fix(sdk): make instrumentation scope glob matching case-sensitive

[ocelotl]

Description

Fixes #5583.

_scope_name_matches_glob in opentelemetry-sdk/src/opentelemetry/sdk/util/instrumentation.py used fnmatch.fnmatch, which normalizes both the scope name and the glob pattern through os.path.normcase. On Windows normcase lower-cases its argument, so instrumentation-scope name matching was case-insensitive there while staying case-sensitive on Linux.

That predicate backs scope name matching for the tracer, meter and logger configurators, so the host platform leaked into observable SDK behavior: the same configuration disabled a different set of scopes depending on the operating system.

The declarative configuration schema requires the opposite. From ExperimentalTracerMatcherAndConfig.name in opentelemetry-configuration/src/opentelemetry/configuration/schema.json (the meter and logger matchers carry the same wording):

Configure tracer names to match. Matching is case-sensitive, evaluated as follows:

• If the tracer name exactly matches.
• If the tracer name matches the wildcard pattern, where '?' matches any single character and '*' matches any number of characters including none.

This switches the predicate to fnmatchcase, which is what the rest of the SDK already does. opentelemetry-sdk/src/opentelemetry/sdk/metrics/_internal/view.py and opentelemetry-sdk/src/opentelemetry/sdk/trace/_sampling_experimental/_rule_based.py both use fnmatchcase, and view.py already documents the reason: "fnmatchcase is used instead of fnmatch so it does not rely on the host platform's filename case sensitivity (normcase)".

Reported by @lzchen while reviewing #5418: #5418 (comment)

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Added two tests next to the existing _scope_name_matches_glob tests in opentelemetry-sdk/tests/metrics/test_metrics.py:

• test_scope_name_matches_glob_is_case_sensitive_on_every_platform: a scope name that differs from the pattern only by case must not match, for both an exact pattern and a wildcard pattern.
• test_scope_name_matches_glob_pattern_case_is_not_normalized: an upper-case pattern must not match a lower-case scope name.

Both assertions fail on Windows with fnmatch and pass with fnmatchcase. On Linux they pass either way, so I confirmed the regression coverage by running fnmatch and fnmatchcase with os.path.normcase patched to ntpath.normcase:

fnmatch('My.Meter', 'my.meter')     = True
fnmatchcase('My.Meter', 'my.meter') = False
fnmatch('MY.meter', 'my.*')     = True
fnmatchcase('MY.meter', 'my.*') = False
fnmatch('my.meter', 'MY.*')     = True
fnmatchcase('my.meter', 'MY.*') = False

The repository's Windows CI jobs cover the real case.

Local runs:

• pytest opentelemetry-sdk/tests/metrics opentelemetry-sdk/tests/logs opentelemetry-sdk/tests/trace — 705 passed
• pytest opentelemetry-configuration/tests — 381 passed
• ruff check and ruff format --check on both changed files — clean

Does This PR Require a Contrib Repo Change?

• 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 2026-08-25 10:15 UTC

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