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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.64 by root, Fri Aug 28 00:58:44 2009 UTC vs.
Revision 1.77 by elmex, Thu Sep 3 07:57:30 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44	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.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 API, 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
…		…
71		67
72	Ports allow you to register C<rcv> handlers that can match all or just	68	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	69	some messages. Messages send to ports will not be queued, regardless of
74	anything was listening for them or not.	70	anything was listening for them or not.
75		71
76	=item port ID - C<noderef#portname>	72	=item port ID - C<nodeid#portname>
77		73
78	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	74	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	75	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		76
83	=item node	77	=item node
84		78
85	A node is a single process containing at least one port - the node port,	79	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	80	which enables nodes to manage each other remotely, and to create new
87	ports.	81	ports.
88		82
89	Nodes are either private (single-process only), slaves (can only talk to	83	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	84	(no listening ports). Private nodes cannot talk to other private nodes
91	from any other node).	85	currently.
92		86
93	=item node ID - C<[a-za-Z0-9_\-.:]+>	87	=item node ID - C<[a-za-Z0-9_\-.:]+>
94		88
95	A node ID is a string that uniquely identifies the node within a	89	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	90	network. Depending on the configuration used, node IDs can look like a
…		…
114	are expected to be long-running, and at least one of those should always	108	are expected to be long-running, and at least one of those should always
115	be available. When nodes run out of connections (e.g. due to a network	109	be available. When nodes run out of connections (e.g. due to a network
116	error), they try to re-establish connections to some seednodes again to	110	error), they try to re-establish connections to some seednodes again to
117	join the network.	111	join the network.
118		112
		113	Apart from being sued for seeding, seednodes are not special in any way -
		114	every public node can be a seednode.
		115
119	=back	116	=back
120		117
121	=head1 VARIABLES/FUNCTIONS	118	=head1 VARIABLES/FUNCTIONS
122		119
123	=over 4	120	=over 4
…		…
138		135
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	136	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
140		137
141	our @EXPORT = qw(	138	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	139	NODE $NODE *SELF node_of after
143	resolve_node initialise_node	140	configure
144	snd rcv mon mon_guard kil reg psub spawn	141	snd rcv mon mon_guard kil reg psub spawn
145	port	142	port
146	);	143	);
147		144
148	our $SELF;	145	our $SELF;
…		…
153	kil $SELF, die => $msg;	150	kil $SELF, die => $msg;
154	}	151	}
155		152
156	=item $thisnode = NODE / $NODE	153	=item $thisnode = NODE / $NODE
157		154
158	The C<NODE> function returns, and the C<$NODE> variable contains the node	155	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	156	ID of the node running in the current process. This value is initialised by
160	a call to C<initialise_node>.	157	a call to C<configure>.
161		158
162	=item $nodeid = node_of $port	159	=item $nodeid = node_of $port
163		160
164	Extracts and returns the node ID part from a port ID or a node ID.	161	Extracts and returns the node ID from a port ID or a node ID.
165		162
166	=item initialise_node $profile_name	163	=item configure key => value...
167		164
168	Before a node can talk to other nodes on the network (i.e. enter	165	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	166	"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	167	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.	168	some other nodes in the network to discover other nodes.
172		169
173	This function initialises a node - it must be called exactly once (or	170	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	171	never) before calling other AnyEvent::MP functions.
175		172
176	The first argument is a profile name. If it is C<undef> or missing, then	173	=over 4
177	the current nodename will be used instead (i.e. F<uname -n>).
178		174
		175	=item step 1, gathering configuration from profiles
		176
179	The function then looks up the profile in the aemp configuration (see the	177	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility).	178	L<aemp> commandline utility). The profile name can be specified via the
		179	named C<profile> parameter. If it is missing, then the nodename (F<uname
		180	-n>) will be used as profile name.
		181
		182	The profile data is then gathered as follows:
		183
		184	First, all remaining key => value pairs (all of which are conveniently
		185	undocumented at the moment) will be interpreted as configuration
		186	data. Then they will be overwritten by any values specified in the global
		187	default configuration (see the F<aemp> utility), then the chain of
		188	profiles chosen by the profile name (and any C<parent> attributes).
		189
		190	That means that the values specified in the profile have highest priority
		191	and the values specified directly via C<configure> have lowest priority,
		192	and can only be used to specify defaults.
181		193
182	If the profile specifies a node ID, then this will become the node ID of	194	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	195	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.	196	special node ID of C<anon/> will be replaced by a random node ID.
		197
		198	=item step 2, bind listener sockets
185		199
186	The next step is to look up the binds in the profile, followed by binding	200	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	201	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	202	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	203	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).	204	binds, but it can still talk to all "normal" nodes).
191		205
192	If the profile does not specify a binds list, then the node ID will be	206	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	207	used, meaning the node will bind on a dynamically-assigned port on every
194	used as binds list.	208	local IP address it finds.
195		209
		210	=item step 3, connect to seed nodes
		211
196	Lastly, the seeds list from the profile is passed to the	212	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	213	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.	214	connectivity with at least one node at any point in time.
199		215
200	Example: become a distributed node listening on the guessed noderef, or	216	=back
201	the one specified via C<aemp> for the current node. This should be the	217
		218	Example: become a distributed node using the locla node name as profile.
202	most common form of invocation for "daemon"-type nodes.	219	This should be the most common form of invocation for "daemon"-type nodes.
203		220
204	initialise_node;	221	configure
205		222
206	Example: become an anonymous node. This form is often used for commandline	223	Example: become an anonymous node. This form is often used for commandline
207	clients.	224	clients.
208		225
209	initialise_node "anon/";	226	configure nodeid => "anon/";
210		227
211	Example: become a distributed node. If there is no profile of the given	228	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	229	for a seed node as it binds on all local addresses on a fixed port (4040,
213	on the resulting addresses.	230	customary for aemp).
214		231
215	initialise_node "localhost:4044";	232	# use the aemp commandline utility
		233	# aemp profile seed nodeid anon/ binds '*:4040'
		234
		235	# then use it
		236	configure profile => "seed";
		237
		238	# or simply use aemp from the shell again:
		239	# aemp run profile seed
		240
		241	# or provide a nicer-to-remember nodeid
		242	# aemp run profile seed nodeid "$(hostname)"
216		243
217	=item $SELF	244	=item $SELF
218		245
219	Contains the current port id while executing C<rcv> callbacks or C<psub>	246	Contains the current port id while executing C<rcv> callbacks or C<psub>
220	blocks.	247	blocks.
221		248
222	=item SELF, %SELF, @SELF...	249	=item *SELF, SELF, %SELF, @SELF...
223		250
224	Due to some quirks in how perl exports variables, it is impossible to	251	Due to some quirks in how perl exports variables, it is impossible to
225	just export C<$SELF>, all the symbols called C<SELF> are exported by this	252	just export C<$SELF>, all the symbols named C<SELF> are exported by this
226	module, but only C<$SELF> is currently used.	253	module, but only C<$SELF> is currently used.
227		254
228	=item snd $port, type => @data	255	=item snd $port, type => @data
229		256
230	=item snd $port, @msg	257	=item snd $port, @msg
231		258
232	Send the given message to the given port ID, which can identify either	259	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.	260	local or a remote port, and must be a port ID.
234		261
235	While the message can be about anything, it is highly recommended to use a	262	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	263	use a string as first element (a port ID, or some word that indicates a
237	type etc.).	264	request type etc.) and to consist if only simple perl values (scalars,
		265	arrays, hashes) - if you think you need to pass an object, think again.
238		266
239	The message data effectively becomes read-only after a call to this	267	The message data logically becomes read-only after a call to this
240	function: modifying any argument is not allowed and can cause many	268	function: modifying any argument (or values referenced by them) is
241	problems.	269	forbidden, as there can be considerable time between the call to C<snd>
		270	and the time the message is actually being serialised - in fact, it might
		271	never be copied as within the same process it is simply handed to the
		272	receiving port.
242		273
243	The type of data you can transfer depends on the transport protocol: when	274	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	275	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	276	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	277	that Storable can serialise and deserialise is allowed, and for the local
247	node, anything can be passed.	278	node, anything can be passed. Best rely only on the common denominator of
		279	these.
248		280
249	=item $local_port = port	281	=item $local_port = port
250		282
251	Create a new local port object and returns its port ID. Initially it has	283	Create a new local port object and returns its port ID. Initially it has
252	no callbacks set and will throw an error when it receives messages.	284	no callbacks set and will throw an error when it receives messages.
…		…
337		369
338	=cut	370	=cut
339		371
340	sub rcv($@) {	372	sub rcv($@) {
341	my $port = shift;	373	my $port = shift;
342	my ($noderef, $portid) = split /#/, $port, 2;	374	my ($nodeid, $portid) = split /#/, $port, 2;
343		375
344	$NODE{$noderef} == $NODE{""}	376	$NODE{$nodeid} == $NODE{""}
345	or Carp::croak "$port: rcv can only be called on local ports, caught";	377	or Carp::croak "$port: rcv can only be called on local ports, caught";
346		378
347	while (@_) {	379	while (@_) {
348	if (ref $_[0]) {	380	if (ref $_[0]) {
349	if (my $self = $PORT_DATA{$portid}) {	381	if (my $self = $PORT_DATA{$portid}) {
…		…
428	$res	460	$res
429	}	461	}
430	}	462	}
431	}	463	}
432		464
433	=item $guard = mon $port, $cb->(@reason)	465	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
434		466
435	=item $guard = mon $port, $rcvport	467	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
436		468
437	=item $guard = mon $port	469	=item $guard = mon $port # kill $SELF when $port dies
438		470
439	=item $guard = mon $port, $rcvport, @msg	471	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
440		472
441	Monitor the given port and do something when the port is killed or	473	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	474	messages to it were lost, and optionally return a guard that can be used
443	to stop monitoring again.	475	to stop monitoring again.
444		476
445	C<mon> effectively guarantees that, in the absence of hardware failures,	477	C<mon> effectively guarantees that, in the absence of hardware failures,
446	that after starting the monitor, either all messages sent to the port	478	after starting the monitor, either all messages sent to the port will
447	will arrive, or the monitoring action will be invoked after possible	479	arrive, or the monitoring action will be invoked after possible message
448	message loss has been detected. No messages will be lost "in between"	480	loss has been detected. No messages will be lost "in between" (after
449	(after the first lost message no further messages will be received by the	481	the first lost message no further messages will be received by the
450	port). After the monitoring action was invoked, further messages might get	482	port). After the monitoring action was invoked, further messages might get
451	delivered again.	483	delivered again.
452		484
453	Note that monitoring-actions are one-shot: once released, they are removed	485	Note that monitoring-actions are one-shot: once messages are lost (and a
454	and will not trigger again.	486	monitoring alert was raised), they are removed and will not trigger again.
455		487
456	In the first form (callback), the callback is simply called with any	488	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	489	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	490	"normally"). Note also that I<< the callback B<must> never die >>, so use
459	C<eval> if unsure.	491	C<eval> if unsure.
460		492
461	In the second form (another port given), the other port (C<$rcvport>)	493	In the second form (another port given), the other port (C<$rcvport>)
462	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	494	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
463	"normal" kils nothing happens, while under all other conditions, the other	495	"normal" kils nothing happens, while under all other conditions, the other
464	port is killed with the same reason.	496	port is killed with the same reason.
465		497
466	The third form (kill self) is the same as the second form, except that	498	The third form (kill self) is the same as the second form, except that
467	C<$rvport> defaults to C<$SELF>.	499	C<$rvport> defaults to C<$SELF>.
…		…
470	C<snd>.	502	C<snd>.
471		503
472	As a rule of thumb, monitoring requests should always monitor a port from	504	As a rule of thumb, monitoring requests should always monitor a port from
473	a local port (or callback). The reason is that kill messages might get	505	a local port (or callback). The reason is that kill messages might get
474	lost, just like any other message. Another less obvious reason is that	506	lost, just like any other message. Another less obvious reason is that
475	even monitoring requests can get lost (for exmaple, when the connection	507	even monitoring requests can get lost (for example, when the connection
476	to the other node goes down permanently). When monitoring a port locally	508	to the other node goes down permanently). When monitoring a port locally
477	these problems do not exist.	509	these problems do not exist.
478		510
479	Example: call a given callback when C<$port> is killed.	511	Example: call a given callback when C<$port> is killed.
480		512
…		…
489	mon $port, $self => "restart";	521	mon $port, $self => "restart";
490		522
491	=cut	523	=cut
492		524
493	sub mon {	525	sub mon {
494	my ($noderef, $port) = split /#/, shift, 2;	526	my ($nodeid, $port) = split /#/, shift, 2;
495		527
496	my $node = $NODE{$noderef} \|\| add_node $noderef;	528	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
497		529
498	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	530	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
499		531
500	unless (ref $cb) {	532	unless (ref $cb) {
501	if (@_) {	533	if (@_) {
…		…
521	is killed, the references will be freed.	553	is killed, the references will be freed.
522		554
523	Optionally returns a guard that will stop the monitoring.	555	Optionally returns a guard that will stop the monitoring.
524		556
525	This function is useful when you create e.g. timers or other watchers and	557	This function is useful when you create e.g. timers or other watchers and
526	want to free them when the port gets killed:	558	want to free them when the port gets killed (note the use of C<psub>):
527		559
528	$port->rcv (start => sub {	560	$port->rcv (start => sub {
529	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	561	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
530	undef $timer if 0.9 < rand;	562	undef $timer if 0.9 < rand;
531	});	563	});
532	});	564	});
533		565
534	=cut	566	=cut
…		…
543		575
544	=item kil $port[, @reason]	576	=item kil $port[, @reason]
545		577
546	Kill the specified port with the given C<@reason>.	578	Kill the specified port with the given C<@reason>.
547		579
548	If no C<@reason> is specified, then the port is killed "normally" (linked	580	If no C<@reason> is specified, then the port is killed "normally" (ports
549	ports will not be kileld, or even notified).	581	monitoring other ports will not necessarily die because a port dies
		582	"normally").
550		583
551	Otherwise, linked ports get killed with the same reason (second form of	584	Otherwise, linked ports get killed with the same reason (second form of
552	C<mon>, see below).	585	C<mon>, see above).
553		586
554	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	587	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
555	will be reported as reason C<< die => $@ >>.	588	will be reported as reason C<< die => $@ >>.
556		589
557	Transport/communication errors are reported as C<< transport_error =>	590	Transport/communication errors are reported as C<< transport_error =>
…		…
562	=item $port = spawn $node, $initfunc[, @initdata]	595	=item $port = spawn $node, $initfunc[, @initdata]
563		596
564	Creates a port on the node C<$node> (which can also be a port ID, in which	597	Creates a port on the node C<$node> (which can also be a port ID, in which
565	case it's the node where that port resides).	598	case it's the node where that port resides).
566		599
567	The port ID of the newly created port is return immediately, and it is	600	The port ID of the newly created port is returned immediately, and it is
568	permissible to immediately start sending messages or monitor the port.	601	possible to immediately start sending messages or to monitor the port.
569		602
570	After the port has been created, the init function is	603	After the port has been created, the init function is called on the remote
571	called. This function must be a fully-qualified function name	604	node, in the same context as a C<rcv> callback. This function must be a
572	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	605	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
573	program, use C<::name>.	606	specify a function in the main program, use C<::name>.
574		607
575	If the function doesn't exist, then the node tries to C<require>	608	If the function doesn't exist, then the node tries to C<require>
576	the package, then the package above the package and so on (e.g.	609	the package, then the package above the package and so on (e.g.
577	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	610	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
578	exists or it runs out of package names.	611	exists or it runs out of package names.
579		612
580	The init function is then called with the newly-created port as context	613	The init function is then called with the newly-created port as context
581	object (C<$SELF>) and the C<@initdata> values as arguments.	614	object (C<$SELF>) and the C<@initdata> values as arguments.
582		615
583	A common idiom is to pass your own port, monitor the spawned port, and	616	A common idiom is to pass a local port, immediately monitor the spawned
584	in the init function, monitor the original port. This two-way monitoring	617	port, and in the remote init function, immediately monitor the passed
585	ensures that both ports get cleaned up when there is a problem.	618	local port. This two-way monitoring ensures that both ports get cleaned up
		619	when there is a problem.
586		620
587	Example: spawn a chat server port on C<$othernode>.	621	Example: spawn a chat server port on C<$othernode>.
588		622
589	# this node, executed from within a port context:	623	# this node, executed from within a port context:
590	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	624	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
613	};	647	};
614	_self_die if $@;	648	_self_die if $@;
615	}	649	}
616		650
617	sub spawn(@) {	651	sub spawn(@) {
618	my ($noderef, undef) = split /#/, shift, 2;	652	my ($nodeid, undef) = split /#/, shift, 2;
619		653
620	my $id = "$RUNIQ." . $ID++;	654	my $id = "$RUNIQ." . $ID++;
621		655
622	$_[0] =~ /::/	656	$_[0] =~ /::/
623	or Carp::croak "spawn init function must be a fully-qualified name, caught";	657	or Carp::croak "spawn init function must be a fully-qualified name, caught";
624		658
625	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	659	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
626		660
627	"$noderef#$id"	661	"$nodeid#$id"
628	}	662	}
629		663
630	=item after $timeout, @msg	664	=item after $timeout, @msg
631		665
632	=item after $timeout, $callback	666	=item after $timeout, $callback
633		667
634	Either sends the given message, or call the given callback, after the	668	Either sends the given message, or call the given callback, after the
635	specified number of seconds.	669	specified number of seconds.
636		670
637	This is simply a utility function that come sin handy at times.	671	This is simply a utility function that comes in handy at times - the
		672	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		673	so it may go away in the future.
638		674
639	=cut	675	=cut
640		676
641	sub after($@) {	677	sub after($@) {
642	my ($timeout, @action) = @_;	678	my ($timeout, @action) = @_;
…		…
665		701
666	Despite the similarities, there are also some important differences:	702	Despite the similarities, there are also some important differences:
667		703
668	=over 4	704	=over 4
669		705
670	=item * Node references contain the recipe on how to contact them.	706	=item * Node IDs are arbitrary strings in AEMP.
671		707
672	Erlang relies on special naming and DNS to work everywhere in the	708	Erlang relies on special naming and DNS to work everywhere in the same
673	same way. AEMP relies on each node knowing it's own address(es), with	709	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
674	convenience functionality.	710	configuration or DNS), but will otherwise discover other odes itself.
675
676	This means that AEMP requires a less tightly controlled environment at the
677	cost of longer node references and a slightly higher management overhead.
678		711
679	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	712	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
680	uses "local ports are like remote ports".	713	uses "local ports are like remote ports".
681		714
682	The failure modes for local ports are quite different (runtime errors	715	The failure modes for local ports are quite different (runtime errors
…		…
695		728
696	Erlang uses processes that selectively receive messages, and therefore	729	Erlang uses processes that selectively receive messages, and therefore
697	needs a queue. AEMP is event based, queuing messages would serve no	730	needs a queue. AEMP is event based, queuing messages would serve no
698	useful purpose. For the same reason the pattern-matching abilities of	731	useful purpose. For the same reason the pattern-matching abilities of
699	AnyEvent::MP are more limited, as there is little need to be able to	732	AnyEvent::MP are more limited, as there is little need to be able to
700	filter messages without dequeing them.	733	filter messages without dequeuing them.
701		734
702	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	735	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
703		736
704	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	737	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
705		738
…		…
711		744
712	Erlang makes few guarantees on messages delivery - messages can get lost	745	Erlang makes few guarantees on messages delivery - messages can get lost
713	without any of the processes realising it (i.e. you send messages a, b,	746	without any of the processes realising it (i.e. you send messages a, b,
714	and c, and the other side only receives messages a and c).	747	and c, and the other side only receives messages a and c).
715		748
716	AEMP guarantees correct ordering, and the guarantee that there are no	749	AEMP guarantees correct ordering, and the guarantee that after one message
717	holes in the message sequence.	750	is lost, all following ones sent to the same port are lost as well, until
718		751	monitoring raises an error, so there are no silent "holes" in the message
719	=item * In Erlang, processes can be declared dead and later be found to be	752	sequence.
720	alive.
721
722	In Erlang it can happen that a monitored process is declared dead and
723	linked processes get killed, but later it turns out that the process is
724	still alive - and can receive messages.
725
726	In AEMP, when port monitoring detects a port as dead, then that port will
727	eventually be killed - it cannot happen that a node detects a port as dead
728	and then later sends messages to it, finding it is still alive.
729		753
730	=item * Erlang can send messages to the wrong port, AEMP does not.	754	=item * Erlang can send messages to the wrong port, AEMP does not.
731		755
732	In Erlang it is quite likely that a node that restarts reuses a process ID	756	In Erlang it is quite likely that a node that restarts reuses a process ID
733	known to other nodes for a completely different process, causing messages	757	known to other nodes for a completely different process, causing messages
…		…
737	around in the network will not be sent to an unrelated port.	761	around in the network will not be sent to an unrelated port.
738		762
739	=item * Erlang uses unprotected connections, AEMP uses secure	763	=item * Erlang uses unprotected connections, AEMP uses secure
740	authentication and can use TLS.	764	authentication and can use TLS.
741		765
742	AEMP can use a proven protocol - SSL/TLS - to protect connections and	766	AEMP can use a proven protocol - TLS - to protect connections and
743	securely authenticate nodes.	767	securely authenticate nodes.
744		768
745	=item * The AEMP protocol is optimised for both text-based and binary	769	=item * The AEMP protocol is optimised for both text-based and binary
746	communications.	770	communications.
747		771
748	The AEMP protocol, unlike the Erlang protocol, supports both	772	The AEMP protocol, unlike the Erlang protocol, supports both programming
749	language-independent text-only protocols (good for debugging) and binary,	773	language independent text-only protocols (good for debugging) and binary,
750	language-specific serialisers (e.g. Storable).	774	language-specific serialisers (e.g. Storable). By default, unless TLS is
		775	used, the protocol is actually completely text-based.
751		776
752	It has also been carefully designed to be implementable in other languages	777	It has also been carefully designed to be implementable in other languages
753	with a minimum of work while gracefully degrading fucntionality to make the	778	with a minimum of work while gracefully degrading functionality to make the
754	protocol simple.	779	protocol simple.
755		780
756	=item * AEMP has more flexible monitoring options than Erlang.	781	=item * AEMP has more flexible monitoring options than Erlang.
757		782
758	In Erlang, you can chose to receive I<all> exit signals as messages	783	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
761	Erlang, as one can choose between automatic kill, exit message or callback	786	Erlang, as one can choose between automatic kill, exit message or callback
762	on a per-process basis.	787	on a per-process basis.
763		788
764	=item * Erlang tries to hide remote/local connections, AEMP does not.	789	=item * Erlang tries to hide remote/local connections, AEMP does not.
765		790
766	Monitoring in Erlang is not an indicator of process death/crashes,	791	Monitoring in Erlang is not an indicator of process death/crashes, in the
767	as linking is (except linking is unreliable in Erlang).	792	same way as linking is (except linking is unreliable in Erlang).
768		793
769	In AEMP, you don't "look up" registered port names or send to named ports	794	In AEMP, you don't "look up" registered port names or send to named ports
770	that might or might not be persistent. Instead, you normally spawn a port	795	that might or might not be persistent. Instead, you normally spawn a port
771	on the remote node. The init function monitors the you, and you monitor	796	on the remote node. The init function monitors you, and you monitor the
772	the remote port. Since both monitors are local to the node, they are much	797	remote port. Since both monitors are local to the node, they are much more
773	more reliable.	798	reliable (no need for C<spawn_link>).
774		799
775	This also saves round-trips and avoids sending messages to the wrong port	800	This also saves round-trips and avoids sending messages to the wrong port
776	(hard to do in Erlang).	801	(hard to do in Erlang).
777		802
778	=back	803	=back
779		804
780	=head1 RATIONALE	805	=head1 RATIONALE
781		806
782	=over 4	807	=over 4
783		808
784	=item Why strings for ports and noderefs, why not objects?	809	=item Why strings for port and node IDs, why not objects?
785		810
786	We considered "objects", but found that the actual number of methods	811	We considered "objects", but found that the actual number of methods
787	thatc an be called are very low. Since port IDs and noderefs travel over	812	that can be called are quite low. Since port and node IDs travel over
788	the network frequently, the serialising/deserialising would add lots of	813	the network frequently, the serialising/deserialising would add lots of
789	overhead, as well as having to keep a proxy object.	814	overhead, as well as having to keep a proxy object everywhere.
790		815
791	Strings can easily be printed, easily serialised etc. and need no special	816	Strings can easily be printed, easily serialised etc. and need no special
792	procedures to be "valid".	817	procedures to be "valid".
793		818
794	And a a miniport consists of a single closure stored in a global hash - it	819	And as a result, a miniport consists of a single closure stored in a
795	can't become much cheaper.	820	global hash - it can't become much cheaper.
796		821
797	=item Why favour JSON, why not real serialising format such as Storable?	822	=item Why favour JSON, why not a real serialising format such as Storable?
798		823
799	In fact, any AnyEvent::MP node will happily accept Storable as framing	824	In fact, any AnyEvent::MP node will happily accept Storable as framing
800	format, but currently there is no way to make a node use Storable by	825	format, but currently there is no way to make a node use Storable by
801	default.	826	default (although all nodes will accept it).
802		827
803	The default framing protocol is JSON because a) JSON::XS is many times	828	The default framing protocol is JSON because a) JSON::XS is many times
804	faster for small messages and b) most importantly, after years of	829	faster for small messages and b) most importantly, after years of
805	experience we found that object serialisation is causing more problems	830	experience we found that object serialisation is causing more problems
806	than it gains: Just like function calls, objects simply do not travel	831	than it solves: Just like function calls, objects simply do not travel
807	easily over the network, mostly because they will always be a copy, so you	832	easily over the network, mostly because they will always be a copy, so you
808	always have to re-think your design.	833	always have to re-think your design.
809		834
810	Keeping your messages simple, concentrating on data structures rather than	835	Keeping your messages simple, concentrating on data structures rather than
811	objects, will keep your messages clean, tidy and efficient.	836	objects, will keep your messages clean, tidy and efficient.
812		837
813	=back	838	=back
814		839
815	=head1 SEE ALSO	840	=head1 SEE ALSO
816		841
		842	L<AnyEvent::MP::Intro> - a gentle introduction.
		843
		844	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		845
		846	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		847	your applications.
		848
817	L<AnyEvent>.	849	L<AnyEvent>.
818		850
819	=head1 AUTHOR	851	=head1 AUTHOR
820		852
821	Marc Lehmann <schmorp@schmorp.de>	853	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.77 by elmex, Thu Sep 3 07:57:30 2009 UTC