@Override
  public void disconnect(String connectionId) {
    SelectionKey key = this.keyMap.get(connectionId);
    if (key != null) {
      key.cancel();
    }
  }
Disconnect any connections for the given id (if there are any). The disconnection is asynchronous and will not be
processed until the next {@link #poll(long) poll()} call.
ambry-network/src/main/java/com/github/ambry/network/Selector.java