[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 1.30 by root, Tue Aug 4 23:35:51 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 = '0.02';	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) = split /#/, shift, 2;
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	my $cb = shift;
		250
		251	unless (ref $cb) {
		252	if (@_) {
		253	# send a kill info message
		254	my (@msg) = ($cb, @_);
		255	$cb = sub { snd @msg, @_ };
		256	} else {
		257	# simply kill other port
		258	my $port = $cb;
		259	$cb = sub { kil $port, @_ if @_ };
		260	}
		261	}
135		262
136	$node->monitor ($port, $cb);	263	$node->monitor ($port, $cb);
137		264
138	defined wantarray	265	defined wantarray
139	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	266	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
140	}	267	}
141		268
142	=item $local_port = create_port	269	=item $guard = mon_guard $port, $ref, $ref...
143		270
144	Create a new local port object. See the next section for allowed methods.	271	Monitors the given C<$port> and keeps the passed references. When the port
		272	is killed, the references will be freed.
145		273
146	=cut	274	Optionally returns a guard that will stop the monitoring.
147		275
148	sub create_port {	276	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++;	277	want to free them when the port gets killed:
150		278
151	my $self = bless {	279	$port->rcv (start => sub {
152	id => "$NODE#$id",	280	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
153	names => [$id],	281	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	}	282	});
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	};	283	});
176		284
177	$self	285	=cut
		286
		287	sub mon_guard {
		288	my ($port, @refs) = @_;
		289
		290	mon $port, sub { 0 && @refs }
178	}	291	}
179		292
		293	=item lnk $port1, $port2
		294
		295	Link two ports. This is simply a shorthand for:
		296
		297	mon $port1, $port2;
		298	mon $port2, $port1;
		299
		300	It means that if either one is killed abnormally, the other one gets
		301	killed as well.
		302
		303	=item $local_port = port
		304
		305	Create a new local port object that supports message matching.
		306
180	=item $portid = miniport { my @msg = @_; $finished }	307	=item $portid = port { my @msg = @_; $finished }
181		308
182	Creates a "mini port", that is, a very lightweight port without any	309	Creates a "mini port", that is, a very lightweight port without any
183	pattern matching behind it, and returns its ID.	310	pattern matching behind it, and returns its ID.
184		311
185	The block will be called for every message received on the port. When the	312	The block will be called for every message received on the port. When the
…		…
195	snd $otherport, reply => $port;	322	snd $otherport, reply => $port;
196	};	323	};
197		324
198	=cut	325	=cut
199		326
200	sub miniport(&) {	327	sub port(;&) {
		328	my $id = "$UNIQ." . $ID++;
		329	my $port = "$NODE#$id";
		330
		331	if (@_) {
201	my $cb = shift;	332	my $cb = shift;
202	my $id = "$AnyEvent::MP::Base::UNIQ." . $AnyEvent::MP::Base::ID++;	333	$PORT{$id} = sub {
203		334	local $SELF = $port;
204	$AnyEvent::MP::Base::PORT{$id} = sub {	335	eval {
205	&$cb	336	&$cb
206	and delete $AnyEvent::MP::Base::PORT{$id};	337	and kil $id;
		338	};
		339	_self_die if $@;
		340	};
		341	} else {
		342	my $self = bless {
		343	id => "$NODE#$id",
		344	}, "AnyEvent::MP::Port";
		345
		346	$PORT_DATA{$id} = $self;
		347	$PORT{$id} = sub {
		348	local $SELF = $port;
		349
		350	eval {
		351	for (@{ $self->{rc0}{$_[0]} }) {
		352	$_ && &{$_->[0]}
		353	&& undef $_;
		354	}
		355
		356	for (@{ $self->{rcv}{$_[0]} }) {
		357	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
		358	&& &{$_->[0]}
		359	&& undef $_;
		360	}
		361
		362	for (@{ $self->{any} }) {
		363	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
		364	&& &{$_->[0]}
		365	&& undef $_;
		366	}
		367	};
		368	_self_die if $@;
		369	};
207	};	370	}
208		371
209	"$NODE#$id"	372	$port
210	}	373	}
211		374
212	package AnyEvent::MP::Port;	375	=item reg $portid, $name
213		376
214	=back	377	Registers the given port under the name C<$name>. If the name already
		378	exists it is replaced.
215		379
216	=head1 METHODS FOR PORT OBJECTS	380	A port can only be registered under one well known name.
217		381
218	=over 4	382	A port automatically becomes unregistered when it is killed.
219		383
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	384	=cut
226		385
227	use overload	386	sub reg(@) {
228	'""' => sub { $_[0]{id} },	387	my ($portid, $name) = @_;
229	fallback => 1;
230		388
231	sub TO_JSON { $_[0]{id} }	389	$REG{$name} = $portid;
		390	}
232		391
233	=item $port->rcv (type => $callback->($port, @msg))	392	=item rcv $portid, tagstring => $callback->(@msg), ...
