How to run the python application and postgres in one docker container? - postgresql

Question

I have a python application that interacts with the postgresql database and i need to run it all in one docker container.
I get a connection error when running the container:
...
File "/usr/lib/python3.6/asyncio/tasks.py", line 358, in wait_for
return fut.result()
File "/usr/lib/python3.6/asyncio/base_events.py", line 787, in create_connection
', '.join(str(exc) for exc in exceptions)))
OSError: Multiple exceptions: [Errno 111] Connect call failed ('::1', 5432), [Errno 111] Connect call failed ('127.0.0.1', 5432)
My Dockerfile:
FROM postgres:10.0-alpine
RUN apk add --update --no-cache g++ alpine-sdk
RUN apk --no-cache add python3-dev
RUN apk add --no-cache python3 && \
python3 -m ensurepip && \
rm -r /usr/lib/python*/ensurepip && \
pip3 install --upgrade pip setuptools && \
if [ ! -e /usr/bin/pip ]; then ln -s pip3 /usr/bin/pip ; fi && \
if [[ ! -e /usr/bin/python ]]; then ln -sf /usr/bin/python3 /usr/bin/python; fi && \
rm -r /root/.cache
ADD app /app/
RUN chmod -R 777 /app
WORKDIR /app
ADD requirements.txt requirements.txt
RUN pip3 install -r requirements.txt
USER postgres
RUN chmod 0700 /var/lib/postgresql/data &&\
initdb /var/lib/postgresql/data &&\
echo "host all all 0.0.0.0/0 md5" >> /var/lib/postgresql/data/pg_hba.conf &&\
echo "listen_addresses='*'" >> /var/lib/postgresql/data/postgresql.conf &&\
pg_ctl start &&\
psql --command "ALTER USER postgres WITH ENCRYPTED PASSWORD 'postgres';"
EXPOSE 5432
EXPOSE 80
CMD ["python3", "main.py"]

Answer 1

Although this is not recommended, it's doable. The problem is pg_ctl in RUN instruction is executed at build time, not in the container. You need to run it with CMD.
You can have a script like
pg_ctl start
psql --command "ALTER USER postgres WITH ENCRYPTED PASSWORD 'postgres';"
python3 main.py
COPY the script in the image and at the end of the dockerfile, `CMD ["./script.sh"]

Answer 2

#Anton, it is not recommended to run multiple processes inside a docker container. Have a look at this link https://docs.docker.com/config/containers/multi-service_container/ it will explain more and demonstrate a manner to accomplish this. You probably are aware, but your container will be running the postgresql instance and have the data in it, so if you ever re-create the container, you will lose any data in that container.