ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/AnyEvent-MP/MP.pm

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.58 by root, Sun Aug 16 02:55:16 2009 UTC vs.
Revision 1.143 by root, Fri Mar 23 17:54:36 2012 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $simple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, tagged message matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
38	# monitoring	39	# monitoring
39	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $port, $cb->(@msg) # callback is invoked on death
40	mon $port, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
41	mon $port, $otherport, @msg # send message on death	42	mon $port, $localport, @msg # send message on death
42		43
43	=head1 CURRENT STATUS	44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
44		46
45	AnyEvent::MP - stable API, should work	47	# execute callbacks in $SELF port context
46	AnyEvent::MP::Intro - outdated	48	my $timer = AE::timer 1, 0, psub {
47	AnyEvent::MP::Kernel - WIP	49	die "kill the port, delayed";
48	AnyEvent::MP::Transport - mostly stable	50	};
49		51
50	stay tuned.	52	# distributed database - modification
		53	db_set $family => $subkey [=> $value] # add a subkey
		54	db_del $family => $subkey... # delete one or more subkeys
		55	db_reg $family => $port [=> $value] # register a port
		56
		57	# distributed database - queries
		58	db_family $family => $cb->(\%familyhash)
		59	db_keys $family => $cb->(\@keys)
		60	db_values $family => $cb->(\@values)
		61
		62	# distributed database - monitoring a family
		63	db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
51		64
52	=head1 DESCRIPTION	65	=head1 DESCRIPTION
53		66
54	This module (-family) implements a simple message passing framework.	67	This module (-family) implements a simple message passing framework.
55		68
56	Despite its simplicity, you can securely message other processes running	69	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	70	on the same or other hosts, and you can supervise entities remotely.
58		71
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	72	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	73	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		74
66	=head1 CONCEPTS	75	=head1 CONCEPTS
67		76
68	=over 4	77	=over 4
69		78
70	=item port	79	=item port
71		80
72	A port is something you can send messages to (with the C<snd> function).	81	Not to be confused with a TCP port, a "port" is something you can send
		82	messages to (with the C<snd> function).
73		83
74	Ports allow you to register C<rcv> handlers that can match all or just	84	Ports allow you to register C<rcv> handlers that can match all or just
75	some messages. Messages will not be queued.	85	some messages. Messages send to ports will not be queued, regardless of
		86	anything was listening for them or not.
76		87
		88	Ports are represented by (printable) strings called "port IDs".
		89
77	=item port id - C<noderef#portname>	90	=item port ID - C<nodeid#portname>
78		91
79	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	92	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
80	separator, and a port name (a printable string of unspecified format). An	93	as separator, and a port name (a printable string of unspecified
81	exception is the the node port, whose ID is identical to its node	94	format created by AnyEvent::MP).
82	reference.
83		95
84	=item node	96	=item node
85		97
86	A node is a single process containing at least one port - the node port,	98	A node is a single process containing at least one port - the node port,
87	which provides nodes to manage each other remotely, and to create new	99	which enables nodes to manage each other remotely, and to create new
88	ports.	100	ports.
89		101
90	Nodes are either private (single-process only), slaves (connected to a	102	Nodes are either public (have one or more listening ports) or private
91	master node only) or public nodes (connectable from unrelated nodes).	103	(no listening ports). Private nodes cannot talk to other private nodes
		104	currently, but all nodes can talk to public nodes.
92		105
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	106	Nodes is represented by (printable) strings called "node IDs".
94		107
95	A node reference is a string that either simply identifies the node (for	108	=item node ID - C<[A-Za-z0-9_\-.:]*>
96	private and slave nodes), or contains a recipe on how to reach a given
97	node (for public nodes).
98		109
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	110	A node ID is a string that uniquely identifies the node within a
100	TCP/IP, other protocols might look different).	111	network. Depending on the configuration used, node IDs can look like a
		112	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		113	doesn't interpret node IDs in any way except to uniquely identify a node.
101		114
102	Node references come in two flavours: resolved (containing only numerical	115	=item binds - C<ip:port>
103	addresses) or unresolved (where hostnames are used instead of addresses).
104		116
105	Before using an unresolved node reference in a message you first have to	117	Nodes can only talk to each other by creating some kind of connection to
106	resolve it.	118	each other. To do this, nodes should listen on one or more local transport
		119	endpoints - binds.
		120
		121	Currently, only standard C<ip:port> specifications can be used, which
		122	specify TCP ports to listen on. So a bind is basically just a tcp socket
		123	in listening mode thta accepts conenctions form other nodes.
		124
		125	=item seed nodes
		126
		127	When a node starts, it knows nothing about the network it is in - it
		128	needs to connect to at least one other node that is already in the
		129	network. These other nodes are called "seed nodes".
		130
		131	Seed nodes themselves are not special - they are seed nodes only because
		132	some other node I<uses> them as such, but any node can be used as seed
		133	node for other nodes, and eahc node cna use a different set of seed nodes.
		134
		135	In addition to discovering the network, seed nodes are also used to
		136	maintain the network - all nodes using the same seed node form are part of
		137	the same network. If a network is split into multiple subnets because e.g.
		138	the network link between the parts goes down, then using the same seed
		139	nodes for all nodes ensures that eventually the subnets get merged again.
		140
		141	Seed nodes are expected to be long-running, and at least one seed node
		142	should always be available. They should also be relatively responsive - a
		143	seed node that blocks for long periods will slow down everybody else.
		144
		145	For small networks, it's best if every node uses the same set of seed
		146	nodes. For large networks, it can be useful to specify "regional" seed
		147	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		148	each other. What's important is that all seed nodes connections form a
		149	complete graph, so that the network cannot split into separate subnets
		150	forever.
		151
		152	Seed nodes are represented by seed IDs.
		153
		154	=item seed IDs - C<host:port>
		155
		156	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
		157	TCP port) of nodes that should be used as seed nodes.
		158
		159	=item global nodes
		160
		161	An AEMP network needs a discovery service - nodes need to know how to
		162	connect to other nodes they only know by name. In addition, AEMP offers a
		163	distributed "group database", which maps group names to a list of strings
		164	- for example, to register worker ports.
		165
		166	A network needs at least one global node to work, and allows every node to
		167	be a global node.
		168
		169	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		170	node and tries to keep connections to all other nodes. So while it can
		171	make sense to make every node "global" in small networks, it usually makes
		172	sense to only make seed nodes into global nodes in large networks (nodes
		173	keep connections to seed nodes and global nodes, so makign them the same
		174	reduces overhead).
107		175
108	=back	176	=back
109		177
110	=head1 VARIABLES/FUNCTIONS	178	=head1 VARIABLES/FUNCTIONS
111		179
…		…
113		181
114	=cut	182	=cut
115		183
116	package AnyEvent::MP;	184	package AnyEvent::MP;
117		185
		186	use AnyEvent::MP::Config ();
118	use AnyEvent::MP::Kernel;	187	use AnyEvent::MP::Kernel;
		188	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
119		189
120	use common::sense;	190	use common::sense;
121		191
122	use Carp ();	192	use Carp ();
123		193
124	use AE ();	194	use AnyEvent ();
		195	use Guard ();
125		196
126	use base "Exporter";	197	use base "Exporter";
127		198
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	199	our $VERSION = $AnyEvent::MP::Config::VERSION;
129		200
130	our @EXPORT = qw(	201	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	202	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	203	configure
133	snd rcv mon kil reg psub spawn	204	snd rcv mon mon_guard kil psub peval spawn cal
134	port	205	port
		206	db_set db_del db_reg
		207	db_mon db_family db_keys db_values
135	);	208	);
136		209
137	our $SELF;	210	our $SELF;
138		211
139	sub _self_die() {	212	sub _self_die() {
…		…
142	kil $SELF, die => $msg;	215	kil $SELF, die => $msg;
143	}	216	}
144		217
145	=item $thisnode = NODE / $NODE	218	=item $thisnode = NODE / $NODE
146		219
147	The C<NODE> function returns, and the C<$NODE> variable contains the	220	The C<NODE> function returns, and the C<$NODE> variable contains, the node
148	noderef of the local node. The value is initialised by a call to	221	ID of the node running in the current process. This value is initialised by
149	C<initialise_node>.	222	a call to C<configure>.
150		223
151	=item $noderef = node_of $port	224	=item $nodeid = node_of $port
152		225
153	Extracts and returns the noderef from a port ID or a noderef.	226	Extracts and returns the node ID from a port ID or a node ID.
154		227
155	=item initialise_node $noderef, $seednode, $seednode...	228	=item configure $profile, key => value...
156		229
157	=item initialise_node "slave/", $master, $master...	230	=item configure key => value...
158		231
159	Before a node can talk to other nodes on the network it has to initialise	232	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	233	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	234	to know is its own name, and optionally it should know the addresses of
		235	some other nodes in the network to discover other nodes.
162		236
163	This function initialises a node - it must be called exactly once (or	237	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	238	never) before calling other AnyEvent::MP functions.
165		239
166	All arguments (optionally except for the first) are noderefs, which can be	240	The key/value pairs are basically the same ones as documented for the
167	either resolved or unresolved.	241	F<aemp> command line utility (sans the set/del prefix), with these additions:
168
169	The first argument will be looked up in the configuration database first
170	(if it is C<undef> then the current nodename will be used instead) to find
171	the relevant configuration profile (see L<aemp>). If none is found then
172	the default configuration is used. The configuration supplies additional
173	seed/master nodes and can override the actual noderef.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176		242
177	=over 4	243	=over 4
178		244
179	=item public nodes	245	=item norc => $boolean (default false)
180		246
181	For public nodes, C<$noderef> (supplied either directly to	247	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
182	C<initialise_node> or indirectly via a profile or the nodename) must be a	248	be consulted - all configuraiton options must be specified in the
183	noderef (possibly unresolved, in which case it will be resolved).	249	C<configure> call.
184		250
185	After resolving, the node will bind itself on all endpoints and try to	251	=item force => $boolean (default false)
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189		252
190	=item slave nodes	253	IF true, then the values specified in the C<configure> will take
191		254	precedence over any values configured via the rc file. The default is for
192	When the C<$noderef> (either as given or overriden by the config file)	255	the rc file to override any options specified in the program.
193	is the special string C<slave/>, then the node will become a slave
194	node. Slave nodes cannot be contacted from outside and will route most of
195	their traffic to the master node that they attach to.
196
197	At least one additional noderef is required (either by specifying it
198	directly or because it is part of the configuration profile): The node
199	will try to connect to all of them and will become a slave attached to the
200	first node it can successfully connect to.
201
202	Note that slave nodes cannot change their name, and consequently, their
203	master, so if the master goes down, the slave node will not function well
204	anymore until it can re-establish conenciton to its master. This makes
205	slave nodes unsuitable for long-term nodes or fault-tolerant networks.
206		256
207	=back	257	=back
208		258
209	This function will block until all nodes have been resolved and, for slave
210	nodes, until it has successfully established a connection to a master
211	server.
212
213	All the seednodes will also be specially marked to automatically retry
214	connecting to them infinitely.
215
216	Example: become a public node listening on the guessed noderef, or the one
217	specified via C<aemp> for the current node. This should be the most common
218	form of invocation for "daemon"-type nodes.
219
220	initialise_node;
221
222	Example: become a slave node to any of the the seednodes specified via
223	C<aemp>. This form is often used for commandline clients.
224
225	initialise_node "slave/";
226
227	Example: become a slave node to any of the specified master servers. This
228	form is also often used for commandline clients.
229
230	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";
231
232	Example: become a public node, and try to contact some well-known master
233	servers to become part of the network.
234
235	initialise_node undef, "master1", "master2";
236
237	Example: become a public node listening on port C<4041>.
238
239	initialise_node 4041;
240
241	Example: become a public node, only visible on localhost port 4044.
242
243	initialise_node "localhost:4044";
244
245	=item $cv = resolve_node $noderef
246
247	Takes an unresolved node reference that may contain hostnames and
248	abbreviated IDs, resolves all of them and returns a resolved node
249	reference.
250
251	In addition to C<address:port> pairs allowed in resolved noderefs, the
252	following forms are supported:
253
254	=over 4	259	=over 4
255		260
256	=item the empty string	261	=item step 1, gathering configuration from profiles
257		262
258	An empty-string component gets resolved as if the default port (4040) was	263	The function first looks up a profile in the aemp configuration (see the
259	specified.	264	L<aemp> commandline utility). The profile name can be specified via the
		265	named C<profile> parameter or can simply be the first parameter). If it is
		266	missing, then the nodename (F<uname -n>) will be used as profile name.
260		267
261	=item naked port numbers (e.g. C<1234>)	268	The profile data is then gathered as follows:
262		269
263	These are resolved by prepending the local nodename and a colon, to be	270	First, all remaining key => value pairs (all of which are conveniently
264	further resolved.	271	undocumented at the moment) will be interpreted as configuration
		272	data. Then they will be overwritten by any values specified in the global
		273	default configuration (see the F<aemp> utility), then the chain of
		274	profiles chosen by the profile name (and any C<parent> attributes).
265		275
266	=item hostnames (e.g. C<localhost:1234>, C<localhost>)	276	That means that the values specified in the profile have highest priority
		277	and the values specified directly via C<configure> have lowest priority,
		278	and can only be used to specify defaults.
267		279
268	These are resolved by using AnyEvent::DNS to resolve them, optionally	280	If the profile specifies a node ID, then this will become the node ID of
269	looking up SRV records for the C<aemp=4040> port, if no port was	281	this process. If not, then the profile name will be used as node ID, with
270	specified.	282	a unique randoms tring (C</%u>) appended.
		283
		284	The node ID can contain some C<%> sequences that are expanded: C<%n>
		285	is expanded to the local nodename, C<%u> is replaced by a random
		286	strign to make the node unique. For example, the F<aemp> commandline
		287	utility uses C<aemp/%n/%u> as nodename, which might expand to
		288	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
		289
		290	=item step 2, bind listener sockets
		291
		292	The next step is to look up the binds in the profile, followed by binding
		293	aemp protocol listeners on all binds specified (it is possible and valid
		294	to have no binds, meaning that the node cannot be contacted form the
		295	outside. This means the node cannot talk to other nodes that also have no
		296	binds, but it can still talk to all "normal" nodes).
		297
		298	If the profile does not specify a binds list, then a default of C<*> is
		299	used, meaning the node will bind on a dynamically-assigned port on every
		300	local IP address it finds.
		301
		302	=item step 3, connect to seed nodes
		303
		304	As the last step, the seed ID list from the profile is passed to the
		305	L<AnyEvent::MP::Global> module, which will then use it to keep
		306	connectivity with at least one node at any point in time.
271		307
272	=back	308	=back
		309
		310	Example: become a distributed node using the local node name as profile.
		311	This should be the most common form of invocation for "daemon"-type nodes.
		312
		313	configure
		314
		315	Example: become a semi-anonymous node. This form is often used for
		316	commandline clients.
		317
		318	configure nodeid => "myscript/%n/%u";
		319
		320	Example: configure a node using a profile called seed, which is suitable
		321	for a seed node as it binds on all local addresses on a fixed port (4040,
		322	customary for aemp).
		323
		324	# use the aemp commandline utility
		325	# aemp profile seed binds '*:4040'
		326
		327	# then use it
		328	configure profile => "seed";
		329
		330	# or simply use aemp from the shell again:
		331	# aemp run profile seed
		332
		333	# or provide a nicer-to-remember nodeid
		334	# aemp run profile seed nodeid "$(hostname)"
273		335
274	=item $SELF	336	=item $SELF
275		337
276	Contains the current port id while executing C<rcv> callbacks or C<psub>	338	Contains the current port id while executing C<rcv> callbacks or C<psub>
277	blocks.	339	blocks.
278		340
279	=item SELF, %SELF, @SELF...	341	=item *SELF, SELF, %SELF, @SELF...
280		342
281	Due to some quirks in how perl exports variables, it is impossible to	343	Due to some quirks in how perl exports variables, it is impossible to
282	just export C<$SELF>, all the symbols called C<SELF> are exported by this	344	just export C<$SELF>, all the symbols named C<SELF> are exported by this
283	module, but only C<$SELF> is currently used.	345	module, but only C<$SELF> is currently used.
284		346
285	=item snd $port, type => @data	347	=item snd $port, type => @data
286		348
287	=item snd $port, @msg	349	=item snd $port, @msg
288		350
289	Send the given message to the given port ID, which can identify either	351	Send the given message to the given port, which can identify either a
290	a local or a remote port, and must be a port ID.	352	local or a remote port, and must be a port ID.
291		353
292	While the message can be about anything, it is highly recommended to use a	354	While the message can be almost anything, it is highly recommended to
293	string as first element (a port ID, or some word that indicates a request	355	use a string as first element (a port ID, or some word that indicates a
294	type etc.).	356	request type etc.) and to consist if only simple perl values (scalars,
		357	arrays, hashes) - if you think you need to pass an object, think again.
295		358
296	The message data effectively becomes read-only after a call to this	359	The message data logically becomes read-only after a call to this
297	function: modifying any argument is not allowed and can cause many	360	function: modifying any argument (or values referenced by them) is
298	problems.	361	forbidden, as there can be considerable time between the call to C<snd>
		362	and the time the message is actually being serialised - in fact, it might
		363	never be copied as within the same process it is simply handed to the
		364	receiving port.
299		365
300	The type of data you can transfer depends on the transport protocol: when	366	The type of data you can transfer depends on the transport protocol: when
301	JSON is used, then only strings, numbers and arrays and hashes consisting	367	JSON is used, then only strings, numbers and arrays and hashes consisting
302	of those are allowed (no objects). When Storable is used, then anything	368	of those are allowed (no objects). When Storable is used, then anything
303	that Storable can serialise and deserialise is allowed, and for the local	369	that Storable can serialise and deserialise is allowed, and for the local
304	node, anything can be passed.	370	node, anything can be passed. Best rely only on the common denominator of
		371	these.
305		372
306	=item $local_port = port	373	=item $local_port = port
307		374
308	Create a new local port object and returns its port ID. Initially it has	375	Create a new local port object and returns its port ID. Initially it has
309	no callbacks set and will throw an error when it receives messages.	376	no callbacks set and will throw an error when it receives messages.
…		…
328		395
329	=cut	396	=cut
330		397
331	sub rcv($@);	398	sub rcv($@);
332		399
333	sub _kilme {	400	my $KILME = sub {
334	die "received message on port without callback";	401	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
335	}	402	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		403	};
336		404
337	sub port(;&) {	405	sub port(;&) {
338	my $id = "$UNIQ." . $ID++;	406	my $id = $UNIQ . ++$ID;
339	my $port = "$NODE#$id";	407	my $port = "$NODE#$id";
340		408
341	rcv $port, shift || \&_kilme;	409	rcv $port, shift || $KILME;
342		410
343	$port	411	$port
344	}	412	}
345		413
346	=item rcv $local_port, $callback->(@msg)	414	=item rcv $local_port, $callback->(@msg)
…		…
351		419
352	The global C<$SELF> (exported by this module) contains C<$port> while	420	The global C<$SELF> (exported by this module) contains C<$port> while
353	executing the callback. Runtime errors during callback execution will	421	executing the callback. Runtime errors during callback execution will
354	result in the port being C<kil>ed.	422	result in the port being C<kil>ed.
355		423
356	The default callback received all messages not matched by a more specific	424	The default callback receives all messages not matched by a more specific
357	C<tag> match.	425	C<tag> match.
358		426
359	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	427	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
360		428
361	Register (or replace) callbacks to be called on messages starting with the	429	Register (or replace) callbacks to be called on messages starting with the
…		…
382	msg1 => sub { ... },	450	msg1 => sub { ... },
383	...	451	...
384	;	452	;
385		453
386	Example: temporarily register a rcv callback for a tag matching some port	454	Example: temporarily register a rcv callback for a tag matching some port
387	(e.g. for a rpc reply) and unregister it after a message was received.	455	(e.g. for an rpc reply) and unregister it after a message was received.
388		456
389	rcv $port, $otherport => sub {	457	rcv $port, $otherport => sub {
390	my @reply = @_;	458	my @reply = @_;
391		459
392	rcv $SELF, $otherport;	460	rcv $SELF, $otherport;
…		…
394		462
395	=cut	463	=cut
396		464
397	sub rcv($@) {	465	sub rcv($@) {
398	my $port = shift;	466	my $port = shift;
399	my ($noderef, $portid) = split /#/, $port, 2;	467	my ($nodeid, $portid) = split /#/, $port, 2;
400		468
401	$NODE{$noderef} == $NODE{""}	469	$NODE{$nodeid} == $NODE{""}
402	or Carp::croak "$port: rcv can only be called on local ports, caught";	470	or Carp::croak "$port: rcv can only be called on local ports, caught";
403		471
404	while (@_) {	472	while (@_) {
405	if (ref $_[0]) {	473	if (ref $_[0]) {
406	if (my $self = $PORT_DATA{$portid}) {	474	if (my $self = $PORT_DATA{$portid}) {
407	"AnyEvent::MP::Port" eq ref $self	475	"AnyEvent::MP::Port" eq ref $self
408	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	476	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
409		477
410	$self->[2] = shift;	478	$self->[0] = shift;
411	} else {	479	} else {
412	my $cb = shift;	480	my $cb = shift;
413	$PORT{$portid} = sub {	481	$PORT{$portid} = sub {
414	local $SELF = $port;	482	local $SELF = $port;
415	eval { &$cb }; _self_die if $@;	483	eval { &$cb }; _self_die if $@;
416	};	484	};
417	}	485	}
418	} elsif (defined $_[0]) {	486	} elsif (defined $_[0]) {
419	my $self = $PORT_DATA{$portid} ||= do {	487	my $self = $PORT_DATA{$portid} ||= do {
420	my $self = bless [$PORT{$port} || sub { }, { }, $port], "AnyEvent::MP::Port";	488	my $self = bless [$PORT{$portid} || sub { }, { }, $port], "AnyEvent::MP::Port";
421		489
422	$PORT{$portid} = sub {	490	$PORT{$portid} = sub {
423	local $SELF = $port;	491	local $SELF = $port;
424		492
425	if (my $cb = $self->[1]{$_[0]}) {	493	if (my $cb = $self->[1]{$_[0]}) {
…		…
447	}	515	}
448		516
449	$port	517	$port
450	}	518	}
451		519
		520	=item peval $port, $coderef[, @args]
		521
		522	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		523	when the code throews an exception the C<$port> will be killed.
