HDFS-8627. NPE thrown if unable to fetch token from Namenode (Contributed by J.Andreina)

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

@@ -338,6 +338,9 @@ Trunk (Unreleased)
 
     HDFS-8412. Fix the test failures in HTTPFS. (umamahesh)
 
+    HDFS-8627. NPE thrown if unable to fetch token from Namenode
+    (J.Andreina via vinayakumarb)
+
 Release 2.8.0 - UNRELEASED
 
   NEW FEATURES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/DelegationTokenFetcher.java

@@ -176,14 +176,17 @@ public class DelegationTokenFetcher {
                                   final String renewer, final Path tokenFile)
           throws IOException {
     Token<?> token = fs.getDelegationToken(renewer);
-
-    Credentials cred = new Credentials();
-    cred.addToken(token.getKind(), token);
-    cred.writeTokenStorageFile(tokenFile, conf);
-
-    if (LOG.isDebugEnabled()) {
-      LOG.debug("Fetched token " + fs.getUri() + " for " + token.getService()
-              + " into " + tokenFile);
+    if (null != token) {
+      Credentials cred = new Credentials();
+      cred.addToken(token.getKind(), token);
+      cred.writeTokenStorageFile(tokenFile, conf);
+
+      if (LOG.isDebugEnabled()) {
+        LOG.debug("Fetched token " + fs.getUri() + " for " +
+            token.getService() + " into " + tokenFile);
+      }
+    } else {
+      System.err.println("ERROR: Failed to fetch token from " + fs.getUri());
     }
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/tools/TestDelegationTokenFetcher.java

@@ -90,4 +90,19 @@ public class TestDelegationTokenFetcher {
     DelegationTokenFetcher.cancelTokens(conf, p);
     Assert.assertEquals(testToken, FakeRenewer.getLastCanceled());
   }
+
+  /**
+   * If token returned is null, saveDelegationToken should not
+   * throw nullPointerException
+   */
+  @Test
+  public void testReturnedTokenIsNull() throws Exception {
+    WebHdfsFileSystem fs = mock(WebHdfsFileSystem.class);
+    doReturn(null).when(fs).getDelegationToken(anyString());
+    Path p = new Path(f.getRoot().getAbsolutePath(), tokenFile);
+    DelegationTokenFetcher.saveDelegationToken(conf, fs, null, p);
+    // When Token returned is null, TokenFile should not exist
+    Assert.assertFalse(p.getFileSystem(conf).exists(p));
+
+  }
 }