OTel opentelemetry-cpp::otlp_grpc_client target is not linked correctly

[alevenberg]

I tried to compile an application using CMake and VcPkg

Steps to reproduce

Here's a simple version

publisher_jaeger.cc

namespace trace_sdk = opentelemetry::sdk::trace;
namespace otlp = opentelemetry::exporter::otlp;

namespace {

void ConfigureOtlpGrpcExporterTracer(ParseResult const& args) {
  otlp::OtlpGrpcExporterOptions opts;
  auto exporter = otlp::OtlpGrpcExporterFactory::Create(opts);
  trace_sdk::BatchSpanProcessorOptions span_options;
  span_options.max_queue_size = args.max_queue_size;
  auto processor = trace_sdk::BatchSpanProcessorFactory::Create(
      std::move(exporter), span_options);
  auto provider =
      trace_sdk::TracerProviderFactory::Create(std::move(processor));
  opentelemetry::trace::Provider::SetTracerProvider(std::move(provider));
}

}  // namespace

int main(int argc, char* argv[]) try {
  ConfigureOtlpGrpcExporterTracer(args);
  return 0;
} 

CMakeLists.txt

add_executable(publisher_jaeger publisher_jaeger.cc)
target_compile_features(publisher_jaeger PRIVATE cxx_std_14)
target_link_libraries(
    publisher_jaeger
    PRIVATE opentelemetry-cpp::otlp_grpc_client
            opentelemetry-cpp::otlp_grpc_exporter
            opentelemetry-cpp::otlp_recordable)

Steps to build

cmake -DWITH_OTLP_GRPC=ON -S . -B .build -DCMAKE_TOOLCHAIN_FILE=$HOME/vcpkg/scripts/buildsystems/vcpkg.cmake -G Ninja
cmake --build .build --target publisher_jaeger

At the build step, it found the target, but produced a linking error.

What is the expected behavior?
What did you expect to see?
No error and a successful linking

What is the actual behavior?
A linking error saying otlp:: symbols were not found

/usr/bin/ld: CMakeFiles/publisher_jaeger.dir/publisher_jaeger.cc.o: in function `(anonymous namespace)::ConfigureOtlpGrpcExporterTracer(ParseResult const&)':
publisher_jaeger.cc:(.text+0x65): undefined reference to `opentelemetry::v1::exporter::otlp::OtlpGrpcExporterFactory::Create(opentelemetry::v1::exporter::otlp::OtlpGrpcExporterOptions const&)'
/usr/bin/ld: CMakeFiles/publisher_jaeger.dir/publisher_jaeger.cc.o: in function `opentelemetry::v1::exporter::otlp::GetOtlpDefaultGrpcEndpoint[abi:cxx11]()':
publisher_jaeger.cc:(.text._ZN13opentelemetry2v18exporter4otlp26GetOtlpDefaultGrpcEndpointB5cxx11Ev[_ZN13opentelemetry2v18exporter4otlp26GetOtlpDefaultGrpcEndpointB5cxx11Ev]+0x14): undefined reference to `opentelemetry::v1::exporter::otlp::GetOtlpDefaultGrpcTracesEndpoint[abi:cxx11]()'
/usr/bin/ld: CMakeFiles/publisher_jaeger.dir/publisher_jaeger.cc.o: in function `opentelemetry::v1::exporter::otlp::GetOtlpDefaultIsSslEnable()':
publisher_jaeger.cc:(.text._ZN13opentelemetry2v18exporter4otlp25GetOtlpDefaultIsSslEnableEv[_ZN13opentelemetry2v18exporter4otlp25GetOtlpDefaultIsSslEnableEv]+0x5): undefined reference to `opentelemetry::v1::exporter::otlp::GetOtlpDefaultGrpcTracesIsInsecure()'
/usr/bin/ld: CMakeFiles/publisher_jaeger.dir/publisher_jaeger.cc.o: in function `opentelemetry::v1::exporter::otlp::GetOtlpDefaultSslCertificatePath[abi:cxx11]()':
publisher_jaeger.cc:(.text._ZN13opentelemetry2v18exporter4otlp32GetOtlpDefaultSslCertificatePathB5cxx11Ev[_ZN13opentelemetry2v18exporter4otlp32GetOtlpDefaultSslCertificatePathB5cxx11Ev]+0x14): undefined reference to `opentelemetry::v1::exporter::otlp::GetOtlpDefaultTracesSslCertificatePath[abi:cxx11]()'
/usr/bin/ld: CMakeFiles/publisher_jaeger.dir/publisher_jaeger.cc.o: in function `opentelemetry::v1::exporter::otlp::GetOtlpDefaultSslCertificateString[abi:cxx11]()':
publisher_jaeger.cc:(.text._ZN13opentelemetry2v18exporter4otlp34GetOtlpDefaultSslCertificateStringB5cxx11Ev[_ZN13opentelemetry2v18exporter4otlp34GetOtlpDefaultSslCertificateStringB5cxx11Ev]+0x14): undefined reference to `opentelemetry::v1::exporter::otlp::GetOtlpDefaultTracesSslCertificateString[abi:cxx11]()'
/usr/bin/ld: CMakeFiles/publisher_jaeger.dir/publisher_jaeger.cc.o: in function `opentelemetry::v1::exporter::otlp::GetOtlpDefaultTimeout()':
publisher_jaeger.cc:(.text._ZN13opentelemetry2v18exporter4otlp21GetOtlpDefaultTimeoutEv[_ZN13opentelemetry2v18exporter4otlp21GetOtlpDefaultTimeoutEv]+0x5): undefined reference to `opentelemetry::v1::exporter::otlp::GetOtlpDefaultTracesTimeout()'
/usr/bin/ld: CMakeFiles/publisher_jaeger.dir/publisher_jaeger.cc.o: in function `opentelemetry::v1::exporter::otlp::GetOtlpDefaultHeaders[abi:cxx11]()':
publisher_jaeger.cc:(.text._ZN13opentelemetry2v18exporter4otlp21GetOtlpDefaultHeadersB5cxx11Ev[_ZN13opentelemetry2v18exporter4otlp21GetOtlpDefaultHeadersB5cxx11Ev]+0x14): undefined reference to `opentelemetry::v1::exporter::otlp::GetOtlpDefaultTracesHeaders[abi:cxx11]()'

Additional context

A workaround is linking to two more libraries, then it compiles and the linking error goes away.

target_link_libraries(
    publisher_jaeger
    PRIVATE publisher_helper parse_args opentelemetry-cpp::otlp_grpc_client
            opentelemetry-cpp::otlp_grpc_exporter
            opentelemetry-cpp::otlp_recordable)

I'm not sure if the solution is to link the additional targets for otlp_grpc_client, or if the common symbols should be refactored into a private library, so filing the issue for the maintainers to decide

This is where the links could be added

opentelemetry-cpp/exporters/otlp/CMakeLists.txt

Lines 37 to 42 in 4bd64c9

	target_link_libraries(
	opentelemetry_exporter_otlp_grpc_client
	PUBLIC opentelemetry_sdk opentelemetry_common opentelemetry_ext
	# gRPC::grpc++ must be linked before opentelemetry_proto_grpc.
	opentelemetry_proto_grpc
	PRIVATE gRPC::grpc++)

.

[owent]

You can use gRPC trace exporter by only link opentelemetry-cpp::otlp_grpc_exporter, opentelemetry-cpp::otlp_grpc_client and opentelemetry-cpp::otlp_recordable should be linked automaticlly because them are depended by opentelemetry-cpp::otlp_grpc_exporter.
But it's not a problem of the linking problem above, could you please add --verbose to cmake --build ... we we can find out which library files are actually linked?And then we can use nm to find out the symbols in libopentelemetry_otlp_recordable.a or libopentelemetry_otlp_recordable.so.
In my guess, there may be more than one otel-cpp in your build system and publisher_jaeger may just link a wrong one.

[alevenberg]

Thanks for taking a look.

I tried it again and only linked opentelemetry-cpp::otlp_grpc_exporter and opentelemetry-cpp::otlp_grpc_client and it built correctly.