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Status
Current state: Under discussionAccepted
Vote thread: https://lists.apache.org/thread/vvw45tcdmb23d8gpgb3x4fklx3tp7hpm
Discussion thread: https://lists.apache.org/thread/w4ml9ffkj1j31j8kjpbywq9jsw5ck5sr
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Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Motivation
Currently, there exists a kafka.server:type=MetadataLoader,name=CurrentMetadataVersion metric which tells the operator the metadata version feature level for every node in a cluster. However, now that there several features with support beyond the metadata.version feature, adding a metric to display those features' levels would be helpful for monitoring upgrade/downgrade scenarios for clusters using those features. Additionally, adding metrics for the minimum and maximum supported feature levels of each node would be helpful for the operator to determine if a feature upgrade/downgrade is safe to perform.
Public Interfaces
Monitoring
Add a metric metrics for each production feature (i.e. metadata.version , kraft.version , transaction.version , group.version , eligible.leader.replicas.version , share.version, and sharestreams.version ).
This can be accomplished via one generic "feature level" metric metrics that is are tagged by feature name. Using a generic metric metrics allows for new production features to automatically expose their feature level and supported feature levels going forward.
| Name | Type | Description |
|---|---|---|
| kafka.server:type=MetadataLoader,name= | ||
| FinalizedLevel,featureName=X | ||
| Short | The finalized value of the feature level for a feature named "X". | |
| kafka.server:type=node-metrics,name=minimum-supported-level,feature-name=X | Short | The minimum supported feature level for a feature named "X" on the node. |
kafka.server:type=node-metrics,name=maximum-supported-level,feature-name=X | Short | The maximum supported feature level for a feature named "X" on the node. |
The FinalizedLevel metric will report the finalized feature level for each production feature if it exists. If a feature does not have a finalized level, it will not have an associated FinalizedLevel metric. Similarly, if the finalized level of the metric is "removed" by setting it to 0, the associated FinalizedLevel metric will also be removed. This does not apply to metadata.version , whose minimum version is 7. This metric should still reside in the MetadataLoader metric group because its value is derived from the metadata log's feature records.
minimum-supported-level and maximum-supported-level are metrics whose values are dependent only on the software version being run, so it seems appropriate to define a new metric type to house these sorts of metrics going forward (release version, commit hash, etc.).The default value of this metric should be the default value of the feature.
Compatibility, Deprecation, and Migration Plan
We might want to will deprecate the kafka.server:type=MetadataLoader,name=CurrentMetadataVersion metric since this per-feature tagged metric can also expose the current metadata versionexposes this value, and the previous metric can be removed starting in 5.0.
Test Plan
We will add junit tests to verify the new metrics.
Rejected Alternatives
Alternatives
Running kafka-feature describe on every node is one way to track feature level upgrades/downgrades, but it is not straightforward to monitor since it is not a metric.
This KIP discusses the above approach: KIP-1160: Enable returning supported features from a specific brokerIf 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.