		524
		525	Any remaining args will be passed to the callback. Any return values will
		526	be returned to the caller.
		527
		528	This is useful when you temporarily want to execute code in the context of
		529	a port.
		530
		531	Example: create a port and run some initialisation code in it's context.
		532
		533	my $port = port { ... };
		534
		535	peval $port, sub {
		536	init
		537	or die "unable to init";
		538	};
		539
		540	=cut
		541
		542	sub peval($$) {
		543	local $SELF = shift;
		544	my $cb = shift;
		545
		546	if (wantarray) {
		547	my @res = eval { &$cb };
		548	_self_die if $@;
		549	@res
		550	} else {
		551	my $res = eval { &$cb };
		552	_self_die if $@;
		553	$res
		554	}
		555	}
		556
452	=item $closure = psub { BLOCK }	557	=item $closure = psub { BLOCK }
453		558
454	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	559	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
455	closure is executed, sets up the environment in the same way as in C<rcv>	560	closure is executed, sets up the environment in the same way as in C<rcv>
456	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	561	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		562
		563	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		564	BLOCK }, @_ } >>.
457		565
458	This is useful when you register callbacks from C<rcv> callbacks:	566	This is useful when you register callbacks from C<rcv> callbacks:
459		567
460	rcv delayed_reply => sub {	568	rcv delayed_reply => sub {
461	my ($delay, @reply) = @_;	569	my ($delay, @reply) = @_;
…		…
485	$res	593	$res
486	}	594	}
487	}	595	}
488	}	596	}
489		597
490	=item $guard = mon $port, $cb->(@reason)	598	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
491		599
492	=item $guard = mon $port, $rcvport	600	=item $guard = mon $port # kill $SELF when $port dies
493		601
494	=item $guard = mon $port	602	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
495		603
496	=item $guard = mon $port, $rcvport, @msg	604	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
497		605
498	Monitor the given port and do something when the port is killed or	606	Monitor the given port and do something when the port is killed or
499	messages to it were lost, and optionally return a guard that can be used	607	messages to it were lost, and optionally return a guard that can be used
500	to stop monitoring again.	608	to stop monitoring again.
501		609
		610	The first two forms distinguish between "normal" and "abnormal" kil's:
		611
		612	In the first form (another port given), if the C<$port> is C<kil>'ed with
		613	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		614	same reason. That is, on "normal" kil's nothing happens, while under all
		615	other conditions, the other port is killed with the same reason.
		616
		617	The second form (kill self) is the same as the first form, except that
		618	C<$rvport> defaults to C<$SELF>.
		619
		620	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		621	- it's up to the callback or receiver to check whether the C<@reason> is
		622	empty and act accordingly.
		623
		624	In the third form (callback), the callback is simply called with any
		625	number of C<@reason> elements (empty @reason means that the port was deleted
		626	"normally"). Note also that I<< the callback B<must> never die >>, so use
		627	C<eval> if unsure.
		628
		629	In the last form (message), a message of the form C<$rcvport, @msg,
		630	@reason> will be C<snd>.
		631
		632	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		633	alert was raised), they are removed and will not trigger again, even if it
		634	turns out that the port is still alive.
		635
		636	As a rule of thumb, monitoring requests should always monitor a remote
		637	port locally (using a local C<$rcvport> or a callback). The reason is that
		638	kill messages might get lost, just like any other message. Another less
		639	obvious reason is that even monitoring requests can get lost (for example,
		640	when the connection to the other node goes down permanently). When
		641	monitoring a port locally these problems do not exist.
		642
502	C<mon> effectively guarantees that, in the absence of hardware failures,	643	C<mon> effectively guarantees that, in the absence of hardware failures,
503	that after starting the monitor, either all messages sent to the port	644	after starting the monitor, either all messages sent to the port will
504	will arrive, or the monitoring action will be invoked after possible	645	arrive, or the monitoring action will be invoked after possible message
505	message loss has been detected. No messages will be lost "in between"	646	loss has been detected. No messages will be lost "in between" (after
506	(after the first lost message no further messages will be received by the	647	the first lost message no further messages will be received by the
507	port). After the monitoring action was invoked, further messages might get	648	port). After the monitoring action was invoked, further messages might get
508	delivered again.	649	delivered again.
509		650
510	Note that monitoring-actions are one-shot: once released, they are removed	651	Inter-host-connection timeouts and monitoring depend on the transport
511	and will not trigger again.	652	used. The only transport currently implemented is TCP, and AnyEvent::MP
		653	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		654	non-idle connection, and usually around two hours for idle connections).
512		655
513	In the first form (callback), the callback is simply called with any	656	This means that monitoring is good for program errors and cleaning up
514	number of C<@reason> elements (no @reason means that the port was deleted	657	stuff eventually, but they are no replacement for a timeout when you need
515	"normally"). Note also that I<< the callback B<must> never die >>, so use	658	to ensure some maximum latency.
516	C<eval> if unsure.
517
518	In the second form (another port given), the other port (C<$rcvport>)
519	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
520	"normal" kils nothing happens, while under all other conditions, the other
521	port is killed with the same reason.
522
523	The third form (kill self) is the same as the second form, except that
524	C<$rvport> defaults to C<$SELF>.
525
526	In the last form (message), a message of the form C<@msg, @reason> will be
527	C<snd>.
528
529	As a rule of thumb, monitoring requests should always monitor a port from
530	a local port (or callback). The reason is that kill messages might get
531	lost, just like any other message. Another less obvious reason is that
532	even monitoring requests can get lost (for exmaple, when the connection
533	to the other node goes down permanently). When monitoring a port locally
534	these problems do not exist.
535		659
536	Example: call a given callback when C<$port> is killed.	660	Example: call a given callback when C<$port> is killed.
537		661
538	mon $port, sub { warn "port died because of <@_>\n" };	662	mon $port, sub { warn "port died because of <@_>\n" };
539		663
…		…
546	mon $port, $self => "restart";	670	mon $port, $self => "restart";
547		671
548	=cut	672	=cut
549		673
550	sub mon {	674	sub mon {
551	my ($noderef, $port) = split /#/, shift, 2;	675	my ($nodeid, $port) = split /#/, shift, 2;
552		676
553	my $node = $NODE{$noderef} || add_node $noderef;	677	my $node = $NODE{$nodeid} || add_node $nodeid;
554		678
555	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';	679	my $cb = @_ ? shift : $SELF || Carp::croak 'mon: called with one argument only, but $SELF not set,';
556		680
557	unless (ref $cb) {	681	unless (ref $cb) {
558	if (@_) {	682	if (@_) {
…		…
567	}	691	}
568		692
569	$node->monitor ($port, $cb);	693	$node->monitor ($port, $cb);
570		694
571	defined wantarray	695	defined wantarray
572	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	696	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
573	}	697	}
574		698
575	=item $guard = mon_guard $port, $ref, $ref...	699	=item $guard = mon_guard $port, $ref, $ref...
