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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;	15	configure;
17		16
18	# ports are message endpoints	17	# ports are message destinations
19		18
20	# sending messages	19	# sending messages
21	snd $port, type => data...;	20	snd $port, type => data...;
22	snd $port, @msg;	21	snd $port, @msg;
23	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
24		23
25	# creating/using ports, the simple way	24	# creating/using ports, the simple way
26	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
27		26
28	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
29	my $port = port;	28	my $port = port;
30	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
31	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
32		31
33	# create a port on another node	32	# create a port on another node
34	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
35		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
36	# monitoring	39	# monitoring
37	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $port, $cb->(@msg) # callback is invoked on death
38	mon $port, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
39	mon $port, $otherport, @msg # send message on death	42	mon $port, $localport, @msg # send message on death
40		43
41	=head1 CURRENT STATUS	44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
42		46
43	AnyEvent::MP - stable API, should work	47	# execute callbacks in $SELF port context
44	AnyEvent::MP::Intro - outdated	48	my $timer = AE::timer 1, 0, psub {
45	AnyEvent::MP::Kernel - WIP	49	die "kill the port, delayed";
46	AnyEvent::MP::Transport - mostly stable	50	};
47		51
48	stay tuned.	52	# distributed database - modification
		53	db_set $family => $subkey [=> $value] # add a subkey
		54	db_del $family => $subkey... # delete one or more subkeys
		55	db_reg $family => $port [=> $value] # register a port
		56
		57	# distributed database - queries
		58	db_family $family => $cb->(\%familyhash)
		59	db_keys $family => $cb->(\@keys)
		60	db_values $family => $cb->(\@values)
		61
		62	# distributed database - monitoring a family
		63	db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
49		64
50	=head1 DESCRIPTION	65	=head1 DESCRIPTION
51		66
52	This module (-family) implements a simple message passing framework.	67	This module (-family) implements a simple message passing framework.
53		68
54	Despite its simplicity, you can securely message other processes running	69	Despite its simplicity, you can securely message other processes running
55	on the same or other hosts.	70	on the same or other hosts, and you can supervise entities remotely.
56		71
57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	72	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
58	manual page.	73	manual page and the examples under F<eg/>.
59
60	At the moment, this module family is severly broken and underdocumented,
61	so do not use. This was uploaded mainly to reserve the CPAN namespace -
62	stay tuned!
63		74
64	=head1 CONCEPTS	75	=head1 CONCEPTS
65		76
66	=over 4	77	=over 4
67		78
68	=item port	79	=item port
69		80
70	A port is something you can send messages to (with the C<snd> function).	81	Not to be confused with a TCP port, a "port" is something you can send
		82	messages to (with the C<snd> function).
71		83
72	Ports allow you to register C<rcv> handlers that can match all or just	84	Ports allow you to register C<rcv> handlers that can match all or just
73	some messages. Messages will not be queued.	85	some messages. Messages send to ports will not be queued, regardless of
		86	anything was listening for them or not.
74		87
		88	Ports are represented by (printable) strings called "port IDs".
		89
75	=item port ID - C<noderef#portname>	90	=item port ID - C<nodeid#portname>
76		91
77	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	92	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
78	separator, and a port name (a printable string of unspecified format). An	93	as separator, and a port name (a printable string of unspecified
79	exception is the the node port, whose ID is identical to its node	94	format created by AnyEvent::MP).
80	reference.
81		95
82	=item node	96	=item node
83		97
84	A node is a single process containing at least one port - the node port,	98	A node is a single process containing at least one port - the node port,
85	which provides nodes to manage each other remotely, and to create new	99	which enables nodes to manage each other remotely, and to create new
86	ports.	100	ports.
87		101
88	Nodes are either private (single-process only), slaves (can only talk to	102	Nodes are either public (have one or more listening ports) or private
89	public nodes, but do not need an open port) or public nodes (connectable	103	(no listening ports). Private nodes cannot talk to other private nodes
90	from any other node).	104	currently, but all nodes can talk to public nodes.
91		105
		106	Nodes is represented by (printable) strings called "node IDs".
		107
92	=item node ID - C<[a-za-Z0-9_\-.:]+>	108	=item node ID - C<[A-Za-z0-9_\-.:]*>
93		109
94	A node ID is a string that either simply identifies the node (for	110	A node ID is a string that uniquely identifies the node within a
95	private and slave nodes), or contains a recipe on how to reach a given	111	network. Depending on the configuration used, node IDs can look like a
96	node (for public nodes).	112	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		113	doesn't interpret node IDs in any way except to uniquely identify a node.
97		114
98	This recipe is simply a comma-separated list of C<address:port> pairs (for	115	=item binds - C<ip:port>
99	TCP/IP, other protocols might look different).
100		116
101	Node references come in two flavours: resolved (containing only numerical	117	Nodes can only talk to each other by creating some kind of connection to
102	addresses) or unresolved (where hostnames are used instead of addresses).	118	each other. To do this, nodes should listen on one or more local transport
		119	endpoints - binds.
103		120
104	Before using an unresolved node reference in a message you first have to	121	Currently, only standard C<ip:port> specifications can be used, which
105	resolve it.	122	specify TCP ports to listen on. So a bind is basically just a tcp socket
		123	in listening mode that accepts connections from other nodes.
		124
		125	=item seed nodes
		126
		127	When a node starts, it knows nothing about the network it is in - it
		128	needs to connect to at least one other node that is already in the
		129	network. These other nodes are called "seed nodes".
		130
		131	Seed nodes themselves are not special - they are seed nodes only because
		132	some other node I<uses> them as such, but any node can be used as seed
		133	node for other nodes, and eahc node can use a different set of seed nodes.
		134
		135	In addition to discovering the network, seed nodes are also used to
		136	maintain the network - all nodes using the same seed node are part of the
		137	same network. If a network is split into multiple subnets because e.g. the
		138	network link between the parts goes down, then using the same seed nodes
		139	for all nodes ensures that eventually the subnets get merged again.
		140
		141	Seed nodes are expected to be long-running, and at least one seed node
		142	should always be available. They should also be relatively responsive - a
		143	seed node that blocks for long periods will slow down everybody else.
		144
		145	For small networks, it's best if every node uses the same set of seed
		146	nodes. For large networks, it can be useful to specify "regional" seed
		147	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		148	each other. What's important is that all seed nodes connections form a
		149	complete graph, so that the network cannot split into separate subnets
		150	forever.
		151
		152	Seed nodes are represented by seed IDs.
		153
		154	=item seed IDs - C<host:port>
		155
		156	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		157	TCP port) of nodes that should be used as seed nodes.
		158
		159	=item global nodes
		160
		161	An AEMP network needs a discovery service - nodes need to know how to
		162	connect to other nodes they only know by name. In addition, AEMP offers a
		163	distributed "group database", which maps group names to a list of strings
		164	- for example, to register worker ports.
		165
		166	A network needs at least one global node to work, and allows every node to
		167	be a global node.
		168
		169	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		170	node and tries to keep connections to all other nodes. So while it can
		171	make sense to make every node "global" in small networks, it usually makes
		172	sense to only make seed nodes into global nodes in large networks (nodes
		173	keep connections to seed nodes and global nodes, so making them the same
		174	reduces overhead).
106		175
107	=back	176	=back
108		177
109	=head1 VARIABLES/FUNCTIONS	178	=head1 VARIABLES/FUNCTIONS
110		179
…		…
112		181
113	=cut	182	=cut
114		183
115	package AnyEvent::MP;	184	package AnyEvent::MP;
116		185
		186	use AnyEvent::MP::Config ();
117	use AnyEvent::MP::Kernel;	187	use AnyEvent::MP::Kernel;
		188	use AnyEvent::MP::Kernel qw(
		189	%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID
		190	add_node load_func
		191
		192	NODE $NODE
		193	configure
		194	node_of port_is_local
		195	snd kil
		196	db_set db_del
		197	db_mon db_family db_keys db_values
		198	);
118		199
119	use common::sense;	200	use common::sense;
120		201
121	use Carp ();	202	use Carp ();
122		203
123	use AE ();	204	use AnyEvent ();
		205	use Guard ();
124		206
125	use base "Exporter";	207	use base "Exporter";
126		208
127	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	209	our $VERSION = '2.02'; # also in MP/Config.pm
128		210
129	our @EXPORT = qw(	211	our @EXPORT = qw(
130	NODE $NODE *SELF node_of after	212	configure
131	resolve_node initialise_node	213
132	snd rcv mon mon_guard kil reg psub spawn	214	NODE $NODE
133	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
134	);	225	);
135		226
136	our $SELF;	227	our $SELF;
137		228
138	sub _self_die() {	229	sub _self_die() {
…		…
141	kil $SELF, die => $msg;	232	kil $SELF, die => $msg;
142	}	233	}
143		234
144	=item $thisnode = NODE / $NODE	235	=item $thisnode = NODE / $NODE
145		236
146	The C<NODE> function returns, and the C<$NODE> variable contains the	237	The C<NODE> function returns, and the C<$NODE> variable contains, the node
147	node id 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
148	C<initialise_node>.	239	a call to C<configure>.
149		240
150	=item $nodeid = node_of $port	241	=item $nodeid = node_of $port
151		242
152	Extracts and returns the noderef from a port ID or a node ID.	243	Extracts and returns the node ID from a port ID or a node ID.
153		244
154	=item initialise_node $profile_name	245	=item $is_local = port_is_local $port
155		246
		247	Returns true iff the port is a local port.
		248
		249	=item configure $profile, key => value...
		250
		251	=item configure key => value...
		252
156	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
157	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
158	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.
159		257
160	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
161	never) before calling other AnyEvent::MP functions.	259	never) before calling other AnyEvent::MP functions.
162		260
163	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
164	either resolved or unresolved.	262	F<aemp> command line utility (sans the set/del prefix), with these additions:
165
166	The first argument will be looked up in the configuration database first
167	(if it is C<undef> then the current nodename will be used instead) to find
168	the relevant configuration profile (see L<aemp>). If none is found then
169	the default configuration is used. The configuration supplies additional
170	seed/master nodes and can override the actual noderef.
171
172	There are two types of networked nodes, public nodes and slave nodes:
173		263
174	=over 4	264	=over 4
175		265
176	=item public nodes	266	=item norc => $boolean (default false)
177		267
178	For public nodes, C<$noderef> (supplied either directly to	268	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
179	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
180	noderef (possibly unresolved, in which case it will be resolved).	270	C<configure> call.
181		271
182	After resolving, the node will bind itself on all endpoints.	272	=item force => $boolean (default false)
183		273
184	=item slave nodes	274	IF true, then the values specified in the C<configure> will take
185		275	precedence over any values configured via the rc file. The default is for
186	When the C<$noderef> (either as given or overriden by the config file)	276	the rc file to override any options specified in the program.
187	is the special string C<slave/>, then the node will become a slave
188	node. Slave nodes cannot be contacted from outside, and cannot talk to
189	each other (at least in this version of AnyEvent::MP).
190
191	Slave nodes work by creating connections to all public nodes, using the
192	L<AnyEvent::MP::Global> service.
193		277
194	=back	278	=back
195		279
196	After initialising itself, the node will connect to all additional
197	C<$seednodes> that are specified diretcly or via a profile. Seednodes are
198	optional and can be used to quickly bootstrap the node into an existing
199	network.
200
201	All the seednodes will also be specially marked to automatically retry
202	connecting to them indefinitely, so make sure that seednodes are really
203	reliable and up (this might also change in the future).
204
205	Example: become a public node listening on the guessed noderef, or the one
206	specified via C<aemp> for the current node. This should be the most common
207	form of invocation for "daemon"-type nodes.
208
209	initialise_node;
210
211	Example: become a slave node to any of the the seednodes specified via
212	C<aemp>. This form is often used for commandline clients.
213
214	initialise_node "slave/";
215
216	Example: become a public node, and try to contact some well-known master
217	servers to become part of the network.
218
219	initialise_node undef, "master1", "master2";
220
221	Example: become a public node listening on port C<4041>.
222
223	initialise_node 4041;
224
225	Example: become a public node, only visible on localhost port 4044.
226
227	initialise_node "localhost:4044";
228
229	=item $cv = resolve_node $noderef
230
231	Takes an unresolved node reference that may contain hostnames and
232	abbreviated IDs, resolves all of them and returns a resolved node
233	reference.
234
235	In addition to C<address:port> pairs allowed in resolved noderefs, the
236	following forms are supported:
237
238	=over 4	280	=over 4
239		281
240	=item the empty string	282	=item step 1, gathering configuration from profiles
241		283
242	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
243	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.
244		288
245	=item naked port numbers (e.g. C<1234>)	289	The profile data is then gathered as follows:
246		290
247	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
248	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).
249		296
250	=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.
251		300
252	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
253	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
254	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.
255		328
256	=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)"
257		356
258	=item $SELF	357	=item $SELF
259		358
260	Contains the current port id while executing C<rcv> callbacks or C<psub>	359	Contains the current port id while executing C<rcv> callbacks or C<psub>
261	blocks.	360	blocks.
262		361
263	=item SELF, %SELF, @SELF...	362	=item *SELF, SELF, %SELF, @SELF...
264		363
265	Due to some quirks in how perl exports variables, it is impossible to	364	Due to some quirks in how perl exports variables, it is impossible to
266	just export C<$SELF>, all the symbols called C<SELF> are exported by this	365	just export C<$SELF>, all the symbols named C<SELF> are exported by this
267	module, but only C<$SELF> is currently used.	366	module, but only C<$SELF> is currently used.
268		367
269	=item snd $port, type => @data	368	=item snd $port, type => @data
270		369
271	=item snd $port, @msg	370	=item snd $port, @msg
272		371
273	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
274	a local or a remote port, and must be a port ID.	373	local or a remote port, and must be a port ID.
275		374
276	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
277	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
278	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.
279		379
280	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
281	function: modifying any argument is not allowed and can cause many	381	function: modifying any argument (or values referenced by them) is
282	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.
283		386
284	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
285	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
286	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
287	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
288	node, anything can be passed.	391	node, anything can be passed. Best rely only on the common denominator of
		392	these.
289		393
290	=item $local_port = port	394	=item $local_port = port
291		395
292	Create a new local port object and returns its port ID. Initially it has	396	Create a new local port object and returns its port ID. Initially it has
293	no callbacks set and will throw an error when it receives messages.	397	no callbacks set and will throw an error when it receives messages.
…		…
312		416
313	=cut	417	=cut
314		418
315	sub rcv($@);	419	sub rcv($@);
316		420
317	sub _kilme {	421	my $KILME = sub {
318	die "received message on port without callback";	422	(my $tag = substr $_[0], 0, 30) =~ s/([^\x20-\x7e])/./g;
319	}	423	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		424	};
320		425
321	sub port(;&) {	426	sub port(;&) {
322	my $id = "$UNIQ." . $ID++;	427	my $id = $UNIQ . ++$ID;
323	my $port = "$NODE#$id";	428	my $port = "$NODE#$id";
324		429
325	rcv $port, shift || \&_kilme;	430	rcv $port, shift || $KILME;
326		431
327	$port	432	$port
328	}	433	}
329		434
330	=item rcv $local_port, $callback->(@msg)	435	=item rcv $local_port, $callback->(@msg)
…		…
335		440
336	The global C<$SELF> (exported by this module) contains C<$port> while	441	The global C<$SELF> (exported by this module) contains C<$port> while
337	executing the callback. Runtime errors during callback execution will	442	executing the callback. Runtime errors during callback execution will
338	result in the port being C<kil>ed.	443	result in the port being C<kil>ed.
339		444
340	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
341	C<tag> match.	446	C<tag> match.
342		447
343	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	448	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
344		449
345	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
…		…
366	msg1 => sub { ... },	471	msg1 => sub { ... },
367	...	472	...
368	;	473	;
369		474
370	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
371	(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.
372		477
373	rcv $port, $otherport => sub {	478	rcv $port, $otherport => sub {
374	my @reply = @_;	479	my @reply = @_;
375		480
376	rcv $SELF, $otherport;	481	rcv $SELF, $otherport;
…		…
378		483
379	=cut	484	=cut
380		485
381	sub rcv($@) {	486	sub rcv($@) {
382	my $port = shift;	487	my $port = shift;
383	my ($noderef, $portid) = split /#/, $port, 2;	488	my ($nodeid, $portid) = split /#/, $port, 2;
384		489
385	$NODE{$noderef} == $NODE{""}	490	$nodeid eq $NODE
386	or Carp::croak "$port: rcv can only be called on local ports, caught";	491	or Carp::croak "$port: rcv can only be called on local ports, caught";
387		492
388	while (@_) {	493	while (@_) {
389	if (ref $_[0]) {	494	if (ref $_[0]) {
390	if (my $self = $PORT_DATA{$portid}) {	495	if (my $self = $PORT_DATA{$portid}) {
391	"AnyEvent::MP::Port" eq ref $self	496	"AnyEvent::MP::Port" eq ref $self
392	or Carp::croak "$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";
393		498
394	$self->[2] = shift;	499	$self->[0] = shift;
395	} else {	500	} else {
396	my $cb = shift;	501	my $cb = shift;
397	$PORT{$portid} = sub {	502	$PORT{$portid} = sub {
398	local $SELF = $port;	503	local $SELF = $port;
399	eval { &$cb }; _self_die if $@;	504	eval { &$cb }; _self_die if $@;
400	};	505	};
401	}	506	}
402	} elsif (defined $_[0]) {	507	} elsif (defined $_[0]) {
403	my $self = $PORT_DATA{$portid} ||= do {	508	my $self = $PORT_DATA{$portid} ||= do {
404	my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port";	509	my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
405		510
406	$PORT{$portid} = sub {	511	$PORT{$portid} = sub {
407	local $SELF = $port;	512	local $SELF = $port;
408		513
409	if (my $cb = $self->[1]{$_[0]}) {	514	if (my $cb = $self->[1]{$_[0]}) {
…		…
431	}	536	}
432		537
433	$port	538	$port
434	}	539	}
435		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
436	=item $closure = psub { BLOCK }	578	=item $closure = psub { BLOCK }
437		579
438	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
439	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>
440	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 }, @_ } >>.
