Make DeepHashObject function deterministic.

duda · Feb 19, 2015 · 14e93a1 · 14e93a1
1 parent 413e1db
commit 14e93a1
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Showing 2 changed files with 27 additions and 23 deletions.
diff --git a/pkg/util/hash.go b/pkg/util/hash.go
@@ -26,5 +26,6 @@ import (
 // which follows pointers and prints actual values of the nested objects
 // ensuring the hash does not change when a pointer changes.
 func DeepHashObject(hasher hash.Hash, objectToWrite interface{}) {
-	spew.Fprintf(hasher, "%#v", objectToWrite)
+  printer := spew.ConfigState{Indent: " ", SortKeys: true}
+  printer.Fprintf(hasher, "%#v", objectToWrite)
 }
diff --git a/pkg/util/hash_test.go b/pkg/util/hash_test.go
@@ -28,6 +28,7 @@ type wheel struct {
 type unicycle struct {
 	primaryWheel   *wheel
 	licencePlateID string
+	tags           map[string]string
 }
 
 func TestDeepObjectPointer(t *testing.T) {
@@ -36,28 +37,30 @@ func TestDeepObjectPointer(t *testing.T) {
 	wheel2 := wheel{radius: 22}
 	wheel3 := wheel{radius: 17}
 
-	myUni1 := unicycle{licencePlateID: "blah", primaryWheel: &wheel1}
-	myUni2 := unicycle{licencePlateID: "blah", primaryWheel: &wheel2}
-	myUni3 := unicycle{licencePlateID: "blah", primaryWheel: &wheel3}
-
-	hasher1 := adler32.New()
-	hasher2 := adler32.New()
-	hasher3 := adler32.New()
-
-	// Act
-	DeepHashObject(hasher1, myUni1)
-	hash1 := hasher1.Sum32()
-	DeepHashObject(hasher2, myUni2)
-	hash2 := hasher2.Sum32()
-	DeepHashObject(hasher3, myUni3)
-	hash3 := hasher3.Sum32()
-
-	// Assert
-	if hash1 == hash2 {
-		t.Errorf("hash1 (%d) and hash2(%d) must be different because they have different values for wheel size", hash1, hash2)
-	}
+	myUni1 := unicycle{licencePlateID: "blah", primaryWheel: &wheel1, tags: map[string]string{"color": "blue", "name": "john"}}
+	myUni2 := unicycle{licencePlateID: "blah", primaryWheel: &wheel2, tags: map[string]string{"color": "blue", "name": "john"}}
+	myUni3 := unicycle{licencePlateID: "blah", primaryWheel: &wheel3, tags: map[string]string{"color": "blue", "name": "john"}}
+
+	// Run it more than once to verify determinism of hasher.
+	for i := 0; i < 100; i++ {
+		hasher1 := adler32.New()
+		hasher2 := adler32.New()
+		hasher3 := adler32.New()
+		// Act
+		DeepHashObject(hasher1, myUni1)
+		hash1 := hasher1.Sum32()
+		DeepHashObject(hasher2, myUni2)
+		hash2 := hasher2.Sum32()
+		DeepHashObject(hasher3, myUni3)
+		hash3 := hasher3.Sum32()
+
+		// Assert
+		if hash1 == hash2 {
+			t.Errorf("hash1 (%d) and hash2(%d) must be different because they have different values for wheel size", hash1, hash2)
+		}
 
-	if hash1 != hash3 {
-		t.Errorf("hash1 (%d) and hash3(%d) must be the same because although they point to different objects, they have the same values for wheel size", hash1, hash3)
+		if hash1 != hash3 {
+			t.Errorf("hash1 (%d) and hash3(%d) must be the same because although they point to different objects, they have the same values for wheel size", hash1, hash3)
+		}
 	}
 }