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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.2 by root, Fri Jul 31 20:55:46 2009 UTC vs.
Revision 1.71 by root, Sun Aug 30 19:52:56 2009 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	NODE # returns this node identifier
10	$NODE # contains this node identifier	9	$NODE # contains this node's noderef
		10	NODE # returns this node's noderef
		11	NODE $port # returns the noderef of the port
11		12
		13	$SELF # receiving/own port id in rcv callbacks
		14
		15	# initialise the node so it can send/receive messages
		16	initialise_node;
		17
		18	# ports are message endpoints
		19
		20	# sending messages
12	snd $port, type => data...;	21	snd $port, type => data...;
		22	snd $port, @msg;
		23	snd @msg_with_first_element_being_a_port;
13		24
14	rcv $port, smartmatch => $cb->($port, @msg);	25	# creating/using ports, the simple way
		26	my $simple_port = port { my @msg = @_; 0 };
15		27
16	# examples:	28	# creating/using ports, tagged message matching
		29	my $port = port;
17	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
18	rcv $port1, pong => sub { warn "pong received\n" };	31	rcv $port, pong => sub { warn "pong received\n"; 0 };
19	snd $port2, ping => $port1;
20		32
21	# more, smarter, matches (_any_ is exported by this module)	33	# create a port on another node
22	rcv $port, [child_died => $pid] => sub { ...	34	my $port = spawn $node, $initfunc, @initdata;
23	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	35
		36	# monitoring
		37	mon $port, $cb->(@msg) # callback is invoked on death
		38	mon $port, $otherport # kill otherport on abnormal death
		39	mon $port, $otherport, @msg # send message on death
		40
		41	=head1 CURRENT STATUS
		42
		43	bin/aemp - stable.
		44	AnyEvent::MP - stable API, should work.
		45	AnyEvent::MP::Intro - uptodate, but incomplete.
		46	AnyEvent::MP::Kernel - mostly stable.
		47	AnyEvent::MP::Global - stable API, protocol not yet final.
		48
		49	stay tuned.
24		50
25	=head1 DESCRIPTION	51	=head1 DESCRIPTION
26		52
27	This module (-family) implements a simple message passing framework.	53	This module (-family) implements a simple message passing framework.
28		54
29	Despite its simplicity, you can securely message other processes running	55	Despite its simplicity, you can securely message other processes running
30	on the same or other hosts.	56	on the same or other hosts, and you can supervise entities remotely.
		57
		58	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
		59	manual page and the examples under F<eg/>.
		60
		61	At the moment, this module family is a bit underdocumented.
31		62
32	=head1 CONCEPTS	63	=head1 CONCEPTS
33		64
34	=over 4	65	=over 4
35		66
36	=item port	67	=item port
37		68
38	A port is something you can send messages to with the C<snd> function, and	69	A port is something you can send messages to (with the C<snd> function).
39	you can register C<rcv> handlers with. All C<rcv> handlers will receive
40	messages they match, messages will not be queued.
41		70
42	=item port id - C<pid@host#portname>	71	Ports allow you to register C<rcv> handlers that can match all or just
		72	some messages. Messages send to ports will not be queued, regardless of
		73	anything was listening for them or not.
43		74
44	A port id is always the node id, a hash-mark (C<#>) as separator, followed	75	=item port ID - C<nodeid#portname>
45	by a port name.
46		76
47	A port name can be a well known port (basically an identifier/bareword),	77	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
48	or a generated name, consisting of node id, a dot (C<.>), and an	78	separator, and a port name (a printable string of unspecified format).
49	identifier.
50		79
51	=item node	80	=item node
52		81
53	A node is a single process containing at least one port - the node	82	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,	83	which enables nodes to manage each other remotely, and to create new
55	among other things.	84	ports.
56		85
57	Initially, nodes are either private (single-process only) or hidden	86	Nodes are either public (have one or more listening ports) or private
58	(connected to a father node only). Only when they epxlicitly "go public"	87	(no listening ports). Private nodes cannot talk to other private nodes
59	can you send them messages form unrelated other nodes.	88	currently.
60		89
61	Public nodes automatically connect to all other public nodes in a network	90	=item node ID - C<[a-za-Z0-9_\-.:]+>
62	when they connect, creating a full mesh.
63		91
64	=item node id - C<host:port>, C<id@host>, C<id>
65
66	A node ID is a string that either uniquely identifies a given node (For	92	A node ID is a string that uniquely identifies the node within a
67	private and hidden nodes), or contains a recipe on how to reach a given	93	network. Depending on the configuration used, node IDs can look like a
68	node (for public nodes).	94	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		95	doesn't interpret node IDs in any way.
		96
		97	=item binds - C<ip:port>
		98
		99	Nodes can only talk to each other by creating some kind of connection to
		100	each other. To do this, nodes should listen on one or more local transport
		101	endpoints - binds. Currently, only standard C<ip:port> specifications can
		102	be used, which specify TCP ports to listen on.
		103
		104	=item seeds - C<host:port>
		105
		106	When a node starts, it knows nothing about the network. To teach the node
		107	about the network it first has to contact some other node within the
		108	network. This node is called a seed.
		109
		110	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		111	are expected to be long-running, and at least one of those should always
		112	be available. When nodes run out of connections (e.g. due to a network
		113	error), they try to re-establish connections to some seednodes again to
		114	join the network.
		115
		116	Apart from being sued for seeding, seednodes are not special in any way -
		117	every public node can be a seednode.
69		118
70	=back	119	=back
71		120
72	=head1 FUNCTIONS	121	=head1 VARIABLES/FUNCTIONS
73		122
74	=over 4	123	=over 4
75		124
76	=cut	125	=cut
77		126
78	package AnyEvent::MP;	127	package AnyEvent::MP;
79		128
80	use AnyEvent::MP::Util ();
81	use AnyEvent::MP::Node;	129	use AnyEvent::MP::Kernel;
82	use AnyEvent::MP::Transport;
83		130
84	use utf8;
85	use common::sense;	131	use common::sense;
86		132
87	use Carp ();	133	use Carp ();
88		134
89	use AE ();	135	use AE ();
90		136
91	use base "Exporter";	137	use base "Exporter";
92		138
93	our $VERSION = '0.0';	139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
94	our @EXPORT = qw(NODE $NODE $PORT snd rcv _any_);
95		140
96	our $DEFAULT_SECRET;	141	our @EXPORT = qw(
97	our $DEFAULT_PORT = "4040";	142	NODE $NODE *SELF node_of after
		143	initialise_node
		144	snd rcv mon mon_guard kil reg psub spawn
		145	port
		146	);
98		147
99	our $CONNECT_INTERVAL = 5; # new connect every 5s, at least	148	our $SELF;
100	our $CONNECT_TIMEOUT = 30; # includes handshake
101		149
102	sub default_secret {	150	sub _self_die() {
103	unless (defined $DEFAULT_SECRET) {	151	my $msg = $@;
104	if (open my $fh, "<$ENV{HOME}/.aemp-secret") {	152	$msg =~ s/\n+$// unless ref $msg;
105	sysread $fh, $DEFAULT_SECRET, -s $fh;	153	kil $SELF, die => $msg;
106	} else {	154	}
107	$DEFAULT_SECRET = AnyEvent::MP::Util::nonce 32;	155
		156	=item $thisnode = NODE / $NODE
		157
		158	The C<NODE> function returns, and the C<$NODE> variable contains, the node
		159	ID of the node running in the current process. This value is initialised by
		160	a call to C<initialise_node>.
		161
		162	=item $nodeid = node_of $port
		163
		164	Extracts and returns the node ID from a port ID or a node ID.
		165
		166	=item initialise_node $profile_name, key => value...
		167
		168	Before a node can talk to other nodes on the network (i.e. enter
		169	"distributed mode") it has to initialise itself - the minimum a node needs
		170	to know is its own name, and optionally it should know the addresses of
		171	some other nodes in the network to discover other nodes.
		172
		173	This function initialises a node - it must be called exactly once (or
		174	never) before calling other AnyEvent::MP functions.
		175
		176	The first argument is a profile name. If it is C<undef> or missing, then
		177	the current nodename will be used instead (i.e. F<uname -n>).
		178
		179	The function first looks up the profile in the aemp configuration (see the
		180	L<aemp> commandline utility). the profile is calculated as follows:
		181
		182	First, all remaining key => value pairs (all of which are conviniently
		183	undocumented at the moment) will be used. Then they will be overwritten by
		184	any values specified in the global default configuration (see the F<aemp>
		185	utility), then the chain of profiles selected, if any. That means that
		186	the values specified in the profile have highest priority and the values
		187	specified via C<initialise_node> have lowest priority.
		188
		189	If the profile specifies a node ID, then this will become the node ID of
		190	this process. If not, then the profile name will be used as node ID. The
		191	special node ID of C<anon/> will be replaced by a random node ID.
		192
		193	The next step is to look up the binds in the profile, followed by binding
		194	aemp protocol listeners on all binds specified (it is possible and valid
		195	to have no binds, meaning that the node cannot be contacted form the
		196	outside. This means the node cannot talk to other nodes that also have no
		197	binds, but it can still talk to all "normal" nodes).
		198
		199	If the profile does not specify a binds list, then a default of C<*> is
		200	used.
		201
		202	Lastly, the seeds list from the profile is passed to the
		203	L<AnyEvent::MP::Global> module, which will then use it to keep
		204	connectivity with at least on of those seed nodes at any point in time.
		205
		206	Example: become a distributed node listening on the guessed noderef, or
		207	the one specified via C<aemp> for the current node. This should be the
		208	most common form of invocation for "daemon"-type nodes.
		209
		210	initialise_node;
		211
		212	Example: become an anonymous node. This form is often used for commandline
		213	clients.
		214
		215	initialise_node "anon/";
		216
		217	Example: become a distributed node. If there is no profile of the given
		218	name, or no binds list was specified, resolve C<localhost:4044> and bind
		219	on the resulting addresses.
		220
		221	initialise_node "localhost:4044";
		222
		223	=item $SELF
		224
		225	Contains the current port id while executing C<rcv> callbacks or C<psub>
		226	blocks.
		227
		228	=item *SELF, SELF, %SELF, @SELF...
		229
		230	Due to some quirks in how perl exports variables, it is impossible to
		231	just export C<$SELF>, all the symbols named C<SELF> are exported by this
		232	module, but only C<$SELF> is currently used.
		233
		234	=item snd $port, type => @data
		235
		236	=item snd $port, @msg
		237
		238	Send the given message to the given port, which can identify either a
		239	local or a remote port, and must be a port ID.
		240
		241	While the message can be almost anything, it is highly recommended to
		242	use a string as first element (a port ID, or some word that indicates a
		243	request type etc.) and to consist if only simple perl values (scalars,
		244	arrays, hashes) - if you think you need to pass an object, think again.
		245
		246	The message data logically becomes read-only after a call to this
		247	function: modifying any argument (or values referenced by them) is
		248	forbidden, as there can be considerable time between the call to C<snd>
		249	and the time the message is actually being serialised - in fact, it might
		250	never be copied as within the same process it is simply handed to the
		251	receiving port.
		252
		253	The type of data you can transfer depends on the transport protocol: when
		254	JSON is used, then only strings, numbers and arrays and hashes consisting
		255	of those are allowed (no objects). When Storable is used, then anything
		256	that Storable can serialise and deserialise is allowed, and for the local
		257	node, anything can be passed. Best rely only on the common denominator of
		258	these.
		259
		260	=item $local_port = port
		261
		262	Create a new local port object and returns its port ID. Initially it has
		263	no callbacks set and will throw an error when it receives messages.
		264
		265	=item $local_port = port { my @msg = @_ }
		266
		267	Creates a new local port, and returns its ID. Semantically the same as
		268	creating a port and calling C<rcv $port, $callback> on it.
		269
		270	The block will be called for every message received on the port, with the
		271	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		272	port to be C<kil>ed. The message will be passed as-is, no extra argument
		273	(i.e. no port ID) will be passed to the callback.
		274
		275	If you want to stop/destroy the port, simply C<kil> it:
		276
		277	my $port = port {
		278	my @msg = @_;
108	}	279	...
