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

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.53 by root, Fri Aug 14 15:31:21 2009 UTC vs.
Revision 1.133 by root, Mon Mar 12 10:34:06 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
38	# monitoring	39	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $port, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
41	mon $port, $otherport, @msg # send message on death	42	mon $port, $localport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
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	Ports allow you to register C<rcv> handlers that can match all or just	79	Ports allow you to register C<rcv> handlers that can match all or just
75	some messages. Messages will not be queued.	80	some messages. Messages send to ports will not be queued, regardless of
		81	anything was listening for them or not.
76		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
77	=item port id - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
78		86
79	A port ID is 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<#>)
80	separator, and a port name (a printable string of unspecified format). An	88	as separator, and a port name (a printable string of unspecified
81	exception is the the node port, whose ID is identical to its node	89	format created by AnyEvent::MP).
82	reference.
83		90
84	=item node	91	=item node
85		92
86	A node is a single process containing at least one port - the node port,	93	A node is a single process containing at least one port - the node port,
87	which provides nodes to manage each other remotely, and to create new	94	which enables nodes to manage each other remotely, and to create new
88	ports.	95	ports.
89		96
90	Nodes are either private (single-process only), slaves (connected to a	97	Nodes are either public (have one or more listening ports) or private
91	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.
92		100
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	101	Nodes is represented by (printable) strings called "node IDs".
94		102
95	A node reference is a string that either simply identifies the node (for	103	=item node ID - C<[A-Za-z0-9_\-.:]*>
96	private and slave nodes), or contains a recipe on how to reach a given
97	node (for public nodes).
98		104
99	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
100	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.
101		109
102	Node references come in two flavours: resolved (containing only numerical	110	=item binds - C<ip:port>
103	addresses) or unresolved (where hostnames are used instead of addresses).
104		111
105	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
106	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).
107		170
108	=back	171	=back
109		172
110	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
111		174
113		176
114	=cut	177	=cut
115		178
116	package AnyEvent::MP;	179	package AnyEvent::MP;
117		180
		181	use AnyEvent::MP::Config ();
118	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
119		184
120	use common::sense;	185	use common::sense;
121		186
122	use Carp ();	187	use Carp ();
123		188
124	use AE ();	189	use AE ();
		190	use Guard ();
125		191
126	use base "Exporter";	192	use base "Exporter";
127		193
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
129		195
130	our @EXPORT = qw(	196	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	197	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	198	configure
133	snd rcv mon kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
134	port	200	port
		201	db_set db_del db_reg
		202	db_mon db_family db_keys db_values
135	);	203	);
136		204
137	our $SELF;	205	our $SELF;
138		206
139	sub _self_die() {	207	sub _self_die() {
…		…
142	kil $SELF, die => $msg;	210	kil $SELF, die => $msg;
143	}	211	}
144		212
145	=item $thisnode = NODE / $NODE	213	=item $thisnode = NODE / $NODE
146		214
147	The C<NODE> function returns, and the C<$NODE> variable contains the	215	The C<NODE> function returns, and the C<$NODE> variable contains, the node
148	noderef of the local node. The value is initialised by a call to	216	ID of the node running in the current process. This value is initialised by
149	C<initialise_node>.	217	a call to C<configure>.
150		218
151	=item $noderef = node_of $port	219	=item $nodeid = node_of $port
152		220
153	Extracts and returns the noderef from a port ID or a noderef.	221	Extracts and returns the node ID from a port ID or a node ID.
154		222
155	=item initialise_node $noderef, $seednode, $seednode...	223	=item configure $profile, key => value...
156		224
157	=item initialise_node "slave/", $master, $master...	225	=item configure key => value...
158		226
159	Before a node can talk to other nodes on the network it has to initialise	227	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	228	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	229	to know is its own name, and optionally it should know the addresses of
		230	some other nodes in the network to discover other nodes.
162		231
163	This function initialises a node - it must be called exactly once (or	232	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
165		234
166	All arguments (optionally except for the first) are noderefs, which can be	235	The key/value pairs are basically the same ones as documented for the
167	either resolved or unresolved.	236	F<aemp> command line utility (sans the set/del prefix), with these additions:
168
169	The first argument will be looked up in the configuration database first
170	(if it is C<undef> then the current nodename will be used instead) to find
171	the relevant configuration profile (see L<aemp>). If none is found then
172	the default configuration is used. The configuration supplies additional
173	seed/master nodes and can override the actual noderef.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176		237
177	=over 4	238	=over 4
178		239
179	=item public nodes	240	=item norc => $boolean (default false)
180		241
181	For public nodes, C<$noderef> (supplied either directly to	242	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
182	C<initialise_node> or indirectly via a profile or the nodename) must be a	243	be consulted - all configuraiton options must be specified in the
183	noderef (possibly unresolved, in which case it will be resolved).	244	C<configure> call.
184		245
185	After resolving, the node will bind itself on all endpoints and try to	246	=item force => $boolean (default false)
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189		247
190	=item slave nodes	248	IF true, then the values specified in the C<configure> will take
		249	precedence over any values configured via the rc file. The default is for
		250	the rc file to override any options specified in the program.
191		251
192	When the C<$noderef> (either as given or overriden by the config file)	252	=item secure => $pass->($nodeid)
193	is the special string C<slave/>, then the node will become a slave
194	node. Slave nodes cannot be contacted from outside and will route most of
195	their traffic to the master node that they attach to.
196		253
197	At least one additional noderef is required (either by specifying it	254	In addition to specifying a boolean, you can specify a code reference that
198	directly or because it is part of the configuration profile): The node	255	is called for every remote execution attempt - the execution request is
199	will try to connect to all of them and will become a slave attached to the	256	granted iff the callback returns a true value.
200	first node it can successfully connect to.	257
		258	See F<semp setsecure> for more info.
201		259
202	=back	260	=back
203		261
204	This function will block until all nodes have been resolved and, for slave
205	nodes, until it has successfully established a connection to a master
206	server.
207
208	Example: become a public node listening on the guessed noderef, or the one
209	specified via C<aemp> for the current node. This should be the most common
210	form of invocation for "daemon"-type nodes.
211
212	initialise_node;
213
214	Example: become a slave node to any of the the seednodes specified via
215	C<aemp>. This form is often used for commandline clients.
216
217	initialise_node "slave/";
218
219	Example: become a slave node to any of the specified master servers. This
220	form is also often used for commandline clients.
221
222	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
223
224	Example: become a public node, and try to contact some well-known master
225	servers to become part of the network.
226
227	initialise_node undef, "master1", "master2";
228
229	Example: become a public node listening on port C<4041>.
230
231	initialise_node 4041;
232
233	Example: become a public node, only visible on localhost port 4044.
234
235	initialise_node "localhost:4044";
236
237	=item $cv = resolve_node $noderef
238
239	Takes an unresolved node reference that may contain hostnames and
240	abbreviated IDs, resolves all of them and returns a resolved node
241	reference.
242
243	In addition to C<address:port> pairs allowed in resolved noderefs, the
244	following forms are supported:
245
246	=over 4	262	=over 4
247		263
248	=item the empty string	264	=item step 1, gathering configuration from profiles
249		265
250	An empty-string component gets resolved as if the default port (4040) was	266	The function first looks up a profile in the aemp configuration (see the
251	specified.	267	L<aemp> commandline utility). The profile name can be specified via the
		268	named C<profile> parameter or can simply be the first parameter). If it is
		269	missing, then the nodename (F<uname -n>) will be used as profile name.
252		270
253	=item naked port numbers (e.g. C<1234>)	271	The profile data is then gathered as follows:
254		272
255	These are resolved by prepending the local nodename and a colon, to be	273	First, all remaining key => value pairs (all of which are conveniently
256	further resolved.	274	undocumented at the moment) will be interpreted as configuration
		275	data. Then they will be overwritten by any values specified in the global
		276	default configuration (see the F<aemp> utility), then the chain of
		277	profiles chosen by the profile name (and any C<parent> attributes).
257		278
258	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	279	That means that the values specified in the profile have highest priority
		280	and the values specified directly via C<configure> have lowest priority,
		281	and can only be used to specify defaults.
259		282
260	These are resolved by using AnyEvent::DNS to resolve them, optionally	283	If the profile specifies a node ID, then this will become the node ID of
261	looking up SRV records for the C<aemp=4040> port, if no port was	284	this process. If not, then the profile name will be used as node ID, with
262	specified.	285	a unique randoms tring (C</%u>) appended.
		286
		287	The node ID can contain some C<%> sequences that are expanded: C<%n>
		288	is expanded to the local nodename, C<%u> is replaced by a random
		289	strign to make the node unique. For example, the F<aemp> commandline
		290	utility uses C<aemp/%n/%u> as nodename, which might expand to
		291	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		292
		293	=item step 2, bind listener sockets
		294
		295	The next step is to look up the binds in the profile, followed by binding
		296	aemp protocol listeners on all binds specified (it is possible and valid
		297	to have no binds, meaning that the node cannot be contacted form the
		298	outside. This means the node cannot talk to other nodes that also have no
		299	binds, but it can still talk to all "normal" nodes).
		300
		301	If the profile does not specify a binds list, then a default of C<*> is
		302	used, meaning the node will bind on a dynamically-assigned port on every
		303	local IP address it finds.
		304
		305	=item step 3, connect to seed nodes
		306
		307	As the last step, the seed ID list from the profile is passed to the
		308	L<AnyEvent::MP::Global> module, which will then use it to keep
		309	connectivity with at least one node at any point in time.
263		310
264	=back	311	=back
		312
		313	Example: become a distributed node using the local node name as profile.
		314	This should be the most common form of invocation for "daemon"-type nodes.
		315
		316	configure
		317
		318	Example: become a semi-anonymous node. This form is often used for
		319	commandline clients.
		320
		321	configure nodeid => "myscript/%n/%u";
		322
		323	Example: configure a node using a profile called seed, which is suitable
		324	for a seed node as it binds on all local addresses on a fixed port (4040,
		325	customary for aemp).
		326
		327	# use the aemp commandline utility
		328	# aemp profile seed binds '*:4040'
		329
		330	# then use it
		331	configure profile => "seed";
		332
		333	# or simply use aemp from the shell again:
		334	# aemp run profile seed
		335
		336	# or provide a nicer-to-remember nodeid
		337	# aemp run profile seed nodeid "$(hostname)"
265		338
266	=item $SELF	339	=item $SELF
267		340
268	Contains the current port id while executing C<rcv> callbacks or C<psub>	341	Contains the current port id while executing C<rcv> callbacks or C<psub>
269	blocks.	342	blocks.
270		343
271	=item SELF, %SELF, @SELF...	344	=item *SELF, SELF, %SELF, @SELF...
272		345
273	Due to some quirks in how perl exports variables, it is impossible to	346	Due to some quirks in how perl exports variables, it is impossible to
274	just export C<$SELF>, all the symbols called C<SELF> are exported by this	347	just export C<$SELF>, all the symbols named C<SELF> are exported by this
275	module, but only C<$SELF> is currently used.	348	module, but only C<$SELF> is currently used.
276		349
277	=item snd $port, type => @data	350	=item snd $port, type => @data
278		351
279	=item snd $port, @msg	352	=item snd $port, @msg
280		353
281	Send the given message to the given port ID, which can identify either	354	Send the given message to the given port, which can identify either a
282	a local or a remote port, and must be a port ID.	355	local or a remote port, and must be a port ID.
283		356
284	While the message can be about anything, it is highly recommended to use a	357	While the message can be almost anything, it is highly recommended to
285	string as first element (a port ID, or some word that indicates a request	358	use a string as first element (a port ID, or some word that indicates a
286	type etc.).	359	request type etc.) and to consist if only simple perl values (scalars,
		360	arrays, hashes) - if you think you need to pass an object, think again.
287		361
288	The message data effectively becomes read-only after a call to this	362	The message data logically becomes read-only after a call to this
289	function: modifying any argument is not allowed and can cause many	363	function: modifying any argument (or values referenced by them) is
290	problems.	364	forbidden, as there can be considerable time between the call to C<snd>
		365	and the time the message is actually being serialised - in fact, it might
		366	never be copied as within the same process it is simply handed to the
		367	receiving port.
291		368
292	The type of data you can transfer depends on the transport protocol: when	369	The type of data you can transfer depends on the transport protocol: when
293	JSON is used, then only strings, numbers and arrays and hashes consisting	370	JSON is used, then only strings, numbers and arrays and hashes consisting
294	of those are allowed (no objects). When Storable is used, then anything	371	of those are allowed (no objects). When Storable is used, then anything
295	that Storable can serialise and deserialise is allowed, and for the local	372	that Storable can serialise and deserialise is allowed, and for the local
296	node, anything can be passed.	373	node, anything can be passed. Best rely only on the common denominator of
		374	these.
297		375
298	=item $local_port = port	376	=item $local_port = port
299		377
300	Create a new local port object and returns its port ID. Initially it has	378	Create a new local port object and returns its port ID. Initially it has
301	no callbacks set and will throw an error when it receives messages.	379	no callbacks set and will throw an error when it receives messages.
…		…
320		398
321	=cut	399	=cut
322		400
323	sub rcv($@);	401	sub rcv($@);
324		402
325	sub _kilme {	403	my $KILME = sub {
326	die "received message on port without callback";	404	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
327	}	405	kil $SELF, unhandled_message => "no callback set for message (first element $tag)";
		406	};
328		407
329	sub port(;&) {	408	sub port(;&) {
330	my $id = "$UNIQ." . $ID++;	409	my $id = $UNIQ . ++$ID;
331	my $port = "$NODE#$id";	410	my $port = "$NODE#$id";
332		411
333	rcv $port, shift \|\| \&_kilme;	412	rcv $port, shift \|\| $KILME;
334		413
335	$port	414	$port
336	}	415	}
337		416
338	=item rcv $local_port, $callback->(@msg)	417	=item rcv $local_port, $callback->(@msg)
…		…
343		422
344	The global C<$SELF> (exported by this module) contains C<$port> while	423	The global C<$SELF> (exported by this module) contains C<$port> while
345	executing the callback. Runtime errors during callback execution will	424	executing the callback. Runtime errors during callback execution will
346	result in the port being C<kil>ed.	425	result in the port being C<kil>ed.
347		426
348	The default callback received all messages not matched by a more specific	427	The default callback receives all messages not matched by a more specific
349	C<tag> match.	428	C<tag> match.
350		429
351	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	430	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
352		431
353	Register callbacks to be called on messages starting with the given tag on	432	Register (or replace) callbacks to be called on messages starting with the
354	the given port (and return the port), or unregister it (when C<$callback>	433	given tag on the given port (and return the port), or unregister it (when
355	is C<$undef>).	434	C<$callback> is C<$undef> or missing). There can only be one callback
		435	registered for each tag.
356		436
357	The original message will be passed to the callback, after the first	437	The original message will be passed to the callback, after the first
358	element (the tag) has been removed. The callback will use the same	438	element (the tag) has been removed. The callback will use the same
359	environment as the default callback (see above).	439	environment as the default callback (see above).
360		440
…		…
372	rcv port,	452	rcv port,
373	msg1 => sub { ... },	453	msg1 => sub { ... },
374	...	454	...
375	;	455	;
376		456
		457	Example: temporarily register a rcv callback for a tag matching some port
		458	(e.g. for an rpc reply) and unregister it after a message was received.
		459
		460	rcv $port, $otherport => sub {
		461	my @reply = @_;
		462
		463	rcv $SELF, $otherport;
		464	};
		465
377	=cut	466	=cut
378		467
379	sub rcv($@) {	468	sub rcv($@) {
380	my $port = shift;	469	my $port = shift;
381	my ($noderef, $portid) = split /#/, $port, 2;	470	my ($nodeid, $portid) = split /#/, $port, 2;
382		471
383	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	472	$NODE{$nodeid} == $NODE{""}
384	or Carp::croak "$port: rcv can only be called on local ports, caught";	473	or Carp::croak "$port: rcv can only be called on local ports, caught";
385		474
386	while (@_) {	475	while (@_) {
387	if (ref $_[0]) {	476	if (ref $_[0]) {
388	if (my $self = $PORT_DATA{$portid}) {	477	if (my $self = $PORT_DATA{$portid}) {
389	"AnyEvent::MP::Port" eq ref $self	478	"AnyEvent::MP::Port" eq ref $self
390	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	479	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
391		480
392	$self->[2] = shift;	481	$self->[0] = shift;
393	} else {	482	} else {
394	my $cb = shift;	483	my $cb = shift;
395	$PORT{$portid} = sub {	484	$PORT{$portid} = sub {
396	local $SELF = $port;	485	local $SELF = $port;
397	eval { &$cb }; _self_die if $@;	486	eval { &$cb }; _self_die if $@;
398	};	487	};
399	}	488	}
400	} elsif (defined $_[0]) {	489	} elsif (defined $_[0]) {
401	my $self = $PORT_DATA{$portid} \|\|= do {	490	my $self = $PORT_DATA{$portid} \|\|= do {
402	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	491	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
403		492
404	$PORT{$portid} = sub {	493	$PORT{$portid} = sub {
405	local $SELF = $port;	494	local $SELF = $port;
406		495
407	if (my $cb = $self->[1]{$_[0]}) {	496	if (my $cb = $self->[1]{$_[0]}) {
…		…
429	}	518	}
430		519
431	$port	520	$port
432	}	521	}
433		522
		523	=item peval $port, $coderef[, @args]
		524
		525	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		526	when the code throews an exception the C<$port> will be killed.
		527
		528	Any remaining args will be passed to the callback. Any return values will
		529	be returned to the caller.
		530
		531	This is useful when you temporarily want to execute code in the context of
		532	a port.
		533
		534	Example: create a port and run some initialisation code in it's context.
		535
		536	my $port = port { ... };
		537
		538	peval $port, sub {
		539	init
		540	or die "unable to init";
		541	};
		542
		543	=cut
		544
		545	sub peval($$) {
		546	local $SELF = shift;
		547	my $cb = shift;
		548
		549	if (wantarray) {
		550	my @res = eval { &$cb };
		551	_self_die if $@;
		552	@res
		553	} else {
		554	my $res = eval { &$cb };
		555	_self_die if $@;
		556	$res
		557	}
		558	}
		559
434	=item $closure = psub { BLOCK }	560	=item $closure = psub { BLOCK }
435		561
436	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	562	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
437	closure is executed, sets up the environment in the same way as in C<rcv>	563	closure is executed, sets up the environment in the same way as in C<rcv>
438	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	564	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		565
		566	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		567	BLOCK }, @_ } >>.
