Handle allocation for NONE direction

Signed-off-by: Lakshya Taragi <lakshya.taragi@gmail.com>

Author: ltaragi

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

@@ -1659,7 +1659,7 @@ public static void validateRefreshIntervalSettings(Settings requestSettings, Clu
      * @param clusterSettings cluster setting
      */
     static void validateTranslogDurabilitySettings(Settings requestSettings, ClusterSettings clusterSettings, Settings settings) {
-        if (isRemoteDataAttributePresent(settings) == false
+        if ((isRemoteDataAttributePresent(settings) == false && isMigratingToRemoteStore(clusterSettings) == false)
             || IndexSettings.INDEX_TRANSLOG_DURABILITY_SETTING.exists(requestSettings) == false
             || clusterSettings.get(IndicesService.CLUSTER_REMOTE_INDEX_RESTRICT_ASYNC_DURABILITY_SETTING) == false) {
             return;

server/src/main/java/org/opensearch/cluster/routing/allocation/decider/RemoteStoreMigrationAllocationDecider.java

@@ -95,18 +95,24 @@ public Decision canAllocate(ShardRouting shardRouting, RoutingNode node, Routing
             );
         }
 
-        if (migrationDirection.equals(Direction.REMOTE_STORE) == false) {
-            // docrep migration direction is currently not supported
+        IndexMetadata indexMetadata = allocation.metadata().getIndexSafe(shardRouting.index());
+        boolean remoteStoreBackedIndex = IndexMetadata.INDEX_REMOTE_STORE_ENABLED_SETTING.get(indexMetadata.getSettings());
+
+        if (migrationDirection.equals(Direction.NONE)) {
+            boolean isNoDecision = (remoteStoreBackedIndex && targetNode.isRemoteStoreNode() == false)
+                || (remoteStoreBackedIndex == false && targetNode.isRemoteStoreNode());
+            String reason = String.format(Locale.ROOT, " for %sremote store backed index", remoteStoreBackedIndex ? "" : "non ");
             return allocation.decision(
-                Decision.YES,
+                isNoDecision ? Decision.NO : Decision.YES,
                 NAME,
-                getDecisionDetails(true, shardRouting, targetNode, " for non remote_store direction")
+                getDecisionDetails(!isNoDecision, shardRouting, targetNode, reason)
             );
+        } else if (migrationDirection.equals(Direction.DOCREP)) {
+            // docrep migration direction is currently not supported
+            return allocation.decision(Decision.YES, NAME, getDecisionDetails(true, shardRouting, targetNode, " for DOCREP direction"));
         }
 
         // check for remote store backed indices
-        IndexMetadata indexMetadata = allocation.metadata().getIndexSafe(shardRouting.index());
-        boolean remoteStoreBackedIndex = IndexMetadata.INDEX_REMOTE_STORE_ENABLED_SETTING.get(indexMetadata.getSettings());
         if (remoteStoreBackedIndex && targetNode.isRemoteStoreNode() == false) {
             // allocations and relocations must be to a remote node
             String reason = String.format(