title: Resource Manager UI is throwing 500 Internal server Error
body: <p>I have a cluster with 1 Master and 1 Slave. My Cluster was working fine and suddenly I started to get following error due to which my Resource manager UI is not loading up:</p>
  
  <pre><code>HTTP ERROR 500
  
  Problem accessing /cluster. Reason:
  
      INTERNAL_SERVER_ERROR
  Caused by:
  
  java.lang.NullPointerException
      at org.apache.http.client.utils.URLEncodedUtils.parse(URLEncodedUtils.java:235)
      at org.apache.hadoop.security.token.delegation.web.ServletUtils.getParameter(ServletUtils.java:48)
      at org.apache.hadoop.security.token.delegation.web.DelegationTokenAuthenticationHandler.managementOperation(DelegationTokenAuthenticationHandler.java:170)
      at org.apache.hadoop.security.authentication.server.AuthenticationFilter.doFilter(AuthenticationFilter.java:502)
      at org.apache.hadoop.yarn.server.security.http.RMAuthenticationFilter.doFilter(RMAuthenticationFilter.java:84)
      at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
      at org.apache.hadoop.http.HttpServer2$QuotingInputFilter.doFilter(HttpServer2.java:1224)
      at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
      at org.apache.hadoop.http.NoCacheFilter.doFilter(NoCacheFilter.java:45)
      at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
      at org.apache.hadoop.http.NoCacheFilter.doFilter(NoCacheFilter.java:45)
      at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
      at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:399)
      at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
      at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
      at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
      at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:450)
      at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
      at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
      at org.mortbay.jetty.Server.handle(Server.java:326)
      at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
      at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:928)
      at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:549)
      at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
      at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
      at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)
      at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
  </code></pre>
  
  <p>If i try to check the daemons running, I can see that RM daemon is running as per:</p>
  
  <pre><code>[hadoop@cluster-test hadoop]$ jps
  22263 Jps
  21549 NameNode
  21888 ResourceManager
  21733 SecondaryNameNode
  </code></pre>
  
  <p>I also got following error logs in my RM logs but these error does not pop up too often. I am not sure if these issues are related. Thought of sharing here as this might be helpful for people who may take a look at the question:</p>
  
  <pre><code>2016-07-05 17:41:49,878 ERROR   org.apache.hadoop.yarn.server.resourcemanager.ResourceManager: RECEIVED SIGNAL   15: SIGTERM
  2016-07-05 17:41:49,884 ERROR  org.apache.hadoop.security.token.delegation.AbstractDelegationTokenSecretManager : ExpiredTokenRemover received java.lang.InterruptedException: sleep interrupted
  </code></pre>
  
  <p>I am using following hadoop version:</p>
  
  <pre><code>Hadoop 2.6.0
  Subversion https://git-wip-us.apache.org/repos/asf/hadoop.git -r    e3496499ecb8d220fba99dc5ed4c99c8f9e33bb1
  Compiled by jenkins on 2014-11-13T21:10Z
  Compiled with protoc 2.5.0
  </code></pre>
  
  <p>Please help as I have been stuck with it for a quite long time and not able to get much help from google.</p>
  
  <p>Any help is very much appreciated!</p>