Starting Postgres in Docker Container

Question

For testing, I'm trying to setup Postgres inside of a docker container so that our python app can run it's test suite against it.

Here's my Dockerfile:

# Set the base image to Ubuntu
FROM ubuntu:16.04

# Update the default application repository sources list
RUN apt-get update && apt-get install -y \
  python2.7 \
  python-pip \
  python-dev \
  build-essential \
  libpq-dev \
  libsasl2-dev \
  libffi-dev \
  postgresql

USER postgres
RUN /etc/init.d/postgresql start && \
  psql -c "CREATE USER circle WITH SUPERUSER PASSWORD 'circle';" && \
  createdb -O darwin circle_test
USER root
RUN service postgresql stop && service postgresql start

# Upgrade pip
RUN pip install --upgrade pip

COPY . /app
WORKDIR /app

RUN pip install -r requirements.txt

EXPOSE 5000

# Set the container entrypoint
ENTRYPOINT ["gunicorn", "--config", "/app/config/gunicorn.py", "--access-logfile", "-", "--error-logfile", "-", "app:app"]

When I run:

docker run --entrypoint python darwin:latest -m unittest discover -v -s test

I'm getting:

could not connect to server: Connection refused
        Is the server running on host "localhost" (127.0.0.1) and accepting
        TCP/IP connections on port 5432?

The only way I can get it to work is if I ssh into the container, restart postgres and run the test suite directly.

Is there something I'm missing here?

Answer 1

In a Dockerfile you have

• a configuration phase, the RUN directive (and some others)

• the process(es) you start, that you put in either

CMD

or

ENTRYPOINT

see the docs

https://docs.docker.com/engine/reference/builder/#cmd

and

https://docs.docker.com/engine/reference/builder/#entrypoint

when a container has completed what it has to do in this start phase, it dies.

This is why the reference Dockerfile for PostgreSQL, at

https://github.com/docker-library/postgres/blob/3d4e5e9f64124b72aa80f80e2635aff0545988c6/9.6/Dockerfile

ends with

CMD ["postgres"]

if you want to start several processes, see supervisord or such tool (s6, daemontools...)

https://docs.docker.com/engine/admin/using_supervisord/