109	}	280	kil $SELF;
110
111	$DEFAULT_SECRET
112	}
113
114	our $UNIQ = sprintf "%x.%x", $$, time; # per-process/node unique cookie
115	our $PUBLIC = 0;
116	our $NODE;
117	our $PORT;
118
119	our %NODE; # node id to transport mapping, or "undef", for local node
120	our %PORT; # local ports
121	our %LISTENER; # local transports
122
123	sub NODE() { $NODE }
124
125	{
126	use POSIX ();
127	my $nodename = (POSIX::uname)[1];
128	$NODE = "$$\@$nodename";
129	}
130
131	sub _ANY_() { 1 }
132	sub _any_() { \&_ANY_ }
133
134	sub add_node {
135	my ($noderef) = @_;
136
137	return $NODE{$noderef}
138	if exists $NODE{$noderef};
139
140	for (split /,/, $noderef) {
141	return $NODE{$noderef} = $NODE{$_}
142	if exists $NODE{$_};
143	}
144
145	# for indirect sends, use a different class
146	my $node = new AnyEvent::MP::Node::Direct $noderef;
147
148	$NODE{$_} = $node
149	for $noderef, split /,/, $noderef;
150
151	$node
152	}
153
154	sub snd($@) {
155	my ($noderef, $port) = split /#/, shift, 2;
156
157	add_node $noderef
158	unless exists $NODE{$noderef};
159
160	$NODE{$noderef}->send ([$port, [@_]]);
161	}
162
163	sub _inject {
164	my ($port, $msg) = @{+shift};
165
166	$port = $PORT{$port}
167	or return;
168
169	use Data::Dumper;
170	warn Dumper $msg;
171	}
172
173	sub normalise_noderef($) {
174	my ($noderef) = @_;
175
176	my $cv = AE::cv;
177	my @res;
178
179	$cv->begin (sub {
180	my %seen;
181	my @refs;
182	for (sort { $a->[0] <=> $b->[0] } @res) {
183	push @refs, $_->[1] unless $seen{$_->[1]}++
184	}
185	shift->send (join ",", @refs);
186	});	281	};
187		282
188	$noderef = $DEFAULT_PORT unless length $noderef;	283	=cut
189		284
190	my $idx;	285	sub rcv($@);
191	for my $t (split /,/, $noderef) {
192	my $pri = ++$idx;
193
194	#TODO: this should be outside normalise_noderef and in become_public
195	if ($t =~ /^\d*$/) {
196	my $nodename = (POSIX::uname)[1];
197		286
198	$cv->begin;	287	sub _kilme {
199	AnyEvent::Socket::resolve_sockaddr $nodename, $t \|\| "aemp=$DEFAULT_PORT", "tcp", 0, undef, sub {	288	die "received message on port without callback";
200	for (@_) {	289	}
201	my ($service, $host) = AnyEvent::Socket::unpack_sockaddr $_->[3];	290
202	push @res, [	291	sub port(;&) {
203	$pri += 1e-5,	292	my $id = "$UNIQ." . $ID++;
204	AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $host, $service	293	my $port = "$NODE#$id";
205	];	294
		295	rcv $port, shift \|\| \&_kilme;
		296
		297	$port
		298	}
		299
		300	=item rcv $local_port, $callback->(@msg)
		301
		302	Replaces the default callback on the specified port. There is no way to
		303	remove the default callback: use C<sub { }> to disable it, or better
		304	C<kil> the port when it is no longer needed.
		305
		306	The global C<$SELF> (exported by this module) contains C<$port> while
		307	executing the callback. Runtime errors during callback execution will
		308	result in the port being C<kil>ed.
		309
		310	The default callback received all messages not matched by a more specific
		311	C<tag> match.
		312
		313	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		314
		315	Register (or replace) callbacks to be called on messages starting with the
		316	given tag on the given port (and return the port), or unregister it (when
		317	C<$callback> is C<$undef> or missing). There can only be one callback
		318	registered for each tag.
		319
		320	The original message will be passed to the callback, after the first
		321	element (the tag) has been removed. The callback will use the same
		322	environment as the default callback (see above).
		323
		324	Example: create a port and bind receivers on it in one go.
		325
		326	my $port = rcv port,
		327	msg1 => sub { ... },
		328	msg2 => sub { ... },
		329	;
		330
		331	Example: create a port, bind receivers and send it in a message elsewhere
		332	in one go:
		333
		334	snd $otherport, reply =>
		335	rcv port,
		336	msg1 => sub { ... },
		337	...
		338	;
		339
		340	Example: temporarily register a rcv callback for a tag matching some port
		341	(e.g. for a rpc reply) and unregister it after a message was received.
