Implementing conversion

With the model for conversion in place, it is time to actually implement the conversion functions. Create a conversion webhook for the CronJob API version v1 (Hub) to Spoke the CronJob API version v2 see:

kubebuilder create webhook --group batch --version v1 --kind CronJob --conversion --spoke v2

The above command generates the cronjob_conversion.go next to the cronjob_types.go file, to avoid cluttering up the main types file with extra functions.

Unlike defaulting and validation webhooks, conversion webhooks do not support custom paths via command-line flags. Conversion webhooks use CRD conversion configuration (.spec.conversion.webhook.clientConfig.service.path in the CRD) rather than webhook marker annotations. The path for conversion webhooks is managed differently and cannot be customized through kubebuilder flags.

Hub...

First, implement the hub. Choose the v1 version as the hub:

{{#literatego ./testdata/project/api/v1/cronjob_conversion.go}}

... and Spokes

Then, implement the spoke, the v2 version:

{{#literatego ./testdata/project/api/v2/cronjob_conversion.go}}

Now that the conversions are in place, all that is needed is to wire up main to serve the webhook!