E-MapReduce:Use node labels

This topic describes YARN node labels, their usage, and common issues.

# Run commands as the default YARN administrator: hadoop
sudo su - hadoop
# Add partitions
yarn rmadmin -addToClusterNodeLabels "DEMO"
yarn rmadmin -addToClusterNodeLabels "CORE"
# List the YARN nodes
yarn node -list
# Map specific nodes to a partition
yarn rmadmin -replaceLabelsOnNode "core-1-1.c-XXX.cn-hangzhou.emr.aliyuncs.com=DEMO"
yarn rmadmin -replaceLabelsOnNode "core-1-2.c-XXX.cn-hangzhou.emr.aliyuncs.com=DEMO"

• On the ResourceManager Nodes page, the Node Labels column for the two core nodes (core-1-1 and core-1-2) shows DEMO, and the Node State is RUNNING. This indicates the node-to-label mapping is active.

• On the Node Labels page, the table shows three added node labels: <DEFAULT_PARTITION>, CORE, and DEMO. Their Label Type is Exclusive Partition.

Configure queue partitions

To use the Capacity Scheduler, ensure that the yarn.resourcemanager.scheduler.class property in the yarn-site.xml file is set to org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityScheduler.

In the capacity-scheduler.xml file, use the following properties to configure a queue's accessible partitions and capacity. Replace <queue-path> with the queue path and <label> with the partition name. For the DEFAULT partition, you can use the regular capacity or maximum-capacity properties.

• For a specified queue to have an actual resource capacity greater than 0, you must configure the capacity for the same partition on all of its ancestor queues. This is because the default value of the yarn.scheduler.capacity.<queue-path>.accessible-node-labels.<label>.capacity parameter is 0. Therefore, you must configure yarn.scheduler.capacity.root.accessible-node-labels.<label>.capacity=100 so that its child queues can have a non-zero capacity on the partition. (Theoretically, any value greater than 0 is sufficient, but configuring a value less than 100 reduces the calculated actual capacity for child queues and serves little purpose). If the capacity configuration for an ancestor queue is missing and defaults to 0, the calculated actual capacity for the target queue on this partition will also be 0.

• After yarn.scheduler.capacity.root.accessible-node-labels.<label>.capacity is set to a value greater than 0, the same rule applies as for the regular yarn.scheduler.capacity.<queue-path>.capacity property: the sum of the capacity values for the same partition across all direct child queues must be 100.

  Example configuration:

  <configuration>
    <!-- Add node label properties in XML -->
    <property>
      <!-- Allow the default queue to access the DEMO partition (required) -->
      <name>yarn.scheduler.capacity.root.default.accessible-node-labels</name>
      <value>DEMO</value>
    </property>
    <property>
      <!-- Set the DEMO partition capacity on all ancestor queues of the default queue (required) -->
      <name>yarn.scheduler.capacity.root.accessible-node-labels.DEMO.capacity</name>
      <value>100</value>
    </property>
    <property>
      <!-- Set the DEMO partition capacity for the default queue (required) -->
      <name>yarn.scheduler.capacity.root.default.accessible-node-labels.DEMO.capacity</name>
      <value>100</value>
    </property>
    <property>
      <!-- Optional: set the maximum capacity for the default queue in the DEMO partition. The default is 100. -->
      <name>yarn.scheduler.capacity.root.default.accessible-node-labels.DEMO.maximum-capacity</name>
      <value>100</value>
    </property>
    <property>
      <!-- Optional: set the default partition for container requests of jobs submitted to the default queue. The default is the DEFAULT partition "" -->
      <name>yarn.scheduler.capacity.root.default.default-node-label-expression</name>
      <value>DEMO</value>
    </property>
  <configuration>