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Pradipta
Pradipta

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Seamless communication between containers - docker compose

#docker #containers

Let's consider an example of a Spring Boot application which interacts with the MySQL database. Couple of images have been created for MySQL and Spring Boot respectively. The images can be run as containers. But how they going to interact with each other?

One way is to create a docker network and spin up the containers within that network. This will work but you have to deal with long commands which is difficult to maintain in bigger projects. This is the problem docker compose solves by making the container communication easy to achieve and maintain.

  • Let's consider the following Spring Boot Application which communicates with a MySQL database and provides a basic JWT implementation for securing Rest service endpoints.
    https://github.com/pradz13/spring-security-jwt.git

  • Spring Boot Application needs to define a Dockerfile as follows -

FROM maven:3.9.3-sapmachine-17 WORKDIR . COPY . . RUN mvn clean install -DskipTests CMD mvn spring-boot:run
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  • Define the docker compose configuration file as follows - 
version: "3.8" services: mysqldb: image: mysql:5.7 restart: unless-stopped env_file: ./.env environment: - MYSQL_ROOT_PASSWORD=$MYSQLDB_ROOT_PASSWORD - MYSQL_DATABASE=$MYSQLDB_DATABASE ports: - $MYSQLDB_LOCAL_PORT:$MYSQLDB_DOCKER_PORT volumes: - db:/var/lib/mysql app: depends_on: - mysqldb build: . restart: on-failure env_file: ./.env ports: - $SPRING_LOCAL_PORT:$SPRING_DOCKER_PORT environment: SPRING_APPLICATION_JSON: '{ "spring.datasource.url" : "jdbc:mysql://mysqldb:$MYSQLDB_DOCKER_PORT/$MYSQLDB_DATABASE?useSSL=false", "spring.datasource.username" : "$MYSQLDB_USER", "spring.datasource.password" : "$MYSQLDB_ROOT_PASSWORD", "spring.jpa.properties.hibernate.dialect" : "org.hibernate.dialect.MySQLDialect", "spring.jpa.hibernate.ddl-auto" : "update" }' volumes: - .m2:/root/.m2 stdin_open: true tty: true volumes: db:
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  • Create the .env file which will have the configurations. 
MYSQLDB_USER=root MYSQLDB_ROOT_PASSWORD=123456 MYSQLDB_DATABASE=bezkoder_db MYSQLDB_LOCAL_PORT=3307 MYSQLDB_DOCKER_PORT=3306 SPRING_LOCAL_PORT=6868 SPRING_DOCKER_PORT=8080
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  • Run the containers with the following command - 
docker-compose up -d
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-d will run it in detached mode.

  • To stop the containers following command can be used - 
docker-compose down
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To stop the containers and delete the images, use the following command -

docker-compose down --rmi all
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Please note, when docker compose is used, no need to create docker network explicitly, it is taken care by docker compose internally.

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