1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
|
-module(mem3_util).
-export([hash/1, name_shard/1, create_partition_map/4, build_shards/2,
n_val/2, to_atom/1, to_integer/1, write_db_doc/1, delete_db_doc/1,
load_shards_from_disk/1, load_shards_from_disk/2]).
-define(RINGTOP, 2 bsl 31). % CRC32 space
-include("mem3.hrl").
-include_lib("couch/include/couch_db.hrl").
hash(Item) when is_binary(Item) ->
erlang:crc32(Item);
hash(Item) ->
erlang:crc32(term_to_binary(Item)).
name_shard(#shard{dbname = DbName, range=[B,E]} = Shard) ->
Name = ["shards/", couch_util:to_hex(<<B:32/integer>>), "-",
couch_util:to_hex(<<E:32/integer>>), "/", DbName],
Shard#shard{name = ?l2b(Name)}.
create_partition_map(DbName, N, Q, Nodes) ->
UniqueShards = make_key_ranges((?RINGTOP) div Q, 0, []),
Shards0 = lists:flatten([lists:duplicate(N, S) || S <- UniqueShards]),
Shards1 = attach_nodes(Shards0, [], Nodes, []),
[name_shard(S#shard{dbname=DbName}) || S <- Shards1].
make_key_ranges(_, CurrentPos, Acc) when CurrentPos >= ?RINGTOP ->
Acc;
make_key_ranges(Increment, Start, Acc) ->
case Start + 2*Increment of
X when X > ?RINGTOP ->
End = ?RINGTOP - 1;
_ ->
End = Start + Increment - 1
end,
make_key_ranges(Increment, End+1, [#shard{range=[Start, End]} | Acc]).
attach_nodes([], Acc, _, _) ->
lists:reverse(Acc);
attach_nodes(Shards, Acc, [], UsedNodes) ->
attach_nodes(Shards, Acc, lists:reverse(UsedNodes), []);
attach_nodes([S | Rest], Acc, [Node | Nodes], UsedNodes) ->
attach_nodes(Rest, [S#shard{node=Node} | Acc], Nodes, [Node | UsedNodes]).
write_db_doc(Doc) ->
{ok, Db} = couch_db:open(<<"dbs">>, []),
try
update_db_doc(Db, Doc)
catch conflict ->
ok % assume this is a race with another shard on this node
after
couch_db:close(Db)
end.
update_db_doc(Db, #doc{id=Id, body=Body} = Doc) ->
case couch_db:open_doc(Db, Id, []) of
{not_found, _} ->
{ok, _} = couch_db:update_doc(Db, Doc, []);
{ok, #doc{body=Body}} ->
ok;
{ok, OldDoc} ->
{ok, _} = couch_db:update_doc(Db, OldDoc#doc{body=Body}, [])
end.
delete_db_doc(DocId) ->
{ok, Db} = couch_db:open(<<"dbs">>, []),
try
delete_db_doc(Db, DocId)
catch conflict ->
ok
after
couch_db:close(Db)
end.
delete_db_doc(Db, DocId) ->
case couch_db:open_doc(Db, DocId, []) of
{not_found, _} ->
ok;
{ok, OldDoc} ->
{ok, _} = couch_db:update_doc(Db, OldDoc#doc{deleted=true}, [])
end.
build_shards(DbName, DocProps) ->
{ByNode} = couch_util:get_value(<<"by_node">>, DocProps, {[]}),
lists:flatmap(fun({Node, Ranges}) ->
lists:map(fun(Range) ->
[B,E] = string:tokens(?b2l(Range), "-"),
Beg = httpd_util:hexlist_to_integer(B),
End = httpd_util:hexlist_to_integer(E),
name_shard(#shard{
dbname = DbName,
node = to_atom(Node),
range = [Beg, End]
})
end, Ranges)
end, ByNode).
to_atom(Node) when is_binary(Node) ->
list_to_atom(binary_to_list(Node));
to_atom(Node) when is_atom(Node) ->
Node.
to_integer(N) when is_integer(N) ->
N;
to_integer(N) when is_binary(N) ->
list_to_integer(binary_to_list(N));
to_integer(N) when is_list(N) ->
list_to_integer(N).
n_val(undefined, NodeCount) ->
n_val(couch_config:get("cluster", "n", "3"), NodeCount);
n_val(N, NodeCount) when is_list(N) ->
n_val(list_to_integer(N), NodeCount);
n_val(N, NodeCount) when is_integer(NodeCount), N > NodeCount ->
?LOG_ERROR("Request to create N=~p DB but only ~p node(s)", [N, NodeCount]),
NodeCount;
n_val(N, _) when N < 1 ->
1;
n_val(N, _) ->
N.
load_shards_from_disk(DbName) when is_binary(DbName) ->
{ok, Db} = couch_db:open(<<"dbs">>, []),
try load_shards_from_db(Db, DbName) after couch_db:close(Db) end.
load_shards_from_db(#db{} = ShardDb, DbName) ->
case couch_db:open_doc(ShardDb, DbName, []) of
{ok, #doc{body = {Props}}} ->
?LOG_INFO("dbs cache miss for ~s", [DbName]),
build_shards(DbName, Props);
{not_found, _} ->
erlang:error(database_does_not_exist)
end.
load_shards_from_disk(DbName, DocId)->
Shards = load_shards_from_disk(DbName),
HashKey = hash(DocId),
[S || #shard{range = [B,E]} = S <- Shards, B < HashKey, HashKey =< E].
|
