ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/AnyEvent-MP/MP.pm

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.52 by root, Fri Aug 14 15:13:20 2009 UTC vs.
Revision 1.143 by root, Fri Mar 23 17:54:36 2012 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $somple_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	Some ports allow you to register C<rcv> handlers that can match specific	84	Ports allow you to register C<rcv> handlers that can match all or just
75	messages. All C<rcv> handlers will receive messages they match, messages	85	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	86	anything was listening for them or not.
77		87
		88	Ports are represented by (printable) strings called "port IDs".
		89
78	=item port id - C<noderef#portname>	90	=item port ID - C<nodeid#portname>
79		91
80	A port id is normaly 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<#>)
81	separator, and a port name (a printable string of unspecified format). An	93	as separator, and a port name (a printable string of unspecified
82	exception is the the node port, whose ID is identical to its node	94	format created by AnyEvent::MP).
83	reference.
84		95
85	=item node	96	=item node
86		97
87	A node is a single process containing at least one port - the node	98	A node is a single process containing at least one port - the node port,
88	port. You can send messages to node ports to find existing ports or to	99	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	100	ports.
90		101
91	Nodes are either private (single-process only), slaves (connected to a	102	Nodes are either public (have one or more listening ports) or private
92	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.
93		105
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	106	Nodes is represented by (printable) strings called "node IDs".
95		107
96	A node reference is a string that either simply identifies the node (for	108	=item node ID - C<[A-Za-z0-9_\-.:]*>
97	private and slave nodes), or contains a recipe on how to reach a given
98	node (for public nodes).
99		109
100	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
101	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.
102		114
103	Node references come in two flavours: resolved (containing only numerical	115	=item binds - C<ip:port>
104	addresses) or unresolved (where hostnames are used instead of addresses).
105		116
106	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
107	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 thta accepts conenctions form 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 cna 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 form are part of
		137	the same network. If a network is split into multiple subnets because e.g.
		138	the network link between the parts goes down, then using the same seed
		139	nodes 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 makign them the same
		174	reduces overhead).
108		175
109	=back	176	=back
110		177
111	=head1 VARIABLES/FUNCTIONS	178	=head1 VARIABLES/FUNCTIONS
112		179
…		…
114		181
115	=cut	182	=cut
116		183
117	package AnyEvent::MP;	184	package AnyEvent::MP;
118		185
		186	use AnyEvent::MP::Config ();
119	use AnyEvent::MP::Kernel;	187	use AnyEvent::MP::Kernel;
		188	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
120		189
121	use common::sense;	190	use common::sense;
122		191
123	use Carp ();	192	use Carp ();
124		193
125	use AE ();	194	use AnyEvent ();
		195	use Guard ();
126		196
127	use base "Exporter";	197	use base "Exporter";
128		198
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	199	our $VERSION = $AnyEvent::MP::Config::VERSION;
130		200
131	our @EXPORT = qw(	201	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	202	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	203	configure
134	snd rcv mon kil reg psub spawn	204	snd rcv mon mon_guard kil psub peval spawn cal
135	port	205	port
		206	db_set db_del db_reg
		207	db_mon db_family db_keys db_values
136	);	208	);
137		209
138	our $SELF;	210	our $SELF;
139		211
140	sub _self_die() {	212	sub _self_die() {
…		…
143	kil $SELF, die => $msg;	215	kil $SELF, die => $msg;
144	}	216	}
145		217
146	=item $thisnode = NODE / $NODE	218	=item $thisnode = NODE / $NODE
147		219
148	The C<NODE> function returns, and the C<$NODE> variable contains the	220	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	noderef of the local node. The value is initialised by a call to	221	ID of the node running in the current process. This value is initialised by
150	C<initialise_node>.	222	a call to C<configure>.
151		223
152	=item $noderef = node_of $port	224	=item $nodeid = node_of $port
153		225
154	Extracts and returns the noderef from a port ID or a noderef.	226	Extracts and returns the node ID from a port ID or a node ID.
155		227
156	=item initialise_node $noderef, $seednode, $seednode...	228	=item configure $profile, key => value...
157		229
158	=item initialise_node "slave/", $master, $master...	230	=item configure key => value...
159		231
160	Before a node can talk to other nodes on the network it has to initialise	232	Before a node can talk to other nodes on the network (i.e. enter
161	itself - the minimum a node needs to know is it's own name, and optionally	233	"distributed mode") it has to configure itself - the minimum a node needs
162	it should know the noderefs of some other nodes in the network.	234	to know is its own name, and optionally it should know the addresses of
		235	some other nodes in the network to discover other nodes.
163		236
164	This function initialises a node - it must be called exactly once (or	237	This function configures a node - it must be called exactly once (or
165	never) before calling other AnyEvent::MP functions.	238	never) before calling other AnyEvent::MP functions.
166		239
167	All arguments (optionally except for the first) are noderefs, which can be	240	The key/value pairs are basically the same ones as documented for the
168	either resolved or unresolved.	241	F<aemp> command line utility (sans the set/del prefix), with these additions:
169
170	The first argument will be looked up in the configuration database first
171	(if it is C<undef> then the current nodename will be used instead) to find
172	the relevant configuration profile (see L<aemp>). If none is found then
173	the default configuration is used. The configuration supplies additional
174	seed/master nodes and can override the actual noderef.
175
176	There are two types of networked nodes, public nodes and slave nodes:
177		242
178	=over 4	243	=over 4
179		244
180	=item public nodes	245	=item norc => $boolean (default false)
181		246
182	For public nodes, C<$noderef> (supplied either directly to	247	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
183	C<initialise_node> or indirectly via a profile or the nodename) must be a	248	be consulted - all configuraiton options must be specified in the
184	noderef (possibly unresolved, in which case it will be resolved).	249	C<configure> call.
185		250
186	After resolving, the node will bind itself on all endpoints and try to	251	=item force => $boolean (default false)
187	connect to all additional C<$seednodes> that are specified. Seednodes are
188	optional and can be used to quickly bootstrap the node into an existing
189	network.
190		252
191	=item slave nodes	253	IF true, then the values specified in the C<configure> will take
192		254	precedence over any values configured via the rc file. The default is for
193	When the C<$noderef> (either as given or overriden by the config file)	255	the rc file to override any options specified in the program.
194	is the special string C<slave/>, then the node will become a slave
195	node. Slave nodes cannot be contacted from outside and will route most of
196	their traffic to the master node that they attach to.
197
198	At least one additional noderef is required (either by specifying it
199	directly or because it is part of the configuration profile): The node
200	will try to connect to all of them and will become a slave attached to the
201	first node it can successfully connect to.
202		256
203	=back	257	=back
204		258
205	This function will block until all nodes have been resolved and, for slave
206	nodes, until it has successfully established a connection to a master
207	server.
208
209	Example: become a public node listening on the guessed noderef, or the one
210	specified via C<aemp> for the current node. This should be the most common
211	form of invocation for "daemon"-type nodes.
212
213	initialise_node;
214
215	Example: become a slave node to any of the the seednodes specified via
216	C<aemp>. This form is often used for commandline clients.
217
218	initialise_node "slave/";
219
220	Example: become a slave node to any of the specified master servers. This
221	form is also often used for commandline clients.
222
223	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
224
225	Example: become a public node, and try to contact some well-known master
226	servers to become part of the network.
227
228	initialise_node undef, "master1", "master2";
229
230	Example: become a public node listening on port C<4041>.
231
232	initialise_node 4041;
233
234	Example: become a public node, only visible on localhost port 4044.
235
236	initialise_node "localhost:4044";
237
238	=item $cv = resolve_node $noderef
239
240	Takes an unresolved node reference that may contain hostnames and
241	abbreviated IDs, resolves all of them and returns a resolved node
242	reference.
243
244	In addition to C<address:port> pairs allowed in resolved noderefs, the
245	following forms are supported:
246
247	=over 4	259	=over 4
248		260
249	=item the empty string	261	=item step 1, gathering configuration from profiles
250		262
251	An empty-string component gets resolved as if the default port (4040) was	263	The function first looks up a profile in the aemp configuration (see the
252	specified.	264	L<aemp> commandline utility). The profile name can be specified via the
		265	named C<profile> parameter or can simply be the first parameter). If it is
		266	missing, then the nodename (F<uname -n>) will be used as profile name.
253		267
254	=item naked port numbers (e.g. C<1234>)	268	The profile data is then gathered as follows:
255		269
256	These are resolved by prepending the local nodename and a colon, to be	270	First, all remaining key => value pairs (all of which are conveniently
257	further resolved.	271	undocumented at the moment) will be interpreted as configuration
		272	data. Then they will be overwritten by any values specified in the global
		273	default configuration (see the F<aemp> utility), then the chain of
		274	profiles chosen by the profile name (and any C<parent> attributes).
258		275
259	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	276	That means that the values specified in the profile have highest priority
		277	and the values specified directly via C<configure> have lowest priority,
		278	and can only be used to specify defaults.
260		279
261	These are resolved by using AnyEvent::DNS to resolve them, optionally	280	If the profile specifies a node ID, then this will become the node ID of
262	looking up SRV records for the C<aemp=4040> port, if no port was	281	this process. If not, then the profile name will be used as node ID, with
263	specified.	282	a unique randoms tring (C</%u>) appended.
		283
		284	The node ID can contain some C<%> sequences that are expanded: C<%n>
		285	is expanded to the local nodename, C<%u> is replaced by a random
		286	strign to make the node unique. For example, the F<aemp> commandline
		287	utility uses C<aemp/%n/%u> as nodename, which might expand to
		288	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		289
		290	=item step 2, bind listener sockets
		291
		292	The next step is to look up the binds in the profile, followed by binding
		293	aemp protocol listeners on all binds specified (it is possible and valid
		294	to have no binds, meaning that the node cannot be contacted form the
		295	outside. This means the node cannot talk to other nodes that also have no
		296	binds, but it can still talk to all "normal" nodes).
		297
		298	If the profile does not specify a binds list, then a default of C<*> is
		299	used, meaning the node will bind on a dynamically-assigned port on every
		300	local IP address it finds.
		301
		302	=item step 3, connect to seed nodes
		303
		304	As the last step, the seed ID list from the profile is passed to the
		305	L<AnyEvent::MP::Global> module, which will then use it to keep
		306	connectivity with at least one node at any point in time.
264		307
265	=back	308	=back
		309
		310	Example: become a distributed node using the local node name as profile.
		311	This should be the most common form of invocation for "daemon"-type nodes.
		312
		313	configure
		314
		315	Example: become a semi-anonymous node. This form is often used for
		316	commandline clients.
		317
		318	configure nodeid => "myscript/%n/%u";
		319
		320	Example: configure a node using a profile called seed, which is suitable
		321	for a seed node as it binds on all local addresses on a fixed port (4040,
		322	customary for aemp).
		323
		324	# use the aemp commandline utility
		325	# aemp profile seed binds '*:4040'
		326
		327	# then use it
		328	configure profile => "seed";
		329
		330	# or simply use aemp from the shell again:
		331	# aemp run profile seed
		332
		333	# or provide a nicer-to-remember nodeid
		334	# aemp run profile seed nodeid "$(hostname)"
266		335
267	=item $SELF	336	=item $SELF
268		337
269	Contains the current port id while executing C<rcv> callbacks or C<psub>	338	Contains the current port id while executing C<rcv> callbacks or C<psub>
270	blocks.	339	blocks.
271		340
272	=item SELF, %SELF, @SELF...	341	=item *SELF, SELF, %SELF, @SELF...
273		342
274	Due to some quirks in how perl exports variables, it is impossible to	343	Due to some quirks in how perl exports variables, it is impossible to
275	just export C<$SELF>, all the symbols called C<SELF> are exported by this	344	just export C<$SELF>, all the symbols named C<SELF> are exported by this
276	module, but only C<$SELF> is currently used.	345	module, but only C<$SELF> is currently used.
277		346
278	=item snd $port, type => @data	347	=item snd $port, type => @data
279		348
280	=item snd $port, @msg	349	=item snd $port, @msg
281		350
282	Send the given message to the given port ID, which can identify either	351	Send the given message to the given port, which can identify either a
283	a local or a remote port, and must be a port ID.	352	local or a remote port, and must be a port ID.
284		353
285	While the message can be about anything, it is highly recommended to use a	354	While the message can be almost anything, it is highly recommended to
286	string as first element (a port ID, or some word that indicates a request	355	use a string as first element (a port ID, or some word that indicates a
287	type etc.).	356	request type etc.) and to consist if only simple perl values (scalars,
		357	arrays, hashes) - if you think you need to pass an object, think again.
288		358
289	The message data effectively becomes read-only after a call to this	359	The message data logically becomes read-only after a call to this
290	function: modifying any argument is not allowed and can cause many	360	function: modifying any argument (or values referenced by them) is
291	problems.	361	forbidden, as there can be considerable time between the call to C<snd>
		362	and the time the message is actually being serialised - in fact, it might
		363	never be copied as within the same process it is simply handed to the
		364	receiving port.
292		365
293	The type of data you can transfer depends on the transport protocol: when	366	The type of data you can transfer depends on the transport protocol: when
294	JSON is used, then only strings, numbers and arrays and hashes consisting	367	JSON is used, then only strings, numbers and arrays and hashes consisting
295	of those are allowed (no objects). When Storable is used, then anything	368	of those are allowed (no objects). When Storable is used, then anything
296	that Storable can serialise and deserialise is allowed, and for the local	369	that Storable can serialise and deserialise is allowed, and for the local
297	node, anything can be passed.	370	node, anything can be passed. Best rely only on the common denominator of
		371	these.
298		372
299	=item $local_port = port	373	=item $local_port = port
300		374
301	Create a new local port object and returns its port ID. Initially it has	375	Create a new local port object and returns its port ID. Initially it has
302	no callbacks set and will throw an error when it receives messages.	376	no callbacks set and will throw an error when it receives messages.
…		…
321		395
322	=cut	396	=cut
323		397
324	sub rcv($@);	398	sub rcv($@);
325		399
326	sub _kilme {	400	my $KILME = sub {
327	die "received message on port without callback";	401	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
328	}	402	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		403	};
329		404
330	sub port(;&) {	405	sub port(;&) {
331	my $id = "$UNIQ." . $ID++;	406	my $id = $UNIQ . ++$ID;
332	my $port = "$NODE#$id";	407	my $port = "$NODE#$id";
333		408
334	rcv $port, shift || \&_kilme;	409	rcv $port, shift || $KILME;
335		410
336	$port	411	$port
337	}	412	}
338		413
339	=item rcv $local_port, $callback->(@msg)	414	=item rcv $local_port, $callback->(@msg)
…		…
344		419
345	The global C<$SELF> (exported by this module) contains C<$port> while	420	The global C<$SELF> (exported by this module) contains C<$port> while
346	executing the callback. Runtime errors during callback execution will	421	executing the callback. Runtime errors during callback execution will
347	result in the port being C<kil>ed.	422	result in the port being C<kil>ed.
348		423
349	The default callback received all messages not matched by a more specific	424	The default callback receives all messages not matched by a more specific
350	C<tag> match.	425	C<tag> match.
351		426
352	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	427	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
353		428
354	Register callbacks to be called on messages starting with the given tag on	429	Register (or replace) callbacks to be called on messages starting with the
355	the given port (and return the port), or unregister it (when C<$callback>	430	given tag on the given port (and return the port), or unregister it (when
356	is C<$undef>).	431	C<$callback> is C<$undef> or missing). There can only be one callback
		432	registered for each tag.
357		433
358	The original message will be passed to the callback, after the first	434	The original message will be passed to the callback, after the first
359	element (the tag) has been removed. The callback will use the same	435	element (the tag) has been removed. The callback will use the same
360	environment as the default callback (see above).	436	environment as the default callback (see above).
361		437
…		…
373	rcv port,	449	rcv port,
374	msg1 => sub { ... },	450	msg1 => sub { ... },
375	...	451	...
376	;	452	;
377		453
		454	Example: temporarily register a rcv callback for a tag matching some port
		455	(e.g. for an rpc reply) and unregister it after a message was received.
		456
		457	rcv $port, $otherport => sub {
		458	my @reply = @_;
		459
		460	rcv $SELF, $otherport;
		461	};
		462
378	=cut	463	=cut
379		464
380	sub rcv($@) {	465	sub rcv($@) {
381	my $port = shift;	466	my $port = shift;
382	my ($noderef, $portid) = split /#/, $port, 2;	467	my ($nodeid, $portid) = split /#/, $port, 2;
383		468
384	($NODE{$noderef} || add_node $noderef) == $NODE{""}	469	$NODE{$nodeid} == $NODE{""}
385	or Carp::croak "$port: rcv can only be called on local ports, caught";	470	or Carp::croak "$port: rcv can only be called on local ports, caught";
386		471
387	while (@_) {	472	while (@_) {
388	if (ref $_[0]) {	473	if (ref $_[0]) {
389	if (my $self = $PORT_DATA{$portid}) {	474	if (my $self = $PORT_DATA{$portid}) {
390	"AnyEvent::MP::Port" eq ref $self	475	"AnyEvent::MP::Port" eq ref $self
391	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	476	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
392		477
393	$self->[2] = shift;	478	$self->[0] = shift;
394	} else {	479	} else {
395	my $cb = shift;	480	my $cb = shift;
396	$PORT{$portid} = sub {	481	$PORT{$portid} = sub {
397	local $SELF = $port;	482	local $SELF = $port;
398	eval { &$cb }; _self_die if $@;	483	eval { &$cb }; _self_die if $@;
399	};	484	};
400	}	485	}
401	} elsif (defined $_[0]) {	486	} elsif (defined $_[0]) {
402	my $self = $PORT_DATA{$portid} ||= do {	487	my $self = $PORT_DATA{$portid} ||= do {
403	my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port";	488	my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
404		489
405	$PORT{$portid} = sub {	490	$PORT{$portid} = sub {
406	local $SELF = $port;	491	local $SELF = $port;
407		492
408	if (my $cb = $self->[1]{$_[0]}) {	493	if (my $cb = $self->[1]{$_[0]}) {
…		…
430	}	515	}
431		516
432	$port	517	$port
433	}	518	}
434		519
		520	=item peval $port, $coderef[, @args]
		521
		522	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		523	when the code throews an exception the C<$port> will be killed.
		524
		525	Any remaining args will be passed to the callback. Any return values will
		526	be returned to the caller.
		527
		528	This is useful when you temporarily want to execute code in the context of
		529	a port.
		530
		531	Example: create a port and run some initialisation code in it's context.
		532
		533	my $port = port { ... };
		534
		535	peval $port, sub {
		536	init
		537	or die "unable to init";
		538	};
		539
		540	=cut
		541
		542	sub peval($$) {
		543	local $SELF = shift;
		544	my $cb = shift;
		545
		546	if (wantarray) {
		547	my @res = eval { &$cb };
		548	_self_die if $@;
		549	@res
		550	} else {
		551	my $res = eval { &$cb };
		552	_self_die if $@;
		553	$res
		554	}
		555	}
		556
435	=item $closure = psub { BLOCK }	557	=item $closure = psub { BLOCK }
436		558
437	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	559	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
438	closure is executed, sets up the environment in the same way as in C<rcv>	560	closure is executed, sets up the environment in the same way as in C<rcv>
439	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	561	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		562
		563	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		564	BLOCK }, @_ } >>.
440		565
441	This is useful when you register callbacks from C<rcv> callbacks:	566	This is useful when you register callbacks from C<rcv> callbacks:
442		567
443	rcv delayed_reply => sub {	568	rcv delayed_reply => sub {
444	my ($delay, @reply) = @_;	569	my ($delay, @reply) = @_;
…		…
468	$res	593	$res
469	}	594	}
470	}	595	}
471	}	596	}
472		597
473	=item $guard = mon $port, $cb->(@reason)	598	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
474		599
475	=item $guard = mon $port, $rcvport	600	=item $guard = mon $port # kill $SELF when $port dies
476		601
477	=item $guard = mon $port	602	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
478		603
479	=item $guard = mon $port, $rcvport, @msg	604	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
480		605
481	Monitor the given port and do something when the port is killed or	606	Monitor the given port and do something when the port is killed or
482	messages to it were lost, and optionally return a guard that can be used	607	messages to it were lost, and optionally return a guard that can be used
483	to stop monitoring again.	608	to stop monitoring again.
484		609
		610	The first two forms distinguish between "normal" and "abnormal" kil's:
		611
		612	In the first form (another port given), if the C<$port> is C<kil>'ed with
		613	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		614	same reason. That is, on "normal" kil's nothing happens, while under all
		615	other conditions, the other port is killed with the same reason.
		616
		617	The second form (kill self) is the same as the first form, except that
		618	C<$rvport> defaults to C<$SELF>.
		619
		620	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		621	- it's up to the callback or receiver to check whether the C<@reason> is
		622	empty and act accordingly.
		623
		624	In the third form (callback), the callback is simply called with any
		625	number of C<@reason> elements (empty @reason means that the port was deleted
		626	"normally"). Note also that I<< the callback B<must> never die >>, so use
		627	C<eval> if unsure.
		628
		629	In the last form (message), a message of the form C<$rcvport, @msg,
		630	@reason> will be C<snd>.
		631
		632	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		633	alert was raised), they are removed and will not trigger again, even if it
		634	turns out that the port is still alive.
		635
		636	As a rule of thumb, monitoring requests should always monitor a remote
		637	port locally (using a local C<$rcvport> or a callback). The reason is that
		638	kill messages might get lost, just like any other message. Another less
		639	obvious reason is that even monitoring requests can get lost (for example,
		640	when the connection to the other node goes down permanently). When
		641	monitoring a port locally these problems do not exist.
		642
485	C<mon> effectively guarantees that, in the absence of hardware failures,	643	C<mon> effectively guarantees that, in the absence of hardware failures,
486	that after starting the monitor, either all messages sent to the port	644	after starting the monitor, either all messages sent to the port will
487	will arrive, or the monitoring action will be invoked after possible	645	arrive, or the monitoring action will be invoked after possible message
488	message loss has been detected. No messages will be lost "in between"	646	loss has been detected. No messages will be lost "in between" (after
489	(after the first lost message no further messages will be received by the	647	the first lost message no further messages will be received by the
490	port). After the monitoring action was invoked, further messages might get	648	port). After the monitoring action was invoked, further messages might get
491	delivered again.	649	delivered again.
492		650
493	In the first form (callback), the callback is simply called with any	651	Inter-host-connection timeouts and monitoring depend on the transport
494	number of C<@reason> elements (no @reason means that the port was deleted	652	used. The only transport currently implemented is TCP, and AnyEvent::MP
495	"normally"). Note also that I<< the callback B<must> never die >>, so use	653	relies on TCP to detect node-downs (this can take 10-15 minutes on a
496	C<eval> if unsure.	654	non-idle connection, and usually around two hours for idle connections).
497		655
498	In the second form (another port given), the other port (C<$rcvport>)	656	This means that monitoring is good for program errors and cleaning up
499	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	657	stuff eventually, but they are no replacement for a timeout when you need
500	"normal" kils nothing happens, while under all other conditions, the other	658	to ensure some maximum latency.
501	port is killed with the same reason.
502
503	The third form (kill self) is the same as the second form, except that
504	C<$rvport> defaults to C<$SELF>.
505
506	In the last form (message), a message of the form C<@msg, @reason> will be
507	C<snd>.
508
509	As a rule of thumb, monitoring requests should always monitor a port from
510	a local port (or callback). The reason is that kill messages might get
511	lost, just like any other message. Another less obvious reason is that
512	even monitoring requests can get lost (for exmaple, when the connection
513	to the other node goes down permanently). When monitoring a port locally
514	these problems do not exist.
515		659
516	Example: call a given callback when C<$port> is killed.	660	Example: call a given callback when C<$port> is killed.
517		661
518	mon $port, sub { warn "port died because of <@_>\n" };	662	mon $port, sub { warn "port died because of <@_>\n" };
519		663
…		…
526	mon $port, $self => "restart";	670	mon $port, $self => "restart";
527		671
528	=cut	672	=cut
529		673
530	sub mon {	674	sub mon {
531	my ($noderef, $port) = split /#/, shift, 2;	675	my ($nodeid, $port) = split /#/, shift, 2;
532		676
533	my $node = $NODE{$noderef} || add_node $noderef;	677	my $node = $NODE{$nodeid} || add_node $nodeid;
534		678
535	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';	679	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
536		680
537	unless (ref $cb) {	681	unless (ref $cb) {
538	if (@_) {	682	if (@_) {
…		…
547	}	691	}
548		692
549	$node->monitor ($port, $cb);	693	$node->monitor ($port, $cb);
550		694
551	defined wantarray	695	defined wantarray
552	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	696	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
553	}	697	}
554		698
555	=item $guard = mon_guard $port, $ref, $ref...	699	=item $guard = mon_guard $port, $ref, $ref...
556		700
557	Monitors the given C<$port> and keeps the passed references. When the port	701	Monitors the given C<$port> and keeps the passed references. When the port
558	is killed, the references will be freed.	702	is killed, the references will be freed.
559		703
560	Optionally returns a guard that will stop the monitoring.	704	Optionally returns a guard that will stop the monitoring.
561		705
562	This function is useful when you create e.g. timers or other watchers and	706	This function is useful when you create e.g. timers or other watchers and
563	want to free them when the port gets killed:	707	want to free them when the port gets killed (note the use of C<psub>):
564		708
565	$port->rcv (start => sub {	709	$port->rcv (start => sub {
566	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	710	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
567	undef $timer if 0.9 < rand;	711	undef $timer if 0.9 < rand;
568	});	712	});
569	});	713	});
570		714
571	=cut	715	=cut
…		…
580		724
581	=item kil $port[, @reason]	725	=item kil $port[, @reason]
582		726
583	Kill the specified port with the given C<@reason>.	727	Kill the specified port with the given C<@reason>.
584		728
585	If no C<@reason> is specified, then the port is killed "normally" (linked	729	If no C<@reason> is specified, then the port is killed "normally" -
586	ports will not be kileld, or even notified).	730	monitor callback will be invoked, but the kil will not cause linked ports
		731	(C<mon $mport, $lport> form) to get killed.
587		732
588	Otherwise, linked ports get killed with the same reason (second form of	733	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
589	C<mon>, see below).	734	form) get killed with the same reason.
590		735
591	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	736	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
592	will be reported as reason C<< die => $@ >>.	737	will be reported as reason C<< die => $@ >>.
593		738
594	Transport/communication errors are reported as C<< transport_error =>	739	Transport/communication errors are reported as C<< transport_error =>
595	$message >>.	740	$message >>.
596		741
597	=cut	742	Common idioms:
		743
		744	# silently remove yourself, do not kill linked ports
		745	kil $SELF;
		746
		747	# report a failure in some detail
		748	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		749
		750	# do not waste much time with killing, just die when something goes wrong
		751	open my $fh, "<file"
		752	or die "file: $!";
598		753
599	=item $port = spawn $node, $initfunc[, @initdata]	754	=item $port = spawn $node, $initfunc[, @initdata]
600		755
601	Creates a port on the node C<$node> (which can also be a port ID, in which	756	Creates a port on the node C<$node> (which can also be a port ID, in which
602	case it's the node where that port resides).	757	case it's the node where that port resides).
603		758
604	The port ID of the newly created port is return immediately, and it is	759	The port ID of the newly created port is returned immediately, and it is
605	permissible to immediately start sending messages or monitor the port.	760	possible to immediately start sending messages or to monitor the port.
606		761
607	After the port has been created, the init function is	762	After the port has been created, the init function is called on the remote
608	called. This function must be a fully-qualified function name	763	node, in the same context as a C<rcv> callback. This function must be a
609	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	764	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
610	program, use C<::name>.	765	specify a function in the main program, use C<::name>.
611		766
612	If the function doesn't exist, then the node tries to C<require>	767	If the function doesn't exist, then the node tries to C<require>
613	the package, then the package above the package and so on (e.g.	768	the package, then the package above the package and so on (e.g.
614	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	769	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
615	exists or it runs out of package names.	770	exists or it runs out of package names.
616		771
617	The init function is then called with the newly-created port as context	772	The init function is then called with the newly-created port as context
618	object (C<$SELF>) and the C<@initdata> values as arguments.	773	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		774	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		775	the port might not get created.
619		776
620	A common idiom is to pass your own port, monitor the spawned port, and	777	A common idiom is to pass a local port, immediately monitor the spawned
621	in the init function, monitor the original port. This two-way monitoring	778	port, and in the remote init function, immediately monitor the passed
622	ensures that both ports get cleaned up when there is a problem.	779	local port. This two-way monitoring ensures that both ports get cleaned up
		780	when there is a problem.
		781
		782	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		783	caller before C<spawn> returns (by delaying invocation when spawn is
		784	called for the local node).
623		785
624	Example: spawn a chat server port on C<$othernode>.	786	Example: spawn a chat server port on C<$othernode>.
625		787
626	# this node, executed from within a port context:	788	# this node, executed from within a port context:
627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	789	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
642		804
643	sub _spawn {	805	sub _spawn {
644	my $port = shift;	806	my $port = shift;
645	my $init = shift;	807	my $init = shift;
646		808
		809	# rcv will create the actual port
647	local $SELF = "$NODE#$port";	810	local $SELF = "$NODE#$port";
648	eval {	811	eval {
649	&{ load_func $init }	812	&{ load_func $init }
650	};	813	};
651	_self_die if $@;	814	_self_die if $@;
652	}	815	}
653		816
654	sub spawn(@) {	817	sub spawn(@) {
655	my ($noderef, undef) = split /#/, shift, 2;	818	my ($nodeid, undef) = split /#/, shift, 2;
656		819
657	my $id = "$RUNIQ." . $ID++;	820	my $id = $RUNIQ . ++$ID;
658		821
659	$_[0] =~ /::/	822	$_[0] =~ /::/
660	or Carp::croak "spawn init function must be a fully-qualified name, caught";	823	or Carp::croak "spawn init function must be a fully-qualified name, caught";
661		824
662	($NODE{$noderef} || add_node $noderef)	825	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
663	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
664		826
665	"$noderef#$id"	827	"$nodeid#$id"
666	}	828	}
667		829
		830
		831	=item after $timeout, @msg
		832
		833	=item after $timeout, $callback
		834
		835	Either sends the given message, or call the given callback, after the
		836	specified number of seconds.
		837
		838	This is simply a utility function that comes in handy at times - the
		839	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		840	so it may go away in the future.
		841
		842	=cut
		843
		844	sub after($@) {
		845	my ($timeout, @action) = @_;
		846
		847	my $t; $t = AE::timer $timeout, 0, sub {
		848	undef $t;
		849	ref $action[0]
		850	? $action[0]()
		851	: snd @action;
		852	};
		853	}
		854
		855	#=item $cb2 = timeout $seconds, $cb[, @args]
		856
		857	=item cal $port, @msg, $callback[, $timeout]
		858
		859	A simple form of RPC - sends a message to the given C<$port> with the
		860	given contents (C<@msg>), but adds a reply port to the message.
		861
		862	The reply port is created temporarily just for the purpose of receiving
		863	the reply, and will be C<kil>ed when no longer needed.
		864
		865	A reply message sent to the port is passed to the C<$callback> as-is.
		866
		867	If an optional time-out (in seconds) is given and it is not C<undef>,
		868	then the callback will be called without any arguments after the time-out
		869	elapsed and the port is C<kil>ed.
		870
		871	If no time-out is given (or it is C<undef>), then the local port will
		872	monitor the remote port instead, so it eventually gets cleaned-up.
		873
		874	Currently this function returns the temporary port, but this "feature"
		875	might go in future versions unless you can make a convincing case that
		876	this is indeed useful for something.
		877
		878	=cut
		879
		880	sub cal(@) {
		881	my $timeout = ref $_[-1] ? undef : pop;
		882	my $cb = pop;
		883
		884	my $port = port {
		885	undef $timeout;
		886	kil $SELF;
		887	&$cb;
		888	};
		889
		890	if (defined $timeout) {
		891	$timeout = AE::timer $timeout, 0, sub {
		892	undef $timeout;
		893	kil $port;
		894	$cb->();
		895	};
		896	} else {
		897	mon $_[0], sub {
		898	kil $port;
		899	$cb->();
		900	};
		901	}
		902
		903	push @_, $port;
		904	&snd;
		905
		906	$port
		907	}
		908
668	=back	909	=back
669		910
670	=head1 NODE MESSAGES	911	=head1 DISTRIBUTED DATABASE
671		912
672	Nodes understand the following messages sent to them. Many of them take	913	AnyEvent::MP comes with a simple distributed database. The database will
673	arguments called C<@reply>, which will simply be used to compose a reply	914	be mirrored asynchronously on all global nodes. Other nodes bind to one
674	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	915	of the global nodes for their needs. Every node has a "local database"
675	the remaining arguments are simply the message data.	916	which contains all the values that are set locally. All local databases
		917	are merged together to form the global database, which can be queried.
676		918
677	While other messages exist, they are not public and subject to change.	919	The database structure is that of a two-level hash - the database hash
		920	contains hashes which contain values, similarly to a perl hash of hashes,
		921	i.e.:
678		922
		923	$DATABASE{$family}{$subkey} = $value
		924
		925	The top level hash key is called "family", and the second-level hash key
		926	is called "subkey" or simply "key".
		927
		928	The family must be alphanumeric, i.e. start with a letter and consist
		929	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		930	pretty much like Perl module names.
		931
		932	As the family namespace is global, it is recommended to prefix family names
		933	with the name of the application or module using it.
		934
		935	The subkeys must be non-empty strings, with no further restrictions.
		936
		937	The values should preferably be strings, but other perl scalars should
		938	work as well (such as C<undef>, arrays and hashes).
		939
		940	Every database entry is owned by one node - adding the same family/subkey
		941	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		942	but the result might be nondeterministic, i.e. the key might have
		943	different values on different nodes.
