Fix OkHttpGrpcSender mTLS when using the platform default trust store

[thswlsqls]

Fixes #8754

Description

• OkHttpGrpcSender installed the client SSLSocketFactory only when both an SSLContext and an X509TrustManager were present. TlsConfigHelper.getTrustManager() stays null unless trusted certificates are configured, so setClientTls(...) alone skipped the branch and the client certificate was never presented.
• It now falls back to TlsUtil.defaultTrustManager(), mirroring OkHttpHttpSender, which Fix OkHttp client mTLS when using the platform default trust store #8565 (issue OTLP HTTP exporter (OkHttp sender) silently drops client mTLS certificate when no ca certificates are configured #8562) fixed the same way without touching the gRPC sender.
• HttpExporterBuilder.build() and GrpcExporterBuilder.build() pass the same isPlainHttp ? null : getSslContext(), so since Fix OkHttp client mTLS when using the platform default trust store #8565 OTLP HTTP exporters already install an explicit SSLSocketFactory on https endpoints with no TLS configured; gRPC now matches.
• gRPC sender only. No public API change, so no apidiff update.

Testing done

• Added OkHttpGrpcSenderTest#constructor_usesDefaultTrustManagerWhenTrustManagerIsNull and #constructor_wrapsDefaultTrustManagerFailure, mirroring the tests Fix OkHttp client mTLS when using the platform default trust store #8565 added to OkHttpHttpSenderTest.
• ./gradlew :exporters:sender:okhttp:check — 48 tests passed.
• Reverting the production change makes constructor_wrapsDefaultTrustManagerFailure fail: OkHttp's own trust manager lookup throws NoSuchAlgorithmException instead of the wrapped IllegalStateException. constructor_usesDefaultTrustManagerWhenTrustManagerIsNull still passes, since without the fix the branch is skipped rather than throwing.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.29%. Comparing base (e2efec5) to head (a916b26).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #8758   +/-   ##
=========================================
  Coverage     91.29%   91.29%           
  Complexity    10498    10498           
=========================================
  Files          1006     1006           
  Lines         28338    28344    +6     
  Branches       3581     3582    +1     
=========================================
+ Hits          25870    25876    +6     
  Misses         1675     1675           
  Partials        793      793           

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Waiting on the author · refreshed 2026-09-02 14:35 UTC

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