spring-cloud-stream-elasticsearch

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.

Technologies used

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

• 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

Project Architecture

Applications

• 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. A news is created in producer-api and, immediately, it is shown in news-client.

  

Start Environment

• Open a terminal and inside spring-boot-kafka-es root folder run

  docker-compose up -d

• Wait a until all containers are Up (healthy). You can check their status by running

  docker-compose ps

Running Applications with Gradle

Inside spring-boot-kafka-es root folder, run the following Gradle commands in different terminals

• eureka-server

  ./gradlew :eureka-server:build

• producer-api

  ./gradlew :producer-api:build

• categorizer-service

  ./gradlew :categorizer-service:build

• collector-service

  ./gradlew :collector-service:build

• publisher-api

  ./gradlew :publisher-api:build

• news-client

  ./gradlew :news-client:build

Running Applications as Docker containers

Build Application’s Docker Image

• In a terminal, make sure you are in spring-boot-kafka-es root folder

• In order to build the applications docker images, run the following script

  ./build-apps.sh

Application’s Environment Variables

• producer-api

  Environment Variable	Description
  KAFKA_HOST	Specify host of the Kafka message broker to use (default localhost)
  KAFKA_PORT	Specify port of the Kafka message broker to use (default 29092)
  EUREKA_HOST	Specify host of the Eureka service discovery to use (default localhost)
  EUREKA_PORT	Specify port of the Eureka service discovery to use (default 8761)
  ZIPKIN_HOST	Specify host of the Zipkin distributed tracing system to use (default localhost)
  ZIPKIN_PORT	Specify port of the Zipkin distributed tracing system to use (default 9411)

• categorizer-service

  Environment Variable	Description
  KAFKA_HOST	Specify host of the Kafka message broker to use (default localhost)
  KAFKA_PORT	Specify port of the Kafka message broker to use (default 29092)
  EUREKA_HOST	Specify host of the Eureka service discovery to use (default localhost)
  EUREKA_PORT	Specify port of the Eureka service discovery to use (default 8761)
  ZIPKIN_HOST	Specify host of the Zipkin distributed tracing system to use (default localhost)
  ZIPKIN_PORT	Specify port of the Zipkin distributed tracing system to use (default 9411)

• collector-service

  Environment Variable	Description
  ELASTICSEARCH_HOST	Specify host of the Elasticsearch search engine to use (default localhost)
  ELASTICSEARCH_NODES_PORT	Specify nodes port of the Elasticsearch search engine to use (default 9300)
  ELASTICSEARCH_REST_PORT	Specify rest port of the Elasticsearch search engine to use (default 9200)
  KAFKA_HOST	Specify host of the Kafka message broker to use (default localhost)
  KAFKA_PORT	Specify port of the Kafka message broker to use (default 29092)
  EUREKA_HOST	Specify host of the Eureka service discovery to use (default localhost)
  EUREKA_PORT	Specify port of the Eureka service discovery to use (default 8761)
  ZIPKIN_HOST	Specify host of the Zipkin distributed tracing system to use (default localhost)
  ZIPKIN_PORT	Specify port of the Zipkin distributed tracing system to use (default 9411)

• publisher-api

  Environment Variable	Description
  ELASTICSEARCH_HOST	Specify host of the Elasticsearch search engine to use (default localhost)
  ELASTICSEARCH_NODES_PORT	Specify nodes port of the Elasticsearch search engine to use (default 9300)
  ELASTICSEARCH_REST_PORT	Specify rest port of the Elasticsearch search engine to use (default 9200)
  EUREKA_HOST	Specify host of the Eureka service discovery to use (default localhost)
  EUREKA_PORT	Specify port of the Eureka service discovery to use (default 8761)
  ZIPKIN_HOST	Specify host of the Zipkin distributed tracing system to use (default localhost)
  ZIPKIN_PORT	Specify port of the Zipkin distributed tracing system to use (default 9411)

• news-client

  Environment Variable	Description
  KAFKA_HOST	Specify host of the Kafka message broker to use (default localhost)
  KAFKA_PORT	Specify port of the Kafka message broker to use (default 29092)
  EUREKA_HOST	Specify host of the Eureka service discovery to use (default localhost)
  EUREKA_PORT	Specify port of the Eureka service discovery to use (default 8761)
  ZIPKIN_HOST	Specify host of the Zipkin distributed tracing system to use (default localhost)
  ZIPKIN_PORT	Specify port of the Zipkin distributed tracing system to use (default 9411)

Start Application’s Docker Container

• In a terminal, make sure you are inside spring-boot-kafka-es root folder

• Run following script

  ./start-apps.sh

Applications URLs

Application	URL
producer-api	http://localhost:9084/swagger-ui.html
publisher-api	http://localhost:9085/swagger-ui.html
news-client	http://localhost:9083

Shutdown

• Stop applications

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

  • If they were started as a Docker container, run the script below

    ./stop-apps.sh

• Stop and remove docker-compose containers, networks and volumes

  docker-compose down -v

Useful links

• Eureka

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

• Kafka Topics UI

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

• 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 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: MyZooCluster

  • 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.

• Elasticsearch REST API

  Check ES is up and running

  curl http://localhost:9200

  Check indexes in ES

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

  Check news index mapping

  curl http://localhost:9200/news/_mapping

  Simple search

  curl http://localhost:9200/news/news/_search