feat: Added anomaly detection support (#36)

Co-authored-by: Enver Cicak <ecicak@eworklabs.io>

Author: enver

examples/lambda-metric-alarm/README.md

@@ -31,6 +31,7 @@ No providers.
 | Name | Source | Version |
 |------|--------|---------|
 | <a name="module_alarm"></a> [alarm](#module\_alarm) | ../../modules/metric-alarm | n/a |
+| <a name="module_alarm_anomaly"></a> [alarm\_anomaly](#module\_alarm\_anomaly) | ../../modules/metric-alarm | n/a |
 | <a name="module_alarm_metric_query"></a> [alarm\_metric\_query](#module\_alarm\_metric\_query) | ../../modules/metric-alarm | n/a |
 | <a name="module_all_lambdas_errors_alarm"></a> [all\_lambdas\_errors\_alarm](#module\_all\_lambdas\_errors\_alarm) | ../../modules/metric-alarm | n/a |
 | <a name="module_aws_lambda_function1"></a> [aws\_lambda\_function1](#module\_aws\_lambda\_function1) | ../fixtures/aws_lambda_function | n/a |

examples/lambda-metric-alarm/main.tf

@@ -106,3 +106,44 @@ module "alarm_metric_query" {
     Secure = "maybe"
   }
 }
+
+module "alarm_anomaly" {
+  source = "../../modules/metric-alarm"
+
+  alarm_name          = "lambda-invocations-anomaly-${module.aws_lambda_function2.random_id}"
+  alarm_description   = "Lambda invocations anomaly"
+  comparison_operator = "LessThanLowerOrGreaterThanUpperThreshold"
+  evaluation_periods  = 1
+  threshold_metric_id = "ad1"
+
+  metric_query = [{
+    id = "ad1"
+
+    return_data = true
+    expression  = "ANOMALY_DETECTION_BAND(m1, 2)"
+    label       = "Invocations (expected)"
+    return_data = "true"
+    },
+    {
+      id = "m1"
+
+      metric = [{
+        namespace   = "AWS/Lambda"
+        metric_name = "Invocations"
+        period      = 60
+        stat        = "Sum"
+        unit        = "Count"
+
+        dimensions = {
+          FunctionName = module.aws_lambda_function2.lambda_function_name
+        }
+      }]
+      return_data = "true"
+  }]
+
+  alarm_actions = [module.aws_sns_topic.sns_topic_arn]
+
+  tags = {
+    Secure = "maybe"
+  }
+}

modules/metric-alarm/README.md

@@ -47,7 +47,8 @@ No modules.
 | <a name="input_period"></a> [period](#input\_period) | The period in seconds over which the specified statistic is applied. | `string` | `null` | no |
 | <a name="input_statistic"></a> [statistic](#input\_statistic) | The statistic to apply to the alarm's associated metric. Either of the following is supported: SampleCount, Average, Sum, Minimum, Maximum | `string` | `null` | no |
 | <a name="input_tags"></a> [tags](#input\_tags) | A mapping of tags to assign to all resources | `map(string)` | `{}` | no |
-| <a name="input_threshold"></a> [threshold](#input\_threshold) | The value against which the specified statistic is compared. | `number` | n/a | yes |
+| <a name="input_threshold"></a> [threshold](#input\_threshold) | The value against which the specified statistic is compared. | `number` | `null` | no |
+| <a name="input_threshold_metric_id"></a> [threshold\_metric\_id](#input\_threshold\_metric\_id) | If this is an alarm based on an anomaly detection model, make this value match the ID of the ANOMALY\_DETECTION\_BAND function. | `string` | `null` | no |
 | <a name="input_treat_missing_data"></a> [treat\_missing\_data](#input\_treat\_missing\_data) | Sets how this alarm is to handle missing data points. The following values are supported: missing, ignore, breaching and notBreaching. | `string` | `"missing"` | no |
 | <a name="input_unit"></a> [unit](#input\_unit) | The unit for the alarm's associated metric. | `string` | `null` | no |
 

modules/metric-alarm/main.tf

@@ -50,6 +50,7 @@ resource "aws_cloudwatch_metric_alarm" "this" {
       }
     }
   }
+  threshold_metric_id = var.threshold_metric_id
 
   tags = var.tags
 }

modules/metric-alarm/variables.tf

@@ -28,6 +28,13 @@ variable "evaluation_periods" {
 variable "threshold" {
   description = "The value against which the specified statistic is compared."
   type        = number
+  default     = null
+}
+
+variable "threshold_metric_id" {
+  description = "If this is an alarm based on an anomaly detection model, make this value match the ID of the ANOMALY_DETECTION_BAND function."
+  type        = string
+  default     = null
 }
 
 variable "unit" {