Sample Controller for K8S

编程环境：

Go v1.13.8
MacOS 10.15.8
Kubernetes v1.17.0

Write a CRD

Project Setup

注意，由于后期使用 code-generator 时，code-generator 不支持 go module 模式，所以项目虽然依然可以使用 go module ，但是目录需要建成 GOPATH 的样式，例如如下

go mod init github.com/schwarzeni/k8s-sample-controller-doc-demo

此时项目 k8s-sample-controller-doc-demo 父文件夹路径应该为 github.com/schwarzeni/

安装相关的依赖，对于 1.17 版本的 Kubernetes ，下载 0.17.0 版本的相关客户端，下载 code-generator 时可能会报错，这个不用管

go get -u k8s.io/code-generator@v0.17.0
go get -u k8s.io/client-go@v0.17.0
go get -u k8s.io/apimachinery@v0.17.0
go get -u k8s.io/api@v0.17.0

建立 hack/tools.go 并写入如下内容，便于之后使用 go mod vendor

// +build tools
// This package imports things required by build scripts, to force `go mod` to see them as dependencies
package tools
import _ "k8s.io/code-generator"

之后执行命令：

go mod vendor

此时项目结构如下：

.
├── go.mod
├── go.sum
├── vendor
    └── ...
├── hack
    └── tools.go

文件 vendor/k8s.io/code-generator/generate-groups.sh 就是用来生成代码的脚本

Code Generation

首先先定义相关的 K8S 资源，然后使用 K8S 提供的工具生成相关的访问代码。这里的代码全部参照 kubernetes/sample-controller 中的相关代码。

在根目录下新建文件夹 pkg/apis/samplecontroller 作为定义资源的目录，在此目录下新建四个文件并填入相应的内容，IDE 可能会报错，这个不用管

pkg/apis/samplecontroller
├── register.go
└── v1alpha1
    ├── doc.go
    ├── register.go
    └── types.go

package samplecontroller
// GroupName is the group name used in this package
const GroupName = "samplecontroller.k8s.io"

v1alpha1/doc.go

// +k8s:deepcopy-gen=package
// +groupName=samplecontroller.k8s.io
// Package v1alpha1 is the v1alpha1 version of the API.
package v1alpha1

v1alpha1/types.go

package v1alpha1
import (
    metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
)
// +genclient
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
// Foo is a specification for a Foo resource
type Foo struct {
    metav1.TypeMeta   `json:",inline"`
    metav1.ObjectMeta `json:"metadata,omitempty"`
    Spec   FooSpec   `json:"spec"`
    Status FooStatus `json:"status"`
}
// FooSpec is the spec for a Foo resource
type FooSpec struct {
    DeploymentName string `json:"deploymentName"`
    Replicas       *int32 `json:"replicas"`
}
// FooStatus is the status for a Foo resource
type FooStatus struct {
    AvailableReplicas int32 `json:"availableReplicas"`
}
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
// FooList is a list of Foo resources
type FooList struct {
    metav1.TypeMeta `json:",inline"`
    metav1.ListMeta `json:"metadata"`
    Items []Foo `json:"items"`
}

v1alpha1/register.go

package v1alpha1
import (
    metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
    "k8s.io/apimachinery/pkg/runtime"
    "k8s.io/apimachinery/pkg/runtime/schema"
    samplecontroller "github.com/schwarzeni/k8s-sample-controller-doc-demo/pkg/apis/samplecontroller"
)
// SchemeGroupVersion is group version used to register these objects
var SchemeGroupVersion = schema.GroupVersion{Group: samplecontroller.GroupName, Version: "v1alpha1"}
// Kind takes an unqualified kind and returns back a Group qualified GroupKind
func Kind(kind string) schema.GroupKind {
    return SchemeGroupVersion.WithKind(kind).GroupKind()
}
// Resource takes an unqualified resource and returns a Group qualified GroupResource
func Resource(resource string) schema.GroupResource {
    return SchemeGroupVersion.WithResource(resource).GroupResource()
}
var (
    // SchemeBuilder initializes a scheme builder
    SchemeBuilder = runtime.NewSchemeBuilder(addKnownTypes)
    // AddToScheme is a global function that registers this API group & version to a scheme
    AddToScheme = SchemeBuilder.AddToScheme
)
// Adds the list of known types to Scheme.
func addKnownTypes(scheme *runtime.Scheme) error {
    scheme.AddKnownTypes(SchemeGroupVersion,
        &Foo{},
        &FooList{},
    )
    metav1.AddToGroupVersion(scheme, SchemeGroupVersion)
    return nil
}

再执行一次 go mod vendor

为自动生成的文件准备一个 header

hack/boilerplate.go.txt

/*
this is a header file
*/

执行如下命令生成代码：（我在 Goland 的终端中执行此命令会报错，但是在普通终端中执行就没问题了，目前还不太清楚原因）

bash vendor/k8s.io/code-generator/generate-groups.sh all \
github.com/schwarzeni/k8s-sample-controller-doc-demo/pkg/generated  github.com/schwarzeni/k8s-sample-controller-doc-demo/pkg/apis \
samplecontroller:v1alpha1 \
--go-header-file hack/boilerplate.go.txt \
--output-base /Users/nizhenyang/my-project/cloud/src

对于 --output-base ，假如你的项目绝对路径为 /Users/nizhenyang/my-project/cloud/src/github.com/schwarzeni/k8s-sample-controller-doc-demo ，将后半段 github.com/schwarzeni/k8s-sample-controller-doc-demo 视为 GOPATH，则这个参数的值就是前半段路径。

执行完代码之后，在 pkg/ 下会出现新生成的 generated 文件夹，大致的结构如下

pkg/generated
├── clientset
│   └── versioned
│       ├── clientset.go
│       ├── doc.go
│       ├── fake
│       ├── scheme
│       └── typed
├── informers
│   └── externalversions
│       ├── factory.go
│       ├── generic.go
│       ├── internalinterfaces
│       └── samplecontroller
└── listers
    └── samplecontroller
        └── v1alpha1

在pkg/apis/samplecontroller/v1alpha1/ 下新生成了 zz_generated.deepcopy.go 文件。

生成代码任务完成，再执行一次 go mod vendor

Testing

这里写一个测试程序来验证我们生产代码的可用性，首先，根据自定义资源的格式准备两份 yaml 配置文件：

crd.yaml

apiVersion: apiextensions.k8s.io/v1beta1
kind: CustomResourceDefinition
metadata:
  name: foos.samplecontroller.k8s.io
spec:
  group: samplecontroller.k8s.io
  version: v1alpha1
  names:
    kind: Foo
    plural: foos
  scope: Namespaced

example-foo.yaml

apiVersion: samplecontroller.k8s.io/v1alpha1
kind: Foo
metadata:
  name: example-foo
spec:
  deploymentName: example-foo
  replicas: 1

执行命令 kubectl apply -f crd.yaml 创建资源定义

删除 vendor 目录，在项目根目录新建 main.go ，内容如下

package main
import (
    "log"
    "time"
    "github.com/schwarzeni/k8s-sample-controller-doc-demo/pkg/apis/samplecontroller/v1alpha1"
    "k8s.io/client-go/tools/cache"
    clientset "github.com/schwarzeni/k8s-sample-controller-doc-demo/pkg/generated/clientset/versioned"
    informers "github.com/schwarzeni/k8s-sample-controller-doc-demo/pkg/generated/informers/externalversions"
    "k8s.io/client-go/tools/clientcmd"
)
func main() {
  // 你的Kubernetes配置文件路径，一般为 ~/.kube/config
    config, err := clientcmd.BuildConfigFromFlags("", "config/config")
    if err != nil {
        panic(err)
    }
    exampleClient, err := clientset.NewForConfig(config)
    sharedInformers := informers.NewSharedInformerFactory(exampleClient, time.Second*2)
    informer := sharedInformers.Samplecontroller().V1alpha1().Foos().Informer()
    informer.AddEventHandler(cache.ResourceEventHandlerFuncs{
        AddFunc: func(obj interface{}) {
            mObj := obj.(*v1alpha1.Foo)
            log.Printf("New Foo Added: %s", mObj.GetName())
        },
        DeleteFunc: func(obj interface{}) {
            mObj := obj.(*v1alpha1.Foo)
            log.Printf("Delete Foo : %s", mObj.GetName())
        },
    })
    stopCh := make(chan struct{})
    defer close(stopCh)
    informer.Run(stopCh)
}

执行该程序

执行 kubectl apply -f foo-example.yaml ，发现程序输出了 “New Foo Added: example-foo”

执行 kubectl delete -f foo-example.yaml ，发现程序输出了 “Delete Foo : example-foo”