Add plan affinity #193
Description
If we have data sources which download files which may need to be cached, then it is important to have some concept of affinity, meaning a particular task which may be responsible for downloading that file always routes to the same node.
We could introduce an extension (similar to NetworkBoundaryExt) called affinity() which lets nodes specify their affinity. Some open questions
- What happens if two nodes in the same task have different affinities?
- How this might interact with any load balancing mechanism which we may or may not have in the future?