Details

Describe the solution you'd like:

Let's assume a test scenario:

An umbrella chart to deploy our application, this chart will have two subcharts:
- A chart using the latest version of the common library
- A "third-party" chart using an outdated version of the common library (something like this chart)

When deploying the umbrella chart Helm will load the templates for both child charts and when template names collide, it will use the template that was loaded last as mentioned here. Best case scenario: it will render a manifest that won't have the desired features, worst case scenario: it will prevent manifest generation entirely. In both cases it's a really tricky thing to troubleshoot and will cause unexpected behaviour.

This is an issue with how Helm handles templates and it's especially bothersome when using library charts. There's no way of isolating templates or assigning priority to which template gets loaded last, and from comments I've seen there are no plans of supporting this in the near future.

Anything else you would like to add:

It seems like the community approaches this problem in one of two ways:

Always keeping all charts/subcharts up to date with the latest version, which is a consuming task, and kind of defeats the purpose of having versions altogether. Also, if it's a "third-party" chart we don't have direct control over when or how the common library gets updated, basically forcing us to rewrite the chart so we stay in control over the version
Adding some sort of versioning tag to the template names, so when they get loaded they can coexist and be referenced by their full name(which seems to me like the more elegant solution). Here are some discussions talking about this:

The only issue I see with the second approach is that if templates are updated manually and independently, this will cause versions to slip out of date, and will be a chore to keep up.

Additional Information:

I think there's a nice way of solving this: Since the only thing needed to load the common library is to have a template including "bjw-s.common.loader.init" and "bjw-s.common.loader.generate" we can use "bjw-s.common.loader.all template, leave that template as unversioned to avoid forcing the users to update their chart's templates and suffixing the chart's version into the other templates` names. It would look something like this:

In the "parent" or "umbrella" chart we can keep calling the same template with no additional versiona:
```
# templates/common.tpl
{{/* Render the templates */}}
{{ include "bjw-s.common.loader.all" . }}
```

In the common library


# templates/loader/_all.tpl
{{- define "bjw-s.common.loader.all" -}}

...

{{- include (printf "bjw-s.common.loader.init.%s" .Chart.Version) . }}

{{/ Render the templates /}} {{ include (printf "bjw-s.common.loader.generate.%s" .Chart.Version) . }}

...


```yaml
# templates/loader/_init.tpl
{{- define (printf "bjw-s.common.loader.init.%s" .Chart.Version) -}}
  {{- /* Merge the local chart values and the common chart defaults */ -}}
  {{- include (printf "bjw-s.common.values.init.%s" .Chart.Version)  . }}
{{- end -}}

# templates/loader/_generate.tpl
{{- define (printf "bjw-s.common.loader.generate.%s" .Chart.Version) -}}
  {{- /* Run global chart validations */ -}}
  {{- include (printf "bjw-s.common.lib.chart.validate.%s" .Chart.Version)  . -}}

  {{- /* Build the templates */ -}}
  {{- include (printf "bjw-s.common.render.pvcs.%s" .Chart.Version) . | nindent 0 -}}
  {{- include (printf "bjw-s.common.render.serviceAccount.%s" .Chart.Version) . | nindent 0 -}}
  {{- include (printf "bjw-s.common.render.controllers.%s" .Chart.Version) . | nindent 0 -}}

...

{{- end -}}

The downside of this is that the replacement will need to happen for all templates except for "bjw-s.common.loader.all", the upside is that it will only need to happen once.

If this is something that looks interesting to you I'll be more that happy to submit a PR with these changes

bjw-s / helm-charts

Template version conflicts #329

Details