rally-openstack/samples/tasks/scenarios/keystone/create-add-and-list-user-roles.json

{
    "KeystoneBasic.create_add_and_list_user_roles": [
    {
            "runner": {
                "type": "constant",
                "times": 100,
                "concurrency": 10
            },
            "context": {
                "users": {
                    "tenants": 3,
                    "users_per_tenant": 2
                }
            }
        }
    ]
}