How to Use Bucket4j for Ratelimiters

Rate-limiting, or limiting the speed of request processing, is an important component in modern web applications and APIs. It allows you to manage traffic and protects the system from overloading due to an excessive number of requests. One of the most effective tools for implementing rating in Java applications is the Bucket4j library.

Introduction to Bucket4j

Bucket4j is a Java language library that provides an API for implementing rate limiting using token buckets. The token bucket method is based on an analogy with a bucket into which tokens drip at a certain rate. Each request to the service extracts a certain number of tokens from this bucket. If there are not enough tokens in the bucket to process the request, the request is postponed or rejected.

The Main Features of Bucket4j

Bucket4j offers a flexible configuration of rating policies:

Multiple restriction strategies: Bucket4j supports various rate limiting strategies, including a limit based on the number of requests per time interval and a bandwidth limit.

Flexible configuration: Developers can customize the bucket size, token replenishment rate, and maximum request queue size.

Distributed limitation: Bucket4j integrates with distributed repositories such as Hazelcast, Ignite, and Redis, which allows the use of rate-limiting in scalable distributed systems.

High performance: The library is optimized to provide high performance and low latency when processing requests.

An Example of Using Bucket4j

Let's look at a simple example of using Bucket4j to limit the number of requests to the REST API. Suppose we need to limit the number of requests to a certain API to no more than 100 requests per minute.

Adding a dependency: First, let's add Bucket4j to the project as a Maven dependency:

<dependency>
    <groupId>io.github.bucket4j</groupId>
    <artifactId>bucket4j-core</artifactId>
    <version>последняя версия</version>
</dependency>

Creating and configuring a bucket:

Bucket bucket = Bucket4j.builder()
    .addLimit(Bandwidth.classic(100, Refill.greedy(100, Duration.ofMinutes(1))))
    .build();

Here, we create a bucket with a limit ofa 100 tokens and a replenishment rate of 100 tokens per minute.

Applying the Restriction

Before processing each API request, we check whether there are enough tokens in the bucket:

if (bucket.tryConsume(1)) {
  // Processing the request
} else {
  // We are sending a response with an error about exceeding the request limit
}

Advantages and Limitations of Bucket4j

Conclusion