Docker wait for postgresql to be running

Question

I am using postgresql with django in my project. I've got them in different containers and the problem is that i need to wait for postgres before running django. At this time i am doing it with sleep 5 in command.sh file for django container. I also found that netcat can do the trick but I would prefer way without additional packages. curl and wget can't do this because they do not support postgres protocol. Is there a way to do it?

Answer 1

I've spent some hours investigating this problem and I got a solution. Docker depends_on just consider service startup to run another service. Than it happens because as soon as db is started, service-app tries to connect to ur db, but it's not ready to receive connections. So you can check db health status in app service to wait for connection. Here is my solution, it solved my problem. :) Important: I'm using docker-compose version 2.1.

version: '2.1'

services:
  my-app:
    build: .
    command: su -c "python manage.py runserver 0.0.0.0:8000"
    ports:
       - "8000:8000"
    depends_on:
      db:
        condition: service_healthy
    links:
      - db
    volumes:
      - .:/app_directory

  db:
    image: postgres:10.5
    ports:
      - "5432:5432"
    volumes:
      - database:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 5s
      timeout: 5s
      retries: 5

volumes:
  database:

In this case it's not necessary to create a .sh file. I hope it helps you guys ;) cya