How to Work with Node.js Apps on Plesk Obsidian
The first thing you need to do is install Plesk Obsidian. I chose Debian as the server OS for this article. You can use either a Linux distro or Windows – just note that there could be some minor differences if you go with a different OS. Assuming Plesk is already installed, let’s install the Node.js extension.
Log in to Plesk, go to “Tools and Settings”, and click “Updates and Upgrades”. Next, go to “Add/Remove Components”. Find the “NodeJS support” component. Select it, and continue with the Node.JS installation. In a few minutes, all the necessary components will be installed and you’ll be ready to go!
Hosting a ‘Hello World’ App
To make sure everything works, let’s try to host a sample Node.js app, such as a “Hello, World” app. You can download one here. Copy/pasting the contents of the app.js file manually is an option. But I suggest trying out another Plesk extension instead – namely, the Git extension.
First, you have to create a subscription (a domain with hosting). Then, you need to create a target directory where the app will be stored. Select your subscription, go to the “Files” tab, and create a directory named “hello-world”. Next, go to the “Domains” tab, choose the website, and click the “Git” button.
Local Repo Set Up
Now, you’ll learn how to set up a local repo as a mirror of a remote one, and deploy the code to the previously created directory. Set this URL as the remote Git repo URL, and change the target to the “hello-world” directory. The settings should look like this:
Differences Between ‘Document Root’ and ‘Application Root’
The next step is to change the “Document root” for the domain. Notice that I’ll be talking about “Document root” and “Application root”: they aren’t one and the same. When we’re talking about web apps (e.g. Node.js based apps or similar), the “Document root” is the location where the static assets can be found. Meanwhile, the “Application root” is the root directory where the app itself is located. In most cases, the “Document root” is a directory inside the “Application root” directory (e.g. “public”).
You need to change the document root now. To do so, go to “Domains”, select your website and go to “Hosting Settings”:
Change the existing document root to ‘hello-world/public’ (without quotes) and click the ‘Ok’ button to save the changes.
Enable Node.js Support
The last thing to do before you run the app is to enable Node.js support on the domain. Go to “Domains”, choose the website and click “Node.js”. Here you’ll see some information about your app and a row of buttons on top. Click “Enable Node.js”, and in a few seconds, your screen will look like this:
First, let’s click on the “Application URL” link to make sure that the app is running. If you see a “Hello, World!” message, congratulations! Your Node.js app is up and running.
App with Dependencies
Real-world Node.js apps always have external dependencies defined in the package.json file and installed in the node_modules directory.
Let’s take a look at an Express-based app – you can download it from the repository here. Either repeat the steps above to set up a repository in Plesk, or download/upload the source code manually. Once you’re done, the Node.js settings screen should look like this – assuming you uploaded the code to the “express-demo” directory:
Before you try accessing the app, you need to initialize it first. Let’s begin by installing dependencies – luckily, in Plesk, it’s as easy as clicking the “NPM install” button. This will install all app dependencies according to the package.json file. Then, you need to tune the app startup file. Plesk uses the Phusion Passenger application server to serve Node.js apps. Our demo app repository contains a file named “server.js”. This file is not a part of a typical Express-based app and contains just a few lines of code, but it’s nonetheless necessary for the app to run:
const app = require('./app'); const http = require('http'); http.createServer(app).listen(process.env.PORT);
You can use the idea behind this file when hosting other Node.js apps (e.g. based on a different framework). The last thing you need to do is to change the “Application Startup File” setting to “server.js”.
Now, try browsing the domain on which you installed the app – you should see the Express welcome message.
By default, the app is running in the “production” mode. If you modify the app, don’t forget to restart it by clicking the “Restart” button.
Knowing how to debug Node.js apps in case any issues appear is essential for a Node.js developer. Here are a few tips that can save you a lot of grief:
Log Files Checkup
The first thing to do when troubleshooting a Node.js app is to check the log files. For example, if you forget to install the dependencies for the demo Express app (you do it via the “NPM install” button, remember?), the Apache error log will contain the “Cannot find module ‘express’” error. Unfortunately due to Phusion Passenger nature, the server-wide error log is used instead of per-domain error logs. In this case, end-users will see the following message:
Bring Error Messages to the Browser
When developing an app, it’s very handy to see the error messages directly on the site – they are still getting logged. Go to the Node.js app settings screen and change the Application Mode to “development”. Next time an issue pops up, the error will be shown in the browser window. Like this:
Moreover, if your app is running in the “development” mode, you don’t need to restart the app every time you modify the contents of a file.
Node.js and Windows
Node.js support is available in both Plesk for Linux and Plesk for Windows. But hosting Node.js apps on Windows has a few caveats you need to take into account.
First, Node.js support in Plesk Obsidian is implemented with the help of the iisnode module (if you would like to learn more about the iisnode project, you can find the documentation here). Second, while in Plesk for Linux you can select a different Node.js version for every domain. In Plesk for Windows, a single Node.js version is used server-wide – you can select the Node.js version during the installation.
Testing Node.js Support
Another difference is the location of the main entry point. In Plesk for Linux, it must be located in the parent directory of the domain’s “Document root”. In Plesk for Windows, it must be placed directly in the “Document root” directory.
To test Node.js support, let’s use the Express-based demo app from here. Create a directory called “node-express” on your domain using FTP access or the built-in File Manager. Then deploy the contents of the “node-express” GitHub repository. After that, click the “Hosting Settings” link (inside Domains -> Website name) and set the domain’s “Document root” directory to “node-express”.
Then, go to Node.js app settings and change the “Application Startup File” to “server.js”. Finally, install the dependencies using the “NPM install” button. Once the dependencies are installed, you can browse your site to make sure that the app is running. Some additional tuning of rewrite rules may be required, but as you can see, it’s possible to launch Node.js app even on Windows hosting.
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