public MasterRequestCallerBuilder<T> pauseForServerOverloaded(long pause, TimeUnit unit) {
      this.pauseNsForServerOverloaded = unit.toNanos(pause);
      return this;
    }
Create retry caller for scanning a region.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncRpcRetryingCallerFactory.java