Dockerfile

FROM yammer/ruby:2.2.0
MAINTAINER Brian Morton "brian@mmm.hm"

# Install package dependencies for pg gem
RUN locale-gen en_US.UTF-8
RUN curl https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add -
RUN echo "deb http://apt.postgresql.org/pub/repos/apt/ precise-pgdg main" >> /etc/apt/sources.list
RUN apt-get -y update
RUN apt-get -y install postgresql-client libpq-dev

# Install javascript runtime
RUN apt-get -y install nodejs

# Install etcd client
ENV ETCD_VERSION v2.0.0-rc.1
ADD https://github.com/coreos/etcd/releases/download/${ETCD_VERSION}/etcd-${ETCD_VERSION}-linux-amd64.tar.gz /tmp/
RUN tar -xvzf /tmp/etcd-${ETCD_VERSION}-linux-amd64.tar.gz -C /tmp
RUN mv /tmp/etcd-${ETCD_VERSION}-linux-amd64/etcdctl /bin/etcdctl
RUN rm -rf /tmp/*

# Add and install gem dependencies
ADD Gemfile       /app/Gemfile
ADD Gemfile.lock  /app/Gemfile.lock
RUN bash -l -c "cd /app && bundle install --deployment --without development test"

ADD . /app

# Use a fake DATABASE_URL for precompiling assets to trick Rails
# since it requires a string, but never connects during compilation
RUN bash -l -c "cd /app && RAILS_GROUPS=assets DATABASE_URL=postgresql://user:pass@127.0.0.1/dbname bundle exec rake assets:precompile"

WORKDIR /app
EXPOSE 3000
ENTRYPOINT ["/app/bin/env"]
CMD ["bundle exec puma -t ${PUMA_MIN_THREADS:-8}:${PUMA_MAX_THREADS:-12} -w ${PUMA_WORKERS:-1} -p 3000 -e ${RACK_ENV:-development} --preload"]

env.sh

#!/bin/bash -l
export DOCKER_HOST_IP=`/sbin/ip route | awk '/default/ { print $3 }'`
export ETCDCTL_PEERS="http://${DOCKER_HOST_IP}:4001/"

if [ -z "$DATABASE_URL" ]; then
  echo "Setting DATABASE_URL via etcd..."
  export DATABASE_URL=`etcdctl get /carousel/database_url`
fi

if [ -z "$SECRET_KEY_BASE" ]; then
  echo "Setting SECRET_KEY_BASE via etcd..."
  export SECRET_KEY_BASE=`etcdctl get /carousel/secret_key_base`
fi

if [ -z "$RACK_ENV" ]; then
  echo "Setting RACK_ENV via etcd..."
  export RACK_ENV=`etcdctl get /carousel/rack_env`
fi

if [ -z "$PUMA_WORKERS" ]; then
  echo "Setting PUMA_WORKERS via etcd..."
  export PUMA_WORKERS=`etcdctl get /carousel/puma_workers`
fi

# Execute the commands passed to this script
$@