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Revision 1.21 by root, Tue Aug 4 14:10:51 2009 UTC vs.
Revision 1.149 by root, Wed Aug 17 19:44:07 2016 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	# distributed database - modification
		53	db_set $family => $subkey [=> $value] # add a subkey
		54	db_del $family => $subkey... # delete one or more subkeys
		55	db_reg $family => $port [=> $value] # register a port
		56
		57	# distributed database - queries
		58	db_family $family => $cb->(\%familyhash)
		59	db_keys $family => $cb->(\@keys)
		60	db_values $family => $cb->(\@values)
		61
		62	# distributed database - monitoring a family
		63	db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
24		64
25	=head1 DESCRIPTION	65	=head1 DESCRIPTION
26		66
27	This module (-family) implements a simple message passing framework.	67	This module (-family) implements a simple message passing framework.
28		68
29	Despite its simplicity, you can securely message other processes running	69	Despite its simplicity, you can securely message other processes running
30	on the same or other hosts.	70	on the same or other hosts, and you can supervise entities remotely.
31		71
32	At the moment, this module family is severly brokena nd underdocumented,	72	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 -	73	manual page and the examples under F<eg/>.
34	stay tuned!
35		74
36	=head1 CONCEPTS	75	=head1 CONCEPTS
37		76
38	=over 4	77	=over 4
39		78
40	=item port	79	=item port
41		80
42	A port is something you can send messages to with the C<snd> function, and	81	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	82	messages to (with the C<snd> function).
44	messages they match, messages will not be queued.
45		83
		84	Ports allow you to register C<rcv> handlers that can match all or just
		85	some messages. Messages send to ports will not be queued, regardless of
		86	anything was listening for them or not.
		87
		88	Ports are represented by (printable) strings called "port IDs".
		89
46	=item port id - C<noderef#portname>	90	=item port ID - C<nodeid#portname>
47		91
48	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	92	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).	93	as separator, and a port name (a printable string of unspecified
		94	format created by AnyEvent::MP).
50		95
51	=item node	96	=item node
52		97
53	A node is a single process containing at least one port - the node	98	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,	99	which enables nodes to manage each other remotely, and to create new
55	among other things.	100	ports.
56		101
57	Initially, nodes are either private (single-process only) or hidden	102	Nodes are either public (have one or more listening ports) or private
58	(connected to a master node only). Only when they epxlicitly "become	103	(no listening ports). Private nodes cannot talk to other private nodes
59	public" can you send them messages from unrelated other nodes.	104	currently, but all nodes can talk to public nodes.
60		105
61	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	106	Nodes is represented by (printable) strings called "node IDs".
62		107
		108	=item node ID - C<[A-Za-z0-9_\-.:]*>
		109
63	A noderef is a string that either uniquely identifies a given node (for	110	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	111	network. Depending on the configuration used, node IDs can look like a
65	node (for public nodes).	112	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		113	doesn't interpret node IDs in any way except to uniquely identify a node.
		114
		115	=item binds - C<ip:port>
		116
		117	Nodes can only talk to each other by creating some kind of connection to
		118	each other. To do this, nodes should listen on one or more local transport
		119	endpoints - binds.
		120
		121	Currently, only standard C<ip:port> specifications can be used, which
		122	specify TCP ports to listen on. So a bind is basically just a tcp socket
		123	in listening mode that accepts connections from other nodes.
		124
		125	=item seed nodes
		126
		127	When a node starts, it knows nothing about the network it is in - it
		128	needs to connect to at least one other node that is already in the
		129	network. These other nodes are called "seed nodes".
		130
		131	Seed nodes themselves are not special - they are seed nodes only because
		132	some other node I<uses> them as such, but any node can be used as seed
		133	node for other nodes, and eahc node can use a different set of seed nodes.
		134
		135	In addition to discovering the network, seed nodes are also used to
		136	maintain the network - all nodes using the same seed node are part of the
		137	same network. If a network is split into multiple subnets because e.g. the
		138	network link between the parts goes down, then using the same seed nodes
		139	for all nodes ensures that eventually the subnets get merged again.
		140
		141	Seed nodes are expected to be long-running, and at least one seed node
		142	should always be available. They should also be relatively responsive - a
		143	seed node that blocks for long periods will slow down everybody else.
		144
		145	For small networks, it's best if every node uses the same set of seed
		146	nodes. For large networks, it can be useful to specify "regional" seed
		147	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		148	each other. What's important is that all seed nodes connections form a
		149	complete graph, so that the network cannot split into separate subnets
		150	forever.
		151
		152	Seed nodes are represented by seed IDs.
		153
		154	=item seed IDs - C<host:port>
		155
		156	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		157	TCP port) of nodes that should be used as seed nodes.
		158
		159	=item global nodes
		160
		161	An AEMP network needs a discovery service - nodes need to know how to
		162	connect to other nodes they only know by name. In addition, AEMP offers a
		163	distributed "group database", which maps group names to a list of strings
		164	- for example, to register worker ports.
		165
		166	A network needs at least one global node to work, and allows every node to
		167	be a global node.
		168
		169	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		170	node and tries to keep connections to all other nodes. So while it can
		171	make sense to make every node "global" in small networks, it usually makes
		172	sense to only make seed nodes into global nodes in large networks (nodes
		173	keep connections to seed nodes and global nodes, so making them the same
		174	reduces overhead).
66		175
67	=back	176	=back
68		177
69	=head1 VARIABLES/FUNCTIONS	178	=head1 VARIABLES/FUNCTIONS
70		179
…		…
72		181
73	=cut	182	=cut
74		183
75	package AnyEvent::MP;	184	package AnyEvent::MP;
76		185
		186	use AnyEvent::MP::Config ();
77	use AnyEvent::MP::Base;	187	use AnyEvent::MP::Kernel;
		188	use AnyEvent::MP::Kernel qw(
		189	%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID
		190	add_node load_func
		191
		192	NODE $NODE
		193	configure
		194	node_of port_is_local
		195	snd kil
		196	db_set db_del
		197	db_mon db_family db_keys db_values
		198	);
78		199
79	use common::sense;	200	use common::sense;
80		201
81	use Carp ();	202	use Carp ();
82		203
83	use AE ();	204	use AnyEvent ();
		205	use Guard ();
84		206
85	use base "Exporter";	207	use base "Exporter";
86		208
87	our $VERSION = '0.02';	209	our $VERSION = $AnyEvent::MP::Config::VERSION;
		210
88	our @EXPORT = qw(	211	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv mon kil _any_	212	NODE $NODE
90	create_port create_port_on	213	configure
91	miniport	214	node_of port_is_local
92	become_slave become_public	215	snd kil
		216	db_set db_del
		217	db_mon db_family db_keys db_values
		218
		219	*SELF
		220
		221	port rcv mon mon_guard psub peval spawn cal
		222	db_set db_del db_reg
		223	db_mon db_family db_keys db_values
		224
		225	after
93	);	226	);
94		227
		228	our $SELF;
		229
		230	sub _self_die() {
		231	my $msg = $@;
		232	$msg =~ s/\n+$// unless ref $msg;
		233	kil $SELF, die => $msg;
		234	}
		235
95	=item NODE / $NODE	236	=item $thisnode = NODE / $NODE
96		237
97	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	238	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	239	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.	240	a call to C<configure>.
