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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.9 by root, Sun Aug 2 15:47:04 2009 UTC vs.
Revision 1.34 by root, Wed Aug 5 23:50:46 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	become_slave become_public	109	snd rcv mon kil reg psub
		110	port
92	);	111	);
93		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
94	=item NODE / $NODE	121	=item $thisnode = NODE / $NODE
95		122
96	The C<NODE ()> function and the C<$NODE> variable contain the noderef of	123	The C<NODE> function returns, and the C<$NODE> variable contains
97	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
98	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.
99		127
		128	=item $noderef = node_of $port
		129
		130	Extracts and returns the noderef from a portid or a noderef.
		131
		132	=item initialise_node $noderef, $seednode, $seednode...
		133
		134	=item initialise_node "slave/", $master, $master...
		135
		136	Before a node can talk to other nodes on the network it has to initialise
		137	itself - the minimum a node needs to know is it's own name, and optionally
		138	it should know the noderefs of some other nodes in the network.
		139
		140	This function initialises a node - it must be called exactly once (or
		141	never) before calling other AnyEvent::MP functions.
		142
		143	All arguments are noderefs, which can be either resolved or unresolved.
		144
		145	There are two types of networked nodes, public nodes and slave nodes:
		146
		147	=over 4
		148
		149	=item public nodes
		150
		151	For public nodes, C<$noderef> must either be a (possibly unresolved)
		152	noderef, in which case it will be resolved, or C<undef> (or missing), in
		153	which case the noderef will be guessed.
		154
		155	Afterwards, the node will bind itself on all endpoints and try to connect
		156	to all additional C<$seednodes> that are specified. Seednodes are optional
		157	and can be used to quickly bootstrap the node into an existing network.
		158
		159	=item slave nodes
		160
		161	When the C<$noderef> is the special string C<slave/>, then the node will
		162	become a slave node. Slave nodes cannot be contacted from outside and will
		163	route most of their traffic to the master node that they attach to.
		164
		165	At least one additional noderef is required: The node will try to connect
		166	to all of them and will become a slave attached to the first node it can
		167	successfully connect to.
		168
		169	=back
		170
		171	This function will block until all nodes have been resolved and, for slave
		172	nodes, until it has successfully established a connection to a master
		173	server.
		174
		175	Example: become a public node listening on the default node.
		176
		177	initialise_node;
		178
		179	Example: become a public node, and try to contact some well-known master
		180	servers to become part of the network.
		181
		182	initialise_node undef, "master1", "master2";
		183
		184	Example: become a public node listening on port C<4041>.
		185
		186	initialise_node 4041;
		187
		188	Example: become a public node, only visible on localhost port 4044.
		189
		190	initialise_node "locahost:4044";
		191
		192	Example: become a slave node to any of the specified master servers.
		193
		194	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
		195
		196	=item $cv = resolve_node $noderef
		197
		198	Takes an unresolved node reference that may contain hostnames and
		199	abbreviated IDs, resolves all of them and returns a resolved node
		200	reference.
		201
		202	In addition to C<address:port> pairs allowed in resolved noderefs, the
		203	following forms are supported:
		204
		205	=over 4
		206
		207	=item the empty string
		208
		209	An empty-string component gets resolved as if the default port (4040) was
		210	specified.
		211
		212	=item naked port numbers (e.g. C<1234>)
		213
		214	These are resolved by prepending the local nodename and a colon, to be
		215	further resolved.
		216
		217	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
		218
		219	These are resolved by using AnyEvent::DNS to resolve them, optionally
		220	looking up SRV records for the C<aemp=4040> port, if no port was
		221	specified.
		222
		223	=back
		224
		225	=item $SELF
		226
		227	Contains the current port id while executing C<rcv> callbacks or C<psub>
		228	blocks.
		229
		230	=item SELF, %SELF, @SELF...
		231
		232	Due to some quirks in how perl exports variables, it is impossible to
		233	just export C<$SELF>, all the symbols called C<SELF> are exported by this
		234	module, but only C<$SELF> is currently used.
		235
100	=item snd $portid, type => @data	236	=item snd $port, type => @data
101		237
102	=item snd $portid, @msg	238	=item snd $port, @msg
103		239
104	Send the given message to the given port ID, which can identify either	240	Send the given message to the given port ID, which can identify either
105	a local or a remote port, and can be either a string or soemthignt hat	241	a local or a remote port, and can be either a string or soemthignt hat
106	stringifies a sa port ID (such as a port object :).	242	stringifies a sa port ID (such as a port object :).
