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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.4 by root, Sat Aug 1 07:36:30 2009 UTC vs.
Revision 1.84 by root, Tue Sep 8 01:42:14 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
		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.
		72
42	=item port id - C<noderef#portname>	73	=item port ID - C<nodeid#portname>
43		74
44	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	75	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
45	by a port name (a printable string of unspecified format).	76	separator, and a port name (a printable string of unspecified format).
46		77
47	=item node	78	=item node
48		79
49	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,
50	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
51	among other things.	82	ports.
52		83
53	Initially, nodes are either private (single-process only) or hidden	84	Nodes are either public (have one or more listening ports) or private
54	(connected to a master node only). Only when they epxlicitly "become	85	(no listening ports). Private nodes cannot talk to other private nodes
55	public" can you send them messages from unrelated other nodes.	86	currently.
56		87
57	=item noderef - C<host:port,host:port...>, C<id@noderef, C<id>	88	=item node ID - C<[A-Z_][a-zA-Z0-9_\-.:]*>
58		89
59	A noderef 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
60	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
61	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.
		118
		119	=item seeds - C<host:port>
		120
		121	Seeds are transport endpoint(s) (usually a hostname/IP address and a
		122	TCP port) of nodes thta should be used as seed nodes.
		123
		124	The nodes listening on those endpoints are expected to be long-running,
		125	and at least one of those should always be available. When nodes run out
		126	of connections (e.g. due to a network error), they try to re-establish
		127	connections to some seednodes again to join the network.
62		128
63	=back	129	=back
64		130
65	=head1 VARIABLES/FUNCTIONS	131	=head1 VARIABLES/FUNCTIONS
66		132
…		…
68		134
69	=cut	135	=cut
70		136
71	package AnyEvent::MP;	137	package AnyEvent::MP;
72		138
73	use AnyEvent::MP::Util ();
74	use AnyEvent::MP::Node;	139	use AnyEvent::MP::Kernel;
75	use AnyEvent::MP::Transport;
76		140
77	use utf8;
78	use common::sense;	141	use common::sense;
79		142
80	use Carp ();	143	use Carp ();
81		144
82	use AE ();	145	use AE ();
83		146
84	use base "Exporter";	147	use base "Exporter";
85		148
86	our $VERSION = '0.0';	149	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
87	our @EXPORT = qw(NODE $NODE $PORT snd rcv _any_);
88		150
89	our $DEFAULT_SECRET;	151	our @EXPORT = qw(
90	our $DEFAULT_PORT = "4040";	152	NODE $NODE *SELF node_of after
		153	configure
		154	snd rcv mon mon_guard kil reg psub spawn
		155	port
		156	);
91		157
92	our $CONNECT_INTERVAL = 5; # new connect every 5s, at least	158	our $SELF;
93	our $CONNECT_TIMEOUT = 30; # includes handshake
94		159
95	sub default_secret {	160	sub _self_die() {
96	unless (defined $DEFAULT_SECRET) {	161	my $msg = $@;
97	if (open my $fh, "<$ENV{HOME}/.aemp-secret") {	162	$msg =~ s/\n+$// unless ref $msg;
98	sysread $fh, $DEFAULT_SECRET, -s $fh;	163	kil $SELF, die => $msg;
99	} else {
100	$DEFAULT_SECRET = AnyEvent::MP::Util::nonce 32;
101	}
102	}
103
104	$DEFAULT_SECRET
105	}	164	}
106		165
107	=item NODE / $NODE	166	=item $thisnode = NODE / $NODE
108		167
109	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	168	The C<NODE> function returns, and the C<$NODE> variable contains, the node
110	the local node. The value is initialised by a call to C<become_public> or	169	ID of the node running in the current process. This value is initialised by
111	C<become_slave>, after which all local port identifiers become invalid.	170	a call to C<configure>.
112		171
113	=cut	172	=item $nodeid = node_of $port
114		173
115	our $UNIQ = sprintf "%x.%x", $$, time; # per-process/node unique cookie	174	Extracts and returns the node ID from a port ID or a node ID.
116	our $PUBLIC = 0;
117	our $NODE;
118	our $PORT;
119		175
120	our %NODE; # node id to transport mapping, or "undef", for local node	176	=item configure $profile, key => value...
121	our %PORT; # local ports
122	our %LISTENER; # local transports
123		177
124	sub NODE() { $NODE }	178	=item configure key => value...
125		179
126	{	180	Before a node can talk to other nodes on the network (i.e. enter
127	use POSIX ();	181	"distributed mode") it has to configure itself - the minimum a node needs
128	my $nodename = (POSIX::uname)[1];	182	to know is its own name, and optionally it should know the addresses of
129	$NODE = "$$\@$nodename";	183	some other nodes in the network to discover other nodes.
130	}
131		184
132	sub _ANY_() { 1 }	185	This function configures a node - it must be called exactly once (or
133	sub _any_() { \&_ANY_ }	186	never) before calling other AnyEvent::MP functions.
134		187
135	sub add_node {	188	=over 4
136	my ($noderef) = @_;
137		189
138	return $NODE{$noderef}	190	=item step 1, gathering configuration from profiles
139	if exists $NODE{$noderef};
140		191
141	for (split /,/, $noderef) {	192	The function first looks up a profile in the aemp configuration (see the
142	return $NODE{$noderef} = $NODE{$_}	193	L<aemp> commandline utility). The profile name can be specified via the
143	if exists $NODE{$_};	194	named C<profile> parameter or can simply be the first parameter). If it is
144	}	195	missing, then the nodename (F<uname -n>) will be used as profile name.
145		196
146	# for indirect sends, use a different class	197	The profile data is then gathered as follows:
147	my $node = new AnyEvent::MP::Node::Direct $noderef;
148		198
149	$NODE{$_} = $node	199	First, all remaining key => value pairs (all of which are conveniently
150	for $noderef, split /,/, $noderef;	200	undocumented at the moment) will be interpreted as configuration
		201	data. Then they will be overwritten by any values specified in the global
		202	default configuration (see the F<aemp> utility), then the chain of
		203	profiles chosen by the profile name (and any C<parent> attributes).
151		204
152	$node	205	That means that the values specified in the profile have highest priority
153	}	206	and the values specified directly via C<configure> have lowest priority,
		207	and can only be used to specify defaults.
154		208
		209	If the profile specifies a node ID, then this will become the node ID of
		210	this process. If not, then the profile name will be used as node ID. The
		211	special node ID of C<anon/> will be replaced by a random node ID.
		212
		213	=item step 2, bind listener sockets
		214
		215	The next step is to look up the binds in the profile, followed by binding
		216	aemp protocol listeners on all binds specified (it is possible and valid
		217	to have no binds, meaning that the node cannot be contacted form the
		218	outside. This means the node cannot talk to other nodes that also have no
		219	binds, but it can still talk to all "normal" nodes).
		220
		221	If the profile does not specify a binds list, then a default of C<*> is
		222	used, meaning the node will bind on a dynamically-assigned port on every
		223	local IP address it finds.
		224
		225	=item step 3, connect to seed nodes
		226
		227	As the last step, the seeds list from the profile is passed to the
		228	L<AnyEvent::MP::Global> module, which will then use it to keep
		229	connectivity with at least one node at any point in time.
		230
		231	=back
		232
		233	Example: become a distributed node using the locla node name as profile.
		234	This should be the most common form of invocation for "daemon"-type nodes.
		235
		236	configure
		237
		238	Example: become an anonymous node. This form is often used for commandline
		239	clients.
		240
		241	configure nodeid => "anon/";
		242
		243	Example: configure a node using a profile called seed, which si suitable
		244	for a seed node as it binds on all local addresses on a fixed port (4040,
		245	customary for aemp).
		246
		247	# use the aemp commandline utility
		248	# aemp profile seed nodeid anon/ binds '*:4040'
		249
		250	# then use it
		251	configure profile => "seed";
		252
		253	# or simply use aemp from the shell again:
		254	# aemp run profile seed
		255
		256	# or provide a nicer-to-remember nodeid
		257	# aemp run profile seed nodeid "$(hostname)"
		258
		259	=item $SELF
		260
		261	Contains the current port id while executing C<rcv> callbacks or C<psub>
		262	blocks.
		263
		264	=item *SELF, SELF, %SELF, @SELF...
		265
		266	Due to some quirks in how perl exports variables, it is impossible to
		267	just export C<$SELF>, all the symbols named C<SELF> are exported by this
		268	module, but only C<$SELF> is currently used.
		269
155	=item snd $portid, type => @data	270	=item snd $port, type => @data
156		271
157	=item snd $portid, @msg	272	=item snd $port, @msg
158		273
159	Send the given message to the given port ID, which can identify either a	274	Send the given message to the given port, which can identify either a
160	local or a remote port.	275	local or a remote port, and must be a port ID.
161		276
162	While the message can be about anything, it is highly recommended to use	277	While the message can be almost anything, it is highly recommended to
163	a constant string as first element.	278	use a string as first element (a port ID, or some word that indicates a
		279	request type etc.) and to consist if only simple perl values (scalars,
		280	arrays, hashes) - if you think you need to pass an object, think again.
164		281
165	The message data effectively becomes read-only after a call to this	282	The message data logically becomes read-only after a call to this
166	function: modifying any argument is not allowed and can cause many	283	function: modifying any argument (or values referenced by them) is
167	problems.	284	forbidden, as there can be considerable time between the call to C<snd>
		285	and the time the message is actually being serialised - in fact, it might
		286	never be copied as within the same process it is simply handed to the
		287	receiving port.
168		288
169	The type of data you can transfer depends on the transport protocol: when	289	The type of data you can transfer depends on the transport protocol: when
170	JSON is used, then only strings, numbers and arrays and hashes consisting	290	JSON is used, then only strings, numbers and arrays and hashes consisting
171	of those are allowed (no objects). When Storable is used, then anything	291	of those are allowed (no objects). When Storable is used, then anything
172	that Storable can serialise and deserialise is allowed, and for the local	292	that Storable can serialise and deserialise is allowed, and for the local
173	node, anything can be passed.	293	node, anything can be passed. Best rely only on the common denominator of
		294	these.
174		295
175	=cut	296	=item $local_port = port
176		297
177	sub snd(@) {	298	Create a new local port object and returns its port ID. Initially it has
178	my ($noderef, $port) = split /#/, shift, 2;	299	no callbacks set and will throw an error when it receives messages.
179		300
180	add_node $noderef	301	=item $local_port = port { my @msg = @_ }
181	unless exists $NODE{$noderef};
182		302
183	$NODE{$noderef}->send (["$port", [@_]]);	303	Creates a new local port, and returns its ID. Semantically the same as
184	}	304	creating a port and calling C<rcv $port, $callback> on it.
185		305
		306	The block will be called for every message received on the port, with the
		307	global variable C<$SELF> set to the port ID. Runtime errors will cause the
		308	port to be C<kil>ed. The message will be passed as-is, no extra argument
		309	(i.e. no port ID) will be passed to the callback.
		310
		311	If you want to stop/destroy the port, simply C<kil> it:
		312
		313	my $port = port {
		314	my @msg = @_;
		315	...
		316	kil $SELF;
		317	};
		318
		319	=cut
		320
		321	sub rcv($@);
		322
		323	sub _kilme {
		324	die "received message on port without callback";
		325	}
		326
		327	sub port(;&) {
		328	my $id = "$UNIQ." . $ID++;
		329	my $port = "$NODE#$id";
		330
		331	rcv $port, shift \|\| \&_kilme;
		332
		333	$port
		334	}
		335
186	=item rcv $portid, type => $callback->(@msg)	336	=item rcv $local_port, $callback->(@msg)
187		337
188	=item rcv $portid, $smartmatch => $callback->(@msg)	338	Replaces the default callback on the specified port. There is no way to
		339	remove the default callback: use C<sub { }> to disable it, or better
		340	C<kil> the port when it is no longer needed.
189		341
190	=item rcv $portid, [$smartmatch...] => $callback->(@msg)	342	The global C<$SELF> (exported by this module) contains C<$port> while
		343	executing the callback. Runtime errors during callback execution will
		344	result in the port being C<kil>ed.
191		345
192	Register a callback on the port identified by C<$portid>, which I<must> be	346	The default callback received all messages not matched by a more specific
193	a local port.	347	C<tag> match.
194		348
195	The callback has to return a true value when its work is done, after	349	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
196	which is will be removed, or a false value in which case it will stay
197	registered.
198		350
199	If the match is an array reference, then it will be matched against the	351	Register (or replace) callbacks to be called on messages starting with the
200	first elements of the message, otherwise only the first element is being	352	given tag on the given port (and return the port), or unregister it (when
201	matched.	353	C<$callback> is C<$undef> or missing). There can only be one callback
		354	registered for each tag.
202		355
203	Any element in the match that is specified as C<_any_> (a function	356	The original message will be passed to the callback, after the first
204	exported by this module) matches any single element of the message.	357	element (the tag) has been removed. The callback will use the same
		358	environment as the default callback (see above).
205		359
206	While not required, it is highly recommended that the first matching	360	Example: create a port and bind receivers on it in one go.
207	element is a string identifying the message. The one-string-only match is	361
208	also the most efficient match (by far).	362	my $port = rcv port,
		363	msg1 => sub { ... },
		364	msg2 => sub { ... },
		365	;
		366
		367	Example: create a port, bind receivers and send it in a message elsewhere
		368	in one go:
		369
		370	snd $otherport, reply =>
		371	rcv port,
		372	msg1 => sub { ... },
		373	...
		374	;
		375
		376	Example: temporarily register a rcv callback for a tag matching some port
		377	(e.g. for a rpc reply) and unregister it after a message was received.
		378
		379	rcv $port, $otherport => sub {
		380	my @reply = @_;
		381
		382	rcv $SELF, $otherport;
		383	};
209		384
210	=cut	385	=cut
211		386
212	sub rcv($@) {	387	sub rcv($@) {
213	my ($port, $match, $cb) = @_;	388	my $port = shift;
214
215	my $port = $PORT{$port}
216	or do {
217	my ($noderef, $lport) = split /#/, $port;	389	my ($nodeid, $portid) = split /#/, $port, 2;
218	"AnyEvent::MP::Node::Self" eq ref $NODE{$noderef}	390
		391	$NODE{$nodeid} == $NODE{""}
219	or Carp::croak "$port: can only rcv on local ports";	392	or Carp::croak "$port: rcv can only be called on local ports, caught";
220		393
221	$PORT{$lport}	394	while (@_) {
222	or Carp::croak "$port: port does not exist";	395	if (ref $_[0]) {
223		396	if (my $self = $PORT_DATA{$portid}) {
224	$PORT{$port} = $PORT{$lport} # also return	397	"AnyEvent::MP::Port" eq ref $self
225	};	398	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
226		399
227	if (!ref $match) {	400	$self->[2] = shift;
228	push @{ $port->{rc0}{$match} }, [$cb];
229	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
230	my ($type, @match) = @$match;
231	@match
232	? push @{ $port->{rcv}{$match->[0]} }, [$cb, \@match]
233	: push @{ $port->{rc0}{$match->[0]} }, [$cb];
234	} else {	401	} else {
235	push @{ $port->{any} }, [$cb, $match];	402	my $cb = shift;
236	}	403	$PORT{$portid} = sub {
237	}	404	local $SELF = $port;
238		405	eval { &$cb }; _self_die if $@;
239	sub _inject {
240	my ($port, $msg) = @{+shift};
241
242	$port = $PORT{$port}
243	or return;
244
245	@_ = @$msg;
246
247	for (@{ $port->{rc0}{$msg->[0]} }) {
248	$_ && &{$_->[0]}
249	&& undef $_;
250	}
251
252	for (@{ $port->{rcv}{$msg->[0]} }) {
253	$_ && [@_[1..$#{$_->[1]}]] ~~ $_->[1]
254	&& &{$_->[0]}
255	&& undef $_;
256	}
257
258	for (@{ $port->{any} }) {
259	$_ && [@_[0..$#{$_->[1]}]] ~~ $_->[1]
260	&& &{$_->[0]}
261	&& undef $_;
262	}
263	}
264
265	sub normalise_noderef($) {
266	my ($noderef) = @_;
267
268	my $cv = AE::cv;
269	my @res;
270
271	$cv->begin (sub {
272	my %seen;
273	my @refs;
274	for (sort { $a->[0] <=> $b->[0] } @res) {
275	push @refs, $_->[1] unless $seen{$_->[1]}++
276	}
277	shift->send (join ",", @refs);
278	});
279
280	$noderef = $DEFAULT_PORT unless length $noderef;
281
282	my $idx;
283	for my $t (split /,/, $noderef) {
284	my $pri = ++$idx;
285
286	#TODO: this should be outside normalise_noderef and in become_public
287	if ($t =~ /^\d*$/) {
288	my $nodename = (POSIX::uname)[1];
289
290	$cv->begin;
291	AnyEvent::Socket::resolve_sockaddr $nodename, $t \|\| "aemp=$DEFAULT_PORT", "tcp", 0, undef, sub {
292	for (@_) {
293	my ($service, $host) = AnyEvent::Socket::unpack_sockaddr $_->[3];
294	push @res, [
295	$pri += 1e-5,
296	AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $host, $service
297	];
298	}	406	};
299	$cv->end;	407	}
		408	} elsif (defined $_[0]) {
		409	my $self = $PORT_DATA{$portid} \|\|= do {
		410	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		411
		412	$PORT{$portid} = sub {
		413	local $SELF = $port;
		414
		415	if (my $cb = $self->[1]{$_[0]}) {
		416	shift;
		417	eval { &$cb }; _self_die if $@;
		418	} else {
		419	&{ $self->[0] };
		420	}
		421	};
		422
		423	$self
300	};	424	};
301		425
302	# my (undef, undef, undef, undef, @ipv4) = gethostbyname $nodename;	426	"AnyEvent::MP::Port" eq ref $self
303	#	427	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
304	# for (@ipv4) {	428
305	# push @res, [	429	my ($tag, $cb) = splice @_, 0, 2;
306	# $pri,	430
307	# AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $_, $t \|\| $DEFAULT_PORT,	431	if (defined $cb) {
308	# ];	432	$self->[1]{$tag} = $cb;
309	# }
310	} else {	433	} else {
311	my ($host, $port) = AnyEvent::Socket::parse_hostport $t, "aemp=$DEFAULT_PORT"	434	delete $self->[1]{$tag};
312	or Carp::croak "$t: unparsable transport descriptor";
313
314	$cv->begin;
315	AnyEvent::Socket::resolve_sockaddr $host, $port, "tcp", 0, undef, sub {
316	for (@_) {
317	my ($service, $host) = AnyEvent::Socket::unpack_sockaddr $_->[3];
318	push @res, [
319	$pri += 1e-5,
320	AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $host, $service
321	];
322	}
323	$cv->end;
324	}	435	}
325	}	436	}
326	}	437	}
327		438
328	$cv->end;	439	$port
329
330	$cv
331	}	440	}
332		441
333	sub become_public {	442	=item $closure = psub { BLOCK }
334	return if $PUBLIC;
335		443
336	my $noderef = join ",", ref $_[0] ? @{+shift} : shift;	444	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
337	my @args = @_;	445	closure is executed, sets up the environment in the same way as in C<rcv>
		446	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
338		447
339	$NODE = (normalise_noderef $noderef)->recv;	448	This is useful when you register callbacks from C<rcv> callbacks:
340		449
341	for my $t (split /,/, $NODE) {	450	rcv delayed_reply => sub {
342	$NODE{$t} = $NODE{""};	451	my ($delay, @reply) = @_;
343		452	my $timer = AE::timer $delay, 0, psub {
344	my ($host, $port) = AnyEvent::Socket::parse_hostport $t;	453	snd @reply, $SELF;
345
346	$LISTENER{$t} = AnyEvent::MP::Transport::mp_server $host, $port,
347	@args,
348	on_error => sub {
349	die "on_error<@_>\n";#d#
350	},
351	on_connect => sub {
352	my ($tp) = @_;
353
354	$NODE{$tp->{remote_id}} = $_[0];
355	},
356	sub {
357	my ($tp) = @_;
358
359	$NODE{"$tp->{peerhost}:$tp->{peerport}"} = $tp;
360	},
361	;	454	};
		455	};
		456
		457	=cut
		458
		459	sub psub(&) {
		460	my $cb = shift;
		461
		462	my $port = $SELF
		463	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		464
		465	sub {
		466	local $SELF = $port;
		467
		468	if (wantarray) {
		469	my @res = eval { &$cb };
		470	_self_die if $@;
		471	@res
		472	} else {
		473	my $res = eval { &$cb };
		474	_self_die if $@;
		475	$res
		476	}
362	}	477	}
		478	}
363		479
364	$PUBLIC = 1;	480	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
		481
		482	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		483
		484	=item $guard = mon $port # kill $SELF when $port dies
		485
		486	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		487
		488	Monitor the given port and do something when the port is killed or
		489	messages to it were lost, and optionally return a guard that can be used
		490	to stop monitoring again.
		491
		492	In the first form (callback), the callback is simply called with any
		493	number of C<@reason> elements (no @reason means that the port was deleted
		494	"normally"). Note also that I<< the callback B<must> never die >>, so use
		495	C<eval> if unsure.
		496
		497	In the second form (another port given), the other port (C<$rcvport>)
		498	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		499	"normal" kils nothing happens, while under all other conditions, the other
		500	port is killed with the same reason.
		501
		502	The third form (kill self) is the same as the second form, except that
		503	C<$rvport> defaults to C<$SELF>.
		504
		505	In the last form (message), a message of the form C<@msg, @reason> will be
		506	C<snd>.
		507
		508	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		509	alert was raised), they are removed and will not trigger again.
		510
		511	As a rule of thumb, monitoring requests should always monitor a port from
		512	a local port (or callback). The reason is that kill messages might get
		513	lost, just like any other message. Another less obvious reason is that
		514	even monitoring requests can get lost (for example, when the connection
		515	to the other node goes down permanently). When monitoring a port locally
		516	these problems do not exist.
		517
		518	C<mon> effectively guarantees that, in the absence of hardware failures,
		519	after starting the monitor, either all messages sent to the port will
		520	arrive, or the monitoring action will be invoked after possible message
		521	loss has been detected. No messages will be lost "in between" (after
		522	the first lost message no further messages will be received by the
		523	port). After the monitoring action was invoked, further messages might get
		524	delivered again.
		525
		526	Inter-host-connection timeouts and monitoring depend on the transport
		527	used. The only transport currently implemented is TCP, and AnyEvent::MP
		528	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		529	non-idle connection, and usually around two hours for idle conenctions).
		530
		531	This means that monitoring is good for program errors and cleaning up
		532	stuff eventually, but they are no replacement for a timeout when you need
		533	to ensure some maximum latency.
		534
		535	Example: call a given callback when C<$port> is killed.
		536
		537	mon $port, sub { warn "port died because of <@_>\n" };
		538
		539	Example: kill ourselves when C<$port> is killed abnormally.
		540
		541	mon $port;
		542
		543	Example: send us a restart message when another C<$port> is killed.
		544
		545	mon $port, $self => "restart";
		546
		547	=cut
		548
		549	sub mon {
		550	my ($nodeid, $port) = split /#/, shift, 2;
		551
		552	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
		553
		554	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		555
		556	unless (ref $cb) {
		557	if (@_) {
		558	# send a kill info message
		559	my (@msg) = ($cb, @_);
		560	$cb = sub { snd @msg, @_ };
		561	} else {
		562	# simply kill other port
		563	my $port = $cb;
		564	$cb = sub { kil $port, @_ if @_ };
		565	}
		566	}
		567
		568	$node->monitor ($port, $cb);
		569
		570	defined wantarray
		571	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		572	}
		573
		574	=item $guard = mon_guard $port, $ref, $ref...
		575
		576	Monitors the given C<$port> and keeps the passed references. When the port
		577	is killed, the references will be freed.
		578
		579	Optionally returns a guard that will stop the monitoring.
		580
		581	This function is useful when you create e.g. timers or other watchers and
		582	want to free them when the port gets killed (note the use of C<psub>):
		583
		584	$port->rcv (start => sub {
		585	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
		586	undef $timer if 0.9 < rand;
		587	});
		588	});
		589
		590	=cut
		591
		592	sub mon_guard {
		593	my ($port, @refs) = @_;
		594
		595	#TODO: mon-less form?
		596
		597	mon $port, sub { 0 && @refs }
		598	}
		599
		600	=item kil $port[, @reason]
		601
		602	Kill the specified port with the given C<@reason>.
		603
		604	If no C<@reason> is specified, then the port is killed "normally" (ports
		605	monitoring other ports will not necessarily die because a port dies
		606	"normally").
		607
		608	Otherwise, linked ports get killed with the same reason (second form of
		609	C<mon>, see above).
		610
		611	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		612	will be reported as reason C<< die => $@ >>.
		613
		614	Transport/communication errors are reported as C<< transport_error =>
		615	$message >>.
		616
		617	=cut
		618
		619	=item $port = spawn $node, $initfunc[, @initdata]
		620
		621	Creates a port on the node C<$node> (which can also be a port ID, in which
		622	case it's the node where that port resides).
		623
		624	The port ID of the newly created port is returned immediately, and it is
		625	possible to immediately start sending messages or to monitor the port.
		626
		627	After the port has been created, the init function is called on the remote
		628	node, in the same context as a C<rcv> callback. This function must be a
		629	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		630	specify a function in the main program, use C<::name>.
		631
		632	If the function doesn't exist, then the node tries to C<require>
		633	the package, then the package above the package and so on (e.g.
		634	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		635	exists or it runs out of package names.
		636
		637	The init function is then called with the newly-created port as context
		638	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		639	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		640	the port might not get created.
		641
		642	A common idiom is to pass a local port, immediately monitor the spawned
		643	port, and in the remote init function, immediately monitor the passed
		644	local port. This two-way monitoring ensures that both ports get cleaned up
		645	when there is a problem.
		646
		647	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		648	caller before C<spawn> returns (by delaying invocation when spawn is
		649	called for the local node).
		650
		651	Example: spawn a chat server port on C<$othernode>.
		652
		653	# this node, executed from within a port context:
		654	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		655	mon $server;
		656
		657	# init function on C<$othernode>
		658	sub connect {
		659	my ($srcport) = @_;
		660
		661	mon $srcport;
		662
		663	rcv $SELF, sub {
		664	...
		665	};
		666	}
		667
		668	=cut
		669
		670	sub _spawn {
		671	my $port = shift;
		672	my $init = shift;
		673
		674	# rcv will create the actual port
		675	local $SELF = "$NODE#$port";
		676	eval {
		677	&{ load_func $init }
		678	};
		679	_self_die if $@;
		680	}
		681
		682	sub spawn(@) {
		683	my ($nodeid, undef) = split /#/, shift, 2;
		684
		685	my $id = "$RUNIQ." . $ID++;
		686
		687	$_[0] =~ /::/
		688	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		689
		690	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
		691
		692	"$nodeid#$id"
		693	}
		694
		695	=item after $timeout, @msg
		696
		697	=item after $timeout, $callback
		698
		699	Either sends the given message, or call the given callback, after the
		700	specified number of seconds.
		701
		702	This is simply a utility function that comes in handy at times - the
		703	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		704	so it may go away in the future.
		705
		706	=cut
		707
		708	sub after($@) {
		709	my ($timeout, @action) = @_;
		710
		711	my $t; $t = AE::timer $timeout, 0, sub {
		712	undef $t;
		713	ref $action[0]
		714	? $action[0]()
		715	: snd @action;
		716	};
365	}	717	}
366		718
367	=back	719	=back
368		720
369	=head1 NODE MESSAGES	721	=head1 AnyEvent::MP vs. Distributed Erlang
370		722
371	Nodes understand the following messages sent to them:	723	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		724	== aemp node, Erlang process == aemp port), so many of the documents and
		725	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		726	sample:
		727
		728	http://www.Erlang.se/doc/programming_rules.shtml
		729	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		730	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		731	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		732
		733	Despite the similarities, there are also some important differences:
372		734
373	=over 4	735	=over 4
374		736
375	=cut	737	=item * Node IDs are arbitrary strings in AEMP.
376		738
377	#############################################################################	739	Erlang relies on special naming and DNS to work everywhere in the same
378	# self node code	740	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		741	configuration or DNS), but will otherwise discover other odes itself.
379		742
380	sub _new_port($) {	743	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
381	my ($name) = @_;	744	uses "local ports are like remote ports".
382		745
383	my ($noderef, $portname) = split /#/, $name;	746	The failure modes for local ports are quite different (runtime errors
		747	only) then for remote ports - when a local port dies, you I<know> it dies,
		748	when a connection to another node dies, you know nothing about the other
		749	port.
384		750
385	$PORT{$name} =	751	Erlang pretends remote ports are as reliable as local ports, even when
386	$PORT{$portname} = {	752	they are not.
387	names => [$name, $portname],
388	};
389	}
390		753
391	$NODE{""} = new AnyEvent::MP::Node::Self noderef => $NODE;	754	AEMP encourages a "treat remote ports differently" philosophy, with local
392	_new_port "";	755	ports being the special case/exception, where transport errors cannot
		756	occur.
393		757
394	=item relay => $port, @msg	758	=item * Erlang uses processes and a mailbox, AEMP does not queue.
395		759
396	Simply forwards the message to the given port.	760	Erlang uses processes that selectively receive messages, and therefore
		761	needs a queue. AEMP is event based, queuing messages would serve no
		762	useful purpose. For the same reason the pattern-matching abilities of
		763	AnyEvent::MP are more limited, as there is little need to be able to
		764	filter messages without dequeuing them.
397		765
398	=cut	766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
399		767
400	rcv "", relay => \&snd;	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
401		769
402	=item eval => $string[ @reply]	770	Sending messages in Erlang is synchronous and blocks the process (and
		771	so does not need a queue that can overflow). AEMP sends are immediate,
		772	connection establishment is handled in the background.
403		773
404	Evaluates the given string. If C<@reply> is given, then a message of the	774	=item * Erlang suffers from silent message loss, AEMP does not.
405	form C<@reply, $@, @evalres> is sent (C<$reply[0]> is the port to reply to).
406		775
407	=cut	776	Erlang makes few guarantees on messages delivery - messages can get lost
		777	without any of the processes realising it (i.e. you send messages a, b,
		778	and c, and the other side only receives messages a and c).
408		779
409	rcv "", eval => sub {	780	AEMP guarantees correct ordering, and the guarantee that after one message
410	my (undef, $string, @reply) = @_;	781	is lost, all following ones sent to the same port are lost as well, until
411	my @res = eval $string;	782	monitoring raises an error, so there are no silent "holes" in the message
412	snd @reply, "$@", @res if @reply;	783	sequence.
413	};
414		784
415	=item time => @reply	785	=item * Erlang can send messages to the wrong port, AEMP does not.
416		786
417	Replies the the current node time to C<@reply>.	787	In Erlang it is quite likely that a node that restarts reuses a process ID
		788	known to other nodes for a completely different process, causing messages
		789	destined for that process to end up in an unrelated process.
418		790
419	=cut	791	AEMP never reuses port IDs, so old messages or old port IDs floating
		792	around in the network will not be sent to an unrelated port.
420		793
421	rcv "", time => sub { shift; snd @_, AE::time };	794	=item * Erlang uses unprotected connections, AEMP uses secure
		795	authentication and can use TLS.
		796
		797	AEMP can use a proven protocol - TLS - to protect connections and
		798	securely authenticate nodes.
		799
		800	=item * The AEMP protocol is optimised for both text-based and binary
		801	communications.
		802
		803	The AEMP protocol, unlike the Erlang protocol, supports both programming
		804	language independent text-only protocols (good for debugging) and binary,
		805	language-specific serialisers (e.g. Storable). By default, unless TLS is
		806	used, the protocol is actually completely text-based.
		807
		808	It has also been carefully designed to be implementable in other languages
		809	with a minimum of work while gracefully degrading functionality to make the
		810	protocol simple.
		811
		812	=item * AEMP has more flexible monitoring options than Erlang.
		813
		814	In Erlang, you can chose to receive I<all> exit signals as messages
		815	or I<none>, there is no in-between, so monitoring single processes is
		816	difficult to implement. Monitoring in AEMP is more flexible than in
		817	Erlang, as one can choose between automatic kill, exit message or callback
		818	on a per-process basis.
		819
		820	=item * Erlang tries to hide remote/local connections, AEMP does not.
		821
		822	Monitoring in Erlang is not an indicator of process death/crashes, in the
		823	same way as linking is (except linking is unreliable in Erlang).
		824
		825	In AEMP, you don't "look up" registered port names or send to named ports
		826	that might or might not be persistent. Instead, you normally spawn a port
		827	on the remote node. The init function monitors you, and you monitor the
		828	remote port. Since both monitors are local to the node, they are much more
		829	reliable (no need for C<spawn_link>).
		830
		831	This also saves round-trips and avoids sending messages to the wrong port
		832	(hard to do in Erlang).
422		833
423	=back	834	=back
424		835
		836	=head1 RATIONALE
		837
		838	=over 4
		839
		840	=item Why strings for port and node IDs, why not objects?
		841
		842	We considered "objects", but found that the actual number of methods
		843	that can be called are quite low. Since port and node IDs travel over
		844	the network frequently, the serialising/deserialising would add lots of
		845	overhead, as well as having to keep a proxy object everywhere.
		846
		847	Strings can easily be printed, easily serialised etc. and need no special
		848	procedures to be "valid".
		849
		850	And as a result, a miniport consists of a single closure stored in a
		851	global hash - it can't become much cheaper.
		852
		853	=item Why favour JSON, why not a real serialising format such as Storable?
		854
		855	In fact, any AnyEvent::MP node will happily accept Storable as framing
		856	format, but currently there is no way to make a node use Storable by
		857	default (although all nodes will accept it).
		858
		859	The default framing protocol is JSON because a) JSON::XS is many times
		860	faster for small messages and b) most importantly, after years of
		861	experience we found that object serialisation is causing more problems
		862	than it solves: Just like function calls, objects simply do not travel
		863	easily over the network, mostly because they will always be a copy, so you
		864	always have to re-think your design.
		865
		866	Keeping your messages simple, concentrating on data structures rather than
		867	objects, will keep your messages clean, tidy and efficient.
		868
		869	=back
		870
425	=head1 SEE ALSO	871	=head1 SEE ALSO
		872
		873	L<AnyEvent::MP::Intro> - a gentle introduction.
		874
		875	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		876
		877	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		878	your applications.
		879
		880	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		881	all nodes.
426		882
427	L<AnyEvent>.	883	L<AnyEvent>.
428		884
429	=head1 AUTHOR	885	=head1 AUTHOR
430		886

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Revision 1.84 by root, Tue Sep 8 01:42:14 2009 UTC