Connections for ReadFrom settings

[akshagr]

Hi @mp911de

I do have a Redis cluster with 1 shard (1 master, 1 Replica). I have created a RedisClusterClient, and StatefulRedisClusterConnection. I am using ReadFrom settings on connections, have some doubts -

1. While using ReadFrom.MASTER on connection, and we are passing read, write calls over this connection. Will it create TCP connection on Replica node too ?
2. While using ReadFrom.MASTER on connection, what if connection is exhausted with the read calls, will it create connection to Replica and pass calls to it ?
3. While using ReadFrom.REPLICA_PREFERRED on connection, will it create connection to Master, if we are passing read calls only over this connection ?

Thanks

[mp911de]

ReadFrom.MASTER uses internally an optimization to the write-connection only. Since replicas aren't master nodes, ReadFrom.MASTER does not create read connections to replicas. You might see connections to replicas only in two cases:

1. Topology update
2. Topology changes when a replica is being promoted to a MASTER and if a MASTER is demoted to REPLICA, then the connection remains still open.

If a master is down, then the command is going to timeout. If a slot is not covered, then you will experience a PartitionSelectorException exception.

About REPLICA_PREFERRED: PREFERRED modes prefer to use a particular type of node. We always check if the connection is open and try to use a healthy connection during node selection. Any other ReadFrom than UPSTREAM leads to additional connection creation that are configured with the READONLY flag to avoid cluster redirects when issuing read commands to replicas.

[akshagr]

Thanks a lot for answer !!