How can I make a VM in a scale set wait for systemd to gracefully shutdown?

Question

I am interested in using VM scale sets for a workload with automatic scale in policies. Unfortunately it seems the scale down policy for shutting down the VMs that part of the scale set is overly aggressive. In my testing I've found that it waits at most 5 seconds before forcibly shutting off the VM. I have an application that needs more time to gracefully shutdown than that.

There are situations where my workload might need hours to shutdown the VM. I'd almost rather the VMs never shut themselves off without a graceful shutdown. In that scenario I can intervene if the data from the workload isn't offloaded.

Is there any way to achieve anything like this with VM scale sets?

Answer

Thanks for posting your question in the Microsoft Q&A forum.

Unfortunately, Azure Virtual Machine Scale Sets do not currently provide a built-in way to allow for extended graceful shutdown periods during scale-in operations. The default behavior is indeed quite aggressive, with only a short window before forcibly terminating VMs.

You can implement a custom scale-in policy that selects VMs for removal based on specific criteria. This allows you to potentially flag VMs that are ready for shutdown
Configure a custom script extension on the VMs that runs before shutdown. This script could initiate your graceful shutdown process, though it would still be limited by the short termination window

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How can I make a VM in a scale set wait for systemd to gracefully shutdown?

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