resource "aws_cloudwatch_metric_alarm" "ddb_read_throttle" {
  alarm_name          = "DDB-ReadThrottle-${local.table_name}"
  alarm_description   = "afterhours-shifts table had one or more read throttle events"
  namespace           = "AWS/DynamoDB"
  metric_name         = "ReadThrottleEvents"
  dimensions          = { TableName = aws_dynamodb_table.shifts.name }
  statistic           = "Sum"
  period              = 300
  evaluation_periods  = 1
  threshold           = 0
  comparison_operator = "GreaterThanThreshold"
  treat_missing_data  = "notBreaching"
  alarm_actions       = [local.site_alerts_arn]
}

resource "aws_cloudwatch_metric_alarm" "ddb_write_throttle" {
  alarm_name          = "DDB-WriteThrottle-${local.table_name}"
  alarm_description   = "afterhours-shifts table had one or more write throttle events"
  namespace           = "AWS/DynamoDB"
  metric_name         = "WriteThrottleEvents"
  dimensions          = { TableName = aws_dynamodb_table.shifts.name }
  statistic           = "Sum"
  period              = 300
  evaluation_periods  = 1
  threshold           = 0
  comparison_operator = "GreaterThanThreshold"
  treat_missing_data  = "notBreaching"
  alarm_actions       = [local.site_alerts_arn]
}

resource "aws_cloudwatch_metric_alarm" "alb_5xx" {
  alarm_name          = "ALB-5xx-${local.project}"
  alarm_description   = "ALB 5xx from afterhours-shift-manager"
  namespace           = "AWS/ApplicationELB"
  metric_name         = "HTTPCode_Target_5XX_Count"
  dimensions          = { LoadBalancer = aws_lb.api.arn_suffix }
  statistic           = "Sum"
  period              = 300
  evaluation_periods  = 1
  threshold           = 0
  comparison_operator = "GreaterThanThreshold"
  treat_missing_data  = "notBreaching"
  alarm_actions       = [local.site_alerts_arn]
}

resource "aws_cloudwatch_metric_alarm" "alb_latency" {
  alarm_name          = "ALB-Latency-${local.project}"
  alarm_description   = "p99 target response time on the afterhours ALB exceeded 3s"
  namespace           = "AWS/ApplicationELB"
  metric_name         = "TargetResponseTime"
  dimensions          = { LoadBalancer = aws_lb.api.arn_suffix }
  extended_statistic  = "p99"
  period              = 300
  evaluation_periods  = 3
  datapoints_to_alarm = 2
  threshold           = 3
  comparison_operator = "GreaterThanOrEqualToThreshold"
  treat_missing_data  = "notBreaching"
  alarm_actions       = [local.site_alerts_arn]
}

resource "aws_cloudwatch_metric_alarm" "alb_unhealthy_hosts" {
  alarm_name        = "ALB-UnhealthyHost-${local.project}"
  alarm_description = "Unhealthy Fargate targets on the afterhours ALB"
  namespace         = "AWS/ApplicationELB"
  metric_name       = "UnHealthyHostCount"
  dimensions = {
    LoadBalancer = aws_lb.api.arn_suffix
    TargetGroup  = aws_lb_target_group.api.arn_suffix
  }
  statistic           = "Maximum"
  period              = 60
  evaluation_periods  = 3
  datapoints_to_alarm = 3
  threshold           = 0
  comparison_operator = "GreaterThanThreshold"
  treat_missing_data  = "notBreaching"
  alarm_actions       = [local.site_alerts_arn]
}