Simple Terraform demo on how to use AWS ALB with multiple apps and host header with different names / FQDN

README.md

This is the common component:

# Create a single load balancer for all Atlassian services
resource "aws_alb" "atlassian" {
  name            = "${var.name}"
  internal        = false
  idle_timeout    = "300"
  security_groups = [ 
    "${aws_security_group.atlassian-alb.id}",
    "${module.open-egress-sg.id}"
  ]
  subnets = ["${module.vpc.public_subnet_ids}"]

  enable_deletion_protection = true

# access_logs {
#   bucket = "${aws_s3_bucket.alb_logs.bucket}"
#   prefix = "test-alb"
# }

  tags {
    Name = "${var.name}"
    Apps = "Crowd-Docker_Registry-Bitbucket-JIRA"
  } 
} 
# Define a listener
resource "aws_alb_listener" "atlassian" {
  load_balancer_arn = "${aws_alb.atlassian.arn}"
  port              = "443"
  protocol          = "HTTPS"
  ssl_policy        = "ELBSecurityPolicy-2015-05"
  certificate_arn   = "${var.ssl_arn}"

  default_action {
    target_group_arn = "${aws_alb_target_group.bitbucket.arn}"
    type             = "forward"
  }
}

Then each application you want to hookup to the ALB would get something like the following:

## Connect crowd ASG up to the Application Load Balancer (see load-balancer.tf)
resource "aws_alb_target_group" "crowd" {
  name     = "${var.name}-crowd"
  port     = 8095
  protocol = "HTTP"
  vpc_id   = "${module.vpc.vpc_id}"
}

resource "aws_alb_listener_rule" "crowd" {
  listener_arn = "${aws_alb_listener.atlassian.arn}"
  priority     = 98

  action {
    type = "forward"
    target_group_arn = "${aws_alb_target_group.crowd.arn}"
  }

  condition {
    field  = "host-header"
    values = ["crowd.foobar.com"]
  }
}