YARN-9568. Fixed NPE in MiniYarnCluster during FileSystemNodeAttributeStore.recover.

           Contributed by Steve Loughran

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-tests/src/test/java/org/apache/hadoop/yarn/server/MiniYARNCluster.java

@@ -313,7 +313,13 @@ public class MiniYARNCluster extends CompositeService {
         YarnConfiguration.DEFAULT_TIMELINE_SERVICE_ENABLED) || enableAHS) {
         addService(new ApplicationHistoryServerWrapper());
     }
-    
+    // to ensure that any FileSystemNodeAttributeStore started by the RM always
+    // uses a unique path, if unset, force it under the test dir.
+    if (conf.get(YarnConfiguration.FS_NODE_ATTRIBUTE_STORE_ROOT_DIR) == null) {
+      File nodeAttrDir = new File(getTestWorkDir(), "nodeattributes");
+      conf.set(YarnConfiguration.FS_NODE_ATTRIBUTE_STORE_ROOT_DIR,
+          nodeAttrDir.getCanonicalPath());
+    }
     super.serviceInit(
         conf instanceof YarnConfiguration ? conf : new YarnConfiguration(conf));
   }