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
|
local prefix = KEYS[1]
local key = KEYS[2]
local data = ARGV[1]
local schemes = cjson.decode(ARGV[2])
local conj_keys = cjson.decode(ARGV[3])
local timeout = tonumber(ARGV[4])
local rnd = ARGV[5] -- A new value for empty stamps
local expected_checksum = ARGV[6]
-- Ensure schemes are known
for db_table, _schemes in pairs(schemes) do
redis.call('sadd', prefix .. 'schemes:' .. db_table, unpack(_schemes))
end
-- Fill in invalidators and collect stamps
local stamps = {}
for _, conj_key in ipairs(conj_keys) do
-- REDIS_7
local stamp = redis.call('set', conj_key, rnd, 'nx', 'get') or rnd
-- /REDIS_7
-- REDIS_4
local stamp = redis.call('get', conj_key)
if not stamp then
stamp = rnd
redis.call('set', conj_key, rnd)
end
-- /REDIS_4
table.insert(stamps, stamp)
-- NOTE: an invalidator should live longer than any key it references.
-- So we update its ttl on every key if needed.
-- NOTE: we also can't use "EXPIRE conj_key timeout GT" because it will have no effect on
-- newly created and thus involatile conj keys.
local conj_ttl = redis.call('ttl', conj_key)
if conj_ttl < timeout then
-- We set conj_key life with a margin over key life to call expire rarer
-- And add few extra seconds to be extra safe
redis.call('expire', conj_key, timeout * 2 + 10)
end
end
-- Write data to cache along with a checksum of the stamps to see if any of them changed
local all_stamps = table.concat(stamps, ' ')
local stamp_checksum = redis.sha1hex(all_stamps)
if expected_checksum ~= '' and stamp_checksum ~= expected_checksum then
-- Cached data was invalidated during the function call. The data is
-- stale and should not be cached.
return stamp_checksum -- This one is used for keep_fresh implementation
end
redis.call('set', key, stamp_checksum .. ':' .. data, 'ex', timeout)
|