234		393
235	=item $port->rcv ($smartmatch => $callback->($port, @msg))	394	=item rcv $portid, $smartmatch => $callback->(@msg), ...
236		395
237	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	396	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
238		397
239	Register a callback on the given port.	398	Register callbacks to be called on matching messages on the given port.
240		399
241	The callback has to return a true value when its work is done, after	400	The callback has to return a true value when its work is done, after
242	which is will be removed, or a false value in which case it will stay	401	which is will be removed, or a false value in which case it will stay
243	registered.	402	registered.
244		403
		404	The global C<$SELF> (exported by this module) contains C<$portid> while
		405	executing the callback.
		406
		407	Runtime errors wdurign callback execution will result in the port being
		408	C<kil>ed.
		409
245	If the match is an array reference, then it will be matched against the	410	If the match is an array reference, then it will be matched against the
246	first elements of the message, otherwise only the first element is being	411	first elements of the message, otherwise only the first element is being
247	matched.	412	matched.
248		413
249	Any element in the match that is specified as C<_any_> (a function	414	Any element in the match that is specified as C<_any_> (a function
…		…
254	also the most efficient match (by far).	419	also the most efficient match (by far).
255		420
256	=cut	421	=cut
257		422
258	sub rcv($@) {	423	sub rcv($@) {
259	my ($self, $match, $cb) = @_;	424	my ($noderef, $port) = split /#/, shift, 2;
260		425
		426	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
		427	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
		428
		429	my $self = $PORT_DATA{$port}
		430	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
		431
		432	"AnyEvent::MP::Port" eq ref $self
		433	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
		434
		435	while (@_) {
		436	my ($match, $cb) = splice @_, 0, 2;
		437
261	if (!ref $match) {	438	if (!ref $match) {
262	push @{ $self->{rc0}{$match} }, [$cb];	439	push @{ $self->{rc0}{$match} }, [$cb];
263	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	440	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
264	my ($type, @match) = @$match;	441	my ($type, @match) = @$match;
265	@match	442	@match
266	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	443	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
267	: push @{ $self->{rc0}{$match->[0]} }, [$cb];	444	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
268	} else {	445	} else {
269	push @{ $self->{any} }, [$cb, $match];	446	push @{ $self->{any} }, [$cb, $match];
		447	}
270	}	448	}
271	}	449	}
272		450
273	=item $port->register ($name)	451	=item $closure = psub { BLOCK }
274		452
275	Registers the given port under the well known name C<$name>. If the name	453	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
276	already exists it is replaced.	454	closure is executed, sets up the environment in the same way as in C<rcv>
		455	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
277		456
278	A port can only be registered under one well known name.	457	This is useful when you register callbacks from C<rcv> callbacks:
279		458
280	=cut	459	rcv delayed_reply => sub {
		460	my ($delay, @reply) = @_;
		461	my $timer = AE::timer $delay, 0, psub {
		462	snd @reply, $SELF;
		463	};
		464	};
281		465
282	sub register {	466	=cut
283	my ($self, $name) = @_;
284		467
285	$self->{wkname} = $name;	468	sub psub(&) {
286	$AnyEvent::MP::Base::WKP{$name} = "$self";	469	my $cb = shift;
		470
		471	my $port = $SELF
		472	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		473
		474	sub {
		475	local $SELF = $port;
		476
		477	if (wantarray) {
		478	my @res = eval { &$cb };
		479	_self_die if $@;
		480	@res
		481	} else {
		482	my $res = eval { &$cb };
		483	_self_die if $@;
		484	$res
		485	}
		486	}
287	}	487	}
288		488
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	489	=back
310		490
311	=head1 FUNCTIONS FOR NODES	491	=head1 FUNCTIONS FOR NODES
312		492
313	=over 4	493	=over 4
314		494
315	=item mon $noderef, $callback->($noderef, $status, $)	495	=item become_public $noderef
316
317	Monitors the given noderef.
318
319	=item become_public endpoint...
320		496
321	Tells the node to become a public node, i.e. reachable from other nodes.	497	Tells the node to become a public node, i.e. reachable from other nodes.
322		498
323	If no arguments are given, or the first argument is C<undef>, then	499	The first argument is the (unresolved) node reference of the local node
324	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the	500	(if missing then the empty string is used).
325	local nodename resolves to.
326		501
327	Otherwise the first argument must be an array-reference with transport	502	It is quite common to not specify anything, in which case the local node
328	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	503	tries to listen on the default port, or to only specify a port number, in
329	local nodename is used as hostname). The endpoints are all resolved and	504	which case AnyEvent::MP tries to guess the local addresses.
330	will become the node reference.
331		505
332	=cut	506	=cut
333		507
334	=back	508	=back
335		509
…		…
338	Nodes understand the following messages sent to them. Many of them take	512	Nodes understand the following messages sent to them. Many of them take
339	arguments called C<@reply>, which will simply be used to compose a reply	513	arguments called C<@reply>, which will simply be used to compose a reply
340	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	514	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
341	the remaining arguments are simply the message data.	515	the remaining arguments are simply the message data.
342		516
		517	While other messages exist, they are not public and subject to change.
		518
343	=over 4	519	=over 4
344		520
345	=cut	521	=cut
346		522
347	=item wkp => $name, @reply	523	=item lookup => $name, @reply
348		524
349	Replies with the port ID of the specified well-known port, or C<undef>.	525	Replies with the port ID of the specified well-known port, or C<undef>.
350		526
351	=item devnull => ...	527	=item devnull => ...
352		528
…		…
375	snd $NODE, time => $myport, timereply => 1, 2;	551	snd $NODE, time => $myport, timereply => 1, 2;
376	# => snd $myport, timereply => 1, 2, <time>	552	# => snd $myport, timereply => 1, 2, <time>
377		553
378	=back	554	=back
379		555
		556	=head1 AnyEvent::MP vs. Distributed Erlang
		557
		558	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
		559	== aemp node, erlang process == aemp port), so many of the documents and
		560	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
		561	sample:
		562
		563	http://www.erlang.se/doc/programming_rules.shtml
		564	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		565	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
		566	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		567
		568	Despite the similarities, there are also some important differences:
		569
		570	=over 4
		571
		572	=item * Node references contain the recipe on how to contact them.
		573
		574	Erlang relies on special naming and DNS to work everywhere in the
		575	same way. AEMP relies on each node knowing it's own address(es), with
		576	convenience functionality.
		577
		578	This means that AEMP requires a less tightly controlled environment at the
		579	cost of longer node references and a slightly higher management overhead.
		580
		581	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		582
		583	Erlang uses processes that selctively receive messages, and therefore
		584	needs a queue. AEMP is event based, queuing messages would serve no useful
		585	purpose.
		586
		587	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).
		588
		589	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		590
		591	Sending messages in erlang is synchronous and blocks the process. AEMP
		592	sends are immediate, connection establishment is handled in the
		593	background.
		594
		595	=item * Erlang can silently lose messages, AEMP cannot.
		596
		597	Erlang makes few guarantees on messages delivery - messages can get lost
		598	without any of the processes realising it (i.e. you send messages a, b,
		599	and c, and the other side only receives messages a and c).
		600
		601	AEMP guarantees correct ordering, and the guarantee that there are no
		602	holes in the message sequence.
		603
		604	=item * In erlang, processes can be declared dead and later be found to be
		605	alive.
		606
		607	In erlang it can happen that a monitored process is declared dead and
		608	linked processes get killed, but later it turns out that the process is
		609	still alive - and can receive messages.
		610
		611	In AEMP, when port monitoring detects a port as dead, then that port will
		612	eventually be killed - it cannot happen that a node detects a port as dead
		613	and then later sends messages to it, finding it is still alive.
		614
		615	=item * Erlang can send messages to the wrong port, AEMP does not.
		616
		617	In erlang it is quite possible that a node that restarts reuses a process
		618	ID known to other nodes for a completely different process, causing
		619	messages destined for that process to end up in an unrelated process.
		620
		621	AEMP never reuses port IDs, so old messages or old port IDs floating
		622	around in the network will not be sent to an unrelated port.
		623
		624	=item * Erlang uses unprotected connections, AEMP uses secure
		625	authentication and can use TLS.
		626
		627	AEMP can use a proven protocol - SSL/TLS - to protect connections and
		628	securely authenticate nodes.
		629
		630	=item * The AEMP protocol is optimised for both text-based and binary
		631	communications.
		632
		633	The AEMP protocol, unlike the erlang protocol, supports both
		634	language-independent text-only protocols (good for debugging) and binary,
		635	language-specific serialisers (e.g. Storable).
		636
		637	It has also been carefully designed to be implementable in other languages
		638	with a minimum of work while gracefully degrading fucntionality to make the
		639	protocol simple.
		640
		641	=back
		642
380	=head1 SEE ALSO	643	=head1 SEE ALSO
381		644
382	L<AnyEvent>.	645	L<AnyEvent>.
383		646
384	=head1 AUTHOR	647	=head1 AUTHOR

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Revision 1.18 by root, Mon Aug 3 21:35:03 2009 UTC vs.
Revision 1.30 by root, Tue Aug 4 23:35:51 2009 UTC