ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/AnyEvent-MP/MP.pm

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.54 by root, Fri Aug 14 16:15:37 2009 UTC vs.
Revision 1.153 by root, Sat Nov 2 01:30:49 2019 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
42		43
43	=head1 CURRENT STATUS	44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
44		46
45	AnyEvent::MP - stable API, should work	47	# execute callbacks in $SELF port context
46	AnyEvent::MP::Intro - outdated	48	my $timer = AE::timer 1, 0, psub {
47	AnyEvent::MP::Kernel - WIP	49	die "kill the port, delayed";
48	AnyEvent::MP::Transport - mostly stable	50	};
49		51
50	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)
51		64
52	=head1 DESCRIPTION	65	=head1 DESCRIPTION
53		66
54	This module (-family) implements a simple message passing framework.	67	This module (-family) implements a simple message passing framework.
55		68
56	Despite its simplicity, you can securely message other processes running	69	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	70	on the same or other hosts, and you can supervise entities remotely.
58		71
59	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>
60	manual page.	73	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		74
66	=head1 CONCEPTS	75	=head1 CONCEPTS
67		76
68	=over 4	77	=over 4
69		78
70	=item port	79	=item port
71		80
72	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).
73		83
74	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
75	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.
76		87
		88	Ports are represented by (printable) strings called "port IDs".
		89
77	=item port id - C<noderef#portname>	90	=item port ID - C<nodeid#portname>
78		91
79	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<#>)
80	separator, and a port name (a printable string of unspecified format). An	93	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	94	format created by AnyEvent::MP).
82	reference.
83		95
84	=item node	96	=item node
85		97
86	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,
87	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
88	ports.	100	ports.
89		101
90	Nodes are either private (single-process only), slaves (connected to a	102	Nodes are either public (have one or more listening ports) or private
91	master node only) or public nodes (connectable from unrelated nodes).	103	(no listening ports). Private nodes cannot talk to other private nodes
		104	currently, but all nodes can talk to public nodes.
92		105
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	106	Nodes is represented by (printable) strings called "node IDs".
94		107
95	A node reference is a string that either simply identifies the node (for	108	=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		109
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	110	A node ID is a string that uniquely identifies the node within a
100	TCP/IP, other protocols might look different).	111	network. Depending on the configuration used, node IDs can look like a
		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.
101		114
102	Node references come in two flavours: resolved (containing only numerical	115	=item binds - C<ip:port>
103	addresses) or unresolved (where hostnames are used instead of addresses).
104		116
105	Before using an unresolved node reference in a message you first have to	117	Nodes can only talk to each other by creating some kind of connection to
106	resolve it.	118	each other. To do this, nodes should listen on one or more local transport
		119	endpoints - binds.
		120
		121	Currently, only standard C<ip:port> specifications can be used, which
		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).
107		175
108	=back	176	=back
109		177
110	=head1 VARIABLES/FUNCTIONS	178	=head1 VARIABLES/FUNCTIONS
111		179
…		…
113		181
114	=cut	182	=cut
115		183
116	package AnyEvent::MP;	184	package AnyEvent::MP;
117		185
		186	use AnyEvent::MP::Config ();
118	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	);
119		199
120	use common::sense;	200	use common::sense;
121		201
122	use Carp ();	202	use Carp ();
123		203
124	use AE ();	204	use AnyEvent ();
		205	use Guard ();
125		206
126	use base "Exporter";	207	use base "Exporter";
127		208
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	209	our $VERSION = '2.02'; # also in MP/Config.pm
129		210
130	our @EXPORT = qw(	211	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	212	configure
132	resolve_node initialise_node	213
133	snd rcv mon kil reg psub spawn	214	NODE $NODE
134	port	215	*SELF
		216
		217	node_of port_is_local
		218
		219	snd kil
		220	port rcv mon mon_guard psub peval spawn cal
		221	db_set db_del db_reg
		222	db_mon db_family db_keys db_values
		223
		224	after
135	);	225	);
136		226
137	our $SELF;	227	our $SELF;
138		228
139	sub _self_die() {	229	sub _self_die() {
…		…
142	kil $SELF, die => $msg;	232	kil $SELF, die => $msg;
143	}	233	}
144		234
145	=item $thisnode = NODE / $NODE	235	=item $thisnode = NODE / $NODE
146		236
147	The C<NODE> function returns, and the C<$NODE> variable contains the	237	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	238	ID of the node running in the current process. This value is initialised by
149	C<initialise_node>.	239	a call to C<configure>.
150		240
151	=item $noderef = node_of $port	241	=item $nodeid = node_of $port
152		242
153	Extracts and returns the noderef from a port ID or a noderef.	243	Extracts and returns the node ID from a port ID or a node ID.
154		244
155	=item initialise_node $noderef, $seednode, $seednode...	245	=item $is_local = port_is_local $port
156		246
157	=item initialise_node "slave/", $master, $master...	247	Returns true iff the port is a local port.
158		248
		249	=item configure $profile, key => value...
		250
		251	=item configure key => value...
		252
159	Before a node can talk to other nodes on the network it has to initialise	253	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	254	"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.	255	to know is its own name, and optionally it should know the addresses of
		256	some other nodes in the network to discover other nodes.
162		257
163	This function initialises a node - it must be called exactly once (or	258	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	259	never) before calling other AnyEvent::MP functions.
165		260
166	All arguments (optionally except for the first) are noderefs, which can be	261	The key/value pairs are basically the same ones as documented for the
167	either resolved or unresolved.	262	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		263
177	=over 4	264	=over 4
178		265
179	=item public nodes	266	=item norc => $boolean (default false)
180		267
181	For public nodes, C<$noderef> (supplied either directly to	268	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	269	be consulted - all configuration options must be specified in the
183	noderef (possibly unresolved, in which case it will be resolved).	270	C<configure> call.
184		271
185	After resolving, the node will bind itself on all endpoints and try to	272	=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		273
190	=item slave nodes	274	IF true, then the values specified in the C<configure> will take
191		275	precedence over any values configured via the rc file. The default is for
192	When the C<$noderef> (either as given or overriden by the config file)	276	the rc file to override any options specified in the program.
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
197	At least one additional noderef is required (either by specifying it
198	directly or because it is part of the configuration profile): The node
199	will try to connect to all of them and will become a slave attached to the
200	first node it can successfully connect to.
201		277
202	=back	278	=back
203		279
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	280	=over 4
247		281
248	=item the empty string	282	=item step 1, gathering configuration from profiles
249		283
250	An empty-string component gets resolved as if the default port (4040) was	284	The function first looks up a profile in the aemp configuration (see the
251	specified.	285	L<aemp> commandline utility). The profile name can be specified via the
		286	named C<profile> parameter or can simply be the first parameter). If it is
		287	missing, then the nodename (F<uname -n>) will be used as profile name.
252		288
253	=item naked port numbers (e.g. C<1234>)	289	The profile data is then gathered as follows:
254		290
255	These are resolved by prepending the local nodename and a colon, to be	291	First, all remaining key => value pairs (all of which are conveniently
256	further resolved.	292	undocumented at the moment) will be interpreted as configuration
		293	data. Then they will be overwritten by any values specified in the global
		294	default configuration (see the F<aemp> utility), then the chain of
		295	profiles chosen by the profile name (and any C<parent> attributes).
257		296
258	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	297	That means that the values specified in the profile have highest priority
		298	and the values specified directly via C<configure> have lowest priority,
		299	and can only be used to specify defaults.
259		300
260	These are resolved by using AnyEvent::DNS to resolve them, optionally	301	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	302	this process. If not, then the profile name will be used as node ID, with
262	specified.	303	a unique randoms tring (C</%u>) appended.
		304
		305	The node ID can contain some C<%> sequences that are expanded: C<%n>
		306	is expanded to the local nodename, C<%u> is replaced by a random
		307	strign to make the node unique. For example, the F<aemp> commandline
		308	utility uses C<aemp/%n/%u> as nodename, which might expand to
		309	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		310
		311	=item step 2, bind listener sockets
		312
		313	The next step is to look up the binds in the profile, followed by binding
		314	aemp protocol listeners on all binds specified (it is possible and valid
		315	to have no binds, meaning that the node cannot be contacted from the
		316	outside. This means the node cannot talk to other nodes that also have no
		317	binds, but it can still talk to all "normal" nodes).
		318
		319	If the profile does not specify a binds list, then a default of C<*> is
		320	used, meaning the node will bind on a dynamically-assigned port on every
		321	local IP address it finds.
		322
		323	=item step 3, connect to seed nodes
		324
		325	As the last step, the seed ID list from the profile is passed to the
		326	L<AnyEvent::MP::Global> module, which will then use it to keep
		327	connectivity with at least one node at any point in time.
263		328
264	=back	329	=back
		330
		331	Example: become a distributed node using the local node name as profile.
		332	This should be the most common form of invocation for "daemon"-type nodes.
		333
		334	configure
		335
		336	Example: become a semi-anonymous node. This form is often used for
		337	commandline clients.
		338
		339	configure nodeid => "myscript/%n/%u";
		340
		341	Example: configure a node using a profile called seed, which is suitable
		342	for a seed node as it binds on all local addresses on a fixed port (4040,
		343	customary for aemp).
		344
		345	# use the aemp commandline utility
		346	# aemp profile seed binds '*:4040'
		347
		348	# then use it
		349	configure profile => "seed";
		350
		351	# or simply use aemp from the shell again:
		352	# aemp run profile seed
		353
		354	# or provide a nicer-to-remember nodeid
		355	# aemp run profile seed nodeid "$(hostname)"
265		356
266	=item $SELF	357	=item $SELF
267		358
268	Contains the current port id while executing C<rcv> callbacks or C<psub>	359	Contains the current port id while executing C<rcv> callbacks or C<psub>
269	blocks.	360	blocks.
270		361
271	=item SELF, %SELF, @SELF...	362	=item *SELF, SELF, %SELF, @SELF...
272		363
273	Due to some quirks in how perl exports variables, it is impossible to	364	Due to some quirks in how perl exports variables, it is impossible to
274	just export C<$SELF>, all the symbols called C<SELF> are exported by this	365	just export C<$SELF>, all the symbols named C<SELF> are exported by this
275	module, but only C<$SELF> is currently used.	366	module, but only C<$SELF> is currently used.
276		367
277	=item snd $port, type => @data	368	=item snd $port, type => @data
278		369
279	=item snd $port, @msg	370	=item snd $port, @msg
280		371
281	Send the given message to the given port ID, which can identify either	372	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.	373	local or a remote port, and must be a port ID.
283		374
284	While the message can be about anything, it is highly recommended to use a	375	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	376	use a string as first element (a port ID, or some word that indicates a
286	type etc.).	377	request type etc.) and to consist if only simple perl values (scalars,
		378	arrays, hashes) - if you think you need to pass an object, think again.
287		379
288	The message data effectively becomes read-only after a call to this	380	The message data logically becomes read-only after a call to this
289	function: modifying any argument is not allowed and can cause many	381	function: modifying any argument (or values referenced by them) is
290	problems.	382	forbidden, as there can be considerable time between the call to C<snd>
		383	and the time the message is actually being serialised - in fact, it might
		384	never be copied as within the same process it is simply handed to the
		385	receiving port.
291		386
292	The type of data you can transfer depends on the transport protocol: when	387	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	388	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	389	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	390	that Storable can serialise and deserialise is allowed, and for the local
296	node, anything can be passed.	391	node, anything can be passed. Best rely only on the common denominator of
		392	these.
297		393
298	=item $local_port = port	394	=item $local_port = port
299		395
300	Create a new local port object and returns its port ID. Initially it has	396	Create a new local port object and returns its port ID. Initially it has
301	no callbacks set and will throw an error when it receives messages.	397	no callbacks set and will throw an error when it receives messages.
…		…
320		416
321	=cut	417	=cut
322		418
323	sub rcv($@);	419	sub rcv($@);
324		420
325	sub _kilme {	421	my $KILME = sub {
326	die "received message on port without callback";	422	(my $tag = substr $_[0], 0, 30) =~ s/([^\x20-\x7e])/./g;
327	}	423	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		424	};
328		425
329	sub port(;&) {	426	sub port(;&) {
330	my $id = "$UNIQ." . $ID++;	427	my $id = $UNIQ . ++$ID;
331	my $port = "$NODE#$id";	428	my $port = "$NODE#$id";
332		429
333	rcv $port, shift || \&_kilme;	430	rcv $port, shift || $KILME;
334		431
335	$port	432	$port
336	}	433	}
337		434
338	=item rcv $local_port, $callback->(@msg)	435	=item rcv $local_port, $callback->(@msg)
…		…
343		440
344	The global C<$SELF> (exported by this module) contains C<$port> while	441	The global C<$SELF> (exported by this module) contains C<$port> while
345	executing the callback. Runtime errors during callback execution will	442	executing the callback. Runtime errors during callback execution will
346	result in the port being C<kil>ed.	443	result in the port being C<kil>ed.
347		444
348	The default callback received all messages not matched by a more specific	445	The default callback receives all messages not matched by a more specific
349	C<tag> match.	446	C<tag> match.
350		447
351	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	448	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
352		449
353	Register (or replace) callbacks to be called on messages starting with the	450	Register (or replace) callbacks to be called on messages starting with the
…		…
374	msg1 => sub { ... },	471	msg1 => sub { ... },
375	...	472	...
376	;	473	;
377		474
378	Example: temporarily register a rcv callback for a tag matching some port	475	Example: temporarily register a rcv callback for a tag matching some port
379	(e.g. for a rpc reply) and unregister it after a message was received.	476	(e.g. for an rpc reply) and unregister it after a message was received.
380		477
381	rcv $port, $otherport => sub {	478	rcv $port, $otherport => sub {
382	my @reply = @_;	479	my @reply = @_;
383		480
384	rcv $SELF, $otherport;	481	rcv $SELF, $otherport;
…		…
386		483
387	=cut	484	=cut
388		485
389	sub rcv($@) {	486	sub rcv($@) {
390	my $port = shift;	487	my $port = shift;
391	my ($noderef, $portid) = split /#/, $port, 2;	488	my ($nodeid, $portid) = split /#/, $port, 2;
392		489
393	($NODE{$noderef} || add_node $noderef) == $NODE{""}	490	$nodeid eq $NODE
394	or Carp::croak "$port: rcv can only be called on local ports, caught";	491	or Carp::croak "$port: rcv can only be called on local ports, caught";
395		492
396	while (@_) {	493	while (@_) {
397	if (ref $_[0]) {	494	if (ref $_[0]) {
398	if (my $self = $PORT_DATA{$portid}) {	495	if (my $self = $PORT_DATA{$portid}) {
399	"AnyEvent::MP::Port" eq ref $self	496	"AnyEvent::MP::Port" eq ref $self
400	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	497	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
401		498
402	$self->[2] = shift;	499	$self->[0] = shift;
403	} else {	500	} else {
404	my $cb = shift;	501	my $cb = shift;
405	$PORT{$portid} = sub {	502	$PORT{$portid} = sub {
406	local $SELF = $port;	503	local $SELF = $port;
407	eval { &$cb }; _self_die if $@;	504	eval { &$cb }; _self_die if $@;
408	};	505	};
409	}	506	}
410	} elsif (defined $_[0]) {	507	} elsif (defined $_[0]) {
411	my $self = $PORT_DATA{$portid} ||= do {	508	my $self = $PORT_DATA{$portid} ||= do {
412	my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port";	509	my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
413		510
414	$PORT{$portid} = sub {	511	$PORT{$portid} = sub {
415	local $SELF = $port;	512	local $SELF = $port;
416		513
417	if (my $cb = $self->[1]{$_[0]}) {	514	if (my $cb = $self->[1]{$_[0]}) {
…		…
439	}	536	}
440		537
441	$port	538	$port
442	}	539	}
443		540
		541	=item peval $port, $coderef[, @args]
		542
		543	Evaluates the given C<$codref> within the context of C<$port>, that is,
		544	when the code throws an exception the C<$port> will be killed.
		545
		546	Any remaining args will be passed to the callback. Any return values will
		547	be returned to the caller.
		548
		549	This is useful when you temporarily want to execute code in the context of
		550	a port.
		551
		552	Example: create a port and run some initialisation code in it's context.
		553
		554	my $port = port { ... };
		555
		556	peval $port, sub {
		557	init
		558	or die "unable to init";
		559	};
		560
		561	=cut
		562
		563	sub peval($$) {
		564	local $SELF = shift;
		565	my $cb = shift;
		566
		567	if (wantarray) {
		568	my @res = eval { &$cb };
		569	_self_die if $@;
		570	@res
		571	} else {
		572	my $res = eval { &$cb };
		573	_self_die if $@;
		574	$res
		575	}
		576	}
		577
444	=item $closure = psub { BLOCK }	578	=item $closure = psub { BLOCK }
445		579
446	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	580	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
447	closure is executed, sets up the environment in the same way as in C<rcv>	581	closure is executed, sets up the environment in the same way as in C<rcv>
448	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	582	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		583
		584	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		585	BLOCK }, @_ } >>.
449		586
450	This is useful when you register callbacks from C<rcv> callbacks:	587	This is useful when you register callbacks from C<rcv> callbacks:
451		588
452	rcv delayed_reply => sub {	589	rcv delayed_reply => sub {
453	my ($delay, @reply) = @_;	590	my ($delay, @reply) = @_;
…		…
477	$res	614	$res
478	}	615	}
479	}	616	}
480	}	617	}
481		618
482	=item $guard = mon $port, $cb->(@reason)	619	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
483		620
484	=item $guard = mon $port, $rcvport	621	=item $guard = mon $port # kill $SELF when $port dies
485		622
486	=item $guard = mon $port	623	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
487		624
488	=item $guard = mon $port, $rcvport, @msg	625	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
489		626
490	Monitor the given port and do something when the port is killed or	627	Monitor the given port and do something when the port is killed or
491	messages to it were lost, and optionally return a guard that can be used	628	messages to it were lost, and optionally return a guard that can be used
492	to stop monitoring again.	629	to stop monitoring again.
493		630
		631	The first two forms distinguish between "normal" and "abnormal" kil's:
		632
		633	In the first form (another port given), if the C<$port> is C<kil>'ed with
		634	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		635	same reason. That is, on "normal" kil's nothing happens, while under all
		636	other conditions, the other port is killed with the same reason.
		637
		638	The second form (kill self) is the same as the first form, except that
		639	C<$rvport> defaults to C<$SELF>.
		640
		641	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		642	- it's up to the callback or receiver to check whether the C<@reason> is
		643	empty and act accordingly.
		644
		645	In the third form (callback), the callback is simply called with any
		646	number of C<@reason> elements (empty @reason means that the port was deleted
		647	"normally"). Note also that I<< the callback B<must> never die >>, so use
		648	C<eval> if unsure.
		649
		650	In the last form (message), a message of the form C<$rcvport, @msg,
		651	@reason> will be C<snd>.
		652
		653	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		654	alert was raised), they are removed and will not trigger again, even if it
		655	turns out that the port is still alive.
		656
		657	As a rule of thumb, monitoring requests should always monitor a remote
		658	port locally (using a local C<$rcvport> or a callback). The reason is that
		659	kill messages might get lost, just like any other message. Another less
		660	obvious reason is that even monitoring requests can get lost (for example,
		661	when the connection to the other node goes down permanently). When
		662	monitoring a port locally these problems do not exist.
		663
494	C<mon> effectively guarantees that, in the absence of hardware failures,	664	C<mon> effectively guarantees that, in the absence of hardware failures,
495	that after starting the monitor, either all messages sent to the port	665	after starting the monitor, either all messages sent to the port will
496	will arrive, or the monitoring action will be invoked after possible	666	arrive, or the monitoring action will be invoked after possible message
497	message loss has been detected. No messages will be lost "in between"	667	loss has been detected. No messages will be lost "in between" (after
498	(after the first lost message no further messages will be received by the	668	the first lost message no further messages will be received by the
499	port). After the monitoring action was invoked, further messages might get	669	port). After the monitoring action was invoked, further messages might get
500	delivered again.	670	delivered again.
501		671
502	In the first form (callback), the callback is simply called with any	672	Inter-host-connection timeouts and monitoring depend on the transport
503	number of C<@reason> elements (no @reason means that the port was deleted	673	used. The only transport currently implemented is TCP, and AnyEvent::MP
504	"normally"). Note also that I<< the callback B<must> never die >>, so use	674	relies on TCP to detect node-downs (this can take 10-15 minutes on a
505	C<eval> if unsure.	675	non-idle connection, and usually around two hours for idle connections).
506		676
507	In the second form (another port given), the other port (C<$rcvport>)	677	This means that monitoring is good for program errors and cleaning up
508	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	678	stuff eventually, but they are no replacement for a timeout when you need
509	"normal" kils nothing happens, while under all other conditions, the other	679	to ensure some maximum latency.
510	port is killed with the same reason.
511
512	The third form (kill self) is the same as the second form, except that
513	C<$rvport> defaults to C<$SELF>.
514
515	In the last form (message), a message of the form C<@msg, @reason> will be
516	C<snd>.
517
518	As a rule of thumb, monitoring requests should always monitor a port from
519	a local port (or callback). The reason is that kill messages might get
520	lost, just like any other message. Another less obvious reason is that
521	even monitoring requests can get lost (for exmaple, when the connection
522	to the other node goes down permanently). When monitoring a port locally
523	these problems do not exist.
524		680
525	Example: call a given callback when C<$port> is killed.	681	Example: call a given callback when C<$port> is killed.
526		682
527	mon $port, sub { warn "port died because of <@_>\n" };	683	mon $port, sub { warn "port died because of <@_>\n" };
528		684
…		…
535	mon $port, $self => "restart";	691	mon $port, $self => "restart";
536		692
537	=cut	693	=cut
538		694
539	sub mon {	695	sub mon {
540	my ($noderef, $port) = split /#/, shift, 2;	696	my ($nodeid, $port) = split /#/, shift, 2;
541		697
542	my $node = $NODE{$noderef} || add_node $noderef;	698	my $node = $NODE{$nodeid} || add_node $nodeid;
543		699
544	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';	700	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
545		701
546	unless (ref $cb) {	702	unless (ref $cb) {
547	if (@_) {	703	if (@_) {
…		…
556	}	712	}
557		713
558	$node->monitor ($port, $cb);	714	$node->monitor ($port, $cb);
559		715
560	defined wantarray	716	defined wantarray
561	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	717	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
562	}	718	}
563		719
564	=item $guard = mon_guard $port, $ref, $ref...	720	=item $guard = mon_guard $port, $ref, $ref...
565		721
566	Monitors the given C<$port> and keeps the passed references. When the port	722	Monitors the given C<$port> and keeps the passed references. When the port
567	is killed, the references will be freed.	723	is killed, the references will be freed.
568		724
569	Optionally returns a guard that will stop the monitoring.	725	Optionally returns a guard that will stop the monitoring.
570		726
571	This function is useful when you create e.g. timers or other watchers and	727	This function is useful when you create e.g. timers or other watchers and
572	want to free them when the port gets killed:	728	want to free them when the port gets killed (note the use of C<psub>):
573		729
574	$port->rcv (start => sub {	730	$port->rcv (start => sub {
575	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	731	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
576	undef $timer if 0.9 < rand;	732	undef $timer if 0.9 < rand;
577	});	733	});
578	});	734	});
579		735
580	=cut	736	=cut
…		…
589		745
590	=item kil $port[, @reason]	746	=item kil $port[, @reason]
591		747
592	Kill the specified port with the given C<@reason>.	748	Kill the specified port with the given C<@reason>.
593		749
594	If no C<@reason> is specified, then the port is killed "normally" (linked	750	If no C<@reason> is specified, then the port is killed "normally" -
595	ports will not be kileld, or even notified).	751	monitor callback will be invoked, but the kil will not cause linked ports
		752	(C<mon $mport, $lport> form) to get killed.
596		753
597	Otherwise, linked ports get killed with the same reason (second form of	754	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
598	C<mon>, see below).	755	form) get killed with the same reason.
599		756
600	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	757	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
601	will be reported as reason C<< die => $@ >>.	758	will be reported as reason C<< die => $@ >>.
602		759
603	Transport/communication errors are reported as C<< transport_error =>	760	Transport/communication errors are reported as C<< transport_error =>
604	$message >>.	761	$message >>.
605		762
606	=cut	763	Common idioms:
		764
		765	# silently remove yourself, do not kill linked ports
		766	kil $SELF;
		767
		768	# report a failure in some detail
		769	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		770
		771	# do not waste much time with killing, just die when something goes wrong
		772	open my $fh, "<file"
		773	or die "file: $!";
607		774
608	=item $port = spawn $node, $initfunc[, @initdata]	775	=item $port = spawn $node, $initfunc[, @initdata]
609		776
610	Creates a port on the node C<$node> (which can also be a port ID, in which	777	Creates a port on the node C<$node> (which can also be a port ID, in which
611	case it's the node where that port resides).	778	case it's the node where that port resides).
612		779
613	The port ID of the newly created port is return immediately, and it is	780	The port ID of the newly created port is returned immediately, and it is
614	permissible to immediately start sending messages or monitor the port.	781	possible to immediately start sending messages or to monitor the port.
615		782
616	After the port has been created, the init function is	783	After the port has been created, the init function is called on the remote
617	called. This function must be a fully-qualified function name	784	node, in the same context as a C<rcv> callback. This function must be a
618	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	785	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
619	program, use C<::name>.	786	specify a function in the main program, use C<::name>.
620		787
621	If the function doesn't exist, then the node tries to C<require>	788	If the function doesn't exist, then the node tries to C<require>
622	the package, then the package above the package and so on (e.g.	789	the package, then the package above the package and so on (e.g.
623	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	790	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
624	exists or it runs out of package names.	791	exists or it runs out of package names.
625		792
626	The init function is then called with the newly-created port as context	793	The init function is then called with the newly-created port as context
627	object (C<$SELF>) and the C<@initdata> values as arguments.	794	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		795	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		796	the port might not get created.
628		797
629	A common idiom is to pass your own port, monitor the spawned port, and	798	A common idiom is to pass a local port, immediately monitor the spawned
630	in the init function, monitor the original port. This two-way monitoring	799	port, and in the remote init function, immediately monitor the passed
631	ensures that both ports get cleaned up when there is a problem.	800	local port. This two-way monitoring ensures that both ports get cleaned up
		801	when there is a problem.
		802
		803	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		804	caller before C<spawn> returns (by delaying invocation when spawn is
		805	called for the local node).
632		806
633	Example: spawn a chat server port on C<$othernode>.	807	Example: spawn a chat server port on C<$othernode>.
634		808
635	# this node, executed from within a port context:	809	# this node, executed from within a port context:
636	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	810	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
651		825
652	sub _spawn {	826	sub _spawn {
653	my $port = shift;	827	my $port = shift;
654	my $init = shift;	828	my $init = shift;
655		829
		830	# rcv will create the actual port
656	local $SELF = "$NODE#$port";	831	local $SELF = "$NODE#$port";
657	eval {	832	eval {
658	&{ load_func $init }	833	&{ load_func $init }
659	};	834	};
660	_self_die if $@;	835	_self_die if $@;
661	}	836	}
662		837
663	sub spawn(@) {	838	sub spawn(@) {
664	my ($noderef, undef) = split /#/, shift, 2;	839	my ($nodeid, undef) = split /#/, shift, 2;
665		840
666	my $id = "$RUNIQ." . $ID++;	841	my $id = $RUNIQ . ++$ID;
667		842
668	$_[0] =~ /::/	843	$_[0] =~ /::/
669	or Carp::croak "spawn init function must be a fully-qualified name, caught";	844	or Carp::croak "spawn init function must be a fully-qualified name, caught";
670		845
671	($NODE{$noderef} || add_node $noderef)	846	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
672	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
673		847
674	"$noderef#$id"	848	"$nodeid#$id"
675	}	849	}
676		850
		851
		852	=item after $timeout, @msg
		853
		854	=item after $timeout, $callback
		855
		856	Either sends the given message, or call the given callback, after the
		857	specified number of seconds.
		858
		859	This is simply a utility function that comes in handy at times - the
		860	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		861	so it may go away in the future.
		862
		863	=cut
		864
		865	sub after($@) {
		866	my ($timeout, @action) = @_;
		867
		868	my $t; $t = AE::timer $timeout, 0, sub {
		869	undef $t;
		870	ref $action[0]
		871	? $action[0]()
		872	: snd @action;
		873	};
		874	}
		875
		876	#=item $cb2 = timeout $seconds, $cb[, @args]
		877
		878	=item cal $port, @msg, $callback[, $timeout]
		879
		880	A simple form of RPC - sends a message to the given C<$port> with the
		881	given contents (C<@msg>), but adds a reply port to the message.
		882
		883	The reply port is created temporarily just for the purpose of receiving
		884	the reply, and will be C<kil>ed when no longer needed.
		885
		886	A reply message sent to the port is passed to the C<$callback> as-is.
		887
		888	If an optional time-out (in seconds) is given and it is not C<undef>,
		889	then the callback will be called without any arguments after the time-out
		890	elapsed and the port is C<kil>ed.
		891
		892	If no time-out is given (or it is C<undef>), then the local port will
		893	monitor the remote port instead, so it eventually gets cleaned-up.
		894
		895	Currently this function returns the temporary port, but this "feature"
		896	might go in future versions unless you can make a convincing case that
		897	this is indeed useful for something.
		898
		899	=cut
		900
		901	sub cal(@) {
		902	my $timeout = ref $_[-1] ? undef : pop;
		903	my $cb = pop;
		904
		905	my $port = port {
		906	undef $timeout;
		907	kil $SELF;
		908	&$cb;
		909	};
		910
		911	if (defined $timeout) {
		912	$timeout = AE::timer $timeout, 0, sub {
		913	undef $timeout;
		914	kil $port;
		915	$cb->();
		916	};
		917	} else {
		918	mon $_[0], sub {
		919	kil $port;
		920	$cb->();
		921	};
		922	}
		923
		924	push @_, $port;
		925	&snd;
		926
		927	$port
		928	}
		929
677	=back	930	=back
678		931
679	=head1 NODE MESSAGES	932	=head1 DISTRIBUTED DATABASE
680		933
681	Nodes understand the following messages sent to them. Many of them take	934	AnyEvent::MP comes with a simple distributed database. The database will
682	arguments called C<@reply>, which will simply be used to compose a reply	935	be mirrored asynchronously on all global nodes. Other nodes bind to one
683	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	936	of the global nodes for their needs. Every node has a "local database"
684	the remaining arguments are simply the message data.	937	which contains all the values that are set locally. All local databases
		938	are merged together to form the global database, which can be queried.
685		939
686	While other messages exist, they are not public and subject to change.	940	The database structure is that of a two-level hash - the database hash
		941	contains hashes which contain values, similarly to a perl hash of hashes,
		942	i.e.:
687		943
		944	$DATABASE{$family}{$subkey} = $value
		945
		946	The top level hash key is called "family", and the second-level hash key
		947	is called "subkey" or simply "key".
		948
		949	The family must be alphanumeric, i.e. start with a letter and consist
		950	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		951	pretty much like Perl module names.
		952
		953	As the family namespace is global, it is recommended to prefix family names
		954	with the name of the application or module using it.
		955
		956	The subkeys must be non-empty strings, with no further restrictions.
		957
		958	The values should preferably be strings, but other perl scalars should
		959	work as well (such as C<undef>, arrays and hashes).
		960
		961	Every database entry is owned by one node - adding the same family/subkey
		962	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		963	but the result might be nondeterministic, i.e. the key might have
		964	different values on different nodes.
		965
		966	Different subkeys in the same family can be owned by different nodes
		967	without problems, and in fact, this is the common method to create worker
		968	pools. For example, a worker port for image scaling might do this:
		969
		970	db_set my_image_scalers => $port;
		971
		972	And clients looking for an image scaler will want to get the
		973	C<my_image_scalers> keys from time to time:
		974
		975	db_keys my_image_scalers => sub {
		976	@ports = @{ $_[0] };
		977	};
		978
		979	Or better yet, they want to monitor the database family, so they always
		980	have a reasonable up-to-date copy:
		981
		982	db_mon my_image_scalers => sub {
		983	@ports = keys %{ $_[0] };
		984	};
		985
		986	In general, you can set or delete single subkeys, but query and monitor
		987	whole families only.
		988
		989	If you feel the need to monitor or query a single subkey, try giving it
		990	it's own family.
		991
688	=over 4	992	=over
		993
		994	=item $guard = db_set $family => $subkey [=> $value]
		995
		996	Sets (or replaces) a key to the database - if C<$value> is omitted,
		997	C<undef> is used instead.
		998
		999	When called in non-void context, C<db_set> returns a guard that
		1000	automatically calls C<db_del> when it is destroyed.
		1001
		1002	=item db_del $family => $subkey...
		1003
		1004	Deletes one or more subkeys from the database family.
		1005
		1006	=item $guard = db_reg $family => $port => $value
		1007
		1008	=item $guard = db_reg $family => $port
		1009
		1010	=item $guard = db_reg $family
		1011
		1012	Registers a port in the given family and optionally returns a guard to
		1013	remove it.
		1014
		1015	This function basically does the same as:
		1016
		1017	db_set $family => $port => $value
		1018
		1019	Except that the port is monitored and automatically removed from the
		1020	database family when it is kil'ed.
		1021
		1022	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1023	C<$SELF> is used.
		1024
		1025	This function is most useful to register a port in some port group (which
		1026	is just another name for a database family), and have it removed when the
		1027	port is gone. This works best when the port is a local port.
689		1028
690	=cut	1029	=cut
691		1030
692	=item lookup => $name, @reply	1031	sub db_reg($$;$) {
		1032	my $family = shift;
		1033	my $port = @_ ? shift : $SELF;
693		1034
694	Replies with the port ID of the specified well-known port, or C<undef>.	1035	my $clr = sub { db_del $family => $port };
		1036	mon $port, $clr;
695		1037
696	=item devnull => ...	1038	db_set $family => $port => $_[0];
697		1039
698	Generic data sink/CPU heat conversion.	1040	defined wantarray
		1041	and &Guard::guard ($clr)
		1042	}
699		1043
700	=item relay => $port, @msg	1044	=item db_family $family => $cb->(\%familyhash)
701		1045
702	Simply forwards the message to the given port.	1046	Queries the named database C<$family> and call the callback with the
		1047	family represented as a hash. You can keep and freely modify the hash.
703		1048
704	=item eval => $string[ @reply]	1049	=item db_keys $family => $cb->(\@keys)
705		1050
706	Evaluates the given string. If C<@reply> is given, then a message of the	1051	Same as C<db_family>, except it only queries the family I<subkeys> and passes
707	form C<@reply, $@, @evalres> is sent.	1052	them as array reference to the callback.
708		1053
709	Example: crash another node.	1054	=item db_values $family => $cb->(\@values)
710		1055
711	snd $othernode, eval => "exit";	1056	Same as C<db_family>, except it only queries the family I<values> and passes them
		1057	as array reference to the callback.
712		1058
713	=item time => @reply	1059	=item $guard = db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
714		1060
715	Replies the the current node time to C<@reply>.	1061	Creates a monitor on the given database family. Each time a key is
		1062	set or is deleted the callback is called with a hash containing the
		1063	database family and three lists of added, changed and deleted subkeys,
		1064	respectively. If no keys have changed then the array reference might be
		1065	C<undef> or even missing.
716		1066
717	Example: tell the current node to send the current time to C<$myport> in a	1067	If not called in void context, a guard object is returned that, when
718	C<timereply> message.	1068	destroyed, stops the monitor.
719		1069
720	snd $NODE, time => $myport, timereply => 1, 2;	1070	The family hash reference and the key arrays belong to AnyEvent::MP and
721	# => snd $myport, timereply => 1, 2, <time>	1071	B<must not be modified or stored> by the callback. When in doubt, make a
		1072	copy.
		1073
		1074	As soon as possible after the monitoring starts, the callback will be
		1075	called with the intiial contents of the family, even if it is empty,
		1076	i.e. there will always be a timely call to the callback with the current
		1077	contents.
		1078
		1079	It is possible that the callback is called with a change event even though
		1080	the subkey is already present and the value has not changed.
		1081
		1082	The monitoring stops when the guard object is destroyed.
		1083
		1084	Example: on every change to the family "mygroup", print out all keys.
		1085
		1086	my $guard = db_mon mygroup => sub {
		1087	my ($family, $a, $c, $d) = @_;
		1088	print "mygroup members: ", (join " ", keys %$family), "\n";
		1089	};
		1090
		1091	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1092
		1093	my $guard; $guard = db_mon My::Module::workers => sub {
		1094	my ($family, $a, $c, $d) = @_;
		1095	return unless %$family;
		1096	undef $guard;
		1097	print "My::Module::workers now nonempty\n";
		1098	};
		1099
		1100	Example: print all changes to the family "AnyEvent::Fantasy::Module".
		1101
		1102	my $guard = db_mon AnyEvent::Fantasy::Module => sub {
		1103	my ($family, $a, $c, $d) = @_;
		1104
		1105	print "+$_=$family->{$_}\n" for @$a;
		1106	print "*$_=$family->{$_}\n" for @$c;
		1107	print "-$_=$family->{$_}\n" for @$d;
		1108	};
		1109
		1110	=cut
722		1111
723	=back	1112	=back
724		1113
725	=head1 AnyEvent::MP vs. Distributed Erlang	1114	=head1 AnyEvent::MP vs. Distributed Erlang
726		1115
727	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1116	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
728	== aemp node, Erlang process == aemp port), so many of the documents and	1117	== aemp node, Erlang process == aemp port), so many of the documents and
729	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1118	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
730	sample:	1119	sample:
731		1120
732	http://www.Erlang.se/doc/programming_rules.shtml	1121	http://www.erlang.se/doc/programming_rules.shtml
733	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1122	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
734	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1123	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
735	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1124	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
736		1125
737	Despite the similarities, there are also some important differences:	1126	Despite the similarities, there are also some important differences:
738		1127
739	=over 4	1128	=over 4
740		1129
741	=item * Node references contain the recipe on how to contact them.	1130	=item * Node IDs are arbitrary strings in AEMP.
742		1131
743	Erlang relies on special naming and DNS to work everywhere in the	1132	Erlang relies on special naming and DNS to work everywhere in the same
744	same way. AEMP relies on each node knowing it's own address(es), with	1133	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
745	convenience functionality.	1134	configuration or DNS), and possibly the addresses of some seed nodes, but
746		1135	will otherwise discover other nodes (and their IDs) itself.
747	This means that AEMP requires a less tightly controlled environment at the
748	cost of longer node references and a slightly higher management overhead.
749		1136
750	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1137	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
751	uses "local ports are like remote ports".	1138	uses "local ports are like remote ports".
752		1139
753	The failure modes for local ports are quite different (runtime errors	1140	The failure modes for local ports are quite different (runtime errors
…		…
762	ports being the special case/exception, where transport errors cannot	1149	ports being the special case/exception, where transport errors cannot
763	occur.	1150	occur.
764		1151
765	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1152	=item * Erlang uses processes and a mailbox, AEMP does not queue.
766		1153
767	Erlang uses processes that selectively receive messages, and therefore	1154	Erlang uses processes that selectively receive messages out of order, and
768	needs a queue. AEMP is event based, queuing messages would serve no	1155	therefore needs a queue. AEMP is event based, queuing messages would serve
769	useful purpose. For the same reason the pattern-matching abilities of	1156	no useful purpose. For the same reason the pattern-matching abilities
770	AnyEvent::MP are more limited, as there is little need to be able to	1157	of AnyEvent::MP are more limited, as there is little need to be able to
771	filter messages without dequeing them.	1158	filter messages without dequeuing them.
772		1159
773	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1160	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1161	being event-based, while Erlang is process-based.
		1162
		1163	You can have a look at L<Coro::MP> for a more Erlang-like process model on
		1164	top of AEMP and Coro threads.
774		1165
775	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1166	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
776		1167
777	Sending messages in Erlang is synchronous and blocks the process (and	1168	Sending messages in Erlang is synchronous and blocks the process until
		1169	a connection has been established and the message sent (and so does not
778	so does not need a queue that can overflow). AEMP sends are immediate,	1170	need a queue that can overflow). AEMP sends return immediately, connection
779	connection establishment is handled in the background.	1171	establishment is handled in the background.
780		1172
781	=item * Erlang suffers from silent message loss, AEMP does not.	1173	=item * Erlang suffers from silent message loss, AEMP does not.
782		1174
783	Erlang makes few guarantees on messages delivery - messages can get lost	1175	Erlang implements few guarantees on messages delivery - messages can get
784	without any of the processes realising it (i.e. you send messages a, b,	1176	lost without any of the processes realising it (i.e. you send messages a,
785	and c, and the other side only receives messages a and c).	1177	b, and c, and the other side only receives messages a and c).
786		1178
787	AEMP guarantees correct ordering, and the guarantee that there are no	1179	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1180	guarantee that after one message is lost, all following ones sent to the
		1181	same port are lost as well, until monitoring raises an error, so there are
788	holes in the message sequence.	1182	no silent "holes" in the message sequence.
789		1183
790	=item * In Erlang, processes can be declared dead and later be found to be	1184	If you want your software to be very reliable, you have to cope with
791	alive.	1185	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
792		1186	simply tries to work better in common error cases, such as when a network
793	In Erlang it can happen that a monitored process is declared dead and	1187	link goes down.
794	linked processes get killed, but later it turns out that the process is
795	still alive - and can receive messages.
796
797	In AEMP, when port monitoring detects a port as dead, then that port will
798	eventually be killed - it cannot happen that a node detects a port as dead
799	and then later sends messages to it, finding it is still alive.
800		1188
801	=item * Erlang can send messages to the wrong port, AEMP does not.	1189	=item * Erlang can send messages to the wrong port, AEMP does not.
802		1190
803	In Erlang it is quite likely that a node that restarts reuses a process ID	1191	In Erlang it is quite likely that a node that restarts reuses an Erlang
804	known to other nodes for a completely different process, causing messages	1192	process ID known to other nodes for a completely different process,
805	destined for that process to end up in an unrelated process.	1193	causing messages destined for that process to end up in an unrelated
		1194	process.
806		1195
807	AEMP never reuses port IDs, so old messages or old port IDs floating	1196	AEMP does not reuse port IDs, so old messages or old port IDs floating
808	around in the network will not be sent to an unrelated port.	1197	around in the network will not be sent to an unrelated port.
809		1198
810	=item * Erlang uses unprotected connections, AEMP uses secure	1199	=item * Erlang uses unprotected connections, AEMP uses secure
811	authentication and can use TLS.	1200	authentication and can use TLS.
812		1201
813	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1202	AEMP can use a proven protocol - TLS - to protect connections and
814	securely authenticate nodes.	1203	securely authenticate nodes.
815		1204
816	=item * The AEMP protocol is optimised for both text-based and binary	1205	=item * The AEMP protocol is optimised for both text-based and binary
817	communications.	1206	communications.
818		1207
819	The AEMP protocol, unlike the Erlang protocol, supports both	1208	The AEMP protocol, unlike the Erlang protocol, supports both programming
820	language-independent text-only protocols (good for debugging) and binary,	1209	language independent text-only protocols (good for debugging), and binary,
821	language-specific serialisers (e.g. Storable).	1210	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1211	used, the protocol is actually completely text-based.
822		1212
823	It has also been carefully designed to be implementable in other languages	1213	It has also been carefully designed to be implementable in other languages
824	with a minimum of work while gracefully degrading fucntionality to make the	1214	with a minimum of work while gracefully degrading functionality to make the
825	protocol simple.	1215	protocol simple.
826		1216
827	=item * AEMP has more flexible monitoring options than Erlang.	1217	=item * AEMP has more flexible monitoring options than Erlang.
828		1218
829	In Erlang, you can chose to receive I<all> exit signals as messages	1219	In Erlang, you can chose to receive I<all> exit signals as messages or
830	or I<none>, there is no in-between, so monitoring single processes is	1220	I<none>, there is no in-between, so monitoring single Erlang processes is
831	difficult to implement. Monitoring in AEMP is more flexible than in	1221	difficult to implement.
832	Erlang, as one can choose between automatic kill, exit message or callback	1222
833	on a per-process basis.	1223	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1224	between automatic kill, exit message or callback on a per-port basis.
834		1225
835	=item * Erlang tries to hide remote/local connections, AEMP does not.	1226	=item * Erlang tries to hide remote/local connections, AEMP does not.
836		1227
837	Monitoring in Erlang is not an indicator of process death/crashes,	1228	Monitoring in Erlang is not an indicator of process death/crashes, in the
838	as linking is (except linking is unreliable in Erlang).	1229	same way as linking is (except linking is unreliable in Erlang).
839		1230
840	In AEMP, you don't "look up" registered port names or send to named ports	1231	In AEMP, you don't "look up" registered port names or send to named ports
841	that might or might not be persistent. Instead, you normally spawn a port	1232	that might or might not be persistent. Instead, you normally spawn a port
842	on the remote node. The init function monitors the you, and you monitor	1233	on the remote node. The init function monitors you, and you monitor the
843	the remote port. Since both monitors are local to the node, they are much	1234	remote port. Since both monitors are local to the node, they are much more
844	more reliable.	1235	reliable (no need for C<spawn_link>).
845		1236
846	This also saves round-trips and avoids sending messages to the wrong port	1237	This also saves round-trips and avoids sending messages to the wrong port
847	(hard to do in Erlang).	1238	(hard to do in Erlang).
848		1239
849	=back	1240	=back
850		1241
851	=head1 RATIONALE	1242	=head1 RATIONALE
852		1243
853	=over 4	1244	=over 4
854		1245
855	=item Why strings for ports and noderefs, why not objects?	1246	=item Why strings for port and node IDs, why not objects?
856		1247
857	We considered "objects", but found that the actual number of methods	1248	We considered "objects", but found that the actual number of methods
858	thatc an be called are very low. Since port IDs and noderefs travel over	1249	that can be called are quite low. Since port and node IDs travel over
859	the network frequently, the serialising/deserialising would add lots of	1250	the network frequently, the serialising/deserialising would add lots of
860	overhead, as well as having to keep a proxy object.	1251	overhead, as well as having to keep a proxy object everywhere.
861		1252
862	Strings can easily be printed, easily serialised etc. and need no special	1253	Strings can easily be printed, easily serialised etc. and need no special
863	procedures to be "valid".	1254	procedures to be "valid".
864		1255
865	And a a miniport consists of a single closure stored in a global hash - it	1256	And as a result, a port with just a default receiver consists of a single
866	can't become much cheaper.	1257	code reference stored in a global hash - it can't become much cheaper.
867		1258
868	=item Why favour JSON, why not real serialising format such as Storable?	1259	=item Why favour JSON, why not a real serialising format such as Storable?
869		1260
870	In fact, any AnyEvent::MP node will happily accept Storable as framing	1261	In fact, any AnyEvent::MP node will happily accept Storable as framing
871	format, but currently there is no way to make a node use Storable by	1262	format, but currently there is no way to make a node use Storable by
872	default.	1263	default (although all nodes will accept it).
873		1264
874	The default framing protocol is JSON because a) JSON::XS is many times	1265	The default framing protocol is JSON because a) JSON::XS is many times
875	faster for small messages and b) most importantly, after years of	1266	faster for small messages and b) most importantly, after years of
876	experience we found that object serialisation is causing more problems	1267	experience we found that object serialisation is causing more problems
877	than it gains: Just like function calls, objects simply do not travel	1268	than it solves: Just like function calls, objects simply do not travel
878	easily over the network, mostly because they will always be a copy, so you	1269	easily over the network, mostly because they will always be a copy, so you
879	always have to re-think your design.	1270	always have to re-think your design.
880		1271
881	Keeping your messages simple, concentrating on data structures rather than	1272	Keeping your messages simple, concentrating on data structures rather than
882	objects, will keep your messages clean, tidy and efficient.	1273	objects, will keep your messages clean, tidy and efficient.
883		1274
884	=back	1275	=back
885		1276
		1277	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1278
		1279	AEMP version 2 has a few major incompatible changes compared to version 1:
		1280
		1281	=over 4
		1282
		1283	=item AnyEvent::MP::Global no longer has group management functions.
		1284
		1285	At least not officially - the grp_* functions are still exported and might
		1286	work, but they will be removed in some later release.
		1287
		1288	AnyEvent::MP now comes with a distributed database that is more
		1289	powerful. Its database families map closely to port groups, but the API
		1290	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1291	a rough porting guide:
		1292
		1293	grp_reg $group, $port # old
		1294	db_reg $group, $port # new
		1295
		1296	$list = grp_get $group # old
		1297	db_keys $group, sub { my $list = shift } # new
		1298
		1299	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1300	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1301
		1302	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1303	no longer instant, because the local node might not have a copy of the
		1304	group. You can either modify your code to allow for a callback, or use
		1305	C<db_mon> to keep an updated copy of the group:
		1306
		1307	my $local_group_copy;
		1308	db_mon $group => sub { $local_group_copy = $_[0] };
		1309
		1310	# now "keys %$local_group_copy" always returns the most up-to-date
		1311	# list of ports in the group.
		1312
		1313	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1314	passes a hash as first argument, and an extra C<$chg> argument that can be
		1315	ignored:
		1316
		1317	db_mon $group => sub {
		1318	my ($ports, $add, $chg, $del) = @_;
		1319	$ports = [keys %$ports];
		1320
		1321	# now $ports, $add and $del are the same as
		1322	# were originally passed by grp_mon.
		1323	...
		1324	};
		1325
		1326	=item Nodes not longer connect to all other nodes.
		1327
		1328	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1329	module, which in turn would create connections to all other nodes in the
		1330	network (helped by the seed nodes).
		1331
		1332	In version 2.x, global nodes still connect to all other global nodes, but
		1333	other nodes don't - now every node either is a global node itself, or
		1334	attaches itself to another global node.
		1335
		1336	If a node isn't a global node itself, then it attaches itself to one
		1337	of its seed nodes. If that seed node isn't a global node yet, it will
		1338	automatically be upgraded to a global node.
		1339
		1340	So in many cases, nothing needs to be changed - one just has to make sure
		1341	that all seed nodes are meshed together with the other seed nodes (as with
		1342	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1343	achieved by specifying the same set of seed nodes for all nodes in the
		1344	network.
		1345
		1346	Not opening a connection to every other node is usually an advantage,
		1347	except when you need the lower latency of an already established
		1348	connection. To ensure a node establishes a connection to another node,
		1349	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1350	create the connection (and notify you when the connection fails).
		1351
		1352	=item Listener-less nodes (nodes without binds) are gone.
		1353
		1354	And are not coming back, at least not in their old form. If no C<binds>
		1355	are specified for a node, AnyEvent::MP assumes a default of C<*:*>.
		1356
		1357	There are vague plans to implement some form of routing domains, which
		1358	might or might not bring back listener-less nodes, but don't count on it.
		1359
		1360	The fact that most connections are now optional somewhat mitigates this,
		1361	as a node can be effectively unreachable from the outside without any
		1362	problems, as long as it isn't a global node and only reaches out to other
		1363	nodes (as opposed to being contacted from other nodes).
		1364
		1365	=item $AnyEvent::MP::Kernel::WARN has gone.
		1366
		1367	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1368	uses this, and so should your programs.
		1369
		1370	Every module now documents what kinds of messages it generates, with
		1371	AnyEvent::MP acting as a catch all.
		1372
		1373	On the positive side, this means that instead of setting
		1374	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1375	much less to type.
		1376
		1377	=back
		1378
		1379	=head1 LOGGING
		1380
		1381	AnyEvent::MP does not normally log anything by itself, but since it is the
		1382	root of the context hierarchy for AnyEvent::MP modules, it will receive
		1383	all log messages by submodules.
		1384
886	=head1 SEE ALSO	1385	=head1 SEE ALSO
		1386
		1387	L<AnyEvent::MP::Intro> - a gentle introduction.
		1388
		1389	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1390
		1391	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1392	your applications.
		1393
		1394	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1395
		1396	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1397	all nodes.
887		1398
888	L<AnyEvent>.	1399	L<AnyEvent>.
889		1400
890	=head1 AUTHOR	1401	=head1 AUTHOR
891		1402

Diff Legend

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