Elasticache replication group with Cloudformation and controlled by Terraform

tf

resource "template_file" "cf" {
  vars {
    cluster_name = "${var.cluster_name}"
    csg_name = "${aws_elasticache_subnet_group.default_redis_sg.name}"
    cluster_internal_sg_id = "${module.ecs-cluster.cluster_internal_sg_id}"
  }

  template = <<STACK
{
"Resources" : {
  "replgrp": {
    "Type" : "AWS::ElastiCache::ReplicationGroup",
    "Properties" : {
      "AutomaticFailoverEnabled" : "true",
      "AutoMinorVersionUpgrade" : "true",
      "CacheNodeType" : "cache.m3.medium",
      "CacheSubnetGroupName" : "${csg_name}",
      "Engine" : "redis",
      "NumCacheClusters" : "3",
      "Port" : "6379",
      "ReplicationGroupDescription" : "Replication Group for ${cluster_name}",
      "SecurityGroupIds" : ["${cluster_internal_sg_id}"]
    }
  }
},
"Outputs" : {
  "endpoint" : {
    "Description": "Redis Cluster Endpoint",
    "Value" : { "Fn::GetAtt" : [ "replgrp", "PrimaryEndPoint.Address"]}
  },
  "clusterid" : {
    "Description": "Cluster ID",
    "Value" : { "Ref": "replgrp" }
  }
  }
}
STACK

}

resource "aws_cloudformation_stack" "elasticache" {
  name = "${var.cluster_name}-replication-group"
  on_failure = "ROLLBACK"
  template_body = "${template_file.cf.rendered}"

  lifecycle {
    create_before_destroy = false
  }
}

output "elasticache-endpoint" {
  value = "${aws_cloudformation_stack.elasticache.outputs.endpoint}"
}

output "clusterid" {
  value = "${aws_cloudformation_stack.elasticache.outputs.clusterid}"
}

resource "null_resource" "modify-replication-group" {
  provisioner "local-exec" {
    command = "aws elasticache modify-replication-group --replication-group-id ${aws_cloudformation_stack.elasticache.outputs.clusterid} --snapshotting-cluster-id ${aws_cloudformation_stack.elasticache.outputs.clusterid}-001  --snapshot-retention-limit 7"
  }
}