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twisted / txmongo

asynchronous python driver for mongo
https://txmongo.readthedocs.io
Apache License 2.0
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support read preferences #165

Open linearb opened 8 years ago

linearb commented 8 years ago

txmongo should, like pymongo, fully support read preferences, to permit, for example, failover to primary, or nearest. Behavior, should be like pymongo 3.2.2 as described here: https://api.mongodb.org/python/current/api/pymongo/read_preferences.html#module-pymongo.read_preferences.

PRIMARY: Read from the primary. This is the default read preference, and provides the strongest consistency. If no primary is available, raise AutoReconnect. PRIMARY_PREFERRED: Read from the primary if available, otherwise read from a secondary. SECONDARY: Read from a secondary. If no matching secondary is available, raise AutoReconnect. SECONDARY_PREFERRED: Read from a secondary if available, otherwise from the primary. NEAREST: Read from any available member.

(Note an edge case that should be handled correctly: pymongo, when connected to a mongod that happens to be a member of a replica set, using SECONDARY and the replicaSet option unset, does not failover to other replicaset members. But the current txmongo code seems to append the members of the set to __allnodes whether or not replicaSet is set. )

E4gle commented 6 years ago

Are there any updates regarding this request ? It would be really useful if this was supported, without this feature using replicaSet is pointless since all connections are always directed to the primary.

psi29a commented 6 years ago

If someone would like to get their hands dirty and contribute a PR, we'd be happy to review. :)