Client-gen is an automatic tool that generates [clientset](../../docs/proposals/client-package-structure.md#high-level-client-sets) based on API types. This doc introduces the use the client-gen, and the release cycle of the generated clientsets.
1. Marking API types with tags: in `pkg/apis/${GROUP}/${VERSION}/types.go`, mark the types (e.g., Pods) that you want to generate clients for with the `// +genclient=true` tag. If the resource associated with the type is not namespace scoped (e.g., PersistentVolume), you need to append the `nonNamespaced=true` tag as well.
- b. If you are running client-gen outside of k8s.io/kubernetes, you need to use the command line argument `--input` to specify the groups and versions of the APIs you want to generate clients for, client-gen will then look into `pkg/apis/${GROUP}/${VERSION}/types.go` and generate clients for the types you have marked with the `genclient` tags. For example, to generated a clientset named "my_release" including clients for api/v1 objects and extensions/v1beta1 objects, you need to run:
3.***Adding expansion methods***: client-gen only generates the common methods, such as CRUD. You can manually add additional methods through the expansion interface. For example, this [file](../../pkg/client/clientset_generated/release_1_5/typed/core/v1/pod_expansion.go) adds additional methods to Pod's client. As a convention, we put the expansion interface and its methods in file ${TYPE}_expansion.go. In most cases, you don't want to remove existing expansion files. So to make life easier, instead of creating a new clientset from scratch, ***you can copy and rename an existing clientset (so that all the expansion files are copied)***, and then run client-gen.
- clientset: the clientset will be generated at `pkg/client/clientset_generated/` by default, and you can change the path via the `--clientset-path` command line argument.
- Individual typed clients and client for group: They will be generated at `pkg/client/clientset_generated/${clientset_name}/typed/generated/${GROUP}/${VERSION}/`
