my_jupyter_extension.py

"""
Extension to list active kernels

attempting to sort by likely 'focus'
"""

from tornado import web
from notebook.base.handlers import IPythonHandler
from notebook.utils import url_path_join

def activity_sort_key(kernel):
    """Sort kernels by probable 'focus'

    - First priority: any active connections (no connections means no connected UI)
    - Second priority: recent activity (active tab before open but not executed in a while)
    """
    # TODO: third priority: execution state (busy/idle/etc.)?
    return (kernel["connections"], kernel["last_activity"])


class LastActiveKernelHandler(IPythonHandler):
    @web.authenticated
    def get(self):
        km = self.kernel_manager
        kernel_models = sorted(self.kernel_manager.list_kernels(), key=activity_sort_key, reverse=True)
        if not kernel_models:
            self.write("No kernels!")
            return

        most_active = kernel_models[0]
        self.write(
            f"<p>The most active kernel is {most_active['id']} with {most_active['connections']} connections, last active on {most_active['last_activity']}</p>"
        )
        self.write("<p>Other kernels:</p><ul>")
        for kernel in kernel_models[1:]:
            self.write(
                f"<li>{kernel['id']}: {kernel['connections']} connections, last active on {kernel['last_activity']}"
            )
        self.write("</ul>")


def load_jupyter_server_extension(nb_server_app):
    """
    Called when the extension is loaded.

    Args:
        nb_server_app (NotebookWebApplication): handle to the Notebook webserver instance.
    """
    web_app = nb_server_app.web_app
    host_pattern = ".*$"
    route_pattern = url_path_join(web_app.settings["base_url"], "/lastactive")
    web_app.add_handlers(host_pattern, [(route_pattern, LastActiveKernelHandler)])