Method ServeHTTP

modules/caddyhttp/metrics.go:314–385

(w http.ResponseWriter, r *http.Request)

}

func (h *metricsInstrumentedRoute) ServeHTTP(w http.ResponseWriter, r *http.Request) error {
	server := serverNameFromContext(r.Context())
	labels := prometheus.Labels{"server": server, "handler": h.handler}
	method := caddymetrics.SanitizeMethod(r.Method)
	// the "code" value is set later, but initialized here to eliminate the possibility
	// of a panic
	statusLabels := prometheus.Labels{"server": server, "handler": h.handler, "method": method, "code": ""}

	// Determine if this is an HTTPS request
	isHTTPS := r.TLS != nil

	if h.metrics.PerHost {
		// Apply cardinality protection for host metrics
		if h.metrics.shouldAllowHostMetrics(r.Host, isHTTPS) {
			labels["host"] = strings.ToLower(r.Host)
			statusLabels["host"] = strings.ToLower(r.Host)
		} else {
			// Use a catch-all label for unallowed hosts to prevent cardinality explosion
			labels["host"] = "_other"
			statusLabels["host"] = "_other"
		}
	}

	inFlight := h.metrics.httpMetrics.requestInFlight.With(labels)
	inFlight.Inc()
	defer inFlight.Dec()

	start := time.Now()

	// This is a _bit_ of a hack - it depends on the ShouldBufferFunc always
	// being called when the headers are written.
	// Effectively the same behaviour as promhttp.InstrumentHandlerTimeToWriteHeader.
	writeHeaderRecorder := ShouldBufferFunc(func(status int, header http.Header) bool {
		statusLabels["code"] = caddymetrics.SanitizeCode(status)
		ttfb := time.Since(start).Seconds()
		h.metrics.httpMetrics.responseDuration.With(statusLabels).Observe(ttfb)
		return false
	})
	wrec := NewResponseRecorder(w, nil, writeHeaderRecorder)
	err := h.next.ServeHTTP(wrec, r)
	dur := time.Since(start).Seconds()
	h.metrics.httpMetrics.requestCount.With(labels).Inc()

	observeRequest := func(status int) {
		// If the code hasn't been set yet, and we didn't encounter an error, we're
		// probably falling through with an empty handler.
		if statusLabels["code"] == "" {
			// we still sanitize it, even though it's likely to be 0. A 200 is
			// returned on fallthrough so we want to reflect that.
			statusLabels["code"] = caddymetrics.SanitizeCode(status)
		}

		h.metrics.httpMetrics.requestDuration.With(statusLabels).Observe(dur)
		h.metrics.httpMetrics.requestSize.With(statusLabels).Observe(float64(computeApproximateRequestSize(r)))
		h.metrics.httpMetrics.responseSize.With(statusLabels).Observe(float64(wrec.Size()))
	}

	if err != nil {