Luke Chen created KAFKA-15414:
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             Summary: remote logs get deleted after partition reassignment
                 Key: KAFKA-15414
                 URL: https://issues.apache.org/jira/browse/KAFKA-15414
             Project: Kafka
          Issue Type: Bug
            Reporter: Luke Chen
         Attachments: image-2023-08-29-11-12-58-875.png

it seems I'm reaching that codepath when running reassignments on my cluster 
and segment are deleted from remote store despite a huge retention (topic 
created a few hours ago with 1000h retention).
It seems to happen consistently on some partitions when reassigning but not all 
partitions.

My test:

I have a test topic with 30 partition configured with 1000h global retention 
and 2 minutes local retention
I have a load tester producing to all partitions evenly
I have consumer load tester consuming that topic
I regularly reset offsets to earliest on my consumer to test backfilling from 
tiered storage.

My consumer was catching up consuming the backlog and I wanted to upscale my 
cluster to speed up recovery: I upscaled my cluster from 3 to 12 brokers and 
reassigned my test topic to all available brokers to have an even 
leader/follower count per broker.

When I triggered the reassignment, the consumer lag dropped on some of my topic 
partitions:
!image-2023-08-29-11-12-58-875.png|width=800,height=79! Screenshot 2023-08-28 
at 20 57 09

Later I tried to reassign back my topic to 3 brokers and the issue happened 
again.

Both times in my logs, I've seen a bunch of logs like:

[RemoteLogManager=10005 partition=uR3O_hk3QRqsn4mPXGFoOw:loadtest11-17] Deleted 
remote log segment RemoteLogSegmentId

{topicIdPartition=uR3O_hk3QRqsn4mPXGFoOw:loadtest11-17, 
id=Mk0chBQrTyKETTawIulQog}

due to leader epoch cache truncation. Current earliest epoch: 
EpochEntry(epoch=14, startOffset=46776780), segmentEndOffset: 46437796 and 
segmentEpochs: [10]

Looking at my s3 bucket. The segments prior to my reassignment have been indeed 
deleted.



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