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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.13 by root, Sun Aug 2 18:14:43 2009 UTC vs.
Revision 1.31 by root, Wed Aug 5 19:55:58 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 _any_	107	NODE $NODE *SELF node_of _any_
90	create_port create_port_on	108	resolve_node initialise_node
91	create_miniport	109	snd rcv mon kil reg psub
92	become_slave become_public	110	port
93	);	111	);
94		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
95	=item NODE / $NODE	121	=item $thisnode = NODE / $NODE
96		122
97	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	123	The C<NODE> function returns, and the C<$NODE> variable contains
98	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
99	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.
		127
		128	=item $noderef = node_of $portid
		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.
100		171
101	=item snd $portid, type => @data	172	=item snd $portid, type => @data
102		173
103	=item snd $portid, @msg	174	=item snd $portid, @msg
104		175
…		…
118	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
119	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
120	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
121	node, anything can be passed.	192	node, anything can be passed.
122		193
123	=item $local_port = create_port	194	=item kil $portid[, @reason]
124		195
125	Create a new local port object. See the next section for allowed methods.	196	Kill the specified port with the given C<@reason>.
126		197
127	=cut	198	If no C<@reason> is specified, then the port is killed "normally" (linked
		199	ports will not be kileld, or even notified).
128		200
129	sub create_port {	201	Otherwise, linked ports get killed with the same reason (second form of
130	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;	202	C<mon>, see below).
131		203
132	my $self = bless {	204	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
133	id => "$NODE#$id",	205	will be reported as reason C<< die => $@ >>.
134	names => [$id],
135	}, "AnyEvent::MP::Port";
136		206
137	$AnyEvent::MP::Base::PORT{$id} = sub {	207	Transport/communication errors are reported as C<< transport_error =>
138	unshift @_, $self;	208	$message >>.
139		209
140	for (@{ $self->{rc0}{$_[1]} }) {	210	=item $guard = mon $portid, $cb->(@reason)
141	$_ && &{$_->[0]}	211
142	&& undef $_;	212	=item $guard = mon $portid, $otherport
		213
		214	=item $guard = mon $portid, $otherport, @msg
		215
		216	Monitor the given port and do something when the port is killed.
		217
		218	In the first form, the callback is simply called with any number
		219	of C<@reason> elements (no @reason means that the port was deleted
		220	"normally"). Note also that I<< the callback B<must> never die >>, so use
		221	C<eval> if unsure.
		222
		223	In the second form, the other port will be C<kil>'ed with C<@reason>, iff
		224	a @reason was specified, i.e. on "normal" kils nothing happens, while
		225	under all other conditions, the other port is killed with the same reason.
		226
		227	In the last form, a message of the form C<@msg, @reason> will be C<snd>.
		228
		229	Example: call a given callback when C<$port> is killed.
		230
		231	mon $port, sub { warn "port died because of <@_>\n" };
		232
		233	Example: kill ourselves when C<$port> is killed abnormally.
		234
		235	mon $port, $self;
		236
		237	Example: send us a restart message another C<$port> is killed.
		238
		239	mon $port, $self => "restart";
		240
		241	=cut
		242
		243	sub mon {
		244	my ($noderef, $port) = split /#/, shift, 2;
		245
		246	my $node = $NODE{$noderef} \|\| add_node $noderef;
		247
		248	my $cb = shift;
		249
		250	unless (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 @_ };
143	}	259	}
		260	}
144		261
145	for (@{ $self->{rcv}{$_[1]} }) {	262	$node->monitor ($port, $cb);
146	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	263
147	&& &{$_->[0]}	264	defined wantarray
148	&& undef $_;	265	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		266	}
		267
		268	=item $guard = mon_guard $port, $ref, $ref...
		269
		270	Monitors the given C<$port> and keeps the passed references. When the port
		271	is killed, the references will be freed.
		272
		273	Optionally returns a guard that will stop the monitoring.
		274
		275	This function is useful when you create e.g. timers or other watchers and
		276	want to free them when the port gets killed:
		277
		278	$port->rcv (start => sub {
		279	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		280	undef $timer if 0.9 < rand;
149	}	281	});
		282	});
150		283
151	for (@{ $self->{any} }) {	284	=cut
152	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	285
153	&& &{$_->[0]}	286	sub mon_guard {
154	&& undef $_;	287	my ($port, @refs) = @_;
155	}	288
		289	mon $port, sub { 0 && @refs }
		290	}
		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 can be used either as a pattern
		305	matching port ("full port") or a single-callback port ("miniport"),
		306	depending on how C<rcv> callbacks are bound to the object.
		307
		308	=item $portid = port { my @msg = @_; $finished }
		309
		310	Creates a "mini port", that is, a very lightweight port without any
		311	pattern matching behind it, and returns its ID.
		312
		313	The block will be called for every message received on the port. When the
		314	callback returns a true value its job is considered "done" and the port
		315	will be destroyed. Otherwise it will stay alive.
		316
		317	The message will be passed as-is, no extra argument (i.e. no port id) will
		318	be passed to the callback.
		319
		320	If you need the local port id in the callback, this works nicely:
		321
		322	my $port; $port = port {
		323	snd $otherport, reply => $port;
156	};	324	};
157		325
158	$self	326	=cut
		327
		328	sub port(;&) {
		329	my $id = "$UNIQ." . $ID++;
		330	my $port = "$NODE#$id";
		331
		332	if (@_) {
		333	my $cb = shift;
		334	$PORT{$id} = sub {
		335	local $SELF = $port;
		336	eval {
		337	&$cb
		338	and kil $id;
		339	};
		340	_self_die if $@;
		341	};
		342	} else {
		343	my $self = bless {
		344	id => "$NODE#$id",
		345	}, "AnyEvent::MP::Port";
		346
		347	$PORT_DATA{$id} = $self;
		348	$PORT{$id} = sub {
		349	local $SELF = $port;
		350
		351	eval {
		352	for (@{ $self->{rc0}{$_[0]} }) {
		353	$_ && &{$_->[0]}
		354	&& undef $_;
		355	}
		356
		357	for (@{ $self->{rcv}{$_[0]} }) {
		358	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
		359	&& &{$_->[0]}
		360	&& undef $_;
		361	}
		362
		363	for (@{ $self->{any} }) {
		364	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
		365	&& &{$_->[0]}
		366	&& undef $_;
		367	}
		368	};
		369	_self_die if $@;
		370	};
		371	}
		372
		373	$port
159	}	374	}
160		375
161	=item $portid = create_miniport { }	376	=item reg $portid, $name
162		377
163	Creates a "mini port", that is, a port without much #TODO	378	Registers the given port under the name C<$name>. If the name already
		379	exists it is replaced.
164		380
165	=cut	381	A port can only be registered under one well known name.
166		382
167	sub create_miniport(&) {	383	A port automatically becomes unregistered when it is killed.
168	my $cb = shift;
169	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;
170		384
171	$AnyEvent::MP::Base::PORT{$id} = sub {	385	=cut
172	unshift @_, "$NODE#$id";
173	&$cb
174	and delete $AnyEvent::MP::Base::PORT{$id};
175	};
176		386
177	"$NODE#$id"	387	sub reg(@) {
		388	my ($portid, $name) = @_;
		389
		390	$REG{$name} = $portid;
178	}	391	}
179		392
180	package AnyEvent::MP::Port;	393	=item rcv $portid, $callback->(@msg)
181		394
182	=back	395	Replaces the callback on the specified miniport (or newly created port
		396	object, see C<port>). Full ports are configured with the following calls:
183		397
184	=head1 METHODS FOR PORT OBJECTS	398	=item rcv $portid, tagstring => $callback->(@msg), ...
185		399
186	=over 4	400	=item rcv $portid, $smartmatch => $callback->(@msg), ...
187		401
188	=item "$port"
189
190	A port object stringifies to its port ID, so can be used directly for
191	C<snd> operations.
192
193	=cut
194
195	use overload
196	'""' => sub { $_[0]{id} },
197	fallback => 1;
198
199	=item $port->rcv (type => $callback->($port, @msg))
200
201	=item $port->rcv ($smartmatch => $callback->($port, @msg))
202
203	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	402	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
204		403
205	Register a callback on the given port.	404	Register callbacks to be called on matching messages on the given port.
206		405
207	The callback has to return a true value when its work is done, after	406	The callback has to return a true value when its work is done, after
208	which is will be removed, or a false value in which case it will stay	407	which is will be removed, or a false value in which case it will stay
209	registered.	408	registered.
210		409
		410	The global C<$SELF> (exported by this module) contains C<$portid> while
		411	executing the callback.
		412
		413	Runtime errors wdurign callback execution will result in the port being
		414	C<kil>ed.
		415
211	If the match is an array reference, then it will be matched against the	416	If the match is an array reference, then it will be matched against the
212	first elements of the message, otherwise only the first element is being	417	first elements of the message, otherwise only the first element is being
213	matched.	418	matched.
214		419
215	Any element in the match that is specified as C<_any_> (a function	420	Any element in the match that is specified as C<_any_> (a function
…		…
220	also the most efficient match (by far).	425	also the most efficient match (by far).
221		426
222	=cut	427	=cut
223		428
224	sub rcv($@) {	429	sub rcv($@) {
225	my ($self, $match, $cb) = @_;	430	my $portid = shift;
		431	my ($noderef, $port) = split /#/, $port, 2;
226		432
		433	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
		434	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
		435
		436	my $self = $PORT_DATA{$port}
		437	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
		438
		439	"AnyEvent::MP::Port" eq ref $self
		440	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
		441
		442	while (@_) {
		443	my ($match, $cb) = splice @_, 0, 2;
		444
227	if (!ref $match) {	445	if (!ref $match) {
228	push @{ $self->{rc0}{$match} }, [$cb];	446	push @{ $self->{rc0}{$match} }, [$cb];
229	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	447	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
230	my ($type, @match) = @$match;	448	my ($type, @match) = @$match;
231	@match	449	@match
232	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	450	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
233	: push @{ $self->{rc0}{$match->[0]} }, [$cb];	451	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
234	} else {	452	} else {
235	push @{ $self->{any} }, [$cb, $match];	453	push @{ $self->{any} }, [$cb, $match];
		454	}
		455	}
		456
		457	$portid
		458	}
		459
		460	=item $closure = psub { BLOCK }
		461
		462	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		463	closure is executed, sets up the environment in the same way as in C<rcv>
		464	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		465
		466	This is useful when you register callbacks from C<rcv> callbacks:
		467
		468	rcv delayed_reply => sub {
		469	my ($delay, @reply) = @_;
		470	my $timer = AE::timer $delay, 0, psub {
		471	snd @reply, $SELF;
		472	};
		473	};
		474
		475	=cut
		476
		477	sub psub(&) {
		478	my $cb = shift;
		479
		480	my $port = $SELF
		481	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		482
		483	sub {
		484	local $SELF = $port;
		485
		486	if (wantarray) {
		487	my @res = eval { &$cb };
		488	_self_die if $@;
		489	@res
		490	} else {
		491	my $res = eval { &$cb };
		492	_self_die if $@;
		493	$res
		494	}
236	}	495	}
237	}	496	}
238		497
239	=item $port->register ($name)
240
241	Registers the given port under the well known name C<$name>. If the name
242	already exists it is replaced.
243
244	A port can only be registered under one well known name.
245
246	=cut
247
248	sub register {
249	my ($self, $name) = @_;
250
251	$self->{wkname} = $name;
252	$AnyEvent::MP::Base::WKP{$name} = "$self";
253	}
254
255	=item $port->destroy
256
257	Explicitly destroy/remove/nuke/vaporise the port.
258
259	Ports are normally kept alive by there mere existance alone, and need to
260	be destroyed explicitly.
261
262	=cut
263
264	sub destroy {
265	my ($self) = @_;
266
267	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };
268
269	delete $AnyEvent::MP::Base::PORT{$_}
270	for @{ $self->{names} };
271	}
272
273	=back	498	=back
274		499
275	=head1 FUNCTIONS FOR NODES	500	=head1 FUNCTIONS FOR NODES
276		501
277	=over 4	502	=over 4
278		503
279	=item mon $noderef, $callback->($noderef, $status, $)	504	=item become_public $noderef
280
281	Monitors the given noderef.
282
283	=item become_public endpoint...
284		505
285	Tells the node to become a public node, i.e. reachable from other nodes.	506	Tells the node to become a public node, i.e. reachable from other nodes.
286		507
287	If no arguments are given, or the first argument is C<undef>, then	508	The first argument is the (unresolved) node reference of the local node
288	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the	509	(if missing then the empty string is used).
289	local nodename resolves to.
290		510
291	Otherwise the first argument must be an array-reference with transport	511	It is quite common to not specify anything, in which case the local node
292	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	512	tries to listen on the default port, or to only specify a port number, in
293	local nodename is used as hostname). The endpoints are all resolved and	513	which case AnyEvent::MP tries to guess the local addresses.
294	will become the node reference.
295		514
296	=cut	515	=cut
297		516
298	=back	517	=back
299		518
…		…
302	Nodes understand the following messages sent to them. Many of them take	521	Nodes understand the following messages sent to them. Many of them take
303	arguments called C<@reply>, which will simply be used to compose a reply	522	arguments called C<@reply>, which will simply be used to compose a reply
304	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	523	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
305	the remaining arguments are simply the message data.	524	the remaining arguments are simply the message data.
306		525
		526	While other messages exist, they are not public and subject to change.
		527
307	=over 4	528	=over 4
308		529
309	=cut	530	=cut
310		531
311	=item wkp => $name, @reply	532	=item lookup => $name, @reply
312		533
313	Replies with the port ID of the specified well-known port, or C<undef>.	534	Replies with the port ID of the specified well-known port, or C<undef>.
314		535
315	=item devnull => ...	536	=item devnull => ...
316		537
…		…
339	snd $NODE, time => $myport, timereply => 1, 2;	560	snd $NODE, time => $myport, timereply => 1, 2;
340	# => snd $myport, timereply => 1, 2, <time>	561	# => snd $myport, timereply => 1, 2, <time>
341		562
342	=back	563	=back
343		564
		565	=head1 AnyEvent::MP vs. Distributed Erlang
		566
		567	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
		568	== aemp node, erlang process == aemp port), so many of the documents and
		569	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
		570	sample:
		571
		572	http://www.erlang.se/doc/programming_rules.shtml
		573	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		574	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
		575	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		576
		577	Despite the similarities, there are also some important differences:
		578
		579	=over 4
		580
		581	=item * Node references contain the recipe on how to contact them.
		582
		583	Erlang relies on special naming and DNS to work everywhere in the
		584	same way. AEMP relies on each node knowing it's own address(es), with
		585	convenience functionality.
		586
		587	This means that AEMP requires a less tightly controlled environment at the
		588	cost of longer node references and a slightly higher management overhead.
		589
		590	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		591
		592	Erlang uses processes that selctively receive messages, and therefore
		593	needs a queue. AEMP is event based, queuing messages would serve no useful
		594	purpose.
		595
		596	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).
		597
		598	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		599
		600	Sending messages in erlang is synchronous and blocks the process. AEMP
		601	sends are immediate, connection establishment is handled in the
		602	background.
		603
		604	=item * Erlang can silently lose messages, AEMP cannot.
		605
		606	Erlang makes few guarantees on messages delivery - messages can get lost
		607	without any of the processes realising it (i.e. you send messages a, b,
		608	and c, and the other side only receives messages a and c).
		609
		610	AEMP guarantees correct ordering, and the guarantee that there are no
		611	holes in the message sequence.
		612
		613	=item * In erlang, processes can be declared dead and later be found to be
		614	alive.
		615
		616	In erlang it can happen that a monitored process is declared dead and
		617	linked processes get killed, but later it turns out that the process is
		618	still alive - and can receive messages.
		619
		620	In AEMP, when port monitoring detects a port as dead, then that port will
		621	eventually be killed - it cannot happen that a node detects a port as dead
		622	and then later sends messages to it, finding it is still alive.
		623
		624	=item * Erlang can send messages to the wrong port, AEMP does not.
		625
		626	In erlang it is quite possible that a node that restarts reuses a process
		627	ID known to other nodes for a completely different process, causing
		628	messages destined for that process to end up in an unrelated process.
		629
		630	AEMP never reuses port IDs, so old messages or old port IDs floating
		631	around in the network will not be sent to an unrelated port.
		632
		633	=item * Erlang uses unprotected connections, AEMP uses secure
		634	authentication and can use TLS.
		635
		636	AEMP can use a proven protocol - SSL/TLS - to protect connections and
		637	securely authenticate nodes.
		638
		639	=item * The AEMP protocol is optimised for both text-based and binary
		640	communications.
		641
		642	The AEMP protocol, unlike the erlang protocol, supports both
		643	language-independent text-only protocols (good for debugging) and binary,
		644	language-specific serialisers (e.g. Storable).
		645
		646	It has also been carefully designed to be implementable in other languages
		647	with a minimum of work while gracefully degrading fucntionality to make the
		648	protocol simple.
		649
		650	=back
		651
344	=head1 SEE ALSO	652	=head1 SEE ALSO
345		653
346	L<AnyEvent>.	654	L<AnyEvent>.
347		655
348	=head1 AUTHOR	656	=head1 AUTHOR

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Revision 1.13 by root, Sun Aug 2 18:14:43 2009 UTC vs.
Revision 1.31 by root, Wed Aug 5 19:55:58 2009 UTC