Feature Request: Add `--dry-run` option

[osterman]

what

• Add option to process helmfile.yaml, but not execute helm

why

• This would be helmfile for development

use-case

We're working on a master helmfile, kind of like a "distribution" of charts. Part of this involves a lot of parameterization. It would make it easier to safely iterate using a --dry-run flag as is common with many command line tools.

[mumoshu]

@osterman Hi! Thanks for trying helmfile.

Would you mind elaborating a bit more about your expected output from helmfile?

I guess it suffices your expectation if helmfile diff is extended to show diff even in case there's no installed releases yet?(Btw it requires an enhancement in helm-diff side)

[mumoshu]

Or maybe you'd want something like ver=0.4.0 bash -c 'helm fetch stable/mysql --version $ver && helm template mysql-$ver.tgz' for all the releases defined in helmfile.yml?

[osterman]

In this particular use-case, I don't even have access to kubernetes or helm. I just want to validate the helmfile.yaml template results is valid yaml and that the --set arguments are correct.

[mumoshu]

@osterman Thanks for the clarification!

Just to be certain, would you mind running ver=0.4.0 bash -c 'helm fetch stable/mysql --version $ver && helm template mysql-$ver.tgz'?

The output contains the rendered kubernetes manifests which should reflect everything you provided - chart and values. So I guess you can use that for the validation? If it makes sense, I'm eager to implement --dry-run which outputs something like that for every release.

[osterman]

Just to be extra clear, with the upcoming 0.13.0 release, the entire helmfile.yaml is a template. We're using the current master. No mechanism exists to validate the output from the sprig template and thus the execution of helm upgade..... from the generated yaml.

I want to know what helmfile will execute before helmfile executes anything.

This is kind of like rsync --dry-run. I am familiar with helm template as I use that when I iterate on my charts. Right now, I'm developing a very advanced helmfile.yaml but I lack the ability to validate the templatized yaml.

Currently, helmfile will output: (and a subsequent call to helm)

exec: helm upgrade --install charts stable/chartmuseum .............

Instead, I want to see: (with no execution of helm)

[dry-run] exec: helm upgrade --install charts stable/chartmuseum .............

For example, I've tried using sprigcli to render the template, but it doesn't implement coalesce or uses an old version.

[osterman]

Here's an example of the complex helmfile.yaml: https://github.com/cloudposse/geodesic/pull/124/files

[mumoshu]

Thanks! Got it. Yeah, such feature would be useful 👍

[sstarcher]

Would it make sense to add a helmfile lint similar to helm lint. That could do validating and maybe other checking?

[mumoshu]

@sstarcher I think so. Actually, we have the exact discussion in #58 😉

[osterman]

Yes, that sounds like a great idea. The lint would satisfy the helmfile validation. That said, I still want to know what the command looks like before executing it as the helmfile syntax is a big divergence from a standard values.yaml.

[sstarcher]

@osterman Agreed I was thinking we needed a command to output a generated helmfile. We could either treat this as a part of lint. helmfile lint --generate or as a separate command helmfile generate

I guess the equivalent would be helms helm install --dry-run --debug. Possibly a helmfile lint --debug to lint and output the generated helmfile?

[mumoshu]

@sstarcher @osterman Just to be extra clear, I was thinking that --dry-run and lint to be two different things.

So, I'd expect:

• 👍 helmfile sync --dry-run to do everything but running helm upgrade --install - it renders helmfile and print the commands without actually running them. I believe this is what @osterman like via this feature request.
• 👍 helmfile lint to render helmfile and run helm lint. It doesn't print the rendered helmfile normally, but it does print helmfile if the lint failed. Also, we probably won't add helmfile lint --dry-run as there seems like no motivation to not actually running helm lint.
• 🤔 helmfile lint --debug would print the rendered helmfile even if there was no lint error. But given the vanilla helmfile lint prints the rendered helmfile on a lint error, I think we have no specific need for this feature?
• 🤔 helmfile template(after helm template) to output a generated helmfile. But I'm not sure about an exact use-case for this feature too, because the vanilla helmfile lint would print the rendered helmfile when necessary.