fix(sdk): correctly merge exponential histogram buckets that start empty#5378
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ocelotl wants to merge 2 commits into
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fix(sdk): correctly merge exponential histogram buckets that start empty#5378ocelotl wants to merge 2 commits into
ocelotl wants to merge 2 commits into
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Add a test verifying that merging two exponential histograms across cumulative collections produces the same result as aggregating all values in one pass, per issue open-telemetry#3219. This uncovered a bug: when one side (positive or negative) of the histogram has never received a value, its placeholder index_start/index_end (0) was treated as a real boundary during merge, corrupting or crashing the merge instead of being initialized from the first incoming value.
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Summary
_ExponentialBucketHistogramAggregation._merge: when one side of the histogram (positive or negative buckets) has never received a value, its placeholderindex_start/index_end(0) was treated as a real boundary during merge, which could corrupt bucket offsets or raise a spuriousIncorrect merge scaleexception. Fixed by initializing the empty side from the first incoming index, mirroring the existing logic inaggregate().Fixes #3219
Test plan
test_merge_into_empty_buckets: minimal deterministic repro of the bug.test_merging_two_histograms_equals_aggregating_independently: randomized property test comparing split-and-merge vs. single-pass aggregation.opentelemetry-sdkmetrics test suite passes (296 tests).