code: public void markServerDown(SuroConnection connection) {
          if (connection != null) {
              lb.markServerDown(connection.getServer());
              removeConnection(new ImmutableSet.Builder<Server>().add(connection.getServer()).build());
          }
      }
docs: Mark up the server related with the connection as down
  When the client fails to communicate with the connection,
  this method should be called to remove the server from the pool
  @param connection