Lua script used for atomically handling api rate counter

CheckCounter.lua

local logchannel = "tokenbucketdebug"
-- This function will be used to log debug messages to redis pub/sub channel
local function logit(msg)
    redis.pcall("PUBLISH", logchannel, msg)
end

local key = KEYS[1]
local logPrependText = "User: "..key
local availableToken = redis.call('GET', 'tokens_'..key)
if availableToken == false then
    availableToken = 0
end
availableToken = tonumber(availableToken)
if availableToken > 0 then
    -- Since we have valid tokens, just decrease the token count and return true
    logit(logPrependText.." Token Count "..availableToken)
    redis.call('decr', 'tokens_'..key)
    return 'True'
else
    -- If token is not present, check if the key with TTL exists, if it doesn' refil the token bucket
    -- else return false
    local refilTime = redis.call('GET', 'refill_'..key)
    if type(refilTime) == 'boolean' and refilTime == false then
        logit(logPrependText.." Refilling token bucket")
        redis.call('SET', 'refill_'..key, key)
        redis.call('EXPIRE', 'refill_'..key, 60)
        redis.call('SET', 'tokens_'..key, 5)
        return 'True'
    else
        logit(logPrependText.."Time limit hasn't expired")
        return 'False'
    end
end