Practical Examples of Redis Scripting

Let’s explore some practical examples of Redis scripting:

Example 1: Atomic Counter

In this example, we’ll create an atomic counter using Redis scripting. We’ll increment the counter by a specified value.

local key = KEYS[1]
local increment = tonumber(ARGV[1])

local current = tonumber(redis.call('GET', key) or '0')
current = current + increment

redis.call('SET', key, current)
return current

You can execute this script in Redis using the EVAL command, passing the key and the increment value as arguments.

Example 2: Leaderboard

Imagine Geeks for Geeks wants to create a leaderboard for coding challenges. Redis scripting can help manage the leaderboard efficiently.

Syntax:

local variable1 = ARGV[index1] -- Accessing the arguments passed to the script
local variable2 = ARGV[index2] -- Accessing additional arguments if needed

-- Perform operations using Redis commands and Lua logic
redis.call('REDIS_COMMAND', key, arg1, arg2, ...) -- Execute Redis commands within the script

-- Perform custom logic and operations
if condition then
    -- Perform action
end

-- Return the result or value at the end
return result

Example:

local username = ARGV[1]
local score = tonumber(ARGV[2])
local currentScore = tonumber(redis.call('ZSCORE', 'leaderboard', username) or 0)
if score > currentScore then
    redis.call('ZADD', 'leaderboard', score, username)
end
return redis.call('ZRANK', 'leaderboard', username)

This script checks if the request count exceeds the limit and returns a result indicating whether the request is allowed or not.

Redis scripting is primarily implemented using the Lua programming language, enabling users to create custom server-side scripts that can be executed with a single command.