Frontend¶

class lightning.app.frontend.frontend.Frontend[source]¶

Bases: ABC

Base class for any frontend that gets exposed by LightningFlows.

The flow attribute will be set by the app while bootstrapping.

abstract start_server(host, port, root_path='')[source]¶

Start the process that serves the UI at the given hostname and port number.

Parameters

host¶ (str) – The hostname where the UI will be served. This gets determined by the dispatcher (e.g., cloud), but defaults to localhost when running locally.
port¶ (int) – The port number where the UI will be served. This gets determined by the dispatcher, which by default chooses any free port when running locally.
root_path¶ (str) – root_path for the server if app in exposed via a proxy at /<root_path>

Return type

None

Example

An custom implementation could look like this:

def start_server(self, host, port, root_path=""):
    self._process = subprocess.Popen(["flask", "run" "--host", host, "--port", str(port)])

abstract stop_server()[source]¶

Stop the process that was started with start_server() so the App can shut down.

This method gets called when the LightningApp terminates.

Example

def stop_server(self):
    self._process.kill()