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feat(go): change in-flight metric to only count expensive requests #845

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Merged
merged 1 commit into from
Nov 3, 2025
Merged

feat(go): change in-flight metric to only count expensive requests #845

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17 changes: 14 additions & 3 deletions pkg/api/middleware/metrics.go
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ import (
var (
MetricRequestsInFlight = prometheus.NewGauge(prometheus.GaugeOpts{
Name: "http_requests_in_flight",
Help: "How many requests are in flight?",
Help: "How many expensive requests are in flight?",
})
MetricRequestDurations = prometheus.NewHistogramVec(prometheus.HistogramOpts{
Name: "http_request_duration",
Expand All @@ -39,14 +39,25 @@ func RequestMetrics(h http.Handler) http.Handler {
r = r.WithContext(ctx)

now := time.Now()
MetricRequestsInFlight.Inc()
recorder := &statusRecordingResponseWriter{rw: w}
h.ServeHTTP(recorder, r)
MetricRequestsInFlight.Dec()
MetricRequestDurations.WithLabelValues(r.Method, r.Pattern, strconv.Itoa(recorder.status)).Observe(time.Since(now).Seconds())
})
}

func InFlightMetrics(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
tracer := tracer(r.Context())
ctx, span := tracer.Start(r.Context(), "InFlightMetrics")
defer span.End()
r = r.WithContext(ctx)

MetricRequestsInFlight.Inc()
defer MetricRequestsInFlight.Dec() // defer to run despite panics
h.ServeHTTP(w, r)
})
}

var (
_ http.ResponseWriter = (*statusRecordingResponseWriter)(nil)
_ http.Flusher = (*statusRecordingResponseWriter)(nil)
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16 changes: 14 additions & 2 deletions pkg/api/mux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -35,8 +35,20 @@ func NewHandler(
mux.Handle("GET /metrics", middleware.TracingFor("promhttp.HandlerFor", promhttp.HandlerFor(metrics, promhttp.HandlerOpts{Registry: metrics})))
mux.Handle("GET /healthz", HandleGetHealthz())
mux.Handle("GET /version", HandleGetVersion(versions, browser))
mux.Handle("GET /render", middleware.RequireAuthToken(middleware.TrustedURL(limiter.Limit(HandleGetRender(browser))), serverConfig.AuthTokens...))
mux.Handle("GET /render/csv", middleware.RequireAuthToken(middleware.TrustedURL(limiter.Limit(HandleGetRenderCSV(browser))), serverConfig.AuthTokens...))
mux.Handle("GET /render",
middleware.RequireAuthToken(
middleware.TrustedURL(
limiter.Limit(
middleware.InFlightMetrics(
HandleGetRender(browser)))),
serverConfig.AuthTokens...))
mux.Handle("GET /render/csv",
middleware.RequireAuthToken(
middleware.TrustedURL(
limiter.Limit(
middleware.InFlightMetrics(
HandleGetRenderCSV(browser)))),
serverConfig.AuthTokens...))
mux.Handle("GET /render/version", HandleGetRenderVersion(versions))

handler := middleware.RequestMetrics(mux)
Expand Down
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