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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.48 by root, Thu Aug 13 02:59:42 2009 UTC vs.
Revision 1.126 by root, Sat Mar 3 19:43:41 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using miniports	24	# creating/using ports, the simple way
28	my $miniport = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using full ports	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, smartmatch => $cb->(@msg);
33	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
34	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
35
36	# more, smarter, matches (_any_ is exported by this module)
37	rcv $port, [child_died => $pid] => sub { ...
38	rcv $port, [_any_, _any_, 3] => sub { .. $_[2] is 3
39		31
40	# create a port on another node	32	# create a port on another node
41	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
42		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
43	# monitoring	39	# monitoring
44	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $localport, $cb->(@msg) # callback is invoked on death
45	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
46	mon $port, $otherport, @msg # send message on death	42	mon $localport, $otherport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
47		51
48	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
49		53
		54	bin/aemp - stable.
50	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
51	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
52	AnyEvent::MP::Kernel - WIP
53	AnyEvent::MP::Transport - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
54		58	AnyEvent::MP::Global - stable API.
55	stay tuned.
56		59
57	=head1 DESCRIPTION	60	=head1 DESCRIPTION
58		61
59	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
60		63
61	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
62	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
63		66
64	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
65	manual page.	68	manual page and the examples under F<eg/>.
66
67	At the moment, this module family is severly broken and underdocumented,
68	so do not use. This was uploaded mainly to reserve the CPAN namespace -
69	stay tuned!
70		69
71	=head1 CONCEPTS	70	=head1 CONCEPTS
72		71
73	=over 4	72	=over 4
74		73
75	=item port	74	=item port
76		75
77	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
78		78
79	Some ports allow you to register C<rcv> handlers that can match specific	79	Ports allow you to register C<rcv> handlers that can match all or just
80	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
81	will not be queued.	81	anything was listening for them or not.
82		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
83	=item port id - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
84		86
85	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
86	separator, and a port name (a printable string of unspecified format). An	88	as separator, and a port name (a printable string of unspecified
87	exception is the the node port, whose ID is identical to its node	89	format created by AnyEvent::MP).
88	reference.
89		90
90	=item node	91	=item node
91		92
92	A node is a single process containing at least one port - the node	93	A node is a single process containing at least one port - the node port,
93	port. You can send messages to node ports to find existing ports or to	94	which enables nodes to manage each other remotely, and to create new
94	create new ports, among other things.	95	ports.
95		96
96	Nodes are either private (single-process only), slaves (connected to a	97	Nodes are either public (have one or more listening ports) or private
97	master node only) or public nodes (connectable from unrelated nodes).	98	(no listening ports). Private nodes cannot talk to other private nodes
		99	currently, but all nodes can talk to public nodes.
98		100
99	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	101	Nodes is represented by (printable) strings called "node IDs".
100		102
101	A node reference is a string that either simply identifies the node (for	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
102	private and slave nodes), or contains a recipe on how to reach a given
103	node (for public nodes).
104		104
105	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	A node ID is a string that uniquely identifies the node within a
106	TCP/IP, other protocols might look different).	106	network. Depending on the configuration used, node IDs can look like a
		107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		108	doesn't interpret node IDs in any way except to uniquely identify a node.
107		109
108	Node references come in two flavours: resolved (containing only numerical	110	=item binds - C<ip:port>
109	addresses) or unresolved (where hostnames are used instead of addresses).
110		111
111	Before using an unresolved node reference in a message you first have to	112	Nodes can only talk to each other by creating some kind of connection to
112	resolve it.	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
		116	Currently, only standard C<ip:port> specifications can be used, which
		117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
		119
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
		149	=item seed IDs - C<host:port>
		150
		151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		152	TCP port) of nodes that should be used as seed nodes.
		153
		154	=item global nodes
		155
		156	An AEMP network needs a discovery service - nodes need to know how to
		157	connect to other nodes they only know by name. In addition, AEMP offers a
		158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
113		170
114	=back	171	=back
115		172
116	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
117		174
119		176
120	=cut	177	=cut
121		178
122	package AnyEvent::MP;	179	package AnyEvent::MP;
123		180
		181	use AnyEvent::MP::Config ();
124	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
125		184
126	use common::sense;	185	use common::sense;
127		186
128	use Carp ();	187	use Carp ();
129		188
130	use AE ();	189	use AE ();
		190	use Guard ();
131		191
132	use base "Exporter";	192	use base "Exporter";
133		193
134	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
135		195
136	our @EXPORT = qw(	196	our @EXPORT = qw(
137	NODE $NODE *SELF node_of _any_	197	NODE $NODE *SELF node_of after
138	resolve_node initialise_node	198	configure
139	snd rcv mon kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
140	port	200	port
		201	db_set db_del db_reg
141	);	202	);
142		203
143	our $SELF;	204	our $SELF;
144		205
145	sub _self_die() {	206	sub _self_die() {
…		…
148	kil $SELF, die => $msg;	209	kil $SELF, die => $msg;
149	}	210	}
150		211
151	=item $thisnode = NODE / $NODE	212	=item $thisnode = NODE / $NODE
152		213
153	The C<NODE> function returns, and the C<$NODE> variable contains	214	The C<NODE> function returns, and the C<$NODE> variable contains, the node
154	the noderef of the local node. The value is initialised by a call	215	ID of the node running in the current process. This value is initialised by
155	to C<become_public> or C<become_slave>, after which all local port	216	a call to C<configure>.
156	identifiers become invalid.
157		217
158	=item $noderef = node_of $port	218	=item $nodeid = node_of $port
159		219
160	Extracts and returns the noderef from a portid or a noderef.	220	Extracts and returns the node ID from a port ID or a node ID.
161		221
162	=item initialise_node $noderef, $seednode, $seednode...	222	=item configure $profile, key => value...
163		223
164	=item initialise_node "slave/", $master, $master...	224	=item configure key => value...
165		225
166	Before a node can talk to other nodes on the network it has to initialise	226	Before a node can talk to other nodes on the network (i.e. enter
167	itself - the minimum a node needs to know is it's own name, and optionally	227	"distributed mode") it has to configure itself - the minimum a node needs
168	it should know the noderefs of some other nodes in the network.	228	to know is its own name, and optionally it should know the addresses of
		229	some other nodes in the network to discover other nodes.
169		230
170	This function initialises a node - it must be called exactly once (or	231	This function configures a node - it must be called exactly once (or
171	never) before calling other AnyEvent::MP functions.	232	never) before calling other AnyEvent::MP functions.
172		233
173	All arguments are noderefs, which can be either resolved or unresolved.	234	The key/value pairs are basically the same ones as documented for the
174		235	F<aemp> command line utility (sans the set/del prefix), with two additions:
175	There are two types of networked nodes, public nodes and slave nodes:
176		236
177	=over 4	237	=over 4
178		238
179	=item public nodes	239	=item norc => $boolean (default false)
180		240
181	For public nodes, C<$noderef> must either be a (possibly unresolved)	241	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
182	noderef, in which case it will be resolved, or C<undef> (or missing), in	242	be consulted - all configuraiton options must be specified in the
183	which case the noderef will be guessed.	243	C<configure> call.
184		244
185	Afterwards, the node will bind itself on all endpoints and try to connect	245	=item force => $boolean (default false)
186	to all additional C<$seednodes> that are specified. Seednodes are optional
187	and can be used to quickly bootstrap the node into an existing network.
188		246
189	=item slave nodes	247	IF true, then the values specified in the C<configure> will take
190		248	precedence over any values configured via the rc file. The default is for
191	When the C<$noderef> is the special string C<slave/>, then the node will	249	the rc file to override any options specified in the program.
192	become a slave node. Slave nodes cannot be contacted from outside and will
193	route most of their traffic to the master node that they attach to.
194
195	At least one additional noderef is required: The node will try to connect
196	to all of them and will become a slave attached to the first node it can
197	successfully connect to.
198		250
199	=back	251	=back
200		252
201	This function will block until all nodes have been resolved and, for slave
202	nodes, until it has successfully established a connection to a master
203	server.
204
205	Example: become a public node listening on the default node.
206
207	initialise_node;
208
209	Example: become a public node, and try to contact some well-known master
210	servers to become part of the network.
211
212	initialise_node undef, "master1", "master2";
213
214	Example: become a public node listening on port C<4041>.
215
216	initialise_node 4041;
217
218	Example: become a public node, only visible on localhost port 4044.
219
220	initialise_node "locahost:4044";
221
222	Example: become a slave node to any of the specified master servers.
223
224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
225
226	=item $cv = resolve_node $noderef
227
228	Takes an unresolved node reference that may contain hostnames and
229	abbreviated IDs, resolves all of them and returns a resolved node
230	reference.
231
232	In addition to C<address:port> pairs allowed in resolved noderefs, the
233	following forms are supported:
234
235	=over 4	253	=over 4
236		254
237	=item the empty string	255	=item step 1, gathering configuration from profiles
238		256
239	An empty-string component gets resolved as if the default port (4040) was	257	The function first looks up a profile in the aemp configuration (see the
240	specified.	258	L<aemp> commandline utility). The profile name can be specified via the
		259	named C<profile> parameter or can simply be the first parameter). If it is
		260	missing, then the nodename (F<uname -n>) will be used as profile name.
241		261
242	=item naked port numbers (e.g. C<1234>)	262	The profile data is then gathered as follows:
243		263
244	These are resolved by prepending the local nodename and a colon, to be	264	First, all remaining key => value pairs (all of which are conveniently
245	further resolved.	265	undocumented at the moment) will be interpreted as configuration
		266	data. Then they will be overwritten by any values specified in the global
		267	default configuration (see the F<aemp> utility), then the chain of
		268	profiles chosen by the profile name (and any C<parent> attributes).
246		269
247	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	270	That means that the values specified in the profile have highest priority
		271	and the values specified directly via C<configure> have lowest priority,
		272	and can only be used to specify defaults.
248		273
249	These are resolved by using AnyEvent::DNS to resolve them, optionally	274	If the profile specifies a node ID, then this will become the node ID of
250	looking up SRV records for the C<aemp=4040> port, if no port was	275	this process. If not, then the profile name will be used as node ID, with
251	specified.	276	a unique randoms tring (C</%u>) appended.
		277
		278	The node ID can contain some C<%> sequences that are expanded: C<%n>
		279	is expanded to the local nodename, C<%u> is replaced by a random
		280	strign to make the node unique. For example, the F<aemp> commandline
		281	utility uses C<aemp/%n/%u> as nodename, which might expand to
		282	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		283
		284	=item step 2, bind listener sockets
		285
		286	The next step is to look up the binds in the profile, followed by binding
		287	aemp protocol listeners on all binds specified (it is possible and valid
		288	to have no binds, meaning that the node cannot be contacted form the
		289	outside. This means the node cannot talk to other nodes that also have no
		290	binds, but it can still talk to all "normal" nodes).
		291
		292	If the profile does not specify a binds list, then a default of C<*> is
		293	used, meaning the node will bind on a dynamically-assigned port on every
		294	local IP address it finds.
		295
		296	=item step 3, connect to seed nodes
		297
		298	As the last step, the seed ID list from the profile is passed to the
		299	L<AnyEvent::MP::Global> module, which will then use it to keep
		300	connectivity with at least one node at any point in time.
252		301
253	=back	302	=back
		303
		304	Example: become a distributed node using the local node name as profile.
		305	This should be the most common form of invocation for "daemon"-type nodes.
		306
		307	configure
		308
		309	Example: become a semi-anonymous node. This form is often used for
		310	commandline clients.
		311
		312	configure nodeid => "myscript/%n/%u";
		313
		314	Example: configure a node using a profile called seed, which is suitable
		315	for a seed node as it binds on all local addresses on a fixed port (4040,
		316	customary for aemp).
		317
		318	# use the aemp commandline utility
		319	# aemp profile seed binds '*:4040'
		320
		321	# then use it
		322	configure profile => "seed";
		323
		324	# or simply use aemp from the shell again:
		325	# aemp run profile seed
		326
		327	# or provide a nicer-to-remember nodeid
		328	# aemp run profile seed nodeid "$(hostname)"
254		329
255	=item $SELF	330	=item $SELF
256		331
257	Contains the current port id while executing C<rcv> callbacks or C<psub>	332	Contains the current port id while executing C<rcv> callbacks or C<psub>
258	blocks.	333	blocks.
259		334
260	=item SELF, %SELF, @SELF...	335	=item *SELF, SELF, %SELF, @SELF...
261		336
262	Due to some quirks in how perl exports variables, it is impossible to	337	Due to some quirks in how perl exports variables, it is impossible to
263	just export C<$SELF>, all the symbols called C<SELF> are exported by this	338	just export C<$SELF>, all the symbols named C<SELF> are exported by this
264	module, but only C<$SELF> is currently used.	339	module, but only C<$SELF> is currently used.
265		340
266	=item snd $port, type => @data	341	=item snd $port, type => @data
267		342
268	=item snd $port, @msg	343	=item snd $port, @msg
269		344
270	Send the given message to the given port ID, which can identify either	345	Send the given message to the given port, which can identify either a
271	a local or a remote port, and can be either a string or soemthignt hat	346	local or a remote port, and must be a port ID.
272	stringifies a sa port ID (such as a port object :).
273		347
274	While the message can be about anything, it is highly recommended to use a	348	While the message can be almost anything, it is highly recommended to
275	string as first element (a portid, or some word that indicates a request	349	use a string as first element (a port ID, or some word that indicates a
276	type etc.).	350	request type etc.) and to consist if only simple perl values (scalars,
		351	arrays, hashes) - if you think you need to pass an object, think again.
277		352
278	The message data effectively becomes read-only after a call to this	353	The message data logically becomes read-only after a call to this
279	function: modifying any argument is not allowed and can cause many	354	function: modifying any argument (or values referenced by them) is
280	problems.	355	forbidden, as there can be considerable time between the call to C<snd>
		356	and the time the message is actually being serialised - in fact, it might
		357	never be copied as within the same process it is simply handed to the
		358	receiving port.
281		359
282	The type of data you can transfer depends on the transport protocol: when	360	The type of data you can transfer depends on the transport protocol: when
283	JSON is used, then only strings, numbers and arrays and hashes consisting	361	JSON is used, then only strings, numbers and arrays and hashes consisting
284	of those are allowed (no objects). When Storable is used, then anything	362	of those are allowed (no objects). When Storable is used, then anything
285	that Storable can serialise and deserialise is allowed, and for the local	363	that Storable can serialise and deserialise is allowed, and for the local
286	node, anything can be passed.	364	node, anything can be passed. Best rely only on the common denominator of
		365	these.
287		366
288	=item $local_port = port	367	=item $local_port = port
289		368
290	Create a new local port object that can be used either as a pattern	369	Create a new local port object and returns its port ID. Initially it has
291	matching port ("full port") or a single-callback port ("miniport"),	370	no callbacks set and will throw an error when it receives messages.
292	depending on how C<rcv> callbacks are bound to the object.
293		371
294	=item $port = port { my @msg = @_; $finished }	372	=item $local_port = port { my @msg = @_ }
295		373
296	Creates a "miniport", that is, a very lightweight port without any pattern	374	Creates a new local port, and returns its ID. Semantically the same as
297	matching behind it, and returns its ID. Semantically the same as creating
298	a port and calling C<rcv $port, $callback> on it.	375	creating a port and calling C<rcv $port, $callback> on it.
299		376
300	The block will be called for every message received on the port. When the	377	The block will be called for every message received on the port, with the
301	callback returns a true value its job is considered "done" and the port	378	global variable C<$SELF> set to the port ID. Runtime errors will cause the
302	will be destroyed. Otherwise it will stay alive.	379	port to be C<kil>ed. The message will be passed as-is, no extra argument
		380	(i.e. no port ID) will be passed to the callback.
303		381
304	The message will be passed as-is, no extra argument (i.e. no port id) will	382	If you want to stop/destroy the port, simply C<kil> it:
305	be passed to the callback.
306		383
307	If you need the local port id in the callback, this works nicely:	384	my $port = port {
308		385	my @msg = @_;
309	my $port; $port = port {	386	...
310	snd $otherport, reply => $port;	387	kil $SELF;
311	};	388	};
312		389
313	=cut	390	=cut
314		391
315	sub rcv($@);	392	sub rcv($@);
316		393
		394	sub _kilme {
		395	die "received message on port without callback";
		396	}
		397
317	sub port(;&) {	398	sub port(;&) {
318	my $id = "$UNIQ." . $ID++;	399	my $id = $UNIQ . ++$ID;
319	my $port = "$NODE#$id";	400	my $port = "$NODE#$id";
320		401
321	if (@_) {	402	rcv $port, shift \|\| \&_kilme;
322	rcv $port, shift;
323	} else {
324	$PORT{$id} = sub { }; # nop
325	}
326		403
327	$port	404	$port
328	}	405	}
329		406
330	=item reg $port, $name
331
332	=item reg $name
333
334	Registers the given port (or C<$SELF><<< if missing) under the name
335	C<$name>. If the name already exists it is replaced.
336
337	A port can only be registered under one well known name.
338
339	A port automatically becomes unregistered when it is killed.
340
341	=cut
342
343	sub reg(@) {
344	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
345
346	$REG{$_[0]} = $port;
347	}
348
349	=item rcv $port, $callback->(@msg)	407	=item rcv $local_port, $callback->(@msg)
350		408
351	Replaces the callback on the specified miniport (after converting it to	409	Replaces the default callback on the specified port. There is no way to
352	one if required).	410	remove the default callback: use C<sub { }> to disable it, or better
353		411	C<kil> the port when it is no longer needed.
354	=item rcv $port, tagstring => $callback->(@msg), ...
355
356	=item rcv $port, $smartmatch => $callback->(@msg), ...
357
358	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
359
360	Register callbacks to be called on matching messages on the given full
361	port (after converting it to one if required) and return the port.
362
363	The callback has to return a true value when its work is done, after
364	which is will be removed, or a false value in which case it will stay
365	registered.
366		412
367	The global C<$SELF> (exported by this module) contains C<$port> while	413	The global C<$SELF> (exported by this module) contains C<$port> while
368	executing the callback.	414	executing the callback. Runtime errors during callback execution will
		415	result in the port being C<kil>ed.
369		416
370	Runtime errors during callback execution will result in the port being	417	The default callback received all messages not matched by a more specific
371	C<kil>ed.	418	C<tag> match.
372		419
373	If the match is an array reference, then it will be matched against the	420	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
374	first elements of the message, otherwise only the first element is being
375	matched.
376		421
377	Any element in the match that is specified as C<_any_> (a function	422	Register (or replace) callbacks to be called on messages starting with the
378	exported by this module) matches any single element of the message.	423	given tag on the given port (and return the port), or unregister it (when
		424	C<$callback> is C<$undef> or missing). There can only be one callback
		425	registered for each tag.
379		426
380	While not required, it is highly recommended that the first matching	427	The original message will be passed to the callback, after the first
381	element is a string identifying the message. The one-string-only match is	428	element (the tag) has been removed. The callback will use the same
382	also the most efficient match (by far).	429	environment as the default callback (see above).
383		430
384	Example: create a port and bind receivers on it in one go.	431	Example: create a port and bind receivers on it in one go.
385		432
386	my $port = rcv port,	433	my $port = rcv port,
387	msg1 => sub { ...; 0 },	434	msg1 => sub { ... },
388	msg2 => sub { ...; 0 },	435	msg2 => sub { ... },
389	;	436	;
390		437
391	Example: create a port, bind receivers and send it in a message elsewhere	438	Example: create a port, bind receivers and send it in a message elsewhere
392	in one go:	439	in one go:
393		440
394	snd $otherport, reply =>	441	snd $otherport, reply =>
395	rcv port,	442	rcv port,
396	msg1 => sub { ...; 0 },	443	msg1 => sub { ... },
397	...	444	...
398	;	445	;
399		446
		447	Example: temporarily register a rcv callback for a tag matching some port
		448	(e.g. for an rpc reply) and unregister it after a message was received.
		449
		450	rcv $port, $otherport => sub {
		451	my @reply = @_;
		452
		453	rcv $SELF, $otherport;
		454	};
		455
400	=cut	456	=cut
401		457
402	sub rcv($@) {	458	sub rcv($@) {
403	my $port = shift;	459	my $port = shift;
404	my ($noderef, $portid) = split /#/, $port, 2;	460	my ($nodeid, $portid) = split /#/, $port, 2;
405		461
406	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	462	$NODE{$nodeid} == $NODE{""}
407	or Carp::croak "$port: rcv can only be called on local ports, caught";	463	or Carp::croak "$port: rcv can only be called on local ports, caught";
408		464
409	if (@_ == 1) {	465	while (@_) {
		466	if (ref $_[0]) {
		467	if (my $self = $PORT_DATA{$portid}) {
		468	"AnyEvent::MP::Port" eq ref $self
		469	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		470
		471	$self->[0] = shift;
		472	} else {
410	my $cb = shift;	473	my $cb = shift;
411	delete $PORT_DATA{$portid};
412	$PORT{$portid} = sub {	474	$PORT{$portid} = sub {
413	local $SELF = $port;	475	local $SELF = $port;
414	eval {	476	eval { &$cb }; _self_die if $@;
415	&$cb	477	};
416	and kil $port;
417	};	478	}
418	_self_die if $@;	479	} elsif (defined $_[0]) {
419	};
420	} else {
421	my $self = $PORT_DATA{$portid} \|\|= do {	480	my $self = $PORT_DATA{$portid} \|\|= do {
422	my $self = bless {	481	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
423	id => $port,
424	}, "AnyEvent::MP::Port";
425		482
426	$PORT{$portid} = sub {	483	$PORT{$portid} = sub {
427	local $SELF = $port;	484	local $SELF = $port;
428		485
429	eval {
430	for (@{ $self->{rc0}{$_[0]} }) {	486	if (my $cb = $self->[1]{$_[0]}) {
431	$_ && &{$_->[0]}	487	shift;
432	&& undef $_;	488	eval { &$cb }; _self_die if $@;
433	}	489	} else {
434
435	for (@{ $self->{rcv}{$_[0]} }) {
436	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
437	&& &{$_->[0]}	490	&{ $self->[0] };
438	&& undef $_;
439	}
440
441	for (@{ $self->{any} }) {
442	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
443	&& &{$_->[0]}
444	&& undef $_;
445	}	491	}
446	};	492	};
447	_self_die if $@;	493
		494	$self
448	};	495	};
449		496
450	$self
451	};
452
453	"AnyEvent::MP::Port" eq ref $self	497	"AnyEvent::MP::Port" eq ref $self
454	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	498	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
455		499
456	while (@_) {
457	my ($match, $cb) = splice @_, 0, 2;	500	my ($tag, $cb) = splice @_, 0, 2;
458		501
459	if (!ref $match) {	502	if (defined $cb) {
460	push @{ $self->{rc0}{$match} }, [$cb];	503	$self->[1]{$tag} = $cb;
461	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
462	my ($type, @match) = @$match;
463	@match
464	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
465	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
466	} else {	504	} else {
467	push @{ $self->{any} }, [$cb, $match];	505	delete $self->[1]{$tag};
468	}	506	}
469	}	507	}
470	}	508	}
471		509
472	$port	510	$port
473	}	511	}
474		512
		513	=item peval $port, $coderef[, @args]
		514
		515	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		516	when the code throews an exception the C<$port> will be killed.
		517
		518	Any remaining args will be passed to the callback. Any return values will
		519	be returned to the caller.
		520
		521	This is useful when you temporarily want to execute code in the context of
		522	a port.
		523
		524	Example: create a port and run some initialisation code in it's context.
		525
		526	my $port = port { ... };
		527
		528	peval $port, sub {
		529	init
		530	or die "unable to init";
		531	};
		532
		533	=cut
		534
		535	sub peval($$) {
		536	local $SELF = shift;
		537	my $cb = shift;
		538
		539	if (wantarray) {
		540	my @res = eval { &$cb };
		541	_self_die if $@;
		542	@res
		543	} else {
		544	my $res = eval { &$cb };
		545	_self_die if $@;
		546	$res
		547	}
		548	}
		549
475	=item $closure = psub { BLOCK }	550	=item $closure = psub { BLOCK }
476		551
477	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	552	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
478	closure is executed, sets up the environment in the same way as in C<rcv>	553	closure is executed, sets up the environment in the same way as in C<rcv>
479	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	554	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		555
		556	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		557	BLOCK }, @_ } >>.
480		558
481	This is useful when you register callbacks from C<rcv> callbacks:	559	This is useful when you register callbacks from C<rcv> callbacks:
482		560
483	rcv delayed_reply => sub {	561	rcv delayed_reply => sub {
484	my ($delay, @reply) = @_;	562	my ($delay, @reply) = @_;
…		…
508	$res	586	$res
509	}	587	}
510	}	588	}
511	}	589	}
512		590
513	=item $guard = mon $port, $cb->(@reason)	591	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
514		592
515	=item $guard = mon $port, $rcvport	593	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
516		594
517	=item $guard = mon $port	595	=item $guard = mon $port # kill $SELF when $port dies
518		596
519	=item $guard = mon $port, $rcvport, @msg	597	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
520		598
521	Monitor the given port and do something when the port is killed or	599	Monitor the given port and do something when the port is killed or
522	messages to it were lost, and optionally return a guard that can be used	600	messages to it were lost, and optionally return a guard that can be used
523	to stop monitoring again.	601	to stop monitoring again.
524
525	C<mon> effectively guarantees that, in the absence of hardware failures,
526	that after starting the monitor, either all messages sent to the port
527	will arrive, or the monitoring action will be invoked after possible
528	message loss has been detected. No messages will be lost "in between"
529	(after the first lost message no further messages will be received by the
530	port). After the monitoring action was invoked, further messages might get
531	delivered again.
532		602
533	In the first form (callback), the callback is simply called with any	603	In the first form (callback), the callback is simply called with any
534	number of C<@reason> elements (no @reason means that the port was deleted	604	number of C<@reason> elements (no @reason means that the port was deleted
535	"normally"). Note also that I<< the callback B<must> never die >>, so use	605	"normally"). Note also that I<< the callback B<must> never die >>, so use
536	C<eval> if unsure.	606	C<eval> if unsure.
537		607
538	In the second form (another port given), the other port (C<$rcvport>)	608	In the second form (another port given), the other port (C<$rcvport>)
539	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	609	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
540	"normal" kils nothing happens, while under all other conditions, the other	610	"normal" kils nothing happens, while under all other conditions, the other
541	port is killed with the same reason.	611	port is killed with the same reason.
542		612
543	The third form (kill self) is the same as the second form, except that	613	The third form (kill self) is the same as the second form, except that
544	C<$rvport> defaults to C<$SELF>.	614	C<$rvport> defaults to C<$SELF>.
545		615
546	In the last form (message), a message of the form C<@msg, @reason> will be	616	In the last form (message), a message of the form C<@msg, @reason> will be
547	C<snd>.	617	C<snd>.
		618
		619	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		620	alert was raised), they are removed and will not trigger again.
548		621
549	As a rule of thumb, monitoring requests should always monitor a port from	622	As a rule of thumb, monitoring requests should always monitor a port from
550	a local port (or callback). The reason is that kill messages might get	623	a local port (or callback). The reason is that kill messages might get
551	lost, just like any other message. Another less obvious reason is that	624	lost, just like any other message. Another less obvious reason is that
552	even monitoring requests can get lost (for exmaple, when the connection	625	even monitoring requests can get lost (for example, when the connection
553	to the other node goes down permanently). When monitoring a port locally	626	to the other node goes down permanently). When monitoring a port locally
554	these problems do not exist.	627	these problems do not exist.
555		628
		629	C<mon> effectively guarantees that, in the absence of hardware failures,
		630	after starting the monitor, either all messages sent to the port will
		631	arrive, or the monitoring action will be invoked after possible message
		632	loss has been detected. No messages will be lost "in between" (after
		633	the first lost message no further messages will be received by the
		634	port). After the monitoring action was invoked, further messages might get
		635	delivered again.
		636
		637	Inter-host-connection timeouts and monitoring depend on the transport
		638	used. The only transport currently implemented is TCP, and AnyEvent::MP
		639	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		640	non-idle connection, and usually around two hours for idle connections).
		641
		642	This means that monitoring is good for program errors and cleaning up
		643	stuff eventually, but they are no replacement for a timeout when you need
		644	to ensure some maximum latency.
		645
556	Example: call a given callback when C<$port> is killed.	646	Example: call a given callback when C<$port> is killed.
557		647
558	mon $port, sub { warn "port died because of <@_>\n" };	648	mon $port, sub { warn "port died because of <@_>\n" };
559		649
560	Example: kill ourselves when C<$port> is killed abnormally.	650	Example: kill ourselves when C<$port> is killed abnormally.
…		…
566	mon $port, $self => "restart";	656	mon $port, $self => "restart";
567		657
568	=cut	658	=cut
569		659
570	sub mon {	660	sub mon {
571	my ($noderef, $port) = split /#/, shift, 2;	661	my ($nodeid, $port) = split /#/, shift, 2;
572		662
573	my $node = $NODE{$noderef} \|\| add_node $noderef;	663	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
574		664
575	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	665	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
576		666
577	unless (ref $cb) {	667	unless (ref $cb) {
578	if (@_) {	668	if (@_) {
…		…
587	}	677	}
588		678
589	$node->monitor ($port, $cb);	679	$node->monitor ($port, $cb);
590		680
591	defined wantarray	681	defined wantarray
592	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	682	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
593	}	683	}
594		684
595	=item $guard = mon_guard $port, $ref, $ref...	685	=item $guard = mon_guard $port, $ref, $ref...
596		686
597	Monitors the given C<$port> and keeps the passed references. When the port	687	Monitors the given C<$port> and keeps the passed references. When the port
598	is killed, the references will be freed.	688	is killed, the references will be freed.
599		689
600	Optionally returns a guard that will stop the monitoring.	690	Optionally returns a guard that will stop the monitoring.
601		691
602	This function is useful when you create e.g. timers or other watchers and	692	This function is useful when you create e.g. timers or other watchers and
603	want to free them when the port gets killed:	693	want to free them when the port gets killed (note the use of C<psub>):
604		694
605	$port->rcv (start => sub {	695	$port->rcv (start => sub {
606	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	696	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
607	undef $timer if 0.9 < rand;	697	undef $timer if 0.9 < rand;
608	});	698	});
609	});	699	});
610		700
611	=cut	701	=cut
…		…
620		710
621	=item kil $port[, @reason]	711	=item kil $port[, @reason]
622		712
623	Kill the specified port with the given C<@reason>.	713	Kill the specified port with the given C<@reason>.
624		714
625	If no C<@reason> is specified, then the port is killed "normally" (linked	715	If no C<@reason> is specified, then the port is killed "normally" -
626	ports will not be kileld, or even notified).	716	monitor callback will be invoked, but the kil will not cause linked ports
		717	(C<mon $mport, $lport> form) to get killed.
627		718
628	Otherwise, linked ports get killed with the same reason (second form of	719	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
629	C<mon>, see below).	720	form) get killed with the same reason.
630		721
631	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	722	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
632	will be reported as reason C<< die => $@ >>.	723	will be reported as reason C<< die => $@ >>.
633		724
634	Transport/communication errors are reported as C<< transport_error =>	725	Transport/communication errors are reported as C<< transport_error =>
…		…
639	=item $port = spawn $node, $initfunc[, @initdata]	730	=item $port = spawn $node, $initfunc[, @initdata]
640		731
641	Creates a port on the node C<$node> (which can also be a port ID, in which	732	Creates a port on the node C<$node> (which can also be a port ID, in which
642	case it's the node where that port resides).	733	case it's the node where that port resides).
643		734
644	The port ID of the newly created port is return immediately, and it is	735	The port ID of the newly created port is returned immediately, and it is
645	permissible to immediately start sending messages or monitor the port.	736	possible to immediately start sending messages or to monitor the port.
646		737
647	After the port has been created, the init function is	738	After the port has been created, the init function is called on the remote
648	called. This function must be a fully-qualified function name	739	node, in the same context as a C<rcv> callback. This function must be a
649	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	740	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
650	program, use C<::name>.	741	specify a function in the main program, use C<::name>.
651		742
652	If the function doesn't exist, then the node tries to C<require>	743	If the function doesn't exist, then the node tries to C<require>
653	the package, then the package above the package and so on (e.g.	744	the package, then the package above the package and so on (e.g.
654	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	745	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
655	exists or it runs out of package names.	746	exists or it runs out of package names.
656		747
657	The init function is then called with the newly-created port as context	748	The init function is then called with the newly-created port as context
658	object (C<$SELF>) and the C<@initdata> values as arguments.	749	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		750	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		751	the port might not get created.
659		752
660	A common idiom is to pass your own port, monitor the spawned port, and	753	A common idiom is to pass a local port, immediately monitor the spawned
661	in the init function, monitor the original port. This two-way monitoring	754	port, and in the remote init function, immediately monitor the passed
662	ensures that both ports get cleaned up when there is a problem.	755	local port. This two-way monitoring ensures that both ports get cleaned up
		756	when there is a problem.
		757
		758	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		759	caller before C<spawn> returns (by delaying invocation when spawn is
		760	called for the local node).
663		761
664	Example: spawn a chat server port on C<$othernode>.	762	Example: spawn a chat server port on C<$othernode>.
665		763
666	# this node, executed from within a port context:	764	# this node, executed from within a port context:
667	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	765	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
682		780
683	sub _spawn {	781	sub _spawn {
684	my $port = shift;	782	my $port = shift;
685	my $init = shift;	783	my $init = shift;
686		784
		785	# rcv will create the actual port
687	local $SELF = "$NODE#$port";	786	local $SELF = "$NODE#$port";
688	eval {	787	eval {
689	&{ load_func $init }	788	&{ load_func $init }
690	};	789	};
691	_self_die if $@;	790	_self_die if $@;
692	}	791	}
693		792
694	sub spawn(@) {	793	sub spawn(@) {
695	my ($noderef, undef) = split /#/, shift, 2;	794	my ($nodeid, undef) = split /#/, shift, 2;
696		795
697	my $id = "$RUNIQ." . $ID++;	796	my $id = $RUNIQ . ++$ID;
698		797
699	$_[0] =~ /::/	798	$_[0] =~ /::/
700	or Carp::croak "spawn init function must be a fully-qualified name, caught";	799	or Carp::croak "spawn init function must be a fully-qualified name, caught";
701		800
702	($NODE{$noderef} \|\| add_node $noderef)	801	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
703	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
704		802
705	"$noderef#$id"	803	"$nodeid#$id"
706	}	804	}
707		805
		806
		807	=item after $timeout, @msg
		808
		809	=item after $timeout, $callback
		810
		811	Either sends the given message, or call the given callback, after the
		812	specified number of seconds.
		813
		814	This is simply a utility function that comes in handy at times - the
		815	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		816	so it may go away in the future.
		817
		818	=cut
		819
		820	sub after($@) {
		821	my ($timeout, @action) = @_;
		822
		823	my $t; $t = AE::timer $timeout, 0, sub {
		824	undef $t;
		825	ref $action[0]
		826	? $action[0]()
		827	: snd @action;
		828	};
		829	}
		830
		831	=item cal $port, @msg, $callback[, $timeout]
		832
		833	A simple form of RPC - sends a message to the given C<$port> with the
		834	given contents (C<@msg>), but adds a reply port to the message.
		835
		836	The reply port is created temporarily just for the purpose of receiving
		837	the reply, and will be C<kil>ed when no longer needed.
		838
		839	A reply message sent to the port is passed to the C<$callback> as-is.
		840
		841	If an optional time-out (in seconds) is given and it is not C<undef>,
		842	then the callback will be called without any arguments after the time-out
		843	elapsed and the port is C<kil>ed.
		844
		845	If no time-out is given (or it is C<undef>), then the local port will
		846	monitor the remote port instead, so it eventually gets cleaned-up.
		847
		848	Currently this function returns the temporary port, but this "feature"
		849	might go in future versions unless you can make a convincing case that
		850	this is indeed useful for something.
		851
		852	=cut
		853
		854	sub cal(@) {
		855	my $timeout = ref $_[-1] ? undef : pop;
		856	my $cb = pop;
		857
		858	my $port = port {
		859	undef $timeout;
		860	kil $SELF;
		861	&$cb;
		862	};
		863
		864	if (defined $timeout) {
		865	$timeout = AE::timer $timeout, 0, sub {
		866	undef $timeout;
		867	kil $port;
		868	$cb->();
		869	};
		870	} else {
		871	mon $_[0], sub {
		872	kil $port;
		873	$cb->();
		874	};
		875	}
		876
		877	push @_, $port;
		878	&snd;
		879
		880	$port
		881	}
		882
708	=back	883	=back
709		884
710	=head1 NODE MESSAGES	885	=head1 DISTRIBUTED DATABASE
711		886
712	Nodes understand the following messages sent to them. Many of them take	887	AnyEvent::MP comes with a simple distributed database. The database will
713	arguments called C<@reply>, which will simply be used to compose a reply	888	be mirrored asynchronously at all global nodes. Other nodes bind to one of
714	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	889	the global nodes for their needs.
715	the remaining arguments are simply the message data.
716		890
717	While other messages exist, they are not public and subject to change.	891	The database consists of a two-level hash - a hash contains a hash which
		892	contains values.
718		893
		894	The top level hash key is called "family", and the second-level hash key
		895	is called "subkey" or simply "key".
		896
		897	The family must be alphanumeric, i.e. start with a letter and consist
		898	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		899	pretty much like Perl module names.
		900
		901	As the family namespace is global, it is recommended to prefix family names
		902	with the name of the application or module using it.
		903
		904	The subkeys must be non-empty strings, with no further restrictions.
		905
		906	The values should preferably be strings, but other perl scalars should
		907	work as well (such as undef, arrays and hashes).
		908
		909	Every database entry is owned by one node - adding the same family/subkey
		910	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		911	but the result might be nondeterministic, i.e. the key might have
		912	different values on different nodes.
		913
		914	Different subkeys in the same family can be owned by different nodes
		915	without problems, and in fact, this is the common method to create worker
		916	pools. For example, a worker port for image scaling might do this:
		917
		918	db_set my_image_scalers => $port;
		919
		920	And clients looking for an image scaler will want to get the
		921	C<my_image_scalers> keys:
		922
		923	db_keys "my_image_scalers" => 60 => sub {
		924	#d##TODO#
		925
719	=over 4	926	=over
720		927
721	=cut	928	=item db_set $family => $subkey [=> $value]
722		929
723	=item lookup => $name, @reply	930	Sets (or replaces) a key to the database - if C<$value> is omitted,
		931	C<undef> is used instead.
724		932
725	Replies with the port ID of the specified well-known port, or C<undef>.	933	=item db_del $family => $subkey
726		934
727	=item devnull => ...	935	Deletes a key from the database.
728		936
729	Generic data sink/CPU heat conversion.	937	=item $guard = db_reg $family => $subkey [=> $value]
730		938
731	=item relay => $port, @msg	939	Sets the key on the database and returns a guard. When the guard is
		940	destroyed, the key is deleted from the database. If C<$value> is missing,
		941	then C<undef> is used.
732		942
733	Simply forwards the message to the given port.	943	=cut
734
735	=item eval => $string[ @reply]
736
737	Evaluates the given string. If C<@reply> is given, then a message of the
738	form C<@reply, $@, @evalres> is sent.
739
740	Example: crash another node.
741
742	snd $othernode, eval => "exit";
743
744	=item time => @reply
745
746	Replies the the current node time to C<@reply>.
747
748	Example: tell the current node to send the current time to C<$myport> in a
749	C<timereply> message.
750
751	snd $NODE, time => $myport, timereply => 1, 2;
752	# => snd $myport, timereply => 1, 2, <time>
753		944
754	=back	945	=back
755		946
756	=head1 AnyEvent::MP vs. Distributed Erlang	947	=head1 AnyEvent::MP vs. Distributed Erlang
757		948
758	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	949	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
759	== aemp node, Erlang process == aemp port), so many of the documents and	950	== aemp node, Erlang process == aemp port), so many of the documents and
760	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	951	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
761	sample:	952	sample:
762		953
763	http://www.Erlang.se/doc/programming_rules.shtml	954	http://www.erlang.se/doc/programming_rules.shtml
764	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	955	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
765	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	956	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
766	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	957	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
767		958
768	Despite the similarities, there are also some important differences:	959	Despite the similarities, there are also some important differences:
769		960
770	=over 4	961	=over 4
771		962
772	=item * Node references contain the recipe on how to contact them.	963	=item * Node IDs are arbitrary strings in AEMP.
773		964
774	Erlang relies on special naming and DNS to work everywhere in the	965	Erlang relies on special naming and DNS to work everywhere in the same
775	same way. AEMP relies on each node knowing it's own address(es), with	966	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
776	convenience functionality.	967	configuration or DNS), and possibly the addresses of some seed nodes, but
		968	will otherwise discover other nodes (and their IDs) itself.
777		969
778	This means that AEMP requires a less tightly controlled environment at the	970	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
779	cost of longer node references and a slightly higher management overhead.	971	uses "local ports are like remote ports".
		972
		973	The failure modes for local ports are quite different (runtime errors
		974	only) then for remote ports - when a local port dies, you I<know> it dies,
		975	when a connection to another node dies, you know nothing about the other
		976	port.
		977
		978	Erlang pretends remote ports are as reliable as local ports, even when
		979	they are not.
		980
		981	AEMP encourages a "treat remote ports differently" philosophy, with local
		982	ports being the special case/exception, where transport errors cannot
		983	occur.
780		984
781	=item * Erlang uses processes and a mailbox, AEMP does not queue.	985	=item * Erlang uses processes and a mailbox, AEMP does not queue.
782		986
783	Erlang uses processes that selctively receive messages, and therefore	987	Erlang uses processes that selectively receive messages out of order, and
784	needs a queue. AEMP is event based, queuing messages would serve no useful	988	therefore needs a queue. AEMP is event based, queuing messages would serve
785	purpose.	989	no useful purpose. For the same reason the pattern-matching abilities
		990	of AnyEvent::MP are more limited, as there is little need to be able to
		991	filter messages without dequeuing them.
786		992
787	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	993	This is not a philosophical difference, but simply stems from AnyEvent::MP
		994	being event-based, while Erlang is process-based.
		995
		996	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		997	top of AEMP and Coro threads.
788		998
789	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	999	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
790		1000
791	Sending messages in Erlang is synchronous and blocks the process. AEMP	1001	Sending messages in Erlang is synchronous and blocks the process until
792	sends are immediate, connection establishment is handled in the	1002	a conenction has been established and the message sent (and so does not
793	background.	1003	need a queue that can overflow). AEMP sends return immediately, connection
		1004	establishment is handled in the background.
794		1005
795	=item * Erlang can silently lose messages, AEMP cannot.	1006	=item * Erlang suffers from silent message loss, AEMP does not.
796		1007
797	Erlang makes few guarantees on messages delivery - messages can get lost	1008	Erlang implements few guarantees on messages delivery - messages can get
798	without any of the processes realising it (i.e. you send messages a, b,	1009	lost without any of the processes realising it (i.e. you send messages a,
799	and c, and the other side only receives messages a and c).	1010	b, and c, and the other side only receives messages a and c).
800		1011
801	AEMP guarantees correct ordering, and the guarantee that there are no	1012	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1013	guarantee that after one message is lost, all following ones sent to the
		1014	same port are lost as well, until monitoring raises an error, so there are
802	holes in the message sequence.	1015	no silent "holes" in the message sequence.
803		1016
804	=item * In Erlang, processes can be declared dead and later be found to be	1017	If you want your software to be very reliable, you have to cope with
805	alive.	1018	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
806		1019	simply tries to work better in common error cases, such as when a network
807	In Erlang it can happen that a monitored process is declared dead and	1020	link goes down.
808	linked processes get killed, but later it turns out that the process is
809	still alive - and can receive messages.
810
811	In AEMP, when port monitoring detects a port as dead, then that port will
812	eventually be killed - it cannot happen that a node detects a port as dead
813	and then later sends messages to it, finding it is still alive.
814		1021
815	=item * Erlang can send messages to the wrong port, AEMP does not.	1022	=item * Erlang can send messages to the wrong port, AEMP does not.
816		1023
817	In Erlang it is quite possible that a node that restarts reuses a process	1024	In Erlang it is quite likely that a node that restarts reuses an Erlang
818	ID known to other nodes for a completely different process, causing	1025	process ID known to other nodes for a completely different process,
819	messages destined for that process to end up in an unrelated process.	1026	causing messages destined for that process to end up in an unrelated
		1027	process.
820		1028
821	AEMP never reuses port IDs, so old messages or old port IDs floating	1029	AEMP does not reuse port IDs, so old messages or old port IDs floating
822	around in the network will not be sent to an unrelated port.	1030	around in the network will not be sent to an unrelated port.
823		1031
824	=item * Erlang uses unprotected connections, AEMP uses secure	1032	=item * Erlang uses unprotected connections, AEMP uses secure
825	authentication and can use TLS.	1033	authentication and can use TLS.
826		1034
827	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1035	AEMP can use a proven protocol - TLS - to protect connections and
828	securely authenticate nodes.	1036	securely authenticate nodes.
829		1037
830	=item * The AEMP protocol is optimised for both text-based and binary	1038	=item * The AEMP protocol is optimised for both text-based and binary
831	communications.	1039	communications.
832		1040
833	The AEMP protocol, unlike the Erlang protocol, supports both	1041	The AEMP protocol, unlike the Erlang protocol, supports both programming
834	language-independent text-only protocols (good for debugging) and binary,	1042	language independent text-only protocols (good for debugging), and binary,
835	language-specific serialisers (e.g. Storable).	1043	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1044	used, the protocol is actually completely text-based.
836		1045
837	It has also been carefully designed to be implementable in other languages	1046	It has also been carefully designed to be implementable in other languages
838	with a minimum of work while gracefully degrading fucntionality to make the	1047	with a minimum of work while gracefully degrading functionality to make the
839	protocol simple.	1048	protocol simple.
840		1049
841	=item * AEMP has more flexible monitoring options than Erlang.	1050	=item * AEMP has more flexible monitoring options than Erlang.
842		1051
843	In Erlang, you can chose to receive I<all> exit signals as messages	1052	In Erlang, you can chose to receive I<all> exit signals as messages or
844	or I<none>, there is no in-between, so monitoring single processes is	1053	I<none>, there is no in-between, so monitoring single Erlang processes is
845	difficult to implement. Monitoring in AEMP is more flexible than in	1054	difficult to implement.
846	Erlang, as one can choose between automatic kill, exit message or callback	1055
847	on a per-process basis.	1056	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1057	between automatic kill, exit message or callback on a per-port basis.
848		1058
849	=item * Erlang tries to hide remote/local connections, AEMP does not.	1059	=item * Erlang tries to hide remote/local connections, AEMP does not.
850		1060
851	Monitoring in Erlang is not an indicator of process death/crashes,	1061	Monitoring in Erlang is not an indicator of process death/crashes, in the
852	as linking is (except linking is unreliable in Erlang).	1062	same way as linking is (except linking is unreliable in Erlang).
853		1063
854	In AEMP, you don't "look up" registered port names or send to named ports	1064	In AEMP, you don't "look up" registered port names or send to named ports
855	that might or might not be persistent. Instead, you normally spawn a port	1065	that might or might not be persistent. Instead, you normally spawn a port
856	on the remote node. The init function monitors the you, and you monitor	1066	on the remote node. The init function monitors you, and you monitor the
857	the remote port. Since both monitors are local to the node, they are much	1067	remote port. Since both monitors are local to the node, they are much more
858	more reliable.	1068	reliable (no need for C<spawn_link>).
859		1069
860	This also saves round-trips and avoids sending messages to the wrong port	1070	This also saves round-trips and avoids sending messages to the wrong port
861	(hard to do in Erlang).	1071	(hard to do in Erlang).
862		1072
863	=back	1073	=back
864		1074
865	=head1 RATIONALE	1075	=head1 RATIONALE
866		1076
867	=over 4	1077	=over 4
868		1078
869	=item Why strings for ports and noderefs, why not objects?	1079	=item Why strings for port and node IDs, why not objects?
870		1080
871	We considered "objects", but found that the actual number of methods	1081	We considered "objects", but found that the actual number of methods
872	thatc an be called are very low. Since port IDs and noderefs travel over	1082	that can be called are quite low. Since port and node IDs travel over
873	the network frequently, the serialising/deserialising would add lots of	1083	the network frequently, the serialising/deserialising would add lots of
874	overhead, as well as having to keep a proxy object.	1084	overhead, as well as having to keep a proxy object everywhere.
875		1085
876	Strings can easily be printed, easily serialised etc. and need no special	1086	Strings can easily be printed, easily serialised etc. and need no special
877	procedures to be "valid".	1087	procedures to be "valid".
878		1088
879	And a a miniport consists of a single closure stored in a global hash - it	1089	And as a result, a port with just a default receiver consists of a single
880	can't become much cheaper.	1090	code reference stored in a global hash - it can't become much cheaper.
881		1091
882	=item Why favour JSON, why not real serialising format such as Storable?	1092	=item Why favour JSON, why not a real serialising format such as Storable?
883		1093
884	In fact, any AnyEvent::MP node will happily accept Storable as framing	1094	In fact, any AnyEvent::MP node will happily accept Storable as framing
885	format, but currently there is no way to make a node use Storable by	1095	format, but currently there is no way to make a node use Storable by
886	default.	1096	default (although all nodes will accept it).
887		1097
888	The default framing protocol is JSON because a) JSON::XS is many times	1098	The default framing protocol is JSON because a) JSON::XS is many times
889	faster for small messages and b) most importantly, after years of	1099	faster for small messages and b) most importantly, after years of
890	experience we found that object serialisation is causing more problems	1100	experience we found that object serialisation is causing more problems
891	than it gains: Just like function calls, objects simply do not travel	1101	than it solves: Just like function calls, objects simply do not travel
892	easily over the network, mostly because they will always be a copy, so you	1102	easily over the network, mostly because they will always be a copy, so you
893	always have to re-think your design.	1103	always have to re-think your design.
894		1104
895	Keeping your messages simple, concentrating on data structures rather than	1105	Keeping your messages simple, concentrating on data structures rather than
896	objects, will keep your messages clean, tidy and efficient.	1106	objects, will keep your messages clean, tidy and efficient.
897		1107
898	=back	1108	=back
899		1109
900	=head1 SEE ALSO	1110	=head1 SEE ALSO
901		1111
		1112	L<AnyEvent::MP::Intro> - a gentle introduction.
		1113
		1114	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1115
		1116	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1117	your applications.
		1118
		1119	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1120
		1121	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1122	all nodes.
		1123
902	L<AnyEvent>.	1124	L<AnyEvent>.
903		1125
904	=head1 AUTHOR	1126	=head1 AUTHOR
905		1127
906	Marc Lehmann <schmorp@schmorp.de>	1128	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.48 by root, Thu Aug 13 02:59:42 2009 UTC vs.
Revision 1.126 by root, Sat Mar 3 19:43:41 2012 UTC