Deal will dict Using Maps in terraform - google-cloud-platform

Question

I'm looking for way to define a list of ssh keys in a variables file so that I could retrieve them in the tf module code for my compute instance like this :
metadata = {
ssh-keys = join("\n", [for user, key in var.ssh_keys : "${user}:${key}"])
}
Here is the content of the variables file I wrote to achieve that :
variable "ssh_keys" {
type = "map"
default = {
{
user = "amary"
key = "${file("/Users/nixmind/.ssh/amary.pub")}"
}
{
user = "nixmind"
key = "${file("/Users/nixmind/.ssh/nixmind.pub")}"
}
}
}
But I'm having this error :
Error: Missing attribute value
on variables.tf line 8, in variable "ssh_keys":
4:
5:
6:
7:
8:
9:
Expected an attribute value, introduced by an equals sign ("=").
I'm not sure to really get what to do there.

Answer 1

There are a few different problems here. I'll talk about them one at a time.
The first is that your default expression is not using correct map syntax. Here's a corrected version:
variable "ssh_keys" {
type = map(string)
default = {
amary = file("/Users/nixmind/.ssh/amary.pub")
nixmind = file("/Users/nixmind/.ssh/nixmind.pub")
}
}
The second problem is that a variable default value cannot include function calls, so the calls to file above are invalid. There are a few different options here about how to deal with this, but if this is a variable in a root module then I expect it would be most convenient to have the variable be a map of filenames rather than a map of the contents of those files, and then the module itself can read the contents of those files in a later step:
variable "ssh_key_files" {
type = map(string)
default = {
amary = "/Users/nixmind/.ssh/amary.pub"
nixmind = "/Users/nixmind/.ssh/nixmind.pub"
}
}
Your for expression for building the list of "user:key" strings was correct with how you had the variable defined before, but with the adjustment I've made above to use filenames instead of contents we'll need an extra step to actually read the files:
locals {
ssh_keys = { for u, fn in var.ssh_key_files : u => file(fn) }
}
We can then use local.ssh_keys to get the map from username to key needed for the metadata expression:
metadata = {
ssh-keys = join("\n", [for user, key in local.ssh_keys : "${user}:${key}"])
}
If you do want this module to accept already-loaded SSH key data rather than filenames then that is possible but the variable will need to be required rather than having a default, because it'll be up to the calling module to load the files.
The definition without the default value will look like this:
variable "ssh_keys" {
type = map(string)
}
Then your calling module, if there is one (that is, if this isn't a root module) can be the one to call file to load those in:
module "example" {
source = "./modules/example"
ssh_keys = {
amary = file("/Users/nixmind/.ssh/amary.pub")
nixmind = file("/Users/nixmind/.ssh/nixmind.pub")
}
}
The above is a reasonable interface for a shared module that will be called from another module like this, but it's not a convenient design for a root module because the "caller" in that case is the person or script running the terraform program, and so providing the data from those files would require reading them outside of Terraform and passing in the results.

Answer 2

My problem was semantic not syntactic, cause I can't use a map of map as tried to. Instead I used a liste and the error desapeared.
variable ssh_keys {
type = list(object({
user=string
key=string
}))
default = [
{
"user" = "amaret93"
"key" = "/Users/valerietchala/.ssh/amaret93.pub"
},
{
"user" = "nixmind"
"key" = "/Users/valerietchala/.ssh/nixmind.pub"
}
]
}
But the Martin's answer above is also a more good approach