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Table of Contents

Status

Current state: "Under DiscussionAccepted"

Discussion thread: here

Vote thread: here

JIRA:

Jira
serverASF JIRA
columnIdsissuekey,summary,issuetype,created,updated,duedate,assignee,reporter,customfield_12311032,customfield_12311037,customfield_12311022,customfield_12311027,priority,status,resolution
columnskey,summary,type,created,updated,due,assignee,reporter,Priority,Priority,Priority,Priority,priority,status,resolution
serverId5aa69414-a9e9-3523-82ec-879b028fb15b
keyKAFKA-17876
Jira
serverASF JIRA
columnIdsissuekey,summary,issuetype,created,updated,duedate,assignee,reporter,customfield_12311032,customfield_12311037,customfield_12311022,customfield_12311027,priority,status,resolution
columnskey,summary,type,created,updated,due,assignee,reporter,Priority,Priority,Priority,Priority,priority,status,resolution
serverId5aa69414-a9e9-3523-82ec-879b028fb15b
keyKAFKA-19150

Motivation

Kafka metrics have traditionally followed a consistent naming convention using the kafka.<COMPONENT> format. However, some inconsistencies were unintentionally introduced during recent refactorings:

  • The metrics under org.apache.kafka.server:type=AssignmentsManager were originally named

...

  • using the

...

  • kafka.

...

  • <COMPONENT> format. This changed unexpectedly when classes were moved from the kafka.server package to org.apache.kafka.

...

  • server as part of

...

  • this commit.
  • Similarly, the org.apache.kafka.storage.internals.log:type=RemoteStorageThreadPool metric was initially intended to follow the same convention. However, an incorrect metric name was introduced during initialization in a later patch.

These changes went unnoticed, and subsequent users began using the new org.apache.kafka.<COMPONENT> pattern, diverging from the established convention.

This KIP proposes

Subsequent developers didn’t notice this change and began using the new package name as the `metricName`. The correct naming should actually revert to `kafka.<COMPONENT>`.

...

to standardize Kafka metric naming by

...

reverting the following metrics to the correct kafka.<COMPONENT> format to ensure consistency across the system:

  • org.apache.kafka.server:type=AssignmentsManager → kafka.server:type=

...

  • AssignmentsManager

  • org.apache.kafka.storage.internals.log:type=RemoteStorageThreadPool → kafka.log.remote:type=RemoteStorageThreadPool

This change will align these metrics with the broader Kafka metrics ecosystem and avoid confusion for users and tooling that rely on consistent naming.

Public Interface

  • org.apache.kafka.storage.internals.log.RemoteStorageThreadPool 
  • org.apache.kafka.server.log.remote.storage.RemoteStorageMetrics 

...

  • org.apache.kafka.server.AssignmentsManager

Proposed Changes

...

Introduce new metrics, consistent with other Kafka metrics.

This change will impact external monitoring systems that rely on the old metric name; corresponding updates will be required.

Deprecate the following metrics

  • org.apache.kafka.storage.internals.log:type=RemoteStorageThreadPool.RemoteLogReaderTaskQueueSize
  • org.apache.kafka.storage.internals.log:type=RemoteStorageThreadPool.RemoteLogReaderAvgIdlePercent
  • Deprecate the metric org.apache.kafka.server:type=AssignmentsManager.QueuedReplicaToDirAssignments

Introduce

...

following new metric: 

  • kafka.log.remote:type=RemoteStorageThreadPool.RemoteLogReaderAvgIdlePercent
  • kafka.log.remote:type=RemoteStorageThreadPool.RemoteLogReaderTaskQueueSize
  • kafka.server:type=AssignmentsManager, consistent with other Kafka metrics.QueuedReplicaToDirAssignments

This change will impact external monitoring systems that rely on the old metric name; corresponding updates will be required.

Due to 

Compatibility, Deprecation, and Migration Plan

  1. Add We will add a @Deprecated annotation to deprecated annotation on following constant
    1. `RemoteStorageMetrics#REMOTE_LOG_READER_TASK_QUEUE_SIZE_METRIC`
    2. `RemoteStorageMetrics#REMOTE_LOG_READER_AVG_IDLE_PERCENT_METRIC`
    3. `AssignmentsManager#QUEUED_REPLICA_TO_DIR_ASSIGNMENTS_METRIC`
    .
  2. Update the Kafka documentation to note MBean will be replaced
    1. `org.apache.kafka.storage.internals.log:type=RemoteStorageThreadPool.RemoteLogReaderTaskQueueSize`
    2. `org.apache.kafka.storage.internals.log:
    3. type=RemoteStorageThreadPool.RemoteLogReaderAvgIdlePercent`
    4. Note the deprecation of `org.apache.kafka.server:type=AssignmentsManager.QueuedReplicaToDirAssignments`
  3. Register folowing new metrics
    1. `kafka.log.remote:type=RemoteStorageThreadPool.RemoteLogReaderTaskQueueSize`
    2. `kafka.log.remote:type=AssignmentsManager`RemoteStorageThreadPool.RemoteLogReaderAvgIdlePercent`
    3. Introduce `kafka.server:type=AssignmentsManager` as its replacement.
  4. Introduce a new constant `AssignmentsManager#QUEUED_REPLICA_TO_DIR_ASSIGNMENTS_METRIC_NAME` with the metricName set to `kafka.server:type=AssignmentsManager`, and register it in `AssignmentsManager#metricsRegistry`.
    1. AssignmentsManager.QueuedReplicaToDirAssignments`
  6. Delete following all usage in code base at the Kafka 5.0In the next major release: Remove the deprecated
    1. `RemoteStorageMetrics#REMOTE_LOG_READER_TASK_QUEUE_SIZE_METRIC`
    2. `RemoteStorageMetrics#REMOTE_LOG_READER_AVG_IDLE_PERCENT_METRIC`
    1. `AssignmentsManager#QUEUED_REPLICA_TO_DIR_ASSIGNMENTS_METRIC`
    . Clean it up from `AssignmentsManager#metricsRegistry`.

Test Plan

  • Add new tests to verify the new metric is correctly registered and behaves as expected.
  • Ensure backward compatibility by verifying deprecated metric behavior until removal.

Rejected Alternatives

n/a