Avoiding lambda invocation during terraform plan phase

Question

I have a lambda which I want to invoke once during terraform apply since it updates a database and should be triggered only once in the apply phase.
My problem is that terraform invokes it during the plan phase as well.
Is there a way to run it only during the apply phase?
Example:

data "aws_lambda_invocation" "run_lambda" {
  function_name = "test"

  input = <<JSON
  {}
  JSON
}

Answer 1

You need to use the aws_lambda_invocation resource rather than data source (this tripped me up as well). From the docs:

This resource only invokes the function when the arguments call for a create or update. In other words, after an initial invocation on apply, if the arguments do not change, a subsequent apply does not invoke the function again. To dynamically invoke the function, see the triggers example below. To always invoke a function on each apply, see the aws_lambda_invocation data source.

https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/lambda_function

Answer 2

late for requester but answer for future reference: Try using depends_on: [some_resource] construct in aws_lamdbda_invocation. let the invocation depend on any other resource. If no dependency (which I hardly believe), introduce artificial one, like time_sleep. Let execution waits for 1s and make lambda dependant on it. This way terraform plan would not complain.