Fabric task to restart gunicorn without downtime, killing workers sequentially, sleeping in between to let new ones get ready.

fabfile.py

@task
def reloadapp(sleep=5):
    """
    Reloads lead-ratings app and the celery workers.
    """
    supervisorctl = os.path.join(env.venv_path, 'bin', 'supervisorctl')

    # kill all gunicorn master children, sleeping in between
    master_pid = run('sudo %s pid app' % supervisorctl)
    children = run('pgrep -P %s' % master_pid).split('\r\n')
    for child in children:
        time.sleep(sleep)
        run('kill %s' % child)