58 lines
2.4 KiB
Markdown
58 lines
2.4 KiB
Markdown
# Custom Resource Example
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**Note:** CustomResourceDefinition is the successor of the deprecated ThirdPartyResource.
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This particular example demonstrates how to generate a client for CustomResources using [`k8s.io/code-generator`](https://github.com/kubernetes/code-generator). The clientset can
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be generated using the `./hack/update-codegen.sh` script.
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The `update-codegen` script will automatically generate the following files and
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directories:
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* `pkg/apis/cr/v1/zz_generated.deepcopy.go`
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* `pkg/client/`
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The following code-generators are used:
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* `deepcopy-gen` - creates a method `func (t* T) DeepCopy() *T` for each type T
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* `client-gen` - creates typed clientsets for CustomResource APIGroups
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* `informer-gen` - creates informers for CustomResources which offer an event based
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interface to react on changes of CustomResources on the server
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* `lister-gen` - creates listers for CustomResources which offer a read-only caching layer for GET and LIST requests.
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Changes should not be made to these files manually, and when creating your own
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controller based off of this implementation you should not copy these files and
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instead run the `update-codegen` script to generate your own.
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Please see [`k8s.io/sample-controller`](https://github.com/kubernetes/sample-controller) for an example
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controller for CustomResources using the generated client.
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## Use Cases
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CustomResourceDefinitions can be used to implement custom resource types for your Kubernetes cluster.
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These act like most other Resources in Kubernetes, and may be `kubectl apply`'d, etc.
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Some example use cases:
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* Provisioning/Management of external datastores/databases (eg. CloudSQL/RDS instances)
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* Higher level abstractions around Kubernetes primitives (eg. a single Resource to define an etcd cluster, backed by a Service and a ReplicationController)
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## Defining types
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Each instance of your custom resource has an attached Spec, which should be defined via a `struct{}` to provide data format validation.
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In practice, this Spec is arbitrary key-value data that specifies the configuration/behavior of your Resource.
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For example, if you were implementing a custom resource for a Database, you might provide a DatabaseSpec like the following:
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``` go
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type DatabaseSpec struct {
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Databases []string `json:"databases"`
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Users []User `json:"users"`
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Version string `json:"version"`
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}
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type User struct {
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Name string `json:"name"`
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Password string `json:"password"`
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}
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```
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