locustio/locust · error · Exception

Tried to stop User in an unexpected state: {self._state}. Th

Error message

Tried to stop User in an unexpected state: {self._state}. This should never happen.

What it means

User.stop() only knows how to stop users in WAITING or RUNNING states. If the user's internal _state is anything else (e.g. stopped/starting), the else-branch raises, since this state should be unreachable.

Source

Thrown at locust/user/users.py:221

        return self._greenlet

    def stop(self, force: bool = False):
        """
        Stop the user greenlet.

        :param force: If False (the default) the stopping is done gracefully by setting the state to LOCUST_STATE_STOPPING
                      which will make the User instance stop once any currently running task is complete and on_stop
                      methods are called. If force is True the greenlet will be killed immediately.
        :returns: True if the greenlet was killed immediately, otherwise False
        """
        if force or self._state == LOCUST_STATE_WAITING:
            self._group.killone(self._greenlet)
            return True
        elif self._state == LOCUST_STATE_RUNNING:
            self._state = LOCUST_STATE_STOPPING
            return False
        else:
            raise Exception(f"Tried to stop User in an unexpected state: {self._state}. This should never happen.")

    @property
    def group(self):
        return self._group

    @property
    def greenlet(self):
        return self._greenlet

    def context(self) -> dict:
        """
        Adds the returned value (a dict) to the context for :ref:`request event <request_context>`.
        Override this in your User class to customize the context.
        """
        return {}

    @classmethod
    def json(cls):

View on GitHub (pinned to f391a716e1)

Solutions

1. Only call stop() on running/waiting users managed by the runner
2. Let the environment/runner stop users instead of calling stop() manually
3. Report to Locust if reproducible — message says this should never happen

if user._state in (LOCUST_STATE_WAITING, LOCUST_STATE_RUNNING): user.stop()

try:
    user.stop()
except Exception as e:
    logging.warning("User in unexpected state: %s", e)

When it happens

Trigger: Calling user.stop() while the user greenlet is in an unexpected _state (neither LOCUST_STATE_WAITING nor LOCUST_STATE_RUNNING), typically a race or manual state manipulation.

Common situations: Programmatically stopping users outside the normal runner lifecycle; custom scripts calling stop() at odd times; bugs in state transitions.

Related errors

• In order to use a with-block for requests, you must also pas
• Tried to set status on a request that has not yet been made.
• User.run() is a method used internally by Locust, and you mu
• No tag name was supplied
• No tasks defined on {self.__class__.__name__}{extra_message}

AI-assisted analysis of locustio/locust@f391a716e1 (2026-08-29). Data as JSON: /api/errors/60f75fae3f812331. Report an issue: GitHub.