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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.32 by root, Wed Aug 5 19:58:46 2009 UTC vs.
Revision 1.36 by root, Thu Aug 6 10:46:48 2009 UTC

…		…
22	snd $port2, ping => $port1;	22	snd $port2, ping => $port1;
23		23
24	# more, smarter, matches (_any_ is exported by this module)	24	# more, smarter, matches (_any_ is exported by this module)
25	rcv $port, [child_died => $pid] => sub { ...	25	rcv $port, [child_died => $pid] => sub { ...
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
		27
		28	# linking two ports, so they both crash together
		29	lnk $port1, $port2;
		30
		31	# monitoring
		32	mon $port, $cb->(@msg) # callback is invoked on death
		33	mon $port, $otherport # kill otherport on abnormal death
		34	mon $port, $otherport, @msg # send message on death
27		35
28	=head1 DESCRIPTION	36	=head1 DESCRIPTION
29		37
30	This module (-family) implements a simple message passing framework.	38	This module (-family) implements a simple message passing framework.
31		39
…		…
123	The C<NODE> function returns, and the C<$NODE> variable contains	131	The C<NODE> function returns, and the C<$NODE> variable contains
124	the noderef of the local node. The value is initialised by a call	132	the noderef of the local node. The value is initialised by a call
125	to C<become_public> or C<become_slave>, after which all local port	133	to C<become_public> or C<become_slave>, after which all local port
126	identifiers become invalid.	134	identifiers become invalid.
127		135
128	=item $noderef = node_of $portid	136	=item $noderef = node_of $port
129		137
130	Extracts and returns the noderef from a portid or a noderef.	138	Extracts and returns the noderef from a portid or a noderef.
		139
		140	=item initialise_node $noderef, $seednode, $seednode...
		141
		142	=item initialise_node "slave/", $master, $master...
		143
		144	Before a node can talk to other nodes on the network it has to initialise
		145	itself - the minimum a node needs to know is it's own name, and optionally
		146	it should know the noderefs of some other nodes in the network.
		147
		148	This function initialises a node - it must be called exactly once (or
		149	never) before calling other AnyEvent::MP functions.
		150
		151	All arguments are noderefs, which can be either resolved or unresolved.
		152
		153	There are two types of networked nodes, public nodes and slave nodes:
		154
		155	=over 4
		156
		157	=item public nodes
		158
		159	For public nodes, C<$noderef> must either be a (possibly unresolved)
		160	noderef, in which case it will be resolved, or C<undef> (or missing), in
		161	which case the noderef will be guessed.
		162
		163	Afterwards, the node will bind itself on all endpoints and try to connect
		164	to all additional C<$seednodes> that are specified. Seednodes are optional
		165	and can be used to quickly bootstrap the node into an existing network.
		166
		167	=item slave nodes
		168
		169	When the C<$noderef> is the special string C<slave/>, then the node will
		170	become a slave node. Slave nodes cannot be contacted from outside and will
		171	route most of their traffic to the master node that they attach to.
		172
		173	At least one additional noderef is required: The node will try to connect
		174	to all of them and will become a slave attached to the first node it can
		175	successfully connect to.
		176
		177	=back
		178
		179	This function will block until all nodes have been resolved and, for slave
		180	nodes, until it has successfully established a connection to a master
		181	server.
		182
		183	Example: become a public node listening on the default node.
		184
		185	initialise_node;
		186
		187	Example: become a public node, and try to contact some well-known master
		188	servers to become part of the network.
		189
		190	initialise_node undef, "master1", "master2";
		191
		192	Example: become a public node listening on port C<4041>.
		193
		194	initialise_node 4041;
		195
		196	Example: become a public node, only visible on localhost port 4044.
		197
		198	initialise_node "locahost:4044";
		199
		200	Example: become a slave node to any of the specified master servers.
		201
		202	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
131		203
132	=item $cv = resolve_node $noderef	204	=item $cv = resolve_node $noderef
133		205
134	Takes an unresolved node reference that may contain hostnames and	206	Takes an unresolved node reference that may contain hostnames and
135	abbreviated IDs, resolves all of them and returns a resolved node	207	abbreviated IDs, resolves all of them and returns a resolved node
…		…
167		239
168	Due to some quirks in how perl exports variables, it is impossible to	240	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	241	just export C<$SELF>, all the symbols called C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	242	module, but only C<$SELF> is currently used.
171		243
172	=item snd $portid, type => @data	244	=item snd $port, type => @data
173		245
174	=item snd $portid, @msg	246	=item snd $port, @msg
175		247
176	Send the given message to the given port ID, which can identify either	248	Send the given message to the given port ID, which can identify either
177	a local or a remote port, and can be either a string or soemthignt hat	249	a local or a remote port, and can be either a string or soemthignt hat
178	stringifies a sa port ID (such as a port object :).	250	stringifies a sa port ID (such as a port object :).
179		251
…		…
195		267
196	Create a new local port object that can be used either as a pattern	268	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"),	269	matching port ("full port") or a single-callback port ("miniport"),
198	depending on how C<rcv> callbacks are bound to the object.	270	depending on how C<rcv> callbacks are bound to the object.
199		271
200	=item $portid = port { my @msg = @_; $finished }	272	=item $port = port { my @msg = @_; $finished }
201		273
202	Creates a "mini port", that is, a very lightweight port without any	274	Creates a "miniport", that is, a very lightweight port without any pattern
203	pattern matching behind it, and returns its ID.	275	matching behind it, and returns its ID. Semantically the same as creating
		276	a port and calling C<rcv $port, $callback> on it.
204		277
205	The block will be called for every message received on the port. When the	278	The block will be called for every message received on the port. When the
206	callback returns a true value its job is considered "done" and the port	279	callback returns a true value its job is considered "done" and the port
207	will be destroyed. Otherwise it will stay alive.	280	will be destroyed. Otherwise it will stay alive.
208		281
…		…
215	snd $otherport, reply => $port;	288	snd $otherport, reply => $port;
216	};	289	};
217		290
218	=cut	291	=cut
219		292
		293	sub rcv($@);
		294
220	sub port(;&) {	295	sub port(;&) {
221	my $id = "$UNIQ." . $ID++;	296	my $id = "$UNIQ." . $ID++;
222	my $port = "$NODE#$id";	297	my $port = "$NODE#$id";
223		298
224	if (@_) {	299	if (@_) {
		300	rcv $port, shift;
		301	} else {
		302	$PORT{$id} = sub { }; # nop
		303	}
		304
		305	$port
		306	}
		307
		308	=item reg $port, $name
		309
		310	=item reg $name
		311
		312	Registers the given port (or C<$SELF><<< if missing) under the name
		313	C<$name>. If the name already exists it is replaced.
		314
		315	A port can only be registered under one well known name.
		316
		317	A port automatically becomes unregistered when it is killed.
		318
		319	=cut
		320
		321	sub reg(@) {
		322	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
		323
		324	$REG{$_[0]} = $port;
		325	}
		326
		327	=item rcv $port, $callback->(@msg)
		328
		329	Replaces the callback on the specified miniport (after converting it to
		330	one if required).
		331
		332	=item rcv $port, tagstring => $callback->(@msg), ...
		333
		334	=item rcv $port, $smartmatch => $callback->(@msg), ...
		335
		336	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
		337
		338	Register callbacks to be called on matching messages on the given full
		339	port (after converting it to one if required) and return the port.
		340
		341	The callback has to return a true value when its work is done, after
		342	which is will be removed, or a false value in which case it will stay
		343	registered.
		344
		345	The global C<$SELF> (exported by this module) contains C<$port> while
		346	executing the callback.
		347
		348	Runtime errors wdurign callback execution will result in the port being
		349	C<kil>ed.
		350
		351	If the match is an array reference, then it will be matched against the
		352	first elements of the message, otherwise only the first element is being
		353	matched.
		354
		355	Any element in the match that is specified as C<_any_> (a function
		356	exported by this module) matches any single element of the message.
		357
		358	While not required, it is highly recommended that the first matching
		359	element is a string identifying the message. The one-string-only match is
		360	also the most efficient match (by far).
		361
		362	Example: create a port and bind receivers on it in one go.
		363
		364	my $port = rcv port,
		365	msg1 => sub { ...; 0 },
		366	msg2 => sub { ...; 0 },
		367	;
		368
		369	Example: create a port, bind receivers and send it in a message elsewhere
		370	in one go:
		371
		372	snd $otherport, reply =>
		373	rcv port,
		374	msg1 => sub { ...; 0 },
		375	...
		376	;
		377
		378	=cut
		379
		380	sub rcv($@) {
		381	my $port = shift;
		382	my ($noderef, $portid) = split /#/, $port, 2;
		383
		384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
		385	or Carp::croak "$port: rcv can only be called on local ports, caught";
		386
		387	if (@_ == 1) {
225	my $cb = shift;	388	my $cb = shift;
		389	delete $PORT_DATA{$portid};
226	$PORT{$id} = sub {	390	$PORT{$portid} = sub {
227	local $SELF = $port;	391	local $SELF = $port;
228	eval {	392	eval {
229	&$cb	393	&$cb
230	and kil $id;	394	and kil $port;
231	};	395	};
232	_self_die if $@;	396	_self_die if $@;
233	};	397	};
234	} else {	398	} else {
		399	my $self = $PORT_DATA{$portid} \|\|= do {
235	my $self = bless {	400	my $self = bless {
236	id => "$NODE#$id",	401	id => $port,
237	}, "AnyEvent::MP::Port";	402	}, "AnyEvent::MP::Port";
238		403
239	$PORT_DATA{$id} = $self;
240	$PORT{$id} = sub {	404	$PORT{$portid} = sub {
241	local $SELF = $port;	405	local $SELF = $port;
242		406
243	eval {	407	eval {
244	for (@{ $self->{rc0}{$_[0]} }) {	408	for (@{ $self->{rc0}{$_[0]} }) {
245	$_ && &{$_->[0]}	409	$_ && &{$_->[0]}
246	&& undef $_;	410	&& undef $_;
247	}	411	}
248		412
249	for (@{ $self->{rcv}{$_[0]} }) {	413	for (@{ $self->{rcv}{$_[0]} }) {
250	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	414	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
251	&& &{$_->[0]}	415	&& &{$_->[0]}
252	&& undef $_;	416	&& undef $_;
253	}	417	}
254		418
255	for (@{ $self->{any} }) {	419	for (@{ $self->{any} }) {
256	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	420	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
257	&& &{$_->[0]}	421	&& &{$_->[0]}
258	&& undef $_;	422	&& undef $_;
		423	}
259	}	424	};
		425	_self_die if $@;
260	};	426	};
261	_self_die if $@;	427
		428	$self
262	};	429	};
263	}
264		430
265	$port
266	}
267
268	=item reg $portid, $name
269
270	Registers the given port under the name C<$name>. If the name already
271	exists it is replaced.
272
273	A port can only be registered under one well known name.
274
275	A port automatically becomes unregistered when it is killed.
276
277	=cut
278
279	sub reg(@) {
280	my ($portid, $name) = @_;
281
282	$REG{$name} = $portid;
283	}
284
285	=item rcv $portid, $callback->(@msg)
286
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:
289
290	=item rcv $portid, tagstring => $callback->(@msg), ...
291
292	=item rcv $portid, $smartmatch => $callback->(@msg), ...
293
294	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
295
296	Register callbacks to be called on matching messages on the given full
297	port (or newly created port).
298
299	The callback has to return a true value when its work is done, after
300	which is will be removed, or a false value in which case it will stay
301	registered.
302
303	The global C<$SELF> (exported by this module) contains C<$portid> while
304	executing the callback.
305
306	Runtime errors wdurign callback execution will result in the port being
307	C<kil>ed.
308
309	If the match is an array reference, then it will be matched against the
310	first elements of the message, otherwise only the first element is being
311	matched.
