[KAFKA-9600] EndTxn handler should check strict epoch equality

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.6.0
• Assignee: Boyang Chen
• Reporter: Jason Gustafson
• Created: 24/Feb/20 18:42
• Updated: 28/Mar/20 17:55
• Resolved: 28/Mar/20 17:55

Description

The EndTxn path in TransactionCoordinator is shared between direct calls to EndTxn from the client and internal transaction abort logic. To support the latter, the code is written to allow an epoch bump. However, if the client bumps the epoch unexpectedly (e.g. due to a buggy implementation), then the internal invariants are violated which results in a hanging transaction. Specifically, the transaction is left in a pending state because the epoch following append to the log does not match what we expect.

To fix this, we should ensure that an EndTxn from the client checks for strict epoch equality.

Issue Links

• links to: GitHub Pull Request #8164