add custom metric

k8s/app.yaml

@@ -16,7 +16,8 @@ spec:
         - name: fastapi-app-container
           image: igit.danilkolesnikov.ru/danil/playground_app
           ports:
-            - containerPort: 8000
+            - name: web
+              containerPort: 8000
 
 ---
 apiVersion: v1
@@ -30,3 +31,14 @@ spec:
     - protocol: TCP
       port: 8000
       targetPort: 8000
+---
+apiVersion: monitoring.coreos.com/v1
+kind: PodMonitor
+metadata:
+  name: fastapi-app-pod-monitor
+spec:
+  selector:
+    matchLabels:
+      app: fastapi-app
+  podMetricsEndpoints:
+    - port: web

src/main.py

@@ -1,8 +1,27 @@
+from typing import Callable
+
 from fastapi import FastAPI
+from prometheus_client import Counter
+from prometheus_fastapi_instrumentator import Instrumentator
+from prometheus_fastapi_instrumentator.metrics import Info
+
+REQUEST_COUNT = Counter(
+    "label_counter", "How many times called with specific label", labelnames=("label",)
+)
+
+
+def http_requested_languages_total() -> Callable[[Info], None]:
+    def instrumentation(info: Info) -> None: ...
+
+    return instrumentation
+
 
 app = FastAPI()
+Instrumentator().add(http_requested_languages_total()).instrument(app).expose(app)
 
 
 @app.get("/")
-async def read_root():
+async def read_root(label=None):
+    if label:
+        REQUEST_COUNT.labels(label).inc()
     return {"Hello": "World"}