"nova-manage db online_data_migrations" exit code is strange

[Chris Friesen]

If I'm reading the code right, the return value for "nova-manage db online_data_migrations" will be 1 if we actually performed some migrations and 0 if we performed no migrations, either because there were no remaining migrations or because the migration code raised an exception.

This seems less than useful for someone attempting to script repeated calls to this with --max-count set. The caller needs to parse the output to determine whether or not it was successful.

I think it would make more sense to have the return code as follows:

0 -- no errors and completed
1 -- one of the migrations raised an exception, needs manual action
2 -- no errors but not yet complete, need to call again

since it would allow for an automated retry based solely on the exit code.

At the very least, the return code should be nonzero for the case where one of the migrations raised an exception, and 0 for the case where no exception was raised.

[Sylvain Bauza (sylvain-bauza)]

Chris, I'm not seeing this as a bug, rather some possible code improvement. Closing it as Invalid/Wishlist and just open a change for reviews, that's it :-)