What are docker networks are needed for?-CodePudding

Please explain why docker network is needed? I read some documentation, but on a practical example, I don't understand why we need to manipulate the network. Here I have a docker-compose in which everything works fine with and without network. Explain me please, what benefits will be in practical use if you uncomment docker-compose in the right places? Now my containers interact perfectly, there are migrations from the ORM to the database, why do I need a networks?

 version: '3.4'

services:
  main:
    container_name: main
    build:
      context: .
      target: development
    volumes:
      - .:/usr/src/app
      - /usr/src/app/node_modules
    ports:
      - ${PORT}:${PORT}
    command: npm run start:dev
    env_file:
      - .env
#     networks:
#       - webnet
    depends_on:
      - postgres
  postgres:
    container_name: postgres
    image: postgres:12
#     networks:
#       - webnet
    environment:
      POSTGRES_PASSWORD: ${DB_PASSWORD}
      POSTGRES_USER: ${DB_USERNAME}
      POSTGRES_DB: ${DB_DATABASE_NAME}
      PG_DATA: /var/lib/postgresql/data
    ports:
      - 5432:5432
    volumes:
      - pgdata:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 1m30s
      timeout: 10s
      retries: 3
# networks:
#   webnet:
volumes:
  pgdata:

CodePudding user response：

If no networks are defined, docker-compose will create a default network with a generated name. Otherwise you can manually specify the network and its name in the compose file.

You can read more at Networking in Compose

CodePudding user response：

Here explained Docker network - Networking overview, and here are tutorials:

Macvlan network tutorial,

Overlay networking tutorial,

Host networking tutorial,

Bridge network tutorial.