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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.15 by root, Sun Aug 2 19:25:27 2009 UTC vs.
Revision 1.83 by root, Tue Sep 8 01:38:16 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.
31		56
32	At the moment, this module family is severly brokena nd underdocumented,	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
33	so do not use. This was uploaded mainly to resreve the CPAN namespace -	58	manual page and the examples under F<eg/>.
34	stay tuned!
35		59
36	=head1 CONCEPTS	60	=head1 CONCEPTS
37		61
38	=over 4	62	=over 4
39		63
40	=item port	64	=item port
41		65
42	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
43	you can register C<rcv> handlers with. All C<rcv> handlers will receive	67	messages to (with the C<snd> function).
44	messages they match, messages will not be queued.
45		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
46	=item port id - C<noderef#portname>	73	=item port ID - C<nodeid#portname>
47		74
48	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
49	by a port name (a printable string of unspecified format).	76	separator, and a port name (a printable string of unspecified format).
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 master node only). Only when they epxlicitly "become	85	(no listening ports). Private nodes cannot talk to other private nodes
59	public" can you send them messages from unrelated other nodes.	86	currently.
60		87
61	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	88	=item node ID - C<[a-za-Z0-9_\-.:]+>
62		89
63	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
64	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
65	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.
66		128
67	=back	129	=back
68		130
69	=head1 VARIABLES/FUNCTIONS	131	=head1 VARIABLES/FUNCTIONS
70		132
…		…
72		134
73	=cut	135	=cut
74		136
75	package AnyEvent::MP;	137	package AnyEvent::MP;
76		138
77	use AnyEvent::MP::Base;	139	use AnyEvent::MP::Kernel;
78		140
79	use common::sense;	141	use common::sense;
80		142
81	use Carp ();	143	use Carp ();
82		144
83	use AE ();	145	use AE ();
84		146
85	use base "Exporter";	147	use base "Exporter";
86		148
87	our $VERSION = '0.02';	149	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		150
88	our @EXPORT = qw(	151	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv _any_	152	NODE $NODE *SELF node_of after
90	create_port create_port_on	153	configure
91	create_miniport	154	snd rcv mon mon_guard kil reg psub spawn
92	become_slave become_public	155	port
93	);	156	);
94		157
		158	our $SELF;
		159
		160	sub _self_die() {
		161	my $msg = $@;
		162	$msg =~ s/\n+$// unless ref $msg;
		163	kil $SELF, die => $msg;
		164	}
		165
95	=item NODE / $NODE	166	=item $thisnode = NODE / $NODE
96		167
97	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	168	The C<NODE> function returns, and the C<$NODE> variable contains, the node
98	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
99	C<become_slave>, after which all local port identifiers become invalid.	170	a call to C<configure>.
100		171
		172	=item $nodeid = node_of $port
		173
		174	Extracts and returns the node ID from a port ID or a node ID.
		175
		176	=item configure $profile, key => value...
		177
		178	=item configure key => value...
		179
		180	Before a node can talk to other nodes on the network (i.e. enter
		181	"distributed mode") it has to configure itself - the minimum a node needs
		182	to know is its own name, and optionally it should know the addresses of
		183	some other nodes in the network to discover other nodes.
		184
		185	This function configures a node - it must be called exactly once (or
		186	never) before calling other AnyEvent::MP functions.
		187
		188	=over 4
		189
		190	=item step 1, gathering configuration from profiles
		191
		192	The function first looks up a profile in the aemp configuration (see the
		193	L<aemp> commandline utility). The profile name can be specified via the
		194	named C<profile> parameter or can simply be the first parameter). If it is
		195	missing, then the nodename (F<uname -n>) will be used as profile name.
		196
		197	The profile data is then gathered as follows:
		198
		199	First, all remaining key => value pairs (all of which are conveniently
		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).
		204
		205	That means that the values specified in the profile have highest priority
		206	and the values specified directly via C<configure> have lowest priority,
		207	and can only be used to specify defaults.
		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
101	=item snd $portid, type => @data	270	=item snd $port, type => @data
102		271
103	=item snd $portid, @msg	272	=item snd $port, @msg
104		273
105	Send the given message to the given port ID, which can identify either	274	Send the given message to the given port, which can identify either a
106	a local or a remote port, and can be either a string or soemthignt hat	275	local or a remote port, and must be a port ID.
107	stringifies a sa port ID (such as a port object :).
108		276
109	While the message can be about anything, it is highly recommended to use a	277	While the message can be almost anything, it is highly recommended to
110	string as first element (a portid, or some word that indicates a request	278	use a string as first element (a port ID, or some word that indicates a
111	type etc.).	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.
112		281
113	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
114	function: modifying any argument is not allowed and can cause many	283	function: modifying any argument (or values referenced by them) is
115	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.
116		288
117	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
118	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
119	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
120	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
121	node, anything can be passed.	293	node, anything can be passed. Best rely only on the common denominator of
		294	these.
122		295
123	=item $local_port = create_port	296	=item $local_port = port
124		297
125	Create a new local port object. See the next section for allowed methods.	298	Create a new local port object and returns its port ID. Initially it has
		299	no callbacks set and will throw an error when it receives messages.
126		300
127	=cut	301	=item $local_port = port { my @msg = @_ }
128		302
129	sub create_port {	303	Creates a new local port, and returns its ID. Semantically the same as
130	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;	304	creating a port and calling C<rcv $port, $callback> on it.
131		305
132	my $self = bless {	306	The block will be called for every message received on the port, with the
133	id => "$NODE#$id",	307	global variable C<$SELF> set to the port ID. Runtime errors will cause the
134	names => [$id],	308	port to be C<kil>ed. The message will be passed as-is, no extra argument
135	}, "AnyEvent::MP::Port";	309	(i.e. no port ID) will be passed to the callback.
136		310
137	$AnyEvent::MP::Base::PORT{$id} = sub {	311	If you want to stop/destroy the port, simply C<kil> it:
138	unshift @_, $self;
139		312
140	for (@{ $self->{rc0}{$_[1]} }) {	313	my $port = port {
141	$_ && &{$_->[0]}	314	my @msg = @_;
142	&& undef $_;	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
		336	=item rcv $local_port, $callback->(@msg)
		337
		338	Replaces the default callback on the specified port. There is no way to
		339	remove the default callback: use C<sub { }> to disable it, or better
		340	C<kil> the port when it is no longer needed.
		341
		342	The global C<$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.
		345
		346	The default callback received all messages not matched by a more specific
		347	C<tag> match.
		348
		349	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		350
		351	Register (or replace) callbacks to be called on messages starting with the
		352	given tag on the given port (and return the port), or unregister it (when
		353	C<$callback> is C<$undef> or missing). There can only be one callback
		354	registered for each tag.
		355
		356	The original message will be passed to the callback, after the first
		357	element (the tag) has been removed. The callback will use the same
		358	environment as the default callback (see above).
		359
		360	Example: create a port and bind receivers on it in one go.
		361
		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, $otherport;
		383	};
		384
		385	=cut
		386
		387	sub rcv($@) {
		388	my $port = shift;
		389	my ($nodeid, $portid) = split /#/, $port, 2;
		390
		391	$NODE{$nodeid} == $NODE{""}
		392	or Carp::croak "$port: rcv can only be called on local ports, caught";
		393
		394	while (@_) {
		395	if (ref $_[0]) {
		396	if (my $self = $PORT_DATA{$portid}) {
		397	"AnyEvent::MP::Port" eq ref $self
		398	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		399
		400	$self->[2] = shift;
		401	} else {
		402	my $cb = shift;
		403	$PORT{$portid} = sub {
		404	local $SELF = $port;
		405	eval { &$cb }; _self_die if $@;
		406	};
		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
		424	};
		425
		426	"AnyEvent::MP::Port" eq ref $self
		427	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		428
		429	my ($tag, $cb) = splice @_, 0, 2;
		430
		431	if (defined $cb) {
		432	$self->[1]{$tag} = $cb;
		433	} else {
		434	delete $self->[1]{$tag};
		435	}
143	}	436	}
		437	}
144		438
145	for (@{ $self->{rcv}{$_[1]} }) {	439	$port
146	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	440	}
147	&& &{$_->[0]}	441
148	&& undef $_;	442	=item $closure = psub { BLOCK }
		443
		444	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		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.
		447
		448	This is useful when you register callbacks from C<rcv> callbacks:
		449
		450	rcv delayed_reply => sub {
		451	my ($delay, @reply) = @_;
		452	my $timer = AE::timer $delay, 0, psub {
		453	snd @reply, $SELF;
		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
149	}	476	}
		477	}
		478	}
150		479
151	for (@{ $self->{any} }) {	480	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
152	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	481
153	&& &{$_->[0]}	482	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
154	&& undef $_;	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 @_ };
155	}	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 }
156	};	678	};
157		679	_self_die if $@;
158	$self
159	}	680	}
160		681
161	=item $portid = miniport { my @msg = @_; $finished }	682	sub spawn(@) {
		683	my ($nodeid, undef) = split /#/, shift, 2;
162		684
163	Creates a "mini port", that is, a very lightweight port without any	685	my $id = "$RUNIQ." . $ID++;
164	pattern matching behind it, and returns its ID.
