private void initSessionImplClassName() {
    this.sessionImplclassName = hiveConf.getVar(ConfVars.HIVE_SESSION_IMPL_CLASSNAME);
    this.sessionImplWithUGIclassName = hiveConf.getVar(ConfVars.HIVE_SESSION_IMPL_WITH_UGI_CLASSNAME);
  }
The lock that synchronizes the allowSessions flag and handleToSession map.
      Active-passive HA first disables the connections, then closes existing one, making sure
      there are no races between these two processes.
service/src/java/org/apache/hive/service/cli/session/SessionManager.java