How can I use a git repository as an AWS Lambda source within Terraform?

Question

I'm working within Terraform to configure an AWS Lambda - and initially, I've had the JS file that is the entirety of the lambda function within my Terraform directory:

data "archive_file" "auth_requests" {
  type        = "zip"
  source_file = "${path.module}/auth_requests/index.js"
  output_path = "${path.module}/auth_requests.zip"
}

resource "aws_lambda_function" "auth_requests" {
  function_name    = "auth_requests"
  filename         = "${data.archive_file.auth_requests.output_path}"
  role             = "${aws_iam_role.auth_requests.arn}"
  handler          = "index.handler"
  source_code_hash = "${data.archive_file.auth_requests.output_base64sha256}"
  runtime          = "nodejs8.10"
}

However, it's clear that the Lambda function should get its own git repo, rather than living within our broader Terraform repo. Is there a way to use Terraform to source files from a git repo (and then brought into the generated archive)?

I could define the lambda's GitHub repo as a resource, but then what would be the next steps for getting it cloned/updated so the archive_file can refer to it? Or can a Terraform module be repurposed for something like this?

Any reason you wouldn't want the Lambda function's repo to deal with deploying it? — ydaetskcoR
Currently we've got all of our infrastructure in one repo - there's some overlapping access between apps/projects. Certainly, if we split that off more distinctly, then it could very well make sense to do what you suggest. — pat
I find it a useful model to have app specific infrastructure in the app's repo and allow the CI for the repo deploy things but I guess not everyone is happy with that. If you didn't want to do that you could have the Lambda repo be responsible for pushing it to S3 and then have your infrastructure repo be responsible for deploying it. — ydaetskcoR

moebius moebius · Accepted Answer · 2018-07-20T11:20:48

Assuming you use a Github repository to store your JS function, you can make use of the Github Content API to download a zip of the repo using curl:

curl -L -o <output zip filename> https://<github repo url>/zipball/master

You can achieve this in Terraform using the External provider instead of the Archive provider:

data "external" "download_function" {
  program = ["curl", "-L", "-o", 
"${path.module}/auth_requests.zip", "${var.github_repo_url}"]
}

The downside is that you now have an external dependency (curl).

How can I use a git repository as an AWS Lambda source within Terraform?

1 Answers