[KAFKA-15607] Possible NPE is thrown in MirrorCheckpointTask

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 2.8.1, 3.6.0
• Fix Version/s: 3.5.2, 3.7.0, 3.6.1
• Component/s: mirrormaker
• Assignee: hudeqi
• Reporter: hudeqi
• Created: 14/Oct/23 16:19
• Updated: 20/Oct/23 16:33
• Resolved: 20/Oct/23 16:33

Description

In the `syncGroupOffset` method, if `targetConsumerOffset.get(topicPartition)` gets null, then the calculation of `latestDownstreamOffset` will throw NPE. This usually occurs in this situation: a group consumed a topic in the target cluster previously. Later, the group offset of some partitions was reset to -1, the `OffsetAndMetadata` of these partitions was null.

It is possible that when reset offsets are performed in the java kafka client, the reset to -1 will be intercepted. However, there are some other types of clients such as sarama, which can magically reset the group offset to -1, so MM2 will trigger an NPE exception in this scenario. Therefore, a defensive measure to avoid NPE is needed here.

Issue Links

• links to: GitHub Pull Request #14587