Cumulative ExponentialHistogram resets start time each collection #3931
Closed
Description
What happened?
Cumulative ExponentialHistogram points have their startTime reset each collection. E.g.
// current incorrect behavior
t0-------t1 first collection
t1-------t2 second collection
--------------------------> t
// instead of correct behavior
t0-------t1 first collection
t0-----------------t2 second collection
--------------------------> t
Steps to Reproduce
Expected Result
The startTime should be the same each MetricReader collection for the same metric. The tests in linked PR draft should pass.
Actual Result
The startTime resets each collection (like a delta temporality) while the value continues to grow cumulatively. The linked PR test fails.
Additional Details
Looks like the merge function is not merging the start times: https://github.com/open-telemetry/opentelemetry-js/blob/74393ac6397dcb130b9d5dae35354a2bf9a0d2c3/packages/sdk-metrics/src/aggregator/ExponentialHistogram.ts#LL219C33-L219C33
OpenTelemetry Setup Code
No response
package.json
No response
Relevant log output
No response