feat: update metrics for stable HTTP semconv and adjust service health dashboard queries

Author: simonvanlierde

compose.demo.yml

@@ -21,6 +21,10 @@ services:
       # Ship Python log records via OTLP with trace context attached.
       OTEL_PYTHON_LOGGING_AUTO_INSTRUMENTATION_ENABLED: "true"
       OTEL_METRIC_EXPORT_INTERVAL: "10000"
+      # Emit the *stable* HTTP semconv (http.server.request.duration in seconds,
+      # http.route) rather than the legacy names. Stable metric names are frozen,
+      # so the Service Health dashboard's app-SDK panel survives library bumps.
+      OTEL_SEMCONV_STABILITY_OPT_IN: http
     logging:
       driver: json-file
       options:

dashboards/service-health.json

@@ -116,14 +116,14 @@
       "datasource": { "type": "prometheus", "uid": "prometheus" },
       "targets": [
         {
-          "expr": "histogram_quantile(0.95, sum by (le, http_target) (rate(http_server_duration_milliseconds_bucket{job=\"$service\"}[$__rate_interval])))",
-          "legendFormat": "{{http_target}}",
+          "expr": "histogram_quantile(0.95, sum by (le, http_route) (rate(http_server_request_duration_seconds_bucket{job=\"$service\"}[$__rate_interval])))",
+          "legendFormat": "{{http_route}}",
           "refId": "A"
         }
       ],
       "fieldConfig": {
         "defaults": {
-          "unit": "ms",
+          "unit": "s",
           "custom": { "lineWidth": 2, "fillOpacity": 10 }
         },
         "overrides": []