Specify backend servers' weight via annotation for kubernetes

provider/kubernetes/percentage.go

@@ -0,0 +1,47 @@
+package kubernetes
+
+import (
+	"strconv"
+	"strings"
+)
+
+const defaultPercentageValuePrecision = 3
+
+// percentageValue is int64 form of percentage value with 10^-3 precision.
+type percentageValue int64
+
+// toFloat64 returns its decimal float64 value.
+func (v percentageValue) toFloat64() float64 {
+	return float64(v) / (1000 * 100)
+}
+
+func (v percentageValue) computeWeight(count int) int {
+	if count == 0 {
+		return 0
+	}
+	return int(float64(v) / float64(count))
+}
+
+// String returns its string form of percentage value.
+func (v percentageValue) String() string {
+	return strconv.FormatFloat(v.toFloat64()*100, 'f', defaultPercentageValuePrecision, 64) + "%"
+}
+
+// newPercentageValueFromString tries to read percentage value from string, it can be either "1.1" or "1.1%", "6%".
+// It will lose the extra precision if there are more digits after decimal point.
+func newPercentageValueFromString(rawValue string) (percentageValue, error) {
+	if strings.HasSuffix(rawValue, "%") {
+		rawValue = rawValue[:len(rawValue)-1]
+	}
+	value, err := strconv.ParseFloat(rawValue, 64)
+	if err != nil {
+		return 0, err
+	}
+
+	return newPercentageValueFromFloat64(value) / 100, nil
+}
+
+// newPercentageValueFromFloat64 reads percentage value from float64
+func newPercentageValueFromFloat64(f float64) percentageValue {
+	return percentageValue(f * (1000 * 100))
+}