[ZOOKEEPER-1209] LeaderElection recipe doesn't handle the split-brain issue, n/w disconnection can bring both the client nodes to be in ELECTED - ASF JIRA

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Details

Type: Bug
Status: Patch Available
Priority: Major
Resolution: Unresolved
Affects Version/s: 3.3.3
Fix Version/s: None
Component/s: recipes
Labels:
None

Description

Case1- N/w disconnection can bring both the client nodes to be in ELECTED state. Current LeaderElectionSupport(LES) f/w handles only 'NodeDeletion'.

Consider the scenario where ELECTED and READY nodes are running. Say ELECTED node's n/w got failed and is "Disconnected" from ZooKeeper. But it will behave as ELECTED as it is not getting any events from the LeaderElectionSupport(LES) framework.
After sessiontimeout, node in READY state will be notified by 'NodeDeleted' event and will go to ELECTED state.
Problem:
Both the node becomes ELECTED and finally the user sees two Master (ELECTED) node and cause inconsistencies.

Case2- Also in this case, Let's say if user has started only one client node and becomes ELECTED. After sometime n/w has disconnected with the ZooKeeper server and the session got expired.
Problem:
Still the client node will be in the ELECTED state. After sometime if user has started the second client node. Again both the nodes becomes ELECTED.