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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.15 by root, Sun Aug 2 19:25:27 2009 UTC vs.
Revision 1.71 by root, Sun Aug 30 19:52:56 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 noderef
		10	NODE # returns this node's noderef
		11	NODE $port # returns the noderef of the port
11		12
		13	$SELF # receiving/own port id in rcv callbacks
		14
		15	# initialise the node so it can send/receive messages
		16	initialise_node;
		17
		18	# ports are message endpoints
		19
		20	# sending messages
12	snd $port, type => data...;	21	snd $port, type => data...;
		22	snd $port, @msg;
		23	snd @msg_with_first_element_being_a_port;
13		24
14	rcv $port, smartmatch => $cb->($port, @msg);	25	# creating/using ports, the simple way
		26	my $simple_port = port { my @msg = @_; 0 };
15		27
16	# examples:	28	# creating/using ports, tagged message matching
		29	my $port = port;
17	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
18	rcv $port1, pong => sub { warn "pong received\n" };	31	rcv $port, pong => sub { warn "pong received\n"; 0 };
19	snd $port2, ping => $port1;
20		32
21	# more, smarter, matches (_any_ is exported by this module)	33	# create a port on another node
22	rcv $port, [child_died => $pid] => sub { ...	34	my $port = spawn $node, $initfunc, @initdata;
23	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	35
		36	# monitoring
		37	mon $port, $cb->(@msg) # callback is invoked on death
		38	mon $port, $otherport # kill otherport on abnormal death
		39	mon $port, $otherport, @msg # send message on death
		40
		41	=head1 CURRENT STATUS
		42
		43	bin/aemp - stable.
		44	AnyEvent::MP - stable API, should work.
		45	AnyEvent::MP::Intro - uptodate, but incomplete.
		46	AnyEvent::MP::Kernel - mostly stable.
		47	AnyEvent::MP::Global - stable API, protocol not yet final.
		48
		49	stay tuned.
24		50
25	=head1 DESCRIPTION	51	=head1 DESCRIPTION
26		52
27	This module (-family) implements a simple message passing framework.	53	This module (-family) implements a simple message passing framework.
28		54
29	Despite its simplicity, you can securely message other processes running	55	Despite its simplicity, you can securely message other processes running
30	on the same or other hosts.	56	on the same or other hosts, and you can supervise entities remotely.
31		57
		58	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
		59	manual page and the examples under F<eg/>.
		60
32	At the moment, this module family is severly brokena nd underdocumented,	61	At the moment, this module family is a bit underdocumented.
33	so do not use. This was uploaded mainly to resreve the CPAN namespace -
34	stay tuned!
35		62
36	=head1 CONCEPTS	63	=head1 CONCEPTS
37		64
38	=over 4	65	=over 4
39		66
40	=item port	67	=item port
41		68
42	A port is something you can send messages to with the C<snd> function, and	69	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		70
		71	Ports allow you to register C<rcv> handlers that can match all or just
		72	some messages. Messages send to ports will not be queued, regardless of
		73	anything was listening for them or not.
		74
46	=item port id - C<noderef#portname>	75	=item port ID - C<nodeid#portname>
47		76
48	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	77	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).	78	separator, and a port name (a printable string of unspecified format).
50		79
51	=item node	80	=item node
52		81
53	A node is a single process containing at least one port - the node	82	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,	83	which enables nodes to manage each other remotely, and to create new
55	among other things.	84	ports.
56		85
57	Initially, nodes are either private (single-process only) or hidden	86	Nodes are either public (have one or more listening ports) or private
58	(connected to a master node only). Only when they epxlicitly "become	87	(no listening ports). Private nodes cannot talk to other private nodes
59	public" can you send them messages from unrelated other nodes.	88	currently.
60		89
61	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	90	=item node ID - C<[a-za-Z0-9_\-.:]+>
62		91
63	A noderef is a string that either uniquely identifies a given node (for	92	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	93	network. Depending on the configuration used, node IDs can look like a
65	node (for public nodes).	94	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		95	doesn't interpret node IDs in any way.
		96
		97	=item binds - C<ip:port>
		98
		99	Nodes can only talk to each other by creating some kind of connection to
		100	each other. To do this, nodes should listen on one or more local transport
		101	endpoints - binds. Currently, only standard C<ip:port> specifications can
		102	be used, which specify TCP ports to listen on.
		103
		104	=item seeds - C<host:port>
		105
		106	When a node starts, it knows nothing about the network. To teach the node
		107	about the network it first has to contact some other node within the
		108	network. This node is called a seed.
		109
		110	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		111	are expected to be long-running, and at least one of those should always
		112	be available. When nodes run out of connections (e.g. due to a network
		113	error), they try to re-establish connections to some seednodes again to
		114	join the network.
		115
		116	Apart from being sued for seeding, seednodes are not special in any way -
		117	every public node can be a seednode.
66		118
67	=back	119	=back
68		120
69	=head1 VARIABLES/FUNCTIONS	121	=head1 VARIABLES/FUNCTIONS
70		122
…		…
72		124
73	=cut	125	=cut
74		126
75	package AnyEvent::MP;	127	package AnyEvent::MP;
76		128
77	use AnyEvent::MP::Base;	129	use AnyEvent::MP::Kernel;
78		130
79	use common::sense;	131	use common::sense;
80		132
81	use Carp ();	133	use Carp ();
82		134
83	use AE ();	135	use AE ();
84		136
85	use base "Exporter";	137	use base "Exporter";
86		138
87	our $VERSION = '0.02';	139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		140
88	our @EXPORT = qw(	141	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv _any_	142	NODE $NODE *SELF node_of after
90	create_port create_port_on	143	initialise_node
91	create_miniport	144	snd rcv mon mon_guard kil reg psub spawn
92	become_slave become_public	145	port
93	);	146	);
94		147
		148	our $SELF;
		149
		150	sub _self_die() {
		151	my $msg = $@;
		152	$msg =~ s/\n+$// unless ref $msg;
		153	kil $SELF, die => $msg;
		154	}
		155
95	=item NODE / $NODE	156	=item $thisnode = NODE / $NODE
96		157
97	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	158	The C<NODE> function returns, and the C<$NODE> variable contains, the node
98	the local node. The value is initialised by a call to C<become_public> or	159	ID of the node running in the current process. This value is initialised by
99	C<become_slave>, after which all local port identifiers become invalid.	160	a call to C<initialise_node>.
100		161
		162	=item $nodeid = node_of $port
		163
		164	Extracts and returns the node ID from a port ID or a node ID.
		165
		166	=item initialise_node $profile_name, key => value...
		167
		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
		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.
		172
		173	This function initialises a node - it must be called exactly once (or
		174	never) before calling other AnyEvent::MP functions.
		175
		176	The first argument is a profile name. If it is C<undef> or missing, then
		177	the current nodename will be used instead (i.e. F<uname -n>).
		178
		179	The function first looks up the profile in the aemp configuration (see the
		180	L<aemp> commandline utility). the profile is calculated as follows:
		181
		182	First, all remaining key => value pairs (all of which are conviniently
		183	undocumented at the moment) will be used. Then they will be overwritten by
		184	any values specified in the global default configuration (see the F<aemp>
		185	utility), then the chain of profiles selected, if any. That means that
		186	the values specified in the profile have highest priority and the values
		187	specified via C<initialise_node> have lowest priority.
		188
		189	If the profile specifies a node ID, then this will become the node ID of
		190	this process. If not, then the profile name will be used as node ID. The
		191	special node ID of C<anon/> will be replaced by a random node ID.
		192
		193	The next step is to look up the binds in the profile, followed by binding
		194	aemp protocol listeners on all binds specified (it is possible and valid
		195	to have no binds, meaning that the node cannot be contacted form the
		196	outside. This means the node cannot talk to other nodes that also have no
		197	binds, but it can still talk to all "normal" nodes).
		198
		199	If the profile does not specify a binds list, then a default of C<*> is
		200	used.
		201
		202	Lastly, the seeds list from the profile is passed to the
		203	L<AnyEvent::MP::Global> module, which will then use it to keep
		204	connectivity with at least on of those seed nodes at any point in time.
		205
		206	Example: become a distributed node listening on the guessed noderef, or
		207	the one specified via C<aemp> for the current node. This should be the
		208	most common form of invocation for "daemon"-type nodes.
		209
		210	initialise_node;
		211
		212	Example: become an anonymous node. This form is often used for commandline
		213	clients.
		214
		215	initialise_node "anon/";
		216
		217	Example: become a distributed node. If there is no profile of the given
		218	name, or no binds list was specified, resolve C<localhost:4044> and bind
		219	on the resulting addresses.
		220
		221	initialise_node "localhost:4044";
		222
		223	=item $SELF
		224
		225	Contains the current port id while executing C<rcv> callbacks or C<psub>
		226	blocks.
		227
		228	=item *SELF, SELF, %SELF, @SELF...
		229
		230	Due to some quirks in how perl exports variables, it is impossible to
		231	just export C<$SELF>, all the symbols named C<SELF> are exported by this
		232	module, but only C<$SELF> is currently used.
		233
101	=item snd $portid, type => @data	234	=item snd $port, type => @data
102		235
103	=item snd $portid, @msg	236	=item snd $port, @msg
104		237
105	Send the given message to the given port ID, which can identify either	238	Send the given message to the given port, which can identify either a
106	a local or a remote port, and can be either a string or soemthignt hat	239	local or a remote port, and must be a port ID.
107	stringifies a sa port ID (such as a port object :).
108		240
109	While the message can be about anything, it is highly recommended to use a	241	While the message can be almost anything, it is highly recommended to
110	string as first element (a portid, or some word that indicates a request	242	use a string as first element (a port ID, or some word that indicates a
111	type etc.).	243	request type etc.) and to consist if only simple perl values (scalars,
		244	arrays, hashes) - if you think you need to pass an object, think again.
112		245
113	The message data effectively becomes read-only after a call to this	246	The message data logically becomes read-only after a call to this
114	function: modifying any argument is not allowed and can cause many	247	function: modifying any argument (or values referenced by them) is
115	problems.	248	forbidden, as there can be considerable time between the call to C<snd>
		249	and the time the message is actually being serialised - in fact, it might
		250	never be copied as within the same process it is simply handed to the
		251	receiving port.
116		252
117	The type of data you can transfer depends on the transport protocol: when	253	The type of data you can transfer depends on the transport protocol: when
118	JSON is used, then only strings, numbers and arrays and hashes consisting	254	JSON is used, then only strings, numbers and arrays and hashes consisting
119	of those are allowed (no objects). When Storable is used, then anything	255	of those are allowed (no objects). When Storable is used, then anything
120	that Storable can serialise and deserialise is allowed, and for the local	256	that Storable can serialise and deserialise is allowed, and for the local
121	node, anything can be passed.	257	node, anything can be passed. Best rely only on the common denominator of
		258	these.
122		259
123	=item $local_port = create_port	260	=item $local_port = port
124		261
125	Create a new local port object. See the next section for allowed methods.	262	Create a new local port object and returns its port ID. Initially it has
		263	no callbacks set and will throw an error when it receives messages.
126		264
127	=cut	265	=item $local_port = port { my @msg = @_ }
128		266
129	sub create_port {	267	Creates a new local port, and returns its ID. Semantically the same as
130	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;	268	creating a port and calling C<rcv $port, $callback> on it.
131		269
132	my $self = bless {	270	The block will be called for every message received on the port, with the
133	id => "$NODE#$id",	271	global variable C<$SELF> set to the port ID. Runtime errors will cause the
134	names => [$id],	272	port to be C<kil>ed. The message will be passed as-is, no extra argument
135	}, "AnyEvent::MP::Port";	273	(i.e. no port ID) will be passed to the callback.
136		274
137	$AnyEvent::MP::Base::PORT{$id} = sub {	275	If you want to stop/destroy the port, simply C<kil> it:
138	unshift @_, $self;
139		276
140	for (@{ $self->{rc0}{$_[1]} }) {	277	my $port = port {
141	$_ && &{$_->[0]}	278	my @msg = @_;
142	&& undef $_;	279	...
		280	kil $SELF;
		281	};
		282
		283	=cut
		284
		285	sub rcv($@);
		286
		287	sub _kilme {
		288	die "received message on port without callback";
		289	}
		290
		291	sub port(;&) {
		292	my $id = "$UNIQ." . $ID++;
		293	my $port = "$NODE#$id";
		294
		295	rcv $port, shift \|\| \&_kilme;
		296
		297	$port
		298	}
		299
		300	=item rcv $local_port, $callback->(@msg)
		301
		302	Replaces the default callback on the specified port. There is no way to
		303	remove the default callback: use C<sub { }> to disable it, or better
		304	C<kil> the port when it is no longer needed.
		305
		306	The global C<$SELF> (exported by this module) contains C<$port> while
		307	executing the callback. Runtime errors during callback execution will
		308	result in the port being C<kil>ed.
		309
		310	The default callback received all messages not matched by a more specific
		311	C<tag> match.
		312
		313	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		314
		315	Register (or replace) callbacks to be called on messages starting with the
		316	given tag on the given port (and return the port), or unregister it (when
		317	C<$callback> is C<$undef> or missing). There can only be one callback
		318	registered for each tag.
		319
		320	The original message will be passed to the callback, after the first
		321	element (the tag) has been removed. The callback will use the same
		322	environment as the default callback (see above).
		323
		324	Example: create a port and bind receivers on it in one go.
		325
		326	my $port = rcv port,
		327	msg1 => sub { ... },
		328	msg2 => sub { ... },
		329	;
		330
		331	Example: create a port, bind receivers and send it in a message elsewhere
		332	in one go:
		333
		334	snd $otherport, reply =>
		335	rcv port,
		336	msg1 => sub { ... },
		337	...
		338	;
		339
		340	Example: temporarily register a rcv callback for a tag matching some port
		341	(e.g. for a rpc reply) and unregister it after a message was received.
		342
		343	rcv $port, $otherport => sub {
		344	my @reply = @_;
		345
		346	rcv $SELF, $otherport;
		347	};
		348
		349	=cut
		350
		351	sub rcv($@) {
		352	my $port = shift;
		353	my ($noderef, $portid) = split /#/, $port, 2;
		354
		355	$NODE{$noderef} == $NODE{""}
		356	or Carp::croak "$port: rcv can only be called on local ports, caught";
		357
		358	while (@_) {
		359	if (ref $_[0]) {
		360	if (my $self = $PORT_DATA{$portid}) {
		361	"AnyEvent::MP::Port" eq ref $self
		362	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		363
		364	$self->[2] = shift;
		365	} else {
		366	my $cb = shift;
		367	$PORT{$portid} = sub {
		368	local $SELF = $port;
		369	eval { &$cb }; _self_die if $@;
		370	};
		371	}
		372	} elsif (defined $_[0]) {
		373	my $self = $PORT_DATA{$portid} \|\|= do {
		374	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		375
		376	$PORT{$portid} = sub {
		377	local $SELF = $port;
		378
		379	if (my $cb = $self->[1]{$_[0]}) {
		380	shift;
		381	eval { &$cb }; _self_die if $@;
		382	} else {
		383	&{ $self->[0] };
		384	}
		385	};
		386
		387	$self
		388	};
		389
		390	"AnyEvent::MP::Port" eq ref $self
		391	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		392
		393	my ($tag, $cb) = splice @_, 0, 2;
		394
		395	if (defined $cb) {
		396	$self->[1]{$tag} = $cb;
		397	} else {
		398	delete $self->[1]{$tag};
		399	}
143	}	400	}
		401	}
144		402
145	for (@{ $self->{rcv}{$_[1]} }) {	403	$port
146	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	404	}
147	&& &{$_->[0]}	405
148	&& undef $_;	406	=item $closure = psub { BLOCK }
		407
		408	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		409	closure is executed, sets up the environment in the same way as in C<rcv>
		410	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		411
		412	This is useful when you register callbacks from C<rcv> callbacks:
		413
		414	rcv delayed_reply => sub {
		415	my ($delay, @reply) = @_;
		416	my $timer = AE::timer $delay, 0, psub {
		417	snd @reply, $SELF;
		418	};
		419	};
		420
		421	=cut
		422
		423	sub psub(&) {
		424	my $cb = shift;
		425
		426	my $port = $SELF
		427	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		428
		429	sub {
		430	local $SELF = $port;
		431
		432	if (wantarray) {
		433	my @res = eval { &$cb };
		434	_self_die if $@;
		435	@res
		436	} else {
		437	my $res = eval { &$cb };
		438	_self_die if $@;
		439	$res
149	}	440	}
		441	}
		442	}
150		443
151	for (@{ $self->{any} }) {	444	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
152	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	445
153	&& &{$_->[0]}	446	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
154	&& undef $_;	447
		448	=item $guard = mon $port # kill $SELF when $port dies
		449
		450	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		451
		452	Monitor the given port and do something when the port is killed or
		453	messages to it were lost, and optionally return a guard that can be used
		454	to stop monitoring again.
		455
		456	C<mon> effectively guarantees that, in the absence of hardware failures,
		457	after starting the monitor, either all messages sent to the port will
		458	arrive, or the monitoring action will be invoked after possible message
		459	loss has been detected. No messages will be lost "in between" (after
		460	the first lost message no further messages will be received by the
		461	port). After the monitoring action was invoked, further messages might get
		462	delivered again.
		463
		464	Note that monitoring-actions are one-shot: once messages are lost (and a
		465	monitoring alert was raised), they are removed and will not trigger again.
		466
		467	In the first form (callback), the callback is simply called with any
		468	number of C<@reason> elements (no @reason means that the port was deleted
		469	"normally"). Note also that I<< the callback B<must> never die >>, so use
		470	C<eval> if unsure.
		471
		472	In the second form (another port given), the other port (C<$rcvport>)
		473	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
		474	"normal" kils nothing happens, while under all other conditions, the other
		475	port is killed with the same reason.
		476
		477	The third form (kill self) is the same as the second form, except that
		478	C<$rvport> defaults to C<$SELF>.
		479
		480	In the last form (message), a message of the form C<@msg, @reason> will be
		481	C<snd>.
		482
		483	As a rule of thumb, monitoring requests should always monitor a port from
		484	a local port (or callback). The reason is that kill messages might get
		485	lost, just like any other message. Another less obvious reason is that
		486	even monitoring requests can get lost (for exmaple, when the connection
		487	to the other node goes down permanently). When monitoring a port locally
		488	these problems do not exist.
		489
		490	Example: call a given callback when C<$port> is killed.
		491
		492	mon $port, sub { warn "port died because of <@_>\n" };
		493
		494	Example: kill ourselves when C<$port> is killed abnormally.
		495
		496	mon $port;
		497
		498	Example: send us a restart message when another C<$port> is killed.
		499
		500	mon $port, $self => "restart";
		501
		502	=cut
		503
		504	sub mon {
		505	my ($noderef, $port) = split /#/, shift, 2;
		506
		507	my $node = $NODE{$noderef} \|\| add_node $noderef;
		508
		509	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		510
		511	unless (ref $cb) {
		512	if (@_) {
		513	# send a kill info message
		514	my (@msg) = ($cb, @_);
		515	$cb = sub { snd @msg, @_ };
		516	} else {
		517	# simply kill other port
		518	my $port = $cb;
		519	$cb = sub { kil $port, @_ if @_ };
155	}	520	}
		521	}
		522
		523	$node->monitor ($port, $cb);
		524
		525	defined wantarray
		526	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		527	}
		528
		529	=item $guard = mon_guard $port, $ref, $ref...
		530
		531	Monitors the given C<$port> and keeps the passed references. When the port
		532	is killed, the references will be freed.
		533
		534	Optionally returns a guard that will stop the monitoring.
		535
		536	This function is useful when you create e.g. timers or other watchers and
		537	want to free them when the port gets killed (note the use of C<psub>):
		538
		539	$port->rcv (start => sub {
		540	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
		541	undef $timer if 0.9 < rand;
		542	});
		543	});
		544
		545	=cut
		546
		547	sub mon_guard {
		548	my ($port, @refs) = @_;
		549
		550	#TODO: mon-less form?
		551
		552	mon $port, sub { 0 && @refs }
		553	}
		554
		555	=item kil $port[, @reason]
		556
		557	Kill the specified port with the given C<@reason>.
		558
		559	If no C<@reason> is specified, then the port is killed "normally" (ports
		560	monitoring other ports will not necessarily die because a port dies
		561	"normally").
		562
		563	Otherwise, linked ports get killed with the same reason (second form of
		564	C<mon>, see above).
		565
		566	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		567	will be reported as reason C<< die => $@ >>.
		568
		569	Transport/communication errors are reported as C<< transport_error =>
		570	$message >>.
		571
		572	=cut
		573
		574	=item $port = spawn $node, $initfunc[, @initdata]
		575
		576	Creates a port on the node C<$node> (which can also be a port ID, in which
		577	case it's the node where that port resides).
		578
		579	The port ID of the newly created port is returned immediately, and it is
		580	possible to immediately start sending messages or to monitor the port.
		581
		582	After the port has been created, the init function is called on the remote
		583	node, in the same context as a C<rcv> callback. This function must be a
		584	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		585	specify a function in the main program, use C<::name>.
