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https://issues.apache.org/jira/browse/FLINK-14174?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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John Lonergan closed FLINK-14174.
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Resolution: Abandoned
> Don't swallow exception when rethrowing type mismatches with side outputs
> -------------------------------------------------------------------------
>
> Key: FLINK-14174
> URL: https://issues.apache.org/jira/browse/FLINK-14174
> Project: Flink
> Issue Type: Bug
> Components: API / DataStream
> Affects Versions: 1.8.1, 1.9.0
> Reporter: John Lonergan
> Priority: Minor
> Labels: auto-deprioritized-major, stale-minor
>
> The change made by https://github.com/apache/flink/pull/4663/files introduces
> a "helpful hint" that a class cast at that location might be due a Flink
> pipeline cfg error and the code goes onto swallows the original exception and
> masked a protocol buffer serialisation problem we were having.
> Recorded as a bug because this "helpful hint" masks exceptions and is
> sometimes a complete red herring and in my case wasted a lot of peoples time.
> In my case I had a class cast error in some proto serialisation code and
> because the "helpful hint" traps ClassCastException I wasn't able to discover
> the error easily. In the end we modified the Flink distribution to remove
> this "helpful hint" at which point the real error was found and we quickly
> fixed it - but not without a lot of burned time.
> I am not convinced of the cost/benefit of the "helpful hint" introduced by
> FLINK-4663 for two reasons
> - it can be a red herring - in mine case and also and [at least one other
> person
> |https://stackoverflow.com/questions/56069797/multiple-outputtags-in-stream-process-function-with-classcastexception]
> - I don't agree with ever throwing away or masking causal exceptions - these
> must always be propagated (I raised a similar issue in my previous
> contribution)
> ----
> My suggestion is to either back out FLINK-4663 so that we get to see the raw
> underlying exception and call stack -or- come up with a way to distinguish
> the specific case "FLINK-4663" was attempting to cover and only emit that
> hint hint if the specific case is encountered.
> For all other cases the helpful hint should not be emitted.
> And - regardless of whether the helpful hint it emitted or not +the causal
> exception must always be propagated+.
> My vote is to back out FLINK-4663 and maybe add some logging instead.
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