Updated on 2026-06-27 GMT+08:00

Submitting a Task Using the YARN Client

Scenarios

This section guides users to use a Yarn client in an O&M or service scenario.

Prerequisites

Service component users have been created by the MRS cluster administrator. In a cluster in security mode, machine-machine users need to download the keytab file. A human-machine user must change the password upon the first login. In a cluster in normal mode, you do not need to download the keytab file or change the password.

Using the YARN Client

Install the client. If the client has been installed, skip this step.

For example, if the installation directory is /opt/client. The client directory path used in the following steps is only an example. Replace it with your actual installation directory path.

For details about how to download and install the cluster client, see Installing an MRS Cluster Client.
Log in to the node where the client is installed as the client installation user.
Run the following command to go to the client installation directory:
```
cd /opt/client
```
Run the following command to configure environment variables:
```
source bigdata_env
```
If Kerberos authentication is enabled for the cluster (in security mode), run the following command to authenticate the user. If Kerberos authentication is disabled for the cluster (in normal mode), user authentication is not required. In this case, skip this step.
```
kinit Component service user
```

Run the YARN command. For example, run the following command to view all applications in the YARN cluster:

yarn application -list

The command output is as follows:

Total number of applications (application-types: [], states: [SUBMITTED, ACCEPTED, RUNNING] and tags: []):2
Application-Id      Application-Name        Application-Type          User      Queue-User           Queue                   State             Final-State             Progress                        Tracking-URL
application_1749532996066_0002        default-worker            yarn-service    hetuserver      hetuserver         default                 RUNNING               UNDEFINED                 100%                                 N/A
application_1749532996066_0001   default-coordinator            yarn-service    hetuserver      hetuserver         default                 RUNNING               UNDEFINED                 100%                                 N/A

Helpful Links

If an error occurs and the process terminates when you run the YARN client command to query historical jobs, resolve the issue by referring to An Error Is Reported When a YARN Client Command Is Used to Query Historical Jobs.
If the YARN ResourceManager reports a "connection refused" error when requesting a job submission and the configured YARN port is 8032, resolve the issue by referring to Incorrect Port Information of the Yarn Client Causes Error "connection refused" After a Task Is Submitted.
The following are common problems encountered when you use the YARN client:

When a YARN Client Command Is Executed, the Client Program Exits Unexpectedly and the Error Message "java.lang.OutOfMemoryError" Is Displayed

This problem occurs because the memory required to run the YARN client exceeds the maximum limit (128 MB by default) configured for the client.

You can change the maximum memory of the YARN client by modifying the CLIENT_GC_OPTS value in <Client installation path>/HDFS/component_env.

For example, to set the maximum memory limit to 1 GB, run the following command:

cd <Client installation path>/HDFS/component_env

export CLIENT_GC_OPTS="-Xmx1G"

After the modification, run the following command to make the modification take effect:

source <Client installation path>/bigdata_env

How Can I Set the Log Level When the YARN Client Is Running?

By default, YARN client logs are printed to the console, and the default log level is INFO. To enable the DEBUG log level for fault locating, you can export the required environment variable.

Run the following command to enable DEBUG logs:
```
export YARN_ROOT_LOGGER=DEBUG,console
```
Then, run the YARN shell command to print DEBUG logs.

To restore the log level to INFO, run the following command:
```
export YARN_ROOT_LOGGER=INFO,console
```

Parent topic: Using YARN