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

["Robert Metzger (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-30454?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Robert Metzger reassigned FLINK-30454:
--------------------------------------

    Assignee: Gunnar Morling

> 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
>            Assignee: Gunnar Morling
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.17.0
>
>
> 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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