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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.18 by root, Mon Aug 3 21:35:03 2009 UTC vs.
Revision 1.29 by root, Tue Aug 4 23:16:57 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 it's 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 = '0.02';	105	our $VERSION = '0.1';
88	our @EXPORT = qw(	106	our @EXPORT = qw(
89	NODE $NODE $PORT snd rcv mon del _any_	107	NODE $NODE *SELF node_of _any_
90	create_port create_port_on	108	resolve_node
91	create_miniport
92	become_slave become_public	109	become_slave become_public
		110	snd rcv mon kil reg psub
		111	port
93	);	112	);
94		113
		114	our $SELF;
		115
		116	sub _self_die() {
		117	my $msg = $@;
		118	$msg =~ s/\n+$// unless ref $msg;
		119	kil $SELF, die => $msg;
		120	}
		121
95	=item NODE / $NODE	122	=item $thisnode = NODE / $NODE
96		123
97	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	124	The C<NODE> function returns, and the C<$NODE> variable contains
98	the local node. The value is initialised by a call to C<become_public> or	125	the noderef of the local node. The value is initialised by a call
99	C<become_slave>, after which all local port identifiers become invalid.	126	to C<become_public> or C<become_slave>, after which all local port
		127	identifiers become invalid.
		128
		129	=item $noderef = node_of $portid
		130
		131	Extracts and returns the noderef from a portid or a noderef.
		132
		133	=item $cv = resolve_node $noderef
		134
		135	Takes an unresolved node reference that may contain hostnames and
		136	abbreviated IDs, resolves all of them and returns a resolved node
		137	reference.
		138
		139	In addition to C<address:port> pairs allowed in resolved noderefs, the
		140	following forms are supported:
		141
		142	=over 4
		143
		144	=item the empty string
		145
		146	An empty-string component gets resolved as if the default port (4040) was
		147	specified.
		148
		149	=item naked port numbers (e.g. C<1234>)
		150
		151	These are resolved by prepending the local nodename and a colon, to be
		152	further resolved.
		153
		154	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
		155
		156	These are resolved by using AnyEvent::DNS to resolve them, optionally
		157	looking up SRV records for the C<aemp=4040> port, if no port was
		158	specified.
		159
		160	=back
		161
		162	=item $SELF
		163
		164	Contains the current port id while executing C<rcv> callbacks or C<psub>
		165	blocks.
		166
		167	=item SELF, %SELF, @SELF...
		168
		169	Due to some quirks in how perl exports variables, it is impossible to
		170	just export C<$SELF>, all the symbols called C<SELF> are exported by this
		171	module, but only C<$SELF> is currently used.
100		172
101	=item snd $portid, type => @data	173	=item snd $portid, type => @data
102		174
103	=item snd $portid, @msg	175	=item snd $portid, @msg
104		176
…		…
118	JSON is used, then only strings, numbers and arrays and hashes consisting	190	JSON is used, then only strings, numbers and arrays and hashes consisting
119	of those are allowed (no objects). When Storable is used, then anything	191	of those are allowed (no objects). When Storable is used, then anything
120	that Storable can serialise and deserialise is allowed, and for the local	192	that Storable can serialise and deserialise is allowed, and for the local
121	node, anything can be passed.	193	node, anything can be passed.
122		194
123	=item mon $portid, sub { }	195	=item kil $portid[, @reason]
124		196
125	#TODO monitor the given port	197	Kill the specified port with the given C<@reason>.
		198
		199	If no C<@reason> is specified, then the port is killed "normally" (linked
		200	ports will not be kileld, or even notified).
		201
		202	Otherwise, linked ports get killed with the same reason (second form of
		203	C<mon>, see below).
		204
		205	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		206	will be reported as reason C<< die => $@ >>.
		207
		208	Transport/communication errors are reported as C<< transport_error =>
		209	$message >>.
		210
		211	=item $guard = mon $portid, $cb->(@reason)
		212
		213	=item $guard = mon $portid, $otherport
		214
		215	=item $guard = mon $portid, $otherport, @msg
		216
		217	Monitor the given port and do something when the port is killed.
		218
		219	In the first form, the callback is simply called with any number
		220	of C<@reason> elements (no @reason means that the port was deleted
		221	"normally"). Note also that I<< the callback B<must> never die >>, so use
		222	C<eval> if unsure.
		223
		224	In the second form, the other port will be C<kil>'ed with C<@reason>, iff
		225	a @reason was specified, i.e. on "normal" kils nothing happens, while
		226	under all other conditions, the other port is killed with the same reason.
		227
		228	In the last form, a message of the form C<@msg, @reason> will be C<snd>.
		229
		230	Example: call a given callback when C<$port> is killed.
		231
		232	mon $port, sub { warn "port died because of <@_>\n" };
		233
		234	Example: kill ourselves when C<$port> is killed abnormally.
		235
		236	mon $port, $self;
		237
		238	Example: send us a restart message another C<$port> is killed.
		239
		240	mon $port, $self => "restart";
126		241
127	=cut	242	=cut
128		243
129	sub mon {	244	sub mon {
130	my ($noderef, $port) = split /#/, shift, 2;	245	my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);
131		246
132	my $node = AnyEvent::MP::Base::add_node $noderef;	247	my $node = $NODE{$noderef} \|\| add_node $noderef;
133		248
134	my $cb = shift;	249	#TODO: ports must not be references
		250	if (!ref $cb or "AnyEvent::MP::Port" eq ref $cb) {
		251	if (@_) {
		252	# send a kill info message
		253	my (@msg) = ($cb, @_);
		254	$cb = sub { snd @msg, @_ };
		255	} else {
		256	# simply kill other port
		257	my $port = $cb;
		258	$cb = sub { kil $port, @_ if @_ };
		259	}
		260	}
135		261
136	$node->monitor ($port, $cb);	262	$node->monitor ($port, $cb);
137		263
138	defined wantarray	264	defined wantarray
139	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	265	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
140	}	266	}
141		267
142	=item $local_port = create_port	268	=item $guard = mon_guard $port, $ref, $ref...
143		269
144	Create a new local port object. See the next section for allowed methods.	270	Monitors the given C<$port> and keeps the passed references. When the port
		271	is killed, the references will be freed.
145		272
146	=cut	273	Optionally returns a guard that will stop the monitoring.
147		274
148	sub create_port {	275	This function is useful when you create e.g. timers or other watchers and
149	my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;	276	want to free them when the port gets killed:
150		277
151	my $self = bless {	278	$port->rcv (start => sub {
152	id => "$NODE#$id",	279	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
153	names => [$id],	280	undef $timer if 0.9 < rand;
154	}, "AnyEvent::MP::Port";
155
156	$AnyEvent::MP::Base::PORT{$id} = sub {
157	unshift @_, $self;
158
159	for (@{ $self->{rc0}{$_[1]} }) {
160	$_ && &{$_->[0]}
161	&& undef $_;
162	}	281	});
163
164	for (@{ $self->{rcv}{$_[1]} }) {
165	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
166	&& &{$_->[0]}
167	&& undef $_;
168	}
169
170	for (@{ $self->{any} }) {
171	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
172	&& &{$_->[0]}
173	&& undef $_;
174	}
175	};	282	});
176		283
177	$self	284	=cut
		285
		286	sub mon_guard {
		287	my ($port, @refs) = @_;
		288
		289	mon $port, sub { 0 && @refs }
178	}	290	}
179		291
		292	=item lnk $port1, $port2
		293
		294	Link two ports. This is simply a shorthand for:
		295
		296	mon $port1, $port2;
		297	mon $port2, $port1;
		298
		299	It means that if either one is killed abnormally, the other one gets
		300	killed as well.
		301
		302	=item $local_port = port
		303
		304	Create a new local port object that supports message matching.
		305
180	=item $portid = miniport { my @msg = @_; $finished }	306	=item $portid = port { my @msg = @_; $finished }
181		307
182	Creates a "mini port", that is, a very lightweight port without any	308	Creates a "mini port", that is, a very lightweight port without any
183	pattern matching behind it, and returns its ID.	309	pattern matching behind it, and returns its ID.
