The controller elects a new leader from the ISR for a partition when the current one dies. My understanding is that this data is persisted in Zookeeper. What happens when a Zookeeper node dies during this write? Can this mean that some brokers might still different leader for the newly-leader-elected partition?
I tried digging around the docs but could not find anything satisfactory.
My understanding is that this data is persisted in Zookeeper
Yes, This ISR set is persisted to ZooKeeper whenever it changes. (Reference)
What happens when a Zookeeper node dies during this write?
Zookeeper works on quorum and it means majority of servers from the cluster. (See this SO answer) (snippet below)
With a 3 node cluster, the majority is 2 nodes. So you can tolerate only 1 node not being in sync at the same time.
With a 5 node cluster, the majority is 3 nodes. So you can tolerate only 2 nodes not being in sync at the same time.
So long as there is majority, the decision is made and so the leader election will continue.
