Why Impala Admission Control root.[username] is not recommended?

[#1]

Hi,

I'm setting up Impala Admission Control.

For the user.<username> placement rules, there is "Not recommended" remark "Use the resource pool that matches the username. (Not Recommended)"

(https://www.cloudera.com/documentation/enterprise/5-16-x/topics/cm_mc_resource_pools.html)

In my use-case, specific limitation for a set (a dozen) of users should be applied. At the same time the group management is relatively hard, therefore, I would prefer the root.[username] approach.

I would like to better understand the drawbacks of this approach: are there any technical limitations from Impala point of view, or it is just a bad practice due to it is harder to maintain&support&manage (from Administrator's perspective)?

[#2 · Accepted solution]

If you have more than a handful of users it becomes difficult to manage the large number of pools. Resource limits are also of limited use - you can limit the total consumption per user, but you can't guarantee that any group of users gets memory.