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

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.44 by root, Wed Aug 12 21:39:58 2009 UTC vs.
Revision 1.127 by root, Sat Mar 3 20:35:10 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 $localport, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	41	mon $localport, $otherport # kill otherport on abnormal death
41	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	};
		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::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
111		184
112	use common::sense;	185	use common::sense;
113		186
114	use Carp ();	187	use Carp ();
115		188
116	use AE ();	189	use AE ();
		190	use Guard ();
117		191
118	use base "Exporter";	192	use base "Exporter";
119		193
120	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
121		195
122	our @EXPORT = qw(	196	our @EXPORT = qw(
123	NODE $NODE *SELF node_of _any_	197	NODE $NODE *SELF node_of after
124	resolve_node initialise_node	198	configure
125	snd rcv mon kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
126	port	200	port
		201	db_set db_del db_reg
127	);	202	);
128		203
129	our $SELF;	204	our $SELF;
130		205
131	sub _self_die() {	206	sub _self_die() {
…		…
134	kil $SELF, die => $msg;	209	kil $SELF, die => $msg;
135	}	210	}
136		211
137	=item $thisnode = NODE / $NODE	212	=item $thisnode = NODE / $NODE
138		213
139	The C<NODE> function returns, and the C<$NODE> variable contains	214	The C<NODE> function returns, and the C<$NODE> variable contains, the node
140	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
141	to C<become_public> or C<become_slave>, after which all local port	216	a call to C<configure>.
142	identifiers become invalid.
143		217
144	=item $noderef = node_of $port	218	=item $nodeid = node_of $port
145		219
146	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.
147		221
148	=item initialise_node $noderef, $seednode, $seednode...	222	=item configure $profile, key => value...
149		223
150	=item initialise_node "slave/", $master, $master...	224	=item configure key => value...
151		225
152	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
153	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
154	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.
155		230
156	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
157	never) before calling other AnyEvent::MP functions.	232	never) before calling other AnyEvent::MP functions.
158		233
159	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
160		235	F<aemp> command line utility (sans the set/del prefix), with these additions:
161	There are two types of networked nodes, public nodes and slave nodes:
162		236
163	=over 4	237	=over 4
164		238
165	=item public nodes	239	=item norc => $boolean (default false)
166		240
167	For public nodes, C<$noderef> must either be a (possibly unresolved)	241	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
168	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
169	which case the noderef will be guessed.	243	C<configure> call.
170		244
171	Afterwards, the node will bind itself on all endpoints and try to connect	245	=item force => $boolean (default false)
172	to all additional C<$seednodes> that are specified. Seednodes are optional
173	and can be used to quickly bootstrap the node into an existing network.
174		246
175	=item slave nodes	247	IF true, then the values specified in the C<configure> will take
		248	precedence over any values configured via the rc file. The default is for
		249	the rc file to override any options specified in the program.
176		250
177	When the C<$noderef> is the special string C<slave/>, then the node will	251	=item secure => $pass->($nodeid)
178	become a slave node. Slave nodes cannot be contacted from outside and will
179	route most of their traffic to the master node that they attach to.
180		252
181	At least one additional noderef is required: The node will try to connect	253	In addition to specifying a boolean, you can specify a code reference that
182	to all of them and will become a slave attached to the first node it can	254	is called for every remote execution attempt - the execution request is
183	successfully connect to.	255	granted iff the callback returns a true value.
		256
		257	See F<semp setsecure> for more info.
184		258
185	=back	259	=back
186		260
187	This function will block until all nodes have been resolved and, for slave
188	nodes, until it has successfully established a connection to a master
189	server.
190
191	Example: become a public node listening on the default node.
192
193	initialise_node;
194
195	Example: become a public node, and try to contact some well-known master
196	servers to become part of the network.
197
198	initialise_node undef, "master1", "master2";
199
200	Example: become a public node listening on port C<4041>.
201
202	initialise_node 4041;
203
204	Example: become a public node, only visible on localhost port 4044.
205
206	initialise_node "locahost:4044";
207
208	Example: become a slave node to any of the specified master servers.
209
210	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
211
212	=item $cv = resolve_node $noderef
213
214	Takes an unresolved node reference that may contain hostnames and
215	abbreviated IDs, resolves all of them and returns a resolved node
216	reference.
217
218	In addition to C<address:port> pairs allowed in resolved noderefs, the
219	following forms are supported:
220
221	=over 4	261	=over 4
222		262
223	=item the empty string	263	=item step 1, gathering configuration from profiles
224		264
225	An empty-string component gets resolved as if the default port (4040) was	265	The function first looks up a profile in the aemp configuration (see the
226	specified.	266	L<aemp> commandline utility). The profile name can be specified via the
		267	named C<profile> parameter or can simply be the first parameter). If it is
		268	missing, then the nodename (F<uname -n>) will be used as profile name.
227		269
228	=item naked port numbers (e.g. C<1234>)	270	The profile data is then gathered as follows:
229		271
230	These are resolved by prepending the local nodename and a colon, to be	272	First, all remaining key => value pairs (all of which are conveniently
231	further resolved.	273	undocumented at the moment) will be interpreted as configuration
		274	data. Then they will be overwritten by any values specified in the global
		275	default configuration (see the F<aemp> utility), then the chain of
		276	profiles chosen by the profile name (and any C<parent> attributes).
232		277
233	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	278	That means that the values specified in the profile have highest priority
		279	and the values specified directly via C<configure> have lowest priority,
		280	and can only be used to specify defaults.
234		281
235	These are resolved by using AnyEvent::DNS to resolve them, optionally	282	If the profile specifies a node ID, then this will become the node ID of
236	looking up SRV records for the C<aemp=4040> port, if no port was	283	this process. If not, then the profile name will be used as node ID, with
237	specified.	284	a unique randoms tring (C</%u>) appended.
