[KAFKA-13632] MirrorMaker 2.0 NPE and Warning "Failure to commit records" for filtered records

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.1.0, 3.2.0, 3.3.0
• Fix Version/s: 3.4.0
• Component/s: mirrormaker
• Assignee: Rens Groothuijsen
• Reporter: Bert Baron
• Created: 31/Jan/22 08:31
• Updated: 14/Feb/23 14:31
• Resolved: 15/Sep/22 13:56

Description

We have a setup where we filter records with MirrorMaker 2.0 (see below). This results in the following warning messages as a result of NPE's in MirrorSourceTask.commitRecord for each filtered record:

[2022-01-31 08:01:29,581] WARN [MirrorSourceConnector|task-0] Failure committing record. (org.apache.kafka.connect.mirror.MirrorSourceTask:190)
java.lang.NullPointerException
	at org.apache.kafka.connect.mirror.MirrorSourceTask.commitRecord(MirrorSourceTask.java:177)
	at org.apache.kafka.connect.runtime.WorkerSourceTask.commitTaskRecord(WorkerSourceTask.java:463)
	at org.apache.kafka.connect.runtime.WorkerSourceTask.sendRecords(WorkerSourceTask.java:358)
	at org.apache.kafka.connect.runtime.WorkerSourceTask.execute(WorkerSourceTask.java:257)
	at org.apache.kafka.connect.runtime.WorkerTask.doRun(WorkerTask.java:188)
	at org.apache.kafka.connect.runtime.WorkerTask.run(WorkerTask.java:243)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:829) 

The reason seems to be that for filtered records metadata is null. Note that in the overridden SourceTask.commitRecord the javadoc clearly states that metadata will be null if the record was filtered.

In our case we use a custom predicate, but the issue can be reproduced with the following configuration:

clusters = source,target

tasks.max = 1

source.bootstrap.servers = <cluster1>
target.bootstrap.servers = <cluster2>

offset.storage.replication.factor=1
status.storage.replication.factor=1
config.storage.replication.factor=1

source->target.enabled = true
source->target.topics = topic1
source->target.transforms=Filter
source->target.transforms.Filter.type=org.apache.kafka.connect.transforms.Filter
source->target.transforms.Filter.predicate=HeaderPredicate
source->target.predicates=HeaderPredicate
source->target.predicates.HeaderPredicate.type=org.apache.kafka.connect.transforms.predicates.HasHeaderKey
source->target.predicates.HeaderPredicate.name=someheader
 

Each record with the header key 'someheader' will result in the NPE and warning message.

On a side note, we couldn't find clear documentation on how to configure (SMT) filtering with MirrorMaker 2 or whether this is supported at all, but apart from the NPE's and warning messages this seems to functionally work for us with our custom filter.

 

Issue Links

• is duplicated by: KAFKA-13985 MirrorSourceTask commitRecord throws NPE if SMT is filtering out source record
• links to: GitHub Pull Request #12602