441		586
442	This is useful when you register callbacks from C<rcv> callbacks:	587	This is useful when you register callbacks from C<rcv> callbacks:
443		588
444	rcv delayed_reply => sub {	589	rcv delayed_reply => sub {
445	my ($delay, @reply) = @_;	590	my ($delay, @reply) = @_;
…		…
469	$res	614	$res
470	}	615	}
471	}	616	}
472	}	617	}
473		618
474	=item $guard = mon $port, $cb->(@reason)	619	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
475		620
476	=item $guard = mon $port, $rcvport	621	=item $guard = mon $port # kill $SELF when $port dies
477		622
478	=item $guard = mon $port	623	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
479		624
480	=item $guard = mon $port, $rcvport, @msg	625	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
481		626
482	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
483	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
484	to stop monitoring again.	629	to stop monitoring again.
485		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
486	C<mon> effectively guarantees that, in the absence of hardware failures,	664	C<mon> effectively guarantees that, in the absence of hardware failures,
487	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
488	will arrive, or the monitoring action will be invoked after possible	666	arrive, or the monitoring action will be invoked after possible message
489	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
490	(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
491	port). After the monitoring action was invoked, further messages might get	669	port). After the monitoring action was invoked, further messages might get
492	delivered again.	670	delivered again.
493		671
494	Note that monitoring-actions are one-shot: once released, they are removed	672	Inter-host-connection timeouts and monitoring depend on the transport
495	and will not trigger again.	673	used. The only transport currently implemented is TCP, and AnyEvent::MP
		674	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		675	non-idle connection, and usually around two hours for idle connections).
496		676
497	In the first form (callback), the callback is simply called with any	677	This means that monitoring is good for program errors and cleaning up
498	number of C<@reason> elements (no @reason means that the port was deleted	678	stuff eventually, but they are no replacement for a timeout when you need
499	"normally"). Note also that I<< the callback B<must> never die >>, so use	679	to ensure some maximum latency.
500	C<eval> if unsure.
501
502	In the second form (another port given), the other port (C<$rcvport>)
503	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
504	"normal" kils nothing happens, while under all other conditions, the other
505	port is killed with the same reason.
506
507	The third form (kill self) is the same as the second form, except that
508	C<$rvport> defaults to C<$SELF>.
509
510	In the last form (message), a message of the form C<@msg, @reason> will be
511	C<snd>.
512
513	As a rule of thumb, monitoring requests should always monitor a port from
514	a local port (or callback). The reason is that kill messages might get
515	lost, just like any other message. Another less obvious reason is that
516	even monitoring requests can get lost (for exmaple, when the connection
517	to the other node goes down permanently). When monitoring a port locally
518	these problems do not exist.
519		680
520	Example: call a given callback when C<$port> is killed.	681	Example: call a given callback when C<$port> is killed.
521		682
522	mon $port, sub { warn "port died because of <@_>\n" };	683	mon $port, sub { warn "port died because of <@_>\n" };
523		684
…		…
530	mon $port, $self => "restart";	691	mon $port, $self => "restart";
531		692
532	=cut	693	=cut
533		694
534	sub mon {	695	sub mon {
535	my ($noderef, $port) = split /#/, shift, 2;	696	my ($nodeid, $port) = split /#/, shift, 2;
536		697
537	my $node = $NODE{$noderef} || add_node $noderef;	698	my $node = $NODE{$nodeid} || add_node $nodeid;
538		699
539	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,';
540		701
541	unless (ref $cb) {	702	unless (ref $cb) {
542	if (@_) {	703	if (@_) {
…		…
551	}	712	}
552		713
553	$node->monitor ($port, $cb);	714	$node->monitor ($port, $cb);
554		715
555	defined wantarray	716	defined wantarray
556	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	717	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
557	}	718	}
558		719
559	=item $guard = mon_guard $port, $ref, $ref...	720	=item $guard = mon_guard $port, $ref, $ref...
560		721
561	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
562	is killed, the references will be freed.	723	is killed, the references will be freed.
563		724
564	Optionally returns a guard that will stop the monitoring.	725	Optionally returns a guard that will stop the monitoring.
565		726
566	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
567	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>):
568		729
569	$port->rcv (start => sub {	730	$port->rcv (start => sub {
570	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	731	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
571	undef $timer if 0.9 < rand;	732	undef $timer if 0.9 < rand;
572	});	733	});
573	});	734	});
574		735
575	=cut	736	=cut
…		…
584		745
585	=item kil $port[, @reason]	746	=item kil $port[, @reason]
586		747
587	Kill the specified port with the given C<@reason>.	748	Kill the specified port with the given C<@reason>.
588		749
589	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" -
590	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.
591		753
592	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>
593	C<mon>, see below).	755	form) get killed with the same reason.
594		756
595	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
596	will be reported as reason C<< die => $@ >>.	758	will be reported as reason C<< die => $@ >>.
597		759
598	Transport/communication errors are reported as C<< transport_error =>	760	Transport/communication errors are reported as C<< transport_error =>
599	$message >>.	761	$message >>.
600		762
601	=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: $!";
602		774
603	=item $port = spawn $node, $initfunc[, @initdata]	775	=item $port = spawn $node, $initfunc[, @initdata]
604		776
605	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
606	case it's the node where that port resides).	778	case it's the node where that port resides).
607		779
608	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
609	permissible to immediately start sending messages or monitor the port.	781	possible to immediately start sending messages or to monitor the port.
610		782
611	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
612	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
613	(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
614	program, use C<::name>.	786	specify a function in the main program, use C<::name>.
615		787
616	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>
617	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.
618	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
619	exists or it runs out of package names.	791	exists or it runs out of package names.
620		792
621	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
622	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.
623		797
624	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
625	in the init function, monitor the original port. This two-way monitoring	799	port, and in the remote init function, immediately monitor the passed
626	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).
627		806
628	Example: spawn a chat server port on C<$othernode>.	807	Example: spawn a chat server port on C<$othernode>.
629		808
630	# this node, executed from within a port context:	809	# this node, executed from within a port context:
631	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	810	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
646		825
647	sub _spawn {	826	sub _spawn {
648	my $port = shift;	827	my $port = shift;
649	my $init = shift;	828	my $init = shift;
650		829
		830	# rcv will create the actual port
651	local $SELF = "$NODE#$port";	831	local $SELF = "$NODE#$port";
652	eval {	832	eval {
653	&{ load_func $init }	833	&{ load_func $init }
654	};	834	};
655	_self_die if $@;	835	_self_die if $@;
656	}	836	}
657		837
658	sub spawn(@) {	838	sub spawn(@) {
659	my ($noderef, undef) = split /#/, shift, 2;	839	my ($nodeid, undef) = split /#/, shift, 2;
660		840
661	my $id = "$RUNIQ." . $ID++;	841	my $id = $RUNIQ . ++$ID;
662		842
663	$_[0] =~ /::/	843	$_[0] =~ /::/
664	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";
665		845
666	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	846	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
667		847
668	"$noderef#$id"	848	"$nodeid#$id"
669	}	849	}
		850
670		851
671	=item after $timeout, @msg	852	=item after $timeout, @msg
672		853
673	=item after $timeout, $callback	854	=item after $timeout, $callback
674		855
675	Either sends the given message, or call the given callback, after the	856	Either sends the given message, or call the given callback, after the
676	specified number of seconds.	857	specified number of seconds.
677		858
678	This is simply a utility function that come sin handy at times.	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.
