add alarms for failed lambdas

terraform/modules/alpr_clusters/main.tf

@@ -89,3 +89,23 @@ resource "aws_cloudwatch_log_group" "lambda_log_group" {
   name              = "/aws/lambda/${aws_lambda_function.overpass_lambda.function_name}"
   retention_in_days = 14
 }
+
+resource "aws_sns_topic" "lambda_alarms" {
+  name = "${var.module_name}_lambda_alarms"
+}
+
+resource "aws_cloudwatch_metric_alarm" "lambda_error_alarm" {
+  alarm_name          = "${var.module_name}_execution_error"
+  alarm_description   = "An error has occurred while executing the ${var.module_name} Lambda"
+  namespace           = "AWS/Lambda"
+  metric_name         = "Errors"
+  dimensions          = {
+    FunctionName = aws_lambda_function.overpass_lambda.function_name
+  }
+  statistic           = "Sum"
+  period              = 86400 # 1 day
+  evaluation_periods  = 1
+  threshold           = 0
+  comparison_operator = "GreaterThanThreshold"
+  alarm_actions       = [var.sns_topic_arn]
+}

terraform/modules/alpr_clusters/variables.tf

@@ -9,3 +9,8 @@ variable "deflock_cdn_bucket" {
 variable "rate" {
   description = "Rate at which to run the Lambda function"
 }
+
+variable "sns_topic_arn" {
+  description = "The ARN of the SNS topic for Lambda alarms"
+  type        = string
+}

terraform/modules/alpr_counts/main.tf

@@ -120,3 +120,22 @@ resource "aws_iam_role_policy_attachment" "lambda_cloudwatch_logs_attachment" {
   role       = aws_iam_role.lambda_role.name
   policy_arn = aws_iam_policy.lambda_cloudwatch_logs_policy.arn
 }
+
+# Alarms for Failure
+
+resource "aws_cloudwatch_metric_alarm" "lambda_error_alarm" {
+  alarm_name          = "${var.module_name}_execution_error"
+  alarm_description   = "An error has occurred while executing the ${var.module_name} Lambda"
+  comparison_operator = "GreaterThanThreshold"
+  evaluation_periods  = 1
+  metric_name         = "Errors"
+  namespace           = "AWS/Lambda"
+  period              = 86400 # 1 day
+  statistic           = "Sum"
+  threshold           = 0
+  dimensions = {
+    FunctionName = aws_lambda_function.overpass_lambda.function_name
+  }
+
+  alarm_actions = [var.sns_topic_arn]
+}

terraform/modules/alpr_counts/variables.tf

@@ -26,3 +26,8 @@ variable "aws_account_id" {
   type        = string
   default     = "912821578123"
 }
+
+variable "sns_topic_arn" {
+  description = "The ARN of the SNS topic for Lambda alarms"
+  type        = string
+}