100		241
		242	=item $nodeid = node_of $port
		243
		244	Extracts and returns the node ID from a port ID or a node ID.
		245
		246	=item $is_local = port_is_local $port
		247
		248	Returns true iff the port is a local port.
		249
		250	=item configure $profile, key => value...
		251
		252	=item configure key => value...
		253
		254	Before a node can talk to other nodes on the network (i.e. enter
		255	"distributed mode") it has to configure itself - the minimum a node needs
		256	to know is its own name, and optionally it should know the addresses of
		257	some other nodes in the network to discover other nodes.
		258
		259	This function configures a node - it must be called exactly once (or
		260	never) before calling other AnyEvent::MP functions.
		261
		262	The key/value pairs are basically the same ones as documented for the
		263	F<aemp> command line utility (sans the set/del prefix), with these additions:
		264
		265	=over 4
		266
		267	=item norc => $boolean (default false)
		268
		269	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		270	be consulted - all configuration options must be specified in the
		271	C<configure> call.
		272
		273	=item force => $boolean (default false)
		274
		275	IF true, then the values specified in the C<configure> will take
		276	precedence over any values configured via the rc file. The default is for
		277	the rc file to override any options specified in the program.
		278
		279	=back
		280
		281	=over 4
		282
		283	=item step 1, gathering configuration from profiles
		284
		285	The function first looks up a profile in the aemp configuration (see the
		286	L<aemp> commandline utility). The profile name can be specified via the
		287	named C<profile> parameter or can simply be the first parameter). If it is
		288	missing, then the nodename (F<uname -n>) will be used as profile name.
		289
		290	The profile data is then gathered as follows:
		291
		292	First, all remaining key => value pairs (all of which are conveniently
		293	undocumented at the moment) will be interpreted as configuration
		294	data. Then they will be overwritten by any values specified in the global
		295	default configuration (see the F<aemp> utility), then the chain of
		296	profiles chosen by the profile name (and any C<parent> attributes).
		297
		298	That means that the values specified in the profile have highest priority
		299	and the values specified directly via C<configure> have lowest priority,
		300	and can only be used to specify defaults.
		301
		302	If the profile specifies a node ID, then this will become the node ID of
		303	this process. If not, then the profile name will be used as node ID, with
		304	a unique randoms tring (C</%u>) appended.
		305
		306	The node ID can contain some C<%> sequences that are expanded: C<%n>
		307	is expanded to the local nodename, C<%u> is replaced by a random
		308	strign to make the node unique. For example, the F<aemp> commandline
		309	utility uses C<aemp/%n/%u> as nodename, which might expand to
		310	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		311
		312	=item step 2, bind listener sockets
		313
		314	The next step is to look up the binds in the profile, followed by binding
		315	aemp protocol listeners on all binds specified (it is possible and valid
		316	to have no binds, meaning that the node cannot be contacted from the
		317	outside. This means the node cannot talk to other nodes that also have no
		318	binds, but it can still talk to all "normal" nodes).
		319
		320	If the profile does not specify a binds list, then a default of C<*> is
		321	used, meaning the node will bind on a dynamically-assigned port on every
		322	local IP address it finds.
		323
		324	=item step 3, connect to seed nodes
		325
		326	As the last step, the seed ID list from the profile is passed to the
		327	L<AnyEvent::MP::Global> module, which will then use it to keep
		328	connectivity with at least one node at any point in time.
		329
		330	=back
		331
		332	Example: become a distributed node using the local node name as profile.
		333	This should be the most common form of invocation for "daemon"-type nodes.
		334
		335	configure
		336
		337	Example: become a semi-anonymous node. This form is often used for
		338	commandline clients.
		339
		340	configure nodeid => "myscript/%n/%u";
		341
		342	Example: configure a node using a profile called seed, which is suitable
		343	for a seed node as it binds on all local addresses on a fixed port (4040,
		344	customary for aemp).
		345
		346	# use the aemp commandline utility
		347	# aemp profile seed binds '*:4040'
		348
		349	# then use it
		350	configure profile => "seed";
		351
		352	# or simply use aemp from the shell again:
		353	# aemp run profile seed
		354
		355	# or provide a nicer-to-remember nodeid
		356	# aemp run profile seed nodeid "$(hostname)"
		357
		358	=item $SELF
		359
		360	Contains the current port id while executing C<rcv> callbacks or C<psub>
		361	blocks.
		362
		363	=item *SELF, SELF, %SELF, @SELF...
		364
		365	Due to some quirks in how perl exports variables, it is impossible to
		366	just export C<$SELF>, all the symbols named C<SELF> are exported by this
		367	module, but only C<$SELF> is currently used.
		368
101	=item snd $portid, type => @data	369	=item snd $port, type => @data
102		370
103	=item snd $portid, @msg	371	=item snd $port, @msg
104		372
105	Send the given message to the given port ID, which can identify either	373	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	374	local or a remote port, and must be a port ID.
107	stringifies a sa port ID (such as a port object :).
108		375
109	While the message can be about anything, it is highly recommended to use a	376	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	377	use a string as first element (a port ID, or some word that indicates a
111	type etc.).	378	request type etc.) and to consist if only simple perl values (scalars,
		379	arrays, hashes) - if you think you need to pass an object, think again.
112		380
113	The message data effectively becomes read-only after a call to this	381	The message data logically becomes read-only after a call to this
114	function: modifying any argument is not allowed and can cause many	382	function: modifying any argument (or values referenced by them) is
115	problems.	383	forbidden, as there can be considerable time between the call to C<snd>
		384	and the time the message is actually being serialised - in fact, it might
		385	never be copied as within the same process it is simply handed to the
		386	receiving port.
116		387
117	The type of data you can transfer depends on the transport protocol: when	388	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	389	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	390	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	391	that Storable can serialise and deserialise is allowed, and for the local
121	node, anything can be passed.	392	node, anything can be passed. Best rely only on the common denominator of
		393	these.
122		394
123	=item $guard = mon $portid, $cb->()	395	=item $local_port = port
124		396
125	=item $guard = mon $portid, $otherport	397	Create a new local port object and returns its port ID. Initially it has
		398	no callbacks set and will throw an error when it receives messages.
126		399
127	=item $guard = mon $portid, $otherport, @msg	400	=item $local_port = port { my @msg = @_ }
128		401
129	Monitor the given port and call the given callback when the port is	402	Creates a new local port, and returns its ID. Semantically the same as
130	destroyed or connection to it's node is lost.	403	creating a port and calling C<rcv $port, $callback> on it.
131		404
132	#TODO	405	The block will be called for every message received on the port, with the
		406	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		407	port to be C<kil>ed. The message will be passed as-is, no extra argument
		408	(i.e. no port ID) will be passed to the callback.
		409
		410	If you want to stop/destroy the port, simply C<kil> it:
		411
		412	my $port = port {
		413	my @msg = @_;
		414	...
		415	kil $SELF;
		416	};
133		417
134	=cut	418	=cut
135		419
		420	sub rcv($@);
		421
		422	my $KILME = sub {
		423	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
		424	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		425	};
		426
		427	sub port(;&) {
		428	my $id = $UNIQ . ++$ID;
		429	my $port = "$NODE#$id";
		430
		431	rcv $port, shift || $KILME;
		432
		433	$port
		434	}
		435
		436	=item rcv $local_port, $callback->(@msg)
		437
		438	Replaces the default callback on the specified port. There is no way to
		439	remove the default callback: use C<sub { }> to disable it, or better
		440	C<kil> the port when it is no longer needed.
		441
		442	The global C<$SELF> (exported by this module) contains C<$port> while
		443	executing the callback. Runtime errors during callback execution will
		444	result in the port being C<kil>ed.
		445
		446	The default callback receives all messages not matched by a more specific
		447	C<tag> match.
		448
		449	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		450
		451	Register (or replace) callbacks to be called on messages starting with the
		452	given tag on the given port (and return the port), or unregister it (when
		453	C<$callback> is C<$undef> or missing). There can only be one callback
		454	registered for each tag.
		455
		456	The original message will be passed to the callback, after the first
		457	element (the tag) has been removed. The callback will use the same
		458	environment as the default callback (see above).
		459
		460	Example: create a port and bind receivers on it in one go.
		461
		462	my $port = rcv port,
		463	msg1 => sub { ... },
		464	msg2 => sub { ... },
		465	;
		466
		467	Example: create a port, bind receivers and send it in a message elsewhere
		468	in one go:
		469
		470	snd $otherport, reply =>
		471	rcv port,
		472	msg1 => sub { ... },
		473	...
		474	;
		475
		476	Example: temporarily register a rcv callback for a tag matching some port
		477	(e.g. for an rpc reply) and unregister it after a message was received.
		478
		479	rcv $port, $otherport => sub {
		480	my @reply = @_;
		481
		482	rcv $SELF, $otherport;
		483	};
		484
		485	=cut
		486
		487	sub rcv($@) {
		488	my $port = shift;
		489	my ($nodeid, $portid) = split /#/, $port, 2;
		490
		491	$nodeid eq $NODE
		492	or Carp::croak "$port: rcv can only be called on local ports, caught";
		493
		494	while (@_) {
		495	if (ref $_[0]) {
		496	if (my $self = $PORT_DATA{$portid}) {
		497	"AnyEvent::MP::Port" eq ref $self
		498	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		499
		500	$self->[0] = shift;
		501	} else {
		502	my $cb = shift;
		503	$PORT{$portid} = sub {
		504	local $SELF = $port;
		505	eval { &$cb }; _self_die if $@;
		506	};
		507	}
		508	} elsif (defined $_[0]) {
		509	my $self = $PORT_DATA{$portid} ||= do {
		510	my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
		511
		512	$PORT{$portid} = sub {
		513	local $SELF = $port;
		514
		515	if (my $cb = $self->[1]{$_[0]}) {
		516	shift;
		517	eval { &$cb }; _self_die if $@;
		518	} else {
		519	&{ $self->[0] };
		520	}
		521	};
		522
		523	$self
		524	};
		525
		526	"AnyEvent::MP::Port" eq ref $self
		527	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		528
		529	my ($tag, $cb) = splice @_, 0, 2;
		530
		531	if (defined $cb) {
		532	$self->[1]{$tag} = $cb;
		533	} else {
		534	delete $self->[1]{$tag};
		535	}
		536	}
		537	}
		538
		539	$port
		540	}
		541
		542	=item peval $port, $coderef[, @args]
		543
		544	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		545	when the code throws an exception the C<$port> will be killed.
		546
		547	Any remaining args will be passed to the callback. Any return values will
		548	be returned to the caller.
		549
		550	This is useful when you temporarily want to execute code in the context of
		551	a port.
		552
		553	Example: create a port and run some initialisation code in it's context.
		554
		555	my $port = port { ... };
		556
		557	peval $port, sub {
		558	init
		559	or die "unable to init";
		560	};
		561
		562	=cut
		563
		564	sub peval($$) {
		565	local $SELF = shift;
		566	my $cb = shift;
		567
		568	if (wantarray) {
		569	my @res = eval { &$cb };
		570	_self_die if $@;
		571	@res
		572	} else {
		573	my $res = eval { &$cb };
		574	_self_die if $@;
		575	$res
		576	}
		577	}
		578
		579	=item $closure = psub { BLOCK }
		580
		581	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		582	closure is executed, sets up the environment in the same way as in C<rcv>
		583	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		584
		585	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		586	BLOCK }, @_ } >>.
		587
		588	This is useful when you register callbacks from C<rcv> callbacks:
		589
		590	rcv delayed_reply => sub {
		591	my ($delay, @reply) = @_;
		592	my $timer = AE::timer $delay, 0, psub {
		593	snd @reply, $SELF;
		594	};
		595	};
		596
		597	=cut
		598
		599	sub psub(&) {
		600	my $cb = shift;
		601
		602	my $port = $SELF
		603	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		604
		605	sub {
		606	local $SELF = $port;
		607
		608	if (wantarray) {
		609	my @res = eval { &$cb };
		610	_self_die if $@;
		611	@res
		612	} else {
		613	my $res = eval { &$cb };
		614	_self_die if $@;
		615	$res
		616	}
		617	}
		618	}
		619
		620	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		621
		622	=item $guard = mon $port # kill $SELF when $port dies
		623
		624	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
		625
		626	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		627
		628	Monitor the given port and do something when the port is killed or
		629	messages to it were lost, and optionally return a guard that can be used
		630	to stop monitoring again.
		631
		632	The first two forms distinguish between "normal" and "abnormal" kil's:
		633
		634	In the first form (another port given), if the C<$port> is C<kil>'ed with
		635	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		636	same reason. That is, on "normal" kil's nothing happens, while under all
		637	other conditions, the other port is killed with the same reason.
		638
		639	The second form (kill self) is the same as the first form, except that
		640	C<$rvport> defaults to C<$SELF>.
		641
		642	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		643	- it's up to the callback or receiver to check whether the C<@reason> is
		644	empty and act accordingly.
		645
		646	In the third form (callback), the callback is simply called with any
		647	number of C<@reason> elements (empty @reason means that the port was deleted
		648	"normally"). Note also that I<< the callback B<must> never die >>, so use
		649	C<eval> if unsure.
		650
		651	In the last form (message), a message of the form C<$rcvport, @msg,
		652	@reason> will be C<snd>.
		653
		654	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		655	alert was raised), they are removed and will not trigger again, even if it
		656	turns out that the port is still alive.
		657
		658	As a rule of thumb, monitoring requests should always monitor a remote
		659	port locally (using a local C<$rcvport> or a callback). The reason is that
		660	kill messages might get lost, just like any other message. Another less
		661	obvious reason is that even monitoring requests can get lost (for example,
		662	when the connection to the other node goes down permanently). When
		663	monitoring a port locally these problems do not exist.
		664
		665	C<mon> effectively guarantees that, in the absence of hardware failures,
		666	after starting the monitor, either all messages sent to the port will
		667	arrive, or the monitoring action will be invoked after possible message
		668	loss has been detected. No messages will be lost "in between" (after
		669	the first lost message no further messages will be received by the
		670	port). After the monitoring action was invoked, further messages might get
		671	delivered again.
		672
		673	Inter-host-connection timeouts and monitoring depend on the transport
		674	used. The only transport currently implemented is TCP, and AnyEvent::MP
		675	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		676	non-idle connection, and usually around two hours for idle connections).
		677
		678	This means that monitoring is good for program errors and cleaning up
		679	stuff eventually, but they are no replacement for a timeout when you need
		680	to ensure some maximum latency.
		681
		682	Example: call a given callback when C<$port> is killed.
		683
		684	mon $port, sub { warn "port died because of <@_>\n" };
		685
		686	Example: kill ourselves when C<$port> is killed abnormally.
		687
		688	mon $port;
		689
		690	Example: send us a restart message when another C<$port> is killed.
		691
		692	mon $port, $self => "restart";
		693
		694	=cut
		695
136	sub mon {	696	sub mon {
137	my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);	697	my ($nodeid, $port) = split /#/, shift, 2;
138		698
139	my $node = AnyEvent::MP::Base::add_node $noderef;	699	my $node = $NODE{$nodeid} || add_node $nodeid;
140		700
141	#TODO: ports must not be references	701	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) {	702
		703	unless (ref $cb) {
143	if (@_) {	704	if (@_) {
144	# send a kill info message	705	# send a kill info message
145	my (@msg) = ($cb, @_);	706	my (@msg) = ($cb, @_);
146	$cb = sub { snd @msg, @_ };	707	$cb = sub { snd @msg, @_ };
147	} else {	708	} else {
148	# simply kill other port	709	# simply kill other port
149	my $port = $cb;	710	my $port = $cb;
150	$cb = sub { kil $port, @_ };	711	$cb = sub { kil $port, @_ if @_ };
151	}	712	}
152	}	713	}
153		714
154	$node->monitor ($port, $cb);	715	$node->monitor ($port, $cb);
155		716
156	defined wantarray	717	defined wantarray
157	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	718	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
158	}	719	}
159		720
160	=item $guard = mon_guard $port, $ref, $ref...	721	=item $guard = mon_guard $port, $ref, $ref...
161		722
162	Monitors the given C<$port> and keeps the passed references. When the port	723	Monitors the given C<$port> and keeps the passed references. When the port
163	is killed, the references will be freed.	724	is killed, the references will be freed.
164		725
165	Optionally returns a guard that will stop the monitoring.	726	Optionally returns a guard that will stop the monitoring.
166		727
167	This function is useful when you create e.g. timers or other watchers and	728	This function is useful when you create e.g. timers or other watchers and
168	want to free them when the port gets killed:	729	want to free them when the port gets killed (note the use of C<psub>):
169		730
170	$port->rcv (start => sub {	731	$port->rcv (start => sub {
171	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	732	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
172	undef $timer if 0.9 < rand;	733	undef $timer if 0.9 < rand;
173	});	734	});
174	});	735	});
175		736
176	=cut	737	=cut
177		738
178	sub mon_guard {	739	sub mon_guard {
179	my ($port, @refs) = @_;	740	my ($port, @refs) = @_;
180		741
		742	#TODO: mon-less form?
		743
181	mon $port, sub { 0 && @refs }	744	mon $port, sub { 0 && @refs }
182	}	745	}
183		746
184	=item $local_port = create_port	747	=item kil $port[, @reason]
185		748
186	Create a new local port object. See the next section for allowed methods.	749	Kill the specified port with the given C<@reason>.
		750
		751	If no C<@reason> is specified, then the port is killed "normally" -
		752	monitor callback will be invoked, but the kil will not cause linked ports
		753	(C<mon $mport, $lport> form) to get killed.
		754
		755	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
		756	form) get killed with the same reason.
		757
		758	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		759	will be reported as reason C<< die => $@ >>.
		760
		761	Transport/communication errors are reported as C<< transport_error =>
		762	$message >>.
		763
		764	Common idioms:
		765
		766	# silently remove yourself, do not kill linked ports
		767	kil $SELF;
		768
		769	# report a failure in some detail
		770	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		771
		772	# do not waste much time with killing, just die when something goes wrong
		773	open my $fh, "<file"
		774	or die "file: $!";
		775
		776	=item $port = spawn $node, $initfunc[, @initdata]
		777
		778	Creates a port on the node C<$node> (which can also be a port ID, in which
		779	case it's the node where that port resides).
		780
		781	The port ID of the newly created port is returned immediately, and it is
		782	possible to immediately start sending messages or to monitor the port.
		783
		784	After the port has been created, the init function is called on the remote
		785	node, in the same context as a C<rcv> callback. This function must be a
		786	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		787	specify a function in the main program, use C<::name>.
		788
		789	If the function doesn't exist, then the node tries to C<require>
		790	the package, then the package above the package and so on (e.g.
		791	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		792	exists or it runs out of package names.
		793
		794	The init function is then called with the newly-created port as context
		795	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		796	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		797	the port might not get created.
		798
		799	A common idiom is to pass a local port, immediately monitor the spawned
		800	port, and in the remote init function, immediately monitor the passed
		801	local port. This two-way monitoring ensures that both ports get cleaned up
		802	when there is a problem.
		803
		804	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		805	caller before C<spawn> returns (by delaying invocation when spawn is
		806	called for the local node).
		807
		808	Example: spawn a chat server port on C<$othernode>.
		809
		810	# this node, executed from within a port context:
		811	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		812	mon $server;
		813
		814	# init function on C<$othernode>
		815	sub connect {
		816	my ($srcport) = @_;
		817
		818	mon $srcport;
		819
		820	rcv $SELF, sub {
		821	...
		822	};
		823	}
187		824
188	=cut	825	=cut
189		826
190	sub create_port {	827	sub _spawn {
191	my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;	828	my $port = shift;
		829	my $init = shift;
192		830
193	my $self = bless {	831	# rcv will create the actual port
194	id => "$NODE#$id",	832	local $SELF = "$NODE#$port";
195	}, "AnyEvent::MP::Port";	833	eval {
196		834	&{ 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	};	835	};
217		836	_self_die if $@;
218	$self
219	}	837	}
220		838
221	=item $portid = miniport { my @msg = @_; $finished }	839	sub spawn(@) {
		840	my ($nodeid, undef) = split /#/, shift, 2;
222		841
223	Creates a "mini port", that is, a very lightweight port without any	842	my $id = $RUNIQ . ++$ID;
224	pattern matching behind it, and returns its ID.
225		843
226	The block will be called for every message received on the port. When the	844	$_[0] =~ /::/
227	callback returns a true value its job is considered "done" and the port	845	or Carp::croak "spawn init function must be a fully-qualified name, caught";
228	will be destroyed. Otherwise it will stay alive.
229		846
230	The message will be passed as-is, no extra argument (i.e. no port id) will	847	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
231	be passed to the callback.
232		848
233	If you need the local port id in the callback, this works nicely:	849	"$nodeid#$id"
		850	}
234		851
235	my $port; $port = miniport {	852
236	snd $otherport, reply => $port;	853	=item after $timeout, @msg
		854
		855	=item after $timeout, $callback
		856
		857	Either sends the given message, or call the given callback, after the
		858	specified number of seconds.
		859
		860	This is simply a utility function that comes in handy at times - the
		861	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		862	so it may go away in the future.
		863
		864	=cut
		865
		866	sub after($@) {
		867	my ($timeout, @action) = @_;
		868
		869	my $t; $t = AE::timer $timeout, 0, sub {
		870	undef $t;
		871	ref $action[0]
		872	? $action[0]()
		873	: snd @action;
237	};	874	};
		875	}
		876
		877	#=item $cb2 = timeout $seconds, $cb[, @args]
		878
		879	=item cal $port, @msg, $callback[, $timeout]
		880
		881	A simple form of RPC - sends a message to the given C<$port> with the
		882	given contents (C<@msg>), but adds a reply port to the message.
		883
		884	The reply port is created temporarily just for the purpose of receiving
		885	the reply, and will be C<kil>ed when no longer needed.
		886
		887	A reply message sent to the port is passed to the C<$callback> as-is.
		888
		889	If an optional time-out (in seconds) is given and it is not C<undef>,
		890	then the callback will be called without any arguments after the time-out
		891	elapsed and the port is C<kil>ed.
		892
		893	If no time-out is given (or it is C<undef>), then the local port will
		894	monitor the remote port instead, so it eventually gets cleaned-up.
		895
		896	Currently this function returns the temporary port, but this "feature"
		897	might go in future versions unless you can make a convincing case that
		898	this is indeed useful for something.
238		899
239	=cut	900	=cut
240		901
241	sub miniport(&) {	902	sub cal(@) {
		903	my $timeout = ref $_[-1] ? undef : pop;
242	my $cb = shift;	904	my $cb = pop;
243	my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;
244		905
245	$AnyEvent::MP::Base::PORT{$id} = sub {	906	my $port = port {
		907	undef $timeout;
		908	kil $SELF;
246	&$cb	909	&$cb;
247	and kil $id;
248	};	910	};
249		911
250	"$NODE#$id"	912	if (defined $timeout) {
		913	$timeout = AE::timer $timeout, 0, sub {
		914	undef $timeout;
		915	kil $port;
		916	$cb->();
		917	};
		918	} else {
		919	mon $_[0], sub {
		920	kil $port;
		921	$cb->();
		922	};
		923	}
		924
		925	push @_, $port;
		926	&snd;
		927
		928	$port
251	}	929	}
252		930
253	package AnyEvent::MP::Port;
254
255	=back	931	=back
256		932
257	=head1 METHODS FOR PORT OBJECTS	933	=head1 DISTRIBUTED DATABASE
		934
		935	AnyEvent::MP comes with a simple distributed database. The database will
		936	be mirrored asynchronously on all global nodes. Other nodes bind to one
		937	of the global nodes for their needs. Every node has a "local database"
		938	which contains all the values that are set locally. All local databases
		939	are merged together to form the global database, which can be queried.
		940
		941	The database structure is that of a two-level hash - the database hash
		942	contains hashes which contain values, similarly to a perl hash of hashes,
		943	i.e.:
		944
		945	$DATABASE{$family}{$subkey} = $value
		946
		947	The top level hash key is called "family", and the second-level hash key
		948	is called "subkey" or simply "key".
