ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/AnyEvent-MP/MP.pm

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.43 by root, Sun Aug 9 16:08:16 2009 UTC vs.
Revision 1.138 by root, Thu Mar 22 00:48:29 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	};
		51
		52	=head1 CURRENT STATUS
		53
		54	bin/aemp - stable.
		55	AnyEvent::MP - stable API, should work.
		56	AnyEvent::MP::Intro - explains most concepts.
		57	AnyEvent::MP::Kernel - mostly stable API.
		58	AnyEvent::MP::Global - stable API.
42		59
43	=head1 DESCRIPTION	60	=head1 DESCRIPTION
44		61
45	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
46		63
47	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
48	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
49		66
50	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
51	manual page.	68	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		69
57	=head1 CONCEPTS	70	=head1 CONCEPTS
58		71
59	=over 4	72	=over 4
60		73
61	=item port	74	=item port
62		75
63	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
64		78
65	Some ports allow you to register C<rcv> handlers that can match specific	79	Ports allow you to register C<rcv> handlers that can match all or just
66	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
67	will not be queued.	81	anything was listening for them or not.
68		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
69	=item port id - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
70		86
71	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
72	separator, and a port name (a printable string of unspecified format). An	88	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	89	format created by AnyEvent::MP).
74	reference.
75		90
76	=item node	91	=item node
77		92
78	A node is a single process containing at least one port - the node	93	A node is a single process containing at least one port - the node port,
79	port. You can send messages to node ports to find existing ports or to	94	which enables nodes to manage each other remotely, and to create new
80	create new ports, among other things.	95	ports.
81		96
82	Nodes are either private (single-process only), slaves (connected to a	97	Nodes are either public (have one or more listening ports) or private
83	master node only) or public nodes (connectable from unrelated nodes).	98	(no listening ports). Private nodes cannot talk to other private nodes
		99	currently, but all nodes can talk to public nodes.
84		100
85	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	101	Nodes is represented by (printable) strings called "node IDs".
86		102
87	A node reference is a string that either simply identifies the node (for	103	=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		104
91	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	A node ID is a string that uniquely identifies the node within a
92	TCP/IP, other protocols might look different).	106	network. Depending on the configuration used, node IDs can look like a
		107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		108	doesn't interpret node IDs in any way except to uniquely identify a node.
93		109
94	Node references come in two flavours: resolved (containing only numerical	110	=item binds - C<ip:port>
95	addresses) or unresolved (where hostnames are used instead of addresses).
96		111
97	Before using an unresolved node reference in a message you first have to	112	Nodes can only talk to each other by creating some kind of connection to
98	resolve it.	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
		116	Currently, only standard C<ip:port> specifications can be used, which
		117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
		119
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
		149	=item seed IDs - C<host:port>
		150
		151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		152	TCP port) of nodes that should be used as seed nodes.
		153
		154	=item global nodes
		155
		156	An AEMP network needs a discovery service - nodes need to know how to
		157	connect to other nodes they only know by name. In addition, AEMP offers a
		158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
99		170
100	=back	171	=back
101		172
102	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
103		174
…		…
105		176
106	=cut	177	=cut
107		178
108	package AnyEvent::MP;	179	package AnyEvent::MP;
109		180
		181	use AnyEvent::MP::Config ();
110	use AnyEvent::MP::Base;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
111		184
112	use common::sense;	185	use common::sense;
113		186
114	use Carp ();	187	use Carp ();
115		188
116	use AE ();	189	use AE ();
		190	use Guard ();
117		191
118	use base "Exporter";	192	use base "Exporter";
119		193
120	our $VERSION = $AnyEvent::MP::Base::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
121		195
122	our @EXPORT = qw(	196	our @EXPORT = qw(
123	NODE $NODE *SELF node_of _any_	197	NODE $NODE *SELF node_of after
124	resolve_node initialise_node	198	configure
125	snd rcv mon kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
126	port	200	port
		201	db_set db_del db_reg
		202	db_mon db_family db_keys db_values
127	);	203	);
128		204
129	our $SELF;	205	our $SELF;
130		206
131	sub _self_die() {	207	sub _self_die() {
…		…
134	kil $SELF, die => $msg;	210	kil $SELF, die => $msg;
135	}	211	}
136		212
137	=item $thisnode = NODE / $NODE	213	=item $thisnode = NODE / $NODE
138		214
139	The C<NODE> function returns, and the C<$NODE> variable contains	215	The C<NODE> function returns, and the C<$NODE> variable contains, the node
140	the noderef of the local node. The value is initialised by a call	216	ID of the node running in the current process. This value is initialised by
141	to C<become_public> or C<become_slave>, after which all local port	217	a call to C<configure>.
142	identifiers become invalid.
143		218
144	=item $noderef = node_of $port	219	=item $nodeid = node_of $port
145		220
146	Extracts and returns the noderef from a portid or a noderef.	221	Extracts and returns the node ID from a port ID or a node ID.
147		222
148	=item initialise_node $noderef, $seednode, $seednode...	223	=item configure $profile, key => value...
149		224
150	=item initialise_node "slave/", $master, $master...	225	=item configure key => value...
151		226
152	Before a node can talk to other nodes on the network it has to initialise	227	Before a node can talk to other nodes on the network (i.e. enter
153	itself - the minimum a node needs to know is it's own name, and optionally	228	"distributed mode") it has to configure itself - the minimum a node needs
154	it should know the noderefs of some other nodes in the network.	229	to know is its own name, and optionally it should know the addresses of
		230	some other nodes in the network to discover other nodes.
155		231
156	This function initialises a node - it must be called exactly once (or	232	This function configures a node - it must be called exactly once (or
157	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
158		234
159	All arguments are noderefs, which can be either resolved or unresolved.	235	The key/value pairs are basically the same ones as documented for the
160		236	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		237
163	=over 4	238	=over 4
164		239
165	=item public nodes	240	=item norc => $boolean (default false)
166		241
167	For public nodes, C<$noderef> must either be a (possibly unresolved)	242	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
168	noderef, in which case it will be resolved, or C<undef> (or missing), in	243	be consulted - all configuraiton options must be specified in the
169	which case the noderef will be guessed.	244	C<configure> call.
170		245
171	Afterwards, the node will bind itself on all endpoints and try to connect	246	=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		247
175	=item slave nodes	248	IF true, then the values specified in the C<configure> will take
		249	precedence over any values configured via the rc file. The default is for
		250	the rc file to override any options specified in the program.
176		251
177	When the C<$noderef> is the special string C<slave/>, then the node will	252	=item secure => $pass->(@msg)
178	become a slave node. Slave nodes cannot be contacted from outside and will
179	route most of their traffic to the master node that they attach to.
