Question 110680 in Json Question posted in
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How to skip or avoid duplicate keys from json when using for_each

I am trying to generate Terraform resources from a JSON file that has duplicate keys.
Is there any way to avoid the duplicate?

Here is an example JSON

{
  "my-ptr-zone": {
    "21-10": {
      "zone"  : "21.10.in-addr.arpa"
    },

    "21-10": {
      "zone"  : "21.10.in-addr.arpa"
    }
  }
}

Both the keys are the same here.

And here is the resource

resource "aws_route53_zone" "my-ptr-zone" {
  for_each = var.my-ptr-zone
  name     = each.value.zone
}

Is there any way to skip the duplicates when looping?

I have tried to avoid generating duplicate values in the JSON file from the source, but that is another challenge.

Tags:

3

Answers


  1. 0

    If you want to generate only one resource per unique key in a map, ask Terraform to generate a set of the keys, then loop over those.

    Consider the following example using the hashicorp/random provider.

    locals {
  my-ptr-zone = {
    "21-10" = {
      zone = "21.10.in-addr.arpa"
    }
    "21-10" = {
      zone = "21.10.in-addr.arpa"
    }
  }
}

resource "random_id" "example" {
  for_each = toset(keys(local.my-ptr-zone))
  byte_length = 8
}

    Planning that with terraform plan, you’ll see that terraform only wants to generate one resource.

    # random_id.example["21-10"] will be created
+ resource "random_id" "example" {
  + b64_std     = (known after apply)
  + b64_url     = (known after apply)
  + byte_length = 8
  + dec         = (known after apply)
  + hex         = (known after apply)
  + id          = (known after apply)
}

Plan: 1 to add, 0 to change, 0 to destroy.

    Change one of the keys to something different, and terraform will want to create two resources.

    # random_id.example["21-10"] will be created
...

# random_id.example["21-11"] will be created
...

Plan: 2 to add, 0 to change, 0 to destroy.

    If you instead are interested in some other uniqueness (e.g. only the unique values of zone), the same approach could be applied … generate a set of the things you want to be unique, then iterate over that set.

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  2. 0

    A simple way to approach this would be to run a merge on the map twice.

    JSON File:

    {
  "my-ptr-zone": {
    "21-10": {
      "zone"  : "21.10.in-addr.arpa"
    },

    "21-10": {
      "zone"  : "21.10.in-addr.arpa"
    }
  }
}

    TF Code:

    locals {
  data  = jsondecode(file("data.json"))
  zones = merge(local.data.my-ptr-zone, local.data.my-ptr-zone)
}

output "zones" {
  value = local.zones
}

# This will now be a unique resource
resource "aws_route53_zone" "my-ptr-zone" {
  for_each = local.zones
  name     = each.value.zone
}

    Output:

    Outputs:

zones = {
  "21-10" = {
    "zone" = "21.10.in-addr.arpa"
  }
}
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  3. 0

    Terraform’s jsondecode function reacts to duplicate property names in a single object by discarding all but the last definition of a particular name.

    In the example shown in your question, jsondecode of the JSON document shown would produce the following Terraform value:

    {
  "my-ptr-zone" = {
    "21-10" = {
      "zone" = "21.10.in-addr.arpa"
    }
  }
}
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