title: WSO2 NPE Cannot initialize / load logging configuration from the registry
body: <p>We have an AS 5.3.0 cluster with 3 nodes, a manager and 2 workers; we're trying to use this functionality: <i>"update logging configuration through the manager web console for all the nodes of the cluster"</i>, frequently when we make an update from the web console, we get registered an error in the log of one worker (just until now in only one worker) saying:
  <br><br></p>
  
  <pre><code>TID: [-1234] [] [2016-03-22 09:52:14,753] ERROR
  {org.wso2.carbon.logging.service.sync.LoggingConfigSyncRequest} - Cannot load logging configuration from the registry {org.wso2.carbon.logging.service.sync.LoggingConfigSyncRequest}
  
  java.lang.NullPointerException
  at org.wso2.carbon.logging.service.util.LoggingUtil.getAppenderFromSet(LoggingUtil.java:331)
  at org.wso2.carbon.logging.service.util.LoggingUtil.loadCustomConfiguration(LoggingUtil.java:274)
  at org.wso2.carbon.logging.service.sync.LoggingConfigSyncRequest.execute(LoggingConfigSyncRequest.java:56)
  at org.wso2.carbon.core.clustering.hazelcast.HazelcastClusterMessageListener.onMessage(HazelcastClusterMessageListener.java:54)
  at com.hazelcast.topic.impl.TopicService.dispatchEvent(TopicService.java:138)
  at com.hazelcast.spi.impl.eventservice.impl.EventPacketProcessor.process(EventPacketProcessor.java:52)
  at com.hazelcast.spi.impl.eventservice.impl.RemoteEventPacketProcessor.run(RemoteEventPacketProcessor.java:38)
  at com.hazelcast.util.executor.StripedExecutor$Worker.process(StripedExecutor.java:190)
  at com.hazelcast.util.executor.StripedExecutor$Worker.run(StripedExecutor.java:174)
  and this error occurred exactly after this event:
  TID: [-1] [] [2016-03-22 09:52:14,598] INFO
  {org.wso2.carbon.core.clustering.hazelcast.HazelcastClusterMessageListener} - Received ClusteringMessage: LoggingConfigSyncRequest{messageId=8ffd145d-bca7-4c50-88b9-1ffceab02031} {org.wso2.carbon.core.clustering.hazelcast.HazelcastClusterMessageListener}
  </code></pre>
  
  <p><br><br>
  sometimes, when we restart the worker reporting the error the issue disappears and everything works fine but sometimes when we restart that worker, we get registered an error similar to the one described above and in this case saying "Cannot initialize logging configuration"; if the server starts registering this message, all the requests made to sync the logging configuration will register an error saying it cannot load the logging configuration from the registry; also we discovered that the error saying ...cannot load logging configuration from the registry is not always associated to the error registered starting the server.
  <br><br>
  We have not identified yet what is the root cause of this issue and how to make it shows up.
  <br><br>
  We have tested this locally in a laptop using ubuntu 14.04 and MySQL and also in a formal dev environment using RedHat 5.11 and Oracle; the result is exactly the same.
  <br><br>
  We are concerned by the fact when the error arises in one worker, that server does not apply the changes we are requesting in any way.
  <br>
  <br>
  Any help would be greatly appreciated, thanks in advance</p>