server-spawn ()

When the development server boots up it emits this event if plugins want to spawn their own development tools. For instance it can be used to start a background process that kicks off webpack or similar tools. There is a second event called server-stop which can be used to detect server shutdowns.

Example

import os
from subprocess import Popen

class MyPlugin(Plugin):
    ...

    webpack = None

    def on_server_spawn(self, **extra):
        path = os.path.join(self.env.root_path, 'webpack')
        self.webpack = Popen(['webpack', '--watch'], cwd=path)

    def on_server_stop(self, **extra):
        if self.webpack is not None:
            self.webpack.kill()

A list of some plugins that make use of this event is available here.