How To Restart Your Node.js Apps Automatically with nodemon

In this article we are going to learn how we can automatically restart the nodejs application with nodemon.

Here is what we are going to learn in this article

What is Nodemon?
Installation and basic setup
Setting an example Express Js project with Nodemon
Advanced Configuration
Containerization and NodeMon
Debugging with NodeMon

Nodemon is a utility that monitors for any changes in your code base and restarts your server

This utility is primarily used in the development of NodeJs applications. Let us consider how to install and setup the nodemon with your express and nodejs project

Installation and basic setup of Nodemon

There are two ways you can install the nodemon. You can either install the nodemon globally in your machine or install it only in your project.

Global installation

you can install the nodemon globally using the following command. By installing it globally all the programs running on your machine will have access to nodemon

sudo npm install -g nodemon

installing nodemon globally

2. Project Specific installation

If you do not want to pollute your machine with unnecessary software, you can also install nodemon in specific projects.

Doing this the nodemon is contained and available only for those programmes

npm install --save-dev nodemon

Setting an example Express Js project with Nodemon

In this section let us setup an expressjs project with nodemon to see how it works.

initialize your project

Create a new directory and name it node-express, cd in it and then initialize the project with npm init -y

mkdir my-node-project
cd my-node-project
npm init -y

initialize a new project

then install the dependencies including expressjs and nodemon

npm install express
npm install nodemon

then create an index.js file and write the below code

const express = require('express');
const app = express();

app.get('/', (req, res) => {
  res.send('Hello World!');
});

app.listen(3000, () => {
  console.log('Application is running on http://localhost:3000');
});

lastly start the app using nodemon like

nodemon index.js

you can see the app running on localhost://3000 like

Advanced NodeMon Configuration

Configure nodemon to ignore certain files and folders

You can configure nodemon to ignore changes in specific files and folders. For example you want a folder that has assets, you do not want to restart server whenever there are changes to that folder.

To do this you need to create a nodemon.json file in your root directory and list the files and folders.

{
"ignore":["README.md", "node_modules/*"]
}

using `nodemon.json` for complex configurations

For more detailed configuration, such as specifying watched file extensions or if you want to set env variables nodemon.json files is the way to go

Here is a sample complex configuration for your reference

{
  "watch": ["src/"],
  "ext": "js,ts",
  "ignore": ["src/tests/"],
  "env": {
    "NODE_ENV": "development"
  },
  "delay": 1000
}

javascript

This configuration watches the src/ directory and restarts for changes in the js and the ts files

the configuration also ignores the changes in the src/tests/ directory, set the NODE_ENV to development and wait for 1000 miliseconds

Containerization and NodeMon

You can integrate nodemon with docker container as well. You can restart the nodejs app within docker container. here is how you can do this

Dockerfile Configuration
Create a Dockerfile for your Node.Js app
Install the nodemon globally in your docker container, this is probably the easier way. Or you can include it as a dependency in your development project as well in the docker container
Set up the docker container to run the app using Nodemon. You can use this by defining the start command with nodemon in the CMD directive of your Dockerfile

Let us consider a docker example

FROM node:latest

WORKDIR /app

COPY package*.json ./

RUN npm install

COPY . .

CMD ["nodemon", "./src/app.js"]

Using Docker compose for ease of development

You can use Docker Compose to manage your app services
you can also mount your root project directory within the Docker container to enable the real time syncing of changes

Best Practices for using Docker in Development environment

Make sure that local development environment is exactly looks like the Docker environment.
Using volume mounts to sync source code between your host and container, allowing NodeMon to restart the app upon detecting changes

Debugging with Nodemon

Nodemon can be easily configured to work with nodejs built-in debugger or other debugging tools like chrome devtools or VSCode

You can do this by forwarding appropriate arguments to the NodeJs process

Debugging config in nodemon.json

You can specify the nodejs debugging arguments in the exec command int he nodemon.js file

Let us consider this example configuration


{
  "exec": "node --inspect=9229 src/app.js"
}

for VS code you can setup a .vscode/launch.json file to attach to the node process.

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Conclusion

In this article we have learned how we can use nodemon in development to automatically restart servers.

This is especially useful when you are developing an app and you need to see how the code changes are working without manually restarting the server again and again

Keep in mind though nodemon is for development use only, using nodemon in production poses security chanllenges and it is strongly advised not to use it.

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