312
313	Any element in the match that is specified as C<_any_> (a function
314	exported by this module) matches any single element of the message.
315
316	While not required, it is highly recommended that the first matching
317	element is a string identifying the message. The one-string-only match is
318	also the most efficient match (by far).
319
320	=cut
321
322	sub rcv($@) {
323	my $portid = shift;
324	my ($noderef, $port) = split /#/, $port, 2;
325
326	($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	431	"AnyEvent::MP::Port" eq ref $self
333	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";	432	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
334		433
335	while (@_) {	434	while (@_) {
336	my ($match, $cb) = splice @_, 0, 2;	435	my ($match, $cb) = splice @_, 0, 2;
337		436
338	if (!ref $match) {	437	if (!ref $match) {
339	push @{ $self->{rc0}{$match} }, [$cb];	438	push @{ $self->{rc0}{$match} }, [$cb];
340	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	439	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
341	my ($type, @match) = @$match;	440	my ($type, @match) = @$match;
342	@match	441	@match
343	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	442	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
344	: push @{ $self->{rc0}{$match->[0]} }, [$cb];	443	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
345	} else {	444	} else {
346	push @{ $self->{any} }, [$cb, $match];	445	push @{ $self->{any} }, [$cb, $match];
		446	}
347	}	447	}
348	}	448	}
349		449
350	$portid	450	$port
351	}	451	}
352		452
353	=item $closure = psub { BLOCK }	453	=item $closure = psub { BLOCK }
354		454
355	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	455	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
386	$res	486	$res
387	}	487	}
388	}	488	}
389	}	489	}
390		490
391	=item $guard = mon $portid, $cb->(@reason)	491	=item $guard = mon $port, $cb->(@reason)
392		492
393	=item $guard = mon $portid, $otherport	493	=item $guard = mon $port, $rcvport
394		494
		495	=item $guard = mon $port
		496
395	=item $guard = mon $portid, $otherport, @msg	497	=item $guard = mon $port, $rcvport, @msg
396		498
397	Monitor the given port and do something when the port is killed.	499	Monitor the given port and do something when the port is killed, and
		500	optionally return a guard that can be used to stop monitoring again.
398		501
399	In the first form, the callback is simply called with any number	502	In the first form (callback), the callback is simply called with any
400	of C<@reason> elements (no @reason means that the port was deleted	503	number of C<@reason> elements (no @reason means that the port was deleted
401	"normally"). Note also that I<< the callback B<must> never die >>, so use	504	"normally"). Note also that I<< the callback B<must> never die >>, so use
402	C<eval> if unsure.	505	C<eval> if unsure.
403		506
404	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	507	In the second form (another port given), the other port (C<$rcvport)
405	a @reason was specified, i.e. on "normal" kils nothing happens, while	508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
406	under all other conditions, the other port is killed with the same reason.	509	"normal" kils nothing happens, while under all other conditions, the other
		510	port is killed with the same reason.
407		511
		512	The third form (kill self) is the same as the second form, except that
		513	C<$rvport> defaults to C<$SELF>.
		514
408	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	515	In the last form (message), a message of the form C<@msg, @reason> will be
		516	C<snd>.
409		517
410	Example: call a given callback when C<$port> is killed.	518	Example: call a given callback when C<$port> is killed.
411		519
412	mon $port, sub { warn "port died because of <@_>\n" };	520	mon $port, sub { warn "port died because of <@_>\n" };
413		521
414	Example: kill ourselves when C<$port> is killed abnormally.	522	Example: kill ourselves when C<$port> is killed abnormally.
415		523
416	mon $port, $self;	524	mon $port;
417		525
418	Example: send us a restart message another C<$port> is killed.	526	Example: send us a restart message when another C<$port> is killed.
419		527
420	mon $port, $self => "restart";	528	mon $port, $self => "restart";
421		529
422	=cut	530	=cut
423		531
424	sub mon {	532	sub mon {
425	my ($noderef, $port) = split /#/, shift, 2;	533	my ($noderef, $port) = split /#/, shift, 2;
426		534
427	my $node = $NODE{$noderef} \|\| add_node $noderef;	535	my $node = $NODE{$noderef} \|\| add_node $noderef;
428		536
429	my $cb = shift;	537	my $cb = @_ ? $_[0] : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
430		538
431	unless (ref $cb) {	539	unless (ref $cb) {
432	if (@_) {	540	if (@_) {
433	# send a kill info message	541	# send a kill info message
434	my (@msg) = ($cb, @_);	542	my (@msg) = @_;
435	$cb = sub { snd @msg, @_ };	543	$cb = sub { snd @msg, @_ };
436	} else {	544	} else {
437	# simply kill other port	545	# simply kill other port
438	my $port = $cb;	546	my $port = $cb;
439	$cb = sub { kil $port, @_ if @_ };	547	$cb = sub { kil $port, @_ if @_ };
…		…
465	=cut	573	=cut
466		574
467	sub mon_guard {	575	sub mon_guard {
468	my ($port, @refs) = @_;	576	my ($port, @refs) = @_;
469		577
		578	#TODO: mon-less form?
		579
470	mon $port, sub { 0 && @refs }	580	mon $port, sub { 0 && @refs }
471	}	581	}
472		582
473	=item lnk $port1, $port2	583	=item lnk $port1, $port2
474		584
		585	=item lnk $otherport
		586
475	Link two ports. This is simply a shorthand for:	587	Link two ports. This is simply a shorthand for:
476		588
477	mon $port1, $port2;	589	mon $port1, $port2;
478	mon $port2, $port1;	590	mon $port2, $port1;
479		591
480	It means that if either one is killed abnormally, the other one gets	592	It means that if either one is killed abnormally, the other one gets
481	killed as well.	593	killed as well.
482		594
		595	The one-argument form assumes that one port is C<$SELF>.
		596
		597	=cut
		598
		599	sub lnk {
		600	my $port1 = shift;
		601	my $port2 = @_ ? shift : $SELF \|\| Carp::croak 'lnk: called with one argument only, but $SELF not set,';
		602
		603	mon $port1, $port2;
		604	mon $port2, $port1;
		605	}
		606
483	=item kil $portid[, @reason]	607	=item kil $port[, @reason]
484		608
485	Kill the specified port with the given C<@reason>.	609	Kill the specified port with the given C<@reason>.
486		610
487	If no C<@reason> is specified, then the port is killed "normally" (linked	611	If no C<@reason> is specified, then the port is killed "normally" (linked
488	ports will not be kileld, or even notified).	612	ports will not be kileld, or even notified).
…		…
493	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	617	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
494	will be reported as reason C<< die => $@ >>.	618	will be reported as reason C<< die => $@ >>.
495		619
496	Transport/communication errors are reported as C<< transport_error =>	620	Transport/communication errors are reported as C<< transport_error =>
497	$message >>.	621	$message >>.
498
499	=back
500
501	=head1 FUNCTIONS FOR NODES
502
503	=over 4
504
505	=item become_public $noderef
506
507	Tells the node to become a public node, i.e. reachable from other nodes.
508
509	The first argument is the (unresolved) node reference of the local node
510	(if missing then the empty string is used).
511
512	It is quite common to not specify anything, in which case the local node
513	tries to listen on the default port, or to only specify a port number, in
514	which case AnyEvent::MP tries to guess the local addresses.
515
516	=cut
517		622
518	=back	623	=back
519		624
520	=head1 NODE MESSAGES	625	=head1 NODE MESSAGES
521		626
…		…
563		668
564	=back	669	=back
565		670
566	=head1 AnyEvent::MP vs. Distributed Erlang	671	=head1 AnyEvent::MP vs. Distributed Erlang
567		672
568	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	673	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	674	== 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	675	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
571	sample:	676	sample:
572		677
573	http://www.erlang.se/doc/programming_rules.shtml	678	http://www.Erlang.se/doc/programming_rules.shtml
574	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	679	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	680	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	681	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
577		682
578	Despite the similarities, there are also some important differences:	683	Despite the similarities, there are also some important differences:
579		684
580	=over 4	685	=over 4
581		686
…		…
592		697
593	Erlang uses processes that selctively receive messages, and therefore	698	Erlang uses processes that selctively receive messages, and therefore
594	needs a queue. AEMP is event based, queuing messages would serve no useful	699	needs a queue. AEMP is event based, queuing messages would serve no useful
595	purpose.	700	purpose.
596		701
597	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	702	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
598		703
599	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	704	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
600		705
601	Sending messages in erlang is synchronous and blocks the process. AEMP	706	Sending messages in Erlang is synchronous and blocks the process. AEMP
602	sends are immediate, connection establishment is handled in the	707	sends are immediate, connection establishment is handled in the
603	background.	708	background.
604		709
605	=item * Erlang can silently lose messages, AEMP cannot.	710	=item * Erlang can silently lose messages, AEMP cannot.
606		711
…		…
609	and c, and the other side only receives messages a and c).	714	and c, and the other side only receives messages a and c).
610		715
611	AEMP guarantees correct ordering, and the guarantee that there are no	716	AEMP guarantees correct ordering, and the guarantee that there are no
612	holes in the message sequence.	717	holes in the message sequence.
613		718
614	=item * In erlang, processes can be declared dead and later be found to be	719	=item * In Erlang, processes can be declared dead and later be found to be
615	alive.	720	alive.
616		721
617	In erlang it can happen that a monitored process is declared dead and	722	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	723	linked processes get killed, but later it turns out that the process is
619	still alive - and can receive messages.	724	still alive - and can receive messages.
620		725
621	In AEMP, when port monitoring detects a port as dead, then that port will	726	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	727	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.	728	and then later sends messages to it, finding it is still alive.
624		729
625	=item * Erlang can send messages to the wrong port, AEMP does not.	730	=item * Erlang can send messages to the wrong port, AEMP does not.
626		731
627	In erlang it is quite possible that a node that restarts reuses a process	732	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	733	ID known to other nodes for a completely different process, causing
629	messages destined for that process to end up in an unrelated process.	734	messages destined for that process to end up in an unrelated process.
630		735
631	AEMP never reuses port IDs, so old messages or old port IDs floating	736	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.	737	around in the network will not be sent to an unrelated port.
…		…
638	securely authenticate nodes.	743	securely authenticate nodes.
639		744
640	=item * The AEMP protocol is optimised for both text-based and binary	745	=item * The AEMP protocol is optimised for both text-based and binary
641	communications.	746	communications.
642		747
643	The AEMP protocol, unlike the erlang protocol, supports both	748	The AEMP protocol, unlike the Erlang protocol, supports both
644	language-independent text-only protocols (good for debugging) and binary,	749	language-independent text-only protocols (good for debugging) and binary,
645	language-specific serialisers (e.g. Storable).	750	language-specific serialisers (e.g. Storable).
646		751
647	It has also been carefully designed to be implementable in other languages	752	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	753	with a minimum of work while gracefully degrading fucntionality to make the
649	protocol simple.	754	protocol simple.
650		755
		756	=item * AEMP has more flexible monitoring options than Erlang.
		757
		758	In Erlang, you can chose to receive I<all> exit signals as messages
		759	or I<none>, there is no in-between, so monitoring single processes is
		760	difficult to implement. Monitoring in AEMP is more flexible than in
		761	Erlang, as one can choose between automatic kill, exit message or callback
		762	on a per-process basis.
		763
		764	=item * Erlang has different semantics for monitoring and linking, AEMP has the same.
		765
		766	Monitoring in Erlang is not an indicator of process death/crashes,
		767	as linking is (except linking is unreliable in Erlang). In AEMP, the
		768	semantics of monitoring and linking are identical, linking is simply
		769	two-way monitoring with automatic kill.
		770
651	=back	771	=back
652		772
653	=head1 SEE ALSO	773	=head1 SEE ALSO
654		774
655	L<AnyEvent>.	775	L<AnyEvent>.

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Revision 1.36 by root, Thu Aug 6 10:46:48 2009 UTC