xdr-terraform-modules/thirdparty/terraform-aws-github-runner/modules/runners/scale-down.tf

locals {
  # Windows Runners can take their sweet time to do anything
  min_runtime_defaults = {
    "windows" = 15
    "linux"   = 5
  }
}

# tfsec:ignore:aws-lambda-enable-tracing We do not enable X-Ray Tracing for Lambda
resource "aws_lambda_function" "scale_down" {
	# checkov:skip=CKV_AWS_50: see tfsec ignore X-Ray Tracing
  s3_bucket         = var.lambda_s3_bucket != null ? var.lambda_s3_bucket : null
  s3_key            = var.runners_lambda_s3_key != null ? var.runners_lambda_s3_key : null
  s3_object_version = var.runners_lambda_s3_object_version != null ? var.runners_lambda_s3_object_version : null
  filename          = var.lambda_s3_bucket == null ? local.lambda_zip : null
  source_code_hash  = var.lambda_s3_bucket == null ? filebase64sha256(local.lambda_zip) : null
  function_name     = "${var.prefix}-scale-down"
  role              = aws_iam_role.scale_down.arn
  handler           = "index.scaleDownHandler"
  runtime           = var.lambda_runtime
  timeout           = var.lambda_timeout_scale_down
  tags              = local.tags
  memory_size       = 512
  architectures     = var.lambda_architecture == "x86_64" ? [] : [var.lambda_architecture]

  environment {
    variables = {
      ENVIRONMENT                          = var.prefix
      GHES_URL                             = var.ghes_url
      LOG_LEVEL                            = var.log_level
      LOG_TYPE                             = var.log_type
      MINIMUM_RUNNING_TIME_IN_MINUTES      = coalesce(var.minimum_running_time_in_minutes, local.min_runtime_defaults[var.runner_os])
      NODE_TLS_REJECT_UNAUTHORIZED         = var.ghes_url != null && !var.ghes_ssl_verify ? 0 : 1
      PARAMETER_GITHUB_APP_ID_NAME         = var.github_app_parameters.id.name
      PARAMETER_GITHUB_APP_KEY_BASE64_NAME = var.github_app_parameters.key_base64.name
      RUNNER_BOOT_TIME_IN_MINUTES          = var.runner_boot_time_in_minutes
      SCALE_DOWN_CONFIG                    = jsonencode(var.idle_config)
    }
  }

  dynamic "vpc_config" {
    for_each = var.lambda_subnet_ids != null && var.lambda_security_group_ids != null ? [true] : []
    content {
      security_group_ids = var.lambda_security_group_ids
      subnet_ids         = var.lambda_subnet_ids
    }
  }
}

resource "aws_cloudwatch_log_group" "scale_down" {
  name              = "/aws/lambda/${aws_lambda_function.scale_down.function_name}"
  retention_in_days = var.logging_retention_in_days
  kms_key_id        = var.logging_kms_key_id
  tags              = var.tags
}

resource "aws_cloudwatch_event_rule" "scale_down" {
  name                = "${var.prefix}-scale-down-rule"
  schedule_expression = var.scale_down_schedule_expression
  tags                = var.tags
}

resource "aws_cloudwatch_event_target" "scale_down" {
  rule = aws_cloudwatch_event_rule.scale_down.name
  arn  = aws_lambda_function.scale_down.arn
}

resource "aws_lambda_permission" "scale_down" {
  statement_id  = "AllowExecutionFromCloudWatch"
  action        = "lambda:InvokeFunction"
  function_name = aws_lambda_function.scale_down.function_name
  principal     = "events.amazonaws.com"
  source_arn    = aws_cloudwatch_event_rule.scale_down.arn
}

resource "aws_iam_role" "scale_down" {
  name                 = "${var.prefix}-action-scale-down-lambda-role"
  assume_role_policy   = data.aws_iam_policy_document.lambda_assume_role_policy.json
  path                 = local.role_path
  permissions_boundary = var.role_permissions_boundary
  tags                 = local.tags
}

resource "aws_iam_role_policy" "scale_down" {
  name = "${var.prefix}-lambda-scale-down-policy"
  role = aws_iam_role.scale_down.name
  policy = templatefile("${path.module}/policies/lambda-scale-down.json", {
    github_app_id_arn         = var.github_app_parameters.id.arn
    github_app_key_base64_arn = var.github_app_parameters.key_base64.arn
    kms_key_arn               = local.kms_key_arn
  })
}

resource "aws_iam_role_policy" "scale_down_logging" {
  name = "${var.prefix}-lambda-logging"
  role = aws_iam_role.scale_down.name
  policy = templatefile("${path.module}/policies/lambda-cloudwatch.json", {
    log_group_arn = aws_cloudwatch_log_group.scale_down.arn
  })
}

resource "aws_iam_role_policy_attachment" "scale_down_vpc_execution_role" {
  count      = length(var.lambda_subnet_ids) > 0 ? 1 : 0
  role       = aws_iam_role.scale_down.name
  policy_arn = "arn:${var.aws_partition}:iam::aws:policy/service-role/AWSLambdaVPCAccessExecutionRole"
}