SOLR-6860: Re-enable REBALANCELEADERS for 5.1. going to let this bake in trunk only until 5.0 is cut

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1647849 13f79535-47bb-0310-9956-ffa450edef68

solr/core/src/java/org/apache/solr/cloud/OverseerCollectionProcessor.java

@@ -658,9 +658,9 @@ public class OverseerCollectionProcessor implements Runnable, Closeable {
           case BALANCESHARDUNIQUE:
             balanceProperty(message);
             break;
-//          case REBALANCELEADERS:
-//            processAssignLeaders(message);
-//            break;
+          case REBALANCELEADERS:
+            processAssignLeaders(message);
+            break;
           default:
             throw new SolrException(ErrorCode.BAD_REQUEST, "Unknown operation:"
                 + operation);

solr/core/src/java/org/apache/solr/handler/admin/CollectionsHandler.java

@@ -268,10 +268,10 @@ public class CollectionsHandler extends RequestHandlerBase {
         this.handleBalanceShardUnique(req, rsp);
         break;
       }
-//      case REBALANCELEADERS: {
-//        this.handleBalanceLeaders(req, rsp);
-//        break;
-//      }
+      case REBALANCELEADERS: {
+        this.handleBalanceLeaders(req, rsp);
+        break;
+      }
       default: {
           throw new RuntimeException("Unknown action: " + action);
       }

solr/core/src/test/org/apache/solr/cloud/TestReplicaProperties.java

@@ -193,17 +193,11 @@ public class TestReplicaProperties extends ReplicaPropertiesBase {
       // leaders _also_ have the preferredLeader property set.
 
 
-      try {
       NamedList<Object> res = doPropertyAction(client,
           "action", CollectionParams.CollectionAction.REBALANCELEADERS.toString(),
           "collection", COLLECTION_NAME);
-        fail("Should have thrown 'Unknown action' error");
-      } catch (SolrServerException e) {
-        assertTrue("Should have gotten an error message that REBALANCELEADERS is not supported",
-            e.getCause().getMessage().contains("Unknown action: REBALANCELEADERS"));
-      }
 
-//      verifyLeaderAssignment(client, COLLECTION_NAME);
+      verifyLeaderAssignment(client, COLLECTION_NAME);
 
     } finally {
       client.shutdown();