title: Break terraform aws_rds_cluster replication in the Cross Region Cluster
body: <p>Using Terraform, I am able to successfully create a RDS cluster using the following config in Region 1 -</p>
  
  <pre><code>resource "aws_rds_cluster" "aurora_cluster" {
  
      cluster_identifier              = "${var.environment_name}-aurora-cluster"
      database_name                   = "mydb"
      master_username                 = "${var.rds_master_username}"
      master_password                 = "${var.rds_master_password}"
      backup_retention_period         = 14
      final_snapshot_identifier       = "${var.environment_name}AuroraCluster"
  
      apply_immediately               = true
      db_cluster_parameter_group_name = "${aws_rds_cluster_parameter_group.default.name}"
  
      tags {
          Name         = "${var.environment_name}-Aurora-DB-Cluster"
          ManagedBy    = "terraform"
          Environment  = "${var.environment_name}"
      }
  
      lifecycle {
          create_before_destroy = true
      }
  }
  
  resource "aws_rds_cluster_instance" "aurora_cluster_instance" {
  
      count                 = "${length(split(",", var.multi_azs))}"
  
      identifier            = "${var.environment_name}-aurora-instance-${count.index}"
      cluster_identifier    = "${aws_rds_cluster.aurora_cluster.id}"
      instance_class        = "db.t2.small"
      publicly_accessible   = true
      apply_immediately     = true
  
      tags {
          Name         = "${var.environment_name}-Aurora-DB-Instance-${count.index}"
          ManagedBy    = "terraform"
          Environment  = "${var.environment_name}"
      }
  
      lifecycle {
          create_before_destroy = true
      }
  }
  
  output "db_primary_cluster_arn" {
   rds_cluster.aurora_cluster.cluster_identifier}"
    value = "${"${format("arn:aws:rds:%s:%s:cluster:%s", "${var.db_region}", "${data.aws_caller_identity.current.account_id}", "${aws_rds_cluster.aurora_cluster.cluster_identifier}")}"}"
  }
  </code></pre>
  
  <p>and create a Cross Region replica using the below, in region 2 -</p>
  
  <pre><code>resource "aws_rds_cluster" "aurora_crr_cluster" {
  
      cluster_identifier            = "${var.environment_name}-aurora-crr-cluster"
      database_name                 = "mydb"
      master_username               = "${var.rds_master_username}"
      master_password               = "${var.rds_master_password}"
      backup_retention_period       = 14
      final_snapshot_identifier     = "${var.environment_name}AuroraCRRCluster"
      apply_immediately             = true
  
      # Referencing to the primary region's cluster
      replication_source_identifier = "${var.db_primary_cluster_arn}"
  
      tags {
          Name         = "${var.environment_name}-Aurora-DB-CRR-Cluster"
          ManagedBy    = "terraform"
          Environment  = "${var.environment_name}"
      }
  
      lifecycle {
          create_before_destroy = true
      }
  
  }
  
  resource "aws_rds_cluster_instance" "aurora_crr_cluster_instance" {
  
      count                 = "${length(split(",", var.multi_azs))}"
  
      identifier            = "${var.environment_name}-aurora-crr-instance-${count.index}"
      cluster_identifier    = "${aws_rds_cluster.aurora_crr_cluster.id}"
      instance_class        = "db.t2.small"
      publicly_accessible   = true
      apply_immediately     = true
  
      tags {
          Name         = "${var.environment_name}-Aurora-DB-Instance-${count.index}"
          ManagedBy    = "terraform"
          Environment  = "${var.environment_name}"
      }
  
      lifecycle {
          create_before_destroy = true
      }
  
  }
  </code></pre>
  
  <p>When I want to promote the Cross Region Replica in Region 2 to a stand alone cluster - I try to remove the replication source (replication_source_identifier) from the Cross Region RDS Cluster and do "terraform apply". I see that the output from Terraform says - </p>
  
  <pre><code>module.db_replica.aws_rds_cluster.aurora_crr_cluster: Modifying... (ID: dev-aurora-crr-cluster)
    replication_source_identifier: "arn:aws:rds:us-east-2:account_nbr:cluster:dev-aurora-cluster" =&gt; ""
  module.db_replica.aws_rds_cluster.aurora_crr_cluster: Modifications complete after 1s (ID: dev-aurora-crr-cluster)
  
  Apply complete! Resources: 0 added, 1 changed, 0 destroyed.
  </code></pre>
  
  <p>But, I see "NO CHANGE" happening to the cross region cluster on the AWS console. I still see that the replication source is existing and same and the cross region cluster is NOT updated to a "standalone" in AWS.</p>
  
  <p>If I try to do the same thing via the AWS CLI - </p>
  
  <pre><code>aws rds promote-read-replica-db-cluster --db-cluster-identifier="dev-aurora-crr-cluster" --region="us-west-1"
  </code></pre>
  
  <p>I see that the change is triggered immediately and the Cross Region Replica is promoted to a stand alone cluster. Does anyone know where I may be doing things wrong?
   or Terraform does not support promoting Cross Regional Replica's to standalone clusters. Please advice.</p>