RecoveryIT.testHistoryUUIDIsGenerated should reduce unassigned shards delay instead of ensure green.

The ensure green approach to avoid allocation delays caused problems with other indices created by other tests which didn't use ensure green in the various cluster stages. This aligns testHistoryUUIDIsGenerated to use the same approach used by the other test.

qa/rolling-upgrade/src/test/java/org/elasticsearch/upgrades/RecoveryIT.java

@@ -33,6 +33,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+import static org.elasticsearch.cluster.routing.UnassignedInfo.INDEX_DELAYED_NODE_LEFT_TIMEOUT_SETTING;
 import static org.hamcrest.Matchers.anyOf;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.hasSize;
@@ -103,16 +104,15 @@ public class RecoveryIT extends ESRestTestCase {
     public void testHistoryUUIDIsGenerated() throws Exception {
         final String index = "index_history_uuid";
         if (clusterType == CLUSTER_TYPE.OLD) {
-            assertOK(client().performRequest("PUT", "_cluster/settings", Collections.emptyMap(),
-                new StringEntity("{ \"persistent\": " +
-                    "{ \"logger._root\": \"DEBUG\", \"logger.org.elasticsearch.cluster.service\": \"TRACE\" } " +
-                    "}", ContentType.APPLICATION_JSON)));
             Settings.Builder settings = Settings.builder()
                 .put(IndexMetaData.INDEX_NUMBER_OF_SHARDS_SETTING.getKey(), 1)
-                .put(IndexMetaData.INDEX_NUMBER_OF_REPLICAS_SETTING.getKey(), 1);
+                .put(IndexMetaData.INDEX_NUMBER_OF_REPLICAS_SETTING.getKey(), 1)
+                // if the node with the replica is the first to be restarted, while a replica is still recovering
+                // then delayed allocation will kick in. When the node comes back, the master will search for a copy
+                // but the recovering copy will be seen as invalid and the cluster health won't return to GREEN
+                // before timing out
+                .put(INDEX_DELAYED_NODE_LEFT_TIMEOUT_SETTING.getKey(), "100ms");
             createIndex(index, settings.build());
-            ensureGreen();
-
         } else if (clusterType == CLUSTER_TYPE.UPGRADED) {
             ensureGreen();
             Response response = client().performRequest("GET", index + "/_stats", Collections.singletonMap("level", "shards"));
@@ -131,11 +131,6 @@ public class RecoveryIT extends ESRestTestCase {
                     assertThat("different history uuid found for shard on " + nodeID, historyUUID, equalTo(expectHistoryUUID));
                 }
             }
-        } else {
-            // we are now in mixed cluster mode. we want to make sure the shard is fully allocated on the new node that was just
-            // started in order not to run into delayed unassigned shards when we bring down the old node (there must be a fully valid
-            // copy)
-            ensureGreen();
         }
     }