The PULUMI_STACK variable

This is the story of a small open-source contribution I made to Pulumi 🎉

What we wanted

• My team loves using direnv to select between deployment environments using directories.
  • cd deployment/clusters/dev –> magically your kubectl is configured for the dev cluster
• We wanted to use this same approach to select which pulumi stack pulumi is pointed to
  • cd deployment/pulumi/stacks/network –> pulumi up deploys the network stack
• Otherwise, you have to pass in your stack each time with -s (e.g. pulumi up -s network -r ...)
  • (or else it would just give you an interactive selection menu to pick each time, which gets tiring when you’re applying a lot)
• There was also pulumi stack select which is a bit like using kubectl config set-context --current --namespace=... to avoid the -n on every command
  • But when you’re talking about infrastructure stacks, you really want it to be obvious which stack you are deploying (even though the diff stage is a bit of a failsafe)

The problem

• Surprisingly, the --stack flag didn’t have any env variable support ❌
  • We also appeared to not be the only ones who wanted this

The solution

• This seemed small enough to just take some initiative and propose as an open-source PR
  • I just had to read up on how to contribute / how to test my changes
  • And then, of course, overdo it a bit on the PR description to make it super easy to review 😎

Impact

• Today, if you check https://www.pulumi.com/docs/iac/cli/environment-variables you will see that the PULUMI_STACK variable is supported 🎉
  • Once this came down the nix flake pipes, we were able to use direnv like we wanted to 💯

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