In an MRS cluster, users can logically divide Yarn cluster nodes to combine multiple NodeManagers into a Yarn resource pool. Each NodeManager belongs to one resource pool only. The system contains a default resource pool by default. All NodeManagers that are not added to customized resource pools belong to this resource pool.
You can create a customized resource pool on MRS and add hosts that have not been added to other customized resource pools to it.
You have synchronized IAM users. (On the Dashboard page, click Synchronize on the right side of IAM User Sync to synchronize IAM users.)
The name consists of 1 to 20 characters and can contain digits, letters, and underscores (_) but cannot start with an underscore (_).