[EKS] [Feature Request]: InsufficientInstanceCapacity Should Not Caused Managed NodeGroup CREATE_FAILED If Nodes Can Be Provisioned From Other AZs

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**Tell us about your request**

InsufficientInstanceCapacity should not caused Managed NodeGroup CREATE_FAILED if the Nodes can be provisioned from other AZs.

**Which service(s) is this request for?**

EKS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**

A customer tried to update their Managed NodeGroup and received the message:

``* error updating EKS Node Group (:) config: ResourceInUseException: Nodegroup cannot be updated as it is currently not in Active State``
 
NodeGroup events showed that there was an **InsufficientInstanceCapacity** message:

``Could not launch On-Demand Instances. InsufficientInstanceCapacity - We currently do not have sufficient p4d.24xlarge capacity in the Availability Zone you requested (us-west-2b). Our system will be working on provisioning additional capacity. You can currently get p4d.24xlarge capacity by not specifying an Availability Zone in your request or choosing us-west-2a, us-west-2c. Launching EC2 instance failed.``
 
The requested amount of Nodes were able to be provisioned from the other AZs specified in the NodeGroup but the NodeGroup stayed in the **CREATE_FAILED** status.

The NodeGroup can't be edited to remove the subnet that the Nodes couldn't be provisioned in and if the subnet is removed from the ASG any Nodes that are running in the subnet will be terminated and the NodeGroup will report a health issue related to not having the expected subnets.

The customer is requesting that InsufficientInstanceCapacity should not result in a Managed NodeGroup being in the **CREATE_FAILED** status and should instead be health as the capacity was able to be fulfilled from the other AZs.

**Are you currently working around this issue?**

No. The customer would have to create a new NodeGroup that doesn't specify the subnet that the Nodes couldn't be provisioned in.

**Additional context**

N/A

**Attachments**

N/A

Start by reviewing the EKS Managed NodeGroup behavior described in the issue, especially nodegroup events for InsufficientInstanceCapacity across the listed Availability Zones. Determine whether the requested CREATE_FAILED-to-healthy behavior is supported by the EKS service and what acceptance criteria would define success; the issue names no repository files or tests.

Written by the indexing model from the issue text.