Hi Ben, and thank you for answering.
> > For frameworks in the same role on the other hand we choose to normalize > > with the allocated resources > > Within a role, the framework's share is evaluated using the *role*'s total > allocation as a denominator. Were you referring to the role's total > allocation when you said "allocated resources"? Yes. > I believe this was just to reflect the "total pool" we're sharing within. > For roles, we're sharing the total cluster as a pool. For frameworks within > a role, we're sharing the role's total allocation as a pool amongst the > frameworks. Make sense? Looking at the allocation loop, I see that while a role sorter uses the actual cluster resources when generating a sorting, we only seem to update the total in the picked framework sorter with an `add` at the end of the allocation loop, so at the very least the "total pool" of resources in a single role seems to lag. Should this update be moved to the top of the loop? > The sort ordering should be the same no matter which denominator you > choose, since everyone gets the same denominator. i.e. 1,2,3 are ordered > the same whether you're evaluating their share as 1/10,2/10,3/10 or > 1/100,2/100,3/100, etc. This seems to be only true if we have just a single resource kind. For multiple resource kinds we are not just dealing with a single scale factor, but will also end up comparing single-resource scales against each other in DRF. Here's a brief example of a cluster with two frameworks where we end up with different DRF weights `f` depending on whether the frameworks are in the same role or not. - Setup: * cluster total: cpus:40; mem:100; disk:1000 * cluster used: cpus:30; mem: 2; disk: 5 * framework 'a': used=cpus:20; mem:1; disk:1 * framework 'b': used=cpus:10; mem:1; disk:4 - both frameworks in separate roles * framework 'a', role 'A'; role shares: cpus:2/4; mem:1/100; disk:1/1000; f=2/4 * framework 'b', role 'B'; role shares: cpus:1/4; mem:1/100; disk:2/1000; f=1/4 - both frameworks in same role: * framework 'a': framework shares: cpus:2/3; mem:1/2; disk:1/4; f=1/2 * framework 'b': framework shares: cpus:1/3; mem:1/2; disk:4/5; f=4/5 If each framework is in its own role we would allocate the next resource to 'b'; if the frameworks are in the same role we would allocate to 'a' instead. This is what I meant with > It appears to me that by normalizing with the used resources inside a role > we somehow bias allocations inside a role against frameworks with “unusual” > usage vectors (relative to other frameworks in the same role). In this example we would penalize 'b' for having a usage vector very different from 'a' (here: along the `disk` axis). Benjamin
