[KAFKA-10465] Potential Bug/Doc update in Transactional Producer and Isolation Level

• Type: Bug
• Status: Open
• Priority: Critical
• Resolution: Unresolved
• Affects Version/s: 2.4.1
• Component/s: clients
• Flags: Important
• Assignee: Unassigned
• Reporter: M. Manna
• Created: 07/Sep/20 12:16
• Updated: 01/Oct/20 03:48

Description

Issue

Difference between LSO and High Watermark offsets when a consumer with "read_committed" aren't probably explained in the correct place.

Expected Behaviour
According to documentation, the offset returned should be the one committed last (and successfully).

Observed (with steps)

1. Start a local or test kafka cluster (2.4.1 or above)
2. Create a topic (I have used 3 replication-factor with 1 partition, but 1 and 1 is good)
3. Use the attached producer app file and set debug pointer to be able to pause on print
4. Use the attached consumer app file to start a consumer and debug through steps.

It can be seen that the consumer is actually able to fetch an offset that's not committed by the producer yet.

Just trying to raise this ticket to confirm whether:

1) this is well-documented anywhere (which I have missed) - Please refer to this documentation as a resolution

2) This is a bug - please confirm and provide a timeline when this can be fixed.