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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.62 by root, Thu Aug 27 07:12:48 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46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - uptodate, but incomplete.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 (can only talk to	85	Nodes are either public (have one or more listening ports) or private
91	public nodes, but do not need an open port) or public nodes (connectable	86	(no listening ports). Private nodes cannot talk to other private nodes
92	from any other node).	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
…		…
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 after	141	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	142	configure
134	snd rcv mon mon_guard 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;
…		…
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.	184	The profile data is then gathered as follows:
187		185
188	=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).
189		191
190	When the C<$noderef> (either as given or overriden by the config file)	192	That means that the values specified in the profile have highest priority
191	is the special string C<slave/>, then the node will become a slave	193	and the values specified directly via C<configure> have lowest priority,
192	node. Slave nodes cannot be contacted from outside, and cannot talk to	194	and can only be used to specify defaults.
193	each other (at least in this version of AnyEvent::MP).
194		195
195	Slave nodes work by creating connections to all public nodes, using the	196	If the profile specifies a node ID, then this will become the node ID of
196	L<AnyEvent::MP::Global> service.	197	this process. If not, then the profile name will be used as node ID. The
		198	special node ID of C<anon/> will be replaced by a random node ID.
		199
		200	=item step 2, bind listener sockets
		201
		202	The next step is to look up the binds in the profile, followed by binding
		203	aemp protocol listeners on all binds specified (it is possible and valid
		204	to have no binds, meaning that the node cannot be contacted form the
		205	outside. This means the node cannot talk to other nodes that also have no
		206	binds, but it can still talk to all "normal" nodes).
		207
		208	If the profile does not specify a binds list, then a default of C<*> is
		209	used, meaning the node will bind on a dynamically-assigned port on every
		210	local IP address it finds.
		211
		212	=item step 3, connect to seed nodes
		213
		214	As the last step, the seeds list from the profile is passed to the
		215	L<AnyEvent::MP::Global> module, which will then use it to keep
		216	connectivity with at least one node at any point in time.
197		217
198	=back	218	=back
199		219
200	After initialising itself, the node will connect to all additional	220	Example: become a distributed node using the locla node name as profile.
201	C<$seednodes> that are specified diretcly or via a profile. Seednodes are	221	This should be the most common form of invocation for "daemon"-type nodes.
202	optional and can be used to quickly bootstrap the node into an existing
203	network.
204		222
205	All the seednodes will also be specially marked to automatically retry	223	configure
206	connecting to them indefinitely, so make sure that seednodes are really
207	reliable and up (this might also change in the future).
208		224
209	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
210	specified via C<aemp> for the current node. This should be the most common	226	clients.
211	form of invocation for "daemon"-type nodes.
212		227
213	initialise_node;	228	configure nodeid => "anon/";
214		229
215	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
216	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).
217		233
218	initialise_node "slave/";	234	# use the aemp commandline utility
		235	# aemp profile seed nodeid anon/ binds '*:4040'
219		236
220	Example: become a public node, and try to contact some well-known master	237	# then use it
221	servers to become part of the network.	238	configure profile => "seed";
222		239
223	initialise_node undef, "master1", "master2";	240	# or simply use aemp from the shell again:
		241	# aemp run profile seed
224		242
225	Example: become a public node listening on port C<4041>.	243	# or provide a nicer-to-remember nodeid
226		244	# aemp run profile seed nodeid "$(hostname)"
227	initialise_node 4041;
228
229	Example: become a public node, only visible on localhost port 4044.
230
231	initialise_node "localhost:4044";
232
233	=item $cv = resolve_node $noderef
234
235	Takes an unresolved node reference that may contain hostnames and
236	abbreviated IDs, resolves all of them and returns a resolved node
237	reference.
238
239	In addition to C<address:port> pairs allowed in resolved noderefs, the
240	following forms are supported:
241
242	=over 4
243
244	=item the empty string
245
246	An empty-string component gets resolved as if the default port (4040) was
247	specified.
248
249	=item naked port numbers (e.g. C<1234>)
250
251	These are resolved by prepending the local nodename and a colon, to be
252	further resolved.
253
254	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
255
256	These are resolved by using AnyEvent::DNS to resolve them, optionally
257	looking up SRV records for the C<aemp=4040> port, if no port was
258	specified.
259
260	=back
261		245
262	=item $SELF	246	=item $SELF
263		247
264	Contains the current port id while executing C<rcv> callbacks or C<psub>	248	Contains the current port id while executing C<rcv> callbacks or C<psub>
265	blocks.	249	blocks.
266		250
267	=item SELF, %SELF, @SELF...	251	=item *SELF, SELF, %SELF, @SELF...
268		252
269	Due to some quirks in how perl exports variables, it is impossible to	253	Due to some quirks in how perl exports variables, it is impossible to
270	just export C<$SELF>, all the symbols called C<SELF> are exported by this	254	just export C<$SELF>, all the symbols named C<SELF> are exported by this
271	module, but only C<$SELF> is currently used.	255	module, but only C<$SELF> is currently used.
272		256
273	=item snd $port, type => @data	257	=item snd $port, type => @data
274		258
275	=item snd $port, @msg	259	=item snd $port, @msg
276		260
277	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
278	a local or a remote port, and must be a port ID.	262	local or a remote port, and must be a port ID.
279		263
280	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
281	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
282	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.
283		268
284	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
285	function: modifying any argument is not allowed and can cause many	270	function: modifying any argument (or values referenced by them) is
286	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.
287		275
288	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
289	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
290	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
291	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
292	node, anything can be passed.	280	node, anything can be passed. Best rely only on the common denominator of
		281	these.
293		282
294	=item $local_port = port	283	=item $local_port = port
295		284
296	Create a new local port object and returns its port ID. Initially it has	285	Create a new local port object and returns its port ID. Initially it has
297	no callbacks set and will throw an error when it receives messages.	286	no callbacks set and will throw an error when it receives messages.
…		…
382		371
383	=cut	372	=cut
384		373
385	sub rcv($@) {	374	sub rcv($@) {
386	my $port = shift;	375	my $port = shift;
387	my ($noderef, $portid) = split /#/, $port, 2;	376	my ($nodeid, $portid) = split /#/, $port, 2;
388		377
389	$NODE{$noderef} == $NODE{""}	378	$NODE{$nodeid} == $NODE{""}
390	or Carp::croak "$port: rcv can only be called on local ports, caught";	379	or Carp::croak "$port: rcv can only be called on local ports, caught";
391		380
392	while (@_) {	381	while (@_) {
393	if (ref $_[0]) {	382	if (ref $_[0]) {
394	if (my $self = $PORT_DATA{$portid}) {	383	if (my $self = $PORT_DATA{$portid}) {
…		…
473	$res	462	$res
474	}	463	}
475	}	464	}
476	}	465	}
477		466
478	=item $guard = mon $port, $cb->(@reason)	467	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
479		468
480	=item $guard = mon $port, $rcvport	469	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
481		470
482	=item $guard = mon $port	471	=item $guard = mon $port # kill $SELF when $port dies
483		472
484	=item $guard = mon $port, $rcvport, @msg	473	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
485		474
486	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
487	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
488	to stop monitoring again.	477	to stop monitoring again.
489		478
490	C<mon> effectively guarantees that, in the absence of hardware failures,	479	C<mon> effectively guarantees that, in the absence of hardware failures,
491	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
492	will arrive, or the monitoring action will be invoked after possible	481	arrive, or the monitoring action will be invoked after possible message
493	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
494	(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
495	port). After the monitoring action was invoked, further messages might get	484	port). After the monitoring action was invoked, further messages might get
496	delivered again.	485	delivered again.
497		486
498	Note that monitoring-actions are one-shot: once released, they are removed	487	Note that monitoring-actions are one-shot: once messages are lost (and a
499	and will not trigger again.	488	monitoring alert was raised), they are removed and will not trigger again.
500		489
501	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
502	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
503	"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
504	C<eval> if unsure.	493	C<eval> if unsure.
…		…
534	mon $port, $self => "restart";	523	mon $port, $self => "restart";
535		524
536	=cut	525	=cut
537		526
538	sub mon {	527	sub mon {
539	my ($noderef, $port) = split /#/, shift, 2;	528	my ($nodeid, $port) = split /#/, shift, 2;
540		529
541	my $node = $NODE{$noderef} \|\| add_node $noderef;	530	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
542		531
543	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,';
544		533
545	unless (ref $cb) {	534	unless (ref $cb) {
546	if (@_) {	535	if (@_) {
…		…
566	is killed, the references will be freed.	555	is killed, the references will be freed.
567		556
568	Optionally returns a guard that will stop the monitoring.	557	Optionally returns a guard that will stop the monitoring.
569		558
570	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
571	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>):
572		561
573	$port->rcv (start => sub {	562	$port->rcv (start => sub {
574	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	563	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
575	undef $timer if 0.9 < rand;	564	undef $timer if 0.9 < rand;
576	});	565	});
577	});	566	});
578		567
579	=cut	568	=cut
…		…
588		577
589	=item kil $port[, @reason]	578	=item kil $port[, @reason]
590		579
591	Kill the specified port with the given C<@reason>.	580	Kill the specified port with the given C<@reason>.
592		581
593	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
594	ports will not be kileld, or even notified).	583	monitoring other ports will not necessarily die because a port dies
		584	"normally").
595		585
596	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
597	C<mon>, see below).	587	C<mon>, see above).
598		588
599	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
600	will be reported as reason C<< die => $@ >>.	590	will be reported as reason C<< die => $@ >>.
601		591
602	Transport/communication errors are reported as C<< transport_error =>	592	Transport/communication errors are reported as C<< transport_error =>
…		…
607	=item $port = spawn $node, $initfunc[, @initdata]	597	=item $port = spawn $node, $initfunc[, @initdata]
608		598
609	Creates a port on the node C<$node> (which can also be a port ID, in which	599	Creates a port on the node C<$node> (which can also be a port ID, in which
610	case it's the node where that port resides).	600	case it's the node where that port resides).
611		601
612	The port ID of the newly created port is return immediately, and it is	602	The port ID of the newly created port is returned immediately, and it is
613	permissible to immediately start sending messages or monitor the port.	603	possible to immediately start sending messages or to monitor the port.
614		604
615	After the port has been created, the init function is	605	After the port has been created, the init function is called on the remote
616	called. This function must be a fully-qualified function name	606	node, in the same context as a C<rcv> callback. This function must be a
617	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	607	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
618	program, use C<::name>.	608	specify a function in the main program, use C<::name>.
619		609
620	If the function doesn't exist, then the node tries to C<require>	610	If the function doesn't exist, then the node tries to C<require>
621	the package, then the package above the package and so on (e.g.	611	the package, then the package above the package and so on (e.g.
622	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	612	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
623	exists or it runs out of package names.	613	exists or it runs out of package names.
624		614
625	The init function is then called with the newly-created port as context	615	The init function is then called with the newly-created port as context
626	object (C<$SELF>) and the C<@initdata> values as arguments.	616	object (C<$SELF>) and the C<@initdata> values as arguments.
627		617
628	A common idiom is to pass your own port, monitor the spawned port, and	618	A common idiom is to pass a local port, immediately monitor the spawned
629	in the init function, monitor the original port. This two-way monitoring	619	port, and in the remote init function, immediately monitor the passed
630	ensures that both ports get cleaned up when there is a problem.	620	local port. This two-way monitoring ensures that both ports get cleaned up
		621	when there is a problem.
631		622
632	Example: spawn a chat server port on C<$othernode>.	623	Example: spawn a chat server port on C<$othernode>.
633		624
634	# this node, executed from within a port context:	625	# this node, executed from within a port context:
635	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
658	};	649	};
659	_self_die if $@;	650	_self_die if $@;
660	}	651	}
661		652
662	sub spawn(@) {	653	sub spawn(@) {
663	my ($noderef, undef) = split /#/, shift, 2;	654	my ($nodeid, undef) = split /#/, shift, 2;
664		655
665	my $id = "$RUNIQ." . $ID++;	656	my $id = "$RUNIQ." . $ID++;
666		657
667	$_[0] =~ /::/	658	$_[0] =~ /::/
668	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";
669		660
670	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	661	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
671		662
672	"$noderef#$id"	663	"$nodeid#$id"
673	}	664	}
674		665
675	=item after $timeout, @msg	666	=item after $timeout, @msg
676		667
677	=item after $timeout, $callback	668	=item after $timeout, $callback
678		669
679	Either sends the given message, or call the given callback, after the	670	Either sends the given message, or call the given callback, after the
680	specified number of seconds.	671	specified number of seconds.
681		672
682	This is simply a utility function that come sin handy at times.	673	This is simply a utility function that comes in handy at times - the
		674	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		675	so it may go away in the future.
683		676
684	=cut	677	=cut
685		678
686	sub after($@) {	679	sub after($@) {
687	my ($timeout, @action) = @_;	680	my ($timeout, @action) = @_;
…		…
710		703
711	Despite the similarities, there are also some important differences:	704	Despite the similarities, there are also some important differences:
712		705
713	=over 4	706	=over 4
714		707
715	=item * Node references contain the recipe on how to contact them.	708	=item * Node IDs are arbitrary strings in AEMP.
716		709
717	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
718	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
719	convenience functionality.	712	configuraiton or DNS), but will otherwise discover other odes itself.
720
721	This means that AEMP requires a less tightly controlled environment at the
722	cost of longer node references and a slightly higher management overhead.
723		713
724	=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
725	uses "local ports are like remote ports".	715	uses "local ports are like remote ports".
726		716
727	The failure modes for local ports are quite different (runtime errors	717	The failure modes for local ports are quite different (runtime errors
…		…
756		746
757	Erlang makes few guarantees on messages delivery - messages can get lost	747	Erlang makes few guarantees on messages delivery - messages can get lost
758	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,
759	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).
760		750
761	AEMP guarantees correct ordering, and the guarantee that there are no	751	AEMP guarantees correct ordering, and the guarantee that after one message
762	holes in the message sequence.	752	is lost, all following ones sent to the same port are lost as well, until
763		753	monitoring raises an error, so there are no silent "holes" in the message
764	=item * In Erlang, processes can be declared dead and later be found to be	754	sequence.
765	alive.
766
767	In Erlang it can happen that a monitored process is declared dead and
768	linked processes get killed, but later it turns out that the process is
769	still alive - and can receive messages.
770
771	In AEMP, when port monitoring detects a port as dead, then that port will
772	eventually be killed - it cannot happen that a node detects a port as dead
773	and then later sends messages to it, finding it is still alive.
774		755
775	=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.
776		757
777	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
778	known to other nodes for a completely different process, causing messages	759	known to other nodes for a completely different process, causing messages
…		…
782	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.
783		764
784	=item * Erlang uses unprotected connections, AEMP uses secure	765	=item * Erlang uses unprotected connections, AEMP uses secure
785	authentication and can use TLS.	766	authentication and can use TLS.
786		767
787	AEMP can use a proven protocol - SSL/TLS - to protect connections and	768	AEMP can use a proven protocol - TLS - to protect connections and
788	securely authenticate nodes.	769	securely authenticate nodes.
789		770
790	=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
791	communications.	772	communications.
792		773
793	The AEMP protocol, unlike the Erlang protocol, supports both	774	The AEMP protocol, unlike the Erlang protocol, supports both programming
794	language-independent text-only protocols (good for debugging) and binary,	775	language independent text-only protocols (good for debugging) and binary,
795	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.
796		778
797	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
798	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
799	protocol simple.	781	protocol simple.
800		782
801	=item * AEMP has more flexible monitoring options than Erlang.	783	=item * AEMP has more flexible monitoring options than Erlang.
802		784
803	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
…		…
806	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
807	on a per-process basis.	789	on a per-process basis.
808		790
809	=item * Erlang tries to hide remote/local connections, AEMP does not.	791	=item * Erlang tries to hide remote/local connections, AEMP does not.
810		792
811	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
812	as linking is (except linking is unreliable in Erlang).	794	same way as linking is (except linking is unreliable in Erlang).
813		795
814	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
815	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
816	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
817	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
818	more reliable.	800	reliable (no need for C<spawn_link>).
819		801
820	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
821	(hard to do in Erlang).	803	(hard to do in Erlang).
822		804
823	=back	805	=back
824		806
825	=head1 RATIONALE	807	=head1 RATIONALE
826		808
827	=over 4	809	=over 4
828		810
829	=item Why strings for ports and noderefs, why not objects?	811	=item Why strings for port and node IDs, why not objects?
830		812
831	We considered "objects", but found that the actual number of methods	813	We considered "objects", but found that the actual number of methods
832	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
833	the network frequently, the serialising/deserialising would add lots of	815	the network frequently, the serialising/deserialising would add lots of
834	overhead, as well as having to keep a proxy object.	816	overhead, as well as having to keep a proxy object everywhere.
835		817
836	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
837	procedures to be "valid".	819	procedures to be "valid".
838		820
839	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
840	can't become much cheaper.	822	global hash - it can't become much cheaper.
841		823
842	=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?
843		825
844	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
845	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
846	default.	828	default (although all nodes will accept it).
847		829
848	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
849	faster for small messages and b) most importantly, after years of	831	faster for small messages and b) most importantly, after years of
850	experience we found that object serialisation is causing more problems	832	experience we found that object serialisation is causing more problems
851	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
852	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
853	always have to re-think your design.	835	always have to re-think your design.
854		836
855	Keeping your messages simple, concentrating on data structures rather than	837	Keeping your messages simple, concentrating on data structures rather than
856	objects, will keep your messages clean, tidy and efficient.	838	objects, will keep your messages clean, tidy and efficient.
857		839
858	=back	840	=back
859		841
860	=head1 SEE ALSO	842	=head1 SEE ALSO
861		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
862	L<AnyEvent>.	851	L<AnyEvent>.
863		852
864	=head1 AUTHOR	853	=head1 AUTHOR
865		854
866	Marc Lehmann <schmorp@schmorp.de>	855	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.62 by root, Thu Aug 27 07:12:48 2009 UTC vs.
Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC