Terraform Interpolation Into a var with map lookup

1
votes

I have exported my current resources using Terraforming and got a huge file which holds all the security groups.

The thing is, that in each security group there are some rules which refers to the security groups IDs - which doesnt exists in the new region i'm planning to run terraform on. for example:

resource "aws_security_group" "my-group" {
    name        = "my-group"
    description = ""
    vpc_id      = "${var.vpc["production"]}"

    ingress {
        from_port       = 80
        to_port         = 80
        protocol        = "tcp"
        security_groups = ["sg-25bee542"] <-- this ID doesnt exists in the new region i'm planning to work on
        self            = false
    }

I've created a map with all the old security groups:

variable "security_groups" {
    type    = "map"
    default = {
        "sg-acd22fdb" = "default"
        "sg-52cd3025" = "my-group"
        "sg-25bee542" = "my-group2"
        ...
    }
}

Now I am trying to resolve the hard coded sg-*id* to the corresponding security group name and interpolate that into a variable so the first example will work this way:

resource "aws_security_group" "my-group" {
    name        = "my-group"
    description = ""
    vpc_id      = "${var.vpc["production"]}"

    ingress {
        from_port       = 80
        to_port         = 80
        protocol        = "tcp"
        security_groups = ["${aws_security_group.my-group2.id}"] <-- the 'my-group2' should be resolved from the map variable
        self            = false
    }

Something like:

resource "aws_security_group" "my-group" {
    name        = "my-group"
    description = ""
    vpc_id      = "${var.vpc["production"]}"

    ingress {
        from_port       = 80
        to_port         = 80
        protocol        = "tcp"
        security_groups = ["${aws_security_group.[lookup(security_groups,sg-25bee542]].id}"] <-- the 'my-group2' string should be resolved from the map variable by looking its sg ID
        self            = false
    }

I hope I made myself clear on that issue...any ideas?

2
terraform
Why not just find and replace in your editor since you already know what you want to replace them with? Why make Terraform do this? – Brandon Miller
that will be the last option, its still a lot of work to replace all these security groups. – Broshi
It looks like its impossible: github.com/hashicorp/terraform/issues/4816 – Broshi

2 Answers

2
votes

The way you access a map variable in terraform is like this

${var.security_groups["sg-acd22fdb"]}

If you want to get the sg_ID, you can create the map the other way around.

variable "security_groups" {
    type    = "map"
    default = {
        "default = "sg-acd22fdb"
        "my-group" = "sg-52cd3025"
        "my-group2" = "sg-25bee542"
        ...
    }
}

And then use 

${var.security_groups["my-group2"]}
1
votes

As suggested, you need to reverse the map. you can either reverse it at the origin (variable declaration) or use the transpose(map) function. something like

${transpose(var.security_groups)["sg-acd22fdb"]}

might work