[FLINK-27848] ZooKeeperLeaderElectionDriver keeps writing leader information, using up zxid

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.15.0, 1.17.0, 1.16.1
• Fix Version/s: 1.15.1, 1.17.0, 1.16.2
• Component/s: Runtime / Coordination
• Labels: pull-request-available
• Assignee: Matthias Pohl
• Reporter: Xintong Song
• Created: 31/May/22 06:46
• Updated: 03/Feb/23 08:29
• Resolved: 03/Feb/23 08:29

Description

After a leadership change, the new leader may keeps writing its information (which is identical) to ZK, causing the zxid on ZK quickly used up.

The problem is that, in ZooKeeperLeaderElectionDriver#retrieveLeaderInformationFromZooKeeper, leaderElectionEventHandler.onLeaderInformationChange(LeaderInformation.empty()) is called no matter childData is null or not. In case of non-null, this will cause the driver keeps re-writing the leader information to ZK.

The problem was introduced in FLINK-24038, and only affects the legacy ZooKeeperHaServices. Thus, only 1.15 are affected.

Issue Links

• links to: GitHub Pull Request #19853
• links to: GitHub Pull Request #21825
• links to: GitHub Pull Request #21826