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https://issues.apache.org/jira/browse/YARN-4477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15067629#comment-15067629
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Arun Suresh commented on YARN-4477:
-----------------------------------
Thanks for updating the patch [~Tao Jie].
Verified that the tests run fine locally..
committed to trunk, branch-2 and branch-2.8
> FairScheduler: Handle condition which can result in an infinite loop in
> attemptScheduling.
> ------------------------------------------------------------------------------------------
>
> Key: YARN-4477
> URL: https://issues.apache.org/jira/browse/YARN-4477
> Project: Hadoop YARN
> Issue Type: Bug
> Components: fairscheduler
> Reporter: Tao Jie
> Assignee: Tao Jie
> Fix For: 2.8.0
>
> Attachments: YARN-4477.001.patch, YARN-4477.002.patch,
> YARN-4477.003.patch, YARN-4477.004.patch
>
>
> This problem is introduced by YARN-4270 which add limitation on reservation.
> In FSAppAttempt.reserve():
> {code}
> if (!reservationExceedsThreshold(node, type)) {
> LOG.info("Making reservation: node=" + node.getNodeName() +
> " app_id=" + getApplicationId());
> if (!alreadyReserved) {
> getMetrics().reserveResource(getUser(), container.getResource());
> RMContainer rmContainer =
> super.reserve(node, priority, null, container);
> node.reserveResource(this, priority, rmContainer);
> setReservation(node);
> } else {
> RMContainer rmContainer = node.getReservedContainer();
> super.reserve(node, priority, rmContainer, container);
> node.reserveResource(this, priority, rmContainer);
> setReservation(node);
> }
> }
> {code}
> If reservation over threshod, current node will not set reservation.
> But in attemptScheduling in FairSheduler:
> {code}
> while (node.getReservedContainer() == null) {
> boolean assignedContainer = false;
> if (!queueMgr.getRootQueue().assignContainer(node).equals(
> Resources.none())) {
> assignedContainers++;
> assignedContainer = true;
>
> }
>
> if (!assignedContainer) { break; }
> if (!assignMultiple) { break; }
> if ((assignedContainers >= maxAssign) && (maxAssign > 0)) { break; }
> }
> {code}
> assignContainer(node) still return FairScheduler.CONTAINER_RESERVED, which not
> equals to Resources.none().
> As a result, if multiple assign is enabled and maxAssign is unlimited, this
> while loop would never break.
> I suppose that assignContainer(node) should return Resource.none rather than
> CONTAINER_RESERVED when the attempt doesn't take the reservation because of
> the limitation.
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