All applications have specific usage patterns that comprise peaks and troughs. These load variations can be dynamic in nature and difficult to predict, given that they depend on several factors that are intrinsic to the use case. Cloud users have to constantly monitor the load on their application fleet and make sure that these variations have minimum impact on end users. During periods of peak usage, when the application fleet is overloaded and end users experience significant latency, they have to deploy additional application instances. During trough periods, the expanded fleet is underutilized. So they might have to remove additional instances or bear unnecessary cost overheads. In most cases, they have to perform these tasks manually.
If your organization uses Citrix CloudPlatform to deploy and manage the cloud environment, users can use the AutoScale feature in CloudPlatform, in conjunction with a Citrix NetScaler appliance, to automatically scale their applications as needed. The AutoScale feature is part of the elastic load balancing feature in CloudPlatform. A CloudPlatform user can use the AutoScale feature to specify thresholds for various conditions for automatically scaling the application fleet upward and downward. CloudPlatform, in turn, configures the NetScaler appliance (by using the NetScaler NITRO API) to load balance traffic to the application virtual machines (VMs), monitor application thresholds and performance, and trigger scale-up and scale-down actions to add or remove VMs to or from the application fleet.
As the NetScaler administrator, you do not have to perform any tasks for configuring AutoScale on the NetScaler appliance. However, you might have to be aware of certain prerequisites, and you might have to troubleshoot the configuration if issues arise in the AutoScale configuration. To troubleshoot the configuration, you have to be aware of how CloudPlatform works and what configuration CloudPlatform pushes to the NetScaler appliance. You also need a working knowledge of how to troubleshoot issues on a NetScaler appliance.
For more information about AutoScale, see "AutoScale: Automatic Scaling in the Citrix CloudPlatform Environment."