Merge pull request #3 from digirati-co-uk/feature/deadletter

Support optional deadletter config

readme.md

@@ -42,9 +42,11 @@ Terraform creates:
 | slack_webhook_url    | Slack webhook URL to call (optional)                                   |            |
 | slack_webhook_secret | AWS SecretsManager secret storing Slack webhook URL to call (optional) |            |
 | runtime              | Python runtime to use for lambda                                       | python3.11 |
+| dead_letter_arn      | (Optional) ARN of SNS topic or SQS queue to notify if invocation fails |            |
 
 ### Outputs
 
 | Variable      | Description                                    |
 | ------------- | ---------------------------------------------- |
-| sns_topic_arn | ARN of SNS topic for handling Cloudwatch Alarm |
+| sns_topic_arn | ARN of SNS topic for handling Cloudwatch Alarm |
+| role_arn      | ARN of lambda role                             |

terraform/lambda.tf

@@ -10,6 +10,14 @@ resource "aws_lambda_function" "cloudwatch_to_slack" {
 
   role = aws_iam_role.cloudwatch_to_slack_exec_role.arn
 
+  dynamic "dead_letter_config" {
+    for_each = var.dead_letter_arn == null ? [] : [{}]
+
+    content {
+      target_arn = var.dead_letter_arn
+    }
+  }
+
   environment {
     variables = local.env_vars
   }

terraform/outputs.tf

@@ -2,3 +2,8 @@ output "sns_topic_arn" {
   value       = aws_sns_topic.cloudwatch_alarm.arn
   description = "ARN of SNS topic"
 }
+
+output "role_name" {
+  value       = aws_iam_role.cloudwatch_to_slack_exec_role.name
+  description = "Name of Lambda role"
+}

terraform/variables.tf

@@ -46,6 +46,12 @@ variable "region" {
   type        = string
 }
 
+variable "dead_letter_arn" {
+  description = "ARN of SNS topic or SQS queue to notify when invocation fails"
+  type        = string
+  default     = null
+}
+
 locals {
   env_candidates = {
     SLACK_WEBHOOK_URL    = var.slack_webhook_url