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