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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.39 by root, Fri Aug 7 23:21:48 2009 UTC vs.
Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC

…		…
9	$NODE # contains this node's noderef	9	$NODE # contains this node's noderef
10	NODE # returns this node's noderef	10	NODE # returns this node's noderef
11	NODE $port # returns the noderef of the port	11	NODE $port # returns the noderef of the port
12		12
13	$SELF # receiving/own port id in rcv callbacks	13	$SELF # receiving/own port id in rcv callbacks
		14
		15	# initialise the node so it can send/receive messages
		16	initialise_node; # -OR-
		17	initialise_node "localhost:4040"; # -OR-
		18	initialise_node "slave/", "localhost:4040"
14		19
15	# ports are message endpoints	20	# ports are message endpoints
16		21
17	# sending messages	22	# sending messages
18	snd $port, type => data...;	23	snd $port, type => data...;
19	snd $port, @msg;	24	snd $port, @msg;
20	snd @msg_with_first_element_being_a_port;	25	snd @msg_with_first_element_being_a_port;
21		26
22	# miniports	27	# creating/using ports, the simple way
23	my $miniport = port { my @msg = @_; 0 };	28	my $somple_port = port { my @msg = @_; 0 };
24		29
25	# full ports	30	# creating/using ports, tagged message matching
26	my $port = port;	31	my $port = port;
27	rcv $port, smartmatch => $cb->(@msg);
28	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
29	rcv $port, pong => sub { warn "pong received\n"; 0 };	33	rcv $port, pong => sub { warn "pong received\n"; 0 };
30		34
31	# remote ports	35	# create a port on another node
32	my $port = spawn $node, $initfunc, @initdata;	36	my $port = spawn $node, $initfunc, @initdata;
33
34	# more, smarter, matches (_any_ is exported by this module)
35	rcv $port, [child_died => $pid] => sub { ...
36	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
37		37
38	# monitoring	38	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	39	mon $port, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	40	mon $port, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	41	mon $port, $otherport, @msg # send message on death
42		42
		43	=head1 CURRENT STATUS
		44
		45	AnyEvent::MP - stable API, should work
		46	AnyEvent::MP::Intro - outdated
		47	AnyEvent::MP::Kernel - WIP
		48	AnyEvent::MP::Transport - mostly stable
		49
		50	stay tuned.
		51
43	=head1 DESCRIPTION	52	=head1 DESCRIPTION
44		53
45	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
46		55
47	Despite its simplicity, you can securely message other processes running	56	Despite its simplicity, you can securely message other processes running
…		…
50	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
51	manual page.	60	manual page.
52		61
53	At the moment, this module family is severly broken and underdocumented,	62	At the moment, this module family is severly broken and underdocumented,
54	so do not use. This was uploaded mainly to reserve the CPAN namespace -	63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
55	stay tuned! The basic API should be finished, however.	64	stay tuned!
56		65
57	=head1 CONCEPTS	66	=head1 CONCEPTS
58		67
59	=over 4	68	=over 4
60		69
…		…
105		114
106	=cut	115	=cut
107		116
108	package AnyEvent::MP;	117	package AnyEvent::MP;
109		118
110	use AnyEvent::MP::Base;	119	use AnyEvent::MP::Kernel;
111		120
112	use common::sense;	121	use common::sense;
113		122
114	use Carp ();	123	use Carp ();
115		124
116	use AE ();	125	use AE ();
117		126
118	use base "Exporter";	127	use base "Exporter";
119		128
120	our $VERSION = '0.1';	129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		130
121	our @EXPORT = qw(	131	our @EXPORT = qw(
122	NODE $NODE *SELF node_of _any_	132	NODE $NODE *SELF node_of _any_
123	resolve_node initialise_node	133	resolve_node initialise_node
124	snd rcv mon kil reg psub spawn	134	snd rcv mon kil reg psub spawn
125	port	135	port
…		…
133	kil $SELF, die => $msg;	143	kil $SELF, die => $msg;
134	}	144	}
135		145
136	=item $thisnode = NODE / $NODE	146	=item $thisnode = NODE / $NODE
137		147
138	The C<NODE> function returns, and the C<$NODE> variable contains	148	The C<NODE> function returns, and the C<$NODE> variable contains the
139	the noderef of the local node. The value is initialised by a call	149	noderef of the local node. The value is initialised by a call to
140	to C<become_public> or C<become_slave>, after which all local port	150	C<initialise_node>.
141	identifiers become invalid.
142		151
143	=item $noderef = node_of $port	152	=item $noderef = node_of $port
144		153
145	Extracts and returns the noderef from a portid or a noderef.	154	Extracts and returns the noderef from a port ID or a noderef.
146		155
147	=item initialise_node $noderef, $seednode, $seednode...	156	=item initialise_node $noderef, $seednode, $seednode...
148		157
149	=item initialise_node "slave/", $master, $master...	158	=item initialise_node "slave/", $master, $master...
150		159
…		…
153	it should know the noderefs of some other nodes in the network.	162	it should know the noderefs of some other nodes in the network.
154		163
155	This function initialises a node - it must be called exactly once (or	164	This function initialises a node - it must be called exactly once (or
156	never) before calling other AnyEvent::MP functions.	165	never) before calling other AnyEvent::MP functions.
157		166
158	All arguments are noderefs, which can be either resolved or unresolved.	167	All arguments (optionally except for the first) are noderefs, which can be
		168	either resolved or unresolved.
		169
		170	The first argument will be looked up in the configuration database first
		171	(if it is C<undef> then the current nodename will be used instead) to find
		172	the relevant configuration profile (see L<aemp>). If none is found then
		173	the default configuration is used. The configuration supplies additional
		174	seed/master nodes and can override the actual noderef.
159		175
160	There are two types of networked nodes, public nodes and slave nodes:	176	There are two types of networked nodes, public nodes and slave nodes:
161		177
162	=over 4	178	=over 4
163		179
164	=item public nodes	180	=item public nodes
165		181
166	For public nodes, C<$noderef> must either be a (possibly unresolved)	182	For public nodes, C<$noderef> (supplied either directly to
167	noderef, in which case it will be resolved, or C<undef> (or missing), in	183	C<initialise_node> or indirectly via a profile or the nodename) must be a
168	which case the noderef will be guessed.	184	noderef (possibly unresolved, in which case it will be resolved).
169		185
170	Afterwards, the node will bind itself on all endpoints and try to connect	186	After resolving, the node will bind itself on all endpoints and try to
171	to all additional C<$seednodes> that are specified. Seednodes are optional	187	connect to all additional C<$seednodes> that are specified. Seednodes are
172	and can be used to quickly bootstrap the node into an existing network.	188	optional and can be used to quickly bootstrap the node into an existing
		189	network.
173		190
174	=item slave nodes	191	=item slave nodes
175		192
176	When the C<$noderef> is the special string C<slave/>, then the node will	193	When the C<$noderef> (either as given or overriden by the config file)
		194	is the special string C<slave/>, then the node will become a slave
177	become a slave node. Slave nodes cannot be contacted from outside and will	195	node. Slave nodes cannot be contacted from outside and will route most of
178	route most of their traffic to the master node that they attach to.	196	their traffic to the master node that they attach to.
179		197
180	At least one additional noderef is required: The node will try to connect	198	At least one additional noderef is required (either by specifying it
181	to all of them and will become a slave attached to the first node it can	199	directly or because it is part of the configuration profile): The node
182	successfully connect to.	200	will try to connect to all of them and will become a slave attached to the
		201	first node it can successfully connect to.
183		202
184	=back	203	=back
185		204
186	This function will block until all nodes have been resolved and, for slave	205	This function will block until all nodes have been resolved and, for slave
187	nodes, until it has successfully established a connection to a master	206	nodes, until it has successfully established a connection to a master
188	server.	207	server.
