Kezhu Wang created ZOOKEEPER-4882:
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Summary: Data loss after restarting an node experienced temporary
disk error and rejoin
Key: ZOOKEEPER-4882
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-4882
Project: ZooKeeper
Issue Type: Bug
Components: server
Affects Versions: 3.9.3, 3.8.4
Reporter: Kezhu Wang
The cause is multifold:
1. Leader will commit a proposal once quorum acked.
2. Proposal is able to be committed in node's memory even if it has not
been written to that node's disk.
3. In case of disk error, the txn log could lag behind memory database.
The above applies to both leader and follower. I have not verified leader
branch, let's consider only follower for now.
f4. A follower experienced temporary disk error will have hole in txn log
after re-join.
f5. Restarted follower will lose the data. Worse, it is able to win
election and propagate data loss to whole cluster.
I authored commits in my repo to expose this.
https://github.com/kezhuw/zookeeper/commits/data-loss-temporary-sync-disk-error/
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