		285
		286	The node ID can contain some C<%> sequences that are expanded: C<%n>
		287	is expanded to the local nodename, C<%u> is replaced by a random
		288	strign to make the node unique. For example, the F<aemp> commandline
		289	utility uses C<aemp/%n/%u> as nodename, which might expand to
		290	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		291
		292	=item step 2, bind listener sockets
		293
		294	The next step is to look up the binds in the profile, followed by binding
		295	aemp protocol listeners on all binds specified (it is possible and valid
		296	to have no binds, meaning that the node cannot be contacted form the
		297	outside. This means the node cannot talk to other nodes that also have no
		298	binds, but it can still talk to all "normal" nodes).
		299
		300	If the profile does not specify a binds list, then a default of C<*> is
		301	used, meaning the node will bind on a dynamically-assigned port on every
		302	local IP address it finds.
		303
		304	=item step 3, connect to seed nodes
		305
		306	As the last step, the seed ID list from the profile is passed to the
		307	L<AnyEvent::MP::Global> module, which will then use it to keep
		308	connectivity with at least one node at any point in time.
238		309
239	=back	310	=back
		311
		312	Example: become a distributed node using the local node name as profile.
		313	This should be the most common form of invocation for "daemon"-type nodes.
		314
		315	configure
		316
		317	Example: become a semi-anonymous node. This form is often used for
		318	commandline clients.
		319
		320	configure nodeid => "myscript/%n/%u";
		321
		322	Example: configure a node using a profile called seed, which is suitable
		323	for a seed node as it binds on all local addresses on a fixed port (4040,
		324	customary for aemp).
		325
		326	# use the aemp commandline utility
		327	# aemp profile seed binds '*:4040'
		328
		329	# then use it
		330	configure profile => "seed";
		331
		332	# or simply use aemp from the shell again:
		333	# aemp run profile seed
		334
		335	# or provide a nicer-to-remember nodeid
		336	# aemp run profile seed nodeid "$(hostname)"
240		337
241	=item $SELF	338	=item $SELF
242		339
243	Contains the current port id while executing C<rcv> callbacks or C<psub>	340	Contains the current port id while executing C<rcv> callbacks or C<psub>
244	blocks.	341	blocks.
245		342
246	=item SELF, %SELF, @SELF...	343	=item *SELF, SELF, %SELF, @SELF...
247		344
248	Due to some quirks in how perl exports variables, it is impossible to	345	Due to some quirks in how perl exports variables, it is impossible to
249	just export C<$SELF>, all the symbols called C<SELF> are exported by this	346	just export C<$SELF>, all the symbols named C<SELF> are exported by this
250	module, but only C<$SELF> is currently used.	347	module, but only C<$SELF> is currently used.
251		348
252	=item snd $port, type => @data	349	=item snd $port, type => @data
253		350
254	=item snd $port, @msg	351	=item snd $port, @msg
255		352
256	Send the given message to the given port ID, which can identify either	353	Send the given message to the given port, which can identify either a
257	a local or a remote port, and can be either a string or soemthignt hat	354	local or a remote port, and must be a port ID.
258	stringifies a sa port ID (such as a port object :).
259		355
260	While the message can be about anything, it is highly recommended to use a	356	While the message can be almost anything, it is highly recommended to
261	string as first element (a portid, or some word that indicates a request	357	use a string as first element (a port ID, or some word that indicates a
262	type etc.).	358	request type etc.) and to consist if only simple perl values (scalars,
		359	arrays, hashes) - if you think you need to pass an object, think again.
263		360
264	The message data effectively becomes read-only after a call to this	361	The message data logically becomes read-only after a call to this
265	function: modifying any argument is not allowed and can cause many	362	function: modifying any argument (or values referenced by them) is
266	problems.	363	forbidden, as there can be considerable time between the call to C<snd>
		364	and the time the message is actually being serialised - in fact, it might
		365	never be copied as within the same process it is simply handed to the
		366	receiving port.
267		367
268	The type of data you can transfer depends on the transport protocol: when	368	The type of data you can transfer depends on the transport protocol: when
269	JSON is used, then only strings, numbers and arrays and hashes consisting	369	JSON is used, then only strings, numbers and arrays and hashes consisting
270	of those are allowed (no objects). When Storable is used, then anything	370	of those are allowed (no objects). When Storable is used, then anything
271	that Storable can serialise and deserialise is allowed, and for the local	371	that Storable can serialise and deserialise is allowed, and for the local
272	node, anything can be passed.	372	node, anything can be passed. Best rely only on the common denominator of
		373	these.
273		374
274	=item $local_port = port	375	=item $local_port = port
275		376
276	Create a new local port object that can be used either as a pattern	377	Create a new local port object and returns its port ID. Initially it has
277	matching port ("full port") or a single-callback port ("miniport"),	378	no callbacks set and will throw an error when it receives messages.
278	depending on how C<rcv> callbacks are bound to the object.
279		379
280	=item $port = port { my @msg = @_; $finished }	380	=item $local_port = port { my @msg = @_ }
281		381
282	Creates a "miniport", that is, a very lightweight port without any pattern	382	Creates a new local port, and returns its ID. Semantically the same as
283	matching behind it, and returns its ID. Semantically the same as creating
284	a port and calling C<rcv $port, $callback> on it.	383	creating a port and calling C<rcv $port, $callback> on it.
285		384
286	The block will be called for every message received on the port. When the	385	The block will be called for every message received on the port, with the
287	callback returns a true value its job is considered "done" and the port	386	global variable C<$SELF> set to the port ID. Runtime errors will cause the
288	will be destroyed. Otherwise it will stay alive.	387	port to be C<kil>ed. The message will be passed as-is, no extra argument
		388	(i.e. no port ID) will be passed to the callback.
289		389
290	The message will be passed as-is, no extra argument (i.e. no port id) will	390	If you want to stop/destroy the port, simply C<kil> it:
291	be passed to the callback.
292		391
293	If you need the local port id in the callback, this works nicely:	392	my $port = port {
294		393	my @msg = @_;
295	my $port; $port = port {	394	...
296	snd $otherport, reply => $port;	395	kil $SELF;
297	};	396	};
298		397
299	=cut	398	=cut
300		399
301	sub rcv($@);	400	sub rcv($@);
302		401
		402	sub _kilme {
		403	die "received message on port without callback";
		404	}
		405
303	sub port(;&) {	406	sub port(;&) {
304	my $id = "$UNIQ." . $ID++;	407	my $id = $UNIQ . ++$ID;
305	my $port = "$NODE#$id";	408	my $port = "$NODE#$id";
306		409
307	if (@_) {	410	rcv $port, shift \|\| \&_kilme;
308	rcv $port, shift;
309	} else {
310	$PORT{$id} = sub { }; # nop
311	}
312		411
313	$port	412	$port
314	}	413	}
315		414
316	=item reg $port, $name
317
318	=item reg $name
319
320	Registers the given port (or C<$SELF><<< if missing) under the name
321	C<$name>. If the name already exists it is replaced.
322
323	A port can only be registered under one well known name.
324
325	A port automatically becomes unregistered when it is killed.
326
327	=cut
328
329	sub reg(@) {
330	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
331
332	$REG{$_[0]} = $port;
333	}
334
335	=item rcv $port, $callback->(@msg)	415	=item rcv $local_port, $callback->(@msg)
336		416
337	Replaces the callback on the specified miniport (after converting it to	417	Replaces the default callback on the specified port. There is no way to
338	one if required).	418	remove the default callback: use C<sub { }> to disable it, or better
339		419	C<kil> the port when it is no longer needed.
340	=item rcv $port, tagstring => $callback->(@msg), ...
341
342	=item rcv $port, $smartmatch => $callback->(@msg), ...
343
344	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
345
346	Register callbacks to be called on matching messages on the given full
347	port (after converting it to one if required) and return the port.
348
349	The callback has to return a true value when its work is done, after
350	which is will be removed, or a false value in which case it will stay
351	registered.
352		420
353	The global C<$SELF> (exported by this module) contains C<$port> while	421	The global C<$SELF> (exported by this module) contains C<$port> while
354	executing the callback.	422	executing the callback. Runtime errors during callback execution will
		423	result in the port being C<kil>ed.
355		424
356	Runtime errors during callback execution will result in the port being	425	The default callback received all messages not matched by a more specific
357	C<kil>ed.	426	C<tag> match.
358		427
359	If the match is an array reference, then it will be matched against the	428	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
360	first elements of the message, otherwise only the first element is being
361	matched.
362		429
363	Any element in the match that is specified as C<_any_> (a function	430	Register (or replace) callbacks to be called on messages starting with the
364	exported by this module) matches any single element of the message.	431	given tag on the given port (and return the port), or unregister it (when
		432	C<$callback> is C<$undef> or missing). There can only be one callback
		433	registered for each tag.
365		434
366	While not required, it is highly recommended that the first matching	435	The original message will be passed to the callback, after the first
367	element is a string identifying the message. The one-string-only match is	436	element (the tag) has been removed. The callback will use the same
368	also the most efficient match (by far).	437	environment as the default callback (see above).
369		438
370	Example: create a port and bind receivers on it in one go.	439	Example: create a port and bind receivers on it in one go.
371		440
372	my $port = rcv port,	441	my $port = rcv port,
373	msg1 => sub { ...; 0 },	442	msg1 => sub { ... },
374	msg2 => sub { ...; 0 },	443	msg2 => sub { ... },
375	;	444	;
376		445
377	Example: create a port, bind receivers and send it in a message elsewhere	446	Example: create a port, bind receivers and send it in a message elsewhere
378	in one go:	447	in one go:
379		448
380	snd $otherport, reply =>	449	snd $otherport, reply =>
381	rcv port,	450	rcv port,
382	msg1 => sub { ...; 0 },	451	msg1 => sub { ... },
383	...	452	...
384	;	453	;
385		454
		455	Example: temporarily register a rcv callback for a tag matching some port
		456	(e.g. for an rpc reply) and unregister it after a message was received.
		457
		458	rcv $port, $otherport => sub {
		459	my @reply = @_;
		460
		461	rcv $SELF, $otherport;
		462	};
		463
386	=cut	464	=cut
387		465
388	sub rcv($@) {	466	sub rcv($@) {
389	my $port = shift;	467	my $port = shift;
390	my ($noderef, $portid) = split /#/, $port, 2;	468	my ($nodeid, $portid) = split /#/, $port, 2;
391		469
392	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	470	$NODE{$nodeid} == $NODE{""}
393	or Carp::croak "$port: rcv can only be called on local ports, caught";	471	or Carp::croak "$port: rcv can only be called on local ports, caught";
394		472
395	if (@_ == 1) {	473	while (@_) {
		474	if (ref $_[0]) {
		475	if (my $self = $PORT_DATA{$portid}) {
		476	"AnyEvent::MP::Port" eq ref $self
		477	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
		478
		479	$self->[0] = shift;
		480	} else {
396	my $cb = shift;	481	my $cb = shift;
397	delete $PORT_DATA{$portid};
398	$PORT{$portid} = sub {	482	$PORT{$portid} = sub {
399	local $SELF = $port;	483	local $SELF = $port;
400	eval {	484	eval { &$cb }; _self_die if $@;
401	&$cb	485	};
402	and kil $port;
403	};	486	}
404	_self_die if $@;	487	} elsif (defined $_[0]) {
405	};
406	} else {
407	my $self = $PORT_DATA{$portid} \|\|= do {	488	my $self = $PORT_DATA{$portid} \|\|= do {
408	my $self = bless {	489	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
409	id => $port,
410	}, "AnyEvent::MP::Port";
411		490
412	$PORT{$portid} = sub {	491	$PORT{$portid} = sub {
413	local $SELF = $port;	492	local $SELF = $port;
414		493
415	eval {
416	for (@{ $self->{rc0}{$_[0]} }) {	494	if (my $cb = $self->[1]{$_[0]}) {
417	$_ && &{$_->[0]}	495	shift;
418	&& undef $_;	496	eval { &$cb }; _self_die if $@;
419	}	497	} else {
420
421	for (@{ $self->{rcv}{$_[0]} }) {
422	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
423	&& &{$_->[0]}	498	&{ $self->[0] };
424	&& undef $_;
425	}
426
427	for (@{ $self->{any} }) {
428	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
429	&& &{$_->[0]}
430	&& undef $_;
431	}	499	}
432	};	500	};
433	_self_die if $@;	501
		502	$self
434	};	503	};
435		504
436	$self
437	};
438
439	"AnyEvent::MP::Port" eq ref $self	505	"AnyEvent::MP::Port" eq ref $self
440	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	506	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
441		507
442	while (@_) {
443	my ($match, $cb) = splice @_, 0, 2;	508	my ($tag, $cb) = splice @_, 0, 2;
444		509
445	if (!ref $match) {	510	if (defined $cb) {
446	push @{ $self->{rc0}{$match} }, [$cb];	511	$self->[1]{$tag} = $cb;
447	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
448	my ($type, @match) = @$match;
449	@match
450	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
451	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
452	} else {	512	} else {
453	push @{ $self->{any} }, [$cb, $match];	513	delete $self->[1]{$tag};
454	}	514	}
455	}	515	}
456	}	516	}
457		517
458	$port	518	$port
459	}	519	}
460		520
		521	=item peval $port, $coderef[, @args]
		522
		523	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		524	when the code throews an exception the C<$port> will be killed.
		525
		526	Any remaining args will be passed to the callback. Any return values will
		527	be returned to the caller.
		528
		529	This is useful when you temporarily want to execute code in the context of
		530	a port.
		531
		532	Example: create a port and run some initialisation code in it's context.
		533
		534	my $port = port { ... };
		535
		536	peval $port, sub {
		537	init
		538	or die "unable to init";
		539	};
		540
		541	=cut
		542
		543	sub peval($$) {
		544	local $SELF = shift;
		545	my $cb = shift;
		546
		547	if (wantarray) {
		548	my @res = eval { &$cb };
		549	_self_die if $@;
		550	@res
		551	} else {
		552	my $res = eval { &$cb };
		553	_self_die if $@;
		554	$res
		555	}
		556	}
		557
461	=item $closure = psub { BLOCK }	558	=item $closure = psub { BLOCK }
462		559
463	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	560	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
464	closure is executed, sets up the environment in the same way as in C<rcv>	561	closure is executed, sets up the environment in the same way as in C<rcv>
465	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	562	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		563
		564	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		565	BLOCK }, @_ } >>.
466		566
467	This is useful when you register callbacks from C<rcv> callbacks:	567	This is useful when you register callbacks from C<rcv> callbacks:
468		568
469	rcv delayed_reply => sub {	569	rcv delayed_reply => sub {
470	my ($delay, @reply) = @_;	570	my ($delay, @reply) = @_;
…		…
494	$res	594	$res
495	}	595	}
496	}	596	}
497	}	597	}
498		598
499	=item $guard = mon $port, $cb->(@reason)	599	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
500		600
501	=item $guard = mon $port, $rcvport	601	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
502		602
503	=item $guard = mon $port	603	=item $guard = mon $port # kill $SELF when $port dies
504		604
505	=item $guard = mon $port, $rcvport, @msg	605	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
506		606
507	Monitor the given port and do something when the port is killed or	607	Monitor the given port and do something when the port is killed or
508	messages to it were lost, and optionally return a guard that can be used	608	messages to it were lost, and optionally return a guard that can be used
509	to stop monitoring again.	609	to stop monitoring again.
510
511	C<mon> effectively guarantees that, in the absence of hardware failures,
512	that after starting the monitor, either all messages sent to the port
513	will arrive, or the monitoring action will be invoked after possible
514	message loss has been detected. No messages will be lost "in between"
515	(after the first lost message no further messages will be received by the
516	port). After the monitoring action was invoked, further messages might get
517	delivered again.
518		610
519	In the first form (callback), the callback is simply called with any	611	In the first form (callback), the callback is simply called with any
520	number of C<@reason> elements (no @reason means that the port was deleted	612	number of C<@reason> elements (no @reason means that the port was deleted
521	"normally"). Note also that I<< the callback B<must> never die >>, so use	613	"normally"). Note also that I<< the callback B<must> never die >>, so use
522	C<eval> if unsure.	614	C<eval> if unsure.
523		615
524	In the second form (another port given), the other port (C<$rcvport>)	616	In the second form (another port given), the other port (C<$rcvport>)
525	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	617	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
526	"normal" kils nothing happens, while under all other conditions, the other	618	"normal" kils nothing happens, while under all other conditions, the other
527	port is killed with the same reason.	619	port is killed with the same reason.
528		620
529	The third form (kill self) is the same as the second form, except that	621	The third form (kill self) is the same as the second form, except that
530	C<$rvport> defaults to C<$SELF>.	622	C<$rvport> defaults to C<$SELF>.
531		623
532	In the last form (message), a message of the form C<@msg, @reason> will be	624	In the last form (message), a message of the form C<@msg, @reason> will be
533	C<snd>.	625	C<snd>.
		626
		627	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		628	alert was raised), they are removed and will not trigger again.
534		629
535	As a rule of thumb, monitoring requests should always monitor a port from	630	As a rule of thumb, monitoring requests should always monitor a port from
536	a local port (or callback). The reason is that kill messages might get	631	a local port (or callback). The reason is that kill messages might get
537	lost, just like any other message. Another less obvious reason is that	632	lost, just like any other message. Another less obvious reason is that
538	even monitoring requests can get lost (for exmaple, when the connection	633	even monitoring requests can get lost (for example, when the connection
539	to the other node goes down permanently). When monitoring a port locally	634	to the other node goes down permanently). When monitoring a port locally
540	these problems do not exist.	635	these problems do not exist.
541		636
		637	C<mon> effectively guarantees that, in the absence of hardware failures,
		638	after starting the monitor, either all messages sent to the port will
		639	arrive, or the monitoring action will be invoked after possible message
		640	loss has been detected. No messages will be lost "in between" (after
		641	the first lost message no further messages will be received by the
		642	port). After the monitoring action was invoked, further messages might get
		643	delivered again.
		644
		645	Inter-host-connection timeouts and monitoring depend on the transport
		646	used. The only transport currently implemented is TCP, and AnyEvent::MP
		647	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		648	non-idle connection, and usually around two hours for idle connections).
		649
		650	This means that monitoring is good for program errors and cleaning up
		651	stuff eventually, but they are no replacement for a timeout when you need
		652	to ensure some maximum latency.
		653
542	Example: call a given callback when C<$port> is killed.	654	Example: call a given callback when C<$port> is killed.
543		655
544	mon $port, sub { warn "port died because of <@_>\n" };	656	mon $port, sub { warn "port died because of <@_>\n" };
545		657
546	Example: kill ourselves when C<$port> is killed abnormally.	658	Example: kill ourselves when C<$port> is killed abnormally.
…		…
552	mon $port, $self => "restart";	664	mon $port, $self => "restart";
553		665
554	=cut	666	=cut
555		667
556	sub mon {	668	sub mon {
557	my ($noderef, $port) = split /#/, shift, 2;	669	my ($nodeid, $port) = split /#/, shift, 2;
558		670
559	my $node = $NODE{$noderef} \|\| add_node $noderef;	671	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
560		672
561	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	673	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
562		674
563	unless (ref $cb) {	675	unless (ref $cb) {
564	if (@_) {	676	if (@_) {
…		…
573	}	685	}
574		686
575	$node->monitor ($port, $cb);	687	$node->monitor ($port, $cb);
576		688
577	defined wantarray	689	defined wantarray
578	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	690	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
579	}	691	}
580		692
581	=item $guard = mon_guard $port, $ref, $ref...	693	=item $guard = mon_guard $port, $ref, $ref...
582		694
583	Monitors the given C<$port> and keeps the passed references. When the port	695	Monitors the given C<$port> and keeps the passed references. When the port
584	is killed, the references will be freed.	696	is killed, the references will be freed.
585		697
586	Optionally returns a guard that will stop the monitoring.	698	Optionally returns a guard that will stop the monitoring.
587		699
588	This function is useful when you create e.g. timers or other watchers and	700	This function is useful when you create e.g. timers or other watchers and
589	want to free them when the port gets killed:	701	want to free them when the port gets killed (note the use of C<psub>):
590		702
591	$port->rcv (start => sub {	703	$port->rcv (start => sub {
592	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	704	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
593	undef $timer if 0.9 < rand;	705	undef $timer if 0.9 < rand;
594	});	706	});
595	});	707	});
596		708
597	=cut	709	=cut
…		…
606		718
607	=item kil $port[, @reason]	719	=item kil $port[, @reason]
608		720
609	Kill the specified port with the given C<@reason>.	721	Kill the specified port with the given C<@reason>.
610		722
611	If no C<@reason> is specified, then the port is killed "normally" (linked	723	If no C<@reason> is specified, then the port is killed "normally" -
612	ports will not be kileld, or even notified).	724	monitor callback will be invoked, but the kil will not cause linked ports
		725	(C<mon $mport, $lport> form) to get killed.
613		726
614	Otherwise, linked ports get killed with the same reason (second form of	727	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
615	C<mon>, see below).	728	form) get killed with the same reason.
616		729
617	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	730	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
618	will be reported as reason C<< die => $@ >>.	731	will be reported as reason C<< die => $@ >>.
619		732
620	Transport/communication errors are reported as C<< transport_error =>	733	Transport/communication errors are reported as C<< transport_error =>
…		…
625	=item $port = spawn $node, $initfunc[, @initdata]	738	=item $port = spawn $node, $initfunc[, @initdata]
626		739
627	Creates a port on the node C<$node> (which can also be a port ID, in which	740	Creates a port on the node C<$node> (which can also be a port ID, in which
628	case it's the node where that port resides).	741	case it's the node where that port resides).
629		742
630	The port ID of the newly created port is return immediately, and it is	743	The port ID of the newly created port is returned immediately, and it is
631	permissible to immediately start sending messages or monitor the port.	744	possible to immediately start sending messages or to monitor the port.
632		745
633	After the port has been created, the init function is	746	After the port has been created, the init function is called on the remote
634	called. This function must be a fully-qualified function name	747	node, in the same context as a C<rcv> callback. This function must be a
635	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	748	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
636	program, use C<::name>.	749	specify a function in the main program, use C<::name>.
637		750
638	If the function doesn't exist, then the node tries to C<require>	751	If the function doesn't exist, then the node tries to C<require>
639	the package, then the package above the package and so on (e.g.	752	the package, then the package above the package and so on (e.g.
640	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	753	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
641	exists or it runs out of package names.	754	exists or it runs out of package names.
642		755
643	The init function is then called with the newly-created port as context	756	The init function is then called with the newly-created port as context
644	object (C<$SELF>) and the C<@initdata> values as arguments.	757	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		758	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		759	the port might not get created.
645		760
646	A common idiom is to pass your own port, monitor the spawned port, and	761	A common idiom is to pass a local port, immediately monitor the spawned
647	in the init function, monitor the original port. This two-way monitoring	762	port, and in the remote init function, immediately monitor the passed
648	ensures that both ports get cleaned up when there is a problem.	763	local port. This two-way monitoring ensures that both ports get cleaned up
		764	when there is a problem.
		765
		766	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		767	caller before C<spawn> returns (by delaying invocation when spawn is
		768	called for the local node).
649		769
650	Example: spawn a chat server port on C<$othernode>.	770	Example: spawn a chat server port on C<$othernode>.
651		771
652	# this node, executed from within a port context:	772	# this node, executed from within a port context:
653	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	773	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
668		788
669	sub _spawn {	789	sub _spawn {
670	my $port = shift;	790	my $port = shift;
671	my $init = shift;	791	my $init = shift;
672		792
		793	# rcv will create the actual port
673	local $SELF = "$NODE#$port";	794	local $SELF = "$NODE#$port";
674	eval {	795	eval {
675	&{ load_func $init }	796	&{ load_func $init }
676	};	797	};
677	_self_die if $@;	798	_self_die if $@;
678	}	799	}
679		800
680	sub spawn(@) {	801	sub spawn(@) {
681	my ($noderef, undef) = split /#/, shift, 2;	802	my ($nodeid, undef) = split /#/, shift, 2;
682		803
683	my $id = "$RUNIQ." . $ID++;	804	my $id = $RUNIQ . ++$ID;
684		805
685	$_[0] =~ /::/	806	$_[0] =~ /::/
686	or Carp::croak "spawn init function must be a fully-qualified name, caught";	807	or Carp::croak "spawn init function must be a fully-qualified name, caught";
687		808
688	($NODE{$noderef} \|\| add_node $noderef)	809	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
689	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
690		810
691	"$noderef#$id"	811	"$nodeid#$id"
692	}	812	}
693		813
		814
		815	=item after $timeout, @msg
		816
		817	=item after $timeout, $callback
		818
		819	Either sends the given message, or call the given callback, after the
		820	specified number of seconds.
		821
		822	This is simply a utility function that comes in handy at times - the
		823	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		824	so it may go away in the future.
		825
		826	=cut
		827
		828	sub after($@) {
		829	my ($timeout, @action) = @_;
		830
		831	my $t; $t = AE::timer $timeout, 0, sub {
		832	undef $t;
		833	ref $action[0]
		834	? $action[0]()
		835	: snd @action;
		836	};
		837	}
		838
		839	=item cal $port, @msg, $callback[, $timeout]
		840
		841	A simple form of RPC - sends a message to the given C<$port> with the
		842	given contents (C<@msg>), but adds a reply port to the message.
		843
		844	The reply port is created temporarily just for the purpose of receiving
		845	the reply, and will be C<kil>ed when no longer needed.
		846
		847	A reply message sent to the port is passed to the C<$callback> as-is.
		848
		849	If an optional time-out (in seconds) is given and it is not C<undef>,
		850	then the callback will be called without any arguments after the time-out
		851	elapsed and the port is C<kil>ed.
		852
		853	If no time-out is given (or it is C<undef>), then the local port will
		854	monitor the remote port instead, so it eventually gets cleaned-up.
		855
		856	Currently this function returns the temporary port, but this "feature"
		857	might go in future versions unless you can make a convincing case that
		858	this is indeed useful for something.
		859
		860	=cut
		861
		862	sub cal(@) {
		863	my $timeout = ref $_[-1] ? undef : pop;
		864	my $cb = pop;
		865
		866	my $port = port {
		867	undef $timeout;
		868	kil $SELF;
		869	&$cb;
		870	};
		871
		872	if (defined $timeout) {
		873	$timeout = AE::timer $timeout, 0, sub {
		874	undef $timeout;
		875	kil $port;
		876	$cb->();
		877	};
		878	} else {
		879	mon $_[0], sub {
		880	kil $port;
		881	$cb->();
		882	};
		883	}
		884
		885	push @_, $port;
		886	&snd;
		887
		888	$port
		889	}
		890
694	=back	891	=back
695		892
696	=head1 NODE MESSAGES	893	=head1 DISTRIBUTED DATABASE
697		894
698	Nodes understand the following messages sent to them. Many of them take	895	AnyEvent::MP comes with a simple distributed database. The database will
699	arguments called C<@reply>, which will simply be used to compose a reply	896	be mirrored asynchronously at all global nodes. Other nodes bind to one of
700	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	897	the global nodes for their needs.
701	the remaining arguments are simply the message data.
702		898
703	While other messages exist, they are not public and subject to change.	899	The database consists of a two-level hash - a hash contains a hash which
		900	contains values.
704		901
		902	The top level hash key is called "family", and the second-level hash key
		903	is called "subkey" or simply "key".
		904
		905	The family must be alphanumeric, i.e. start with a letter and consist
		906	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		907	pretty much like Perl module names.
		908
		909	As the family namespace is global, it is recommended to prefix family names
		910	with the name of the application or module using it.
		911
		912	The subkeys must be non-empty strings, with no further restrictions.
		913
		914	The values should preferably be strings, but other perl scalars should
		915	work as well (such as undef, arrays and hashes).
		916
		917	Every database entry is owned by one node - adding the same family/subkey
		918	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		919	but the result might be nondeterministic, i.e. the key might have
		920	different values on different nodes.
		921
		922	Different subkeys in the same family can be owned by different nodes
		923	without problems, and in fact, this is the common method to create worker
		924	pools. For example, a worker port for image scaling might do this:
		925
		926	db_set my_image_scalers => $port;
		927
		928	And clients looking for an image scaler will want to get the
		929	C<my_image_scalers> keys:
		930
		931	db_keys "my_image_scalers" => 60 => sub {
		932	#d##TODO#
		933
705	=over 4	934	=over
706		935
707	=cut	936	=item db_set $family => $subkey [=> $value]
708		937
709	=item lookup => $name, @reply	938	Sets (or replaces) a key to the database - if C<$value> is omitted,
		939	C<undef> is used instead.
710		940
711	Replies with the port ID of the specified well-known port, or C<undef>.	941	=item db_del $family => $subkey
712		942
713	=item devnull => ...	943	Deletes a key from the database.
714		944
715	Generic data sink/CPU heat conversion.	945	=item $guard = db_reg $family => $subkey [=> $value]
716		946
717	=item relay => $port, @msg	947	Sets the key on the database and returns a guard. When the guard is
		948	destroyed, the key is deleted from the database. If C<$value> is missing,
		949	then C<undef> is used.
718		950
719	Simply forwards the message to the given port.	951	=cut
720
721	=item eval => $string[ @reply]
722
723	Evaluates the given string. If C<@reply> is given, then a message of the
724	form C<@reply, $@, @evalres> is sent.
725
726	Example: crash another node.
727
728	snd $othernode, eval => "exit";
729
730	=item time => @reply
731
732	Replies the the current node time to C<@reply>.
733
734	Example: tell the current node to send the current time to C<$myport> in a
735	C<timereply> message.
736
737	snd $NODE, time => $myport, timereply => 1, 2;
738	# => snd $myport, timereply => 1, 2, <time>
739		952
740	=back	953	=back
741		954
742	=head1 AnyEvent::MP vs. Distributed Erlang	955	=head1 AnyEvent::MP vs. Distributed Erlang
743		956
744	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	957	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
745	== aemp node, Erlang process == aemp port), so many of the documents and	958	== aemp node, Erlang process == aemp port), so many of the documents and
746	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	959	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
747	sample:	960	sample:
748		961
749	http://www.Erlang.se/doc/programming_rules.shtml	962	http://www.erlang.se/doc/programming_rules.shtml
750	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	963	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
751	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	964	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
752	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	965	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
753		966
754	Despite the similarities, there are also some important differences:	967	Despite the similarities, there are also some important differences:
755		968
756	=over 4	969	=over 4
757		970
758	=item * Node references contain the recipe on how to contact them.	971	=item * Node IDs are arbitrary strings in AEMP.
759		972
760	Erlang relies on special naming and DNS to work everywhere in the	973	Erlang relies on special naming and DNS to work everywhere in the same
761	same way. AEMP relies on each node knowing it's own address(es), with	974	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
762	convenience functionality.	975	configuration or DNS), and possibly the addresses of some seed nodes, but
		976	will otherwise discover other nodes (and their IDs) itself.
763		977
764	This means that AEMP requires a less tightly controlled environment at the	978	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
765	cost of longer node references and a slightly higher management overhead.	979	uses "local ports are like remote ports".
		980
		981	The failure modes for local ports are quite different (runtime errors
		982	only) then for remote ports - when a local port dies, you I<know> it dies,
		983	when a connection to another node dies, you know nothing about the other
		984	port.
		985
		986	Erlang pretends remote ports are as reliable as local ports, even when
		987	they are not.
		988
		989	AEMP encourages a "treat remote ports differently" philosophy, with local
		990	ports being the special case/exception, where transport errors cannot
		991	occur.
766		992
767	=item * Erlang uses processes and a mailbox, AEMP does not queue.	993	=item * Erlang uses processes and a mailbox, AEMP does not queue.
768		994
769	Erlang uses processes that selctively receive messages, and therefore	995	Erlang uses processes that selectively receive messages out of order, and
770	needs a queue. AEMP is event based, queuing messages would serve no useful	996	therefore needs a queue. AEMP is event based, queuing messages would serve
771	purpose.	997	no useful purpose. For the same reason the pattern-matching abilities
		998	of AnyEvent::MP are more limited, as there is little need to be able to
		999	filter messages without dequeuing them.
772		1000
773	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1001	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1002	being event-based, while Erlang is process-based.
		1003
		1004	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1005	top of AEMP and Coro threads.
774		1006
775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1007	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
776		1008
777	Sending messages in Erlang is synchronous and blocks the process. AEMP	1009	Sending messages in Erlang is synchronous and blocks the process until
778	sends are immediate, connection establishment is handled in the	1010	a conenction has been established and the message sent (and so does not
779	background.	1011	need a queue that can overflow). AEMP sends return immediately, connection
		1012	establishment is handled in the background.
780		1013
781	=item * Erlang can silently lose messages, AEMP cannot.	1014	=item * Erlang suffers from silent message loss, AEMP does not.
782		1015
783	Erlang makes few guarantees on messages delivery - messages can get lost	1016	Erlang implements few guarantees on messages delivery - messages can get
784	without any of the processes realising it (i.e. you send messages a, b,	1017	lost without any of the processes realising it (i.e. you send messages a,
785	and c, and the other side only receives messages a and c).	1018	b, and c, and the other side only receives messages a and c).
786		1019
787	AEMP guarantees correct ordering, and the guarantee that there are no	1020	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1021	guarantee that after one message is lost, all following ones sent to the
		1022	same port are lost as well, until monitoring raises an error, so there are
788	holes in the message sequence.	1023	no silent "holes" in the message sequence.
789		1024
790	=item * In Erlang, processes can be declared dead and later be found to be	1025	If you want your software to be very reliable, you have to cope with
791	alive.	1026	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
792		1027	simply tries to work better in common error cases, such as when a network
793	In Erlang it can happen that a monitored process is declared dead and	1028	link goes down.
794	linked processes get killed, but later it turns out that the process is
795	still alive - and can receive messages.
796
797	In AEMP, when port monitoring detects a port as dead, then that port will
798	eventually be killed - it cannot happen that a node detects a port as dead
799	and then later sends messages to it, finding it is still alive.
800		1029
801	=item * Erlang can send messages to the wrong port, AEMP does not.	1030	=item * Erlang can send messages to the wrong port, AEMP does not.
802		1031
803	In Erlang it is quite possible that a node that restarts reuses a process	1032	In Erlang it is quite likely that a node that restarts reuses an Erlang
804	ID known to other nodes for a completely different process, causing	1033	process ID known to other nodes for a completely different process,
805	messages destined for that process to end up in an unrelated process.	1034	causing messages destined for that process to end up in an unrelated
		1035	process.
806		1036
807	AEMP never reuses port IDs, so old messages or old port IDs floating	1037	AEMP does not reuse port IDs, so old messages or old port IDs floating
808	around in the network will not be sent to an unrelated port.	1038	around in the network will not be sent to an unrelated port.
809		1039
810	=item * Erlang uses unprotected connections, AEMP uses secure	1040	=item * Erlang uses unprotected connections, AEMP uses secure
811	authentication and can use TLS.	1041	authentication and can use TLS.
812		1042
813	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1043	AEMP can use a proven protocol - TLS - to protect connections and
814	securely authenticate nodes.	1044	securely authenticate nodes.
815		1045
816	=item * The AEMP protocol is optimised for both text-based and binary	1046	=item * The AEMP protocol is optimised for both text-based and binary
817	communications.	1047	communications.
818		1048
819	The AEMP protocol, unlike the Erlang protocol, supports both	1049	The AEMP protocol, unlike the Erlang protocol, supports both programming
820	language-independent text-only protocols (good for debugging) and binary,	1050	language independent text-only protocols (good for debugging), and binary,
821	language-specific serialisers (e.g. Storable).	1051	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1052	used, the protocol is actually completely text-based.
822		1053
823	It has also been carefully designed to be implementable in other languages	1054	It has also been carefully designed to be implementable in other languages
824	with a minimum of work while gracefully degrading fucntionality to make the	1055	with a minimum of work while gracefully degrading functionality to make the
825	protocol simple.	1056	protocol simple.
826		1057
827	=item * AEMP has more flexible monitoring options than Erlang.	1058	=item * AEMP has more flexible monitoring options than Erlang.
828		1059
829	In Erlang, you can chose to receive I<all> exit signals as messages	1060	In Erlang, you can chose to receive I<all> exit signals as messages or
830	or I<none>, there is no in-between, so monitoring single processes is	1061	I<none>, there is no in-between, so monitoring single Erlang processes is
831	difficult to implement. Monitoring in AEMP is more flexible than in	1062	difficult to implement.
832	Erlang, as one can choose between automatic kill, exit message or callback	1063
833	on a per-process basis.	1064	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1065	between automatic kill, exit message or callback on a per-port basis.
834		1066
835	=item * Erlang tries to hide remote/local connections, AEMP does not.	1067	=item * Erlang tries to hide remote/local connections, AEMP does not.
836		1068
837	Monitoring in Erlang is not an indicator of process death/crashes,	1069	Monitoring in Erlang is not an indicator of process death/crashes, in the
838	as linking is (except linking is unreliable in Erlang).	1070	same way as linking is (except linking is unreliable in Erlang).
839		1071
840	In AEMP, you don't "look up" registered port names or send to named ports	1072	In AEMP, you don't "look up" registered port names or send to named ports
841	that might or might not be persistent. Instead, you normally spawn a port	1073	that might or might not be persistent. Instead, you normally spawn a port
842	on the remote node. The init function monitors the you, and you monitor	1074	on the remote node. The init function monitors you, and you monitor the
843	the remote port. Since both monitors are local to the node, they are much	1075	remote port. Since both monitors are local to the node, they are much more
844	more reliable.	1076	reliable (no need for C<spawn_link>).
845		1077
846	This also saves round-trips and avoids sending messages to the wrong port	1078	This also saves round-trips and avoids sending messages to the wrong port
847	(hard to do in Erlang).	1079	(hard to do in Erlang).
848		1080
849	=back	1081	=back
850		1082
		1083	=head1 RATIONALE
		1084
		1085	=over 4
		1086
		1087	=item Why strings for port and node IDs, why not objects?
		1088
		1089	We considered "objects", but found that the actual number of methods
		1090	that can be called are quite low. Since port and node IDs travel over
		1091	the network frequently, the serialising/deserialising would add lots of
		1092	overhead, as well as having to keep a proxy object everywhere.
		1093
		1094	Strings can easily be printed, easily serialised etc. and need no special
		1095	procedures to be "valid".
		1096
		1097	And as a result, a port with just a default receiver consists of a single
		1098	code reference stored in a global hash - it can't become much cheaper.
		1099
		1100	=item Why favour JSON, why not a real serialising format such as Storable?
		1101
		1102	In fact, any AnyEvent::MP node will happily accept Storable as framing
		1103	format, but currently there is no way to make a node use Storable by
		1104	default (although all nodes will accept it).
		1105
		1106	The default framing protocol is JSON because a) JSON::XS is many times
		1107	faster for small messages and b) most importantly, after years of
		1108	experience we found that object serialisation is causing more problems
		1109	than it solves: Just like function calls, objects simply do not travel
		1110	easily over the network, mostly because they will always be a copy, so you
		1111	always have to re-think your design.
		1112
		1113	Keeping your messages simple, concentrating on data structures rather than
		1114	objects, will keep your messages clean, tidy and efficient.
		1115
		1116	=back
		1117
851	=head1 SEE ALSO	1118	=head1 SEE ALSO
		1119
		1120	L<AnyEvent::MP::Intro> - a gentle introduction.
		1121
		1122	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1123
		1124	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1125	your applications.
		1126
		1127	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1128
		1129	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1130	all nodes.
852		1131
853	L<AnyEvent>.	1132	L<AnyEvent>.
854		1133
855	=head1 AUTHOR	1134	=head1 AUTHOR
856		1135

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Revision 1.127 by root, Sat Mar 3 20:35:10 2012 UTC