A Redis-based Ring Buffer for Java

A ring buffer (also known as a circular buffer, circular queue, or cyclic buffer) is a fixed-size data structure that develops on the basic idea of a queue data structure. The elements of a ring buffer are handled as if they were arranged in a circular order. This property makes ring buffers useful for implementing a FIFO (first in, first out) queue for use cases such as buffering data streams.

In the Java programming language, developers can make use of pre-built ring buffer implementations, such as the EvictingQueue from Google's Guava core Java libraries, or write their own.

Redis is an open-source in-memory data structure store that is often used to implement a NoSQL database. Java developers face one major roadblock with Redis, however: the two technologies are not immediately compatible out of the box.

To use both Redis and Java, developers need to use a Redis Java client such as Redisson. In this article, we'll discuss how Redisson offers easy access to the ring buffer data structure in Java and Redis.

Ring Buffers in Redis and Java with Redisson

Redisson is a user-friendly, lightweight Redis Java client. By offering many familiar Java distributed objects and services, Redisson makes it much easier for Java developers to work with Redis.

The concept of a ring buffer is implemented in Redisson via the RRingBuffer interface. The following example code illustrates the use of RRingBuffer in Redisson:

RRingBuffer<Integer> buffer = redisson.getRingBuffer("test");

// buffer capacity is 4 elements


// buffer state is 1, 2, 3, 4


// buffer state is 3, 4, 5, 6

As the code above demonstrates, the size of the RRingBuffer must be fixed using the trySetCapacity() method after instantiating the object. The capacity() and remainingCapacity() methods return the ring buffer's current number of objects and its remaining capacity, respectively.

When the RRingBuffer reaches capacity, the head of the queue is evicted and the new element is added to the end of the queue.

RRingBuffer inherits from the RQueue interface. Developers using RRingBuffer also have access to Queue-based methods such as add(), peek(), poll(), and remove(), as well as Collection-based methods such as contains() and isEmpty().

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