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Revision 1.135 by root, Mon Mar 12 14:55:55 2012 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using miniports	24	# creating/using ports, the simple way
28	my $miniport = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using full ports	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, smartmatch => $cb->(@msg);
33	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
34	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
35
36	# more, smarter, matches (_any_ is exported by this module)
37	rcv $port, [child_died => $pid] => sub { ...
38	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
39		31
40	# create a port on another node	32	# create a port on another node
41	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
42		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
43	# monitoring	39	# monitoring
44	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $port, $cb->(@msg) # callback is invoked on death
45	mon $port, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
46	mon $port, $otherport, @msg # send message on death	42	mon $port, $localport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
47		51
48	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
49		53
		54	bin/aemp - stable.
50	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
51	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
52	AnyEvent::MP::Kernel - WIP
53	AnyEvent::MP::Transport - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
54		58	AnyEvent::MP::Global - stable API.
55	stay tuned.
56		59
57	=head1 DESCRIPTION	60	=head1 DESCRIPTION
58		61
59	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
60		63
61	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
62	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
63		66
64	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
65	manual page.	68	manual page and the examples under F<eg/>.
66
67	At the moment, this module family is severly broken and underdocumented,
68	so do not use. This was uploaded mainly to reserve the CPAN namespace -
69	stay tuned!
70		69
71	=head1 CONCEPTS	70	=head1 CONCEPTS
72		71
73	=over 4	72	=over 4
74		73
75	=item port	74	=item port
76		75
77	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
78		78
79	Some ports allow you to register C<rcv> handlers that can match specific	79	Ports allow you to register C<rcv> handlers that can match all or just
80	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
81	will not be queued.	81	anything was listening for them or not.
82		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
83	=item port id - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
84		86
85	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
86	separator, and a port name (a printable string of unspecified format). An	88	as separator, and a port name (a printable string of unspecified
87	exception is the the node port, whose ID is identical to its node	89	format created by AnyEvent::MP).
88	reference.
89		90
90	=item node	91	=item node
91		92
92	A node is a single process containing at least one port - the node	93	A node is a single process containing at least one port - the node port,
93	port. You can send messages to node ports to find existing ports or to	94	which enables nodes to manage each other remotely, and to create new
94	create new ports, among other things.	95	ports.
95		96
96	Nodes are either private (single-process only), slaves (connected to a	97	Nodes are either public (have one or more listening ports) or private
97	master node only) or public nodes (connectable from unrelated nodes).	98	(no listening ports). Private nodes cannot talk to other private nodes
		99	currently, but all nodes can talk to public nodes.
98		100
99	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	101	Nodes is represented by (printable) strings called "node IDs".
100		102
101	A node reference is a string that either simply identifies the node (for	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
102	private and slave nodes), or contains a recipe on how to reach a given
103	node (for public nodes).
104		104
105	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	A node ID is a string that uniquely identifies the node within a
106	TCP/IP, other protocols might look different).	106	network. Depending on the configuration used, node IDs can look like a
		107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		108	doesn't interpret node IDs in any way except to uniquely identify a node.
107		109
108	Node references come in two flavours: resolved (containing only numerical	110	=item binds - C<ip:port>
109	addresses) or unresolved (where hostnames are used instead of addresses).
110		111
111	Before using an unresolved node reference in a message you first have to	112	Nodes can only talk to each other by creating some kind of connection to
112	resolve it.	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
		116	Currently, only standard C<ip:port> specifications can be used, which
		117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
		119
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
		149	=item seed IDs - C<host:port>
		150
		151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		152	TCP port) of nodes that should be used as seed nodes.
		153
		154	=item global nodes
		155
		156	An AEMP network needs a discovery service - nodes need to know how to
		157	connect to other nodes they only know by name. In addition, AEMP offers a
		158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
113		170
114	=back	171	=back
115		172
116	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
117		174
…		…
119		176
120	=cut	177	=cut
121		178
122	package AnyEvent::MP;	179	package AnyEvent::MP;
123		180
		181	use AnyEvent::MP::Config ();
124	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
125		184
126	use common::sense;	185	use common::sense;
127		186
128	use Carp ();	187	use Carp ();
129		188
130	use AE ();	189	use AE ();
		190	use Guard ();
131		191
132	use base "Exporter";	192	use base "Exporter";
133		193
134	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
135		195
136	our @EXPORT = qw(	196	our @EXPORT = qw(
137	NODE $NODE *SELF node_of _any_	197	NODE $NODE *SELF node_of after
138	resolve_node initialise_node	198	configure
139	snd rcv mon kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
140	port	200	port
		201	db_set db_del db_reg
		202	db_mon db_family db_keys db_values
141	);	203	);
142		204
143	our $SELF;	205	our $SELF;
144		206
145	sub _self_die() {	207	sub _self_die() {
…		…
148	kil $SELF, die => $msg;	210	kil $SELF, die => $msg;
149	}	211	}
150		212
151	=item $thisnode = NODE / $NODE	213	=item $thisnode = NODE / $NODE
152		214
153	The C<NODE> function returns, and the C<$NODE> variable contains	215	The C<NODE> function returns, and the C<$NODE> variable contains, the node
154	the noderef of the local node. The value is initialised by a call	216	ID of the node running in the current process. This value is initialised by
155	to C<become_public> or C<become_slave>, after which all local port	217	a call to C<configure>.
156	identifiers become invalid.
157		218
158	=item $noderef = node_of $port	219	=item $nodeid = node_of $port
159		220
160	Extracts and returns the noderef from a portid or a noderef.	221	Extracts and returns the node ID from a port ID or a node ID.
161		222
162	=item initialise_node $noderef, $seednode, $seednode...	223	=item configure $profile, key => value...
163		224
164	=item initialise_node "slave/", $master, $master...	225	=item configure key => value...
165		226
166	Before a node can talk to other nodes on the network it has to initialise	227	Before a node can talk to other nodes on the network (i.e. enter
167	itself - the minimum a node needs to know is it's own name, and optionally	228	"distributed mode") it has to configure itself - the minimum a node needs
168	it should know the noderefs of some other nodes in the network.	229	to know is its own name, and optionally it should know the addresses of
		230	some other nodes in the network to discover other nodes.
169		231
170	This function initialises a node - it must be called exactly once (or	232	This function configures a node - it must be called exactly once (or
171	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
172		234
173	All arguments are noderefs, which can be either resolved or unresolved.	235	The key/value pairs are basically the same ones as documented for the
174		236	F<aemp> command line utility (sans the set/del prefix), with these additions:
175	There are two types of networked nodes, public nodes and slave nodes:
176		237
177	=over 4	238	=over 4
178		239
179	=item public nodes	240	=item norc => $boolean (default false)
180		241
181	For public nodes, C<$noderef> must either be a (possibly unresolved)	242	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
182	noderef, in which case it will be resolved, or C<undef> (or missing), in	243	be consulted - all configuraiton options must be specified in the
183	which case the noderef will be guessed.	244	C<configure> call.
184		245
185	Afterwards, the node will bind itself on all endpoints and try to connect	246	=item force => $boolean (default false)
186	to all additional C<$seednodes> that are specified. Seednodes are optional
187	and can be used to quickly bootstrap the node into an existing network.
188		247
189	=item slave nodes	248	IF true, then the values specified in the C<configure> will take
		249	precedence over any values configured via the rc file. The default is for
		250	the rc file to override any options specified in the program.
190		251
191	When the C<$noderef> is the special string C<slave/>, then the node will	252	=item secure => $pass->($nodeid)
192	become a slave node. Slave nodes cannot be contacted from outside and will
193	route most of their traffic to the master node that they attach to.
194		253
195	At least one additional noderef is required: The node will try to connect	254	In addition to specifying a boolean, you can specify a code reference that
196	to all of them and will become a slave attached to the first node it can	255	is called for every remote execution attempt - the execution request is
197	successfully connect to.	256	granted iff the callback returns a true value.
		257
		258	See F<semp setsecure> for more info.
198		259
199	=back	260	=back
200		261
201	This function will block until all nodes have been resolved and, for slave
202	nodes, until it has successfully established a connection to a master
203	server.
204
205	Example: become a public node listening on the default node.
206
207	initialise_node;
208
209	Example: become a public node, and try to contact some well-known master
210	servers to become part of the network.
211
212	initialise_node undef, "master1", "master2";
213
214	Example: become a public node listening on port C<4041>.
215
216	initialise_node 4041;
217
218	Example: become a public node, only visible on localhost port 4044.
219
220	initialise_node "locahost:4044";
221
222	Example: become a slave node to any of the specified master servers.
223
224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
225
226	=item $cv = resolve_node $noderef
227
228	Takes an unresolved node reference that may contain hostnames and
229	abbreviated IDs, resolves all of them and returns a resolved node
230	reference.
231
232	In addition to C<address:port> pairs allowed in resolved noderefs, the
233	following forms are supported:
234
235	=over 4	262	=over 4
236		263
237	=item the empty string	264	=item step 1, gathering configuration from profiles
238		265
239	An empty-string component gets resolved as if the default port (4040) was	266	The function first looks up a profile in the aemp configuration (see the
240	specified.	267	L<aemp> commandline utility). The profile name can be specified via the
		268	named C<profile> parameter or can simply be the first parameter). If it is
		269	missing, then the nodename (F<uname -n>) will be used as profile name.
241		270
242	=item naked port numbers (e.g. C<1234>)	271	The profile data is then gathered as follows:
243		272
244	These are resolved by prepending the local nodename and a colon, to be	273	First, all remaining key => value pairs (all of which are conveniently
245	further resolved.	274	undocumented at the moment) will be interpreted as configuration
		275	data. Then they will be overwritten by any values specified in the global
		276	default configuration (see the F<aemp> utility), then the chain of
		277	profiles chosen by the profile name (and any C<parent> attributes).
246		278
247	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	279	That means that the values specified in the profile have highest priority
		280	and the values specified directly via C<configure> have lowest priority,
		281	and can only be used to specify defaults.
248		282
249	These are resolved by using AnyEvent::DNS to resolve them, optionally	283	If the profile specifies a node ID, then this will become the node ID of
250	looking up SRV records for the C<aemp=4040> port, if no port was	284	this process. If not, then the profile name will be used as node ID, with
251	specified.	285	a unique randoms tring (C</%u>) appended.
		286
		287	The node ID can contain some C<%> sequences that are expanded: C<%n>
		288	is expanded to the local nodename, C<%u> is replaced by a random
		289	strign to make the node unique. For example, the F<aemp> commandline
		290	utility uses C<aemp/%n/%u> as nodename, which might expand to
		291	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		292
		293	=item step 2, bind listener sockets
		294
		295	The next step is to look up the binds in the profile, followed by binding
		296	aemp protocol listeners on all binds specified (it is possible and valid
		297	to have no binds, meaning that the node cannot be contacted form the
		298	outside. This means the node cannot talk to other nodes that also have no
		299	binds, but it can still talk to all "normal" nodes).
		300
		301	If the profile does not specify a binds list, then a default of C<*> is
		302	used, meaning the node will bind on a dynamically-assigned port on every
		303	local IP address it finds.
		304
		305	=item step 3, connect to seed nodes
		306
		307	As the last step, the seed ID list from the profile is passed to the
		308	L<AnyEvent::MP::Global> module, which will then use it to keep
		309	connectivity with at least one node at any point in time.
252		310
253	=back	311	=back
		312
		313	Example: become a distributed node using the local node name as profile.
		314	This should be the most common form of invocation for "daemon"-type nodes.
		315
		316	configure
		317
		318	Example: become a semi-anonymous node. This form is often used for
		319	commandline clients.
		320
		321	configure nodeid => "myscript/%n/%u";
		322
		323	Example: configure a node using a profile called seed, which is suitable
		324	for a seed node as it binds on all local addresses on a fixed port (4040,
		325	customary for aemp).
		326
		327	# use the aemp commandline utility
		328	# aemp profile seed binds '*:4040'
		329
		330	# then use it
		331	configure profile => "seed";
		332
		333	# or simply use aemp from the shell again:
		334	# aemp run profile seed
		335
		336	# or provide a nicer-to-remember nodeid
		337	# aemp run profile seed nodeid "$(hostname)"
254		338
255	=item $SELF	339	=item $SELF
256		340
257	Contains the current port id while executing C<rcv> callbacks or C<psub>	341	Contains the current port id while executing C<rcv> callbacks or C<psub>
258	blocks.	342	blocks.
259		343
260	=item SELF, %SELF, @SELF...	344	=item *SELF, SELF, %SELF, @SELF...
261		345
262	Due to some quirks in how perl exports variables, it is impossible to	346	Due to some quirks in how perl exports variables, it is impossible to
263	just export C<$SELF>, all the symbols called C<SELF> are exported by this	347	just export C<$SELF>, all the symbols named C<SELF> are exported by this
264	module, but only C<$SELF> is currently used.	348	module, but only C<$SELF> is currently used.
265		349
266	=item snd $port, type => @data	350	=item snd $port, type => @data
267		351
268	=item snd $port, @msg	352	=item snd $port, @msg
269		353
270	Send the given message to the given port ID, which can identify either	354	Send the given message to the given port, which can identify either a
271	a local or a remote port, and can be either a string or soemthignt hat	355	local or a remote port, and must be a port ID.
272	stringifies a sa port ID (such as a port object :).
273		356
274	While the message can be about anything, it is highly recommended to use a	357	While the message can be almost anything, it is highly recommended to
275	string as first element (a portid, or some word that indicates a request	358	use a string as first element (a port ID, or some word that indicates a
276	type etc.).	359	request type etc.) and to consist if only simple perl values (scalars,
		360	arrays, hashes) - if you think you need to pass an object, think again.
277		361
278	The message data effectively becomes read-only after a call to this	362	The message data logically becomes read-only after a call to this
279	function: modifying any argument is not allowed and can cause many	363	function: modifying any argument (or values referenced by them) is
280	problems.	364	forbidden, as there can be considerable time between the call to C<snd>
		365	and the time the message is actually being serialised - in fact, it might
		366	never be copied as within the same process it is simply handed to the
		367	receiving port.
281		368
282	The type of data you can transfer depends on the transport protocol: when	369	The type of data you can transfer depends on the transport protocol: when
283	JSON is used, then only strings, numbers and arrays and hashes consisting	370	JSON is used, then only strings, numbers and arrays and hashes consisting
284	of those are allowed (no objects). When Storable is used, then anything	371	of those are allowed (no objects). When Storable is used, then anything
285	that Storable can serialise and deserialise is allowed, and for the local	372	that Storable can serialise and deserialise is allowed, and for the local
286	node, anything can be passed.	373	node, anything can be passed. Best rely only on the common denominator of
		374	these.
287		375
288	=item $local_port = port	376	=item $local_port = port
289		377
290	Create a new local port object that can be used either as a pattern	378	Create a new local port object and returns its port ID. Initially it has
291	matching port ("full port") or a single-callback port ("miniport"),	379	no callbacks set and will throw an error when it receives messages.
292	depending on how C<rcv> callbacks are bound to the object.
293		380
294	=item $port = port { my @msg = @_; $finished }	381	=item $local_port = port { my @msg = @_ }
295		382
296	Creates a "miniport", that is, a very lightweight port without any pattern	383	Creates a new local port, and returns its ID. Semantically the same as
297	matching behind it, and returns its ID. Semantically the same as creating
298	a port and calling C<rcv $port, $callback> on it.	384	creating a port and calling C<rcv $port, $callback> on it.
299		385
300	The block will be called for every message received on the port. When the	386	The block will be called for every message received on the port, with the
301	callback returns a true value its job is considered "done" and the port	387	global variable C<$SELF> set to the port ID. Runtime errors will cause the
302	will be destroyed. Otherwise it will stay alive.	388	port to be C<kil>ed. The message will be passed as-is, no extra argument
		389	(i.e. no port ID) will be passed to the callback.
303		390
304	The message will be passed as-is, no extra argument (i.e. no port id) will	391	If you want to stop/destroy the port, simply C<kil> it:
305	be passed to the callback.
306		392
307	If you need the local port id in the callback, this works nicely:	393	my $port = port {
308		394	my @msg = @_;
309	my $port; $port = port {	395	...
310	snd $otherport, reply => $port;	396	kil $SELF;
311	};	397	};
312		398
313	=cut	399	=cut
314		400
315	sub rcv($@);	401	sub rcv($@);
316		402
		403	my $KILME = sub {
		404	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
		405	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		406	};
		407
317	sub port(;&) {	408	sub port(;&) {
318	my $id = "$UNIQ." . $ID++;	409	my $id = $UNIQ . ++$ID;
319	my $port = "$NODE#$id";	410	my $port = "$NODE#$id";
320		411
321	if (@_) {
322	rcv $port, shift;	412	rcv $port, shift || $KILME;
323	} else {
324	$PORT{$id} = sub { }; # nop
325	}
326		413
327	$port	414	$port
328	}	415	}
329		416
330	=item reg $port, $name
331
332	=item reg $name
333
334	Registers the given port (or C<$SELF><<< if missing) under the name
335	C<$name>. If the name already exists it is replaced.
336
337	A port can only be registered under one well known name.
338
339	A port automatically becomes unregistered when it is killed.
340
341	=cut
342
343	sub reg(@) {
344	my $port = @_ > 1 ? shift : $SELF || Carp::croak 'reg: called with one argument only, but $SELF not set,';
345
346	$REG{$_[0]} = $port;
347	}
348
349	=item rcv $port, $callback->(@msg)	417	=item rcv $local_port, $callback->(@msg)
350		418
351	Replaces the callback on the specified miniport (after converting it to	419	Replaces the default callback on the specified port. There is no way to
352	one if required).	420	remove the default callback: use C<sub { }> to disable it, or better
353		421	C<kil> the port when it is no longer needed.
354	=item rcv $port, tagstring => $callback->(@msg), ...
355
356	=item rcv $port, $smartmatch => $callback->(@msg), ...
357
358	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
359
360	Register callbacks to be called on matching messages on the given full
361	port (after converting it to one if required) and return the port.
362
363	The callback has to return a true value when its work is done, after
364	which is will be removed, or a false value in which case it will stay
365	registered.
366		422
367	The global C<$SELF> (exported by this module) contains C<$port> while	423	The global C<$SELF> (exported by this module) contains C<$port> while
368	executing the callback.	424	executing the callback. Runtime errors during callback execution will
		425	result in the port being C<kil>ed.
369		426
370	Runtime errors during callback execution will result in the port being	427	The default callback receives all messages not matched by a more specific
371	C<kil>ed.	428	C<tag> match.
372		429
373	If the match is an array reference, then it will be matched against the	430	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
374	first elements of the message, otherwise only the first element is being
375	matched.
376		431
377	Any element in the match that is specified as C<_any_> (a function	432	Register (or replace) callbacks to be called on messages starting with the
378	exported by this module) matches any single element of the message.	433	given tag on the given port (and return the port), or unregister it (when
		434	C<$callback> is C<$undef> or missing). There can only be one callback
		435	registered for each tag.
379		436
380	While not required, it is highly recommended that the first matching	437	The original message will be passed to the callback, after the first
381	element is a string identifying the message. The one-string-only match is	438	element (the tag) has been removed. The callback will use the same
382	also the most efficient match (by far).	439	environment as the default callback (see above).
383		440
384	Example: create a port and bind receivers on it in one go.	441	Example: create a port and bind receivers on it in one go.
385		442
386	my $port = rcv port,	443	my $port = rcv port,
387	msg1 => sub { ...; 0 },	444	msg1 => sub { ... },
388	msg2 => sub { ...; 0 },	445	msg2 => sub { ... },
389	;	446	;
390		447
391	Example: create a port, bind receivers and send it in a message elsewhere	448	Example: create a port, bind receivers and send it in a message elsewhere
392	in one go:	449	in one go:
393		450
394	snd $otherport, reply =>	451	snd $otherport, reply =>
395	rcv port,	452	rcv port,
396	msg1 => sub { ...; 0 },	453	msg1 => sub { ... },
397	...	454	...
398	;	455	;
399		456
		457	Example: temporarily register a rcv callback for a tag matching some port
		458	(e.g. for an rpc reply) and unregister it after a message was received.
		459
		460	rcv $port, $otherport => sub {
		461	my @reply = @_;
		462
		463	rcv $SELF, $otherport;
		464	};
		465
400	=cut	466	=cut
401		467
402	sub rcv($@) {	468	sub rcv($@) {
403	my $port = shift;	469	my $port = shift;
404	my ($noderef, $portid) = split /#/, $port, 2;	470	my ($nodeid, $portid) = split /#/, $port, 2;
405		471
406	($NODE{$noderef} || add_node $noderef) == $NODE{""}	472	$NODE{$nodeid} == $NODE{""}
407	or Carp::croak "$port: rcv can only be called on local ports, caught";	473	or Carp::croak "$port: rcv can only be called on local ports, caught";
408		474
409	if (@_ == 1) {	475	while (@_) {
		476	if (ref $_[0]) {
		477	if (my $self = $PORT_DATA{$portid}) {
		478	"AnyEvent::MP::Port" eq ref $self
		479	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		480
		481	$self->[0] = shift;
		482	} else {
410	my $cb = shift;	483	my $cb = shift;
411	delete $PORT_DATA{$portid};
412	$PORT{$portid} = sub {	484	$PORT{$portid} = sub {
413	local $SELF = $port;	485	local $SELF = $port;
414	eval {	486	eval { &$cb }; _self_die if $@;
415	&$cb	487	};
416	and kil $port;
417	};	488	}
418	_self_die if $@;	489	} elsif (defined $_[0]) {
419	};
420	} else {
421	my $self = $PORT_DATA{$portid} ||= do {	490	my $self = $PORT_DATA{$portid} ||= do {
422	my $self = bless {	491	my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
423	id => $port,
424	}, "AnyEvent::MP::Port";
425		492
426	$PORT{$portid} = sub {	493	$PORT{$portid} = sub {
427	local $SELF = $port;	494	local $SELF = $port;
428		495
429	eval {
430	for (@{ $self->{rc0}{$_[0]} }) {	496	if (my $cb = $self->[1]{$_[0]}) {
431	$_ && &{$_->[0]}	497	shift;
432	&& undef $_;	498	eval { &$cb }; _self_die if $@;
433	}	499	} else {
434
435	for (@{ $self->{rcv}{$_[0]} }) {
436	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
437	&& &{$_->[0]}	500	&{ $self->[0] };
438	&& undef $_;
439	}
440
441	for (@{ $self->{any} }) {
442	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
443	&& &{$_->[0]}
444	&& undef $_;
445	}	501	}
446	};	502	};
447	_self_die if $@;	503
		504	$self
448	};	505	};
449		506
450	$self
451	};
452
453	"AnyEvent::MP::Port" eq ref $self	507	"AnyEvent::MP::Port" eq ref $self
454	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	508	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
455		509
456	while (@_) {
457	my ($match, $cb) = splice @_, 0, 2;	510	my ($tag, $cb) = splice @_, 0, 2;
458		511
459	if (!ref $match) {	512	if (defined $cb) {
460	push @{ $self->{rc0}{$match} }, [$cb];	513	$self->[1]{$tag} = $cb;
461	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
462	my ($type, @match) = @$match;
463	@match
464	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
465	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
466	} else {	514	} else {
467	push @{ $self->{any} }, [$cb, $match];	515	delete $self->[1]{$tag};
468	}	516	}
469	}	517	}
470	}	518	}
471		519
472	$port	520	$port
473	}	521	}
474		522
		523	=item peval $port, $coderef[, @args]
		524
		525	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		526	when the code throews an exception the C<$port> will be killed.
		527
		528	Any remaining args will be passed to the callback. Any return values will
		529	be returned to the caller.
		530
		531	This is useful when you temporarily want to execute code in the context of
		532	a port.
		533
		534	Example: create a port and run some initialisation code in it's context.
		535
		536	my $port = port { ... };
		537
		538	peval $port, sub {
		539	init
		540	or die "unable to init";
		541	};
		542
		543	=cut
		544
		545	sub peval($$) {
		546	local $SELF = shift;
		547	my $cb = shift;
		548
		549	if (wantarray) {
		550	my @res = eval { &$cb };
		551	_self_die if $@;
		552	@res
		553	} else {
		554	my $res = eval { &$cb };
		555	_self_die if $@;
		556	$res
		557	}
		558	}
		559
475	=item $closure = psub { BLOCK }	560	=item $closure = psub { BLOCK }
476		561
477	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	562	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
478	closure is executed, sets up the environment in the same way as in C<rcv>	563	closure is executed, sets up the environment in the same way as in C<rcv>
479	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	564	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		565
		566	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		567	BLOCK }, @_ } >>.
480		568
481	This is useful when you register callbacks from C<rcv> callbacks:	569	This is useful when you register callbacks from C<rcv> callbacks:
482		570
483	rcv delayed_reply => sub {	571	rcv delayed_reply => sub {
484	my ($delay, @reply) = @_;	572	my ($delay, @reply) = @_;
…		…
508	$res	596	$res
509	}	597	}
510	}	598	}
511	}	599	}
512		600
513	=item $guard = mon $port, $cb->(@reason)	601	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
514		602
515	=item $guard = mon $port, $rcvport	603	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
516		604
517	=item $guard = mon $port	605	=item $guard = mon $port # kill $SELF when $port dies
518		606
519	=item $guard = mon $port, $rcvport, @msg	607	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
520		608
521	Monitor the given port and do something when the port is killed or	609	Monitor the given port and do something when the port is killed or
522	messages to it were lost, and optionally return a guard that can be used	610	messages to it were lost, and optionally return a guard that can be used
523	to stop monitoring again.	611	to stop monitoring again.
524
525	C<mon> effectively guarantees that, in the absence of hardware failures,
526	that after starting the monitor, either all messages sent to the port
527	will arrive, or the monitoring action will be invoked after possible
528	message loss has been detected. No messages will be lost "in between"
529	(after the first lost message no further messages will be received by the
530	port). After the monitoring action was invoked, further messages might get
531	delivered again.
532		612
533	In the first form (callback), the callback is simply called with any	613	In the first form (callback), the callback is simply called with any
534	number of C<@reason> elements (no @reason means that the port was deleted	614	number of C<@reason> elements (no @reason means that the port was deleted
535	"normally"). Note also that I<< the callback B<must> never die >>, so use	615	"normally"). Note also that I<< the callback B<must> never die >>, so use
536	C<eval> if unsure.	616	C<eval> if unsure.
537		617
538	In the second form (another port given), the other port (C<$rcvport>)	618	In the second form (another port given), the other port (C<$rcvport>)
539	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	619	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
540	"normal" kils nothing happens, while under all other conditions, the other	620	"normal" kils nothing happens, while under all other conditions, the other
541	port is killed with the same reason.	621	port is killed with the same reason.
542		622
543	The third form (kill self) is the same as the second form, except that	623	The third form (kill self) is the same as the second form, except that
544	C<$rvport> defaults to C<$SELF>.	624	C<$rvport> defaults to C<$SELF>.
545		625
546	In the last form (message), a message of the form C<@msg, @reason> will be	626	In the last form (message), a message of the form C<@msg, @reason> will be
547	C<snd>.	627	C<snd>.
		628
		629	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		630	alert was raised), they are removed and will not trigger again.
548		631
549	As a rule of thumb, monitoring requests should always monitor a port from	632	As a rule of thumb, monitoring requests should always monitor a port from
550	a local port (or callback). The reason is that kill messages might get	633	a local port (or callback). The reason is that kill messages might get
551	lost, just like any other message. Another less obvious reason is that	634	lost, just like any other message. Another less obvious reason is that
552	even monitoring requests can get lost (for exmaple, when the connection	635	even monitoring requests can get lost (for example, when the connection
553	to the other node goes down permanently). When monitoring a port locally	636	to the other node goes down permanently). When monitoring a port locally
554	these problems do not exist.	637	these problems do not exist.
555		638
		639	C<mon> effectively guarantees that, in the absence of hardware failures,
		640	after starting the monitor, either all messages sent to the port will
		641	arrive, or the monitoring action will be invoked after possible message
		642	loss has been detected. No messages will be lost "in between" (after
		643	the first lost message no further messages will be received by the
		644	port). After the monitoring action was invoked, further messages might get
		645	delivered again.
		646
		647	Inter-host-connection timeouts and monitoring depend on the transport
		648	used. The only transport currently implemented is TCP, and AnyEvent::MP
		649	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		650	non-idle connection, and usually around two hours for idle connections).
		651
		652	This means that monitoring is good for program errors and cleaning up
		653	stuff eventually, but they are no replacement for a timeout when you need
		654	to ensure some maximum latency.
		655
556	Example: call a given callback when C<$port> is killed.	656	Example: call a given callback when C<$port> is killed.
557		657
558	mon $port, sub { warn "port died because of <@_>\n" };	658	mon $port, sub { warn "port died because of <@_>\n" };
559		659
560	Example: kill ourselves when C<$port> is killed abnormally.	660	Example: kill ourselves when C<$port> is killed abnormally.
…		…
566	mon $port, $self => "restart";	666	mon $port, $self => "restart";
567		667
568	=cut	668	=cut
569		669
570	sub mon {	670	sub mon {
571	my ($noderef, $port) = split /#/, shift, 2;	671	my ($nodeid, $port) = split /#/, shift, 2;
572		672
573	my $node = $NODE{$noderef} || add_node $noderef;	673	my $node = $NODE{$nodeid} || add_node $nodeid;
574		674
575	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';	675	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
576		676
577	unless (ref $cb) {	677	unless (ref $cb) {
578	if (@_) {	678	if (@_) {
…		…
587	}	687	}
588		688
589	$node->monitor ($port, $cb);	689	$node->monitor ($port, $cb);
590		690
591	defined wantarray	691	defined wantarray
592	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	692	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
593	}	693	}
594		694
595	=item $guard = mon_guard $port, $ref, $ref...	695	=item $guard = mon_guard $port, $ref, $ref...
596		696
597	Monitors the given C<$port> and keeps the passed references. When the port	697	Monitors the given C<$port> and keeps the passed references. When the port
598	is killed, the references will be freed.	698	is killed, the references will be freed.
599		699
600	Optionally returns a guard that will stop the monitoring.	700	Optionally returns a guard that will stop the monitoring.
601		701
602	This function is useful when you create e.g. timers or other watchers and	702	This function is useful when you create e.g. timers or other watchers and
603	want to free them when the port gets killed:	703	want to free them when the port gets killed (note the use of C<psub>):
604		704
605	$port->rcv (start => sub {	705	$port->rcv (start => sub {
606	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	706	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
607	undef $timer if 0.9 < rand;	707	undef $timer if 0.9 < rand;
608	});	708	});
609	});	709	});
610		710
611	=cut	711	=cut
…		…
620		720
621	=item kil $port[, @reason]	721	=item kil $port[, @reason]
622		722
623	Kill the specified port with the given C<@reason>.	723	Kill the specified port with the given C<@reason>.
624		724
625	If no C<@reason> is specified, then the port is killed "normally" (linked	725	If no C<@reason> is specified, then the port is killed "normally" -
626	ports will not be kileld, or even notified).	726	monitor callback will be invoked, but the kil will not cause linked ports
		727	(C<mon $mport, $lport> form) to get killed.
627		728
628	Otherwise, linked ports get killed with the same reason (second form of	729	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
629	C<mon>, see below).	730	form) get killed with the same reason.
630		731
631	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	732	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
632	will be reported as reason C<< die => $@ >>.	733	will be reported as reason C<< die => $@ >>.
633		734
634	Transport/communication errors are reported as C<< transport_error =>	735	Transport/communication errors are reported as C<< transport_error =>
635	$message >>.	736	$message >>.
636		737
637	=cut	738	Common idioms:
		739
		740	# silently remove yourself, do not kill linked ports
		741	kil $SELF;
		742
		743	# report a failure in some detail
		744	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		745
		746	# do not waste much time with killing, just die when something goes wrong
		747	open my $fh, "<file"
		748	or die "file: $!";
638		749
639	=item $port = spawn $node, $initfunc[, @initdata]	750	=item $port = spawn $node, $initfunc[, @initdata]
640		751
641	Creates a port on the node C<$node> (which can also be a port ID, in which	752	Creates a port on the node C<$node> (which can also be a port ID, in which
642	case it's the node where that port resides).	753	case it's the node where that port resides).
643		754
644	The port ID of the newly created port is return immediately, and it is	755	The port ID of the newly created port is returned immediately, and it is
645	permissible to immediately start sending messages or monitor the port.	756	possible to immediately start sending messages or to monitor the port.
646		757
647	After the port has been created, the init function is	758	After the port has been created, the init function is called on the remote
648	called. This function must be a fully-qualified function name	759	node, in the same context as a C<rcv> callback. This function must be a
649	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	760	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
650	program, use C<::name>.	761	specify a function in the main program, use C<::name>.
651		762
652	If the function doesn't exist, then the node tries to C<require>	763	If the function doesn't exist, then the node tries to C<require>
653	the package, then the package above the package and so on (e.g.	764	the package, then the package above the package and so on (e.g.
654	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	765	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
655	exists or it runs out of package names.	766	exists or it runs out of package names.
656		767
657	The init function is then called with the newly-created port as context	768	The init function is then called with the newly-created port as context
658	object (C<$SELF>) and the C<@initdata> values as arguments.	769	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		770	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		771	the port might not get created.
659		772
660	A common idiom is to pass your own port, monitor the spawned port, and	773	A common idiom is to pass a local port, immediately monitor the spawned
661	in the init function, monitor the original port. This two-way monitoring	774	port, and in the remote init function, immediately monitor the passed
662	ensures that both ports get cleaned up when there is a problem.	775	local port. This two-way monitoring ensures that both ports get cleaned up
		776	when there is a problem.
		777
		778	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		779	caller before C<spawn> returns (by delaying invocation when spawn is
		780	called for the local node).
663		781
664	Example: spawn a chat server port on C<$othernode>.	782	Example: spawn a chat server port on C<$othernode>.
665		783
666	# this node, executed from within a port context:	784	# this node, executed from within a port context:
667	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	785	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
682		800
683	sub _spawn {	801	sub _spawn {
684	my $port = shift;	802	my $port = shift;
685	my $init = shift;	803	my $init = shift;
686		804
		805	# rcv will create the actual port
687	local $SELF = "$NODE#$port";	806	local $SELF = "$NODE#$port";
688	eval {	807	eval {
689	&{ load_func $init }	808	&{ load_func $init }
690	};	809	};
691	_self_die if $@;	810	_self_die if $@;
692	}	811	}
693		812
694	sub spawn(@) {	813	sub spawn(@) {
695	my ($noderef, undef) = split /#/, shift, 2;	814	my ($nodeid, undef) = split /#/, shift, 2;
696		815
697	my $id = "$RUNIQ." . $ID++;	816	my $id = $RUNIQ . ++$ID;
698		817
699	$_[0] =~ /::/	818	$_[0] =~ /::/
700	or Carp::croak "spawn init function must be a fully-qualified name, caught";	819	or Carp::croak "spawn init function must be a fully-qualified name, caught";
701		820
702	($NODE{$noderef} || add_node $noderef)	821	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
703	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
704		822
705	"$noderef#$id"	823	"$nodeid#$id"
706	}	824	}
707		825
		826
		827	=item after $timeout, @msg
		828
		829	=item after $timeout, $callback
		830
		831	Either sends the given message, or call the given callback, after the
		832	specified number of seconds.
		833
		834	This is simply a utility function that comes in handy at times - the
		835	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		836	so it may go away in the future.
		837
		838	=cut
		839
		840	sub after($@) {
		841	my ($timeout, @action) = @_;
		842
		843	my $t; $t = AE::timer $timeout, 0, sub {
		844	undef $t;
		845	ref $action[0]
		846	? $action[0]()
		847	: snd @action;
		848	};
		849	}
		850
		851	#=item $cb2 = timeout $seconds, $cb[, @args]
		852
		853	=item cal $port, @msg, $callback[, $timeout]
		854
		855	A simple form of RPC - sends a message to the given C<$port> with the
		856	given contents (C<@msg>), but adds a reply port to the message.
		857
		858	The reply port is created temporarily just for the purpose of receiving
		859	the reply, and will be C<kil>ed when no longer needed.
		860
		861	A reply message sent to the port is passed to the C<$callback> as-is.
		862
		863	If an optional time-out (in seconds) is given and it is not C<undef>,
		864	then the callback will be called without any arguments after the time-out
		865	elapsed and the port is C<kil>ed.
		866
		867	If no time-out is given (or it is C<undef>), then the local port will
		868	monitor the remote port instead, so it eventually gets cleaned-up.
		869
		870	Currently this function returns the temporary port, but this "feature"
		871	might go in future versions unless you can make a convincing case that
		872	this is indeed useful for something.
		873
		874	=cut
		875
		876	sub cal(@) {
		877	my $timeout = ref $_[-1] ? undef : pop;
		878	my $cb = pop;
		879
		880	my $port = port {
		881	undef $timeout;
		882	kil $SELF;
		883	&$cb;
		884	};
		885
		886	if (defined $timeout) {
		887	$timeout = AE::timer $timeout, 0, sub {
		888	undef $timeout;
		889	kil $port;
		890	$cb->();
		891	};
		892	} else {
		893	mon $_[0], sub {
		894	kil $port;
		895	$cb->();
		896	};
		897	}
		898
		899	push @_, $port;
		900	&snd;
		901
		902	$port
		903	}
		904
708	=back	905	=back
709		906
710	=head1 NODE MESSAGES	907	=head1 DISTRIBUTED DATABASE
711		908
712	Nodes understand the following messages sent to them. Many of them take	909	AnyEvent::MP comes with a simple distributed database. The database will
713	arguments called C<@reply>, which will simply be used to compose a reply	910	be mirrored asynchronously on all global nodes. Other nodes bind to one
714	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	911	of the global nodes for their needs. Every node has a "local database"
715	the remaining arguments are simply the message data.	912	which contains all the values that are set locally. All local databases
		913	are merged together to form the global database, which can be queried.
716		914
717	While other messages exist, they are not public and subject to change.	915	The database structure is that of a two-level hash - the database hash
		916	contains hashes which contain values, similarly to a perl hash of hashes,
		917	i.e.:
718		918
		919	$DATABASE{$family}{$subkey} = $value
		920
		921	The top level hash key is called "family", and the second-level hash key
		922	is called "subkey" or simply "key".
		923
		924	The family must be alphanumeric, i.e. start with a letter and consist
		925	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		926	pretty much like Perl module names.
		927
		928	As the family namespace is global, it is recommended to prefix family names
		929	with the name of the application or module using it.
		930
		931	The subkeys must be non-empty strings, with no further restrictions.
		932
		933	The values should preferably be strings, but other perl scalars should
		934	work as well (such as C<undef>, arrays and hashes).
		935
		936	Every database entry is owned by one node - adding the same family/subkey
		937	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		938	but the result might be nondeterministic, i.e. the key might have
		939	different values on different nodes.
		940
		941	Different subkeys in the same family can be owned by different nodes
		942	without problems, and in fact, this is the common method to create worker
		943	pools. For example, a worker port for image scaling might do this:
		944
		945	db_set my_image_scalers => $port;
		946
		947	And clients looking for an image scaler will want to get the
		948	C<my_image_scalers> keys from time to time:
		949
		950	db_keys my_image_scalers => sub {
		951	@ports = @{ $_[0] };
		952	};
		953
		954	Or better yet, they want to monitor the database family, so they always
		955	have a reasonable up-to-date copy:
		956
		957	db_mon my_image_scalers => sub {
		958	@ports = keys %{ $_[0] };
		959	};
		960
		961	In general, you can set or delete single subkeys, but query and monitor
		962	whole families only.
		963
		964	If you feel the need to monitor or query a single subkey, try giving it
		965	it's own family.
		966
719	=over 4	967	=over
		968
		969	=item db_set $family => $subkey [=> $value]
		970
		971	Sets (or replaces) a key to the database - if C<$value> is omitted,
		972	C<undef> is used instead.
		973
		974	=item db_del $family => $subkey...
		975
		976	Deletes one or more subkeys from the database family.
		977
		978	=item $guard = db_reg $family => $subkey [=> $value]
		979
		980	Sets the key on the database and returns a guard. When the guard is
		981	destroyed, the key is deleted from the database. If C<$value> is missing,
		982	then C<undef> is used.
		983
		984	=item db_family $family => $cb->(\%familyhash)
		985
		986	Queries the named database C<$family> and call the callback with the
		987	family represented as a hash. You can keep and freely modify the hash.
		988
		989	=item db_keys $family => $cb->(\@keys)
		990
		991	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		992	them as array reference to the callback.
		993
		994	=item db_values $family => $cb->(\@values)
		995
		996	Same as C<db_family>, except it only queries the family I<values> and passes them
		997	as array reference to the callback.
		998
		999	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1000
		1001	Creates a monitor on the given database family. Each time a key is set
		1002	or or is deleted the callback is called with a hash containing the
		1003	database family and three lists of added, changed and deleted subkeys,
		1004	respectively. If no keys have changed then the array reference might be
		1005	C<undef> or even missing.
		1006
		1007	If not called in void context, a guard object is returned that, when
		1008	destroyed, stops the monitor.
		1009
		1010	The family hash reference and the key arrays belong to AnyEvent::MP and
		1011	B<must not be modified or stored> by the callback. When in doubt, make a
		1012	copy.
		1013
		1014	As soon as possible after the monitoring starts, the callback will be
		1015	called with the intiial contents of the family, even if it is empty,
		1016	i.e. there will always be a timely call to the callback with the current
		1017	contents.
		1018
		1019	It is possible that the callback is called with a change event even though
		1020	the subkey is already present and the value has not changed.
		1021
		1022	The monitoring stops when the guard object is destroyed.
		1023
		1024	Example: on every change to the family "mygroup", print out all keys.
		1025
		1026	my $guard = db_mon mygroup => sub {
		1027	my ($family, $a, $c, $d) = @_;
		1028	print "mygroup members: ", (join " ", keys %$family), "\n";
		1029	};
		1030
		1031	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1032
		1033	my $guard; $guard = db_mon My::Module::workers => sub {
		1034	my ($family, $a, $c, $d) = @_;
		1035	return unless %$family;
		1036	undef $guard;
		1037	print "My::Module::workers now nonempty\n";
		1038	};
		1039
		1040	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1041
		1042	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1043	my ($family, $a, $c, $d) = @_;
		1044
		1045	print "+$_=$family->{$_}\n" for @$a;
		1046	print "*$_=$family->{$_}\n" for @$c;
		1047	print "-$_=$family->{$_}\n" for @$d;
		1048	};
720		1049
721	=cut	1050	=cut
722
723	=item lookup => $name, @reply
724
725	Replies with the port ID of the specified well-known port, or C<undef>.
726
727	=item devnull => ...
728
729	Generic data sink/CPU heat conversion.
730
731	=item relay => $port, @msg
732
733	Simply forwards the message to the given port.
734
735	=item eval => $string[ @reply]
736
737	Evaluates the given string. If C<@reply> is given, then a message of the
738	form C<@reply, $@, @evalres> is sent.
739
740	Example: crash another node.
741
742	snd $othernode, eval => "exit";
743
744	=item time => @reply
745
746	Replies the the current node time to C<@reply>.
747
748	Example: tell the current node to send the current time to C<$myport> in a
749	C<timereply> message.
750
751	snd $NODE, time => $myport, timereply => 1, 2;
752	# => snd $myport, timereply => 1, 2, <time>
753		1051
754	=back	1052	=back
755		1053
756	=head1 AnyEvent::MP vs. Distributed Erlang	1054	=head1 AnyEvent::MP vs. Distributed Erlang
757		1055
758	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1056	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
759	== aemp node, Erlang process == aemp port), so many of the documents and	1057	== aemp node, Erlang process == aemp port), so many of the documents and
760	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1058	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
761	sample:	1059	sample:
762		1060
763	http://www.Erlang.se/doc/programming_rules.shtml	1061	http://www.erlang.se/doc/programming_rules.shtml
764	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1062	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
765	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1063	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
766	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1064	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
767		1065
768	Despite the similarities, there are also some important differences:	1066	Despite the similarities, there are also some important differences:
769		1067
770	=over 4	1068	=over 4
771		1069
772	=item * Node references contain the recipe on how to contact them.	1070	=item * Node IDs are arbitrary strings in AEMP.
773		1071
774	Erlang relies on special naming and DNS to work everywhere in the	1072	Erlang relies on special naming and DNS to work everywhere in the same
775	same way. AEMP relies on each node knowing it's own address(es), with	1073	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
776	convenience functionality.	1074	configuration or DNS), and possibly the addresses of some seed nodes, but
		1075	will otherwise discover other nodes (and their IDs) itself.
777		1076
778	This means that AEMP requires a less tightly controlled environment at the	1077	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
779	cost of longer node references and a slightly higher management overhead.	1078	uses "local ports are like remote ports".
		1079
		1080	The failure modes for local ports are quite different (runtime errors
		1081	only) then for remote ports - when a local port dies, you I<know> it dies,
		1082	when a connection to another node dies, you know nothing about the other
		1083	port.
		1084
		1085	Erlang pretends remote ports are as reliable as local ports, even when
		1086	they are not.
		1087
		1088	AEMP encourages a "treat remote ports differently" philosophy, with local
		1089	ports being the special case/exception, where transport errors cannot
		1090	occur.
780		1091
781	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1092	=item * Erlang uses processes and a mailbox, AEMP does not queue.
782		1093
783	Erlang uses processes that selctively receive messages, and therefore	1094	Erlang uses processes that selectively receive messages out of order, and
784	needs a queue. AEMP is event based, queuing messages would serve no useful	1095	therefore needs a queue. AEMP is event based, queuing messages would serve
785	purpose.	1096	no useful purpose. For the same reason the pattern-matching abilities
		1097	of AnyEvent::MP are more limited, as there is little need to be able to
		1098	filter messages without dequeuing them.
786		1099
787	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1100	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1101	being event-based, while Erlang is process-based.
		1102
		1103	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1104	top of AEMP and Coro threads.
788		1105
789	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1106	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
790		1107
791	Sending messages in Erlang is synchronous and blocks the process. AEMP	1108	Sending messages in Erlang is synchronous and blocks the process until
792	sends are immediate, connection establishment is handled in the	1109	a conenction has been established and the message sent (and so does not
793	background.	1110	need a queue that can overflow). AEMP sends return immediately, connection
		1111	establishment is handled in the background.
794		1112
795	=item * Erlang can silently lose messages, AEMP cannot.	1113	=item * Erlang suffers from silent message loss, AEMP does not.
796		1114
797	Erlang makes few guarantees on messages delivery - messages can get lost	1115	Erlang implements few guarantees on messages delivery - messages can get
798	without any of the processes realising it (i.e. you send messages a, b,	1116	lost without any of the processes realising it (i.e. you send messages a,
799	and c, and the other side only receives messages a and c).	1117	b, and c, and the other side only receives messages a and c).
800		1118
801	AEMP guarantees correct ordering, and the guarantee that there are no	1119	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1120	guarantee that after one message is lost, all following ones sent to the
		1121	same port are lost as well, until monitoring raises an error, so there are
802	holes in the message sequence.	1122	no silent "holes" in the message sequence.
803		1123
804	=item * In Erlang, processes can be declared dead and later be found to be	1124	If you want your software to be very reliable, you have to cope with
805	alive.	1125	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
806		1126	simply tries to work better in common error cases, such as when a network
807	In Erlang it can happen that a monitored process is declared dead and	1127	link goes down.
808	linked processes get killed, but later it turns out that the process is
809	still alive - and can receive messages.
810
811	In AEMP, when port monitoring detects a port as dead, then that port will
812	eventually be killed - it cannot happen that a node detects a port as dead
813	and then later sends messages to it, finding it is still alive.
814		1128
815	=item * Erlang can send messages to the wrong port, AEMP does not.	1129	=item * Erlang can send messages to the wrong port, AEMP does not.
816		1130
817	In Erlang it is quite possible that a node that restarts reuses a process	1131	In Erlang it is quite likely that a node that restarts reuses an Erlang
818	ID known to other nodes for a completely different process, causing	1132	process ID known to other nodes for a completely different process,
819	messages destined for that process to end up in an unrelated process.	1133	causing messages destined for that process to end up in an unrelated
		1134	process.
820		1135
821	AEMP never reuses port IDs, so old messages or old port IDs floating	1136	AEMP does not reuse port IDs, so old messages or old port IDs floating
822	around in the network will not be sent to an unrelated port.	1137	around in the network will not be sent to an unrelated port.
823		1138
824	=item * Erlang uses unprotected connections, AEMP uses secure	1139	=item * Erlang uses unprotected connections, AEMP uses secure
825	authentication and can use TLS.	1140	authentication and can use TLS.
826		1141
827	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1142	AEMP can use a proven protocol - TLS - to protect connections and
828	securely authenticate nodes.	1143	securely authenticate nodes.
829		1144
830	=item * The AEMP protocol is optimised for both text-based and binary	1145	=item * The AEMP protocol is optimised for both text-based and binary
831	communications.	1146	communications.
832		1147
833	The AEMP protocol, unlike the Erlang protocol, supports both	1148	The AEMP protocol, unlike the Erlang protocol, supports both programming
834	language-independent text-only protocols (good for debugging) and binary,	1149	language independent text-only protocols (good for debugging), and binary,
835	language-specific serialisers (e.g. Storable).	1150	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1151	used, the protocol is actually completely text-based.
836		1152
837	It has also been carefully designed to be implementable in other languages	1153	It has also been carefully designed to be implementable in other languages
838	with a minimum of work while gracefully degrading fucntionality to make the	1154	with a minimum of work while gracefully degrading functionality to make the
839	protocol simple.	1155	protocol simple.
840		1156
841	=item * AEMP has more flexible monitoring options than Erlang.	1157	=item * AEMP has more flexible monitoring options than Erlang.
842		1158
843	In Erlang, you can chose to receive I<all> exit signals as messages	1159	In Erlang, you can chose to receive I<all> exit signals as messages or
844	or I<none>, there is no in-between, so monitoring single processes is	1160	I<none>, there is no in-between, so monitoring single Erlang processes is
845	difficult to implement. Monitoring in AEMP is more flexible than in	1161	difficult to implement.
846	Erlang, as one can choose between automatic kill, exit message or callback	1162
847	on a per-process basis.	1163	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1164	between automatic kill, exit message or callback on a per-port basis.
848		1165
849	=item * Erlang tries to hide remote/local connections, AEMP does not.	1166	=item * Erlang tries to hide remote/local connections, AEMP does not.
850		1167
851	Monitoring in Erlang is not an indicator of process death/crashes,	1168	Monitoring in Erlang is not an indicator of process death/crashes, in the
852	as linking is (except linking is unreliable in Erlang).	1169	same way as linking is (except linking is unreliable in Erlang).
853		1170
854	In AEMP, you don't "look up" registered port names or send to named ports	1171	In AEMP, you don't "look up" registered port names or send to named ports
855	that might or might not be persistent. Instead, you normally spawn a port	1172	that might or might not be persistent. Instead, you normally spawn a port
856	on the remote node. The init function monitors the you, and you monitor	1173	on the remote node. The init function monitors you, and you monitor the
857	the remote port. Since both monitors are local to the node, they are much	1174	remote port. Since both monitors are local to the node, they are much more
858	more reliable.	1175	reliable (no need for C<spawn_link>).
859		1176
860	This also saves round-trips and avoids sending messages to the wrong port	1177	This also saves round-trips and avoids sending messages to the wrong port
861	(hard to do in Erlang).	1178	(hard to do in Erlang).
862		1179
863	=back	1180	=back
864		1181
865	=head1 RATIONALE	1182	=head1 RATIONALE
866		1183
867	=over 4	1184	=over 4
868		1185
869	=item Why strings for ports and noderefs, why not objects?	1186	=item Why strings for port and node IDs, why not objects?
870		1187
871	We considered "objects", but found that the actual number of methods	1188	We considered "objects", but found that the actual number of methods
872	thatc an be called are very low. Since port IDs and noderefs travel over	1189	that can be called are quite low. Since port and node IDs travel over
873	the network frequently, the serialising/deserialising would add lots of	1190	the network frequently, the serialising/deserialising would add lots of
874	overhead, as well as having to keep a proxy object.	1191	overhead, as well as having to keep a proxy object everywhere.
875		1192
876	Strings can easily be printed, easily serialised etc. and need no special	1193	Strings can easily be printed, easily serialised etc. and need no special
877	procedures to be "valid".	1194	procedures to be "valid".
878		1195
879	And a a miniport consists of a single closure stored in a global hash - it	1196	And as a result, a port with just a default receiver consists of a single
880	can't become much cheaper.	1197	code reference stored in a global hash - it can't become much cheaper.
881		1198
882	=item Why favour JSON, why not real serialising format such as Storable?	1199	=item Why favour JSON, why not a real serialising format such as Storable?
883		1200
884	In fact, any AnyEvent::MP node will happily accept Storable as framing	1201	In fact, any AnyEvent::MP node will happily accept Storable as framing
885	format, but currently there is no way to make a node use Storable by	1202	format, but currently there is no way to make a node use Storable by
886	default.	1203	default (although all nodes will accept it).
887		1204
888	The default framing protocol is JSON because a) JSON::XS is many times	1205	The default framing protocol is JSON because a) JSON::XS is many times
889	faster for small messages and b) most importantly, after years of	1206	faster for small messages and b) most importantly, after years of
890	experience we found that object serialisation is causing more problems	1207	experience we found that object serialisation is causing more problems
891	than it gains: Just like function calls, objects simply do not travel	1208	than it solves: Just like function calls, objects simply do not travel
892	easily over the network, mostly because they will always be a copy, so you	1209	easily over the network, mostly because they will always be a copy, so you
893	always have to re-think your design.	1210	always have to re-think your design.
894		1211
895	Keeping your messages simple, concentrating on data structures rather than	1212	Keeping your messages simple, concentrating on data structures rather than
896	objects, will keep your messages clean, tidy and efficient.	1213	objects, will keep your messages clean, tidy and efficient.
897		1214
898	=back	1215	=back
899		1216
900	=head1 SEE ALSO	1217	=head1 SEE ALSO
901		1218
		1219	L<AnyEvent::MP::Intro> - a gentle introduction.
		1220
		1221	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1222
		1223	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1224	your applications.
		1225
		1226	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1227
		1228	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1229	all nodes.
		1230
902	L<AnyEvent>.	1231	L<AnyEvent>.
903		1232
904	=head1 AUTHOR	1233	=head1 AUTHOR
905		1234
906	Marc Lehmann <schmorp@schmorp.de>	1235	Marc Lehmann <schmorp@schmorp.de>

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