Justinwins created KAFKA-14171:
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             Summary: mm2-offsets topic should be set retention.ms=1h or less 
as default
                 Key: KAFKA-14171
                 URL: https://issues.apache.org/jira/browse/KAFKA-14171
             Project: Kafka
          Issue Type: Bug
    Affects Versions: 3.2.1
            Reporter: Justinwins


- This seems a small bug (or improvment) ,but it really impacts perf of mm2.

- When DistributedHerder starts, it will   startServices()-->  
this.worker.start() --> 

offsetBackingStore.start()  -->  offsetLog.start() ,and finally  in 
`KafkaBasedLog` class ,we 

see `consumer.seekToBeginning(partitions)` . 

Take a look at `org.apache.kafka.connect.util.KafkaBasedLog#start` ,you will 
get to know it.

- Basically, mm2-offsets topic will be kept for 7 days (as defined by 
'retention.ms' ) . If there are many paritions for mm2 to replicate ,then 
mm2-offsets  topic may be quite 'big' in 7 days.  And it  may take a few 
minutes or more to poll unitil the consumer reaches the latest . This is a VERY 
 Cpu-consuming action, and it incurs cpu throttle in the  k8s container.

- I think mm-offsets topic ,or to be specific , KafkaBasedLog  is a special 
topic .At least, we can set a much shorter ttl for it to avoid this bug .

 

 

 

 

 



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