How do you define a network in a version 2 docker-

Question

The documentation about networking is currently very vague on this ― how do you accomplish a docker-compose.yml that creates a virtual network, letting the services (containers) defined by it communicate on that network?

Goal in this scenario being not relying on a pre-defined network, for an ensemble of containers defined for docker-compose. Rather have the network definition self-contained in the docker-compose definition file.

With a pre-defined network, this below would work if the application in A used the name B as the hostname for accessing the application packaged inside B listening on its port 9000. The host:port it would use for it would be B:9000 (more specifically the uri mongodb://B:9000 in my particular case).

foo:
  net: my-pre-defined-network
  container_name: A
  image: foo
bar:
  net: my-pre-defined-network
  container_name: B
  image: bar
  ports:
    - "9000:9000"

But my point is defining a network inside the docker-compose configuration, not assuming one was a-priori defined...

TL;DR

A default network is automatically created. See the beginning section of https://docs.docker.com/compose/networking/ for how to address containers within this network.

Answer 1

Compose will create a default network for you as long as you use the version 2 format, but if you'd like to customize the networks the docs are here:

• https://docs.docker.com/compose/compose-file/#network-configuration-reference
• https://docs.docker.com/compose/networking/#specifying-custom-networks

You can create a networks section at the top level of the Compose file and reference them in the networks section of each service. But you don't need to, just use the default network as described in the comments below.

Answer 2

Please find one example.
Which include network definition, traefic implementation etc
Areogear -push server deployment

version: '2.2' services: unifiedpushserver: image: docker.io/aerogear/unifiedpush-wildfly:2.1.0 networks: - network volumes: - ./helper:/ups-helper:z
entrypoint: "/ups-helper/exportKeycloakHost.sh" depends_on: unifiedpushDB: condition: service_healthy environment: <br> POSTGRES_SERVICE_HOST: ${POSTGRES_SERVICE_HOST} POSTGRES_USER: ${POSTGRES_USER} POSTGRES_PASSWORD: ${POSTGRES_PASSWORD} POSTGRES_SERVICE_PORT: ${POSTGRES_SERVICE_PORT} POSTGRES_DATABASE: ${POSTGRES_DATABASE} KEYCLOAK_SERVICE_HOST: ${KEYCLOAK_SERVICE_HOST} KEYCLOAK_SERVICE_PORT: ${KEYCLOAK_SERVICE_PORT} labels: traefik.backend: "aerogear" traefik.docker.network: "appliance" traefik.domain: "notification.com" traefik.enable: "true" traefik.frontend.entryPoints: "http, https" traefik.frontend.redirect: "false" traefik.frontend.rule: "Host: notification.com" links: - unifiedpushDB:unifiedpush - keycloakServer:keycloak ports: - 9999:8080 unifiedpushDB: image: postgres:9.6 networks: - network environment: POSTGRES_USER: ${POSTGRES_USER} POSTGRES_PASSWORD: ${POSTGRES_PASSWORD} POSTGRES_DB: ${POSTGRES_DATABASE} healthcheck: test: ["CMD-SHELL", "pg_isready -U postgres"] timeout: 20s retries: 10 keycloakServer: networks: - network image: docker.io/jboss/keycloak:4.1.0.Final command: "-b 0.0.0.0 -Dkeycloak.import=/ups-keycloak-config/ups-realm-sample.json" volumes: - ./keycloak-realm:/ups-keycloak-config:z environment: KEYCLOAK_USER: ${KEYCLOAK_USER} KEYCLOAK_PASSWORD: ${KEYCLOAK_PASSWORD} networks: network: external: name: appliance