HDFS-4259. Improve pipeline DN replacement failure message. Contributed by Harsh J. (harsh)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1439127 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -208,6 +208,8 @@ Release 2.0.3-alpha - Unreleased
     HDFS-4403. DFSClient can infer checksum type when not provided by reading
     first byte (todd)
 
+    HDFS-4259. Improve pipeline DN replacement failure message (harsh)
+
   OPTIMIZATIONS
 
     HDFS-3429. DataNode reads checksums even if client does not need them (todd)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSOutputStream.java

@@ -790,13 +790,18 @@ public class DFSOutputStream extends FSOutputSummer implements Syncable {
     private int findNewDatanode(final DatanodeInfo[] original
         ) throws IOException {
       if (nodes.length != original.length + 1) {
-        throw new IOException("Failed to add a datanode.  "
-            + "User may turn off this feature by setting "
-            + DFSConfigKeys.DFS_CLIENT_WRITE_REPLACE_DATANODE_ON_FAILURE_POLICY_KEY
-            + " in configuration, where the current policy is "
-            + dfsClient.dtpReplaceDatanodeOnFailure
-            + ".  (Nodes: current=" + Arrays.asList(nodes)
-            + ", original=" + Arrays.asList(original) + ")");
+        throw new IOException(
+            new StringBuilder()
+            .append("Failed to replace a bad datanode on the existing pipeline ")
+            .append("due to no more good datanodes being available to try. ")
+            .append("(Nodes: current=").append(Arrays.asList(nodes))
+            .append(", original=").append(Arrays.asList(original)).append("). ")
+            .append("The current failed datanode replacement policy is ")
+            .append(dfsClient.dtpReplaceDatanodeOnFailure).append(", and ")
+            .append("a client may configure this via '")
+            .append(DFSConfigKeys.DFS_CLIENT_WRITE_REPLACE_DATANODE_ON_FAILURE_POLICY_KEY)
+            .append("' in its configuration.")
+            .toString());
       }
       for(int i = 0; i < nodes.length; i++) {
         int j = 0;