107		243
…		…
117	JSON is used, then only strings, numbers and arrays and hashes consisting	253	JSON is used, then only strings, numbers and arrays and hashes consisting
118	of those are allowed (no objects). When Storable is used, then anything	254	of those are allowed (no objects). When Storable is used, then anything
119	that Storable can serialise and deserialise is allowed, and for the local	255	that Storable can serialise and deserialise is allowed, and for the local
120	node, anything can be passed.	256	node, anything can be passed.
121		257
122	=item $local_port = create_port	258	=item $local_port = port
123		259
124	Create a new local port object. See the next section for allowed methods.	260	Create a new local port object that can be used either as a pattern
		261	matching port ("full port") or a single-callback port ("miniport"),
		262	depending on how C<rcv> callbacks are bound to the object.
125		263
126	=cut	264	=item $port = port { my @msg = @_; $finished }
127		265
128	sub create_port {	266	Creates a "miniport", that is, a very lightweight port without any pattern
129	my $id = "$AnyEvent::MP::Base::UNIQ." . ++$AnyEvent::MP::Base::ID;	267	matching behind it, and returns its ID. Semantically the same as creating
		268	a port and calling C<rcv $port, $callback> on it.
130		269
131	my $self = bless {	270	The block will be called for every message received on the port. When the
132	id => "$NODE#$id",	271	callback returns a true value its job is considered "done" and the port
133	names => [$id],	272	will be destroyed. Otherwise it will stay alive.
134	}, "AnyEvent::MP::Port";
135		273
136	$AnyEvent::MP::Base::PORT{$id} = sub {	274	The message will be passed as-is, no extra argument (i.e. no port id) will
137	unshift @_, $self;	275	be passed to the callback.
138		276
139	for (@{ $self->{rc0}{$_[1]} }) {	277	If you need the local port id in the callback, this works nicely:
140	$_ && &{$_->[0]}
141	&& undef $_;
142	}
143		278
144	for (@{ $self->{rcv}{$_[1]} }) {	279	my $port; $port = port {
145	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	280	snd $otherport, reply => $port;
146	&& &{$_->[0]}
147	&& undef $_;
148	}
149
150	for (@{ $self->{any} }) {
151	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
152	&& &{$_->[0]}
153	&& undef $_;
154	}
155	};	281	};
156		282
157	$self	283	=cut
		284
		285	sub rcv($@);
		286
		287	sub port(;&) {
		288	my $id = "$UNIQ." . $ID++;
		289	my $port = "$NODE#$id";
		290
		291	if (@_) {
		292	rcv $port, shift;
		293	} else {
		294	$PORT{$id} = sub { }; # nop
		295	}
		296
		297	$port
158	}	298	}
159		299
160	package AnyEvent::MP::Port;	300	=item reg $port, $name
161		301
162	=back	302	Registers the given port under the name C<$name>. If the name already
		303	exists it is replaced.
163		304
164	=head1 METHODS FOR PORT OBJECTS	305	A port can only be registered under one well known name.
165		306
166	=over 4	307	A port automatically becomes unregistered when it is killed.
167		308
168	=item "$port"
169
170	A port object stringifies to its port ID, so can be used directly for
171	C<snd> operations.
172
173	=cut	309	=cut
174		310
175	use overload	311	sub reg(@) {
176	'""' => sub { $_[0]{id} },	312	my ($port, $name) = @_;
177	fallback => 1;
178		313
179	=item $port->rcv (type => $callback->($port, @msg))	314	$REG{$name} = $port;
		315	}
180		316
181	=item $port->rcv ($smartmatch => $callback->($port, @msg))	317	=item rcv $port, $callback->(@msg)
182		318
		319	Replaces the callback on the specified miniport (after converting it to
		320	one if required).
		321
		322	=item rcv $port, tagstring => $callback->(@msg), ...
		323
		324	=item rcv $port, $smartmatch => $callback->(@msg), ...
		325
183	=item $port->rcv ([$smartmatch...] => $callback->($port, @msg))	326	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
184		327
185	Register a callback on the given port.	328	Register callbacks to be called on matching messages on the given full
		329	port (after converting it to one if required).
186		330
187	The callback has to return a true value when its work is done, after	331	The callback has to return a true value when its work is done, after
188	which is will be removed, or a false value in which case it will stay	332	which is will be removed, or a false value in which case it will stay
189	registered.	333	registered.
190		334
		335	The global C<$SELF> (exported by this module) contains C<$port> while
		336	executing the callback.
		337
		338	Runtime errors wdurign callback execution will result in the port being
		339	C<kil>ed.
		340
191	If the match is an array reference, then it will be matched against the	341	If the match is an array reference, then it will be matched against the
192	first elements of the message, otherwise only the first element is being	342	first elements of the message, otherwise only the first element is being
193	matched.	343	matched.
194		344
195	Any element in the match that is specified as C<_any_> (a function	345	Any element in the match that is specified as C<_any_> (a function
…		…
200	also the most efficient match (by far).	350	also the most efficient match (by far).
201		351
202	=cut	352	=cut
203		353
204	sub rcv($@) {	354	sub rcv($@) {
205	my ($self, $match, $cb) = @_;	355	my $port = shift;
		356	my ($noderef, $portid) = split /#/, $port, 2;
206		357
207	if (!ref $match) {	358	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
208	push @{ $self->{rc0}{$match} }, [$cb];	359	or Carp::croak "$port: rcv can only be called on local ports, caught";
209	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	360
210	my ($type, @match) = @$match;	361	if (@_ == 1) {
211	@match	362	my $cb = shift;
212	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	363	delete $PORT_DATA{$portid};
213	: push @{ $self->{rc0}{$match->[0]} }, [$cb];	364	$PORT{$portid} = sub {
		365	local $SELF = $port;
		366	eval {
		367	&$cb
		368	and kil $port;
		369	};
		370	_self_die if $@;
		371	};
214	} else {	372	} else {
		373	my $self = $PORT_DATA{$portid} \|\|= do {
		374	my $self = bless {
		375	id => $port,
		376	}, "AnyEvent::MP::Port";
		377
		378	$PORT{$portid} = sub {
		379	local $SELF = $port;
		380
		381	eval {
		382	for (@{ $self->{rc0}{$_[0]} }) {
		383	$_ && &{$_->[0]}
		384	&& undef $_;
		385	}
		386
		387	for (@{ $self->{rcv}{$_[0]} }) {
		388	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
		389	&& &{$_->[0]}
		390	&& undef $_;
		391	}
		392
		393	for (@{ $self->{any} }) {
		394	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
		395	&& &{$_->[0]}
		396	&& undef $_;
		397	}
		398	};
		399	_self_die if $@;
		400	};
		401
		402	$self
		403	};
		404
		405	"AnyEvent::MP::Port" eq ref $self
		406	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		407
		408	while (@_) {
		409	my ($match, $cb) = splice @_, 0, 2;
		410
		411	if (!ref $match) {
		412	push @{ $self->{rc0}{$match} }, [$cb];
		413	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
		414	my ($type, @match) = @$match;
		415	@match
		416	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
		417	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
		418	} else {
215	push @{ $self->{any} }, [$cb, $match];	419	push @{ $self->{any} }, [$cb, $match];
		420	}
		421	}
		422	}
		423
		424	$port
		425	}
		426
		427	=item $closure = psub { BLOCK }
		428
		429	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
		430	closure is executed, sets up the environment in the same way as in C<rcv>
		431	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		432
		433	This is useful when you register callbacks from C<rcv> callbacks:
		434
		435	rcv delayed_reply => sub {
		436	my ($delay, @reply) = @_;
		437	my $timer = AE::timer $delay, 0, psub {
		438	snd @reply, $SELF;
		439	};
		440	};
		441
		442	=cut
		443
		444	sub psub(&) {
		445	my $cb = shift;
		446
		447	my $port = $SELF
		448	or Carp::croak "psub can only be called from within rcv or psub callbacks, not";
		449
		450	sub {
		451	local $SELF = $port;
		452
		453	if (wantarray) {
		454	my @res = eval { &$cb };
		455	_self_die if $@;
		456	@res
		457	} else {
		458	my $res = eval { &$cb };
		459	_self_die if $@;
		460	$res
		461	}
216	}	462	}
217	}	463	}
218		464
219	=item $port->register ($name)	465	=item $guard = mon $port, $cb->(@reason)
220		466
221	Registers the given port under the well known name C<$name>. If the name	467	=item $guard = mon $port, $otherport
222	already exists it is replaced.
223		468
224	A port can only be registered under one well known name.	469	=item $guard = mon $port, $otherport, @msg
225		470
226	=cut	471	Monitor the given port and do something when the port is killed.
227		472
228	sub register {	473	In the first form, the callback is simply called with any number
229	my ($self, $name) = @_;	474	of C<@reason> elements (no @reason means that the port was deleted
		475	"normally"). Note also that I<< the callback B<must> never die >>, so use
		476	C<eval> if unsure.
230		477
231	$self->{wkname} = $name;	478	In the second form, the other port will be C<kil>'ed with C<@reason>, iff
232	$AnyEvent::MP::Base::WKP{$name} = "$self";	479	a @reason was specified, i.e. on "normal" kils nothing happens, while
		480	under all other conditions, the other port is killed with the same reason.
		481
		482	In the last form, a message of the form C<@msg, @reason> will be C<snd>.
		483
		484	Example: call a given callback when C<$port> is killed.
		485
		486	mon $port, sub { warn "port died because of <@_>\n" };
		487
		488	Example: kill ourselves when C<$port> is killed abnormally.
		489
		490	mon $port, $self;
		491
		492	Example: send us a restart message another C<$port> is killed.
		493
		494	mon $port, $self => "restart";
		495
		496	=cut
		497
		498	sub mon {
		499	my ($noderef, $port) = split /#/, shift, 2;
		500
		501	my $node = $NODE{$noderef} \|\| add_node $noderef;
		502
		503	my $cb = shift;
		504
		505	unless (ref $cb) {
		506	if (@_) {
		507	# send a kill info message
		508	my (@msg) = ($cb, @_);
		509	$cb = sub { snd @msg, @_ };
		510	} else {
		511	# simply kill other port
		512	my $port = $cb;
		513	$cb = sub { kil $port, @_ if @_ };
		514	}
		515	}
		516
		517	$node->monitor ($port, $cb);
		518
		519	defined wantarray
		520	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
233	}	521	}
234		522
235	=item $port->destroy	523	=item $guard = mon_guard $port, $ref, $ref...
236		524
237	Explicitly destroy/remove/nuke/vaporise the port.	525	Monitors the given C<$port> and keeps the passed references. When the port
		526	is killed, the references will be freed.
238		527
239	Ports are normally kept alive by there mere existance alone, and need to	528	Optionally returns a guard that will stop the monitoring.
240	be destroyed explicitly.
241		529
242	=cut	530	This function is useful when you create e.g. timers or other watchers and
		531	want to free them when the port gets killed:
243		532
244	sub destroy {	533	$port->rcv (start => sub {
245	my ($self) = @_;	534	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		535	undef $timer if 0.9 < rand;
		536	});
		537	});
246		538
247	delete $AnyEvent::MP::Base::WKP{ $self->{wkname} };	539	=cut
248		540
249	delete $AnyEvent::MP::Base::PORT{$_}	541	sub mon_guard {
250	for @{ $self->{names} };	542	my ($port, @refs) = @_;
		543
		544	mon $port, sub { 0 && @refs }
251	}	545	}
252		546
253	=back	547	=item lnk $port1, $port2
254		548
255	=head1 FUNCTIONS FOR NODES	549	Link two ports. This is simply a shorthand for:
256		550
257	=over 4	551	mon $port1, $port2;
		552	mon $port2, $port1;
258		553
259	=item mon $noderef, $callback->($noderef, $status, $)	554	It means that if either one is killed abnormally, the other one gets
		555	killed as well.
260		556
261	Monitors the given noderef.	557	=item kil $port[, @reason]
262		558
263	=item become_public endpoint...	559	Kill the specified port with the given C<@reason>.
264		560
265	Tells the node to become a public node, i.e. reachable from other nodes.	561	If no C<@reason> is specified, then the port is killed "normally" (linked
		562	ports will not be kileld, or even notified).
266		563
267	If no arguments are given, or the first argument is C<undef>, then	564	Otherwise, linked ports get killed with the same reason (second form of
268	AnyEvent::MP tries to bind on port C<4040> on all IP addresses that the	565	C<mon>, see below).
269	local nodename resolves to.
270		566
271	Otherwise the first argument must be an array-reference with transport	567	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
272	endpoints ("ip:port", "hostname:port") or port numbers (in which case the	568	will be reported as reason C<< die => $@ >>.
273	local nodename is used as hostname). The endpoints are all resolved and
274	will become the node reference.
275		569
276	=cut	570	Transport/communication errors are reported as C<< transport_error =>
		571	$message >>.
277		572
278	=back	573	=back
279		574
280	=head1 NODE MESSAGES	575	=head1 NODE MESSAGES
281		576
282	Nodes understand the following messages sent to them. Many of them take	577	Nodes understand the following messages sent to them. Many of them take
283	arguments called C<@reply>, which will simply be used to compose a reply	578	arguments called C<@reply>, which will simply be used to compose a reply
284	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	579	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
285	the remaining arguments are simply the message data.	580	the remaining arguments are simply the message data.
286		581
		582	While other messages exist, they are not public and subject to change.
		583
287	=over 4	584	=over 4
288		585
289	=cut	586	=cut
290		587
291	=item wkp => $name, @reply	588	=item lookup => $name, @reply
292		589
293	Replies with the port ID of the specified well-known port, or C<undef>.	590	Replies with the port ID of the specified well-known port, or C<undef>.
294		591
295	=item devnull => ...	592	=item devnull => ...
296		593
…		…
319	snd $NODE, time => $myport, timereply => 1, 2;	616	snd $NODE, time => $myport, timereply => 1, 2;
320	# => snd $myport, timereply => 1, 2, <time>	617	# => snd $myport, timereply => 1, 2, <time>
321		618
322	=back	619	=back
323		620
		621	=head1 AnyEvent::MP vs. Distributed Erlang
		622
		623	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node
		624	== aemp node, erlang process == aemp port), so many of the documents and
		625	programming techniques employed by erlang apply to AnyEvent::MP. Here is a
		626	sample:
		627
		628	http://www.erlang.se/doc/programming_rules.shtml
		629	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
		630	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
		631	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
		632
		633	Despite the similarities, there are also some important differences:
		634
		635	=over 4
		636
		637	=item * Node references contain the recipe on how to contact them.
		638
		639	Erlang relies on special naming and DNS to work everywhere in the
		640	same way. AEMP relies on each node knowing it's own address(es), with
		641	convenience functionality.
		642
		643	This means that AEMP requires a less tightly controlled environment at the
		644	cost of longer node references and a slightly higher management overhead.
		645
		646	=item * Erlang uses processes and a mailbox, AEMP does not queue.
		647
		648	Erlang uses processes that selctively receive messages, and therefore
		649	needs a queue. AEMP is event based, queuing messages would serve no useful
		650	purpose.
		651
		652	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).
		653
		654	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
		655
		656	Sending messages in erlang is synchronous and blocks the process. AEMP
		657	sends are immediate, connection establishment is handled in the
		658	background.
		659
		660	=item * Erlang can silently lose messages, AEMP cannot.
		661
		662	Erlang makes few guarantees on messages delivery - messages can get lost
		663	without any of the processes realising it (i.e. you send messages a, b,
		664	and c, and the other side only receives messages a and c).
		665
		666	AEMP guarantees correct ordering, and the guarantee that there are no
		667	holes in the message sequence.
		668
		669	=item * In erlang, processes can be declared dead and later be found to be
		670	alive.
		671
		672	In erlang it can happen that a monitored process is declared dead and
		673	linked processes get killed, but later it turns out that the process is
		674	still alive - and can receive messages.
		675
		676	In AEMP, when port monitoring detects a port as dead, then that port will
		677	eventually be killed - it cannot happen that a node detects a port as dead
		678	and then later sends messages to it, finding it is still alive.
		679
		680	=item * Erlang can send messages to the wrong port, AEMP does not.
		681
		682	In erlang it is quite possible that a node that restarts reuses a process
		683	ID known to other nodes for a completely different process, causing
		684	messages destined for that process to end up in an unrelated process.
		685
		686	AEMP never reuses port IDs, so old messages or old port IDs floating
		687	around in the network will not be sent to an unrelated port.
		688
		689	=item * Erlang uses unprotected connections, AEMP uses secure
		690	authentication and can use TLS.
		691
		692	AEMP can use a proven protocol - SSL/TLS - to protect connections and
		693	securely authenticate nodes.
		694
		695	=item * The AEMP protocol is optimised for both text-based and binary
		696	communications.
		697
		698	The AEMP protocol, unlike the erlang protocol, supports both
		699	language-independent text-only protocols (good for debugging) and binary,
		700	language-specific serialisers (e.g. Storable).
		701
		702	It has also been carefully designed to be implementable in other languages
		703	with a minimum of work while gracefully degrading fucntionality to make the
		704	protocol simple.
		705
		706	=back
		707
324	=head1 SEE ALSO	708	=head1 SEE ALSO
325		709
326	L<AnyEvent>.	710	L<AnyEvent>.
327		711
328	=head1 AUTHOR	712	=head1 AUTHOR

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Revision 1.9 by root, Sun Aug 2 15:47:04 2009 UTC vs.
Revision 1.34 by root, Wed Aug 5 23:50:46 2009 UTC