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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.57 by root, Sat Aug 15 04:34:34 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46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - uptodate, but incomplete.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.
201		199
202	Note that slave nodes cannot change their name, and consequently, their	200	=item step 2, bind listener sockets
203	master, so if the master goes down, the slave node will not function well	201
204	anymore until it can re-establish conenciton to its master. This makes	202	The next step is to look up the binds in the profile, followed by binding
205	slave nodes unsuitable for long-term nodes or fault-tolerant networks.	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.
206		217
207	=back	218	=back
208		219
209	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.
210	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.
211	server.
212		222
213	All the seednodes will also be specially marked to automatically retry	223	configure
214	connecting to them infinitely.
215		224
216	Example: become a public node listening on the guessed noderef, or the one	225	Example: become an anonymous node. This form is often used for commandline
217	specified via C<aemp> for the current node. This should be the most common	226	clients.
218	form of invocation for "daemon"-type nodes.
219		227
220	initialise_node;	228	configure nodeid => "anon/";
221		229
222	Example: become a slave node to any of the the seednodes specified via	230	Example: configure a node using a profile called seed, which si suitable
223	C<aemp>. This form is often used for commandline clients.	231	for a seed node as it binds on all local addresses on a fixed port (4040,
		232	customary for aemp).
224		233
225	initialise_node "slave/";	234	# use the aemp commandline utility
		235	# aemp profile seed nodeid anon/ binds '*:4040'
226		236
227	Example: become a slave node to any of the specified master servers. This	237	# then use it
228	form is also often used for commandline clients.	238	configure profile => "seed";
229		239
230	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	240	# or simply use aemp from the shell again:
		241	# aemp run profile seed
231		242
232	Example: become a public node, and try to contact some well-known master	243	# or provide a nicer-to-remember nodeid
233	servers to become part of the network.	244	# aemp run profile seed nodeid "$(hostname)"
234
235	initialise_node undef, "master1", "master2";
236
237	Example: become a public node listening on port C<4041>.
238
239	initialise_node 4041;
240
241	Example: become a public node, only visible on localhost port 4044.
242
243	initialise_node "localhost:4044";
244
245	=item $cv = resolve_node $noderef
246
247	Takes an unresolved node reference that may contain hostnames and
248	abbreviated IDs, resolves all of them and returns a resolved node
249	reference.
250
251	In addition to C<address:port> pairs allowed in resolved noderefs, the
252	following forms are supported:
253
254	=over 4
255
256	=item the empty string
257
258	An empty-string component gets resolved as if the default port (4040) was
259	specified.
260
261	=item naked port numbers (e.g. C<1234>)
262
263	These are resolved by prepending the local nodename and a colon, to be
264	further resolved.
265
266	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
267
268	These are resolved by using AnyEvent::DNS to resolve them, optionally
269	looking up SRV records for the C<aemp=4040> port, if no port was
270	specified.
271
272	=back
273		245
274	=item $SELF	246	=item $SELF
275		247
276	Contains the current port id while executing C<rcv> callbacks or C<psub>	248	Contains the current port id while executing C<rcv> callbacks or C<psub>
277	blocks.	249	blocks.
278		250
279	=item SELF, %SELF, @SELF...	251	=item *SELF, SELF, %SELF, @SELF...
280		252
281	Due to some quirks in how perl exports variables, it is impossible to	253	Due to some quirks in how perl exports variables, it is impossible to
282	just export C<$SELF>, all the symbols called C<SELF> are exported by this	254	just export C<$SELF>, all the symbols named C<SELF> are exported by this
283	module, but only C<$SELF> is currently used.	255	module, but only C<$SELF> is currently used.
284		256
285	=item snd $port, type => @data	257	=item snd $port, type => @data
286		258
287	=item snd $port, @msg	259	=item snd $port, @msg
288		260
289	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
290	a local or a remote port, and must be a port ID.	262	local or a remote port, and must be a port ID.
291		263
292	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
293	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
294	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.
295		268
296	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
297	function: modifying any argument is not allowed and can cause many	270	function: modifying any argument (or values referenced by them) is
298	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.
299		275
300	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
301	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
302	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
303	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
304	node, anything can be passed.	280	node, anything can be passed. Best rely only on the common denominator of
		281	these.
