HDFS-5939. WebHdfs returns misleading error code and logs nothing if trying to create a file with no DNs in cluster. Contributed by Yongjun Zhang.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1571781 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/NetworkTopology.java

@@ -712,6 +712,11 @@ public class NetworkTopology {
         numOfDatanodes -= ((InnerNode)node).getNumOfLeaves();
       }
     }
+    if (numOfDatanodes == 0) {
+      throw new InvalidTopologyException(
+          "Failed to find datanode (scope=\"" + String.valueOf(scope) +
+          "\" excludedScope=\"" + String.valueOf(excludedScope) + "\").");
+    }
     int leaveIndex = r.nextInt(numOfDatanodes);
     return innerNode.getLeaf(leaveIndex, node);
   }

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

@@ -433,6 +433,9 @@ Release 2.4.0 - UNRELEASED
     HDFS-5935. New Namenode UI FS browser should throw smarter error messages.
     (Travis Thompson via jing9)
 
+    HDFS-5939. WebHdfs returns misleading error code and logs nothing if trying
+    to create a file with no DNs in cluster. (Yongjun Zhang via jing9)
+
   OPTIMIZATIONS
 
     HDFS-5790. LeaseManager.findPath is very slow when many leases need recovery

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

@@ -103,6 +103,7 @@ import org.apache.hadoop.hdfs.web.resources.UriFsPathParam;
 import org.apache.hadoop.hdfs.web.resources.UserParam;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.ipc.Server;
+import org.apache.hadoop.net.NetworkTopology.InvalidTopologyException;
 import org.apache.hadoop.net.NodeBase;
 import org.apache.hadoop.security.Credentials;
 import org.apache.hadoop.security.UserGroupInformation;
@@ -244,8 +245,12 @@ public class NamenodeWebHdfsMethods {
       final String path, final HttpOpParam.Op op, final long openOffset,
       final long blocksize,
       final Param<?, ?>... parameters) throws URISyntaxException, IOException {
-    final DatanodeInfo dn = chooseDatanode(namenode, path, op, openOffset,
-        blocksize);
+    final DatanodeInfo dn;
+    try {
+      dn = chooseDatanode(namenode, path, op, openOffset, blocksize);
+    } catch (InvalidTopologyException ite) {
+      throw new IOException("Failed to find datanode, suggest to check cluster health.", ite);
+    }
 
     final String delegationQuery;
     if (!UserGroupInformation.isSecurityEnabled()) {

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/web/TestWebHDFS.java

@@ -36,9 +36,10 @@ import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
-import org.apache.hadoop.hdfs.TestDFSClientRetries;
 import org.apache.hadoop.hdfs.server.namenode.web.resources.NamenodeWebHdfsMethods;
+import org.apache.hadoop.hdfs.TestDFSClientRetries;
 import org.apache.hadoop.security.UserGroupInformation;
+import org.apache.hadoop.test.GenericTestUtils;
 import org.apache.log4j.Level;
 import org.junit.Assert;
 import org.junit.Test;
@@ -289,6 +290,31 @@ public class TestWebHDFS {
     }
   }
 
+  /**
+   * Test for catching "no datanode" IOException, when to create a file
+   * but datanode is not running for some reason.
+   */
+  @Test(timeout=300000)
+  public void testCreateWithNoDN() throws Exception {
+    MiniDFSCluster cluster = null;
+    final Configuration conf = WebHdfsTestUtil.createConf();
+    try {
+      cluster = new MiniDFSCluster.Builder(conf).numDataNodes(0).build();
+      conf.setInt(DFSConfigKeys.DFS_REPLICATION_KEY, 1);
+      cluster.waitActive();
+      FileSystem fs = WebHdfsTestUtil.getWebHdfsFileSystem(conf,
+          WebHdfsFileSystem.SCHEME);
+      fs.create(new Path("/testnodatanode"));
+      Assert.fail("No exception was thrown");
+    } catch (IOException ex) {
+      GenericTestUtils.assertExceptionContains("Failed to find datanode", ex);
+    } finally {
+      if (cluster != null) {
+        cluster.shutdown();
+      }
+    }
+  }
+  
   /**
    * WebHdfs should be enabled by default after HDFS-5532
    *