184		310
185	The block will be called for every message received on the port. When the	311	The block will be called for every message received on the port. When the
…		…
195	snd $otherport, reply => $port;	321	snd $otherport, reply => $port;
196	};	322	};
197		323
198	=cut	324	=cut
199		325
200	sub miniport(&) {	326	sub port(;&) {
		327	my $id = "$UNIQ." . $ID++;
		328	my $port = "$NODE#$id";
		329
		330	if (@_) {
201	my $cb = shift;	331	my $cb = shift;
202	my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;	332	$PORT{$id} = sub {
203		333	local $SELF = $port;
204	$AnyEvent::MP::Base::PORT{$id} = sub {	334	eval {
205	&$cb	335	&$cb
206	and delete $AnyEvent::MP::Base::PORT{$id};	336	and kil $id;
		337	};
		338	_self_die if $@;
		339	};
		340	} else {
		341	my $self = bless {
		342	id => "$NODE#$id",
		343	}, "AnyEvent::MP::Port";
		344
		345	$PORT_DATA{$id} = $self;
		346	$PORT{$id} = sub {
		347	local $SELF = $port;
		348
		349	eval {
		350	for (@{ $self->{rc0}{$_[0]} }) {
		351	$_ && &{$_->[0]}
		352	&& undef $_;
		353	}
		354
		355	for (@{ $self->{rcv}{$_[0]} }) {
		356	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
		357	&& &{$_->[0]}
		358	&& undef $_;
		359	}
		360
		361	for (@{ $self->{any} }) {
		362	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
		363	&& &{$_->[0]}
		364	&& undef $_;
		365	}
		366	};
		367	_self_die if $@;
		368	};
207	};	369	}
208		370
209	"$NODE#$id"	371	$port
210	}	372	}
211		373
212	package AnyEvent::MP::Port;	374	=item reg $portid, $name
213		375
214	=back	376	Registers the given port under the name C<$name>. If the name already
		377	exists it is replaced.
215		378
216	=head1 METHODS FOR PORT OBJECTS	379	A port can only be registered under one well known name.
217		380
218	=over 4	381	A port automatically becomes unregistered when it is killed.
219		382
220	=item "$port"
221
222	A port object stringifies to its port ID, so can be used directly for
223	C<snd> operations.
224
225	=cut	383	=cut
226		384
227	use overload	385	sub reg(@) {
228	'""' => sub { $_[0]{id} },	386	my ($portid, $name) = @_;
229	fallback => 1;
230		387
231	sub TO_JSON { $_[0]{id} }	388	$REG{$name} = $portid;
		389	}
232		390
233	=item $port->rcv (type => $callback->($port, @msg))	391	=item rcv $portid, tagstring => $callback->(@msg), ...
234		392
235	=item $port->rcv ($smartmatch => $callback->($port, @msg))	393	=item rcv $portid, $smartmatch => $callback->(@msg), ...
236		394
237	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	395	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
238		396
239	Register a callback on the given port.	397	Register callbacks to be called on matching messages on the given port.
240		398
241	The callback has to return a true value when its work is done, after	399	The callback has to return a true value when its work is done, after
242	which is will be removed, or a false value in which case it will stay	400	which is will be removed, or a false value in which case it will stay
243	registered.	401	registered.
244		402
		403	The global C<$SELF> (exported by this module) contains C<$portid> while
		404	executing the callback.
		405
		406	Runtime errors wdurign callback execution will result in the port being
		407	C<kil>ed.
		408
245	If the match is an array reference, then it will be matched against the	409	If the match is an array reference, then it will be matched against the
246	first elements of the message, otherwise only the first element is being	410	first elements of the message, otherwise only the first element is being
247	matched.	411	matched.
248		412
249	Any element in the match that is specified as C<_any_> (a function	413	Any element in the match that is specified as C<_any_> (a function
…		…
254	also the most efficient match (by far).	418	also the most efficient match (by far).
255		419
256	=cut	420	=cut
257		421
258	sub rcv($@) {	422	sub rcv($@) {
259	my ($self, $match, $cb) = @_;	423	my ($noderef, $port) = split /#/, shift, 2;
260		424
		425	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
		426	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
		427
		428	my $self = $PORT_DATA{$port}
		429	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
		430
		431	"AnyEvent::MP::Port" eq ref $self
		432	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
		433
		434	while (@_) {
		435	my ($match, $cb) = splice @_, 0, 2;
		436
261	if (!ref $match) {	437	if (!ref $match) {
262	push @{ $self->{rc0}{$match} }, [$cb];	438	push @{ $self->{rc0}{$match} }, [$cb];
263	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	439	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
264	my ($type, @match) = @$match;	440	my ($type, @match) = @$match;
265	@match	441	@match
266	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	442	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
267	: push @{ $self->{rc0}{$match->[0]} }, [$cb];	443	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
268	} else {	444	} else {
269	push @{ $self->{any} }, [$cb, $match];	445	push @{ $self->{any} }, [$cb, $match];
		446	}
270	}	447	}
271	}	448	}
272		449
273	=item $port->register ($name)	450	=item $closure = psub { BLOCK }
274		451
275	Registers the given port under the well known name C<$name>. If the name	452	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
276	already exists it is replaced.	453	closure is executed, sets up the environment in the same way as in C<rcv>
		454	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
277		455
278	A port can only be registered under one well known name.	456	This is useful when you register callbacks from C<rcv> callbacks:
279		457
280	=cut	458	rcv delayed_reply => sub {
		459	my ($delay, @reply) = @_;
		460	my $timer = AE::timer $delay, 0, psub {
		461	snd @reply, $SELF;
		462	};
		463	};
281		464
282	sub register {	465	=cut
283	my ($self, $name) = @_;
284		466
285	$self->{wkname} = $name;	467	sub psub(&) {
286	$AnyEvent::MP::Base::WKP{$name} = "$self";	468	my $cb = shift;
		469
		470	my $port = $SELF
		471	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		472
		473	sub {
		474	local $SELF = $port;
		475
		476	if (wantarray) {
		477	my @res = eval { &$cb };
		478	_self_die if $@;
		479	@res
		480	} else {
		481	my $res = eval { &$cb };
		482	_self_die if $@;
		483	$res
		484	}
		485	}
287	}	486	}
288		487
289	=item $port->destroy
290
291	Explicitly destroy/remove/nuke/vaporise the port.
292
293	Ports are normally kept alive by there mere existance alone, and need to
294	be destroyed explicitly.
295
296	=cut
297
298	sub destroy {
299	my ($self) = @_;
300
301	AnyEvent::MP::Base::del $self->{id};
302
303	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };
304
305	delete $AnyEvent::MP::Base::PORT{$_}
306	for @{ $self->{names} };
307	}
308
309	=back	488	=back
310		489
311	=head1 FUNCTIONS FOR NODES	490	=head1 FUNCTIONS FOR NODES
312		491
313	=over 4	492	=over 4
314		493
315	=item mon $noderef, $callback->($noderef, $status, $)	494	=item become_public $noderef
316
317	Monitors the given noderef.
318
319	=item become_public endpoint...
320		495
321	Tells the node to become a public node, i.e. reachable from other nodes.	496	Tells the node to become a public node, i.e. reachable from other nodes.
322		497
323	If no arguments are given, or the first argument is C<undef>, then	498	The first argument is the (unresolved) node reference of the local node
324	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the	499	(if missing then the empty string is used).
325	local nodename resolves to.
326		500
327	Otherwise the first argument must be an array-reference with transport	501	It is quite common to not specify anything, in which case the local node
328	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	502	tries to listen on the default port, or to only specify a port number, in
329	local nodename is used as hostname). The endpoints are all resolved and	503	which case AnyEvent::MP tries to guess the local addresses.
330	will become the node reference.
331		504
332	=cut	505	=cut
333		506
334	=back	507	=back
335		508
…		…
338	Nodes understand the following messages sent to them. Many of them take	511	Nodes understand the following messages sent to them. Many of them take
339	arguments called C<@reply>, which will simply be used to compose a reply	512	arguments called C<@reply>, which will simply be used to compose a reply
340	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	513	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
341	the remaining arguments are simply the message data.	514	the remaining arguments are simply the message data.
342		515
		516	While other messages exist, they are not public and subject to change.
		517
343	=over 4	518	=over 4
344		519
345	=cut	520	=cut
346		521
347	=item wkp => $name, @reply	522	=item lookup => $name, @reply
348		523
349	Replies with the port ID of the specified well-known port, or C<undef>.	524	Replies with the port ID of the specified well-known port, or C<undef>.
350		525
351	=item devnull => ...	526	=item devnull => ...
352		527
…		…
375	snd $NODE, time => $myport, timereply => 1, 2;	550	snd $NODE, time => $myport, timereply => 1, 2;
376	# => snd $myport, timereply => 1, 2, <time>	551	# => snd $myport, timereply => 1, 2, <time>
377		552
378	=back	553	=back
379		554
		555	=head1 AnyEvent::MP vs. Distributed Erlang
		556
		557	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
		558	== aemp node, erlang process == aemp port), so many of the documents and
		559	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
		560	sample:
		561
		562	http://www.erlang.se/doc/programming_rules.shtml
		563	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		564	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
		565	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		566
		567	Despite the similarities, there are also some important differences:
		568
		569	=over 4
		570
		571	=item * Node references contain the recipe on how to contact them.
		572
		573	Erlang relies on special naming and DNS to work everywhere in the
		574	same way. AEMP relies on each node knowing it's own address(es), with
		575	convenience functionality.
		576
		577	This means that AEMP requires a less tightly controlled environment at the
		578	cost of longer node references and a slightly higher management overhead.
		579
		580	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		581
		582	Erlang uses processes that selctively receive messages, and therefore
		583	needs a queue. AEMP is event based, queuing messages would serve no useful
		584	purpose.
		585
		586	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).
		587
		588	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		589
		590	Sending messages in erlang is synchronous and blocks the process. AEMP
		591	sends are immediate, connection establishment is handled in the
		592	background.
		593
		594	=item * Erlang can silently lose messages, AEMP cannot.
		595
		596	Erlang makes few guarantees on messages delivery - messages can get lost
		597	without any of the processes realising it (i.e. you send messages a, b,
		598	and c, and the other side only receives messages a and c).
		599
		600	AEMP guarantees correct ordering, and the guarantee that there are no
		601	holes in the message sequence.
		602
		603	=item * In erlang, processes can be declared dead and later be found to be
		604	alive.
		605
		606	In erlang it can happen that a monitored process is declared dead and
		607	linked processes get killed, but later it turns out that the process is
		608	still alive - and can receive messages.
		609
		610	In AEMP, when port monitoring detects a port as dead, then that port will
		611	eventually be killed - it cannot happen that a node detects a port as dead
		612	and then later sends messages to it, finding it is still alive.
		613
		614	=item * Erlang can send messages to the wrong port, AEMP does not.
		615
		616	In erlang it is quite possible that a node that restarts reuses a process
		617	ID known to other nodes for a completely different process, causing
		618	messages destined for that process to end up in an unrelated process.
		619
		620	AEMP never reuses port IDs, so old messages or old port IDs floating
		621	around in the network will not be sent to an unrelated port.
		622
		623	=item * Erlang uses unprotected connections, AEMP uses secure
		624	authentication and can use TLS.
		625
		626	AEMP can use a proven protocol - SSL/TLS - to protect connections and
		627	securely authenticate nodes.
		628
		629	=item * The AEMP protocol is optimised for both text-based and binary
		630	communications.
		631
		632	The AEMP protocol, unlike the erlang protocol, supports both
		633	language-independent text-only protocols (good for debugging) and binary,
		634	language-specific serialisers (e.g. Storable).
		635
		636	It has also been carefully designed to be implementable in other languages
		637	with a minimum of work while gracefully degrading fucntionality to make the
		638	protocol simple.
		639
		640	=back
		641
380	=head1 SEE ALSO	642	=head1 SEE ALSO
381		643
382	L<AnyEvent>.	644	L<AnyEvent>.
383		645
384	=head1 AUTHOR	646	=head1 AUTHOR

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Revision 1.18 by root, Mon Aug 3 21:35:03 2009 UTC vs.
Revision 1.29 by root, Tue Aug 4 23:16:57 2009 UTC