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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.12 by root, Sun Aug 2 18:11:48 2009 UTC vs.
Revision 1.32 by root, Wed Aug 5 19:58:46 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 $local_port = port
124		195
125	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.
126		199
127	=cut	200	=item $portid = port { my @msg = @_; $finished }
128		201
129	sub create_port {	202	Creates a "mini port", that is, a very lightweight port without any
130	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;	203	pattern matching behind it, and returns its ID.
131		204
132	my $self = bless {	205	The block will be called for every message received on the port. When the
133	id => "$NODE#$id",	206	callback returns a true value its job is considered "done" and the port
134	names => [$id],	207	will be destroyed. Otherwise it will stay alive.
135	}, "AnyEvent::MP::Port";
136		208
137	$AnyEvent::MP::Base::PORT{$id} = sub {	209	The message will be passed as-is, no extra argument (i.e. no port id) will
138	unshift @_, $self;	210	be passed to the callback.
139		211
140	for (@{ $self->{rc0}{$_[1]} }) {	212	If you need the local port id in the callback, this works nicely:
141	$_ && &{$_->[0]}
142	&& undef $_;
143	}
144		213
145	for (@{ $self->{rcv}{$_[1]} }) {	214	my $port; $port = port {
146	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	215	snd $otherport, reply => $port;
147	&& &{$_->[0]}
148	&& undef $_;
149	}
150
151	for (@{ $self->{any} }) {
152	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
153	&& &{$_->[0]}
154	&& undef $_;
155	}
156	};	216	};
157		217
158	$self	218	=cut
		219
		220	sub port(;&) {
		221	my $id = "$UNIQ." . $ID++;
		222	my $port = "$NODE#$id";
		223
		224	if (@_) {
		225	my $cb = shift;
		226	$PORT{$id} = sub {
		227	local $SELF = $port;
		228	eval {
		229	&$cb
		230	and kil $id;
		231	};
		232	_self_die if $@;
		233	};
		234	} else {
		235	my $self = bless {
		236	id => "$NODE#$id",
		237	}, "AnyEvent::MP::Port";
		238
		239	$PORT_DATA{$id} = $self;
		240	$PORT{$id} = sub {
		241	local $SELF = $port;
		242
		243	eval {
		244	for (@{ $self->{rc0}{$_[0]} }) {
		245	$_ && &{$_->[0]}
		246	&& undef $_;
		247	}
		248
		249	for (@{ $self->{rcv}{$_[0]} }) {
		250	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
		251	&& &{$_->[0]}
		252	&& undef $_;
		253	}
		254
		255	for (@{ $self->{any} }) {
		256	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
		257	&& &{$_->[0]}
		258	&& undef $_;
		259	}
		260	};
		261	_self_die if $@;
		262	};
		263	}
		264
		265	$port
159	}	266	}
160		267
161	=item $portid = create_miniport { }	268	=item reg $portid, $name
162		269
163	Creates a "mini port", that is, a port without much #TODO	270	Registers the given port under the name C<$name>. If the name already
		271	exists it is replaced.
164		272
165	=cut	273	A port can only be registered under one well known name.
166		274
167	sub create_miniport(&) {	275	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		276
171	$AnyEvent::MP::Base::PORT{$id} = sub {	277	=cut
172	$_[0] = "$NODE#$id";
173	&$cb
174	and delete $AnyEvent::MP::Base::PORT{$id};
175	};
176		278
177	"$NODE#$id"	279	sub reg(@) {
		280	my ($portid, $name) = @_;
		281
		282	$REG{$name} = $portid;
178	}	283	}
179		284
180	package AnyEvent::MP::Port;	285	=item rcv $portid, $callback->(@msg)
181		286
182	=back	287	Replaces the callback on the specified miniport (or newly created port
		288	object, see C<port>). Full ports are configured with the following calls:
183		289
184	=head1 METHODS FOR PORT OBJECTS	290	=item rcv $portid, tagstring => $callback->(@msg), ...
185		291
186	=over 4	292	=item rcv $portid, $smartmatch => $callback->(@msg), ...
187		293
188	=item "$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))	294	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
204		295
205	Register a callback on the given port.	296	Register callbacks to be called on matching messages on the given full
		297	port (or newly created port).
