spring-redis-websocket

Multi-instance Reactive Chat App using Spring Boot WebFlux and Redis Pub/Sub

Scalable Java 21 Spring Boot 3.x WebFlux Chat Application to demonstrate use of Reactive Redis Pub/Sub using Reactive WebSocket Handler, without using any external Message Broker like RabbitMQ to sync messages between different instances.

Both JVM based application and GraalVM Native Image is supported. Additionally, the Docker Image for JVM base is available for AMD64 and ARM64 architecture.

The older non-reactive servlet based spring-redis-websocket application can be found in below:

1. Spring-Boot 2.3: Java-11 version
2. Spring-Boot 1.5: Java-8 version

The older reactive spring-boot 2.x (java 11) based spring-redis-websocket application can be found in below:

1. Spring-Boot 2.4.6: Java-11 Reactive JVM & GraalVM Native version
2. Spring-Boot 2.5.2: Java-11 Reactive JVM & GraalVM Native version

The older reactive spring-boot 3.2.x (java 17) based spring-redis-websocket application can be found in below:

1. Spring-Boot 3.2.0: Java-11 Reactive JVM & GraalVM Native version

Deploy to Play-with-Docker

Ctrl + Click this button to deploy multiple instances of the spring-redis-websocket load balanced by Traefik:

Installation and Configuration

Pre-requisite for Java Image:

Install and run Redis locally or on Docker.

To run Redis in Docker:

$ docker run -d -p 6379:6379 -e REDIS_PASSWORD=SuperSecretRedisPassword bitnami/redis:7.2.3

Pre-requisite for GraalVM Native Image:

This application uses Spring Data Redis APIs which doesn't have default GraalVM hints/config and graalvm-native image fails to run with errors.

Hence, this application is configured to use GraalVMVM native image tracing agent allows intercepting reflection, resources or proxy usage on the JVM by running simple Integration Tests which requires Redis.

1. To run integration test which uses Redis TestContainers so Docker should be configured properly to run Testcontainers
2. You also need to install GraalVMVM JDK and native-image component:

   $ sdk install java 21.0.2-graalce         # Using [SDKMAN](https://sdkman.io/jdks) install GraalVMVM distribution of JDK
   $ sdk use java 21.0.2-graalce

Clone repo:

$ git clone https://github.com/RawSanj/spring-redis-websocket.git

Build and Run the application:

Build and run the spring-redis-websocket application:

$ cd spring-redis-websocket

$ mvn clean package

$ mvn spring-boot:run

Build GraalVM Native Image of the application:

Build and run the spring-redis-websocket native image:

$ cd spring-redis-websocket

$ mvn -Pnative clean package

$ target/spring-redis-websocket # run the executable binary

Note: Above steps are applicable for Linux only and creates linux executable binary. To create Windows executable there are few additional set-ups required, follow this Steps.

Run in Docker

Build and run the spring-redis-websocket locally in Docker:

Build the JAR file:

$ mvn clean package

Build Docker image:

$ mvn clean spring-boot:build-image

Build GraalVM Native Docker image:

$ mvn -Pnative clean spring-boot:build-image

Run docker image:

$ docker run -d -p 8080:8080 rawsanj/spring-redis-websocket:3.4.4-jvm # JVM based Docker Image

$ docker run -d -p 8080:8080 rawsanj/spring-redis-websocket:3.4.4-native  # GraalVM Native Image based Docker Image

Run multiple instances using docker-compose locally

Run multiple instances of spring-redis-websocket locally load balanced via Traefik connected to redis container in Docker:

$ cd src/main/docker
$ docker-compose up

Or try Play with Docker to quickly setup Docker and run in browser:

1. Click Create Instance to quickly setup Docker host.
2. Install git by running:

   $ apk add git --no-cache

3. Clone the repository:

   $ git clone https://github.com/RawSanj/spring-redis-websocket.git

4. Run multiple instances of spring-redis-websocket:

   $ cd spring-redis-websocket/src/main/docker
   $ docker-compose up

Run in Kubernetes

Assuming you have a Kubernetes Cluster up and running locally:

$ kubectl apply -f src/main/k8s

Or try Play with Kubernetes to quickly setup a K8S cluster:

1. Follow the instructions to create Kuberenetes cluster.
2. Install git by running:

   $ yum install git -y

3. Clone the repository:

   $ git clone https://github.com/RawSanj/spring-redis-websocket.git

4. Run multiple instances of spring-redis-websocket load balanced by native Kubernetes Service. All instances connected to a single Redis pod.

   $ cd spring-redis-websocket
   $ kubectl apply -f src/main/k8s

Tech

spring-redis-websocket uses a number of open source projects:

• Spring Boot - An opinionated framework for building production-ready Spring applications. It favors convention over configuration and is designed to get you up and running as quickly as possible.
• Spring Data Redis - Spring Data Redis provides easy configuration and access to Redis from Spring applications.
• GraalVM Native Image - Native Image is a technology to ahead-of-time compile Java code to a standalone executable, called a native image.
• Redis - Redis is an open source (BSD licensed), in-memory data structure store, used as a database, cache and message broker.
• Testcontainers - Testcontainers is a Java library that supports JUnit tests, providing lightweight, throwaway instances of common databases or anything else that can run in a Docker container.
• Bootstrap - Bootstrap is an open source toolkit for developing with HTML, CSS, and JS. Custom Bootstrap theme
  • Bootswatch Sketch.
• Docker - Docker is an open platform for developers and sysadmins to build, ship, and run distributed applications.
• Traefik - Traefik is a Cloud Native Application Proxy - Simplifies networking complexity while designing, deploying, and operating applications.
• Kubernetes - Kubernetes is an open-source system for automating deployment, scaling, and management of containerized applications.

License

Apache License 2.0

Copyright (c) 2025 Sanjay Rawat