redis_lua_atomic_operations

🛡️ Atomic Multi-key Operations with Lua Scripts

Leverage Redis' built‑in Lua engine to execute complex, multi‑key operations atomically, avoiding race conditions in high‑concurrency environments. By preloading scripts with SCRIPT LOAD and invoking them via EVALSHA, you minimize network overhead and ensure deterministic execution. This approach is invaluable for token buckets, rate limiters, and distributed locks.

# config/initializers/redis.rb
$redis = Redis.new(url: ENV.fetch("REDIS_URL"))

# lib/redis_scripts.rb
module RedisScripts
  LUA_TRANSFER = <<~LUA
    local src, dest, amount = KEYS[1], KEYS[2], tonumber(ARGV[1])
    if redis.call('GET', src) == false or tonumber(redis.call('GET', src)) < amount then
      return {err = 'Insufficient funds'}
    end
    redis.call('DECRBY', src, amount)
    redis.call('INCRBY', dest, amount)
    return {ok = 'Transfer complete'}
  LUA
  SHA_TRANSFER = $redis.script(:load, LUA_TRANSFER)
end

# Usage
result = $redis.evalsha(RedisScripts::SHA_TRANSFER, keys: ["account:1:balance", "account:2:balance"], argv: [100])
puts result # => "Transfer complete"