Uncovering the Truth Behind Lua and Redis Data Consistency

This post details the investigation and resolution of Redis master/replica data inconsistency caused by Lua scripts executing differently on master and replica nodes, leading to divergent hash encodings (hashtable vs. ziplist). The root cause was identified as Redis's behavior of executing Lua scripts independently on replicas and the potential for different hash encodings during RDB loading. The solution implemented was to ensure deterministic Lua script behavior by sorting the outputs of HKEYS/HGETALL, preventing data divergence and high CPU usage on replicas.