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https://issues.apache.org/jira/browse/FLINK-30454?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17649383#comment-17649383
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Gunnar Morling commented on FLINK-30454:
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Ok, cool. Logged
[https://github.com/apache/flink/pull/21531/.|https://github.com/apache/flink/pull/21531/]
> 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
> Priority: Major
> Labels: pull-request-available
>
> 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:java}
> 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.
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