private void closeBatch() {
    batch.close();
    batchMetrics.updateBatchDuration(clock.nanoTime() - batchOpenTimestamp);
  }
@param operation The Put/Delete/Update operation to be added to the batch.
@return A {@link CompletableFuture} to indicate whether the operation is finished.
samza-core/src/main/java/org/apache/samza/table/batching/BatchProcessor.java