180		253
181	At least one additional noderef is required: The node will try to connect	254	In addition to specifying a boolean, you can specify a code reference that
182	to all of them and will become a slave attached to the first node it can	255	is called for every code execution attempt - the execution request is
183	successfully connect to.	256	granted iff the callback returns a true value.
		257
		258	Most of the time the callback should look only at
		259	C<$AnyEvent::MP::Kernel::SRCNODE> to make a decision, and not at the
		260	actual message (which can be about anything, and is mostly provided for
		261	diagnostic purposes).
		262
		263	See F<semp setsecure> for more info.
184		264
185	=back	265	=back
186		266
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	267	=over 4
222		268
223	=item the empty string	269	=item step 1, gathering configuration from profiles
224		270
225	An empty-string component gets resolved as if the default port (4040) was	271	The function first looks up a profile in the aemp configuration (see the
226	specified.	272	L<aemp> commandline utility). The profile name can be specified via the
		273	named C<profile> parameter or can simply be the first parameter). If it is
		274	missing, then the nodename (F<uname -n>) will be used as profile name.
227		275
228	=item naked port numbers (e.g. C<1234>)	276	The profile data is then gathered as follows:
229		277
230	These are resolved by prepending the local nodename and a colon, to be	278	First, all remaining key => value pairs (all of which are conveniently
231	further resolved.	279	undocumented at the moment) will be interpreted as configuration
		280	data. Then they will be overwritten by any values specified in the global
		281	default configuration (see the F<aemp> utility), then the chain of
		282	profiles chosen by the profile name (and any C<parent> attributes).
232		283
233	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	284	That means that the values specified in the profile have highest priority
		285	and the values specified directly via C<configure> have lowest priority,
		286	and can only be used to specify defaults.
234		287
235	These are resolved by using AnyEvent::DNS to resolve them, optionally	288	If the profile specifies a node ID, then this will become the node ID of
236	looking up SRV records for the C<aemp=4040> port, if no port was	289	this process. If not, then the profile name will be used as node ID, with
237	specified.	290	a unique randoms tring (C</%u>) appended.
		291
		292	The node ID can contain some C<%> sequences that are expanded: C<%n>
		293	is expanded to the local nodename, C<%u> is replaced by a random
		294	strign to make the node unique. For example, the F<aemp> commandline
		295	utility uses C<aemp/%n/%u> as nodename, which might expand to
		296	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		297
		298	=item step 2, bind listener sockets
		299
		300	The next step is to look up the binds in the profile, followed by binding
		301	aemp protocol listeners on all binds specified (it is possible and valid
		302	to have no binds, meaning that the node cannot be contacted form the
		303	outside. This means the node cannot talk to other nodes that also have no
		304	binds, but it can still talk to all "normal" nodes).
		305
		306	If the profile does not specify a binds list, then a default of C<*> is
		307	used, meaning the node will bind on a dynamically-assigned port on every
		308	local IP address it finds.
		309
		310	=item step 3, connect to seed nodes
		311
		312	As the last step, the seed ID list from the profile is passed to the
		313	L<AnyEvent::MP::Global> module, which will then use it to keep
		314	connectivity with at least one node at any point in time.
238		315
239	=back	316	=back
		317
		318	Example: become a distributed node using the local node name as profile.
		319	This should be the most common form of invocation for "daemon"-type nodes.
		320
		321	configure
		322
		323	Example: become a semi-anonymous node. This form is often used for
		324	commandline clients.
		325
		326	configure nodeid => "myscript/%n/%u";
		327
		328	Example: configure a node using a profile called seed, which is suitable
		329	for a seed node as it binds on all local addresses on a fixed port (4040,
		330	customary for aemp).
		331
		332	# use the aemp commandline utility
		333	# aemp profile seed binds '*:4040'
		334
		335	# then use it
		336	configure profile => "seed";
		337
		338	# or simply use aemp from the shell again:
		339	# aemp run profile seed
		340
		341	# or provide a nicer-to-remember nodeid
		342	# aemp run profile seed nodeid "$(hostname)"
240		343
241	=item $SELF	344	=item $SELF
242		345
243	Contains the current port id while executing C<rcv> callbacks or C<psub>	346	Contains the current port id while executing C<rcv> callbacks or C<psub>
244	blocks.	347	blocks.
245		348
246	=item SELF, %SELF, @SELF...	349	=item *SELF, SELF, %SELF, @SELF...
247		350
248	Due to some quirks in how perl exports variables, it is impossible to	351	Due to some quirks in how perl exports variables, it is impossible to
249	just export C<$SELF>, all the symbols called C<SELF> are exported by this	352	just export C<$SELF>, all the symbols named C<SELF> are exported by this
250	module, but only C<$SELF> is currently used.	353	module, but only C<$SELF> is currently used.
251		354
252	=item snd $port, type => @data	355	=item snd $port, type => @data
253		356
254	=item snd $port, @msg	357	=item snd $port, @msg
255		358
256	Send the given message to the given port ID, which can identify either	359	Send the given message to the given port, which can identify either a
257	a local or a remote port, and can be either a string or soemthignt hat	360	local or a remote port, and must be a port ID.
258	stringifies a sa port ID (such as a port object :).
259		361
260	While the message can be about anything, it is highly recommended to use a	362	While the message can be almost anything, it is highly recommended to
261	string as first element (a portid, or some word that indicates a request	363	use a string as first element (a port ID, or some word that indicates a
262	type etc.).	364	request type etc.) and to consist if only simple perl values (scalars,
		365	arrays, hashes) - if you think you need to pass an object, think again.
263		366
264	The message data effectively becomes read-only after a call to this	367	The message data logically becomes read-only after a call to this
265	function: modifying any argument is not allowed and can cause many	368	function: modifying any argument (or values referenced by them) is
266	problems.	369	forbidden, as there can be considerable time between the call to C<snd>
		370	and the time the message is actually being serialised - in fact, it might
		371	never be copied as within the same process it is simply handed to the
		372	receiving port.
267		373
268	The type of data you can transfer depends on the transport protocol: when	374	The type of data you can transfer depends on the transport protocol: when
269	JSON is used, then only strings, numbers and arrays and hashes consisting	375	JSON is used, then only strings, numbers and arrays and hashes consisting
270	of those are allowed (no objects). When Storable is used, then anything	376	of those are allowed (no objects). When Storable is used, then anything
271	that Storable can serialise and deserialise is allowed, and for the local	377	that Storable can serialise and deserialise is allowed, and for the local
272	node, anything can be passed.	378	node, anything can be passed. Best rely only on the common denominator of
		379	these.
