Merge pull request #2541 from hashicorp/f-stable-distributed-id

Hash host ID so its stable and well distributed

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()

helper/funcs.go

@@ -1,6 +1,8 @@
 package helper
 
 import (
+	"crypto/sha512"
+	"fmt"
 	"regexp"
 	"time"
 )
@@ -18,6 +20,25 @@ 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
+	}
+
+	// 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