Re: [HTCondor-users] priority and rank-based preemption

[Todd Tannenbaum <tannenba@xxxxxxxxxxx>]

On 2/15/2016 9:09 AM, Vladimir Brik wrote:
> Hello.
>
> How does condor decide which running job to preempt when a higher-rank
> job is submitted? More specifically, if all startds in our pool are
> configured to rank jobs of a certain user higher than everybody else,
> will condor preempt jobs with worst priority first?

Likely answer is yes, HTCondor will preempt jobs from users with the 
worst priority first due to the default value for the PREEMPTION_RANK 
knob.  But it is hard to say for certain without seeing all the inputs 
since almost nothing in HTCondor is hard-coded.

For all the slots that match a given job, the slots are sorted and then 
subsorted four more times (!) according to the below values:
  1. NEGOTIATOR_PRE_JOB_RANK (which by default looks at the startd RANK 
value)
  2. Rank expression from the job (i.e. what the submitter wants)
  3. NEGOTIATOR_POST_JOB_RANK
  4. preemption state (2=no preemption, 1=startd-rank-preempt, 
0=user-prio-preempt)
  5. PREEMPTION_RANK (if preempting)
So the slots are first sorted by the NEGOTIATOR_PRE_JOB_RANK expression, 
then sub-sorted by the rank from the job, etc.  The slot with the 
highest sort score is the one selected (i.e. the higher the value, the 
"better" the match).

You can view the current settings for the above knobs via the following 
command on your central manager:

condor_config_val -v NEGOTIATOR_PRE_JOB_RANK NEGOTIATOR_POST_JOB_RANK 
PREEMPTION_RANK

Hope this helps,
regards,
Todd