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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.46 by root, Thu Aug 13 01:46:10 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	};
42		51
43	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
44		53
		54	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
49		58	AnyEvent::MP::Global - stable API.
50	stay tuned.
51		59
52	=head1 DESCRIPTION	60	=head1 DESCRIPTION
53		61
54	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
55		63
56	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
58		66
59	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>
60	manual page.	68	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		69
66	=head1 CONCEPTS	70	=head1 CONCEPTS
67		71
68	=over 4	72	=over 4
69		73
70	=item port	74	=item port
71		75
72	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).
73		78
74	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
75	messages. All C<rcv> handlers will receive messages they match, messages	80	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	81	anything was listening for them or not.
77		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
78	=item port id - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
79		86
80	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<#>)
81	separator, and a port name (a printable string of unspecified format). An	88	as separator, and a port name (a printable string of unspecified
82	exception is the the node port, whose ID is identical to its node	89	format created by AnyEvent::MP).
83	reference.
84		90
85	=item node	91	=item node
86		92
87	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,
88	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
89	create new ports, among other things.	95	ports.
90		96
91	Nodes are either private (single-process only), slaves (connected to a	97	Nodes are either public (have one or more listening ports) or private
92	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.
93		100
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	101	Nodes is represented by (printable) strings called "node IDs".
95		102
96	A node reference is a string that either simply identifies the node (for	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
97	private and slave nodes), or contains a recipe on how to reach a given
98	node (for public nodes).
99		104
100	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
101	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.
102		109
103	Node references come in two flavours: resolved (containing only numerical	110	=item binds - C<ip:port>
104	addresses) or unresolved (where hostnames are used instead of addresses).
105		111
106	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
107	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).
108		170
109	=back	171	=back
110		172
111	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
112		174
114		176
115	=cut	177	=cut
116		178
117	package AnyEvent::MP;	179	package AnyEvent::MP;
118		180
		181	use AnyEvent::MP::Config ();
119	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
120		184
121	use common::sense;	185	use common::sense;
122		186
123	use Carp ();	187	use Carp ();
124		188
125	use AE ();	189	use AE ();
		190	use Guard ();
126		191
127	use base "Exporter";	192	use base "Exporter";
128		193
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
130		195
131	our @EXPORT = qw(	196	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	197	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	198	configure
134	snd rcv mon kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
135	port	200	port
		201	db_set db_del db_reg
136	);	202	);
137		203
138	our $SELF;	204	our $SELF;
139		205
140	sub _self_die() {	206	sub _self_die() {
…		…
143	kil $SELF, die => $msg;	209	kil $SELF, die => $msg;
144	}	210	}
145		211
146	=item $thisnode = NODE / $NODE	212	=item $thisnode = NODE / $NODE
147		213
148	The C<NODE> function returns, and the C<$NODE> variable contains	214	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	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
150	to C<become_public> or C<become_slave>, after which all local port	216	a call to C<configure>.
151	identifiers become invalid.
152		217
153	=item $noderef = node_of $port	218	=item $nodeid = node_of $port
154		219
155	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.
156		221
157	=item initialise_node $noderef, $seednode, $seednode...	222	=item configure $profile, key => value...
158		223
159	=item initialise_node "slave/", $master, $master...	224	=item configure key => value...
160		225
161	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
162	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
163	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.
164		230
165	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
166	never) before calling other AnyEvent::MP functions.	232	never) before calling other AnyEvent::MP functions.
167		233
168	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
169		235	F<aemp> command line utility (sans the set/del prefix), with these additions:
170	There are two types of networked nodes, public nodes and slave nodes:
171		236
172	=over 4	237	=over 4
173		238
174	=item public nodes	239	=item norc => $boolean (default false)
175		240
176	For public nodes, C<$noderef> must either be a (possibly unresolved)	241	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
177	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
178	which case the noderef will be guessed.	243	C<configure> call.
179		244
180	Afterwards, the node will bind itself on all endpoints and try to connect	245	=item force => $boolean (default false)
181	to all additional C<$seednodes> that are specified. Seednodes are optional
182	and can be used to quickly bootstrap the node into an existing network.
183		246
184	=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.
185		250
186	When the C<$noderef> is the special string C<slave/>, then the node will	251	=item secure => $pass->($nodeid)
187	become a slave node. Slave nodes cannot be contacted from outside and will
188	route most of their traffic to the master node that they attach to.
189		252
190	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
191	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
192	successfully connect to.	255	granted iff the callback returns a true value.
		256
		257	See F<semp setsecure> for more info.
193		258
194	=back	259	=back
195		260
196	This function will block until all nodes have been resolved and, for slave
197	nodes, until it has successfully established a connection to a master
198	server.
199
200	Example: become a public node listening on the default node.
201
202	initialise_node;
203
204	Example: become a public node, and try to contact some well-known master
205	servers to become part of the network.
206
207	initialise_node undef, "master1", "master2";
208
209	Example: become a public node listening on port C<4041>.
210
211	initialise_node 4041;
212
213	Example: become a public node, only visible on localhost port 4044.
214
215	initialise_node "locahost:4044";
216
217	Example: become a slave node to any of the specified master servers.
218
219	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
220
221	=item $cv = resolve_node $noderef
222
223	Takes an unresolved node reference that may contain hostnames and
224	abbreviated IDs, resolves all of them and returns a resolved node
225	reference.
226
227	In addition to C<address:port> pairs allowed in resolved noderefs, the
228	following forms are supported:
229
230	=over 4	261	=over 4
231		262
232	=item the empty string	263	=item step 1, gathering configuration from profiles
233		264
234	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
235	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.
236		269
237	=item naked port numbers (e.g. C<1234>)	270	The profile data is then gathered as follows:
238		271
239	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
240	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).
241		277
242	=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.
243		281
244	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
245	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
246	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.
247		309
248	=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)"
249		337
250	=item $SELF	338	=item $SELF
251		339
252	Contains the current port id while executing C<rcv> callbacks or C<psub>	340	Contains the current port id while executing C<rcv> callbacks or C<psub>
253	blocks.	341	blocks.
254		342
255	=item SELF, %SELF, @SELF...	343	=item *SELF, SELF, %SELF, @SELF...
256		344
257	Due to some quirks in how perl exports variables, it is impossible to	345	Due to some quirks in how perl exports variables, it is impossible to
258	just export C<$SELF>, all the symbols called C<SELF> are exported by this	346	just export C<$SELF>, all the symbols named C<SELF> are exported by this
259	module, but only C<$SELF> is currently used.	347	module, but only C<$SELF> is currently used.
260		348
261	=item snd $port, type => @data	349	=item snd $port, type => @data
262		350
263	=item snd $port, @msg	351	=item snd $port, @msg
264		352
265	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
266	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.
267	stringifies a sa port ID (such as a port object :).
268		355
269	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
270	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
271	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.
272		360
273	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
274	function: modifying any argument is not allowed and can cause many	362	function: modifying any argument (or values referenced by them) is
275	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.
276		367
277	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
278	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
279	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
280	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
281	node, anything can be passed.	372	node, anything can be passed. Best rely only on the common denominator of
		373	these.
282		374
283	=item $local_port = port	375	=item $local_port = port
284		376
285	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
286	matching port ("full port") or a single-callback port ("miniport"),	378	no callbacks set and will throw an error when it receives messages.
287	depending on how C<rcv> callbacks are bound to the object.
288		379
289	=item $port = port { my @msg = @_; $finished }	380	=item $local_port = port { my @msg = @_ }
290		381
291	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
292	matching behind it, and returns its ID. Semantically the same as creating
293	a port and calling C<rcv $port, $callback> on it.	383	creating a port and calling C<rcv $port, $callback> on it.
294		384
295	The block will be called for every message received on the port. When the	385	The block will be called for every message received on the port, with the
296	callback returns a true value its job is considered "done" and the port	386	global variable C<$SELF> set to the port ID. Runtime errors will cause the
297	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.
298		389
299	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:
300	be passed to the callback.
301		391
302	If you need the local port id in the callback, this works nicely:	392	my $port = port {
303		393	my @msg = @_;
304	my $port; $port = port {	394	...
