Zili Chen created CURATOR-653:
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Summary: Double leader for LeaderLatch
Key: CURATOR-653
URL: https://issues.apache.org/jira/browse/CURATOR-653
Project: Apache Curator
Issue Type: Task
Components: Recipes
Reporter: Zili Chen
Assignee: Zili Chen
Fix For: 5.4.0
Reported by @woaishixiaoxiao:
When I use the LeaderLatch to select leader, there is a double-leader
phenomenon.
The timeline is as follows：
1. The zk cluster switch leader node bescause of zxid overflow. The cluster is
unavailable to the outside world
2. A client(not leader befor zxid overflow) and B client(is leader before zxid
overflow) enter the suspend state, B client set its leader status to false
3. The zk cluster complete the leader node election and the cluster back to
normal
4. A client enter the reconnect state and call the reset function, set its
leader status to false.
5. B client enter the reconnect state, call the reset function. set its leader
status to false. Delete its old path.
6. A client receive preNodeDeleteEvent. Then getChildren from zkServer. Find
itself is the smallest number and set itself as a leader.
7. B client create a new temporary node and then getChildren from zkServer.
Find itself not the node with the smallest serial number and listen to the
previous node delete event.
8. A client delete its old path.
9. B client receive the preNodeDeleteEvent. then getchildren from zkServer.
Find itself is the smallest sequence number and then set itself as a leader
10. A client create a new temporary node and then getChildren from zkServer.
Find itself not the node with the smallest serial number and listen to the
previous node delete event. but it doesn't set itself as a non-leader state.
because of the sixth step operation, A still is leader state now.
11. now A client and B client are the leader at the same time
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