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

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.50 by root, Fri Aug 14 14:01:05 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, type 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 };
34		32
35	# create a port on another node	33	# create a port on another node
…		…
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46	AnyEvent::MP::Intro - outdated	45	AnyEvent::MP::Intro - uptodate, but incomplete.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	158	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	the noderef of the local node. The value is initialised by a call	159	ID of the node running in the current process. This value is initialised by
150	to C<become_public> or C<become_slave>, after which all local port	160	a call to C<initialise_node>.
151	identifiers become invalid.
152		161
153	=item $noderef = node_of $port	162	=item $nodeid = node_of $port
154		163
155	Extracts and returns the noderef from a portid or a noderef.	164	Extracts and returns the node ID from a port ID or a node ID.
156		165
157	=item initialise_node $noderef, $seednode, $seednode...	166	=item initialise_node $profile_name, key => value...
158		167
159	=item initialise_node "slave/", $master, $master...
160
161	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
162	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
163	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.
164		172
165	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
166	never) before calling other AnyEvent::MP functions.	174	never) before calling other AnyEvent::MP functions.
167		175
168	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
169	either resolved or unresolved.	177	the current nodename will be used instead (i.e. F<uname -n>).
170		178
171	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
172	(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:
173	the relevant configuration profile (see L<aemp>). If none is found then
174	the default configuration is used. The configuration supplies additional
175	seed/master nodes and can override the actual noderef.
176		181
177	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.
178		188
179	=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.
180		192
181	=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).
182		198
183	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
184	C<initialise_node> or indirectly via a profile or the nodename) must be a	200	used.
185	noderef (possibly unresolved, in which case it will be resolved).
186		201
187	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
188	connect to all additional C<$seednodes> that are specified. Seednodes are	203	L<AnyEvent::MP::Global> module, which will then use it to keep
189	optional and can be used to quickly bootstrap the node into an existing	204	connectivity with at least on of those seed nodes at any point in time.
190	network.
191		205
192	=item slave nodes
193
194	When the C<$noderef> (either as given or overriden by the config file)
195	is the special string C<slave/>, then the node will become a slave
196	node. Slave nodes cannot be contacted from outside and will route most of
197	their traffic to the master node that they attach to.
198
199	At least one additional noderef is required (either by specifying it
200	directly or because it is part of the configuration profile): The node
201	will try to connect to all of them and will become a slave attached to the
202	first node it can successfully connect to.
203
204	=back
205
206	This function will block until all nodes have been resolved and, for slave
207	nodes, until it has successfully established a connection to a master
208	server.
209
210	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
211	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
212	form of invocation for "daemon"-type nodes.	208	most common form of invocation for "daemon"-type nodes.
213		209
214	initialise_node;	210	initialise_node;
215		211
216	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
217	C<aemp>. This form is often used for commandline clients.	213	clients.
218		214
219	initialise_node "slave/";	215	initialise_node "anon/";
220		216
221	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
222	form is also often used for commandline clients.	218	name, or no binds list was specified, resolve C<localhost:4044> and bind
223		219	on the resulting addresses.
224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
225
226	Example: become a public node, and try to contact some well-known master
227	servers to become part of the network.
228
229	initialise_node undef, "master1", "master2";
230
231	Example: become a public node listening on port C<4041>.
232
233	initialise_node 4041;
234
235	Example: become a public node, only visible on localhost port 4044.
236		220
237	initialise_node "localhost:4044";	221	initialise_node "localhost:4044";
238
239	=item $cv = resolve_node $noderef
240
241	Takes an unresolved node reference that may contain hostnames and
242	abbreviated IDs, resolves all of them and returns a resolved node
243	reference.
244
245	In addition to C<address:port> pairs allowed in resolved noderefs, the
246	following forms are supported:
247
248	=over 4
249
250	=item the empty string
251
252	An empty-string component gets resolved as if the default port (4040) was
253	specified.
254
255	=item naked port numbers (e.g. C<1234>)
256
257	These are resolved by prepending the local nodename and a colon, to be
258	further resolved.
259
260	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
261
262	These are resolved by using AnyEvent::DNS to resolve them, optionally
263	looking up SRV records for the C<aemp=4040> port, if no port was
264	specified.
265
266	=back
267		222
268	=item $SELF	223	=item $SELF
269		224
270	Contains the current port id while executing C<rcv> callbacks or C<psub>	225	Contains the current port id while executing C<rcv> callbacks or C<psub>
271	blocks.	226	blocks.
272		227
273	=item SELF, %SELF, @SELF...	228	=item *SELF, SELF, %SELF, @SELF...
274		229
275	Due to some quirks in how perl exports variables, it is impossible to	230	Due to some quirks in how perl exports variables, it is impossible to
276	just export C<$SELF>, all the symbols called C<SELF> are exported by this	231	just export C<$SELF>, all the symbols named C<SELF> are exported by this
277	module, but only C<$SELF> is currently used.	232	module, but only C<$SELF> is currently used.
278		233
279	=item snd $port, type => @data	234	=item snd $port, type => @data
280		235
281	=item snd $port, @msg	236	=item snd $port, @msg
282		237
283	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
284	a local or a remote port, and can be either a string or soemthignt hat	239	local or a remote port, and must be a port ID.
285	stringifies a sa port ID (such as a port object :).
286		240
287	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
288	string as first element (a portid, or some word that indicates a request	242	use a string as first element (a port ID, or some word that indicates a
289	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.
290		245
291	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
292	function: modifying any argument is not allowed and can cause many	247	function: modifying any argument (or values referenced by them) is
293	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.
294		252
295	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
296	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
297	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
298	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
299	node, anything can be passed.	257	node, anything can be passed. Best rely only on the common denominator of
		258	these.
300		259
301	=item $local_port = port	260	=item $local_port = port
302		261
303	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
304	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.
…		…
351	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
352	C<tag> match.	311	C<tag> match.
353		312
354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	313	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
355		314
356	Register callbacks to be called on messages starting with the given tag on	315	Register (or replace) callbacks to be called on messages starting with the
357	the given port (and return the port), or unregister it (when C<$callback>	316	given tag on the given port (and return the port), or unregister it (when
358	is C<$undef>).	317	C<$callback> is C<$undef> or missing). There can only be one callback
		318	registered for each tag.
359		319
360	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
361	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
362	environment as the default callback (see above).	322	environment as the default callback (see above).
363		323
…		…
375	rcv port,	335	rcv port,
376	msg1 => sub { ... },	336	msg1 => sub { ... },
377	...	337	...
378	;	338	;
379		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, $otherport;
		347	};
		348
380	=cut	349	=cut
381		350
382	sub rcv($@) {	351	sub rcv($@) {
383	my $port = shift;	352	my $port = shift;
384	my ($noderef, $portid) = split /#/, $port, 2;	353	my ($noderef, $portid) = split /#/, $port, 2;
385		354
386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	355	$NODE{$noderef} == $NODE{""}
387	or Carp::croak "$port: rcv can only be called on local ports, caught";	356	or Carp::croak "$port: rcv can only be called on local ports, caught";
388		357
389	while (@_) {	358	while (@_) {
390	if (ref $_[0]) {	359	if (ref $_[0]) {
391	if (my $self = $PORT_DATA{$portid}) {	360	if (my $self = $PORT_DATA{$portid}) {
…		…
470	$res	439	$res
471	}	440	}
472	}	441	}
473	}	442	}
474		443
475	=item $guard = mon $port, $cb->(@reason)	444	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
476		445
477	=item $guard = mon $port, $rcvport	446	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
478		447
479	=item $guard = mon $port	448	=item $guard = mon $port # kill $SELF when $port dies
480		449
481	=item $guard = mon $port, $rcvport, @msg	450	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
482		451
483	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
484	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
485	to stop monitoring again.	454	to stop monitoring again.
486		455
487	C<mon> effectively guarantees that, in the absence of hardware failures,	456	C<mon> effectively guarantees that, in the absence of hardware failures,
488	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
489	will arrive, or the monitoring action will be invoked after possible	458	arrive, or the monitoring action will be invoked after possible message
490	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
491	(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
492	port). After the monitoring action was invoked, further messages might get	461	port). After the monitoring action was invoked, further messages might get
493	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.
494		466
495	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
496	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
497	"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
498	C<eval> if unsure.	470	C<eval> if unsure.
…		…
560	is killed, the references will be freed.	532	is killed, the references will be freed.
561		533
562	Optionally returns a guard that will stop the monitoring.	534	Optionally returns a guard that will stop the monitoring.
563		535
564	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
565	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>):
566		538
567	$port->rcv (start => sub {	539	$port->rcv (start => sub {
568	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	540	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
569	undef $timer if 0.9 < rand;	541	undef $timer if 0.9 < rand;
570	});	542	});
571	});	543	});
572		544
573	=cut	545	=cut
…		…
582		554
583	=item kil $port[, @reason]	555	=item kil $port[, @reason]
584		556
585	Kill the specified port with the given C<@reason>.	557	Kill the specified port with the given C<@reason>.
586		558
587	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
588	ports will not be kileld, or even notified).	560	monitoring other ports will not necessarily die because a port dies
		561	"normally").
589		562
590	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
591	C<mon>, see below).	564	C<mon>, see above).
592		565
593	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
594	will be reported as reason C<< die => $@ >>.	567	will be reported as reason C<< die => $@ >>.
595		568
596	Transport/communication errors are reported as C<< transport_error =>	569	Transport/communication errors are reported as C<< transport_error =>
…		…
601	=item $port = spawn $node, $initfunc[, @initdata]	574	=item $port = spawn $node, $initfunc[, @initdata]
602		575
603	Creates a port on the node C<$node> (which can also be a port ID, in which	576	Creates a port on the node C<$node> (which can also be a port ID, in which
604	case it's the node where that port resides).	577	case it's the node where that port resides).
605		578
606	The port ID of the newly created port is return immediately, and it is	579	The port ID of the newly created port is returned immediately, and it is
607	permissible to immediately start sending messages or monitor the port.	580	possible to immediately start sending messages or to monitor the port.
608		581
609	After the port has been created, the init function is	582	After the port has been created, the init function is called on the remote
610	called. This function must be a fully-qualified function name	583	node, in the same context as a C<rcv> callback. This function must be a
611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	584	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
612	program, use C<::name>.	585	specify a function in the main program, use C<::name>.
613		586
614	If the function doesn't exist, then the node tries to C<require>	587	If the function doesn't exist, then the node tries to C<require>
615	the package, then the package above the package and so on (e.g.	588	the package, then the package above the package and so on (e.g.
616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	589	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
617	exists or it runs out of package names.	590	exists or it runs out of package names.
618		591
619	The init function is then called with the newly-created port as context	592	The init function is then called with the newly-created port as context
620	object (C<$SELF>) and the C<@initdata> values as arguments.	593	object (C<$SELF>) and the C<@initdata> values as arguments.
621		594
622	A common idiom is to pass your own port, monitor the spawned port, and	595	A common idiom is to pass a local port, immediately monitor the spawned
623	in the init function, monitor the original port. This two-way monitoring	596	port, and in the remote init function, immediately monitor the passed
624	ensures that both ports get cleaned up when there is a problem.	597	local port. This two-way monitoring ensures that both ports get cleaned up
		598	when there is a problem.
625		599
626	Example: spawn a chat server port on C<$othernode>.	600	Example: spawn a chat server port on C<$othernode>.
627		601
628	# this node, executed from within a port context:	602	# this node, executed from within a port context:
629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	603	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
659	my $id = "$RUNIQ." . $ID++;	633	my $id = "$RUNIQ." . $ID++;
660		634
661	$_[0] =~ /::/	635	$_[0] =~ /::/
662	or Carp::croak "spawn init function must be a fully-qualified name, caught";	636	or Carp::croak "spawn init function must be a fully-qualified name, caught";
663		637
664	($NODE{$noderef} \|\| add_node $noderef)	638	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
666		639
667	"$noderef#$id"	640	"$noderef#$id"
668	}	641	}
669		642
670	=back	643	=item after $timeout, @msg
671		644
672	=head1 NODE MESSAGES	645	=item after $timeout, $callback
673		646
674	Nodes understand the following messages sent to them. Many of them take	647	Either sends the given message, or call the given callback, after the
675	arguments called C<@reply>, which will simply be used to compose a reply	648	specified number of seconds.
676	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
677	the remaining arguments are simply the message data.
678		649
679	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.
680		653
681	=over 4
682
683	=cut	654	=cut
684		655
685	=item lookup => $name, @reply	656	sub after($@) {
		657	my ($timeout, @action) = @_;
686		658
687	Replies with the port ID of the specified well-known port, or C<undef>.	659	my $t; $t = AE::timer $timeout, 0, sub {
688		660	undef $t;
689	=item devnull => ...	661	ref $action[0]
690		662	? $action[0]()
691	Generic data sink/CPU heat conversion.	663	: snd @action;
692		664	};
693	=item relay => $port, @msg	665	}
694
695	Simply forwards the message to the given port.
696
697	=item eval => $string[ @reply]
698
699	Evaluates the given string. If C<@reply> is given, then a message of the
700	form C<@reply, $@, @evalres> is sent.
701
702	Example: crash another node.
703
704	snd $othernode, eval => "exit";
705
706	=item time => @reply
707
708	Replies the the current node time to C<@reply>.
709
710	Example: tell the current node to send the current time to C<$myport> in a
711	C<timereply> message.
712
713	snd $NODE, time => $myport, timereply => 1, 2;
714	# => snd $myport, timereply => 1, 2, <time>
715		666
716	=back	667	=back
717		668
718	=head1 AnyEvent::MP vs. Distributed Erlang	669	=head1 AnyEvent::MP vs. Distributed Erlang
719		670
…		…
729		680
730	Despite the similarities, there are also some important differences:	681	Despite the similarities, there are also some important differences:
731		682
732	=over 4	683	=over 4
733		684
734	=item * Node references contain the recipe on how to contact them.	685	=item * Node IDs are arbitrary strings in AEMP.
735		686
736	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
737	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
738	convenience functionality.	689	configuraiton or DNS), but will otherwise discover other odes itself.
739		690
740	This means that AEMP requires a less tightly controlled environment at the	691	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
741	cost of longer node references and a slightly higher management overhead.	692	uses "local ports are like remote ports".
		693
		694	The failure modes for local ports are quite different (runtime errors
		695	only) then for remote ports - when a local port dies, you I<know> it dies,
		696	when a connection to another node dies, you know nothing about the other
		697	port.
		698
		699	Erlang pretends remote ports are as reliable as local ports, even when
		700	they are not.
		701
		702	AEMP encourages a "treat remote ports differently" philosophy, with local
		703	ports being the special case/exception, where transport errors cannot
		704	occur.
742		705
743	=item * Erlang uses processes and a mailbox, AEMP does not queue.	706	=item * Erlang uses processes and a mailbox, AEMP does not queue.
744		707
745	Erlang uses processes that selctively receive messages, and therefore	708	Erlang uses processes that selectively receive messages, and therefore
746	needs a queue. AEMP is event based, queuing messages would serve no useful	709	needs a queue. AEMP is event based, queuing messages would serve no
747	purpose.	710	useful purpose. For the same reason the pattern-matching abilities of
		711	AnyEvent::MP are more limited, as there is little need to be able to
		712	filter messages without dequeing them.
748		713
749	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	714	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
750		715
751	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	716	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
752		717
753	Sending messages in Erlang is synchronous and blocks the process. AEMP	718	Sending messages in Erlang is synchronous and blocks the process (and
754	sends are immediate, connection establishment is handled in the	719	so does not need a queue that can overflow). AEMP sends are immediate,
755	background.	720	connection establishment is handled in the background.
756		721
757	=item * Erlang can silently lose messages, AEMP cannot.	722	=item * Erlang suffers from silent message loss, AEMP does not.
758		723
759	Erlang makes few guarantees on messages delivery - messages can get lost	724	Erlang makes few guarantees on messages delivery - messages can get lost
760	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,
761	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).
762		727
763	AEMP guarantees correct ordering, and the guarantee that there are no	728	AEMP guarantees correct ordering, and the guarantee that after one message
764	holes in the message sequence.	729	is lost, all following ones sent to the same port are lost as well, until
765		730	monitoring raises an error, so there are no silent "holes" in the message
766	=item * In Erlang, processes can be declared dead and later be found to be	731	sequence.
767	alive.
768
769	In Erlang it can happen that a monitored process is declared dead and
770	linked processes get killed, but later it turns out that the process is
771	still alive - and can receive messages.
772
773	In AEMP, when port monitoring detects a port as dead, then that port will
774	eventually be killed - it cannot happen that a node detects a port as dead
775	and then later sends messages to it, finding it is still alive.
776		732
777	=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.
778		734
779	In Erlang it is quite possible that a node that restarts reuses a process	735	In Erlang it is quite likely that a node that restarts reuses a process ID
780	ID known to other nodes for a completely different process, causing	736	known to other nodes for a completely different process, causing messages
781	messages destined for that process to end up in an unrelated process.	737	destined for that process to end up in an unrelated process.
782		738
783	AEMP never reuses port IDs, so old messages or old port IDs floating	739	AEMP never reuses port IDs, so old messages or old port IDs floating
784	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.
785		741
786	=item * Erlang uses unprotected connections, AEMP uses secure	742	=item * Erlang uses unprotected connections, AEMP uses secure
787	authentication and can use TLS.	743	authentication and can use TLS.
788		744
789	AEMP can use a proven protocol - SSL/TLS - to protect connections and	745	AEMP can use a proven protocol - TLS - to protect connections and
790	securely authenticate nodes.	746	securely authenticate nodes.
791		747
792	=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
793	communications.	749	communications.
794		750
795	The AEMP protocol, unlike the Erlang protocol, supports both	751	The AEMP protocol, unlike the Erlang protocol, supports both programming
796	language-independent text-only protocols (good for debugging) and binary,	752	language independent text-only protocols (good for debugging) and binary,
797	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.
798		755
799	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
800	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
801	protocol simple.	758	protocol simple.
802		759
803	=item * AEMP has more flexible monitoring options than Erlang.	760	=item * AEMP has more flexible monitoring options than Erlang.
804		761
805	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
…		…
808	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
809	on a per-process basis.	766	on a per-process basis.
810		767
811	=item * Erlang tries to hide remote/local connections, AEMP does not.	768	=item * Erlang tries to hide remote/local connections, AEMP does not.
812		769
813	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
814	as linking is (except linking is unreliable in Erlang).	771	same way as linking is (except linking is unreliable in Erlang).
815		772
816	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
817	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
818	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
819	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
820	more reliable.	777	reliable (no need for C<spawn_link>).
821		778
822	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
823	(hard to do in Erlang).	780	(hard to do in Erlang).
824		781
825	=back	782	=back
826		783
827	=head1 RATIONALE	784	=head1 RATIONALE
828		785
829	=over 4	786	=over 4
830		787
831	=item Why strings for ports and noderefs, why not objects?	788	=item Why strings for port and node IDs, why not objects?
832		789
833	We considered "objects", but found that the actual number of methods	790	We considered "objects", but found that the actual number of methods
834	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
835	the network frequently, the serialising/deserialising would add lots of	792	the network frequently, the serialising/deserialising would add lots of
836	overhead, as well as having to keep a proxy object.	793	overhead, as well as having to keep a proxy object everywhere.
837		794
838	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
839	procedures to be "valid".	796	procedures to be "valid".
840		797
841	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
842	can't become much cheaper.	799	global hash - it can't become much cheaper.
843		800
844	=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?
845		802
846	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
847	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
848	default.	805	default (although all nodes will accept it).
849		806
850	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
851	faster for small messages and b) most importantly, after years of	808	faster for small messages and b) most importantly, after years of
852	experience we found that object serialisation is causing more problems	809	experience we found that object serialisation is causing more problems
853	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
854	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
855	always have to re-think your design.	812	always have to re-think your design.
856		813
857	Keeping your messages simple, concentrating on data structures rather than	814	Keeping your messages simple, concentrating on data structures rather than
858	objects, will keep your messages clean, tidy and efficient.	815	objects, will keep your messages clean, tidy and efficient.
859		816
860	=back	817	=back
861		818
862	=head1 SEE ALSO	819	=head1 SEE ALSO
863		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
864	L<AnyEvent>.	828	L<AnyEvent>.
865		829
866	=head1 AUTHOR	830	=head1 AUTHOR
867		831
868	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