PyMongo MongoClient replica set won't connect - mongodb

Question

A bit of background: I used Bitnami to spin up a 3 node Mongo cluster on Azure (1 arbiter), each mongod hosted on separate VMs. I've confirmed that the replica set exists, and that each node is able to connect to one another. I've confirmed that when I take down my primary node, the secondary node steps up. When the primary node returns, it assumes the primary position again.
My problem is that I can't connect to my MongoDB replica set using MongoClient when specifying replicaset. I would get this error:
pymongo.errors.ServerSelectionTimeoutError: ArbiterIP:27017: [WinError
10061] No connection could be made because the target machine actively
refused it,PrimaryIP:27017: [WinError 10061] No connection could be
made because the target machine actively refused it,SecondaryIP:27017:
timed out
Using MongoClient, if I do:
connection = MongoClient('MyIP1:27017', w=2)
, it connects fine. When I do
connection = MongoClient('MyIP1:27017', w=2, replicaset="repsetname")
, that's when I get the error.
Would it be related to the fact that the arbiter node has no user info for authentication?

Answer 1

Taking a stab at it: if you connect with the shell and do db.isMaster(), are the hostnames you see in the config the same as the hostnames like "MyIP" that you're passing to PyMongo?
It sounds like when you pass "replicaset=", PyMongo takes the hostnames from the isMaster response and connects to those instead of MyIP, but the way your replica set is configured, that set of hostnames isn't available.
For more info on why PyMongo acts this way:
https://github.com/mongodb/specifications/blob/master/source/server-discovery-and-monitoring/server-discovery-and-monitoring.rst#clients-use-the-hostnames-listed-in-the-replica-set-config-not-the-seed-list