206		298
207	The callback has to return a true value when its work is done, after	299	The callback has to return a true value when its work is done, after
208	which is will be removed, or a false value in which case it will stay	300	which is will be removed, or a false value in which case it will stay
209	registered.	301	registered.
210		302
		303	The global C<$SELF> (exported by this module) contains C<$portid> while
		304	executing the callback.
		305
		306	Runtime errors wdurign callback execution will result in the port being
		307	C<kil>ed.
		308
211	If the match is an array reference, then it will be matched against the	309	If the match is an array reference, then it will be matched against the
212	first elements of the message, otherwise only the first element is being	310	first elements of the message, otherwise only the first element is being
213	matched.	311	matched.
214		312
215	Any element in the match that is specified as C<_any_> (a function	313	Any element in the match that is specified as C<_any_> (a function
…		…
220	also the most efficient match (by far).	318	also the most efficient match (by far).
221		319
222	=cut	320	=cut
223		321
224	sub rcv($@) {	322	sub rcv($@) {
225	my ($self, $match, $cb) = @_;	323	my $portid = shift;
		324	my ($noderef, $port) = split /#/, $port, 2;
226		325
		326	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
		327	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
		328
		329	my $self = $PORT_DATA{$port}
		330	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
		331
		332	"AnyEvent::MP::Port" eq ref $self
		333	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
		334
		335	while (@_) {
		336	my ($match, $cb) = splice @_, 0, 2;
		337
227	if (!ref $match) {	338	if (!ref $match) {
228	push @{ $self->{rc0}{$match} }, [$cb];	339	push @{ $self->{rc0}{$match} }, [$cb];
229	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	340	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
230	my ($type, @match) = @$match;	341	my ($type, @match) = @$match;
231	@match	342	@match
232	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	343	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
233	: push @{ $self->{rc0}{$match->[0]} }, [$cb];	344	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
234	} else {	345	} else {
235	push @{ $self->{any} }, [$cb, $match];	346	push @{ $self->{any} }, [$cb, $match];
		347	}
		348	}
		349
		350	$portid
		351	}
		352
		353	=item $closure = psub { BLOCK }
		354
		355	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		356	closure is executed, sets up the environment in the same way as in C<rcv>
		357	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		358
		359	This is useful when you register callbacks from C<rcv> callbacks:
		360
		361	rcv delayed_reply => sub {
		362	my ($delay, @reply) = @_;
		363	my $timer = AE::timer $delay, 0, psub {
		364	snd @reply, $SELF;
		365	};
		366	};
		367
		368	=cut
		369
		370	sub psub(&) {
		371	my $cb = shift;
		372
		373	my $port = $SELF
		374	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		375
		376	sub {
		377	local $SELF = $port;
		378
		379	if (wantarray) {
		380	my @res = eval { &$cb };
		381	_self_die if $@;
		382	@res
		383	} else {
		384	my $res = eval { &$cb };
		385	_self_die if $@;
		386	$res
		387	}
236	}	388	}
237	}	389	}
238		390
239	=item $port->register ($name)	391	=item $guard = mon $portid, $cb->(@reason)
240		392
241	Registers the given port under the well known name C<$name>. If the name	393	=item $guard = mon $portid, $otherport
242	already exists it is replaced.
243		394
244	A port can only be registered under one well known name.	395	=item $guard = mon $portid, $otherport, @msg
245		396
246	=cut	397	Monitor the given port and do something when the port is killed.
247		398
248	sub register {	399	In the first form, the callback is simply called with any number
249	my ($self, $name) = @_;	400	of C<@reason> elements (no @reason means that the port was deleted
		401	"normally"). Note also that I<< the callback B<must> never die >>, so use
		402	C<eval> if unsure.
250		403
251	$self->{wkname} = $name;	404	In the second form, the other port will be C<kil>'ed with C<@reason>, iff
252	$AnyEvent::MP::Base::WKP{$name} = "$self";	405	a @reason was specified, i.e. on "normal" kils nothing happens, while
		406	under all other conditions, the other port is killed with the same reason.
		407
		408	In the last form, a message of the form C<@msg, @reason> will be C<snd>.
		409
		410	Example: call a given callback when C<$port> is killed.
		411
		412	mon $port, sub { warn "port died because of <@_>\n" };
		413
		414	Example: kill ourselves when C<$port> is killed abnormally.
		415
		416	mon $port, $self;
		417
		418	Example: send us a restart message another C<$port> is killed.
		419
		420	mon $port, $self => "restart";
		421
		422	=cut
		423
		424	sub mon {
		425	my ($noderef, $port) = split /#/, shift, 2;
		426
		427	my $node = $NODE{$noderef} \|\| add_node $noderef;
		428
		429	my $cb = shift;
		430
		431	unless (ref $cb) {
		432	if (@_) {
		433	# send a kill info message
		434	my (@msg) = ($cb, @_);
		435	$cb = sub { snd @msg, @_ };
		436	} else {
		437	# simply kill other port
		438	my $port = $cb;
		439	$cb = sub { kil $port, @_ if @_ };
		440	}
		441	}
		442
		443	$node->monitor ($port, $cb);
		444
		445	defined wantarray
		446	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
253	}	447	}
254		448
255	=item $port->destroy	449	=item $guard = mon_guard $port, $ref, $ref...
256		450
257	Explicitly destroy/remove/nuke/vaporise the port.	451	Monitors the given C<$port> and keeps the passed references. When the port
		452	is killed, the references will be freed.
258		453
259	Ports are normally kept alive by there mere existance alone, and need to	454	Optionally returns a guard that will stop the monitoring.
260	be destroyed explicitly.
261		455
262	=cut	456	This function is useful when you create e.g. timers or other watchers and
		457	want to free them when the port gets killed:
263		458
264	sub destroy {	459	$port->rcv (start => sub {
265	my ($self) = @_;	460	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		461	undef $timer if 0.9 < rand;
		462	});
		463	});
266		464
267	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	465	=cut
268		466
269	delete $AnyEvent::MP::Base::PORT{$_}	467	sub mon_guard {
270	for @{ $self->{names} };	468	my ($port, @refs) = @_;
		469
		470	mon $port, sub { 0 && @refs }
271	}	471	}
272		472
		473	=item lnk $port1, $port2
		474
		475	Link two ports. This is simply a shorthand for:
		476
		477	mon $port1, $port2;
		478	mon $port2, $port1;
		479
		480	It means that if either one is killed abnormally, the other one gets
		481	killed as well.
		482
		483	=item kil $portid[, @reason]
		484
		485	Kill the specified port with the given C<@reason>.
		486
		487	If no C<@reason> is specified, then the port is killed "normally" (linked
		488	ports will not be kileld, or even notified).
		489
		490	Otherwise, linked ports get killed with the same reason (second form of
		491	C<mon>, see below).
		492
		493	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		494	will be reported as reason C<< die => $@ >>.
		495
		496	Transport/communication errors are reported as C<< transport_error =>
		497	$message >>.
		498
273	=back	499	=back
274		500
275	=head1 FUNCTIONS FOR NODES	501	=head1 FUNCTIONS FOR NODES
276		502
277	=over 4	503	=over 4
278		504
279	=item mon $noderef, $callback->($noderef, $status, $)	505	=item become_public $noderef
280
281	Monitors the given noderef.
282
283	=item become_public endpoint...
284		506
285	Tells the node to become a public node, i.e. reachable from other nodes.	507	Tells the node to become a public node, i.e. reachable from other nodes.
286		508
287	If no arguments are given, or the first argument is C<undef>, then	509	The first argument is the (unresolved) node reference of the local node
288	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the	510	(if missing then the empty string is used).
289	local nodename resolves to.
290		511
291	Otherwise the first argument must be an array-reference with transport	512	It is quite common to not specify anything, in which case the local node
292	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	513	tries to listen on the default port, or to only specify a port number, in
293	local nodename is used as hostname). The endpoints are all resolved and	514	which case AnyEvent::MP tries to guess the local addresses.
294	will become the node reference.
295		515
296	=cut	516	=cut
297		517
298	=back	518	=back
299		519
…		…
302	Nodes understand the following messages sent to them. Many of them take	522	Nodes understand the following messages sent to them. Many of them take
303	arguments called C<@reply>, which will simply be used to compose a reply	523	arguments called C<@reply>, which will simply be used to compose a reply
304	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	524	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
305	the remaining arguments are simply the message data.	525	the remaining arguments are simply the message data.
306		526
		527	While other messages exist, they are not public and subject to change.
		528
307	=over 4	529	=over 4
308		530
309	=cut	531	=cut
310		532
311	=item wkp => $name, @reply	533	=item lookup => $name, @reply
312		534
313	Replies with the port ID of the specified well-known port, or C<undef>.	535	Replies with the port ID of the specified well-known port, or C<undef>.
314		536
315	=item devnull => ...	537	=item devnull => ...
316		538
…		…
339	snd $NODE, time => $myport, timereply => 1, 2;	561	snd $NODE, time => $myport, timereply => 1, 2;
340	# => snd $myport, timereply => 1, 2, <time>	562	# => snd $myport, timereply => 1, 2, <time>
341		563
342	=back	564	=back
343		565
		566	=head1 AnyEvent::MP vs. Distributed Erlang
		567
		568	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
		569	== aemp node, erlang process == aemp port), so many of the documents and
		570	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
		571	sample:
		572
		573	http://www.erlang.se/doc/programming_rules.shtml
		574	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		575	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
		576	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		577
		578	Despite the similarities, there are also some important differences:
		579
		580	=over 4
		581
		582	=item * Node references contain the recipe on how to contact them.
		583
		584	Erlang relies on special naming and DNS to work everywhere in the
		585	same way. AEMP relies on each node knowing it's own address(es), with
		586	convenience functionality.
		587
		588	This means that AEMP requires a less tightly controlled environment at the
		589	cost of longer node references and a slightly higher management overhead.
		590
		591	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		592
		593	Erlang uses processes that selctively receive messages, and therefore
		594	needs a queue. AEMP is event based, queuing messages would serve no useful
		595	purpose.
		596
		597	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).
		598
		599	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		600
		601	Sending messages in erlang is synchronous and blocks the process. AEMP
		602	sends are immediate, connection establishment is handled in the
		603	background.
		604
		605	=item * Erlang can silently lose messages, AEMP cannot.
		606
		607	Erlang makes few guarantees on messages delivery - messages can get lost
		608	without any of the processes realising it (i.e. you send messages a, b,
		609	and c, and the other side only receives messages a and c).
		610
		611	AEMP guarantees correct ordering, and the guarantee that there are no
		612	holes in the message sequence.
		613
		614	=item * In erlang, processes can be declared dead and later be found to be
		615	alive.
		616
		617	In erlang it can happen that a monitored process is declared dead and
		618	linked processes get killed, but later it turns out that the process is
		619	still alive - and can receive messages.
		620
		621	In AEMP, when port monitoring detects a port as dead, then that port will
		622	eventually be killed - it cannot happen that a node detects a port as dead
		623	and then later sends messages to it, finding it is still alive.
		624
		625	=item * Erlang can send messages to the wrong port, AEMP does not.
		626
		627	In erlang it is quite possible that a node that restarts reuses a process
		628	ID known to other nodes for a completely different process, causing
		629	messages destined for that process to end up in an unrelated process.
		630
		631	AEMP never reuses port IDs, so old messages or old port IDs floating
		632	around in the network will not be sent to an unrelated port.
		633
		634	=item * Erlang uses unprotected connections, AEMP uses secure
		635	authentication and can use TLS.
		636
		637	AEMP can use a proven protocol - SSL/TLS - to protect connections and
		638	securely authenticate nodes.
		639
		640	=item * The AEMP protocol is optimised for both text-based and binary
		641	communications.
		642
		643	The AEMP protocol, unlike the erlang protocol, supports both
		644	language-independent text-only protocols (good for debugging) and binary,
		645	language-specific serialisers (e.g. Storable).
		646
		647	It has also been carefully designed to be implementable in other languages
		648	with a minimum of work while gracefully degrading fucntionality to make the
		649	protocol simple.
		650
		651	=back
		652
344	=head1 SEE ALSO	653	=head1 SEE ALSO
345		654
346	L<AnyEvent>.	655	L<AnyEvent>.
347		656
348	=head1 AUTHOR	657	=head1 AUTHOR

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Revision 1.12 by root, Sun Aug 2 18:11:48 2009 UTC vs.
Revision 1.32 by root, Wed Aug 5 19:58:46 2009 UTC