Reject exponential histogram aggregation views for async instruments

[Eason09053360]

Description

A View configuring ExponentialBucketHistogramAggregation on an
asynchronous instrument (e.g. ObservableCounter) is currently accepted
without any warning, but silently produces no data points forever:
asynchronous instruments report with CUMULATIVE instrument temporality, and
_ExponentialBucketHistogramAggregation.collect() only implements the DELTA
instrument temporality path, so every collection falls through and returnsNone.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• opentelemetry-sdk/tests/metrics/
• test_metric_reader_storage.py

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

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Waiting on the author · refreshed 2026-08-30 10:20 UTC

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[Copilot]

Pull request overview

This pull request addresses a metrics SDK edge case where a View configured with ExponentialBucketHistogramAggregation on an asynchronous instrument (e.g., ObservableCounter) would previously be accepted but then produce no data points due to temporality/aggregation incompatibility. The change aligns behavior with existing handling for explicit histograms by warning and not applying the incompatible view, falling back to the default view instead.

Changes:

• Reject (warn + do not apply) View/instrument matches where an asynchronous instrument is paired with ExponentialBucketHistogramAggregation.
• Add a unit test to verify the exponential-histogram + async-instrument view is rejected and the default view is used.
• Add a changelog entry documenting the fix.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
opentelemetry-sdk/src/opentelemetry/sdk/metrics/_internal/metric_reader_storage.py	Extends async-instrument compatibility checks to also reject exponential histogram aggregations.
opentelemetry-sdk/tests/metrics/test_metric_reader_storage.py	Adds coverage for rejecting exponential histogram aggregation views on async instruments (warning emitted; default view applied).
.changelog/5461.fixed	Documents the behavior change/fix in the changelog system.

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[Eason09053360]

The CI failures here are unrelated to this change:

opentelemetry-sdk pypy-3.10 Windows: test_shutdown_allows_1_export_to_finish[BatchSpanProcessor-telemetry1] fails on assert processor._batch_processor._worker_thread.is_alive() is True right after shutdown(timeout_millis=3000) returns — a timing assumption that doesn't hold on slow pypy/Windows runners.

This PR only touches metrics view compatibility. Could you rerun the failed jobs when you get a chance?