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Hadoop: YARN Capacity Scheduler UI

Overview

The YARN Capacity Scheduler UI is a modern web interface for managing the YARN Capacity Scheduler configuration. It provides visual queue management, node label administration, placement rule editing, and global scheduler settings — all from the browser.

Key features include:

• Queue Management — View and edit the queue hierarchy with an interactive tree visualization.
• Staged Changes — Stage configuration changes, review them as a batch, and apply them to the cluster in one operation.
• Validation — Real-time validation of configuration changes with error and warning severity levels.
• Node Labels — Create, delete, and assign node labels to cluster nodes.
• Placement Rules — Configure application placement policies.
• Global Settings — Manage cluster-wide scheduler parameters.
• Read-Only Mode — Optionally restrict the UI to view-only access.

Prerequisites

The Capacity Scheduler UI must be built by passing -Pyarn-ui to Maven. Refer to BUILDING.txt for more details.

Configurations

In yarn-site.xml

Configuration Property	Description
yarn.webapp.scheduler-ui.enable	(Required) Enables the Capacity Scheduler UI on the ResourceManager. Defaults to false.
yarn.webapp.scheduler-ui.war-file-path	(Optional) WAR file path for the Capacity Scheduler UI web application. By default this is empty and YARN will look up the required WAR file from the classpath.
yarn.webapp.scheduler-ui.read-only.enable	(Optional) When set to true, the UI operates in read-only mode: users can view configuration and stage changes for review, but cannot apply mutations to the cluster. Defaults to false.

If you run YARN daemons locally for testing, you need the following configurations added to yarn-site.xml to enable cross-origin (CORS) support.

Configuration Property	Value	Description
yarn.resourcemanager.webapp.cross-origin.enabled	true	Enable CORS support for Resource Manager

Also ensure that CORS related configurations are enabled in core-site.xml. Refer to HTTP Authentication for details.

Use it

Open your browser and go to rm-address:8088/scheduler-ui.

Notes

• The Capacity Scheduler UI is served by the ResourceManager as a separate web application context at the /scheduler-ui path.
• The UI communicates with the ResourceManager via its REST API endpoints under /ws/v1/cluster/.
• In read-only mode, mutation endpoints (updating scheduler configuration, adding/removing node labels, replacing node-to-label mappings) are blocked on the client side.
• This UI framework is verified under security environment as well.