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Build your own container


Here I will be using the node container as my base image and will build a new container that will host my custom webhook application

First create a webhook application using node.js on the host machine
  • Install node.js
  • Initiate a project with npm init
npm init should prompt some project related questions.
Install the required dependencies for the project, for our example we need express and body-parser

Update index.js to create a webhook 
Run the project as node index.js
Test that webhook from the browser.

We should get a response back.

Now lets convert this web application into a docker container and execute the same from docker.
To get started, create a file in the same folder where we have created the node project, call it as Dockerfile
Update the contents of the file as below:

FROM node:latest
We are pulling the node image tagged as latest from the docker hub

WORKDIR /app
Create a working directory called app in the container root

COPY . .
This will copy all the contents of the host current directory to /app directory in the container

ENV PORT=1337
This will create an environment variable PORT and set the value to 1337

RUN npm install
This will install all the required dependent node libraries

EXPOSE $PORT
This will expose port 1337 on the container for communication

ENTRY ["node", "index.js"]
This is an array and will have the entry point for the application. Here the container will run "node index.js" to start the application

Build the docker image as docker build -t srinu259/node:latest .

docker build as the name suggest is for building your own images
-t is to tag the image

Example of how tag works:
Here we are building an image with repository srinu259/webhook. This image is tagged with version 1.0


We can verify that the image is successfully downloaded by running docker images

Run the container as docker run -d -p 2337:1337 srinu259/node

-d indicates to run the container in the detached mode
-p is for port mapping. 2337 is the host port mapped to 1337 container port
srinu259/node is our image

Test the webhook from the browser

That's it, the webhook application is now running inside a container!


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