[CURATOR-570] Excessive calls to ZooKeeper.updateServerList (which can result in session death)

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 4.2.0, 4.3.0
• Component/s: Framework
• Assignee: Unassigned
• Reporter: Rhys Yarranton
• Created: 12/May/20 00:37
• Updated: 24/Jun/20 22:46

Description

On suspend and reconnect, Curator calls ZooKeeper.updateServerList via ConnectionState.checkState --> ConnectionState.handleNewConnectionString.  In addition, recipes may be triggered by this as well, and they too make calls ZooKeeper.updateServerList via ConnectState.checkTimeouts --> ConnectionState.handleNewConnectionString.

This happens even though the connection string has not actually changed.

Due to ZOOKEEPER-3825, this can cause the connection to be closed immediately.  On its own this would be perceived as a glitch.  But due to the Curator-induced calls, what we see is a cycle of SUSPENDED/RECONNECTED, until eventually the session dies and a new session is recreated.

Based on the source code (at time of writing), ZooKeeper.updateServerList is not intended to be called frequently like this.

Issue Links

• relates to: ZOOKEEPER-3825 StaticHostProvider.updateServerList address matching fails when connectString uses IP addresses
• relates to: CURATOR-551 Curator client always call updateServerList with original serverList value, not the ones updated by EnsembleTracker