again.
288		240
289	The message data effectively becomes read-only after a call to this	241	The message data logically becomes read-only after a call to this
290	function: modifying any argument is not allowed and can cause many	242	function: modifying any argument (or values referenced by them) is
291	problems.	243	forbidden, as there can be considerable time between the call to C<snd>
		244	and the time the message is actually being serialised - in fact, it might
		245	never be copied as within the same process it is simply handed to the
		246	receiving port.
292		247
293	The type of data you can transfer depends on the transport protocol: when	248	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	249	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	250	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	251	that Storable can serialise and deserialise is allowed, and for the local
297	node, anything can be passed.	252	node, anything can be passed. Best rely only on the common denominator of
		253	these.
298		254
299	=item $local_port = port	255	=item $local_port = port
300		256
301	Create a new local port object and returns its port ID. Initially it has	257	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.	258	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	305	The default callback received all messages not matched by a more specific
350	C<tag> match.	306	C<tag> match.
351		307
352	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	308	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
353		309
354	Register callbacks to be called on messages starting with the given tag on	310	Register (or replace) callbacks to be called on messages starting with the
355	the given port (and return the port), or unregister it (when C<$callback>	311	given tag on the given port (and return the port), or unregister it (when
356	is C<$undef>).	312	C<$callback> is C<$undef> or missing). There can only be one callback
		313	registered for each tag.
357		314
358	The original message will be passed to the callback, after the first	315	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	316	element (the tag) has been removed. The callback will use the same
360	environment as the default callback (see above).	317	environment as the default callback (see above).
361		318
…		…
373	rcv port,	330	rcv port,
374	msg1 => sub { ... },	331	msg1 => sub { ... },
375	...	332	...
376	;	333	;
377		334
		335	Example: temporarily register a rcv callback for a tag matching some port
		336	(e.g. for a rpc reply) and unregister it after a message was received.
		337
		338	rcv $port, $otherport => sub {
		339	my @reply = @_;
		340
		341	rcv $SELF, $otherport;
		342	};
		343
378	=cut	344	=cut
379		345
380	sub rcv($@) {	346	sub rcv($@) {
381	my $port = shift;	347	my $port = shift;
382	my ($noderef, $portid) = split /#/, $port, 2;	348	my ($noderef, $portid) = split /#/, $port, 2;
383		349
384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	350	$NODE{$noderef} == $NODE{""}
385	or Carp::croak "$port: rcv can only be called on local ports, caught";	351	or Carp::croak "$port: rcv can only be called on local ports, caught";
386		352
387	while (@_) {	353	while (@_) {
388	if (ref $_[0]) {	354	if (ref $_[0]) {
389	if (my $self = $PORT_DATA{$portid}) {	355	if (my $self = $PORT_DATA{$portid}) {
…		…
468	$res	434	$res
469	}	435	}
470	}	436	}
471	}	437	}
472		438
473	=item $guard = mon $port, $cb->(@reason)	439	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
474		440
475	=item $guard = mon $port, $rcvport	441	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
476		442
477	=item $guard = mon $port	443	=item $guard = mon $port # kill $SELF when $port dies
478		444
479	=item $guard = mon $port, $rcvport, @msg	445	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
480		446
481	Monitor the given port and do something when the port is killed or	447	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	448	messages to it were lost, and optionally return a guard that can be used
483	to stop monitoring again.	449	to stop monitoring again.
484		450
485	C<mon> effectively guarantees that, in the absence of hardware failures,	451	C<mon> effectively guarantees that, in the absence of hardware failures,
486	that after starting the monitor, either all messages sent to the port	452	after starting the monitor, either all messages sent to the port will
487	will arrive, or the monitoring action will be invoked after possible	453	arrive, or the monitoring action will be invoked after possible message
488	message loss has been detected. No messages will be lost "in between"	454	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	455	the first lost message no further messages will be received by the
490	port). After the monitoring action was invoked, further messages might get	456	port). After the monitoring action was invoked, further messages might get
491	delivered again.	457	delivered again.
		458
		459	Note that monitoring-actions are one-shot: once messages are lost (and a
		460	monitoring alert was raised), they are removed and will not trigger again.
492		461
493	In the first form (callback), the callback is simply called with any	462	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	463	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	464	"normally"). Note also that I<< the callback B<must> never die >>, so use
496	C<eval> if unsure.	465	C<eval> if unsure.
…		…
558	is killed, the references will be freed.	527	is killed, the references will be freed.
559		528
560	Optionally returns a guard that will stop the monitoring.	529	Optionally returns a guard that will stop the monitoring.
561		530
562	This function is useful when you create e.g. timers or other watchers and	531	This function is useful when you create e.g. timers or other watchers and
563	want to free them when the port gets killed:	532	want to free them when the port gets killed (note the use of C<psub>):
564		533
565	$port->rcv (start => sub {	534	$port->rcv (start => sub {
566	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	535	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
567	undef $timer if 0.9 < rand;	536	undef $timer if 0.9 < rand;
568	});	537	});
569	});	538	});
570		539
571	=cut	540	=cut
…		…
580		549
581	=item kil $port[, @reason]	550	=item kil $port[, @reason]
582		551
583	Kill the specified port with the given C<@reason>.	552	Kill the specified port with the given C<@reason>.
584		553
585	If no C<@reason> is specified, then the port is killed "normally" (linked	554	If no C<@reason> is specified, then the port is killed "normally" (ports
586	ports will not be kileld, or even notified).	555	monitoring other ports will not necessarily die because a port dies
		556	"normally").
587		557
588	Otherwise, linked ports get killed with the same reason (second form of	558	Otherwise, linked ports get killed with the same reason (second form of
589	C<mon>, see below).	559	C<mon>, see above).
590		560
591	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	561	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
592	will be reported as reason C<< die => $@ >>.	562	will be reported as reason C<< die => $@ >>.
593		563
594	Transport/communication errors are reported as C<< transport_error =>	564	Transport/communication errors are reported as C<< transport_error =>
…		…
599	=item $port = spawn $node, $initfunc[, @initdata]	569	=item $port = spawn $node, $initfunc[, @initdata]
600		570
601	Creates a port on the node C<$node> (which can also be a port ID, in which	571	Creates a port on the node C<$node> (which can also be a port ID, in which
602	case it's the node where that port resides).	572	case it's the node where that port resides).
603		573
604	The port ID of the newly created port is return immediately, and it is	574	The port ID of the newly created port is returned immediately, and it is
605	permissible to immediately start sending messages or monitor the port.	575	possible to immediately start sending messages or to monitor the port.
606		576
607	After the port has been created, the init function is	577	After the port has been created, the init function is called on the remote
608	called. This function must be a fully-qualified function name	578	node, in the same context as a C<rcv> callback. This function must be a
609	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	579	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
610	program, use C<::name>.	580	specify a function in the main program, use C<::name>.
611		581
612	If the function doesn't exist, then the node tries to C<require>	582	If the function doesn't exist, then the node tries to C<require>
613	the package, then the package above the package and so on (e.g.	583	the package, then the package above the package and so on (e.g.
614	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	584	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
615	exists or it runs out of package names.	585	exists or it runs out of package names.
616		586
617	The init function is then called with the newly-created port as context	587	The init function is then called with the newly-created port as context
618	object (C<$SELF>) and the C<@initdata> values as arguments.	588	object (C<$SELF>) and the C<@initdata> values as arguments.
619		589
620	A common idiom is to pass your own port, monitor the spawned port, and	590	A common idiom is to pass a local port, immediately monitor the spawned
621	in the init function, monitor the original port. This two-way monitoring	591	port, and in the remote init function, immediately monitor the passed
622	ensures that both ports get cleaned up when there is a problem.	592	local port. This two-way monitoring ensures that both ports get cleaned up
		593	when there is a problem.
623		594
624	Example: spawn a chat server port on C<$othernode>.	595	Example: spawn a chat server port on C<$othernode>.
625		596
626	# this node, executed from within a port context:	597	# this node, executed from within a port context:
627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	598	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
657	my $id = "$RUNIQ." . $ID++;	628	my $id = "$RUNIQ." . $ID++;
658		629
659	$_[0] =~ /::/	630	$_[0] =~ /::/
660	or Carp::croak "spawn init function must be a fully-qualified name, caught";	631	or Carp::croak "spawn init function must be a fully-qualified name, caught";
661		632
662	($NODE{$noderef} \|\| add_node $noderef)	633	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
663	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
664		634
665	"$noderef#$id"	635	"$noderef#$id"
666	}	636	}
667		637
668	=back	638	=item after $timeout, @msg
669		639
670	=head1 NODE MESSAGES	640	=item after $timeout, $callback
671		641
672	Nodes understand the following messages sent to them. Many of them take	642	Either sends the given message, or call the given callback, after the
673	arguments called C<@reply>, which will simply be used to compose a reply	643	specified number of seconds.
674	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
675	the remaining arguments are simply the message data.
676		644
677	While other messages exist, they are not public and subject to change.	645	This is simply a utility function that comes in handy at times - the
		646	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		647	so it may go away in the future.
678		648
679	=over 4
680
681	=cut	649	=cut
682		650
683	=item lookup => $name, @reply	651	sub after($@) {
		652	my ($timeout, @action) = @_;
684		653
685	Replies with the port ID of the specified well-known port, or C<undef>.	654	my $t; $t = AE::timer $timeout, 0, sub {
686		655	undef $t;
687	=item devnull => ...	656	ref $action[0]
688		657	? $action[0]()
689	Generic data sink/CPU heat conversion.	658	: snd @action;
690		659	};
691	=item relay => $port, @msg	660	}
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		661
714	=back	662	=back
715		663
716	=head1 AnyEvent::MP vs. Distributed Erlang	664	=head1 AnyEvent::MP vs. Distributed Erlang
717		665
…		…
727		675
728	Despite the similarities, there are also some important differences:	676	Despite the similarities, there are also some important differences:
729		677
730	=over 4	678	=over 4
731		679
732	=item * Node references contain the recipe on how to contact them.	680	=item * Node IDs are arbitrary strings in AEMP.
733		681
734	Erlang relies on special naming and DNS to work everywhere in the	682	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	683	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
736	convenience functionality.	684	configuraiton or DNS), but will otherwise discover other odes itself.
737		685
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	686	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
742	uses "local ports are like remote ports".	687	uses "local ports are like remote ports".
743		688
744	The failure modes for local ports are quite different (runtime errors	689	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,	690	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	691	when a connection to another node dies, you know nothing about the other
…		…
773		718
774	Erlang makes few guarantees on messages delivery - messages can get lost	719	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,	720	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).	721	and c, and the other side only receives messages a and c).
777		722
778	AEMP guarantees correct ordering, and the guarantee that there are no	723	AEMP guarantees correct ordering, and the guarantee that after one message
779	holes in the message sequence.	724	is lost, all following ones sent to the same port are lost as well, until
780		725	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	726	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		727
792	=item * Erlang can send messages to the wrong port, AEMP does not.	728	=item * Erlang can send messages to the wrong port, AEMP does not.
793		729
794	In Erlang it is quite likely that a node that restarts reuses a process ID	730	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	731	known to other nodes for a completely different process, causing messages
…		…
799	around in the network will not be sent to an unrelated port.	735	around in the network will not be sent to an unrelated port.
800		736
801	=item * Erlang uses unprotected connections, AEMP uses secure	737	=item * Erlang uses unprotected connections, AEMP uses secure
802	authentication and can use TLS.	738	authentication and can use TLS.
803		739
804	AEMP can use a proven protocol - SSL/TLS - to protect connections and	740	AEMP can use a proven protocol - TLS - to protect connections and
805	securely authenticate nodes.	741	securely authenticate nodes.
806		742
807	=item * The AEMP protocol is optimised for both text-based and binary	743	=item * The AEMP protocol is optimised for both text-based and binary
808	communications.	744	communications.
809		745
810	The AEMP protocol, unlike the Erlang protocol, supports both	746	The AEMP protocol, unlike the Erlang protocol, supports both programming
811	language-independent text-only protocols (good for debugging) and binary,	747	language independent text-only protocols (good for debugging) and binary,
812	language-specific serialisers (e.g. Storable).	748	language-specific serialisers (e.g. Storable). By default, unless TLS is
		749	used, the protocol is actually completely text-based.
813		750
814	It has also been carefully designed to be implementable in other languages	751	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	752	with a minimum of work while gracefully degrading functionality to make the
816	protocol simple.	753	protocol simple.
817		754
818	=item * AEMP has more flexible monitoring options than Erlang.	755	=item * AEMP has more flexible monitoring options than Erlang.
819		756
820	In Erlang, you can chose to receive I<all> exit signals as messages	757	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	760	Erlang, as one can choose between automatic kill, exit message or callback
824	on a per-process basis.	761	on a per-process basis.
825		762
826	=item * Erlang tries to hide remote/local connections, AEMP does not.	763	=item * Erlang tries to hide remote/local connections, AEMP does not.
827		764
828	Monitoring in Erlang is not an indicator of process death/crashes,	765	Monitoring in Erlang is not an indicator of process death/crashes, in the
829	as linking is (except linking is unreliable in Erlang).	766	same way as linking is (except linking is unreliable in Erlang).
830		767
831	In AEMP, you don't "look up" registered port names or send to named ports	768	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	769	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	770	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	771	remote port. Since both monitors are local to the node, they are much more
835	more reliable.	772	reliable (no need for C<spawn_link>).
836		773
837	This also saves round-trips and avoids sending messages to the wrong port	774	This also saves round-trips and avoids sending messages to the wrong port
838	(hard to do in Erlang).	775	(hard to do in Erlang).
839		776
840	=back	777	=back
841		778
842	=head1 RATIONALE	779	=head1 RATIONALE
843		780
844	=over 4	781	=over 4
845		782
846	=item Why strings for ports and noderefs, why not objects?	783	=item Why strings for port and node IDs, why not objects?
847		784
848	We considered "objects", but found that the actual number of methods	785	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	786	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	787	the network frequently, the serialising/deserialising would add lots of
851	overhead, as well as having to keep a proxy object.	788	overhead, as well as having to keep a proxy object everywhere.
852		789
853	Strings can easily be printed, easily serialised etc. and need no special	790	Strings can easily be printed, easily serialised etc. and need no special
854	procedures to be "valid".	791	procedures to be "valid".
855		792
856	And a a miniport consists of a single closure stored in a global hash - it	793	And as a result, a miniport consists of a single closure stored in a
857	can't become much cheaper.	794	global hash - it can't become much cheaper.
858		795
859	=item Why favour JSON, why not real serialising format such as Storable?	796	=item Why favour JSON, why not a real serialising format such as Storable?
860		797
861	In fact, any AnyEvent::MP node will happily accept Storable as framing	798	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	799	format, but currently there is no way to make a node use Storable by
863	default.	800	default (although all nodes will accept it).
864		801
865	The default framing protocol is JSON because a) JSON::XS is many times	802	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	803	faster for small messages and b) most importantly, after years of
867	experience we found that object serialisation is causing more problems	804	experience we found that object serialisation is causing more problems
868	than it gains: Just like function calls, objects simply do not travel	805	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	806	easily over the network, mostly because they will always be a copy, so you
870	always have to re-think your design.	807	always have to re-think your design.
871		808
872	Keeping your messages simple, concentrating on data structures rather than	809	Keeping your messages simple, concentrating on data structures rather than
873	objects, will keep your messages clean, tidy and efficient.	810	objects, will keep your messages clean, tidy and efficient.

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC vs. Revision 1.67 by root, Fri Aug 28 22:21:53 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC vs.
Revision 1.67 by root, Fri Aug 28 22:21:53 2009 UTC