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https://issues.apache.org/jira/browse/YARN-11813?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Benjamin Teke resolved YARN-11813.
----------------------------------
Hadoop Flags: Reviewed
Target Version/s: 3.5.0
Resolution: Fixed
> YARN incorrectly falls back to cgroup v1 when cgroup v2 has v1 named
> subhierarchies
> -----------------------------------------------------------------------------------
>
> Key: YARN-11813
> URL: https://issues.apache.org/jira/browse/YARN-11813
> Project: Hadoop YARN
> Issue Type: Sub-task
> Reporter: Benjamin Teke
> Assignee: Benjamin Teke
> Priority: Major
> Labels: pull-request-available
>
> YARN-11743 introduced a fallback behaviour, where if a controller is not
> mounted in v1, YARN tries to use it with v2. This is handled by the following
> init step:
> {code:java}
> private static void initializeCGroupHandlers(Configuration conf,
> CGroupsHandler.CGroupController controller) throws
> ResourceHandlerException {
> initializeCGroupV1Handler(conf);
> if (cgroupsV2Enabled && !isMountedInCGroupsV1(controller)) {
> initializeCGroupV2Handler(conf);
> }
> }
> {code}
> There is an issue with this when we're using preconfigured mount paths
> (yarn.nodemanager.linux-container-executor.cgroups.mount-path): with
> preconfigured mount paths the /etc/mtab files are no longer checked, hence if
> there is a subhierarchy that's called the same as a v1 controller (e.g cpu,
> memory, devices, etc) YARN will think it's mounted in v1 (without checking
> the contents of the folder), and will try to update the v1 controller files
> on application launch, causing application failures.
> The reason for this is the !isMountedInCGroupsV1(controller) check and the
> fact that v1 handler is initited first, and v2 is essentially used as a
> fallback. To overcome this the order should be reversed, v1 should be the
> fallback handler.
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