[ZOOKEEPER-2988] NPE triggered if server receives a vote for a server id not in their voting view

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.5.3, 3.4.11, 3.4.12
• Fix Version/s: 3.5.4, 3.6.0, 3.4.13
• Component/s: leaderElection
• Assignee: Brian Nixon
• Reporter: Brian Nixon
• Created: 01/Mar/18 20:18
• Updated: 17/Jul/18 04:49
• Resolved: 30/Apr/18 04:35

Description

We've observed the following behavior in elections when a node is lagging behind the quorum in its view of the ensemble topology.

• Node A is operating with node B in its voting view, but without view of node C.

• B votes for C.

• A then switches its vote to C, but throws a NPE when attempting to connect.

This causes the QuorumPeer to spin up a Follower only to immediately have it shutdown by the exception.

Ideally, A would not advertise a vote for a server that it will not follow.

Issue Links

• links to: GitHub Pull Request #476
• links to: GitHub Pull Request #477
• links to: GitHub Pull Request #478