redis_lua_scripting

🎯 Use Lua Scripting for Atomic Operations

Lua scripts in Redis ensure that a sequence of operations is executed atomically, avoiding race conditions without external locks. You can bundle complex logic (e.g., conditional updates, increments, and expirations) into one script and call it via EVAL, reducing latency and improving consistency. Always load scripts with SCRIPT LOAD to get a SHA for faster execution with EVALSHA.

require 'redis'
redis = Redis.new

# Define a Lua script that increments a counter and sets an expiry only on first use
lua = <<~LUA
  local current = redis.call('INCR', KEYS[1])
  if current == 1 then
    redis.call('EXPIRE', KEYS[1], ARGV[1])
  end
  return current
LUA

# Load script and store its SHA1 hash
sha = redis.script(:load, lua)

# Execute the script atomically using EVALSHA
count = redis.evalsha(sha, keys: ['page:42:views'], argv: ['3600'])
puts "Page 42 view count: #{count}"