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

Motivation

FLIP-274: Introduce metric group for OperatorCoordinator introduced a new metric group for source enumerators to emit metrics. However, there is no way from the Flink REST API to fetch these metrics.

The current metric related REST APIs are the following:

/jobmanager/metrics
/taskmanagers/<taskmanagerid>/metrics
/jobs/<jobid>/metrics
/jobs/<jobid>/vertices/<vertexid>/subtasks/<subtaskindex>
Request metrics aggregated across all entities of the respective type:

/taskmanagers/metrics
/jobs/metrics
/jobs/<jobid>/vertices/<vertexid>/subtasks/metrics

These APIs allow external services to fetch, for example, subtask metrics to do analysis. The coordinator metrics are also an essential set of metrics for jobs that expose how a job is behaving.

Public Interfaces

The REST API needs to change to support this.

Proposed Changes

Thus, I propose a new REST API

/jobs/<jobid>/vertices/<vertexid>/operators/<operatorid>/metrics

with the query parameter get  that accepts comma separated metric names, like the other APIs. This path is based on https://github.com/apache/flink/blob/7bebd2d9fac517c28afc24c0c034d77cfe2b43a6/flink-runtime/src/main/java/org/apache/flink/runtime/metrics/dump/QueryScopeInfo.java#L234.

Compatibility, Deprecation, and Migration Plan

No compatibility concerns as this is introducing a new API without modifying older APIs.

Test Plan

Unit tests.

Rejected Alternatives

None.