On-Demand CPU Count Change for Virtual Machines with vRA

Use Case

The goal is to allow users to increase or decrease CPU count of their virtual machines (VMs) on-demand using vRA, with backend automation handled by vRO.

 High-Level Workflow

1. User Request in vRA

   • User selects the VM and specifies the new vCPU count (increase or decrease).

2. vRO Workflow Triggered

   • vRA Event Broker or Day-2 Action calls the vRO workflow.

3. Workflow Steps in vRO

   • Find the VM in vCenter via API.

   • Check Power Status:

     • If Powered On → Check if CPU Hot-Add is enabled.

       • If enabled → Update CPU count live.

       • If not enabled → Shutdown VM, apply changes.

   • Apply the requested vCPU change.

   • If VM was shutdown → Power it back on.

4. Status Update

• Workflow updates back to vRA, showing success/failure status

Flow Diagram

Benefits

Self-Service – Users can request CPU changes anytime without admin involvement.
Non-Disruptive – If hot-add is enabled, CPUs are added while VM is powered on.
Governance – All changes tracked and controlled via vRA catalog.
Consistency – Automated workflow ensures correct process is followed every time.

Scriptable Task (JavaScript in vRO)

/*

Purpose:

This workflow is used on-demand change the CPU Count the virtual machine.

Inputs Parameters:

– noOfCpu(string)

– vmName (string)

*/

try

{ 

            

            // Find VM object in vCenter

            var vms = VcPlugin.getAllVirtualMachines(null, "name == '" + vmName + "'");

            if (vms == null || vms.length == 0) {

                throw "VM with name '" + vmName + "' not found in vCenter.";

            }

              var vm = vms[0];

              System.log("Found VM: " + vm.name);

             

              System.log("VM object- "+vm);

              System.log("VM Name- "+vm.Id);

              //cpuRatio = vm.config.cpuAllocation.shares.level.value;

              var currentCpu = vm.summary.config.numCpu;

              // Getting the CPU that is being increased to the VM

              numCpu = Number(noOfCpu) - currentCpu;

              if(numCpu < 0 && vm.runtime.powerState.value == "poweredOn"){

                             var task = System.getModule("com.vmware.library.vc.vm.power").forcePowerOff(vm) ;

                             var actionResult = System.getModule("com.vmware.library.vc.basic").vim3WaitTaskEnd(task,"No",2) ;

              }

             

              if(vm != null){

                             //vcpu = vm.cpu.split(' ')[0];

                             var configSpec = new VcVirtualMachineConfigSpec();

                             configSpec.numCPUs = Number(noOfCpu);

                             var task = vm.reconfigVM_Task(configSpec);

                             //var actionResult = System.getModule("com.vmware.library.vc.basic").vim3WaitTaskEnd(task) ;

                             var actionResult = System.getModule("com.vmware.library.vc.basic").vim3WaitTaskEnd(task,"No",2) ;

              }

}

catch(error){

                             throw error;

}

Workflow Design in vRO

1. Inputs:

   • vmName (string)

   • targetCpuCount (number)

2. Scriptable Task: Paste the above code.

3. Outputs:

   • statusMessage (string) → For logging back to vRA.

4. Event Subscription / Day-2 Action in vRA:

   • Bind inputs (VM name + requested CPU count) from vRA catalog request.

   • Show output in request status.