feat: add response time histogram metric

doc/fr/references/metrics.md

@@ -24,6 +24,31 @@ Chaque layer associé à un proxy peut également ses propres métriques spécif
   bouncer_proxy_director_proxy_requests_total{proxy="cadoles"} 64
   ```
 
+#### `bouncer_proxy_director_proxy_responses_duration_seconds{proxy=<proxyName>}`
+
+- **Type:** `histogram`
+- **Description**: Histogramme du temps de traitement du cycle requête/réponse par proxy
+- **Exemple**
+
+  ```
+  # HELP bouncer_proxy_director_proxy_responses_duration_seconds Bouncer proxy responses duration
+  # TYPE bouncer_proxy_director_proxy_responses_duration_seconds histogram
+  bouncer_proxy_director_proxy_responses_duration_seconds_bucket{proxy="dummy",le="0.005"} 13
+  bouncer_proxy_director_proxy_responses_duration_seconds_bucket{proxy="dummy",le="0.01"} 13
+  bouncer_proxy_director_proxy_responses_duration_seconds_bucket{proxy="dummy",le="0.025"} 13
+  bouncer_proxy_director_proxy_responses_duration_seconds_bucket{proxy="dummy",le="0.05"} 13
+  bouncer_proxy_director_proxy_responses_duration_seconds_bucket{proxy="dummy",le="0.1"} 13
+  bouncer_proxy_director_proxy_responses_duration_seconds_bucket{proxy="dummy",le="0.25"} 13
+  bouncer_proxy_director_proxy_responses_duration_seconds_bucket{proxy="dummy",le="0.5"} 13
+  bouncer_proxy_director_proxy_responses_duration_seconds_bucket{proxy="dummy",le="1"} 13
+  bouncer_proxy_director_proxy_responses_duration_seconds_bucket{proxy="dummy",le="2.5"} 13
+  bouncer_proxy_director_proxy_responses_duration_seconds_bucket{proxy="dummy",le="5"} 13
+  bouncer_proxy_director_proxy_responses_duration_seconds_bucket{proxy="dummy",le="10"} 13
+  bouncer_proxy_director_proxy_responses_duration_seconds_bucket{proxy="dummy",le="+Inf"} 13
+  bouncer_proxy_director_proxy_responses_duration_seconds_sum{proxy="dummy"} 0.009556884
+  bouncer_proxy_director_proxy_responses_duration_seconds_count{proxy="dummy"} 13
+  ```
+
 ### Serveur d'administration
 
 _Pas de métrique supplémentaire._

internal/proxy/director/director.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"net/http"
 	"sort"
+	"time"
 
 	"forge.cadoles.com/Cadoles/go-proxy"
 	"forge.cadoles.com/Cadoles/go-proxy/wildcard"
@@ -28,12 +29,12 @@ type Director struct {
 
 const proxiesCacheKey = "proxies"
 
-func (d *Director) rewriteRequest(r *http.Request) (*http.Request, error) {
+func (d *Director) rewriteRequest(r *http.Request) (*http.Request, []store.ProxyName, error) {
 	ctx := r.Context()
 
 	proxies, _, err := d.cachedProxies.Get(ctx, proxiesCacheKey)
 	if err != nil {
-		return r, errors.WithStack(err)
+		return r, nil, errors.WithStack(err)
 	}
 
 	url := getRequestURL(r)
@@ -42,12 +43,16 @@ func (d *Director) rewriteRequest(r *http.Request) (*http.Request, error) {
 
 	layers := make([]*store.Layer, 0)
 
+	matchingProxies := make([]store.ProxyName, 0)
+
 	for _, p := range proxies {
 		for _, from := range p.From {
 			if matches := wildcard.Match(url.String(), from); !matches {
 				continue
 			}
 
+			matchingProxies = append(matchingProxies, p.Name)
+
 			proxyCtx := logger.With(ctx,
 				logger.F("proxy", p.Name),
 				logger.F("host", r.Host),
@@ -58,7 +63,7 @@ func (d *Director) rewriteRequest(r *http.Request) (*http.Request, error) {
 
 			proxyLayers, _, err := d.cachedLayers.Get(proxyCtx, string(p.Name))
 			if err != nil {
-				return r, errors.WithStack(err)
+				return r, nil, errors.WithStack(err)
 			}
 
 			layers = append(layers, proxyLayers...)
@@ -69,7 +74,7 @@ func (d *Director) rewriteRequest(r *http.Request) (*http.Request, error) {
 
 			toURL, err := url.Parse(p.To)
 			if err != nil {
-				return r, errors.WithStack(err)
+				return r, nil, errors.WithStack(err)
 			}
 
 			r.URL.Host = toURL.Host
@@ -87,14 +92,14 @@ func (d *Director) rewriteRequest(r *http.Request) (*http.Request, error) {
 				})
 			}
 
-			return r, nil
+			return r, matchingProxies, nil
 		}
 	}
 
 	ctx = withLayers(ctx, layers)
 	r = r.WithContext(ctx)
 
-	return r, nil
+	return r, matchingProxies, nil
 }
 
 func (d *Director) getProxies(ctx context.Context, key string) ([]*store.Proxy, error) {
@@ -215,17 +220,26 @@ func (d *Director) ResponseTransformer() proxy.ResponseTransformer {
 func (d *Director) Middleware() proxy.Middleware {
 	return func(next http.Handler) http.Handler {
 		fn := func(w http.ResponseWriter, r *http.Request) {
+			start := time.Now()
+
 			sentry.ConfigureScope(func(scope *sentry.Scope) {
 				ctx := withHandleError(r.Context(), d.handleError)
 				ctx = withSentryScope(ctx, scope)
 				r = r.WithContext(ctx)
 
-				r, err := d.rewriteRequest(r)
+				r, matched, err := d.rewriteRequest(r)
 				if err != nil {
 					HandleError(ctx, w, r, http.StatusInternalServerError, errors.Wrap(err, "could not rewrite request"))
 					return
 				}
 
+				defer func() {
+					elapsed := time.Since(start)
+					for _, p := range matched {
+						metricProxyResponsesDurationSeconds.WithLabelValues(string(p)).Observe(elapsed.Seconds())
+					}
+				}()
+
 				ctx = r.Context()
 
 				layers, err := ctxLayers(ctx)

internal/proxy/director/metrics.go

@@ -18,3 +18,12 @@ var metricProxyRequestsTotal = promauto.NewCounterVec(
 	},
 	[]string{metricLabelProxy},
 )
+
+var metricProxyResponsesDurationSeconds = promauto.NewHistogramVec(
+	prometheus.HistogramOpts{
+		Name:      "proxy_responses_duration_seconds",
+		Help:      "Bouncer proxy responses duration",
+		Namespace: metricNamespace,
+	},
+	[]string{metricLabelProxy},
+)