		944
		945	Different subkeys in the same family can be owned by different nodes
		946	without problems, and in fact, this is the common method to create worker
		947	pools. For example, a worker port for image scaling might do this:
		948
		949	db_set my_image_scalers => $port;
		950
		951	And clients looking for an image scaler will want to get the
		952	C<my_image_scalers> keys from time to time:
		953
		954	db_keys my_image_scalers => sub {
		955	@ports = @{ $_[0] };
		956	};
		957
		958	Or better yet, they want to monitor the database family, so they always
		959	have a reasonable up-to-date copy:
		960
		961	db_mon my_image_scalers => sub {
		962	@ports = keys %{ $_[0] };
		963	};
		964
		965	In general, you can set or delete single subkeys, but query and monitor
		966	whole families only.
		967
		968	If you feel the need to monitor or query a single subkey, try giving it
		969	it's own family.
		970
679	=over 4	971	=over
		972
		973	=item $guard = db_set $family => $subkey [=> $value]
		974
		975	Sets (or replaces) a key to the database - if C<$value> is omitted,
		976	C<undef> is used instead.
		977
		978	When called in non-void context, C<db_set> returns a guard that
		979	automatically calls C<db_del> when it is destroyed.
		980
		981	=item db_del $family => $subkey...
		982
		983	Deletes one or more subkeys from the database family.
		984
		985	=item $guard = db_reg $family => $port => $value
		986
		987	=item $guard = db_reg $family => $port
		988
		989	=item $guard = db_reg $family
		990
		991	Registers a port in the given family and optionally returns a guard to
		992	remove it.
		993
		994	This function basically does the same as:
		995
		996	db_set $family => $port => $value
		997
		998	Except that the port is monitored and automatically removed from the
		999	database family when it is kil'ed.
		1000
		1001	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1002	C<$SELF> is used.
		1003
		1004	This function is most useful to register a port in some port group (which
		1005	is just another name for a database family), and have it removed when the
		1006	port is gone. This works best when the port is a local port.
680		1007
681	=cut	1008	=cut
682		1009
683	=item lookup => $name, @reply	1010	sub db_reg($$;$) {
		1011	my $family = shift;
		1012	my $port = @_ ? shift : $SELF;
684		1013
685	Replies with the port ID of the specified well-known port, or C<undef>.	1014	my $clr = sub { db_del $family => $port };
		1015	mon $port, $clr;
686		1016
687	=item devnull => ...	1017	db_set $family => $port => $_[0];
688		1018
689	Generic data sink/CPU heat conversion.	1019	defined wantarray
		1020	and &Guard::guard ($clr)
		1021	}
690		1022
691	=item relay => $port, @msg	1023	=item db_family $family => $cb->(\%familyhash)
692		1024
693	Simply forwards the message to the given port.	1025	Queries the named database C<$family> and call the callback with the
		1026	family represented as a hash. You can keep and freely modify the hash.
694		1027
695	=item eval => $string[ @reply]	1028	=item db_keys $family => $cb->(\@keys)
696		1029
697	Evaluates the given string. If C<@reply> is given, then a message of the	1030	Same as C<db_family>, except it only queries the family I<subkeys> and passes
698	form C<@reply, $@, @evalres> is sent.	1031	them as array reference to the callback.
699		1032
700	Example: crash another node.	1033	=item db_values $family => $cb->(\@values)
701		1034
702	snd $othernode, eval => "exit";	1035	Same as C<db_family>, except it only queries the family I<values> and passes them
		1036	as array reference to the callback.
703		1037
704	=item time => @reply	1038	=item $guard = db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
705		1039
706	Replies the the current node time to C<@reply>.	1040	Creates a monitor on the given database family. Each time a key is set
		1041	or or is deleted the callback is called with a hash containing the
		1042	database family and three lists of added, changed and deleted subkeys,
		1043	respectively. If no keys have changed then the array reference might be
		1044	C<undef> or even missing.
707		1045
708	Example: tell the current node to send the current time to C<$myport> in a	1046	If not called in void context, a guard object is returned that, when
709	C<timereply> message.	1047	destroyed, stops the monitor.
710		1048
711	snd $NODE, time => $myport, timereply => 1, 2;	1049	The family hash reference and the key arrays belong to AnyEvent::MP and
712	# => snd $myport, timereply => 1, 2, <time>	1050	B<must not be modified or stored> by the callback. When in doubt, make a
		1051	copy.
		1052
		1053	As soon as possible after the monitoring starts, the callback will be
		1054	called with the intiial contents of the family, even if it is empty,
		1055	i.e. there will always be a timely call to the callback with the current
		1056	contents.
		1057
		1058	It is possible that the callback is called with a change event even though
		1059	the subkey is already present and the value has not changed.
		1060
		1061	The monitoring stops when the guard object is destroyed.
		1062
		1063	Example: on every change to the family "mygroup", print out all keys.
		1064
		1065	my $guard = db_mon mygroup => sub {
		1066	my ($family, $a, $c, $d) = @_;
		1067	print "mygroup members: ", (join " ", keys %$family), "\n";
		1068	};
		1069
		1070	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1071
		1072	my $guard; $guard = db_mon My::Module::workers => sub {
		1073	my ($family, $a, $c, $d) = @_;
		1074	return unless %$family;
		1075	undef $guard;
		1076	print "My::Module::workers now nonempty\n";
		1077	};
		1078
		1079	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1080
		1081	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1082	my ($family, $a, $c, $d) = @_;
		1083
		1084	print "+$_=$family->{$_}\n" for @$a;
		1085	print "*$_=$family->{$_}\n" for @$c;
		1086	print "-$_=$family->{$_}\n" for @$d;
		1087	};
		1088
		1089	=cut
713		1090
714	=back	1091	=back
715		1092
716	=head1 AnyEvent::MP vs. Distributed Erlang	1093	=head1 AnyEvent::MP vs. Distributed Erlang
717		1094
718	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1095	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
719	== aemp node, Erlang process == aemp port), so many of the documents and	1096	== aemp node, Erlang process == aemp port), so many of the documents and
720	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1097	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
721	sample:	1098	sample:
722		1099
723	http://www.Erlang.se/doc/programming_rules.shtml	1100	http://www.erlang.se/doc/programming_rules.shtml
724	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1101	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
725	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1102	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
726	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1103	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
727		1104
728	Despite the similarities, there are also some important differences:	1105	Despite the similarities, there are also some important differences:
729		1106
730	=over 4	1107	=over 4
731		1108
732	=item * Node references contain the recipe on how to contact them.	1109	=item * Node IDs are arbitrary strings in AEMP.
733		1110
734	Erlang relies on special naming and DNS to work everywhere in the	1111	Erlang relies on special naming and DNS to work everywhere in the same
735	same way. AEMP relies on each node knowing it's own address(es), with	1112	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
736	convenience functionality.	1113	configuration or DNS), and possibly the addresses of some seed nodes, but
		1114	will otherwise discover other nodes (and their IDs) itself.
737		1115
738	This means that AEMP requires a less tightly controlled environment at the
739	cost of longer node references and a slightly higher management overhead.
740
741	=item Erlang has a "remote ports are like local ports" philosophy, AEMP	1116	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
742	uses "local ports are like remote ports".	1117	uses "local ports are like remote ports".
743		1118
744	The failure modes for local ports are quite different (runtime errors	1119	The failure modes for local ports are quite different (runtime errors
745	only) then for remote ports - when a local port dies, you I<know> it dies,	1120	only) then for remote ports - when a local port dies, you I<know> it dies,
746	when a connection to another node dies, you know nothing about the other	1121	when a connection to another node dies, you know nothing about the other
…		…
753	ports being the special case/exception, where transport errors cannot	1128	ports being the special case/exception, where transport errors cannot
754	occur.	1129	occur.
755		1130
756	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1131	=item * Erlang uses processes and a mailbox, AEMP does not queue.
757		1132
758	Erlang uses processes that selectively receive messages, and therefore	1133	Erlang uses processes that selectively receive messages out of order, and
759	needs a queue. AEMP is event based, queuing messages would serve no	1134	therefore needs a queue. AEMP is event based, queuing messages would serve
760	useful purpose. For the same reason the pattern-matching abilities of	1135	no useful purpose. For the same reason the pattern-matching abilities
761	AnyEvent::MP are more limited, as there is little need to be able to	1136	of AnyEvent::MP are more limited, as there is little need to be able to
762	filter messages without dequeing them.	1137	filter messages without dequeuing them.
763		1138
764	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1139	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1140	being event-based, while Erlang is process-based.
		1141
		1142	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1143	top of AEMP and Coro threads.
765		1144
766	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1145	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
767		1146
768	Sending messages in Erlang is synchronous and blocks the process (and	1147	Sending messages in Erlang is synchronous and blocks the process until
		1148	a conenction has been established and the message sent (and so does not
769	so does not need a queue that can overflow). AEMP sends are immediate,	1149	need a queue that can overflow). AEMP sends return immediately, connection
770	connection establishment is handled in the background.	1150	establishment is handled in the background.
771		1151
772	=item * Erlang suffers from silent message loss, AEMP does not.	1152	=item * Erlang suffers from silent message loss, AEMP does not.
773		1153
774	Erlang makes few guarantees on messages delivery - messages can get lost	1154	Erlang implements few guarantees on messages delivery - messages can get
775	without any of the processes realising it (i.e. you send messages a, b,	1155	lost without any of the processes realising it (i.e. you send messages a,
776	and c, and the other side only receives messages a and c).	1156	b, and c, and the other side only receives messages a and c).
777		1157
778	AEMP guarantees correct ordering, and the guarantee that there are no	1158	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1159	guarantee that after one message is lost, all following ones sent to the
		1160	same port are lost as well, until monitoring raises an error, so there are
779	holes in the message sequence.	1161	no silent "holes" in the message sequence.
780		1162
781	=item * In Erlang, processes can be declared dead and later be found to be	1163	If you want your software to be very reliable, you have to cope with
782	alive.	1164	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
783		1165	simply tries to work better in common error cases, such as when a network
784	In Erlang it can happen that a monitored process is declared dead and	1166	link goes down.
785	linked processes get killed, but later it turns out that the process is
786	still alive - and can receive messages.
787
788	In AEMP, when port monitoring detects a port as dead, then that port will
789	eventually be killed - it cannot happen that a node detects a port as dead
790	and then later sends messages to it, finding it is still alive.
791		1167
792	=item * Erlang can send messages to the wrong port, AEMP does not.	1168	=item * Erlang can send messages to the wrong port, AEMP does not.
793		1169
794	In Erlang it is quite likely that a node that restarts reuses a process ID	1170	In Erlang it is quite likely that a node that restarts reuses an Erlang
795	known to other nodes for a completely different process, causing messages	1171	process ID known to other nodes for a completely different process,
796	destined for that process to end up in an unrelated process.	1172	causing messages destined for that process to end up in an unrelated
		1173	process.
797		1174
798	AEMP never reuses port IDs, so old messages or old port IDs floating	1175	AEMP does not reuse port IDs, so old messages or old port IDs floating
799	around in the network will not be sent to an unrelated port.	1176	around in the network will not be sent to an unrelated port.
800		1177
801	=item * Erlang uses unprotected connections, AEMP uses secure	1178	=item * Erlang uses unprotected connections, AEMP uses secure
802	authentication and can use TLS.	1179	authentication and can use TLS.
803		1180
804	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1181	AEMP can use a proven protocol - TLS - to protect connections and
805	securely authenticate nodes.	1182	securely authenticate nodes.
806		1183
807	=item * The AEMP protocol is optimised for both text-based and binary	1184	=item * The AEMP protocol is optimised for both text-based and binary
808	communications.	1185	communications.
809		1186
810	The AEMP protocol, unlike the Erlang protocol, supports both	1187	The AEMP protocol, unlike the Erlang protocol, supports both programming
811	language-independent text-only protocols (good for debugging) and binary,	1188	language independent text-only protocols (good for debugging), and binary,
812	language-specific serialisers (e.g. Storable).	1189	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1190	used, the protocol is actually completely text-based.
813		1191
814	It has also been carefully designed to be implementable in other languages	1192	It has also been carefully designed to be implementable in other languages
815	with a minimum of work while gracefully degrading fucntionality to make the	1193	with a minimum of work while gracefully degrading functionality to make the
816	protocol simple.	1194	protocol simple.
817		1195
818	=item * AEMP has more flexible monitoring options than Erlang.	1196	=item * AEMP has more flexible monitoring options than Erlang.
819		1197
820	In Erlang, you can chose to receive I<all> exit signals as messages	1198	In Erlang, you can chose to receive I<all> exit signals as messages or
821	or I<none>, there is no in-between, so monitoring single processes is	1199	I<none>, there is no in-between, so monitoring single Erlang processes is
822	difficult to implement. Monitoring in AEMP is more flexible than in	1200	difficult to implement.
823	Erlang, as one can choose between automatic kill, exit message or callback	1201
824	on a per-process basis.	1202	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1203	between automatic kill, exit message or callback on a per-port basis.
825		1204
826	=item * Erlang tries to hide remote/local connections, AEMP does not.	1205	=item * Erlang tries to hide remote/local connections, AEMP does not.
827		1206
828	Monitoring in Erlang is not an indicator of process death/crashes,	1207	Monitoring in Erlang is not an indicator of process death/crashes, in the
829	as linking is (except linking is unreliable in Erlang).	1208	same way as linking is (except linking is unreliable in Erlang).
830		1209
831	In AEMP, you don't "look up" registered port names or send to named ports	1210	In AEMP, you don't "look up" registered port names or send to named ports
832	that might or might not be persistent. Instead, you normally spawn a port	1211	that might or might not be persistent. Instead, you normally spawn a port
833	on the remote node. The init function monitors the you, and you monitor	1212	on the remote node. The init function monitors you, and you monitor the
834	the remote port. Since both monitors are local to the node, they are much	1213	remote port. Since both monitors are local to the node, they are much more
835	more reliable.	1214	reliable (no need for C<spawn_link>).
836		1215
837	This also saves round-trips and avoids sending messages to the wrong port	1216	This also saves round-trips and avoids sending messages to the wrong port
838	(hard to do in Erlang).	1217	(hard to do in Erlang).
839		1218
840	=back	1219	=back
841		1220
842	=head1 RATIONALE	1221	=head1 RATIONALE
843		1222
844	=over 4	1223	=over 4
845		1224
846	=item Why strings for ports and noderefs, why not objects?	1225	=item Why strings for port and node IDs, why not objects?
847		1226
848	We considered "objects", but found that the actual number of methods	1227	We considered "objects", but found that the actual number of methods
849	thatc an be called are very low. Since port IDs and noderefs travel over	1228	that can be called are quite low. Since port and node IDs travel over
850	the network frequently, the serialising/deserialising would add lots of	1229	the network frequently, the serialising/deserialising would add lots of
851	overhead, as well as having to keep a proxy object.	1230	overhead, as well as having to keep a proxy object everywhere.
852		1231
853	Strings can easily be printed, easily serialised etc. and need no special	1232	Strings can easily be printed, easily serialised etc. and need no special
854	procedures to be "valid".	1233	procedures to be "valid".
855		1234
856	And a a miniport consists of a single closure stored in a global hash - it	1235	And as a result, a port with just a default receiver consists of a single
857	can't become much cheaper.	1236	code reference stored in a global hash - it can't become much cheaper.
858		1237
859	=item Why favour JSON, why not real serialising format such as Storable?	1238	=item Why favour JSON, why not a real serialising format such as Storable?
860		1239
861	In fact, any AnyEvent::MP node will happily accept Storable as framing	1240	In fact, any AnyEvent::MP node will happily accept Storable as framing
862	format, but currently there is no way to make a node use Storable by	1241	format, but currently there is no way to make a node use Storable by
863	default.	1242	default (although all nodes will accept it).
864		1243
865	The default framing protocol is JSON because a) JSON::XS is many times	1244	The default framing protocol is JSON because a) JSON::XS is many times
866	faster for small messages and b) most importantly, after years of	1245	faster for small messages and b) most importantly, after years of
867	experience we found that object serialisation is causing more problems	1246	experience we found that object serialisation is causing more problems
868	than it gains: Just like function calls, objects simply do not travel	1247	than it solves: Just like function calls, objects simply do not travel
869	easily over the network, mostly because they will always be a copy, so you	1248	easily over the network, mostly because they will always be a copy, so you
870	always have to re-think your design.	1249	always have to re-think your design.
871		1250
872	Keeping your messages simple, concentrating on data structures rather than	1251	Keeping your messages simple, concentrating on data structures rather than
873	objects, will keep your messages clean, tidy and efficient.	1252	objects, will keep your messages clean, tidy and efficient.
874		1253
875	=back	1254	=back
876		1255
		1256	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1257
		1258	AEMP version 2 has a few major incompatible changes compared to version 1:
		1259
		1260	=over 4
		1261
		1262	=item AnyEvent::MP::Global no longer has group management functions.
		1263
		1264	At least not officially - the grp_* functions are still exported and might
		1265	work, but they will be removed in some later release.
		1266
		1267	AnyEvent::MP now comes with a distributed database that is more
		1268	powerful. Its database families map closely to port groups, but the API
		1269	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1270	a rough porting guide:
		1271
		1272	grp_reg $group, $port # old
		1273	db_reg $group, $port # new
		1274
		1275	$list = grp_get $group # old
		1276	db_keys $group, sub { my $list = shift } # new
		1277
		1278	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1279	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1280
		1281	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1282	no longer instant, because the local node might not have a copy of the
		1283	group. You can either modify your code to allow for a callback, or use
		1284	C<db_mon> to keep an updated copy of the group:
		1285
		1286	my $local_group_copy;
		1287	db_mon $group => sub { $local_group_copy = $_[0] };
		1288
		1289	# now "keys %$local_group_copy" always returns the most up-to-date
		1290	# list of ports in the group.
		1291
		1292	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1293	passes a hash as first argument, and an extra C<$chg> argument that can be
		1294	ignored:
		1295
		1296	db_mon $group => sub {
		1297	my ($ports, $add, $chg, $lde) = @_;
		1298	$ports = [keys %$ports];
		1299
		1300	# now $ports, $add and $del are the same as
		1301	# were originally passed by grp_mon.
		1302	...
		1303	};
		1304
		1305	=item Nodes not longer connect to all other nodes.
		1306
		1307	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1308	module, which in turn would create connections to all other nodes in the
		1309	network (helped by the seed nodes).
		1310
		1311	In version 2.x, global nodes still connect to all other global nodes, but
		1312	other nodes don't - now every node either is a global node itself, or
		1313	attaches itself to another global node.
		1314
		1315	If a node isn't a global node itself, then it attaches itself to one
		1316	of its seed nodes. If that seed node isn't a global node yet, it will
		1317	automatically be upgraded to a global node.
		1318
		1319	So in many cases, nothing needs to be changed - one just has to make sure
		1320	that all seed nodes are meshed together with the other seed nodes (as with
		1321	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1322	achieved by specifying the same set of seed nodes for all nodes in the
		1323	network.
		1324
		1325	Not opening a connection to every other node is usually an advantage,
		1326	except when you need the lower latency of an already established
		1327	connection. To ensure a node establishes a connection to another node,
		1328	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1329	create the connection (and notify you when the connection fails).
		1330
		1331	=item Listener-less nodes (nodes without binds) are gone.
		1332
		1333	And are not coming back, at least not in their old form. If no C<binds>
		1334	are specified for a node, AnyEvent::MP assumes a default of C<*:*>.
		1335
		1336	There are vague plans to implement some form of routing domains, which
		1337	might or might not bring back listener-less nodes, but don't count on it.
		1338
		1339	The fact that most connections are now optional somewhat mitigates this,
		1340	as a node can be effectively unreachable from the outside without any
		1341	problems, as long as it isn't a global node and only reaches out to other
		1342	nodes (as opposed to being contacted from other nodes).
		1343
		1344	=item $AnyEvent::MP::Kernel::WARN has gone.
		1345
		1346	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1347	uses this, and so should your programs.
		1348
		1349	Every module now documents what kinds of messages it generates, with
		1350	AnyEvent::MP acting as a catch all.
		1351
		1352	On the positive side, this means that instead of setting
		1353	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1354	much less to type.
		1355
		1356	=back
		1357
		1358	=head1 LOGGING
		1359
		1360	AnyEvent::MP does not normally log anything by itself, but sinc eit is the
		1361	root of the contetx hierarchy for AnyEvent::MP modules, it will receive
		1362	all log messages by submodules.
		1363
877	=head1 SEE ALSO	1364	=head1 SEE ALSO
		1365
		1366	L<AnyEvent::MP::Intro> - a gentle introduction.
		1367
		1368	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1369
		1370	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1371	your applications.
		1372
		1373	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1374
		1375	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1376	all nodes.
878		1377
879	L<AnyEvent>.	1378	L<AnyEvent>.
880		1379
881	=head1 AUTHOR	1380	=head1 AUTHOR
882		1381

Diff Legend

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