[ZOOKEEPER-1202] Prevent certain state transitions in Java client on close(); improve exception handling and enhance client testability

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.4.0
• Component/s: java client
• Tags: Java client
• Assignee: Matthias Spycher
• Reporter: Matthias Spycher
• Created: 23/Sep/11 01:56
• Updated: 03/Feb/22 08:50

Description

ZooKeeper.close() doesn't force the client into a CLOSED state. While the closing flag ensures that the client will close, its state may end up in CLOSED, CONNECTING or CONNECTED.
I developed a patch and in the process cleaned up a few other things primarily to enable testing of state transitions.

• ClientCnxnState is new and enforces certain state transitions
• ZooKeeper.isExpired() is new
• ClientCnxn no longer refers to ZooKeeper, WatchManager is externalized, and ClientWatchManager includes 3 new methods
• The SendThread terminates the EventThread on a call to close() via the event-of-death
• Polymorphism is used to handle internal exceptions (SendIOExceptions)
• The patch incorporates ZOOKEEPER-126.patch and prevents close() from blocking

Issue Links

• incorporates: ZOOKEEPER-126 zookeeper client close operation may block indefinitely