679		862
680	=cut	863	=cut
681		864
682	sub after($@) {	865	sub after($@) {
683	my ($timeout, @action) = @_;	866	my ($timeout, @action) = @_;
…		…
688	? $action[0]()	871	? $action[0]()
689	: snd @action;	872	: snd @action;
690	};	873	};
691	}	874	}
692		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
		930	=back
		931
		932	=head1 DISTRIBUTED DATABASE
		933
		934	AnyEvent::MP comes with a simple distributed database. The database will
		935	be mirrored asynchronously on all global nodes. Other nodes bind to one
		936	of the global nodes for their needs. Every node has a "local database"
		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.
		939
		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.:
		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
		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.
		1028
		1029	=cut
		1030
		1031	sub db_reg($$;$) {
		1032	my $family = shift;
		1033	my $port = @_ ? shift : $SELF;
		1034
		1035	my $clr = sub { db_del $family => $port };
		1036	mon $port, $clr;
		1037
		1038	db_set $family => $port => $_[0];
		1039
		1040	defined wantarray
		1041	and &Guard::guard ($clr)
		1042	}
		1043
		1044	=item db_family $family => $cb->(\%familyhash)
		1045
		1046	Queries the named database C<$family> and call the callback with the
		1047	family represented as a hash. You can keep and freely modify the hash.
		1048
		1049	=item db_keys $family => $cb->(\@keys)
		1050
		1051	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1052	them as array reference to the callback.
		1053
		1054	=item db_values $family => $cb->(\@values)
		1055
		1056	Same as C<db_family>, except it only queries the family I<values> and passes them
		1057	as array reference to the callback.
		1058
		1059	=item $guard = db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
		1060
		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.
		1066
		1067	If not called in void context, a guard object is returned that, when
		1068	destroyed, stops the monitor.
		1069
		1070	The family hash reference and the key arrays belong to AnyEvent::MP and
		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
		1111
693	=back	1112	=back
694		1113
695	=head1 AnyEvent::MP vs. Distributed Erlang	1114	=head1 AnyEvent::MP vs. Distributed Erlang
696		1115
697	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
698	== 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
699	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
700	sample:	1119	sample:
701		1120
702	http://www.Erlang.se/doc/programming_rules.shtml	1121	http://www.erlang.se/doc/programming_rules.shtml
703	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
704	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
705	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
706		1125
707	Despite the similarities, there are also some important differences:	1126	Despite the similarities, there are also some important differences:
708		1127
709	=over 4	1128	=over 4
710		1129
711	=item * Node references contain the recipe on how to contact them.	1130	=item * Node IDs are arbitrary strings in AEMP.
712		1131
713	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
714	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
715	convenience functionality.	1134	configuration or DNS), and possibly the addresses of some seed nodes, but
716		1135	will otherwise discover other nodes (and their IDs) itself.
717	This means that AEMP requires a less tightly controlled environment at the
718	cost of longer node references and a slightly higher management overhead.
719		1136
720	=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
721	uses "local ports are like remote ports".	1138	uses "local ports are like remote ports".
722		1139
723	The failure modes for local ports are quite different (runtime errors	1140	The failure modes for local ports are quite different (runtime errors
…		…
732	ports being the special case/exception, where transport errors cannot	1149	ports being the special case/exception, where transport errors cannot
733	occur.	1150	occur.
734		1151
735	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1152	=item * Erlang uses processes and a mailbox, AEMP does not queue.
736		1153
737	Erlang uses processes that selectively receive messages, and therefore	1154	Erlang uses processes that selectively receive messages out of order, and
738	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
739	useful purpose. For the same reason the pattern-matching abilities of	1156	no useful purpose. For the same reason the pattern-matching abilities
740	AnyEvent::MP are more limited, as there is little need to be able to	1157	of AnyEvent::MP are more limited, as there is little need to be able to
741	filter messages without dequeing them.	1158	filter messages without dequeuing them.
742		1159
743	(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.
744		1165
745	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1166	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
746		1167
747	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
748	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
749	connection establishment is handled in the background.	1171	establishment is handled in the background.
750		1172
751	=item * Erlang suffers from silent message loss, AEMP does not.	1173	=item * Erlang suffers from silent message loss, AEMP does not.
752		1174
753	Erlang makes few guarantees on messages delivery - messages can get lost	1175	Erlang implements few guarantees on messages delivery - messages can get
754	without any of the processes realising it (i.e. you send messages a, b,	1176	lost without any of the processes realising it (i.e. you send messages a,
755	and c, and the other side only receives messages a and c).	1177	b, and c, and the other side only receives messages a and c).
756		1178
757	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
758	holes in the message sequence.	1182	no silent "holes" in the message sequence.
759		1183
760	=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
761	alive.	1185	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
762		1186	simply tries to work better in common error cases, such as when a network
763	In Erlang it can happen that a monitored process is declared dead and	1187	link goes down.
764	linked processes get killed, but later it turns out that the process is
765	still alive - and can receive messages.
766
767	In AEMP, when port monitoring detects a port as dead, then that port will
768	eventually be killed - it cannot happen that a node detects a port as dead
769	and then later sends messages to it, finding it is still alive.
770		1188
771	=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.
772		1190
773	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
774	known to other nodes for a completely different process, causing messages	1192	process ID known to other nodes for a completely different process,
775	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.
776		1195
777	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
778	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.
779		1198
780	=item * Erlang uses unprotected connections, AEMP uses secure	1199	=item * Erlang uses unprotected connections, AEMP uses secure
781	authentication and can use TLS.	1200	authentication and can use TLS.
782		1201
783	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1202	AEMP can use a proven protocol - TLS - to protect connections and
784	securely authenticate nodes.	1203	securely authenticate nodes.
785		1204
786	=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
787	communications.	1206	communications.
788		1207
789	The AEMP protocol, unlike the Erlang protocol, supports both	1208	The AEMP protocol, unlike the Erlang protocol, supports both programming
790	language-independent text-only protocols (good for debugging) and binary,	1209	language independent text-only protocols (good for debugging), and binary,
791	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.
792		1212
793	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
794	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
795	protocol simple.	1215	protocol simple.
796		1216
797	=item * AEMP has more flexible monitoring options than Erlang.	1217	=item * AEMP has more flexible monitoring options than Erlang.
798		1218
799	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
800	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
801	difficult to implement. Monitoring in AEMP is more flexible than in	1221	difficult to implement.
802	Erlang, as one can choose between automatic kill, exit message or callback	1222
803	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.
804		1225
805	=item * Erlang tries to hide remote/local connections, AEMP does not.	1226	=item * Erlang tries to hide remote/local connections, AEMP does not.
806		1227
807	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
808	as linking is (except linking is unreliable in Erlang).	1229	same way as linking is (except linking is unreliable in Erlang).
809		1230
810	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
811	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
812	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
813	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
814	more reliable.	1235	reliable (no need for C<spawn_link>).
815		1236
816	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
817	(hard to do in Erlang).	1238	(hard to do in Erlang).
818		1239
819	=back	1240	=back
820		1241
821	=head1 RATIONALE	1242	=head1 RATIONALE
822		1243
823	=over 4	1244	=over 4
824		1245
825	=item Why strings for ports and noderefs, why not objects?	1246	=item Why strings for port and node IDs, why not objects?
826		1247
827	We considered "objects", but found that the actual number of methods	1248	We considered "objects", but found that the actual number of methods
828	thatc an be called are very low. Since port IDs and noderefs travel over	1249	that can be called are quite low. Since port and node IDs travel over
829	the network frequently, the serialising/deserialising would add lots of	1250	the network frequently, the serialising/deserialising would add lots of
830	overhead, as well as having to keep a proxy object.	1251	overhead, as well as having to keep a proxy object everywhere.
831		1252
832	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
833	procedures to be "valid".	1254	procedures to be "valid".
834		1255
835	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
836	can't become much cheaper.	1257	code reference stored in a global hash - it can't become much cheaper.
837		1258
838	=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?
839		1260
840	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
841	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
842	default.	1263	default (although all nodes will accept it).
843		1264
844	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
845	faster for small messages and b) most importantly, after years of	1266	faster for small messages and b) most importantly, after years of
846	experience we found that object serialisation is causing more problems	1267	experience we found that object serialisation is causing more problems
847	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
848	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
849	always have to re-think your design.	1270	always have to re-think your design.
850		1271
851	Keeping your messages simple, concentrating on data structures rather than	1272	Keeping your messages simple, concentrating on data structures rather than
852	objects, will keep your messages clean, tidy and efficient.	1273	objects, will keep your messages clean, tidy and efficient.
853		1274
854	=back	1275	=back
855		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
856	=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.
857		1398
858	L<AnyEvent>.	1399	L<AnyEvent>.
859		1400
860	=head1 AUTHOR	1401	=head1 AUTHOR
861		1402

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