Add metrics server check at startup

cmd/controller/main.go

@@ -14,7 +14,6 @@ import (
 	"github.com/stefanprodan/steerer/pkg/logging"
 	"github.com/stefanprodan/steerer/pkg/server"
 	"github.com/stefanprodan/steerer/pkg/version"
-	"go.uber.org/zap"
 	"k8s.io/client-go/kubernetes"
 	_ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
 	"k8s.io/client-go/tools/cache"
@@ -73,16 +72,21 @@ func main() {
 	rolloutInformerFactory := informers.NewSharedInformerFactory(rolloutClient, time.Second*30)
 	rolloutInformer := rolloutInformerFactory.Apps().V1beta1().Rollouts()
 
+	logger.Infof("Starting steerer version %s revision %s", version.VERSION, version.REVISION)
+
 	ver, err := kubeClient.Discovery().ServerVersion()
 	if err != nil {
 		logger.Fatalf("Error calling Kubernetes API: %v", err)
 	}
 
-	logger.Infow("Starting steerer",
-		zap.String("version", version.VERSION),
-		zap.String("revision", version.REVISION),
-		zap.String("metrics provider", metricsServer),
-		zap.Any("kubernetes version", ver))
+	logger.Infof("Connected to Kubernetes API %s", ver)
+
+	ok, err := controller.CheckMetricsServer(metricsServer)
+	if ok {
+		logger.Infof("Connected to metrics server %s", metricsServer)
+	} else {
+		logger.Errorf("Metrics server %s unreachable %v", metricsServer, err)
+	}
 
 	// start HTTP server
 	go server.ListenAndServe(port, 3*time.Second, logger, stopCh)

pkg/controller/controller.go

@@ -158,7 +158,6 @@ func (c *Controller) processNextWorkItem() bool {
 		// Finally, if no error occurs we Forget this item so it does not
 		// get queued again until another change happens.
 		c.workqueue.Forget(obj)
-		c.logger.Infof("Successfully synced '%s'", key)
 		return nil
 	}(obj)
 

pkg/controller/observer.go

@@ -66,7 +66,6 @@ func (c *Controller) queryMetric(query string) (*VectorQueryResponse, error) {
 	}
 
 	return &values, nil
-
 }
 
 func (c *Controller) getDeploymentMetric(name string, namespace string, counter string, interval string) (float64, error) {
@@ -97,3 +96,42 @@ func (c *Controller) getDeploymentMetric(name string, namespace string, counter
 	}
 	return rate, nil
 }
+
+func CheckMetricsServer(address string) (bool, error) {
+	promURL, err := url.Parse(address)
+	if err != nil {
+		return false, err
+	}
+
+	u, err := url.Parse("./api/v1/status/flags")
+	if err != nil {
+		return false, err
+	}
+
+	u = promURL.ResolveReference(u)
+
+	req, err := http.NewRequest("GET", u.String(), nil)
+	if err != nil {
+		return false, err
+	}
+
+	ctx, cancel := context.WithTimeout(req.Context(), 5*time.Second)
+	defer cancel()
+
+	r, err := http.DefaultClient.Do(req.WithContext(ctx))
+	if err != nil {
+		return false, err
+	}
+	defer r.Body.Close()
+
+	b, err := ioutil.ReadAll(r.Body)
+	if err != nil {
+		return false, fmt.Errorf("error reading body: %s", err.Error())
+	}
+
+	if 400 <= r.StatusCode {
+		return false, fmt.Errorf("error response: %s", string(b))
+	}
+
+	return true, nil
+}