Terraform for aws_alb_listener how to add multiple target_group_arn in default action for type="forw

My Approach: I have to create an "aws_lb_listener" resource , in the default action I have type = " forward" but I don't have one target_group_arn . I have more than one target_group_arn values.

Below snippet shows frontend-listener but the target_group_arn should include more than one arn values.

resource "aws_alb_listener" "frontend-listener" { load_balancer_arn = aws_alb.ss_alb.arn port = "443" #"80" protocol = "HTTPS" depends_on = [aws_alb_target_group.aws_alb_target_group] default_action { #target_group_arn = aws_alb_target_group.aws_alb_target_group.arn type = "forward" } } 

The aws_alb_target_group resource shows multiple target-group being created .

resource "aws_alb_target_group" "aws_alb_target_group" { for_each = local.ebapp_name name = "${each.value.name}-tg" port = 80 protocol = "HTTP" vpc_id = var.vpc_id } 

I have looked at the terraform documentation but couldn't get a solution. (https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/lb_listener)

resource "aws_alb_listener_rule" "aws_alb_listener_rule"{ for_each = local.ebapp_name listener_arn = aws_alb_listener.frontend-listener.arn action { type = "forward" target_group_arn = aws_alb_target_group.aws_alb_target_group[each.value.name].arn } condition { path_pattern { values = ["/${each.value.name}/*"] } } } 

I have also mentioned the Listener rules .

The error is shown with terraform apply command and it is as below:

for actions of type 'forward', you must specify a 'forward' block or 'target_group_arn'

What changes to make to solve this error?

2 Answers

I think you could achieve that using dynamic blocks. For example:

resource "aws_alb_listener" "frontend-listener" { load_balancer_arn = aws_alb.ss_alb.arn port = "443" #"80" protocol = "HTTPS" depends_on = [aws_alb_target_group.aws_alb_target_group] default_action { type = "forward" forward { dynamic "target_group" { for_each = aws_alb_target_group.aws_alb_target_group content { arn = target_group.value["arn"] } } } } } 

The above is example only, and some adjustment may still be required to make it work as expected.

This worked for me. It adds now all three target groups to the defualt action of the listener.

locals { target_groups = ["1", "2", "3"] } resource "aws_lb_listener" "https_to_target_group" { count = length(local.target_groups) certificate_arn = aws_acm_certificate.cd.arn load_balancer_arn = aws_lb.cd.arn port = var.alb.port protocol = var.alb.protocol ssl_policy = var.alb.ssl_policy default_action { type = "forward" forward { dynamic "target_group" { for_each = local.target_groups content { arn = aws_lb_target_group.cd[target_group.key].arn } } } } 

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