576		700
577	Monitors the given C<$port> and keeps the passed references. When the port	701	Monitors the given C<$port> and keeps the passed references. When the port
578	is killed, the references will be freed.	702	is killed, the references will be freed.
579		703
580	Optionally returns a guard that will stop the monitoring.	704	Optionally returns a guard that will stop the monitoring.
581		705
582	This function is useful when you create e.g. timers or other watchers and	706	This function is useful when you create e.g. timers or other watchers and
583	want to free them when the port gets killed:	707	want to free them when the port gets killed (note the use of C<psub>):
584		708
585	$port->rcv (start => sub {	709	$port->rcv (start => sub {
586	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	710	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
587	undef $timer if 0.9 < rand;	711	undef $timer if 0.9 < rand;
588	});	712	});
589	});	713	});
590		714
591	=cut	715	=cut
…		…
600		724
601	=item kil $port[, @reason]	725	=item kil $port[, @reason]
602		726
603	Kill the specified port with the given C<@reason>.	727	Kill the specified port with the given C<@reason>.
604		728
605	If no C<@reason> is specified, then the port is killed "normally" (linked	729	If no C<@reason> is specified, then the port is killed "normally" -
606	ports will not be kileld, or even notified).	730	monitor callback will be invoked, but the kil will not cause linked ports
		731	(C<mon $mport, $lport> form) to get killed.
607		732
608	Otherwise, linked ports get killed with the same reason (second form of	733	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
609	C<mon>, see below).	734	form) get killed with the same reason.
610		735
611	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	736	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
612	will be reported as reason C<< die => $@ >>.	737	will be reported as reason C<< die => $@ >>.
613		738
614	Transport/communication errors are reported as C<< transport_error =>	739	Transport/communication errors are reported as C<< transport_error =>
615	$message >>.	740	$message >>.
616		741
617	=cut	742	Common idioms:
		743
		744	# silently remove yourself, do not kill linked ports
		745	kil $SELF;
		746
		747	# report a failure in some detail
		748	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		749
		750	# do not waste much time with killing, just die when something goes wrong
		751	open my $fh, "<file"
		752	or die "file: $!";
618		753
619	=item $port = spawn $node, $initfunc[, @initdata]	754	=item $port = spawn $node, $initfunc[, @initdata]
620		755
621	Creates a port on the node C<$node> (which can also be a port ID, in which	756	Creates a port on the node C<$node> (which can also be a port ID, in which
622	case it's the node where that port resides).	757	case it's the node where that port resides).
623		758
624	The port ID of the newly created port is return immediately, and it is	759	The port ID of the newly created port is returned immediately, and it is
625	permissible to immediately start sending messages or monitor the port.	760	possible to immediately start sending messages or to monitor the port.
626		761
627	After the port has been created, the init function is	762	After the port has been created, the init function is called on the remote
628	called. This function must be a fully-qualified function name	763	node, in the same context as a C<rcv> callback. This function must be a
629	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	764	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
630	program, use C<::name>.	765	specify a function in the main program, use C<::name>.
631		766
632	If the function doesn't exist, then the node tries to C<require>	767	If the function doesn't exist, then the node tries to C<require>
633	the package, then the package above the package and so on (e.g.	768	the package, then the package above the package and so on (e.g.
634	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	769	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
635	exists or it runs out of package names.	770	exists or it runs out of package names.
636		771
637	The init function is then called with the newly-created port as context	772	The init function is then called with the newly-created port as context
638	object (C<$SELF>) and the C<@initdata> values as arguments.	773	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		774	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		775	the port might not get created.
639		776
640	A common idiom is to pass your own port, monitor the spawned port, and	777	A common idiom is to pass a local port, immediately monitor the spawned
641	in the init function, monitor the original port. This two-way monitoring	778	port, and in the remote init function, immediately monitor the passed
642	ensures that both ports get cleaned up when there is a problem.	779	local port. This two-way monitoring ensures that both ports get cleaned up
		780	when there is a problem.
		781
		782	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		783	caller before C<spawn> returns (by delaying invocation when spawn is
		784	called for the local node).
643		785
644	Example: spawn a chat server port on C<$othernode>.	786	Example: spawn a chat server port on C<$othernode>.
645		787
646	# this node, executed from within a port context:	788	# this node, executed from within a port context:
647	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	789	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
662		804
663	sub _spawn {	805	sub _spawn {
664	my $port = shift;	806	my $port = shift;
665	my $init = shift;	807	my $init = shift;
666		808
		809	# rcv will create the actual port
667	local $SELF = "$NODE#$port";	810	local $SELF = "$NODE#$port";
668	eval {	811	eval {
669	&{ load_func $init }	812	&{ load_func $init }
670	};	813	};
671	_self_die if $@;	814	_self_die if $@;
672	}	815	}
673		816
674	sub spawn(@) {	817	sub spawn(@) {
675	my ($noderef, undef) = split /#/, shift, 2;	818	my ($nodeid, undef) = split /#/, shift, 2;
676		819
677	my $id = "$RUNIQ." . $ID++;	820	my $id = $RUNIQ . ++$ID;
678		821
679	$_[0] =~ /::/	822	$_[0] =~ /::/
680	or Carp::croak "spawn init function must be a fully-qualified name, caught";	823	or Carp::croak "spawn init function must be a fully-qualified name, caught";
681		824
682	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;	825	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
683		826
684	"$noderef#$id"	827	"$nodeid#$id"
685	}	828	}
		829
		830
		831	=item after $timeout, @msg
		832
		833	=item after $timeout, $callback
		834
		835	Either sends the given message, or call the given callback, after the
		836	specified number of seconds.
		837
		838	This is simply a utility function that comes in handy at times - the
		839	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		840	so it may go away in the future.
		841
		842	=cut
		843
		844	sub after($@) {
		845	my ($timeout, @action) = @_;
		846
		847	my $t; $t = AE::timer $timeout, 0, sub {
		848	undef $t;
		849	ref $action[0]
		850	? $action[0]()
		851	: snd @action;
		852	};
		853	}
		854
		855	#=item $cb2 = timeout $seconds, $cb[, @args]
		856
		857	=item cal $port, @msg, $callback[, $timeout]
		858
		859	A simple form of RPC - sends a message to the given C<$port> with the
		860	given contents (C<@msg>), but adds a reply port to the message.
		861
		862	The reply port is created temporarily just for the purpose of receiving
		863	the reply, and will be C<kil>ed when no longer needed.
		864
		865	A reply message sent to the port is passed to the C<$callback> as-is.
		866
		867	If an optional time-out (in seconds) is given and it is not C<undef>,
		868	then the callback will be called without any arguments after the time-out
		869	elapsed and the port is C<kil>ed.
		870
		871	If no time-out is given (or it is C<undef>), then the local port will
		872	monitor the remote port instead, so it eventually gets cleaned-up.
		873
		874	Currently this function returns the temporary port, but this "feature"
		875	might go in future versions unless you can make a convincing case that
		876	this is indeed useful for something.
		877
		878	=cut
		879
		880	sub cal(@) {
		881	my $timeout = ref $_[-1] ? undef : pop;
		882	my $cb = pop;
		883
		884	my $port = port {
		885	undef $timeout;
		886	kil $SELF;
		887	&$cb;
		888	};
		889
		890	if (defined $timeout) {
		891	$timeout = AE::timer $timeout, 0, sub {
		892	undef $timeout;
		893	kil $port;
		894	$cb->();
		895	};
		896	} else {
		897	mon $_[0], sub {
		898	kil $port;
		899	$cb->();
		900	};
		901	}
		902
		903	push @_, $port;
		904	&snd;
		905
		906	$port
		907	}
		908
		909	=back
		910
		911	=head1 DISTRIBUTED DATABASE
		912
		913	AnyEvent::MP comes with a simple distributed database. The database will
		914	be mirrored asynchronously on all global nodes. Other nodes bind to one
		915	of the global nodes for their needs. Every node has a "local database"
		916	which contains all the values that are set locally. All local databases
		917	are merged together to form the global database, which can be queried.
		918
		919	The database structure is that of a two-level hash - the database hash
		920	contains hashes which contain values, similarly to a perl hash of hashes,
		921	i.e.:
		922
		923	$DATABASE{$family}{$subkey} = $value
		924
		925	The top level hash key is called "family", and the second-level hash key
		926	is called "subkey" or simply "key".
		927
		928	The family must be alphanumeric, i.e. start with a letter and consist
		929	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		930	pretty much like Perl module names.
		931
		932	As the family namespace is global, it is recommended to prefix family names
		933	with the name of the application or module using it.
		934
		935	The subkeys must be non-empty strings, with no further restrictions.
		936
		937	The values should preferably be strings, but other perl scalars should
		938	work as well (such as C<undef>, arrays and hashes).
		939
		940	Every database entry is owned by one node - adding the same family/subkey
		941	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		942	but the result might be nondeterministic, i.e. the key might have
		943	different values on different nodes.
		944
		945	Different subkeys in the same family can be owned by different nodes
		946	without problems, and in fact, this is the common method to create worker
		947	pools. For example, a worker port for image scaling might do this:
		948
		949	db_set my_image_scalers => $port;
		950
		951	And clients looking for an image scaler will want to get the
		952	C<my_image_scalers> keys from time to time:
		953
		954	db_keys my_image_scalers => sub {
		955	@ports = @{ $_[0] };
		956	};
		957
		958	Or better yet, they want to monitor the database family, so they always
		959	have a reasonable up-to-date copy:
		960
		961	db_mon my_image_scalers => sub {
		962	@ports = keys %{ $_[0] };
		963	};
		964
		965	In general, you can set or delete single subkeys, but query and monitor
		966	whole families only.
		967
		968	If you feel the need to monitor or query a single subkey, try giving it
		969	it's own family.
		970
		971	=over
		972
		973	=item $guard = db_set $family => $subkey [=> $value]
		974
		975	Sets (or replaces) a key to the database - if C<$value> is omitted,
		976	C<undef> is used instead.
		977
		978	When called in non-void context, C<db_set> returns a guard that
		979	automatically calls C<db_del> when it is destroyed.
		980
		981	=item db_del $family => $subkey...
		982
		983	Deletes one or more subkeys from the database family.
		984
		985	=item $guard = db_reg $family => $port => $value
		986
		987	=item $guard = db_reg $family => $port
		988
		989	=item $guard = db_reg $family
		990
		991	Registers a port in the given family and optionally returns a guard to
		992	remove it.
		993
		994	This function basically does the same as:
		995
		996	db_set $family => $port => $value
		997
		998	Except that the port is monitored and automatically removed from the
		999	database family when it is kil'ed.
		1000
		1001	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1002	C<$SELF> is used.
		1003
		1004	This function is most useful to register a port in some port group (which
		1005	is just another name for a database family), and have it removed when the
		1006	port is gone. This works best when the port is a local port.
		1007
		1008	=cut
		1009
		1010	sub db_reg($$;$) {
		1011	my $family = shift;
		1012	my $port = @_ ? shift : $SELF;
		1013
		1014	my $clr = sub { db_del $family => $port };
		1015	mon $port, $clr;
		1016
		1017	db_set $family => $port => $_[0];
		1018
		1019	defined wantarray
		1020	and &Guard::guard ($clr)
		1021	}
		1022
		1023	=item db_family $family => $cb->(\%familyhash)
		1024
		1025	Queries the named database C<$family> and call the callback with the
		1026	family represented as a hash. You can keep and freely modify the hash.
		1027
		1028	=item db_keys $family => $cb->(\@keys)
		1029
		1030	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1031	them as array reference to the callback.
		1032
		1033	=item db_values $family => $cb->(\@values)
		1034
		1035	Same as C<db_family>, except it only queries the family I<values> and passes them
		1036	as array reference to the callback.
		1037
		1038	=item $guard = db_mon $family => $cb->(\%familyhash, \@added, \@changed, \@deleted)
		1039
		1040	Creates a monitor on the given database family. Each time a key is set
		1041	or or is deleted the callback is called with a hash containing the
		1042	database family and three lists of added, changed and deleted subkeys,
		1043	respectively. If no keys have changed then the array reference might be
		1044	C<undef> or even missing.
		1045
		1046	If not called in void context, a guard object is returned that, when
		1047	destroyed, stops the monitor.
		1048
		1049	The family hash reference and the key arrays belong to AnyEvent::MP and
		1050	B<must not be modified or stored> by the callback. When in doubt, make a
		1051	copy.
		1052
		1053	As soon as possible after the monitoring starts, the callback will be
		1054	called with the intiial contents of the family, even if it is empty,
		1055	i.e. there will always be a timely call to the callback with the current
		1056	contents.
		1057
		1058	It is possible that the callback is called with a change event even though
		1059	the subkey is already present and the value has not changed.
		1060
		1061	The monitoring stops when the guard object is destroyed.
		1062
		1063	Example: on every change to the family "mygroup", print out all keys.
		1064
		1065	my $guard = db_mon mygroup => sub {
		1066	my ($family, $a, $c, $d) = @_;
		1067	print "mygroup members: ", (join " ", keys %$family), "\n";
		1068	};
		1069
		1070	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1071
		1072	my $guard; $guard = db_mon My::Module::workers => sub {
		1073	my ($family, $a, $c, $d) = @_;
		1074	return unless %$family;
		1075	undef $guard;
		1076	print "My::Module::workers now nonempty\n";
		1077	};
		1078
		1079	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1080
		1081	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1082	my ($family, $a, $c, $d) = @_;
		1083
		1084	print "+$_=$family->{$_}\n" for @$a;
		1085	print "*$_=$family->{$_}\n" for @$c;
		1086	print "-$_=$family->{$_}\n" for @$d;
		1087	};
		1088
		1089	=cut
686		1090
687	=back	1091	=back
688		1092
689	=head1 AnyEvent::MP vs. Distributed Erlang	1093	=head1 AnyEvent::MP vs. Distributed Erlang
690		1094
691	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1095	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
692	== aemp node, Erlang process == aemp port), so many of the documents and	1096	== aemp node, Erlang process == aemp port), so many of the documents and
693	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1097	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
694	sample:	1098	sample:
695		1099
696	http://www.Erlang.se/doc/programming_rules.shtml	1100	http://www.erlang.se/doc/programming_rules.shtml
697	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1101	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
698	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1102	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
699	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1103	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
700		1104
701	Despite the similarities, there are also some important differences:	1105	Despite the similarities, there are also some important differences:
702		1106
703	=over 4	1107	=over 4
704		1108
705	=item * Node references contain the recipe on how to contact them.	1109	=item * Node IDs are arbitrary strings in AEMP.
706		1110
707	Erlang relies on special naming and DNS to work everywhere in the	1111	Erlang relies on special naming and DNS to work everywhere in the same
708	same way. AEMP relies on each node knowing it's own address(es), with	1112	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
709	convenience functionality.	1113	configuration or DNS), and possibly the addresses of some seed nodes, but
710		1114	will otherwise discover other nodes (and their IDs) itself.
711	This means that AEMP requires a less tightly controlled environment at the
712	cost of longer node references and a slightly higher management overhead.
713		1115
714	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1116	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
715	uses "local ports are like remote ports".	1117	uses "local ports are like remote ports".
716		1118
717	The failure modes for local ports are quite different (runtime errors	1119	The failure modes for local ports are quite different (runtime errors
…		…
726	ports being the special case/exception, where transport errors cannot	1128	ports being the special case/exception, where transport errors cannot
727	occur.	1129	occur.
728		1130
729	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1131	=item * Erlang uses processes and a mailbox, AEMP does not queue.
730		1132
731	Erlang uses processes that selectively receive messages, and therefore	1133	Erlang uses processes that selectively receive messages out of order, and
732	needs a queue. AEMP is event based, queuing messages would serve no	1134	therefore needs a queue. AEMP is event based, queuing messages would serve
733	useful purpose. For the same reason the pattern-matching abilities of	1135	no useful purpose. For the same reason the pattern-matching abilities
734	AnyEvent::MP are more limited, as there is little need to be able to	1136	of AnyEvent::MP are more limited, as there is little need to be able to
735	filter messages without dequeing them.	1137	filter messages without dequeuing them.
736		1138
737	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1139	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1140	being event-based, while Erlang is process-based.
		1141
		1142	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1143	top of AEMP and Coro threads.
738		1144
739	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1145	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
740		1146
741	Sending messages in Erlang is synchronous and blocks the process (and	1147	Sending messages in Erlang is synchronous and blocks the process until
		1148	a conenction has been established and the message sent (and so does not
742	so does not need a queue that can overflow). AEMP sends are immediate,	1149	need a queue that can overflow). AEMP sends return immediately, connection
743	connection establishment is handled in the background.	1150	establishment is handled in the background.
744		1151
745	=item * Erlang suffers from silent message loss, AEMP does not.	1152	=item * Erlang suffers from silent message loss, AEMP does not.
746		1153
747	Erlang makes few guarantees on messages delivery - messages can get lost	1154	Erlang implements few guarantees on messages delivery - messages can get
748	without any of the processes realising it (i.e. you send messages a, b,	1155	lost without any of the processes realising it (i.e. you send messages a,
749	and c, and the other side only receives messages a and c).	1156	b, and c, and the other side only receives messages a and c).
750		1157
751	AEMP guarantees correct ordering, and the guarantee that there are no	1158	AEMP guarantees (modulo hardware errors) correct ordering, and the
		1159	guarantee that after one message is lost, all following ones sent to the
		1160	same port are lost as well, until monitoring raises an error, so there are
752	holes in the message sequence.	1161	no silent "holes" in the message sequence.
753		1162
754	=item * In Erlang, processes can be declared dead and later be found to be	1163	If you want your software to be very reliable, you have to cope with
755	alive.	1164	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
756		1165	simply tries to work better in common error cases, such as when a network
757	In Erlang it can happen that a monitored process is declared dead and	1166	link goes down.
758	linked processes get killed, but later it turns out that the process is
759	still alive - and can receive messages.
760
761	In AEMP, when port monitoring detects a port as dead, then that port will
762	eventually be killed - it cannot happen that a node detects a port as dead
763	and then later sends messages to it, finding it is still alive.
764		1167
765	=item * Erlang can send messages to the wrong port, AEMP does not.	1168	=item * Erlang can send messages to the wrong port, AEMP does not.
766		1169
767	In Erlang it is quite likely that a node that restarts reuses a process ID	1170	In Erlang it is quite likely that a node that restarts reuses an Erlang
768	known to other nodes for a completely different process, causing messages	1171	process ID known to other nodes for a completely different process,
769	destined for that process to end up in an unrelated process.	1172	causing messages destined for that process to end up in an unrelated
		1173	process.
770		1174
771	AEMP never reuses port IDs, so old messages or old port IDs floating	1175	AEMP does not reuse port IDs, so old messages or old port IDs floating
772	around in the network will not be sent to an unrelated port.	1176	around in the network will not be sent to an unrelated port.
773		1177
774	=item * Erlang uses unprotected connections, AEMP uses secure	1178	=item * Erlang uses unprotected connections, AEMP uses secure
775	authentication and can use TLS.	1179	authentication and can use TLS.
776		1180
777	AEMP can use a proven protocol - SSL/TLS - to protect connections and	1181	AEMP can use a proven protocol - TLS - to protect connections and
778	securely authenticate nodes.	1182	securely authenticate nodes.
779		1183
780	=item * The AEMP protocol is optimised for both text-based and binary	1184	=item * The AEMP protocol is optimised for both text-based and binary
781	communications.	1185	communications.
782		1186
783	The AEMP protocol, unlike the Erlang protocol, supports both	1187	The AEMP protocol, unlike the Erlang protocol, supports both programming
784	language-independent text-only protocols (good for debugging) and binary,	1188	language independent text-only protocols (good for debugging), and binary,
785	language-specific serialisers (e.g. Storable).	1189	language-specific serialisers (e.g. Storable). By default, unless TLS is
		1190	used, the protocol is actually completely text-based.
786		1191
787	It has also been carefully designed to be implementable in other languages	1192	It has also been carefully designed to be implementable in other languages
788	with a minimum of work while gracefully degrading fucntionality to make the	1193	with a minimum of work while gracefully degrading functionality to make the
789	protocol simple.	1194	protocol simple.
790		1195
791	=item * AEMP has more flexible monitoring options than Erlang.	1196	=item * AEMP has more flexible monitoring options than Erlang.
792		1197
793	In Erlang, you can chose to receive I<all> exit signals as messages	1198	In Erlang, you can chose to receive I<all> exit signals as messages or
794	or I<none>, there is no in-between, so monitoring single processes is	1199	I<none>, there is no in-between, so monitoring single Erlang processes is
795	difficult to implement. Monitoring in AEMP is more flexible than in	1200	difficult to implement.
796	Erlang, as one can choose between automatic kill, exit message or callback	1201
797	on a per-process basis.	1202	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1203	between automatic kill, exit message or callback on a per-port basis.
798		1204
799	=item * Erlang tries to hide remote/local connections, AEMP does not.	1205	=item * Erlang tries to hide remote/local connections, AEMP does not.
800		1206
801	Monitoring in Erlang is not an indicator of process death/crashes,	1207	Monitoring in Erlang is not an indicator of process death/crashes, in the
802	as linking is (except linking is unreliable in Erlang).	1208	same way as linking is (except linking is unreliable in Erlang).
803		1209
804	In AEMP, you don't "look up" registered port names or send to named ports	1210	In AEMP, you don't "look up" registered port names or send to named ports
805	that might or might not be persistent. Instead, you normally spawn a port	1211	that might or might not be persistent. Instead, you normally spawn a port
806	on the remote node. The init function monitors the you, and you monitor	1212	on the remote node. The init function monitors you, and you monitor the
807	the remote port. Since both monitors are local to the node, they are much	1213	remote port. Since both monitors are local to the node, they are much more
808	more reliable.	1214	reliable (no need for C<spawn_link>).
809		1215
810	This also saves round-trips and avoids sending messages to the wrong port	1216	This also saves round-trips and avoids sending messages to the wrong port
811	(hard to do in Erlang).	1217	(hard to do in Erlang).
812		1218
813	=back	1219	=back
814		1220
815	=head1 RATIONALE	1221	=head1 RATIONALE
816		1222
817	=over 4	1223	=over 4
818		1224
819	=item Why strings for ports and noderefs, why not objects?	1225	=item Why strings for port and node IDs, why not objects?
820		1226
821	We considered "objects", but found that the actual number of methods	1227	We considered "objects", but found that the actual number of methods
822	thatc an be called are very low. Since port IDs and noderefs travel over	1228	that can be called are quite low. Since port and node IDs travel over
823	the network frequently, the serialising/deserialising would add lots of	1229	the network frequently, the serialising/deserialising would add lots of
824	overhead, as well as having to keep a proxy object.	1230	overhead, as well as having to keep a proxy object everywhere.
825		1231
826	Strings can easily be printed, easily serialised etc. and need no special	1232	Strings can easily be printed, easily serialised etc. and need no special
827	procedures to be "valid".	1233	procedures to be "valid".
828		1234
829	And a a miniport consists of a single closure stored in a global hash - it	1235	And as a result, a port with just a default receiver consists of a single
830	can't become much cheaper.	1236	code reference stored in a global hash - it can't become much cheaper.
831		1237
832	=item Why favour JSON, why not real serialising format such as Storable?	1238	=item Why favour JSON, why not a real serialising format such as Storable?
833		1239
834	In fact, any AnyEvent::MP node will happily accept Storable as framing	1240	In fact, any AnyEvent::MP node will happily accept Storable as framing
835	format, but currently there is no way to make a node use Storable by	1241	format, but currently there is no way to make a node use Storable by
836	default.	1242	default (although all nodes will accept it).
837		1243
838	The default framing protocol is JSON because a) JSON::XS is many times	1244	The default framing protocol is JSON because a) JSON::XS is many times
839	faster for small messages and b) most importantly, after years of	1245	faster for small messages and b) most importantly, after years of
840	experience we found that object serialisation is causing more problems	1246	experience we found that object serialisation is causing more problems
841	than it gains: Just like function calls, objects simply do not travel	1247	than it solves: Just like function calls, objects simply do not travel
842	easily over the network, mostly because they will always be a copy, so you	1248	easily over the network, mostly because they will always be a copy, so you
843	always have to re-think your design.	1249	always have to re-think your design.
844		1250
845	Keeping your messages simple, concentrating on data structures rather than	1251	Keeping your messages simple, concentrating on data structures rather than
846	objects, will keep your messages clean, tidy and efficient.	1252	objects, will keep your messages clean, tidy and efficient.
847		1253
848	=back	1254	=back
849		1255
		1256	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1257
		1258	AEMP version 2 has a few major incompatible changes compared to version 1:
		1259
		1260	=over 4
		1261
		1262	=item AnyEvent::MP::Global no longer has group management functions.
		1263
		1264	At least not officially - the grp_* functions are still exported and might
		1265	work, but they will be removed in some later release.
		1266
		1267	AnyEvent::MP now comes with a distributed database that is more
		1268	powerful. Its database families map closely to port groups, but the API
		1269	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1270	a rough porting guide:
		1271
		1272	grp_reg $group, $port # old
		1273	db_reg $group, $port # new
		1274
		1275	$list = grp_get $group # old
		1276	db_keys $group, sub { my $list = shift } # new
		1277
		1278	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1279	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1280
		1281	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1282	no longer instant, because the local node might not have a copy of the
		1283	group. You can either modify your code to allow for a callback, or use
		1284	C<db_mon> to keep an updated copy of the group:
		1285
		1286	my $local_group_copy;
		1287	db_mon $group => sub { $local_group_copy = $_[0] };
		1288
		1289	# now "keys %$local_group_copy" always returns the most up-to-date
		1290	# list of ports in the group.
		1291
		1292	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1293	passes a hash as first argument, and an extra C<$chg> argument that can be
		1294	ignored:
		1295
		1296	db_mon $group => sub {
		1297	my ($ports, $add, $chg, $lde) = @_;
		1298	$ports = [keys %$ports];
		1299
		1300	# now $ports, $add and $del are the same as
		1301	# were originally passed by grp_mon.
		1302	...
		1303	};
		1304
		1305	=item Nodes not longer connect to all other nodes.
		1306
		1307	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1308	module, which in turn would create connections to all other nodes in the
		1309	network (helped by the seed nodes).
		1310
		1311	In version 2.x, global nodes still connect to all other global nodes, but
		1312	other nodes don't - now every node either is a global node itself, or
		1313	attaches itself to another global node.
		1314
		1315	If a node isn't a global node itself, then it attaches itself to one
		1316	of its seed nodes. If that seed node isn't a global node yet, it will
		1317	automatically be upgraded to a global node.
		1318
		1319	So in many cases, nothing needs to be changed - one just has to make sure
		1320	that all seed nodes are meshed together with the other seed nodes (as with
		1321	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1322	achieved by specifying the same set of seed nodes for all nodes in the
		1323	network.
		1324
		1325	Not opening a connection to every other node is usually an advantage,
		1326	except when you need the lower latency of an already established
		1327	connection. To ensure a node establishes a connection to another node,
		1328	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1329	create the connection (and notify you when the connection fails).
		1330
		1331	=item Listener-less nodes (nodes without binds) are gone.
		1332
		1333	And are not coming back, at least not in their old form. If no C<binds>
		1334	are specified for a node, AnyEvent::MP assumes a default of C<*:*>.
		1335
		1336	There are vague plans to implement some form of routing domains, which
		1337	might or might not bring back listener-less nodes, but don't count on it.
		1338
		1339	The fact that most connections are now optional somewhat mitigates this,
		1340	as a node can be effectively unreachable from the outside without any
		1341	problems, as long as it isn't a global node and only reaches out to other
		1342	nodes (as opposed to being contacted from other nodes).
		1343
		1344	=item $AnyEvent::MP::Kernel::WARN has gone.
		1345
		1346	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1347	uses this, and so should your programs.
		1348
		1349	Every module now documents what kinds of messages it generates, with
		1350	AnyEvent::MP acting as a catch all.
		1351
		1352	On the positive side, this means that instead of setting
		1353	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1354	much less to type.
		1355
		1356	=back
		1357
		1358	=head1 LOGGING
		1359
		1360	AnyEvent::MP does not normally log anything by itself, but sinc eit is the
		1361	root of the contetx hierarchy for AnyEvent::MP modules, it will receive
		1362	all log messages by submodules.
		1363
850	=head1 SEE ALSO	1364	=head1 SEE ALSO
		1365
		1366	L<AnyEvent::MP::Intro> - a gentle introduction.
		1367
		1368	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		1369
		1370	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
		1371	your applications.
		1372
		1373	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1374
		1375	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1376	all nodes.
851		1377
852	L<AnyEvent>.	1378	L<AnyEvent>.
853		1379
854	=head1 AUTHOR	1380	=head1 AUTHOR
855		1381

Diff Legend

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