Docker - Node.js + MongoDB - "Error: failed to connect to [localhost:27017]" - node.js

Question

I am trying to create a container for my Node app. This app uses MongoDB to ensure some data persistence.
So I created this Dockerfile:
FROM ubuntu:latest
# --- Installing MongoDB
# Add 10gen official apt source to the sources list
RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 7F0CEB10
RUN echo 'deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen' | tee /etc/apt/sources.list.d/10gen.list
# Hack for initctl not being available in Ubuntu
RUN dpkg-divert --local --rename --add /sbin/initctl
RUN ln -s /bin/true /sbin/initctl
# Install MongoDB
RUN apt-get update
RUN apt-get install mongodb-10gen
# Create the MongoDB data directory
RUN mkdir -p /data/db
CMD ["usr/bin/mongod", "--smallfiles"]
# --- Installing Node.js
RUN apt-get update
RUN apt-get install -y python-software-properties python python-setuptools ruby rubygems
RUN add-apt-repository ppa:chris-lea/node.js
# Fixing broken dependencies ("nodejs : Depends: rlwrap but it is not installable"):
RUN echo "deb http://archive.ubuntu.com/ubuntu precise universe" >> /etc/apt/sources.list
RUN echo "deb http://us.archive.ubuntu.com/ubuntu/ precise universe" >> /etc/apt/sources.list
RUN apt-get update
RUN apt-get install -y nodejs
# Removed unnecessary packages
RUN apt-get purge -y python-software-properties python python-setuptools ruby rubygems
RUN apt-get autoremove -y
# Clear package repository cache
RUN apt-get clean all
# --- Bundle app source
ADD . /src
# Install app dependencies
RUN cd /src; npm install
EXPOSE 8080
CMD ["node", "/src/start.js"]
Then I build and launch the whole thing through:
$ sudo docker build -t aldream/myApp
$ sudo docker run aldream/myApp
But the machine displays the following error:
[error] Error: failed to connect to [localhost:27017]
Any idea what I am doing wrong? Thanks!

Answer 1

Do you actually docker run aldream/myApp? In that case, with the Dockerfile that you provided, it should run MongODB, but not your app. Is there another CMD command, or another Dockerfile, or are you running docker run aldream/myApp <somethingelse>? In the latter case, it will override the CMD directive and MongoDB will not be started.
If you want to run multiple processes in a single container, you need a process manager (like e.g. Supervisor, god, monit) or start the processes in the background from a script; e.g.:
#!/bin/sh
mongod &
node myapp.js &
wait

Answer 2

Redefine your Dockerfile as follows;
COPY supervisord.conf /etc/supervisor/conf.d/supervisord.conf
# ENTRYPOINT should not be used as it wont allow commands from run to be executed
# Define mountable directories.
VOLUME ["/data/db"]
# Expose ports.
# - 27017: process
# - 28017: http
# - 9191: web app
EXPOSE 27017 28017 9191
ENTRYPOINT ["/usr/bin/supervisord"]
supervisord.conf will contain the following;
[supervisord]
nodaemon=true
[program:mongod]
command=/usr/bin/mongod --smallfiles
stdout_logfile=/var/log/supervisor/%(program_name)s.log
stderr_logfile=/var/log/supervisor/%(program_name)s.log
autorestart=true
[program:nodejs]
command=nodejs /opt/app/server/server.js