web: Add benchmark for respond()

web/api/v1/api_test.go

@@ -853,3 +853,26 @@ func TestOptionsMethod(t *testing.T) {
 		}
 	}
 }
+
+// This is a global to avoid the benchmark being optimized away.
+var testResponseWriter = httptest.ResponseRecorder{}
+
+func BenchmarkRespond(b *testing.B) {
+	b.ReportAllocs()
+	points := []promql.Point{}
+	for i := 0; i < 10000; i++ {
+		points = append(points, promql.Point{V: float64(i * 1000000), T: int64(i)})
+	}
+	response := &queryData{
+		ResultType: promql.ValueTypeMatrix,
+		Result: promql.Matrix{
+			promql.Series{
+				Points: points,
+				Metric: nil,
+			},
+		},
+	}
+	for n := 0; n < b.N; n++ {
+		respond(&testResponseWriter, response)
+	}
+}