code: private boolean changeRequestedSessionId( final Request request, final Response response ) {
          /*
           * Check for session relocation only if a session id was requested
           */
          if ( request.getRequestedSessionId() != null ) {
  
          	String newSessionId = _sessionBackupService.changeSessionIdOnTomcatFailover( request.getRequestedSessionId() );
          	if ( newSessionId == null ) {
                  newSessionId = _sessionBackupService.changeSessionIdOnMemcachedFailover( request.getRequestedSessionId() );
              }
  
              if ( newSessionId != null ) {
                  request.changeSessionId( newSessionId );
                  return true;
              }
  
          }
          return false;
      }
docs: If there's a session for a requested session id that is taken over (tomcat failover) or
  that will be relocated (memcached failover), the new session id will be set (via {@link Request#changeSessionId(String)}).
  
  @param request the request
  @param response the response
  
  @return <code>true</code> if the id of a valid session was changed.
  
  @see Request#changeSessionId(String)