HDFS-7894. Rolling upgrade readiness is not updated in jmx until query command is issued. Contributed by Brahma Reddy Battula.

(cherry picked from commit 6f622672b62aa8d719060063ef0e47480cdc8655)

(cherry picked from commit 802a5775f3522c57c60ae29ecb9533dbbfecfe76)
(cherry picked from commit 995382c5234ad6c07f327e5d1f2a1c7e391a0b60)

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -132,6 +132,9 @@ Release 2.6.1 - UNRELEASED
     HDFS-8219. setStoragePolicy with folder behavior is different after cluster restart.
     (surendra singh lilhore via Xiaoyu Yao)
 
+    HDFS-7894. Rolling upgrade readiness is not updated in jmx until query
+    command is issued. (Brahma Reddy Battula  via kihwal)
+
 Release 2.6.0 - 2014-11-18
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java

@@ -8417,11 +8417,30 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
 
   @Override  // NameNodeMXBean
   public RollingUpgradeInfo.Bean getRollingUpgradeStatus() {
+    if (!isRollingUpgrade()) {
+      return null;
+    }
     RollingUpgradeInfo upgradeInfo = getRollingUpgradeInfo();
-    if (upgradeInfo != null) {
+    if (upgradeInfo.createdRollbackImages()) {
       return new RollingUpgradeInfo.Bean(upgradeInfo);
     }
-    return null;
+    readLock();
+    try {
+      // check again after acquiring the read lock.
+      upgradeInfo = getRollingUpgradeInfo();
+      if (upgradeInfo == null) {
+        return null;
+      }
+      if (!upgradeInfo.createdRollbackImages()) {
+        boolean hasRollbackImage = this.getFSImage().hasRollbackFSImage();
+        upgradeInfo.setCreatedRollbackImages(hasRollbackImage);
+      }
+    } catch (IOException ioe) {
+      LOG.warn("Encountered exception setting Rollback Image", ioe);
+    } finally {
+      readUnlock();
+    }
+    return new RollingUpgradeInfo.Bean(upgradeInfo);
   }
 
   /** Is rolling upgrade in progress? */