{"id":572,"date":"2018-11-14T07:03:00","date_gmt":"2018-11-14T07:03:00","guid":{"rendered":"http:\/\/droitthemes.com\/wp\/saasland\/2018\/11\/14\/why-i-say-old-chap-that-is-spiffing-jolly-good-copy\/"},"modified":"2020-09-04T18:53:55","modified_gmt":"2020-09-04T18:53:55","slug":"how-to-build-a-node-js-application-with-docker","status":"publish","type":"post","link":"https:\/\/www.championjoy.com\/?p=572","title":{"rendered":"How To Build a Node.js Application with Docker"},"content":{"rendered":"\n

<\/a><\/p>\n\n\n\n

Dockerizing a Node.js web app<\/h1>\n\n\n\n

The goal of this example is to show you how to get a Node.js application into a Docker container. The guide is intended for development, and not<\/em> for a production deployment. The guide also assumes you have a working Docker installation<\/a> and a basic understanding of how a Node.js application is structured.<\/p>\n\n\n\n

In the first part of this guide we will create a simple web application in Node.js, then we will build a Docker image for that application, and lastly we will instantiate a container from that image.<\/p>\n\n\n\n

Docker allows you to package an application with its environment and all of its dependencies into a “box”, called a container. Usually, a container consists of an application running in a stripped-to-basics version of a Linux operating system. An image is the blueprint for a container, a container is a running instance of an image.<\/p>\n\n\n\n

Create the Node.js app<\/h2>\n\n\n\n

First, create a new directory where all the files would live. In this directory create a package.json<\/code> file that describes your app and its dependencies:<\/p>\n\n\n\n

{\n  \"name\": \"docker_web_app\",\n  \"version\": \"1.0.0\",\n  \"description\": \"Node.js on Docker\",\n  \"author\": \"First Last <first.last@example.com>\",\n  \"main\": \"server.js\",\n  \"scripts\": {\n    \"start\": \"node server.js\"\n  },\n  \"dependencies\": {\n    \"express\": \"^4.16.1\"\n  }\n}<\/code><\/pre>\n\n\n\n
With your new package.json<\/code> file, run npm install<\/code>. If you are using npm<\/code> version 5 or later, this will generate a package-lock.json<\/code> file which will be copied to your Docker image.<\/p>\n\n\n\n
Then, create a server.js<\/code> file that defines a web app using the Express.js<\/a> framework:<\/p>\n\n\n\n
'use strict';\n\nconst express = require('express');\n\n\/\/ Constants\nconst PORT = 8080;\nconst HOST = '0.0.0.0';\n\n\/\/ App\nconst app = express();\napp.get('\/', (req, res) => {\n  res.send('Hello World');\n});\n\napp.listen(PORT, HOST);\nconsole.log(`Running on http:\/\/${HOST}:${PORT}`);<\/code><\/pre>\n\n\n\n
In the next steps, we’ll look at how you can run this app inside a Docker container using the official Docker image. First, you’ll need to build a Docker image of your app.<\/p>\n\n\n\n
Creating a Dockerfile<\/h2>\n\n\n\n
Create an empty file called Dockerfile<\/code>:<\/p>\n\n\n\n
touch Dockerfile<\/code><\/pre>\n\n\n\n
Open the Dockerfile<\/code> in your favorite text editor<\/p>\n\n\n\n
The first thing we need to do is define from what image we want to build from. Here we will use the latest LTS (long term support) version 12<\/code> of node<\/code> available from the Docker Hub<\/a>:<\/p>\n\n\n\n
FROM node:12<\/code><\/pre>\n\n\n\n
Next we create a directory to hold the application code inside the image, this will be the working directory for your application:<\/p>\n\n\n\n
# Create app directory\nWORKDIR \/usr\/src\/app<\/code><\/pre>\n\n\n\n
This image comes with Node.js and NPM already installed so the next thing we need to do is to install your app dependencies using the npm<\/code> binary. Please note that if you are using npm<\/code> version 4 or earlier a package-lock.json<\/code> file will not<\/em> be generated.<\/p>\n\n\n\n
# Install app dependencies\n# A wildcard is used to ensure both package.json AND package-lock.json are copied\n# where available (npm@5+)\nCOPY package*.json .\/\n\nRUN npm install\n# If you are building your code for production\n# RUN npm ci --only=production<\/code><\/pre>\n\n\n\n
Note that, rather than copying the entire working directory, we are only copying the package.json<\/code> file. This allows us to take advantage of cached Docker layers. bitJudo has a good explanation of this here<\/a>. Furthermore, the npm ci<\/code> command, specified in the comments, helps provide faster, reliable, reproducible builds for production environments. You can read more about this here<\/a>.<\/p>\n\n\n\n
To bundle your app’s source code inside the Docker image, use the COPY<\/code> instruction:<\/p>\n\n\n\n
# Bundle app source\nCOPY . .<\/code><\/pre>\n\n\n\n
Your app binds to port 8080<\/code> so you’ll use the EXPOSE<\/code> instruction to have it mapped by the docker<\/code> daemon:<\/p>\n\n\n\n
EXPOSE 8080<\/code><\/pre>\n\n\n\n
Last but not least, define the command to run your app using CMD<\/code> which defines your runtime. Here we will use node server.js<\/code> to start your server:<\/p>\n\n\n\n
CMD [ \"node\", \"server.js\" ]<\/code><\/pre>\n\n\n\n
Your Dockerfile<\/code> should now look like this:<\/p>\n\n\n\n
FROM node:12\n\n# Create app directory\nWORKDIR \/usr\/src\/app\n\n# Install app dependencies\n# A wildcard is used to ensure both package.json AND package-lock.json are copied\n# where available (npm@5+)\nCOPY package*.json .\/\n\nRUN npm install\n# If you are building your code for production\n# RUN npm ci --only=production\n\n# Bundle app source\nCOPY . .\n\nEXPOSE 8080\nCMD [ \"node\", \"server.js\" ]<\/code><\/pre>\n\n\n\n
.dockerignore file<\/h2>\n\n\n\n
Create a .dockerignore<\/code> file in the same directory as your Dockerfile<\/code> with following content:<\/p>\n\n\n\n
node_modules\nnpm-debug.log<\/code><\/pre>\n\n\n\n
This will prevent your local modules and debug logs from being copied onto your Docker image and possibly overwriting modules installed within your image.<\/p>\n\n\n\n
Building your image<\/h2>\n\n\n\n
Go to the directory that has your Dockerfile<\/code> and run the following command to build the Docker image. The -t<\/code> flag lets you tag your image so it’s easier to find later using the docker images<\/code> command:<\/p>\n\n\n\n
docker build -t <your username>\/node-web-app .<\/code><\/pre>\n\n\n\n
Your image will now be listed by Docker:<\/p>\n\n\n\n
$ docker images\n\n# Example\nREPOSITORY                      TAG        ID              CREATED\nnode                            12         1934b0b038d1    5 days ago\n<your username>\/node-web-app    latest     d64d3505b0d2    1 minute ago<\/code><\/pre>\n\n\n\n
Run the image<\/h2>\n\n\n\n
Running your image with -d<\/code> runs the container in detached mode, leaving the container running in the background. The -p<\/code> flag redirects a public port to a private port inside the container. Run the image you previously built:<\/p>\n\n\n\n
docker run -p 49160:8080 -d <your username>\/node-web-app<\/code><\/pre>\n\n\n\n
Print the output of your app:<\/p>\n\n\n\n
# Get container ID\n$ docker ps\n\n# Print app output\n$ docker logs <container id>\n\n# Example\nRunning on http:\/\/localhost:8080<\/code><\/pre>\n\n\n\n
If you need to go inside the container you can use the exec<\/code> command:<\/p>\n\n\n\n
# Enter the container\n$ docker exec -it <container id> \/bin\/bash<\/code><\/pre>\n\n\n\n
Test<\/h2>\n\n\n\n
To test your app, get the port of your app that Docker mapped:<\/p>\n\n\n\n
$ docker ps\n\n# Example\nID            IMAGE                                COMMAND    ...   PORTS\necce33b30ebf  <your username>\/node-web-app:latest  npm start  ...   49160->8080<\/code><\/pre>\n\n\n\n
In the example above, Docker mapped the 8080<\/code> port inside of the container to the port 49160<\/code> on your machine.<\/p>\n\n\n\n
Now you can call your app using curl<\/code> (install if needed via: sudo apt-get install curl<\/code>):<\/p>\n\n\n\n
$ curl -i localhost:49160\n\nHTTP\/1.1 200 OK\nX-Powered-By: Express\nContent-Type: text\/html; charset=utf-8\nContent-Length: 12\nETag: W\/\"c-M6tWOb\/Y57lesdjQuHeB1P\/qTV0\"\nDate: Mon, 13 Nov 2017 20:53:59 GMT\nConnection: keep-alive\n\nHello world<\/code><\/pre>\n\n\n\n
We hope this tutorial helped you get up and running a simple Node.js application on Docker.<\/p>\n\n\n\n
You can find more information about Docker and Node.js on Docker in the following places:<\/p>\n\n\n\n