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

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.19 by root, Mon Aug 3 21:37:19 2009 UTC vs.
Revision 1.54 by root, Fri Aug 14 16:15:37 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		46	AnyEvent::MP::Intro - outdated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 (connected to a
58	(connected to a master node only). Only when they epxlicitly "become	91	master node only) or public nodes (connectable from unrelated nodes).
59	public" can you send them messages from unrelated other nodes.
60		92
61	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
62		94
63	A noderef is a string that either uniquely identifies a given node (for	95	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	96	private and slave nodes), or contains a recipe on how to reach a given
65	node (for public nodes).	97	node (for public nodes).
66		98
		99	This recipe is simply a comma-separated list of C<address:port> pairs (for
		100	TCP/IP, other protocols might look different).
		101
		102	Node references come in two flavours: resolved (containing only numerical
		103	addresses) or unresolved (where hostnames are used instead of addresses).
		104
		105	Before using an unresolved node reference in a message you first have to
		106	resolve it.
		107
67	=back	108	=back
68		109
69	=head1 VARIABLES/FUNCTIONS	110	=head1 VARIABLES/FUNCTIONS
70		111
71	=over 4	112	=over 4
72		113
73	=cut	114	=cut
74		115
75	package AnyEvent::MP;	116	package AnyEvent::MP;
76		117
77	use AnyEvent::MP::Base;	118	use AnyEvent::MP::Kernel;
78		119
79	use common::sense;	120	use common::sense;
80		121
81	use Carp ();	122	use Carp ();
82		123
83	use AE ();	124	use AE ();
84		125
85	use base "Exporter";	126	use base "Exporter";
86		127
87	our $VERSION = '0.02';	128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		129
88	our @EXPORT = qw(	130	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv mon del _any_	131	NODE $NODE *SELF node_of _any_
90	create_port create_port_on	132	resolve_node initialise_node
91	create_miniport	133	snd rcv mon kil reg psub spawn
92	become_slave become_public	134	port
93	);	135	);
94		136
		137	our $SELF;
		138
		139	sub _self_die() {
		140	my $msg = $@;
		141	$msg =~ s/\n+$// unless ref $msg;
		142	kil $SELF, die => $msg;
		143	}
		144
95	=item NODE / $NODE	145	=item $thisnode = NODE / $NODE
96		146
97	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	147	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	148	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.	149	C<initialise_node>.
100		150
		151	=item $noderef = node_of $port
		152
		153	Extracts and returns the noderef from a port ID or a noderef.
		154
		155	=item initialise_node $noderef, $seednode, $seednode...
		156
		157	=item initialise_node "slave/", $master, $master...
		158
		159	Before a node can talk to other nodes on the network it has to initialise
		160	itself - the minimum a node needs to know is it's own name, and optionally
		161	it should know the noderefs of some other nodes in the network.
		162
		163	This function initialises a node - it must be called exactly once (or
		164	never) before calling other AnyEvent::MP functions.
		165
		166	All arguments (optionally except for the first) are noderefs, which can be
		167	either resolved or unresolved.
		168
		169	The first argument will be looked up in the configuration database first
		170	(if it is C<undef> then the current nodename will be used instead) to find
		171	the relevant configuration profile (see L<aemp>). If none is found then
		172	the default configuration is used. The configuration supplies additional
		173	seed/master nodes and can override the actual noderef.
		174
		175	There are two types of networked nodes, public nodes and slave nodes:
		176
		177	=over 4
		178
		179	=item public nodes
		180
		181	For public nodes, C<$noderef> (supplied either directly to
		182	C<initialise_node> or indirectly via a profile or the nodename) must be a
		183	noderef (possibly unresolved, in which case it will be resolved).
		184
		185	After resolving, the node will bind itself on all endpoints and try to
		186	connect to all additional C<$seednodes> that are specified. Seednodes are
		187	optional and can be used to quickly bootstrap the node into an existing
		188	network.
		189
		190	=item slave nodes
		191
		192	When the C<$noderef> (either as given or overriden by the config file)
		193	is the special string C<slave/>, then the node will become a slave
		194	node. Slave nodes cannot be contacted from outside and will route most of
		195	their traffic to the master node that they attach to.
		196
		197	At least one additional noderef is required (either by specifying it
		198	directly or because it is part of the configuration profile): The node
		199	will try to connect to all of them and will become a slave attached to the
		200	first node it can successfully connect to.
		201
		202	=back
		203
		204	This function will block until all nodes have been resolved and, for slave
		205	nodes, until it has successfully established a connection to a master
		206	server.
		207
		208	Example: become a public node listening on the guessed noderef, or the one
		209	specified via C<aemp> for the current node. This should be the most common
		210	form of invocation for "daemon"-type nodes.
		211
		212	initialise_node;
		213
		214	Example: become a slave node to any of the the seednodes specified via
		215	C<aemp>. This form is often used for commandline clients.
		216
		217	initialise_node "slave/";
		218
		219	Example: become a slave node to any of the specified master servers. This
		220	form is also often used for commandline clients.
		221
		222	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
		223
		224	Example: become a public node, and try to contact some well-known master
		225	servers to become part of the network.
		226
		227	initialise_node undef, "master1", "master2";
		228
		229	Example: become a public node listening on port C<4041>.
		230
		231	initialise_node 4041;
		232
		233	Example: become a public node, only visible on localhost port 4044.
		234
		235	initialise_node "localhost:4044";
		236
		237	=item $cv = resolve_node $noderef
		238
		239	Takes an unresolved node reference that may contain hostnames and
		240	abbreviated IDs, resolves all of them and returns a resolved node
		241	reference.
		242
		243	In addition to C<address:port> pairs allowed in resolved noderefs, the
		244	following forms are supported:
		245
		246	=over 4
		247
		248	=item the empty string
		249
		250	An empty-string component gets resolved as if the default port (4040) was
		251	specified.
		252
		253	=item naked port numbers (e.g. C<1234>)
		254
		255	These are resolved by prepending the local nodename and a colon, to be
		256	further resolved.
		257
		258	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
		259
		260	These are resolved by using AnyEvent::DNS to resolve them, optionally
		261	looking up SRV records for the C<aemp=4040> port, if no port was
		262	specified.
		263
		264	=back
		265
		266	=item $SELF
		267
		268	Contains the current port id while executing C<rcv> callbacks or C<psub>
		269	blocks.
		270
		271	=item SELF, %SELF, @SELF...
		272
		273	Due to some quirks in how perl exports variables, it is impossible to
		274	just export C<$SELF>, all the symbols called C<SELF> are exported by this
		275	module, but only C<$SELF> is currently used.
		276
101	=item snd $portid, type => @data	277	=item snd $port, type => @data
102		278
103	=item snd $portid, @msg	279	=item snd $port, @msg
104		280
105	Send the given message to the given port ID, which can identify either	281	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	282	a local or a remote port, and must be a port ID.
107	stringifies a sa port ID (such as a port object :).
108		283
109	While the message can be about anything, it is highly recommended to use a	284	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	285	string as first element (a port ID, or some word that indicates a request
111	type etc.).	286	type etc.).
112		287
113	The message data effectively becomes read-only after a call to this	288	The message data effectively becomes read-only after a call to this
114	function: modifying any argument is not allowed and can cause many	289	function: modifying any argument is not allowed and can cause many
115	problems.	290	problems.
…		…
118	JSON is used, then only strings, numbers and arrays and hashes consisting	293	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	294	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	295	that Storable can serialise and deserialise is allowed, and for the local
121	node, anything can be passed.	296	node, anything can be passed.
122		297
123	=item mon $portid, sub { }	298	=item $local_port = port
124		299
125	#TODO monitor the given port	300	Create a new local port object and returns its port ID. Initially it has
		301	no callbacks set and will throw an error when it receives messages.
