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https://issues.apache.org/jira/browse/YARN-7591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16274710#comment-16274710
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Wangda Tan commented on YARN-7591:
----------------------------------
Thanks [~Tao Yang],
Rest of the fixes looks good except #3:
bq. (3) If proposal1 (allocate containerX on node1) and proposal2 (reserve
containerY on node1) were generated by different async-scheduling threads
around the same time and proposal2 was submitted in front of proposal1, NPE is
raised when trying to submit proposal2 in
FiCaSchedulerApp#commonCheckContainerAllocation.
When I check the implementation:
{code}
if (null == rmContainer) {
return null;
}
FiCaSchedulerApp app = getApplicationAttempt(
rmContainer.getApplicationAttemptId());
if (null == app) {
return null;
}
NodeId nodeId;
// Get nodeId
if (rmContainer.getState() == RMContainerState.RESERVED) {
nodeId = rmContainer.getReservedNode();
} else{
nodeId = rmContainer.getNodeId();
}
FiCaSchedulerNode node = getNode(nodeId);
if (null == node) {
return null;
}
{code}
I'm still not sure why commit reserved container before allocate container can
result in NPE? And could you add such explanations to the code as well so we
can understand why the additional null check is required.
> NPE in async-scheduling mode of CapacityScheduler
> -------------------------------------------------
>
> Key: YARN-7591
> URL: https://issues.apache.org/jira/browse/YARN-7591
> Project: Hadoop YARN
> Issue Type: Bug
> Components: capacityscheduler
> Affects Versions: 3.0.0-alpha4, 2.9.1
> Reporter: Tao Yang
> Assignee: Tao Yang
> Priority: Critical
> Attachments: YARN-7591.001.patch
>
>
> Currently in async-scheduling mode of CapacityScheduler, NPE may be raised in
> special scenarios as below.
> (1) The user should be removed after its last application finished, NPE may
> be raised if getting something from user object without the null check in
> async-scheduling threads.
> (2) NPE may be raised when trying fulfill reservation for a finished
> application in {{CapacityScheduler#allocateContainerOnSingleNode}}.
> {code}
> RMContainer reservedContainer = node.getReservedContainer();
> if (reservedContainer != null) {
> FiCaSchedulerApp reservedApplication = getCurrentAttemptForContainer(
> reservedContainer.getContainerId());
> // NPE here: reservedApplication could be null after this application
> finished
> // Try to fulfill the reservation
> LOG.info(
> "Trying to fulfill reservation for application " +
> reservedApplication
> .getApplicationId() + " on node: " + node.getNodeID());
> {code}
> (3) If proposal1 (allocate containerX on node1) and proposal2 (reserve
> containerY on node1) were generated by different async-scheduling threads
> around the same time and proposal2 was submitted in front of proposal1, NPE
> is raised when trying to submit proposal2 in
> {{FiCaSchedulerApp#commonCheckContainerAllocation}}.
> {code}
> if (reservedContainerOnNode != null) {
> // NPE here: allocation.getAllocateFromReservedContainer() should be
> null for proposal2 in this case
> RMContainer fromReservedContainer =
> allocation.getAllocateFromReservedContainer().getRmContainer();
> if (fromReservedContainer != reservedContainerOnNode) {
> if (LOG.isDebugEnabled()) {
> LOG.debug(
> "Try to allocate from a non-existed reserved container");
> }
> return false;
> }
> }
> {code}
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