@Override
  public void onConfigurationChange(Configuration newConf) {
    ThroughputController old = this.flushThroughputController;
    if (old != null) {
      old.stop("configuration change");
    }
    this.flushThroughputController = FlushThroughputControllerFactory.create(this, newConf);
    try {
      Superusers.initialize(newConf);
    } catch (IOException e) {
      LOG.warn("Failed to initialize SuperUsers on reloading of the configuration");
    }

    // update region server coprocessor if the configuration has changed.
    if (
      CoprocessorConfigurationUtil.checkConfigurationChange(getConfiguration(), newConf,
        CoprocessorHost.REGIONSERVER_COPROCESSOR_CONF_KEY)
    ) {
      LOG.info("Update region server coprocessors because the configuration has changed");
      this.rsHost = new RegionServerCoprocessorHost(this, newConf);
    }
  }
For testing
@return whether all wal roll request finished for this regionserver
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java