mirror of
https://github.com/jpetazzo/container.training.git
synced 2026-07-28 09:11:18 +00:00
b56e54eaec
Now that we have a good number of longer exercises, it makes sense to rename the shorter demos/labs into 'labs' to avoid confusion between the two.
192 lines
3.7 KiB
Markdown
192 lines
3.7 KiB
Markdown
# Helm and invalid values
|
|
|
|
- A lot of Helm charts let us specify an image tag like this:
|
|
```bash
|
|
helm install ... --set image.tag=v1.0
|
|
```
|
|
|
|
- What happens if we make a small mistake, like this:
|
|
```bash
|
|
helm install ... --set imagetag=v1.0
|
|
```
|
|
|
|
- Or even, like this:
|
|
```bash
|
|
helm install ... --set image=v1.0
|
|
```
|
|
|
|
🤔
|
|
|
|
---
|
|
|
|
## Making mistakes
|
|
|
|
- In the first case:
|
|
|
|
- we set `imagetag=v1.0` instead of `image.tag=v1.0`
|
|
|
|
- Helm will ignore that value (if it's not used anywhere in templates)
|
|
|
|
- the chart is deployed with the default value instead
|
|
|
|
- In the second case:
|
|
|
|
- we set `image=v1.0` instead of `image.tag=v1.0`
|
|
|
|
- `image` will be a string instead of an object
|
|
|
|
- Helm will *probably* fail when trying to evaluate `image.tag`
|
|
|
|
---
|
|
|
|
## Preventing mistakes
|
|
|
|
- To prevent the first mistake, we need to tell Helm:
|
|
|
|
*"let me know if any additional (unknown) value was set!"*
|
|
|
|
- To prevent the second mistake, we need to tell Helm:
|
|
|
|
*"`image` should be an object, and `image.tag` should be a string!"*
|
|
|
|
- We can do this with *values schema validation*
|
|
|
|
---
|
|
|
|
## Helm values schema validation
|
|
|
|
- We can write a spec representing the possible values accepted by the chart
|
|
|
|
- Helm will check the validity of the values before trying to install/upgrade
|
|
|
|
- If it finds problems, it will stop immediately
|
|
|
|
- The spec uses [JSON Schema](https://json-schema.org/):
|
|
|
|
*JSON Schema is a vocabulary that allows you to annotate and validate JSON documents.*
|
|
|
|
- JSON Schema is designed for JSON, but can easily work with YAML too
|
|
|
|
(or any language with `map|dict|associativearray` and `list|array|sequence|tuple`)
|
|
|
|
---
|
|
|
|
## In practice
|
|
|
|
- We need to put the JSON Schema spec in a file called `values.schema.json`
|
|
|
|
(at the root of our chart; right next to `values.yaml` etc.)
|
|
|
|
- The file is optional
|
|
|
|
- We don't need to register or declare it in `Chart.yaml` or anywhere
|
|
|
|
- Let's write a schema that will verify that ...
|
|
|
|
- `image.repository` is an official image (string without slashes or dots)
|
|
|
|
- `image.pullPolicy` can only be `Always`, `Never`, `IfNotPresent`
|
|
|
|
---
|
|
|
|
## `values.schema.json`
|
|
|
|
```json
|
|
{
|
|
"$schema": "http://json-schema.org/schema#",
|
|
"type": "object",
|
|
"properties": {
|
|
"image": {
|
|
"type": "object",
|
|
"properties": {
|
|
"repository": {
|
|
"type": "string",
|
|
"pattern": "^[a-z0-9-_]+$"
|
|
},
|
|
"pullPolicy": {
|
|
"type": "string",
|
|
"pattern": "^(Always|Never|IfNotPresent)$"
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
```
|
|
|
|
---
|
|
|
|
## Testing our schema
|
|
|
|
- Let's try to install a couple releases with that schema!
|
|
|
|
.lab[
|
|
|
|
- Try an invalid `pullPolicy`:
|
|
```bash
|
|
helm install broken --set image.pullPolicy=ShallNotPass
|
|
```
|
|
|
|
- Try an invalid value:
|
|
```bash
|
|
helm install should-break --set ImAgeTAg=toto
|
|
```
|
|
|
|
]
|
|
|
|
- The first one fails, but the second one still passes ...
|
|
|
|
- Why?
|
|
|
|
---
|
|
|
|
## Bailing out on unkown properties
|
|
|
|
- We told Helm what properties (values) were valid
|
|
|
|
- We didn't say what to do about additional (unknown) properties!
|
|
|
|
- We can fix that with `"additionalProperties": false`
|
|
|
|
.lab[
|
|
|
|
- Edit `values.schema.json` to add `"additionalProperties": false`
|
|
```json
|
|
{
|
|
"$schema": "http://json-schema.org/schema#",
|
|
"type": "object",
|
|
"additionalProperties": false,
|
|
"properties": {
|
|
...
|
|
```
|
|
|
|
]
|
|
|
|
---
|
|
|
|
## Testing with unknown properties
|
|
|
|
.lab[
|
|
|
|
- Try to pass an extra property:
|
|
```bash
|
|
helm install should-break --set ImAgeTAg=toto
|
|
```
|
|
|
|
- Try to pass an extra nested property:
|
|
```bash
|
|
helm install does-it-work --set image.hello=world
|
|
```
|
|
|
|
]
|
|
|
|
The first command should break.
|
|
|
|
The second will not.
|
|
|
|
`"additionalProperties": false` needs to be specified at each level.
|
|
|
|
???
|
|
|
|
:EN:- Helm schema validation
|
|
:FR:- Validation de schema Helm
|