I apologize if this is spelled out somewhere in the documentation. There is a certain amount of fuzzyness around the notion of a FlowFile. Is this really always a file? or is it a "document" or an "item" which may have a link to an actual file / byte content, whether on disk or elsewhere? My noob-level understanding is that it's the latter - could someone confirm?
Furthermore, when data is moving between Processors in a Dataflow, how is that done? Is the data streamed in memory? Is there a spill-to-disk option to configure how disk spillage would be done? Or do FlowFiles always get written to disk prior to being sent to the next destination? I would think that persisting to disk after every step would be quite expensive. Is that simply not what NiFi does? Thanks.
