HDFS-15443. Setting dfs.datanode.max.transfer.threads to a very small value can cause strange failure. Contributed by AMC-team.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataXceiverServer.java

@@ -188,6 +188,9 @@ class DataXceiverServer implements Runnable {
     this.maxXceiverCount =
       conf.getInt(DFSConfigKeys.DFS_DATANODE_MAX_RECEIVER_THREADS_KEY,
                   DFSConfigKeys.DFS_DATANODE_MAX_RECEIVER_THREADS_DEFAULT);
+    Preconditions.checkArgument(this.maxXceiverCount >= 1,
+        DFSConfigKeys.DFS_DATANODE_MAX_RECEIVER_THREADS_KEY +
+        " should not be less than 1.");
 
     this.estimateBlockSize = conf.getLongBytes(DFSConfigKeys.DFS_BLOCK_SIZE_KEY,
         DFSConfigKeys.DFS_BLOCK_SIZE_DEFAULT);