## Motivation¶

There are two very important reasons from the production world of why it is preferable to use some already existing users to test your OpenStack cloud:

1. Read-only Keystone Backends: creating temporary users for running scenarios in Rally is just impossible in case of r/o Keystone backends like LDAP and AD.

2. Safety: Rally can be run from an isolated group of users, and if something goes wrong, this won’t affect the rest of the cloud users.

## Registering deployment with existing users in Rally¶

The information about existing users in your OpenStack cloud should be passed to Rally at the deployment initialization step. The difference from the deployment configuration we’ve seen previously is that you should set up the “users” section with the credentials of already existing users. Let’s call this deployment configuration file existing_users.json:

{
"openstack": {
"auth_url": "http://example.net:5000/v2.0/",
"region_name": "RegionOne",
"endpoint_type": "public",
"tenant_name": "demo"
},
"users": [
{
"tenant_name": "testing"
},
{
"tenant_name": "testing"
}
]
}
}


This deployment configuration requires some basic information about the OpenStack cloud like the region name, auth url. admin user credentials, and any amount of users already existing in the system. Rally will use their credentials to generate load in against this deployment as soon as we register it as usual:

$rally deployment create --file existing_users --name our_cloud +--------------------------------------+----------------------------+-----------+------------------+--------+ | uuid | created_at | name | status | active | +--------------------------------------+----------------------------+-----------+------------------+--------+ | 1849a9bf-4b18-4fd5-89f0-ddcc56eae4c9 | 2015-03-28 02:43:27.759702 | our_cloud | deploy->finished | | +--------------------------------------+----------------------------+-----------+------------------+--------+ Using deployment: 1849a9bf-4b18-4fd5-89f0-ddcc56eae4c9 ~/.rally/openrc was updated  With this new deployment being active, Rally will use the already existing users instead of creating the temporary ones when launching task that do not specify the “users” context. ## Running tasks that uses existing users¶ After you have registered a deployment with existing users, don’t forget to remove the “users” context from your task input file if you want to use existing users, like in the following configuration file (boot-and-delete.json): { "NovaServers.boot_and_delete_server": [ { "args": { "flavor": { "name": "m1.tiny" }, "image": { "name": "^cirros.*-disk$"
},
"force_delete": false
},
"runner": {
"type": "constant",
"times": 10,
"concurrency": 2
},
"context": {}
}
]
}


When you start this task, it is going to use “b1” and “b2” for running subtask instead of creating the temporary users:

rally task start samples/tasks/scenarios/nova/boot-and-delete.json


It goes without saying that support of running with predefined users simplifies the usage of Rally for generating loads against production clouds.