Invalid count argument error with aws_ssm_parameter.runner_matcher_config in v6.9.0

[m-artin-t]

Describe the bug

When using module version 6.9.0, Terraform planning fails with an invalid count argument error in the webhook module.

Error Message

Error: Invalid count argument
  on .terraform/modules/github_runners_v4.github_runner/modules/webhook/webhook.tf line 41, in resource "aws_ssm_parameter" "runner_matcher_config":
  41:   count = local.total_chunks

The "count" value depends on resource attributes that cannot be determined until apply, so Terraform cannot predict how many instances will be created. To work around this, use the -target argument to first apply only the resources that the count depends on.

Configuration

Using the module with standard configuration:

module "github_runner" {
  source  = "github-aws-runners/github-runner/aws"
  version = "6.9.0"

  # Standard configuration
  aws_region = "us-east-1"
  vpc_id     = "vpc-xxx"
  subnet_ids = ["subnet-xxx"]
  
  github_app = {
    key_base64    = "..."
    id            = "..."
    client_id     = "..."
    client_secret = "..."
  }
  
  enable_organization_runners = true
  runners_maximum_count       = 400
  
  # Using default matcher_config_parameter_store_tier = "Standard"
}

Environment

• Terraform Cloud (remote execution)
• Module version: 6.9.0
• AWS Provider: 5.77.0

Context

This appears related to PR #4792 which added support for multiple SSM parameters for large runner matcher configs. The PR description mentions fixing a for_each error, but the count issue in aws_ssm_parameter.runner_matcher_config still exists.

The local.total_chunks calculation depends on runtime values, making it impossible for Terraform to determine the count during plan phase.

Workaround

The suggested -target workaround doesn't work with Terraform Cloud's remote execution model.

Expected behavior

The module should be able to plan successfully without requiring staged applies. Either:

• Make local.total_chunks computable at plan time
• Provide a variable to set a fixed chunk count
• Use a different approach that doesn't require dynamic count

Additional notes

This issue doesn't occur in v6.8.5 (before PR #4792). The multi-SSM parameter feature is useful for large configs, but breaks standard deployments.

[npalm]

@m-artin-t thx for reporting the problem.

[npalm]

Quickly validated the example with the default example. And having the same issue.

[edersonbrilhante]

@npalm I can check tomorrow.

[npalm]

Fix released https://github.com/github-aws-runners/terraform-aws-github-runner/releases/tag/v6.9.1