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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.10 by root, Sun Aug 2 18:05:43 2009 UTC vs.
Revision 1.82 by root, Mon Sep 7 18:42:09 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 seeds - C<host:port>
		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	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		109	are expected to be long-running, and at least one of those should always
		110	be available. When nodes run out of connections (e.g. due to a network
		111	error), they try to re-establish connections to some seednodes again to
		112	join the network.
		113
		114	Apart from being sued for seeding, seednodes are not special in any way -
		115	every public node can be a seednode.
66		116
67	=back	117	=back
68		118
69	=head1 VARIABLES/FUNCTIONS	119	=head1 VARIABLES/FUNCTIONS
70		120
…		…
72		122
73	=cut	123	=cut
74		124
75	package AnyEvent::MP;	125	package AnyEvent::MP;
76		126
77	use AnyEvent::MP::Base;	127	use AnyEvent::MP::Kernel;
78		128
79	use common::sense;	129	use common::sense;
80		130
81	use Carp ();	131	use Carp ();
82		132
83	use AE ();	133	use AE ();
84		134
85	use base "Exporter";	135	use base "Exporter";
86		136
87	our $VERSION = '0.02';	137	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		138
88	our @EXPORT = qw(	139	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv _any_	140	NODE $NODE *SELF node_of after
90	create_port create_port_on	141	configure
91	become_slave become_public	142	snd rcv mon mon_guard kil reg psub spawn
		143	port
92	);	144	);
93		145
		146	our $SELF;
		147
		148	sub _self_die() {
		149	my $msg = $@;
		150	$msg =~ s/\n+$// unless ref $msg;
		151	kil $SELF, die => $msg;
		152	}
		153
94	=item NODE / $NODE	154	=item $thisnode = NODE / $NODE
95		155
96	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	156	The C<NODE> function returns, and the C<$NODE> variable contains, the node
97	the local node. The value is initialised by a call to C<become_public> or	157	ID of the node running in the current process. This value is initialised by
98	C<become_slave>, after which all local port identifiers become invalid.	158	a call to C<configure>.
99		159
		160	=item $nodeid = node_of $port
		161
		162	Extracts and returns the node ID from a port ID or a node ID.
		163
		164	=item configure $profile, key => value...
		165
		166	=item configure key => value...
		167
		168	Before a node can talk to other nodes on the network (i.e. enter
		169	"distributed mode") it has to configure itself - the minimum a node needs
		170	to know is its own name, and optionally it should know the addresses of
		171	some other nodes in the network to discover other nodes.
		172
		173	This function configures a node - it must be called exactly once (or
		174	never) before calling other AnyEvent::MP functions.
		175
		176	=over 4
		177
		178	=item step 1, gathering configuration from profiles
		179
		180	The function first looks up a profile in the aemp configuration (see the
		181	L<aemp> commandline utility). The profile name can be specified via the
		182	named C<profile> parameter or can simply be the first parameter). If it is
		183	missing, then the nodename (F<uname -n>) will be used as profile name.
		184
		185	The profile data is then gathered as follows:
		186
		187	First, all remaining key => value pairs (all of which are conveniently
		188	undocumented at the moment) will be interpreted as configuration
		189	data. Then they will be overwritten by any values specified in the global
		190	default configuration (see the F<aemp> utility), then the chain of
		191	profiles chosen by the profile name (and any C<parent> attributes).
		192
		193	That means that the values specified in the profile have highest priority
		194	and the values specified directly via C<configure> have lowest priority,
		195	and can only be used to specify defaults.
		196
		197	If the profile specifies a node ID, then this will become the node ID of
		198	this process. If not, then the profile name will be used as node ID. The
		199	special node ID of C<anon/> will be replaced by a random node ID.
		200
		201	=item step 2, bind listener sockets
		202
		203	The next step is to look up the binds in the profile, followed by binding
		204	aemp protocol listeners on all binds specified (it is possible and valid
		205	to have no binds, meaning that the node cannot be contacted form the
		206	outside. This means the node cannot talk to other nodes that also have no
		207	binds, but it can still talk to all "normal" nodes).
		208
		209	If the profile does not specify a binds list, then a default of C<*> is
		210	used, meaning the node will bind on a dynamically-assigned port on every
		211	local IP address it finds.
		212
		213	=item step 3, connect to seed nodes
		214
		215	As the last step, the seeds list from the profile is passed to the
		216	L<AnyEvent::MP::Global> module, which will then use it to keep
		217	connectivity with at least one node at any point in time.
		218
		219	=back
		220
		221	Example: become a distributed node using the locla node name as profile.
		222	This should be the most common form of invocation for "daemon"-type nodes.
		223
		224	configure
		225
		226	Example: become an anonymous node. This form is often used for commandline
		227	clients.
		228
		229	configure nodeid => "anon/";
		230
		231	Example: configure a node using a profile called seed, which si suitable
		232	for a seed node as it binds on all local addresses on a fixed port (4040,
		233	customary for aemp).
		234
		235	# use the aemp commandline utility
		236	# aemp profile seed nodeid anon/ binds '*:4040'
		237
		238	# then use it
		239	configure profile => "seed";
		240
		241	# or simply use aemp from the shell again:
		242	# aemp run profile seed
		243
		244	# or provide a nicer-to-remember nodeid
		245	# aemp run profile seed nodeid "$(hostname)"
		246
		247	=item $SELF
		248
		249	Contains the current port id while executing C<rcv> callbacks or C<psub>
		250	blocks.
		251
		252	=item *SELF, SELF, %SELF, @SELF...
		253
		254	Due to some quirks in how perl exports variables, it is impossible to
		255	just export C<$SELF>, all the symbols named C<SELF> are exported by this
		256	module, but only C<$SELF> is currently used.
		257
100	=item snd $portid, type => @data	258	=item snd $port, type => @data
101		259
102	=item snd $portid, @msg	260	=item snd $port, @msg
103		261
104	Send the given message to the given port ID, which can identify either	262	Send the given message to the given port, which can identify either a
105	a local or a remote port, and can be either a string or soemthignt hat	263	local or a remote port, and must be a port ID.
106	stringifies a sa port ID (such as a port object :).
107		264
108	While the message can be about anything, it is highly recommended to use a	265	While the message can be almost anything, it is highly recommended to
109	string as first element (a portid, or some word that indicates a request	266	use a string as first element (a port ID, or some word that indicates a
110	type etc.).	267	request type etc.) and to consist if only simple perl values (scalars,
		268	arrays, hashes) - if you think you need to pass an object, think again.
111		269
112	The message data effectively becomes read-only after a call to this	270	The message data logically becomes read-only after a call to this
113	function: modifying any argument is not allowed and can cause many	271	function: modifying any argument (or values referenced by them) is
114	problems.	272	forbidden, as there can be considerable time between the call to C<snd>
		273	and the time the message is actually being serialised - in fact, it might
		274	never be copied as within the same process it is simply handed to the
		275	receiving port.
115		276
116	The type of data you can transfer depends on the transport protocol: when	277	The type of data you can transfer depends on the transport protocol: when
117	JSON is used, then only strings, numbers and arrays and hashes consisting	278	JSON is used, then only strings, numbers and arrays and hashes consisting
118	of those are allowed (no objects). When Storable is used, then anything	279	of those are allowed (no objects). When Storable is used, then anything
119	that Storable can serialise and deserialise is allowed, and for the local	280	that Storable can serialise and deserialise is allowed, and for the local
120	node, anything can be passed.	281	node, anything can be passed. Best rely only on the common denominator of
		282	these.
121		283
122	=item $local_port = create_port	284	=item $local_port = port
123		285
124	Create a new local port object. See the next section for allowed methods.	286	Create a new local port object and returns its port ID. Initially it has
		287	no callbacks set and will throw an error when it receives messages.
