Docker Compose: depends

depends_on

depends_on expresses startup and shutdown dependencies between services.

Short syntax

The short syntax variant only specifies service names of the dependencies. Service dependencies cause the following behaviors:

Compose creates services in dependency order. In the following example, db and redis are created before web.
Compose removes services in dependency order. In the following example, web is removed before db and redis.

Simple example:

services:
  web:
    build: .
    depends_on:
      - db
      - redis
  redis:
    image: redis
  db:
    image: postgres

Compose guarantees dependency services have been started before starting a dependent service. Compose waits for dependency services to be "ready" before starting a dependent service.

Copied from: https://docs.docker.com/compose/compose-file/05-services/#depends_on