[jira] [Created] (FLINK-8213) Prevent potential metric-related ClassCastExceptions

["Chesnay Schepler (JIRA)" <ji...@apache.org>]

Chesnay Schepler created FLINK-8213:
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             Summary: Prevent potential metric-related ClassCastExceptions
                 Key: FLINK-8213
                 URL: https://issues.apache.org/jira/browse/FLINK-8213
             Project: Flink
          Issue Type: Bug
          Components: Metrics, Streaming
    Affects Versions: 1.5.0
            Reporter: Chesnay Schepler
            Assignee: Chesnay Schepler
            Priority: Minor


There are a few places, in particular revolving around the {{StreamOperator}}, that may run into ClassCastExceptions.

For example, in the {{DataSinkTask}} you can find this line:
{{final Counter numRecordsIn = ((OperatorMetricGroup) ctx.getMetricGroup()).getIOMetricGroup().getNumRecordsInCounter();}}

The cast here is necessary since the {{AbstractStreamOperator}} exposes the {{OperatorMetricGroup}} as a plain {{MetricGroup}} since it is an internal class. However there is obviously no guarantee that {{StreamOperator#getMetricGroup()}} returns an actual {{OperatorMetricGroup}}. In fact, a fall-back case in {{AbstractStreamOperator#setup}} causes exactly this assumption to be violated.



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