ECS: Use FARGATE_SPOT capacity provider

db.tf

@@ -31,6 +31,9 @@ resource "aws_rds_cluster" "this" {
 }
 
 resource "aws_rds_cluster_instance" "cluster_instances" {
+  count              = 3
+  availability_zone = module.vpc.azs[count.index % length(module.vpc.azs)]
+
   engine             = "aurora-mysql"
   engine_version     = "8.0.mysql_aurora.3.04.1"
   cluster_identifier = "${var.prefix}-${var.environment}"

fargate.tf

@@ -106,11 +106,11 @@ resource "aws_ecs_cluster" "this" {
 }
 
 resource "aws_ecs_cluster_capacity_providers" "cluster" {
-  cluster_name = "${var.prefix}-${var.environment}"
-
-  capacity_providers = ["FARGATE_SPOT", "FARGATE"]
-
+  cluster_name       = "${var.prefix}-${var.environment}"
+  capacity_providers = ["FARGATE_SPOT"]
   default_capacity_provider_strategy {
+    base              = 0
+    weight            = 10
     capacity_provider = "FARGATE_SPOT"
   }
 }
@@ -148,14 +148,15 @@ resource "aws_ecs_service" "this" {
   desired_count          = var.desired_count
   launch_type            = "FARGATE"
   enable_execute_command = true
+
   network_configuration {
     security_groups = [
       aws_security_group.alb.id,
       aws_security_group.db.id,
       aws_security_group.efs.id,
       aws_security_group.elasticache.id
-      ]
-    subnets         = module.vpc.private_subnets
+    ]
+    subnets = module.vpc.private_subnets
   }
 
   load_balancer {
@@ -165,12 +166,14 @@ resource "aws_ecs_service" "this" {
   }
 
   lifecycle {
-    ignore_changes = [desired_count]
+    ignore_changes = [
+      task_definition,
+      desired_count,
+      capacity_provider_strategy
+    ]
   }
-
 }
 
-
 resource "aws_ecs_task_definition" "this" {
   family                   = "${var.prefix}-${var.environment}"
   execution_role_arn       = aws_iam_role.task_execution_role.arn

variables.tf

@@ -27,7 +27,7 @@ variable "error_ttl" {
 
 variable "desired_count" {
   description = "The number of instances of fargate tasks to keep running"
-  default     = "2"
+  default     = "3"
 }
 variable "log_retention_in_days" {
   description = "The number of days to retain cloudwatch log"