189		208
190	Example: become a public node listening on the default node.	209	Example: become a public node listening on the guessed noderef, or the one
		210	specified via C<aemp> for the current node. This should be the most common
		211	form of invocation for "daemon"-type nodes.
191		212
192	initialise_node;	213	initialise_node;
		214
		215	Example: become a slave node to any of the the seednodes specified via
		216	C<aemp>. This form is often used for commandline clients.
		217
		218	initialise_node "slave/";
		219
		220	Example: become a slave node to any of the specified master servers. This
		221	form is also often used for commandline clients.
		222
		223	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
193		224
194	Example: become a public node, and try to contact some well-known master	225	Example: become a public node, and try to contact some well-known master
195	servers to become part of the network.	226	servers to become part of the network.
196		227
197	initialise_node undef, "master1", "master2";	228	initialise_node undef, "master1", "master2";
…		…
200		231
201	initialise_node 4041;	232	initialise_node 4041;
202		233
203	Example: become a public node, only visible on localhost port 4044.	234	Example: become a public node, only visible on localhost port 4044.
204		235
205	initialise_node "locahost:4044";	236	initialise_node "localhost:4044";
206
207	Example: become a slave node to any of the specified master servers.
208
209	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
210		237
211	=item $cv = resolve_node $noderef	238	=item $cv = resolve_node $noderef
212		239
213	Takes an unresolved node reference that may contain hostnames and	240	Takes an unresolved node reference that may contain hostnames and
214	abbreviated IDs, resolves all of them and returns a resolved node	241	abbreviated IDs, resolves all of them and returns a resolved node
…		…
251	=item snd $port, type => @data	278	=item snd $port, type => @data
252		279
253	=item snd $port, @msg	280	=item snd $port, @msg
254		281
255	Send the given message to the given port ID, which can identify either	282	Send the given message to the given port ID, which can identify either
256	a local or a remote port, and can be either a string or soemthignt hat	283	a local or a remote port, and must be a port ID.
257	stringifies a sa port ID (such as a port object :).
258		284
259	While the message can be about anything, it is highly recommended to use a	285	While the message can be about anything, it is highly recommended to use a
260	string as first element (a portid, or some word that indicates a request	286	string as first element (a port ID, or some word that indicates a request
261	type etc.).	287	type etc.).
262		288
263	The message data effectively becomes read-only after a call to this	289	The message data effectively becomes read-only after a call to this
264	function: modifying any argument is not allowed and can cause many	290	function: modifying any argument is not allowed and can cause many
265	problems.	291	problems.
…		…
270	that Storable can serialise and deserialise is allowed, and for the local	296	that Storable can serialise and deserialise is allowed, and for the local
271	node, anything can be passed.	297	node, anything can be passed.
272		298
273	=item $local_port = port	299	=item $local_port = port
274		300
275	Create a new local port object that can be used either as a pattern	301	Create a new local port object and returns its port ID. Initially it has
276	matching port ("full port") or a single-callback port ("miniport"),	302	no callbacks set and will throw an error when it receives messages.
277	depending on how C<rcv> callbacks are bound to the object.
278		303
279	=item $port = port { my @msg = @_; $finished }	304	=item $local_port = port { my @msg = @_ }
280		305
281	Creates a "miniport", that is, a very lightweight port without any pattern	306	Creates a new local port, and returns its ID. Semantically the same as
282	matching behind it, and returns its ID. Semantically the same as creating
283	a port and calling C<rcv $port, $callback> on it.	307	creating a port and calling C<rcv $port, $callback> on it.
284		308
285	The block will be called for every message received on the port. When the	309	The block will be called for every message received on the port, with the
286	callback returns a true value its job is considered "done" and the port	310	global variable C<$SELF> set to the port ID. Runtime errors will cause the
287	will be destroyed. Otherwise it will stay alive.	311	port to be C<kil>ed. The message will be passed as-is, no extra argument
		312	(i.e. no port ID) will be passed to the callback.
288		313
289	The message will be passed as-is, no extra argument (i.e. no port id) will	314	If you want to stop/destroy the port, simply C<kil> it:
290	be passed to the callback.
291		315
292	If you need the local port id in the callback, this works nicely:	316	my $port = port {
293		317	my @msg = @_;
294	my $port; $port = port {	318	...
295	snd $otherport, reply => $port;	319	kil $SELF;
296	};	320	};
297		321
298	=cut	322	=cut
299		323
300	sub rcv($@);	324	sub rcv($@);
		325
		326	sub _kilme {
		327	die "received message on port without callback";
		328	}
301		329
302	sub port(;&) {	330	sub port(;&) {
303	my $id = "$UNIQ." . $ID++;	331	my $id = "$UNIQ." . $ID++;
304	my $port = "$NODE#$id";	332	my $port = "$NODE#$id";
305		333
306	if (@_) {	334	rcv $port, shift \|\| \&_kilme;
307	rcv $port, shift;
308	} else {
309	$PORT{$id} = sub { }; # nop
310	}
311		335
312	$port	336	$port
313	}	337	}
314		338
315	=item reg $port, $name
316
317	=item reg $name
318
319	Registers the given port (or C<$SELF><<< if missing) under the name
320	C<$name>. If the name already exists it is replaced.
321
322	A port can only be registered under one well known name.
323
324	A port automatically becomes unregistered when it is killed.
325
326	=cut
327
328	sub reg(@) {
329	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
330
331	$REG{$_[0]} = $port;
332	}
333
334	=item rcv $port, $callback->(@msg)	339	=item rcv $local_port, $callback->(@msg)
335		340
336	Replaces the callback on the specified miniport (after converting it to	341	Replaces the default callback on the specified port. There is no way to
337	one if required).	342	remove the default callback: use C<sub { }> to disable it, or better
338		343	C<kil> the port when it is no longer needed.
339	=item rcv $port, tagstring => $callback->(@msg), ...
340
341	=item rcv $port, $smartmatch => $callback->(@msg), ...
342
343	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
344
345	Register callbacks to be called on matching messages on the given full
346	port (after converting it to one if required) and return the port.
347
348	The callback has to return a true value when its work is done, after
349	which is will be removed, or a false value in which case it will stay
350	registered.
351		344
352	The global C<$SELF> (exported by this module) contains C<$port> while	345	The global C<$SELF> (exported by this module) contains C<$port> while
353	executing the callback.	346	executing the callback. Runtime errors during callback execution will
		347	result in the port being C<kil>ed.
354		348
355	Runtime errors during callback execution will result in the port being	349	The default callback received all messages not matched by a more specific
356	C<kil>ed.	350	C<tag> match.
357		351
358	If the match is an array reference, then it will be matched against the	352	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
359	first elements of the message, otherwise only the first element is being
360	matched.
361		353
362	Any element in the match that is specified as C<_any_> (a function	354	Register callbacks to be called on messages starting with the given tag on
363	exported by this module) matches any single element of the message.	355	the given port (and return the port), or unregister it (when C<$callback>
		356	is C<$undef>).
364		357
365	While not required, it is highly recommended that the first matching	358	The original message will be passed to the callback, after the first
366	element is a string identifying the message. The one-string-only match is	359	element (the tag) has been removed. The callback will use the same
367	also the most efficient match (by far).	360	environment as the default callback (see above).
368		361
369	Example: create a port and bind receivers on it in one go.	362	Example: create a port and bind receivers on it in one go.
370		363
371	my $port = rcv port,	364	my $port = rcv port,
372	msg1 => sub { ...; 0 },	365	msg1 => sub { ... },
373	msg2 => sub { ...; 0 },	366	msg2 => sub { ... },
374	;	367	;
375		368
376	Example: create a port, bind receivers and send it in a message elsewhere	369	Example: create a port, bind receivers and send it in a message elsewhere
377	in one go:	370	in one go:
378		371
379	snd $otherport, reply =>	372	snd $otherport, reply =>
380	rcv port,	373	rcv port,
381	msg1 => sub { ...; 0 },	374	msg1 => sub { ... },
382	...	375	...
