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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.17 by root, Mon Aug 3 08:35:40 2009 UTC vs.
Revision 1.75 by root, Mon Aug 31 13:18:06 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 - uptodate, but incomplete.
		45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable API, 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
		57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
		58	manual page and the examples under F<eg/>.
		59
32	At the moment, this module family is severly brokena nd underdocumented,	60	At the moment, this module family is a bit underdocumented.
33	so do not use. This was uploaded mainly to resreve the CPAN namespace -
34	stay tuned!
35		61
36	=head1 CONCEPTS	62	=head1 CONCEPTS
37		63
38	=over 4	64	=over 4
39		65
40	=item port	66	=item port
41		67
42	A port is something you can send messages to with the C<snd> function, and	68	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		69
		70	Ports allow you to register C<rcv> handlers that can match all or just
		71	some messages. Messages send to ports will not be queued, regardless of
		72	anything was listening for them or not.
		73
46	=item port id - C<noderef#portname>	74	=item port ID - C<nodeid#portname>
47		75
48	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	76	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).	77	separator, and a port name (a printable string of unspecified format).
50		78
51	=item node	79	=item node
52		80
53	A node is a single process containing at least one port - the node	81	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,	82	which enables nodes to manage each other remotely, and to create new
55	among other things.	83	ports.
56		84
57	Initially, nodes are either private (single-process only) or hidden	85	Nodes are either public (have one or more listening ports) or private
58	(connected to a master node only). Only when they epxlicitly "become	86	(no listening ports). Private nodes cannot talk to other private nodes
59	public" can you send them messages from unrelated other nodes.	87	currently.
60		88
61	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	89	=item node ID - C<[a-za-Z0-9_\-.:]+>
62		90
63	A noderef is a string that either uniquely identifies a given node (for	91	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	92	network. Depending on the configuration used, node IDs can look like a
65	node (for public nodes).	93	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		94	doesn't interpret node IDs in any way.
		95
		96	=item binds - C<ip:port>
		97
		98	Nodes can only talk to each other by creating some kind of connection to
		99	each other. To do this, nodes should listen on one or more local transport
		100	endpoints - binds. Currently, only standard C<ip:port> specifications can
		101	be used, which specify TCP ports to listen on.
		102
		103	=item seeds - C<host:port>
		104
		105	When a node starts, it knows nothing about the network. To teach the node
		106	about the network it first has to contact some other node within the
		107	network. This node is called a seed.
		108
		109	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		110	are expected to be long-running, and at least one of those should always
		111	be available. When nodes run out of connections (e.g. due to a network
		112	error), they try to re-establish connections to some seednodes again to
		113	join the network.
		114
		115	Apart from being sued for seeding, seednodes are not special in any way -
		116	every public node can be a seednode.
66		117
67	=back	118	=back
68		119
69	=head1 VARIABLES/FUNCTIONS	120	=head1 VARIABLES/FUNCTIONS
70		121
…		…
72		123
73	=cut	124	=cut
74		125
75	package AnyEvent::MP;	126	package AnyEvent::MP;
76		127
77	use AnyEvent::MP::Base;	128	use AnyEvent::MP::Kernel;
78		129
79	use common::sense;	130	use common::sense;
80		131
81	use Carp ();	132	use Carp ();
82		133
83	use AE ();	134	use AE ();
84		135
85	use base "Exporter";	136	use base "Exporter";
86		137
87	our $VERSION = '0.02';	138	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		139
88	our @EXPORT = qw(	140	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv _any_	141	NODE $NODE *SELF node_of after
90	create_port create_port_on	142	configure
91	create_miniport	143	snd rcv mon mon_guard kil reg psub spawn
92	become_slave become_public	144	port
93	);	145	);
94		146
		147	our $SELF;
		148
		149	sub _self_die() {
		150	my $msg = $@;
		151	$msg =~ s/\n+$// unless ref $msg;
		152	kil $SELF, die => $msg;
		153	}
		154
95	=item NODE / $NODE	155	=item $thisnode = NODE / $NODE
96		156
97	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	157	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	158	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.	159	a call to C<configure>.
100		160
		161	=item $nodeid = node_of $port
		162
		163	Extracts and returns the node ID from a port ID or a node ID.
		164
		165	=item configure key => value...
		166
		167	Before a node can talk to other nodes on the network (i.e. enter
		168	"distributed mode") it has to configure itself - the minimum a node needs
		169	to know is its own name, and optionally it should know the addresses of
		170	some other nodes in the network to discover other nodes.
		171
		172	This function configures a node - it must be called exactly once (or
		173	never) before calling other AnyEvent::MP functions.
		174
		175	=over 4
		176
		177	=item step 1, gathering configuration from profiles
		178
		179	The function first looks up a profile in the aemp configuration (see the
		180	L<aemp> commandline utility). The profile name can be specified via the
		181	named C<profile> parameter. If it is missing, then the nodename (F<uname
		182	-n>) will be used as profile name.
		183
		184	The profile data is then gathered as follows:
		185
		186	First, all remaining key => value pairs (all of which are conviniently
		187	undocumented at the moment) will be interpreted as configuration
		188	data. Then they will be overwritten by any values specified in the global
		189	default configuration (see the F<aemp> utility), then the chain of
		190	profiles chosen by the profile name (and any C<parent> attributes).
		191
		192	That means that the values specified in the profile have highest priority
		193	and the values specified directly via C<configure> have lowest priority,
		194	and can only be used to specify defaults.
		195
		196	If the profile specifies a node ID, then this will become the node ID of
		197	this process. If not, then the profile name will be used as node ID. The
		198	special node ID of C<anon/> will be replaced by a random node ID.
		199
		200	=item step 2, bind listener sockets
		201
		202	The next step is to look up the binds in the profile, followed by binding
		203	aemp protocol listeners on all binds specified (it is possible and valid
		204	to have no binds, meaning that the node cannot be contacted form the
		205	outside. This means the node cannot talk to other nodes that also have no
		206	binds, but it can still talk to all "normal" nodes).
		207
		208	If the profile does not specify a binds list, then a default of C<*> is
		209	used, meaning the node will bind on a dynamically-assigned port on every
		210	local IP address it finds.
		211
		212	=item step 3, connect to seed nodes
		213
		214	As the last step, the seeds list from the profile is passed to the
		215	L<AnyEvent::MP::Global> module, which will then use it to keep
		216	connectivity with at least one node at any point in time.
		217
		218	=back
		219
		220	Example: become a distributed node using the locla node name as profile.
		221	This should be the most common form of invocation for "daemon"-type nodes.
		222
		223	configure
		224
		225	Example: become an anonymous node. This form is often used for commandline
		226	clients.
		227
		228	configure nodeid => "anon/";
		229
		230	Example: configure a node using a profile called seed, which si suitable
		231	for a seed node as it binds on all local addresses on a fixed port (4040,
		232	customary for aemp).
		233
		234	# use the aemp commandline utility
		235	# aemp profile seed nodeid anon/ binds '*:4040'
		236
		237	# then use it
		238	configure profile => "seed";
		239
		240	# or simply use aemp from the shell again:
		241	# aemp run profile seed
		242
		243	# or provide a nicer-to-remember nodeid
		244	# aemp run profile seed nodeid "$(hostname)"
		245
		246	=item $SELF
		247
		248	Contains the current port id while executing C<rcv> callbacks or C<psub>
		249	blocks.
		250
		251	=item *SELF, SELF, %SELF, @SELF...
		252
		253	Due to some quirks in how perl exports variables, it is impossible to
		254	just export C<$SELF>, all the symbols named C<SELF> are exported by this
		255	module, but only C<$SELF> is currently used.
		256
101	=item snd $portid, type => @data	257	=item snd $port, type => @data
102		258
103	=item snd $portid, @msg	259	=item snd $port, @msg
104		260
105	Send the given message to the given port ID, which can identify either	261	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	262	local or a remote port, and must be a port ID.
107	stringifies a sa port ID (such as a port object :).
108		263
109	While the message can be about anything, it is highly recommended to use a	264	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	265	use a string as first element (a port ID, or some word that indicates a
111	type etc.).	266	request type etc.) and to consist if only simple perl values (scalars,
		267	arrays, hashes) - if you think you need to pass an object, think again.
112		268
113	The message data effectively becomes read-only after a call to this	269	The message data logically becomes read-only after a call to this
114	function: modifying any argument is not allowed and can cause many	270	function: modifying any argument (or values referenced by them) is
115	problems.	271	forbidden, as there can be considerable time between the call to C<snd>
		272	and the time the message is actually being serialised - in fact, it might
		273	never be copied as within the same process it is simply handed to the
		274	receiving port.
116		275
117	The type of data you can transfer depends on the transport protocol: when	276	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	277	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	278	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	279	that Storable can serialise and deserialise is allowed, and for the local
121	node, anything can be passed.	280	node, anything can be passed. Best rely only on the common denominator of
		281	these.
122		282
123	=item $local_port = create_port	283	=item $local_port = port
124		284
125	Create a new local port object. See the next section for allowed methods.	285	Create a new local port object and returns its port ID. Initially it has
		286	no callbacks set and will throw an error when it receives messages.
126		287
127	=cut	288	=item $local_port = port { my @msg = @_ }
128		289
129	sub create_port {	290	Creates a new local port, and returns its ID. Semantically the same as
130	my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;	291	creating a port and calling C<rcv $port, $callback> on it.
131		292
132	my $self = bless {	293	The block will be called for every message received on the port, with the
133	id => "$NODE#$id",	294	global variable C<$SELF> set to the port ID. Runtime errors will cause the
134	names => [$id],	295	port to be C<kil>ed. The message will be passed as-is, no extra argument
135	}, "AnyEvent::MP::Port";	296	(i.e. no port ID) will be passed to the callback.
136		297
137	$AnyEvent::MP::Base::PORT{$id} = sub {	298	If you want to stop/destroy the port, simply C<kil> it:
138	unshift @_, $self;
139		299
140	for (@{ $self->{rc0}{$_[1]} }) {	300	my $port = port {
141	$_ && &{$_->[0]}	301	my @msg = @_;
142	&& undef $_;	302	...
		303	kil $SELF;
		304	};
		305
		306	=cut
		307
		308	sub rcv($@);
		309
		310	sub _kilme {
		311	die "received message on port without callback";
		312	}
		313
		314	sub port(;&) {
		315	my $id = "$UNIQ." . $ID++;
		316	my $port = "$NODE#$id";
		317
		318	rcv $port, shift \|\| \&_kilme;
		319
		320	$port
		321	}
		322
		323	=item rcv $local_port, $callback->(@msg)
		324
		325	Replaces the default callback on the specified port. There is no way to
		326	remove the default callback: use C<sub { }> to disable it, or better
		327	C<kil> the port when it is no longer needed.
		328
		329	The global C<$SELF> (exported by this module) contains C<$port> while
		330	executing the callback. Runtime errors during callback execution will
		331	result in the port being C<kil>ed.
		332
		333	The default callback received all messages not matched by a more specific
		334	C<tag> match.
		335
		336	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		337
		338	Register (or replace) callbacks to be called on messages starting with the
		339	given tag on the given port (and return the port), or unregister it (when
		340	C<$callback> is C<$undef> or missing). There can only be one callback
		341	registered for each tag.
		342
		343	The original message will be passed to the callback, after the first
		344	element (the tag) has been removed. The callback will use the same
		345	environment as the default callback (see above).
		346
		347	Example: create a port and bind receivers on it in one go.
		348
		349	my $port = rcv port,
		350	msg1 => sub { ... },
		351	msg2 => sub { ... },
		352	;
		353
		354	Example: create a port, bind receivers and send it in a message elsewhere
		355	in one go:
		356
		357	snd $otherport, reply =>
		358	rcv port,
		359	msg1 => sub { ... },
		360	...
		361	;
		362
		363	Example: temporarily register a rcv callback for a tag matching some port
		364	(e.g. for a rpc reply) and unregister it after a message was received.
		365
		366	rcv $port, $otherport => sub {
		367	my @reply = @_;
		368
		369	rcv $SELF, $otherport;
		370	};
		371
		372	=cut
		373
		374	sub rcv($@) {
		375	my $port = shift;
		376	my ($nodeid, $portid) = split /#/, $port, 2;
		377
		378	$NODE{$nodeid} == $NODE{""}
		379	or Carp::croak "$port: rcv can only be called on local ports, caught";
		380
		381	while (@_) {
		382	if (ref $_[0]) {
		383	if (my $self = $PORT_DATA{$portid}) {
		384	"AnyEvent::MP::Port" eq ref $self
		385	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		386
		387	$self->[2] = shift;
		388	} else {
		389	my $cb = shift;
		390	$PORT{$portid} = sub {
		391	local $SELF = $port;
		392	eval { &$cb }; _self_die if $@;
		393	};
		394	}
		395	} elsif (defined $_[0]) {
		396	my $self = $PORT_DATA{$portid} \|\|= do {
		397	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		398
		399	$PORT{$portid} = sub {
		400	local $SELF = $port;
		401
		402	if (my $cb = $self->[1]{$_[0]}) {
		403	shift;
		404	eval { &$cb }; _self_die if $@;
		405	} else {
		406	&{ $self->[0] };
		407	}
		408	};
		409
		410	$self
		411	};
		412
		413	"AnyEvent::MP::Port" eq ref $self
		414	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		415
		416	my ($tag, $cb) = splice @_, 0, 2;
		417
		418	if (defined $cb) {
		419	$self->[1]{$tag} = $cb;
		420	} else {
		421	delete $self->[1]{$tag};
		422	}
143	}	423	}
		424	}
144		425
145	for (@{ $self->{rcv}{$_[1]} }) {	426	$port
146	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	427	}
147	&& &{$_->[0]}	428
148	&& undef $_;	429	=item $closure = psub { BLOCK }
		430
		431	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		432	closure is executed, sets up the environment in the same way as in C<rcv>
		433	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		434
		435	This is useful when you register callbacks from C<rcv> callbacks:
		436
		437	rcv delayed_reply => sub {
		438	my ($delay, @reply) = @_;
		439	my $timer = AE::timer $delay, 0, psub {
		440	snd @reply, $SELF;
		441	};
		442	};
		443
		444	=cut
		445
		446	sub psub(&) {
		447	my $cb = shift;
		448
		449	my $port = $SELF
		450	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		451
		452	sub {
		453	local $SELF = $port;
		454
		455	if (wantarray) {
		456	my @res = eval { &$cb };
		457	_self_die if $@;
		458	@res
		459	} else {
		460	my $res = eval { &$cb };
		461	_self_die if $@;
		462	$res
149	}	463	}
		464	}
		465	}
150		466
151	for (@{ $self->{any} }) {	467	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
152	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	468
153	&& &{$_->[0]}	469	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
154	&& undef $_;	470
		471	=item $guard = mon $port # kill $SELF when $port dies
		472
		473	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		474
		475	Monitor the given port and do something when the port is killed or
		476	messages to it were lost, and optionally return a guard that can be used
		477	to stop monitoring again.
		478
		479	C<mon> effectively guarantees that, in the absence of hardware failures,
		480	after starting the monitor, either all messages sent to the port will
		481	arrive, or the monitoring action will be invoked after possible message
		482	loss has been detected. No messages will be lost "in between" (after
		483	the first lost message no further messages will be received by the
		484	port). After the monitoring action was invoked, further messages might get
		485	delivered again.
		486
		487	Note that monitoring-actions are one-shot: once messages are lost (and a
		488	monitoring alert was raised), they are removed and will not trigger again.
		489
		490	In the first form (callback), the callback is simply called with any
		491	number of C<@reason> elements (no @reason means that the port was deleted
		492	"normally"). Note also that I<< the callback B<must> never die >>, so use
		493	C<eval> if unsure.
		494
		495	In the second form (another port given), the other port (C<$rcvport>)
		496	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
		497	"normal" kils nothing happens, while under all other conditions, the other
		498	port is killed with the same reason.
		499
		500	The third form (kill self) is the same as the second form, except that
		501	C<$rvport> defaults to C<$SELF>.
		502
		503	In the last form (message), a message of the form C<@msg, @reason> will be
		504	C<snd>.
		505
		506	As a rule of thumb, monitoring requests should always monitor a port from
		507	a local port (or callback). The reason is that kill messages might get
		508	lost, just like any other message. Another less obvious reason is that
		509	even monitoring requests can get lost (for exmaple, when the connection
		510	to the other node goes down permanently). When monitoring a port locally
		511	these problems do not exist.
		512
		513	Example: call a given callback when C<$port> is killed.
		514
		515	mon $port, sub { warn "port died because of <@_>\n" };
		516
		517	Example: kill ourselves when C<$port> is killed abnormally.
		518
		519	mon $port;
		520
		521	Example: send us a restart message when another C<$port> is killed.
		522
		523	mon $port, $self => "restart";
		524
		525	=cut
		526
		527	sub mon {
		528	my ($nodeid, $port) = split /#/, shift, 2;
		529
		530	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
		531
		532	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		533
		534	unless (ref $cb) {
		535	if (@_) {
		536	# send a kill info message
		537	my (@msg) = ($cb, @_);
		538	$cb = sub { snd @msg, @_ };
		539	} else {
		540	# simply kill other port
		541	my $port = $cb;
		542	$cb = sub { kil $port, @_ if @_ };
155	}	543	}
		544	}
		545
		546	$node->monitor ($port, $cb);
		547
		548	defined wantarray
		549	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		550	}
		551
		552	=item $guard = mon_guard $port, $ref, $ref...
		553
		554	Monitors the given C<$port> and keeps the passed references. When the port
		555	is killed, the references will be freed.
		556
		557	Optionally returns a guard that will stop the monitoring.
		558
		559	This function is useful when you create e.g. timers or other watchers and
		560	want to free them when the port gets killed (note the use of C<psub>):
		561
		562	$port->rcv (start => sub {
		563	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
		564	undef $timer if 0.9 < rand;
		565	});
		566	});
		567
		568	=cut
		569
		570	sub mon_guard {
		571	my ($port, @refs) = @_;
		572
		573	#TODO: mon-less form?
		574
		575	mon $port, sub { 0 && @refs }
		576	}
		577
		578	=item kil $port[, @reason]
		579
		580	Kill the specified port with the given C<@reason>.
		581
		582	If no C<@reason> is specified, then the port is killed "normally" (ports
		583	monitoring other ports will not necessarily die because a port dies
		584	"normally").
		585
		586	Otherwise, linked ports get killed with the same reason (second form of
		587	C<mon>, see above).
		588
		589	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		590	will be reported as reason C<< die => $@ >>.
		591
		592	Transport/communication errors are reported as C<< transport_error =>
		593	$message >>.
		594
		595	=cut
		596
		597	=item $port = spawn $node, $initfunc[, @initdata]
		598
		599	Creates a port on the node C<$node> (which can also be a port ID, in which
		600	case it's the node where that port resides).
		601
		602	The port ID of the newly created port is returned immediately, and it is
		603	possible to immediately start sending messages or to monitor the port.
		604
		605	After the port has been created, the init function is called on the remote
		606	node, in the same context as a C<rcv> callback. This function must be a
		607	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		608	specify a function in the main program, use C<::name>.
		609
		610	If the function doesn't exist, then the node tries to C<require>
		611	the package, then the package above the package and so on (e.g.
		612	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		613	exists or it runs out of package names.
		614
		615	The init function is then called with the newly-created port as context
		616	object (C<$SELF>) and the C<@initdata> values as arguments.
		617
		618	A common idiom is to pass a local port, immediately monitor the spawned
		619	port, and in the remote init function, immediately monitor the passed
		620	local port. This two-way monitoring ensures that both ports get cleaned up
		621	when there is a problem.
		622
		623	Example: spawn a chat server port on C<$othernode>.
		624
		625	# this node, executed from within a port context:
		626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		627	mon $server;
		628
		629	# init function on C<$othernode>
		630	sub connect {
		631	my ($srcport) = @_;
		632
		633	mon $srcport;
		634
		635	rcv $SELF, sub {
		636	...
		637	};
		638	}
		639
		640	=cut
		641
		642	sub _spawn {
		643	my $port = shift;
		644	my $init = shift;
		645
		646	local $SELF = "$NODE#$port";
		647	eval {
		648	&{ load_func $init }
156	};	649	};
157		650	_self_die if $@;
158	$self
159	}	651	}
160		652
161	=item $portid = miniport { my @msg = @_; $finished }	653	sub spawn(@) {
		654	my ($nodeid, undef) = split /#/, shift, 2;
162		655
163	Creates a "mini port", that is, a very lightweight port without any	656	my $id = "$RUNIQ." . $ID++;
164	pattern matching behind it, and returns its ID.
165		657
166	The block will be called for every message received on the port. When the	658	$_[0] =~ /::/
167	callback returns a true value its job is considered "done" and the port	659	or Carp::croak "spawn init function must be a fully-qualified name, caught";
168	will be destroyed. Otherwise it will stay alive.
169		660
170	The message will be passed as-is, no extra argument (i.e. no port id) will	661	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
171	be passed to the callback.
172		662
173	If you need the local port id in the callback, this works nicely:	663	"$nodeid#$id"
		664	}
174		665
175	my $port; $port = miniport {	666	=item after $timeout, @msg
176	snd $otherport, reply => $port;	667
		668	=item after $timeout, $callback
		669
		670	Either sends the given message, or call the given callback, after the
		671	specified number of seconds.
		672
		673	This is simply a utility function that comes in handy at times - the
		674	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		675	so it may go away in the future.
		676
		677	=cut
		678
		679	sub after($@) {
		680	my ($timeout, @action) = @_;
		681
		682	my $t; $t = AE::timer $timeout, 0, sub {
		683	undef $t;
		684	ref $action[0]
		685	? $action[0]()
		686	: snd @action;
177	};	687	};
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	}	688	}
192
193	package AnyEvent::MP::Port;
194		689
195	=back	690	=back
196		691
197	=head1 METHODS FOR PORT OBJECTS	692	=head1 AnyEvent::MP vs. Distributed Erlang
		693
		694	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		695	== aemp node, Erlang process == aemp port), so many of the documents and
		696	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		697	sample:
		698
		699	http://www.Erlang.se/doc/programming_rules.shtml
		700	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		701	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		702	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		703
		704	Despite the similarities, there are also some important differences:
198		705
199	=over 4	706	=over 4
200		707
201	=item "$port"	708	=item * Node IDs are arbitrary strings in AEMP.
202		709
203	A port object stringifies to its port ID, so can be used directly for	710	Erlang relies on special naming and DNS to work everywhere in the same
204	C<snd> operations.	711	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		712	configuraiton or DNS), but will otherwise discover other odes itself.
205		713
206	=cut	714	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		715	uses "local ports are like remote ports".
207		716
208	use overload	717	The failure modes for local ports are quite different (runtime errors
209	'""' => sub { $_[0]{id} },	718	only) then for remote ports - when a local port dies, you I<know> it dies,
210	fallback => 1;	719	when a connection to another node dies, you know nothing about the other
		720	port.
211		721
212	=item $port->rcv (type => $callback->($port, @msg))	722	Erlang pretends remote ports are as reliable as local ports, even when
		723	they are not.
213		724
214	=item $port->rcv ($smartmatch => $callback->($port, @msg))	725	AEMP encourages a "treat remote ports differently" philosophy, with local
		726	ports being the special case/exception, where transport errors cannot
		727	occur.
215		728
216	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	729	=item * Erlang uses processes and a mailbox, AEMP does not queue.
217		730
218	Register a callback on the given port.	731	Erlang uses processes that selectively receive messages, and therefore
		732	needs a queue. AEMP is event based, queuing messages would serve no
		733	useful purpose. For the same reason the pattern-matching abilities of
		734	AnyEvent::MP are more limited, as there is little need to be able to
		735	filter messages without dequeing them.
219		736
220	The callback has to return a true value when its work is done, after	737	(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		738
224	If the match is an array reference, then it will be matched against the	739	=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		740
228	Any element in the match that is specified as C<_any_> (a function	741	Sending messages in Erlang is synchronous and blocks the process (and
229	exported by this module) matches any single element of the message.	742	so does not need a queue that can overflow). AEMP sends are immediate,
		743	connection establishment is handled in the background.
230		744
231	While not required, it is highly recommended that the first matching	745	=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		746
235	=cut	747	Erlang makes few guarantees on messages delivery - messages can get lost
		748	without any of the processes realising it (i.e. you send messages a, b,
		749	and c, and the other side only receives messages a and c).
236		750
237	sub rcv($@) {	751	AEMP guarantees correct ordering, and the guarantee that after one message
238	my ($self, $match, $cb) = @_;	752	is lost, all following ones sent to the same port are lost as well, until
		753	monitoring raises an error, so there are no silent "holes" in the message
		754	sequence.
239		755
240	if (!ref $match) {	756	=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		757
252	=item $port->register ($name)	758	In Erlang it is quite likely that a node that restarts reuses a process ID
		759	known to other nodes for a completely different process, causing messages
		760	destined for that process to end up in an unrelated process.
253		761
254	Registers the given port under the well known name C<$name>. If the name	762	AEMP never reuses port IDs, so old messages or old port IDs floating
255	already exists it is replaced.	763	around in the network will not be sent to an unrelated port.
256		764
257	A port can only be registered under one well known name.	765	=item * Erlang uses unprotected connections, AEMP uses secure
		766	authentication and can use TLS.
258		767
259	=cut	768	AEMP can use a proven protocol - TLS - to protect connections and
		769	securely authenticate nodes.
260		770
261	sub register {	771	=item * The AEMP protocol is optimised for both text-based and binary
262	my ($self, $name) = @_;	772	communications.
263		773
264	$self->{wkname} = $name;	774	The AEMP protocol, unlike the Erlang protocol, supports both programming
265	$AnyEvent::MP::Base::WKP{$name} = "$self";	775	language independent text-only protocols (good for debugging) and binary,
266	}	776	language-specific serialisers (e.g. Storable). By default, unless TLS is
		777	used, the protocol is actually completely text-based.
267		778
268	=item $port->destroy	779	It has also been carefully designed to be implementable in other languages
		780	with a minimum of work while gracefully degrading functionality to make the
		781	protocol simple.
269		782
270	Explicitly destroy/remove/nuke/vaporise the port.	783	=item * AEMP has more flexible monitoring options than Erlang.
271		784
272	Ports are normally kept alive by there mere existance alone, and need to	785	In Erlang, you can chose to receive I<all> exit signals as messages
273	be destroyed explicitly.	786	or I<none>, there is no in-between, so monitoring single processes is
		787	difficult to implement. Monitoring in AEMP is more flexible than in
		788	Erlang, as one can choose between automatic kill, exit message or callback
		789	on a per-process basis.
274		790
275	=cut	791	=item * Erlang tries to hide remote/local connections, AEMP does not.
276		792
277	sub destroy {	793	Monitoring in Erlang is not an indicator of process death/crashes, in the
278	my ($self) = @_;	794	same way as linking is (except linking is unreliable in Erlang).
279		795
280	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	796	In AEMP, you don't "look up" registered port names or send to named ports
		797	that might or might not be persistent. Instead, you normally spawn a port
		798	on the remote node. The init function monitors you, and you monitor the
		799	remote port. Since both monitors are local to the node, they are much more
		800	reliable (no need for C<spawn_link>).
281		801
282	delete $AnyEvent::MP::Base::PORT{$_}	802	This also saves round-trips and avoids sending messages to the wrong port
283	for @{ $self->{names} };	803	(hard to do in Erlang).
284	}
285		804
286	=back	805	=back
287		806
288	=head1 FUNCTIONS FOR NODES	807	=head1 RATIONALE
289		808
290	=over 4	809	=over 4
291		810
292	=item mon $noderef, $callback->($noderef, $status, $)	811	=item Why strings for port and node IDs, why not objects?
293		812
294	Monitors the given noderef.	813	We considered "objects", but found that the actual number of methods
		814	that can be called are quite low. Since port and node IDs travel over
		815	the network frequently, the serialising/deserialising would add lots of
		816	overhead, as well as having to keep a proxy object everywhere.
295		817
296	=item become_public endpoint...	818	Strings can easily be printed, easily serialised etc. and need no special
		819	procedures to be "valid".
297		820
298	Tells the node to become a public node, i.e. reachable from other nodes.	821	And as a result, a miniport consists of a single closure stored in a
		822	global hash - it can't become much cheaper.
299		823
300	If no arguments are given, or the first argument is C<undef>, then	824	=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		825
304	Otherwise the first argument must be an array-reference with transport	826	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	827	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	828	default (although all nodes will accept it).
307	will become the node reference.
308		829
309	=cut	830	The default framing protocol is JSON because a) JSON::XS is many times
		831	faster for small messages and b) most importantly, after years of
		832	experience we found that object serialisation is causing more problems
		833	than it solves: Just like function calls, objects simply do not travel
		834	easily over the network, mostly because they will always be a copy, so you
		835	always have to re-think your design.
		836
		837	Keeping your messages simple, concentrating on data structures rather than
		838	objects, will keep your messages clean, tidy and efficient.
310		839
311	=back	840	=back
312		841
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	842	=head1 SEE ALSO
		843
		844	L<AnyEvent::MP::Intro> - a gentle introduction.
		845
		846	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		847
		848	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		849	your applications.
358		850
359	L<AnyEvent>.	851	L<AnyEvent>.
360		852
361	=head1 AUTHOR	853	=head1 AUTHOR
362		854

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Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC