code: public BatcherBuilder bufferSize(int bufferSize) {
          checkState(this.maxBufferSize == UNSET_INT, "Max buffer size already set to %d", this.maxBufferSize);
          checkArgument(bufferSize > 0, "Required to have a buffer size greater than 0");
          this.maxBufferSize = bufferSize;
          return this;
      }
docs: Bound the buffer size used by the batchers.  By specifying a max size, the {@link Batcher}
  will allow producers to start blocking when adding data to the batcher.  Producers can determine how to handle
  a full buffer using one of the {@link Batcher}'s add methods.  By default the buffer size is unbounded.