383	;	376	;
384		377
385	=cut	378	=cut
386		379
…		…
389	my ($noderef, $portid) = split /#/, $port, 2;	382	my ($noderef, $portid) = split /#/, $port, 2;
390		383
391	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
392	or Carp::croak "$port: rcv can only be called on local ports, caught";	385	or Carp::croak "$port: rcv can only be called on local ports, caught";
393		386
394	if (@_ == 1) {	387	while (@_) {
		388	if (ref $_[0]) {
		389	if (my $self = $PORT_DATA{$portid}) {
		390	"AnyEvent::MP::Port" eq ref $self
		391	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		392
		393	$self->[2] = shift;
		394	} else {
395	my $cb = shift;	395	my $cb = shift;
396	delete $PORT_DATA{$portid};
397	$PORT{$portid} = sub {	396	$PORT{$portid} = sub {
398	local $SELF = $port;	397	local $SELF = $port;
399	eval {	398	eval { &$cb }; _self_die if $@;
400	&$cb	399	};
401	and kil $port;
402	};	400	}
403	_self_die if $@;	401	} elsif (defined $_[0]) {
404	};
405	} else {
406	my $self = $PORT_DATA{$portid} \|\|= do {	402	my $self = $PORT_DATA{$portid} \|\|= do {
407	my $self = bless {	403	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
408	id => $port,
409	}, "AnyEvent::MP::Port";
410		404
411	$PORT{$portid} = sub {	405	$PORT{$portid} = sub {
412	local $SELF = $port;	406	local $SELF = $port;
413		407
414	eval {
415	for (@{ $self->{rc0}{$_[0]} }) {	408	if (my $cb = $self->[1]{$_[0]}) {
416	$_ && &{$_->[0]}	409	shift;
417	&& undef $_;	410	eval { &$cb }; _self_die if $@;
418	}	411	} else {
419
420	for (@{ $self->{rcv}{$_[0]} }) {
421	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
422	&& &{$_->[0]}	412	&{ $self->[0] };
423	&& undef $_;
424	}
425
426	for (@{ $self->{any} }) {
427	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
428	&& &{$_->[0]}
429	&& undef $_;
430	}	413	}
431	};	414	};
432	_self_die if $@;	415
		416	$self
433	};	417	};
434		418
435	$self
436	};
437
438	"AnyEvent::MP::Port" eq ref $self	419	"AnyEvent::MP::Port" eq ref $self
439	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	420	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
440		421
441	while (@_) {
442	my ($match, $cb) = splice @_, 0, 2;	422	my ($tag, $cb) = splice @_, 0, 2;
443		423
444	if (!ref $match) {	424	if (defined $cb) {
445	push @{ $self->{rc0}{$match} }, [$cb];	425	$self->[1]{$tag} = $cb;
446	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
447	my ($type, @match) = @$match;
448	@match
449	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
450	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
451	} else {	426	} else {
452	push @{ $self->{any} }, [$cb, $match];	427	delete $self->[1]{$tag};
453	}	428	}
454	}	429	}
455	}	430	}
456		431
457	$port	432	$port
…		…
501		476
502	=item $guard = mon $port	477	=item $guard = mon $port
503		478
504	=item $guard = mon $port, $rcvport, @msg	479	=item $guard = mon $port, $rcvport, @msg
505		480
506	Monitor the given port and do something when the port is killed, and	481	Monitor the given port and do something when the port is killed or
507	optionally return a guard that can be used to stop monitoring again.	482	messages to it were lost, and optionally return a guard that can be used
		483	to stop monitoring again.
		484
		485	C<mon> effectively guarantees that, in the absence of hardware failures,
		486	that after starting the monitor, either all messages sent to the port
		487	will arrive, or the monitoring action will be invoked after possible
		488	message loss has been detected. No messages will be lost "in between"
		489	(after the first lost message no further messages will be received by the
		490	port). After the monitoring action was invoked, further messages might get
		491	delivered again.
