Github user zentol commented on the issue:
https://github.com/apache/flink/pull/6047
No, this still doesn't work.
The MetricGroup you're trying to expose is created in
`AbstractStreamOperator#setup`. However, the parent MetricGroup retrieved
through `Environment#getMetricGroup` is null since this method is never mocked
for the `MockEnvironment` in `AbstractStreamOperatorTestHarness`. Thus, in
`AbstractStreamOperator#setup` we're entering the fail-safe block which creates
a dummy `MetricGroup` that never stores anything.
As such no metric can actually be retrieved from the `MetricGroup`.
Please, ask questions if you don't know to fix an issue, or hot verify the
fix. And at the very least try it out _once_, otherwise you're just wasting the
committers' time.
For a proper solution you have to create a `TaskMetricGroup` in the
`AbstractStreamOperatorTestHarness`, which you then use in the
`MockEnvironment` by returning it from `Environment#getMetricGroup`
With this scheme however metrics are only available while the task hasn't
been closed (as metrics are cleaned up), so for better usability your
`TaskMetricGroup` must override `TaskMetricGroup#getOperator` to return a
special `OperatorMetricGroup` that also stores registered metrics in the
`AbstractStreamOperatorTestHarness`. We do not store them indefinitely in the
`OperatorMetricGroup` since that would change one of the core behaviors of the
`MetricGroup`. Finally, add a `getMetrics` method to the
`AbstractStreamOperatorTestHarness` to actually access registered metrics.
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