fixes to tests

Signed-off-by: AnnTian Shao <anntians@amazon.com>

Author: AnnTian Shao

client/rest-high-level/src/test/java/org/opensearch/client/IndicesClientIT.java

@@ -1468,17 +1468,6 @@ public void testIndexPutSettings() throws IOException {
             )
         );
 
-        UpdateSettingsRequest privateSettingRequest = new UpdateSettingsRequest(index);
-        privateSettingRequest.settings(Settings.builder().put(privateSettingKey, privateSettingValue).build());
-        exception = expectThrows(
-            OpenSearchException.class,
-            () -> execute(privateSettingRequest, highLevelClient().indices()::putSettings, highLevelClient().indices()::putSettingsAsync)
-        );
-        assertThat(
-            exception.getMessage(),
-            containsString("can not update private setting [index.creation_date]; this setting is managed by OpenSearch")
-        );
-
         closeIndex(index);
         exception = expectThrows(
             OpenSearchException.class,

server/src/main/java/org/opensearch/cluster/metadata/IndexMetadata.java

@@ -581,7 +581,6 @@ public static APIBlock readFrom(StreamInput input) throws IOException {
         -1,
         -1,
         Property.IndexScope,
-        Property.NodeScope,
         Property.PrivateIndex,
         Property.UnmodifiableOnRestore
     );

server/src/main/java/org/opensearch/common/settings/IndexScopedSettings.java

@@ -313,9 +313,6 @@ protected void validateSettingKey(Setting setting) {
     @Override
     public boolean isPrivateSetting(String key) {
         switch (key) {
-            case IndexMetadata.SETTING_CREATION_DATE:
-            case IndexMetadata.SETTING_INDEX_UUID:
-            case IndexMetadata.SETTING_HISTORY_UUID:
             case IndexMetadata.SETTING_VERSION_UPGRADED:
             case IndexMetadata.SETTING_INDEX_PROVIDED_NAME:
             case MergePolicyProvider.INDEX_MERGE_ENABLED:

server/src/test/java/org/opensearch/index/IndexSettingsTests.java

@@ -607,6 +607,10 @@ public void testTranslogGenerationSizeThreshold() {
         assertEquals(actual, settings.getGenerationThresholdSize());
     }
 
+    /**
+     * Test private setting validation for private settings defined in isPrivateSetting()
+     * https://github.com/opensearch-project/OpenSearch/blob/main/server/src/main/java/org/opensearch/common/settings/IndexScopedSettings.java
+     */
     public void testPrivateSettingsValidation() {
         final Settings settings = Settings.builder().put(IndexMetadata.SETTING_VERSION_UPGRADED, Version.V_EMPTY).build();
         final IndexScopedSettings indexScopedSettings = new IndexScopedSettings(settings, IndexScopedSettings.BUILT_IN_INDEX_SETTINGS);