Websocket API Demo

This is a simple demo showing how to configure websockets in Spring Boot. It uses the spring-boot-starter-websocket dependency to enable websocket support in the application. It allows any topic under the /private prefix to be subscribed to by any client. The client can then send messages to the server, which will be broadcast to all clients subscribed to the same topic.

There are two endpoints exposed by the server: /automation and /kafka/automation. These endpoints are used to simulate triggering an automation event. When a client sends a message to this endpoint, the server will broadcast a message to all clients subscribed to the topic key that was passed in the body of the request. This service method simulates long-running tasks with Thread.sleep() and will use websockets to notify the client after each task is complete.

In order to use the /kafka/automation endpoint, you need to have kafka running on your local machine. You can find the instructions on how to start kafka in the Kafka profile section.

Pre-requisites

• Java 17
• Docker

To build the project, run the following command:

./gradlew build

The server runs on port 8080 and can be accessed at http://localhost:8080. The server can be started with the following command:

./gradlew bootRun

Customizing the Server

The server can be customized by modifying the application.properties file, located under src/main/resources/. The following properties can be set:

• server.port: The port the server will run on. Default is 8080. Can be overridden by setting the SERVER_PORT environment variable.
• websocket.allowed-origins: The allowed origins for websocket connections. Default is http://localhost:3000. Can be overridden by setting the WEBSOCKET_ALLOWED_ORIGINS environment variable.

Kafka profile

To use kafka profile, you need to have kafka running on your local machine. You can start kafka using the following command, located in the local directory:

docker compose up -d

To simulate multiple pods, you can run the following command in the local directory:

./run.sh .envrc.pod1

Open a new terminal and run the following command in the local directory:

./run.sh .envrc.pod2

Kafka properties

The following properties can be set in the application-kafka.properties file, located under src/main/resources/:

• kafka.topic: The topic to subscribe to. Default is test.topic. Can be overridden by setting the KAFKA_TOPIC environment variable.
• kafka.group-id: The group id for the kafka consumer. Default is test-group. Can be overridden by setting the KAFKA_GROUP_ID environment variable.
• spring.kafka.bootstrap-servers: The kafka server to connect to. Default is localhost:9092.
• spring.kafka.properties.security,protocol: The security protocol to use. Default is PLAINTEXT.