[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 1.33 by root, Wed Aug 5 22:40:51 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
12	snd $port, type => data...;	13	snd $port, type => data...;
		14
		15	$SELF # receiving/own port id in rcv callbacks
13		16
14	rcv $port, smartmatch => $cb->($port, @msg);	17	rcv $port, smartmatch => $cb->($port, @msg);
15		18
16	# examples:	19	# examples:
17	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };
…		…
27	This module (-family) implements a simple message passing framework.	30	This module (-family) implements a simple message passing framework.
28		31
29	Despite its simplicity, you can securely message other processes running	32	Despite its simplicity, you can securely message other processes running
30	on the same or other hosts.	33	on the same or other hosts.
31		34
		35	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
		36	manual page.
		37
32	At the moment, this module family is severly brokena nd underdocumented,	38	At the moment, this module family is severly broken and underdocumented,
33	so do not use. This was uploaded mainly to resreve the CPAN namespace -	39	so do not use. This was uploaded mainly to reserve the CPAN namespace -
34	stay tuned!	40	stay tuned! The basic API should be finished, however.
35		41
36	=head1 CONCEPTS	42	=head1 CONCEPTS
37		43
38	=over 4	44	=over 4
39		45
40	=item port	46	=item port
41		47
42	A port is something you can send messages to with the C<snd> function, and	48	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	49
44	messages they match, messages will not be queued.	50	Some ports allow you to register C<rcv> handlers that can match specific
		51	messages. All C<rcv> handlers will receive messages they match, messages
		52	will not be queued.
45		53
46	=item port id - C<noderef#portname>	54	=item port id - C<noderef#portname>
47		55
48	A port id is always the noderef, a hash-mark (C<#>) as separator, followed	56	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as
49	by a port name (a printable string of unspecified format).	57	separator, and a port name (a printable string of unspecified format). An
		58	exception is the the node port, whose ID is identical to its node
		59	reference.
50		60
51	=item node	61	=item node
52		62
53	A node is a single process containing at least one port - the node	63	A node is a single process containing at least one port - the node
54	port. You can send messages to node ports to let them create new ports,	64	port. You can send messages to node ports to find existing ports or to
55	among other things.	65	create new ports, among other things.
56		66
57	Initially, nodes are either private (single-process only) or hidden	67	Nodes are either private (single-process only), slaves (connected to a
58	(connected to a master node only). Only when they epxlicitly "become	68	master node only) or public nodes (connectable from unrelated nodes).
59	public" can you send them messages from unrelated other nodes.
60		69
61	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	70	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
62		71
63	A noderef is a string that either uniquely identifies a given node (for	72	A node reference is a string that either simply identifies the node (for
64	private and hidden nodes), or contains a recipe on how to reach a given	73	private and slave nodes), or contains a recipe on how to reach a given
65	node (for public nodes).	74	node (for public nodes).
66		75
		76	This recipe is simply a comma-separated list of C<address:port> pairs (for
		77	TCP/IP, other protocols might look different).
		78
		79	Node references come in two flavours: resolved (containing only numerical
		80	addresses) or unresolved (where hostnames are used instead of addresses).
		81
		82	Before using an unresolved node reference in a message you first have to
		83	resolve it.
		84
67	=back	85	=back
68		86
69	=head1 VARIABLES/FUNCTIONS	87	=head1 VARIABLES/FUNCTIONS
70		88
71	=over 4	89	=over 4
…		…
82		100
83	use AE ();	101	use AE ();
84		102
85	use base "Exporter";	103	use base "Exporter";
86		104
87	our $VERSION = '0.01';	105	our $VERSION = '0.1';
88	our @EXPORT = qw(	106	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv _any_	107	NODE $NODE *SELF node_of _any_
90	create_port create_port_on	108	resolve_node initialise_node
91	become_slave become_public	109	snd rcv mon kil reg psub
		110	port
92	);	111	);
93		112
		113	our $SELF;
		114
		115	sub _self_die() {
		116	my $msg = $@;
		117	$msg =~ s/\n+$// unless ref $msg;
		118	kil $SELF, die => $msg;
		119	}
		120
94	=item NODE / $NODE	121	=item $thisnode = NODE / $NODE
95		122
96	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	123	The C<NODE> function returns, and the C<$NODE> variable contains
97	the local node. The value is initialised by a call to C<become_public> or	124	the noderef of the local node. The value is initialised by a call
98	C<become_slave>, after which all local port identifiers become invalid.	125	to C<become_public> or C<become_slave>, after which all local port
		126	identifiers become invalid.
99		127
		128	=item $noderef = node_of $port
		129
		130	Extracts and returns the noderef from a portid or a noderef.
		131
		132	=item $cv = resolve_node $noderef
		133
		134	Takes an unresolved node reference that may contain hostnames and
		135	abbreviated IDs, resolves all of them and returns a resolved node
		136	reference.
		137
		138	In addition to C<address:port> pairs allowed in resolved noderefs, the
		139	following forms are supported:
		140
		141	=over 4
		142
		143	=item the empty string
		144
		145	An empty-string component gets resolved as if the default port (4040) was
		146	specified.
		147
		148	=item naked port numbers (e.g. C<1234>)
		149
		150	These are resolved by prepending the local nodename and a colon, to be
		151	further resolved.
		152
		153	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
		154
		155	These are resolved by using AnyEvent::DNS to resolve them, optionally
		156	looking up SRV records for the C<aemp=4040> port, if no port was
		157	specified.
		158
		159	=back
		160
		161	=item $SELF
		162
		163	Contains the current port id while executing C<rcv> callbacks or C<psub>
		164	blocks.
		165
		166	=item SELF, %SELF, @SELF...
		167
		168	Due to some quirks in how perl exports variables, it is impossible to
		169	just export C<$SELF>, all the symbols called C<SELF> are exported by this
		170	module, but only C<$SELF> is currently used.
		171
100	=item snd $portid, type => @data	172	=item snd $port, type => @data
101		173
102	=item snd $portid, @msg	174	=item snd $port, @msg
103		175
104	Send the given message to the given port ID, which can identify either	176	Send the given message to the given port ID, which can identify either
105	a local or a remote port, and can be either a string or soemthignt hat	177	a local or a remote port, and can be either a string or soemthignt hat
106	stringifies a sa port ID (such as a port object :).	178	stringifies a sa port ID (such as a port object :).
107		179
…		…
117	JSON is used, then only strings, numbers and arrays and hashes consisting	189	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	190	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	191	that Storable can serialise and deserialise is allowed, and for the local
120	node, anything can be passed.	192	node, anything can be passed.
121		193
122	=item $local_port = create_port	194	=item $local_port = port
123		195
124	Create a new local port object. See the next section for allowed methods.	196	Create a new local port object that can be used either as a pattern
		197	matching port ("full port") or a single-callback port ("miniport"),
		198	depending on how C<rcv> callbacks are bound to the object.
125		199
126	=cut	200	=item $port = port { my @msg = @_; $finished }
127		201
128	sub create_port {	202	Creates a "miniport", that is, a very lightweight port without any pattern
129	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;	203	matching behind it, and returns its ID. Semantically the same as creating
		204	a port and calling C<rcv $port, $callback> on it.
130		205
131	my $self = bless {	206	The block will be called for every message received on the port. When the
132	id => "$NODE#$id",	207	callback returns a true value its job is considered "done" and the port
133	names => [$id],	208	will be destroyed. Otherwise it will stay alive.
134	}, "AnyEvent::MP::Port";
135		209
136	$AnyEvent::MP::Base::PORT{$id} = sub {	210	The message will be passed as-is, no extra argument (i.e. no port id) will
137	unshift @_, $self;	211	be passed to the callback.
138		212
139	for (@{ $self->{rc0}{$_[1]} }) {	213	If you need the local port id in the callback, this works nicely:
140	$_ && &{$_->[0]}
141	&& undef $_;
142	}
143		214
144	for (@{ $self->{rcv}{$_[1]} }) {	215	my $port; $port = port {
145	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	216	snd $otherport, reply => $port;
146	&& &{$_->[0]}
147	&& undef $_;
148	}
149
150	for (@{ $self->{any} }) {
151	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
152	&& &{$_->[0]}
153	&& undef $_;
154	}
155	};	217	};
156		218
157	$self	219	=cut
		220
		221	sub rcv($@);
		222
		223	sub port(;&) {
		224	my $id = "$UNIQ." . $ID++;
		225	my $port = "$NODE#$id";
		226
		227	if (@_) {
		228	rcv $port, shift;
		229	} else {
		230	$PORT{$id} = sub { }; # nop
		231	}
		232
		233	$port
158	}	234	}
159		235
160	package AnyEvent::MP::Port;	236	=item reg $port, $name
161		237
162	=back	238	Registers the given port under the name C<$name>. If the name already
		239	exists it is replaced.
163		240
164	=head1 METHODS FOR PORT OBJECTS	241	A port can only be registered under one well known name.
165		242
166	=over 4	243	A port automatically becomes unregistered when it is killed.
167		244
168	=item "$port"
169
170	A port object stringifies to its port ID, so can be used directly for
171	C<snd> operations.
172
173	=cut	245	=cut
174		246
175	use overload	247	sub reg(@) {
176	'""' => sub { $_[0]{id} },	248	my ($port, $name) = @_;
177	fallback => 1;
178		249
179	=item $port->rcv (type => $callback->($port, @msg))	250	$REG{$name} = $port;
		251	}
180		252
181	=item $port->rcv ($smartmatch => $callback->($port, @msg))	253	=item rcv $port, $callback->(@msg)
182		254
		255	Replaces the callback on the specified miniport (after converting it to
		256	one if required).
		257
		258	=item rcv $port, tagstring => $callback->(@msg), ...
		259
		260	=item rcv $port, $smartmatch => $callback->(@msg), ...
		261
183	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	262	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
184		263
185	Register a callback on the given port.	264	Register callbacks to be called on matching messages on the given full
		265	port (after converting it to one if required).
186		266
187	The callback has to return a true value when its work is done, after	267	The callback has to return a true value when its work is done, after
188	which is will be removed, or a false value in which case it will stay	268	which is will be removed, or a false value in which case it will stay
189	registered.	269	registered.
190		270
		271	The global C<$SELF> (exported by this module) contains C<$port> while
		272	executing the callback.
		273
		274	Runtime errors wdurign callback execution will result in the port being
		275	C<kil>ed.
		276
191	If the match is an array reference, then it will be matched against the	277	If the match is an array reference, then it will be matched against the
192	first elements of the message, otherwise only the first element is being	278	first elements of the message, otherwise only the first element is being
193	matched.	279	matched.
194		280
195	Any element in the match that is specified as C<_any_> (a function	281	Any element in the match that is specified as C<_any_> (a function
…		…
200	also the most efficient match (by far).	286	also the most efficient match (by far).
201		287
202	=cut	288	=cut
203		289
204	sub rcv($@) {	290	sub rcv($@) {
205	my ($self, $match, $cb) = @_;	291	my $port = shift;
		292	my ($noderef, $portid) = split /#/, $port, 2;
206		293
207	if (!ref $match) {	294	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
208	push @{ $self->{rc0}{$match} }, [$cb];	295	or Carp::croak "$port: rcv can only be called on local ports, caught";
209	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	296
210	my ($type, @match) = @$match;	297	if (@_ == 1) {
211	@match	298	my $cb = shift;
212	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	299	delete $PORT_DATA{$portid};
213	: push @{ $self->{rc0}{$match->[0]} }, [$cb];	300	$PORT{$portid} = sub {
		301	local $SELF = $port;
		302	eval {
		303	&$cb
		304	and kil $port;
		305	};
		306	_self_die if $@;
		307	};
214	} else {	308	} else {
		309	my $self = $PORT_DATA{$portid} \|\|= do {
		310	my $self = bless {
		311	id => $port,
		312	}, "AnyEvent::MP::Port";
		313
		314	$PORT{$portid} = sub {
		315	local $SELF = $port;
		316
		317	eval {
		318	for (@{ $self->{rc0}{$_[0]} }) {
		319	$_ && &{$_->[0]}
		320	&& undef $_;
		321	}
		322
		323	for (@{ $self->{rcv}{$_[0]} }) {
		324	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
		325	&& &{$_->[0]}
		326	&& undef $_;
		327	}
		328
		329	for (@{ $self->{any} }) {
		330	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
		331	&& &{$_->[0]}
		332	&& undef $_;
		333	}
		334	};
		335	_self_die if $@;
		336	};
		337
		338	$self
		339	};
		340
		341	"AnyEvent::MP::Port" eq ref $self
		342	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		343
