HDFS-8290. WebHDFS calls before namesystem initialization can cause NullPointerException. Contributed by Chris Nauroth.

(cherry picked from commit c4578760b67d5b5169949a1b059f4472a268ff1b)

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

@@ -286,6 +286,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-8309. Skip unit test using DataNodeTestUtils#injectDataDirFailure() on Windows.
     (xyao)
 
+    HDFS-8290. WebHDFS calls before namesystem initialization can cause
+    NullPointerException. (cnauroth)
+
 Release 2.7.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/web/resources/NamenodeWebHdfsMethods.java

@@ -69,6 +69,7 @@
 import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor;
 import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeStorageInfo;
 import org.apache.hadoop.hdfs.server.common.JspHelper;
+import org.apache.hadoop.hdfs.server.namenode.FSNamesystem;
 import org.apache.hadoop.hdfs.server.namenode.NameNode;
 import org.apache.hadoop.hdfs.server.protocol.NamenodeProtocols;
 import org.apache.hadoop.hdfs.web.JsonUtil;
@@ -164,7 +165,11 @@ private static NamenodeProtocols getRPCServer(NameNode namenode)
   static DatanodeInfo chooseDatanode(final NameNode namenode,
       final String path, final HttpOpParam.Op op, final long openOffset,
       final long blocksize, final String excludeDatanodes) throws IOException {
-    final BlockManager bm = namenode.getNamesystem().getBlockManager();
+    FSNamesystem fsn = namenode.getNamesystem();
+    if (fsn == null) {
+      throw new IOException("Namesystem has not been intialized yet.");
+    }
+    final BlockManager bm = fsn.getBlockManager();
     
     HashSet<Node> excludes = new HashSet<Node>();
     if (excludeDatanodes != null) {

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/web/resources/TestWebHdfsDataLocality.java

@@ -17,6 +17,9 @@
  */
 package org.apache.hadoop.hdfs.server.namenode.web.resources;
 
+import static org.mockito.Mockito.*;
+
+import java.io.IOException;
 import java.util.Arrays;
 import java.util.List;
 
@@ -42,7 +45,9 @@
 import org.apache.hadoop.hdfs.web.resources.PutOpParam;
 import org.apache.log4j.Level;
 import org.junit.Assert;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 
 /**
  * Test WebHDFS which provides data locality using HTTP redirection.
@@ -57,6 +62,9 @@ public class TestWebHdfsDataLocality {
   private static final String RACK1 = "/rack1";
   private static final String RACK2 = "/rack2";
 
+  @Rule
+  public final ExpectedException exception = ExpectedException.none();
+
   @Test
   public void testDataLocality() throws Exception {
     final Configuration conf = WebHdfsTestUtil.createConf();
@@ -213,4 +221,14 @@ public void testExcludeDataNodes() throws Exception {
       cluster.shutdown();
     }
   }
-}
+
+  @Test
+  public void testChooseDatanodeBeforeNamesystemInit() throws Exception {
+    NameNode nn = mock(NameNode.class);
+    when(nn.getNamesystem()).thenReturn(null);
+    exception.expect(IOException.class);
+    exception.expectMessage("Namesystem has not been intialized yet.");
+    NamenodeWebHdfsMethods.chooseDatanode(nn, "/path", PutOpParam.Op.CREATE, 0,
+        DFSConfigKeys.DFS_BLOCK_SIZE_DEFAULT, null);
+  }
+}