public AsyncMasterRequestRpcRetryingCaller<T> build() {
      preCheck();
      return new AsyncMasterRequestRpcRetryingCaller<T>(retryTimer, conn, callable, priority,
        pauseNs, pauseNsForServerOverloaded, maxAttempts, operationTimeoutNs, rpcTimeoutNs,
        startLogErrorsCnt);
    }
Create retry caller for scanning a region.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncRpcRetryingCallerFactory.java