From 68ba51c600af7cf64efcbf0e03d55e9ca6dcc590 Mon Sep 17 00:00:00 2001
From: Alex Dadgar <alex.dadgar@gmail.com>
Date: Mon, 10 Apr 2017 11:44:51 -0700
Subject: [PATCH 1/2] Hash host ID so its stable and well distributed

This PR takes the host ID and runs it through a hash so that it is well
distributed. This makes it so that machines that report similar host IDs
are easily distinguished.

Instances of similar IDs occur on EC2 where the ID is prefixed and on
motherboards created in the same batch.

Fixes https://github.com/hashicorp/nomad/issues/2534
---
 client/client.go | 10 +++++++---
 helper/funcs.go  | 19 +++++++++++++++++++
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/client/client.go b/client/client.go
index 9894dd482369..7183c939f1df 100644
--- a/client/client.go
+++ b/client/client.go
@@ -655,9 +655,13 @@ func (c *Client) getAllocRunners() map[string]*AllocRunner {
 func (c *Client) nodeID() (id, secret string, err error) {
 	var hostID string
 	hostInfo, err := host.Info()
-	if !c.config.NoHostUUID && err == nil && helper.IsUUID(hostInfo.HostID) {
-		hostID = hostInfo.HostID
-	} else {
+	if !c.config.NoHostUUID && err == nil {
+		if hashed, ok := helper.HashUUID(hostInfo.HostID); ok {
+			hostID = hashed
+		}
+	}
+
+	if hostID == "" {
 		// Generate a random hostID if no constant ID is available on
 		// this platform.
 		hostID = structs.GenerateUUID()
diff --git a/helper/funcs.go b/helper/funcs.go
index 8c62e06f2a67..04440f5c9900 100644
--- a/helper/funcs.go
+++ b/helper/funcs.go
@@ -1,6 +1,8 @@
 package helper
 
 import (
+	"crypto/sha512"
+	"fmt"
 	"regexp"
 	"time"
 )
@@ -18,6 +20,23 @@ func IsUUID(str string) bool {
 	return validUUID.MatchString(str)
 }
 
+func HashUUID(input string) (output string, hashed bool) {
+	if !IsUUID(input) {
+		return "", false
+	}
+
+	// Hash the input
+	buf := sha512.Sum512([]byte(input))
+	output = fmt.Sprintf("%08x-%04x-%04x-%04x-%12x",
+		buf[0:4],
+		buf[4:6],
+		buf[6:8],
+		buf[8:10],
+		buf[10:16])
+
+	return output, true
+}
+
 // boolToPtr returns the pointer to a boolean
 func BoolToPtr(b bool) *bool {
 	return &b

From 7a78eeed162e1ff05a51ba4132f28d79c10a7af6 Mon Sep 17 00:00:00 2001
From: Alex Dadgar <alex.dadgar@gmail.com>
Date: Mon, 10 Apr 2017 12:07:57 -0700
Subject: [PATCH 2/2] Add a comment

---
 helper/funcs.go | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/helper/funcs.go b/helper/funcs.go
index 04440f5c9900..44a3e57c4ddb 100644
--- a/helper/funcs.go
+++ b/helper/funcs.go
@@ -20,6 +20,8 @@ func IsUUID(str string) bool {
 	return validUUID.MatchString(str)
 }
 
+// HashUUID takes an input UUID and returns a hashed version of the UUID to
+// ensure it is well distributed.
 func HashUUID(input string) (output string, hashed bool) {
 	if !IsUUID(input) {
 		return "", false