Add FastAPI service, Dockerfile and compose

webapp/app/main.py

@@ -0,0 +1,44 @@
+import time
+
+from fastapi import FastAPI, HTTPException, Request, Response
+from prometheus_client import CONTENT_TYPE_LATEST, Counter, Histogram, generate_latest
+
+app = FastAPI(title="DevOps Test Service")
+
+REQUESTS = Counter(
+    "http_requests_total", "Total HTTP requests", ["method", "path", "status"]
+)
+LATENCY = Histogram(
+    "http_request_duration_seconds", "Request latency in seconds", ["path"]
+)
+
+
+@app.middleware("http")
+async def track_metrics(request: Request, call_next):
+    start = time.perf_counter()
+    response = await call_next(request)
+    path = request.url.path
+    REQUESTS.labels(request.method, path, response.status_code).inc()
+    LATENCY.labels(path).observe(time.perf_counter() - start)
+    return response
+
+
+@app.get("/")
+def index():
+    return {"message": "Hello from the DevOps test service"}
+
+
+@app.get("/health")
+def health():
+    return {"status": "ok"}
+
+
+@app.get("/error")
+def error():
+    # Used to generate 5xx responses and trigger the high-error-rate alert
+    raise HTTPException(status_code=500, detail="simulated failure")
+
+
+@app.get("/metrics")
+def metrics():
+    return Response(generate_latest(), media_type=CONTENT_TYPE_LATEST)