Initial QSfera import

Server/vendor/github.com/sercand/kuberesolver/v5/util.go

@@ -0,0 +1,41 @@
+package kuberesolver
+
+import (
+	"runtime/debug"
+	"time"
+
+	"google.golang.org/grpc/grpclog"
+)
+
+func until(f func(), initialPeriod, maxPeriod time.Duration, stopCh <-chan struct{}) {
+	select {
+	case <-stopCh:
+		return
+	default:
+	}
+	period := initialPeriod
+	for {
+		func() {
+			defer handleCrash()
+			f()
+		}()
+		select {
+		case <-stopCh:
+			return
+		case <-time.After(period):
+			if period*2 <= maxPeriod {
+				period *= 2
+			} else {
+				period = initialPeriod
+			}
+		}
+	}
+}
+
+// HandleCrash simply catches a crash and logs an error. Meant to be called via defer.
+func handleCrash() {
+	if r := recover(); r != nil {
+		callers := string(debug.Stack())
+		grpclog.Errorf("kuberesolver: recovered from panic: %#v (%v)\n%v", r, r, callers)
+	}
+}