Everything About the Azure Autoscale Feature (With Examples)

Azure Autoscale is a feature that automatically adjusts the number of virtual machine (VM) instances in your application in response to changes in demand. It’s a crucial aspect of cloud computing as it ensures that your application has the necessary resources to perform optimally while minimizing costs by not over-provisioning.

Key Features of Azure Autoscale:

Automatic Scaling: Azure Autoscale automatically increases or decreases the number of VM instances based on metrics like CPU utilization, memory usage, or custom metrics.

Scheduled Scaling: You can configure autoscale to scale resources at specific times and days of the week, which is useful for predictable workload changes.

Multiple Scaling Rules: You can set up multiple scaling rules based on different metrics, providing flexibility in how resources are scaled.

Cool Down Periods: After performing a scaling operation, Autoscale can enforce a cool down period during which no further scaling will occur. This prevents rapid, repeated scaling changes which could be disruptive.

Notifications: Autoscale can send email notifications when scaling actions are taken.

How to Set Up Autoscale in Azure:

Select the Resource: Autoscale can be applied to various resources in Azure, including Virtual Machine Scale Sets, App Service Plans, and Cloud Services.

Define the Scale Mode: Choose whether to scale based on a metric (like CPU usage) or on a schedule.

Create Scaling Rules: Define rules for when to scale out (add resources) and scale in (remove resources). For example, you might set a rule to add VM instances when CPU usage exceeds 70% and remove instances when it drops below 30%.

Configure Notifications and Additional Settings: Set up notifications and any additional configurations like cool down periods.

Review and Save: Review your settings and save the configuration.

Example Scenario:

Imagine you have an Azure Virtual Machine Scale Set running a web application. You can set up Autoscale to:

  • Add more VMs when the average CPU usage goes above 70% for 5 minutes.
  • Remove VMs when the average CPU usage drops below 30% for 5 minutes.
  • Enforce a cool down period of 10 minutes to prevent rapid fluctuations.

By doing so, you ensure that during high traffic periods, your application remains responsive as more VMs are added to handle the load. Conversely, during low traffic periods, the scale set will reduce the number of VMs, thereby reducing costs.

Important Points:

Cost Implications: While Autoscale helps in optimizing costs, increased resource usage (scale-out) will lead to higher charges. It’s important to monitor and adjust Autoscale settings to find the right balance.

Performance vs. Cost: There’s often a trade-off between performance and cost. More aggressive scaling can ensure performance but might increase costs.

Testing: It’s crucial to test your Autoscale settings under different load conditions to ensure they work as expected.

Azure CLI Example

Here’s an example of how to create an autoscale setting for a Virtual Machine Scale Set using Azure CLI:

  1. Create a Virtual Machine Scale Set (if you haven’t already):
    az vmss create \
    --resource-group myResourceGroup \
    --name myScaleSet \
    --image UbuntuLTS \
    --upgrade-policy-mode automatic \
    --admin-username azureuser \
  2. Create an Autoscale Setting:
    az monitor autoscale create \
    --resource-group myResourceGroup \
    --resource myScaleSet \
    --resource-type Microsoft.Compute/virtualMachineScaleSets \
    --name myAutoscaleSetting \
    --min-count 1 \
    --max-count 5 \
    --count 2
  3. Add a Rule to Scale Out (e.g., when CPU usage is more than 70%):
    az monitor autoscale rule create \
    --resource-group myResourceGroup \
    --autoscale-name myAutoscaleSetting \
    --condition "Percentage CPU > 70 avg 5m" \
    --scale out 2
  4. Add a Rule to Scale In (e.g., when CPU usage is less than 30%):
    az monitor autoscale rule create \
    --resource-group myResourceGroup \
    --autoscale-name myAutoscaleSetting \
    --condition "Percentage CPU < 30 avg 5m" \
    --scale in 1

Azure PowerShell Example

Here’s an example of how to create an autoscale setting for a Virtual Machine Scale Set using Azure PowerShell:

Create a Virtual Machine Scale Set (if you haven’t already):

New-AzVmss `
-ResourceGroupName "myResourceGroup" `
-Location "EastUS" `
-VMScaleSetName "myScaleSet" `
-VirtualNetworkName "myVnet" `
-SubnetName "mySubnet" `
-PublicIpAddressName "myPublicIpAddress" `
-LoadBalancerName "myLoadBalancer" `
-UpgradePolicyMode "Automatic"

Define Scale Conditions:

$scaleOutCondition = New-AzAutoscaleRule -MetricName "Percentage CPU" -MetricResourceId $resourceId -Operator GreaterThan -Threshold 70 -TimeGrain 00:01:00 -TimeWindow 00:05:00 -ScaleActionCooldown 00:05:00 -ScaleActionDirection Increase -ScaleActionValue 2

$scaleInCondition = New-AzAutoscaleRule -MetricName "Percentage CPU" -MetricResourceId $resourceId -Operator LessThan -Threshold 30 -TimeGrain 00:01:00 -TimeWindow 00:05:00 -ScaleActionCooldown 00:05:00 -ScaleActionDirection Decrease -ScaleActionValue 1

Create Autoscale Profile and Setting:

$profile = New-AzAutoscaleProfile -Name "autoProfile" -DefaultCapacity 2 -MaximumCapacity 5 -MinimumCapacity 1 -Rule $scaleOutCondition, $scaleInCondition

Add-AzAutoscaleSetting -Name "myAutoscaleSetting" -ResourceGroup "myResourceGroup" -TargetResourceId $resourceId -Profile $profile

In these examples, replace myResourceGroup, myScaleSet, myVnet, mySubnet, myPublicIpAddress, myLoadBalancer, and $resourceId with your actual resource names and IDs.

These scripts set up autoscaling for a VM scale set, specifying conditions when to scale out (increase instances) and scale in (decrease instances) based on CPU usage.

Make sure to install Azure CLI or Azure PowerShell and log in to your Azure account before running these commands. Also, always test such configurations in a non-production environment to ensure they work as expected.

Leave a Reply

Your email address will not be published. Required fields are marked *