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Revision 1.21 by root, Tue Aug 4 14:10:51 2009 UTC vs.
Revision 1.136 by root, Wed Mar 21 15:22:16 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 $port, $cb->(@msg) # callback is invoked on death
		41	mon $port, $localport # kill localport on abnormal death
		42	mon $port, $localport, @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
		202	db_mon db_family db_keys db_values
93	);	203	);
94		204
		205	our $SELF;
		206
		207	sub _self_die() {
		208	my $msg = $@;
		209	$msg =~ s/\n+$// unless ref $msg;
		210	kil $SELF, die => $msg;
		211	}
		212
95	=item NODE / $NODE	213	=item $thisnode = NODE / $NODE
96		214
97	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	215	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	216	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.	217	a call to C<configure>.
100		218
		219	=item $nodeid = node_of $port
		220
		221	Extracts and returns the node ID from a port ID or a node ID.
		222
		223	=item configure $profile, key => value...
		224
		225	=item configure key => value...
		226
		227	Before a node can talk to other nodes on the network (i.e. enter
		228	"distributed mode") it has to configure itself - the minimum a node needs
		229	to know is its own name, and optionally it should know the addresses of
		230	some other nodes in the network to discover other nodes.
		231
		232	This function configures a node - it must be called exactly once (or
		233	never) before calling other AnyEvent::MP functions.
		234
		235	The key/value pairs are basically the same ones as documented for the
		236	F<aemp> command line utility (sans the set/del prefix), with these additions:
		237
		238	=over 4
		239
		240	=item norc => $boolean (default false)
		241
		242	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		243	be consulted - all configuraiton options must be specified in the
		244	C<configure> call.
		245
		246	=item force => $boolean (default false)
		247
		248	IF true, then the values specified in the C<configure> will take
		249	precedence over any values configured via the rc file. The default is for
		250	the rc file to override any options specified in the program.
		251
		252	=item secure => $pass->(@msg)
		253
		254	In addition to specifying a boolean, you can specify a code reference that
		255	is called for every code execution attempt - the execution request is
		256	granted iff the callback returns a true value.
		257
		258	Most of the time the callback should look only at
		259	C<$AnyEvent::MP::Kernel::SRCNODE> to make a decision, and not at the
		260	actual message (which can be about anything, and is mostly provided for
		261	diagnostic purposes).
		262
		263	See F<semp setsecure> for more info.
		264
		265	=back
		266
		267	=over 4
		268
		269	=item step 1, gathering configuration from profiles
		270
		271	The function first looks up a profile in the aemp configuration (see the
		272	L<aemp> commandline utility). The profile name can be specified via the
		273	named C<profile> parameter or can simply be the first parameter). If it is
		274	missing, then the nodename (F<uname -n>) will be used as profile name.
		275
		276	The profile data is then gathered as follows:
		277
		278	First, all remaining key => value pairs (all of which are conveniently
		279	undocumented at the moment) will be interpreted as configuration
		280	data. Then they will be overwritten by any values specified in the global
		281	default configuration (see the F<aemp> utility), then the chain of
		282	profiles chosen by the profile name (and any C<parent> attributes).
		283
		284	That means that the values specified in the profile have highest priority
		285	and the values specified directly via C<configure> have lowest priority,
		286	and can only be used to specify defaults.
		287
		288	If the profile specifies a node ID, then this will become the node ID of
		289	this process. If not, then the profile name will be used as node ID, with
		290	a unique randoms tring (C</%u>) appended.
		291
		292	The node ID can contain some C<%> sequences that are expanded: C<%n>
		293	is expanded to the local nodename, C<%u> is replaced by a random
		294	strign to make the node unique. For example, the F<aemp> commandline
		295	utility uses C<aemp/%n/%u> as nodename, which might expand to
		296	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		297
		298	=item step 2, bind listener sockets
		299
		300	The next step is to look up the binds in the profile, followed by binding
		301	aemp protocol listeners on all binds specified (it is possible and valid
		302	to have no binds, meaning that the node cannot be contacted form the
		303	outside. This means the node cannot talk to other nodes that also have no
		304	binds, but it can still talk to all "normal" nodes).
		305
		306	If the profile does not specify a binds list, then a default of C<*> is
		307	used, meaning the node will bind on a dynamically-assigned port on every
		308	local IP address it finds.
		309
		310	=item step 3, connect to seed nodes
		311
		312	As the last step, the seed ID list from the profile is passed to the
		313	L<AnyEvent::MP::Global> module, which will then use it to keep
		314	connectivity with at least one node at any point in time.
		315
		316	=back
		317
		318	Example: become a distributed node using the local node name as profile.
		319	This should be the most common form of invocation for "daemon"-type nodes.
		320
		321	configure
		322
		323	Example: become a semi-anonymous node. This form is often used for
		324	commandline clients.
		325
		326	configure nodeid => "myscript/%n/%u";
		327
		328	Example: configure a node using a profile called seed, which is suitable
		329	for a seed node as it binds on all local addresses on a fixed port (4040,
		330	customary for aemp).
		331
		332	# use the aemp commandline utility
		333	# aemp profile seed binds '*:4040'
		334
		335	# then use it
		336	configure profile => "seed";
		337
		338	# or simply use aemp from the shell again:
		339	# aemp run profile seed
		340
		341	# or provide a nicer-to-remember nodeid
		342	# aemp run profile seed nodeid "$(hostname)"
		343
		344	=item $SELF
		345
		346	Contains the current port id while executing C<rcv> callbacks or C<psub>
		347	blocks.
		348
		349	=item *SELF, SELF, %SELF, @SELF...
		350
		351	Due to some quirks in how perl exports variables, it is impossible to
		352	just export C<$SELF>, all the symbols named C<SELF> are exported by this
		353	module, but only C<$SELF> is currently used.
		354
101	=item snd $portid, type => @data	355	=item snd $port, type => @data
102		356
103	=item snd $portid, @msg	357	=item snd $port, @msg
104		358
105	Send the given message to the given port ID, which can identify either	359	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	360	local or a remote port, and must be a port ID.
107	stringifies a sa port ID (such as a port object :).
108		361
109	While the message can be about anything, it is highly recommended to use a	362	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	363	use a string as first element (a port ID, or some word that indicates a
111	type etc.).	364	request type etc.) and to consist if only simple perl values (scalars,
		365	arrays, hashes) - if you think you need to pass an object, think again.
112		366
113	The message data effectively becomes read-only after a call to this	367	The message data logically becomes read-only after a call to this
114	function: modifying any argument is not allowed and can cause many	368	function: modifying any argument (or values referenced by them) is
115	problems.	369	forbidden, as there can be considerable time between the call to C<snd>
		370	and the time the message is actually being serialised - in fact, it might
		371	never be copied as within the same process it is simply handed to the
		372	receiving port.
116		373
117	The type of data you can transfer depends on the transport protocol: when	374	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	375	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	376	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	377	that Storable can serialise and deserialise is allowed, and for the local
121	node, anything can be passed.	378	node, anything can be passed. Best rely only on the common denominator of
		379	these.
122		380
123	=item $guard = mon $portid, $cb->()	381	=item $local_port = port
124		382
125	=item $guard = mon $portid, $otherport	383	Create a new local port object and returns its port ID. Initially it has
		384	no callbacks set and will throw an error when it receives messages.
126		385
127	=item $guard = mon $portid, $otherport, @msg	386	=item $local_port = port { my @msg = @_ }
128		387
129	Monitor the given port and call the given callback when the port is	388	Creates a new local port, and returns its ID. Semantically the same as
130	destroyed or connection to it's node is lost.	389	creating a port and calling C<rcv $port, $callback> on it.
131		390
132	#TODO	391	The block will be called for every message received on the port, with the
		392	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		393	port to be C<kil>ed. The message will be passed as-is, no extra argument
		394	(i.e. no port ID) will be passed to the callback.
		395
		396	If you want to stop/destroy the port, simply C<kil> it:
		397
		398	my $port = port {
		399	my @msg = @_;
		400	...
		401	kil $SELF;
		402	};
133		403
134	=cut	404	=cut
135		405
		406	sub rcv($@);
		407
		408	my $KILME = sub {
		409	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
		410	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		411	};
		412
		413	sub port(;&) {
		414	my $id = $UNIQ . ++$ID;
		415	my $port = "$NODE#$id";
		416
		417	rcv $port, shift || $KILME;
		418
		419	$port
		420	}
		421
		422	=item rcv $local_port, $callback->(@msg)
		423
		424	Replaces the default callback on the specified port. There is no way to
		425	remove the default callback: use C<sub { }> to disable it, or better
		426	C<kil> the port when it is no longer needed.
		427
		428	The global C<$SELF> (exported by this module) contains C<$port> while
		429	executing the callback. Runtime errors during callback execution will
		430	result in the port being C<kil>ed.
		431
		432	The default callback receives all messages not matched by a more specific
		433	C<tag> match.
		434
		435	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		436
		437	Register (or replace) callbacks to be called on messages starting with the
		438	given tag on the given port (and return the port), or unregister it (when
		439	C<$callback> is C<$undef> or missing). There can only be one callback
		440	registered for each tag.
		441
		442	The original message will be passed to the callback, after the first
		443	element (the tag) has been removed. The callback will use the same
		444	environment as the default callback (see above).
		445
		446	Example: create a port and bind receivers on it in one go.
		447
		448	my $port = rcv port,
		449	msg1 => sub { ... },
		450	msg2 => sub { ... },
		451	;
		452
		453	Example: create a port, bind receivers and send it in a message elsewhere
		454	in one go:
		455
		456	snd $otherport, reply =>
		457	rcv port,
		458	msg1 => sub { ... },
		459	...
		460	;
		461
		462	Example: temporarily register a rcv callback for a tag matching some port
		463	(e.g. for an rpc reply) and unregister it after a message was received.
		464
		465	rcv $port, $otherport => sub {
		466	my @reply = @_;
		467
		468	rcv $SELF, $otherport;
		469	};
		470
		471	=cut
		472
		473	sub rcv($@) {
		474	my $port = shift;
		475	my ($nodeid, $portid) = split /#/, $port, 2;
		476
		477	$NODE{$nodeid} == $NODE{""}
		478	or Carp::croak "$port: rcv can only be called on local ports, caught";
		479
		480	while (@_) {
		481	if (ref $_[0]) {
		482	if (my $self = $PORT_DATA{$portid}) {
		483	"AnyEvent::MP::Port" eq ref $self
		484	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		485
		486	$self->[0] = shift;
		487	} else {
		488	my $cb = shift;
		489	$PORT{$portid} = sub {
		490	local $SELF = $port;
		491	eval { &$cb }; _self_die if $@;
		492	};
		493	}
		494	} elsif (defined $_[0]) {
		495	my $self = $PORT_DATA{$portid} ||= do {
		496	my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
		497
		498	$PORT{$portid} = sub {
		499	local $SELF = $port;
		500
		501	if (my $cb = $self->[1]{$_[0]}) {
		502	shift;
		503	eval { &$cb }; _self_die if $@;
		504	} else {
		505	&{ $self->[0] };
		506	}
		507	};
		508
		509	$self
		510	};
		511
		512	"AnyEvent::MP::Port" eq ref $self
		513	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		514
		515	my ($tag, $cb) = splice @_, 0, 2;
		516
		517	if (defined $cb) {
		518	$self->[1]{$tag} = $cb;
		519	} else {
		520	delete $self->[1]{$tag};
		521	}
		522	}
		523	}
		524
		525	$port
		526	}
		527
		528	=item peval $port, $coderef[, @args]
		529
		530	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		531	when the code throews an exception the C<$port> will be killed.
		532
		533	Any remaining args will be passed to the callback. Any return values will
		534	be returned to the caller.
		535
		536	This is useful when you temporarily want to execute code in the context of
		537	a port.
		538
		539	Example: create a port and run some initialisation code in it's context.
		540
		541	my $port = port { ... };
		542
		543	peval $port, sub {
		544	init
		545	or die "unable to init";
		546	};
		547
		548	=cut
		549
		550	sub peval($$) {
		551	local $SELF = shift;
		552	my $cb = shift;
		553
		554	if (wantarray) {
		555	my @res = eval { &$cb };
		556	_self_die if $@;
		557	@res
		558	} else {
		559	my $res = eval { &$cb };
		560	_self_die if $@;
		561	$res
		562	}
		563	}
		564
		565	=item $closure = psub { BLOCK }
		566
		567	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		568	closure is executed, sets up the environment in the same way as in C<rcv>
		569	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		570
		571	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		572	BLOCK }, @_ } >>.
		573
		574	This is useful when you register callbacks from C<rcv> callbacks:
		575
		576	rcv delayed_reply => sub {
		577	my ($delay, @reply) = @_;
		578	my $timer = AE::timer $delay, 0, psub {
		579	snd @reply, $SELF;
		580	};
		581	};
		582
		583	=cut
		584
		585	sub psub(&) {
		586	my $cb = shift;
		587
		588	my $port = $SELF
		589	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		590
		591	sub {
		592	local $SELF = $port;
		593
		594	if (wantarray) {
		595	my @res = eval { &$cb };
		596	_self_die if $@;
		597	@res
		598	} else {
		599	my $res = eval { &$cb };
		600	_self_die if $@;
		601	$res
		602	}
		603	}
		604	}
		605
		606	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
		607
		608	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		609
		610	=item $guard = mon $port # kill $SELF when $port dies
		611
		612	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		613
		614	Monitor the given port and do something when the port is killed or
		615	messages to it were lost, and optionally return a guard that can be used
		616	to stop monitoring again.
		617
		618	In the first form (callback), the callback is simply called with any
		619	number of C<@reason> elements (no @reason means that the port was deleted
		620	"normally"). Note also that I<< the callback B<must> never die >>, so use
		621	C<eval> if unsure.
		622
		623	In the second form (another port given), the other port (C<$rcvport>)
		624	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		625	"normal" kils nothing happens, while under all other conditions, the other
		626	port is killed with the same reason.
		627
		628	The third form (kill self) is the same as the second form, except that
		629	C<$rvport> defaults to C<$SELF>.
		630
		631	In the last form (message), a message of the form C<@msg, @reason> will be
		632	C<snd>.
		633
		634	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		635	alert was raised), they are removed and will not trigger again.
		636
		637	As a rule of thumb, monitoring requests should always monitor a port from
		638	a local port (or callback). The reason is that kill messages might get
		639	lost, just like any other message. Another less obvious reason is that
		640	even monitoring requests can get lost (for example, when the connection
		641	to the other node goes down permanently). When monitoring a port locally
		642	these problems do not exist.
		643
		644	C<mon> effectively guarantees that, in the absence of hardware failures,
		645	after starting the monitor, either all messages sent to the port will
		646	arrive, or the monitoring action will be invoked after possible message
		647	loss has been detected. No messages will be lost "in between" (after
		648	the first lost message no further messages will be received by the
		649	port). After the monitoring action was invoked, further messages might get
		650	delivered again.
		651
		652	Inter-host-connection timeouts and monitoring depend on the transport
		653	used. The only transport currently implemented is TCP, and AnyEvent::MP
		654	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		655	non-idle connection, and usually around two hours for idle connections).
		656
		657	This means that monitoring is good for program errors and cleaning up
		658	stuff eventually, but they are no replacement for a timeout when you need
		659	to ensure some maximum latency.
		660
		661	Example: call a given callback when C<$port> is killed.
		662
		663	mon $port, sub { warn "port died because of <@_>\n" };
		664
		665	Example: kill ourselves when C<$port> is killed abnormally.
		666
		667	mon $port;
		668
		669	Example: send us a restart message when another C<$port> is killed.
		670
		671	mon $port, $self => "restart";
		672
		673	=cut
		674
136	sub mon {	675	sub mon {
137	my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);	676	my ($nodeid, $port) = split /#/, shift, 2;
138		677
139	my $node = AnyEvent::MP::Base::add_node $noderef;	678	my $node = $NODE{$nodeid} || add_node $nodeid;
140		679
141	#TODO: ports must not be references	680	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) {	681
		682	unless (ref $cb) {
143	if (@_) {	683	if (@_) {
144	# send a kill info message	684	# send a kill info message
145	my (@msg) = ($cb, @_);	685	my (@msg) = ($cb, @_);
146	$cb = sub { snd @msg, @_ };	686	$cb = sub { snd @msg, @_ };
147	} else {	687	} else {
148	# simply kill other port	688	# simply kill other port
149	my $port = $cb;	689	my $port = $cb;
150	$cb = sub { kil $port, @_ };	690	$cb = sub { kil $port, @_ if @_ };
151	}	691	}
152	}	692	}
153		693
154	$node->monitor ($port, $cb);	694	$node->monitor ($port, $cb);
155		695
156	defined wantarray	696	defined wantarray
157	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	697	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
158	}	698	}
159		699
160	=item $guard = mon_guard $port, $ref, $ref...	700	=item $guard = mon_guard $port, $ref, $ref...
161		701
162	Monitors the given C<$port> and keeps the passed references. When the port	702	Monitors the given C<$port> and keeps the passed references. When the port
163	is killed, the references will be freed.	703	is killed, the references will be freed.
164		704
165	Optionally returns a guard that will stop the monitoring.	705	Optionally returns a guard that will stop the monitoring.
166		706
167	This function is useful when you create e.g. timers or other watchers and	707	This function is useful when you create e.g. timers or other watchers and
168	want to free them when the port gets killed:	708	want to free them when the port gets killed (note the use of C<psub>):
169		709
170	$port->rcv (start => sub {	710	$port->rcv (start => sub {
171	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	711	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
172	undef $timer if 0.9 < rand;	712	undef $timer if 0.9 < rand;
173	});	713	});
174	});	714	});
175		715
176	=cut	716	=cut
177		717
178	sub mon_guard {	718	sub mon_guard {
179	my ($port, @refs) = @_;	719	my ($port, @refs) = @_;
180		720
		721	#TODO: mon-less form?
		722
181	mon $port, sub { 0 && @refs }	723	mon $port, sub { 0 && @refs }
182	}	724	}
183		725
184	=item $local_port = create_port	726	=item kil $port[, @reason]
185		727
186	Create a new local port object. See the next section for allowed methods.	728	Kill the specified port with the given C<@reason>.
		729
		730	If no C<@reason> is specified, then the port is killed "normally" -
		731	monitor callback will be invoked, but the kil will not cause linked ports
		732	(C<mon $mport, $lport> form) to get killed.
		733
		734	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
		735	form) get killed with the same reason.
		736
		737	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		738	will be reported as reason C<< die => $@ >>.
		739
		740	Transport/communication errors are reported as C<< transport_error =>
		741	$message >>.
		742
		743	Common idioms:
		744
		745	# silently remove yourself, do not kill linked ports
		746	kil $SELF;
		747
		748	# report a failure in some detail
		749	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		750
		751	# do not waste much time with killing, just die when something goes wrong
		752	open my $fh, "<file"
		753	or die "file: $!";
		754
		755	=item $port = spawn $node, $initfunc[, @initdata]
		756
		757	Creates a port on the node C<$node> (which can also be a port ID, in which
		758	case it's the node where that port resides).
		759
		760	The port ID of the newly created port is returned immediately, and it is
		761	possible to immediately start sending messages or to monitor the port.
		762
		763	After the port has been created, the init function is called on the remote
		764	node, in the same context as a C<rcv> callback. This function must be a
		765	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		766	specify a function in the main program, use C<::name>.
		767
		768	If the function doesn't exist, then the node tries to C<require>
		769	the package, then the package above the package and so on (e.g.
		770	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		771	exists or it runs out of package names.
		772
		773	The init function is then called with the newly-created port as context
		774	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		775	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		776	the port might not get created.
		777
		778	A common idiom is to pass a local port, immediately monitor the spawned
		779	port, and in the remote init function, immediately monitor the passed
		780	local port. This two-way monitoring ensures that both ports get cleaned up
		781	when there is a problem.
		782
		783	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		784	caller before C<spawn> returns (by delaying invocation when spawn is
		785	called for the local node).
		786
		787	Example: spawn a chat server port on C<$othernode>.
		788
		789	# this node, executed from within a port context:
		790	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		791	mon $server;
		792
		793	# init function on C<$othernode>
		794	sub connect {
		795	my ($srcport) = @_;
		796
		797	mon $srcport;
		798
		799	rcv $SELF, sub {
		800	...
		801	};
		802	}
187		803
188	=cut	804	=cut
189		805
190	sub create_port {	806	sub _spawn {
191	my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;	807	my $port = shift;
		808	my $init = shift;
192		809
193	my $self = bless {	810	# rcv will create the actual port
194	id => "$NODE#$id",	811	local $SELF = "$NODE#$port";
195	}, "AnyEvent::MP::Port";	812	eval {
196		813	&{ load_func $init }
197	$AnyEvent::MP::Base::PORT{$id} = sub {
198	unshift @_, $self;
199
200	for (@{ $self->{rc0}{$_[1]} }) {
201	$_ && &{$_->[0]}
202	&& undef $_;
203	}
204
205	for (@{ $self->{rcv}{$_[1]} }) {
206	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
207	&& &{$_->[0]}
208	&& undef $_;
209	}
210
211	for (@{ $self->{any} }) {
212	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
213	&& &{$_->[0]}
214	&& undef $_;
215	}
216	};	814	};
217		815	_self_die if $@;
218	$self
219	}	816	}
220		817
221	=item $portid = miniport { my @msg = @_; $finished }	818	sub spawn(@) {
		819	my ($nodeid, undef) = split /#/, shift, 2;
222		820
223	Creates a "mini port", that is, a very lightweight port without any	821	my $id = $RUNIQ . ++$ID;
224	pattern matching behind it, and returns its ID.
225		822
226	The block will be called for every message received on the port. When the	823	$_[0] =~ /::/
227	callback returns a true value its job is considered "done" and the port	824	or Carp::croak "spawn init function must be a fully-qualified name, caught";
228	will be destroyed. Otherwise it will stay alive.
229		825
230	The message will be passed as-is, no extra argument (i.e. no port id) will	826	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
231	be passed to the callback.
232		827
233	If you need the local port id in the callback, this works nicely:	828	"$nodeid#$id"
		829	}
234		830
235	my $port; $port = miniport {	831
236	snd $otherport, reply => $port;	832	=item after $timeout, @msg
		833
		834	=item after $timeout, $callback
		835
		836	Either sends the given message, or call the given callback, after the
		837	specified number of seconds.
		838
		839	This is simply a utility function that comes in handy at times - the
		840	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		841	so it may go away in the future.
		842
		843	=cut
		844
		845	sub after($@) {
		846	my ($timeout, @action) = @_;
		847
		848	my $t; $t = AE::timer $timeout, 0, sub {
		849	undef $t;
		850	ref $action[0]
		851	? $action[0]()
		852	: snd @action;
237	};	853	};
		854	}
		855
		856	#=item $cb2 = timeout $seconds, $cb[, @args]
		857
		858	=item cal $port, @msg, $callback[, $timeout]
		859
		860	A simple form of RPC - sends a message to the given C<$port> with the
		861	given contents (C<@msg>), but adds a reply port to the message.
		862
		863	The reply port is created temporarily just for the purpose of receiving
		864	the reply, and will be C<kil>ed when no longer needed.
		865
		866	A reply message sent to the port is passed to the C<$callback> as-is.
		867
		868	If an optional time-out (in seconds) is given and it is not C<undef>,
		869	then the callback will be called without any arguments after the time-out
		870	elapsed and the port is C<kil>ed.
		871
		872	If no time-out is given (or it is C<undef>), then the local port will
		873	monitor the remote port instead, so it eventually gets cleaned-up.
		874
		875	Currently this function returns the temporary port, but this "feature"
		876	might go in future versions unless you can make a convincing case that
		877	this is indeed useful for something.
238		878
239	=cut	879	=cut
240		880
241	sub miniport(&) {	881	sub cal(@) {
		882	my $timeout = ref $_[-1] ? undef : pop;
242	my $cb = shift;	883	my $cb = pop;
243	my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;
244		884
245	$AnyEvent::MP::Base::PORT{$id} = sub {	885	my $port = port {
		886	undef $timeout;
		887	kil $SELF;
246	&$cb	888	&$cb;
247	and kil $id;
248	};	889	};
249		890
250	"$NODE#$id"	891	if (defined $timeout) {
		892	$timeout = AE::timer $timeout, 0, sub {
		893	undef $timeout;
		894	kil $port;
		895	$cb->();
		896	};
		897	} else {
		898	mon $_[0], sub {
		899	kil $port;
		900	$cb->();
		901	};
		902	}
		903
		904	push @_, $port;
		905	&snd;
		906
		907	$port
251	}	908	}
252		909
253	package AnyEvent::MP::Port;
254
255	=back	910	=back
256		911
257	=head1 METHODS FOR PORT OBJECTS	912	=head1 DISTRIBUTED DATABASE
		913
		914	AnyEvent::MP comes with a simple distributed database. The database will
		915	be mirrored asynchronously on all global nodes. Other nodes bind to one
		916	of the global nodes for their needs. Every node has a "local database"
		917	which contains all the values that are set locally. All local databases
		918	are merged together to form the global database, which can be queried.
		919
		920	The database structure is that of a two-level hash - the database hash
		921	contains hashes which contain values, similarly to a perl hash of hashes,
		922	i.e.:
		923
		924	$DATABASE{$family}{$subkey} = $value
		925
		926	The top level hash key is called "family", and the second-level hash key
		927	is called "subkey" or simply "key".
		928
		929	The family must be alphanumeric, i.e. start with a letter and consist
		930	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		931	pretty much like Perl module names.
		932
		933	As the family namespace is global, it is recommended to prefix family names
		934	with the name of the application or module using it.
		935
		936	The subkeys must be non-empty strings, with no further restrictions.
		937
		938	The values should preferably be strings, but other perl scalars should
		939	work as well (such as C<undef>, arrays and hashes).
		940
		941	Every database entry is owned by one node - adding the same family/subkey
		942	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		943	but the result might be nondeterministic, i.e. the key might have
		944	different values on different nodes.
		945
		946	Different subkeys in the same family can be owned by different nodes
		947	without problems, and in fact, this is the common method to create worker
		948	pools. For example, a worker port for image scaling might do this:
		949
		950	db_set my_image_scalers => $port;
		951
		952	And clients looking for an image scaler will want to get the
		953	C<my_image_scalers> keys from time to time:
		954
		955	db_keys my_image_scalers => sub {
		956	@ports = @{ $_[0] };
		957	};
		958
		959	Or better yet, they want to monitor the database family, so they always
		960	have a reasonable up-to-date copy:
		961
		962	db_mon my_image_scalers => sub {
		963	@ports = keys %{ $_[0] };
		964	};
		965
		966	In general, you can set or delete single subkeys, but query and monitor
		967	whole families only.
		968
		969	If you feel the need to monitor or query a single subkey, try giving it
		970	it's own family.
		971
		972	=over
		973
		974	=item db_set $family => $subkey [=> $value]
		975
		976	Sets (or replaces) a key to the database - if C<$value> is omitted,
		977	C<undef> is used instead.
		978
		979	=item db_del $family => $subkey...
		980
		981	Deletes one or more subkeys from the database family.
		982
		983	=item $guard = db_reg $family => $subkey [=> $value]
		984
		985	Sets the key on the database and returns a guard. When the guard is
		986	destroyed, the key is deleted from the database. If C<$value> is missing,
		987	then C<undef> is used.
		988
		989	=item db_family $family => $cb->(\%familyhash)
		990
		991	Queries the named database C<$family> and call the callback with the
		992	family represented as a hash. You can keep and freely modify the hash.
		993
		994	=item db_keys $family => $cb->(\@keys)
		995
		996	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		997	them as array reference to the callback.
		998
		999	=item db_values $family => $cb->(\@values)
		1000
		1001	Same as C<db_family>, except it only queries the family I<values> and passes them
		1002	as array reference to the callback.
		1003
		1004	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1005
		1006	Creates a monitor on the given database family. Each time a key is set
		1007	or or is deleted the callback is called with a hash containing the
		1008	database family and three lists of added, changed and deleted subkeys,
		1009	respectively. If no keys have changed then the array reference might be
		1010	C<undef> or even missing.
		1011
		1012	If not called in void context, a guard object is returned that, when
		1013	destroyed, stops the monitor.
		1014
		1015	The family hash reference and the key arrays belong to AnyEvent::MP and
		1016	B<must not be modified or stored> by the callback. When in doubt, make a
		1017	copy.
		1018
		1019	As soon as possible after the monitoring starts, the callback will be
		1020	called with the intiial contents of the family, even if it is empty,
		1021	i.e. there will always be a timely call to the callback with the current
		1022	contents.
		1023
		1024	It is possible that the callback is called with a change event even though
		1025	the subkey is already present and the value has not changed.
		1026
		1027	The monitoring stops when the guard object is destroyed.
		1028
		1029	Example: on every change to the family "mygroup", print out all keys.
		1030
		1031	my $guard = db_mon mygroup => sub {
		1032	my ($family, $a, $c, $d) = @_;
		1033	print "mygroup members: ", (join " ", keys %$family), "\n";
		1034	};
		1035
		1036	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1037
		1038	my $guard; $guard = db_mon My::Module::workers => sub {
		1039	my ($family, $a, $c, $d) = @_;
		1040	return unless %$family;
		1041	undef $guard;
		1042	print "My::Module::workers now nonempty\n";
		1043	};
		1044
		1045	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1046
		1047	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1048	my ($family, $a, $c, $d) = @_;
		1049
		1050	print "+$_=$family->{$_}\n" for @$a;
		1051	print "*$_=$family->{$_}\n" for @$c;
		1052	print "-$_=$family->{$_}\n" for @$d;
		1053	};
		1054
		1055	=cut
		1056
		1057	=back
		1058
		1059	=head1 AnyEvent::MP vs. Distributed Erlang
		1060
		1061	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		1062	== aemp node, Erlang process == aemp port), so many of the documents and
		1063	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		1064	sample:
		1065
		1066	http://www.erlang.se/doc/programming_rules.shtml
		1067	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		1068	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
		1069	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		1070
		1071	Despite the similarities, there are also some important differences:
258		1072
259	=over 4	1073	=over 4
260		1074
261	=item "$port"	1075	=item * Node IDs are arbitrary strings in AEMP.
262		1076
263	A port object stringifies to its port ID, so can be used directly for	1077	Erlang relies on special naming and DNS to work everywhere in the same
264	C<snd> operations.	1078	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		1079	configuration or DNS), and possibly the addresses of some seed nodes, but
		1080	will otherwise discover other nodes (and their IDs) itself.
265		1081
266	=cut	1082	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		1083	uses "local ports are like remote ports".
267		1084
268	use overload	1085	The failure modes for local ports are quite different (runtime errors
269	'""' => sub { $_[0]{id} },	1086	only) then for remote ports - when a local port dies, you I<know> it dies,
270	fallback => 1;	1087	when a connection to another node dies, you know nothing about the other
		1088	port.
271		1089
272	sub TO_JSON { $_[0]{id} }	1090	Erlang pretends remote ports are as reliable as local ports, even when
		1091	they are not.
273		1092
274	=item $port->rcv (type => $callback->($port, @msg))	1093	AEMP encourages a "treat remote ports differently" philosophy, with local
		1094	ports being the special case/exception, where transport errors cannot
		1095	occur.
275		1096
276	=item $port->rcv ($smartmatch => $callback->($port, @msg))	1097	=item * Erlang uses processes and a mailbox, AEMP does not queue.
277		1098
278	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	1099	Erlang uses processes that selectively receive messages out of order, and
		1100	therefore needs a queue. AEMP is event based, queuing messages would serve
		1101	no useful purpose. For the same reason the pattern-matching abilities
		1102	of AnyEvent::MP are more limited, as there is little need to be able to
		1103	filter messages without dequeuing them.
279		1104
280	Register a callback on the given port.	1105	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1106	being event-based, while Erlang is process-based.
281		1107
282	The callback has to return a true value when its work is done, after	1108	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	1109	top of AEMP and Coro threads.
284	registered.
285		1110
286	If the match is an array reference, then it will be matched against the	1111	=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		1112
290	Any element in the match that is specified as C<_any_> (a function	1113	Sending messages in Erlang is synchronous and blocks the process until
291	exported by this module) matches any single element of the message.	1114	a conenction has been established and the message sent (and so does not
		1115	need a queue that can overflow). AEMP sends return immediately, connection
		1116	establishment is handled in the background.
292		1117
293	While not required, it is highly recommended that the first matching	1118	=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		1119
297	=cut	1120	Erlang implements few guarantees on messages delivery - messages can get
		1121	lost without any of the processes realising it (i.e. you send messages a,
		1122	b, and c, and the other side only receives messages a and c).
298		1123
299	sub rcv($@) {	1124	AEMP guarantees (modulo hardware errors) correct ordering, and the
300	my ($self, $match, $cb) = @_;	1125	guarantee that after one message is lost, all following ones sent to the
		1126	same port are lost as well, until monitoring raises an error, so there are
		1127	no silent "holes" in the message sequence.
301		1128
302	if (!ref $match) {	1129	If you want your software to be very reliable, you have to cope with
303	push @{ $self->{rc0}{$match} }, [$cb];	1130	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
304	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	1131	simply tries to work better in common error cases, such as when a network
305	my ($type, @match) = @$match;	1132	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		1133
314	=item $port->register ($name)	1134	=item * Erlang can send messages to the wrong port, AEMP does not.
315		1135
316	Registers the given port under the well known name C<$name>. If the name	1136	In Erlang it is quite likely that a node that restarts reuses an Erlang
317	already exists it is replaced.	1137	process ID known to other nodes for a completely different process,
		1138	causing messages destined for that process to end up in an unrelated
		1139	process.
318		1140
319	A port can only be registered under one well known name.	1141	AEMP does not reuse port IDs, so old messages or old port IDs floating
		1142	around in the network will not be sent to an unrelated port.
320		1143
321	=cut	1144	=item * Erlang uses unprotected connections, AEMP uses secure
		1145	authentication and can use TLS.
322		1146
323	sub register {	1147	AEMP can use a proven protocol - TLS - to protect connections and
324	my ($self, $name) = @_;	1148	securely authenticate nodes.
325		1149
326	$self->{wkname} = $name;	1150	=item * The AEMP protocol is optimised for both text-based and binary
327	$AnyEvent::MP::Base::WKP{$name} = "$self";	1151	communications.
328	}
329		1152
330	=item $port->destroy	1153	The AEMP protocol, unlike the Erlang protocol, supports both programming
		1154	language independent text-only protocols (good for debugging), and binary,
		1155	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1156	used, the protocol is actually completely text-based.
331		1157
332	Explicitly destroy/remove/nuke/vaporise the port.	1158	It has also been carefully designed to be implementable in other languages
		1159	with a minimum of work while gracefully degrading functionality to make the
		1160	protocol simple.
333		1161
334	Ports are normally kept alive by their mere existance alone, and need to	1162	=item * AEMP has more flexible monitoring options than Erlang.
335	be destroyed explicitly.
336		1163
337	=cut	1164	In Erlang, you can chose to receive I<all> exit signals as messages or
		1165	I<none>, there is no in-between, so monitoring single Erlang processes is
		1166	difficult to implement.
338		1167
339	sub destroy {	1168	Monitoring in AEMP is more flexible than in Erlang, as one can choose
340	my ($self) = @_;	1169	between automatic kill, exit message or callback on a per-port basis.
341		1170
342	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	1171	=item * Erlang tries to hide remote/local connections, AEMP does not.
343		1172
344	AnyEvent::MP::Base::kil $self->{id};	1173	Monitoring in Erlang is not an indicator of process death/crashes, in the
345	}	1174	same way as linking is (except linking is unreliable in Erlang).
		1175
		1176	In AEMP, you don't "look up" registered port names or send to named ports
		1177	that might or might not be persistent. Instead, you normally spawn a port
		1178	on the remote node. The init function monitors you, and you monitor the
		1179	remote port. Since both monitors are local to the node, they are much more
		1180	reliable (no need for C<spawn_link>).
		1181
		1182	This also saves round-trips and avoids sending messages to the wrong port
		1183	(hard to do in Erlang).
346		1184
347	=back	1185	=back
348		1186
349	=head1 FUNCTIONS FOR NODES	1187	=head1 RATIONALE
350		1188
351	=over 4	1189	=over 4
352		1190
353	=item mon $noderef, $callback->($noderef, $status, $)	1191	=item Why strings for port and node IDs, why not objects?
354		1192
355	Monitors the given noderef.	1193	We considered "objects", but found that the actual number of methods
		1194	that can be called are quite low. Since port and node IDs travel over
		1195	the network frequently, the serialising/deserialising would add lots of
		1196	overhead, as well as having to keep a proxy object everywhere.
356		1197
357	=item become_public endpoint...	1198	Strings can easily be printed, easily serialised etc. and need no special
		1199	procedures to be "valid".
358		1200
359	Tells the node to become a public node, i.e. reachable from other nodes.	1201	And as a result, a port with just a default receiver consists of a single
		1202	code reference stored in a global hash - it can't become much cheaper.
360		1203
361	If no arguments are given, or the first argument is C<undef>, then	1204	=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		1205
365	Otherwise the first argument must be an array-reference with transport	1206	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	1207	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	1208	default (although all nodes will accept it).
368	will become the node reference.
369		1209
370	=cut	1210	The default framing protocol is JSON because a) JSON::XS is many times
		1211	faster for small messages and b) most importantly, after years of
		1212	experience we found that object serialisation is causing more problems
		1213	than it solves: Just like function calls, objects simply do not travel
		1214	easily over the network, mostly because they will always be a copy, so you
		1215	always have to re-think your design.
		1216
		1217	Keeping your messages simple, concentrating on data structures rather than
		1218	objects, will keep your messages clean, tidy and efficient.
371		1219
372	=back	1220	=back
373		1221
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	1222	=head1 SEE ALSO
		1223
		1224	L<AnyEvent::MP::Intro> - a gentle introduction.
		1225
		1226	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1227
		1228	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1229	your applications.
		1230
		1231	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1232
		1233	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1234	all nodes.
419		1235
420	L<AnyEvent>.	1236	L<AnyEvent>.
421		1237
422	=head1 AUTHOR	1238	=head1 AUTHOR
423		1239

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