feat(go): add realtime pipeline observability

go/vehicle-gateway/internal/gateway/tcp_server.go

@@ -211,6 +211,7 @@ func (s *TCPServer) handleFrame(ctx context.Context, conn net.Conn, raw []byte,
 			ParseError:     err.Error(),
 		}
 		env.EventID = env.StableEventID()
+		s.recordParseErrorMetric(err)
 	} else {
 		resolved, resolveErr := s.resolver.Resolve(frameCtx, env)
 		if resolveErr != nil {
@@ -220,8 +221,11 @@ func (s *TCPServer) handleFrame(ctx context.Context, conn net.Conn, raw []byte,
 			}
 			env.Parsed["identity"] = map[string]any{"resolved": false, "error": resolveErr.Error()}
 			env.ParseStatus = envelope.ParsePartial
+			s.recordIdentityMetric("error")
 		} else {
 			env = resolved
+			annotateIdentityUnresolved(&env)
+			s.recordIdentityMetric(identityStatus(env))
 		}
 		enrichConnectionPlatform(&env, state)
 	}
@@ -314,6 +318,26 @@ func (s *TCPServer) recordPublishMetric(kind string, status string) {
 	})
 }
 
+func (s *TCPServer) recordParseErrorMetric(err error) {
+	if s.metrics == nil {
+		return
+	}
+	s.metrics.IncCounter("vehicle_gateway_parse_errors_total", metrics.Labels{
+		"protocol": string(s.protocol.Protocol),
+		"reason":   classifyError(err),
+	})
+}
+
+func (s *TCPServer) recordIdentityMetric(status string) {
+	if s.metrics == nil {
+		return
+	}
+	s.metrics.IncCounter("vehicle_gateway_identity_total", metrics.Labels{
+		"protocol": string(s.protocol.Protocol),
+		"status":   status,
+	})
+}
+
 func (s *TCPServer) recordConnectionMetric(delta float64) {
 	if s.metrics == nil {
 		return
@@ -323,6 +347,50 @@ func (s *TCPServer) recordConnectionMetric(delta float64) {
 	}, delta)
 }
 
+func identityStatus(env envelope.FrameEnvelope) string {
+	if strings.TrimSpace(env.VIN) != "" {
+		return "resolved"
+	}
+	if env.ParseStatus == envelope.ParsePartial {
+		return "error"
+	}
+	return "unresolved"
+}
+
+func annotateIdentityUnresolved(env *envelope.FrameEnvelope) {
+	if env == nil || env.ParseStatus == envelope.ParseBadFrame || strings.TrimSpace(env.VIN) != "" {
+		return
+	}
+	if env.Parsed == nil {
+		env.Parsed = map[string]any{}
+	}
+	if _, exists := env.Parsed["identity"]; exists {
+		return
+	}
+	env.Parsed["identity"] = map[string]any{
+		"resolved": false,
+		"reason":   "no_binding",
+	}
+}
+
+func classifyError(err error) string {
+	text := strings.ToLower(strings.TrimSpace(fmt.Sprint(err)))
+	switch {
+	case text == "":
+		return "unknown"
+	case strings.Contains(text, "bcc") || strings.Contains(text, "checksum"):
+		return "checksum"
+	case strings.Contains(text, "short") || strings.Contains(text, "truncated") || strings.Contains(text, "length"):
+		return "length"
+	case strings.Contains(text, "json"):
+		return "json"
+	case strings.Contains(text, "start"):
+		return "start_symbol"
+	default:
+		return "parse"
+	}
+}
+
 func (p TCPProtocol) String() string {
 	return fmt.Sprintf("%s@%s", p.Protocol, p.Addr)
 }