/spring-cloud-stream-kafka-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.

Primary LanguageJava

spring-cloud-stream-kafka-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 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.

Note
 In docker-swarm-environment repository, it is shown how to deploy this project into a cluster of Docker Engines in swarm mode.

Project Architecture

project diagram

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

    websocket operation

Prerequisites

Generate NewsEvent

  • 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.

Start Environment

  • 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

Running Applications with Maven

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

Running Applications as Docker containers

Build Application’s Docker Image

  • In a terminal, make sure you are in spring-cloud-stream-kafka-elasticsearch root folder

  • In order to build the application’s docker images, run the following script

    ./docker-build.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)

    SCHEMA_REGISTRY_HOST

    Specify host of the Schema Registry to use (default localhost)

    SCHEMA_REGISTRY_PORT

    Specify port of the Schema Registry to use (default 8081)

    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)

    SCHEMA_REGISTRY_HOST

    Specify host of the Schema Registry to use (default localhost)

    SCHEMA_REGISTRY_PORT

    Specify port of the Schema Registry to use (default 8081)

    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)

    SCHEMA_REGISTRY_HOST

    Specify host of the Schema Registry to use (default localhost)

    SCHEMA_REGISTRY_PORT

    Specify port of the Schema Registry to use (default 8081)

    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)

    SCHEMA_REGISTRY_HOST

    Specify host of the Schema Registry to use (default localhost)

    SCHEMA_REGISTRY_PORT

    Specify port of the Schema Registry to use (default 8081)

    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)

Run Application’s Docker Container

  • In a terminal, make sure you are inside spring-cloud-stream-kafka-elasticsearch root folder

  • Run following script

    ./start-apps.sh

Applications URLs

Application URL

producer-api

http://localhost:9080/swagger-ui.html

publisher-api

http://localhost:9083/swagger-ui.html

news-client

http://localhost:8080

Useful links

  • Eureka

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

    eureka with apps

  • 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.

    zipkin sample

  • 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

    kafka manager consumers

    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

    schema registry

  • 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"

Shutdown

  • 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

Cleanup

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

./remove-docker-images.sh