provider/aws: Add support for evaluate_low_sample_count_percentiles to cloudwatch_metric_alarm (#13371)

```

```

builtin/providers/aws/resource_aws_cloudwatch_metric_alarm.go

@@ -105,6 +105,12 @@ func resourceAwsCloudWatchMetricAlarm() *schema.Resource {
 				Default:      "missing",
 				ValidateFunc: validation.StringInSlice([]string{"breaching", "notBreaching", "ignore", "missing"}, true),
 			},
+			"evaluate_low_sample_count_percentiles": {
+				Type:         schema.TypeString,
+				Optional:     true,
+				Computed:     true,
+				ValidateFunc: validation.StringInSlice([]string{"evaluate", "ignore"}, true),
+			},
 		},
 	}
 }
@@ -172,6 +178,7 @@ func resourceAwsCloudWatchMetricAlarmRead(d *schema.ResourceData, meta interface
 	d.Set("unit", a.Unit)
 	d.Set("extended_statistic", a.ExtendedStatistic)
 	d.Set("treat_missing_data", a.TreatMissingData)
+	d.Set("evaluate_low_sample_count_percentiles", a.EvaluateLowSampleCountPercentile)
 
 	return nil
 }
@@ -248,6 +255,10 @@ func getAwsCloudWatchPutMetricAlarmInput(d *schema.ResourceData) cloudwatch.PutM
 		params.ExtendedStatistic = aws.String(v.(string))
 	}
 
+	if v, ok := d.GetOk("evaluate_low_sample_count_percentiles"); ok {
+		params.EvaluateLowSampleCountPercentile = aws.String(v.(string))
+	}
+
 	var alarmActions []*string
 	if v := d.Get("alarm_actions"); v != nil {
 		for _, v := range v.(*schema.Set).List() {

builtin/providers/aws/resource_aws_cloudwatch_metric_alarm_test.go

@@ -61,6 +61,33 @@ func TestAccAWSCloudWatchMetricAlarm_treatMissingData(t *testing.T) {
 	})
 }
 
+func TestAccAWSCloudWatchMetricAlarm_evaluateLowSampleCountPercentiles(t *testing.T) {
+	var alarm cloudwatch.MetricAlarm
+	rInt := acctest.RandInt()
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckAWSCloudWatchMetricAlarmDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccAWSCloudWatchMetricAlarmConfigTreatEvaluateLowSampleCountPercentiles(rInt),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckCloudWatchMetricAlarmExists("aws_cloudwatch_metric_alarm.foobar", &alarm),
+					resource.TestCheckResourceAttr("aws_cloudwatch_metric_alarm.foobar", "evaluate_low_sample_count_percentiles", "evaluate"),
+				),
+			},
+			{
+				Config: testAccAWSCloudWatchMetricAlarmConfigTreatEvaluateLowSampleCountPercentilesUpdated(rInt),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckCloudWatchMetricAlarmExists("aws_cloudwatch_metric_alarm.foobar", &alarm),
+					resource.TestCheckResourceAttr("aws_cloudwatch_metric_alarm.foobar", "evaluate_low_sample_count_percentiles", "ignore"),
+				),
+			},
+		},
+	})
+}
+
 func TestAccAWSCloudWatchMetricAlarm_extendedStatistic(t *testing.T) {
 	var alarm cloudwatch.MetricAlarm
 	rInt := acctest.RandInt()
@@ -222,6 +249,46 @@ resource "aws_cloudwatch_metric_alarm" "foobar" {
 }`, rInt)
 }
 
+func testAccAWSCloudWatchMetricAlarmConfigTreatEvaluateLowSampleCountPercentiles(rInt int) string {
+	return fmt.Sprintf(`
+resource "aws_cloudwatch_metric_alarm" "foobar" {
+  alarm_name                = "terraform-test-foobar%d"
+  comparison_operator       = "GreaterThanOrEqualToThreshold"
+  evaluation_periods        = "2"
+  metric_name               = "CPUUtilization"
+  namespace                 = "AWS/EC2"
+  period                    = "120"
+  extended_statistic        = "p88.0"
+  threshold                 = "80"
+  alarm_description         = "This metric monitors ec2 cpu utilization"
+  evaluate_low_sample_count_percentiles = "evaluate"
+  insufficient_data_actions = []
+  dimensions {
+    InstanceId = "i-abc123"
+  }
+}`, rInt)
+}
+
+func testAccAWSCloudWatchMetricAlarmConfigTreatEvaluateLowSampleCountPercentilesUpdated(rInt int) string {
+	return fmt.Sprintf(`
+resource "aws_cloudwatch_metric_alarm" "foobar" {
+  alarm_name                = "terraform-test-foobar%d"
+  comparison_operator       = "GreaterThanOrEqualToThreshold"
+  evaluation_periods        = "2"
+  metric_name               = "CPUUtilization"
+  namespace                 = "AWS/EC2"
+  period                    = "120"
+  extended_statistic        = "p88.0"
+  threshold                 = "80"
+  alarm_description         = "This metric monitors ec2 cpu utilization"
+  evaluate_low_sample_count_percentiles = "ignore"
+  insufficient_data_actions = []
+  dimensions {
+    InstanceId = "i-abc123"
+  }
+}`, rInt)
+}
+
 func testAccAWSCloudWatchMetricAlarmConfigExtendedStatistic(rInt int) string {
 	return fmt.Sprintf(`
 resource "aws_cloudwatch_metric_alarm" "foobar" {

website/source/docs/providers/aws/r/cloudwatch_metric_alarm.html.markdown

@@ -85,6 +85,12 @@ The following arguments are supported:
 * `unit` - (Optional) The unit for the alarm's associated metric.
 * `extended_statistic` - (Optional) The percentile statistic for the metric associated with the alarm. Specify a value between p0.0 and p100.
 * `treat_missing_data` - (Optional) Sets how this alarm is to handle missing data points. The following values are supported: `missing`, `ignore`, `breaching` and `notBreaching`. Defaults to `missing`.
+* `evaluate_low_sample_count_percentiles` - (Optional) Used only for alarms
+based on percentiles. If you specify `ignore`, the alarm state will not
+change during periods with too few data points to be statistically significant.
+If you specify `evaluate` or omit this parameter, the alarm will always be
+evaluated and possibly change state no matter how many data points are available.
+The following values are supported: `ignore`, and `evaluate`.
 
 ## Attributes Reference