Dockerize your Project

Create a Dockerfile

• Suppose you have a NodeJs project and you want to dockerize it.
• Create a Dockerfile and .Dockerignore in the root of your project.
• Add the following code to the Dockerfile.

Code

FROM node:18-alpine
WORKDIR /home/app
COPY package.json* .
RUN npm install
COPY . .
EXPOSE 3000
CMD ["npm", "start"]

Build Image

docker build -t my-node-app .

• it by default search Dockerfile in the current directory,if you used above command.

Custom Dockerfile Name

• Suppose i create a dockerfile with name Dockerfile.dev in the root of my project.
• Then i can build the image with the following command.

docker build -t my-node-app -f Dockerfile.dev .

• -f is used to specify the dockerfile name.
• -t is used to specify the image name.

Run Container

docker run -d -p 3000:3000 my-node-app

Note:

• FROM is used to specify the base image.
• WORKDIR Means location of your project in container.
• COPY is used to copy the whole project in container.
• * is used to copy all the files in the current directory.
• RUN is used to run the command.
• EXPOSE is used to expose the port.
• CMD It is the default command that will be executed when the container is run.
• node:18-alpine is the base image. and alpine is the lightweight version of the image.

Important Points

• Docker build any image Layerwise means it will build the image in layers.
• Count the number of lines in the dockerfile = Number of layers.
• In the above code we have 7 layers.
• So when you build the image it will build the image layer by layer.
• It is most important to follow the correct order of the code in the dockerfile.

Setup Env Value

• You can setup the env value in the dockerfile by using the following command.

FROM node:18-alpine
WORKDIR /home/app
ENV PORT=3000
COPY package.json* .
RUN npm install
COPY . .
EXPOSE 3000
CMD ["npm", "start"]

Note:

• ENV is used to setup the env value in the dockerfile.
• PORT=3000 is used to setup the port value in the dockerfile.
• EXPOSE 3000 is used to expose the port of the app.
• CMD ["npm", "start"] is used to start the app.

While running image

 docker run -d -e PORT=3000 -p 3001:3000 your-image

• We can also set multiple env value.

Using an environment file

docker run --env-file .env your-image

Port Mapping

Problem

• Like, you run any Node.js app image that is exposing or running the project on port 3000, but when accessing this 3000 port from your local machine, you will not be able to access that port. This is happening because your Node.js image is running in a virtual container — suppose the container is a virtual laptop — and there is no connection between your local machine and the virtual laptop. That is why you are not able to access that port.

Solution

• You can solve this problem by doing port mapping. You can map your local machine port to the virtual laptop (container). Then you will be able to access that Node.js project properly and use it.

Custom Port Mapping

docker run -d -p 3000:3000 my-node-app

Note:

• -p is used to map the port of the container to the port of the local machine.
• 3000:3000 is used to map the port of the container to the port of the local machine.
• You can use whatever port you want to use in the local machine. but make sure it is mapped to the port of the container.
• You can run the same image multiple times with different ports.

Random Port Mapping

docker run -d -P my-node-app

• It will map assign the random port to your local machine and map it to the port of the container.

Push Image to Docker Hub

• 1st Make sure you have a docker hub account and login to it.
• Then you can push your image to docker hub.
• You can push your image to docker hub by using the following command.

docker tag my-node-app gautamxd/nodejsapp

docker push gautamxd/nodejsapp

Here

• gautamxd/nodejsapp is the repository name where you want to push your image.
• my-node-app is the image name.