'readPreference' param in config URI was ignored in mongoengine.register_connection

[kkzxak47]

I have a config string 'mongodb://mongodb01.test.vpc,mongodb02.test.vpc,mongodb03.test.vpc/prod?readPreference=secondaryPreferred'

it was parsed to dict below by pymongo.uri_parser.parse_uri

{'collection': None,
 'database': 'prod',
 'nodelist': [('mongodb01.test.vpc', 27017),
  ('mongodb02.test.vpc', 27017),
  ('mongodb03.test.vpc', 27017)],
 'options': {'readpreference': 'secondaryPreferred'},
 'password': None,
 'username': None}

but mongoengine only read in 3 params if I read correctly, ignored 'readpreference'

            if 'replicaset' in uri_options:
                conn_settings['replicaSet'] = uri_options['replicaset']
            if 'authsource' in uri_options:
                conn_settings['authentication_source'] = uri_options['authsource']
            if 'authmechanism' in uri_options:
                conn_settings['authentication_mechanism'] = uri_options['authmechanism']

thus made my config not functioning as I needed.

I don't know if this is a bug or a feature. To achieve my goal do I have to explicitly invoke connect(..., read_preference=secondaryPreferred)? Isn't controlling readpreference in a config string be more flexible?

[erdenezul]

duplicate of #1578 but this issue have more clear and concrete example.

[erdenezul]

from mongoengine import * #pylint: disable=wildcard-import
from pymongo import ReadPreference
connect(host="mongodb://mongodb01.test.vpc,mongodb02.test.vpc,mongodb03.test.vpc/prod", read_preference=ReadPreference.SECONDARY_PREFFERED)

[erdenezul]

and I also made PR for your request.