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Run Several Processes in Docker Container

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Run Several Processes in Docker Container

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What I like the most about Docker project is new opportunity to deploy and distribute software. Many times I’ve been to situation when I wanted to play with some software and get exited about, but after I read installation manual my excitement totally gone. Non trivial applications, requires quite a lot dependencies: runtimes, libraries, databases.

With docker, the installation instruction got reduced to something like:

$ docker pull vendor/package
$ docker run vendor/package

Simply like that, forget about missing Java Runtime on your server. It suits perfectly for TCP/HTTP applications.

Being messing around Seismo project I realized, I want to go exactly same way. Since it has few dependencies now, MongoDB and NodeJS – it should be easier to anyone to try it, even if they do not use that setup. I was happy to see, that GitHub currently offers great support for Docker. Namely, if you have repo with Dockerfile inside, each time you push the code, docker image got rebuild and pushed to publicindex.

I’ve created Dockerfile that would build up image, ready to have Seismo run inside.

FROM ubuntu:latest

# Git
RUN apt-get install -y git

# MongoDB
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
RUN dpkg-divert --local --rename --add /sbin/initctl
RUN ln -s /bin/true /sbin/initctl
RUN apt-get update
RUN apt-get install mongodb-10gen
RUN mkdir -p /data/db

# NodeJS
RUN apt-get update --fix-missing && apt-get upgrade -y
RUN apt-get install -y wget curl build-essential patch git-core openssl libssl-dev unzip ca-certificates
RUN curl http://nodejs.org/dist/v0.10.22/node-v0.10.22-linux-x64.tar.gz | tar xzvf - --strip-components=1 -C "/usr"
RUN apt-get clean && rm -rf /var/cache/apt/archives/* /var/lib/apt/lists/*

# Seismo
RUN git clone https://github.com/seismolabs/seismo.git /seismo
RUN cd /seismo; npm install
ENV PORT 8080
EXPOSE 8080

WORKDIR /seismo
ENTRYPOINT ["./bin/run.sh"]

It’s based on latest Ubuntu server, installs Git, MongoDB and NodeJS runtime and clones Seismo itself inside image.

But, I’ve met a problem to start few processes inside the container. Since I need both MongoDB for storage and NodeJS for API server, it’s required both be running inside one container. If shell script just starts one,mongod for example, node app.js is not executed.

I was a little worried, thinking it’s not possible to run more that one process inside container.

But solution was found. I’ve created another shell script that starts mongod as background process and starts node after.

#!/bin/bash
mongod & node ./source/server.js

That worked as charm.

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Published at DZone with permission of Alexander Beletsky, DZone MVB. See the original article here.

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