Loki sink shouldn't convert label names to lowercase during template expansion

[precisionconage]

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Problem

Vector converts label names to lowercase during template expansion. Since labels in Loki are case-sensitive, this can result in logs' being assigned the wrong labels.

Configuration

No response

Version

vector 0.33.0 (x86_64-pc-windows-msvc 89605fb 2023-09-27 14:18:24.180809939)

Debug Output

No response

Example Data

No response

Additional Context

No response

References

No response

[StephenWakely]

Good call. I'm not sure why it would be converting to lowercase. It's an easy fix, but one we'd need to do carefully in case there are some users relying on that conversion.

[dsmith3197]

We looked at the original change that introduced this (#12041) and agree that it is not needed. We can remove the lowercase function but need to treat this as a breaking change.

[tiantangkuohai]

Any updates on this issue? I see lower case label when I use Label Expansion in Loki Sink. It's really annoying.

[pront]

Hello, I understand this can be frustrating. Unfortunately, a fix is not prioritized currently. PRs are always welcome.