Add destroy invocation to aws_lambda_invocation resource

[KyleKotowick]

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Description

The aws_lambda_invocation resource is quite new, and is an excellent addition. However, it does not offer the ability to invoke a Lambda upon destruction of the resource, which limits its usefulness.

For example, I'd like to use this resource to automatically create database users when I create RDS clusters in a private VPC that cannot be accessed from the machine running Terraform. I can now do that by creating a Lambda in that VPC that can create users, and then using this resource to invoke that Lambda once for each user I'd like to create.

But then, how can I delete the database users if I no longer need them? Ideally, I'd be able to set a destruction configuration block which would allow me to do that, similar to the local-exec provisioner with when = destroy. If this configuration block is provided, the Lambda would be invoked again upon destruction with the associated configuration.

New or Affected Resource(s)

• aws_lambda_invocation (resource)

Potential Terraform Configuration

resource "aws_lambda_invocation" "example" {
  function_name = aws_lambda_function.db_user_manager.function_name
  qualifier = "$LATEST"

  input = jsonencode({
    db_host = "db.host.com"
    db_port = "5432"
    username = local.username 
    action = "mydbuser"
  })

  destroy {
    function_name = self.function_name
    qualifier = self.qualifier
    input = jsonencode({
      db_host = self.input .db_host
      db_port = self.input .db_port
      username = self.input .username 
      action = "DESTROY"
   })
  }
}

[ugurzongur]

We have recently developed a provider to address this, along with some other issues, if you'd like to check: https://registry.terraform.io/providers/thetradedesk/lambdabased

[pvbouwel]

I've opened #29367 which would trigger the Lambda function on every resource state transition. It will manipulate the JSON payload to provide details to the Lambda function. It will add a key tf which holds the action [create, update, delete] and the prev_input (null for a create otherwise the event from the previous invocation.
So the lambda handler can decide which processing to do based on event.tf.action.
In case of an update you can also do the required changes since tf.prev_input.username and username in the JSON body will allow you to create an alter user SQL statement to implement the required changes.

This way there is no need to provision multiple lambda functions as a single function can handle each event accordingly.

[skorfmann]

We have recently developed a provider to address this, along with some other issues, if you'd like to check: https://registry.terraform.io/providers/thetradedesk/lambdabased

That's quite nice, thanks for sharing!

Would love to see the something like the finalizer in the aws provider resource as well.

[kaushal02]

We have recently developed a provider to address this, along with some other issues, if you'd like to check: https://registry.terraform.io/providers/thetradedesk/lambdabased

This seems to have been moved to a private repo now.

[github-actions]

This functionality has been released in v5.1.0 of the Terraform AWS Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
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