Docker Compose: Exposing Environment Variables to linked service

Question

I'm playing around with Docker Compose to make a container running a Rails App with a Oracle backend.

This works great until my Docker container tries to install the ruby-oci8 gem, which looks for some oracle specific environment variables.

These variables are exposed in the oracle container's Dockerfile:

RUN 'export ORACLE_HOME=/u01/app/oracle/product/11.2.0/xe'

The question is, how do I expose this environment variable on the oracle container to the web container?

DVG · Accepted Answer · 2015-04-15 20:06:52Z

The problem here is that the web container needs an oracle client to talk to the oracle database in the db container. This took a bit of doing, since oracle does not provide a client on apt-get, so I downloaded the RPMs from Oracle's site, put them in vendor/ and did the following in the dockerfile:

FROM ruby:2.2.2

RUN apt-get update && apt-get install -y build-essential
RUN apt-get install -y libxml2-dev libxslt1-dev
RUN apt-get install -y libqt4-webkit libqt4-dev xvfb
RUN apt-get install -y nodejs
# Needed for Oracle Client
RUN apt-get install -y libaio1 libaio-dev

# Required for Oracle RPMs
RUN apt-get install -y alien

# Set up app at /code
ENV APP_HOME /code
RUN mkdir $APP_HOME
WORKDIR $APP_HOME

ADD vendor/*.rpm $APP_HOME/vendor/
# Oracle Client Environment Variables
ENV ORACLE_HOME /usr/lib/oracle/12.1/client64
ENV LD_LIBRARY_PATH $ORACLE_HOME/lib/:$LD_LIBRARY_PATH
ENV NLS_LANG American_America.UTF8
ENV PATH $ORACLE_HOME/bin:$PATH
# Set this so you don't have to type it in with rake db:create
ENV ORACLE_SYSTEM_PASSWORD myoraclecontainerspassword

# Install Oracle Client
RUN alien -i vendor/oracle-instantclient.rpm && alien -i vendor/oracle-sdk.rpm && alien -i vendor/oracle-sqlplus.rpm

ADD Gemfile* $APP_HOME/
RUN bundle install

ADD . $APP_HOME/

christian · Accepted Answer · 2015-04-12 05:47:04Z

0

Could you add a line

ENV ORACLE_HOME=/u01/app/oracle/product/11.2.0/xe

to your web Dockerfile?

There is some discussion to support environment variables in docker-compose, but its around supporting variables from your host system in docker-compose.yml.

Nothing that would help your question is currently discussed.

https://github.com/docker/compose/issues/495

answered Apr 12, 2015 at 5:47

christian

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1 Comment

DVG Over a year ago

This touches on what the issue actually was, which is the ruby-oci8 gem requires access to an oracle client, which is not provided by the oracle xe container. I had to add some lines to the docker file to install the client from RPMs and then add the necessary environment variables for that install.

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