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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.36 by root, Thu Aug 6 10:46:48 2009 UTC vs.
Revision 1.63 by root, Thu Aug 27 21:29:37 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;
		17
		18	# ports are message endpoints
		19
		20	# sending messages
13	snd $port, type => data...;	21	snd $port, type => data...;
		22	snd $port, @msg;
		23	snd @msg_with_first_element_being_a_port;
14		24
15	$SELF # receiving/own port id in rcv callbacks	25	# creating/using ports, the simple way
		26	my $simple_port = port { my @msg = @_; 0 };
16		27
17	rcv $port, smartmatch => $cb->($port, @msg);	28	# creating/using ports, tagged message matching
18		29	my $port = port;
19	# examples:
20	rcv $port2, ping => sub { snd $_[0], "pong"; 0 };	30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };
21	rcv $port1, pong => sub { warn "pong received\n" };	31	rcv $port, pong => sub { warn "pong received\n"; 0 };
22	snd $port2, ping => $port1;
23		32
24	# more, smarter, matches (_any_ is exported by this module)	33	# create a port on another node
25	rcv $port, [child_died => $pid] => sub { ...	34	my $port = spawn $node, $initfunc, @initdata;
26	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
27
28	# linking two ports, so they both crash together
29	lnk $port1, $port2;
30		35
31	# monitoring	36	# monitoring
32	mon $port, $cb->(@msg) # callback is invoked on death	37	mon $port, $cb->(@msg) # callback is invoked on death
33	mon $port, $otherport # kill otherport on abnormal death	38	mon $port, $otherport # kill otherport on abnormal death
34	mon $port, $otherport, @msg # send message on death	39	mon $port, $otherport, @msg # send message on death
35		40
		41	=head1 CURRENT STATUS
		42
		43	AnyEvent::MP - stable API, should work
		44	AnyEvent::MP::Intro - outdated
		45	AnyEvent::MP::Kernel - WIP
		46	AnyEvent::MP::Transport - mostly stable
		47
		48	stay tuned.
		49
36	=head1 DESCRIPTION	50	=head1 DESCRIPTION
37		51
38	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
39		53
40	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
…		…
43	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
44	manual page.	58	manual page.
45		59
46	At the moment, this module family is severly broken and underdocumented,	60	At the moment, this module family is severly broken and underdocumented,
47	so do not use. This was uploaded mainly to reserve the CPAN namespace -	61	so do not use. This was uploaded mainly to reserve the CPAN namespace -
48	stay tuned! The basic API should be finished, however.	62	stay tuned!
49		63
50	=head1 CONCEPTS	64	=head1 CONCEPTS
51		65
52	=over 4	66	=over 4
53		67
54	=item port	68	=item port
55		69
56	A port is something you can send messages to (with the C<snd> function).	70	A port is something you can send messages to (with the C<snd> function).
57		71
58	Some ports allow you to register C<rcv> handlers that can match specific	72	Ports allow you to register C<rcv> handlers that can match all or just
59	messages. All C<rcv> handlers will receive messages they match, messages	73	some messages. Messages will not be queued.
60	will not be queued.
61		74
62	=item port id - C<noderef#portname>	75	=item port ID - C<noderef#portname>
63		76
64	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	77	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as
65	separator, and a port name (a printable string of unspecified format). An	78	separator, and a port name (a printable string of unspecified format). An
66	exception is the the node port, whose ID is identical to its node	79	exception is the the node port, whose ID is identical to its node
67	reference.	80	reference.
68		81
69	=item node	82	=item node
70		83
71	A node is a single process containing at least one port - the node	84	A node is a single process containing at least one port - the node port,
72	port. You can send messages to node ports to find existing ports or to	85	which provides nodes to manage each other remotely, and to create new
73	create new ports, among other things.	86	ports.
74		87
75	Nodes are either private (single-process only), slaves (connected to a	88	Nodes are either private (single-process only), slaves (can only talk to
76	master node only) or public nodes (connectable from unrelated nodes).	89	public nodes, but do not need an open port) or public nodes (connectable
		90	from any other node).
77		91
78	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	92	=item node ID - C<[a-za-Z0-9_\-.:]+>
79		93
80	A node reference is a string that either simply identifies the node (for	94	A node ID is a string that either simply identifies the node (for
81	private and slave nodes), or contains a recipe on how to reach a given	95	private and slave nodes), or contains a recipe on how to reach a given
82	node (for public nodes).	96	node (for public nodes).
83		97
84	This recipe is simply a comma-separated list of C<address:port> pairs (for	98	This recipe is simply a comma-separated list of C<address:port> pairs (for
85	TCP/IP, other protocols might look different).	99	TCP/IP, other protocols might look different).
…		…
98		112
99	=cut	113	=cut
100		114
101	package AnyEvent::MP;	115	package AnyEvent::MP;
102		116
103	use AnyEvent::MP::Base;	117	use AnyEvent::MP::Kernel;
104		118
105	use common::sense;	119	use common::sense;
106		120
107	use Carp ();	121	use Carp ();
108		122
109	use AE ();	123	use AE ();
110		124
111	use base "Exporter";	125	use base "Exporter";
112		126
113	our $VERSION = '0.1';	127	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		128
114	our @EXPORT = qw(	129	our @EXPORT = qw(
115	NODE $NODE *SELF node_of _any_	130	NODE $NODE *SELF node_of after
116	resolve_node initialise_node	131	resolve_node initialise_node
117	snd rcv mon kil reg psub	132	snd rcv mon mon_guard kil reg psub spawn
118	port	133	port
119	);	134	);
120		135
121	our $SELF;	136	our $SELF;
122		137
…		…
126	kil $SELF, die => $msg;	141	kil $SELF, die => $msg;
127	}	142	}
128		143
129	=item $thisnode = NODE / $NODE	144	=item $thisnode = NODE / $NODE
130		145
131	The C<NODE> function returns, and the C<$NODE> variable contains	146	The C<NODE> function returns, and the C<$NODE> variable contains the
132	the noderef of the local node. The value is initialised by a call	147	node id of the local node. The value is initialised by a call to
133	to C<become_public> or C<become_slave>, after which all local port	148	C<initialise_node>.
134	identifiers become invalid.
135		149
136	=item $noderef = node_of $port	150	=item $nodeid = node_of $port
137		151
138	Extracts and returns the noderef from a portid or a noderef.	152	Extracts and returns the noderef from a port ID or a node ID.
139		153
140	=item initialise_node $noderef, $seednode, $seednode...	154	=item initialise_node $profile_name
141
142	=item initialise_node "slave/", $master, $master...
143		155
144	Before a node can talk to other nodes on the network it has to initialise	156	Before a node can talk to other nodes on the network it has to initialise
145	itself - the minimum a node needs to know is it's own name, and optionally	157	itself - the minimum a node needs to know is it's own name, and optionally
146	it should know the noderefs of some other nodes in the network.	158	it should know the noderefs of some other nodes in the network.
147		159
148	This function initialises a node - it must be called exactly once (or	160	This function initialises a node - it must be called exactly once (or
149	never) before calling other AnyEvent::MP functions.	161	never) before calling other AnyEvent::MP functions.
150		162
151	All arguments are noderefs, which can be either resolved or unresolved.	163	All arguments (optionally except for the first) are noderefs, which can be
		164	either resolved or unresolved.
		165
		166	The first argument will be looked up in the configuration database first
		167	(if it is C<undef> then the current nodename will be used instead) to find
		168	the relevant configuration profile (see L<aemp>). If none is found then
		169	the default configuration is used. The configuration supplies additional
		170	seed/master nodes and can override the actual noderef.
152		171
153	There are two types of networked nodes, public nodes and slave nodes:	172	There are two types of networked nodes, public nodes and slave nodes:
154		173
155	=over 4	174	=over 4
156		175
157	=item public nodes	176	=item public nodes
158		177
159	For public nodes, C<$noderef> must either be a (possibly unresolved)	178	For public nodes, C<$noderef> (supplied either directly to
160	noderef, in which case it will be resolved, or C<undef> (or missing), in	179	C<initialise_node> or indirectly via a profile or the nodename) must be a
161	which case the noderef will be guessed.	180	noderef (possibly unresolved, in which case it will be resolved).
162		181
163	Afterwards, the node will bind itself on all endpoints and try to connect	182	After resolving, the node will bind itself on all endpoints.
164	to all additional C<$seednodes> that are specified. Seednodes are optional
165	and can be used to quickly bootstrap the node into an existing network.
166		183
167	=item slave nodes	184	=item slave nodes
168		185
169	When the C<$noderef> is the special string C<slave/>, then the node will	186	When the C<$noderef> (either as given or overriden by the config file)
		187	is the special string C<slave/>, then the node will become a slave
170	become a slave node. Slave nodes cannot be contacted from outside and will	188	node. Slave nodes cannot be contacted from outside, and cannot talk to
171	route most of their traffic to the master node that they attach to.	189	each other (at least in this version of AnyEvent::MP).
172		190
173	At least one additional noderef is required: The node will try to connect	191	Slave nodes work by creating connections to all public nodes, using the
174	to all of them and will become a slave attached to the first node it can	192	L<AnyEvent::MP::Global> service.
175	successfully connect to.
176		193
177	=back	194	=back
178		195
179	This function will block until all nodes have been resolved and, for slave	196	After initialising itself, the node will connect to all additional
180	nodes, until it has successfully established a connection to a master	197	C<$seednodes> that are specified diretcly or via a profile. Seednodes are
181	server.	198	optional and can be used to quickly bootstrap the node into an existing
		199	network.
182		200
		201	All the seednodes will also be specially marked to automatically retry
		202	connecting to them indefinitely, so make sure that seednodes are really
		203	reliable and up (this might also change in the future).
		204
183	Example: become a public node listening on the default node.	205	Example: become a public node listening on the guessed noderef, or the one
		206	specified via C<aemp> for the current node. This should be the most common
		207	form of invocation for "daemon"-type nodes.
184		208
185	initialise_node;	209	initialise_node;
		210
		211	Example: become a slave node to any of the the seednodes specified via
		212	C<aemp>. This form is often used for commandline clients.
		213
		214	initialise_node "slave/";
186		215
187	Example: become a public node, and try to contact some well-known master	216	Example: become a public node, and try to contact some well-known master
188	servers to become part of the network.	217	servers to become part of the network.
189		218
190	initialise_node undef, "master1", "master2";	219	initialise_node undef, "master1", "master2";
…		…
193		222
194	initialise_node 4041;	223	initialise_node 4041;
195		224
196	Example: become a public node, only visible on localhost port 4044.	225	Example: become a public node, only visible on localhost port 4044.
197		226
198	initialise_node "locahost:4044";	227	initialise_node "localhost:4044";
199
200	Example: become a slave node to any of the specified master servers.
201
202	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
203		228
204	=item $cv = resolve_node $noderef	229	=item $cv = resolve_node $noderef
205		230
206	Takes an unresolved node reference that may contain hostnames and	231	Takes an unresolved node reference that may contain hostnames and
207	abbreviated IDs, resolves all of them and returns a resolved node	232	abbreviated IDs, resolves all of them and returns a resolved node
…		…
244	=item snd $port, type => @data	269	=item snd $port, type => @data
245		270
246	=item snd $port, @msg	271	=item snd $port, @msg
247		272
248	Send the given message to the given port ID, which can identify either	273	Send the given message to the given port ID, which can identify either
249	a local or a remote port, and can be either a string or soemthignt hat	274	a local or a remote port, and must be a port ID.
250	stringifies a sa port ID (such as a port object :).
251		275
252	While the message can be about anything, it is highly recommended to use a	276	While the message can be about anything, it is highly recommended to use a
253	string as first element (a portid, or some word that indicates a request	277	string as first element (a port ID, or some word that indicates a request
254	type etc.).	278	type etc.).
255		279
256	The message data effectively becomes read-only after a call to this	280	The message data effectively becomes read-only after a call to this
257	function: modifying any argument is not allowed and can cause many	281	function: modifying any argument is not allowed and can cause many
258	problems.	282	problems.
…		…
263	that Storable can serialise and deserialise is allowed, and for the local	287	that Storable can serialise and deserialise is allowed, and for the local
264	node, anything can be passed.	288	node, anything can be passed.
265		289
266	=item $local_port = port	290	=item $local_port = port
267		291
268	Create a new local port object that can be used either as a pattern	292	Create a new local port object and returns its port ID. Initially it has
269	matching port ("full port") or a single-callback port ("miniport"),	293	no callbacks set and will throw an error when it receives messages.
270	depending on how C<rcv> callbacks are bound to the object.
271		294
272	=item $port = port { my @msg = @_; $finished }	295	=item $local_port = port { my @msg = @_ }
273		296
274	Creates a "miniport", that is, a very lightweight port without any pattern	297	Creates a new local port, and returns its ID. Semantically the same as
275	matching behind it, and returns its ID. Semantically the same as creating
276	a port and calling C<rcv $port, $callback> on it.	298	creating a port and calling C<rcv $port, $callback> on it.
277		299
278	The block will be called for every message received on the port. When the	300	The block will be called for every message received on the port, with the
279	callback returns a true value its job is considered "done" and the port	301	global variable C<$SELF> set to the port ID. Runtime errors will cause the
280	will be destroyed. Otherwise it will stay alive.	302	port to be C<kil>ed. The message will be passed as-is, no extra argument
		303	(i.e. no port ID) will be passed to the callback.
281		304
282	The message will be passed as-is, no extra argument (i.e. no port id) will	305	If you want to stop/destroy the port, simply C<kil> it:
283	be passed to the callback.
284		306
285	If you need the local port id in the callback, this works nicely:	307	my $port = port {
286		308	my @msg = @_;
287	my $port; $port = port {	309	...
288	snd $otherport, reply => $port;	310	kil $SELF;
289	};	311	};
290		312
291	=cut	313	=cut
292		314
293	sub rcv($@);	315	sub rcv($@);
		316
		317	sub _kilme {
		318	die "received message on port without callback";
		319	}
294		320
295	sub port(;&) {	321	sub port(;&) {
296	my $id = "$UNIQ." . $ID++;	322	my $id = "$UNIQ." . $ID++;
297	my $port = "$NODE#$id";	323	my $port = "$NODE#$id";
298		324
299	if (@_) {	325	rcv $port, shift \|\| \&_kilme;
300	rcv $port, shift;
301	} else {
302	$PORT{$id} = sub { }; # nop
303	}
304		326
305	$port	327	$port
306	}	328	}
307		329
308	=item reg $port, $name
309
310	=item reg $name
311
312	Registers the given port (or C<$SELF><<< if missing) under the name
313	C<$name>. If the name already exists it is replaced.
314
315	A port can only be registered under one well known name.
316
317	A port automatically becomes unregistered when it is killed.
318
319	=cut
320
321	sub reg(@) {
322	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
323
324	$REG{$_[0]} = $port;
325	}
326
327	=item rcv $port, $callback->(@msg)	330	=item rcv $local_port, $callback->(@msg)
328		331
329	Replaces the callback on the specified miniport (after converting it to	332	Replaces the default callback on the specified port. There is no way to
330	one if required).	333	remove the default callback: use C<sub { }> to disable it, or better
331		334	C<kil> the port when it is no longer needed.
332	=item rcv $port, tagstring => $callback->(@msg), ...
333
334	=item rcv $port, $smartmatch => $callback->(@msg), ...
335
336	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
337
338	Register callbacks to be called on matching messages on the given full
339	port (after converting it to one if required) and return the port.
340
341	The callback has to return a true value when its work is done, after
342	which is will be removed, or a false value in which case it will stay
343	registered.
344		335
345	The global C<$SELF> (exported by this module) contains C<$port> while	336	The global C<$SELF> (exported by this module) contains C<$port> while
346	executing the callback.	337	executing the callback. Runtime errors during callback execution will
		338	result in the port being C<kil>ed.
347		339
348	Runtime errors wdurign callback execution will result in the port being	340	The default callback received all messages not matched by a more specific
349	C<kil>ed.	341	C<tag> match.
350		342
351	If the match is an array reference, then it will be matched against the	343	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
352	first elements of the message, otherwise only the first element is being
353	matched.
354		344
355	Any element in the match that is specified as C<_any_> (a function	345	Register (or replace) callbacks to be called on messages starting with the
356	exported by this module) matches any single element of the message.	346	given tag on the given port (and return the port), or unregister it (when
		347	C<$callback> is C<$undef> or missing). There can only be one callback
		348	registered for each tag.
357		349
358	While not required, it is highly recommended that the first matching	350	The original message will be passed to the callback, after the first
359	element is a string identifying the message. The one-string-only match is	351	element (the tag) has been removed. The callback will use the same
360	also the most efficient match (by far).	352	environment as the default callback (see above).
361		353
362	Example: create a port and bind receivers on it in one go.	354	Example: create a port and bind receivers on it in one go.
363		355
364	my $port = rcv port,	356	my $port = rcv port,
365	msg1 => sub { ...; 0 },	357	msg1 => sub { ... },
366	msg2 => sub { ...; 0 },	358	msg2 => sub { ... },
367	;	359	;
368		360
369	Example: create a port, bind receivers and send it in a message elsewhere	361	Example: create a port, bind receivers and send it in a message elsewhere
370	in one go:	362	in one go:
371		363
372	snd $otherport, reply =>	364	snd $otherport, reply =>
373	rcv port,	365	rcv port,
374	msg1 => sub { ...; 0 },	366	msg1 => sub { ... },
375	...	367	...
376	;	368	;
		369
		370	Example: temporarily register a rcv callback for a tag matching some port
		371	(e.g. for a rpc reply) and unregister it after a message was received.
		372
		373	rcv $port, $otherport => sub {
		374	my @reply = @_;
		375
		376	rcv $SELF, $otherport;
		377	};
377		378
378	=cut	379	=cut
379		380
380	sub rcv($@) {	381	sub rcv($@) {
381	my $port = shift;	382	my $port = shift;
382	my ($noderef, $portid) = split /#/, $port, 2;	383	my ($noderef, $portid) = split /#/, $port, 2;
383		384
384	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	385	$NODE{$noderef} == $NODE{""}
385	or Carp::croak "$port: rcv can only be called on local ports, caught";	386	or Carp::croak "$port: rcv can only be called on local ports, caught";
386		387
387	if (@_ == 1) {	388	while (@_) {
		389	if (ref $_[0]) {
		390	if (my $self = $PORT_DATA{$portid}) {
		391	"AnyEvent::MP::Port" eq ref $self
		392	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		393
		394	$self->[2] = shift;
		395	} else {
388	my $cb = shift;	396	my $cb = shift;
389	delete $PORT_DATA{$portid};
390	$PORT{$portid} = sub {	397	$PORT{$portid} = sub {
391	local $SELF = $port;	398	local $SELF = $port;
392	eval {	399	eval { &$cb }; _self_die if $@;
393	&$cb	400	};
394	and kil $port;
395	};	401	}
396	_self_die if $@;	402	} elsif (defined $_[0]) {
397	};
398	} else {
399	my $self = $PORT_DATA{$portid} \|\|= do {	403	my $self = $PORT_DATA{$portid} \|\|= do {
400	my $self = bless {	404	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
401	id => $port,
402	}, "AnyEvent::MP::Port";
403		405
404	$PORT{$portid} = sub {	406	$PORT{$portid} = sub {
405	local $SELF = $port;	407	local $SELF = $port;
406		408
407	eval {
408	for (@{ $self->{rc0}{$_[0]} }) {	409	if (my $cb = $self->[1]{$_[0]}) {
409	$_ && &{$_->[0]}	410	shift;
410	&& undef $_;	411	eval { &$cb }; _self_die if $@;
411	}	412	} else {
412
413	for (@{ $self->{rcv}{$_[0]} }) {
414	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
415	&& &{$_->[0]}	413	&{ $self->[0] };
416	&& undef $_;
417	}
418
419	for (@{ $self->{any} }) {
420	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
421	&& &{$_->[0]}
422	&& undef $_;
423	}	414	}
424	};	415	};
425	_self_die if $@;	416
		417	$self
426	};	418	};
427		419
428	$self
429	};
430
431	"AnyEvent::MP::Port" eq ref $self	420	"AnyEvent::MP::Port" eq ref $self
432	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	421	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
433		422
434	while (@_) {
435	my ($match, $cb) = splice @_, 0, 2;	423	my ($tag, $cb) = splice @_, 0, 2;
436		424
437	if (!ref $match) {	425	if (defined $cb) {
438	push @{ $self->{rc0}{$match} }, [$cb];	426	$self->[1]{$tag} = $cb;
439	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
440	my ($type, @match) = @$match;
441	@match
442	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
443	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
444	} else {	427	} else {
445	push @{ $self->{any} }, [$cb, $match];	428	delete $self->[1]{$tag};
446	}	429	}
447	}	430	}
448	}	431	}
449		432
450	$port	433	$port
…		…
494		477
495	=item $guard = mon $port	478	=item $guard = mon $port
496		479
497	=item $guard = mon $port, $rcvport, @msg	480	=item $guard = mon $port, $rcvport, @msg
498		481
499	Monitor the given port and do something when the port is killed, and	482	Monitor the given port and do something when the port is killed or
500	optionally return a guard that can be used to stop monitoring again.	483	messages to it were lost, and optionally return a guard that can be used
		484	to stop monitoring again.
		485
		486	C<mon> effectively guarantees that, in the absence of hardware failures,
		487	that after starting the monitor, either all messages sent to the port
		488	will arrive, or the monitoring action will be invoked after possible
		489	message loss has been detected. No messages will be lost "in between"
		490	(after the first lost message no further messages will be received by the
		491	port). After the monitoring action was invoked, further messages might get
		492	delivered again.
		493
		494	Note that monitoring-actions are one-shot: once released, they are removed
		495	and will not trigger again.
501		496
502	In the first form (callback), the callback is simply called with any	497	In the first form (callback), the callback is simply called with any
503	number of C<@reason> elements (no @reason means that the port was deleted	498	number of C<@reason> elements (no @reason means that the port was deleted
504	"normally"). Note also that I<< the callback B<must> never die >>, so use	499	"normally"). Note also that I<< the callback B<must> never die >>, so use
505	C<eval> if unsure.	500	C<eval> if unsure.
506		501
507	In the second form (another port given), the other port (C<$rcvport)	502	In the second form (another port given), the other port (C<$rcvport>)
508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	503	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
509	"normal" kils nothing happens, while under all other conditions, the other	504	"normal" kils nothing happens, while under all other conditions, the other
510	port is killed with the same reason.	505	port is killed with the same reason.
511		506
512	The third form (kill self) is the same as the second form, except that	507	The third form (kill self) is the same as the second form, except that
513	C<$rvport> defaults to C<$SELF>.	508	C<$rvport> defaults to C<$SELF>.
514		509
515	In the last form (message), a message of the form C<@msg, @reason> will be	510	In the last form (message), a message of the form C<@msg, @reason> will be
516	C<snd>.	511	C<snd>.
517		512
		513	As a rule of thumb, monitoring requests should always monitor a port from
		514	a local port (or callback). The reason is that kill messages might get
		515	lost, just like any other message. Another less obvious reason is that
		516	even monitoring requests can get lost (for exmaple, when the connection
		517	to the other node goes down permanently). When monitoring a port locally
		518	these problems do not exist.
		519
518	Example: call a given callback when C<$port> is killed.	520	Example: call a given callback when C<$port> is killed.
519		521
520	mon $port, sub { warn "port died because of <@_>\n" };	522	mon $port, sub { warn "port died because of <@_>\n" };
521		523
522	Example: kill ourselves when C<$port> is killed abnormally.	524	Example: kill ourselves when C<$port> is killed abnormally.
…		…
532	sub mon {	534	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	535	my ($noderef, $port) = split /#/, shift, 2;
534		536
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	537	my $node = $NODE{$noderef} \|\| add_node $noderef;
536		538
537	my $cb = @_ ? $_[0] : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	539	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
538		540
539	unless (ref $cb) {	541	unless (ref $cb) {
540	if (@_) {	542	if (@_) {
541	# send a kill info message	543	# send a kill info message
542	my (@msg) = @_;	544	my (@msg) = ($cb, @_);
543	$cb = sub { snd @msg, @_ };	545	$cb = sub { snd @msg, @_ };
544	} else {	546	} else {
545	# simply kill other port	547	# simply kill other port
546	my $port = $cb;	548	my $port = $cb;
547	$cb = sub { kil $port, @_ if @_ };	549	$cb = sub { kil $port, @_ if @_ };
…		…
578	#TODO: mon-less form?	580	#TODO: mon-less form?
579		581
580	mon $port, sub { 0 && @refs }	582	mon $port, sub { 0 && @refs }
581	}	583	}
582		584
583	=item lnk $port1, $port2
584
585	=item lnk $otherport
586
587	Link two ports. This is simply a shorthand for:
588
589	mon $port1, $port2;
590	mon $port2, $port1;
591
592	It means that if either one is killed abnormally, the other one gets
593	killed as well.
594
595	The one-argument form assumes that one port is C<$SELF>.
596
597	=cut
598
599	sub lnk {
600	my $port1 = shift;
601	my $port2 = @_ ? shift : $SELF \|\| Carp::croak 'lnk: called with one argument only, but $SELF not set,';
602
603	mon $port1, $port2;
604	mon $port2, $port1;
605	}
606
607	=item kil $port[, @reason]	585	=item kil $port[, @reason]
608		586
609	Kill the specified port with the given C<@reason>.	587	Kill the specified port with the given C<@reason>.
610		588
611	If no C<@reason> is specified, then the port is killed "normally" (linked	589	If no C<@reason> is specified, then the port is killed "normally" (linked
…		…
618	will be reported as reason C<< die => $@ >>.	596	will be reported as reason C<< die => $@ >>.
619		597
620	Transport/communication errors are reported as C<< transport_error =>	598	Transport/communication errors are reported as C<< transport_error =>
621	$message >>.	599	$message >>.
622		600
623	=back
624
625	=head1 NODE MESSAGES
626
627	Nodes understand the following messages sent to them. Many of them take
628	arguments called C<@reply>, which will simply be used to compose a reply
629	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
630	the remaining arguments are simply the message data.
631
632	While other messages exist, they are not public and subject to change.
633
634	=over 4
635
636	=cut	601	=cut
637		602
638	=item lookup => $name, @reply	603	=item $port = spawn $node, $initfunc[, @initdata]
639		604
640	Replies with the port ID of the specified well-known port, or C<undef>.	605	Creates a port on the node C<$node> (which can also be a port ID, in which
		606	case it's the node where that port resides).
641		607
642	=item devnull => ...	608	The port ID of the newly created port is return immediately, and it is
		609	permissible to immediately start sending messages or monitor the port.
643		610
644	Generic data sink/CPU heat conversion.	611	After the port has been created, the init function is
		612	called. This function must be a fully-qualified function name
		613	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		614	program, use C<::name>.
645		615
646	=item relay => $port, @msg	616	If the function doesn't exist, then the node tries to C<require>
		617	the package, then the package above the package and so on (e.g.
		618	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		619	exists or it runs out of package names.
647		620
648	Simply forwards the message to the given port.	621	The init function is then called with the newly-created port as context
		622	object (C<$SELF>) and the C<@initdata> values as arguments.
649		623
650	=item eval => $string[ @reply]	624	A common idiom is to pass your own port, monitor the spawned port, and
		625	in the init function, monitor the original port. This two-way monitoring
		626	ensures that both ports get cleaned up when there is a problem.
651		627
652	Evaluates the given string. If C<@reply> is given, then a message of the	628	Example: spawn a chat server port on C<$othernode>.
653	form C<@reply, $@, @evalres> is sent.
654		629
655	Example: crash another node.	630	# this node, executed from within a port context:
		631	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		632	mon $server;
656		633
657	snd $othernode, eval => "exit";	634	# init function on C<$othernode>
		635	sub connect {
		636	my ($srcport) = @_;
658		637
659	=item time => @reply	638	mon $srcport;
660		639
661	Replies the the current node time to C<@reply>.	640	rcv $SELF, sub {
		641	...
		642	};
		643	}
662		644
663	Example: tell the current node to send the current time to C<$myport> in a	645	=cut
664	C<timereply> message.
665		646
666	snd $NODE, time => $myport, timereply => 1, 2;	647	sub _spawn {
667	# => snd $myport, timereply => 1, 2, <time>	648	my $port = shift;
		649	my $init = shift;
		650
		651	local $SELF = "$NODE#$port";
		652	eval {
		653	&{ load_func $init }
		654	};
		655	_self_die if $@;
		656	}
		657
		658	sub spawn(@) {
		659	my ($noderef, undef) = split /#/, shift, 2;
		660
		661	my $id = "$RUNIQ." . $ID++;
		662
		663	$_[0] =~ /::/
		664	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		665
		666	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
		667
		668	"$noderef#$id"
		669	}
		670
		671	=item after $timeout, @msg
		672
		673	=item after $timeout, $callback
		674
		675	Either sends the given message, or call the given callback, after the
		676	specified number of seconds.
		677
		678	This is simply a utility function that come sin handy at times.
		679
		680	=cut
		681
		682	sub after($@) {
		683	my ($timeout, @action) = @_;
		684
		685	my $t; $t = AE::timer $timeout, 0, sub {
		686	undef $t;
		687	ref $action[0]
		688	? $action[0]()
		689	: snd @action;
		690	};
		691	}
668		692
669	=back	693	=back
670		694
671	=head1 AnyEvent::MP vs. Distributed Erlang	695	=head1 AnyEvent::MP vs. Distributed Erlang
672		696
…		…
691	convenience functionality.	715	convenience functionality.
692		716
693	This means that AEMP requires a less tightly controlled environment at the	717	This means that AEMP requires a less tightly controlled environment at the
694	cost of longer node references and a slightly higher management overhead.	718	cost of longer node references and a slightly higher management overhead.
695		719
		720	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		721	uses "local ports are like remote ports".
		722
		723	The failure modes for local ports are quite different (runtime errors
		724	only) then for remote ports - when a local port dies, you I<know> it dies,
		725	when a connection to another node dies, you know nothing about the other
		726	port.
		727
		728	Erlang pretends remote ports are as reliable as local ports, even when
		729	they are not.
		730
		731	AEMP encourages a "treat remote ports differently" philosophy, with local
		732	ports being the special case/exception, where transport errors cannot
		733	occur.
		734
696	=item * Erlang uses processes and a mailbox, AEMP does not queue.	735	=item * Erlang uses processes and a mailbox, AEMP does not queue.
697		736
698	Erlang uses processes that selctively receive messages, and therefore	737	Erlang uses processes that selectively receive messages, and therefore
699	needs a queue. AEMP is event based, queuing messages would serve no useful	738	needs a queue. AEMP is event based, queuing messages would serve no
700	purpose.	739	useful purpose. For the same reason the pattern-matching abilities of
		740	AnyEvent::MP are more limited, as there is little need to be able to
		741	filter messages without dequeing them.
701		742
702	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	743	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
703		744
704	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	745	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
705		746
706	Sending messages in Erlang is synchronous and blocks the process. AEMP	747	Sending messages in Erlang is synchronous and blocks the process (and
707	sends are immediate, connection establishment is handled in the	748	so does not need a queue that can overflow). AEMP sends are immediate,
708	background.	749	connection establishment is handled in the background.
709		750
710	=item * Erlang can silently lose messages, AEMP cannot.	751	=item * Erlang suffers from silent message loss, AEMP does not.
711		752
712	Erlang makes few guarantees on messages delivery - messages can get lost	753	Erlang makes few guarantees on messages delivery - messages can get lost
713	without any of the processes realising it (i.e. you send messages a, b,	754	without any of the processes realising it (i.e. you send messages a, b,
714	and c, and the other side only receives messages a and c).	755	and c, and the other side only receives messages a and c).
715		756
…		…
727	eventually be killed - it cannot happen that a node detects a port as dead	768	eventually be killed - it cannot happen that a node detects a port as dead
728	and then later sends messages to it, finding it is still alive.	769	and then later sends messages to it, finding it is still alive.
729		770
730	=item * Erlang can send messages to the wrong port, AEMP does not.	771	=item * Erlang can send messages to the wrong port, AEMP does not.
731		772
732	In Erlang it is quite possible that a node that restarts reuses a process	773	In Erlang it is quite likely that a node that restarts reuses a process ID
733	ID known to other nodes for a completely different process, causing	774	known to other nodes for a completely different process, causing messages
734	messages destined for that process to end up in an unrelated process.	775	destined for that process to end up in an unrelated process.
735		776
736	AEMP never reuses port IDs, so old messages or old port IDs floating	777	AEMP never reuses port IDs, so old messages or old port IDs floating
737	around in the network will not be sent to an unrelated port.	778	around in the network will not be sent to an unrelated port.
738		779
739	=item * Erlang uses unprotected connections, AEMP uses secure	780	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
759	or I<none>, there is no in-between, so monitoring single processes is	800	or I<none>, there is no in-between, so monitoring single processes is
760	difficult to implement. Monitoring in AEMP is more flexible than in	801	difficult to implement. Monitoring in AEMP is more flexible than in
761	Erlang, as one can choose between automatic kill, exit message or callback	802	Erlang, as one can choose between automatic kill, exit message or callback
762	on a per-process basis.	803	on a per-process basis.
763		804
764	=item * Erlang has different semantics for monitoring and linking, AEMP has the same.	805	=item * Erlang tries to hide remote/local connections, AEMP does not.
765		806
766	Monitoring in Erlang is not an indicator of process death/crashes,	807	Monitoring in Erlang is not an indicator of process death/crashes,
767	as linking is (except linking is unreliable in Erlang). In AEMP, the	808	as linking is (except linking is unreliable in Erlang).
768	semantics of monitoring and linking are identical, linking is simply	809
769	two-way monitoring with automatic kill.	810	In AEMP, you don't "look up" registered port names or send to named ports
		811	that might or might not be persistent. Instead, you normally spawn a port
		812	on the remote node. The init function monitors the you, and you monitor
		813	the remote port. Since both monitors are local to the node, they are much
		814	more reliable.
		815
		816	This also saves round-trips and avoids sending messages to the wrong port
		817	(hard to do in Erlang).
		818
		819	=back
		820
		821	=head1 RATIONALE
		822
		823	=over 4
		824
		825	=item Why strings for ports and noderefs, why not objects?
		826
		827	We considered "objects", but found that the actual number of methods
		828	thatc an be called are very low. Since port IDs and noderefs travel over
		829	the network frequently, the serialising/deserialising would add lots of
		830	overhead, as well as having to keep a proxy object.
		831
		832	Strings can easily be printed, easily serialised etc. and need no special
		833	procedures to be "valid".
		834
		835	And a a miniport consists of a single closure stored in a global hash - it
		836	can't become much cheaper.
		837
		838	=item Why favour JSON, why not real serialising format such as Storable?
		839
		840	In fact, any AnyEvent::MP node will happily accept Storable as framing
		841	format, but currently there is no way to make a node use Storable by
		842	default.
		843
		844	The default framing protocol is JSON because a) JSON::XS is many times
		845	faster for small messages and b) most importantly, after years of
		846	experience we found that object serialisation is causing more problems
		847	than it gains: Just like function calls, objects simply do not travel
		848	easily over the network, mostly because they will always be a copy, so you
		849	always have to re-think your design.
		850
		851	Keeping your messages simple, concentrating on data structures rather than
		852	objects, will keep your messages clean, tidy and efficient.
770		853
771	=back	854	=back
772		855
773	=head1 SEE ALSO	856	=head1 SEE ALSO
774		857

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Revision 1.63 by root, Thu Aug 27 21:29:37 2009 UTC