[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 1.47 by root, Thu Aug 13 01:57:10 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	# ports are message endpoints
		16
		17	# sending messages
12	snd $port, type => data...;	18	snd $port, type => data...;
		19	snd $port, @msg;
		20	snd @msg_with_first_element_being_a_port;
13		21
		22	# miniports
		23	my $miniport = port { my @msg = @_; 0 };
		24
		25	# full ports
		26	my $port = port;
14	rcv $port, smartmatch => $cb->($port, @msg);	27	rcv $port, smartmatch => $cb->(@msg);
15
16	# examples:
17	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	28	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
18	rcv $port1, pong => sub { warn "pong received\n" };	29	rcv $port, pong => sub { warn "pong received\n"; 0 };
19	snd $port2, ping => $port1;	30
		31	# remote ports
		32	my $port = spawn $node, $initfunc, @initdata;
20		33
21	# more, smarter, matches (_any_ is exported by this module)	34	# more, smarter, matches (_any_ is exported by this module)
22	rcv $port, [child_died => $pid] => sub { ...	35	rcv $port, [child_died => $pid] => sub { ...
23	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	36	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
24		37
		38	# monitoring
		39	mon $port, $cb->(@msg) # callback is invoked on death
		40	mon $port, $otherport # kill otherport on abnormal death
		41	mon $port, $otherport, @msg # send message on death
		42
		43	=head1 CURRENT STATUS
		44
		45	AnyEvent::MP - stable API, should work
		46	AnyEvent::MP::Intro - outdated
		47	AnyEvent::MP::Kernel - WIP
		48	AnyEvent::MP::Transport - mostly stable
		49
		50	stay tuned.
		51
25	=head1 DESCRIPTION	52	=head1 DESCRIPTION
26		53
27	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
28		55
29	Despite its simplicity, you can securely message other processes running	56	Despite its simplicity, you can securely message other processes running
30	on the same or other hosts.	57	on the same or other hosts.
31		58
		59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
		60	manual page.
		61
		62	At the moment, this module family is severly broken and underdocumented,
		63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
		64	stay tuned!
		65
32	=head1 CONCEPTS	66	=head1 CONCEPTS
33		67
34	=over 4	68	=over 4
35		69
36	=item port	70	=item port
37		71
38	A port is something you can send messages to with the C<snd> function, and	72	A port is something you can send messages to (with the C<snd> function).
39	you can register C<rcv> handlers with. All C<rcv> handlers will receive
40	messages they match, messages will not be queued.
41		73
		74	Some ports allow you to register C<rcv> handlers that can match specific
		75	messages. All C<rcv> handlers will receive messages they match, messages
		76	will not be queued.
		77
42	=item port id - C<pid@host#portname>	78	=item port id - C<noderef#portname>
43		79
44	A port id is always the node id, a hash-mark (C<#>) as separator, followed	80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as
45	by a port name.	81	separator, and a port name (a printable string of unspecified format). An
46		82	exception is the the node port, whose ID is identical to its node
47	A port name can be a well known port (basically an identifier/bareword),	83	reference.
48	or a generated name, consisting of node id, a dot (C<.>), and an
49	identifier.
50		84
51	=item node	85	=item node
52		86
53	A node is a single process containing at least one port - the node	87	A node is a single process containing at least one port - the node
54	port. You can send messages to node ports to let them create new ports,	88	port. You can send messages to node ports to find existing ports or to
55	among other things.	89	create new ports, among other things.
56		90
57	Initially, nodes are either private (single-process only) or hidden	91	Nodes are either private (single-process only), slaves (connected to a
58	(connected to a father node only). Only when they epxlicitly "go public"	92	master node only) or public nodes (connectable from unrelated nodes).
59	can you send them messages form unrelated other nodes.
60		93
61	Public nodes automatically connect to all other public nodes in a network	94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
62	when they connect, creating a full mesh.
63		95
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	96	A node reference is a string that either simply identifies the node (for
67	private and hidden nodes), or contains a recipe on how to reach a given	97	private and slave nodes), or contains a recipe on how to reach a given
68	node (for public nodes).	98	node (for public nodes).
69		99
		100	This recipe is simply a comma-separated list of C<address:port> pairs (for
		101	TCP/IP, other protocols might look different).
		102
		103	Node references come in two flavours: resolved (containing only numerical
		104	addresses) or unresolved (where hostnames are used instead of addresses).
		105
		106	Before using an unresolved node reference in a message you first have to
		107	resolve it.
		108
70	=back	109	=back
71		110
72	=head1 FUNCTIONS	111	=head1 VARIABLES/FUNCTIONS
73		112
74	=over 4	113	=over 4
75		114
76	=cut	115	=cut
77		116
78	package AnyEvent::MP;	117	package AnyEvent::MP;
79		118
80	use AnyEvent::MP::Util ();
81	use AnyEvent::MP::Node;	119	use AnyEvent::MP::Kernel;
82	use AnyEvent::MP::Transport;
83		120
84	use utf8;
85	use common::sense;	121	use common::sense;
86		122
87	use Carp ();	123	use Carp ();
88		124
89	use AE ();	125	use AE ();
90		126
91	use base "Exporter";	127	use base "Exporter";
92		128
93	our $VERSION = '0.0';	129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
94	our @EXPORT = qw(NODE $NODE $PORT snd rcv _any_);
95		130
96	our $DEFAULT_SECRET;	131	our @EXPORT = qw(
97	our $DEFAULT_PORT = "4040";	132	NODE $NODE *SELF node_of _any_
		133	resolve_node initialise_node
		134	snd rcv mon kil reg psub spawn
		135	port
		136	);
98		137
99	our $CONNECT_INTERVAL = 5; # new connect every 5s, at least	138	our $SELF;
100	our $CONNECT_TIMEOUT = 30; # includes handshake
101		139
102	sub default_secret {	140	sub _self_die() {
103	unless (defined $DEFAULT_SECRET) {	141	my $msg = $@;
104	if (open my $fh, "<$ENV{HOME}/.aemp-secret") {	142	$msg =~ s/\n+$// unless ref $msg;
105	sysread $fh, $DEFAULT_SECRET, -s $fh;	143	kil $SELF, die => $msg;
		144	}
		145
		146	=item $thisnode = NODE / $NODE
		147
		148	The C<NODE> function returns, and the C<$NODE> variable contains
		149	the noderef of the local node. The value is initialised by a call
		150	to C<become_public> or C<become_slave>, after which all local port
		151	identifiers become invalid.
		152
		153	=item $noderef = node_of $port
		154
		155	Extracts and returns the noderef from a portid or a noderef.
		156
		157	=item initialise_node $noderef, $seednode, $seednode...
		158
		159	=item initialise_node "slave/", $master, $master...
		160
		161	Before a node can talk to other nodes on the network it has to initialise
		162	itself - the minimum a node needs to know is it's own name, and optionally
		163	it should know the noderefs of some other nodes in the network.
		164
		165	This function initialises a node - it must be called exactly once (or
		166	never) before calling other AnyEvent::MP functions.
		167
		168	All arguments are noderefs, which can be either resolved or unresolved.
		169
		170	There are two types of networked nodes, public nodes and slave nodes:
		171
		172	=over 4
		173
		174	=item public nodes
		175
		176	For public nodes, C<$noderef> must either be a (possibly unresolved)
		177	noderef, in which case it will be resolved, or C<undef> (or missing), in
		178	which case the noderef will be guessed.
		179
		180	Afterwards, the node will bind itself on all endpoints and try to connect
		181	to all additional C<$seednodes> that are specified. Seednodes are optional
		182	and can be used to quickly bootstrap the node into an existing network.
		183
		184	=item slave nodes
		185
		186	When the C<$noderef> is the special string C<slave/>, then the node will
		187	become a slave node. Slave nodes cannot be contacted from outside and will
		188	route most of their traffic to the master node that they attach to.
		189
		190	At least one additional noderef is required: The node will try to connect
		191	to all of them and will become a slave attached to the first node it can
		192	successfully connect to.
		193
		194	=back
		195
		196	This function will block until all nodes have been resolved and, for slave
		197	nodes, until it has successfully established a connection to a master
		198	server.
		199
		200	Example: become a public node listening on the default node.
		201
		202	initialise_node;
		203
		204	Example: become a public node, and try to contact some well-known master
		205	servers to become part of the network.
		206
		207	initialise_node undef, "master1", "master2";
		208
		209	Example: become a public node listening on port C<4041>.
		210
		211	initialise_node 4041;
		212
		213	Example: become a public node, only visible on localhost port 4044.
		214
		215	initialise_node "locahost:4044";
		216
		217	Example: become a slave node to any of the specified master servers.
		218
		219	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
		220
		221	=item $cv = resolve_node $noderef
		222
		223	Takes an unresolved node reference that may contain hostnames and
		224	abbreviated IDs, resolves all of them and returns a resolved node
		225	reference.
		226
		227	In addition to C<address:port> pairs allowed in resolved noderefs, the
		228	following forms are supported:
		229
		230	=over 4
		231
		232	=item the empty string
		233
		234	An empty-string component gets resolved as if the default port (4040) was
		235	specified.
		236
		237	=item naked port numbers (e.g. C<1234>)
		238
		239	These are resolved by prepending the local nodename and a colon, to be
		240	further resolved.
		241
		242	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
		243
		244	These are resolved by using AnyEvent::DNS to resolve them, optionally
		245	looking up SRV records for the C<aemp=4040> port, if no port was
		246	specified.
		247
		248	=back
		249
		250	=item $SELF
		251
		252	Contains the current port id while executing C<rcv> callbacks or C<psub>
		253	blocks.
		254
		255	=item SELF, %SELF, @SELF...
		256
		257	Due to some quirks in how perl exports variables, it is impossible to
		258	just export C<$SELF>, all the symbols called C<SELF> are exported by this
		259	module, but only C<$SELF> is currently used.
		260
		261	=item snd $port, type => @data
		262
		263	=item snd $port, @msg
		264
		265	Send the given message to the given port ID, which can identify either
		266	a local or a remote port, and can be either a string or soemthignt hat
		267	stringifies a sa port ID (such as a port object :).
		268
		269	While the message can be about anything, it is highly recommended to use a
		270	string as first element (a portid, or some word that indicates a request
		271	type etc.).
		272
		273	The message data effectively becomes read-only after a call to this
		274	function: modifying any argument is not allowed and can cause many
		275	problems.
		276
		277	The type of data you can transfer depends on the transport protocol: when
		278	JSON is used, then only strings, numbers and arrays and hashes consisting
		279	of those are allowed (no objects). When Storable is used, then anything
		280	that Storable can serialise and deserialise is allowed, and for the local
		281	node, anything can be passed.
		282
		283	=item $local_port = port
		284
		285	Create a new local port object that can be used either as a pattern
		286	matching port ("full port") or a single-callback port ("miniport"),
		287	depending on how C<rcv> callbacks are bound to the object.
		288
		289	=item $port = port { my @msg = @_; $finished }
		290
		291	Creates a "miniport", that is, a very lightweight port without any pattern
		292	matching behind it, and returns its ID. Semantically the same as creating
		293	a port and calling C<rcv $port, $callback> on it.
		294
		295	The block will be called for every message received on the port. When the
		296	callback returns a true value its job is considered "done" and the port
		297	will be destroyed. Otherwise it will stay alive.
		298
		299	The message will be passed as-is, no extra argument (i.e. no port id) will
		300	be passed to the callback.
		301
		302	If you need the local port id in the callback, this works nicely:
		303
		304	my $port; $port = port {
		305	snd $otherport, reply => $port;
		306	};
		307
		308	=cut
		309
		310	sub rcv($@);
		311
		312	sub port(;&) {
		313	my $id = "$UNIQ." . $ID++;
		314	my $port = "$NODE#$id";
		315
		316	if (@_) {
		317	rcv $port, shift;
106	} else {	318	} else {
107	$DEFAULT_SECRET = AnyEvent::MP::Util::nonce 32;	319	$PORT{$id} = sub { }; # nop
108	}
109	}	320	}
110		321
111	$DEFAULT_SECRET	322	$port
112	}	323	}
113		324
114	our $UNIQ = sprintf "%x.%x", $$, time; # per-process/node unique cookie	325	=item reg $port, $name
115	our $PUBLIC = 0;
116	our $NODE;
117	our $PORT;
118		326
119	our %NODE; # node id to transport mapping, or "undef", for local node	327	=item reg $name
120	our %PORT; # local ports
121	our %LISTENER; # local transports
122		328
123	sub NODE() { $NODE }	329	Registers the given port (or C<$SELF><<< if missing) under the name
		330	C<$name>. If the name already exists it is replaced.
124		331
125	{	332	A port can only be registered under one well known name.
126	use POSIX ();	333
127	my $nodename = (POSIX::uname)[1];	334	A port automatically becomes unregistered when it is killed.
128	$NODE = "$$\@$nodename";	335
		336	=cut
		337
		338	sub reg(@) {
		339	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
		340
		341	$REG{$_[0]} = $port;
129	}	342	}
130		343
131	sub _ANY_() { 1 }	344	=item rcv $port, $callback->(@msg)
132	sub _any_() { \&_ANY_ }
133		345
134	sub add_node {	346	Replaces the callback on the specified miniport (after converting it to
135	my ($noderef) = @_;	347	one if required).
136		348
137	return $NODE{$noderef}	349	=item rcv $port, tagstring => $callback->(@msg), ...
138	if exists $NODE{$noderef};
139		350
140	for (split /,/, $noderef) {	351	=item rcv $port, $smartmatch => $callback->(@msg), ...
141	return $NODE{$noderef} = $NODE{$_}	352
142	if exists $NODE{$_};	353	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
		354
		355	Register callbacks to be called on matching messages on the given full
		356	port (after converting it to one if required) and return the port.
		357
		358	The callback has to return a true value when its work is done, after
		359	which is will be removed, or a false value in which case it will stay
		360	registered.
		361
		362	The global C<$SELF> (exported by this module) contains C<$port> while
		363	executing the callback.
		364
		365	Runtime errors during callback execution will result in the port being
		366	C<kil>ed.
		367
		368	If the match is an array reference, then it will be matched against the
		369	first elements of the message, otherwise only the first element is being
		370	matched.
		371
		372	Any element in the match that is specified as C<_any_> (a function
		373	exported by this module) matches any single element of the message.
		374
		375	While not required, it is highly recommended that the first matching
		376	element is a string identifying the message. The one-string-only match is
		377	also the most efficient match (by far).
		378
		379	Example: create a port and bind receivers on it in one go.
		380
		381	my $port = rcv port,
		382	msg1 => sub { ...; 0 },
		383	msg2 => sub { ...; 0 },
		384	;
		385
		386	Example: create a port, bind receivers and send it in a message elsewhere
		387	in one go:
		388
		389	snd $otherport, reply =>
		390	rcv port,
		391	msg1 => sub { ...; 0 },
		392	...
143	}	393	;
144		394
145	# for indirect sends, use a different class	395	=cut
146	my $node = new AnyEvent::MP::Node::Direct $noderef;
147		396
148	$NODE{$_} = $node
149	for $noderef, split /,/, $noderef;
150
151	$node
152	}
153
154	sub snd($@) {	397	sub rcv($@) {
		398	my $port = shift;
155	my ($noderef, $port) = split /#/, shift, 2;	399	my ($noderef, $portid) = split /#/, $port, 2;
156		400
157	add_node $noderef	401	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
158	unless exists $NODE{$noderef};	402	or Carp::croak "$port: rcv can only be called on local ports, caught";
159		403
160	$NODE{$noderef}->send ([$port, [@_]]);	404	if (@_ == 1) {
161	}	405	my $cb = shift;
162		406	delete $PORT_DATA{$portid};
163	sub _inject {	407	$PORT{$portid} = sub {
164	my ($port, $msg) = @{+shift};	408	local $SELF = $port;
165		409	eval {
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	});
187
188	$noderef = $DEFAULT_PORT unless length $noderef;
189
190	my $idx;
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
198	$cv->begin;
199	AnyEvent::Socket::resolve_sockaddr $nodename, $t \|\| "aemp=$DEFAULT_PORT", "tcp", 0, undef, sub {
200	for (@_) {
201	my ($service, $host) = AnyEvent::Socket::unpack_sockaddr $_->[3];
202	push @res, [
203	$pri += 1e-5,
204	AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $host, $service
205	];
206	}	410	&$cb
207	$cv->end;	411	and kil $port;
208	};	412	};
209		413	_self_die if $@;
210	# my (undef, undef, undef, undef, @ipv4) = gethostbyname $nodename;	414	};
211	#
212	# for (@ipv4) {
213	# push @res, [
214	# $pri,
215	# AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $_, $t \|\| $DEFAULT_PORT,
216	# ];
217	# }
218	} else {	415	} else {
219	my ($host, $port) = AnyEvent::Socket::parse_hostport $t, "aemp=$DEFAULT_PORT"	416	my $self = $PORT_DATA{$portid} \|\|= do {
220	or Carp::croak "$t: unparsable transport descriptor";	417	my $self = bless {
		418	id => $port,
		419	}, "AnyEvent::MP::Port";
221		420
222	$cv->begin;	421	$PORT{$portid} = sub {
223	AnyEvent::Socket::resolve_sockaddr $host, $port, "tcp", 0, undef, sub {	422	local $SELF = $port;
224	for (@_) {	423
225	my ($service, $host) = AnyEvent::Socket::unpack_sockaddr $_->[3];	424	eval {
226	push @res, [	425	for (@{ $self->{rc0}{$_[0]} }) {
227	$pri += 1e-5,	426	$_ && &{$_->[0]}
228	AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $host, $service	427	&& undef $_;
229	];	428	}
		429
		430	for (@{ $self->{rcv}{$_[0]} }) {
		431	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
		432	&& &{$_->[0]}
		433	&& undef $_;
		434	}
		435
		436	for (@{ $self->{any} }) {
		437	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
		438	&& &{$_->[0]}
		439	&& undef $_;
		440	}
230	}	441	};
231	$cv->end;	442	_self_die if $@;
		443	};
		444
		445	$self
		446	};
		447
		448	"AnyEvent::MP::Port" eq ref $self
		449	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		450
		451	while (@_) {
		452	my ($match, $cb) = splice @_, 0, 2;
		453
		454	if (!ref $match) {
		455	push @{ $self->{rc0}{$match} }, [$cb];
		456	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
		457	my ($type, @match) = @$match;
		458	@match
		459	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
		460	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
		461	} else {
		462	push @{ $self->{any} }, [$cb, $match];
232	}	463	}
233	}	464	}
234	}	465	}
235		466
236	$cv->end;	467	$port
237
238	$cv
239	}	468	}
240		469
241	sub become_public {	470	=item $closure = psub { BLOCK }
242	return if $PUBLIC;
243		471
244	my $noderef = join ",", ref $_[0] ? @{+shift} : shift;	472	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
245	my @args = @_;	473	closure is executed, sets up the environment in the same way as in C<rcv>
		474	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
246		475
247	$NODE = (normalise_noderef $noderef)->recv;	476	This is useful when you register callbacks from C<rcv> callbacks:
248		477
249	my $self = new AnyEvent::MP::Node::Self noderef => $NODE;	478	rcv delayed_reply => sub {
250		479	my ($delay, @reply) = @_;
251	$NODE{""} = $self; # empty string == local node	480	my $timer = AE::timer $delay, 0, psub {
252		481	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	;	482	};
		483	};
		484
		485	=cut
		486
		487	sub psub(&) {
		488	my $cb = shift;
		489
		490	my $port = $SELF
		491	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		492
		493	sub {
		494	local $SELF = $port;
		495
		496	if (wantarray) {
		497	my @res = eval { &$cb };
		498	_self_die if $@;
		499	@res
		500	} else {
		501	my $res = eval { &$cb };
		502	_self_die if $@;
		503	$res
		504	}
274	}	505	}
275
276	$PUBLIC = 1;
277	}	506	}
		507
		508	=item $guard = mon $port, $cb->(@reason)
		509
		510	=item $guard = mon $port, $rcvport
		511
		512	=item $guard = mon $port
		513
		514	=item $guard = mon $port, $rcvport, @msg
		515
		516	Monitor the given port and do something when the port is killed or
		517	messages to it were lost, and optionally return a guard that can be used
		518	to stop monitoring again.
		519
		520	C<mon> effectively guarantees that, in the absence of hardware failures,
		521	that after starting the monitor, either all messages sent to the port
		522	will arrive, or the monitoring action will be invoked after possible
		523	message loss has been detected. No messages will be lost "in between"
		524	(after the first lost message no further messages will be received by the
		525	port). After the monitoring action was invoked, further messages might get
		526	delivered again.
		527
		528	In the first form (callback), the callback is simply called with any
		529	number of C<@reason> elements (no @reason means that the port was deleted
		530	"normally"). Note also that I<< the callback B<must> never die >>, so use
		531	C<eval> if unsure.
		532
		533	In the second form (another port given), the other port (C<$rcvport>)
		534	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
		535	"normal" kils nothing happens, while under all other conditions, the other
		536	port is killed with the same reason.
		537
		538	The third form (kill self) is the same as the second form, except that
		539	C<$rvport> defaults to C<$SELF>.
		540
		541	In the last form (message), a message of the form C<@msg, @reason> will be
		542	C<snd>.
		543
		544	As a rule of thumb, monitoring requests should always monitor a port from
		545	a local port (or callback). The reason is that kill messages might get
		546	lost, just like any other message. Another less obvious reason is that
		547	even monitoring requests can get lost (for exmaple, when the connection
		548	to the other node goes down permanently). When monitoring a port locally
		549	these problems do not exist.
		550
		551	Example: call a given callback when C<$port> is killed.
		552
		553	mon $port, sub { warn "port died because of <@_>\n" };
		554
		555	Example: kill ourselves when C<$port> is killed abnormally.
		556
		557	mon $port;
		558
		559	Example: send us a restart message when another C<$port> is killed.
		560
		561	mon $port, $self => "restart";
		562
		563	=cut
		564
		565	sub mon {
		566	my ($noderef, $port) = split /#/, shift, 2;
		567
		568	my $node = $NODE{$noderef} \|\| add_node $noderef;
		569
		570	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		571
		572	unless (ref $cb) {
		573	if (@_) {
		574	# send a kill info message
		575	my (@msg) = ($cb, @_);
		576	$cb = sub { snd @msg, @_ };
		577	} else {
		578	# simply kill other port
		579	my $port = $cb;
		580	$cb = sub { kil $port, @_ if @_ };
		581	}
		582	}
		583
		584	$node->monitor ($port, $cb);
		585
		586	defined wantarray
		587	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		588	}
		589
		590	=item $guard = mon_guard $port, $ref, $ref...
		591
		592	Monitors the given C<$port> and keeps the passed references. When the port
		593	is killed, the references will be freed.
		594
		595	Optionally returns a guard that will stop the monitoring.
		596
		597	This function is useful when you create e.g. timers or other watchers and
		598	want to free them when the port gets killed:
		599
		600	$port->rcv (start => sub {
		601	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		602	undef $timer if 0.9 < rand;
		603	});
		604	});
		605
		606	=cut
		607
		608	sub mon_guard {
		609	my ($port, @refs) = @_;
		610
		611	#TODO: mon-less form?
		612
		613	mon $port, sub { 0 && @refs }
		614	}
		615
		616	=item kil $port[, @reason]
		617
		618	Kill the specified port with the given C<@reason>.
		619
		620	If no C<@reason> is specified, then the port is killed "normally" (linked
		621	ports will not be kileld, or even notified).
		622
		623	Otherwise, linked ports get killed with the same reason (second form of
		624	C<mon>, see below).
		625
		626	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		627	will be reported as reason C<< die => $@ >>.
		628
		629	Transport/communication errors are reported as C<< transport_error =>
		630	$message >>.
		631
		632	=cut
		633
		634	=item $port = spawn $node, $initfunc[, @initdata]
		635
		636	Creates a port on the node C<$node> (which can also be a port ID, in which
		637	case it's the node where that port resides).
		638
		639	The port ID of the newly created port is return immediately, and it is
		640	permissible to immediately start sending messages or monitor the port.
		641
		642	After the port has been created, the init function is
		643	called. This function must be a fully-qualified function name
		644	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		645	program, use C<::name>.
		646
		647	If the function doesn't exist, then the node tries to C<require>
		648	the package, then the package above the package and so on (e.g.
		649	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		650	exists or it runs out of package names.
		651
		652	The init function is then called with the newly-created port as context
		653	object (C<$SELF>) and the C<@initdata> values as arguments.
		654
		655	A common idiom is to pass your own port, monitor the spawned port, and
		656	in the init function, monitor the original port. This two-way monitoring
		657	ensures that both ports get cleaned up when there is a problem.
		658
		659	Example: spawn a chat server port on C<$othernode>.
		660
		661	# this node, executed from within a port context:
		662	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		663	mon $server;
		664
		665	# init function on C<$othernode>
		666	sub connect {
		667	my ($srcport) = @_;
		668
		669	mon $srcport;
		670
		671	rcv $SELF, sub {
		672	...
		673	};
		674	}
		675
		676	=cut
		677
		678	sub _spawn {
		679	my $port = shift;
		680	my $init = shift;
		681
		682	local $SELF = "$NODE#$port";
		683	eval {
		684	&{ load_func $init }
		685	};
		686	_self_die if $@;
		687	}
		688
		689	sub spawn(@) {
		690	my ($noderef, undef) = split /#/, shift, 2;
		691
		692	my $id = "$RUNIQ." . $ID++;
		693
		694	$_[0] =~ /::/
		695	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		696
		697	($NODE{$noderef} \|\| add_node $noderef)
		698	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
		699
		700	"$noderef#$id"
		701	}
		702
		703	=back
		704
		705	=head1 NODE MESSAGES
		706
		707	Nodes understand the following messages sent to them. Many of them take
		708	arguments called C<@reply>, which will simply be used to compose a reply
		709	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
		710	the remaining arguments are simply the message data.
		711
		712	While other messages exist, they are not public and subject to change.
		713
		714	=over 4
		715
		716	=cut
		717
		718	=item lookup => $name, @reply
		719
		720	Replies with the port ID of the specified well-known port, or C<undef>.
		721
		722	=item devnull => ...
		723
		724	Generic data sink/CPU heat conversion.
		725
		726	=item relay => $port, @msg
		727
		728	Simply forwards the message to the given port.
		729
		730	=item eval => $string[ @reply]
		731
		732	Evaluates the given string. If C<@reply> is given, then a message of the
		733	form C<@reply, $@, @evalres> is sent.
		734
		735	Example: crash another node.
		736
		737	snd $othernode, eval => "exit";
		738
		739	=item time => @reply
		740
		741	Replies the the current node time to C<@reply>.
		742
		743	Example: tell the current node to send the current time to C<$myport> in a
		744	C<timereply> message.
		745
		746	snd $NODE, time => $myport, timereply => 1, 2;
		747	# => snd $myport, timereply => 1, 2, <time>
		748
		749	=back
		750
		751	=head1 AnyEvent::MP vs. Distributed Erlang
		752
		753	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		754	== aemp node, Erlang process == aemp port), so many of the documents and
		755	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		756	sample:
		757
		758	http://www.Erlang.se/doc/programming_rules.shtml
		759	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		760	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		761	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		762
		763	Despite the similarities, there are also some important differences:
		764
		765	=over 4
		766
		767	=item * Node references contain the recipe on how to contact them.
		768
		769	Erlang relies on special naming and DNS to work everywhere in the
		770	same way. AEMP relies on each node knowing it's own address(es), with
		771	convenience functionality.
		772
		773	This means that AEMP requires a less tightly controlled environment at the
		774	cost of longer node references and a slightly higher management overhead.
		775
		776	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		777
		778	Erlang uses processes that selctively receive messages, and therefore
		779	needs a queue. AEMP is event based, queuing messages would serve no useful
		780	purpose.
		781
		782	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
		783
		784	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		785
		786	Sending messages in Erlang is synchronous and blocks the process. AEMP
		787	sends are immediate, connection establishment is handled in the
		788	background.
		789
		790	=item * Erlang can silently lose messages, AEMP cannot.
		791
		792	Erlang makes few guarantees on messages delivery - messages can get lost
		793	without any of the processes realising it (i.e. you send messages a, b,
		794	and c, and the other side only receives messages a and c).
		795
		796	AEMP guarantees correct ordering, and the guarantee that there are no
		797	holes in the message sequence.
		798
		799	=item * In Erlang, processes can be declared dead and later be found to be
		800	alive.
		801
		802	In Erlang it can happen that a monitored process is declared dead and
		803	linked processes get killed, but later it turns out that the process is
		804	still alive - and can receive messages.
		805
		806	In AEMP, when port monitoring detects a port as dead, then that port will
		807	eventually be killed - it cannot happen that a node detects a port as dead
		808	and then later sends messages to it, finding it is still alive.
		809
		810	=item * Erlang can send messages to the wrong port, AEMP does not.
		811
		812	In Erlang it is quite possible that a node that restarts reuses a process
		813	ID known to other nodes for a completely different process, causing
		814	messages destined for that process to end up in an unrelated process.
		815
		816	AEMP never reuses port IDs, so old messages or old port IDs floating
		817	around in the network will not be sent to an unrelated port.
		818
		819	=item * Erlang uses unprotected connections, AEMP uses secure
		820	authentication and can use TLS.
		821
		822	AEMP can use a proven protocol - SSL/TLS - to protect connections and
		823	securely authenticate nodes.
		824
		825	=item * The AEMP protocol is optimised for both text-based and binary
		826	communications.
		827
		828	The AEMP protocol, unlike the Erlang protocol, supports both
		829	language-independent text-only protocols (good for debugging) and binary,
		830	language-specific serialisers (e.g. Storable).
		831
		832	It has also been carefully designed to be implementable in other languages
		833	with a minimum of work while gracefully degrading fucntionality to make the
		834	protocol simple.
		835
		836	=item * AEMP has more flexible monitoring options than Erlang.
		837
		838	In Erlang, you can chose to receive I<all> exit signals as messages
		839	or I<none>, there is no in-between, so monitoring single processes is
		840	difficult to implement. Monitoring in AEMP is more flexible than in
		841	Erlang, as one can choose between automatic kill, exit message or callback
		842	on a per-process basis.
		843
		844	=item * Erlang tries to hide remote/local connections, AEMP does not.
		845
		846	Monitoring in Erlang is not an indicator of process death/crashes,
		847	as linking is (except linking is unreliable in Erlang).
		848
		849	In AEMP, you don't "look up" registered port names or send to named ports
		850	that might or might not be persistent. Instead, you normally spawn a port
		851	on the remote node. The init function monitors the you, and you monitor
		852	the remote port. Since both monitors are local to the node, they are much
		853	more reliable.
		854
		855	This also saves round-trips and avoids sending messages to the wrong port
		856	(hard to do in Erlang).
		857
		858	=back
		859
		860	=head1 RATIONALE
		861
		862	=over 4
		863
		864	=item Why strings for ports and noderefs, why not objects?
		865
		866	We considered "objects", but found that the actual number of methods
		867	thatc an be called are very low. Since port IDs and noderefs travel over
		868	the network frequently, the serialising/deserialising would add lots of
		869	overhead, as well as having to keep a proxy object.
		870
		871	Strings can easily be printed, easily serialised etc. and need no special
		872	procedures to be "valid".
		873
		874	And a a miniport consists of a single closure stored in a global hash - it
		875	can't become much cheaper.
		876
		877	=item Why favour JSON, why not real serialising format such as Storable?
		878
		879	In fact, any AnyEvent::MP node will happily accept Storable as framing
		880	format, but currently there is no way to make a node use Storable by
		881	default.
		882
		883	The default framing protocol is JSON because a) JSON::XS is many times
		884	faster for small messages and b) most importantly, after years of
		885	experience we found that object serialisation is causing more problems
		886	than it gains: Just like function calls, objects simply do not travel
		887	easily over the network, mostly because they will always be a copy, so you
		888	always have to re-think your design.
		889
		890	Keeping your messages simple, concentrating on data structures rather than
		891	objects, will keep your messages clean, tidy and efficient.
278		892
279	=back	893	=back
280		894
281	=head1 SEE ALSO	895	=head1 SEE ALSO
282		896

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Revision 1.47 by root, Thu Aug 13 01:57:10 2009 UTC