Starlette§

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

1. Install Unit with a Python 3.5+ language module.

2. Create a virtual environment to install Starlette’s PIP package:

   $ cd /path/to/app/
   $ python3 --version
         Python 3.Y.Z
   $ python3 -m venv venv
   $ source venv/bin/activate
   $ pip install 'starlette[full]'
   $ deactivate
   

   Warning

   Create your virtual environment with a Python version that matches the language module from Step 1 up to the minor number (3.Y in this example). Also, the app type in Step 5 must resolve to a similarly matching version; Unit doesn’t infer it from the environment.

3. Let’s try a version of a tutorial app, saving it as /path/to/app/asgi.py:

   from starlette.applications import Starlette
   from starlette.responses import PlainTextResponse
   from starlette.routing import Route, Mount, WebSocketRoute
   
   
   def homepage(request):
       return PlainTextResponse('Hello, world!')
   
   def user_me(request):
       username = "John Doe"
       return PlainTextResponse('Hello, %s!' % username)
   
   def user(request):
       username = request.path_params['username']
       return PlainTextResponse('Hello, %s!' % username)
   
   async def websocket_endpoint(websocket):
       await websocket.accept()
       await websocket.send_text('Hello, websocket!')
       await websocket.close()
   
   def startup():
       print('Ready to go')
   
   
   routes = [
       Route('/', homepage),
       Route('/user/me', user_me),
       Route('/user/{username}', user),
       WebSocketRoute('/ws', websocket_endpoint)
   ]
   
   app = Starlette(debug=True, routes=routes, on_startup=[startup])
   

   Note

   This sample omits the static route because Unit’s quite capable of serving static files itself if needed.

4. Run the following command 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 Starlette configuration for Unit (use real values for type, home, and path), adding a route to serve static content:

   {
       "listeners": {
           "*:80": {
               "pass": "routes"
           }
       },
   
       "routes": [
           {
               "match": {
                   "uri": "/static/*"
               },
   
               "action": {
                   "share": "/path/to/app$uri"
               }
           },
   
           {
               "action": {
                   "pass": "applications/starlette"
               }
           }
       ],
   
       "applications": {
           "starlette": {
               "type": "python 3.Y",
               "path": "/path/to/app/",
               "home": "/path/to/app/venv/",
               "module": "asgi",
               "callable": "app"
           }
       }
   }
   

6. Upload the updated configuration. Assuming the JSON above was added to config.json:

   # 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:

   $ curl http://localhost
   
         Hello, world!
   

   $ curl http://localhost/user/me
   
         Hello, John Doe!
   

   $ wscat -c ws://localhost/ws
   
         Connected (press CTRL+C to quit)
         < Hello, websocket!
         Disconnected (code: 1000, reason: "")