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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.21 by root, Tue Aug 4 14:10:51 2009 UTC vs.
Revision 1.127 by root, Sat Mar 3 20:35:10 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	NODE # returns this node identifier
10	$NODE # contains this node identifier	9	$NODE # contains this node's node ID
		10	NODE # returns this node's node ID
11		11
		12	$SELF # receiving/own port id in rcv callbacks
		13
		14	# initialise the node so it can send/receive messages
		15	configure;
		16
		17	# ports are message destinations
		18
		19	# sending messages
12	snd $port, type => data...;	20	snd $port, type => data...;
		21	snd $port, @msg;
		22	snd @msg_with_first_element_being_a_port;
13		23
14	rcv $port, smartmatch => $cb->($port, @msg);	24	# creating/using ports, the simple way
		25	my $simple_port = port { my @msg = @_ };
15		26
16	# examples:	27	# creating/using ports, tagged message matching
		28	my $port = port;
17	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
18	rcv $port1, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
19	snd $port2, ping => $port1;
20		31
21	# more, smarter, matches (_any_ is exported by this module)	32	# create a port on another node
22	rcv $port, [child_died => $pid] => sub { ...	33	my $port = spawn $node, $initfunc, @initdata;
23	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
		39	# monitoring
		40	mon $localport, $cb->(@msg) # callback is invoked on death
		41	mon $localport, $otherport # kill otherport on abnormal death
		42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
		51
		52	=head1 CURRENT STATUS
		53
		54	bin/aemp - stable.
		55	AnyEvent::MP - stable API, should work.
		56	AnyEvent::MP::Intro - explains most concepts.
		57	AnyEvent::MP::Kernel - mostly stable API.
		58	AnyEvent::MP::Global - stable API.
24		59
25	=head1 DESCRIPTION	60	=head1 DESCRIPTION
26		61
27	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
28		63
29	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
30	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
31		66
32	At the moment, this module family is severly brokena nd underdocumented,	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
33	so do not use. This was uploaded mainly to reserve the CPAN namespace -	68	manual page and the examples under F<eg/>.
34	stay tuned!
35		69
36	=head1 CONCEPTS	70	=head1 CONCEPTS
37		71
38	=over 4	72	=over 4
39		73
40	=item port	74	=item port
41		75
42	A port is something you can send messages to with the C<snd> function, and	76	Not to be confused with a TCP port, a "port" is something you can send
43	you can register C<rcv> handlers with. All C<rcv> handlers will receive	77	messages to (with the C<snd> function).
44	messages they match, messages will not be queued.
45		78
		79	Ports allow you to register C<rcv> handlers that can match all or just
		80	some messages. Messages send to ports will not be queued, regardless of
		81	anything was listening for them or not.
		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
46	=item port id - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
47		86
48	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
49	by a port name (a printable string of unspecified format).	88	as separator, and a port name (a printable string of unspecified
		89	format created by AnyEvent::MP).
50		90
51	=item node	91	=item node
52		92
53	A node is a single process containing at least one port - the node	93	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,	94	which enables nodes to manage each other remotely, and to create new
55	among other things.	95	ports.
56		96
57	Initially, nodes are either private (single-process only) or hidden	97	Nodes are either public (have one or more listening ports) or private
58	(connected to a master node only). Only when they epxlicitly "become	98	(no listening ports). Private nodes cannot talk to other private nodes
59	public" can you send them messages from unrelated other nodes.	99	currently, but all nodes can talk to public nodes.
60		100
61	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	101	Nodes is represented by (printable) strings called "node IDs".
62		102
		103	=item node ID - C<[A-Za-z0-9_\-.:]*>
		104
63	A noderef is a string that either uniquely identifies a given node (for	105	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	106	network. Depending on the configuration used, node IDs can look like a
65	node (for public nodes).	107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		108	doesn't interpret node IDs in any way except to uniquely identify a node.
		109
		110	=item binds - C<ip:port>
		111
		112	Nodes can only talk to each other by creating some kind of connection to
		113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
		116	Currently, only standard C<ip:port> specifications can be used, which
		117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
		119
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
		149	=item seed IDs - C<host:port>
		150
		151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		152	TCP port) of nodes that should be used as seed nodes.
		153
		154	=item global nodes
		155
		156	An AEMP network needs a discovery service - nodes need to know how to
		157	connect to other nodes they only know by name. In addition, AEMP offers a
		158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
66		170
67	=back	171	=back
68		172
69	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
70		174
72		176
73	=cut	177	=cut
74		178
75	package AnyEvent::MP;	179	package AnyEvent::MP;
76		180
		181	use AnyEvent::MP::Config ();
77	use AnyEvent::MP::Base;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
78		184
79	use common::sense;	185	use common::sense;
80		186
81	use Carp ();	187	use Carp ();
82		188
83	use AE ();	189	use AE ();
		190	use Guard ();
84		191
85	use base "Exporter";	192	use base "Exporter";
86		193
87	our $VERSION = '0.02';	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
		195
88	our @EXPORT = qw(	196	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv mon kil _any_	197	NODE $NODE *SELF node_of after
90	create_port create_port_on	198	configure
		199	snd rcv mon mon_guard kil psub peval spawn cal
91	miniport	200	port
92	become_slave become_public	201	db_set db_del db_reg
93	);	202	);
94		203
		204	our $SELF;
		205
		206	sub _self_die() {
		207	my $msg = $@;
		208	$msg =~ s/\n+$// unless ref $msg;
		209	kil $SELF, die => $msg;
		210	}
		211
95	=item NODE / $NODE	212	=item $thisnode = NODE / $NODE
96		213
97	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	214	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	215	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.	216	a call to C<configure>.
100		217
		218	=item $nodeid = node_of $port
		219
		220	Extracts and returns the node ID from a port ID or a node ID.
		221
		222	=item configure $profile, key => value...
		223
		224	=item configure key => value...
		225
		226	Before a node can talk to other nodes on the network (i.e. enter
		227	"distributed mode") it has to configure itself - the minimum a node needs
		228	to know is its own name, and optionally it should know the addresses of
		229	some other nodes in the network to discover other nodes.
		230
		231	This function configures a node - it must be called exactly once (or
		232	never) before calling other AnyEvent::MP functions.
		233
		234	The key/value pairs are basically the same ones as documented for the
		235	F<aemp> command line utility (sans the set/del prefix), with these additions:
		236
		237	=over 4
		238
		239	=item norc => $boolean (default false)
		240
		241	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		242	be consulted - all configuraiton options must be specified in the
		243	C<configure> call.
		244
		245	=item force => $boolean (default false)
		246
		247	IF true, then the values specified in the C<configure> will take
		248	precedence over any values configured via the rc file. The default is for
		249	the rc file to override any options specified in the program.
		250
		251	=item secure => $pass->($nodeid)
		252
		253	In addition to specifying a boolean, you can specify a code reference that
		254	is called for every remote execution attempt - the execution request is
		255	granted iff the callback returns a true value.
		256
		257	See F<semp setsecure> for more info.
		258
		259	=back
		260
		261	=over 4
		262
		263	=item step 1, gathering configuration from profiles
		264
		265	The function first looks up a profile in the aemp configuration (see the
		266	L<aemp> commandline utility). The profile name can be specified via the
		267	named C<profile> parameter or can simply be the first parameter). If it is
		268	missing, then the nodename (F<uname -n>) will be used as profile name.
		269
		270	The profile data is then gathered as follows:
		271
		272	First, all remaining key => value pairs (all of which are conveniently
		273	undocumented at the moment) will be interpreted as configuration
		274	data. Then they will be overwritten by any values specified in the global
		275	default configuration (see the F<aemp> utility), then the chain of
		276	profiles chosen by the profile name (and any C<parent> attributes).
		277
		278	That means that the values specified in the profile have highest priority
		279	and the values specified directly via C<configure> have lowest priority,
		280	and can only be used to specify defaults.
		281
		282	If the profile specifies a node ID, then this will become the node ID of
		283	this process. If not, then the profile name will be used as node ID, with
		284	a unique randoms tring (C</%u>) appended.
		285
		286	The node ID can contain some C<%> sequences that are expanded: C<%n>
		287	is expanded to the local nodename, C<%u> is replaced by a random
		288	strign to make the node unique. For example, the F<aemp> commandline
		289	utility uses C<aemp/%n/%u> as nodename, which might expand to
		290	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		291
		292	=item step 2, bind listener sockets
		293
		294	The next step is to look up the binds in the profile, followed by binding
		295	aemp protocol listeners on all binds specified (it is possible and valid
		296	to have no binds, meaning that the node cannot be contacted form the
		297	outside. This means the node cannot talk to other nodes that also have no
		298	binds, but it can still talk to all "normal" nodes).
		299
		300	If the profile does not specify a binds list, then a default of C<*> is
		301	used, meaning the node will bind on a dynamically-assigned port on every
		302	local IP address it finds.
		303
		304	=item step 3, connect to seed nodes
		305
		306	As the last step, the seed ID list from the profile is passed to the
		307	L<AnyEvent::MP::Global> module, which will then use it to keep
		308	connectivity with at least one node at any point in time.
		309
		310	=back
		311
		312	Example: become a distributed node using the local node name as profile.
		313	This should be the most common form of invocation for "daemon"-type nodes.
		314
		315	configure
		316
		317	Example: become a semi-anonymous node. This form is often used for
		318	commandline clients.
		319
		320	configure nodeid => "myscript/%n/%u";
		321
		322	Example: configure a node using a profile called seed, which is suitable
		323	for a seed node as it binds on all local addresses on a fixed port (4040,
		324	customary for aemp).
		325
		326	# use the aemp commandline utility
		327	# aemp profile seed binds '*:4040'
		328
		329	# then use it
		330	configure profile => "seed";
		331
		332	# or simply use aemp from the shell again:
		333	# aemp run profile seed
		334
		335	# or provide a nicer-to-remember nodeid
		336	# aemp run profile seed nodeid "$(hostname)"
		337
		338	=item $SELF
		339
		340	Contains the current port id while executing C<rcv> callbacks or C<psub>
		341	blocks.
		342
		343	=item *SELF, SELF, %SELF, @SELF...
		344
		345	Due to some quirks in how perl exports variables, it is impossible to
		346	just export C<$SELF>, all the symbols named C<SELF> are exported by this
		347	module, but only C<$SELF> is currently used.
		348
101	=item snd $portid, type => @data	349	=item snd $port, type => @data
102		350
103	=item snd $portid, @msg	351	=item snd $port, @msg
104		352
105	Send the given message to the given port ID, which can identify either	353	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	354	local or a remote port, and must be a port ID.
107	stringifies a sa port ID (such as a port object :).
108		355
109	While the message can be about anything, it is highly recommended to use a	356	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	357	use a string as first element (a port ID, or some word that indicates a
111	type etc.).	358	request type etc.) and to consist if only simple perl values (scalars,
		359	arrays, hashes) - if you think you need to pass an object, think again.
112		360
113	The message data effectively becomes read-only after a call to this	361	The message data logically becomes read-only after a call to this
114	function: modifying any argument is not allowed and can cause many	362	function: modifying any argument (or values referenced by them) is
115	problems.	363	forbidden, as there can be considerable time between the call to C<snd>
		364	and the time the message is actually being serialised - in fact, it might
		365	never be copied as within the same process it is simply handed to the
		366	receiving port.
116		367
117	The type of data you can transfer depends on the transport protocol: when	368	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	369	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	370	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	371	that Storable can serialise and deserialise is allowed, and for the local
121	node, anything can be passed.	372	node, anything can be passed. Best rely only on the common denominator of
		373	these.
122		374
123	=item $guard = mon $portid, $cb->()	375	=item $local_port = port
124		376
125	=item $guard = mon $portid, $otherport	377	Create a new local port object and returns its port ID. Initially it has
		378	no callbacks set and will throw an error when it receives messages.
126		379
127	=item $guard = mon $portid, $otherport, @msg	380	=item $local_port = port { my @msg = @_ }
128		381
129	Monitor the given port and call the given callback when the port is	382	Creates a new local port, and returns its ID. Semantically the same as
130	destroyed or connection to it's node is lost.	383	creating a port and calling C<rcv $port, $callback> on it.
131		384
132	#TODO	385	The block will be called for every message received on the port, with the
		386	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		387	port to be C<kil>ed. The message will be passed as-is, no extra argument
		388	(i.e. no port ID) will be passed to the callback.
		389
		390	If you want to stop/destroy the port, simply C<kil> it:
		391
		392	my $port = port {
		393	my @msg = @_;
		394	...
		395	kil $SELF;
		396	};
		397
		398	=cut
		399
		400	sub rcv($@);
		401
		402	sub _kilme {
		403	die "received message on port without callback";
		404	}
		405
		406	sub port(;&) {
		407	my $id = $UNIQ . ++$ID;
		408	my $port = "$NODE#$id";
		409
		410	rcv $port, shift \|\| \&_kilme;
		411
		412	$port
		413	}
		414
		415	=item rcv $local_port, $callback->(@msg)
		416
		417	Replaces the default callback on the specified port. There is no way to
		418	remove the default callback: use C<sub { }> to disable it, or better
		419	C<kil> the port when it is no longer needed.
		420
		421	The global C<$SELF> (exported by this module) contains C<$port> while
		422	executing the callback. Runtime errors during callback execution will
		423	result in the port being C<kil>ed.
		424
		425	The default callback received all messages not matched by a more specific
		426	C<tag> match.
		427
		428	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		429
		430	Register (or replace) callbacks to be called on messages starting with the
		431	given tag on the given port (and return the port), or unregister it (when
		432	C<$callback> is C<$undef> or missing). There can only be one callback
		433	registered for each tag.
		434
		435	The original message will be passed to the callback, after the first
		436	element (the tag) has been removed. The callback will use the same
		437	environment as the default callback (see above).
		438
		439	Example: create a port and bind receivers on it in one go.
		440
		441	my $port = rcv port,
		442	msg1 => sub { ... },
		443	msg2 => sub { ... },
		444	;
		445
		446	Example: create a port, bind receivers and send it in a message elsewhere
		447	in one go:
		448
		449	snd $otherport, reply =>
		450	rcv port,
		451	msg1 => sub { ... },
		452	...
		453	;
		454
		455	Example: temporarily register a rcv callback for a tag matching some port
		456	(e.g. for an rpc reply) and unregister it after a message was received.
		457
		458	rcv $port, $otherport => sub {
		459	my @reply = @_;
		460
		461	rcv $SELF, $otherport;
		462	};
		463
		464	=cut
		465
		466	sub rcv($@) {
		467	my $port = shift;
		468	my ($nodeid, $portid) = split /#/, $port, 2;
		469
		470	$NODE{$nodeid} == $NODE{""}
		471	or Carp::croak "$port: rcv can only be called on local ports, caught";
		472
		473	while (@_) {
		474	if (ref $_[0]) {
		475	if (my $self = $PORT_DATA{$portid}) {
		476	"AnyEvent::MP::Port" eq ref $self
		477	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		478
		479	$self->[0] = shift;
		480	} else {
		481	my $cb = shift;
		482	$PORT{$portid} = sub {
		483	local $SELF = $port;
		484	eval { &$cb }; _self_die if $@;
		485	};
		486	}
		487	} elsif (defined $_[0]) {
		488	my $self = $PORT_DATA{$portid} \|\|= do {
		489	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		490
		491	$PORT{$portid} = sub {
		492	local $SELF = $port;
		493
		494	if (my $cb = $self->[1]{$_[0]}) {
		495	shift;
		496	eval { &$cb }; _self_die if $@;
		497	} else {
		498	&{ $self->[0] };
		499	}
		500	};
		501
		502	$self
		503	};
		504
		505	"AnyEvent::MP::Port" eq ref $self
		506	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		507
		508	my ($tag, $cb) = splice @_, 0, 2;
		509
		510	if (defined $cb) {
		511	$self->[1]{$tag} = $cb;
		512	} else {
		513	delete $self->[1]{$tag};
		514	}
		515	}
		516	}
		517
		518	$port
		519	}
		520
		521	=item peval $port, $coderef[, @args]
		522
		523	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		524	when the code throews an exception the C<$port> will be killed.
		525
		526	Any remaining args will be passed to the callback. Any return values will
		527	be returned to the caller.
		528
		529	This is useful when you temporarily want to execute code in the context of
		530	a port.
		531
		532	Example: create a port and run some initialisation code in it's context.
		533
		534	my $port = port { ... };
		535
		536	peval $port, sub {
		537	init
		538	or die "unable to init";
		539	};
		540
		541	=cut
		542
		543	sub peval($$) {
		544	local $SELF = shift;
		545	my $cb = shift;
		546
		547	if (wantarray) {
		548	my @res = eval { &$cb };
		549	_self_die if $@;
		550	@res
		551	} else {
		552	my $res = eval { &$cb };
		553	_self_die if $@;
		554	$res
		555	}
		556	}
		557
		558	=item $closure = psub { BLOCK }
		559
		560	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		561	closure is executed, sets up the environment in the same way as in C<rcv>
		562	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		563
		564	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		565	BLOCK }, @_ } >>.
		566
		567	This is useful when you register callbacks from C<rcv> callbacks:
		568
		569	rcv delayed_reply => sub {
		570	my ($delay, @reply) = @_;
		571	my $timer = AE::timer $delay, 0, psub {
		572	snd @reply, $SELF;
		573	};
		574	};
		575
		576	=cut
		577
		578	sub psub(&) {
		579	my $cb = shift;
		580
		581	my $port = $SELF
		582	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		583
		584	sub {
		585	local $SELF = $port;
		586
		587	if (wantarray) {
		588	my @res = eval { &$cb };
		589	_self_die if $@;
		590	@res
		591	} else {
		592	my $res = eval { &$cb };
		593	_self_die if $@;
		594	$res
		595	}
		596	}
		597	}
		598
		599	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
		600
		601	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		602
		603	=item $guard = mon $port # kill $SELF when $port dies
		604
		605	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		606
		607	Monitor the given port and do something when the port is killed or
		608	messages to it were lost, and optionally return a guard that can be used
		609	to stop monitoring again.
		610
		611	In the first form (callback), the callback is simply called with any
		612	number of C<@reason> elements (no @reason means that the port was deleted
		613	"normally"). Note also that I<< the callback B<must> never die >>, so use
		614	C<eval> if unsure.
		615
		616	In the second form (another port given), the other port (C<$rcvport>)
		617	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		618	"normal" kils nothing happens, while under all other conditions, the other
		619	port is killed with the same reason.
		620
		621	The third form (kill self) is the same as the second form, except that
		622	C<$rvport> defaults to C<$SELF>.
		623
		624	In the last form (message), a message of the form C<@msg, @reason> will be
		625	C<snd>.
		626
		627	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		628	alert was raised), they are removed and will not trigger again.
		629
		630	As a rule of thumb, monitoring requests should always monitor a port from
		631	a local port (or callback). The reason is that kill messages might get
		632	lost, just like any other message. Another less obvious reason is that
		633	even monitoring requests can get lost (for example, when the connection
		634	to the other node goes down permanently). When monitoring a port locally
		635	these problems do not exist.
		636
		637	C<mon> effectively guarantees that, in the absence of hardware failures,
		638	after starting the monitor, either all messages sent to the port will
		639	arrive, or the monitoring action will be invoked after possible message
		640	loss has been detected. No messages will be lost "in between" (after
		641	the first lost message no further messages will be received by the
		642	port). After the monitoring action was invoked, further messages might get
		643	delivered again.
		644
		645	Inter-host-connection timeouts and monitoring depend on the transport
		646	used. The only transport currently implemented is TCP, and AnyEvent::MP
		647	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		648	non-idle connection, and usually around two hours for idle connections).
		649
		650	This means that monitoring is good for program errors and cleaning up
		651	stuff eventually, but they are no replacement for a timeout when you need
		652	to ensure some maximum latency.
		653
		654	Example: call a given callback when C<$port> is killed.
		655
		656	mon $port, sub { warn "port died because of <@_>\n" };
		657
		658	Example: kill ourselves when C<$port> is killed abnormally.
		659
		660	mon $port;
		661
		662	Example: send us a restart message when another C<$port> is killed.
		663
		664	mon $port, $self => "restart";
133		665
134	=cut	666	=cut
135		667
136	sub mon {	668	sub mon {
137	my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);	669	my ($nodeid, $port) = split /#/, shift, 2;
138		670
139	my $node = AnyEvent::MP::Base::add_node $noderef;	671	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
140		672
141	#TODO: ports must not be references	673	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
142	if (!ref $cb or "AnyEvent::MP::Port" eq ref $cb) {	674
		675	unless (ref $cb) {
143	if (@_) {	676	if (@_) {
144	# send a kill info message	677	# send a kill info message
145	my (@msg) = ($cb, @_);	678	my (@msg) = ($cb, @_);
146	$cb = sub { snd @msg, @_ };	679	$cb = sub { snd @msg, @_ };
147	} else {	680	} else {
148	# simply kill other port	681	# simply kill other port
149	my $port = $cb;	682	my $port = $cb;
150	$cb = sub { kil $port, @_ };	683	$cb = sub { kil $port, @_ if @_ };
151	}	684	}
152	}	685	}
153		686
154	$node->monitor ($port, $cb);	687	$node->monitor ($port, $cb);
155		688
156	defined wantarray	689	defined wantarray
157	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	690	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
158	}	691	}
159		692
160	=item $guard = mon_guard $port, $ref, $ref...	693	=item $guard = mon_guard $port, $ref, $ref...
161		694
162	Monitors the given C<$port> and keeps the passed references. When the port	695	Monitors the given C<$port> and keeps the passed references. When the port
163	is killed, the references will be freed.	696	is killed, the references will be freed.
164		697
165	Optionally returns a guard that will stop the monitoring.	698	Optionally returns a guard that will stop the monitoring.
166		699
167	This function is useful when you create e.g. timers or other watchers and	700	This function is useful when you create e.g. timers or other watchers and
168	want to free them when the port gets killed:	701	want to free them when the port gets killed (note the use of C<psub>):
169		702
170	$port->rcv (start => sub {	703	$port->rcv (start => sub {
171	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	704	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
172	undef $timer if 0.9 < rand;	705	undef $timer if 0.9 < rand;
173	});	706	});
174	});	707	});
175		708
176	=cut	709	=cut
177		710
178	sub mon_guard {	711	sub mon_guard {
179	my ($port, @refs) = @_;	712	my ($port, @refs) = @_;
180		713
		714	#TODO: mon-less form?
		715
181	mon $port, sub { 0 && @refs }	716	mon $port, sub { 0 && @refs }
182	}	717	}
183		718
184	=item $local_port = create_port	719	=item kil $port[, @reason]
185		720
186	Create a new local port object. See the next section for allowed methods.	721	Kill the specified port with the given C<@reason>.
187		722
188	=cut	723	If no C<@reason> is specified, then the port is killed "normally" -
		724	monitor callback will be invoked, but the kil will not cause linked ports
		725	(C<mon $mport, $lport> form) to get killed.
189		726
190	sub create_port {	727	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
191	my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;	728	form) get killed with the same reason.
192		729
193	my $self = bless {	730	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
194	id => "$NODE#$id",	731	will be reported as reason C<< die => $@ >>.
195	}, "AnyEvent::MP::Port";
196		732
197	$AnyEvent::MP::Base::PORT{$id} = sub {	733	Transport/communication errors are reported as C<< transport_error =>
198	unshift @_, $self;	734	$message >>.
199		735
200	for (@{ $self->{rc0}{$_[1]} }) {	736	=cut
201	$_ && &{$_->[0]}	737
202	&& undef $_;	738	=item $port = spawn $node, $initfunc[, @initdata]
		739
		740	Creates a port on the node C<$node> (which can also be a port ID, in which
		741	case it's the node where that port resides).
		742
		743	The port ID of the newly created port is returned immediately, and it is
		744	possible to immediately start sending messages or to monitor the port.
		745
		746	After the port has been created, the init function is called on the remote
		747	node, in the same context as a C<rcv> callback. This function must be a
		748	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		749	specify a function in the main program, use C<::name>.
		750
		751	If the function doesn't exist, then the node tries to C<require>
		752	the package, then the package above the package and so on (e.g.
		753	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		754	exists or it runs out of package names.
		755
		756	The init function is then called with the newly-created port as context
		757	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		758	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		759	the port might not get created.
		760
		761	A common idiom is to pass a local port, immediately monitor the spawned
		762	port, and in the remote init function, immediately monitor the passed
		763	local port. This two-way monitoring ensures that both ports get cleaned up
		764	when there is a problem.
		765
		766	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		767	caller before C<spawn> returns (by delaying invocation when spawn is
		768	called for the local node).
		769
		770	Example: spawn a chat server port on C<$othernode>.
		771
		772	# this node, executed from within a port context:
		773	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		774	mon $server;
		775
		776	# init function on C<$othernode>
		777	sub connect {
		778	my ($srcport) = @_;
		779
		780	mon $srcport;
		781
		782	rcv $SELF, sub {
		783	...
203	}	784	};
		785	}
204		786
205	for (@{ $self->{rcv}{$_[1]} }) {	787	=cut
206	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
207	&& &{$_->[0]}
208	&& undef $_;
209	}
210		788
211	for (@{ $self->{any} }) {	789	sub _spawn {
212	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	790	my $port = shift;
213	&& &{$_->[0]}	791	my $init = shift;
214	&& undef $_;	792
215	}	793	# rcv will create the actual port
		794	local $SELF = "$NODE#$port";
		795	eval {
		796	&{ load_func $init }
216	};	797	};
217		798	_self_die if $@;
218	$self
219	}	799	}
220		800
221	=item $portid = miniport { my @msg = @_; $finished }	801	sub spawn(@) {
		802	my ($nodeid, undef) = split /#/, shift, 2;
222		803
223	Creates a "mini port", that is, a very lightweight port without any	804	my $id = $RUNIQ . ++$ID;
224	pattern matching behind it, and returns its ID.
225		805
226	The block will be called for every message received on the port. When the	806	$_[0] =~ /::/
227	callback returns a true value its job is considered "done" and the port	807	or Carp::croak "spawn init function must be a fully-qualified name, caught";
228	will be destroyed. Otherwise it will stay alive.
229		808
230	The message will be passed as-is, no extra argument (i.e. no port id) will	809	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
231	be passed to the callback.
232		810
233	If you need the local port id in the callback, this works nicely:	811	"$nodeid#$id"
		812	}
234		813
235	my $port; $port = miniport {	814
236	snd $otherport, reply => $port;	815	=item after $timeout, @msg
		816
		817	=item after $timeout, $callback
		818
		819	Either sends the given message, or call the given callback, after the
		820	specified number of seconds.
		821
		822	This is simply a utility function that comes in handy at times - the
		823	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		824	so it may go away in the future.
		825
		826	=cut
		827
		828	sub after($@) {
		829	my ($timeout, @action) = @_;
		830
		831	my $t; $t = AE::timer $timeout, 0, sub {
		832	undef $t;
		833	ref $action[0]
		834	? $action[0]()
		835	: snd @action;
237	};	836	};
		837	}
238		838
239	=cut	839	=item cal $port, @msg, $callback[, $timeout]
240		840
241	sub miniport(&) {	841	A simple form of RPC - sends a message to the given C<$port> with the
		842	given contents (C<@msg>), but adds a reply port to the message.
		843
		844	The reply port is created temporarily just for the purpose of receiving
		845	the reply, and will be C<kil>ed when no longer needed.
		846
		847	A reply message sent to the port is passed to the C<$callback> as-is.
		848
		849	If an optional time-out (in seconds) is given and it is not C<undef>,
		850	then the callback will be called without any arguments after the time-out
		851	elapsed and the port is C<kil>ed.
		852
		853	If no time-out is given (or it is C<undef>), then the local port will
		854	monitor the remote port instead, so it eventually gets cleaned-up.
		855
		856	Currently this function returns the temporary port, but this "feature"
		857	might go in future versions unless you can make a convincing case that
		858	this is indeed useful for something.
		859
		860	=cut
		861
		862	sub cal(@) {
		863	my $timeout = ref $_[-1] ? undef : pop;
242	my $cb = shift;	864	my $cb = pop;
243	my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;
244		865
245	$AnyEvent::MP::Base::PORT{$id} = sub {	866	my $port = port {
		867	undef $timeout;
		868	kil $SELF;
246	&$cb	869	&$cb;
247	and kil $id;
248	};	870	};
249		871
250	"$NODE#$id"	872	if (defined $timeout) {
		873	$timeout = AE::timer $timeout, 0, sub {
		874	undef $timeout;
		875	kil $port;
		876	$cb->();
		877	};
		878	} else {
		879	mon $_[0], sub {
		880	kil $port;
		881	$cb->();
		882	};
		883	}
		884
		885	push @_, $port;
		886	&snd;
		887
		888	$port
251	}	889	}
252		890
253	package AnyEvent::MP::Port;
254
255	=back	891	=back
256		892
257	=head1 METHODS FOR PORT OBJECTS	893	=head1 DISTRIBUTED DATABASE
		894
		895	AnyEvent::MP comes with a simple distributed database. The database will
		896	be mirrored asynchronously at all global nodes. Other nodes bind to one of
		897	the global nodes for their needs.
		898
		899	The database consists of a two-level hash - a hash contains a hash which
		900	contains values.
		901
		902	The top level hash key is called "family", and the second-level hash key
		903	is called "subkey" or simply "key".
		904
		905	The family must be alphanumeric, i.e. start with a letter and consist
		906	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		907	pretty much like Perl module names.
		908
		909	As the family namespace is global, it is recommended to prefix family names
		910	with the name of the application or module using it.
		911
		912	The subkeys must be non-empty strings, with no further restrictions.
		913
		914	The values should preferably be strings, but other perl scalars should
		915	work as well (such as undef, arrays and hashes).
		916
		917	Every database entry is owned by one node - adding the same family/subkey
		918	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		919	but the result might be nondeterministic, i.e. the key might have
		920	different values on different nodes.
		921
		922	Different subkeys in the same family can be owned by different nodes
		923	without problems, and in fact, this is the common method to create worker
		924	pools. For example, a worker port for image scaling might do this:
		925
		926	db_set my_image_scalers => $port;
		927
		928	And clients looking for an image scaler will want to get the
		929	C<my_image_scalers> keys:
		930
		931	db_keys "my_image_scalers" => 60 => sub {
		932	#d##TODO#
		933
		934	=over
		935
		936	=item db_set $family => $subkey [=> $value]
		937
		938	Sets (or replaces) a key to the database - if C<$value> is omitted,
		939	C<undef> is used instead.
		940
		941	=item db_del $family => $subkey
		942
		943	Deletes a key from the database.
		944
		945	=item $guard = db_reg $family => $subkey [=> $value]
		946
		947	Sets the key on the database and returns a guard. When the guard is
		948	destroyed, the key is deleted from the database. If C<$value> is missing,
		949	then C<undef> is used.
		950
		951	=cut
		952
		953	=back
		954
		955	=head1 AnyEvent::MP vs. Distributed Erlang
		956
		957	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		958	== aemp node, Erlang process == aemp port), so many of the documents and
		959	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		960	sample:
		961
		962	http://www.erlang.se/doc/programming_rules.shtml
		963	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		964	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
		965	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		966
		967	Despite the similarities, there are also some important differences:
258		968
259	=over 4	969	=over 4
260		970
261	=item "$port"	971	=item * Node IDs are arbitrary strings in AEMP.
262		972
263	A port object stringifies to its port ID, so can be used directly for	973	Erlang relies on special naming and DNS to work everywhere in the same
264	C<snd> operations.	974	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		975	configuration or DNS), and possibly the addresses of some seed nodes, but
		976	will otherwise discover other nodes (and their IDs) itself.
265		977
266	=cut	978	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		979	uses "local ports are like remote ports".
267		980
268	use overload	981	The failure modes for local ports are quite different (runtime errors
269	'""' => sub { $_[0]{id} },	982	only) then for remote ports - when a local port dies, you I<know> it dies,
270	fallback => 1;	983	when a connection to another node dies, you know nothing about the other
		984	port.
271		985
272	sub TO_JSON { $_[0]{id} }	986	Erlang pretends remote ports are as reliable as local ports, even when
		987	they are not.
273		988
274	=item $port->rcv (type => $callback->($port, @msg))	989	AEMP encourages a "treat remote ports differently" philosophy, with local
		990	ports being the special case/exception, where transport errors cannot
		991	occur.
275		992
276	=item $port->rcv ($smartmatch => $callback->($port, @msg))	993	=item * Erlang uses processes and a mailbox, AEMP does not queue.
277		994
278	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	995	Erlang uses processes that selectively receive messages out of order, and
		996	therefore needs a queue. AEMP is event based, queuing messages would serve
		997	no useful purpose. For the same reason the pattern-matching abilities
		998	of AnyEvent::MP are more limited, as there is little need to be able to
		999	filter messages without dequeuing them.
279		1000
280	Register a callback on the given port.	1001	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1002	being event-based, while Erlang is process-based.
281		1003
282	The callback has to return a true value when its work is done, after	1004	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
283	which is will be removed, or a false value in which case it will stay	1005	top of AEMP and Coro threads.
284	registered.
285		1006
286	If the match is an array reference, then it will be matched against the	1007	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
287	first elements of the message, otherwise only the first element is being
288	matched.
289		1008
290	Any element in the match that is specified as C<_any_> (a function	1009	Sending messages in Erlang is synchronous and blocks the process until
291	exported by this module) matches any single element of the message.	1010	a conenction has been established and the message sent (and so does not
		1011	need a queue that can overflow). AEMP sends return immediately, connection
		1012	establishment is handled in the background.
292		1013
293	While not required, it is highly recommended that the first matching	1014	=item * Erlang suffers from silent message loss, AEMP does not.
294	element is a string identifying the message. The one-string-only match is
295	also the most efficient match (by far).
296		1015
297	=cut	1016	Erlang implements few guarantees on messages delivery - messages can get
		1017	lost without any of the processes realising it (i.e. you send messages a,
		1018	b, and c, and the other side only receives messages a and c).
298		1019
299	sub rcv($@) {	1020	AEMP guarantees (modulo hardware errors) correct ordering, and the
300	my ($self, $match, $cb) = @_;	1021	guarantee that after one message is lost, all following ones sent to the
		1022	same port are lost as well, until monitoring raises an error, so there are
		1023	no silent "holes" in the message sequence.
301		1024
302	if (!ref $match) {	1025	If you want your software to be very reliable, you have to cope with
303	push @{ $self->{rc0}{$match} }, [$cb];	1026	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
304	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	1027	simply tries to work better in common error cases, such as when a network
305	my ($type, @match) = @$match;	1028	link goes down.
306	@match
307	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
308	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
309	} else {
310	push @{ $self->{any} }, [$cb, $match];
311	}
312	}
313		1029
314	=item $port->register ($name)	1030	=item * Erlang can send messages to the wrong port, AEMP does not.
315		1031
316	Registers the given port under the well known name C<$name>. If the name	1032	In Erlang it is quite likely that a node that restarts reuses an Erlang
317	already exists it is replaced.	1033	process ID known to other nodes for a completely different process,
		1034	causing messages destined for that process to end up in an unrelated
		1035	process.
318		1036
319	A port can only be registered under one well known name.	1037	AEMP does not reuse port IDs, so old messages or old port IDs floating
		1038	around in the network will not be sent to an unrelated port.
320		1039
321	=cut	1040	=item * Erlang uses unprotected connections, AEMP uses secure
		1041	authentication and can use TLS.
322		1042
323	sub register {	1043	AEMP can use a proven protocol - TLS - to protect connections and
324	my ($self, $name) = @_;	1044	securely authenticate nodes.
325		1045
326	$self->{wkname} = $name;	1046	=item * The AEMP protocol is optimised for both text-based and binary
327	$AnyEvent::MP::Base::WKP{$name} = "$self";	1047	communications.
328	}
329		1048
330	=item $port->destroy	1049	The AEMP protocol, unlike the Erlang protocol, supports both programming
		1050	language independent text-only protocols (good for debugging), and binary,
		1051	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1052	used, the protocol is actually completely text-based.
331		1053
332	Explicitly destroy/remove/nuke/vaporise the port.	1054	It has also been carefully designed to be implementable in other languages
		1055	with a minimum of work while gracefully degrading functionality to make the
		1056	protocol simple.
333		1057
334	Ports are normally kept alive by their mere existance alone, and need to	1058	=item * AEMP has more flexible monitoring options than Erlang.
335	be destroyed explicitly.
336		1059
337	=cut	1060	In Erlang, you can chose to receive I<all> exit signals as messages or
		1061	I<none>, there is no in-between, so monitoring single Erlang processes is
		1062	difficult to implement.
338		1063
339	sub destroy {	1064	Monitoring in AEMP is more flexible than in Erlang, as one can choose
340	my ($self) = @_;	1065	between automatic kill, exit message or callback on a per-port basis.
341		1066
342	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	1067	=item * Erlang tries to hide remote/local connections, AEMP does not.
343		1068
344	AnyEvent::MP::Base::kil $self->{id};	1069	Monitoring in Erlang is not an indicator of process death/crashes, in the
345	}	1070	same way as linking is (except linking is unreliable in Erlang).
		1071
		1072	In AEMP, you don't "look up" registered port names or send to named ports
		1073	that might or might not be persistent. Instead, you normally spawn a port
		1074	on the remote node. The init function monitors you, and you monitor the
		1075	remote port. Since both monitors are local to the node, they are much more
		1076	reliable (no need for C<spawn_link>).
		1077
		1078	This also saves round-trips and avoids sending messages to the wrong port
		1079	(hard to do in Erlang).
346		1080
347	=back	1081	=back
348		1082
349	=head1 FUNCTIONS FOR NODES	1083	=head1 RATIONALE
350		1084
351	=over 4	1085	=over 4
352		1086
353	=item mon $noderef, $callback->($noderef, $status, $)	1087	=item Why strings for port and node IDs, why not objects?
354		1088
355	Monitors the given noderef.	1089	We considered "objects", but found that the actual number of methods
		1090	that can be called are quite low. Since port and node IDs travel over
		1091	the network frequently, the serialising/deserialising would add lots of
		1092	overhead, as well as having to keep a proxy object everywhere.
356		1093
357	=item become_public endpoint...	1094	Strings can easily be printed, easily serialised etc. and need no special
		1095	procedures to be "valid".
358		1096
359	Tells the node to become a public node, i.e. reachable from other nodes.	1097	And as a result, a port with just a default receiver consists of a single
		1098	code reference stored in a global hash - it can't become much cheaper.
360		1099
361	If no arguments are given, or the first argument is C<undef>, then	1100	=item Why favour JSON, why not a real serialising format such as Storable?
362	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the
363	local nodename resolves to.
364		1101
365	Otherwise the first argument must be an array-reference with transport	1102	In fact, any AnyEvent::MP node will happily accept Storable as framing
366	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	1103	format, but currently there is no way to make a node use Storable by
367	local nodename is used as hostname). The endpoints are all resolved and	1104	default (although all nodes will accept it).
368	will become the node reference.
369		1105
370	=cut	1106	The default framing protocol is JSON because a) JSON::XS is many times
		1107	faster for small messages and b) most importantly, after years of
		1108	experience we found that object serialisation is causing more problems
		1109	than it solves: Just like function calls, objects simply do not travel
		1110	easily over the network, mostly because they will always be a copy, so you
		1111	always have to re-think your design.
		1112
		1113	Keeping your messages simple, concentrating on data structures rather than
		1114	objects, will keep your messages clean, tidy and efficient.
371		1115
372	=back	1116	=back
373		1117
374	=head1 NODE MESSAGES
375
376	Nodes understand the following messages sent to them. Many of them take
377	arguments called C<@reply>, which will simply be used to compose a reply
378	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
379	the remaining arguments are simply the message data.
380
381	=over 4
382
383	=cut
384
385	=item wkp => $name, @reply
386
387	Replies with the port ID of the specified well-known port, or C<undef>.
388
389	=item devnull => ...
390
391	Generic data sink/CPU heat conversion.
392
393	=item relay => $port, @msg
394
395	Simply forwards the message to the given port.
396
397	=item eval => $string[ @reply]
398
399	Evaluates the given string. If C<@reply> is given, then a message of the
400	form C<@reply, $@, @evalres> is sent.
401
402	Example: crash another node.
403
404	snd $othernode, eval => "exit";
405
406	=item time => @reply
407
408	Replies the the current node time to C<@reply>.
409
410	Example: tell the current node to send the current time to C<$myport> in a
411	C<timereply> message.
412
413	snd $NODE, time => $myport, timereply => 1, 2;
414	# => snd $myport, timereply => 1, 2, <time>
415
416	=back
417
418	=head1 SEE ALSO	1118	=head1 SEE ALSO
		1119
		1120	L<AnyEvent::MP::Intro> - a gentle introduction.
		1121
		1122	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1123
		1124	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1125	your applications.
		1126
		1127	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1128
		1129	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1130	all nodes.
419		1131
420	L<AnyEvent>.	1132	L<AnyEvent>.
421		1133
422	=head1 AUTHOR	1134	=head1 AUTHOR
423		1135

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.21 by root, Tue Aug 4 14:10:51 2009 UTC vs.
Revision 1.127 by root, Sat Mar 3 20:35:10 2012 UTC