Use initial target group variable

* Set the variable for preview since the currently active target group is green

Author: bogsi17

terraform/app/ecs.tf

@@ -146,7 +146,7 @@ module "web_service" {
     vpc_id  = aws_vpc.application_vpc.id
   }
   loadbalancer = {
-    target_group_arn = aws_lb_target_group.green.arn
+    target_group_arn = local.ecs_initial_lb_target_group
     container_port   = 4000
   }
   cluster_id            = aws_ecs_cluster.cluster.id

terraform/app/env/preview.tfvars

@@ -26,3 +26,4 @@ http_hosts = {
 
 minimum_replicas = 3
 appspec_bucket   = "nhse-mavis-appspec-bucket-preview"
+ecs_initial_lb_target_group = "green"

terraform/app/loadbalancer.tf

@@ -150,7 +150,7 @@ resource "aws_lb_listener_rule" "forward_to_app" {
   priority     = 50000
   action {
     type             = "forward"
-    target_group_arn = local.default_lb_target_group_arn
+    target_group_arn = local.ecs_initial_lb_target_group
   }
   condition {
     path_pattern {

terraform/app/variables.tf

@@ -257,6 +257,6 @@ variable "active_lb_target_group" {
 }
 
 locals {
-  default_lb_target_group_arn = var.active_lb_target_group == "green" ? aws_lb_target_group.green.arn : aws_lb_target_group.blue.arn
+  ecs_initial_lb_target_group = var.active_lb_target_group == "green" ? aws_lb_target_group.green.arn : aws_lb_target_group.blue.arn
   ecs_sg_ids                  = [module.web_service.security_group_id, module.good_job_service.security_group_id]
 }