finish the main code

app/routers/metrics.py

@@ -0,0 +1,23 @@
+from fastapi import APIRouter
+from k8s_client import get_custom_client
+
+router = APIRouter(prefix="/metrics", tags=["metrics"])
+
+
+@router.get("/nodes")
+def node_metrics():
+    api = get_custom_client()
+    try:
+        data = api.list_cluster_custom_object(
+            group="metrics.k8s.io", version="v1beta1", plural="nodes"
+        )
+        return [
+            {
+                "name": item["metadata"]["name"],
+                "cpu_usage": item["usage"]["cpu"],  # e.g. "250m"
+                "memory_usage": item["usage"]["memory"],  # e.g. "512Mi"
+            }
+            for item in data["items"]
+        ]
+    except Exception as e:
+        return {"error": str(e), "hint": "Is metrics-server installed?"}