@Override
  public void wakeup() {
    selector.wakeup();
  }
Wake up the SocketNetworkClient if it is within a {@link #sendAndPoll(List, Set, int)} sleep. This wakes
up the {@link Selector}, which in turn wakes up the {@link java.nio.channels.Selector}.
<br>
@see java.nio.channels.Selector#wakeup()
ambry-network/src/main/java/com/github/ambry/network/SocketNetworkClient.java