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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.8 by root, Sun Aug 2 14:44:37 2009 UTC vs.
Revision 1.74 by root, Mon Aug 31 11:11:27 2009 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	NODE # returns this node identifier
10	$NODE # contains this node identifier	9	$NODE # contains this node's noderef
		10	NODE # returns this node's noderef
		11	NODE $port # returns the noderef of the port
11		12
		13	$SELF # receiving/own port id in rcv callbacks
		14
		15	# initialise the node so it can send/receive messages
		16	configure;
		17
		18	# ports are message endpoints
		19
		20	# sending messages
12	snd $port, type => data...;	21	snd $port, type => data...;
		22	snd $port, @msg;
		23	snd @msg_with_first_element_being_a_port;
13		24
14	rcv $port, smartmatch => $cb->($port, @msg);	25	# creating/using ports, the simple way
		26	my $simple_port = port { my @msg = @_ };
15		27
16	# examples:	28	# creating/using ports, tagged message matching
		29	my $port = port;
17	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	30	rcv $port, ping => sub { snd $_[0], "pong" };
18	rcv $port1, pong => sub { warn "pong received\n" };	31	rcv $port, pong => sub { warn "pong received\n" };
19	snd $port2, ping => $port1;
20		32
21	# more, smarter, matches (_any_ is exported by this module)	33	# create a port on another node
22	rcv $port, [child_died => $pid] => sub { ...	34	my $port = spawn $node, $initfunc, @initdata;
23	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	35
		36	# monitoring
		37	mon $port, $cb->(@msg) # callback is invoked on death
		38	mon $port, $otherport # kill otherport on abnormal death
		39	mon $port, $otherport, @msg # send message on death
		40
		41	=head1 CURRENT STATUS
		42
		43	bin/aemp - stable.
		44	AnyEvent::MP - stable API, should work.
		45	AnyEvent::MP::Intro - uptodate, but incomplete.
		46	AnyEvent::MP::Kernel - mostly stable.
		47	AnyEvent::MP::Global - stable API, protocol not yet final.
		48
		49	stay tuned.
24		50
25	=head1 DESCRIPTION	51	=head1 DESCRIPTION
26		52
27	This module (-family) implements a simple message passing framework.	53	This module (-family) implements a simple message passing framework.
28		54
29	Despite its simplicity, you can securely message other processes running	55	Despite its simplicity, you can securely message other processes running
30	on the same or other hosts.	56	on the same or other hosts, and you can supervise entities remotely.
31		57
		58	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
		59	manual page and the examples under F<eg/>.
		60
32	At the moment, this module family is severly brokena nd underdocumented,	61	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		62
36	=head1 CONCEPTS	63	=head1 CONCEPTS
37		64
38	=over 4	65	=over 4
39		66
40	=item port	67	=item port
41		68
42	A port is something you can send messages to with the C<snd> function, and	69	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		70
		71	Ports allow you to register C<rcv> handlers that can match all or just
		72	some messages. Messages send to ports will not be queued, regardless of
		73	anything was listening for them or not.
		74
46	=item port id - C<noderef#portname>	75	=item port ID - C<nodeid#portname>
47		76
48	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	77	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).	78	separator, and a port name (a printable string of unspecified format).
50		79
51	=item node	80	=item node
52		81
53	A node is a single process containing at least one port - the node	82	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,	83	which enables nodes to manage each other remotely, and to create new
55	among other things.	84	ports.
56		85
57	Initially, nodes are either private (single-process only) or hidden	86	Nodes are either public (have one or more listening ports) or private
58	(connected to a master node only). Only when they epxlicitly "become	87	(no listening ports). Private nodes cannot talk to other private nodes
59	public" can you send them messages from unrelated other nodes.	88	currently.
60		89
61	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	90	=item node ID - C<[a-za-Z0-9_\-.:]+>
62		91
63	A noderef is a string that either uniquely identifies a given node (for	92	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	93	network. Depending on the configuration used, node IDs can look like a
65	node (for public nodes).	94	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		95	doesn't interpret node IDs in any way.
		96
		97	=item binds - C<ip:port>
		98
		99	Nodes can only talk to each other by creating some kind of connection to
		100	each other. To do this, nodes should listen on one or more local transport
		101	endpoints - binds. Currently, only standard C<ip:port> specifications can
		102	be used, which specify TCP ports to listen on.
		103
		104	=item seeds - C<host:port>
		105
		106	When a node starts, it knows nothing about the network. To teach the node
		107	about the network it first has to contact some other node within the
		108	network. This node is called a seed.
		109
		110	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		111	are expected to be long-running, and at least one of those should always
		112	be available. When nodes run out of connections (e.g. due to a network
		113	error), they try to re-establish connections to some seednodes again to
		114	join the network.
		115
		116	Apart from being sued for seeding, seednodes are not special in any way -
		117	every public node can be a seednode.
66		118
67	=back	119	=back
68		120
69	=head1 VARIABLES/FUNCTIONS	121	=head1 VARIABLES/FUNCTIONS
70		122
…		…
72		124
73	=cut	125	=cut
74		126
75	package AnyEvent::MP;	127	package AnyEvent::MP;
76		128
77	use AnyEvent::MP::Base;	129	use AnyEvent::MP::Kernel;
78		130
79	use common::sense;	131	use common::sense;
80		132
81	use Carp ();	133	use Carp ();
82		134
83	use AE ();	135	use AE ();
84		136
85	use base "Exporter";	137	use base "Exporter";
86		138
87	our $VERSION = '0.01';	139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		140
88	our @EXPORT = qw(	141	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv _any_	142	NODE $NODE *SELF node_of after
90	create_port create_port_on	143	configure
91	become_slave become_public	144	snd rcv mon mon_guard kil reg psub spawn
		145	port
92	);	146	);
93		147
		148	our $SELF;
		149
		150	sub _self_die() {
		151	my $msg = $@;
		152	$msg =~ s/\n+$// unless ref $msg;
		153	kil $SELF, die => $msg;
		154	}
		155
94	=item NODE / $NODE	156	=item $thisnode = NODE / $NODE
95		157
96	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	158	The C<NODE> function returns, and the C<$NODE> variable contains, the node
97	the local node. The value is initialised by a call to C<become_public> or	159	ID of the node running in the current process. This value is initialised by
98	C<become_slave>, after which all local port identifiers become invalid.	160	a call to C<configure>.
99		161
		162	=item $nodeid = node_of $port
		163
		164	Extracts and returns the node ID from a port ID or a node ID.
		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. If it is missing, then the nodename (F<uname
		183	-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 conviniently
		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 $port = shift;
		377	my ($noderef, $portid) = split /#/, $port, 2;
		378
		379	$NODE{$noderef} == $NODE{""}
		380	or Carp::croak "$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 $port dies
		475
		476	Monitor the given port and do something when the port is killed or
		477	messages to it were lost, and optionally return a guard that can be used
		478	to stop monitoring again.
		479
		480	C<mon> effectively guarantees that, in the absence of hardware failures,
		481	after starting the monitor, either all messages sent to the port will
		482	arrive, or the monitoring action will be invoked after possible message
		483	loss has been detected. No messages will be lost "in between" (after
		484	the first lost message no further messages will be received by the
		485	port). After the monitoring action was invoked, further messages might get
		486	delivered again.
		487
		488	Note that monitoring-actions are one-shot: once messages are lost (and a
		489	monitoring alert was raised), they are removed and will not trigger again.
		490
		491	In the first form (callback), the callback is simply called with any
		492	number of C<@reason> elements (no @reason means that the port was deleted
		493	"normally"). Note also that I<< the callback B<must> never die >>, so use
		494	C<eval> if unsure.
		495
		496	In the second form (another port given), the other port (C<$rcvport>)
		497	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
		498	"normal" kils nothing happens, while under all other conditions, the other
		499	port is killed with the same reason.
		500
		501	The third form (kill self) is the same as the second form, except that
		502	C<$rvport> defaults to C<$SELF>.
		503
		504	In the last form (message), a message of the form C<@msg, @reason> will be
		505	C<snd>.
		506
		507	As a rule of thumb, monitoring requests should always monitor a port from
		508	a local port (or callback). The reason is that kill messages might get
		509	lost, just like any other message. Another less obvious reason is that
		510	even monitoring requests can get lost (for exmaple, when the connection
		511	to the other node goes down permanently). When monitoring a port locally
		512	these problems do not exist.
		513
		514	Example: call a given callback when C<$port> is killed.
		515
		516	mon $port, sub { warn "port died because of <@_>\n" };
		517
		518	Example: kill ourselves when C<$port> is killed abnormally.
		519
		520	mon $port;
		521
		522	Example: send us a restart message when another C<$port> is killed.
		523
		524	mon $port, $self => "restart";
		525
		526	=cut
		527
		528	sub mon {
		529	my ($noderef, $port) = split /#/, shift, 2;
		530
		531	my $node = $NODE{$noderef} \|\| add_node $noderef;
		532
		533	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		534
		535	unless (ref $cb) {
		536	if (@_) {
		537	# send a kill info message
		538	my (@msg) = ($cb, @_);
		539	$cb = sub { snd @msg, @_ };
		540	} else {
		541	# simply kill other port
		542	my $port = $cb;
		543	$cb = sub { kil $port, @_ if @_ };
154	}	544	}
		545	}
		546
		547	$node->monitor ($port, $cb);
		548
		549	defined wantarray
		550	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		551	}
		552
		553	=item $guard = mon_guard $port, $ref, $ref...
		554
		555	Monitors the given C<$port> and keeps the passed references. When the port
		556	is killed, the references will be freed.
		557
		558	Optionally returns a guard that will stop the monitoring.
		559
		560	This function is useful when you create e.g. timers or other watchers and
		561	want to free them when the port gets killed (note the use of C<psub>):
		562
		563	$port->rcv (start => sub {
		564	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
		565	undef $timer if 0.9 < rand;
		566	});
		567	});
		568
		569	=cut
		570
		571	sub mon_guard {
		572	my ($port, @refs) = @_;
		573
		574	#TODO: mon-less form?
		575
		576	mon $port, sub { 0 && @refs }
		577	}
		578
		579	=item kil $port[, @reason]
		580
		581	Kill the specified port with the given C<@reason>.
		582
		583	If no C<@reason> is specified, then the port is killed "normally" (ports
		584	monitoring other ports will not necessarily die because a port dies
		585	"normally").
		586
		587	Otherwise, linked ports get killed with the same reason (second form of
		588	C<mon>, see above).
		589
		590	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		591	will be reported as reason C<< die => $@ >>.
		592
		593	Transport/communication errors are reported as C<< transport_error =>
		594	$message >>.
		595
		596	=cut
		597
		598	=item $port = spawn $node, $initfunc[, @initdata]
		599
		600	Creates a port on the node C<$node> (which can also be a port ID, in which
		601	case it's the node where that port resides).
		602
		603	The port ID of the newly created port is returned immediately, and it is
		604	possible to immediately start sending messages or to monitor the port.
		605
		606	After the port has been created, the init function is called on the remote
		607	node, in the same context as a C<rcv> callback. This function must be a
		608	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
		609	specify a function in the main program, use C<::name>.
		610
		611	If the function doesn't exist, then the node tries to C<require>
		612	the package, then the package above the package and so on (e.g.
		613	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		614	exists or it runs out of package names.
		615
		616	The init function is then called with the newly-created port as context
		617	object (C<$SELF>) and the C<@initdata> values as arguments.
		618
		619	A common idiom is to pass a local port, immediately monitor the spawned
		620	port, and in the remote init function, immediately monitor the passed
		621	local port. This two-way monitoring ensures that both ports get cleaned up
		622	when there is a problem.