125		288
126	=cut	289	=item $local_port = port { my @msg = @_ }
127		290
128	sub create_port {	291	Creates a new local port, and returns its ID. Semantically the same as
129	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;	292	creating a port and calling C<rcv $port, $callback> on it.
130		293
131	my $self = bless {	294	The block will be called for every message received on the port, with the
132	id => "$NODE#$id",	295	global variable C<$SELF> set to the port ID. Runtime errors will cause the
133	names => [$id],	296	port to be C<kil>ed. The message will be passed as-is, no extra argument
134	}, "AnyEvent::MP::Port";	297	(i.e. no port ID) will be passed to the callback.
135		298
136	$AnyEvent::MP::Base::PORT{$id} = sub {	299	If you want to stop/destroy the port, simply C<kil> it:
137	unshift @_, $self;
138		300
139	for (@{ $self->{rc0}{$_[1]} }) {	301	my $port = port {
140	$_ && &{$_->[0]}	302	my @msg = @_;
141	&& undef $_;	303	...
		304	kil $SELF;
		305	};
		306
		307	=cut
		308
		309	sub rcv($@);
		310
		311	sub _kilme {
		312	die "received message on port without callback";
		313	}
		314
		315	sub port(;&) {
		316	my $id = "$UNIQ." . $ID++;
		317	my $port = "$NODE#$id";
		318
		319	rcv $port, shift \|\| \&_kilme;
		320
		321	$port
		322	}
		323
		324	=item rcv $local_port, $callback->(@msg)
		325
		326	Replaces the default callback on the specified port. There is no way to
		327	remove the default callback: use C<sub { }> to disable it, or better
		328	C<kil> the port when it is no longer needed.
		329
		330	The global C<$SELF> (exported by this module) contains C<$port> while
		331	executing the callback. Runtime errors during callback execution will
		332	result in the port being C<kil>ed.
		333
		334	The default callback received all messages not matched by a more specific
		335	C<tag> match.
		336
		337	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
		338
		339	Register (or replace) callbacks to be called on messages starting with the
		340	given tag on the given port (and return the port), or unregister it (when
		341	C<$callback> is C<$undef> or missing). There can only be one callback
		342	registered for each tag.
		343
		344	The original message will be passed to the callback, after the first
		345	element (the tag) has been removed. The callback will use the same
		346	environment as the default callback (see above).
		347
		348	Example: create a port and bind receivers on it in one go.
		349
		350	my $port = rcv port,
		351	msg1 => sub { ... },
		352	msg2 => sub { ... },
		353	;
		354
		355	Example: create a port, bind receivers and send it in a message elsewhere
		356	in one go:
		357
		358	snd $otherport, reply =>
		359	rcv port,
		360	msg1 => sub { ... },
		361	...
		362	;
		363
		364	Example: temporarily register a rcv callback for a tag matching some port
		365	(e.g. for a rpc reply) and unregister it after a message was received.
		366
		367	rcv $port, $otherport => sub {
		368	my @reply = @_;
		369
		370	rcv $SELF, $otherport;
		371	};
		372
		373	=cut
		374
		375	sub rcv($@) {
		376	my $port = shift;
		377	my ($nodeid, $portid) = split /#/, $port, 2;
		378
		379	$NODE{$nodeid} == $NODE{""}
		380	or Carp::croak "$port: rcv can only be called on local ports, caught";
		381
		382	while (@_) {
		383	if (ref $_[0]) {
		384	if (my $self = $PORT_DATA{$portid}) {
		385	"AnyEvent::MP::Port" eq ref $self
		386	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		387
		388	$self->[2] = shift;
		389	} else {
		390	my $cb = shift;
		391	$PORT{$portid} = sub {
		392	local $SELF = $port;
		393	eval { &$cb }; _self_die if $@;
		394	};
		395	}
		396	} elsif (defined $_[0]) {
		397	my $self = $PORT_DATA{$portid} \|\|= do {
		398	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		399
		400	$PORT{$portid} = sub {
		401	local $SELF = $port;
		402
		403	if (my $cb = $self->[1]{$_[0]}) {
		404	shift;
		405	eval { &$cb }; _self_die if $@;
		406	} else {
		407	&{ $self->[0] };
		408	}
		409	};
		410
		411	$self
		412	};
		413
		414	"AnyEvent::MP::Port" eq ref $self
		415	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		416
		417	my ($tag, $cb) = splice @_, 0, 2;
		418
		419	if (defined $cb) {
		420	$self->[1]{$tag} = $cb;
		421	} else {
		422	delete $self->[1]{$tag};
		423	}
142	}	424	}
		425	}
143		426
144	for (@{ $self->{rcv}{$_[1]} }) {	427	$port
145	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	428	}
146	&& &{$_->[0]}	429
147	&& undef $_;	430	=item $closure = psub { BLOCK }
		431
		432	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		433	closure is executed, sets up the environment in the same way as in C<rcv>
		434	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		435
		436	This is useful when you register callbacks from C<rcv> callbacks:
		437
		438	rcv delayed_reply => sub {
		439	my ($delay, @reply) = @_;
		440	my $timer = AE::timer $delay, 0, psub {
		441	snd @reply, $SELF;
		442	};
		443	};
		444
		445	=cut
		446
		447	sub psub(&) {
		448	my $cb = shift;
		449
		450	my $port = $SELF
		451	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		452
		453	sub {
		454	local $SELF = $port;
		455
		456	if (wantarray) {
		457	my @res = eval { &$cb };
		458	_self_die if $@;
		459	@res
		460	} else {
		461	my $res = eval { &$cb };
		462	_self_die if $@;
		463	$res
148	}	464	}
		465	}
		466	}
149		467
150	for (@{ $self->{any} }) {	468	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
151	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	469
152	&& &{$_->[0]}	470	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
153	&& undef $_;	471
		472	=item $guard = mon $port # kill $SELF when $port dies
		473
		474	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
		475
		476	Monitor the given port and do something when the port is killed or
		477	messages to it were lost, and optionally return a guard that can be used
		478	to stop monitoring again.
		479
		480	In the first form (callback), the callback is simply called with any
		481	number of C<@reason> elements (no @reason means that the port was deleted
		482	"normally"). Note also that I<< the callback B<must> never die >>, so use
		483	C<eval> if unsure.
		484
		485	In the second form (another port given), the other port (C<$rcvport>)
		486	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
		487	"normal" kils nothing happens, while under all other conditions, the other
		488	port is killed with the same reason.
		489
		490	The third form (kill self) is the same as the second form, except that
		491	C<$rvport> defaults to C<$SELF>.
		492
		493	In the last form (message), a message of the form C<@msg, @reason> will be
		494	C<snd>.
		495
		496	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		497	alert was raised), they are removed and will not trigger again.
		498
		499	As a rule of thumb, monitoring requests should always monitor a port from
		500	a local port (or callback). The reason is that kill messages might get
		501	lost, just like any other message. Another less obvious reason is that
		502	even monitoring requests can get lost (for example, when the connection
		503	to the other node goes down permanently). When monitoring a port locally
		504	these problems do not exist.
		505
		506	C<mon> effectively guarantees that, in the absence of hardware failures,
		507	after starting the monitor, either all messages sent to the port will
		508	arrive, or the monitoring action will be invoked after possible message
		509	loss has been detected. No messages will be lost "in between" (after
		510	the first lost message no further messages will be received by the
		511	port). After the monitoring action was invoked, further messages might get
		512	delivered again.
		513
		514	Inter-host-connection timeouts and monitoring depend on the transport
		515	used. The only transport currently implemented is TCP, and AnyEvent::MP
		516	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		517	non-idle connection, and usually around two hours for idle conenctions).
		518
		519	This means that monitoring is good for program errors and cleaning up
		520	stuff eventually, but they are no replacement for a timeout when you need
		521	to ensure some maximum latency.
		522
		523	Example: call a given callback when C<$port> is killed.
		524
		525	mon $port, sub { warn "port died because of <@_>\n" };
		526
		527	Example: kill ourselves when C<$port> is killed abnormally.
		528
		529	mon $port;
		530
		531	Example: send us a restart message when another C<$port> is killed.
		532
		533	mon $port, $self => "restart";
		534
		535	=cut
		536
		537	sub mon {
		538	my ($nodeid, $port) = split /#/, shift, 2;
		539
		540	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
		541
		542	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		543
		544	unless (ref $cb) {
		545	if (@_) {
		546	# send a kill info message
		547	my (@msg) = ($cb, @_);
		548	$cb = sub { snd @msg, @_ };
		549	} else {
		550	# simply kill other port
		551	my $port = $cb;
		552	$cb = sub { kil $port, @_ if @_ };
154	}	553	}
		554	}
		555
		556	$node->monitor ($port, $cb);
		557
		558	defined wantarray
		559	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		560	}
		561
		562	=item $guard = mon_guard $port, $ref, $ref...
		563
		564	Monitors the given C<$port> and keeps the passed references. When the port
		565	is killed, the references will be freed.
		566
		567	Optionally returns a guard that will stop the monitoring.
		568
		569	This function is useful when you create e.g. timers or other watchers and
		570	want to free them when the port gets killed (note the use of C<psub>):
		571
		572	$port->rcv (start => sub {
		573	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
		574	undef $timer if 0.9 < rand;
		575	});
		576	});
		577
		578	=cut
		579
		580	sub mon_guard {
		581	my ($port, @refs) = @_;
		582
		583	#TODO: mon-less form?
		584
		585	mon $port, sub { 0 && @refs }
		586	}
		587
		588	=item kil $port[, @reason]
		589
		590	Kill the specified port with the given C<@reason>.
		591
		592	If no C<@reason> is specified, then the port is killed "normally" (ports
		593	monitoring other ports will not necessarily die because a port dies
		594	"normally").
		595
		596	Otherwise, linked ports get killed with the same reason (second form of
		597	C<mon>, see above).
		598
		599	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		600	will be reported as reason C<< die => $@ >>.
		601
		602	Transport/communication errors are reported as C<< transport_error =>
		603	$message >>.
		604
		605	=cut
		606
		607	=item $port = spawn $node, $initfunc[, @initdata]
		608
		609	Creates a port on the node C<$node> (which can also be a port ID, in which
		610	case it's the node where that port resides).
		611
		612	The port ID of the newly created port is returned immediately, and it is
		613	possible to immediately start sending messages or to monitor the port.
		614
		615	After the port has been created, the init function is called on the remote
		616	node, in the same context as a C<rcv> callback. This function must be a
		617	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		618	specify a function in the main program, use C<::name>.
		619
		620	If the function doesn't exist, then the node tries to C<require>
		621	the package, then the package above the package and so on (e.g.
		622	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		623	exists or it runs out of package names.
		624
		625	The init function is then called with the newly-created port as context
		626	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		627	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		628	the port might not get created.
		629
		630	A common idiom is to pass a local port, immediately monitor the spawned
		631	port, and in the remote init function, immediately monitor the passed
		632	local port. This two-way monitoring ensures that both ports get cleaned up
		633	when there is a problem.
		634
		635	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		636	caller before C<spawn> returns (by delaying invocation when spawn is
		637	called for the local node).
		638
		639	Example: spawn a chat server port on C<$othernode>.
		640
		641	# this node, executed from within a port context:
		642	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		643	mon $server;
		644
		645	# init function on C<$othernode>
		646	sub connect {
		647	my ($srcport) = @_;
		648
		649	mon $srcport;
		650
		651	rcv $SELF, sub {
		652	...
