public IsRpcThrottleEnabledResponse isRpcThrottleEnabled(IsRpcThrottleEnabledRequest request)
    throws IOException {
    if (initialized) {
      masterServices.getMasterCoprocessorHost().preIsRpcThrottleEnabled();
      boolean enabled = isRpcThrottleEnabled();
      IsRpcThrottleEnabledResponse response =
        IsRpcThrottleEnabledResponse.newBuilder().setRpcThrottleEnabled(enabled).build();
      masterServices.getMasterCoprocessorHost().postIsRpcThrottleEnabled(enabled);
      return response;
    } else {
      LOG.warn("Skip get rpc throttle because rpc quota is disabled");
      return IsRpcThrottleEnabledResponse.newBuilder().setRpcThrottleEnabled(false).build();
    }
  }
Master Quota Manager. It is responsible for initialize the quota table on the first-run and
provide the admin operations to interact with the quota table. TODO: FUTURE: The master will be
responsible to notify each RS of quota changes and it will do the "quota aggregation" when the
QuotaScope is CLUSTER.
hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/MasterQuotaManager.java