Fallback instance type

[Kostiantyn-Vorobiov]

A feature request: The possibility to specify secondary instance type in case of "There is no Spot capacity available that matches your request", code: 'InsufficientInstanceCapacity' error.

I think we could have a fallback launch template with another instance type or overwrite InstanceType in the current launch template in case if AWS answers with 'InsufficientInstanceCapacity' error.

[MitkoTschimev]

Yes, we had the same issue and our idea was to do the same. Is someone already working on it?

[Kostiantyn-Vorobiov]

Here is a WIP for this idea - Kostiantyn-Vorobiov#1 (haven't tested in the real environment)
Any thoughts? I'm not a TS guy @gertjanmaas, @npalm

[gertjanmaas]

Hi @Kostiantyn-Vorobiov.

I really like the idea. I don't think the implementation will work because we use EC2 Launch Templates. As far as I know the Launch Templates options and the instance type options do not mix in the runInstances call.

So instead of changing the instance type, we could create a second Launch Template in Terraform and change the launchTemplateName and launchTemplateVersion to the secondary template on a InsufficientInstanceCapacity error. See terraform code here: https://github.com/philips-labs/terraform-aws-github-runner/blob/8ed8a8491298d5023f37b207e432e92129183adc/modules/runners/main.tf#L36

@npalm how does this sound to you?

[Kostiantyn-Vorobiov]

According to the documentation -
"LaunchTemplate — (map) -
The launch template to use to launch the instances. Any parameters that you specify in RunInstances override the same parameters in the launch template."
So there is a chance that it could work in this way. But the second launch template could also work fine.

Also, there is a more robust solution with spot fleet requests. But that requires a lot of changes.

[npalm]

In that case overwriting should be the way forward

link to docs: https://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_RunInstances.html

[npalm]

@Kostiantyn-Vorobiov feel free to open a draft (WIP) PR

[mcaulifn]

This should be resolved by #898

[npalm]

Fallback is available