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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.10 by root, Sun Aug 2 18:05:43 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 # returns this node identifier
10	$NODE # contains this node identifier	9	$NODE # contains this node's node ID
		10	NODE # returns this node's node ID
11		11
		12	$SELF # receiving/own port id in rcv callbacks
		13
		14	# initialise the node so it can send/receive messages
		15	configure;
		16
		17	# ports are message destinations
		18
		19	# sending messages
12	snd $port, type => data...;	20	snd $port, type => data...;
		21	snd $port, @msg;
		22	snd @msg_with_first_element_being_a_port;
13		23
14	rcv $port, smartmatch => $cb->($port, @msg);	24	# creating/using ports, the simple way
		25	my $simple_port = port { my @msg = @_ };
15		26
16	# examples:	27	# creating/using ports, tagged message matching
		28	my $port = port;
17	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
18	rcv $port1, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
19	snd $port2, ping => $port1;
20		31
21	# more, smarter, matches (_any_ is exported by this module)	32	# create a port on another node
22	rcv $port, [child_died => $pid] => sub { ...	33	my $port = spawn $node, $initfunc, @initdata;
23	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	34
		35	# monitoring
		36	mon $port, $cb->(@msg) # callback is invoked on death
		37	mon $port, $otherport # kill otherport on abnormal death
		38	mon $port, $otherport, @msg # send message on death
		39
		40	=head1 CURRENT STATUS
		41
		42	bin/aemp - stable.
		43	AnyEvent::MP - stable API, should work.
		44	AnyEvent::MP::Intro - explains most concepts.
		45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable API, protocol not yet final.
		47
		48	stay tuned.
24		49
25	=head1 DESCRIPTION	50	=head1 DESCRIPTION
26		51
27	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
28		53
29	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
30	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
31		56
32	At the moment, this module family is severly brokena nd underdocumented,	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
33	so do not use. This was uploaded mainly to resreve the CPAN namespace -	58	manual page and the examples under F<eg/>.
34	stay tuned!
35		59
36	=head1 CONCEPTS	60	=head1 CONCEPTS
37		61
38	=over 4	62	=over 4
39		63
40	=item port	64	=item port
41		65
42	A port is something you can send messages to with the C<snd> function, and	66	A port is something you can send messages to (with the C<snd> function).
43	you can register C<rcv> handlers with. All C<rcv> handlers will receive
44	messages they match, messages will not be queued.
45		67
		68	Ports allow you to register C<rcv> handlers that can match all or just
		69	some messages. Messages send to ports will not be queued, regardless of
		70	anything was listening for them or not.
		71
46	=item port id - C<noderef#portname>	72	=item port ID - C<nodeid#portname>
47		73
48	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	74	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
49	by a port name (a printable string of unspecified format).	75	separator, and a port name (a printable string of unspecified format).
50		76
51	=item node	77	=item node
52		78
53	A node is a single process containing at least one port - the node	79	A node is a single process containing at least one port - the node port,
54	port. You can send messages to node ports to let them create new ports,	80	which enables nodes to manage each other remotely, and to create new
55	among other things.	81	ports.
56		82
57	Initially, nodes are either private (single-process only) or hidden	83	Nodes are either public (have one or more listening ports) or private
58	(connected to a master node only). Only when they epxlicitly "become	84	(no listening ports). Private nodes cannot talk to other private nodes
59	public" can you send them messages from unrelated other nodes.	85	currently.
60		86
61	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	87	=item node ID - C<[a-za-Z0-9_\-.:]+>
62		88
63	A noderef is a string that either uniquely identifies a given node (for	89	A node ID is a string that uniquely identifies the node within a
64	private and hidden nodes), or contains a recipe on how to reach a given	90	network. Depending on the configuration used, node IDs can look like a
65	node (for public nodes).	91	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		92	doesn't interpret node IDs in any way.
		93
		94	=item binds - C<ip:port>
		95
		96	Nodes can only talk to each other by creating some kind of connection to
		97	each other. To do this, nodes should listen on one or more local transport
		98	endpoints - binds. Currently, only standard C<ip:port> specifications can
		99	be used, which specify TCP ports to listen on.
		100
		101	=item seeds - C<host:port>
		102
		103	When a node starts, it knows nothing about the network. To teach the node
		104	about the network it first has to contact some other node within the
		105	network. This node is called a seed.
		106
		107	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		108	are expected to be long-running, and at least one of those should always
		109	be available. When nodes run out of connections (e.g. due to a network
		110	error), they try to re-establish connections to some seednodes again to
		111	join the network.
		112
		113	Apart from being sued for seeding, seednodes are not special in any way -
		114	every public node can be a seednode.
66		115
67	=back	116	=back
68		117
69	=head1 VARIABLES/FUNCTIONS	118	=head1 VARIABLES/FUNCTIONS
70		119
…		…
72		121
73	=cut	122	=cut
74		123
75	package AnyEvent::MP;	124	package AnyEvent::MP;
76		125
77	use AnyEvent::MP::Base;	126	use AnyEvent::MP::Kernel;
78		127
79	use common::sense;	128	use common::sense;
80		129
81	use Carp ();	130	use Carp ();
82		131
83	use AE ();	132	use AE ();
84		133
85	use base "Exporter";	134	use base "Exporter";
86		135
87	our $VERSION = '0.02';	136	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		137
88	our @EXPORT = qw(	138	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv _any_	139	NODE $NODE *SELF node_of after
90	create_port create_port_on	140	configure
91	become_slave become_public	141	snd rcv mon mon_guard kil reg psub spawn
		142	port
92	);	143	);
93		144
		145	our $SELF;
		146
		147	sub _self_die() {
		148	my $msg = $@;
		149	$msg =~ s/\n+$// unless ref $msg;
		150	kil $SELF, die => $msg;
		151	}
		152
94	=item NODE / $NODE	153	=item $thisnode = NODE / $NODE
95		154
96	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	155	The C<NODE> function returns, and the C<$NODE> variable contains, the node
97	the local node. The value is initialised by a call to C<become_public> or	156	ID of the node running in the current process. This value is initialised by
98	C<become_slave>, after which all local port identifiers become invalid.	157	a call to C<configure>.
99		158
		159	=item $nodeid = node_of $port
		160
		161	Extracts and returns the node ID from a port ID or a node ID.
		162
		163	=item configure key => value...
		164
		165	Before a node can talk to other nodes on the network (i.e. enter
		166	"distributed mode") it has to configure itself - the minimum a node needs
		167	to know is its own name, and optionally it should know the addresses of
		168	some other nodes in the network to discover other nodes.
		169
		170	This function configures a node - it must be called exactly once (or
		171	never) before calling other AnyEvent::MP functions.
		172
		173	=over 4
		174
		175	=item step 1, gathering configuration from profiles
		176
		177	The function first looks up a profile in the aemp configuration (see the
		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.
		193
		194	If the profile specifies a node ID, then this will become the node ID of
		195	this process. If not, then the profile name will be used as node ID. The
		196	special node ID of C<anon/> will be replaced by a random node ID.
		197
		198	=item step 2, bind listener sockets
		199
		200	The next step is to look up the binds in the profile, followed by binding
		201	aemp protocol listeners on all binds specified (it is possible and valid
		202	to have no binds, meaning that the node cannot be contacted form the
		203	outside. This means the node cannot talk to other nodes that also have no
		204	binds, but it can still talk to all "normal" nodes).
		205
		206	If the profile does not specify a binds list, then a default of C<*> is
		207	used, meaning the node will bind on a dynamically-assigned port on every
		208	local IP address it finds.
		209
		210	=item step 3, connect to seed nodes
		211
		212	As the last step, the seeds list from the profile is passed to the
		213	L<AnyEvent::MP::Global> module, which will then use it to keep
		214	connectivity with at least one node at any point in time.
		215
		216	=back
		217
		218	Example: become a distributed node using the locla node name as profile.
		219	This should be the most common form of invocation for "daemon"-type nodes.
		220
		221	configure
		222
		223	Example: become an anonymous node. This form is often used for commandline
		224	clients.
		225
		226	configure nodeid => "anon/";
		227
		228	Example: configure a node using a profile called seed, which si suitable
		229	for a seed node as it binds on all local addresses on a fixed port (4040,
		230	customary for aemp).
		231
		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)"
		243
		244	=item $SELF
		245
		246	Contains the current port id while executing C<rcv> callbacks or C<psub>
		247	blocks.
		248
		249	=item *SELF, SELF, %SELF, @SELF...
		250
		251	Due to some quirks in how perl exports variables, it is impossible to
		252	just export C<$SELF>, all the symbols named C<SELF> are exported by this
		253	module, but only C<$SELF> is currently used.
		254
100	=item snd $portid, type => @data	255	=item snd $port, type => @data
101		256
102	=item snd $portid, @msg	257	=item snd $port, @msg
103		258
104	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
105	a local or a remote port, and can be either a string or soemthignt hat	260	local or a remote port, and must be a port ID.
106	stringifies a sa port ID (such as a port object :).
107		261
108	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
109	string as first element (a portid, or some word that indicates a request	263	use a string as first element (a port ID, or some word that indicates a
110	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.
111		266
112	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
113	function: modifying any argument is not allowed and can cause many	268	function: modifying any argument (or values referenced by them) is
114	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.
115		273
116	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
117	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
118	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
119	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
120	node, anything can be passed.	278	node, anything can be passed. Best rely only on the common denominator of
		279	these.
121		280
122	=item $local_port = create_port	281	=item $local_port = port
123		282
124	Create a new local port object. See the next section for allowed methods.	283	Create a new local port object and returns its port ID. Initially it has
		284	no callbacks set and will throw an error when it receives messages.
125		285
126	=cut	286	=item $local_port = port { my @msg = @_ }
127		287
128	sub create_port {	288	Creates a new local port, and returns its ID. Semantically the same as
129	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;	289	creating a port and calling C<rcv $port, $callback> on it.
130		290
131	my $self = bless {	291	The block will be called for every message received on the port, with the
132	id => "$NODE#$id",	292	global variable C<$SELF> set to the port ID. Runtime errors will cause the
133	names => [$id],	293	port to be C<kil>ed. The message will be passed as-is, no extra argument
134	}, "AnyEvent::MP::Port";	294	(i.e. no port ID) will be passed to the callback.
135		295
136	$AnyEvent::MP::Base::PORT{$id} = sub {	296	If you want to stop/destroy the port, simply C<kil> it:
137	unshift @_, $self;
138		297
139	for (@{ $self->{rc0}{$_[1]} }) {	298	my $port = port {
140	$_ && &{$_->[0]}	299	my @msg = @_;
141	&& undef $_;	300	...
		301	kil $SELF;
		302	};
		303
		304	=cut
		305
		306	sub rcv($@);
		307
		308	sub _kilme {
		309	die "received message on port without callback";
		310	}
		311
		312	sub port(;&) {
		313	my $id = "$UNIQ." . $ID++;
		314	my $port = "$NODE#$id";
		315
		316	rcv $port, shift \|\| \&_kilme;
		317
		318	$port
		319	}
		320
		321	=item rcv $local_port, $callback->(@msg)
		322
		323	Replaces the default callback on the specified port. There is no way to
		324	remove the default callback: use C<sub { }> to disable it, or better
		325	C<kil> the port when it is no longer needed.
		326
		327	The global C<$SELF> (exported by this module) contains C<$port> while
		328	executing the callback. Runtime errors during callback execution will
		329	result in the port being C<kil>ed.
		330
		331	The default callback received all messages not matched by a more specific
		332	C<tag> match.
		333
		334	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		335
		336	Register (or replace) callbacks to be called on messages starting with the
		337	given tag on the given port (and return the port), or unregister it (when
		338	C<$callback> is C<$undef> or missing). There can only be one callback
		339	registered for each tag.
		340
		341	The original message will be passed to the callback, after the first
		342	element (the tag) has been removed. The callback will use the same
		343	environment as the default callback (see above).
		344
		345	Example: create a port and bind receivers on it in one go.
		346
		347	my $port = rcv port,
		348	msg1 => sub { ... },
		349	msg2 => sub { ... },
		350	;
		351
		352	Example: create a port, bind receivers and send it in a message elsewhere
		353	in one go:
		354
		355	snd $otherport, reply =>
		356	rcv port,
		357	msg1 => sub { ... },
		358	...
		359	;
		360
		361	Example: temporarily register a rcv callback for a tag matching some port
		362	(e.g. for a rpc reply) and unregister it after a message was received.
		363
		364	rcv $port, $otherport => sub {
		365	my @reply = @_;
		366
		367	rcv $SELF, $otherport;
		368	};
		369
		370	=cut
		371
		372	sub rcv($@) {
		373	my $port = shift;
		374	my ($nodeid, $portid) = split /#/, $port, 2;
		375
		376	$NODE{$nodeid} == $NODE{""}
		377	or Carp::croak "$port: rcv can only be called on local ports, caught";
		378
		379	while (@_) {
		380	if (ref $_[0]) {
		381	if (my $self = $PORT_DATA{$portid}) {
		382	"AnyEvent::MP::Port" eq ref $self
		383	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		384
		385	$self->[2] = shift;
		386	} else {
		387	my $cb = shift;
		388	$PORT{$portid} = sub {
		389	local $SELF = $port;
		390	eval { &$cb }; _self_die if $@;
		391	};
		392	}
		393	} elsif (defined $_[0]) {
		394	my $self = $PORT_DATA{$portid} \|\|= do {
		395	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		396
		397	$PORT{$portid} = sub {
		398	local $SELF = $port;
		399
		400	if (my $cb = $self->[1]{$_[0]}) {
		401	shift;
		402	eval { &$cb }; _self_die if $@;
		403	} else {
		404	&{ $self->[0] };
		405	}
		406	};
		407
		408	$self
		409	};
		410
		411	"AnyEvent::MP::Port" eq ref $self
		412	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		413
		414	my ($tag, $cb) = splice @_, 0, 2;
		415
		416	if (defined $cb) {
		417	$self->[1]{$tag} = $cb;
		418	} else {
		419	delete $self->[1]{$tag};
		420	}
142	}	421	}
		422	}
143		423
144	for (@{ $self->{rcv}{$_[1]} }) {	424	$port
145	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	425	}
146	&& &{$_->[0]}	426
147	&& undef $_;	427	=item $closure = psub { BLOCK }
		428
		429	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		430	closure is executed, sets up the environment in the same way as in C<rcv>
		431	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		432
		433	This is useful when you register callbacks from C<rcv> callbacks:
		434
		435	rcv delayed_reply => sub {
		436	my ($delay, @reply) = @_;
		437	my $timer = AE::timer $delay, 0, psub {
		438	snd @reply, $SELF;
		439	};
		440	};
		441
		442	=cut
		443
		444	sub psub(&) {
		445	my $cb = shift;
		446
		447	my $port = $SELF
		448	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		449
		450	sub {
		451	local $SELF = $port;
		452
		453	if (wantarray) {
		454	my @res = eval { &$cb };
		455	_self_die if $@;
		456	@res
		457	} else {
		458	my $res = eval { &$cb };
		459	_self_die if $@;
		460	$res
148	}	461	}
		462	}
		463	}
149		464
150	for (@{ $self->{any} }) {	465	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
151	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	466
152	&& &{$_->[0]}	467	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
153	&& undef $_;	468
		469	=item $guard = mon $port # kill $SELF when $port dies
		470
		471	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		472
		473	Monitor the given port and do something when the port is killed or
		474	messages to it were lost, and optionally return a guard that can be used
		475	to stop monitoring again.
		476
		477	C<mon> effectively guarantees that, in the absence of hardware failures,
		478	after starting the monitor, either all messages sent to the port will
		479	arrive, or the monitoring action will be invoked after possible message
		480	loss has been detected. No messages will be lost "in between" (after
		481	the first lost message no further messages will be received by the
		482	port). After the monitoring action was invoked, further messages might get
		483	delivered again.
		484
		485	Note that monitoring-actions are one-shot: once messages are lost (and a
		486	monitoring alert was raised), they are removed and will not trigger again.
		487
		488	In the first form (callback), the callback is simply called with any
		489	number of C<@reason> elements (no @reason means that the port was deleted
		490	"normally"). Note also that I<< the callback B<must> never die >>, so use
		491	C<eval> if unsure.
		492
		493	In the second form (another port given), the other port (C<$rcvport>)
		494	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		495	"normal" kils nothing happens, while under all other conditions, the other
		496	port is killed with the same reason.
		497
		498	The third form (kill self) is the same as the second form, except that
		499	C<$rvport> defaults to C<$SELF>.
		500
		501	In the last form (message), a message of the form C<@msg, @reason> will be
		502	C<snd>.
		503
		504	As a rule of thumb, monitoring requests should always monitor a port from
		505	a local port (or callback). The reason is that kill messages might get
		506	lost, just like any other message. Another less obvious reason is that
		507	even monitoring requests can get lost (for example, when the connection
		508	to the other node goes down permanently). When monitoring a port locally
		509	these problems do not exist.
		510
		511	Example: call a given callback when C<$port> is killed.
		512
		513	mon $port, sub { warn "port died because of <@_>\n" };
		514
		515	Example: kill ourselves when C<$port> is killed abnormally.
		516
		517	mon $port;
		518
		519	Example: send us a restart message when another C<$port> is killed.
		520
		521	mon $port, $self => "restart";
		522
		523	=cut
		524
		525	sub mon {
		526	my ($nodeid, $port) = split /#/, shift, 2;
		527
		528	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
		529
		530	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		531
		532	unless (ref $cb) {
		533	if (@_) {
		534	# send a kill info message
		535	my (@msg) = ($cb, @_);
		536	$cb = sub { snd @msg, @_ };
		537	} else {
		538	# simply kill other port
		539	my $port = $cb;
		540	$cb = sub { kil $port, @_ if @_ };
154	}	541	}
		542	}
		543
		544	$node->monitor ($port, $cb);
		545
		546	defined wantarray
		547	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		548	}
		549
		550	=item $guard = mon_guard $port, $ref, $ref...
		551
		552	Monitors the given C<$port> and keeps the passed references. When the port
		553	is killed, the references will be freed.
		554
		555	Optionally returns a guard that will stop the monitoring.
		556
		557	This function is useful when you create e.g. timers or other watchers and
		558	want to free them when the port gets killed (note the use of C<psub>):
		559
		560	$port->rcv (start => sub {
		561	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
		562	undef $timer if 0.9 < rand;
		563	});
		564	});
		565
		566	=cut
		567
		568	sub mon_guard {
		569	my ($port, @refs) = @_;
		570
		571	#TODO: mon-less form?
		572
		573	mon $port, sub { 0 && @refs }
		574	}
		575
		576	=item kil $port[, @reason]
		577
		578	Kill the specified port with the given C<@reason>.
		579
		580	If no C<@reason> is specified, then the port is killed "normally" (ports
		581	monitoring other ports will not necessarily die because a port dies
		582	"normally").
		583
		584	Otherwise, linked ports get killed with the same reason (second form of
		585	C<mon>, see above).
		586
		587	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		588	will be reported as reason C<< die => $@ >>.
		589
		590	Transport/communication errors are reported as C<< transport_error =>
		591	$message >>.
		592
		593	=cut
		594
		595	=item $port = spawn $node, $initfunc[, @initdata]
		596
		597	Creates a port on the node C<$node> (which can also be a port ID, in which
		598	case it's the node where that port resides).
		599
		600	The port ID of the newly created port is returned immediately, and it is
		601	possible to immediately start sending messages or to monitor the port.
		602
		603	After the port has been created, the init function is called on the remote
		604	node, in the same context as a C<rcv> callback. This function must be a
		605	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		606	specify a function in the main program, use C<::name>.
		607
		608	If the function doesn't exist, then the node tries to C<require>
		609	the package, then the package above the package and so on (e.g.
		610	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		611	exists or it runs out of package names.
		612
		613	The init function is then called with the newly-created port as context
		614	object (C<$SELF>) and the C<@initdata> values as arguments.
		615
		616	A common idiom is to pass a local port, immediately monitor the spawned
		617	port, and in the remote init function, immediately monitor the passed
		618	local port. This two-way monitoring ensures that both ports get cleaned up
		619	when there is a problem.
		620
		621	Example: spawn a chat server port on C<$othernode>.
		622
		623	# this node, executed from within a port context:
		624	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		625	mon $server;
		626
		627	# init function on C<$othernode>
		628	sub connect {
		629	my ($srcport) = @_;
		630
		631	mon $srcport;
		632
		633	rcv $SELF, sub {
		634	...
		635	};
		636	}
		637
		638	=cut
		639
		640	sub _spawn {
		641	my $port = shift;
		642	my $init = shift;
		643
		644	local $SELF = "$NODE#$port";
		645	eval {
		646	&{ load_func $init }
155	};	647	};
156		648	_self_die if $@;
157	$self
158	}	649	}
159		650
160	=item $portid = create_miniport { }	651	sub spawn(@) {
		652	my ($nodeid, undef) = split /#/, shift, 2;
161		653
162	Creates a "mini port", that is, a port without much #TODO	654	my $id = "$RUNIQ." . $ID++;
163		655
164	=cut	656	$_[0] =~ /::/
		657	or Carp::croak "spawn init function must be a fully-qualified name, caught";
165		658
166	sub create_miniport(&) {	659	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
167	my $cb = shift;
168	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;
169		660
170	$AnyEvent::MP::Base::PORT{$id} = sub {	661	"$nodeid#$id"
171	&$cb	662	}
172	and delete $AnyEvent::MP::Base::PORT{$id};	663
		664	=item after $timeout, @msg
		665
		666	=item after $timeout, $callback
		667
		668	Either sends the given message, or call the given callback, after the
		669	specified number of seconds.
		670
		671	This is simply a utility function that comes in handy at times - the
		672	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		673	so it may go away in the future.
		674
		675	=cut
		676
		677	sub after($@) {
		678	my ($timeout, @action) = @_;
		679
		680	my $t; $t = AE::timer $timeout, 0, sub {
		681	undef $t;
		682	ref $action[0]
		683	? $action[0]()
		684	: snd @action;
173	};	685	};
174
175	"$NODE#$id"
176	}	686	}
177
178	package AnyEvent::MP::Port;
179		687
180	=back	688	=back
181		689
182	=head1 METHODS FOR PORT OBJECTS	690	=head1 AnyEvent::MP vs. Distributed Erlang
		691
		692	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		693	== aemp node, Erlang process == aemp port), so many of the documents and
		694	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		695	sample:
		696
		697	http://www.Erlang.se/doc/programming_rules.shtml
		698	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		699	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		700	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		701
		702	Despite the similarities, there are also some important differences:
183		703
184	=over 4	704	=over 4
185		705
186	=item "$port"	706	=item * Node IDs are arbitrary strings in AEMP.
187		707
188	A port object stringifies to its port ID, so can be used directly for	708	Erlang relies on special naming and DNS to work everywhere in the same
189	C<snd> operations.	709	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		710	configuration or DNS), but will otherwise discover other odes itself.
190		711
191	=cut	712	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		713	uses "local ports are like remote ports".
192		714
193	use overload	715	The failure modes for local ports are quite different (runtime errors
194	'""' => sub { $_[0]{id} },	716	only) then for remote ports - when a local port dies, you I<know> it dies,
195	fallback => 1;	717	when a connection to another node dies, you know nothing about the other
		718	port.
196		719
197	=item $port->rcv (type => $callback->($port, @msg))	720	Erlang pretends remote ports are as reliable as local ports, even when
		721	they are not.
198		722
199	=item $port->rcv ($smartmatch => $callback->($port, @msg))	723	AEMP encourages a "treat remote ports differently" philosophy, with local
		724	ports being the special case/exception, where transport errors cannot
		725	occur.
200		726
201	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	727	=item * Erlang uses processes and a mailbox, AEMP does not queue.
202		728
203	Register a callback on the given port.	729	Erlang uses processes that selectively receive messages, and therefore
		730	needs a queue. AEMP is event based, queuing messages would serve no
		731	useful purpose. For the same reason the pattern-matching abilities of
		732	AnyEvent::MP are more limited, as there is little need to be able to
		733	filter messages without dequeuing them.
204		734
205	The callback has to return a true value when its work is done, after	735	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
206	which is will be removed, or a false value in which case it will stay
207	registered.
208		736
209	If the match is an array reference, then it will be matched against the	737	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
210	first elements of the message, otherwise only the first element is being
211	matched.
212		738
213	Any element in the match that is specified as C<_any_> (a function	739	Sending messages in Erlang is synchronous and blocks the process (and
214	exported by this module) matches any single element of the message.	740	so does not need a queue that can overflow). AEMP sends are immediate,
		741	connection establishment is handled in the background.
215		742
216	While not required, it is highly recommended that the first matching	743	=item * Erlang suffers from silent message loss, AEMP does not.
217	element is a string identifying the message. The one-string-only match is
218	also the most efficient match (by far).
219		744
220	=cut	745	Erlang makes few guarantees on messages delivery - messages can get lost
		746	without any of the processes realising it (i.e. you send messages a, b,
		747	and c, and the other side only receives messages a and c).
221		748
222	sub rcv($@) {	749	AEMP guarantees correct ordering, and the guarantee that after one message
223	my ($self, $match, $cb) = @_;	750	is lost, all following ones sent to the same port are lost as well, until
		751	monitoring raises an error, so there are no silent "holes" in the message
		752	sequence.
224		753
225	if (!ref $match) {	754	=item * Erlang can send messages to the wrong port, AEMP does not.
226	push @{ $self->{rc0}{$match} }, [$cb];
227	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
228	my ($type, @match) = @$match;
229	@match
230	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
231	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
232	} else {
233	push @{ $self->{any} }, [$cb, $match];
234	}
235	}
236		755
237	=item $port->register ($name)	756	In Erlang it is quite likely that a node that restarts reuses a process ID
		757	known to other nodes for a completely different process, causing messages
		758	destined for that process to end up in an unrelated process.
238		759
239	Registers the given port under the well known name C<$name>. If the name	760	AEMP never reuses port IDs, so old messages or old port IDs floating
240	already exists it is replaced.	761	around in the network will not be sent to an unrelated port.
241		762
242	A port can only be registered under one well known name.	763	=item * Erlang uses unprotected connections, AEMP uses secure
		764	authentication and can use TLS.
243		765
244	=cut	766	AEMP can use a proven protocol - TLS - to protect connections and
		767	securely authenticate nodes.
245		768
246	sub register {	769	=item * The AEMP protocol is optimised for both text-based and binary
247	my ($self, $name) = @_;	770	communications.
248		771
249	$self->{wkname} = $name;	772	The AEMP protocol, unlike the Erlang protocol, supports both programming
250	$AnyEvent::MP::Base::WKP{$name} = "$self";	773	language independent text-only protocols (good for debugging) and binary,
251	}	774	language-specific serialisers (e.g. Storable). By default, unless TLS is
		775	used, the protocol is actually completely text-based.
252		776
253	=item $port->destroy	777	It has also been carefully designed to be implementable in other languages
		778	with a minimum of work while gracefully degrading functionality to make the
		779	protocol simple.
254		780
255	Explicitly destroy/remove/nuke/vaporise the port.	781	=item * AEMP has more flexible monitoring options than Erlang.
256		782
257	Ports are normally kept alive by there mere existance alone, and need to	783	In Erlang, you can chose to receive I<all> exit signals as messages
258	be destroyed explicitly.	784	or I<none>, there is no in-between, so monitoring single processes is
		785	difficult to implement. Monitoring in AEMP is more flexible than in
		786	Erlang, as one can choose between automatic kill, exit message or callback
		787	on a per-process basis.
259		788
260	=cut	789	=item * Erlang tries to hide remote/local connections, AEMP does not.
261		790
262	sub destroy {	791	Monitoring in Erlang is not an indicator of process death/crashes, in the
263	my ($self) = @_;	792	same way as linking is (except linking is unreliable in Erlang).
264		793
265	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	794	In AEMP, you don't "look up" registered port names or send to named ports
		795	that might or might not be persistent. Instead, you normally spawn a port
		796	on the remote node. The init function monitors you, and you monitor the
		797	remote port. Since both monitors are local to the node, they are much more
		798	reliable (no need for C<spawn_link>).
266		799
267	delete $AnyEvent::MP::Base::PORT{$_}	800	This also saves round-trips and avoids sending messages to the wrong port
268	for @{ $self->{names} };	801	(hard to do in Erlang).
269	}
270		802
271	=back	803	=back
272		804
273	=head1 FUNCTIONS FOR NODES	805	=head1 RATIONALE
274		806
275	=over 4	807	=over 4
276		808
277	=item mon $noderef, $callback->($noderef, $status, $)	809	=item Why strings for port and node IDs, why not objects?
278		810
279	Monitors the given noderef.	811	We considered "objects", but found that the actual number of methods
		812	that can be called are quite low. Since port and node IDs travel over
		813	the network frequently, the serialising/deserialising would add lots of
		814	overhead, as well as having to keep a proxy object everywhere.
280		815
281	=item become_public endpoint...	816	Strings can easily be printed, easily serialised etc. and need no special
		817	procedures to be "valid".
282		818
283	Tells the node to become a public node, i.e. reachable from other nodes.	819	And as a result, a miniport consists of a single closure stored in a
		820	global hash - it can't become much cheaper.
284		821
285	If no arguments are given, or the first argument is C<undef>, then	822	=item Why favour JSON, why not a real serialising format such as Storable?
286	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the
287	local nodename resolves to.
288		823
289	Otherwise the first argument must be an array-reference with transport	824	In fact, any AnyEvent::MP node will happily accept Storable as framing
290	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	825	format, but currently there is no way to make a node use Storable by
291	local nodename is used as hostname). The endpoints are all resolved and	826	default (although all nodes will accept it).
292	will become the node reference.
293		827
294	=cut	828	The default framing protocol is JSON because a) JSON::XS is many times
		829	faster for small messages and b) most importantly, after years of
		830	experience we found that object serialisation is causing more problems
		831	than it solves: Just like function calls, objects simply do not travel
		832	easily over the network, mostly because they will always be a copy, so you
		833	always have to re-think your design.
		834
		835	Keeping your messages simple, concentrating on data structures rather than
		836	objects, will keep your messages clean, tidy and efficient.
295		837
296	=back	838	=back
297		839
298	=head1 NODE MESSAGES
299
300	Nodes understand the following messages sent to them. Many of them take
301	arguments called C<@reply>, which will simply be used to compose a reply
302	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
303	the remaining arguments are simply the message data.
304
305	=over 4
306
307	=cut
308
309	=item wkp => $name, @reply
310
311	Replies with the port ID of the specified well-known port, or C<undef>.
312
313	=item devnull => ...
314
315	Generic data sink/CPU heat conversion.
316
317	=item relay => $port, @msg
318
319	Simply forwards the message to the given port.
320
321	=item eval => $string[ @reply]
322
323	Evaluates the given string. If C<@reply> is given, then a message of the
324	form C<@reply, $@, @evalres> is sent.
325
326	Example: crash another node.
327
328	snd $othernode, eval => "exit";
329
330	=item time => @reply
331
332	Replies the the current node time to C<@reply>.
333
334	Example: tell the current node to send the current time to C<$myport> in a
335	C<timereply> message.
336
337	snd $NODE, time => $myport, timereply => 1, 2;
338	# => snd $myport, timereply => 1, 2, <time>
339
340	=back
341
342	=head1 SEE ALSO	840	=head1 SEE ALSO
		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.
343		848
344	L<AnyEvent>.	849	L<AnyEvent>.
345		850
346	=head1 AUTHOR	851	=head1 AUTHOR
347		852

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