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Userverse includes built-in support for Prometheus metrics, optional OpenTelemetry tracing, and structured HTTP request logging via LogMiddleware.

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Prometheus metrics

A /metrics endpoint is registered automatically by create_app. It returns Prometheus-compatible metrics in the standard text format.
app/main.py
@app.get("/metrics")
def metrics():
    return Response(generate_latest(), media_type=CONTENT_TYPE_LATEST)
Unhandled exceptions are tracked with a dedicated counter:
app/main.py
UNHANDLED_EXCEPTIONS = Counter(
    "unhandled_exceptions_total",
    "Total number of unhandled exceptions",
    ["method", "endpoint"],
)
Scrape the endpoint from your Prometheus instance:
prometheus.yml
scrape_configs:
  - job_name: userverse
    static_configs:
      - targets: ['localhost:8500']
    metrics_path: /metrics

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OpenTelemetry tracing

The setup_otel function in app/middleware/otel.py configures tracing with an OTLP HTTP exporter. It instruments FastAPI automatically using FastAPIInstrumentor.
app/middleware/otel.py
def setup_otel(
    app,
    service_name: str = "fastapi-app",
    collector_endpoint="http://otel-collector:4318/v1/traces",
):
    resource = Resource(attributes={SERVICE_NAME: service_name})
    tracer_provider = TracerProvider(resource=resource)

    otlp_exporter = OTLPSpanExporter(endpoint=collector_endpoint)
    span_processor = BatchSpanProcessor(otlp_exporter)

    tracer_provider.add_span_processor(span_processor)
    trace.set_tracer_provider(tracer_provider)

    FastAPIInstrumentor.instrument_app(app)
    RequestsInstrumentor().instrument()
OpenTelemetry tracing is commented out by default in app/main.py. To enable it, uncomment the setup_otel(app) call inside create_app.
app/main.py
# setup_otel(app)   ← uncomment to enable tracing
app.add_middleware(LogMiddleware)

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Request logging

LogMiddleware is applied to every request. It records the HTTP method, URL, client IP, user agent, response status code, and duration in milliseconds.
app/middleware/logging.py
class LogMiddleware(BaseHTTPMiddleware):
    async def dispatch(self, request: Request, call_next):
        start_time = time.time()
        ...
        logger.info(
            "Request handled",
            extra={
                "extra": {
                    "method": request.method,
                    "url": str(request.url),
                    "client": request.client.host if request.client else None,
                    "user_agent": request.headers.get("user-agent"),
                    "status_code": response.status_code,
                    "duration_ms": round(process_time, 2),
                }
            },
        )
Failed requests are logged at the ERROR level with the exception message included.