implement Scylla database

vendor/github.com/hailocab/go-hostpool/host_entry.go

@@ -0,0 +1,62 @@
+package hostpool
+
+import (
+	"time"
+)
+
+// --- hostEntry - this is due to get upgraded
+
+type hostEntry struct {
+	host              string
+	nextRetry         time.Time
+	retryCount        int16
+	retryDelay        time.Duration
+	dead              bool
+	epsilonCounts     []int64
+	epsilonValues     []int64
+	epsilonIndex      int
+	epsilonValue      float64
+	epsilonPercentage float64
+}
+
+func (h *hostEntry) canTryHost(now time.Time) bool {
+	if !h.dead {
+		return true
+	}
+	if h.nextRetry.Before(now) {
+		return true
+	}
+	return false
+}
+
+func (h *hostEntry) willRetryHost(maxRetryInterval time.Duration) {
+	h.retryCount += 1
+	newDelay := h.retryDelay * 2
+	if newDelay < maxRetryInterval {
+		h.retryDelay = newDelay
+	} else {
+		h.retryDelay = maxRetryInterval
+	}
+	h.nextRetry = time.Now().Add(h.retryDelay)
+}
+
+func (h *hostEntry) getWeightedAverageResponseTime() float64 {
+	var value float64
+	var lastValue float64
+
+	// start at 1 so we start with the oldest entry
+	for i := 1; i <= epsilonBuckets; i += 1 {
+		pos := (h.epsilonIndex + i) % epsilonBuckets
+		bucketCount := h.epsilonCounts[pos]
+		// Changing the line below to what I think it should be to get the weights right
+		weight := float64(i) / float64(epsilonBuckets)
+		if bucketCount > 0 {
+			currentValue := float64(h.epsilonValues[pos]) / float64(bucketCount)
+			value += currentValue * weight
+			lastValue = currentValue
+		} else {
+			value += lastValue * weight
+		}
+	}
+	return value
+}