This page is meant as a template for writing a KIP. To create a KIP choose Tools->Copy on this page and modify with your content and replace the heading with the next KIP number and a description of your issue. Replace anything in italics with your own description.

Status

Current state: "Under Discussion" (Draft)

Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]

JIRA: here 

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

Motivation

Currently Mirrormaker uses deprecated alterConfigs API when syncing topic configurations for broker compatibility to 0.11.0. However, the deprecated alterConfigs() API replaces any existing configuration with the new configuration. Due to this, additional configurations set on a remote topic get cleared up when MirrorMaker syncs topic configurations even if the configurations are filtered.  For example this prevents running Cruise Control on the target cluster as it may set follower.replication.throttled.replicas and leader.replication.throttled.replicas.

MirrorMaker should not clear topic configurations that are filtered on the target cluster.

Public Interfaces

This KIP proposes to migrate to incrementalAlterConfigs API for syncing topic configurations in MirrorMaker. The incrementalAlterConfigs API has been around for several years since it was introduced in Kafka 2.3.0 and addresses the shortcoming of the deprecated alterConfigs API. In order to not break the compatibility, we will introduce a new configuration to MirrorMaker connector to give the option to enable incrementalAlterConfigs API for syncing topic configurations. This new configuration is expected to serve as a temporary measure until the next major release when incrementalAlterConfigs API is always used. 

Proposed Changes

1) A new configuration setting:

Name: enable.incremental.alter.configs

Description: Deprecated. Whether to automatically use incrementalAlterConfigs API for syncing topic configurations. This configuration will be removed in Kafka 4.0 and the incrementalAlterConfigs API will be used by default. Users should make sure that the target cluster is running at least Kafka 2.1.0 or later. 

Type: Boolean

Default: false

Update Mode: 

When set to false, MirrorMaker will keep using deprecated alterConfigs API for syncing topic configurations.

When explicitly set to true, MirrorMaker will use incrementalAlterConfigs API for syncing topic configurations. If it receives an error from an incompatible broker, the MirrorMaker will report this to the user and fail the connector. 

2) Add 

Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users?
• If we are changing behavior how will we phase out the older behavior?
• If we need special migration tools, describe them here.
• When will we remove the existing behavior?

Test Plan

Describe in few sentences how the KIP will be tested. We are mostly interested in system tests (since unit-tests are specific to implementation details). How will we know that the implementation works as expected? How will we know nothing broke?

Rejected Alternatives

If there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.