		623
		624	Example: spawn a chat server port on C<$othernode>.
		625
		626	# this node, executed from within a port context:
		627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		628	mon $server;
		629
		630	# init function on C<$othernode>
		631	sub connect {
		632	my ($srcport) = @_;
		633
		634	mon $srcport;
		635
		636	rcv $SELF, sub {
		637	...
		638	};
		639	}
		640
		641	=cut
		642
		643	sub _spawn {
		644	my $port = shift;
		645	my $init = shift;
		646
		647	local $SELF = "$NODE#$port";
		648	eval {
		649	&{ load_func $init }
155	};	650	};
156		651	_self_die if $@;
157	$self
158	}	652	}
159		653
160	package AnyEvent::MP::Port;	654	sub spawn(@) {
		655	my ($noderef, undef) = split /#/, shift, 2;
		656
		657	my $id = "$RUNIQ." . $ID++;
		658
		659	$_[0] =~ /::/
		660	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		661
		662	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
		663
		664	"$noderef#$id"
		665	}
		666
		667	=item after $timeout, @msg
		668
		669	=item after $timeout, $callback
		670
		671	Either sends the given message, or call the given callback, after the
		672	specified number of seconds.
		673
		674	This is simply a utility function that comes in handy at times - the
		675	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		676	so it may go away in the future.
		677
		678	=cut
		679
		680	sub after($@) {
		681	my ($timeout, @action) = @_;
		682
		683	my $t; $t = AE::timer $timeout, 0, sub {
		684	undef $t;
		685	ref $action[0]
		686	? $action[0]()
		687	: snd @action;
		688	};
		689	}
161		690
162	=back	691	=back
163		692
164	=head1 METHODS FOR PORT OBJECTS	693	=head1 AnyEvent::MP vs. Distributed Erlang
		694
		695	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
		696	== aemp node, Erlang process == aemp port), so many of the documents and
		697	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
		698	sample:
		699
		700	http://www.Erlang.se/doc/programming_rules.shtml
		701	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		702	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
		703	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		704
		705	Despite the similarities, there are also some important differences:
165		706
166	=over 4	707	=over 4
167		708
168	=item "$port"	709	=item * Node IDs are arbitrary strings in AEMP.
169		710
170	A port object stringifies to its port ID, so can be used directly for	711	Erlang relies on special naming and DNS to work everywhere in the same
171	C<snd> operations.	712	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
		713	configuraiton or DNS), but will otherwise discover other odes itself.
172		714
173	=cut	715	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		716	uses "local ports are like remote ports".
174		717
175	use overload	718	The failure modes for local ports are quite different (runtime errors
176	'""' => sub { $_[0]{id} },	719	only) then for remote ports - when a local port dies, you I<know> it dies,
177	fallback => 1;	720	when a connection to another node dies, you know nothing about the other
		721	port.
178		722
179	=item $port->rcv (type => $callback->($port, @msg))	723	Erlang pretends remote ports are as reliable as local ports, even when
		724	they are not.
180		725
181	=item $port->rcv ($smartmatch => $callback->($port, @msg))	726	AEMP encourages a "treat remote ports differently" philosophy, with local
		727	ports being the special case/exception, where transport errors cannot
		728	occur.
182		729
183	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	730	=item * Erlang uses processes and a mailbox, AEMP does not queue.
184		731
185	Register a callback on the given port.	732	Erlang uses processes that selectively receive messages, and therefore
		733	needs a queue. AEMP is event based, queuing messages would serve no
		734	useful purpose. For the same reason the pattern-matching abilities of
		735	AnyEvent::MP are more limited, as there is little need to be able to
		736	filter messages without dequeing them.
186		737
187	The callback has to return a true value when its work is done, after	738	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
188	which is will be removed, or a false value in which case it will stay
189	registered.
190		739
191	If the match is an array reference, then it will be matched against the	740	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
192	first elements of the message, otherwise only the first element is being
193	matched.
194		741
195	Any element in the match that is specified as C<_any_> (a function	742	Sending messages in Erlang is synchronous and blocks the process (and
196	exported by this module) matches any single element of the message.	743	so does not need a queue that can overflow). AEMP sends are immediate,
		744	connection establishment is handled in the background.
197		745
198	While not required, it is highly recommended that the first matching	746	=item * Erlang suffers from silent message loss, AEMP does not.
199	element is a string identifying the message. The one-string-only match is
200	also the most efficient match (by far).
201		747
202	=cut	748	Erlang makes few guarantees on messages delivery - messages can get lost
		749	without any of the processes realising it (i.e. you send messages a, b,
		750	and c, and the other side only receives messages a and c).
203		751
204	sub rcv($@) {	752	AEMP guarantees correct ordering, and the guarantee that after one message
205	my ($self, $match, $cb) = @_;	753	is lost, all following ones sent to the same port are lost as well, until
		754	monitoring raises an error, so there are no silent "holes" in the message
		755	sequence.
206		756
207	if (!ref $match) {	757	=item * Erlang can send messages to the wrong port, AEMP does not.
208	push @{ $self->{rc0}{$match} }, [$cb];
209	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
210	my ($type, @match) = @$match;
211	@match
212	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
213	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
214	} else {
215	push @{ $self->{any} }, [$cb, $match];
216	}
217	}
218		758
219	=item $port->register ($name)	759	In Erlang it is quite likely that a node that restarts reuses a process ID
		760	known to other nodes for a completely different process, causing messages
		761	destined for that process to end up in an unrelated process.
220		762
221	Registers the given port under the well known name C<$name>. If the name	763	AEMP never reuses port IDs, so old messages or old port IDs floating
222	already exists it is replaced.	764	around in the network will not be sent to an unrelated port.
223		765
224	A port can only be registered under one well known name.	766	=item * Erlang uses unprotected connections, AEMP uses secure
		767	authentication and can use TLS.
225		768
226	=cut	769	AEMP can use a proven protocol - TLS - to protect connections and
		770	securely authenticate nodes.
227		771
228	sub register {	772	=item * The AEMP protocol is optimised for both text-based and binary
229	my ($self, $name) = @_;	773	communications.
230		774
231	$self->{wkname} = $name;	775	The AEMP protocol, unlike the Erlang protocol, supports both programming
232	$AnyEvent::MP::Base::WKP{$name} = "$self";	776	language independent text-only protocols (good for debugging) and binary,
233	}	777	language-specific serialisers (e.g. Storable). By default, unless TLS is
		778	used, the protocol is actually completely text-based.
234		779
235	=item $port->destroy	780	It has also been carefully designed to be implementable in other languages
		781	with a minimum of work while gracefully degrading functionality to make the
		782	protocol simple.
236		783
237	Explicitly destroy/remove/nuke/vaporise the port.	784	=item * AEMP has more flexible monitoring options than Erlang.
238		785
239	Ports are normally kept alive by there mere existance alone, and need to	786	In Erlang, you can chose to receive I<all> exit signals as messages
240	be destroyed explicitly.	787	or I<none>, there is no in-between, so monitoring single processes is
		788	difficult to implement. Monitoring in AEMP is more flexible than in
		789	Erlang, as one can choose between automatic kill, exit message or callback
		790	on a per-process basis.
241		791
242	=cut	792	=item * Erlang tries to hide remote/local connections, AEMP does not.
243		793
244	sub destroy {	794	Monitoring in Erlang is not an indicator of process death/crashes, in the
245	my ($self) = @_;	795	same way as linking is (except linking is unreliable in Erlang).
246		796
247	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	797	In AEMP, you don't "look up" registered port names or send to named ports
		798	that might or might not be persistent. Instead, you normally spawn a port
		799	on the remote node. The init function monitors you, and you monitor the
		800	remote port. Since both monitors are local to the node, they are much more
		801	reliable (no need for C<spawn_link>).
248		802
249	delete $AnyEvent::MP::Base::PORT{$_}	803	This also saves round-trips and avoids sending messages to the wrong port
250	for @{ $self->{names} };	804	(hard to do in Erlang).
251	}
252		805
253	=back	806	=back
254		807
255	=head1 FUNCTIONS FOR NODES	808	=head1 RATIONALE
256		809
257	=over 4	810	=over 4
258		811
259	=item mon $noderef, $callback->($noderef, $status, $)	812	=item Why strings for port and node IDs, why not objects?
260		813
261	Monitors the given noderef.	814	We considered "objects", but found that the actual number of methods
		815	that can be called are quite low. Since port and node IDs travel over
		816	the network frequently, the serialising/deserialising would add lots of
		817	overhead, as well as having to keep a proxy object everywhere.
262		818
263	=item become_public endpoint...	819	Strings can easily be printed, easily serialised etc. and need no special
		820	procedures to be "valid".
264		821
265	Tells the node to become a public node, i.e. reachable from other nodes.	822	And as a result, a miniport consists of a single closure stored in a
		823	global hash - it can't become much cheaper.
266		824
267	If no arguments are given, or the first argument is C<undef>, then	825	=item Why favour JSON, why not a real serialising format such as Storable?
268	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the
269	local nodename resolves to.
270		826
271	Otherwise the first argument must be an array-reference with transport	827	In fact, any AnyEvent::MP node will happily accept Storable as framing
272	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	828	format, but currently there is no way to make a node use Storable by
273	local nodename is used as hostname). The endpoints are all resolved and	829	default (although all nodes will accept it).
274	will become the node reference.
275		830
276	=cut	831	The default framing protocol is JSON because a) JSON::XS is many times
		832	faster for small messages and b) most importantly, after years of
		833	experience we found that object serialisation is causing more problems
		834	than it solves: Just like function calls, objects simply do not travel
		835	easily over the network, mostly because they will always be a copy, so you
		836	always have to re-think your design.
		837
		838	Keeping your messages simple, concentrating on data structures rather than
		839	objects, will keep your messages clean, tidy and efficient.
277		840
278	=back	841	=back
279		842
280	=head1 NODE MESSAGES
281
282	Nodes understand the following messages sent to them. Many of them take
283	arguments called C<@reply>, which will simply be used to compose a reply
284	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
285	the remaining arguments are simply the message data.
286
287	=over 4
288
289	=cut
290
291	=item wkp => $name, @reply
292
293	Replies with the port ID of the specified well-known port, or C<undef>.
294
295	=item devnull => ...
296
297	Generic data sink/CPU heat conversion.
298
299	=item relay => $port, @msg
300
301	Simply forwards the message to the given port.
302
303	=item eval => $string[ @reply]
304
305	Evaluates the given string. If C<@reply> is given, then a message of the
306	form C<@reply, $@, @evalres> is sent.
307
308	Example: crash another node.
309
310	snd $othernode, eval => "exit";
311
312	=item time => @reply
313
314	Replies the the current node time to C<@reply>.
315
316	Example: tell the current node to send the current time to C<$myport> in a
317	C<timereply> message.
318
319	snd $NODE, time => $myport, timereply => 1, 2;
320	# => snd $myport, timereply => 1, 2, <time>
321
322	=back
323
324	=head1 SEE ALSO	843	=head1 SEE ALSO
		844
		845	L<AnyEvent::MP::Intro> - a gentle introduction.
		846
		847	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		848
		849	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		850	your applications.
325		851
326	L<AnyEvent>.	852	L<AnyEvent>.
327		853
328	=head1 AUTHOR	854	=head1 AUTHOR
329		855

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.8 by root, Sun Aug 2 14:44:37 2009 UTC vs. Revision 1.74 by root, Mon Aug 31 11:11:27 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.8 by root, Sun Aug 2 14:44:37 2009 UTC vs.
Revision 1.74 by root, Mon Aug 31 11:11:27 2009 UTC