[redis-db] Cluster mutation: one extra master with 0 slots.

[shariq islam]

Hi Guys,

We have noticed a strange scenario recently with our Redis Cluster. We have
configured our cluster with 8 masters and 2 slaves per node which makes
total of 24 nodes. This was running fine, but we noticed somehow our
cluster got mutated and the mutation resulted us in having 9 masters and 6
masters having 2 slaves 3 masters having one slave. Also the extra master
had two slaves, On further checking it was found that the extra master had
no hash slots assigned.

We tried to replicate the scenario by creating network partitions (We
believe a network partition might cause this). But all our efforts went in
vain and we basically figured out that no matter what we do the partition
side with majority of masters keeps functioning and side with minority
masters goes in state of cluster down.

We want to find out what might have caused this? and we want to prevent
this in future.

Thanks,
Shariq Islam