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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.29 by root, Tue Aug 4 23:16:57 2009 UTC vs.
Revision 1.37 by root, Fri Aug 7 16:47:23 2009 UTC

…		…
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		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
		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
32	Despite its simplicity, you can securely message other processes running	37	Despite its simplicity, you can securely message other processes running
…		…
53		58
54	=item port id - C<noderef#portname>	59	=item port id - C<noderef#portname>
55		60
56	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	61	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as
57	separator, and a port name (a printable string of unspecified format). An	62	separator, and a port name (a printable string of unspecified format). An
58	exception is the the node port, whose ID is identical to it's node	63	exception is the the node port, whose ID is identical to its node
59	reference.	64	reference.
60		65
61	=item node	66	=item node
62		67
63	A node is a single process containing at least one port - the node	68	A node is a single process containing at least one port - the node
…		…
103	use base "Exporter";	108	use base "Exporter";
104		109
105	our $VERSION = '0.1';	110	our $VERSION = '0.1';
106	our @EXPORT = qw(	111	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	112	NODE $NODE *SELF node_of _any_
108	resolve_node	113	resolve_node initialise_node
109	become_slave become_public
110	snd rcv mon kil reg psub	114	snd rcv mon kil reg psub
111	port	115	port
112	);	116	);
113		117
114	our $SELF;	118	our $SELF;
…		…
124	The C<NODE> function returns, and the C<$NODE> variable contains	128	The C<NODE> function returns, and the C<$NODE> variable contains
125	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
126	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
127	identifiers become invalid.	131	identifiers become invalid.
128		132
129	=item $noderef = node_of $portid	133	=item $noderef = node_of $port
130		134
131	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";
132		200
133	=item $cv = resolve_node $noderef	201	=item $cv = resolve_node $noderef
134		202
135	Takes an unresolved node reference that may contain hostnames and	203	Takes an unresolved node reference that may contain hostnames and
136	abbreviated IDs, resolves all of them and returns a resolved node	204	abbreviated IDs, resolves all of them and returns a resolved node
…		…
168		236
169	Due to some quirks in how perl exports variables, it is impossible to	237	Due to some quirks in how perl exports variables, it is impossible to
170	just export C<$SELF>, all the symbols called C<SELF> are exported by this	238	just export C<$SELF>, all the symbols called C<SELF> are exported by this
171	module, but only C<$SELF> is currently used.	239	module, but only C<$SELF> is currently used.
172		240
173	=item snd $portid, type => @data	241	=item snd $port, type => @data
174		242
175	=item snd $portid, @msg	243	=item snd $port, @msg
176		244
177	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
178	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
179	stringifies a sa port ID (such as a port object :).	247	stringifies a sa port ID (such as a port object :).
180		248
…		…
190	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
191	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
192	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
193	node, anything can be passed.	261	node, anything can be passed.
194		262
195	=item kil $portid[, @reason]
196
197	Kill the specified port with the given C<@reason>.
198
199	If no C<@reason> is specified, then the port is killed "normally" (linked
200	ports will not be kileld, or even notified).
201
202	Otherwise, linked ports get killed with the same reason (second form of
203	C<mon>, see below).
204
205	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
206	will be reported as reason C<< die => $@ >>.
207
208	Transport/communication errors are reported as C<< transport_error =>
209	$message >>.
210
211	=item $guard = mon $portid, $cb->(@reason)
212
213	=item $guard = mon $portid, $otherport
214
215	=item $guard = mon $portid, $otherport, @msg
216
217	Monitor the given port and do something when the port is killed.
218
219	In the first form, the callback is simply called with any number
220	of C<@reason> elements (no @reason means that the port was deleted
221	"normally"). Note also that I<< the callback B<must> never die >>, so use
222	C<eval> if unsure.
223
224	In the second form, the other port will be C<kil>'ed with C<@reason>, iff
225	a @reason was specified, i.e. on "normal" kils nothing happens, while
226	under all other conditions, the other port is killed with the same reason.
227
228	In the last form, a message of the form C<@msg, @reason> will be C<snd>.
229
230	Example: call a given callback when C<$port> is killed.
231
232	mon $port, sub { warn "port died because of <@_>\n" };
233
234	Example: kill ourselves when C<$port> is killed abnormally.
235
236	mon $port, $self;
237
238	Example: send us a restart message another C<$port> is killed.
239
240	mon $port, $self => "restart";
241
242	=cut
243
244	sub mon {
245	my ($noderef, $port, $cb) = ((split /#/, shift, 2), shift);
246
247	my $node = $NODE{$noderef} \|\| add_node $noderef;
248
249	#TODO: ports must not be references
250	if (!ref $cb or "AnyEvent::MP::Port" eq 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 supports message matching.	265	Create a new local port object that can be used either as a pattern
		266	matching port ("full port") or a single-callback port ("miniport"),
		267	depending on how C<rcv> callbacks are bound to the object.
305		268
306	=item $portid = port { my @msg = @_; $finished }	269	=item $port = port { my @msg = @_; $finished }
307		270
308	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
309	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.
310		274
311	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
312	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
313	will be destroyed. Otherwise it will stay alive.	277	will be destroyed. Otherwise it will stay alive.
314		278
315	The message will be passed as-is, no extra argument (i.e. no port id) will	279	The message will be passed as-is, no extra argument (i.e. no port id) will
316	be passed to the callback.	280	be passed to the callback.
317		281
318	If you need the local port id in the callback, this works nicely:	282	If you need the local port id in the callback, this works nicely:
319		283
320	my $port; $port = miniport {	284	my $port; $port = port {
321	snd $otherport, reply => $port;	285	snd $otherport, reply => $port;
322	};	286	};
323		287
324	=cut	288	=cut
		289
		290	sub rcv($@);
325		291
326	sub port(;&) {	292	sub port(;&) {
327	my $id = "$UNIQ." . $ID++;	293	my $id = "$UNIQ." . $ID++;
328	my $port = "$NODE#$id";	294	my $port = "$NODE#$id";
329		295
330	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) {
331	my $cb = shift;	385	my $cb = shift;
		386	delete $PORT_DATA{$portid};
332	$PORT{$id} = sub {	387	$PORT{$portid} = sub {
333	local $SELF = $port;	388	local $SELF = $port;
334	eval {	389	eval {
335	&$cb	390	&$cb
336	and kil $id;	391	and kil $port;
337	};	392	};
338	_self_die if $@;	393	_self_die if $@;
339	};	394	};
340	} else {	395	} else {
		396	my $self = $PORT_DATA{$portid} \|\|= do {
341	my $self = bless {	397	my $self = bless {
342	id => "$NODE#$id",	398	id => $port,
343	}, "AnyEvent::MP::Port";	399	}, "AnyEvent::MP::Port";
344		400
345	$PORT_DATA{$id} = $self;
346	$PORT{$id} = sub {	401	$PORT{$portid} = sub {
347	local $SELF = $port;	402	local $SELF = $port;
348		403
349	eval {	404	eval {
350	for (@{ $self->{rc0}{$_[0]} }) {	405	for (@{ $self->{rc0}{$_[0]} }) {
351	$_ && &{$_->[0]}	406	$_ && &{$_->[0]}
352	&& undef $_;	407	&& undef $_;
353	}	408	}
354		409
355	for (@{ $self->{rcv}{$_[0]} }) {	410	for (@{ $self->{rcv}{$_[0]} }) {
356	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]	411	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
357	&& &{$_->[0]}	412	&& &{$_->[0]}
358	&& undef $_;	413	&& undef $_;
359	}	414	}
360		415
361	for (@{ $self->{any} }) {	416	for (@{ $self->{any} }) {
362	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]	417	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
363	&& &{$_->[0]}	418	&& &{$_->[0]}
364	&& undef $_;	419	&& undef $_;
		420	}
365	}	421	};
		422	_self_die if $@;
366	};	423	};
367	_self_die if $@;	424
		425	$self
368	};	426	};
369	}
370		427
371	$port
372	}
373
374	=item reg $portid, $name
375
376	Registers the given port under the name C<$name>. If the name already
377	exists it is replaced.
378
379	A port can only be registered under one well known name.
380
381	A port automatically becomes unregistered when it is killed.
382
383	=cut
384
385	sub reg(@) {
386	my ($portid, $name) = @_;
387
388	$REG{$name} = $portid;
389	}
390
391	=item rcv $portid, tagstring => $callback->(@msg), ...
392
393	=item rcv $portid, $smartmatch => $callback->(@msg), ...
394
395	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
396
397	Register callbacks to be called on matching messages on the given port.
398
399	The callback has to return a true value when its work is done, after
400	which is will be removed, or a false value in which case it will stay
401	registered.
402
403	The global C<$SELF> (exported by this module) contains C<$portid> while
404	executing the callback.
405
406	Runtime errors wdurign callback execution will result in the port being
407	C<kil>ed.
408
409	If the match is an array reference, then it will be matched against the
410	first elements of the message, otherwise only the first element is being
411	matched.
412
413	Any element in the match that is specified as C<_any_> (a function
414	exported by this module) matches any single element of the message.
415
416	While not required, it is highly recommended that the first matching
417	element is a string identifying the message. The one-string-only match is
418	also the most efficient match (by far).
419
420	=cut
421
422	sub rcv($@) {
423	my ($noderef, $port) = split /#/, shift, 2;
424
425	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
426	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";
427
428	my $self = $PORT_DATA{$port}
429	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
430
431	"AnyEvent::MP::Port" eq ref $self	428	"AnyEvent::MP::Port" eq ref $self
432	or Carp::croak "$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";
433		430
434	while (@_) {	431	while (@_) {
435	my ($match, $cb) = splice @_, 0, 2;	432	my ($match, $cb) = splice @_, 0, 2;
436		433
437	if (!ref $match) {	434	if (!ref $match) {
438	push @{ $self->{rc0}{$match} }, [$cb];	435	push @{ $self->{rc0}{$match} }, [$cb];
439	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	436	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
440	my ($type, @match) = @$match;	437	my ($type, @match) = @$match;
441	@match	438	@match
442	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	439	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
443	: push @{ $self->{rc0}{$match->[0]} }, [$cb];	440	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
444	} else {	441	} else {
445	push @{ $self->{any} }, [$cb, $match];	442	push @{ $self->{any} }, [$cb, $match];
		443	}
446	}	444	}
447	}	445	}
		446
		447	$port
448	}	448	}
449		449
450	=item $closure = psub { BLOCK }	450	=item $closure = psub { BLOCK }
451		451
452	Remembers C<$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
…		…
483	$res	483	$res
484	}	484	}
485	}	485	}
486	}	486	}
487		487
488	=back	488	=item $guard = mon $port, $cb->(@reason)
489		489
490	=head1 FUNCTIONS FOR NODES	490	=item $guard = mon $port, $rcvport
491		491
492	=over 4	492	=item $guard = mon $port
493		493
494	=item become_public $noderef	494	=item $guard = mon $port, $rcvport, @msg
495		495
496	Tells the node to become a public node, i.e. reachable from other nodes.	496	Monitor the given port and do something when the port is killed, and
		497	optionally return a guard that can be used to stop monitoring again.
497		498
498	The first argument is the (unresolved) node reference of the local node	499	In the first form (callback), the callback is simply called with any
499	(if missing then the empty string is used).	500	number of C<@reason> elements (no @reason means that the port was deleted
		501	"normally"). Note also that I<< the callback B<must> never die >>, so use
		502	C<eval> if unsure.
500		503
501	It is quite common to not specify anything, in which case the local node	504	In the second form (another port given), the other port (C<$rcvport)
502	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
503	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.
504		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, $self => "restart";
		533
505	=cut	534	=cut
		535
		536	sub mon {
		537	my ($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 >>.
506		602
507	=back	603	=back
508		604
509	=head1 NODE MESSAGES	605	=head1 NODE MESSAGES
510		606
…		…
552		648
553	=back	649	=back
554		650
555	=head1 AnyEvent::MP vs. Distributed Erlang	651	=head1 AnyEvent::MP vs. Distributed Erlang
556		652
557	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
558	== 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
559	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
560	sample:	656	sample:
561		657
562	http://www.erlang.se/doc/programming_rules.shtml	658	http://www.Erlang.se/doc/programming_rules.shtml
563	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
564	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
565	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
566		662
567	Despite the similarities, there are also some important differences:	663	Despite the similarities, there are also some important differences:
568		664
569	=over 4	665	=over 4
570		666
…		…
581		677
582	Erlang uses processes that selctively receive messages, and therefore	678	Erlang uses processes that selctively receive messages, and therefore
583	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
584	purpose.	680	purpose.
585		681
586	(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).
587		683
588	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	684	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
589		685
590	Sending messages in erlang is synchronous and blocks the process. AEMP	686	Sending messages in Erlang is synchronous and blocks the process. AEMP
591	sends are immediate, connection establishment is handled in the	687	sends are immediate, connection establishment is handled in the
592	background.	688	background.
593		689
594	=item * Erlang can silently lose messages, AEMP cannot.	690	=item * Erlang can silently lose messages, AEMP cannot.
595		691
…		…
598	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).
599		695
600	AEMP guarantees correct ordering, and the guarantee that there are no	696	AEMP guarantees correct ordering, and the guarantee that there are no
601	holes in the message sequence.	697	holes in the message sequence.
602		698
603	=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
604	alive.	700	alive.
605		701
606	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
607	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
608	still alive - and can receive messages.	704	still alive - and can receive messages.
609		705
610	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
611	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
612	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.
613		709
614	=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.
615		711
616	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
617	ID known to other nodes for a completely different process, causing	713	ID known to other nodes for a completely different process, causing
618	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.
619		715
620	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
621	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.
…		…
627	securely authenticate nodes.	723	securely authenticate nodes.
628		724
629	=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
630	communications.	726	communications.
631		727
632	The AEMP protocol, unlike the erlang protocol, supports both	728	The AEMP protocol, unlike the Erlang protocol, supports both
633	language-independent text-only protocols (good for debugging) and binary,	729	language-independent text-only protocols (good for debugging) and binary,
634	language-specific serialisers (e.g. Storable).	730	language-specific serialisers (e.g. Storable).
635		731
636	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
637	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
638	protocol simple.	734	protocol simple.
639		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
640	=back	758	=back
641		759
642	=head1 SEE ALSO	760	=head1 SEE ALSO
643		761
644	L<AnyEvent>.	762	L<AnyEvent>.

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