tvl-depot/docs/resource-sets.md

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Resource Sets
================
Resource sets are collections of Kubernetes resources that should be passed to `kubectl` together.
Technically a resource set is simply a folder with a few YAML and/or JSON templates in it.
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**Table of Contents**
- [Resource Sets](#resource-sets)
- [Creating resource sets](#creating-resource-sets)
- [Default variables](#default-variables)
- [Including resource sets](#including-resource-sets)
- [Fields](#fields)
- [`name`](#name)
- [`path`](#path)
- [`values`](#values)
- [`args`](#args)
- [`include`](#include)
- [Multiple includes](#multiple-includes)
- [Nesting resource sets](#nesting-resource-sets)
- [Caveats](#caveats)
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# Creating resource sets
Simply create a folder in your Kontemplate repository and place a YAML or JSON file in it. These
files get interpreted as [templates][] during Kontemplate runs and variables (as well as template
logic or functions) will be interpolated.
Refer to the template documentation for information on how to write templates.
## Default variables
Sometimes it is useful to specify default values for variables that should be interpolated during
a run if the [cluster configuration][] does not specify a variable explicitly.
This can be done simply by placing a `default.yaml` or `default.json` file in the resource set
folder and filling it with key/value pairs of the intended default variables.
Kontemplate will error during interpolation if any variables are left unspecified.
# Including resource sets
Under the cluster configuration `include` key resource sets are included and required variables
are specified. For example:
```yaml
include:
- name: some-api
values:
version: 1.2-SNAPSHOT
```
This will include a resource set from a folder called `some-api` and set the specified `version` variable.
## Fields
The available fields when including a resource set are these:
### `name`
The `name` field contains the name of the resource set. This name can be used to refer to the resource set
when specifying explicit includes or excludes during a run.
By default it is assumed that the `name` is the path to the resource set folder, but this can be overridden.
This field is **required**.
### `path`
The `path` field specifies an explicit path to a resource set folder in the case that it should differ from
the resource set's `name`.
This field is **optional**.
### `values`
The `values` field specifies key/values pairs of variables that should be available during templating.
This field is **optional**.
### `args`
The `args` field specifies a list of arguments that should be passed to `kubectl`.
This field is **optional**.
### `include`
The `include` field specifies additional resource sets that should be included and that should inherit the
variables of this resource set.
The fully qualified names of "nested" resource sets are set to `${PARENT_NAME}/${CHILD_NAME}` and paths are
merged in the same way.
This makes it easy to organise different resource sets as "groups" to include / exclude them collectively
during runs.
This field is **optional**.
## Multiple includes
Resource sets can be included multiple times with different configurations. In this case it is recommended
to set the `path` and `name` fields explicitly. For example:
```yaml
include:
- name: forwarder-europe
path: tools/forwarder
values:
source: europe
- name: forwarder-asia
path: tools/forwarder
values:
source: asia
```
The two different configurations can be referred to by their set names, but will use the same resource
templates with different configurations.
## Nesting resource sets
As mentioned above for the `include` field, resource sets can be nested. This lets users group resource
sets in logical ways using simple folder structures.
Assuming a folder structure like:
```
├── backend
│   ├── auth-api
│   ├── message-api
│   └── order-api
└── frontend
├── app-page
└── login-page
```
With each of these folders being a resource set, they could be included in a cluster configuration like so:
```yaml
include:
- name: backend
include:
- name: auth-api
- name: message-api
- name: order-api
- name: frontend:
include:
- name: app-page
- name: login-page
```
Kontemplate could then be run with, for example, `--include backend` to only include the resource sets nested
in the backend group. Specific resource sets can also be targeted, for example as `--include backend/order-api`.
Variables specified in the parent resource set are inherited by the children.
### Caveats
Two caveats apply that users should be aware of:
1. The parent resource set can not contain any resource templates itself.
2. Only one level of nesting is supported. Specifying `include` again on a nested resource set will be ignored.
[templates]: templates.md
[cluster configuration]: cluster-config.md