Question: How to store an arbitrary value in state?

[gtmtech]

Terraform Version

N/A

Use Cases

I want to store an arbitrary value in state. I will know the value (passed in by an environment variable), and I just want to store it in state. I imagine there is a provider for this somewhere but I couldn't see an easy one to use .

My actual usecase is that I want to know from which git commit a terraform infra was last deployed. I have all my terraform resources in a module (module.root), so i figure outside the top level module I'll have some arbirary resource like this:

resource "some_resource" "git_commit_hash" {
    value = var.git_commit_hash
    depends_on = [ 
        module.root
    ]
}

This will mean the some_resource only gets applied when everything in the module.root is successfully applied - great!

By looking at all my git_commit_hash resources across all my statefiles I will understand the last successful githash that was applied.

Attempted Solutions

I am looking for a provider or terraform resource that can just store a value, and I cant think of one, despite searching. I'm sure there is one

Proposal

No response

References

No response

[gtmtech]

Related somewhat to #2550 which @crw closed recently

[bflad]

Related: #31757

[jbardin]

Hi @gtmtech,

The objects which are stored in state consist of managed resources, and root modules output. The canonical utility resource for storing arbitrary values is the null_resource, but as @bflad mentioned, there is a proposal for a more flexible builtin resources to take its place.

[gtmtech]

@jbardin I didn't think null_resource stored any values in state? - what am I missing?

[jonwtech]

How about:

resource "local_file" "hash" {
  content  = var.git_commit_hash
  filename = "/dev/null"
  depends_on = [ 
    module.root
  ]
}

Not perfect as Terraform will always want to create the resource, but the value is stored in state.

[jbardin]

@gtmtech, null_resource has a triggers attribute which is a map that can store any number of string values. The above PR for a terraform_data resource has been merged for v1.4, which has dynamically typed attributes that can store any type.

Closed via #31757

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