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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.50 by root, Fri Aug 14 14:01:05 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, 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
…		…
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46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - outdated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	159	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	160	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	161	a call to C<initialise_node>.
151	identifiers become invalid.
152		162
153	=item $noderef = node_of $port	163	=item $nodeid = node_of $port
154		164
155	Extracts and returns the noderef from a portid or a noderef.	165	Extracts and returns the node ID from a port ID or a node ID.
156		166
157	=item initialise_node $noderef, $seednode, $seednode...	167	=item initialise_node $profile_name
158		168
159	=item initialise_node "slave/", $master, $master...
160
161	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
162	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
163	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.
164		173
165	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
166	never) before calling other AnyEvent::MP functions.	175	never) before calling other AnyEvent::MP functions.
167		176
168	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
169	either resolved or unresolved.	178	the current nodename will be used instead (i.e. F<uname -n>).
170		179
171	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
172	(if it is C<undef> then the current nodename will be used instead) to find	181	L<aemp> commandline utility).
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		182
177	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.
178		186
179	=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).
180		192
181	=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.
182		196
183	For public nodes, C<$noderef> (supplied either directly to	197	Lastly, the seeds list from the profile is passed to the
184	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
185	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.
186		200
187	After resolving, the node will bind itself on all endpoints and try to
188	connect to all additional C<$seednodes> that are specified. Seednodes are
189	optional and can be used to quickly bootstrap the node into an existing
190	network.
191
192	=item slave nodes
193
194	When the C<$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	201	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	202	the one specified via C<aemp> for the current node. This should be the
212	form of invocation for "daemon"-type nodes.	203	most common form of invocation for "daemon"-type nodes.
213		204
214	initialise_node;	205	initialise_node;
215		206
216	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
217	C<aemp>. This form is often used for commandline clients.	208	clients.
218		209
219	initialise_node "slave/";	210	initialise_node "anon/";
220		211
221	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
222	form is also often used for commandline clients.	213	name, or no binds list was specified, resolve C<localhost:4044> and bind
223		214	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		215
237	initialise_node "localhost:4044";	216	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		217
268	=item $SELF	218	=item $SELF
269		219
270	Contains the current port id while executing C<rcv> callbacks or C<psub>	220	Contains the current port id while executing C<rcv> callbacks or C<psub>
271	blocks.	221	blocks.
272		222
273	=item SELF, %SELF, @SELF...	223	=item *SELF, SELF, %SELF, @SELF...
274		224
275	Due to some quirks in how perl exports variables, it is impossible to	225	Due to some quirks in how perl exports variables, it is impossible to
276	just export C<$SELF>, all the symbols called C<SELF> are exported by this	226	just export C<$SELF>, all the symbols named C<SELF> are exported by this
277	module, but only C<$SELF> is currently used.	227	module, but only C<$SELF> is currently used.
278		228
279	=item snd $port, type => @data	229	=item snd $port, type => @data
280		230
281	=item snd $port, @msg	231	=item snd $port, @msg
282		232
283	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
284	a local or a remote port, and can be either a string or soemthignt hat	234	local or a remote port, and must be a port ID.
285	stringifies a sa port ID (such as a port object :).
286		235
287	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
288	string as first element (a portid, or some word that indicates a request	237	use a string as first element (a port ID, or some word that indicates a
289	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.
290		240
291	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
292	function: modifying any argument is not allowed and can cause many	242	function: modifying any argument (or values referenced by them) is
293	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.
294		247
295	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
296	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
297	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
298	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
299	node, anything can be passed.	252	node, anything can be passed. Best rely only on the common denominator of
		253	these.
300		254
301	=item $local_port = port	255	=item $local_port = port
302		256
303	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
304	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.
…		…
351	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
352	C<tag> match.	306	C<tag> match.
353		307
354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	308	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
355		309
356	Register callbacks to be called on messages starting with the given tag on	310	Register (or replace) callbacks to be called on messages starting with the
357	the given port (and return the port), or unregister it (when C<$callback>	311	given tag on the given port (and return the port), or unregister it (when
358	is C<$undef>).	312	C<$callback> is C<$undef> or missing). There can only be one callback
		313	registered for each tag.
359		314
360	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
361	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
362	environment as the default callback (see above).	317	environment as the default callback (see above).
363		318
…		…
375	rcv port,	330	rcv port,
376	msg1 => sub { ... },	331	msg1 => sub { ... },
377	...	332	...
378	;	333	;
379		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, $otherport;
		342	};
		343
380	=cut	344	=cut
381		345
382	sub rcv($@) {	346	sub rcv($@) {
383	my $port = shift;	347	my $port = shift;
384	my ($noderef, $portid) = split /#/, $port, 2;	348	my ($noderef, $portid) = split /#/, $port, 2;
385		349
386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	350	$NODE{$noderef} == $NODE{""}
387	or Carp::croak "$port: rcv can only be called on local ports, caught";	351	or Carp::croak "$port: rcv can only be called on local ports, caught";
388		352
389	while (@_) {	353	while (@_) {
390	if (ref $_[0]) {	354	if (ref $_[0]) {
391	if (my $self = $PORT_DATA{$portid}) {	355	if (my $self = $PORT_DATA{$portid}) {
…		…
470	$res	434	$res
471	}	435	}
472	}	436	}
473	}	437	}
474		438
475	=item $guard = mon $port, $cb->(@reason)	439	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
476		440
477	=item $guard = mon $port, $rcvport	441	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
478		442
479	=item $guard = mon $port	443	=item $guard = mon $port # kill $SELF when $port dies
480		444
481	=item $guard = mon $port, $rcvport, @msg	445	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
482		446
483	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
484	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
485	to stop monitoring again.	449	to stop monitoring again.
486		450
487	C<mon> effectively guarantees that, in the absence of hardware failures,	451	C<mon> effectively guarantees that, in the absence of hardware failures,
488	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
489	will arrive, or the monitoring action will be invoked after possible	453	arrive, or the monitoring action will be invoked after possible message
490	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
491	(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
492	port). After the monitoring action was invoked, further messages might get	456	port). After the monitoring action was invoked, further messages might get
493	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.
494		461
495	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
496	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
497	"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
498	C<eval> if unsure.	465	C<eval> if unsure.
…		…
560	is killed, the references will be freed.	527	is killed, the references will be freed.
561		528
562	Optionally returns a guard that will stop the monitoring.	529	Optionally returns a guard that will stop the monitoring.
563		530
564	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
565	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>):
566		533
567	$port->rcv (start => sub {	534	$port->rcv (start => sub {
568	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	535	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
569	undef $timer if 0.9 < rand;	536	undef $timer if 0.9 < rand;
570	});	537	});
571	});	538	});
572		539
573	=cut	540	=cut
…		…
582		549
583	=item kil $port[, @reason]	550	=item kil $port[, @reason]
584		551
585	Kill the specified port with the given C<@reason>.	552	Kill the specified port with the given C<@reason>.
586		553
587	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
588	ports will not be kileld, or even notified).	555	monitoring other ports will not necessarily die because a port dies
		556	"normally").
589		557
590	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
591	C<mon>, see below).	559	C<mon>, see above).
592		560
593	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
594	will be reported as reason C<< die => $@ >>.	562	will be reported as reason C<< die => $@ >>.
595		563
596	Transport/communication errors are reported as C<< transport_error =>	564	Transport/communication errors are reported as C<< transport_error =>
…		…
601	=item $port = spawn $node, $initfunc[, @initdata]	569	=item $port = spawn $node, $initfunc[, @initdata]
602		570
603	Creates a port on the node C<$node> (which can also be a port ID, in which	571	Creates a port on the node C<$node> (which can also be a port ID, in which
604	case it's the node where that port resides).	572	case it's the node where that port resides).
605		573
606	The port ID of the newly created port is return immediately, and it is	574	The port ID of the newly created port is returned immediately, and it is
607	permissible to immediately start sending messages or monitor the port.	575	possible to immediately start sending messages or to monitor the port.
608		576
609	After the port has been created, the init function is	577	After the port has been created, the init function is called on the remote
610	called. This function must be a fully-qualified function name	578	node, in the same context as a C<rcv> callback. This function must be a
611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	579	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
612	program, use C<::name>.	580	specify a function in the main program, use C<::name>.
613		581
614	If the function doesn't exist, then the node tries to C<require>	582	If the function doesn't exist, then the node tries to C<require>
615	the package, then the package above the package and so on (e.g.	583	the package, then the package above the package and so on (e.g.
616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	584	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
617	exists or it runs out of package names.	585	exists or it runs out of package names.
618		586
619	The init function is then called with the newly-created port as context	587	The init function is then called with the newly-created port as context
620	object (C<$SELF>) and the C<@initdata> values as arguments.	588	object (C<$SELF>) and the C<@initdata> values as arguments.
621		589
622	A common idiom is to pass your own port, monitor the spawned port, and	590	A common idiom is to pass a local port, immediately monitor the spawned
623	in the init function, monitor the original port. This two-way monitoring	591	port, and in the remote init function, immediately monitor the passed
624	ensures that both ports get cleaned up when there is a problem.	592	local port. This two-way monitoring ensures that both ports get cleaned up
		593	when there is a problem.
625		594
626	Example: spawn a chat server port on C<$othernode>.	595	Example: spawn a chat server port on C<$othernode>.
627		596
628	# this node, executed from within a port context:	597	# this node, executed from within a port context:
629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	598	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
659	my $id = "$RUNIQ." . $ID++;	628	my $id = "$RUNIQ." . $ID++;
660		629
661	$_[0] =~ /::/	630	$_[0] =~ /::/
662	or Carp::croak "spawn init function must be a fully-qualified name, caught";	631	or Carp::croak "spawn init function must be a fully-qualified name, caught";
663		632
664	($NODE{$noderef} \|\| add_node $noderef)	633	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
666		634
667	"$noderef#$id"	635	"$noderef#$id"
668	}	636	}
669		637
670	=back	638	=item after $timeout, @msg
671		639
672	=head1 NODE MESSAGES	640	=item after $timeout, $callback
673		641
674	Nodes understand the following messages sent to them. Many of them take	642	Either sends the given message, or call the given callback, after the
675	arguments called C<@reply>, which will simply be used to compose a reply	643	specified number of seconds.
676	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
677	the remaining arguments are simply the message data.
678		644
679	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.
680		648
681	=over 4
682
683	=cut	649	=cut
684		650
685	=item lookup => $name, @reply	651	sub after($@) {
		652	my ($timeout, @action) = @_;
686		653
687	Replies with the port ID of the specified well-known port, or C<undef>.	654	my $t; $t = AE::timer $timeout, 0, sub {
688		655	undef $t;
689	=item devnull => ...	656	ref $action[0]
690		657	? $action[0]()
691	Generic data sink/CPU heat conversion.	658	: snd @action;
692		659	};
693	=item relay => $port, @msg	660	}
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		661
716	=back	662	=back
717		663
718	=head1 AnyEvent::MP vs. Distributed Erlang	664	=head1 AnyEvent::MP vs. Distributed Erlang
719		665
…		…
729		675
730	Despite the similarities, there are also some important differences:	676	Despite the similarities, there are also some important differences:
731		677
732	=over 4	678	=over 4
733		679
734	=item * Node references contain the recipe on how to contact them.	680	=item * Node IDs are arbitrary strings in AEMP.
735		681
736	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
737	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
738	convenience functionality.	684	configuraiton or DNS), but will otherwise discover other odes itself.
739		685
740	This means that AEMP requires a less tightly controlled environment at the	686	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
741	cost of longer node references and a slightly higher management overhead.	687	uses "local ports are like remote ports".
		688
		689	The failure modes for local ports are quite different (runtime errors
		690	only) then for remote ports - when a local port dies, you I<know> it dies,
		691	when a connection to another node dies, you know nothing about the other
		692	port.
		693
		694	Erlang pretends remote ports are as reliable as local ports, even when
		695	they are not.
		696
		697	AEMP encourages a "treat remote ports differently" philosophy, with local
		698	ports being the special case/exception, where transport errors cannot
		699	occur.
742		700
743	=item * Erlang uses processes and a mailbox, AEMP does not queue.	701	=item * Erlang uses processes and a mailbox, AEMP does not queue.
744		702
745	Erlang uses processes that selctively receive messages, and therefore	703	Erlang uses processes that selectively receive messages, and therefore
746	needs a queue. AEMP is event based, queuing messages would serve no useful	704	needs a queue. AEMP is event based, queuing messages would serve no
747	purpose.	705	useful purpose. For the same reason the pattern-matching abilities of
		706	AnyEvent::MP are more limited, as there is little need to be able to
		707	filter messages without dequeing them.
748		708
749	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	709	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
750		710
751	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	711	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
752		712
753	Sending messages in Erlang is synchronous and blocks the process. AEMP	713	Sending messages in Erlang is synchronous and blocks the process (and
754	sends are immediate, connection establishment is handled in the	714	so does not need a queue that can overflow). AEMP sends are immediate,
755	background.	715	connection establishment is handled in the background.
756		716
757	=item * Erlang can silently lose messages, AEMP cannot.	717	=item * Erlang suffers from silent message loss, AEMP does not.
758		718
759	Erlang makes few guarantees on messages delivery - messages can get lost	719	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,	720	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).	721	and c, and the other side only receives messages a and c).
762		722
763	AEMP guarantees correct ordering, and the guarantee that there are no	723	AEMP guarantees correct ordering, and the guarantee that after one message
764	holes in the message sequence.	724	is lost, all following ones sent to the same port are lost as well, until
765		725	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	726	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		727
777	=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.
778		729
779	In Erlang it is quite possible that a node that restarts reuses a process	730	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	731	known to other nodes for a completely different process, causing messages
781	messages destined for that process to end up in an unrelated process.	732	destined for that process to end up in an unrelated process.
782		733
783	AEMP never reuses port IDs, so old messages or old port IDs floating	734	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.	735	around in the network will not be sent to an unrelated port.
785		736
786	=item * Erlang uses unprotected connections, AEMP uses secure	737	=item * Erlang uses unprotected connections, AEMP uses secure
787	authentication and can use TLS.	738	authentication and can use TLS.
788		739
789	AEMP can use a proven protocol - SSL/TLS - to protect connections and	740	AEMP can use a proven protocol - TLS - to protect connections and
790	securely authenticate nodes.	741	securely authenticate nodes.
791		742
792	=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
793	communications.	744	communications.
794		745
795	The AEMP protocol, unlike the Erlang protocol, supports both	746	The AEMP protocol, unlike the Erlang protocol, supports both programming
796	language-independent text-only protocols (good for debugging) and binary,	747	language independent text-only protocols (good for debugging) and binary,
797	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.
798		750
799	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
800	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
801	protocol simple.	753	protocol simple.
802		754
803	=item * AEMP has more flexible monitoring options than Erlang.	755	=item * AEMP has more flexible monitoring options than Erlang.
804		756
805	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
…		…
808	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
809	on a per-process basis.	761	on a per-process basis.
810		762
811	=item * Erlang tries to hide remote/local connections, AEMP does not.	763	=item * Erlang tries to hide remote/local connections, AEMP does not.
812		764
813	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
814	as linking is (except linking is unreliable in Erlang).	766	same way as linking is (except linking is unreliable in Erlang).
815		767
816	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
817	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
818	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
819	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
820	more reliable.	772	reliable (no need for C<spawn_link>).
821		773
822	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
823	(hard to do in Erlang).	775	(hard to do in Erlang).
824		776
825	=back	777	=back
826		778
827	=head1 RATIONALE	779	=head1 RATIONALE
828		780
829	=over 4	781	=over 4
830		782
831	=item Why strings for ports and noderefs, why not objects?	783	=item Why strings for port and node IDs, why not objects?
832		784
833	We considered "objects", but found that the actual number of methods	785	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	786	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	787	the network frequently, the serialising/deserialising would add lots of
836	overhead, as well as having to keep a proxy object.	788	overhead, as well as having to keep a proxy object everywhere.
837		789
838	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
839	procedures to be "valid".	791	procedures to be "valid".
840		792
841	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
842	can't become much cheaper.	794	global hash - it can't become much cheaper.
843		795
844	=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?
845		797
846	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
847	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
848	default.	800	default (although all nodes will accept it).
849		801
850	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
851	faster for small messages and b) most importantly, after years of	803	faster for small messages and b) most importantly, after years of
852	experience we found that object serialisation is causing more problems	804	experience we found that object serialisation is causing more problems
853	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
854	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
855	always have to re-think your design.	807	always have to re-think your design.
856		808
857	Keeping your messages simple, concentrating on data structures rather than	809	Keeping your messages simple, concentrating on data structures rather than
858	objects, will keep your messages clean, tidy and efficient.	810	objects, will keep your messages clean, tidy and efficient.

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC vs.
Revision 1.67 by root, Fri Aug 28 22:21:53 2009 UTC