305	snd $otherport, reply => $port;	395	kil $SELF;
306	};	396	};
307		397
308	=cut	398	=cut
309		399
310	sub rcv($@);	400	sub rcv($@);
311		401
		402	sub _kilme {
		403	die "received message on port without callback";
		404	}
		405
312	sub port(;&) {	406	sub port(;&) {
313	my $id = "$UNIQ." . $ID++;	407	my $id = $UNIQ . ++$ID;
314	my $port = "$NODE#$id";	408	my $port = "$NODE#$id";
315		409
316	if (@_) {	410	rcv $port, shift \|\| \&_kilme;
317	rcv $port, shift;
318	} else {
319	$PORT{$id} = sub { }; # nop
320	}
321		411
322	$port	412	$port
323	}	413	}
324		414
325	=item reg $port, $name
326
327	=item reg $name
328
329	Registers the given port (or C<$SELF><<< if missing) under the name
330	C<$name>. If the name already exists it is replaced.
331
332	A port can only be registered under one well known name.
333
334	A port automatically becomes unregistered when it is killed.
335
336	=cut
337
338	sub reg(@) {
339	my $port = @_ > 1 ? shift : $SELF \|\| Carp::croak 'reg: called with one argument only, but $SELF not set,';
340
341	$REG{$_[0]} = $port;
342	}
343
344	=item rcv $port, $callback->(@msg)	415	=item rcv $local_port, $callback->(@msg)
345		416
346	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
347	one if required).	418	remove the default callback: use C<sub { }> to disable it, or better
348		419	C<kil> the port when it is no longer needed.
349	=item rcv $port, tagstring => $callback->(@msg), ...
350
351	=item rcv $port, $smartmatch => $callback->(@msg), ...
352
353	=item rcv $port, [$smartmatch...] => $callback->(@msg), ...
354
355	Register callbacks to be called on matching messages on the given full
356	port (after converting it to one if required) and return the port.
357
358	The callback has to return a true value when its work is done, after
359	which is will be removed, or a false value in which case it will stay
360	registered.
361		420
362	The global C<$SELF> (exported by this module) contains C<$port> while	421	The global C<$SELF> (exported by this module) contains C<$port> while
363	executing the callback.	422	executing the callback. Runtime errors during callback execution will
		423	result in the port being C<kil>ed.
364		424
365	Runtime errors during callback execution will result in the port being	425	The default callback received all messages not matched by a more specific
366	C<kil>ed.	426	C<tag> match.
367		427
368	If the match is an array reference, then it will be matched against the	428	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
369	first elements of the message, otherwise only the first element is being
370	matched.
371		429
372	Any element in the match that is specified as C<_any_> (a function	430	Register (or replace) callbacks to be called on messages starting with the
373	exported by this module) matches any single element of the message.	431	given tag on the given port (and return the port), or unregister it (when
		432	C<$callback> is C<$undef> or missing). There can only be one callback
		433	registered for each tag.
374		434
375	While not required, it is highly recommended that the first matching	435	The original message will be passed to the callback, after the first
376	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
377	also the most efficient match (by far).	437	environment as the default callback (see above).
378		438
379	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.
380		440
381	my $port = rcv port,	441	my $port = rcv port,
382	msg1 => sub { ...; 0 },	442	msg1 => sub { ... },
383	msg2 => sub { ...; 0 },	443	msg2 => sub { ... },
384	;	444	;
385		445
386	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
387	in one go:	447	in one go:
388		448
389	snd $otherport, reply =>	449	snd $otherport, reply =>
390	rcv port,	450	rcv port,
391	msg1 => sub { ...; 0 },	451	msg1 => sub { ... },
392	...	452	...
393	;	453	;
394		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, $otherport;
		462	};
		463
395	=cut	464	=cut
396		465
397	sub rcv($@) {	466	sub rcv($@) {
398	my $port = shift;	467	my $port = shift;
399	my ($noderef, $portid) = split /#/, $port, 2;	468	my ($nodeid, $portid) = split /#/, $port, 2;
400		469
401	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	470	$NODE{$nodeid} == $NODE{""}
402	or Carp::croak "$port: rcv can only be called on local ports, caught";	471	or Carp::croak "$port: rcv can only be called on local ports, caught";
403		472
404	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 {
405	my $cb = shift;	481	my $cb = shift;
406	delete $PORT_DATA{$portid};
407	$PORT{$portid} = sub {	482	$PORT{$portid} = sub {
408	local $SELF = $port;	483	local $SELF = $port;
409	eval {	484	eval { &$cb }; _self_die if $@;
410	&$cb	485	};
411	and kil $port;
412	};	486	}
413	_self_die if $@;	487	} elsif (defined $_[0]) {
414	};
415	} else {
416	my $self = $PORT_DATA{$portid} \|\|= do {	488	my $self = $PORT_DATA{$portid} \|\|= do {
417	my $self = bless {	489	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
418	id => $port,
419	}, "AnyEvent::MP::Port";
420		490
421	$PORT{$portid} = sub {	491	$PORT{$portid} = sub {
422	local $SELF = $port;	492	local $SELF = $port;
423		493
424	eval {
425	for (@{ $self->{rc0}{$_[0]} }) {	494	if (my $cb = $self->[1]{$_[0]}) {
426	$_ && &{$_->[0]}	495	shift;
427	&& undef $_;	496	eval { &$cb }; _self_die if $@;
428	}	497	} else {
429
430	for (@{ $self->{rcv}{$_[0]} }) {
431	$_ && [@_[1 .. @{$_->[1]}]] ~~ $_->[1]
432	&& &{$_->[0]}	498	&{ $self->[0] };
433	&& undef $_;
434	}
435
436	for (@{ $self->{any} }) {
437	$_ && [@_[0 .. $#{$_->[1]}]] ~~ $_->[1]
438	&& &{$_->[0]}
439	&& undef $_;
440	}	499	}
441	};	500	};
442	_self_die if $@;	501
		502	$self
443	};	503	};
444		504
445	$self
446	};
447
448	"AnyEvent::MP::Port" eq ref $self	505	"AnyEvent::MP::Port" eq ref $self
449	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	506	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
450		507
451	while (@_) {
452	my ($match, $cb) = splice @_, 0, 2;	508	my ($tag, $cb) = splice @_, 0, 2;
453		509
454	if (!ref $match) {	510	if (defined $cb) {
455	push @{ $self->{rc0}{$match} }, [$cb];	511	$self->[1]{$tag} = $cb;
456	} elsif (("ARRAY" eq ref $match && !ref $match->[0])) {
457	my ($type, @match) = @$match;
458	@match
459	? push @{ $self->{rcv}{$match->[0]} }, [$cb, \@match]
460	: push @{ $self->{rc0}{$match->[0]} }, [$cb];
461	} else {	512	} else {
462	push @{ $self->{any} }, [$cb, $match];	513	delete $self->[1]{$tag};
463	}	514	}
464	}	515	}
465	}	516	}
466		517
467	$port	518	$port
468	}	519	}
469		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
470	=item $closure = psub { BLOCK }	558	=item $closure = psub { BLOCK }
471		559
472	Remembers C<$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
473	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>
474	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 $SELF, sub {
		565	BLOCK }, @_ } >>.
475		566
476	This is useful when you register callbacks from C<rcv> callbacks:	567	This is useful when you register callbacks from C<rcv> callbacks:
477		568
478	rcv delayed_reply => sub {	569	rcv delayed_reply => sub {
479	my ($delay, @reply) = @_;	570	my ($delay, @reply) = @_;
…		…
503	$res	594	$res
504	}	595	}
505	}	596	}
506	}	597	}
507		598
508	=item $guard = mon $port, $cb->(@reason)	599	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
509		600
510	=item $guard = mon $port, $rcvport	601	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
511		602
512	=item $guard = mon $port	603	=item $guard = mon $port # kill $SELF when $port dies
513		604
514	=item $guard = mon $port, $rcvport, @msg	605	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
515		606
516	Monitor the given port and do something when the port is killed or	607	Monitor the given port and do something when the port is killed or
517	messages to it were lost, and optionally return a guard that can be used	608	messages to it were lost, and optionally return a guard that can be used
518	to stop monitoring again.	609	to stop monitoring again.
519
520	C<mon> effectively guarantees that, in the absence of hardware failures,
521	that after starting the monitor, either all messages sent to the port
522	will arrive, or the monitoring action will be invoked after possible
523	message loss has been detected. No messages will be lost "in between"
524	(after the first lost message no further messages will be received by the
525	port). After the monitoring action was invoked, further messages might get
526	delivered again.
527		610
528	In the first form (callback), the callback is simply called with any	611	In the first form (callback), the callback is simply called with any
529	number of C<@reason> elements (no @reason means that the port was deleted	612	number of C<@reason> elements (no @reason means that the port was deleted
530	"normally"). Note also that I<< the callback B<must> never die >>, so use	613	"normally"). Note also that I<< the callback B<must> never die >>, so use
531	C<eval> if unsure.	614	C<eval> if unsure.
532		615
533	In the second form (another port given), the other port (C<$rcvport>)	616	In the second form (another port given), the other port (C<$rcvport>)
534	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	617	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
535	"normal" kils nothing happens, while under all other conditions, the other	618	"normal" kils nothing happens, while under all other conditions, the other
536	port is killed with the same reason.	619	port is killed with the same reason.
537		620
538	The third form (kill self) is the same as the second form, except that	621	The third form (kill self) is the same as the second form, except that
539	C<$rvport> defaults to C<$SELF>.	622	C<$rvport> defaults to C<$SELF>.
540		623
541	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
542	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.
543		629
544	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
545	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
546	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
547	even monitoring requests can get lost (for exmaple, when the connection	633	even monitoring requests can get lost (for example, when the connection
548	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
549	these problems do not exist.	635	these problems do not exist.
550		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
551	Example: call a given callback when C<$port> is killed.	654	Example: call a given callback when C<$port> is killed.
552		655
553	mon $port, sub { warn "port died because of <@_>\n" };	656	mon $port, sub { warn "port died because of <@_>\n" };
554		657
555	Example: kill ourselves when C<$port> is killed abnormally.	658	Example: kill ourselves when C<$port> is killed abnormally.
…		…
561	mon $port, $self => "restart";	664	mon $port, $self => "restart";
562		665
563	=cut	666	=cut
564		667
565	sub mon {	668	sub mon {
566	my ($noderef, $port) = split /#/, shift, 2;	669	my ($nodeid, $port) = split /#/, shift, 2;
567		670
568	my $node = $NODE{$noderef} \|\| add_node $noderef;	671	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
569		672
570	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,';
571		674
572	unless (ref $cb) {	675	unless (ref $cb) {
573	if (@_) {	676	if (@_) {
…		…
582	}	685	}
583		686
584	$node->monitor ($port, $cb);	687	$node->monitor ($port, $cb);
585		688
586	defined wantarray	689	defined wantarray
587	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	690	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
588	}	691	}
589		692
590	=item $guard = mon_guard $port, $ref, $ref...	693	=item $guard = mon_guard $port, $ref, $ref...
591		694
592	Monitors the given C<$port> and keeps the passed references. When the port	695	Monitors the given C<$port> and keeps the passed references. When the port
593	is killed, the references will be freed.	696	is killed, the references will be freed.
594		697
595	Optionally returns a guard that will stop the monitoring.	698	Optionally returns a guard that will stop the monitoring.
596		699
597	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
598	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>):
599		702
600	$port->rcv (start => sub {	703	$port->rcv (start => sub {
601	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	704	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
602	undef $timer if 0.9 < rand;	705	undef $timer if 0.9 < rand;
603	});	706	});
604	});	707	});
605		708
606	=cut	709	=cut
…		…
615		718
616	=item kil $port[, @reason]	719	=item kil $port[, @reason]
617		720
618	Kill the specified port with the given C<@reason>.	721	Kill the specified port with the given C<@reason>.
619		722
620	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" -
621	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.
622		726
623	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>
624	C<mon>, see below).	728	form) get killed with the same reason.
625		729
626	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
627	will be reported as reason C<< die => $@ >>.	731	will be reported as reason C<< die => $@ >>.
628		732
629	Transport/communication errors are reported as C<< transport_error =>	733	Transport/communication errors are reported as C<< transport_error =>
…		…
634	=item $port = spawn $node, $initfunc[, @initdata]	738	=item $port = spawn $node, $initfunc[, @initdata]
635		739
636	Creates a port on the node C<$node> (which can also be a port ID, in which	740	Creates a port on the node C<$node> (which can also be a port ID, in which
637	case it's the node where that port resides).	741	case it's the node where that port resides).
638		742
639	The port ID of the newly created port is return immediately, and it is	743	The port ID of the newly created port is returned immediately, and it is
640	permissible to immediately start sending messages or monitor the port.	744	possible to immediately start sending messages or to monitor the port.
641		745
642	After the port has been created, the init function is	746	After the port has been created, the init function is called on the remote
643	called. This function must be a fully-qualified function name	747	node, in the same context as a C<rcv> callback. This function must be a
644	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	748	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
645	program, use C<::name>.	749	specify a function in the main program, use C<::name>.
646		750
647	If the function doesn't exist, then the node tries to C<require>	751	If the function doesn't exist, then the node tries to C<require>
648	the package, then the package above the package and so on (e.g.	752	the package, then the package above the package and so on (e.g.
649	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	753	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
650	exists or it runs out of package names.	754	exists or it runs out of package names.
651		755
652	The init function is then called with the newly-created port as context	756	The init function is then called with the newly-created port as context
653	object (C<$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.
654		760
655	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
656	in the init function, monitor the original port. This two-way monitoring	762	port, and in the remote init function, immediately monitor the passed
657	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<$initfunc> has no visible effects on the
		767	caller before C<spawn> returns (by delaying invocation when spawn is
		768	called for the local node).
658		769
659	Example: spawn a chat server port on C<$othernode>.	770	Example: spawn a chat server port on C<$othernode>.
660		771
661	# this node, executed from within a port context:	772	# this node, executed from within a port context:
662	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	773	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
677		788
678	sub _spawn {	789	sub _spawn {
679	my $port = shift;	790	my $port = shift;
680	my $init = shift;	791	my $init = shift;
681		792
		793	# rcv will create the actual port
682	local $SELF = "$NODE#$port";	794	local $SELF = "$NODE#$port";
683	eval {	795	eval {
684	&{ load_func $init }	796	&{ load_func $init }
685	};	797	};
686	_self_die if $@;	798	_self_die if $@;
687	}	799	}
688		800
689	sub spawn(@) {	801	sub spawn(@) {
690	my ($noderef, undef) = split /#/, shift, 2;	802	my ($nodeid, undef) = split /#/, shift, 2;
691		803
692	my $id = "$RUNIQ." . $ID++;	804	my $id = $RUNIQ . ++$ID;
693		805
694	$_[0] =~ /::/	806	$_[0] =~ /::/
695	or Carp::croak "spawn init function must be a fully-qualified name, caught";	807	or Carp::croak "spawn init function must be a fully-qualified name, caught";
696		808
697	($NODE{$noderef} \|\| add_node $noderef)	809	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
698	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
699		810
700	"$noderef#$id"	811	"$nodeid#$id"
701	}	812	}
702		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	$port
		889	}
		890
703	=back	891	=back
704		892
705	=head1 NODE MESSAGES	893	=head1 DISTRIBUTED DATABASE
706		894
707	Nodes understand the following messages sent to them. Many of them take	895	AnyEvent::MP comes with a simple distributed database. The database will
708	arguments called C<@reply>, which will simply be used to compose a reply	896	be mirrored asynchronously at all global nodes. Other nodes bind to one of
709	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	897	the global nodes for their needs.
710	the remaining arguments are simply the message data.
711		898
712	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.
713		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
714	=over 4	934	=over
715		935
716	=cut	936	=item db_set $family => $subkey [=> $value]
717		937
718	=item lookup => $name, @reply	938	Sets (or replaces) a key to the database - if C<$value> is omitted,
		939	C<undef> is used instead.
719		940
720	Replies with the port ID of the specified well-known port, or C<undef>.	941	=item db_del $family => $subkey
721		942
722	=item devnull => ...	943	Deletes a key from the database.
723		944
724	Generic data sink/CPU heat conversion.	945	=item $guard = db_reg $family => $subkey [=> $value]
725		946
726	=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.
727		950
728	Simply forwards the message to the given port.	951	=cut
729
730	=item eval => $string[ @reply]
731
732	Evaluates the given string. If C<@reply> is given, then a message of the
733	form C<@reply, $@, @evalres> is sent.
734
735	Example: crash another node.
736
737	snd $othernode, eval => "exit";
738
739	=item time => @reply
740
741	Replies the the current node time to C<@reply>.
742
743	Example: tell the current node to send the current time to C<$myport> in a
744	C<timereply> message.
745
746	snd $NODE, time => $myport, timereply => 1, 2;
747	# => snd $myport, timereply => 1, 2, <time>
748		952
749	=back	953	=back
750		954
751	=head1 AnyEvent::MP vs. Distributed Erlang	955	=head1 AnyEvent::MP vs. Distributed Erlang
752		956
753	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
754	== 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
755	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
756	sample:	960	sample:
757		961
758	http://www.Erlang.se/doc/programming_rules.shtml	962	http://www.erlang.se/doc/programming_rules.shtml
759	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
760	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
761	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
762		966
763	Despite the similarities, there are also some important differences:	967	Despite the similarities, there are also some important differences:
764		968
765	=over 4	969	=over 4
766		970
767	=item * Node references contain the recipe on how to contact them.	971	=item * Node IDs are arbitrary strings in AEMP.
768		972
769	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
770	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
771	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.
772		977
773	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
774	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.
775		992
776	=item * Erlang uses processes and a mailbox, AEMP does not queue.	993	=item * Erlang uses processes and a mailbox, AEMP does not queue.
777		994
778	Erlang uses processes that selctively receive messages, and therefore	995	Erlang uses processes that selectively receive messages out of order, and
779	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
780	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.
781		1000
782	(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.
783		1006
784	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1007	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
785		1008
786	Sending messages in Erlang is synchronous and blocks the process. AEMP	1009	Sending messages in Erlang is synchronous and blocks the process until
787	sends are immediate, connection establishment is handled in the	1010	a conenction has been established and the message sent (and so does not
788	background.	1011	need a queue that can overflow). AEMP sends return immediately, connection
		1012	establishment is handled in the background.
789		1013
790	=item * Erlang can silently lose messages, AEMP cannot.	1014	=item * Erlang suffers from silent message loss, AEMP does not.
791		1015
792	Erlang makes few guarantees on messages delivery - messages can get lost	1016	Erlang implements few guarantees on messages delivery - messages can get
793	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,
794	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).
795		1019
796	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
797	holes in the message sequence.	1023	no silent "holes" in the message sequence.
798		1024
799	=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
800	alive.	1026	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
801		1027	simply tries to work better in common error cases, such as when a network
802	In Erlang it can happen that a monitored process is declared dead and	1028	link goes down.
803	linked processes get killed, but later it turns out that the process is
804	still alive - and can receive messages.
805
806	In AEMP, when port monitoring detects a port as dead, then that port will
807	eventually be killed - it cannot happen that a node detects a port as dead
808	and then later sends messages to it, finding it is still alive.
809		1029
810	=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.
811		1031
812	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
813	ID known to other nodes for a completely different process, causing	1033	process ID known to other nodes for a completely different process,
814	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.
815		1036
816	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
817	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.
818		1039
819	=item * Erlang uses unprotected connections, AEMP uses secure	1040	=item * Erlang uses unprotected connections, AEMP uses secure
820	authentication and can use TLS.	1041	authentication and can use TLS.
821		1042
822	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1043	AEMP can use a proven protocol - TLS - to protect connections and
823	securely authenticate nodes.	1044	securely authenticate nodes.
824		1045
825	=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
826	communications.	1047	communications.
827		1048
828	The AEMP protocol, unlike the Erlang protocol, supports both	1049	The AEMP protocol, unlike the Erlang protocol, supports both programming
829	language-independent text-only protocols (good for debugging) and binary,	1050	language independent text-only protocols (good for debugging), and binary,
830	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.
831		1053
832	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
833	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
834	protocol simple.	1056	protocol simple.
835		1057
836	=item * AEMP has more flexible monitoring options than Erlang.	1058	=item * AEMP has more flexible monitoring options than Erlang.
837		1059
838	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
839	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
840	difficult to implement. Monitoring in AEMP is more flexible than in	1062	difficult to implement.
841	Erlang, as one can choose between automatic kill, exit message or callback	1063
842	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.
843		1066
844	=item * Erlang tries to hide remote/local connections, AEMP does not.	1067	=item * Erlang tries to hide remote/local connections, AEMP does not.
845		1068
846	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
847	as linking is (except linking is unreliable in Erlang).	1070	same way as linking is (except linking is unreliable in Erlang).
848		1071
849	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
850	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
851	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
852	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
853	more reliable.	1076	reliable (no need for C<spawn_link>).
854		1077
855	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
856	(hard to do in Erlang).	1079	(hard to do in Erlang).
857		1080
858	=back	1081	=back
859		1082
860	=head1 RATIONALE	1083	=head1 RATIONALE
861		1084
862	=over 4	1085	=over 4
863		1086
864	=item Why strings for ports and noderefs, why not objects?	1087	=item Why strings for port and node IDs, why not objects?
865		1088
866	We considered "objects", but found that the actual number of methods	1089	We considered "objects", but found that the actual number of methods
867	thatc an be called are very low. Since port IDs and noderefs travel over	1090	that can be called are quite low. Since port and node IDs travel over
868	the network frequently, the serialising/deserialising would add lots of	1091	the network frequently, the serialising/deserialising would add lots of
869	overhead, as well as having to keep a proxy object.	1092	overhead, as well as having to keep a proxy object everywhere.
870		1093
871	Strings can easily be printed, easily serialised etc. and need no special	1094	Strings can easily be printed, easily serialised etc. and need no special
872	procedures to be "valid".	1095	procedures to be "valid".
873		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
874	=item Why favour JSON, why not real serialising format such as Storable?	1100	=item Why favour JSON, why not a real serialising format such as Storable?
875		1101
876	In fact, any AnyEvent::MP node will happily accept Storable as framing	1102	In fact, any AnyEvent::MP node will happily accept Storable as framing
877	format, but currently there is no way to make a node use Storable by	1103	format, but currently there is no way to make a node use Storable by
878	default.	1104	default (although all nodes will accept it).
879		1105
880	The default framing protocol is JSON because a) JSON::XS is many times	1106	The default framing protocol is JSON because a) JSON::XS is many times
881	faster for small messages and b) most importantly, after years of	1107	faster for small messages and b) most importantly, after years of
882	experience we found that object serialisation is causing more problems	1108	experience we found that object serialisation is causing more problems
883	than it gains: Just like function calls, objects simply do not travel	1109	than it solves: Just like function calls, objects simply do not travel
884	easily over the network, mostly because they will always be a copy, so you	1110	easily over the network, mostly because they will always be a copy, so you
885	always have to re-think your design.	1111	always have to re-think your design.
886		1112
887	Keeping your messages simple, concentrating on data structures rather than	1113	Keeping your messages simple, concentrating on data structures rather than
888	objects, will keep your messages clean, tidy and efficient.	1114	objects, will keep your messages clean, tidy and efficient.
889		1115
890	=back	1116	=back
891		1117
892	=head1 SEE ALSO	1118	=head1 SEE ALSO
893		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.
		1131
894	L<AnyEvent>.	1132	L<AnyEvent>.
895		1133
896	=head1 AUTHOR	1134	=head1 AUTHOR
897		1135
898	Marc Lehmann <schmorp@schmorp.de>	1136	Marc Lehmann <schmorp@schmorp.de>

Diff Legend

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

Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.46 by root, Thu Aug 13 01:46:10 2009 UTC vs. Revision 1.127 by root, Sat Mar 3 20:35:10 2012 UTC

Diff Legend

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.46 by root, Thu Aug 13 01:46:10 2009 UTC vs.
Revision 1.127 by root, Sat Mar 3 20:35:10 2012 UTC