439		568
440	This is useful when you register callbacks from C<rcv> callbacks:	569	This is useful when you register callbacks from C<rcv> callbacks:
441		570
442	rcv delayed_reply => sub {	571	rcv delayed_reply => sub {
443	my ($delay, @reply) = @_;	572	my ($delay, @reply) = @_;
…		…
467	$res	596	$res
468	}	597	}
469	}	598	}
470	}	599	}
471		600
472	=item $guard = mon $port, $cb->(@reason)	601	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
473		602
474	=item $guard = mon $port, $rcvport	603	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
475		604
476	=item $guard = mon $port	605	=item $guard = mon $port # kill $SELF when $port dies
477		606
478	=item $guard = mon $port, $rcvport, @msg	607	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
479		608
480	Monitor the given port and do something when the port is killed or	609	Monitor the given port and do something when the port is killed or
481	messages to it were lost, and optionally return a guard that can be used	610	messages to it were lost, and optionally return a guard that can be used
482	to stop monitoring again.	611	to stop monitoring again.
483
484	C<mon> effectively guarantees that, in the absence of hardware failures,
485	that after starting the monitor, either all messages sent to the port
486	will arrive, or the monitoring action will be invoked after possible
487	message loss has been detected. No messages will be lost "in between"
488	(after the first lost message no further messages will be received by the
489	port). After the monitoring action was invoked, further messages might get
490	delivered again.
491		612
492	In the first form (callback), the callback is simply called with any	613	In the first form (callback), the callback is simply called with any
493	number of C<@reason> elements (no @reason means that the port was deleted	614	number of C<@reason> elements (no @reason means that the port was deleted
494	"normally"). Note also that I<< the callback B<must> never die >>, so use	615	"normally"). Note also that I<< the callback B<must> never die >>, so use
495	C<eval> if unsure.	616	C<eval> if unsure.
496		617
497	In the second form (another port given), the other port (C<$rcvport>)	618	In the second form (another port given), the other port (C<$rcvport>)
498	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	619	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
499	"normal" kils nothing happens, while under all other conditions, the other	620	"normal" kils nothing happens, while under all other conditions, the other
500	port is killed with the same reason.	621	port is killed with the same reason.
501		622
502	The third form (kill self) is the same as the second form, except that	623	The third form (kill self) is the same as the second form, except that
503	C<$rvport> defaults to C<$SELF>.	624	C<$rvport> defaults to C<$SELF>.
504		625
505	In the last form (message), a message of the form C<@msg, @reason> will be	626	In the last form (message), a message of the form C<@msg, @reason> will be
506	C<snd>.	627	C<snd>.
		628
		629	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		630	alert was raised), they are removed and will not trigger again.
507		631
508	As a rule of thumb, monitoring requests should always monitor a port from	632	As a rule of thumb, monitoring requests should always monitor a port from
509	a local port (or callback). The reason is that kill messages might get	633	a local port (or callback). The reason is that kill messages might get
510	lost, just like any other message. Another less obvious reason is that	634	lost, just like any other message. Another less obvious reason is that
511	even monitoring requests can get lost (for exmaple, when the connection	635	even monitoring requests can get lost (for example, when the connection
512	to the other node goes down permanently). When monitoring a port locally	636	to the other node goes down permanently). When monitoring a port locally
513	these problems do not exist.	637	these problems do not exist.
514		638
		639	C<mon> effectively guarantees that, in the absence of hardware failures,
		640	after starting the monitor, either all messages sent to the port will
		641	arrive, or the monitoring action will be invoked after possible message
		642	loss has been detected. No messages will be lost "in between" (after
		643	the first lost message no further messages will be received by the
		644	port). After the monitoring action was invoked, further messages might get
		645	delivered again.
		646
		647	Inter-host-connection timeouts and monitoring depend on the transport
		648	used. The only transport currently implemented is TCP, and AnyEvent::MP
		649	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		650	non-idle connection, and usually around two hours for idle connections).
		651
		652	This means that monitoring is good for program errors and cleaning up
		653	stuff eventually, but they are no replacement for a timeout when you need
		654	to ensure some maximum latency.
		655
515	Example: call a given callback when C<$port> is killed.	656	Example: call a given callback when C<$port> is killed.
516		657
517	mon $port, sub { warn "port died because of <@_>\n" };	658	mon $port, sub { warn "port died because of <@_>\n" };
518		659
519	Example: kill ourselves when C<$port> is killed abnormally.	660	Example: kill ourselves when C<$port> is killed abnormally.
…		…
525	mon $port, $self => "restart";	666	mon $port, $self => "restart";
526		667
527	=cut	668	=cut
528		669
529	sub mon {	670	sub mon {
530	my ($noderef, $port) = split /#/, shift, 2;	671	my ($nodeid, $port) = split /#/, shift, 2;
531		672
532	my $node = $NODE{$noderef} \|\| add_node $noderef;	673	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
533		674
534	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	675	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
535		676
536	unless (ref $cb) {	677	unless (ref $cb) {
537	if (@_) {	678	if (@_) {
…		…
546	}	687	}
547		688
548	$node->monitor ($port, $cb);	689	$node->monitor ($port, $cb);
549		690
550	defined wantarray	691	defined wantarray
551	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	692	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
552	}	693	}
553		694
554	=item $guard = mon_guard $port, $ref, $ref...	695	=item $guard = mon_guard $port, $ref, $ref...
555		696
556	Monitors the given C<$port> and keeps the passed references. When the port	697	Monitors the given C<$port> and keeps the passed references. When the port
557	is killed, the references will be freed.	698	is killed, the references will be freed.
558		699
559	Optionally returns a guard that will stop the monitoring.	700	Optionally returns a guard that will stop the monitoring.
560		701
561	This function is useful when you create e.g. timers or other watchers and	702	This function is useful when you create e.g. timers or other watchers and
562	want to free them when the port gets killed:	703	want to free them when the port gets killed (note the use of C<psub>):
563		704
564	$port->rcv (start => sub {	705	$port->rcv (start => sub {
565	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	706	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
566	undef $timer if 0.9 < rand;	707	undef $timer if 0.9 < rand;
567	});	708	});
568	});	709	});
569		710
570	=cut	711	=cut
…		…
579		720
580	=item kil $port[, @reason]	721	=item kil $port[, @reason]
581		722
582	Kill the specified port with the given C<@reason>.	723	Kill the specified port with the given C<@reason>.
583		724
584	If no C<@reason> is specified, then the port is killed "normally" (linked	725	If no C<@reason> is specified, then the port is killed "normally" -
585	ports will not be kileld, or even notified).	726	monitor callback will be invoked, but the kil will not cause linked ports
		727	(C<mon $mport, $lport> form) to get killed.
586		728
587	Otherwise, linked ports get killed with the same reason (second form of	729	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
588	C<mon>, see below).	730	form) get killed with the same reason.
589		731
590	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	732	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
591	will be reported as reason C<< die => $@ >>.	733	will be reported as reason C<< die => $@ >>.
592		734
593	Transport/communication errors are reported as C<< transport_error =>	735	Transport/communication errors are reported as C<< transport_error =>
594	$message >>.	736	$message >>.
595		737
596	=cut	738	Common idioms:
		739
		740	# silently remove yourself, do not kill linked ports
		741	kil $SELF;
		742
		743	# report a failure in some detail
		744	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		745
		746	# do not waste much time with killing, just die when something goes wrong
		747	open my $fh, "<file"
		748	or die "file: $!";
597		749
598	=item $port = spawn $node, $initfunc[, @initdata]	750	=item $port = spawn $node, $initfunc[, @initdata]
599		751
600	Creates a port on the node C<$node> (which can also be a port ID, in which	752	Creates a port on the node C<$node> (which can also be a port ID, in which
601	case it's the node where that port resides).	753	case it's the node where that port resides).
602		754
603	The port ID of the newly created port is return immediately, and it is	755	The port ID of the newly created port is returned immediately, and it is
604	permissible to immediately start sending messages or monitor the port.	756	possible to immediately start sending messages or to monitor the port.
605		757
606	After the port has been created, the init function is	758	After the port has been created, the init function is called on the remote
607	called. This function must be a fully-qualified function name	759	node, in the same context as a C<rcv> callback. This function must be a
608	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	760	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
609	program, use C<::name>.	761	specify a function in the main program, use C<::name>.
610		762
611	If the function doesn't exist, then the node tries to C<require>	763	If the function doesn't exist, then the node tries to C<require>
612	the package, then the package above the package and so on (e.g.	764	the package, then the package above the package and so on (e.g.
613	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	765	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
614	exists or it runs out of package names.	766	exists or it runs out of package names.
615		767
616	The init function is then called with the newly-created port as context	768	The init function is then called with the newly-created port as context
617	object (C<$SELF>) and the C<@initdata> values as arguments.	769	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		770	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		771	the port might not get created.
618		772
619	A common idiom is to pass your own port, monitor the spawned port, and	773	A common idiom is to pass a local port, immediately monitor the spawned
620	in the init function, monitor the original port. This two-way monitoring	774	port, and in the remote init function, immediately monitor the passed
621	ensures that both ports get cleaned up when there is a problem.	775	local port. This two-way monitoring ensures that both ports get cleaned up
		776	when there is a problem.
		777
		778	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		779	caller before C<spawn> returns (by delaying invocation when spawn is
		780	called for the local node).
622		781
623	Example: spawn a chat server port on C<$othernode>.	782	Example: spawn a chat server port on C<$othernode>.
624		783
625	# this node, executed from within a port context:	784	# this node, executed from within a port context:
626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	785	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
641		800
642	sub _spawn {	801	sub _spawn {
643	my $port = shift;	802	my $port = shift;
644	my $init = shift;	803	my $init = shift;
645		804
		805	# rcv will create the actual port
646	local $SELF = "$NODE#$port";	806	local $SELF = "$NODE#$port";
647	eval {	807	eval {
648	&{ load_func $init }	808	&{ load_func $init }
649	};	809	};
650	_self_die if $@;	810	_self_die if $@;
651	}	811	}
652		812
653	sub spawn(@) {	813	sub spawn(@) {
654	my ($noderef, undef) = split /#/, shift, 2;	814	my ($nodeid, undef) = split /#/, shift, 2;
655		815
656	my $id = "$RUNIQ." . $ID++;	816	my $id = $RUNIQ . ++$ID;
657		817
658	$_[0] =~ /::/	818	$_[0] =~ /::/
659	or Carp::croak "spawn init function must be a fully-qualified name, caught";	819	or Carp::croak "spawn init function must be a fully-qualified name, caught";
660		820
661	($NODE{$noderef} \|\| add_node $noderef)	821	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
662	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
663		822
664	"$noderef#$id"	823	"$nodeid#$id"
665	}	824	}
666		825
		826
		827	=item after $timeout, @msg
		828
		829	=item after $timeout, $callback
		830
		831	Either sends the given message, or call the given callback, after the
		832	specified number of seconds.
		833
		834	This is simply a utility function that comes in handy at times - the
		835	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		836	so it may go away in the future.
		837
		838	=cut
		839
		840	sub after($@) {
		841	my ($timeout, @action) = @_;
		842
		843	my $t; $t = AE::timer $timeout, 0, sub {
		844	undef $t;
		845	ref $action[0]
		846	? $action[0]()
		847	: snd @action;
		848	};
		849	}
		850
		851	#=item $cb2 = timeout $seconds, $cb[, @args]
		852
		853	=item cal $port, @msg, $callback[, $timeout]
		854
		855	A simple form of RPC - sends a message to the given C<$port> with the
		856	given contents (C<@msg>), but adds a reply port to the message.
		857
		858	The reply port is created temporarily just for the purpose of receiving
		859	the reply, and will be C<kil>ed when no longer needed.
		860
		861	A reply message sent to the port is passed to the C<$callback> as-is.
		862
		863	If an optional time-out (in seconds) is given and it is not C<undef>,
		864	then the callback will be called without any arguments after the time-out
		865	elapsed and the port is C<kil>ed.
		866
		867	If no time-out is given (or it is C<undef>), then the local port will
		868	monitor the remote port instead, so it eventually gets cleaned-up.
		869
		870	Currently this function returns the temporary port, but this "feature"
		871	might go in future versions unless you can make a convincing case that
		872	this is indeed useful for something.
		873
		874	=cut
		875
		876	sub cal(@) {
		877	my $timeout = ref $_[-1] ? undef : pop;
		878	my $cb = pop;
		879
		880	my $port = port {
		881	undef $timeout;
		882	kil $SELF;
		883	&$cb;
		884	};
		885
		886	if (defined $timeout) {
		887	$timeout = AE::timer $timeout, 0, sub {
		888	undef $timeout;
		889	kil $port;
		890	$cb->();
		891	};
		892	} else {
		893	mon $_[0], sub {
		894	kil $port;
		895	$cb->();
		896	};
		897	}
		898
		899	push @_, $port;
		900	&snd;
		901
		902	$port
		903	}
		904
667	=back	905	=back
668		906
669	=head1 NODE MESSAGES	907	=head1 DISTRIBUTED DATABASE
670		908
671	Nodes understand the following messages sent to them. Many of them take	909	AnyEvent::MP comes with a simple distributed database. The database will
672	arguments called C<@reply>, which will simply be used to compose a reply	910	be mirrored asynchronously on all global nodes. Other nodes bind to one
673	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	911	of the global nodes for their needs. Every node has a "local database"
674	the remaining arguments are simply the message data.	912	which contains all the values that are set locally. All local databases
		913	are merged together to form the global database, which can be queried.
675		914
676	While other messages exist, they are not public and subject to change.	915	The database structure is that of a two-level hash - the database hash
		916	contains hashes which contain values, similarly to a perl hash of hashes,
		917	i.e.:
677		918
		919	$DATABASE{$family}{$subkey} = $value
		920
		921	The top level hash key is called "family", and the second-level hash key
		922	is called "subkey" or simply "key".
		923
		924	The family must be alphanumeric, i.e. start with a letter and consist
		925	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		926	pretty much like Perl module names.
		927
		928	As the family namespace is global, it is recommended to prefix family names
		929	with the name of the application or module using it.
		930
		931	The subkeys must be non-empty strings, with no further restrictions.
		932
		933	The values should preferably be strings, but other perl scalars should
		934	work as well (such as C<undef>, arrays and hashes).
		935
		936	Every database entry is owned by one node - adding the same family/subkey
		937	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		938	but the result might be nondeterministic, i.e. the key might have
		939	different values on different nodes.
		940
		941	Different subkeys in the same family can be owned by different nodes
		942	without problems, and in fact, this is the common method to create worker
		943	pools. For example, a worker port for image scaling might do this:
		944
		945	db_set my_image_scalers => $port;
		946
		947	And clients looking for an image scaler will want to get the
		948	C<my_image_scalers> keys from time to time:
		949
		950	db_keys my_image_scalers => sub {
		951	@ports = @{ $_[0] };
		952	};
		953
		954	Or better yet, they want to monitor the database family, so they always
		955	have a reasonable up-to-date copy:
		956
		957	db_mon my_image_scalers => sub {
		958	@ports = keys %{ $_[0] };
		959	};
		960
		961	In general, you can set or delete single subkeys, but query and monitor
		962	whole families only.
		963
		964	If you feel the need to monitor or query a single subkey, try giving it
		965	it's own family.
		966
678	=over 4	967	=over
		968
		969	=item db_set $family => $subkey [=> $value]
		970
		971	Sets (or replaces) a key to the database - if C<$value> is omitted,
		972	C<undef> is used instead.
		973
		974	=item db_del $family => $subkey...
		975
		976	Deletes one or more subkeys from the database family.
		977
		978	=item $guard = db_reg $family => $subkey [=> $value]
		979
		980	Sets the key on the database and returns a guard. When the guard is
		981	destroyed, the key is deleted from the database. If C<$value> is missing,
		982	then C<undef> is used.
		983
		984	=item db_family $family => $cb->(\%familyhash)
		985
		986	Queries the named database C<$family> and call the callback with the
		987	family represented as a hash. You can keep and freely modify the hash.
		988
		989	=item db_keys $family => $cb->(\@keys)
		990
		991	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		992	them as array reference to the callback.
		993
		994	=item db_values $family => $cb->(\@values)
		995
		996	Same as C<db_family>, except it only queries the family I<values> and passes them
		997	as array reference to the callback.
		998
		999	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1000
		1001	Creates a monitor on the given database family. Each time a key is set
		1002	or or is deleted the callback is called with a hash containing the
		1003	database family and three lists of added, changed and deleted subkeys,
		1004	respectively. If no keys have changed then the array reference might be
		1005	C<undef> or even missing.
		1006
		1007	If not called in void context, a guard object is returned that, when
		1008	destroyed, stops the monitor.
		1009
		1010	The family hash reference and the key arrays belong to AnyEvent::MP and
		1011	B<must not be modified or stored> by the callback. When in doubt, make a
		1012	copy.
		1013
		1014	As soon as possible after the monitoring starts, the callback will be
		1015	called with the intiial contents of the family, even if it is empty,
		1016	i.e. there will always be a timely call to the callback with the current
		1017	contents.
		1018
		1019	It is possible that the callback is called with a change event even though
		1020	the subkey is already present and the value has not changed.
		1021
		1022	The monitoring stops when the guard object is destroyed.
		1023
		1024	Example: on every change to the family "mygroup", print out all keys.
		1025
		1026	my $guard = db_mon mygroup => sub {
		1027	my ($family, $a, $c, $d) = @_;
		1028	print "mygroup members: ", (join " ", keys %$family), "\n";
		1029	};
		1030
		1031	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1032
		1033	my $guard; $guard = db_mon My::Module::workers => sub {
		1034	my ($family, $a, $c, $d) = @_;
		1035	return unless %$family;
		1036	undef $guard;
		1037	print "My::Module::workers now nonempty\n";
		1038	};
		1039
		1040	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1041
		1042	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1043	my ($family, $a, $c, $d) = @_;
		1044
		1045	print "+$_=$family->{$_}\n" for @$a;
		1046	print "*$_=$family->{$_}\n" for @$c;
		1047	print "-$_=$family->{$_}\n" for @$d;
		1048	};
679		1049
680	=cut	1050	=cut
681
682	=item lookup => $name, @reply
683
684	Replies with the port ID of the specified well-known port, or C<undef>.
685
686	=item devnull => ...
687
688	Generic data sink/CPU heat conversion.
689
690	=item relay => $port, @msg
691
692	Simply forwards the message to the given port.
693
694	=item eval => $string[ @reply]
695
696	Evaluates the given string. If C<@reply> is given, then a message of the
697	form C<@reply, $@, @evalres> is sent.
698
699	Example: crash another node.
700
701	snd $othernode, eval => "exit";
702
703	=item time => @reply
704
705	Replies the the current node time to C<@reply>.
706
707	Example: tell the current node to send the current time to C<$myport> in a
708	C<timereply> message.
709
710	snd $NODE, time => $myport, timereply => 1, 2;
711	# => snd $myport, timereply => 1, 2, <time>
712		1051
713	=back	1052	=back
714		1053
715	=head1 AnyEvent::MP vs. Distributed Erlang	1054	=head1 AnyEvent::MP vs. Distributed Erlang
716		1055
717	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1056	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
718	== aemp node, Erlang process == aemp port), so many of the documents and	1057	== aemp node, Erlang process == aemp port), so many of the documents and
719	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1058	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
720	sample:	1059	sample:
721		1060
722	http://www.Erlang.se/doc/programming_rules.shtml	1061	http://www.erlang.se/doc/programming_rules.shtml
723	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1062	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
724	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1063	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
725	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1064	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
726		1065
727	Despite the similarities, there are also some important differences:	1066	Despite the similarities, there are also some important differences:
728		1067
729	=over 4	1068	=over 4
730		1069
731	=item * Node references contain the recipe on how to contact them.	1070	=item * Node IDs are arbitrary strings in AEMP.
732		1071
733	Erlang relies on special naming and DNS to work everywhere in the	1072	Erlang relies on special naming and DNS to work everywhere in the same
734	same way. AEMP relies on each node knowing it's own address(es), with	1073	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
735	convenience functionality.	1074	configuration or DNS), and possibly the addresses of some seed nodes, but
		1075	will otherwise discover other nodes (and their IDs) itself.
736		1076
737	This means that AEMP requires a less tightly controlled environment at the
738	cost of longer node references and a slightly higher management overhead.
739
740	=item Erlang has a "remote ports are like local ports" philosophy, AEMP	1077	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
741	uses "local ports are like remote ports".	1078	uses "local ports are like remote ports".
742		1079
743	The failure modes for local ports are quite different (runtime errors	1080	The failure modes for local ports are quite different (runtime errors
744	only) then for remote ports - when a local port dies, you I<know> it dies,	1081	only) then for remote ports - when a local port dies, you I<know> it dies,
745	when a connection to another node dies, you know nothing about the other	1082	when a connection to another node dies, you know nothing about the other
…		…
752	ports being the special case/exception, where transport errors cannot	1089	ports being the special case/exception, where transport errors cannot
753	occur.	1090	occur.
754		1091
755	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1092	=item * Erlang uses processes and a mailbox, AEMP does not queue.
756		1093
757	Erlang uses processes that selectively receive messages, and therefore	1094	Erlang uses processes that selectively receive messages out of order, and
758	needs a queue. AEMP is event based, queuing messages would serve no	1095	therefore needs a queue. AEMP is event based, queuing messages would serve
759	useful purpose. For the same reason the pattern-matching abilities of	1096	no useful purpose. For the same reason the pattern-matching abilities
760	AnyEvent::MP are more limited, as there is little need to be able to	1097	of AnyEvent::MP are more limited, as there is little need to be able to
761	filter messages without dequeing them.	1098	filter messages without dequeuing them.
762		1099
763	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1100	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1101	being event-based, while Erlang is process-based.
		1102
		1103	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1104	top of AEMP and Coro threads.
764		1105
765	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1106	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
766		1107
767	Sending messages in Erlang is synchronous and blocks the process (and	1108	Sending messages in Erlang is synchronous and blocks the process until
		1109	a conenction has been established and the message sent (and so does not
768	so does not need a queue that can overflow). AEMP sends are immediate,	1110	need a queue that can overflow). AEMP sends return immediately, connection
769	connection establishment is handled in the background.	1111	establishment is handled in the background.
770		1112
771	=item * Erlang suffers from silent message loss, AEMP does not.	1113	=item * Erlang suffers from silent message loss, AEMP does not.
772		1114
773	Erlang makes few guarantees on messages delivery - messages can get lost	1115	Erlang implements few guarantees on messages delivery - messages can get
774	without any of the processes realising it (i.e. you send messages a, b,	1116	lost without any of the processes realising it (i.e. you send messages a,
775	and c, and the other side only receives messages a and c).	1117	b, and c, and the other side only receives messages a and c).
776		1118
777	AEMP guarantees correct ordering, and the guarantee that there are no	1119	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1120	guarantee that after one message is lost, all following ones sent to the
		1121	same port are lost as well, until monitoring raises an error, so there are
778	holes in the message sequence.	1122	no silent "holes" in the message sequence.
779		1123
780	=item * In Erlang, processes can be declared dead and later be found to be	1124	If you want your software to be very reliable, you have to cope with
781	alive.	1125	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
782		1126	simply tries to work better in common error cases, such as when a network
783	In Erlang it can happen that a monitored process is declared dead and	1127	link goes down.
784	linked processes get killed, but later it turns out that the process is
785	still alive - and can receive messages.
786
787	In AEMP, when port monitoring detects a port as dead, then that port will
788	eventually be killed - it cannot happen that a node detects a port as dead
789	and then later sends messages to it, finding it is still alive.
790		1128
791	=item * Erlang can send messages to the wrong port, AEMP does not.	1129	=item * Erlang can send messages to the wrong port, AEMP does not.
792		1130
793	In Erlang it is quite likely that a node that restarts reuses a process ID	1131	In Erlang it is quite likely that a node that restarts reuses an Erlang
794	known to other nodes for a completely different process, causing messages	1132	process ID known to other nodes for a completely different process,
795	destined for that process to end up in an unrelated process.	1133	causing messages destined for that process to end up in an unrelated
		1134	process.
796		1135
797	AEMP never reuses port IDs, so old messages or old port IDs floating	1136	AEMP does not reuse port IDs, so old messages or old port IDs floating
798	around in the network will not be sent to an unrelated port.	1137	around in the network will not be sent to an unrelated port.
799		1138
800	=item * Erlang uses unprotected connections, AEMP uses secure	1139	=item * Erlang uses unprotected connections, AEMP uses secure
801	authentication and can use TLS.	1140	authentication and can use TLS.
802		1141
803	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1142	AEMP can use a proven protocol - TLS - to protect connections and
804	securely authenticate nodes.	1143	securely authenticate nodes.
805		1144
806	=item * The AEMP protocol is optimised for both text-based and binary	1145	=item * The AEMP protocol is optimised for both text-based and binary
807	communications.	1146	communications.
808		1147
809	The AEMP protocol, unlike the Erlang protocol, supports both	1148	The AEMP protocol, unlike the Erlang protocol, supports both programming
810	language-independent text-only protocols (good for debugging) and binary,	1149	language independent text-only protocols (good for debugging), and binary,
811	language-specific serialisers (e.g. Storable).	1150	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1151	used, the protocol is actually completely text-based.
812		1152
813	It has also been carefully designed to be implementable in other languages	1153	It has also been carefully designed to be implementable in other languages
814	with a minimum of work while gracefully degrading fucntionality to make the	1154	with a minimum of work while gracefully degrading functionality to make the
815	protocol simple.	1155	protocol simple.
816		1156
817	=item * AEMP has more flexible monitoring options than Erlang.	1157	=item * AEMP has more flexible monitoring options than Erlang.
818		1158
819	In Erlang, you can chose to receive I<all> exit signals as messages	1159	In Erlang, you can chose to receive I<all> exit signals as messages or
820	or I<none>, there is no in-between, so monitoring single processes is	1160	I<none>, there is no in-between, so monitoring single Erlang processes is
821	difficult to implement. Monitoring in AEMP is more flexible than in	1161	difficult to implement.
822	Erlang, as one can choose between automatic kill, exit message or callback	1162
823	on a per-process basis.	1163	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1164	between automatic kill, exit message or callback on a per-port basis.
824		1165
825	=item * Erlang tries to hide remote/local connections, AEMP does not.	1166	=item * Erlang tries to hide remote/local connections, AEMP does not.
826		1167
827	Monitoring in Erlang is not an indicator of process death/crashes,	1168	Monitoring in Erlang is not an indicator of process death/crashes, in the
828	as linking is (except linking is unreliable in Erlang).	1169	same way as linking is (except linking is unreliable in Erlang).
829		1170
830	In AEMP, you don't "look up" registered port names or send to named ports	1171	In AEMP, you don't "look up" registered port names or send to named ports
831	that might or might not be persistent. Instead, you normally spawn a port	1172	that might or might not be persistent. Instead, you normally spawn a port
832	on the remote node. The init function monitors the you, and you monitor	1173	on the remote node. The init function monitors you, and you monitor the
833	the remote port. Since both monitors are local to the node, they are much	1174	remote port. Since both monitors are local to the node, they are much more
834	more reliable.	1175	reliable (no need for C<spawn_link>).
835		1176
836	This also saves round-trips and avoids sending messages to the wrong port	1177	This also saves round-trips and avoids sending messages to the wrong port
837	(hard to do in Erlang).	1178	(hard to do in Erlang).
838		1179
839	=back	1180	=back
840		1181
841	=head1 RATIONALE	1182	=head1 RATIONALE
842		1183
843	=over 4	1184	=over 4
844		1185
845	=item Why strings for ports and noderefs, why not objects?	1186	=item Why strings for port and node IDs, why not objects?
846		1187
847	We considered "objects", but found that the actual number of methods	1188	We considered "objects", but found that the actual number of methods
848	thatc an be called are very low. Since port IDs and noderefs travel over	1189	that can be called are quite low. Since port and node IDs travel over
849	the network frequently, the serialising/deserialising would add lots of	1190	the network frequently, the serialising/deserialising would add lots of
850	overhead, as well as having to keep a proxy object.	1191	overhead, as well as having to keep a proxy object everywhere.
851		1192
852	Strings can easily be printed, easily serialised etc. and need no special	1193	Strings can easily be printed, easily serialised etc. and need no special
853	procedures to be "valid".	1194	procedures to be "valid".
854		1195
855	And a a miniport consists of a single closure stored in a global hash - it	1196	And as a result, a port with just a default receiver consists of a single
856	can't become much cheaper.	1197	code reference stored in a global hash - it can't become much cheaper.
857		1198
858	=item Why favour JSON, why not real serialising format such as Storable?	1199	=item Why favour JSON, why not a real serialising format such as Storable?
859		1200
860	In fact, any AnyEvent::MP node will happily accept Storable as framing	1201	In fact, any AnyEvent::MP node will happily accept Storable as framing
861	format, but currently there is no way to make a node use Storable by	1202	format, but currently there is no way to make a node use Storable by
862	default.	1203	default (although all nodes will accept it).
863		1204
864	The default framing protocol is JSON because a) JSON::XS is many times	1205	The default framing protocol is JSON because a) JSON::XS is many times
865	faster for small messages and b) most importantly, after years of	1206	faster for small messages and b) most importantly, after years of
866	experience we found that object serialisation is causing more problems	1207	experience we found that object serialisation is causing more problems
867	than it gains: Just like function calls, objects simply do not travel	1208	than it solves: Just like function calls, objects simply do not travel
868	easily over the network, mostly because they will always be a copy, so you	1209	easily over the network, mostly because they will always be a copy, so you
869	always have to re-think your design.	1210	always have to re-think your design.
870		1211
871	Keeping your messages simple, concentrating on data structures rather than	1212	Keeping your messages simple, concentrating on data structures rather than
872	objects, will keep your messages clean, tidy and efficient.	1213	objects, will keep your messages clean, tidy and efficient.
873		1214
874	=back	1215	=back
875		1216
876	=head1 SEE ALSO	1217	=head1 SEE ALSO
877		1218
		1219	L<AnyEvent::MP::Intro> - a gentle introduction.
		1220
		1221	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1222
		1223	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1224	your applications.
		1225
		1226	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1227
		1228	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1229	all nodes.
		1230
878	L<AnyEvent>.	1231	L<AnyEvent>.
879		1232
880	=head1 AUTHOR	1233	=head1 AUTHOR
881		1234
882	Marc Lehmann <schmorp@schmorp.de>	1235	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.133 by root, Mon Mar 12 10:34:06 2012 UTC