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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.31 by root, Wed Aug 5 19:55:58 2009 UTC vs.
Revision 1.37 by root, Fri Aug 7 16:47:23 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	# monitoring
		29	mon $port, $cb->(@msg) # callback is invoked on death
		30	mon $port, $otherport # kill otherport on abnormal death
		31	mon $port, $otherport, @msg # send message on death
27		32
28	=head1 DESCRIPTION	33	=head1 DESCRIPTION
29		34
30	This module (-family) implements a simple message passing framework.	35	This module (-family) implements a simple message passing framework.
31		36
…		…
123	The C<NODE> function returns, and the C<$NODE> variable contains	128	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	129	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	130	to C<become_public> or C<become_slave>, after which all local port
126	identifiers become invalid.	131	identifiers become invalid.
127		132
128	=item $noderef = node_of $portid	133	=item $noderef = node_of $port
129		134
130	Extracts and returns the noderef from a portid or a noderef.	135	Extracts and returns the noderef from a portid or a noderef.
		136
		137	=item initialise_node $noderef, $seednode, $seednode...
		138
		139	=item initialise_node "slave/", $master, $master...
		140
		141	Before a node can talk to other nodes on the network it has to initialise
		142	itself - the minimum a node needs to know is it's own name, and optionally
		143	it should know the noderefs of some other nodes in the network.
		144
		145	This function initialises a node - it must be called exactly once (or
		146	never) before calling other AnyEvent::MP functions.
		147
		148	All arguments are noderefs, which can be either resolved or unresolved.
		149
		150	There are two types of networked nodes, public nodes and slave nodes:
		151
		152	=over 4
		153
		154	=item public nodes
		155
		156	For public nodes, C<$noderef> must either be a (possibly unresolved)
		157	noderef, in which case it will be resolved, or C<undef> (or missing), in
		158	which case the noderef will be guessed.
		159
		160	Afterwards, the node will bind itself on all endpoints and try to connect
		161	to all additional C<$seednodes> that are specified. Seednodes are optional
		162	and can be used to quickly bootstrap the node into an existing network.
		163
		164	=item slave nodes
		165
		166	When the C<$noderef> is the special string C<slave/>, then the node will
		167	become a slave node. Slave nodes cannot be contacted from outside and will
		168	route most of their traffic to the master node that they attach to.
		169
		170	At least one additional noderef is required: The node will try to connect
		171	to all of them and will become a slave attached to the first node it can
		172	successfully connect to.
		173
		174	=back
		175
		176	This function will block until all nodes have been resolved and, for slave
		177	nodes, until it has successfully established a connection to a master
		178	server.
		179
		180	Example: become a public node listening on the default node.
		181
		182	initialise_node;
		183
		184	Example: become a public node, and try to contact some well-known master
		185	servers to become part of the network.
		186
		187	initialise_node undef, "master1", "master2";
		188
		189	Example: become a public node listening on port C<4041>.
		190
		191	initialise_node 4041;
		192
		193	Example: become a public node, only visible on localhost port 4044.
		194
		195	initialise_node "locahost:4044";
		196
		197	Example: become a slave node to any of the specified master servers.
		198
		199	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
131		200
132	=item $cv = resolve_node $noderef	201	=item $cv = resolve_node $noderef
133		202
134	Takes an unresolved node reference that may contain hostnames and	203	Takes an unresolved node reference that may contain hostnames and
135	abbreviated IDs, resolves all of them and returns a resolved node	204	abbreviated IDs, resolves all of them and returns a resolved node
…		…
167		236
168	Due to some quirks in how perl exports variables, it is impossible to	237	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	238	just export C<$SELF>, all the symbols called C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	239	module, but only C<$SELF> is currently used.
171		240
172	=item snd $portid, type => @data	241	=item snd $port, type => @data
173		242
174	=item snd $portid, @msg	243	=item snd $port, @msg
175		244
176	Send the given message to the given port ID, which can identify either	245	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	246	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 :).	247	stringifies a sa port ID (such as a port object :).
179		248
…		…
189	JSON is used, then only strings, numbers and arrays and hashes consisting	258	JSON is used, then only strings, numbers and arrays and hashes consisting
190	of those are allowed (no objects). When Storable is used, then anything	259	of those are allowed (no objects). When Storable is used, then anything
191	that Storable can serialise and deserialise is allowed, and for the local	260	that Storable can serialise and deserialise is allowed, and for the local
192	node, anything can be passed.	261	node, anything can be passed.
193		262
194	=item kil $portid[, @reason]
195
196	Kill the specified port with the given C<@reason>.
197
198	If no C<@reason> is specified, then the port is killed "normally" (linked
199	ports will not be kileld, or even notified).
200
201	Otherwise, linked ports get killed with the same reason (second form of
202	C<mon>, see below).
203
204	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
205	will be reported as reason C<< die => $@ >>.
206
207	Transport/communication errors are reported as C<< transport_error =>
208	$message >>.
209
210	=item $guard = mon $portid, $cb->(@reason)
211
212	=item $guard = mon $portid, $otherport
213
214	=item $guard = mon $portid, $otherport, @msg
215
216	Monitor the given port and do something when the port is killed.
217
218	In the first form, the callback is simply called with any number
219	of C<@reason> elements (no @reason means that the port was deleted
220	"normally"). Note also that I<< the callback B<must> never die >>, so use
221	C<eval> if unsure.
222
223	In the second form, the other port will be C<kil>'ed with C<@reason>, iff
224	a @reason was specified, i.e. on "normal" kils nothing happens, while
225	under all other conditions, the other port is killed with the same reason.
226
227	In the last form, a message of the form C<@msg, @reason> will be C<snd>.
228
229	Example: call a given callback when C<$port> is killed.
230
231	mon $port, sub { warn "port died because of <@_>\n" };
232
233	Example: kill ourselves when C<$port> is killed abnormally.
234
235	mon $port, $self;
236
237	Example: send us a restart message another C<$port> is killed.
238
239	mon $port, $self => "restart";
240
241	=cut
242
243	sub mon {
244	my ($noderef, $port) = split /#/, shift, 2;
245
246	my $node = $NODE{$noderef} \|\| add_node $noderef;
247
248	my $cb = shift;
249
250	unless (ref $cb) {
251	if (@_) {
252	# send a kill info message
253	my (@msg) = ($cb, @_);
254	$cb = sub { snd @msg, @_ };
255	} else {
256	# simply kill other port
257	my $port = $cb;
258	$cb = sub { kil $port, @_ if @_ };
259	}
260	}
261
262	$node->monitor ($port, $cb);
263
264	defined wantarray
265	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
266	}
267
268	=item $guard = mon_guard $port, $ref, $ref...
269
270	Monitors the given C<$port> and keeps the passed references. When the port
271	is killed, the references will be freed.
272
273	Optionally returns a guard that will stop the monitoring.
274
275	This function is useful when you create e.g. timers or other watchers and
276	want to free them when the port gets killed:
277
278	$port->rcv (start => sub {
279	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
280	undef $timer if 0.9 < rand;
281	});
282	});
283
284	=cut
285
286	sub mon_guard {
287	my ($port, @refs) = @_;
288
289	mon $port, sub { 0 && @refs }
290	}
291
292	=item lnk $port1, $port2
293
294	Link two ports. This is simply a shorthand for:
295
296	mon $port1, $port2;
297	mon $port2, $port1;
298
299	It means that if either one is killed abnormally, the other one gets
300	killed as well.
301
302	=item $local_port = port	263	=item $local_port = port
303		264
304	Create a new local port object that can be used either as a pattern	265	Create a new local port object that can be used either as a pattern
305	matching port ("full port") or a single-callback port ("miniport"),	266	matching port ("full port") or a single-callback port ("miniport"),
306	depending on how C<rcv> callbacks are bound to the object.	267	depending on how C<rcv> callbacks are bound to the object.
307		268
308	=item $portid = port { my @msg = @_; $finished }	269	=item $port = port { my @msg = @_; $finished }
309		270
310	Creates a "mini port", that is, a very lightweight port without any	271	Creates a "miniport", that is, a very lightweight port without any pattern
311	pattern matching behind it, and returns its ID.	272	matching behind it, and returns its ID. Semantically the same as creating
		273	a port and calling C<rcv $port, $callback> on it.
312		274
313	The block will be called for every message received on the port. When the	275	The block will be called for every message received on the port. When the
314	callback returns a true value its job is considered "done" and the port	276	callback returns a true value its job is considered "done" and the port
315	will be destroyed. Otherwise it will stay alive.	277	will be destroyed. Otherwise it will stay alive.
316		278
…		…
323	snd $otherport, reply => $port;	285	snd $otherport, reply => $port;
324	};	286	};
325		287
326	=cut	288	=cut
327		289
		290	sub rcv($@);
		291
328	sub port(;&) {	292	sub port(;&) {
329	my $id = "$UNIQ." . $ID++;	293	my $id = "$UNIQ." . $ID++;
330	my $port = "$NODE#$id";	294	my $port = "$NODE#$id";
331		295
332	if (@_) {	296	if (@_) {
		297	rcv $port, shift;
		298	} else {
		299	$PORT{$id} = sub { }; # nop
		300	}
		301
		302	$port
		303	}
		304
		305	=item reg $port, $name
		306
		307	=item reg $name
		308
		309	Registers the given port (or C<$SELF><<< if missing) under the name
		310	C<$name>. If the name already exists it is replaced.
		311
		312	A port can only be registered under one well known name.
		313
		314	A port automatically becomes unregistered when it is killed.
		315
		316	=cut
		317
		318	sub reg(@) {
		319	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
		320
		321	$REG{$_[0]} = $port;
		322	}
		323
		324	=item rcv $port, $callback->(@msg)
		325
		326	Replaces the callback on the specified miniport (after converting it to
		327	one if required).
		328
		329	=item rcv $port, tagstring => $callback->(@msg), ...
		330
		331	=item rcv $port, $smartmatch => $callback->(@msg), ...
		332
		333	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
		334
		335	Register callbacks to be called on matching messages on the given full
		336	port (after converting it to one if required) and return the port.
		337
		338	The callback has to return a true value when its work is done, after
		339	which is will be removed, or a false value in which case it will stay
		340	registered.
		341
		342	The global C<$SELF> (exported by this module) contains C<$port> while
		343	executing the callback.
		344
		345	Runtime errors wdurign callback execution will result in the port being
		346	C<kil>ed.
		347
		348	If the match is an array reference, then it will be matched against the
		349	first elements of the message, otherwise only the first element is being
		350	matched.
		351
		352	Any element in the match that is specified as C<_any_> (a function
		353	exported by this module) matches any single element of the message.
		354
		355	While not required, it is highly recommended that the first matching
		356	element is a string identifying the message. The one-string-only match is
		357	also the most efficient match (by far).
		358
		359	Example: create a port and bind receivers on it in one go.
		360
		361	my $port = rcv port,
		362	msg1 => sub { ...; 0 },
		363	msg2 => sub { ...; 0 },
		364	;
		365
		366	Example: create a port, bind receivers and send it in a message elsewhere
		367	in one go:
		368
		369	snd $otherport, reply =>
		370	rcv port,
		371	msg1 => sub { ...; 0 },
		372	...
		373	;
		374
		375	=cut
		376
		377	sub rcv($@) {
		378	my $port = shift;
		379	my ($noderef, $portid) = split /#/, $port, 2;
		380
		381	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
		382	or Carp::croak "$port: rcv can only be called on local ports, caught";
		383
		384	if (@_ == 1) {
333	my $cb = shift;	385	my $cb = shift;
		386	delete $PORT_DATA{$portid};
334	$PORT{$id} = sub {	387	$PORT{$portid} = sub {
335	local $SELF = $port;	388	local $SELF = $port;
336	eval {	389	eval {
337	&$cb	390	&$cb
338	and kil $id;	391	and kil $port;
339	};	392	};
340	_self_die if $@;	393	_self_die if $@;
341	};	394	};
342	} else {	395	} else {
		396	my $self = $PORT_DATA{$portid} \|\|= do {
343	my $self = bless {	397	my $self = bless {
344	id => "$NODE#$id",	398	id => $port,
345	}, "AnyEvent::MP::Port";	399	}, "AnyEvent::MP::Port";
346		400
347	$PORT_DATA{$id} = $self;
348	$PORT{$id} = sub {	401	$PORT{$portid} = sub {
349	local $SELF = $port;	402	local $SELF = $port;
350		403
351	eval {	404	eval {
352	for (@{ $self->{rc0}{$_[0]} }) {	405	for (@{ $self->{rc0}{$_[0]} }) {
353	$_ && &{$_->[0]}	406	$_ && &{$_->[0]}
354	&& undef $_;	407	&& undef $_;
355	}	408	}
356		409
357	for (@{ $self->{rcv}{$_[0]} }) {	410	for (@{ $self->{rcv}{$_[0]} }) {
358	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	411	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
359	&& &{$_->[0]}	412	&& &{$_->[0]}
360	&& undef $_;	413	&& undef $_;
361	}	414	}
362		415
363	for (@{ $self->{any} }) {	416	for (@{ $self->{any} }) {
364	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	417	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
365	&& &{$_->[0]}	418	&& &{$_->[0]}
366	&& undef $_;	419	&& undef $_;
		420	}
367	}	421	};
		422	_self_die if $@;
368	};	423	};
369	_self_die if $@;	424
		425	$self
370	};	426	};
371	}
372		427
373	$port
374	}
375
376	=item reg $portid, $name
377
378	Registers the given port under the name C<$name>. If the name already
379	exists it is replaced.
380
381	A port can only be registered under one well known name.
382
383	A port automatically becomes unregistered when it is killed.
384
385	=cut
386
387	sub reg(@) {
388	my ($portid, $name) = @_;
389
390	$REG{$name} = $portid;
391	}
392
393	=item rcv $portid, $callback->(@msg)
394
395	Replaces the callback on the specified miniport (or newly created port
396	object, see C<port>). Full ports are configured with the following calls:
397
398	=item rcv $portid, tagstring => $callback->(@msg), ...
399
400	=item rcv $portid, $smartmatch => $callback->(@msg), ...
401
402	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
403
404	Register callbacks to be called on matching messages on the given port.
405
406	The callback has to return a true value when its work is done, after
407	which is will be removed, or a false value in which case it will stay
408	registered.
409
410	The global C<$SELF> (exported by this module) contains C<$portid> while
411	executing the callback.
412
413	Runtime errors wdurign callback execution will result in the port being
414	C<kil>ed.
415
416	If the match is an array reference, then it will be matched against the
417	first elements of the message, otherwise only the first element is being
418	matched.
419
420	Any element in the match that is specified as C<_any_> (a function
421	exported by this module) matches any single element of the message.
422
423	While not required, it is highly recommended that the first matching
424	element is a string identifying the message. The one-string-only match is
425	also the most efficient match (by far).
426
427	=cut
428
429	sub rcv($@) {
430	my $portid = shift;
431	my ($noderef, $port) = split /#/, $port, 2;
432
433	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
434	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
435
436	my $self = $PORT_DATA{$port}
437	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
438
439	"AnyEvent::MP::Port" eq ref $self	428	"AnyEvent::MP::Port" eq ref $self
440	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";	429	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
441		430
442	while (@_) {	431	while (@_) {
443	my ($match, $cb) = splice @_, 0, 2;	432	my ($match, $cb) = splice @_, 0, 2;
444		433
445	if (!ref $match) {	434	if (!ref $match) {
446	push @{ $self->{rc0}{$match} }, [$cb];	435	push @{ $self->{rc0}{$match} }, [$cb];
447	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	436	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
448	my ($type, @match) = @$match;	437	my ($type, @match) = @$match;
449	@match	438	@match
450	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	439	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
451	: push @{ $self->{rc0}{$match->[0]} }, [$cb];	440	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
452	} else {	441	} else {
453	push @{ $self->{any} }, [$cb, $match];	442	push @{ $self->{any} }, [$cb, $match];
		443	}
454	}	444	}
455	}	445	}
456		446
457	$portid	447	$port
458	}	448	}
459		449
460	=item $closure = psub { BLOCK }	450	=item $closure = psub { BLOCK }
461		451
462	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	452	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
493	$res	483	$res
494	}	484	}
495	}	485	}
496	}	486	}
497		487
498	=back	488	=item $guard = mon $port, $cb->(@reason)
499		489
500	=head1 FUNCTIONS FOR NODES	490	=item $guard = mon $port, $rcvport
501		491
502	=over 4	492	=item $guard = mon $port
503		493
504	=item become_public $noderef	494	=item $guard = mon $port, $rcvport, @msg
505		495
506	Tells the node to become a public node, i.e. reachable from other nodes.	496	Monitor the given port and do something when the port is killed, and
		497	optionally return a guard that can be used to stop monitoring again.
507		498
508	The first argument is the (unresolved) node reference of the local node	499	In the first form (callback), the callback is simply called with any
509	(if missing then the empty string is used).	500	number of C<@reason> elements (no @reason means that the port was deleted
		501	"normally"). Note also that I<< the callback B<must> never die >>, so use
		502	C<eval> if unsure.
510		503
511	It is quite common to not specify anything, in which case the local node	504	In the second form (another port given), the other port (C<$rcvport)
512	tries to listen on the default port, or to only specify a port number, in	505	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
513	which case AnyEvent::MP tries to guess the local addresses.	506	"normal" kils nothing happens, while under all other conditions, the other
		507	port is killed with the same reason.
514		508
		509	The third form (kill self) is the same as the second form, except that
		510	C<$rvport> defaults to C<$SELF>.
		511
		512	In the last form (message), a message of the form C<@msg, @reason> will be
		513	C<snd>.
		514
		515	As a rule of thumb, monitoring requests should always monitor a port from
		516	a local port (or callback). The reason is that kill messages might get
		517	lost, just like any other message. Another less obvious reason is that
		518	even monitoring requests can get lost (for exmaple, when the connection
		519	to the other node goes down permanently). When monitoring a port locally
		520	these problems do not exist.
		521
		522	Example: call a given callback when C<$port> is killed.
		523
		524	mon $port, sub { warn "port died because of <@_>\n" };
		525
		526	Example: kill ourselves when C<$port> is killed abnormally.
		527
		528	mon $port;
		529
		530	Example: send us a restart message when another C<$port> is killed.
		531
		532	mon $port, $self => "restart";
		533
515	=cut	534	=cut
		535
		536	sub mon {
		537	my ($noderef, $port) = split /#/, shift, 2;
		538
		539	my $node = $NODE{$noderef} \|\| add_node $noderef;
		540
		541	my $cb = @_ ? $_[0] : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
		542
		543	unless (ref $cb) {
		544	if (@_) {
		545	# send a kill info message
		546	my (@msg) = @_;
		547	$cb = sub { snd @msg, @_ };
		548	} else {
		549	# simply kill other port
		550	my $port = $cb;
		551	$cb = sub { kil $port, @_ if @_ };
		552	}
		553	}
		554
		555	$node->monitor ($port, $cb);
		556
		557	defined wantarray
		558	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }
		559	}
		560
		561	=item $guard = mon_guard $port, $ref, $ref...
		562
		563	Monitors the given C<$port> and keeps the passed references. When the port
		564	is killed, the references will be freed.
		565
		566	Optionally returns a guard that will stop the monitoring.
		567
		568	This function is useful when you create e.g. timers or other watchers and
		569	want to free them when the port gets killed:
		570
		571	$port->rcv (start => sub {
		572	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {
		573	undef $timer if 0.9 < rand;
		574	});
		575	});
		576
		577	=cut
		578
		579	sub mon_guard {
		580	my ($port, @refs) = @_;
		581
		582	#TODO: mon-less form?
		583
		584	mon $port, sub { 0 && @refs }
		585	}
		586
		587	=item kil $port[, @reason]
		588
		589	Kill the specified port with the given C<@reason>.
		590
		591	If no C<@reason> is specified, then the port is killed "normally" (linked
		592	ports will not be kileld, or even notified).
		593
		594	Otherwise, linked ports get killed with the same reason (second form of
		595	C<mon>, see below).
		596
		597	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
		598	will be reported as reason C<< die => $@ >>.
		599
		600	Transport/communication errors are reported as C<< transport_error =>
		601	$message >>.
516		602
517	=back	603	=back
518		604
519	=head1 NODE MESSAGES	605	=head1 NODE MESSAGES
520		606
…		…
562		648
563	=back	649	=back
564		650
565	=head1 AnyEvent::MP vs. Distributed Erlang	651	=head1 AnyEvent::MP vs. Distributed Erlang
566		652
567	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	653	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
568	== aemp node, erlang process == aemp port), so many of the documents and	654	== aemp node, Erlang process == aemp port), so many of the documents and
569	programming techniques employed by erlang apply to AnyEvent::MP. Here is a	655	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
570	sample:	656	sample:
571		657
572	http://www.erlang.se/doc/programming_rules.shtml	658	http://www.Erlang.se/doc/programming_rules.shtml
573	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	659	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
574	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6	660	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
575	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	661	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
576		662
577	Despite the similarities, there are also some important differences:	663	Despite the similarities, there are also some important differences:
578		664
579	=over 4	665	=over 4
580		666
…		…
591		677
592	Erlang uses processes that selctively receive messages, and therefore	678	Erlang uses processes that selctively receive messages, and therefore
593	needs a queue. AEMP is event based, queuing messages would serve no useful	679	needs a queue. AEMP is event based, queuing messages would serve no useful
594	purpose.	680	purpose.
595		681
596	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	682	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
597		683
598	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	684	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
599		685
600	Sending messages in erlang is synchronous and blocks the process. AEMP	686	Sending messages in Erlang is synchronous and blocks the process. AEMP
601	sends are immediate, connection establishment is handled in the	687	sends are immediate, connection establishment is handled in the
602	background.	688	background.
603		689
604	=item * Erlang can silently lose messages, AEMP cannot.	690	=item * Erlang can silently lose messages, AEMP cannot.
605		691
…		…
608	and c, and the other side only receives messages a and c).	694	and c, and the other side only receives messages a and c).
609		695
610	AEMP guarantees correct ordering, and the guarantee that there are no	696	AEMP guarantees correct ordering, and the guarantee that there are no
611	holes in the message sequence.	697	holes in the message sequence.
612		698
613	=item * In erlang, processes can be declared dead and later be found to be	699	=item * In Erlang, processes can be declared dead and later be found to be
614	alive.	700	alive.
615		701
616	In erlang it can happen that a monitored process is declared dead and	702	In Erlang it can happen that a monitored process is declared dead and
617	linked processes get killed, but later it turns out that the process is	703	linked processes get killed, but later it turns out that the process is
618	still alive - and can receive messages.	704	still alive - and can receive messages.
619		705
620	In AEMP, when port monitoring detects a port as dead, then that port will	706	In AEMP, when port monitoring detects a port as dead, then that port will
621	eventually be killed - it cannot happen that a node detects a port as dead	707	eventually be killed - it cannot happen that a node detects a port as dead
622	and then later sends messages to it, finding it is still alive.	708	and then later sends messages to it, finding it is still alive.
623		709
624	=item * Erlang can send messages to the wrong port, AEMP does not.	710	=item * Erlang can send messages to the wrong port, AEMP does not.
625		711
626	In erlang it is quite possible that a node that restarts reuses a process	712	In Erlang it is quite possible that a node that restarts reuses a process
627	ID known to other nodes for a completely different process, causing	713	ID known to other nodes for a completely different process, causing
628	messages destined for that process to end up in an unrelated process.	714	messages destined for that process to end up in an unrelated process.
629		715
630	AEMP never reuses port IDs, so old messages or old port IDs floating	716	AEMP never reuses port IDs, so old messages or old port IDs floating
631	around in the network will not be sent to an unrelated port.	717	around in the network will not be sent to an unrelated port.
…		…
637	securely authenticate nodes.	723	securely authenticate nodes.
638		724
639	=item * The AEMP protocol is optimised for both text-based and binary	725	=item * The AEMP protocol is optimised for both text-based and binary
640	communications.	726	communications.
641		727
642	The AEMP protocol, unlike the erlang protocol, supports both	728	The AEMP protocol, unlike the Erlang protocol, supports both
643	language-independent text-only protocols (good for debugging) and binary,	729	language-independent text-only protocols (good for debugging) and binary,
644	language-specific serialisers (e.g. Storable).	730	language-specific serialisers (e.g. Storable).
645		731
646	It has also been carefully designed to be implementable in other languages	732	It has also been carefully designed to be implementable in other languages
647	with a minimum of work while gracefully degrading fucntionality to make the	733	with a minimum of work while gracefully degrading fucntionality to make the
648	protocol simple.	734	protocol simple.
649		735
		736	=item * AEMP has more flexible monitoring options than Erlang.
		737
		738	In Erlang, you can chose to receive I<all> exit signals as messages
		739	or I<none>, there is no in-between, so monitoring single processes is
		740	difficult to implement. Monitoring in AEMP is more flexible than in
		741	Erlang, as one can choose between automatic kill, exit message or callback
		742	on a per-process basis.
		743
		744	=item * Erlang tries to hide remote/local connections, AEMP does not.
		745
		746	Monitoring in Erlang is not an indicator of process death/crashes,
		747	as linking is (except linking is unreliable in Erlang).
		748
		749	In AEMP, you don't "look up" registered port names or send to named ports
		750	that might or might not be persistent. Instead, you normally spawn a port
		751	on the remote node. The init function monitors the you, and you monitor
		752	the remote port. Since both monitors are local to the node, they are much
		753	more reliable.
		754
		755	This also saves round-trips and avoids sending messages to the wrong port
		756	(hard to do in Erlang).
		757
650	=back	758	=back
651		759
652	=head1 SEE ALSO	760	=head1 SEE ALSO
653		761
654	L<AnyEvent>.	762	L<AnyEvent>.

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Revision 1.37 by root, Fri Aug 7 16:47:23 2009 UTC