[jira] [Created] (YUNIKORN-2370) Handle events when headroom checks fail on a per-request basis

["Peter Bacsko (Jira)" <ji...@apache.org>]

Peter Bacsko created YUNIKORN-2370:
--------------------------------------

             Summary: Handle events when headroom checks fail on a per-request basis
                 Key: YUNIKORN-2370
                 URL: https://issues.apache.org/jira/browse/YUNIKORN-2370
             Project: Apache YuniKorn
          Issue Type: Sub-task
          Components: core - scheduler
            Reporter: Peter Bacsko


Currently, we have this code inside tryAllocate:

{noformat}
unc (sa *Application) tryAllocate(headRoom *resources.Resource, allowPreemption bool, preemptionDelay time.Duration, preemptAttemptsRemaining *int, nodeIterator func() NodeIterator, fullNodeIterator func() NodeIterator, getNodeFn func(string) *Node) *Allocation {
	sa.Lock()
	defer sa.Unlock()
	if sa.sortedRequests == nil {
		return nil
	}
	// calculate the users' headroom, includes group check which requires the applicationID
	userHeadroom := ugm.GetUserManager().Headroom(sa.queuePath, sa.ApplicationID, sa.user)
	// get all the requests from the app sorted in order
	for _, request := range sa.sortedRequests {
		if request.GetPendingAskRepeat() == 0 {
			continue
		}
		// check if there is a replacement possible
		if sa.canReplace(request) {
			continue
		}
		// check if this fits in the users' headroom first, if that fits check the queues' headroom
		// NOTE: preemption most likely will not help in this case. The chance that preemption helps is mall
		// as the preempted allocation must be for the same user in a different queue in the hierarchy...
		if !userHeadroom.FitInMaxUndef(request.GetAllocatedResource()) {
			continue
		}

		// resource must fit in headroom otherwise skip the request (unless preemption could help)
		if !headRoom.FitInMaxUndef(request.GetAllocatedResource()) {
			// attempt preemption
			if allowPreemption && *preemptAttemptsRemaining > 0 {
				*preemptAttemptsRemaining--
				fullIterator := fullNodeIterator()
				if fullIterator != nil {
					if alloc, ok := sa.tryPreemption(headRoom, preemptionDelay, request, fullIterator, false); ok {
						// preemption occurred, and possibly reservation
						return alloc
					}
				}
			}
			sa.appEvents.sendAppDoesNotFitEvent(request, headRoom)   <--- event
			continue
		}
{noformat}

There are issues with this approach:
1. We say "the application doesn't fit" while it's really the request that doesn't fit.
2. If there's no quota at all, then a request gets its own event, but the rest doesn't.

Suggested approach:
1. Have a per-request event
2. When an event is sent (eg. failed user headroom) for a given request, remember it and don't send it anymore



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