[jira] [Created] (FLINK-40295) Document UDF metrics

["Weiqing Yang (Jira)" <ji...@apache.org>]

Weiqing Yang created FLINK-40295:
------------------------------------

             Summary: Document UDF metrics
                 Key: FLINK-40295
                 URL: https://issues.apache.org/jira/browse/FLINK-40295
             Project: Flink
          Issue Type: Sub-task
          Components: Documentation
            Reporter: Weiqing Yang


This is the fourth of four sub-tasks implementing FLIP-485.

FLIP: https://cwiki.apache.org/confluence/spaces/FLINK/pages/373885706/FLIP-485+Add+UDF+Metrics
Vote thread: https://lists.apache.org/thread/symqpswsohl2s5wmtkcw0jjp1w5dot0n

Document the UDF metrics feature in docs/content/docs/ops/metrics.md and its Chinese
counterpart.

Two additions:

* A UDF section in the metrics reference listing {{udfProcessingTime}} and
  {{udfExceptionCount}}, their types, and their operator-scoped naming, where the full
  identifier is {{<operator_name>.udf.<udf_name>.<metric>}}.
* A "UDF metrics" section alongside the existing state-access-latency section, covering
  how to enable the feature with {{table.exec.udf-metric-enabled}}, how
  {{table.exec.udf-metric.sample-interval}} trades accuracy against overhead, the fact
  that exceptions are counted on every invocation rather than sampled, which function
  kinds are covered, and the recommendation to use the metrics for debugging.

The overhead wording notes that because only the sampled invocations are timed, the
remaining invocations cost a single counter increment, so the default interval keeps the
overhead of the enabled path small. This answers a question raised on the reference
implementation about the cost of the feature when it is switched on.

Not covered, and stated as such in the docs: process table functions (PROCESS_TABLE),
aggregate functions, and functions registered through the deprecated registerFunction
API.




--
This message was sent by Atlassian Jira
(v8.20.10#820010)