[da-vinci] Add OTel metrics to StuckConsumerRepairStats

[m-nagarajan]

Problem Statement

StuckConsumerRepairStats has 3 Tehuti OccurrenceRate sensors for the stuck consumer detection and repair lifecycle but no OTel counterparts, making these metrics unavailable in OTel-based monitoring dashboards.

Solution

Add 3 OTel COUNTER metrics under the ingestion.pubsub.consumer.stuck.* namespace using the joint Tehuti+OTel API (MetricEntityStateBase):

• ingestion.pubsub.consumer.stuck.detected_count — scans that detected a stuck PubSub consumer
• ingestion.pubsub.consumer.stuck.task_repaired_count — ingestion tasks killed to unblock a stuck consumer
• ingestion.pubsub.consumer.stuck.unresolved_count — stuck consumers found with no fixable task identified

This is a singleton stats class with CLUSTER_NAME as the only dimension. clusterName was added to the constructor, passed from AggKafkaConsumerService via serverConfig.getClusterName().

Code changes

• Added new code behind a config.
• Introduced new log lines.
  • Confirmed if logs need to be rate limited to avoid excessive logging.

Concurrency-Specific Checks

Both reviewer and PR author to verify

• Code has no race conditions or thread safety issues.
• Proper synchronization mechanisms (e.g., synchronized, RWLock) are used where needed.
• No blocking calls inside critical sections that could lead to deadlocks or performance degradation.
• Verified thread-safe collections are used (e.g., ConcurrentHashMap, CopyOnWriteArrayList).
• Validated proper exception handling in multi-threaded code to avoid silent thread termination.

How was this PR tested?

• New unit tests added.
• New integration tests added.
• Modified or extended existing tests.
• Verified backward compatibility (if applicable).

New tests:

• StuckConsumerRepairStatsTest (6 tests): OTel counter accumulation for all 3 metrics, Tehuti sensor registration + recording, NPE prevention with OTel disabled and plain MetricsRepository.
• StuckConsumerRepairOtelMetricEntityTest: metric entity validation for all 3 metrics.
• StuckConsumerRepairTehutiMetricNameTest: Tehuti name validation for all 3 enum values.

Does this PR introduce any user-facing or breaking changes?

• No. You can skip the rest of this section.
• Yes. Clearly explain the behavior change and its impact.

[Copilot]

Pull request overview

Adds OpenTelemetry (OTel) COUNTER metrics for the stuck PubSub consumer detection/repair lifecycle so these signals are available in OTel-based dashboards, while preserving existing Tehuti sensors.

Changes:

• Introduces StuckConsumerRepairOtelMetricEntity with 3 new ingestion.pubsub.consumer.stuck.* counters (cluster-name dimensioned).
• Refactors StuckConsumerRepairStats to use MetricEntityStateBase (joint Tehuti + OTel) and requires clusterName in the constructor.
• Wires the new metric entity into ServerMetricEntity and adds unit tests validating OTel entities, Tehuti names, and counter accumulation.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
clients/da-vinci-client/src/main/java/com/linkedin/davinci/stats/StuckConsumerRepairStats.java	Switches stuck-consumer stats recording to joint Tehuti+OTel metric state with cluster dimension setup.
clients/da-vinci-client/src/main/java/com/linkedin/davinci/stats/StuckConsumerRepairOtelMetricEntity.java	Defines 3 new OTel COUNTER metric entities under ingestion.pubsub.consumer.stuck.*.
clients/da-vinci-client/src/main/java/com/linkedin/davinci/stats/ServerMetricEntity.java	Registers the new metric entity enum so it’s included in aggregated server metric entities.
clients/da-vinci-client/src/main/java/com/linkedin/davinci/kafka/consumer/AggKafkaConsumerService.java	Passes serverConfig.getClusterName() into the stats constructor when stuck-consumer repair is enabled.
clients/da-vinci-client/src/test/java/com/linkedin/davinci/stats/StuckConsumerRepairStatsTest.java	Adds unit tests for OTel counter accumulation, Tehuti sensor presence, and NPE safety when OTel is disabled.
clients/da-vinci-client/src/test/java/com/linkedin/davinci/stats/StuckConsumerRepairOtelMetricEntityTest.java	Validates the OTel metric entity definitions (name/type/unit/description/dimensions).
clients/da-vinci-client/src/test/java/com/linkedin/davinci/stats/StuckConsumerRepairTehutiMetricNameTest.java	Validates Tehuti metric name enum mappings.
clients/da-vinci-client/src/test/java/com/linkedin/davinci/stats/ServerMetricEntityTest.java	Updates expected aggregated server metric entity count (+3).

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

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