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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.55 by root, Fri Aug 14 23:17:17 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 $simple_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46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - uptodate, but incomplete.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	Ports allow you to register C<rcv> handlers that can match all or just	70	Ports allow you to register C<rcv> handlers that can match all or just
75	some messages. Messages will not be queued.	71	some messages. Messages send to ports will not be queued, regardless of
		72	anything was listening for them or not.
76		73
77	=item port id - C<noderef#portname>	74	=item port ID - C<nodeid#portname>
78		75
79	A port ID is 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
80	separator, and a port name (a printable string of unspecified format). An	77	separator, and a port name (a printable string of unspecified format).
81	exception is the the node port, whose ID is identical to its node
82	reference.
83		78
84	=item node	79	=item node
85		80
86	A node is a single process containing at least one port - the node port,	81	A node is a single process containing at least one port - the node port,
87	which provides nodes to manage each other remotely, and to create new	82	which enables nodes to manage each other remotely, and to create new
88	ports.	83	ports.
89		84
90	Nodes are either private (single-process only), slaves (connected to a	85	Nodes are either public (have one or more listening ports) or private
91	master node only) or public nodes (connectable from unrelated nodes).	86	(no listening ports). Private nodes cannot talk to other private nodes
		87	currently.
92		88
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	89	=item node ID - C<[a-za-Z0-9_\-.:]+>
94		90
95	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
96	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
97	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.
98		95
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	96	=item binds - C<ip:port>
100	TCP/IP, other protocols might look different).
101		97
102	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
103	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.
104		102
105	Before using an unresolved node reference in a message you first have to	103	=item seeds - C<host:port>
106	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.
107		117
108	=back	118	=back
109		119
110	=head1 VARIABLES/FUNCTIONS	120	=head1 VARIABLES/FUNCTIONS
111		121
…		…
126	use base "Exporter";	136	use base "Exporter";
127		137
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	138	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
129		139
130	our @EXPORT = qw(	140	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	141	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	142	configure
133	snd rcv mon kil reg psub spawn	143	snd rcv mon mon_guard kil reg psub spawn
134	port	144	port
135	);	145	);
136		146
137	our $SELF;	147	our $SELF;
138		148
…		…
142	kil $SELF, die => $msg;	152	kil $SELF, die => $msg;
143	}	153	}
144		154
145	=item $thisnode = NODE / $NODE	155	=item $thisnode = NODE / $NODE
146		156
147	The C<NODE> function returns, and the C<$NODE> variable contains the	157	The C<NODE> function returns, and the C<$NODE> variable contains, the node
148	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
149	C<initialise_node>.	159	a call to C<configure>.
150		160
151	=item $noderef = node_of $port	161	=item $nodeid = node_of $port
152		162
153	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.
154		164
155	=item initialise_node $noderef, $seednode, $seednode...	165	=item configure key => value...
156		166
157	=item initialise_node "slave/", $master, $master...
158
159	Before a node can talk to other nodes on the network it has to initialise	167	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	168	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	169	to know is its own name, and optionally it should know the addresses of
		170	some other nodes in the network to discover other nodes.
162		171
163	This function initialises a node - it must be called exactly once (or	172	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	173	never) before calling other AnyEvent::MP functions.
165		174
166	All arguments (optionally except for the first) are noderefs, which can be
167	either resolved or unresolved.
168
169	The first argument will be looked up in the configuration database first
170	(if it is C<undef> then the current nodename will be used instead) to find
171	the relevant configuration profile (see L<aemp>). If none is found then
172	the default configuration is used. The configuration supplies additional
173	seed/master nodes and can override the actual noderef.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176
177	=over 4	175	=over 4
178		176
179	=item public nodes	177	=item step 1, gathering configuration from profiles
180		178
181	For public nodes, C<$noderef> (supplied either directly to	179	The function first looks up a profile in the aemp configuration (see the
182	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
183	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.
184		183
185	After resolving, the node will bind itself on all endpoints and try to	184	The profile data is then gathered as follows:
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189		185
190	=item slave nodes	186	First, all remaining key => value pairs (all of which are conviniently
		187	undocumented at the moment) will be interpreted as configuration
		188	data. Then they will be overwritten by any values specified in the global
		189	default configuration (see the F<aemp> utility), then the chain of
		190	profiles chosen by the profile name (and any C<parent> attributes).
191		191
192	When the C<$noderef> (either as given or overriden by the config file)	192	That means that the values specified in the profile have highest priority
193	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,
194	node. Slave nodes cannot be contacted from outside and will route most of	194	and can only be used to specify defaults.
195	their traffic to the master node that they attach to.
196		195
197	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
198	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
199	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.
200	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.
201		217
202	=back	218	=back
203		219
204	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.
205	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.
206	server.
207		222
208	Example: become a public node listening on the guessed noderef, or the one	223	configure
209	specified via C<aemp> for the current node. This should be the most common
210	form of invocation for "daemon"-type nodes.
211		224
212	initialise_node;	225	Example: become an anonymous node. This form is often used for commandline
		226	clients.
213		227
214	Example: become a slave node to any of the the seednodes specified via	228	configure nodeid => "anon/";
215	C<aemp>. This form is often used for commandline clients.
216		229
217	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).
218		233
219	Example: become a slave node to any of the specified master servers. This	234	# use the aemp commandline utility
220	form is also often used for commandline clients.	235	# aemp profile seed nodeid anon/ binds '*:4040'
221		236
222	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	237	# then use it
		238	configure profile => "seed";
223		239
224	Example: become a public node, and try to contact some well-known master	240	# or simply use aemp from the shell again:
225	servers to become part of the network.	241	# aemp run profile seed
226		242
227	initialise_node undef, "master1", "master2";	243	# or provide a nicer-to-remember nodeid
228		244	# aemp run profile seed nodeid "$(hostname)"
229	Example: become a public node listening on port C<4041>.
230
231	initialise_node 4041;
232
233	Example: become a public node, only visible on localhost port 4044.
234
235	initialise_node "localhost:4044";
236
237	=item $cv = resolve_node $noderef
238
239	Takes an unresolved node reference that may contain hostnames and
240	abbreviated IDs, resolves all of them and returns a resolved node
241	reference.
242
243	In addition to C<address:port> pairs allowed in resolved noderefs, the
244	following forms are supported:
245
246	=over 4
247
248	=item the empty string
249
250	An empty-string component gets resolved as if the default port (4040) was
251	specified.
252
253	=item naked port numbers (e.g. C<1234>)
254
255	These are resolved by prepending the local nodename and a colon, to be
256	further resolved.
257
258	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
259
260	These are resolved by using AnyEvent::DNS to resolve them, optionally
261	looking up SRV records for the C<aemp=4040> port, if no port was
262	specified.
263
264	=back
265		245
266	=item $SELF	246	=item $SELF
267		247
268	Contains the current port id while executing C<rcv> callbacks or C<psub>	248	Contains the current port id while executing C<rcv> callbacks or C<psub>
269	blocks.	249	blocks.
270		250
271	=item SELF, %SELF, @SELF...	251	=item *SELF, SELF, %SELF, @SELF...
272		252
273	Due to some quirks in how perl exports variables, it is impossible to	253	Due to some quirks in how perl exports variables, it is impossible to
274	just export C<$SELF>, all the symbols called C<SELF> are exported by this	254	just export C<$SELF>, all the symbols named C<SELF> are exported by this
275	module, but only C<$SELF> is currently used.	255	module, but only C<$SELF> is currently used.
276		256
277	=item snd $port, type => @data	257	=item snd $port, type => @data
278		258
279	=item snd $port, @msg	259	=item snd $port, @msg
280		260
281	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
282	a local or a remote port, and must be a port ID.	262	local or a remote port, and must be a port ID.
283		263
284	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
285	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
286	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.
287		268
288	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
289	function: modifying any argument is not allowed and can cause many	270	function: modifying any argument (or values referenced by them) is
290	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.
291		275
292	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
293	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
294	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
295	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
296	node, anything can be passed.	280	node, anything can be passed. Best rely only on the common denominator of
		281	these.
297		282
298	=item $local_port = port	283	=item $local_port = port
299		284
300	Create a new local port object and returns its port ID. Initially it has	285	Create a new local port object and returns its port ID. Initially it has
301	no callbacks set and will throw an error when it receives messages.	286	no callbacks set and will throw an error when it receives messages.
…		…
386		371
387	=cut	372	=cut
388		373
389	sub rcv($@) {	374	sub rcv($@) {
390	my $port = shift;	375	my $port = shift;
391	my ($noderef, $portid) = split /#/, $port, 2;	376	my ($nodeid, $portid) = split /#/, $port, 2;
392		377
393	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	378	$NODE{$nodeid} == $NODE{""}
394	or Carp::croak "$port: rcv can only be called on local ports, caught";	379	or Carp::croak "$port: rcv can only be called on local ports, caught";
395		380
396	while (@_) {	381	while (@_) {
397	if (ref $_[0]) {	382	if (ref $_[0]) {
398	if (my $self = $PORT_DATA{$portid}) {	383	if (my $self = $PORT_DATA{$portid}) {
…		…
477	$res	462	$res
478	}	463	}
479	}	464	}
480	}	465	}
481		466
482	=item $guard = mon $port, $cb->(@reason)	467	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
483		468
484	=item $guard = mon $port, $rcvport	469	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
485		470
486	=item $guard = mon $port	471	=item $guard = mon $port # kill $SELF when $port dies
487		472
488	=item $guard = mon $port, $rcvport, @msg	473	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
489		474
490	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
491	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
492	to stop monitoring again.	477	to stop monitoring again.
493		478
494	C<mon> effectively guarantees that, in the absence of hardware failures,	479	C<mon> effectively guarantees that, in the absence of hardware failures,
495	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
496	will arrive, or the monitoring action will be invoked after possible	481	arrive, or the monitoring action will be invoked after possible message
497	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
498	(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
499	port). After the monitoring action was invoked, further messages might get	484	port). After the monitoring action was invoked, further messages might get
500	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.
501		489
502	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
503	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
504	"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
505	C<eval> if unsure.	493	C<eval> if unsure.
…		…
535	mon $port, $self => "restart";	523	mon $port, $self => "restart";
536		524
537	=cut	525	=cut
538		526
539	sub mon {	527	sub mon {
540	my ($noderef, $port) = split /#/, shift, 2;	528	my ($nodeid, $port) = split /#/, shift, 2;
541		529
542	my $node = $NODE{$noderef} \|\| add_node $noderef;	530	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
543		531
544	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,';
545		533
546	unless (ref $cb) {	534	unless (ref $cb) {
547	if (@_) {	535	if (@_) {
…		…
567	is killed, the references will be freed.	555	is killed, the references will be freed.
568		556
569	Optionally returns a guard that will stop the monitoring.	557	Optionally returns a guard that will stop the monitoring.
570		558
571	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
572	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>):
573		561
574	$port->rcv (start => sub {	562	$port->rcv (start => sub {
575	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	563	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
576	undef $timer if 0.9 < rand;	564	undef $timer if 0.9 < rand;
577	});	565	});
578	});	566	});
579		567
580	=cut	568	=cut
…		…
589		577
590	=item kil $port[, @reason]	578	=item kil $port[, @reason]
591		579
592	Kill the specified port with the given C<@reason>.	580	Kill the specified port with the given C<@reason>.
593		581
594	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
595	ports will not be kileld, or even notified).	583	monitoring other ports will not necessarily die because a port dies
		584	"normally").
596		585
597	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
598	C<mon>, see below).	587	C<mon>, see above).
599		588
600	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
601	will be reported as reason C<< die => $@ >>.	590	will be reported as reason C<< die => $@ >>.
602		591
603	Transport/communication errors are reported as C<< transport_error =>	592	Transport/communication errors are reported as C<< transport_error =>
…		…
608	=item $port = spawn $node, $initfunc[, @initdata]	597	=item $port = spawn $node, $initfunc[, @initdata]
609		598
610	Creates a port on the node C<$node> (which can also be a port ID, in which	599	Creates a port on the node C<$node> (which can also be a port ID, in which
611	case it's the node where that port resides).	600	case it's the node where that port resides).
612		601
613	The port ID of the newly created port is return immediately, and it is	602	The port ID of the newly created port is returned immediately, and it is
614	permissible to immediately start sending messages or monitor the port.	603	possible to immediately start sending messages or to monitor the port.
615		604
616	After the port has been created, the init function is	605	After the port has been created, the init function is called on the remote
617	called. This function must be a fully-qualified function name	606	node, in the same context as a C<rcv> callback. This function must be a
618	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	607	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
619	program, use C<::name>.	608	specify a function in the main program, use C<::name>.
620		609
621	If the function doesn't exist, then the node tries to C<require>	610	If the function doesn't exist, then the node tries to C<require>
622	the package, then the package above the package and so on (e.g.	611	the package, then the package above the package and so on (e.g.
623	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	612	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
624	exists or it runs out of package names.	613	exists or it runs out of package names.
625		614
626	The init function is then called with the newly-created port as context	615	The init function is then called with the newly-created port as context
627	object (C<$SELF>) and the C<@initdata> values as arguments.	616	object (C<$SELF>) and the C<@initdata> values as arguments.
628		617
629	A common idiom is to pass your own port, monitor the spawned port, and	618	A common idiom is to pass a local port, immediately monitor the spawned
630	in the init function, monitor the original port. This two-way monitoring	619	port, and in the remote init function, immediately monitor the passed
631	ensures that both ports get cleaned up when there is a problem.	620	local port. This two-way monitoring ensures that both ports get cleaned up
		621	when there is a problem.
632		622
633	Example: spawn a chat server port on C<$othernode>.	623	Example: spawn a chat server port on C<$othernode>.
634		624
635	# this node, executed from within a port context:	625	# this node, executed from within a port context:
636	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
659	};	649	};
660	_self_die if $@;	650	_self_die if $@;
661	}	651	}
662		652
663	sub spawn(@) {	653	sub spawn(@) {
664	my ($noderef, undef) = split /#/, shift, 2;	654	my ($nodeid, undef) = split /#/, shift, 2;
665		655
666	my $id = "$RUNIQ." . $ID++;	656	my $id = "$RUNIQ." . $ID++;
667		657
668	$_[0] =~ /::/	658	$_[0] =~ /::/
669	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";
670		660
671	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	661	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
672		662
673	"$noderef#$id"	663	"$nodeid#$id"
674	}	664	}
675		665
676	=back	666	=item after $timeout, @msg
677		667
678	=head1 NODE MESSAGES	668	=item after $timeout, $callback
679		669
680	Nodes understand the following messages sent to them. Many of them take	670	Either sends the given message, or call the given callback, after the
681	arguments called C<@reply>, which will simply be used to compose a reply	671	specified number of seconds.
682	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
683	the remaining arguments are simply the message data.
684		672
685	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.
686		676
687	=over 4
688
689	=cut	677	=cut
690		678
691	=item lookup => $name, @reply	679	sub after($@) {
		680	my ($timeout, @action) = @_;
692		681
693	Replies with the port ID of the specified well-known port, or C<undef>.	682	my $t; $t = AE::timer $timeout, 0, sub {
694		683	undef $t;
695	=item devnull => ...	684	ref $action[0]
696		685	? $action[0]()
697	Generic data sink/CPU heat conversion.	686	: snd @action;
698		687	};
699	=item relay => $port, @msg	688	}
700
701	Simply forwards the message to the given port.
702
703	=item eval => $string[ @reply]
704
705	Evaluates the given string. If C<@reply> is given, then a message of the
706	form C<@reply, $@, @evalres> is sent.
707
708	Example: crash another node.
709
710	snd $othernode, eval => "exit";
711
712	=item time => @reply
713
714	Replies the the current node time to C<@reply>.
715
716	Example: tell the current node to send the current time to C<$myport> in a
717	C<timereply> message.
718
719	snd $NODE, time => $myport, timereply => 1, 2;
720	# => snd $myport, timereply => 1, 2, <time>
721		689
722	=back	690	=back
723		691
724	=head1 AnyEvent::MP vs. Distributed Erlang	692	=head1 AnyEvent::MP vs. Distributed Erlang
725		693
…		…
735		703
736	Despite the similarities, there are also some important differences:	704	Despite the similarities, there are also some important differences:
737		705
738	=over 4	706	=over 4
739		707
740	=item * Node references contain the recipe on how to contact them.	708	=item * Node IDs are arbitrary strings in AEMP.
741		709
742	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
743	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
744	convenience functionality.	712	configuraiton or DNS), but will otherwise discover other odes itself.
745
746	This means that AEMP requires a less tightly controlled environment at the
747	cost of longer node references and a slightly higher management overhead.
748		713
749	=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
750	uses "local ports are like remote ports".	715	uses "local ports are like remote ports".
751		716
752	The failure modes for local ports are quite different (runtime errors	717	The failure modes for local ports are quite different (runtime errors
…		…
781		746
782	Erlang makes few guarantees on messages delivery - messages can get lost	747	Erlang makes few guarantees on messages delivery - messages can get lost
783	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,
784	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).
785		750
786	AEMP guarantees correct ordering, and the guarantee that there are no	751	AEMP guarantees correct ordering, and the guarantee that after one message
787	holes in the message sequence.	752	is lost, all following ones sent to the same port are lost as well, until
788		753	monitoring raises an error, so there are no silent "holes" in the message
789	=item * In Erlang, processes can be declared dead and later be found to be	754	sequence.
790	alive.
791
792	In Erlang it can happen that a monitored process is declared dead and
793	linked processes get killed, but later it turns out that the process is
794	still alive - and can receive messages.
795
796	In AEMP, when port monitoring detects a port as dead, then that port will
797	eventually be killed - it cannot happen that a node detects a port as dead
798	and then later sends messages to it, finding it is still alive.
799		755
800	=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.
801		757
802	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
803	known to other nodes for a completely different process, causing messages	759	known to other nodes for a completely different process, causing messages
…		…
807	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.
808		764
809	=item * Erlang uses unprotected connections, AEMP uses secure	765	=item * Erlang uses unprotected connections, AEMP uses secure
810	authentication and can use TLS.	766	authentication and can use TLS.
811		767
812	AEMP can use a proven protocol - SSL/TLS - to protect connections and	768	AEMP can use a proven protocol - TLS - to protect connections and
813	securely authenticate nodes.	769	securely authenticate nodes.
814		770
815	=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
816	communications.	772	communications.
817		773
818	The AEMP protocol, unlike the Erlang protocol, supports both	774	The AEMP protocol, unlike the Erlang protocol, supports both programming
819	language-independent text-only protocols (good for debugging) and binary,	775	language independent text-only protocols (good for debugging) and binary,
820	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.
821		778
822	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
823	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
824	protocol simple.	781	protocol simple.
825		782
826	=item * AEMP has more flexible monitoring options than Erlang.	783	=item * AEMP has more flexible monitoring options than Erlang.
827		784
828	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
…		…
831	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
832	on a per-process basis.	789	on a per-process basis.
833		790
834	=item * Erlang tries to hide remote/local connections, AEMP does not.	791	=item * Erlang tries to hide remote/local connections, AEMP does not.
835		792
836	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
837	as linking is (except linking is unreliable in Erlang).	794	same way as linking is (except linking is unreliable in Erlang).
838		795
839	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
840	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
841	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
842	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
843	more reliable.	800	reliable (no need for C<spawn_link>).
844		801
845	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
846	(hard to do in Erlang).	803	(hard to do in Erlang).
847		804
848	=back	805	=back
849		806
850	=head1 RATIONALE	807	=head1 RATIONALE
851		808
852	=over 4	809	=over 4
853		810
854	=item Why strings for ports and noderefs, why not objects?	811	=item Why strings for port and node IDs, why not objects?
855		812
856	We considered "objects", but found that the actual number of methods	813	We considered "objects", but found that the actual number of methods
857	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
858	the network frequently, the serialising/deserialising would add lots of	815	the network frequently, the serialising/deserialising would add lots of
859	overhead, as well as having to keep a proxy object.	816	overhead, as well as having to keep a proxy object everywhere.
860		817
861	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
862	procedures to be "valid".	819	procedures to be "valid".
863		820
864	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
865	can't become much cheaper.	822	global hash - it can't become much cheaper.
866		823
867	=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?
868		825
869	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
870	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
871	default.	828	default (although all nodes will accept it).
872		829
873	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
874	faster for small messages and b) most importantly, after years of	831	faster for small messages and b) most importantly, after years of
875	experience we found that object serialisation is causing more problems	832	experience we found that object serialisation is causing more problems
876	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
877	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
878	always have to re-think your design.	835	always have to re-think your design.
879		836
880	Keeping your messages simple, concentrating on data structures rather than	837	Keeping your messages simple, concentrating on data structures rather than
881	objects, will keep your messages clean, tidy and efficient.	838	objects, will keep your messages clean, tidy and efficient.
882		839
883	=back	840	=back
884		841
885	=head1 SEE ALSO	842	=head1 SEE ALSO
886		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
887	L<AnyEvent>.	851	L<AnyEvent>.
888		852
889	=head1 AUTHOR	853	=head1 AUTHOR
890		854
891	Marc Lehmann <schmorp@schmorp.de>	855	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.55 by root, Fri Aug 14 23:17:17 2009 UTC vs.
Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC