Introduce new preview auto-scaling mode for ARC. (#2153)

Co-authored-by: Cory Miller <cory-miller@github.com>
Co-authored-by: Nikola Jokic <nikola-jokic@github.com>
Co-authored-by: Ava Stancu <AvaStancu@github.com>
Co-authored-by: Ferenc Hammerl <fhammerl@github.com>
Co-authored-by: Francesco Renzi <rentziass@github.com>
Co-authored-by: Bassem Dghaidi <Link-@github.com>

hash/hash.go

@@ -5,9 +5,12 @@
 package hash
 
 import (
+	"fmt"
 	"hash"
+	"hash/fnv"
 
 	"github.com/davecgh/go-spew/spew"
+	"k8s.io/apimachinery/pkg/util/rand"
 )
 
 // DeepHashObject writes specified object to hash using the spew library
@@ -23,3 +26,26 @@ func DeepHashObject(hasher hash.Hash, objectToWrite interface{}) {
 	}
 	printer.Fprintf(hasher, "%#v", objectToWrite)
 }
+
+// ComputeHash returns a hash value calculated from template and
+// a collisionCount to avoid hash collision. The hash will be safe encoded to
+// avoid bad words. It expects **template. In other words, you should pass an address
+// of a DeepCopy result.
+//
+// Proudly modified and adopted from k8s.io/kubernetes/pkg/util/hash.DeepHashObject and
+// k8s.io/kubernetes/pkg/controller.ComputeHash.
+func ComputeTemplateHash(template interface{}) string {
+	hasher := fnv.New32a()
+
+	hasher.Reset()
+
+	printer := spew.ConfigState{
+		Indent:         " ",
+		SortKeys:       true,
+		DisableMethods: true,
+		SpewKeys:       true,
+	}
+	printer.Fprintf(hasher, "%#v", template)
+
+	return rand.SafeEncodeString(fmt.Sprint(hasher.Sum32()))
+}