How to restore a Postgresdump while building a Docker image?

问题

I'm trying to avoid touching a shared dev database in my workflow; to make this easier, I want to have Docker image definitions on my disk for the schemas I need. I'm stuck however at making a Dockerfile that will create a Postgres image with the dump already restored. My problem is that while the Docker image is being built, the Postgres server isn't running.

While messing around in the container in a shell, I tried starting the container manually, but I'm not sure what the proper way to do so. /docker-entrypoint.sh doesn't seem to do anything, and I can't figure out how to "correctly" start the server.

So what I need to do is:

start with "FROM postgres"
copy the dump file into the container
start the PG server
run psql to restore the dump file
kill the PG server

(Steps I don't know are in italics, the rest is easy.)

What I'd like to avoid is:

Running the restore manually into an existing container, the whole idea is to be able to switch between different databases without having to touch the application config.
Saving the restored image, I'd like to be able to rebuild the image for a database easily with a different dump. (Also it doesn't feel very Docker to have unrepeatable image builds.)

回答1:

This can be done with the following Dockerfile by providing an example.pg dump file:

FROM postgres:9.6.16-alpine

LABEL maintainer="lu@cobrainer.com"
LABEL org="Cobrainer GmbH"

ARG PG_POSTGRES_PWD=postgres
ARG DBUSER=someuser
ARG DBUSER_PWD=P@ssw0rd
ARG DBNAME=sampledb
ARG DB_DUMP_FILE=example.pg

ENV POSTGRES_DB launchpad
ENV POSTGRES_USER postgres
ENV POSTGRES_PASSWORD ${PG_POSTGRES_PWD}
ENV PGDATA /pgdata

COPY wait-for-pg-isready.sh /tmp/wait-for-pg-isready.sh
COPY ${DB_DUMP_FILE} /tmp/pgdump.pg

RUN set -e && \
    nohup bash -c "docker-entrypoint.sh postgres &" && \
    /tmp/wait-for-pg-isready.sh && \
    psql -U postgres -c "CREATE USER ${DBUSER} WITH SUPERUSER CREATEDB CREATEROLE ENCRYPTED PASSWORD '${DBUSER_PWD}';" && \
    psql -U ${DBUSER} -d ${POSTGRES_DB} -c "CREATE DATABASE ${DBNAME} TEMPLATE template0;" && \
    pg_restore -v --no-owner --role=${DBUSER} --exit-on-error -U ${DBUSER} -d ${DBNAME} /tmp/pgdump.pg && \
    psql -U postgres -c "ALTER USER ${DBUSER} WITH NOSUPERUSER;" && \
    rm -rf /tmp/pgdump.pg

HEALTHCHECK --interval=30s --timeout=30s --start-period=5s --retries=3 \
  CMD pg_isready -U postgres -d launchpad

where the wait-for-pg-isready.sh is:

#!/bin/bash
set -e

get_non_lo_ip() {
  local _ip _non_lo_ip _line _nl=$'\n'
  while IFS=$': \t' read -a _line ;do
    [ -z "${_line%inet}" ] &&
        _ip=${_line[${#_line[1]}>4?1:2]} &&
        [ "${_ip#127.0.0.1}" ] && _non_lo_ip=$_ip
    done< <(LANG=C /sbin/ifconfig)
  printf ${1+-v} $1 "%s${_nl:0:$[${#1}>0?0:1]}" $_non_lo_ip
}

get_non_lo_ip NON_LO_IP
until pg_isready -h $NON_LO_IP -U "postgres" -d "launchpad"; do
  >&2 echo "Postgres is not ready - sleeping..."
  sleep 4
done

>&2 echo "Postgres is up - you can execute commands now"

For the two "unsure steps":

start the PG server

nohup bash -c "docker-entrypoint.sh postgres &" can take care of it

kill the PG server

It's not really necessary

The above scripts together with a more detailed README are available at https://github.com/cobrainer/pg-docker-with-restored-db

回答2:

You can utilise volumes.

The postgres image has an enviroment variable you could set with: PGDATA

See docs: https://hub.docker.com/_/postgres/

You could then point a pre created volume with the exact db data that you require and pass this as an argument to the image. https://docs.docker.com/storage/volumes/#start-a-container-with-a-volume

Alternate solution can also be found here: Starting and populating a Postgres container in Docker

来源：https://stackoverflow.com/questions/48643774/how-to-restore-a-postgresdump-while-building-a-docker-image

标签

postgresql

Docker

database-backups