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  1. Python Driver
  2. PYTHON-4298

Raise informative error when server_description.round_trip_time is None in server selection

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    • Type: Icon: Bug Bug
    • Resolution: Fixed
    • Priority: Icon: Unknown Unknown
    • 4.7
    • Affects Version/s: None
    • Component/s: None
    • None
    • Python Drivers
    • Not Needed
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      1. What would you like to communicate to the user about this feature?
      2. Would you like the user to see examples of the syntax and/or executable code and its output?
      3. Which versions of the driver/connector does this apply to?

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      1. What would you like to communicate to the user about this feature? 2. Would you like the user to see examples of the syntax and/or executable code and its output? 3. Which versions of the driver/connector does this apply to?

      https://github.com/mongodb/mongo-python-driver/pull/1361 outlines an unexpected error case where a server description is in an unknown state but is attempting to access its round_trip_time. This behavior should result in a more useful error that contains the server description states.

      Here's an example:

      for doc in collection.find(
  File "/opt/venv/lib/python3.8/site-packages/pymongo/cursor.py", line 1264, in next
    if len(self.__data) or self._refresh():
  File "/opt/venv/lib/python3.8/site-packages/pymongo/cursor.py", line 1181, in _refresh
    self.__send_message(q)
  File "/opt/venv/lib/python3.8/site-packages/pymongo/cursor.py", line 1060, in __send_message
    response = client._run_operation(
  File "/opt/venv/lib/python3.8/site-packages/pymongo/_csot.py", line 107, in csot_wrapper
    return func(self, *args, **kwargs)
  File "/opt/venv/lib/python3.8/site-packages/pymongo/mongo_client.py", line 1394, in _run_operation
    return self._retryable_read(
  File "/opt/venv/lib/python3.8/site-packages/pymongo/mongo_client.py", line 1492, in _retryable_read
    return self._retry_internal(
  File "/opt/venv/lib/python3.8/site-packages/pymongo/_csot.py", line 107, in csot_wrapper
    return func(self, *args, **kwargs)
  File "/opt/venv/lib/python3.8/site-packages/pymongo/mongo_client.py", line 1453, in _retry_internal
    return _ClientConnectionRetryable(
  File "/opt/venv/lib/python3.8/site-packages/pymongo/mongo_client.py", line 2315, in run
    return self._read() if self._is_read else self._write()
  File "/opt/venv/lib/python3.8/site-packages/pymongo/mongo_client.py", line 2437, in _read
    self._server = self._get_server()
  File "/opt/venv/lib/python3.8/site-packages/pymongo/mongo_client.py", line 2400, in _get_server
    return self._client._select_server(
  File "/opt/venv/lib/python3.8/site-packages/pymongo/mongo_client.py", line 1303, in _select_server
    server = topology.select_server(server_selector)
  File "/opt/venv/lib/python3.8/site-packages/pymongo/topology.py", line 302, in select_server
    server = self._select_server(selector, server_selection_timeout, address)
  File "/opt/venv/lib/python3.8/site-packages/pymongo/topology.py", line 286, in _select_server
    servers = self.select_servers(selector, server_selection_timeout, address)
  File "/opt/venv/lib/python3.8/site-packages/pymongo/topology.py", line 237, in select_servers
    server_descriptions = self._select_servers_loop(selector, server_timeout, address)
  File "/opt/venv/lib/python3.8/site-packages/pymongo/topology.py", line 252, in _select_servers_loop
    server_descriptions = self._description.apply_selector(
  File "/opt/venv/lib/python3.8/site-packages/pymongo/topology_description.py", line 330, in apply_selector
    return self._apply_local_threshold(selection)
  File "/opt/venv/lib/python3.8/site-packages/pymongo/topology_description.py", line 272, in _apply_local_threshold
    return [
  File "/opt/venv/lib/python3.8/site-packages/pymongo/topology_description.py", line 275, in <listcomp>
    if (cast(float, s.round_trip_time) - fastest) <= threshold
TypeError: unsupported operand type(s) for -: 'NoneType' and 'NoneType'

            Assignee:
            shane.harvey@mongodb.com Shane Harvey
            Reporter:
            noah.stapp@mongodb.com Noah Stapp
            Votes:
            1 Vote for this issue
            Watchers:
            3 Start watching this issue

              Created:
              Updated:
              Resolved: