[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 1.49 by root, Thu Aug 13 15:29:58 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; # -OR-
		17	initialise_node "localhost:4040"; # -OR-
		18	initialise_node "slave/", "localhost:4040"
		19
		20	# ports are message endpoints
		21
		22	# sending messages
12	snd $port, type => data...;	23	snd $port, type => data...;
		24	snd $port, @msg;
		25	snd @msg_with_first_element_being_a_port;
13		26
		27	# creating/using miniports
		28	my $miniport = port { my @msg = @_; 0 };
		29
		30	# creating/using full ports
		31	my $port = port;
14	rcv $port, smartmatch => $cb->($port, @msg);	32	rcv $port, smartmatch => $cb->(@msg);
15
16	# examples:
17	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	33	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
18	rcv $port1, pong => sub { warn "pong received\n" };	34	rcv $port, pong => sub { warn "pong received\n"; 0 };
19	snd $port2, ping => $port1;
20		35
21	# more, smarter, matches (_any_ is exported by this module)	36	# more, smarter, matches (_any_ is exported by this module)
22	rcv $port, [child_died => $pid] => sub { ...	37	rcv $port, [child_died => $pid] => sub { ...
23	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	38	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
24		39
		40	# create a port on another node
		41	my $port = spawn $node, $initfunc, @initdata;
		42
		43	# monitoring
		44	mon $port, $cb->(@msg) # callback is invoked on death
		45	mon $port, $otherport # kill otherport on abnormal death
		46	mon $port, $otherport, @msg # send message on death
		47
		48	=head1 CURRENT STATUS
		49
		50	AnyEvent::MP - stable API, should work
		51	AnyEvent::MP::Intro - outdated
		52	AnyEvent::MP::Kernel - WIP
		53	AnyEvent::MP::Transport - mostly stable
		54
		55	stay tuned.
		56
25	=head1 DESCRIPTION	57	=head1 DESCRIPTION
26		58
27	This module (-family) implements a simple message passing framework.	59	This module (-family) implements a simple message passing framework.
28		60
29	Despite its simplicity, you can securely message other processes running	61	Despite its simplicity, you can securely message other processes running
30	on the same or other hosts.	62	on the same or other hosts.
31		63
		64	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
		65	manual page.
		66
		67	At the moment, this module family is severly broken and underdocumented,
		68	so do not use. This was uploaded mainly to reserve the CPAN namespace -
		69	stay tuned!
		70
32	=head1 CONCEPTS	71	=head1 CONCEPTS
33		72
34	=over 4	73	=over 4
35		74
36	=item port	75	=item port
37		76
38	A port is something you can send messages to with the C<snd> function, and	77	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		78
		79	Some ports allow you to register C<rcv> handlers that can match specific
		80	messages. All C<rcv> handlers will receive messages they match, messages
		81	will not be queued.
		82
42	=item port id - C<pid@host#portname>	83	=item port id - C<noderef#portname>
43		84
44	A port id is always the node id, a hash-mark (C<#>) as separator, followed	85	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as
45	by a port name.	86	separator, and a port name (a printable string of unspecified format). An
46		87	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),	88	reference.
48	or a generated name, consisting of node id, a dot (C<.>), and an
49	identifier.
50		89
51	=item node	90	=item node
52		91
53	A node is a single process containing at least one port - the node	92	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,	93	port. You can send messages to node ports to find existing ports or to
55	among other things.	94	create new ports, among other things.
56		95
57	Initially, nodes are either private (single-process only) or hidden	96	Nodes are either private (single-process only), slaves (connected to a
58	(connected to a father node only). Only when they epxlicitly "go public"	97	master node only) or public nodes (connectable from unrelated nodes).
59	can you send them messages form unrelated other nodes.
60		98
61	Public nodes automatically connect to all other public nodes in a network	99	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
62	when they connect, creating a full mesh.
63		100
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	101	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	102	private and slave nodes), or contains a recipe on how to reach a given
68	node (for public nodes).	103	node (for public nodes).
69		104
		105	This recipe is simply a comma-separated list of C<address:port> pairs (for
		106	TCP/IP, other protocols might look different).
		107
		108	Node references come in two flavours: resolved (containing only numerical
		109	addresses) or unresolved (where hostnames are used instead of addresses).
		110
		111	Before using an unresolved node reference in a message you first have to
		112	resolve it.
		113
70	=back	114	=back
71		115
72	=head1 FUNCTIONS	116	=head1 VARIABLES/FUNCTIONS
73		117
74	=over 4	118	=over 4
75		119
76	=cut	120	=cut
77		121
78	package AnyEvent::MP;	122	package AnyEvent::MP;
79		123
80	use AnyEvent::MP::Util ();
81	use AnyEvent::MP::Node;	124	use AnyEvent::MP::Kernel;
82	use AnyEvent::MP::Transport;
83		125
84	use utf8;
85	use common::sense;	126	use common::sense;
86		127
87	use Carp ();	128	use Carp ();
88		129
89	use AE ();	130	use AE ();
90		131
91	use base "Exporter";	132	use base "Exporter";
92		133
93	our $VERSION = '0.0';	134	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
94	our @EXPORT = qw(NODE $NODE $PORT snd rcv _any_);
95		135
96	our $DEFAULT_SECRET;	136	our @EXPORT = qw(
97	our $DEFAULT_PORT = "4040";	137	NODE $NODE *SELF node_of _any_
		138	resolve_node initialise_node
		139	snd rcv mon kil reg psub spawn
		140	port
		141	);
98		142
99	our $CONNECT_INTERVAL = 5; # new connect every 5s, at least	143	our $SELF;
100	our $CONNECT_TIMEOUT = 30; # includes handshake
101		144
102	sub default_secret {	145	sub _self_die() {
103	unless (defined $DEFAULT_SECRET) {	146	my $msg = $@;
104	if (open my $fh, "<$ENV{HOME}/.aemp-secret") {	147	$msg =~ s/\n+$// unless ref $msg;
105	sysread $fh, $DEFAULT_SECRET, -s $fh;	148	kil $SELF, die => $msg;
		149	}
		150
		151	=item $thisnode = NODE / $NODE
		152
		153	The C<NODE> function returns, and the C<$NODE> variable contains
		154	the noderef of the local node. The value is initialised by a call
		155	to C<become_public> or C<become_slave>, after which all local port
		156	identifiers become invalid.
		157
		158	=item $noderef = node_of $port
		159
		160	Extracts and returns the noderef from a portid or a noderef.
		161
		162	=item initialise_node $noderef, $seednode, $seednode...
		163
		164	=item initialise_node "slave/", $master, $master...
		165
		166	Before a node can talk to other nodes on the network it has to initialise
		167	itself - the minimum a node needs to know is it's own name, and optionally
		168	it should know the noderefs of some other nodes in the network.
		169
		170	This function initialises a node - it must be called exactly once (or
		171	never) before calling other AnyEvent::MP functions.
		172
		173	All arguments (optionally except for the first) are noderefs, which can be
		174	either resolved or unresolved.
		175
		176	The first argument will be looked up in the configuration database first
		177	(if it is C<undef> then the current nodename will be used instead) to find
		178	the relevant configuration profile (see L<aemp>). If none is found then
		179	the default configuration is used. The configuration supplies additional
		180	seed/master nodes and can override the actual noderef.
		181
		182	There are two types of networked nodes, public nodes and slave nodes:
		183
		184	=over 4
		185
		186	=item public nodes
		187
		188	For public nodes, C<$noderef> (supplied either directly to
		189	C<initialise_node> or indirectly via a profile or the nodename) must be a
		190	noderef (possibly unresolved, in which case it will be resolved).
		191
		192	After resolving, the node will bind itself on all endpoints and try to
		193	connect to all additional C<$seednodes> that are specified. Seednodes are
		194	optional and can be used to quickly bootstrap the node into an existing
		195	network.
		196
		197	=item slave nodes
		198
		199	When the C<$noderef> (either as given or overriden by the config file)
		200	is the special string C<slave/>, then the node will become a slave
		201	node. Slave nodes cannot be contacted from outside and will route most of
		202	their traffic to the master node that they attach to.
		203
		204	At least one additional noderef is required (either by specifying it
		205	directly or because it is part of the configuration profile): The node
		206	will try to connect to all of them and will become a slave attached to the
		207	first node it can successfully connect to.
		208
		209	=back
		210
		211	This function will block until all nodes have been resolved and, for slave
		212	nodes, until it has successfully established a connection to a master
		213	server.
		214
		215	Example: become a public node listening on the guessed noderef, or the one
		216	specified via C<aemp> for the current node. This should be the most common
		217	form of invocation for "daemon"-type nodes.
		218
		219	initialise_node;
		220
		221	Example: become a slave node to any of the the seednodes specified via
		222	C<aemp>. This form is often used for commandline clients.
		223
		224	initialise_node "slave/";
		225
		226	Example: become a slave node to any of the specified master servers. This
		227	form is also often used for commandline clients.
		228
		229	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
		230
		231	Example: become a public node, and try to contact some well-known master
		232	servers to become part of the network.
		233
		234	initialise_node undef, "master1", "master2";
		235
		236	Example: become a public node listening on port C<4041>.
		237
		238	initialise_node 4041;
		239
		240	Example: become a public node, only visible on localhost port 4044.
		241
		242	initialise_node "localhost:4044";
		243
		244	=item $cv = resolve_node $noderef
		245
		246	Takes an unresolved node reference that may contain hostnames and
		247	abbreviated IDs, resolves all of them and returns a resolved node
		248	reference.
		249
		250	In addition to C<address:port> pairs allowed in resolved noderefs, the
		251	following forms are supported:
		252
		253	=over 4
		254
		255	=item the empty string
		256
		257	An empty-string component gets resolved as if the default port (4040) was
		258	specified.
		259
		260	=item naked port numbers (e.g. C<1234>)
		261
		262	These are resolved by prepending the local nodename and a colon, to be
		263	further resolved.
		264
		265	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
		266
		267	These are resolved by using AnyEvent::DNS to resolve them, optionally
		268	looking up SRV records for the C<aemp=4040> port, if no port was
		269	specified.
		270
		271	=back
		272
		273	=item $SELF
		274
		275	Contains the current port id while executing C<rcv> callbacks or C<psub>
		276	blocks.
		277
		278	=item SELF, %SELF, @SELF...
		279
		280	Due to some quirks in how perl exports variables, it is impossible to
		281	just export C<$SELF>, all the symbols called C<SELF> are exported by this
		282	module, but only C<$SELF> is currently used.
		283
		284	=item snd $port, type => @data
		285
		286	=item snd $port, @msg
		287
		288	Send the given message to the given port ID, which can identify either
		289	a local or a remote port, and can be either a string or soemthignt hat
		290	stringifies a sa port ID (such as a port object :).
		291
		292	While the message can be about anything, it is highly recommended to use a
		293	string as first element (a portid, or some word that indicates a request
		294	type etc.).
		295
		296	The message data effectively becomes read-only after a call to this
		297	function: modifying any argument is not allowed and can cause many
		298	problems.
		299
		300	The type of data you can transfer depends on the transport protocol: when
		301	JSON is used, then only strings, numbers and arrays and hashes consisting
		302	of those are allowed (no objects). When Storable is used, then anything
		303	that Storable can serialise and deserialise is allowed, and for the local
		304	node, anything can be passed.
		305
		306	=item $local_port = port
		307
		308	Create a new local port object that can be used either as a pattern
		309	matching port ("full port") or a single-callback port ("miniport"),
		310	depending on how C<rcv> callbacks are bound to the object.
		311
		312	=item $port = port { my @msg = @_; $finished }
		313
		314	Creates a "miniport", that is, a very lightweight port without any pattern
		315	matching behind it, and returns its ID. Semantically the same as creating
		316	a port and calling C<rcv $port, $callback> on it.
		317
		318	The block will be called for every message received on the port. When the
		319	callback returns a true value its job is considered "done" and the port
		320	will be destroyed. Otherwise it will stay alive.
		321
		322	The message will be passed as-is, no extra argument (i.e. no port id) will
		323	be passed to the callback.
		324
		325	If you need the local port id in the callback, this works nicely:
		326
		327	my $port; $port = port {
		328	snd $otherport, reply => $port;
		329	};
		330
		331	=cut
		332
		333	sub rcv($@);
		334
		335	sub port(;&) {
		336	my $id = "$UNIQ." . $ID++;
		337	my $port = "$NODE#$id";
		338
		339	if (@_) {
		340	rcv $port, shift;
106	} else {	341	} else {
107	$DEFAULT_SECRET = AnyEvent::MP::Util::nonce 32;	342	$PORT{$id} = sub { }; # nop
108	}
109	}	343	}
110		344
111	$DEFAULT_SECRET	345	$port
112	}	346	}
113		347
114	our $UNIQ = sprintf "%x.%x", $$, time; # per-process/node unique cookie	348	=item reg $port, $name
115	our $PUBLIC = 0;
116	our $NODE;
117	our $PORT;
118		349
119	our %NODE; # node id to transport mapping, or "undef", for local node	350	=item reg $name
120	our %PORT; # local ports
121	our %LISTENER; # local transports
122		351
123	sub NODE() { $NODE }	352	Registers the given port (or C<$SELF><<< if missing) under the name
		353	C<$name>. If the name already exists it is replaced.
124		354
125	{	355	A port can only be registered under one well known name.
126	use POSIX ();	356
127	my $nodename = (POSIX::uname)[1];	357	A port automatically becomes unregistered when it is killed.
128	$NODE = "$$\@$nodename";	358
		359	=cut
		360
		361	sub reg(@) {
		362	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
		363
		364	$REG{$_[0]} = $port;
129	}	365	}
130		366
131	sub _ANY_() { 1 }	367	=item rcv $port, $callback->(@msg)
132	sub _any_() { \&_ANY_ }
133		368
134	sub add_node {	369	Replaces the callback on the specified miniport (after converting it to
135	my ($noderef) = @_;	370	one if required).
136		371
137	return $NODE{$noderef}	372	=item rcv $port, tagstring => $callback->(@msg), ...
138	if exists $NODE{$noderef};
139		373
140	for (split /,/, $noderef) {	374	=item rcv $port, $smartmatch => $callback->(@msg), ...
141	return $NODE{$noderef} = $NODE{$_}	375
142	if exists $NODE{$_};	376	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
		377
		378	Register callbacks to be called on matching messages on the given full
		379	port (after converting it to one if required) and return the port.
		380
		381	The callback has to return a true value when its work is done, after
		382	which is will be removed, or a false value in which case it will stay
		383	registered.
		384
		385	The global C<$SELF> (exported by this module) contains C<$port> while
		386	executing the callback.
		387
		388	Runtime errors during callback execution will result in the port being
		389	C<kil>ed.
		390
		391	If the match is an array reference, then it will be matched against the
		392	first elements of the message, otherwise only the first element is being
		393	matched.
		394
		395	Any element in the match that is specified as C<_any_> (a function
		396	exported by this module) matches any single element of the message.
		397
		398	While not required, it is highly recommended that the first matching
		399	element is a string identifying the message. The one-string-only match is
		400	also the most efficient match (by far).
		401
		402	Example: create a port and bind receivers on it in one go.
		403
		404	my $port = rcv port,
		405	msg1 => sub { ...; 0 },
		406	msg2 => sub { ...; 0 },
		407	;
		408
		409	Example: create a port, bind receivers and send it in a message elsewhere
		410	in one go:
		411
		412	snd $otherport, reply =>
		413	rcv port,
		414	msg1 => sub { ...; 0 },
		415	...
143	}	416	;
144		417
145	# for indirect sends, use a different class	418	=cut
146	my $node = new AnyEvent::MP::Node::Direct $noderef;
147		419
148	$NODE{$_} = $node
149	for $noderef, split /,/, $noderef;
150
151	$node
152	}
153
154	sub snd($@) {	420	sub rcv($@) {
		421	my $port = shift;
155	my ($noderef, $port) = split /#/, shift, 2;	422	my ($noderef, $portid) = split /#/, $port, 2;
156		423
157	add_node $noderef	424	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
158	unless exists $NODE{$noderef};	425	or Carp::croak "$port: rcv can only be called on local ports, caught";
159		426
160	$NODE{$noderef}->send ([$port, [@_]]);	427	if (@_ == 1) {
161	}	428	my $cb = shift;
162		429	delete $PORT_DATA{$portid};
163	sub _inject {	430	$PORT{$portid} = sub {
164	my ($port, $msg) = @{+shift};	431	local $SELF = $port;
165		432	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, $service
205	];
206	}	433	&$cb
207	$cv->end;	434	and kil $port;
208	};	435	};
209		436	_self_die if $@;
210	# my (undef, undef, undef, undef, @ipv4) = gethostbyname $nodename;	437	};
211	#
212	# for (@ipv4) {
213	# push @res, [
214	# $pri,
215	# AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $_, $t \|\| $DEFAULT_PORT,
216	# ];
217	# }
218	} else {	438	} else {
219	my ($host, $port) = AnyEvent::Socket::parse_hostport $t, "aemp=$DEFAULT_PORT"	439	my $self = $PORT_DATA{$portid} \|\|= do {
220	or Carp::croak "$t: unparsable transport descriptor";	440	my $self = bless {
		441	id => $port,
		442	}, "AnyEvent::MP::Port";
221		443
222	$cv->begin;	444	$PORT{$portid} = sub {
223	AnyEvent::Socket::resolve_sockaddr $host, $port, "tcp", 0, undef, sub {	445	local $SELF = $port;
224	for (@_) {	446
225	my ($service, $host) = AnyEvent::Socket::unpack_sockaddr $_->[3];	447	eval {
226	push @res, [	448	for (@{ $self->{rc0}{$_[0]} }) {
227	$pri += 1e-5,	449	$_ && &{$_->[0]}
228	AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $host, $service	450	&& undef $_;
229	];	451	}
		452
		453	for (@{ $self->{rcv}{$_[0]} }) {
		454	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
		455	&& &{$_->[0]}
		456	&& undef $_;
		457	}
		458
		459	for (@{ $self->{any} }) {
		460	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
		461	&& &{$_->[0]}
		462	&& undef $_;
		463	}
230	}	464	};
231	$cv->end;	465	_self_die if $@;
		466	};
		467
		468	$self
		469	};
		470
		471	"AnyEvent::MP::Port" eq ref $self
		472	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		473
		474	while (@_) {
		475	my ($match, $cb) = splice @_, 0, 2;
		476
		477	if (!ref $match) {
		478	push @{ $self->{rc0}{$match} }, [$cb];
		479	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
		480	my ($type, @match) = @$match;
		481	@match
		482	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
		483	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
		484	} else {
		485	push @{ $self->{any} }, [$cb, $match];
232	}	486	}
233	}	487	}
234	}	488	}
235		489
236	$cv->end;	490	$port
237
238	$cv
239	}	491	}
240		492
241	sub become_public {	493	=item $closure = psub { BLOCK }
242	return if $PUBLIC;
243		494
244	my $noderef = join ",", ref $_[0] ? @{+shift} : shift;	495	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
245	my @args = @_;	496	closure is executed, sets up the environment in the same way as in C<rcv>
		497	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
246		498
247	$NODE = (normalise_noderef $noderef)->recv;	499	This is useful when you register callbacks from C<rcv> callbacks:
248		500
249	my $self = new AnyEvent::MP::Node::Self noderef => $NODE;	501	rcv delayed_reply => sub {
250		502	my ($delay, @reply) = @_;
251	$NODE{""} = $self; # empty string == local node	503	my $timer = AE::timer $delay, 0, psub {
252		504	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	;	505	};
		506	};
		507
		508	=cut
		509
		510	sub psub(&) {
		511	my $cb = shift;
		512
		513	my $port = $SELF
		514	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		515
		516	sub {
		517	local $SELF = $port;
		518
		519	if (wantarray) {
		520	my @res = eval { &$cb };
		521	_self_die if $@;
		522	@res
		523	} else {
		524	my $res = eval { &$cb };
		525	_self_die if $@;
		526	$res
		527	}
274	}	528	}
275
276	$PUBLIC = 1;
277	}	529	}
		530
		531	=item $guard = mon $port, $cb->(@reason)
		532
		533	=item $guard = mon $port, $rcvport
		534
		535	=item $guard = mon $port
		536
		537	=item $guard = mon $port, $rcvport, @msg
		538
		539	Monitor the given port and do something when the port is killed or
		540	messages to it were lost, and optionally return a guard that can be used
		541	to stop monitoring again.
		542
		543	C<mon> effectively guarantees that, in the absence of hardware failures,
		544	that after starting the monitor, either all messages sent to the port
		545	will arrive, or the monitoring action will be invoked after possible
		546	message loss has been detected. No messages will be lost "in between"
		547	(after the first lost message no further messages will be received by the
		548	port). After the monitoring action was invoked, further messages might get
		549	delivered again.
		550
		551	In the first form (callback), the callback is simply called with any
		552	number of C<@reason> elements (no @reason means that the port was deleted
		553	"normally"). Note also that I<< the callback B<must> never die >>, so use
		554	C<eval> if unsure.
		555
		556	In the second form (another port given), the other port (C<$rcvport>)
		557	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
		558	"normal" kils nothing happens, while under all other conditions, the other
		559	port is killed with the same reason.
		560
		561	The third form (kill self) is the same as the second form, except that
		562	C<$rvport> defaults to C<$SELF>.
		563
		564	In the last form (message), a message of the form C<@msg, @reason> will be
		565	C<snd>.
		566
		567	As a rule of thumb, monitoring requests should always monitor a port from
		568	a local port (or callback). The reason is that kill messages might get
		569	lost, just like any other message. Another less obvious reason is that
		570	even monitoring requests can get lost (for exmaple, when the connection
		571	to the other node goes down permanently). When monitoring a port locally
		572	these problems do not exist.
		573
		574	Example: call a given callback when C<$port> is killed.
		575
		576	mon $port, sub { warn "port died because of <@_>\n" };
		577
		578	Example: kill ourselves when C<$port> is killed abnormally.
		579
		580	mon $port;
		581
		582	Example: send us a restart message when another C<$port> is killed.
		583
		584	mon $port, $self => "restart";
		585
		586	=cut
		587
		588	sub mon {
		589	my ($noderef, $port) = split /#/, shift, 2;
		590
		591	my $node = $NODE{$noderef} \|\| add_node $noderef;
		592
		593	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		594
		595	unless (ref $cb) {
		596	if (@_) {
		597	# send a kill info message
		598	my (@msg) = ($cb, @_);
		599	$cb = sub { snd @msg, @_ };
		600	} else {
		601	# simply kill other port
		602	my $port = $cb;
		603	$cb = sub { kil $port, @_ if @_ };
		604	}
		605	}
		606
		607	$node->monitor ($port, $cb);
		608
		609	defined wantarray
		610	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		611	}
		612
		613	=item $guard = mon_guard $port, $ref, $ref...
		614
		615	Monitors the given C<$port> and keeps the passed references. When the port
		616	is killed, the references will be freed.
		617
		618	Optionally returns a guard that will stop the monitoring.
		619
		620	This function is useful when you create e.g. timers or other watchers and
		621	want to free them when the port gets killed:
		622
		623	$port->rcv (start => sub {
		624	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		625	undef $timer if 0.9 < rand;
		626	});
		627	});
		628
		629	=cut
		630
		631	sub mon_guard {
		632	my ($port, @refs) = @_;
		633
		634	#TODO: mon-less form?
		635
		636	mon $port, sub { 0 && @refs }
		637	}
		638
		639	=item kil $port[, @reason]
		640
		641	Kill the specified port with the given C<@reason>.
		642
		643	If no C<@reason> is specified, then the port is killed "normally" (linked
		644	ports will not be kileld, or even notified).
		645
		646	Otherwise, linked ports get killed with the same reason (second form of
		647	C<mon>, see below).
		648
		649	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		650	will be reported as reason C<< die => $@ >>.
		651
		652	Transport/communication errors are reported as C<< transport_error =>
		653	$message >>.
		654
		655	=cut
		656
		657	=item $port = spawn $node, $initfunc[, @initdata]
		658
		659	Creates a port on the node C<$node> (which can also be a port ID, in which
		660	case it's the node where that port resides).
		661
		662	The port ID of the newly created port is return immediately, and it is
		663	permissible to immediately start sending messages or monitor the port.
		664
		665	After the port has been created, the init function is
		666	called. This function must be a fully-qualified function name
		667	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		668	program, use C<::name>.
		669
		670	If the function doesn't exist, then the node tries to C<require>
		671	the package, then the package above the package and so on (e.g.
		672	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		673	exists or it runs out of package names.
		674
		675	The init function is then called with the newly-created port as context
		676	object (C<$SELF>) and the C<@initdata> values as arguments.
		677
		678	A common idiom is to pass your own port, monitor the spawned port, and
		679	in the init function, monitor the original port. This two-way monitoring
		680	ensures that both ports get cleaned up when there is a problem.
		681
		682	Example: spawn a chat server port on C<$othernode>.
		683
		684	# this node, executed from within a port context:
		685	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		686	mon $server;
		687
		688	# init function on C<$othernode>
		689	sub connect {
		690	my ($srcport) = @_;
		691
		692	mon $srcport;
		693
		694	rcv $SELF, sub {
		695	...
		696	};
		697	}
		698
		699	=cut
		700
		701	sub _spawn {
		702	my $port = shift;
		703	my $init = shift;
		704
		705	local $SELF = "$NODE#$port";
		706	eval {
		707	&{ load_func $init }
		708	};
		709	_self_die if $@;
		710	}
		711
		712	sub spawn(@) {
		713	my ($noderef, undef) = split /#/, shift, 2;
		714
		715	my $id = "$RUNIQ." . $ID++;
		716
		717	$_[0] =~ /::/
		718	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		719
		720	($NODE{$noderef} \|\| add_node $noderef)
		721	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
		722
		723	"$noderef#$id"
		724	}
		725
		726	=back
		727
		728	=head1 NODE MESSAGES
		729
		730	Nodes understand the following messages sent to them. Many of them take
		731	arguments called C<@reply>, which will simply be used to compose a reply
		732	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
		733	the remaining arguments are simply the message data.
		734
		735	While other messages exist, they are not public and subject to change.
		736
		737	=over 4
		738
		739	=cut
		740
		741	=item lookup => $name, @reply
		742
		743	Replies with the port ID of the specified well-known port, or C<undef>.
		744
		745	=item devnull => ...
		746
		747	Generic data sink/CPU heat conversion.
		748
		749	=item relay => $port, @msg
		750
		751	Simply forwards the message to the given port.
		752
		753	=item eval => $string[ @reply]
		754
		755	Evaluates the given string. If C<@reply> is given, then a message of the
		756	form C<@reply, $@, @evalres> is sent.
		757
		758	Example: crash another node.
		759
		760	snd $othernode, eval => "exit";
		761
		762	=item time => @reply
		763
		764	Replies the the current node time to C<@reply>.
		765
		766	Example: tell the current node to send the current time to C<$myport> in a
		767	C<timereply> message.
		768
		769	snd $NODE, time => $myport, timereply => 1, 2;
		770	# => snd $myport, timereply => 1, 2, <time>
		771
		772	=back
		773
		774	=head1 AnyEvent::MP vs. Distributed Erlang
		775
		776	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		777	== aemp node, Erlang process == aemp port), so many of the documents and
		778	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		779	sample:
		780
		781	http://www.Erlang.se/doc/programming_rules.shtml
		782	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		783	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		784	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		785
		786	Despite the similarities, there are also some important differences:
		787
		788	=over 4
		789
		790	=item * Node references contain the recipe on how to contact them.
		791
		792	Erlang relies on special naming and DNS to work everywhere in the
		793	same way. AEMP relies on each node knowing it's own address(es), with
		794	convenience functionality.
		795
		796	This means that AEMP requires a less tightly controlled environment at the
		797	cost of longer node references and a slightly higher management overhead.
		798
		799	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		800
		801	Erlang uses processes that selctively receive messages, and therefore
		802	needs a queue. AEMP is event based, queuing messages would serve no useful
		803	purpose.
		804
		805	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
		806
		807	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		808
		809	Sending messages in Erlang is synchronous and blocks the process. AEMP
		810	sends are immediate, connection establishment is handled in the
		811	background.
		812
		813	=item * Erlang can silently lose messages, AEMP cannot.
		814
		815	Erlang makes few guarantees on messages delivery - messages can get lost
		816	without any of the processes realising it (i.e. you send messages a, b,
		817	and c, and the other side only receives messages a and c).
		818
		819	AEMP guarantees correct ordering, and the guarantee that there are no
		820	holes in the message sequence.
		821
		822	=item * In Erlang, processes can be declared dead and later be found to be
		823	alive.
		824
		825	In Erlang it can happen that a monitored process is declared dead and
		826	linked processes get killed, but later it turns out that the process is
		827	still alive - and can receive messages.
		828
		829	In AEMP, when port monitoring detects a port as dead, then that port will
		830	eventually be killed - it cannot happen that a node detects a port as dead
		831	and then later sends messages to it, finding it is still alive.
		832
		833	=item * Erlang can send messages to the wrong port, AEMP does not.
		834
		835	In Erlang it is quite possible that a node that restarts reuses a process
		836	ID known to other nodes for a completely different process, causing
		837	messages destined for that process to end up in an unrelated process.
		838
		839	AEMP never reuses port IDs, so old messages or old port IDs floating
		840	around in the network will not be sent to an unrelated port.
		841
		842	=item * Erlang uses unprotected connections, AEMP uses secure
		843	authentication and can use TLS.
		844
		845	AEMP can use a proven protocol - SSL/TLS - to protect connections and
		846	securely authenticate nodes.
		847
		848	=item * The AEMP protocol is optimised for both text-based and binary
		849	communications.
		850
		851	The AEMP protocol, unlike the Erlang protocol, supports both
		852	language-independent text-only protocols (good for debugging) and binary,
		853	language-specific serialisers (e.g. Storable).
		854
		855	It has also been carefully designed to be implementable in other languages
		856	with a minimum of work while gracefully degrading fucntionality to make the
		857	protocol simple.
		858
		859	=item * AEMP has more flexible monitoring options than Erlang.
		860
		861	In Erlang, you can chose to receive I<all> exit signals as messages
		862	or I<none>, there is no in-between, so monitoring single processes is
		863	difficult to implement. Monitoring in AEMP is more flexible than in
		864	Erlang, as one can choose between automatic kill, exit message or callback
		865	on a per-process basis.
		866
		867	=item * Erlang tries to hide remote/local connections, AEMP does not.
		868
		869	Monitoring in Erlang is not an indicator of process death/crashes,
		870	as linking is (except linking is unreliable in Erlang).
		871
		872	In AEMP, you don't "look up" registered port names or send to named ports
		873	that might or might not be persistent. Instead, you normally spawn a port
		874	on the remote node. The init function monitors the you, and you monitor
		875	the remote port. Since both monitors are local to the node, they are much
		876	more reliable.
		877
		878	This also saves round-trips and avoids sending messages to the wrong port
		879	(hard to do in Erlang).
		880
		881	=back
		882
		883	=head1 RATIONALE
		884
		885	=over 4
		886
		887	=item Why strings for ports and noderefs, why not objects?
		888
		889	We considered "objects", but found that the actual number of methods
		890	thatc an be called are very low. Since port IDs and noderefs travel over
		891	the network frequently, the serialising/deserialising would add lots of
		892	overhead, as well as having to keep a proxy object.
		893
		894	Strings can easily be printed, easily serialised etc. and need no special
		895	procedures to be "valid".
		896
		897	And a a miniport consists of a single closure stored in a global hash - it
		898	can't become much cheaper.
		899
		900	=item Why favour JSON, why not real serialising format such as Storable?
		901
		902	In fact, any AnyEvent::MP node will happily accept Storable as framing
		903	format, but currently there is no way to make a node use Storable by
		904	default.
		905
		906	The default framing protocol is JSON because a) JSON::XS is many times
		907	faster for small messages and b) most importantly, after years of
		908	experience we found that object serialisation is causing more problems
		909	than it gains: Just like function calls, objects simply do not travel
		910	easily over the network, mostly because they will always be a copy, so you
		911	always have to re-think your design.
		912
		913	Keeping your messages simple, concentrating on data structures rather than
		914	objects, will keep your messages clean, tidy and efficient.
278		915
279	=back	916	=back
280		917
281	=head1 SEE ALSO	918	=head1 SEE ALSO
282		919

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Revision 1.49 by root, Thu Aug 13 15:29:58 2009 UTC