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

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC vs.
Revision 1.138 by root, Thu Mar 22 00:48:29 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, type matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
38	# monitoring	39	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $port, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
41	mon $port, $otherport, @msg # send message on death	42	mon $port, $localport, @msg # send message on death
		43
		44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
		46
		47	# execute callbacks in $SELF port context
		48	my $timer = AE::timer 1, 0, psub {
		49	die "kill the port, delayed";
		50	};
42		51
43	=head1 CURRENT STATUS	52	=head1 CURRENT STATUS
44		53
		54	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	55	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	56	AnyEvent::MP::Intro - explains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	57	AnyEvent::MP::Kernel - mostly stable API.
49		58	AnyEvent::MP::Global - stable API.
50	stay tuned.
51		59
52	=head1 DESCRIPTION	60	=head1 DESCRIPTION
53		61
54	This module (-family) implements a simple message passing framework.	62	This module (-family) implements a simple message passing framework.
55		63
56	Despite its simplicity, you can securely message other processes running	64	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	65	on the same or other hosts, and you can supervise entities remotely.
58		66
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	67	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	68	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		69
66	=head1 CONCEPTS	70	=head1 CONCEPTS
67		71
68	=over 4	72	=over 4
69		73
70	=item port	74	=item port
71		75
72	A port is something you can send messages to (with the C<snd> function).	76	Not to be confused with a TCP port, a "port" is something you can send
		77	messages to (with the C<snd> function).
73		78
74	Some ports allow you to register C<rcv> handlers that can match specific	79	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	80	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	81	anything was listening for them or not.
77		82
		83	Ports are represented by (printable) strings called "port IDs".
		84
78	=item port id - C<noderef#portname>	85	=item port ID - C<nodeid#portname>
79		86
80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	87	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
81	separator, and a port name (a printable string of unspecified format). An	88	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	89	format created by AnyEvent::MP).
83	reference.
84		90
85	=item node	91	=item node
86		92
87	A node is a single process containing at least one port - the node	93	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	94	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	95	ports.
90		96
91	Nodes are either private (single-process only), slaves (connected to a	97	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	98	(no listening ports). Private nodes cannot talk to other private nodes
		99	currently, but all nodes can talk to public nodes.
93		100
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	101	Nodes is represented by (printable) strings called "node IDs".
95		102
96	A node reference is a string that either simply identifies the node (for	103	=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		104
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	105	A node ID is a string that uniquely identifies the node within a
101	TCP/IP, other protocols might look different).	106	network. Depending on the configuration used, node IDs can look like a
		107	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		108	doesn't interpret node IDs in any way except to uniquely identify a node.
102		109
103	Node references come in two flavours: resolved (containing only numerical	110	=item binds - C<ip:port>
104	addresses) or unresolved (where hostnames are used instead of addresses).
105		111
106	Before using an unresolved node reference in a message you first have to	112	Nodes can only talk to each other by creating some kind of connection to
107	resolve it.	113	each other. To do this, nodes should listen on one or more local transport
		114	endpoints - binds.
		115
		116	Currently, only standard C<ip:port> specifications can be used, which
		117	specify TCP ports to listen on. So a bind is basically just a tcp socket
		118	in listening mode thta accepts conenctions form other nodes.
		119
		120	=item seed nodes
		121
		122	When a node starts, it knows nothing about the network it is in - it
		123	needs to connect to at least one other node that is already in the
		124	network. These other nodes are called "seed nodes".
		125
		126	Seed nodes themselves are not special - they are seed nodes only because
		127	some other node I<uses> them as such, but any node can be used as seed
		128	node for other nodes, and eahc node cna use a different set of seed nodes.
		129
		130	In addition to discovering the network, seed nodes are also used to
		131	maintain the network - all nodes using the same seed node form are part of
		132	the same network. If a network is split into multiple subnets because e.g.
		133	the network link between the parts goes down, then using the same seed
		134	nodes for all nodes ensures that eventually the subnets get merged again.
		135
		136	Seed nodes are expected to be long-running, and at least one seed node
		137	should always be available. They should also be relatively responsive - a
		138	seed node that blocks for long periods will slow down everybody else.
		139
		140	For small networks, it's best if every node uses the same set of seed
		141	nodes. For large networks, it can be useful to specify "regional" seed
		142	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		143	each other. What's important is that all seed nodes connections form a
		144	complete graph, so that the network cannot split into separate subnets
		145	forever.
		146
		147	Seed nodes are represented by seed IDs.
		148
		149	=item seed IDs - C<host:port>
		150
		151	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		152	TCP port) of nodes that should be used as seed nodes.
		153
		154	=item global nodes
		155
		156	An AEMP network needs a discovery service - nodes need to know how to
		157	connect to other nodes they only know by name. In addition, AEMP offers a
		158	distributed "group database", which maps group names to a list of strings
		159	- for example, to register worker ports.
		160
		161	A network needs at least one global node to work, and allows every node to
		162	be a global node.
		163
		164	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		165	node and tries to keep connections to all other nodes. So while it can
		166	make sense to make every node "global" in small networks, it usually makes
		167	sense to only make seed nodes into global nodes in large networks (nodes
		168	keep connections to seed nodes and global nodes, so makign them the same
		169	reduces overhead).
108		170
109	=back	171	=back
110		172
111	=head1 VARIABLES/FUNCTIONS	173	=head1 VARIABLES/FUNCTIONS
112		174
114		176
115	=cut	177	=cut
116		178
117	package AnyEvent::MP;	179	package AnyEvent::MP;
118		180
		181	use AnyEvent::MP::Config ();
119	use AnyEvent::MP::Kernel;	182	use AnyEvent::MP::Kernel;
		183	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
120		184
121	use common::sense;	185	use common::sense;
122		186
123	use Carp ();	187	use Carp ();
124		188
125	use AE ();	189	use AE ();
		190	use Guard ();
126		191
127	use base "Exporter";	192	use base "Exporter";
128		193
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	194	our $VERSION = $AnyEvent::MP::Config::VERSION;
130		195
131	our @EXPORT = qw(	196	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	197	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	198	configure
134	snd rcv mon kil reg psub spawn	199	snd rcv mon mon_guard kil psub peval spawn cal
135	port	200	port
		201	db_set db_del db_reg
		202	db_mon db_family db_keys db_values
136	);	203	);
137		204
138	our $SELF;	205	our $SELF;
139		206
140	sub _self_die() {	207	sub _self_die() {
…		…
143	kil $SELF, die => $msg;	210	kil $SELF, die => $msg;
144	}	211	}
145		212
146	=item $thisnode = NODE / $NODE	213	=item $thisnode = NODE / $NODE
147		214
148	The C<NODE> function returns, and the C<$NODE> variable contains	215	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	the noderef of the local node. The value is initialised by a call	216	ID of the node running in the current process. This value is initialised by
150	to C<become_public> or C<become_slave>, after which all local port	217	a call to C<configure>.
151	identifiers become invalid.
152		218
153	=item $noderef = node_of $port	219	=item $nodeid = node_of $port
154		220
155	Extracts and returns the noderef from a portid or a noderef.	221	Extracts and returns the node ID from a port ID or a node ID.
156		222
157	=item initialise_node $noderef, $seednode, $seednode...	223	=item configure $profile, key => value...
158		224
159	=item initialise_node "slave/", $master, $master...	225	=item configure key => value...
160		226
161	Before a node can talk to other nodes on the network it has to initialise	227	Before a node can talk to other nodes on the network (i.e. enter
162	itself - the minimum a node needs to know is it's own name, and optionally	228	"distributed mode") it has to configure itself - the minimum a node needs
163	it should know the noderefs of some other nodes in the network.	229	to know is its own name, and optionally it should know the addresses of
		230	some other nodes in the network to discover other nodes.
164		231
165	This function initialises a node - it must be called exactly once (or	232	This function configures a node - it must be called exactly once (or
166	never) before calling other AnyEvent::MP functions.	233	never) before calling other AnyEvent::MP functions.
167		234
168	All arguments (optionally except for the first) are noderefs, which can be	235	The key/value pairs are basically the same ones as documented for the
169	either resolved or unresolved.	236	F<aemp> command line utility (sans the set/del prefix), with these additions:
170
171	The first argument will be looked up in the configuration database first
172	(if it is C<undef> then the current nodename will be used instead) to find
173	the relevant configuration profile (see L<aemp>). If none is found then
174	the default configuration is used. The configuration supplies additional
175	seed/master nodes and can override the actual noderef.
176
177	There are two types of networked nodes, public nodes and slave nodes:
178		237
179	=over 4	238	=over 4
180		239
181	=item public nodes	240	=item norc => $boolean (default false)
182		241
183	For public nodes, C<$noderef> (supplied either directly to	242	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
184	C<initialise_node> or indirectly via a profile or the nodename) must be a	243	be consulted - all configuraiton options must be specified in the
185	noderef (possibly unresolved, in which case it will be resolved).	244	C<configure> call.
186		245
187	After resolving, the node will bind itself on all endpoints and try to	246	=item force => $boolean (default false)
188	connect to all additional C<$seednodes> that are specified. Seednodes are
189	optional and can be used to quickly bootstrap the node into an existing
190	network.
191		247
192	=item slave nodes	248	IF true, then the values specified in the C<configure> will take
		249	precedence over any values configured via the rc file. The default is for
		250	the rc file to override any options specified in the program.
193		251
194	When the C<$noderef> (either as given or overriden by the config file)	252	=item secure => $pass->(@msg)
195	is the special string C<slave/>, then the node will become a slave
196	node. Slave nodes cannot be contacted from outside and will route most of
197	their traffic to the master node that they attach to.
198		253
199	At least one additional noderef is required (either by specifying it	254	In addition to specifying a boolean, you can specify a code reference that
200	directly or because it is part of the configuration profile): The node	255	is called for every code execution attempt - the execution request is
201	will try to connect to all of them and will become a slave attached to the	256	granted iff the callback returns a true value.
202	first node it can successfully connect to.	257
		258	Most of the time the callback should look only at
		259	C<$AnyEvent::MP::Kernel::SRCNODE> to make a decision, and not at the
		260	actual message (which can be about anything, and is mostly provided for
		261	diagnostic purposes).
		262
		263	See F<semp setsecure> for more info.
203		264
204	=back	265	=back
205		266
206	This function will block until all nodes have been resolved and, for slave
207	nodes, until it has successfully established a connection to a master
208	server.
209
210	Example: become a public node listening on the guessed noderef, or the one
211	specified via C<aemp> for the current node. This should be the most common
212	form of invocation for "daemon"-type nodes.
213
214	initialise_node;
215
216	Example: become a slave node to any of the the seednodes specified via
217	C<aemp>. This form is often used for commandline clients.
218
219	initialise_node "slave/";
220
221	Example: become a slave node to any of the specified master servers. This
222	form is also often used for commandline clients.
223
224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
225
226	Example: become a public node, and try to contact some well-known master
227	servers to become part of the network.
228
229	initialise_node undef, "master1", "master2";
230
231	Example: become a public node listening on port C<4041>.
232
233	initialise_node 4041;
234
235	Example: become a public node, only visible on localhost port 4044.
236
237	initialise_node "localhost:4044";
238
239	=item $cv = resolve_node $noderef
240
241	Takes an unresolved node reference that may contain hostnames and
242	abbreviated IDs, resolves all of them and returns a resolved node
243	reference.
244
245	In addition to C<address:port> pairs allowed in resolved noderefs, the
246	following forms are supported:
247
248	=over 4	267	=over 4
249		268
250	=item the empty string	269	=item step 1, gathering configuration from profiles
251		270
252	An empty-string component gets resolved as if the default port (4040) was	271	The function first looks up a profile in the aemp configuration (see the
253	specified.	272	L<aemp> commandline utility). The profile name can be specified via the
		273	named C<profile> parameter or can simply be the first parameter). If it is
		274	missing, then the nodename (F<uname -n>) will be used as profile name.
254		275
255	=item naked port numbers (e.g. C<1234>)	276	The profile data is then gathered as follows:
256		277
257	These are resolved by prepending the local nodename and a colon, to be	278	First, all remaining key => value pairs (all of which are conveniently
258	further resolved.	279	undocumented at the moment) will be interpreted as configuration
		280	data. Then they will be overwritten by any values specified in the global
		281	default configuration (see the F<aemp> utility), then the chain of
		282	profiles chosen by the profile name (and any C<parent> attributes).
259		283
260	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	284	That means that the values specified in the profile have highest priority
		285	and the values specified directly via C<configure> have lowest priority,
		286	and can only be used to specify defaults.
261		287
262	These are resolved by using AnyEvent::DNS to resolve them, optionally	288	If the profile specifies a node ID, then this will become the node ID of
263	looking up SRV records for the C<aemp=4040> port, if no port was	289	this process. If not, then the profile name will be used as node ID, with
264	specified.	290	a unique randoms tring (C</%u>) appended.
		291
		292	The node ID can contain some C<%> sequences that are expanded: C<%n>
		293	is expanded to the local nodename, C<%u> is replaced by a random
		294	strign to make the node unique. For example, the F<aemp> commandline
		295	utility uses C<aemp/%n/%u> as nodename, which might expand to
		296	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		297
		298	=item step 2, bind listener sockets
		299
		300	The next step is to look up the binds in the profile, followed by binding
		301	aemp protocol listeners on all binds specified (it is possible and valid
		302	to have no binds, meaning that the node cannot be contacted form the
		303	outside. This means the node cannot talk to other nodes that also have no
		304	binds, but it can still talk to all "normal" nodes).
		305
		306	If the profile does not specify a binds list, then a default of C<*> is
		307	used, meaning the node will bind on a dynamically-assigned port on every
		308	local IP address it finds.
		309
		310	=item step 3, connect to seed nodes
		311
		312	As the last step, the seed ID list from the profile is passed to the
		313	L<AnyEvent::MP::Global> module, which will then use it to keep
		314	connectivity with at least one node at any point in time.
265		315
266	=back	316	=back
		317
		318	Example: become a distributed node using the local node name as profile.
		319	This should be the most common form of invocation for "daemon"-type nodes.
		320
		321	configure
		322
		323	Example: become a semi-anonymous node. This form is often used for
		324	commandline clients.
		325
		326	configure nodeid => "myscript/%n/%u";
		327
		328	Example: configure a node using a profile called seed, which is suitable
		329	for a seed node as it binds on all local addresses on a fixed port (4040,
		330	customary for aemp).
