Use user provided otel header to start grpc proxy tracing. (#628)

Author: dcherednik

ydb/core/grpc_services/base/base.h

@@ -534,8 +534,7 @@ class TRefreshTokenImpl
     }
 
     const TMaybe<TString> GetPeerMetaValues(const TString&) const override {
-        Y_ABORT("Unimplemented");
-        return TMaybe<TString>{};
+        return {};
     }
 
     TVector<TStringBuf> FindClientCert() const override {

ydb/core/grpc_services/grpc_request_proxy.cpp

@@ -151,7 +151,7 @@ class TGRpcRequestProxyImpl
         }
 
 
-        //StartTracing(*requestBaseCtx);
+        StartTracing(*requestBaseCtx);
 
         if (IsAuthStateOK(*requestBaseCtx)) {
             Handle(event, ctx);
@@ -410,9 +410,12 @@ bool TGRpcRequestProxyImpl::IsAuthStateOK(const IRequestProxyCtx& ctx) {
 }
 
 void TGRpcRequestProxyImpl::StartTracing(IRequestProxyCtx& ctx) {
-    auto traceId = NWilson::TTraceId::NewTraceId(15, Max<ui32>());
-    NWilson::TSpan grpcRequestProxySpan(TWilsonGrpc::RequestProxy, std::move(traceId), "GrpcRequestProxy");
-    ctx.StartTracing(std::move(grpcRequestProxySpan));
+    if (const auto otelHeader = ctx.GetPeerMetaValues(NYdb::OTEL_TRACE_HEADER)) {
+        if (auto traceId = NWilson::TTraceId::FromTraceparentHeader(otelHeader.GetRef())) {
+            NWilson::TSpan grpcRequestProxySpan(TWilsonGrpc::RequestProxy, std::move(traceId), "GrpcRequestProxy");
+            ctx.StartTracing(std::move(grpcRequestProxySpan));
+        }
+    }
 }
 
 void TGRpcRequestProxyImpl::HandleSchemeBoard(TSchemeBoardEvents::TEvNotifyUpdate::TPtr& ev, const TActorContext& ctx) {