title: Hadoop keytab authentication not considering jaas configurations
body: <p>I have a spring boot app connecting to Hadoop hive. Kerberos authentication is used. The setup works perfectly. </p>
  
  <p>Now, I am trying to expose an actuator endpoint which can tell me the kerb tickets validity info. </p>
  
  <p>To access the kerb tickets I tried a few ways and after some debugging, I found when the login is via keytab, Hadoop configuration doesn't consider the jaas.conf file I am supplying. In fact, it doesn't consider any jaas configuration, even the ones from env except the debug flag. Is there any specific reason for this implementation? I am trying to force the login module to use a ticket cache somehow. Tried setting default cache names in conf file and env variables. Since the Hadoop configuration doesn't populate these into the login options, the <code>Krb5LoginModule</code> class doesn't use a ticket cache. </p>
  
  <p>The maven dependency I use for Hadoop connectivity is hadoop-commons, v2.7.0.
  The login happens through <code>UserGroupInformation.loginUserFromKeytab</code></p>
  
  <p>PS: the account for login is a system account and my app runs on cloud foundry. So native OS login is not an option. </p>
  
  <p>TIA</p>