From 3e145a364f5db1cba2442ef036603b5ee697b5b6 Mon Sep 17 00:00:00 2001
From: Ankit Gupta <ankit.gupta.iiith@gmail.com>
Date: Sat, 26 May 2018 14:59:50 +0530
Subject: [PATCH] Bug fix: findCeilIn

---
 algorithm/randomize.go      | 12 ++++++++++++
 algorithm/select_service.go | 35 ++++++++++++++++++++++++++++-------
 2 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/algorithm/randomize.go b/algorithm/randomize.go
index da499b4..e60a58a 100644
--- a/algorithm/randomize.go
+++ b/algorithm/randomize.go
@@ -16,3 +16,15 @@ func randomize(init int, set int) int {
 
 	return choice
 }
+
+func randomize64(init int64, set int64) int64 {
+
+	if set <= init {
+		return int64(0)
+	}
+
+	rand.Seed(time.Now().UTC().UnixNano())
+	choice := rand.Int63n(set - init) + init
+
+	return choice
+}
diff --git a/algorithm/select_service.go b/algorithm/select_service.go
index 38f59bd..7c4682f 100644
--- a/algorithm/select_service.go
+++ b/algorithm/select_service.go
@@ -43,15 +43,36 @@ func ChooseServiceIndex(sqp *model.ServiceQProperties, initialChoice int, retry
 					prefixes[i] = weights[i] + prefixes[i-1]
 				}
 			}
-			randx := randomize(1, int(prefixes[len(prefixes) - 1]))
-			for i, n := range prefixes {
-				if int(n) >= randx {
-					return i
-					}
-				}
+			prLen := len(prefixes) - 1
+			randx := randomize64(1, int64(prefixes[prLen]))
+			ceil := findCeilIn(randx, prefixes, 0, prLen)
+			if ceil >= 0 {
+				return ceil
 			}
-			return randomize(0, noOfServices)
+		}
+		return randomize(0, noOfServices)
 	} else {
 		return roundrobin(noOfServices, initialChoice)
 	}
 }
+
+func findCeilIn(randx int64, prefixes []float64, start int, end int) int {
+
+	var mid int
+	for {
+		if start >= end {
+			break
+		}
+		mid = start + ((end - start) >> 1)
+		if randx > int64(prefixes[mid]) {
+			start = mid + 1
+		} else {
+			end = mid
+		}
+	}
+
+	if randx <= int64(prefixes[start]) {
+		return start
+	}
+	return -1
+}