Upcoming allocator change to clusters using oversubscribed resources with quota under DRF

[Meng Zhu <mz...@mesosphere.com>]

Folks:

If you are not using oversubscribed resources
<http://mesos.apache.org/documentation/latest/oversubscription/#oversubscription>
along
with quota under DRF (all three at the same time), read no further. Just
stay tuned for the upcoming shiny new allocator with decoupled quota
guarantees and limits :)

OK, for the rest of you, you are truly advanced users! Here is the news.

As part of the tech debt cleanup in the allocator, we plan to remove the
quota role sorter in the allocator and only keep a single role sorter for
all the roles.This would simplify the allocator logic to help speedup
feature development.

This will result in one behavior change if you are using oversubscribed
resources with quota under DRF. Previously, in the quota allocation stage,
revocable resources are counted towards *neither* the total resource pool
*nor* a role’s allocated resources when sorting with DRF. This is arguably
the right behavior. However, after the aforementioned removal, all
resources, both revocable and non-revocable ones, will be counted when
calculating DRF shares in the quota allocation stage. This means, for a
quota role that also consumes a lot of revocable resources but no-so-much
non-revocable ones, previously it would be sorted towards the head of the
queue, now it is likely to be sorted towards the tail of the queue.

If you have concerns over this behavior change, feel free to chime in and
reach out.

Link to the ticket: MESOS-9802
<https://issues.apache.org/jira/browse/MESOS-9802>

-Meng