[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 1.85 by root, Tue Sep 8 01:54:13 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 node ID
		10	NODE # returns this node's node ID
11		11
		12	$SELF # receiving/own port id in rcv callbacks
		13
		14	# initialise the node so it can send/receive messages
		15	configure;
		16
		17	# ports are message destinations
		18
		19	# sending messages
12	snd $port, type => data...;	20	snd $port, type => data...;
		21	snd $port, @msg;
		22	snd @msg_with_first_element_being_a_port;
13		23
14	rcv $port, smartmatch => $cb->($port, @msg);	24	# creating/using ports, the simple way
		25	my $simple_port = port { my @msg = @_ };
15		26
16	# examples:	27	# creating/using ports, tagged message matching
		28	my $port = port;
17	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
18	rcv $port1, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
19	snd $port2, ping => $port1;
20		31
21	# more, smarter, matches (_any_ is exported by this module)	32	# create a port on another node
22	rcv $port, [child_died => $pid] => sub { ...	33	my $port = spawn $node, $initfunc, @initdata;
23	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	34
		35	# monitoring
		36	mon $port, $cb->(@msg) # callback is invoked on death
		37	mon $port, $otherport # kill otherport on abnormal death
		38	mon $port, $otherport, @msg # send message on death
		39
		40	=head1 CURRENT STATUS
		41
		42	bin/aemp - stable.
		43	AnyEvent::MP - stable API, should work.
		44	AnyEvent::MP::Intro - explains most concepts.
		45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable but incomplete, protocol not yet final.
		47
		48	stay tuned.
24		49
25	=head1 DESCRIPTION	50	=head1 DESCRIPTION
26		51
27	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
28		53
29	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
30	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
		56
		57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
		58	manual page and the examples under F<eg/>.
31		59
32	=head1 CONCEPTS	60	=head1 CONCEPTS
33		61
34	=over 4	62	=over 4
35		63
36	=item port	64	=item port
37		65
38	A port is something you can send messages to with the C<snd> function, and	66	Not to be confused with a TCP port, a "port" is something you can send
39	you can register C<rcv> handlers with. All C<rcv> handlers will receive	67	messages to (with the C<snd> function).
40	messages they match, messages will not be queued.
41		68
42	=item port id - C<pid@host#portname>	69	Ports allow you to register C<rcv> handlers that can match all or just
		70	some messages. Messages send to ports will not be queued, regardless of
		71	anything was listening for them or not.
43		72
44	A port id is always the node id, a hash-mark (C<#>) as separator, followed	73	=item port ID - C<nodeid#portname>
45	by a port name.
46		74
47	A port name can be a well known port (basically an identifier/bareword),	75	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	76	separator, and a port name (a printable string of unspecified format).
49	identifier.
50		77
51	=item node	78	=item node
52		79
53	A node is a single process containing at least one port - the node	80	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,	81	which enables nodes to manage each other remotely, and to create new
55	among other things.	82	ports.
56		83
57	Initially, nodes are either private (single-process only) or hidden	84	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"	85	(no listening ports). Private nodes cannot talk to other private nodes
59	can you send them messages form unrelated other nodes.	86	currently.
60		87
61	Public nodes automatically connect to all other public nodes in a network	88	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
62	when they connect, creating a full mesh.
63		89
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	90	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	91	network. Depending on the configuration used, node IDs can look like a
68	node (for public nodes).	92	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		93	doesn't interpret node IDs in any way.
		94
		95	=item binds - C<ip:port>
		96
		97	Nodes can only talk to each other by creating some kind of connection to
		98	each other. To do this, nodes should listen on one or more local transport
		99	endpoints - binds. Currently, only standard C<ip:port> specifications can
		100	be used, which specify TCP ports to listen on.
		101
		102	=item seed nodes
		103
		104	When a node starts, it knows nothing about the network. To teach the node
		105	about the network it first has to contact some other node within the
		106	network. This node is called a seed.
		107
		108	Apart from the fact that other nodes know them as seed nodes and they have
		109	to have fixed listening addresses, seed nodes are perfectly normal nodes -
		110	any node can function as a seed node for others.
		111
		112	In addition to discovering the network, seed nodes are also used to
		113	maintain the network and to connect nodes that otherwise would have
		114	trouble connecting. They form the backbone of the AnyEvent::MP network.
		115
		116	Seed nodes are expected to be long-running, and at least one seed node
		117	should always be available. They should also be relatively responsive - a
		118	seed node that blocks for long periods will slow down everybody else.
		119
		120	=item seeds - C<host:port>
		121
		122	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		123	TCP port) of nodes thta should be used as seed nodes.
		124
		125	The nodes listening on those endpoints are expected to be long-running,
		126	and at least one of those should always be available. When nodes run out
		127	of connections (e.g. due to a network error), they try to re-establish
		128	connections to some seednodes again to join the network.
69		129
70	=back	130	=back
71		131
72	=head1 FUNCTIONS	132	=head1 VARIABLES/FUNCTIONS
73		133
74	=over 4	134	=over 4
75		135
76	=cut	136	=cut
77		137
78	package AnyEvent::MP;	138	package AnyEvent::MP;
79		139
80	use AnyEvent::MP::Util ();
81	use AnyEvent::MP::Node;	140	use AnyEvent::MP::Kernel;
82	use AnyEvent::MP::Transport;
83		141
84	use utf8;
85	use common::sense;	142	use common::sense;
86		143
87	use Carp ();	144	use Carp ();
88		145
89	use AE ();	146	use AE ();
90		147
91	use base "Exporter";	148	use base "Exporter";
92		149
93	our $VERSION = '0.0';	150	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
94	our @EXPORT = qw(NODE $NODE $PORT snd rcv _any_);
95		151
96	our $DEFAULT_SECRET;	152	our @EXPORT = qw(
97	our $DEFAULT_PORT = "4040";	153	NODE $NODE *SELF node_of after
		154	configure
		155	snd rcv mon mon_guard kil reg psub spawn
		156	port
		157	);
98		158
99	our $CONNECT_INTERVAL = 5; # new connect every 5s, at least	159	our $SELF;
100	our $CONNECT_TIMEOUT = 30; # includes handshake
101		160
102	sub default_secret {	161	sub _self_die() {
103	unless (defined $DEFAULT_SECRET) {	162	my $msg = $@;
104	if (open my $fh, "<$ENV{HOME}/.aemp-secret") {	163	$msg =~ s/\n+$// unless ref $msg;
105	sysread $fh, $DEFAULT_SECRET, -s $fh;	164	kil $SELF, die => $msg;
106	} else {	165	}
107	$DEFAULT_SECRET = AnyEvent::MP::Util::nonce 32;	166
		167	=item $thisnode = NODE / $NODE
		168
		169	The C<NODE> function returns, and the C<$NODE> variable contains, the node
		170	ID of the node running in the current process. This value is initialised by
		171	a call to C<configure>.
		172
		173	=item $nodeid = node_of $port
		174
		175	Extracts and returns the node ID from a port ID or a node ID.
		176
		177	=item configure $profile, key => value...
		178
		179	=item configure key => value...
		180
		181	Before a node can talk to other nodes on the network (i.e. enter
		182	"distributed mode") it has to configure itself - the minimum a node needs
		183	to know is its own name, and optionally it should know the addresses of
		184	some other nodes in the network to discover other nodes.
		185
		186	This function configures a node - it must be called exactly once (or
		187	never) before calling other AnyEvent::MP functions.
		188
		189	=over 4
		190
		191	=item step 1, gathering configuration from profiles
		192
		193	The function first looks up a profile in the aemp configuration (see the
		194	L<aemp> commandline utility). The profile name can be specified via the
		195	named C<profile> parameter or can simply be the first parameter). If it is
		196	missing, then the nodename (F<uname -n>) will be used as profile name.
		197
		198	The profile data is then gathered as follows:
		199
		200	First, all remaining key => value pairs (all of which are conveniently
		201	undocumented at the moment) will be interpreted as configuration
		202	data. Then they will be overwritten by any values specified in the global
		203	default configuration (see the F<aemp> utility), then the chain of
		204	profiles chosen by the profile name (and any C<parent> attributes).
		205
		206	That means that the values specified in the profile have highest priority
		207	and the values specified directly via C<configure> have lowest priority,
		208	and can only be used to specify defaults.
		209
		210	If the profile specifies a node ID, then this will become the node ID of
		211	this process. If not, then the profile name will be used as node ID. The
		212	special node ID of C<anon/> will be replaced by a random node ID.
		213
		214	=item step 2, bind listener sockets
		215
		216	The next step is to look up the binds in the profile, followed by binding
		217	aemp protocol listeners on all binds specified (it is possible and valid
		218	to have no binds, meaning that the node cannot be contacted form the
		219	outside. This means the node cannot talk to other nodes that also have no
		220	binds, but it can still talk to all "normal" nodes).
		221
		222	If the profile does not specify a binds list, then a default of C<*> is
		223	used, meaning the node will bind on a dynamically-assigned port on every
		224	local IP address it finds.
		225
		226	=item step 3, connect to seed nodes
		227
		228	As the last step, the seeds list from the profile is passed to the
		229	L<AnyEvent::MP::Global> module, which will then use it to keep
		230	connectivity with at least one node at any point in time.
		231
		232	=back
		233
		234	Example: become a distributed node using the locla node name as profile.
		235	This should be the most common form of invocation for "daemon"-type nodes.
		236
		237	configure
		238
		239	Example: become an anonymous node. This form is often used for commandline
		240	clients.
		241
		242	configure nodeid => "anon/";
		243
		244	Example: configure a node using a profile called seed, which si suitable
		245	for a seed node as it binds on all local addresses on a fixed port (4040,
		246	customary for aemp).
		247
		248	# use the aemp commandline utility
		249	# aemp profile seed nodeid anon/ binds '*:4040'
		250
		251	# then use it
		252	configure profile => "seed";
		253
		254	# or simply use aemp from the shell again:
		255	# aemp run profile seed
		256
		257	# or provide a nicer-to-remember nodeid
		258	# aemp run profile seed nodeid "$(hostname)"
		259
		260	=item $SELF
		261
		262	Contains the current port id while executing C<rcv> callbacks or C<psub>
		263	blocks.
		264
		265	=item *SELF, SELF, %SELF, @SELF...
		266
		267	Due to some quirks in how perl exports variables, it is impossible to
		268	just export C<$SELF>, all the symbols named C<SELF> are exported by this
		269	module, but only C<$SELF> is currently used.
		270
		271	=item snd $port, type => @data
		272
		273	=item snd $port, @msg
		274
		275	Send the given message to the given port, which can identify either a
		276	local or a remote port, and must be a port ID.
		277
		278	While the message can be almost anything, it is highly recommended to
		279	use a string as first element (a port ID, or some word that indicates a
		280	request type etc.) and to consist if only simple perl values (scalars,
		281	arrays, hashes) - if you think you need to pass an object, think again.
		282
		283	The message data logically becomes read-only after a call to this
		284	function: modifying any argument (or values referenced by them) is
		285	forbidden, as there can be considerable time between the call to C<snd>
		286	and the time the message is actually being serialised - in fact, it might
		287	never be copied as within the same process it is simply handed to the
		288	receiving port.
		289
		290	The type of data you can transfer depends on the transport protocol: when
		291	JSON is used, then only strings, numbers and arrays and hashes consisting
		292	of those are allowed (no objects). When Storable is used, then anything
		293	that Storable can serialise and deserialise is allowed, and for the local
		294	node, anything can be passed. Best rely only on the common denominator of
		295	these.
		296
		297	=item $local_port = port
		298
		299	Create a new local port object and returns its port ID. Initially it has
		300	no callbacks set and will throw an error when it receives messages.
		301
		302	=item $local_port = port { my @msg = @_ }
		303
		304	Creates a new local port, and returns its ID. Semantically the same as
		305	creating a port and calling C<rcv $port, $callback> on it.
		306
		307	The block will be called for every message received on the port, with the
		308	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		309	port to be C<kil>ed. The message will be passed as-is, no extra argument
		310	(i.e. no port ID) will be passed to the callback.
		311
		312	If you want to stop/destroy the port, simply C<kil> it:
		313
		314	my $port = port {
		315	my @msg = @_;
108	}	316	...
109	}	317	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	});	318	};
187		319
188	$noderef = $DEFAULT_PORT unless length $noderef;	320	=cut
189		321
190	my $idx;	322	sub rcv($@);
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		323
198	$cv->begin;	324	sub _kilme {
199	AnyEvent::Socket::resolve_sockaddr $nodename, $t \|\| "aemp=$DEFAULT_PORT", "tcp", 0, undef, sub {	325	die "received message on port without callback";
200	for (@_) {	326	}
201	my ($service, $host) = AnyEvent::Socket::unpack_sockaddr $_->[3];	327
202	push @res, [	328	sub port(;&) {
203	$pri += 1e-5,	329	my $id = "$UNIQ." . $ID++;
204	AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $host, $service	330	my $port = "$NODE#$id";
205	];	331
		332	rcv $port, shift \|\| \&_kilme;
		333
		334	$port
		335	}
		336
		337	=item rcv $local_port, $callback->(@msg)
		338
		339	Replaces the default callback on the specified port. There is no way to
		340	remove the default callback: use C<sub { }> to disable it, or better
		341	C<kil> the port when it is no longer needed.
		342
		343	The global C<$SELF> (exported by this module) contains C<$port> while
		344	executing the callback. Runtime errors during callback execution will
		345	result in the port being C<kil>ed.
		346
		347	The default callback received all messages not matched by a more specific
		348	C<tag> match.
		349
		350	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		351
		352	Register (or replace) callbacks to be called on messages starting with the
		353	given tag on the given port (and return the port), or unregister it (when
		354	C<$callback> is C<$undef> or missing). There can only be one callback
		355	registered for each tag.
		356
		357	The original message will be passed to the callback, after the first
		358	element (the tag) has been removed. The callback will use the same
		359	environment as the default callback (see above).
		360
		361	Example: create a port and bind receivers on it in one go.
		362
		363	my $port = rcv port,
		364	msg1 => sub { ... },
		365	msg2 => sub { ... },
		366	;
		367
		368	Example: create a port, bind receivers and send it in a message elsewhere
		369	in one go:
		370
		371	snd $otherport, reply =>
		372	rcv port,
		373	msg1 => sub { ... },
		374	...
		375	;
		376
		377	Example: temporarily register a rcv callback for a tag matching some port
		378	(e.g. for a rpc reply) and unregister it after a message was received.
		379
		380	rcv $port, $otherport => sub {
		381	my @reply = @_;
		382
		383	rcv $SELF, $otherport;
		384	};
		385
		386	=cut
		387
		388	sub rcv($@) {
		389	my $port = shift;
		390	my ($nodeid, $portid) = split /#/, $port, 2;
		391
		392	$NODE{$nodeid} == $NODE{""}
		393	or Carp::croak "$port: rcv can only be called on local ports, caught";
		394
		395	while (@_) {
		396	if (ref $_[0]) {
		397	if (my $self = $PORT_DATA{$portid}) {
		398	"AnyEvent::MP::Port" eq ref $self
		399	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		400
		401	$self->[2] = shift;
		402	} else {
		403	my $cb = shift;
		404	$PORT{$portid} = sub {
		405	local $SELF = $port;
		406	eval { &$cb }; _self_die if $@;
206	}	407	};
207	$cv->end;	408	}
		409	} elsif (defined $_[0]) {
		410	my $self = $PORT_DATA{$portid} \|\|= do {
		411	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		412
		413	$PORT{$portid} = sub {
		414	local $SELF = $port;
		415
		416	if (my $cb = $self->[1]{$_[0]}) {
		417	shift;
		418	eval { &$cb }; _self_die if $@;
		419	} else {
		420	&{ $self->[0] };
		421	}
		422	};
		423
		424	$self
208	};	425	};
209		426
210	# my (undef, undef, undef, undef, @ipv4) = gethostbyname $nodename;	427	"AnyEvent::MP::Port" eq ref $self
211	#	428	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
212	# for (@ipv4) {	429
213	# push @res, [	430	my ($tag, $cb) = splice @_, 0, 2;
214	# $pri,	431
215	# AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $_, $t \|\| $DEFAULT_PORT,	432	if (defined $cb) {
216	# ];	433	$self->[1]{$tag} = $cb;
217	# }
218	} else {	434	} else {
219	my ($host, $port) = AnyEvent::Socket::parse_hostport $t, "aemp=$DEFAULT_PORT"	435	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	}	436	}
233	}	437	}
234	}	438	}
235		439
236	$cv->end;	440	$port
237
238	$cv
239	}	441	}
240		442
241	sub become_public {	443	=item $closure = psub { BLOCK }
242	return if $PUBLIC;
243		444
244	my $noderef = join ",", ref $_[0] ? @{+shift} : shift;	445	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
245	my @args = @_;	446	closure is executed, sets up the environment in the same way as in C<rcv>
		447	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
246		448
247	$NODE = (normalise_noderef $noderef)->recv;	449	This is useful when you register callbacks from C<rcv> callbacks:
248		450
249	my $self = new AnyEvent::MP::Node::Self noderef => $NODE;	451	rcv delayed_reply => sub {
250		452	my ($delay, @reply) = @_;
251	$NODE{""} = $self; # empty string == local node	453	my $timer = AE::timer $delay, 0, psub {
252		454	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	;	455	};
		456	};
		457
		458	=cut
		459
		460	sub psub(&) {
		461	my $cb = shift;
		462
		463	my $port = $SELF
		464	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		465
		466	sub {
		467	local $SELF = $port;
		468
		469	if (wantarray) {
		470	my @res = eval { &$cb };
		471	_self_die if $@;
		472	@res
		473	} else {
		474	my $res = eval { &$cb };
		475	_self_die if $@;
		476	$res
		477	}
274	}	478	}
		479	}
275		480
276	$PUBLIC = 1;	481	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
		482
		483	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		484
		485	=item $guard = mon $port # kill $SELF when $port dies
		486
		487	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		488
		489	Monitor the given port and do something when the port is killed or
		490	messages to it were lost, and optionally return a guard that can be used
		491	to stop monitoring again.
		492
		493	In the first form (callback), the callback is simply called with any
		494	number of C<@reason> elements (no @reason means that the port was deleted
		495	"normally"). Note also that I<< the callback B<must> never die >>, so use
		496	C<eval> if unsure.
		497
		498	In the second form (another port given), the other port (C<$rcvport>)
		499	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		500	"normal" kils nothing happens, while under all other conditions, the other
		501	port is killed with the same reason.
		502
		503	The third form (kill self) is the same as the second form, except that
		504	C<$rvport> defaults to C<$SELF>.
		505
		506	In the last form (message), a message of the form C<@msg, @reason> will be
		507	C<snd>.
		508
		509	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		510	alert was raised), they are removed and will not trigger again.
		511
		512	As a rule of thumb, monitoring requests should always monitor a port from
		513	a local port (or callback). The reason is that kill messages might get
		514	lost, just like any other message. Another less obvious reason is that
		515	even monitoring requests can get lost (for example, when the connection
		516	to the other node goes down permanently). When monitoring a port locally
		517	these problems do not exist.
		518
		519	C<mon> effectively guarantees that, in the absence of hardware failures,
		520	after starting the monitor, either all messages sent to the port will
		521	arrive, or the monitoring action will be invoked after possible message
		522	loss has been detected. No messages will be lost "in between" (after
		523	the first lost message no further messages will be received by the
		524	port). After the monitoring action was invoked, further messages might get
		525	delivered again.
		526
		527	Inter-host-connection timeouts and monitoring depend on the transport
		528	used. The only transport currently implemented is TCP, and AnyEvent::MP
		529	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		530	non-idle connection, and usually around two hours for idle conenctions).
		531
		532	This means that monitoring is good for program errors and cleaning up
		533	stuff eventually, but they are no replacement for a timeout when you need
		534	to ensure some maximum latency.
		535
		536	Example: call a given callback when C<$port> is killed.
		537
		538	mon $port, sub { warn "port died because of <@_>\n" };
		539
		540	Example: kill ourselves when C<$port> is killed abnormally.
		541
		542	mon $port;
		543
		544	Example: send us a restart message when another C<$port> is killed.
		545
		546	mon $port, $self => "restart";
		547
		548	=cut
		549
		550	sub mon {
		551	my ($nodeid, $port) = split /#/, shift, 2;
		552
		553	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
		554
		555	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		556
		557	unless (ref $cb) {
		558	if (@_) {
		559	# send a kill info message
		560	my (@msg) = ($cb, @_);
		561	$cb = sub { snd @msg, @_ };
		562	} else {
		563	# simply kill other port
		564	my $port = $cb;
		565	$cb = sub { kil $port, @_ if @_ };
		566	}
		567	}
		568
		569	$node->monitor ($port, $cb);
		570
		571	defined wantarray
		572	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		573	}
		574
		575	=item $guard = mon_guard $port, $ref, $ref...
		576
		577	Monitors the given C<$port> and keeps the passed references. When the port
		578	is killed, the references will be freed.
		579
		580	Optionally returns a guard that will stop the monitoring.
		581
		582	This function is useful when you create e.g. timers or other watchers and
		583	want to free them when the port gets killed (note the use of C<psub>):
		584
		585	$port->rcv (start => sub {
		586	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
		587	undef $timer if 0.9 < rand;
		588	});
		589	});
		590
		591	=cut
		592
		593	sub mon_guard {
		594	my ($port, @refs) = @_;
		595
		596	#TODO: mon-less form?
		597
		598	mon $port, sub { 0 && @refs }
		599	}
		600
		601	=item kil $port[, @reason]
		602
		603	Kill the specified port with the given C<@reason>.
		604
		605	If no C<@reason> is specified, then the port is killed "normally" (ports
		606	monitoring other ports will not necessarily die because a port dies
		607	"normally").
		608
		609	Otherwise, linked ports get killed with the same reason (second form of
		610	C<mon>, see above).
		611
		612	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		613	will be reported as reason C<< die => $@ >>.
		614
		615	Transport/communication errors are reported as C<< transport_error =>
		616	$message >>.
		617
		618	=cut
		619
		620	=item $port = spawn $node, $initfunc[, @initdata]
		621
		622	Creates a port on the node C<$node> (which can also be a port ID, in which
		623	case it's the node where that port resides).
		624
		625	The port ID of the newly created port is returned immediately, and it is
		626	possible to immediately start sending messages or to monitor the port.
		627
		628	After the port has been created, the init function is called on the remote
		629	node, in the same context as a C<rcv> callback. This function must be a
		630	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		631	specify a function in the main program, use C<::name>.
		632
		633	If the function doesn't exist, then the node tries to C<require>
		634	the package, then the package above the package and so on (e.g.
		635	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		636	exists or it runs out of package names.
		637
		638	The init function is then called with the newly-created port as context
		639	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		640	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		641	the port might not get created.
		642
		643	A common idiom is to pass a local port, immediately monitor the spawned
		644	port, and in the remote init function, immediately monitor the passed
		645	local port. This two-way monitoring ensures that both ports get cleaned up
		646	when there is a problem.
		647
		648	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		649	caller before C<spawn> returns (by delaying invocation when spawn is
		650	called for the local node).
		651
		652	Example: spawn a chat server port on C<$othernode>.
		653
		654	# this node, executed from within a port context:
		655	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		656	mon $server;
		657
		658	# init function on C<$othernode>
		659	sub connect {
		660	my ($srcport) = @_;
		661
		662	mon $srcport;
		663
		664	rcv $SELF, sub {
		665	...
		666	};
		667	}
		668
		669	=cut
		670
		671	sub _spawn {
		672	my $port = shift;
		673	my $init = shift;
		674
		675	# rcv will create the actual port
		676	local $SELF = "$NODE#$port";
		677	eval {
		678	&{ load_func $init }
		679	};
		680	_self_die if $@;
		681	}
		682
		683	sub spawn(@) {
		684	my ($nodeid, undef) = split /#/, shift, 2;
		685
		686	my $id = "$RUNIQ." . $ID++;
		687
		688	$_[0] =~ /::/
		689	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		690
		691	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		692
		693	"$nodeid#$id"
		694	}
		695
		696	=item after $timeout, @msg
		697
		698	=item after $timeout, $callback
		699
		700	Either sends the given message, or call the given callback, after the
		701	specified number of seconds.
		702
		703	This is simply a utility function that comes in handy at times - the
		704	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		705	so it may go away in the future.
		706
		707	=cut
		708
		709	sub after($@) {
		710	my ($timeout, @action) = @_;
		711
		712	my $t; $t = AE::timer $timeout, 0, sub {
		713	undef $t;
		714	ref $action[0]
		715	? $action[0]()
		716	: snd @action;
		717	};
277	}	718	}
278		719
279	=back	720	=back
280		721
		722	=head1 AnyEvent::MP vs. Distributed Erlang
		723
		724	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		725	== aemp node, Erlang process == aemp port), so many of the documents and
		726	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		727	sample:
		728
		729	http://www.Erlang.se/doc/programming_rules.shtml
		730	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		731	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		732	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		733
		734	Despite the similarities, there are also some important differences:
		735
		736	=over 4
		737
		738	=item * Node IDs are arbitrary strings in AEMP.
		739
		740	Erlang relies on special naming and DNS to work everywhere in the same
		741	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		742	configuration or DNS), but will otherwise discover other odes itself.
		743
		744	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		745	uses "local ports are like remote ports".
		746
		747	The failure modes for local ports are quite different (runtime errors
		748	only) then for remote ports - when a local port dies, you I<know> it dies,
		749	when a connection to another node dies, you know nothing about the other
		750	port.
		751
		752	Erlang pretends remote ports are as reliable as local ports, even when
		753	they are not.
		754
		755	AEMP encourages a "treat remote ports differently" philosophy, with local
		756	ports being the special case/exception, where transport errors cannot
		757	occur.
		758
		759	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		760
		761	Erlang uses processes that selectively receive messages, and therefore
		762	needs a queue. AEMP is event based, queuing messages would serve no
		763	useful purpose. For the same reason the pattern-matching abilities of
		764	AnyEvent::MP are more limited, as there is little need to be able to
		765	filter messages without dequeuing them.
		766
		767	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
		768
		769	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		770
		771	Sending messages in Erlang is synchronous and blocks the process (and
		772	so does not need a queue that can overflow). AEMP sends are immediate,
		773	connection establishment is handled in the background.
		774
		775	=item * Erlang suffers from silent message loss, AEMP does not.
		776
		777	Erlang makes few guarantees on messages delivery - messages can get lost
		778	without any of the processes realising it (i.e. you send messages a, b,
		779	and c, and the other side only receives messages a and c).
		780
		781	AEMP guarantees correct ordering, and the guarantee that after one message
		782	is lost, all following ones sent to the same port are lost as well, until
		783	monitoring raises an error, so there are no silent "holes" in the message
		784	sequence.
		785
		786	=item * Erlang can send messages to the wrong port, AEMP does not.
		787
		788	In Erlang it is quite likely that a node that restarts reuses a process ID
		789	known to other nodes for a completely different process, causing messages
		790	destined for that process to end up in an unrelated process.
		791
		792	AEMP never reuses port IDs, so old messages or old port IDs floating
		793	around in the network will not be sent to an unrelated port.
		794
		795	=item * Erlang uses unprotected connections, AEMP uses secure
		796	authentication and can use TLS.
		797
		798	AEMP can use a proven protocol - TLS - to protect connections and
		799	securely authenticate nodes.
		800
		801	=item * The AEMP protocol is optimised for both text-based and binary
		802	communications.
		803
		804	The AEMP protocol, unlike the Erlang protocol, supports both programming
		805	language independent text-only protocols (good for debugging) and binary,
		806	language-specific serialisers (e.g. Storable). By default, unless TLS is
		807	used, the protocol is actually completely text-based.
		808
		809	It has also been carefully designed to be implementable in other languages
		810	with a minimum of work while gracefully degrading functionality to make the
		811	protocol simple.
		812
		813	=item * AEMP has more flexible monitoring options than Erlang.
		814
		815	In Erlang, you can chose to receive I<all> exit signals as messages
		816	or I<none>, there is no in-between, so monitoring single processes is
		817	difficult to implement. Monitoring in AEMP is more flexible than in
		818	Erlang, as one can choose between automatic kill, exit message or callback
		819	on a per-process basis.
		820
		821	=item * Erlang tries to hide remote/local connections, AEMP does not.
		822
		823	Monitoring in Erlang is not an indicator of process death/crashes, in the
		824	same way as linking is (except linking is unreliable in Erlang).
		825
		826	In AEMP, you don't "look up" registered port names or send to named ports
		827	that might or might not be persistent. Instead, you normally spawn a port
		828	on the remote node. The init function monitors you, and you monitor the
		829	remote port. Since both monitors are local to the node, they are much more
		830	reliable (no need for C<spawn_link>).
		831
		832	This also saves round-trips and avoids sending messages to the wrong port
		833	(hard to do in Erlang).
		834
		835	=back
		836
		837	=head1 RATIONALE
		838
		839	=over 4
		840
		841	=item Why strings for port and node IDs, why not objects?
		842
		843	We considered "objects", but found that the actual number of methods
		844	that can be called are quite low. Since port and node IDs travel over
		845	the network frequently, the serialising/deserialising would add lots of
		846	overhead, as well as having to keep a proxy object everywhere.
		847
		848	Strings can easily be printed, easily serialised etc. and need no special
		849	procedures to be "valid".
		850
		851	And as a result, a miniport consists of a single closure stored in a
		852	global hash - it can't become much cheaper.
		853
		854	=item Why favour JSON, why not a real serialising format such as Storable?
		855
		856	In fact, any AnyEvent::MP node will happily accept Storable as framing
		857	format, but currently there is no way to make a node use Storable by
		858	default (although all nodes will accept it).
		859
		860	The default framing protocol is JSON because a) JSON::XS is many times
		861	faster for small messages and b) most importantly, after years of
		862	experience we found that object serialisation is causing more problems
		863	than it solves: Just like function calls, objects simply do not travel
		864	easily over the network, mostly because they will always be a copy, so you
		865	always have to re-think your design.
		866
		867	Keeping your messages simple, concentrating on data structures rather than
		868	objects, will keep your messages clean, tidy and efficient.
		869
		870	=back
		871
281	=head1 SEE ALSO	872	=head1 SEE ALSO
		873
		874	L<AnyEvent::MP::Intro> - a gentle introduction.
		875
		876	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		877
		878	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		879	your applications.
		880
		881	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		882	all nodes.
282		883
283	L<AnyEvent>.	884	L<AnyEvent>.
284		885
285	=head1 AUTHOR	886	=head1 AUTHOR
286		887

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Revision 1.85 by root, Tue Sep 8 01:54:13 2009 UTC