		331
		332	# use the aemp commandline utility
		333	# aemp profile seed binds '*:4040'
		334
		335	# then use it
		336	configure profile => "seed";
		337
		338	# or simply use aemp from the shell again:
		339	# aemp run profile seed
		340
		341	# or provide a nicer-to-remember nodeid
		342	# aemp run profile seed nodeid "$(hostname)"
267		343
268	=item $SELF	344	=item $SELF
269		345
270	Contains the current port id while executing C<rcv> callbacks or C<psub>	346	Contains the current port id while executing C<rcv> callbacks or C<psub>
271	blocks.	347	blocks.
272		348
273	=item SELF, %SELF, @SELF...	349	=item *SELF, SELF, %SELF, @SELF...
274		350
275	Due to some quirks in how perl exports variables, it is impossible to	351	Due to some quirks in how perl exports variables, it is impossible to
276	just export C<$SELF>, all the symbols called C<SELF> are exported by this	352	just export C<$SELF>, all the symbols named C<SELF> are exported by this
277	module, but only C<$SELF> is currently used.	353	module, but only C<$SELF> is currently used.
278		354
279	=item snd $port, type => @data	355	=item snd $port, type => @data
280		356
281	=item snd $port, @msg	357	=item snd $port, @msg
282		358
283	Send the given message to the given port ID, which can identify either	359	Send the given message to the given port, which can identify either a
284	a local or a remote port, and can be either a string or soemthignt hat	360	local or a remote port, and must be a port ID.
285	stringifies a sa port ID (such as a port object :).
286		361
287	While the message can be about anything, it is highly recommended to use a	362	While the message can be almost anything, it is highly recommended to
288	string as first element (a portid, or some word that indicates a request	363	use a string as first element (a port ID, or some word that indicates a
289	type etc.).	364	request type etc.) and to consist if only simple perl values (scalars,
		365	arrays, hashes) - if you think you need to pass an object, think again.
290		366
291	The message data effectively becomes read-only after a call to this	367	The message data logically becomes read-only after a call to this
292	function: modifying any argument is not allowed and can cause many	368	function: modifying any argument (or values referenced by them) is
293	problems.	369	forbidden, as there can be considerable time between the call to C<snd>
		370	and the time the message is actually being serialised - in fact, it might
		371	never be copied as within the same process it is simply handed to the
		372	receiving port.
294		373
295	The type of data you can transfer depends on the transport protocol: when	374	The type of data you can transfer depends on the transport protocol: when
296	JSON is used, then only strings, numbers and arrays and hashes consisting	375	JSON is used, then only strings, numbers and arrays and hashes consisting
297	of those are allowed (no objects). When Storable is used, then anything	376	of those are allowed (no objects). When Storable is used, then anything
298	that Storable can serialise and deserialise is allowed, and for the local	377	that Storable can serialise and deserialise is allowed, and for the local
299	node, anything can be passed.	378	node, anything can be passed. Best rely only on the common denominator of
		379	these.
300		380
301	=item $local_port = port	381	=item $local_port = port
302		382
303	Create a new local port object and returns its port ID. Initially it has	383	Create a new local port object and returns its port ID. Initially it has
304	no callbacks set and will throw an error when it receives messages.	384	no callbacks set and will throw an error when it receives messages.
…		…
323		403
324	=cut	404	=cut
325		405
326	sub rcv($@);	406	sub rcv($@);
327		407
328	sub _kilme {	408	my $KILME = sub {
329	die "received message on port without callback";	409	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
330	}	410	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		411	};
331		412
332	sub port(;&) {	413	sub port(;&) {
333	my $id = "$UNIQ." . $ID++;	414	my $id = $UNIQ . ++$ID;
334	my $port = "$NODE#$id";	415	my $port = "$NODE#$id";
335		416
336	rcv $port, shift \|\| \&_kilme;	417	rcv $port, shift \|\| $KILME;
337		418
338	$port	419	$port
339	}	420	}
340		421
341	=item rcv $local_port, $callback->(@msg)	422	=item rcv $local_port, $callback->(@msg)
…		…
346		427
347	The global C<$SELF> (exported by this module) contains C<$port> while	428	The global C<$SELF> (exported by this module) contains C<$port> while
348	executing the callback. Runtime errors during callback execution will	429	executing the callback. Runtime errors during callback execution will
349	result in the port being C<kil>ed.	430	result in the port being C<kil>ed.
350		431
351	The default callback received all messages not matched by a more specific	432	The default callback receives all messages not matched by a more specific
352	C<tag> match.	433	C<tag> match.
353		434
354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	435	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
355		436
356	Register callbacks to be called on messages starting with the given tag on	437	Register (or replace) callbacks to be called on messages starting with the
357	the given port (and return the port), or unregister it (when C<$callback>	438	given tag on the given port (and return the port), or unregister it (when
358	is C<$undef>).	439	C<$callback> is C<$undef> or missing). There can only be one callback
		440	registered for each tag.
359		441
360	The original message will be passed to the callback, after the first	442	The original message will be passed to the callback, after the first
361	element (the tag) has been removed. The callback will use the same	443	element (the tag) has been removed. The callback will use the same
362	environment as the default callback (see above).	444	environment as the default callback (see above).
363		445
…		…
375	rcv port,	457	rcv port,
376	msg1 => sub { ... },	458	msg1 => sub { ... },
377	...	459	...
378	;	460	;
379		461
		462	Example: temporarily register a rcv callback for a tag matching some port
		463	(e.g. for an rpc reply) and unregister it after a message was received.
		464
		465	rcv $port, $otherport => sub {
		466	my @reply = @_;
		467
		468	rcv $SELF, $otherport;
		469	};
		470
380	=cut	471	=cut
381		472
382	sub rcv($@) {	473	sub rcv($@) {
383	my $port = shift;	474	my $port = shift;
384	my ($noderef, $portid) = split /#/, $port, 2;	475	my ($nodeid, $portid) = split /#/, $port, 2;
385		476
386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	477	$NODE{$nodeid} == $NODE{""}
387	or Carp::croak "$port: rcv can only be called on local ports, caught";	478	or Carp::croak "$port: rcv can only be called on local ports, caught";
388		479
389	while (@_) {	480	while (@_) {
390	if (ref $_[0]) {	481	if (ref $_[0]) {
391	if (my $self = $PORT_DATA{$portid}) {	482	if (my $self = $PORT_DATA{$portid}) {
392	"AnyEvent::MP::Port" eq ref $self	483	"AnyEvent::MP::Port" eq ref $self
393	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	484	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
394		485
395	$self->[2] = shift;	486	$self->[0] = shift;
396	} else {	487	} else {
397	my $cb = shift;	488	my $cb = shift;
398	$PORT{$portid} = sub {	489	$PORT{$portid} = sub {
399	local $SELF = $port;	490	local $SELF = $port;
400	eval { &$cb }; _self_die if $@;	491	eval { &$cb }; _self_die if $@;
401	};	492	};
402	}	493	}
403	} elsif (defined $_[0]) {	494	} elsif (defined $_[0]) {
404	my $self = $PORT_DATA{$portid} \|\|= do {	495	my $self = $PORT_DATA{$portid} \|\|= do {
405	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	496	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
406		497
407	$PORT{$portid} = sub {	498	$PORT{$portid} = sub {
408	local $SELF = $port;	499	local $SELF = $port;
409		500
410	if (my $cb = $self->[1]{$_[0]}) {	501	if (my $cb = $self->[1]{$_[0]}) {
…		…
432	}	523	}
433		524
434	$port	525	$port
435	}	526	}
436		527
		528	=item peval $port, $coderef[, @args]
		529
		530	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		531	when the code throews an exception the C<$port> will be killed.
		532
		533	Any remaining args will be passed to the callback. Any return values will
		534	be returned to the caller.
		535
		536	This is useful when you temporarily want to execute code in the context of
		537	a port.
		538
		539	Example: create a port and run some initialisation code in it's context.
		540
		541	my $port = port { ... };
		542
		543	peval $port, sub {
		544	init
		545	or die "unable to init";
		546	};
		547
		548	=cut
		549
		550	sub peval($$) {
		551	local $SELF = shift;
		552	my $cb = shift;
		553
		554	if (wantarray) {
		555	my @res = eval { &$cb };
		556	_self_die if $@;
		557	@res
		558	} else {
		559	my $res = eval { &$cb };
		560	_self_die if $@;
		561	$res
		562	}
		563	}
		564
437	=item $closure = psub { BLOCK }	565	=item $closure = psub { BLOCK }
438		566
439	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	567	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
440	closure is executed, sets up the environment in the same way as in C<rcv>	568	closure is executed, sets up the environment in the same way as in C<rcv>
441	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	569	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		570
		571	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		572	BLOCK }, @_ } >>.
442		573
443	This is useful when you register callbacks from C<rcv> callbacks:	574	This is useful when you register callbacks from C<rcv> callbacks:
444		575
445	rcv delayed_reply => sub {	576	rcv delayed_reply => sub {
446	my ($delay, @reply) = @_;	577	my ($delay, @reply) = @_;
…		…
470	$res	601	$res
471	}	602	}
472	}	603	}
473	}	604	}
474		605
475	=item $guard = mon $port, $cb->(@reason)	606	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
476		607
477	=item $guard = mon $port, $rcvport	608	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
478		609
479	=item $guard = mon $port	610	=item $guard = mon $port # kill $SELF when $port dies
480		611
481	=item $guard = mon $port, $rcvport, @msg	612	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
482		613
483	Monitor the given port and do something when the port is killed or	614	Monitor the given port and do something when the port is killed or
484	messages to it were lost, and optionally return a guard that can be used	615	messages to it were lost, and optionally return a guard that can be used
485	to stop monitoring again.	616	to stop monitoring again.
486
487	C<mon> effectively guarantees that, in the absence of hardware failures,
488	that after starting the monitor, either all messages sent to the port
489	will arrive, or the monitoring action will be invoked after possible
490	message loss has been detected. No messages will be lost "in between"
491	(after the first lost message no further messages will be received by the
492	port). After the monitoring action was invoked, further messages might get
493	delivered again.
494		617
495	In the first form (callback), the callback is simply called with any	618	In the first form (callback), the callback is simply called with any
496	number of C<@reason> elements (no @reason means that the port was deleted	619	number of C<@reason> elements (no @reason means that the port was deleted
497	"normally"). Note also that I<< the callback B<must> never die >>, so use	620	"normally"). Note also that I<< the callback B<must> never die >>, so use
498	C<eval> if unsure.	621	C<eval> if unsure.
499		622
500	In the second form (another port given), the other port (C<$rcvport>)	623	In the second form (another port given), the other port (C<$rcvport>)
501	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on	624	will be C<kil>'ed with C<@reason>, if a @reason was specified, i.e. on
502	"normal" kils nothing happens, while under all other conditions, the other	625	"normal" kils nothing happens, while under all other conditions, the other
503	port is killed with the same reason.	626	port is killed with the same reason.
504		627
505	The third form (kill self) is the same as the second form, except that	628	The third form (kill self) is the same as the second form, except that
506	C<$rvport> defaults to C<$SELF>.	629	C<$rvport> defaults to C<$SELF>.
507		630
508	In the last form (message), a message of the form C<@msg, @reason> will be	631	In the last form (message), a message of the form C<@msg, @reason> will be
509	C<snd>.	632	C<snd>.
		633
		634	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		635	alert was raised), they are removed and will not trigger again.
510		636
511	As a rule of thumb, monitoring requests should always monitor a port from	637	As a rule of thumb, monitoring requests should always monitor a port from
512	a local port (or callback). The reason is that kill messages might get	638	a local port (or callback). The reason is that kill messages might get
513	lost, just like any other message. Another less obvious reason is that	639	lost, just like any other message. Another less obvious reason is that
514	even monitoring requests can get lost (for exmaple, when the connection	640	even monitoring requests can get lost (for example, when the connection
515	to the other node goes down permanently). When monitoring a port locally	641	to the other node goes down permanently). When monitoring a port locally
516	these problems do not exist.	642	these problems do not exist.
517		643
		644	C<mon> effectively guarantees that, in the absence of hardware failures,
		645	after starting the monitor, either all messages sent to the port will
		646	arrive, or the monitoring action will be invoked after possible message
		647	loss has been detected. No messages will be lost "in between" (after
		648	the first lost message no further messages will be received by the
		649	port). After the monitoring action was invoked, further messages might get
		650	delivered again.
		651
		652	Inter-host-connection timeouts and monitoring depend on the transport
		653	used. The only transport currently implemented is TCP, and AnyEvent::MP
		654	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		655	non-idle connection, and usually around two hours for idle connections).
		656
		657	This means that monitoring is good for program errors and cleaning up
		658	stuff eventually, but they are no replacement for a timeout when you need
		659	to ensure some maximum latency.
		660
518	Example: call a given callback when C<$port> is killed.	661	Example: call a given callback when C<$port> is killed.
519		662
520	mon $port, sub { warn "port died because of <@_>\n" };	663	mon $port, sub { warn "port died because of <@_>\n" };
521		664
522	Example: kill ourselves when C<$port> is killed abnormally.	665	Example: kill ourselves when C<$port> is killed abnormally.
…		…
528	mon $port, $self => "restart";	671	mon $port, $self => "restart";
529		672
530	=cut	673	=cut
531		674
532	sub mon {	675	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	676	my ($nodeid, $port) = split /#/, shift, 2;
534		677
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	678	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
536		679
537	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	680	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
538		681
539	unless (ref $cb) {	682	unless (ref $cb) {
540	if (@_) {	683	if (@_) {
…		…
549	}	692	}
550		693
551	$node->monitor ($port, $cb);	694	$node->monitor ($port, $cb);
552		695
553	defined wantarray	696	defined wantarray
554	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	697	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
555	}	698	}
556		699
557	=item $guard = mon_guard $port, $ref, $ref...	700	=item $guard = mon_guard $port, $ref, $ref...
558		701
559	Monitors the given C<$port> and keeps the passed references. When the port	702	Monitors the given C<$port> and keeps the passed references. When the port
560	is killed, the references will be freed.	703	is killed, the references will be freed.
561		704
562	Optionally returns a guard that will stop the monitoring.	705	Optionally returns a guard that will stop the monitoring.
563		706
564	This function is useful when you create e.g. timers or other watchers and	707	This function is useful when you create e.g. timers or other watchers and
565	want to free them when the port gets killed:	708	want to free them when the port gets killed (note the use of C<psub>):
566		709
567	$port->rcv (start => sub {	710	$port->rcv (start => sub {
568	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	711	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
569	undef $timer if 0.9 < rand;	712	undef $timer if 0.9 < rand;
570	});	713	});
571	});	714	});
572		715
573	=cut	716	=cut
…		…
582		725
583	=item kil $port[, @reason]	726	=item kil $port[, @reason]
584		727
585	Kill the specified port with the given C<@reason>.	728	Kill the specified port with the given C<@reason>.
586		729
587	If no C<@reason> is specified, then the port is killed "normally" (linked	730	If no C<@reason> is specified, then the port is killed "normally" -
588	ports will not be kileld, or even notified).	731	monitor callback will be invoked, but the kil will not cause linked ports
		732	(C<mon $mport, $lport> form) to get killed.
589		733
590	Otherwise, linked ports get killed with the same reason (second form of	734	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
591	C<mon>, see below).	735	form) get killed with the same reason.
592		736
593	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	737	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
594	will be reported as reason C<< die => $@ >>.	738	will be reported as reason C<< die => $@ >>.
595		739
596	Transport/communication errors are reported as C<< transport_error =>	740	Transport/communication errors are reported as C<< transport_error =>
597	$message >>.	741	$message >>.
598		742
599	=cut	743	Common idioms:
		744
		745	# silently remove yourself, do not kill linked ports
		746	kil $SELF;
		747
		748	# report a failure in some detail
		749	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		750
		751	# do not waste much time with killing, just die when something goes wrong
		752	open my $fh, "<file"
		753	or die "file: $!";
600		754
601	=item $port = spawn $node, $initfunc[, @initdata]	755	=item $port = spawn $node, $initfunc[, @initdata]
602		756
603	Creates a port on the node C<$node> (which can also be a port ID, in which	757	Creates a port on the node C<$node> (which can also be a port ID, in which
604	case it's the node where that port resides).	758	case it's the node where that port resides).
605		759
606	The port ID of the newly created port is return immediately, and it is	760	The port ID of the newly created port is returned immediately, and it is
607	permissible to immediately start sending messages or monitor the port.	761	possible to immediately start sending messages or to monitor the port.
608		762
609	After the port has been created, the init function is	763	After the port has been created, the init function is called on the remote
610	called. This function must be a fully-qualified function name	764	node, in the same context as a C<rcv> callback. This function must be a
611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	765	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
612	program, use C<::name>.	766	specify a function in the main program, use C<::name>.
613		767
614	If the function doesn't exist, then the node tries to C<require>	768	If the function doesn't exist, then the node tries to C<require>
615	the package, then the package above the package and so on (e.g.	769	the package, then the package above the package and so on (e.g.
616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	770	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
617	exists or it runs out of package names.	771	exists or it runs out of package names.
618		772
619	The init function is then called with the newly-created port as context	773	The init function is then called with the newly-created port as context
620	object (C<$SELF>) and the C<@initdata> values as arguments.	774	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		775	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		776	the port might not get created.
621		777
622	A common idiom is to pass your own port, monitor the spawned port, and	778	A common idiom is to pass a local port, immediately monitor the spawned
623	in the init function, monitor the original port. This two-way monitoring	779	port, and in the remote init function, immediately monitor the passed
624	ensures that both ports get cleaned up when there is a problem.	780	local port. This two-way monitoring ensures that both ports get cleaned up
		781	when there is a problem.
		782
		783	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		784	caller before C<spawn> returns (by delaying invocation when spawn is
		785	called for the local node).
625		786
626	Example: spawn a chat server port on C<$othernode>.	787	Example: spawn a chat server port on C<$othernode>.
627		788
628	# this node, executed from within a port context:	789	# this node, executed from within a port context:
629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	790	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
644		805
645	sub _spawn {	806	sub _spawn {
646	my $port = shift;	807	my $port = shift;
647	my $init = shift;	808	my $init = shift;
648		809
		810	# rcv will create the actual port
649	local $SELF = "$NODE#$port";	811	local $SELF = "$NODE#$port";
650	eval {	812	eval {
651	&{ load_func $init }	813	&{ load_func $init }
652	};	814	};
653	_self_die if $@;	815	_self_die if $@;
654	}	816	}
655		817
656	sub spawn(@) {	818	sub spawn(@) {
657	my ($noderef, undef) = split /#/, shift, 2;	819	my ($nodeid, undef) = split /#/, shift, 2;
658		820
659	my $id = "$RUNIQ." . $ID++;	821	my $id = $RUNIQ . ++$ID;
660		822
661	$_[0] =~ /::/	823	$_[0] =~ /::/
662	or Carp::croak "spawn init function must be a fully-qualified name, caught";	824	or Carp::croak "spawn init function must be a fully-qualified name, caught";
663		825
664	($NODE{$noderef} \|\| add_node $noderef)	826	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
666		827
667	"$noderef#$id"	828	"$nodeid#$id"
668	}	829	}
669		830
		831
		832	=item after $timeout, @msg
		833
		834	=item after $timeout, $callback
		835
		836	Either sends the given message, or call the given callback, after the
		837	specified number of seconds.
		838
		839	This is simply a utility function that comes in handy at times - the
		840	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		841	so it may go away in the future.
		842
		843	=cut
		844
		845	sub after($@) {
		846	my ($timeout, @action) = @_;
		847
		848	my $t; $t = AE::timer $timeout, 0, sub {
		849	undef $t;
		850	ref $action[0]
		851	? $action[0]()
		852	: snd @action;
		853	};
		854	}
		855
		856	#=item $cb2 = timeout $seconds, $cb[, @args]
		857
		858	=item cal $port, @msg, $callback[, $timeout]
		859
		860	A simple form of RPC - sends a message to the given C<$port> with the
		861	given contents (C<@msg>), but adds a reply port to the message.
		862
		863	The reply port is created temporarily just for the purpose of receiving
		864	the reply, and will be C<kil>ed when no longer needed.
		865
		866	A reply message sent to the port is passed to the C<$callback> as-is.
		867
		868	If an optional time-out (in seconds) is given and it is not C<undef>,
		869	then the callback will be called without any arguments after the time-out
		870	elapsed and the port is C<kil>ed.
		871
		872	If no time-out is given (or it is C<undef>), then the local port will
		873	monitor the remote port instead, so it eventually gets cleaned-up.
		874
		875	Currently this function returns the temporary port, but this "feature"
		876	might go in future versions unless you can make a convincing case that
		877	this is indeed useful for something.
		878
		879	=cut
		880
		881	sub cal(@) {
		882	my $timeout = ref $_[-1] ? undef : pop;
		883	my $cb = pop;
		884
		885	my $port = port {
		886	undef $timeout;
		887	kil $SELF;
		888	&$cb;
		889	};
		890
		891	if (defined $timeout) {
		892	$timeout = AE::timer $timeout, 0, sub {
		893	undef $timeout;
		894	kil $port;
		895	$cb->();
		896	};
		897	} else {
		898	mon $_[0], sub {
		899	kil $port;
		900	$cb->();
		901	};
		902	}
		903
		904	push @_, $port;
		905	&snd;
		906
		907	$port
		908	}
		909
670	=back	910	=back
671		911
672	=head1 NODE MESSAGES	912	=head1 DISTRIBUTED DATABASE
673		913
674	Nodes understand the following messages sent to them. Many of them take	914	AnyEvent::MP comes with a simple distributed database. The database will
675	arguments called C<@reply>, which will simply be used to compose a reply	915	be mirrored asynchronously on all global nodes. Other nodes bind to one
676	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and	916	of the global nodes for their needs. Every node has a "local database"
677	the remaining arguments are simply the message data.	917	which contains all the values that are set locally. All local databases
		918	are merged together to form the global database, which can be queried.
678		919
679	While other messages exist, they are not public and subject to change.	920	The database structure is that of a two-level hash - the database hash
		921	contains hashes which contain values, similarly to a perl hash of hashes,
		922	i.e.:
680		923
		924	$DATABASE{$family}{$subkey} = $value
		925
		926	The top level hash key is called "family", and the second-level hash key
		927	is called "subkey" or simply "key".
		928
		929	The family must be alphanumeric, i.e. start with a letter and consist
		930	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		931	pretty much like Perl module names.
		932
		933	As the family namespace is global, it is recommended to prefix family names
		934	with the name of the application or module using it.
		935
		936	The subkeys must be non-empty strings, with no further restrictions.
		937
		938	The values should preferably be strings, but other perl scalars should
		939	work as well (such as C<undef>, arrays and hashes).
		940
		941	Every database entry is owned by one node - adding the same family/subkey
		942	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		943	but the result might be nondeterministic, i.e. the key might have
		944	different values on different nodes.
		945
		946	Different subkeys in the same family can be owned by different nodes
		947	without problems, and in fact, this is the common method to create worker
		948	pools. For example, a worker port for image scaling might do this:
		949
		950	db_set my_image_scalers => $port;
		951
		952	And clients looking for an image scaler will want to get the
		953	C<my_image_scalers> keys from time to time:
		954
		955	db_keys my_image_scalers => sub {
		956	@ports = @{ $_[0] };
		957	};
		958
		959	Or better yet, they want to monitor the database family, so they always
		960	have a reasonable up-to-date copy:
		961
		962	db_mon my_image_scalers => sub {
		963	@ports = keys %{ $_[0] };
		964	};
		965
		966	In general, you can set or delete single subkeys, but query and monitor
		967	whole families only.
		968
		969	If you feel the need to monitor or query a single subkey, try giving it
		970	it's own family.
		971
681	=over 4	972	=over
		973
		974	=item $guard = db_set $family => $subkey [=> $value]
		975
		976	Sets (or replaces) a key to the database - if C<$value> is omitted,
		977	C<undef> is used instead.
		978
		979	When called in non-void context, C<db_set> returns a guard that
		980	automatically calls C<db_del> when it is destroyed.
		981
		982	=item db_del $family => $subkey...
		983
		984	Deletes one or more subkeys from the database family.
		985
		986	=item $guard = db_reg $family => $port => $value
		987
		988	=item $guard = db_reg $family => $port
		989
		990	=item $guard = db_reg $family
		991
		992	Registers a port in the given family and optionally returns a guard to
		993	remove it.
		994
		995	This function basically does the same as:
		996
		997	db_set $family => $port => $value
		998
		999	Except that the port is monitored and automatically removed from the
		1000	database family when it is kil'ed.
		1001
		1002	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1003	C<$SELF> is used.
		1004
		1005	This function is most useful to register a port in some port group (which
		1006	is just another name for a database family), and have it removed when the
		1007	port is gone. This works best when the port is a local port.
682		1008
683	=cut	1009	=cut
684		1010
685	=item lookup => $name, @reply	1011	sub db_reg($$;$) {
		1012	my $family = shift;
		1013	my $port = @_ ? shift : $SELF;
686		1014
687	Replies with the port ID of the specified well-known port, or C<undef>.	1015	my $clr = sub { db_del $family => $port };
		1016	mon $port, $clr;
688		1017
689	=item devnull => ...	1018	db_set $family => $port => $_[0];
690		1019
691	Generic data sink/CPU heat conversion.	1020	defined wantarray
		1021	and &Guard::guard ($clr)
		1022	}
692		1023
693	=item relay => $port, @msg	1024	=item db_family $family => $cb->(\%familyhash)
694		1025
695	Simply forwards the message to the given port.	1026	Queries the named database C<$family> and call the callback with the
		1027	family represented as a hash. You can keep and freely modify the hash.
696		1028
697	=item eval => $string[ @reply]	1029	=item db_keys $family => $cb->(\@keys)
698		1030
699	Evaluates the given string. If C<@reply> is given, then a message of the	1031	Same as C<db_family>, except it only queries the family I<subkeys> and passes
700	form C<@reply, $@, @evalres> is sent.	1032	them as array reference to the callback.
701		1033
702	Example: crash another node.	1034	=item db_values $family => $cb->(\@values)
703		1035
704	snd $othernode, eval => "exit";	1036	Same as C<db_family>, except it only queries the family I<values> and passes them
		1037	as array reference to the callback.
705		1038
706	=item time => @reply	1039	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
707		1040
708	Replies the the current node time to C<@reply>.	1041	Creates a monitor on the given database family. Each time a key is set
		1042	or or is deleted the callback is called with a hash containing the
		1043	database family and three lists of added, changed and deleted subkeys,
		1044	respectively. If no keys have changed then the array reference might be
		1045	C<undef> or even missing.
709		1046
710	Example: tell the current node to send the current time to C<$myport> in a	1047	If not called in void context, a guard object is returned that, when
711	C<timereply> message.	1048	destroyed, stops the monitor.
712		1049
713	snd $NODE, time => $myport, timereply => 1, 2;	1050	The family hash reference and the key arrays belong to AnyEvent::MP and
714	# => snd $myport, timereply => 1, 2, <time>	1051	B<must not be modified or stored> by the callback. When in doubt, make a
		1052	copy.
		1053
		1054	As soon as possible after the monitoring starts, the callback will be
		1055	called with the intiial contents of the family, even if it is empty,
		1056	i.e. there will always be a timely call to the callback with the current
		1057	contents.
		1058
		1059	It is possible that the callback is called with a change event even though
		1060	the subkey is already present and the value has not changed.
		1061
		1062	The monitoring stops when the guard object is destroyed.
		1063
		1064	Example: on every change to the family "mygroup", print out all keys.
		1065
		1066	my $guard = db_mon mygroup => sub {
		1067	my ($family, $a, $c, $d) = @_;
		1068	print "mygroup members: ", (join " ", keys %$family), "\n";
		1069	};
		1070
		1071	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1072
		1073	my $guard; $guard = db_mon My::Module::workers => sub {
		1074	my ($family, $a, $c, $d) = @_;
		1075	return unless %$family;
		1076	undef $guard;
		1077	print "My::Module::workers now nonempty\n";
		1078	};
		1079
		1080	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1081
		1082	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1083	my ($family, $a, $c, $d) = @_;
		1084
		1085	print "+$_=$family->{$_}\n" for @$a;
		1086	print "*$_=$family->{$_}\n" for @$c;
		1087	print "-$_=$family->{$_}\n" for @$d;
		1088	};
		1089
		1090	=cut
715		1091
716	=back	1092	=back
717		1093
718	=head1 AnyEvent::MP vs. Distributed Erlang	1094	=head1 AnyEvent::MP vs. Distributed Erlang
719		1095
720	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1096	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
721	== aemp node, Erlang process == aemp port), so many of the documents and	1097	== aemp node, Erlang process == aemp port), so many of the documents and
722	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1098	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
723	sample:	1099	sample:
724		1100
725	http://www.Erlang.se/doc/programming_rules.shtml	1101	http://www.erlang.se/doc/programming_rules.shtml
726	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1102	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
727	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1103	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
728	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1104	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
729		1105
730	Despite the similarities, there are also some important differences:	1106	Despite the similarities, there are also some important differences:
731		1107
732	=over 4	1108	=over 4
733		1109
734	=item * Node references contain the recipe on how to contact them.	1110	=item * Node IDs are arbitrary strings in AEMP.
735		1111
736	Erlang relies on special naming and DNS to work everywhere in the	1112	Erlang relies on special naming and DNS to work everywhere in the same
737	same way. AEMP relies on each node knowing it's own address(es), with	1113	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
738	convenience functionality.	1114	configuration or DNS), and possibly the addresses of some seed nodes, but
		1115	will otherwise discover other nodes (and their IDs) itself.
739		1116
740	This means that AEMP requires a less tightly controlled environment at the	1117	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
741	cost of longer node references and a slightly higher management overhead.	1118	uses "local ports are like remote ports".
		1119
		1120	The failure modes for local ports are quite different (runtime errors
		1121	only) then for remote ports - when a local port dies, you I<know> it dies,
		1122	when a connection to another node dies, you know nothing about the other
		1123	port.
		1124
		1125	Erlang pretends remote ports are as reliable as local ports, even when
		1126	they are not.
		1127
		1128	AEMP encourages a "treat remote ports differently" philosophy, with local
		1129	ports being the special case/exception, where transport errors cannot
		1130	occur.
742		1131
743	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1132	=item * Erlang uses processes and a mailbox, AEMP does not queue.
744		1133
745	Erlang uses processes that selctively receive messages, and therefore	1134	Erlang uses processes that selectively receive messages out of order, and
746	needs a queue. AEMP is event based, queuing messages would serve no useful	1135	therefore needs a queue. AEMP is event based, queuing messages would serve
747	purpose.	1136	no useful purpose. For the same reason the pattern-matching abilities
		1137	of AnyEvent::MP are more limited, as there is little need to be able to
		1138	filter messages without dequeuing them.
748		1139
749	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1140	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1141	being event-based, while Erlang is process-based.
		1142
		1143	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1144	top of AEMP and Coro threads.
750		1145
751	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1146	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
752		1147
753	Sending messages in Erlang is synchronous and blocks the process. AEMP	1148	Sending messages in Erlang is synchronous and blocks the process until
754	sends are immediate, connection establishment is handled in the	1149	a conenction has been established and the message sent (and so does not
755	background.	1150	need a queue that can overflow). AEMP sends return immediately, connection
		1151	establishment is handled in the background.
756		1152
757	=item * Erlang can silently lose messages, AEMP cannot.	1153	=item * Erlang suffers from silent message loss, AEMP does not.
758		1154
759	Erlang makes few guarantees on messages delivery - messages can get lost	1155	Erlang implements few guarantees on messages delivery - messages can get
760	without any of the processes realising it (i.e. you send messages a, b,	1156	lost without any of the processes realising it (i.e. you send messages a,
761	and c, and the other side only receives messages a and c).	1157	b, and c, and the other side only receives messages a and c).
762		1158
763	AEMP guarantees correct ordering, and the guarantee that there are no	1159	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1160	guarantee that after one message is lost, all following ones sent to the
		1161	same port are lost as well, until monitoring raises an error, so there are
764	holes in the message sequence.	1162	no silent "holes" in the message sequence.
765		1163
766	=item * In Erlang, processes can be declared dead and later be found to be	1164	If you want your software to be very reliable, you have to cope with
767	alive.	1165	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
768		1166	simply tries to work better in common error cases, such as when a network
769	In Erlang it can happen that a monitored process is declared dead and	1167	link goes down.
770	linked processes get killed, but later it turns out that the process is
771	still alive - and can receive messages.
772
773	In AEMP, when port monitoring detects a port as dead, then that port will
774	eventually be killed - it cannot happen that a node detects a port as dead
775	and then later sends messages to it, finding it is still alive.
776		1168
777	=item * Erlang can send messages to the wrong port, AEMP does not.	1169	=item * Erlang can send messages to the wrong port, AEMP does not.
778		1170
779	In Erlang it is quite possible that a node that restarts reuses a process	1171	In Erlang it is quite likely that a node that restarts reuses an Erlang
780	ID known to other nodes for a completely different process, causing	1172	process ID known to other nodes for a completely different process,
781	messages destined for that process to end up in an unrelated process.	1173	causing messages destined for that process to end up in an unrelated
		1174	process.
782		1175
783	AEMP never reuses port IDs, so old messages or old port IDs floating	1176	AEMP does not reuse port IDs, so old messages or old port IDs floating
784	around in the network will not be sent to an unrelated port.	1177	around in the network will not be sent to an unrelated port.
785		1178
786	=item * Erlang uses unprotected connections, AEMP uses secure	1179	=item * Erlang uses unprotected connections, AEMP uses secure
787	authentication and can use TLS.	1180	authentication and can use TLS.
788		1181
789	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1182	AEMP can use a proven protocol - TLS - to protect connections and
790	securely authenticate nodes.	1183	securely authenticate nodes.
791		1184
792	=item * The AEMP protocol is optimised for both text-based and binary	1185	=item * The AEMP protocol is optimised for both text-based and binary
793	communications.	1186	communications.
794		1187
795	The AEMP protocol, unlike the Erlang protocol, supports both	1188	The AEMP protocol, unlike the Erlang protocol, supports both programming
796	language-independent text-only protocols (good for debugging) and binary,	1189	language independent text-only protocols (good for debugging), and binary,
797	language-specific serialisers (e.g. Storable).	1190	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1191	used, the protocol is actually completely text-based.
798		1192
799	It has also been carefully designed to be implementable in other languages	1193	It has also been carefully designed to be implementable in other languages
800	with a minimum of work while gracefully degrading fucntionality to make the	1194	with a minimum of work while gracefully degrading functionality to make the
801	protocol simple.	1195	protocol simple.
802		1196
803	=item * AEMP has more flexible monitoring options than Erlang.	1197	=item * AEMP has more flexible monitoring options than Erlang.
804		1198
805	In Erlang, you can chose to receive I<all> exit signals as messages	1199	In Erlang, you can chose to receive I<all> exit signals as messages or
806	or I<none>, there is no in-between, so monitoring single processes is	1200	I<none>, there is no in-between, so monitoring single Erlang processes is
807	difficult to implement. Monitoring in AEMP is more flexible than in	1201	difficult to implement.
808	Erlang, as one can choose between automatic kill, exit message or callback	1202
809	on a per-process basis.	1203	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1204	between automatic kill, exit message or callback on a per-port basis.
810		1205
811	=item * Erlang tries to hide remote/local connections, AEMP does not.	1206	=item * Erlang tries to hide remote/local connections, AEMP does not.
812		1207
813	Monitoring in Erlang is not an indicator of process death/crashes,	1208	Monitoring in Erlang is not an indicator of process death/crashes, in the
814	as linking is (except linking is unreliable in Erlang).	1209	same way as linking is (except linking is unreliable in Erlang).
815		1210
816	In AEMP, you don't "look up" registered port names or send to named ports	1211	In AEMP, you don't "look up" registered port names or send to named ports
817	that might or might not be persistent. Instead, you normally spawn a port	1212	that might or might not be persistent. Instead, you normally spawn a port
818	on the remote node. The init function monitors the you, and you monitor	1213	on the remote node. The init function monitors you, and you monitor the
819	the remote port. Since both monitors are local to the node, they are much	1214	remote port. Since both monitors are local to the node, they are much more
820	more reliable.	1215	reliable (no need for C<spawn_link>).
821		1216
822	This also saves round-trips and avoids sending messages to the wrong port	1217	This also saves round-trips and avoids sending messages to the wrong port
823	(hard to do in Erlang).	1218	(hard to do in Erlang).
824		1219
825	=back	1220	=back
826		1221
827	=head1 RATIONALE	1222	=head1 RATIONALE
828		1223
829	=over 4	1224	=over 4
830		1225
831	=item Why strings for ports and noderefs, why not objects?	1226	=item Why strings for port and node IDs, why not objects?
832		1227
833	We considered "objects", but found that the actual number of methods	1228	We considered "objects", but found that the actual number of methods
834	thatc an be called are very low. Since port IDs and noderefs travel over	1229	that can be called are quite low. Since port and node IDs travel over
835	the network frequently, the serialising/deserialising would add lots of	1230	the network frequently, the serialising/deserialising would add lots of
836	overhead, as well as having to keep a proxy object.	1231	overhead, as well as having to keep a proxy object everywhere.
837		1232
838	Strings can easily be printed, easily serialised etc. and need no special	1233	Strings can easily be printed, easily serialised etc. and need no special
839	procedures to be "valid".	1234	procedures to be "valid".
840		1235
841	And a a miniport consists of a single closure stored in a global hash - it	1236	And as a result, a port with just a default receiver consists of a single
842	can't become much cheaper.	1237	code reference stored in a global hash - it can't become much cheaper.
843		1238
844	=item Why favour JSON, why not real serialising format such as Storable?	1239	=item Why favour JSON, why not a real serialising format such as Storable?
845		1240
846	In fact, any AnyEvent::MP node will happily accept Storable as framing	1241	In fact, any AnyEvent::MP node will happily accept Storable as framing
847	format, but currently there is no way to make a node use Storable by	1242	format, but currently there is no way to make a node use Storable by
848	default.	1243	default (although all nodes will accept it).
849		1244
850	The default framing protocol is JSON because a) JSON::XS is many times	1245	The default framing protocol is JSON because a) JSON::XS is many times
851	faster for small messages and b) most importantly, after years of	1246	faster for small messages and b) most importantly, after years of
852	experience we found that object serialisation is causing more problems	1247	experience we found that object serialisation is causing more problems
853	than it gains: Just like function calls, objects simply do not travel	1248	than it solves: Just like function calls, objects simply do not travel
854	easily over the network, mostly because they will always be a copy, so you	1249	easily over the network, mostly because they will always be a copy, so you
855	always have to re-think your design.	1250	always have to re-think your design.
856		1251
857	Keeping your messages simple, concentrating on data structures rather than	1252	Keeping your messages simple, concentrating on data structures rather than
858	objects, will keep your messages clean, tidy and efficient.	1253	objects, will keep your messages clean, tidy and efficient.
859		1254
860	=back	1255	=back
861		1256
		1257	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1258
		1259	AEMP version 2 has three major incompatible changes compared to version 1:
		1260
		1261	=over 4
		1262
		1263	=item AnyEvent::MP::Global no longer has group management functions.
		1264
		1265	AnyEvent::MP now comes with a distributed database that is more
		1266	powerful. It's database families map closely to ports, but the API has
		1267	minor differences:
		1268
		1269	grp_reg $group, $port # old
		1270	db_reg $group, $port # new
		1271
		1272	$list = grp_get $group # old
		1273	db_keys $group, sub { my $list = shift } # new
		1274
		1275	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1276	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1277
		1278	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get>
		1279	is no longer instant, because the local node might not have a copy of
		1280	the group. This can be partially remedied by using C<db_mon> to keep an
		1281	updated copy of the group:
		1282
		1283	my $local_group_copy;
		1284	db_mon $group => sub { $local_group_copy = shift };
		1285
		1286	# no keys %$local_group_copy always returns the most up-to-date
		1287	# list of ports in the group.
		1288
		1289	C<grp_mon> can almost be replaced by C<db_mon>:
		1290
		1291	db_mon $group => sub {
		1292	my ($ports, $add, $chg, $lde) = @_;
		1293	$ports = [keys %$ports];
		1294
		1295	# now $ports, $add and $del are the same as
		1296	# were originally passed by grp_mon.
		1297	...
		1298	};
		1299
		1300	=item Nodes not longer connect to all other nodes.
		1301
		1302	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1303	module, which in turn would create connections to all other nodes in the
		1304	network (helped by the seed nodes).
		1305
		1306	In version 2.x, global nodes still connect to all other global nodes, but
		1307	other nodes don't - now every node either is a global node itself, or
		1308	attaches itself to another global node.
		1309
		1310	If a node isn't a global node itself, then it attaches itself to one
		1311	of its seed nodes. If that seed node isn't a global node yet, it will
		1312	automatically be upgraded to a global node.
		1313
		1314	So in many cases, nothing needs to be changed - one just has to make sure
		1315	that all seed nodes are meshed together with the other seed nodes (as with
		1316	AEMP 1.x), and other nodes specify them as seed nodes.
		1317
		1318	Not opening a connection to every other node is usually an advantage,
		1319	except when you need the lower latency of an already established
		1320	connection. To ensure a node establishes a connection to another node,
		1321	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1322	create the connection (and notify you when the connection fails).
		1323
		1324	=item Listener-less nodes (nodes without binds) are gone.
		1325
		1326	And are not coming back, at least not in their old form. If no C<binds>
		1327	are specified for a node, AnyEvent::MP now assumes a default of C<:>.
		1328
		1329	There are vague plans to implement some form of routing domains, which
		1330	might or might not bring back listener-less nodes, but don't count on it.
		1331
		1332	The fact that most connections are now optional somewhat mitigates this,
		1333	as a node can be effectively unreachable from the outside without any
		1334	problems, as long as it isn't a global node and only reaches out to other
		1335	nodes (as opposed to being contacted from other nodes).
		1336
		1337	=item $AnyEvent::MP::Kernel::WARN has gone.
		1338
		1339	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1340	uses this, and so should your programs.
		1341
		1342	Every module now documents what kinds of messages it generates, with
		1343	AnyEvent::MP acting as a catch all.
		1344
		1345	On the positive side, this means that instead of setting
		1346	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE>,
		1347	much less to type.
		1348
		1349	=back
		1350
862	=head1 SEE ALSO	1351	=head1 SEE ALSO
		1352
		1353	L<AnyEvent::MP::Intro> - a gentle introduction.
		1354
		1355	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1356
		1357	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1358	your applications.
		1359
		1360	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1361
		1362	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1363	all nodes.
863		1364
864	L<AnyEvent>.	1365	L<AnyEvent>.
865		1366
866	=head1 AUTHOR	1367	=head1 AUTHOR
867		1368

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC vs. Revision 1.138 by root, Thu Mar 22 00:48:29 2012 UTC

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Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC vs.
Revision 1.138 by root, Thu Mar 22 00:48:29 2012 UTC