Github user bbende commented on the issue:
https://github.com/apache/nifi/pull/2939
Just started reviewing, there are a bunch of files with missing license
headers...
```
[WARNING] Files with unapproved licenses:
/home/travis/build/apache/nifi/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/test/java/org/apache/nifi/controller/status/history/TestMetricRollingBuffer.java
/home/travis/build/apache/nifi/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/test/java/org/apache/nifi/controller/repository/metrics/TestSecondPrecisionEventContainer.java
/home/travis/build/apache/nifi/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/util/ComponentMetrics.java
/home/travis/build/apache/nifi/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/status/history/ComponentStatusHistory.java
/home/travis/build/apache/nifi/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/status/history/MetricRollingBuffer.java
/home/travis/build/apache/nifi/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/status/history/ComponentDetails.java
/home/travis/build/apache/nifi/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/status/history/EmptyStatusSnapshot.java
/home/travis/build/apache/nifi/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/status/history/IndexableMetric.java
/home/travis/build/apache/nifi/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/repository/metrics/EmptyFlowFileEvent.java
```
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