Fangmin Lv created ZOOKEEPER-2846:
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Summary: Leader follower sync with on disk txns can possibly leads
to data inconsistency
Key: ZOOKEEPER-2846
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2846
Project: ZooKeeper
Issue Type: Bug
Components: quorum
Affects Versions: 3.5.3, 3.4.10, 3.6.0
Reporter: Fangmin Lv
Priority: Critical
On disk txn sync could cause data inconsistency if the current leader just had
a snap sync before it became leader, and then having diff sync with its
followers may synced the txns gap on disk. Here is scenario:
Let's say S0 - S3 are followers, and S4 is leader at the beginning:
1. Stop S2 and send one more request
2. Stop S3 and send more requests to the quorum to let S3 have a snap sync with
S4 when it started up
3. Stop S4 and S3 became the new leader
4. Start S2 and had a diff sync with S3, now there are gaps in S2
Attached the test case to verify the issue. Currently, there is no efficient
way to check the gap in txn files is a real gap or due to Epoch change. We need
to add that support, but before that, it would be safer to disable the on disk
txn leader-follower sync.
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