[processor/metricstransform]: Add scaling exponential histogram support #34039
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Jul 11, 2024
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The code looks sane, but I need help from someone who understands about histograms.
@carrieedwards, are you available to review this one?
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Description: This PR adds support for the exponential histograms for the
experimental_scale_valuein the metricstransformprocessor.The scaling works by scaling the middle value of the first bucket (the one that corresponds to the offset) and finding the offset corresponding to this new value (the method used is described here: https://opentelemetry.io/docs/specs/otel/metrics/data-model/#all-scales-use-the-logarithm-function).
The buckets are actually unchanged because they are "shifted" by the new offset. I initially remapped all the values but I ended up always having the same buckets so I left the buckets untouched to make the code simpler and save on performance.
Link to tracking Issue: #29803
Testing: unit test + e2e local test