Hi Kamal, The scenario you described only happened with the old version RemoteLogSegmentUpdateMetadata message, since the endOffset will be added in the new RemoteLogSegmentUpdateMetadata schema. For the existing RemoteLogSegmentUpdateMetadata messages, we rely on the time based retention policy to clean up. Does that make sense?
Best, Lijun Tong Kamal Chandraprakash <[email protected]> 于2026年3月30日周一 18:14写道： > Hi Lijun, > > RemoteLogSegmentUpdateMetadata event does not have all the > fields/attributes similar to RemoteLogSegmentMetadata event. > > Assume that after compaction, for a segment, we have only > COPY_SEGMENT_FINISHED records. How do you plan to retrieve the other fields > after broker restart? > > Thanks, > Kamal > > On Mon, Mar 30, 2026, 23:22 Lijun Tong <[email protected]> wrote: > > > Hi Kamal, > > > > Thanks for taking another look at the KIP. > > 1. I have removed the left-over line about using another new topic from > the > > KIP. > > 2. > > > > > 2. Assume that the topic is enabled with compaction and only one event > is > > > maintained per segment. If there is a transient error in the remote log > > > deletion, > > > then the COPY_SEGMENT started / finished events might be compacted > by > > > the DELETE_SEGMENT_STARTED events. If the broker is restarted during > > > this time, will there be dangling remote log segments? Currently, > > > during restart, the broker discards the events if it does not see the > > > COPY_SEGMENT_STARTED events. > > > > > > I am glad you asked this question, I didn't mention this part in my > current > > design to avoid distractions from the main design, but I plan to add > > another background thread to clean up all the stale messages by comparing > > the message's endOffset with the topic partition's log start offset. I > > believe this would help remove all the dangling messages. > > > > Thanks, > > Lijun TOng > > > > Kamal Chandraprakash <[email protected]> 于2026年3月29日周日 > > 22:48写道： > > > > > Hi Lijun, > > > > > > Sorry for the late reply. Went over the KIP again. Overall LGTM. Few > > > points: > > > > > > > This KIP aims to solve this issue through introducing another > compacted > > > topic for the brokers to bootstrap the state from > > > > > > 1. Shall we update the motivation section to mention that another topic > > is > > > not introduced? > > > 2. Assume that the topic is enabled with compaction and only one event > is > > > maintained per segment. If there is a transient error in the remote log > > > deletion, > > > then the COPY_SEGMENT started / finished events might be compacted > by > > > the DELETE_SEGMENT_STARTED events. If the broker is restarted during > > > this time, will there be dangling remote log segments? Currently, > > > during restart, the broker discards the events if it does not see the > > > COPY_SEGMENT_STARTED events. > > > > > > Thanks, > > > Kamal > > > > > > On Thu, Mar 26, 2026 at 5:08 AM Lijun Tong <[email protected]> > > > wrote: > > > > > > > Hi, > > > > > > > > I have started a Vote thread for this KIP, considering all questions > > > raised > > > > so far have been answered. I am happy to continue the discussion if > > > needed, > > > > otherwise, this is a friendly reminder on the vote for this KIP. > > > > > > > > Thanks, > > > > Lijun Tong > > > > > > > > > > > > > > > > Lijun Tong <[email protected]> 于2026年1月19日周一 17:59写道： > > > > > > > > > Hey Kamal, > > > > > > > > > > Thanks for raising these questions. Here are my responses to your > > > > > questions: > > > > > Q1 and Q2: > > > > > I think both questions boil down to how to release this new > feature, > > > both > > > > > questions are valid concerns. The solution I have in mind is this > > > feature > > > > > is *gated by the metadata version*. The new tombstone semantics and > > the > > > > > additional fields (for example in RemoteLogSegmentUpdateRecord) are > > > only > > > > > enabled once the cluster metadata version is upgraded to the > version > > > that > > > > > introduces this feature. As long as the cluster metadata version is > > not > > > > > bumped, the system will not produce tombstone records. Therefore, > > > during > > > > > rolling upgrades (mixed 4.2/4.3 brokers), the feature remains > > > effectively > > > > > disabled. Tombstones will only start being produced after the > > metadata > > > > > version is upgraded, at which point all brokers are already > required > > to > > > > > support the new behavior. > > > > > > > > > > Since Kafka does not support metadata version downgrades at the > > moment, > > > > > once a metadata version that supports this feature is enabled, it > > > cannot > > > > be > > > > > downgraded to a version that does not support it. I will add these > > > > details > > > > > to the KIP later. > > > > > Q3. This is an *editing mistake* in the KIP. Thanks for pointing it > > > out — > > > > > the enum value has already been corrected in the latest revision to > > > > remove > > > > > the unused placeholder and keep the state values contiguous and > > > > consistent. > > > > > Q4. I don't foresee the quota mechanism will interfere with the > state > > > > > transition in any way so far, let me know if any concern hits you. > > > > > > > > > > Thanks, > > > > > Lijun > > > > > > > > > > Kamal Chandraprakash <[email protected]> > 于2026年1月18日周日 > > > > > 00:40写道： > > > > > > > > > >> Hi Lijun, > > > > >> > > > > >> Thanks for updating the KIP! > > > > >> > > > > >> The updated migration plan looks clean to me. Few questions: > > > > >> > > > > >> 1. The ConsumerTask in 4.2 Kafka build does not handle the > tombstone > > > > >> records. Should the tombstone records be sent only when all the > > > brokers > > > > >> are > > > > >> upgraded to 4.3 version? > > > > >> > > > > >> 2. Once all the brokers are upgraded and the __remote_log_metadata > > > topic > > > > >> cleanup policy changed to compact. Then, downgrading the brokers > is > > > not > > > > >> allowed as the records without key will throw an error while > > producing > > > > the > > > > >> compacted topic. Shall we mention this in the compatibility > section? > > > > >> > > > > >> 3. In the RemoteLogSegmentState Enum, why is the value 1 marked as > > > > unused? > > > > >> > > > > >> 4. Regarding the key > (TopicIdPartition:EndOffset:BrokerLeaderEpoch), > > > we > > > > >> may > > > > >> have to check for scenarios where there is segment lag due to > remote > > > log > > > > >> write quota. Will the state transition work correctly? Will come > > back > > > to > > > > >> this later. > > > > >> > > > > >> Thanks, > > > > >> Kamal > > > > >> > > > > >> On Fri, Jan 16, 2026 at 4:50 AM jian fu <[email protected]> > > wrote: > > > > >> > > > > >> > Hi Lijun and Kamal > > > > >> > I also think we don't need to keep delJIanpolicy in final > > config，if > > > > >> so，we > > > > >> > should always keep remembering all of our topic retention time > > must > > > > less > > > > >> > than the value，right？It is one protect with risk involved. > > > > >> > Regards > > > > >> > JIan > > > > >> > > > > > >> > > > > > >> > > > > > >> > Lijun Tong <[email protected]>于2026年1月16日 周五06:45写道： > > > > >> > > > > > >> > > Hey Kamal, > > > > >> > > > > > > >> > > Some additional points about the Q4, > > > > >> > > > > > > >> > > > The user can decide when to change their internal topic > > cleanup > > > > >> policy > > > > >> > to > > > > >> > > > compact. If someone retains > > > > >> > > > the data in the remote storage for 3 months, then they can > > > migrate > > > > >> to > > > > >> > the > > > > >> > > > compacted topic after 3 months > > > > >> > > > post rolling out this change. And, update their cleanup > policy > > > to > > > > >> > > [compact, > > > > >> > > > delete]. > > > > >> > > > > > > >> > > > > > > >> > > I don't think it's a good idea to keep delete in the final > > cleanup > > > > >> policy > > > > >> > > for the topic `__remote_log_metadata`, as this still requires > > the > > > > >> user to > > > > >> > > keep track of the max retention hours of topics that have > remote > > > > >> storage > > > > >> > > enabled, and it's operational burden. It's also hard to reason > > > about > > > > >> what > > > > >> > > will happen if the user configures the wrong retention.ms. I > > hope > > > > >> this > > > > >> > > makes sense. > > > > >> > > > > > > >> > > > > > > >> > > Thanks, > > > > >> > > Lijun Tong > > > > >> > > > > > > >> > > Lijun Tong <[email protected]> 于2026年1月15日周四 11:43写道： > > > > >> > > > > > > >> > > > Hey Kamal, > > > > >> > > > > > > > >> > > > Thanks for your reply! I am glad we are on the same page > with > > > > making > > > > >> > the > > > > >> > > > __remote_log_metadata topic compacted optional for the user > > > now, I > > > > >> will > > > > >> > > > update the KIP with this change. > > > > >> > > > > > > > >> > > > For the Q2: > > > > >> > > > With the key designed as > > > > >> TopicId:Partition:EndOffset:BrokerLeaderEpoch, > > > > >> > > > even the same broker retries the upload multiple times for > the > > > > same > > > > >> log > > > > >> > > > segment, the latest retry attempt with the latest segment > UUID > > > > will > > > > >> > > > overwrite the previous attempts' value since they share the > > same > > > > >> key, > > > > >> > so > > > > >> > > we > > > > >> > > > don't need to explicitly track the failed upload metadata, > > > because > > > > >> it's > > > > >> > > > gone already by the later attempt. That's my understanding > > about > > > > the > > > > >> > > > RLMCopyTask, correct me if I am wrong. > > > > >> > > > > > > > >> > > > Thanks, > > > > >> > > > Lijun Tong > > > > >> > > > > > > > >> > > > Kamal Chandraprakash <[email protected]> > > > > 于2026年1月14日周三 > > > > >> > > > 21:18写道： > > > > >> > > > > > > > >> > > >> Hi Lijun, > > > > >> > > >> > > > > >> > > >> Thanks for the reply! > > > > >> > > >> > > > > >> > > >> Q1: Sounds good. Could you clarify it in the KIP that the > > same > > > > >> > > partitioner > > > > >> > > >> will be used? > > > > >> > > >> > > > > >> > > >> Q2: With TopicId:Partition:EndOffset:BrokerLeaderEpoch key, > > if > > > > the > > > > >> > same > > > > >> > > >> broker retries the upload due to intermittent > > > > >> > > >> issues in object storage (or) RLMM. Then, those failed > upload > > > > >> metadata > > > > >> > > >> also > > > > >> > > >> need to be cleared. > > > > >> > > >> > > > > >> > > >> Q3: We may have to skip the null value records in the > > > > ConsumerTask. > > > > >> > > >> > > > > >> > > >> Q4a: The idea is to keep the cleanup policy as "delete" and > > > also > > > > >> send > > > > >> > > the > > > > >> > > >> tombstone markers > > > > >> > > >> to the existing `__remote_log_metadata` topic. And, handle > > the > > > > >> > tombstone > > > > >> > > >> records in the ConsumerTask. > > > > >> > > >> > > > > >> > > >> The user can decide when to change their internal topic > > cleanup > > > > >> policy > > > > >> > > to > > > > >> > > >> compact. If someone retains > > > > >> > > >> the data in the remote storage for 3 months, then they can > > > > migrate > > > > >> to > > > > >> > > the > > > > >> > > >> compacted topic after 3 months > > > > >> > > >> post rolling out this change. And, update their cleanup > > policy > > > to > > > > >> > > >> [compact, > > > > >> > > >> delete]. > > > > >> > > >> > > > > >> > > >> Thanks, > > > > >> > > >> Kamal > > > > >> > > >> > > > > >> > > >> On Thu, Jan 15, 2026 at 4:12 AM Lijun Tong < > > > > >> [email protected]> > > > > >> > > >> wrote: > > > > >> > > >> > > > > >> > > >> > Hey Jian, > > > > >> > > >> > > > > > >> > > >> > Thanks for your time to review this KIP. I appreciate > that > > > you > > > > >> > > propose a > > > > >> > > >> > simpler migration solution to onboard the new feature. > > > > >> > > >> > > > > > >> > > >> > There are 2 points that I think can be further refined > on: > > > > >> > > >> > > > > > >> > > >> > 1). make the topic compacted optional, although the new > > > feature > > > > >> will > > > > >> > > >> > continue to emit tombstone message for those expired log > > > > segments > > > > >> > even > > > > >> > > >> when > > > > >> > > >> > the topic is still on time-based retention mode, so once > > user > > > > >> > switched > > > > >> > > >> to > > > > >> > > >> > using the compacted topic, those expired messages can > still > > > be > > > > >> > deleted > > > > >> > > >> > despite the topic is not retention based anymore. > > > > >> > > >> > 2). we need to expose some flag to the user to indicate > > > whether > > > > >> the > > > > >> > > >> topic > > > > >> > > >> > can be flipped to compacted by checking whether all the > old > > > > >> format > > > > >> > > >> > keyed-less message has expired, and allow user to choose > to > > > > flip > > > > >> to > > > > >> > > >> > compacted only when the flag is true. > > > > >> > > >> > > > > > >> > > >> > Thanks for sharing your idea. I will update the KIP later > > > with > > > > >> this > > > > >> > > new > > > > >> > > >> > idea. > > > > >> > > >> > > > > > >> > > >> > Best, > > > > >> > > >> > Lijun Tong > > > > >> > > >> > > > > > >> > > >> > > > > > >> > > >> > jian fu <[email protected]> 于2026年1月12日周一 04:55写道： > > > > >> > > >> > > > > > >> > > >> > > Hi Lijun Tong: > > > > >> > > >> > > > > > > >> > > >> > > Thanks for your KIP which raise this critical issue. > > > > >> > > >> > > > > > > >> > > >> > > what about just keep one topic instead of involve > another > > > > >> topic. > > > > >> > > >> > > for existed topic data's migration. maybe we can use > this > > > way > > > > >> to > > > > >> > > solve > > > > >> > > >> > the > > > > >> > > >> > > issue: > > > > >> > > >> > > (1) set the retention date > all of topic which enable > > > remote > > > > >> > > >> storage's > > > > >> > > >> > > retention time > > > > >> > > >> > > (2) deploy new kafka version with feature: which send > > the > > > > >> message > > > > >> > > >> with > > > > >> > > >> > key > > > > >> > > >> > > (3) wait all the message expired and new message with > key > > > > >> coming > > > > >> > to > > > > >> > > >> the > > > > >> > > >> > > topic > > > > >> > > >> > > (4) convert the topic to compact > > > > >> > > >> > > > > > > >> > > >> > > I don't test it. Just propose this solution according > to > > > code > > > > >> > review > > > > >> > > >> > > result. just for your reference. > > > > >> > > >> > > The steps maybe a little complex. but it can avoiding > add > > > new > > > > >> > topic. > > > > >> > > >> > > > > > > >> > > >> > > Regards > > > > >> > > >> > > Jian > > > > >> > > >> > > > > > > >> > > >> > > Lijun Tong <[email protected]> 于2026年1月8日周四 > > 09:17写道： > > > > >> > > >> > > > > > > >> > > >> > > > Hey Kamal, > > > > >> > > >> > > > > > > > >> > > >> > > > > > > > >> > > >> > > > Thanks for your time for the review. > > > > >> > > >> > > > > > > > >> > > >> > > > > > > > >> > > >> > > > Here is my response to your questions: > > > > >> > > >> > > > > > > > >> > > >> > > > Q1 At this point, I don’t see a need to change > > > > >> > > >> > > > RemoteLogMetadataTopicPartitioner for this design. > > > Nothing > > > > in > > > > >> > the > > > > >> > > >> > current > > > > >> > > >> > > > approach appears to require a partitioner change, but > > I’m > > > > >> open > > > > >> > to > > > > >> > > >> > > > revisiting if a concrete need arises. > > > > >> > > >> > > > > > > > >> > > >> > > > Q2 I have some reservations about using > SegmentId:State > > > as > > > > >> the > > > > >> > > key. > > > > >> > > >> A > > > > >> > > >> > > > practical challenge we see today is that the same > > logical > > > > >> > segment > > > > >> > > >> can > > > > >> > > >> > be > > > > >> > > >> > > > retried multiple times with different SegmentIds > across > > > > >> brokers. > > > > >> > > If > > > > >> > > >> the > > > > >> > > >> > > key > > > > >> > > >> > > > is SegmentId-based, it becomes harder to discover and > > > > >> tombstone > > > > >> > > all > > > > >> > > >> > > related > > > > >> > > >> > > > attempts when the segment eventually expires. The > > > > >> > > >> > > > TopicId:Partition:EndOffset:BrokerLeaderEpoch key is > > > > >> > deterministic > > > > >> > > >> for > > > > >> > > >> > a > > > > >> > > >> > > > logical segment attempt and helps group retries by > > epoch, > > > > >> which > > > > >> > > >> > > simplifies > > > > >> > > >> > > > cleanup and reasoning about state. I’d love to > > understand > > > > the > > > > >> > > >> benefits > > > > >> > > >> > > > you’re seeing with SegmentId:State compared to the > > > > >> > > >> offset/epoch-based > > > > >> > > >> > key > > > > >> > > >> > > > so we can weigh the trade-offs. > > > > >> > > >> > > > > > > > >> > > >> > > > On partitioning: with this proposal, all states for a > > > given > > > > >> user > > > > >> > > >> > > > topic-partition still map to the same metadata > > partition. > > > > >> That > > > > >> > > >> remains > > > > >> > > >> > > true > > > > >> > > >> > > > for the existing __remote_log_metadata (unchanged > > > > >> partitioner) > > > > >> > and > > > > >> > > >> for > > > > >> > > >> > > the > > > > >> > > >> > > > new __remote_log_metadata_compacted, preserving the > > > > >> properties > > > > >> > > >> > > > RemoteMetadataCache relies on. > > > > >> > > >> > > > > > > > >> > > >> > > > Q3 It should be fine for ConsumerTask to ignore > > tombstone > > > > >> > records > > > > >> > > >> (null > > > > >> > > >> > > > values) and no-op. > > > > >> > > >> > > > > > > > >> > > >> > > > Q4 Although TBRLMM is a sample RLMM implementation, > > it’s > > > > >> > currently > > > > >> > > >> the > > > > >> > > >> > > only > > > > >> > > >> > > > OSS option and is widely used. The new > > > > >> > > >> __remote_log_metadata_compacted > > > > >> > > >> > > > topic offers clear operational benefits in that > > context. > > > We > > > > >> can > > > > >> > > also > > > > >> > > >> > > > provide a configuration to let users choose whether > > they > > > > >> want to > > > > >> > > >> keep > > > > >> > > >> > the > > > > >> > > >> > > > audit topic (__remote_log_metadata) in their cluster. > > > > >> > > >> > > > > > > > >> > > >> > > > Q4a Enabling compaction on __remote_log_metadata > alone > > > may > > > > >> not > > > > >> > > fully > > > > >> > > >> > > > address the unbounded growth, since we also need to > > emit > > > > >> > > tombstones > > > > >> > > >> for > > > > >> > > >> > > > expired keys to delete them. Deferring compaction and > > > > >> > tombstoning > > > > >> > > to > > > > >> > > >> > user > > > > >> > > >> > > > configuration could make the code flow complicated, > > also > > > > add > > > > >> > > >> > operational > > > > >> > > >> > > > complexity and make outcomes less predictable. The > > > proposal > > > > >> aims > > > > >> > > to > > > > >> > > >> > > provide > > > > >> > > >> > > > a consistent experience by defining deterministic > keys > > > and > > > > >> > > emitting > > > > >> > > >> > > > tombstones as part of the broker’s responsibilities, > > > while > > > > >> still > > > > >> > > >> > allowing > > > > >> > > >> > > > users to opt out of the audit topic if they prefer. > > But I > > > > am > > > > >> > open > > > > >> > > to > > > > >> > > >> > more > > > > >> > > >> > > > discussion if there is any concrete need I don't > > foresee. > > > > >> > > >> > > > > > > > >> > > >> > > > > > > > >> > > >> > > > Thanks, > > > > >> > > >> > > > > > > > >> > > >> > > > Lijun Tong > > > > >> > > >> > > > > > > > >> > > >> > > > Kamal Chandraprakash <[email protected] > > > > > > >> > > 于2026年1月6日周二 > > > > >> > > >> > > > 01:01写道： > > > > >> > > >> > > > > > > > >> > > >> > > > > Hi Lijun, > > > > >> > > >> > > > > > > > > >> > > >> > > > > Thanks for the KIP! Went over the first pass. > > > > >> > > >> > > > > > > > > >> > > >> > > > > Few Questions: > > > > >> > > >> > > > > > > > > >> > > >> > > > > 1. Are we going to maintain the same > > > > >> > > >> > RemoteLogMetadataTopicPartitioner > > > > >> > > >> > > > > < > > > > >> > > >> > > > > > > > > >> > > >> > > > > > > > >> > > >> > > > > > > >> > > >> > > > > > >> > > >> > > > > >> > > > > > > >> > > > > > >> > > > > > > > > > > https://sourcegraph.com/github.com/apache/kafka/-/blob/storage/src/main/java/org/apache/kafka/server/log/remote/metadata/storage/RemoteLogMetadataTopicPartitioner.java > > > > >> > > >> > > > > > > > > > >> > > >> > > > > for both the topics? It is not clear in the KIP, > > could > > > > you > > > > >> > > clarify > > > > >> > > >> > it? > > > > >> > > >> > > > > 2. Can the key be changed to SegmentId:State > instead > > of > > > > >> > > >> > > > > TopicId:Partition:EndOffset:BrokerLeaderEpoch if > the > > > same > > > > >> > > >> partitioner > > > > >> > > >> > > is > > > > >> > > >> > > > > used? It is good to maintain all the segment states > > > for a > > > > >> > > >> > > > > user-topic-partition in the same metadata > partition. > > > > >> > > >> > > > > 3. Should we have to handle the records with null > > value > > > > >> > > >> (tombstone) > > > > >> > > >> > in > > > > >> > > >> > > > the > > > > >> > > >> > > > > ConsumerTask > > > > >> > > >> > > > > < > > > > >> > > >> > > > > > > > > >> > > >> > > > > > > > >> > > >> > > > > > > >> > > >> > > > > > >> > > >> > > > > >> > > > > > > >> > > > > > >> > > > > > > > > > > https://sourcegraph.com/github.com/apache/kafka/-/blob/storage/src/main/java/org/apache/kafka/server/log/remote/metadata/storage/ConsumerTask.java?L166 > > > > >> > > >> > > > > > > > > > >> > > >> > > > > ? > > > > >> > > >> > > > > 4. TBRLMM > > > > >> > > >> > > > > < > > > > >> > > >> > > > > > > > > >> > > >> > > > > > > > >> > > >> > > > > > > >> > > >> > > > > > >> > > >> > > > > >> > > > > > > >> > > > > > >> > > > > > > > > > > https://sourcegraph.com/github.com/apache/kafka/-/blob/storage/src/main/java/org/apache/kafka/server/log/remote/metadata/storage/TopicBasedRemoteLogMetadataManager.java > > > > >> > > >> > > > > > > > > > >> > > >> > > > > is a sample plugin implementation of RLMM. Not sure > > > > whether > > > > >> > the > > > > >> > > >> > > community > > > > >> > > >> > > > > will agree to add one more internal topic for this > > > plugin > > > > >> > impl. > > > > >> > > >> > > > > 4a. Can we modify the new messages to the > > > > >> > __remote_log_metadata > > > > >> > > >> topic > > > > >> > > >> > > to > > > > >> > > >> > > > > contain the key and leave it to the user to enable > > > > >> compaction > > > > >> > > for > > > > >> > > >> > this > > > > >> > > >> > > > > topic if they need? > > > > >> > > >> > > > > > > > > >> > > >> > > > > Thanks, > > > > >> > > >> > > > > Kamal > > > > >> > > >> > > > > > > > > >> > > >> > > > > On Tue, Jan 6, 2026 at 7:35 AM Lijun Tong < > > > > >> > > >> [email protected]> > > > > >> > > >> > > > wrote: > > > > >> > > >> > > > > > > > > >> > > >> > > > > > Hey Henry, > > > > >> > > >> > > > > > > > > > >> > > >> > > > > > Thank you for your time and response! I really > like > > > > your > > > > >> > > >> KIP-1248 > > > > >> > > >> > > about > > > > >> > > >> > > > > > offloading the consumption of remote log away > from > > > the > > > > >> > broker, > > > > >> > > >> and > > > > >> > > >> > I > > > > >> > > >> > > > > think > > > > >> > > >> > > > > > with that change, the topic that enables the > tiered > > > > >> storage > > > > >> > > can > > > > >> > > >> > also > > > > >> > > >> > > > have > > > > >> > > >> > > > > > longer retention configurations and would benefit > > > from > > > > >> this > > > > >> > > KIP > > > > >> > > >> > too. > > > > >> > > >> > > > > > > > > > >> > > >> > > > > > Some suggestions: In your example scenarios, it > > would > > > > >> also > > > > >> > be > > > > >> > > >> good > > > > >> > > >> > to > > > > >> > > >> > > > add > > > > >> > > >> > > > > > > an example of remote log segment deletion > > triggered > > > > by > > > > >> > > >> retention > > > > >> > > >> > > > policy > > > > >> > > >> > > > > > > which will trigger generation of tombstone > event > > > into > > > > >> > > metadata > > > > >> > > >> > > topic > > > > >> > > >> > > > > and > > > > >> > > >> > > > > > > trigger log compaction/deletion 24 hour later, > I > > > > think > > > > >> > this > > > > >> > > is > > > > >> > > >> > the > > > > >> > > >> > > > key > > > > >> > > >> > > > > > > event to cap the metadata topic size. > > > > >> > > >> > > > > > > > > > >> > > >> > > > > > > > > > >> > > >> > > > > > Regarding to this suggestion, I am not sure > whether > > > > >> > Scenario 4 > > > > >> > > >> > > > > > < > > > > >> > > >> > > > > > > > > > >> > > >> > > > > > > > > >> > > >> > > > > > > > >> > > >> > > > > > > >> > > >> > > > > > >> > > >> > > > > >> > > > > > > >> > > > > > >> > > > > > > > > > > https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=406618613#KIP1266:BoundingTheNumberOfRemoteLogMetadataMessagesviaCompactedTopic-Scenario4:SegmentDeletion > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > has > > > > >> > > >> > > > > > covered it. I can add more rows in the Timeline > > Table > > > > >> like > > > > >> > > >> > T5+24hour > > > > >> > > >> > > to > > > > >> > > >> > > > > > indicate the messages are gone by then to > > explicitly > > > > show > > > > >> > that > > > > >> > > >> > > messages > > > > >> > > >> > > > > are > > > > >> > > >> > > > > > deleted, thus the number of messages are capped > in > > > the > > > > >> > topic. > > > > >> > > >> > > > > > > > > > >> > > >> > > > > > Regarding whether the topic __remote_log_metadata > > is > > > > >> still > > > > >> > > >> > > necessary, I > > > > >> > > >> > > > > am > > > > >> > > >> > > > > > inclined to continue to have this topic at least > > for > > > > >> > debugging > > > > >> > > >> > > purposes > > > > >> > > >> > > > > so > > > > >> > > >> > > > > > we can build confidence about the compacted topic > > > > >> change, we > > > > >> > > can > > > > >> > > >> > > > > > always choose to remove this topic in the future > > once > > > > we > > > > >> all > > > > >> > > >> agree > > > > >> > > >> > it > > > > >> > > >> > > > > > provides limited value for the users. > > > > >> > > >> > > > > > > > > > >> > > >> > > > > > Thanks, > > > > >> > > >> > > > > > Lijun Tong > > > > >> > > >> > > > > > > > > > >> > > >> > > > > > > > > > >> > > >> > > > > > Henry Haiying Cai via dev <[email protected]> > > > > >> > 于2026年1月5日周一 > > > > >> > > >> > > 16:19写道： > > > > >> > > >> > > > > > > > > > >> > > >> > > > > > > Lijun, > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > Thanks for the proposal and I liked your idea > of > > > > using > > > > >> a > > > > >> > > >> > compacted > > > > >> > > >> > > > > topic > > > > >> > > >> > > > > > > for tiered storage metadata topic. > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > In our setup, we have set a shorter retention > (3 > > > > days) > > > > >> for > > > > >> > > the > > > > >> > > >> > > tiered > > > > >> > > >> > > > > > > storage metadata topic to control the size > > growth. > > > > We > > > > >> can > > > > >> > > do > > > > >> > > >> > that > > > > >> > > >> > > > > since > > > > >> > > >> > > > > > we > > > > >> > > >> > > > > > > control all topic's retention policy in our > > > clusters > > > > >> and > > > > >> > we > > > > >> > > >> set a > > > > >> > > >> > > > > uniform > > > > >> > > >> > > > > > > retention.policy for all our tiered storage > > topics. > > > > I > > > > >> can > > > > >> > > see > > > > >> > > >> > > other > > > > >> > > >> > > > > > > users/companies will not be able to enforce > that > > > > >> retention > > > > >> > > >> policy > > > > >> > > >> > > to > > > > >> > > >> > > > > all > > > > >> > > >> > > > > > > tiered storage topics. > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > Some suggestions: In your example scenarios, it > > > would > > > > >> also > > > > >> > > be > > > > >> > > >> > good > > > > >> > > >> > > to > > > > >> > > >> > > > > add > > > > >> > > >> > > > > > > an example of remote log segment deletion > > triggered > > > > by > > > > >> > > >> retention > > > > >> > > >> > > > policy > > > > >> > > >> > > > > > > which will trigger generation of tombstone > event > > > into > > > > >> > > metadata > > > > >> > > >> > > topic > > > > >> > > >> > > > > and > > > > >> > > >> > > > > > > trigger log compaction/deletion 24 hour later, > I > > > > think > > > > >> > this > > > > >> > > is > > > > >> > > >> > the > > > > >> > > >> > > > key > > > > >> > > >> > > > > > > event to cap the metadata topic size. > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > For the original unbounded remote_log_metadata > > > topic, > > > > >> I am > > > > >> > > not > > > > >> > > >> > sure > > > > >> > > >> > > > > > > whether we still need it or not. If it is left > > > only > > > > >> for > > > > >> > > audit > > > > >> > > >> > > trail > > > > >> > > >> > > > > > > purpose, people can set up a data ingestion > > > pipeline > > > > to > > > > >> > > ingest > > > > >> > > >> > the > > > > >> > > >> > > > > > content > > > > >> > > >> > > > > > > of metadata topic into a separate storage > > location. > > > > I > > > > >> > think > > > > >> > > >> we > > > > >> > > >> > can > > > > >> > > >> > > > > have > > > > >> > > >> > > > > > a > > > > >> > > >> > > > > > > flag to have only one metadata topic (the > > compacted > > > > >> > > version). > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > On Monday, January 5, 2026 at 01:22:42 PM PST, > > > Lijun > > > > >> Tong > > > > >> > < > > > > >> > > >> > > > > > > [email protected]> wrote: > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > Hello Kafka Community, > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > I would like to start a discussion on KIP-1266, > > > which > > > > >> > > >> proposes to > > > > >> > > >> > > add > > > > >> > > >> > > > > > > another new compacted remote log metadata topic > > for > > > > the > > > > >> > > tiered > > > > >> > > >> > > > storage, > > > > >> > > >> > > > > > to > > > > >> > > >> > > > > > > limit the number of messages that need to be > > > iterated > > > > >> to > > > > >> > > build > > > > >> > > >> > the > > > > >> > > >> > > > > remote > > > > >> > > >> > > > > > > metadata state. > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > KIP link: KIP-1266 Bounding The Number Of > > > > >> > RemoteLogMetadata > > > > >> > > >> > > Messages > > > > >> > > >> > > > > via > > > > >> > > >> > > > > > > Compacted RemoteLogMetadata Topic > > > > >> > > >> > > > > > > < > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > > > > >> > > >> > > > > > > > > >> > > >> > > > > > > > >> > > >> > > > > > > >> > > >> > > > > > >> > > >> > > > > >> > > > > > > >> > > > > > >> > > > > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-1266%3A+Bounding+The+Number+Of+RemoteLogMetadata+Messages+via+Compacted+Topic > > > > >> > > >> > > > > > > > > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > Background: > > > > >> > > >> > > > > > > The current Tiered Storage implementation uses > a > > > > >> > > >> > > > __remote_log_metadata > > > > >> > > >> > > > > > > topic with infinite retention and delete-based > > > > cleanup > > > > >> > > policy, > > > > >> > > >> > > > causing > > > > >> > > >> > > > > > > unbounded growth, slow broker bootstrap, no > > > mechanism > > > > >> to > > > > >> > > >> clean up > > > > >> > > >> > > > > expired > > > > >> > > >> > > > > > > segment metadata, and inefficient re-reading > from > > > > >> offset 0 > > > > >> > > >> during > > > > >> > > >> > > > > > > leadership changes. > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > Proposal: > > > > >> > > >> > > > > > > A dual-topic approach that introduces a new > > > > >> > > >> > > > > > __remote_log_metadata_compacted > > > > >> > > >> > > > > > > topic using log compaction with deterministic > > > > >> offset-based > > > > >> > > >> keys, > > > > >> > > >> > > > while > > > > >> > > >> > > > > > > preserving the existing topic for audit > history; > > > this > > > > >> > allows > > > > >> > > >> > > brokers > > > > >> > > >> > > > to > > > > >> > > >> > > > > > > build their metadata cache exclusively from the > > > > >> compacted > > > > >> > > >> topic, > > > > >> > > >> > > > > enables > > > > >> > > >> > > > > > > cleanup of expired segment metadata through > > > > tombstones, > > > > >> > and > > > > >> > > >> > > includes > > > > >> > > >> > > > a > > > > >> > > >> > > > > > > migration strategy to populate the new topic > > during > > > > >> > > >> > > > upgrade—delivering > > > > >> > > >> > > > > > > bounded metadata growth and faster broker > startup > > > > while > > > > >> > > >> > maintaining > > > > >> > > >> > > > > > > backward compatibility. > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > More details are in the attached KIP link. > > > > >> > > >> > > > > > > Looking forward to your thoughts. > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > Thank you for your time! > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > Best, > > > > >> > > >> > > > > > > Lijun Tong > > > > >> > > >> > > > > > > > > > > >> > > >> > > > > > > > > > >> > > >> > > > > > > > > >> > > >> > > > > > > > >> > > >> > > > > > > >> > > >> > > > > > >> > > >> > > > > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > > > > > > > > > > > >
