How to scale Azure VMSS linux VMs based on custom metric e.g. Memory Utilization?

Question

How to scale Azure VMSS Linux VMs based on custom metric e.g. Memory Utilization?

I created a VMSS(manual scale) based on Ubuntu(22.04) Linux VMs. Then I created a Log analytics workspace and configured data collection rules in Azure Monitor by mentioning the source as the VMs inside VMSS and destination as Log analytics workspace. But it seems Perf logs are not getting captured.

When I logged into the VMSS VM instances it seems Azure monitor agents are not installed(though in case of standalone VM it gets automatically installed when we enable DCR).

My objective is to dynamically scale the VMSS based on memory usage of the VMs in VMSS, captured in Azure Monitor Logs.

Could not find any step by step guide in Microsoft document or internet.

Thanks in advance

Answer 1

Hello, @Abhi !

How do I scale my Virtual Machine Scale Set based on custom metrics (like memory)?

After you create your Virtual Machine Scale Set (VMSS), you can go to Monitoring > Metrics to view metrics (including available memory) and you can go to Availability + scale > Scaling to set new custom autoscale rules.

https://learn.microsoft.com/en-us/azure/virtual-machine-scale-sets/virtual-machine-scale-sets-autoscale-portal#create-a-rule-to-automatically-scale-out

1. Go to your VMSS
2. Go to Availability + scale > Scaling
3. Click on Custom autoscale
4. Under Scale mode, select Scale based on a metric
5. Click Add a rule
6. Configure the rule using Current resource (for built in metrics, like available memory), Azure Monitor workspaces, or any of the other resources you would like to use.
7. Set the Operator, Metric threshold to trigger scale action, Duration, Operation, and instance count to your desired values.
8. Click Add
9. Save your configuration.

Custom autoscale for a VMSS using current resource/Available Memory:

Custom autoscale for a VMSS using Azure Monitor workspaces:

Additional Reading:

• Automatically scale a Virtual Machine Scale Set in the Azure portal
• Send guest OS metrics to the Azure Monitor metric store by using an Azure Resource Manager template for a Windows virtual machine scale set
• FAQ for Azure Virtual Machine Scale Sets
• Azure Monitor autoscaling common metrics
• Supported metrics with Azure Monitor
• Application Insights for Azure VMs and virtual machine scale sets
• Q&A: VMSS autoscaling based on Memory usage in RHEL 8

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