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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.33 by root, Wed Aug 5 22:40:51 2009 UTC vs.
Revision 1.53 by root, Fri Aug 14 15:31:21 2009 UTC

…		…
8		8
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
		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"
		19
		20	# ports are message endpoints
		21
		22	# sending messages
13	snd $port, type => data...;	23	snd $port, type => data...;
		24	snd $port, @msg;
		25	snd @msg_with_first_element_being_a_port;
14		26
15	$SELF # receiving/own port id in rcv callbacks	27	# creating/using ports, the simple way
		28	my $simple_port = port { my @msg = @_; 0 };
16		29
17	rcv $port, smartmatch => $cb->($port, @msg);	30	# creating/using ports, tagged message matching
18		31	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
21	rcv $port1, pong => sub { warn "pong received\n" };	33	rcv $port, pong => sub { warn "pong received\n"; 0 };
22	snd $port2, ping => $port1;
23		34
24	# more, smarter, matches (_any_ is exported by this module)	35	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	36	my $port = spawn $node, $initfunc, @initdata;
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	37
		38	# monitoring
		39	mon $port, $cb->(@msg) # callback is invoked on death
		40	mon $port, $otherport # kill otherport on abnormal death
		41	mon $port, $otherport, @msg # send message on death
		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		46	AnyEvent::MP::Intro - outdated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.
27		51
28	=head1 DESCRIPTION	52	=head1 DESCRIPTION
29		53
30	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
31		55
…		…
35	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>
36	manual page.	60	manual page.
37		61
38	At the moment, this module family is severly broken and underdocumented,	62	At the moment, this module family is severly broken and underdocumented,
39	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 -
40	stay tuned! The basic API should be finished, however.	64	stay tuned!
41		65
42	=head1 CONCEPTS	66	=head1 CONCEPTS
43		67
44	=over 4	68	=over 4
45		69
46	=item port	70	=item port
47		71
48	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).
49		73
50	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
51	messages. All C<rcv> handlers will receive messages they match, messages	75	some messages. Messages will not be queued.
52	will not be queued.
53		76
54	=item port id - C<noderef#portname>	77	=item port id - C<noderef#portname>
55		78
56	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
57	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
58	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
59	reference.	82	reference.
60		83
61	=item node	84	=item node
62		85
63	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,
64	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
65	create new ports, among other things.	88	ports.
66		89
67	Nodes are either private (single-process only), slaves (connected to a	90	Nodes are either private (single-process only), slaves (connected to a
68	master node only) or public nodes (connectable from unrelated nodes).	91	master node only) or public nodes (connectable from unrelated nodes).
69		92
70	=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>
…		…
90		113
91	=cut	114	=cut
92		115
93	package AnyEvent::MP;	116	package AnyEvent::MP;
94		117
95	use AnyEvent::MP::Base;	118	use AnyEvent::MP::Kernel;
96		119
97	use common::sense;	120	use common::sense;
98		121
99	use Carp ();	122	use Carp ();
100		123
101	use AE ();	124	use AE ();
102		125
103	use base "Exporter";	126	use base "Exporter";
104		127
105	our $VERSION = '0.1';	128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		129
106	our @EXPORT = qw(	130	our @EXPORT = qw(
107	NODE $NODE *SELF node_of _any_	131	NODE $NODE *SELF node_of _any_
108	resolve_node initialise_node	132	resolve_node initialise_node
109	snd rcv mon kil reg psub	133	snd rcv mon kil reg psub spawn
110	port	134	port
111	);	135	);
112		136
113	our $SELF;	137	our $SELF;
114		138
…		…
118	kil $SELF, die => $msg;	142	kil $SELF, die => $msg;
119	}	143	}
120		144
121	=item $thisnode = NODE / $NODE	145	=item $thisnode = NODE / $NODE
122		146
123	The C<NODE> function returns, and the C<$NODE> variable contains	147	The C<NODE> function returns, and the C<$NODE> variable contains the
124	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
125	to C<become_public> or C<become_slave>, after which all local port	149	C<initialise_node>.
126	identifiers become invalid.
127		150
128	=item $noderef = node_of $port	151	=item $noderef = node_of $port
129		152
130	Extracts and returns the noderef from a portid or a noderef.	153	Extracts and returns the noderef from a port ID or a noderef.
		154
		155	=item initialise_node $noderef, $seednode, $seednode...
		156
		157	=item initialise_node "slave/", $master, $master...
		158
		159	Before a node can talk to other nodes on the network it has to initialise
		160	itself - the minimum a node needs to know is it's own name, and optionally
		161	it should know the noderefs of some other nodes in the network.
		162
		163	This function initialises a node - it must be called exactly once (or
		164	never) before calling other AnyEvent::MP functions.
		165
		166	All arguments (optionally except for the first) are noderefs, which can be
		167	either resolved or unresolved.
		168
		169	The first argument will be looked up in the configuration database first
		170	(if it is C<undef> then the current nodename will be used instead) to find
		171	the relevant configuration profile (see L<aemp>). If none is found then
		172	the default configuration is used. The configuration supplies additional
		173	seed/master nodes and can override the actual noderef.
		174
		175	There are two types of networked nodes, public nodes and slave nodes:
		176
		177	=over 4
		178
		179	=item public nodes
		180
		181	For public nodes, C<$noderef> (supplied either directly to
		182	C<initialise_node> or indirectly via a profile or the nodename) must be a
		183	noderef (possibly unresolved, in which case it will be resolved).
		184
		185	After resolving, the node will bind itself on all endpoints and try to
		186	connect to all additional C<$seednodes> that are specified. Seednodes are
		187	optional and can be used to quickly bootstrap the node into an existing
		188	network.
		189
		190	=item slave nodes
		191
		192	When the C<$noderef> (either as given or overriden by the config file)
		193	is the special string C<slave/>, then the node will become a slave
		194	node. Slave nodes cannot be contacted from outside and will route most of
		195	their traffic to the master node that they attach to.
		196
		197	At least one additional noderef is required (either by specifying it
		198	directly or because it is part of the configuration profile): The node
		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.
		201
		202	=back
		203
		204	This function will block until all nodes have been resolved and, for slave
		205	nodes, until it has successfully established a connection to a master
		206	server.
		207
		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.
		211
		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";
		223
		224	Example: become a public node, and try to contact some well-known master
		225	servers to become part of the network.
		226
		227	initialise_node undef, "master1", "master2";
		228
		229	Example: become a public node listening on port C<4041>.
		230
		231	initialise_node 4041;
		232
		233	Example: become a public node, only visible on localhost port 4044.
		234
		235	initialise_node "localhost:4044";
131		236
132	=item $cv = resolve_node $noderef	237	=item $cv = resolve_node $noderef
133		238
134	Takes an unresolved node reference that may contain hostnames and	239	Takes an unresolved node reference that may contain hostnames and
135	abbreviated IDs, resolves all of them and returns a resolved node	240	abbreviated IDs, resolves all of them and returns a resolved node
…		…
172	=item snd $port, type => @data	277	=item snd $port, type => @data
173		278
174	=item snd $port, @msg	279	=item snd $port, @msg
175		280
176	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
177	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.
178	stringifies a sa port ID (such as a port object :).
179		283
180	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
181	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
182	type etc.).	286	type etc.).
183		287
184	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
185	function: modifying any argument is not allowed and can cause many	289	function: modifying any argument is not allowed and can cause many
186	problems.	290	problems.
…		…
191	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
192	node, anything can be passed.	296	node, anything can be passed.
193		297
194	=item $local_port = port	298	=item $local_port = port
195		299
196	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
197	matching port ("full port") or a single-callback port ("miniport"),	301	no callbacks set and will throw an error when it receives messages.
198	depending on how C<rcv> callbacks are bound to the object.
199		302
200	=item $port = port { my @msg = @_; $finished }	303	=item $local_port = port { my @msg = @_ }
201		304
202	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
203	matching behind it, and returns its ID. Semantically the same as creating
204	a port and calling C<rcv $port, $callback> on it.	306	creating a port and calling C<rcv $port, $callback> on it.
205		307
206	The block will be called for every message received on the port. When the	308	The block will be called for every message received on the port, with the
207	callback returns a true value its job is considered "done" and the port	309	global variable C<$SELF> set to the port ID. Runtime errors will cause the
208	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.
209		312
210	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:
211	be passed to the callback.
212		314
213	If you need the local port id in the callback, this works nicely:	315	my $port = port {
214		316	my @msg = @_;
215	my $port; $port = port {	317	...
216	snd $otherport, reply => $port;	318	kil $SELF;
217	};	319	};
218		320
219	=cut	321	=cut
220		322
221	sub rcv($@);	323	sub rcv($@);
		324
		325	sub _kilme {
		326	die "received message on port without callback";
		327	}
222		328
223	sub port(;&) {	329	sub port(;&) {
224	my $id = "$UNIQ." . $ID++;	330	my $id = "$UNIQ." . $ID++;
225	my $port = "$NODE#$id";	331	my $port = "$NODE#$id";
226		332
227	if (@_) {	333	rcv $port, shift \|\| \&_kilme;
228	rcv $port, shift;
229	} else {
230	$PORT{$id} = sub { }; # nop
231	}
232		334
233	$port	335	$port
234	}	336	}
235		337
236	=item reg $port, $name
237
238	Registers the given port under the name C<$name>. If the name already
239	exists it is replaced.
240
241	A port can only be registered under one well known name.
242
243	A port automatically becomes unregistered when it is killed.
244
245	=cut
246
247	sub reg(@) {
248	my ($port, $name) = @_;
249
250	$REG{$name} = $port;
251	}
252
253	=item rcv $port, $callback->(@msg)	338	=item rcv $local_port, $callback->(@msg)
254		339
255	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
256	one if required).	341	remove the default callback: use C<sub { }> to disable it, or better
257		342	C<kil> the port when it is no longer needed.
258	=item rcv $port, tagstring => $callback->(@msg), ...
259
260	=item rcv $port, $smartmatch => $callback->(@msg), ...
261
262	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
263
264	Register callbacks to be called on matching messages on the given full
265	port (after converting it to one if required).
266
267	The callback has to return a true value when its work is done, after
268	which is will be removed, or a false value in which case it will stay
269	registered.
270		343
271	The global C<$SELF> (exported by this module) contains C<$port> while	344	The global C<$SELF> (exported by this module) contains C<$port> while
272	executing the callback.	345	executing the callback. Runtime errors during callback execution will
		346	result in the port being C<kil>ed.
273		347
274	Runtime errors wdurign callback execution will result in the port being	348	The default callback received all messages not matched by a more specific
275	C<kil>ed.	349	C<tag> match.
276		350
277	If the match is an array reference, then it will be matched against the	351	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
278	first elements of the message, otherwise only the first element is being
279	matched.
280		352
281	Any element in the match that is specified as C<_any_> (a function	353	Register callbacks to be called on messages starting with the given tag on
282	exported by this module) matches any single element of the message.	354	the given port (and return the port), or unregister it (when C<$callback>
		355	is C<$undef>).
283		356
284	While not required, it is highly recommended that the first matching	357	The original message will be passed to the callback, after the first
285	element is a string identifying the message. The one-string-only match is	358	element (the tag) has been removed. The callback will use the same
286	also the most efficient match (by far).	359	environment as the default callback (see above).
		360
		361	Example: create a port and bind receivers on it in one go.
		362
		363	my $port = rcv port,
		364	msg1 => sub { ... },
		365	msg2 => sub { ... },
		366	;
		367
		368	Example: create a port, bind receivers and send it in a message elsewhere
		369	in one go:
		370
		371	snd $otherport, reply =>
		372	rcv port,
		373	msg1 => sub { ... },
		374	...
		375	;
287		376
288	=cut	377	=cut
289		378
290	sub rcv($@) {	379	sub rcv($@) {
291	my $port = shift;	380	my $port = shift;
292	my ($noderef, $portid) = split /#/, $port, 2;	381	my ($noderef, $portid) = split /#/, $port, 2;
293		382
294	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	383	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
295	or Carp::croak "$port: rcv can only be called on local ports, caught";	384	or Carp::croak "$port: rcv can only be called on local ports, caught";
296		385
297	if (@_ == 1) {	386	while (@_) {
		387	if (ref $_[0]) {
		388	if (my $self = $PORT_DATA{$portid}) {
		389	"AnyEvent::MP::Port" eq ref $self
		390	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		391
		392	$self->[2] = shift;
		393	} else {
298	my $cb = shift;	394	my $cb = shift;
299	delete $PORT_DATA{$portid};
300	$PORT{$portid} = sub {	395	$PORT{$portid} = sub {
301	local $SELF = $port;	396	local $SELF = $port;
302	eval {	397	eval { &$cb }; _self_die if $@;
303	&$cb	398	};
304	and kil $port;
305	};	399	}
306	_self_die if $@;	400	} elsif (defined $_[0]) {
307	};
308	} else {
309	my $self = $PORT_DATA{$portid} \|\|= do {	401	my $self = $PORT_DATA{$portid} \|\|= do {
310	my $self = bless {	402	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
311	id => $port,
312	}, "AnyEvent::MP::Port";
313		403
314	$PORT{$portid} = sub {	404	$PORT{$portid} = sub {
315	local $SELF = $port;	405	local $SELF = $port;
316		406
317	eval {
318	for (@{ $self->{rc0}{$_[0]} }) {	407	if (my $cb = $self->[1]{$_[0]}) {
319	$_ && &{$_->[0]}	408	shift;
320	&& undef $_;	409	eval { &$cb }; _self_die if $@;
321	}	410	} else {
322
323	for (@{ $self->{rcv}{$_[0]} }) {
324	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
325	&& &{$_->[0]}	411	&{ $self->[0] };
326	&& undef $_;
327	}
328
329	for (@{ $self->{any} }) {
330	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
331	&& &{$_->[0]}
332	&& undef $_;
333	}	412	}
334	};	413	};
335	_self_die if $@;	414
		415	$self
336	};	416	};
337		417
338	$self
339	};
340
341	"AnyEvent::MP::Port" eq ref $self	418	"AnyEvent::MP::Port" eq ref $self
342	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	419	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
343		420
344	while (@_) {
345	my ($match, $cb) = splice @_, 0, 2;	421	my ($tag, $cb) = splice @_, 0, 2;
346		422
347	if (!ref $match) {	423	if (defined $cb) {
348	push @{ $self->{rc0}{$match} }, [$cb];	424	$self->[1]{$tag} = $cb;
349	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
350	my ($type, @match) = @$match;
351	@match
352	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
353	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
354	} else {	425	} else {
355	push @{ $self->{any} }, [$cb, $match];	426	delete $self->[1]{$tag};
356	}	427	}
357	}	428	}
358	}	429	}
359		430
360	$port	431	$port
…		…
398	}	469	}
399	}	470	}
400		471
401	=item $guard = mon $port, $cb->(@reason)	472	=item $guard = mon $port, $cb->(@reason)
402		473
403	=item $guard = mon $port, $otherport	474	=item $guard = mon $port, $rcvport
404		475
		476	=item $guard = mon $port
		477
405	=item $guard = mon $port, $otherport, @msg	478	=item $guard = mon $port, $rcvport, @msg
406		479
407	Monitor the given port and do something when the port is killed.	480	Monitor the given port and do something when the port is killed or
		481	messages to it were lost, and optionally return a guard that can be used
		482	to stop monitoring again.
408		483
		484	C<mon> effectively guarantees that, in the absence of hardware failures,
		485	that after starting the monitor, either all messages sent to the port
		486	will arrive, or the monitoring action will be invoked after possible
		487	message loss has been detected. No messages will be lost "in between"
		488	(after the first lost message no further messages will be received by the
		489	port). After the monitoring action was invoked, further messages might get
		490	delivered again.
		491
409	In the first form, the callback is simply called with any number	492	In the first form (callback), the callback is simply called with any
410	of C<@reason> elements (no @reason means that the port was deleted	493	number of C<@reason> elements (no @reason means that the port was deleted
411	"normally"). Note also that I<< the callback B<must> never die >>, so use	494	"normally"). Note also that I<< the callback B<must> never die >>, so use
412	C<eval> if unsure.	495	C<eval> if unsure.
413		496
414	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	497	In the second form (another port given), the other port (C<$rcvport>)
415	a @reason was specified, i.e. on "normal" kils nothing happens, while	498	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
416	under all other conditions, the other port is killed with the same reason.	499	"normal" kils nothing happens, while under all other conditions, the other
		500	port is killed with the same reason.
417		501
		502	The third form (kill self) is the same as the second form, except that
		503	C<$rvport> defaults to C<$SELF>.
		504
418	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	505	In the last form (message), a message of the form C<@msg, @reason> will be
		506	C<snd>.
		507
		508	As a rule of thumb, monitoring requests should always monitor a port from
		509	a local port (or callback). The reason is that kill messages might get
		510	lost, just like any other message. Another less obvious reason is that
		511	even monitoring requests can get lost (for exmaple, when the connection
		512	to the other node goes down permanently). When monitoring a port locally
		513	these problems do not exist.
419		514
420	Example: call a given callback when C<$port> is killed.	515	Example: call a given callback when C<$port> is killed.
421		516
422	mon $port, sub { warn "port died because of <@_>\n" };	517	mon $port, sub { warn "port died because of <@_>\n" };
423		518
424	Example: kill ourselves when C<$port> is killed abnormally.	519	Example: kill ourselves when C<$port> is killed abnormally.
425		520
426	mon $port, $self;	521	mon $port;
427		522
428	Example: send us a restart message another C<$port> is killed.	523	Example: send us a restart message when another C<$port> is killed.
429		524
430	mon $port, $self => "restart";	525	mon $port, $self => "restart";
431		526
432	=cut	527	=cut
433		528
434	sub mon {	529	sub mon {
435	my ($noderef, $port) = split /#/, shift, 2;	530	my ($noderef, $port) = split /#/, shift, 2;
436		531
437	my $node = $NODE{$noderef} \|\| add_node $noderef;	532	my $node = $NODE{$noderef} \|\| add_node $noderef;
438		533
439	my $cb = shift;	534	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
440		535
441	unless (ref $cb) {	536	unless (ref $cb) {
442	if (@_) {	537	if (@_) {
443	# send a kill info message	538	# send a kill info message
444	my (@msg) = ($cb, @_);	539	my (@msg) = ($cb, @_);
…		…
475	=cut	570	=cut
476		571
477	sub mon_guard {	572	sub mon_guard {
478	my ($port, @refs) = @_;	573	my ($port, @refs) = @_;
479		574
		575	#TODO: mon-less form?
		576
480	mon $port, sub { 0 && @refs }	577	mon $port, sub { 0 && @refs }
481	}	578	}
482		579
483	=item lnk $port1, $port2
484
485	Link two ports. This is simply a shorthand for:
486
487	mon $port1, $port2;
488	mon $port2, $port1;
489
490	It means that if either one is killed abnormally, the other one gets
491	killed as well.
492
493	=item kil $port[, @reason]	580	=item kil $port[, @reason]
494		581
495	Kill the specified port with the given C<@reason>.	582	Kill the specified port with the given C<@reason>.
496		583
497	If no C<@reason> is specified, then the port is killed "normally" (linked	584	If no C<@reason> is specified, then the port is killed "normally" (linked
…		…
504	will be reported as reason C<< die => $@ >>.	591	will be reported as reason C<< die => $@ >>.
505		592
506	Transport/communication errors are reported as C<< transport_error =>	593	Transport/communication errors are reported as C<< transport_error =>
507	$message >>.	594	$message >>.
508		595
509	=back
510
511	=head1 FUNCTIONS FOR NODES
512
513	=over 4
514
515	=item initialise_node $noderef, $seednode, $seednode...
516
517	=item initialise_node "slave/", $master, $master...
