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Revision 1.63 by root, Thu Aug 27 21:29:37 2009 UTC vs.
Revision 1.150 by root, Wed Aug 17 19:45:18 2016 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;	15	configure;
17		16
18	# ports are message endpoints	17	# ports are message destinations
19		18
20	# sending messages	19	# sending messages
21	snd $port, type => data...;	20	snd $port, type => data...;
22	snd $port, @msg;	21	snd $port, @msg;
23	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
24		23
25	# creating/using ports, the simple way	24	# creating/using ports, the simple way
26	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
27		26
28	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
29	my $port = port;	28	my $port = port;
30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
31	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
32		31
33	# create a port on another node	32	# create a port on another node
34	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
35		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
36	# monitoring	39	# monitoring
37	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $port, $cb->(@msg) # callback is invoked on death
38	mon $port, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
39	mon $port, $otherport, @msg # send message on death	42	mon $port, $localport, @msg # send message on death
40		43
41	=head1 CURRENT STATUS	44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
42		46
43	AnyEvent::MP - stable API, should work	47	# execute callbacks in $SELF port context
44	AnyEvent::MP::Intro - outdated	48	my $timer = AE::timer 1, 0, psub {
45	AnyEvent::MP::Kernel - WIP	49	die "kill the port, delayed";
46	AnyEvent::MP::Transport - mostly stable	50	};
47		51
48	stay tuned.	52	# distributed database - modification
		53	db_set $family => $subkey [=> $value] # add a subkey
		54	db_del $family => $subkey... # delete one or more subkeys
		55	db_reg $family => $port [=> $value] # register a port
		56
		57	# distributed database - queries
		58	db_family $family => $cb->(\%familyhash)
		59	db_keys $family => $cb->(\@keys)
		60	db_values $family => $cb->(\@values)
		61
		62	# distributed database - monitoring a family
		63	db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
49		64
50	=head1 DESCRIPTION	65	=head1 DESCRIPTION
51		66
52	This module (-family) implements a simple message passing framework.	67	This module (-family) implements a simple message passing framework.
53		68
54	Despite its simplicity, you can securely message other processes running	69	Despite its simplicity, you can securely message other processes running
55	on the same or other hosts.	70	on the same or other hosts, and you can supervise entities remotely.
56		71
57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	72	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
58	manual page.	73	manual page and the examples under F<eg/>.
59
60	At the moment, this module family is severly broken and underdocumented,
61	so do not use. This was uploaded mainly to reserve the CPAN namespace -
62	stay tuned!
63		74
64	=head1 CONCEPTS	75	=head1 CONCEPTS
65		76
66	=over 4	77	=over 4
67		78
68	=item port	79	=item port
69		80
70	A port is something you can send messages to (with the C<snd> function).	81	Not to be confused with a TCP port, a "port" is something you can send
		82	messages to (with the C<snd> function).
71		83
72	Ports allow you to register C<rcv> handlers that can match all or just	84	Ports allow you to register C<rcv> handlers that can match all or just
73	some messages. Messages will not be queued.	85	some messages. Messages send to ports will not be queued, regardless of
		86	anything was listening for them or not.
74		87
		88	Ports are represented by (printable) strings called "port IDs".
		89
75	=item port ID - C<noderef#portname>	90	=item port ID - C<nodeid#portname>
76		91
77	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	92	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
78	separator, and a port name (a printable string of unspecified format). An	93	as separator, and a port name (a printable string of unspecified
79	exception is the the node port, whose ID is identical to its node	94	format created by AnyEvent::MP).
80	reference.
81		95
82	=item node	96	=item node
83		97
84	A node is a single process containing at least one port - the node port,	98	A node is a single process containing at least one port - the node port,
85	which provides nodes to manage each other remotely, and to create new	99	which enables nodes to manage each other remotely, and to create new
86	ports.	100	ports.
87		101
88	Nodes are either private (single-process only), slaves (can only talk to	102	Nodes are either public (have one or more listening ports) or private
89	public nodes, but do not need an open port) or public nodes (connectable	103	(no listening ports). Private nodes cannot talk to other private nodes
90	from any other node).	104	currently, but all nodes can talk to public nodes.
91		105
		106	Nodes is represented by (printable) strings called "node IDs".
		107
92	=item node ID - C<[a-za-Z0-9_\-.:]+>	108	=item node ID - C<[A-Za-z0-9_\-.:]*>
93		109
94	A node ID is a string that either simply identifies the node (for	110	A node ID is a string that uniquely identifies the node within a
95	private and slave nodes), or contains a recipe on how to reach a given	111	network. Depending on the configuration used, node IDs can look like a
96	node (for public nodes).	112	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		113	doesn't interpret node IDs in any way except to uniquely identify a node.
97		114
98	This recipe is simply a comma-separated list of C<address:port> pairs (for	115	=item binds - C<ip:port>
99	TCP/IP, other protocols might look different).
100		116
101	Node references come in two flavours: resolved (containing only numerical	117	Nodes can only talk to each other by creating some kind of connection to
102	addresses) or unresolved (where hostnames are used instead of addresses).	118	each other. To do this, nodes should listen on one or more local transport
		119	endpoints - binds.
103		120
104	Before using an unresolved node reference in a message you first have to	121	Currently, only standard C<ip:port> specifications can be used, which
105	resolve it.	122	specify TCP ports to listen on. So a bind is basically just a tcp socket
		123	in listening mode that accepts connections from other nodes.
		124
		125	=item seed nodes
		126
		127	When a node starts, it knows nothing about the network it is in - it
		128	needs to connect to at least one other node that is already in the
		129	network. These other nodes are called "seed nodes".
		130
		131	Seed nodes themselves are not special - they are seed nodes only because
		132	some other node I<uses> them as such, but any node can be used as seed
		133	node for other nodes, and eahc node can use a different set of seed nodes.
		134
		135	In addition to discovering the network, seed nodes are also used to
		136	maintain the network - all nodes using the same seed node are part of the
		137	same network. If a network is split into multiple subnets because e.g. the
		138	network link between the parts goes down, then using the same seed nodes
		139	for all nodes ensures that eventually the subnets get merged again.
		140
		141	Seed nodes are expected to be long-running, and at least one seed node
		142	should always be available. They should also be relatively responsive - a
		143	seed node that blocks for long periods will slow down everybody else.
		144
		145	For small networks, it's best if every node uses the same set of seed
		146	nodes. For large networks, it can be useful to specify "regional" seed
		147	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		148	each other. What's important is that all seed nodes connections form a
		149	complete graph, so that the network cannot split into separate subnets
		150	forever.
		151
		152	Seed nodes are represented by seed IDs.
		153
		154	=item seed IDs - C<host:port>
		155
		156	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		157	TCP port) of nodes that should be used as seed nodes.
		158
		159	=item global nodes
		160
		161	An AEMP network needs a discovery service - nodes need to know how to
		162	connect to other nodes they only know by name. In addition, AEMP offers a
		163	distributed "group database", which maps group names to a list of strings
		164	- for example, to register worker ports.
		165
		166	A network needs at least one global node to work, and allows every node to
		167	be a global node.
		168
		169	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		170	node and tries to keep connections to all other nodes. So while it can
		171	make sense to make every node "global" in small networks, it usually makes
		172	sense to only make seed nodes into global nodes in large networks (nodes
		173	keep connections to seed nodes and global nodes, so making them the same
		174	reduces overhead).
106		175
107	=back	176	=back
108		177
109	=head1 VARIABLES/FUNCTIONS	178	=head1 VARIABLES/FUNCTIONS
110		179
…		…
112		181
113	=cut	182	=cut
114		183
115	package AnyEvent::MP;	184	package AnyEvent::MP;
116		185
		186	use AnyEvent::MP::Config ();
117	use AnyEvent::MP::Kernel;	187	use AnyEvent::MP::Kernel;
		188	use AnyEvent::MP::Kernel qw(
		189	%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID
		190	add_node load_func
		191
		192	NODE $NODE
		193	configure
		194	node_of port_is_local
		195	snd kil
		196	db_set db_del
		197	db_mon db_family db_keys db_values
		198	);
118		199
119	use common::sense;	200	use common::sense;
120		201
121	use Carp ();	202	use Carp ();
122		203
123	use AE ();	204	use AnyEvent ();
		205	use Guard ();
124		206
125	use base "Exporter";	207	use base "Exporter";
126		208
127	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	209	our $VERSION = $AnyEvent::MP::Config::VERSION;
128		210
129	our @EXPORT = qw(	211	our @EXPORT = qw(
130	NODE $NODE *SELF node_of after	212	NODE $NODE
131	resolve_node initialise_node	213	configure
132	snd rcv mon mon_guard kil reg psub spawn	214	node_of port_is_local
133	port	215	snd kil
		216	db_set db_del
		217	db_mon db_family db_keys db_values
		218
		219	*SELF
		220
		221	port rcv mon mon_guard psub peval spawn cal
		222	db_set db_del db_reg
		223	db_mon db_family db_keys db_values
		224
		225	after
134	);	226	);
135		227
136	our $SELF;	228	our $SELF;
137		229
138	sub _self_die() {	230	sub _self_die() {
…		…
141	kil $SELF, die => $msg;	233	kil $SELF, die => $msg;
142	}	234	}
143		235
144	=item $thisnode = NODE / $NODE	236	=item $thisnode = NODE / $NODE
145		237
146	The C<NODE> function returns, and the C<$NODE> variable contains the	238	The C<NODE> function returns, and the C<$NODE> variable contains, the node
147	node id of the local node. The value is initialised by a call to	239	ID of the node running in the current process. This value is initialised by
148	C<initialise_node>.	240	a call to C<configure>.
149		241
150	=item $nodeid = node_of $port	242	=item $nodeid = node_of $port
151		243
152	Extracts and returns the noderef from a port ID or a node ID.	244	Extracts and returns the node ID from a port ID or a node ID.
153		245
154	=item initialise_node $profile_name	246	=item $is_local = port_is_local $port
155		247
		248	Returns true iff the port is a local port.
		249
		250	=item configure $profile, key => value...
		251
		252	=item configure key => value...
		253
156	Before a node can talk to other nodes on the network it has to initialise	254	Before a node can talk to other nodes on the network (i.e. enter
157	itself - the minimum a node needs to know is it's own name, and optionally	255	"distributed mode") it has to configure itself - the minimum a node needs
158	it should know the noderefs of some other nodes in the network.	256	to know is its own name, and optionally it should know the addresses of
		257	some other nodes in the network to discover other nodes.
159		258
160	This function initialises a node - it must be called exactly once (or	259	This function configures a node - it must be called exactly once (or
161	never) before calling other AnyEvent::MP functions.	260	never) before calling other AnyEvent::MP functions.
162		261
163	All arguments (optionally except for the first) are noderefs, which can be	262	The key/value pairs are basically the same ones as documented for the
164	either resolved or unresolved.	263	F<aemp> command line utility (sans the set/del prefix), with these additions:
165
166	The first argument will be looked up in the configuration database first
167	(if it is C<undef> then the current nodename will be used instead) to find
168	the relevant configuration profile (see L<aemp>). If none is found then
169	the default configuration is used. The configuration supplies additional
170	seed/master nodes and can override the actual noderef.
171
172	There are two types of networked nodes, public nodes and slave nodes:
173		264
174	=over 4	265	=over 4
175		266
176	=item public nodes	267	=item norc => $boolean (default false)
177		268
178	For public nodes, C<$noderef> (supplied either directly to	269	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
179	C<initialise_node> or indirectly via a profile or the nodename) must be a	270	be consulted - all configuration options must be specified in the
180	noderef (possibly unresolved, in which case it will be resolved).	271	C<configure> call.
181		272
182	After resolving, the node will bind itself on all endpoints.	273	=item force => $boolean (default false)
183		274
184	=item slave nodes	275	IF true, then the values specified in the C<configure> will take
185		276	precedence over any values configured via the rc file. The default is for
186	When the C<$noderef> (either as given or overriden by the config file)	277	the rc file to override any options specified in the program.
187	is the special string C<slave/>, then the node will become a slave
188	node. Slave nodes cannot be contacted from outside, and cannot talk to
189	each other (at least in this version of AnyEvent::MP).
190
191	Slave nodes work by creating connections to all public nodes, using the
192	L<AnyEvent::MP::Global> service.
193		278
194	=back	279	=back
195		280
196	After initialising itself, the node will connect to all additional
197	C<$seednodes> that are specified diretcly or via a profile. Seednodes are
198	optional and can be used to quickly bootstrap the node into an existing
199	network.
200
201	All the seednodes will also be specially marked to automatically retry
202	connecting to them indefinitely, so make sure that seednodes are really
203	reliable and up (this might also change in the future).
204
205	Example: become a public node listening on the guessed noderef, or the one
206	specified via C<aemp> for the current node. This should be the most common
207	form of invocation for "daemon"-type nodes.
208
209	initialise_node;
210
211	Example: become a slave node to any of the the seednodes specified via
212	C<aemp>. This form is often used for commandline clients.
213
214	initialise_node "slave/";
215
216	Example: become a public node, and try to contact some well-known master
217	servers to become part of the network.
218
219	initialise_node undef, "master1", "master2";
220
221	Example: become a public node listening on port C<4041>.
222
223	initialise_node 4041;
224
225	Example: become a public node, only visible on localhost port 4044.
226
227	initialise_node "localhost:4044";
228
229	=item $cv = resolve_node $noderef
230
231	Takes an unresolved node reference that may contain hostnames and
232	abbreviated IDs, resolves all of them and returns a resolved node
233	reference.
234
235	In addition to C<address:port> pairs allowed in resolved noderefs, the
236	following forms are supported:
237
238	=over 4	281	=over 4
239		282
240	=item the empty string	283	=item step 1, gathering configuration from profiles
241		284
242	An empty-string component gets resolved as if the default port (4040) was	285	The function first looks up a profile in the aemp configuration (see the
243	specified.	286	L<aemp> commandline utility). The profile name can be specified via the
		287	named C<profile> parameter or can simply be the first parameter). If it is
		288	missing, then the nodename (F<uname -n>) will be used as profile name.
244		289
245	=item naked port numbers (e.g. C<1234>)	290	The profile data is then gathered as follows:
246		291
247	These are resolved by prepending the local nodename and a colon, to be	292	First, all remaining key => value pairs (all of which are conveniently
248	further resolved.	293	undocumented at the moment) will be interpreted as configuration
		294	data. Then they will be overwritten by any values specified in the global
		295	default configuration (see the F<aemp> utility), then the chain of
		296	profiles chosen by the profile name (and any C<parent> attributes).
249		297
250	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	298	That means that the values specified in the profile have highest priority
		299	and the values specified directly via C<configure> have lowest priority,
		300	and can only be used to specify defaults.
251		301
252	These are resolved by using AnyEvent::DNS to resolve them, optionally	302	If the profile specifies a node ID, then this will become the node ID of
253	looking up SRV records for the C<aemp=4040> port, if no port was	303	this process. If not, then the profile name will be used as node ID, with
254	specified.	304	a unique randoms tring (C</%u>) appended.
		305
		306	The node ID can contain some C<%> sequences that are expanded: C<%n>
		307	is expanded to the local nodename, C<%u> is replaced by a random
		308	strign to make the node unique. For example, the F<aemp> commandline
		309	utility uses C<aemp/%n/%u> as nodename, which might expand to
		310	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		311
		312	=item step 2, bind listener sockets
		313
		314	The next step is to look up the binds in the profile, followed by binding
		315	aemp protocol listeners on all binds specified (it is possible and valid
		316	to have no binds, meaning that the node cannot be contacted from the
		317	outside. This means the node cannot talk to other nodes that also have no
		318	binds, but it can still talk to all "normal" nodes).
		319
		320	If the profile does not specify a binds list, then a default of C<*> is
		321	used, meaning the node will bind on a dynamically-assigned port on every
		322	local IP address it finds.
		323
		324	=item step 3, connect to seed nodes
		325
		326	As the last step, the seed ID list from the profile is passed to the
		327	L<AnyEvent::MP::Global> module, which will then use it to keep
		328	connectivity with at least one node at any point in time.
255		329
256	=back	330	=back
		331
		332	Example: become a distributed node using the local node name as profile.
		333	This should be the most common form of invocation for "daemon"-type nodes.
		334
		335	configure
		336
		337	Example: become a semi-anonymous node. This form is often used for
		338	commandline clients.
		339
		340	configure nodeid => "myscript/%n/%u";
		341
		342	Example: configure a node using a profile called seed, which is suitable
		343	for a seed node as it binds on all local addresses on a fixed port (4040,
		344	customary for aemp).
		345
		346	# use the aemp commandline utility
		347	# aemp profile seed binds '*:4040'
		348
		349	# then use it
		350	configure profile => "seed";
		351
		352	# or simply use aemp from the shell again:
		353	# aemp run profile seed
		354
		355	# or provide a nicer-to-remember nodeid
		356	# aemp run profile seed nodeid "$(hostname)"
257		357
258	=item $SELF	358	=item $SELF
259		359
260	Contains the current port id while executing C<rcv> callbacks or C<psub>	360	Contains the current port id while executing C<rcv> callbacks or C<psub>
261	blocks.	361	blocks.
262		362
263	=item SELF, %SELF, @SELF...	363	=item *SELF, SELF, %SELF, @SELF...
264		364
265	Due to some quirks in how perl exports variables, it is impossible to	365	Due to some quirks in how perl exports variables, it is impossible to
266	just export C<$SELF>, all the symbols called C<SELF> are exported by this	366	just export C<$SELF>, all the symbols named C<SELF> are exported by this
267	module, but only C<$SELF> is currently used.	367	module, but only C<$SELF> is currently used.
268		368
269	=item snd $port, type => @data	369	=item snd $port, type => @data
270		370
271	=item snd $port, @msg	371	=item snd $port, @msg
272		372
273	Send the given message to the given port ID, which can identify either	373	Send the given message to the given port, which can identify either a
274	a local or a remote port, and must be a port ID.	374	local or a remote port, and must be a port ID.
275		375
276	While the message can be about anything, it is highly recommended to use a	376	While the message can be almost anything, it is highly recommended to
277	string as first element (a port ID, or some word that indicates a request	377	use a string as first element (a port ID, or some word that indicates a
278	type etc.).	378	request type etc.) and to consist if only simple perl values (scalars,
		379	arrays, hashes) - if you think you need to pass an object, think again.
279		380
280	The message data effectively becomes read-only after a call to this	381	The message data logically becomes read-only after a call to this
281	function: modifying any argument is not allowed and can cause many	382	function: modifying any argument (or values referenced by them) is
282	problems.	383	forbidden, as there can be considerable time between the call to C<snd>
		384	and the time the message is actually being serialised - in fact, it might
		385	never be copied as within the same process it is simply handed to the
		386	receiving port.
283		387
284	The type of data you can transfer depends on the transport protocol: when	388	The type of data you can transfer depends on the transport protocol: when
285	JSON is used, then only strings, numbers and arrays and hashes consisting	389	JSON is used, then only strings, numbers and arrays and hashes consisting
286	of those are allowed (no objects). When Storable is used, then anything	390	of those are allowed (no objects). When Storable is used, then anything
287	that Storable can serialise and deserialise is allowed, and for the local	391	that Storable can serialise and deserialise is allowed, and for the local
288	node, anything can be passed.	392	node, anything can be passed. Best rely only on the common denominator of
		393	these.
289		394
290	=item $local_port = port	395	=item $local_port = port
291		396
292	Create a new local port object and returns its port ID. Initially it has	397	Create a new local port object and returns its port ID. Initially it has
293	no callbacks set and will throw an error when it receives messages.	398	no callbacks set and will throw an error when it receives messages.
…		…
312		417
313	=cut	418	=cut
314		419
315	sub rcv($@);	420	sub rcv($@);
316		421
317	sub _kilme {	422	my $KILME = sub {
318	die "received message on port without callback";	423	(my $tag = substr $_[0], 0, 30) =~ s/([^\x20-\x7e])/./g;
319	}	424	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		425	};
320		426
321	sub port(;&) {	427	sub port(;&) {
322	my $id = "$UNIQ." . $ID++;	428	my $id = $UNIQ . ++$ID;
323	my $port = "$NODE#$id";	429	my $port = "$NODE#$id";
324		430
325	rcv $port, shift || \&_kilme;	431	rcv $port, shift || $KILME;
326		432
327	$port	433	$port
328	}	434	}
329		435
330	=item rcv $local_port, $callback->(@msg)	436	=item rcv $local_port, $callback->(@msg)
…		…
335		441
336	The global C<$SELF> (exported by this module) contains C<$port> while	442	The global C<$SELF> (exported by this module) contains C<$port> while
337	executing the callback. Runtime errors during callback execution will	443	executing the callback. Runtime errors during callback execution will
338	result in the port being C<kil>ed.	444	result in the port being C<kil>ed.
339		445
340	The default callback received all messages not matched by a more specific	446	The default callback receives all messages not matched by a more specific
341	C<tag> match.	447	C<tag> match.
342		448
343	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	449	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
344		450
345	Register (or replace) callbacks to be called on messages starting with the	451	Register (or replace) callbacks to be called on messages starting with the
…		…
366	msg1 => sub { ... },	472	msg1 => sub { ... },
367	...	473	...
368	;	474	;
369		475
370	Example: temporarily register a rcv callback for a tag matching some port	476	Example: temporarily register a rcv callback for a tag matching some port
371	(e.g. for a rpc reply) and unregister it after a message was received.	477	(e.g. for an rpc reply) and unregister it after a message was received.
372		478
373	rcv $port, $otherport => sub {	479	rcv $port, $otherport => sub {
374	my @reply = @_;	480	my @reply = @_;
375		481
376	rcv $SELF, $otherport;	482	rcv $SELF, $otherport;
…		…
378		484
379	=cut	485	=cut
380		486
381	sub rcv($@) {	487	sub rcv($@) {
382	my $port = shift;	488	my $port = shift;
383	my ($noderef, $portid) = split /#/, $port, 2;	489	my ($nodeid, $portid) = split /#/, $port, 2;
384		490
385	$NODE{$noderef} == $NODE{""}	491	$nodeid eq $NODE
386	or Carp::croak "$port: rcv can only be called on local ports, caught";	492	or Carp::croak "$port: rcv can only be called on local ports, caught";
387		493
388	while (@_) {	494	while (@_) {
389	if (ref $_[0]) {	495	if (ref $_[0]) {
390	if (my $self = $PORT_DATA{$portid}) {	496	if (my $self = $PORT_DATA{$portid}) {
391	"AnyEvent::MP::Port" eq ref $self	497	"AnyEvent::MP::Port" eq ref $self
392	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	498	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
393		499
394	$self->[2] = shift;	500	$self->[0] = shift;
395	} else {	501	} else {
396	my $cb = shift;	502	my $cb = shift;
397	$PORT{$portid} = sub {	503	$PORT{$portid} = sub {
398	local $SELF = $port;	504	local $SELF = $port;
399	eval { &$cb }; _self_die if $@;	505	eval { &$cb }; _self_die if $@;
400	};	506	};
401	}	507	}
402	} elsif (defined $_[0]) {	508	} elsif (defined $_[0]) {
403	my $self = $PORT_DATA{$portid} ||= do {	509	my $self = $PORT_DATA{$portid} ||= do {
404	my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port";	510	my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
405		511
406	$PORT{$portid} = sub {	512	$PORT{$portid} = sub {
407	local $SELF = $port;	513	local $SELF = $port;
408		514
409	if (my $cb = $self->[1]{$_[0]}) {	515	if (my $cb = $self->[1]{$_[0]}) {
…		…
431	}	537	}
432		538
433	$port	539	$port
434	}	540	}
435		541
		542	=item peval $port, $coderef[, @args]
		543
		544	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		545	when the code throws an exception the C<$port> will be killed.
		546
		547	Any remaining args will be passed to the callback. Any return values will
		548	be returned to the caller.
		549
		550	This is useful when you temporarily want to execute code in the context of
		551	a port.
		552
		553	Example: create a port and run some initialisation code in it's context.
		554
		555	my $port = port { ... };
		556
		557	peval $port, sub {
		558	init
		559	or die "unable to init";
		560	};
		561
		562	=cut
		563
		564	sub peval($$) {
		565	local $SELF = shift;
		566	my $cb = shift;
		567
		568	if (wantarray) {
		569	my @res = eval { &$cb };
		570	_self_die if $@;
		571	@res
		572	} else {
		573	my $res = eval { &$cb };
		574	_self_die if $@;
		575	$res
		576	}
		577	}
		578
436	=item $closure = psub { BLOCK }	579	=item $closure = psub { BLOCK }
437		580
438	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	581	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
439	closure is executed, sets up the environment in the same way as in C<rcv>	582	closure is executed, sets up the environment in the same way as in C<rcv>
440	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	583	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		584
		585	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		586	BLOCK }, @_ } >>.
441		587
442	This is useful when you register callbacks from C<rcv> callbacks:	588	This is useful when you register callbacks from C<rcv> callbacks:
443		589
444	rcv delayed_reply => sub {	590	rcv delayed_reply => sub {
445	my ($delay, @reply) = @_;	591	my ($delay, @reply) = @_;
…		…
469	$res	615	$res
470	}	616	}
471	}	617	}
472	}	618	}
473		619
474	=item $guard = mon $port, $cb->(@reason)	620	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
475		621
476	=item $guard = mon $port, $rcvport	622	=item $guard = mon $port # kill $SELF when $port dies
477		623
478	=item $guard = mon $port	624	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
479		625
480	=item $guard = mon $port, $rcvport, @msg	626	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
481		627
482	Monitor the given port and do something when the port is killed or	628	Monitor the given port and do something when the port is killed or
483	messages to it were lost, and optionally return a guard that can be used	629	messages to it were lost, and optionally return a guard that can be used
484	to stop monitoring again.	630	to stop monitoring again.
485		631
		632	The first two forms distinguish between "normal" and "abnormal" kil's:
		633
		634	In the first form (another port given), if the C<$port> is C<kil>'ed with
		635	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		636	same reason. That is, on "normal" kil's nothing happens, while under all
		637	other conditions, the other port is killed with the same reason.
		638
		639	The second form (kill self) is the same as the first form, except that
		640	C<$rvport> defaults to C<$SELF>.
		641
		642	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		643	- it's up to the callback or receiver to check whether the C<@reason> is
		644	empty and act accordingly.
		645
		646	In the third form (callback), the callback is simply called with any
		647	number of C<@reason> elements (empty @reason means that the port was deleted
		648	"normally"). Note also that I<< the callback B<must> never die >>, so use
		649	C<eval> if unsure.
		650
		651	In the last form (message), a message of the form C<$rcvport, @msg,
		652	@reason> will be C<snd>.
		653
		654	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		655	alert was raised), they are removed and will not trigger again, even if it
		656	turns out that the port is still alive.
		657
		658	As a rule of thumb, monitoring requests should always monitor a remote
		659	port locally (using a local C<$rcvport> or a callback). The reason is that
		660	kill messages might get lost, just like any other message. Another less
		661	obvious reason is that even monitoring requests can get lost (for example,
		662	when the connection to the other node goes down permanently). When
		663	monitoring a port locally these problems do not exist.
		664
486	C<mon> effectively guarantees that, in the absence of hardware failures,	665	C<mon> effectively guarantees that, in the absence of hardware failures,
487	that after starting the monitor, either all messages sent to the port	666	after starting the monitor, either all messages sent to the port will
488	will arrive, or the monitoring action will be invoked after possible	667	arrive, or the monitoring action will be invoked after possible message
489	message loss has been detected. No messages will be lost "in between"	668	loss has been detected. No messages will be lost "in between" (after
490	(after the first lost message no further messages will be received by the	669	the first lost message no further messages will be received by the
491	port). After the monitoring action was invoked, further messages might get	670	port). After the monitoring action was invoked, further messages might get
492	delivered again.	671	delivered again.
493		672
494	Note that monitoring-actions are one-shot: once released, they are removed	673	Inter-host-connection timeouts and monitoring depend on the transport
495	and will not trigger again.	674	used. The only transport currently implemented is TCP, and AnyEvent::MP
		675	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		676	non-idle connection, and usually around two hours for idle connections).
496		677
497	In the first form (callback), the callback is simply called with any	678	This means that monitoring is good for program errors and cleaning up
498	number of C<@reason> elements (no @reason means that the port was deleted	679	stuff eventually, but they are no replacement for a timeout when you need
499	"normally"). Note also that I<< the callback B<must> never die >>, so use	680	to ensure some maximum latency.
500	C<eval> if unsure.
501
502	In the second form (another port given), the other port (C<$rcvport>)
503	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
504	"normal" kils nothing happens, while under all other conditions, the other
505	port is killed with the same reason.
506
507	The third form (kill self) is the same as the second form, except that
508	C<$rvport> defaults to C<$SELF>.
509
510	In the last form (message), a message of the form C<@msg, @reason> will be
511	C<snd>.
512
513	As a rule of thumb, monitoring requests should always monitor a port from
514	a local port (or callback). The reason is that kill messages might get
515	lost, just like any other message. Another less obvious reason is that
516	even monitoring requests can get lost (for exmaple, when the connection
517	to the other node goes down permanently). When monitoring a port locally
518	these problems do not exist.
519		681
520	Example: call a given callback when C<$port> is killed.	682	Example: call a given callback when C<$port> is killed.
521		683
522	mon $port, sub { warn "port died because of <@_>\n" };	684	mon $port, sub { warn "port died because of <@_>\n" };
523		685
…		…
530	mon $port, $self => "restart";	692	mon $port, $self => "restart";
531		693
532	=cut	694	=cut
533		695
534	sub mon {	696	sub mon {
535	my ($noderef, $port) = split /#/, shift, 2;	697	my ($nodeid, $port) = split /#/, shift, 2;
536		698
537	my $node = $NODE{$noderef} || add_node $noderef;	699	my $node = $NODE{$nodeid} || add_node $nodeid;
538		700
539	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';	701	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
540		702
541	unless (ref $cb) {	703	unless (ref $cb) {
542	if (@_) {	704	if (@_) {
…		…
551	}	713	}
552		714
553	$node->monitor ($port, $cb);	715	$node->monitor ($port, $cb);
554		716
555	defined wantarray	717	defined wantarray
556	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	718	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
557	}	719	}
558		720
559	=item $guard = mon_guard $port, $ref, $ref...	721	=item $guard = mon_guard $port, $ref, $ref...
560		722
561	Monitors the given C<$port> and keeps the passed references. When the port	723	Monitors the given C<$port> and keeps the passed references. When the port
562	is killed, the references will be freed.	724	is killed, the references will be freed.
563		725
564	Optionally returns a guard that will stop the monitoring.	726	Optionally returns a guard that will stop the monitoring.
565		727
566	This function is useful when you create e.g. timers or other watchers and	728	This function is useful when you create e.g. timers or other watchers and
567	want to free them when the port gets killed:	729	want to free them when the port gets killed (note the use of C<psub>):
568		730
569	$port->rcv (start => sub {	731	$port->rcv (start => sub {
570	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	732	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
571	undef $timer if 0.9 < rand;	733	undef $timer if 0.9 < rand;
572	});	734	});
573	});	735	});
574		736
575	=cut	737	=cut
…		…
584		746
585	=item kil $port[, @reason]	747	=item kil $port[, @reason]
586		748
587	Kill the specified port with the given C<@reason>.	749	Kill the specified port with the given C<@reason>.
588		750
589	If no C<@reason> is specified, then the port is killed "normally" (linked	751	If no C<@reason> is specified, then the port is killed "normally" -
590	ports will not be kileld, or even notified).	752	monitor callback will be invoked, but the kil will not cause linked ports
		753	(C<mon $mport, $lport> form) to get killed.
591		754
592	Otherwise, linked ports get killed with the same reason (second form of	755	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
593	C<mon>, see below).	756	form) get killed with the same reason.
594		757
595	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	758	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
596	will be reported as reason C<< die => $@ >>.	759	will be reported as reason C<< die => $@ >>.
597		760
598	Transport/communication errors are reported as C<< transport_error =>	761	Transport/communication errors are reported as C<< transport_error =>
599	$message >>.	762	$message >>.
600		763
601	=cut	764	Common idioms:
		765
		766	# silently remove yourself, do not kill linked ports
		767	kil $SELF;
		768
		769	# report a failure in some detail
		770	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		771
		772	# do not waste much time with killing, just die when something goes wrong
		773	open my $fh, "<file"
		774	or die "file: $!";
602		775
603	=item $port = spawn $node, $initfunc[, @initdata]	776	=item $port = spawn $node, $initfunc[, @initdata]
604		777
605	Creates a port on the node C<$node> (which can also be a port ID, in which	778	Creates a port on the node C<$node> (which can also be a port ID, in which
606	case it's the node where that port resides).	779	case it's the node where that port resides).
607		780
608	The port ID of the newly created port is return immediately, and it is	781	The port ID of the newly created port is returned immediately, and it is
609	permissible to immediately start sending messages or monitor the port.	782	possible to immediately start sending messages or to monitor the port.
610		783
611	After the port has been created, the init function is	784	After the port has been created, the init function is called on the remote
612	called. This function must be a fully-qualified function name	785	node, in the same context as a C<rcv> callback. This function must be a
613	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	786	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
614	program, use C<::name>.	787	specify a function in the main program, use C<::name>.
615		788
616	If the function doesn't exist, then the node tries to C<require>	789	If the function doesn't exist, then the node tries to C<require>
617	the package, then the package above the package and so on (e.g.	790	the package, then the package above the package and so on (e.g.
618	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	791	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
619	exists or it runs out of package names.	792	exists or it runs out of package names.
620		793
621	The init function is then called with the newly-created port as context	794	The init function is then called with the newly-created port as context
622	object (C<$SELF>) and the C<@initdata> values as arguments.	795	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		796	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		797	the port might not get created.
623		798
624	A common idiom is to pass your own port, monitor the spawned port, and	799	A common idiom is to pass a local port, immediately monitor the spawned
625	in the init function, monitor the original port. This two-way monitoring	800	port, and in the remote init function, immediately monitor the passed
626	ensures that both ports get cleaned up when there is a problem.	801	local port. This two-way monitoring ensures that both ports get cleaned up
		802	when there is a problem.
		803
		804	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		805	caller before C<spawn> returns (by delaying invocation when spawn is
		806	called for the local node).
627		807
628	Example: spawn a chat server port on C<$othernode>.	808	Example: spawn a chat server port on C<$othernode>.
629		809
630	# this node, executed from within a port context:	810	# this node, executed from within a port context:
631	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	811	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
646		826
647	sub _spawn {	827	sub _spawn {
648	my $port = shift;	828	my $port = shift;
649	my $init = shift;	829	my $init = shift;
650		830
		831	# rcv will create the actual port
651	local $SELF = "$NODE#$port";	832	local $SELF = "$NODE#$port";
652	eval {	833	eval {
653	&{ load_func $init }	834	&{ load_func $init }
654	};	835	};
655	_self_die if $@;	836	_self_die if $@;
656	}	837	}
657		838
658	sub spawn(@) {	839	sub spawn(@) {
659	my ($noderef, undef) = split /#/, shift, 2;	840	my ($nodeid, undef) = split /#/, shift, 2;
660		841
661	my $id = "$RUNIQ." . $ID++;	842	my $id = $RUNIQ . ++$ID;
662		843
663	$_[0] =~ /::/	844	$_[0] =~ /::/
664	or Carp::croak "spawn init function must be a fully-qualified name, caught";	845	or Carp::croak "spawn init function must be a fully-qualified name, caught";
665		846
666	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	847	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
667		848
668	"$noderef#$id"	849	"$nodeid#$id"
669	}	850	}
		851
670		852
671	=item after $timeout, @msg	853	=item after $timeout, @msg
672		854
673	=item after $timeout, $callback	855	=item after $timeout, $callback
674		856
675	Either sends the given message, or call the given callback, after the	857	Either sends the given message, or call the given callback, after the
676	specified number of seconds.	858	specified number of seconds.
677		859
678	This is simply a utility function that come sin handy at times.	860	This is simply a utility function that comes in handy at times - the
		861	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		862	so it may go away in the future.
679		863
680	=cut	864	=cut
681		865
682	sub after($@) {	866	sub after($@) {
683	my ($timeout, @action) = @_;	867	my ($timeout, @action) = @_;
…		…
688	? $action[0]()	872	? $action[0]()
689	: snd @action;	873	: snd @action;
690	};	874	};
691	}	875	}
692		876
		877	#=item $cb2 = timeout $seconds, $cb[, @args]
		878
		879	=item cal $port, @msg, $callback[, $timeout]
		880
		881	A simple form of RPC - sends a message to the given C<$port> with the
		882	given contents (C<@msg>), but adds a reply port to the message.
		883
		884	The reply port is created temporarily just for the purpose of receiving
		885	the reply, and will be C<kil>ed when no longer needed.
		886
		887	A reply message sent to the port is passed to the C<$callback> as-is.
		888
		889	If an optional time-out (in seconds) is given and it is not C<undef>,
		890	then the callback will be called without any arguments after the time-out
		891	elapsed and the port is C<kil>ed.
		892
		893	If no time-out is given (or it is C<undef>), then the local port will
		894	monitor the remote port instead, so it eventually gets cleaned-up.
		895
		896	Currently this function returns the temporary port, but this "feature"
		897	might go in future versions unless you can make a convincing case that
		898	this is indeed useful for something.
		899
		900	=cut
		901
		902	sub cal(@) {
		903	my $timeout = ref $_[-1] ? undef : pop;
		904	my $cb = pop;
		905
		906	my $port = port {
		907	undef $timeout;
		908	kil $SELF;
		909	&$cb;
		910	};
		911
		912	if (defined $timeout) {
		913	$timeout = AE::timer $timeout, 0, sub {
		914	undef $timeout;
		915	kil $port;
		916	$cb->();
		917	};
		918	} else {
		919	mon $_[0], sub {
		920	kil $port;
		921	$cb->();
		922	};
		923	}
		924
		925	push @_, $port;
		926	&snd;
		927
		928	$port
		929	}
		930
		931	=back
		932
		933	=head1 DISTRIBUTED DATABASE
		934
		935	AnyEvent::MP comes with a simple distributed database. The database will
		936	be mirrored asynchronously on all global nodes. Other nodes bind to one
		937	of the global nodes for their needs. Every node has a "local database"
		938	which contains all the values that are set locally. All local databases
		939	are merged together to form the global database, which can be queried.
		940
		941	The database structure is that of a two-level hash - the database hash
		942	contains hashes which contain values, similarly to a perl hash of hashes,
		943	i.e.:
		944
		945	$DATABASE{$family}{$subkey} = $value
		946
		947	The top level hash key is called "family", and the second-level hash key
		948	is called "subkey" or simply "key".
		949
		950	The family must be alphanumeric, i.e. start with a letter and consist
		951	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		952	pretty much like Perl module names.
		953
		954	As the family namespace is global, it is recommended to prefix family names
		955	with the name of the application or module using it.
		956
		957	The subkeys must be non-empty strings, with no further restrictions.
		958
		959	The values should preferably be strings, but other perl scalars should
		960	work as well (such as C<undef>, arrays and hashes).
		961
		962	Every database entry is owned by one node - adding the same family/subkey
		963	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		964	but the result might be nondeterministic, i.e. the key might have
		965	different values on different nodes.
		966
		967	Different subkeys in the same family can be owned by different nodes
		968	without problems, and in fact, this is the common method to create worker
		969	pools. For example, a worker port for image scaling might do this:
		970
		971	db_set my_image_scalers => $port;
		972
		973	And clients looking for an image scaler will want to get the
		974	C<my_image_scalers> keys from time to time:
		975
		976	db_keys my_image_scalers => sub {
		977	@ports = @{ $_[0] };
		978	};
		979
		980	Or better yet, they want to monitor the database family, so they always
		981	have a reasonable up-to-date copy:
		982
		983	db_mon my_image_scalers => sub {
		984	@ports = keys %{ $_[0] };
		985	};
		986
		987	In general, you can set or delete single subkeys, but query and monitor
		988	whole families only.
		989
		990	If you feel the need to monitor or query a single subkey, try giving it
		991	it's own family.
		992
		993	=over
		994
		995	=item $guard = db_set $family => $subkey [=> $value]
		996
		997	Sets (or replaces) a key to the database - if C<$value> is omitted,
		998	C<undef> is used instead.
		999
		1000	When called in non-void context, C<db_set> returns a guard that
		1001	automatically calls C<db_del> when it is destroyed.
		1002
		1003	=item db_del $family => $subkey...
		1004
		1005	Deletes one or more subkeys from the database family.
		1006
		1007	=item $guard = db_reg $family => $port => $value
		1008
		1009	=item $guard = db_reg $family => $port
		1010
		1011	=item $guard = db_reg $family
		1012
		1013	Registers a port in the given family and optionally returns a guard to
		1014	remove it.
		1015
		1016	This function basically does the same as:
		1017
		1018	db_set $family => $port => $value
		1019
		1020	Except that the port is monitored and automatically removed from the
		1021	database family when it is kil'ed.
		1022
		1023	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1024	C<$SELF> is used.
		1025
		1026	This function is most useful to register a port in some port group (which
		1027	is just another name for a database family), and have it removed when the
		1028	port is gone. This works best when the port is a local port.
		1029
		1030	=cut
		1031
		1032	sub db_reg($$;$) {
		1033	my $family = shift;
		1034	my $port = @_ ? shift : $SELF;
		1035
		1036	my $clr = sub { db_del $family => $port };
		1037	mon $port, $clr;
		1038
		1039	db_set $family => $port => $_[0];
		1040
		1041	defined wantarray
		1042	and &Guard::guard ($clr)
		1043	}
		1044
		1045	=item db_family $family => $cb->(\%familyhash)
		1046
		1047	Queries the named database C<$family> and call the callback with the
		1048	family represented as a hash. You can keep and freely modify the hash.
		1049
		1050	=item db_keys $family => $cb->(\@keys)
		1051
		1052	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1053	them as array reference to the callback.
		1054
		1055	=item db_values $family => $cb->(\@values)
		1056
		1057	Same as C<db_family>, except it only queries the family I<values> and passes them
		1058	as array reference to the callback.
		1059
		1060	=item $guard = db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
		1061
		1062	Creates a monitor on the given database family. Each time a key is
		1063	set or is deleted the callback is called with a hash containing the
		1064	database family and three lists of added, changed and deleted subkeys,
		1065	respectively. If no keys have changed then the array reference might be
		1066	C<undef> or even missing.
		1067
		1068	If not called in void context, a guard object is returned that, when
		1069	destroyed, stops the monitor.
		1070
		1071	The family hash reference and the key arrays belong to AnyEvent::MP and
		1072	B<must not be modified or stored> by the callback. When in doubt, make a
		1073	copy.
		1074
		1075	As soon as possible after the monitoring starts, the callback will be
		1076	called with the intiial contents of the family, even if it is empty,
		1077	i.e. there will always be a timely call to the callback with the current
		1078	contents.
		1079
		1080	It is possible that the callback is called with a change event even though
		1081	the subkey is already present and the value has not changed.
		1082
		1083	The monitoring stops when the guard object is destroyed.
		1084
		1085	Example: on every change to the family "mygroup", print out all keys.
		1086
		1087	my $guard = db_mon mygroup => sub {
		1088	my ($family, $a, $c, $d) = @_;
		1089	print "mygroup members: ", (join " ", keys %$family), "\n";
		1090	};
		1091
		1092	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1093
		1094	my $guard; $guard = db_mon My::Module::workers => sub {
		1095	my ($family, $a, $c, $d) = @_;
		1096	return unless %$family;
		1097	undef $guard;
		1098	print "My::Module::workers now nonempty\n";
		1099	};
		1100
		1101	Example: print all changes to the family "AnyEvent::Fantasy::Module".
		1102
		1103	my $guard = db_mon AnyEvent::Fantasy::Module => sub {
		1104	my ($family, $a, $c, $d) = @_;
		1105
		1106	print "+$_=$family->{$_}\n" for @$a;
		1107	print "*$_=$family->{$_}\n" for @$c;
		1108	print "-$_=$family->{$_}\n" for @$d;
		1109	};
		1110
		1111	=cut
		1112
693	=back	1113	=back
694		1114
695	=head1 AnyEvent::MP vs. Distributed Erlang	1115	=head1 AnyEvent::MP vs. Distributed Erlang
696		1116
697	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1117	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
698	== aemp node, Erlang process == aemp port), so many of the documents and	1118	== aemp node, Erlang process == aemp port), so many of the documents and
699	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1119	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
700	sample:	1120	sample:
701		1121
702	http://www.Erlang.se/doc/programming_rules.shtml	1122	http://www.erlang.se/doc/programming_rules.shtml
703	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1123	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
704	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1124	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
705	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1125	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
706		1126
707	Despite the similarities, there are also some important differences:	1127	Despite the similarities, there are also some important differences:
708		1128
709	=over 4	1129	=over 4
710		1130
711	=item * Node references contain the recipe on how to contact them.	1131	=item * Node IDs are arbitrary strings in AEMP.
712		1132
713	Erlang relies on special naming and DNS to work everywhere in the	1133	Erlang relies on special naming and DNS to work everywhere in the same
714	same way. AEMP relies on each node knowing it's own address(es), with	1134	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
715	convenience functionality.	1135	configuration or DNS), and possibly the addresses of some seed nodes, but
716		1136	will otherwise discover other nodes (and their IDs) itself.
717	This means that AEMP requires a less tightly controlled environment at the
718	cost of longer node references and a slightly higher management overhead.
719		1137
720	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1138	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
721	uses "local ports are like remote ports".	1139	uses "local ports are like remote ports".
722		1140
723	The failure modes for local ports are quite different (runtime errors	1141	The failure modes for local ports are quite different (runtime errors
…		…
732	ports being the special case/exception, where transport errors cannot	1150	ports being the special case/exception, where transport errors cannot
733	occur.	1151	occur.
734		1152
735	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1153	=item * Erlang uses processes and a mailbox, AEMP does not queue.
736		1154
737	Erlang uses processes that selectively receive messages, and therefore	1155	Erlang uses processes that selectively receive messages out of order, and
738	needs a queue. AEMP is event based, queuing messages would serve no	1156	therefore needs a queue. AEMP is event based, queuing messages would serve
739	useful purpose. For the same reason the pattern-matching abilities of	1157	no useful purpose. For the same reason the pattern-matching abilities
740	AnyEvent::MP are more limited, as there is little need to be able to	1158	of AnyEvent::MP are more limited, as there is little need to be able to
741	filter messages without dequeing them.	1159	filter messages without dequeuing them.
742		1160
743	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1161	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1162	being event-based, while Erlang is process-based.
		1163
		1164	You can have a look at L<Coro::MP> for a more Erlang-like process model on
		1165	top of AEMP and Coro threads.
744		1166
745	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1167	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
746		1168
747	Sending messages in Erlang is synchronous and blocks the process (and	1169	Sending messages in Erlang is synchronous and blocks the process until
		1170	a connection has been established and the message sent (and so does not
748	so does not need a queue that can overflow). AEMP sends are immediate,	1171	need a queue that can overflow). AEMP sends return immediately, connection
749	connection establishment is handled in the background.	1172	establishment is handled in the background.
750		1173
751	=item * Erlang suffers from silent message loss, AEMP does not.	1174	=item * Erlang suffers from silent message loss, AEMP does not.
752		1175
753	Erlang makes few guarantees on messages delivery - messages can get lost	1176	Erlang implements few guarantees on messages delivery - messages can get
754	without any of the processes realising it (i.e. you send messages a, b,	1177	lost without any of the processes realising it (i.e. you send messages a,
755	and c, and the other side only receives messages a and c).	1178	b, and c, and the other side only receives messages a and c).
756		1179
757	AEMP guarantees correct ordering, and the guarantee that there are no	1180	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1181	guarantee that after one message is lost, all following ones sent to the
		1182	same port are lost as well, until monitoring raises an error, so there are
758	holes in the message sequence.	1183	no silent "holes" in the message sequence.
759		1184
760	=item * In Erlang, processes can be declared dead and later be found to be	1185	If you want your software to be very reliable, you have to cope with
761	alive.	1186	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
762		1187	simply tries to work better in common error cases, such as when a network
763	In Erlang it can happen that a monitored process is declared dead and	1188	link goes down.
764	linked processes get killed, but later it turns out that the process is
765	still alive - and can receive messages.
766
767	In AEMP, when port monitoring detects a port as dead, then that port will
768	eventually be killed - it cannot happen that a node detects a port as dead
769	and then later sends messages to it, finding it is still alive.
770		1189
771	=item * Erlang can send messages to the wrong port, AEMP does not.	1190	=item * Erlang can send messages to the wrong port, AEMP does not.
772		1191
773	In Erlang it is quite likely that a node that restarts reuses a process ID	1192	In Erlang it is quite likely that a node that restarts reuses an Erlang
774	known to other nodes for a completely different process, causing messages	1193	process ID known to other nodes for a completely different process,
775	destined for that process to end up in an unrelated process.	1194	causing messages destined for that process to end up in an unrelated
		1195	process.
776		1196
777	AEMP never reuses port IDs, so old messages or old port IDs floating	1197	AEMP does not reuse port IDs, so old messages or old port IDs floating
778	around in the network will not be sent to an unrelated port.	1198	around in the network will not be sent to an unrelated port.
779		1199
780	=item * Erlang uses unprotected connections, AEMP uses secure	1200	=item * Erlang uses unprotected connections, AEMP uses secure
781	authentication and can use TLS.	1201	authentication and can use TLS.
782		1202
783	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1203	AEMP can use a proven protocol - TLS - to protect connections and
784	securely authenticate nodes.	1204	securely authenticate nodes.
785		1205
786	=item * The AEMP protocol is optimised for both text-based and binary	1206	=item * The AEMP protocol is optimised for both text-based and binary
787	communications.	1207	communications.
788		1208
789	The AEMP protocol, unlike the Erlang protocol, supports both	1209	The AEMP protocol, unlike the Erlang protocol, supports both programming
790	language-independent text-only protocols (good for debugging) and binary,	1210	language independent text-only protocols (good for debugging), and binary,
791	language-specific serialisers (e.g. Storable).	1211	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1212	used, the protocol is actually completely text-based.
792		1213
793	It has also been carefully designed to be implementable in other languages	1214	It has also been carefully designed to be implementable in other languages
794	with a minimum of work while gracefully degrading fucntionality to make the	1215	with a minimum of work while gracefully degrading functionality to make the
795	protocol simple.	1216	protocol simple.
796		1217
797	=item * AEMP has more flexible monitoring options than Erlang.	1218	=item * AEMP has more flexible monitoring options than Erlang.
798		1219
799	In Erlang, you can chose to receive I<all> exit signals as messages	1220	In Erlang, you can chose to receive I<all> exit signals as messages or
800	or I<none>, there is no in-between, so monitoring single processes is	1221	I<none>, there is no in-between, so monitoring single Erlang processes is
801	difficult to implement. Monitoring in AEMP is more flexible than in	1222	difficult to implement.
802	Erlang, as one can choose between automatic kill, exit message or callback	1223
803	on a per-process basis.	1224	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1225	between automatic kill, exit message or callback on a per-port basis.
804		1226
805	=item * Erlang tries to hide remote/local connections, AEMP does not.	1227	=item * Erlang tries to hide remote/local connections, AEMP does not.
806		1228
807	Monitoring in Erlang is not an indicator of process death/crashes,	1229	Monitoring in Erlang is not an indicator of process death/crashes, in the
808	as linking is (except linking is unreliable in Erlang).	1230	same way as linking is (except linking is unreliable in Erlang).
809		1231
810	In AEMP, you don't "look up" registered port names or send to named ports	1232	In AEMP, you don't "look up" registered port names or send to named ports
811	that might or might not be persistent. Instead, you normally spawn a port	1233	that might or might not be persistent. Instead, you normally spawn a port
812	on the remote node. The init function monitors the you, and you monitor	1234	on the remote node. The init function monitors you, and you monitor the
813	the remote port. Since both monitors are local to the node, they are much	1235	remote port. Since both monitors are local to the node, they are much more
814	more reliable.	1236	reliable (no need for C<spawn_link>).
815		1237
816	This also saves round-trips and avoids sending messages to the wrong port	1238	This also saves round-trips and avoids sending messages to the wrong port
817	(hard to do in Erlang).	1239	(hard to do in Erlang).
818		1240
819	=back	1241	=back
820		1242
821	=head1 RATIONALE	1243	=head1 RATIONALE
822		1244
823	=over 4	1245	=over 4
824		1246
825	=item Why strings for ports and noderefs, why not objects?	1247	=item Why strings for port and node IDs, why not objects?
826		1248
827	We considered "objects", but found that the actual number of methods	1249	We considered "objects", but found that the actual number of methods
828	thatc an be called are very low. Since port IDs and noderefs travel over	1250	that can be called are quite low. Since port and node IDs travel over
829	the network frequently, the serialising/deserialising would add lots of	1251	the network frequently, the serialising/deserialising would add lots of
830	overhead, as well as having to keep a proxy object.	1252	overhead, as well as having to keep a proxy object everywhere.
831		1253
832	Strings can easily be printed, easily serialised etc. and need no special	1254	Strings can easily be printed, easily serialised etc. and need no special
833	procedures to be "valid".	1255	procedures to be "valid".
834		1256
835	And a a miniport consists of a single closure stored in a global hash - it	1257	And as a result, a port with just a default receiver consists of a single
836	can't become much cheaper.	1258	code reference stored in a global hash - it can't become much cheaper.
837		1259
838	=item Why favour JSON, why not real serialising format such as Storable?	1260	=item Why favour JSON, why not a real serialising format such as Storable?
839		1261
840	In fact, any AnyEvent::MP node will happily accept Storable as framing	1262	In fact, any AnyEvent::MP node will happily accept Storable as framing
841	format, but currently there is no way to make a node use Storable by	1263	format, but currently there is no way to make a node use Storable by
842	default.	1264	default (although all nodes will accept it).
843		1265
844	The default framing protocol is JSON because a) JSON::XS is many times	1266	The default framing protocol is JSON because a) JSON::XS is many times
845	faster for small messages and b) most importantly, after years of	1267	faster for small messages and b) most importantly, after years of
846	experience we found that object serialisation is causing more problems	1268	experience we found that object serialisation is causing more problems
847	than it gains: Just like function calls, objects simply do not travel	1269	than it solves: Just like function calls, objects simply do not travel
848	easily over the network, mostly because they will always be a copy, so you	1270	easily over the network, mostly because they will always be a copy, so you
849	always have to re-think your design.	1271	always have to re-think your design.
850		1272
851	Keeping your messages simple, concentrating on data structures rather than	1273	Keeping your messages simple, concentrating on data structures rather than
852	objects, will keep your messages clean, tidy and efficient.	1274	objects, will keep your messages clean, tidy and efficient.
853		1275
854	=back	1276	=back
855		1277
		1278	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1279
		1280	AEMP version 2 has a few major incompatible changes compared to version 1:
		1281
		1282	=over 4
		1283
		1284	=item AnyEvent::MP::Global no longer has group management functions.
		1285
		1286	At least not officially - the grp_* functions are still exported and might
		1287	work, but they will be removed in some later release.
		1288
		1289	AnyEvent::MP now comes with a distributed database that is more
		1290	powerful. Its database families map closely to port groups, but the API
		1291	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1292	a rough porting guide:
		1293
		1294	grp_reg $group, $port # old
		1295	db_reg $group, $port # new
		1296
		1297	$list = grp_get $group # old
		1298	db_keys $group, sub { my $list = shift } # new
		1299
		1300	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1301	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1302
		1303	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1304	no longer instant, because the local node might not have a copy of the
		1305	group. You can either modify your code to allow for a callback, or use
		1306	C<db_mon> to keep an updated copy of the group:
		1307
		1308	my $local_group_copy;
		1309	db_mon $group => sub { $local_group_copy = $_[0] };
		1310
		1311	# now "keys %$local_group_copy" always returns the most up-to-date
		1312	# list of ports in the group.
		1313
		1314	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1315	passes a hash as first argument, and an extra C<$chg> argument that can be
		1316	ignored:
		1317
		1318	db_mon $group => sub {
		1319	my ($ports, $add, $chg, $del) = @_;
		1320	$ports = [keys %$ports];
		1321
		1322	# now $ports, $add and $del are the same as
		1323	# were originally passed by grp_mon.
		1324	...
		1325	};
		1326
		1327	=item Nodes not longer connect to all other nodes.
		1328
		1329	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1330	module, which in turn would create connections to all other nodes in the
		1331	network (helped by the seed nodes).
		1332
		1333	In version 2.x, global nodes still connect to all other global nodes, but
		1334	other nodes don't - now every node either is a global node itself, or
		1335	attaches itself to another global node.
		1336
		1337	If a node isn't a global node itself, then it attaches itself to one
		1338	of its seed nodes. If that seed node isn't a global node yet, it will
		1339	automatically be upgraded to a global node.
		1340
		1341	So in many cases, nothing needs to be changed - one just has to make sure
		1342	that all seed nodes are meshed together with the other seed nodes (as with
		1343	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1344	achieved by specifying the same set of seed nodes for all nodes in the
		1345	network.
		1346
		1347	Not opening a connection to every other node is usually an advantage,
		1348	except when you need the lower latency of an already established
		1349	connection. To ensure a node establishes a connection to another node,
		1350	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1351	create the connection (and notify you when the connection fails).
		1352
		1353	=item Listener-less nodes (nodes without binds) are gone.
		1354
		1355	And are not coming back, at least not in their old form. If no C<binds>
		1356	are specified for a node, AnyEvent::MP assumes a default of C<*:*>.
		1357
		1358	There are vague plans to implement some form of routing domains, which
		1359	might or might not bring back listener-less nodes, but don't count on it.
		1360
		1361	The fact that most connections are now optional somewhat mitigates this,
		1362	as a node can be effectively unreachable from the outside without any
		1363	problems, as long as it isn't a global node and only reaches out to other
		1364	nodes (as opposed to being contacted from other nodes).
		1365
		1366	=item $AnyEvent::MP::Kernel::WARN has gone.
		1367
		1368	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1369	uses this, and so should your programs.
		1370
		1371	Every module now documents what kinds of messages it generates, with
		1372	AnyEvent::MP acting as a catch all.
		1373
		1374	On the positive side, this means that instead of setting
		1375	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1376	much less to type.
		1377
		1378	=back
		1379
		1380	=head1 LOGGING
		1381
		1382	AnyEvent::MP does not normally log anything by itself, but since it is the
		1383	root of the contetx hierarchy for AnyEvent::MP modules, it will receive
		1384	all log messages by submodules.
		1385
856	=head1 SEE ALSO	1386	=head1 SEE ALSO
		1387
		1388	L<AnyEvent::MP::Intro> - a gentle introduction.
		1389
		1390	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1391
		1392	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1393	your applications.
		1394
		1395	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1396
		1397	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1398	all nodes.
857		1399
858	L<AnyEvent>.	1400	L<AnyEvent>.
859		1401
860	=head1 AUTHOR	1402	=head1 AUTHOR
861		1403

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