Check for empty region before invoking API in AWS SDK

[a2ush]

Description

Currently, you will receive the following error if you forget to set the AWS region code.

$ eksctl create cluster
Error: checking AWS STS access – cannot get role ARN for current session: operation error STS: GetCallerIdentity, https response error StatusCode: 0, RequestID: , request send failed, Post "https://sts..amazonaws.com/": Bad Request

When you look closely, you can notice that there is something wrong with this endpoint "https://sts..amazonaws.com/".
However, it is difficult to immediately resolve the problem from this error message.

This PR provides a more understandable error message if you run into the same situation.
I think it helps to navigate the next action to solve the problem.

(demo)
$ ./eksctl create cluster
Error: no region code: please set the AWS region to ~/.aws/config file or environment variables.

note:
The Installation document already has "prerequisite" description about aws configs.
https://eksctl.io/installation/#prerequisite

You can use ~/.aws/credentials file or environment variables.

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the userdocs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes
• (Core team) Added labels for change area (e.g. area/nodegroup) and kind (e.g. kind/improvement)

[yuxiang-zhang]

eksctl/pkg/eks/apiv2.go

Lines 48 to 50 in 4e3d0e4

	if pc.Region != "" {
	options = append(options, config.WithRegion(pc.Region))
	}

Looks like cfg.Region is set from spec.Region in newV2Config() on L184.

We should just move this check on spec.Region to before L184 and error if it's empty then.

[a2ush]

Thank you for your suggestion.

I understood the current logic as the following;

• if Spec.Region is not empty, cfg.Region is set from spec.Region in newV2Config()
• if Spec.Region is empty, cfg.Region is set from ~/.aws/config or AWS_REGION in newV2Config()

So, I think we should check the value of cfg.Region after L184.
If cfg.Region is empty, we can determine AWS region is not defined.

//note

	cfg, err := newV2Config(spec, credentialsCacheFilePath, configurationLoader)
	if err != nil {
		return nil, err
	}

	fmt.Printf("spec.Region : %v\n", spec.Region)
	fmt.Printf("cfg.Region : %v\n", cfg.Region)

	if cfg.Region == "" {
		return nil, fmt.Errorf("AWS Region must be set, please set the AWS Region in AWS config file or as AWS_REGION environment variable")
	}

[result]

$ ./eksctl create cluster --dry-run
spec.Region : 
cfg.Region : ap-northeast-1

$ rm ~/.aws/config
$ ./eksctl create cluster --dry-run 
spec.Region : 
cfg.Region : 
Error: AWS Region must be set, please set the AWS Region in AWS config file or as AWS_REGION environment variable

$ export AWS_REGION=us-east-1      
$ ./eksctl create cluster --dry-run
spec.Region : 
cfg.Region : us-east-1

$ ./eksctl create cluster -f sample.yaml --dry-run
spec.Region : ap-northeast-1
cfg.Region : ap-northeast-1