		949
		950	The family must be alphanumeric, i.e. start with a letter and consist
		951	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		952	pretty much like Perl module names.
		953
		954	As the family namespace is global, it is recommended to prefix family names
		955	with the name of the application or module using it.
		956
		957	The subkeys must be non-empty strings, with no further restrictions.
		958
		959	The values should preferably be strings, but other perl scalars should
		960	work as well (such as C<undef>, arrays and hashes).
		961
		962	Every database entry is owned by one node - adding the same family/subkey
		963	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		964	but the result might be nondeterministic, i.e. the key might have
		965	different values on different nodes.
		966
		967	Different subkeys in the same family can be owned by different nodes
		968	without problems, and in fact, this is the common method to create worker
		969	pools. For example, a worker port for image scaling might do this:
		970
		971	db_set my_image_scalers => $port;
		972
		973	And clients looking for an image scaler will want to get the
		974	C<my_image_scalers> keys from time to time:
		975
		976	db_keys my_image_scalers => sub {
		977	@ports = @{ $_[0] };
		978	};
		979
		980	Or better yet, they want to monitor the database family, so they always
		981	have a reasonable up-to-date copy:
		982
		983	db_mon my_image_scalers => sub {
		984	@ports = keys %{ $_[0] };
		985	};
		986
		987	In general, you can set or delete single subkeys, but query and monitor
		988	whole families only.
		989
		990	If you feel the need to monitor or query a single subkey, try giving it
		991	it's own family.
		992
		993	=over
		994
		995	=item $guard = db_set $family => $subkey [=> $value]
		996
		997	Sets (or replaces) a key to the database - if C<$value> is omitted,
		998	C<undef> is used instead.
		999
		1000	When called in non-void context, C<db_set> returns a guard that
		1001	automatically calls C<db_del> when it is destroyed.
		1002
		1003	=item db_del $family => $subkey...
		1004
		1005	Deletes one or more subkeys from the database family.
		1006
		1007	=item $guard = db_reg $family => $port => $value
		1008
		1009	=item $guard = db_reg $family => $port
		1010
		1011	=item $guard = db_reg $family
		1012
		1013	Registers a port in the given family and optionally returns a guard to
		1014	remove it.
		1015
		1016	This function basically does the same as:
		1017
		1018	db_set $family => $port => $value
		1019
		1020	Except that the port is monitored and automatically removed from the
		1021	database family when it is kil'ed.
		1022
		1023	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1024	C<$SELF> is used.
		1025
		1026	This function is most useful to register a port in some port group (which
		1027	is just another name for a database family), and have it removed when the
		1028	port is gone. This works best when the port is a local port.
		1029
		1030	=cut
		1031
		1032	sub db_reg($$;$) {
		1033	my $family = shift;
		1034	my $port = @_ ? shift : $SELF;
		1035
		1036	my $clr = sub { db_del $family => $port };
		1037	mon $port, $clr;
		1038
		1039	db_set $family => $port => $_[0];
		1040
		1041	defined wantarray
		1042	and &Guard::guard ($clr)
		1043	}
		1044
		1045	=item db_family $family => $cb->(\%familyhash)
		1046
		1047	Queries the named database C<$family> and call the callback with the
		1048	family represented as a hash. You can keep and freely modify the hash.
		1049
		1050	=item db_keys $family => $cb->(\@keys)
		1051
		1052	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1053	them as array reference to the callback.
		1054
		1055	=item db_values $family => $cb->(\@values)
		1056
		1057	Same as C<db_family>, except it only queries the family I<values> and passes them
		1058	as array reference to the callback.
		1059
		1060	=item $guard = db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
		1061
		1062	Creates a monitor on the given database family. Each time a key is
		1063	set or is deleted the callback is called with a hash containing the
		1064	database family and three lists of added, changed and deleted subkeys,
		1065	respectively. If no keys have changed then the array reference might be
		1066	C<undef> or even missing.
		1067
		1068	If not called in void context, a guard object is returned that, when
		1069	destroyed, stops the monitor.
		1070
		1071	The family hash reference and the key arrays belong to AnyEvent::MP and
		1072	B<must not be modified or stored> by the callback. When in doubt, make a
		1073	copy.
		1074
		1075	As soon as possible after the monitoring starts, the callback will be
		1076	called with the intiial contents of the family, even if it is empty,
		1077	i.e. there will always be a timely call to the callback with the current
		1078	contents.
		1079
		1080	It is possible that the callback is called with a change event even though
		1081	the subkey is already present and the value has not changed.
		1082
		1083	The monitoring stops when the guard object is destroyed.
		1084
		1085	Example: on every change to the family "mygroup", print out all keys.
		1086
		1087	my $guard = db_mon mygroup => sub {
		1088	my ($family, $a, $c, $d) = @_;
		1089	print "mygroup members: ", (join " ", keys %$family), "\n";
		1090	};
		1091
		1092	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1093
		1094	my $guard; $guard = db_mon My::Module::workers => sub {
		1095	my ($family, $a, $c, $d) = @_;
		1096	return unless %$family;
		1097	undef $guard;
		1098	print "My::Module::workers now nonempty\n";
		1099	};
		1100
		1101	Example: print all changes to the family "AnyEvent::Fantasy::Module".
		1102
		1103	my $guard = db_mon AnyEvent::Fantasy::Module => sub {
		1104	my ($family, $a, $c, $d) = @_;
		1105
		1106	print "+$_=$family->{$_}\n" for @$a;
		1107	print "*$_=$family->{$_}\n" for @$c;
		1108	print "-$_=$family->{$_}\n" for @$d;
		1109	};
		1110
		1111	=cut
		1112
		1113	=back
		1114
		1115	=head1 AnyEvent::MP vs. Distributed Erlang
		1116
		1117	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		1118	== aemp node, Erlang process == aemp port), so many of the documents and
		1119	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		1120	sample:
		1121
		1122	http://www.erlang.se/doc/programming_rules.shtml
		1123	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		1124	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
		1125	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		1126
		1127	Despite the similarities, there are also some important differences:
258		1128
259	=over 4	1129	=over 4
260		1130
261	=item "$port"	1131	=item * Node IDs are arbitrary strings in AEMP.
262		1132
263	A port object stringifies to its port ID, so can be used directly for	1133	Erlang relies on special naming and DNS to work everywhere in the same
264	C<snd> operations.	1134	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		1135	configuration or DNS), and possibly the addresses of some seed nodes, but
		1136	will otherwise discover other nodes (and their IDs) itself.
265		1137
266	=cut	1138	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		1139	uses "local ports are like remote ports".
267		1140
268	use overload	1141	The failure modes for local ports are quite different (runtime errors
269	'""' => sub { $_[0]{id} },	1142	only) then for remote ports - when a local port dies, you I<know> it dies,
270	fallback => 1;	1143	when a connection to another node dies, you know nothing about the other
		1144	port.
271		1145
272	sub TO_JSON { $_[0]{id} }	1146	Erlang pretends remote ports are as reliable as local ports, even when
		1147	they are not.
273		1148
274	=item $port->rcv (type => $callback->($port, @msg))	1149	AEMP encourages a "treat remote ports differently" philosophy, with local
		1150	ports being the special case/exception, where transport errors cannot
		1151	occur.
275		1152
276	=item $port->rcv ($smartmatch => $callback->($port, @msg))	1153	=item * Erlang uses processes and a mailbox, AEMP does not queue.
277		1154
278	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	1155	Erlang uses processes that selectively receive messages out of order, and
		1156	therefore needs a queue. AEMP is event based, queuing messages would serve
		1157	no useful purpose. For the same reason the pattern-matching abilities
		1158	of AnyEvent::MP are more limited, as there is little need to be able to
		1159	filter messages without dequeuing them.
279		1160
280	Register a callback on the given port.	1161	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1162	being event-based, while Erlang is process-based.
281		1163
282	The callback has to return a true value when its work is done, after	1164	You can 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	1165	top of AEMP and Coro threads.
284	registered.
285		1166
286	If the match is an array reference, then it will be matched against the	1167	=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		1168
290	Any element in the match that is specified as C<_any_> (a function	1169	Sending messages in Erlang is synchronous and blocks the process until
291	exported by this module) matches any single element of the message.	1170	a connection has been established and the message sent (and so does not
		1171	need a queue that can overflow). AEMP sends return immediately, connection
		1172	establishment is handled in the background.
292		1173
293	While not required, it is highly recommended that the first matching	1174	=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		1175
297	=cut	1176	Erlang implements few guarantees on messages delivery - messages can get
		1177	lost without any of the processes realising it (i.e. you send messages a,
		1178	b, and c, and the other side only receives messages a and c).
298		1179
299	sub rcv($@) {	1180	AEMP guarantees (modulo hardware errors) correct ordering, and the
300	my ($self, $match, $cb) = @_;	1181	guarantee that after one message is lost, all following ones sent to the
		1182	same port are lost as well, until monitoring raises an error, so there are
		1183	no silent "holes" in the message sequence.
301		1184
302	if (!ref $match) {	1185	If you want your software to be very reliable, you have to cope with
303	push @{ $self->{rc0}{$match} }, [$cb];	1186	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
304	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	1187	simply tries to work better in common error cases, such as when a network
305	my ($type, @match) = @$match;	1188	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		1189
314	=item $port->register ($name)	1190	=item * Erlang can send messages to the wrong port, AEMP does not.
315		1191
316	Registers the given port under the well known name C<$name>. If the name	1192	In Erlang it is quite likely that a node that restarts reuses an Erlang
317	already exists it is replaced.	1193	process ID known to other nodes for a completely different process,
		1194	causing messages destined for that process to end up in an unrelated
		1195	process.
318		1196
319	A port can only be registered under one well known name.	1197	AEMP does not reuse port IDs, so old messages or old port IDs floating
		1198	around in the network will not be sent to an unrelated port.
320		1199
321	=cut	1200	=item * Erlang uses unprotected connections, AEMP uses secure
		1201	authentication and can use TLS.
322		1202
323	sub register {	1203	AEMP can use a proven protocol - TLS - to protect connections and
324	my ($self, $name) = @_;	1204	securely authenticate nodes.
325		1205
326	$self->{wkname} = $name;	1206	=item * The AEMP protocol is optimised for both text-based and binary
327	$AnyEvent::MP::Base::WKP{$name} = "$self";	1207	communications.
328	}
329		1208
330	=item $port->destroy	1209	The AEMP protocol, unlike the Erlang protocol, supports both programming
		1210	language independent text-only protocols (good for debugging), and binary,
		1211	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1212	used, the protocol is actually completely text-based.
331		1213
332	Explicitly destroy/remove/nuke/vaporise the port.	1214	It has also been carefully designed to be implementable in other languages
		1215	with a minimum of work while gracefully degrading functionality to make the
		1216	protocol simple.
333		1217
334	Ports are normally kept alive by their mere existance alone, and need to	1218	=item * AEMP has more flexible monitoring options than Erlang.
335	be destroyed explicitly.
336		1219
337	=cut	1220	In Erlang, you can chose to receive I<all> exit signals as messages or
		1221	I<none>, there is no in-between, so monitoring single Erlang processes is
		1222	difficult to implement.
338		1223
339	sub destroy {	1224	Monitoring in AEMP is more flexible than in Erlang, as one can choose
340	my ($self) = @_;	1225	between automatic kill, exit message or callback on a per-port basis.
341		1226
342	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	1227	=item * Erlang tries to hide remote/local connections, AEMP does not.
343		1228
344	AnyEvent::MP::Base::kil $self->{id};	1229	Monitoring in Erlang is not an indicator of process death/crashes, in the
345	}	1230	same way as linking is (except linking is unreliable in Erlang).
		1231
		1232	In AEMP, you don't "look up" registered port names or send to named ports
		1233	that might or might not be persistent. Instead, you normally spawn a port
		1234	on the remote node. The init function monitors you, and you monitor the
		1235	remote port. Since both monitors are local to the node, they are much more
		1236	reliable (no need for C<spawn_link>).
		1237
		1238	This also saves round-trips and avoids sending messages to the wrong port
		1239	(hard to do in Erlang).
346		1240
347	=back	1241	=back
348		1242
349	=head1 FUNCTIONS FOR NODES	1243	=head1 RATIONALE
350		1244
351	=over 4	1245	=over 4
352		1246
353	=item mon $noderef, $callback->($noderef, $status, $)	1247	=item Why strings for port and node IDs, why not objects?
354		1248
355	Monitors the given noderef.	1249	We considered "objects", but found that the actual number of methods
		1250	that can be called are quite low. Since port and node IDs travel over
		1251	the network frequently, the serialising/deserialising would add lots of
		1252	overhead, as well as having to keep a proxy object everywhere.
356		1253
357	=item become_public endpoint...	1254	Strings can easily be printed, easily serialised etc. and need no special
		1255	procedures to be "valid".
358		1256
359	Tells the node to become a public node, i.e. reachable from other nodes.	1257	And as a result, a port with just a default receiver consists of a single
		1258	code reference stored in a global hash - it can't become much cheaper.
360		1259
361	If no arguments are given, or the first argument is C<undef>, then	1260	=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		1261
365	Otherwise the first argument must be an array-reference with transport	1262	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	1263	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	1264	default (although all nodes will accept it).
368	will become the node reference.
369		1265
370	=cut	1266	The default framing protocol is JSON because a) JSON::XS is many times
		1267	faster for small messages and b) most importantly, after years of
		1268	experience we found that object serialisation is causing more problems
		1269	than it solves: Just like function calls, objects simply do not travel
		1270	easily over the network, mostly because they will always be a copy, so you
		1271	always have to re-think your design.
		1272
		1273	Keeping your messages simple, concentrating on data structures rather than
		1274	objects, will keep your messages clean, tidy and efficient.
371		1275
372	=back	1276	=back
373		1277
374	=head1 NODE MESSAGES	1278	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
375		1279
376	Nodes understand the following messages sent to them. Many of them take	1280	AEMP version 2 has a few major incompatible changes compared to version 1:
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		1281
381	=over 4	1282	=over 4
382		1283
383	=cut	1284	=item AnyEvent::MP::Global no longer has group management functions.
384		1285
385	=item wkp => $name, @reply	1286	At least not officially - the grp_* functions are still exported and might
		1287	work, but they will be removed in some later release.
386		1288
387	Replies with the port ID of the specified well-known port, or C<undef>.	1289	AnyEvent::MP now comes with a distributed database that is more
		1290	powerful. Its database families map closely to port groups, but the API
		1291	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1292	a rough porting guide:
388		1293
389	=item devnull => ...	1294	grp_reg $group, $port # old
		1295	db_reg $group, $port # new
390		1296
391	Generic data sink/CPU heat conversion.	1297	$list = grp_get $group # old
		1298	db_keys $group, sub { my $list = shift } # new
392		1299
393	=item relay => $port, @msg	1300	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1301	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
394		1302
395	Simply forwards the message to the given port.	1303	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1304	no longer instant, because the local node might not have a copy of the
		1305	group. You can either modify your code to allow for a callback, or use
		1306	C<db_mon> to keep an updated copy of the group:
396		1307
397	=item eval => $string[ @reply]	1308	my $local_group_copy;
		1309	db_mon $group => sub { $local_group_copy = $_[0] };
398		1310
399	Evaluates the given string. If C<@reply> is given, then a message of the	1311	# now "keys %$local_group_copy" always returns the most up-to-date
400	form C<@reply, $@, @evalres> is sent.	1312	# list of ports in the group.
401		1313
402	Example: crash another node.	1314	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1315	passes a hash as first argument, and an extra C<$chg> argument that can be
		1316	ignored:
403		1317
404	snd $othernode, eval => "exit";	1318	db_mon $group => sub {
		1319	my ($ports, $add, $chg, $del) = @_;
		1320	$ports = [keys %$ports];
405		1321
406	=item time => @reply	1322	# now $ports, $add and $del are the same as
		1323	# were originally passed by grp_mon.
		1324	...
		1325	};
407		1326
408	Replies the the current node time to C<@reply>.	1327	=item Nodes not longer connect to all other nodes.
409		1328
410	Example: tell the current node to send the current time to C<$myport> in a	1329	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
411	C<timereply> message.	1330	module, which in turn would create connections to all other nodes in the
		1331	network (helped by the seed nodes).
412		1332
413	snd $NODE, time => $myport, timereply => 1, 2;	1333	In version 2.x, global nodes still connect to all other global nodes, but
414	# => snd $myport, timereply => 1, 2, <time>	1334	other nodes don't - now every node either is a global node itself, or
		1335	attaches itself to another global node.
		1336
		1337	If a node isn't a global node itself, then it attaches itself to one
		1338	of its seed nodes. If that seed node isn't a global node yet, it will
		1339	automatically be upgraded to a global node.
		1340
		1341	So in many cases, nothing needs to be changed - one just has to make sure
		1342	that all seed nodes are meshed together with the other seed nodes (as with
		1343	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1344	achieved by specifying the same set of seed nodes for all nodes in the
		1345	network.
		1346
		1347	Not opening a connection to every other node is usually an advantage,
		1348	except when you need the lower latency of an already established
		1349	connection. To ensure a node establishes a connection to another node,
		1350	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1351	create the connection (and notify you when the connection fails).
		1352
		1353	=item Listener-less nodes (nodes without binds) are gone.
		1354
		1355	And are not coming back, at least not in their old form. If no C<binds>
		1356	are specified for a node, AnyEvent::MP assumes a default of C<*:*>.
		1357
		1358	There are vague plans to implement some form of routing domains, which
		1359	might or might not bring back listener-less nodes, but don't count on it.
		1360
		1361	The fact that most connections are now optional somewhat mitigates this,
		1362	as a node can be effectively unreachable from the outside without any
		1363	problems, as long as it isn't a global node and only reaches out to other
		1364	nodes (as opposed to being contacted from other nodes).
		1365
		1366	=item $AnyEvent::MP::Kernel::WARN has gone.
		1367
		1368	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1369	uses this, and so should your programs.
		1370
		1371	Every module now documents what kinds of messages it generates, with
		1372	AnyEvent::MP acting as a catch all.
		1373
		1374	On the positive side, this means that instead of setting
		1375	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1376	much less to type.
415		1377
416	=back	1378	=back
417		1379
		1380	=head1 LOGGING
		1381
		1382	AnyEvent::MP does not normally log anything by itself, but since it is the
		1383	root of the contetx hierarchy for AnyEvent::MP modules, it will receive
		1384	all log messages by submodules.
		1385
418	=head1 SEE ALSO	1386	=head1 SEE ALSO
		1387
		1388	L<AnyEvent::MP::Intro> - a gentle introduction.
		1389
		1390	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1391
		1392	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1393	your applications.
		1394
		1395	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1396
		1397	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1398	all nodes.
419		1399
420	L<AnyEvent>.	1400	L<AnyEvent>.
421		1401
422	=head1 AUTHOR	1402	=head1 AUTHOR
423		1403

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