Metrics

GET /metrics exports a Prometheus text exposition of the serving app’s own traffic and generation series — flat prometheus_client names, no OpenTelemetry. The names are chosen to match dashboard/lib/metrics/prometheus.ts’s PROM_QUERIES exactly, so the dashboard’s PromQL is correct against a stock create_app out of the box.

curl -sf http://127.0.0.1:8100/metrics | head -20

The series

Series	Type	Meaning
http_requests_total	counter	requests received, labelled by method, route, status; excludes /metrics itself
http_requests_in_flight	gauge	requests currently being handled
http_request_errors_total	counter	requests that ended in a 5xx response or an unhandled exception
llm_time_to_first_token_seconds	histogram	time from the start of a generation to its first token reaching the client
llm_time_to_last_token_seconds	histogram	time from the start of a generation to it reaching a terminal state (done, timed out, errored, or interrupted)
llm_question_length_chars	histogram	length of each accepted user message
llm_answer_length_chars	histogram	length of each persisted assistant message
rejected_requests_total	counter	requests rejected by rate limiting — every 429 the limiter raised
requests_per_ip_total	counter	requests seen by the rate limiter, labelled by route

route is the matched route’s path template (e.g. /v1/chats/{chat_id}/messages), not the raw URL, so a chat or message id never becomes its own timeseries. A request rejected before routing — by the request guard, or a genuine 404 — falls back to the raw path.

Both llm_time_to_first_token_seconds and llm_time_to_last_token_seconds are measured against the same clock, started once per generation, so a generation that streams tokens over several seconds always records a TTFT strictly smaller than its TTLT.

requests_per_ip_total is, despite its name, not labelled by the client IP itself — only by route — to keep its cardinality bounded; see Admission: rate limiting and client IP/country for the rate limiter that feeds both of these series and for why they read zero until ServeConfig.rate_limiting_enabled=True.

Configuration

GET /metrics is on by default; ServeConfig.metrics_enabled=False withholds the route entirely (a 404, not a 401). ServeConfig.metrics_token optionally guards it — a request without a matching Authorization: Bearer <token> header gets 401 and no metric text. See Configuration for both fields.

See also

Configuration for the fields that gate this route; HTTP API and Streaming for the /v1 routes these series describe; Admission: rate limiting and client IP/country for the rate limiter and IP/country resolution behind the last two series.