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  1. Python Driver
  2. PYTHON-4348

MongoClient opened before fork warning is never raised

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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?

      In PYTHON-2484 we added a MongoClient._after_fork() hook that resets the topology state in hopes of making the client slightly more fork-safe. We later discovered in PYTHON-3406 that network I/O + threads in general is not fork-safe and we attempted to reinstate the warning:

                  warnings.warn(
                "MongoClient opened before fork. May not be entirely fork-safe, "
                "proceed with caution. See PyMongo's documentation for details: "
                "https://pymongo.readthedocs.io/en/stable/faq.html#"
                "is-pymongo-fork-safe",
                stacklevel=2,
            )

      https://github.com/mongodb/mongo-python-driver/blob/ebb94b669ec2be5968f2cdfd7928b68808539216/pymongo/topology.py#L190-L196

      However, the MongoClient._after_fork() makes it such that the "MongoClient opened before fork" warning will never appear.

      Note that in Python 3.12 the interpreter itself issues this warning:

      /Library/Frameworks/Python.framework/Versions/3.12/lib/python3.12/multiprocessing/popen_fork.py:66: DeprecationWarning: This process (pid=96002) is multi-threaded, use of fork() may lead to deadlocks in the child.

            Assignee:
            shane.harvey@mongodb.com Shane Harvey
            Reporter:
            shane.harvey@mongodb.com Shane Harvey
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              Created:
              Updated:
              Resolved: