Mini tasks as output files

[btovar]

Currently only local files and buffers can be used as output files. This is because they act the same regardless of the direction of the data (e.g., the local file just needs the path to the file).

With mini task based declarations, such as declare_chirp or declare_xrootd, there is the possibility of having output files. E.g., instead of chirp_get we would use chirp_put, and instead of xrdcp server//file local.file', we would do xrdcp local.file server//file`. This means that such declarations need two mini tasks commands that get selected according to the function of the file.

Some things to consider:

• Should such files be composed of two mini tasks? E.g., have a new file type which is an aggregate of other files. This may be a powerful abstraction to switch the file instantiation according to the context.
• When does the output transfer happen? I.e.:
  • As part of the task, and if the transfer fails then the task fails.
  • When commanded by the manager. The manager can block until the transfer happens, or may continue and wait for cache-update type of message.