docker / cli

The following sections detail configuration options specific to the development environment of the Docker CLI.

Docker Compose Configuration

The primary tool for configuring services within your Docker development environment is docker-compose.yml. Below is an example configuration file that illustrates how different services are defined, their dependencies, build contexts, and network configurations.

version: "2"
services:
  server:
    build:
      context: .
      dockerfile: server.Dockerfile
    networks:
      - mdb
      - sig
    ports:
      - "8080"
      - "4443:4443"
    entrypoint: /usr/bin/env sh
    command: -c "./migrations/migrate.sh && notary-server -config=fixtures/server-config.json"
    depends_on:
      - mysql
      - signer

  signer:
    build:
      context: .
      dockerfile: signer.Dockerfile
    networks:
      mdb:
      sig:
        aliases:
          - notarysigner
    entrypoint: /usr/bin/env sh
    command: -c "./migrations/migrate.sh && notary-signer -config=fixtures/signer-config.json"
    depends_on:
      - mysql

  mysql:
    networks:
      - mdb
    volumes:
      - ./notarysql/mysql-initdb.d:/docker-entrypoint-initdb.d
      - notary_data:/var/lib/mysql
    image: mariadb:10.4
    environment:
      - TERM=dumb
      - MYSQL_ALLOW_EMPTY_PASSWORD="true"
    command: mysqld --innodb_file_per_table

volumes:
  notary_data:
    external: false

networks:
  mdb:
    external: false
  sig:
    external: false

Breakdown of Configuration

  • Version: Indicates which version of the Docker Compose file format is being used. In this case, version 2 is selected for better compatibility with older Docker versions.

  • Services: Each service is defined with attributes including:

    • build: Determines the context and specific Dockerfile for building the service. For example, the server service specifies its context as . and the Dockerfile as server.Dockerfile.

    • networks: Lists the networks the service connects to. Services may belong to multiple networks. For example, the server service connects to both mdb and sig.

    • ports: Maps the container ports to the host system. For instance, the server exposes ports 8080 and 4443.

    • entrypoint: Sets the command that is executed when the container starts. Here, it is using sh to run the subsequent command.

    • command: This allows for a custom command to be executed inside the container upon startup. The command first runs migrations and then starts the respective services using configuration files.

    • depends_on: Specifies service dependencies to ensure that dependent services start in the correct order.

  • Volumes: This section provides persistent storage for the MySQL service. It maps a directory (./notarysql/mysql-initdb.d) from the host to an initialization directory in the container. The volume notary_data is used to persist MySQL data across container restarts.

  • Networks: Defines custom networks for inter-service communication. Both mdb and sig are configured as non-external networks.

Building the Project

In the context of building the Docker images, the build command should be run only after confirming the configuration is correct. Use the following command to build the specified services defined within docker-compose.yml:

docker-compose build

Running the Development Environment

Once the images are built, bring up the containers defined in the docker-compose.yml configuration with:

docker-compose up

This command will start all defined services and respect the dependencies set. Logs of the output can be inspected directly in the terminal.

Environment Variables

In the context of the mysql service, several environment variables are defined:

  • TERM=dumb: This is set to avoid terminal issues that might arise since MySQL does not require a terminal interface.

  • MYSQL_ALLOW_EMPTY_PASSWORD=true: This allows MySQL to start without requiring a password for the root user, simplifying local development configurations.

Conclusion

This section has provided an overview of configuring a Docker-based development environment by leveraging a docker-compose.yml file. The settings illustrate how to define service dependencies, manage persistent storage, and control networking between services.

Source: docker/cli GitHub Documentation