Starlette

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

Install Unit with a Python 3.5+ language module.

Create a virtual environment to install Starlette’s PIP package, for instance:

$ cd /path/to/app/  # Path to the application directory; use a real path in your configuration
$ python --version  # Make sure your virtual environment version matches the module version
      Python X.Y.Z  # Major version, minor version, and revision number
$ python -m venv venv  # Arbitrary name of the virtual environment
$ source venv/bin/activate  # Name of the virtual environment from the previous command
$ 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 (X.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.

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])

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

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

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",
         "share_comment": "Serves static files. Thus, URIs starting with /static/ are served from /path/to/app/static/; use a real path in your configuration"
         }
      },
      {
         "action": {
         "pass": "applications/starlette"
         }
      }
   ],
   "applications": {
      "starlette": {
         "type": "python 3.Y",
         "type_comment": "Must match language module version and virtual environment version",
         "path": "/path/to/app/",
         "path_comment": "Path to the ASGI module",
         "home": "/path/to/app/venv/",
         "home_comment": "Path to the virtual environment, if any",
         "module": "asgi",
         "module_comment": "ASGI module filename with extension omitted",
         "callable": "app",
         "callable_comment": "Name of the callable in the module to run"
      }
   }
}

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

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: "")

Last modified February 6, 2025