November 20, 2020

Terraformer Imports

I recently inherited an AWS account at my present employer which has a few VPC, managed Data Stores, a few stray instances & a couple of EKS cluters.

The Problem : No IaC

The Solution : terraform imports

Now this isnt new, here the thing was there was a lot of things to get rid off ( looking at you launchwizard7 security group ), so i needed to bring a certain part of the AWS cloud under terraform while ignoring the others. That would actually provide a definitive guideline as for me to mark resources to get rid of.

I decided to use terraform import to pull things i need into the control of terraform. So here is something that you need to know, terraform imports things from the provider to the statefile, thats it, the rest is upto you. By that i mean, you need to have an empty resource like

resource "aws_s3_bucket" "kindle-images" {

So that you can import the resource from the provider to terraform, which you would do like so

terraform import amazon-pottery-images

where the syntax is resource.desired-name actual-bucket-name

After which you need to add to the all the resource definition to complete the resource. Thats just way too much work.

Now since this isnt the first time i needed to do this, i started making notes on what needs to be kept and what needs to move. Now the last time i did this there was this very useful tool terraforming, which i could use to import resources in bulk and even have it merge states. But unfortunetely the prokect seems to have run aground, There are missing resources, fixes which have not been merged and updates to terraform version 0.12 which have not been merged.

I decided to split up the components, get the basic tier in, such as the VPC, route tables, subnets etc, which i had to use terraforming to get, then use terraform import to have a sane state. Once i got all the basic components within the purvue of terraform things started getting easier. There were issues since the latest version of terraform wasnt supported but most of those were due to the tags.

So terraforming pulled the data and tags were in the format

   tags {
      XXXX = YYYY

which needed to be converted to

   tags = {
      XXXX = YYYY

which looks like terraform moves to a map structure, which was a minor change to do especially since one has sed

Next i had to get the EKS cluster into terraform, which looks like was initially brought up using eksctl, i ended up writing a module so that i could bring up self manages nodes for them. The problem was the clusters themselves, so i put on my ruby hat and wrote what i needed to import eks resources using terraforming. So thats where the story stops, since i believed i had the bare minimum i needed to manage the infra.

I was on a slack channel a couple of months later, where i had stopped moving resources to terraform, where someone mentioned handcrafting terraform statefile since they had to move resources, so i pointed them to terraforming since i had worked with it before, but was thrown back another tool terraformer, now this peaked my interest and tried out the tool, where i got to know some of its usefulness and some of its caveats.

Let me first tell you what i dont like about it

  • New Generated Folder

    It creates a generated/<provider>/<resource>/ folder and places all the files in there, the provider, the output, the .tf file & the terraform.tfstate

  • Filters are per resource

    Filters are anyones game, i had to look at the code to figure out some of this

  • Statefiles are separate

    As mentioned above, the statefile is in the generated directory and there is no merge state in the tooling, so if you wants to move each resource into its own state, you can stop here.

  • Naming Conventions

    It would name things as some conversion of the Name tag with a prefix, to me it looked ridiculous. Imagine running terraform state get tf----www2D--**** something, it wasnt for me.

What ended up doing was to use the terraforming plan command to generate a plan file, edit it with what changes i need, naming convention, references to other resources etc was all made in the plan file post which you can import the plan file, which is an interesting feature

terraformer plan aws --resources=route53 --filter="Name=id;Value=QWWWQWQWQWQWQ" --regions=ap-southeast-2
vim generated/aws/terraformer/plan.json
terraformer import plan generated/aws/terraformer/plan.json

Post which i moved the file from generated and ran the good old terraform import to secure my infra in place.


Now to using the filters, this is something i found tricky to say the least, this field is accepted by the command line interface but how its used and interpreted is entirely upto the resource you are trying to fetch, this lead me down a path prior to reading up and figuring out what i needed to do.

I am going to use an example of 2 aws_instance and 2 aws_eip which i needed to import as those instances have a critical role, so anyone would want it in source control and under terraform.

terraformer import aws --resources=eip,ec2_instance --filter="Type=aws_eip;Name=id;Value=eipalloc-xxxxxxxx:eipalloc-yyyyyyy,Type=aws_instance;Name=id;Value=i-xxxxxxx:i-yyyyyyy" --regions=ap-south-1

Here im looking to import 2 resources aws_instance & aws_eip, these can be specified in a , separated value in the --resource field. Now the filter, since i need to apply different filters to each of aws_instance & aws_eip, you can make use of Type in filter so that you can direct terraformer to use certain filters for certain resources, what is followed by specifying the Name of the filter as id and providing the Value of it as whats required.

More examples

Here i am importing all the confirm maps in the kube-system namespace

terraformer import kubernetes --resources=configmaps --filter="Name=metadata.namespace;Value=kube-system"

Here is how you would import a specific configmap

terraformer import kubernetes --resources=configmaps --filter=";Value=aws-auth"

You get the idea, i think tool is something great to have, there is a lot of would you would need to put into it, but i think getting any infra into terraform is important.

If you have comments or thoughts hit me up

© Rahul Menon 2018