Average metrics using redis operations

retrieve_metric_avg.lua

# retrieve_metric_avg.lua $operation_type
local operation_type = ARGV[1];
local count = redis.call("HGET", "operations_count", operation_type)
local total = redis.call("HGET", "operations_total", operation_type)
if not count or not total then
    return 0
else
    local avg = tonumber(total)/tonumber(count)
    return tostring(avg)
end

update_metric_avg.lua

# update_metric_avg.lua $operation_type $uuid
local operation_type = ARGV[1]
local uuid = ARGV[2]
redis.call("HINCRBY", "operations_count", operation_type, 1)
local not_exists = redis.call("HSETNX", "operations_" .. operation_type .. "_users", uuid, 1)
if not_exists == 1 then
    redis.call("HINCRBY", "operations_total", operation_type, 1)
end