273		380
274	=item $local_port = port	381	=item $local_port = port
275		382
276	Create a new local port object that can be used either as a pattern	383	Create a new local port object and returns its port ID. Initially it has
277	matching port ("full port") or a single-callback port ("miniport"),	384	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		385
280	=item $port = port { my @msg = @_; $finished }	386	=item $local_port = port { my @msg = @_ }
281		387
282	Creates a "miniport", that is, a very lightweight port without any pattern	388	Creates a new local port, and returns its ID. Semantically the same as
283	matching behind it, and returns its ID. Semantically the same as creating
284	a port and calling C<rcv $port, $callback> on it.	389	creating a port and calling C<rcv $port, $callback> on it.
285		390
286	The block will be called for every message received on the port. When the	391	The block will be called for every message received on the port, with the
287	callback returns a true value its job is considered "done" and the port	392	global variable C<$SELF> set to the port ID. Runtime errors will cause the
288	will be destroyed. Otherwise it will stay alive.	393	port to be C<kil>ed. The message will be passed as-is, no extra argument
		394	(i.e. no port ID) will be passed to the callback.
289		395
290	The message will be passed as-is, no extra argument (i.e. no port id) will	396	If you want to stop/destroy the port, simply C<kil> it:
291	be passed to the callback.
292		397
293	If you need the local port id in the callback, this works nicely:	398	my $port = port {
294		399	my @msg = @_;
295	my $port; $port = port {	400	...
296	snd $otherport, reply => $port;	401	kil $SELF;
297	};	402	};
298		403
299	=cut	404	=cut
300		405
301	sub rcv($@);	406	sub rcv($@);
302		407
		408	my $KILME = sub {
		409	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
		410	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		411	};
		412
303	sub port(;&) {	413	sub port(;&) {
304	my $id = "$UNIQ." . $ID++;	414	my $id = $UNIQ . ++$ID;
305	my $port = "$NODE#$id";	415	my $port = "$NODE#$id";
306		416
307	if (@_) {
308	rcv $port, shift;	417	rcv $port, shift || $KILME;
309	} else {
310	$PORT{$id} = sub { }; # nop
311	}
312		418
313	$port	419	$port
314	}	420	}
315		421
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)	422	=item rcv $local_port, $callback->(@msg)
336		423
337	Replaces the callback on the specified miniport (after converting it to	424	Replaces the default callback on the specified port. There is no way to
338	one if required).	425	remove the default callback: use C<sub { }> to disable it, or better
339		426	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...] => $callback->(@msg), ...
345
346	Register callbacks to be called on matching messages on the given full
347	port (after converting it to one if required) and return the port.
348
349	The callback has to return a true value when its work is done, after
350	which is will be removed, or a false value in which case it will stay
351	registered.
352		427
353	The global C<$SELF> (exported by this module) contains C<$port> while	428	The global C<$SELF> (exported by this module) contains C<$port> while
354	executing the callback.	429	executing the callback. Runtime errors during callback execution will
		430	result in the port being C<kil>ed.
355		431
356	Runtime errors during callback execution will result in the port being	432	The default callback receives all messages not matched by a more specific
357	C<kil>ed.	433	C<tag> match.
358		434
359	If the match is an array reference, then it will be matched against the	435	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
360	first elements of the message, otherwise only the first element is being
361	matched.
362		436
363	Any element in the match that is specified as C<_any_> (a function	437	Register (or replace) callbacks to be called on messages starting with the
364	exported by this module) matches any single element of the message.	438	given tag on the given port (and return the port), or unregister it (when
		439	C<$callback> is C<$undef> or missing). There can only be one callback
		440	registered for each tag.
365		441
366	While not required, it is highly recommended that the first matching	442	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	443	element (the tag) has been removed. The callback will use the same
368	also the most efficient match (by far).	444	environment as the default callback (see above).
369		445
370	Example: create a port and bind receivers on it in one go.	446	Example: create a port and bind receivers on it in one go.
371		447
372	my $port = rcv port,	448	my $port = rcv port,
373	msg1 => sub { ...; 0 },	449	msg1 => sub { ... },
374	msg2 => sub { ...; 0 },	450	msg2 => sub { ... },
375	;	451	;
376		452
377	Example: create a port, bind receivers and send it in a message elsewhere	453	Example: create a port, bind receivers and send it in a message elsewhere
378	in one go:	454	in one go:
379		455
380	snd $otherport, reply =>	456	snd $otherport, reply =>
381	rcv port,	457	rcv port,
382	msg1 => sub { ...; 0 },	458	msg1 => sub { ... },
383	...	459	...
384	;	460	;
385		461
		462	Example: temporarily register a rcv callback for a tag matching some port
		463	(e.g. for an rpc reply) and unregister it after a message was received.
		464
		465	rcv $port, $otherport => sub {
		466	my @reply = @_;
		467
		468	rcv $SELF, $otherport;
		469	};
		470
386	=cut	471	=cut
387		472
388	sub rcv($@) {	473	sub rcv($@) {
389	my $port = shift;	474	my $port = shift;
390	my ($noderef, $portid) = split /#/, $port, 2;	475	my ($nodeid, $portid) = split /#/, $port, 2;
391		476
392	($NODE{$noderef} || add_node $noderef) == $NODE{""}	477	$NODE{$nodeid} == $NODE{""}
393	or Carp::croak "$port: rcv can only be called on local ports, caught";	478	or Carp::croak "$port: rcv can only be called on local ports, caught";
394		479
395	if (@_ == 1) {	480	while (@_) {
		481	if (ref $_[0]) {
		482	if (my $self = $PORT_DATA{$portid}) {
		483	"AnyEvent::MP::Port" eq ref $self
		484	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		485
		486	$self->[0] = shift;
		487	} else {
396	my $cb = shift;	488	my $cb = shift;
397	delete $PORT_DATA{$portid};
398	$PORT{$portid} = sub {	489	$PORT{$portid} = sub {
399	local $SELF = $port;	490	local $SELF = $port;
400	eval {	491	eval { &$cb }; _self_die if $@;
401	&$cb	492	};
402	and kil $port;
403	};	493	}
404	_self_die if $@;	494	} elsif (defined $_[0]) {
405	};
406	} else {
407	my $self = $PORT_DATA{$portid} ||= do {	495	my $self = $PORT_DATA{$portid} ||= do {
408	my $self = bless {	496	my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
409	id => $port,
410	}, "AnyEvent::MP::Port";
411		497
412	$PORT{$portid} = sub {	498	$PORT{$portid} = sub {
413	local $SELF = $port;	499	local $SELF = $port;
414		500
415	eval {
416	for (@{ $self->{rc0}{$_[0]} }) {	501	if (my $cb = $self->[1]{$_[0]}) {
417	$_ && &{$_->[0]}	502	shift;
418	&& undef $_;	503	eval { &$cb }; _self_die if $@;
419	}	504	} else {
420
421	for (@{ $self->{rcv}{$_[0]} }) {
422	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
423	&& &{$_->[0]}	505	&{ $self->[0] };
424	&& undef $_;
425	}
426
427	for (@{ $self->{any} }) {
428	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
429	&& &{$_->[0]}
430	&& undef $_;
431	}	506	}
432	};	507	};
433	_self_die if $@;	508
		509	$self
434	};	510	};
435		511
436	$self
437	};
438
439	"AnyEvent::MP::Port" eq ref $self	512	"AnyEvent::MP::Port" eq ref $self
440	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	513	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
441		514
442	while (@_) {
443	my ($match, $cb) = splice @_, 0, 2;	515	my ($tag, $cb) = splice @_, 0, 2;
444		516
445	if (!ref $match) {	517	if (defined $cb) {
446	push @{ $self->{rc0}{$match} }, [$cb];	518	$self->[1]{$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 {	519	} else {
453	push @{ $self->{any} }, [$cb, $match];	520	delete $self->[1]{$tag};
454	}	521	}
455	}	522	}
456	}	523	}
457		524
458	$port	525	$port
459	}	526	}
460		527
		528	=item peval $port, $coderef[, @args]
		529
		530	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		531	when the code throews an exception the C<$port> will be killed.
		532
		533	Any remaining args will be passed to the callback. Any return values will
		534	be returned to the caller.
		535
		536	This is useful when you temporarily want to execute code in the context of
		537	a port.
		538
		539	Example: create a port and run some initialisation code in it's context.
		540
		541	my $port = port { ... };
		542
		543	peval $port, sub {
		544	init
		545	or die "unable to init";
		546	};
		547
		548	=cut
		549
		550	sub peval($$) {
		551	local $SELF = shift;
		552	my $cb = shift;
		553
		554	if (wantarray) {
		555	my @res = eval { &$cb };
		556	_self_die if $@;
		557	@res
		558	} else {
		559	my $res = eval { &$cb };
		560	_self_die if $@;
		561	$res
		562	}
		563	}
		564
461	=item $closure = psub { BLOCK }	565	=item $closure = psub { BLOCK }
462		566
463	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	567	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
464	closure is executed, sets up the environment in the same way as in C<rcv>	568	closure is executed, sets up the environment in the same way as in C<rcv>
465	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	569	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		570
		571	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		572	BLOCK }, @_ } >>.
466		573
467	This is useful when you register callbacks from C<rcv> callbacks:	574	This is useful when you register callbacks from C<rcv> callbacks:
468		575
469	rcv delayed_reply => sub {	576	rcv delayed_reply => sub {
470	my ($delay, @reply) = @_;	577	my ($delay, @reply) = @_;
…		…
494	$res	601	$res
495	}	602	}
496	}	603	}
497	}	604	}
498		605
499	=item $guard = mon $port, $cb->(@reason)	606	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
500		607
501	=item $guard = mon $port, $rcvport	608	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
502		609
503	=item $guard = mon $port	610	=item $guard = mon $port # kill $SELF when $port dies
504		611
505	=item $guard = mon $port, $rcvport, @msg	612	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
506		613
507	Monitor the given port and do something when the port is killed or	614	Monitor the given port and do something when the port is killed or
508	messages to it were lost, and optionally return a guard that can be used	615	messages to it were lost, and optionally return a guard that can be used
509	to stop monitoring again.	616	to stop monitoring again.
510
511	C<mon> effectively guarantees that, in the absence of hardware failures,
512	that after starting the monitor, either all messages sent to the port
513	will arrive, or the monitoring action will be invoked after possible
514	message loss has been detected. No messages will be lost "in between"
515	(after the first lost message no further messages will be received by the
516	port). After the monitoring action was invoked, further messages might get
517	delivered again.
518		617
519	In the first form (callback), the callback is simply called with any	618	In the first form (callback), the callback is simply called with any
520	number of C<@reason> elements (no @reason means that the port was deleted	619	number of C<@reason> elements (no @reason means that the port was deleted
521	"normally"). Note also that I<< the callback B<must> never die >>, so use	620	"normally"). Note also that I<< the callback B<must> never die >>, so use
522	C<eval> if unsure.	621	C<eval> if unsure.
523		622
524	In the second form (another port given), the other port (C<$rcvport>)	623	In the second form (another port given), the other port (C<$rcvport>)
525	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	624	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
526	"normal" kils nothing happens, while under all other conditions, the other	625	"normal" kils nothing happens, while under all other conditions, the other
527	port is killed with the same reason.	626	port is killed with the same reason.
528		627
529	The third form (kill self) is the same as the second form, except that	628	The third form (kill self) is the same as the second form, except that
530	C<$rvport> defaults to C<$SELF>.	629	C<$rvport> defaults to C<$SELF>.
531		630
532	In the last form (message), a message of the form C<@msg, @reason> will be	631	In the last form (message), a message of the form C<@msg, @reason> will be
533	C<snd>.	632	C<snd>.
		633
		634	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		635	alert was raised), they are removed and will not trigger again.
534		636
535	As a rule of thumb, monitoring requests should always monitor a port from	637	As a rule of thumb, monitoring requests should always monitor a port from
536	a local port (or callback). The reason is that kill messages might get	638	a local port (or callback). The reason is that kill messages might get
537	lost, just like any other message. Another less obvious reason is that	639	lost, just like any other message. Another less obvious reason is that
538	even monitoring requests can get lost (for exmaple, when the connection	640	even monitoring requests can get lost (for example, when the connection
539	to the other node goes down permanently). When monitoring a port locally	641	to the other node goes down permanently). When monitoring a port locally
540	these problems do not exist.	642	these problems do not exist.
541		643
		644	C<mon> effectively guarantees that, in the absence of hardware failures,
		645	after starting the monitor, either all messages sent to the port will
		646	arrive, or the monitoring action will be invoked after possible message
		647	loss has been detected. No messages will be lost "in between" (after
		648	the first lost message no further messages will be received by the
		649	port). After the monitoring action was invoked, further messages might get
		650	delivered again.
		651
		652	Inter-host-connection timeouts and monitoring depend on the transport
		653	used. The only transport currently implemented is TCP, and AnyEvent::MP
		654	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		655	non-idle connection, and usually around two hours for idle connections).
		656
		657	This means that monitoring is good for program errors and cleaning up
		658	stuff eventually, but they are no replacement for a timeout when you need
		659	to ensure some maximum latency.
		660
542	Example: call a given callback when C<$port> is killed.	661	Example: call a given callback when C<$port> is killed.
543		662
544	mon $port, sub { warn "port died because of <@_>\n" };	663	mon $port, sub { warn "port died because of <@_>\n" };
545		664
546	Example: kill ourselves when C<$port> is killed abnormally.	665	Example: kill ourselves when C<$port> is killed abnormally.
…		…
552	mon $port, $self => "restart";	671	mon $port, $self => "restart";
553		672
554	=cut	673	=cut
555		674
556	sub mon {	675	sub mon {
557	my ($noderef, $port) = split /#/, shift, 2;	676	my ($nodeid, $port) = split /#/, shift, 2;
558		677
559	my $node = $NODE{$noderef} || add_node $noderef;	678	my $node = $NODE{$nodeid} || add_node $nodeid;
560		679
561	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';	680	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
562		681
563	unless (ref $cb) {	682	unless (ref $cb) {
564	if (@_) {	683	if (@_) {
…		…
573	}	692	}
574		693
575	$node->monitor ($port, $cb);	694	$node->monitor ($port, $cb);
576		695
577	defined wantarray	696	defined wantarray
578	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	697	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
579	}	698	}
580		699
581	=item $guard = mon_guard $port, $ref, $ref...	700	=item $guard = mon_guard $port, $ref, $ref...
582		701
583	Monitors the given C<$port> and keeps the passed references. When the port	702	Monitors the given C<$port> and keeps the passed references. When the port
584	is killed, the references will be freed.	703	is killed, the references will be freed.
585		704
586	Optionally returns a guard that will stop the monitoring.	705	Optionally returns a guard that will stop the monitoring.
587		706
588	This function is useful when you create e.g. timers or other watchers and	707	This function is useful when you create e.g. timers or other watchers and
589	want to free them when the port gets killed:	708	want to free them when the port gets killed (note the use of C<psub>):
590		709
591	$port->rcv (start => sub {	710	$port->rcv (start => sub {
592	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	711	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
593	undef $timer if 0.9 < rand;	712	undef $timer if 0.9 < rand;
594	});	713	});
595	});	714	});
596		715
597	=cut	716	=cut
…		…
606		725
607	=item kil $port[, @reason]	726	=item kil $port[, @reason]
608		727
609	Kill the specified port with the given C<@reason>.	728	Kill the specified port with the given C<@reason>.
610		729
611	If no C<@reason> is specified, then the port is killed "normally" (linked	730	If no C<@reason> is specified, then the port is killed "normally" -
612	ports will not be kileld, or even notified).	731	monitor callback will be invoked, but the kil will not cause linked ports
		732	(C<mon $mport, $lport> form) to get killed.
613		733
614	Otherwise, linked ports get killed with the same reason (second form of	734	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
615	C<mon>, see below).	735	form) get killed with the same reason.
616		736
617	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	737	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
618	will be reported as reason C<< die => $@ >>.	738	will be reported as reason C<< die => $@ >>.
619		739
620	Transport/communication errors are reported as C<< transport_error =>	740	Transport/communication errors are reported as C<< transport_error =>
621	$message >>.	741	$message >>.
622		742
623	=cut	743	Common idioms:
		744
		745	# silently remove yourself, do not kill linked ports
		746	kil $SELF;
		747
		748	# report a failure in some detail
		749	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		750
		751	# do not waste much time with killing, just die when something goes wrong
		752	open my $fh, "<file"
		753	or die "file: $!";
624		754
625	=item $port = spawn $node, $initfunc[, @initdata]	755	=item $port = spawn $node, $initfunc[, @initdata]
626		756
627	Creates a port on the node C<$node> (which can also be a port ID, in which	757	Creates a port on the node C<$node> (which can also be a port ID, in which
628	case it's the node where that port resides).	758	case it's the node where that port resides).
629		759
630	The port ID of the newly created port is return immediately, and it is	760	The port ID of the newly created port is returned immediately, and it is
631	permissible to immediately start sending messages or monitor the port.	761	possible to immediately start sending messages or to monitor the port.
632		762
633	After the port has been created, the init function is	763	After the port has been created, the init function is called on the remote
634	called. This function must be a fully-qualified function name	764	node, in the same context as a C<rcv> callback. This function must be a
635	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	765	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
636	program, use C<::name>.	766	specify a function in the main program, use C<::name>.
637		767
638	If the function doesn't exist, then the node tries to C<require>	768	If the function doesn't exist, then the node tries to C<require>
639	the package, then the package above the package and so on (e.g.	769	the package, then the package above the package and so on (e.g.
640	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	770	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
641	exists or it runs out of package names.	771	exists or it runs out of package names.
642		772
643	The init function is then called with the newly-created port as context	773	The init function is then called with the newly-created port as context
644	object (C<$SELF>) and the C<@initdata> values as arguments.	774	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		775	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		776	the port might not get created.
645		777
646	A common idiom is to pass your own port, monitor the spawned port, and	778	A common idiom is to pass a local port, immediately monitor the spawned
647	in the init function, monitor the original port. This two-way monitoring	779	port, and in the remote init function, immediately monitor the passed
648	ensures that both ports get cleaned up when there is a problem.	780	local port. This two-way monitoring ensures that both ports get cleaned up
		781	when there is a problem.
		782
		783	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		784	caller before C<spawn> returns (by delaying invocation when spawn is
		785	called for the local node).
649		786
650	Example: spawn a chat server port on C<$othernode>.	787	Example: spawn a chat server port on C<$othernode>.
651		788
652	# this node, executed from within a port context:	789	# this node, executed from within a port context:
653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	790	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
668		805
669	sub _spawn {	806	sub _spawn {
670	my $port = shift;	807	my $port = shift;
671	my $init = shift;	808	my $init = shift;
672		809
		810	# rcv will create the actual port
673	local $SELF = "$NODE#$port";	811	local $SELF = "$NODE#$port";
674	eval {	812	eval {
675	&{ load_func $init }	813	&{ load_func $init }
676	};	814	};
677	_self_die if $@;	815	_self_die if $@;
678	}	816	}
679		817
680	sub spawn(@) {	818	sub spawn(@) {
681	my ($noderef, undef) = split /#/, shift, 2;	819	my ($nodeid, undef) = split /#/, shift, 2;
682		820
683	my $id = "$RUNIQ." . $ID++;	821	my $id = $RUNIQ . ++$ID;
684		822
685	$_[0] =~ /::/	823	$_[0] =~ /::/
686	or Carp::croak "spawn init function must be a fully-qualified name, caught";	824	or Carp::croak "spawn init function must be a fully-qualified name, caught";
687		825
688	($NODE{$noderef} || add_node $noderef)	826	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
689	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
690		827
691	"$noderef#$id"	828	"$nodeid#$id"
692	}	829	}
693		830
		831
		832	=item after $timeout, @msg
		833
		834	=item after $timeout, $callback
		835
		836	Either sends the given message, or call the given callback, after the
		837	specified number of seconds.
		838
		839	This is simply a utility function that comes in handy at times - the
		840	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		841	so it may go away in the future.
		842
		843	=cut
		844
		845	sub after($@) {
		846	my ($timeout, @action) = @_;
		847
		848	my $t; $t = AE::timer $timeout, 0, sub {
		849	undef $t;
		850	ref $action[0]
		851	? $action[0]()
		852	: snd @action;
		853	};
		854	}
		855
		856	#=item $cb2 = timeout $seconds, $cb[, @args]
		857
		858	=item cal $port, @msg, $callback[, $timeout]
		859
		860	A simple form of RPC - sends a message to the given C<$port> with the
		861	given contents (C<@msg>), but adds a reply port to the message.
		862
		863	The reply port is created temporarily just for the purpose of receiving
		864	the reply, and will be C<kil>ed when no longer needed.
		865
		866	A reply message sent to the port is passed to the C<$callback> as-is.
		867
		868	If an optional time-out (in seconds) is given and it is not C<undef>,
		869	then the callback will be called without any arguments after the time-out
		870	elapsed and the port is C<kil>ed.
		871
		872	If no time-out is given (or it is C<undef>), then the local port will
		873	monitor the remote port instead, so it eventually gets cleaned-up.
		874
		875	Currently this function returns the temporary port, but this "feature"
		876	might go in future versions unless you can make a convincing case that
		877	this is indeed useful for something.
		878
		879	=cut
		880
		881	sub cal(@) {
		882	my $timeout = ref $_[-1] ? undef : pop;
		883	my $cb = pop;
		884
		885	my $port = port {
		886	undef $timeout;
		887	kil $SELF;
		888	&$cb;
		889	};
		890
		891	if (defined $timeout) {
		892	$timeout = AE::timer $timeout, 0, sub {
		893	undef $timeout;
		894	kil $port;
		895	$cb->();
		896	};
		897	} else {
		898	mon $_[0], sub {
		899	kil $port;
		900	$cb->();
		901	};
		902	}
		903
		904	push @_, $port;
		905	&snd;
		906
		907	$port
		908	}
		909
694	=back	910	=back
695		911
696	=head1 NODE MESSAGES	912	=head1 DISTRIBUTED DATABASE
697		913
698	Nodes understand the following messages sent to them. Many of them take	914	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	915	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	916	of the global nodes for their needs. Every node has a "local database"
701	the remaining arguments are simply the message data.	917	which contains all the values that are set locally. All local databases
		918	are merged together to form the global database, which can be queried.
702		919
703	While other messages exist, they are not public and subject to change.	920	The database structure is that of a two-level hash - the database hash
		921	contains hashes which contain values, similarly to a perl hash of hashes,
		922	i.e.:
704		923
		924	$DATABASE{$family}{$subkey} = $value
		925
		926	The top level hash key is called "family", and the second-level hash key
		927	is called "subkey" or simply "key".
		928
		929	The family must be alphanumeric, i.e. start with a letter and consist
		930	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		931	pretty much like Perl module names.
		932
		933	As the family namespace is global, it is recommended to prefix family names
		934	with the name of the application or module using it.
		935
		936	The subkeys must be non-empty strings, with no further restrictions.
		937
		938	The values should preferably be strings, but other perl scalars should
		939	work as well (such as C<undef>, arrays and hashes).
		940
		941	Every database entry is owned by one node - adding the same family/subkey
		942	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		943	but the result might be nondeterministic, i.e. the key might have
		944	different values on different nodes.
		945
		946	Different subkeys in the same family can be owned by different nodes
		947	without problems, and in fact, this is the common method to create worker
		948	pools. For example, a worker port for image scaling might do this:
		949
		950	db_set my_image_scalers => $port;
		951
		952	And clients looking for an image scaler will want to get the
		953	C<my_image_scalers> keys from time to time:
		954
		955	db_keys my_image_scalers => sub {
		956	@ports = @{ $_[0] };
		957	};
		958
		959	Or better yet, they want to monitor the database family, so they always
		960	have a reasonable up-to-date copy:
		961
		962	db_mon my_image_scalers => sub {
		963	@ports = keys %{ $_[0] };
		964	};
		965
		966	In general, you can set or delete single subkeys, but query and monitor
		967	whole families only.
		968
		969	If you feel the need to monitor or query a single subkey, try giving it
		970	it's own family.
		971
705	=over 4	972	=over
		973
		974	=item $guard = db_set $family => $subkey [=> $value]
		975
		976	Sets (or replaces) a key to the database - if C<$value> is omitted,
		977	C<undef> is used instead.
		978
		979	When called in non-void context, C<db_set> returns a guard that
		980	automatically calls C<db_del> when it is destroyed.
		981
		982	=item db_del $family => $subkey...
		983
		984	Deletes one or more subkeys from the database family.
		985
		986	=item $guard = db_reg $family => $port => $value
		987
		988	=item $guard = db_reg $family => $port
		989
		990	=item $guard = db_reg $family
		991
		992	Registers a port in the given family and optionally returns a guard to
		993	remove it.
		994
		995	This function basically does the same as:
		996
		997	db_set $family => $port => $value
		998
		999	Except that the port is monitored and automatically removed from the
		1000	database family when it is kil'ed.
		1001
		1002	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1003	C<$SELF> is used.
		1004
		1005	This function is most useful to register a port in some port group (which
		1006	is just another name for a database family), and have it removed when the
		1007	port is gone. This works best when the port is a local port.
706		1008
707	=cut	1009	=cut
708		1010
709	=item lookup => $name, @reply	1011	sub db_reg($$;$) {
		1012	my $family = shift;
		1013	my $port = @_ ? shift : $SELF;
710		1014
711	Replies with the port ID of the specified well-known port, or C<undef>.	1015	my $clr = sub { db_del $family => $port };
		1016	mon $port, $clr;
712		1017
713	=item devnull => ...	1018	db_set $family => $port => $_[0];
714		1019
715	Generic data sink/CPU heat conversion.	1020	defined wantarray
		1021	and &Guard::guard ($clr)
		1022	}
716		1023
717	=item relay => $port, @msg	1024	=item db_family $family => $cb->(\%familyhash)
718		1025
719	Simply forwards the message to the given port.	1026	Queries the named database C<$family> and call the callback with the
		1027	family represented as a hash. You can keep and freely modify the hash.
720		1028
721	=item eval => $string[ @reply]	1029	=item db_keys $family => $cb->(\@keys)
722		1030
723	Evaluates the given string. If C<@reply> is given, then a message of the	1031	Same as C<db_family>, except it only queries the family I<subkeys> and passes
724	form C<@reply, $@, @evalres> is sent.	1032	them as array reference to the callback.
725		1033
726	Example: crash another node.	1034	=item db_values $family => $cb->(\@values)
727		1035
728	snd $othernode, eval => "exit";	1036	Same as C<db_family>, except it only queries the family I<values> and passes them
		1037	as array reference to the callback.
729		1038
730	=item time => @reply	1039	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
731		1040
732	Replies the the current node time to C<@reply>.	1041	Creates a monitor on the given database family. Each time a key is set
		1042	or or is deleted the callback is called with a hash containing the
		1043	database family and three lists of added, changed and deleted subkeys,
		1044	respectively. If no keys have changed then the array reference might be
		1045	C<undef> or even missing.
733		1046
734	Example: tell the current node to send the current time to C<$myport> in a	1047	If not called in void context, a guard object is returned that, when
735	C<timereply> message.	1048	destroyed, stops the monitor.
736		1049
737	snd $NODE, time => $myport, timereply => 1, 2;	1050	The family hash reference and the key arrays belong to AnyEvent::MP and
738	# => snd $myport, timereply => 1, 2, <time>	1051	B<must not be modified or stored> by the callback. When in doubt, make a
		1052	copy.
		1053
		1054	As soon as possible after the monitoring starts, the callback will be
		1055	called with the intiial contents of the family, even if it is empty,
		1056	i.e. there will always be a timely call to the callback with the current
		1057	contents.
		1058
		1059	It is possible that the callback is called with a change event even though
		1060	the subkey is already present and the value has not changed.
		1061
		1062	The monitoring stops when the guard object is destroyed.
		1063
		1064	Example: on every change to the family "mygroup", print out all keys.
		1065
		1066	my $guard = db_mon mygroup => sub {
		1067	my ($family, $a, $c, $d) = @_;
		1068	print "mygroup members: ", (join " ", keys %$family), "\n";
		1069	};
		1070
		1071	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1072
		1073	my $guard; $guard = db_mon My::Module::workers => sub {
		1074	my ($family, $a, $c, $d) = @_;
		1075	return unless %$family;
		1076	undef $guard;
		1077	print "My::Module::workers now nonempty\n";
		1078	};
		1079
		1080	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1081
		1082	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1083	my ($family, $a, $c, $d) = @_;
		1084
		1085	print "+$_=$family->{$_}\n" for @$a;
		1086	print "*$_=$family->{$_}\n" for @$c;
		1087	print "-$_=$family->{$_}\n" for @$d;
		1088	};
		1089
		1090	=cut
739		1091
740	=back	1092	=back
741		1093
742	=head1 AnyEvent::MP vs. Distributed Erlang	1094	=head1 AnyEvent::MP vs. Distributed Erlang
743		1095
744	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1096	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	1097	== 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	1098	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
747	sample:	1099	sample:
748		1100
749	http://www.Erlang.se/doc/programming_rules.shtml	1101	http://www.erlang.se/doc/programming_rules.shtml
750	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1102	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	1103	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	1104	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
753		1105
754	Despite the similarities, there are also some important differences:	1106	Despite the similarities, there are also some important differences:
755		1107
756	=over 4	1108	=over 4
757		1109
758	=item * Node references contain the recipe on how to contact them.	1110	=item * Node IDs are arbitrary strings in AEMP.
759		1111
760	Erlang relies on special naming and DNS to work everywhere in the	1112	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	1113	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
762	convenience functionality.	1114	configuration or DNS), and possibly the addresses of some seed nodes, but
		1115	will otherwise discover other nodes (and their IDs) itself.
763		1116
764	This means that AEMP requires a less tightly controlled environment at the	1117	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
765	cost of longer node references and a slightly higher management overhead.	1118	uses "local ports are like remote ports".
		1119
		1120	The failure modes for local ports are quite different (runtime errors
		1121	only) then for remote ports - when a local port dies, you I<know> it dies,
		1122	when a connection to another node dies, you know nothing about the other
		1123	port.
		1124
		1125	Erlang pretends remote ports are as reliable as local ports, even when
		1126	they are not.
		1127
		1128	AEMP encourages a "treat remote ports differently" philosophy, with local
		1129	ports being the special case/exception, where transport errors cannot
		1130	occur.
766		1131
767	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1132	=item * Erlang uses processes and a mailbox, AEMP does not queue.
768		1133
769	Erlang uses processes that selctively receive messages, and therefore	1134	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	1135	therefore needs a queue. AEMP is event based, queuing messages would serve
771	purpose.	1136	no useful purpose. For the same reason the pattern-matching abilities
		1137	of AnyEvent::MP are more limited, as there is little need to be able to
		1138	filter messages without dequeuing them.
772		1139
773	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1140	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1141	being event-based, while Erlang is process-based.
		1142
		1143	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1144	top of AEMP and Coro threads.
774		1145
775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1146	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
776		1147
777	Sending messages in Erlang is synchronous and blocks the process. AEMP	1148	Sending messages in Erlang is synchronous and blocks the process until
778	sends are immediate, connection establishment is handled in the	1149	a conenction has been established and the message sent (and so does not
779	background.	1150	need a queue that can overflow). AEMP sends return immediately, connection
		1151	establishment is handled in the background.
780		1152
781	=item * Erlang can silently lose messages, AEMP cannot.	1153	=item * Erlang suffers from silent message loss, AEMP does not.
782		1154
783	Erlang makes few guarantees on messages delivery - messages can get lost	1155	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,	1156	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).	1157	b, and c, and the other side only receives messages a and c).
786		1158
787	AEMP guarantees correct ordering, and the guarantee that there are no	1159	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1160	guarantee that after one message is lost, all following ones sent to the
		1161	same port are lost as well, until monitoring raises an error, so there are
788	holes in the message sequence.	1162	no silent "holes" in the message sequence.
789		1163
790	=item * In Erlang, processes can be declared dead and later be found to be	1164	If you want your software to be very reliable, you have to cope with
791	alive.	1165	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
792		1166	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	1167	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		1168
801	=item * Erlang can send messages to the wrong port, AEMP does not.	1169	=item * Erlang can send messages to the wrong port, AEMP does not.
802		1170
803	In Erlang it is quite possible that a node that restarts reuses a process	1171	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	1172	process ID known to other nodes for a completely different process,
805	messages destined for that process to end up in an unrelated process.	1173	causing messages destined for that process to end up in an unrelated
		1174	process.
806		1175
807	AEMP never reuses port IDs, so old messages or old port IDs floating	1176	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.	1177	around in the network will not be sent to an unrelated port.
809		1178
810	=item * Erlang uses unprotected connections, AEMP uses secure	1179	=item * Erlang uses unprotected connections, AEMP uses secure
811	authentication and can use TLS.	1180	authentication and can use TLS.
812		1181
813	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1182	AEMP can use a proven protocol - TLS - to protect connections and
814	securely authenticate nodes.	1183	securely authenticate nodes.
815		1184
816	=item * The AEMP protocol is optimised for both text-based and binary	1185	=item * The AEMP protocol is optimised for both text-based and binary
817	communications.	1186	communications.
818		1187
819	The AEMP protocol, unlike the Erlang protocol, supports both	1188	The AEMP protocol, unlike the Erlang protocol, supports both programming
820	language-independent text-only protocols (good for debugging) and binary,	1189	language independent text-only protocols (good for debugging), and binary,
821	language-specific serialisers (e.g. Storable).	1190	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1191	used, the protocol is actually completely text-based.
822		1192
823	It has also been carefully designed to be implementable in other languages	1193	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	1194	with a minimum of work while gracefully degrading functionality to make the
825	protocol simple.	1195	protocol simple.
826		1196
827	=item * AEMP has more flexible monitoring options than Erlang.	1197	=item * AEMP has more flexible monitoring options than Erlang.
828		1198
829	In Erlang, you can chose to receive I<all> exit signals as messages	1199	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	1200	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	1201	difficult to implement.
832	Erlang, as one can choose between automatic kill, exit message or callback	1202
833	on a per-process basis.	1203	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1204	between automatic kill, exit message or callback on a per-port basis.
834		1205
835	=item * Erlang tries to hide remote/local connections, AEMP does not.	1206	=item * Erlang tries to hide remote/local connections, AEMP does not.
836		1207
837	Monitoring in Erlang is not an indicator of process death/crashes,	1208	Monitoring in Erlang is not an indicator of process death/crashes, in the
838	as linking is (except linking is unreliable in Erlang).	1209	same way as linking is (except linking is unreliable in Erlang).
839		1210
840	In AEMP, you don't "look up" registered port names or send to named ports	1211	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	1212	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	1213	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	1214	remote port. Since both monitors are local to the node, they are much more
844	more reliable.	1215	reliable (no need for C<spawn_link>).
845		1216
846	This also saves round-trips and avoids sending messages to the wrong port	1217	This also saves round-trips and avoids sending messages to the wrong port
847	(hard to do in Erlang).	1218	(hard to do in Erlang).
848		1219
849	=back	1220	=back
850		1221
		1222	=head1 RATIONALE
		1223
		1224	=over 4
		1225
		1226	=item Why strings for port and node IDs, why not objects?
		1227
		1228	We considered "objects", but found that the actual number of methods
		1229	that can be called are quite low. Since port and node IDs travel over
		1230	the network frequently, the serialising/deserialising would add lots of
		1231	overhead, as well as having to keep a proxy object everywhere.
		1232
		1233	Strings can easily be printed, easily serialised etc. and need no special
		1234	procedures to be "valid".
		1235
		1236	And as a result, a port with just a default receiver consists of a single
		1237	code reference stored in a global hash - it can't become much cheaper.
		1238
		1239	=item Why favour JSON, why not a real serialising format such as Storable?
		1240
		1241	In fact, any AnyEvent::MP node will happily accept Storable as framing
		1242	format, but currently there is no way to make a node use Storable by
		1243	default (although all nodes will accept it).
		1244
		1245	The default framing protocol is JSON because a) JSON::XS is many times
		1246	faster for small messages and b) most importantly, after years of
		1247	experience we found that object serialisation is causing more problems
		1248	than it solves: Just like function calls, objects simply do not travel
		1249	easily over the network, mostly because they will always be a copy, so you
		1250	always have to re-think your design.
		1251
		1252	Keeping your messages simple, concentrating on data structures rather than
		1253	objects, will keep your messages clean, tidy and efficient.
		1254
		1255	=back
		1256
		1257	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1258
		1259	AEMP version 2 has three major incompatible changes compared to version 1:
		1260
		1261	=over 4
		1262
		1263	=item AnyEvent::MP::Global no longer has group management functions.
		1264
		1265	AnyEvent::MP now comes with a distributed database that is more
		1266	powerful. It's database families map closely to ports, but the API has
		1267	minor differences:
		1268
		1269	grp_reg $group, $port # old
		1270	db_reg $group, $port # new
		1271
		1272	$list = grp_get $group # old
		1273	db_keys $group, sub { my $list = shift } # new
		1274
		1275	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1276	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1277
		1278	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get>
		1279	is no longer instant, because the local node might not have a copy of
		1280	the group. This can be partially remedied by using C<db_mon> to keep an
		1281	updated copy of the group:
		1282
		1283	my $local_group_copy;
		1284	db_mon $group => sub { $local_group_copy = shift };
		1285
		1286	# no keys %$local_group_copy always returns the most up-to-date
		1287	# list of ports in the group.
		1288
		1289	C<grp_mon> can almost be replaced by C<db_mon>:
		1290
		1291	db_mon $group => sub {
		1292	my ($ports, $add, $chg, $lde) = @_;
		1293	$ports = [keys %$ports];
		1294
		1295	# now $ports, $add and $del are the same as
		1296	# were originally passed by grp_mon.
		1297	...
		1298	};
		1299
		1300	=item Nodes not longer connect to all other nodes.
		1301
		1302	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1303	module, which in turn would create connections to all other nodes in the
		1304	network (helped by the seed nodes).
		1305
		1306	In version 2.x, global nodes still connect to all other global nodes, but
		1307	other nodes don't - now every node either is a global node itself, or
		1308	attaches itself to another global node.
		1309
		1310	If a node isn't a global node itself, then it attaches itself to one
		1311	of its seed nodes. If that seed node isn't a global node yet, it will
		1312	automatically be upgraded to a global node.
		1313
		1314	So in many cases, nothing needs to be changed - one just has to make sure
		1315	that all seed nodes are meshed together with the other seed nodes (as with
		1316	AEMP 1.x), and other nodes specify them as seed nodes.
		1317
		1318	Not opening a connection to every other node is usually an advantage,
		1319	except when you need the lower latency of an already established
		1320	connection. To ensure a node establishes a connection to another node,
		1321	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1322	create the connection (and notify you when the connection fails).
		1323
		1324	=item Listener-less nodes (nodes without binds) are gone.
		1325
		1326	And are not coming back, at least not in their old form. If no C<binds>
		1327	are specified for a node, AnyEvent::MP now assumes a default of C<*:*>.
		1328
		1329	There are vague plans to implement some form of routing domains, which
		1330	might or might not bring back listener-less nodes, but don't count on it.
		1331
		1332	The fact that most connections are now optional somewhat mitigates this,
		1333	as a node can be effectively unreachable from the outside without any
		1334	problems, as long as it isn't a global node and only reaches out to other
		1335	nodes (as opposed to being contacted from other nodes).
		1336
		1337	=item $AnyEvent::MP::Kernel::WARN has gone.
		1338
		1339	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1340	uses this, and so should your programs.
		1341
		1342	Every module now documents what kinds of messages it generates, with
		1343	AnyEvent::MP acting as a catch all.
		1344
		1345	On the positive side, this means that instead of setting
		1346	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE>,
		1347	much less to type.
		1348
		1349	=back
		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

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines