[KAFKA-8375] Offset jumps back after commit

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Later
• Affects Version/s: 1.1.1
• Fix Version/s: 2.4.2
• Component/s: offset manager
• Assignee: Unassigned
• Reporter: Markus Dybeck
• Created: 16/May/19 08:03
• Updated: 14/Oct/21 13:39
• Resolved: 14/Oct/21 13:39

Description

Setup

Kafka: 1.1.1
Kafka-client: 1.1.1
Zookeeper: 3.4.11
Akka streams: 0.20

Topic config

DELETE_RETENTION_MS_CONFIG: "5000"
CLEANUP_POLICY_CONFIG: "compact,delete"
RETENTION_BYTES_CONFIG: 200000000000L
RETENTION_MS_CONFIG: 36000000

Consumer config
AUTO_OFFSET_RESET_CONFIG: "earliest"

Behavior
We have 7 Consumers consuming from 7 partitions, and some of the consumers lag jumped back a bit randomly. No new messages were pushed to the topic during the time.  We didn't see any strange logs during the time, and the brokers did not restart either.

Either way, if there would be a restart or rebalance going on, we can not understand why the offset would jump back after it was committed? 

We did observe it both with logs and by watching metrics of the lag. Our logs pointed out that after we committed the offset, around 30-35 seconds later we consumed an earlier committed message and then the loop begun. The behavior was the same after a restart of all the consumers. The behavior then stopped after a while all by itself.

We have no clue going forward, or if these might be an issue with akka. But is there any known issue that might cause this?

Attaching a screendump with metrics that shows the lag for one partition.