feat: Create a KEDA deployment

[matheusmazzoni]

What does this PR do?

This PR introduces the implementation of KEDA (Kubernetes Event-Driven Autoscaling) to the EKS Blueprints Addons repository. KEDA enables event-driven autoscaling for Kubernetes workloads, supporting a wide range of scalers like AWS SQS, CloudWatch, and DynamoDB. The integration is achieved by adding a simple configuration option to enable KEDA.

Motivation

The motivation behind this PR is to provide efficient resource utilization, enhance performance by dynamically adjusting workloads, and offer broad compatibility with various event sources.

• Resolves [ADDON] - Keda #245

More

• Yes, I have tested the PR using my local account setup (Provide any test evidence report under Additional Notes)
• Yes, I ran pre-commit run -a with this PR

For Moderators

• E2E Test successfully complete before merge?

Additional Notes

In my local environment, KEDA successfully scaled applications based on event-driven triggers.

[matheusmazzoni]

@bryantbiggs do you think this implementation is valid?

[bryantbiggs]

no, I do not in its current form. As previously stated, this is just re-wrapping helm which is not providing much (if any) value. Users can deploy this today without any code changes required by the module #245 (comment)

What benefit is there to having just Terraform wrappers around Helm charts?

[vvchik]

It is logical to onboard it as It is a very popular hpa replacement. It is popular in the same way as Karpenter is a replacement for cluster-autoscaler.

[vvchik]

The main issue in that PR is it is not supporting irsa roles, like karpenter for example does.

so smth like that (maybe plain and not module) should be added

module "iam_assumable_role_keda" {
  source      = "terraform-aws-modules/iam/aws//modules/iam-assumable-role-with-oidc"
  create_role = true
  role_name   = "keda-role-${var.eks_cluster_name}"
  tags = {
    Role = "keda-role-${var.eks_cluster_name}"
  }
  # provider_url  = replace(var.eks_oidc_provider, "https://", "")
  provider_url = data.aws_eks_cluster.this.identity[0].oidc[0].issuer
  role_policy_arns = [
    "arn:aws:iam::aws:policy/CloudWatchReadOnlyAccess",
  ]
  oidc_fully_qualified_subjects = [
    "system:serviceaccount:keda:keda-operator",
  ]
}

and the following helm values should become configurable variables if irsa used

podIdentity:
  aws:
    irsa:
      enabled: true
      roleArn: "${keda_operator_role_arn}"    

serviceAccount:
  annotations:
    eks.amazonaws.com/role-arn: ${keda_operator_role_arn}