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Revision 1.136 by root, Wed Mar 21 15:22:16 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 => $pass->(@msg)
192	become a slave node. Slave nodes cannot be contacted from outside and will
193	route most of their traffic to the master node that they attach to.
194		253
195	At least one additional noderef is required: The node will try to connect	254	In addition to specifying a boolean, you can specify a code reference that
196	to all of them and will become a slave attached to the first node it can	255	is called for every code execution attempt - the execution request is
197	successfully connect to.	256	granted iff the callback returns a true value.
		257
		258	Most of the time the callback should look only at
		259	C<$AnyEvent::MP::Kernel::SRCNODE> to make a decision, and not at the
		260	actual message (which can be about anything, and is mostly provided for
		261	diagnostic purposes).
		262
		263	See F<semp setsecure> for more info.
198		264
199	=back	265	=back
200		266
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	267	=over 4
236		268
237	=item the empty string	269	=item step 1, gathering configuration from profiles
238		270
239	An empty-string component gets resolved as if the default port (4040) was	271	The function first looks up a profile in the aemp configuration (see the
240	specified.	272	L<aemp> commandline utility). The profile name can be specified via the
		273	named C<profile> parameter or can simply be the first parameter). If it is
		274	missing, then the nodename (F<uname -n>) will be used as profile name.
241		275
242	=item naked port numbers (e.g. C<1234>)	276	The profile data is then gathered as follows:
243		277
244	These are resolved by prepending the local nodename and a colon, to be	278	First, all remaining key => value pairs (all of which are conveniently
245	further resolved.	279	undocumented at the moment) will be interpreted as configuration
		280	data. Then they will be overwritten by any values specified in the global
		281	default configuration (see the F<aemp> utility), then the chain of
		282	profiles chosen by the profile name (and any C<parent> attributes).
246		283
247	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	284	That means that the values specified in the profile have highest priority
		285	and the values specified directly via C<configure> have lowest priority,
		286	and can only be used to specify defaults.
248		287
249	These are resolved by using AnyEvent::DNS to resolve them, optionally	288	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	289	this process. If not, then the profile name will be used as node ID, with
251	specified.	290	a unique randoms tring (C</%u>) appended.
		291
		292	The node ID can contain some C<%> sequences that are expanded: C<%n>
		293	is expanded to the local nodename, C<%u> is replaced by a random
		294	strign to make the node unique. For example, the F<aemp> commandline
		295	utility uses C<aemp/%n/%u> as nodename, which might expand to
		296	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		297
		298	=item step 2, bind listener sockets
		299
		300	The next step is to look up the binds in the profile, followed by binding
		301	aemp protocol listeners on all binds specified (it is possible and valid
		302	to have no binds, meaning that the node cannot be contacted form the
		303	outside. This means the node cannot talk to other nodes that also have no
		304	binds, but it can still talk to all "normal" nodes).
		305
		306	If the profile does not specify a binds list, then a default of C<*> is
		307	used, meaning the node will bind on a dynamically-assigned port on every
		308	local IP address it finds.
		309
		310	=item step 3, connect to seed nodes
		311
		312	As the last step, the seed ID list from the profile is passed to the
		313	L<AnyEvent::MP::Global> module, which will then use it to keep
		314	connectivity with at least one node at any point in time.
252		315
253	=back	316	=back
		317
		318	Example: become a distributed node using the local node name as profile.
		319	This should be the most common form of invocation for "daemon"-type nodes.
		320
		321	configure
		322
		323	Example: become a semi-anonymous node. This form is often used for
		324	commandline clients.
		325
		326	configure nodeid => "myscript/%n/%u";
		327
		328	Example: configure a node using a profile called seed, which is suitable
		329	for a seed node as it binds on all local addresses on a fixed port (4040,
		330	customary for aemp).
		331
		332	# use the aemp commandline utility
		333	# aemp profile seed binds '*:4040'
		334
		335	# then use it
		336	configure profile => "seed";
		337
		338	# or simply use aemp from the shell again:
		339	# aemp run profile seed
		340
		341	# or provide a nicer-to-remember nodeid
		342	# aemp run profile seed nodeid "$(hostname)"
254		343
255	=item $SELF	344	=item $SELF
256		345
257	Contains the current port id while executing C<rcv> callbacks or C<psub>	346	Contains the current port id while executing C<rcv> callbacks or C<psub>
258	blocks.	347	blocks.
259		348
260	=item SELF, %SELF, @SELF...	349	=item *SELF, SELF, %SELF, @SELF...
261		350
262	Due to some quirks in how perl exports variables, it is impossible to	351	Due to some quirks in how perl exports variables, it is impossible to
263	just export C<$SELF>, all the symbols called C<SELF> are exported by this	352	just export C<$SELF>, all the symbols named C<SELF> are exported by this
264	module, but only C<$SELF> is currently used.	353	module, but only C<$SELF> is currently used.
265		354
266	=item snd $port, type => @data	355	=item snd $port, type => @data
267		356
268	=item snd $port, @msg	357	=item snd $port, @msg
269		358
270	Send the given message to the given port ID, which can identify either	359	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	360	local or a remote port, and must be a port ID.
272	stringifies a sa port ID (such as a port object :).
273		361
274	While the message can be about anything, it is highly recommended to use a	362	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	363	use a string as first element (a port ID, or some word that indicates a
276	type etc.).	364	request type etc.) and to consist if only simple perl values (scalars,
		365	arrays, hashes) - if you think you need to pass an object, think again.
277		366
278	The message data effectively becomes read-only after a call to this	367	The message data logically becomes read-only after a call to this
279	function: modifying any argument is not allowed and can cause many	368	function: modifying any argument (or values referenced by them) is
280	problems.	369	forbidden, as there can be considerable time between the call to C<snd>
		370	and the time the message is actually being serialised - in fact, it might
		371	never be copied as within the same process it is simply handed to the
		372	receiving port.
281		373
282	The type of data you can transfer depends on the transport protocol: when	374	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	375	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	376	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	377	that Storable can serialise and deserialise is allowed, and for the local
286	node, anything can be passed.	378	node, anything can be passed. Best rely only on the common denominator of
		379	these.
287		380
288	=item $local_port = port	381	=item $local_port = port
289		382
290	Create a new local port object that can be used either as a pattern	383	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"),	384	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		385
294	=item $port = port { my @msg = @_; $finished }	386	=item $local_port = port { my @msg = @_ }
295		387
296	Creates a "miniport", that is, a very lightweight port without any pattern	388	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.	389	creating a port and calling C<rcv $port, $callback> on it.
299		390
300	The block will be called for every message received on the port. When the	391	The block will be called for every message received on the port, with the
301	callback returns a true value its job is considered "done" and the port	392	global variable C<$SELF> set to the port ID. Runtime errors will cause the
302	will be destroyed. Otherwise it will stay alive.	393	port to be C<kil>ed. The message will be passed as-is, no extra argument
		394	(i.e. no port ID) will be passed to the callback.
303		395
304	The message will be passed as-is, no extra argument (i.e. no port id) will	396	If you want to stop/destroy the port, simply C<kil> it:
305	be passed to the callback.
306		397
307	If you need the local port id in the callback, this works nicely:	398	my $port = port {
308		399	my @msg = @_;
309	my $port; $port = port {	400	...
310	snd $otherport, reply => $port;	401	kil $SELF;
311	};	402	};
312		403
313	=cut	404	=cut
314		405
315	sub rcv($@);	406	sub rcv($@);
316		407
		408	my $KILME = sub {
		409	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
		410	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		411	};
		412
317	sub port(;&) {	413	sub port(;&) {
318	my $id = "$UNIQ." . $ID++;	414	my $id = $UNIQ . ++$ID;
319	my $port = "$NODE#$id";	415	my $port = "$NODE#$id";
320		416
321	if (@_) {
322	rcv $port, shift;	417	rcv $port, shift || $KILME;
323	} else {
324	$PORT{$id} = sub { }; # nop
325	}
326		418
327	$port	419	$port
328	}	420	}
329		421
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)	422	=item rcv $local_port, $callback->(@msg)
350		423
351	Replaces the callback on the specified miniport (after converting it to	424	Replaces the default callback on the specified port. There is no way to
352	one if required).	425	remove the default callback: use C<sub { }> to disable it, or better
353		426	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...] => $callback->(@msg), ...
359
360	Register callbacks to be called on matching messages on the given full
361	port (after converting it to one if required) and return the port.
362
363	The callback has to return a true value when its work is done, after
364	which is will be removed, or a false value in which case it will stay
365	registered.
366		427
367	The global C<$SELF> (exported by this module) contains C<$port> while	428	The global C<$SELF> (exported by this module) contains C<$port> while
368	executing the callback.	429	executing the callback. Runtime errors during callback execution will
		430	result in the port being C<kil>ed.
369		431
370	Runtime errors during callback execution will result in the port being	432	The default callback receives all messages not matched by a more specific
371	C<kil>ed.	433	C<tag> match.
372		434
373	If the match is an array reference, then it will be matched against the	435	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
374	first elements of the message, otherwise only the first element is being
375	matched.
376		436
377	Any element in the match that is specified as C<_any_> (a function	437	Register (or replace) callbacks to be called on messages starting with the
378	exported by this module) matches any single element of the message.	438	given tag on the given port (and return the port), or unregister it (when
		439	C<$callback> is C<$undef> or missing). There can only be one callback
		440	registered for each tag.
379		441
380	While not required, it is highly recommended that the first matching	442	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	443	element (the tag) has been removed. The callback will use the same
382	also the most efficient match (by far).	444	environment as the default callback (see above).
383		445
384	Example: create a port and bind receivers on it in one go.	446	Example: create a port and bind receivers on it in one go.
385		447
386	my $port = rcv port,	448	my $port = rcv port,
387	msg1 => sub { ...; 0 },	449	msg1 => sub { ... },
388	msg2 => sub { ...; 0 },	450	msg2 => sub { ... },
389	;	451	;
390		452
391	Example: create a port, bind receivers and send it in a message elsewhere	453	Example: create a port, bind receivers and send it in a message elsewhere
392	in one go:	454	in one go:
393		455
394	snd $otherport, reply =>	456	snd $otherport, reply =>
395	rcv port,	457	rcv port,
396	msg1 => sub { ...; 0 },	458	msg1 => sub { ... },
397	...	459	...
398	;	460	;
399		461
		462	Example: temporarily register a rcv callback for a tag matching some port
		463	(e.g. for an rpc reply) and unregister it after a message was received.
