Autoscaling of ADC instances in public clouds

Autoscaling is a cloud computing method that automatically adds or removes resources depending upon the actual usage. Autoscaling is useful whenever your site or application needs an on-demand resource allocation to satisfy the fluctuating number of client requests or processing jobs.

The demand for web applications or services can vary significantly. Maintaining the correct number of Citrix ADC instances for the different traffic needs is important. You can increase or decrease the network resources on a public cloud depending on the demand. Thus, it provides cost optimization without compromising the performance. Citrix Application Delivery and Management autoscaling maintains the exact number of Citrix ADC instances for fluctuating resource consumption. Citrix Application Delivery and Management determines the traffic flow based on the fluctuating resource consumption, it decides to scale out or scale in the Citrix ADC instances dynamically. Thus, it provides you the flexibility to maintain the correct number of Citrix ADC instances.

Citrix Application Delivery and Management monitors the resource usage of Citrix ADC instances and matches with the configured threshold value. It triggers the scale-out action if one of the configured resources exceeds the specified threshold value. Citrix Application Delivery and Management triggers the scale-in action only when the usage of all the configured resources falls below the normal threshold value.

Important

Autoscaling supports Citrix ADC features along with Citrix Gateway - ICA proxy feature. However, the following features that require a spotted configuration on cluster nodes are not supported:

  • GSLB
  • Other Citrix Gateway features
  • Telco features

For more information on spotted configuration, see Striped, partially striped, and spotted configurations.

Benefits

High availability of applications. Autoscaling ensures that your application always has the right number of Citrix ADC VPX instances to handle the traffic demands. This is to ensure that your application is up and running all the time irrespective of traffic demands.

Smart scaling decisions and zero touch configuration. Autoscaling continuously monitors your application and adds or removes Citrix ADC instances dynamically depending on the demand. When demand spikes upward, the instances are automatically added. When the demand spikes downward, the instances are automatically removed. The addition and removal of Citrix ADC instances happens automatically making it a zero-touch manual configuration.

Automatic DNS management. The Citrix Application Delivery and Management Autoscale feature offers automatic DNS management. Whenever new Citrix ADC instances are added, the domain names are updated automatically.

Graceful connection termination. During a scale-in, the Citrix ADC instances are gracefully removed avoiding the loss of client connections.

Better cost management. Autoscaling dynamically increases or decreases Citrix ADC instances as needed. This enables you to optimize the costs involved. You save money by launching instances only when they are needed and terminate them when they are not needed. Thus, you pay only for the resources you use.

Observability. Observability is the key to application dev-ops or IT personnel to monitor the health of the application. The Citrix Application Delivery and Management’s Autoscale dashboard enables you to visualize the threshold parameter values, Autoscale trigger time stamps, events, and the instances participating in Autoscale.

Licensing requirements

The Citrix ADC instances that are created for the Citrix Autoscale group uses Citrix ADC Advanced or Premium ADC licenses.

You can choose one of the following methods to license Citrix ADCs provisioned by Citrix Application Delivery and Management:

  • Using ADC licenses present in Citrix Application Delivery and Management: Configure pooled capacity, VPX licenses, or virtual CPU licenses while creating the Autoscale group. So, when a new instance is provisioned for an Autoscale group, the already configured license type is automatically applied to the provisioned instance.

    • Pooled Capacity: Allocates bandwidth to every provisioned instance in the Autoscale group. Ensure you have the necessary bandwidth available in Citrix Application Delivery and Management to provision new instances. For more information, see Configure Pooled Capacity.

      Each ADC instance in the Autoscale group checks out one instance license and the specified bandwidth from the pool.

    • VPX licenses: Applies the VPX licenses to newly provisioned instances. Ensure you have the necessary number of VPX licenses available in Citrix Application Delivery and Management to provision new instances.

      When a Citrix ADC VPX instance is provisioned, the instance checks out the license from the Citrix Application Delivery and Management. For more information, see Citrix ADC VPX check-in and check-out licensing.

    • Virtual CPU licenses: Applies virtual CPU licenses to newly provisioned instances. This license specifies the number of CPUs entitled to a Citrix ADC VPX instance. Ensure you have the necessary number of Virtual CPUs in Citrix Application Delivery and Management to provision new instances.

      When a Citrix ADC VPX instance is provisioned, the instance checks out the virtual CPU license from the Citrix Application Delivery and Management. For more information, see Citrix ADC virtual CPU licensing.

    When the provisioned instances are destroyed or de-provisioned, the applied licenses are automatically returned to Citrix Application Delivery and Management.

    To monitor the consumed licenses, navigate to the Networks > Licenses page.

  • Using cloud subscription licenses: Configure Citrix ADC licenses available in the cloud marketplace while creating the Autoscale group. So, when a new instance is provisioned for the Autoscale group, the license is obtained from the following marketplaces:

    • AWS
    • Microsoft Azure
    • Google Cloud
Autoscaling of ADC instances in public clouds