Dockerizing a Node.js web app

Prerequisites

• Install Docker

Steps

1. Building your image

Go to the directory that has your Dockerfile and run the following command to build the Docker image. The -t flag lets you tag your image so it's easier to find later using the docker images command:

docker build . -t my-node-web-app

Your image will now be listed by Docker:

docker images

# Example
REPOSITORY        TAG       IMAGE ID       CREATED         SIZE
my-node-web-app   latest    19c9f9ba0e3c   5 seconds ago   1.1GB

2. Run the image

Running your image with -d runs the container in detached mode, leaving the container running in the background. The -p flag redirects a public port to a private port inside the container. Run the image you previously built:

docker run -p 49160:8080 -d my-node-web-app

3. Print the output of your app

Get the container's ID:

docker ps

CONTAINER ID   IMAGE             COMMAND                  CREATED         STATUS         PORTS                                         NAMES
7c1c9b4f6457   my-node-web-app   "docker-entrypoint.s…"   2 minutes ago   Up 2 minutes   0.0.0.0:49160->8080/tcp, :::49160->8080/tcp   elastic_benz

Print app output with the container's ID:

docker logs 7c1c9b4f6457

Running on http://0.0.0.0:8080

If you need to go inside the container, you can use the exec command:

docker exec -it 7c1c9b4f6457 /bin/bash

root@7c1c9b4f6457:/usr/src/app#

Now, you can execute commands in the container. For example:

root@7c1c9b4f6457:/usr/src/app# ls -l 
total 44
-rw-r--r--  1 root root   370 Sep 22 08:08 Dockerfile
-rw-r--r--  1 root root  3431 Sep 22 09:23 README.md
drwxr-xr-x 60 root root  4096 Sep 22 08:11 node_modules
-rw-r--r--  1 root root 22276 Sep 22 08:11 package-lock.json
-rw-r--r--  1 root root   264 Sep 22 08:07 package.json
-rw-r--r--  1 root root   290 Sep 22 08:07 server.js

Just type the exit command to exit the container:

root@f95121aa40b6:/usr/src/app# exit
exit

4. Test your app

To test your app, get the port of your app that Docker mapped:

docker ps

CONTAINER ID   IMAGE             COMMAND                  CREATED         STATUS         PORTS                                         NAMES
7c1c9b4f6457   my-node-web-app   "docker-entrypoint.s…"   2 minutes ago   Up 2 minutes   0.0.0.0:49160->8080/tcp, :::49160->8080/tcp   elastic_benz

In the example above, Docker mapped the 8080 port inside of the container to the port 49160 on your machine. Now you can call your app using curl:

curl -i localhost:49160

HTTP/1.1 200 OK
X-Powered-By: Express
Content-Type: text/html; charset=utf-8
Content-Length: 11
ETag: W/"b-Ck1VqNd45QIvq3AZd8XYQLvEhtA"
Date: Fri, 22 Sep 2023 12:24:14 GMT
Connection: keep-alive
Keep-Alive: timeout=5

Hello World

Install cURL if needed via:

sudo apt-get install curl

Or use directly the file localhost.http of this repository with the HTTP Client of your IDE (for example with VSCode REST Client or PHPStorm HTTP Client):

# localhost.http
GET http://localhost:49160

5. Shut down the image

In order to shut down the app we started, we run the kill command. This uses the container's ID, which in this example was 7c1c9b4f6457.

docker kill 7c1c9b4f6457

7c1c9b4f6457

Confirm that the app has stopped:

curl -i localhost:49160

curl: (7) Failed to connect to localhost port 49160: Connection refused

Resources

• https://nodejs.org/fr/docs/guides/nodejs-docker-webapp