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/ # Path to the application directory; use a real path in your configuration
   

   $ cd /path/to/app/ # Path to the application directory; use a real path in your configuration
   

   $ 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/ # Path to the application directory; use a real path in your configuration
   

   $ 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 # Application file; use a real path in your configuration
   

4. Change ownership:

   Run the following command (as root) so Unit can access the application directory (If the application uses several directories, run the command for each one):

   # chown -R unit:unit /path/to/app/  # User and group that Unit's router runs as by default
      

   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/",
            "working_directory_comment": "Needed to use the installed NPM modules; use a real path in your configuration",
            "executable": "/usr/bin/env",
            "executable_comment": "The external app type allows to run arbitrary executables, provided they establish communication with Unit",
            "arguments": [
            "node",
            "--loader",
            "unit-http/loader.mjs",
            "--require",
            "unit-http/loader",
            "app.js"
            ],
            "arguments_comment": "The env executable runs Node.js, supplying Unit's loader module and your app code as arguments",
            "app_js_comment": "Basename of the application file; be sure to make it executable"
         }
      }
   }
   

6. 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 \  # Path to Unit's control socket in your installation
      http://localhost/config/      # Path to the config section in Unit's control API
   

   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: