The goal of this project is to implement a "News" processing pipeline composed of five Spring Boot applications: producer-api, categorizer-service, collector-service, publisher-api and news-client.

On ivangfr.github.io, I have compiled my Proof-of-Concepts (PoCs) and articles. You can easily search for the technology you are interested in by using the filter. Who knows, perhaps I have already implemented a PoC or written an article about what you are looking for.

• [Medium]: Implementing a Kafka Producer and Consumer using Spring Cloud Stream

• [Medium]: Implementing Unit Tests for a Kafka Producer and Consumer that uses Spring Cloud Stream

• [Medium]: Implementing End-to-End testing for a Kafka Producer and Consumer that uses Spring Cloud Stream

• [Medium]: Configuring Distributed Tracing with Zipkin in a Kafka Producer and Consumer that uses Spring Cloud Stream

• [Medium]: Using CloudEvents in a Kafka Producer and Consumer that uses Spring Cloud Stream

• Spring Cloud Stream to build highly scalable event-driven applications connected with shared messaging systems;

• Spring Cloud Schema Registry that supports schema evolution so that the data can be evolved over time; besides, it lets you store schema information in a textual format (typically JSON) and makes that information accessible to various applications that need it to receive and send data in binary format;

• Spring Data Elasticsearch to persist data in Elasticsearch;

• Spring Cloud OpenFeign to write web service clients easily;

• Thymeleaf as HTML template;

• Zipkin to visualize traces between and within applications;

• Eureka as service registration and discovery.

• producer-api

  Spring Boot Web Java application that creates news and pushes news events to producer.news topic in Kafka.

• categorizer-service

  Spring Boot Web Java application that listens to news events in producer.news topic in Kafka, categorizes and pushes them to categorizer.news topic.

• collector-service

  Spring Boot Web Java application that listens for news events in categorizer.news topic in Kafka, saves them in Elasticsearch and pushes the news events to collector.news topic.

• publisher-api

  Spring Boot Web Java application that reads directly from Elasticsearch and exposes a REST API. It doesn’t listen from Kafka.

• news-client

  Spring Boot Web java application that provides a User Interface to see the news. It implements a Websocket that consumes news events from the topic collector.news. So, news are updated on the fly on the main page. Besides, news-client communicates directly with publisher-api whenever search for a specific news or news update are needed.

  The Websocket operation is shown in the short gif below. News is created in producer-api and, immediately, it appears in news-client.

  websocket operation

• Java 21 or higher;

• A containerization tool Docker, Podman, etc.

• Open a terminal and navigate to the spring-cloud-stream-kafka-elasticsearch root folder;

• Run the following command to generate NewsEvent:

  ./mvnw clean install --projects commons-news

  It will install commons-news-1.0.0.jar in your local Maven repository, so that it can be visible by all services.

• In a terminal, navigate to the spring-cloud-stream-kafka-elasticsearch root folder, and run:

  docker compose up -d

• Wait for Docker containers to be up and running. To check it, run:

  docker ps -a

Inside the spring-cloud-stream-kafka-elasticsearch root folder, run the following Maven commands in different terminals:

• eureka-server

  ./mvnw clean spring-boot:run --projects eureka-server

• producer-api

  ./mvnw clean spring-boot:run --projects producer-api -Dspring-boot.run.jvmArguments="-Dserver.port=9080"

• categorizer-service

  ./mvnw clean spring-boot:run --projects categorizer-service -Dspring-boot.run.jvmArguments="-Dserver.port=9081"

• collector-service

  ./mvnw clean spring-boot:run --projects collector-service -Dspring-boot.run.jvmArguments="-Dserver.port=9082"

• publisher-api

  ./mvnw clean spring-boot:run --projects publisher-api -Dspring-boot.run.jvmArguments="-Dserver.port=9083"

• news-client

  ./mvnw clean spring-boot:run --projects news-client

• Eureka

  Eureka can be accessed at http://localhost:8761

  eureka

• Zipkin

  Zipkin can be accessed at http://localhost:9411

  zipkin

• Kafdrop

  Kafdrop can be accessed at http://localhost:9000

• Schema Registry UI

  Schema Registry UI can be accessed at http://localhost:8001

• Elasticsearch REST API

  Check if ES is up and running

  curl localhost:9200

  Check indexes

  curl "localhost:9200/_cat/indices?v"

  Check news index mapping

  curl "localhost:9200/news/_mapping?pretty"

  Simple search

  curl "localhost:9200/news/_search?pretty"

  Delete news index

  curl -X DELETE localhost:9200/news

• To stop applications:

  • If they were started with Maven, go to the terminals where they are running and press Ctrl+C.

  • If they were started as Docker containers, in a terminal and inside the spring-cloud-stream-kafka-elasticsearch root folder, run the script below:

    ./stop-apps.sh

• To stop and remove Docker Compose containers, network and volumes, in a terminal, navigate to the spring-cloud-stream-kafka-elasticsearch root folder, and run the following command:

  docker compose down -v

To remove the Docker images created by this project, in a terminal and inside the spring-cloud-stream-kafka-elasticsearch root folder, run the script below: