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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.32 by root, Wed Aug 5 19:58:46 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		46	AnyEvent::MP::Intro - outdated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 $portid	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 $noderef
133		238
134	Takes an unresolved node reference that may contain hostnames and	239	Takes an unresolved node reference that may contain hostnames and
135	abbreviated IDs, resolves all of them and returns a resolved node	240	abbreviated IDs, resolves all of them and returns a resolved node
…		…
167		272
168	Due to some quirks in how perl exports variables, it is impossible to	273	Due to some quirks in how perl exports variables, it is impossible to
169	just export C<$SELF>, all the symbols called C<SELF> are exported by this	274	just export C<$SELF>, all the symbols called C<SELF> are exported by this
170	module, but only C<$SELF> is currently used.	275	module, but only C<$SELF> is currently used.
171		276
172	=item snd $portid, type => @data	277	=item snd $port, type => @data
173		278
174	=item snd $portid, @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 $portid = port { my @msg = @_; $finished }	303	=item $local_port = port { my @msg = @_ }
201		304
202	Creates a "mini port", that is, a very lightweight port without any	305	Creates a new local port, and returns its ID. Semantically the same as
203	pattern matching behind it, and returns its ID.	306	creating a port and calling C<rcv $port, $callback> on it.
204		307
205	The block will be called for every message received on the port. When the	308	The block will be called for every message received on the port, with the
206	callback returns a true value its job is considered "done" and the port	309	global variable C<$SELF> set to the port ID. Runtime errors will cause the
207	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.
208		312
209	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:
210	be passed to the callback.
211		314
212	If you need the local port id in the callback, this works nicely:	315	my $port = port {
213		316	my @msg = @_;
214	my $port; $port = port {	317	...
215	snd $otherport, reply => $port;	318	kil $SELF;
216	};	319	};
217		320
218	=cut	321	=cut
		322
		323	sub rcv($@);
		324
		325	sub _kilme {
		326	die "received message on port without callback";
		327	}
219		328
220	sub port(;&) {	329	sub port(;&) {
221	my $id = "$UNIQ." . $ID++;	330	my $id = "$UNIQ." . $ID++;
222	my $port = "$NODE#$id";	331	my $port = "$NODE#$id";
223		332
224	if (@_) {	333	rcv $port, shift \|\| \&_kilme;
225	my $cb = shift;
226	$PORT{$id} = sub {
227	local $SELF = $port;
228	eval {
229	&$cb
230	and kil $id;
231	};
232	_self_die if $@;
233	};
234	} else {
235	my $self = bless {
236	id => "$NODE#$id",
237	}, "AnyEvent::MP::Port";
238
239	$PORT_DATA{$id} = $self;
240	$PORT{$id} = sub {
241	local $SELF = $port;
242
243	eval {
244	for (@{ $self->{rc0}{$_[0]} }) {
245	$_ && &{$_->[0]}
246	&& undef $_;
247	}
248
249	for (@{ $self->{rcv}{$_[0]} }) {
250	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
251	&& &{$_->[0]}
252	&& undef $_;
253	}
254
255	for (@{ $self->{any} }) {
256	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
257	&& &{$_->[0]}
258	&& undef $_;
259	}
260	};
261	_self_die if $@;
262	};
263	}
264		334
265	$port	335	$port
266	}	336	}
267		337
268	=item reg $portid, $name
269
270	Registers the given port under the name C<$name>. If the name already
271	exists it is replaced.
272
273	A port can only be registered under one well known name.
274
275	A port automatically becomes unregistered when it is killed.
276
277	=cut
278
279	sub reg(@) {
280	my ($portid, $name) = @_;
281
282	$REG{$name} = $portid;
283	}
284
285	=item rcv $portid, $callback->(@msg)	338	=item rcv $local_port, $callback->(@msg)
286		339
287	Replaces the callback on the specified miniport (or newly created port	340	Replaces the default callback on the specified port. There is no way to
288	object, see C<port>). Full ports are configured with the following calls:	341	remove the default callback: use C<sub { }> to disable it, or better
		342	C<kil> the port when it is no longer needed.
289		343
290	=item rcv $portid, tagstring => $callback->(@msg), ...
291
292	=item rcv $portid, $smartmatch => $callback->(@msg), ...
293
294	=item rcv $portid, [$smartmatch...] => $callback->(@msg), ...
295
296	Register callbacks to be called on matching messages on the given full
297	port (or newly created port).
298
299	The callback has to return a true value when its work is done, after
300	which is will be removed, or a false value in which case it will stay
301	registered.
302
303	The global C<$SELF> (exported by this module) contains C<$portid> while	344	The global C<$SELF> (exported by this module) contains C<$port> while
304	executing the callback.	345	executing the callback. Runtime errors during callback execution will
		346	result in the port being C<kil>ed.
305		347
306	Runtime errors wdurign callback execution will result in the port being	348	The default callback received all messages not matched by a more specific
307	C<kil>ed.	349	C<tag> match.
308		350
309	If the match is an array reference, then it will be matched against the	351	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
310	first elements of the message, otherwise only the first element is being
311	matched.
312		352
313	Any element in the match that is specified as C<_any_> (a function	353	Register callbacks to be called on messages starting with the given tag on
314	exported by this module) matches any single element of the message.	354	the given port (and return the port), or unregister it (when C<$callback>
		355	is C<$undef>).
315		356
316	While not required, it is highly recommended that the first matching	357	The original message will be passed to the callback, after the first
317	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
318	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 $otherport, reply =>
		372	rcv port,
		373	msg1 => sub { ... },
		374	...
		375	;
319		376
320	=cut	377	=cut
321		378
322	sub rcv($@) {	379	sub rcv($@) {
323	my $portid = shift;	380	my $port = shift;
324	my ($noderef, $port) = split /#/, $port, 2;	381	my ($noderef, $portid) = split /#/, $port, 2;
325		382
326	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	383	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}
327	or Carp::croak "$noderef#$port: rcv can only be called on local ports, caught";	384	or Carp::croak "$port: rcv can only be called on local ports, caught";
328
329	my $self = $PORT_DATA{$port}
330	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
331
332	"AnyEvent::MP::Port" eq ref $self
333	or Carp::croak "$noderef#$port: rcv can only be called on message matching ports, caught";
334		385
335	while (@_) {	386	while (@_) {
336	my ($match, $cb) = splice @_, 0, 2;
337
338	if (!ref $match) {	387	if (ref $_[0]) {
339	push @{ $self->{rc0}{$match} }, [$cb];	388	if (my $self = $PORT_DATA{$portid}) {
340	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {	389	"AnyEvent::MP::Port" eq ref $self
341	my ($type, @match) = @$match;	390	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
342	@match	391
343	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]	392	$self->[2] = shift;
344	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
345	} else {	393	} else {
346	push @{ $self->{any} }, [$cb, $match];	394	my $cb = shift;
		395	$PORT{$portid} = sub {
		396	local $SELF = $port;
		397	eval { &$cb }; _self_die if $@;
		398	};
		399	}
		400	} elsif (defined $_[0]) {
		401	my $self = $PORT_DATA{$portid} \|\|= do {
		402	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
		403
		404	$PORT{$portid} = sub {
		405	local $SELF = $port;
		406
		407	if (my $cb = $self->[1]{$_[0]}) {
		408	shift;
		409	eval { &$cb }; _self_die if $@;
		410	} else {
		411	&{ $self->[0] };
		412	}
		413	};
		414
		415	$self
		416	};
		417
		418	"AnyEvent::MP::Port" eq ref $self
		419	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		420
		421	my ($tag, $cb) = splice @_, 0, 2;
		422
		423	if (defined $cb) {
		424	$self->[1]{$tag} = $cb;
		425	} else {
		426	delete $self->[1]{$tag};
		427	}
347	}	428	}
348	}	429	}
349		430
350	$portid	431	$port
351	}	432	}
352		433
353	=item $closure = psub { BLOCK }	434	=item $closure = psub { BLOCK }
354		435
355	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	436	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
…		…
386	$res	467	$res
387	}	468	}
388	}	469	}
389	}	470	}
390		471
391	=item $guard = mon $portid, $cb->(@reason)	472	=item $guard = mon $port, $cb->(@reason)
392		473
393	=item $guard = mon $portid, $otherport	474	=item $guard = mon $port, $rcvport
394		475
		476	=item $guard = mon $port
		477
395	=item $guard = mon $portid, $otherport, @msg	478	=item $guard = mon $port, $rcvport, @msg
396		479
397	Monitor the given port and do something when the port is killed.	480	Monitor the given port and do something when the port is killed or
		481	messages to it were lost, and optionally return a guard that can be used
		482	to stop monitoring again.
