Understanding Redis High-Availability Architectures

High-Availability is crucial in Redis to ensure the continuous availability of data and prevent downtime. Although Redis is known for its high performance, there are instances where a single server might not be sufficient to meet the data requirements of an organization. Running Redis across multiple servers provides a resilient architecture where the system can continue to operate without interruption and data loss in-spite of one or more server failures. This also has an added benefit of enhanced performance. This article covers Redis High-Availability (HA) strategies. We will start off with Leader-Follower architecture which is based on data replication and learn how Redis Cluster builds on top of it. This will be followed by a discussion of Redis Sentinel, which uses a set of external processes (sentinels) to monitor Leader-Follower deployments before closing off by covering Proxy based setup. <h1>What is Redis?</h1> <a href="https://redis.io/" rel="noopener ugc nofollow" target="_blank">Redis</a> is an open-source, in-memory data structure store. Its core data types include <code>String</code>,<code> Lis</code>t, <code>Has</code>h, <code>Se</code>t, Sorted Set <code>Geospatial </code>indexes, <code>HyperLogLog</code> and <code>Bitmap</code>. You can use Redis as a messaging system, thanks to its support for Redis Streams, Pub/Sub as well as <code>List</code> (which can act as a queue). Although it’s an in-memory store, you can choose from a spectrum of persistence options. Transactions and Pipeline capabilities help build performant applications at scale, while Lua scripting, server-side Functions and Redis Modules enable you to extend Redis’ functionality. Now, let’s dive into the various Redis HA architectures. <h1>Leader-Follower topology</h1> A Leader-Follower architecture consists of multiple Redis nodes, where one node is designated as the Leader (also known as the Primary), while the others function as Followers (or Replicas). The Leader-Follower replication mechanism in Redis is the cornerstone of operating Redis in a distributed and highly-available manner. By default, replicas are configured to be read-only, which means they reject all writecommands. This design ensures that the data on the replicas remains consistent with that of the primary node. Writable replicas can introduce inconsistencies between the primary and the replica, hence they are not recommended for use. <a href="https://semaphoreci.medium.com/understanding-redis-high-availability-architectures-2b544fe3ec1e">Read More</a>