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Current state: ["Under Discussion"]

Discussion thread: here

JIRA: KAFKA-15777

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

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When remote storage is enabled on a topic, and the consumer is doing backfill, then the data is read from the remote storage. Currently, Kafka remote storage supports reading data only reading from the first remote partition in the given FETCH request (see KAFKA-14915). The default value of max.partition.fetch.bytes  is configured to 1 MB. Reading one 1 MB of data per FETCH request from remote, increases the round-trip time for the consumer and the cloud storages provider connectors are often tuned to read data in chunks of 4 MB. 

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• Introduce new remote.max.partition.fetch.bytes consumer config, with default value to 1 MB. If not configured, fallback to use max.partition.fetch.bytes value.
• Bump FetchRequest to v18 to add the RemotePartitionMaxBytes field to propagate the value configured on the consumer to the broker. 

• Binary log format

• The network protocol and api behavior

• Any class in the public packages under clientsConfiguration, especially client configuration

• org/apache/kafka/common/serialization

org/apache/kafka/common

• org/apache/kafka/common/errors

• org/apache/kafka/clients/producer

• org/apache/kafka/clients/consumer (eventually, once stable)

• Monitoring

• Command line tools and arguments

• Anything else that will likely break existing users in some way when they upgrade

Proposed Changes

The proposal is to introduce a new Consumer config: remote.max.partition.fetch.bytes to configure the number of bytes returned from remote storage in a FETCH request. The reason for not re-using the existing the max.partition.fetch.bytes is that:

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If the remote.max.partition.fetch.bytes is not configured / FETCH request is from the old client, then it fallbacks to the use the max.partition.fetch.bytes  config.

Compatibility, Deprecation, and Migration Plan

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