From e5c8fce96a10ef8b0c313afd0c64fa783588e7d4 Mon Sep 17 00:00:00 2001
From: Armon Dadgar <armon.dadgar@gmail.com>
Date: Thu, 14 May 2015 17:59:11 -0700
Subject: [PATCH] consul: adding randomStagger util method

---
 consul/util.go      |  7 +++++++
 consul/util_test.go | 11 +++++++++++
 2 files changed, 18 insertions(+)

diff --git a/consul/util.go b/consul/util.go
index d0ce256fe..6cc785899 100644
--- a/consul/util.go
+++ b/consul/util.go
@@ -4,12 +4,14 @@ import (
 	crand "crypto/rand"
 	"encoding/binary"
 	"fmt"
+	"math/rand"
 	"net"
 	"os"
 	"path/filepath"
 	"runtime"
 	"strconv"
 	"strings"
+	"time"
 
 	"github.com/hashicorp/serf/serf"
 )
@@ -222,3 +224,8 @@ func generateUUID() string {
 		buf[8:10],
 		buf[10:16])
 }
+
+// Returns a random stagger interval between 0 and the duration
+func randomStagger(intv time.Duration) time.Duration {
+	return time.Duration(uint64(rand.Int63()) % uint64(intv))
+}
diff --git a/consul/util_test.go b/consul/util_test.go
index 24d9f7299..5803e95a9 100644
--- a/consul/util_test.go
+++ b/consul/util_test.go
@@ -4,6 +4,7 @@ import (
 	"net"
 	"regexp"
 	"testing"
+	"time"
 
 	"github.com/hashicorp/serf/serf"
 )
@@ -124,3 +125,13 @@ func TestGenerateUUID(t *testing.T) {
 		}
 	}
 }
+
+func TestRandomStagger(t *testing.T) {
+	intv := time.Minute
+	for i := 0; i < 10; i++ {
+		stagger := randomStagger(intv)
+		if stagger < 0 || stagger >= intv {
+			t.Fatalf("Bad: %v", stagger)
+		}
+	}
+}