		342
		343	rcv $port, $otherport => sub {
		344	my @reply = @_;
		345
		346	rcv $SELF, $otherport;
		347	};
		348
		349	=cut
		350
		351	sub rcv($@) {
		352	my $port = shift;
		353	my ($noderef, $portid) = split /#/, $port, 2;
		354
		355	$NODE{$noderef} == $NODE{""}
		356	or Carp::croak "$port: rcv can only be called on local ports, caught";
		357
		358	while (@_) {
		359	if (ref $_[0]) {
		360	if (my $self = $PORT_DATA{$portid}) {
		361	"AnyEvent::MP::Port" eq ref $self
		362	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		363
		364	$self->[2] = shift;
		365	} else {
		366	my $cb = shift;
		367	$PORT{$portid} = sub {
		368	local $SELF = $port;
		369	eval { &$cb }; _self_die if $@;
206	}	370	};
207	$cv->end;	371	}
		372	} elsif (defined $_[0]) {
		373	my $self = $PORT_DATA{$portid} \|\|= do {
		374	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		375
		376	$PORT{$portid} = sub {
		377	local $SELF = $port;
		378
		379	if (my $cb = $self->[1]{$_[0]}) {
		380	shift;
		381	eval { &$cb }; _self_die if $@;
		382	} else {
		383	&{ $self->[0] };
		384	}
		385	};
		386
		387	$self
208	};	388	};
209		389
210	# my (undef, undef, undef, undef, @ipv4) = gethostbyname $nodename;	390	"AnyEvent::MP::Port" eq ref $self
211	#	391	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
212	# for (@ipv4) {	392
213	# push @res, [	393	my ($tag, $cb) = splice @_, 0, 2;
214	# $pri,	394
215	# AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $_, $t \|\| $DEFAULT_PORT,	395	if (defined $cb) {
216	# ];	396	$self->[1]{$tag} = $cb;
217	# }
218	} else {	397	} else {
219	my ($host, $port) = AnyEvent::Socket::parse_hostport $t, "aemp=$DEFAULT_PORT"	398	delete $self->[1]{$tag};
220	or Carp::croak "$t: unparsable transport descriptor";
221
222	$cv->begin;
223	AnyEvent::Socket::resolve_sockaddr $host, $port, "tcp", 0, undef, sub {
224	for (@_) {
225	my ($service, $host) = AnyEvent::Socket::unpack_sockaddr $_->[3];
226	push @res, [
227	$pri += 1e-5,
228	AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $host, $service
229	];
230	}
231	$cv->end;
232	}	399	}
233	}	400	}
234	}	401	}
235		402
236	$cv->end;	403	$port
237
238	$cv
239	}	404	}
240		405
241	sub become_public {	406	=item $closure = psub { BLOCK }
242	return if $PUBLIC;
243		407
244	my $noderef = join ",", ref $_[0] ? @{+shift} : shift;	408	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
245	my @args = @_;	409	closure is executed, sets up the environment in the same way as in C<rcv>
		410	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
246		411
247	$NODE = (normalise_noderef $noderef)->recv;	412	This is useful when you register callbacks from C<rcv> callbacks:
248		413
249	my $self = new AnyEvent::MP::Node::Self noderef => $NODE;	414	rcv delayed_reply => sub {
250		415	my ($delay, @reply) = @_;
251	$NODE{""} = $self; # empty string == local node	416	my $timer = AE::timer $delay, 0, psub {
252		417	snd @reply, $SELF;
253	for my $t (split /,/, $NODE) {
254	$NODE{$t} = $self;
255
256	my ($host, $port) = AnyEvent::Socket::parse_hostport $t;
257
258	$LISTENER{$t} = AnyEvent::MP::Transport::mp_server $host, $port,
259	@args,
260	on_error => sub {
261	die "on_error<@_>\n";#d#
262	},
263	on_connect => sub {
264	my ($tp) = @_;
265
266	$NODE{$tp->{remote_id}} = $_[0];
267	},
268	sub {
269	my ($tp) = @_;
270
271	$NODE{"$tp->{peerhost}:$tp->{peerport}"} = $tp;
272	},
273	;	418	};
		419	};
		420
		421	=cut
		422
		423	sub psub(&) {
		424	my $cb = shift;
		425
		426	my $port = $SELF
		427	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		428
		429	sub {
		430	local $SELF = $port;
		431
		432	if (wantarray) {
		433	my @res = eval { &$cb };
		434	_self_die if $@;
		435	@res
		436	} else {
		437	my $res = eval { &$cb };
		438	_self_die if $@;
		439	$res
		440	}
274	}	441	}
		442	}
275		443
276	$PUBLIC = 1;	444	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
		445
		446	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		447
		448	=item $guard = mon $port # kill $SELF when $port dies
		449
		450	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		451
		452	Monitor the given port and do something when the port is killed or
		453	messages to it were lost, and optionally return a guard that can be used
		454	to stop monitoring again.
