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https://issues.apache.org/jira/browse/HDFS-8738?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16723678#comment-16723678
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Xiang Li commented on HDFS-8738:
--------------------------------

Agree with Arpit. Add the link as a dup of HDFS-9572.

> Limit Exceptions thrown by DataNode when a client makes socket connection and 
> sends an empty message
> ----------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-8738
>                 URL: https://issues.apache.org/jira/browse/HDFS-8738
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 2.7.1
>            Reporter: Rajesh Kartha
>            Assignee: Rajesh Kartha
>            Priority: Minor
>         Attachments: HDFS-8738.001.patch
>
>
> When a client creates a socket connection to the Datanode and sends an empty 
> message, the datanode logs have exceptions like these:
> 2015-07-08 20:00:55,427 ERROR datanode.DataNode (DataXceiver.java:run(278)) - 
> bidev17.rtp.ibm.com:50010:DataXceiver error processing unknown operation  
> src: /127.0.0.1:41508 dst: /127.0.0.1:50010
> java.io.EOFException
>         at java.io.DataInputStream.readShort(DataInputStream.java:315)
>         at 
> org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.readOp(Receiver.java:58)
>         at 
> org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:227)
>         at java.lang.Thread.run(Thread.java:745)
> 2015-07-08 20:00:56,671 ERROR datanode.DataNode (DataXceiver.java:run(278)) - 
> bidev17.rtp.ibm.com:50010:DataXceiver error processing unknown operation  
> src: /127.0.0.1:41509 dst: /127.0.0.1:50010
> java.io.EOFException
>         at java.io.DataInputStream.readShort(DataInputStream.java:315)
>         at 
> org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.readOp(Receiver.java:58)
>         at 
> org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:227)
>         at java.lang.Thread.run(Thread.java:745)
> These can fill up the logs and was recently noticed with an Ambari 2.1 based 
> install which tries to check if the datanode is up.
> Can be easily reproduced with a simple Java client creating a Socket 
> connection:
>         public static void main(String[] args) {
>             Socket DNClient;
>             try {
>                 DNClient = new Socket("127.0.0.1", 50010);
>                         DataOutputStream os= new 
> DataOutputStream(DNClient.getOutputStream());
>                         os.writeBytes("");
>                         os.close();
>                 } catch (UnknownHostException e) {
>                         // TODO Auto-generated catch block
>                         e.printStackTrace();
>                 } catch (IOException e) {
>                         // TODO Auto-generated catch block
>                         e.printStackTrace();
>                 }
>         }



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