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.

• 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 is shown in news-client.

  

• Java 11+

• Docker

• Docker-Compose

• In a terminal, make sure you are in 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 you local Maven repository, so that it can be visible by all services.

• Open a terminal and inside spring-cloud-stream-kafka-elasticsearch root folder run

  docker-compose up -d

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

  docker-compose ps

Inside 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

Build Application’s Docker Image

Application’s Environment Variables

Run Application’s Docker Container

• Eureka

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

  

• Zipkin

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

  The figure below shows an example of the complete flow a news passes through. It goes since producer-api, where the news is created, until news-client.

  

• Kafka Topics UI

  Kafka Topics UI can be accessed at http://localhost:8085

• Kafka Manager

  Kafka Manager can be accessed at http://localhost:9000

  The figure below shows the Kafka topics consumers. As we can see, the consumers are updated as the lag is 0

  

  Configuration

  • First, you must create a new cluster. Click on Cluster (dropdown button on the header) and then on Add Cluster

  • Type the name of your cluster in Cluster Name field, for example: MyCluster

  • Type zookeeper:2181 in Cluster Zookeeper Hosts field

  • Enable checkbox Poll consumer information (Not recommended for large # of consumers if ZK is used for offsets tracking on older Kafka versions)

  • Click on Save button at the bottom of the page.

• Schema Registry UI

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

  

• Elasticsearch REST API

  Check ES is up and running

  curl localhost:9200

  Check indexes in ES

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

  Check news index mapping

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

  Simple search

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

• 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, go to a terminal and, inside spring-cloud-stream-kafka-elasticsearch root folder, run the script below

    ./stop-apps.sh

• To stop and remove docker-compose containers, network and volumes, go to a terminal and, inside spring-cloud-stream-kafka-elasticsearch root folder, run the following command

  docker-compose down -v

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