How to keep your Terraform code DRY by using Terramate

https://blog.mineiros.io/how-to-keep-your-terraform-code-dry-by-using-terramate-be5807fef8f6

by katcipis • 4 years ago

17 16 4 years ago

blog.mineiros.io

I feel like teams should be using tfe workspaces and env vars to instantiate environments rather than having a folder per-environment. It's pretty easy to replicate this workflow and results in substantially less env drift and code duplication when we do it.

oarmstrong• 4 years ago

I tend to use a similar approach, though with Terraform var files instead of env vars. It was also possible to have this work with TF Cloud (and presumably Enterprise?) with a single workspace env var specifying the var file. It might have been improved recently to be a first class feature.

I found this to be my favourite workflow for managing workspace variables in a way that was also flexible to being run outside of TFC/TFE for when that makes sense.

LazyMans• 4 years ago

How do you only deploy certain resources to certain environment this way? We don't always have matching dev/qa/prod environments.

davidjfelix5• 4 years ago

branch or tag from main if they have different release cadences. control the creation or non-creation ENTIRELY thru env vars with either boolean or count. If you have some thing that doesn't exist in all envs it should be obvious and maybe painful. Having to define it in the vars file makes it clear what differences each env has at a glance.

davidjfelix5• 4 years ago

Alternatively, consider splitting your environment up into multiple stacks which can run independently and deploy each to a workspace per env. If one env lacks the app, don't have a workspace for it.

It sounds like a lot, but it ends up being fewer files to manage and edit and your workflow can be captured in github/terraform rather than in some arbitrary file structure. It also helps prevent mistakes like updating dev and having prod rerun by accident which I've seen happen.

fumplethumb• 4 years ago

You can conditionally deploy resources by setting the count on most resources. So you can have an environment variable with something like has_cache. Then in your terraform use a ternary or something to set the count to 1 if has_cache is true and 0 if it’s false. I have done this without much fuss.

tn890• 4 years ago

I used to be obsessed with DRY. After having written tens of thousands of terraform lines in the last few years across a multitude of platforms and use cases, I say everything in moderation.

Going DRY is a decision you pay for in complexity, it's the typical programming problem of genericity. Sometimes it absolutely makes sense and you're a mad man if you skip it, but in isolated cases making things DRY just for the sake of it is just as nuts as not doing it when required.

It's a fine line to walk and it requires hands-on experience to know when to employ DRY and when to repeat yourself.

dolni• 4 years ago

I don't think it is a question of moderation. It's a question of "does this chunk of code make sense as an abstraction?"

If I change the common code, do I want all users of it to realize those changes implicitly?

Terraform provides good enough tools to allow for deviations (even significant ones) between dev, staging, and prod.

IMO one of the most valuable things Terraform can do for you is stand up _the exact same stuff_ in multiple environments. If you're applying different code, your confidence in that shrinks significantly.

raffraffraff3• 4 years ago

I've been using Hiera (Puppet yaml data store) to source data for terraform. As a long time puppet user, when I started writing terraform code I really missed hiera. Turns out someone ported it to Go, and someone else turned that into a terraform provider. It's a game changer. No need for terragrunt or terramate. Hiera can return anything from a single value to a very complex data block that can be used to feed a module or a whole stack. Hiera needs some information about where you're deploying to, and it gets this in the in the provider configuration in the form of key/vals: I use environment, region & stack. I decided to use a workspace naming convention that encodes these (eg: prod_use1.network). For each workspace, terraform can automatically figure out exactly what lookups it needs to do, and hiera returns native terraform data relevant to that workspace only. I have 100% dry code, and no need to create a separate directory for each environment/region state. I run my terraform init/apply in the top-level directory no matter where I'm deploying. The result is that once I've written my modules and stacks, I can build out a whole data center by creating few workspaces and running "terraform init && terraform apply" in each one. Zero extra files or directories. Dry as a bone

dpifke• 4 years ago

Cursory Googling returns two Terraform hiera providers, borh last updated in 2020. Are you using either of these, or something else?

https://github.com/ribbybibby/terraform-provider-hiera https://github.com/lyraproj/hiera_terraform

raffraffraff3• 4 years ago

Neither! It's this one: https://github.com/chriskuchin/terraform-provider-hiera5

On the terraform registry here: https://registry.terraform.io/providers/chriskuchin/hiera5

raffraffraff3• 4 years ago

Over the weekend I plan to cut out the heart of my setup, make it generic enough to share on GitHub and do an extremely short video walkthrough of how I use it. (Except I know how my plans don't always get turned into actions)

How to keep your Terraform code DRY by using Terramate

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