Express§

To run apps built with the Express web framework using Unit:

1. Install Unit with the unit-dev/unit-devel package. Next, install Unit’s unit-http package. Run the following command as root:

   # npm install -g --unsafe-perm unit-http
   

2. Create your app directory, install Express, and link unit-http:

   $ mkdir -p /path/to/app/
   

   $ cd /path/to/app/
   

   $ npm install express --save
   

   Run the following command as root:

   # npm link unit-http
   

3. Create your Express app; let’s store it as /path/to/app/app.js. First, initialize the directory:

   $ cd /path/to/app/
   

   $ npm init
   

   Next, add your application code:

   #!/usr/bin/env node
   
   const http = require('http')
   const express = require('express')
   const app = express()
   
   app.get('/', (req, res) => res.send('Hello, Express on Unit!'))
   
   http.createServer(app).listen()
   

   The file should be made executable so the application can run on Unit:

   $ chmod +x app.js
   

4. Run the following command (as root) so Unit can access the application directory:

   # chown -R unit:unit /path/to/app/
   

   Note

   The unit:unit user-group pair is available only with official packages, Docker images, and some third-party repos. Otherwise, account names may differ; run the ps aux | grep unitd command to be sure.

   For further details, including permissions, see the security checklist.

5. Next, prepare the Express configuration for Unit:

   {
       "listeners": {
           "*:80": {
               "pass": "applications/express"
           }
       },
   
       "applications": {
           "express": {
               "type": "external",
               "working_directory": "/path/to/app/",
               "executable": "/usr/bin/env",
               "arguments": [
                   "node",
                   "--loader",
                   "unit-http/loader.mjs",
                   "--require",
                   "unit-http/loader",
                   "app.js"
               ]
           }
       }
   }
   

6. Upload the updated configuration. Assuming the JSON above was added to config.json. Run the following command as root:

   # curl -X PUT --data-binary @config.json --unix-socket \
          /path/to/control.unit.sock http://localhost/config/
   

   Note

   The control socket path may vary; run unitd -h or see Startup and Shutdown for details.

   After a successful update, your app should be available on the listener’s IP address and port: