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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.7 by root, Sat Aug 1 15:04:30 2009 UTC vs.
Revision 1.65 by root, Fri Aug 28 01:00:34 2009 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	NODE # returns this node identifier
10	$NODE # contains this node identifier	9	$NODE # contains this node's noderef
		10	NODE # returns this node's noderef
		11	NODE $port # returns the noderef of the port
11		12
		13	$SELF # receiving/own port id in rcv callbacks
		14
		15	# initialise the node so it can send/receive messages
		16	initialise_node;
		17
		18	# ports are message endpoints
		19
		20	# sending messages
12	snd $port, type => data...;	21	snd $port, type => data...;
		22	snd $port, @msg;
		23	snd @msg_with_first_element_being_a_port;
13		24
14	rcv $port, smartmatch => $cb->($port, @msg);	25	# creating/using ports, the simple way
		26	my $simple_port = port { my @msg = @_; 0 };
15		27
16	# examples:	28	# creating/using ports, tagged message matching
		29	my $port = port;
17	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
18	rcv $port1, pong => sub { warn "pong received\n" };	31	rcv $port, pong => sub { warn "pong received\n"; 0 };
19	snd $port2, ping => $port1;
20		32
21	# more, smarter, matches (_any_ is exported by this module)	33	# create a port on another node
22	rcv $port, [child_died => $pid] => sub { ...	34	my $port = spawn $node, $initfunc, @initdata;
23	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	35
		36	# monitoring
		37	mon $port, $cb->(@msg) # callback is invoked on death
		38	mon $port, $otherport # kill otherport on abnormal death
		39	mon $port, $otherport, @msg # send message on death
		40
		41	=head1 CURRENT STATUS
		42
		43	AnyEvent::MP - stable API, should work
		44	AnyEvent::MP::Intro - outdated
		45	AnyEvent::MP::Kernel - WIP
		46	AnyEvent::MP::Transport - mostly stable
		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.
31		56
		57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
		58	manual page.
		59
32	At the moment, this module family is severly brokena nd underdocumented,	60	At the moment, this module family is severly broken and underdocumented,
33	so do not use. This was uploaded mainly to resreve the CPAN namespace -	61	so do not use. This was uploaded mainly to reserve the CPAN namespace -
34	stay tuned!	62	stay tuned!
35		63
36	=head1 CONCEPTS	64	=head1 CONCEPTS
37		65
38	=over 4	66	=over 4
39		67
40	=item port	68	=item port
41		69
42	A port is something you can send messages to with the C<snd> function, and	70	A port is something you can send messages to (with the C<snd> function).
43	you can register C<rcv> handlers with. All C<rcv> handlers will receive
44	messages they match, messages will not be queued.
45		71
		72	Ports allow you to register C<rcv> handlers that can match all or just
		73	some messages. Messages send to ports will not be queued, regardless of
		74	anything was listening for them or not.
		75
46	=item port id - C<noderef#portname>	76	=item port ID - C<noderef#portname>
47		77
48	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	78	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as
49	by a port name (a printable string of unspecified format).	79	separator, and a port name (a printable string of unspecified format). An
		80	exception is the the node port, whose ID is identical to its node
		81	reference.
50		82
51	=item node	83	=item node
52		84
53	A node is a single process containing at least one port - the node	85	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,	86	which provides nodes to manage each other remotely, and to create new
55	among other things.	87	ports.
56		88
57	Initially, nodes are either private (single-process only) or hidden	89	Nodes are either private (single-process only), slaves (can only talk to
58	(connected to a master node only). Only when they epxlicitly "become	90	public nodes, but do not need an open port) or public nodes (connectable
59	public" can you send them messages from unrelated other nodes.	91	from any other node).
60		92
61	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	93	=item node ID - C<[a-za-Z0-9_\-.:]+>
62		94
63	A noderef is a string that either uniquely identifies a given node (for	95	A node ID is a string that uniquely identifies the node within a
64	private and hidden nodes), or contains a recipe on how to reach a given	96	network. Depending on the configuration used, node IDs can look like a
65	node (for public nodes).	97	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		98	doesn't interpret node IDs in any way.
		99
		100	=item binds - C<ip:port>
		101
		102	Nodes can only talk to each other by creating some kind of connection to
		103	each other. To do this, nodes should listen on one or more local transport
		104	endpoints - binds. Currently, only standard C<ip:port> specifications can
		105	be used, which specify TCP ports to listen on.
		106
		107	=item seeds - C<host:port>
		108
		109	When a node starts, it knows nothing about the network. To teach the node
		110	about the network it first has to contact some other node within the
		111	network. This node is called a seed.
