@Override
      public void stop(String why) {
        isStopped = true;
      }
A utility to store user specific HConnections in memory. There is a chore to clean up connections
idle for too long. This class is used by REST server and Thrift server to support authentication
and impersonation.
hbase-server/src/main/java/org/apache/hadoop/hbase/util/ConnectionCache.java