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2_application_image.md

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Create the application's image

  • We will use 2 images to package the application
    • one image for the database
    • one image for the application

The application

  • There are several possibilities to create the image
    • extend an official Linux distribution image (Ubuntu, CentOS, ...) and install Node.js runtime
    • use the official Node.js image (https://hub.docker.com/_/node/)

We'll go for the second option as it offers an optimized image.

Database

Dockerfile

We'll use the following Dockerfile to build our application's image:

# Use node 4.4.5 LTS
FROM node:4.4.5
ENV LAST_UPDATED 20160605T165400

# Copy source code
COPY . /app

# Change working directory
WORKDIR /app

# Install dependencies
RUN npm install

# Expose API port to the outside
EXPOSE 80

# Launch application
CMD ["npm","start"]

Basically, the Dockerfile performs the following actions

  • use the official node:4.4.5 (LTS) image
  • copy application sources
  • install dependencies
  • expose port to the outside from the Docker host
  • define default command ran when instantiating the image

Image creation

  • Create the image docker build -t message-app .

  • List all images available on the Docker host docker images

Let's instantiate a container

$ docker run message-app
npm info it worked if it ends with ok
...
error: A hook (`orm`) failed to load!
error: Error: Failed to connect to MongoDB.  Are you sure your configured Mongo instance is running?
 Error details:
{ [MongoError: connect ECONNREFUSED 127.0.0.1:27017]
  name: 'MongoError',
  message: 'connect ECONNREFUSED 127.0.0.1:27017' }]
  originalError:
   { [MongoError: connect ECONNREFUSED 127.0.0.1:27017]
     name: 'MongoError',
     message: 'connect ECONNREFUSED 127.0.0.1:27017' } }

The application cannot connect to a database as we did not provide external db information nor container running mongodb