165		686
166	The block will be called for every message received on the port. When the	687	$_[0] =~ /::/
167	callback returns a true value its job is considered "done" and the port	688	or Carp::croak "spawn init function must be a fully-qualified name, caught";
168	will be destroyed. Otherwise it will stay alive.
169		689
170	The message will be passed as-is, no extra argument (ie.. no port id) will	690	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
171	be passed to the callback.
172		691
173	If you need the local port id in the callback, this works nicely:	692	"$nodeid#$id"
		693	}
174		694
175	my $port; $port = miniport {	695	=item after $timeout, @msg
176	snd $otherport, reply => $port;	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;
177	};	716	};
178
179	=cut
180
181	sub miniport(&) {
182	my $cb = shift;
183	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;
184
185	$AnyEvent::MP::Base::PORT{$id} = sub {
186	&$cb
187	and delete $AnyEvent::MP::Base::PORT{$id};
188	};
189
190	"$NODE#$id"
191	}	717	}
192
193	package AnyEvent::MP::Port;
194		718
195	=back	719	=back
196		720
197	=head1 METHODS FOR PORT OBJECTS	721	=head1 AnyEvent::MP vs. Distributed Erlang
		722
		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:
198		734
199	=over 4	735	=over 4
200		736
201	=item "$port"	737	=item * Node IDs are arbitrary strings in AEMP.
202		738
203	A port object stringifies to its port ID, so can be used directly for	739	Erlang relies on special naming and DNS to work everywhere in the same
204	C<snd> operations.	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.
205		742
206	=cut	743	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		744	uses "local ports are like remote ports".
207		745
208	use overload	746	The failure modes for local ports are quite different (runtime errors
209	'""' => sub { $_[0]{id} },	747	only) then for remote ports - when a local port dies, you I<know> it dies,
210	fallback => 1;	748	when a connection to another node dies, you know nothing about the other
		749	port.
211		750
212	=item $port->rcv (type => $callback->($port, @msg))	751	Erlang pretends remote ports are as reliable as local ports, even when
		752	they are not.
213		753
214	=item $port->rcv ($smartmatch => $callback->($port, @msg))	754	AEMP encourages a "treat remote ports differently" philosophy, with local
		755	ports being the special case/exception, where transport errors cannot
		756	occur.
215		757
216	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	758	=item * Erlang uses processes and a mailbox, AEMP does not queue.
217		759
218	Register a callback on 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.
219		765
220	The callback has to return a true value when its work is done, after	766	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
221	which is will be removed, or a false value in which case it will stay
222	registered.
223		767
224	If the match is an array reference, then it will be matched against the	768	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
225	first elements of the message, otherwise only the first element is being
226	matched.
227		769
228	Any element in the match that is specified as C<_any_> (a function	770	Sending messages in Erlang is synchronous and blocks the process (and
229	exported by this module) matches any single element of the message.	771	so does not need a queue that can overflow). AEMP sends are immediate,
		772	connection establishment is handled in the background.
230		773
231	While not required, it is highly recommended that the first matching	774	=item * Erlang suffers from silent message loss, AEMP does not.
232	element is a string identifying the message. The one-string-only match is
233	also the most efficient match (by far).
234		775
235	=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).
236		779
237	sub rcv($@) {	780	AEMP guarantees correct ordering, and the guarantee that after one message
238	my ($self, $match, $cb) = @_;	781	is lost, all following ones sent to the same port are lost as well, until
		782	monitoring raises an error, so there are no silent "holes" in the message
		783	sequence.
239		784
240	if (!ref $match) {	785	=item * Erlang can send messages to the wrong port, AEMP does not.
241	push @{ $self->{rc0}{$match} }, [$cb];
242	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
243	my ($type, @match) = @$match;
244	@match
245	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
246	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
247	} else {
248	push @{ $self->{any} }, [$cb, $match];
249	}
250	}
251		786
252	=item $port->register ($name)	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.
253		790
254	Registers the given port under the well known name C<$name>. If the name	791	AEMP never reuses port IDs, so old messages or old port IDs floating
255	already exists it is replaced.	792	around in the network will not be sent to an unrelated port.
256		793
257	A port can only be registered under one well known name.	794	=item * Erlang uses unprotected connections, AEMP uses secure
		795	authentication and can use TLS.
258		796
259	=cut	797	AEMP can use a proven protocol - TLS - to protect connections and
		798	securely authenticate nodes.
260		799
261	sub register {	800	=item * The AEMP protocol is optimised for both text-based and binary
262	my ($self, $name) = @_;	801	communications.
263		802
264	$self->{wkname} = $name;	803	The AEMP protocol, unlike the Erlang protocol, supports both programming
265	$AnyEvent::MP::Base::WKP{$name} = "$self";	804	language independent text-only protocols (good for debugging) and binary,
266	}	805	language-specific serialisers (e.g. Storable). By default, unless TLS is
		806	used, the protocol is actually completely text-based.
267		807
268	=item $port->destroy	808	It has also been carefully designed to be implementable in other languages
		809	with a minimum of work while gracefully degrading functionality to make the
		810	protocol simple.
269		811
270	Explicitly destroy/remove/nuke/vaporise the port.	812	=item * AEMP has more flexible monitoring options than Erlang.
271		813
272	Ports are normally kept alive by there mere existance alone, and need to	814	In Erlang, you can chose to receive I<all> exit signals as messages
273	be destroyed explicitly.	815	or I<none>, there is no in-between, so monitoring single processes is
		816	difficult to implement. Monitoring in AEMP is more flexible than in
		817	Erlang, as one can choose between automatic kill, exit message or callback
		818	on a per-process basis.
274		819
275	=cut	820	=item * Erlang tries to hide remote/local connections, AEMP does not.
276		821
277	sub destroy {	822	Monitoring in Erlang is not an indicator of process death/crashes, in the
278	my ($self) = @_;	823	same way as linking is (except linking is unreliable in Erlang).
279		824
280	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	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>).
281		830
282	delete $AnyEvent::MP::Base::PORT{$_}	831	This also saves round-trips and avoids sending messages to the wrong port
283	for @{ $self->{names} };	832	(hard to do in Erlang).
284	}
285		833
286	=back	834	=back
287		835
288	=head1 FUNCTIONS FOR NODES	836	=head1 RATIONALE
289		837
290	=over 4	838	=over 4
291		839
292	=item mon $noderef, $callback->($noderef, $status, $)	840	=item Why strings for port and node IDs, why not objects?
293		841
294	Monitors the given noderef.	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.
295		846
296	=item become_public endpoint...	847	Strings can easily be printed, easily serialised etc. and need no special
		848	procedures to be "valid".
297		849
298	Tells the node to become a public node, i.e. reachable from other nodes.	850	And as a result, a miniport consists of a single closure stored in a
		851	global hash - it can't become much cheaper.
299		852
300	If no arguments are given, or the first argument is C<undef>, then	853	=item Why favour JSON, why not a real serialising format such as Storable?
301	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the
302	local nodename resolves to.
303		854
304	Otherwise the first argument must be an array-reference with transport	855	In fact, any AnyEvent::MP node will happily accept Storable as framing
305	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	856	format, but currently there is no way to make a node use Storable by
306	local nodename is used as hostname). The endpoints are all resolved and	857	default (although all nodes will accept it).
307	will become the node reference.
308		858
309	=cut	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.
310		868
311	=back	869	=back
312		870
313	=head1 NODE MESSAGES
314
315	Nodes understand the following messages sent to them. Many of them take
316	arguments called C<@reply>, which will simply be used to compose a reply
317	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
318	the remaining arguments are simply the message data.
319
320	=over 4
321
322	=cut
323
324	=item wkp => $name, @reply
325
326	Replies with the port ID of the specified well-known port, or C<undef>.
327
328	=item devnull => ...
329
330	Generic data sink/CPU heat conversion.
331
332	=item relay => $port, @msg
333
334	Simply forwards the message to the given port.
335
336	=item eval => $string[ @reply]
337
338	Evaluates the given string. If C<@reply> is given, then a message of the
339	form C<@reply, $@, @evalres> is sent.
340
341	Example: crash another node.
342
343	snd $othernode, eval => "exit";
344
345	=item time => @reply
346
347	Replies the the current node time to C<@reply>.
348
349	Example: tell the current node to send the current time to C<$myport> in a
350	C<timereply> message.
351
352	snd $NODE, time => $myport, timereply => 1, 2;
353	# => snd $myport, timereply => 1, 2, <time>
354
355	=back
356
357	=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.
358		882
359	L<AnyEvent>.	883	L<AnyEvent>.
360		884
361	=head1 AUTHOR	885	=head1 AUTHOR
362		886

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Revision 1.83 by root, Tue Sep 8 01:38:16 2009 UTC