Maintaining tight accounting group quota usage with preemption

Many metrics in a distributed system should be viewed over time. However, desires are often for instantaneous views. Take for example usage data.

Usage data in Condor is commonly viewed through accounting groups. Accounting groups can be given quotas that specify what percent of a pool each can use.

Instead of viewing accounting group usage summed over a week or a day or even hours, it is common to want any snapshot of usage to match configured quotas. At the same time, it is common to want accounting groups to exceed their quota if resources are available. These two desires are at odds.

Erik Erlandson has written about how to use preemption to maintain tight accounting group quota usage.

Instantaneous views should not be relied on, but with preemption it is possible to reduce the window you sum over.

Now, if preemption is not an option, the desire to see usage snapshots matching configured quotas must be abandoned.

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