		112
		113	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		114	are expected to be long-running, and at least one of those should always
		115	be available. When nodes run out of connections (e.g. due to a network
		116	error), they try to re-establish connections to some seednodes again to
		117	join the network.
66		118
67	=back	119	=back
68		120
69	=head1 VARIABLES/FUNCTIONS	121	=head1 VARIABLES/FUNCTIONS
70		122
…		…
72		124
73	=cut	125	=cut
74		126
75	package AnyEvent::MP;	127	package AnyEvent::MP;
76		128
77	use AnyEvent::MP::Util ();
78	use AnyEvent::MP::Node;	129	use AnyEvent::MP::Kernel;
79	use AnyEvent::MP::Transport;
80		130
81	use utf8;
82	use common::sense;	131	use common::sense;
83		132
84	use Carp ();	133	use Carp ();
85		134
86	use AE ();	135	use AE ();
87		136
88	use base "Exporter";	137	use base "Exporter";
89		138
90	our $VERSION = '0.01';	139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
91	our @EXPORT = qw(NODE $NODE $PORT snd rcv _any_);
92		140
93	our $DEFAULT_SECRET;	141	our @EXPORT = qw(
94	our $DEFAULT_PORT = "4040";	142	NODE $NODE *SELF node_of after
		143	resolve_node initialise_node
		144	snd rcv mon mon_guard kil reg psub spawn
		145	port
		146	);
95		147
96	our $CONNECT_INTERVAL = 5; # new connect every 5s, at least	148	our $SELF;
97	our $CONNECT_TIMEOUT = 30; # includes handshake
98		149
99	sub default_secret {	150	sub _self_die() {
100	unless (defined $DEFAULT_SECRET) {	151	my $msg = $@;
101	if (open my $fh, "<$ENV{HOME}/.aemp-secret") {	152	$msg =~ s/\n+$// unless ref $msg;
102	sysread $fh, $DEFAULT_SECRET, -s $fh;	153	kil $SELF, die => $msg;
103	} else {
104	$DEFAULT_SECRET = AnyEvent::MP::Util::nonce 32;
105	}
106	}
107
108	$DEFAULT_SECRET
109	}	154	}
110		155
111	=item NODE / $NODE	156	=item $thisnode = NODE / $NODE
112		157
113	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	158	The C<NODE> function returns, and the C<$NODE> variable contains the node
114	the local node. The value is initialised by a call to C<become_public> or	159	ID of the node running in the current process. This value is initialised by
115	C<become_slave>, after which all local port identifiers become invalid.	160	a call to C<initialise_node>.
116		161
117	=cut	162	=item $nodeid = node_of $port
118		163
119	our $UNIQ = sprintf "%x.%x", $$, time; # per-process/node unique cookie	164	Extracts and returns the node ID part from a port ID or a node ID.
120	our $ID = "a0";
121	our $PUBLIC = 0;
122	our $NODE;
123	our $PORT;
124		165
125	our %NODE; # node id to transport mapping, or "undef", for local node	166	=item initialise_node $profile_name
126	our %PORT; # local ports
127	our %LISTENER; # local transports
128		167
129	sub NODE() { $NODE }	168	Before a node can talk to other nodes on the network (i.e. enter
		169	"distributed mode") it has to initialise itself - the minimum a node needs
		170	to know is its own name, and optionally it should know the addresses of
		171	some other nodes in the network to discover other nodes.
130		172
131	{	173	This function initialises a node - it must be called exactly once (or
132	use POSIX ();	174	never) before calling other AnyEvent::MP functions.
133	my $nodename = (POSIX::uname)[1];
134	$NODE = "$$\@$nodename";
135	}
136		175
137	sub _ANY_() { 1 }	176	The first argument is a profile name. If it is C<undef> or missing, then
138	sub _any_() { \&_ANY_ }	177	the current nodename will be used instead (i.e. F<uname -n>).
139		178
140	sub add_node {	179	The function then looks up the profile in the aemp configuration (see the
141	my ($noderef) = @_;	180	L<aemp> commandline utility).
142		181
143	return $NODE{$noderef}	182	If the profile specifies a node ID, then this will become the node ID of
144	if exists $NODE{$noderef};	183	this process. If not, then the profile name will be used as node ID. The
		184	special node ID of C<anon/> will be replaced by a random node ID.
145		185
146	for (split /,/, $noderef) {	186	The next step is to look up the binds in the profile, followed by binding
147	return $NODE{$noderef} = $NODE{$_}	187	aemp protocol listeners on all binds specified (it is possible and valid
148	if exists $NODE{$_};	188	to have no binds, meaning that the node cannot be contacted form the
149	}	189	outside. This means the node cannot talk to other nodes that also have no
		190	binds, but it can still talk to all "normal" nodes).
