Socket Activation

While waitress does not support the various implementations of socket activation, for example using systemd or launchd, it is prepared to receive pre-bound sockets from init systems, process and socket managers, or other launchers that can provide pre-bound sockets.

The following shows a code example starting waitress with two pre-bound Internet sockets.

import socket
import waitress


def app(environ, start_response):
    content_length = environ.get('CONTENT_LENGTH', None)
    if content_length is not None:
        content_length = int(content_length)
    body = environ['wsgi.input'].read(content_length)
    content_length = str(len(body))
    start_response(
        '200 OK',
        [('Content-Length', content_length), ('Content-Type', 'text/plain')]
    )
    return [body]


if __name__ == '__main__':
    sockets = [
        socket.socket(socket.AF_INET, socket.SOCK_STREAM),
        socket.socket(socket.AF_INET, socket.SOCK_STREAM)]
    sockets[0].bind(('127.0.0.1', 8080))
    sockets[1].bind(('127.0.0.1', 9090))
    waitress.serve(app, sockets=sockets)
    for socket in sockets:
        socket.close()

Generally, to implement socket activation for a given init system, a wrapper script uses the init system specific libraries to retrieve the sockets from the init system. Afterwards it starts waitress, passing the sockets with the parameter sockets. Note that the sockets have to be bound, which all init systems supporting socket activation do.