gistfile1.txt

### terraform alarms for schedulers
resource "aws_cloudwatch_metric_alarm" "memory-critical-scheduler-1" {
  alarm_name          = "exago-${var.environment}-scheduler-1-memory-critical"
  alarm_description   = "Exago ${var.environment} scheduler-1 memory is critical."
  comparison_operator = "LessThanOrEqualToThreshold"
  evaluation_periods  = "2"
  alarm_description   = "This alarm is for critical scheduler memory usage"
  alarm_actions       = ["${var.sns_topics["sev1"]}"]
  threshold   = "262144000"
  metric_query {
    id = "m1"
    metric {
      metric_name = "mem_total"
      namespace   = "exago-schedulers"
      period      = "60"
      stat        = "Average"
      dimensions  = {  
        host  = "ip-172-31-30-70.us-west-2.compute.internal"
      }
    }
  }
}

gistfile2.txt

Error: Error applying plan:

1 error(s) occurred:

* module.alarms.aws_cloudwatch_metric_alarm.memory-critical-scheduler-1: 1 error(s) occurred:

* aws_cloudwatch_metric_alarm.memory-critical-scheduler-1: Creating metric alarm failed: ValidationError: Exactly one element of the metrics list should return data.
	status code: 400, request id: f8e3ff7e-7e17-11e9-a1de-eb8f55cf2e51

Terraform does not automatically rollback in the face of errors.
Instead, your Terraform state file has been partially updated with
any resources that successfully completed. Please address the error
above and apply again to incrementally change your infrastructure.

perhaps this?
https://gist.github.com/lupupaulsv/f7c19cfc2d1822715e8a90bbe4374fd9#file-gistfile1-txt-L8

might need just to return one element and not the whole list. Don't see the metric list anywhere tho

alarm_actions = ["${var.sns_topics["sev1"]}"]