What is a YML file in Docker?

#What is a YML file in Docker?

The YML file in Docker generally refers to the Docker default template file "docker-compose.yml". Each service used to define this file must specify the image through the image command, or use the Dockerfile The build command performs automatic building.

Compose file

The Compose file is a YAML file that defines services, networks, and volumes. The default path is. /docker-compose.yml, you can use .yml or .yaml as the file extension.

Service services definition contains configuration that applies to each container started for that service, similar to passing command line parameters to docker container create. Likewise, networks and volumes are defined similarly to docker network create and docker volume create. Just as docker container create specifies options in the Dockerfile, such as CMD, EXPOSE, VOLUME, and ENV, by default, there is no need to specify them again in the docker-compose.yml configuration. Environment variables can be used in configuration values ​​using the Bash class ${VARIABLE} syntax.

version: "3"
services:
  redis:
    image: redis:alpine
    ports:
      - "6379"
    networks:
      - frontend
    deploy:
      replicas: 2
      update_config:
        parallelism: 2
        delay: 10s
      restart_policy:
        condition: on-failure
  db:
    image: postgres:9.4
    volumes:
      - db-data:/var/lib/postgresql/data
    networks:
      - backend
    deploy:
      placement:
        constraints: [node.role == manager]
  vote:
    image: dockersamples/examplevotingapp_vote:before
    ports:
      - 5000:80
    networks:
      - frontend
    depends_on:
      - redis
    deploy:
      replicas: 2
      update_config:
        parallelism: 2
      restart_policy:
        condition: on-failure
  result:
    image: dockersamples/examplevotingapp_result:before
    ports:
      - 5001:80
    networks:
      - backend
    depends_on:
      - db
    deploy:
      replicas: 1
      update_config:
        parallelism: 2
        delay: 10s
      restart_policy:
        condition: on-failure
  worker:
    image: dockersamples/examplevotingapp_worker
    networks:
      - frontend
      - backend
    deploy:
      mode: replicated
      replicas: 1
      labels: [APP=VOTING]
      restart_policy:
        condition: on-failure
        delay: 10s
        max_attempts: 3
        window: 120s
      placement:
        constraints: [node.role == manager]
  visualizer:
    image: dockersamples/visualizer:stable
    ports:
      - "8080:8080"
    stop_grace_period: 1m30s
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock"
    deploy:
      placement:
        constraints: [node.role == manager]
networks:
  frontend:
  backend:
volumes:
  db-data:

Recommended tutorial: "Docker"

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