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Redis script (Lua) to implement a leaky bucket
-- Redis script to implement a leaky bucket
-- see https://medium.com/callr-techblog/rate-limiting-for-distributed-systems-with-redis-and-lua-eeea745cb260
-- (c) Florent CHAUVEAU <florent.chauveau@gmail.com>
local ts = tonumber(ARGV[1])
local cps = tonumber(ARGV[2])
local key = KEYS[1]
-- remove tokens < min (older than now() -1s)
local min = ts -1
redis.call('ZREMRANGEBYSCORE', key, '-inf', min)
local last = redis.call('ZRANGE', key, -1, -1)
local next = ts
if type(last) == 'table' and #last > 0 then
for key,value in pairs(last) do
next = tonumber(value) + 1/cps
break -- break at first item
end
end
if ts > next then
-- the current ts is > than last+1/cps
-- we'll keep ts
next = ts
end
redis.call('ZADD', key, next, next)
return tostring(next - ts)
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