305		282
306	=item $local_port = port	283	=item $local_port = port
307		284
308	Create a new local port object and returns its port ID. Initially it has	285	Create a new local port object and returns its port ID. Initially it has
309	no callbacks set and will throw an error when it receives messages.	286	no callbacks set and will throw an error when it receives messages.
…		…
394		371
395	=cut	372	=cut
396		373
397	sub rcv($@) {	374	sub rcv($@) {
398	my $port = shift;	375	my $port = shift;
399	my ($noderef, $portid) = split /#/, $port, 2;	376	my ($nodeid, $portid) = split /#/, $port, 2;
400		377
401	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	378	$NODE{$nodeid} == $NODE{""}
402	or Carp::croak "$port: rcv can only be called on local ports, caught";	379	or Carp::croak "$port: rcv can only be called on local ports, caught";
403		380
404	while (@_) {	381	while (@_) {
405	if (ref $_[0]) {	382	if (ref $_[0]) {
406	if (my $self = $PORT_DATA{$portid}) {	383	if (my $self = $PORT_DATA{$portid}) {
…		…
485	$res	462	$res
486	}	463	}
487	}	464	}
488	}	465	}
489		466
490	=item $guard = mon $port, $cb->(@reason)	467	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
491		468
492	=item $guard = mon $port, $rcvport	469	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
493		470
494	=item $guard = mon $port	471	=item $guard = mon $port # kill $SELF when $port dies
495		472
496	=item $guard = mon $port, $rcvport, @msg	473	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
497		474
498	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
499	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
500	to stop monitoring again.	477	to stop monitoring again.
501		478
502	C<mon> effectively guarantees that, in the absence of hardware failures,	479	C<mon> effectively guarantees that, in the absence of hardware failures,
503	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
504	will arrive, or the monitoring action will be invoked after possible	481	arrive, or the monitoring action will be invoked after possible message
505	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
506	(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
507	port). After the monitoring action was invoked, further messages might get	484	port). After the monitoring action was invoked, further messages might get
508	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.
509		489
510	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
511	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
512	"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
513	C<eval> if unsure.	493	C<eval> if unsure.
…		…
543	mon $port, $self => "restart";	523	mon $port, $self => "restart";
544		524
545	=cut	525	=cut
546		526
547	sub mon {	527	sub mon {
548	my ($noderef, $port) = split /#/, shift, 2;	528	my ($nodeid, $port) = split /#/, shift, 2;
549		529
550	my $node = $NODE{$noderef} \|\| add_node $noderef;	530	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
551		531
552	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,';
553		533
554	unless (ref $cb) {	534	unless (ref $cb) {
555	if (@_) {	535	if (@_) {
…		…
575	is killed, the references will be freed.	555	is killed, the references will be freed.
576		556
577	Optionally returns a guard that will stop the monitoring.	557	Optionally returns a guard that will stop the monitoring.
578		558
579	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
580	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>):
581		561
582	$port->rcv (start => sub {	562	$port->rcv (start => sub {
583	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	563	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
584	undef $timer if 0.9 < rand;	564	undef $timer if 0.9 < rand;
585	});	565	});
586	});	566	});
587		567
588	=cut	568	=cut
…		…
597		577
598	=item kil $port[, @reason]	578	=item kil $port[, @reason]
599		579
600	Kill the specified port with the given C<@reason>.	580	Kill the specified port with the given C<@reason>.
601		581
602	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
603	ports will not be kileld, or even notified).	583	monitoring other ports will not necessarily die because a port dies
		584	"normally").
604		585
605	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
606	C<mon>, see below).	587	C<mon>, see above).
607		588
608	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
609	will be reported as reason C<< die => $@ >>.	590	will be reported as reason C<< die => $@ >>.
610		591
611	Transport/communication errors are reported as C<< transport_error =>	592	Transport/communication errors are reported as C<< transport_error =>
…		…
616	=item $port = spawn $node, $initfunc[, @initdata]	597	=item $port = spawn $node, $initfunc[, @initdata]
617		598
618	Creates a port on the node C<$node> (which can also be a port ID, in which	599	Creates a port on the node C<$node> (which can also be a port ID, in which
619	case it's the node where that port resides).	600	case it's the node where that port resides).
620		601
621	The port ID of the newly created port is return immediately, and it is	602	The port ID of the newly created port is returned immediately, and it is
622	permissible to immediately start sending messages or monitor the port.	603	possible to immediately start sending messages or to monitor the port.
623		604
624	After the port has been created, the init function is	605	After the port has been created, the init function is called on the remote
625	called. This function must be a fully-qualified function name	606	node, in the same context as a C<rcv> callback. This function must be a
626	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	607	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
627	program, use C<::name>.	608	specify a function in the main program, use C<::name>.
628		609
629	If the function doesn't exist, then the node tries to C<require>	610	If the function doesn't exist, then the node tries to C<require>
630	the package, then the package above the package and so on (e.g.	611	the package, then the package above the package and so on (e.g.
631	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	612	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
632	exists or it runs out of package names.	613	exists or it runs out of package names.
633		614
634	The init function is then called with the newly-created port as context	615	The init function is then called with the newly-created port as context
635	object (C<$SELF>) and the C<@initdata> values as arguments.	616	object (C<$SELF>) and the C<@initdata> values as arguments.
636		617
637	A common idiom is to pass your own port, monitor the spawned port, and	618	A common idiom is to pass a local port, immediately monitor the spawned
638	in the init function, monitor the original port. This two-way monitoring	619	port, and in the remote init function, immediately monitor the passed
639	ensures that both ports get cleaned up when there is a problem.	620	local port. This two-way monitoring ensures that both ports get cleaned up
		621	when there is a problem.
640		622
641	Example: spawn a chat server port on C<$othernode>.	623	Example: spawn a chat server port on C<$othernode>.
642		624
643	# this node, executed from within a port context:	625	# this node, executed from within a port context:
644	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
667	};	649	};
668	_self_die if $@;	650	_self_die if $@;
669	}	651	}
670		652
671	sub spawn(@) {	653	sub spawn(@) {
672	my ($noderef, undef) = split /#/, shift, 2;	654	my ($nodeid, undef) = split /#/, shift, 2;
673		655
674	my $id = "$RUNIQ." . $ID++;	656	my $id = "$RUNIQ." . $ID++;
675		657
676	$_[0] =~ /::/	658	$_[0] =~ /::/
677	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";
678		660
679	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	661	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
680		662
681	"$noderef#$id"	663	"$nodeid#$id"
		664	}
		665
		666	=item after $timeout, @msg
		667
		668	=item after $timeout, $callback
		669
		670	Either sends the given message, or call the given callback, after the
		671	specified number of seconds.
		672
		673	This is simply a utility function that comes in handy at times - the
		674	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		675	so it may go away in the future.
		676
		677	=cut
		678
		679	sub after($@) {
		680	my ($timeout, @action) = @_;
		681
		682	my $t; $t = AE::timer $timeout, 0, sub {
		683	undef $t;
		684	ref $action[0]
		685	? $action[0]()
		686	: snd @action;
		687	};
682	}	688	}
683		689
684	=back	690	=back
685		691
686	=head1 AnyEvent::MP vs. Distributed Erlang	692	=head1 AnyEvent::MP vs. Distributed Erlang
…		…
697		703
698	Despite the similarities, there are also some important differences:	704	Despite the similarities, there are also some important differences:
699		705
700	=over 4	706	=over 4
701		707
702	=item * Node references contain the recipe on how to contact them.	708	=item * Node IDs are arbitrary strings in AEMP.
703		709
704	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
705	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
706	convenience functionality.	712	configuraiton or DNS), but will otherwise discover other odes itself.
707
708	This means that AEMP requires a less tightly controlled environment at the
709	cost of longer node references and a slightly higher management overhead.
710		713
711	=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
712	uses "local ports are like remote ports".	715	uses "local ports are like remote ports".
713		716
714	The failure modes for local ports are quite different (runtime errors	717	The failure modes for local ports are quite different (runtime errors
…		…
743		746
744	Erlang makes few guarantees on messages delivery - messages can get lost	747	Erlang makes few guarantees on messages delivery - messages can get lost
745	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,
746	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).
747		750
748	AEMP guarantees correct ordering, and the guarantee that there are no	751	AEMP guarantees correct ordering, and the guarantee that after one message
749	holes in the message sequence.	752	is lost, all following ones sent to the same port are lost as well, until
750		753	monitoring raises an error, so there are no silent "holes" in the message
751	=item * In Erlang, processes can be declared dead and later be found to be	754	sequence.
752	alive.
753
754	In Erlang it can happen that a monitored process is declared dead and
755	linked processes get killed, but later it turns out that the process is
756	still alive - and can receive messages.
757
758	In AEMP, when port monitoring detects a port as dead, then that port will
759	eventually be killed - it cannot happen that a node detects a port as dead
760	and then later sends messages to it, finding it is still alive.
761		755
762	=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.
763		757
764	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
765	known to other nodes for a completely different process, causing messages	759	known to other nodes for a completely different process, causing messages
…		…
769	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.
770		764
771	=item * Erlang uses unprotected connections, AEMP uses secure	765	=item * Erlang uses unprotected connections, AEMP uses secure
772	authentication and can use TLS.	766	authentication and can use TLS.
773		767
774	AEMP can use a proven protocol - SSL/TLS - to protect connections and	768	AEMP can use a proven protocol - TLS - to protect connections and
775	securely authenticate nodes.	769	securely authenticate nodes.
776		770
777	=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
778	communications.	772	communications.
779		773
780	The AEMP protocol, unlike the Erlang protocol, supports both	774	The AEMP protocol, unlike the Erlang protocol, supports both programming
781	language-independent text-only protocols (good for debugging) and binary,	775	language independent text-only protocols (good for debugging) and binary,
782	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.
783		778
784	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
785	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
786	protocol simple.	781	protocol simple.
787		782
788	=item * AEMP has more flexible monitoring options than Erlang.	783	=item * AEMP has more flexible monitoring options than Erlang.
789		784
790	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
…		…
793	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
794	on a per-process basis.	789	on a per-process basis.
795		790
796	=item * Erlang tries to hide remote/local connections, AEMP does not.	791	=item * Erlang tries to hide remote/local connections, AEMP does not.
797		792
798	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
799	as linking is (except linking is unreliable in Erlang).	794	same way as linking is (except linking is unreliable in Erlang).
800		795
801	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
802	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
803	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
804	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
805	more reliable.	800	reliable (no need for C<spawn_link>).
806		801
807	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
808	(hard to do in Erlang).	803	(hard to do in Erlang).
809		804
810	=back	805	=back
811		806
812	=head1 RATIONALE	807	=head1 RATIONALE
813		808
814	=over 4	809	=over 4
815		810
816	=item Why strings for ports and noderefs, why not objects?	811	=item Why strings for port and node IDs, why not objects?
817		812
818	We considered "objects", but found that the actual number of methods	813	We considered "objects", but found that the actual number of methods
819	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
820	the network frequently, the serialising/deserialising would add lots of	815	the network frequently, the serialising/deserialising would add lots of
821	overhead, as well as having to keep a proxy object.	816	overhead, as well as having to keep a proxy object everywhere.
822		817
823	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
824	procedures to be "valid".	819	procedures to be "valid".
825		820
826	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
827	can't become much cheaper.	822	global hash - it can't become much cheaper.
828		823
829	=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?
830		825
831	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
832	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
833	default.	828	default (although all nodes will accept it).
834		829
835	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
836	faster for small messages and b) most importantly, after years of	831	faster for small messages and b) most importantly, after years of
837	experience we found that object serialisation is causing more problems	832	experience we found that object serialisation is causing more problems
838	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
839	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
840	always have to re-think your design.	835	always have to re-think your design.
841		836
842	Keeping your messages simple, concentrating on data structures rather than	837	Keeping your messages simple, concentrating on data structures rather than
843	objects, will keep your messages clean, tidy and efficient.	838	objects, will keep your messages clean, tidy and efficient.
844		839
845	=back	840	=back
846		841
847	=head1 SEE ALSO	842	=head1 SEE ALSO
848		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
849	L<AnyEvent>.	851	L<AnyEvent>.
850		852
851	=head1 AUTHOR	853	=head1 AUTHOR
852		854
853	Marc Lehmann <schmorp@schmorp.de>	855	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.57 by root, Sat Aug 15 04:34:34 2009 UTC vs.
Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC