From 1ceb15c11c7db0348c1c8a99e2d85e3591f135b0 Mon Sep 17 00:00:00 2001 From: Phillip Wittrock Date: Tue, 3 Apr 2018 20:58:55 -0700 Subject: [PATCH] Flesh out documentation on homepage --- README.md | 241 +++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 239 insertions(+), 2 deletions(-) diff --git a/README.md b/README.md index 25c8dd272b..7f1d85ada2 100644 --- a/README.md +++ b/README.md @@ -49,7 +49,245 @@ kubebuilder docs See the [user guide](docs/tools_user_guide.md) for more details -## Godocs +## Project structure + +Following describes the project structure setup by kubebuilder commands. + +### cmd/ + +*Most users do not need to edit this package.* + +The `cmd` package contains the main function for launching a new controller manager. It is responsible for parsing +a `rest.Config` and invoking the `inject` package to run the various controllers. It may optionally install CRDs +as part of starting up. + +This package is created automatically by running: + +```sh +kubebuilder init --domain k8s.io +``` + +### pkg/apis + +**Users must edit packages under this package** + +The `apis` package contains the schema definitions for the resource types you define. Resources are defined under +`pkg/apis///_types.go`. Resources may be annotated with comments to identify resources +to code generators. Comments are also used to generated field validation. + +Notably client generation, CRD generation, docs generation and config generation are all driven off of annotations +on resources package. + +See documentation and examples of annotations in godoc format here: +[gen/apis](https://godoc.org/github.com/kubernetes-sigs/kubebuilder/pkg/gen/apis#example-package) + +Subpackages of apis are created when running the following command to create a new resource and controller: + +```sh +kubebuilder create resource --group mygroup --version v1beta1 --kind MyKind +``` + +### pkg/controllers + +**Users must packages under this package** + +The `controllers` package contains the controllers to implement the resource APIs. Controllers are defined under +`pkg/controllers//controller.go`. Controllers may be annotated with comments to wire the controller into the +inject package, start informers they require and install RBAC rules they require. + +Subpackages of controllers are created when running the following command to create a new resource and controller: + +```sh +kubebuilder create resource --group mygroup --version v1beta1 --kind MyKind +``` + +See documentation and examples of annotations in godoc format here: +- [gen/controller](https://godoc.org/github.com/kubernetes-sigs/kubebuilder/pkg/gen/controller#example-package) + +### pkg/inject + +*Most users do not need to edit this package.* + +The `inject` package contains the `RunAll` function used to start all of the registered controllers and informers. +Wiring is autogenerated based on resource and controller annotations. + +Generated wiring: +- Installing CRDs +- Instantiating and starting controllers +- Starting sharedinformers +- Installing RBAC rules + +### pkg/inject/args + +*Only some users need to edit this package.* + +The `args` package contains the struct passed to the `ProvideController` function used to instantiating controllers. +The `InjectArgs` struct and `CreateInjectArgs` function in this package may be edited to pass additional information +to the controller provider functions. This is typically an advanced use case. + +The `args` package uses the `kubebuilder/pkg/inject/args` package documented here: +[inject/args](https://godoc.org/github.com/kubernetes-sigs/kubebuilder/pkg/inject/args) + +### hack/ + +The `hack` directory contains generated samples and config. + +The hack/install.yaml config file for installing the API extension into a cluster will be created under this +directory by running. + +```sh +kubebuilder create config --controller-image mycontrollerimage --name myextensionname +``` + +### docs/ + +The `docs` package contains your examples and content for generating reference documentation for your APIs. + +The docs package is created when running either + +```sh +kubebuilder docs +``` + +or + +```sh +kubebuilder create example --group mygroup --version v1beta1 --kind MyKind +``` + +Example reference documentation lives under `docs/reference/examples`. Conceptual reference documentation +lives under `docs/reference/static_includes`. + +### / + +The project root directory contains several files + +- Dockerfile.controller + +Running `docker build` on this file will build a container image for running your controller. + +- Gopkg.toml / Gopkg.lock + +These files are used to update vendored go dependencies. + +## Available controller operations + +Controllers watch Kubernetes resources and call a "Reconcile" function in response to events. Reconcile functions +are typically "level-based", that is they are notified that something has changed for given resource namespace/name key, +but not specifically what changed (e.g. add, delete, update). This allows Reconcile functions to reconcile multiple +events at a time and more easily self-heal, as actions are taken by comparing the current desired state (resource Spec) +and the observed state of the system. + +### Creating a new controller + +A new GenericController is created for you by kubebuilder when creating a resource. If you are not using +kubebuilder to create resources and manage your project, you may create a controller directly by following +this example: + +[GenericController](https://godoc.org/github.com/kubernetes-sigs/kubebuilder/pkg/controller#example-GenericController) + +Use the following annotation to start additional informers for any resources you are watching in your controller. + +```go +// +informers:group=apps,version=v1,kind=Deployment +``` + +Use the following annotation to generate RBAC rules to allow your controller to read and write resources when +running in a container in a Kubernetes cluster. + +```go +// +rbac:groups=apps,resources=deployments,verbs=get;list;watch;create;update;patch;delete +``` + + +### Watching resources + +Controllers watch resources to trigger reconcile functions. It is common for controllers to reconcile a single resource +type, but watch many other resource types to trigger a reconcile. An example of this is a Deployment controller that +watches Deployments, ReplicaSets (created by the controller) and Pods (created by the ReplicaSet controller). Pod +status events, such as becoming healthy, may trigger actions in the Deployment controller, such as continuing +a rolling update. + +#### Watching the resource managed by the controller + +Controllers typically watch for events on the resource they control and in response reconcile that resource instance. + +Note: Kubebuilder will automatically call the Watch function for controllers it creates when creating a resources. If +you are not using kubebuilder to create resources and manager your project, you may have your controller watch +a resource by following this example: + +[GenericController.Watch](https://godoc.org/github.com/kubernetes-sigs/kubebuilder/pkg/controller#example-GenericController-Watch) + +#### Watching resources created by a controller and reconciling in the controller + +Controllers frequently watch for events on the resources created by the controller or transitively created by the +controller (e.g. controller creates a ReplicaSet and the ReplicaSet creates a Pod). + +Events for created resources need to be mapped back to the resource instance responsible for their creation - +e.g. if there is a Pod event -then reconcile the Deployment that owns the Pod. The owning resource is found by +looking at the instance (Pod) controller reference, looking up the object with the same namespace and name as the +owner reference and comparing the UID of the found object to the UID in the owner reference. This is check is done +to ensure the object is infact the owner and to disambiguate multiple resources with the same name and Kind that +are logically different (e.g. they are in different groups and are totally different things). + +e.g. In response to a Pod event, find the owner reference for the Pod that has `controller=true`. +Lookup the ReplicaSet with this name and compare its UID to the ownerref UID. If they are the same +find the owner reference for the ReplicaSet that has `controller=true`. Lookup the Deployment +with this name and compare the UID to the ownerref UID. If they are the same reconcile the Deployment with +this namespace/name. + +In order to watch objects created by a controller and reconcile the owning resource in response, the functions +to lookup the ancestors object must be provided (e.g. lookup a ReplicaSet for a namespace/name, +lookup a Deployment for a namespace/name). + +You may have you controller watch a resource created by the controller and then reconcile the owning object by +following this example: + +[GenericController.WatchControllerOf](https://godoc.org/github.com/kubernetes-sigs/kubebuilder/pkg/controller#example-GenericController-WatchControllerOf) + +[Sample](https://github.com/kubernetes-sigs/kubebuilder/blob/master/samples/controller/controller.go#L91) + +#### Watching arbitrary resources and mapping them so the are reconciled in the controller + +In some cases it may be necessary to watch resources not owned or created by your controller, but respond to them. +An example would be taking some action in response to the deletion or creation of Nodes in the cluster. To do +this, your controller must watch that object (Node) and map events to the resource type of the controller. + +You may watch a resource and transform it into the key of the resource the controller manages by following this example: + +[GenericController.WatchTransformationOf](https://godoc.org/github.com/kubernetes-sigs/kubebuilder/pkg/controller#example-GenericController-WatchTransformationOf) + +#### Watching arbitrary resources and handling the events that may caused a reconciliation in the controller + +In some cases it may be necessary to directly handle events and enqueue keys to be reconciled. You may do so +by following this example: + +[GenericController.WatchEvents](https://godoc.org/github.com/kubernetes-sigs/kubebuilder/pkg/controller#example-GenericController-WatchEvents) + +### Watching a channel for resource names and reconciling them in the controller + +In some cases it may be necessary to respond to external events such as webhooks. You may enqueue reconcile events +from arbitrary sources by using a channel and following this example: + +[GenericController.WatchChannel](https://godoc.org/github.com/kubernetes-sigs/kubebuilder/pkg/controller#example-GenericController-WatchChannel) + +## Running tests + +In order to run the integration tests, the following environment variables must be set to bring up the test environment: + +```sh +export TEST_ASSET_KUBECTL=/usr/local/kubebuilder/bin/kubectl +export TEST_ASSET_KUBE_APISERVER=/usr/local/kubebuilder/bin/kube-apiserver +export TEST_ASSET_ETCD=/usr/local/kubebuilder/bin/etcd +``` + +Tests can then be run with: + +```sh +go test ./pkg/... +``` + +## Godoc Links Many of the kubebuilder libraries can be used on their own without the kubebuilder code generation and scaffolding. @@ -64,7 +302,6 @@ Kubebuilder generates codes for custom resource fields, and controller component - [resource code generation tags](https://godoc.org/github.com/kubernetes-sigs/kubebuilder/pkg/gen/apis) - [controller code generation tags](https://godoc.org/github.com/kubernetes-sigs/kubebuilder/pkg/gen/controller) - For example, you have to add controller code generation tags such as `+rbac` and `+informers` in `pkg/controller/foo/controller.go` file: ``` // +controller:group=foo,version=v1beta1,kind=Bar,resource=bars