fix(telemetry): address Phase 2 code review findings

- Move node health attribute strings to compile-time constants in
  SpanNames.h (attr::nodeAmendmentBlocked, attr::nodeServerState)
- Add Tempo search filters for node health attributes
- Remove unnecessary .c_str() on strOperatingMode() return
- Add samplingRatio clamping test (values > 1.0 and < 0.0)
- Fix Task 2.3 status: delivered in Phase 1c, not Phase 2

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenTelemetryPlan/Phase2_taskList.md

@@ -167,13 +167,13 @@ This surfaces all RPCs served during a blocked period — critical for post-inci
 | ---- | ------------------------------------------- | ------------------- | ------------------------------------------------ |
 | 2.1  | W3C Trace Context header extraction         | Deferred → Phase 3  | No consumer in Phase 2; needs cross-node tracing |
 | 2.2  | Per-category span creation                  | Complete (Phase 1c) | Superseded by TraceCategory enum + SpanGuard     |
-| 2.3  | Add shouldTraceLedger() interface method    | Complete            | All 3 implementations present                    |
+| 2.3  | Add shouldTraceLedger() interface method    | Complete (Phase 1c) | Delivered in Phase 1c base branch                |
 | 2.4  | Unit tests for core telemetry               | Complete            | TelemetryConfig + SpanGuardFactory tests         |
 | 2.5  | Enhanced RPC span attributes (HTTP-level)   | Deferred            | Low value; span duration covers timing natively  |
 | 2.6  | Build verification and performance baseline | Complete            | Verified in CI on Phase 1c                       |
 | 2.7  | Grafana Tempo search filters                | Complete            | rpc-command, rpc-status, rpc-role filters        |
 | 2.8  | RPC span attribute enrichment (node health) | Complete            | amendment_blocked + server_state                 |
 
-**Delivered in this branch**: Tasks 2.3, 2.4, 2.6, 2.7, 2.8.
+**Delivered in this branch**: Tasks 2.4, 2.7, 2.8.
 **Deferred with rationale**: Tasks 2.1 (→Phase 3), 2.5 (low priority).
 **Superseded**: Task 2.2 (Phase 1c SpanGuard factory covers this).

docker/telemetry/grafana/provisioning/datasources/tempo.yaml

@@ -106,3 +106,14 @@ datasources:
             operator: "="
             scope: span
             type: dynamic
+          # Phase 2: Node health filters (Task 2.8)
+          - id: node-amendment-blocked
+            tag: xrpl.node.amendment_blocked
+            operator: "="
+            scope: span
+            type: static
+          - id: node-server-state
+            tag: xrpl.node.server_state
+            operator: "="
+            scope: span
+            type: dynamic

include/xrpl/telemetry/SpanNames.h

@@ -100,6 +100,13 @@ namespace attr {
 inline constexpr auto networkId = join(join(seg::xrpl, seg::network), makeStr("id"));
 inline constexpr auto networkType = join(join(seg::xrpl, seg::network), makeStr("type"));
 inline constexpr auto linkType = join(join(seg::xrpl, seg::link), makeStr("type"));
+
+/// Node health attributes (cross-cutting, used by RPC/consensus/tx spans).
+inline constexpr auto xrplNode = join(seg::xrpl, makeStr("node"));
+/// "xrpl.node.amendment_blocked"
+inline constexpr auto nodeAmendmentBlocked = join(xrplNode, makeStr("amendment_blocked"));
+/// "xrpl.node.server_state"
+inline constexpr auto nodeServerState = join(xrplNode, makeStr("server_state"));
 }  // namespace attr
 
 // ===== Shared attribute values =============================================

src/tests/libxrpl/telemetry/TelemetryConfig.cpp

@@ -106,3 +106,16 @@ TEST(TelemetryConfig, null_telemetry_factory)
     tel->start();
     tel->stop();
 }
+
+TEST(TelemetryConfig, sampling_ratio_clamped)
+{
+    Section section;
+    section.set("sampling_ratio", "2.5");
+    auto setup = telemetry::setup_Telemetry(section, "nHUtest123", "2.0.0", 0);
+    EXPECT_DOUBLE_EQ(setup.samplingRatio, 1.0);
+
+    Section section2;
+    section2.set("sampling_ratio", "-0.5");
+    auto setup2 = telemetry::setup_Telemetry(section2, "nHUtest123", "2.0.0", 0);
+    EXPECT_DOUBLE_EQ(setup2.samplingRatio, 0.0);
+}

src/xrpld/rpc/detail/RPCHandler.cpp

@@ -167,8 +167,8 @@ callMethod(JsonContext& context, Method method, std::string const& name, Object&
         rpc_span::attr::role,
         context.role == Role::ADMIN ? std::string_view(rpc_span::val::admin)
                                     : std::string_view(rpc_span::val::user));
-    span.setAttribute("xrpl.node.amendment_blocked", context.app.getOPs().isAmendmentBlocked());
-    span.setAttribute("xrpl.node.server_state", context.app.getOPs().strOperatingMode().c_str());
+    span.setAttribute(attr::nodeAmendmentBlocked, context.app.getOPs().isAmendmentBlocked());
+    span.setAttribute(attr::nodeServerState, context.app.getOPs().strOperatingMode());
 
     static std::atomic<std::uint64_t> requestId{0};
     auto& perfLog = context.app.getPerfLog();