Proposal: add execution_state filed on terminal

[Wh1isper]

Problem

As I am working on a plugin to check if user is running code, so that user can running code as a background task without being killed by my modified jupyterhub
but I found terminal don't have execution_state filed, so I cant check terminal's state
Hope I can check both kernel and terminal,

Proposed Solution

I have tried add some process on on_message and write_message and TerminalManager's get_terminal_model

class TermSocket(WebSocketMixin, JupyterHandler, terminado.TermSocket):
    ... # some code 
    def on_message(self, message):
        super(TermSocket, self).on_message(message)
        self._update_activity()
        self._set_state_busy()

    def write_message(self, message, binary=False):
        super(TermSocket, self).write_message(message, binary=binary)
        self._update_activity()
        if message != '["stdout", "\\r\\n"]':
            self._set_state_idle()

    def _update_activity(self):
        self.application.settings["terminal_last_activity"] = utcnow()
        # terminal may not be around on deletion/cull
        if self.term_name in self.terminal_manager.terminals:
            self.terminal_manager.terminals[self.term_name].last_activity = utcnow()

    def _set_state_busy(self):
        if self.term_name in self.terminal_manager.terminals:
            self.terminal_manager.terminals[self.term_name].execution_state = 'busy'

    def _set_state_idle(self):
        if self.term_name in self.terminal_manager.terminals:
            self.terminal_manager.terminals[self.term_name].execution_state = 'idle'

class TerminalManager(LoggingConfigurable, terminado.NamedTermManager):
    ... # some code 
    def get_terminal_model(self, name):
        """Return a JSON-safe dict representing a terminal.
        For use in representing terminals in the JSON APIs.
        """
        self._check_terminal(name)
        term = self.terminals[name]
        model = {
            "name": name,
            "last_activity": isoformat(term.last_activity),
        }
        # added
        if hasattr(term, 'execution_state'):
            model['execution_state'] = term.execution_state

        return model

Additional context

[Wh1isper]

and anothoer question, why we didn't move terminal into service and make its websocket route as /api/terminals/websocket/

[Wh1isper]

#626 meets my needs, but may not be a good general approach
Maybe we need to raise an issue with terminado?

[Wh1isper]

#626 meets my needs, but may not be a good general approach Maybe we need to raise an issue with terminado?

Let me update the progress, in the development of terminal with status, I found that we need to extend the functionality of terminal_manager, finally made terminal_manager a configurable item and implemented a terminal_manager that uses logging of terminal returns to determine the status ( StatefulTerminalManager), which currently works in most linux and linux docker containers, hopefully someone will make it support more operating systems later.

The code is all here #626, feel free to make comments

[Wh1isper]

Turn to #640
Thanks all !