		464
		465	rcv $port, $otherport => sub {
		466	my @reply = @_;
		467
		468	rcv $SELF, $otherport;
		469	};
		470
400	=cut	471	=cut
401		472
402	sub rcv($@) {	473	sub rcv($@) {
403	my $port = shift;	474	my $port = shift;
404	my ($noderef, $portid) = split /#/, $port, 2;	475	my ($nodeid, $portid) = split /#/, $port, 2;
405		476
406	($NODE{$noderef} || add_node $noderef) == $NODE{""}	477	$NODE{$nodeid} == $NODE{""}
407	or Carp::croak "$port: rcv can only be called on local ports, caught";	478	or Carp::croak "$port: rcv can only be called on local ports, caught";
408		479
409	if (@_ == 1) {	480	while (@_) {
		481	if (ref $_[0]) {
		482	if (my $self = $PORT_DATA{$portid}) {
		483	"AnyEvent::MP::Port" eq ref $self
		484	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		485
		486	$self->[0] = shift;
		487	} else {
410	my $cb = shift;	488	my $cb = shift;
411	delete $PORT_DATA{$portid};
412	$PORT{$portid} = sub {	489	$PORT{$portid} = sub {
413	local $SELF = $port;	490	local $SELF = $port;
414	eval {	491	eval { &$cb }; _self_die if $@;
415	&$cb	492	};
416	and kil $port;
417	};	493	}
418	_self_die if $@;	494	} elsif (defined $_[0]) {
419	};
420	} else {
421	my $self = $PORT_DATA{$portid} ||= do {	495	my $self = $PORT_DATA{$portid} ||= do {
422	my $self = bless {	496	my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
423	id => $port,
424	}, "AnyEvent::MP::Port";
425		497
426	$PORT{$portid} = sub {	498	$PORT{$portid} = sub {
427	local $SELF = $port;	499	local $SELF = $port;
428		500
429	eval {
430	for (@{ $self->{rc0}{$_[0]} }) {	501	if (my $cb = $self->[1]{$_[0]}) {
431	$_ && &{$_->[0]}	502	shift;
432	&& undef $_;	503	eval { &$cb }; _self_die if $@;
433	}	504	} else {
434
435	for (@{ $self->{rcv}{$_[0]} }) {
436	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
437	&& &{$_->[0]}	505	&{ $self->[0] };
438	&& undef $_;
439	}
440
441	for (@{ $self->{any} }) {
442	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
443	&& &{$_->[0]}
444	&& undef $_;
445	}	506	}
446	};	507	};
447	_self_die if $@;	508
		509	$self
448	};	510	};
449		511
450	$self
451	};
452
453	"AnyEvent::MP::Port" eq ref $self	512	"AnyEvent::MP::Port" eq ref $self
454	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	513	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
455		514
456	while (@_) {
457	my ($match, $cb) = splice @_, 0, 2;	515	my ($tag, $cb) = splice @_, 0, 2;
458		516
459	if (!ref $match) {	517	if (defined $cb) {
460	push @{ $self->{rc0}{$match} }, [$cb];	518	$self->[1]{$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 {	519	} else {
467	push @{ $self->{any} }, [$cb, $match];	520	delete $self->[1]{$tag};
468	}	521	}
469	}	522	}
470	}	523	}
471		524
472	$port	525	$port
473	}	526	}
474		527
		528	=item peval $port, $coderef[, @args]
		529
		530	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		531	when the code throews an exception the C<$port> will be killed.
		532
		533	Any remaining args will be passed to the callback. Any return values will
		534	be returned to the caller.
		535
		536	This is useful when you temporarily want to execute code in the context of
		537	a port.
		538
		539	Example: create a port and run some initialisation code in it's context.
		540
		541	my $port = port { ... };
		542
		543	peval $port, sub {
		544	init
		545	or die "unable to init";
		546	};
		547
		548	=cut
		549
		550	sub peval($$) {
		551	local $SELF = shift;
		552	my $cb = shift;
		553
		554	if (wantarray) {
		555	my @res = eval { &$cb };
		556	_self_die if $@;
		557	@res
		558	} else {
		559	my $res = eval { &$cb };
		560	_self_die if $@;
		561	$res
		562	}
		563	}
		564
475	=item $closure = psub { BLOCK }	565	=item $closure = psub { BLOCK }
476		566
477	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	567	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>	568	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.	569	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		570
		571	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		572	BLOCK }, @_ } >>.
480		573
481	This is useful when you register callbacks from C<rcv> callbacks:	574	This is useful when you register callbacks from C<rcv> callbacks:
482		575
483	rcv delayed_reply => sub {	576	rcv delayed_reply => sub {
484	my ($delay, @reply) = @_;	577	my ($delay, @reply) = @_;
…		…
508	$res	601	$res
509	}	602	}
510	}	603	}
511	}	604	}
512		605
513	=item $guard = mon $port, $cb->(@reason)	606	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
514		607
515	=item $guard = mon $port, $rcvport	608	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
516		609
517	=item $guard = mon $port	610	=item $guard = mon $port # kill $SELF when $port dies
518		611
519	=item $guard = mon $port, $rcvport, @msg	612	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
520		613
521	Monitor the given port and do something when the port is killed or	614	Monitor the given port and do something when the port is killed or
522	messages to it were lost, and optionally return a guard that can be used	615	messages to it were lost, and optionally return a guard that can be used
523	to stop monitoring again.	616	to stop monitoring again.
524
525	C<mon> effectively guarantees that, in the absence of hardware failures,
526	that after starting the monitor, either all messages sent to the port
527	will arrive, or the monitoring action will be invoked after possible
528	message loss has been detected. No messages will be lost "in between"
529	(after the first lost message no further messages will be received by the
530	port). After the monitoring action was invoked, further messages might get
531	delivered again.
532		617
533	In the first form (callback), the callback is simply called with any	618	In the first form (callback), the callback is simply called with any
534	number of C<@reason> elements (no @reason means that the port was deleted	619	number of C<@reason> elements (no @reason means that the port was deleted
535	"normally"). Note also that I<< the callback B<must> never die >>, so use	620	"normally"). Note also that I<< the callback B<must> never die >>, so use
536	C<eval> if unsure.	621	C<eval> if unsure.
537		622
538	In the second form (another port given), the other port (C<$rcvport>)	623	In the second form (another port given), the other port (C<$rcvport>)
539	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	624	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
540	"normal" kils nothing happens, while under all other conditions, the other	625	"normal" kils nothing happens, while under all other conditions, the other
541	port is killed with the same reason.	626	port is killed with the same reason.
542		627
543	The third form (kill self) is the same as the second form, except that	628	The third form (kill self) is the same as the second form, except that
544	C<$rvport> defaults to C<$SELF>.	629	C<$rvport> defaults to C<$SELF>.
545		630
546	In the last form (message), a message of the form C<@msg, @reason> will be	631	In the last form (message), a message of the form C<@msg, @reason> will be
547	C<snd>.	632	C<snd>.
		633
		634	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		635	alert was raised), they are removed and will not trigger again.
548		636
549	As a rule of thumb, monitoring requests should always monitor a port from	637	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	638	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	639	lost, just like any other message. Another less obvious reason is that
552	even monitoring requests can get lost (for exmaple, when the connection	640	even monitoring requests can get lost (for example, when the connection
553	to the other node goes down permanently). When monitoring a port locally	641	to the other node goes down permanently). When monitoring a port locally
554	these problems do not exist.	642	these problems do not exist.
555		643
		644	C<mon> effectively guarantees that, in the absence of hardware failures,
		645	after starting the monitor, either all messages sent to the port will
		646	arrive, or the monitoring action will be invoked after possible message
		647	loss has been detected. No messages will be lost "in between" (after
		648	the first lost message no further messages will be received by the
		649	port). After the monitoring action was invoked, further messages might get
		650	delivered again.
		651
		652	Inter-host-connection timeouts and monitoring depend on the transport
		653	used. The only transport currently implemented is TCP, and AnyEvent::MP
		654	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		655	non-idle connection, and usually around two hours for idle connections).
		656
		657	This means that monitoring is good for program errors and cleaning up
		658	stuff eventually, but they are no replacement for a timeout when you need
		659	to ensure some maximum latency.
		660
556	Example: call a given callback when C<$port> is killed.	661	Example: call a given callback when C<$port> is killed.
557		662
558	mon $port, sub { warn "port died because of <@_>\n" };	663	mon $port, sub { warn "port died because of <@_>\n" };
559		664
560	Example: kill ourselves when C<$port> is killed abnormally.	665	Example: kill ourselves when C<$port> is killed abnormally.
…		…
566	mon $port, $self => "restart";	671	mon $port, $self => "restart";
567		672
568	=cut	673	=cut
569		674
570	sub mon {	675	sub mon {
571	my ($noderef, $port) = split /#/, shift, 2;	676	my ($nodeid, $port) = split /#/, shift, 2;
572		677
573	my $node = $NODE{$noderef} || add_node $noderef;	678	my $node = $NODE{$nodeid} || add_node $nodeid;
574		679
575	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';	680	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
576		681
577	unless (ref $cb) {	682	unless (ref $cb) {
578	if (@_) {	683	if (@_) {
…		…
587	}	692	}
588		693
589	$node->monitor ($port, $cb);	694	$node->monitor ($port, $cb);
590		695
591	defined wantarray	696	defined wantarray
592	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	697	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
593	}	698	}
594		699
595	=item $guard = mon_guard $port, $ref, $ref...	700	=item $guard = mon_guard $port, $ref, $ref...
596		701
597	Monitors the given C<$port> and keeps the passed references. When the port	702	Monitors the given C<$port> and keeps the passed references. When the port
598	is killed, the references will be freed.	703	is killed, the references will be freed.
599		704
600	Optionally returns a guard that will stop the monitoring.	705	Optionally returns a guard that will stop the monitoring.
601		706
602	This function is useful when you create e.g. timers or other watchers and	707	This function is useful when you create e.g. timers or other watchers and
603	want to free them when the port gets killed:	708	want to free them when the port gets killed (note the use of C<psub>):
604		709
605	$port->rcv (start => sub {	710	$port->rcv (start => sub {
606	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	711	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
607	undef $timer if 0.9 < rand;	712	undef $timer if 0.9 < rand;
608	});	713	});
609	});	714	});
610		715
611	=cut	716	=cut
…		…
620		725
621	=item kil $port[, @reason]	726	=item kil $port[, @reason]
622		727
623	Kill the specified port with the given C<@reason>.	728	Kill the specified port with the given C<@reason>.
624		729
625	If no C<@reason> is specified, then the port is killed "normally" (linked	730	If no C<@reason> is specified, then the port is killed "normally" -
626	ports will not be kileld, or even notified).	731	monitor callback will be invoked, but the kil will not cause linked ports
		732	(C<mon $mport, $lport> form) to get killed.
627		733
628	Otherwise, linked ports get killed with the same reason (second form of	734	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
629	C<mon>, see below).	735	form) get killed with the same reason.
630		736
631	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	737	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
632	will be reported as reason C<< die => $@ >>.	738	will be reported as reason C<< die => $@ >>.
633		739
634	Transport/communication errors are reported as C<< transport_error =>	740	Transport/communication errors are reported as C<< transport_error =>
635	$message >>.	741	$message >>.
636		742
637	=cut	743	Common idioms:
		744
		745	# silently remove yourself, do not kill linked ports
		746	kil $SELF;
		747
		748	# report a failure in some detail
		749	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		750
		751	# do not waste much time with killing, just die when something goes wrong
		752	open my $fh, "<file"
		753	or die "file: $!";
638		754
639	=item $port = spawn $node, $initfunc[, @initdata]	755	=item $port = spawn $node, $initfunc[, @initdata]
640		756
641	Creates a port on the node C<$node> (which can also be a port ID, in which	757	Creates a port on the node C<$node> (which can also be a port ID, in which
642	case it's the node where that port resides).	758	case it's the node where that port resides).
643		759
644	The port ID of the newly created port is return immediately, and it is	760	The port ID of the newly created port is returned immediately, and it is
645	permissible to immediately start sending messages or monitor the port.	761	possible to immediately start sending messages or to monitor the port.
646		762
647	After the port has been created, the init function is	763	After the port has been created, the init function is called on the remote
648	called. This function must be a fully-qualified function name	764	node, in the same context as a C<rcv> callback. This function must be a
649	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	765	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
650	program, use C<::name>.	766	specify a function in the main program, use C<::name>.
651		767
652	If the function doesn't exist, then the node tries to C<require>	768	If the function doesn't exist, then the node tries to C<require>
653	the package, then the package above the package and so on (e.g.	769	the package, then the package above the package and so on (e.g.
654	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	770	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
655	exists or it runs out of package names.	771	exists or it runs out of package names.
656		772
657	The init function is then called with the newly-created port as context	773	The init function is then called with the newly-created port as context
658	object (C<$SELF>) and the C<@initdata> values as arguments.	774	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		775	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		776	the port might not get created.
659		777
660	A common idiom is to pass your own port, monitor the spawned port, and	778	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	779	port, and in the remote init function, immediately monitor the passed
662	ensures that both ports get cleaned up when there is a problem.	780	local port. This two-way monitoring ensures that both ports get cleaned up
		781	when there is a problem.
		782
		783	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		784	caller before C<spawn> returns (by delaying invocation when spawn is
		785	called for the local node).
663		786
664	Example: spawn a chat server port on C<$othernode>.	787	Example: spawn a chat server port on C<$othernode>.
665		788
666	# this node, executed from within a port context:	789	# this node, executed from within a port context:
667	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	790	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
682		805
683	sub _spawn {	806	sub _spawn {
684	my $port = shift;	807	my $port = shift;
685	my $init = shift;	808	my $init = shift;
686		809
		810	# rcv will create the actual port
687	local $SELF = "$NODE#$port";	811	local $SELF = "$NODE#$port";
688	eval {	812	eval {
689	&{ load_func $init }	813	&{ load_func $init }
690	};	814	};
691	_self_die if $@;	815	_self_die if $@;
692	}	816	}
693		817
694	sub spawn(@) {	818	sub spawn(@) {
695	my ($noderef, undef) = split /#/, shift, 2;	819	my ($nodeid, undef) = split /#/, shift, 2;
696		820
697	my $id = "$RUNIQ." . $ID++;	821	my $id = $RUNIQ . ++$ID;
698		822
699	$_[0] =~ /::/	823	$_[0] =~ /::/
700	or Carp::croak "spawn init function must be a fully-qualified name, caught";	824	or Carp::croak "spawn init function must be a fully-qualified name, caught";
701		825
702	($NODE{$noderef} || add_node $noderef)	826	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
703	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
704		827
705	"$noderef#$id"	828	"$nodeid#$id"
706	}	829	}
707		830
		831
		832	=item after $timeout, @msg
		833
		834	=item after $timeout, $callback
		835
		836	Either sends the given message, or call the given callback, after the
		837	specified number of seconds.
		838
		839	This is simply a utility function that comes in handy at times - the
		840	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		841	so it may go away in the future.
		842
		843	=cut
		844
		845	sub after($@) {
		846	my ($timeout, @action) = @_;
		847
		848	my $t; $t = AE::timer $timeout, 0, sub {
		849	undef $t;
		850	ref $action[0]
		851	? $action[0]()
		852	: snd @action;
		853	};
		854	}
		855
		856	#=item $cb2 = timeout $seconds, $cb[, @args]
		857
		858	=item cal $port, @msg, $callback[, $timeout]
		859
		860	A simple form of RPC - sends a message to the given C<$port> with the
		861	given contents (C<@msg>), but adds a reply port to the message.
		862
		863	The reply port is created temporarily just for the purpose of receiving
		864	the reply, and will be C<kil>ed when no longer needed.
		865
		866	A reply message sent to the port is passed to the C<$callback> as-is.
		867
		868	If an optional time-out (in seconds) is given and it is not C<undef>,
		869	then the callback will be called without any arguments after the time-out
		870	elapsed and the port is C<kil>ed.
		871
		872	If no time-out is given (or it is C<undef>), then the local port will
		873	monitor the remote port instead, so it eventually gets cleaned-up.
		874
		875	Currently this function returns the temporary port, but this "feature"
		876	might go in future versions unless you can make a convincing case that
		877	this is indeed useful for something.
		878
		879	=cut
		880
		881	sub cal(@) {
		882	my $timeout = ref $_[-1] ? undef : pop;
		883	my $cb = pop;
		884
		885	my $port = port {
		886	undef $timeout;
		887	kil $SELF;
		888	&$cb;
		889	};
		890
		891	if (defined $timeout) {
		892	$timeout = AE::timer $timeout, 0, sub {
		893	undef $timeout;
		894	kil $port;
		895	$cb->();
		896	};
		897	} else {
		898	mon $_[0], sub {
		899	kil $port;
		900	$cb->();
		901	};
		902	}
		903
		904	push @_, $port;
		905	&snd;
		906
		907	$port
		908	}
		909
708	=back	910	=back
709		911
710	=head1 NODE MESSAGES	912	=head1 DISTRIBUTED DATABASE
711		913
712	Nodes understand the following messages sent to them. Many of them take	914	AnyEvent::MP comes with a simple distributed database. The database will
713	arguments called C<@reply>, which will simply be used to compose a reply	915	be mirrored asynchronously on all global nodes. Other nodes bind to one
714	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	916	of the global nodes for their needs. Every node has a "local database"
715	the remaining arguments are simply the message data.	917	which contains all the values that are set locally. All local databases
		918	are merged together to form the global database, which can be queried.
716		919
717	While other messages exist, they are not public and subject to change.	920	The database structure is that of a two-level hash - the database hash
		921	contains hashes which contain values, similarly to a perl hash of hashes,
		922	i.e.:
718		923
		924	$DATABASE{$family}{$subkey} = $value
		925
		926	The top level hash key is called "family", and the second-level hash key
		927	is called "subkey" or simply "key".
		928
		929	The family must be alphanumeric, i.e. start with a letter and consist
		930	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		931	pretty much like Perl module names.
		932
		933	As the family namespace is global, it is recommended to prefix family names
		934	with the name of the application or module using it.
		935
		936	The subkeys must be non-empty strings, with no further restrictions.
		937
		938	The values should preferably be strings, but other perl scalars should
		939	work as well (such as C<undef>, arrays and hashes).
		940
		941	Every database entry is owned by one node - adding the same family/subkey
		942	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		943	but the result might be nondeterministic, i.e. the key might have
		944	different values on different nodes.
		945
		946	Different subkeys in the same family can be owned by different nodes
		947	without problems, and in fact, this is the common method to create worker
		948	pools. For example, a worker port for image scaling might do this:
		949
		950	db_set my_image_scalers => $port;
		951
		952	And clients looking for an image scaler will want to get the
		953	C<my_image_scalers> keys from time to time:
		954
		955	db_keys my_image_scalers => sub {
		956	@ports = @{ $_[0] };
		957	};
		958
		959	Or better yet, they want to monitor the database family, so they always
		960	have a reasonable up-to-date copy:
		961
		962	db_mon my_image_scalers => sub {
		963	@ports = keys %{ $_[0] };
		964	};
		965
		966	In general, you can set or delete single subkeys, but query and monitor
		967	whole families only.
		968
		969	If you feel the need to monitor or query a single subkey, try giving it
		970	it's own family.
		971
719	=over 4	972	=over
		973
		974	=item db_set $family => $subkey [=> $value]
		975
		976	Sets (or replaces) a key to the database - if C<$value> is omitted,
		977	C<undef> is used instead.
		978
		979	=item db_del $family => $subkey...
		980
		981	Deletes one or more subkeys from the database family.
		982
		983	=item $guard = db_reg $family => $subkey [=> $value]
		984
		985	Sets the key on the database and returns a guard. When the guard is
		986	destroyed, the key is deleted from the database. If C<$value> is missing,
		987	then C<undef> is used.
		988
		989	=item db_family $family => $cb->(\%familyhash)
		990
		991	Queries the named database C<$family> and call the callback with the
		992	family represented as a hash. You can keep and freely modify the hash.
		993
		994	=item db_keys $family => $cb->(\@keys)
		995
		996	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		997	them as array reference to the callback.
		998
		999	=item db_values $family => $cb->(\@values)
		1000
		1001	Same as C<db_family>, except it only queries the family I<values> and passes them
		1002	as array reference to the callback.
		1003
		1004	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1005
		1006	Creates a monitor on the given database family. Each time a key is set
		1007	or or is deleted the callback is called with a hash containing the
		1008	database family and three lists of added, changed and deleted subkeys,
		1009	respectively. If no keys have changed then the array reference might be
		1010	C<undef> or even missing.
		1011
		1012	If not called in void context, a guard object is returned that, when
		1013	destroyed, stops the monitor.
		1014
		1015	The family hash reference and the key arrays belong to AnyEvent::MP and
		1016	B<must not be modified or stored> by the callback. When in doubt, make a
		1017	copy.
		1018
		1019	As soon as possible after the monitoring starts, the callback will be
		1020	called with the intiial contents of the family, even if it is empty,
		1021	i.e. there will always be a timely call to the callback with the current
		1022	contents.
		1023
		1024	It is possible that the callback is called with a change event even though
		1025	the subkey is already present and the value has not changed.
		1026
		1027	The monitoring stops when the guard object is destroyed.
		1028
		1029	Example: on every change to the family "mygroup", print out all keys.
		1030
		1031	my $guard = db_mon mygroup => sub {
		1032	my ($family, $a, $c, $d) = @_;
		1033	print "mygroup members: ", (join " ", keys %$family), "\n";
		1034	};
		1035
		1036	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1037
		1038	my $guard; $guard = db_mon My::Module::workers => sub {
		1039	my ($family, $a, $c, $d) = @_;
		1040	return unless %$family;
		1041	undef $guard;
		1042	print "My::Module::workers now nonempty\n";
		1043	};
		1044
		1045	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1046
		1047	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1048	my ($family, $a, $c, $d) = @_;
		1049
		1050	print "+$_=$family->{$_}\n" for @$a;
		1051	print "*$_=$family->{$_}\n" for @$c;
		1052	print "-$_=$family->{$_}\n" for @$d;
		1053	};
720		1054
721	=cut	1055	=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		1056
754	=back	1057	=back
755		1058
756	=head1 AnyEvent::MP vs. Distributed Erlang	1059	=head1 AnyEvent::MP vs. Distributed Erlang
757		1060
758	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1061	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	1062	== 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	1063	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
761	sample:	1064	sample:
762		1065
763	http://www.Erlang.se/doc/programming_rules.shtml	1066	http://www.erlang.se/doc/programming_rules.shtml
764	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1067	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	1068	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	1069	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
767		1070
768	Despite the similarities, there are also some important differences:	1071	Despite the similarities, there are also some important differences:
769		1072
770	=over 4	1073	=over 4
771		1074
772	=item * Node references contain the recipe on how to contact them.	1075	=item * Node IDs are arbitrary strings in AEMP.
773		1076
774	Erlang relies on special naming and DNS to work everywhere in the	1077	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	1078	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
776	convenience functionality.	1079	configuration or DNS), and possibly the addresses of some seed nodes, but
		1080	will otherwise discover other nodes (and their IDs) itself.
777		1081
778	This means that AEMP requires a less tightly controlled environment at the	1082	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
779	cost of longer node references and a slightly higher management overhead.	1083	uses "local ports are like remote ports".
		1084
		1085	The failure modes for local ports are quite different (runtime errors
		1086	only) then for remote ports - when a local port dies, you I<know> it dies,
		1087	when a connection to another node dies, you know nothing about the other
		1088	port.
		1089
		1090	Erlang pretends remote ports are as reliable as local ports, even when
		1091	they are not.
		1092
		1093	AEMP encourages a "treat remote ports differently" philosophy, with local
		1094	ports being the special case/exception, where transport errors cannot
		1095	occur.
780		1096
781	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1097	=item * Erlang uses processes and a mailbox, AEMP does not queue.
782		1098
783	Erlang uses processes that selctively receive messages, and therefore	1099	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	1100	therefore needs a queue. AEMP is event based, queuing messages would serve
785	purpose.	1101	no useful purpose. For the same reason the pattern-matching abilities
		1102	of AnyEvent::MP are more limited, as there is little need to be able to
		1103	filter messages without dequeuing them.
786		1104
787	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1105	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1106	being event-based, while Erlang is process-based.
		1107
		1108	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1109	top of AEMP and Coro threads.
788		1110
789	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1111	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
790		1112
791	Sending messages in Erlang is synchronous and blocks the process. AEMP	1113	Sending messages in Erlang is synchronous and blocks the process until
792	sends are immediate, connection establishment is handled in the	1114	a conenction has been established and the message sent (and so does not
793	background.	1115	need a queue that can overflow). AEMP sends return immediately, connection
		1116	establishment is handled in the background.
794		1117
795	=item * Erlang can silently lose messages, AEMP cannot.	1118	=item * Erlang suffers from silent message loss, AEMP does not.
796		1119
797	Erlang makes few guarantees on messages delivery - messages can get lost	1120	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,	1121	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).	1122	b, and c, and the other side only receives messages a and c).
800		1123
801	AEMP guarantees correct ordering, and the guarantee that there are no	1124	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1125	guarantee that after one message is lost, all following ones sent to the
		1126	same port are lost as well, until monitoring raises an error, so there are
802	holes in the message sequence.	1127	no silent "holes" in the message sequence.
803		1128
804	=item * In Erlang, processes can be declared dead and later be found to be	1129	If you want your software to be very reliable, you have to cope with
805	alive.	1130	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
806		1131	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	1132	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		1133
815	=item * Erlang can send messages to the wrong port, AEMP does not.	1134	=item * Erlang can send messages to the wrong port, AEMP does not.
816		1135
817	In Erlang it is quite possible that a node that restarts reuses a process	1136	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	1137	process ID known to other nodes for a completely different process,
819	messages destined for that process to end up in an unrelated process.	1138	causing messages destined for that process to end up in an unrelated
		1139	process.
820		1140
821	AEMP never reuses port IDs, so old messages or old port IDs floating	1141	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.	1142	around in the network will not be sent to an unrelated port.
823		1143
824	=item * Erlang uses unprotected connections, AEMP uses secure	1144	=item * Erlang uses unprotected connections, AEMP uses secure
825	authentication and can use TLS.	1145	authentication and can use TLS.
826		1146
827	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1147	AEMP can use a proven protocol - TLS - to protect connections and
828	securely authenticate nodes.	1148	securely authenticate nodes.
829		1149
830	=item * The AEMP protocol is optimised for both text-based and binary	1150	=item * The AEMP protocol is optimised for both text-based and binary
831	communications.	1151	communications.
832		1152
833	The AEMP protocol, unlike the Erlang protocol, supports both	1153	The AEMP protocol, unlike the Erlang protocol, supports both programming
834	language-independent text-only protocols (good for debugging) and binary,	1154	language independent text-only protocols (good for debugging), and binary,
835	language-specific serialisers (e.g. Storable).	1155	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1156	used, the protocol is actually completely text-based.
836		1157
837	It has also been carefully designed to be implementable in other languages	1158	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	1159	with a minimum of work while gracefully degrading functionality to make the
839	protocol simple.	1160	protocol simple.
840		1161
841	=item * AEMP has more flexible monitoring options than Erlang.	1162	=item * AEMP has more flexible monitoring options than Erlang.
842		1163
843	In Erlang, you can chose to receive I<all> exit signals as messages	1164	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	1165	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	1166	difficult to implement.
846	Erlang, as one can choose between automatic kill, exit message or callback	1167
847	on a per-process basis.	1168	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1169	between automatic kill, exit message or callback on a per-port basis.
848		1170
849	=item * Erlang tries to hide remote/local connections, AEMP does not.	1171	=item * Erlang tries to hide remote/local connections, AEMP does not.
850		1172
851	Monitoring in Erlang is not an indicator of process death/crashes,	1173	Monitoring in Erlang is not an indicator of process death/crashes, in the
852	as linking is (except linking is unreliable in Erlang).	1174	same way as linking is (except linking is unreliable in Erlang).
853		1175
854	In AEMP, you don't "look up" registered port names or send to named ports	1176	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	1177	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	1178	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	1179	remote port. Since both monitors are local to the node, they are much more
858	more reliable.	1180	reliable (no need for C<spawn_link>).
859		1181
860	This also saves round-trips and avoids sending messages to the wrong port	1182	This also saves round-trips and avoids sending messages to the wrong port
861	(hard to do in Erlang).	1183	(hard to do in Erlang).
862		1184
863	=back	1185	=back
864		1186
865	=head1 RATIONALE	1187	=head1 RATIONALE
866		1188
867	=over 4	1189	=over 4
868		1190
869	=item Why strings for ports and noderefs, why not objects?	1191	=item Why strings for port and node IDs, why not objects?
870		1192
871	We considered "objects", but found that the actual number of methods	1193	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	1194	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	1195	the network frequently, the serialising/deserialising would add lots of
874	overhead, as well as having to keep a proxy object.	1196	overhead, as well as having to keep a proxy object everywhere.
875		1197
876	Strings can easily be printed, easily serialised etc. and need no special	1198	Strings can easily be printed, easily serialised etc. and need no special
877	procedures to be "valid".	1199	procedures to be "valid".
878		1200
879	And a a miniport consists of a single closure stored in a global hash - it	1201	And as a result, a port with just a default receiver consists of a single
880	can't become much cheaper.	1202	code reference stored in a global hash - it can't become much cheaper.
881		1203
882	=item Why favour JSON, why not real serialising format such as Storable?	1204	=item Why favour JSON, why not a real serialising format such as Storable?
883		1205
884	In fact, any AnyEvent::MP node will happily accept Storable as framing	1206	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	1207	format, but currently there is no way to make a node use Storable by
886	default.	1208	default (although all nodes will accept it).
887		1209
888	The default framing protocol is JSON because a) JSON::XS is many times	1210	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	1211	faster for small messages and b) most importantly, after years of
890	experience we found that object serialisation is causing more problems	1212	experience we found that object serialisation is causing more problems
891	than it gains: Just like function calls, objects simply do not travel	1213	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	1214	easily over the network, mostly because they will always be a copy, so you
893	always have to re-think your design.	1215	always have to re-think your design.
894		1216
895	Keeping your messages simple, concentrating on data structures rather than	1217	Keeping your messages simple, concentrating on data structures rather than
896	objects, will keep your messages clean, tidy and efficient.	1218	objects, will keep your messages clean, tidy and efficient.
897		1219
898	=back	1220	=back
899		1221
900	=head1 SEE ALSO	1222	=head1 SEE ALSO
901		1223
		1224	L<AnyEvent::MP::Intro> - a gentle introduction.
		1225
		1226	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1227
		1228	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1229	your applications.
		1230
		1231	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1232
		1233	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1234	all nodes.
		1235
902	L<AnyEvent>.	1236	L<AnyEvent>.
903		1237
904	=head1 AUTHOR	1238	=head1 AUTHOR
905		1239
906	Marc Lehmann <schmorp@schmorp.de>	1240	Marc Lehmann <schmorp@schmorp.de>

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