Should this be:

ray start --labels-file labels.txt

Or more specifically it should be an absolute path

ray start --labels-file /path/to/labels.yaml

I started implementing it here: https://github.com/ray-project/ray/pull/51706/files as --labels-from-file (I need to update the name) where it just sources the contents of the file with $(cat labels.txt) and expects a string. If we want to read directly from a file instead I can change it. Should we support both txt and yaml files (I guess both would be expected in yaml format)?

If we just want to source from a file with cat labels.txt we don't need to add anything inside of Ray -- bash does the trick :)

Andrew mentioned it'd be better to support reading YAML files for the "downward" API, that's the impetus for supporting --labels-file explicitly.

yeah agreed, $(cat labels.txt) is perfectly fine, but you would pass that into ray start --labels, not --labels-file was my point.

So if I understand correctly, for the string input, no matter if it is specified in the command or if it is sourcing from a file, we want to use the --labels. And in both cases, we expects the input format to be key1=value1,key2=value2.

And at the same time, if we want to support using "downward" API with yamal file as well, the idea is either to have a --labels-file option and pass in the yaml file name so that ray start can read the file directory, or more simply, just use the --labels options and add the file read & translation logic outside of the ray logic.

And I believe we can always start from the simpler solution. Is that right?

Ahh I see, I was expecting --labels-file to source from the file but just to expect the string in yaml format (so both options would take a string but then parse them from different formats). I updated the REP to reflect reading directly from a file in 3c444e7. I'll update ray-project/ray#51706 to that implementation as well.