		586
		587	If the function doesn't exist, then the node tries to C<require>
		588	the package, then the package above the package and so on (e.g.
		589	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		590	exists or it runs out of package names.
		591
		592	The init function is then called with the newly-created port as context
		593	object (C<$SELF>) and the C<@initdata> values as arguments.
		594
		595	A common idiom is to pass a local port, immediately monitor the spawned
		596	port, and in the remote init function, immediately monitor the passed
		597	local port. This two-way monitoring ensures that both ports get cleaned up
		598	when there is a problem.
		599
		600	Example: spawn a chat server port on C<$othernode>.
		601
		602	# this node, executed from within a port context:
		603	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		604	mon $server;
		605
		606	# init function on C<$othernode>
		607	sub connect {
		608	my ($srcport) = @_;
		609
		610	mon $srcport;
		611
		612	rcv $SELF, sub {
		613	...
		614	};
		615	}
		616
		617	=cut
		618
		619	sub _spawn {
		620	my $port = shift;
		621	my $init = shift;
		622
		623	local $SELF = "$NODE#$port";
		624	eval {
		625	&{ load_func $init }
156	};	626	};
157		627	_self_die if $@;
158	$self
159	}	628	}
160		629
161	=item $portid = miniport { my @msg = @_; $finished }	630	sub spawn(@) {
		631	my ($noderef, undef) = split /#/, shift, 2;
162		632
163	Creates a "mini port", that is, a very lightweight port without any	633	my $id = "$RUNIQ." . $ID++;
164	pattern matching behind it, and returns its ID.
165		634
166	The block will be called for every message received on the port. When the	635	$_[0] =~ /::/
167	callback returns a true value its job is considered "done" and the port	636	or Carp::croak "spawn init function must be a fully-qualified name, caught";
168	will be destroyed. Otherwise it will stay alive.
169		637
170	The message will be passed as-is, no extra argument (ie.. no port id) will	638	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
171	be passed to the callback.
172		639
173	If you need the local port id in the callback, this works nicely:	640	"$noderef#$id"
		641	}
174		642
175	my $port; $port = miniport {	643	=item after $timeout, @msg
176	snd $otherport, reply => $port;	644
		645	=item after $timeout, $callback
		646
		647	Either sends the given message, or call the given callback, after the
		648	specified number of seconds.
		649
		650	This is simply a utility function that comes in handy at times - the
		651	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		652	so it may go away in the future.
		653
		654	=cut
		655
		656	sub after($@) {
		657	my ($timeout, @action) = @_;
		658
		659	my $t; $t = AE::timer $timeout, 0, sub {
		660	undef $t;
		661	ref $action[0]
		662	? $action[0]()
		663	: snd @action;
177	};	664	};
178
179	=cut
180
181	sub miniport(&) {
182	my $cb = shift;
183	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;
184
185	$AnyEvent::MP::Base::PORT{$id} = sub {
186	&$cb
187	and delete $AnyEvent::MP::Base::PORT{$id};
188	};
189
190	"$NODE#$id"
191	}	665	}
192
193	package AnyEvent::MP::Port;
194		666
195	=back	667	=back
196		668
197	=head1 METHODS FOR PORT OBJECTS	669	=head1 AnyEvent::MP vs. Distributed Erlang
		670
		671	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		672	== aemp node, Erlang process == aemp port), so many of the documents and
		673	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		674	sample:
		675
		676	http://www.Erlang.se/doc/programming_rules.shtml
		677	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		678	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		679	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		680
		681	Despite the similarities, there are also some important differences:
198		682
199	=over 4	683	=over 4
200		684
201	=item "$port"	685	=item * Node IDs are arbitrary strings in AEMP.
202		686
203	A port object stringifies to its port ID, so can be used directly for	687	Erlang relies on special naming and DNS to work everywhere in the same
204	C<snd> operations.	688	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		689	configuraiton or DNS), but will otherwise discover other odes itself.
205		690
206	=cut	691	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		692	uses "local ports are like remote ports".
207		693
208	use overload	694	The failure modes for local ports are quite different (runtime errors
209	'""' => sub { $_[0]{id} },	695	only) then for remote ports - when a local port dies, you I<know> it dies,
210	fallback => 1;	696	when a connection to another node dies, you know nothing about the other
		697	port.
211		698
212	=item $port->rcv (type => $callback->($port, @msg))	699	Erlang pretends remote ports are as reliable as local ports, even when
		700	they are not.
213		701
214	=item $port->rcv ($smartmatch => $callback->($port, @msg))	702	AEMP encourages a "treat remote ports differently" philosophy, with local
		703	ports being the special case/exception, where transport errors cannot
		704	occur.
215		705
216	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	706	=item * Erlang uses processes and a mailbox, AEMP does not queue.
217		707
218	Register a callback on the given port.	708	Erlang uses processes that selectively receive messages, and therefore
		709	needs a queue. AEMP is event based, queuing messages would serve no
		710	useful purpose. For the same reason the pattern-matching abilities of
		711	AnyEvent::MP are more limited, as there is little need to be able to
		712	filter messages without dequeing them.
219		713
220	The callback has to return a true value when its work is done, after	714	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
221	which is will be removed, or a false value in which case it will stay
222	registered.
223		715
224	If the match is an array reference, then it will be matched against the	716	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
225	first elements of the message, otherwise only the first element is being
226	matched.
227		717
228	Any element in the match that is specified as C<_any_> (a function	718	Sending messages in Erlang is synchronous and blocks the process (and
229	exported by this module) matches any single element of the message.	719	so does not need a queue that can overflow). AEMP sends are immediate,
		720	connection establishment is handled in the background.
230		721
231	While not required, it is highly recommended that the first matching	722	=item * Erlang suffers from silent message loss, AEMP does not.
232	element is a string identifying the message. The one-string-only match is
233	also the most efficient match (by far).
234		723
235	=cut	724	Erlang makes few guarantees on messages delivery - messages can get lost
		725	without any of the processes realising it (i.e. you send messages a, b,
		726	and c, and the other side only receives messages a and c).
236		727
237	sub rcv($@) {	728	AEMP guarantees correct ordering, and the guarantee that after one message
238	my ($self, $match, $cb) = @_;	729	is lost, all following ones sent to the same port are lost as well, until
		730	monitoring raises an error, so there are no silent "holes" in the message
		731	sequence.
239		732
240	if (!ref $match) {	733	=item * Erlang can send messages to the wrong port, AEMP does not.
241	push @{ $self->{rc0}{$match} }, [$cb];
242	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
243	my ($type, @match) = @$match;
244	@match
245	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
246	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
247	} else {
248	push @{ $self->{any} }, [$cb, $match];
249	}
250	}
251		734
252	=item $port->register ($name)	735	In Erlang it is quite likely that a node that restarts reuses a process ID
		736	known to other nodes for a completely different process, causing messages
		737	destined for that process to end up in an unrelated process.
253		738
254	Registers the given port under the well known name C<$name>. If the name	739	AEMP never reuses port IDs, so old messages or old port IDs floating
255	already exists it is replaced.	740	around in the network will not be sent to an unrelated port.
256		741
257	A port can only be registered under one well known name.	742	=item * Erlang uses unprotected connections, AEMP uses secure
		743	authentication and can use TLS.
258		744
259	=cut	745	AEMP can use a proven protocol - TLS - to protect connections and
		746	securely authenticate nodes.
260		747
261	sub register {	748	=item * The AEMP protocol is optimised for both text-based and binary
262	my ($self, $name) = @_;	749	communications.
263		750
264	$self->{wkname} = $name;	751	The AEMP protocol, unlike the Erlang protocol, supports both programming
265	$AnyEvent::MP::Base::WKP{$name} = "$self";	752	language independent text-only protocols (good for debugging) and binary,
266	}	753	language-specific serialisers (e.g. Storable). By default, unless TLS is
		754	used, the protocol is actually completely text-based.
267		755
268	=item $port->destroy	756	It has also been carefully designed to be implementable in other languages
		757	with a minimum of work while gracefully degrading functionality to make the
		758	protocol simple.
269		759
270	Explicitly destroy/remove/nuke/vaporise the port.	760	=item * AEMP has more flexible monitoring options than Erlang.
271		761
272	Ports are normally kept alive by there mere existance alone, and need to	762	In Erlang, you can chose to receive I<all> exit signals as messages
273	be destroyed explicitly.	763	or I<none>, there is no in-between, so monitoring single processes is
		764	difficult to implement. Monitoring in AEMP is more flexible than in
		765	Erlang, as one can choose between automatic kill, exit message or callback
		766	on a per-process basis.
274		767
275	=cut	768	=item * Erlang tries to hide remote/local connections, AEMP does not.
276		769
277	sub destroy {	770	Monitoring in Erlang is not an indicator of process death/crashes, in the
278	my ($self) = @_;	771	same way as linking is (except linking is unreliable in Erlang).
279		772
280	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	773	In AEMP, you don't "look up" registered port names or send to named ports
		774	that might or might not be persistent. Instead, you normally spawn a port
		775	on the remote node. The init function monitors you, and you monitor the
		776	remote port. Since both monitors are local to the node, they are much more
		777	reliable (no need for C<spawn_link>).
281		778
282	delete $AnyEvent::MP::Base::PORT{$_}	779	This also saves round-trips and avoids sending messages to the wrong port
283	for @{ $self->{names} };	780	(hard to do in Erlang).
284	}
285		781
286	=back	782	=back
287		783
288	=head1 FUNCTIONS FOR NODES	784	=head1 RATIONALE
289		785
290	=over 4	786	=over 4
291		787
292	=item mon $noderef, $callback->($noderef, $status, $)	788	=item Why strings for port and node IDs, why not objects?
293		789
294	Monitors the given noderef.	790	We considered "objects", but found that the actual number of methods
		791	that can be called are quite low. Since port and node IDs travel over
		792	the network frequently, the serialising/deserialising would add lots of
		793	overhead, as well as having to keep a proxy object everywhere.
295		794
296	=item become_public endpoint...	795	Strings can easily be printed, easily serialised etc. and need no special
		796	procedures to be "valid".
297		797
298	Tells the node to become a public node, i.e. reachable from other nodes.	798	And as a result, a miniport consists of a single closure stored in a
		799	global hash - it can't become much cheaper.
299		800
300	If no arguments are given, or the first argument is C<undef>, then	801	=item Why favour JSON, why not a real serialising format such as Storable?
301	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the
302	local nodename resolves to.
303		802
304	Otherwise the first argument must be an array-reference with transport	803	In fact, any AnyEvent::MP node will happily accept Storable as framing
305	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	804	format, but currently there is no way to make a node use Storable by
306	local nodename is used as hostname). The endpoints are all resolved and	805	default (although all nodes will accept it).
307	will become the node reference.
308		806
309	=cut	807	The default framing protocol is JSON because a) JSON::XS is many times
		808	faster for small messages and b) most importantly, after years of
		809	experience we found that object serialisation is causing more problems
		810	than it solves: Just like function calls, objects simply do not travel
		811	easily over the network, mostly because they will always be a copy, so you
		812	always have to re-think your design.
		813
		814	Keeping your messages simple, concentrating on data structures rather than
		815	objects, will keep your messages clean, tidy and efficient.
310		816
311	=back	817	=back
312		818
313	=head1 NODE MESSAGES
314
315	Nodes understand the following messages sent to them. Many of them take
316	arguments called C<@reply>, which will simply be used to compose a reply
317	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
318	the remaining arguments are simply the message data.
319
320	=over 4
321
322	=cut
323
324	=item wkp => $name, @reply
325
326	Replies with the port ID of the specified well-known port, or C<undef>.
327
328	=item devnull => ...
329
330	Generic data sink/CPU heat conversion.
331
332	=item relay => $port, @msg
333
334	Simply forwards the message to the given port.
335
336	=item eval => $string[ @reply]
337
338	Evaluates the given string. If C<@reply> is given, then a message of the
339	form C<@reply, $@, @evalres> is sent.
340
341	Example: crash another node.
342
343	snd $othernode, eval => "exit";
344
345	=item time => @reply
346
347	Replies the the current node time to C<@reply>.
348
349	Example: tell the current node to send the current time to C<$myport> in a
350	C<timereply> message.
351
352	snd $NODE, time => $myport, timereply => 1, 2;
353	# => snd $myport, timereply => 1, 2, <time>
354
355	=back
356
357	=head1 SEE ALSO	819	=head1 SEE ALSO
		820
		821	L<AnyEvent::MP::Intro> - a gentle introduction.
		822
		823	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		824
		825	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		826	your applications.
358		827
359	L<AnyEvent>.	828	L<AnyEvent>.
360		829
361	=head1 AUTHOR	830	=head1 AUTHOR
362		831

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Revision 1.71 by root, Sun Aug 30 19:52:56 2009 UTC