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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.5 by root, Sat Aug 1 07:44:02 2009 UTC vs.
Revision 1.27 by root, Tue Aug 4 22:13:45 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
		38	At the moment, this module family is severly broken and underdocumented,
		39	so do not use. This was uploaded mainly to reserve the CPAN namespace -
		40	stay tuned! The basic API should be finished, however.
		41
32	=head1 CONCEPTS	42	=head1 CONCEPTS
33		43
34	=over 4	44	=over 4
35		45
36	=item port	46	=item port
…		…
68		78
69	=cut	79	=cut
70		80
71	package AnyEvent::MP;	81	package AnyEvent::MP;
72		82
73	use AnyEvent::MP::Util ();
74	use AnyEvent::MP::Node;	83	use AnyEvent::MP::Base;
75	use AnyEvent::MP::Transport;
76		84
77	use utf8;
78	use common::sense;	85	use common::sense;
79		86
80	use Carp ();	87	use Carp ();
81		88
82	use AE ();	89	use AE ();
83		90
84	use base "Exporter";	91	use base "Exporter";
85		92
86	our $VERSION = '0.0';	93	our $VERSION = '0.1';
87	our @EXPORT = qw(NODE $NODE $PORT snd rcv _any_);	94	our @EXPORT = qw(
		95	NODE $NODE *SELF node_of _any_
		96	become_slave become_public
		97	snd rcv mon kil reg psub
		98	port
		99	);
88		100
89	our $DEFAULT_SECRET;	101	our $SELF;
90	our $DEFAULT_PORT = "4040";
91		102
92	our $CONNECT_INTERVAL = 5; # new connect every 5s, at least	103	sub _self_die() {
93	our $CONNECT_TIMEOUT = 30; # includes handshake	104	my $msg = $@;
94		105	$msg =~ s/\n+$// unless ref $msg;
95	sub default_secret {	106	kil $SELF, die => $msg;
96	unless (defined $DEFAULT_SECRET) {
97	if (open my $fh, "<$ENV{HOME}/.aemp-secret") {
98	sysread $fh, $DEFAULT_SECRET, -s $fh;
99	} else {
100	$DEFAULT_SECRET = AnyEvent::MP::Util::nonce 32;
101	}
102	}
103
104	$DEFAULT_SECRET
105	}	107	}
106		108
107	=item NODE / $NODE	109	=item $thisnode = NODE / $NODE
108		110
109	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	111	The C<NODE> function returns, and the C<$NODE> variable contains
110	the local node. The value is initialised by a call to C<become_public> or	112	the noderef of the local node. The value is initialised by a call
111	C<become_slave>, after which all local port identifiers become invalid.	113	to C<become_public> or C<become_slave>, after which all local port
		114	identifiers become invalid.
112		115
113	=cut	116	=item $noderef = node_of $portid
114		117
115	our $UNIQ = sprintf "%x.%x", $$, time; # per-process/node unique cookie	118	Extracts and returns the noderef from a portid or a noderef.
116	our $PUBLIC = 0;
117	our $NODE;
118	our $PORT;
119		119
120	our %NODE; # node id to transport mapping, or "undef", for local node	120	=item $SELF
121	our %PORT; # local ports
122	our %LISTENER; # local transports
123		121
124	sub NODE() { $NODE }	122	Contains the current port id while executing C<rcv> callbacks or C<psub>
		123	blocks.
125		124
126	{	125	=item SELF, %SELF, @SELF...
127	use POSIX ();
128	my $nodename = (POSIX::uname)[1];
129	$NODE = "$$\@$nodename";
130	}
131		126
132	sub _ANY_() { 1 }	127	Due to some quirks in how perl exports variables, it is impossible to
133	sub _any_() { \&_ANY_ }	128	just export C<$SELF>, all the symbols called C<SELF> are exported by this
134		129	module, but only C<$SELF> is currently used.
135	sub add_node {
136	my ($noderef) = @_;
137
138	return $NODE{$noderef}
139	if exists $NODE{$noderef};
140
141	for (split /,/, $noderef) {
142	return $NODE{$noderef} = $NODE{$_}
143	if exists $NODE{$_};
144	}
145
146	# for indirect sends, use a different class
147	my $node = new AnyEvent::MP::Node::Direct $noderef;
148
149	$NODE{$_} = $node
150	for $noderef, split /,/, $noderef;
151
152	$node
153	}
154		130
155	=item snd $portid, type => @data	131	=item snd $portid, type => @data
156		132
157	=item snd $portid, @msg	133	=item snd $portid, @msg
158		134
159	Send the given message to the given port ID, which can identify either a	135	Send the given message to the given port ID, which can identify either
160	local or a remote port.	136	a local or a remote port, and can be either a string or soemthignt hat
		137	stringifies a sa port ID (such as a port object :).
161		138
162	While the message can be about anything, it is highly recommended to use	139	While the message can be about anything, it is highly recommended to use a
163	a constant string as first element.	140	string as first element (a portid, or some word that indicates a request
		141	type etc.).
164		142
165	The message data effectively becomes read-only after a call to this	143	The message data effectively becomes read-only after a call to this
166	function: modifying any argument is not allowed and can cause many	144	function: modifying any argument is not allowed and can cause many
167	problems.	145	problems.
168		146
…		…
170	JSON is used, then only strings, numbers and arrays and hashes consisting	148	JSON is used, then only strings, numbers and arrays and hashes consisting
171	of those are allowed (no objects). When Storable is used, then anything	149	of those are allowed (no objects). When Storable is used, then anything
172	that Storable can serialise and deserialise is allowed, and for the local	150	that Storable can serialise and deserialise is allowed, and for the local
173	node, anything can be passed.	151	node, anything can be passed.
174		152
175	=cut	153	=item kil $portid[, @reason]
176		154
177	sub snd(@) {	155	Kill the specified port with the given C<@reason>.
		156
		157	If no C<@reason> is specified, then the port is killed "normally" (linked
		158	ports will not be kileld, or even notified).
		159
		160	Otherwise, linked ports get killed with the same reason (second form of
		161	C<mon>, see below).
		162
		163	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		164	will be reported as reason C<< die => $@ >>.
		165
		166	Transport/communication errors are reported as C<< transport_error =>
		167	$message >>.
		168
		169	=item $guard = mon $portid, $cb->(@reason)
		170
		171	=item $guard = mon $portid, $otherport
		172
		173	=item $guard = mon $portid, $otherport, @msg
		174
		175	Monitor the given port and do something when the port is killed.
		176
		177	In the first form, the callback is simply called with any number
		178	of C<@reason> elements (no @reason means that the port was deleted
		179	"normally"). Note also that I<< the callback B<must> never die >>, so use
		180	C<eval> if unsure.
		181
		182	In the second form, the other port will be C<kil>'ed with C<@reason>, iff
		183	a @reason was specified, i.e. on "normal" kils nothing happens, while
		184	under all other conditions, the other port is killed with the same reason.
		185
		186	In the last form, a message of the form C<@msg, @reason> will be C<snd>.
		187
		188	Example: call a given callback when C<$port> is killed.
		189
		190	mon $port, sub { warn "port died because of <@_>\n" };
		191
		192	Example: kill ourselves when C<$port> is killed abnormally.
		193
		194	mon $port, $self;
		195
		196	Example: send us a restart message another C<$port> is killed.
		197
		198	mon $port, $self => "restart";
		199
		200	=cut
		201
		202	sub mon {
178	my ($noderef, $port) = split /#/, shift, 2;	203	my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);
179		204
180	add_node $noderef	205	my $node = $NODE{$noderef} \|\| add_node $noderef;
181	unless exists $NODE{$noderef};
182		206
183	$NODE{$noderef}->send (["$port", [@_]]);	207	#TODO: ports must not be references
		208	if (!ref $cb or "AnyEvent::MP::Port" eq ref $cb) {
		209	if (@_) {
		210	# send a kill info message
		211	my (@msg) = ($cb, @_);
		212	$cb = sub { snd @msg, @_ };
		213	} else {
		214	# simply kill other port
		215	my $port = $cb;
		216	$cb = sub { kil $port, @_ if @_ };
		217	}
		218	}
		219
		220	$node->monitor ($port, $cb);
		221
		222	defined wantarray
		223	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
184	}	224	}
185		225
		226	=item $guard = mon_guard $port, $ref, $ref...