		653	};
		654	}
		655
		656	=cut
		657
		658	sub _spawn {
		659	my $port = shift;
		660	my $init = shift;
		661
		662	# rcv will create the actual port
		663	local $SELF = "$NODE#$port";
		664	eval {
		665	&{ load_func $init }
155	};	666	};
156		667	_self_die if $@;
157	$self
158	}	668	}
159		669
160	=item $portid = create_miniport { }	670	sub spawn(@) {
		671	my ($nodeid, undef) = split /#/, shift, 2;
161		672
162	Creates a "mini port", that is, a port without much #TODO	673	my $id = "$RUNIQ." . $ID++;
163		674
164	=cut	675	$_[0] =~ /::/
		676	or Carp::croak "spawn init function must be a fully-qualified name, caught";
165		677
166	sub create_miniport(&) {	678	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
167	my $cb = shift;
168	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;
169		679
170	$AnyEvent::MP::Base::PORT{$id} = sub {	680	"$nodeid#$id"
171	&$cb	681	}
172	and delete $AnyEvent::MP::Base::PORT{$id};	682
		683	=item after $timeout, @msg
		684
		685	=item after $timeout, $callback
		686
		687	Either sends the given message, or call the given callback, after the
		688	specified number of seconds.
		689
		690	This is simply a utility function that comes in handy at times - the
		691	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		692	so it may go away in the future.
		693
		694	=cut
		695
		696	sub after($@) {
		697	my ($timeout, @action) = @_;
		698
		699	my $t; $t = AE::timer $timeout, 0, sub {
		700	undef $t;
		701	ref $action[0]
		702	? $action[0]()
		703	: snd @action;
173	};	704	};
174
175	"$NODE#$id"
176	}	705	}
177
178	package AnyEvent::MP::Port;
179		706
180	=back	707	=back
181		708
182	=head1 METHODS FOR PORT OBJECTS	709	=head1 AnyEvent::MP vs. Distributed Erlang
		710
		711	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		712	== aemp node, Erlang process == aemp port), so many of the documents and
		713	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		714	sample:
		715
		716	http://www.Erlang.se/doc/programming_rules.shtml
		717	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		718	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		719	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		720
		721	Despite the similarities, there are also some important differences:
183		722
184	=over 4	723	=over 4
185		724
186	=item "$port"	725	=item * Node IDs are arbitrary strings in AEMP.
187		726
188	A port object stringifies to its port ID, so can be used directly for	727	Erlang relies on special naming and DNS to work everywhere in the same
189	C<snd> operations.	728	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		729	configuration or DNS), but will otherwise discover other odes itself.
190		730
191	=cut	731	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		732	uses "local ports are like remote ports".
192		733
193	use overload	734	The failure modes for local ports are quite different (runtime errors
194	'""' => sub { $_[0]{id} },	735	only) then for remote ports - when a local port dies, you I<know> it dies,
195	fallback => 1;	736	when a connection to another node dies, you know nothing about the other
		737	port.
196		738
197	=item $port->rcv (type => $callback->($port, @msg))	739	Erlang pretends remote ports are as reliable as local ports, even when
		740	they are not.
198		741
199	=item $port->rcv ($smartmatch => $callback->($port, @msg))	742	AEMP encourages a "treat remote ports differently" philosophy, with local
		743	ports being the special case/exception, where transport errors cannot
		744	occur.
200		745
201	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	746	=item * Erlang uses processes and a mailbox, AEMP does not queue.
202		747
203	Register a callback on the given port.	748	Erlang uses processes that selectively receive messages, and therefore
		749	needs a queue. AEMP is event based, queuing messages would serve no
		750	useful purpose. For the same reason the pattern-matching abilities of
		751	AnyEvent::MP are more limited, as there is little need to be able to
		752	filter messages without dequeuing them.
204		753
205	The callback has to return a true value when its work is done, after	754	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
206	which is will be removed, or a false value in which case it will stay
207	registered.
208		755
209	If the match is an array reference, then it will be matched against the	756	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
210	first elements of the message, otherwise only the first element is being
211	matched.
212		757
213	Any element in the match that is specified as C<_any_> (a function	758	Sending messages in Erlang is synchronous and blocks the process (and
214	exported by this module) matches any single element of the message.	759	so does not need a queue that can overflow). AEMP sends are immediate,
		760	connection establishment is handled in the background.
215		761
216	While not required, it is highly recommended that the first matching	762	=item * Erlang suffers from silent message loss, AEMP does not.
217	element is a string identifying the message. The one-string-only match is
218	also the most efficient match (by far).
219		763
220	=cut	764	Erlang makes few guarantees on messages delivery - messages can get lost
		765	without any of the processes realising it (i.e. you send messages a, b,
		766	and c, and the other side only receives messages a and c).
221		767
222	sub rcv($@) {	768	AEMP guarantees correct ordering, and the guarantee that after one message
223	my ($self, $match, $cb) = @_;	769	is lost, all following ones sent to the same port are lost as well, until
		770	monitoring raises an error, so there are no silent "holes" in the message
		771	sequence.
224		772
225	if (!ref $match) {	773	=item * Erlang can send messages to the wrong port, AEMP does not.
226	push @{ $self->{rc0}{$match} }, [$cb];
227	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
228	my ($type, @match) = @$match;
229	@match
230	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
231	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
232	} else {
233	push @{ $self->{any} }, [$cb, $match];
234	}
235	}
236		774
237	=item $port->register ($name)	775	In Erlang it is quite likely that a node that restarts reuses a process ID
		776	known to other nodes for a completely different process, causing messages
		777	destined for that process to end up in an unrelated process.
238		778
239	Registers the given port under the well known name C<$name>. If the name	779	AEMP never reuses port IDs, so old messages or old port IDs floating
240	already exists it is replaced.	780	around in the network will not be sent to an unrelated port.
241		781
242	A port can only be registered under one well known name.	782	=item * Erlang uses unprotected connections, AEMP uses secure
		783	authentication and can use TLS.
243		784
244	=cut	785	AEMP can use a proven protocol - TLS - to protect connections and
		786	securely authenticate nodes.
245		787
246	sub register {	788	=item * The AEMP protocol is optimised for both text-based and binary
247	my ($self, $name) = @_;	789	communications.
248		790
249	$self->{wkname} = $name;	791	The AEMP protocol, unlike the Erlang protocol, supports both programming
250	$AnyEvent::MP::Base::WKP{$name} = "$self";	792	language independent text-only protocols (good for debugging) and binary,
251	}	793	language-specific serialisers (e.g. Storable). By default, unless TLS is
		794	used, the protocol is actually completely text-based.
252		795
253	=item $port->destroy	796	It has also been carefully designed to be implementable in other languages
		797	with a minimum of work while gracefully degrading functionality to make the
		798	protocol simple.
254		799
255	Explicitly destroy/remove/nuke/vaporise the port.	800	=item * AEMP has more flexible monitoring options than Erlang.
256		801
257	Ports are normally kept alive by there mere existance alone, and need to	802	In Erlang, you can chose to receive I<all> exit signals as messages
258	be destroyed explicitly.	803	or I<none>, there is no in-between, so monitoring single processes is
		804	difficult to implement. Monitoring in AEMP is more flexible than in
		805	Erlang, as one can choose between automatic kill, exit message or callback
		806	on a per-process basis.
259		807
260	=cut	808	=item * Erlang tries to hide remote/local connections, AEMP does not.
261		809
262	sub destroy {	810	Monitoring in Erlang is not an indicator of process death/crashes, in the
263	my ($self) = @_;	811	same way as linking is (except linking is unreliable in Erlang).
264		812
265	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	813	In AEMP, you don't "look up" registered port names or send to named ports
		814	that might or might not be persistent. Instead, you normally spawn a port
		815	on the remote node. The init function monitors you, and you monitor the
		816	remote port. Since both monitors are local to the node, they are much more
		817	reliable (no need for C<spawn_link>).
266		818
267	delete $AnyEvent::MP::Base::PORT{$_}	819	This also saves round-trips and avoids sending messages to the wrong port
268	for @{ $self->{names} };	820	(hard to do in Erlang).
269	}
270		821
271	=back	822	=back
272		823
273	=head1 FUNCTIONS FOR NODES	824	=head1 RATIONALE
274		825
275	=over 4	826	=over 4
276		827
277	=item mon $noderef, $callback->($noderef, $status, $)	828	=item Why strings for port and node IDs, why not objects?
278		829
279	Monitors the given noderef.	830	We considered "objects", but found that the actual number of methods
		831	that can be called are quite low. Since port and node IDs travel over
		832	the network frequently, the serialising/deserialising would add lots of
		833	overhead, as well as having to keep a proxy object everywhere.
280		834
281	=item become_public endpoint...	835	Strings can easily be printed, easily serialised etc. and need no special
		836	procedures to be "valid".
282		837
283	Tells the node to become a public node, i.e. reachable from other nodes.	838	And as a result, a miniport consists of a single closure stored in a
		839	global hash - it can't become much cheaper.
284		840
285	If no arguments are given, or the first argument is C<undef>, then	841	=item Why favour JSON, why not a real serialising format such as Storable?
286	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the
287	local nodename resolves to.
288		842
289	Otherwise the first argument must be an array-reference with transport	843	In fact, any AnyEvent::MP node will happily accept Storable as framing
290	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	844	format, but currently there is no way to make a node use Storable by
291	local nodename is used as hostname). The endpoints are all resolved and	845	default (although all nodes will accept it).
292	will become the node reference.
293		846
294	=cut	847	The default framing protocol is JSON because a) JSON::XS is many times
		848	faster for small messages and b) most importantly, after years of
		849	experience we found that object serialisation is causing more problems
		850	than it solves: Just like function calls, objects simply do not travel
		851	easily over the network, mostly because they will always be a copy, so you
		852	always have to re-think your design.
		853
		854	Keeping your messages simple, concentrating on data structures rather than
		855	objects, will keep your messages clean, tidy and efficient.
295		856
296	=back	857	=back
297		858
298	=head1 NODE MESSAGES
299
300	Nodes understand the following messages sent to them. Many of them take
301	arguments called C<@reply>, which will simply be used to compose a reply
302	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
303	the remaining arguments are simply the message data.
304
305	=over 4
306
307	=cut
308
309	=item wkp => $name, @reply
310
311	Replies with the port ID of the specified well-known port, or C<undef>.
312
313	=item devnull => ...
314
315	Generic data sink/CPU heat conversion.
316
317	=item relay => $port, @msg
318
319	Simply forwards the message to the given port.
320
321	=item eval => $string[ @reply]
322
323	Evaluates the given string. If C<@reply> is given, then a message of the
324	form C<@reply, $@, @evalres> is sent.
325
326	Example: crash another node.
327
328	snd $othernode, eval => "exit";
329
330	=item time => @reply
331
332	Replies the the current node time to C<@reply>.
333
334	Example: tell the current node to send the current time to C<$myport> in a
335	C<timereply> message.
336
337	snd $NODE, time => $myport, timereply => 1, 2;
338	# => snd $myport, timereply => 1, 2, <time>
339
340	=back
341
342	=head1 SEE ALSO	859	=head1 SEE ALSO
		860
		861	L<AnyEvent::MP::Intro> - a gentle introduction.
		862
		863	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		864
		865	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		866	your applications.
		867
		868	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		869	all nodes.
343		870
344	L<AnyEvent>.	871	L<AnyEvent>.
345		872
346	=head1 AUTHOR	873	=head1 AUTHOR
347		874

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Revision 1.82 by root, Mon Sep 7 18:42:09 2009 UTC