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Revision 1.43 by root, Sun Aug 9 16:08:16 2009 UTC vs.
Revision 1.142 by root, Fri Mar 23 13:44:01 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
		14	# initialise the node so it can send/receive messages
		15	configure;
		16
15	# ports are message endpoints	17	# ports are message destinations
16		18
17	# sending messages	19	# sending messages
18	snd $port, type => data...;	20	snd $port, type => data...;
19	snd $port, @msg;	21	snd $port, @msg;
20	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
21		23
22	# miniports	24	# creating/using ports, the simple way
23	my $miniport = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
24		26
25	# full ports	27	# creating/using ports, tagged message matching
26	my $port = port;	28	my $port = port;
27	rcv $port, smartmatch => $cb->(@msg);
28	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
29	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
30		31
31	# remote ports	32	# create a port on another node
32	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
33		34
34	# more, smarter, matches (_any_ is exported by this module)	35	# destroy a port again
35	rcv $port, [child_died => $pid] => sub { ...	36	kil $port; # "normal" kill
36	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3	37	kil $port, my_error => "everything is broken"; # error kill
37		38
38	# monitoring	39	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $port, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
41	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	};
42		51
43	=head1 DESCRIPTION	52	=head1 DESCRIPTION
44		53
45	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
46		55
47	Despite its simplicity, you can securely message other processes running	56	Despite its simplicity, you can securely message other processes running
48	on the same or other hosts.	57	on the same or other hosts, and you can supervise entities remotely.
49		58
50	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
51	manual page.	60	manual page and the examples under F<eg/>.
52
53	At the moment, this module family is severly broken and underdocumented,
54	so do not use. This was uploaded mainly to reserve the CPAN namespace -
55	stay tuned! The basic API should be finished, however.
56		61
57	=head1 CONCEPTS	62	=head1 CONCEPTS
58		63
59	=over 4	64	=over 4
60		65
61	=item port	66	=item port
62		67
63	A port is something you can send messages to (with the C<snd> function).	68	Not to be confused with a TCP port, a "port" is something you can send
		69	messages to (with the C<snd> function).
64		70
65	Some ports allow you to register C<rcv> handlers that can match specific	71	Ports allow you to register C<rcv> handlers that can match all or just
66	messages. All C<rcv> handlers will receive messages they match, messages	72	some messages. Messages send to ports will not be queued, regardless of
67	will not be queued.	73	anything was listening for them or not.
68		74
		75	Ports are represented by (printable) strings called "port IDs".
		76
69	=item port id - C<noderef#portname>	77	=item port ID - C<nodeid#portname>
70		78
71	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	79	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
72	separator, and a port name (a printable string of unspecified format). An	80	as separator, and a port name (a printable string of unspecified
73	exception is the the node port, whose ID is identical to its node	81	format created by AnyEvent::MP).
74	reference.
75		82
76	=item node	83	=item node
77		84
78	A node is a single process containing at least one port - the node	85	A node is a single process containing at least one port - the node port,
79	port. You can send messages to node ports to find existing ports or to	86	which enables nodes to manage each other remotely, and to create new
80	create new ports, among other things.	87	ports.
81		88
82	Nodes are either private (single-process only), slaves (connected to a	89	Nodes are either public (have one or more listening ports) or private
83	master node only) or public nodes (connectable from unrelated nodes).	90	(no listening ports). Private nodes cannot talk to other private nodes
		91	currently, but all nodes can talk to public nodes.
84		92
85	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	93	Nodes is represented by (printable) strings called "node IDs".
86		94
87	A node reference is a string that either simply identifies the node (for	95	=item node ID - C<[A-Za-z0-9_\-.:]*>
88	private and slave nodes), or contains a recipe on how to reach a given
89	node (for public nodes).
90		96
91	This recipe is simply a comma-separated list of C<address:port> pairs (for	97	A node ID is a string that uniquely identifies the node within a
92	TCP/IP, other protocols might look different).	98	network. Depending on the configuration used, node IDs can look like a
		99	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		100	doesn't interpret node IDs in any way except to uniquely identify a node.
93		101
94	Node references come in two flavours: resolved (containing only numerical	102	=item binds - C<ip:port>
95	addresses) or unresolved (where hostnames are used instead of addresses).
96		103
97	Before using an unresolved node reference in a message you first have to	104	Nodes can only talk to each other by creating some kind of connection to
98	resolve it.	105	each other. To do this, nodes should listen on one or more local transport
		106	endpoints - binds.
		107
		108	Currently, only standard C<ip:port> specifications can be used, which
		109	specify TCP ports to listen on. So a bind is basically just a tcp socket
		110	in listening mode thta accepts conenctions form other nodes.
		111
		112	=item seed nodes
		113
		114	When a node starts, it knows nothing about the network it is in - it
		115	needs to connect to at least one other node that is already in the
		116	network. These other nodes are called "seed nodes".
		117
		118	Seed nodes themselves are not special - they are seed nodes only because
		119	some other node I<uses> them as such, but any node can be used as seed
		120	node for other nodes, and eahc node cna use a different set of seed nodes.
		121
		122	In addition to discovering the network, seed nodes are also used to
		123	maintain the network - all nodes using the same seed node form are part of
		124	the same network. If a network is split into multiple subnets because e.g.
		125	the network link between the parts goes down, then using the same seed
		126	nodes for all nodes ensures that eventually the subnets get merged again.
		127
		128	Seed nodes are expected to be long-running, and at least one seed node
		129	should always be available. They should also be relatively responsive - a
		130	seed node that blocks for long periods will slow down everybody else.
		131
		132	For small networks, it's best if every node uses the same set of seed
		133	nodes. For large networks, it can be useful to specify "regional" seed
		134	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		135	each other. What's important is that all seed nodes connections form a
		136	complete graph, so that the network cannot split into separate subnets
		137	forever.
		138
		139	Seed nodes are represented by seed IDs.
		140
		141	=item seed IDs - C<host:port>
		142
		143	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		144	TCP port) of nodes that should be used as seed nodes.
		145
		146	=item global nodes
		147
		148	An AEMP network needs a discovery service - nodes need to know how to
		149	connect to other nodes they only know by name. In addition, AEMP offers a
		150	distributed "group database", which maps group names to a list of strings
		151	- for example, to register worker ports.
		152
		153	A network needs at least one global node to work, and allows every node to
		154	be a global node.
		155
		156	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		157	node and tries to keep connections to all other nodes. So while it can
		158	make sense to make every node "global" in small networks, it usually makes
		159	sense to only make seed nodes into global nodes in large networks (nodes
		160	keep connections to seed nodes and global nodes, so makign them the same
		161	reduces overhead).
99		162
100	=back	163	=back
101		164
102	=head1 VARIABLES/FUNCTIONS	165	=head1 VARIABLES/FUNCTIONS
103		166
…		…
105		168
106	=cut	169	=cut
107		170
108	package AnyEvent::MP;	171	package AnyEvent::MP;
109		172
		173	use AnyEvent::MP::Config ();
110	use AnyEvent::MP::Base;	174	use AnyEvent::MP::Kernel;
		175	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
111		176
112	use common::sense;	177	use common::sense;
113		178
114	use Carp ();	179	use Carp ();
115		180
116	use AE ();	181	use AnyEvent ();
		182	use Guard ();
117		183
118	use base "Exporter";	184	use base "Exporter";
119		185
120	our $VERSION = $AnyEvent::MP::Base::VERSION;	186	our $VERSION = $AnyEvent::MP::Config::VERSION;
121		187
122	our @EXPORT = qw(	188	our @EXPORT = qw(
123	NODE $NODE *SELF node_of _any_	189	NODE $NODE *SELF node_of after
124	resolve_node initialise_node	190	configure
125	snd rcv mon kil reg psub spawn	191	snd rcv mon mon_guard kil psub peval spawn cal
126	port	192	port
		193	db_set db_del db_reg
		194	db_mon db_family db_keys db_values
127	);	195	);
128		196
129	our $SELF;	197	our $SELF;
130		198
131	sub _self_die() {	199	sub _self_die() {
…		…
134	kil $SELF, die => $msg;	202	kil $SELF, die => $msg;
135	}	203	}
136		204
137	=item $thisnode = NODE / $NODE	205	=item $thisnode = NODE / $NODE
138		206
139	The C<NODE> function returns, and the C<$NODE> variable contains	207	The C<NODE> function returns, and the C<$NODE> variable contains, the node
140	the noderef of the local node. The value is initialised by a call	208	ID of the node running in the current process. This value is initialised by
141	to C<become_public> or C<become_slave>, after which all local port	209	a call to C<configure>.
142	identifiers become invalid.
143		210
144	=item $noderef = node_of $port	211	=item $nodeid = node_of $port
145		212
146	Extracts and returns the noderef from a portid or a noderef.	213	Extracts and returns the node ID from a port ID or a node ID.
147		214
148	=item initialise_node $noderef, $seednode, $seednode...	215	=item configure $profile, key => value...
149		216
150	=item initialise_node "slave/", $master, $master...	217	=item configure key => value...
151		218
152	Before a node can talk to other nodes on the network it has to initialise	219	Before a node can talk to other nodes on the network (i.e. enter
153	itself - the minimum a node needs to know is it's own name, and optionally	220	"distributed mode") it has to configure itself - the minimum a node needs
154	it should know the noderefs of some other nodes in the network.	221	to know is its own name, and optionally it should know the addresses of
		222	some other nodes in the network to discover other nodes.
155		223
156	This function initialises a node - it must be called exactly once (or	224	This function configures a node - it must be called exactly once (or
157	never) before calling other AnyEvent::MP functions.	225	never) before calling other AnyEvent::MP functions.
158		226
159	All arguments are noderefs, which can be either resolved or unresolved.	227	The key/value pairs are basically the same ones as documented for the
160		228	F<aemp> command line utility (sans the set/del prefix), with these additions:
161	There are two types of networked nodes, public nodes and slave nodes:
162		229
163	=over 4	230	=over 4
164		231
165	=item public nodes	232	=item norc => $boolean (default false)
166		233
167	For public nodes, C<$noderef> must either be a (possibly unresolved)	234	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
168	noderef, in which case it will be resolved, or C<undef> (or missing), in	235	be consulted - all configuraiton options must be specified in the
169	which case the noderef will be guessed.	236	C<configure> call.
170		237
171	Afterwards, the node will bind itself on all endpoints and try to connect	238	=item force => $boolean (default false)
172	to all additional C<$seednodes> that are specified. Seednodes are optional
173	and can be used to quickly bootstrap the node into an existing network.
174		239
175	=item slave nodes	240	IF true, then the values specified in the C<configure> will take
176		241	precedence over any values configured via the rc file. The default is for
177	When the C<$noderef> is the special string C<slave/>, then the node will	242	the rc file to override any options specified in the program.
178	become a slave node. Slave nodes cannot be contacted from outside and will
179	route most of their traffic to the master node that they attach to.
180
181	At least one additional noderef is required: The node will try to connect
182	to all of them and will become a slave attached to the first node it can
183	successfully connect to.
184		243
185	=back	244	=back
186		245
187	This function will block until all nodes have been resolved and, for slave
188	nodes, until it has successfully established a connection to a master
189	server.
190
191	Example: become a public node listening on the default node.
192
193	initialise_node;
194
195	Example: become a public node, and try to contact some well-known master
196	servers to become part of the network.
197
198	initialise_node undef, "master1", "master2";
199
200	Example: become a public node listening on port C<4041>.
201
202	initialise_node 4041;
203
204	Example: become a public node, only visible on localhost port 4044.
205
206	initialise_node "locahost:4044";
207
208	Example: become a slave node to any of the specified master servers.
209
210	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
211
212	=item $cv = resolve_node $noderef
213
214	Takes an unresolved node reference that may contain hostnames and
215	abbreviated IDs, resolves all of them and returns a resolved node
216	reference.
217
218	In addition to C<address:port> pairs allowed in resolved noderefs, the
219	following forms are supported:
220
221	=over 4	246	=over 4
222		247
223	=item the empty string	248	=item step 1, gathering configuration from profiles
224		249
225	An empty-string component gets resolved as if the default port (4040) was	250	The function first looks up a profile in the aemp configuration (see the
226	specified.	251	L<aemp> commandline utility). The profile name can be specified via the
		252	named C<profile> parameter or can simply be the first parameter). If it is
		253	missing, then the nodename (F<uname -n>) will be used as profile name.
227		254
228	=item naked port numbers (e.g. C<1234>)	255	The profile data is then gathered as follows:
229		256
230	These are resolved by prepending the local nodename and a colon, to be	257	First, all remaining key => value pairs (all of which are conveniently
231	further resolved.	258	undocumented at the moment) will be interpreted as configuration
		259	data. Then they will be overwritten by any values specified in the global
		260	default configuration (see the F<aemp> utility), then the chain of
		261	profiles chosen by the profile name (and any C<parent> attributes).
232		262
233	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	263	That means that the values specified in the profile have highest priority
		264	and the values specified directly via C<configure> have lowest priority,
		265	and can only be used to specify defaults.
234		266
235	These are resolved by using AnyEvent::DNS to resolve them, optionally	267	If the profile specifies a node ID, then this will become the node ID of
236	looking up SRV records for the C<aemp=4040> port, if no port was	268	this process. If not, then the profile name will be used as node ID, with
237	specified.	269	a unique randoms tring (C</%u>) appended.
		270
		271	The node ID can contain some C<%> sequences that are expanded: C<%n>
		272	is expanded to the local nodename, C<%u> is replaced by a random
		273	strign to make the node unique. For example, the F<aemp> commandline
		274	utility uses C<aemp/%n/%u> as nodename, which might expand to
		275	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		276
		277	=item step 2, bind listener sockets
		278
		279	The next step is to look up the binds in the profile, followed by binding
		280	aemp protocol listeners on all binds specified (it is possible and valid
		281	to have no binds, meaning that the node cannot be contacted form the
		282	outside. This means the node cannot talk to other nodes that also have no
		283	binds, but it can still talk to all "normal" nodes).
		284
		285	If the profile does not specify a binds list, then a default of C<*> is
		286	used, meaning the node will bind on a dynamically-assigned port on every
		287	local IP address it finds.
		288
		289	=item step 3, connect to seed nodes
		290
		291	As the last step, the seed ID list from the profile is passed to the
		292	L<AnyEvent::MP::Global> module, which will then use it to keep
		293	connectivity with at least one node at any point in time.
238		294
239	=back	295	=back
		296
		297	Example: become a distributed node using the local node name as profile.
		298	This should be the most common form of invocation for "daemon"-type nodes.
		299
		300	configure
		301
		302	Example: become a semi-anonymous node. This form is often used for
		303	commandline clients.
		304
		305	configure nodeid => "myscript/%n/%u";
		306
		307	Example: configure a node using a profile called seed, which is suitable
		308	for a seed node as it binds on all local addresses on a fixed port (4040,
		309	customary for aemp).
		310
		311	# use the aemp commandline utility
		312	# aemp profile seed binds '*:4040'
		313
		314	# then use it
		315	configure profile => "seed";
		316
		317	# or simply use aemp from the shell again:
		318	# aemp run profile seed
		319
		320	# or provide a nicer-to-remember nodeid
		321	# aemp run profile seed nodeid "$(hostname)"
240		322
241	=item $SELF	323	=item $SELF
242		324
243	Contains the current port id while executing C<rcv> callbacks or C<psub>	325	Contains the current port id while executing C<rcv> callbacks or C<psub>
244	blocks.	326	blocks.
245		327
246	=item SELF, %SELF, @SELF...	328	=item *SELF, SELF, %SELF, @SELF...
247		329
248	Due to some quirks in how perl exports variables, it is impossible to	330	Due to some quirks in how perl exports variables, it is impossible to
249	just export C<$SELF>, all the symbols called C<SELF> are exported by this	331	just export C<$SELF>, all the symbols named C<SELF> are exported by this
250	module, but only C<$SELF> is currently used.	332	module, but only C<$SELF> is currently used.
251		333
252	=item snd $port, type => @data	334	=item snd $port, type => @data
253		335
254	=item snd $port, @msg	336	=item snd $port, @msg
255		337
256	Send the given message to the given port ID, which can identify either	338	Send the given message to the given port, which can identify either a
257	a local or a remote port, and can be either a string or soemthignt hat	339	local or a remote port, and must be a port ID.
258	stringifies a sa port ID (such as a port object :).
259		340
260	While the message can be about anything, it is highly recommended to use a	341	While the message can be almost anything, it is highly recommended to
261	string as first element (a portid, or some word that indicates a request	342	use a string as first element (a port ID, or some word that indicates a
262	type etc.).	343	request type etc.) and to consist if only simple perl values (scalars,
		344	arrays, hashes) - if you think you need to pass an object, think again.
263		345
264	The message data effectively becomes read-only after a call to this	346	The message data logically becomes read-only after a call to this
265	function: modifying any argument is not allowed and can cause many	347	function: modifying any argument (or values referenced by them) is
266	problems.	348	forbidden, as there can be considerable time between the call to C<snd>
		349	and the time the message is actually being serialised - in fact, it might
		350	never be copied as within the same process it is simply handed to the
		351	receiving port.
267		352
268	The type of data you can transfer depends on the transport protocol: when	353	The type of data you can transfer depends on the transport protocol: when
269	JSON is used, then only strings, numbers and arrays and hashes consisting	354	JSON is used, then only strings, numbers and arrays and hashes consisting
270	of those are allowed (no objects). When Storable is used, then anything	355	of those are allowed (no objects). When Storable is used, then anything
271	that Storable can serialise and deserialise is allowed, and for the local	356	that Storable can serialise and deserialise is allowed, and for the local
272	node, anything can be passed.	357	node, anything can be passed. Best rely only on the common denominator of
		358	these.
273		359
274	=item $local_port = port	360	=item $local_port = port
275		361
276	Create a new local port object that can be used either as a pattern	362	Create a new local port object and returns its port ID. Initially it has
277	matching port ("full port") or a single-callback port ("miniport"),	363	no callbacks set and will throw an error when it receives messages.
278	depending on how C<rcv> callbacks are bound to the object.
279		364
280	=item $port = port { my @msg = @_; $finished }	365	=item $local_port = port { my @msg = @_ }
281		366
282	Creates a "miniport", that is, a very lightweight port without any pattern	367	Creates a new local port, and returns its ID. Semantically the same as
283	matching behind it, and returns its ID. Semantically the same as creating
284	a port and calling C<rcv $port, $callback> on it.	368	creating a port and calling C<rcv $port, $callback> on it.
285		369
286	The block will be called for every message received on the port. When the	370	The block will be called for every message received on the port, with the
287	callback returns a true value its job is considered "done" and the port	371	global variable C<$SELF> set to the port ID. Runtime errors will cause the
288	will be destroyed. Otherwise it will stay alive.	372	port to be C<kil>ed. The message will be passed as-is, no extra argument
		373	(i.e. no port ID) will be passed to the callback.
289		374
290	The message will be passed as-is, no extra argument (i.e. no port id) will	375	If you want to stop/destroy the port, simply C<kil> it:
291	be passed to the callback.
292		376
293	If you need the local port id in the callback, this works nicely:	377	my $port = port {
294		378	my @msg = @_;
295	my $port; $port = port {	379	...
296	snd $otherport, reply => $port;	380	kil $SELF;
297	};	381	};
298		382
299	=cut	383	=cut
300		384
301	sub rcv($@);	385	sub rcv($@);
302		386
		387	my $KILME = sub {
		388	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
		389	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		390	};
		391
303	sub port(;&) {	392	sub port(;&) {
304	my $id = "$UNIQ." . $ID++;	393	my $id = $UNIQ . ++$ID;
305	my $port = "$NODE#$id";	394	my $port = "$NODE#$id";
306		395
307	if (@_) {
308	rcv $port, shift;	396	rcv $port, shift || $KILME;
309	} else {
310	$PORT{$id} = sub { }; # nop
311	}
312		397
313	$port	398	$port
314	}	399	}
315		400
316	=item reg $port, $name
317
318	=item reg $name
319
320	Registers the given port (or C<$SELF><<< if missing) under the name
321	C<$name>. If the name already exists it is replaced.
322
323	A port can only be registered under one well known name.
324
325	A port automatically becomes unregistered when it is killed.
326
327	=cut
328
329	sub reg(@) {
330	my $port = @_ > 1 ? shift : $SELF || Carp::croak 'reg: called with one argument only, but $SELF not set,';
331
332	$REG{$_[0]} = $port;
333	}
334
335	=item rcv $port, $callback->(@msg)	401	=item rcv $local_port, $callback->(@msg)
336		402
337	Replaces the callback on the specified miniport (after converting it to	403	Replaces the default callback on the specified port. There is no way to
338	one if required).	404	remove the default callback: use C<sub { }> to disable it, or better
339		405	C<kil> the port when it is no longer needed.
340	=item rcv $port, tagstring => $callback->(@msg), ...
341
342	=item rcv $port, $smartmatch => $callback->(@msg), ...
343
344	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
345
346	Register callbacks to be called on matching messages on the given full
347	port (after converting it to one if required) and return the port.
348
349	The callback has to return a true value when its work is done, after
350	which is will be removed, or a false value in which case it will stay
351	registered.
352		406
353	The global C<$SELF> (exported by this module) contains C<$port> while	407	The global C<$SELF> (exported by this module) contains C<$port> while
354	executing the callback.	408	executing the callback. Runtime errors during callback execution will
		409	result in the port being C<kil>ed.
355		410
356	Runtime errors during callback execution will result in the port being	411	The default callback receives all messages not matched by a more specific
357	C<kil>ed.	412	C<tag> match.
358		413
359	If the match is an array reference, then it will be matched against the	414	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
360	first elements of the message, otherwise only the first element is being
361	matched.
362		415
363	Any element in the match that is specified as C<_any_> (a function	416	Register (or replace) callbacks to be called on messages starting with the
364	exported by this module) matches any single element of the message.	417	given tag on the given port (and return the port), or unregister it (when
		418	C<$callback> is C<$undef> or missing). There can only be one callback
		419	registered for each tag.
365		420
366	While not required, it is highly recommended that the first matching	421	The original message will be passed to the callback, after the first
367	element is a string identifying the message. The one-string-only match is	422	element (the tag) has been removed. The callback will use the same
368	also the most efficient match (by far).	423	environment as the default callback (see above).
369		424
370	Example: create a port and bind receivers on it in one go.	425	Example: create a port and bind receivers on it in one go.
371		426
372	my $port = rcv port,	427	my $port = rcv port,
373	msg1 => sub { ...; 0 },	428	msg1 => sub { ... },
374	msg2 => sub { ...; 0 },	429	msg2 => sub { ... },
375	;	430	;
376		431
377	Example: create a port, bind receivers and send it in a message elsewhere	432	Example: create a port, bind receivers and send it in a message elsewhere
378	in one go:	433	in one go:
379		434
380	snd $otherport, reply =>	435	snd $otherport, reply =>
381	rcv port,	436	rcv port,
382	msg1 => sub { ...; 0 },	437	msg1 => sub { ... },
383	...	438	...
384	;	439	;
385		440
		441	Example: temporarily register a rcv callback for a tag matching some port
		442	(e.g. for an rpc reply) and unregister it after a message was received.
		443
		444	rcv $port, $otherport => sub {
		445	my @reply = @_;
		446
		447	rcv $SELF, $otherport;
		448	};
		449
386	=cut	450	=cut
387		451
388	sub rcv($@) {	452	sub rcv($@) {
389	my $port = shift;	453	my $port = shift;
390	my ($noderef, $portid) = split /#/, $port, 2;	454	my ($nodeid, $portid) = split /#/, $port, 2;
391		455
392	($NODE{$noderef} || add_node $noderef) == $NODE{""}	456	$NODE{$nodeid} == $NODE{""}
393	or Carp::croak "$port: rcv can only be called on local ports, caught";	457	or Carp::croak "$port: rcv can only be called on local ports, caught";
394		458
395	if (@_ == 1) {	459	while (@_) {
		460	if (ref $_[0]) {
		461	if (my $self = $PORT_DATA{$portid}) {
		462	"AnyEvent::MP::Port" eq ref $self
		463	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		464
		465	$self->[0] = shift;
		466	} else {
396	my $cb = shift;	467	my $cb = shift;
397	delete $PORT_DATA{$portid};
398	$PORT{$portid} = sub {	468	$PORT{$portid} = sub {
399	local $SELF = $port;	469	local $SELF = $port;
400	eval {	470	eval { &$cb }; _self_die if $@;
401	&$cb	471	};
402	and kil $port;
403	};	472	}
404	_self_die if $@;	473	} elsif (defined $_[0]) {
405	};
406	} else {
407	my $self = $PORT_DATA{$portid} ||= do {	474	my $self = $PORT_DATA{$portid} ||= do {
408	my $self = bless {	475	my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
409	id => $port,
410	}, "AnyEvent::MP::Port";
411		476
412	$PORT{$portid} = sub {	477	$PORT{$portid} = sub {
413	local $SELF = $port;	478	local $SELF = $port;
414		479
415	eval {
416	for (@{ $self->{rc0}{$_[0]} }) {	480	if (my $cb = $self->[1]{$_[0]}) {
417	$_ && &{$_->[0]}	481	shift;
418	&& undef $_;	482	eval { &$cb }; _self_die if $@;
419	}	483	} else {
420
421	for (@{ $self->{rcv}{$_[0]} }) {
422	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
423	&& &{$_->[0]}	484	&{ $self->[0] };
424	&& undef $_;
425	}
426
427	for (@{ $self->{any} }) {
428	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
429	&& &{$_->[0]}
430	&& undef $_;
431	}	485	}
432	};	486	};
433	_self_die if $@;	487
		488	$self
434	};	489	};
435		490
436	$self
437	};
438
439	"AnyEvent::MP::Port" eq ref $self	491	"AnyEvent::MP::Port" eq ref $self
440	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	492	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
441		493
442	while (@_) {
443	my ($match, $cb) = splice @_, 0, 2;	494	my ($tag, $cb) = splice @_, 0, 2;
444		495
445	if (!ref $match) {	496	if (defined $cb) {
446	push @{ $self->{rc0}{$match} }, [$cb];	497	$self->[1]{$tag} = $cb;
447	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
448	my ($type, @match) = @$match;
449	@match
450	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
451	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
452	} else {	498	} else {
453	push @{ $self->{any} }, [$cb, $match];	499	delete $self->[1]{$tag};
454	}	500	}
455	}	501	}
456	}	502	}
457		503
458	$port	504	$port
459	}	505	}
460		506
		507	=item peval $port, $coderef[, @args]
		508
		509	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		510	when the code throews an exception the C<$port> will be killed.
		511
		512	Any remaining args will be passed to the callback. Any return values will
		513	be returned to the caller.
		514
		515	This is useful when you temporarily want to execute code in the context of
		516	a port.
		517
		518	Example: create a port and run some initialisation code in it's context.
		519
		520	my $port = port { ... };
		521
		522	peval $port, sub {
		523	init
		524	or die "unable to init";
		525	};
		526
		527	=cut
		528
		529	sub peval($$) {
		530	local $SELF = shift;
		531	my $cb = shift;
		532
		533	if (wantarray) {
		534	my @res = eval { &$cb };
		535	_self_die if $@;
		536	@res
		537	} else {
		538	my $res = eval { &$cb };
		539	_self_die if $@;
		540	$res
		541	}
		542	}
		543
461	=item $closure = psub { BLOCK }	544	=item $closure = psub { BLOCK }
462		545
463	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	546	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
464	closure is executed, sets up the environment in the same way as in C<rcv>	547	closure is executed, sets up the environment in the same way as in C<rcv>
465	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	548	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		549
		550	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		551	BLOCK }, @_ } >>.
466		552
467	This is useful when you register callbacks from C<rcv> callbacks:	553	This is useful when you register callbacks from C<rcv> callbacks:
468		554
469	rcv delayed_reply => sub {	555	rcv delayed_reply => sub {
470	my ($delay, @reply) = @_;	556	my ($delay, @reply) = @_;
…		…
494	$res	580	$res
495	}	581	}
496	}	582	}
497	}	583	}
498		584
499	=item $guard = mon $port, $cb->(@reason)	585	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
500		586
501	=item $guard = mon $port, $rcvport	587	=item $guard = mon $port # kill $SELF when $port dies
502		588
503	=item $guard = mon $port	589	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
504		590
505	=item $guard = mon $port, $rcvport, @msg	591	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
506		592
507	Monitor the given port and do something when the port is killed or	593	Monitor the given port and do something when the port is killed or
508	messages to it were lost, and optionally return a guard that can be used	594	messages to it were lost, and optionally return a guard that can be used
509	to stop monitoring again.	595	to stop monitoring again.
510		596
		597	The first two forms distinguish between "normal" and "abnormal" kil's:
		598
		599	In the first form (another port given), if the C<$port> is C<kil>'ed with
		600	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		601	same reason. That is, on "normal" kil's nothing happens, while under all
		602	other conditions, the other port is killed with the same reason.
		603
		604	The second form (kill self) is the same as the first form, except that
		605	C<$rvport> defaults to C<$SELF>.
		606
		607	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		608	- it's up to the callback or receiver to check whether the C<@reason> is
		609	empty and act accordingly.
		610
		611	In the third form (callback), the callback is simply called with any
		612	number of C<@reason> elements (empty @reason means that the port was deleted
		613	"normally"). Note also that I<< the callback B<must> never die >>, so use
		614	C<eval> if unsure.
		615
		616	In the last form (message), a message of the form C<$rcvport, @msg,
		617	@reason> will be C<snd>.
		618
		619	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		620	alert was raised), they are removed and will not trigger again, even if it
		621	turns out that the port is still alive.
		622
		623	As a rule of thumb, monitoring requests should always monitor a remote
		624	port locally (using a local C<$rcvport> or a callback). The reason is that
		625	kill messages might get lost, just like any other message. Another less
		626	obvious reason is that even monitoring requests can get lost (for example,
		627	when the connection to the other node goes down permanently). When
		628	monitoring a port locally these problems do not exist.
		629
511	C<mon> effectively guarantees that, in the absence of hardware failures,	630	C<mon> effectively guarantees that, in the absence of hardware failures,
512	that after starting the monitor, either all messages sent to the port	631	after starting the monitor, either all messages sent to the port will
513	will arrive, or the monitoring action will be invoked after possible	632	arrive, or the monitoring action will be invoked after possible message
514	message loss has been detected. No messages will be lost "in between"	633	loss has been detected. No messages will be lost "in between" (after
515	(after the first lost message no further messages will be received by the	634	the first lost message no further messages will be received by the
516	port). After the monitoring action was invoked, further messages might get	635	port). After the monitoring action was invoked, further messages might get
517	delivered again.	636	delivered again.
