Safeguard boundedtrie result

[rohitsinha54]

in Stringset metrics which were being emitted by default from SDK and then later once service started processing and returning them a bug on parsing it on SDK side caused the job to fail with cast exception.

Since BoundedTrie metrics for lineage are guarded by flag and not emitted by default the result query will not try to parse it but since it is publicly exposed metric type someone can try to use it regardless. This safeguards till we update QM and do e2e testing.

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[rohitsinha54]

R: @robertwb

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[robertwb]

I'm not super comfortable with returning an incorrect result here due to a class cast exception...

[robertwb]

Will this code only be triggered if the user requests these values, or would it be triggered by other metrics request (like the last bug)? If the latter, could we skip these metrics rather than inject empty values on class cast failure?

[chamikaramj]

@rohitsinha54 any updates ?

[rohitsinha54]

Sorry for the late reply. This is not an urgent change (i.e. not essential for 2.64 release hence not actively following this on my time off).

This will only be triggered if the metric result contains bounded trie. So for 2.64 this would not happen unless a customer specifically opt-in to track lineage with boundedtrie or uses boundedtrie metrics (undocumented) in any other way. For the StringSet it happened in that way because lineage emission is enabled by default and was being tracked as StringSet and hence querying /metric for any metric results in StringSet being in result.

Yes, we can change it to do something else other than empty values. I will work on that. We will need this as a safeguard before we switch to bounded trie as default metric type for lineage tracking.

[robertwb]

Thanks for following up.

We had a ClassCastException because of a bug + lack of any testing when StringSet was released. I don't know that we need to over-index on this bug here (both because we know we should test for it, and also because unlike the case with StringSet there's not a variety of Container types that make it hard to "guess" which one we should cast to).

But, as you say, not urgent.