Common or Global Variables

[ghost]

Is your feature request related to a problem? Please describe.
It's feasible that multiple configurations could warrant the same values. For example, an auto-tag rule and an application could share the same name.

Describe the solution you'd like
A file where we can define these globals which are shared across all projects and configuration types.

For example:
globals.yaml

foo: "bar"

Then applications.yaml

config:
  - my_application: "application.json"

my_application:
  - name: "{{ .Globals.foo }}"

Describe alternatives you've considered
This is possible now via environment variables but that means we lose the ability to track these globals as variables that are committed to Git.

[arunkrishnan-dt]

I second this - the feature will be really useful. It will make it easy for different end users to run same monaco projects after changing variables in a file.

[tatomir146]

@UnseenWizzard @patrickpichler please put your thoughts here.

[UnseenWizzard]

Absolutely! This is a valuable feature and something we have already discussed as an improvement following our configuration structure rework. A single "manifest" in which configuration folders and environments are defined should in the future also allows setting global variables to be used in all configurations.

[patrickpichler]

+1 for putting the global values into the manifest

The only open question for me is, how do we reference them in the config files?
We reserve the parameter name global and have a syntax like {{ .global.XYZ }}.
Also should those global parameters be seen like "constants", or should they also
be able to reference non global parameters?

[patrickpichler]

From a short discussion with @dynatrace-oss/mac-maintainers we came up with the following solution:

• Global will be defined in the deployment manifest
• They are only allowed to be fixed value params or environment variables, which will get evaluated once
  at the beginning at runtime (so no referencing parameters from configs)
• If an referenced env variable is not present, the deployment will fail
• global will become a reserved parameter name to avoid clashed
• In version 1 it will not be possible to override globals
• One can access them via {{ .global.XYZ }} syntax in the template files

[163a]

I have a similar but not directly same requirement.
Say, I have two configs in a YAML file which share common placeholders, so I only want to define once these placeholder variables and simply re-use them between configs without having to repeat these exact same variables. Will this be possible?