Node.js Koa app and CouchDB in single container

Question

I have a koa.js app which I want to run in a docker container. This loa app requires couchdb to run, which I want to ship in the same container. I know this is not best practise but it is indeed the best way for my users to get started.

Dockerfile:

# DOCKER-VERSION 1.2.0
FROM centos:centos6

# Enable EPEL for CouchDB and Node.js
RUN yum -y update; yum clean all
RUN yum -y install epel-release; yum clean all
RUN yum -y install tar

# Install Node.js and CouchDB
RUN yum -y install couchdb; yum clean all
RUN service couchdb start
RUN yum install -y nodejs
RUN yum install -y npm

# Bundle app source

ADD . .

# Install app dependencies

RUN npm install
RUN npm install -g n
RUN n 0.11.12

# Expose port and run
EXPOSE 8080
CMD ["npm", "start"]

which works fine, app gets launched but it can't connect to the couchdb. throwing in a

RUN service couchdb start

response with OK, so it seems to work, but

curl -X GET 127.0.0.1:5984

response with

curl: (7) couldn't connect to host

same for the koa.js app:

error: error stack=Error: connect ECONNREFUSED
at exports._errnoException (util.js:745:11)
at Object.afterConnect [as oncomplete] (net.js:995:19), code=ECONNREFUSED, errno=ECONNREFUSED, syscall=connect

someone knows what I am missing or what I am doing wrong?

Answer 1

The only command that is run when you start this image is what is in the CMD line. Every line before that creates a read only, non-running image. Thus, the line RUN service couchdb start will start the service for an instant, until it is marked as successful, then docker will stop that image, save it, and move on to the next line. The "running" state of the service doesn't persist.

It is a common misconception, and one I fell into when I started.

The three options, top being fastest yet most hacky, and last being most work but most proper:

1. Put service couchdb start && npm start as your CMD line.
2. Create a startup.sh script, do all the "running" that you need to do in there, and call that as your CMD line
3. Use a service designed to do this stuff for you, supervisord is often recommended.

This is a common issue, so if you have a read through google results searching for "start service in docker" you'll see more information around the subject.