title: How to do kerberos authentication on a flink standalone installation?
body: <p>I have a standalone Flink installation on top of which I want to run a streaming job that is writing data into a HDFS installation. The HDFS installation is part of a Cloudera deployment and requires Kerberos authentication in order to read and write the HDFS. Since I found no documentation on how to make Flink connect with a Kerberos-protected HDFS I had to make some educated guesses about the procedure. Here is what I did so far:</p>
  
  <ul>
  <li>I created a keytab file for my user.</li>
  <li><p>In my Flink job, I added the following code:</p>
  
  <pre><code>UserGroupInformation.loginUserFromKeytab("myusername", "/path/to/keytab");
  </code></pre></li>
  <li><p>Finally I am using a <code>TextOutputFormat</code>to write data to the HDFS. </p></li>
  </ul>
  
  <p>When I run the job, I'm getting the following error:</p>
  
  <pre><code>org.apache.hadoop.security.AccessControlException: SIMPLE authentication is not enabled.  Available:[TOKEN, KERBE
  ROS]
          at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
          at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
          at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
          at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
          at org.apache.hadoop.ipc.RemoteException.instantiateException(RemoteException.java:106)
          at org.apache.hadoop.ipc.RemoteException.unwrapRemoteException(RemoteException.java:73)
          at org.apache.hadoop.hdfs.DFSOutputStream.newStreamForCreate(DFSOutputStream.java:1730)
          at org.apache.hadoop.hdfs.DFSClient.create(DFSClient.java:1668)
          at org.apache.hadoop.hdfs.DFSClient.create(DFSClient.java:1593)
          at org.apache.hadoop.hdfs.DistributedFileSystem$6.doCall(DistributedFileSystem.java:397)
          at org.apache.hadoop.hdfs.DistributedFileSystem$6.doCall(DistributedFileSystem.java:393)
          at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
          at org.apache.hadoop.hdfs.DistributedFileSystem.create(DistributedFileSystem.java:393)
          at org.apache.hadoop.hdfs.DistributedFileSystem.create(DistributedFileSystem.java:337)
          at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:908)
          at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:889)
          at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:786)
          at org.apache.flink.runtime.fs.hdfs.HadoopFileSystem.create(HadoopFileSystem.java:405)
  </code></pre>
  
  <p>For some odd reason, Flink seems to try SIMPLE authentication, even though I called <code>loginUserFromKeytab</code>.  I found another similar issue on Stackoverflow (<a href="https://stackoverflow.com/questions/32085990/error-with-kerberos-authentication-when-executing-flink-example-code-on-yarn-clu">Error with Kerberos authentication when executing Flink example code on YARN cluster (Cloudera)</a>) which had an answer explaining that:</p>
  
  <blockquote>
    <p>Standalone Flink currently only supports accessing Kerberos secured HDFS if the user is authenticated on all worker nodes.</p>
  </blockquote>
  
  <p>That may mean that I have to do some authentication at the OS level e.g. with <code>kinit</code>. Since my knowledge of Kerberos is very limited I have no idea how I would do it. Also I would like to understand how the program running after <code>kinit</code> actually knows which Kerberos ticket to pick from the local cache when there is no configuration whatsoever regarding this.</p>