Trying to get a handle on expected poolSize and we’ve looked through the other posts here. Latest nodejs driver/nodejs v14; 3 shard cluster (4.4.9) with 3 voting/2 non-voting members in each plus 3 member config replicaset. 7 mongos, each with a number of nodejs applications accessing the cluster (all with connection pooling in the applications).
Is our maths right:
For each application connection to mongos, there are 6 monitoring connections to other mongos, 18 monitoring connections to each mongod (3 x 5 + 3), and then the default maxPoolSize (5) times 18, so per application we could expect 114 connections?
We are seeing a lot of connection pool constraints messages in the mongos logs and we’re just trying to adjust things so it quietens down the reconnections.
Any guidance or clarity very much appreciated,
Rob