Lua ScriptingAdvanced
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luaWhy should you use Lua Scripting in Redis using EVAL?
Explanation & Concept
Redis executes Lua scripts atomically on the server. While a Lua script runs, no other script or Redis command can execute, eliminating race conditions between read and write steps without `WATCH` loops.
It reduces network latency by compressing multiple round trips into a single server-side execution.
Code Example
lua
-- Atomic Rate Limiter in Lua (Keys: [rate_key], Args: [limit, window_seconds])
local current = redis.call('INCR', KEYS[1])
if tonumber(current) == 1 then
redis.call('EXPIRE', KEYS[1], ARGV[2])
end
if tonumber(current) > tonumber(ARGV[1]) then
return 0 -- Rejected (rate limit exceeded)
else
return 1 -- Allowed
endHow It Works & Key Takeaways
Because this entire check-and-increment script runs atomically on the Redis thread, two simultaneous requests can never bypass the rate limiter.
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