remove abseil as a public dependency. update install notes on how to install abseil, protobuf, and grpc so the transitive abseil depenedency is found implicitly

Author: dbarker

.github/workflows/ci.yml

@@ -302,24 +302,6 @@ jobs:
       run: |
         ./ci/do_ci.sh cmake.with_async_export.test
 
-#  cmake_abseil_stl_test:
-#    name: CMake test (with abseil)
-#    runs-on: ubuntu-20.04
-#    steps:
-#    - uses: actions/checkout@v4
-#      with:
-#        submodules: 'recursive'
-#    - name: setup
-#      run: |
-
-#        sudo -E ./ci/setup_ci_environment.sh
-#        sudo -E ./ci/setup_cmake.sh
-#        sudo -E ./ci/setup_googletest.sh
-#    - name: run cmake tests (enable abseil-cpp)
-#      run: |
-#        sudo ./ci/install_abseil.sh
-#        ./ci/do_ci.sh cmake.abseil.test
-
   cmake_opentracing_shim_test:
     name: CMake test (with opentracing-shim)
     runs-on: ubuntu-latest

CMakeLists.txt

@@ -415,10 +415,6 @@ if(WITH_PROMETHEUS)
   endif()
 endif()
 
-if(WITH_OTLP_GRPC)
-  find_package(absl CONFIG REQUIRED)
-endif()
-
 if(WITH_OTLP_GRPC
    OR WITH_OTLP_HTTP
    OR WITH_OTLP_FILE)
@@ -738,7 +734,6 @@ message(STATUS "OTELCPP_VERSIONED_LIBS: ${OTELCPP_VERSIONED_LIBS}")
 message(STATUS "OTELCPP_MAINTAINER_MODE: ${OTELCPP_MAINTAINER_MODE}")
 message(STATUS "WITH_STL: ${WITH_STL}")
 message(STATUS "WITH_GSL: ${WITH_GSL}")
-message(STATUS "WITH_ABSEIL: ${WITH_ABSEIL}")
 message(STATUS "WITH_NO_GETENV: ${WITH_NO_GETENV}")
 
 message(STATUS "---------------------------------------------")

INSTALL.md

@@ -38,10 +38,20 @@ You can link OpenTelemetry C++ SDK with libraries provided in
   [GoogleBenchmark Build
   Instructions](https://github.com/google/benchmark#installation).
 - Apart from above core requirements, the Exporters and Propagators have their
-  build dependencies which are not covered here. E.g, the OTLP Exporter needs
-  grpc/protobuf library, the Zipkin exporter needs nlohmann-json and libcurl,
-  the ETW exporter needs nlohmann-json to build. This is covered in the build
-  instructions for each of these components.
+  build dependencies.
+
+### Building dependencies for the OTLP exporters 
+
+The opentelemetry-cpp OTLP exporters depend on Protobuf and gRPC (in the case of the otlp grpc exporters). Protobuf (since version 3.22.0) and gRPC depend on Abseil.  
+For cmake builds, it is best practice to build and install Abseil, Protobuf, and gPRC as independent packages - configuring cmake for Protobuf and gRPC to build against the installed packages instead of using their submodule option. 
+
+If building and installing Protobuf and gRPC manually with cmake the recommended approach is: 
+1. Choose the desired tag version of grpc. Find the compatible versions of abseil and protobuf by inspecting the submodules of grpc at that tag. 
+2. Build and install the required version of abseil 
+3. Build and install the required version of protobuf 
+    - Set the cmake option of Protobuf to build against the installed package of Abseil (`protobuf_ABSL_PROVIDER=package`)
+4. Build and install the required version of grpc 
+    - Set the cmake option of grpc to build against the installed packages of Abseil and Protobuf (cmake options - `gRPC_ABSL_PROVIDER=package` and `gRPC_PROTOBUF_PROVIDER=package`)
 
 ### Building as standalone CMake Project
 

ci/do_ci.ps1

@@ -373,7 +373,6 @@ switch ($action) {
       "-DCMAKE_INSTALL_PREFIX=$INSTALL_TEST_DIR" `
       -DWITH_ABI_VERSION_1=OFF `
       -DWITH_ABI_VERSION_2=ON `
-      -DWITH_ABSEIL=OFF `
       -DWITH_THREAD_INSTRUMENTATION_PREVIEW=ON `
       -DWITH_METRICS_EXEMPLAR_PREVIEW=ON `
       -DWITH_ASYNC_EXPORT_PREVIEW=ON `
@@ -473,7 +472,6 @@ switch ($action) {
       -DOPENTELEMETRY_BUILD_DLL=1 `
       -DWITH_ABI_VERSION_1=ON `
       -DWITH_ABI_VERSION_2=OFF `
-      -DWITH_ABSEIL=OFF `
       -DWITH_THREAD_INSTRUMENTATION_PREVIEW=ON `
       -DWITH_METRICS_EXEMPLAR_PREVIEW=ON `
       -DWITH_ASYNC_EXPORT_PREVIEW=ON `

ci/do_ci.sh

@@ -232,18 +232,6 @@ elif [[ "$1" == "cmake.with_async_export.test" ]]; then
   make -j $(nproc)
   make test
   exit 0
-elif [[ "$1" == "cmake.abseil.test" ]]; then
-  cd "${BUILD_DIR}"
-  rm -rf *
-  cmake "${CMAKE_OPTIONS[@]}"  \
-        -DWITH_METRICS_EXEMPLAR_PREVIEW=ON \
-        -DCMAKE_CXX_FLAGS="-Werror $CXXFLAGS" \
-        -DWITH_ASYNC_EXPORT_PREVIEW=ON \
-        -DWITH_ABSEIL=ON \
-        "${SRC_DIR}"
-  make -j $(nproc)
-  make test
-  exit 0
 elif [[ "$1" == "cmake.opentracing_shim.test" ]]; then
   cd "${BUILD_DIR}"
   rm -rf *
@@ -387,9 +375,6 @@ elif [[ "$1" == "cmake.legacy.exporter.otprotocol.test" ]]; then
 elif [[ "$1" == "cmake.exporter.otprotocol.test" ]]; then
   cd "${BUILD_DIR}"
   rm -rf *
-  if [[ ! -z "${WITH_ABSEIL}" ]]; then
-    CMAKE_OPTIONS=(${CMAKE_OPTIONS[@]} "-DWITH_ABSEIL=${WITH_ABSEIL}")
-  fi
   cmake "${CMAKE_OPTIONS[@]}"  \
         -DWITH_OTLP_GRPC=ON \
         -DWITH_OTLP_HTTP=ON \
@@ -477,7 +462,6 @@ elif [[ "$1" == "cmake.install.test" ]]; then
         -DCMAKE_INSTALL_PREFIX=${INSTALL_TEST_DIR} \
         -DWITH_ABI_VERSION_1=OFF \
         -DWITH_ABI_VERSION_2=ON \
-        -DWITH_ABSEIL=OFF \
         -DWITH_METRICS_EXEMPLAR_PREVIEW=ON \
         -DWITH_ASYNC_EXPORT_PREVIEW=ON \
         -DWITH_THREAD_INSTRUMENTATION_PREVIEW=ON \

cmake/opentelemetry-proto.cmake

@@ -318,11 +318,6 @@ set_target_version(opentelemetry_proto)
 # Disable include-what-you-use on generated code.
 set_target_properties(opentelemetry_proto PROPERTIES CXX_INCLUDE_WHAT_YOU_USE
                                                      "")
-
-if(TARGET absl::bad_variant_access)
-  target_link_libraries(opentelemetry_proto PUBLIC absl::bad_variant_access)
-endif()
-
 if(NOT Protobuf_INCLUDE_DIRS AND TARGET protobuf::libprotobuf)
   get_target_property(Protobuf_INCLUDE_DIRS protobuf::libprotobuf
                       INTERFACE_INCLUDE_DIRECTORIES)
@@ -402,13 +397,6 @@ else() # cmake 3.8 or lower
   target_link_libraries(opentelemetry_proto PUBLIC ${Protobuf_LIBRARIES})
 endif()
 
-if(WITH_OTLP_GRPC)
-  if(TARGET absl::synchronization)
-    target_link_libraries(opentelemetry_proto_grpc
-                          PRIVATE absl::synchronization)
-  endif()
-endif()
-
 if(BUILD_SHARED_LIBS)
   foreach(proto_target ${OPENTELEMETRY_PROTO_TARGETS})
     set_property(TARGET ${proto_target} PROPERTY POSITION_INDEPENDENT_CODE ON)

cmake/templates/thirdparty-built-with-flags.cmake.in

@@ -10,7 +10,6 @@
 
 # Initialize dependency expected flags
 set(BUILT_WITH_Threads TRUE)
-set(BUILT_WITH_absl FALSE)
 set(BUILT_WITH_CURL FALSE)
 set(BUILT_WITH_ZLIB FALSE)
 set(BUILT_WITH_nlohmann_json FALSE)
@@ -19,17 +18,6 @@ set(BUILT_WITH_gRPC FALSE)
 set(BUILT_WITH_prometheus-cpp FALSE)
 set(BUILT_WITH_OpenTracing FALSE)
 
-# absl:
-if(@WITH_ABSEIL@)
-  set(BUILT_WITH_absl TRUE)
-elseif(@WITH_OTLP_HTTP@ OR @WITH_OTLP_FILE@ OR @WITH_OTLP_GRPC@)
-  if( @WITH_OTLP_GRPC@ )
-    set(BUILT_WITH_absl TRUE)
-  elseif(@Protobuf_VERSION@ VERSION_GREATER_EQUAL 3.22.0)
-    set(BUILT_WITH_absl TRUE)
-  endif()
-endif()
-
 # CURL and ZLIB:
 if(@WITH_HTTP_CLIENT_CURL@)
   if("@CURL_FOUND@")
@@ -69,10 +57,6 @@ endif()
 #-----------------------------------------------------------------------
 # Third party dependency versions
 #-----------------------------------------------------------------------
-if(BUILT_WITH_absl)
-  set(BUILT_WITH_absl_VERSION @absl_VERSION@)
-endif()
-
 if(BUILT_WITH_CURL)
   set(BUILT_WITH_CURL_VERSION @CURL_VERSION_STRING@)
 endif()
@@ -104,7 +88,6 @@ endif()
 #-----------------------------------------------------------------------
 # Flags to determine if CONFIG search mode should be used in find_dependency(...)
 #-----------------------------------------------------------------------
-set(FIND_DEPENDENCY_absl_USE_CONFIG TRUE)
 set(FIND_DEPENDENCY_Threads_USE_CONFIG FALSE)
 set(FIND_DEPENDENCY_ZLIB_USE_CONFIG FALSE)
 set(FIND_DEPENDENCY_CURL_USE_CONFIG FALSE)

cmake/thirdparty-dependency-definitions.cmake

@@ -6,7 +6,6 @@
 #    Dependencies will be found in this order when find_package(opentelemetry-cpp ...)  is called.
 #-----------------------------------------------------------------------
 set(THIRD_PARTY_DEPENDENCIES_SUPPORTED
-     absl
      Threads
      ZLIB
      CURL
@@ -22,14 +21,6 @@ set(THIRD_PARTY_DEPENDENCIES_SUPPORTED
 #   These are the components that may require the third party dependency
 #-----------------------------------------------------------------------
 
-# Components that may require absl
-set(THIRD_PARTY_absl_DEPENDENT_COMPONENTS
-    api
-    sdk
-    exporters_otlp_common
-    exporters_otlp_grpc
-)
-
 # Components that require Threads
 set(THIRD_PARTY_Threads_DEPENDENT_COMPONENTS
     sdk
@@ -55,9 +46,6 @@ set(THIRD_PARTY_nlohmann_json_DEPENDENT_COMPONENTS
 # Components that require Protobuf
 set(THIRD_PARTY_Protobuf_DEPENDENT_COMPONENTS
     exporters_otlp_common
-    exporters_otlp_file
-    exporters_otlp_http
-    exporters_otlp_grpc
 )
 
 # Components that require gRPC

examples/grpc/CMakeLists.txt

@@ -42,9 +42,6 @@ else()
   target_link_libraries(example_grpc_proto PUBLIC gRPC::grpc++
                                                   ${Protobuf_LIBRARIES})
 endif()
-if(WITH_OTLP_GRPC)
-  target_link_libraries(example_grpc_proto PUBLIC absl::bad_variant_access)
-endif()
 
 foreach(_target client server)
   add_executable(${_target} "${_target}.cc")

examples/otlp/README.md

@@ -67,19 +67,3 @@ Once you have the Collector running, see
 [CONTRIBUTING.md](../../CONTRIBUTING.md) for instructions on building and
 running the example.
 
-## Additional notes regarding Abseil library
-
-gRPC internally uses a different version of Abseil than OpenTelemetry C++ SDK.
-
-One option to optimize your code is to build the SDK with system-provided
-Abseil library. If you are using CMake, then `-DWITH_ABSEIL=ON` may be passed
-during the build of SDK to reuse the same Abseil library as gRPC. If you are
-using Bazel, then `--@io_opentelemetry_cpp/api:with_abseil=true` may be passed
-to reuse your Abseil library in your project.
-
-If you do not want to pursue the above option, and in case if you run into
-conflict between Abseil library and OpenTelemetry C++ `absl::variant`
-implementation, please include either `grpcpp/grpcpp.h` or
-`opentelemetry/exporters/otlp/otlp_grpc_exporter.h` BEFORE any other API
-headers. This approach efficiently avoids the conflict between the two different
-versions of Abseil.