HDFS-8164. cTime is 0 in VERSION file for newly formatted NameNode. Contributed by Xiao Chen.

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

@@ -1491,6 +1491,9 @@ Release 2.8.0 - UNRELEASED
 
     HDFS-9170. Move libhdfs / fuse-dfs / libwebhdfs to hdfs-client. (wheat9)
 
+    HDFS-8164. cTime is 0 in VERSION file for newly formatted NameNode.
+    (Xiao Chen via Yongjun Zhang)
+
   OPTIMIZATIONS
 
     HDFS-8026. Trace FSOutputSummer#writeChecksumChunks rather than

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

@@ -1520,6 +1520,18 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
     }
   }
 
+  /**
+   * Get the creation time of the file system.
+   * Notice that this time is initialized to NameNode format time, and updated
+   * to upgrade time during upgrades.
+   * @return time in milliseconds.
+   * See {@link org.apache.hadoop.util.Time#now()}.
+   */
+  @VisibleForTesting
+  long getCTime() {
+    return fsImage == null ? 0 : fsImage.getStorage().getCTime();
+  }
+
   /**
    * Version of @see #getNamespaceInfo() that is not protected by a lock.
    */

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

@@ -573,7 +573,7 @@ public class NNStorage extends Storage implements Closeable,
   public static NamespaceInfo newNamespaceInfo()
       throws UnknownHostException {
     return new NamespaceInfo(newNamespaceID(), newClusterID(),
-        newBlockPoolID(), 0L);
+        newBlockPoolID(), Time.now());
   }
   
   public void format() throws IOException {

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestFSImage.java

@@ -62,6 +62,7 @@ import org.apache.hadoop.hdfs.server.namenode.NNStorage.NameNodeDirType;
 import org.apache.hadoop.hdfs.util.MD5FileUtils;
 import org.apache.hadoop.test.GenericTestUtils;
 import org.apache.hadoop.test.PathUtils;
+import org.apache.hadoop.util.Time;
 import org.junit.Test;
 
 import static org.junit.Assert.assertArrayEquals;
@@ -368,7 +369,30 @@ public class TestFSImage {
       }
     }
   }
-  
+
+  /**
+   * Ensure ctime is set during namenode formatting.
+   */
+  @Test(timeout=60000)
+  public void testCtime() throws Exception {
+    Configuration conf = new Configuration();
+    MiniDFSCluster cluster = null;
+    try {
+      final long pre = Time.now();
+      cluster = new MiniDFSCluster.Builder(conf).numDataNodes(1).build();
+      cluster.waitActive();
+      final long post = Time.now();
+      final long ctime = cluster.getNamesystem().getCTime();
+
+      assertTrue(pre <= ctime);
+      assertTrue(ctime <= post);
+    } finally {
+      if (cluster != null) {
+        cluster.shutdown();
+      }
+    }
+  }
+
   /**
    * In this test case, I have created an image with a file having
    * preferredblockSize = 0. We are trying to read this image (since file with