398		483
		484	C<mon> effectively guarantees that, in the absence of hardware failures,
		485	that after starting the monitor, either all messages sent to the port
		486	will arrive, or the monitoring action will be invoked after possible
		487	message loss has been detected. No messages will be lost "in between"
		488	(after the first lost message no further messages will be received by the
		489	port). After the monitoring action was invoked, further messages might get
		490	delivered again.
		491
399	In the first form, the callback is simply called with any number	492	In the first form (callback), the callback is simply called with any
400	of C<@reason> elements (no @reason means that the port was deleted	493	number of C<@reason> elements (no @reason means that the port was deleted
401	"normally"). Note also that I<< the callback B<must> never die >>, so use	494	"normally"). Note also that I<< the callback B<must> never die >>, so use
402	C<eval> if unsure.	495	C<eval> if unsure.
403		496
404	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	497	In the second form (another port given), the other port (C<$rcvport>)
405	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
406	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.
407		501
		502	The third form (kill self) is the same as the second form, except that
		503	C<$rvport> defaults to C<$SELF>.
		504
408	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.
409		514
410	Example: call a given callback when C<$port> is killed.	515	Example: call a given callback when C<$port> is killed.
411		516
412	mon $port, sub { warn "port died because of <@_>\n" };	517	mon $port, sub { warn "port died because of <@_>\n" };
413		518
414	Example: kill ourselves when C<$port> is killed abnormally.	519	Example: kill ourselves when C<$port> is killed abnormally.
415		520
416	mon $port, $self;	521	mon $port;
417		522
418	Example: send us a restart message another C<$port> is killed.	523	Example: send us a restart message when another C<$port> is killed.
419		524
420	mon $port, $self => "restart";	525	mon $port, $self => "restart";
421		526
422	=cut	527	=cut
423		528
424	sub mon {	529	sub mon {
425	my ($noderef, $port) = split /#/, shift, 2;	530	my ($noderef, $port) = split /#/, shift, 2;
426		531
427	my $node = $NODE{$noderef} \|\| add_node $noderef;	532	my $node = $NODE{$noderef} \|\| add_node $noderef;
428		533
429	my $cb = shift;	534	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
430		535
431	unless (ref $cb) {	536	unless (ref $cb) {
432	if (@_) {	537	if (@_) {
433	# send a kill info message	538	# send a kill info message
434	my (@msg) = ($cb, @_);	539	my (@msg) = ($cb, @_);
…		…
465	=cut	570	=cut
466		571
467	sub mon_guard {	572	sub mon_guard {
468	my ($port, @refs) = @_;	573	my ($port, @refs) = @_;
469		574
		575	#TODO: mon-less form?
		576
470	mon $port, sub { 0 && @refs }	577	mon $port, sub { 0 && @refs }
471	}	578	}
472		579
473	=item lnk $port1, $port2
474
475	Link two ports. This is simply a shorthand for:
476
477	mon $port1, $port2;
478	mon $port2, $port1;
479
480	It means that if either one is killed abnormally, the other one gets
481	killed as well.
482
483	=item kil $portid[, @reason]	580	=item kil $port[, @reason]
484		581
485	Kill the specified port with the given C<@reason>.	582	Kill the specified port with the given C<@reason>.
486		583
487	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
488	ports will not be kileld, or even notified).	585	ports will not be kileld, or even notified).
…		…
494	will be reported as reason C<< die => $@ >>.	591	will be reported as reason C<< die => $@ >>.
495		592
496	Transport/communication errors are reported as C<< transport_error =>	593	Transport/communication errors are reported as C<< transport_error =>
497	$message >>.	594	$message >>.
498		595
499	=back
500
501	=head1 FUNCTIONS FOR NODES
502
503	=over 4
504
505	=item become_public $noderef
506
507	Tells the node to become a public node, i.e. reachable from other nodes.
508
509	The first argument is the (unresolved) node reference of the local node
510	(if missing then the empty string is used).
511
512	It is quite common to not specify anything, in which case the local node
513	tries to listen on the default port, or to only specify a port number, in
514	which case AnyEvent::MP tries to guess the local addresses.
515
516	=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	}
517		666
518	=back	667	=back
519		668
520	=head1 NODE MESSAGES	669	=head1 NODE MESSAGES
521		670
…		…
563		712
564	=back	713	=back
565		714
566	=head1 AnyEvent::MP vs. Distributed Erlang	715	=head1 AnyEvent::MP vs. Distributed Erlang
567		716
568	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
569	== 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
570	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
571	sample:	720	sample:
572		721
573	http://www.erlang.se/doc/programming_rules.shtml	722	http://www.Erlang.se/doc/programming_rules.shtml
574	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
575	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
576	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
577		726
578	Despite the similarities, there are also some important differences:	727	Despite the similarities, there are also some important differences:
579		728
580	=over 4	729	=over 4
581		730
…		…
586	convenience functionality.	735	convenience functionality.
587		736
588	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
589	cost of longer node references and a slightly higher management overhead.	738	cost of longer node references and a slightly higher management overhead.
590		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
591	=item * Erlang uses processes and a mailbox, AEMP does not queue.	755	=item * Erlang uses processes and a mailbox, AEMP does not queue.
592		756
593	Erlang uses processes that selctively receive messages, and therefore	757	Erlang uses processes that selectively receive messages, and therefore
594	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
595	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.
596		762
597	(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).
598		764
599	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	765	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
600		766
601	Sending messages in erlang is synchronous and blocks the process. AEMP	767	Sending messages in Erlang is synchronous and blocks the process (and
602	sends are immediate, connection establishment is handled in the	768	so does not need a queue that can overflow). AEMP sends are immediate,
603	background.	769	connection establishment is handled in the background.
604		770
605	=item * Erlang can silently lose messages, AEMP cannot.	771	=item * Erlang suffers from silent message loss, AEMP does not.
606		772
607	Erlang makes few guarantees on messages delivery - messages can get lost	773	Erlang makes few guarantees on messages delivery - messages can get lost
608	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,
609	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).
610		776
611	AEMP guarantees correct ordering, and the guarantee that there are no	777	AEMP guarantees correct ordering, and the guarantee that there are no
612	holes in the message sequence.	778	holes in the message sequence.
613		779
614	=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
615	alive.	781	alive.
616		782
617	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
618	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
619	still alive - and can receive messages.	785	still alive - and can receive messages.
620		786
621	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
622	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
623	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.
624		790
625	=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.
626		792
627	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
628	ID known to other nodes for a completely different process, causing	794	known to other nodes for a completely different process, causing messages
629	messages destined for that process to end up in an unrelated process.	795	destined for that process to end up in an unrelated process.
630		796
631	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
632	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.
633		799
634	=item * Erlang uses unprotected connections, AEMP uses secure	800	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
638	securely authenticate nodes.	804	securely authenticate nodes.
639		805
640	=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
641	communications.	807	communications.
642		808
643	The AEMP protocol, unlike the erlang protocol, supports both	809	The AEMP protocol, unlike the Erlang protocol, supports both
644	language-independent text-only protocols (good for debugging) and binary,	810	language-independent text-only protocols (good for debugging) and binary,
645	language-specific serialisers (e.g. Storable).	811	language-specific serialisers (e.g. Storable).
646		812
647	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
648	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
649	protocol simple.	815	protocol simple.
650		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
651	=back	874	=back
652		875
653	=head1 SEE ALSO	876	=head1 SEE ALSO
654		877
655	L<AnyEvent>.	878	L<AnyEvent>.

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