518
519	Initialises a node - must be called exactly once before calling other
520	AnyEvent::MP functions when talking to other nodes is required.
521
522	All arguments are noderefs, which can be either resolved or unresolved.
523
524	There are two types of networked nodes, public nodes and slave nodes:
525
526	=over 4
527
528	=item public nodes
529
530	For public nodes, C<$noderef> must either be a (possibly unresolved)
531	noderef, in which case it will be resolved, or C<undef> (or missing), in
532	which case the noderef will be guessed.
533
534	Afterwards, the node will bind itself on all endpoints and try to connect
535	to all additional C<$seednodes> that are specified. Seednodes are optional
536	and can be used to quickly bootstrap the node into an existing network.
537
538	=item slave nodes
539
540	When the C<$noderef> is the special string C<slave/>, then the node will
541	become a slave node. Slave nodes cannot be contacted from outside and will
542	route most of their traffic to the master node that they attach to.
543
544	At least one additional noderef is required: The node will try to connect
545	to all of them and will become a slave attached to the first node it can
546	successfully connect to.
547
548	=back
549
550	This function will block until all nodes have been resolved and, for slave
551	nodes, until it has successfully established a connection to a master
552	server.
553
554	Example: become a public node listening on the default node.
555
556	initialise_node;
557
558	Example: become a public node, and try to contact some well-known master
559	servers to become part of the network.
560
561	initialise_node undef, "master1", "master2";
562
563	Example: become a public node listening on port C<4041>.
564
565	initialise_node 4041;
566
567	Example: become a public node, only visible on localhost port 4044.
568
569	initialise_node "locahost:4044";
570
571	Example: become a slave node to any of the specified master servers.
572
573	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
574
575	=cut	596	=cut
		597
		598	=item $port = spawn $node, $initfunc[, @initdata]
		599
		600	Creates a port on the node C<$node> (which can also be a port ID, in which
		601	case it's the node where that port resides).
		602
		603	The port ID of the newly created port is return immediately, and it is
		604	permissible to immediately start sending messages or monitor the port.
		605
		606	After the port has been created, the init function is
		607	called. This function must be a fully-qualified function name
		608	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		609	program, use C<::name>.
		610
		611	If the function doesn't exist, then the node tries to C<require>
		612	the package, then the package above the package and so on (e.g.
		613	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		614	exists or it runs out of package names.
		615
		616	The init function is then called with the newly-created port as context
		617	object (C<$SELF>) and the C<@initdata> values as arguments.
		618
		619	A common idiom is to pass your own port, monitor the spawned port, and
		620	in the init function, monitor the original port. This two-way monitoring
		621	ensures that both ports get cleaned up when there is a problem.
		622
		623	Example: spawn a chat server port on C<$othernode>.
		624
		625	# this node, executed from within a port context:
		626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		627	mon $server;
		628
		629	# init function on C<$othernode>
		630	sub connect {
		631	my ($srcport) = @_;
		632
		633	mon $srcport;
		634
		635	rcv $SELF, sub {
		636	...
		637	};
		638	}
		639
		640	=cut
		641
		642	sub _spawn {
		643	my $port = shift;
		644	my $init = shift;
		645
		646	local $SELF = "$NODE#$port";
		647	eval {
		648	&{ load_func $init }
		649	};
		650	_self_die if $@;
		651	}
		652
		653	sub spawn(@) {
		654	my ($noderef, undef) = split /#/, shift, 2;
		655
		656	my $id = "$RUNIQ." . $ID++;
		657
		658	$_[0] =~ /::/
		659	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		660
		661	($NODE{$noderef} \|\| add_node $noderef)
		662	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
		663
		664	"$noderef#$id"
		665	}
576		666
577	=back	667	=back
578		668
579	=head1 NODE MESSAGES	669	=head1 NODE MESSAGES
580		670
…		…
622		712
623	=back	713	=back
624		714
625	=head1 AnyEvent::MP vs. Distributed Erlang	715	=head1 AnyEvent::MP vs. Distributed Erlang
626		716
627	AnyEvent::MP got lots of its ideas from distributed erlang (erlang node	717	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
628	== aemp node, erlang process == aemp port), so many of the documents and	718	== aemp node, Erlang process == aemp port), so many of the documents and
629	programming techniques employed by erlang apply to AnyEvent::MP. Here is a	719	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
630	sample:	720	sample:
631		721
632	http://www.erlang.se/doc/programming_rules.shtml	722	http://www.Erlang.se/doc/programming_rules.shtml
633	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	723	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
634	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6	724	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6
635	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	725	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
636		726
637	Despite the similarities, there are also some important differences:	727	Despite the similarities, there are also some important differences:
638		728
639	=over 4	729	=over 4
640		730
…		…
645	convenience functionality.	735	convenience functionality.
