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https://issues.apache.org/jira/browse/YARN-10295?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Szilard Nemeth updated YARN-10295:
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Fix Version/s: 3.2.2
> CapacityScheduler NPE can cause apps to get stuck without resources
> -------------------------------------------------------------------
>
> Key: YARN-10295
> URL: https://issues.apache.org/jira/browse/YARN-10295
> Project: Hadoop YARN
> Issue Type: Bug
> Components: capacityscheduler
> Affects Versions: 3.1.0, 3.2.0
> Reporter: Benjamin Teke
> Assignee: Benjamin Teke
> Priority: Major
> Fix For: 3.2.2, 3.1.5
>
> Attachments: YARN-10295.001.branch-3.1.patch,
> YARN-10295.001.branch-3.2.patch, YARN-10295.002.branch-3.1.patch,
> YARN-10295.002.branch-3.2.patch
>
>
> When the CapacityScheduler Asynchronous scheduling is enabled and log level
> is set to DEBUG there is an edge-case where a NullPointerException can cause
> the scheduler thread to exit and the apps to get stuck without allocated
> resources. Consider the following log:
> {code:java}
> 2020-05-27 10:13:49,106 INFO fica.FiCaSchedulerApp
> (FiCaSchedulerApp.java:apply(681)) - Reserved
> container=container_e10_1590502305306_0660_01_000115, on node=host:
> ctr-e148-1588963324989-31443-01-000002.hwx.site:25454 #containers=14
> available=<memory:2048, vCores:11> used=<memory:182272, vCores:14> with
> resource=<memory:4096, vCores:1>
> 2020-05-27 10:13:49,134 INFO fica.FiCaSchedulerApp
> (FiCaSchedulerApp.java:internalUnreserve(743)) - Application
> application_1590502305306_0660 unreserved on node host:
> ctr-e148-1588963324989-31443-01-000002.hwx.site:25454 #containers=14
> available=<memory:2048, vCores:11> used=<memory:182272, vCores:14>, currently
> has 0 at priority 11; currentReservation <memory:0, vCores:0> on node-label=
> 2020-05-27 10:13:49,134 INFO capacity.CapacityScheduler
> (CapacityScheduler.java:tryCommit(3042)) - Allocation proposal accepted
> 2020-05-27 10:13:49,163 ERROR yarn.YarnUncaughtExceptionHandler
> (YarnUncaughtExceptionHandler.java:uncaughtException(68)) - Thread
> Thread[Thread-4953,5,main] threw an Exception.
> java.lang.NullPointerException
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityScheduler.allocateContainerOnSingleNode(CapacityScheduler.java:1580)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityScheduler.allocateContainersToNode(CapacityScheduler.java:1767)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityScheduler.allocateContainersToNode(CapacityScheduler.java:1505)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityScheduler.schedule(CapacityScheduler.java:546)
> at
> org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityScheduler$AsyncScheduleThread.run(CapacityScheduler.java:593)
> {code}
> A container gets allocated on a host, but the host doesn't have enough
> memory, so after a short while it gets unreserved. However because the
> scheduler thread is running asynchronously it might have entered into the
> following if block located in
> [CapacityScheduler.java#L1602|https://github.com/apache/hadoop/blob/7136ebbb7aa197717619c23a841d28f1c46ad40b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/CapacityScheduler.java#L1602],
> because at the time _node.getReservedContainer()_ wasn't null. Calling it a
> second time for getting the ApplicationAttemptId would be an NPE, as the
> container got unreserved in the meantime.
> {code:java}
> // Do not schedule if there are any reservations to fulfill on the node
> if (node.getReservedContainer() != null) {
> if (LOG.isDebugEnabled()) {
> LOG.debug("Skipping scheduling since node " + node.getNodeID()
> + " is reserved by application " + node.getReservedContainer()
> .getContainerId().getApplicationAttemptId());
> }
> return null;
> }
> {code}
> A fix would be to store the container object before the if block.
> Only branch-3.1/3.2 is affected, because the newer branches have YARN-9664
> which indirectly fixed this.
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