PyMongo supports Gevent. Simply call Gevent's monkey.patch_all() before loading any other modules:

>>> # You must call patch_all() *before* importing any other modules
>>> from gevent import monkey
>>> monkey.patch_all()
>>> from pymongo import MongoClient
>>> client = MongoClient()

PyMongo uses thread and socket functions from the Python standard library. Gevent's monkey-patching replaces those standard functions so that PyMongo does asynchronous I/O with non-blocking sockets, and schedules operations on greenlets instead of threads.

By default, PyMongo uses threads to discover and monitor your servers' topology (see :ref:`health-monitoring`). If you execute monkey.patch_all() when your application first begins, PyMongo automatically uses greenlets instead of threads.

When shutting down, if your application calls :meth:`~gevent.hub.Hub.join` on Gevent's :class:`~gevent.hub.Hub` without first terminating these background greenlets, the call to :meth:`~gevent.hub.Hub.join` blocks indefinitely. You therefore must close or dereference any active :class:`~pymongo.mongo_client.MongoClient` before exiting.

An example solution to this issue in some application frameworks is a signal handler to end background greenlets when your application receives SIGHUP:

import signal

def graceful_reload(signum, traceback):
    """Explicitly close some global MongoClient object."""
    client.close()

signal.signal(signal.SIGHUP, graceful_reload)

Applications using uWSGI prior to 1.9.16 are affected by this issue, or newer uWSGI versions with the -gevent-wait-for-hub option. See the uWSGI changelog for details.