Race Conditions - Wait For Database

You may run into a situation where your app attempts to access the database before it is ready to accept connections, resulting in a failure. It this case it is necessary to wait for the database to come online fully before continuing.

We suggest dockerize: https://github.com/jwilder/dockerize

In this example PostgreSQL  is our database. Our first run step downloads the newest Dockerize binary and the next run step `Wait for db` waits on the port for our database until it receives a response, with a 1 minute timeout.

version: 2.0

jobs:

  build:

    docker:

      - image: your/image_for_primary_container

      - image: postgres:9.6.2-alpine

    environment:

      POSTGRES_USER: your_postgres_user

      POSTGRES_DB: your_postgres_test

    workDir: /your/workdir

    steps:

      - checkout

      - run:

        name: install dockerize

        command: wget https://github.com/jwilder/dockerize/releases/download/$DOCKERIZE_VERSION/dockerize-linux-amd64-$DOCKERIZE_VERSION.tar.gz && sudo tar -C /usr/local/bin -xzvf dockerize-linux-amd64-$DOCKERIZE_VERSION.tar.gz && rm dockerize-linux-amd64-$DOCKERIZE_VERSION.tar.gz

        environment:

          DOCKERIZE_VERSION: v0.3.0

      - run:

        name: Wait for db

        command: dockerize -wait tcp://localhost:5432 -timeout 1m

You can apply the same principle for MySQL:

dockerize -wait tcp://localhost:3306 -timeout 1m

Redis:

dockerize -wait tcp://localhost:6379 -timeout 1m

and other services such as web servers

dockerize -wait http://localhost:80 -timeout 1m