Add helper to extract prometheus metrics in e2e tests

test/e2e/framework/metrics.go

@@ -0,0 +1,59 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package framework
+
+import (
+	"fmt"
+	"net/http"
+
+	dto "github.com/prometheus/client_model/go"
+	"github.com/prometheus/common/expfmt"
+)
+
+// GetMetric returns the current prometheus metric exposed by NGINX
+func (f *Framework) GetMetric(metricName, ip string) (*dto.MetricFamily, error) {
+	url := fmt.Sprintf("http://%v:10254/metrics", ip)
+
+	client := &http.Client{}
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, fmt.Errorf("creating GET request for URL %q failed: %v", url, err)
+	}
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("executing GET request for URL %q failed: %v", url, err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("GET request for URL %q returned HTTP status %s", url, resp.Status)
+	}
+
+	var parser expfmt.TextParser
+	metrics, err := parser.TextToMetricFamilies(resp.Body)
+
+	if err != nil {
+		return nil, fmt.Errorf("reading text format failed: %v", err)
+	}
+
+	for _, m := range metrics {
+		if m.GetName() == metricName {
+			return m, nil
+		}
+	}
+
+	return nil, fmt.Errorf("there is no metric with name %v", metricName)
+}