		302
		303	=item $local_port = port { my @msg = @_ }
		304
		305	Creates a new local port, and returns its ID. Semantically the same as
		306	creating a port and calling C<rcv $port, $callback> on it.
		307
		308	The block will be called for every message received on the port, with the
		309	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		310	port to be C<kil>ed. The message will be passed as-is, no extra argument
		311	(i.e. no port ID) will be passed to the callback.
		312
		313	If you want to stop/destroy the port, simply C<kil> it:
		314
		315	my $port = port {
		316	my @msg = @_;
		317	...
		318	kil $SELF;
		319	};
		320
		321	=cut
		322
		323	sub rcv($@);
		324
		325	sub _kilme {
		326	die "received message on port without callback";
		327	}
		328
		329	sub port(;&) {
		330	my $id = "$UNIQ." . $ID++;
		331	my $port = "$NODE#$id";
		332
		333	rcv $port, shift \|\| \&_kilme;
		334
		335	$port
		336	}
		337
		338	=item rcv $local_port, $callback->(@msg)
		339
		340	Replaces the default callback on the specified port. There is no way to
		341	remove the default callback: use C<sub { }> to disable it, or better
		342	C<kil> the port when it is no longer needed.
		343
		344	The global C<$SELF> (exported by this module) contains C<$port> while
		345	executing the callback. Runtime errors during callback execution will
		346	result in the port being C<kil>ed.
		347
		348	The default callback received all messages not matched by a more specific
		349	C<tag> match.
		350
		351	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		352
		353	Register (or replace) callbacks to be called on messages starting with the
		354	given tag on the given port (and return the port), or unregister it (when
		355	C<$callback> is C<$undef> or missing). There can only be one callback
		356	registered for each tag.
		357
		358	The original message will be passed to the callback, after the first
		359	element (the tag) has been removed. The callback will use the same
		360	environment as the default callback (see above).
		361
		362	Example: create a port and bind receivers on it in one go.
		363
		364	my $port = rcv port,
		365	msg1 => sub { ... },
		366	msg2 => sub { ... },
		367	;
		368
		369	Example: create a port, bind receivers and send it in a message elsewhere
		370	in one go:
		371
		372	snd $otherport, reply =>
		373	rcv port,
		374	msg1 => sub { ... },
		375	...
		376	;
		377
		378	Example: temporarily register a rcv callback for a tag matching some port
		379	(e.g. for a rpc reply) and unregister it after a message was received.
		380
		381	rcv $port, $otherport => sub {
		382	my @reply = @_;
		383
		384	rcv $SELF, $otherport;
		385	};
		386
		387	=cut
		388
		389	sub rcv($@) {
		390	my $port = shift;
		391	my ($noderef, $portid) = split /#/, $port, 2;
		392
		393	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
		394	or Carp::croak "$port: rcv can only be called on local ports, caught";
		395
		396	while (@_) {
		397	if (ref $_[0]) {
		398	if (my $self = $PORT_DATA{$portid}) {
		399	"AnyEvent::MP::Port" eq ref $self
		400	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		401
		402	$self->[2] = shift;
		403	} else {
		404	my $cb = shift;
		405	$PORT{$portid} = sub {
		406	local $SELF = $port;
		407	eval { &$cb }; _self_die if $@;
		408	};
		409	}
		410	} elsif (defined $_[0]) {
		411	my $self = $PORT_DATA{$portid} \|\|= do {
		412	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		413
		414	$PORT{$portid} = sub {
		415	local $SELF = $port;
		416
		417	if (my $cb = $self->[1]{$_[0]}) {
		418	shift;
		419	eval { &$cb }; _self_die if $@;
		420	} else {
		421	&{ $self->[0] };
		422	}
		423	};
		424
		425	$self
		426	};
		427
		428	"AnyEvent::MP::Port" eq ref $self
		429	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		430
		431	my ($tag, $cb) = splice @_, 0, 2;
		432
		433	if (defined $cb) {
		434	$self->[1]{$tag} = $cb;
		435	} else {
		436	delete $self->[1]{$tag};
		437	}
		438	}
		439	}
		440
		441	$port
		442	}
		443
		444	=item $closure = psub { BLOCK }
		445
		446	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		447	closure is executed, sets up the environment in the same way as in C<rcv>
		448	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		449
		450	This is useful when you register callbacks from C<rcv> callbacks:
		451
		452	rcv delayed_reply => sub {
		453	my ($delay, @reply) = @_;
		454	my $timer = AE::timer $delay, 0, psub {
		455	snd @reply, $SELF;
		456	};
		457	};
		458
		459	=cut
		460
		461	sub psub(&) {
		462	my $cb = shift;
		463
		464	my $port = $SELF
		465	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		466
		467	sub {
		468	local $SELF = $port;
		469
		470	if (wantarray) {
		471	my @res = eval { &$cb };
		472	_self_die if $@;
		473	@res
		474	} else {
		475	my $res = eval { &$cb };
		476	_self_die if $@;
		477	$res
		478	}
		479	}
		480	}
		481
		482	=item $guard = mon $port, $cb->(@reason)
		483
		484	=item $guard = mon $port, $rcvport
		485
		486	=item $guard = mon $port
		487
		488	=item $guard = mon $port, $rcvport, @msg
		489
		490	Monitor the given port and do something when the port is killed or
		491	messages to it were lost, and optionally return a guard that can be used
		492	to stop monitoring again.
		493
		494	C<mon> effectively guarantees that, in the absence of hardware failures,
		495	that after starting the monitor, either all messages sent to the port
		496	will arrive, or the monitoring action will be invoked after possible
		497	message loss has been detected. No messages will be lost "in between"
		498	(after the first lost message no further messages will be received by the
		499	port). After the monitoring action was invoked, further messages might get
		500	delivered again.
		501
		502	In the first form (callback), the callback is simply called with any
		503	number of C<@reason> elements (no @reason means that the port was deleted
		504	"normally"). Note also that I<< the callback B<must> never die >>, so use
		505	C<eval> if unsure.
		506
		507	In the second form (another port given), the other port (C<$rcvport>)
		508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
		509	"normal" kils nothing happens, while under all other conditions, the other
		510	port is killed with the same reason.
		511
		512	The third form (kill self) is the same as the second form, except that
		513	C<$rvport> defaults to C<$SELF>.
		514
		515	In the last form (message), a message of the form C<@msg, @reason> will be
		516	C<snd>.
		517
		518	As a rule of thumb, monitoring requests should always monitor a port from
		519	a local port (or callback). The reason is that kill messages might get
		520	lost, just like any other message. Another less obvious reason is that
		521	even monitoring requests can get lost (for exmaple, when the connection
		522	to the other node goes down permanently). When monitoring a port locally
		523	these problems do not exist.
		524
		525	Example: call a given callback when C<$port> is killed.
		526
		527	mon $port, sub { warn "port died because of <@_>\n" };
		528
		529	Example: kill ourselves when C<$port> is killed abnormally.
		530
		531	mon $port;
		532
		533	Example: send us a restart message when another C<$port> is killed.
		534
		535	mon $port, $self => "restart";
126		536
127	=cut	537	=cut
128		538
129	sub mon {	539	sub mon {
130	my ($noderef, $port) = split /#/, shift, 2;	540	my ($noderef, $port) = split /#/, shift, 2;
131		541
132	my $node = AnyEvent::MP::Base::add_node $noderef;	542	my $node = $NODE{$noderef} \|\| add_node $noderef;
133		543
134	my $cb = shift;	544	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		545
		546	unless (ref $cb) {
		547	if (@_) {
		548	# send a kill info message
		549	my (@msg) = ($cb, @_);
		550	$cb = sub { snd @msg, @_ };
		551	} else {
		552	# simply kill other port
		553	my $port = $cb;
		554	$cb = sub { kil $port, @_ if @_ };
		555	}
		556	}
135		557
136	$node->monitor ($port, $cb);	558	$node->monitor ($port, $cb);
137		559
138	defined wantarray	560	defined wantarray
139	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	561	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
140	}	562	}
141		563
142	=item $local_port = create_port	564	=item $guard = mon_guard $port, $ref, $ref...
143		565
144	Create a new local port object. See the next section for allowed methods.	566	Monitors the given C<$port> and keeps the passed references. When the port
		567	is killed, the references will be freed.
145		568
146	=cut	569	Optionally returns a guard that will stop the monitoring.
147		570
148	sub create_port {	571	This function is useful when you create e.g. timers or other watchers and
149	my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;	572	want to free them when the port gets killed:
150		573
151	my $self = bless {	574	$port->rcv (start => sub {
152	id => "$NODE#$id",	575	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
153	names => [$id],	576	undef $timer if 0.9 < rand;
154	}, "AnyEvent::MP::Port";	577	});
		578	});
155		579
156	$AnyEvent::MP::Base::PORT{$id} = sub {	580	=cut
157	unshift @_, $self;
158		581
159	for (@{ $self->{rc0}{$_[1]} }) {	582	sub mon_guard {
160	$_ && &{$_->[0]}	583	my ($port, @refs) = @_;
161	&& undef $_;	584
		585	#TODO: mon-less form?
		586
		587	mon $port, sub { 0 && @refs }
		588	}
		589
		590	=item kil $port[, @reason]
		591
		592	Kill the specified port with the given C<@reason>.
		593
		594	If no C<@reason> is specified, then the port is killed "normally" (linked
		595	ports will not be kileld, or even notified).
		596
		597	Otherwise, linked ports get killed with the same reason (second form of
		598	C<mon>, see below).
		599
		600	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		601	will be reported as reason C<< die => $@ >>.
		602
		603	Transport/communication errors are reported as C<< transport_error =>
		604	$message >>.
		605
		606	=cut
		607
		608	=item $port = spawn $node, $initfunc[, @initdata]
		609
		610	Creates a port on the node C<$node> (which can also be a port ID, in which
		611	case it's the node where that port resides).
		612
		613	The port ID of the newly created port is return immediately, and it is
		614	permissible to immediately start sending messages or monitor the port.
		615
		616	After the port has been created, the init function is
		617	called. This function must be a fully-qualified function name
		618	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		619	program, use C<::name>.
		620
		621	If the function doesn't exist, then the node tries to C<require>
		622	the package, then the package above the package and so on (e.g.
		623	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		624	exists or it runs out of package names.
		625
		626	The init function is then called with the newly-created port as context
		627	object (C<$SELF>) and the C<@initdata> values as arguments.
		628
		629	A common idiom is to pass your own port, monitor the spawned port, and
		630	in the init function, monitor the original port. This two-way monitoring
		631	ensures that both ports get cleaned up when there is a problem.
		632
		633	Example: spawn a chat server port on C<$othernode>.
		634
		635	# this node, executed from within a port context:
		636	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		637	mon $server;
		638
		639	# init function on C<$othernode>
		640	sub connect {
		641	my ($srcport) = @_;
		642
		643	mon $srcport;
		644
		645	rcv $SELF, sub {
		646	...
162	}	647	};
		648	}
163		649
164	for (@{ $self->{rcv}{$_[1]} }) {	650	=cut
165	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
166	&& &{$_->[0]}
167	&& undef $_;
168	}
169		651
170	for (@{ $self->{any} }) {	652	sub _spawn {
171	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	653	my $port = shift;
172	&& &{$_->[0]}	654	my $init = shift;
173	&& undef $_;	655
174	}	656	local $SELF = "$NODE#$port";
		657	eval {
		658	&{ load_func $init }
175	};	659	};
176		660	_self_die if $@;
177	$self
178	}	661	}
179		662
180	=item $portid = miniport { my @msg = @_; $finished }	663	sub spawn(@) {
		664	my ($noderef, undef) = split /#/, shift, 2;
181		665
182	Creates a "mini port", that is, a very lightweight port without any	666	my $id = "$RUNIQ." . $ID++;
183	pattern matching behind it, and returns its ID.
184		667
185	The block will be called for every message received on the port. When the	668	$_[0] =~ /::/
186	callback returns a true value its job is considered "done" and the port	669	or Carp::croak "spawn init function must be a fully-qualified name, caught";
187	will be destroyed. Otherwise it will stay alive.
188		670
189	The message will be passed as-is, no extra argument (i.e. no port id) will	671	($NODE{$noderef} \|\| add_node $noderef)
190	be passed to the callback.	672	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
191		673
192	If you need the local port id in the callback, this works nicely:	674	"$noderef#$id"
193
194	my $port; $port = miniport {
195	snd $otherport, reply => $port;
196	};
197
198	=cut
199
200	sub miniport(&) {
201	my $cb = shift;
202	my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;
203
204	$AnyEvent::MP::Base::PORT{$id} = sub {
205	&$cb
206	and del $id;
207	};
208
209	"$NODE#$id"
210	}	675	}
211
212	package AnyEvent::MP::Port;
213
214	=back
215
216	=head1 METHODS FOR PORT OBJECTS
217
218	=over 4
219
220	=item "$port"
221
222	A port object stringifies to its port ID, so can be used directly for
223	C<snd> operations.
224
225	=cut
226
227	use overload
228	'""' => sub { $_[0]{id} },
229	fallback => 1;
230
231	sub TO_JSON { $_[0]{id} }
232
233	=item $port->rcv (type => $callback->($port, @msg))
234
235	=item $port->rcv ($smartmatch => $callback->($port, @msg))
236
237	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))
238
239	Register a callback on the given port.
240
241	The callback has to return a true value when its work is done, after
242	which is will be removed, or a false value in which case it will stay
243	registered.
244
245	If the match is an array reference, then it will be matched against the
246	first elements of the message, otherwise only the first element is being
247	matched.
248
249	Any element in the match that is specified as C<_any_> (a function
250	exported by this module) matches any single element of the message.
251
252	While not required, it is highly recommended that the first matching
253	element is a string identifying the message. The one-string-only match is
254	also the most efficient match (by far).
255
256	=cut
257
258	sub rcv($@) {
259	my ($self, $match, $cb) = @_;
260
261	if (!ref $match) {
262	push @{ $self->{rc0}{$match} }, [$cb];
263	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
264	my ($type, @match) = @$match;
265	@match
266	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
267	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
268	} else {
269	push @{ $self->{any} }, [$cb, $match];
270	}
271	}
272
273	=item $port->register ($name)
274
275	Registers the given port under the well known name C<$name>. If the name
276	already exists it is replaced.
277
278	A port can only be registered under one well known name.
279
280	=cut
281
282	sub register {
283	my ($self, $name) = @_;
284
285	$self->{wkname} = $name;
286	$AnyEvent::MP::Base::WKP{$name} = "$self";
287	}
288
289	=item $port->destroy
290
291	Explicitly destroy/remove/nuke/vaporise the port.
292
293	Ports are normally kept alive by there mere existance alone, and need to
294	be destroyed explicitly.
295
296	=cut
297
298	sub destroy {
299	my ($self) = @_;
300
301	AnyEvent::MP::Base::del $self->{id};
302
303	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };
304
305	delete $AnyEvent::MP::Base::PORT{$_}
306	for @{ $self->{names} };
307	}
308
309	=back
310
311	=head1 FUNCTIONS FOR NODES
312
313	=over 4
314
315	=item mon $noderef, $callback->($noderef, $status, $)
316
317	Monitors the given noderef.
318
319	=item become_public endpoint...
320
321	Tells the node to become a public node, i.e. reachable from other nodes.
322
323	If no arguments are given, or the first argument is C<undef>, then
324	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the
325	local nodename resolves to.
326
327	Otherwise the first argument must be an array-reference with transport
328	endpoints ("ip:port", "hostname:port") or port numbers (in which case the
329	local nodename is used as hostname). The endpoints are all resolved and
330	will become the node reference.
331
332	=cut
333		676
334	=back	677	=back
335		678
336	=head1 NODE MESSAGES	679	=head1 NODE MESSAGES
337		680
338	Nodes understand the following messages sent to them. Many of them take	681	Nodes understand the following messages sent to them. Many of them take
339	arguments called C<@reply>, which will simply be used to compose a reply	682	arguments called C<@reply>, which will simply be used to compose a reply
340	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	683	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
341	the remaining arguments are simply the message data.	684	the remaining arguments are simply the message data.
342		685
		686	While other messages exist, they are not public and subject to change.
		687
343	=over 4	688	=over 4
344		689
345	=cut	690	=cut
346		691
347	=item wkp => $name, @reply	692	=item lookup => $name, @reply
348		693
349	Replies with the port ID of the specified well-known port, or C<undef>.	694	Replies with the port ID of the specified well-known port, or C<undef>.
350		695
351	=item devnull => ...	696	=item devnull => ...
352		697
…		…
375	snd $NODE, time => $myport, timereply => 1, 2;	720	snd $NODE, time => $myport, timereply => 1, 2;
376	# => snd $myport, timereply => 1, 2, <time>	721	# => snd $myport, timereply => 1, 2, <time>
377		722
378	=back	723	=back
379		724
		725	=head1 AnyEvent::MP vs. Distributed Erlang
		726
		727	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		728	== aemp node, Erlang process == aemp port), so many of the documents and
		729	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		730	sample:
		731
		732	http://www.Erlang.se/doc/programming_rules.shtml
		733	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		734	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		735	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		736
		737	Despite the similarities, there are also some important differences:
		738
		739	=over 4
		740
		741	=item * Node references contain the recipe on how to contact them.
		742
		743	Erlang relies on special naming and DNS to work everywhere in the
		744	same way. AEMP relies on each node knowing it's own address(es), with
		745	convenience functionality.
		746
		747	This means that AEMP requires a less tightly controlled environment at the
		748	cost of longer node references and a slightly higher management overhead.
		749
		750	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		751	uses "local ports are like remote ports".
		752
		753	The failure modes for local ports are quite different (runtime errors
		754	only) then for remote ports - when a local port dies, you I<know> it dies,
		755	when a connection to another node dies, you know nothing about the other
		756	port.
		757
		758	Erlang pretends remote ports are as reliable as local ports, even when
		759	they are not.
		760
		761	AEMP encourages a "treat remote ports differently" philosophy, with local
		762	ports being the special case/exception, where transport errors cannot
		763	occur.
		764
		765	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		766
		767	Erlang uses processes that selectively receive messages, and therefore
		768	needs a queue. AEMP is event based, queuing messages would serve no
		769	useful purpose. For the same reason the pattern-matching abilities of
		770	AnyEvent::MP are more limited, as there is little need to be able to
		771	filter messages without dequeing them.
		772
		773	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
		774
		775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		776
		777	Sending messages in Erlang is synchronous and blocks the process (and
		778	so does not need a queue that can overflow). AEMP sends are immediate,
		779	connection establishment is handled in the background.
		780
		781	=item * Erlang suffers from silent message loss, AEMP does not.
		782
		783	Erlang makes few guarantees on messages delivery - messages can get lost
		784	without any of the processes realising it (i.e. you send messages a, b,
		785	and c, and the other side only receives messages a and c).
		786
		787	AEMP guarantees correct ordering, and the guarantee that there are no
		788	holes in the message sequence.
		789
		790	=item * In Erlang, processes can be declared dead and later be found to be
		791	alive.
		792
		793	In Erlang it can happen that a monitored process is declared dead and
		794	linked processes get killed, but later it turns out that the process is
		795	still alive - and can receive messages.
		796
		797	In AEMP, when port monitoring detects a port as dead, then that port will
		798	eventually be killed - it cannot happen that a node detects a port as dead
		799	and then later sends messages to it, finding it is still alive.
		800
		801	=item * Erlang can send messages to the wrong port, AEMP does not.
		802
		803	In Erlang it is quite likely that a node that restarts reuses a process ID
		804	known to other nodes for a completely different process, causing messages
		805	destined for that process to end up in an unrelated process.
		806
		807	AEMP never reuses port IDs, so old messages or old port IDs floating
		808	around in the network will not be sent to an unrelated port.
		809
		810	=item * Erlang uses unprotected connections, AEMP uses secure
		811	authentication and can use TLS.
		812
		813	AEMP can use a proven protocol - SSL/TLS - to protect connections and
		814	securely authenticate nodes.
		815
		816	=item * The AEMP protocol is optimised for both text-based and binary
		817	communications.
		818
		819	The AEMP protocol, unlike the Erlang protocol, supports both
		820	language-independent text-only protocols (good for debugging) and binary,
		821	language-specific serialisers (e.g. Storable).
		822
		823	It has also been carefully designed to be implementable in other languages
		824	with a minimum of work while gracefully degrading fucntionality to make the
		825	protocol simple.
		826
		827	=item * AEMP has more flexible monitoring options than Erlang.
		828
		829	In Erlang, you can chose to receive I<all> exit signals as messages
		830	or I<none>, there is no in-between, so monitoring single processes is
		831	difficult to implement. Monitoring in AEMP is more flexible than in
		832	Erlang, as one can choose between automatic kill, exit message or callback
		833	on a per-process basis.
		834
		835	=item * Erlang tries to hide remote/local connections, AEMP does not.
		836
		837	Monitoring in Erlang is not an indicator of process death/crashes,
		838	as linking is (except linking is unreliable in Erlang).
		839
		840	In AEMP, you don't "look up" registered port names or send to named ports
		841	that might or might not be persistent. Instead, you normally spawn a port
		842	on the remote node. The init function monitors the you, and you monitor
		843	the remote port. Since both monitors are local to the node, they are much
		844	more reliable.
		845
		846	This also saves round-trips and avoids sending messages to the wrong port
		847	(hard to do in Erlang).
		848
		849	=back
		850
		851	=head1 RATIONALE
		852
		853	=over 4
		854
		855	=item Why strings for ports and noderefs, why not objects?
		856
		857	We considered "objects", but found that the actual number of methods
		858	thatc an be called are very low. Since port IDs and noderefs travel over
		859	the network frequently, the serialising/deserialising would add lots of
		860	overhead, as well as having to keep a proxy object.
		861
		862	Strings can easily be printed, easily serialised etc. and need no special
		863	procedures to be "valid".
		864
		865	And a a miniport consists of a single closure stored in a global hash - it
		866	can't become much cheaper.
		867
		868	=item Why favour JSON, why not real serialising format such as Storable?
		869
		870	In fact, any AnyEvent::MP node will happily accept Storable as framing
		871	format, but currently there is no way to make a node use Storable by
		872	default.
		873
		874	The default framing protocol is JSON because a) JSON::XS is many times
		875	faster for small messages and b) most importantly, after years of
		876	experience we found that object serialisation is causing more problems
		877	than it gains: Just like function calls, objects simply do not travel
		878	easily over the network, mostly because they will always be a copy, so you
		879	always have to re-think your design.
		880
		881	Keeping your messages simple, concentrating on data structures rather than
		882	objects, will keep your messages clean, tidy and efficient.
		883
		884	=back
		885
380	=head1 SEE ALSO	886	=head1 SEE ALSO
381		887
382	L<AnyEvent>.	888	L<AnyEvent>.
383		889
384	=head1 AUTHOR	890	=head1 AUTHOR

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Revision 1.54 by root, Fri Aug 14 16:15:37 2009 UTC