v1.21.0 release

Release of:

• opentelemetry-api
• opentelemetry-sdk
• exporter packages

What's Changed

• [BUILD] Remove WITH_ABSEIL by @owent in #3318
• [INSTALL] add cmake components to the package by @dbarker in #3220
• [CI] Harden GitHub Actions by @khanhtc1202 in #3338
• [StepSecurity] Harden GibHub Actions, part 2 by @marcalff in #3340
• Bump github/codeql-action from 3.28.12 to 3.28.13 by @dependabot in #3341
• [DEVCONTAINER] expose cmake version setting as docker arg and environment variable by @dbarker in #3347
• [CI] disable bzip2 in conan builds by @dbarker in #3352
• [SEMANTIC CONVENTIONS] Upgrade semantic conventions to 1.32.0 by @marcalff in #3351
• Bump github/codeql-action from 3.28.13 to 3.28.15 by @dependabot in #3353
• [CMAKE] bump cmake minimum required version to 3.14 by @dbarker in #3349
• Bump codecov/codecov-action from 5.4.0 to 5.4.2 by @dependabot in #3362
• [DOC] Fix documentation tags in logger API by @zurex in #3371
• [CI] fix artifacts download/upload by @esigo in #3369
• [API] Add Enabled method to Tracer by @psx95 in #3357
• [BUILD] Fixes warnings of ciso646 in C++17 by @owent in #3360
• Bump github/codeql-action from 3.28.15 to 3.28.16 by @dependabot in #3377
• Bump step-security/harden-runner from 2.11.1 to 2.12.0 by @dependabot in #3373
• Bump docker/build-push-action from 6.15.0 to 6.16.0 by @dependabot in #3382
• Bump actions/download-artifact from 4.2.1 to 4.3.0 by @dependabot in #3381
• [CI] Harden Github actions - pinned-dependencies (part -1) by @lalitb in #3380
• [StepSecurity] ci: Harden GitHub Actions by @step-security-bot in #3378
• [SDK] Base2 exponential histogram aggregation by @ethandmd in #3346
• [StepSecurity] ci: Harden GitHub Actions by @step-security-bot in #3379
• [BUILD] Fixes glibc++ 5 checking by @owent in #3355
• [TEST] Add stress test for histogram metric for multiple threads validation by @ThomsonTan in #3388
• Bump github/codeql-action from 3.28.16 to 3.28.17 by @dependabot in #3389
• [SDK] Optimize PeriodicExportingMetricReader Thread Usage by @ColeVanOphem in #3383
• [Metrics SDK] Use nostd::function_ref in AttributesHashMap by @yashykt in #3393
• [SDK] support aggregation of identical instruments by @dbarker in #3358
• [BUILD] Fixes unused var by @owent in #3397
• [INSTALL] Unify cmake install functions and dynamically set component dependencies by @dbarker in #3368
• [BUILD] Upgrade nlohmann_json to 3.12.0 by @marcalff in #3406
• [BUILD] Upgrade opentelemetry-proto to 1.6.0 by @marcalff in #3407
• [CMAKE] add generated protobuf headers to the opentelemetry_proto target by @dbarker in #3400
• [MERGE] Fix accidental rollback of nlohmann-json submodule by @dbarker in #3415
• Bump fossas/fossa-action from 1.6.0 to 1.7.0 by @dependabot in #3414
• Bump docker/build-push-action from 6.16.0 to 6.17.0 by @dependabot in #3420
• Bump codecov/codecov-action from 5.4.2 to 5.4.3 by @dependabot in #3419
• [SEMANTIC CONVENTIONS] Upgrade semantic conventions to 1.33 by @marcalff in #3416
• [DOCS] update the INSTALL guide on cmake components by @dbarker in #3422
• Bump github/codeql-action from 3.28.17 to 3.28.18 by @dependabot in #3423
• [CMAKE] update cmake files in examples directory by @dbarker in #3421
• [SDK] Fix Base2ExponentialHistogramAggregation Merge with empty buckets by @dbarker in #3425
• [SDK] Fix MetricProducer interface by @yashykt in #3413
• [CMAKE] remove global include_directories usage and rely on target properties by @dbarker in #3426
• [BUILD] remove unused WITH_CURL build flag by @marcalff in #3429
• [SEMANTIC CONVENTIONS] Upgrade to semantic conventions 1.34.0 by @marcalff in #3428
• [EXPORTER] ostream log exporter, fix memory ownership issues by @marcalff in #3417
• [TEST] add all components to the cmake fetch content test by @dbarker in #3433
• [BUILD] Error out when building DLL without MSVC by @ThomsonTan in #3438
• [BUILD] Add missing CMake keyword for target_link_libraries by @ThomsonTan in #3442
• [CMAKE] Remove third-party version mismatch warning by @dbarker in #3432
• Bump docker/build-push-action from 6.17.0 to 6.18.0 by @dependabot in #3446
• [SEMANTIC CONVENTIONS] Fix comment style to preserve markup by @marcalff in #3444
• [EXPORTER] support unix sockets in grpc client by @ethandmd in #3410
• [BUILD] Propagate INTERFACE_COMPILE_DEFINITIONS from API through common_foo_library by @ThomsonTan in #3440
• [RELEASE] Release opentelemetry-cpp 1.21.0 by @marcalff in #3445

New Features

• [SDK] Base2 exponential histogram aggregation
  #3346

  • Add base2 exponential histogram aggregation. Includes a new aggregation type,
    ostream exporter, and otlp/grpc exporter. Updated histogram aggregation and
    benchmark tests.

Important changes

• [EXPORTER] ostream log exporter, fixed memory ownership issues
  #3417

  • In the SDK, the following classes implementation has changed:

    • opentelemetry::sdk::logs::ReadableLogRecord
    • opentelemetry::sdk::logs::ReadWriteLogRecord

  • An application implementing a custom log record exporter,
    that reuses these classes from the opentelemetry-cpp SDK,
    will need code adjustments, in particular for methods:

    • GetBody()
    • GetAttributes()

  • Applications not using these SDK classes directly are not affected.

• [BUILD] Remove WITH_ABSEIL
  #3318

  • The build option WITH_ABSEIL is no longer used, and opentelemetry-cpp
    will no longer use any release of abseil provided externally,
    for its own use.

  • Instead, opentelemetry-cpp will only use an internal abseil version.

  • This change resolves long standing binary integrity issues,
    that occurred in the past when mixing several versions of abseil
    in the build.

Deprecations

• This release contains deprecations, see file DEPRECATED.md for details.

New Contributors

• @khanhtc1202 made their first contribution in #3338
• @step-security-bot made their first contribution in #3378
• @ethandmd made their first contribution in #3346
• @ColeVanOphem made their first contribution in #3383

Full Changelog: v1.20.0...v1.21.0