v1.16.0 release

Release of core packages

• opentelemetry-api
• opentelemetry-sdk

and exporter packages:

• opentelemetry-exporter-otlp (gRPC + HTTP/JSON)
• opentelemetry-exporter-prometheus

What's Changed

• [BUILD] Upgrade bazel abseil from 20220623.1 to 20230802.2 by @marcalff in #2650
• [BUILD] Use nostd::enable_if_t instead of std::enable_if_t by @owent in #2648
• [EXEMPLAR] Update ExemplarFilter and ExemplarReservoir for spec by @ThomsonTan in #2372
• [BUILD] Link CoreFoundation on apple systems because some dependency packages require it by @owent in #2655
• [SDK] Avoid missing conditional variable update and simplify atomic bool by @arekay in #2553
• [BUILD] Build break in OLTP_FILE tests by @marcalff in #2659
• [EXPORTER] General cleanup for is_shutdown_ flags in exporters. by @marcalff in #2663
• [CI] Upgrade Maintainers CI to ubuntu-24.04 by @marcalff in #2670
• [BUILD] Upgrade to opentelemetry-proto 1.3.1 by @marcalff in #2669
• [API] Return NoopLogRecord from NoopLogger by @marcalff in #2668
• [BUILD] Remove the hard-coded separator in tracestate by @ThomsonTan in #2672
• [SDK] Fix forceflush may wait for ever by @owent in #2584
• [API] DO not allow unsafe Logger::EmitLogRecord by @owent in #2673
• [BUILD] Read default proto version from third_party_release by @owent in #2677
• [CI] include-what-you-use by @marcalff in #2629
• [CI] Upgrade to clang-format 18 by @marcalff in #2684
• [CI] Fix CI failures on Ubuntu 24.04 by @lalitb in #2686
• [SEMANTIC CONVENTIONS] Upgrade to version 1.26.0 by @marcalff in #2687
• [API/SDK] Provider cleanup by @marcalff in #2664
• [ETW] Add table name mapping for Logs other than the default Log table by @ThomsonTan in #2691
• [CI] Remove benchmark overlay for vcpkg by @ThomsonTan in #2695
• [BUILD] Remove the incorrect set of CMAKE_MSVC_RUNTIME_LIBRARY for vcpkg by @ThomsonTan in #2696
• [BUILD] CMakeLists.txt: Enable CMAKE_MSVC_RUNTIME_LIBRARY support by @t-b in #2652
• [EXPORTER] OTLP file: use thread-safe file/io by @owent in #2675
• [bazel] Bump version and deps by @keith in #2679
• [BUILD] Add support for bzlmod by @keith in #2608
• [BUILD] Fix Import Abseil-cpp by @LeiZhang-Hunter in #2701
• [Code health] include-what-you-use cleanup by @marcalff in #2692
• [BUILD] Restore Bazel flag removed from public API by @dbolduc in #2702
• [DOC] Fix typo tace_id -> trace_id in logger.h by @yijiem in #2703
• Bump docker/build-push-action from 5 to 6 by @dependabot in #2705
• [CI] Enable ARM64 build in CI by @esigo in #2699
• [Code health] Remove Unicode Text from Source files by @perhapsmaple in #2707
• [BUILD] Add option WITH_OTLP_GRPC_SSL_MTLS_PREVIEW by @owent in #2714
• [EXPORTER] All 2xx return codes should be considered successful. by @owent in #2712
• [RELEASE] Release opentelemetry-cpp version 1.16.0 by @marcalff in #2711

Important changes

• [API/SDK] Provider cleanup
  #2664
  • Before this fix:
    • The API class opentelemetry::trace::Tracer exposed methods such
      as ForceFlush(), ForceFlushWithMicroseconds(), Close()
      and CloseWithMicroseconds().
    • These methods are meant to be used when configuring the SDK,
      and should not be part of the API. Exposing them was an oversight.
    • Two of these methods are virtual, and therefore part of the ABI.
  • After this fix:
    • In OPENTELEMETRY_ABI_VERSION_NO 1, nothing is changed,
      because removing this code would break the ABI.
    • In OPENTELEMETRY_ABI_VERSION_NO 2, these methods are moved
      from the API to the SDK. This is a breaking change for ABI version 2,
      which is still experimental.
  • In all cases, instrumenting an application should not
    invoke flush or close on a tracer, do not use these methods.

Breaking changes

• [API/SDK] Provider cleanup
  #2664
  • Before this fix:
    • SDK factory methods such as:
      • opentelemetry::sdk::trace::TracerProviderFactory::Create()
      • opentelemetry::sdk::metrics::MeterProviderFactory::Create()
      • opentelemetry::sdk::logs::LoggerProviderFactory::Create()
      • opentelemetry::sdk::logs::EventLoggerProviderFactory::Create()
        returned an API object (opentelemetry::trace::TracerProvider)
        to the caller.
  • After this fix, these methods return an SDK level object
    (opentelemetry::sdk::trace::TracerProvider) to the caller.
  • Returning an SDK object is necessary for the application to
    cleanup and invoke SDK level methods, such as ForceFlush(),
    on a provider.
  • The application code that configures the SDK, by calling
    the various provider factories, may need adjustment.
  • All the examples have been updated, and in particular no
    longer perform static_cast do convert an API object to an SDK object.
    Please refer to examples for guidance on how to adjust.
  • If adjusting application code is impractical,
    an alternate and temporary solution is to build with option
    WITH_DEPRECATED_SDK_FACTORY=ON in CMake.
  • Option WITH_DEPRECATED_SDK_FACTORY=ON will allow to build code
    without application changes, posponing changes for later.
  • WITH_DEPRECATED_SDK_FACTORY=ON is temporary, only to provide
    an easier migration path. Expect this flag to be removed,
    as early as by the next release.

Notes on experimental features

• #2372
  introduced MeterProvider::SetExemplar() which accepts an
  ExemplarFilterType enumeration with kAlwaysOff, kAlwaysOn and
  kTraceBased.

New Contributors

• @arekay made their first contribution in #2553
• @t-b made their first contribution in #2652
• @LeiZhang-Hunter made their first contribution in #2701

Full Changelog: v1.15.0...v1.16.0