		344	while (@_) {
		345	my ($match, $cb) = splice @_, 0, 2;
		346
		347	if (!ref $match) {
		348	push @{ $self->{rc0}{$match} }, [$cb];
		349	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
		350	my ($type, @match) = @$match;
		351	@match
		352	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
		353	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
		354	} else {
215	push @{ $self->{any} }, [$cb, $match];	355	push @{ $self->{any} }, [$cb, $match];
		356	}
		357	}
		358	}
		359
		360	$port
		361	}
		362
		363	=item $closure = psub { BLOCK }
		364
		365	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		366	closure is executed, sets up the environment in the same way as in C<rcv>
		367	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		368
		369	This is useful when you register callbacks from C<rcv> callbacks:
		370
		371	rcv delayed_reply => sub {
		372	my ($delay, @reply) = @_;
		373	my $timer = AE::timer $delay, 0, psub {
		374	snd @reply, $SELF;
		375	};
		376	};
		377
		378	=cut
		379
		380	sub psub(&) {
		381	my $cb = shift;
		382
		383	my $port = $SELF
		384	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		385
		386	sub {
		387	local $SELF = $port;
		388
		389	if (wantarray) {
		390	my @res = eval { &$cb };
		391	_self_die if $@;
		392	@res
		393	} else {
		394	my $res = eval { &$cb };
		395	_self_die if $@;
		396	$res
		397	}
216	}	398	}
217	}	399	}
218		400
219	=item $port->register ($name)	401	=item $guard = mon $port, $cb->(@reason)
220		402
221	Registers the given port under the well known name C<$name>. If the name	403	=item $guard = mon $port, $otherport
222	already exists it is replaced.
223		404
224	A port can only be registered under one well known name.	405	=item $guard = mon $port, $otherport, @msg
225		406
226	=cut	407	Monitor the given port and do something when the port is killed.
227		408
228	sub register {	409	In the first form, the callback is simply called with any number
229	my ($self, $name) = @_;	410	of C<@reason> elements (no @reason means that the port was deleted
		411	"normally"). Note also that I<< the callback B<must> never die >>, so use
		412	C<eval> if unsure.
230		413
231	$self->{wkname} = $name;	414	In the second form, the other port will be C<kil>'ed with C<@reason>, iff
232	$AnyEvent::MP::Base::WKP{$name} = "$self";	415	a @reason was specified, i.e. on "normal" kils nothing happens, while
		416	under all other conditions, the other port is killed with the same reason.
		417
		418	In the last form, a message of the form C<@msg, @reason> will be C<snd>.
		419
		420	Example: call a given callback when C<$port> is killed.
		421
		422	mon $port, sub { warn "port died because of <@_>\n" };
		423
		424	Example: kill ourselves when C<$port> is killed abnormally.
		425
		426	mon $port, $self;
		427
		428	Example: send us a restart message another C<$port> is killed.
		429
		430	mon $port, $self => "restart";
		431
		432	=cut
		433
		434	sub mon {
		435	my ($noderef, $port) = split /#/, shift, 2;
		436
		437	my $node = $NODE{$noderef} \|\| add_node $noderef;
		438
		439	my $cb = shift;
		440
		441	unless (ref $cb) {
		442	if (@_) {
		443	# send a kill info message
		444	my (@msg) = ($cb, @_);
		445	$cb = sub { snd @msg, @_ };
		446	} else {
		447	# simply kill other port
		448	my $port = $cb;
		449	$cb = sub { kil $port, @_ if @_ };
		450	}
		451	}
		452
		453	$node->monitor ($port, $cb);
		454
		455	defined wantarray
		456	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
233	}	457	}
234		458
235	=item $port->destroy	459	=item $guard = mon_guard $port, $ref, $ref...
236		460
237	Explicitly destroy/remove/nuke/vaporise the port.	461	Monitors the given C<$port> and keeps the passed references. When the port
		462	is killed, the references will be freed.
238		463
239	Ports are normally kept alive by there mere existance alone, and need to	464	Optionally returns a guard that will stop the monitoring.
240	be destroyed explicitly.
241		465
242	=cut	466	This function is useful when you create e.g. timers or other watchers and
		467	want to free them when the port gets killed:
243		468
244	sub destroy {	469	$port->rcv (start => sub {
245	my ($self) = @_;	470	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		471	undef $timer if 0.9 < rand;
		472	});
		473	});
246		474
247	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	475	=cut
248		476
249	delete $AnyEvent::MP::Base::PORT{$_}	477	sub mon_guard {
250	for @{ $self->{names} };	478	my ($port, @refs) = @_;
		479
		480	mon $port, sub { 0 && @refs }
251	}	481	}
252		482
		483	=item lnk $port1, $port2
		484
		485	Link two ports. This is simply a shorthand for:
		486
		487	mon $port1, $port2;
		488	mon $port2, $port1;
		489
		490	It means that if either one is killed abnormally, the other one gets
		491	killed as well.
		492
		493	=item kil $port[, @reason]
		494
		495	Kill the specified port with the given C<@reason>.
		496
		497	If no C<@reason> is specified, then the port is killed "normally" (linked
		498	ports will not be kileld, or even notified).
		499
		500	Otherwise, linked ports get killed with the same reason (second form of
		501	C<mon>, see below).
		502
		503	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		504	will be reported as reason C<< die => $@ >>.
		505
		506	Transport/communication errors are reported as C<< transport_error =>
		507	$message >>.
		508
253	=back	509	=back
254		510
255	=head1 FUNCTIONS FOR NODES	511	=head1 FUNCTIONS FOR NODES
256		512
257	=over 4	513	=over 4
258		514
259	=item mon $noderef, $callback->($noderef, $status, $)	515	=item initialise_node $noderef, $seednode, $seednode...
260		516
261	Monitors the given noderef.	517	=item initialise_node "slave/", $master, $master...
262		518
263	=item become_public endpoint...	519	Initialises a node - must be called exactly once before calling other
		520	AnyEvent::MP functions when talking to other nodes is required.
264		521
265	Tells the node to become a public node, i.e. reachable from other nodes.	522	All arguments are noderefs, which can be either resolved or unresolved.
266		523
267	If no arguments are given, or the first argument is C<undef>, then	524	There are two types of networked nodes, public nodes and slave nodes:
268	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the
269	local nodename resolves to.
270		525
271	Otherwise the first argument must be an array-reference with transport	526	=over 4
272	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	527
273	local nodename is used as hostname). The endpoints are all resolved and	528	=item public nodes
274	will become the node reference.	529
		530	For public nodes, C<$noderef> must either be a (possibly unresolved)
		531	noderef, in which case it will be resolved, or C<undef> (or missing), in
		532	which case the noderef will be guessed.
		533
		534	Afterwards, the node will bind itself on all endpoints and try to connect
		535	to all additional C<$seednodes> that are specified. Seednodes are optional
		536	and can be used to quickly bootstrap the node into an existing network.
		537
		538	=item slave nodes
		539
		540	When the C<$noderef> is the special string C<slave/>, then the node will
		541	become a slave node. Slave nodes cannot be contacted from outside and will
		542	route most of their traffic to the master node that they attach to.
		543
		544	At least one additional noderef is required: The node will try to connect
		545	to all of them and will become a slave attached to the first node it can
		546	successfully connect to.
		547
		548	=back
		549
		550	This function will block until all nodes have been resolved and, for slave
		551	nodes, until it has successfully established a connection to a master
		552	server.
		553
		554	Example: become a public node listening on the default node.
		555
		556	initialise_node;
		557
		558	Example: become a public node, and try to contact some well-known master
		559	servers to become part of the network.
		560
		561	initialise_node undef, "master1", "master2";
		562
		563	Example: become a public node listening on port C<4041>.
		564
		565	initialise_node 4041;
		566
		567	Example: become a public node, only visible on localhost port 4044.
		568
		569	initialise_node "locahost:4044";
		570
		571	Example: become a slave node to any of the specified master servers.
		572
		573	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
275		574
276	=cut	575	=cut
277		576
278	=back	577	=back
279		578
…		…
282	Nodes understand the following messages sent to them. Many of them take	581	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	582	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	583	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.	584	the remaining arguments are simply the message data.
286		585
		586	While other messages exist, they are not public and subject to change.
		587
287	=over 4	588	=over 4
288		589
289	=cut	590	=cut
290		591
291	=item wkp => $name, @reply	592	=item lookup => $name, @reply
292		593
293	Replies with the port ID of the specified well-known port, or C<undef>.	594	Replies with the port ID of the specified well-known port, or C<undef>.
294		595
295	=item devnull => ...	596	=item devnull => ...
296		597
…		…
319	snd $NODE, time => $myport, timereply => 1, 2;	620	snd $NODE, time => $myport, timereply => 1, 2;
320	# => snd $myport, timereply => 1, 2, <time>	621	# => snd $myport, timereply => 1, 2, <time>
321		622
322	=back	623	=back
323		624
		625	=head1 AnyEvent::MP vs. Distributed Erlang
		626
		627	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
		628	== aemp node, erlang process == aemp port), so many of the documents and
		629	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
		630	sample:
		631
		632	http://www.erlang.se/doc/programming_rules.shtml
		633	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		634	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
		635	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		636
		637	Despite the similarities, there are also some important differences:
		638
		639	=over 4
		640
		641	=item * Node references contain the recipe on how to contact them.
		642
		643	Erlang relies on special naming and DNS to work everywhere in the
		644	same way. AEMP relies on each node knowing it's own address(es), with
		645	convenience functionality.
		646
		647	This means that AEMP requires a less tightly controlled environment at the
		648	cost of longer node references and a slightly higher management overhead.
		649
		650	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		651
		652	Erlang uses processes that selctively receive messages, and therefore
		653	needs a queue. AEMP is event based, queuing messages would serve no useful
		654	purpose.
		655
		656	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).
		657
		658	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		659
		660	Sending messages in erlang is synchronous and blocks the process. AEMP
		661	sends are immediate, connection establishment is handled in the
		662	background.
		663
		664	=item * Erlang can silently lose messages, AEMP cannot.
		665
		666	Erlang makes few guarantees on messages delivery - messages can get lost
		667	without any of the processes realising it (i.e. you send messages a, b,
		668	and c, and the other side only receives messages a and c).
		669
		670	AEMP guarantees correct ordering, and the guarantee that there are no
		671	holes in the message sequence.
		672
		673	=item * In erlang, processes can be declared dead and later be found to be
		674	alive.
		675
		676	In erlang it can happen that a monitored process is declared dead and
		677	linked processes get killed, but later it turns out that the process is
		678	still alive - and can receive messages.
		679
		680	In AEMP, when port monitoring detects a port as dead, then that port will
		681	eventually be killed - it cannot happen that a node detects a port as dead
		682	and then later sends messages to it, finding it is still alive.
		683
		684	=item * Erlang can send messages to the wrong port, AEMP does not.
		685
		686	In erlang it is quite possible that a node that restarts reuses a process
		687	ID known to other nodes for a completely different process, causing
		688	messages destined for that process to end up in an unrelated process.
		689
		690	AEMP never reuses port IDs, so old messages or old port IDs floating
		691	around in the network will not be sent to an unrelated port.
		692
		693	=item * Erlang uses unprotected connections, AEMP uses secure
		694	authentication and can use TLS.
		695
		696	AEMP can use a proven protocol - SSL/TLS - to protect connections and
		697	securely authenticate nodes.
		698
		699	=item * The AEMP protocol is optimised for both text-based and binary
		700	communications.
		701
		702	The AEMP protocol, unlike the erlang protocol, supports both
		703	language-independent text-only protocols (good for debugging) and binary,
		704	language-specific serialisers (e.g. Storable).
		705
		706	It has also been carefully designed to be implementable in other languages
		707	with a minimum of work while gracefully degrading fucntionality to make the
		708	protocol simple.
		709
		710	=back
		711
324	=head1 SEE ALSO	712	=head1 SEE ALSO
325		713
326	L<AnyEvent>.	714	L<AnyEvent>.
327		715
328	=head1 AUTHOR	716	=head1 AUTHOR

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Revision 1.33 by root, Wed Aug 5 22:40:51 2009 UTC