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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 the API is always used.
Proposed Changes
1) Add a new method updateTopicConfigsUsingIncrementalAlterConfigs() to MirrorSourceConnector.java
which takes a list topic configurations as a parameter and calls incrementalAlterConfigs()
to the target cluster.
2) Add a new configuration setting to MirrorMaker:
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 2.3.0 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.
3) Update syncTopicConfigs()
in MirrorSourceConnector.java
to call the updateTopicConfigsUsingIncrementalAlterConfigs()
instead of updateTopicConfigs()
if enable.incremental.alter.configs
is set to true.
4) From Kafka 4.0, syncTopicConfigs()
will only call updateTopicConfigsUsingIncrementalAlterConfigs()
by default. The existing updateTopicConfigs()
will be removed.
Compatibility, Deprecation, and Migration Plan
By default, the new setting will be set to false so it does not change the current behaviour. This setting will be marked as deprecated immediately.
In the next major version:
- enable.incremental.alter.configs will be removed
- MirrorMaker will use the
incrementalAlterConfigs
API to sync topic configurations.
Users running the latest MirrorMaker connector against a target cluster with brokers older than Kafka 2.3.0, will have to upgrade.
Test Plan
Currently, the integration tests for MirrorMaker do not check if the target topic have the expected configurations after applying configuration filters, hence this bug was not caught. We will add a new integration test that checks target topic configurations once they have been synced.
(Is it necessary to add system tests)
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.