EBOOK – REDIS IN ACTION

This book covers the use of Redis, an in-memory database/data structure server.

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Chapter 11: Scripting Redis with Lua

This chapter covers

  • Adding functionality without writing C
  • Rewriting locks and semaphores with Lua
  • Doing away with WATCH/MULTI/EXEC
  • Sharding LISTs with Lua

Over the last several chapters, you’ve built up a collection of tools that you can use
in existing applications, while also encountering techniques you can use to solve a
variety of problems. This chapter does much of the same, but will turn some of
your expectations on their heads. As of Redis 2.6, Redis includes server-side scripting
with the Lua programming language. This lets you perform a variety of operations
inside Redis, which can both simplify your code and increase performance.

In this chapter, we’ll start by discussing some of the advantages of Lua over performing
operations on the client, showing an example from the social network in
chapter 8. We’ll then go through two problems from chapters 4 and 6 to show examples
where using Lua can remove the need for WATCH/MULTI/EXEC transactions.
Later, we’ll revisit our locks and semaphores from chapter 6 to show how they can be
implemented using Lua for fair multiple client access and higher performance.
Finally, we’ll build a sharded LIST using Lua that supports many (but not all) standard
LIST command equivalents.

Let’s get started by learning about some of the things that we can do with Lua
scripting.