Add support to ignore request in metrics

pkg/http/header/header.go

@@ -78,6 +78,9 @@ const (
 	// load balancers to not load balance the respective request but to
 	// send it to the request's target directly.
 	PassthroughLoadbalancingKey = "K-Passthrough-Lb"
+
+	// IgnoreMetricsKey is used to mark requests that should not be counted in metrics.
+	IgnoreMetricsKey = "K-Ignore-Metrics"
 )
 
 // User Agent Key & Values
@@ -135,6 +138,11 @@ func IsKubeletProbe(r *http.Request) bool {
 		r.Header.Get(KubeletProbeKey) != ""
 }
 
+// IsMetricsIgnored returns true if the request is marked to be ignored by metrics.
+func IsMetricsIgnored(r *http.Request) bool {
+	return r.Header.Get(IgnoreMetricsKey) != ""
+}
+
 // RewriteHostIn removes the `Host` header from the inbound (server) request
 // and replaces it with our custom header.
 // This is done to avoid Istio Host based routing, see #3870.

pkg/http/header/header_test.go

@@ -104,6 +104,21 @@ func TestIsProbe(t *testing.T) {
 	}
 }
 
+func TestIsMetricsIgnored(t *testing.T) {
+	// Not a metrics ignored
+	req, err := http.NewRequest(http.MethodGet, "http://example.com/", nil)
+	if err != nil {
+		t.Fatal("Error building request:", err)
+	}
+	if IsMetricsIgnored(req) {
+		t.Error("Not a metrics ignored but counted as such")
+	}
+	req.Header.Set(IgnoreMetricsKey, "true")
+	if !IsMetricsIgnored(req) {
+		t.Error("Metrics ignored but not counted as such")
+	}
+}
+
 func TestRewriteHost(t *testing.T) {
 	r := httptest.NewRequest(http.MethodGet, "http://love.is/not-hate", nil)
 	r.Header.Set("Host", "love.is")