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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.35 by root, Thu Aug 6 10:21:48 2009 UTC vs.
Revision 1.64 by root, Fri Aug 28 00:58:44 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		44	AnyEvent::MP::Intro - outdated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 send to ports will not be queued, regardless of
60	will not be queued.	74	anything was listening for them or not.
61		75
62	=item port id - C<noderef#portname>	76	=item port ID - C<noderef#portname>
63		77
64	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	78	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	79	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	80	exception is the the node port, whose ID is identical to its node
67	reference.	81	reference.
68		82
69	=item node	83	=item node
70		84
71	A node is a single process containing at least one port - the node	85	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	86	which provides nodes to manage each other remotely, and to create new
73	create new ports, among other things.	87	ports.
74		88
75	Nodes are either private (single-process only), slaves (connected to a	89	Nodes are either private (single-process only), slaves (can only talk to
76	master node only) or public nodes (connectable from unrelated nodes).	90	public nodes, but do not need an open port) or public nodes (connectable
		91	from any other node).
77		92
78	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	93	=item node ID - C<[a-za-Z0-9_\-.:]+>
79		94
80	A node reference is a string that either simply identifies the node (for	95	A node ID is a string that uniquely identifies the node within a
81	private and slave nodes), or contains a recipe on how to reach a given	96	network. Depending on the configuration used, node IDs can look like a
82	node (for public nodes).	97	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		98	doesn't interpret node IDs in any way.
83		99
84	This recipe is simply a comma-separated list of C<address:port> pairs (for	100	=item binds - C<ip:port>
85	TCP/IP, other protocols might look different).
86		101
87	Node references come in two flavours: resolved (containing only numerical	102	Nodes can only talk to each other by creating some kind of connection to
88	addresses) or unresolved (where hostnames are used instead of addresses).	103	each other. To do this, nodes should listen on one or more local transport
		104	endpoints - binds. Currently, only standard C<ip:port> specifications can
		105	be used, which specify TCP ports to listen on.
89		106
90	Before using an unresolved node reference in a message you first have to	107	=item seeds - C<host:port>
91	resolve it.	108
		109	When a node starts, it knows nothing about the network. To teach the node
		110	about the network it first has to contact some other node within the
		111	network. This node is called a seed.
		112
		113	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		114	are expected to be long-running, and at least one of those should always
		115	be available. When nodes run out of connections (e.g. due to a network
		116	error), they try to re-establish connections to some seednodes again to
		117	join the network.
92		118
93	=back	119	=back
94		120
95	=head1 VARIABLES/FUNCTIONS	121	=head1 VARIABLES/FUNCTIONS
96		122
…		…
98		124
99	=cut	125	=cut
100		126
101	package AnyEvent::MP;	127	package AnyEvent::MP;
102		128
103	use AnyEvent::MP::Base;	129	use AnyEvent::MP::Kernel;
104		130
105	use common::sense;	131	use common::sense;
106		132
107	use Carp ();	133	use Carp ();
108		134
109	use AE ();	135	use AE ();
110		136
111	use base "Exporter";	137	use base "Exporter";
112		138
113	our $VERSION = '0.1';	139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
		140
114	our @EXPORT = qw(	141	our @EXPORT = qw(
115	NODE $NODE *SELF node_of _any_	142	NODE $NODE *SELF node_of after
116	resolve_node initialise_node	143	resolve_node initialise_node
117	snd rcv mon kil reg psub	144	snd rcv mon mon_guard kil reg psub spawn
118	port	145	port
119	);	146	);
120		147
121	our $SELF;	148	our $SELF;
122		149
…		…
126	kil $SELF, die => $msg;	153	kil $SELF, die => $msg;
127	}	154	}
128		155
129	=item $thisnode = NODE / $NODE	156	=item $thisnode = NODE / $NODE
130		157
131	The C<NODE> function returns, and the C<$NODE> variable contains	158	The C<NODE> function returns, and the C<$NODE> variable contains the node
132	the noderef of the local node. The value is initialised by a call	159	ID of the node running in the current process. This value is initialised by
133	to C<become_public> or C<become_slave>, after which all local port	160	a call to C<initialise_node>.
134	identifiers become invalid.
135		161
136	=item $noderef = node_of $port	162	=item $nodeid = node_of $port
137		163
138	Extracts and returns the noderef from a portid or a noderef.	164	Extracts and returns the node ID part from a port ID or a node ID.
139		165
140	=item initialise_node $noderef, $seednode, $seednode...	166	=item initialise_node $profile_name
141		167
142	=item initialise_node "slave/", $master, $master...
143
144	Before a node can talk to other nodes on the network it has to initialise	168	Before a node can talk to other nodes on the network (i.e. enter
145	itself - the minimum a node needs to know is it's own name, and optionally	169	"distributed mode") it has to initialise itself - the minimum a node needs
146	it should know the noderefs of some other nodes in the network.	170	to know is its own name, and optionally it should know the addresses of
		171	some other nodes in the network to discover other nodes.
147		172
148	This function initialises a node - it must be called exactly once (or	173	This function initialises a node - it must be called exactly once (or
149	never) before calling other AnyEvent::MP functions.	174	never) before calling other AnyEvent::MP functions.
150		175
151	All arguments are noderefs, which can be either resolved or unresolved.	176	The first argument is a profile name. If it is C<undef> or missing, then
		177	the current nodename will be used instead (i.e. F<uname -n>).
152		178
153	There are two types of networked nodes, public nodes and slave nodes:	179	The function then looks up the profile in the aemp configuration (see the
		180	L<aemp> commandline utility).
154		181
155	=over 4	182	If the profile specifies a node ID, then this will become the node ID of
		183	this process. If not, then the profile name will be used as node ID. The
		184	special node ID of C<anon/> will be replaced by a random node ID.
156		185
157	=item public nodes	186	The next step is to look up the binds in the profile, followed by binding
		187	aemp protocol listeners on all binds specified (it is possible and valid
		188	to have no binds, meaning that the node cannot be contacted form the
		189	outside. This means the node cannot talk to other nodes that also have no
		190	binds, but it can still talk to all "normal" nodes).
158		191
159	For public nodes, C<$noderef> must either be a (possibly unresolved)	192	If the profile does not specify a binds list, then the node ID will be
160	noderef, in which case it will be resolved, or C<undef> (or missing), in	193	treated as if it were of the form C<host:port>, which will be resolved and
161	which case the noderef will be guessed.	194	used as binds list.
162		195
163	Afterwards, the node will bind itself on all endpoints and try to connect	196	Lastly, the seeds list from the profile is passed to the
164	to all additional C<$seednodes> that are specified. Seednodes are optional	197	L<AnyEvent::MP::Global> module, which will then use it to keep
165	and can be used to quickly bootstrap the node into an existing network.	198	connectivity with at least on of those seed nodes at any point in time.
166		199
167	=item slave nodes	200	Example: become a distributed node listening on the guessed noderef, or
168		201	the one specified via C<aemp> for the current node. This should be the
169	When the C<$noderef> is the special string C<slave/>, then the node will	202	most common form of invocation for "daemon"-type nodes.
170	become a slave node. Slave nodes cannot be contacted from outside and will
171	route most of their traffic to the master node that they attach to.
172
173	At least one additional noderef is required: The node will try to connect
174	to all of them and will become a slave attached to the first node it can
175	successfully connect to.
176
177	=back
178
179	This function will block until all nodes have been resolved and, for slave
180	nodes, until it has successfully established a connection to a master
181	server.
182
183	Example: become a public node listening on the default node.
184		203
185	initialise_node;	204	initialise_node;
186		205
187	Example: become a public node, and try to contact some well-known master	206	Example: become an anonymous node. This form is often used for commandline
188	servers to become part of the network.	207	clients.
189		208
190	initialise_node undef, "master1", "master2";
191
192	Example: become a public node listening on port C<4041>.
193
194	initialise_node 4041;	209	initialise_node "anon/";
195		210
196	Example: become a public node, only visible on localhost port 4044.	211	Example: become a distributed node. If there is no profile of the given
		212	name, or no binds list was specified, resolve C<localhost:4044> and bind
		213	on the resulting addresses.
197		214
198	initialise_node "locahost:4044";	215	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
204	=item $cv = resolve_node $noderef
205
206	Takes an unresolved node reference that may contain hostnames and
207	abbreviated IDs, resolves all of them and returns a resolved node
208	reference.
209
210	In addition to C<address:port> pairs allowed in resolved noderefs, the
211	following forms are supported:
212
213	=over 4
214
215	=item the empty string
216
217	An empty-string component gets resolved as if the default port (4040) was
218	specified.
219
220	=item naked port numbers (e.g. C<1234>)
221
222	These are resolved by prepending the local nodename and a colon, to be
223	further resolved.
224
225	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
226
227	These are resolved by using AnyEvent::DNS to resolve them, optionally
228	looking up SRV records for the C<aemp=4040> port, if no port was
229	specified.
230
231	=back
232		216
233	=item $SELF	217	=item $SELF
234		218
235	Contains the current port id while executing C<rcv> callbacks or C<psub>	219	Contains the current port id while executing C<rcv> callbacks or C<psub>
236	blocks.	220	blocks.
…		…
244	=item snd $port, type => @data	228	=item snd $port, type => @data
245		229
246	=item snd $port, @msg	230	=item snd $port, @msg
247		231
248	Send the given message to the given port ID, which can identify either	232	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	233	a local or a remote port, and must be a port ID.
250	stringifies a sa port ID (such as a port object :).
251		234
252	While the message can be about anything, it is highly recommended to use a	235	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	236	string as first element (a port ID, or some word that indicates a request
254	type etc.).	237	type etc.).
255		238
256	The message data effectively becomes read-only after a call to this	239	The message data effectively becomes read-only after a call to this
257	function: modifying any argument is not allowed and can cause many	240	function: modifying any argument is not allowed and can cause many
258	problems.	241	problems.
…		…
263	that Storable can serialise and deserialise is allowed, and for the local	246	that Storable can serialise and deserialise is allowed, and for the local
264	node, anything can be passed.	247	node, anything can be passed.
265		248
266	=item $local_port = port	249	=item $local_port = port
267		250
268	Create a new local port object that can be used either as a pattern	251	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"),	252	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		253
272	=item $port = port { my @msg = @_; $finished }	254	=item $local_port = port { my @msg = @_ }
273		255
274	Creates a "miniport", that is, a very lightweight port without any pattern	256	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.	257	creating a port and calling C<rcv $port, $callback> on it.
277		258
278	The block will be called for every message received on the port. When the	259	The block will be called for every message received on the port, with the
279	callback returns a true value its job is considered "done" and the port	260	global variable C<$SELF> set to the port ID. Runtime errors will cause the
280	will be destroyed. Otherwise it will stay alive.	261	port to be C<kil>ed. The message will be passed as-is, no extra argument
		262	(i.e. no port ID) will be passed to the callback.
281		263
282	The message will be passed as-is, no extra argument (i.e. no port id) will	264	If you want to stop/destroy the port, simply C<kil> it:
283	be passed to the callback.
284		265
285	If you need the local port id in the callback, this works nicely:	266	my $port = port {
286		267	my @msg = @_;
287	my $port; $port = port {	268	...
288	snd $otherport, reply => $port;	269	kil $SELF;
289	};	270	};
290		271
291	=cut	272	=cut
292		273
293	sub rcv($@);	274	sub rcv($@);
		275
		276	sub _kilme {
		277	die "received message on port without callback";
		278	}
294		279
295	sub port(;&) {	280	sub port(;&) {
296	my $id = "$UNIQ." . $ID++;	281	my $id = "$UNIQ." . $ID++;
297	my $port = "$NODE#$id";	282	my $port = "$NODE#$id";
298		283
299	if (@_) {	284	rcv $port, shift \|\| \&_kilme;
300	rcv $port, shift;
301	} else {
302	$PORT{$id} = sub { }; # nop
303	}
304		285
305	$port	286	$port
306	}	287	}
307		288
308	=item reg $port, $name
309
310	Registers the given port under the name C<$name>. If the name already
311	exists it is replaced.
312
313	A port can only be registered under one well known name.
314
315	A port automatically becomes unregistered when it is killed.
316
317	=cut
318
319	sub reg(@) {
320	my ($port, $name) = @_;
321
322	$REG{$name} = $port;
323	}
324
325	=item rcv $port, $callback->(@msg)	289	=item rcv $local_port, $callback->(@msg)
326		290
327	Replaces the callback on the specified miniport (after converting it to	291	Replaces the default callback on the specified port. There is no way to
328	one if required).	292	remove the default callback: use C<sub { }> to disable it, or better
329		293	C<kil> the port when it is no longer needed.
330	=item rcv $port, tagstring => $callback->(@msg), ...
331
332	=item rcv $port, $smartmatch => $callback->(@msg), ...
333
334	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
335
336	Register callbacks to be called on matching messages on the given full
337	port (after converting it to one if required).
338
339	The callback has to return a true value when its work is done, after
340	which is will be removed, or a false value in which case it will stay
341	registered.
342		294
343	The global C<$SELF> (exported by this module) contains C<$port> while	295	The global C<$SELF> (exported by this module) contains C<$port> while
344	executing the callback.	296	executing the callback. Runtime errors during callback execution will
		297	result in the port being C<kil>ed.
345		298
346	Runtime errors wdurign callback execution will result in the port being	299	The default callback received all messages not matched by a more specific
347	C<kil>ed.	300	C<tag> match.
348		301
349	If the match is an array reference, then it will be matched against the	302	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
350	first elements of the message, otherwise only the first element is being
351	matched.
352		303
353	Any element in the match that is specified as C<_any_> (a function	304	Register (or replace) callbacks to be called on messages starting with the
354	exported by this module) matches any single element of the message.	305	given tag on the given port (and return the port), or unregister it (when
		306	C<$callback> is C<$undef> or missing). There can only be one callback
		307	registered for each tag.
355		308
356	While not required, it is highly recommended that the first matching	309	The original message will be passed to the callback, after the first
357	element is a string identifying the message. The one-string-only match is	310	element (the tag) has been removed. The callback will use the same
358	also the most efficient match (by far).	311	environment as the default callback (see above).
		312
		313	Example: create a port and bind receivers on it in one go.
		314
		315	my $port = rcv port,
		316	msg1 => sub { ... },
		317	msg2 => sub { ... },
		318	;
		319
		320	Example: create a port, bind receivers and send it in a message elsewhere
		321	in one go:
		322
		323	snd $otherport, reply =>
		324	rcv port,
		325	msg1 => sub { ... },
		326	...
		327	;
		328
		329	Example: temporarily register a rcv callback for a tag matching some port
		330	(e.g. for a rpc reply) and unregister it after a message was received.
		331
		332	rcv $port, $otherport => sub {
		333	my @reply = @_;
		334
		335	rcv $SELF, $otherport;
		336	};
359		337
360	=cut	338	=cut
361		339
362	sub rcv($@) {	340	sub rcv($@) {
363	my $port = shift;	341	my $port = shift;
364	my ($noderef, $portid) = split /#/, $port, 2;	342	my ($noderef, $portid) = split /#/, $port, 2;
365		343
366	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	344	$NODE{$noderef} == $NODE{""}
367	or Carp::croak "$port: rcv can only be called on local ports, caught";	345	or Carp::croak "$port: rcv can only be called on local ports, caught";
368		346
369	if (@_ == 1) {	347	while (@_) {
		348	if (ref $_[0]) {
		349	if (my $self = $PORT_DATA{$portid}) {
		350	"AnyEvent::MP::Port" eq ref $self
		351	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		352
		353	$self->[2] = shift;
		354	} else {
370	my $cb = shift;	355	my $cb = shift;
371	delete $PORT_DATA{$portid};
372	$PORT{$portid} = sub {	356	$PORT{$portid} = sub {
373	local $SELF = $port;	357	local $SELF = $port;
374	eval {	358	eval { &$cb }; _self_die if $@;
375	&$cb	359	};
376	and kil $port;
377	};	360	}
378	_self_die if $@;	361	} elsif (defined $_[0]) {
379	};
380	} else {
381	my $self = $PORT_DATA{$portid} \|\|= do {	362	my $self = $PORT_DATA{$portid} \|\|= do {
382	my $self = bless {	363	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
383	id => $port,
384	}, "AnyEvent::MP::Port";
385		364
386	$PORT{$portid} = sub {	365	$PORT{$portid} = sub {
387	local $SELF = $port;	366	local $SELF = $port;
388		367
389	eval {
390	for (@{ $self->{rc0}{$_[0]} }) {	368	if (my $cb = $self->[1]{$_[0]}) {
391	$_ && &{$_->[0]}	369	shift;
392	&& undef $_;	370	eval { &$cb }; _self_die if $@;
393	}	371	} else {
394
395	for (@{ $self->{rcv}{$_[0]} }) {
396	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
397	&& &{$_->[0]}	372	&{ $self->[0] };
398	&& undef $_;
399	}
400
401	for (@{ $self->{any} }) {
402	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
403	&& &{$_->[0]}
404	&& undef $_;
405	}	373	}
406	};	374	};
407	_self_die if $@;	375
		376	$self
408	};	377	};
409		378
410	$self
411	};
412
413	"AnyEvent::MP::Port" eq ref $self	379	"AnyEvent::MP::Port" eq ref $self
414	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	380	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
415		381
416	while (@_) {
417	my ($match, $cb) = splice @_, 0, 2;	382	my ($tag, $cb) = splice @_, 0, 2;
418		383
419	if (!ref $match) {	384	if (defined $cb) {
420	push @{ $self->{rc0}{$match} }, [$cb];	385	$self->[1]{$tag} = $cb;
421	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
422	my ($type, @match) = @$match;
423	@match
424	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
425	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
426	} else {	386	} else {
427	push @{ $self->{any} }, [$cb, $match];	387	delete $self->[1]{$tag};
428	}	388	}
429	}	389	}
430	}	390	}
431		391
432	$port	392	$port
…		…
470	}	430	}
471	}	431	}
472		432
473	=item $guard = mon $port, $cb->(@reason)	433	=item $guard = mon $port, $cb->(@reason)
474		434
475	=item $guard = mon $port, $otherport	435	=item $guard = mon $port, $rcvport
476		436
		437	=item $guard = mon $port
		438
477	=item $guard = mon $port, $otherport, @msg	439	=item $guard = mon $port, $rcvport, @msg
478		440
479	Monitor the given port and do something when the port is killed.	441	Monitor the given port and do something when the port is killed or
		442	messages to it were lost, and optionally return a guard that can be used
		443	to stop monitoring again.
480		444
		445	C<mon> effectively guarantees that, in the absence of hardware failures,
		446	that after starting the monitor, either all messages sent to the port
		447	will arrive, or the monitoring action will be invoked after possible
		448	message loss has been detected. No messages will be lost "in between"
		449	(after the first lost message no further messages will be received by the
		450	port). After the monitoring action was invoked, further messages might get
		451	delivered again.
		452
		453	Note that monitoring-actions are one-shot: once released, they are removed
		454	and will not trigger again.
		455
481	In the first form, the callback is simply called with any number	456	In the first form (callback), the callback is simply called with any
482	of C<@reason> elements (no @reason means that the port was deleted	457	number of C<@reason> elements (no @reason means that the port was deleted
483	"normally"). Note also that I<< the callback B<must> never die >>, so use	458	"normally"). Note also that I<< the callback B<must> never die >>, so use
484	C<eval> if unsure.	459	C<eval> if unsure.
485		460
486	In the second form, the other port will be C<kil>'ed with C<@reason>, iff	461	In the second form (another port given), the other port (C<$rcvport>)
487	a @reason was specified, i.e. on "normal" kils nothing happens, while	462	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
488	under all other conditions, the other port is killed with the same reason.	463	"normal" kils nothing happens, while under all other conditions, the other
		464	port is killed with the same reason.
489		465
		466	The third form (kill self) is the same as the second form, except that
		467	C<$rvport> defaults to C<$SELF>.
		468
490	In the last form, a message of the form C<@msg, @reason> will be C<snd>.	469	In the last form (message), a message of the form C<@msg, @reason> will be
		470	C<snd>.
		471
		472	As a rule of thumb, monitoring requests should always monitor a port from
		473	a local port (or callback). The reason is that kill messages might get
		474	lost, just like any other message. Another less obvious reason is that
		475	even monitoring requests can get lost (for exmaple, when the connection
		476	to the other node goes down permanently). When monitoring a port locally
		477	these problems do not exist.
491		478
492	Example: call a given callback when C<$port> is killed.	479	Example: call a given callback when C<$port> is killed.
493		480
494	mon $port, sub { warn "port died because of <@_>\n" };	481	mon $port, sub { warn "port died because of <@_>\n" };
495		482
496	Example: kill ourselves when C<$port> is killed abnormally.	483	Example: kill ourselves when C<$port> is killed abnormally.
497		484
498	mon $port, $self;	485	mon $port;
499		486
500	Example: send us a restart message another C<$port> is killed.	487	Example: send us a restart message when another C<$port> is killed.
501		488
502	mon $port, $self => "restart";	489	mon $port, $self => "restart";
503		490
504	=cut	491	=cut
505		492
506	sub mon {	493	sub mon {
507	my ($noderef, $port) = split /#/, shift, 2;	494	my ($noderef, $port) = split /#/, shift, 2;
508		495
509	my $node = $NODE{$noderef} \|\| add_node $noderef;	496	my $node = $NODE{$noderef} \|\| add_node $noderef;
510		497
511	my $cb = shift;	498	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
512		499
513	unless (ref $cb) {	500	unless (ref $cb) {
514	if (@_) {	501	if (@_) {
515	# send a kill info message	502	# send a kill info message
516	my (@msg) = ($cb, @_);	503	my (@msg) = ($cb, @_);
…		…
547	=cut	534	=cut
548		535
549	sub mon_guard {	536	sub mon_guard {
550	my ($port, @refs) = @_;	537	my ($port, @refs) = @_;
551		538
		539	#TODO: mon-less form?
		540
552	mon $port, sub { 0 && @refs }	541	mon $port, sub { 0 && @refs }
553	}	542	}
554
555	=item lnk $port1, $port2
556
557	Link two ports. This is simply a shorthand for:
558
559	mon $port1, $port2;
560	mon $port2, $port1;
561
562	It means that if either one is killed abnormally, the other one gets
563	killed as well.
564		543
565	=item kil $port[, @reason]	544	=item kil $port[, @reason]
566		545
567	Kill the specified port with the given C<@reason>.	546	Kill the specified port with the given C<@reason>.
568		547
…		…
576	will be reported as reason C<< die => $@ >>.	555	will be reported as reason C<< die => $@ >>.
577		556
578	Transport/communication errors are reported as C<< transport_error =>	557	Transport/communication errors are reported as C<< transport_error =>
579	$message >>.	558	$message >>.
580		559
581	=back
582
583	=head1 NODE MESSAGES
584
585	Nodes understand the following messages sent to them. Many of them take
586	arguments called C<@reply>, which will simply be used to compose a reply
587	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
588	the remaining arguments are simply the message data.
589
590	While other messages exist, they are not public and subject to change.
591
592	=over 4
593
594	=cut	560	=cut
595		561
596	=item lookup => $name, @reply	562	=item $port = spawn $node, $initfunc[, @initdata]
597		563
598	Replies with the port ID of the specified well-known port, or C<undef>.	564	Creates a port on the node C<$node> (which can also be a port ID, in which
		565	case it's the node where that port resides).
599		566
600	=item devnull => ...	567	The port ID of the newly created port is return immediately, and it is
		568	permissible to immediately start sending messages or monitor the port.
601		569
602	Generic data sink/CPU heat conversion.	570	After the port has been created, the init function is
		571	called. This function must be a fully-qualified function name
		572	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main
		573	program, use C<::name>.
603		574
604	=item relay => $port, @msg	575	If the function doesn't exist, then the node tries to C<require>
		576	the package, then the package above the package and so on (e.g.
		577	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
		578	exists or it runs out of package names.
605		579
606	Simply forwards the message to the given port.	580	The init function is then called with the newly-created port as context
		581	object (C<$SELF>) and the C<@initdata> values as arguments.
607		582
608	=item eval => $string[ @reply]	583	A common idiom is to pass your own port, monitor the spawned port, and
		584	in the init function, monitor the original port. This two-way monitoring
		585	ensures that both ports get cleaned up when there is a problem.
609		586
610	Evaluates the given string. If C<@reply> is given, then a message of the	587	Example: spawn a chat server port on C<$othernode>.
611	form C<@reply, $@, @evalres> is sent.
612		588
613	Example: crash another node.	589	# this node, executed from within a port context:
		590	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
		591	mon $server;
614		592
615	snd $othernode, eval => "exit";	593	# init function on C<$othernode>
		594	sub connect {
		595	my ($srcport) = @_;
616		596
617	=item time => @reply	597	mon $srcport;
618		598
619	Replies the the current node time to C<@reply>.	599	rcv $SELF, sub {
		600	...
		601	};
		602	}
620		603
621	Example: tell the current node to send the current time to C<$myport> in a	604	=cut
622	C<timereply> message.
623		605
624	snd $NODE, time => $myport, timereply => 1, 2;	606	sub _spawn {
625	# => snd $myport, timereply => 1, 2, <time>	607	my $port = shift;
		608	my $init = shift;
		609
		610	local $SELF = "$NODE#$port";
		611	eval {
		612	&{ load_func $init }
		613	};
		614	_self_die if $@;
		615	}
		616
		617	sub spawn(@) {
		618	my ($noderef, undef) = split /#/, shift, 2;
		619
		620	my $id = "$RUNIQ." . $ID++;
		621
		622	$_[0] =~ /::/
		623	or Carp::croak "spawn init function must be a fully-qualified name, caught";
		624
		625	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
		626
		627	"$noderef#$id"
		628	}
		629
		630	=item after $timeout, @msg
		631
		632	=item after $timeout, $callback
		633
		634	Either sends the given message, or call the given callback, after the
		635	specified number of seconds.
		636
		637	This is simply a utility function that come sin handy at times.
		638
		639	=cut
		640
		641	sub after($@) {
		642	my ($timeout, @action) = @_;
		643
		644	my $t; $t = AE::timer $timeout, 0, sub {
		645	undef $t;
		646	ref $action[0]
		647	? $action[0]()
		648	: snd @action;
		649	};
		650	}
626		651
627	=back	652	=back
628		653
629	=head1 AnyEvent::MP vs. Distributed Erlang	654	=head1 AnyEvent::MP vs. Distributed Erlang
630		655
…		…
649	convenience functionality.	674	convenience functionality.
650		675
651	This means that AEMP requires a less tightly controlled environment at the	676	This means that AEMP requires a less tightly controlled environment at the
652	cost of longer node references and a slightly higher management overhead.	677	cost of longer node references and a slightly higher management overhead.
653		678
		679	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
		680	uses "local ports are like remote ports".
		681
		682	The failure modes for local ports are quite different (runtime errors
		683	only) then for remote ports - when a local port dies, you I<know> it dies,
		684	when a connection to another node dies, you know nothing about the other
		685	port.
		686
		687	Erlang pretends remote ports are as reliable as local ports, even when
		688	they are not.
		689
		690	AEMP encourages a "treat remote ports differently" philosophy, with local
		691	ports being the special case/exception, where transport errors cannot
		692	occur.
		693
654	=item * Erlang uses processes and a mailbox, AEMP does not queue.	694	=item * Erlang uses processes and a mailbox, AEMP does not queue.
655		695
656	Erlang uses processes that selctively receive messages, and therefore	696	Erlang uses processes that selectively receive messages, and therefore
657	needs a queue. AEMP is event based, queuing messages would serve no useful	697	needs a queue. AEMP is event based, queuing messages would serve no
658	purpose.	698	useful purpose. For the same reason the pattern-matching abilities of
		699	AnyEvent::MP are more limited, as there is little need to be able to
		700	filter messages without dequeing them.
659		701
660	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	702	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
661		703
662	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	704	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
663		705
664	Sending messages in Erlang is synchronous and blocks the process. AEMP	706	Sending messages in Erlang is synchronous and blocks the process (and
665	sends are immediate, connection establishment is handled in the	707	so does not need a queue that can overflow). AEMP sends are immediate,
666	background.	708	connection establishment is handled in the background.
667		709
668	=item * Erlang can silently lose messages, AEMP cannot.	710	=item * Erlang suffers from silent message loss, AEMP does not.
669		711
670	Erlang makes few guarantees on messages delivery - messages can get lost	712	Erlang makes few guarantees on messages delivery - messages can get lost
671	without any of the processes realising it (i.e. you send messages a, b,	713	without any of the processes realising it (i.e. you send messages a, b,
672	and c, and the other side only receives messages a and c).	714	and c, and the other side only receives messages a and c).
673		715
…		…
685	eventually be killed - it cannot happen that a node detects a port as dead	727	eventually be killed - it cannot happen that a node detects a port as dead
686	and then later sends messages to it, finding it is still alive.	728	and then later sends messages to it, finding it is still alive.
687		729
688	=item * Erlang can send messages to the wrong port, AEMP does not.	730	=item * Erlang can send messages to the wrong port, AEMP does not.
689		731
690	In Erlang it is quite possible that a node that restarts reuses a process	732	In Erlang it is quite likely that a node that restarts reuses a process ID
691	ID known to other nodes for a completely different process, causing	733	known to other nodes for a completely different process, causing messages
692	messages destined for that process to end up in an unrelated process.	734	destined for that process to end up in an unrelated process.
693		735
694	AEMP never reuses port IDs, so old messages or old port IDs floating	736	AEMP never reuses port IDs, so old messages or old port IDs floating
695	around in the network will not be sent to an unrelated port.	737	around in the network will not be sent to an unrelated port.
696		738
697	=item * Erlang uses unprotected connections, AEMP uses secure	739	=item * Erlang uses unprotected connections, AEMP uses secure
…		…
717	or I<none>, there is no in-between, so monitoring single processes is	759	or I<none>, there is no in-between, so monitoring single processes is
718	difficult to implement. Monitoring in AEMP is more flexible than in	760	difficult to implement. Monitoring in AEMP is more flexible than in
719	Erlang, as one can choose between automatic kill, exit message or callback	761	Erlang, as one can choose between automatic kill, exit message or callback
720	on a per-process basis.	762	on a per-process basis.
721		763
722	=item * Erlang has different semantics for monitoring and linking, AEMP has the same.	764	=item * Erlang tries to hide remote/local connections, AEMP does not.
723		765
724	Monitoring in Erlang is not an indicator of process death/crashes,	766	Monitoring in Erlang is not an indicator of process death/crashes,
725	as linking is (except linking is unreliable in Erlang). In AEMP, the	767	as linking is (except linking is unreliable in Erlang).
726	semantics of monitoring and linking are identical, linking is simply	768
727	two-way monitoring with automatic kill.	769	In AEMP, you don't "look up" registered port names or send to named ports
		770	that might or might not be persistent. Instead, you normally spawn a port
		771	on the remote node. The init function monitors the you, and you monitor
		772	the remote port. Since both monitors are local to the node, they are much
		773	more reliable.
		774
		775	This also saves round-trips and avoids sending messages to the wrong port
		776	(hard to do in Erlang).
		777
		778	=back
		779
		780	=head1 RATIONALE
		781
		782	=over 4
		783
		784	=item Why strings for ports and noderefs, why not objects?
		785
		786	We considered "objects", but found that the actual number of methods
		787	thatc an be called are very low. Since port IDs and noderefs travel over
		788	the network frequently, the serialising/deserialising would add lots of
		789	overhead, as well as having to keep a proxy object.
		790
		791	Strings can easily be printed, easily serialised etc. and need no special
		792	procedures to be "valid".
		793
		794	And a a miniport consists of a single closure stored in a global hash - it
		795	can't become much cheaper.
		796
		797	=item Why favour JSON, why not real serialising format such as Storable?
		798
		799	In fact, any AnyEvent::MP node will happily accept Storable as framing
		800	format, but currently there is no way to make a node use Storable by
		801	default.
		802
		803	The default framing protocol is JSON because a) JSON::XS is many times
		804	faster for small messages and b) most importantly, after years of
		805	experience we found that object serialisation is causing more problems
		806	than it gains: Just like function calls, objects simply do not travel
		807	easily over the network, mostly because they will always be a copy, so you
		808	always have to re-think your design.
		809
		810	Keeping your messages simple, concentrating on data structures rather than
		811	objects, will keep your messages clean, tidy and efficient.
728		812
729	=back	813	=back
730		814
731	=head1 SEE ALSO	815	=head1 SEE ALSO
732		816

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Revision 1.64 by root, Fri Aug 28 00:58:44 2009 UTC