[ViewVC] Diff of: cvs/AnyEvent-MP/MP.pm

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.41 by root, Sat Aug 8 21:56:29 2009 UTC vs.
Revision 1.132 by root, Sat Mar 10 20:34:11 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 = '0.1';	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
		195
121	our @EXPORT = qw(	196	our @EXPORT = qw(
122	NODE $NODE *SELF node_of _any_	197	NODE $NODE *SELF node_of after
123	resolve_node initialise_node	198	configure
124	snd rcv mon kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
125	port	200	port
		201	db_set db_del db_reg
		202	db_mon db_family db_keys db_values
126	);	203	);
127		204
128	our $SELF;	205	our $SELF;
129		206
130	sub _self_die() {	207	sub _self_die() {
…		…
133	kil $SELF, die => $msg;	210	kil $SELF, die => $msg;
134	}	211	}
135		212
136	=item $thisnode = NODE / $NODE	213	=item $thisnode = NODE / $NODE
137		214
138	The C<NODE> function returns, and the C<$NODE> variable contains	215	The C<NODE> function returns, and the C<$NODE> variable contains, the node
139	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
140	to C<become_public> or C<become_slave>, after which all local port	217	a call to C<configure>.
141	identifiers become invalid.
142		218
143	=item $noderef = node_of $port	219	=item $nodeid = node_of $port
144		220
145	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.
146		222
147	=item initialise_node $noderef, $seednode, $seednode...	223	=item configure $profile, key => value...
148		224
149	=item initialise_node "slave/", $master, $master...	225	=item configure key => value...
150		226
151	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
152	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
153	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.
154		231
155	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
156	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
157		234
158	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
159		236	F<aemp> command line utility (sans the set/del prefix), with these additions:
160	There are two types of networked nodes, public nodes and slave nodes:
161		237
162	=over 4	238	=over 4
163		239
164	=item public nodes	240	=item norc => $boolean (default false)
165		241
166	For public nodes, C<$noderef> must either be a (possibly unresolved)	242	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
167	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
168	which case the noderef will be guessed.	244	C<configure> call.
169		245
170	Afterwards, the node will bind itself on all endpoints and try to connect	246	=item force => $boolean (default false)
171	to all additional C<$seednodes> that are specified. Seednodes are optional
172	and can be used to quickly bootstrap the node into an existing network.
173		247
174	=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.
175		251
176	When the C<$noderef> is the special string C<slave/>, then the node will	252	=item secure => $pass->($nodeid)
177	become a slave node. Slave nodes cannot be contacted from outside and will
178	route most of their traffic to the master node that they attach to.
179		253
180	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
181	to all of them and will become a slave attached to the first node it can	255	is called for every remote execution attempt - the execution request is
182	successfully connect to.	256	granted iff the callback returns a true value.
		257
		258	See F<semp setsecure> for more info.
183		259
184	=back	260	=back
185		261
186	This function will block until all nodes have been resolved and, for slave
187	nodes, until it has successfully established a connection to a master
188	server.
189
190	Example: become a public node listening on the default node.
191
192	initialise_node;
193
194	Example: become a public node, and try to contact some well-known master
195	servers to become part of the network.
196
197	initialise_node undef, "master1", "master2";
198
199	Example: become a public node listening on port C<4041>.
200
201	initialise_node 4041;
202
203	Example: become a public node, only visible on localhost port 4044.
204
205	initialise_node "locahost:4044";
206
207	Example: become a slave node to any of the specified master servers.
208
209	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
210
211	=item $cv = resolve_node $noderef
212
213	Takes an unresolved node reference that may contain hostnames and
214	abbreviated IDs, resolves all of them and returns a resolved node
215	reference.
216
217	In addition to C<address:port> pairs allowed in resolved noderefs, the
218	following forms are supported:
219
220	=over 4	262	=over 4
221		263
222	=item the empty string	264	=item step 1, gathering configuration from profiles
223		265
224	An empty-string component gets resolved as if the default port (4040) was	266	The function first looks up a profile in the aemp configuration (see the
225	specified.	267	L<aemp> commandline utility). The profile name can be specified via the
		268	named C<profile> parameter or can simply be the first parameter). If it is
		269	missing, then the nodename (F<uname -n>) will be used as profile name.
226		270
227	=item naked port numbers (e.g. C<1234>)	271	The profile data is then gathered as follows:
228		272
229	These are resolved by prepending the local nodename and a colon, to be	273	First, all remaining key => value pairs (all of which are conveniently
230	further resolved.	274	undocumented at the moment) will be interpreted as configuration
		275	data. Then they will be overwritten by any values specified in the global
		276	default configuration (see the F<aemp> utility), then the chain of
		277	profiles chosen by the profile name (and any C<parent> attributes).
231		278
232	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	279	That means that the values specified in the profile have highest priority
		280	and the values specified directly via C<configure> have lowest priority,
		281	and can only be used to specify defaults.
233		282
234	These are resolved by using AnyEvent::DNS to resolve them, optionally	283	If the profile specifies a node ID, then this will become the node ID of
235	looking up SRV records for the C<aemp=4040> port, if no port was	284	this process. If not, then the profile name will be used as node ID, with
236	specified.	285	a unique randoms tring (C</%u>) appended.
		286
		287	The node ID can contain some C<%> sequences that are expanded: C<%n>
		288	is expanded to the local nodename, C<%u> is replaced by a random
		289	strign to make the node unique. For example, the F<aemp> commandline
		290	utility uses C<aemp/%n/%u> as nodename, which might expand to
		291	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		292
		293	=item step 2, bind listener sockets
		294
		295	The next step is to look up the binds in the profile, followed by binding
		296	aemp protocol listeners on all binds specified (it is possible and valid
		297	to have no binds, meaning that the node cannot be contacted form the
		298	outside. This means the node cannot talk to other nodes that also have no
		299	binds, but it can still talk to all "normal" nodes).
		300
		301	If the profile does not specify a binds list, then a default of C<*> is
		302	used, meaning the node will bind on a dynamically-assigned port on every
		303	local IP address it finds.
		304
		305	=item step 3, connect to seed nodes
		306
		307	As the last step, the seed ID list from the profile is passed to the
		308	L<AnyEvent::MP::Global> module, which will then use it to keep
		309	connectivity with at least one node at any point in time.
237		310
238	=back	311	=back
		312
		313	Example: become a distributed node using the local node name as profile.
		314	This should be the most common form of invocation for "daemon"-type nodes.
		315
		316	configure
		317
		318	Example: become a semi-anonymous node. This form is often used for
		319	commandline clients.
		320
		321	configure nodeid => "myscript/%n/%u";
		322
		323	Example: configure a node using a profile called seed, which is suitable
		324	for a seed node as it binds on all local addresses on a fixed port (4040,
		325	customary for aemp).
		326
		327	# use the aemp commandline utility
		328	# aemp profile seed binds '*:4040'
		329
		330	# then use it
		331	configure profile => "seed";
		332
		333	# or simply use aemp from the shell again:
		334	# aemp run profile seed
		335
		336	# or provide a nicer-to-remember nodeid
		337	# aemp run profile seed nodeid "$(hostname)"
239		338
240	=item $SELF	339	=item $SELF
241		340
242	Contains the current port id while executing C<rcv> callbacks or C<psub>	341	Contains the current port id while executing C<rcv> callbacks or C<psub>
243	blocks.	342	blocks.
244		343
245	=item SELF, %SELF, @SELF...	344	=item *SELF, SELF, %SELF, @SELF...
246		345
247	Due to some quirks in how perl exports variables, it is impossible to	346	Due to some quirks in how perl exports variables, it is impossible to
248	just export C<$SELF>, all the symbols called C<SELF> are exported by this	347	just export C<$SELF>, all the symbols named C<SELF> are exported by this
249	module, but only C<$SELF> is currently used.	348	module, but only C<$SELF> is currently used.
250		349
251	=item snd $port, type => @data	350	=item snd $port, type => @data
252		351
253	=item snd $port, @msg	352	=item snd $port, @msg
254		353
255	Send the given message to the given port ID, which can identify either	354	Send the given message to the given port, which can identify either a
256	a local or a remote port, and can be either a string or soemthignt hat	355	local or a remote port, and must be a port ID.
257	stringifies a sa port ID (such as a port object :).
258		356
259	While the message can be about anything, it is highly recommended to use a	357	While the message can be almost anything, it is highly recommended to
260	string as first element (a portid, or some word that indicates a request	358	use a string as first element (a port ID, or some word that indicates a
261	type etc.).	359	request type etc.) and to consist if only simple perl values (scalars,
		360	arrays, hashes) - if you think you need to pass an object, think again.
262		361
263	The message data effectively becomes read-only after a call to this	362	The message data logically becomes read-only after a call to this
264	function: modifying any argument is not allowed and can cause many	363	function: modifying any argument (or values referenced by them) is
265	problems.	364	forbidden, as there can be considerable time between the call to C<snd>
		365	and the time the message is actually being serialised - in fact, it might
		366	never be copied as within the same process it is simply handed to the
		367	receiving port.
266		368
267	The type of data you can transfer depends on the transport protocol: when	369	The type of data you can transfer depends on the transport protocol: when
268	JSON is used, then only strings, numbers and arrays and hashes consisting	370	JSON is used, then only strings, numbers and arrays and hashes consisting
269	of those are allowed (no objects). When Storable is used, then anything	371	of those are allowed (no objects). When Storable is used, then anything
270	that Storable can serialise and deserialise is allowed, and for the local	372	that Storable can serialise and deserialise is allowed, and for the local
271	node, anything can be passed.	373	node, anything can be passed. Best rely only on the common denominator of
		374	these.
272		375
273	=item $local_port = port	376	=item $local_port = port
274		377
275	Create a new local port object that can be used either as a pattern	378	Create a new local port object and returns its port ID. Initially it has
276	matching port ("full port") or a single-callback port ("miniport"),	379	no callbacks set and will throw an error when it receives messages.
277	depending on how C<rcv> callbacks are bound to the object.
278		380
279	=item $port = port { my @msg = @_; $finished }	381	=item $local_port = port { my @msg = @_ }
280		382
281	Creates a "miniport", that is, a very lightweight port without any pattern	383	Creates a new local port, and returns its ID. Semantically the same as
282	matching behind it, and returns its ID. Semantically the same as creating
283	a port and calling C<rcv $port, $callback> on it.	384	creating a port and calling C<rcv $port, $callback> on it.
284		385
285	The block will be called for every message received on the port. When the	386	The block will be called for every message received on the port, with the
286	callback returns a true value its job is considered "done" and the port	387	global variable C<$SELF> set to the port ID. Runtime errors will cause the
287	will be destroyed. Otherwise it will stay alive.	388	port to be C<kil>ed. The message will be passed as-is, no extra argument
		389	(i.e. no port ID) will be passed to the callback.
288		390
289	The message will be passed as-is, no extra argument (i.e. no port id) will	391	If you want to stop/destroy the port, simply C<kil> it:
290	be passed to the callback.
291		392
292	If you need the local port id in the callback, this works nicely:	393	my $port = port {
293		394	my @msg = @_;
294	my $port; $port = port {	395	...
295	snd $otherport, reply => $port;	396	kil $SELF;
296	};	397	};
297		398
298	=cut	399	=cut
299		400
300	sub rcv($@);	401	sub rcv($@);
301		402
		403	my $KILME = sub {
		404	die "received message on port without callback";
		405	};
		406
302	sub port(;&) {	407	sub port(;&) {
303	my $id = "$UNIQ." . $ID++;	408	my $id = $UNIQ . ++$ID;
304	my $port = "$NODE#$id";	409	my $port = "$NODE#$id";
305		410
306	if (@_) {
307	rcv $port, shift;	411	rcv $port, shift \|\| $KILME;
308	} else {
309	$PORT{$id} = sub { }; # nop
310	}
311		412
312	$port	413	$port
313	}	414	}
314		415
315	=item reg $port, $name
316
317	=item reg $name
318
319	Registers the given port (or C<$SELF><<< if missing) under the name
320	C<$name>. If the name already exists it is replaced.
321
322	A port can only be registered under one well known name.
323
324	A port automatically becomes unregistered when it is killed.
325
326	=cut
327
328	sub reg(@) {
329	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
330
331	$REG{$_[0]} = $port;
332	}
333
334	=item rcv $port, $callback->(@msg)	416	=item rcv $local_port, $callback->(@msg)
335		417
336	Replaces the callback on the specified miniport (after converting it to	418	Replaces the default callback on the specified port. There is no way to
337	one if required).	419	remove the default callback: use C<sub { }> to disable it, or better
338		420	C<kil> the port when it is no longer needed.
339	=item rcv $port, tagstring => $callback->(@msg), ...
340
341	=item rcv $port, $smartmatch => $callback->(@msg), ...
342
343	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
344
345	Register callbacks to be called on matching messages on the given full
346	port (after converting it to one if required) and return the port.
347
348	The callback has to return a true value when its work is done, after
349	which is will be removed, or a false value in which case it will stay
350	registered.
351		421
352	The global C<$SELF> (exported by this module) contains C<$port> while	422	The global C<$SELF> (exported by this module) contains C<$port> while
353	executing the callback.	423	executing the callback. Runtime errors during callback execution will
		424	result in the port being C<kil>ed.
354		425
355	Runtime errors during callback execution will result in the port being	426	The default callback received all messages not matched by a more specific
356	C<kil>ed.	427	C<tag> match.
357		428
358	If the match is an array reference, then it will be matched against the	429	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
359	first elements of the message, otherwise only the first element is being
360	matched.
361		430
362	Any element in the match that is specified as C<_any_> (a function	431	Register (or replace) callbacks to be called on messages starting with the
363	exported by this module) matches any single element of the message.	432	given tag on the given port (and return the port), or unregister it (when
		433	C<$callback> is C<$undef> or missing). There can only be one callback
		434	registered for each tag.
364		435
365	While not required, it is highly recommended that the first matching	436	The original message will be passed to the callback, after the first
366	element is a string identifying the message. The one-string-only match is	437	element (the tag) has been removed. The callback will use the same
367	also the most efficient match (by far).	438	environment as the default callback (see above).
368		439
369	Example: create a port and bind receivers on it in one go.	440	Example: create a port and bind receivers on it in one go.
370		441
371	my $port = rcv port,	442	my $port = rcv port,
372	msg1 => sub { ...; 0 },	443	msg1 => sub { ... },
373	msg2 => sub { ...; 0 },	444	msg2 => sub { ... },
374	;	445	;
375		446
376	Example: create a port, bind receivers and send it in a message elsewhere	447	Example: create a port, bind receivers and send it in a message elsewhere
377	in one go:	448	in one go:
378		449
379	snd $otherport, reply =>	450	snd $otherport, reply =>
380	rcv port,	451	rcv port,
381	msg1 => sub { ...; 0 },	452	msg1 => sub { ... },
382	...	453	...
383	;	454	;
384		455
		456	Example: temporarily register a rcv callback for a tag matching some port
		457	(e.g. for an rpc reply) and unregister it after a message was received.
		458
		459	rcv $port, $otherport => sub {
		460	my @reply = @_;
		461
		462	rcv $SELF, $otherport;
		463	};
		464
385	=cut	465	=cut
386		466
387	sub rcv($@) {	467	sub rcv($@) {
388	my $port = shift;	468	my $port = shift;
389	my ($noderef, $portid) = split /#/, $port, 2;	469	my ($nodeid, $portid) = split /#/, $port, 2;
390		470
391	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	471	$NODE{$nodeid} == $NODE{""}
392	or Carp::croak "$port: rcv can only be called on local ports, caught";	472	or Carp::croak "$port: rcv can only be called on local ports, caught";
393		473
394	if (@_ == 1) {	474	while (@_) {
		475	if (ref $_[0]) {
		476	if (my $self = $PORT_DATA{$portid}) {
		477	"AnyEvent::MP::Port" eq ref $self
		478	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		479
		480	$self->[0] = shift;
		481	} else {
395	my $cb = shift;	482	my $cb = shift;
396	delete $PORT_DATA{$portid};
397	$PORT{$portid} = sub {	483	$PORT{$portid} = sub {
398	local $SELF = $port;	484	local $SELF = $port;
399	eval {	485	eval { &$cb }; _self_die if $@;
400	&$cb	486	};
401	and kil $port;
402	};	487	}
403	_self_die if $@;	488	} elsif (defined $_[0]) {
404	};
405	} else {
406	my $self = $PORT_DATA{$portid} \|\|= do {	489	my $self = $PORT_DATA{$portid} \|\|= do {
407	my $self = bless {	490	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
408	id => $port,
409	}, "AnyEvent::MP::Port";
410		491
411	$PORT{$portid} = sub {	492	$PORT{$portid} = sub {
412	local $SELF = $port;	493	local $SELF = $port;
413		494
414	eval {
415	for (@{ $self->{rc0}{$_[0]} }) {	495	if (my $cb = $self->[1]{$_[0]}) {
416	$_ && &{$_->[0]}	496	shift;
417	&& undef $_;	497	eval { &$cb }; _self_die if $@;
418	}	498	} else {
419
420	for (@{ $self->{rcv}{$_[0]} }) {
421	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
422	&& &{$_->[0]}	499	&{ $self->[0] };
423	&& undef $_;
424	}
425
426	for (@{ $self->{any} }) {
427	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
428	&& &{$_->[0]}
429	&& undef $_;
430	}	500	}
431	};	501	};
432	_self_die if $@;	502
		503	$self
433	};	504	};
434		505
435	$self
436	};
437
438	"AnyEvent::MP::Port" eq ref $self	506	"AnyEvent::MP::Port" eq ref $self
439	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	507	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
440		508
441	while (@_) {
442	my ($match, $cb) = splice @_, 0, 2;	509	my ($tag, $cb) = splice @_, 0, 2;
443		510
444	if (!ref $match) {	511	if (defined $cb) {
445	push @{ $self->{rc0}{$match} }, [$cb];	512	$self->[1]{$tag} = $cb;
446	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
447	my ($type, @match) = @$match;
448	@match
449	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
450	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
451	} else {	513	} else {
452	push @{ $self->{any} }, [$cb, $match];	514	delete $self->[1]{$tag};
453	}	515	}
454	}	516	}
455	}	517	}
456		518
457	$port	519	$port
458	}	520	}
459		521
		522	=item peval $port, $coderef[, @args]
		523
		524	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		525	when the code throews an exception the C<$port> will be killed.
		526
		527	Any remaining args will be passed to the callback. Any return values will
		528	be returned to the caller.
		529
		530	This is useful when you temporarily want to execute code in the context of
		531	a port.
		532
		533	Example: create a port and run some initialisation code in it's context.
		534
		535	my $port = port { ... };
		536
		537	peval $port, sub {
		538	init
		539	or die "unable to init";
		540	};
		541
		542	=cut
		543
		544	sub peval($$) {
		545	local $SELF = shift;
		546	my $cb = shift;
		547
		548	if (wantarray) {
		549	my @res = eval { &$cb };
		550	_self_die if $@;
		551	@res
		552	} else {
		553	my $res = eval { &$cb };
		554	_self_die if $@;
		555	$res
		556	}
		557	}
		558
460	=item $closure = psub { BLOCK }	559	=item $closure = psub { BLOCK }
461		560
462	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	561	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
463	closure is executed, sets up the environment in the same way as in C<rcv>	562	closure is executed, sets up the environment in the same way as in C<rcv>
464	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	563	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		564
		565	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		566	BLOCK }, @_ } >>.
465		567
466	This is useful when you register callbacks from C<rcv> callbacks:	568	This is useful when you register callbacks from C<rcv> callbacks:
467		569
468	rcv delayed_reply => sub {	570	rcv delayed_reply => sub {
469	my ($delay, @reply) = @_;	571	my ($delay, @reply) = @_;
…		…
493	$res	595	$res
494	}	596	}
495	}	597	}
496	}	598	}
497		599
498	=item $guard = mon $port, $cb->(@reason)	600	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
499		601
500	=item $guard = mon $port, $rcvport	602	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
501		603
502	=item $guard = mon $port	604	=item $guard = mon $port # kill $SELF when $port dies
503		605
504	=item $guard = mon $port, $rcvport, @msg	606	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
505		607
506	Monitor the given port and do something when the port is killed, and	608	Monitor the given port and do something when the port is killed or
507	optionally return a guard that can be used to stop monitoring again.	609	messages to it were lost, and optionally return a guard that can be used
		610	to stop monitoring again.
508		611
509	In the first form (callback), the callback is simply called with any	612	In the first form (callback), the callback is simply called with any
510	number of C<@reason> elements (no @reason means that the port was deleted	613	number of C<@reason> elements (no @reason means that the port was deleted
511	"normally"). Note also that I<< the callback B<must> never die >>, so use	614	"normally"). Note also that I<< the callback B<must> never die >>, so use
512	C<eval> if unsure.	615	C<eval> if unsure.
513		616
514	In the second form (another port given), the other port (C<$rcvport)	617	In the second form (another port given), the other port (C<$rcvport>)
515	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	618	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
516	"normal" kils nothing happens, while under all other conditions, the other	619	"normal" kils nothing happens, while under all other conditions, the other
517	port is killed with the same reason.	620	port is killed with the same reason.
518		621
519	The third form (kill self) is the same as the second form, except that	622	The third form (kill self) is the same as the second form, except that
520	C<$rvport> defaults to C<$SELF>.	623	C<$rvport> defaults to C<$SELF>.
521		624
522	In the last form (message), a message of the form C<@msg, @reason> will be	625	In the last form (message), a message of the form C<@msg, @reason> will be
523	C<snd>.	626	C<snd>.
		627
		628	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		629	alert was raised), they are removed and will not trigger again.
524		630
525	As a rule of thumb, monitoring requests should always monitor a port from	631	As a rule of thumb, monitoring requests should always monitor a port from
526	a local port (or callback). The reason is that kill messages might get	632	a local port (or callback). The reason is that kill messages might get
527	lost, just like any other message. Another less obvious reason is that	633	lost, just like any other message. Another less obvious reason is that
528	even monitoring requests can get lost (for exmaple, when the connection	634	even monitoring requests can get lost (for example, when the connection
529	to the other node goes down permanently). When monitoring a port locally	635	to the other node goes down permanently). When monitoring a port locally
530	these problems do not exist.	636	these problems do not exist.
531		637
		638	C<mon> effectively guarantees that, in the absence of hardware failures,
		639	after starting the monitor, either all messages sent to the port will
		640	arrive, or the monitoring action will be invoked after possible message
		641	loss has been detected. No messages will be lost "in between" (after
		642	the first lost message no further messages will be received by the
		643	port). After the monitoring action was invoked, further messages might get
		644	delivered again.
		645
		646	Inter-host-connection timeouts and monitoring depend on the transport
		647	used. The only transport currently implemented is TCP, and AnyEvent::MP
		648	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		649	non-idle connection, and usually around two hours for idle connections).
		650
		651	This means that monitoring is good for program errors and cleaning up
		652	stuff eventually, but they are no replacement for a timeout when you need
		653	to ensure some maximum latency.
		654
532	Example: call a given callback when C<$port> is killed.	655	Example: call a given callback when C<$port> is killed.
533		656
534	mon $port, sub { warn "port died because of <@_>\n" };	657	mon $port, sub { warn "port died because of <@_>\n" };
535		658
536	Example: kill ourselves when C<$port> is killed abnormally.	659	Example: kill ourselves when C<$port> is killed abnormally.
…		…
542	mon $port, $self => "restart";	665	mon $port, $self => "restart";
543		666
544	=cut	667	=cut
545		668
546	sub mon {	669	sub mon {
547	my ($noderef, $port) = split /#/, shift, 2;	670	my ($nodeid, $port) = split /#/, shift, 2;
548		671
549	my $node = $NODE{$noderef} \|\| add_node $noderef;	672	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
550		673
551	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	674	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
552		675
553	unless (ref $cb) {	676	unless (ref $cb) {
554	if (@_) {	677	if (@_) {
…		…
563	}	686	}
564		687
565	$node->monitor ($port, $cb);	688	$node->monitor ($port, $cb);
566		689
567	defined wantarray	690	defined wantarray
568	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	691	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
569	}	692	}
570		693
571	=item $guard = mon_guard $port, $ref, $ref...	694	=item $guard = mon_guard $port, $ref, $ref...
572		695
573	Monitors the given C<$port> and keeps the passed references. When the port	696	Monitors the given C<$port> and keeps the passed references. When the port
574	is killed, the references will be freed.	697	is killed, the references will be freed.
575		698
576	Optionally returns a guard that will stop the monitoring.	699	Optionally returns a guard that will stop the monitoring.
577		700
578	This function is useful when you create e.g. timers or other watchers and	701	This function is useful when you create e.g. timers or other watchers and
579	want to free them when the port gets killed:	702	want to free them when the port gets killed (note the use of C<psub>):
580		703
581	$port->rcv (start => sub {	704	$port->rcv (start => sub {
582	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	705	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
583	undef $timer if 0.9 < rand;	706	undef $timer if 0.9 < rand;
584	});	707	});
585	});	708	});
586		709
587	=cut	710	=cut
…		…
596		719
597	=item kil $port[, @reason]	720	=item kil $port[, @reason]
598		721
599	Kill the specified port with the given C<@reason>.	722	Kill the specified port with the given C<@reason>.
600		723
601	If no C<@reason> is specified, then the port is killed "normally" (linked	724	If no C<@reason> is specified, then the port is killed "normally" -
602	ports will not be kileld, or even notified).	725	monitor callback will be invoked, but the kil will not cause linked ports
		726	(C<mon $mport, $lport> form) to get killed.
603		727
604	Otherwise, linked ports get killed with the same reason (second form of	728	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
605	C<mon>, see below).	729	form) get killed with the same reason.
606		730
607	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	731	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
608	will be reported as reason C<< die => $@ >>.	732	will be reported as reason C<< die => $@ >>.
609		733
610	Transport/communication errors are reported as C<< transport_error =>	734	Transport/communication errors are reported as C<< transport_error =>
…		…
615	=item $port = spawn $node, $initfunc[, @initdata]	739	=item $port = spawn $node, $initfunc[, @initdata]
616		740
617	Creates a port on the node C<$node> (which can also be a port ID, in which	741	Creates a port on the node C<$node> (which can also be a port ID, in which
618	case it's the node where that port resides).	742	case it's the node where that port resides).
619		743
620	The port ID of the newly created port is return immediately, and it is	744	The port ID of the newly created port is returned immediately, and it is
621	permissible to immediately start sending messages or monitor the port.	745	possible to immediately start sending messages or to monitor the port.
622		746
623	After the port has been created, the init function is	747	After the port has been created, the init function is called on the remote
624	called. This function must be a fully-qualified function name	748	node, in the same context as a C<rcv> callback. This function must be a
625	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	749	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
626	program, use C<::name>.	750	specify a function in the main program, use C<::name>.
627		751
628	If the function doesn't exist, then the node tries to C<require>	752	If the function doesn't exist, then the node tries to C<require>
629	the package, then the package above the package and so on (e.g.	753	the package, then the package above the package and so on (e.g.
630	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	754	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
631	exists or it runs out of package names.	755	exists or it runs out of package names.
632		756
633	The init function is then called with the newly-created port as context	757	The init function is then called with the newly-created port as context
634	object (C<$SELF>) and the C<@initdata> values as arguments.	758	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		759	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		760	the port might not get created.
635		761
636	A common idiom is to pass your own port, monitor the spawned port, and	762	A common idiom is to pass a local port, immediately monitor the spawned
637	in the init function, monitor the original port. This two-way monitoring	763	port, and in the remote init function, immediately monitor the passed
638	ensures that both ports get cleaned up when there is a problem.	764	local port. This two-way monitoring ensures that both ports get cleaned up
		765	when there is a problem.
		766
		767	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		768	caller before C<spawn> returns (by delaying invocation when spawn is
		769	called for the local node).
639		770
640	Example: spawn a chat server port on C<$othernode>.	771	Example: spawn a chat server port on C<$othernode>.
641		772
642	# this node, executed from within a port context:	773	# this node, executed from within a port context:
643	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	774	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
658		789
659	sub _spawn {	790	sub _spawn {
660	my $port = shift;	791	my $port = shift;
661	my $init = shift;	792	my $init = shift;
662		793
		794	# rcv will create the actual port
663	local $SELF = "$NODE#$port";	795	local $SELF = "$NODE#$port";
664	eval {	796	eval {
665	&{ load_func $init }	797	&{ load_func $init }
666	};	798	};
667	_self_die if $@;	799	_self_die if $@;
668	}	800	}
669		801
670	sub spawn(@) {	802	sub spawn(@) {
671	my ($noderef, undef) = split /#/, shift, 2;	803	my ($nodeid, undef) = split /#/, shift, 2;
672		804
673	my $id = "$RUNIQ." . $ID++;	805	my $id = $RUNIQ . ++$ID;
674		806
675	$_[0] =~ /::/	807	$_[0] =~ /::/
676	or Carp::croak "spawn init function must be a fully-qualified name, caught";	808	or Carp::croak "spawn init function must be a fully-qualified name, caught";
677		809
678	($NODE{$noderef} \|\| add_node $noderef)	810	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
679	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
680		811
681	"$noderef#$id"	812	"$nodeid#$id"
682	}	813	}
683		814
		815
		816	=item after $timeout, @msg
		817
		818	=item after $timeout, $callback
		819
		820	Either sends the given message, or call the given callback, after the
		821	specified number of seconds.
		822
		823	This is simply a utility function that comes in handy at times - the
		824	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		825	so it may go away in the future.
		826
		827	=cut
		828
		829	sub after($@) {
		830	my ($timeout, @action) = @_;
		831
		832	my $t; $t = AE::timer $timeout, 0, sub {
		833	undef $t;
		834	ref $action[0]
		835	? $action[0]()
		836	: snd @action;
		837	};
		838	}
		839
		840	#=item $cb2 = timeout $seconds, $cb[, @args]
		841
		842	=item cal $port, @msg, $callback[, $timeout]
		843
		844	A simple form of RPC - sends a message to the given C<$port> with the
		845	given contents (C<@msg>), but adds a reply port to the message.
		846
		847	The reply port is created temporarily just for the purpose of receiving
		848	the reply, and will be C<kil>ed when no longer needed.
		849
		850	A reply message sent to the port is passed to the C<$callback> as-is.
		851
		852	If an optional time-out (in seconds) is given and it is not C<undef>,
		853	then the callback will be called without any arguments after the time-out
		854	elapsed and the port is C<kil>ed.
		855
		856	If no time-out is given (or it is C<undef>), then the local port will
		857	monitor the remote port instead, so it eventually gets cleaned-up.
		858
		859	Currently this function returns the temporary port, but this "feature"
		860	might go in future versions unless you can make a convincing case that
		861	this is indeed useful for something.
		862
		863	=cut
		864
		865	sub cal(@) {
		866	my $timeout = ref $_[-1] ? undef : pop;
		867	my $cb = pop;
		868
		869	my $port = port {
		870	undef $timeout;
		871	kil $SELF;
		872	&$cb;
		873	};
		874
		875	if (defined $timeout) {
		876	$timeout = AE::timer $timeout, 0, sub {
		877	undef $timeout;
		878	kil $port;
		879	$cb->();
		880	};
		881	} else {
		882	mon $_[0], sub {
		883	kil $port;
		884	$cb->();
		885	};
		886	}
		887
		888	push @_, $port;
		889	&snd;
		890
		891	$port
		892	}
		893
684	=back	894	=back
685		895
686	=head1 NODE MESSAGES	896	=head1 DISTRIBUTED DATABASE
687		897
688	Nodes understand the following messages sent to them. Many of them take	898	AnyEvent::MP comes with a simple distributed database. The database will
689	arguments called C<@reply>, which will simply be used to compose a reply	899	be mirrored asynchronously on all global nodes. Other nodes bind to one
690	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	900	of the global nodes for their needs. Every node has a "local database"
691	the remaining arguments are simply the message data.	901	which contains all the values that are set locally. All local databases
		902	are merged together to form the global database, which can be queried.
692		903
693	While other messages exist, they are not public and subject to change.	904	The database structure is that of a two-level hash - the database hash
		905	contains hashes which contain values, similarly to a perl hash of hashes,
		906	i.e.:
694		907
		908	$DATABASE{$family}{$subkey} = $value
		909
		910	The top level hash key is called "family", and the second-level hash key
		911	is called "subkey" or simply "key".
		912
		913	The family must be alphanumeric, i.e. start with a letter and consist
		914	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		915	pretty much like Perl module names.
		916
		917	As the family namespace is global, it is recommended to prefix family names
		918	with the name of the application or module using it.
		919
		920	The subkeys must be non-empty strings, with no further restrictions.
		921
		922	The values should preferably be strings, but other perl scalars should
		923	work as well (such as C<undef>, arrays and hashes).
		924
		925	Every database entry is owned by one node - adding the same family/subkey
		926	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		927	but the result might be nondeterministic, i.e. the key might have
		928	different values on different nodes.
		929
		930	Different subkeys in the same family can be owned by different nodes
		931	without problems, and in fact, this is the common method to create worker
		932	pools. For example, a worker port for image scaling might do this:
		933
		934	db_set my_image_scalers => $port;
		935
		936	And clients looking for an image scaler will want to get the
		937	C<my_image_scalers> keys from time to time:
		938
		939	db_keys my_image_scalers => sub {
		940	@ports = @{ $_[0] };
		941	};
		942
		943	Or better yet, they want to monitor the database family, so they always
		944	have a reasonable up-to-date copy:
		945
		946	db_mon my_image_scalers => sub {
		947	@ports = keys %{ $_[0] };
		948	};
		949
		950	In general, you can set or delete single subkeys, but query and monitor
		951	whole families only.
		952
		953	If you feel the need to monitor or query a single subkey, try giving it
		954	it's own family.
		955
695	=over 4	956	=over
		957
		958	=item db_set $family => $subkey [=> $value]
		959
		960	Sets (or replaces) a key to the database - if C<$value> is omitted,
		961	C<undef> is used instead.
		962
		963	=item db_del $family => $subkey...
		964
		965	Deletes one or more subkeys from the database family.
		966
		967	=item $guard = db_reg $family => $subkey [=> $value]
		968
		969	Sets the key on the database and returns a guard. When the guard is
		970	destroyed, the key is deleted from the database. If C<$value> is missing,
		971	then C<undef> is used.
		972
		973	=item db_family $family => $cb->(\%familyhash)
		974
		975	Queries the named database C<$family> and call the callback with the
		976	family represented as a hash. You can keep and freely modify the hash.
		977
		978	=item db_keys $family => $cb->(\@keys)
		979
		980	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		981	them as array reference to the callback.
		982
		983	=item db_values $family => $cb->(\@values)
		984
		985	Same as C<db_family>, except it only queries the family I<values> and passes them
		986	as array reference to the callback.
		987
		988	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		989
		990	Creates a monitor on the given database family. Each time a key is set
		991	or or is deleted the callback is called with a hash containing the
		992	database family and three lists of added, changed and deleted subkeys,
		993	respectively. If no keys have changed then the array reference might be
		994	C<undef> or even missing.
		995
		996	If not called in void context, a guard object is returned that, when
		997	destroyed, stops the monitor.
		998
		999	The family hash reference and the key arrays belong to AnyEvent::MP and
		1000	B<must not be modified or stored> by the callback. When in doubt, make a
		1001	copy.
		1002
		1003	As soon as possible after the monitoring starts, the callback will be
		1004	called with the intiial contents of the family, even if it is empty,
		1005	i.e. there will always be a timely call to the callback with the current
		1006	contents.
		1007
		1008	It is possible that the callback is called with a change event even though
		1009	the subkey is already present and the value has not changed.
		1010
		1011	The monitoring stops when the guard object is destroyed.
		1012
		1013	Example: on every change to the family "mygroup", print out all keys.
		1014
		1015	my $guard = db_mon mygroup => sub {
		1016	my ($family, $a, $c, $d) = @_;
		1017	print "mygroup members: ", (join " ", keys %$family), "\n";
		1018	};
		1019
		1020	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1021
		1022	my $guard; $guard = db_mon My::Module::workers => sub {
		1023	my ($family, $a, $c, $d) = @_;
		1024	return unless %$family;
		1025	undef $guard;
		1026	print "My::Module::workers now nonempty\n";
		1027	};
		1028
		1029	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1030
		1031	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1032	my ($family, $a, $c, $d) = @_;
		1033
		1034	print "+$_=$family->{$_}\n" for @$a;
		1035	print "*$_=$family->{$_}\n" for @$c;
		1036	print "-$_=$family->{$_}\n" for @$d;
		1037	};
696		1038
697	=cut	1039	=cut
698
699	=item lookup => $name, @reply
700
701	Replies with the port ID of the specified well-known port, or C<undef>.
702
703	=item devnull => ...
704
705	Generic data sink/CPU heat conversion.
706
707	=item relay => $port, @msg
708
709	Simply forwards the message to the given port.
710
711	=item eval => $string[ @reply]
712
713	Evaluates the given string. If C<@reply> is given, then a message of the
714	form C<@reply, $@, @evalres> is sent.
715
716	Example: crash another node.
717
718	snd $othernode, eval => "exit";
719
720	=item time => @reply
721
722	Replies the the current node time to C<@reply>.
723
724	Example: tell the current node to send the current time to C<$myport> in a
725	C<timereply> message.
726
727	snd $NODE, time => $myport, timereply => 1, 2;
728	# => snd $myport, timereply => 1, 2, <time>
729		1040
730	=back	1041	=back
731		1042
732	=head1 AnyEvent::MP vs. Distributed Erlang	1043	=head1 AnyEvent::MP vs. Distributed Erlang
733		1044
734	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1045	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
735	== aemp node, Erlang process == aemp port), so many of the documents and	1046	== aemp node, Erlang process == aemp port), so many of the documents and
736	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1047	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
737	sample:	1048	sample:
738		1049
739	http://www.Erlang.se/doc/programming_rules.shtml	1050	http://www.erlang.se/doc/programming_rules.shtml
740	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1051	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
741	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1052	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
742	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1053	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
743		1054
744	Despite the similarities, there are also some important differences:	1055	Despite the similarities, there are also some important differences:
745		1056
746	=over 4	1057	=over 4
747		1058
748	=item * Node references contain the recipe on how to contact them.	1059	=item * Node IDs are arbitrary strings in AEMP.
749		1060
750	Erlang relies on special naming and DNS to work everywhere in the	1061	Erlang relies on special naming and DNS to work everywhere in the same
751	same way. AEMP relies on each node knowing it's own address(es), with	1062	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
752	convenience functionality.	1063	configuration or DNS), and possibly the addresses of some seed nodes, but
		1064	will otherwise discover other nodes (and their IDs) itself.
753		1065
754	This means that AEMP requires a less tightly controlled environment at the	1066	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
755	cost of longer node references and a slightly higher management overhead.	1067	uses "local ports are like remote ports".
		1068
		1069	The failure modes for local ports are quite different (runtime errors
		1070	only) then for remote ports - when a local port dies, you I<know> it dies,
		1071	when a connection to another node dies, you know nothing about the other
		1072	port.
		1073
		1074	Erlang pretends remote ports are as reliable as local ports, even when
		1075	they are not.
		1076
		1077	AEMP encourages a "treat remote ports differently" philosophy, with local
		1078	ports being the special case/exception, where transport errors cannot
		1079	occur.
756		1080
757	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1081	=item * Erlang uses processes and a mailbox, AEMP does not queue.
758		1082
759	Erlang uses processes that selctively receive messages, and therefore	1083	Erlang uses processes that selectively receive messages out of order, and
760	needs a queue. AEMP is event based, queuing messages would serve no useful	1084	therefore needs a queue. AEMP is event based, queuing messages would serve
761	purpose.	1085	no useful purpose. For the same reason the pattern-matching abilities
		1086	of AnyEvent::MP are more limited, as there is little need to be able to
		1087	filter messages without dequeuing them.
762		1088
763	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1089	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1090	being event-based, while Erlang is process-based.
		1091
		1092	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1093	top of AEMP and Coro threads.
764		1094
765	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1095	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
766		1096
767	Sending messages in Erlang is synchronous and blocks the process. AEMP	1097	Sending messages in Erlang is synchronous and blocks the process until
768	sends are immediate, connection establishment is handled in the	1098	a conenction has been established and the message sent (and so does not
769	background.	1099	need a queue that can overflow). AEMP sends return immediately, connection
		1100	establishment is handled in the background.
770		1101
771	=item * Erlang can silently lose messages, AEMP cannot.	1102	=item * Erlang suffers from silent message loss, AEMP does not.
772		1103
773	Erlang makes few guarantees on messages delivery - messages can get lost	1104	Erlang implements few guarantees on messages delivery - messages can get
774	without any of the processes realising it (i.e. you send messages a, b,	1105	lost without any of the processes realising it (i.e. you send messages a,
775	and c, and the other side only receives messages a and c).	1106	b, and c, and the other side only receives messages a and c).
776		1107
777	AEMP guarantees correct ordering, and the guarantee that there are no	1108	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1109	guarantee that after one message is lost, all following ones sent to the
		1110	same port are lost as well, until monitoring raises an error, so there are
778	holes in the message sequence.	1111	no silent "holes" in the message sequence.
779		1112
780	=item * In Erlang, processes can be declared dead and later be found to be	1113	If you want your software to be very reliable, you have to cope with
781	alive.	1114	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
782		1115	simply tries to work better in common error cases, such as when a network
783	In Erlang it can happen that a monitored process is declared dead and	1116	link goes down.
784	linked processes get killed, but later it turns out that the process is
785	still alive - and can receive messages.
786
787	In AEMP, when port monitoring detects a port as dead, then that port will
788	eventually be killed - it cannot happen that a node detects a port as dead
789	and then later sends messages to it, finding it is still alive.
790		1117
791	=item * Erlang can send messages to the wrong port, AEMP does not.	1118	=item * Erlang can send messages to the wrong port, AEMP does not.
792		1119
793	In Erlang it is quite possible that a node that restarts reuses a process	1120	In Erlang it is quite likely that a node that restarts reuses an Erlang
794	ID known to other nodes for a completely different process, causing	1121	process ID known to other nodes for a completely different process,
795	messages destined for that process to end up in an unrelated process.	1122	causing messages destined for that process to end up in an unrelated
		1123	process.
796		1124
797	AEMP never reuses port IDs, so old messages or old port IDs floating	1125	AEMP does not reuse port IDs, so old messages or old port IDs floating
798	around in the network will not be sent to an unrelated port.	1126	around in the network will not be sent to an unrelated port.
799		1127
800	=item * Erlang uses unprotected connections, AEMP uses secure	1128	=item * Erlang uses unprotected connections, AEMP uses secure
801	authentication and can use TLS.	1129	authentication and can use TLS.
802		1130
803	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1131	AEMP can use a proven protocol - TLS - to protect connections and
804	securely authenticate nodes.	1132	securely authenticate nodes.
805		1133
806	=item * The AEMP protocol is optimised for both text-based and binary	1134	=item * The AEMP protocol is optimised for both text-based and binary
807	communications.	1135	communications.
808		1136
809	The AEMP protocol, unlike the Erlang protocol, supports both	1137	The AEMP protocol, unlike the Erlang protocol, supports both programming
810	language-independent text-only protocols (good for debugging) and binary,	1138	language independent text-only protocols (good for debugging), and binary,
811	language-specific serialisers (e.g. Storable).	1139	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1140	used, the protocol is actually completely text-based.
812		1141
813	It has also been carefully designed to be implementable in other languages	1142	It has also been carefully designed to be implementable in other languages
814	with a minimum of work while gracefully degrading fucntionality to make the	1143	with a minimum of work while gracefully degrading functionality to make the
815	protocol simple.	1144	protocol simple.
816		1145
817	=item * AEMP has more flexible monitoring options than Erlang.	1146	=item * AEMP has more flexible monitoring options than Erlang.
818		1147
819	In Erlang, you can chose to receive I<all> exit signals as messages	1148	In Erlang, you can chose to receive I<all> exit signals as messages or
820	or I<none>, there is no in-between, so monitoring single processes is	1149	I<none>, there is no in-between, so monitoring single Erlang processes is
821	difficult to implement. Monitoring in AEMP is more flexible than in	1150	difficult to implement.
822	Erlang, as one can choose between automatic kill, exit message or callback	1151
823	on a per-process basis.	1152	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1153	between automatic kill, exit message or callback on a per-port basis.
824		1154
825	=item * Erlang tries to hide remote/local connections, AEMP does not.	1155	=item * Erlang tries to hide remote/local connections, AEMP does not.
826		1156
827	Monitoring in Erlang is not an indicator of process death/crashes,	1157	Monitoring in Erlang is not an indicator of process death/crashes, in the
828	as linking is (except linking is unreliable in Erlang).	1158	same way as linking is (except linking is unreliable in Erlang).
829		1159
830	In AEMP, you don't "look up" registered port names or send to named ports	1160	In AEMP, you don't "look up" registered port names or send to named ports
831	that might or might not be persistent. Instead, you normally spawn a port	1161	that might or might not be persistent. Instead, you normally spawn a port
832	on the remote node. The init function monitors the you, and you monitor	1162	on the remote node. The init function monitors you, and you monitor the
833	the remote port. Since both monitors are local to the node, they are much	1163	remote port. Since both monitors are local to the node, they are much more
834	more reliable.	1164	reliable (no need for C<spawn_link>).
835		1165
836	This also saves round-trips and avoids sending messages to the wrong port	1166	This also saves round-trips and avoids sending messages to the wrong port
837	(hard to do in Erlang).	1167	(hard to do in Erlang).
838		1168
839	=back	1169	=back
840		1170
		1171	=head1 RATIONALE
		1172
		1173	=over 4
		1174
		1175	=item Why strings for port and node IDs, why not objects?
		1176
		1177	We considered "objects", but found that the actual number of methods
		1178	that can be called are quite low. Since port and node IDs travel over
		1179	the network frequently, the serialising/deserialising would add lots of
		1180	overhead, as well as having to keep a proxy object everywhere.
		1181
		1182	Strings can easily be printed, easily serialised etc. and need no special
		1183	procedures to be "valid".
		1184
		1185	And as a result, a port with just a default receiver consists of a single
		1186	code reference stored in a global hash - it can't become much cheaper.
		1187
		1188	=item Why favour JSON, why not a real serialising format such as Storable?
		1189
		1190	In fact, any AnyEvent::MP node will happily accept Storable as framing
		1191	format, but currently there is no way to make a node use Storable by
		1192	default (although all nodes will accept it).
		1193
		1194	The default framing protocol is JSON because a) JSON::XS is many times
		1195	faster for small messages and b) most importantly, after years of
		1196	experience we found that object serialisation is causing more problems
		1197	than it solves: Just like function calls, objects simply do not travel
		1198	easily over the network, mostly because they will always be a copy, so you
		1199	always have to re-think your design.
		1200
		1201	Keeping your messages simple, concentrating on data structures rather than
		1202	objects, will keep your messages clean, tidy and efficient.
		1203
		1204	=back
		1205
841	=head1 SEE ALSO	1206	=head1 SEE ALSO
		1207
		1208	L<AnyEvent::MP::Intro> - a gentle introduction.
		1209
		1210	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1211
		1212	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1213	your applications.
		1214
		1215	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1216
		1217	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1218	all nodes.
842		1219
843	L<AnyEvent>.	1220	L<AnyEvent>.
844		1221
845	=head1 AUTHOR	1222	=head1 AUTHOR
846		1223

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Revision 1.132 by root, Sat Mar 10 20:34:11 2012 UTC