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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.16 by root, Sun Aug 2 19:29:41 2009 UTC vs.
Revision 1.62 by root, Thu Aug 27 07:12:48 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; # -OR-
		17	initialise_node "localhost:4040"; # -OR-
		18	initialise_node "slave/", "localhost:4040"
		19
		20	# ports are message endpoints
		21
		22	# sending messages
12	snd $port, type => data...;	23	snd $port, type => data...;
		24	snd $port, @msg;
		25	snd @msg_with_first_element_being_a_port;
13		26
14	rcv $port, smartmatch => $cb->($port, @msg);	27	# creating/using ports, the simple way
		28	my $simple_port = port { my @msg = @_; 0 };
15		29
16	# examples:	30	# creating/using ports, tagged message matching
		31	my $port = port;
17	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
18	rcv $port1, pong => sub { warn "pong received\n" };	33	rcv $port, pong => sub { warn "pong received\n"; 0 };
19	snd $port2, ping => $port1;
20		34
21	# more, smarter, matches (_any_ is exported by this module)	35	# create a port on another node
22	rcv $port, [child_died => $pid] => sub { ...	36	my $port = spawn $node, $initfunc, @initdata;
23	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	37
		38	# monitoring
		39	mon $port, $cb->(@msg) # callback is invoked on death
		40	mon $port, $otherport # kill otherport on abnormal death
		41	mon $port, $otherport, @msg # send message on death
		42
		43	=head1 CURRENT STATUS
		44
		45	AnyEvent::MP - stable API, should work
		46	AnyEvent::MP::Intro - outdated
		47	AnyEvent::MP::Kernel - WIP
		48	AnyEvent::MP::Transport - mostly stable
		49
		50	stay tuned.
24		51
25	=head1 DESCRIPTION	52	=head1 DESCRIPTION
26		53
27	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
28		55
29	Despite its simplicity, you can securely message other processes running	56	Despite its simplicity, you can securely message other processes running
30	on the same or other hosts.	57	on the same or other hosts.
31		58
		59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
		60	manual page.
		61
32	At the moment, this module family is severly brokena nd underdocumented,	62	At the moment, this module family is severly broken and underdocumented,
33	so do not use. This was uploaded mainly to resreve the CPAN namespace -	63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
34	stay tuned!	64	stay tuned!
35		65
36	=head1 CONCEPTS	66	=head1 CONCEPTS
37		67
38	=over 4	68	=over 4
39		69
40	=item port	70	=item port
41		71
42	A port is something you can send messages to with the C<snd> function, and	72	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	73
		74	Ports allow you to register C<rcv> handlers that can match all or just
44	messages they match, messages will not be queued.	75	some messages. Messages will not be queued.
45		76
46	=item port id - C<noderef#portname>	77	=item port id - C<noderef#portname>
47		78
48	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	79	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as
49	by a port name (a printable string of unspecified format).	80	separator, and a port name (a printable string of unspecified format). An
		81	exception is the the node port, whose ID is identical to its node
		82	reference.
50		83
51	=item node	84	=item node
52		85
53	A node is a single process containing at least one port - the node	86	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,	87	which provides nodes to manage each other remotely, and to create new
55	among other things.	88	ports.
56		89
57	Initially, nodes are either private (single-process only) or hidden	90	Nodes are either private (single-process only), slaves (can only talk to
58	(connected to a master node only). Only when they epxlicitly "become	91	public nodes, but do not need an open port) or public nodes (connectable
59	public" can you send them messages from unrelated other nodes.	92	from any other node).
60		93
61	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
62		95
63	A noderef is a string that either uniquely identifies a given node (for	96	A node reference is a string that either simply identifies the node (for
64	private and hidden nodes), or contains a recipe on how to reach a given	97	private and slave nodes), or contains a recipe on how to reach a given
65	node (for public nodes).	98	node (for public nodes).
66		99
		100	This recipe is simply a comma-separated list of C<address:port> pairs (for
		101	TCP/IP, other protocols might look different).
		102
		103	Node references come in two flavours: resolved (containing only numerical
		104	addresses) or unresolved (where hostnames are used instead of addresses).
