mongodb not using local database in replica set

Question

I have 4 servers each hosting a website and a mongo replica set.

MongoDB version: v3.4.13
Driver: PHP

Server 1 is PRIMARY.

Located on the west coast

Server 2 is SECONDARY with tag: { location: 'east' }

Located on the east coast
I'm connecting to the db with connection string: mongodb://localhost:27017/?replicaSet=rs&readPreference=nearest&readPreferenceTags=location:east

Server 3 and 4 are SECONDARY with no tags.

I want server 2 to read from it's local database, but instead it is reading from primary (or another secondary, I can't tell, but it's definitely not reading from it's local database)

I suspect it's not reading from it's own SECONDARY db because there is about a 3 second lag for any query I run.

How can I tell server 2 to read from it's own local SECONDARY db?

Can you clarify what you mean by local? This could either be the local database (where the replication oplog and other non-replicated collections live) or local data (i.e. reading from any other database). I suspect you mean the latter, but it's not clear from the current description. It would also be helpful to edit your description to include information on the driver & version you are connecting with as well as how you are verifying data is being returned from the expected server. — Stennie
@Stennie You are correct, I want it to read from it's own local data so that reads are super fast. The db is on the east coast and I don't want it reading from the west coast db. I've updated my question. — Andrew

simagix simagix · Accepted Answer · 2019-01-29T23:18:09

Include readPreferenceTags in your connection string. Refer to the online doc.

By the way, you shouldn't have a even number of nodes in a replica set unless one of them has no voting right.

mongodb not using local database in replica set

2 Answers