[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 1.75 by root, Mon Aug 31 13:18:06 2009 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $somple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
38	# monitoring	35	# monitoring
…		…
40	mon $port, $otherport # kill otherport on abnormal death	37	mon $port, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	38	mon $port, $otherport, @msg # send message on death
42		39
43	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
44		41
		42	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - uptodate, but incomplete.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable API, protocol not yet final.
49		47
50	stay tuned.	48	stay tuned.
51		49
52	=head1 DESCRIPTION	50	=head1 DESCRIPTION
53		51
54	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
55		53
56	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
58		56
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	58	manual page and the examples under F<eg/>.
61		59
62	At the moment, this module family is severly broken and underdocumented,	60	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		61
66	=head1 CONCEPTS	62	=head1 CONCEPTS
67		63
68	=over 4	64	=over 4
69		65
70	=item port	66	=item port
71		67
72	A port is something you can send messages to (with the C<snd> function).	68	A port is something you can send messages to (with the C<snd> function).
73		69
74	Some ports allow you to register C<rcv> handlers that can match specific	70	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	71	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	72	anything was listening for them or not.
77		73
78	=item port id - C<noderef#portname>	74	=item port ID - C<nodeid#portname>
79		75
80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	76	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	77	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		78
85	=item node	79	=item node
86		80
87	A node is a single process containing at least one port - the node	81	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	82	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	83	ports.
90		84
91	Nodes are either private (single-process only), slaves (connected to a	85	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	86	(no listening ports). Private nodes cannot talk to other private nodes
		87	currently.
93		88
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	89	=item node ID - C<[a-za-Z0-9_\-.:]+>
95		90
96	A node reference is a string that either simply identifies the node (for	91	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	92	network. Depending on the configuration used, node IDs can look like a
98	node (for public nodes).	93	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		94	doesn't interpret node IDs in any way.
99		95
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	96	=item binds - C<ip:port>
101	TCP/IP, other protocols might look different).
102		97
103	Node references come in two flavours: resolved (containing only numerical	98	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).	99	each other. To do this, nodes should listen on one or more local transport
		100	endpoints - binds. Currently, only standard C<ip:port> specifications can
		101	be used, which specify TCP ports to listen on.
105		102
106	Before using an unresolved node reference in a message you first have to	103	=item seeds - C<host:port>
107	resolve it.	104
		105	When a node starts, it knows nothing about the network. To teach the node
		106	about the network it first has to contact some other node within the
		107	network. This node is called a seed.
		108
		109	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		110	are expected to be long-running, and at least one of those should always
		111	be available. When nodes run out of connections (e.g. due to a network
		112	error), they try to re-establish connections to some seednodes again to
		113	join the network.
		114
		115	Apart from being sued for seeding, seednodes are not special in any way -
		116	every public node can be a seednode.
108		117
109	=back	118	=back
110		119
111	=head1 VARIABLES/FUNCTIONS	120	=head1 VARIABLES/FUNCTIONS
112		121
…		…
127	use base "Exporter";	136	use base "Exporter";
128		137
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	138	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
130		139
131	our @EXPORT = qw(	140	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	141	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	142	configure
134	snd rcv mon kil reg psub spawn	143	snd rcv mon mon_guard kil reg psub spawn
135	port	144	port
136	);	145	);
137		146
138	our $SELF;	147	our $SELF;
139		148
…		…
143	kil $SELF, die => $msg;	152	kil $SELF, die => $msg;
144	}	153	}
145		154
146	=item $thisnode = NODE / $NODE	155	=item $thisnode = NODE / $NODE
147		156
148	The C<NODE> function returns, and the C<$NODE> variable contains the	157	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	158	ID of the node running in the current process. This value is initialised by
150	C<initialise_node>.	159	a call to C<configure>.
151		160
152	=item $noderef = node_of $port	161	=item $nodeid = node_of $port
153		162
154	Extracts and returns the noderef from a port ID or a noderef.	163	Extracts and returns the node ID from a port ID or a node ID.
155		164
156	=item initialise_node $noderef, $seednode, $seednode...	165	=item configure key => value...
157		166
158	=item initialise_node "slave/", $master, $master...
159
160	Before a node can talk to other nodes on the network it has to initialise	167	Before a node can talk to other nodes on the network (i.e. enter
161	itself - the minimum a node needs to know is it's own name, and optionally	168	"distributed mode") it has to configure itself - the minimum a node needs
162	it should know the noderefs of some other nodes in the network.	169	to know is its own name, and optionally it should know the addresses of
		170	some other nodes in the network to discover other nodes.
163		171
164	This function initialises a node - it must be called exactly once (or	172	This function configures a node - it must be called exactly once (or
165	never) before calling other AnyEvent::MP functions.	173	never) before calling other AnyEvent::MP functions.
166		174
167	All arguments (optionally except for the first) are noderefs, which can be
168	either resolved or unresolved.
169
170	The first argument will be looked up in the configuration database first
171	(if it is C<undef> then the current nodename will be used instead) to find
172	the relevant configuration profile (see L<aemp>). If none is found then
173	the default configuration is used. The configuration supplies additional
174	seed/master nodes and can override the actual noderef.
175
176	There are two types of networked nodes, public nodes and slave nodes:
177
178	=over 4	175	=over 4
179		176
180	=item public nodes	177	=item step 1, gathering configuration from profiles
181		178
182	For public nodes, C<$noderef> (supplied either directly to	179	The function first looks up a profile in the aemp configuration (see the
183	C<initialise_node> or indirectly via a profile or the nodename) must be a	180	L<aemp> commandline utility). The profile name can be specified via the
184	noderef (possibly unresolved, in which case it will be resolved).	181	named C<profile> parameter. If it is missing, then the nodename (F<uname
		182	-n>) will be used as profile name.
185		183
186	After resolving, the node will bind itself on all endpoints and try to	184	The profile data is then gathered as follows:
187	connect to all additional C<$seednodes> that are specified. Seednodes are
188	optional and can be used to quickly bootstrap the node into an existing
189	network.
190		185
191	=item slave nodes	186	First, all remaining key => value pairs (all of which are conviniently
		187	undocumented at the moment) will be interpreted as configuration
		188	data. Then they will be overwritten by any values specified in the global
		189	default configuration (see the F<aemp> utility), then the chain of
		190	profiles chosen by the profile name (and any C<parent> attributes).
192		191
193	When the C<$noderef> (either as given or overriden by the config file)	192	That means that the values specified in the profile have highest priority
194	is the special string C<slave/>, then the node will become a slave	193	and the values specified directly via C<configure> have lowest priority,
195	node. Slave nodes cannot be contacted from outside and will route most of	194	and can only be used to specify defaults.
196	their traffic to the master node that they attach to.
197		195
198	At least one additional noderef is required (either by specifying it	196	If the profile specifies a node ID, then this will become the node ID of
199	directly or because it is part of the configuration profile): The node	197	this process. If not, then the profile name will be used as node ID. The
200	will try to connect to all of them and will become a slave attached to the	198	special node ID of C<anon/> will be replaced by a random node ID.
201	first node it can successfully connect to.	199
		200	=item step 2, bind listener sockets
		201
		202	The next step is to look up the binds in the profile, followed by binding
		203	aemp protocol listeners on all binds specified (it is possible and valid
		204	to have no binds, meaning that the node cannot be contacted form the
		205	outside. This means the node cannot talk to other nodes that also have no
		206	binds, but it can still talk to all "normal" nodes).
		207
		208	If the profile does not specify a binds list, then a default of C<*> is
		209	used, meaning the node will bind on a dynamically-assigned port on every
		210	local IP address it finds.
		211
		212	=item step 3, connect to seed nodes
		213
		214	As the last step, the seeds list from the profile is passed to the
		215	L<AnyEvent::MP::Global> module, which will then use it to keep
		216	connectivity with at least one node at any point in time.
202		217
203	=back	218	=back
204		219
205	This function will block until all nodes have been resolved and, for slave	220	Example: become a distributed node using the locla node name as profile.
206	nodes, until it has successfully established a connection to a master	221	This should be the most common form of invocation for "daemon"-type nodes.
207	server.
208		222
209	Example: become a public node listening on the guessed noderef, or the one	223	configure
210	specified via C<aemp> for the current node. This should be the most common
211	form of invocation for "daemon"-type nodes.
212		224
213	initialise_node;	225	Example: become an anonymous node. This form is often used for commandline
		226	clients.
214		227
215	Example: become a slave node to any of the the seednodes specified via	228	configure nodeid => "anon/";
216	C<aemp>. This form is often used for commandline clients.
217		229
218	initialise_node "slave/";	230	Example: configure a node using a profile called seed, which si suitable
		231	for a seed node as it binds on all local addresses on a fixed port (4040,
		232	customary for aemp).
219		233
220	Example: become a slave node to any of the specified master servers. This	234	# use the aemp commandline utility
221	form is also often used for commandline clients.	235	# aemp profile seed nodeid anon/ binds '*:4040'
222		236
223	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	237	# then use it
		238	configure profile => "seed";
224		239
225	Example: become a public node, and try to contact some well-known master	240	# or simply use aemp from the shell again:
226	servers to become part of the network.	241	# aemp run profile seed
227		242
228	initialise_node undef, "master1", "master2";	243	# or provide a nicer-to-remember nodeid
229		244	# aemp run profile seed nodeid "$(hostname)"
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
236	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		245
267	=item $SELF	246	=item $SELF
268		247
269	Contains the current port id while executing C<rcv> callbacks or C<psub>	248	Contains the current port id while executing C<rcv> callbacks or C<psub>
270	blocks.	249	blocks.
271		250
272	=item SELF, %SELF, @SELF...	251	=item *SELF, SELF, %SELF, @SELF...
273		252
274	Due to some quirks in how perl exports variables, it is impossible to	253	Due to some quirks in how perl exports variables, it is impossible to
275	just export C<$SELF>, all the symbols called C<SELF> are exported by this	254	just export C<$SELF>, all the symbols named C<SELF> are exported by this
276	module, but only C<$SELF> is currently used.	255	module, but only C<$SELF> is currently used.
277		256
278	=item snd $port, type => @data	257	=item snd $port, type => @data
279		258
280	=item snd $port, @msg	259	=item snd $port, @msg
281		260
282	Send the given message to the given port ID, which can identify either	261	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.	262	local or a remote port, and must be a port ID.
284		263
285	While the message can be about anything, it is highly recommended to use a	264	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	265	use a string as first element (a port ID, or some word that indicates a
287	type etc.).	266	request type etc.) and to consist if only simple perl values (scalars,
		267	arrays, hashes) - if you think you need to pass an object, think again.
288		268
289	The message data effectively becomes read-only after a call to this	269	The message data logically becomes read-only after a call to this
290	function: modifying any argument is not allowed and can cause many	270	function: modifying any argument (or values referenced by them) is
291	problems.	271	forbidden, as there can be considerable time between the call to C<snd>
		272	and the time the message is actually being serialised - in fact, it might
		273	never be copied as within the same process it is simply handed to the
		274	receiving port.
292		275
293	The type of data you can transfer depends on the transport protocol: when	276	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	277	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	278	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	279	that Storable can serialise and deserialise is allowed, and for the local
297	node, anything can be passed.	280	node, anything can be passed. Best rely only on the common denominator of
		281	these.
298		282
299	=item $local_port = port	283	=item $local_port = port
300		284
301	Create a new local port object and returns its port ID. Initially it has	285	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.	286	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	333	The default callback received all messages not matched by a more specific
350	C<tag> match.	334	C<tag> match.
351		335
352	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	336	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
353		337
354	Register callbacks to be called on messages starting with the given tag on	338	Register (or replace) callbacks to be called on messages starting with the
355	the given port (and return the port), or unregister it (when C<$callback>	339	given tag on the given port (and return the port), or unregister it (when
356	is C<$undef>).	340	C<$callback> is C<$undef> or missing). There can only be one callback
		341	registered for each tag.
357		342
358	The original message will be passed to the callback, after the first	343	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	344	element (the tag) has been removed. The callback will use the same
360	environment as the default callback (see above).	345	environment as the default callback (see above).
361		346
…		…
373	rcv port,	358	rcv port,
374	msg1 => sub { ... },	359	msg1 => sub { ... },
375	...	360	...
376	;	361	;
377		362
		363	Example: temporarily register a rcv callback for a tag matching some port
		364	(e.g. for a rpc reply) and unregister it after a message was received.
		365
		366	rcv $port, $otherport => sub {
		367	my @reply = @_;
		368
		369	rcv $SELF, $otherport;
		370	};
		371
378	=cut	372	=cut
379		373
380	sub rcv($@) {	374	sub rcv($@) {
381	my $port = shift;	375	my $port = shift;
382	my ($noderef, $portid) = split /#/, $port, 2;	376	my ($nodeid, $portid) = split /#/, $port, 2;
383		377
384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	378	$NODE{$nodeid} == $NODE{""}
385	or Carp::croak "$port: rcv can only be called on local ports, caught";	379	or Carp::croak "$port: rcv can only be called on local ports, caught";
386		380
387	while (@_) {	381	while (@_) {
388	if (ref $_[0]) {	382	if (ref $_[0]) {
389	if (my $self = $PORT_DATA{$portid}) {	383	if (my $self = $PORT_DATA{$portid}) {
…		…
468	$res	462	$res
469	}	463	}
470	}	464	}
471	}	465	}
472		466
473	=item $guard = mon $port, $cb->(@reason)	467	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
474		468
475	=item $guard = mon $port, $rcvport	469	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
476		470
477	=item $guard = mon $port	471	=item $guard = mon $port # kill $SELF when $port dies
478		472
479	=item $guard = mon $port, $rcvport, @msg	473	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
480		474
481	Monitor the given port and do something when the port is killed or	475	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	476	messages to it were lost, and optionally return a guard that can be used
483	to stop monitoring again.	477	to stop monitoring again.
484		478
485	C<mon> effectively guarantees that, in the absence of hardware failures,	479	C<mon> effectively guarantees that, in the absence of hardware failures,
486	that after starting the monitor, either all messages sent to the port	480	after starting the monitor, either all messages sent to the port will
487	will arrive, or the monitoring action will be invoked after possible	481	arrive, or the monitoring action will be invoked after possible message
488	message loss has been detected. No messages will be lost "in between"	482	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	483	the first lost message no further messages will be received by the
490	port). After the monitoring action was invoked, further messages might get	484	port). After the monitoring action was invoked, further messages might get
491	delivered again.	485	delivered again.
		486
		487	Note that monitoring-actions are one-shot: once messages are lost (and a
		488	monitoring alert was raised), they are removed and will not trigger again.
492		489
493	In the first form (callback), the callback is simply called with any	490	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	491	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	492	"normally"). Note also that I<< the callback B<must> never die >>, so use
496	C<eval> if unsure.	493	C<eval> if unsure.
…		…
526	mon $port, $self => "restart";	523	mon $port, $self => "restart";
527		524
528	=cut	525	=cut
529		526
530	sub mon {	527	sub mon {
531	my ($noderef, $port) = split /#/, shift, 2;	528	my ($nodeid, $port) = split /#/, shift, 2;
532		529
533	my $node = $NODE{$noderef} \|\| add_node $noderef;	530	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
534		531
535	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	532	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
536		533
537	unless (ref $cb) {	534	unless (ref $cb) {
538	if (@_) {	535	if (@_) {
…		…
558	is killed, the references will be freed.	555	is killed, the references will be freed.
559		556
560	Optionally returns a guard that will stop the monitoring.	557	Optionally returns a guard that will stop the monitoring.
561		558
562	This function is useful when you create e.g. timers or other watchers and	559	This function is useful when you create e.g. timers or other watchers and
563	want to free them when the port gets killed:	560	want to free them when the port gets killed (note the use of C<psub>):
564		561
565	$port->rcv (start => sub {	562	$port->rcv (start => sub {
566	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	563	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
567	undef $timer if 0.9 < rand;	564	undef $timer if 0.9 < rand;
568	});	565	});
569	});	566	});
570		567
571	=cut	568	=cut
…		…
580		577
581	=item kil $port[, @reason]	578	=item kil $port[, @reason]
582		579
583	Kill the specified port with the given C<@reason>.	580	Kill the specified port with the given C<@reason>.
584		581
585	If no C<@reason> is specified, then the port is killed "normally" (linked	582	If no C<@reason> is specified, then the port is killed "normally" (ports
586	ports will not be kileld, or even notified).	583	monitoring other ports will not necessarily die because a port dies
		584	"normally").
587		585
588	Otherwise, linked ports get killed with the same reason (second form of	586	Otherwise, linked ports get killed with the same reason (second form of
589	C<mon>, see below).	587	C<mon>, see above).
590		588
591	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	589	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
592	will be reported as reason C<< die => $@ >>.	590	will be reported as reason C<< die => $@ >>.
593		591
594	Transport/communication errors are reported as C<< transport_error =>	592	Transport/communication errors are reported as C<< transport_error =>
…		…
599	=item $port = spawn $node, $initfunc[, @initdata]	597	=item $port = spawn $node, $initfunc[, @initdata]
600		598
601	Creates a port on the node C<$node> (which can also be a port ID, in which	599	Creates a port on the node C<$node> (which can also be a port ID, in which
602	case it's the node where that port resides).	600	case it's the node where that port resides).
603		601
604	The port ID of the newly created port is return immediately, and it is	602	The port ID of the newly created port is returned immediately, and it is
605	permissible to immediately start sending messages or monitor the port.	603	possible to immediately start sending messages or to monitor the port.
606		604
607	After the port has been created, the init function is	605	After the port has been created, the init function is called on the remote
608	called. This function must be a fully-qualified function name	606	node, in the same context as a C<rcv> callback. This function must be a
609	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	607	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
610	program, use C<::name>.	608	specify a function in the main program, use C<::name>.
611		609
612	If the function doesn't exist, then the node tries to C<require>	610	If the function doesn't exist, then the node tries to C<require>
613	the package, then the package above the package and so on (e.g.	611	the package, then the package above the package and so on (e.g.
614	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	612	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
615	exists or it runs out of package names.	613	exists or it runs out of package names.
616		614
617	The init function is then called with the newly-created port as context	615	The init function is then called with the newly-created port as context
618	object (C<$SELF>) and the C<@initdata> values as arguments.	616	object (C<$SELF>) and the C<@initdata> values as arguments.
619		617
620	A common idiom is to pass your own port, monitor the spawned port, and	618	A common idiom is to pass a local port, immediately monitor the spawned
621	in the init function, monitor the original port. This two-way monitoring	619	port, and in the remote init function, immediately monitor the passed
622	ensures that both ports get cleaned up when there is a problem.	620	local port. This two-way monitoring ensures that both ports get cleaned up
		621	when there is a problem.
623		622
624	Example: spawn a chat server port on C<$othernode>.	623	Example: spawn a chat server port on C<$othernode>.
625		624
626	# this node, executed from within a port context:	625	# this node, executed from within a port context:
627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
650	};	649	};
651	_self_die if $@;	650	_self_die if $@;
652	}	651	}
653		652
654	sub spawn(@) {	653	sub spawn(@) {
655	my ($noderef, undef) = split /#/, shift, 2;	654	my ($nodeid, undef) = split /#/, shift, 2;
656		655
657	my $id = "$RUNIQ." . $ID++;	656	my $id = "$RUNIQ." . $ID++;
658		657
659	$_[0] =~ /::/	658	$_[0] =~ /::/
660	or Carp::croak "spawn init function must be a fully-qualified name, caught";	659	or Carp::croak "spawn init function must be a fully-qualified name, caught";
661		660
662	($NODE{$noderef} \|\| add_node $noderef)	661	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
663	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
664		662
665	"$noderef#$id"	663	"$nodeid#$id"
666	}	664	}
667		665
668	=back	666	=item after $timeout, @msg
669		667
670	=head1 NODE MESSAGES	668	=item after $timeout, $callback
671		669
672	Nodes understand the following messages sent to them. Many of them take	670	Either sends the given message, or call the given callback, after the
673	arguments called C<@reply>, which will simply be used to compose a reply	671	specified number of seconds.
674	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
675	the remaining arguments are simply the message data.
676		672
677	While other messages exist, they are not public and subject to change.	673	This is simply a utility function that comes in handy at times - the
		674	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		675	so it may go away in the future.
678		676
679	=over 4
680
681	=cut	677	=cut
682		678
683	=item lookup => $name, @reply	679	sub after($@) {
		680	my ($timeout, @action) = @_;
684		681
685	Replies with the port ID of the specified well-known port, or C<undef>.	682	my $t; $t = AE::timer $timeout, 0, sub {
686		683	undef $t;
687	=item devnull => ...	684	ref $action[0]
688		685	? $action[0]()
689	Generic data sink/CPU heat conversion.	686	: snd @action;
690		687	};
691	=item relay => $port, @msg	688	}
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		689
714	=back	690	=back
715		691
716	=head1 AnyEvent::MP vs. Distributed Erlang	692	=head1 AnyEvent::MP vs. Distributed Erlang
717		693
…		…
727		703
728	Despite the similarities, there are also some important differences:	704	Despite the similarities, there are also some important differences:
729		705
730	=over 4	706	=over 4
731		707
732	=item * Node references contain the recipe on how to contact them.	708	=item * Node IDs are arbitrary strings in AEMP.
733		709
734	Erlang relies on special naming and DNS to work everywhere in the	710	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	711	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
736	convenience functionality.	712	configuraiton or DNS), but will otherwise discover other odes itself.
737		713
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	714	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
742	uses "local ports are like remote ports".	715	uses "local ports are like remote ports".
743		716
744	The failure modes for local ports are quite different (runtime errors	717	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,	718	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	719	when a connection to another node dies, you know nothing about the other
…		…
773		746
774	Erlang makes few guarantees on messages delivery - messages can get lost	747	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,	748	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).	749	and c, and the other side only receives messages a and c).
777		750
778	AEMP guarantees correct ordering, and the guarantee that there are no	751	AEMP guarantees correct ordering, and the guarantee that after one message
779	holes in the message sequence.	752	is lost, all following ones sent to the same port are lost as well, until
780		753	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	754	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		755
792	=item * Erlang can send messages to the wrong port, AEMP does not.	756	=item * Erlang can send messages to the wrong port, AEMP does not.
793		757
794	In Erlang it is quite likely that a node that restarts reuses a process ID	758	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	759	known to other nodes for a completely different process, causing messages
…		…
799	around in the network will not be sent to an unrelated port.	763	around in the network will not be sent to an unrelated port.
800		764
801	=item * Erlang uses unprotected connections, AEMP uses secure	765	=item * Erlang uses unprotected connections, AEMP uses secure
802	authentication and can use TLS.	766	authentication and can use TLS.
803		767
804	AEMP can use a proven protocol - SSL/TLS - to protect connections and	768	AEMP can use a proven protocol - TLS - to protect connections and
805	securely authenticate nodes.	769	securely authenticate nodes.
806		770
807	=item * The AEMP protocol is optimised for both text-based and binary	771	=item * The AEMP protocol is optimised for both text-based and binary
808	communications.	772	communications.
809		773
810	The AEMP protocol, unlike the Erlang protocol, supports both	774	The AEMP protocol, unlike the Erlang protocol, supports both programming
811	language-independent text-only protocols (good for debugging) and binary,	775	language independent text-only protocols (good for debugging) and binary,
812	language-specific serialisers (e.g. Storable).	776	language-specific serialisers (e.g. Storable). By default, unless TLS is
		777	used, the protocol is actually completely text-based.
813		778
814	It has also been carefully designed to be implementable in other languages	779	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	780	with a minimum of work while gracefully degrading functionality to make the
816	protocol simple.	781	protocol simple.
817		782
818	=item * AEMP has more flexible monitoring options than Erlang.	783	=item * AEMP has more flexible monitoring options than Erlang.
819		784
820	In Erlang, you can chose to receive I<all> exit signals as messages	785	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	788	Erlang, as one can choose between automatic kill, exit message or callback
824	on a per-process basis.	789	on a per-process basis.
825		790
826	=item * Erlang tries to hide remote/local connections, AEMP does not.	791	=item * Erlang tries to hide remote/local connections, AEMP does not.
827		792
828	Monitoring in Erlang is not an indicator of process death/crashes,	793	Monitoring in Erlang is not an indicator of process death/crashes, in the
829	as linking is (except linking is unreliable in Erlang).	794	same way as linking is (except linking is unreliable in Erlang).
830		795
831	In AEMP, you don't "look up" registered port names or send to named ports	796	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	797	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	798	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	799	remote port. Since both monitors are local to the node, they are much more
835	more reliable.	800	reliable (no need for C<spawn_link>).
836		801
837	This also saves round-trips and avoids sending messages to the wrong port	802	This also saves round-trips and avoids sending messages to the wrong port
838	(hard to do in Erlang).	803	(hard to do in Erlang).
839		804
840	=back	805	=back
841		806
842	=head1 RATIONALE	807	=head1 RATIONALE
843		808
844	=over 4	809	=over 4
845		810
846	=item Why strings for ports and noderefs, why not objects?	811	=item Why strings for port and node IDs, why not objects?
847		812
848	We considered "objects", but found that the actual number of methods	813	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	814	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	815	the network frequently, the serialising/deserialising would add lots of
851	overhead, as well as having to keep a proxy object.	816	overhead, as well as having to keep a proxy object everywhere.
852		817
853	Strings can easily be printed, easily serialised etc. and need no special	818	Strings can easily be printed, easily serialised etc. and need no special
854	procedures to be "valid".	819	procedures to be "valid".
855		820
856	And a a miniport consists of a single closure stored in a global hash - it	821	And as a result, a miniport consists of a single closure stored in a
857	can't become much cheaper.	822	global hash - it can't become much cheaper.
858		823
859	=item Why favour JSON, why not real serialising format such as Storable?	824	=item Why favour JSON, why not a real serialising format such as Storable?
860		825
861	In fact, any AnyEvent::MP node will happily accept Storable as framing	826	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	827	format, but currently there is no way to make a node use Storable by
863	default.	828	default (although all nodes will accept it).
864		829
865	The default framing protocol is JSON because a) JSON::XS is many times	830	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	831	faster for small messages and b) most importantly, after years of
867	experience we found that object serialisation is causing more problems	832	experience we found that object serialisation is causing more problems
868	than it gains: Just like function calls, objects simply do not travel	833	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	834	easily over the network, mostly because they will always be a copy, so you
870	always have to re-think your design.	835	always have to re-think your design.
871		836
872	Keeping your messages simple, concentrating on data structures rather than	837	Keeping your messages simple, concentrating on data structures rather than
873	objects, will keep your messages clean, tidy and efficient.	838	objects, will keep your messages clean, tidy and efficient.
874		839
875	=back	840	=back
876		841
877	=head1 SEE ALSO	842	=head1 SEE ALSO
878		843
		844	L<AnyEvent::MP::Intro> - a gentle introduction.
		845
		846	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		847
		848	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		849	your applications.
		850
879	L<AnyEvent>.	851	L<AnyEvent>.
880		852
881	=head1 AUTHOR	853	=head1 AUTHOR
882		854
883	Marc Lehmann <schmorp@schmorp.de>	855	Marc Lehmann <schmorp@schmorp.de>

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC vs. Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC

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Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC vs.
Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC