Skip to content
This repository has been archived by the owner on Jan 28, 2023. It is now read-only.

Latest commit

 

History

History
43 lines (34 loc) · 2.44 KB

kubernetes_manifest_templates_and_variables.md

File metadata and controls

43 lines (34 loc) · 2.44 KB
Raw

Kubernetes manifest templates and variables

Kubernetes manifest templates are standard Go templates, so you can find the whole necessary information about the format at the documentation for text/template package: https://golang.org/pkg/text/template/

At the templates you can use two kinds of variables:

  • Package properties which are filled by Carbon automatically:
  • User-defined variables

Package properties

Package properties are filled by Carbon automatically. Currently, these properties are exposed:

  • .Pkg.Name - name of the Carbon package
  • .Pkg.Version - version of the Carbon package
  • .Pkg.DockerName - name of the Focker image which is used for the installation (for example ubuntu)
  • .Pkg.DockerTag - tag suffix of the Docker image which is used for the installation (for example latest)

It's up to you how to use these properties, but here we want to give some recommendations:

  • .Pkg.Name may be useful for naming Kubernetes resources and thus to avoid conflicts with other packages.
  • combination of .Pkg.DockerName and .Pkg.DockerTag properties will let you avoid hardcoding of a Pod image

User-defined variables

All user-defined variables must be defined at variables section of the main config. Each variable may have such parameters:

Parameter Required Default Description
name true - variable name
default false "" Default value for the variable
description false "" Description for the variable

Variable name may contain alphanumeric symbols and undescores. But we recommend to use only alphanumeric symbols with CamelCase format.

When you use these variables at a Kubernetes manifest template, they must be prefixed by .Var., for example: .Var.Environment.

At the installation stage, variables can be taken from different sources and are applied in the following order:

  1. Default values defined at the main config
  2. ~/.carbon/carbon.vars - variables file from a user home directory
  3. Variables files provided by --var-file flag
  4. Variables provided by --var flag

Variables file, in fact is a .property file (https://en.wikipedia.org/wiki/.properties). In most cases it's enough to use a simple key=value notation:

Cluster = core
Environment=Local

But if you have an advanced use-case, please follow the .properties format and remember that variables are disallowed to have spaces at name.