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Revision 1.43 by root, Sun Aug 9 16:08:16 2009 UTC vs.
Revision 1.154 by root, Fri Nov 15 09:47:38 2019 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	};
		51
		52	# distributed database - modification
		53	db_set $family => $subkey [=> $value] # add a subkey
		54	db_del $family => $subkey... # delete one or more subkeys
		55	db_reg $family => $port [=> $value] # register a port
		56
		57	# distributed database - queries
		58	db_family $family => $cb->(\%familyhash)
		59	db_keys $family => $cb->(\@keys)
		60	db_values $family => $cb->(\@values)
		61
		62	# distributed database - monitoring a family
		63	db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
42		64
43	=head1 DESCRIPTION	65	=head1 DESCRIPTION
44		66
45	This module (-family) implements a simple message passing framework.	67	This module (-family) implements a simple message passing framework.
46		68
47	Despite its simplicity, you can securely message other processes running	69	Despite its simplicity, you can securely message other processes running
48	on the same or other hosts.	70	on the same or other hosts, and you can supervise entities remotely.
49		71
50	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	72	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
51	manual page.	73	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		74
57	=head1 CONCEPTS	75	=head1 CONCEPTS
58		76
59	=over 4	77	=over 4
60		78
61	=item port	79	=item port
62		80
63	A port is something you can send messages to (with the C<snd> function).	81	Not to be confused with a TCP port, a "port" is something you can send
		82	messages to (with the C<snd> function).
64		83
65	Some ports allow you to register C<rcv> handlers that can match specific	84	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	85	some messages. Messages send to ports will not be queued, regardless of
67	will not be queued.	86	anything was listening for them or not.
68		87
		88	Ports are represented by (printable) strings called "port IDs".
		89
69	=item port id - C<noderef#portname>	90	=item port ID - C<nodeid#portname>
70		91
71	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	92	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	93	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	94	format created by AnyEvent::MP).
74	reference.
75		95
76	=item node	96	=item node
77		97
78	A node is a single process containing at least one port - the node	98	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	99	which enables nodes to manage each other remotely, and to create new
80	create new ports, among other things.	100	ports.
81		101
82	Nodes are either private (single-process only), slaves (connected to a	102	Nodes are either public (have one or more listening ports) or private
83	master node only) or public nodes (connectable from unrelated nodes).	103	(no listening ports). Private nodes cannot talk to other private nodes
		104	currently, but all nodes can talk to public nodes.
84		105
85	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	106	Nodes is represented by (printable) strings called "node IDs".
86		107
87	A node reference is a string that either simply identifies the node (for	108	=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		109
91	This recipe is simply a comma-separated list of C<address:port> pairs (for	110	A node ID is a string that uniquely identifies the node within a
92	TCP/IP, other protocols might look different).	111	network. Depending on the configuration used, node IDs can look like a
		112	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		113	doesn't interpret node IDs in any way except to uniquely identify a node.
93		114
94	Node references come in two flavours: resolved (containing only numerical	115	=item binds - C<ip:port>
95	addresses) or unresolved (where hostnames are used instead of addresses).
96		116
97	Before using an unresolved node reference in a message you first have to	117	Nodes can only talk to each other by creating some kind of connection to
98	resolve it.	118	each other. To do this, nodes should listen on one or more local transport
		119	endpoints - binds.
		120
		121	Currently, only standard C<ip:port> specifications can be used, which
		122	specify TCP ports to listen on. So a bind is basically just a tcp socket
		123	in listening mode that accepts connections from other nodes.
		124
		125	=item seed nodes
		126
		127	When a node starts, it knows nothing about the network it is in - it
		128	needs to connect to at least one other node that is already in the
		129	network. These other nodes are called "seed nodes".
		130
		131	Seed nodes themselves are not special - they are seed nodes only because
		132	some other node I<uses> them as such, but any node can be used as seed
		133	node for other nodes, and eahc node can use a different set of seed nodes.
		134
		135	In addition to discovering the network, seed nodes are also used to
		136	maintain the network - all nodes using the same seed node are part of the
		137	same network. If a network is split into multiple subnets because e.g. the
		138	network link between the parts goes down, then using the same seed nodes
		139	for all nodes ensures that eventually the subnets get merged again.
		140
		141	Seed nodes are expected to be long-running, and at least one seed node
		142	should always be available. They should also be relatively responsive - a
		143	seed node that blocks for long periods will slow down everybody else.
		144
		145	For small networks, it's best if every node uses the same set of seed
		146	nodes. For large networks, it can be useful to specify "regional" seed
		147	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		148	each other. What's important is that all seed nodes connections form a
		149	complete graph, so that the network cannot split into separate subnets
		150	forever.
		151
		152	Seed nodes are represented by seed IDs.
		153
		154	=item seed IDs - C<host:port>
		155
		156	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		157	TCP port) of nodes that should be used as seed nodes.
		158
		159	=item global nodes
		160
		161	An AEMP network needs a discovery service - nodes need to know how to
		162	connect to other nodes they only know by name. In addition, AEMP offers a
		163	distributed "group database", which maps group names to a list of strings
		164	- for example, to register worker ports.
		165
		166	A network needs at least one global node to work, and allows every node to
		167	be a global node.
		168
		169	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		170	node and tries to keep connections to all other nodes. So while it can
		171	make sense to make every node "global" in small networks, it usually makes
		172	sense to only make seed nodes into global nodes in large networks (nodes
		173	keep connections to seed nodes and global nodes, so making them the same
		174	reduces overhead).
99		175
100	=back	176	=back
101		177
102	=head1 VARIABLES/FUNCTIONS	178	=head1 VARIABLES/FUNCTIONS
103		179
…		…
105		181
106	=cut	182	=cut
107		183
108	package AnyEvent::MP;	184	package AnyEvent::MP;
109		185
		186	use AnyEvent::MP::Config ();
110	use AnyEvent::MP::Base;	187	use AnyEvent::MP::Kernel;
		188	use AnyEvent::MP::Kernel qw(
		189	%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID
		190	add_node load_func
		191
		192	NODE $NODE
		193	configure
		194	node_of port_is_local
		195	snd kil
		196	db_set db_del
		197	db_mon db_family db_keys db_values
		198	);
111		199
112	use common::sense;	200	use common::sense;
113		201
114	use Carp ();	202	use Carp ();
115		203
116	use AE ();	204	use AnyEvent ();
		205	use Guard ();
117		206
118	use base "Exporter";	207	use base "Exporter";
119		208
120	our $VERSION = $AnyEvent::MP::Base::VERSION;	209	our $VERSION = '2.02'; # also in MP/Config.pm
121		210
122	our @EXPORT = qw(	211	our @EXPORT = qw(
123	NODE $NODE *SELF node_of _any_	212	configure
124	resolve_node initialise_node	213
125	snd rcv mon kil reg psub spawn	214	NODE $NODE
126	port	215	*SELF
		216
		217	node_of port_is_local
		218
		219	snd kil
		220	port rcv mon mon_guard psub peval spawn cal
		221	db_set db_del db_reg
		222	db_mon db_family db_keys db_values
		223
		224	after
127	);	225	);
128		226
129	our $SELF;	227	our $SELF;
130		228
131	sub _self_die() {	229	sub _self_die() {
…		…
134	kil $SELF, die => $msg;	232	kil $SELF, die => $msg;
135	}	233	}
136		234
137	=item $thisnode = NODE / $NODE	235	=item $thisnode = NODE / $NODE
138		236
139	The C<NODE> function returns, and the C<$NODE> variable contains	237	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	238	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	239	a call to C<configure>.
142	identifiers become invalid.
143		240
144	=item $noderef = node_of $port	241	=item $nodeid = node_of $port
145		242
146	Extracts and returns the noderef from a portid or a noderef.	243	Extracts and returns the node ID from a port ID or a node ID.
147		244
148	=item initialise_node $noderef, $seednode, $seednode...	245	=item $is_local = port_is_local $port
149		246
150	=item initialise_node "slave/", $master, $master...	247	Returns true iff the port is a local port.
151		248
		249	=item configure $profile, key => value...
		250
		251	=item configure key => value...
		252
152	Before a node can talk to other nodes on the network it has to initialise	253	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	254	"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.	255	to know is its own name, and optionally it should know the addresses of
		256	some other nodes in the network to discover other nodes.
155		257
156	This function initialises a node - it must be called exactly once (or	258	This function configures a node - it must be called exactly once (or
157	never) before calling other AnyEvent::MP functions.	259	never) before calling other AnyEvent::MP functions.
158		260
159	All arguments are noderefs, which can be either resolved or unresolved.	261	The key/value pairs are basically the same ones as documented for the
160		262	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		263
163	=over 4	264	=over 4
164		265
165	=item public nodes	266	=item norc => $boolean (default false)
166		267
167	For public nodes, C<$noderef> must either be a (possibly unresolved)	268	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	269	be consulted - all configuration options must be specified in the
169	which case the noderef will be guessed.	270	C<configure> call.
170		271
171	Afterwards, the node will bind itself on all endpoints and try to connect	272	=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		273
175	=item slave nodes	274	IF true, then the values specified in the C<configure> will take
176		275	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	276	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		277
185	=back	278	=back
186		279
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	280	=over 4
222		281
223	=item the empty string	282	=item step 1, gathering configuration from profiles
224		283
225	An empty-string component gets resolved as if the default port (4040) was	284	The function first looks up a profile in the aemp configuration (see the
226	specified.	285	L<aemp> commandline utility). The profile name can be specified via the
		286	named C<profile> parameter or can simply be the first parameter). If it is
		287	missing, then the nodename (F<uname -n>) will be used as profile name.
227		288
228	=item naked port numbers (e.g. C<1234>)	289	The profile data is then gathered as follows:
229		290
230	These are resolved by prepending the local nodename and a colon, to be	291	First, all remaining key => value pairs (all of which are conveniently
231	further resolved.	292	undocumented at the moment) will be interpreted as configuration
		293	data. Then they will be overwritten by any values specified in the global
		294	default configuration (see the F<aemp> utility), then the chain of
		295	profiles chosen by the profile name (and any C<parent> attributes).
232		296
233	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	297	That means that the values specified in the profile have highest priority
		298	and the values specified directly via C<configure> have lowest priority,
		299	and can only be used to specify defaults.
234		300
235	These are resolved by using AnyEvent::DNS to resolve them, optionally	301	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	302	this process. If not, then the profile name will be used as node ID, with
237	specified.	303	a unique randoms tring (C</%u>) appended.
		304
		305	The node ID can contain some C<%> sequences that are expanded: C<%n>
		306	is expanded to the local nodename, C<%u> is replaced by a random
		307	strign to make the node unique. For example, the F<aemp> commandline
		308	utility uses C<aemp/%n/%u> as nodename, which might expand to
		309	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		310
		311	=item step 2, bind listener sockets
		312
		313	The next step is to look up the binds in the profile, followed by binding
		314	aemp protocol listeners on all binds specified (it is possible and valid
		315	to have no binds, meaning that the node cannot be contacted from the
		316	outside. This means the node cannot talk to other nodes that also have no
		317	binds, but it can still talk to all "normal" nodes).
		318
		319	If the profile does not specify a binds list, then a default of C<*> is
		320	used, meaning the node will bind on a dynamically-assigned port on every
		321	local IP address it finds.
		322
		323	=item step 3, connect to seed nodes
		324
		325	As the last step, the seed ID list from the profile is passed to the
		326	L<AnyEvent::MP::Global> module, which will then use it to keep
		327	connectivity with at least one node at any point in time.
238		328
239	=back	329	=back
		330
		331	Example: become a distributed node using the local node name as profile.
		332	This should be the most common form of invocation for "daemon"-type nodes.
		333
		334	configure
		335
		336	Example: become a semi-anonymous node. This form is often used for
		337	commandline clients.
		338
		339	configure nodeid => "myscript/%n/%u";
		340
		341	Example: configure a node using a profile called seed, which is suitable
		342	for a seed node as it binds on all local addresses on a fixed port (4040,
		343	customary for aemp).
		344
		345	# use the aemp commandline utility
		346	# aemp profile seed binds '*:4040'
		347
		348	# then use it
		349	configure profile => "seed";
		350
		351	# or simply use aemp from the shell again:
		352	# aemp run profile seed
		353
		354	# or provide a nicer-to-remember nodeid
		355	# aemp run profile seed nodeid "$(hostname)"
240		356
241	=item $SELF	357	=item $SELF
242		358
243	Contains the current port id while executing C<rcv> callbacks or C<psub>	359	Contains the current port id while executing C<rcv> callbacks or C<psub>
244	blocks.	360	blocks.
245		361
246	=item SELF, %SELF, @SELF...	362	=item *SELF, SELF, %SELF, @SELF...
247		363
248	Due to some quirks in how perl exports variables, it is impossible to	364	Due to some quirks in how perl exports variables, it is impossible to
249	just export C<$SELF>, all the symbols called C<SELF> are exported by this	365	just export C<$SELF>, all the symbols named C<SELF> are exported by this
250	module, but only C<$SELF> is currently used.	366	module, but only C<$SELF> is currently used.
251		367
252	=item snd $port, type => @data	368	=item snd $port, type => @data
253		369
254	=item snd $port, @msg	370	=item snd $port, @msg
255		371
256	Send the given message to the given port ID, which can identify either	372	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	373	local or a remote port, and must be a port ID.
258	stringifies a sa port ID (such as a port object :).
259		374
260	While the message can be about anything, it is highly recommended to use a	375	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	376	use a string as first element (a port ID, or some word that indicates a
262	type etc.).	377	request type etc.) and to consist if only simple perl values (scalars,
		378	arrays, hashes) - if you think you need to pass an object, think again.
263		379
264	The message data effectively becomes read-only after a call to this	380	The message data logically becomes read-only after a call to this
265	function: modifying any argument is not allowed and can cause many	381	function: modifying any argument (or values referenced by them) is
266	problems.	382	forbidden, as there can be considerable time between the call to C<snd>
		383	and the time the message is actually being serialised - in fact, it might
		384	never be copied as within the same process it is simply handed to the
		385	receiving port.
267		386
268	The type of data you can transfer depends on the transport protocol: when	387	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	388	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	389	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	390	that Storable can serialise and deserialise is allowed, and for the local
272	node, anything can be passed.	391	node, anything can be passed. Best rely only on the common denominator of
		392	these.
273		393
274	=item $local_port = port	394	=item $local_port = port
275		395
276	Create a new local port object that can be used either as a pattern	396	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"),	397	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		398
280	=item $port = port { my @msg = @_; $finished }	399	=item $local_port = port { my @msg = @_ }
281		400
282	Creates a "miniport", that is, a very lightweight port without any pattern	401	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.	402	creating a port and calling C<rcv $port, $callback> on it.
285		403
286	The block will be called for every message received on the port. When the	404	The block will be called for every message received on the port, with the
287	callback returns a true value its job is considered "done" and the port	405	global variable C<$SELF> set to the port ID. Runtime errors will cause the
288	will be destroyed. Otherwise it will stay alive.	406	port to be C<kil>ed. The message will be passed as-is, no extra argument
		407	(i.e. no port ID) will be passed to the callback.
289		408
290	The message will be passed as-is, no extra argument (i.e. no port id) will	409	If you want to stop/destroy the port, simply C<kil> it:
291	be passed to the callback.
292		410
293	If you need the local port id in the callback, this works nicely:	411	my $port = port {
294		412	my @msg = @_;
295	my $port; $port = port {	413	...
296	snd $otherport, reply => $port;	414	kil $SELF;
297	};	415	};
298		416
299	=cut	417	=cut
300		418
301	sub rcv($@);	419	sub rcv($@);
302		420
		421	my $KILME = sub {
		422	(my $tag = substr $_[0], 0, 30) =~ s/([^\x20-\x7e])/./g;
		423	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		424	};
		425
303	sub port(;&) {	426	sub port(;&) {
304	my $id = "$UNIQ." . $ID++;	427	my $id = $UNIQ . ++$ID;
305	my $port = "$NODE#$id";	428	my $port = "$NODE#$id";
306		429
307	if (@_) {
308	rcv $port, shift;	430	rcv $port, shift || $KILME;
309	} else {
310	$PORT{$id} = sub { }; # nop
311	}
312		431
313	$port	432	$port
314	}	433	}
315		434
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)	435	=item rcv $local_port, $callback->(@msg)
336		436
337	Replaces the callback on the specified miniport (after converting it to	437	Replaces the default callback on the specified port. There is no way to
338	one if required).	438	remove the default callback: use C<sub { }> to disable it, or better
339		439	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...] => $callback->(@msg), ...
345
346	Register callbacks to be called on matching messages on the given full
347	port (after converting it to one if required) and return the port.
348
349	The callback has to return a true value when its work is done, after
350	which is will be removed, or a false value in which case it will stay
351	registered.
352		440
353	The global C<$SELF> (exported by this module) contains C<$port> while	441	The global C<$SELF> (exported by this module) contains C<$port> while
354	executing the callback.	442	executing the callback. Runtime errors during callback execution will
		443	result in the port being C<kil>ed.
355		444
356	Runtime errors during callback execution will result in the port being	445	The default callback receives all messages not matched by a more specific
357	C<kil>ed.	446	C<tag> match.
358		447
359	If the match is an array reference, then it will be matched against the	448	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
360	first elements of the message, otherwise only the first element is being
361	matched.
362		449
363	Any element in the match that is specified as C<_any_> (a function	450	Register (or replace) callbacks to be called on messages starting with the
364	exported by this module) matches any single element of the message.	451	given tag on the given port (and return the port), or unregister it (when
		452	C<$callback> is C<$undef> or missing). There can only be one callback
		453	registered for each tag.
365		454
366	While not required, it is highly recommended that the first matching	455	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	456	element (the tag) has been removed. The callback will use the same
368	also the most efficient match (by far).	457	environment as the default callback (see above).
369		458
370	Example: create a port and bind receivers on it in one go.	459	Example: create a port and bind receivers on it in one go.
371		460
372	my $port = rcv port,	461	my $port = rcv port,
373	msg1 => sub { ...; 0 },	462	msg1 => sub { ... },
374	msg2 => sub { ...; 0 },	463	msg2 => sub { ... },
375	;	464	;
376		465
377	Example: create a port, bind receivers and send it in a message elsewhere	466	Example: create a port, bind receivers and send it in a message elsewhere
378	in one go:	467	in one go:
379		468
380	snd $otherport, reply =>	469	snd $otherport, reply =>
381	rcv port,	470	rcv port,
382	msg1 => sub { ...; 0 },	471	msg1 => sub { ... },
383	...	472	...
384	;	473	;
385		474
		475	Example: temporarily register a rcv callback for a tag matching some port
		476	(e.g. for an rpc reply) and unregister it after a message was received.
		477
		478	rcv $port, $otherport => sub {
		479	my @reply = @_;
		480
		481	rcv $SELF, $otherport;
		482	};
		483
386	=cut	484	=cut
387		485
388	sub rcv($@) {	486	sub rcv($@) {
389	my $port = shift;	487	my $port = shift;
390	my ($noderef, $portid) = split /#/, $port, 2;	488	my ($nodeid, $portid) = split /#/, $port, 2;
391		489
392	($NODE{$noderef} || add_node $noderef) == $NODE{""}	490	$nodeid eq $NODE
393	or Carp::croak "$port: rcv can only be called on local ports, caught";	491	or Carp::croak "$port: rcv can only be called on local ports, caught";
394		492
395	if (@_ == 1) {	493	while (@_) {
		494	if (ref $_[0]) {
		495	if (my $self = $PORT_DATA{$portid}) {
		496	"AnyEvent::MP::Port" eq ref $self
		497	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		498
		499	$self->[0] = shift;
		500	} else {
396	my $cb = shift;	501	my $cb = shift;
397	delete $PORT_DATA{$portid};
398	$PORT{$portid} = sub {	502	$PORT{$portid} = sub {
399	local $SELF = $port;	503	local $SELF = $port;
400	eval {	504	eval { &$cb }; _self_die if $@;
401	&$cb	505	};
402	and kil $port;
403	};	506	}
404	_self_die if $@;	507	} elsif (defined $_[0]) {
405	};
406	} else {
407	my $self = $PORT_DATA{$portid} ||= do {	508	my $self = $PORT_DATA{$portid} ||= do {
408	my $self = bless {	509	my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
409	id => $port,
410	}, "AnyEvent::MP::Port";
411		510
412	$PORT{$portid} = sub {	511	$PORT{$portid} = sub {
413	local $SELF = $port;	512	local $SELF = $port;
414		513
415	eval {
416	for (@{ $self->{rc0}{$_[0]} }) {	514	if (my $cb = $self->[1]{$_[0]}) {
417	$_ && &{$_->[0]}	515	shift;
418	&& undef $_;	516	eval { &$cb }; _self_die if $@;
419	}	517	} else {
420
421	for (@{ $self->{rcv}{$_[0]} }) {
422	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
423	&& &{$_->[0]}	518	&{ $self->[0] };
424	&& undef $_;
425	}
426
427	for (@{ $self->{any} }) {
428	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
429	&& &{$_->[0]}
430	&& undef $_;
431	}	519	}
432	};	520	};
433	_self_die if $@;	521
		522	$self
434	};	523	};
435		524
436	$self
437	};
438
439	"AnyEvent::MP::Port" eq ref $self	525	"AnyEvent::MP::Port" eq ref $self
440	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	526	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
441		527
442	while (@_) {
443	my ($match, $cb) = splice @_, 0, 2;	528	my ($tag, $cb) = splice @_, 0, 2;
444		529
445	if (!ref $match) {	530	if (defined $cb) {
446	push @{ $self->{rc0}{$match} }, [$cb];	531	$self->[1]{$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 {	532	} else {
453	push @{ $self->{any} }, [$cb, $match];	533	delete $self->[1]{$tag};
454	}	534	}
455	}	535	}
456	}	536	}
457		537
458	$port	538	$port
459	}	539	}
460		540
		541	=item peval $port, $coderef[, @args]
		542
		543	Evaluates the given C<$codref> within the context of C<$port>, that is,
		544	when the code throws an exception the C<$port> will be killed.
		545
		546	Any remaining args will be passed to the callback. Any return values will
		547	be returned to the caller.
		548
		549	This is useful when you temporarily want to execute code in the context of
		550	a port.
		551
		552	Example: create a port and run some initialisation code in it's context.
		553
		554	my $port = port { ... };
		555
		556	peval $port, sub {
		557	init
		558	or die "unable to init";
		559	};
		560
		561	=cut
		562
		563	sub peval($$) {
		564	local $SELF = shift;
		565	my $cb = shift;
		566
		567	if (wantarray) {
		568	my @res = eval { &$cb };
		569	_self_die if $@;
		570	@res
		571	} else {
		572	my $res = eval { &$cb };
		573	_self_die if $@;
		574	$res
		575	}
		576	}
		577
461	=item $closure = psub { BLOCK }	578	=item $closure = psub { BLOCK }
462		579
463	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	580	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>	581	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.	582	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		583
		584	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		585	BLOCK }, @_ } >>.
466		586
467	This is useful when you register callbacks from C<rcv> callbacks:	587	This is useful when you register callbacks from C<rcv> callbacks:
468		588
469	rcv delayed_reply => sub {	589	rcv delayed_reply => sub {
470	my ($delay, @reply) = @_;	590	my ($delay, @reply) = @_;
…		…
494	$res	614	$res
495	}	615	}
496	}	616	}
497	}	617	}
498		618
499	=item $guard = mon $port, $cb->(@reason)	619	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
500		620
501	=item $guard = mon $port, $rcvport	621	=item $guard = mon $port # kill $SELF when $port dies
502		622
503	=item $guard = mon $port	623	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
504		624
505	=item $guard = mon $port, $rcvport, @msg	625	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
506		626
507	Monitor the given port and do something when the port is killed or	627	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	628	messages to it were lost, and optionally return a guard that can be used
509	to stop monitoring again.	629	to stop monitoring again.
510		630
		631	The first two forms distinguish between "normal" and "abnormal" kil's:
		632
		633	In the first form (another port given), if the C<$port> is C<kil>'ed with
		634	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		635	same reason. That is, on "normal" kil's nothing happens, while under all
		636	other conditions, the other port is killed with the same reason.
		637
		638	The second form (kill self) is the same as the first form, except that
		639	C<$rvport> defaults to C<$SELF>.
		640
		641	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		642	- it's up to the callback or receiver to check whether the C<@reason> is
		643	empty and act accordingly.
		644
		645	In the third form (callback), the callback is simply called with any
		646	number of C<@reason> elements (empty @reason means that the port was deleted
		647	"normally"). Note also that I<< the callback B<must> never die >>, so use
		648	C<eval> if unsure.
		649
		650	In the last form (message), a message of the form C<$rcvport, @msg,
		651	@reason> will be C<snd>.
		652
		653	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		654	alert was raised), they are removed and will not trigger again, even if it
		655	turns out that the port is still alive (but monitoring actions added after
		656	that will again trigger).
		657
		658	As a rule of thumb, monitoring requests should always monitor a remote
		659	port locally (using a local C<$rcvport> or a callback). The reason is that
		660	kill messages might get lost, just like any other message. Another less
		661	obvious reason is that even monitoring requests can get lost (for example,
		662	when the connection to the other node goes down permanently). When
		663	monitoring a port locally these problems do not exist.
		664
511	C<mon> effectively guarantees that, in the absence of hardware failures,	665	C<mon> effectively guarantees that, in the absence of hardware failures,
512	that after starting the monitor, either all messages sent to the port	666	after starting the monitor, either all messages sent to the port will
513	will arrive, or the monitoring action will be invoked after possible	667	arrive, or the monitoring action will be invoked after possible message
514	message loss has been detected. No messages will be lost "in between"	668	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	669	the first lost message no further messages will be received by the
516	port). After the monitoring action was invoked, further messages might get	670	port). After the monitoring action was invoked, further messages might get
517	delivered again.	671	delivered again.
518		672
519	In the first form (callback), the callback is simply called with any	673	Inter-host-connection timeouts and monitoring depend on the transport
520	number of C<@reason> elements (no @reason means that the port was deleted	674	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	675	relies on TCP to detect node-downs (this can take 10-15 minutes on a
522	C<eval> if unsure.	676	non-idle connection, and usually around two hours for idle connections).
523		677
524	In the second form (another port given), the other port (C<$rcvport>)	678	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	679	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	680	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		681
542	Example: call a given callback when C<$port> is killed.	682	Example: call a given callback when C<$port> is killed.
543		683
544	mon $port, sub { warn "port died because of <@_>\n" };	684	mon $port, sub { warn "port died because of <@_>\n" };
545		685
…		…
552	mon $port, $self => "restart";	692	mon $port, $self => "restart";
553		693
554	=cut	694	=cut
555		695
556	sub mon {	696	sub mon {
557	my ($noderef, $port) = split /#/, shift, 2;	697	my ($nodeid, $port) = split /#/, shift, 2;
558		698
559	my $node = $NODE{$noderef} || add_node $noderef;	699	my $node = $NODE{$nodeid} || add_node $nodeid;
560		700
561	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';	701	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
562		702
563	unless (ref $cb) {	703	unless (ref $cb) {
564	if (@_) {	704	if (@_) {
…		…
573	}	713	}
574		714
575	$node->monitor ($port, $cb);	715	$node->monitor ($port, $cb);
576		716
577	defined wantarray	717	defined wantarray
578	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	718	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
579	}	719	}
580		720
581	=item $guard = mon_guard $port, $ref, $ref...	721	=item $guard = mon_guard $port, $ref, $ref...
582		722
583	Monitors the given C<$port> and keeps the passed references. When the port	723	Monitors the given C<$port> and keeps the passed references. When the port
584	is killed, the references will be freed.	724	is killed, the references will be freed.
585		725
586	Optionally returns a guard that will stop the monitoring.	726	Optionally returns a guard that will stop the monitoring.
587		727
588	This function is useful when you create e.g. timers or other watchers and	728	This function is useful when you create e.g. timers or other watchers and
589	want to free them when the port gets killed:	729	want to free them when the port gets killed (note the use of C<psub>):
590		730
591	$port->rcv (start => sub {	731	$port->rcv (start => sub {
592	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	732	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
593	undef $timer if 0.9 < rand;	733	undef $timer if 0.9 < rand;
594	});	734	});
595	});	735	});
596		736
597	=cut	737	=cut
…		…
606		746
607	=item kil $port[, @reason]	747	=item kil $port[, @reason]
608		748
609	Kill the specified port with the given C<@reason>.	749	Kill the specified port with the given C<@reason>.
610		750
611	If no C<@reason> is specified, then the port is killed "normally" (linked	751	If no C<@reason> is specified, then the port is killed "normally" -
612	ports will not be kileld, or even notified).	752	monitor callback will be invoked, but the kil will not cause linked ports
		753	(C<mon $mport, $lport> form) to get killed.
613		754
614	Otherwise, linked ports get killed with the same reason (second form of	755	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
615	C<mon>, see below).	756	form) get killed with the same reason.
616		757
617	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	758	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
618	will be reported as reason C<< die => $@ >>.	759	will be reported as reason C<< die => $@ >>.
619		760
620	Transport/communication errors are reported as C<< transport_error =>	761	Transport/communication errors are reported as C<< transport_error =>
621	$message >>.	762	$message >>.
622		763
623	=cut	764	Common idioms:
		765
		766	# silently remove yourself, do not kill linked ports
		767	kil $SELF;
		768
		769	# report a failure in some detail
		770	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		771
		772	# do not waste much time with killing, just die when something goes wrong
		773	open my $fh, "<file"
		774	or die "file: $!";
624		775
625	=item $port = spawn $node, $initfunc[, @initdata]	776	=item $port = spawn $node, $initfunc[, @initdata]
626		777
627	Creates a port on the node C<$node> (which can also be a port ID, in which	778	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).	779	case it's the node where that port resides).
629		780
630	The port ID of the newly created port is return immediately, and it is	781	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.	782	possible to immediately start sending messages or to monitor the port.
632		783
633	After the port has been created, the init function is	784	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	785	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	786	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
636	program, use C<::name>.	787	specify a function in the main program, use C<::name>.
637		788
638	If the function doesn't exist, then the node tries to C<require>	789	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.	790	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	791	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
641	exists or it runs out of package names.	792	exists or it runs out of package names.
642		793
643	The init function is then called with the newly-created port as context	794	The init function is then called with the newly-created port as context
644	object (C<$SELF>) and the C<@initdata> values as arguments.	795	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		796	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		797	the port might not get created.
645		798
646	A common idiom is to pass your own port, monitor the spawned port, and	799	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	800	port, and in the remote init function, immediately monitor the passed
648	ensures that both ports get cleaned up when there is a problem.	801	local port. This two-way monitoring ensures that both ports get cleaned up
		802	when there is a problem.
		803
		804	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		805	caller before C<spawn> returns (by delaying invocation when spawn is
		806	called for the local node).
649		807
650	Example: spawn a chat server port on C<$othernode>.	808	Example: spawn a chat server port on C<$othernode>.
651		809
652	# this node, executed from within a port context:	810	# this node, executed from within a port context:
653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	811	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
668		826
669	sub _spawn {	827	sub _spawn {
670	my $port = shift;	828	my $port = shift;
671	my $init = shift;	829	my $init = shift;
672		830
		831	# rcv will create the actual port
673	local $SELF = "$NODE#$port";	832	local $SELF = "$NODE#$port";
674	eval {	833	eval {
675	&{ load_func $init }	834	&{ load_func $init }
676	};	835	};
677	_self_die if $@;	836	_self_die if $@;
678	}	837	}
679		838
680	sub spawn(@) {	839	sub spawn(@) {
681	my ($noderef, undef) = split /#/, shift, 2;	840	my ($nodeid, undef) = split /#/, shift, 2;
682		841
683	my $id = "$RUNIQ." . $ID++;	842	my $id = $RUNIQ . ++$ID;
684		843
685	$_[0] =~ /::/	844	$_[0] =~ /::/
686	or Carp::croak "spawn init function must be a fully-qualified name, caught";	845	or Carp::croak "spawn init function must be a fully-qualified name, caught";
687		846
688	($NODE{$noderef} || add_node $noderef)	847	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
689	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
690		848
691	"$noderef#$id"	849	"$nodeid#$id"
692	}	850	}
693		851
		852
		853	=item after $timeout, @msg
		854
		855	=item after $timeout, $callback
		856
		857	Either sends the given message, or call the given callback, after the
		858	specified number of seconds.
		859
		860	This is simply a utility function that comes in handy at times - the
		861	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		862	so it may go away in the future.
		863
		864	=cut
		865
		866	sub after($@) {
		867	my ($timeout, @action) = @_;
		868
		869	my $t; $t = AE::timer $timeout, 0, sub {
		870	undef $t;
		871	ref $action[0]
		872	? $action[0]()
		873	: snd @action;
		874	};
		875	}
		876
		877	#=item $cb2 = timeout $seconds, $cb[, @args]
		878
		879	=item cal $port, @msg, $callback[, $timeout]
		880
		881	A simple form of RPC - sends a message to the given C<$port> with the
		882	given contents (C<@msg>), but appends a reply port to the message.
		883
		884	The reply port is created temporarily just for the purpose of receiving
		885	the reply, and will be C<kil>ed when no longer needed.
		886
		887	A reply message sent to the port is passed to the C<$callback> as-is.
		888
		889	If an optional time-out (in seconds) is given and it is not C<undef>,
		890	then the callback will be called without any arguments after the time-out
		891	elapsed and the port is C<kil>ed.
		892
		893	If no time-out is given (or it is C<undef>), then the local port will
		894	monitor the remote port instead, so it eventually gets cleaned-up.
		895
		896	Currently this function returns the temporary port, but this "feature"
		897	might go in future versions unless you can make a convincing case that
		898	this is indeed useful for something.
		899
		900	=cut
		901
		902	sub cal(@) {
		903	my $timeout = ref $_[-1] ? undef : pop;
		904	my $cb = pop;
		905
		906	my $port = port {
		907	undef $timeout;
		908	kil $SELF;
		909	&$cb;
		910	};
		911
		912	if (defined $timeout) {
		913	$timeout = AE::timer $timeout, 0, sub {
		914	undef $timeout;
		915	kil $port;
		916	$cb->();
		917	};
		918	} else {
		919	mon $_[0], sub {
		920	kil $port;
		921	$cb->();
		922	};
		923	}
		924
		925	push @_, $port;
		926	&snd;
		927
		928	$port
		929	}
		930
694	=back	931	=back
695		932
696	=head1 NODE MESSAGES	933	=head1 DISTRIBUTED DATABASE
697		934
698	Nodes understand the following messages sent to them. Many of them take	935	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	936	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	937	of the global nodes for their needs. Every node has a "local database"
701	the remaining arguments are simply the message data.	938	which contains all the values that are set locally. All local databases
		939	are merged together to form the global database, which can be queried.
702		940
703	While other messages exist, they are not public and subject to change.	941	The database structure is that of a two-level hash - the database hash
		942	contains hashes which contain values, similarly to a perl hash of hashes,
		943	i.e.:
704		944
		945	$DATABASE{$family}{$subkey} = $value
		946
		947	The top level hash key is called "family", and the second-level hash key
		948	is called "subkey" or simply "key".
		949
		950	The family must be alphanumeric, i.e. start with a letter and consist
		951	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		952	pretty much like Perl module names.
		953
		954	As the family namespace is global, it is recommended to prefix family names
		955	with the name of the application or module using it.
		956
		957	The subkeys must be non-empty strings, with no further restrictions.
		958
		959	The values should preferably be strings, but other perl scalars should
		960	work as well (such as C<undef>, arrays and hashes).
		961
		962	Every database entry is owned by one node - adding the same family/subkey
		963	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		964	but the result might be nondeterministic, i.e. the key might have
		965	different values on different nodes.
		966
		967	Different subkeys in the same family can be owned by different nodes
		968	without problems, and in fact, this is the common method to create worker
		969	pools. For example, a worker port for image scaling might do this:
		970
		971	db_set my_image_scalers => $port;
		972
		973	And clients looking for an image scaler will want to get the
		974	C<my_image_scalers> keys from time to time:
		975
		976	db_keys my_image_scalers => sub {
		977	@ports = @{ $_[0] };
		978	};
		979
		980	Or better yet, they want to monitor the database family, so they always
		981	have a reasonable up-to-date copy:
		982
		983	db_mon my_image_scalers => sub {
		984	@ports = keys %{ $_[0] };
		985	};
		986
		987	In general, you can set or delete single subkeys, but query and monitor
		988	whole families only.
		989
		990	If you feel the need to monitor or query a single subkey, try giving it
		991	it's own family.
		992
705	=over 4	993	=over
		994
		995	=item $guard = db_set $family => $subkey [=> $value]
		996
		997	Sets (or replaces) a key to the database - if C<$value> is omitted,
		998	C<undef> is used instead.
		999
		1000	When called in non-void context, C<db_set> returns a guard that
		1001	automatically calls C<db_del> when it is destroyed.
		1002
		1003	=item db_del $family => $subkey...
		1004
		1005	Deletes one or more subkeys from the database family.
		1006
		1007	=item $guard = db_reg $family => $port => $value
		1008
		1009	=item $guard = db_reg $family => $port
		1010
		1011	=item $guard = db_reg $family
		1012
		1013	Registers a port in the given family and optionally returns a guard to
		1014	remove it.
		1015
		1016	This function basically does the same as:
		1017
		1018	db_set $family => $port => $value
		1019
		1020	Except that the port is monitored and automatically removed from the
		1021	database family when it is kil'ed.
		1022
		1023	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1024	C<$SELF> is used.
		1025
		1026	This function is most useful to register a port in some port group (which
		1027	is just another name for a database family), and have it removed when the
		1028	port is gone. This works best when the port is a local port.
706		1029
707	=cut	1030	=cut
708		1031
709	=item lookup => $name, @reply	1032	sub db_reg($$;$) {
		1033	my $family = shift;
		1034	my $port = @_ ? shift : $SELF;
710		1035
711	Replies with the port ID of the specified well-known port, or C<undef>.	1036	my $clr = sub { db_del $family => $port };
		1037	mon $port, $clr;
712		1038
713	=item devnull => ...	1039	db_set $family => $port => $_[0];
714		1040
715	Generic data sink/CPU heat conversion.	1041	defined wantarray
		1042	and &Guard::guard ($clr)
		1043	}
716		1044
717	=item relay => $port, @msg	1045	=item db_family $family => $cb->(\%familyhash)
718		1046
719	Simply forwards the message to the given port.	1047	Queries the named database C<$family> and call the callback with the
		1048	family represented as a hash. You can keep and freely modify the hash.
720		1049
721	=item eval => $string[ @reply]	1050	=item db_keys $family => $cb->(\@keys)
722		1051
723	Evaluates the given string. If C<@reply> is given, then a message of the	1052	Same as C<db_family>, except it only queries the family I<subkeys> and passes
724	form C<@reply, $@, @evalres> is sent.	1053	them as array reference to the callback.
725		1054
726	Example: crash another node.	1055	=item db_values $family => $cb->(\@values)
727		1056
728	snd $othernode, eval => "exit";	1057	Same as C<db_family>, except it only queries the family I<values> and passes them
		1058	as array reference to the callback.
729		1059
730	=item time => @reply	1060	=item $guard = db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
731		1061
732	Replies the the current node time to C<@reply>.	1062	Creates a monitor on the given database family. Each time a key is
		1063	set or is deleted the callback is called with a hash containing the
		1064	database family and three lists of added, changed and deleted subkeys,
		1065	respectively. If no keys have changed then the array reference might be
		1066	C<undef> or even missing.
733		1067
734	Example: tell the current node to send the current time to C<$myport> in a	1068	If not called in void context, a guard object is returned that, when
735	C<timereply> message.	1069	destroyed, stops the monitor.
736		1070
737	snd $NODE, time => $myport, timereply => 1, 2;	1071	The family hash reference and the key arrays belong to AnyEvent::MP and
738	# => snd $myport, timereply => 1, 2, <time>	1072	B<must not be modified or stored> by the callback. When in doubt, make a
		1073	copy.
		1074
		1075	As soon as possible after the monitoring starts, the callback will be
		1076	called with the intiial contents of the family, even if it is empty,
		1077	i.e. there will always be a timely call to the callback with the current
		1078	contents.
		1079
		1080	It is possible that the callback is called with a change event even though
		1081	the subkey is already present and the value has not changed.
		1082
		1083	The monitoring stops when the guard object is destroyed.
		1084
		1085	Example: on every change to the family "mygroup", print out all keys.
		1086
		1087	my $guard = db_mon mygroup => sub {
		1088	my ($family, $a, $c, $d) = @_;
		1089	print "mygroup members: ", (join " ", keys %$family), "\n";
		1090	};
		1091
		1092	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1093
		1094	my $guard; $guard = db_mon My::Module::workers => sub {
		1095	my ($family, $a, $c, $d) = @_;
		1096	return unless %$family;
		1097	undef $guard;
		1098	print "My::Module::workers now nonempty\n";
		1099	};
		1100
		1101	Example: print all changes to the family "AnyEvent::Fantasy::Module".
		1102
		1103	my $guard = db_mon AnyEvent::Fantasy::Module => sub {
		1104	my ($family, $a, $c, $d) = @_;
		1105
		1106	print "+$_=$family->{$_}\n" for @$a;
		1107	print "*$_=$family->{$_}\n" for @$c;
		1108	print "-$_=$family->{$_}\n" for @$d;
		1109	};
		1110
		1111	=cut
739		1112
740	=back	1113	=back
741		1114
742	=head1 AnyEvent::MP vs. Distributed Erlang	1115	=head1 AnyEvent::MP vs. Distributed Erlang
743		1116
744	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1117	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	1118	== 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	1119	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
747	sample:	1120	sample:
748		1121
749	http://www.Erlang.se/doc/programming_rules.shtml	1122	http://www.erlang.se/doc/programming_rules.shtml
750	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1123	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	1124	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	1125	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
753		1126
754	Despite the similarities, there are also some important differences:	1127	Despite the similarities, there are also some important differences:
755		1128
756	=over 4	1129	=over 4
757		1130
758	=item * Node references contain the recipe on how to contact them.	1131	=item * Node IDs are arbitrary strings in AEMP.
759		1132
760	Erlang relies on special naming and DNS to work everywhere in the	1133	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	1134	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
762	convenience functionality.	1135	configuration or DNS), and possibly the addresses of some seed nodes, but
		1136	will otherwise discover other nodes (and their IDs) itself.
763		1137
764	This means that AEMP requires a less tightly controlled environment at the	1138	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
765	cost of longer node references and a slightly higher management overhead.	1139	uses "local ports are like remote ports".
		1140
		1141	The failure modes for local ports are quite different (runtime errors
		1142	only) then for remote ports - when a local port dies, you I<know> it dies,
		1143	when a connection to another node dies, you know nothing about the other
		1144	port.
		1145
		1146	Erlang pretends remote ports are as reliable as local ports, even when
		1147	they are not.
		1148
		1149	AEMP encourages a "treat remote ports differently" philosophy, with local
		1150	ports being the special case/exception, where transport errors cannot
		1151	occur.
766		1152
767	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1153	=item * Erlang uses processes and a mailbox, AEMP does not queue.
768		1154
769	Erlang uses processes that selctively receive messages, and therefore	1155	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	1156	therefore needs a queue. AEMP is event based, queuing messages would serve
771	purpose.	1157	no useful purpose. For the same reason the pattern-matching abilities
		1158	of AnyEvent::MP are more limited, as there is little need to be able to
		1159	filter messages without dequeuing them.
772		1160
773	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1161	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1162	being event-based, while Erlang is process-based.
		1163
		1164	You can have a look at L<Coro::MP> for a more Erlang-like process model on
		1165	top of AEMP and Coro threads.
774		1166
775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1167	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
776		1168
777	Sending messages in Erlang is synchronous and blocks the process. AEMP	1169	Sending messages in Erlang is synchronous and blocks the process until
778	sends are immediate, connection establishment is handled in the	1170	a connection has been established and the message sent (and so does not
779	background.	1171	need a queue that can overflow). AEMP sends return immediately, connection
		1172	establishment is handled in the background.
780		1173
781	=item * Erlang can silently lose messages, AEMP cannot.	1174	=item * Erlang suffers from silent message loss, AEMP does not.
782		1175
783	Erlang makes few guarantees on messages delivery - messages can get lost	1176	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,	1177	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).	1178	b, and c, and the other side only receives messages a and c).
786		1179
787	AEMP guarantees correct ordering, and the guarantee that there are no	1180	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1181	guarantee that after one message is lost, all following ones sent to the
		1182	same port are lost as well, until monitoring raises an error, so there are
788	holes in the message sequence.	1183	no silent "holes" in the message sequence.
789		1184
790	=item * In Erlang, processes can be declared dead and later be found to be	1185	If you want your software to be very reliable, you have to cope with
791	alive.	1186	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
792		1187	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	1188	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		1189
801	=item * Erlang can send messages to the wrong port, AEMP does not.	1190	=item * Erlang can send messages to the wrong port, AEMP does not.
802		1191
803	In Erlang it is quite possible that a node that restarts reuses a process	1192	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	1193	process ID known to other nodes for a completely different process,
805	messages destined for that process to end up in an unrelated process.	1194	causing messages destined for that process to end up in an unrelated
		1195	process.
806		1196
807	AEMP never reuses port IDs, so old messages or old port IDs floating	1197	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.	1198	around in the network will not be sent to an unrelated port.
809		1199
810	=item * Erlang uses unprotected connections, AEMP uses secure	1200	=item * Erlang uses unprotected connections, AEMP uses secure
811	authentication and can use TLS.	1201	authentication and can use TLS.
812		1202
813	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1203	AEMP can use a proven protocol - TLS - to protect connections and
814	securely authenticate nodes.	1204	securely authenticate nodes.
815		1205
816	=item * The AEMP protocol is optimised for both text-based and binary	1206	=item * The AEMP protocol is optimised for both text-based and binary
817	communications.	1207	communications.
818		1208
819	The AEMP protocol, unlike the Erlang protocol, supports both	1209	The AEMP protocol, unlike the Erlang protocol, supports both programming
820	language-independent text-only protocols (good for debugging) and binary,	1210	language independent text-only protocols (good for debugging), and binary,
821	language-specific serialisers (e.g. Storable).	1211	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1212	used, the protocol is actually completely text-based.
822		1213
823	It has also been carefully designed to be implementable in other languages	1214	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	1215	with a minimum of work while gracefully degrading functionality to make the
825	protocol simple.	1216	protocol simple.
826		1217
827	=item * AEMP has more flexible monitoring options than Erlang.	1218	=item * AEMP has more flexible monitoring options than Erlang.
828		1219
829	In Erlang, you can chose to receive I<all> exit signals as messages	1220	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	1221	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	1222	difficult to implement.
832	Erlang, as one can choose between automatic kill, exit message or callback	1223
833	on a per-process basis.	1224	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1225	between automatic kill, exit message or callback on a per-port basis.
834		1226
835	=item * Erlang tries to hide remote/local connections, AEMP does not.	1227	=item * Erlang tries to hide remote/local connections, AEMP does not.
836		1228
837	Monitoring in Erlang is not an indicator of process death/crashes,	1229	Monitoring in Erlang is not an indicator of process death/crashes, in the
838	as linking is (except linking is unreliable in Erlang).	1230	same way as linking is (except linking is unreliable in Erlang).
839		1231
840	In AEMP, you don't "look up" registered port names or send to named ports	1232	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	1233	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	1234	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	1235	remote port. Since both monitors are local to the node, they are much more
844	more reliable.	1236	reliable (no need for C<spawn_link>).
845		1237
846	This also saves round-trips and avoids sending messages to the wrong port	1238	This also saves round-trips and avoids sending messages to the wrong port
847	(hard to do in Erlang).	1239	(hard to do in Erlang).
848		1240
849	=back	1241	=back
850		1242
		1243	=head1 RATIONALE
		1244
		1245	=over 4
		1246
		1247	=item Why strings for port and node IDs, why not objects?
		1248
		1249	We considered "objects", but found that the actual number of methods
		1250	that can be called are quite low. Since port and node IDs travel over
		1251	the network frequently, the serialising/deserialising would add lots of
		1252	overhead, as well as having to keep a proxy object everywhere.
		1253
		1254	Strings can easily be printed, easily serialised etc. and need no special
		1255	procedures to be "valid".
		1256
		1257	And as a result, a port with just a default receiver consists of a single
		1258	code reference stored in a global hash - it can't become much cheaper.
		1259
		1260	=item Why favour JSON, why not a real serialising format such as Storable?
		1261
		1262	In fact, any AnyEvent::MP node will happily accept Storable as framing
		1263	format, but currently there is no way to make a node use Storable by
		1264	default (although all nodes will accept it).
		1265
		1266	The default framing protocol is JSON because a) JSON::XS is many times
		1267	faster for small messages and b) most importantly, after years of
		1268	experience we found that object serialisation is causing more problems
		1269	than it solves: Just like function calls, objects simply do not travel
		1270	easily over the network, mostly because they will always be a copy, so you
		1271	always have to re-think your design.
		1272
		1273	Keeping your messages simple, concentrating on data structures rather than
		1274	objects, will keep your messages clean, tidy and efficient.
		1275
		1276	=back
		1277
		1278	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1279
		1280	AEMP version 2 has a few major incompatible changes compared to version 1:
		1281
		1282	=over 4
		1283
		1284	=item AnyEvent::MP::Global no longer has group management functions.
		1285
		1286	At least not officially - the grp_* functions are still exported and might
		1287	work, but they will be removed in some later release.
		1288
		1289	AnyEvent::MP now comes with a distributed database that is more
		1290	powerful. Its database families map closely to port groups, but the API
		1291	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1292	a rough porting guide:
		1293
		1294	grp_reg $group, $port # old
		1295	db_reg $group, $port # new
		1296
		1297	$list = grp_get $group # old
		1298	db_keys $group, sub { my $list = shift } # new
		1299
		1300	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1301	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1302
		1303	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1304	no longer instant, because the local node might not have a copy of the
		1305	group. You can either modify your code to allow for a callback, or use
		1306	C<db_mon> to keep an updated copy of the group:
		1307
		1308	my $local_group_copy;
		1309	db_mon $group => sub { $local_group_copy = $_[0] };
		1310
		1311	# now "keys %$local_group_copy" always returns the most up-to-date
		1312	# list of ports in the group.
		1313
		1314	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1315	passes a hash as first argument, and an extra C<$chg> argument that can be
		1316	ignored:
		1317
		1318	db_mon $group => sub {
		1319	my ($ports, $add, $chg, $del) = @_;
		1320	$ports = [keys %$ports];
		1321
		1322	# now $ports, $add and $del are the same as
		1323	# were originally passed by grp_mon.
		1324	...
		1325	};
		1326
		1327	=item Nodes not longer connect to all other nodes.
		1328
		1329	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1330	module, which in turn would create connections to all other nodes in the
		1331	network (helped by the seed nodes).
		1332
		1333	In version 2.x, global nodes still connect to all other global nodes, but
		1334	other nodes don't - now every node either is a global node itself, or
		1335	attaches itself to another global node.
		1336
		1337	If a node isn't a global node itself, then it attaches itself to one
		1338	of its seed nodes. If that seed node isn't a global node yet, it will
		1339	automatically be upgraded to a global node.
		1340
		1341	So in many cases, nothing needs to be changed - one just has to make sure
		1342	that all seed nodes are meshed together with the other seed nodes (as with
		1343	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1344	achieved by specifying the same set of seed nodes for all nodes in the
		1345	network.
		1346
		1347	Not opening a connection to every other node is usually an advantage,
		1348	except when you need the lower latency of an already established
		1349	connection. To ensure a node establishes a connection to another node,
		1350	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1351	create the connection (and notify you when the connection fails).
		1352
		1353	=item Listener-less nodes (nodes without binds) are gone.
		1354
		1355	And are not coming back, at least not in their old form. If no C<binds>
		1356	are specified for a node, AnyEvent::MP assumes a default of C<*:*>.
		1357
		1358	There are vague plans to implement some form of routing domains, which
		1359	might or might not bring back listener-less nodes, but don't count on it.
		1360
		1361	The fact that most connections are now optional somewhat mitigates this,
		1362	as a node can be effectively unreachable from the outside without any
		1363	problems, as long as it isn't a global node and only reaches out to other
		1364	nodes (as opposed to being contacted from other nodes).
		1365
		1366	=item $AnyEvent::MP::Kernel::WARN has gone.
		1367
		1368	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1369	uses this, and so should your programs.
		1370
		1371	Every module now documents what kinds of messages it generates, with
		1372	AnyEvent::MP acting as a catch all.
		1373
		1374	On the positive side, this means that instead of setting
		1375	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1376	much less to type.
		1377
		1378	=back
		1379
		1380	=head1 LOGGING
		1381
		1382	AnyEvent::MP does not normally log anything by itself, but since it is the
		1383	root of the context hierarchy for AnyEvent::MP modules, it will receive
		1384	all log messages by submodules.
		1385
851	=head1 SEE ALSO	1386	=head1 SEE ALSO
		1387
		1388	L<AnyEvent::MP::Intro> - a gentle introduction.
		1389
		1390	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1391
		1392	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1393	your applications.
		1394
		1395	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1396
		1397	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1398	all nodes.
852		1399
853	L<AnyEvent>.	1400	L<AnyEvent>.
854		1401
855	=head1 AUTHOR	1402	=head1 AUTHOR
856		1403

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