Installing a Node app on a server

Before I write a fancy Ansible playbook to automatically set up the Nginx/Node combo on my web servers, it might be worth going through how to deploy a Node app so it can run on a server without you being logged in.

Until now, I’ve been running my tests on my laptop, or in a server logged in as myself – sometimes detaching from tmux. But we need a bit more professional set up than that. The process will look something like this:

• Install Node and npm (I’m assuming we’ve done that since I’ve covered the playbook for it before).
• Copy the app files over
• Install the dependencies
• Write the systemd config file
• Start it up

App files

We’ll use the very simple server (index.js) I’ve written for the future Ansible post. All it does is listen on port 3000 to serve a tiny piece of text if someone hits the /api route.

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

const PORT = 3000;

app.get("/api", (req, res) => {
    res.status(200).send('Success - from /api route via node.js');
});

app.listen(PORT, () => {console.log(`Listening on port ${PORT}`)});

We’ll also have our package.json, of which the only interesting thing to notice is that we’ve got a dependency on the express package which I originally installed with npm. All the files for our dependencies are stored in the ./node_modules directory, but we don’t need to copy them to the server.

Where to put the app files

If I was doing this for a commercial app, I might store the app under /var/www/<app name> since that’s where a future sysadmin might look for it if they don’t have access to the playbooks. Another good place might be the home directory of the ansible/node user. Since that’s me in this case, they’re just going to go in my home directory – it makes the playbook commands shorter. We can use scp to copy the files in.

Once the files are there, we can install the dependencies with npm install. This looks at the package.json, then grabs them down.

systemd

systemd manages the init and daemon processes in most Linux distros, so we’ll be using that to get our node app running as a service. It was a present from Red Hat. Processes that run like this need a configuration file in /lib/systemd/system, ours will be called

/lib/systemd/system/test-server.service

[Unit]
Description=index.js - test server                     
After=network.target

[Service]
Type=simple
User=ian   
ExecStart=/usr/bin/node /home/ian/index.js
Restart=on-failure

[Install]
WantedBy=multi-user.target   

This file needs to say that we should wait for the network to come up before starting, what we’re running and what to do if it dies. ‘on-failure’ means it will be restarted in pretty much any case but us stopping it cleanly. The multi-user.target bit is saying we want this service up and running for the system to be considered ready as a server.

Once that file is in place, we can reload the configs, and start the service, this can be from anywhere, including a user home directory, and check it’s status.

sudo systemctl daemon-reload
sudo systemctl start test-server

That all looks good, and if I visit the endpoint, there’s the expected response, even after we’ve logged out of the server.