646		736
647	This means that AEMP requires a less tightly controlled environment at the	737	This means that AEMP requires a less tightly controlled environment at the
648	cost of longer node references and a slightly higher management overhead.	738	cost of longer node references and a slightly higher management overhead.
649		739
		740	=item Erlang has a "remote ports are like local ports" philosophy, AEMP
		741	uses "local ports are like remote ports".
		742
		743	The failure modes for local ports are quite different (runtime errors
		744	only) then for remote ports - when a local port dies, you I<know> it dies,
		745	when a connection to another node dies, you know nothing about the other
		746	port.
		747
		748	Erlang pretends remote ports are as reliable as local ports, even when
		749	they are not.
		750
		751	AEMP encourages a "treat remote ports differently" philosophy, with local
		752	ports being the special case/exception, where transport errors cannot
		753	occur.
		754
650	=item * Erlang uses processes and a mailbox, AEMP does not queue.	755	=item * Erlang uses processes and a mailbox, AEMP does not queue.
651		756
652	Erlang uses processes that selctively receive messages, and therefore	757	Erlang uses processes that selectively receive messages, and therefore
653	needs a queue. AEMP is event based, queuing messages would serve no useful	758	needs a queue. AEMP is event based, queuing messages would serve no
654	purpose.	759	useful purpose. For the same reason the pattern-matching abilities of
		760	AnyEvent::MP are more limited, as there is little need to be able to
		761	filter messages without dequeing them.
655		762
656	(But see L<Coro::MP> for a more erlang-like process model on top of AEMP).	763	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
657		764
658	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	765	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
659		766
660	Sending messages in erlang is synchronous and blocks the process. AEMP	767	Sending messages in Erlang is synchronous and blocks the process (and
661	sends are immediate, connection establishment is handled in the	768	so does not need a queue that can overflow). AEMP sends are immediate,
662	background.	769	connection establishment is handled in the background.
663		770
664	=item * Erlang can silently lose messages, AEMP cannot.	771	=item * Erlang suffers from silent message loss, AEMP does not.
665		772
666	Erlang makes few guarantees on messages delivery - messages can get lost	773	Erlang makes few guarantees on messages delivery - messages can get lost
667	without any of the processes realising it (i.e. you send messages a, b,	774	without any of the processes realising it (i.e. you send messages a, b,
668	and c, and the other side only receives messages a and c).	775	and c, and the other side only receives messages a and c).
669		776
670	AEMP guarantees correct ordering, and the guarantee that there are no	777	AEMP guarantees correct ordering, and the guarantee that there are no
671	holes in the message sequence.	778	holes in the message sequence.
672		779
673	=item * In erlang, processes can be declared dead and later be found to be	780	=item * In Erlang, processes can be declared dead and later be found to be
674	alive.	781	alive.
675		782
676	In erlang it can happen that a monitored process is declared dead and	783	In Erlang it can happen that a monitored process is declared dead and
677	linked processes get killed, but later it turns out that the process is	784	linked processes get killed, but later it turns out that the process is
678	still alive - and can receive messages.	785	still alive - and can receive messages.
679		786
680	In AEMP, when port monitoring detects a port as dead, then that port will	787	In AEMP, when port monitoring detects a port as dead, then that port will
681	eventually be killed - it cannot happen that a node detects a port as dead	788	eventually be killed - it cannot happen that a node detects a port as dead
682	and then later sends messages to it, finding it is still alive.	789	and then later sends messages to it, finding it is still alive.
683		790
684	=item * Erlang can send messages to the wrong port, AEMP does not.	791	=item * Erlang can send messages to the wrong port, AEMP does not.
685		792
686	In erlang it is quite possible that a node that restarts reuses a process	793	In Erlang it is quite likely that a node that restarts reuses a process ID
687	ID known to other nodes for a completely different process, causing	794	known to other nodes for a completely different process, causing messages
688	messages destined for that process to end up in an unrelated process.	795	destined for that process to end up in an unrelated process.
689		796
690	AEMP never reuses port IDs, so old messages or old port IDs floating	797	AEMP never reuses port IDs, so old messages or old port IDs floating
691	around in the network will not be sent to an unrelated port.	798	around in the network will not be sent to an unrelated port.
692		799
693	=item * Erlang uses unprotected connections, AEMP uses secure	800	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
697	securely authenticate nodes.	804	securely authenticate nodes.
698		805
699	=item * The AEMP protocol is optimised for both text-based and binary	806	=item * The AEMP protocol is optimised for both text-based and binary
700	communications.	807	communications.
701		808
702	The AEMP protocol, unlike the erlang protocol, supports both	809	The AEMP protocol, unlike the Erlang protocol, supports both
703	language-independent text-only protocols (good for debugging) and binary,	810	language-independent text-only protocols (good for debugging) and binary,
704	language-specific serialisers (e.g. Storable).	811	language-specific serialisers (e.g. Storable).
705		812
706	It has also been carefully designed to be implementable in other languages	813	It has also been carefully designed to be implementable in other languages
707	with a minimum of work while gracefully degrading fucntionality to make the	814	with a minimum of work while gracefully degrading fucntionality to make the
708	protocol simple.	815	protocol simple.
709		816
		817	=item * AEMP has more flexible monitoring options than Erlang.
		818
		819	In Erlang, you can chose to receive I<all> exit signals as messages
		820	or I<none>, there is no in-between, so monitoring single processes is
		821	difficult to implement. Monitoring in AEMP is more flexible than in
		822	Erlang, as one can choose between automatic kill, exit message or callback
		823	on a per-process basis.
		824
		825	=item * Erlang tries to hide remote/local connections, AEMP does not.
		826
		827	Monitoring in Erlang is not an indicator of process death/crashes,
		828	as linking is (except linking is unreliable in Erlang).
		829
		830	In AEMP, you don't "look up" registered port names or send to named ports
		831	that might or might not be persistent. Instead, you normally spawn a port
		832	on the remote node. The init function monitors the you, and you monitor
		833	the remote port. Since both monitors are local to the node, they are much
		834	more reliable.
		835
		836	This also saves round-trips and avoids sending messages to the wrong port
		837	(hard to do in Erlang).
		838
		839	=back
		840
		841	=head1 RATIONALE
		842
		843	=over 4
		844
		845	=item Why strings for ports and noderefs, why not objects?
		846
		847	We considered "objects", but found that the actual number of methods
		848	thatc an be called are very low. Since port IDs and noderefs travel over
		849	the network frequently, the serialising/deserialising would add lots of
		850	overhead, as well as having to keep a proxy object.
		851
		852	Strings can easily be printed, easily serialised etc. and need no special
		853	procedures to be "valid".
		854
		855	And a a miniport consists of a single closure stored in a global hash - it
		856	can't become much cheaper.
		857
		858	=item Why favour JSON, why not real serialising format such as Storable?
		859
		860	In fact, any AnyEvent::MP node will happily accept Storable as framing
		861	format, but currently there is no way to make a node use Storable by
		862	default.
		863
		864	The default framing protocol is JSON because a) JSON::XS is many times
		865	faster for small messages and b) most importantly, after years of
		866	experience we found that object serialisation is causing more problems
		867	than it gains: Just like function calls, objects simply do not travel
		868	easily over the network, mostly because they will always be a copy, so you
		869	always have to re-think your design.
		870
		871	Keeping your messages simple, concentrating on data structures rather than
		872	objects, will keep your messages clean, tidy and efficient.
		873
710	=back	874	=back
711		875
712	=head1 SEE ALSO	876	=head1 SEE ALSO
713		877
714	L<AnyEvent>.	878	L<AnyEvent>.

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Revision 1.53 by root, Fri Aug 14 15:31:21 2009 UTC