		105
		106	Before using an unresolved node reference in a message you first have to
		107	resolve it.
		108
67	=back	109	=back
68		110
69	=head1 VARIABLES/FUNCTIONS	111	=head1 VARIABLES/FUNCTIONS
70		112
71	=over 4	113	=over 4
72		114
73	=cut	115	=cut
74		116
75	package AnyEvent::MP;	117	package AnyEvent::MP;
76		118
77	use AnyEvent::MP::Base;	119	use AnyEvent::MP::Kernel;
78		120
79	use common::sense;	121	use common::sense;
80		122
81	use Carp ();	123	use Carp ();
82		124
83	use AE ();	125	use AE ();
84		126
85	use base "Exporter";	127	use base "Exporter";
86		128
87	our $VERSION = '0.02';	129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		130
88	our @EXPORT = qw(	131	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv _any_	132	NODE $NODE *SELF node_of after
90	create_port create_port_on	133	resolve_node initialise_node
91	create_miniport	134	snd rcv mon mon_guard kil reg psub spawn
92	become_slave become_public	135	port
93	);	136	);
94		137
		138	our $SELF;
		139
		140	sub _self_die() {
		141	my $msg = $@;
		142	$msg =~ s/\n+$// unless ref $msg;
		143	kil $SELF, die => $msg;
		144	}
		145
95	=item NODE / $NODE	146	=item $thisnode = NODE / $NODE
96		147
97	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	148	The C<NODE> function returns, and the C<$NODE> variable contains the
98	the local node. The value is initialised by a call to C<become_public> or	149	noderef of the local node. The value is initialised by a call to
99	C<become_slave>, after which all local port identifiers become invalid.	150	C<initialise_node>.
100		151
		152	=item $noderef = node_of $port
		153
		154	Extracts and returns the noderef from a port ID or a noderef.
		155
		156	=item initialise_node $noderef, $seednode, $seednode...
		157
		158	=item initialise_node "slave/", $master, $master...
		159
		160	Before a node can talk to other nodes on the network it has to initialise
		161	itself - the minimum a node needs to know is it's own name, and optionally
		162	it should know the noderefs of some other nodes in the network.
		163
		164	This function initialises a node - it must be called exactly once (or
		165	never) before calling other AnyEvent::MP functions.
		166
		167	All arguments (optionally except for the first) are noderefs, which can be
		168	either resolved or unresolved.
		169
		170	The first argument will be looked up in the configuration database first
		171	(if it is C<undef> then the current nodename will be used instead) to find
		172	the relevant configuration profile (see L<aemp>). If none is found then
		173	the default configuration is used. The configuration supplies additional
		174	seed/master nodes and can override the actual noderef.
		175
		176	There are two types of networked nodes, public nodes and slave nodes:
		177
		178	=over 4
		179
		180	=item public nodes
		181
		182	For public nodes, C<$noderef> (supplied either directly to
		183	C<initialise_node> or indirectly via a profile or the nodename) must be a
		184	noderef (possibly unresolved, in which case it will be resolved).
		185
		186	After resolving, the node will bind itself on all endpoints.
		187
		188	=item slave nodes
		189
		190	When the C<$noderef> (either as given or overriden by the config file)
		191	is the special string C<slave/>, then the node will become a slave
		192	node. Slave nodes cannot be contacted from outside, and cannot talk to
		193	each other (at least in this version of AnyEvent::MP).
		194
		195	Slave nodes work by creating connections to all public nodes, using the
		196	L<AnyEvent::MP::Global> service.
		197
		198	=back
		199
		200	After initialising itself, the node will connect to all additional
		201	C<$seednodes> that are specified diretcly or via a profile. Seednodes are
		202	optional and can be used to quickly bootstrap the node into an existing
		203	network.
		204
		205	All the seednodes will also be specially marked to automatically retry
		206	connecting to them indefinitely, so make sure that seednodes are really
		207	reliable and up (this might also change in the future).
		208
		209	Example: become a public node listening on the guessed noderef, or the one
		210	specified via C<aemp> for the current node. This should be the most common
		211	form of invocation for "daemon"-type nodes.
		212
		213	initialise_node;
		214
		215	Example: become a slave node to any of the the seednodes specified via
		216	C<aemp>. This form is often used for commandline clients.
		217
		218	initialise_node "slave/";
		219
		220	Example: become a public node, and try to contact some well-known master
		221	servers to become part of the network.
		222
		223	initialise_node undef, "master1", "master2";
		224
		225	Example: become a public node listening on port C<4041>.
		226
		227	initialise_node 4041;
		228
		229	Example: become a public node, only visible on localhost port 4044.
		230
		231	initialise_node "localhost:4044";
		232
		233	=item $cv = resolve_node $noderef
		234
		235	Takes an unresolved node reference that may contain hostnames and
		236	abbreviated IDs, resolves all of them and returns a resolved node
		237	reference.
		238
		239	In addition to C<address:port> pairs allowed in resolved noderefs, the
		240	following forms are supported:
		241
		242	=over 4
		243
		244	=item the empty string
		245
		246	An empty-string component gets resolved as if the default port (4040) was
		247	specified.
		248
		249	=item naked port numbers (e.g. C<1234>)
		250
		251	These are resolved by prepending the local nodename and a colon, to be
		252	further resolved.
		253
		254	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
		255
		256	These are resolved by using AnyEvent::DNS to resolve them, optionally
		257	looking up SRV records for the C<aemp=4040> port, if no port was
		258	specified.
		259
		260	=back
		261
		262	=item $SELF
		263
		264	Contains the current port id while executing C<rcv> callbacks or C<psub>
		265	blocks.
		266
		267	=item SELF, %SELF, @SELF...
		268
		269	Due to some quirks in how perl exports variables, it is impossible to
		270	just export C<$SELF>, all the symbols called C<SELF> are exported by this
		271	module, but only C<$SELF> is currently used.
		272
101	=item snd $portid, type => @data	273	=item snd $port, type => @data
102		274
103	=item snd $portid, @msg	275	=item snd $port, @msg
104		276
105	Send the given message to the given port ID, which can identify either	277	Send the given message to the given port ID, which can identify either
106	a local or a remote port, and can be either a string or soemthignt hat	278	a local or a remote port, and must be a port ID.
107	stringifies a sa port ID (such as a port object :).
108		279
109	While the message can be about anything, it is highly recommended to use a	280	While the message can be about anything, it is highly recommended to use a
110	string as first element (a portid, or some word that indicates a request	281	string as first element (a port ID, or some word that indicates a request
111	type etc.).	282	type etc.).
112		283
113	The message data effectively becomes read-only after a call to this	284	The message data effectively becomes read-only after a call to this
114	function: modifying any argument is not allowed and can cause many	285	function: modifying any argument is not allowed and can cause many
115	problems.	286	problems.
…		…
118	JSON is used, then only strings, numbers and arrays and hashes consisting	289	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	290	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	291	that Storable can serialise and deserialise is allowed, and for the local
121	node, anything can be passed.	292	node, anything can be passed.
122		293
123	=item $local_port = create_port	294	=item $local_port = port
124		295
125	Create a new local port object. See the next section for allowed methods.	296	Create a new local port object and returns its port ID. Initially it has
		297	no callbacks set and will throw an error when it receives messages.
126		298
127	=cut	299	=item $local_port = port { my @msg = @_ }
128		300
129	sub create_port {	301	Creates a new local port, and returns its ID. Semantically the same as
130	my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;	302	creating a port and calling C<rcv $port, $callback> on it.
131		303
132	my $self = bless {	304	The block will be called for every message received on the port, with the
133	id => "$NODE#$id",	305	global variable C<$SELF> set to the port ID. Runtime errors will cause the
134	names => [$id],	306	port to be C<kil>ed. The message will be passed as-is, no extra argument
135	}, "AnyEvent::MP::Port";	307	(i.e. no port ID) will be passed to the callback.
136		308
137	$AnyEvent::MP::Base::PORT{$id} = sub {	309	If you want to stop/destroy the port, simply C<kil> it:
138	unshift @_, $self;
139		310
140	for (@{ $self->{rc0}{$_[1]} }) {	311	my $port = port {
141	$_ && &{$_->[0]}	312	my @msg = @_;
142	&& undef $_;	313	...
		314	kil $SELF;
		315	};
		316
		317	=cut
		318
		319	sub rcv($@);
		320
		321	sub _kilme {
		322	die "received message on port without callback";
		323	}
		324
		325	sub port(;&) {
		326	my $id = "$UNIQ." . $ID++;
		327	my $port = "$NODE#$id";
		328
		329	rcv $port, shift \|\| \&_kilme;
		330
		331	$port
		332	}
		333
		334	=item rcv $local_port, $callback->(@msg)
		335
		336	Replaces the default callback on the specified port. There is no way to
		337	remove the default callback: use C<sub { }> to disable it, or better
		338	C<kil> the port when it is no longer needed.
		339
		340	The global C<$SELF> (exported by this module) contains C<$port> while
		341	executing the callback. Runtime errors during callback execution will
		342	result in the port being C<kil>ed.
		343
		344	The default callback received all messages not matched by a more specific
		345	C<tag> match.
		346
		347	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		348
		349	Register (or replace) callbacks to be called on messages starting with the
		350	given tag on the given port (and return the port), or unregister it (when
		351	C<$callback> is C<$undef> or missing). There can only be one callback
		352	registered for each tag.
		353
		354	The original message will be passed to the callback, after the first
		355	element (the tag) has been removed. The callback will use the same
		356	environment as the default callback (see above).
		357
		358	Example: create a port and bind receivers on it in one go.
		359
		360	my $port = rcv port,
		361	msg1 => sub { ... },
		362	msg2 => sub { ... },
		363	;
		364
		365	Example: create a port, bind receivers and send it in a message elsewhere
		366	in one go:
		367
		368	snd $otherport, reply =>
		369	rcv port,
		370	msg1 => sub { ... },
		371	...
		372	;
		373
		374	Example: temporarily register a rcv callback for a tag matching some port
		375	(e.g. for a rpc reply) and unregister it after a message was received.
		376
		377	rcv $port, $otherport => sub {
		378	my @reply = @_;
		379
		380	rcv $SELF, $otherport;
		381	};
		382
		383	=cut
		384
		385	sub rcv($@) {
		386	my $port = shift;
		387	my ($noderef, $portid) = split /#/, $port, 2;
		388
		389	$NODE{$noderef} == $NODE{""}
		390	or Carp::croak "$port: rcv can only be called on local ports, caught";
		391
		392	while (@_) {
		393	if (ref $_[0]) {
		394	if (my $self = $PORT_DATA{$portid}) {
		395	"AnyEvent::MP::Port" eq ref $self
		396	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		397
		398	$self->[2] = shift;
		399	} else {
		400	my $cb = shift;
		401	$PORT{$portid} = sub {
		402	local $SELF = $port;
		403	eval { &$cb }; _self_die if $@;
		404	};
		405	}
		406	} elsif (defined $_[0]) {
		407	my $self = $PORT_DATA{$portid} \|\|= do {
		408	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		409
		410	$PORT{$portid} = sub {
		411	local $SELF = $port;
		412
		413	if (my $cb = $self->[1]{$_[0]}) {
		414	shift;
		415	eval { &$cb }; _self_die if $@;
		416	} else {
		417	&{ $self->[0] };
		418	}
		419	};
		420
		421	$self
		422	};
		423
		424	"AnyEvent::MP::Port" eq ref $self
		425	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		426
		427	my ($tag, $cb) = splice @_, 0, 2;
		428
		429	if (defined $cb) {
		430	$self->[1]{$tag} = $cb;
		431	} else {
		432	delete $self->[1]{$tag};
		433	}
143	}	434	}
		435	}
144		436
145	for (@{ $self->{rcv}{$_[1]} }) {	437	$port
146	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	438	}
147	&& &{$_->[0]}	439
148	&& undef $_;	440	=item $closure = psub { BLOCK }
		441
		442	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		443	closure is executed, sets up the environment in the same way as in C<rcv>
		444	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		445
		446	This is useful when you register callbacks from C<rcv> callbacks:
		447
		448	rcv delayed_reply => sub {
		449	my ($delay, @reply) = @_;
		450	my $timer = AE::timer $delay, 0, psub {
		451	snd @reply, $SELF;
		452	};
		453	};
		454
		455	=cut
		456
		457	sub psub(&) {
		458	my $cb = shift;
		459
		460	my $port = $SELF
		461	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		462
		463	sub {
		464	local $SELF = $port;
		465
		466	if (wantarray) {
		467	my @res = eval { &$cb };
		468	_self_die if $@;
		469	@res
		470	} else {
		471	my $res = eval { &$cb };
		472	_self_die if $@;
		473	$res
149	}	474	}
		475	}
		476	}
150		477
151	for (@{ $self->{any} }) {	478	=item $guard = mon $port, $cb->(@reason)
152	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	479
153	&& &{$_->[0]}	480	=item $guard = mon $port, $rcvport
154	&& undef $_;	481
		482	=item $guard = mon $port
		483
		484	=item $guard = mon $port, $rcvport, @msg
		485
		486	Monitor the given port and do something when the port is killed or
		487	messages to it were lost, and optionally return a guard that can be used
		488	to stop monitoring again.
		489
		490	C<mon> effectively guarantees that, in the absence of hardware failures,
		491	that after starting the monitor, either all messages sent to the port
		492	will arrive, or the monitoring action will be invoked after possible
		493	message loss has been detected. No messages will be lost "in between"
		494	(after the first lost message no further messages will be received by the
		495	port). After the monitoring action was invoked, further messages might get
		496	delivered again.
		497
		498	Note that monitoring-actions are one-shot: once released, they are removed
		499	and will not trigger again.
		500
		501	In the first form (callback), the callback is simply called with any
		502	number of C<@reason> elements (no @reason means that the port was deleted
		503	"normally"). Note also that I<< the callback B<must> never die >>, so use
		504	C<eval> if unsure.
		505
		506	In the second form (another port given), the other port (C<$rcvport>)
		507	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
		508	"normal" kils nothing happens, while under all other conditions, the other
		509	port is killed with the same reason.
		510
		511	The third form (kill self) is the same as the second form, except that
		512	C<$rvport> defaults to C<$SELF>.
		513
		514	In the last form (message), a message of the form C<@msg, @reason> will be
		515	C<snd>.
		516
		517	As a rule of thumb, monitoring requests should always monitor a port from
		518	a local port (or callback). The reason is that kill messages might get
		519	lost, just like any other message. Another less obvious reason is that
		520	even monitoring requests can get lost (for exmaple, when the connection
		521	to the other node goes down permanently). When monitoring a port locally
		522	these problems do not exist.
		523
		524	Example: call a given callback when C<$port> is killed.
		525
		526	mon $port, sub { warn "port died because of <@_>\n" };
		527
		528	Example: kill ourselves when C<$port> is killed abnormally.
		529
		530	mon $port;
		531
		532	Example: send us a restart message when another C<$port> is killed.
		533
		534	mon $port, $self => "restart";
		535
		536	=cut
		537
		538	sub mon {
		539	my ($noderef, $port) = split /#/, shift, 2;
		540
		541	my $node = $NODE{$noderef} \|\| add_node $noderef;
		542
		543	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		544
		545	unless (ref $cb) {
		546	if (@_) {
		547	# send a kill info message
		548	my (@msg) = ($cb, @_);
		549	$cb = sub { snd @msg, @_ };
		550	} else {
		551	# simply kill other port
		552	my $port = $cb;
		553	$cb = sub { kil $port, @_ if @_ };
155	}	554	}
		555	}
		556
		557	$node->monitor ($port, $cb);
		558
		559	defined wantarray
		560	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		561	}
		562
		563	=item $guard = mon_guard $port, $ref, $ref...
		564
		565	Monitors the given C<$port> and keeps the passed references. When the port
		566	is killed, the references will be freed.
		567
		568	Optionally returns a guard that will stop the monitoring.
		569
		570	This function is useful when you create e.g. timers or other watchers and
		571	want to free them when the port gets killed:
		572
		573	$port->rcv (start => sub {
		574	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		575	undef $timer if 0.9 < rand;
		576	});
		577	});
		578
		579	=cut
		580
		581	sub mon_guard {
		582	my ($port, @refs) = @_;
		583
		584	#TODO: mon-less form?
		585
		586	mon $port, sub { 0 && @refs }
		587	}
		588
		589	=item kil $port[, @reason]
		590
		591	Kill the specified port with the given C<@reason>.
		592
		593	If no C<@reason> is specified, then the port is killed "normally" (linked
		594	ports will not be kileld, or even notified).
		595
		596	Otherwise, linked ports get killed with the same reason (second form of
		597	C<mon>, see below).
		598
		599	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		600	will be reported as reason C<< die => $@ >>.
		601
		602	Transport/communication errors are reported as C<< transport_error =>
		603	$message >>.
		604
		605	=cut
		606
		607	=item $port = spawn $node, $initfunc[, @initdata]
		608
		609	Creates a port on the node C<$node> (which can also be a port ID, in which
		610	case it's the node where that port resides).
		611
		612	The port ID of the newly created port is return immediately, and it is
		613	permissible to immediately start sending messages or monitor the port.
		614
		615	After the port has been created, the init function is
		616	called. This function must be a fully-qualified function name
		617	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		618	program, use C<::name>.
		619
		620	If the function doesn't exist, then the node tries to C<require>
		621	the package, then the package above the package and so on (e.g.
		622	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		623	exists or it runs out of package names.
		624
		625	The init function is then called with the newly-created port as context
		626	object (C<$SELF>) and the C<@initdata> values as arguments.
		627
		628	A common idiom is to pass your own port, monitor the spawned port, and
		629	in the init function, monitor the original port. This two-way monitoring
		630	ensures that both ports get cleaned up when there is a problem.
		631
		632	Example: spawn a chat server port on C<$othernode>.
		633
		634	# this node, executed from within a port context:
		635	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		636	mon $server;
		637
		638	# init function on C<$othernode>
		639	sub connect {
		640	my ($srcport) = @_;
		641
		642	mon $srcport;
		643
		644	rcv $SELF, sub {
		645	...
		646	};
		647	}
		648
		649	=cut
		650
		651	sub _spawn {
		652	my $port = shift;
		653	my $init = shift;
		654
		655	local $SELF = "$NODE#$port";
		656	eval {
		657	&{ load_func $init }
156	};	658	};
157		659	_self_die if $@;
158	$self
159	}	660	}
160		661
161	=item $portid = miniport { my @msg = @_; $finished }	662	sub spawn(@) {
		663	my ($noderef, undef) = split /#/, shift, 2;
162		664
163	Creates a "mini port", that is, a very lightweight port without any	665	my $id = "$RUNIQ." . $ID++;
164	pattern matching behind it, and returns its ID.
165		666
166	The block will be called for every message received on the port. When the	667	$_[0] =~ /::/
167	callback returns a true value its job is considered "done" and the port	668	or Carp::croak "spawn init function must be a fully-qualified name, caught";
168	will be destroyed. Otherwise it will stay alive.
169		669
170	The message will be passed as-is, no extra argument (ie.. no port id) will	670	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
171	be passed to the callback.
172		671
173	If you need the local port id in the callback, this works nicely:	672	"$noderef#$id"
		673	}
174		674
175	my $port; $port = miniport {	675	=item after $timeout, @msg
176	snd $otherport, reply => $port;	676
		677	=item after $timeout, $callback
		678
		679	Either sends the given message, or call the given callback, after the
		680	specified number of seconds.
		681
		682	This is simply a utility function that come sin handy at times.
		683
		684	=cut
		685
		686	sub after($@) {
		687	my ($timeout, @action) = @_;
		688
		689	my $t; $t = AE::timer $timeout, 0, sub {
		690	undef $t;
		691	ref $action[0]
		692	? $action[0]()
		693	: snd @action;
177	};	694	};
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	}	695	}
192
193	package AnyEvent::MP::Port;
194		696
195	=back	697	=back
196		698
197	=head1 METHODS FOR PORT OBJECTS	699	=head1 AnyEvent::MP vs. Distributed Erlang
		700
		701	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		702	== aemp node, Erlang process == aemp port), so many of the documents and
		703	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		704	sample:
		705
		706	http://www.Erlang.se/doc/programming_rules.shtml
		707	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		708	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		709	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		710
		711	Despite the similarities, there are also some important differences:
198		712
199	=over 4	713	=over 4
200		714
201	=item "$port"	715	=item * Node references contain the recipe on how to contact them.
202		716
203	A port object stringifies to its port ID, so can be used directly for	717	Erlang relies on special naming and DNS to work everywhere in the
204	C<snd> operations.	718	same way. AEMP relies on each node knowing it's own address(es), with
		719	convenience functionality.
205		720
206	=cut	721	This means that AEMP requires a less tightly controlled environment at the
		722	cost of longer node references and a slightly higher management overhead.
207		723
208	use overload	724	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
209	'""' => sub { $_[0]{id} },	725	uses "local ports are like remote ports".
210	fallback => 1;
211		726
212	=item $port->rcv (type => $callback->($port, @msg))	727	The failure modes for local ports are quite different (runtime errors
		728	only) then for remote ports - when a local port dies, you I<know> it dies,
		729	when a connection to another node dies, you know nothing about the other
		730	port.
213		731
214	=item $port->rcv ($smartmatch => $callback->($port, @msg))	732	Erlang pretends remote ports are as reliable as local ports, even when
		733	they are not.
215		734
216	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	735	AEMP encourages a "treat remote ports differently" philosophy, with local
		736	ports being the special case/exception, where transport errors cannot
		737	occur.
217		738
218	Register a callback on the given port.	739	=item * Erlang uses processes and a mailbox, AEMP does not queue.
219		740
220	The callback has to return a true value when its work is done, after	741	Erlang uses processes that selectively receive messages, and therefore
221	which is will be removed, or a false value in which case it will stay	742	needs a queue. AEMP is event based, queuing messages would serve no
222	registered.	743	useful purpose. For the same reason the pattern-matching abilities of
		744	AnyEvent::MP are more limited, as there is little need to be able to
		745	filter messages without dequeing them.
223		746
224	If the match is an array reference, then it will be matched against the	747	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
225	first elements of the message, otherwise only the first element is being
226	matched.
227		748
228	Any element in the match that is specified as C<_any_> (a function	749	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
229	exported by this module) matches any single element of the message.
230		750
231	While not required, it is highly recommended that the first matching	751	Sending messages in Erlang is synchronous and blocks the process (and
232	element is a string identifying the message. The one-string-only match is	752	so does not need a queue that can overflow). AEMP sends are immediate,
233	also the most efficient match (by far).	753	connection establishment is handled in the background.
234		754
235	=cut	755	=item * Erlang suffers from silent message loss, AEMP does not.
236		756
237	sub rcv($@) {	757	Erlang makes few guarantees on messages delivery - messages can get lost
238	my ($self, $match, $cb) = @_;	758	without any of the processes realising it (i.e. you send messages a, b,
		759	and c, and the other side only receives messages a and c).
239		760
240	if (!ref $match) {	761	AEMP guarantees correct ordering, and the guarantee that there are no
241	push @{ $self->{rc0}{$match} }, [$cb];	762	holes in the message sequence.
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		763
252	=item $port->register ($name)	764	=item * In Erlang, processes can be declared dead and later be found to be
		765	alive.
253		766
254	Registers the given port under the well known name C<$name>. If the name	767	In Erlang it can happen that a monitored process is declared dead and
255	already exists it is replaced.	768	linked processes get killed, but later it turns out that the process is
		769	still alive - and can receive messages.
256		770
257	A port can only be registered under one well known name.	771	In AEMP, when port monitoring detects a port as dead, then that port will
		772	eventually be killed - it cannot happen that a node detects a port as dead
		773	and then later sends messages to it, finding it is still alive.
258		774
259	=cut	775	=item * Erlang can send messages to the wrong port, AEMP does not.
260		776
261	sub register {	777	In Erlang it is quite likely that a node that restarts reuses a process ID
262	my ($self, $name) = @_;	778	known to other nodes for a completely different process, causing messages
		779	destined for that process to end up in an unrelated process.
