Configure node labels

You can configure node labels on a cluster by making configuration changes on the YARN ResourceManager host.

Enable Node Labels

To enable Node Labels on a cluster, make the following configuration changes on the YARN ResourceManager host.

Create a Label Directory in HDFS
Use the following commands to create a "node-labels" directory in which to store the Node Labels in HDFS.
```
sudo su hdfs
hadoop fs -mkdir -p /yarn/node-labels
hadoop fs -chown -R yarn:yarn /yarn
hadoop fs -chmod -R 700 /yarn
```
-chmod -R 700 specifies that only the yarn user can access the "node-labels" directory.
You can then use the following command to confirm that the directory was created in HDFS.
```
hadoop fs -ls /yarn
```
The new node label directory should appear in the list returned by the following command. The owner should be yarn, and the permission should be drwx.
```
Found 1 items
drwx------ - yarn yarn 0 2014-11-24 13:09 /yarn/node-labels
```
Use the following commands to create a /user/<user_name> directory that is required by the distributed shell.
```
hadoop fs -mkdir -p /user/<user_name>
hadoop fs -chown -R yarn:yarn /user/<user_name>
hadoop fs -chmod -R 700 /user/<user_name>
```
In Cloudera Manager, select the YARN service.
Click the Configuration tab.
Search for YARN Service Advanced Configuration.
In YARN Service Advanced Configuration Snippet (Safety Valve) for yarn-site.xml add the following:
- Set the following property to enable Node Labels:
```
Name: yarn.node-labels.enabled
Value: true
```
- Set the following property to reference the HDFS node label directory
```
Name: yarn.node-labels.fs-store.root-dir
Value: hdfs://:/
```
  For example,
```
Name: yarn.node-labels.fs-store.root-dir
Value: hdfs://node-1.example.com:8020/yarn/node-labels/ 
```
Start or Restart the YARN ResourceManager.

Add Node Labels

Use the following command format to add Node Labels. You should run these commands as the yarn user. Node labels must be added before they can be assigned to nodes and associated with queues.

sudo su yarn
yarn rmadmin -addToClusterNodeLabels "<label1>(exclusive=<true|false>),<label2>(exclusive=<true|false>)"

For example, the following commands add the node label "x" as exclusive, and "y" as shareable (non-exclusive).

sudo su yarn
yarn rmadmin -addToClusterNodeLabels "x(exclusive=true),y(exclusive=false)"

You can use the yarn cluster --list-node-labels command to confirm that Node Labels have been added:

[root@node-1 /]# yarn cluster --list-node-labels
15/07/11 13:55:43 INFO impl.TimelineClientImpl: Timeline service address: http://node-1.example.com:8188/ws/v1/timeline/
15/07/11 13:55:43 INFO client.RMProxy: Connecting to ResourceManager at node-1.example.com/240.0.0.10:8032
Node Labels: <x:exclusivity=true>,<y:exclusivity=false>

You can use the following command format to remove Node Labels:

yarn rmadmin -removeFromClusterNodeLabels "<label1>,<label2>"

Confirm Node Label Assignments

You can use the following commands to view information about node labels.

List all running nodes in the cluster: yarn node -list

Example:

[root@node-1 /]# yarn node -list
14/11/21 12:14:06 INFO impl.TimelineClientImpl: Timeline service address: http://node-1.example.com:8188/ws/v1/timeline/
14/11/21 12:14:07 INFO client.RMProxy: Connecting to ResourceManager at node-1.example.com/240.0.0.10:8032
Total Nodes:3
 Node-Id Node-State Node-Http-Address Number-of-Running-Containers
node-3.example.com:45454 RUNNING node-3.example.com:50060 0
node-1.example.com:45454 RUNNING node-1.example.com:50060 0
node-2.example.com:45454 RUNNING node-2.example.com:50060 0

List all node labels in the cluster: yarn cluster --list-node-labels

Example:

[root@node-1 /]# yarn cluster --list-node-labels
15/07/11 13:55:43 INFO impl.TimelineClientImpl: Timeline service address: http://node-1.example.com:8188/ws/v1/timeline/
15/07/11 13:55:43 INFO client.RMProxy: Connecting to ResourceManager at node-1.example.com/240.0.0.10:8032
Node Labels: <x:exclusivity=true>,<y:exclusivity=false>

List the status of a node (includes node labels): yarn node -status <Node_ID>

Example:

[root@node-1 /]# yarn node -status node-1.example.com:45454
14/11/21 06:32:35 INFO impl.TimelineClientImpl: Timeline service address: http://node-1.example.com:8188/ws/v1/timeline/
14/11/21 06:32:35 INFO client.RMProxy: Connecting to ResourceManager at node-1.example.com/240.0.0.10:8032
Node Report : 
 Node-Id : node-1.example.com:45454
 Rack : /default-rack
 Node-State : RUNNING
 Node-Http-Address : node-1.example.com:50060
 Last-Health-Update : Fri 21/Nov/14 06:32:09:473PST
 Health-Report : 
 Containers : 0
 Memory-Used : 0MB
 Memory-Capacity : 1408MB
 CPU-Used : 0 vcores
 CPU-Capacity : 8 vcores
 Node-Labels : x

Node labels are also displayed in the ResourceManager UI on the Nodes and Scheduler pages.