[kalragauri]

EnableGrpcMetricsImpl() stores its MeterProvider in ExporterRegistry::Singleton() and registers it with gRPC via OpenTelemetryPluginBuilder::BuildAndRegisterGlobal(). Neither singleton is ever destroyed, so the provider's PeriodicExportingMetricReader thread is still running when a test binary exits. That thread runs its first collection immediately upon startup; if the collection overlaps exit(), SyncMetricStorage::Collect() reads cardinality_limit_ from the function-local static in AggregationConfig::GetOrDefault() after ~AggregationConfig() has poisoned it under MemorySanitizer. Three unit tests that call EnableGrpcMetricsImpl() hit this race intermittently and were skipped in #16588.

This PR adds a ScopedProviderShutdown RAII guard in channel_metrics_test.cc and metrics_exporter_impl_test.cc that downcasts the MeterProvider to opentelemetry::sdk::metrics::MeterProvider and calls Shutdown() when the test ends (including after a failed ASSERT_*), joining the reader thread before exit() runs.

Fixes #16587

[gemini-code-assist]

Code Review

This pull request re-enables several previously flaky gRPC metrics tests by introducing a ScopedProviderShutdown helper class. This helper ensures that process-wide MeterProvider instances are properly shut down when a test ends, preventing background collection threads from racing with test exit. The review feedback suggests optimizing the RegisteredAuthorityHonorsOption test by avoiding redundant calls to FindMeterProvider and instead reusing the retrieved provider.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.40%. Comparing base (608aeef) to head (5e05556).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main   #16604    +/-   ##
========================================
  Coverage   92.40%   92.40%            
========================================
  Files        2266     2266            
  Lines      220810   221043   +233     
========================================
+ Hits       204036   204255   +219     
- Misses      16774    16788    +14     

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