For past six months I’ve been working with terragrunt which is a thin wrapper for terraform that provides extra tools for working with multiple terraform modules.
Idea behind is awesome - make repository of modules which follows best practices and show how to write IaC properly. In this post I will outline upgrading and write some commands that helped me to automate this process.

Terraform 0.12

It’s all fun and games until new, backward incompatible terraform version is out.
If you haven’t already read upgrading to Terraform v0.12 I definitely encourage you to read it. There are a lot of changes which you should be aware of.
Next in line would be document from terragrunt Upgrading your Reference Architecture Deployment to Terraform 0.12.x and Terragrunt 0.19.x.
It does say what should be done but it does not specify how. This you must come up with yourself. As I already did it I can share some of my thoughts about that.



Infrastructure live

I’m the type of guy that don’t want to do the same job twice. With terragrunt upgrade it would be just silly to make same changes over and over again for every module.
That’s why I have focused on automatization of this task as amount of manual work can be overwhelming.

First I’ve create helper commands migrating envs in infra-live to terragrunt19:

  • renaming terraform.tfvars to terragrunt.hcl:
find . -name 'terraform.tfvars' | 
xargs rename 's/terraform.tfvars/terragrunt.hcl/' -v
  • adjusting file format:
find . -name 'terragrunt.hcl' -exec sed -i.bak \
-e '/terragrunt =/d' -e 's/^}$/inputs = {/' -e '$s#$#}#' 
-e 's/include =/include/' -e 's/dependencies =/dependencies/' {} \;
  • validating hcl:
terragrunt hclfmt
  • repeat validating hcl until all is good
  • rename env.tfvars:
find . -name 'env.tfvars' | xargs rename 's/env.tfvars/env.yaml/' -v
  • yaml it:
find . -name 'env.yaml' -exec sed -i.bak -e 's/ =/:/' {} \;
  • rename region.tfvars:
find . -name 'region.tfvars' | xargs rename 's/region.tfvars/region.yaml/' -v
  • yaml it:
find . -name 'region.yaml' -exec sed -i.bak -e 's/ =/:/' {} \;
  • clean temp files:
git clean -e '*.hcl' -e '*.yaml' -f

Infrastructure modules

  • find modules to upgrade and do the upgrade:
for dir in $(find . -type d | grep -v -e '.git\|.terraform\|^.$'); do 
    echo $dir; cd $dir; 
    if [ -f ]; then 
        sed -i.bak -e 's/0.11.7/0.12.10/g'; 
        terraform init --backend=false; terraform 0.12upgrade  --yes; 
    cd $REPO_BASE; 
  • clean temp files:
git clean -fd

Finding and updating modules is toil. In case of any errors you should investigate yourself.

Upgrading modules

Here we have two options:

  1. You have clean repository that is a mirror of terragrunt.
    If that is the case you can just copy, and (and any other additional files if module has them)
  2. You’ve either have own logic in modules, modified variables or made any other changes which are not in terragrunt.
    Bummer. You need to upgrade it on your own and make sure it works in the same way as it was before.

When it’s done you can revisit terragrunt terraform version compatibility chart and upgrade terragrunt modules used in module to first release after tf12 upgrade.

terragrunt plan

Now you can run terragrunt plan and check if there are any changes or errors. If plan is clean try to upgrade terragrunt modules to more recent or most recent version maybe it will stay clean.

Note: Be vary of applying because tf12 has incompatible state with tf11.


Know what you are doing and have fun!