508		492
509	In the first form (callback), the callback is simply called with any	493	In the first form (callback), the callback is simply called with any
510	number of C<@reason> elements (no @reason means that the port was deleted	494	number of C<@reason> elements (no @reason means that the port was deleted
511	"normally"). Note also that I<< the callback B<must> never die >>, so use	495	"normally"). Note also that I<< the callback B<must> never die >>, so use
512	C<eval> if unsure.	496	C<eval> if unsure.
513		497
514	In the second form (another port given), the other port (C<$rcvport)	498	In the second form (another port given), the other port (C<$rcvport>)
515	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	499	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
516	"normal" kils nothing happens, while under all other conditions, the other	500	"normal" kils nothing happens, while under all other conditions, the other
517	port is killed with the same reason.	501	port is killed with the same reason.
518		502
519	The third form (kill self) is the same as the second form, except that	503	The third form (kill self) is the same as the second form, except that
…		…
546	sub mon {	530	sub mon {
547	my ($noderef, $port) = split /#/, shift, 2;	531	my ($noderef, $port) = split /#/, shift, 2;
548		532
549	my $node = $NODE{$noderef} \|\| add_node $noderef;	533	my $node = $NODE{$noderef} \|\| add_node $noderef;
550		534
551	my $cb = @_ ? $_[0] : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	535	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
552		536
553	unless (ref $cb) {	537	unless (ref $cb) {
554	if (@_) {	538	if (@_) {
555	# send a kill info message	539	# send a kill info message
556	my (@msg) = @_;	540	my (@msg) = ($cb, @_);
557	$cb = sub { snd @msg, @_ };	541	$cb = sub { snd @msg, @_ };
558	} else {	542	} else {
559	# simply kill other port	543	# simply kill other port
560	my $port = $cb;	544	my $port = $cb;
561	$cb = sub { kil $port, @_ if @_ };	545	$cb = sub { kil $port, @_ if @_ };
…		…
620	The port ID of the newly created port is return immediately, and it is	604	The port ID of the newly created port is return immediately, and it is
621	permissible to immediately start sending messages or monitor the port.	605	permissible to immediately start sending messages or monitor the port.
622		606
623	After the port has been created, the init function is	607	After the port has been created, the init function is
624	called. This function must be a fully-qualified function name	608	called. This function must be a fully-qualified function name
625	(e.g. C<MyApp::Chat::Server::init>).	609	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		610	program, use C<::name>.
626		611
627	If the function doesn't exist, then the node tries to C<require>	612	If the function doesn't exist, then the node tries to C<require>
628	the package, then the package above the package and so on (e.g.	613	the package, then the package above the package and so on (e.g.
629	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	614	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
630	exists or it runs out of package names.	615	exists or it runs out of package names.
…		…
751	convenience functionality.	736	convenience functionality.
752		737
753	This means that AEMP requires a less tightly controlled environment at the	738	This means that AEMP requires a less tightly controlled environment at the
754	cost of longer node references and a slightly higher management overhead.	739	cost of longer node references and a slightly higher management overhead.
755		740
		741	=item Erlang has a "remote ports are like local ports" philosophy, AEMP
		742	uses "local ports are like remote ports".
		743
		744	The failure modes for local ports are quite different (runtime errors
		745	only) then for remote ports - when a local port dies, you I<know> it dies,
		746	when a connection to another node dies, you know nothing about the other
		747	port.
		748
		749	Erlang pretends remote ports are as reliable as local ports, even when
		750	they are not.
		751
		752	AEMP encourages a "treat remote ports differently" philosophy, with local
		753	ports being the special case/exception, where transport errors cannot
		754	occur.
		755
756	=item * Erlang uses processes and a mailbox, AEMP does not queue.	756	=item * Erlang uses processes and a mailbox, AEMP does not queue.
757		757
758	Erlang uses processes that selctively receive messages, and therefore	758	Erlang uses processes that selectively receive messages, and therefore
759	needs a queue. AEMP is event based, queuing messages would serve no useful	759	needs a queue. AEMP is event based, queuing messages would serve no
760	purpose.	760	useful purpose. For the same reason the pattern-matching abilities of
		761	AnyEvent::MP are more limited, as there is little need to be able to
		762	filter messages without dequeing them.
761		763
762	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	764	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
763		765
764	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	766	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
765		767
766	Sending messages in Erlang is synchronous and blocks the process. AEMP	768	Sending messages in Erlang is synchronous and blocks the process (and
767	sends are immediate, connection establishment is handled in the	769	so does not need a queue that can overflow). AEMP sends are immediate,
768	background.	770	connection establishment is handled in the background.
769		771
770	=item * Erlang can silently lose messages, AEMP cannot.	772	=item * Erlang suffers from silent message loss, AEMP does not.
771		773
772	Erlang makes few guarantees on messages delivery - messages can get lost	774	Erlang makes few guarantees on messages delivery - messages can get lost
773	without any of the processes realising it (i.e. you send messages a, b,	775	without any of the processes realising it (i.e. you send messages a, b,
774	and c, and the other side only receives messages a and c).	776	and c, and the other side only receives messages a and c).
775		777
…		…
787	eventually be killed - it cannot happen that a node detects a port as dead	789	eventually be killed - it cannot happen that a node detects a port as dead
788	and then later sends messages to it, finding it is still alive.	790	and then later sends messages to it, finding it is still alive.
789		791
790	=item * Erlang can send messages to the wrong port, AEMP does not.	792	=item * Erlang can send messages to the wrong port, AEMP does not.
791		793
792	In Erlang it is quite possible that a node that restarts reuses a process	794	In Erlang it is quite likely that a node that restarts reuses a process ID
793	ID known to other nodes for a completely different process, causing	795	known to other nodes for a completely different process, causing messages
794	messages destined for that process to end up in an unrelated process.	796	destined for that process to end up in an unrelated process.
795		797
796	AEMP never reuses port IDs, so old messages or old port IDs floating	798	AEMP never reuses port IDs, so old messages or old port IDs floating
797	around in the network will not be sent to an unrelated port.	799	around in the network will not be sent to an unrelated port.
798		800
799	=item * Erlang uses unprotected connections, AEMP uses secure	801	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
835	This also saves round-trips and avoids sending messages to the wrong port	837	This also saves round-trips and avoids sending messages to the wrong port
836	(hard to do in Erlang).	838	(hard to do in Erlang).
837		839
838	=back	840	=back
839		841
		842	=head1 RATIONALE
		843
		844	=over 4
		845
		846	=item Why strings for ports and noderefs, why not objects?
		847
		848	We considered "objects", but found that the actual number of methods
		849	thatc an be called are very low. Since port IDs and noderefs travel over
		850	the network frequently, the serialising/deserialising would add lots of
		851	overhead, as well as having to keep a proxy object.
		852
		853	Strings can easily be printed, easily serialised etc. and need no special
		854	procedures to be "valid".
		855
		856	And a a miniport consists of a single closure stored in a global hash - it
		857	can't become much cheaper.
		858
		859	=item Why favour JSON, why not real serialising format such as Storable?
		860
		861	In fact, any AnyEvent::MP node will happily accept Storable as framing
		862	format, but currently there is no way to make a node use Storable by
		863	default.
		864
		865	The default framing protocol is JSON because a) JSON::XS is many times
		866	faster for small messages and b) most importantly, after years of
		867	experience we found that object serialisation is causing more problems
		868	than it gains: Just like function calls, objects simply do not travel
		869	easily over the network, mostly because they will always be a copy, so you
		870	always have to re-think your design.
		871
		872	Keeping your messages simple, concentrating on data structures rather than
		873	objects, will keep your messages clean, tidy and efficient.
		874
		875	=back
		876
840	=head1 SEE ALSO	877	=head1 SEE ALSO
841		878
842	L<AnyEvent>.	879	L<AnyEvent>.
843		880
844	=head1 AUTHOR	881	=head1 AUTHOR

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.39 by root, Fri Aug 7 23:21:48 2009 UTC vs.
Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC