Scripting
Redis 2.6 introduced the scripting feature, and the language that was chosen to extend Redis was Lua. Before Redis 2.6, there was only one way to extend Redis—changing its source code, which was written in C.
Lua was chosen because it is very small and simple, and its C API is very easy to integrate with other libraries. Although it is lightweight, Lua is a very powerful language (it is commonly used in game development).
Lua scripts are atomically executed, which means that the Redis server is blocked during script execution. Because of this, Redis has a default timeout of 5 seconds to run any script, although this value can be changed through the configuration lua-time-limit.
Redis will not automatically terminate a Lua script when it times out. Instead, it will start to reply with a BUSY message to every command, stating that a script is running. The only way to make the server return to normalcy is by aborting the script execution with the command SCRIPT KILL or SHUTDOWN NOSAVE...
