feat: add sns topic for grafana alerts

Resolves #8 by adding an SNS topic for grafana alerts.

Changes made:
- Exposed SNS as a vpc endpoint.
- Created the SNS topic.
- Assigned necessary IAM roles to the Grafana workspace.
- Added an email subscription to the new topic, the email list can be configured through
  a variable.

pillarbox-monitoring-terraform/20-pillarbox-monitoring-app/data_transfer_service.tf

@@ -26,7 +26,7 @@ resource "aws_security_group" "transfer_task_sg" {
 
 resource "aws_cloudwatch_log_group" "transfer_log_group" {
   name              = "/ecs/pillarbox-monitoring-transfer"
-  retention_in_days = 7 # Adjust the retention period as necessary
+  retention_in_days = 7
 
   tags = {
     Name = "data-transfer-log-group"

pillarbox-monitoring-terraform/20-pillarbox-monitoring-app/grafana.tf

@@ -33,12 +33,13 @@ resource "aws_security_group" "grafana_sg" {
 ## Create a Grafana Workspace for monitoring with OpenSearch as the data source
 
 resource "aws_grafana_workspace" "grafana_workspace" {
-  name                     = "${var.application_name}-grafana"
-  account_access_type      = "CURRENT_ACCOUNT"                       # Restrict Grafana workspace to the current AWS account
-  authentication_providers = ["AWS_SSO"]                             # Use AWS SSO for authentication
-  permission_type          = "SERVICE_MANAGED"                       # Permissions managed by the service
-  role_arn                 = aws_iam_role.grafana_workspace_role.arn # IAM Role to assume for workspace access
-  data_sources             = ["AMAZON_OPENSEARCH_SERVICE"]           # Data source for Grafana
+  name                      = "${var.application_name}-grafana"
+  account_access_type       = "CURRENT_ACCOUNT"                       # Restrict Grafana workspace to the current AWS account
+  authentication_providers  = ["AWS_SSO"]                             # Use AWS SSO for authentication
+  permission_type           = "SERVICE_MANAGED"                       # Permissions managed by the service
+  role_arn                  = aws_iam_role.grafana_workspace_role.arn # IAM Role to assume for workspace access
+  data_sources              = ["AMAZON_OPENSEARCH_SERVICE"]           # Data source for Grafana
+  notification_destinations = ["SNS"]
 
   # VPC Configuration: Attach workspace to subnets and security group
   vpc_configuration {
@@ -62,3 +63,25 @@ resource "aws_grafana_workspace" "grafana_workspace" {
     Name = "grafana-workspace"
   }
 }
+
+# -----------------------------------
+# AWS SNS Topic for Alerts
+# -----------------------------------
+
+# Create an SNS Topic for Grafana Alerts
+resource "aws_sns_topic" "grafana_alerts" {
+  name = "grafana-alerts"
+
+  tags = {
+    Name = "grafana-alert-sns-topic"
+  }
+}
+
+# Create SNS Topic Subscriptions for Email List
+resource "aws_sns_topic_subscription" "email_subscriptions" {
+  for_each = toset(var.alert_emails)
+
+  topic_arn = aws_sns_topic.grafana_alerts.arn
+  protocol  = "email"
+  endpoint  = each.key
+}

pillarbox-monitoring-terraform/20-pillarbox-monitoring-app/iam.tf

@@ -130,6 +130,27 @@ resource "aws_iam_role_policy_attachment" "grafana_opensearch_policy_attach" {
   policy_arn = aws_iam_policy.grafana_opensearch_policy.arn
 }
 
+# SNS Publish Policy Document for Grafana
+data "aws_iam_policy_document" "grafana_sns_publish_policy" {
+  statement {
+    actions   = ["sns:Publish", "sns:GetTopicAttributes"]
+    resources = [aws_sns_topic.grafana_alerts.arn]
+  }
+}
+
+# SNS Publish Policy for Grafana
+resource "aws_iam_policy" "grafana_sns_publish_policy" {
+  name   = "grafana-sns-publish-policy"
+  policy = data.aws_iam_policy_document.grafana_sns_publish_policy.json
+}
+
+# Attach SNS Publish Policy to Grafana Role
+resource "aws_iam_role_policy_attachment" "grafana_sns_publish_policy_attach" {
+  role       = aws_iam_role.grafana_workspace_role.name
+  policy_arn = aws_iam_policy.grafana_sns_publish_policy.arn
+}
+
+
 # -----------------------------------
 # OpenSearch Access Policies
 # -----------------------------------

pillarbox-monitoring-terraform/20-pillarbox-monitoring-app/main.tf

@@ -128,7 +128,7 @@ resource "aws_security_group" "vpc_endpoints_sg" {
     to_port     = 443
     security_groups = [
       aws_security_group.dispatch_task_sg.id,
-      aws_security_group.transfer_task_sg.id
+      aws_security_group.transfer_task_sg.id,
     ]
   }
 
@@ -191,3 +191,38 @@ resource "aws_vpc_endpoint" "cloudwatch_logs" {
     Name = "vpc-cloudwatch-logs-endpoint"
   }
 }
+
+
+# Security Group for the SNS VPC Endpoint
+resource "aws_security_group" "sns_vpc_endpoint_sg" {
+  name        = "sns-vpc-endpoint-sg"
+  description = "Associated to SNS Endpoint"
+  vpc_id      = local.vpc_id
+
+  # Ingress rule to allow access to VPC endpoints
+  ingress {
+    description     = "Allow Grafana to publish to SNS topics"
+    protocol        = "tcp"
+    from_port       = 443
+    to_port         = 443
+    security_groups = [aws_security_group.grafana_sg.id]
+  }
+
+  tags = {
+    Name = "sns-vpc-endpoint-sg"
+  }
+}
+
+# VPC Endpoint for SNS
+resource "aws_vpc_endpoint" "sns" {
+  vpc_id              = data.aws_vpc.main_vpc.id
+  service_name        = "com.amazonaws.${data.aws_region.current.name}.sns"
+  vpc_endpoint_type   = "Interface"
+  subnet_ids          = data.aws_subnets.private_subnets.ids
+  security_group_ids  = [aws_security_group.sns_vpc_endpoint_sg.id]
+  private_dns_enabled = true
+
+  tags = {
+    Name = "vpc-sns-endpoint"
+  }
+}

pillarbox-monitoring-terraform/20-pillarbox-monitoring-app/outputs.tf

@@ -12,3 +12,8 @@ output "dispatch_dns_name" {
   description = "The DNS name of the Dispatch Service Load Balancer"
   value       = aws_alb.dispatch_alb.dns_name
 }
+
+output "grafana_alert_topic" {
+  description = "The ARN of the topic for grafana alerts"
+  value       = aws_sns_topic.grafana_alerts.arn
+}

pillarbox-monitoring-terraform/20-pillarbox-monitoring-app/variables.tf

@@ -24,5 +24,9 @@ variable "pillarbox_domain_name" {
   description = "The public domain name of the service"
   type        = string
   default     = "pillarbox.ch"
+}
 
+variable "alert_emails" {
+  description = "List of email addresses to subscribe to SNS topic for Grafana alerts"
+  type        = list(string)
 }