		455
		456	C<mon> effectively guarantees that, in the absence of hardware failures,
		457	after starting the monitor, either all messages sent to the port will
		458	arrive, or the monitoring action will be invoked after possible message
		459	loss has been detected. No messages will be lost "in between" (after
		460	the first lost message no further messages will be received by the
		461	port). After the monitoring action was invoked, further messages might get
		462	delivered again.
		463
		464	Note that monitoring-actions are one-shot: once messages are lost (and a
		465	monitoring alert was raised), they are removed and will not trigger again.
		466
		467	In the first form (callback), the callback is simply called with any
		468	number of C<@reason> elements (no @reason means that the port was deleted
		469	"normally"). Note also that I<< the callback B<must> never die >>, so use
		470	C<eval> if unsure.
		471
		472	In the second form (another port given), the other port (C<$rcvport>)
		473	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
		474	"normal" kils nothing happens, while under all other conditions, the other
		475	port is killed with the same reason.
		476
		477	The third form (kill self) is the same as the second form, except that
		478	C<$rvport> defaults to C<$SELF>.
		479
		480	In the last form (message), a message of the form C<@msg, @reason> will be
		481	C<snd>.
		482
		483	As a rule of thumb, monitoring requests should always monitor a port from
		484	a local port (or callback). The reason is that kill messages might get
		485	lost, just like any other message. Another less obvious reason is that
		486	even monitoring requests can get lost (for exmaple, when the connection
		487	to the other node goes down permanently). When monitoring a port locally
		488	these problems do not exist.
		489
		490	Example: call a given callback when C<$port> is killed.
		491
		492	mon $port, sub { warn "port died because of <@_>\n" };
		493
		494	Example: kill ourselves when C<$port> is killed abnormally.
		495
		496	mon $port;
		497
		498	Example: send us a restart message when another C<$port> is killed.
		499
		500	mon $port, $self => "restart";
		501
		502	=cut
		503
		504	sub mon {
		505	my ($noderef, $port) = split /#/, shift, 2;
		506
		507	my $node = $NODE{$noderef} \|\| add_node $noderef;
		508
		509	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		510
		511	unless (ref $cb) {
		512	if (@_) {
		513	# send a kill info message
		514	my (@msg) = ($cb, @_);
		515	$cb = sub { snd @msg, @_ };
		516	} else {
		517	# simply kill other port
		518	my $port = $cb;
		519	$cb = sub { kil $port, @_ if @_ };
		520	}
		521	}
		522
		523	$node->monitor ($port, $cb);
		524
		525	defined wantarray
		526	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		527	}
		528
		529	=item $guard = mon_guard $port, $ref, $ref...
		530
		531	Monitors the given C<$port> and keeps the passed references. When the port
		532	is killed, the references will be freed.
		533
		534	Optionally returns a guard that will stop the monitoring.
		535
		536	This function is useful when you create e.g. timers or other watchers and
		537	want to free them when the port gets killed (note the use of C<psub>):
		538
		539	$port->rcv (start => sub {
		540	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
		541	undef $timer if 0.9 < rand;
		542	});
		543	});
		544
		545	=cut
		546
		547	sub mon_guard {
		548	my ($port, @refs) = @_;
		549
		550	#TODO: mon-less form?
		551
		552	mon $port, sub { 0 && @refs }
		553	}
		554
		555	=item kil $port[, @reason]
		556
		557	Kill the specified port with the given C<@reason>.
		558
		559	If no C<@reason> is specified, then the port is killed "normally" (ports
		560	monitoring other ports will not necessarily die because a port dies
		561	"normally").
		562
		563	Otherwise, linked ports get killed with the same reason (second form of
		564	C<mon>, see above).
		565
		566	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		567	will be reported as reason C<< die => $@ >>.
		568
		569	Transport/communication errors are reported as C<< transport_error =>
		570	$message >>.
		571
		572	=cut
		573
		574	=item $port = spawn $node, $initfunc[, @initdata]
		575
		576	Creates a port on the node C<$node> (which can also be a port ID, in which
		577	case it's the node where that port resides).
		578
		579	The port ID of the newly created port is returned immediately, and it is
		580	possible to immediately start sending messages or to monitor the port.
		581
		582	After the port has been created, the init function is called on the remote
		583	node, in the same context as a C<rcv> callback. This function must be a
		584	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		585	specify a function in the main program, use C<::name>.
		586
		587	If the function doesn't exist, then the node tries to C<require>
		588	the package, then the package above the package and so on (e.g.
		589	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		590	exists or it runs out of package names.
		591
		592	The init function is then called with the newly-created port as context
		593	object (C<$SELF>) and the C<@initdata> values as arguments.
		594
		595	A common idiom is to pass a local port, immediately monitor the spawned
		596	port, and in the remote init function, immediately monitor the passed
		597	local port. This two-way monitoring ensures that both ports get cleaned up
		598	when there is a problem.
		599
		600	Example: spawn a chat server port on C<$othernode>.
		601
		602	# this node, executed from within a port context:
		603	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		604	mon $server;
		605
		606	# init function on C<$othernode>
		607	sub connect {
		608	my ($srcport) = @_;
		609
		610	mon $srcport;
		611
		612	rcv $SELF, sub {
		613	...
		614	};
		615	}
		616
		617	=cut
		618
		619	sub _spawn {
		620	my $port = shift;
		621	my $init = shift;
		622
		623	local $SELF = "$NODE#$port";
		624	eval {
		625	&{ load_func $init }
		626	};
		627	_self_die if $@;
		628	}
		629
		630	sub spawn(@) {
		631	my ($noderef, undef) = split /#/, shift, 2;
		632
		633	my $id = "$RUNIQ." . $ID++;
		634
		635	$_[0] =~ /::/
		636	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		637
		638	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
		639
		640	"$noderef#$id"
		641	}
		642
		643	=item after $timeout, @msg
		644
		645	=item after $timeout, $callback
		646
		647	Either sends the given message, or call the given callback, after the
		648	specified number of seconds.
		649
		650	This is simply a utility function that comes in handy at times - the
		651	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		652	so it may go away in the future.
		653
		654	=cut
		655
		656	sub after($@) {
		657	my ($timeout, @action) = @_;
		658
		659	my $t; $t = AE::timer $timeout, 0, sub {
		660	undef $t;
		661	ref $action[0]
		662	? $action[0]()
		663	: snd @action;
		664	};
277	}	665	}
278		666
279	=back	667	=back
280		668
		669	=head1 AnyEvent::MP vs. Distributed Erlang
		670
		671	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		672	== aemp node, Erlang process == aemp port), so many of the documents and
		673	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		674	sample:
		675
		676	http://www.Erlang.se/doc/programming_rules.shtml
		677	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		678	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		679	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		680
		681	Despite the similarities, there are also some important differences:
		682
		683	=over 4
		684
		685	=item * Node IDs are arbitrary strings in AEMP.
		686
		687	Erlang relies on special naming and DNS to work everywhere in the same
		688	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		689	configuraiton or DNS), but will otherwise discover other odes itself.
		690
		691	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		692	uses "local ports are like remote ports".
		693
		694	The failure modes for local ports are quite different (runtime errors
		695	only) then for remote ports - when a local port dies, you I<know> it dies,
		696	when a connection to another node dies, you know nothing about the other
		697	port.
		698
		699	Erlang pretends remote ports are as reliable as local ports, even when
		700	they are not.
		701
		702	AEMP encourages a "treat remote ports differently" philosophy, with local
		703	ports being the special case/exception, where transport errors cannot
		704	occur.
		705
		706	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		707
		708	Erlang uses processes that selectively receive messages, and therefore
		709	needs a queue. AEMP is event based, queuing messages would serve no
		710	useful purpose. For the same reason the pattern-matching abilities of
		711	AnyEvent::MP are more limited, as there is little need to be able to
		712	filter messages without dequeing them.
		713
		714	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
		715
		716	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		717
		718	Sending messages in Erlang is synchronous and blocks the process (and
		719	so does not need a queue that can overflow). AEMP sends are immediate,
		720	connection establishment is handled in the background.
		721
		722	=item * Erlang suffers from silent message loss, AEMP does not.
		723
		724	Erlang makes few guarantees on messages delivery - messages can get lost
		725	without any of the processes realising it (i.e. you send messages a, b,
		726	and c, and the other side only receives messages a and c).
		727
		728	AEMP guarantees correct ordering, and the guarantee that after one message
		729	is lost, all following ones sent to the same port are lost as well, until
		730	monitoring raises an error, so there are no silent "holes" in the message
		731	sequence.
		732
		733	=item * Erlang can send messages to the wrong port, AEMP does not.
		734
		735	In Erlang it is quite likely that a node that restarts reuses a process ID
		736	known to other nodes for a completely different process, causing messages
		737	destined for that process to end up in an unrelated process.
		738
		739	AEMP never reuses port IDs, so old messages or old port IDs floating
		740	around in the network will not be sent to an unrelated port.
		741
		742	=item * Erlang uses unprotected connections, AEMP uses secure
		743	authentication and can use TLS.
		744
		745	AEMP can use a proven protocol - TLS - to protect connections and
		746	securely authenticate nodes.
		747
		748	=item * The AEMP protocol is optimised for both text-based and binary
		749	communications.
		750
		751	The AEMP protocol, unlike the Erlang protocol, supports both programming
		752	language independent text-only protocols (good for debugging) and binary,
		753	language-specific serialisers (e.g. Storable). By default, unless TLS is
		754	used, the protocol is actually completely text-based.
		755
		756	It has also been carefully designed to be implementable in other languages
		757	with a minimum of work while gracefully degrading functionality to make the
		758	protocol simple.
		759
		760	=item * AEMP has more flexible monitoring options than Erlang.
		761
		762	In Erlang, you can chose to receive I<all> exit signals as messages
		763	or I<none>, there is no in-between, so monitoring single processes is
		764	difficult to implement. Monitoring in AEMP is more flexible than in
		765	Erlang, as one can choose between automatic kill, exit message or callback
		766	on a per-process basis.
		767
		768	=item * Erlang tries to hide remote/local connections, AEMP does not.
		769
		770	Monitoring in Erlang is not an indicator of process death/crashes, in the
		771	same way as linking is (except linking is unreliable in Erlang).
		772
		773	In AEMP, you don't "look up" registered port names or send to named ports
		774	that might or might not be persistent. Instead, you normally spawn a port
		775	on the remote node. The init function monitors you, and you monitor the
		776	remote port. Since both monitors are local to the node, they are much more
		777	reliable (no need for C<spawn_link>).
		778
		779	This also saves round-trips and avoids sending messages to the wrong port
		780	(hard to do in Erlang).
		781
		782	=back
		783
		784	=head1 RATIONALE
		785
		786	=over 4
		787
		788	=item Why strings for port and node IDs, why not objects?
		789
		790	We considered "objects", but found that the actual number of methods
		791	that can be called are quite low. Since port and node IDs travel over
		792	the network frequently, the serialising/deserialising would add lots of
		793	overhead, as well as having to keep a proxy object everywhere.
		794
		795	Strings can easily be printed, easily serialised etc. and need no special
		796	procedures to be "valid".
		797
		798	And as a result, a miniport consists of a single closure stored in a
		799	global hash - it can't become much cheaper.
		800
		801	=item Why favour JSON, why not a real serialising format such as Storable?
		802
		803	In fact, any AnyEvent::MP node will happily accept Storable as framing
		804	format, but currently there is no way to make a node use Storable by
		805	default (although all nodes will accept it).
		806
		807	The default framing protocol is JSON because a) JSON::XS is many times
		808	faster for small messages and b) most importantly, after years of
		809	experience we found that object serialisation is causing more problems
		810	than it solves: Just like function calls, objects simply do not travel
		811	easily over the network, mostly because they will always be a copy, so you
		812	always have to re-think your design.
		813
		814	Keeping your messages simple, concentrating on data structures rather than
		815	objects, will keep your messages clean, tidy and efficient.
		816
		817	=back
		818
281	=head1 SEE ALSO	819	=head1 SEE ALSO
		820
		821	L<AnyEvent::MP::Intro> - a gentle introduction.
		822
		823	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		824
		825	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		826	your applications.
282		827
283	L<AnyEvent>.	828	L<AnyEvent>.
284		829
285	=head1 AUTHOR	830	=head1 AUTHOR
286		831

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