YARN Cgroups

Configure YARN to use Control Groups (Cgroups) when you want to limit and monitor the CPU resources that are available to process YARN containers on a node. CGroups are a Linux kernel feature that is available through the LinuxContainerExecutor program.

Note: MapR does not support YARN cgroups on RHEL 7. In RHEL 7, libcgroup is deprecated and systemd maintains cgroups. Moving default hierarchies that systemd manages might generate unexpected results.
Complete the following steps to configure YARN to use Cgroups:
  1. Configure CGroup Properties for the LinuxContainerExecutor.
    1. Cgroups are a Linux kernel feature that is available through the LinuxContainerExecutor program. Configure or verify the configuration of the following LinuxContainerExecutor properties in the yarn-site.xml on each NodeManager and ResourceManager node:
      Properties Configuration Description
      yarn.nodemanager.container-executor.class Verify that this property is set to org.apache.hadoop.yarn.server.nodemanager.LinuxContainerExecutor.
      yarn.nodemanager.linux-container-executor.resources-handler.class Set this property to org.apache.hadoop.yarn.server.nodemanager.util.CgroupsLCEResourcesHandler
      yarn.nodemanager.linux-container-executor.cgroups.hierarchy Verify or set this property to the location of the Cgroups hierarchy. If yarn.nodemanager.linux-container-executor.cgroups.mount is false then this cgroups hierarchy must already exist in this location. By default, this is set to /hadoop-yarn.
      yarn.nodemanager.linux-container-executor.cgroups.mount If the Cgroup hierarchy is already configured, verify that this value is set to the default, false. Otherwise, set this value to true.
      yarn.nodemanager.linux-container-executor.cgroups.mount-path Set this property to the path where the LinuxContainerExecutor should attempt to mount cgroups if the hierarchy is not found. The container-executor binary will try to mount to <mountPath>/cpu, which must exists before the NodeManager service is started on this node.
      yarn.nodemanager.linux-container-executor.group Verify that this setting matches the yarn.nodemanager.linux-container-executor.group setting in container-executor.cfg (/opt/mapr/hadoop/hadoop-2.x.x/etc/hadoop/container-executor.cfg).
  2. Configure Resource Limits for YARN Container.
    1. To limit the YARN container resources, you have the following options which you configure in the yarn-site.xml :
      To Perform
      Limit the CPU resources available to container processes Set yarn.nodemanager.resource.percentage-physical-cpu-limit to the percentage at which you want to limit the CPU usage of all YARN containers. For example, if you set this value to 75, YARN containers on this node cannot use more than 75% of the CPU that is available on the node.
      Specify if CPU allocation should have a hard or soft limit

      If containers should not use more CPU that what was originally allocates, set yarn.nodemanager.linux-container-executor.cgroups.strict-resource-usage to true.

      Set yarn.nodemanager.linux-container-executor.cgroups.strict-resource-usage to false, if containers can use additional amounts of unused, available CPU.

  3. Restart the Services.
    1. Restart each NodeManager and ResourceManager service so that changes to yarn-site.xml take effect. For more information, see Starting, Stopping, and Restarting Services.