Hi Jun,
> JR20. Could you fix the inconsistency?
> org.apache.kafka.common.serialization.largemessage.PayloadStore vs
> org.apache.kafka.common.serialization.largemessage.store.PayloadStore
Updated
>
> JR21. "Encapsulate that ID into a simple Kafka event using a structured
> format.". Could you define the structured format explicitly?
This was from the initial design we had Id format but after discussing this
with Luke I ended up simplifying this by removing the format and I guess I
forgot this line. I have updated the kip now.
> JR22. TTL for object stores: Could the new serializer be used on a
> compacted topic? If so, how should a user configure the TTL since the Kafka
> retention is infinite.
Great question about compacted topics! There are few usage of compacted topic
to consider:
1. Typical Compacted Topic Usage: The compacted topics are commonly used as
cache/state layers where the latest value for each key represents the current
state. These use cases typically involve smaller records since they need to be
loaded efficiently for state reconstruction. Large message serialization would
be unusual for this pattern.
2. User-Defined Compacted Topics with Large Payloads: for applications that do
use compacted topics with large payloads, the PayloadStore implementation
should handle this by:
a. Consistent ID Generation: Use deterministic IDs based on the Kafka
key (rather than random UUIDs) so that when a payload id is updated, it
overwrites the same payload store object instead of creating new ones.
b. TTL Strategy: Since compacted topics can retain data indefinitely,
users have two options:
- Set a business-appropriate TTL (basically "we know our cache
data becomes stale after 30 days”)
- Configure no TTL and accept indefinite storage costs as a
trade-off for the architectural benefits
3. Compact + Delete Policy: Topics with `cleanup.policy=compact,delete` will
eventually remove old data, so standard TTL approaches work normally. The key
insight is that TTL configuration depends on the business requirements and
usage patterns rather than just the Kafka retention policy. The PayloadStore
implementation should provide flexibility for users to make this trade-off
consciously.
I have update the consideration section with this.
Thanks
Omnia
> On 11 Aug 2025, at 23:32, Jun Rao <j...@confluent.io.INVALID> wrote:
>
> Hi, Omnia,
>
> Thanks for the reply. A few more comments.
>
> JR20. Could you fix the inconsistency?
> org.apache.kafka.common.serialization.largemessage.PayloadStore vs
> org.apache.kafka.common.serialization.largemessage.store.PayloadStore
>
> JR21. "Encapsulate that ID into a simple Kafka event using a structured
> format.". Could you define the structured format explicitly?
>
> JR22. TTL for object stores: Could the new serializer be used on a
> compacted topic? If so, how should a user configure the TTL since the Kafka
> retention is infinite.
>
> Jun
>
> On Mon, Aug 11, 2025 at 10:08 AM Omnia Ibrahim <o.g.h.ibra...@gmail.com
> <mailto:o.g.h.ibra...@gmail.com>>
> wrote:
>
>> Hi Jun
>>> JR11. Do you think that we need to add key.serializers and
>>> key.deserializers or do you think covering large messages in value is
>>> enough?
>> The large message issue usually is a value issue, I never saw a key that
>> is bigger than broker message size. If I would add key.serializers and
>> key.deserializers it would be for consistency and maybe there are use-cases
>> where developers want to apply multiple serializations in order on the key
>> as well outside the context of the large message support.
>> I updated the KIP to add these two configs now.
>>
>>> JR12. We can load ComposableSerializer automatically if value.serializers
>>> or value.deserializers are specified. But, it seems that we could keep
>>> ComposableSerializer as an internal implementation. For example,
>>> ProducerInterceptors is automatically loaded when multiple interceptors
>> are
>>> specified and is an internal class.
>> I updated the kip to highlight that the changes is updating ProducerConfig
>> and ConsumerConfig to have new config for serializers/deserializers and not
>> the actual class this is implementation details and not public interfaces.
>>
>>> JR17. We could estimate the size after compression, but the estimator is
>>> not 100% accurate. It seems that it's simpler to just use the original
>>> message size.
>> We can keep it as original message size, I was thinking if it is good
>> enough for max.request.size it might be good enough for this. I updated the
>> KIP anyway to simplify it and keep it to the original size.
>>
>> Hope the final version addressed all feedbacks and we can resume with the
>> voting
>>
>> Thanks
>> Omnia
>>
>>> On 8 Aug 2025, at 22:10, Jun Rao <j...@confluent.io.INVALID> wrote:
>>>
>>> Hi, Omnia,
>>>
>>> Thanks for the reply.
>>>
>>> JR11. Do you think that we need to add key.serializers and
>>> key.deserializers or do you think covering large messages in value is
>>> enough?
>>>
>>> JR12. We can load ComposableSerializer automatically if value.serializers
>>> or value.deserializers are specified. But, it seems that we could keep
>>> ComposableSerializer as an internal implementation. For example,
>>> ProducerInterceptors is automatically loaded when multiple interceptors
>> are
>>> specified and is an internal class.
>>>
>>> JR17. We could estimate the size after compression, but the estimator is
>>> not 100% accurate. It seems that it's simpler to just use the original
>>> message size.
>>>
>>> Jun
>>>
>>> On Mon, Aug 4, 2025 at 10:33 AM Omnia Ibrahim <o.g.h.ibra...@gmail.com
>> <mailto:o.g.h.ibra...@gmail.com>>
>>> wrote:
>>>
>>>>
>>>> Hi Jun
>>>>> JR11. value.serializers and value.deserializers: Should they be of type
>>>>> List? Also, where are key.serializers and key.deserializers?
>>>>>
>>>> Updated now
>>>>> JR12. Do we still need ComposableSerializer and ComposableDeserializer?
>>>> The initial thinking here was if `value.serializers or
>> value.deserializers
>>>> ` exists the client will load ComposableSerializer or
>>>> ComposableDeserializer automatically and use them. Unfortunately this
>>>> would need us to define these serializers.
>>>>
>>>> The other option is to update `Plugin<Serializer<V>>
>>>> valueSerializerPlugin` and KafkaProducer constructor to accept
>>>> List<Serializer<V>> and move the logic of the ComposableSerializer into
>>>> KafkaProducer::doSend which when we do serialization (same with
>>>> KafkaConsumer). This option hide the logic and reduce exposure for
>> client
>>>> to these.
>>>> WDYT?
>>>>
>>>>>
>>>>> JR13. large.message.payload.store.class : should it be of type class?
>>>> Updated
>>>>>
>>>>> JR14.
>>>>>
>>>>
>> org.apache.kafka.common.serialization.largemessage.LargeMessageSerializer :
>>>>> The name seems redundant since largemessage appears twice.
>>>> Updated
>>>>>
>>>>> JR15. PayloadResponse: It still mentions response code. It mentions
>>>>> "isRetryable flag", which no longer exists in PayloadStoreException.
>>>> There
>>>>> are typos in "then it will serialiser will”.
>>>> The KIP is updated now
>>>>
>>>>> JR16. Regarding returning new byte[0] if
>>>> large.message.skip.not.found.error
>>>>> is true, this will likely fail the next deserializer and the
>> application
>>>>> won't have the right context of the error. It's probably better to just
>>>>> propagate the specific exception and let the caller handle it.
>>>> You right this will cause issue if there is another deserializer waiting
>>>> for the data. I have updated the KIP with this.
>>>>
>>>>>
>>>>> JR17. LargeMessageSerializer: "Check if the estimated size of the data
>>>>> (bytes) after applying provided compression (if there is one)"
>>>> Compression
>>>>> actually happens after serialization and is done on a batch of records.
>>>> Yes the compression itself happened after but we also have
>>>> `estimateSizeInBytesUpperBound` which my understanding is this take the
>>>> compression type into the account as well
>>>>>
>>>>>
>>>>> JR18. Could you define the type T for LargeMessageSerializer?
>>>> Update the KIP this T would be byte[]
>>>>
>>>> Thanks
>>>> Omnia
>>>>>
>>>>> Jun
>>>>>
>>>>> On Fri, Jul 25, 2025 at 6:28 AM Omnia Ibrahim <o.g.h.ibra...@gmail.com
>>>> <mailto:o.g.h.ibra...@gmail.com>>
>>>>> wrote:
>>>>>
>>>>>> Hi Jun, thanks for having the time to review this
>>>>>>
>>>>>>> JR1. While the KIP is potentially useful, I am wondering who is
>>>>>> responsible
>>>>>>> for retention for the objects in the payload store. Once a message
>>>> with a
>>>>>>> reference is deleted, the key of the external object is lost and the
>>>>>> object
>>>>>>> may never be deleted.
>>>>>>
>>>>>> The `ttl` in the object store is the responsibility of the owner of
>> this
>>>>>> store it should be configured in away that is reasonable with the
>>>> retention
>>>>>> config in Kafka.
>>>>>> I have updated the KIP with `Consideration` section.
>>>>>>>
>>>>>>> JR2. Configs: For all new configs, it would be useful to list their
>>>>>> types.
>>>>>> Updated the KIP now
>>>>>>>
>>>>>>> JR3. value.serializers: Why is this required? If a user doesn't set
>> it,
>>>>>> we
>>>>>>> should just use value.serializer, right? Ditto for key.serializers.
>>>>>> No you right this was copy/past mistake
>>>>>>
>>>>>>>
>>>>>>> JR4. For all new public interfaces such as LargeMessageSerializer,
>>>>>>> PayloadStore and PayloadResponse, it would be useful to include the
>>>> full
>>>>>>> package name.
>>>>>> Updated the KIP now
>>>>>>>
>>>>>>> JR5. large.message.payload.store.retry.max.backoff.ms and
>>>>>>> large.message.payload.store.retry.delay.backoff.ms: Is the intention
>>>> to
>>>>>>> implement exponential backoff on retries? If so, it's more consistent
>>>> if
>>>>>> we
>>>>>>> can follow the existing naming convention like retry.backoff.max.ms
>> <
>>>>>> http://retry.backoff.max.ms/> and
>>>>>>> retry.backoff.ms <http://retry.backoff.ms/> <
>> http://retry.backoff.ms/> <http://retry.backoff.ms/
>>>>> .
>>>>>> I have removed these to simplify the config more (as Luke suggested
>>>>>> initially) and added these to the consideration section.
>>>>>>
>>>>>>>
>>>>>>> JR6. large.message.skip.not.found.error : If the reference can't be
>>>>>> found,
>>>>>>> what value does the deserializer return? Note that null has a special
>>>>>>> meaning for tombstone in compacted topics.
>>>>>> The deserialiser will return `new byte[0]` not null.
>>>>>>>
>>>>>>> JR7. PayloadResponse: Why do we have both responseCode and
>>>>>>> PayloadStoreException?
>>>>>> We can do without responseCode, the initial though was to report
>>>> response
>>>>>> code form payload store.
>>>>>> Update the KIP.
>>>>>>> JR8. Why do we need PayloadStore.metrics? Note that we could monitor
>>>> the
>>>>>>> metrics in a plugin through the Monitorable interface.
>>>>>> Oh nice, I didn’t know about this interface before. Updated the KIP
>> with
>>>>>> this now.
>>>>>>>
>>>>>>> JR9. Why do we need the protected field
>>>>>> PayloadStoreException.isRetryable?
>>>>>> Initial thought here was the serializer can retry the upload. But I
>> have
>>>>>> removed all the retry logic from serializer and it will be up to the
>>>>>> PayloadStore provider to implement this if they need it.
>>>>>>>
>>>>>>> JR10. As Luke mentioned earlier, we could turn PayloadStore to an
>>>>>> interface.
>>>>>> It is updated now to interface.
>>>>>>
>>>>>> Hope the last version of the KIP is more simpler now
>>>>>>
>>>>>> Thanks
>>>>>> Omnia
>>>>>>
>>>>>>> On 23 Jul 2025, at 00:43, Jun Rao <j...@confluent.io.INVALID
>>>>>>> <mailto:j...@confluent.io.INVALID> <mailto:
>> j...@confluent.io.INVALID <mailto:j...@confluent.io.INVALID>> <mailto:
>>>> j...@confluent.io.INVALID <mailto:j...@confluent.io.INVALID>
>>>> <mailto:j...@confluent.io.INVALID>>> wrote:
>>>>>>>
>>>>>>> Thanks for the KIP. A few comments.
>>>>>>>
>>>>>>> JR1. While the KIP is potentially useful, I am wondering who is
>>>>>> responsible
>>>>>>> for retention for the objects in the payload store. Once a message
>>>> with a
>>>>>>> reference is deleted, the key of the external object is lost and the
>>>>>> object
>>>>>>> may never be deleted.
>>>>>>>
>>>>>>> JR2. Configs: For all new configs, it would be useful to list their
>>>>>> types.
>>>>>>>
>>>>>>> JR3. value.serializers: Why is this required? If a user doesn't set
>> it,
>>>>>> we
>>>>>>> should just use value.serializer, right? Ditto for key.serializers.
>>>>>>>
>>>>>>> JR4. For all new public interfaces such as LargeMessageSerializer,
>>>>>>> PayloadStore and PayloadResponse, it would be useful to include the
>>>> full
>>>>>>> package name.
>>>>>>>
>>>>>>> JR5. large.message.payload.store.retry.max.backoff.ms and
>>>>>>> large.message.payload.store.retry.delay.backoff.ms: Is the intention
>>>> to
>>>>>>> implement exponential backoff on retries? If so, it's more consistent
>>>> if
>>>>>> we
>>>>>>> can follow the existing naming convention like retry.backoff.max.ms
>>>>>>> <http://retry.backoff.max.ms/>
>> <http://retry.backoff.max.ms/> <
>>>> http://retry.backoff.max.ms/> <
>>>>>> http://retry.backoff.max.ms/> and
>>>>>>> retry.backoff.ms <http://retry.backoff.ms/> <http://retry.backoff.ms/> <
>> http://retry.backoff.ms/> <http://retry.backoff.ms/
>>>>> .
>>>>>>>
>>>>>>> JR6. large.message.skip.not.found.error : If the reference can't be
>>>>>> found,
>>>>>>> what value does the deserializer return? Note that null has a special
>>>>>>> meaning for tombstone in compacted topics.
>>>>>>>
>>>>>>> JR7. PayloadResponse: Why do we have both responseCode and
>>>>>>> PayloadStoreException?
>>>>>>>
>>>>>>> JR8. Why do we need PayloadStore.metrics? Note that we could monitor
>>>> the
>>>>>>> metrics in a plugin through the Monitorable interface.
>>>>>>>
>>>>>>> JR9. Why do we need the protected field
>>>>>> PayloadStoreException.isRetryable?
>>>>>>>
>>>>>>> JR10. As Luke mentioned earlier, we could turn PayloadStore to an
>>>>>> interface.
>>>>>>>
>>>>>>> Thanks,