518		637
519	In the first form (callback), the callback is simply called with any	638	Inter-host-connection timeouts and monitoring depend on the transport
520	number of C<@reason> elements (no @reason means that the port was deleted	639	used. The only transport currently implemented is TCP, and AnyEvent::MP
521	"normally"). Note also that I<< the callback B<must> never die >>, so use	640	relies on TCP to detect node-downs (this can take 10-15 minutes on a
522	C<eval> if unsure.	641	non-idle connection, and usually around two hours for idle connections).
523		642
524	In the second form (another port given), the other port (C<$rcvport>)	643	This means that monitoring is good for program errors and cleaning up
525	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	644	stuff eventually, but they are no replacement for a timeout when you need
526	"normal" kils nothing happens, while under all other conditions, the other	645	to ensure some maximum latency.
527	port is killed with the same reason.
528
529	The third form (kill self) is the same as the second form, except that
530	C<$rvport> defaults to C<$SELF>.
531
532	In the last form (message), a message of the form C<@msg, @reason> will be
533	C<snd>.
534
535	As a rule of thumb, monitoring requests should always monitor a port from
536	a local port (or callback). The reason is that kill messages might get
537	lost, just like any other message. Another less obvious reason is that
538	even monitoring requests can get lost (for exmaple, when the connection
539	to the other node goes down permanently). When monitoring a port locally
540	these problems do not exist.
541		646
542	Example: call a given callback when C<$port> is killed.	647	Example: call a given callback when C<$port> is killed.
543		648
544	mon $port, sub { warn "port died because of <@_>\n" };	649	mon $port, sub { warn "port died because of <@_>\n" };
545		650
…		…
552	mon $port, $self => "restart";	657	mon $port, $self => "restart";
553		658
554	=cut	659	=cut
555		660
556	sub mon {	661	sub mon {
557	my ($noderef, $port) = split /#/, shift, 2;	662	my ($nodeid, $port) = split /#/, shift, 2;
558		663
559	my $node = $NODE{$noderef} || add_node $noderef;	664	my $node = $NODE{$nodeid} || add_node $nodeid;
560		665
561	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';	666	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
562		667
563	unless (ref $cb) {	668	unless (ref $cb) {
564	if (@_) {	669	if (@_) {
…		…
573	}	678	}
574		679
575	$node->monitor ($port, $cb);	680	$node->monitor ($port, $cb);
576		681
577	defined wantarray	682	defined wantarray
578	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	683	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
579	}	684	}
580		685
581	=item $guard = mon_guard $port, $ref, $ref...	686	=item $guard = mon_guard $port, $ref, $ref...
582		687
583	Monitors the given C<$port> and keeps the passed references. When the port	688	Monitors the given C<$port> and keeps the passed references. When the port
584	is killed, the references will be freed.	689	is killed, the references will be freed.
585		690
586	Optionally returns a guard that will stop the monitoring.	691	Optionally returns a guard that will stop the monitoring.
587		692
588	This function is useful when you create e.g. timers or other watchers and	693	This function is useful when you create e.g. timers or other watchers and
589	want to free them when the port gets killed:	694	want to free them when the port gets killed (note the use of C<psub>):
590		695
591	$port->rcv (start => sub {	696	$port->rcv (start => sub {
592	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	697	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
593	undef $timer if 0.9 < rand;	698	undef $timer if 0.9 < rand;
594	});	699	});
595	});	700	});
596		701
597	=cut	702	=cut
…		…
606		711
607	=item kil $port[, @reason]	712	=item kil $port[, @reason]
608		713
609	Kill the specified port with the given C<@reason>.	714	Kill the specified port with the given C<@reason>.
610		715
611	If no C<@reason> is specified, then the port is killed "normally" (linked	716	If no C<@reason> is specified, then the port is killed "normally" -
612	ports will not be kileld, or even notified).	717	monitor callback will be invoked, but the kil will not cause linked ports
		718	(C<mon $mport, $lport> form) to get killed.
613		719
614	Otherwise, linked ports get killed with the same reason (second form of	720	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
615	C<mon>, see below).	721	form) get killed with the same reason.
616		722
617	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	723	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
618	will be reported as reason C<< die => $@ >>.	724	will be reported as reason C<< die => $@ >>.
619		725
620	Transport/communication errors are reported as C<< transport_error =>	726	Transport/communication errors are reported as C<< transport_error =>
621	$message >>.	727	$message >>.
622		728
623	=cut	729	Common idioms:
		730
		731	# silently remove yourself, do not kill linked ports
		732	kil $SELF;
		733
		734	# report a failure in some detail
		735	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		736
		737	# do not waste much time with killing, just die when something goes wrong
		738	open my $fh, "<file"
		739	or die "file: $!";
624		740
625	=item $port = spawn $node, $initfunc[, @initdata]	741	=item $port = spawn $node, $initfunc[, @initdata]
626		742
627	Creates a port on the node C<$node> (which can also be a port ID, in which	743	Creates a port on the node C<$node> (which can also be a port ID, in which
628	case it's the node where that port resides).	744	case it's the node where that port resides).
629		745
630	The port ID of the newly created port is return immediately, and it is	746	The port ID of the newly created port is returned immediately, and it is
631	permissible to immediately start sending messages or monitor the port.	747	possible to immediately start sending messages or to monitor the port.
632		748
633	After the port has been created, the init function is	749	After the port has been created, the init function is called on the remote
634	called. This function must be a fully-qualified function name	750	node, in the same context as a C<rcv> callback. This function must be a
635	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	751	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
636	program, use C<::name>.	752	specify a function in the main program, use C<::name>.
637		753
638	If the function doesn't exist, then the node tries to C<require>	754	If the function doesn't exist, then the node tries to C<require>
639	the package, then the package above the package and so on (e.g.	755	the package, then the package above the package and so on (e.g.
640	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	756	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
641	exists or it runs out of package names.	757	exists or it runs out of package names.
642		758
643	The init function is then called with the newly-created port as context	759	The init function is then called with the newly-created port as context
644	object (C<$SELF>) and the C<@initdata> values as arguments.	760	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		761	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		762	the port might not get created.
645		763
646	A common idiom is to pass your own port, monitor the spawned port, and	764	A common idiom is to pass a local port, immediately monitor the spawned
647	in the init function, monitor the original port. This two-way monitoring	765	port, and in the remote init function, immediately monitor the passed
648	ensures that both ports get cleaned up when there is a problem.	766	local port. This two-way monitoring ensures that both ports get cleaned up
		767	when there is a problem.
		768
		769	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		770	caller before C<spawn> returns (by delaying invocation when spawn is
		771	called for the local node).
649		772
650	Example: spawn a chat server port on C<$othernode>.	773	Example: spawn a chat server port on C<$othernode>.
651		774
652	# this node, executed from within a port context:	775	# this node, executed from within a port context:
653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	776	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
668		791
669	sub _spawn {	792	sub _spawn {
670	my $port = shift;	793	my $port = shift;
671	my $init = shift;	794	my $init = shift;
672		795
		796	# rcv will create the actual port
673	local $SELF = "$NODE#$port";	797	local $SELF = "$NODE#$port";
674	eval {	798	eval {
675	&{ load_func $init }	799	&{ load_func $init }
676	};	800	};
677	_self_die if $@;	801	_self_die if $@;
678	}	802	}
679		803
680	sub spawn(@) {	804	sub spawn(@) {
681	my ($noderef, undef) = split /#/, shift, 2;	805	my ($nodeid, undef) = split /#/, shift, 2;
682		806
683	my $id = "$RUNIQ." . $ID++;	807	my $id = $RUNIQ . ++$ID;
684		808
685	$_[0] =~ /::/	809	$_[0] =~ /::/
686	or Carp::croak "spawn init function must be a fully-qualified name, caught";	810	or Carp::croak "spawn init function must be a fully-qualified name, caught";
687		811
688	($NODE{$noderef} || add_node $noderef)	812	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
689	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
690		813
691	"$noderef#$id"	814	"$nodeid#$id"
692	}	815	}
693		816
		817
		818	=item after $timeout, @msg
		819
		820	=item after $timeout, $callback
		821
		822	Either sends the given message, or call the given callback, after the
		823	specified number of seconds.
		824
		825	This is simply a utility function that comes in handy at times - the
		826	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		827	so it may go away in the future.
		828
		829	=cut
		830
		831	sub after($@) {
		832	my ($timeout, @action) = @_;
		833
		834	my $t; $t = AE::timer $timeout, 0, sub {
		835	undef $t;
		836	ref $action[0]
		837	? $action[0]()
		838	: snd @action;
		839	};
		840	}
		841
		842	#=item $cb2 = timeout $seconds, $cb[, @args]
		843
		844	=item cal $port, @msg, $callback[, $timeout]
		845
		846	A simple form of RPC - sends a message to the given C<$port> with the
		847	given contents (C<@msg>), but adds a reply port to the message.
		848
		849	The reply port is created temporarily just for the purpose of receiving
		850	the reply, and will be C<kil>ed when no longer needed.
		851
		852	A reply message sent to the port is passed to the C<$callback> as-is.
		853
		854	If an optional time-out (in seconds) is given and it is not C<undef>,
		855	then the callback will be called without any arguments after the time-out
		856	elapsed and the port is C<kil>ed.
		857
		858	If no time-out is given (or it is C<undef>), then the local port will
		859	monitor the remote port instead, so it eventually gets cleaned-up.
		860
		861	Currently this function returns the temporary port, but this "feature"
		862	might go in future versions unless you can make a convincing case that
		863	this is indeed useful for something.
		864
		865	=cut
		866
		867	sub cal(@) {
		868	my $timeout = ref $_[-1] ? undef : pop;
		869	my $cb = pop;
		870
		871	my $port = port {
		872	undef $timeout;
		873	kil $SELF;
		874	&$cb;
		875	};
		876
		877	if (defined $timeout) {
		878	$timeout = AE::timer $timeout, 0, sub {
		879	undef $timeout;
		880	kil $port;
		881	$cb->();
		882	};
		883	} else {
		884	mon $_[0], sub {
		885	kil $port;
		886	$cb->();
		887	};
		888	}
		889
		890	push @_, $port;
		891	&snd;
		892
		893	$port
		894	}
		895
694	=back	896	=back
695		897
696	=head1 NODE MESSAGES	898	=head1 DISTRIBUTED DATABASE
697		899
698	Nodes understand the following messages sent to them. Many of them take	900	AnyEvent::MP comes with a simple distributed database. The database will
699	arguments called C<@reply>, which will simply be used to compose a reply	901	be mirrored asynchronously on all global nodes. Other nodes bind to one
700	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	902	of the global nodes for their needs. Every node has a "local database"
701	the remaining arguments are simply the message data.	903	which contains all the values that are set locally. All local databases
		904	are merged together to form the global database, which can be queried.
702		905
703	While other messages exist, they are not public and subject to change.	906	The database structure is that of a two-level hash - the database hash
		907	contains hashes which contain values, similarly to a perl hash of hashes,
		908	i.e.:
704		909
		910	$DATABASE{$family}{$subkey} = $value
		911
		912	The top level hash key is called "family", and the second-level hash key
		913	is called "subkey" or simply "key".
		914
		915	The family must be alphanumeric, i.e. start with a letter and consist
		916	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		917	pretty much like Perl module names.
		918
		919	As the family namespace is global, it is recommended to prefix family names
		920	with the name of the application or module using it.
		921
		922	The subkeys must be non-empty strings, with no further restrictions.
		923
		924	The values should preferably be strings, but other perl scalars should
		925	work as well (such as C<undef>, arrays and hashes).
		926
		927	Every database entry is owned by one node - adding the same family/subkey
		928	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		929	but the result might be nondeterministic, i.e. the key might have
		930	different values on different nodes.
		931
		932	Different subkeys in the same family can be owned by different nodes
		933	without problems, and in fact, this is the common method to create worker
		934	pools. For example, a worker port for image scaling might do this:
		935
		936	db_set my_image_scalers => $port;
		937
		938	And clients looking for an image scaler will want to get the
		939	C<my_image_scalers> keys from time to time:
		940
		941	db_keys my_image_scalers => sub {
		942	@ports = @{ $_[0] };
		943	};
		944
		945	Or better yet, they want to monitor the database family, so they always
		946	have a reasonable up-to-date copy:
		947
		948	db_mon my_image_scalers => sub {
		949	@ports = keys %{ $_[0] };
		950	};
		951
		952	In general, you can set or delete single subkeys, but query and monitor
		953	whole families only.
		954
		955	If you feel the need to monitor or query a single subkey, try giving it
		956	it's own family.
		957
705	=over 4	958	=over
		959
		960	=item $guard = db_set $family => $subkey [=> $value]
		961
		962	Sets (or replaces) a key to the database - if C<$value> is omitted,
		963	C<undef> is used instead.
		964
		965	When called in non-void context, C<db_set> returns a guard that
		966	automatically calls C<db_del> when it is destroyed.
		967
		968	=item db_del $family => $subkey...
		969
		970	Deletes one or more subkeys from the database family.
		971
		972	=item $guard = db_reg $family => $port => $value
		973
		974	=item $guard = db_reg $family => $port
		975
		976	=item $guard = db_reg $family
		977
		978	Registers a port in the given family and optionally returns a guard to
		979	remove it.
		980
		981	This function basically does the same as:
		982
		983	db_set $family => $port => $value
		984
		985	Except that the port is monitored and automatically removed from the
		986	database family when it is kil'ed.
		987
		988	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		989	C<$SELF> is used.
		990
		991	This function is most useful to register a port in some port group (which
		992	is just another name for a database family), and have it removed when the
		993	port is gone. This works best when the port is a local port.
706		994
707	=cut	995	=cut
708		996
709	=item lookup => $name, @reply	997	sub db_reg($$;$) {
		998	my $family = shift;
		999	my $port = @_ ? shift : $SELF;
710		1000
711	Replies with the port ID of the specified well-known port, or C<undef>.	1001	my $clr = sub { db_del $family => $port };
		1002	mon $port, $clr;
712		1003
713	=item devnull => ...	1004	db_set $family => $port => $_[0];
714		1005
715	Generic data sink/CPU heat conversion.	1006	defined wantarray
		1007	and &Guard::guard ($clr)
		1008	}
716		1009
717	=item relay => $port, @msg	1010	=item db_family $family => $cb->(\%familyhash)
718		1011
719	Simply forwards the message to the given port.	1012	Queries the named database C<$family> and call the callback with the
		1013	family represented as a hash. You can keep and freely modify the hash.
720		1014
721	=item eval => $string[ @reply]	1015	=item db_keys $family => $cb->(\@keys)
722		1016
723	Evaluates the given string. If C<@reply> is given, then a message of the	1017	Same as C<db_family>, except it only queries the family I<subkeys> and passes
724	form C<@reply, $@, @evalres> is sent.	1018	them as array reference to the callback.
725		1019
726	Example: crash another node.	1020	=item db_values $family => $cb->(\@values)
727		1021
728	snd $othernode, eval => "exit";	1022	Same as C<db_family>, except it only queries the family I<values> and passes them
		1023	as array reference to the callback.
729		1024
730	=item time => @reply	1025	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
731		1026
732	Replies the the current node time to C<@reply>.	1027	Creates a monitor on the given database family. Each time a key is set
		1028	or or is deleted the callback is called with a hash containing the
		1029	database family and three lists of added, changed and deleted subkeys,
		1030	respectively. If no keys have changed then the array reference might be
		1031	C<undef> or even missing.
733		1032
734	Example: tell the current node to send the current time to C<$myport> in a	1033	If not called in void context, a guard object is returned that, when
735	C<timereply> message.	1034	destroyed, stops the monitor.
736		1035
737	snd $NODE, time => $myport, timereply => 1, 2;	1036	The family hash reference and the key arrays belong to AnyEvent::MP and
738	# => snd $myport, timereply => 1, 2, <time>	1037	B<must not be modified or stored> by the callback. When in doubt, make a
		1038	copy.
		1039
		1040	As soon as possible after the monitoring starts, the callback will be
		1041	called with the intiial contents of the family, even if it is empty,
		1042	i.e. there will always be a timely call to the callback with the current
		1043	contents.
		1044
		1045	It is possible that the callback is called with a change event even though
		1046	the subkey is already present and the value has not changed.
		1047
		1048	The monitoring stops when the guard object is destroyed.
		1049
		1050	Example: on every change to the family "mygroup", print out all keys.
		1051
		1052	my $guard = db_mon mygroup => sub {
		1053	my ($family, $a, $c, $d) = @_;
		1054	print "mygroup members: ", (join " ", keys %$family), "\n";
		1055	};
		1056
		1057	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1058
		1059	my $guard; $guard = db_mon My::Module::workers => sub {
		1060	my ($family, $a, $c, $d) = @_;
		1061	return unless %$family;
		1062	undef $guard;
		1063	print "My::Module::workers now nonempty\n";
		1064	};
		1065
		1066	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1067
		1068	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1069	my ($family, $a, $c, $d) = @_;
		1070
		1071	print "+$_=$family->{$_}\n" for @$a;
		1072	print "*$_=$family->{$_}\n" for @$c;
		1073	print "-$_=$family->{$_}\n" for @$d;
		1074	};
		1075
		1076	=cut
739		1077
740	=back	1078	=back
741		1079
742	=head1 AnyEvent::MP vs. Distributed Erlang	1080	=head1 AnyEvent::MP vs. Distributed Erlang
743		1081
744	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1082	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
745	== aemp node, Erlang process == aemp port), so many of the documents and	1083	== aemp node, Erlang process == aemp port), so many of the documents and
746	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1084	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
747	sample:	1085	sample:
748		1086
749	http://www.Erlang.se/doc/programming_rules.shtml	1087	http://www.erlang.se/doc/programming_rules.shtml
750	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1088	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
751	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1089	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
752	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1090	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
753		1091
754	Despite the similarities, there are also some important differences:	1092	Despite the similarities, there are also some important differences:
755		1093
756	=over 4	1094	=over 4
757		1095
758	=item * Node references contain the recipe on how to contact them.	1096	=item * Node IDs are arbitrary strings in AEMP.
759		1097
760	Erlang relies on special naming and DNS to work everywhere in the	1098	Erlang relies on special naming and DNS to work everywhere in the same
761	same way. AEMP relies on each node knowing it's own address(es), with	1099	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
762	convenience functionality.	1100	configuration or DNS), and possibly the addresses of some seed nodes, but
		1101	will otherwise discover other nodes (and their IDs) itself.
763		1102
764	This means that AEMP requires a less tightly controlled environment at the	1103	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
765	cost of longer node references and a slightly higher management overhead.	1104	uses "local ports are like remote ports".
		1105
		1106	The failure modes for local ports are quite different (runtime errors
		1107	only) then for remote ports - when a local port dies, you I<know> it dies,
		1108	when a connection to another node dies, you know nothing about the other
		1109	port.
		1110
		1111	Erlang pretends remote ports are as reliable as local ports, even when
		1112	they are not.
		1113
		1114	AEMP encourages a "treat remote ports differently" philosophy, with local
		1115	ports being the special case/exception, where transport errors cannot
		1116	occur.
766		1117
767	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1118	=item * Erlang uses processes and a mailbox, AEMP does not queue.
768		1119
769	Erlang uses processes that selctively receive messages, and therefore	1120	Erlang uses processes that selectively receive messages out of order, and
770	needs a queue. AEMP is event based, queuing messages would serve no useful	1121	therefore needs a queue. AEMP is event based, queuing messages would serve
771	purpose.	1122	no useful purpose. For the same reason the pattern-matching abilities
		1123	of AnyEvent::MP are more limited, as there is little need to be able to
		1124	filter messages without dequeuing them.
772		1125
773	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1126	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1127	being event-based, while Erlang is process-based.
		1128
		1129	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1130	top of AEMP and Coro threads.
774		1131
775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1132	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
776		1133
777	Sending messages in Erlang is synchronous and blocks the process. AEMP	1134	Sending messages in Erlang is synchronous and blocks the process until
778	sends are immediate, connection establishment is handled in the	1135	a conenction has been established and the message sent (and so does not
779	background.	1136	need a queue that can overflow). AEMP sends return immediately, connection
		1137	establishment is handled in the background.
780		1138
781	=item * Erlang can silently lose messages, AEMP cannot.	1139	=item * Erlang suffers from silent message loss, AEMP does not.
782		1140
783	Erlang makes few guarantees on messages delivery - messages can get lost	1141	Erlang implements few guarantees on messages delivery - messages can get
784	without any of the processes realising it (i.e. you send messages a, b,	1142	lost without any of the processes realising it (i.e. you send messages a,
785	and c, and the other side only receives messages a and c).	1143	b, and c, and the other side only receives messages a and c).
786		1144
787	AEMP guarantees correct ordering, and the guarantee that there are no	1145	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1146	guarantee that after one message is lost, all following ones sent to the
		1147	same port are lost as well, until monitoring raises an error, so there are
788	holes in the message sequence.	1148	no silent "holes" in the message sequence.
789		1149
790	=item * In Erlang, processes can be declared dead and later be found to be	1150	If you want your software to be very reliable, you have to cope with
791	alive.	1151	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
792		1152	simply tries to work better in common error cases, such as when a network
793	In Erlang it can happen that a monitored process is declared dead and	1153	link goes down.
794	linked processes get killed, but later it turns out that the process is
795	still alive - and can receive messages.
796
797	In AEMP, when port monitoring detects a port as dead, then that port will
798	eventually be killed - it cannot happen that a node detects a port as dead
799	and then later sends messages to it, finding it is still alive.
800		1154
801	=item * Erlang can send messages to the wrong port, AEMP does not.	1155	=item * Erlang can send messages to the wrong port, AEMP does not.
802		1156
803	In Erlang it is quite possible that a node that restarts reuses a process	1157	In Erlang it is quite likely that a node that restarts reuses an Erlang
804	ID known to other nodes for a completely different process, causing	1158	process ID known to other nodes for a completely different process,
805	messages destined for that process to end up in an unrelated process.	1159	causing messages destined for that process to end up in an unrelated
		1160	process.
806		1161
807	AEMP never reuses port IDs, so old messages or old port IDs floating	1162	AEMP does not reuse port IDs, so old messages or old port IDs floating
808	around in the network will not be sent to an unrelated port.	1163	around in the network will not be sent to an unrelated port.
809		1164
810	=item * Erlang uses unprotected connections, AEMP uses secure	1165	=item * Erlang uses unprotected connections, AEMP uses secure
811	authentication and can use TLS.	1166	authentication and can use TLS.
812		1167
813	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1168	AEMP can use a proven protocol - TLS - to protect connections and
814	securely authenticate nodes.	1169	securely authenticate nodes.
815		1170
816	=item * The AEMP protocol is optimised for both text-based and binary	1171	=item * The AEMP protocol is optimised for both text-based and binary
817	communications.	1172	communications.
818		1173
819	The AEMP protocol, unlike the Erlang protocol, supports both	1174	The AEMP protocol, unlike the Erlang protocol, supports both programming
820	language-independent text-only protocols (good for debugging) and binary,	1175	language independent text-only protocols (good for debugging), and binary,
821	language-specific serialisers (e.g. Storable).	1176	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1177	used, the protocol is actually completely text-based.
822		1178
823	It has also been carefully designed to be implementable in other languages	1179	It has also been carefully designed to be implementable in other languages
824	with a minimum of work while gracefully degrading fucntionality to make the	1180	with a minimum of work while gracefully degrading functionality to make the
825	protocol simple.	1181	protocol simple.
826		1182
827	=item * AEMP has more flexible monitoring options than Erlang.	1183	=item * AEMP has more flexible monitoring options than Erlang.
828		1184
829	In Erlang, you can chose to receive I<all> exit signals as messages	1185	In Erlang, you can chose to receive I<all> exit signals as messages or
830	or I<none>, there is no in-between, so monitoring single processes is	1186	I<none>, there is no in-between, so monitoring single Erlang processes is
831	difficult to implement. Monitoring in AEMP is more flexible than in	1187	difficult to implement.
832	Erlang, as one can choose between automatic kill, exit message or callback	1188
833	on a per-process basis.	1189	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1190	between automatic kill, exit message or callback on a per-port basis.
834		1191
835	=item * Erlang tries to hide remote/local connections, AEMP does not.	1192	=item * Erlang tries to hide remote/local connections, AEMP does not.
836		1193
837	Monitoring in Erlang is not an indicator of process death/crashes,	1194	Monitoring in Erlang is not an indicator of process death/crashes, in the
838	as linking is (except linking is unreliable in Erlang).	1195	same way as linking is (except linking is unreliable in Erlang).
839		1196
840	In AEMP, you don't "look up" registered port names or send to named ports	1197	In AEMP, you don't "look up" registered port names or send to named ports
841	that might or might not be persistent. Instead, you normally spawn a port	1198	that might or might not be persistent. Instead, you normally spawn a port
842	on the remote node. The init function monitors the you, and you monitor	1199	on the remote node. The init function monitors you, and you monitor the
843	the remote port. Since both monitors are local to the node, they are much	1200	remote port. Since both monitors are local to the node, they are much more
844	more reliable.	1201	reliable (no need for C<spawn_link>).
845		1202
846	This also saves round-trips and avoids sending messages to the wrong port	1203	This also saves round-trips and avoids sending messages to the wrong port
847	(hard to do in Erlang).	1204	(hard to do in Erlang).
848		1205
849	=back	1206	=back
850		1207
		1208	=head1 RATIONALE
		1209
		1210	=over 4
		1211
		1212	=item Why strings for port and node IDs, why not objects?
		1213
		1214	We considered "objects", but found that the actual number of methods
		1215	that can be called are quite low. Since port and node IDs travel over
		1216	the network frequently, the serialising/deserialising would add lots of
		1217	overhead, as well as having to keep a proxy object everywhere.
		1218
		1219	Strings can easily be printed, easily serialised etc. and need no special
		1220	procedures to be "valid".
		1221
		1222	And as a result, a port with just a default receiver consists of a single
		1223	code reference stored in a global hash - it can't become much cheaper.
		1224
		1225	=item Why favour JSON, why not a real serialising format such as Storable?
		1226
		1227	In fact, any AnyEvent::MP node will happily accept Storable as framing
		1228	format, but currently there is no way to make a node use Storable by
		1229	default (although all nodes will accept it).
		1230
		1231	The default framing protocol is JSON because a) JSON::XS is many times
		1232	faster for small messages and b) most importantly, after years of
		1233	experience we found that object serialisation is causing more problems
		1234	than it solves: Just like function calls, objects simply do not travel
		1235	easily over the network, mostly because they will always be a copy, so you
		1236	always have to re-think your design.
		1237
		1238	Keeping your messages simple, concentrating on data structures rather than
		1239	objects, will keep your messages clean, tidy and efficient.
		1240
		1241	=back
		1242
		1243	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1244
		1245	AEMP version 2 has a few major incompatible changes compared to version 1:
		1246
		1247	=over 4
		1248
		1249	=item AnyEvent::MP::Global no longer has group management functions.
		1250
		1251	At least not officially - the grp_* functions are still exported and might
		1252	work, but they will be removed in some later release.
		1253
		1254	AnyEvent::MP now comes with a distributed database that is more
		1255	powerful. Its database families map closely to port groups, but the API
		1256	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1257	a rough porting guide:
		1258
		1259	grp_reg $group, $port # old
		1260	db_reg $group, $port # new
		1261
		1262	$list = grp_get $group # old
		1263	db_keys $group, sub { my $list = shift } # new
		1264
		1265	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1266	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1267
		1268	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1269	no longer instant, because the local node might not have a copy of the
		1270	group. You can either modify your code to allow for a callback, or use
		1271	C<db_mon> to keep an updated copy of the group:
		1272
		1273	my $local_group_copy;
		1274	db_mon $group => sub { $local_group_copy = $_[0] };
		1275
		1276	# now "keys %$local_group_copy" always returns the most up-to-date
		1277	# list of ports in the group.
		1278
		1279	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1280	passes a hash as first argument, and an extra C<$chg> argument that can be
		1281	ignored:
		1282
		1283	db_mon $group => sub {
		1284	my ($ports, $add, $chg, $lde) = @_;
		1285	$ports = [keys %$ports];
		1286
		1287	# now $ports, $add and $del are the same as
		1288	# were originally passed by grp_mon.
		1289	...
		1290	};
		1291
		1292	=item Nodes not longer connect to all other nodes.
		1293
		1294	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1295	module, which in turn would create connections to all other nodes in the
		1296	network (helped by the seed nodes).
		1297
		1298	In version 2.x, global nodes still connect to all other global nodes, but
		1299	other nodes don't - now every node either is a global node itself, or
		1300	attaches itself to another global node.
		1301
		1302	If a node isn't a global node itself, then it attaches itself to one
		1303	of its seed nodes. If that seed node isn't a global node yet, it will
		1304	automatically be upgraded to a global node.
		1305
		1306	So in many cases, nothing needs to be changed - one just has to make sure
		1307	that all seed nodes are meshed together with the other seed nodes (as with
		1308	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1309	achieved by specifying the same set of seed nodes for all nodes in the
		1310	network.
		1311
		1312	Not opening a connection to every other node is usually an advantage,
		1313	except when you need the lower latency of an already established
		1314	connection. To ensure a node establishes a connection to another node,
		1315	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1316	create the connection (and notify you when the connection fails).
		1317
		1318	=item Listener-less nodes (nodes without binds) are gone.
		1319
		1320	And are not coming back, at least not in their old form. If no C<binds>
		1321	are specified for a node, AnyEvent::MP assumes a default of C<*:*>.
		1322
		1323	There are vague plans to implement some form of routing domains, which
		1324	might or might not bring back listener-less nodes, but don't count on it.
		1325
		1326	The fact that most connections are now optional somewhat mitigates this,
		1327	as a node can be effectively unreachable from the outside without any
		1328	problems, as long as it isn't a global node and only reaches out to other
		1329	nodes (as opposed to being contacted from other nodes).
		1330
		1331	=item $AnyEvent::MP::Kernel::WARN has gone.
		1332
		1333	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1334	uses this, and so should your programs.
		1335
		1336	Every module now documents what kinds of messages it generates, with
		1337	AnyEvent::MP acting as a catch all.
		1338
		1339	On the positive side, this means that instead of setting
		1340	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1341	much less to type.
		1342
		1343	=back
		1344
		1345	=head1 LOGGING
		1346
		1347	AnyEvent::MP does not normally log anything by itself, but sinc eit is the
		1348	root of the contetx hierarchy for AnyEvent::MP modules, it will receive
		1349	all log messages by submodules.
		1350
851	=head1 SEE ALSO	1351	=head1 SEE ALSO
		1352
		1353	L<AnyEvent::MP::Intro> - a gentle introduction.
		1354
		1355	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1356
		1357	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1358	your applications.
		1359
		1360	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1361
		1362	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1363	all nodes.
852		1364
853	L<AnyEvent>.	1365	L<AnyEvent>.
854		1366
855	=head1 AUTHOR	1367	=head1 AUTHOR
856		1368

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