fix(telemetry): use resolved command/method name as span suffix

Per PR #6438 review thread r3250432621: known-command errors
(rpcTOO_BUSY, rpcNO_PERMISSION, etc.) were collapsing into a
single rpc.command.unknown span name, hiding per-command error
rates in dashboards. Same anti-pattern existed for gRPC, where
every method was bucketed under grpc.request with the method
relegated to an attribute.

- RPCHandler.cpp: doCommand error path uses cmdName as the span
  suffix; the rpc_span::val::unknownCommand fallback only applies
  when the request truly omits both command and method fields.
- GRPCServer.cpp: gRPC span name is now grpc.<MethodName>
  (e.g. grpc.GetLedger). Method also retained as an attribute.
- GrpcSpanNames.h: drop the unused op::request constant; update
  the span-hierarchy comment.
- RpcSpanNames.h: update the gRPC span diagram to match.

Dashboards on downstream phases will benefit from per-command
breakdowns without needing TraceQL attribute filters.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/xrpld/app/main/GRPCServer.cpp

@@ -169,8 +169,7 @@ void
 GRPCServerImpl::CallData<Request, Response>::process(std::shared_ptr<JobQueue::Coro> coro)
 {
     using namespace telemetry;
-    auto span =
-        SpanGuard::span(TraceCategory::Rpc, grpc_span::prefix::grpc, grpc_span::op::request);
+    auto span = SpanGuard::span(TraceCategory::Rpc, grpc_span::prefix::grpc, name_);
     span.setAttribute(grpc_span::attr::method, name_);
 
     try

src/xrpld/app/main/GrpcSpanNames.h

@@ -9,13 +9,16 @@
  *  Span hierarchy:
  *
  *    +-------------------------------------------------------+
- *    | grpc.request                                          |
+ *    | grpc.<MethodName>  (e.g. grpc.GetLedger)              |
  *    | CallData::process(coro)                               |
  *    |   attrs: method, grpc_role, grpc_status               |
  *    +-------------------------------------------------------+
  *
  *  Unlike the HTTP/WS RPC path, gRPC has a flat single-span structure
  *  per request since each CallData handles exactly one RPC method.
+ *  The method name is embedded in the span name (rather than only as
+ *  an attribute) so dashboards can break out per-method latency and
+ *  error rates without needing TraceQL attribute filters.
  */
 
 #include <xrpl/telemetry/SpanNames.h>
@@ -25,16 +28,11 @@ namespace xrpl::telemetry::grpc_span {
 // ===== Span prefixes =======================================================
 
 namespace prefix {
-/// "grpc" — root prefix for gRPC transport spans.
+/// "grpc" — root prefix for gRPC transport spans. The full span name is
+/// formed at the call site as `grpc.<MethodName>` (see GRPCServer.cpp).
 inline constexpr auto grpc = makeStr("grpc");
 }  // namespace prefix
 
-// ===== Span operation suffixes =============================================
-
-namespace op {
-inline constexpr auto request = makeStr("request");
-}  // namespace op
-
 // ===== Attribute keys ======================================================
 
 namespace attr {

src/xrpld/rpc/detail/RPCHandler.cpp

@@ -229,8 +229,11 @@ doCommand(RPC::JsonContext& context, Json::Value& result)
         {
             cmdName = "unknown";
         }
-        auto span = SpanGuard::span(
-            TraceCategory::Rpc, rpc_span::prefix::command, rpc_span::val::unknownCommand);
+        // Use the resolved command name as the span suffix so dashboards
+        // can break out per-command error rates (e.g. rpc.command.submit
+        // for a submit that hit rpcTOO_BUSY). Falling back to a single
+        // "unknown" name only when the request truly omits both fields.
+        auto span = SpanGuard::span(TraceCategory::Rpc, rpc_span::prefix::command, cmdName);
         span.setAttribute(rpc_span::attr::command, cmdName.c_str());
         span.setError(get_error_info(error).token.c_str());
 

src/xrpld/rpc/detail/RpcSpanNames.h

@@ -86,9 +86,9 @@
  *  gRPC path (see GrpcSpanNames.h for constants):
  *
  *    +-------------------------------------------------------+
- *    | grpc.request                                          |
+ *    | grpc.<MethodName>  (e.g. grpc.GetLedger)              |
  *    | CallData::process(coro)                               |
- *    |   attrs: method, grpc_status                           |
+ *    |   attrs: method, grpc_status                          |
  *    +-------------------------------------------------------+
  *
  *  Covered paths: