[Autoscaler] AWS EC2 Fleet support

[mjrlee]

Description

A best practice with spot instances is to specify many different instance types so that the user is more likely to have their request satisfied by some combination of instance types.

Currently we can specify multiple instance types, but it's not clear what happens when we do (#39788)

One option to handle this is to create an EC2 Fleet instead of requesting individual node types

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-fleet.html

This feature offloads all the logic about which instances to start to AWS. The autoscaler then only needs to change the target capacity of the fleet to match the number of CPUs requested.

Use case

No response

[anyscalesam]

@mjrlee we support something similar on Anyscale Platform. See here. Would that be what you're looking for?

cc @richardliaw

[mjrlee]

Not really, I'm looking for help launching spot instances reliably.

[zakajd]

@mjrlee Have you found a solution for this issue?