150		191
151	# for indirect sends, use a different class	192	If the profile does not specify a binds list, then the node ID will be
152	my $node = new AnyEvent::MP::Node::Direct $noderef;	193	treated as if it were of the form C<host:port>, which will be resolved and
		194	used as binds list.
153		195
154	$NODE{$_} = $node	196	Lastly, the seeds list from the profile is passed to the
155	for $noderef, split /,/, $noderef;	197	L<AnyEvent::MP::Global> module, which will then use it to keep
		198	connectivity with at least on of those seed nodes at any point in time.
156		199
157	$node	200	Example: become a distributed node listening on the guessed noderef, or
158	}	201	the one specified via C<aemp> for the current node. This should be the
		202	most common form of invocation for "daemon"-type nodes.
159		203
		204	initialise_node;
		205
		206	Example: become an anonymous node. This form is often used for commandline
		207	clients.
		208
		209	initialise_node "anon/";
		210
		211	Example: become a distributed node. If there is no profile of the given
		212	name, or no binds list was specified, resolve C<localhost:4044> and bind
		213	on the resulting addresses.
		214
		215	initialise_node "localhost:4044";
		216
		217	=item $SELF
		218
		219	Contains the current port id while executing C<rcv> callbacks or C<psub>
		220	blocks.
		221
		222	=item SELF, %SELF, @SELF...
		223
		224	Due to some quirks in how perl exports variables, it is impossible to
		225	just export C<$SELF>, all the symbols called C<SELF> are exported by this
		226	module, but only C<$SELF> is currently used.
		227
160	=item snd $portid, type => @data	228	=item snd $port, type => @data
161		229
162	=item snd $portid, @msg	230	=item snd $port, @msg
163		231
164	Send the given message to the given port ID, which can identify either a	232	Send the given message to the given port ID, which can identify either
165	local or a remote port.	233	a local or a remote port, and must be a port ID.
166		234
167	While the message can be about anything, it is highly recommended to use	235	While the message can be about anything, it is highly recommended to use a
168	a constant string as first element.	236	string as first element (a port ID, or some word that indicates a request
		237	type etc.).
169		238
170	The message data effectively becomes read-only after a call to this	239	The message data effectively becomes read-only after a call to this
171	function: modifying any argument is not allowed and can cause many	240	function: modifying any argument is not allowed and can cause many
172	problems.	241	problems.
173		242
…		…
175	JSON is used, then only strings, numbers and arrays and hashes consisting	244	JSON is used, then only strings, numbers and arrays and hashes consisting
176	of those are allowed (no objects). When Storable is used, then anything	245	of those are allowed (no objects). When Storable is used, then anything
177	that Storable can serialise and deserialise is allowed, and for the local	246	that Storable can serialise and deserialise is allowed, and for the local
178	node, anything can be passed.	247	node, anything can be passed.
179		248
180	=cut	249	=item $local_port = port
181		250
182	sub snd(@) {	251	Create a new local port object and returns its port ID. Initially it has
183	my ($noderef, $port) = split /#/, shift, 2;	252	no callbacks set and will throw an error when it receives messages.
184		253
185	add_node $noderef	254	=item $local_port = port { my @msg = @_ }
186	unless exists $NODE{$noderef};
187		255
188	$NODE{$noderef}->send (["$port", [@_]]);	256	Creates a new local port, and returns its ID. Semantically the same as
189	}	257	creating a port and calling C<rcv $port, $callback> on it.
190		258
		259	The block will be called for every message received on the port, with the
		260	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		261	port to be C<kil>ed. The message will be passed as-is, no extra argument
		262	(i.e. no port ID) will be passed to the callback.
		263
		264	If you want to stop/destroy the port, simply C<kil> it:
		265
		266	my $port = port {
		267	my @msg = @_;
		268	...
		269	kil $SELF;
		270	};
		271
		272	=cut
		273
		274	sub rcv($@);
		275
		276	sub _kilme {
		277	die "received message on port without callback";
		278	}
		279
		280	sub port(;&) {
		281	my $id = "$UNIQ." . $ID++;
		282	my $port = "$NODE#$id";
		283
		284	rcv $port, shift \|\| \&_kilme;
		285
		286	$port
		287	}
		288
191	=item rcv $portid, type => $callback->(@msg)	289	=item rcv $local_port, $callback->(@msg)
192		290
193	=item rcv $portid, $smartmatch => $callback->(@msg)	291	Replaces the default callback on the specified port. There is no way to
		292	remove the default callback: use C<sub { }> to disable it, or better
		293	C<kil> the port when it is no longer needed.
194		294
195	=item rcv $portid, [$smartmatch...] => $callback->(@msg)	295	The global C<$SELF> (exported by this module) contains C<$port> while
		296	executing the callback. Runtime errors during callback execution will
		297	result in the port being C<kil>ed.
196		298
197	Register a callback on the port identified by C<$portid>, which I<must> be	299	The default callback received all messages not matched by a more specific
198	a local port.	300	C<tag> match.
199		301
200	The callback has to return a true value when its work is done, after	302	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
201	which is will be removed, or a false value in which case it will stay
202	registered.
203		303
204	If the match is an array reference, then it will be matched against the	304	Register (or replace) callbacks to be called on messages starting with the
205	first elements of the message, otherwise only the first element is being	305	given tag on the given port (and return the port), or unregister it (when
206	matched.	306	C<$callback> is C<$undef> or missing). There can only be one callback
		307	registered for each tag.
207		308
208	Any element in the match that is specified as C<_any_> (a function	309	The original message will be passed to the callback, after the first
209	exported by this module) matches any single element of the message.	310	element (the tag) has been removed. The callback will use the same
		311	environment as the default callback (see above).
210		312
211	While not required, it is highly recommended that the first matching	313	Example: create a port and bind receivers on it in one go.
212	element is a string identifying the message. The one-string-only match is	314
213	also the most efficient match (by far).	315	my $port = rcv port,
		316	msg1 => sub { ... },
		317	msg2 => sub { ... },
		318	;
		319
		320	Example: create a port, bind receivers and send it in a message elsewhere
		321	in one go:
		322
		323	snd $otherport, reply =>
		324	rcv port,
		325	msg1 => sub { ... },
		326	...
		327	;
		328
		329	Example: temporarily register a rcv callback for a tag matching some port
		330	(e.g. for a rpc reply) and unregister it after a message was received.
		331
		332	rcv $port, $otherport => sub {
		333	my @reply = @_;
		334
		335	rcv $SELF, $otherport;
		336	};
214		337
215	=cut	338	=cut
216		339
217	sub rcv($@) {	340	sub rcv($@) {
218	my ($port, $match, $cb) = @_;	341	my $port = shift;
219
220	my $port = $PORT{$port}
221	or do {
222	my ($noderef, $lport) = split /#/, $port;	342	my ($noderef, $portid) = split /#/, $port, 2;
223	"AnyEvent::MP::Node::Self" eq ref $NODE{$noderef}	343
		344	$NODE{$noderef} == $NODE{""}
224	or Carp::croak "$port: can only rcv on local ports";	345	or Carp::croak "$port: rcv can only be called on local ports, caught";
225		346
226	$PORT{$lport}	347	while (@_) {
227	or Carp::croak "$port: port does not exist";	348	if (ref $_[0]) {
228		349	if (my $self = $PORT_DATA{$portid}) {
229	$PORT{$port} = $PORT{$lport} # also return	350	"AnyEvent::MP::Port" eq ref $self
230	};	351	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
231		352
232	if (!ref $match) {	353	$self->[2] = shift;
233	push @{ $port->{rc0}{$match} }, [$cb];
234	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
235	my ($type, @match) = @$match;
236	@match
237	? push @{ $port->{rcv}{$match->[0]} }, [$cb, \@match]
238	: push @{ $port->{rc0}{$match->[0]} }, [$cb];
239	} else {	354	} else {
240	push @{ $port->{any} }, [$cb, $match];	355	my $cb = shift;
241	}	356	$PORT{$portid} = sub {
242	}	357	local $SELF = $port;
243		358	eval { &$cb }; _self_die if $@;
244	sub _inject {
245	my ($port, $msg) = @{+shift};
246
247	$port = $PORT{$port}
248	or return;
249
250	@_ = @$msg;
251
252	for (@{ $port->{rc0}{$msg->[0]} }) {
253	$_ && &{$_->[0]}
254	&& undef $_;
255	}
256
257	for (@{ $port->{rcv}{$msg->[0]} }) {
258	$_ && [@_[1..$#{$_->[1]}]] ~~ $_->[1]
259	&& &{$_->[0]}
260	&& undef $_;
261	}
262
263	for (@{ $port->{any} }) {
264	$_ && [@_[0..$#{$_->[1]}]] ~~ $_->[1]
265	&& &{$_->[0]}
266	&& undef $_;
267	}
268	}
269
270	sub normalise_noderef($) {
271	my ($noderef) = @_;
272
273	my $cv = AE::cv;
274	my @res;
275
276	$cv->begin (sub {
277	my %seen;
278	my @refs;
279	for (sort { $a->[0] <=> $b->[0] } @res) {
280	push @refs, $_->[1] unless $seen{$_->[1]}++
