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Asked: 2019-05-06 03:45:43 +0800 CST

terraform: force creating route_table_association on every run

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Every time I ran a plan/apply, the two of the aws_route_table_association resources are being forced to be recreated:

Terraform will perform the following actions:

<= module.mon.data.aws_subnet_ids.snetid
      id:             <computed>
      ids.#:          <computed>
      tags.%:         "1"
      tags.Name:      "zencopl-mon-*"
      vpc_id:         "vpc-0xxxxxxxxxxxxxxf"

-/+ module.mon.aws_route_table_association.snet[0] (new resource required)
      id:             "rtbassoc-058a3a92f42c51c9b" => <computed> (forces new resource)
      route_table_id: "rtb-05401d41b7281d81f" => "rtb-05401d41b7281d81f"
      subnet_id:      "subnet-032a4ee6fc6ebe945" => "${data.aws_subnet_ids.snetid.ids[count.index]}" (forces new resource)

-/+ module.mon.aws_route_table_association.snet[1] (new resource required)
      id:             "rtbassoc-09858f67c89412e90" => <computed> (forces new resource)
      route_table_id: "rtb-05401d41b7281d81f" => "rtb-05401d41b7281d81f"
      subnet_id:      "subnet-0bd026945b213219d" => "${data.aws_subnet_ids.snetid.ids[count.index]}" (forces new resource)

Looks like, it's because of the data-source that I defined to get the subnet-id:

data "aws_subnet_ids" "snetid" {
  vpc_id     = "${var.vpc_ids[var.idx]}"
  depends_on = [ "aws_subnet.snets" ]
  tags = {
    Name = "${var.vpc_names[var.idx]}-${var.inst_role}-*"
  }
}

and then it's used like this:

locals {
   a_zones = ["${slice(data.aws_availability_zones.azs.names,0,2)}"]
}
#
resource "aws_route_table_association" "snet" {
  count          = "${length(local.a_zones)}"
  route_table_id = "${aws_route_table.rtb.id}"
  subnet_id      = "${data.aws_subnet_ids.snetid.ids[count.index]}"
  depends_on     = [ "aws_subnet.snets" ]
}
#
module "mon" {
  source         = "../../modules/core-network"
  idx            = "0"
  inst_role      = "mon"
  vpc_names      = "${module.vpc.vpc_names}"
  vpc_ids        = "${module.vpc.vpc_ids}"
  ......
  ......
}

and I cannot findout what's going worng (or if it's a bug). I tried using lifecycle { ignore_changes = [ .... ]} but couldn't figure out either what's to ignore. Although it's not creating any real issue (from the deployment side) but creating a lot of confusions and really wnat to get it fixed. Can anyone point out what's I'm doing wrong or missing? Thsanks in advance!!

-San

terraform

0 Answers