[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 1.79 by root, Fri Sep 4 21:52:09 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44	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - explains most concepts.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
…		…
114	are expected to be long-running, and at least one of those should always	109	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	110	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	111	error), they try to re-establish connections to some seednodes again to
117	join the network.	112	join the network.
118		113
		114	Apart from being sued for seeding, seednodes are not special in any way -
		115	every public node can be a seednode.
		116
119	=back	117	=back
120		118
121	=head1 VARIABLES/FUNCTIONS	119	=head1 VARIABLES/FUNCTIONS
122		120
123	=over 4	121	=over 4
…		…
138		136
139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	137	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
140		138
141	our @EXPORT = qw(	139	our @EXPORT = qw(
142	NODE $NODE *SELF node_of after	140	NODE $NODE *SELF node_of after
143	resolve_node initialise_node	141	configure
144	snd rcv mon mon_guard kil reg psub spawn	142	snd rcv mon mon_guard kil reg psub spawn
145	port	143	port
146	);	144	);
147		145
148	our $SELF;	146	our $SELF;
…		…
153	kil $SELF, die => $msg;	151	kil $SELF, die => $msg;
154	}	152	}
155		153
156	=item $thisnode = NODE / $NODE	154	=item $thisnode = NODE / $NODE
157		155
158	The C<NODE> function returns, and the C<$NODE> variable contains the node	156	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	157	ID of the node running in the current process. This value is initialised by
160	a call to C<initialise_node>.	158	a call to C<configure>.
161		159
162	=item $nodeid = node_of $port	160	=item $nodeid = node_of $port
163		161
164	Extracts and returns the node ID part from a port ID or a node ID.	162	Extracts and returns the node ID from a port ID or a node ID.
165		163
166	=item initialise_node $profile_name	164	=item configure $profile, key => value...
		165
		166	=item configure key => value...
167		167
168	Before a node can talk to other nodes on the network (i.e. enter	168	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	169	"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	170	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.	171	some other nodes in the network to discover other nodes.
172		172
173	This function initialises a node - it must be called exactly once (or	173	This function configures a node - it must be called exactly once (or
174	never) before calling other AnyEvent::MP functions.	174	never) before calling other AnyEvent::MP functions.
175		175
176	The first argument is a profile name. If it is C<undef> or missing, then	176	=over 4
177	the current nodename will be used instead (i.e. F<uname -n>).
178		177
		178	=item step 1, gathering configuration from profiles
		179
179	The function then looks up the profile in the aemp configuration (see the	180	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility).	181	L<aemp> commandline utility). The profile name can be specified via the
		182	named C<profile> parameter or can simply be the first parameter). If it is
		183	missing, then the nodename (F<uname -n>) will be used as profile name.
		184
		185	The profile data is then gathered as follows:
		186
		187	First, all remaining key => value pairs (all of which are conveniently
		188	undocumented at the moment) will be interpreted as configuration
		189	data. Then they will be overwritten by any values specified in the global
		190	default configuration (see the F<aemp> utility), then the chain of
		191	profiles chosen by the profile name (and any C<parent> attributes).
		192
		193	That means that the values specified in the profile have highest priority
		194	and the values specified directly via C<configure> have lowest priority,
		195	and can only be used to specify defaults.
181		196
182	If the profile specifies a node ID, then this will become the node ID of	197	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	198	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.	199	special node ID of C<anon/> will be replaced by a random node ID.
		200
		201	=item step 2, bind listener sockets
185		202
186	The next step is to look up the binds in the profile, followed by binding	203	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	204	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	205	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	206	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).	207	binds, but it can still talk to all "normal" nodes).
191		208
192	If the profile does not specify a binds list, then the node ID will be	209	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	210	used, meaning the node will bind on a dynamically-assigned port on every
194	used as binds list.	211	local IP address it finds.
195		212
		213	=item step 3, connect to seed nodes
		214
196	Lastly, the seeds list from the profile is passed to the	215	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	216	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.	217	connectivity with at least one node at any point in time.
199		218
200	Example: become a distributed node listening on the guessed noderef, or	219	=back
201	the one specified via C<aemp> for the current node. This should be the	220
		221	Example: become a distributed node using the locla node name as profile.
202	most common form of invocation for "daemon"-type nodes.	222	This should be the most common form of invocation for "daemon"-type nodes.
203		223
204	initialise_node;	224	configure
205		225
206	Example: become an anonymous node. This form is often used for commandline	226	Example: become an anonymous node. This form is often used for commandline
207	clients.	227	clients.
208		228
209	initialise_node "anon/";	229	configure nodeid => "anon/";
210		230
211	Example: become a distributed node. If there is no profile of the given	231	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	232	for a seed node as it binds on all local addresses on a fixed port (4040,
213	on the resulting addresses.	233	customary for aemp).
214		234
215	initialise_node "localhost:4044";	235	# use the aemp commandline utility
		236	# aemp profile seed nodeid anon/ binds '*:4040'
		237
		238	# then use it
		239	configure profile => "seed";
		240
		241	# or simply use aemp from the shell again:
		242	# aemp run profile seed
		243
		244	# or provide a nicer-to-remember nodeid
		245	# aemp run profile seed nodeid "$(hostname)"
216		246
217	=item $SELF	247	=item $SELF
218		248
219	Contains the current port id while executing C<rcv> callbacks or C<psub>	249	Contains the current port id while executing C<rcv> callbacks or C<psub>
220	blocks.	250	blocks.
221		251
222	=item SELF, %SELF, @SELF...	252	=item *SELF, SELF, %SELF, @SELF...
223		253
224	Due to some quirks in how perl exports variables, it is impossible to	254	Due to some quirks in how perl exports variables, it is impossible to
225	just export C<$SELF>, all the symbols called C<SELF> are exported by this	255	just export C<$SELF>, all the symbols named C<SELF> are exported by this
226	module, but only C<$SELF> is currently used.	256	module, but only C<$SELF> is currently used.
227		257
228	=item snd $port, type => @data	258	=item snd $port, type => @data
229		259
230	=item snd $port, @msg	260	=item snd $port, @msg
231		261
232	Send the given message to the given port ID, which can identify either	262	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.	263	local or a remote port, and must be a port ID.
234		264
235	While the message can be about anything, it is highly recommended to use a	265	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	266	use a string as first element (a port ID, or some word that indicates a
237	type etc.).	267	request type etc.) and to consist if only simple perl values (scalars,
		268	arrays, hashes) - if you think you need to pass an object, think again.
238		269
239	The message data effectively becomes read-only after a call to this	270	The message data logically becomes read-only after a call to this
240	function: modifying any argument is not allowed and can cause many	271	function: modifying any argument (or values referenced by them) is
241	problems.	272	forbidden, as there can be considerable time between the call to C<snd>
		273	and the time the message is actually being serialised - in fact, it might
		274	never be copied as within the same process it is simply handed to the
		275	receiving port.
242		276
243	The type of data you can transfer depends on the transport protocol: when	277	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	278	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	279	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	280	that Storable can serialise and deserialise is allowed, and for the local
247	node, anything can be passed.	281	node, anything can be passed. Best rely only on the common denominator of
		282	these.
248		283
249	=item $local_port = port	284	=item $local_port = port
250		285
251	Create a new local port object and returns its port ID. Initially it has	286	Create a new local port object and returns its port ID. Initially it has
252	no callbacks set and will throw an error when it receives messages.	287	no callbacks set and will throw an error when it receives messages.
…		…
337		372
338	=cut	373	=cut
339		374
340	sub rcv($@) {	375	sub rcv($@) {
341	my $port = shift;	376	my $port = shift;
342	my ($noderef, $portid) = split /#/, $port, 2;	377	my ($nodeid, $portid) = split /#/, $port, 2;
343		378
344	$NODE{$noderef} == $NODE{""}	379	$NODE{$nodeid} == $NODE{""}
345	or Carp::croak "$port: rcv can only be called on local ports, caught";	380	or Carp::croak "$port: rcv can only be called on local ports, caught";
346		381
347	while (@_) {	382	while (@_) {
348	if (ref $_[0]) {	383	if (ref $_[0]) {
349	if (my $self = $PORT_DATA{$portid}) {	384	if (my $self = $PORT_DATA{$portid}) {
…		…
428	$res	463	$res
429	}	464	}
430	}	465	}
431	}	466	}
432		467
433	=item $guard = mon $port, $cb->(@reason)	468	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
434		469
435	=item $guard = mon $port, $rcvport	470	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
436		471
437	=item $guard = mon $port	472	=item $guard = mon $port # kill $SELF when $port dies
438		473
439	=item $guard = mon $port, $rcvport, @msg	474	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
440		475
441	Monitor the given port and do something when the port is killed or	476	Monitor the given port and do something when the port is killed or
442	messages to it were lost, and optionally return a guard that can be used	477	messages to it were lost, and optionally return a guard that can be used
443	to stop monitoring again.	478	to stop monitoring again.
444
445	C<mon> effectively guarantees that, in the absence of hardware failures,
446	that after starting the monitor, either all messages sent to the port
447	will arrive, or the monitoring action will be invoked after possible
448	message loss has been detected. No messages will be lost "in between"
449	(after the first lost message no further messages will be received by the
450	port). After the monitoring action was invoked, further messages might get
451	delivered again.
452
453	Note that monitoring-actions are one-shot: once released, they are removed
454	and will not trigger again.
455		479
456	In the first form (callback), the callback is simply called with any	480	In the first form (callback), the callback is simply called with any
457	number of C<@reason> elements (no @reason means that the port was deleted	481	number of C<@reason> elements (no @reason means that the port was deleted
458	"normally"). Note also that I<< the callback B<must> never die >>, so use	482	"normally"). Note also that I<< the callback B<must> never die >>, so use
459	C<eval> if unsure.	483	C<eval> if unsure.
460		484
461	In the second form (another port given), the other port (C<$rcvport>)	485	In the second form (another port given), the other port (C<$rcvport>)
462	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	486	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
463	"normal" kils nothing happens, while under all other conditions, the other	487	"normal" kils nothing happens, while under all other conditions, the other
464	port is killed with the same reason.	488	port is killed with the same reason.
465		489
466	The third form (kill self) is the same as the second form, except that	490	The third form (kill self) is the same as the second form, except that
467	C<$rvport> defaults to C<$SELF>.	491	C<$rvport> defaults to C<$SELF>.
468		492
469	In the last form (message), a message of the form C<@msg, @reason> will be	493	In the last form (message), a message of the form C<@msg, @reason> will be
470	C<snd>.	494	C<snd>.
		495
		496	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		497	alert was raised), they are removed and will not trigger again.
471		498
472	As a rule of thumb, monitoring requests should always monitor a port from	499	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	500	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	501	lost, just like any other message. Another less obvious reason is that
475	even monitoring requests can get lost (for exmaple, when the connection	502	even monitoring requests can get lost (for example, when the connection
476	to the other node goes down permanently). When monitoring a port locally	503	to the other node goes down permanently). When monitoring a port locally
477	these problems do not exist.	504	these problems do not exist.
478		505
		506	C<mon> effectively guarantees that, in the absence of hardware failures,
		507	after starting the monitor, either all messages sent to the port will
		508	arrive, or the monitoring action will be invoked after possible message
		509	loss has been detected. No messages will be lost "in between" (after
		510	the first lost message no further messages will be received by the
		511	port). After the monitoring action was invoked, further messages might get
		512	delivered again.
		513
		514	Inter-host-connection timeouts and monitoring depend on the transport
		515	used. The only transport currently implemented is TCP, and AnyEvent::MP
		516	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		517	non-idle connection, and usually around two hours for idle conenctions).
		518
		519	This means that monitoring is good for program errors and cleaning up
		520	stuff eventually, but they are no replacement for a timeout when you need
		521	to ensure some maximum latency.
		522
479	Example: call a given callback when C<$port> is killed.	523	Example: call a given callback when C<$port> is killed.
480		524
481	mon $port, sub { warn "port died because of <@_>\n" };	525	mon $port, sub { warn "port died because of <@_>\n" };
482		526
483	Example: kill ourselves when C<$port> is killed abnormally.	527	Example: kill ourselves when C<$port> is killed abnormally.
…		…
489	mon $port, $self => "restart";	533	mon $port, $self => "restart";
490		534
491	=cut	535	=cut
492		536
493	sub mon {	537	sub mon {
494	my ($noderef, $port) = split /#/, shift, 2;	538	my ($nodeid, $port) = split /#/, shift, 2;
495		539
496	my $node = $NODE{$noderef} \|\| add_node $noderef;	540	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
497		541
498	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	542	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
499		543
500	unless (ref $cb) {	544	unless (ref $cb) {
501	if (@_) {	545	if (@_) {
…		…
521	is killed, the references will be freed.	565	is killed, the references will be freed.
522		566
523	Optionally returns a guard that will stop the monitoring.	567	Optionally returns a guard that will stop the monitoring.
524		568
525	This function is useful when you create e.g. timers or other watchers and	569	This function is useful when you create e.g. timers or other watchers and
526	want to free them when the port gets killed:	570	want to free them when the port gets killed (note the use of C<psub>):
527		571
528	$port->rcv (start => sub {	572	$port->rcv (start => sub {
529	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	573	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
530	undef $timer if 0.9 < rand;	574	undef $timer if 0.9 < rand;
531	});	575	});
532	});	576	});
533		577
534	=cut	578	=cut
…		…
543		587
544	=item kil $port[, @reason]	588	=item kil $port[, @reason]
545		589
546	Kill the specified port with the given C<@reason>.	590	Kill the specified port with the given C<@reason>.
547		591
548	If no C<@reason> is specified, then the port is killed "normally" (linked	592	If no C<@reason> is specified, then the port is killed "normally" (ports
549	ports will not be kileld, or even notified).	593	monitoring other ports will not necessarily die because a port dies
		594	"normally").
550		595
551	Otherwise, linked ports get killed with the same reason (second form of	596	Otherwise, linked ports get killed with the same reason (second form of
552	C<mon>, see below).	597	C<mon>, see above).
553		598
554	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	599	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
555	will be reported as reason C<< die => $@ >>.	600	will be reported as reason C<< die => $@ >>.
556		601
557	Transport/communication errors are reported as C<< transport_error =>	602	Transport/communication errors are reported as C<< transport_error =>
…		…
562	=item $port = spawn $node, $initfunc[, @initdata]	607	=item $port = spawn $node, $initfunc[, @initdata]
563		608
564	Creates a port on the node C<$node> (which can also be a port ID, in which	609	Creates a port on the node C<$node> (which can also be a port ID, in which
565	case it's the node where that port resides).	610	case it's the node where that port resides).
566		611
567	The port ID of the newly created port is return immediately, and it is	612	The port ID of the newly created port is returned immediately, and it is
568	permissible to immediately start sending messages or monitor the port.	613	possible to immediately start sending messages or to monitor the port.
569		614
570	After the port has been created, the init function is	615	After the port has been created, the init function is called on the remote
571	called. This function must be a fully-qualified function name	616	node, in the same context as a C<rcv> callback. This function must be a
572	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	617	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
573	program, use C<::name>.	618	specify a function in the main program, use C<::name>.
574		619
575	If the function doesn't exist, then the node tries to C<require>	620	If the function doesn't exist, then the node tries to C<require>
576	the package, then the package above the package and so on (e.g.	621	the package, then the package above the package and so on (e.g.
577	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	622	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
578	exists or it runs out of package names.	623	exists or it runs out of package names.
579		624
580	The init function is then called with the newly-created port as context	625	The init function is then called with the newly-created port as context
581	object (C<$SELF>) and the C<@initdata> values as arguments.	626	object (C<$SELF>) and the C<@initdata> values as arguments.
582		627
583	A common idiom is to pass your own port, monitor the spawned port, and	628	A common idiom is to pass a local port, immediately monitor the spawned
584	in the init function, monitor the original port. This two-way monitoring	629	port, and in the remote init function, immediately monitor the passed
585	ensures that both ports get cleaned up when there is a problem.	630	local port. This two-way monitoring ensures that both ports get cleaned up
		631	when there is a problem.
586		632
587	Example: spawn a chat server port on C<$othernode>.	633	Example: spawn a chat server port on C<$othernode>.
588		634
589	# this node, executed from within a port context:	635	# this node, executed from within a port context:
590	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	636	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
613	};	659	};
614	_self_die if $@;	660	_self_die if $@;
615	}	661	}
616		662
617	sub spawn(@) {	663	sub spawn(@) {
618	my ($noderef, undef) = split /#/, shift, 2;	664	my ($nodeid, undef) = split /#/, shift, 2;
619		665
620	my $id = "$RUNIQ." . $ID++;	666	my $id = "$RUNIQ." . $ID++;
621		667
622	$_[0] =~ /::/	668	$_[0] =~ /::/
623	or Carp::croak "spawn init function must be a fully-qualified name, caught";	669	or Carp::croak "spawn init function must be a fully-qualified name, caught";
624		670
625	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	671	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
626		672
627	"$noderef#$id"	673	"$nodeid#$id"
628	}	674	}
629		675
630	=item after $timeout, @msg	676	=item after $timeout, @msg
631		677
632	=item after $timeout, $callback	678	=item after $timeout, $callback
633		679
634	Either sends the given message, or call the given callback, after the	680	Either sends the given message, or call the given callback, after the
635	specified number of seconds.	681	specified number of seconds.
636		682
637	This is simply a utility function that come sin handy at times.	683	This is simply a utility function that comes in handy at times - the
		684	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		685	so it may go away in the future.
638		686
639	=cut	687	=cut
640		688
641	sub after($@) {	689	sub after($@) {
642	my ($timeout, @action) = @_;	690	my ($timeout, @action) = @_;
…		…
665		713
666	Despite the similarities, there are also some important differences:	714	Despite the similarities, there are also some important differences:
667		715
668	=over 4	716	=over 4
669		717
670	=item * Node references contain the recipe on how to contact them.	718	=item * Node IDs are arbitrary strings in AEMP.
671		719
672	Erlang relies on special naming and DNS to work everywhere in the	720	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	721	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
674	convenience functionality.	722	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		723
679	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	724	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
680	uses "local ports are like remote ports".	725	uses "local ports are like remote ports".
681		726
682	The failure modes for local ports are quite different (runtime errors	727	The failure modes for local ports are quite different (runtime errors
…		…
695		740
696	Erlang uses processes that selectively receive messages, and therefore	741	Erlang uses processes that selectively receive messages, and therefore
697	needs a queue. AEMP is event based, queuing messages would serve no	742	needs a queue. AEMP is event based, queuing messages would serve no
698	useful purpose. For the same reason the pattern-matching abilities of	743	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	744	AnyEvent::MP are more limited, as there is little need to be able to
700	filter messages without dequeing them.	745	filter messages without dequeuing them.
701		746
702	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	747	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
703		748
704	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	749	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
705		750
…		…
711		756
712	Erlang makes few guarantees on messages delivery - messages can get lost	757	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,	758	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).	759	and c, and the other side only receives messages a and c).
715		760
716	AEMP guarantees correct ordering, and the guarantee that there are no	761	AEMP guarantees correct ordering, and the guarantee that after one message
717	holes in the message sequence.	762	is lost, all following ones sent to the same port are lost as well, until
718		763	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	764	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		765
730	=item * Erlang can send messages to the wrong port, AEMP does not.	766	=item * Erlang can send messages to the wrong port, AEMP does not.
731		767
732	In Erlang it is quite likely that a node that restarts reuses a process ID	768	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	769	known to other nodes for a completely different process, causing messages
…		…
737	around in the network will not be sent to an unrelated port.	773	around in the network will not be sent to an unrelated port.
738		774
739	=item * Erlang uses unprotected connections, AEMP uses secure	775	=item * Erlang uses unprotected connections, AEMP uses secure
740	authentication and can use TLS.	776	authentication and can use TLS.
741		777
742	AEMP can use a proven protocol - SSL/TLS - to protect connections and	778	AEMP can use a proven protocol - TLS - to protect connections and
743	securely authenticate nodes.	779	securely authenticate nodes.
744		780
745	=item * The AEMP protocol is optimised for both text-based and binary	781	=item * The AEMP protocol is optimised for both text-based and binary
746	communications.	782	communications.
747		783
748	The AEMP protocol, unlike the Erlang protocol, supports both	784	The AEMP protocol, unlike the Erlang protocol, supports both programming
749	language-independent text-only protocols (good for debugging) and binary,	785	language independent text-only protocols (good for debugging) and binary,
750	language-specific serialisers (e.g. Storable).	786	language-specific serialisers (e.g. Storable). By default, unless TLS is
		787	used, the protocol is actually completely text-based.
751		788
752	It has also been carefully designed to be implementable in other languages	789	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	790	with a minimum of work while gracefully degrading functionality to make the
754	protocol simple.	791	protocol simple.
755		792
756	=item * AEMP has more flexible monitoring options than Erlang.	793	=item * AEMP has more flexible monitoring options than Erlang.
757		794
758	In Erlang, you can chose to receive I<all> exit signals as messages	795	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	798	Erlang, as one can choose between automatic kill, exit message or callback
762	on a per-process basis.	799	on a per-process basis.
763		800
764	=item * Erlang tries to hide remote/local connections, AEMP does not.	801	=item * Erlang tries to hide remote/local connections, AEMP does not.
765		802
766	Monitoring in Erlang is not an indicator of process death/crashes,	803	Monitoring in Erlang is not an indicator of process death/crashes, in the
767	as linking is (except linking is unreliable in Erlang).	804	same way as linking is (except linking is unreliable in Erlang).
768		805
769	In AEMP, you don't "look up" registered port names or send to named ports	806	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	807	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	808	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	809	remote port. Since both monitors are local to the node, they are much more
773	more reliable.	810	reliable (no need for C<spawn_link>).
774		811
775	This also saves round-trips and avoids sending messages to the wrong port	812	This also saves round-trips and avoids sending messages to the wrong port
776	(hard to do in Erlang).	813	(hard to do in Erlang).
777		814
778	=back	815	=back
779		816
780	=head1 RATIONALE	817	=head1 RATIONALE
781		818
782	=over 4	819	=over 4
783		820
784	=item Why strings for ports and noderefs, why not objects?	821	=item Why strings for port and node IDs, why not objects?
785		822
786	We considered "objects", but found that the actual number of methods	823	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	824	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	825	the network frequently, the serialising/deserialising would add lots of
789	overhead, as well as having to keep a proxy object.	826	overhead, as well as having to keep a proxy object everywhere.
790		827
791	Strings can easily be printed, easily serialised etc. and need no special	828	Strings can easily be printed, easily serialised etc. and need no special
792	procedures to be "valid".	829	procedures to be "valid".
793		830
794	And a a miniport consists of a single closure stored in a global hash - it	831	And as a result, a miniport consists of a single closure stored in a
795	can't become much cheaper.	832	global hash - it can't become much cheaper.
796		833
797	=item Why favour JSON, why not real serialising format such as Storable?	834	=item Why favour JSON, why not a real serialising format such as Storable?
798		835
799	In fact, any AnyEvent::MP node will happily accept Storable as framing	836	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	837	format, but currently there is no way to make a node use Storable by
801	default.	838	default (although all nodes will accept it).
802		839
803	The default framing protocol is JSON because a) JSON::XS is many times	840	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	841	faster for small messages and b) most importantly, after years of
805	experience we found that object serialisation is causing more problems	842	experience we found that object serialisation is causing more problems
806	than it gains: Just like function calls, objects simply do not travel	843	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	844	easily over the network, mostly because they will always be a copy, so you
808	always have to re-think your design.	845	always have to re-think your design.
809		846
810	Keeping your messages simple, concentrating on data structures rather than	847	Keeping your messages simple, concentrating on data structures rather than
811	objects, will keep your messages clean, tidy and efficient.	848	objects, will keep your messages clean, tidy and efficient.
812		849
813	=back	850	=back
814		851
815	=head1 SEE ALSO	852	=head1 SEE ALSO
816		853
		854	L<AnyEvent::MP::Intro> - a gentle introduction.
		855
		856	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		857
		858	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		859	your applications.
		860
817	L<AnyEvent>.	861	L<AnyEvent>.
818		862
819	=head1 AUTHOR	863	=head1 AUTHOR
820		864
821	Marc Lehmann <schmorp@schmorp.de>	865	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.64 by root, Fri Aug 28 00:58:44 2009 UTC vs.
Revision 1.79 by root, Fri Sep 4 21:52:09 2009 UTC