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?

your RUN service postgresql stop && service postgresql start is in a RUN, not in a CMD or ENTRYPOINT, so it is "forgotten" when the container starts — user2915097
– user2915097, Commented Apr 19, 2017 at 18:03
have a look at the reference PostgreSQL Dockerfile at github.com/docker-library/postgres/blob/… — user2915097
– user2915097, Commented Apr 19, 2017 at 18:09
I changed RUN to CMD but it still exhibits the same error. — doremi
– doremi, Commented Apr 19, 2017 at 18:17
you can have only one CMD in a Dockerfile, the latest is used, see the links in my answer, and the supervisor one — user2915097
– user2915097, Commented Apr 19, 2017 at 18:19

user2915097 · Accepted Answer · 2017-04-19 18:18:22Z

2

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/

answered Apr 19, 2017 at 18:18

user2915097

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2 Comments

doremi Over a year ago

That makes a lot of sense. Could I exchange my final ENTRYPOINT with a bash script that both starts PG and gunicorn?

user2915097 Over a year ago

yes that is an option, read stackoverflow.com/questions/21553353/… you can see the entrypoint as a verb, the CMD as an argument, see hub.docker.com/r/k3ck3c/nethogs if you just run it, it starts monitoring the wlan0 device, if you add wlp2s0 (or eth1 or any) at the end of you docker run... it monitors wlp2s0 (or eth1 or any)

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