263		780
264	$self->{wkname} = $name;	781	AEMP never reuses port IDs, so old messages or old port IDs floating
265	$AnyEvent::MP::Base::WKP{$name} = "$self";	782	around in the network will not be sent to an unrelated port.
266	}
267		783
268	=item $port->destroy	784	=item * Erlang uses unprotected connections, AEMP uses secure
		785	authentication and can use TLS.
269		786
270	Explicitly destroy/remove/nuke/vaporise the port.	787	AEMP can use a proven protocol - SSL/TLS - to protect connections and
		788	securely authenticate nodes.
271		789
272	Ports are normally kept alive by there mere existance alone, and need to	790	=item * The AEMP protocol is optimised for both text-based and binary
273	be destroyed explicitly.	791	communications.
274		792
275	=cut	793	The AEMP protocol, unlike the Erlang protocol, supports both
		794	language-independent text-only protocols (good for debugging) and binary,
		795	language-specific serialisers (e.g. Storable).
276		796
277	sub destroy {	797	It has also been carefully designed to be implementable in other languages
278	my ($self) = @_;	798	with a minimum of work while gracefully degrading fucntionality to make the
		799	protocol simple.
279		800
280	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	801	=item * AEMP has more flexible monitoring options than Erlang.
281		802
282	delete $AnyEvent::MP::Base::PORT{$_}	803	In Erlang, you can chose to receive I<all> exit signals as messages
283	for @{ $self->{names} };	804	or I<none>, there is no in-between, so monitoring single processes is
284	}	805	difficult to implement. Monitoring in AEMP is more flexible than in
		806	Erlang, as one can choose between automatic kill, exit message or callback
		807	on a per-process basis.
		808
		809	=item * Erlang tries to hide remote/local connections, AEMP does not.
		810
		811	Monitoring in Erlang is not an indicator of process death/crashes,
		812	as linking is (except linking is unreliable in Erlang).
		813
		814	In AEMP, you don't "look up" registered port names or send to named ports
		815	that might or might not be persistent. Instead, you normally spawn a port
		816	on the remote node. The init function monitors the you, and you monitor
		817	the remote port. Since both monitors are local to the node, they are much
		818	more reliable.
		819
		820	This also saves round-trips and avoids sending messages to the wrong port
		821	(hard to do in Erlang).
285		822
286	=back	823	=back
287		824
288	=head1 FUNCTIONS FOR NODES	825	=head1 RATIONALE
289		826
290	=over 4	827	=over 4
291		828
292	=item mon $noderef, $callback->($noderef, $status, $)	829	=item Why strings for ports and noderefs, why not objects?
293		830
294	Monitors the given noderef.	831	We considered "objects", but found that the actual number of methods
		832	thatc an be called are very low. Since port IDs and noderefs travel over
		833	the network frequently, the serialising/deserialising would add lots of
		834	overhead, as well as having to keep a proxy object.
295		835
296	=item become_public endpoint...	836	Strings can easily be printed, easily serialised etc. and need no special
		837	procedures to be "valid".
297		838
298	Tells the node to become a public node, i.e. reachable from other nodes.	839	And a a miniport consists of a single closure stored in a global hash - it
		840	can't become much cheaper.
299		841
300	If no arguments are given, or the first argument is C<undef>, then	842	=item Why favour JSON, why not 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		843
304	Otherwise the first argument must be an array-reference with transport	844	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	845	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	846	default.
307	will become the node reference.
308		847
309	=cut	848	The default framing protocol is JSON because a) JSON::XS is many times
		849	faster for small messages and b) most importantly, after years of
		850	experience we found that object serialisation is causing more problems
		851	than it gains: Just like function calls, objects simply do not travel
		852	easily over the network, mostly because they will always be a copy, so you
		853	always have to re-think your design.
310		854
311	=back	855	Keeping your messages simple, concentrating on data structures rather than
312		856	objects, will keep your messages clean, tidy and efficient.
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		857
355	=back	858	=back
356		859
357	=head1 SEE ALSO	860	=head1 SEE ALSO
358		861

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Revision 1.62 by root, Thu Aug 27 07:12:48 2009 UTC