Terraform AWS Cloudwatch Alarm

If you are looking for an example, it would look as follows.

First you need to create your alarm and in the in the alarm actions field reference to your sns topic arn:

resource "aws_cloudwatch_metric_alarm" "nlb_healthyhosts" {
  alarm_name        	  = "alarm name"
  Comparison_operator   = "LessThanThreshold"
  evaluation_periods 	  = "1"
  metric_name         	  = "HealthyHostCount"
  namespace           	  = "AWS/NetworkELB"
  period              	  = "60"
  statistic           		  = "Average"
  threshold           	  = var.logstash_servers_count
  alarm_description   	  = "Number of healthy nodes in Target Group"
  actions_enabled     	  = "true"
  alarm_actions       	  = [aws_sns_topic.alarm.arn]
  dimensions = {
    TargetGroup     = aws_lb_target_group.lb-tg.arn_suffix
    LoadBalancer   = aws_lb.lb.arn_suffix
  }
}

Then create the SNS topic and subscribe your email to that topic:

# SNS topic to send emails with the Alerts
resource "aws_sns_topic" "alarm" {
  name             		 = "my-alarm-topic"
  kms_master_key_id      = aws_kms_key.sns_encryption_key.id
  delivery_policy   	 = 
EOF
{
  "http": {
    "defaultHealthyRetryPolicy": {
      "minDelayTarget": 20,
      "maxDelayTarget": 20,
      "numRetries": 3,
      "numMaxDelayRetries": 0,
      "numNoDelayRetries": 0,
      "numMinDelayRetries": 0,
      "backoffFunction": "linear"
    },
    "disableSubscriptionOverrides": false,
    "defaultThrottlePolicy": {
      "maxReceivesPerSecond": 1
    }
  }
}
EOF
  ## This local exec, subscribe your email to the topic 
  provisioner "local-exec" {
    command = "aws sns subscribe --topic-arn ${self.arn} --protocol email --notification-endpoint ${var.your_email} --region ${var.main_region}"
  }
}

## KMS Key to encrypt the SNS topic (security best practises)
resource "aws_kms_key" "sns_encryption_key" {
  description             	       = "alarms sns topic encryption key"
  deletion_window_in_days = 30
  enable_key_rotation          = true

}