[jira] [Created] (FLINK-30454) Inconsistent class hierarchy in TaskIOMetricGroup

["Gunnar Morling (Jira)" <ji...@apache.org>]

Gunnar Morling created FLINK-30454:
--------------------------------------

             Summary: Inconsistent class hierarchy in TaskIOMetricGroup
                 Key: FLINK-30454
                 URL: https://issues.apache.org/jira/browse/FLINK-30454
             Project: Flink
          Issue Type: Improvement
          Components: Runtime / Metrics
            Reporter: Gunnar Morling


I noticed an interesting issue when trying to compile the flink-runtime module with Eclipse (same for VSCode): the _private_ inner class {{org.apache.flink.runtime.metrics.groups.TaskIOMetricGroup.SizeGauge}} has yet another _public_ inner class, {{SizeSupplier}}. The public method {{org.apache.flink.runtime.metrics.groups.TaskIOMetricGroup.registerMailboxSizeSupplier(SizeSupplier<Integer>)}} has a parameter of that type. The invocation of this method in {{org.apache.flink.streaming.runtime.tasks.StreamTask.StreamTask(Environment, TimerService, UncaughtExceptionHandler, StreamTaskActionExecutor, TaskMailbox)}} can be compiled with the javac compiler of the JDK but fails to compile with ecj:

{code}
The type TaskIOMetricGroup.SizeGauge from the descriptor computed for the target context is not visible here.  
{code}

I tend to believe that the behavior of Eclipse's compiler is the correct one. After all, you couldn't explicitly reference the {{SizeSupplier}} type either. One possible fix would be to promote {{SizeSupplier}} to the same level as {{SizeGauge}}. This would be source-compatible but not binary-compatible, though. I.e. code compiled against the earlier signature of {{registerMailboxSizeSupplier()}} would be broken with a {{NoSuchMethodError}}. Depending on whether {{registerMailboxSizeSupplier()}} are expected in client code or not, this may or may not be acceptable. Another fix would be to make {{SizeGauge}} public. I think that's the change I'd do. Curious what other folks here think.



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