API to interact with terraform cli

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Description

It would be very useful to have an API to interact with terraform cli (not cloud) from cdk.

Example below:

app = App()
MyStack(app, "automate-everything")
synth = app.synth()
plan = app.plan(synth)

if plan.changes is not None:
    if len(plan.changes.module.custom.fruits) > 4:
       app.apply(synth, target='module.custom.fruits')

References

https://github.com/hashicorp/terraform-cdk/issues/225

[skorfmann]

Was playing around with this a bit. While it requires the usage of JS / Typescript, it’s sort of possible to drive synth and deploy / destroy bypassing the full cdktf-cli workflow. It’s a bit clunky, but works. Please be aware, that this is using internal APIs of the cdktf-cli which might break without prior warning.

deploy

import { SynthStack } from 'cdktf-cli/bin/cmds/helper/synth-stack';
import { TerraformCli } from 'cdktf-cli/bin/cmds/ui/models/terraform-cli';

const setup = async () => {
  const stacks = await SynthStack.synth('node stack.js', 'cdktf.test.out');
  const cli = new TerraformCli(stacks[0]);
  await cli.init();
  await cli.deploy('', (chunk: Buffer) => (console.log(chunk.toString('utf-8'))));
}

(async function() { await setup() } ());

destroy

import { SynthStack } from 'cdktf-cli/bin/cmds/helper/synth-stack';
import { TerraformCli } from 'cdktf-cli/bin/cmds/ui/models/terraform-cli';

const teardown = async () => {
  const stacks = await SynthStack.synth('node stack.js', 'cdktf.test.out');
  const cli = new TerraformCli(stacks[0]);
  await cli.init();
  await cli.destroy((chunk: Buffer) => (console.log(chunk.toString('utf-8'))));
}

(async function() { await teardown() } ());

I’m using this right now for driving automated test setups / teardowns. Since this skips generating the plan and is running headless, it’s also a bit faster compared to using the cdktf-cli directly.

[kc-dot-io]

Thanks for these examples @skorfmann! This is my new favorite way to use CDKTF. I’d love to see a more formal API…

A few things from my experience that would help this…

1. Better error handling with remote runners using try/catch or promise
2. Better API for handing / templating response to stdin/stdout
3. Ideally JSON events with lifecycle hooks would be great
4. API support for multi-stack delpoyments / cross stack references

Looking forward to seeing this evolve. This is the most excited I’ve been about IaC in a while.