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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.41 by root, Sat Aug 8 21:56:29 2009 UTC vs.
Revision 1.54 by root, Fri Aug 14 16:15:37 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 $simple_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		46	AnyEvent::MP::Intro - outdated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
61	=item port	70	=item port
62		71
63	A port is something you can send messages to (with the C<snd> function).	72	A port is something you can send messages to (with the C<snd> function).
64		73
65	Some ports allow you to register C<rcv> handlers that can match specific	74	Ports allow you to register C<rcv> handlers that can match all or just
66	messages. All C<rcv> handlers will receive messages they match, messages	75	some messages. Messages will not be queued.
67	will not be queued.
68		76
69	=item port id - C<noderef#portname>	77	=item port id - C<noderef#portname>
70		78
71	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	79	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as
72	separator, and a port name (a printable string of unspecified format). An	80	separator, and a port name (a printable string of unspecified format). An
73	exception is the the node port, whose ID is identical to its node	81	exception is the the node port, whose ID is identical to its node
74	reference.	82	reference.
75		83
76	=item node	84	=item node
77		85
78	A node is a single process containing at least one port - the node	86	A node is a single process containing at least one port - the node port,
79	port. You can send messages to node ports to find existing ports or to	87	which provides nodes to manage each other remotely, and to create new
80	create new ports, among other things.	88	ports.
81		89
82	Nodes are either private (single-process only), slaves (connected to a	90	Nodes are either private (single-process only), slaves (connected to a
83	master node only) or public nodes (connectable from unrelated nodes).	91	master node only) or public nodes (connectable from unrelated nodes).
84		92
85	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>
…		…
105		113
106	=cut	114	=cut
107		115
108	package AnyEvent::MP;	116	package AnyEvent::MP;
109		117
110	use AnyEvent::MP::Base;	118	use AnyEvent::MP::Kernel;
111		119
112	use common::sense;	120	use common::sense;
113		121
114	use Carp ();	122	use Carp ();
115		123
116	use AE ();	124	use AE ();
117		125
118	use base "Exporter";	126	use base "Exporter";
119		127
120	our $VERSION = '0.1';	128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		129
121	our @EXPORT = qw(	130	our @EXPORT = qw(
122	NODE $NODE *SELF node_of _any_	131	NODE $NODE *SELF node_of _any_
123	resolve_node initialise_node	132	resolve_node initialise_node
124	snd rcv mon kil reg psub spawn	133	snd rcv mon kil reg psub spawn
125	port	134	port
…		…
133	kil $SELF, die => $msg;	142	kil $SELF, die => $msg;
134	}	143	}
135		144
136	=item $thisnode = NODE / $NODE	145	=item $thisnode = NODE / $NODE
137		146
138	The C<NODE> function returns, and the C<$NODE> variable contains	147	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	148	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	149	C<initialise_node>.
141	identifiers become invalid.
142		150
143	=item $noderef = node_of $port	151	=item $noderef = node_of $port
144		152
145	Extracts and returns the noderef from a portid or a noderef.	153	Extracts and returns the noderef from a port ID or a noderef.
146		154
147	=item initialise_node $noderef, $seednode, $seednode...	155	=item initialise_node $noderef, $seednode, $seednode...
148		156
149	=item initialise_node "slave/", $master, $master...	157	=item initialise_node "slave/", $master, $master...
150		158
…		…
153	it should know the noderefs of some other nodes in the network.	161	it should know the noderefs of some other nodes in the network.
154		162
155	This function initialises a node - it must be called exactly once (or	163	This function initialises a node - it must be called exactly once (or
156	never) before calling other AnyEvent::MP functions.	164	never) before calling other AnyEvent::MP functions.
157		165
158	All arguments are noderefs, which can be either resolved or unresolved.	166	All arguments (optionally except for the first) are noderefs, which can be
		167	either resolved or unresolved.
		168
		169	The first argument will be looked up in the configuration database first
		170	(if it is C<undef> then the current nodename will be used instead) to find
		171	the relevant configuration profile (see L<aemp>). If none is found then
		172	the default configuration is used. The configuration supplies additional
		173	seed/master nodes and can override the actual noderef.
159		174
160	There are two types of networked nodes, public nodes and slave nodes:	175	There are two types of networked nodes, public nodes and slave nodes:
161		176
162	=over 4	177	=over 4
163		178
164	=item public nodes	179	=item public nodes
165		180
166	For public nodes, C<$noderef> must either be a (possibly unresolved)	181	For public nodes, C<$noderef> (supplied either directly to
167	noderef, in which case it will be resolved, or C<undef> (or missing), in	182	C<initialise_node> or indirectly via a profile or the nodename) must be a
168	which case the noderef will be guessed.	183	noderef (possibly unresolved, in which case it will be resolved).
169		184
170	Afterwards, the node will bind itself on all endpoints and try to connect	185	After resolving, the node will bind itself on all endpoints and try to
171	to all additional C<$seednodes> that are specified. Seednodes are optional	186	connect to all additional C<$seednodes> that are specified. Seednodes are
172	and can be used to quickly bootstrap the node into an existing network.	187	optional and can be used to quickly bootstrap the node into an existing
		188	network.
173		189
174	=item slave nodes	190	=item slave nodes
175		191
176	When the C<$noderef> is the special string C<slave/>, then the node will	192	When the C<$noderef> (either as given or overriden by the config file)
		193	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	194	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.	195	their traffic to the master node that they attach to.
179		196
180	At least one additional noderef is required: The node will try to connect	197	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	198	directly or because it is part of the configuration profile): The node
182	successfully connect to.	199	will try to connect to all of them and will become a slave attached to the
		200	first node it can successfully connect to.
183		201
184	=back	202	=back
185		203
186	This function will block until all nodes have been resolved and, for slave	204	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	205	nodes, until it has successfully established a connection to a master
188	server.	206	server.
189		207
190	Example: become a public node listening on the default node.	208	Example: become a public node listening on the guessed noderef, or the one
		209	specified via C<aemp> for the current node. This should be the most common
		210	form of invocation for "daemon"-type nodes.
191		211
192	initialise_node;	212	initialise_node;
		213
		214	Example: become a slave node to any of the the seednodes specified via
		215	C<aemp>. This form is often used for commandline clients.
		216
		217	initialise_node "slave/";
		218
		219	Example: become a slave node to any of the specified master servers. This
		220	form is also often used for commandline clients.
		221
		222	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
193		223
194	Example: become a public node, and try to contact some well-known master	224	Example: become a public node, and try to contact some well-known master
195	servers to become part of the network.	225	servers to become part of the network.
196		226
197	initialise_node undef, "master1", "master2";	227	initialise_node undef, "master1", "master2";
…		…
200		230
201	initialise_node 4041;	231	initialise_node 4041;
202		232
203	Example: become a public node, only visible on localhost port 4044.	233	Example: become a public node, only visible on localhost port 4044.
204		234
205	initialise_node "locahost:4044";	235	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		236
211	=item $cv = resolve_node $noderef	237	=item $cv = resolve_node $noderef
212		238
213	Takes an unresolved node reference that may contain hostnames and	239	Takes an unresolved node reference that may contain hostnames and
214	abbreviated IDs, resolves all of them and returns a resolved node	240	abbreviated IDs, resolves all of them and returns a resolved node
…		…
251	=item snd $port, type => @data	277	=item snd $port, type => @data
252		278
253	=item snd $port, @msg	279	=item snd $port, @msg
254		280
255	Send the given message to the given port ID, which can identify either	281	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	282	a local or a remote port, and must be a port ID.
257	stringifies a sa port ID (such as a port object :).
258		283
259	While the message can be about anything, it is highly recommended to use a	284	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	285	string as first element (a port ID, or some word that indicates a request
261	type etc.).	286	type etc.).
262		287
263	The message data effectively becomes read-only after a call to this	288	The message data effectively becomes read-only after a call to this
264	function: modifying any argument is not allowed and can cause many	289	function: modifying any argument is not allowed and can cause many
265	problems.	290	problems.
…		…
270	that Storable can serialise and deserialise is allowed, and for the local	295	that Storable can serialise and deserialise is allowed, and for the local
271	node, anything can be passed.	296	node, anything can be passed.
272		297
273	=item $local_port = port	298	=item $local_port = port
274		299
275	Create a new local port object that can be used either as a pattern	300	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"),	301	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		302
279	=item $port = port { my @msg = @_; $finished }	303	=item $local_port = port { my @msg = @_ }
280		304
281	Creates a "miniport", that is, a very lightweight port without any pattern	305	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.	306	creating a port and calling C<rcv $port, $callback> on it.
284		307
285	The block will be called for every message received on the port. When the	308	The block will be called for every message received on the port, with the
286	callback returns a true value its job is considered "done" and the port	309	global variable C<$SELF> set to the port ID. Runtime errors will cause the
287	will be destroyed. Otherwise it will stay alive.	310	port to be C<kil>ed. The message will be passed as-is, no extra argument
		311	(i.e. no port ID) will be passed to the callback.
288		312
289	The message will be passed as-is, no extra argument (i.e. no port id) will	313	If you want to stop/destroy the port, simply C<kil> it:
290	be passed to the callback.
291		314
292	If you need the local port id in the callback, this works nicely:	315	my $port = port {
293		316	my @msg = @_;
294	my $port; $port = port {	317	...
295	snd $otherport, reply => $port;	318	kil $SELF;
296	};	319	};
297		320
298	=cut	321	=cut
299		322
300	sub rcv($@);	323	sub rcv($@);
		324
		325	sub _kilme {
		326	die "received message on port without callback";
		327	}
301		328
302	sub port(;&) {	329	sub port(;&) {
303	my $id = "$UNIQ." . $ID++;	330	my $id = "$UNIQ." . $ID++;
304	my $port = "$NODE#$id";	331	my $port = "$NODE#$id";
305		332
306	if (@_) {	333	rcv $port, shift \|\| \&_kilme;
307	rcv $port, shift;
308	} else {
309	$PORT{$id} = sub { }; # nop
310	}
311		334
312	$port	335	$port
313	}	336	}
314		337
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)	338	=item rcv $local_port, $callback->(@msg)
335		339
336	Replaces the callback on the specified miniport (after converting it to	340	Replaces the default callback on the specified port. There is no way to
337	one if required).	341	remove the default callback: use C<sub { }> to disable it, or better
338		342	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...] => $callback->(@msg), ...
344
345	Register callbacks to be called on matching messages on the given full
346	port (after converting it to one if required) and return the port.
347
348	The callback has to return a true value when its work is done, after
349	which is will be removed, or a false value in which case it will stay
350	registered.
351		343
352	The global C<$SELF> (exported by this module) contains C<$port> while	344	The global C<$SELF> (exported by this module) contains C<$port> while
353	executing the callback.	345	executing the callback. Runtime errors during callback execution will
		346	result in the port being C<kil>ed.
354		347
355	Runtime errors during callback execution will result in the port being	348	The default callback received all messages not matched by a more specific
356	C<kil>ed.	349	C<tag> match.
357		350
358	If the match is an array reference, then it will be matched against the	351	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
359	first elements of the message, otherwise only the first element is being
360	matched.
361		352
362	Any element in the match that is specified as C<_any_> (a function	353	Register (or replace) callbacks to be called on messages starting with the
363	exported by this module) matches any single element of the message.	354	given tag on the given port (and return the port), or unregister it (when
		355	C<$callback> is C<$undef> or missing). There can only be one callback
		356	registered for each tag.
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	;
		377
		378	Example: temporarily register a rcv callback for a tag matching some port
		379	(e.g. for a rpc reply) and unregister it after a message was received.
		380
		381	rcv $port, $otherport => sub {
		382	my @reply = @_;
		383
		384	rcv $SELF, $otherport;
		385	};
384		386
385	=cut	387	=cut
386		388
387	sub rcv($@) {	389	sub rcv($@) {
388	my $port = shift;	390	my $port = shift;
389	my ($noderef, $portid) = split /#/, $port, 2;	391	my ($noderef, $portid) = split /#/, $port, 2;
390		392
391	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	393	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
392	or Carp::croak "$port: rcv can only be called on local ports, caught";	394	or Carp::croak "$port: rcv can only be called on local ports, caught";
393		395
394	if (@_ == 1) {	396	while (@_) {
		397	if (ref $_[0]) {
		398	if (my $self = $PORT_DATA{$portid}) {
		399	"AnyEvent::MP::Port" eq ref $self
		400	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		401
		402	$self->[2] = shift;
		403	} else {
395	my $cb = shift;	404	my $cb = shift;
396	delete $PORT_DATA{$portid};
397	$PORT{$portid} = sub {	405	$PORT{$portid} = sub {
398	local $SELF = $port;	406	local $SELF = $port;
399	eval {	407	eval { &$cb }; _self_die if $@;
400	&$cb	408	};
401	and kil $port;
402	};	409	}
403	_self_die if $@;	410	} elsif (defined $_[0]) {
404	};
405	} else {
406	my $self = $PORT_DATA{$portid} \|\|= do {	411	my $self = $PORT_DATA{$portid} \|\|= do {
407	my $self = bless {	412	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
408	id => $port,
409	}, "AnyEvent::MP::Port";
410		413
411	$PORT{$portid} = sub {	414	$PORT{$portid} = sub {
412	local $SELF = $port;	415	local $SELF = $port;
413		416
414	eval {
415	for (@{ $self->{rc0}{$_[0]} }) {	417	if (my $cb = $self->[1]{$_[0]}) {
416	$_ && &{$_->[0]}	418	shift;
417	&& undef $_;	419	eval { &$cb }; _self_die if $@;
418	}	420	} else {
419
420	for (@{ $self->{rcv}{$_[0]} }) {
421	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
422	&& &{$_->[0]}	421	&{ $self->[0] };
423	&& undef $_;
424	}
425
426	for (@{ $self->{any} }) {
427	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
428	&& &{$_->[0]}
429	&& undef $_;
430	}	422	}
431	};	423	};
432	_self_die if $@;	424
		425	$self
433	};	426	};
434		427
435	$self
436	};
437
438	"AnyEvent::MP::Port" eq ref $self	428	"AnyEvent::MP::Port" eq ref $self
439	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	429	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
440		430
441	while (@_) {
442	my ($match, $cb) = splice @_, 0, 2;	431	my ($tag, $cb) = splice @_, 0, 2;
443		432
444	if (!ref $match) {	433	if (defined $cb) {
445	push @{ $self->{rc0}{$match} }, [$cb];	434	$self->[1]{$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 {	435	} else {
452	push @{ $self->{any} }, [$cb, $match];	436	delete $self->[1]{$tag};
453	}	437	}
454	}	438	}
455	}	439	}
456		440
457	$port	441	$port
…		…
501		485
502	=item $guard = mon $port	486	=item $guard = mon $port
503		487
504	=item $guard = mon $port, $rcvport, @msg	488	=item $guard = mon $port, $rcvport, @msg
505		489
506	Monitor the given port and do something when the port is killed, and	490	Monitor the given port and do something when the port is killed or
507	optionally return a guard that can be used to stop monitoring again.	491	messages to it were lost, and optionally return a guard that can be used
		492	to stop monitoring again.
		493
		494	C<mon> effectively guarantees that, in the absence of hardware failures,
		495	that after starting the monitor, either all messages sent to the port
		496	will arrive, or the monitoring action will be invoked after possible
		497	message loss has been detected. No messages will be lost "in between"
		498	(after the first lost message no further messages will be received by the
		499	port). After the monitoring action was invoked, further messages might get
		500	delivered again.
508		501
509	In the first form (callback), the callback is simply called with any	502	In the first form (callback), the callback is simply called with any
510	number of C<@reason> elements (no @reason means that the port was deleted	503	number of C<@reason> elements (no @reason means that the port was deleted
511	"normally"). Note also that I<< the callback B<must> never die >>, so use	504	"normally"). Note also that I<< the callback B<must> never die >>, so use
512	C<eval> if unsure.	505	C<eval> if unsure.
513		506
514	In the second form (another port given), the other port (C<$rcvport)	507	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	508	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	509	"normal" kils nothing happens, while under all other conditions, the other
517	port is killed with the same reason.	510	port is killed with the same reason.
518		511
519	The third form (kill self) is the same as the second form, except that	512	The third form (kill self) is the same as the second form, except that
…		…
752	convenience functionality.	745	convenience functionality.
753		746
754	This means that AEMP requires a less tightly controlled environment at the	747	This means that AEMP requires a less tightly controlled environment at the
755	cost of longer node references and a slightly higher management overhead.	748	cost of longer node references and a slightly higher management overhead.
756		749
		750	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		751	uses "local ports are like remote ports".
		752
		753	The failure modes for local ports are quite different (runtime errors
		754	only) then for remote ports - when a local port dies, you I<know> it dies,
		755	when a connection to another node dies, you know nothing about the other
		756	port.
		757
		758	Erlang pretends remote ports are as reliable as local ports, even when
		759	they are not.
		760
		761	AEMP encourages a "treat remote ports differently" philosophy, with local
		762	ports being the special case/exception, where transport errors cannot
		763	occur.
		764
757	=item * Erlang uses processes and a mailbox, AEMP does not queue.	765	=item * Erlang uses processes and a mailbox, AEMP does not queue.
758		766
759	Erlang uses processes that selctively receive messages, and therefore	767	Erlang uses processes that selectively receive messages, and therefore
760	needs a queue. AEMP is event based, queuing messages would serve no useful	768	needs a queue. AEMP is event based, queuing messages would serve no
761	purpose.	769	useful purpose. For the same reason the pattern-matching abilities of
		770	AnyEvent::MP are more limited, as there is little need to be able to
		771	filter messages without dequeing them.
762		772
763	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	773	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
764		774
765	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
766		776
767	Sending messages in Erlang is synchronous and blocks the process. AEMP	777	Sending messages in Erlang is synchronous and blocks the process (and
768	sends are immediate, connection establishment is handled in the	778	so does not need a queue that can overflow). AEMP sends are immediate,
769	background.	779	connection establishment is handled in the background.
770		780
771	=item * Erlang can silently lose messages, AEMP cannot.	781	=item * Erlang suffers from silent message loss, AEMP does not.
772		782
773	Erlang makes few guarantees on messages delivery - messages can get lost	783	Erlang makes few guarantees on messages delivery - messages can get lost
774	without any of the processes realising it (i.e. you send messages a, b,	784	without any of the processes realising it (i.e. you send messages a, b,
775	and c, and the other side only receives messages a and c).	785	and c, and the other side only receives messages a and c).
776		786
…		…
788	eventually be killed - it cannot happen that a node detects a port as dead	798	eventually be killed - it cannot happen that a node detects a port as dead
789	and then later sends messages to it, finding it is still alive.	799	and then later sends messages to it, finding it is still alive.
790		800
791	=item * Erlang can send messages to the wrong port, AEMP does not.	801	=item * Erlang can send messages to the wrong port, AEMP does not.
792		802
793	In Erlang it is quite possible that a node that restarts reuses a process	803	In Erlang it is quite likely that a node that restarts reuses a process ID
794	ID known to other nodes for a completely different process, causing	804	known to other nodes for a completely different process, causing messages
795	messages destined for that process to end up in an unrelated process.	805	destined for that process to end up in an unrelated process.
796		806
797	AEMP never reuses port IDs, so old messages or old port IDs floating	807	AEMP never reuses port IDs, so old messages or old port IDs floating
798	around in the network will not be sent to an unrelated port.	808	around in the network will not be sent to an unrelated port.
799		809
800	=item * Erlang uses unprotected connections, AEMP uses secure	810	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
836	This also saves round-trips and avoids sending messages to the wrong port	846	This also saves round-trips and avoids sending messages to the wrong port
837	(hard to do in Erlang).	847	(hard to do in Erlang).
838		848
839	=back	849	=back
840		850
		851	=head1 RATIONALE
		852
		853	=over 4
		854
		855	=item Why strings for ports and noderefs, why not objects?
		856
		857	We considered "objects", but found that the actual number of methods
		858	thatc an be called are very low. Since port IDs and noderefs travel over
		859	the network frequently, the serialising/deserialising would add lots of
		860	overhead, as well as having to keep a proxy object.
		861
		862	Strings can easily be printed, easily serialised etc. and need no special
		863	procedures to be "valid".
		864
		865	And a a miniport consists of a single closure stored in a global hash - it
		866	can't become much cheaper.
		867
		868	=item Why favour JSON, why not real serialising format such as Storable?
		869
		870	In fact, any AnyEvent::MP node will happily accept Storable as framing
		871	format, but currently there is no way to make a node use Storable by
		872	default.
		873
		874	The default framing protocol is JSON because a) JSON::XS is many times
		875	faster for small messages and b) most importantly, after years of
		876	experience we found that object serialisation is causing more problems
		877	than it gains: Just like function calls, objects simply do not travel
		878	easily over the network, mostly because they will always be a copy, so you
		879	always have to re-think your design.
		880
		881	Keeping your messages simple, concentrating on data structures rather than
		882	objects, will keep your messages clean, tidy and efficient.
		883
		884	=back
		885
841	=head1 SEE ALSO	886	=head1 SEE ALSO
842		887
843	L<AnyEvent>.	888	L<AnyEvent>.
844		889
845	=head1 AUTHOR	890	=head1 AUTHOR

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.41 by root, Sat Aug 8 21:56:29 2009 UTC vs. Revision 1.54 by root, Fri Aug 14 16:15:37 2009 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.41 by root, Sat Aug 8 21:56:29 2009 UTC vs.
Revision 1.54 by root, Fri Aug 14 16:15:37 2009 UTC