Farmer > API Overview > Resources > Virtual Machine Scale Set

Virtual Machine Scale Set

Overview

The Virtual Machine Scale Set builder (vmss) creates a virtual machine scale set that can grow and shrink it’s capacity by creating virtual machines and their dependent resources from a common profile.

Virtual Machine Scale Sets (Microsoft.Compute/virtualMachineScaleSets)

Builder Keywords

Builder	Keyword	Purpose
vmss	name	Sets the name of the VM scale set.
vmss	vm_profile	Defines a profile for VM’s in the scale set using the `vm` builder to support all the same functionality as a single VM.
vmss	add_availability_zones	Adds one or more availability zones so VM resources will be distributed across those zones.
vmss	add_extensions	Adds extensions that will be automatically installed on VMs when scaling out.
vmss	automatic_repair_policy	Enables automatically replacing VMs in the scale set that report as unhealthy. Requires adding the Application Health Extension.
vmss	automatic_repair_enabled_after	Defines a grace period after becoming unhealthy before replacing the instance.
vmss	capacity	The number of VM instances in the scale set.
vmss	health_probe	If not using an application health extension, this refers to a load balancer health probe that can indicate instance health.
vmss	scale_in_policy	Specify the policy for determining which VMs to remove when scaling in.
vmss	scale_in_force_deletion	Indicates the VMs should be force deleted so they free the resources more quickly.
vmss	upgrade_mode	Specify Manual, Automatic, or Rolling upgrades. Rolling upgrades require the Application Health Extension or a Health Probe to ensure newly replaced instances are healthy before replacing more of them.
vmss	osupgrade_automatic	Indicates whether OS upgrades should automatically be applied to scale set instances in a rolling fashion when a newer version of the OS image becomes available. Default value is false. If this is set to true for Windows based scale sets, enableAutomaticUpdates is automatically set to false and cannot be set to true.
vmss	osupgrade_automatic_rollback	Whether OS image rollback feature should be enabled. Enabled by default.
vmss	osupgrade_rolling_upgrade	Indicates whether rolling upgrade policy should be used during Auto OS Upgrade. Default value is false. Auto OS Upgrade will fallback to the default policy if no policy is defined on the VMSS.
vmss	osupgrade_rolling_upgrade_deferral	Indicates whether Auto OS Upgrade should undergo deferral. Deferred OS upgrades will send advanced notifications on a per-VM basis that an OS upgrade from rolling upgrades is incoming, via the IMDS tag ‘Platform.PendingOSUpgrade’. The upgrade then defers until the upgrade is approved via an ApproveRollingUpgrade call.
applicationHealthExtension	vmss	When adding the extension as a resource, this specifies the VM scale set it should be applied to.
applicationHealthExtension	os	Operating system (Linux or Windows) to install the correct extension for that OS.
applicationHealthExtension	protocol	Protocol (TCP, HTTP, or HTTPS) to probe, and if specifying HTTP or HTTPS, include the path.
applicationHealthExtension	port	TCP port to probe.
applicationHealthExtension	interval	Interval to probe for health.
applicationHealthExtension	number_of_probes	Sets the number of times the probe must fail to consider this instance a failure.

Example

This example creates a scale set with 3 VM instances and includes the Application Health Extension to support rolling updates and automatic repairs.

open Farmer
open Farmer.Builders
open Farmer.Vm
open Farmer.VmScaleSet

vmss {
    name "my-scale-set"
    capacity 3

    vm_profile (
        vm {
            username "azureuser"
            operating_system UbuntuServer_2204LTS
            vm_size Standard_B1s
            os_disk 128 StandardSSD_LRS
            diagnostics_support_managed
            custom_script "sudo apt update && sudo apt install -y nginx"
        }
    )
    scale_in_policy OldestVM
    upgrade_mode Rolling
    automatic_repair_enabled_after (System.TimeSpan.FromMinutes 10)
    add_extensions [
        applicationHealthExtension {
            protocol (ApplicationHealthExtensionProtocol.HTTP "/healthcheck")
            port 80
            os Linux
        }
    ]

}