addressed code review comments.

Signed-off-by: Pratik Mankawde <3397372+pratikmankawde@users.noreply.github.com>

include/xrpl/telemetry/SpanNames.h

@@ -20,6 +20,7 @@
  *  - Per-span attribute keys: bare field name (span name carries the domain).
  *  - Collision qualifier: <domain>_<field> when bare name collides across
  *    domains or with OTel reserved `status` (e.g. rpc_status, grpc_status).
+ *  - Shared cross-span attributes: <domain>_<field> (underscore) form.
  *  - Resource attribute keys: xrpl.<subsystem>.<field> (process-identity).
  *  - Span prefixes: <subsystem>[.<component>].
  */

include/xrpl/telemetry/Telemetry.h

@@ -3,13 +3,15 @@
 /** Abstract interface for OpenTelemetry distributed tracing.
 
     Provides the Telemetry base class that all components use to create trace
-    spans. Two concrete implementations exist, selected at construction time
+    spans. Three concrete implementations exist, selected at construction time
     by make_Telemetry():
 
       - TelemetryImpl (Telemetry.cpp): real OTel SDK integration, compiled
         only when XRPL_ENABLE_TELEMETRY is defined and enabled at runtime.
       - NullTelemetry (NullTelemetry.cpp): no-op stub used when telemetry is
         disabled at compile time or runtime.
+      - NullTelemetryOtel (Telemetry.cpp): no-op stub that still depends on
+        the OTel API (used during transition or for testing).
 
     Inheritance / dependency diagram:
 
@@ -37,32 +39,33 @@
 
     1. Root span at a subsystem entry point (typical usage):
     @code
+        #include <xrpld/rpc/detail/RpcSpanNames.h>
+        using namespace xrpl::telemetry;
+
         // In an RPC handler dispatch:
-        auto guard = SpanGuard::span(TraceCategory::Rpc, "rpc", commandName);
-        guard.setAttribute("xrpl.rpc.command", commandName);
+        auto guard = SpanGuard::span(
+            TraceCategory::Rpc, rpc_span::prefix::command, commandName);
+        guard.setAttribute(rpc_span::attr::command, commandName);
         // ... process request
         // guard destructor automatically ends the span on scope exit
     @endcode
 
-    2. Child span for a sub-operation (cross-scope):
-    @code
-        auto parent = SpanGuard::span(TraceCategory::Transactions, "tx", "process");
-        {
-            SpanGuard guard(telemetry.startSpan("rpc.command.submit"));
-            guard.setAttribute("command", "submit");
-            // ... guard ends span automatically on scope exit
-        }
-    @endcode
-
-    3. Child span for a sub-operation (cross-scope):
+    2. Child span for a sub-operation (scoped child):
     @code
         auto parent = SpanGuard::span(TraceCategory::Transactions, "tx", "process");
         {
             auto child = parent.childSpan("tx.apply");
-            child.setAttribute("xrpl.tx.type", txType);
+            child.setAttribute("tx_type", txType);
             // child ends here
         }
-        // parent continues, then ends here
+    @endcode
+
+    3. Unrelated span (cross-scope, same thread):
+    @code
+        // Transactions and RPC can be active simultaneously
+        auto txSpan = SpanGuard::span(TraceCategory::Transactions, "tx", "process");
+        auto rpcSpan = SpanGuard::span(TraceCategory::Rpc, "rpc", "info");
+        // both spans end on scope exit
     @endcode
 
     4. Cross-thread context propagation:

src/xrpld/app/main/GRPCServer.cpp

@@ -179,6 +179,7 @@ GRPCServerImpl::CallData<Request, Response>::process(std::shared_ptr<JobQueue::C
         bool const isUnlimited = clientIsUnlimited();
         if (!isUnlimited && usage.disconnect(app_.getJournal("gRPCServer")))
         {
+            span.setAttribute(grpc_span::attr::grpcStatus, grpc_span::val::error);
             span.setError(grpc_span::val::resourceExhausted);
             grpc::Status const status{
                 grpc::StatusCode::RESOURCE_EXHAUSTED, "usage balance exceeds threshold"};
@@ -190,6 +191,10 @@ GRPCServerImpl::CallData<Request, Response>::process(std::shared_ptr<JobQueue::C
             usage.charge(loadType);
             auto role = getRole(isUnlimited);
 
+            span.setAttribute(
+                grpc_span::attr::grpcRole,
+                role == Role::ADMIN ? grpc_span::val::admin : grpc_span::val::user);
+
             {
                 std::stringstream toLog;
                 toLog << "role = " << (int)role;
@@ -225,6 +230,7 @@ GRPCServerImpl::CallData<Request, Response>::process(std::shared_ptr<JobQueue::C
             if (conditionMetRes != rpcSUCCESS)
             {
                 RPC::ErrorInfo const errorInfo = RPC::get_error_info(conditionMetRes);
+                span.setAttribute(grpc_span::attr::grpcStatus, grpc_span::val::error);
                 span.setError(errorInfo.token.c_str());
                 grpc::Status const status{
                     grpc::StatusCode::FAILED_PRECONDITION, errorInfo.message.c_str()};
@@ -234,6 +240,7 @@ GRPCServerImpl::CallData<Request, Response>::process(std::shared_ptr<JobQueue::C
             {
                 std::pair<Response, grpc::Status> result = handler_(context);
                 setIsUnlimited(result.first, isUnlimited);
+                span.setAttribute(grpc_span::attr::grpcStatus, grpc_span::val::success);
                 span.setOk();
                 responder_.Finish(result.first, result.second, this);
             }
@@ -241,6 +248,7 @@ GRPCServerImpl::CallData<Request, Response>::process(std::shared_ptr<JobQueue::C
     }
     catch (std::exception const& ex)
     {
+        span.setAttribute(grpc_span::attr::grpcStatus, grpc_span::val::error);
         span.recordException(ex);
         grpc::Status const status{grpc::StatusCode::INTERNAL, ex.what()};
         responder_.FinishWithError(status, this);

src/xrpld/app/main/GrpcSpanNames.h

@@ -51,6 +51,8 @@ inline constexpr auto grpcStatus = makeStr("grpc_status");
 namespace val {
 using telemetry::attr_val::error;
 using telemetry::attr_val::success;
+inline constexpr auto admin = makeStr("admin");
+inline constexpr auto user = makeStr("user");
 inline constexpr auto resourceExhausted = makeStr("resource_exhausted");
 inline constexpr auto failedPrecondition = makeStr("failed_precondition");
 }  // namespace val

src/xrpld/rpc/detail/RPCHandler.cpp

@@ -185,7 +185,12 @@ callMethod(JsonContext& context, Method method, std::string const& name, Object&
         JLOG(context.j.debug()) << "RPC call " << name << " completed in "
                                 << ((end - start).count() / 1000000000.0) << "seconds";
         perfLog.rpcFinish(name, curId);
-        span.setAttribute(rpc_span::attr::rpcStatus, rpc_span::val::success);
+        // Status::operator bool() returns true when there IS an error
+        // (code_ != OK), so the ternary correctly maps error->error, ok->success.
+        span.setAttribute(
+            rpc_span::attr::rpcStatus, ret ? rpc_span::val::error : rpc_span::val::success);
+        if (!ret)
+            span.setOk();
         return ret;
     }
     catch (std::exception& e)

src/xrpld/rpc/detail/ServerHandler.cpp

@@ -564,6 +564,7 @@ ServerHandler::processSession(
         jr[jss::api_version] = jv[jss::api_version];
 
     jr[jss::type] = jss::response;
+    span.setOk();
     return jr;
 }
 
@@ -598,6 +599,7 @@ ServerHandler::processSession(
     {
         session->close(true);
     }
+    span.setOk();
 }
 
 static Json::Value
@@ -1036,6 +1038,7 @@ ServerHandler::processRequest(
         }
     }
 
+    span.setOk();
     HTTPReply(httpStatus, response, output, rpcJ);
 }