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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.65 by root, Fri Aug 28 01:00:34 2009 UTC vs.
Revision 1.83 by root, Tue Sep 8 01:38:16 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;	15	configure;
17		16
18	# ports are message endpoints	17	# ports are message destinations
19		18
20	# sending messages	19	# sending messages
21	snd $port, type => data...;	20	snd $port, type => data...;
22	snd $port, @msg;	21	snd $port, @msg;
23	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
24		23
25	# creating/using ports, the simple way	24	# creating/using ports, the simple way
26	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
27		26
28	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
29	my $port = port;	28	my $port = port;
30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
31	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
32		31
33	# create a port on another node	32	# create a port on another node
34	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
35		34
36	# monitoring	35	# monitoring
…		…
38	mon $port, $otherport # kill otherport on abnormal death	37	mon $port, $otherport # kill otherport on abnormal death
39	mon $port, $otherport, @msg # send message on death	38	mon $port, $otherport, @msg # send message on death
40		39
41	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
42		41
		42	bin/aemp - stable.
43	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
44	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.
45	AnyEvent::MP::Kernel - WIP
46	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable but incomplete, protocol not yet final.
47		47
48	stay tuned.	48	stay tuned.
49		49
50	=head1 DESCRIPTION	50	=head1 DESCRIPTION
51		51
52	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
53		53
54	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
55	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
56		56
57	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>
58	manual page.	58	manual page and the examples under F<eg/>.
59
60	At the moment, this module family is severly broken and underdocumented,
61	so do not use. This was uploaded mainly to reserve the CPAN namespace -
62	stay tuned!
63		59
64	=head1 CONCEPTS	60	=head1 CONCEPTS
65		61
66	=over 4	62	=over 4
67		63
68	=item port	64	=item port
69		65
70	A port is something you can send messages to (with the C<snd> function).	66	Not to be confused with a TCP port, a "port" is something you can send
		67	messages to (with the C<snd> function).
71		68
72	Ports allow you to register C<rcv> handlers that can match all or just	69	Ports allow you to register C<rcv> handlers that can match all or just
73	some messages. Messages send to ports will not be queued, regardless of	70	some messages. Messages send to ports will not be queued, regardless of
74	anything was listening for them or not.	71	anything was listening for them or not.
75		72
76	=item port ID - C<noderef#portname>	73	=item port ID - C<nodeid#portname>
77		74
78	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	75	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
79	separator, and a port name (a printable string of unspecified format). An	76	separator, and a port name (a printable string of unspecified format).
80	exception is the the node port, whose ID is identical to its node
81	reference.
82		77
83	=item node	78	=item node
84		79
85	A node is a single process containing at least one port - the node port,	80	A node is a single process containing at least one port - the node port,
86	which provides nodes to manage each other remotely, and to create new	81	which enables nodes to manage each other remotely, and to create new
87	ports.	82	ports.
88		83
89	Nodes are either private (single-process only), slaves (can only talk to	84	Nodes are either public (have one or more listening ports) or private
90	public nodes, but do not need an open port) or public nodes (connectable	85	(no listening ports). Private nodes cannot talk to other private nodes
91	from any other node).	86	currently.
92		87
93	=item node ID - C<[a-za-Z0-9_\-.:]+>	88	=item node ID - C<[a-za-Z0-9_\-.:]+>
94		89
95	A node ID is a string that uniquely identifies the node within a	90	A node ID is a string that uniquely identifies the node within a
96	network. Depending on the configuration used, node IDs can look like a	91	network. Depending on the configuration used, node IDs can look like a
…		…
102	Nodes can only talk to each other by creating some kind of connection to	97	Nodes can only talk to each other by creating some kind of connection to
103	each other. To do this, nodes should listen on one or more local transport	98	each other. To do this, nodes should listen on one or more local transport
104	endpoints - binds. Currently, only standard C<ip:port> specifications can	99	endpoints - binds. Currently, only standard C<ip:port> specifications can
105	be used, which specify TCP ports to listen on.	100	be used, which specify TCP ports to listen on.
106		101
107	=item seeds - C<host:port>	102	=item seed nodes
108		103
109	When a node starts, it knows nothing about the network. To teach the node	104	When a node starts, it knows nothing about the network. To teach the node
110	about the network it first has to contact some other node within the	105	about the network it first has to contact some other node within the
111	network. This node is called a seed.	106	network. This node is called a seed.
112		107
113	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	108	Apart from the fact that other nodes know them as seed nodes and they have
		109	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		110	any node can function as a seed node for others.
		111
		112	In addition to discovering the network, seed nodes are also used to
		113	maintain the network and to connect nodes that otherwise would have
		114	trouble connecting. They form the backbone of the AnyEvent::MP network.
		115
114	are expected to be long-running, and at least one of those should always	116	Seed nodes are expected to be long-running, and at least one seed node
115	be available. When nodes run out of connections (e.g. due to a network	117	should always be available.
116	error), they try to re-establish connections to some seednodes again to	118
117	join the network.	119	=item seeds - C<host:port>
		120
		121	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		122	TCP port) of nodes thta should be used as seed nodes.
		123
		124	The nodes listening on those endpoints are expected to be long-running,
		125	and at least one of those should always be available. When nodes run out
		126	of connections (e.g. due to a network error), they try to re-establish
		127	connections to some seednodes again to join the network.
118		128
119	=back	129	=back
120		130
121	=head1 VARIABLES/FUNCTIONS	131	=head1 VARIABLES/FUNCTIONS
122		132
…		…
138		148
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	149	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
140		150
141	our @EXPORT = qw(	151	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	152	NODE $NODE *SELF node_of after
143	resolve_node initialise_node	153	configure
144	snd rcv mon mon_guard kil reg psub spawn	154	snd rcv mon mon_guard kil reg psub spawn
145	port	155	port
146	);	156	);
147		157
148	our $SELF;	158	our $SELF;
…		…
153	kil $SELF, die => $msg;	163	kil $SELF, die => $msg;
154	}	164	}
155		165
156	=item $thisnode = NODE / $NODE	166	=item $thisnode = NODE / $NODE
157		167
158	The C<NODE> function returns, and the C<$NODE> variable contains the node	168	The C<NODE> function returns, and the C<$NODE> variable contains, the node
159	ID of the node running in the current process. This value is initialised by	169	ID of the node running in the current process. This value is initialised by
160	a call to C<initialise_node>.	170	a call to C<configure>.
161		171
162	=item $nodeid = node_of $port	172	=item $nodeid = node_of $port
163		173
164	Extracts and returns the node ID part from a port ID or a node ID.	174	Extracts and returns the node ID from a port ID or a node ID.
165		175
166	=item initialise_node $profile_name	176	=item configure $profile, key => value...
		177
		178	=item configure key => value...
167		179
168	Before a node can talk to other nodes on the network (i.e. enter	180	Before a node can talk to other nodes on the network (i.e. enter
169	"distributed mode") it has to initialise itself - the minimum a node needs	181	"distributed mode") it has to configure itself - the minimum a node needs
170	to know is its own name, and optionally it should know the addresses of	182	to know is its own name, and optionally it should know the addresses of
171	some other nodes in the network to discover other nodes.	183	some other nodes in the network to discover other nodes.
172		184
173	This function initialises a node - it must be called exactly once (or	185	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	186	never) before calling other AnyEvent::MP functions.
175		187
176	The first argument is a profile name. If it is C<undef> or missing, then	188	=over 4
177	the current nodename will be used instead (i.e. F<uname -n>).
178		189
		190	=item step 1, gathering configuration from profiles
		191
179	The function then looks up the profile in the aemp configuration (see the	192	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility).	193	L<aemp> commandline utility). The profile name can be specified via the
		194	named C<profile> parameter or can simply be the first parameter). If it is
		195	missing, then the nodename (F<uname -n>) will be used as profile name.
		196
		197	The profile data is then gathered as follows:
		198
		199	First, all remaining key => value pairs (all of which are conveniently
		200	undocumented at the moment) will be interpreted as configuration
		201	data. Then they will be overwritten by any values specified in the global
		202	default configuration (see the F<aemp> utility), then the chain of
		203	profiles chosen by the profile name (and any C<parent> attributes).
		204
		205	That means that the values specified in the profile have highest priority
		206	and the values specified directly via C<configure> have lowest priority,
		207	and can only be used to specify defaults.
181		208
182	If the profile specifies a node ID, then this will become the node ID of	209	If the profile specifies a node ID, then this will become the node ID of
183	this process. If not, then the profile name will be used as node ID. The	210	this process. If not, then the profile name will be used as node ID. The
184	special node ID of C<anon/> will be replaced by a random node ID.	211	special node ID of C<anon/> will be replaced by a random node ID.
		212
		213	=item step 2, bind listener sockets
185		214
186	The next step is to look up the binds in the profile, followed by binding	215	The next step is to look up the binds in the profile, followed by binding
187	aemp protocol listeners on all binds specified (it is possible and valid	216	aemp protocol listeners on all binds specified (it is possible and valid
188	to have no binds, meaning that the node cannot be contacted form the	217	to have no binds, meaning that the node cannot be contacted form the
189	outside. This means the node cannot talk to other nodes that also have no	218	outside. This means the node cannot talk to other nodes that also have no
190	binds, but it can still talk to all "normal" nodes).	219	binds, but it can still talk to all "normal" nodes).
191		220
192	If the profile does not specify a binds list, then the node ID will be	221	If the profile does not specify a binds list, then a default of C<*> is
193	treated as if it were of the form C<host:port>, which will be resolved and	222	used, meaning the node will bind on a dynamically-assigned port on every
194	used as binds list.	223	local IP address it finds.
195		224
		225	=item step 3, connect to seed nodes
		226
196	Lastly, the seeds list from the profile is passed to the	227	As the last step, the seeds list from the profile is passed to the
197	L<AnyEvent::MP::Global> module, which will then use it to keep	228	L<AnyEvent::MP::Global> module, which will then use it to keep
198	connectivity with at least on of those seed nodes at any point in time.	229	connectivity with at least one node at any point in time.
199		230
200	Example: become a distributed node listening on the guessed noderef, or	231	=back
201	the one specified via C<aemp> for the current node. This should be the	232
		233	Example: become a distributed node using the locla node name as profile.
202	most common form of invocation for "daemon"-type nodes.	234	This should be the most common form of invocation for "daemon"-type nodes.
203		235
204	initialise_node;	236	configure
205		237
206	Example: become an anonymous node. This form is often used for commandline	238	Example: become an anonymous node. This form is often used for commandline
207	clients.	239	clients.
208		240
209	initialise_node "anon/";	241	configure nodeid => "anon/";
210		242
211	Example: become a distributed node. If there is no profile of the given	243	Example: configure a node using a profile called seed, which si suitable
212	name, or no binds list was specified, resolve C<localhost:4044> and bind	244	for a seed node as it binds on all local addresses on a fixed port (4040,
213	on the resulting addresses.	245	customary for aemp).
214		246
215	initialise_node "localhost:4044";	247	# use the aemp commandline utility
		248	# aemp profile seed nodeid anon/ binds '*:4040'
		249
		250	# then use it
		251	configure profile => "seed";
		252
		253	# or simply use aemp from the shell again:
		254	# aemp run profile seed
		255
		256	# or provide a nicer-to-remember nodeid
		257	# aemp run profile seed nodeid "$(hostname)"
216		258
217	=item $SELF	259	=item $SELF
218		260
219	Contains the current port id while executing C<rcv> callbacks or C<psub>	261	Contains the current port id while executing C<rcv> callbacks or C<psub>
220	blocks.	262	blocks.
221		263
222	=item SELF, %SELF, @SELF...	264	=item *SELF, SELF, %SELF, @SELF...
223		265
224	Due to some quirks in how perl exports variables, it is impossible to	266	Due to some quirks in how perl exports variables, it is impossible to
225	just export C<$SELF>, all the symbols called C<SELF> are exported by this	267	just export C<$SELF>, all the symbols named C<SELF> are exported by this
226	module, but only C<$SELF> is currently used.	268	module, but only C<$SELF> is currently used.
227		269
228	=item snd $port, type => @data	270	=item snd $port, type => @data
229		271
230	=item snd $port, @msg	272	=item snd $port, @msg
231		273
232	Send the given message to the given port ID, which can identify either	274	Send the given message to the given port, which can identify either a
233	a local or a remote port, and must be a port ID.	275	local or a remote port, and must be a port ID.
234		276
235	While the message can be about anything, it is highly recommended to use a	277	While the message can be almost anything, it is highly recommended to
236	string as first element (a port ID, or some word that indicates a request	278	use a string as first element (a port ID, or some word that indicates a
237	type etc.).	279	request type etc.) and to consist if only simple perl values (scalars,
		280	arrays, hashes) - if you think you need to pass an object, think again.
238		281
239	The message data effectively becomes read-only after a call to this	282	The message data logically becomes read-only after a call to this
240	function: modifying any argument is not allowed and can cause many	283	function: modifying any argument (or values referenced by them) is
241	problems.	284	forbidden, as there can be considerable time between the call to C<snd>
		285	and the time the message is actually being serialised - in fact, it might
		286	never be copied as within the same process it is simply handed to the
		287	receiving port.
242		288
243	The type of data you can transfer depends on the transport protocol: when	289	The type of data you can transfer depends on the transport protocol: when
244	JSON is used, then only strings, numbers and arrays and hashes consisting	290	JSON is used, then only strings, numbers and arrays and hashes consisting
245	of those are allowed (no objects). When Storable is used, then anything	291	of those are allowed (no objects). When Storable is used, then anything
246	that Storable can serialise and deserialise is allowed, and for the local	292	that Storable can serialise and deserialise is allowed, and for the local
247	node, anything can be passed.	293	node, anything can be passed. Best rely only on the common denominator of
		294	these.
248		295
249	=item $local_port = port	296	=item $local_port = port
250		297
251	Create a new local port object and returns its port ID. Initially it has	298	Create a new local port object and returns its port ID. Initially it has
252	no callbacks set and will throw an error when it receives messages.	299	no callbacks set and will throw an error when it receives messages.
…		…
337		384
338	=cut	385	=cut
339		386
340	sub rcv($@) {	387	sub rcv($@) {
341	my $port = shift;	388	my $port = shift;
342	my ($noderef, $portid) = split /#/, $port, 2;	389	my ($nodeid, $portid) = split /#/, $port, 2;
343		390
344	$NODE{$noderef} == $NODE{""}	391	$NODE{$nodeid} == $NODE{""}
345	or Carp::croak "$port: rcv can only be called on local ports, caught";	392	or Carp::croak "$port: rcv can only be called on local ports, caught";
346		393
347	while (@_) {	394	while (@_) {
348	if (ref $_[0]) {	395	if (ref $_[0]) {
349	if (my $self = $PORT_DATA{$portid}) {	396	if (my $self = $PORT_DATA{$portid}) {
…		…
428	$res	475	$res
429	}	476	}
430	}	477	}
431	}	478	}
432		479
433	=item $guard = mon $port, $cb->(@reason)	480	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
434		481
435	=item $guard = mon $port, $rcvport	482	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
436		483
437	=item $guard = mon $port	484	=item $guard = mon $port # kill $SELF when $port dies
438		485
439	=item $guard = mon $port, $rcvport, @msg	486	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
440		487
441	Monitor the given port and do something when the port is killed or	488	Monitor the given port and do something when the port is killed or
442	messages to it were lost, and optionally return a guard that can be used	489	messages to it were lost, and optionally return a guard that can be used
443	to stop monitoring again.	490	to stop monitoring again.
444
445	C<mon> effectively guarantees that, in the absence of hardware failures,
446	that after starting the monitor, either all messages sent to the port
447	will arrive, or the monitoring action will be invoked after possible
448	message loss has been detected. No messages will be lost "in between"
449	(after the first lost message no further messages will be received by the
450	port). After the monitoring action was invoked, further messages might get
451	delivered again.
452
453	Note that monitoring-actions are one-shot: once released, they are removed
454	and will not trigger again.
455		491
456	In the first form (callback), the callback is simply called with any	492	In the first form (callback), the callback is simply called with any
457	number of C<@reason> elements (no @reason means that the port was deleted	493	number of C<@reason> elements (no @reason means that the port was deleted
458	"normally"). Note also that I<< the callback B<must> never die >>, so use	494	"normally"). Note also that I<< the callback B<must> never die >>, so use
459	C<eval> if unsure.	495	C<eval> if unsure.
460		496
461	In the second form (another port given), the other port (C<$rcvport>)	497	In the second form (another port given), the other port (C<$rcvport>)
462	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	498	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
463	"normal" kils nothing happens, while under all other conditions, the other	499	"normal" kils nothing happens, while under all other conditions, the other
464	port is killed with the same reason.	500	port is killed with the same reason.
465		501
466	The third form (kill self) is the same as the second form, except that	502	The third form (kill self) is the same as the second form, except that
467	C<$rvport> defaults to C<$SELF>.	503	C<$rvport> defaults to C<$SELF>.
468		504
469	In the last form (message), a message of the form C<@msg, @reason> will be	505	In the last form (message), a message of the form C<@msg, @reason> will be
470	C<snd>.	506	C<snd>.
		507
		508	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		509	alert was raised), they are removed and will not trigger again.
471		510
472	As a rule of thumb, monitoring requests should always monitor a port from	511	As a rule of thumb, monitoring requests should always monitor a port from
473	a local port (or callback). The reason is that kill messages might get	512	a local port (or callback). The reason is that kill messages might get
474	lost, just like any other message. Another less obvious reason is that	513	lost, just like any other message. Another less obvious reason is that
475	even monitoring requests can get lost (for exmaple, when the connection	514	even monitoring requests can get lost (for example, when the connection
476	to the other node goes down permanently). When monitoring a port locally	515	to the other node goes down permanently). When monitoring a port locally
477	these problems do not exist.	516	these problems do not exist.
478		517
		518	C<mon> effectively guarantees that, in the absence of hardware failures,
		519	after starting the monitor, either all messages sent to the port will
		520	arrive, or the monitoring action will be invoked after possible message
		521	loss has been detected. No messages will be lost "in between" (after
		522	the first lost message no further messages will be received by the
		523	port). After the monitoring action was invoked, further messages might get
		524	delivered again.
		525
		526	Inter-host-connection timeouts and monitoring depend on the transport
		527	used. The only transport currently implemented is TCP, and AnyEvent::MP
		528	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		529	non-idle connection, and usually around two hours for idle conenctions).
		530
		531	This means that monitoring is good for program errors and cleaning up
		532	stuff eventually, but they are no replacement for a timeout when you need
		533	to ensure some maximum latency.
		534
479	Example: call a given callback when C<$port> is killed.	535	Example: call a given callback when C<$port> is killed.
480		536
481	mon $port, sub { warn "port died because of <@_>\n" };	537	mon $port, sub { warn "port died because of <@_>\n" };
482		538
483	Example: kill ourselves when C<$port> is killed abnormally.	539	Example: kill ourselves when C<$port> is killed abnormally.
…		…
489	mon $port, $self => "restart";	545	mon $port, $self => "restart";
490		546
491	=cut	547	=cut
492		548
493	sub mon {	549	sub mon {
494	my ($noderef, $port) = split /#/, shift, 2;	550	my ($nodeid, $port) = split /#/, shift, 2;
495		551
496	my $node = $NODE{$noderef} \|\| add_node $noderef;	552	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
497		553
498	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	554	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
499		555
500	unless (ref $cb) {	556	unless (ref $cb) {
501	if (@_) {	557	if (@_) {
…		…
521	is killed, the references will be freed.	577	is killed, the references will be freed.
522		578
523	Optionally returns a guard that will stop the monitoring.	579	Optionally returns a guard that will stop the monitoring.
524		580
525	This function is useful when you create e.g. timers or other watchers and	581	This function is useful when you create e.g. timers or other watchers and
526	want to free them when the port gets killed:	582	want to free them when the port gets killed (note the use of C<psub>):
527		583
528	$port->rcv (start => sub {	584	$port->rcv (start => sub {
529	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	585	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
530	undef $timer if 0.9 < rand;	586	undef $timer if 0.9 < rand;
531	});	587	});
532	});	588	});
533		589
534	=cut	590	=cut
…		…
543		599
544	=item kil $port[, @reason]	600	=item kil $port[, @reason]
545		601
546	Kill the specified port with the given C<@reason>.	602	Kill the specified port with the given C<@reason>.
547		603
548	If no C<@reason> is specified, then the port is killed "normally" (linked	604	If no C<@reason> is specified, then the port is killed "normally" (ports
549	ports will not be kileld, or even notified).	605	monitoring other ports will not necessarily die because a port dies
		606	"normally").
550		607
551	Otherwise, linked ports get killed with the same reason (second form of	608	Otherwise, linked ports get killed with the same reason (second form of
552	C<mon>, see below).	609	C<mon>, see above).
553		610
554	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	611	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
555	will be reported as reason C<< die => $@ >>.	612	will be reported as reason C<< die => $@ >>.
556		613
557	Transport/communication errors are reported as C<< transport_error =>	614	Transport/communication errors are reported as C<< transport_error =>
…		…
562	=item $port = spawn $node, $initfunc[, @initdata]	619	=item $port = spawn $node, $initfunc[, @initdata]
563		620
564	Creates a port on the node C<$node> (which can also be a port ID, in which	621	Creates a port on the node C<$node> (which can also be a port ID, in which
565	case it's the node where that port resides).	622	case it's the node where that port resides).
566		623
567	The port ID of the newly created port is return immediately, and it is	624	The port ID of the newly created port is returned immediately, and it is
568	permissible to immediately start sending messages or monitor the port.	625	possible to immediately start sending messages or to monitor the port.
569		626
570	After the port has been created, the init function is	627	After the port has been created, the init function is called on the remote
571	called. This function must be a fully-qualified function name	628	node, in the same context as a C<rcv> callback. This function must be a
572	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	629	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
573	program, use C<::name>.	630	specify a function in the main program, use C<::name>.
574		631
575	If the function doesn't exist, then the node tries to C<require>	632	If the function doesn't exist, then the node tries to C<require>
576	the package, then the package above the package and so on (e.g.	633	the package, then the package above the package and so on (e.g.
577	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	634	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
578	exists or it runs out of package names.	635	exists or it runs out of package names.
579		636
580	The init function is then called with the newly-created port as context	637	The init function is then called with the newly-created port as context
581	object (C<$SELF>) and the C<@initdata> values as arguments.	638	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		639	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		640	the port might not get created.
582		641
583	A common idiom is to pass your own port, monitor the spawned port, and	642	A common idiom is to pass a local port, immediately monitor the spawned
584	in the init function, monitor the original port. This two-way monitoring	643	port, and in the remote init function, immediately monitor the passed
585	ensures that both ports get cleaned up when there is a problem.	644	local port. This two-way monitoring ensures that both ports get cleaned up
		645	when there is a problem.
		646
		647	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		648	caller before C<spawn> returns (by delaying invocation when spawn is
		649	called for the local node).
586		650
587	Example: spawn a chat server port on C<$othernode>.	651	Example: spawn a chat server port on C<$othernode>.
588		652
589	# this node, executed from within a port context:	653	# this node, executed from within a port context:
590	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	654	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
605		669
606	sub _spawn {	670	sub _spawn {
607	my $port = shift;	671	my $port = shift;
608	my $init = shift;	672	my $init = shift;
609		673
		674	# rcv will create the actual port
610	local $SELF = "$NODE#$port";	675	local $SELF = "$NODE#$port";
611	eval {	676	eval {
612	&{ load_func $init }	677	&{ load_func $init }
613	};	678	};
614	_self_die if $@;	679	_self_die if $@;
615	}	680	}
616		681
617	sub spawn(@) {	682	sub spawn(@) {
618	my ($noderef, undef) = split /#/, shift, 2;	683	my ($nodeid, undef) = split /#/, shift, 2;
619		684
620	my $id = "$RUNIQ." . $ID++;	685	my $id = "$RUNIQ." . $ID++;
621		686
622	$_[0] =~ /::/	687	$_[0] =~ /::/
623	or Carp::croak "spawn init function must be a fully-qualified name, caught";	688	or Carp::croak "spawn init function must be a fully-qualified name, caught";
624		689
625	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	690	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
626		691
627	"$noderef#$id"	692	"$nodeid#$id"
628	}	693	}
629		694
630	=item after $timeout, @msg	695	=item after $timeout, @msg
631		696
632	=item after $timeout, $callback	697	=item after $timeout, $callback
633		698
634	Either sends the given message, or call the given callback, after the	699	Either sends the given message, or call the given callback, after the
635	specified number of seconds.	700	specified number of seconds.
636		701
637	This is simply a utility function that come sin handy at times.	702	This is simply a utility function that comes in handy at times - the
		703	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		704	so it may go away in the future.
638		705
639	=cut	706	=cut
640		707
641	sub after($@) {	708	sub after($@) {
642	my ($timeout, @action) = @_;	709	my ($timeout, @action) = @_;
…		…
669		736
670	=item * Node IDs are arbitrary strings in AEMP.	737	=item * Node IDs are arbitrary strings in AEMP.
671		738
672	Erlang relies on special naming and DNS to work everywhere in the same	739	Erlang relies on special naming and DNS to work everywhere in the same
673	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	740	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
674	configuraiton or DNS), but will otherwise discover other odes itself.	741	configuration or DNS), but will otherwise discover other odes itself.
675		742
676	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	743	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
677	uses "local ports are like remote ports".	744	uses "local ports are like remote ports".
678		745
679	The failure modes for local ports are quite different (runtime errors	746	The failure modes for local ports are quite different (runtime errors
…		…
692		759
693	Erlang uses processes that selectively receive messages, and therefore	760	Erlang uses processes that selectively receive messages, and therefore
694	needs a queue. AEMP is event based, queuing messages would serve no	761	needs a queue. AEMP is event based, queuing messages would serve no
695	useful purpose. For the same reason the pattern-matching abilities of	762	useful purpose. For the same reason the pattern-matching abilities of
696	AnyEvent::MP are more limited, as there is little need to be able to	763	AnyEvent::MP are more limited, as there is little need to be able to
697	filter messages without dequeing them.	764	filter messages without dequeuing them.
698		765
699	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
700		767
701	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
702		769
…		…
708		775
709	Erlang makes few guarantees on messages delivery - messages can get lost	776	Erlang makes few guarantees on messages delivery - messages can get lost
710	without any of the processes realising it (i.e. you send messages a, b,	777	without any of the processes realising it (i.e. you send messages a, b,
711	and c, and the other side only receives messages a and c).	778	and c, and the other side only receives messages a and c).
712		779
713	AEMP guarantees correct ordering, and the guarantee that there are no	780	AEMP guarantees correct ordering, and the guarantee that after one message
714	holes in the message sequence.	781	is lost, all following ones sent to the same port are lost as well, until
715		782	monitoring raises an error, so there are no silent "holes" in the message
716	=item * In Erlang, processes can be declared dead and later be found to be	783	sequence.
717	alive.
718
719	In Erlang it can happen that a monitored process is declared dead and
720	linked processes get killed, but later it turns out that the process is
721	still alive - and can receive messages.
722
723	In AEMP, when port monitoring detects a port as dead, then that port will
724	eventually be killed - it cannot happen that a node detects a port as dead
725	and then later sends messages to it, finding it is still alive.
726		784
727	=item * Erlang can send messages to the wrong port, AEMP does not.	785	=item * Erlang can send messages to the wrong port, AEMP does not.
728		786
729	In Erlang it is quite likely that a node that restarts reuses a process ID	787	In Erlang it is quite likely that a node that restarts reuses a process ID
730	known to other nodes for a completely different process, causing messages	788	known to other nodes for a completely different process, causing messages
…		…
734	around in the network will not be sent to an unrelated port.	792	around in the network will not be sent to an unrelated port.
735		793
736	=item * Erlang uses unprotected connections, AEMP uses secure	794	=item * Erlang uses unprotected connections, AEMP uses secure
737	authentication and can use TLS.	795	authentication and can use TLS.
738		796
739	AEMP can use a proven protocol - SSL/TLS - to protect connections and	797	AEMP can use a proven protocol - TLS - to protect connections and
740	securely authenticate nodes.	798	securely authenticate nodes.
741		799
742	=item * The AEMP protocol is optimised for both text-based and binary	800	=item * The AEMP protocol is optimised for both text-based and binary
743	communications.	801	communications.
744		802
745	The AEMP protocol, unlike the Erlang protocol, supports both	803	The AEMP protocol, unlike the Erlang protocol, supports both programming
746	language-independent text-only protocols (good for debugging) and binary,	804	language independent text-only protocols (good for debugging) and binary,
747	language-specific serialisers (e.g. Storable).	805	language-specific serialisers (e.g. Storable). By default, unless TLS is
		806	used, the protocol is actually completely text-based.
748		807
749	It has also been carefully designed to be implementable in other languages	808	It has also been carefully designed to be implementable in other languages
750	with a minimum of work while gracefully degrading fucntionality to make the	809	with a minimum of work while gracefully degrading functionality to make the
751	protocol simple.	810	protocol simple.
752		811
753	=item * AEMP has more flexible monitoring options than Erlang.	812	=item * AEMP has more flexible monitoring options than Erlang.
754		813
755	In Erlang, you can chose to receive I<all> exit signals as messages	814	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
758	Erlang, as one can choose between automatic kill, exit message or callback	817	Erlang, as one can choose between automatic kill, exit message or callback
759	on a per-process basis.	818	on a per-process basis.
760		819
761	=item * Erlang tries to hide remote/local connections, AEMP does not.	820	=item * Erlang tries to hide remote/local connections, AEMP does not.
762		821
763	Monitoring in Erlang is not an indicator of process death/crashes,	822	Monitoring in Erlang is not an indicator of process death/crashes, in the
764	as linking is (except linking is unreliable in Erlang).	823	same way as linking is (except linking is unreliable in Erlang).
765		824
766	In AEMP, you don't "look up" registered port names or send to named ports	825	In AEMP, you don't "look up" registered port names or send to named ports
767	that might or might not be persistent. Instead, you normally spawn a port	826	that might or might not be persistent. Instead, you normally spawn a port
768	on the remote node. The init function monitors the you, and you monitor	827	on the remote node. The init function monitors you, and you monitor the
769	the remote port. Since both monitors are local to the node, they are much	828	remote port. Since both monitors are local to the node, they are much more
770	more reliable.	829	reliable (no need for C<spawn_link>).
771		830
772	This also saves round-trips and avoids sending messages to the wrong port	831	This also saves round-trips and avoids sending messages to the wrong port
773	(hard to do in Erlang).	832	(hard to do in Erlang).
774		833
775	=back	834	=back
776		835
777	=head1 RATIONALE	836	=head1 RATIONALE
778		837
779	=over 4	838	=over 4
780		839
781	=item Why strings for ports and noderefs, why not objects?	840	=item Why strings for port and node IDs, why not objects?
782		841
783	We considered "objects", but found that the actual number of methods	842	We considered "objects", but found that the actual number of methods
784	thatc an be called are very low. Since port IDs and noderefs travel over	843	that can be called are quite low. Since port and node IDs travel over
785	the network frequently, the serialising/deserialising would add lots of	844	the network frequently, the serialising/deserialising would add lots of
786	overhead, as well as having to keep a proxy object.	845	overhead, as well as having to keep a proxy object everywhere.
787		846
788	Strings can easily be printed, easily serialised etc. and need no special	847	Strings can easily be printed, easily serialised etc. and need no special
789	procedures to be "valid".	848	procedures to be "valid".
790		849
791	And a a miniport consists of a single closure stored in a global hash - it	850	And as a result, a miniport consists of a single closure stored in a
792	can't become much cheaper.	851	global hash - it can't become much cheaper.
793		852
794	=item Why favour JSON, why not real serialising format such as Storable?	853	=item Why favour JSON, why not a real serialising format such as Storable?
795		854
796	In fact, any AnyEvent::MP node will happily accept Storable as framing	855	In fact, any AnyEvent::MP node will happily accept Storable as framing
797	format, but currently there is no way to make a node use Storable by	856	format, but currently there is no way to make a node use Storable by
798	default.	857	default (although all nodes will accept it).
799		858
800	The default framing protocol is JSON because a) JSON::XS is many times	859	The default framing protocol is JSON because a) JSON::XS is many times
801	faster for small messages and b) most importantly, after years of	860	faster for small messages and b) most importantly, after years of
802	experience we found that object serialisation is causing more problems	861	experience we found that object serialisation is causing more problems
803	than it gains: Just like function calls, objects simply do not travel	862	than it solves: Just like function calls, objects simply do not travel
804	easily over the network, mostly because they will always be a copy, so you	863	easily over the network, mostly because they will always be a copy, so you
805	always have to re-think your design.	864	always have to re-think your design.
806		865
807	Keeping your messages simple, concentrating on data structures rather than	866	Keeping your messages simple, concentrating on data structures rather than
808	objects, will keep your messages clean, tidy and efficient.	867	objects, will keep your messages clean, tidy and efficient.
809		868
810	=back	869	=back
811		870
812	=head1 SEE ALSO	871	=head1 SEE ALSO
813		872
		873	L<AnyEvent::MP::Intro> - a gentle introduction.
		874
		875	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		876
		877	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		878	your applications.
		879
		880	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		881	all nodes.
		882
814	L<AnyEvent>.	883	L<AnyEvent>.
815		884
816	=head1 AUTHOR	885	=head1 AUTHOR
817		886
818	Marc Lehmann <schmorp@schmorp.de>	887	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.65 by root, Fri Aug 28 01:00:34 2009 UTC vs.
Revision 1.83 by root, Tue Sep 8 01:38:16 2009 UTC