IllegalArgumentException in LifelineSender

while (shouldRun()) {
     try {
        if (lifelineNamenode == null) {
          lifelineNamenode = dn.connectToLifelineNN(lifelineNnAddr);
        }
        sendLifelineIfDue();
        Thread.sleep(scheduler.getLifelineWaitTime());
      } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
      } catch (IOException e) {
        LOG.warn("IOException in LifelineSender for " + BPServiceActor.this, e);
     }
}