Simple node.js workflow with docker - node.js

Question

I'm using Docker on windows for development purposes and i'm trying to create a simple workflow for a node.js project.
I followed this tutorial https://nodejs.org/en/docs/guides/nodejs-docker-webapp/ so my Dockerfile looks like this
FROM node:boron
# Create app directory
WORKDIR /usr/src/app
# Install app dependencies
COPY package.json .
# For npm#5 or later, copy package-lock.json as well
# COPY package.json package-lock.json ./
RUN npm install
# Bundle app source
COPY . .
EXPOSE 8080
CMD [ "npm", "start" ]
My "workflow" for each change would look like this
FIRST BUILD
docker build -t thomas/myApp DockerProjects/myApp ; docker run --name app -p 49160:8080 -d thomas/myApp
AFTER EACH CHANGE
docker build -t thomas/myApp DockerProjects/myApp ; docker stop app ; docker rm app ; docker run --name app -p 49160:8080 -d thomas/myApp
I don't want to have hundreds of containers after each change in the project, that's why i'm deleting it before creating another one.
I see several problems:
Each time there is a change and a new image is build, a new <none>:<none> image is created. These images have the same weight as the original one. How can I avoid that ?
Can I use nodemon somehow ?
Can I launch this process automatically each time I change something in the code ?
Docker is quite new for me and i'm still experimenting with it.
Thanks

Answer 1

You can use nodemon in your project to restart your app automatically while your source code directory would be mounted on a volume.
For instance, with this directory structure (which is using Grunt from package.json to run nodemon) :
app/
├── Dockerfile
├── package.json
├── Gruntfile.js
├── src/
│ └── app.js
└── docker-compose.yml
You can use docker-compose which is a tool used to run multiple container. This can be useful if you want to add a database container your app would talk to or any additionnal services interacting with your app.
The following docker-compose config will mount src folder on /usr/src/app/src on the container. With nodemon looking for changes inside src, you will be able to make changes on your machine that will restart the app on the container automatically
To use this you would do :
cd app
docker-compose up
The command above with build the image from dockerfile and start the containers defined in docker-compose.yml.
docker-compose.yml :
version: '2'
services:
your-app:
build: .
ports:
- "8080:8080"
restart: always
container_name: app_container
volumes:
- ./src:/usr/src/app/src
environment:
- SERVER_PORT=8080
Dockerfile :
FROM node:latest
RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app
COPY package.json .
COPY Gruntfile.js .
RUN npm install
CMD ["npm","start"]
Gruntfile.js :
var path = require('path');
module.exports = function (grunt) {
grunt.initConfig({
pkg: grunt.file.readJSON('package.json'),
concurrent: {
dev: {
tasks: ['nodemon'],
options: {
logConcurrentOutput: true
}
}
},
nodemon: {
dev: {
script: 'src/app.js',
options: {
ignore: [
'node_modules/**'
],
ext: 'js'
}
}
},
clean: {}
});
grunt.loadNpmTasks('grunt-concurrent');
grunt.loadNpmTasks('grunt-nodemon');
grunt.registerTask('default', ['concurrent']);
};
package.json :
{
"name": "your-app",
"version": "1.0.0",
"description": "service",
"scripts": {
"start": "grunt"
},
"author": "someone",
"license": "MIT",
"dependencies": {
"express": "^4.14.0"
},
"devDependencies": {
"grunt": "1.x.x",
"grunt-cli": "1.x.x",
"grunt-concurrent": "2.x.x",
"grunt-nodemon": "0.4.x"
}
}
Sample app.js :
'use strict';
const express = require('express');
const port = process.env.SERVER_PORT;
var app = express();
app.get('/', function(req, res) {
res.send('Hello World');
});
app.listen(port, function() {
console.log('listening on port ' + port);
});
To rebuild the image, you would perform docker-compose build

Answer 2

Each time there is a change and a new image is build, a new <none>:<none> image is created. These images have the same weight as the original one. How can I avoid that ?
You can't. This : iamge is your previous image which was replaced by your new image. So just delete it: docker image prune
Can I use nodemon somehow?
I'm not familiar with that, but it looks like it only restarts your server, but doesnt't do a npm install.
Can I launch this process automatically each time I change something in the code?
I would use Jenkins and automatically build your new Docker image on each git commit.