Consider this sequence of events:
1. Slave connects, with 128MB of disk.
2. Master offers resources at slave to framework
3. Framework creates a dynamic reservation for 1MB and a persistent volume of the same size on the slave's resources.
=> This invokes Master::apply, which invokes allocator->updateAllocation, which invokes Sorter::update() on the framework sorter and role sorter. If the framework's role has a configured quota, it also invokes update on the quota role sorter – in this case, the framework's role has no quota, so the quota role sorter is not updated.
=> DRFSorter::update updates the total resources at a given slave, among updating other state. New total resources will be 127MB of unreserved disk and 1MB of reserved disk with a volume. Note that the quota role sorter still thinks the slave has 128MB of unreserved disk.
4. The slave is removed from the cluster. HierarchicalAllocatorProcess::removeSlave invokes:
slaves[slaveId].total.nonRevocable() is 127MB of unreserved disk and 1MB of reserved disk with a volume. When we remove this from the quota role sorter, we're left with total resources on the reserved slave of 1MB of unreserved disk, since that is the result of subtracting <127MB unreserved, 1MB reserved+volume> from <128MB unreserved>.
The implications of this can't be good: at minimum, we're leaking resources for removed slaves in the quota role sorter. We're also introducing an inconsistency between total_.resources[slaveId] and total_.scalarQuantities, since the latter has already stripped-out volume/reservation information.