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Posted to issues@yunikorn.apache.org by "Kishan Ghetia (Jira)" <ji...@apache.org> on 2026/08/25 09:49:00 UTC
[jira] [Commented] (YUNIKORN-3406) Support queue-headroom-based limits for application unschedulable backoff
[ https://issues.apache.org/jira/browse/YUNIKORN-3406?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18107805#comment-18107805 ]
Kishan Ghetia commented on YUNIKORN-3406:
-----------------------------------------
Relevant discussion over Slack - [https://yunikornworkspace.slack.com/archives/CLNUW68MU/p1787633160295699]
> Support queue-headroom-based limits for application unschedulable backoff
> -------------------------------------------------------------------------
>
> Key: YUNIKORN-3406
> URL: https://issues.apache.org/jira/browse/YUNIKORN-3406
> Project: Apache YuniKorn
> Issue Type: Improvement
> Components: core - scheduler
> Reporter: Kishan Ghetia
> Priority: Major
>
> Application.tryAllocate() currently stops after a fixed number of unschedulable asks. For example with config:
> application.unschedasks.backoff: "50"
> application.unschedasks.backoff.delay: "5s"
> With large Spark executor bursts, the queue may have quota for more than 50 asks, but later asks are not marked {{SchedulingAttempted}} before the application backs off. Consequently, the outstanding-request scan cannot mark those pods {{{}Unschedulable{}}}, delaying autoscaling even though queue quota is available.
> Proposal: add an option for {{tryAllocate()}} to use the remaining queue quota/headroom as the unschedulable-ask limit. It should attempt enough sorted requests to fill the available queue quota, using the same effective limit as outstanding-request marking, and then apply the existing application backoff.
> This preserves the backoff’s protection against unbounded node and predicate checks while exposing all autoscaling demand that the queue can currently accept.
> Acceptance criteria:
> * When queue headroom supports more than the fixed count, enough asks are attempted to fill that headroom.
> * Asks beyond available queue headroom are not exposed for autoscaling.
> * Existing backoff behavior remains after the quota-based limit is reached.
> * Tests cover more than 50 asks and mixed request sizes.
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