281	}
282	shift->send (join ",", @refs);
283	});
284
285	$noderef = $DEFAULT_PORT unless length $noderef;
286
287	my $idx;
288	for my $t (split /,/, $noderef) {
289	my $pri = ++$idx;
290
291	#TODO: this should be outside normalise_noderef and in become_public
292	if ($t =~ /^\d*$/) {
293	my $nodename = (POSIX::uname)[1];
294
295	$cv->begin;
296	AnyEvent::Socket::resolve_sockaddr $nodename, $t \|\| "aemp=$DEFAULT_PORT", "tcp", 0, undef, sub {
297	for (@_) {
298	my ($service, $host) = AnyEvent::Socket::unpack_sockaddr $_->[3];
299	push @res, [
300	$pri += 1e-5,
301	AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $host, $service
302	];
303	}	359	};
304	$cv->end;	360	}
		361	} elsif (defined $_[0]) {
		362	my $self = $PORT_DATA{$portid} \|\|= do {
		363	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		364
		365	$PORT{$portid} = sub {
		366	local $SELF = $port;
		367
		368	if (my $cb = $self->[1]{$_[0]}) {
		369	shift;
		370	eval { &$cb }; _self_die if $@;
		371	} else {
		372	&{ $self->[0] };
		373	}
		374	};
		375
		376	$self
305	};	377	};
306		378
307	# my (undef, undef, undef, undef, @ipv4) = gethostbyname $nodename;	379	"AnyEvent::MP::Port" eq ref $self
308	#	380	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
309	# for (@ipv4) {	381
310	# push @res, [	382	my ($tag, $cb) = splice @_, 0, 2;
311	# $pri,	383
312	# AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $_, $t \|\| $DEFAULT_PORT,	384	if (defined $cb) {
313	# ];	385	$self->[1]{$tag} = $cb;
314	# }
315	} else {	386	} else {
316	my ($host, $port) = AnyEvent::Socket::parse_hostport $t, "aemp=$DEFAULT_PORT"	387	delete $self->[1]{$tag};
317	or Carp::croak "$t: unparsable transport descriptor";
318
319	$cv->begin;
320	AnyEvent::Socket::resolve_sockaddr $host, $port, "tcp", 0, undef, sub {
321	for (@_) {
322	my ($service, $host) = AnyEvent::Socket::unpack_sockaddr $_->[3];
323	push @res, [
324	$pri += 1e-5,
325	AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $host, $service
326	];
327	}
328	$cv->end;
329	}	388	}
330	}	389	}
331	}	390	}
332		391
333	$cv->end;	392	$port
334
335	$cv
336	}	393	}
337		394
338	sub become_public {	395	=item $closure = psub { BLOCK }
339	return if $PUBLIC;
340		396
341	my $noderef = join ",", ref $_[0] ? @{+shift} : shift;	397	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
342	my @args = @_;	398	closure is executed, sets up the environment in the same way as in C<rcv>
		399	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
343		400
344	$NODE = (normalise_noderef $noderef)->recv;	401	This is useful when you register callbacks from C<rcv> callbacks:
345		402
346	for my $t (split /,/, $NODE) {	403	rcv delayed_reply => sub {
347	$NODE{$t} = $NODE{""};	404	my ($delay, @reply) = @_;
348		405	my $timer = AE::timer $delay, 0, psub {
349	my ($host, $port) = AnyEvent::Socket::parse_hostport $t;	406	snd @reply, $SELF;
350
351	$LISTENER{$t} = AnyEvent::MP::Transport::mp_server $host, $port,
352	@args,
353	on_error => sub {
354	die "on_error<@_>\n";#d#
355	},
356	on_connect => sub {
357	my ($tp) = @_;
358
359	$NODE{$tp->{remote_id}} = $_[0];
360	},
361	sub {
362	my ($tp) = @_;
363
364	$NODE{"$tp->{peerhost}:$tp->{peerport}"} = $tp;
365	},
366	;	407	};
		408	};
		409
		410	=cut
		411
		412	sub psub(&) {
		413	my $cb = shift;
		414
		415	my $port = $SELF
		416	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		417
		418	sub {
		419	local $SELF = $port;
		420
		421	if (wantarray) {
		422	my @res = eval { &$cb };
		423	_self_die if $@;
		424	@res
		425	} else {
		426	my $res = eval { &$cb };
		427	_self_die if $@;
		428	$res
		429	}
367	}	430	}
		431	}
368		432
369	$PUBLIC = 1;	433	=item $guard = mon $port, $cb->(@reason)
		434
		435	=item $guard = mon $port, $rcvport
		436
		437	=item $guard = mon $port
		438
		439	=item $guard = mon $port, $rcvport, @msg
		440
		441	Monitor the given port and do something when the port is killed or
		442	messages to it were lost, and optionally return a guard that can be used
		443	to stop monitoring again.
		444
		445	C<mon> effectively guarantees that, in the absence of hardware failures,
		446	that after starting the monitor, either all messages sent to the port
		447	will arrive, or the monitoring action will be invoked after possible
		448	message loss has been detected. No messages will be lost "in between"
		449	(after the first lost message no further messages will be received by the
		450	port). After the monitoring action was invoked, further messages might get
		451	delivered again.
		452
		453	Note that monitoring-actions are one-shot: once released, they are removed
		454	and will not trigger again.
		455
		456	In the first form (callback), the callback is simply called with any
		457	number of C<@reason> elements (no @reason means that the port was deleted
		458	"normally"). Note also that I<< the callback B<must> never die >>, so use
		459	C<eval> if unsure.
		460
		461	In the second form (another port given), the other port (C<$rcvport>)
		462	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
		463	"normal" kils nothing happens, while under all other conditions, the other
		464	port is killed with the same reason.
		465
		466	The third form (kill self) is the same as the second form, except that
		467	C<$rvport> defaults to C<$SELF>.
		468
		469	In the last form (message), a message of the form C<@msg, @reason> will be
		470	C<snd>.
		471
		472	As a rule of thumb, monitoring requests should always monitor a port from
		473	a local port (or callback). The reason is that kill messages might get
		474	lost, just like any other message. Another less obvious reason is that
		475	even monitoring requests can get lost (for exmaple, when the connection
		476	to the other node goes down permanently). When monitoring a port locally
		477	these problems do not exist.
		478
		479	Example: call a given callback when C<$port> is killed.
		480
		481	mon $port, sub { warn "port died because of <@_>\n" };
		482
		483	Example: kill ourselves when C<$port> is killed abnormally.
		484
		485	mon $port;
		486
		487	Example: send us a restart message when another C<$port> is killed.
		488
		489	mon $port, $self => "restart";
		490
		491	=cut
		492
		493	sub mon {
		494	my ($noderef, $port) = split /#/, shift, 2;
		495
		496	my $node = $NODE{$noderef} \|\| add_node $noderef;
		497
		498	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		499
		500	unless (ref $cb) {
		501	if (@_) {
		502	# send a kill info message
		503	my (@msg) = ($cb, @_);
		504	$cb = sub { snd @msg, @_ };
		505	} else {
		506	# simply kill other port
		507	my $port = $cb;
		508	$cb = sub { kil $port, @_ if @_ };
		509	}
		510	}
		511
		512	$node->monitor ($port, $cb);
		513
		514	defined wantarray
		515	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		516	}
		517
		518	=item $guard = mon_guard $port, $ref, $ref...
		519
		520	Monitors the given C<$port> and keeps the passed references. When the port
		521	is killed, the references will be freed.
		522
		523	Optionally returns a guard that will stop the monitoring.
		524
		525	This function is useful when you create e.g. timers or other watchers and
		526	want to free them when the port gets killed:
		527
		528	$port->rcv (start => sub {
		529	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		530	undef $timer if 0.9 < rand;
		531	});
		532	});
		533
		534	=cut
		535
		536	sub mon_guard {
		537	my ($port, @refs) = @_;
		538
		539	#TODO: mon-less form?
		540
		541	mon $port, sub { 0 && @refs }
		542	}
		543
		544	=item kil $port[, @reason]
		545
		546	Kill the specified port with the given C<@reason>.
		547
		548	If no C<@reason> is specified, then the port is killed "normally" (linked
		549	ports will not be kileld, or even notified).
		550
		551	Otherwise, linked ports get killed with the same reason (second form of
		552	C<mon>, see below).
		553
		554	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		555	will be reported as reason C<< die => $@ >>.
		556
		557	Transport/communication errors are reported as C<< transport_error =>
		558	$message >>.
		559
		560	=cut
		561
		562	=item $port = spawn $node, $initfunc[, @initdata]
		563
		564	Creates a port on the node C<$node> (which can also be a port ID, in which
		565	case it's the node where that port resides).
		566
		567	The port ID of the newly created port is return immediately, and it is
		568	permissible to immediately start sending messages or monitor the port.
		569
		570	After the port has been created, the init function is
		571	called. This function must be a fully-qualified function name
		572	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		573	program, use C<::name>.
		574
		575	If the function doesn't exist, then the node tries to C<require>
		576	the package, then the package above the package and so on (e.g.
		577	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		578	exists or it runs out of package names.
		579
		580	The init function is then called with the newly-created port as context
		581	object (C<$SELF>) and the C<@initdata> values as arguments.
		582
		583	A common idiom is to pass your own port, monitor the spawned port, and
		584	in the init function, monitor the original port. This two-way monitoring
		585	ensures that both ports get cleaned up when there is a problem.
		586
		587	Example: spawn a chat server port on C<$othernode>.
		588
		589	# this node, executed from within a port context:
		590	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		591	mon $server;
		592
		593	# init function on C<$othernode>
		594	sub connect {
		595	my ($srcport) = @_;
		596
		597	mon $srcport;
		598
		599	rcv $SELF, sub {
		600	...
		601	};
		602	}
		603
		604	=cut
		605
		606	sub _spawn {
		607	my $port = shift;
		608	my $init = shift;
		609
		610	local $SELF = "$NODE#$port";
		611	eval {
		612	&{ load_func $init }
		613	};
		614	_self_die if $@;
		615	}
		616
		617	sub spawn(@) {
		618	my ($noderef, undef) = split /#/, shift, 2;
		619
		620	my $id = "$RUNIQ." . $ID++;
		621
		622	$_[0] =~ /::/
		623	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		624
		625	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
		626
		627	"$noderef#$id"
		628	}
		629
		630	=item after $timeout, @msg
		631
		632	=item after $timeout, $callback
		633
		634	Either sends the given message, or call the given callback, after the
		635	specified number of seconds.
		636
		637	This is simply a utility function that come sin handy at times.
		638
		639	=cut
		640
		641	sub after($@) {
		642	my ($timeout, @action) = @_;
		643
		644	my $t; $t = AE::timer $timeout, 0, sub {
		645	undef $t;
		646	ref $action[0]
		647	? $action[0]()
		648	: snd @action;
		649	};
370	}	650	}
371		651
372	=back	652	=back
373		653
374	=head1 NODE MESSAGES	654	=head1 AnyEvent::MP vs. Distributed Erlang
375		655
376	Nodes understand the following messages sent to them. Many of them take	656	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
377	arguments called C<@reply>, which will simply be used to compose a reply	657	== aemp node, Erlang process == aemp port), so many of the documents and
378	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	658	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
379	the remaining arguments are simply the message data.	659	sample:
		660
		661	http://www.Erlang.se/doc/programming_rules.shtml
		662	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		663	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		664	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		665
		666	Despite the similarities, there are also some important differences:
380		667
381	=over 4	668	=over 4
382		669
383	=cut	670	=item * Node IDs are arbitrary strings in AEMP.
384		671
385	#############################################################################	672	Erlang relies on special naming and DNS to work everywhere in the same
386	# self node code	673	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		674	configuraiton or DNS), but will otherwise discover other odes itself.
387		675
388	sub _new_port($) {	676	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
389	my ($name) = @_;	677	uses "local ports are like remote ports".
390		678
391	my ($noderef, $portname) = split /#/, $name;	679	The failure modes for local ports are quite different (runtime errors
		680	only) then for remote ports - when a local port dies, you I<know> it dies,
		681	when a connection to another node dies, you know nothing about the other
		682	port.
392		683
393	$PORT{$name} =	684	Erlang pretends remote ports are as reliable as local ports, even when
394	$PORT{$portname} = {	685	they are not.
395	names => [$name, $portname],
396	};
397	}
398		686
399	$NODE{""} = new AnyEvent::MP::Node::Self noderef => $NODE;	687	AEMP encourages a "treat remote ports differently" philosophy, with local
400	_new_port "";	688	ports being the special case/exception, where transport errors cannot
		689	occur.
401		690
402	=item devnull => ...	691	=item * Erlang uses processes and a mailbox, AEMP does not queue.
403		692
404	Generic data sink/CPU heat conversion.	693	Erlang uses processes that selectively receive messages, and therefore
		694	needs a queue. AEMP is event based, queuing messages would serve no
		695	useful purpose. For the same reason the pattern-matching abilities of
		696	AnyEvent::MP are more limited, as there is little need to be able to
		697	filter messages without dequeing them.
405		698
406	=cut	699	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
407		700
408	rcv "", devnull => sub { () };	701	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
409		702
410	=item relay => $port, @msg	703	Sending messages in Erlang is synchronous and blocks the process (and
		704	so does not need a queue that can overflow). AEMP sends are immediate,
		705	connection establishment is handled in the background.
411		706
412	Simply forwards the message to the given port.	707	=item * Erlang suffers from silent message loss, AEMP does not.
413		708
414	=cut	709	Erlang makes few guarantees on messages delivery - messages can get lost
		710	without any of the processes realising it (i.e. you send messages a, b,
		711	and c, and the other side only receives messages a and c).
415		712
416	rcv "", relay => sub { \&snd; () };	713	AEMP guarantees correct ordering, and the guarantee that there are no
		714	holes in the message sequence.
417		715
418	=item eval => $string[ @reply]	716	=item * In Erlang, processes can be declared dead and later be found to be
		717	alive.
419		718
420	Evaluates the given string. If C<@reply> is given, then a message of the	719	In Erlang it can happen that a monitored process is declared dead and
421	form C<@reply, $@, @evalres> is sent.	720	linked processes get killed, but later it turns out that the process is
		721	still alive - and can receive messages.
422		722
423	Example: crash another node.	723	In AEMP, when port monitoring detects a port as dead, then that port will
		724	eventually be killed - it cannot happen that a node detects a port as dead
		725	and then later sends messages to it, finding it is still alive.
424		726
425	snd $othernode, eval => "exit";	727	=item * Erlang can send messages to the wrong port, AEMP does not.
426		728
427	=cut	729	In Erlang it is quite likely that a node that restarts reuses a process ID
		730	known to other nodes for a completely different process, causing messages
		731	destined for that process to end up in an unrelated process.
428		732
429	rcv "", eval => sub {	733	AEMP never reuses port IDs, so old messages or old port IDs floating
430	my (undef, $string, @reply) = @_;	734	around in the network will not be sent to an unrelated port.
431	my @res = eval $string;
432	snd @reply, "$@", @res if @reply;
433	()
434	};
435		735
436	=item time => @reply	736	=item * Erlang uses unprotected connections, AEMP uses secure
		737	authentication and can use TLS.
437		738
438	Replies the the current node time to C<@reply>.	739	AEMP can use a proven protocol - SSL/TLS - to protect connections and
		740	securely authenticate nodes.
439		741
440	Example: tell the current node to send the current time to C<$myport> in a	742	=item * The AEMP protocol is optimised for both text-based and binary
441	C<timereply> message.	743	communications.
442		744
443	snd $NODE, time => $myport, timereply => 1, 2;	745	The AEMP protocol, unlike the Erlang protocol, supports both
444	# => snd $myport, timereply => 1, 2, <time>	746	language-independent text-only protocols (good for debugging) and binary,
		747	language-specific serialisers (e.g. Storable).
445		748
446	=cut	749	It has also been carefully designed to be implementable in other languages
		750	with a minimum of work while gracefully degrading fucntionality to make the
		751	protocol simple.
447		752
448	rcv "", time => sub { shift; snd @_, AE::time; () };	753	=item * AEMP has more flexible monitoring options than Erlang.
		754
		755	In Erlang, you can chose to receive I<all> exit signals as messages
		756	or I<none>, there is no in-between, so monitoring single processes is
		757	difficult to implement. Monitoring in AEMP is more flexible than in
		758	Erlang, as one can choose between automatic kill, exit message or callback
		759	on a per-process basis.
		760
		761	=item * Erlang tries to hide remote/local connections, AEMP does not.
		762
		763	Monitoring in Erlang is not an indicator of process death/crashes,
		764	as linking is (except linking is unreliable in Erlang).
		765
		766	In AEMP, you don't "look up" registered port names or send to named ports
		767	that might or might not be persistent. Instead, you normally spawn a port
		768	on the remote node. The init function monitors the you, and you monitor
		769	the remote port. Since both monitors are local to the node, they are much
		770	more reliable.
		771
		772	This also saves round-trips and avoids sending messages to the wrong port
		773	(hard to do in Erlang).
		774
		775	=back
		776
		777	=head1 RATIONALE
		778
		779	=over 4
		780
		781	=item Why strings for ports and noderefs, why not objects?
		782
		783	We considered "objects", but found that the actual number of methods
		784	thatc an be called are very low. Since port IDs and noderefs travel over
		785	the network frequently, the serialising/deserialising would add lots of
		786	overhead, as well as having to keep a proxy object.
		787
		788	Strings can easily be printed, easily serialised etc. and need no special
		789	procedures to be "valid".
		790
		791	And a a miniport consists of a single closure stored in a global hash - it
		792	can't become much cheaper.
		793
		794	=item Why favour JSON, why not real serialising format such as Storable?
		795
		796	In fact, any AnyEvent::MP node will happily accept Storable as framing
		797	format, but currently there is no way to make a node use Storable by
		798	default.
		799
		800	The default framing protocol is JSON because a) JSON::XS is many times
		801	faster for small messages and b) most importantly, after years of
		802	experience we found that object serialisation is causing more problems
		803	than it gains: Just like function calls, objects simply do not travel
		804	easily over the network, mostly because they will always be a copy, so you
		805	always have to re-think your design.
		806
		807	Keeping your messages simple, concentrating on data structures rather than
		808	objects, will keep your messages clean, tidy and efficient.
449		809
450	=back	810	=back
451		811
452	=head1 SEE ALSO	812	=head1 SEE ALSO
453		813

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Revision 1.65 by root, Fri Aug 28 01:00:34 2009 UTC