Cdktf Trials with TypeScript

Trying out CDKTF with TypeScript

Last updated on Mar 14, 2021 7 min read
Photo by 𝓴𝓘𝓡𝓚 𝕝𝔸𝕀 on Unsplash

tl;dr

  • install the latest version of terraform 0.14.6 when using the docker provider v2.11.0
  • understand the language your using

summary

I have been wanting to try CDKTF for a while, so today seemed like a good time. Googling around for a little bit reveald some more projects that I would like to try in the future:

  • cdk8s to manage K8
  • gitops to manage K8
    1. The entire system described declaratively.
    2. The canonical desired system state versioned in Git.
    3. Approved changes that can be automatically applied to the system.
    4. Software agents to ensure correctness and alert on divergence.

I will be saving those treats for another day, but for now, lets move on with CDKTF. The contributors of CDKTF made a really good starting point CDKTF docs where you can try it out without the need of a cloud provider! Instead you use docker. This is is a really good idea as you can get to writing and running code right away without the need for some type of credentials.

After making the change to LIBSH to fix NPM I was able to proceed with the tutorial.

I went with the stable version as I have been burned way too many times with development (even though today, I use Spacemacs on the develop branch.

reference

setup

Important: must install Terraform 12 or above. This is best accomplished with terraform-env. If your using LIBSH, you can install terraform-env with the command terraform_install_tfenv. This allows you to use the command terraform-env install #.#.# to install which ever version you want installed and enabled.

coding

I made a repo called cdk-typescript-docker to track my experience. Following the tutorial, I decided to type in the small amount of code with VSCode. The auto-complete worked pretty well (even though im totally new to Typescript). Here are some things I noticed:

  1. Autocomplete worked very well and picked up custom libraries
  2. The line of import { Container, Image, DockerProvider } from './.gen/providers/docker' was marked as un-resolved and not sure why. A little annoying. This is resolved with the command cdktf get

testing deploy

Yep! Everything worked really well…

  1. cdktf deploy
    • made things in docker
    • openend localhost:80000 and greated with nginx

testing destroy

Too good to be true. Running cdktf destroy lead to the following:

typescript-docker on  master [!] is 📦 v1.0.0 via ⬢ v15.0.1 took 32s
➜ cdktf destroy
⠋ initializing typescript-docker...
2021/02/15 10:07:30 [DEBUG] Using modified User-Agent: Terraform/0.12.29 cdktf/0.1.0 (+https://github.com/hashicorp/terra⠼ planning typescript-docker...
2021/02/15 10:07:31 [DEBUG] Using modified User-Agent: Terraform/0.12.29 cdktf/0.1.0 (+https://github.com/hashicorp/terra⠴ planning typescript-docker...
2021/02/15 10:07:33 [DEBUG] Using modified User-Agent: Terraform/0.12.29 cdktf/0.1.0 (+https://github.com/hashicorp/terra⠹ Destroying Stack: typescript-docker
Resources
⠧ Destroying Stack: typescript-docker
Resources
 ✔ DOCKER_CONTAINER     nginxContainer      docker_container.nginxContainer
 ✔ DOCKER_IMAGE         nginxImage          docker_image.nginxImage
Summary: 2 destroyed.
TypeError: Cannot read property 'startsWith' of undefined
///trimmed///
Something went wrong.[2021-02-15T10:07:38.142] [ERROR] default - TypeError: Cannot read property 'startsWith' of undefined
///trimmed///

Docker container was destroyed…but not very happy about these results. Lets repeat this deploy and destroy again. Do we get the same results?

No I did not. I ran the cdktf deploy and most of the output was like before, but I got the same error again. The docker container is up, but again greeted with the same error message as above about a typeerror of startsWith being undefined.

Maybe I am using too low of terraform? Lets install the latest version.

➜ tfenv list-remote | head -8
0.15.0-alpha20210210
0.15.0-alpha20210127
0.15.0-alpha20210107
0.14.6
0.14.5
0.14.4
0.14.3
0.14.2

Lets try with 0.14.6 as the latest version.

➜ tfenv install 0.14.6
Installing Terraform v0.14.6
Downloading release tarball from https://releases.hashicorp.com/terraform/0.14.6/terraform_0.14.6_darwin_amd64.zip
################################################################################################################################################### 100.0%
Downloading SHA hash file from https://releases.hashicorp.com/terraform/0.14.6/terraform_0.14.6_SHA256SUMS
Unable to verify OpenPGP signature unless logged into keybase and following hashicorp
Archive:  tfenv_download.qEgNRa/terraform_0.14.6_darwin_amd64.zip
  inflating: /Users/addlema/.tfenv/versions/0.14.6/terraform
Installation of terraform v0.14.6 successful. To make this your default version, run 'tfenv use 0.14.6'

typescript-docker on  master is 📦 v1.0.0 via ⬢ v15.0.1 took 17s
➜ tfenv use 0.14.6
Switching default version to v0.14.6
Switching completed

Verify versions

➜ tf --version
Terraform v0.14.6

Ok lets try destroying again. Awesome. New error.

➜ cdktf destroy
⠙ planning typescript-docker...

Error: Could not load plugin


Plugin reinitialization required. Please run "terraform init".

Plugins are external binaries that Terraform uses to access and manipulate
resources. The configuration provided requires plugins which can't be located,
don't satisfy the version constraints, or are otherwise incompatible.

Terraform automatically discovers provider requirements from your
configuration, including providers used in child modules. To see the
requirements and constraints, run "terraform providers".

Failed to instantiate provider "registry.terraform.io/-/docker" to obtain
schema: unknown provider "registry.terraform.io/-/docker"


non-zero exit code 1

Makes sense. I am using a new version of terraform. In a way, this is good. If someone else were to use different versions, this is the treatment they would get when switching their tool versions. I am going to follow their requirement to proceed. But wait… it says terraform init … I want to stay with CDKTF so I would think that using cdktf init would be the correct course of action. Lets find out!

➜ cdktf init
ERROR: Cannot initialize a project in a non-empty directory

Turns out that cdktf init is only used for making projects. Oh right! We need to use cdktf get for fetching our providers or plugins. First translation!

cdktfterraform
cdktf getterraform init
➜ cdktf get
Generated typescript constructs in the output directory: .gen

Ok that seemed to be happy results. Now lets try doing a destroy again…

➜ cdktf destroy
⠦ planning typescript-docker...

Error: Could not load plugin


Plugin reinitialization required. Please run "terraform init".

Plugins are external binaries that Terraform uses to access and manipulate
resources. The configuration provided requires plugins which can't be located,
don't satisfy the version constraints, or are otherwise incompatible.

Terraform automatically discovers provider requirements from your
configuration, including providers used in child modules. To see the
requirements and constraints, run "terraform providers".

Failed to instantiate provider "registry.terraform.io/-/docker" to obtain
schema: unknown provider "registry.terraform.io/-/docker"


non-zero exit code 1

Thats a big whopping no. Seems like I have some generated code that is borking on me. Lets try to find out what it is by destroying things:

➜ rm -Rf terraform.tfstate* .gen cdktf.out main.d.ts main.js
➜ docker stop tutorial && docker rm tutorial

Now, lets start over and change providers. It seems that HashiCorp gave up on the Docker provider and gave the keys to someone else based on this README.md. With that said, here are my changes:

My applied changes

Lets run our favorite commands again:

typescript-docker on  master [!] is 📦 v1.0.0 via ⬢ v15.0.1 took 9s
➜ terraform --version
Terraform v0.14.6
➜ cdktf deploy
Deploying Stack: typescript-docker
Resources
 ✔ DOCKER_CONTAINER     nginxContainer      docker_container.nginxContainer
 ✔ DOCKER_IMAGE         nginxImage          docker_image.nginxImage

Summary: 2 created, 0 updated, 0 destroyed.

typescript-docker on  master [!] is 📦 v1.0.0 via ⬢ v15.0.1 took 9s
➜ cdktf destroy
Destroying Stack: typescript-docker
Resources
 ✔ DOCKER_CONTAINER     nginxContainer      docker_container.nginxContainer
 ✔ DOCKER_IMAGE         nginxImage          docker_image.nginxImage

Summary: 2 destroyed.

Success! Wow, that was fun.

Conclusions

In short, that was a bit annoying or confusing. I am by no means a TypeScript novice but this seemed to be an issue with the provider. I cannot say that with certainty without adding some more tests to revert back the two things I changed which were Terraform and the provider used. I will say use CDKTF does require having a mass amount of knowledge about the language you are using because when you are faced with errors, you will have to debug the generated code to trace the problem.

After reading some more articles in haste, I wonder what the real usage for Terraform really is? If you can use CDK with Python and it makes CloudFormation code, this really improves (or hides) the flaws of CloudFormation and empowers customers to use a programming language instead of an augmented JSON structure.

I would like to try out CDKTF with Python with TF and with regular CDK.

howto
Aaron Addleman
Aaron Addleman
Principal Automation Engineer

Fun with programming and infrastructure