Lookup function, doesn't

[delitescere]

The lookup function isn't well documented, but it isn't doing what it should:

$ terraform apply ...
aws_instance.admin: Creating...
  ami:                         "" => "${lookup(\"images\", \"us-west-2\")}"
  associate_public_ip_address: "" => "1"
  availability_zone:           "" => "<computed>"
  instance_type:               "" => "t2.micro"
  key_name:                    "" => "admin"
  private_dns:                 "" => "<computed>"
  private_ip:                  "" => "<computed>"
  public_dns:                  "" => "<computed>"
  public_ip:                   "" => "<computed>"
  security_groups.#:           "" => "1"
  security_groups.0:           "" => "sg-..."
  subnet_id:                   "" => "subnet-..."
  tags.Name:                   "" => "admin"
aws_instance.admin: Error: Error launching source instance: Invalid id: "${lookup("images", "us-west-2")}" (expecting "ami-...") (InvalidAMIID.Malformed)

Repro source terraform file, including various combinations of trying to get lookup to work:

provider "aws" {
   region = "${var.region}"
}

variable "region" {
  description = "The mnemonic name of the Region. Typically set using $AWS_DEFAULT_REGION."
  #default = "${env.AWS_DEFAULT_REGION}"
}

variable "images" {
  default = {
    us-east-1 = "ami-123"
    us-west-2 = "ami-456"
  }
}

resource "aws_instance" "admin" {
#  ami = "${file("ami.txt")}" #works if file has content but might as well use an override file
#  ami = "${var.images.us-east-1}" #works but is not dynamic
#  ami = "${lookup("images", "us-east-1")}" #works but is not dynamic
#  ami = "${lookup(images, us-east-1)}" #errors
  ami = "${lookup("images", "${var.region}")}" #fails but interpolates region, escapes quotes
#  ami = "${lookup("images", ${var.region})}" #fails but interpolates region, escapes quotes
#  ami = "${lookup(images, "${var.region}")}" #fails but interpolates region, escapes quotes
#  ami = "${lookup(images, ${var.region})}" #fails but interpolates region
#  ami = "${lookup("images", "region")}" #errors
  security_groups = ["sg-..."]
  subnet_id = "subnet-..."
  instance_type = "t2.micro"
  key_name = "admin"
  associate_public_ip_address = true
  tags {
    Name = "admin"
  }
}

Using (v0.3.1)

[frntn]

+1 on this one.

Plus for the first file attempt, the ami.txt must also be one line with no LF.

echo -n "ami-123" > ami.txt

I found this annoying. Can't terraform trim the content on its own or something ?

[delitescere]

You are correct @frntn. In this case, though, you may be better off creating "override" files that have the region-specific settings, with a file for each region. Then, temporarily copy the specific region's override file into the directory before using terraform apply, and remove it after. I think that's what I'm going to do for now. 😣

[dhoppe]

The lookup does not work because you have used images as a string and not as a variable.

The following example correspond to the current documentation and works with version 0.3.6.

variable "region" {
    default = "eu-west-1"
}

variable "ami" {
    default = {
        ap-northeast-1 = "ami-b25d44b3" # Asia Pacific (Tokyo)
        ap-southeast-1 = "ami-aeb49ffc" # Asia Pacific (Singapore)
        ap-southeast-2 = "ami-6b770351" # Asia Pacific (Sydney)
        eu-central-1 = "ami-98043785"   # EU (Frankfurt)
        eu-west-1 = "ami-61e56916"  # EU (Ireland)
        sa-east-1 = "ami-3d8b3720"  # South America (Sao Paulo)
        us-east-1 = "ami-e0efab88"  # US East (N. Virginia)
        us-west-1 = "ami-b4869ff1"  # US West (N. California)
        us-west-2 = "ami-431a4273"  # US West (Oregon)
    }
}

resource "aws_instance" "example" {
    ami = "${lookup(var.ami, var.region)}"
    ...
}

[delitescere]

Thanks @dhoppe I'll give that a crack!

[mitchellh]

I updated the website. Also, a lot more of your 2nd parameter cases work as of 0.3.7. :)

[ghost]

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