		227
		228	Monitors the given C<$port> and keeps the passed references. When the port
		229	is killed, the references will be freed.
		230
		231	Optionally returns a guard that will stop the monitoring.
		232
		233	This function is useful when you create e.g. timers or other watchers and
		234	want to free them when the port gets killed:
		235
		236	$port->rcv (start => sub {
		237	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		238	undef $timer if 0.9 < rand;
		239	});
		240	});
		241
		242	=cut
		243
		244	sub mon_guard {
		245	my ($port, @refs) = @_;
		246
		247	mon $port, sub { 0 && @refs }
		248	}
		249
		250	=item lnk $port1, $port2
		251
		252	Link two ports. This is simply a shorthand for:
		253
		254	mon $port1, $port2;
		255	mon $port2, $port1;
		256
		257	It means that if either one is killed abnormally, the other one gets
		258	killed as well.
		259
		260	=item $local_port = port
		261
		262	Create a new local port object that supports message matching.
		263
		264	=item $portid = port { my @msg = @_; $finished }
		265
		266	Creates a "mini port", that is, a very lightweight port without any
		267	pattern matching behind it, and returns its ID.
		268
		269	The block will be called for every message received on the port. When the
		270	callback returns a true value its job is considered "done" and the port
		271	will be destroyed. Otherwise it will stay alive.
		272
		273	The message will be passed as-is, no extra argument (i.e. no port id) will
		274	be passed to the callback.
		275
		276	If you need the local port id in the callback, this works nicely:
		277
		278	my $port; $port = miniport {
		279	snd $otherport, reply => $port;
		280	};
		281
		282	=cut
		283
		284	sub port(;&) {
		285	my $id = "$UNIQ." . $ID++;
		286	my $port = "$NODE#$id";
		287
		288	if (@_) {
		289	my $cb = shift;
		290	$PORT{$id} = sub {
		291	local $SELF = $port;
		292	eval {
		293	&$cb
		294	and kil $id;
		295	};
		296	_self_die if $@;
		297	};
		298	} else {
		299	my $self = bless {
		300	id => "$NODE#$id",
		301	}, "AnyEvent::MP::Port";
		302
		303	$PORT_DATA{$id} = $self;
		304	$PORT{$id} = sub {
		305	local $SELF = $port;
		306
		307	eval {
		308	for (@{ $self->{rc0}{$_[0]} }) {
		309	$_ && &{$_->[0]}
		310	&& undef $_;
		311	}
		312
		313	for (@{ $self->{rcv}{$_[0]} }) {
		314	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
		315	&& &{$_->[0]}
		316	&& undef $_;
		317	}
		318
		319	for (@{ $self->{any} }) {
		320	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
		321	&& &{$_->[0]}
		322	&& undef $_;
		323	}
		324	};
		325	_self_die if $@;
		326	};
		327	}
		328
		329	$port
		330	}
		331
		332	=item reg $portid, $name
		333
		334	Registers the given port under the name C<$name>. If the name already
		335	exists it is replaced.
		336
		337	A port can only be registered under one well known name.
		338
		339	A port automatically becomes unregistered when it is killed.
		340
		341	=cut
		342
		343	sub reg(@) {
		344	my ($portid, $name) = @_;
		345
		346	$REG{$name} = $portid;
		347	}
		348
186	=item rcv $portid, type => $callback->(@msg)	349	=item rcv $portid, tagstring => $callback->(@msg), ...
187		350
188	=item rcv $portid, $smartmatch => $callback->(@msg)	351	=item rcv $portid, $smartmatch => $callback->(@msg), ...
189		352
190	=item rcv $portid, [$smartmatch...] => $callback->(@msg)	353	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
191		354
192	Register a callback on the port identified by C<$portid>, which I<must> be	355	Register callbacks to be called on matching messages on the given port.
193	a local port.
194		356
195	The callback has to return a true value when its work is done, after	357	The callback has to return a true value when its work is done, after
196	which is will be removed, or a false value in which case it will stay	358	which is will be removed, or a false value in which case it will stay
197	registered.	359	registered.
198		360
		361	The global C<$SELF> (exported by this module) contains C<$portid> while
		362	executing the callback.
		363
		364	Runtime errors wdurign callback execution will result in the port being
		365	C<kil>ed.
		366
199	If the match is an array reference, then it will be matched against the	367	If the match is an array reference, then it will be matched against the
200	first elements of the message, otherwise only the first element is being	368	first elements of the message, otherwise only the first element is being
201	matched.	369	matched.
202		370
203	Any element in the match that is specified as C<_any_> (a function	371	Any element in the match that is specified as C<_any_> (a function
…		…
208	also the most efficient match (by far).	376	also the most efficient match (by far).
209		377
210	=cut	378	=cut
211		379
212	sub rcv($@) {	380	sub rcv($@) {
213	my ($port, $match, $cb) = @_;
214
215	my $port = $PORT{$port}
216	or do {
217	my ($noderef, $lport) = split /#/, $port;	381	my ($noderef, $port) = split /#/, shift, 2;
218	"AnyEvent::MP::Node::Self" eq ref $NODE{$noderef}	382
		383	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
219	or Carp::croak "$port: can only rcv on local ports";	384	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
220		385
221	$PORT{$lport}	386	my $self = $PORT_DATA{$port}
222	or Carp::croak "$port: port does not exist";	387	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
223
224	$PORT{$port} = $PORT{$lport} # also return
225	};
226		388
		389	"AnyEvent::MP::Port" eq ref $self
		390	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
		391
		392	while (@_) {
		393	my ($match, $cb) = splice @_, 0, 2;
		394
227	if (!ref $match) {	395	if (!ref $match) {
228	push @{ $port->{rc0}{$match} }, [$cb];	396	push @{ $self->{rc0}{$match} }, [$cb];
229	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	397	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
230	my ($type, @match) = @$match;	398	my ($type, @match) = @$match;
231	@match	399	@match
232	? push @{ $port->{rcv}{$match->[0]} }, [$cb, \@match]	400	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
233	: push @{ $port->{rc0}{$match->[0]} }, [$cb];	401	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
234	} else {	402	} else {
235	push @{ $port->{any} }, [$cb, $match];	403	push @{ $self->{any} }, [$cb, $match];
		404	}
236	}	405	}
237	}	406	}
238		407
239	sub _inject {	408	=item $closure = psub { BLOCK }
240	my ($port, $msg) = @{+shift};
241		409
242	$port = $PORT{$port}	410	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
243	or return;	411	closure is executed, sets up the environment in the same way as in C<rcv>
		412	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
244		413
245	@_ = @$msg;	414	This is useful when you register callbacks from C<rcv> callbacks:
246		415
247	for (@{ $port->{rc0}{$msg->[0]} }) {	416	rcv delayed_reply => sub {
248	$_ && &{$_->[0]}	417	my ($delay, @reply) = @_;
249	&& undef $_;	418	my $timer = AE::timer $delay, 0, psub {
		419	snd @reply, $SELF;
		420	};
250	}	421	};
251		422
252	for (@{ $port->{rcv}{$msg->[0]} }) {	423	=cut
253	$_ && [@_[1..$#{$_->[1]}]] ~~ $_->[1]
254	&& &{$_->[0]}
255	&& undef $_;
256	}
257		424
258	for (@{ $port->{any} }) {	425	sub psub(&) {
259	$_ && [@_[0..$#{$_->[1]}]] ~~ $_->[1]	426	my $cb = shift;
260	&& &{$_->[0]}	427
261	&& undef $_;	428	my $port = $SELF
		429	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		430
		431	sub {
		432	local $SELF = $port;
		433
		434	if (wantarray) {
		435	my @res = eval { &$cb };
		436	_self_die if $@;
		437	@res
		438	} else {
		439	my $res = eval { &$cb };
		440	_self_die if $@;
		441	$res
		442	}
262	}	443	}
263	}	444	}
264		445
265	sub normalise_noderef($) {	446	=back
266	my ($noderef) = @_;
267		447
268	my $cv = AE::cv;	448	=head1 FUNCTIONS FOR NODES
269	my @res;
270		449
271	$cv->begin (sub {	450	=over 4
272	my %seen;
273	my @refs;
274	for (sort { $a->[0] <=> $b->[0] } @res) {
275	push @refs, $_->[1] unless $seen{$_->[1]}++
276	}
277	shift->send (join ",", @refs);
278	});
279		451
280	$noderef = $DEFAULT_PORT unless length $noderef;	452	=item become_public endpoint...
281		453
282	my $idx;	454	Tells the node to become a public node, i.e. reachable from other nodes.
283	for my $t (split /,/, $noderef) {
284	my $pri = ++$idx;
285
286	#TODO: this should be outside normalise_noderef and in become_public
287	if ($t =~ /^\d*$/) {
288	my $nodename = (POSIX::uname)[1];
289		455
290	$cv->begin;	456	If no arguments are given, or the first argument is C<undef>, then
291	AnyEvent::Socket::resolve_sockaddr $nodename, $t \|\| "aemp=$DEFAULT_PORT", "tcp", 0, undef, sub {	457	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the
292	for (@_) {	458	local nodename resolves to.
293	my ($service, $host) = AnyEvent::Socket::unpack_sockaddr $_->[3];
294	push @res, [
295	$pri += 1e-5,
296	AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $host, $service
297	];
298	}
299	$cv->end;
300	};
301		459
302	# my (undef, undef, undef, undef, @ipv4) = gethostbyname $nodename;	460	Otherwise the first argument must be an array-reference with transport
303	#	461	endpoints ("ip:port", "hostname:port") or port numbers (in which case the
304	# for (@ipv4) {	462	local nodename is used as hostname). The endpoints are all resolved and
305	# push @res, [	463	will become the node reference.
306	# $pri,
307	# AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $_, $t \|\| $DEFAULT_PORT,
308	# ];
309	# }
310	} else {
311	my ($host, $port) = AnyEvent::Socket::parse_hostport $t, "aemp=$DEFAULT_PORT"
312	or Carp::croak "$t: unparsable transport descriptor";
313		464
314	$cv->begin;	465	=cut
315	AnyEvent::Socket::resolve_sockaddr $host, $port, "tcp", 0, undef, sub {
316	for (@_) {
317	my ($service, $host) = AnyEvent::Socket::unpack_sockaddr $_->[3];
318	push @res, [
319	$pri += 1e-5,
320	AnyEvent::Socket::format_hostport AnyEvent::Socket::format_address $host, $service
321	];
322	}
323	$cv->end;
324	}
325	}
326	}
327
328	$cv->end;
329
330	$cv
331	}
332
333	sub become_public {
334	return if $PUBLIC;
335
336	my $noderef = join ",", ref $_[0] ? @{+shift} : shift;
337	my @args = @_;
338
339	$NODE = (normalise_noderef $noderef)->recv;
340
341	for my $t (split /,/, $NODE) {
342	$NODE{$t} = $NODE{""};
343
344	my ($host, $port) = AnyEvent::Socket::parse_hostport $t;
345
346	$LISTENER{$t} = AnyEvent::MP::Transport::mp_server $host, $port,
347	@args,
348	on_error => sub {
349	die "on_error<@_>\n";#d#
350	},
351	on_connect => sub {
352	my ($tp) = @_;
353
354	$NODE{$tp->{remote_id}} = $_[0];
355	},
356	sub {
357	my ($tp) = @_;
358
359	$NODE{"$tp->{peerhost}:$tp->{peerport}"} = $tp;
360	},
361	;
362	}
363
364	$PUBLIC = 1;
365	}
366		466
367	=back	467	=back
368		468
369	=head1 NODE MESSAGES	469	=head1 NODE MESSAGES
370		470
…		…
375		475
376	=over 4	476	=over 4
377		477
378	=cut	478	=cut
379		479
380	#############################################################################	480	=item lookup => $name, @reply
381	# self node code
382		481
383	sub _new_port($) {	482	Replies with the port ID of the specified well-known port, or C<undef>.
384	my ($name) = @_;
385		483
386	my ($noderef, $portname) = split /#/, $name;	484	=item devnull => ...
387		485
388	$PORT{$name} =	486	Generic data sink/CPU heat conversion.
389	$PORT{$portname} = {
390	names => [$name, $portname],
391	};
392	}
393
394	$NODE{""} = new AnyEvent::MP::Node::Self noderef => $NODE;
395	_new_port "";
396		487
397	=item relay => $port, @msg	488	=item relay => $port, @msg
398		489
399	Simply forwards the message to the given port.	490	Simply forwards the message to the given port.
400
401	=cut
402
403	rcv "", relay => \&snd;
404		491
405	=item eval => $string[ @reply]	492	=item eval => $string[ @reply]
406		493
407	Evaluates the given string. If C<@reply> is given, then a message of the	494	Evaluates the given string. If C<@reply> is given, then a message of the
408	form C<@reply, $@, @evalres> is sent.	495	form C<@reply, $@, @evalres> is sent.
409		496
410	Example: crash another node.	497	Example: crash another node.
411		498
412	snd $othernode, eval => "exit";	499	snd $othernode, eval => "exit";
413		500
414	=cut
415
416	rcv "", eval => sub {
417	my (undef, $string, @reply) = @_;
418	my @res = eval $string;
419	snd @reply, "$@", @res if @reply;
420	};
421
422	=item time => @reply	501	=item time => @reply
423		502
424	Replies the the current node time to C<@reply>.	503	Replies the the current node time to C<@reply>.
425		504
426	Example: tell the current node to send the current time to C<$myport> in a	505	Example: tell the current node to send the current time to C<$myport> in a
427	C<timereply> message.	506	C<timereply> message.
428		507
429	snd $NODE, time => $myport, timereply => 1, 2;	508	snd $NODE, time => $myport, timereply => 1, 2;
430	# => snd $myport, timereply => 1, 2, <time>	509	# => snd $myport, timereply => 1, 2, <time>
431		510
432	=cut	511	=back
433		512
434	rcv "", time => sub { shift; snd @_, AE::time };	513	=head1 AnyEvent::MP vs. Distributed Erlang
		514
		515	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
		516	== aemp node, erlang process == aemp port), so many of the documents and
		517	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
		518	sample:
		519
		520	http://www.erlang.se/doc/programming_rules.shtml
		521	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		522	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
		523	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		524
		525	Despite the similarities, there are also some important differences:
		526
		527	=over 4
		528
		529	=item * Node references contain the recipe on how to contact them.
		530
		531	Erlang relies on special naming and DNS to work everywhere in the
		532	same way. AEMP relies on each node knowing it's own address(es), with
		533	convenience functionality.
		534
		535	This means that AEMP requires a less tightly controlled environment at the
		536	cost of longer node references and a slightly higher management overhead.
		537
		538	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		539
		540	Erlang uses processes that selctively receive messages, and therefore
		541	needs a queue. AEMP is event based, queuing messages would serve no useful
		542	purpose.
		543
		544	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).
		545
		546	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		547
		548	Sending messages in erlang is synchronous and blocks the process. AEMP
		549	sends are immediate, connection establishment is handled in the
		550	background.
		551
		552	=item * Erlang can silently lose messages, AEMP cannot.
		553
		554	Erlang makes few guarantees on messages delivery - messages can get lost
		555	without any of the processes realising it (i.e. you send messages a, b,
		556	and c, and the other side only receives messages a and c).
		557
		558	AEMP guarantees correct ordering, and the guarantee that there are no
		559	holes in the message sequence.
		560
		561	=item * In erlang, processes can be declared dead and later be found to be
		562	alive.
		563
		564	In erlang it can happen that a monitored process is declared dead and
		565	linked processes get killed, but later it turns out that the process is
		566	still alive - and can receive messages.
		567
		568	In AEMP, when port monitoring detects a port as dead, then that port will
		569	eventually be killed - it cannot happen that a node detects a port as dead
		570	and then later sends messages to it, finding it is still alive.
		571
		572	=item * Erlang can send messages to the wrong port, AEMP does not.
		573
		574	In erlang it is quite possible that a node that restarts reuses a process
		575	ID known to other nodes for a completely different process, causing
		576	messages destined for that process to end up in an unrelated process.
		577
		578	AEMP never reuses port IDs, so old messages or old port IDs floating
		579	around in the network will not be sent to an unrelated port.
		580
		581	=item * Erlang uses unprotected connections, AEMP uses secure
		582	authentication and can use TLS.
		583
		584	AEMP can use a proven protocol - SSL/TLS - to protect connections and
		585	securely authenticate nodes.
435		586
436	=back	587	=back
437		588
438	=head1 SEE ALSO	589	=head1 SEE ALSO
439		590

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Revision 1.27 by root, Tue Aug 4 22:13:45 2009 UTC